TW202339931A - Processing method of once physical foam forming of thermoplastic polymer material - Google Patents

Abstract

Processing method of once physical foam forming of thermoplastic polymer material, a mold is disposed in a pressurized space, so that the physical foaming process can be directly performed in a pressure chamber without removing a coarse embryo formed after the mold separately, greatly improving the efficiency of the processing process, and the volume of the pressure chamber is smaller than that of a traditional pressure kettle, the safety performance of the pressurization process is far better than that of the traditional pressure kettle, the coarse embryo is directly foamed in a mold cavity of the mold to limit the process through the top mold, so the foaming density of the coarse embryo is controlled, so as to form a skin layer in the coarse embryo without bubbles.

Description

Processing method and device for one-time physical foaming molding of thermoplastic polymer materials

The invention relates to the technical field of material processing, in particular to a device for one-time physical foaming molding of thermoplastic polymer materials.

The present invention also relates to a processing method of the device for one-time physical foaming molding of the thermoplastic polymer material.

Thermoplastic polymer materials mainly foam through foaming agents. The types of foaming agents can be divided into chemical foaming agents and physical foaming agents. There are many differences between the two. After the chemical foaming agent is added to the thermoplastic polymer material, it is decomposed by heat or a chemical reaction occurs between the raw materials to produce gas, making the thermoplastic polymer material melt full of holes. However, because chemical foaming agents often use nitrates, in The foaming process will produce a large amount of gas containing odor, and because chemical foaming agents may contain carcinogens, it has been reported in recent years that chemical foaming agents may be banned in the future. Therefore, physical foaming has become the most important polymer foaming technology in recent times. .

Physical foaming mainly uses high pressure to dissolve the physical foaming agent into the thermoplastic polymer material to achieve a state of equilibrium between the gas pressure in the material and the gas pressure in the pressure chamber. When the pressure in the pressure chamber is released, the thermoplastic polymer material begins to foam and expand. Due to physical Foaming agents usually use compressed gas, and the processing process does not produce substances harmful to the human body. It is relatively safe and environmentally friendly. Therefore, it has become a high-profile foaming method for thermoplastic polymer materials in recent years.

The aforementioned physical foaming process usually uses autoclave equipment to pressurize thermoplastic polymer materials. The volume of the autoclave is generally very large, and multiple brackets are often installed inside to hang the rough embryos, so that the autoclave can be Each pressurization operation can process a large number of rough embryos at high pressure at the same time. However, although large autoclave equipment can process a large number of rough embryos at one time, due to its large size, it is particularly prone to danger when the pressure is increased, so Not only does the structure of the autoclave itself need to be specially reinforced, but the opening and closing doors also need to be made of a very solid structure. Especially when covering the disc flange cover used in the autoclave, a pair of bolts located on the diagonal line must be Only by tightening the bolts in the correct order can the safety after pressurization be ensured. Not only is it easy to cause danger due to human negligence and omission of the locking bolts, but also the operation time is long because of the tightening of the bolts in sequence.

Furthermore, please refer to the preparation method of polymer products with multi-scale cell structure described in Chinese Patent Announcement No. CN103128973, which discloses two types of equipment that need to be used in the physical foaming process, one of which is forming. equipment, and the other is an autoclave. During the processing process, the thermoplastic polymer material is first placed in the forming equipment and melted to form a rough embryo. The rough embryo is then transferred to the autoclave for heating and pressurization, and is injected into the autoclave. The physical foaming agent is in a supercritical fluid state to allow the physical foaming agent to dissolve into the rough embryo. Finally, the autoclave is opened to quickly release the pressure, allowing the rough embryo containing the physical foaming agent to return to atmospheric pressure, allowing the rough embryo to begin Foam and expand to become the finished product.

Because the foamed thermoplastic polymer material has the advantages of low thermal conductivity, strong sound insulation, high bending tensile strength, high resilience, and hydrophobicity, the foamed thermoplastic polymer material is often used to make shoes. Midsole, but for soles made by the above-mentioned process, after opening the autoclave, bubbles will be generated from the inside to the outside of the rough embryo, resulting in an increase in volume and appearance deformation. It needs to undergo secondary processing and hot and cold shaping to become a midsole. . It is difficult to control the temperature and supercritical fluid distribution in a large autoclave to achieve comprehensive uniformity, which will cause uneven foaming density of the rough embryo and result in poor production yield.

In the aforementioned processing flow, it is necessary to move the rough embryo formed in the mold equipment to the autoclave equipment, and then move the foamed rough embryo into the mold for shaping, which makes the processing process unsmooth and causes low production efficiency, and the aforementioned autoclave Because the size is too large, it is not only dangerous, but also prone to lengthy work times. In view of this, it is indeed necessary to provide a technical means to improve the aforementioned shortcomings.

The first purpose of the present invention is to solve the problem of secondary processing transfer process to control the appearance deformation of thermoplastic polymer materials foamed by physical foaming process in molds and pressure kettles.

The second purpose of the present invention is to solve the problems of unsmooth processing flow and low production efficiency.

In order to achieve the aforementioned objectives, the present invention is a device for one-time physical foaming molding of thermoplastic polymer materials, including:

A pressure chamber has a bottom shell and a top shell. The bottom shell has a bottom space surrounded by a bottom wall, and the bottom shell is open toward the top shell and has a bottom shell end surface. The top housing has a top space surrounded by a top wall, and the top housing is open toward the bottom housing and has a top housing end surface. The top housing is connected to a first driving element, and the top housing is connected to a first driving element through the first driving element. The top shell is driven to be close to or away from the bottom shell. When the top shell is close to the bottom shell, the end surface of the top shell is closely attached to the end face of the bottom shell, so that the bottom space and the top space are connected. And form a sealed pressurized space;

A supercritical fluid system has a tank, an input pipe and a recovery pipe connected to the tank, the supercritical fluid is stored in the tank, and the input pipe and the recovery pipe are respectively connected to the pressurized space;

A mold has a bottom mold and a top mold disposed in the pressurized space. The bottom mold has a mold cavity recessed toward the top mold. The top mold is connected to a second driving element. Through the second driving The component drives the top mold and the bottom mold to close or open the mold.

In a preferred embodiment, there is also a bracket, the pressure chamber is arranged in the bracket, and the first driving element is a pressure cylinder.

In a preferred embodiment, both ends of the input pipe and the recovery pipe are fixedly connected to the container and the bottom shell respectively, and the input pipe and the recovery pipe pass through the bottom wall and are connected to the bottom space.

In a preferred embodiment, the bottom mold is disposed in the bottom space, and the top mold is disposed in the top space.

The present invention also relates to the processing method of the device for one-time physical foaming molding of the thermoplastic polymer material, wherein:

A first step is to place a thermoplastic polymer material into the mold cavity;

a second step, driving the second driving element to close the top mold and the bottom mold so that the thermoplastic polymer material is shaped into a rough embryo;

A third step is to drive the first driving element to make the top housing lean against the bottom housing, and the end surface of the top housing is closely attached to the end surface of the bottom housing, so that the bottom space and the top space are connected and a seal is formed. the pressurized space;

a fourth step, driving the second driving element to open the top mold and move away from the bottom mold so that the mold cavity is connected to the pressurized space;

A fifth step is to increase the temperature in the pressurized space, and allow the supercritical fluid system to input supercritical fluid into the pressurized space through the input pipe to increase the pressure in the pressurized space, thereby allowing The supercritical fluid dissolves into the rough embryo and maintains the high pressure in the pressurized space for a predetermined time. The supercritical fluid system recovers the supercritical fluid in the pressurized space through the recovery pipe to reduce the pressure in the pressurized space. The pressure causes the rough embryo to bubble in the pressurized space and form an inner layer with bubbles, and a skin layer surrounding the inner layer without bubbles;

A sixth step is to drive the upper mold to pressurize the film cavity to foam to complete the rough embryo. After the mold is heated, cooled and shaped, the first driving element is driven to move the top shell away from the bottom shell.

By arranging the mold in the pressurized space, the present invention allows the rough embryo formed after the mold is closed to be directly subjected to the physical foaming process without needing to be taken out separately, thereby greatly improving the smoothness and smoothness of the processing process. efficiency. Moreover, the rough blank is directly foamed in the mold cavity, and certain restrictions are placed on the foaming process of the rough blank through the top mold, thereby achieving appearance deformation control and reducing secondary processing transfer processes.

Please refer to Figure 1. The present invention is a device for one-time physical foaming molding of thermoplastic polymer materials. It mainly has a pressure chamber 10, a supercritical fluid system 20 and a mold 30, wherein:

The pressure chamber 10 has a bottom shell 11 and a top shell 12. The bottom shell 11 has a bottom space 112 surrounded by a bottom wall 111, and the bottom shell 11 is open toward the top shell 12 and is open to the top shell 12. There is a bottom shell end face 113, the top shell 12 has a top space 122 surrounded by a top wall 121, and the top shell 12 is open toward the bottom shell 11 and has a top shell end face 123. The top shell 12 has a top shell end face 113. The body 12 is connected to a first driving element 13, and the first driving element 13 drives the top housing 12 to be close to or away from the bottom housing 11. When the top housing 12 is close to the bottom housing 11, the top housing 12 is moved against the bottom housing 11. The top shell end face 123 is closely attached to the bottom shell end face 113, so that the bottom space 112 and the top space 122 are connected and form a sealed pressurized space 14; in this embodiment, there is also a bracket 40, and the pressure chamber 10 is disposed in the bracket 40, and the first driving element 13 is a pressure cylinder.

The supercritical fluid system 20 has a tank 21 and an input pipe 22 and a recovery pipe 23 connected to the tank 21. The supercritical fluid is stored in the tank 21, and the input pipe 22 and the recovery pipe 23 are connected respectively. The pressurized space 14; in this embodiment, the two ends of the input pipe 22 and the recovery pipe 23 are fixedly connected to the container 21 and the bottom shell 11 respectively, and the input pipe 22 and the recovery pipe 23 pass through The bottom wall 111 is connected to the bottom space 112. Of course, the input pipe 22 and the recovery pipe 23 can also pass through the top wall 121 and be connected to the top space 122, or the input pipe 22 can pass through the top wall 121 And connected to the top space 122, and the recovery pipe 23 passes through the bottom wall 111 and is connected to the bottom space 112. The input pipe 22 and the recovery pipe 23 are configured to pass through the top wall 121 or the bottom wall 111 There are no special restrictions.

The mold 30 has a bottom mold 31 and a top mold 32 disposed in the pressurized space 14. The bottom mold 31 has a mold cavity 311 recessed toward the top mold 32. The top mold 32 is connected to a second mold cavity 311. The driving element 33 drives the top mold 32 and the bottom mold 31 to close or open the mold through the second driving element 33; in this embodiment, the bottom mold 31 and the top mold 32 are mold cores (or inner molds). mold). The bottom mold 31 is disposed in the bottom space 112, and the top mold 32 is disposed in the top space 122. The second driving element 33 is a pressure cylinder.

Secondly, the supercritical fluid stored in the container 21 is preferably nitrogen or carbon dioxide, but is not limited to nitrogen or carbon dioxide. The viscosity of the supercritical fluid (Supercritical Fluid; SCF) is close to that of gas and the density is close to that of gas. Liquid has the characteristics of high mass transfer efficiency, low surface tension, and its solubility can be adjusted with temperature and pressure.

The above is the structural configuration and connection relationship of the present invention in a preferred embodiment. Please refer to Figures 2 to 7 for the processing method and usage steps of the present invention, which are described in sequence as follows:

Please refer to FIG. 2 , which shows a first step S1 , placing a thermoplastic polymer material A into the mold cavity 311 . The thermoplastic polymer material A used in this embodiment can be spandex, and the thermoplastic polymer material A is Thermoplastic polyurethane elastomer, also known as thermoplastic polyurethane rubber (also known as Thermoplastic polyurethane, TPU), is an (AB) n-type block linear polymer. The thermoplastic polymer material A is in a molten state or a solution state at high temperatures. In the state or solution state, the intermolecular force weakens, but after cooling or the solvent evaporates, strong intermolecular forces connect together to restore the original solid properties.

Please refer to FIG. 3 to show a second step S2, driving the second driving element 33 to close the top mold 32 and the bottom mold 31, so that the thermoplastic polymer material A is molded into a rough embryo A'; In this embodiment, the second driving element 33 is driven to drive the top mold 32 toward the bottom mold 31 to close the mold. After the top mold 32 and the bottom mold 31 are closed, the thermoplastic polymer material A is pressed into a specific shape through the top mold 32 and the bottom mold 31, such as soles, heels, watch straps, airbags, and cushioning. Heat-insulating foam material, etc., so that the mold cavity 311 is completely filled with the rough embryo A'.

Please refer to FIG. 4 which simultaneously shows a third step S3, a fourth step S4 and a fifth step S5. In the third step S3, the first driving element 13 is driven to make the top case 12 lean against the bottom case. body 11, and the top shell end face 123 is closely attached to the bottom shell end face 113, so that the bottom space 112 and the top space 122 are connected and form the sealed pressurized space 14; in this embodiment, driving the first The driving element 13 drives the top housing 12 toward and against the bottom housing 11 , so that the top housing end surface 123 is completely attached to the bottom housing end surface 113 , allowing the top space 122 to be connected with the bottom space. 112 are connected to form the pressurized space 14, and because the top shell end face 123 is completely attached to the bottom shell end face 113, the pressurized space 14 is in a completely sealed state.

In the fourth step S4, the second driving element 33 is driven to open the top mold 32 and move away from the bottom mold 31, so that the mold cavity 311 communicates with the pressurized space 14; in this embodiment, the second driving element 33 is driven to open the mold and move away from the bottom mold 31. The driving element 33 drives the top mold 32 and the bottom mold 31 to open the mold to expand the mold cavity 311. After the mold is opened, the distance between the top mold 32 and the bottom mold 31 is not particularly limited, but in this embodiment it is There is a slight gap between the top mold 32 and the bottom mold 31 after molding, which is only to allow the pressurized space 14 to communicate with the mold cavity 311, and because the top mold 32 has not completely left the bottom mold 31, If the rough embryo A' expands during the foaming process, the top mold 32 can prevent the rough embryo A' from being excessively deformed during the foaming process. Also because the rough blank A' is still located in the mold cavity 311, when the rough blank A' is heated to an appropriate temperature (the temperature changes due to different materials) and becomes molten, it can be received by the mold cavity 311 without overflowing.

In the fifth step S5, the temperature in the pressurized space 14 is raised, and the supercritical fluid system 20 is allowed to input the supercritical fluid into the pressurized space 14 through the input pipe 22, so that the temperature in the pressurized space 14 is The pressure is increased, thereby allowing the supercritical fluid to dissolve into the rough embryo A' and maintaining the high pressure in the pressurized space 14 for a predetermined time. Please refer to Figure 6. The rough embryo A' is in the pressurized space 14. Blister and form an inner layer A'1 with bubbles, and a skin layer A'2 surrounding the inner layer A'1 without bubbles; please refer to Figure 4, in this embodiment, nitrogen is used as the super Critical fluid, the supercritical fluid enters the pressurized space 14 through the input pipe 22, gradually increasing the pressure in the pressurized space 14, and increasing the temperature of the pressurized space 14 through the pressure chamber 10, allowing the The rough embryo A' is heated to a molten state. When the rough embryo A' is in a molten state, the supercritical fluid is injected into the molten rough embryo A' through the characteristics of high solubility and high expansibility, and the supercritical fluid causes The rough embryo A' foams to produce the inner layer A'1, and because of the high-pressure environment in the pressurized space 14, the outer layer of the rough embryo A' is unable to generate bubbles, thereby producing the skin surrounding the inner layer A'1. Layer A'2.

Referring to FIG. 5 , a sixth step S6 is shown. The supercritical fluid system 20 recovers the supercritical fluid in the pressurized space 14 through the recovery pipe 23 to reduce the pressure in the pressurized space 14 and simultaneously reduce the pressure in the pressurized space. temperature of 14, and drives the first driving element 13 to move the top housing 12 away from the bottom housing 11; in this embodiment, the supercritical fluid in the pressurized space 14 is first recovered through the recovery pipe 23, In this way, the pressure in the pressurized space 14 is gradually reduced. Through the process of gradually reducing the pressure, the rough embryo A' can be stabilized to maintain its appearance, thereby ensuring that the skin layer A'2 will not be produced in the sixth step S6. Bubbles, and lowering the temperature of the pressurized space 14 can maintain the shape of the rough blank A' molded in the fifth step S5, and take out the finished product after driving the first driving element 13 to open the top housing 12.

By arranging the mold 30 in the pressurized space 14, the present invention allows the rough embryo A' formed after the mold 30 is closed to directly undergo the physical foaming process without needing to be taken out separately, greatly improving processing. The smoothness and efficiency of the process. And the rough embryo A' is directly foamed in the mold cavity 311. The top mold 32 provides certain restrictions during the foaming process of the rough embryo A', thus controlling the foaming density of the rough embryo A'. , thereby enabling the rough embryo A' to form the skin layer A'2. It is worth mentioning that the number of rough blanks that can be processed by the pressure chamber 10 is the same as the number of molds 30 disposed in the pressure chamber 10 , and one or a smaller number of molds 30 is generally disposed in the pressure chamber 10 . , therefore the pressure chamber 10 can seal the pressurized space 14 only through the first driving element 13 , and when the supercritical fluid system 20 increases the pressure of the pressurized space 14 , the first driving element 13 can also maintain sealing. state without leakage. Of course, the number of molds disposed in the pressure chamber 10 can be increased or decreased according to demand, and the number is not limited to one.

10: Pressure chamber 11: Bottom shell 111: Bottom wall 112: Bottom space 113:Bottom shell end face 12:Top shell 121:top wall 122:Headspace 123: Top shell end surface 13: First driving element 14: Pressurized space 20:Supercritical fluid system 21: Container 22:Input tube 23:Recycling tube 30:Mold 31: Bottom mold 311:Mold cavity 32: Top mold 33: Second driving element 40: Bracket A: Thermoplastic polymer material A’: rough embryo A’1: Inner layer A’2: Skin layer S1: The first step S2: The second step S3: The third step S4: The fourth step S5: The fifth step S6: The sixth step

Figure 1 shows a schematic structural diagram of the present invention in a preferred embodiment; Figure 2 shows a schematic diagram of the first step of the present invention in a preferred embodiment; Figure 3 shows a schematic diagram of the second step of the present invention in a preferred embodiment; Figure 4 shows a schematic diagram of the third step, the fourth step and the fifth step of the present invention in a preferred embodiment; Figure 5 shows a schematic diagram of the sixth step of the present invention in a preferred embodiment; Figure 6 shows a cross-sectional view of the rough embryo forming the inner layer and skin layer after foaming; Figure 7 is a schematic diagram of the processing method steps of a device for one-time physical foaming molding of thermoplastic polymer materials.

10: Pressure chamber

11: Bottom shell

111: Bottom wall

112: Bottom space

113:Bottom shell end face

12:Top shell

121:top wall

122:Headspace

123: Top shell end surface

13: First driving element

20:Supercritical fluid system

21: Container

22:Input tube

23:Recycling tube

30:Mold

31: Bottom mold

311:Mold cavity

32: Top mold

33: Second driving element

40: Bracket

Claims (5)

A processing method for one-time physical foaming molding of thermoplastic polymer materials, wherein: A first step, placing a thermoplastic polymer material into the mold cavity; a second step, driving the second driving element to close the top mold and the bottom mold so that the thermoplastic polymer material is shaped into a rough embryo; A third step, driving the first driving element to make the top housing lean against the bottom housing, and the end surface of the top housing is closely attached to the end surface of the bottom housing, so that the bottom space and the top space are connected and a sealed pressurized space is formed; a fourth step, driving the second driving element to open the top mold and move away from the bottom mold so that the mold cavity is connected to the pressurized space; A fifth step is to increase the temperature in the pressurized space, and allow the supercritical fluid system to input the supercritical fluid into the pressurized space through the input pipe to increase the pressure in the pressurized space, thereby allowing the supercritical fluid to dissolve In the rough embryo, and maintaining the high pressure in the pressurized space for a predetermined time, the rough embryo bubbles in the pressurized space and forms an inner layer with bubbles, and a skin layer surrounding the inner layer without bubbles; A sixth step, the supercritical fluid system recovers the supercritical fluid in the pressurized space through the recovery pipe to reduce the pressure in the pressurized space, simultaneously reduces the temperature of the pressurized space, and drives the first driving element to move the top shell away from the bottom shell. A device for one-time physical foaming of thermoplastic polymer materials, including: A pressure chamber has a bottom shell and a top shell. The bottom shell has a bottom space surrounded by a bottom wall, and the bottom shell is open toward the top shell and has a bottom shell end surface. The top housing has a top space surrounded by a top wall, and the top housing is open toward the bottom housing and has a top housing end surface. The top housing is connected to a first driving element, and the top housing is connected to a first driving element through the first driving element. The top shell is driven to be close to or away from the bottom shell. When the top shell is close to the bottom shell, the end surface of the top shell is closely attached to the end face of the bottom shell, so that the bottom space and the top space are connected. And form a sealed pressurized space; A supercritical fluid system has a tank, an input pipe and a recovery pipe connected to the tank, the supercritical fluid is stored in the tank, and the input pipe and the recovery pipe are respectively connected to the pressurized space; A mold has a bottom mold and a top mold disposed in the pressurized space. The bottom mold has a mold cavity recessed toward the top mold. The top mold is connected to a second driving element. Through the second driving The component drives the top mold and the bottom mold to close or open the mold. The device for one-time physical foaming molding of thermoplastic polymer materials as described in claim 2, further comprising a bracket, the pressure chamber is disposed in the bracket, and the first driving element is a pressure cylinder. The device for one-time physical foaming molding of thermoplastic polymer materials as described in claim 2, wherein the two ends of the input pipe and the recovery pipe are fixedly connected to the container and the bottom shell respectively, and the input pipe and the recovery pipe The tube passes through the bottom wall and communicates to the bottom space. The device for one-time physical foaming molding of thermoplastic polymer materials as described in claim 2, wherein the bottom mold is disposed in the bottom space, and the top mold is disposed in the top space.

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