CN114378995A

CN114378995A - Device and method for hot curing and forming of high molecular weight polyethylene

Info

Publication number: CN114378995A
Application number: CN202111522310.6A
Authority: CN
Inventors: 张建辉; 马明栋; 张伟荣; 霍宇轩; 黄茜; 周晓思; 谢堂
Original assignee: Guangzhou University
Current assignee: Guangzhou University
Priority date: 2021-12-13
Filing date: 2021-12-13
Publication date: 2022-04-22

Abstract

The invention provides a device and a method for hot curing molding of high molecular weight polyethylene, wherein the device comprises a pressure barrel, a pressure barrel cover, an upper die and a lower die, the pressure barrel and the pressure barrel cover are matched with each other to form a closed cavity for containing solution, the pressure barrel cover is provided with a pressure gauge and a pressure relief valve, the barrel wall of the pressure barrel is provided with a thermometer, and the upper die and the lower die are matched with each other to form a die cavity for containing a polyethylene sample. The method can ensure that the polyethylene powder is not influenced by temperature gradient in the thermosetting process, the density and the pore space of the obtained product are uniform, and when the shape, the size and the dimension of the polyethylene product are changed, parameters such as temperature, heat preservation time and the like do not need to be searched again in experiments.

Description

Device and method for hot curing and forming of high molecular weight polyethylene

Technical Field

The invention relates to the technical field of material forming processing, in particular to a device and a method for hot curing and forming high molecular weight polyethylene.

Background

The polyethylene filter element has the advantages of good mechanical property, high purification efficiency, low manufacturing cost and the like, and is widely applied to liquid filtration treatment in the fields of production and life, biological medicine, chemical engineering and the like. The polyethylene filter element is internally provided with a through micro-pore structure, so that not only can suspended matters in the filtered liquid be removed, but also pigments and other organic impurities in the liquid can be removed.

The existing general method for manufacturing the polyethylene filter element comprises the following steps: the polyethylene powder is pressed and molded by a mold made of high-temperature resistant materials such as metal, and then the mold is heated and kept warm for a period of time, and the polyethylene is melted and solidified under the action of constant high temperature, so that the final product is obtained. This approach has two problems: firstly, when heating the mould, the heat transfer mode mainly uses heat-conduction as the main, and the existence of temperature gradient makes polyethylene be heated unevenly, thereby the polyethylene that is close to the heat source is heated fast and is sintered excessively, and the polyethylene that keeps away from the heat source is heated slowly and thus is sintered inadequately, and the product that processes like this often density, hole are inhomogeneous, influence the filter effect. Secondly, the processing by the method has strict requirements on the temperature and time of heat preservation, the commonly adopted method for determining the parameters is an experimental method, a plurality of groups of control experiments are required to be set, the experiments are not stopped until the obtained product meets the requirements, and the experimental period is longer. When the shape, size and dimension of the polyethylene product are changed, experiments are needed to determine sintering parameters again, and the production efficiency and enterprise benefit are seriously affected.

Patent CN201910649109.0 proposes a method of mixing metal oxide powder into polyethylene powder and sintering the mixture in a microwave oven, which solves the problem of uneven heating, but the metal oxide powder cannot be separated after molding, the components of the metal oxide powder are changed, and the obtained polyethylene product cannot be used for filtering the solution capable of reacting with the metal oxide powder, and the application of the polyethylene product is limited.

Disclosure of Invention

The first purpose of the invention is to provide a device for hot-curing and molding high molecular weight polyethylene, which takes solution as an intermediate medium for heat transfer, can uniformly heat a product when reaching the hot-curing temperature of polyethylene, takes solution as the intermediate medium for heat transfer, is easy to separate, and does not change the components of the finally obtained polyethylene product;

the second objective of the present invention is to provide a method for thermosetting molding high molecular weight polyethylene, which prevents polyethylene powder from being affected by temperature gradient during thermosetting process, and the density and porosity of the obtained product are uniform, and when the shape, size and dimension of the polyethylene product are changed, it is no longer necessary to re-perform experimental exploration on parameters such as temperature and holding time.

The invention provides a device for hot curing and molding high molecular weight polyethylene, which comprises a pressure barrel, a pressure barrel cover, an upper die and a lower die, wherein the pressure barrel and the pressure barrel cover are matched with each other to form a closed cavity for containing solution, the pressure barrel cover is provided with a pressure gauge and a pressure relief valve, the barrel wall of the pressure barrel is provided with a thermometer, and the upper die and the lower die are matched with each other to form a die cavity for containing a polyethylene sample.

Furthermore, a sample groove is formed in one side, close to the upper die, of the lower die, and a pressing block is arranged on one side, close to the lower die, of the upper die.

Furthermore, the surface of the compaction block is provided with a plurality of upper micro channels, a plurality of lower micro channels are arranged in the sample groove, the upper micro channels and the lower micro channels are matched with each other to form a solution channel, and the mold cavity for containing the polyethylene sample and the closed cavity for containing the solution are communicated through the solution channel.

Furthermore, an upper connecting hole is formed in the upper die, a lower connecting hole corresponding to the upper connecting hole is formed in the lower die, a bolt is arranged on one side, away from the lower die, of the upper die, a nut is arranged on one side, away from the upper die, of the lower die, the bolt penetrates through the upper connecting hole and the lower connecting hole and is connected with the nut, a spring is arranged between the upper die and the bolt, and when the upper die and the lower die are connected with the bolt through the nut, the spring is in a compression state.

The pressure barrel is characterized by further comprising a pulling rope, one end of the pulling rope is fixedly connected with the pressure barrel cover, the other end of the pulling rope is connected with the upper die, and the whole formed by connecting the upper die and the lower die is kept horizontal and does not contact with the inner wall of the pressure barrel.

Further, the upper die and the lower die are made of the same material, and the melting point of the material of the upper die and the material of the lower die are higher than the thermosetting temperature of the polyethylene.

Further, the safety pressure of the pressure relief valve can be adjusted.

A method for thermosetting molding of high molecular weight polyethylene, comprising the steps of:

s1, pretreating polyethylene powder, putting the polyethylene powder into a tabletting mold, and compacting the powder by using a powder tabletting machine;

s2, putting the solution into a pressure barrel;

s3, placing the compacted polyethylene sample into a lower die, connecting an upper die, and completely soaking the whole formed by connecting the upper die and the lower die into a solution through a traction rope without any contact with the wall of the pressure barrel;

s4, heating the solution in the pressure barrel, and keeping the temperature for 5-10 min when the heat curing temperature of the polyethylene reaches 140-155 ℃ until the polyethylene in the die is completely heated and cured;

and S5, stopping heating, releasing the mold when the temperature is reduced to room temperature, taking out the sintered polyethylene product, and removing the solution adsorbed on the polyethylene product by drying, airing or other methods.

Further, in S1, the shape of the pressure cavity of the tablet press die is the same as the shape of the die cavity formed by connecting the upper die and the lower die, and the pressure value range of the powder tablet press is 5Mpa to 10 Mpa.

Further, in S2, any liquid that does not react with the upper mold, the lower mold and the polyethylene may be selected as the solution in the barrel, and the boiling point of the solution may be adjusted by the pressure barrel, so that the temperature of the solution may reach the thermal curing temperature of the polyethylene in S4.

The technical scheme of the invention is that a solution which does not react with polyethylene is used as an intermediate heat transfer medium, the solution can freely enter and exit gaps between polyethylene powder particles in a mould cavity through a solution channel, the heat is brought into the mould and transferred to the polyethylene powder by using the solution as a carrier by utilizing the convection heat transfer principle of liquid, the boiling point of some solutions cannot reach the thermosetting temperature of the polyethylene, so that the working pressure in a pressure barrel is increased to increase the boiling point of the solution by adopting a pressure barrel, the solution in the barrel is heated and is kept at the temperature of 140-155 ℃, under the condition, the solution in the gaps of the polyethylene powder is equivalent to a plurality of tiny heat sources, the heat is transferred to the polyethylene powder, all parts of the polyethylene powder are uniformly heated, the solidification can be almost simultaneously finished, and the problems that the polyethylene product manufactured by the traditional method has density gradient are solved, The pores are uneven, thereby affecting the filtering effect. In addition, after the product is molded, the solution serving as the intermediate medium can be separated from the product by a simple method without changing the components of the product, and when the shape, size and dimension of the polyethylene product are changed, parameters such as temperature, heat preservation time and the like do not need to be searched again in an experiment, so that the production efficiency is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a cross-sectional view of an apparatus for the thermal setting of high molecular weight polyethylene;

FIG. 2 is a cross-sectional view of an integral upper and lower mold;

FIG. 3 is an isometric view of the upper mold;

FIG. 4 is an isometric view of the lower mold;

description of reference numerals:

1-pressure barrel, 2-pressure barrel cover, 3-pressure gauge, 4-pressure release valve, 5-thermometer, 6-upper mould, 601-upper micro channel, 602-upper connecting hole, 7-lower mould, 701-lower micro channel, 702-lower connecting hole, 8-polyethylene sample, 9-solution, 10-bolt, 11-spring and 12-nut;

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise. Furthermore, the terms "mounted," "connected," and "connected" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example 1

As shown in fig. 1, a device for hot curing and molding high molecular weight polyethylene comprises a pressure barrel 1, a pressure barrel cover 2, a pressure gauge 3, a pressure release valve 4, a thermometer 5, an upper die 6 and a lower die 7;

the pressure barrel 1 and the pressure barrel cover 2 are matched with each other to form a closed cavity. The outer surface of the pressure barrel cover 2 is provided with a pressure gauge 3 and a pressure release valve 4. A thermometer 5 is arranged on the wall of the pressure barrel 1. The upper die 6 and the lower die 7 are mutually matched and connected to form a die cavity, and the polyethylene sample 8 is placed in the die cavity.

As shown in fig. 2-4, the upper mold 6 and the lower mold 7 are connected in a matching manner, a sample groove is formed on one side of the lower mold 7 close to the upper mold 6, and a pressing block is formed on one side of the upper mold 6 close to the lower mold 7, and the two are connected in a matching manner to form a mold cavity. The polyethylene sample 8 is placed in the mold cavity, the shape of which depends on the shape of the final polyethylene product desired, i.e. the present invention is suitable for the production of polyethylene products of various shapes, including but not limited to cylindrical, rectangular.

The matched part of the upper die 6 and the lower die 7 is provided with a section of allowance for compressing a polyethylene sample 8, the upper die 6 is connected with the lower die 7 through a bolt 10, a spring 11 and a nut 12, and a plurality of upper connecting holes 602 and a plurality of lower connecting holes 702 are respectively processed on the upper die 6 and the lower die 7 and are used for connection between the upper connecting holes and the lower connecting holes. A bolt 10 is arranged on one side of the upper die 6, which is far away from the lower die 7, a nut 12 is arranged on one side of the lower die 7, which is far away from the upper die 6, and the bolt 10 penetrates through the upper connecting hole 602 and the lower connecting hole 702 to be connected with the nut 12. A spring 11 is arranged between the upper die 6 and the bolt 10, and after the connection is completed, the spring 11 is in a compression state. The connection method is adopted, because the volume of the polyethylene is slightly reduced in the thermosetting process, under the action of the pre-tightening force of the spring 11, the polyethylene can be guaranteed to be compressed in the thermosetting process and keep the original shape basically without large change by matching with a section of allowance designed by the upper die 6.

The contact surfaces of the upper die 6 and the lower die 7, namely the surfaces of the compaction block and the sample groove, with the polyethylene sample 8 are respectively provided with a plurality of upper micro channels 601 and lower micro channels 701, the upper micro channels 601 and the lower micro channels 701 are mutually matched to form a solution channel, and the solution channel is communicated with an external solution 9. The solution channel is used for enabling the solution 9 in the pressure barrel 1 to enter and exit the die, so that the pores among the polyethylene powder particles are filled, and the water in the pores is equivalent to an infinite number of fine heat sources. The temperature outside the mold can be conducted into the mold in time by taking the solution 9 as an intermediate heat transfer medium in a convection mode and acts on the polyethylene powder, so that the aim of uniformly heating the polyethylene sample 8 in the thermal curing process is fulfilled. The section of the micro flow channel can be a circle, a semicircle, a square or other closed figures with any profiles.

The whole device also comprises a traction rope, one end of the traction rope is fixedly connected with the pressure barrel cover 2, the other end of the traction rope is connected with the upper die 6, the purpose of the traction rope is to enable the whole formed by connecting the upper die 6 and the lower die 7 to be always horizontally immersed in the solution 9 and not to have any contact with the inner wall of the pressure barrel 1 when the device works, and the adopted method comprises but not limited to suspension by the traction rope and support by a bracket, but the example of suspension by the traction rope is taken here. The reason for leveling the mould is that the polyethylene in the mould has certain fluidity after being melted, and the polyethylene in the horizontal state can ensure that the polyethylene can not generate larger deformation after being sintered. The mould does not contact with the inner wall of the pressure barrel 1 at all, so that heat is transferred in a convection mode rather than a heat conduction mode, and the temperature of the polyethylene sample 8 tends to be average and does not have a temperature gradient.

The material of the upper mold 6 and the lower mold 7 may be a metal material such as steel, aluminum, copper, etc., or a non-metal material such as ceramic, wood, etc., but is not limited to the mentioned materials. The melting point of the material is at least higher than the sintering temperature of the polyethylene, and under the action of the sintering temperature of the polyethylene, the original basic shape can be kept without change, no chemical reaction occurs, and any substance which is not beneficial to the sintering process is not decomposed.

The pressure of the pressure release valve 4 is adjustable, the pressure adjusting range is 1-3 atmospheric pressures, so that the purpose of adjusting the boiling points of different solutions can be achieved by adjusting the maximum pressure in a closed cavity formed by the pressure barrel 1 and the pressure barrel cover 2 when different solutions are selected. Meanwhile, a solution is provided for the problem that the boiling points of the same solution are different in different areas with different altitudes.

s2, putting the solution into a pressure barrel;

s3, putting the compacted polyethylene sample into a lower die, connecting the lower die with an upper die, and completely soaking the whole formed by connecting the upper die and the lower die into the solution through a traction rope without any contact with the wall of the pressure barrel;

Convective heat transfer is one of three ways of heat transfer, which generally occurs in a fluid or a gas, and the convective heat transfer causes the temperature to tend to be uniform due to the movement of internal molecules in the fluid, and the heat transfer different from the solid has the problem of large temperature gradient. In this example, a solution that does not react with polyethylene is selected as a medium for intermediate heat transfer, and the solution can freely enter and exit from the gaps between polyethylene powder particles in the mold cavity through micro flow channels on the upper mold 6 and the lower mold 7. Under the action of atmospheric pressure, because the boiling point of some solutions can not reach the sintering temperature of polyethylene, the pressure barrel 1 is adopted to increase the pressure in the closed containing cavity so as to increase the boiling point of the solutions. Adjust relief valve 4 pressure, heat and heat preservation liquid, under the heat convection effect of liquid, solution temperature tends to evenly in the bucket, and the liquid in the polyethylene powder hole is equivalent to the tiny heat source of countless, gives the powder heat transfer, and each part of polyethylene sample 8 is heated evenly, can accomplish the solidification simultaneously.

The solution can be selected from various kinds, but the requirement of innocuity and harmlessness must be satisfied, the boiling point of the solution can be any value, the boiling point of the selected solution can be changed at will under the action of the pressure barrel 1, and the temperature can easily reach the sintering temperature of the polyethylene. The selected solution does not react with the polyethylene, the upper die 6 and the lower die 7, and after the polyethylene product is formed, the method for separating the solution from the product needs to meet the requirements of simple operation and low cost, such as airing, drying, replacement and the like, but the method is not limited to the two forms, and the specific method is determined according to the characteristics of the solution and the product.

The pressure value range of the powder tablet press is 5-10 Mpa, and the shape of the pressure inner cavity of the tablet press die is the same as that of a die cavity formed by connecting the upper die 6 and the lower die 7, namely the shape of the finally obtained polyethylene product.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. The utility model provides a device of high molecular weight polyethylene thermosetting molding, its characterized in that includes pressure vessel, pressure bung, goes up mould and bed die, the pressure vessel with the pressure bung is mutually supported and is formed an airtight cavity that is used for holding solution, be equipped with manometer and relief valve on the pressure bung, be equipped with the thermometer on the bucket wall of pressure vessel, go up the mould with the bed die is mutually supported and is formed a mould cavity that is used for holding the polyethylene sample.

2. The apparatus for thermally curing high molecular weight polyethylene according to claim 1, wherein said lower mold has a sample groove on a side thereof adjacent to said upper mold, and said upper mold has a pressing block on a side thereof adjacent to said lower mold.

3. The apparatus of claim 2, wherein said compact block has a plurality of upper micro channels formed on a surface thereof, and a plurality of lower micro channels formed in said sample chamber, said upper micro channels and said lower micro channels cooperating to form a solution channel, said solution channel connecting said mold cavity for holding a polyethylene sample to said closed cavity for holding a solution.

4. The apparatus of claim 1, wherein said upper mold has an upper connecting hole, said lower mold has a lower connecting hole corresponding to said upper connecting hole, a bolt is disposed on a side of said upper mold away from said lower mold, a nut is disposed on a side of said lower mold away from said upper mold, said bolt is connected to said nut through said upper connecting hole and said lower connecting hole, a spring is disposed between said upper mold and said bolt, and said spring is in a compressed state when said upper mold and said lower mold are connected to said bolt through said nut.

5. The apparatus for thermal curing formation of high molecular weight polyethylene according to claim 1, further comprising a pulling rope, wherein one end of said pulling rope is fixedly connected to said pressure barrel cover, and the other end of said pulling rope is connected to said upper mold, and the whole formed by connecting said upper mold to said lower mold is kept horizontal and does not contact with the inner wall of said pressure barrel.

6. The apparatus of claim 1, wherein the upper mold and the lower mold are made of the same material, and the melting point of the material is higher than the thermal curing temperature of polyethylene.

7. The apparatus for thermal curing formation of high molecular weight polyethylene according to claim 1, wherein the safety pressure of said pressure relief valve is adjustable.

8. A method for thermosetting molding of high molecular weight polyethylene, comprising the steps of:

s2, putting the solution into a pressure barrel;

9. The method for thermosetting molding of high molecular weight polyethylene according to claim 8, wherein in S1, the shape of the pressure cavity of the tablet press die is the same as the shape of the die cavity formed by the connection of the upper die and the lower die, and the pressure value of the powder tablet press is in the range of 5Mpa to 10 Mpa.

10. The method of claim 8, wherein in S2, the solution in the barrel is selected from any liquid which does not react with the upper mold, the lower mold and the polyethylene, and the boiling point of the solution is adjusted by the pressure barrel, so that the temperature of the solution can reach the thermal curing temperature of the polyethylene in S4.