CN110900929B

CN110900929B - Method and device for preparing high-thermal-conductivity UHMWPE product pre-pressed sheet and application

Info

Publication number: CN110900929B
Application number: CN201911229034.7A
Authority: CN
Inventors: 吴晓宁; 王涛; 周占玉
Original assignee: Jones Tech Wu Xi PLC; JONES TECH PLC
Current assignee: Jones Tech Wu Xi PLC; JONES TECH PLC
Priority date: 2019-12-04
Filing date: 2019-12-04
Publication date: 2022-02-25
Anticipated expiration: 2039-12-04
Also published as: CN110900929A

Abstract

The invention provides a method and a device for preparing a high-thermal-conductivity UHMWPE product pre-pressed sheet, wherein the method comprises the following steps: conveying UHMWPE raw material powder to the surface of a fixed base station from a feeding end for heating, conveying to a discharging end of the fixed base station at the same time, and forcibly conveying into a gap between the discharging end of the fixed base station and a single calendering roller for hot rolling to obtain a pre-pressed sheet; the UHMWPE raw material powder has a crystallinity of 72% or more and a low degree of entanglement. In the invention, UHMWPE powder is fully mixed and preheated before entering the pressing gap, and is forcedly fed, so that the powder can be preheated at higher temperature, and thus a preforming sheet with a thicker size can be prepared. The invention also provides application of the prepared pre-pressing sheet in preparation of high-thermal-conductivity products, can prepare high-thermal-conductivity UHMWPE products of various sizes, and has wide application.

Description

Method and device for preparing high-thermal-conductivity UHMWPE product pre-pressed sheet and application

Technical Field

The invention belongs to the technical field of heat-conducting polymers, and particularly relates to a method and a device for preparing a high-heat-conductivity UHMWPE product pre-pressed sheet and application of the high-heat-conductivity UHMWPE product pre-pressed sheet.

Background

Polymeric materials have many advantages such as low mass density, chemical stability, high strength to mass ratio, etc. Conventional polymer materials are generally poor in thermal conductivity, and products such as foamed polymers prepared using amorphous polymers are widely used for thermal insulation. However, in the field of heat exchangers and heat control, the materials used need to have high thermal conductivity, and common conductors typically have high thermal conductivity, such as copper, aluminum, titanium, or graphite. However, these high thermal conductivity conductors are generally made of electrically conductive materials, have poor electrical insulation and can shield electromagnetic signals, thereby limiting the range of applications.

Recently, reports on high thermal conductivity of polyethylene nanofibers and natural biopolymers have renewed interest in thermally conductive polymers for researchers. In general, polymers with high crystallinity and a tendency to chain alignment have higher thermal conductivity. It is known therein that Ultra High Molecular Weight Polyethylene (UHMWPE), when super drawn (ultra-high-magnification drawn), can have properties of high thermal conductivity and associated thermal diffusivity in the direction of drawing. The high thermal conductivity is due to the long extended polymer chains, i.e. the stretched film or sheet of UHMWPE containing long extended chains has a high thermal conductivity in the direction of stretching. The UHMWPE product with high thermal conductivity has good electrical insulation, does not shield electromagnetic signals, and can be applied to industries such as batteries, mobile phones and the like. However, if the UHMWPE is stretched at a large magnification, less entanglement between high molecular chains of the UHMWPE material is required, otherwise the high molecular chains are entangled together like a coil and cannot be sufficiently stretched, and the high molecular chains are broken before being stretched at a large magnification, so that the advantage of high thermal conductivity cannot be obtained.

There are two approaches to producing such high thermal conductivity UHMWPE products, one is to dissolve the UHMWPE polymer in a solvent to produce a gel, which is disentangled by macromolecular chains by dissolution in the solvent, to draw the gel to a high draw ratio, and to remove the solvent, as disclosed in US 9109846. The gel-spun UHMWPE fiber filament or membrane material has high thermal conductivity, but the method involves the use of a large amount of solvent, and has complex process and higher cost.

Another idea is to use UHMWPE polymer powder to be directly pressed into a pre-pressed sheet, and then to subject the pre-pressed sheet to a hot drawing with a drawing ratio of 100 to 200 times by means of multi-pass differential rollers, so as to produce the desired high thermal conductive product, such as fiber filaments, films, sheets or tapes, etc., but the UHMWPE polymer powder raw material to be used has a very low degree of entanglement itself. The idea is a feasible mode at present, and the process for preparing the UHMWPE pre-pressed sheet specifically comprises the following steps: the UHMWPE pre-pressed sheet is produced by using low-entanglement ultra-high molecular weight polyethylene powder as raw material, directly introducing the heated UHMWPE powder into a roll gap between at least one pair of calendering rolls, reversely rotating the pair of calendering rolls, heating to a specific temperature, and carrying out hot pressing at a temperature slightly lower than (preferably within 5 ℃) the melting point of the UHMWPE powder, namely the pair of calendering rolls.

Although the method for directly pressing the UHMWPE polymer powder into the pre-pressed sheet is simple and easy to implement, the thickness of the prepared pre-pressed sheet cannot be more than 0.35mm generally, so that the problem that the powder inside the pre-pressed sheet is not well adhered is solved, the size specification of subsequent products is limited, and the wide application of the products is not facilitated.

Disclosure of Invention

In view of the above, the present application provides a method, an apparatus and an application for preparing a high thermal conductivity UHMWPE product preform, and the present invention can prepare a UHMWPE preform having a thicker size, and the UHMWPE preform can be used to prepare high thermal conductivity products of various sizes by performing thermal stretching on the UHMWPE preform.

The invention provides a method for preparing a high-thermal-conductivity UHMWPE product pre-pressed sheet, which comprises the following steps:

conveying UHMWPE raw material powder to the surface of a fixed base station from a feeding end for heating, conveying to a discharging end of the fixed base station at the same time, and forcibly conveying into a gap between the discharging end of the fixed base station and a single calendering roller for hot rolling to obtain a pre-pressed sheet;

the UHMWPE raw material powder has a crystallinity of 72% or more and a low degree of entanglement.

Preferably, the Mw of the UHMWPE raw material powder is more than 500000g/mole, and the bulk density is 0.35g/cm³The following.

The invention provides a device for preparing a high-thermal-conductivity UHMWPE product preforming sheet, which comprises: a fixed base station with a heating function and a single heated calendering roller;

the fixed base station is provided with a feeding end and a discharging end far away from the length direction; the feeding end of the fixed base station is firstly contacted with UHMWPE raw material powder; a gap exists between the discharge end of the fixed base station and the single calendering roller; the fixed base station is optionally provided with a conveying device for conveying and forcibly feeding the fed UHMWPE raw material powder into the gap.

Preferably, the fixed base station is a heating sleeve having a cavity in which the fed UHMWPE raw material powder is heated and conveyed.

Preferably, the heating sleeve is horizontally fixed, and a feeding screw is arranged in the heating sleeve, so that the conveying and forced feeding adopt a screw conveying mode; the discharge end of the heating sleeve is a square machine head with two closed sides.

Preferably, the fixed base station is a heating base station with a non-closed surface, the surface of the feeding end of the heating base station is inclined to convey the fed UHMWPE raw material powder, the surface of the discharging end corresponding to the calendering roller has a certain radian, and the lowest end of the surface reaches a minimum gap.

Preferably, high-strength baffles are arranged on two sides of the heating base platform, the width between the high-strength baffles is consistent with the width of the calendering rollers, and the tail ends of the high-strength baffles in the length direction are attached to the calendering rollers.

Preferably, the surface heating temperature and the hot rolling temperature of the fixed base are both below the melting point of the UHMWPE raw material powder.

Preferably, the surface roughness Ra of the fixed base is within 0.05, and the surface roughness Ra of the reduction rolls is within 0.2.

Preferably, the thickness of the pre-pressed sheet is more than 0.10mm, and the density is more than 0.90g/cm³。

The invention provides the application of the pre-pressing sheet prepared by the method in the preparation of high heat conduction products.

In the conventional method, UHMWPE powder is exposed to air for preheating, and the powder is difficult to ensure uniform temperature. If the powder is melted due to overhigh temperature, the UHMWPE powder as the raw material loses the advantages of high crystallinity and disentanglement, so that the UHMWPE powder cannot reach a larger multiple in subsequent stretching; and the preheating effect cannot be achieved due to too low temperature, and the powder needs to be contacted for a longer time for hot pressing when reaching the roller gap, so that the thickness of the prepared pre-pressing sheet cannot be more than 0.35mm generally to prevent the powder in the pre-pressing sheet from being bonded poorly. On the other hand, if the preheating temperature is too high, the powder is easy to agglomerate to form lumps separated from each other, and if the pressure for feeding the powder into the roll gap is not high, the lumps are easily separated in the pressing process, so that defects are generated.

Compared with the prior art, the method takes UHMWPE powder with the crystallinity of more than 72 percent and low entanglement degree as the raw material, the UHMWPE powder is conveyed from the feeding end to the surface of the fixed base station to be heated and conveyed to the discharging end, and then the UHMWPE powder is forcibly conveyed into a gap between the discharging end of the fixed base station and a single calendering roller to be subjected to hot rolling, so that the pre-pressed sheet is obtained. In the invention, UHMWPE powder is fully mixed and preheated before entering the pressing gap, and is forcedly fed, and the powder can be preheated at higher temperature, so that a preforming sheet with a thicker size can be prepared, and the subsequent product application is facilitated.

In addition, the traditional rolling equipment has no side face width limitation, so that the two sides of the pre-pressing piece are not well pressed, and the edge parts with poor adhesion on the two sides need to be cut off in a large amount. On one hand, high-precision large-scale equipment is required for prepressing, on the other hand, the size specification of a product is limited by the thickness and the like, and the trimming also causes material waste and increases the cost.

And this application further carries out limit for width of limit for edge including fixed base station and single roller's production facility to reduced the cutting edge of preforming effectively, saved the use of raw and other materials.

Drawings

FIG. 1 is a schematic side view of an apparatus for producing UHMWPE preform in some embodiments of the present invention;

fig. 2 is a schematic side view of an alternative apparatus for producing UHMWPE preform in further embodiments of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. 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.

Interpretation of related terms:

ultra-high molecular weight polyethylene: the English name of Ultra-high Molecular Weight Polyethylene (UHMWPE for short) is unbranched linear Polyethylene with Molecular Weight of more than 150 ten thousand, and is one kind of polyolefin material.

Degree of crystallinity: the proportion of the crystalline portion is that the crystal is an ordered arrangement of molecular chains, and generally, the higher the crystallinity, the more regular the molecular chain arrangement, the higher the temperature required for destruction, and thus the higher the melting point. The crystalline part has very low or even no entanglement of the macromolecular chains due to the ordered arrangement; but not necessarily crystalline without entanglement.

Heat of fusion or heat of fusion: refers to the amount of heat, in J/Kg, that a unit mass of crystals needs to absorb when melting to a liquid substance of the same temperature, as measured by Differential Scanning Calorimetry (DSC).

Entanglement of ultra-high molecular weight polyethylene: because the ultrahigh molecular weight polyethylene is a linear long chain structure macromolecule, microscopically, the linear long chains of the raw material ultrahigh molecular weight polyethylene are more or less intertwined with each other like a coil, but because of different qualities of the raw material, the intertwining degree is greatly different, and the raw material ultrahigh molecular weight polyethylene can be defined as low intertwining or disentanglement below a certain intertwining degree.

The degree of entanglement cannot be directly measured and is usually assessed by measuring other properties of the material. For example, the elastic shear modulus GN of the raw material₀Small, which indicates the degree of disentanglement of the material from the side, requires that the material be measured within 15 seconds of being melted at 160 ℃ and, for acceptable material GN₀The maximum is 1.4MPa, and the high-quality material can be as low as 0.7 MPa.

And (3) disentangling: for a homopolymer or copolymer of ultra high molecular weight polyethylene-ethylene, the polymer has the following characteristics: molar mass is between 30 and 2000 ten thousand; the crystallinity is higher than 75%; a heat of fusion of above 200J/g and a bulk density of between 0.01 and 0.3g/cc, wherein the polyethylene chains have low entanglement or complete disentanglement.

Oriented product: refers to a filament, sheet, film, tape or other polymer product having oriented polymer chains.

Prelaminate or prelaminate: the sheet obtained after passing the UHMWPE through the rolls is further subjected to hot stretching to obtain an oriented UHMWPE product.

Tape, plate tape, fiber, film: the above-mentioned prelaminate or prelaminate is subjected to high-stretch (several tens to several hundreds of stretches in the lengthwise direction of the strip passing through the roll gap) to obtain the product. Generally, strips of greater than or equal to 1/2 inches in width, very narrow filaments of less than 1/2 inches in width, fibers, and more widely films, without sharp boundaries between them, are consolidated into a pre-laminated or pre-sheeted final product that is subjected to high-stretch.

Correspondingly, the embodiment of the invention also provides a device for preparing the high-thermal-conductivity UHMWPE product preforming sheet, which comprises the following steps: a fixed base station with a heating function and a single heated calendering roller;

The prepressing sheet prepared by the method can achieve the effect of increasing the thickness of the finished prepressing sheet, and further can prepare high-heat-conductivity products with various dimensions.

The UHMWPE powder used as the raw material in the embodiment of the invention needs to have Mw (weight average molecular weight) at least more than 500000g/mole and the molecular weight distribution is as narrow as possible; the crystallinity is above 72% and has a lower degree of entanglement or disentangled state. According to the results of the ceraniss 2024 powder test in the actual experiment, the crystallinity can be broadened to over 72%. In the embodiment of the invention, the bulk density of UHMWPE raw material powder is 0.35g/cm as much as possible³Below, preferably 0.25g/cm³In the following, the shape and the particle size of the powder are suitable for rapid hot pressing, and the larger particle size and the irregular particle shape easily cause the generation of too many gaps in the pressing process, so that the breakage of the pre-pressing sheet in the subsequent stretching is caused. According to the test result of the three-well 540RU powder in the practical experiment, the bulk density can be widened to 0.35g/cm³The following.

The problems of small thickness and the like of the pre-pressing piece manufactured in the prior art are solved mainly by forcibly feeding the UHMWPE powder raw material into a roller gap and fully preheating the UHMWPE powder raw material.

Referring specifically to fig. 1, fig. 1 is a schematic side view of an apparatus for producing UHMWPE preform in some embodiments of the invention. In fig. 1, 1 is UHMWPE powder, 2 is a hopper, 3 is a motor for driving a screw, 4 is a feed screw, 5 is a heating sleeve, 6 is a calender roll, 7 is a cylindrical feeding cavity, and 8 is a square head.

In the embodiment of the invention, UHMWPE raw material powder 1 can be continuously fed in a metering mode through material containing equipment such as a hopper 2 and then is conveyed to the surface of a fixed base station for heating. In the specific embodiment of the present invention, the fixed base is a heating sleeve 5, the interior of the fixed base is a cavity 7, and the fed UHMWPE raw material powder is heated and conveyed in the cavity 7. Preferably, the heating sleeve 5 is horizontally fixed, and the feed screw 4 is driven by the motor 3, so that the raw material powder is conveyed from the feed end to the discharge end and is forcibly fed into the gap between the calender roll 6 and the square head 8. Furthermore, the square head 8 at the discharge end of the heating sleeve is preferably closed on both sides.

In the above embodiment, UHMWPE powder is continuously fed into the closed feeding chamber 7 through the hopper 1 in a metered manner; the periphery of the cavity 7 is wrapped with the heating sleeve 5 to ensure that the inside of the whole cavity keeps constant temperature, the temperature of the cavity is required to be as high as possible below the melting point of UHMWPE powder, the temperature range is preferably within +/-3 ℃, and the higher temperature precision can ensure more sufficient hot pressing of the powder. The UHMWPE powder fed into the chamber 7 is continuously and forcibly fed by a feed screw 4 driven by a motor 3, which may be a single screw or a twin screw, to ensure that the powder can be forcibly fed, so as to ensure that the powder is accumulated under a certain pressure inside a head 8 having a square cross-section. The outlet of the square head 8 is provided with a single rotating calender roll 6 which needs to be heated to a temperature as high as possible below the melting point of the UHMWPE powder and which can adjust the size of the roll gap by hydraulic means, thereby adjusting the thickness of the finished preform. The powder is fully preheated and mixed, so that the thickness of the pre-pressed sheet rolled by the roller can reach larger thickness, which depends on the sizes of the roller and a square machine head matched with the roller and the precision of temperature control in the cavity, and the thickness of the pre-pressed sheet can reach more than 1mm by adopting the process under normal conditions.

The common plastic screw extrusion molding equipment is mainly used for processing solid silica gel, the solid silica gel is pushed in a cavity through pressure generated by a screw and then is extruded from an outlet at a front machine head, and adhesive tapes (such as long adhesive tapes with square sections, circular sections or special-shaped sections) with various section shapes are formed according to the section shapes of the machine heads. But it is difficult to produce UHMWPE preform simply by this method, because the raw material for producing UHMWPE preform is powder, as distinguished from solid silica gel (rubber clay-like colloid), and the powder does not melt during the whole process of producing UHMWPE preform. If the UHMWPE preform is produced using conventional plastic screw extrusion equipment, the powder does not stick into a sheet at the outlet, but rather comes out as a powdery or intermittent mass of powder. The invention is provided with a single calendering roller at the outlet to ensure that the powder has enough pressure up and down to press the powder into a sheet when passing through the outlet. Meanwhile, the plastic screw extrusion molding equipment also inherits the advantages of forced feeding and good heat preservation.

In the embodiment of the invention, the surface of the square machine head 8, which is in contact with the powder, needs higher finish, so as to ensure the smoothness of the surface of the produced pre-pressing sheet as much as possible, and the roughness Ra is usually required to be within 0.05, so that the roughness can be better than 0.005; the surface roughness Ra of the calender roll is preferably within 0.2, more preferably 0.05. The method for producing the pre-pressing sheet has the advantages that the two sides of the square machine head are sealed, so that the cutting edges of the pre-pressing sheet are effectively reduced, and the use of raw materials is saved.

When wide prepressed sheets are prepared directly through a roller gap of a pair of rollers in the prior art, the prepressing equipment is generally required to have a larger roller diameter so as to ensure that the powder can have enough time to contact with the rollers at the roller gap. The method of the present invention is not particularly limited in roll diameter of the calender roll; the regulation and control of the process in the embodiment of the invention are mainly determined by the speed of producing UHMWPE pre-pressed sheets at the discharge end (outlet end) and the thickness of the pre-pressed sheets.

When the size of the calender roll at the outlet end is 15cm in diameter and 30cm in length, the speed (i.e. the linear speed of the roll surface) for producing the UHMWPE pre-pressed sheet with the thickness of 0.5mm is not more than 40 mm/s; if a 0.3mm thick pre-laminate is produced, the upper limit can be increased appropriately to 60mm/s, and excessive production speeds can result in incomplete lamination of the sheets, creating poorly bonded areas. Of course, the production speed can be increased if the size of the calender roll is increased. For example, when the size of the outlet end calendering roll is 30cm in diameter and 35cm in length, the roll gap area is increased due to the increase of the roll size, and the speed of producing 0.5 mm-thick pre-pressing sheets is preferably not more than 80mm/s, for example, 20-70 mm/s; the upper speed limit can be relaxed to 100mm/s if a pre-tablet of 0.3mm thickness is produced.

The thickness of the UHMWPE pre-pressed sheet produced by the embodiment of the invention is determined according to the clearance between a single calendering roller at the outlet end and the lower surface; for producing 0.5mm thick preforms, the gap is at least 0.45mm +/-0.05 mm, too large gap fluctuation can lead to unstable thickness of the produced preforms and lead to excessive thinning of individual positions and stress concentration cracking during subsequent stretching, and the adjustment of the gap is determined according to the size of the required finished preform. It is emphasized that the slower the production speed, the better the adhesion, but the corresponding decrease in production efficiency, which can be suitably adjusted around the upper limit, results in the best match of efficiency and quality.

The rotating speed of the screw feeding into the cavity is determined according to the size of the cavity and the specific transmission mode of the screw, and the rotating speed is mainly matched with the requirement that enough powder is accumulated at an outlet to generate enough pressure, and the pressure has no fixed index but can be limited by the minimum powder feeding amount of the screw. For example, when the size of the calendering roller is 30cm in diameter and 35cm in length, and a pre-pressing sheet with the thickness of 0.5mm and the width of 35cm is produced at the speed of 50mm/s, the rotating speed of the screw is set to ensure that at least 9g/s of powder is fed into the screw cavity, the value can be simply estimated through the quality of the sheet at the outlet, and the actual measurement of the density of the sheet at the outlet by a density drainage method is 0.93-0.97g/cm³。

The temperature of the cavity and the temperature of the calendering roller in the embodiment of the invention are ensured to be below the melting point of UHMWPE powder; for example, if the melting point of the UHMWPE powder is 143 ℃, the temperature of the cavity and the temperature of the calendering roller are at least 140 ℃, the temperature control precision is within +/-3 ℃, preferably 141 ℃, the temperature control precision is within +/-2 ℃, preferably 142 ℃, and the temperature control precision is within +/-1 ℃. Higher temperature and temperature control accuracy mean faster production speeds.

An alternative apparatus for producing UHMWPE preform according to the design and principles of the present invention is shown in fig. 2. In fig. 2, 1 is UHMWPE powder, 2 is a hopper, 3 is a heating base, and 4 is a calender roll.

In the embodiments of the present invention, the fixed base is the heating base 3, and the surface of the fixed base contacting and heating the powder is not closed. The feeding end of the heating base station 3 is communicated with the hopper 2, and the surface is inclined at a certain angle, so that the fed UHMWPE raw material powder 1 can be conveyed by means of self weight, and other forced feeding components or equipment can be added. A gap is formed between the discharge end of the heating base station 3 and the single calendering roller 4; preferably, the heating base 3 has a surface with a constant curvature corresponding to the discharge end of the reduction roll 4, and reaches a minimum gap at the lowermost end. The heating base 3 belongs to a built-in heating element, and is covered with a metal plate to transfer heat. In addition, high-strength baffles are preferably arranged on two sides of the heating base table 3 to prevent leakage; the width between the high-strength baffle plates is consistent with the width of the calendering rollers, and the tail ends of the high-strength baffle plates in the length direction are attached to the calendering rollers.

In the above-described embodiment, the UHMWPE raw material powder 1 is fed onto the heating base 3 through the hopper 2 in a metered manner and deposited on the side surface of the reduction roll 4. Although not shown in the figures, the two sides of the heating base 3 need to have high-strength baffles, and the width between the baffles is consistent with the width of the calendering rollers 4 and is tightly attached to ensure that the powder does not overflow from the two sides. The temperature of the heating base 3 and the reduction rolls 4 should be set to a temperature as high as possible below the melting point of the UHMWPE powder. The heating base station 3 is excessive at a certain radian at one side of the calendering roller 4 and reaches a minimum gap at the lowest end, so that the powder is gradually rolled into the gap with gradually reduced space after reaching the side surface of the calendering roller 4 until being thermally pressed to form a pre-pressing sheet. Wherein the powder is gradually compressed and forcibly fed in the gap, and has sufficient time to preheat in the gap.

In this embodiment, the surface of the heating base 3 in contact with the powder needs a high degree of finish to ensure the smoothness of the surface of the produced pre-pressed piece as much as possible, and the roughness Ra is usually within 0.05, which is better than 0.005; the surface roughness Ra of the calender roll is preferably within 0.2, more preferably 0.05. By adopting the method to produce the pre-pressing sheet, the two sides of the heating base station 3 are sealed, so that the cutting edges of the pre-pressing sheet are effectively reduced, and the use of raw materials is saved. The method has no closed heating, and the pre-pressed tablet is slightly thin but still can reach more than 0.35mm, even more than 0.5 mm.

In addition, this embodiment has a slower production rate than the previous embodiment method because the powder is transported exposed to air, is less temperature controlled, and is less forcibly fed.

The thickness of the pre-pressing sheet prepared by the method can be more than 0.10mm, and the thickness can exceed 0.35 mm. The pre-compressed tablets may also have a greater width and a density greater than 0.90g/cm³。

The prepressed sheet produced by the method is subjected to hot stretching, and the stretching method can be multi-pass continuous differential roller stretching so as to form assembly line operation, or can be single-pass repeated multi-pass repeated differential roller stretching, wherein the stretching ratio is 100-200 times for example; the stretching needs to be carried out in a closed heat-preserving environment, and the temperature needs to be as high as possible below the melting point of the UHMWPE powder, preferably within 1 ℃ to 3 ℃ below the melting point. These are all stretching methods commonly used in the industry and can be interfaced with the pre-pellet line of the present invention. Further, the highly thermally conductive UHMWPE product of the present invention may be an oriented UHMWPE product of a tape, a slab band, a fiber, or a film, the size of which is not particularly limited.

The prepressing sheet produced by the method can be used for preparing a film product with high heat conductivity and certain size and thickness. As the thickness of the pre-pressing sheet produced by the invention is increased, the thickness of the obtained finished heat-conducting film is also increased correspondingly, the thickness of the heat-conducting film prepared by stretching the pre-pressing sheet with the thickness of more than 0.5mm can reach more than 100 mu m, and the heat-conducting film has the heat conductivity of at least 25W/mK.

Therefore, the method is simple and easy to implement, can prepare prepressed sheets with thicker sizes and reduced cut edges, and can further prepare high-heat-conductivity products with various sizes, thereby effectively widening the size range of the products, reducing the production cost and being beneficial to application.

For further understanding of the present application, the method, apparatus and application for preparing a highly thermally conductive UHMWPE product preform provided herein are specifically described below with reference to the examples. It should be understood, however, that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention, which is defined by the following examples.

In the following examples, the crystallinity of the UHMWPE powder of the grade of Cellanius 2024 was 72%, and the molecular weight was 5.4X 10⁶g/mol, bulk density 0.26g/cm³(ii) a UHMWPE powder of Mitsui 540RU has crystallinity of 77% and molecular weight of 3.5 × 10⁶g/mol, bulk density 0.34g/cm³。

The first embodiment is as follows:

the pre-compressed tablets were prepared using the apparatus described in fig. 1, UHMWPE powder designated selanibs 2024. Wherein the size of the calendering roller is 30cm in diameter, 35cm in length, and the surface roughness Ra is 0.05; the outlet gap was set to 0.45mm, and UHMWPE pre-pellets were produced at a rate of 50mm/s, with the chamber (surface roughness Ra of 0.05) and roll surface temperature measured at 140 ℃, and the screw motor set to 10g/s to feed the powder. The width of the produced pre-pressing sheet after edge cutting is 33cm, and the thickness is measured to be 0.52 mm; the density drainage method of the sheet is actually measured to be 0.94g/cm³。

After the pre-pressed sheet is stretched 150 times on a differential roller stretching device, a film material with the thickness of about 135 mu m is obtained, and the thermal diffusion coefficient of the film material is 23W/mk measured by a laser flash method.

Example two:

the device shown in figure 1 is used for preparing the pre-pressed sheet by selecting UHMWPE powder with the trade mark of Mitsui 540 RU. Wherein the size of the calendering roller is 30cm in diameter, 35cm in length, the outlet gap is set to be 0.14mm, UHMWPE pre-pressed sheets are produced at the speed of 70mm/s, the temperature of a cavity and the roller surface is actually measured to be 141 ℃, and the screw motor is set to be 5g/s to feed powder. The width of the produced pre-pressing sheet after edge cutting is 33cm, and the thickness is measured to be 0.18 mm; the density drainage method of the sheet material is actually measured to be 0.945g/cm³。

After the pre-pressed sheet is stretched 150 times on a differential roller stretching device, a film material with the thickness of about 50 mu m is obtained, and the thermal diffusion coefficient of the film material is 30W/mk measured by a laser flash method.

Example three:

and using the device shown in figure 2, and selecting UHMWPE powder with the trade name of Mitsui 540RU to prepare the pre-pressed sheet. Wherein the size of the calendering roll is 30cm in diameter and 35cm in length, the outlet gap is set to be 0.14mm, UHMWPE pre-pressed sheets are produced at the speed of 20mm/s, the measured temperature of a heating base (vertical baffles are arranged on two sides and are tightly attached to two ends of the calendering roll and are vertical to the horizontal plane, a heating element is arranged in the heating base, a metal plate is covered on the surface of the heating base to transfer heat) is 139 ℃, and the measured temperature of the roll surface is 141 ℃. The width of the produced pre-pressing sheet after edge cutting is 32cm, and the thickness is measured to be 0.17 mm; the sheet has a dense drainage methodMeasured at 0.945g/cm³。

Example four

And using the device shown in figure 2, and selecting UHMWPE powder with the trade name of Mitsui 540RU to prepare the pre-pressed sheet. Wherein the size of the calendering roll is 30cm in diameter and 35cm in length, the outlet gap is set to be 0.26mm, UHMWPE pre-pressed sheets are produced at the speed of 20mm/s, the measured temperature of the heating base table is 139 ℃, and the measured temperature of the roll surface is 141 ℃. The width of the produced pre-pressing sheet after edge cutting is 32cm, and the thickness is measured to be 0.3 mm; the density drainage method of the sheet material is actually measured to be 0.945g/cm³。

From the above examples, it can be seen that the UHMWPE powder is fully mixed and preheated before entering the compaction gap and is forcibly fed in the present invention, which can preheat the powder at a higher temperature, thereby making it possible to prepare a preform with a thicker size. This application further carries out limit for width of limit for edge to the production facility including fixed base station and single roller to reduce the cutting edge of pre-compaction piece effectively, saved the use of raw and other materials. The invention adopts the prepared prepressing sheet to carry out hot stretching, prepares products such as high heat-conducting films with various sizes and the like, and has wider application range.

The above description is only a preferred embodiment of the present invention, and it should be noted that various modifications to these embodiments can be implemented by those skilled in the art without departing from the technical principle of the present invention, and these modifications should be construed as the scope of the present invention.

Claims

1. A method for preparing a highly thermally conductive UHMWPE product preform, comprising the steps of:

conveying UHMWPE raw material powder to the surface of a fixed base station from a feeding end for heating, conveying to a discharging end of the fixed base station at the same time, and forcibly conveying into a gap between the discharging end of the fixed base station and a single calendering roller for hot rolling to obtain a pre-pressed sheet; the surface heating temperature and the hot rolling temperature of the fixed base station are both below the melting point of UHMWPE raw material powder;

2. The method according to claim 1, wherein the UHMWPE raw material powder has an Mw of 500000g/mole or more and a bulk density of 0.35g/cm³The following.

3. An apparatus for preparing a highly thermally conductive UHMWPE product preform, comprising: a fixed base station with a heating function and a single heated calendering roller;

the fixed base station is provided with a feeding end and a discharging end far away from the length direction; the feeding end of the fixed base station is firstly contacted with UHMWPE raw material powder; a gap exists between the discharge end of the fixed base station and the single calendering roller; the surface heating temperature and the hot rolling temperature of the fixed base station are both below the melting point of UHMWPE raw material powder; the fixed base station conveys and forcibly feeds the fed UHMWPE raw material powder into the gap.

4. The apparatus according to claim 3, characterized in that the fixed base station is provided with a conveying device for conveying and forcibly feeding the fed UHMWPE raw material powder into the gap.

5. The apparatus according to claim 4, wherein the fixed base is a heating sleeve having a cavity in which the fed UHMWPE raw material powder is heated and conveyed.

6. The device of claim 5, wherein the heating sleeve is horizontally fixed, and a feeding screw is arranged in the heating sleeve, so that the conveying and forced feeding are realized in a screw conveying manner; the discharge end of the heating sleeve is a square machine head with two closed sides.

7. The apparatus according to claim 3, wherein the fixed base is a heated base having a non-closed surface, and the surface of the inlet end of the heated base is inclined to convey the fed UHMWPE raw material powder and has a certain radian transition corresponding to the surface of the outlet end of the calendering roll, and the lowest end of the heated base reaches a minimum gap.

8. The device of claim 7, wherein high-strength baffles are arranged on two sides of the heating base platform, the width between the high-strength baffles is consistent with the width of the calendering rollers, and the length direction tail ends of the high-strength baffles are attached to the calendering rollers.

9. The apparatus according to any one of claims 3 to 8, wherein the surface roughness Ra of the fixed base is within 0.05, and the surface roughness Ra of the calender roll is within 0.2.

10. Use of a pre-compressed tablet prepared by the method according to any one of claims 1 to 2 for preparing a high thermal conductivity product.