TWI292766B - Ultrahigh molecular weight polyethylene foam and manufacturing method and use thereof - Google Patents

Description

1292766 IX. Description of the Invention: TECHNICAL FIELD OF THE INVENTION The present invention relates to an ultrahigh molecular weight polyethylene foam and a method of producing the same. [Prior Art] Ultra-high molecular weight polyethylene having a viscosity average molecular weight of 300,000 or more is excellent in abrasion resistance, self-lubricity, impact resistance, low-temperature property, chemical resistance, etc. in plastic materials, and its characteristics are utilized. It is used in various applications such as building components, medical appliances, food related, sports and leisure. In recent years, among the unique features of ultrahigh molecular weight polyethylene, it is required to add functions such as weight reduction, heat insulation, sound absorbing property, low dielectric constant, cushioning property, and flexibility as additional functions. A method of attaching such a function can be exemplified by foam molding. However, since the ultrahigh molecular weight polyethylene has a molecular weight of more than 300,000, has high melt viscosity and extremely low fluidity, it is difficult to form and process. Foaming, which is particularly difficult to control the melt viscosity, is considered to be very difficult. The reason for this is that (i) the continuous stable productivity is not established due to the above-mentioned hard formability; (ii) the foam molding is carried out by a conventional method, and the original characteristics of the ultrahigh molecular weight polyethylene are resistant. The so-called mechanical strength properties such as abrasion resistance, self-lubricating property, and impact resistance are greatly reduced, and the actual situation is that the actual product is not circulated. Patent Documents 1 to 3 disclose a technique of supplying carbon dioxide as a foaming agent to a solid conveying portion and/or a liquid conveying portion of an extruder to obtain a foam. However, in order to supply carbon dioxide to the solid transport unit, the screw drive shaft and the raw material supply funnel must be made of special equipment such as a pressure-resistant seal structure. Therefore, the industrial equipment is complicated, and the supply surface of the raw material is 6 312XP/ Invention specification (supplement) /94-02/9313053 5 1292766 Difficult to produce continuous. Further, although a foam molding method using an ultrahigh molecular weight polyethylene using a rod-shaped mold and a tubular mold is disclosed, the specifications of the extruder of the patent documents, the extrusion conditions, and the ultrahigh molecular weight polyethylene which is a raw material are approximately In the same way, even though the temperature of the resin which has just been ejected from the die (mold) is about the same, the expansion ratio and the average bubble diameter are still largely different, and only with these conditions, there is foam which cannot be stabilized. The problem of the foam of the magnification and the average bubble diameter. Further, the two-stage compression type screw which is generally used in extrusion foam molding disclosed in Patent Document 1 or 2 has a short compression zone, and has a pressure fluctuation in the extruder to stably unload the ultrahigh molecular weight polyethylene foam. The problem. Further, if the ultrahigh molecular weight polyethylene foam is molded using the previously used die (mold), appearance defects occur on the surface of the obtained foam. This is a trace (f 1 i gh t mark) caused by the thread of the extruder, and bubbles occurring near the exit of the die are concentrated on the trace portion, so that the trace is conspicuous and the appearance is poor. If this phenomenon is observed as a whole as a foam, the skin layer is partially lost, and the uniformity of the bubbles (cells) is impaired, and the independent bubble rate is also lowered. Namely, there is a problem that the excellent characteristics of the ultrahigh molecular weight polyethylene are lowered. In particular, it has a problem that the impact resistance is greatly reduced. [Patent Document 1] Japanese Patent Laid-Open No. Hei 1 1 - 1 1 6 7 2 1 No. [Patent Document 2] Japanese Patent Laid-Open No. Hei 1 1 _ 3 3 5 4 8 0 [Patent Document 3] Japanese Patent OPERATION 2 0 0 0 - 1 1 9 4 5 3 SUMMARY OF INVENTION [Problem to be Solved by the Invention] The present invention provides a 7 312XP/invention specification that does not have ultrahigh molecular weight polyethylene. ())/94-02/93130535 1292766 Excellent wear resistance, self-lubricity, impact resistance, low-temperature properties, chemical properties, etc., good appearance, and added lightweight, heat insulation and low dielectric constant The foaming of the function, cushioning property, flexibility, and the like, and the method for producing the foam continuously. (Means for Solving the Problems) The present inventors have made efforts to solve the above problems, and as a result, (i) the ultrahigh molecular weight polyethylene resin in which the foaming agent is dissolved is passed from the screw front end of the press machine to the die outlet. The length of stay. The resin pressure in the screw portion is within a specified range, and the crease of the screw can be reduced. The appearance of the foam body is good, and a foam having various mechanical properties and particularly good resistance can be obtained. Further, (i i ) the foamed molded article having a high foaming, a thick skin layer and a good mechanical property value can be obtained by controlling the temperature at the surface of the die and the temperature at the center of the resin at a specific temperature during molding. That is, the present invention provides (1) an ultrahigh molecular weight polyethylene foam obtained by foaming an ultrahigh molecular weight polyethylene having a viscosity of 300,000 to 1,000,000. The density of the foam is 〇. 〇2~0. 7 g / c m3, and the tensile impact value X (KJ / m2) at a temperature of -40 °C is approximated by the density (g/cm3) of the foam. (approximate) in the following formula (1), the coefficient v 75~1 5 0 0 ° X = Ax p (1) (2) provides the ultrahigh molecular weight polyethylene foam as described in the above (1), which Tensile strength Y ( Μ P a ) at a temperature of -1 0 ° °C to the denseness of the foam 312XP / invention specification (supplement) /94-02/93130535

, and the nature, body, found over the front end of the squeeze, the tree of the impact is stable, and the average split foaming degree is PA, the degree P 8 1292766 (g / cm 3) is approximated by the following formula (2), the coefficient B is 5 0~:l Ο Ο 0. Υ = Βχ ρ (2) (3) A method for producing an ultrahigh molecular weight polyethylene foam, which is obtained by foaming an ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 300,000 to 1,000,000 Is 0.  0 2~0 .  A method for producing a foam of 7 g / c m 3 characterized in that the residence time T (minutes) of the ultrahigh molecular weight polyethylene in which the foaming agent is dissolved from the screw front end of the extruder to the die outlet In the following formula (3) which approximates the viscosity average molecular weight Mv of the ultrahigh molecular weight polyethylene, the coefficient Ε is 0.  5 to 10, and the resin pressure at the front end of the screw is 1 0~1 Ο Ο Μ P a. T=Ex(MvxlΟ'6)2 (3) (4) A method for producing an ultrahigh molecular weight polyethylene foam according to the above (3), which comprises melting an ultrahigh molecular weight polyethylene in an extruder a step of adding a foaming agent to the ultrahigh molecular weight polyethylene; the surface temperature of the resin which has just been discharged from the die is 60 to 140 ° C, and the temperature of the central portion of the resin which has just been discharged from the die is 70 to 1 5 The step of extruding and foaming it at 0 °C. (5) The method for producing an ultrahigh molecular weight polyethylene foam according to the above (3) or (4), wherein the amount of the ultrahigh molecular weight polyethylene is 0.  1 to 20 parts by mass of carbon dioxide. (6) Providing a heat insulating material characterized by the ultrahigh molecular weight polyethylene foam according to any one of (1) or (2) above, wherein the thermal conductivity is 0.  0 Bu 0· 3 5 K ca 1 / m · hr · °C 7 (7 ) Provides a material for heat insulation materials for liquefied natural gas, heat insulating materials for liquid hydrogen, superconducting magnetic resonance devices, etc. A material, a cushioning high sliding material, which is an ultra high score 312XP according to any one of the above (1) or (2) / invention specification (supplement) / 94-02/93130535 9 1292766 body. (Effect of the Invention) By using the ultrahigh molecular weight polyethylene foam of the present invention, it is possible to provide excellent wear resistance, self-lubricity, impact resistance, low temperature characteristics, and resistance which are not impaired by ultrahigh molecular weight polyethylene. A foamed product which is excellent in appearance and has a function of lightness, heat insulation, sound absorbing property, low dielectric constant, cushioning property, and flexibility. Moreover, according to the method for producing an ultrahigh molecular weight polyethylene foam of the present invention, the foam can be stably produced, and the shape of the screw is reduced, the appearance is excellent, and the mechanical property value is excellent, and further, it can be manufactured. High foam of ultra high molecular weight polyethylene in the skin layer. [Embodiment] [Ultra High Molecular Weight Polyethylene] The ultrahigh molecular weight polyethylene used in the present invention is composed of ethylene as a main component (the largest molar percentage of the total copolymer component), and examples thereof include homopolymerization of B-bake. A body, an interpolymer of ethylene and a monomer copolymerizable with the ethylene, and the like. The monomer copolymerizable with ethylene may, for example, be an α-olefin having 3 or more carbon atoms. Examples of the α-olefin having 3 or more carbon atoms include, for example, propylene-baked, 1-butadiene, isobutylene, 1-pentyl roasted, 2-mercapto-1-butadiene, 3-methyl-1-butene, and 1 -hexene, 3-methyl-1-pentene, 4-mercapto-1 -pentene, 1-glycol, 1_xin-baked, 1-癸-thin, 1-h-di-carbon, 1-h-4 Carbon thin, 1-hexadecene carbon, 1- h eight-carbon thin, 1- 20 carbon thin. Among them, in terms of economy and the like, a homopolymer of ethylene or an interpolymer of ethylene and the above-mentioned α-olefin is suitable for use, and B 10 312 ΧΡ / invention specification (supplement) / 94- 02/93130535 1292766 The olefin is 80% by mole or more, preferably 90% by mole, and more preferably 9.55% by mole or more of the entire polymer. The ultrahigh molecular weight polyethylene used in the present invention has a viscosity average molecular weight of 300,000 to 1,000,000, preferably a viscosity average molecular weight of 900,000 to 800,000 to 1.9 million to 8 million, and particularly preferably 2.1 million. ~8 million, especially good for 10,000 ~ 800,000, excellent viscosity average molecular weight of 300,000 ~ 600,000 is good when the average molecular weight is within the above range, can make wear resistance, self-running impact Characteristics such as properties, low temperature properties, and chemical resistance are used to the maximum extent. Further, it is also possible to use two or more types of ultrahigh molecular weight polyethylene having a viscosity average molecular weight within the above range. The ultrahigh molecular weight polyolefin resin used in the present invention can be produced by a conventionally known method, for example, in the presence of a catalyst, the above ethylene or α-olefin is polymerized as disclosed in Japanese Patent Laid-Open Publication No. SHO-58-8603. It is preferable to add a well-known kind of polymer in the range which does not impair the subject of this invention. For example, polyolefin (polypropylene having a viscosity average molecular weight of less than 300,000 ethylene, viscosity average molecular weight of 30 to 10 million, polypropylene having a viscosity of less than 300,000, ethylene-propylene copolymer, polybutene methylpentene -1, etc.), elastomer, styrene resin (polystyrene, styrene styrene copolymer, acrylonitrile styrene copolymer, acrylonitrile diene styrene copolymer, etc.), polyester (poly conjugate Ethylene glycol diester, polybutylene acrylate, polylactic acid, etc., polyvinyl chloride, polycarbonate, polyphenyleneoxide, polyethylene glycol, polymethyl acrylate, polyamido resin Polyimine resin, fluorine resin, liquid compound, and the like. 312XP / invention manual (supplement) /94-02/93130535 upper, the amount is more, more than 260 〇 sticky 'sex, the middle and the different sides of the record r ° of each of the points of the distribution of x 4 - Ding 2 · Ding 酞, Polyacid phthalocyanine polymer 11 1292766 [Production of ultrahigh molecular weight polyethylene foam] [Foaming agent] As a foaming agent used in the present invention, specifically, a chemical foaming agent may, for example, be sodium hydrogencarbonate or ammonium carbonate. Ammonium bicarbonate, ammonium nitrite, citric acid, azodicarbonamide, azobisisobutyronitrile, benzathine, arsenazo azodicarboxylate, dinitrosopentamethylenetetramine, P, P '-hydroxybisbenzenesulfonate, p-nonylbenzenesulfonate, p-nonylbenzenesulfonate, acetone, and the like. Further, examples of the physical foaming agent include hydrocarbons such as propane burn, butadiene, pentane, isobutyl, neopentyl, isopentyl, hexyl, ethidium, gamma, bake, propylene, and petroleum scale; Alcohols such as decyl alcohol and ethanol; halogenated hydrocarbons such as methyl chloride, dichloromethane, dichlorofluorodecane, chlorotrifluorodecane, dichlorodifluorodecane, gas difluorodecane, and tri-fluorofluorocarbon Carbon dioxide, nitrogen, argon, water, etc. These foaming agents may be used alone or in combination of two or more. Further, among these foaming agents, carbon dioxide is preferred. Carbon dioxide is different from other physical foaming agents such as butane gas, and there is no danger of explosion, toxicity, and the like, and there is no danger of environmental problems such as destruction of the ozone layer by the Fron-type gas such as dichlorodifluoromethane, and there is no chemical foaming. The problem of the residue of the product. Further, in the extruder, carbon dioxide is in a supercritical state, and the compatibility with the ultrahigh molecular weight polyethylene is improved, and the melt viscosity is lowered by the plasticizing effect, and the molding is remarkably easy. [Method of Forming Foam] The method of molding the foam of the present invention may be continuous molding, and it is preferable to use a squeeze foaming method in terms of low cost production. The type of extruder used in the present invention may, for example, be a single screw extruder, 12 312 XP / invention description _ patch) / 94-02 / 93130535 1292766 twin screw extruder. Among these, a single screw extruder is preferred. Further, a multi-stage extruder in which two or more extruders are connected can be used. In the case of a physical foaming agent, the shape of the screw of the extruder can be such that the ultrahigh molecular weight polyethylene can be melted at a position earlier than the supply portion of the physical foaming agent, and the shape of the length of the compression zone can be sufficiently ensured. If the depth of the groove is gradually reduced, and the metering portion of the front end is a certain full-thread type, the pressure variation of the resin in the extruder can be made small, and the extruded foam can be stabilized, which is preferable. Further, in the present invention, the position of the physical foaming agent to be added to the extruder must be a position where the ultrahigh molecular weight polyethylene composition has been melted and the physical foaming agent can be stably supplied to be added between the extruder and the die. The position of the joint portion, in particular the measuring portion of the mast, is preferred. Further, in the case of using a multi-stage extruder in which two or more extruders are connected, it is also possible to supply a physical foaming agent in a connecting pipe between the extruder and the extruder. The method for supplying carbon dioxide to be used in the present invention includes, for example, a method in which a pressure of a supply portion is controlled by a carbon dioxide cartridge through a pressure sensitive valve, thereby supplying a gas in a gaseous state, and a carbon dioxide cartridge is passed through a metering pump to control a flow rate of carbon dioxide. A method of supplying a liquid state or a supercritical state, etc., wherein a method of supplying in a supercritical state is preferred. The amount of carbon dioxide added is 0% by mass of the ultrahigh molecular weight polyethylene, which is 0.  1 to 20 parts by mass, preferably 0.  3 to 1 5 parts by mass, more preferably 0.  4 to 9 parts by mass. The amount of carbon dioxide in the ultrahigh molecular weight polyethylene is 0 per 100 parts by mass.  When the amount is 1 part by mass or more, the expansion ratio is increased and the formability is improved. In addition, the amount of carbon dioxide in the ultrahigh molecular weight polyethylene is 20 parts by mass or less per 100 parts by mass, and the decrease in the expansion ratio due to foaming is small, and the pressure fluctuation is small, so the cell uniformity and the extrusion stability are small. Good, 13 312XP / invention manual (supplement) /94-02/9313053 5 1292766 is better. Further, the inventors of the present invention have found that the residence time τ (minutes) of the ultrahigh molecular weight polyethylene in which the foaming agent is dissolved from the tip end of the screw of the extruder to the outlet of the die, and the resin pressure at the tip end of the screw are It is particularly important for the appearance of the foamed article, and especially for mechanical properties at low temperatures. The ultrahigh molecular weight polyethylene tends to retain the thread marks (streaks) of the screw on the formed body as compared with a general thermoplastic resin. This situation is more pronounced at higher molecular weights. In the conventional extrusion molding which is not accompanied by foaming, the trace is not too conspicuous and is less likely to cause problems. However, in the case of foam molding, bubbles which occur in the vicinity of the exit of the die are concentrated on the portion of the trace, so that in the case of the foamed article, the trace is very remarkable and the appearance is impaired. Further, since the cortex of the trace portion disappears, there are various mechanical properties, in particular, a problem that the impact strength is lowered. In the present invention, it has been surprisingly found that the ultrahigh molecular weight polyethylene composition in which the foaming agent is dissolved can be obtained without threading after a predetermined time and a specific pressure are maintained after passing through the screw front end of the extruder. An ultrahigh molecular weight polyethylene foam excellent in mechanical properties, and the residence time is related to the viscosity average molecular weight of the ultrahigh molecular weight polyethylene. That is, if the residence time T (minutes) of the ultrahigh molecular weight polyethylene in which the foaming agent is dissolved is passed from the tip end portion of the extruder to the die outlet, the viscosity average molecular weight Mv of the ultrahigh molecular weight polyethylene is approximated. In the following formula (3), the coefficient Ε is 0 · 5 to 1 0, preferably 0 · 5 to 8, more preferably 0 · 5 to 5, and, at this time, the resin pressure at the front end portion of the screw is 10 ~1 OOMPa, preferably 10~50MPa, more preferably 15~30MPa, can not damage the ultra-high molecular weight polyethylene 14 3 ΠΧΡ / invention specification (supplement) / 9102/93130535 1292766 ene has the wear resistance, self A physical property such as lubricity, impact resistance, and chemical resistance is obtained, and a foam having a good appearance without streaks is obtained. T = Ex(Mvxl 0'6)2 (3) The residence time T (minutes) of the ultrahigh molecular weight polyethylene in which the foaming agent is dissolved from the front end portion of the extruder screw to the outlet of the die, from the front end of the screw to The volume of the resin flow path until the exit of the die, the amount of extrusion, and the saturation density determined by the PVT (pressure, volume, temperature) relationship of the ultrahigh molecular weight polyethylene resin were calculated. Further, in order to secure the required residence time T (minutes), it is ensured by increasing the volume of the resin flow path in the die or increasing the volume of the resin flow path in the joint between the extruder and the die. . Further, it is also possible to reduce the amount of extrusion, but to increase the throughput, the ultrahigh molecular weight polyethylene foam is obtained to increase the volume of the resin flow path. Further, the pressure at the tip end portion of the screw can be secured by increasing the length and amount of the resin flow path in the joint between the extruder and the die. It is important to maintain a state of specific pressure and specific pressure. Furthermore, the inventors of the present invention found that in order to obtain the expansion ratio and the average bubble diameter for stability, the thickness of the skin layer was obtained at the same time. The ultrahigh molecular weight polyethylene foam of 2 to 3 mm is important in the temperature of the surface of the resin which has just been spit out of the control die, and the center temperature of the resin which the die has just spit out. The surface temperature of the resin which has just been ejected from the die is 60 to 1 40 ° C, preferably 7 0 to 1 4 0 ° C, more preferably 8 0 to 1 40 ° C. If the surface temperature of the resin which has just been discharged from the die is below 140 ° C, the skin layer of the resulting foam is 0.  2 m m or more, good physical properties such as abrasion resistance, self-lubricity, impact resistance, and chemical resistance. The surface temperature of the resin that has just been discharged from the die is 15 312XP/Invention manual (supplement)/94-02/93130535 1292766 When the degree is above 60 °C, the skin layer becomes 3 mm or less, the expansion ratio is not lowered, and the pressure of the die head is not It rises to the function of lightweight, cushioning, and flexibility that are expected to be difficult to form. The surface temperature is an ultrahigh molecular weight value usually between 0 mm and 10 mm in the extrusion molding of non-contact polyethylene. Further, the resin which has just been ejected from the die is preferably 80 to 140 ° C, more preferably 90 0 - the core temperature is 150 ° C or less and the foaming large hole can be obtained with a high expansion ratio. . In addition, when the die is just spit above, the resin of the resin-sensing Is' that has just been discharged from the above-mentioned die is the tip of the die-like polyethylene foam which is super-south. In the center portion, the method of controlling the tree that has been ejected from the die of the present invention in the needle-shaped sensor portion puncture resin, for example, the temperature of the surface of the resin discharged from the extruder cylinder, the joint, and the die is locally cooled by local cooling. When the temperature in the vicinity of the exit of the die is lowered, the molded article can be formed, and the heat-generating property, the sound absorbing property, and the low dielectric constant can be sufficiently exhibited, and the resin emission thermometer that has just been discharged from the die is measured in ultrahigh molecular weight. The central portion temperature of the number of surface temperatures of the polyethylene foam after the die discharge at the extrusion speed is 70 to 150 ° C, which is more than 140 °C. In the middle of the resin that the die has just spit out, sufficient resin viscosity and body can be obtained. Further, the temperature at the center portion of the resin which is hard to be generated inside the foam is excessively increased at 70 °C, so that the molding is easy. The temperature at the center portion is a value measured by the temperature at which the ultra-high score between 0 mm and 10 mm is usually formed by extrusion molding with a pin-type polyethylene, and the temperature is measured several times until the temperature is stabilized. The temperature of the surface of the grease is controlled by the temperature of the center of the resin at the center of the temperature at the center of the temperature, and the die is cooled near the exit of the die. The skin surface of the resin surface which has just been spouted is formed into a skin layer, which can easily maintain wear resistance. 16 3ΠΧΡ/Invention Manual (Supplement)/94-02/93130535 1292766 Consumption, self-lubricating, impact resistance, chemical resistance, etc. Physical properties, improved appearance (glossiness), etc. Further, examples of the cooling method used for controlling the temperature of the present invention include a method of flowing a refrigerant, a method of air cooling, and the like. For example, the refrigerant to be used usually uses water, but a conventionally known refrigerant such as mechanical oil, lycopene oil or ethylene glycol can also be used. Further, in the case of air cooling, normal temperature, cooling air, or the like can be used. In the present invention, pigments, dyes, lubricants, antioxidants, fillers, stabilizers, flame retardants, antistatic agents, UV inhibitors, and crosslinking agents may be added as needed within the scope of the damage problem. , antibacterial agents, crystal nucleating agents, anti-shrinkage agents, foaming nucleating agents, etc. Among them, it is preferred to add a lubricant and a foaming nucleating agent. The effect of adding a lubricant is a pressure rise which suppresses the most problem in molding of ultrahigh molecular weight polyethylene, and it is possible to stably produce a foam having excellent cell uniformity. Further, it is also expected to prevent the deterioration of the resin caused by excessive shear heat in the extruder. The lubricant is added in an amount of 0% by mass of the ultrahigh molecular weight polyethylene.  0 卜 parts by mass, preferably 0 · 0 3 to 3 parts by mass, more preferably 0.  0 5~2 mass parts. When the lubricant is in the above range, it is possible to suppress a large increase in the pressure in the extruder, and to solve the problem of insufficient foaming due to insufficient kneading of the resin and insufficient pressure. The lubricant used in the present invention is a well-known substance to be blended in a resin which is generally recognized. The lubricant may be at least one selected from the group consisting of fatty acid guanamine, mineral oil, metal soap, esters, carbonic acid carbon and phthalic acid ester. Further, it may be used alone or in combination of two or more kinds, particularly a metal salt of a fatty acid, of which the calcium succinate is preferred. Further, the effect of using the foaming nucleating agent is to reduce the bubble diameter and make it uniform. The amount of the foaming nucleating agent added is 0. 0 parts by mass of the ultrahigh molecular weight polyethylene.  00 1 to 3 parts by mass, preferably 0.  001~0.  5 parts by mass, more preferably 0.  0 1~0.  2 parts by mass, especially good for 0.  0 3~0 .  1 part by mass. When the lubricant is in the above range, the foam having a small pore diameter and uniformity can be easily formed. The foaming nucleating agent used in the present invention may, for example, be calcium carbonate, clay, talc, vermiculite, magnesium oxide, zinc oxide, carbon black, cerium oxide, titanium oxide, plastic microspheres, or phthalic acid (〇rth 〇b 〇) A combination of one or more of ricacid, a soil metal salt of citric acid, citric acid, sodium hydrogencarbonate, and the like. Among them, a combination of citric acid and sodium hydrogencarbonate is preferred. Next, an example of molding the ultrahigh molecular weight polyethylene foam of the present invention will be described below with reference to Fig. 1 . An ultrahigh molecular weight polyethylene composition (1) obtained by mixing an ultrahigh molecular weight polyethylene, a specified amount of a lubricant, and a foaming nucleating agent with a drum type doping machine, a Hanschel mixer, or the like, It is put in by the funnel (2), and is heated and kneaded by an extruder (3) to melt it. The carbon dioxide is supplied by a liquefied carbon dioxide cartridge (4), which is injected into the metering pump (6) while maintaining the carbon dioxide in a liquid state, and is pressurized. At this time, it is preferable to cool the flow line connecting the cartridge and the metering pump with the refrigerant circulation device (5). Secondly, it can be mentioned that the discharge pressure of the dosing pump (6) is at the critical pressure of carbon dioxide (7. 4MPa) ~ lOOMPa within a range of a certain pressure, controlled by the pressure-retaining valve (7) and spit out, supplied to the molten ultra-high molecular weight polyethylene 18 312XP / invention manual (supplement) /94-02/93130535 1292766 The method in the ene. In this case, the ultrahigh molecular weight polyethylene oxide supplied to the molten material may be any of a gas state, a liquid state, and a supercritical state, and it is preferable to use a supercritical state from the viewpoint of stable supply. The resin pressure (8) at this time is 3 to 100 MPa, preferably 8 to 80 MPa, more preferably 1 5 to 6 0 Μ P a , and particularly preferably 2 0 to 4 0 Μ P a . When the resin pressure to be supplied is at least the carbon dioxide has a high solubility in the molten ultrahigh molecular weight polyethylene group, a high foam can be obtained. Further, if the supplied resin is less than 100 Å P a or less, it is difficult to cause air leakage by the molding apparatus, so that it is not necessary to have an expensive gas leakage prevention device, and safety, stability, productivity, cost, and the like are required. It is better. If the added carbon dioxide is added in an amount and the ultrahigh molecular weight polyethylene composition is in a completely molten state, the molten resin itself is melted (me 11 sea 1 ), and does not flow back to the funnel side to diffuse and diffuse carbon dioxide. The molecular weight polyethylene composition is sent to a die (9) at a temperature suitable for foaming. Further, the residence time T from the tip end of the screw to the outlet of the die is the following equation (3) The average viscosity M v of the ultrahigh molecular weight polyethylene used and the coefficient E: 0.  The time of 5~1 0 is adjusted. T = Ex(Mvxl 〇-6)2 (3) The lag between the front end of the screw of the ultra high molecular weight polyethylene and the exit of the die, the number of screw rotations, the barrel temperature, and the front end of the screw to the die outlet are the resin flow path volume. Change to the resin flow path in the die or connect the volume of the resin flow path in the joint between the extruder and the die to adjust, if the number of screw rotations is slowed, the volume from the front end of the screw to the die is increased. Large, you can increase the retention time. 312XP / invention manual (supplement) / 94-02/93130535 two kinds, the supply is preferably 3MPa, the product pressure is specially shaped to be suitable for the volume of the solute to be set by the time of the molecule, and the mouth is 19 1292766 The resin pressure (1 Ο ) at the tip end portion of the screw is adjusted to 10 0. The resin pressure at the tip end portion of the screw can be changed by the length of the resin flow path from the extrusion amount and the resin temperature leading end to the die outlet. When reducing the set temperature of the extruder and the length from the front end of the rod to the exit of the die, the resin pressure can increase the residence time of the screw front end to the exit of the die and the pressure before the screw, and consider the various physical stability of the obtained foam. It is preferable to adjust by changing the volume of the resin flow path from the tip end of the screw to the outlet of the die. In addition, the temperature at the center of the resin that has just been ejected from the die is controlled by the extruder (cylinder temperature and die temperature. The die is placed above the lip (1 i Ρ) and the tube flowing through the refrigerant (1 1 ) is placed near the mouth. Local cooling. The skin layer can be formed by passing through the lip of the die (1 1 ). After the spout is discharged, the pressure can be started to foam. At this time, in order to shape the shape of the foam, The mold (12) is preferred. The extruded ultrahigh molecular weight polyethylene foam is stretched at a constant speed through a stretching machine (14), and becomes a product by designation. Regarding the extruder (3), The type of the ultra-high molecular weight polyethylene of the die (9), the use thereof, the combination thereof, and the like may be appropriately selected. [Ultra High Molecular Weight Polyethylene Foam]] Manufactured by the method of the present invention The ultrahigh molecular weight polyethylene is foam-molded into various molded bodies. The applicable molding method can be applied as long as it is a public method, and can be applied without limitation. For example, a foamed sheet 312ΧΡ/invention specification (supplement)/94-02/93130535 1 OOMPa °, the screw is adjusted and the snail is 0 Productivity, diameter length or 3) The downstream side is opened to cool the lip outlet, and the shape is cut by the length of the body (1 3). According to the forming of the forming device, the hair is 20 1292766. Blow molding, foam molding, foam profile extrusion, foam multilayer molding, foam hollow molding, foam tube molding, and the like. The shape of the foamed molded article may be a sheet shape, a strip shape, a tubular shape, a square material shape, a cylindrical shape or the like, and is not particularly limited. Among them, a foamed sheet formed by a foamed sheet; a shape of a stretched shape formed by a foamed profile, a tubular shape, a square shape, or a cylindrical shape is preferred. In particular, the foamed sheet is preferably used, and the width of the foamed sheet is 30 to 10000 mm, preferably 50 to 5,000 mm, more preferably 50 to 3,000 mm, and the thickness of the foam is 0. 5 to 100 mm, preferably 1 to 80 mm, more preferably 5 to 70 mm, particularly preferably 10 to 50 mm, and most preferably 20 to 50 mm. The ultrahigh molecular weight polyethylene foam of the present invention has a density of 0.  0 2~0 .  7 g / cm 3 , preferably 0. 02~0. 5g/cm3, more preferably 0. 02~0. 4g/cm3. The density of the foam is 0.  When it is 0 2 g / c m3 or more, the mechanical properties of impact resistance are good and the density is 0.  When it is 7 g/cm3 or less, the functions such as lightness, heat insulation, sound absorbing property, low dielectric constant, cushioning property, and flexibility which are expected as a foam can be exhibited. Also, the thickness of the cortex is 0. 2mm~3mm, preferably 0. 5 to 2 mm, more preferably 0 · 8 to 1.  5 m m. When it is 0. 2 mm or more, the physical properties such as the abrasion resistance, the self-lubricating property, the impact resistance, and the chemical resistance are good, and when it is 3 mm or less, the lightweight property and the space desired as the foam can be sufficiently exhibited. Thermal, sound absorbing, low dielectric constant, cushioning, softness and other functions. Also, the average bubble diameter is 0.  1~3 0 0 0 // m, preferably 2 0~1 0 0 0 # m, more preferably 5 0~5 0 0 # m. When the average cell diameter is in the above range, the heat insulating property, the sound absorbing property, and the low dielectric constant expected as the foam can be exhibited, and the cushioning property of the invention can be improved. Softness and other functions. Further, the closed cell ratio is from 50 to 100%, preferably from 6 5 to 10.0%, more preferably from 80 to 100%. When the closed cell ratio is in the above range, it is possible to exhibit functions such as heat insulating properties and low dielectric constant expected as a foam. The ultrahigh molecular weight polyethylene foam obtained by the above-described production method of the present invention has a brittle fracture temperature region of _300 to -1 0 0 °C when subjected to a DuPont impact test at a low temperature as a brittle failure index. It is preferably -3 0 0 - 1 3 0 ° C, more preferably -3 0 0 -1 to 5 0 °C. The case where the non-brittle failure temperature region is within the above range means that it can withstand the use in a very strict environment such as liquid natural gas, liquid nitrogen, liquid hydrogen, liquid oxygen, liquid helium or the like. Further, the tensile impact value (JIS-K7160, having a formed slit at both ends) at -40 ° C is such that the tensile impact strength X ( KJ / m 2 ) is the density p (g/cm 3 ) of the foam. In the following equation (1), the coefficient A is preferably 75 to 1 500, more preferably 1 0 0 to 1 0 0 0, and is preferably 2 0 0 to 5 0 0. X = Ax p (1) Again, the Izod impact strength (ASTM-D 2 5 6 with forming scale) at -40 °C is the Izod impact strength Z (J / m) In the following formula (4) in which the density of the body is p (g / c m3), the coefficient C is preferably 50,000 or more, more preferably more than 1,000, and more preferably unbroken. Z = Cx p (4) The impact strength in the above range is a foam composed of a lightweight poly-baked hydrocarbon (density: 0. 02~0. In 7 g/cm3), it has high impact properties which are not found at other extreme temperatures. Further, the tensile strength at -1 50 °C (JIS - K 7 1 1 3 ) is the tensile strength 22 312XP / invention specification (supplement) / 94-02 / 93130535 (2) 1292766 Y (MPa In the case where the density p (g/cm3) of the foam is approached, the coefficient B is preferably 5 0 to 1 0 0 0, more preferably 7 0 to 800, and is 1 optimal. Y = Bx p (2) -1 When the tensile strength at 50 ° C is within the above range, it has rigidity against use as a material for extremely low temperature. Further, -150 ° (: the tensile elongation under (13-1 (7113) is 2 to 30%, 2 to 20%, more preferably 2 to 10%. - 1 50 °C When the tensile elongation is the above, it can be sufficiently used as a material for extremely low temperature. As described above, the characteristics of excellent abrasion resistance, self-lubricating property, chemical resistance, etc. of the ultrahigh molecular weight polyethylene are not impaired, and lightweight And the ultrahigh molecular weight polyethylene foam which is excellent in mechanical properties such as brittleness, Izod impact strength, tensile impact value, stretchability, and tensile elongation, and which is excellent in appearance, can be manufactured according to the above In addition, it is possible to increase the expansion ratio by the increase in the expansion ratio, and to increase the mechanical strength of the tensile strength and the impact characteristics by the reduction ratio [insulation material] The heat insulating material composed of the foam of the present invention , its thermal conductivity (JIS - A1413) is 0 · (Π ~ (K35Kcal / m · hr · 〇 C is better, more than 0. 05 ~ 0. 35Kcal/m· hr· °C, more preferably Ο”~0. 3Kcal/】 °C. When the thermal conductivity is in the above range, the heat insulating property expected as an extremely low thermal material can be exhibited. For example, if the expansion ratio is increased, the thermal conductivity is adjusted, and the desired expansion ratio can be controlled by adjusting the expansion ratio. The heat insulating material composed of the foam of the present invention is suitably used in the 312XP/invention specification (supplement)/94-02/93130535 00~500, and it is sufficiently preferable to be resistant to low temperature impact in the range of the present invention. Take a low foaming value. Good η · hr · Warm partitions can be low pressure Heat transfer For example, 23 232922 Insulation materials used for sending, storing, operating liquefied natural gas or liquid hydrogen, especially for insulation materials at extremely low temperatures. [Construction material of superconducting magnetic resonance imaging apparatus] The superconducting magnetic resonance apparatus used for examinations in hospitals and the like can perform photography of blood vessels, biliary tracts, and pancreatic ducts that are difficult to perform by conventional magnetic resonance imaging apparatuses, and images can be high-definition. Since it is used in many hospitals, it is a material that is light in weight and excellent in various physical properties due to the use of superconducting magnets. The foam of the present invention is excellent in various mechanical properties such as impact strength and rigidity at a very low temperature, and can be suitably used as a constituent material of a superconducting magnetic resonance device used for liquid helium or liquid nitrogen. [Lightweight and High Sliding Material] The material for sliding use is a fluorine-based resin, an engineering plastic, a polyurethane, or an ultra-high molecular weight polyethylene which is excellent in friction coefficient and abrasion resistance. Among them, ultrahigh molecular weight polyethylene is used in many fields because its specific gravity is 1 or less and is lightweight. The lightweight high-sliding material composed of the foam of the present invention does not impair the excellent wear resistance, self-lubricating property, low-temperature property, chemical resistance and the like of the high molecular weight polyethylene, and is an ultrahigh molecular weight. Polyethylene is lighter. By being lightweight, the energy consumption during use can be reduced. In particular, it is extremely effective in reducing the amount of energy consumed by moldings and members such as bushings, chemical chestnuts, gears, bearings, screws, conveyor belts, artificial joints, prosthetic limbs, and prosthetic balls that are rotated and moved back and forth, and can greatly reduce energy consumption. [Buffering High Sliding Material] For applications in sliding materials, there is a need for cushioning properties. For example, a CMP pad used in a polishing step for a semiconductor wafer, and a 312XP/invention specification (supplement)/94-02/93130535 24 1292766 are used as a guide member for a lifting mechanism (guidesh 〇e) )Wait. In such a conventional use, a combination of a conventional sliding material and a cushioning material can achieve a balance of physical properties of slidability and cushioning property, but the cushioning high sliding material composed of the foam of the present invention is via The ultrahigh molecular weight polyethylene excellent in slidability is foamed and has both slidability and cushioning properties, and is suitable for use as a cushioning high sliding material such as a CMP pad, a guide bar sheath, or a guide rail. [Examples] Hereinafter, the present invention will be more specifically described based on examples, but the present invention is not limited to the examples. The physical properties evaluated in the examples and comparative examples were carried out in accordance with the following methods. 1) The viscosity average molecular weight (Mv) is determined according to A S Τ Μ - D 4 0 2 0 . 2) After the surface temperature of the resin that has just been ejected from the die is spit out from the die, the ultra-high molecular weight polyethylene foam between 0 mm and 10 mm is measured by a non-contact radiation thermometer (HT-10D manufactured by Minolta Co., Ltd.). The surface temperature of the body. 3) After the temperature of the center of the resin that has just been ejected from the die is discharged from the die, the thermometer with the needle sensor is used until the temperature is stabilized. The needle-shaped sensor portion punctures the resin center portion several times to measure 0 mm to 1 The central temperature of the ultrahigh molecular weight polyethylene foam between 0 mm. 4) Retention time of resin from the front end of the extruder screw to the exit of the die The residence time of the ultrahigh molecular weight polyethylene composition in which the foaming agent is dissolved from the front end of the screw to the exit of the die is the front end of the self-threaded end Resin flow path volume to the exit of the die, extrusion amount and ultra-high molecular weight polyethylene 25 312XP / invention manual (supplement) / 94-02/93130535 1292766 resin PVT relationship data, from the molten resin in the die The equivalent melt density is calculated. 5) Continuously manufacturing ultra-high molecular weight polyethylene at a density, collecting a total of 10 samples (5 hours in total) every 30 minutes, and measuring the density using an electron densitometer (M irage MD - 2 Ο 0 S), and Find the average value. 6) Thickness of the skin layer An ultrahigh molecular weight polyethylene foam was continuously produced using a die having a rectangular outlet shape of 20 mm in width and 5 mm in thickness, and three samples of 10 cm in length were obtained every 5 minutes. Next, a cross section of the three samples in the direction perpendicular to the extrusion direction of the resin was photographed by a scanning electron microscope, and a total of eight skin thicknesses at the top, bottom, left, and right sides of the cross section were measured for each sample, and the average value was calculated. Next, from the average value obtained from each sample, the average value of the three samples was determined and regarded as the skin thickness. 7) Average bubble diameter Same as above. 6) The thickness of the cortex was treated to obtain three samples. Next, for the three samples, the center of the cross section perpendicular to the extrusion direction of the resin was photographed by a scanning electron microscope, and the photograph was image-processed, and the cell of the square 5 Ο μ m square of the sample section was calculated. Equivalent circle diameter. Next, from the equivalent circle diameter obtained from each sample, the average equivalent circle diameter was obtained for the three samples, and the average of these was regarded as the average bubble diameter. 8) Independent bubble rate according to ASTM-D2856, using gas pycnometer (Air Pycnometer, 26 312XP / invention manual (supplement) / 94-02/93130535 1292766 Tokyo Science (share) air comparison type hydrometer 1 ο 〇〇 type ), the measurement was carried out. 9) Cell uniformity calculation The case where the maximum equivalent circle diameter among the three samples of the average bubble diameter is within the range of twice the average bubble diameter is evaluated as 〇, and the maximum equivalent circle diameter is twice as large as the average bubble diameter. It is evaluated as Δ in the range of 4 times, and the range of the maximum equivalent circle diameter exceeding 4 times the average bubble diameter is evaluated as X ° 10) Extrusion stability is obtained by sampling every 30 minutes obtained in the above 5) The case where the difference between the density of the total of 10 samples and the average value of the density of the above 5) is 10% or less is regarded as 〇, and the case where it exceeds 10% and within 30% is regarded as Δ, and when it exceeds 30%, it is regarded as X 〇11) DuPont impact strength testing machine uses DuPont impact testing machine (Toyo Seiki mechanism). A chiseled (20 mm wide) core was used, and a 2 kg drop hammer was dropped from a height of 250 mm to visually observe the state of the test piece. For the test piece, a test piece in which the foam was cut into 50 m m X 10 m m was used. The test piece was immersed in liquid nitrogen for 5 hours, taken out, and subjected to the above drop impact test. At this time, the test was carried out within 3 seconds of taking out the liquid. 12) Izod impact strength According to ASTM-D2 56, the Izod impact strength measurement (with a shaped cut) was carried out at -40 °C. The hammer capacity is 3 · 9 2 J and the air swing angle is 1 4 9 .  The condition of 1 degree was measured. The test piece is used for a width of 10 .  1 6 m m, the angle of the cut 45°, the front end of the cut r0. 25mm. 27 312XP/Invention Manual (Repair)/94-02/93130535 1292766 1 3 ) Tensile impact value Determination of tensile impact value according to JIS-K 7 1 60, at -40 °C environment (two The end has a shaped slit). With a hammer capacity of 7.  5 J, the angle of the air swing is 1 4 9 .  The condition of 2 degrees was measured. The test piece is wide for use 6 .  0 in m, the angle of the cut 45°, the front end of the cut rl. Omm. 14) Tensile strength and tensile elongation According to J I S - K 7 1 1 3, tensile strength and tensile elongation at -150 °C were carried out. An A S Τ Μ No. 1 test piece was processed from the foam by a test piece processing machine. The measurement was carried out after maintaining the test temperature for 60 minutes. The distance between the grippers was 110 mm and was measured at a tensile speed of 5 m m / min. The elongation is measured by the cross head movement method. 15) The thermal conductivity of the foam is measured in accordance with J I S - A 1 4 1 3 . [Example 1] The extruder was a single screw extruder (3) (L/D = 32) having a screw diameter of 50 mm as shown in Fig. 1. The die is formed into a rectangular shape having a width of 20 mm and a thickness of 5 mm, and the length from the front end of the screw to the exit of the die is 330 mm (the volume from the front end of the screw to the exit of the die is 78.  4cm3). In this die, a tube through which water (1 1 ) is used as a refrigerant is placed above and below the lip to locally cool the vicinity of the lip outlet. Ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 1,000,000 (HI-ZEX milion 150M manufactured by Mitsui Chemicals Co., Ltd.) 100 parts by mass, calcium stearate (manufactured by Sigma Chemical Industry Co., Ltd.).  1 part by mass, calcium hydrogencarbonate/citric acid (CF manufactured by Boehringer Ingelheim). 05 parts by mass was dry blended to prepare an ultrahigh molecular weight polyethylene composition (1). 28 312XP/Invention Manual (Supplement)/94-02/93130535 1292766 The ultrahigh molecular weight polyethylene composition (1) is fed into the extruder (3) from the funnel (2). At this time, the extruder (3) is a pressing amount of 3 k g / h r in a state where the temperature is set to 180 ° C and the number of screw rotations is 10 μm. At this time, the residence time from the front end of the screw to the die is 1.  3 minutes. Carbon dioxide is a siphonic liquefied carbon dioxide cartridge (4) that is taken directly from the liquid phase. The flow path from the cartridge (4) to the metering pump (6) is cooled by using a refrigerant circulation machine (5) to adjust the ethylene glycol aqueous solution adjusted to _1 2 °C, and the carbon dioxide is supplied to the liquid state in a liquid state. Pump (6). Control the dosing pump (6) and adjust the pressure maintaining valve (7) so that the discharge pressure is 3 Ο Μ P a. The carbon dioxide was supplied from a pressure maintaining valve (7) to an extruder (3) heated to 180 °C. The amount of carbon dioxide supplied at this time was 1 part by mass based on 100 parts by mass of the thermoplastic resin composition, and the supply portion pressure was 20 MPa. By this treatment, carbon dioxide is 2.0 with respect to 100 parts by mass of the molten ultrahigh molecular weight polyethylene composition.  The proportion of 0 parts by mass is supplied to the extruder (3), and it is uniformly dissolved and diffused. The ultrahigh molecular weight polyethylene composition in which carbon dioxide was dissolved by the extruder (3) was sent to a die (9) set at 130 °C. Since the surface is cooled locally near the lip outlet just before being ejected from the die, the surface temperature is lower than the central temperature. At this time, a skin layer of the foam is formed. After being spit out from the die, the pressure is opened to initiate foaming. The surface temperature at which the die was discharged and the temperature at the center were measured. The surface temperature at which the die was discharged was 1 2 0 °C, and the temperature at the center of the die was 13 3 °C. After the completion of the foaming, the shape of the foam was adjusted by the trimming mold (12), and the film was drawn at a constant speed through a stretching machine (14) to cut the sample. The evaluation results of the foam are shown in Table 1. 29 312XP/Invention Manual (Supplement)/94-02/9313053 5 1292766 [Example 2] In addition to carbonization of carbon dioxide with respect to 100 parts by mass of the ultrahigh molecular weight polyethylene composition.  The same experiment as in Example 1 was carried out except that the ratio of 5 parts by mass was supplied to the extruder (3), and the surface temperature of the die was 1 25 ° C, and the temperature at the center portion where the die was discharged was ° C. . The evaluation of the foam is shown in Table 1. [Example 3] In addition to carbonization of 3 parts by mass relative to the ultrahigh molecular weight polyethylene composition.  The same experiment as in Example 1 was carried out except that the ratio of 6 parts by mass was supplied to the extruder (3), and the surface temperature of the die was set to 1 2 3 ° C, and the temperature at the center portion where the die was discharged was ° C. . The evaluation of the foam is shown in Table 1. [Example 4] In addition to carbonization of 3 with respect to 100 parts by mass of the ultrahigh molecular weight polyethylene composition.  The same experiment as in Example 1 was carried out except that the ratio of 5 parts by mass was supplied to the extruder (3), and the surface temperature of the die was set to 120 ° C, and the temperature at the center portion where the die was discharged was ° C. . The evaluation of the foam is shown in Table 1. [Example 5] In addition to 100 parts by mass of ultrahigh molecular weight polyethylene (manufactured by Mitsui Chemicals Co., Ltd. HI-ZEX Meliol 150M) having a viscosity average molecular weight of 1,000,000, hard calcium (manufactured by Seiko Chemical Industry Co., Ltd.).  2 parts by mass, sodium hydrogencarbonate / citric acid (made by Boehringer Ingelheim CF).  05 parts by mass are dry-mixed to prepare ultra-high molecular weight polyethylene composition (1), and compared with ultra-high 312XP/invention specification (supplement)/94-02/93130535 dioxane vomiting 130 results dioxin just vomiting 125 results Dioxane vomiting 125 results bismuth citrate molecular 30 1292766 quantity of polyethylene composition 1 Ο 0 parts by mass of carbon dioxide to 6 .  The ratio of 0 parts by mass is supplied to the extruder (3), and the surface temperature at which the die has just been discharged is 1 2 0 ° C, and the temperature at the center portion where the die has just been discharged is 1 2 3 ° C. 1 the same experiment. The evaluation results of the foam are shown in Table 1. [Example 6] A carbon dioxide was set to 0 with respect to 100 parts by mass of the ultrahigh molecular weight polyethylene composition.  The ratio of 8 parts by mass is supplied to the extruder (3), and the surface temperature at which the die has just been discharged is 135 ° C, and the temperature at the center portion where the die is discharged is 138 ° C. 5 the same experiment. The evaluation results of the foam are shown in Tables 1 and 3. [Example 7] The same experiment as in Example 1 was carried out except that calcium stearate was not added. The evaluation results of the foam are shown in Tables 1 and 3. [Example 8] The same experiment as in Example 1 was carried out except that sodium bicarbonate/citric acid was not added. The evaluation results of the foam are shown in Table 1. [Example 9] The length of the die was 530 mm from the front end of the screw to the exit of the die (the volume from the front end of the screw to the exit of the die was 143. 2cm3), using ultra-high molecular weight polyethylene with a viscosity average molecular weight of 2 million (HI-ZEX Mirion 2 4 0 ME made by Mitsui Chemicals Co., Ltd.), and 100 mass relative to the ultrahigh molecular weight polyethylene composition The carbon dioxide will be 1 part.  The ratio of 8 parts by mass was supplied to the extruder (3), and the surface temperature at which the die was immediately discharged was 139 ° C, and the temperature at the center portion where the die was discharged was 1 4 2 ° C, and Example 1 was carried out. 31 312XP/Invention Manual (supplement)/94-02/93130535 1292766 The same experiment. At this time, the residence time from the front end of the screw to the exit of the die is 2.  3 minutes. The evaluation results of the foam are shown in Table 1. [Example 1 0] The length of the die was 530 mm from the front end of the screw to the exit of the die (the volume from the front end of the screw to the exit of the die was 143. 2cm3), using ultra-high molecular weight polyethylene with a viscosity average molecular weight of 2.3 million (HI-ZEX Mirion 2400 M manufactured by Mitsui Chemicals Co., Ltd.), and 100 mass relative to the ultrahigh molecular weight polyethylene composition The carbon dioxide will be 10%.  The ratio of 0 parts by mass is supplied to the extruder (3) so that the surface temperature at which the die has just been discharged is 1 2 0 ° C, the temperature at the center portion where the die has just been discharged is 1 2 1 ° C, and the number of screw rotations is 6 The same experiment as in Example 1 was carried out except for rpm. At this time, the residence time from the front end of the screw to the exit of the die is 3.  6 minutes. The evaluation results of the foam are shown in Table 1. [Comparative Example 1] Carbon dioxide was 1 in terms of 100 parts by mass of the ultrahigh molecular weight polyethylene composition except that no water was passed near the lip outlet.  The ratio of 0 parts by mass is supplied to the extruder (3), and the surface temperature at which the die has just been discharged is 170 ° C, and the temperature at the center portion where the die has just been discharged is 170 ° C. 1 the same experiment. The evaluation results of the foam are shown in Table 2. [Comparative Example 2] In addition to carbon dioxide of 1 with respect to 100 parts by mass of the ultrahigh molecular weight polyethylene composition.  The ratio of 0 parts by mass is supplied to the extruder (3), and the surface temperature at which the die has just been discharged is 1 2 0 ° C, and the temperature at the center portion where the die has just been discharged is 15 5 ° C. 1 the same experiment. The evaluation results of the foam 32 312XP/invention manual (supplement)/94-02/93130535 1292766 are shown in Table 2. [Comparative Example 3] Except that water was not flowed near the lip outlet, carbon dioxide was 0. 0 parts by mass relative to the ultrahigh molecular weight polyethylene composition.  The ratio of 0 5 parts by mass is supplied to the extruder (3), and the surface temperature at which the die has just been discharged is 170 ° C, and the temperature at the center portion where the die has just been discharged is 170 ° C. Example 1 The same experiment. The evaluation results of the foam are shown in Table 2. [Comparative Example 4] In addition to carbon dioxide of 1 with respect to 100 parts by mass of the ultrahigh molecular weight polyethylene composition.  The ratio of 8 parts by mass was supplied to the extruder (3), and the surface temperature immediately after the die was discharged was 5 5 ° C, and the temperature at the center portion where the die was discharged was 1 38 ° C, and Example 1 was carried out. The same experiment. The evaluation results of the foam are shown in Table 2. [Comparative Example 5] A carbon dioxide was set to 1 with respect to 100 parts by mass of the ultrahigh molecular weight polyethylene composition.  The ratio of 8 parts by mass was supplied to the extruder (3), and the same as in the first embodiment except that the surface temperature at which the die was discharged was 5 8 ° C and the temperature at the center portion where the die was discharged was 68 ° C. Experiment. As a result, since the temperature of the resin is lowered, the pressure is rapidly increased during the process of lowering the set temperature of the extruder and the die, and the ultrahigh molecular weight polyethylene composition cannot be discharged from the die and cannot be extruded. Shown in Table 2. [Comparative Example 6] The same experiment as in Example 1 was carried out except that the number of rotation of the screw was 3 0 r pm. The transit time at this time is 0.  4 minutes. The evaluation results of the foam are shown in Table 3 and Table 3 of 33 312 XP/Invention Manual (supplement)/94-02/93130535 1292766. [Comparative Example 7] The length of the die from the front end of the screw to the exit of the die was 330 mm (the volume from the front end of the screw to the exit of the die was 78.  The same experiment as in Example 9 was carried out, except for 4 cm 3 ). At this time, the residence time from the front end of the screw to the exit of the die is 1.  3 minutes. The evaluation results of the foam are shown in Tables 2 and 3. [Comparative Example 8] Except for the ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 2.3 million (HI-ZEX milion 2400 M manufactured by Mitsui Chemicals Co., Ltd.), compared with the ultrahigh molecular weight polyethylene composition 1 0 0 The mass fraction is supplied to the extruder (3) in a proportion of 10 parts by mass, and the surface temperature at which the die is discharged is 1 2 0 ° C, and the temperature at the center portion where the die is discharged is 1 5 2 The same experiment as in Example 1 was carried out except for °C. At this time, the residence time from the front end of the screw to the exit of the die is 1.  3 minutes. The evaluation results of the foam are shown in Table 2. [Comparative Example 9] The length of the die was 330 mm from the end of the screw to the exit of the die (the volume from the front end of the screw to the exit of the die was 78.  The same experiment as in Example 9 was carried out except that the number of screw rotations was 10 μm. At this time, the residence time from the front end of the screw to the die is 1.  3 minutes. The evaluation results of the foam are shown in Table 2 and Table 3. [Comparative Example 1 0] A high-density polyethylene having a viscosity average molecular weight of 200,000 was used, and an extruder and a T-die were used to obtain a density of 0. 31g/cm3 and with cortical thickness 34 312XP / invention manual (supplement) /94-02/93130535 1292766 Ο .  High density polyethylene foam of 3 m m. The evaluation results of the foam are shown in the table.

312XP/Invention Manual (Supplement)/94-02/93130535 35 1292766 [Table 1] Example 1 2 3 4 5 6 7 8 9 10 Viscosity average molecular weight (xlO4) 100 100 100 100 100 100 100 100 200 230 Hard fat Calcium acid addition amount (parts by mass) 0· 1 0· 1 0. 1 0. 1 0.2 0· 2 0 0· 1 0. 1 0.1 Sodium hydrogencarbonate / citric acid addition amount (parts by mass) 0. 05 0.05 0. 05 0. 05 0.05 0.05 0.05 0 0.05 0. 05 Length from the front end of the screw to the exit of the die (mm) 330 330 330 330 330 330 330 330 330 530 530 Addition amount of carbonized gas (parts by mass) 2.0 2.5 3.6 3.5 6.0 0.8 2.0 2.0 1.8 10. 0 Resin surface temperature just after the die is ejected (°c) 120 125 123 120 120 135 120 120 139 120 Temperature at the center of the resin that the die has just spewed out (°c) 133 130 125 125 123 138 133 133 142 121 Residence time from the front end of the screw to the exit of the die (min.) 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 2.3 3.6 Resin pressure at the front end of the screw (MPa) 29 21 23 25 25 24 30 29 27 31 Density (g/cm3) 0.24 0.15 0.06 0.09 0.07 0.33 0.24 0.27 0.33 0. 06 Cortical thickness (mm) 1. 0 0. 7 0.3 0.9 0.7 0.3 1.0 1.0 0.3 0.6 No traces, no traces, no or no average bubble diameter (//m) 200 250 300 270 280 170 200 550 190 200 Free bubble rate (%) 85 75 68 78 71 74 82 70 81 69 Cell uniformity 〇〇〇〇〇〇Δ Δ 〇Δ Extrusion stability 〇〇〇〇〇〇Δ 〇〇Δ 312XP/Invention manual (supplement)/94-02/93130535 1292766 [Table 2]

Comparative Example 1 2 3 4 5 6 7 8 9 Viscosity average molecular weight (χΙΟ4) 100 100 100 100 100 100 200 230 230 About the amount of stearic acid added (parts by mass) 0.1 0· 1 0.1 0. 1 0.1 0.1 0.1 0.1 0· 1 sodium bicarbonate / citric acid addition (mass parts) 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 Length of screw front end to die exit (mm) 330 330 330 330 330 330 330 330 330 Dioxide barrier addition amount (quality 1.0 1.0 0.05 1.8 1.8 2.0 1.8 10.0 10.0 Surface temperature of resin just ejected from the die (°C) 170 120 170 55 58 120 139 120 120 Temperature at the center of the resin that the die has just spewed out (°C) 170 155 170 138 68 133 142 152 121 Retention time from the front end of the screw to the exit of the die (min.) 1.3 1.3 1.3 1.3 *l 0.4 1.3 1.3 1. 3 Resin pressure at the front end of the screw (MPa) 10 20 18 30 30 26 20 32 Density (g /cm3) 0.85 0.90 0.88 0.75 0.29 0.37 *3 0.08 Cortical thickness (mm) 0.1 0.8 3.2 4.5 *2 *2 *2 No traces, no traces, no average pore diameter (//m) 120 110 120 130 700 800 200 independent bubble rate (%) 41 94 95 93 31 27 12 Square square square hole uniformity square extrusion stability X X X square square square square X X X extrusion pressure increases and can not be. There is no skin layer on the trace. *3: The gas is intermittently blown out and cannot be squeezed. 312XP/Invention Manual (Supplement)/94-02/93130535 1292766 [Table 3] Example Comparative Example 6 7 6 7 9 10 Raw material ultrahigh molecular weight polyethylene high density polyethylene viscosity average molecular weight (χΙΟ4) 100 200 100 200 230 20 Column impact strength (-196° 〇 undestroyed and not destroyed ※4 嵚4 Destruction density (g/cm3) 0. 33 0. 24 0.29 0. 37 0. 08 0. 31 Cortical thickness (mm) 0· 3 1.0 *2 *2 嵚2 0. 3 Izod impact strength (-40°C) (J/m) 231 Not damaged 21 22 5 29 Tensile impact value (-40°C) (kJ/m2) 29. 1 96. 9 8.8 9. 2 4. 1 14. 3 Tensile strength (-150 ° C) (MPa) 25. 2 33. 1 2.2 3. 2 0.8 16. 8 Tensile elongation (-150 ° 〇 (° /〇) 3. 3 3. 9 1.1 1. 1 1.0 1.4 Thermal conductivity of foam (Kcal/m · hr · °C ) 0. 15 0. 15 0. 13 0. 17 0. 04 0. 17 ※ There is no skin layer on the traces. ※ The buckle is partially damaged by the traces. 312XP/Invention Manual (Supplement)/94-02/93130535 1292766 [Industrial Applicability] The foaming system obtained by the present invention is suitable for use in construction. , medical, food, energy, sports, leisure and other fields. High-molecular-weight polyethylene and foam functional heat-insulating materials, precision abrasive materials, lightweight high-sliding materials, cushioning high-sliding materials, high-strength cushioning materials, artificial bone materials, etc. Among them, extremely low-temperature materials can be used. A constituent material such as a heat insulating material used for transportation, storage, and operation of liquid natural gas or liquid hydrogen; a constituent material such as a linear motor vehicle (1 inearm 〇t 〇rcar); and a body fluid such as blood components, bone marrow fluid, and sperm a constituent material such as a cryopreservation container such as a cell or a superconducting magnetic resonance device; a constituent material such as a heat insulating material used for a rocket or a space transportation system; a constituent material such as an ultra-high-density memory, etc. List of bushing materials, guide bushings, elevator jackets, augers, guides, roller guides, bolting rods, aspirator, lids, nozzles, gears, stopcocks, scalpels, buckets for excavators Inner panel, snow shovels components, pistons, gaskets, gaskets, stern tubes, rollers, snowmobile components (bottom, etc.), walker components, skis Inner plate, knee pad, battery spacer, prosthetic material, prosthetic material, artificial bone material, artificial joint, medical machine component, low pressure safety tire, neutron shielding material, C Μ P pad, glass transfer buffer material, liquid crystal glass transfer A cushioning material, a tire member, an insulating plate, a sound absorbing member, a lightweight pile rock cutting material, an engraving material, and the like are used. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic structural view showing an example of a method for producing an ultrahigh molecular weight polyethylene foam. 39 312 ΧΡ / invention manual (supplement) / 94-02 / 93130535 1292766 Figure 2 is a photograph of the test piece of Example 6 after the DuPont impact strength test. Fig. 3 is a comparative example of the DuPont impact strength test. Photograph of the test piece of the 10 0 [Explanation of main component symbols] 1 Ultrahigh molecular weight polyethylene composition 2 Funnel 3 Extruder 4 Liquefied carbon dioxide cartridge

5 Refrigerant circulation device, 6 Dosing pump 7 Pressure-retaining valve 8 Resin pressure gauge (carbon dioxide supply unit) 9 Die 10 Resin pressure gauge (screw front end) 1 1 Refrigerant

13 Ultra high molecular weight polyethylene foam 14 Stretching machine 40 312XP / invention manual (supplement) /94-02/93130535

Claims (1)

Announcement 1292766 X. Patent application scope: 1. Ultra-high molecular weight polyethylene foam, which is a foam obtained by foaming ultra-high molecular weight polyethylene with a viscosity average molecular weight of 300,000 to 1,000,000. The dance is characterized in that the density of the foam is 0 · 0 2~0 · 7 g / c m3, and the tensile impact value X (KJ / m2) at a temperature of -40 ° C is used for the foaming The density of the body p (g/cm3) is approximated in the following formula (1), the coefficient A is 75~1500 X = Ax p (1 ) ° 2 . The ultra-high molecular weight polyethylene foam as claimed in claim 1 a body in which the tensile strength Y ( Μ P a ) at a temperature of -150 ° C is approximated by the density P (g/cm 3 ) of the foam in the following formula (2), the coefficient B is 50~1000 Y = Bx p (2) 〇3 . — A method for producing ultra-high molecular weight polyethylene foam, which is an ultra-high molecular weight polyethylene foam with a viscosity average molecular weight of 300,000 to 1,000,000. The method for producing a foam having a foam density of 0. 02~0. 7g/cm3 is characterized in that the ultrahigh molecular weight polyethylene which dissolves the foaming agent is from the front end of the extruder screw to Die exit The retention time T (minutes) is approximated by the viscosity average molecular weight M v of the ultrahigh molecular weight polyethylene in the following formula (3), the coefficient Ε is 0.5 to 1 0, and the resin pressure at the front end portion of the screw is 10 〜1 0 0 Μ P a = = Ex(Mvxl Ο·6) 2 (3) 〇4. A method for producing an ultrahigh molecular weight polyethylene foam according to claim 3, which is contained in an extruder a step of melting the ultrahigh molecular weight polyethylene; a step of adding a foaming agent to the ultrahigh molecular weight polyethylene; and a surface temperature of the resin which has just been discharged from the die is 60 to 140 ° C, and the die is immediately discharged The step of extruding the foam 41 312XP/invention specification (supplement)/94-02/93130535 1292766 is carried out in the center of the resin at a temperature of 70 to 150 °C. 5) The method for producing an ultrahigh molecular weight polyethylene foam according to claim 3 or 4, wherein, as the foaming agent, the ultrahigh molecular weight polyethylene is added in an amount of 0. 1 to 2 0 per 100 parts by mass. Parts by mass of carbon dioxide. 6. A heat insulating material characterized by being an ultrahigh molecular weight polyethylene foam of claim 1 or 2, and having a thermal conductivity of 0.01 to 0.35 Kcal/m·hr·°C 〇7. An insulating material for liquefied natural gas, characterized in that it is an ultrahigh molecular weight polyethylene foam of claim 1 or 2, and has a thermal conductivity of 0.01 to 0.35 Kcal/m·hr·°C 〇8. The invention relates to an insulating material for liquid hydrogen, which is characterized in that it is an ultrahigh molecular weight polyethylene foam of claim 1 or 2, and has a thermal conductivity of 0.01 to 0.35 Kcal/m·hr·°C 〇9 . A constituent material of a superconducting magnetic resonance device or the like, which is characterized in that it is an ultrahigh molecular weight polyethylene foam of claim 1 or 2. A lightweight high sliding material characterized by being an ultrahigh molecular weight polyethylene foam of claim 1 or 2. A cushioning high sliding material characterized by being an ultrahigh molecular weight polyethylene foam of the first or second aspect of the patent application. 42 312XP/Invention Manual (supplement)/94-02/93130535