JPH0691685A - Production of ultrahigh molecular weight polyethylene molded product - Google Patents

Abstract

PURPOSE:To mass-produce a two-shot molded product by mutually bonding, gathering and integrating raw material powder particles composed of an ultrahigh mol.wt. polyethylene resin by the deformation of powder particles and the melting only of the surfaces of the powder particles without providing interposition layers. CONSTITUTION:A gate 2 is connected to the part constituting the gear shaft of a mold 1 and the raw material powder from a sprue 3 is injected into a mold 1 through the gate 2. When the radius of the gate 2 is set to (r) and the length of a strand is set to l1, 0.2mm<=r<=1.0mm and 0.1mm<=l1<=1.5mm are set. By this constitution, the raw material powder can be developed as quasi- powder flow and powder particles can abe bonded and integrated by the deformation of the powder particles due to pressure and the melting only of the surfaces of the powder particles and, therefore, a large number of molded products can be obtained without changing quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a plastic molded article, and more particularly to a method for producing an ultrahigh molecular weight polyethylene molded article.

[0002]

2. Description of the Related Art Ultra-high molecular weight polyethylene resin has excellent properties such as chemical resistance, abrasion resistance, and abrasion resistance.
It is thought that it is suitable as a plastic gear material and sliding member, and it is actually used, and its effects are low friction and wear resistance, low noise, biosafety, food processing machinery, chemical It is used for special purposes such as engineering equipment.

However, the ultrahigh molecular weight polyethylene resin has a great problem in its processability. That is, because the ultrahigh molecular weight polyethylene resin has a high melt viscosity,
Processing is difficult with ordinary extrusion and injection molding techniques.

The extrusion molding method is essentially a method for producing a plate or sheet,
Further, it is a processing method for providing a member such as a round bar, and it cannot form a complicated shape like the injection molding method. Further, in order to mold the ultra-high molecular weight polyethylene with the same quality maintenance and production efficiency as other general-purpose resins, it becomes necessary to add several kinds of lubricants. Such a lubricant does not guarantee that the material properties of the ultra-high molecular weight polyethylene are retained, and also causes a high material cost.

As a method for forming a product having a more complicated shape (for example, a gear), there is a profile extrusion technique to which an extrusion molding technique is applied. The die is processed into a gear shape and the extruded rod-shaped gear is used. It may be possible to make a gear by slicing in post-processing, but there is a problem of dimensional change due to internal strain that occurs in the extruded rod-shaped gear and deformation during slicing, and it is also three-dimensional in shape. In reality, it cannot be said that this is an effective processing method, such as complicated molding cannot be performed.

Therefore, today, in general, the processing of ultra-high molecular weight polyethylene resin employs a method of forming a block by extrusion molding or compression molding and manufacturing a product by cutting. Therefore, for example, when this is applied to a small precision gear, it is expected that a gear with excellent durability and low noise can be manufactured.

[0007] However, it is difficult to supply a homogeneous product at a low cost and in a large amount, because the cutting must be done one by one in the processing. That is,
The compression molding method is certainly a processing method that can exhibit all the material properties of ultra-high molecular weight polyethylene, but from the viewpoint of productivity, one molding cycle usually takes about 2 hours, and moreover, It has been extremely difficult to inexpensively mass-produce a molded product having such a complicated shape without a post-process such as deburring.

Therefore, in order to improve the processability of the ultrahigh molecular weight polyethylene resin, many new injection molding methods have been proposed as molding techniques (for example, Japanese Examined Patent Publication No. 57-300).
67, JP-B-60-58010, JP-A-6
0-9723, U.S. Pat. No. 3,036,340.
No. 4,271,851).

Japanese Examined Patent Publication No. 57-30067 (Japanese Unexamined Patent Publication No.
1-81861), the mold is opened up to a cavity of 1.5 to 3.0 times the capacity of the injection resin, injected at a shear rate of 50000 l / sec or more, and then the cavity volume is 2.0 times or less. There has been proposed a method of injection compression in which a molded article is obtained by compressing into.

Japanese Examined Patent Publication No. 60-58010 (Japanese Patent Laid-Open No. Sho 5
7-169335), according to the description,
It is said that, in the case of executing the contents of Japanese Patent Laid-Open No. 7-30067, in the case of a multi-cavity mold, there are variations in the weight (unit weight) or the shape between the molded products, and a method for improving it is proposed. That is, the mold cavity volume is opened 1.2 times or more immediately before filling with respect to the required mold cavity volume, and the cavity is compressed to its original volume again while the filled resin is in a molten state. Injection compression molding methods have been proposed.

In Japanese Patent Laid-Open No. Sho 60-9723, an inert gas is injected from a hopper of an injection molding machine to prevent molecular deterioration due to oxidation of a resin at the time of plasticization, and to reduce the pressure inside a mold cavity to form a composite structure. There has been proposed a method of molding the above-described ultra high molecular weight polyethylene resin gear.

US Pat. No. 4,271,851 (197)
7 years), an injection compression molding method has been proposed in which, during the injection molding of ultra-high molecular weight polyethylene, the air in the cavity of the mold is removed in advance, and after the filling, the cavity is compressed so as to compensate the molding shrinkage. .

US Pat. No. 3,036,340 (196)
2 years), a polyethylene resin having a molecular weight of 600,000 or more was first made into a preform, put in a ram extruder and heated to 285 ° C.
A molding method has been proposed in which a mold heated to 0 ° C. is injected, and after holding pressure, the mold is cooled and a molded product is taken out at room temperature.

Furthermore, attempts have been made in the past to accurately manufacture a molded product with a general resin by utilizing injection compression molding, in which a resin filled in a mold is compressed.

As an example, in Japanese Patent Publication No. 40-1664, the cavity of the split mold is slightly opened during the period of injecting the molten resin into the cavity of the closed split mold, and after injection of the molten resin is completed. , A method of pressing the split mold to reduce the cavity of the mold has been proposed.

In Japanese Patent Laid-Open No. 52-14657, a material is injected with a slight gap previously formed between molds, and the gap is held until the injection is completed. Methods have been proposed for compression molding materials.

Japanese Patent Laid-Open No. 53-21258 presupposes a thick-walled molded product, but a molten thermoplastic resin having a preset cavity volume is injected at a high speed to fill the cavity, and subsequently the high-speed injected melt is injected. A method has been proposed in which 0.5 to 3 times the amount of cooling shrinkage of the resin is additionally injected at a low speed to perform mold opening, and the mold is closed as the molten resin cools and solidifies in the mold.

[0018]

However, the conventionally proposed injection molding method for ultrahigh molecular weight polyethylene has the following problems.

That is, Japanese Patent Publication No. 57-30067, Japanese Patent Publication No. 60-58010, and US Pat.
Although the molding method based on injection compression devised in No. 71,851 etc. is certainly effective for a single-die mold,
In the case of taking a large number of molded products, a lot of ingenuity such as installing a hydraulic device separately in the mold is required, which is not always a rational method. In addition, there is a problem that burrs are always generated in the molded product and post-processing is required. Especially when these inventions are used for molding gears,
The compression part of the injection compression mold also needs to be processed into a gear shape, which makes it very difficult to fit the cavity (female mold).
It is almost impossible to take many pieces.

Moreover, since burrs are generated on the tooth surface, post-processing for removing burrs is required, and it is considered that removal is almost impossible with a small gear. The occurrence of burrs is also described in Japanese Patent Publication No. 60-58010, and it can be considered as an essential problem of the compression molding method.

Furthermore, so far, no significant technical problem of how to plasticize the ultra high molecular weight polyethylene resin has been touched upon, and therefore the above-mentioned invention is a general method of conventional injection compression. Can be said to be just one of the.

The method proposed in US Pat. No. 3,036,340 is basically ram extrusion molding, and the ultrahigh molecular weight is caused by the shearing stress of the screw and oxygen which are generated in the case of injection molding of the in-line screw system. Although it is a method that avoids the drawback that polyethylene main chain is easily cleaved to lower the molecular weight and becomes ordinary polyethylene, the molding cycle is far inferior to that of an inline screw injection molding machine, and an efficient molding method is I can not say. Further, since the mold is also kept at a high temperature, it can be said that the method is close to the conventional compression molding. According to the description in this patent, the holding pressure is applied for 16 minutes after the filling, and the mold is cooled for 8 minutes. Although it is certainly shorter than the compression molding cycle, it is longer than normal injection molding and cannot be said to be an efficient molding method.

As described above, with respect to the method for molding ultrahigh molecular weight polyethylene, in the conventional technique, the structure of the mold is complicated, and it is extremely difficult to take many pieces.
There is a problem that it takes longer than a normal molding cycle and productivity is low. In addition, a method of adding various additives to ultra-high molecular weight polyethylene has also been proposed, and certainly,
Although these methods are sufficiently recognized as having an effect of improving moldability, in many cases, the physical properties of ultrahigh molecular weight polyethylene are often sacrificed.

For example, when a lubricant component is added or a low molecular weight olefin resin is added, in the sand slurry test, it is 20% or more as compared with the ultra high molecular weight polyethylene without addition. It can be confirmed that the wear resistance also deteriorates. This means that the abrasion resistance, which is one of the characteristics of ultra high molecular weight polyethylene, is lost. The same applies to impact resistance tests such as Izod and Charpy.

Further, regarding addition of an inorganic substance, even if it has an effect of improving moldability, it is often questionable whether the added inorganic substance is effective with respect to the required characteristics of the molded product. That is, the low frictional force, which is another characteristic of ultra-high molecular weight polyethylene, is lost. Further, depending on the mating material, the mating material may be worn away.

Therefore, the object of the present invention is to make the molding cycle at the same level as in the case of ordinary resin without losing the characteristics of ultra-high molecular weight polyethylene by the addition of optional additives, and also the mechanism of the mold is special. It is to realize a molding method capable of producing a large number of pieces, which is inexpensive and has high mass productivity, without adopting such a material.

[0027]

Means for Solving the Problems As a result of intensive research aimed at achieving the above object, the present inventors have found that an ultrahigh molecular weight polyethylene resin is injected in a plasticized and fluidized state while maintaining the state of powder particles. By molding, the raw material particles are deformed and melted only on the surface so that they are joined and integrated,
The inventors have found that a molded product having excellent characteristics can be obtained by individual picking, and moreover, by multiple picking, and have completed the present invention.

That is, in the method for producing an ultrahigh molecular weight polyethylene molded article of the present invention, raw material powder particles made of an ultrahigh molecular weight polyethylene resin are not deformed by interposing an intervening layer on each other and are only deformed and on the surface. It is characterized in that a single-piece or multi-piece product is formed by joining by melting and integrating them.

The ultrahigh molecular weight polyethylene resin used in the present invention is polyethylene having a molecular weight of about 1,000,000 or more,
Specifically, it means a polyethylene resin having a molecular weight that has an intrinsic viscosity [η] measured in a decalin solvent of 135 ° C. of 6.5 dl / g or more.

In the present invention, the number of multi-cavities is
It is preferably within the range of 2 to 16. When performing a large number of pieces as described above, while maintaining the powder shape of the ultra-high molecular weight polyethylene raw material, individual particles of the powder are heated and the deformation of the particles is recognized, but due to shear stress, After plasticizing with a screw so that the particles do not break, the mold is filled and compressed at a specific injection pressure, while preferably the mold is provided with an air vent to release a large amount of air generated during compression As a result, a molded product with high accuracy can be obtained.

That is, a normal shear rate (10 ² to 10)
⁽³ 1 / sec) to a high shear region (10 ⁵ to 10 ⁶ 1 / sec) are uniformly injected into the mold in a fluidized state of the particles, and the particles are aggregated and integrated by filling and compression. Is preferably injection-molded using an in-line screw injection molding machine under the conditions of a mold internal pressure of 400 to 3000 kg / cm ² and a screw compression ratio of 1.3 to 2.0.

The injection molding is preferably carried out under a temperature condition that is a temperature above which a fluid state is maintained and below which a decrease in the molecular weight of the raw material powder due to oxidation does not occur.

In the present invention, it is not necessary to add any additive (for example, lubricant or binder) in order to impart moldability and fluidity to the ultrahigh molecular weight polyethylene resin.

[0034]

In the present invention, the ultra high molecular weight polyethylene resin is supplied as a raw material in the powder state having an average particle size of about 2 to 400 microns, and it does not go through the molten state (while maintaining the discontinuous particle form). The final molded product is shaped by filling and compressing.
In the capillary rheometer, when setting the olefins of a certain diameter or more, the heated ultra high molecular weight polyethylene resin can pass through the olefins while maintaining the powder state of the raw material, and those powder particles are deformed. Is in a state where it does not break (however, fusion of powder is caused by pressurization), and the outflow rate, that is, the relationship between shear rate and pressure, should be treated as if it were a non-Newtonian fluid that ordinary polyethylene melted shows. It is based on the discovery that

That is, the individual particles forming the ultra high molecular weight polyethylene powder show the same flow behavior as that of the resin which is melted and becomes a continuous body, and in the same process as that of a normal resin. I discovered that molding was possible. This flow behavior is different from the flushing flow generated in the high shear rate region which is said to be exhibited by the molten resin. The flushing flow is a flow of a situation in which the resin which is melted and becomes a continuous body is finely torn and scattered. Ultra-high molecular weight polyethylene is not a flushing flow because the flow behavior is essentially particulate. Also, there is no point in discussing the presence or absence of melt fracture. Therefore, it is different from the flow described in Japanese Patent Publication No. 57-30067 and Japanese Patent Publication No. 60-58010.

Hereinafter, the flow of the ultra-high molecular weight polyethylene resin, as opposed to the usual continuous flow of molten resin, will be referred to as "quasi-powder flow" in order to clearly distinguish the characteristics. An example comparing this quasi-powder flow with a normal flow is shown in FIG.
Shown in. That is, as shown in FIG. 1, the normal flow is H
As shown in DPE (high-density polyethylene), the melt viscosity is low with respect to the shear rate, indicating that it flows easily. In contrast, the "quasi-powder flow" of UHMW-PE (ultra high molecular weight polyethylene) has a high apparent melt viscosity, suggesting that high pressure is required for injection molding.
The important point to note here is that "quasi-powder flow" is uniformly developed from normal shear rate (10 ² to 10 ³ 1 / sec) to high shear region (10 ⁵ to 10 ⁶ 1 / sec). Is to do.

In the present invention, this "quasi-powder flow" is effectively utilized. Next, the present invention will be described based on a specific example in the case of obtaining a gear as a molded product. First, preferable conditions for expressing the “quasi-powder flow” will be described.

As a result of the experiment using the above-mentioned capillary rheometer, it was clarified that the diameter d of the above-mentioned orifice is defined as follows. d ≧ 0.4 mm (1) The definition of d means to determine the minimum diameter of the gate connecting the sprue of the injection molding machine and the mold when designing the mold.

It has also been clarified that the length l of the olefin is defined by the ratio with d as follows. That is, 20 ≧ 1 / d> 0 (2). The gate diameter of the mold and the nozzle portion of the injection molding machine can be defined by the above (1) and (2). For example, when the nozzle diameter of the injection molding machine is 3 mm, the length of the nozzle hole must be 60 mm or less. The relationship with the shape of the gate of the mold is sufficient if its cross-sectional area corresponds to the area calculated in (1).
A more preferable condition for the gate is that 3 mm ≧ l (3) is satisfied.

Regarding the type of gate, the above (1)
Any type of gate may be used as long as it satisfies the conditions (2) and (3). For example, pinpoint gate,
A side gate, a submarine gate, a film gate, etc. are mentioned. The preferred range of the plasticizing condition temperature T of the ultrahigh molecular weight polyethylene resin used in the present invention is as follows. 180 ° C. ≦ T ≦ 280 ° C. (4) More preferable conditions are 210 ° C. ≦ T ≦ 240 ° C. (5). The reason for this is that when T> 280 ° C., deterioration of the molecular weight due to oxidation of the ultrahigh molecular weight polyethylene resin is initiated, and even if molding is possible, the molecular weight of the molded product itself decreases, and It will be no different from ordinary polyethylene molded products.
This is because when T <180 ° C., the quasi-powder flow does not appear (poor fusion between powders).

The above are the preferred conditions for developing the quasi-powder flow. Next, preferable conditions for realizing the “quasi-powder flow” found by the present inventor with an in-line screw type injection molding machine will be specifically described. First, as a condition for plasticizing the ultra high molecular weight polyethylene resin as a powder by the screw of the injection molding machine, the individual particles forming the resin powder rub against each other to generate heat and plasticize. It is preferable to determine the dimensions of the screw so as to reach the reaction conditions. Specifically, the ratio of the length of the screw and its diameter, the angle of flight, the compression ratio of the screw, and the screw feeder zone, its compression zone,
It is determined by the ratio of the metering zone.

First, it is necessary to satisfy the following conditions. When the total length L of the screw and the screw diameter (diameter) are D, 10 ≦ L / D ≦ 25 (6), and more preferably 15 ≦ L / D ≦ 20 (7). The reason for this is that in the case of 10> L / D, even if the screw pitch is made fine, it is not possible to achieve the plasticization required to develop the fusion property between the powders, and 25 <L In the case of / D, even if the screw pitch is large, the residence time in the screw cylinder is long, and the main chain of the ultrahigh molecular weight polyethylene is easily broken by the shearing force, and the molecular weight is reduced to the target. This is because it becomes difficult to obtain a quasi-powder flow.

Regarding the angle of flight of the screw (the inclination of the screw thread) θ, when the screw pitch is P, it is determined by P = πDtan θ (8), but if expressed by the value of θ, 10 ° ≦ θ ≦ 18 ° (9), more preferably 11.5 ° ≦ θ ≦ 14.5 ° (10). The reason for this is that when 10 °> θ, sufficient extrusion torque can be given to the ultrahigh molecular weight polyethylene resin, but unnecessary residence time and friction energy are given to the resin, resulting in a decrease in molecular weight. Cause.
Further, when 18 ° <θ, it is not preferable because sufficient torque cannot be applied to the resin, and the required screw rotation speed also applies too much load to the hydraulic motor or the electric motor. Even if a powerful motor is installed, the screw will be loaded and will be damaged.

The screw compression ratio (compression ratio; CR) is 2.3 ≧ CR (11), and more preferably 1.3 ≦ CR ≦ 2.0 (12). The reason is that in the case of 2.3 <CR, an ideal balance between the amount of the resin fed from the screw feeding zone (feeder zone) and the amount of the resin in the plasticizing zone (metering zone) is obtained. This is because the collapse occurs and more resin than necessary is supplied to the metering zone, and the powder particles are subjected to unnecessary pressure and shear, which makes it difficult to obtain a quasi-powder flow. In the worst case, high compression of the resin starts in the metalling zone, the fluidity is not exhibited at all, and resin retention occurs. In the case of 1.3> CR, the resin is sheared, and it becomes impossible to sufficiently generate shear heat generation between the resins.

Finally, regarding the ratio of the screw feeder zone (FZ), compression zone (CZ), and metering zone (MZ), it is necessary to satisfy the following conditions. That is, when FZ: CZ: MZ = X: Y: 1 (13), the values of X and Y are 2 ≦ X ≦ 6, 1 ≦ Y ≦ 5, X ≧ Y (14), and Preferably, X = Y = 3 (15) is satisfied.

The meanings of the conditions (13) and (14) mean that a stable supply of the ultra-high molecular weight polyethylene resin in the feeder zone is achieved and a basis for achieving the stabilization of the resin amount for each shot is established, and the compression zone This is because gradual plasticization is performed, and in the metalling zone, the minimum required amount of rapid heating and heat generation of the resin is achieved. In the combination of values other than this, academic theoretical proof is still unknown, but it can be confirmed by various experiments that it is not industrially possible. It is difficult to create a “flow”. Also,
In determining the length of the metering zone, it is preferable to provide at least two screw pitches. The reason for this is that sufficient plasticization cannot be achieved if the metering zone has only one pitch.

Regarding the shape of the tip of the screw, it is basically not provided with a backflow prevention ring (check ring), but the method already proposed by the present inventor in JP-A-62-83122 is adopted. You can That is, the screw head and the cylinder nozzle can be partially fitted to each other to prevent the resin from flowing back in the pressure holding step.

Next, the temperature conditions during injection molding will be described. The temperature conditions of the resin itself that causes the "quasi-powder flow" are as described in (4) and (5), but the temperature settings of the inline screw type cylinders that satisfy these conditions are set individually. The screw feeder zone (FZ) and compression zone (C
Z) and the metering zone (MZ) are as follows.

40 ° C. ≦ FZ ≦ 100 ° C. (16) 140 ° C. ≦ CZ ≦ 200 ° C. (17) 210 ° C. ≦ MZ ≦ 280 ° C. (18) More preferably, 60 ° C. ≦ FZ ≦ 80 ° C. (19) ) 160 ° C. ≦ CZ ≦ 180 ° C. (20) 210 ° C. ≦ MZ ≦ 240 ° C. (21)

The temperature of the nozzle portion may be set equal to MZ, but depending on the temperature and shape of the mold, MZ may be set.
It may be set higher by 10 to 20 ° C. Further, the characteristic feature of the present invention is that the upper limit of the temperature setting of (16) must not be exceeded with respect to the temperature setting of the feeder zone (FZ). Therefore, the above temperature setting is an initial temperature setting condition, and in order not to exceed this upper limit, a cooling fin is provided in the feeder zone, a fan for forced cooling, or a cylinder cooling that allows cooling water to flow. It is desirable to provide a device. When the temperature exceeds the upper limit, the ultra high molecular weight polyethylene resin stays in the feeder zone and stable measurement becomes difficult.

Regarding the above temperature setting, "quasi-powder flow"
Although the theoretical explanation for expressing the above has not been sufficiently done, industrially, a stable "quasi-powder flow" can be obtained under the above conditions.

Next to the resin temperature, the mold temperature is important. The mold temperature is appropriately determined according to the size of the mold, the capacity of the cavities, the number of cavities, the length of the runner, and the like. Here, the mold temperature refers to the temperature of the surface of the cavity filled with the molded product and its vicinity. With this mold temperature CT, the preferred temperature condition is 30 ° C. ≦ CT ≦ 130 ° C. (22), and more preferably 60 ° C. ≦ CT ≦ 120 ° C. (23). When 30 ° C.> CT, slips often occur between the surface of the mold and the transferability to the surface of the molded product, which is not preferable because the surface of the molded product is unclean. Further, when 130 ° C. <CT, since the softening point of the molded product is exceeded, the mold cannot be released from the mold well, and deformation due to the ejector pin is likely to occur, which causes poor precision of the molded product, which is not preferable.

For the temperature of the runner, see (2)
It is preferable to satisfy the conditions 2) and (23). Runner methods are roughly classified into cold runners and hot runners. In the case of the present invention, it is preferable to adopt a cold runner. In the case of a hot runner, resin retention often occurs, which causes defective molding. The above is the pre-stage of the molding method within the scope of the present invention,
It is, so to speak, a static condition.

The dynamic conditions of the method of the present invention will be described below. The dynamic conditions here refer to the screw rotation speed, the injection speed and injection pressure provided by the screw, the pressure holding time, and the like. First, regarding the screw rotation speed (SR), depending on the size of the molding machine used,
"Semi-powder flow" although the diameter of the screw is different and the range of the optimum screw speed is also different depending on it.
In the range of the screw diameter from φ15 mm to φ70 mm, the preferable condition for expressing the expression is 30 rpm ≦ SR ≦ 500 rpm (24), and more preferably 70 rpm ≦ SR ≦ 400 rpm (25).

At 30 rpm> SR, it is not possible to give the resin sufficient shearing heat to develop a “quasi-powder flow”, and at 500 rpm <SR, excessive shearing force causes breakage of the main chain, It is not preferable because the molecular weight is lowered.

Regarding the injection speed, Japanese Patent Publication No. 57-300
No. 67, there is a description of filling at a high shear rate, but it does not disclose the conditions for developing the "quasi-powder flow" in the present invention. The range of the injection speed may be changed depending on the size of the molded product, the number of moldings, and the size of the molding machine (screw diameter). In the present invention, the injection rate θ is preferably in the following range. 10 cc / sec <θ <500 cc / sec (26) More preferably, 15 cc / sec <θ <200 cc / sec (27). When 10 cc / sec> θ, compression of the resin in the nozzle portion and the runner system is promoted, resulting in incomplete injection of the resin into the cavity. On the other hand, 500 cc / se
When c <θ, the escape of air in the resin becomes incomplete, and defects such as whitening of the molded product are likely to occur. In the present invention, in order to control the "quasi-powder flow" and to fill the resin in the mold, pay attention to the injection speed and the injection pressure of the molding machine described below. They are finding that they can get the goods.

The injection pressure may vary depending on the product size and the runner size when the "quasi-powder flow" is exhibited, but the actual in-mold pressure of 400 kg / cm ² or more is sufficient. In this case, depending on the shape of the molded product, the molding shrinkage rate often differs depending on the part, and the mold needs to be modified. For example, regarding the molding of gears, the in-mold pressure is preferably 2000 kg / cm ² or more. Here, the in-die pressure means the pressure inside the die, specifically, the pressure at the time of filling in the runner portion or cavity of the die, which is the pressure converted from the hydraulic gauge of the molding machine. is not.

Assuming that the pressure in the mold is P, "quasi-powder flow"
In the general case where "re" occurs, a preferable value is 200 kg / cm.^Two≤P≤3000 kg / cm^Two (28) but in the case of gear molding, 300 kg / cm^Two≤P≤2500 kg / cm^Two (29) is preferable. 300 kg / cm^Two> In case of P
Is difficult to maintain the individual dimensional accuracy required for gears
The gears with a precision of 6 or higher according to the JIGMA standard are
It will be difficult to shape. Also, 2500 kg / cm^Two
<P improves the dimensional accuracy of the molded product,
The mold cavity itself also deforms, making it difficult to release the molded product.
And the durability of the mold cannot be maintained, and the injection molding
Durability against machine screw and cylinder pressure and
It is not preferable because safety cannot be ensured.

The method of controlling the in-mold pressure by the injection molding machine is as follows: in the hydraulically driven type and the electrically driven type, and in the injection molding machine in which these are combined, the set pressure value is reached by the closed loop and open loop control methods. It is possible only by controlling the time. That is, it can be said that molding can be performed by all conventional injection molding machine methods.

However, if a more preferable method is proposed, a resin pressure sensor is provided on the runner or cavity of the mold, and the pressure is fed back to the molding machine to reach the set in-mold pressure in a set time. It is better to adopt such a control method. The reason for this is that the molding quality (dimensions, etc.) greatly changes depending on the pressure value in molding by "quasi-powder flow".

The pressure holding time can usually be determined by using the gate sealing time as a guide. It can also be estimated by a simple thermodynamic calculation. The present invention is also the same. However, it is characteristic that the gate seal time is 2 seconds or less in the case of the "quasi-powder flow" of the ultra high molecular weight polyethylene resin. Therefore, it is not necessary to apply the holding pressure for 2 seconds or more even if the standard does not stand.

Next, the mold used for obtaining the molded product of the present invention will be described by taking a gear mold as a specific example. There are two technical points of the mold for obtaining the gear according to the present invention, one related to the gate shape and one related to the air vent. A cavity having a gear shape may be manufactured by a normal machining method, that is, a wire electric discharge machine or an electric discharge machine using an electrode.

Regarding the gate shape, for example, a pinpoint gate or a film gate is suitable. When the pinpoint gate is adopted, the gear itself has a shaft in the center, and when the film gate is adopted, there is a shaft hole in the center of the gear.

The reason for this is that the "quasi-powder flow" of ultra-high molecular weight polyethylene has a large molding shrinkage ratio in the direction perpendicular to the flow direction, so that a molded product having an axially symmetrical shape such as a gear has the same molding shrinkage. This is because it is necessary to make the resin flow uniform in order to obtain the rate. Normally, when molding a gear with a shaft, rather than providing a gate on the shaft, we try to improve the molding accuracy by providing multiple pinpoint gates around the shaft, but in the case of ultra high molecular weight polyethylene resin, In this case, distortion of the addendum circle corresponding to the arrangement of the pinpoint gates occurs, and it is not possible to form a highly accurate gear. Therefore, it becomes necessary to provide a pinpoint gate at the tip of the gear shaft.

The same applies to the case of a gear having a hollow shaft hole. Normally, a multipoint pinpoint gate is provided around the shaft hole. Generally, two points, three points, four points, six points, etc. are provided to improve the circumferential accuracy of the tip circle, but in the case of ultra-high molecular weight polyethylene resin, the pinpoint gate Distortion of the tooth tip circumference corresponding to the arrangement occurs. For this reason, it is necessary to uniformly provide a circular film gate around the shaft hole. The gate cutting method in the case of using a film gate can cut the gate in the mold by moving the pin of the mold corresponding to the shaft hole.

Next, a specific form of the gate used in the gear mold will be described. The basics of gate design are
It is necessary to satisfy the above conditions (1), (2), and (3).

FIG. 2 is a partial cross-sectional view of the pinpoint gate, in which the gate 2 is connected to the part constituting the gear shaft of the mold 1, and the raw material powder from the sprue 3 is passed through the gate 2 into the mold 1. Is injected into. Such a pinpoint gate is suitable for forming a gear having a shaft at the center. For example, when the gate radius is r and the strand length is l ₁ , 0.2 mm ≦ r ≦ 1. It is preferable to set 0 mm (30). However, the upper limit of r does not exceed the radius of the gear. For the strand l ₁ , 0.1 mm ≦ l ₁ ≦ 1.5 mm (31) is preferable.

FIG. 3 is a sectional view of the film gate,
This gate is suitable for molding a gear having a shaft hole in the center. In this case, when the thickness of the gate is t, the width of the gate is w (this corresponds to the circumference of the shaft hole), and the length of the strand is l ₂ , 0.1 mm ≦ t ≦ 1.0 mm ... (32) However, the upper limit of t does not exceed the thickness of the gear. As for the gate width w, of course, if the radius of the gear shaft hole is R, then w = 2πR (33). The strand l ₂ is 0.2 mm ≦ l ₂ ≦ 1.5 mm (34).

However, the upper limit of l ₂ does not exceed the diameter 2R of the shaft hole. The position of the film gate with respect to the wall surface of the shaft hole may be any position along the axial direction. Preferably, it is provided around the opening of the shaft hole. This is because it is easy to cut the gate. At the time of gate cutting, it is preferable to cut by moving the pin in the mold before filling is completed and the mold is opened.

Next, an air vent for letting air out of the mold during injection molding will be described. The air vent mechanism in the mold comprises an air vent and an air vent groove. Regarding the position and shape of the air vent according to the present invention, first, the position is on either the fixed plate side or the movable plate side of the mold, and is defined based on the diameter of the cutting edge circle of the gear cavity. If the diameter of the cutting edge circle is D _g , D _g
Set so that the circle that is 15% more than the circle created by is the outermost circumference of the air vent. That is, assuming that the diameter of the outermost circumference of the air vent is D _v , the relation is 1.1D _g ≦ D _v ≦ 1.15D _g (35).

There are two types of air vent shapes. There are a donut shape (double circle) and a round shape (single circle). The donut shape and the round shape mean the shapes shown in FIGS. 4 and 5, respectively. For example, in the donut-shaped example shown in FIG. 4, a donut-shaped air vent 4 is formed on the surface of the mold on the gate 2 side, while an air vent groove 5 is provided in the female mold of the mold. . Therefore,
Similarly to the case where the raw material powder is injected through the gate 2, the air in the cavity is removed by the air vent 4 and the air vent groove 5.
Effectively escape through the mold. FIG. 5 shows an example in which the plane shape of the air vent is circular. Which type is selected depends on the value of D _g . A _{0.7D g ≦ D vi ≦ 0.9D g} ... (36).

When 9 mm ≦ D _g ≦ 25 mm, either a donut shape or a round shape can be arbitrarily selected depending on the size and mechanism of the mold. When the donut shape is selected, the conditions (35) and (36) are applied. D _g <9m
In the case of m, basically a round shape is selected. If possible as a processing technique, a donut shape may be selected. When the donut shape is selected, the conditions (35) and (36) are applied. In the case of a round shape, its center and the center of the gear cavity coincide when viewed from the parting surface. Equation (35) is applied to the outer diameter.

The air vent depth t _v basically does not depend on D _vi . A preferable standard of the depth is 0.01 mm ≦ t _v ≦ 0.1 mm (37). (37) The reason for a guideline is, t _v of the material of the mold used, the size of the gear to be processed, by the clamping force at the time of molding, the mold is because the degree of elastic deformation varies.

Next, the air vent groove will be described. The position of the air vent groove must be connected to the outer circumference of the air vent on the same surface of the mold. The width and depth of the air vent groove may satisfy at least the following values, where H _v1 is the width and F _v is the depth, regardless of the type of the air vent described above.

That is, 2.5 mm ≦ H _v1 (38) 1.5 mm ≦ F _v (39)

Furthermore, the air vent groove must be open to the atmosphere outside the mold. The reason for this is that at the time of injection molding, it is necessary to discharge the air accumulated in the cavity to the outside of the cavity as the resin is filled. Through many experiments and calculations, it was discovered that the velocity of the melt front of the filled resin exceeds the speed of sound, and in a sealed space, the air in the cavity is not released to the atmosphere within the filling time of the resin. Because.

It is sufficient to prepare such a mold for injection molding of the ultrahigh molecular weight polyethylene resin, but in order to deal with it more effectively, the cavity space of the mold is depressurized when the mold is closed. The depressurizing method can be performed by a device such as a vacuum pump or an aspirator to which Bernoulli's principle is applied.

As described above, it is possible to plasticize an ultrahigh molecular weight polyethylene resin which has been impossible to be injection molded,
Moreover, in contrast to the conventional injection molding method that has produced special molds and improved shapeability, the present invention enables injection molding of ultra-high molecular weight polyethylene resin simply by providing an air vent, and general-purpose engineering It has become possible to take multiple pieces in a molding cycle equivalent to that of plastic.
In particular, it has become possible to provide a gear that enables the molding of a plastic gear that requires high precision and that exhibits the low frictional force, non-lubricity, low wear, and sound deadening that an ultrahigh molecular weight polyethylene resin has.

According to the present invention described above, an ultrahigh molecular weight polyethylene resin, which has been difficult to plasticize in the past, can be prepared by simply changing the shape of the screw of the injection molding machine and the shape of the gate of the mold. If the "quasi-powder flow" is achieved, it has the advantage of being able to perform multi-cavity molding in the same way as ordinary resins. The cause of this "quasi-powder flow" is still unknown,
This phenomenon is industrially stable and has reproducibility, and its effect can be easily confirmed only by observing the surface of the molded product. That is, it suffices to confirm that the molded product is molded while maintaining the powder shape of the ultrahigh molecular weight polyethylene resin. In addition, it has become possible to take a large number of pieces, which was difficult in the past.

In the above description, the case where a gear is mainly obtained as a molded product has been described, but the present invention can be applied not only to a gear made of ultra-high molecular weight polyethylene resin, but also if the basic technique according to the present invention is applied. This is a versatile molding technology that can be applied to all molded products in the shape of.

The applicable fields and examples of molded articles are as follows. Applicable fields include precision equipment field, OA equipment field, home electric appliances field, automobile field, vending machine field, logistics equipment field, medical field and the like.

In the field of precision instruments, there are parts for VTRs, radio cassette recorders, DATs, CD players, camera parts, sewing machine parts and the like. Specifically, it is a tape reel, a roller, a pulley, an idler gear, a play gear, a general-purpose gear, a worm gear, a cam, or the like.

In the field of OA equipment, there are personal computers, word processors, printer parts, copying machines, facsimile parts, minilab system automatic processors, and the like. Specifically, it is a key slider, a key guide plate, a bearing, a gear, a roller, a slide pad, a shoe, an actuator, a bobbin, or the like.

The field of home electric appliances includes air conditioner parts, electric washing machine parts, electric refrigerator parts, and the like. In particular,
Gears, damper cams, micro switches, bearings, tension pulleys, rollers, etc.

In the field of automobiles, there are suspension parts, interior parts and the like. Specifically, it is a silencer (leaf spring), a suspension bush, a pillow ball receiver, a chain tensioner, a door handle part, a seat lever part, a seat slide part, a seat belt part and the like.

In the field of vending machines, drive parts include gears, rollers, bearings, chutes, and the like. In the field of physical distribution equipment, there are elevators, escalators parts, conveyors, conveyor equipment parts and the like. Specifically, it is a guide shoe, a handrail guide, a bearing, a roller, a bucket, or the like.

In the medical field, sliding parts (sockets, cups) of artificial joints, that is, specifically, artificial ankle joints, artificial knee joints, artificial hip joints, artificial finger joints, artificial elbow joints, artificial joints, As sliding parts for artificial temporomandibular joints,
It is an artificial disc or the like. Other fields include pumps, water supply components such as pump blades, gears and blades for water meters.

As described above, it is a component that makes use of the characteristics of ultrahigh molecular weight polyethylene resin such as low frictional force, self-lubricating property, low noise property, and biosafety, and is stable and stable for the first time by injection molding. It is also a part that needs to be processed in large quantities at low cost. Further, it is clear that the above application examples are representative examples and not all.

[0089]

EXAMPLES Example 1 Module 0.8 (PCD = 25.6 mm, number of teeth 32,
In order to injection mold a gear with a thickness of 3 mm and a shaft hole diameter of 3 mm,
Molding was performed as follows.

The ultrahigh molecular weight polyethylene resin used was HiZex Million 240M manufactured by Mitsui Petrochemical Co., Ltd., and when the molecular weight was confirmed by a viscosity method, [η] was 17.
It was 5 dl / g. It was confirmed that the resin raw material used was indeed ultra-high molecular weight polyethylene, since it had a molecular weight equivalent of 2.7 million or more as specified by ASTM.

Next, the screw and cylinder of the injection molding machine were changed from a diameter of 25 mm to a diameter of 18 mm, and the injection molding machine was modified so that the pressure inside the mold could reach a maximum of 4000 kg / cm ² . When the screw dimensions are expressed using the above-mentioned symbols as they are, the ratio of FZ, CZ, and MZ is FZ: CZ: MZ = 3: 3: 1. CR was set to 1.8. Flight angle θ is 1
It was set to 3.4 degrees.

As for the mold, a cavity of a prospective gear was manufactured with an overall molding shrinkage of 2%. Two pieces were taken.
The gate was provided with a film gate around the shaft hole. The dimensions of this film gate were thickness t = 0.4 mm and strand l ₂ = 0.3 mm. The gate is designed so that it can be cut by moving the core pin forward in the mold. The air vent has a donut shape. (3 of the text
According to 5), (36), and (37), the outer diameter of the air vent is 29 mm, the inner diameter is 22 mm, and the depth is 0.07.
mm. The air vent groove was processed so as to be connected to the outer circumference of the air vent, and the width was 3 mm and the depth was 2 mm. The air vent and the air vent groove were provided in each of two cavities.

Next, the dynamic conditions for developing the "quasi-powder flow" were set. First, the temperature conditions of the cylinder of the injection molding machine are as follows: FZ 70 ° C., CZ 170 ° C., MZ 2
It was set to 20 ° C. The mold temperature was set to 65 ° C. The screw rotation speed was set to 200 rpm. The mold pressure is
2000kg with a pressure sensor installed on the runner of the mold
It was controlled so that it could be filled with / cm ² .

As a result of operating the injection molding machine as described above and molding an ultra-high molecular weight polyethylene gear, it was possible to perform stable molding in a molding cycle of 30 seconds. As a result of confirming the accuracy of the molded gear, a gear corresponding to Class 5 according to the JIGMA standard was obtained. Moreover, as a result of measuring the molecular weight of the molded product by the viscosity method, it was confirmed that the molecular weight was maintained at 2.7 million. As a result of measuring the specific gravity of the molded product,
0.94, there is no void inside the molded product,
The effect of air vent was recognized.

Further, when the filling state of the resin was confirmed by a microscope, as shown in the photograph (FIG. 6), the powder shape of the raw material was used as the minimum unit to be deformed into an arbitrary shape and assembled to form a gear. It was recognized that That is, it was confirmed that the "quasi-powder flow" of the present invention was developed.

Example 2 In order to injection-mold a gear of module 0.2 (PCD = 4.6 mm, number of teeth 23, thickness 0.7 mm, diameter 0.9 mm), molding was carried out as follows. . Resin used,
The molding machine is the same as that of the first embodiment. The molding conditions were the same as in Example 1 except that the injection pressure was set to 1500 kg / cm ² as the mold pressure.

The manufactured mold had two gear cavities, the gate was provided at the tip of the shaft of the molded product, and the gate diameter was 0.
It was 6 mm. The strand was 0.3 mm. The air vent has a round shape. The outer diameter was 5.5 mm.
The depth was 0.03 mm. The width of the air vent groove is 2.
The depth was 5 mm and the depth was 1.5 mm.

In the injection molding, a stable molding could be continuously performed in a molding cycle of 24 seconds. When the specific gravity of the molded product was measured, it was 0.94, which was within the specific gravity of the ultrahigh molecular weight polyethylene resin, and no void could be confirmed even by microscopic observation.

Using the same molecular weight measurement method as in Example 1, the molecular weight of the molded product was measured and found to be 2.6 million.
It was confirmed that the molded product was also ultra-high molecular weight polyethylene. It was also confirmed by microscopic observation of the molded product that the same "quasi-powder flow" as in Example 1 was developed.

Example 3 The sliding member (sliding part diameter: 9 mm, shaft part diameter: 4 mm) of the scanner was injection-molded as follows. The resin used and the molding machine are the same as in Example 1. In addition, the molding condition is 12
The same procedure was performed as in Example 1 except that the setting was set to 00 kg / cm ² .

The manufactured mold had 16 cavities, the gate was provided at the tip of the shaft of the molded product, and the gate diameter was 0.
It was 8 mm. The strand was 1 mm. The air vent has a round shape. The outer diameter was 40 mm. The depth was 0.03 mm. Air vent groove is 2.5m wide
m and the depth was 1.5 mm.

In injection molding, stable molding could be performed continuously in a molding cycle of 24 seconds. When the specific gravity of the molded product was measured, it was 0.94, which was within the specific gravity of the ultrahigh molecular weight polyethylene resin, and no void could be confirmed even by microscopic observation.

Using the same molecular weight measuring method as in Example 1, the molecular weight of the molded product was measured to be 2.6 million.
It was confirmed that the molded product was also ultra-high molecular weight polyethylene. It was also confirmed by microscopic observation of the molded product that the same "quasi-powder flow" as in Example 1 was developed.

[0104]

As described above, in the method for producing an ultrahigh molecular weight polyethylene molded article of the present invention, raw material powder particles made of an ultrahigh molecular weight polyethylene resin are powdered without interposing an intervening layer therebetween. By joining the particles by deformation of the body particles and melting only on the surface, and integrating them together, the molding cycle is the same as in the case of general-purpose resin without adding the optional additives and losing the characteristics of ultra high molecular weight polyethylene. It is possible to carry out multi-cavity production at a low level, with a low product unit price and high mass productivity, without using a special die mechanism.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between shear rate and viscosity.

FIG. 2 is a sectional view showing a form of a gate that can be used in an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing another form of the gate that can be used in the embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating the form of an air vent.

FIG. 5 is a cross-sectional view illustrating another form of the air vent.

FIG. 6 is a micrograph showing a particle structure of a cross section of an ultrahigh molecular weight polyethylene molded article according to the present invention.

[Explanation of symbols]

 1 Mold 2 Gate 3 Sprue 4 Air vent 5 Air vent groove

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] November 2, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 3

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art Ultra-high molecular weight polyethylene resin has excellent properties such as chemical resistance, abrasion resistance and low frictional force.
Believed to be suitable as a plastic gear member and sliding member, actually used have also been, low friction and low wear resistance as its effect, low noise, biosafety is observed, food processing machinery, chemical It is used for special purposes such as engineering equipment.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

Japanese Examined Patent Publication No. 57-30067 (Japanese Unexamined Patent Publication No.
1-81861), a cavity is opened in a mold up to 1.5 to 3.0 times the injection resin capacity, injection is performed at a shear rate of 50000 sec ⁻¹ or more, and then the cavity volume is 2.0 times or less. There has been proposed a method of injection compression in which a molded article is obtained by compressing into.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

That is, a normal shear rate (10 ² to 1)
0 ³ sec ⁻¹ ) to high shear region (10 ⁵ to 10 ^6).
sec- ¹ ) is uniformly injected into the molding die in a fluidized state, and is filled and compressed to be aggregated and integrated. For this purpose, an in-line screw injection molding machine is used to mold the raw material powder into the die. Internal pressure 400-3000kg
It is preferable to carry out injection molding under the conditions of / cm ² and a screw compression ratio of 1.3 to 2.0.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction content]

Hereinafter, the flow of the ultra-high molecular weight polyethylene resin, as opposed to the usual continuous flow of molten resin, will be referred to as "quasi-powder flow" in order to clearly distinguish the characteristics. An example comparing this quasi-powder flow with a normal flow is shown in FIG.
Shown in. That is, as shown in FIG. 1, the normal flow is H
As shown in DPE (high-density polyethylene), the melt viscosity is low with respect to the shear rate, indicating that it flows easily. In contrast, the "quasi-powder flow" of UHMW-PE (ultra high molecular weight polyethylene) has a high apparent melt viscosity, suggesting that high pressure is required for injection molding.
The important point to note here is that the “quasi-powder flow” is uniformly expressed from a normal shear rate (10 ² to 10 ³ sec ⁻¹ ) to a high shear region (10 ⁵ to 10 ⁶ sec ⁻¹ ). Is to do.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

As a result of the above-mentioned experiment using the capillary rheometer, it has been clarified that the diameter d of the orifice is defined as follows. d ≧ 0.4 mm (1) The definition of d means to determine the minimum diameter of the gate connecting the sprue of the injection molding machine and the mold when designing the mold.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0047

[Correction method] Change

[Correction content]

Regarding the shape of the tip of the screw, it is basically not provided with a backflow prevention ring (check ring), but the method already proposed in JP-A-62-83122 can be adopted. That is, the screw head and the cylinder nozzle can be partially fitted to each other to prevent the resin from flowing back in the pressure holding step.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0056

[Correction method] Change

[Correction content]

Regarding the injection speed, Japanese Patent Publication No. 57-300
No. 67, there is a description of filling at a high shear rate, but it does not disclose the conditions for developing the "quasi-powder flow" in the present invention. The range of the injection speed may be changed depending on the size of the molded product, the number of moldings, and the size of the molding machine (screw diameter). In the present invention, the injection rate Q
The following range is preferable. 10 cc / sec < Q <500 cc / sec (26) More preferably, 15 cc / sec < Q <200 cc / sec (27). When 10 cc / sec> Q , the compression of the resin in the nozzle portion and the runner system is promoted, so that the injection of the resin into the cavity becomes incomplete. On the other hand, 500 cc / se
When c < Q , the escape of air in the resin is incomplete, and defects such as whitening of the molded product are likely to occur. In the present invention, in order to control the “quasi-powder flow” and fill the resin in the mold, attention is paid to the injection speed and the injection pressure of the molding machine described below, and if this is controlled, molding with stable accuracy can be achieved. They are finding that they can get the goods.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0078

[Correction method] Change

[Correction content]

As described above, it is possible to plasticize an ultrahigh molecular weight polyethylene resin which has been impossible to be injection molded,
Moreover, in contrast to the conventional injection molding method that has produced special molds and improved shapeability, the present invention enables injection molding of ultra-high molecular weight polyethylene resin simply by providing an air vent, and general-purpose engineering It has become possible to take multiple pieces in a molding cycle equivalent to that of plastic.
In particular, it has become possible to provide a gear that enables the molding of a plastic gear that requires high precision and that exhibits the low frictional force, lubricity, low wear, and sound deadening properties of an ultrahigh molecular weight polyethylene resin.

[Procedure Amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0100

[Correction method] Change

[Correction content]

[0100] Example 3 Scanner sliding member (sliding part diameter: 9 mm, shank diameter: 4 mm) in order to injection molding, molding was conducted as described below. The resin used and the molding machine are the same as in Example 1. In addition, the molding condition is 12
The same procedure was performed as in Example 1 except that the setting was set to 00 kg / cm ² .

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display area // B29K 23:00

Claims (7)

[Claims] 1. A method for producing a molded article by injection-molding an ultra-high molecular weight polyethylene resin, the raw material powder particles comprising an ultra-high molecular weight polyethylene resin,
Ultra-high molecular weight polyethylene molding characterized in that single-piece or multi-piece products are formed by joining and assembling and integrating by deformation of powder particles and melting of only the surface without intervening layers. Method of manufacturing goods. 2. The ultra high molecular weight polyethylene resin is 1
The method for producing an ultra-high molecular weight polyethylene molded article according to claim 1, wherein the intrinsic viscosity [η] measured in a decalin solvent at 35 ° C. is made of polyethylene having a molecular weight showing a value of 6.5 dl / g or more. 3. The method for producing an ultra-high molecular weight polyethylene molded article according to claim 1, wherein the number of multi-cavities is two. 4. A raw material powder particle made of an ultra-high molecular weight polyethylene resin is plasticized and fluidized while maintaining a discontinuous particle form, injected into a molding die in a quasi-powder flow state, and assembled by filling compression. The method for producing an ultra-high molecular weight polyethylene molded article according to claim 1, which is integrated. 5. The ultra high molecular weight polyethylene molding according to claim 4, wherein the molding die comprises an air vent for letting out air in the die at the time of injection and air generated at the time of compression of the powder. Method of manufacturing goods. 6. An in-line screw injection molding machine is used, and the pressure inside the mold is 400 to 3000 kg / for the raw material powder.
The method for producing an ultrahigh molecular weight polyethylene molded article according to claim 4, wherein injection molding is carried out under the conditions of cm ² and screw compression ratio of 1.3 to 2.0. 7. The injection molding is performed under a temperature condition which is a temperature higher than a temperature at which the quasi-powder flow state of the raw material powder is maintained and a temperature at which the molecular weight of the raw material powder does not decrease due to oxidation.
The method for producing an ultrahigh molecular weight polyethylene molded article according to.