JP4236213B2 - Compound molding method of ultra high molecular weight polyethylene and rubber - Google Patents

Description

  The present invention relates to a method of molding a molded article in which ultrahigh molecular weight polyethylene and rubber are bonded together using an injection molding machine.

  The ultra-high molecular weight polyethylene / rubber composite molded product is used, for example, as a guide wheel such as a caterpillar or belt, such as a snowmobile used in an extremely cold environment. In some cases, cold resistance is required, and mechanical strength at low temperatures is required. Therefore, ultrahigh molecular weight polyethylene having a molecular weight of about 1,500,000 to 6,500,000 is usually used. Since these guide wheels (wheels) rotate at a very high speed, the outer peripheral portion of the wheels is made of vulcanized rubber in order to prevent noise from being increased only by ultra high molecular weight polyethylene. In this case, if the adhesion between the interface between the ultra-high molecular weight polyethylene and the vulcanized rubber is poor, when used in a wheel as described above, peeling from the interface between the ultra-high molecular weight polyethylene and the vulcanized rubber occurs, and the wheel is damaged. The problem arises.

  Conventionally, as a method for bonding a polyolefin resin and rubber, a heat bonding method is generally used. For example, an unvulcanized rubber sheet containing a vulcanizing agent such as an organic peroxide and a high molecular weight polyethylene sheet are stacked and sandwiched between hot plates, and heated and bonded at a temperature equal to or higher than the softening point of ultra high molecular weight polyethylene at an appropriate pressure. (Refer to Patent Document 1 below).

  However, this method can be applied only to the case of manufacturing a molded product having a simple shape such as adhesion between sheet-like products, and cannot be applied to a molded product having a more complicated shape.

  Furthermore, the conventional heat bonding method has a drawback that it takes a long time of 30 minutes or more to obtain a product, resulting in extremely low productivity. In other words, the adhesive is limited to a sheet-like material, and has a drawback that a product having a complicated shape cannot be obtained. It is necessary to heat between the hot plates for about 30 minutes. There is a problem that the hot plate is occupied for 30 minutes to obtain one adhesive.

As a method for improving this point and obtaining a product having a complicated shape in a shorter time, the present inventor previously blended carbon black, which is a reinforcing material for rubber, and a vulcanizing agent with a polymer of synthetic rubber. The rubber compound formed in this way is heated in a rubber mold and molded in a semi-vulcanized state, then inserted into an injection mold, and ultrahigh molecular weight polyethylene is injected into the injection mold and compressed. After molding, by taking out from the injection mold and heating to vulcanized state, the molding time in the injection mold is shortened to about 2-5 minutes, the time to occupy the mold is shortened and production A method for improving the performance is proposed (see Patent Document 2 below).
Japanese Patent Publication No.62-24249 JP 2000-309034 A

  However, in the composite molding method of ultra high molecular weight polyethylene and synthetic rubber proposed in Patent Document 2, a rubber compound formed by blending a synthetic rubber polymer with carbon black and a vulcanizing agent is previously placed in a rubber mold. It is necessary to pre-mold in a semi-vulcanized state by heating, but it is difficult to always make a semi-vulcanized state of a certain ratio without variation for each pre-formed product. It was found that there is a problem that the adhesiveness at the interface varies depending on the semi-vulcanized state of the rubber. Moreover, since the synthetic rubber is put in a semi-vulcanized state, it is necessary to preform in advance in a rubber mold, and there is a problem that the cost is increased (that is, the rubber in the semi-vulcanized state is Compared to unvulcanized rubber, it is less likely that the semi-vulcanized rubber will be neatly remolded during the injection molding of ultra-high molecular weight polyethylene in the injection mold. It must be pre-molded into the same shape as the rubber part of the final molded product at the same time as the semi-vulcanized state).

  The present invention solves the above-mentioned problems, enables molding of products with more complicated shapes, maintains good adhesion at the interface between rubber and ultra-high molecular weight polyethylene, and in the mold during injection molding. The molding time can be shortened in the same manner as the invention described in the above-mentioned Patent Document 2, and therefore the rubber and ultra high molecular weight polyethylene between the molded products can be kept while keeping the time to occupy the injection mold. It is an object of the present invention to provide a composite molding method of ultra-high molecular weight polyethylene and rubber with good production efficiency with little variation in adhesion at the interface.

  In order to solve the above problems, the composite molding method of ultrahigh molecular weight polyethylene and rubber of the present invention is as follows.

  (1) An unmolded rubber compound formed by blending rubber with a rubber reinforcing material and a vulcanizing agent, an injection mold comprising a fixed mold part and a movable mold part at least partially movable And insert the ultra-high molecular weight polyethylene into the molding cavity in the injection mold, which is larger than the volume of the final molded product by moving the movable part of the movable mold part, and then injecting the injection part The movable part of the movable mold part is moved and compressed so that the molding cavity in the molding mold becomes the volume of the final finished product, and then the molded product is taken out from the injection mold and heated. Then, a composite molding method of ultrahigh molecular weight polyethylene and rubber, which comprises vulcanizing a rubber compound portion in a semi-vulcanized state.

(2) the (1) in the composite molding method according to claim, unvulcanized rubber compound, unvulcanized rubber compound which is formed by processing the shape and size of the sheet-shaped unvulcanized Gomukonpaun de Preferably there is.

  (3) In the composite molding method according to any one of (1) and (2), the movable part of the movable mold part is injected into the molding cavity in the injection mold and the ultrahigh molecular weight is injected. A movable part for compressing a part made of polyethylene is preferable.

  (4) In the composite molding method according to any one of items (1) to (3), the compression ratio of the movable mold portion by the movable portion is in the thickness direction of the molded product, and the final molded product thickness is compressed. It is preferable to perform compression molding at a ratio of 1 / 1.5 to 1 / 4.5 of the distance in the thickness direction of the mold cavity immediately before molding.

  (5) In the composite molding method according to any one of (1) to (4), the ultrahigh molecular weight polyethylene is injected at an injection molding temperature of 120 ° C. while maintaining the mold temperature at 80 ° C. to 150 ° C. It is preferable to perform injection molding at ˜260 ° C. and compression molding.

  (6) In the composite molding method according to any one of (1) to (5), the temperature at which the rubber compound portion in the semi-vulcanized state is heated to the vulcanized state is 70 to 150 ° C. Preferably there is.

  (7) In the composite molding method according to any one of (1) to (6), the rubber reinforcing material is preferably carbon black or white carbon.

  The composite molding method of ultra high molecular weight polyethylene and rubber according to the present invention can be performed in a short time of about 2 to 5 minutes in a mold of ultra high molecular weight polyethylene and rubber in a conventional bonding method. Compared with this, mass production becomes possible, and the effect of cost reduction is great.

  Further, since an injection mold is used, a product having a complicated shape can be easily obtained.

  In addition, variations in adhesion at the interface between the rubber and the ultra high molecular weight polyethylene can be reduced between the molded articles, and a composite molding of rubber and ultra high molecular weight polyethylene with a constant quality can be manufactured. Therefore, it is possible to provide a composite molding method of ultra-high molecular weight polyethylene and rubber having excellent reliability.

  Hereinafter, in order to facilitate understanding of the present invention, a composite molding method of ultrahigh molecular weight polyethylene and rubber of the present invention will be described with reference to the drawings showing specific embodiments. It is not limited to specific example embodiments.

  As an embodiment of a specific molded article formed by the method of the present invention, for example, the wheel shown in FIGS. 1 to 2 will be taken up and described. This is for the purpose of facilitating the understanding of the present invention. These are citations for citing specific examples, and the composite molding method of ultrahigh molecular weight polyethylene and rubber of the present invention is not limited to this example. FIG. 1 is a front view of a wheel used also for a guide wheel for a snowmobile, which is an embodiment of a composite molded product of ultrahigh molecular weight polyethylene and rubber molded by the method of the present invention. 2 is a cross-sectional view taken along line AA in FIG.

  1 to 2 obtained by the molding method of the present invention, the wheel 2 is made of ultra-high molecular weight polyethylene, and 1 shown on the outer periphery of the wheel is vulcanized rubber (part formed from a rubber compound). 4 is an axle insertion hole for insertion into the axle. 3 is an interface between the vulcanized rubber 1 and the ultrahigh molecular weight polyethylene 2 and is not particularly limited. Usually, the interface 3 has a slightly indeterminate shape having a part bulging outward slightly in the cross-sectional shape of FIG. This seems to be caused by the ultrahigh molecular weight polyethylene 2 trying to advance in the direction in which the rubber 1 exists due to the pressure during compression molding described later. The molded product obtained by the method of the present invention has excellent adhesion between the rubber 1 and the ultrahigh molecular weight polyethylene 2 at the interface 3.

  The wheel taken up in this figure shows a fairly simple wheel for the sake of simplicity of explanation, but the cross-sectional structure of the axle insertion hole 4 has a structure in which a groove into which a bearing or the like can be inserted is formed. It is optional to make other more complex structures as required.

The ultra-high molecular weight polyethylene used in the present invention usually has a molecular weight of about 1,500,000 to 6,500,000 and a melting point of about 120 ° C. to about 230 ° C. In the case where the object of the present invention is not hindered, other appropriate polymers and additives may be added to the ultrahigh molecular weight polyethylene.
In addition, when measuring the average molecular weight of ultra high molecular weight polyethylene, it can measure based on the viscosity method of ASTM D2857.

  Examples of the rubber compound rubber used in the present invention include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, ethylene-propylene rubber, chloroprene rubber, butyl rubber, etc., or two or more thereof. And the like.

  A rubber reinforcing material such as carbon black or white carbon is blended with the rubber component as a base. The amount of the rubber reinforcing material added varies depending on the purpose of use of the molded product and the type of rubber, but is usually preferably 60 to 130 parts by weight, more preferably 75 parts per 100 parts by weight of the rubber component. ~ 105 parts by weight. Usually, carbon black or white carbon is preferably used as the rubber reinforcing material. When white carbon is used as a rubber reinforcing material, it is optional to add a pigment or the like to the rubber compound and color it to a desired color as required.

  Carbon black is not particularly limited as long as it can be used for rubber compounds. Specific examples thereof include those corresponding to SAF (N110), those corresponding to ISAF (N220), those corresponding to HAF (N330), and the like. However, the present invention is not limited to these.

  In the above, SAF is an abbreviation for Super Abrasion Furnace, ISAF is an abbreviation for Intermediate Super Abrasion Furnace, HAF is an abbreviation for High Abrasion Furnace, and shows the quality grade symbol of carbon black conventionally used, N110, N220, N330, and the like are symbols indicating quality grades defined in ASTM D1765.

  A rubber compound is prepared by using sulfur and an organic peroxide peroxide as a vulcanizing agent in combination with this base. Although the addition amount of sulfur also varies depending on the purpose of use of the molded product and the type of rubber, it is usually preferable to use about 0.5 to 3 parts by weight, more preferably 1.5 parts by weight based on 100 parts by weight of the rubber component. -2.5 parts by weight. Also, the amount of organic peroxide added varies depending on the purpose of use of the molded product and the type of rubber, but it is usually preferable to use 0.5 to 3 parts by weight with respect to 100 parts by weight of the rubber component. Preferably it is 1-2 weight part. The peroxide is not particularly limited as long as it can vulcanize rubber. Typically, di-t-butyl peroxide, dicumyl peroxide, t-butyl peroxyisopropyl carbonate and the like are used. Can be mentioned.

  As described above, a rubber reinforcing material and a vulcanizing agent are blended into the rubber component to form an unvulcanized rubber compound, but it is not particularly limited, but normally, an unvulcanized rubber compound is For example, since it is molded into a sheet shape, a rubber compound of an appropriate size may be purchased depending on the shape and size of the final molded product. For example, although not particularly limited, when the above-described snowmobile guide wheel is manufactured, depending on the size, for example, a sheet-like rubber having a thickness of 17 mm × width of 400 mm × length of 600 mm A compound or a sheet-like rubber compound having a thickness of 15 mm × width of 400 mm × length of 450 mm can be used.

  If an unvulcanized rubber compound in the form of a sheet is used in this way, the rubber compound sheet is cut into a rod that is thick enough to match the cross-sectional area of the final molded product of the rubber part of the wheel. 1 is cut to a length substantially the same as the length of the ring of the rubber 1 portion in FIG. 1 (for example, thickness 17 mm × width 10 mm × length 540 mm, or thickness 15 mm × width 7 mm × length Cut into a 395 mm-long rod-like material), and prepare a material obtained by joining the ends of the obtained rod-like material in a rubber ring shape using a rubber solvent such as toluene, and place it on a predetermined part of the mold. It is convenient to fill the mold cavity portion of the mold to be rubber in the final molded product so that the mold can be easily filled and good molding can be easily performed.

  This is an example of molding the wheel, but even when other molded products are manufactured, they are formed by processing into an appropriate shape and size similar to the shape of the rubber of the final molded product as much as possible. It is preferable to use an unvulcanized rubber compound. In addition, when using an unvulcanized rubber compound formed by processing into an appropriate shape and size as described above, naturally, vulcanization proceeds during this processing, resulting in a semi-vulcanized state or a vulcanized state. It must be avoided to adopt processing conditions that lead to The unvulcanized rubber compound is easily molded along the mold shape under the conditions of injection and molding of ultra-high molecular weight polyethylene, so that it has not been formed in an appropriate shape and size in advance. The shape and size of the vulcanized rubber compound need not be exactly the same as the final molded product. In short, it is preferable to make the shape and size easy to insert into the shape of the mold part filled with the rubber compound.

  In the present invention, “predetermined position” of “inserting an unvulcanized rubber compound into a predetermined position in an injection mold including a fixed mold part and a movable mold part at least partially movable”. "Indicates the position corresponding to the position occupied by the vulcanized rubber formed from the unvulcanized rubber compound in the final molded product". If expressed in a simplified manner, the “predetermined position” is “a position corresponding to the position occupied by the vulcanized rubber in the final molded product”.

  Next, an example of a composite molding method of ultrahigh molecular weight polyethylene and rubber according to the present invention will be described with reference to the specific embodiments shown in FIGS. As described above, in order to make the understanding of the present invention easier, these are quotes for explaining with specific examples, and the composite molding method of ultrahigh molecular weight polyethylene and rubber according to the present invention is the citation. It is not limited to examples only.

  3 to 5 illustrate a composite molding method of a wheel (for example, a wheel applied to a guide wheel for a snowmobile, etc.) composed of the ultrahigh molecular weight polyethylene 2 and the rubber 1 described with reference to FIGS. FIG. 3 is a schematic partial cross-sectional view mainly showing a mold part for injection molding showing a part of a molding process for performing the process, and in this embodiment, FIG. 3 is opened with upper and lower mold parts 11 and 14 based on FIG. FIG. 4 shows the volume of the final molded product by closing the upper and lower mold parts 11 and 14 and then moving the movable part 13 of the movable mold part 14 (moving downward on the basis of FIG. 4). FIG. 5 shows a process in which ultra-high molecular weight polyethylene is injected into a molding cavity larger than the above, and FIG. 5 is a process subsequent to the above, in which the molding cavity in the injection mold has a desired volume of the final molded product. Of the movable mold part 14 so that Moving the moving section 13 (pushes up the movable portion in FIG. 5 reference) shows a step in a state of compression molded.

  In addition, illustration of injection apparatus parts, such as an extruder for injecting ultra high molecular weight polyethylene, and hydraulic equipment for moving a movable mold part are abbreviate | omitted, and a metal mold | die is also in FIGS. It is the fragmentary figure which abbreviate | omitted the upper part and the lower part, respectively. Also, the direction of the mold is not specified, but when actually used, it is usually used in a state of being rotated 90 degrees on the basis of FIGS. As shown in FIG. 5, it is generally used in a state in which the fixed mold portion is directed upward, but is not particularly limited thereto.

  3-5, 11 is a fixed mold part, 14 is a movable mold part, The movable mold part 14 consists of the fixed part 12 and the movable part 13, and the movable part 13 is, for example, a hydraulic device ( The movable part 13 of the movable mold part 14 can be moved in the vertical direction in the figure by operating a not shown) or the like.

  An upper part of the fixed mold part 11 is connected to an injection device (not shown) for injecting ultrahigh molecular weight polyethylene, and a sprue 18 is a passage to the mold internal cavity of the ultrahigh molecular weight polyethylene to be injected. , Runner 19 and gate 20.

  Using such a mold, a composite molded product of ultrahigh molecular weight polyethylene and rubber is formed as follows.

  First, as shown in FIG. 3, the movable mold part 14 (fixed part 12) and the fixed mold part 11 do not make their contact surfaces 15, 15 contact each other, but are separated from each other. Of these, the unvulcanized rubber compound 31 as described above is inserted into the portion 21 to be occupied by the vulcanized rubber in the final molded product. Then, the fixed mold part 11 and the movable mold part 14 (fixed part 12) are clamped as shown in FIG. 4 (the fixed mold part 11 and the movable mold part 14 at the boundary contact surface 15). Will come in contact).

  Next, by operating a hydraulic device (not shown), the movable part 13 of the movable mold part 14 is moved in the downward direction in the figure, and the mold cavity 22 preferably has a desired final molded product thickness of 1. It is spread over a cavity corresponding to a thickness of about 5 to 4.5 times. More specifically, assuming that the thickness of the final molded product is within the range of the arrow 16a in FIG. 5, the distance of the arrow 16b in FIG. 4 (the distance in the thickness direction of the mold cavity immediately before compression molding) is preferably The movable part 13 of the movable mold part 14 is illustrated so as to be about 1.5 to 4.5 times the thickness of the arrow 16a in FIG. 5, more preferably about 1.8 to 4.2 times. The mold cavity 22 is expanded by moving downward. The ultrahigh molecular weight polyethylene 32 is injected into the expanded mold cavity 22 at an injection molding temperature of 120 ° C. to 260 ° C., preferably 130 ° C. to 230 ° C. while maintaining the mold temperature at 80 ° C. to 150 ° C. FIG. 4 is a process sectional view showing the state at this time. Since ultra-high molecular weight polyethylene has an extremely large molecular weight, when the ultra-high molecular weight polyethylene 32 as shown in FIG. Yes.

  If the injection molding temperature is too high, the ultra-high molecular weight polyethylene is easily decomposed during molding, and gas is easily generated and peeled off on the adhesive surface with the rubber. Therefore, the molding temperature is preferably within the above range. Since the injection molding temperature cannot be so high, the ultra-high molecular weight polyethylene is in a so-called flash shape when injected into the wide mold cavity 22. If the molded product is taken out in such a state, that is, only by ordinary injection molding, only the physical properties (mechanical strength) of the molded product can be obtained. Therefore, in the method of the present invention, FIG. As will be explained, further compression molding is required. Only the ultrahigh molecular weight polyethylene part is sufficient for direct compression.

  That is, by operating a hydraulic device or the like (not shown) as shown in FIG. 5, the movable part 13 of the movable mold part 14 is moved upward in the figure, and the final molded product intended by the mold cavity is obtained. Compression molding is performed to obtain a thickness. The mold temperature for compression molding is the same as above. The compression ratio of the movable mold portion by the movable portion is the ratio of the length of the arrow 16a in FIG. 5 to the length of the arrow 16b in FIG. 4, and specifically, depending on the shape and type of the molded product, In the product thickness direction, compression molding is preferably performed so that the final molded product thickness is 1 / 1.5 to 1 / 4.5 of the distance in the thickness direction of the mold cavity immediately before compression molding, more preferably 1 / It is about 1.8 to 1 / 4.2.

  After compression molding, the space between the fixed mold part 11 and the movable mold part 14 is opened, and the molded product is taken out. The molding time required for these injection and compression molding is about 180 seconds to 300 seconds. The molding time may be appropriately changed according to the shape, thickness, size, etc. of the product.

  Thus, as soon as the composite molding is completed, the molded product is taken out from the mold and heated at 70 ° C. to 150 ° C. with a heating device such as an oven or a hot air dryer to bring the rubber part into a suitable vulcanized state for the purpose. The heating time for vulcanization varies depending on the rubber composition and the size of the molded product, but is usually about 50 to 70 minutes, and the optimal heating time and temperature are the rubber composition and the size of the molded product. Accordingly, it may be determined in advance by experiments.

  In addition, when the rubber compound portion to be used is relatively thin, or when the volume of the rubber compound is relatively small, the step of taking out the molded product from the mold after the compression molding and heat-treating it may be omitted. is there.

  An example in which a composite molding of ultra high molecular weight polyethylene (melting point: 136 ° C., molecular weight: about 3,000,000, manufactured by Mitsui Chemicals, “Hi-Zex Million 320M”) and rubber will be described. The blending (weight ratio) of the unvulcanized rubber compound is as follows.

  70 parts by weight of natural rubber, 30 parts by weight of SBR (styrene-butadiene rubber: 23.5% by weight of bound styrene), 5 parts by weight of zinc oxide, 1 part by weight of stearic acid, 95 parts by weight of carbon black [ISAF (N220)], process oil 20 parts by weight, anti-aging agent 2 parts by weight, vulcanization accelerator 2 parts by weight, sulfur 2 parts by weight, peroxide 1.5 parts by weight. In addition, 1,1-bis (t-butylperoxide is included in this peroxide. Oxy) -3,3,5-trimethylcyclohexane was used, but other known peroxides such as di-tbutyl peroxide, dicumyl peroxide, t-butylperoxyisopropyl carbonate, etc. It may be changed to

  As described above, this unvulcanized rubber compound sheet was cut into a rod shape having a thickness of 17 mm, a width of 10 mm, and a length of 540 mm, and both ends of the obtained rod-like product were connected to a rubber ring using toluene. As shown in FIG. 3, an unvulcanized rubber compound 31 as described above is inserted into the portion 21 (see FIGS. 3 to 5) that the vulcanized rubber should occupy in the final molded product. . If this process is explained in detail, as mentioned above, the movable mold part 14 (fixed part 12) and the fixed mold part 11 are not brought into contact with each other at their contact surfaces 15 and 15, but they are separated from each other. The unvulcanized rubber compound 31 as described above is inserted into the movable mold portion 14 (fixed portion 12) of the portion 21 in the final molded product where the vulcanized rubber should occupy. Then, the fixed mold part 11 and the movable mold part 14 (fixed part 12) are clamped as in the state shown in FIG.

  Next, as shown in FIG. 4, the movable part 13 of the movable mold part 14 is moved downward in the figure by a hydraulic mechanism (not shown), so that the mold cavity 22 has a final molded product thickness of the target. The movable mold part 14 of the movable mold part 14 is moved downward in the figure so that the distance corresponding to the arrow 16b in FIG. 4 is about three times the length of the arrow 16a in FIG. Move in the direction).

  Next, ultrahigh molecular weight polyethylene 32 was injected into the expanded mold cavity 22 through the sprue 18, runner 19, and gate 20. While maintaining the mold temperature at 80 ° C. to 150 ° C., ultra high molecular weight polyethylene was injected with an injection molding machine at an injection molding temperature of 150 ° C. to 230 ° C. The process chart at this time is the process chart shown in FIG.

  Next, as shown in FIG. 5, the movable part 13 of the movable mold part 14 is moved upward in the figure by a hydraulic mechanism (not shown), so that the mold cavity has a final molded product thickness 16a. Compression molding was performed. The mold temperature for compression molding is the same as above. After compression molding, the space between the fixed mold part 11 and the movable mold part 14 was opened, and the molded product was taken out.

  The composite molded product thus obtained was heated in an oven at 70 ° C. to 120 ° C. for about 1 hour to obtain an optimum vulcanized state. The molding time required for these injection and compression molding was about 200 to 300 seconds. Therefore, the time for monopolizing the mold is short, and the heating for vulcanization can be done by treating a large number of molded parts at once or passing through a continuous moving oven. As a result, it was possible to shorten the molding time in the most problematic mold and improve the production efficiency.

  When the dispersion of the adhesive force at the interface between the vulcanized rubber and the ultrahigh molecular weight polyethylene of the obtained composite molded product was examined, the same raw material was used, and the molding method described in the conventional method example of Patent Document 2 was used. The obtained comparative molded product; that is, the rubber compound was previously molded in a rubber mold at a temperature of 120 to 190 ° C. (3 minutes) in a semi-vulcanized state. Inserted in the same way as the injection mold used in No. 1, and injection-molded ultrahigh molecular weight polyethylene at an injection molding temperature of 130 to 230 ° C. and a mold temperature of 100 to 150 ° C. in the same manner as in Example 1 to take out the molded product. The comparative molded product obtained by re-curing by heating at 100 ° C. to 150 ° C. for about 1 hour in an oven had an occurrence rate of defective products of about 7%. In most cases, defective products are not generated. won. As a result, uniform and stable production became possible.

  In addition, the variation in the adhesive force at the interface between the vulcanized rubber and the ultrahigh molecular weight polyethylene of the composite molded product was tested as follows.

  1 and 2 of the molded product shown in FIG. 2 (to the boundary with the ultra high molecular weight polyethylene 2 at the lower part of the vulcanized rubber 1 in FIG. 1 based on FIG. 1) with a vice (Fixed by vise from the front and back of the portion of vulcanized rubber 1 on the basis of FIG. 1. Referring to FIG. 2, the portion of vulcanized rubber 1 is sandwiched by the vice from the upper surface and the lower surface of FIG. 2. )) When a man with a weight of about 70 kg grabs the molded product by hand and pulls the boundary between the vulcanized rubber 1 and the ultra-high molecular weight polyethylene 2, the case where the separation is not good and the case where the separation is not recognized is accepted. The occurrence rate of defective products is calculated based on 100 molded products.

  Instead of the unvulcanized rubber compound used in Example 1, 100 parts by weight of SBR (styrene-butadiene rubber: 23.5% by weight of bound styrene), 5 parts by weight of zinc white, 1 part by weight of stearic acid, 95 parts by weight of white carbon 20 parts by weight of process oil, 2 parts by weight of anti-aging agent, 2 parts by weight of vulcanization accelerator, 2 parts by weight of sulfur, peroxide (1,1-bis (t-butylperoxy) -3,3,5-trimethyl (Cyclohexane) A composite molded article was produced under the same conditions as in Example 1 except that an unvulcanized rubber compound consisting of 1.5 parts by weight was used. The molding time required for this injection and compression molding was about 200 seconds to 300 seconds as in Example 1. Therefore, the time for monopolizing the mold is short, and the heating for vulcanization can be done by treating a large number of molded parts at once or passing through a continuous moving oven. As a result, it was possible to shorten the molding time in the most problematic mold and improve the production efficiency.

  When the dispersion of the adhesive force at the interface between the vulcanized rubber and the ultrahigh molecular weight polyethylene of the obtained composite molded product was examined, the same raw material was used, and the molding method described in the conventional method example of Patent Document 2 was used. The obtained comparative molded product had a defective product generation rate of about 7%, but the product of the above-described method of the present invention produced almost no defective product. As a result, uniform and stable production became possible.

  A composite molded article is produced under the same conditions as in Example 1 except that the ultra high molecular weight polyethylene of Example 1 is used instead of “Hostalen GUR” (molecular weight of about 3,000,000) manufactured by Ticona Japan Co., Ltd. did. The molding time required for this injection and compression molding was about 200 seconds to 300 seconds as in Example 1. Therefore, the time for monopolizing the mold is short, and the heating for vulcanization can be done by treating a large number of molded parts at once or passing through a continuous moving oven. As a result, it was possible to shorten the molding time in the most problematic mold and improve the production efficiency.

  When the dispersion of the adhesive force at the interface between the vulcanized rubber and the ultrahigh molecular weight polyethylene of the obtained composite molded product was examined, the same raw material was used, and the molding method described in the conventional method example of Patent Document 2 was used. The obtained comparative molded product had a defective product generation rate of about 7%, but the product of the above-described method of the present invention produced almost no defective product. As a result, uniform and stable production became possible.

  The ultra high molecular weight polyethylene of Example 1 was changed to “Hostalen GUR” (molecular weight of about 3,000,000) manufactured by Ticona Japan Co., Ltd., and the unvulcanized rubber compound used in Example 1 was used in Example 2. A composite molded article was produced under the same conditions as in Example 1 except that the unvulcanized rubber compound was used. The molding time required for this injection and compression molding was about 200 seconds to 300 seconds as in Example 1. Therefore, the time for monopolizing the mold is short, and the heating for vulcanization can be done by treating a large number of molded parts at once or passing through a continuous moving oven. As a result, it was possible to shorten the molding time in the most problematic mold and improve the production efficiency.

  When the dispersion of the adhesive force at the interface between the vulcanized rubber and the ultrahigh molecular weight polyethylene of the obtained composite molded product was examined, the same raw material was used, and the molding method described in the conventional method example of Patent Document 2 was used. The obtained comparative molded product had a defective product generation rate of about 7%, but the product of the above-described method of the present invention produced almost no defective product. As a result, uniform and stable production became possible.

  The composite molding method of ultra high molecular weight polyethylene and rubber according to the present invention can perform composite molding of ultra high molecular weight polyethylene and rubber in a mold in a short time of 2 to 5 minutes. Therefore, mass production becomes possible and the effect of cost reduction is great.

  Since an injection mold is used, a product having a complicated shape can be easily obtained. The composite molded product of ultra-high molecular weight polyethylene and rubber obtained by the method of the present invention has no unevenness in adhesion at the interface between rubber and ultra-high molecular weight polyethylene, and can provide a molded product with uniform physical properties. It is possible to provide a method for forming a composite molded product of high ultrahigh molecular weight polyethylene and rubber. Therefore, the method of the present invention can be suitably used for molding a composite molded product of ultrahigh molecular weight polyethylene and rubber.

FIG. 1 is a front view of a wheel as an embodiment of a composite molded product of ultrahigh molecular weight polyethylene and rubber molded by the method of the present invention. 2 is a cross-sectional view taken along line AA of FIG. FIG. 3 is a schematic partial sectional view mainly showing a mold part for injection molding, showing a part of the molding process for explaining the composite molding method of the present invention. FIG. 4 is a schematic partial cross-sectional view of a mold part for injection molding mainly showing a part of the molding process of the composite molding method of the present invention following the process of FIG. FIG. 5 is a schematic partial cross-sectional view mainly showing a mold part for injection molding, showing a part of the molding process of the composite molding method of the present invention following the process of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vulcanized rubber 2 Ultra high molecular weight polyethylene 3 Interface of rubber 1 and ultra high molecular weight polyethylene 2 4 Axle insertion hole 11 Fixed mold part 12 Fixed part of movable mold part 13 Movable part of movable mold part 14 Movable mold Part 15 Contact surface of movable mold part 14 (fixed part 12) and fixed mold part 11 16a Arrow indicating thickness of final molded product 16b Distance in mold cavity thickness direction immediately before compression molding 18 Sprue 19 Runner 20 Gate 21 Parts that the vulcanized rubber should occupy in the final molded product 22 Mold cavity 31 Rubber compound 32 Ultra high molecular weight polyethylene

Claims (7)

  An unvulcanized rubber compound formed by blending rubber with a rubber reinforcing material and a vulcanizing agent, a predetermined mold in an injection mold comprising a fixed mold part and a movable mold part at least partially movable. Insert the ultra-high molecular weight polyethylene into the molding cavity in the injection mold that is inserted at the position and move the movable part of the movable mold part to make it larger than the volume of the final molded product, and then the injection mold The movable part of the movable mold part is moved and compressed so that the molding cavity inside becomes the volume of the desired final molded product, and then the molded product is taken out from the injection mold and heated, A composite molding method of ultrahigh molecular weight polyethylene and rubber, which comprises setting a rubber compound portion in a semi-vulcanized state to a vulcanized state. Unvulcanized rubber compound, a composite molding process according to claim 1 is an unvulcanized rubber compound which is formed by processing the shape and size of the sheet-shaped unvulcanized Gomukonpaun de.   The movable part of a movable mold part is a movable part for compressing the part which consists of ultra high molecular weight polyethylene injected in the shaping | molding cavity in the said injection mold. Composite molding method.   Ratio in which the compression ratio by the movable part of the movable mold part is in the thickness direction of the molded product, and the final molded product thickness is 1 / 1.5 to 1 / 4.5 of the distance in the thickness direction of the mold cavity immediately before the compression molding The composite molding method according to any one of claims 1 to 3, wherein the compression molding is performed.   The composite molding method according to any one of claims 1 to 4, wherein ultra high molecular weight polyethylene is injected and compression molded at an injection molding temperature of 120 ° C to 260 ° C while maintaining the mold temperature at 80 ° C to 150 ° C.   The composite molding method according to any one of claims 1 to 5, wherein a temperature at which the semi-vulcanized rubber compound portion is heated to a vulcanized state is 70 to 150 ° C.   The composite molding method according to any one of claims 1 to 6, wherein the rubber reinforcing material is carbon black or white carbon.

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