Bearings for rubber glove manufacturing equipment

Abstract

To provide a bearing for a rubber glove manufacturing device that at least has longer service life and is more inexpensive than conventional metal rolling bearings.SOLUTION: A bearing 4 is a resin sliding bearing that is used in a rubber glove manufacturing device that forms a rubber film into a glove mold by immersing the glove mold in a liquid rubber bath to manufacture a rubber glove, and rotatably supports the glove mold. The resin sliding bearing is made of an injection molded body of a resin composition comprising: a layered mineral-based filler which uses polyphenylene sulfide resin as a base resin, and has a Mohs hardness of 3 or less; and a fibrous reinforcement material.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a bearing used in a rubber glove manufacturing apparatus. [Background technology]

[0002] BACKGROUND ART Conventionally, a method for manufacturing a rubber glove and an apparatus for manufacturing a rubber glove are known.

[0003] For example, Patent Document 1 discloses a method for manufacturing rubber gloves, in which a glove model is held in a rubber latex bath, then pulled out, and then rotated around its vertical axis before the attached latex dries, to further apply rubber latex to an area where a larger rubber thickness is required.

[0004] Furthermore, Patent Documents 2 and 3 disclose rubber glove manufacturing devices that rotate and move glove molds in the manufacturing process of rubber gloves.

[0005] Bearings are used in the rotating parts of these rubber glove manufacturing machines (hereinafter sometimes referred to as "manufacturing machines") to ensure smooth rotation of the glove molds. The lower the friction torque at the contact point with the shaft, the smoother the bearing can rotate, which can affect the quality of the manufactured rubber gloves. Conventionally, general metal rolling bearings have been used as bearings in rubber glove manufacturing machines. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 55-29814 [Patent Document 2] Japanese Patent Application Publication No. 48-4148 [Patent Document 3] Japanese Patent Application Publication No. 7-148754 Summary of the Invention [Problem to be solved by the invention]

[0007] In manufacturing equipment, alkaline or acidic liquid rubber (latex), cleaning solutions, hot water, etc. are used during the process, and depending on the process, the atmosphere may be high temperature. If a glove mold equipped with a metal rolling bearing is used for a long time in such an environment, the metal rolling bearing may corrode, causing the glove mold to vibrate (vibration perpendicular to the axis extending in the longitudinal direction of the glove mold). For this reason, metal rolling bearings may need to be replaced after a relatively short period of time, for example, after about 1,400 hours of use.

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to provide a bearing for a rubber glove manufacturing apparatus which has a longer life than at least conventional metal rolling bearings and is inexpensive. [Means for solving the problem]

[0009] The bearing for a rubber glove manufacturing apparatus of the present invention (hereinafter also referred to as the bearing of the present invention) is used in a rubber glove manufacturing apparatus that manufactures rubber gloves by immersing a glove mold in a liquid rubber bath to form a rubber film on the glove mold, and is a bearing that rotatably supports the glove mold, and is characterized in that it is a resin sliding bearing made of an injection-molded product of a resin composition that uses polyphenylene sulfide (PPS) resin as a base resin and contains a layered mineral-based filler having a Mohs hardness of 3 or less and a fibrous reinforcing material.

[0010] The resin composition is characterized by containing 40 to 60 parts by mass of the layered mineral filler and 30 to 50 parts by mass of the fibrous reinforcing material relative to 100 parts by mass of the PPS resin.

[0011] The resin composition is characterized in that it further contains 10 to 30 parts by mass of a solid lubricant per 100 parts by mass of the PPS resin.

[0012] The layered mineral filler is characterized by containing at least one selected from talc, mica, graphite, and kaolin.

[0013] The fibrous reinforcing material is characterized by including at least one selected from glass fiber, carbon fiber, and aramid fiber.

[0014] The bearing for a rubber glove manufacturing apparatus is characterized in that it is an annealed injection-molded article. [Effects of the Invention]

[0015] The bearing for rubber glove manufacturing equipment of the present invention is a resin sliding bearing made of an injection-molded article of a resin composition containing PPS resin as the base resin (the binder resin with the largest volume), and therefore can be provided at a lower cost than conventional metal rolling bearings. Furthermore, this bearing is used in a rubber glove manufacturing equipment that produces rubber gloves by immersing a glove mold in a liquid rubber bath to form a rubber film on the glove mold, and supports the glove mold rotatably. Because the bearing is an injection-molded article of a resin composition containing PPS resin, a layered mineral filler having a Mohs hardness of 3 or less, and a fibrous reinforcing material, it has excellent low-friction properties and excellent corrosion resistance even in environments where it is used, such as with liquid rubber, hot water, and cleaning solutions. As a result, this bearing has a longer life and can be provided at a lower cost than at least conventional metal rolling bearings.

[0016] The resin composition contains 40 to 60 parts by mass of layered mineral filler and 30 to 50 parts by mass of fibrous reinforcing material per 100 parts by mass of PPS resin, which makes it possible to produce bearings that are not only corrosion-resistant but also wear-resistant, and have a longer life.

[0017] The resin composition further contains 10 to 30 parts by mass of a solid lubricant per 100 parts by mass of PPS resin, and therefore can provide a bearing with even better low friction characteristics and a longer life.

[0018] The layered mineral filler contains at least one selected from talc, mica, graphite, and kaolin, which allows the bearing to have even lower friction characteristics and better wear resistance, resulting in an even longer life.

[0019] The fibrous reinforcing material contains at least one selected from glass fiber, carbon fiber, and aramid fiber, and therefore is expected to have better mechanical strength and a longer lifespan.

[0020] Since the bearing for rubber glove manufacturing equipment is an annealed injection molded body, the crystallinity of the polymer chains is higher than that of a non-annealed body, and the bearing has better corrosion resistance, wear resistance, and low friction properties. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram of a glove mold used in a rubber glove manufacturing apparatus. [Figure 2] 1 is a perspective view showing an example of a bearing of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] The manufacturing process of a rubber glove manufacturing apparatus to which the bearing of the present invention is applied will be described with reference to FIG. 1. FIG. 1 is a schematic diagram of a glove mold used in the rubber glove manufacturing apparatus. The bearing of the present invention is used in a rubber glove manufacturing apparatus that manufactures rubber gloves by immersing a glove mold 1 in a liquid rubber bath to form a rubber film on the surface of the glove mold 1. A shaft 2 having a length 0.5 to 3 times the length of the glove mold 1 is provided at the longitudinal center of the glove mold 1. A bearing member having the bearing of the present invention therein is inserted into the shaft 2. The bearing member is positioned on the shaft by two retaining rings provided on the outer periphery of the shaft 2 so as to sandwich the bearing member front and rear in the axial direction. The bearing rotatably supports the shaft 2 of the glove mold 1 on the cylindrical inner diameter surface.

[0023] The manufacturing process for rubber gloves includes the steps of forming a rubber membrane on a glove mold 1 shaped to fit a person's wrist or upper arm to the fingertips, and cleaning the formed rubber membrane. In the rubber membrane forming step, the glove mold 1 is hung from a rail with the fingertips facing downwards and immersed in a liquid rubber bath filled with liquid rubber. The glove mold 1 is then lifted up, placed horizontally and rotated while the liquid rubber is dried using a heater. In the rubber membrane cleaning step, the glove mold 1 is immersed in a hot water bath, cleaning tank, etc. The glove mold 1 is then lifted up, placed horizontally and rotated while the moisture is dried using a heater.

[0024] In this way, when the glove mold 1 is immersed in each tank, the glove mold 1 is hung from a rail, and when the glove mold 1 is dried with a heater, the glove mold 1 is rotated in a horizontal position. The reason for rotating the glove mold 1 in a horizontal position is to make the rubber film have a predetermined uniform thickness or to dry the rubber film uniformly.

[0025] The above-mentioned bearing member will be described with reference to Fig. 2. Fig. 2 is a perspective view showing an example of a bearing of the present invention. As shown in Fig. 2, bearing 4 is a cylindrical bushing. Bearing 4 is a resin sliding bearing made from an injection-molded product of a predetermined resin composition with PPS resin as the base resin. This makes it less expensive than conventional metal rolling bearings and more corrosion-resistant.

[0026] Two bearings 4 are used for one glove mold 1 (see Figure 1), and the two bearings are housed in a housing 3 (see Figure 1). The housing 3 is a cylindrical bearing case. A counterbore is formed on the inside of each end of the housing 3, and a bearing is attached to the counterbore. The bearing can be attached to the counterbore mechanically using adhesive or screws, or by press-fitting or insert molding.

[0027] The bearings of the present invention are mounted on two axial positions, one above and one below, of the glove-shaped shaft. Specifically, the bearing member is constructed by mounting the bearings 4 in the counterbore holes at both ends of the housing 3. The housing 3 has a cylindrical gap between the counterbore holes at both ends into which the two bearings 4 are mounted. The inner diameter of the gap is larger than the inner diameter of the bearing 4 and smaller than the outer diameter of the bearing 4. The inner diameter of the counterbore hole is approximately the same as the outer diameter of the bearing 4, and the depth of the counterbore hole (length in the direction of rotational axis) is approximately the same as the length of the bearing 4 in the direction of rotational axis. The inner diameter of the gap is larger than the outer diameter of the glove-shaped shaft, and the inner diameter of the bearing 4 is approximately the same as the outer diameter of the shaft. By providing a certain distance between the bearings in this way, the rotation of the glove-shaped shaft becomes more stable.

[0028] The shape of the housing is not limited to the above shapes and may be, for example, a cylindrical member that penetrates the housing with a constant inner diameter in the direction of the rotation axis. In this case, only one bearing may be attached to the housing, or multiple bearings may be attached. When multiple bearings are attached, the rotation of the glove mold can be made more stable by sandwiching a cylindrical spacer having an inner diameter larger than the inner diameter of the bearings between the bearings. The housing may also be formed with a connecting portion for connecting to a rubber glove manufacturing machine. Furthermore, the housing is preferably made of stainless steel from the viewpoints of corrosion resistance and strength.

[0029] When multiple bearings are mounted in a housing, each bearing may be injection-molded from the same resin composition, or from different resin compositions. In the latter case, for example, the No. 1 bearing closest to each tank, such as a liquid rubber tank, may contain a higher proportion of PPS resin, for example, to provide better corrosion resistance. The No. 2 bearing farther from the tank may contain a higher proportion of layered mineral filler or a solid lubricant, for better low-friction properties. In this case, it is recommended to take measures to prevent misassembly, such as making the No. 1 and No. 2 bearings different outer diameters.

[0030] The resin composition constituting the bearing of the present invention will be described below. The resin composition used in the present invention contains a PPS resin as a base resin, a layered mineral filler having a Mohs hardness of 3 or less, and a fibrous reinforcing material.

[0031] PPS resin is a crystalline thermoplastic resin with a polymer structure shown in formula (1) below, in which benzene rings are linked at the para position by sulfur bonds. PPS resins with the structure of formula (1) below have a melting point of approximately 280°C and a glass transition point of 90°C, and possess extremely high rigidity as well as excellent heat resistance, dimensional stability, abrasion resistance, and sliding properties. PPS resins are classified into crosslinked, semi-crosslinked, linear, and branched types depending on their molecular structure, but the present invention can use any PPS resin without being limited by these molecular structures or molecular weights.

[0032] [ka]

[0033] The resin composition contains a layered mineral filler having a Mohs hardness of 3 or less. If the Mohs hardness exceeds 3, there is a concern that the filler may attack the shaft and increase friction torque. The layered mineral filler more preferably has a Mohs hardness of 1 to 2.

[0034] The Mohs hardness scale is a measure of hardness in which a material is judged to be less hard than ten standard materials if it is scratched. The standard materials are, in order of decreasing hardness, 1: talc, 2: gypsum, 3: calcite, 4: fluorite, 5: apatite, 6: orthoclase, 7: quartz, 8: topaz, 9: corundum, and 10: diamond. For example, if a material is not scratched by gypsum (Mohs hardness 2) but is scratched by calcite (Mohs hardness 3), the hardness is expressed as 2.5. The Mohs hardness indicates the degree of hardness when a force is applied in the lateral direction and is suitable as a measure of wear on sliding surfaces. The Mohs hardness can be measured using a known Mohs hardness scale.

[0035] The layered mineral filler having a Mohs hardness of 3 or less is not particularly limited, and examples that can be used include talc (Mohs hardness 1), mica (Mohs hardness 3), graphite (Mohs hardness 2), kaolin (Mohs hardness 2), and molybdenum disulfide (Mohs hardness 1). One or more of these layered mineral fillers may be used. When using two or more fillers with different Mohs hardnesses, it is preferable to mix more fillers with lower Mohs hardnesses than those with higher Mohs hardnesses.

[0036] The layered mineral filler preferably contains at least one selected from talc, mica, graphite, and kaolin. By including these, the low friction characteristics and wear resistance are further improved. Talc is particularly preferred because it is effective in preventing the generation of abnormal noise. Furthermore, from the viewpoint of low friction characteristics and wear resistance, talc and graphite can be used in combination.

[0037] The content of layered mineral fillers having a Mohs hardness of 3 or less in the resin composition (the total amount if multiple types are used; the same applies hereinafter) is preferably 30 to 60 parts by mass, more preferably 35 to 55 parts by mass, and even more preferably 40 to 50 parts by mass, per 100 parts by mass of PPS resin. By keeping the content within these ranges, it is easy to achieve both wear resistance and mechanical strength, and it is easy to obtain the desired durability (e.g., at least twice that of current rolling bearings).

[0038] When talc and graphite are used in combination as the layered mineral filler, the ratio of talc to graphite is preferably 2:1 to 20:1 within the above range, more preferably 3:1 to 10:1, and even more preferably 5:1 to 9:1.

[0039] The fibrous reinforcing material used in the present invention can be any known fibrous reinforcing material, and one or more types may be used. The fibrous reinforcing material preferably contains at least one selected from glass fiber, carbon fiber, and aramid fiber. These fibers have chemical resistance and can contribute to improving corrosion resistance.

[0040] The content of the fibrous reinforcing material in the resin composition (the total amount if multiple types are used; the same applies hereinafter) is preferably 30 to 50 parts by mass, more preferably 30 to 45 parts by mass, and even more preferably 35 to 40 parts by mass, per 100 parts by mass of the PPS resin. By keeping the content within these ranges, it becomes easier to achieve both mechanical strength and low friction properties.

[0041] In consideration of the above, a particularly preferred embodiment of the resin composition used in the present invention is a resin composition containing 40 to 60 parts by mass of the layered mineral filler and 30 to 50 parts by mass of a fibrous reinforcing material per 100 parts by mass of PPS resin. By using a resin composition with the above composition, the bearing can be excellent in wear resistance as well as corrosion resistance, and can have a longer life.

[0042] The resin composition may further contain a solid lubricant. For example, a fluororesin powder such as PTFE resin can be used as the solid lubricant. The solid lubricant is preferably contained in an amount of 5 to 40 parts by mass, more preferably 10 to 30 parts by mass, and even more preferably 10 to 23 parts by mass, per 100 parts by mass of the PPS resin. By containing the solid lubricant within these ranges, it is possible to improve low-friction properties without impairing wear resistance.

[0043] PTFE resin has excellent heat resistance, with a thermal decomposition temperature of over 300°C, which helps prevent thermal decomposition during injection molding. Furthermore, when used without lubrication, for example, it forms a transfer film with excellent self-lubricating properties on the mating shaft, resulting in low-friction bearing characteristics.

[0044] The PTFE resin used in the present invention may be any of molding powder produced by suspension polymerization, fine powder produced by emulsion polymerization, and recycled PTFE, but recycled PTFE is preferred because of its high lubrication effect.The PTFE resin used in the present invention may also be a PTFE resin modified with a perfluoroalkyl ether group, a fluoroalkyl group, or a side chain group having other fluoroalkyl groups.

[0045] The bearing of the present invention may be formed by injection molding a resin composition containing the above-mentioned PPS resin as a base resin, or may be a treated body obtained by subjecting the resulting injection-molded body to various treatments. The treated body is preferably an annealed injection-molded body. Specifically, it is preferably an annealed body (heat-treated finished body) obtained by annealing (heat-treating) the injection-molded body after injection molding for a predetermined time at a temperature higher than the glass transition temperature of the PPS resin. This increases the crystallinity of the polymer chains of the PPS resin compared to a non-annealed body, thereby further improving wear resistance and heat resistance. Note that heat treatment may cause the shape of the bearing bore to deteriorate. In such cases, the bearing bore may be finished by reaming after heat treatment.

[0046] The temperature pattern of the annealing treatment is not particularly limited, but the maximum temperature of the annealing treatment is preferably in the range of 100°C to 250°C, more preferably 120°C to 230°C, and even more preferably 140°C to 210°C. The annealing treatment time is preferably, for example, 1 hour to 6 hours, and more preferably 1 hour to 4 hours, from the viewpoint of achieving both sufficient crystallization at the predetermined temperature and productivity. [Example]

[0047] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples. Table 1 shows the composition of the resin composition used to manufacture the bearings of each example and comparative example, as well as the evaluation results of durability tests using an actual machine.

[0048] Pellets for injection molding were produced using the raw materials shown in Table 1, and these pellets were fed into an injection molding machine to produce bush-shaped bearings (inner diameter φ15 mm, outer diameter φ21 mm, total length 15 mm) (Examples 1 to 3, Comparative Examples 1 to 3). For Example 3 and Comparative Example 3, the injection-molded articles (bearings) of Example 2 and Comparative Example 2 were heat-treated at 150°C for 3 hours, while the injection-molded articles of Examples 1 to 2 and Comparative Examples 1 to 2 were not heat-treated. The bearing bores of none of the bearings were reamed. Comparative Example 4 is a bearing made from a resin composition in which 100 parts by mass of PTFE resin is blended with 30 parts by mass of glass fiber, and its shape is the same as that of Example 1. The bearing of Comparative Example 4 is a lathe-machined product made from a pipe material with an inner diameter φ13 mm and an outer diameter φ23 mm.

[0049] <Actual machine durability test> Two of the resulting bearings were mounted in a cylindrical housing with an outer diameter of 28 mm and a total length of 45 mm, each with two counterbore holes at both ends, to form test bearing members, and these bearing members were attached to the shafts of glove molds (φ15 mm). The rubber glove manufacturing equipment fitted with these test bearing members was operated to produce rubber gloves, while the durability of the bearings when used in actual equipment was evaluated. Two glove molds were fitted with the test bearing members, and all the others were fitted with conventional metal rolling bearings. At the same time as the endurance test began, the metal rolling bearings in six glove molds were replaced with new ones, and the lifespan of the metal rolling bearings was simultaneously confirmed.

[0050] The rubber glove manufacturing equipment was operated for 1000 hours, and the operation of the glove mold (vibration of the glove mold) with the test bearing member attached was visually confirmed to confirm whether there were any abnormalities in operation. Furthermore, the bearing was removed and the wear depth of the bearing surface (bearing hole) was measured.

[0051] After checking the condition of the bearing surface, the bearing was reattached to the housing to form a bearing member, and the glove mold with this bearing member reattached was then attached to the rubber glove manufacturing device and operated for a further 1,000 hours (total of 2,000 hours), during which the operation of the glove mold was visually confirmed and the wear depth of the bearing surface was measured.

[0052] The glove-shaped runout was judged to have occurred when a rotating glove-shaped runout was visually observed, and judged to have not occurred when no runout was observed. The wear depth was evaluated as follows: when the wear depth of the bearing surface was 13 μm or less, it was marked with "◎", when it was more than 13 μm and less than 25 μm, it was marked with "○", when it was 60 μm or more to 150 μm, it was marked with "△", and when it was 200 μm or more, it was marked with "×". Note that the wear depth of the bearing surface of more than 25 μm and less than 60 μm and more than 150 μm and less than 200 μm were not found in any of Examples 1 to 3 and Comparative Examples 1 to 4, and therefore were omitted. The wear depth was the average value of the wear depth of the bearing surfaces of the two bearings at both ends of the housing. The results are shown in Table 1.

[0053] [Table 1]

[0054] As shown in Table 1, the results of an actual machine durability test using a rubber glove manufacturing machine showed that when the bearings of Examples 1 to 3 were used, no glove mold runout was observed up to 2000 hours of operation. The wear depth of the bearing surface after 2000 hours of operation was also 25 μm or less in all cases, indicating continued usability. Note that current metal rolling bearings begin to show runout after approximately 1400 to 1600 hours, so the bearings of Examples 1 to 3 had a longer life than current bearings.

[0055] In terms of the change in wear depth over time, after 1000 hours of operation, Examples 2 and 3 were rated "◎" and Example 1 was rated "◯", and after 2000 hours of operation, Example 3 was rated "◎" and Examples 1 and 2 were rated "◯". From these results, it was found that the durability when the bearings were used in an actual machine was (excellent) (Example 3) > (Example 2) > (Example 1) (poor), and that the annealed injection-molded body was particularly effective.

[0056] In the durability tests using the bearings of Comparative Examples 1 and 4, the glove-shaped vibration increased by 1000 hours, and the test was discontinued thereafter. In Comparative Examples 2 and 3, the glove-shaped vibration did not occur by 1000 hours, but by 2000 hours, the vibration of the glove-shaped vibration increased. Furthermore, the wear depth was greater in Comparative Example 2 than in Comparative Example 3.

[0057] From the above results, it can be seen that the bearing for rubber glove manufacturing equipment of the present invention is cheaper than the current metal rolling bearings and is expected to have durability at least twice as long. [Industrial Applicability]

[0058] The bearing for rubber glove manufacturing equipment of the present invention has excellent corrosion resistance even in environments where it is used, such as in liquid rubber, hot water, and cleaning solutions, and is inexpensive, and therefore can be widely used as a sliding bearing having a longer life than at least conventional metallic rolling bearings. [Explanation of symbols]

[0059] 1 Glove type 2-axis 3. Housing 4. Bearings (bearings for rubber glove manufacturing equipment)

Claims

1. A bearing for use in a rubber glove manufacturing apparatus for manufacturing rubber gloves by immersing a glove mold in a liquid rubber bath to form a rubber film on the glove mold, the bearing rotatably supporting the glove mold, the bearing is a resin sliding bearing made of an injection-molded article of a resin composition that uses a polyphenylene sulfide resin as a base resin, and that includes a layered mineral-based filler having a Mohs hardness of 3 or less, and a fibrous reinforcing material; the resin composition contains 30 to 60 parts by mass of the layered mineral filler and 30 to 50 parts by mass of the fibrous reinforcing material relative to 100 parts by mass of the polyphenylene sulfide resin, 1. A bearing for a rubber glove manufacturing apparatus, wherein the layered mineral filler contains at least talc.

2. 2. The bearing for a rubber glove manufacturing apparatus according to claim 1, wherein the resin composition further contains 10 to 30 parts by mass of a solid lubricant per 100 parts by mass of the polyphenylene sulfide resin.

3. 3. The bearing for a rubber glove manufacturing apparatus according to claim 1, wherein the layered mineral filler further contains at least one selected from the group consisting of mica, graphite, and kaolin.

4. 4. The bearing for a rubber glove manufacturing apparatus according to claim 1, wherein the fibrous reinforcing material includes at least one selected from the group consisting of glass fiber, carbon fiber, and aramid fiber.

5. 5. The bearing for a rubber glove manufacturing apparatus according to claim 1, wherein the bearing is an annealed injection molded article.

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