Roller and manufacturing method thereof

Abstract

The roller (1) has a bearing (40) and a resin tire (10) arranged on the outer periphery of the bearing (40). The tire (10) has a base portion (11) and an outer periphery portion (12) arranged concentrically with the bearing (40). The base portion (11) is welded to the bearing (40) side of the outer periphery portion (12) and has a hardness different from that of the outer periphery portion (12). The base portion (11) and the outer periphery portion (12) each independently contain a polymer having a hard segment and a soft segment which is a polyol unit. The base portion (11) and the outer periphery portion (12) further contain a polyether.

Description

[Technical field]

[0001] The present disclosure relates to rollers and methods of making same. [Background technology]

[0002] Escalators, walkways, and the like sometimes use rollers with plastic tires attached to the outer circumference of the bearing. Such rollers are exposed to harsh environments of high-speed rotation and high load, and are therefore required to have wear resistance and appropriate elasticity. From this perspective, it is known that the tire placed on the outer circumference of the bearing has a two-layer structure consisting of an outer circumference and a base portion inside the outer circumference, making the outer circumference soft and the base portion hard (for example, Patent Documents 1 and 2). Patent Documents 1 and 2 disclose that the outer circumference and the base portion can be welded together by supplying a molten resin material into a space formed between the bearing and the outer circumference to form the base portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-167871 A [Patent Document 2] JP 2015-55329 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a tire having two layers with different hardness as described above, there is a demand for further improvement in the welding strength between the layers.

[0005] The present disclosure aims to provide a roller with improved welding strength between an outer periphery of a tire and a base portion, and a manufacturing method thereof. [Means for solving the problem]

[0006] The roller of the present disclosure includes a bearing and a resin tire disposed on the outer periphery of the bearing. The tire includes a base portion and an outer periphery disposed concentrically with the bearing. The base portion is welded to the bearing side of the outer periphery and has a hardness different from that of the outer periphery. The base portion and the outer periphery each independently include a polymer having a hard segment and a soft segment that is a polyol unit. The base portion and the outer periphery further include a polyether.

[0007] The method for manufacturing a roller according to the present disclosure is a method for manufacturing a roller having a bearing and a resin tire arranged on the outer periphery of the bearing. The method for manufacturing a roller includes a step of forming a tire, in which a second layer is formed using a second resin composition so as to be welded to a first layer formed using a first resin composition. The first layer and the second layer are formed concentrically with respect to the bearing. The first resin composition and the second resin composition each independently contain a polymer having a hard segment and a soft segment that is a polyol unit. At least one of the first resin composition and the second resin composition further contains a polyether. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a roller having improved welding strength between the outer circumferential portion of a tire and a base portion. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a cross-sectional view of a roller according to the first embodiment. [Diagram 2] FIG. 11 is a cross-sectional view of a roller in the second embodiment. [Diagram 3] FIG. 2 is a perspective view showing test pieces obtained in the examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Embodiment 1 (roller) 1 is a cross-sectional view of a roller in embodiment 1. Roller 1 can be used under conditions of high speed rotation while being subjected to a high load. Roller 1 is used, for example, in escalators, walkways, elevators, etc.

[0011] The roller 1 has a bearing 40 and a resin tire 10 arranged on the outer periphery of the bearing 40. The tire 10 has a base portion 11 and an outer periphery portion 12 arranged concentrically with the bearing 40. The base portion 11 is welded to the bearing 40 side of the outer periphery portion 12, and has a hardness different from that of the outer periphery portion 12. The base portion 11 and the outer periphery portion 12 each independently contain a polymer (hereinafter sometimes referred to as "polymer (P)") having a hard segment and a soft segment that is a polyol unit. The base portion 11 and the outer periphery portion 12 further contain a polyether.

[0012] The bearing 40 is connected to a shaft provided on a cart (not shown). The bearing 40 supports the shaft so as to be freely rotatable around a rotation axis. The bearing 40 may be configured using a ball bearing or a roller bearing. The bearing 40 may be made of metal, for example. As shown in FIG. 1, the bearing 40 may include an inner ring 41, an outer ring 42 disposed on the outer periphery of the inner ring 41, and a rolling element 43 disposed between the inner ring 41 and the outer ring 42.

[0013] The tire 10 is an annular body and is arranged concentrically on the outer periphery of the bearing 40. The tire 10 can have a two-layer structure in which a base portion 11 and an outer periphery portion 12 are laminated in this order from the bearing 40 side. The base portion 11 and the outer periphery portion 12 are also annular bodies. The base portion 11 and the outer periphery portion 12 are formed using a resin such as a synthetic resin and are welded to each other. The base portion 11 and the outer periphery portion 12 are preferably integrated by welding the entire contact surface. The welded surface between the base portion 11 and the outer periphery portion 12 can be a curved surface without a step. The base portion 11 may be directly fixed to the bearing 40. For example, as shown in FIG. 1, the base portion 11 may be fixed to an outer ring 42 of the bearing 40.

[0014] The hardness of the base portion 11 may be different from the hardness of the outer peripheral portion 12, and may be either smaller or larger than the hardness of the outer peripheral portion 12. The hardness of the base portion 11 and the outer peripheral portion 12 can be compared based on the hardness measured with a durometer.

[0015] The base portion 11 may be required to have mechanical strength capable of withstanding high-speed rotation and high load applied to the roller 1 via the shaft. Therefore, it is preferable that the base portion 11 has a greater mechanical strength than the outer peripheral portion 12. The outer peripheral portion 12 can constitute the rolling surface of the roller 1 and can contact a rail or the like when the roller 1 rotates. Therefore, it is preferable that the outer peripheral portion 12 has better wear resistance and is softer than the base portion 11. From this viewpoint, it is preferable that the hardness (Ho) of the outer peripheral portion 12 measured with a durometer is smaller than the hardness (Hs) of the base portion 11 measured with a durometer. The hardness (Hs) of the base portion 11 and the hardness (Ho) of the outer peripheral portion 12 can be measured with a durometer described in JIS-K-7215. When comparing hardness, the hardness is compared based on hardness measured with the same type of durometer. In measuring hardness, it is preferable to disassemble the tire 10 into the base portion 11 and the outer peripheral portion 12 and measure the surface opposite to the welding surface. The hardness of the base part 11 and the outer periphery 12 may be measured on the side surface of the roller without disassembling the base part 11 and the outer periphery 12. When measuring the hardness, in addition to disassembling the base part 11 and the outer periphery 12, cutting may be performed as necessary. However, it is not preferable to use the cut surface for hardness measurement.

[0016] The hardness (Hs) of the base portion 11 and the hardness (Ho) of the outer peripheral portion 12 can be adjusted by one or more selected from the group consisting of the type and content of the polymer (P) contained in the base portion 11 and the outer peripheral portion 12, the type, number average molecular weight, and content of the polyether described below, and the type and content of the additives, etc. Different types of polymer (P) mean different types of structural units such as hard segments and soft segments and their content ratios.

[0017] The hardness (Hs) of the base portion 11 and the hardness (Ho) of the outer peripheral portion 12 may each independently be A60 or more and A100 or less, A70 or more and A99 or less, A75 or more and A98 or less, or A80 or more and A95 or less, as measured with a type A durometer described in JIS-K-7215.

[0018] The hardness (Hs) of the base portion 11 and the hardness (Ho) of the outer peripheral portion 12 may each independently be D20 or more and D90 or less, D65 or more and D85 or less, or D70 or more and D80 or less, as measured with a type D durometer described in JIS-K-7215.

[0019] The base portion 11 and the outer peripheral portion 12 contain a polymer (P). The polymer (P) has a hard segment and a soft segment in the molecular chain, and the soft segment is a polyol unit. The polymer (P) is preferably thermoplastic. The polymer (P) is, for example, a thermoplastic elastomer such as a thermoplastic polyurethane elastomer, a thermoplastic polyamide elastomer, and a thermoplastic polyester elastomer. The polymer (P) contained in the base portion 11 and the outer peripheral portion 12 is preferably both a thermoplastic polyurethane elastomer or a thermoplastic polyamide elastomer, and more preferably a thermoplastic polyurethane elastomer.

[0020] The hard segment may be, for example, one or more selected from the group consisting of a polyurethane unit, a polyamide unit, and a polyester unit. From the viewpoint of hydrolysis resistance in a high-temperature and high-humidity environment, the hard segment is preferably at least one of a polyurethane unit and a polyamide unit, and more preferably a polyurethane unit or a polyamide unit.

[0021] The polyurethane unit is a partial structure of polyurethane obtained by polymerization of diisocyanate and short-chain diol, and has a diisocyanate unit and a short-chain diol unit. The diisocyanate unit may be, for example, one or more units selected from the group consisting of methyl isocyanate unit, diphenylmethane diisocyanate unit, hexamethylene diisocyanate unit, and toluene diisocyanate unit. The short-chain diol unit may be, for example, one or more units selected from the group consisting of ethylene glycol unit, propylene glycol unit, and 1,4-butanediol unit.

[0022] The polyamide unit may be, for example, one or more units selected from the group consisting of nylon 6 units, nylon 66 units, nylon 11 units, and nylon 12 units.

[0023] The polyester unit is a partial structure of a polyester obtained by polymerizing an aromatic diester and a short-chain diol, and has an aromatic diester unit and a short-chain diol unit. An example of the aromatic diester unit is a polybutylene terephthalate unit. An example of the short-chain diol unit is one exemplified as the short-chain diol unit contained in the polyurethane unit.

[0024] The polyol unit which is the soft segment may be, for example, one or more selected from the group consisting of an ester-based polyol unit, an ether-based polyol unit, and a carbonate-based polyol unit. From the viewpoint of hydrolysis resistance and affinity with polyether in a high-temperature and high-humidity environment, the soft segment is preferably an ether-based polyol unit. The polyol unit may contain an ester-based polyol unit and an ether-based polyol unit, and in this case, may be a partial structure of a copolymer of an ester-based polyol and an ether-based polyol.

[0025] The ether-based polyol unit may be, for example, one or more units selected from the group consisting of a polypropylene glycol unit, a polyethylene glycol unit, a polytetramethylene glycol unit, a polytrimethylolpropanol unit, and a polypentaerythritol unit.

[0026] The ester-based polyol unit may be a partial structure of a polyol compound obtained by dehydration condensation of a carboxylic acid and a polyhydric alcohol, and may have a carboxylic acid unit and a polyhydric alcohol unit. The carboxylic acid unit may be at least one of an aliphatic carboxylic acid unit and an aromatic carboxylic acid unit. The carboxylic acid unit may be, for example, one or more units selected from the group consisting of a succinic acid unit, an adipic acid unit, a sepacic acid unit, an azelaic acid unit, a phthalic acid unit, and a dimer acid unit. The polyhydric alcohol unit may be, for example, one or more units selected from the group consisting of an ethylene glycol unit, a butylene glycol unit, and a propylene glycol unit.

[0027] The carbonate-based polyol unit may be a partial structure of a polyol compound obtained by the reaction of a carbonic acid diester with an alkanediol, and may have a carbonic acid diester unit and an alkanediol unit. The carbonic acid diester unit may be, for example, one or more units selected from the group consisting of a diphenyl carbonate unit, a dinaphthyl carbonate unit, a bis(diphenyl)carbonate unit, a dimethyl carbonate unit, a diethyl carbonate unit, and a dibutyl carbonate unit. The alkanediol unit may be, for example, one or more units selected from the group consisting of a 1,6-hexanediol unit, a 1,5-pentanediol unit, a 1,4-butanediol unit, and a 2-methyl-1,3-propanediol unit.

[0028] The polymer (P) preferably has a hard segment which is one or more selected from the group consisting of polyurethane units, polyamide units, and polyester units, and a soft segment which is one or more selected from the group consisting of ester-based polyol units, ether-based polyol units, and carbonate-based polyol units. From the viewpoints of hydrolysis resistance and affinity with polyether in a high-temperature, high-humidity environment, the polymer (P) is more preferably a polymer in which the hard segment is a polyurethane unit or polyamide unit, and the soft segment is an ether-based polyol unit.

[0029] The content of the polymer (P) in the base portion 11 is desirably 40 parts by mass or more and 100 parts by mass or less, based on 100 parts by mass of the base portion 11.

[0030] The content of the polymer (P) in the outer peripheral portion 12 is desirably 50 parts by mass or more and 100 parts by mass or less, assuming that the outer peripheral portion 12 is 100 parts by mass.

[0031] Both the base portion 11 and the outer peripheral portion 12 further contain a polyether. The polyether may be at least one of polyethylene glycol and polypropylene glycol.

[0032] The number average molecular weight of the polyether is preferably 1000 or more, more preferably 2000 or more, further preferably 3000 or more, and may be 4000 or more, and is usually 10000 or less. The number average molecular weight can be determined as a standard polystyrene-equivalent value by gel permeation chromatography (GPC), and can be measured by the method described in the examples below.

[0033] The polyether is preferably polyethylene glycol, more preferably polyethylene glycol having a number average molecular weight in the above range, for example, polyethylene glycol having a number average molecular weight of 1000 or more. The number average molecular weight of the polyethylene glycol of the polymer (P) may be in the range of the number average molecular weight of the polyether described above. When the number average molecular weight of the polyethylene glycol is in the above range, it is easily kneaded with the polymer (P).

[0034] The content of polyether in the base part 11 is from 0 to 20 parts by mass, preferably from more than 0 to 10 parts by mass, and may be from more than 0 to 5 parts by mass, relative to 100 parts by mass of the polymer (P) contained in the base part 11. If the content of polyether is too large, the mechanical strength of the base part 11 decreases, and the durability of the roller 1 tends to decrease.

[0035] The content of polyether in the outer peripheral portion 12 may be 0 to 50 parts by mass, preferably 10 to 50 parts by mass, and may be 10 to 30 parts by mass, relative to 100 parts by mass of the polymer (P) contained in the outer peripheral portion 12. If the content of polyether is too small, it becomes difficult to impart flexibility to the outer peripheral portion 12, and it tends to be difficult to obtain a roller 1 having flexibility on the rolling surface. If the content of polyether is too large, the mechanical strength of the outer peripheral portion 12 tends to decrease.

[0036] The hard segments of the polymer (P) have a higher melting point and a more rigid molecular chain structure than the soft segments, while the soft segments of the polymer (P) have a lower melting point and a more flexible molecular chain structure than the hard segments. Therefore, when the welded surface between the base portion 11 and the outer peripheral portion 12 is formed, it is considered that the soft segments of the polymer (P) melt and diffuse, forming a welded surface in which the soft segments of the polymer (P) are entangled with each other.

[0037] In addition, the polyether contained in the base part 11 and the outer peripheral part 12 also has a low melting point and a flexible molecular structure. When the welded surface between the base part 11 and the outer peripheral part 12 is formed, the polyether melts and diffuses together with the soft segment of the polymer (P), so it is considered that the soft segment is also entangled with the polyether at the welded surface. As a result, in the roller 1, peeling at the welded surface between the base part 11 and the outer peripheral part 12 can be suppressed and the weld strength can be improved, compared to a roller in which neither the base part nor the outer peripheral part contains polyether. In this way, it is considered that the improved weld strength of the welded surface between the base part 11 and the outer peripheral part 12 of the tire 10 can suppress wear of the surface that appears due to peeling of the welded surface when the roller 1 rolls, and suppress the generation of abnormal noise from the roller 1.

[0038] The base portion 11 and the outer peripheral portion 12 have different hardnesses. When different types of polymers (P) are used to achieve different hardnesses, polymers having different ratios of hard segments and soft segments may be used. In this case, the soft segments of the polymer (P) may be less entangled at the welded surface between the base portion 11 and the outer peripheral portion 12. Even in such a case, the polyether in the roller 1 can be entangled with the soft segments of the polymer (P), thereby improving the weld strength at the welded surface between the base portion 11 and the outer peripheral portion 12.

[0039] As described above, the tire 10 contains polyether in both the base portion 11 and the outer circumferential portion 12. The base portion 11 and the outer circumferential portion 12 may contain polyether entirely. Alternatively, one of the base portion 11 and the outer circumferential portion 12 may contain polyether entirely, and the other may contain polyether on the welding surface side, and may not contain polyether on the surface opposite to the welding surface.

[0040] More specifically, the outer peripheral portion 12 may contain polyether throughout its entirety, and the base portion 11 may contain polyether on the welding surface side, but not on the surface opposite the welding surface side. Alternatively, the base portion 11 may contain polyether throughout its entirety, and the outer peripheral portion 12 may contain polyether on the welding surface side, but not on the surface opposite the welding surface side. The presence of polyether in the base portion 11 and the outer peripheral portion 12 can be analyzed by, for example, gel permeation chromatography (GPC) or nuclear magnetic resonance (NMR).

[0041] The base portion 11 and the outer peripheral portion 12 may each independently further contain additives such as a filler, an antioxidant, an ultraviolet absorber, a hydrolysis-resistant stabilizer, and a flame retardant.

[0042] The filler can improve the rigidity of the base portion 11 and the outer peripheral portion 12. The filler may be contained in the base portion 11 and not in the outer peripheral portion 12. By blending a filler in the base portion 11 and improving the rigidity of the base portion 11, a roller 1 having excellent durability can be obtained. Examples of the filler include one or more selected from the group consisting of fibrous fillers such as glass fiber and cellulose fiber, and particulate fillers such as inorganic fillers.

[0043] The antioxidant may be, for example, one or more selected from the group consisting of phenol-based antioxidants, hindered phenol-based antioxidants, and hindered amine-based antioxidants.

[0044] Examples of the ultraviolet absorbing agent include one or more selected from the group consisting of benzotriazole-based ultraviolet absorbing agents, triazine-based ultraviolet absorbing agents, and benzophenone-based ultraviolet absorbing agents.

[0045] The hydrolysis-resistant stabilizer may, for example, be a compound having a carbodiimide group.

[0046] Examples of the flame retardant include one or more selected from the group consisting of phosphoric acid ester compounds such as tricresyl phosphate and triphenyl phosphate, and halogen-based compounds such as decabromodiphenyl ether and brominated polystyrene.

[0047] In the above, a case has been described in which tire 10 has a two-layer structure of base portion 11 and outer circumferential portion 12. However, as long as tire 10 has base portion 11 and outer circumferential portion 12, tire 10 may further have other layers.

[0048] As described above, since the polymer (P) has thermoplasticity, the base portion 11 and the outer peripheral portion 12 can be formed by injection molding. The method for producing the roller 1 is not particularly limited, but it can be produced, for example, by the production method described in the embodiment described later.

[0049] Embodiment 2 (roller) Fig. 2 is a cross-sectional view of a roller in embodiment 2. In Fig. 2, the same or corresponding members as in Fig. 1 are denoted by the same reference characters, and description thereof will not be repeated.

[0050] The roller 2 shown in Fig. 2 has a base portion 21 and an outer periphery 22 instead of the base portion 11 and the outer periphery 12 of the roller 1 shown in Fig. 1. In the roller 2 shown in Fig. 2, the shape of the welded surface between the base portion 21 and the outer periphery 22 is different from the shape of the welded surface between the base portion 11 and the outer periphery 12 of the roller 1 shown in Fig. 1. The base portion 21 and the outer periphery 22 can be similar to the base portion 11 and the outer periphery 12 shown in Fig. 1, except for the shape of the welded surface.

[0051] As shown in Fig. 2, the roller 2 has an uneven shape on the welded surface between the base part 21 and the outer periphery 22. The uneven shape may have steps, and the shape and number of the steps are not limited. By having the uneven shape on the welded surface, the welded area can be increased compared to when the welded surface does not have steps as shown in Fig. 1, and therefore the weld strength between the base part 21 and the outer periphery 22 can be improved. This makes it possible to further suppress peeling at the welded surface between the base part 21 and the outer periphery 22.

[0052] Embodiment 3 (Roller manufacturing method) The method for manufacturing a roller can be, for example, a method for manufacturing the above-mentioned rollers 1 and 2 (FIGS. 1 and 2). The rollers manufactured by the method for manufacturing a roller may be rollers other than rollers 1 and 2.

[0053] The roller has a bearing and a resin tire arranged on the outer periphery of the bearing. The method for manufacturing the roller includes a step of forming a tire (hereinafter sometimes referred to as "step (S)"). In step (S), a second layer is formed using a second resin composition so as to be welded to a first layer formed using a first resin composition. The first layer and the second layer are formed concentrically with respect to the bearing. The first resin composition and the second resin composition each independently contain a polymer having a hard segment and a soft segment which is a polyol unit. At least one of the first resin composition and the second resin composition further contains a polyether.

[0054] The bearing may be any of those described above. The tire may have, for example, the base portions 11 and 21 and the outer peripheral portions 12 and 22 described above. The polymer (P) and the polyether may be any of those described above.

[0055] In step (S), the second layer is formed so as to be welded to the first layer. In step (S), the second layer may be formed by injection molding of the second resin composition. In step (S), the first layer may be formed by using the first resin composition, or may be formed by injection molding of the first resin composition. For example, when the first layer is formed so as to be fixed to a bearing, the first layer may be formed by pouring a molten first resin composition onto the outer periphery of a bearing placed in a mold and molding it.

[0056] The second layer can be formed by, for example, placing the first layer in a mold and pouring a molten second resin composition so as to contact the first layer, thereby forming the second layer welded to the first layer. When the second layer is formed so as to be welded to the surface of the first layer opposite to the bearing side, the first layer or the first layer integrated with the bearing can be placed in a mold, and the molten second resin composition can be poured into the above-mentioned surface side of the first layer to form the second layer. When the second layer is placed between the bearing and the first layer, the bearing and the first layer can be concentrically placed in the mold so as to form a gap therebetween, and the molten second resin composition can be poured into the gap to form the second layer. The first layer and the second layer can be welded to each other by pouring the molten second resin composition so as to contact the first layer to form the second layer.

[0057] When a resin composition is heated and melted to be molded, the resin composition may shrink after curing. When a molten second resin composition is poured into the bearing side of the first layer to mold the second layer, the second layer is formed to shrink toward the bearing side, i.e., in a direction away from the first layer, and is easily peeled off from the first layer. Therefore, it is preferable to form the second layer so as to be welded to the surface of the first layer opposite the bearing side. As a result, the second layer is formed so as to shrink in a direction to adhere to the first layer, and therefore it is possible to suppress a decrease in the weld strength between the first layer and the second layer. For the same reason, it is preferable to form the first layer by pouring the first resin composition into the outer periphery of the bearing so that the first layer is formed so as to shrink in a direction to adhere to the bearing. As a result, the bearing can be firmly held by the first layer, and the first layer and the bearing can be integrated.

[0058] When the second layer is molded by pouring the second resin composition into the gap between the bearing and the first layer, it is possible to adjust the molding conditions to suppress shrinkage of the resin composition after curing. This can suppress a decrease in the welding strength between the first layer and the second layer, but since shrinkage of the resin composition after curing is suppressed, there is a risk that the holding strength of the bearing by the second layer will decrease. Therefore, as described above, it is preferable to mold the first layer on the outer periphery of the bearing and then mold the second layer on the outer periphery of this first layer (the surface opposite the bearing side).

[0059] As described above, the first resin composition and the second resin composition contain the polymer (P), and at least one of the first resin composition and the second resin composition contains a polyether. The soft segment of the polymer (P) has a lower melting point and is easier to melt than the hard segment, and the polyether also melts easily. When forming the second layer, the soft segment of the polymer (P) near the surface of the first layer that contacts the second layer can be melted by pouring the molten second resin composition so as to contact the first layer. At this time, if the first layer is formed by the first resin composition containing polyether, the polyether on the surface of the first layer also melts. As a result, it is presumed that the soft segment of the polymer (P) contained in the first layer, the soft segment of the polymer (P) contained in the second resin composition, and the polyether contained in at least one of the first layer and the second resin composition are mutually diffused and entangled. As a result, at the welding interface between the first layer and the second layer, the soft segments of the polymer (P) contained in the first layer and the soft segments of the polymer (P) contained in the second resin composition become entangled, and these soft segments become entangled with the polyether, which is thought to enable the first layer and the second layer to be welded with excellent welding strength.

[0060] The first layer to which the second layer is welded can become the base portion 11, 21 or the outer peripheral portion 12, 22 of the tire 10, 20 of the roller 1, 2 described above. For example, when the first layer to which the second layer is welded becomes the base portion 11, 21, the second layer becomes the outer peripheral portion 12, 22. When the first layer to which the second layer is welded becomes the outer peripheral portion 12, 22, the second layer becomes the base portion 11, 21. In this way, the first layer can become the base portion 11, 21 or the outer peripheral portion 12, 22 by welding with the second layer. Since the second layer is formed so as to be welded to the first layer, the formed second layer can become the base portion 11, 21 or the outer peripheral portion 12, 22 as it is. When the second layer is formed so as to be welded to the surface of the first layer opposite to the bearing side, the first layer to which the second layer is welded becomes the base portion 11, 21, and the second layer becomes the outer peripheral portion 12, 22. When the second layer is formed so as to be welded to the surface of the first layer on the bearing side, the first layer to which the second layer is welded becomes the outer circumferential portions 12, 22, and the second layer becomes the base portions 11, .

[0061] The first layer and the second layer may have different hardnesses. The hardness of the first layer may be greater or less than the hardness of the second layer. The hardnesses of the first layer and the second layer may be compared based on the hardness measured with a durometer, for example, a durometer as described in JIS-K-7215. When comparing hardnesses, the hardnesses are compared based on the hardness measured with the same type of durometer.

[0062] The hardness of the first layer and the second layer can be adjusted by one or more selected from the group consisting of the type and content of the polymer (P) contained in the first resin composition and the second resin composition, the type, number average molecular weight, and content of the polyether, and additives, etc. Examples of different types of polymers (P) include polymers having different constitutional units and polymers having different content ratios of hard segments and soft segments.

[0063] The first resin composition and the second resin composition may have the same composition, but preferably have different compositions. The first resin composition and the second resin composition have different compositions means that at least one of the types and contents of the components contained in the first resin composition and the second resin composition is different from each other, and preferably at least one of the types of the polymer (P) and the content of the polyether is different from each other.

[0064] When the first resin composition and the second resin composition contain the same type of polymer (P), it is preferable that only one of the first resin composition and the second resin composition contains polyether, and the other does not contain polyether. The polymer (P) contained in the first resin composition and the second resin composition may be a thermoplastic polyurethane elastomer, a thermoplastic polyamide elastomer, or a thermoplastic polyester elastomer. In this case, the content ratio of the hard segment and the soft segment of the thermoplastic elastomer contained in the first resin composition and the second resin composition may be different from each other. It is preferable that both the first resin composition and the second resin composition contain a thermoplastic polyurethane elastomer and have different polyether contents. In this case, the thermoplastic polyurethane elastomer may be the same elastomer or may be an elastomer having a different content ratio of the hard segment and the soft segment. Also, only one of the first resin composition and the second resin composition may contain polyether.

[0065] The hardness of the first layer and the second layer may be, independently, A60 or more and A100 or less, A70 or more and A99 or less, A75 or more and A98 or less, or A80 or more and A95 or less, as measured with a type A durometer described in JIS-K-7215.

[0066] The hardness of the first layer and the second layer may each independently be D20 or more and D90 or less, D65 or more and D85 or less, or D70 or more and D80 or less, as measured with a type D durometer described in JIS-K-7215.

[0067] The content of the polymer (P) in the first resin composition is desirably 40 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the first resin composition.

[0068] The content of the polymer (P) in the second resin composition is desirably 50 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the second resin composition.

[0069] At least one of the first resin composition and the second resin composition further contains a polyether. The polyether may be contained in only one of the first resin composition and the second resin composition, or may be contained in both of them.

[0070] When the hardness of the first layer is greater than that of the second layer, the content of polyether in the first resin composition may be 0 to 20 parts by mass, preferably more than 0 to 10 parts by mass, and more than 0 to 5 parts by mass, relative to 100 parts by mass of the polymer (P). The content of polyether in the second resin composition may be 0 to 50 parts by mass, preferably more than 10 to 50 parts by mass, and more than 10 to 30 parts by mass, relative to 100 parts by mass of the polymer (P). When the content of polyether is smaller, the first and second layers tend to be harder, and when the content of polyether is larger, the first and second layers tend to be softer. The content of polyether in the first and second resin compositions may be adjusted according to the properties required for the first and second layers.

[0071] When the hardness of the first layer is lower than that of the second layer, the content of the polyether in the first resin composition may be 0 to 50 parts by mass, preferably 10 to 50 parts by mass, or 10 to 30 parts by mass, relative to 100 parts by mass of the polymer (P). The content of the polyether in the second resin composition may be 0 to 20 parts by mass, preferably more than 0 to 10 parts by mass, or more than 0 to 5 parts by mass, relative to 100 parts by mass of the polymer (P).

[0072] The first resin composition and the second resin composition may each independently further contain additives such as a filler, an antioxidant, an ultraviolet absorber, a hydrolysis-resistant stabilizer, and a flame retardant, etc. Examples of these additives include those described above.

[0073] When the first resin composition and the second resin composition contain polyether, the first resin composition and the second resin composition may be a mixture obtained by stirring and mixing a pellet-shaped polymer (P) and a powdered or liquid polyether, or may be a kneaded product obtained by melting and kneading the polymer (P) and the polyether. The kneaded product may be molded into a pellet shape. The first resin composition and the second resin composition as a mixture can be formed into the first layer and the second layer by molding the kneaded product obtained by heating and melting the kneaded product. The first resin composition and the second resin composition as a kneaded product can be formed into the first layer and the second layer by heating and melting the kneaded product. EXAMPLES

[0074] The present disclosure will be described in more detail below with reference to examples and comparative examples, but the present disclosure is not limited to these examples.

[0075] [Examples 1 to 4, Comparative Examples 1 and 2] FIG. 3 is a perspective view that typically shows the test pieces obtained in the examples and the comparative examples.

[0076] A first resin composition and a second resin composition containing each component in the content shown in Table 1 were prepared. The first resin composition was melt-molded to form a plate-like first layer 31 having a rectangular shape in plan view and a length of 75 mm, a width of 10 mm, and a thickness of 4 mm. Next, the first layer 31 was placed in a mold, and a plate-like second layer 32 having a rectangular shape in plan view and a length of 75 mm, a width of 10 mm, and a thickness of 4 mm was molded so as to be welded to one short side of the first layer 31, thereby obtaining a strip-like test piece 30 as shown in FIG. 3. When evaluating the weld strength, the dimensions of the test piece are not limited to the above, and any shape can be used.

[0077] In Table 1, each symbol represents the following component. (Polymer (P)) P-1: Thermoplastic polyurethane elastomer (BASF "Elastollan 1174D") P-2: Thermoplastic polyurethane elastomer (BASF "Elastollan 1180A") P-3: Thermoplastic polyurethane elastomer (BASF "Elastollan ET385")

[0078] (Polyether) B-1: Polyethylene glycol (Tokyo Chemical Industry Co., Ltd. "Polyethylene Glycol 4000", number average molecular weight: 4000)

[0079] [Measurement of number average molecular weight] The values ​​were measured as standard polystyrene equivalent values ​​by gel permeation chromatography (GPC). Specifically, a high-speed GPC device ("HLC-8320" manufactured by Tosoh Corporation) was used, and the following columns and mobile phases were used at a column temperature of 25°C. Column: TSKgel ODS-80Ts (4.6 mmφ × 25 cm) (Tosoh) Mobile phase: Water / acetonitrile Column temperature: 40℃ Flow rate: 1mL / min Sample concentration: 1mg / mL Injection volume: 10μL

[0080] [Durometer hardness measurement] The durometer hardness of the first and second layers of the test specimens was measured at 25°C using a type A or type D durometer as specified in JIS-K-7215. The results are shown in Table 1. In Table 1, the letters "A" and "D" before the values ​​indicate the type of durometer used in the measurement. When measurements were performed using both type A and type D durometers, both values ​​are shown in Table 1.

[0081] [Measurement of welding strength] A tensile test was performed using a tensile testing machine ("AG-X20kN" manufactured by Shimadzu Corporation) with a gripping distance of 50 mm and a pulling speed of 50 mm / min, in which the first layer 31 and the second layer 32 were pulled in opposite directions to each other, and the breaking strength [MPa] was measured when the first layer 31 and the second layer 32 of the test piece 30 broke at the welded surface. The tensile test was performed under conditions of 25°C.

[0082] [Table 1]

[0083] From the results shown in Table 1, it can be seen that as the content of polyether in the second resin composition increases, the hardness of the second layer decreases, but the weld strength of the test piece improves. From the comparison between Example 3 and Comparative Example 1, and between Example 4 and Comparative Example 2, it can be seen that even if the hardness of the second layer is about the same, the weld strength can be improved by including polyether in the test piece.

[0084] The embodiments and examples disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0085] 1, 2 roller, 10 tire, 11 base portion, 12 outer periphery, 20 tire, 21 base portion, 22 outer periphery, 30 test piece, 31 first layer, 32 second layer, 40 bearing, 41 inner ring, 42 outer ring, 43 rolling element.

Claims

1. A bearing and a resin tire disposed on an outer periphery of the bearing, The tire has a base portion and an outer circumferential portion arranged concentrically with respect to the bearing, the base portion is welded to the bearing side of the outer circumferential portion and has a hardness different from that of the outer circumferential portion, the base portion and the outer peripheral portion each independently contain a polymer having a hard segment and a soft segment which is a polyol unit; The roller, wherein the base portion and the outer periphery further comprise a polyether.

2. 2. The roller according to claim 1, wherein the hardness (Ho) of the outer periphery is less than the hardness (Hs) of the base portion as measured by a durometer.

3. 3. The roller according to claim 1 or 2, wherein the polyether is a polyethylene glycol having a number average molecular weight of 1000 or more.

4. The hard segment is a polyurethane unit or a polyamide unit, The roller according to claim 1 or 2, wherein the soft segment is an ether-based polyol unit.

5. The roller according to claim 1 or 2, wherein the welded surface between the base portion and the outer circumferential portion has an uneven shape.

6. A method for manufacturing a roller having a bearing and a resin tire disposed on an outer periphery of the bearing, comprising: forming the tire; The step includes forming a second layer using a second resin composition so as to be welded to the first layer formed using the first resin composition, the first layer and the second layer are formed concentrically with respect to the bearing, The first resin composition and the second resin composition each independently contain a polymer having a hard segment and a soft segment which is a polyol unit, At least one of the first resin composition and the second resin composition further contains a polyether.

7. The method for manufacturing a roller according to claim 6 , wherein the step of forming the tire includes forming the second layer so as to be fused to a surface of the first layer opposite to the bearing side.

8. The first resin composition is injection molded to form the first layer; The method for manufacturing a roller according to claim 6 or 7, wherein the second layer is formed by injection molding the second resin composition.

9. The method of claim 6 or 7, wherein the first layer has a different hardness than the second layer.

10. The method for manufacturing a roller according to claim 6 or 7, wherein only one of the first resin composition and the second resin composition contains a polyether.

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