Non-pneumatic tire manufacturing method

Abstract

To provide manufacturing method for non-pneumatic tires that can improve the pigment dispersion of thermosetting resin compositions and the moldability of the support structure.SOLUTION: The method for manufacturing a non-pneumatic tire 1 is a method for manufacturing a non-pneumatic tire 1 provided with a support structure 10. The method of manufacturing the non-pneumatic tire 1 comprises the steps of: mixing the main agent, the hardener, and the pigment at a temperature at which the viscosity of the hardener is between 0.8 Pa-s and 2.6 Pa-s; obtaining the thermosetting resin composition by stirring the mixture using a revolving-centrifugal mixer at a revolving centrifugal force of 1200 N or more, a revolving centrifugal force of 350 N or more, and an agitation time of 60 seconds to 90 seconds or less; and obtaining at least a portion of the support structure 10 by thermally curing the thermosetting resin composition.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a non-pneumatic tire. [Background technology]

[0002] A non-pneumatic tire is known that includes a support structure that supports a load from a vehicle and a tread that is located radially outward of the support structure and extends along the tire circumferential direction. In this case, it is desired to improve the durability of the non-pneumatic tire.

[0003] Patent Document 1 describes a method for manufacturing a non-pneumatic tire. The method for manufacturing a non-pneumatic tire includes the steps of preparing a thermosetting resin stock solution having a liquid viscosity of 600 to 6000 mPa·s, stirring and degassing the prepared thermosetting resin stock solution, and injecting the degassed thermosetting resin stock solution into a mold and curing it to mold a support structure. In the step of stirring and degassing the thermosetting resin stock solution, a rotation-revolution mixer is used to stir the thermosetting resin stock solution under conditions of a revolution speed of 700 rpm or more, a rotation speed of 400 rpm or more, and a stirring time of 1 minute or more. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-103495 A Summary of the Invention [Problem to be solved by the invention]

[0005] Here, when a pigment is added to the raw material liquid in order to improve the design of the non-pneumatic tire, the pigment dispersibility may decrease. In this case, when the stirring time of the raw material liquid is extended in order to improve the pigment dispersibility of the raw material liquid, a part of the thermosetting resin hardens, and the moldability of the support structure decreases. Note that when the pigment dispersibility of the raw material liquid decreases, the design may decrease and the breaking strength of the support structure may decrease.

[0006] An object of the present invention is to provide a method for producing a non-pneumatic tire that can improve the pigment dispersibility of a thermosetting resin composition and the moldability of a support structure. [Means for solving the problem]

[0007] One aspect of the present invention is a method for producing a non-pneumatic tire provided with a support structure, the method including the steps of mixing a base agent, a curing agent, and a pigment at a temperature at which the viscosity of the curing agent is 0.8 Pa·s or more and 2.6 Pa·s or less, and stirring the mixture using a planetary centrifugal mixer under conditions of a revolution centrifugal force of 1200 N or more, a rotation centrifugal force of 350 N or more, and a stirring time of 60 seconds or more and 90 seconds or less to obtain a thermosetting resin composition, and thermally curing the thermosetting resin composition to obtain at least a portion of the support structure. Effect of the Invention

[0008] According to the present invention, it is possible to provide a method for producing a non-pneumatic tire that can improve the pigment dispersibility of a thermosetting resin composition and the moldability of a support structure. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a side view showing an example of a non-pneumatic tire. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Diagram 3] 3 is a partial perspective view of a non-pneumatic tire, as seen obliquely from the portion shown in FIG. 2. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] [Manufacturing method of non-pneumatic tires] The method for producing a non-pneumatic tire of this embodiment is a method for producing a non-pneumatic tire having a support structure described below. The method for producing a non-pneumatic tire of this embodiment includes a step of mixing a base agent, a curing agent, and a pigment at a temperature at which the viscosity of the curing agent is 0.8 Pa·s or more and 2.6 Pa·s or less, and stirring the mixture using a rotation-revolution mixer under conditions of a revolution centrifugal force of 1200 N or more, a rotation centrifugal force of 350 N or more, and a stirring time of 60 seconds or more and 90 seconds or less to obtain a thermosetting resin composition, and a step of thermally curing the thermosetting resin composition to obtain a support structure.

[0012] When the base material, the curing agent, and the pigment are mixed at a predetermined temperature, for example, the base material and the curing agent that have been degassed at a predetermined temperature are used. When the content of the pigment in the thermosetting resin composition is small, the temperature during mixing is not substantially affected, so there is no need to adjust the temperature of the pigment.

[0013] Instead of obtaining the support structure, a part of the support structure may be obtained. Examples of the part of the support structure include an inner annular portion, an outer annular portion, and spokes. The non-pneumatic tire may further include, for example, a member corresponding to a tread, a reinforcing layer, and a member for fitting to an axle or a rim.

[0014] In this embodiment, the mixture is defoamed during mixing using a planetary centrifugal mixer. The viscosity of the curing agent is 0.8 Pa·s or more and 2.6 Pa·s or less, and preferably 0.8 Pa·s or more and 2.0 Pa·s or less. If the viscosity of the curing agent is less than 0.8 Pa·s, a part of the thermosetting resin is cured, and the moldability of the support structure is reduced, and if the viscosity exceeds 2.6 Pa·s, the pigment dispersibility of the thermosetting resin composition and the moldability of the support are reduced.

[0015] If the revolution centrifugal force during stirring is less than 1200N, the pigment dispersibility of the thermosetting resin composition decreases. Here, the revolution centrifugal force during stirring is, for example, 1000N or less. If the rotation centrifugal force during stirring is less than 350N, the pigment dispersibility of the thermosetting resin composition decreases. Here, the rotation centrifugal force during stirring is, for example, 320N or less. If the stirring time is less than 60 seconds, the pigment dispersibility of the thermosetting resin composition decreases, and if it exceeds 90 seconds, the moldability of the support structure decreases. Here, the breaking strength of the support structure is preferably 40MPa or more, more preferably 50MPa or more.

[0016] The revolution centrifugal force F and rotation centrifugal force f can be calculated using the following formulas. F = mRω1 2 f=mrω2 2 (In the formula, m is the total mass of the base resin, hardener, and pigment [kg], R is the revolution radius [m], ω1 is the revolution angular velocity [rad / s], r is the rotation radius [m], and ω2 is the rotation angular velocity [rad / s].)

[0017] Moreover, the angular velocities ω1 and ω2 are calculated by the following formula. ω1=2πN1 / 60 ω2=2πN2 / 60 (In the formula, N1 is the revolution speed [rpm], and N2 is the rotation speed [rpm].)

[0018] The revolution speed during stirring is not particularly limited, but is, for example, 450 rpm or more and 1000 rpm or less. The rotation speed during stirring is not particularly limited, but is, for example, 450 rpm or more and 1000 rpm or less.

[0019] The content of the pigment in the thermosetting resin composition is preferably 0.04% by mass or more and 0.08% by mass or less, and more preferably 0.04% by mass or more and 0.06% by mass or less. When the content of the pigment in the thermosetting resin composition is 0.04% by mass or more, the design of the non-pneumatic tire of the present embodiment is improved, and when it is 0.08% by mass or less, the pigment dispersibility of the thermosetting resin composition is improved.

[0020] The pigment is not particularly limited as long as it is capable of improving the design of the non-pneumatic tire of the present embodiment, and examples thereof include phthalocyanine turquoise, phthalocyanine cyan, phthalocyanine blue, Victoria blue, pigment blue, Prussian blue, cobalt blue, ultramarine blue, phthalocyanine green, pigment green, fast green lake, nitroso green, nickel azo yellow, phthalochrome green, cadmium green, chrome green, ultramarine green, pigment yellow, arylide yellow, diarylide yellow, azo yellow, Hansa Yellow, Benzidine Yellow, Permanent Yellow, Cadmium Yellow, Naphthol Red, Pigment Red, Toluidine Red, Toluidine Maroon, Arylide Maroon, Permanent Red, Rhodamine, Titanium White, Lead White, Lead Sulfate White, Zinc Oxide White, Zinc Sulfide White, Strontium Sulfide, Barium Carbonate, Zirconium Oxide, Tin Oxide, Gypsum, Talc, Silica, Lead Phosphate, Lamp Black, Mars Black, Aniline Black, Carbon Black, Pine Black, Graphite, Cobalt Black, Manganese Black, Zinc Sulfide, and Manganese Ferric Oxide.

[0021] The cured product of the thermosetting resin constituting the support structure is not particularly limited, but may be, for example, polyurethane. Hereinafter, a case where the cured product of the thermosetting resin constituting the support structure is polyurethane will be described.

[0022] The base preferably contains a low molecular weight polyol. The low molecular weight polyol is not particularly limited as long as it has a plurality of hydroxyl groups, and examples of the low molecular weight polyol include aliphatic diols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, methyloctanediol, and 1,9-nonanediol; alicyclic diols such as 1,4-cyclohexanediol; 1,4-bis(β-hydroxyethoxy)benzene, hydroquinone, resorcinol, chlorohydroquinone, bromohydroquinone, methylhydroquinone, phenylhydroquinone, and methylhydroquinone. Examples of the aromatic diols include 4,4'-butanediol, 4,4'-butanediol, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,2-bis(4-hydroxyphenoxy)ethane, 1,4-dihydroxynaphthalene, and 2,6-dihydroxynaphthalene, and more. Among these, 1,4-butanediol is preferred.

[0023] The base material preferably further contains polyether polyol. Examples of polyether polyol include polytetramethylene glycol, polyethylene glycol, and polypropylene glycol, and two or more of them may be used in combination. Among these, polytetramethylene glycol is preferred. The number average molecular weight of polyether polyol is, for example, 200 or more and 3000 or less.

[0024] The base material may further contain polyester polyol. Examples of polyester polyols include polyadipate glycol, polyphthalic acid glycol, polycarbonate diol, and polycaprolactone polyol. The number average molecular weight of the polyester polyol is, for example, 200 or more and 3000 or less.

[0025] The curing agent preferably contains a polyisocyanate. The polyisocyanate is not particularly limited as long as it has a plurality of isocyanate groups, and examples thereof include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, polymeric MDI, carbodiimide-modified MDI, 1,5-naphthalene diisocyanate, 1,4-phenylene diisocyanate, 1,3-phenylene diisocyanate, 1, Examples of the diisocyanates include aromatic diisocyanates such as 4-xylylene diisocyanate and 1,3-xylylene diisocyanate, aliphatic diisocyanates such as ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate and 1,6-hexamethylene diisocyanate, and alicyclic diisocyanates such as 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate and norbornane diisocyanate, and two or more of them may be used in combination. Among these, 1,4-phenylene diisocyanate is preferred.

[0026] The isocyanate index of the thermosetting resin composition is not particularly limited, but is, for example, 1.00 to 1.10, where the isocyanate index is the molar ratio of the isocyanate groups of the curing agent to the hydroxyl groups of the base resin.

[0027] [Non-pneumatic tires] FIG. 1 shows an example of a non-pneumatic tire. The non-pneumatic tire 1 includes a support structure 10 and a tread 50. The support structure 10 supports a load from a vehicle. The tread 50 is located outside the support structure 10 in the tire radial direction X and extends along the tire circumferential direction C. The support structure 10 includes an inner annular portion 20, an outer annular portion 30 arranged coaxially with the inner annular portion 20 outside the inner annular portion 20 in the tire radial direction X, and a plurality of spokes 40 that connect the inner annular portion 20 and the outer annular portion 30 and are arranged along the tire circumferential direction C. Details of the structure of the non-pneumatic tire 1 will be described later.

[0028] The inner annular portion 20, the outer annular portion 30, and the spokes 40 are obtained by thermally curing the above-mentioned thermosetting resin composition. For example, the thermosetting resin composition is injected into a mold and then thermally cured. When the inner annular portion 20, the outer annular portion 30, and the spokes 40 are made of the same material, the inner annular portion 20, the outer annular portion 30, and the spokes 40 can be integrally molded, for example, by a cast molding method.

[0029] The inner annular portion 20, the outer annular portion 30, and a part of the spokes 40 may be obtained by thermally curing the above-mentioned thermosetting resin composition. In this case, the remaining parts of the inner annular portion 20, the outer annular portion 30, and the spokes 40 are made of a known elastic material.

[0030] The non-pneumatic tire 1 is obtained by vulcanizing and bonding the support structure 10 and the rubber composition for the tread using, for example, a vulcanizing adhesive. Specifically, first, the outer peripheral surface of the outer annular portion 30 of the support structure 10 is roughened. This increases the adhesion between the support structure 10 and the tread 50. The method for roughening the outer peripheral surface of the outer annular portion 30 is not particularly limited, but may be, for example, buffing. Next, a vulcanizing adhesive is applied to the outer peripheral surface of the roughened outer annular portion 30 and dried. Next, a rubber composition for the tread is wound around the outer peripheral surface of the outer annular portion 30 to which the vulcanizing adhesive has been applied, and then vulcanizing and bonding is performed.

[0031] The rubber composition for tread contains, for example, natural rubber and carbon black, and may further contain sulfur, silica, etc. Here, the rubber composition for tread may contain synthetic rubber such as polyisoprene rubber, styrene butadiene rubber, etc. together with the natural rubber or instead of the natural rubber.

[0032] The structure of the non-pneumatic tire 1 will be described in detail below. Fig. 1 is a side view of the non-pneumatic tire 1 as viewed from a direction parallel to the tire rotation axis (tire meridian), i.e., from the direction along the front-to-back direction of the paper in Fig. 1. The non-pneumatic tire 1 shown in Fig. 1 is in an unloaded state. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. Fig. 3 is a partial perspective view of the non-pneumatic tire 1 as viewed obliquely from the portion shown in Fig. 2.

[0033] In Fig. 1 and 3, C indicates the tire circumferential direction. In Fig. 1 to 3, X indicates the tire radial direction. In Fig. 2 and 3, Y indicates the tire width direction. In Fig. 1, the tire width direction Y is the front-to-back direction of the page. In Fig. 2, E indicates the tire equatorial plane. In Fig. 2, the tire circumferential direction C is the front-to-back direction of the page.

[0034] The tire circumferential direction C is a direction around the tire rotation axis and is the same direction as the direction in which the non-pneumatic tire 1 rotates. The tire radial direction X is a direction perpendicular to the tire rotation axis. The tire width direction Y is a direction parallel to the tire rotation axis. In Figs. 2 and 3, one side of the tire width direction Y is indicated as Y1, and the other side of the tire width direction Y is indicated as Y2. The tire equatorial plane E shown in Fig. 2 is a plane perpendicular to the tire rotation axis and located at the center of the tire width direction Y.

[0035] The thicknesses of the inner annular portion 20 and the outer annular portion 30 are dimensions in the tire radial direction X. The widths of the inner annular portion 20 and the outer annular portion 30 are dimensions in the tire width direction Y shown in FIG.

[0036] The inner annular portion 20 is an annular portion along the tire circumferential direction C that constitutes the inner circumferential portion of the non-pneumatic tire 1. The thickness and width of the inner annular portion 20 are set to be constant in order to improve uniformity. A tire wheel is placed in the space on the inner circumferential side of the inner annular portion 20. The inner circumferential portion of the inner annular portion 20 is fitted and attached to the outer circumferential portion of the rim of the tire wheel. The inner annular portion 20 is attached to the rim, and the non-pneumatic tire 1 is attached to the tire wheel. The inner circumferential surface of the inner annular portion 20 may be provided with a fitting portion composed of a protrusion, a groove, etc. for fitting with the rim.

[0037] The inner annular portion 20 transmits the rotation of the tire wheel to the spokes 40 and the outer annular portion 30. The thickness of the inner annular portion 20 is determined from the viewpoint of obtaining weight reduction and durability while satisfying the function of sufficiently transmitting rotational force to the spokes 40. The thickness of the inner annular portion 20 is not particularly limited, but is preferably, for example, 2% to 7% of the tire cross-sectional height H shown in Fig. 2, and more preferably 3% to 6%.

[0038] The inner diameter of the inner annular portion 20 is determined according to the dimensions of the rim of the tire wheel on which the non-pneumatic tire 1 is mounted, the use of the vehicle, etc. For example, when assuming a replacement for a general pneumatic tire, the inner diameter of the inner annular portion 20 may be, for example, a dimension of 250 mm or more and 500 mm or less, but is not limited thereto.

[0039] The width of the inner annular portion 20 is appropriately determined depending on the application of the vehicle on which the non-pneumatic tire 1 is mounted, the length of the axle, etc. For example, when assuming a replacement for a general pneumatic tire, the width of the inner annular portion 20 may be, but is not limited to, a dimension of 100 mm or more and 300 mm or less.

[0040] The outer annular portion 30 is an annular portion along the tire circumferential direction C that constitutes the outer periphery of the non-pneumatic tire 1. The outer annular portion 30 is disposed on the outer periphery of the inner annular portion 20 and concentric with the inner annular portion 20. The thickness and width of the outer annular portion 30 are set to be constant in order to improve uniformity.

[0041] The outer annular portion 30 transmits the rotation of the inner annular portion 20 and the spokes 40 to the road surface via the tread 50. The thickness of the outer annular portion 30 is determined from the viewpoint of obtaining light weight and durability while fulfilling the function of sufficiently transmitting rotational force from the spokes 40 to the road surface. The thickness of the outer annular portion 30 is not particularly limited, but is preferably, for example, 2% to 7% of the tire cross-sectional height H shown in Fig. 2, and more preferably 2% to 5%.

[0042] The inner diameter of the outer annular portion 30 is appropriately determined depending on the dimensions of the rim of the tire wheel on which the non-pneumatic tire 1 is mounted, the use of the vehicle, etc. For example, when assuming a replacement for a general pneumatic tire, the inner diameter of the outer annular portion 30 may be, but is not limited to, a dimension of 420 mm or more and 750 mm or less.

[0043] The width of the outer annular portion 30 is appropriately determined depending on the application of the vehicle on which the non-pneumatic tire 1 is mounted, etc. For example, when assuming a replacement for a general pneumatic tire, the width of the outer annular portion 30 may be, but is not limited to, a dimension of 100 mm or more and 300 mm or less.

[0044] The multiple spokes 40 connect the inner annular portion 20 and the outer annular portion 30. The inner annular portion 20 and the outer annular portion 30 connected by the multiple spokes 40 are arranged concentrically with each other. Each of the multiple spokes 40 is arranged independently along the tire circumferential direction C. As shown in Fig. 1, when the non-pneumatic tire 1 is in an unloaded state, the multiple spokes 40 extend linearly in the radial direction approximately parallel to the tire radial direction X in a side view.

[0045] 2 and 3, the multiple spokes 40 of this embodiment include multiple first spokes 41 and multiple second spokes 42. The extension direction of both the first spokes 41 and the second spokes 42 is not parallel to the tire radial direction X when viewed in a direction along the tire circumferential direction C. The first spokes 41 are inclined toward one side in the tire axial direction, i.e., the tire width direction Y. The second spokes 42 are inclined toward the opposite side to the first spokes 41. The first spokes 41 and the second spokes 42 are arranged alternately in the tire circumferential direction C.

[0046] 2 and 3, the first spoke 41 extends at an angle from the Y1 side, which is one side in the tire width direction Y of the outer annular portion 30, toward the Y2 side, which is the other side in the tire width direction Y of the inner annular portion 20. The second spoke 42 extends at an angle from the Y2 side, which is the other side in the tire width direction Y of the outer annular portion 30, toward the Y1 side, which is one side in the tire width direction Y of the inner annular portion 20.

[0047] The inclination angles of the first spokes 41 and the second spokes 42 are the same. Therefore, the first spokes 41 and the second spokes 42 adjacent to each other in the tire circumferential direction C are arranged in a substantially X-shape when viewed from a direction along the tire circumferential direction C. As shown in Fig. 2, the first spokes 41 and the second spokes 42 are inclined at an angle θ with respect to the tire width direction Y, and the angle θ is preferably, for example, greater than or equal to 30° and less than or equal to 60°.

[0048] 2, the first spokes 41 and the second spokes 42 have the same shape and are symmetrical with respect to the tire equatorial plane E when viewed in a direction along the tire circumferential direction C. Therefore, in the following, when there is no need to distinguish between the first spokes 41 and the second spokes 42 and they can be described together, the first spokes 41 and the second spokes 42 will be collectively referred to as spoke 40.

[0049] The spokes 40 are plate-shaped and extend obliquely from the inner annular portion 20 toward the outer annular portion 30 at the angle θ as described above. As shown in FIG. 3, the spokes 40 have a thickness t along the tire circumferential direction that is smaller than the width w, and the direction of the thickness t is along the tire circumferential direction C. That is, the spokes 40 are formed in a plate shape extending along the plane of the tire radial direction X and the tire width direction Y. Note that the width w here is a dimension in a direction perpendicular to the inclined direction in which the spokes 40 extend when the spokes 40 are viewed from the direction along the tire circumferential direction C, as also shown in FIG. 2. In this embodiment, the thickness t of all the spokes 40 is the same. The width w of all the spokes 40 is the same.

[0050] Since the spokes 40 are long and plate-like, even if the plate thickness t is thin, the durability of the spokes 40 can be improved by setting the plate width w wide. Furthermore, by reducing the plate thickness t and increasing the number of spokes 40, the interval between adjacent spokes 40 in the tire circumferential direction C can be reduced while maintaining the rigidity of the entire non-pneumatic tire 1. This distributes the ground contact pressure by the spokes 40 when the tire rolls, and the ground contact pressure can be reduced.

[0051] Although the spokes 40 are parallel to the tire radial direction X in a side view, the spokes 40 may be disposed obliquely with respect to the tire radial direction X so as to intersect with the tire radial direction X in a side view.

[0052] 2 and 3, the first spoke 41 has a first inner connection portion 411 connected to the tire width direction Y2 side of the inner annular portion 20, and a first outer connection portion 412 connected to the tire width direction Y1 side of the outer annular portion 30. The second spoke 42 has a second inner connection portion 421 connected to the tire width direction Y1 side of the inner annular portion 20, and a second outer connection portion 422 connected to the tire width direction Y2 side of the outer annular portion 30. Each of the first outer connection portion 412 and the second outer connection portion 422 is an example of a connection portion of the spoke 40 connected to the outer annular portion 30 in this embodiment.

[0053] 2, the first inner connection portion 411 of the first spoke 41 has a shape that widens in the tire width direction Y as it approaches the inner annular portion 20. A side surface 411a on the tire width direction Y2 side of the first inner connection portion 411 extends while gently curving to an end portion 20b on the tire width direction Y2 side of the inner annular portion 20. A side surface 411b on the tire width direction Y1 side of the first inner connection portion 411 extends while curving toward the tire width direction Y1 side to the position of the tire equatorial plane E of the inner annular portion 20.

[0054] The first outer connection portion 412 of the first spoke 41 has a shape similar to that of the first inner connection portion 411, and has a shape that widens in the tire width direction as it approaches the outer annular portion 30. A side surface 412a on the tire width direction Y1 side of the first outer connection portion 412 extends while gently curving to an end portion 30a on the tire width direction Y1 side of the outer annular portion 30. A side surface 412b on the tire width direction Y2 side of the first outer connection portion 412 extends while curving toward the tire width direction Y2 side to the position of the tire equatorial plane E of the outer annular portion 30.

[0055] The first inner connecting portion 411 is provided in a half area of ​​the inner annular portion 20 on the tire width direction Y2 side. The first outer connecting portion 412 is provided in a half area of ​​the outer annular portion 30 on the tire width direction Y1 side.

[0056] 2, the second inner connection portion 421 of the second spoke 42 has a shape that widens in the tire width direction Y as it approaches the inner annular portion 20. A side surface 421a on the tire width direction Y1 side of the second inner connection portion 421 extends while gently curving to an end portion 20a on the tire width direction Y1 side of the inner annular portion 20. A side surface 421b on the tire width direction Y2 side of the second inner connection portion 421 extends while curving toward the tire width direction Y2 side to the position of the tire equatorial plane E of the inner annular portion 20.

[0057] The second outer connection portion 422 of the second spoke 42 has a shape similar to that of the second inner connection portion 421, and has a shape that widens along the tire width direction as it approaches the outer annular portion 30. A side surface 422a on the tire width direction Y2 side of the second outer connection portion 422 extends while gently curving to an end portion 30b on the tire width direction Y2 side of the outer annular portion 30. A side surface 422b on the tire width direction Y1 side of the second outer connection portion 422 extends while curving toward the tire width direction Y1 side to the position of the tire equatorial plane E of the outer annular portion 30.

[0058] The second inner connecting portion 421 is provided in a half area of ​​the inner annular portion 20 on the tire width direction Y1 side. The second outer connecting portion 422 is provided in a half area of ​​the outer annular portion 30 on the tire width direction Y2 side.

[0059] As described above, in this embodiment, all the spokes 40 have the same thickness t. The dimension of the thickness t is not particularly limited, but in order for the spokes 40 to be able to fully receive the rotational force from the inner annular portion 20 and the outer annular portion 30 while being able to bend and deform appropriately when a load is applied, the thickness t is preferably 1 mm or more and 30 mm or less, and more preferably 5 mm or more and 25 mm or less.

[0060] As described above, the width w of all the spokes 40 in this embodiment is the same. The width w of the spokes 40 is not particularly limited, but is preferably 5 mm or more and 25 mm or less, and more preferably 10 mm or more and 20 mm or less, so as to be able to adequately receive rotational force from the inner annular portion 20 and the outer annular portion 30 and to be able to bend and deform appropriately when a load is applied. Moreover, the width w is preferably 110% or more of the thickness t, and more preferably 115% or more, so as to be able to disperse ground pressure while improving durability.

[0061] The number of spokes 40 is preferably 80 to 300, and more preferably 100 to 200, from the viewpoint of being able to adequately support the load from the vehicle while being lightweight and enabling both improved power transmission and durability.

[0062] The tread 50 is provided on the outer peripheral surface of the outer annular portion 30 and constitutes the outermost peripheral portion of the non-pneumatic tire 1. The tread 50 has a tread surface 51 on its outer peripheral surface that comes into contact with the road surface. The tread surface 51 of the tread 50 is provided with a tread pattern formed of a plurality of grooves and land portions, in the same manner as in conventional pneumatic tires.

[0063] The tread 50 may be configured by laminating a plurality of vulcanized rubber layers having different components and characteristics (for example, two or three layers).

[0064] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and the above embodiment may be modified as appropriate within the scope of the spirit of the present invention.

[0065] The configuration of the embodiment of the present invention is as follows.

[0066] (1) A method for producing a non-pneumatic tire having a support structure and a tread located radially outboard of the support structure and extending circumferentially of the tire, the method comprising the steps of: mixing a base agent, a curing agent, and a pigment at a temperature at which the viscosity of the curing agent is 0.8 Pa s or more and 2.6 Pa s or less; and stirring the mixture using a rotation-revolution mixer under conditions of a revolution centrifugal force of 1200 N or more, a rotation centrifugal force of 350 N or more, and a stirring time of 60 seconds or more and 90 seconds or less to obtain a thermosetting resin composition; and thermally curing the thermosetting resin composition to obtain at least a portion of the support structure.

[0067] (2) The method for producing a non-pneumatic tire according to (1), wherein the thermosetting resin composition has a pigment content of 0.04% by mass or more and 0.08% by mass or less.

[0068] (3) The method for producing a non-pneumatic tire according to (1) or (2), wherein the base agent contains a low molecular weight polyol and the curing agent contains a polyisocyanate.

[0069] (4) The method for producing a non-pneumatic tire according to (3), wherein the low molecular weight polyol is 1,4-butanediol, and the polyisocyanate is 1,4-phenylene diisocyanate.

[0070] (5) The method for producing a non-pneumatic tire according to (3) or (4), wherein the base agent further contains a polyether polyol.

[0071] (6) The method for producing a non-pneumatic tire according to (5), wherein the polyether polyol is polytetramethylene glycol.

[0072] (7) A method for manufacturing a non-pneumatic tire described in any one of (1) to (6), wherein the support structure includes an inner annular portion, an outer annular portion arranged coaxially with the inner annular portion and radially outward of the inner annular portion, and a plurality of spokes connecting the inner annular portion and the outer annular portion and arranged along the tire circumferential direction, and at least a part of the support structure is at least one of the inner annular portion, the outer annular portion, and the spokes. EXAMPLES

[0073] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0074] [Main ingredient] Vibracure A250 (manufactured by LANXESS) as 1,4-butanediol and PTMG1000 (manufactured by Mitsubishi Chemical) as polytetramethylene glycol were mixed in a specified mass ratio, and then the mixture was vacuum degassed for 2 hours at a specified temperature (see Table 1) using a vacuum constant temperature dryer DP63 (manufactured by Yamato Scientific) to obtain the base resin.

[0075] [Hardening agent] Adiprene LFPE560 (manufactured by LANXESS) as 1,4-phenylenediisocyanate was vacuum degassed for 2 hours at a prescribed temperature (see Table 1) using a vacuum constant temperature dryer DP63 (manufactured by Yamato Scientific) to obtain a curing agent.

[0076] [Viscosity of hardener] The viscosity of the curing agent was measured using a vibration viscometer VM-10A (manufactured by Sekonic).

[0077] [Pigment] Phthalocyanine blue, ZA Blue 2200 (manufactured by Mikuni Color Co., Ltd.), was used as the pigment.

[0078] [Examples 1 to 7, Comparative Examples 1 to 15] The base resin, the curing agent and the pigment were mixed and stirred under the specified conditions (see Table 1) using a planetary centrifugal mixer to obtain a thermosetting resin composition. At this time, the isocyanate index of the thermosetting resin composition was set to 1.02, and the content of the pigment in the thermosetting resin composition was set to 0.05 mass%. Next, the thermosetting resin composition was injected into a mold and then thermally cured at 130°C for 16 hours. Next, the mold was removed and cooled to obtain a support structure.

[0079] In this case, the rotation and revolution mixer used was the Mazerustar KK-2000 or KK-5000W (both manufactured by Kuraray Industries, Inc.). When using the Mazerustar KK-2000 as the rotation and revolution mixer, the total mass of the base agent, hardener, and pigment was 1.0 kg, the revolution radius R was 0.175 m, and the rotation radius r was 0.0575 m. When using the Mazerustar KK-5000W as the rotation and revolution mixer, the total mass of the base agent, hardener, and pigment was 2.3 kg, the revolution radius R was 0.325 m, and the rotation radius r was 0.0725 m.

[0080] [Pigment dispersibility in thermosetting resin composition] The thermosetting resin composition was visually inspected to evaluate the pigment dispersibility. The pigment dispersibility of the thermosetting resin composition was evaluated according to the following criteria: A: When no color shading is observed in the thermosetting resin composition B: When color shading is observed in the thermosetting resin composition

[0081] [Formability of support structure] The support structure was visually inspected and evaluated for moldability. The criteria for judging the moldability of the support structure were as follows: A: No defects or voids are found in the support structure. B: Defects and / or voids in the support structure

[0082] [Breaking strength of support structure] After cutting out a No. 3 dumbbell test piece from the support structure, a tensile test was performed using a tensile tester in accordance with JIS K7312:1996 to measure the breaking strength of the test piece. Here, when the moldability of the support structure was judged to be B, the evaluation of the breaking strength of the support structure was omitted. The judging criteria for the breaking strength of the support structure are as follows. A: When the breaking strength of the support structure is 40 MPa or more B: When the breaking strength of the support structure is less than 40 MPa

[0083] Table 1 shows the evaluation results of the pigment dispersibility of the thermosetting resin composition, the moldability of the support structure, and the breaking strength. [Table 1]

[0084] From Table 1, it can be seen that in Examples 1 to 7, the pigment dispersibility of the thermosetting resin composition, the moldability of the support structure, and the breaking strength are high. In contrast, in Comparative Examples 1 to 4, the stirring time is 30 to 50 seconds, so the pigment dispersibility of the thermosetting resin composition is low. In Comparative Example 5, the rotation centrifugal force f is 41 N and the stirring time is 30 seconds, so the pigment dispersibility of the thermosetting resin composition and the breaking strength of the support structure are low. In Comparative Examples 6 and 7, the stirring time is 100 seconds, so the moldability of the support structure is low. In Comparative Examples 8, 9, and 11, the rotation centrifugal force f is 199 to 305 N, so the pigment dispersibility of the thermosetting resin composition is low. In Comparative Examples 10 and 12, the revolution centrifugal force F is 733 to 1051 N and the rotation centrifugal force f is 163 to 305 N, so the pigment dispersibility of the thermosetting resin composition is low. In Comparative Examples 13 and 14, the viscosity of the curing agent was 4.1 to 6.9 Pa s, so the pigment dispersibility of the thermosetting resin composition and the moldability of the support structure were poor. In Comparative Example 15, the viscosity of the curing agent was 0.2 Pa s, so the moldability of the support structure was poor. [Explanation of symbols]

[0085] 1. Non-pneumatic tires 10 Support structure 20 Inner annular part 20a, 20b end 30 Outer annular part 30a, 30b end 40 spokes 41 First Spoke 42 Second Spoke 411 First inner connection 411a, 411b side 412 First outer connection part 412a, 412b side 421 Second inner connection 421a, 421b side 422 Second outer connection 422a, 422b side 50 Tread 51 Tread C Tire Circumferential Direction E Tire equatorial plane O axis center X Tire radial direction Y Tire width direction

Claims

1. 1. A method of manufacturing a non-pneumatic tire having a support structure, comprising: a step of mixing a base material, a curing agent, and a pigment at a temperature at which the viscosity of the curing agent becomes 0.8 Pa·s or more and 2.6 Pa·s or less, and stirring the mixture using a planetary centrifugal mixer under conditions of a revolution centrifugal force of 1200 N or more, a rotation centrifugal force of 350 N or more, and a stirring time of 60 seconds or more and 90 seconds or less to obtain a thermosetting resin composition; a step of heat curing the thermosetting resin composition to obtain at least a portion of the support structure.

2. The method for producing a non-pneumatic tire according to claim 1 , wherein the thermosetting resin composition has a pigment content of 0.04% by mass or more and 0.08% by mass or less.

3. The base agent contains a low molecular weight polyol, The method for producing a non-pneumatic tire according to claim 1 or 2, wherein the curing agent includes a polyisocyanate.

4. The low molecular weight polyol is 1,4-butanediol, The method for producing a non-pneumatic tire according to claim 3, wherein the polyisocyanate is 1,4-phenylene diisocyanate.

5. The method for manufacturing a non-pneumatic tire according to claim 3 , wherein the base material further contains a polyether polyol.

6. The method for producing a non-pneumatic tire according to claim 5, wherein the polyether polyol is polytetramethylene glycol.

7. the support structure includes an inner annular portion, an outer annular portion disposed coaxially with the inner annular portion and radially outward of the inner annular portion, and a plurality of spokes connecting the inner annular portion and the outer annular portion and arranged along a tire circumferential direction, The method of claim 1 or 2, wherein at least a portion of the support structure is at least one of the inner annular portion, the outer annular portion, and the spokes.

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