tire

Abstract

Provided is a tire comprising reinforcing layers 6a, 6b composed of a reinforcing material and vulcanized rubber covering the reinforcing material, wherein: the vulcanized rubber is composed of a rubber composition containing N-cyclohexyl-2-benzothiazolylsulfenamide; the reinforcing material includes a steel cord surface coated with a ternary plating of copper, zinc, and iron; the reinforcing layers 6a, 6b are disposed radially inward of the tread surface of the tire; and the ratio (a / b) of a modulus (a) at 50% elongation of the vulcanized rubber covering the reinforcing material in a tire-width-direction central portion 6C of the reinforcing layers 6a and 6b, and a modulus (b) at 50% elongation of the vulcanized rubber covering the reinforcing material at the tire-width-direction end portions 6E of the reinforcing layers 6a and 6b, is 0.94-1.06. The tire has a high modulus and exceptional producibility.

Description

[Technical Field]

[0001] The present invention relates to a tire. [Background technology]

[0002] Generally, in tires, a reinforcing layer made of a reinforcing material such as a metal cord coated with rubber is arranged as a belt on the radially inner side of the tire tread surface and on the radially outer side of the crown portion of the carcass to improve the durability of the tire (see Patent Document 1). In the manufacture of tires, a reinforcing material-rubber composite is usually prepared in advance by coating a reinforcing material with rubber. In the raw tire molding process, the reinforcing material-rubber composite is laminated together with other rubber components and incorporated into the raw tire, which is then subjected to a vulcanization process to become part of the tire (reinforcing layer).

[0003] Furthermore, Patent Document 2 discloses a steel cord with a brass coating rich in iron particles, which allows the use of a triple alloy coating even with a cobalt-free compound. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-31240 [Patent Document 2] International Publication No. 2020 / 156967 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the tire vulcanization process of Patent Document 1, in order to improve tire productivity, it is necessary to perform vulcanization at as high a temperature as possible for as short a time as possible. However, when a reinforcing material-rubber composite is prepared using conventional belt coating rubber, and a green tire having the reinforcing material-rubber composite as a belt (reinforcing layer) is molded and vulcanized at a high temperature, the portion of the belt (reinforcing layer) where vulcanization proceeds quickly (particularly the central portion of the belt in the tire width direction) undergoes excessive vulcanization, exceeding the appropriate vulcanization state and becoming over-vulcanized. When the over-vulcanization state occurs, the modulus of the portion where vulcanization proceeds quickly decreases, resulting in a modulus distribution across the entire belt. When the modulus distribution in the belt becomes large, tire performance deteriorates, and therefore, conventionally, there has been a limit to improving tire productivity by increasing the vulcanization temperature. Furthermore, Patent Document 2 does not disclose the productivity of tires.

[0006] In view of the above circumstances, an object of the present invention is to provide a tire that has a high modulus and is excellent in productivity, and an object of the present invention is to achieve this object. [Means for solving the problem]

[0007] <1> A tire having a reinforcing layer made of a reinforcing material and vulcanized rubber covering the reinforcing material, the vulcanized rubber is a vulcanized rubber of a rubber composition containing N-cyclohexyl-2-benzothiazolyl sulfenamide, the reinforcing material includes a metal in which the surface of a steel cord is coated with a ternary plating of copper, zinc, and iron; The reinforcing layer is disposed on the radially inner side of the tread surface, A tire in which the ratio (a / b) of the modulus (a) at 50% elongation of the vulcanized rubber covering the reinforcing material at the center of the reinforcing layer in the tire width direction to the modulus (b) at 50% elongation of the vulcanized rubber covering the reinforcing material at the end of the reinforcing layer in the tire width direction is 0.94 or more and 1.06 or less.

[0008] The tire of the present invention has excellent productivity because the modulus of the vulcanized rubber covering the reinforcing material in the reinforcing layer is uniform and vulcanization at high temperature for a short time is possible.

[0009] <2> The amount of the iron in the coating is 1% by mass or more and less than 10% by mass of the total mass of the copper, the zinc, and the iron. <1> A tire as described in <3> The amount of phosphorus in the coating is 0 mg / m 2 More than 4 mg / m 2 is <1> or <2> A tire as described in <4> The steel cord is drawn using a diamond die. <1> ~ <3> 1. A tire according to any one of the preceding items.

[0010] <5> The rubber composition includes a rubber component containing 50% by mass or more of polyisoprene-based rubber. <1> ~ <4> 1. A tire according to any one of the preceding items.

[0011] <6> The rubber composition has a cobalt-containing compound content of 0.01% by mass or less. <1> ~ <5> 1. A tire according to any one of the preceding items. <7> The rubber composition contains an alkylphenol resin. <1> ~ <6> 1. A tire according to any one of the preceding items.

[0012] <8> The cobalt atom content is 1% by mass or less <1> ~ <7> 1. A tire according to any one of the preceding items. [Effects of the Invention]

[0013] According to the present invention, a tire having a high modulus and excellent productivity can be provided. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view of one embodiment of a tire of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, the present invention will be illustrated and described in detail based on its embodiments. In the following description, the description of "A to B" indicating a numerical range represents a numerical range including the endpoints A and B, and represents "A or more and B or less" (when A < B), or "A or less and B or more" (when A > B). Also, parts by mass and mass % are synonymous with parts by weight and weight %, respectively.

[0016] <Tire> The tire of the present invention is a tire having a reinforcing layer composed of a reinforcing material and a vulcanized rubber covering the reinforcing material. The vulcanized rubber is a vulcanized rubber of a rubber composition containing N-cyclohexyl-2-benzothiazolyl sulfenamide. The reinforcing material includes a metal whose steel cord surface is coated with a ternary plating of copper, zinc, and iron. The reinforcing layer is disposed on the inner side in the tire radius direction of the tread surface. In the central portion in the tire width direction of the reinforcing layer, the modulus (a) at 50% elongation of the vulcanized rubber covering the reinforcing material and the modulus (b) at 50% elongation of the vulcanized rubber covering the reinforcing material at the end portion in the tire width direction of the reinforcing layer, the ratio (a / b) is 0.94 or more and 1.06 or less. Such a tire of the present invention includes a metal whose steel cord surface is coated with a ternary plating of copper, zinc, and iron as a reinforcing material, and this metal has excellent adhesion between the vulcanized rubber and the metal. Further, in the reinforcing layer, by including N-cyclohexyl-2-benzothiazolyl sulfenamide as a vulcanization accelerator in the vulcanized rubber covering the cord, the physical properties of the vulcanized rubber are uniform, so that reversion due to over-vulcanization is suppressed, and thus high-temperature and short-time vulcanization is possible, resulting in excellent productivity.

[0017] Here, in the present invention, the tread surface means the outer peripheral surface extending over the entire circumference of the tire that comes into contact with the road surface when a tire assembled to an application rim and filled with a specified internal pressure is rolled under a load corresponding to the maximum load capacity. "Applicable rim" refers to the industrial standard that is valid in the region where the tire is produced and used, and is the standard rim for the applicable size (Measuring Rim in the ETRTO STANDARDS MANUAL, YEAR BOOK in the TRA) that is listed in the JATMA YEAR BOOK (Japan Automobile Tire Manufacturers Association) in Japan, the ETRTO (The European Tyre and Rim Technical Organisation) STANDARDS MANUAL in Europe, and the TRA (The Tire and Rim Association, Inc.) YEAR BOOK in the United States. In the BOOK, this refers to the Design Rim. Also, "specified internal pressure" refers to the air pressure that corresponds to the maximum load capacity of the applicable size and ply rating, as stated in the above JATMA YEAR BOOK, etc., and "maximum load capacity" refers to the maximum mass that can be loaded onto the tire according to the above standards.

[0018] In the present invention, the central portion of the reinforcing layer in the tire width direction refers to a 1 / 5 portion located in the center in the tire width direction when the reinforcing layer is divided equally into 5 parts in the tire width direction along a plane parallel to the tire equatorial plane, while the end portions of the reinforcing layer in the tire width direction refer to a pair of 1 / 5 portions located on both outermost sides in the tire width direction when the reinforcing layer is divided equally into 5 parts in the tire width direction along a plane parallel to the tire equatorial plane.

[0019] The tire of the present invention will be described in detail below by way of example based on an embodiment thereof. Fig. 1 is a cross-sectional view of one embodiment of a tire of the present invention. The tire of this embodiment shown in Fig. 1 comprises a pair of bead portions 1, a pair of sidewall portions 2, a tread portion 3, and a carcass 5 extending in a toroidal shape between bead cores 4 embedded in the bead portions 1. The tire further comprises a belt 6 consisting of two reinforcing layers 6a and 6b in the tread portion 3, on the radially inner side of the tread surface and on the radially outer side of the crown portion of the carcass 5.

[0020] In the tire of this embodiment, the carcass 5 is composed of a single carcass ply, and is composed of a main body portion extending in a toroidal shape between a pair of bead cores 4 each embedded in the bead portion 1, and a turn-up portion wound up radially outward from the inner side to the outer side in the tire width direction around each bead core 4. However, in the tire of the present invention, the number and structure of the plies of the carcass 5 are not limited to this. From the viewpoint of tire durability, a radial carcass is preferable as the carcass. Here, the carcass ply constituting the carcass 5 is composed of a plurality of reinforcing cords coated with coating rubber, and the reinforcing cords may be organic fiber cords such as polyethylene terephthalate cords, nylon cords, rayon cords, aramid cords, etc., or steel cords.

[0021] The tire of this embodiment shown in FIG. 1 has reinforcing layers 6a, 6b in the tread portion 3, each of which is made of a reinforcing material and vulcanized rubber covering the reinforcing material, and the reinforcing layers 6a, 6b are arranged radially inward of the tire tread surface. The vulcanized rubber that coats the reinforcing material (hereinafter sometimes simply referred to as "coating rubber") is a rubber obtained by vulcanizing a rubber composition containing a rubber component. The rubber composition may further contain a filler, a vulcanization accelerator, etc., but details will be described later. The rubber composition that constitutes the coating rubber may also be referred to as a rubber composition for coating rubber.

[0022] The reinforcing material includes at least a metal (ternary plated metal) in which the surface of a steel cord is coated with a ternary plating of copper, zinc, and iron. The reinforcing material may further include a metal other than steel, such as iron, stainless steel, lead, aluminum, copper, brass, bronze, Monel metal alloy, nickel, or zinc. The diameter of the steel cord is appropriately selected depending on the application of the tire, etc. The steel cord may be either a steel monofilament or a multifilament (twisted cord or a bundle of drawn cords), and there is no limitation on its shape. When the steel cord is a twisted cord, there is no particular limitation on the twist structure, and examples of twist structures include single twist, multi-twist, layer twist, and composite twist of multi-twist and layer twist.

[0023] When the steel cord has a ternary plating layer of copper, zinc, and iron, the components constituting the plating layer can play a role in improving adhesion between the rubber and the steel cord, and therefore, even when the content of the cobalt compound in the rubber composition is low (0.01 part by mass or less per 100 parts by mass of the rubber component), high adhesion can be achieved. The steel cord may be further subjected to a surface treatment such as an adhesive treatment in order to ensure favorable adhesion to the rubber composition. When an adhesive treatment is used, an adhesive treatment such as "CHEMLOC" (registered trademark) manufactured by LORD Corporation is preferred.

[0024] Also, for example, a steel filament can be used in which the N atoms on the surface are 2 atomic % or more and 60 atomic % or less, and the Cu / Zn ratio on the surface is 1 or more and 4 or less. Also, the metal filament 1 can be one in which the amount of phosphorus contained as oxide up to 5 nm in the outermost layer of the filament radially inward is 7.0 atomic % or less as a proportion of the total amount excluding the amount of C.

[0025] The metal contained in the reinforcing material of this embodiment is a metal (ternary plated metal) in which the surface of a steel cord is coated with a ternary plating of copper, zinc, and iron. More specifically, the metal is a steel cord containing one or more steel filaments, wherein the filaments include a steel filament base material and a coating (plating layer) that partially or entirely covers the steel filament base material, the coating includes brass composed of copper and zinc, and the coating is reinforced with iron, the iron being present in the brass as particles, and the particles having a size of 10 to 10,000 nanometers. It is even more preferable that the particles have a size of 20 to 5,000 nanometers. "Iron reinforced" means that the iron does not originate from the filamentary steel base material. Here, the brass is made of copper and zinc, and preferably contains at least 63% by mass of copper with the remainder being zinc, more preferably contains 65% by mass or more of copper, and even more preferably contains 67% by mass or more of copper. Furthermore, it is preferable that the amount of iron in the coating (plating layer) is 1% by mass or more and less than 10% by mass relative to the total mass of the brass and iron, and it is more preferable that the amount of iron in the coating is 3% by mass or more and less than 9% by mass relative to the total mass of the brass and iron. More preferably, the coating is substantially free of zinc-iron alloy.

[0026] In the steel cord containing one or more steel filaments, the amount of phosphorus present on the surface of the filament, in other words, the amount of phosphorus in the coating (plating layer) is P s and the amount of iron present on the surface of the filament, in other words, the amount of iron in the coating (plating layer) is Fe s and (P s +Fe s The amount of ) is determined by gently etching the surface of the filament with a weak acid that dissolves phosphorus and iron according to the following methods (a) to (e). (a) Approximately 5 grams of steel cord is weighed, cut into pieces of approximately 5 cm and introduced into a test tube. (b) Add 10 ml of 0.01 molar hydrochloric acid HCl. (c) Shake the sample in the acid solution for 15 seconds. (d) The amount present in the solution is measured by ICP-OES. Here, ICP-OES refers to inductively coupled plasma-optical emission spectroscopy (ICP-OES) using standard solutions of (Cu;Fe;Zn) at (0;0;0), (2;0.02;1), (5;0.1;2), and (10;0.5;5) mg / L, all in a matrix of 10 mL stripping solution. (e) Per unit of surface area of ​​the filament steel (P s +Fe s ) mass in milligrams per square meter (mg / m 2The results are shown in (Fe s +P s ) is sometimes called The amount of phosphorus present on the surface of the filament, in other words, the amount of phosphorus in the coating (plating layer), is 4 mg / m 2 However, it is preferable that the value is greater than zero in order to improve the adhesiveness. <P s ≦4 mg / m 2 The amount of phosphorus (P s ) is 4 mg / m 2 Less (P s <4 mg / m 2 ) is more preferred. Higher amounts of phosphorus s The amount of phosphorus P reduces the growth of the adhesive layer. s The dose is 3 mg / m 2 It may be lower, 1.5 mg / m 2 Lower is even better. In a more preferred embodiment, the amount of iron present on the surface of the filament is 30 mg / m 2 Preferably, it is 35 mg / m or more. 2 More preferably, the surface contains more than 40 mg / m 2 It is even more preferred if more than 100% iron is present at the surface. The mass ratio of the amount of iron present on the surface of the filament to the amount of phosphorus present on the surface of the filament (Fe s / P s ) is preferably greater than 27. the filament surface coating mass SCW is the sum of the masses of brass and iron present in the coating per unit of surface area, the coating mass being expressed in grams per square meter, and the mass ratio [Fe s / (SCW×P s )] is preferably greater than 13. To obtain steel filaments in which the iron is present as particles in the brass, an intermediate wire having a brass coating reinforced with iron particles may be subsequently drawn to a final diameter of 0.28 mm by wet wire drawing the wire through smaller dies in a lubricant to obtain steel filaments. The lubricant contains a high pressure additive which generally contains phosphorus in an organic compound. The die used here may be a Set-D die, in which at least the head die is a sintered diamond die and the remaining dies are tungsten carbide dies. The steel cord is preferably wire-drawn using a diamond die.

[0027] As a method for coating the steel cord with the rubber composition, for example, the following method can be used. A predetermined number of ternary-plated steel cords are arranged in parallel at a predetermined interval, and the steel cords are coated on both the top and bottom with uncrosslinked rubber sheets of the rubber composition of the present invention, each about 0.5 mm thick, to obtain a precursor. The resulting precursor (unvulcanized rubber-metal composite) is then vulcanized. Vulcanization conditions can be, for example, a temperature of about 160°C for about 20 minutes; or a temperature of about 145°C for about 40 minutes. The composite of vulcanized rubber and steel cord thus obtained has excellent vulcanized rubber-to-metal adhesion.

[0028] In the tire of this embodiment, cords constituting the reinforcing layers 6a, 6b are usually laminated so as to cross each other across the tire equatorial plane to form the belt 6. Note that, although the belt 6 in the drawing is made up of two reinforcing layers 6a, 6b, in the tire of the present invention, the number of reinforcing layers constituting the belt 6 is not limited to one and may be one or more.

[0029] In the tire of this embodiment, the tire width direction central portion 6C of the reinforcing layers 6a, 6b refers to a 1 / 5 portion located in the center in the tire width direction when the reinforcing layers 6a, 6b are divided equally into 5 in the tire width direction along a plane parallel to the tire equatorial plane, while the tire width direction end portions 6E of the reinforcing layers 6a, 6b refer to a pair of 1 / 5 portions located on both outermost sides in the tire width direction when the reinforcing layers 6a, 6b are divided equally into 5 in the tire width direction along a plane parallel to the tire equatorial plane. In other words, the tire width direction central portion 6C of the reinforcing layers 6a, 6b is a range that is 1 / 5 of the maximum width W in the tire width direction of the reinforcing layers 6a, 6b, located in the center in the tire width direction when the reinforcing layers 6a, 6b are divided equally into 5 in the tire width direction along a plane parallel to the tire equatorial plane. On the other hand, the tire width direction end portions 6E of the reinforcing layers 6a, 6b are within a range of 1 / 5 of the maximum width W of the reinforcing layers 6a, 6b in the tire width direction, which are located on both outermost sides in the tire width direction when the reinforcing layers 6a, 6b are divided equally into five parts in the tire width direction along a plane parallel to the tire equatorial plane.

[0030] In addition, in the tire of this embodiment, the ratio (a / b) of the modulus (a) at 50% elongation of the vulcanized rubber covering the reinforcing material at the tire width direction central portion 6C of the reinforcing layers 6a, 6b to the modulus (b) at 50% elongation of the vulcanized rubber covering the reinforcing material at the tire width direction end portion 6E of the reinforcing layers 6a, 6b is 0.94 or more and 1.06 or less. Here, the ratio (a / b) of the modulus (a) of the covering rubber at the tire widthwise center 6C of the reinforcing layers 6a, 6b at 50% elongation to the modulus (b) of the covering rubber at the tire widthwise end 6E of the reinforcing layers 6a, 6b at 50% elongation is 0.94 or more and 1.06 or less, which means that the physical properties of the covering rubber of the reinforcing layers 6a, 6b are uniform. This means that the coating rubber is a vulcanized rubber obtained from a rubber composition that is inhibited from reversion due to over-vulcanization and that can be vulcanized at high temperature in a short time. Therefore, the tire of this embodiment has excellent productivity.

[0031] Methods for setting the ratio (a / b) of the modulus (a) of the covering rubber at the tire width direction center portion 6C of the reinforcing layers 6a, 6b at 50% elongation to the modulus (b) of the covering rubber at the tire width direction end portion 6E of the reinforcing layers 6a, 6b at 50% elongation to be 0.94 or more and 1.06 or less include adjusting the blending of the rubber composition used for the covering rubber of the reinforcing layers 6a, 6b, adjusting the kneading conditions of the rubber composition, adjusting the vulcanization conditions of the tire, etc. These methods reduce the dependency of the modulus of the covering rubber on the vulcanization conditions, thereby making it possible to set the ratio (a / b) to be 0.94 or more and 1.06 or less.

[0032] (N-cyclohexyl-2-benzothiazolylsulfenamide) In the tire of this embodiment, the vulcanized rubber (coating rubber) that coats the reinforcing material is a vulcanized rubber of a rubber composition containing N-cyclohexyl-2-benzothiazolylsulfenamide. The rubber composition constituting the coating rubber (rubber composition for the coating rubber) contains N-cyclohexyl-2-benzothiazolylsulfenamide, which suppresses reversion due to over-vulcanization during vulcanization of the rubber composition. As a result, even if the rubber composition is vulcanized at a high temperature in a short time, the physical properties of the vulcanized rubber are easily made uniform between the tire widthwise center portion 6C of the reinforcing layers 6a, 6b and the tire widthwise end portion 6E of the reinforcing layers 6a, 6b, and the ratio (a / b) can be easily adjusted to a range of 0.94 to 1.06. This facilitates high-temperature, short-time vulcanization of the rubber composition without degrading tire performance, and also suppresses a decrease in tire modulus due to reversion. From the above perspectives, the ratio (a / b) may be in the range of 0.94 to 1.03, 0.94 to 1.00, or 0.94 to 0.99. N-cyclohexyl-2-benzothiazolylsulfenamide is also called "vulcanization accelerator CZ" or "vulcanization accelerator CBS" and has the effect of accelerating the vulcanization reaction (hereinafter, N-cyclohexyl-2-benzothiazolylsulfenamide may be referred to as "vulcanization accelerator CZ").

[0033] The content of N-cyclohexyl-2-benzothiazolylsulfenamide in the rubber composition for coating rubber is preferably 0.4 parts by mass or more, more preferably 0.45 parts by mass or more, more preferably 0.5 parts by mass or more, more preferably 0.55 parts by mass or more, and even more preferably 0.6 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 3 parts by mass or less, more preferably 1.5 parts by mass or less, more preferably 1.4 parts by mass or less, more preferably 1.3 parts by mass or less, more preferably 1.2 parts by mass or less, more preferably 1.1 parts by mass or less, and more preferably 1.0 part by mass or less. When the content of N-cyclohexyl-2-benzothiazolylsulfenamide in the rubber composition for coating rubber is 0.4 parts by mass or more, per 100 parts by mass of the rubber component, the effect of accelerating the vulcanization reaction of the rubber composition is increased, and when it is 3 parts by mass or less, the decrease in modulus due to reversion can be further suppressed.

[0034] (Polyisoprene rubber) Furthermore, it is preferable that 50% by mass or more of the rubber component is polyisoprene-based rubber. That is, it is preferable that 50% by mass or more of the rubber component of the rubber composition for the coating rubber is polyisoprene-based rubber. When 50% by mass or more of the rubber component is polyisoprene-based rubber, the strength of the coating rubber is improved, and the durability of the tire can be improved. The content of polyisoprene-based rubber in the rubber component is more preferably 60% by mass or more, and may be 100% by mass (that is, the entire rubber component is polyisoprene-based rubber). Polyisoprene-based rubber includes natural rubber (NR) and synthetic isoprene rubber (IR). The polyisoprene-based rubber may contain either natural rubber (NR) or synthetic isoprene rubber (IR), or may contain both, but natural rubber (NR) is preferred.

[0035] The rubber composition for coating rubber may contain a rubber other than the above-mentioned polyisoprene-based rubber as a rubber component. Examples of rubbers other than polyisoprene rubbers include butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), styrene-isoprene copolymer rubber (SIR), acrylonitrile-butadiene copolymer rubber (NBR), ethylene-propylene copolymer rubber, ethylene-propylene-diene terpolymer rubber, butyl rubber (isobutylene-isoprene copolymer rubber, IIR), halogenated butyl rubber, alkylated chlorosulfonated polyethylene rubber, chloroprene rubber (CR), and other synthetic rubbers. These rubber components may be used alone or as a blend of two or more.

[0036] (Cobalt-containing compounds) The rubber composition for coating rubber preferably contains 0.01% by mass or less of the cobalt-containing compound. By containing 0.01% by mass or less of the cobalt-containing compound in the rubber composition for coating rubber, the heat degradation resistance of the coating rubber is easily improved. The content of the cobalt-containing compound in the rubber composition for coating rubber is more preferably 0.005% by mass or less, and may be 0% by mass. Although the cobalt-containing compound (or cobalt metal or cobalt ions derived from the cobalt compound) may be mixed into the coating rubber as an impurity by migrating from the outside, it is preferable not to compound the cobalt-containing compound at least when producing the rubber composition to be used for the coating rubber.

[0037] (Alkylphenol resin) In addition to N-cyclohexyl-2-benzothiazolylsulfenamide, various compounding agents can be compounded into the rubber composition for coating rubber, and it is preferable to compound, for example, an alkylphenol resin. The rubber composition for coating rubber contains an alkylphenol resin, which improves the strength of the vulcanized rubber coating the reinforcing material, thereby improving the durability of the tire. More specifically, the composite of the coating rubber and the reinforcing material (vulcanized rubber-metal composite), i.e., the reinforcing layer, is less susceptible to deterioration and has better adhesion after moist heat aging.

[0038] The alkylphenol resin is obtained by a condensation reaction of alkylphenol and formaldehyde in the presence of a catalyst. Commercially available alkylphenol resins include those sold under the trade names "Hitanol 1502P" (Hitachi Chemical Co., Ltd.), "Tackirol 201" (Taoka Chemical Co., Ltd.), "Tackirol 250-I" (a brominated alkylphenol formaldehyde resin with a bromination rate of 4%, Taoka Chemical Co., Ltd.), "Tackirol 250-III" (a brominated alkylphenol formaldehyde resin, Taoka Chemical Co., Ltd.), "R7521P," "SP1068," "R7510PJ," "R7572P," and "R7578P" (Schenectady Chemical Co., Ltd.), and "R7510PJ" (SI Group Inc.).

[0039] The content of the alkylphenol resin in the rubber composition for coating rubber is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, more preferably 0.4 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.6 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 3 parts by mass or less, more preferably 1.5 parts by mass or less, more preferably 1.4 parts by mass or less, more preferably 1.3 parts by mass or less, more preferably 1.2 parts by mass or less, and even more preferably 1.1 parts by mass or less. When the content of the alkylphenol resin is 0.2 parts by mass or more, per 100 parts by mass of the rubber component, deterioration of the reinforcing layer is less likely to proceed and vulcanized rubber-metal adhesion after moist heat aging is excellent, and when it is 3 parts by mass or less, a suitably high elastic modulus and low heat buildup during product use can be achieved.

[0040] (filler) The rubber composition for coating rubber preferably contains a filler, and the filler is preferably carbon black, silica, etc. When the rubber composition for coating rubber contains a filler, the strength of the coating rubber is improved, and the durability of the tire is improved.

[0041] The carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF grade carbon black. The silica is also not particularly limited, and examples thereof include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate, and among these, wet silica is preferred. These fillers may be used alone or in combination of two or more.

[0042] Furthermore, the carbon black has a nitrogen adsorption specific surface area (N2SA, measured in accordance with JIS K 6217-2:2001) of 20 to 250 m 2 / g can be used, and the range is 30 to 200m 2 / g can be used, and the range is 30 to 150m 2 / g can be used. The carbon black has a dibutyl phthalate (DBP) oil absorption (measured by the method described in JIS K 6217-4:2001 "Determination of DBP absorption") of 50 to 200 cm 3 / 100g can be used, 60~170cm 3 / 100g can be used.

[0043] The content of the filler in the rubber composition for coating rubber is preferably 30 parts by mass or more, more preferably 35 parts by mass or more, even more preferably 40 parts by mass or more, and is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, more preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less, per 100 parts by mass of the rubber component. When the content of the filler is 30 parts by mass or more, per 100 parts by mass of the rubber component, the strength of the coating rubber is further improved, and when it is 120 parts by mass or less, the processability of the rubber composition for coating rubber is good.

[0044] (vulcanizing agent) The rubber composition for the coating rubber preferably contains a vulcanizing agent, such as sulfur. The content of the vulcanizing agent in the rubber composition for coating rubber is, relative to 100 parts by mass of the rubber component, preferably 0.1 part by mass or more, more preferably 1 part by mass or more, more preferably 2 parts by mass or more, more preferably 3 parts by mass or more, even more preferably 4 parts by mass or more in terms of sulfur content, and is preferably 10 parts by mass or less, more preferably 9 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less. If the content of the vulcanizing agent is 0.1 part by mass or more in terms of sulfur content, relative to 100 parts by mass of the rubber component, the strength etc. of the coating rubber is improved, and if it is 10 parts by mass or less, the rubber elasticity of the coating rubber can be sufficiently ensured.

[0045] (Various compounding agents) In addition to the rubber component, N-cyclohexyl-2-benzothiazolylsulfenamide (vulcanization accelerator CZ), filler, and vulcanizing agent described above, the rubber composition for coating rubber may contain additives such as antioxidants, softeners, silane coupling agents, stearic acid, zinc oxide, bismaleimide compounds (BMI), hexamethylenebisthiosulfate disodium salt dihydrate (HTS), phenolic resins, and methylene donors, selected appropriately within ranges that do not impair the object of the present invention. Commercially available products can be suitably used as these additives.

[0046] [Stearic acid] The content of stearic acid in the rubber composition for coating rubber is, per 100 parts by mass of the rubber component, preferably 0.5 parts by mass or more, more preferably 0.6 parts by mass or more, more preferably 0.7 parts by mass or more, more preferably 0.8 parts by mass or more, even more preferably 0.9 parts by mass or more, and is preferably 3.0 parts by mass or less, more preferably 2.5 parts by mass or less, more preferably 2.3 parts by mass or less, more preferably 2.1 parts by mass or less, and even more preferably 1.9 parts by mass or less.

[0047] [Zinc oxide] The content of zinc oxide in the rubber composition for coating rubber is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, even more preferably 10 parts by mass or less.

[0048] [Bismaleimide compounds] The bismaleimide compound is preferably a compound represented by the following formula (1).

[0049] [ka]

[0050] In formula (1), X represents an alkylene group having 2 to 4 carbon atoms, a phenylene group, or a divalent hydrocarbon group having 6 to 29 carbon atoms and having 1 to 4 aromatic rings; R 1 ~R 4 each independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an -NH2 group, or an -NO2 group.

[0051] In formula (1), examples of the alkylene group having 2 to 4 carbon atoms represented by X include an ethylene group, a propylene group, and a propane-2,2-diyl group. Examples of the divalent hydrocarbon group having 6 to 29 carbon atoms and 1 to 4 aromatic rings include a methylenebis(phenylene) group, a phenylenebis(methylene) group, and a phenoxyphenyl group. The aromatic rings may be bonded via -O-, -S-, -SS-, -SO2-, or the like. Among the above Xs, a phenylene group and a hydrocarbon group having 8 to 17 carbon atoms and 1 or 2 aromatic rings are preferred, and a phenylene group or a hydrocarbon group having 8 to 13 carbon atoms and 1 or 2 aromatic rings is more preferred. In formula (1), X may have a substituent. Examples of the substituent include an alkyl group having 1 to 3 carbon atoms, -NH2, -NO2, -F, -Cl, and -Br. In addition, in formula (1), R 1 ~R 4Examples of the alkyl group having 1 to 5 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, and a propyl group. 1 ~R 4 is preferably a hydrogen atom.

[0052] Suitable examples of bismaleimide compounds include 4,4'-diphenylmethane bismaleimide, m-phenylene bismaleimide, N,N'-1,2-ethylene bismaleimide, N,N'-1,2-propylene bismaleimide, bis(3-ethyl-5-methyl-4-maleimidophenyl)methane, 2,2'-bis[4-(4-maleimidophenoxy)phenyl]propane, m-phenylenebis(methylene)bismaleimide, m-phenylenebis(methylene)biscitraconimide, 1,1'-(methylenedi-4,1-phenylene)bismaleimide, etc. These bismaleimide compounds may be used alone or in combination of two or more. Among these, from the viewpoint of the initial adhesion between the reinforcing material and the coating rubber, 4,4'-diphenylmethane bismaleimide and m-phenylene bismaleimide are preferred, and 4,4'-diphenylmethane bismaleimide is particularly preferred.

[0053] The content of the bismaleimide compound in the rubber composition for coating rubber is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.3 parts by mass or more, and is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less, per 100 parts by mass of the rubber component. If the content of the bismaleimide compound is 0.05 parts by mass or more, per 100 parts by mass of the rubber component, the effect of improving the initial adhesion between the reinforcing material and the coating rubber is significant, and if it is 5 parts by mass or less, the elastic modulus of the coating rubber can be increased, and the heat and humidity adhesion of the vulcanized rubber-metal composite can be improved.

[0054] [Hexamethylenebisthiosulfate disodium salt dihydrate (HTS)] Hexamethylenebisthiosulfate disodium salt dihydrate (HTS) is represented by the following formula (2). NaO3S-S-(CH2)6-S-SO3Na·2H2O ··· (2) HTS contributes to improving the adhesion between the reinforcing material and the coating rubber. The content of HTS in the rubber composition for coating rubber is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, even more preferably 0.5 part by mass or more, and is preferably 3.0 parts by mass or less, more preferably 2.5 parts by mass or less, even more preferably 2 parts by mass or less, per 100 parts by mass of the rubber component.

[0055] [Phenol resin] Phenolic resins are obtained, for example, by the reaction of phenols with aldehydes, and contribute to improving the adhesion between the reinforcing material and the coating rubber. Here, examples of the raw phenols include phenol and cresol, and examples of the aldehydes include formaldehyde. The phenolic resin may be a resol-type phenolic resin or a novolac-type phenolic resin. The phenolic resin may be oil-modified, and examples of the oil include rosin oil, tall oil, cashew oil, oleic acid, linoleic acid, and linolenic acid. The content of the phenolic resin in the rubber composition for coating rubber is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, per 100 parts by mass of the rubber component of the coating rubber, and is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, even more preferably 10 parts by mass or less.

[0056] [Methylene donor] The methylene donor acts as a hardener for the phenolic resin. Examples of the methylene donor include hexamethoxymethylmelamine (HMMM), hexamethylenetetramine, and hexamethylmethylolmelamine. The content of the methylene donor in the rubber composition for coating rubber is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 80 parts by mass or less, relative to 100 parts by mass of the phenolic resin.

[0057] [Anti-aging agent] The antioxidant is not particularly limited, and examples thereof include amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, as well as carbamic acid metal salts.

[0058] Examples of the amine-based antiaging agents include phenylenediamine-based antiaging agents having a phenylenediamine skeleton (-NH-Ph-NH-). Specific examples include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (sometimes referred to as 6PPD), N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N,N'-bis(1-methylheptyl)-p-phenylenediamine, and N,N'-bis(1,4-di Examples of such an alkyl ester include N,N'-bis(1-methylpentyl)-p-phenylenediamine, N,N'-dicyclohexyl-p-phenylenediamine, N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, N-4-methyl-2-pentyl-N'-phenyl-p-phenylenediamine, N,N'-diaryl-p-phenylenediamine, hindered diaryl-p-phenylenediamine, phenylhexyl-p-phenylenediamine, and phenyloctyl-p-phenylenediamine.

[0059] Among these, it is preferable that the phenylenediamine moiety (-NH-Ph-NH-) does not have a double bond other than the double bond. Specifically, it is preferable that the phenylenediamine moiety (R 1 -NH-Ph-NH-R 2 ) is preferred.

[0060] [ka]

[0061] In the above formula (3), R 1 and R 2 are each independently a monovalent saturated hydrocarbon group. R 1 and R 2 may be the same or different, but from the viewpoint of synthesis, it is preferable that they are the same.

[0062] The number of carbon atoms in the monovalent saturated hydrocarbon group is preferably 1 to 20, more preferably 3 to 10, and particularly preferably 6 or 7. When the number of carbon atoms in the saturated hydrocarbon group is 20 or less, the number of moles per unit mass increases, resulting in a greater anti-aging effect and improved ozone resistance of the vulcanized rubber of the rubber composition for coating rubber. R in the above formula (3) 1 and R 2 From the viewpoint of further improving the ozone resistance of the vulcanized rubber of the rubber composition for coating rubber, it is preferable that each of the groups independently represents a linear monovalent saturated hydrocarbon group having 1 to 20 carbon atoms or a cyclic monovalent saturated hydrocarbon group having 5 to 20 carbon atoms.

[0063] Examples of the monovalent saturated hydrocarbon group include an alkyl group and a cycloalkyl group. The alkyl group may be linear or branched, and the cycloalkyl group may further have an alkyl group or the like bonded thereto as a substituent. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a 1,2-dimethylbutyl group, a 1,3-dimethylbutyl group, a 2,3-dimethylbutyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentyl group, a 1,2-dimethylpentyl group, a 1,3-dimethylpentyl group, a 1,4-dimethylpentyl group, a 2,3-dimethylpentyl group, a 2,4-dimethylpentyl group, a 3,4-dimethylpentyl group, an n-hexyl group, a 1-methylhexyl group, a 2-methylhexyl group, various octyl groups, various decyl groups, and various dodecyl groups. Of these, a 1,4-dimethylpentyl group is preferred. Examples of the cycloalkyl group include a cyclopentyl group, a methylcyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, a cycloheptyl group, and a cyclooctyl group, and among these, a cyclohexyl group is preferred.

[0064] The amine-based antiaging agent represented by formula (3) may be supported on any carrier, for example, on an inorganic filler such as silica or calcium carbonate. The amine-based antioxidant represented by formula (3) may be used together with a rubber component to form a masterbatch. The rubber component used to form the masterbatch is not particularly limited, and may be a diene rubber such as natural rubber (NR), or an ethylene-propylene-diene rubber (EPDM). The amine-based antiaging agent represented by formula (3) may be converted into a salt with an organic acid. The organic acid used to convert the salt is not particularly limited, but examples thereof include stearic acid.

[0065] Quinoline-based antioxidants can also be suitably used, and examples of the quinoline-based antioxidants include 2,2,4-trimethyl-1,2-dihydroquinoline polymers and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline. The above antioxidants may be used alone or in combination of two or more kinds. Among the above, the antioxidant preferably includes one or more selected from the group consisting of amine-based antioxidants and quinoline-based antioxidants, and more preferably includes at least an amine-based antioxidant.

[0066] The rubber composition for coating rubber can be produced by a known method, for example, by blending N-cyclohexyl-2-benzothiazolylsulfenamide and, as necessary, various compounding agents appropriately selected, with a rubber component, followed by kneading, heating, extruding, etc. Furthermore, a reinforcing material is coated with the rubber composition for coating rubber to obtain a precursor of the reinforcing layer. The obtained precursor (unvulcanized rubber-reinforcing material composite) is laminated with other rubber members to form a green tire, and the green tire is vulcanized to produce the tire of this embodiment.

[0067] The tire of this embodiment may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, depending on the type of tire to be applied, or by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization step or the like and then further vulcanizing it. The tire of this embodiment is preferably a pneumatic tire, and the gas to be filled into the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.

[0068] The tire of this embodiment preferably has a cobalt atom content of 1% by mass or less. The cobalt atom content in the tire can be said to be 0% by mass if the rubber composition used in tire production (including the rubber composition for coating rubber used in producing the coating rubber of the reinforcing layer) does not contain a cobalt-containing compound and the reinforcing metal does not contain cobalt. The cobalt atom content in the tire can be measured, for example, by a method for measuring the element amount of each component constituting the tire. [Example]

[0069] <Examples 1 and 2 and Comparative Examples 1 and 2> [Preparation of Rubber Composition] A rubber composition was prepared by kneading each component using a conventional Banbury mixer according to the compounding composition shown in Table 1. Details of the components shown in Table 1 are as follows.

[0070] NR: Natural rubber (polyisoprene rubber), TSR10 Carbon black: HAF, manufactured by Asahi Carbon Co., Ltd., product name "Asahi #70L" (nitrogen adsorption specific surface area = 81 m 2 / g) Silica: Tosoh Silica Corporation, product name "Nipsil AQ" (CTAB specific surface area = 155 m 2 / g) Phenolic resin: Unmodified phenolic resin (phenol-formaldehyde resin), manufactured by Sumitomo Bakelite Co., Ltd., product name "Sumilite Resin PR-50235" Hexamethoxymethylmelamine: ALLNEX, product name "CYREZ 964" Organic cobalt salt: OMG, product name "Manobond C" Zinc oxide: Manufactured by Hakusui Tech, product name "Zinc Oxide Type 2" Stearic acid: New Japan Chemical Co., Ltd., product name "Stearic Acid 50S" Antioxidant A: 2,2'-methylenebis(4-methyl-6-tert-butylphenol), manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac NS-6" Antioxidant B: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac 6C" Antioxidant C: Seiko Chemical Co., Ltd., product name "Nonflex RD-S" Sulfur: Tsurumi Chemical Industry Co., Ltd., product name "Powdered sulfur" Bismaleimide: N,N'-(4,4'-diphenylmethane)bismaleimide, manufactured by Daiwa Chemical Industry Co., Ltd., trade name "BMI-RB" Alkylphenol resin: Alkylphenol formaldehyde resin, manufactured by SUMITOMO BAKELITE EUROPE, product name "DUREZ 19900" Vulcanization accelerator DCBS: sulfenamide vulcanization accelerator, N,N-dicyclohexyl benzothiazyl-2-sulfenamide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Noccela DZ" Vulcanization accelerator CBS: sulfenamide vulcanization accelerator, N-cyclohexyl-2-benzothiazolyl sulfenamide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Noccela CZ-G" HTS: Flexis Co., Ltd., hexamethylene bisthiosulfate disodium salt dihydrate Vulcanization retarder: N-cyclohexylthiophthalimide

[0071] 1. Evaluation of coated rubber The obtained rubber composition was subjected to high temperature vulcanization and low temperature vulcanization by the following method, and the modulus under each vulcanization condition was measured. The results are shown in Table 1.

[0072] [Measurement of modulus of rubber composition at high temperature and low temperature vulcanization] Test pieces were prepared by vulcanizing the rubber composition at 170°C for 8 minutes (high temperature vulcanization), and test pieces were prepared by vulcanizing the rubber composition at 145°C for 40 minutes (low temperature vulcanization). A tensile test was carried out on the test piece at room temperature (25°C) in accordance with JIS K6251:2017, and the modulus at 50% elongation (Mod50, tensile stress at 50% elongation) was measured.

[0073] 2. Tire evaluation [Preparation of Precursor of Reinforcing Layer] A steel cord whose surface is coated with a ternary plating of copper, zinc, and iron and contains about 1% by mass of iron can be used as the metal (reinforcement). This ternary plated steel cord is obtained using a Set-D die, and more specifically, is produced by the method described in paragraphs

[0065] to

[0070] of the specification of WO 2020 / 156967. The three-component plated steel cord is coated with the prepared rubber composition to obtain a precursor of the reinforcing layer.

[0074] [Tire manufacturing] The precursor (unvulcanized rubber-reinforcement composite) is used for the reinforcing layer that constitutes the belt to form a green tire, which is then heated until the thickest part of the tire is sufficiently vulcanized to produce a passenger car tire of size 155 / 65R14 with the structure shown in FIG. For the resulting tire, the modulus of the coating rubber of the reinforcing layer is measured by the following method.

[0075] [Measurement of modulus of coating rubber of tire reinforcing layer] The belt (reinforcing layer) is removed from the tire, and test pieces are prepared from the coated rubber portions of the center of the belt (reinforcing layer) in the tire width direction and the end portions of the belt (reinforcing layer) in the tire width direction. The test pieces were subjected to a tensile test at room temperature (25°C) in accordance with JIS K6251:2017 to measure the modulus at 50% elongation (Mod50, tensile stress at 50% elongation). The test was performed four times, and the average values ​​are shown in Table 1.

[0076] [Productivity evaluation] A tire in which the ratio (a / b) of the modulus (a) of the covering rubber at the center of the belt (reinforcing layer) in the tire width direction at 50% elongation to the modulus (b) of the covering rubber at the end of the tire width direction at 50% elongation is 0.94 or more and 1.06 or less is evaluated as having good productivity (◯), and a tire in which the ratio (a / b) is less than 0.94 or more than 1.06 is evaluated as having poor productivity (×).

[0077] [Table 1]

[0078] From Table 1, it can be seen that the tires of the examples according to the present invention have excellent productivity because the difference in modulus of the coating rubber between the center part in the tire width direction and the end parts in the tire width direction of the reinforcing layer is small, and vulcanization at high temperature in a short time is possible without deteriorating tire performance. [Explanation of symbols]

[0079] 1: Bead part 2: Sidewall 3: Tread section 4: Bead core 5: Carcass 6: Belt 6a, 6b: Reinforcement layer 6C: Center of the reinforcing layer in the tire width direction 6E: End of reinforcing layer in the tire width direction W: Maximum width of the reinforcing layer in the tire width direction

Claims

1. A tire having a reinforcing layer made of a reinforcing material and vulcanized rubber covering the reinforcing material, the vulcanized rubber is a vulcanized rubber of a rubber composition containing N-cyclohexyl-2-benzothiazolyl sulfenamide, the reinforcing material includes a metal in which the surface of a steel cord is coated with a ternary plating of copper, zinc, and iron; The reinforcing layer is disposed on the radially inner side of the tread surface, A tire in which the ratio (a / b) of the modulus (a) at 50% elongation of the vulcanized rubber covering the reinforcing material at the center part of the reinforcing layer in the tire width direction to the modulus (b) at 50% elongation of the vulcanized rubber covering the reinforcing material at the end part of the reinforcing layer in the tire width direction is 0.94 or more and 1.06 or less.

2. The tire according to claim 1 , wherein the amount of the iron in the coating is equal to or greater than 1 mass % and less than 10 mass % of the total mass of the copper, the zinc, and the iron.

3. The amount of phosphorus in the coating is 0 mg / m ２ More than 4 mg / m ２ 3. The tire according to claim 1 or 2, wherein:

4. The tire according to any one of claims 1 to 3, wherein the steel cord is subjected to wire drawing processing using a diamond die.

5. The tire according to any one of claims 1 to 4, wherein the rubber composition includes a rubber component containing 50% by mass or more of a polyisoprene-based rubber.

6. The vulcanized rubber-metal composite according to any one of claims 1 to 5, wherein the rubber composition has a cobalt-containing compound content of 0.01% by mass or less.

7. The vulcanized rubber-metal composite according to any one of claims 1 to 6, wherein the rubber composition contains an alkylphenol resin.

8. The tire according to any one of claims 1 to 7, wherein the content of cobalt atoms is 1% by mass or less.

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