JP2009292310A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire improving productivity by increasing vulcanization rates without impairing scorching performance and having excellent durability of a bead part. <P>SOLUTION: In a chafer pad 9 interposed between a ply folded-back part 2A of a carcass 2 and a rubber chafer 8, a rubber composition in which 30 to 60 pts.wt. of carbon black, 2 to 5 pts.wt. of sulfur, a phenolic compound or phenolic resin that the phenolic compound is condensed by formaldehyde, hexamethylenetetramine derivative or melamine derivative as a methylene donor and 1, 6-bis(N, N-dibenzylthiocarbamoyldithio)-hexane of 0.1 to 1.0 times pts.wt. of the sulfur are blended in 100 pts.wt. of diene based rubber is used. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire including a chafer pad using a specific rubber composition.

  Generally, in a pneumatic radial tire, both end portions of the carcass are folded and locked so as to wind up around the bead core at the bead portion. In order to protect the folded portion of the carcass, a rubber chafer (also referred to as a rim strip) is provided on the outer surface portion of the bead portion that contacts the rim flange.

  As a cause of the failure in such a bead portion, the rubber sandwiched between the carcass folded portion and the rim flange is greatly compressed, so that the rubber sags, the carcass cord and the coating rubber covering the cord, Causing separation in the rubber or near the cord. Further, heat is accumulated due to the deformation caused by the compression, and blow occurs beyond the heat resistance limit, which causes separation in the bead portion.

  Therefore, in order to improve such a failure of the bead portion, the following Patent Document 1 provides a reinforcing rubber (chafer pad) between the rubber chafer and the folded portion of the carcass in the bead portion. It is disclosed to form a rubber composition in which sodium 1,6-hexamethylenedithiosulfate dihydrate is blended with rubber.

  On the other hand, in order to improve the durability of the tire bead portion, it is known that a bead filler is formed using a rubber composition in which resorcin or a resorcin derivative and a methylene donor hexamethylenetetramine or melamine derivative are blended. (See Patent Document 2 below). Therefore, it can be considered that such a phenol-based adhesive resin is blended into the rubber composition for chafer pads.

  However, when the above phenol-based adhesive resin is blended, there is a problem that the vulcanization speed becomes slow. Since the bead portion, particularly the bead portion of a heavy duty tire used for trucks and buses, has a large thickness, it is difficult for heat to be transmitted during tire vulcanization molding. For this reason, when the vulcanization speed is low, productivity is greatly impaired.

  Therefore, it is conceivable to increase the vulcanization accelerator in order to increase the vulcanization speed. However, if the vulcanization accelerator is increased, problems such as rubber burning may occur in the calendering process, or the bead portion may be deteriorated due to poor adhesion. The durability may be reduced.

Patent Document 3 below discloses the use of a rubber composition in which 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane is blended with a rubber chafer. However, the rubber chafer is a non-adhesive rubber member different from the chafer pad that requires adhesion to the carcass, and ozone resistance as a tire outer surface is required. The required characteristics are completely different from the chafer pad. In addition, it does not disclose the point that the thiocarbamoyl compound, which is a feature of the present invention, is used in combination with the above-mentioned phenol-based adhesive resin, and thereby, by increasing the vulcanization rate without impairing the scorch property, There is no disclosure about the point that the productivity can be improved and the excellent durability of the bead portion can be maintained or improved.
JP-A-2005-219606 JP 2006-152043 A JP 2005-171016 A

  The present invention has been made in view of the above points, and provides a pneumatic radial tire that improves the productivity by increasing the vulcanization speed without impairing the scorch, and is excellent in the durability of the bead portion. For the purpose.

  A pneumatic radial tire according to the present invention includes a bead core embedded in a bead portion, a carcass that is folded back and locked around the bead core from the inner side in the tire axial direction, and an outer surface portion of the bead portion that contacts the rim flange. In a pneumatic radial tire comprising a rubber chafer constituting a chafer pad interposed between the carcass ply folded portion and the rubber chafer, the chafer pad has 100 parts by weight of diene rubber 30 to 60 parts by weight of carbon black, 2 to 5 parts by weight of sulfur, a phenolic resin obtained by condensing a phenolic compound or a phenolic compound with formaldehyde, and a hexamethylenetetramine or melamine derivative as a methylene donor And 1,6 to 0.1-1.0 parts by weight of the sulfur It is characterized in that using bis (N, N-dibenzylthiocarbamoyldithio) rubber composition containing a hexane, a.

  In the pneumatic radial tire of the present invention, by blending a predetermined amount of 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane together with a phenol-based adhesive resin, the scorch property is not impaired. The vulcanization speed can be increased and productivity can be improved. And the durability of the bead part excellent by adhesive resin can be maintained thru | or improved. In addition, by incorporating 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane, reversion resistance and heat aging resistance can be improved, and low exothermicity can be maintained or improved. Therefore, the durability which was excellent in the bead part also from this point can be provided.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  In the pneumatic radial tire of the present invention, the rubber composition used for the chafer pad contains a diene rubber as a rubber component. Examples of the diene rubber include natural rubber, isoprene rubber, styrene butadiene rubber, and polybutadiene rubber. Among these, natural rubber having excellent destructive properties is preferably used. Therefore, the rubber component is a diene rubber having natural rubber as a main component, that is, natural rubber alone, or 50% by weight or more of natural rubber. A blend with a diene rubber is preferred.

  The carbon black used in the rubber composition is not particularly limited, and grades generally used for chafer pads, for example, those of ISAF, HAF, and FEF can be used. Carbon black is blended in an amount of 30 to 60 parts by weight, more preferably 40 to 50 parts by weight, based on 100 parts by weight of the diene rubber in order to satisfy the properties as a chafer pad.

  Examples of the sulfur used in the rubber composition include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and oil-treated sulfur. Sulfur is blended at 2 to 5 parts by weight with respect to 100 parts by weight of the diene rubber. If the amount of sulfur is too small, it will be difficult to ensure the rigidity required for the chafer pad. Conversely, if it is too large, the vulcanization rate will be slow, and the heat resistance will deteriorate.

  The phenolic compound or phenol-based resin used in the rubber composition is a methylene acceptor corresponding to hexamethylenetetramine or a melamine derivative as a methylene donor, and is subjected to a curing reaction with a methylene group of the methylene donor. It acts as an adhesive resin that improves the adhesion to the ply.

  The phenol compounds include phenol, resorcin, or alkyl derivatives thereof. Alkyl derivatives include derivatives of relatively long-chain alkyl groups such as nonylphenol and octylphenol, as well as methyl group derivatives such as cresol and xylenol. The phenol compound may contain an acyl group such as an acetyl group as a substituent.

  In addition, phenolic resins obtained by condensing phenolic compounds with formaldehyde include resorcin-formaldehyde resins, phenolic resins (that is, phenol-formaldehyde resins), cresol resins (that is, cresol-formaldehyde resins), and a plurality of phenols. Formaldehyde resins made of compounds are included. These are uncured resins that have liquid or heat fluidity.

  Among these, resorcin or a resorcin derivative is preferable from the viewpoint of compatibility with the rubber component and other components, and the density and reliability of the resin after curing, and a resorcin-alkylphenol co-condensed formalin resin is particularly preferable.

  It is preferable that the compounding quantity of a phenol compound or a phenol-type resin is 0.5-3 weight part with respect to 100 weight part of diene rubbers, More preferably, it is 1-2 weight part. If the amount is too small, the adhesiveness is inferior. On the other hand, if the amount is too large, the low heat buildup and heat aging resistance are impaired, and the durability is inferior.

  Examples of the melamine derivative as the methylene donor include hexamethoxymethyl melamine, methylol melamine, a partially etherified product of methylol melamine, and a condensate of melamine, formaldehyde, and methanol. Among them, hexamethoxymethyl melamine is particularly preferable. .

  The amount of hexamethylenetetramine or melamine derivative used as a methylene donor is an amount sufficient to cause sufficient reaction and curing with respect to the methylene acceptor. Specifically, the phenolic compound or phenolic resin The amount is preferably 0.5 to 2 parts by weight of the amount. If the blending amount is less than 0.5 parts by weight, sufficient reaction and curing cannot be performed. Conversely, if it exceeds 2 parts by weight, physical properties of the rubber composition may be deteriorated. .

  1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane (hereinafter sometimes referred to as thiocarbamoyl compound) used in the rubber composition is 0.1 to 1 with respect to the amount of sulfur. It is blended at 0.0 parts by weight. More preferably, it is blended at 0.2 to 0.5 parts by weight of sulfur. In addition, the compounding quantity with respect to 100 weight part of diene rubbers of a thiocarbamoyl compound is although it does not specifically limit, It is preferable that it is 0.5-3.0 weight part.

  Thus, by blending a predetermined amount of the thiocarbamoyl compound, the vulcanization rate can be increased without impairing the scorch property. Moreover, this thiocarbamoyl compound acts as a reversion-resistant crosslinking agent, and can improve reversion resistance and heat aging resistance. Moreover, low exothermic property can be maintained or improved, and furthermore, the adhesive fracture resistance by the adhesive resin can be maintained. Therefore, a pneumatic radial tire excellent in durability of the bead portion can be obtained while improving productivity by the combination with the adhesive resin.

  As the thiocarbamoyl compound, “Vulcuren VP KA9188” (manufactured by LANXESS) can be exemplified and used.

  The rubber composition includes various additives generally used in chafer pad rubber compositions, such as other fillers such as silica, vulcanization accelerators, anti-aging agents, zinc white, stearic acid, and oil. Can be blended.

  The pneumatic radial tire of the present invention uses a rubber composition comprising the above as a chafer pad. FIG. 1 is a half sectional view of a tire (T) according to the embodiment.

  The tire (T) includes a pair of left and right bead portions (4) and sidewall portions (5), and a tread portion (3) straddling the both sidewall portions (5). The bead portion (4) is provided with an annular bead core (6) formed by winding a steel wire a plurality of times.

  Between the pair of left and right bead cores (6), there is provided a carcass (2) formed of at least one layer of a carcass ply formed by extending a large number of cords arranged at right angles to the tire circumferential direction. And both ends of the carcass (2) are folded back and locked so as to wrap the bead core (6) from the inner side in the tire axial direction to the outer side. A belt (1) in which at least two belt plies are overlapped is disposed outside the carcass (2) in the tread portion (3) in the radial direction. Further, on the tire outer peripheral side of the bead core (6), a rubber bead filler (7) is provided so as to have a substantially triangular cross section extending in a tapered shape outward in the tire radial direction.

  A bead part (4) is provided with a rubber chafer (8) as a rubber part which comprises the outer surface part of the part which contacts a rim flange (R). The rubber chafer (8) constitutes an outer surface portion of the bead portion that is opposed to the rim flange (R) and abuts against the rim flange (R) in a state where the tire (T) is mounted on the regular rim. As described above, the rubber chafer (8) is a rubber portion that abuts the rim flange (R) and forms the outer surface portion of the tire, and is thus formed of a rubber compound that is non-adhesive and has ozone resistance. .

  A chafer pad (9) made of a relatively thin rubber layer is interposed between the rubber chafer (8) and the ply turn-up portion (2A) of the carcass (2). Specifically, the chafer pad (9) has a tire axially inner surface that is in contact with a tire axially outer surface of the carcass folded portion (2A) and the tire axially outer surface is a rubber chafer (8) tire. It is formed in a state in contact with the axially inner side surface. The chafer pad (9) serves as a buffer layer between the carcass (2) coating rubber composed of an adhesive rubber compound and the rubber chafer (8) composed of a non-adhesive rubber compound, and couples them together. It is formed using the rubber composition according to the present invention described above.

  The tire (T) of this embodiment is a heavy-duty pneumatic radial tire used for trucks, buses, and the like. In general, heavy load tires require a considerable amount of time for vulcanization due to the large bead thickness. However, in this embodiment, the rubber composition is used for the chafer pad, so that the scorch is impaired. Therefore, the vulcanization speed can be increased without significantly increasing the productivity. In addition, a heavy duty tire requires particularly high durability, but excellent durability can be imparted by using the above rubber composition for the chafer pad. As described above, the present invention is particularly effective when applied to heavy-duty pneumatic radial tires used for trucks, buses and the like.

  Examples and Comparative Examples are shown below, but the present invention is not limited to these Examples.

  Using a Banbury mixer, a chafer pad rubber composition was prepared according to the formulation shown in Table 1 below. The details of each formulation in Table 1 are as follows.

・ Natural rubber: RSS # 3,
-Carbon black: HAF, “Seast 300” manufactured by Tokai Carbon Co., Ltd.
P-phenylenediamine: “Sant Flex 6PPD” manufactured by Flexis,
Styrenated diphenylamine: “LAS-P” manufactured by Seiko Chemical Industry Co., Ltd.
Resorcin derivative: resorcin-alkylphenol-formalin resin, “SUMIKANOL 620” manufactured by Sumitomo Chemical Co., Ltd.
Hexamethoxymethyl melamine: “Cyretz 963L (HMMM)” manufactured by Mitsui Cytec
Insoluble sulfur: “Cristex HS OT-20” (80% by weight is sulfur content) manufactured by Flexis,
・ Vulcanization accelerator NS: “Noxeller NS-P” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Thiocarbamoyl compound: 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane, “Vulcuren VP KA9188” manufactured by LANXESS.

  In each rubber composition, 3 parts by weight of oil (“JOMO Process P200” manufactured by Japan Energy Co., Ltd.) and zinc white (“Zinc Hana No. 3” manufactured by Mitsui Mining & Smelting Co., Ltd.) are used per 100 parts by weight of natural rubber. 5 parts by weight and 3 parts by weight of stearic acid (“Lunac S20” manufactured by Kao Corporation) were added.

  Each rubber composition obtained was evaluated for scorch properties, vulcanization speed, reversion resistance, heat aging resistance, and heat generation. In addition, a heavy-duty pneumatic radial tire (tire size: 11R22.5) having the cross-sectional structure shown in FIG. 1 using each rubber composition as a chafer pad was prepared, and the prototype tire obtained was subjected to ply rubber coverage and The drum durability was evaluated. Each evaluation method is as follows, and the results are shown in Table 1.

Scorch resistance: in conformity with JIS K6300, using a L-shaped rotor, was measured scorch time _{t 35} (minute) when measured at 125 ° C.. It means that scorch property is excellent, so that a numerical value is large.

- vulcanization rate: in conformity with JIS K6300, using a L-shaped rotor, was measured scorch time _{t 50} (minute) when measured at 0.99 ° C..

-Reversion resistance: Measured at 180 ° C. using an L-shaped rotor in accordance with JIS K6300, the time Δt ₁₀ (min) until the torque decreases by 10% from the maximum value (MH) Was measured. It means that it is excellent in reversion resistance, so that a numerical value is large.

Heat aging resistance: Each rubber composition was vulcanized at 150 ° C. for 30 minutes to prepare a test sample. The test piece was aged in a gear oven at 90 ° C. for 96 hours. Was used to conduct a tensile test in accordance with JIS K6253 (using No. 3 type dumbbell) and measure 100% modulus. The measured value after aging was determined as a percentage of the unaged measured value and was defined as the 100% modulus change rate. The smaller the value, the better the heat aging resistance.

Low exothermic property: Each rubber composition was vulcanized at 150 ° C. for 30 minutes to prepare a test sample. Each sample was subjected to a spectrometer manufactured by Toyo Seiki Co., Ltd. at a temperature of 60 ° C., a frequency of 50 Hz, and an initial strain of 10%. Tan δ was measured at a dynamic strain of 2%. It displays with the index | exponent which set the value of the comparative example 2 to 100, and shows that it is excellent in low heat generation property, so that a numerical value is small.

Ply rubber coverage: Each prototype tire was mounted on the rear wheel of a truck, and after traveling 100,000 km, the bead portion was disassembled, and the ply rubber coverage of the carcass portion in contact with the chafer pad was measured. For the ply rubber coverage, a steel cord constituting the carcass was taken out, and it was determined how much area ratio the steel cord was covered with rubber. That is, when 100% of the steel cord is covered with rubber is evaluated as 100, the closer to 100, the better the adhesiveness (adhesive fracture resistance, heat aging resistance).

Drum durability: For each prototype tire, an indoor drum tester equipped with a steel drum with a diameter of 1.7 m was used, the air pressure was 100% as specified in JIS D4230, the speed was 40 km / h, and the tire load was JIS. Starting from the specified 140%, the load was increased by 10% every 150 hours and a running test was conducted until a failure occurred in the tire. Based on the distance traveled until the failure of the prototype tire of Comparative Example 2, the case where the distance traveled until the failure was 10% or more shorter than that of Comparative Example 2 was “x (inferior)”, and the case where the distance was 10% or longer was “◯” (Good) ”and less than ± 10% were evaluated as“ Δ (equivalent) ”.

  As shown in Table 1, in Comparative Example 1, since there was no adhesive resin, ply rubber coverage and drum durability were inferior. On the other hand, in Comparative Example 2, although the ply coverage and the drum durability were improved, the vulcanization speed was slow.

  In Comparative Example 3, although the amount of sulfur was reduced and the amount of vulcanization accelerator was increased, the vulcanization speed was increased and the heat aging resistance was improved, but the scorch property was deteriorated and the low heat generation property was also inferior. In Comparative Example 4, a thiocarbamoyl compound was blended, but since the blending amount was small, no improvement effect was obtained with respect to Comparative Example 2. On the other hand, in Comparative Example 5 in which the amount of the thiocarbamoyl compound was too large, the reversion resistance, heat aging resistance and low heat build-up were good, but the scorch properties were poor. In Comparative Example 5, although there was an improvement effect such as heat aging resistance, internal damage occurred and the drum durability was the same as that in Comparative Example 2 and was not improved. This is presumed to be due to the poor fatigue resistance of Comparative Example 5.

  In Comparative Example 6, although the thiocarbamoyl compound was blended, the ply rubber coverage and the drum durability were inferior because the adhesive resin was not blended. On the other hand, in Comparative Example 7 in which the compounding amount of the adhesive resin was too large, the deterioration in low heat generation was large. Therefore, although it was excellent in reversion resistance, destruction within the member occurred and drum durability was equivalent to that of Comparative Example 2. This is presumed to be due to poor low heat generation.

  On the other hand, in Examples 1 to 3 according to the present invention, the scorch property was not deteriorated, and the vulcanization speed, reversion resistance and heat aging resistance were improved. The drum durability was also improved.

  Also in Example 4, the scorch property was not deteriorated, the vulcanization speed, the heat aging property and the heat aging property were improved, and the low heat build-up property was also excellent. However, because the amount of the thiocarbamoyl compound was large, the fatigue resistance was slightly deteriorated, so the drum durability was not improved as in Examples 1 to 3, and was equivalent to Comparative Example 2. .

  In Example 5 in which the blending amount of the adhesive resin was reduced with respect to Example 1, an effect of further improving low heat generation was obtained. Moreover, in Example 6 using styrenated diphenylamine instead of p-phenylenediamine as an anti-aging agent, an effect of improving low heat buildup was obtained as compared to Example 1.

1 is a half sectional view of a pneumatic radial tire according to an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Belt, 2 ... Carcass, 2A ... Ply turn part, 3 ... Tread part, 4 ... Bead part, 5 ... Side worm part, 6 ... Bead core, 7 ... Bead filler, 8 ... Rubber chafer, 9 ... Chafer pad

Claims (3)

A bead core embedded in the bead part; a carcass that is folded and locked around the bead core from the inner side to the outer side in the tire axial direction; a rubber chafer that forms an outer surface part of the bead part that abuts the rim flange; In a pneumatic radial tire including a chafer pad interposed between a ply turn-up portion and the rubber chafer,
To the chafer pad,
30 to 60 parts by weight of carbon black, 2 to 5 parts by weight of sulfur, a phenolic resin obtained by condensing a phenolic compound or a phenolic compound with formaldehyde, and a methylene donor as to 100 parts by weight of diene rubber A rubber composition containing hexamethylenetetramine or a melamine derivative and 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane in an amount of 0.1 to 1.0 parts by weight of the sulfur was used. A pneumatic radial tire characterized by that.   The rubber composition contains 0.5 to 3 parts by weight of the phenolic compound or phenolic resin based on 100 parts by weight of the diene rubber, and the hexamethylenetetramine or melamine derivative is mixed with the phenolic compound. Or the pneumatic radial tire of Claim 1 formed by mix | blending 0.5 to 2 times weight part of phenol-type resin.   The pneumatic radial tire according to claim 1 or 2, wherein a blending amount of 1,6-bis (N, N-dibenzylthiocarbamoyldithio) hexane with respect to sulfur is 0.2 to 0.5 times by weight.

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