JP2020196831A - Sealant material composition - Google Patents

Abstract

To provide a sealant material composition that ensures excellent sealability and can suppress the flowing of a sealant with traveling.SOLUTION: The present invention provides a sealant material composition that forms a sealant layer disposed on the inner surface of a pneumatic tire. Relative to 100 pts.mass of a rubber component containing chlorinated butyl rubber, the sealant material composition contains an organic peroxide of 1 pts.mass-40 pts.mass and a crosslinker of 0.1 pts.mass-40 pts.mass.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sealant material composition that constitutes a sealant layer of a self-sealing type pneumatic tire having a sealant layer on the inner surface of the tire.

In a pneumatic tire, it has been proposed to provide a sealant layer inside the inner liner layer in the tread portion in the tire radial direction (see, for example, Patent Document 1). In such a pneumatic tire, when a foreign substance such as a nail pierces the tread portion, the sealant flows into the through hole, so that the decrease in air pressure can be suppressed and the running can be maintained.

In the self-sealing type pneumatic tire described above, if the sealant has a low viscosity, the sealant can be expected to improve in that the sealant easily flows into the through hole, but due to the influence of heat and centrifugal force applied during running, If the sealant flows toward the tire center side and, as a result, the through hole deviates from the tire center region, the sealant may be insufficient and sufficient sealing property may not be obtained. On the other hand, if the sealant has a high viscosity, the above-mentioned flow of the sealant can be prevented, but the sealant does not easily flow into the through hole, and the sealing property may be deteriorated. Therefore, it is difficult to suppress the flow of the sealant during running and to secure good sealing performance, and measures are taken to improve the physical properties of the sealant material composition constituting the sealant layer and balance these performances. It has been demanded.

Japanese Unexamined Patent Publication No. 2006-152110

An object of the present invention is to provide a sealant material composition capable of ensuring good sealing property and suppressing the flow of the sealant during running.

The sealant material composition of the present invention that achieves the above object is a sealant material composition constituting a sealant layer arranged on the inner surface of a pneumatic tire, with respect to 100 parts by mass of a rubber component containing chlorinated butyl rubber. , 1 part by mass to 40 parts by mass of the organic peroxide and 0.1 parts by mass to 40 parts by mass of the cross-linking agent are blended.

When the sealant material composition of the present invention has the above-mentioned composition, it can ensure good sealing properties when used in the sealant layer of a pneumatic tire and can suppress the flow of the sealant during running. .. In particular, by containing chlorinated butyl rubber and cross-linking with a cross-linking agent and an organic peroxide in combination, an appropriate viscosity that does not flow during running is ensured while ensuring sufficient viscosity to obtain good sealing properties. It is possible to obtain elasticity and achieve both of these performances in a well-balanced manner.

In the present invention, it is preferable that the rubber component further contains a halogenated butyl rubber other than the chlorinated butyl rubber. By using chlorinated butyl rubber in combination with other halogenated butyl rubber in this way, the viscosity, elasticity, etc., depending on the part of the sealant composition (sealant layer) after vulcanization due to the difference in vulcanization rate of these rubbers. There is a difference in the physical properties of the rubber, which is advantageous for achieving a good balance between good sealing performance and appropriate fluidity.

In the present invention, it is preferable that the cross-linking agent contains a sulfur component. As a result, the reactivity of the rubber component (butyl halogenated rubber) with the cross-linking agent (sulfur) or the organic peroxide is enhanced, and the processability of the sealant material composition can be improved.

In the present invention, it is preferable that 50 parts by mass to 400 parts by mass of the liquid polymer is blended with respect to 100 parts by mass of the rubber component. At this time, the liquid polymer is preferably paraffin oil. Further, the molecular weight of paraffin oil is preferably 800 or more. As a result, it is possible to impart an appropriately high viscosity to the rubber component, which is advantageous for improving the sealing property.

In the present invention, it is preferable to include a vulcanization accelerator. At this time, it is preferable that the vulcanization accelerator is a thiuram-based vulcanization accelerator. As a result, the vulcanization rate can be increased and the productivity can be increased.

In the pneumatic tire provided with the sealant layer made of the sealant material composition of the present invention described above, it is possible to achieve both ensuring the sealing property and suppressing the flow of the sealant in a well-balanced manner due to the excellent physical properties of the sealant material composition. ..

It is a meridian cross-sectional view which shows an example of the self-seal type pneumatic tire to which this invention is applied.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

In the sealant material composition of the present invention, the rubber component always contains butyl halogenated rubber. The halogenated rubber always contains chlorinated butyl rubber, and other halogenated butyl rubber such as brominated butyl rubber can be optionally used in combination. By using butyl halogenated rubber (butyl chlorinated rubber) in this way, the reactivity of the rubber component with the cross-linking agent and organic peroxide described later is enhanced, and both ensuring sealing properties and suppressing the flow of the sealant can be achieved at the same time. Will be advantageous. In addition, the processability of the sealant material composition can be improved. As the halogenated butyl rubber, those usually used in a sealant material composition can be used.

The proportion of chlorinated butyl rubber in the halogenated butyl rubber is preferably 1% by mass or more, more preferably 10% by mass or more. If the proportion of chlorinated butyl rubber is less than 1% by mass, the reactivity between the rubber component and the cross-linking agent or organic peroxide described later is not sufficiently improved, and the desired effect cannot be sufficiently obtained.

In the sealant material composition of the present invention, the entire amount of the rubber component does not have to be halogenated butyl rubber, and non-halogenated butyl rubber can also be used in combination. Examples of the non-halogenated butyl rubber include unmodified butyl rubber usually used in a sealant material composition, for example, BUTYL-065 manufactured by JSR Corporation and BUTYL-301 manufactured by LANXESS Corporation. When the halogenated butyl rubber and the non-halogenated butyl rubber are used in combination, the blending amount of the non-halogenated butyl rubber is preferably less than 20% by mass, more preferably less than 10% by mass in 100% by mass of the rubber component.

In the sealant material composition of the present invention, it is preferable to use two or more kinds of rubbers in combination. That is, it is preferable to use another halogenated butyl rubber (for example, brominated butyl rubber) or non-halogenated butyl rubber in combination with the chlorinated butyl rubber. Since the vulcanization rates of chlorinated butyl rubber, other halogenated butyl rubber, and non-halogenated butyl rubber are different from each other, by using at least two types in combination, vulcanization is caused by the difference in their vulcanization rates. Physical properties such as viscosity and elasticity will differ depending on the site of the sealant composition (sealant layer) after vulcanization. As a result, the fluidity is suppressed in the relatively hard portion, and the sealing property is exhibited in the relatively soft portion, which is advantageous for achieving both of these performances in a well-balanced manner.

The sealant material composition of the present invention always contains a cross-linking agent and an organic peroxide. The organic peroxide is also a kind of cross-linking agent, but the "cross-linking agent" in the present invention is a cross-linking agent excluding the organic peroxide, for example, sulfur, zinc flower, cyclic sulfide, resin (resin addition). (Sulfide), amine (amine vulcanization), quinonedioxime and the like can be exemplified. As the cross-linking agent other than the organic peroxide, it is particularly preferable to use one containing a sulfur component (for example, sulfur). By blending the cross-linking agent and the organic peroxide in combination in this way, it is possible to realize an appropriate cross-linking for both ensuring the sealing property and preventing the flow of the sealant. The blending amount of the cross-linking agent is 0.1 parts by mass to 40 parts by mass, preferably 0.5 parts by mass to 10 parts by mass with respect to 100 parts by mass of the above-mentioned rubber component. The amount of the organic peroxide compounded is 1 part by mass to 40 parts by mass, preferably 5 parts by mass to 20 parts by mass with respect to 100 parts by mass of the above-mentioned rubber component. If the blending amount of the cross-linking agent is less than 0.1 parts by mass, it is substantially equivalent to not containing the cross-linking agent, and appropriate cross-linking cannot be performed. If the blending amount of the cross-linking agent exceeds 40 parts by mass, the cross-linking of the sealant material composition proceeds too much and the sealing property deteriorates. If the blending amount of the organic peroxide is less than 1 part by mass, it is substantially equivalent to containing no organic peroxide, and appropriate crosslinking cannot be performed. If the amount of the organic peroxide compounded exceeds 40 parts by mass, the sealant composition is crosslinked too much and the sealing property is deteriorated.

When the cross-linking agent and the organic peroxide are used in combination in this way, the ratio A / B of the cross-linking agent blending amount A and the organic peroxide blending amount B is preferably 5/1 to 1/200. It is preferably 1/10 to 1/20. With such a blending ratio, it is possible to achieve both ensuring the sealing property and preventing the flow of the sealant in a more balanced manner.

Examples of the organic peroxide include dicumyl peroxide, t-butyl cumyl peroxide, benzoyl peroxide, dibenzoyl peroxide, butyl hydroperoxide, p-chlorobenzoyl peroxide, 1,1,3,3-. Examples thereof include tetramethylbutyl hydroperoxide. In particular, an organic peroxide having a one-minute half-life temperature of 100 ° C. to 200 ° C. is preferable, and among the above-mentioned specific examples, dicumyl peroxide and t-butyl cumyl peroxide are particularly preferable. In the present invention, the "1 minute half-life temperature" generally adopts the value described in "Organic Peroxide Catalog 10th Edition" of NOF CORPORATION, and if not described, it is described in the catalog. The value obtained from thermal decomposition in an organic solvent is adopted in the same manner as in the above method.

The sealant material composition of the present invention can contain a liquid polymer. By blending the liquid polymer in this way, the viscosity of the sealant material composition can be increased and the sealing property can be improved. The blending amount of the liquid polymer is preferably 50 parts by mass to 400 parts by mass, and more preferably 70 parts by mass to 200 parts by mass with respect to 100 parts by mass of the above-mentioned rubber component. If the blending amount of the liquid polymer is less than 50 parts by mass, the effect of increasing the viscosity of the sealant material composition may not be sufficiently obtained. If the blending amount of the liquid polymer exceeds 400 parts by mass, the flow of the sealant cannot be sufficiently prevented.

The liquid polymer is preferably co-crosslinked with the rubber component (butyl rubber) in the sealant composition, and examples thereof include aroma oil, polybutene oil, paraffin oil, polyisoprene oil, polybutadiene oil, and polyisobutene oil. .. Among these, paraffin oil is preferably used from the viewpoint of suppressing the temperature dependence of the physical properties of the sealant material composition to be low. When paraffin oil is used, its molecular weight is preferably 800 or more, more preferably 1000 or more, still more preferably 1200 or more and 3000 or less. By using a tire having a large molecular weight in this way, it is possible to prevent the oil component from migrating from the sealant layer provided on the inner surface of the tire to the tire body and affecting the tire.

A vulcanization accelerator may be added to the sealant material composition of the present invention. By blending the vulcanization accelerator, the vulcanization rate can be increased and the productivity of the sealant material composition can be increased. The blending amount of the vulcanization accelerator is preferably 0.1 part by mass to 10.0 parts by mass, and more preferably 1.0 part by mass to 5.0 parts by mass with respect to 100 parts by mass of the above-mentioned rubber component. ..

As the vulcanization accelerator, for example, guanidine-based, thiuram-based, dithiocarbamate-based, and thiazole-based vulcanization accelerators can be used. Examples of the guanidine-based vulcanization accelerator include diphenylguanidine and dioltotrilguanidine. Examples of the thiuram-based vulcanization accelerator include tetramethylthiuram monosulfide and tetramethylthiuram disulfide. Examples of the dithiocarbamate-based vulcanization accelerator include sodium dimethyldithiocarbamate and sodium diethyldithiocarbamate. Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole and dibenzothiazyl disulfide. Among these, a thiuram-based vulcanization accelerator is preferable, and variations in the performance of the obtained sealant material composition can be suppressed. Among the thiuram-based vulcanization accelerators, tetramethylthiuram disulfide is particularly suitable because it has a high vulcanization promoting effect.

Since the sealant material composition of the present invention contains at least chlorinated butyl rubber, it is good to carry out cross-linking by using a cross-linking agent and an organic peroxide in combination while imparting an appropriately high viscosity to the rubber component. While ensuring sufficient viscosity to obtain a good sealing property, it is possible to obtain appropriate elasticity that does not flow during traveling, and to achieve both of these performances in a well-balanced manner. Therefore, if it is used for the sealant layer of the self-sealing type pneumatic tire described later, good sealing performance can be exhibited without causing the sealant layer to flow during traveling.

As shown in FIG. 1, for example, a self-sealing type pneumatic tire to which the present invention is applied includes a tread portion 1 extending in the tire circumferential direction and forming an annular shape, and a pair arranged on both sides of the tread portion 1. A pair of bead portions 3 arranged inside the sidewall portion 2 in the tire radial direction are provided. In FIG. 1, reference numeral CL indicates the tire equator. Although FIG. 1 is a cross-sectional view of the meridian, the tread portion 1, the sidewall portion 2, and the bead portion 3 each extend in the tire circumferential direction to form an annular shape, whereby the pneumatic tire is formed. The toroidal basic structure of is constructed. Further, other tire components in the meridian cross-sectional view also extend in the tire circumferential direction to form an annular shape unless otherwise specified.

In the example of FIG. 1, a carcass layer 4 is mounted between the pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the inside to the outside of the vehicle around the bead core 5 and the bead filler 6 arranged in each bead portion 3. The bead filler 6 is arranged on the outer peripheral side of the bead core 5, and is wrapped by a main body portion and a folded portion of the carcass layer.

A plurality of layers (two layers in FIG. 1) of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. Among these plurality of belt layers 7, the layer having the smallest belt width is referred to as the minimum belt layer 7a, and the layer having the largest belt width is referred to as the maximum belt layer 7b. Each belt layer 7 includes a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to intersect each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in the range of, for example, 10 ° to 40 °. A belt reinforcing layer 8 is provided on the outer peripheral side of the belt layer 7 in the tread portion 1. In the illustrated example, two belt reinforcing layers 8 are provided, one is a full cover layer covering the entire width of the belt layer 7, and the other is an edge cover layer arranged on the outer peripheral side of the full cover layer and covering only the end portion of the belt layer 7. ing. The belt reinforcing layer 8 includes an organic fiber cord oriented in the tire circumferential direction, and the angle of the organic fiber cord with respect to the tire circumferential direction is set to, for example, 0 ° to 5 °.

An inner liner layer 9 is provided on the inner surface of the tire along the carcass layer 4. The inner liner layer 9 is a layer for preventing the air filled in the tire from permeating to the outside of the tire. The inner liner layer 9 is composed of, for example, a rubber composition mainly composed of butyl rubber having an air permeation prevention property. Alternatively, it may be composed of a resin layer having a thermoplastic resin as a matrix. In the case of the resin layer, the elastomer component may be dispersed in the matrix of the thermoplastic resin.

As shown in FIG. 1, a sealant layer 10 is provided inside the inner liner layer 9 in the tread portion 1 in the tire radial direction. The sealant material composition of the present invention is used for the sealant layer 10. The sealant layer 10 is attached to the inner surface of a pneumatic tire having the above-mentioned basic structure. For example, when a foreign substance such as a nail pierces the tread portion 1, the sealant layer 10 is formed in the through hole thereof. The inflow of the sealant material suppresses the decrease in air pressure and makes it possible to maintain running.

The sealant layer 10 has a thickness of, for example, 0.5 mm to 5.0 mm. By having such a thickness, it is possible to suppress the flow of the sealant during traveling while ensuring good sealing performance. In addition, the workability when the sealant layer 10 is attached to the inner surface of the tire is also improved. If the thickness of the sealant layer 10 is less than 0.5 mm, it becomes difficult to secure sufficient sealing properties. If the thickness of the sealant layer 10 exceeds 5.0 mm, the tire weight increases and the rolling resistance deteriorates. The thickness of the sealant layer 10 is an average thickness.

The sealant layer 10 can be formed by later attaching it to the inner surface of the vulcanized pneumatic tire. For example, a sealant material made of the sealant material composition described later and molded into a sheet shape may be attached over the entire circumference of the inner surface of the tire, or a sealant material made of the sealant material composition described later and molded into a string shape or a band shape. Can be spirally attached to the inner surface of the tire to form the sealant layer 10. Further, at that time, by heating the sealant material composition, it is possible to suppress variations in the performance of the sealant material composition. As the heating conditions, the temperature is preferably 140 ° C. to 180 ° C., more preferably 160 ° C. to 180 ° C., and the heating time is preferably 5 minutes to 30 minutes, more preferably 10 minutes to 20 minutes. According to this method for manufacturing a pneumatic tire, it is possible to efficiently manufacture a pneumatic tire having a good sealing property at the time of puncture and less likely to cause the flow of the sealant.

The sealant layer 10 is provided on the inner surface of the tire corresponding to a region where foreign matter such as a nail may pierce during traveling, that is, a ground contact region of the tread portion 1. As described above, in the sealant layer 10 provided over a wide range on the inner surface of the tire, the flow of the sealant material is remarkable at the end portion in the tire width direction, but not only that, but also the overall flow in the entire area in the tire width direction. It may occur. On the other hand, in the sealant material composition of the present invention, the sealing property and the fluidity are well-balanced and highly compatible by the above-mentioned formulation, so that the flow of the sealant material during high-speed running, particularly the overall flow, is achieved. The flow can also be effectively suppressed.

Hereinafter, the present invention will be further described with reference to Examples, but the scope of the present invention is not limited to these Examples.

A sealant material composition constituting a sealant layer in a pneumatic tire having a tire size of 255 / 40R20, having the basic structure shown in FIG. 1, and having a sealant layer made of a sealant inside the inner liner layer in the tread portion in the tire radial direction. The tires of Comparative Examples 1 to 3 and Examples 1 to 19 in which the compositions of the above were prepared as shown in Table 1 were produced.

For these test tires, the sealing property and the fluidity of the sealant material were evaluated by the following test methods, and the results are shown in Tables 1 and 2.

Sealability Each test tire is assembled to a wheel with a rim size of 20 x 9J and mounted on the test vehicle. The initial air pressure is 250 kPa, the load is 8.5 kN, a nail with a diameter of 4 mm is driven into the tread, and then the nail is pulled out. The air pressure was measured after the tire was allowed to stand for 1 hour in the state of being in the state. The evaluation results are shown in the following five stages.
5: Air pressure after standing still is 240 kPa or more and 250 kPa or less 4: Air pressure after standing is 230 kPa or more and less than 240 kPa 3: Air pressure after standing is 220 kPa or more and less than 230 kPa 2: Air pressure after standing is 200 kPa or more and less than 230 kPa Less than 220 kPa 1: Air pressure after standing is less than 200 kPa

Sealant fluidity test tires are assembled on wheels with a rim size of 20 x 9J and mounted on a drum tester, with an air pressure of 220 kPa, a load of 8.5 kN, and running speeds of 100 km / h, 150 km / h, and 200 km / h. It was run in three stages for one hour at each speed, and the flow state of the sealant after running at each speed was examined. The evaluation result is that a line of 5 mm grid ruled 20 x 40 squares is drawn on the surface of the sealant layer before running, the number of squares whose shape is distorted after running is counted, and no flow of sealant is observed (distorted squares). The number of distorted cells is 0) is indicated by "○", the case where the number of distorted cells is less than 1/4 of the total is indicated by "△", and the number of distorted cells is 1/4 or more of the total. Is indicated by "x".

The types of raw materials used in Tables 1 and 2 are shown below.
-Halogenated IIR1: Chlorinated butyl rubber, JSR CHLOROBUTYL 1066
-Halogenated IIR2: Butyl brominated rubber, BROMOBUTYL2222 manufactured by JSR Corporation
-Halogenated IIR: BUTYL065 manufactured by JSR Corporation
-Organic peroxide: Dibenzoyl peroxide, NOF NS manufactured by NOF CORPORATION (1 minute half-life temperature: 133 ° C)
・ Cross-linking agent 1: Sulfur, small-lump sulfur manufactured by Hosoi Chemical Industry Co., Ltd.
-Crosslinking agent 3: Phenolic resin, TD-2620 manufactured by DIC Corporation
・ Vulcanization accelerator 1: Thiram-based vulcanization accelerator, Noxeller DM-PO manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
-Vulcanization accelerator 2: Guanidine-based vulcanization accelerator, Noxeller D manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
-Liquid polymer 1: Liquid butyl rubber, Karen 800 manufactured by Royal Elastomer (molecular weight: 36000)
-Liquid polymer 2: Paraffin oil, Idemitsu Kosan Diana Process PW-380 (Molecular weight: 1500)
-Liquid polymer 3: Paraffin oil, Idemitsu Kosan Diana Process K-350 (Molecular weight: 800)

As is clear from Tables 1 and 2, the pneumatic tires of Examples 1 to 19 suppressed the flow of the sealant while exhibiting good sealing properties. In particular, the flow of the sealant could be effectively suppressed even during high-speed driving.

On the other hand, in Comparative Example 1, since the sealant material composition did not contain chlorinated butyl rubber, the fluidity of the sealant at high speed was deteriorated. In Comparative Example 2, since the amount of the organic peroxide compounded was small, the sealing property was deteriorated. Since Comparative Example 3 did not contain a cross-linking agent, the fluidity deteriorated under all speed conditions.

1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt reinforcement layer 9 Inner liner layer 10 Sealant layer CL Tire equator

Claims (9)

A sealant material composition constituting a sealant layer arranged on the inner surface of a pneumatic tire, in which 1 part by mass to 40 parts by mass of an organic peroxide is crosslinked with respect to 100 parts by mass of a rubber component containing chlorinated butyl rubber. A sealant material composition comprising 0.1 parts by mass to 40 parts by mass of an agent. The sealant composition according to claim 1, wherein the rubber component further contains a halogenated butyl rubber other than the chlorinated butyl rubber. The sealant composition according to claim 1 or 2, wherein the cross-linking agent contains a sulfur component. The sealant material composition according to any one of claims 1 to 3, wherein 50 parts by mass to 400 parts by mass of a liquid polymer is blended with respect to 100 parts by mass of a rubber component. The sealant composition according to claim 4, wherein the liquid polymer is paraffin oil. The sealant material composition according to claim 5, wherein the paraffin oil has a molecular weight of 800 or more. The sealant composition according to any one of claims 1 to 6, which comprises a vulcanization accelerator. The sealant composition according to claim 7, wherein the vulcanization accelerator is a thiuram-based vulcanization accelerator. A pneumatic tire provided with the sealant layer comprising the sealant material composition according to any one of claims 1 to 8.

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