JP7127617B2 - sealant composition - Google Patents

Description

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

In pneumatic tires, it has been proposed to provide a sealant layer radially inward of an inner liner layer in a tread portion (see, for example, Patent Document 1). In such a pneumatic tire, when a foreign object such as a nail pierces the tread portion, the sealant flows into the through hole, thereby suppressing a decrease in air pressure and making it possible to maintain running.

In the self-sealing pneumatic tire described above, if the viscosity of the sealant is low, the sealant can easily flow into the through-holes, which can improve the sealing performance. If the sealant flows toward the tire center side and, as a result, the through-hole deviates from the tire center region, there is a possibility that the sealant will be insufficient and sufficient sealing performance will not be obtained. On the other hand, if the viscosity of the sealant is high, the flow of the sealant described above can be prevented, but the sealant is less likely to flow into the through-hole, and there is a risk that the sealability will deteriorate. Therefore, it is difficult to suppress the flow of the sealant during running and to ensure good sealing properties. It has been demanded. In addition, since the sealant layer continues to be held in the tire as long as foreign objects such as nails do not pierce the tread portion, it is necessary to maintain performance over a long period of time, for example, to suppress oxidation deterioration and improve sealing performance. It is also required to maintain

JP-A-2006-152110

SUMMARY OF THE INVENTION An object of the present invention is to provide a sealant material composition that can ensure good sealing performance and suppress the flow of the sealant during running.

The sealant material composition of the present invention for achieving the above object is a sealant material composition constituting a sealant layer disposed on the inner surface of a pneumatic tire, comprising more than 10% by mass of non-halogenated butyl rubber and halogenated butyl rubber. 1 part by mass to 40 parts by mass of an organic peroxide and 0.1 part by mass to 40 parts by mass of a cross-linking agent are blended with respect to 100 parts by mass of a rubber component containing

Since the sealant material composition of the present invention has the above-mentioned formulation, when it is used in the sealant layer of a pneumatic tire, it can ensure good sealing performance and suppress the flow of the sealant during running. . In particular, by containing more than 10% by mass of non-halogenated butyl rubber, and by performing cross-linking with a combination of a cross-linking agent and an organic peroxide, while ensuring sufficient viscosity to obtain good sealing properties, the It is possible to achieve both these performances in a well-balanced manner by obtaining an appropriate elasticity that does not flow easily. In addition, due to the low reactivity of the non-halogenated butyl rubber, it is possible to suppress oxidative deterioration and maintain good sealing properties.

In the present invention, as described above, the rubber component contains halogenated butyl rubber together with the non-halogenated butyl rubber . By using a non-halogenated butyl rubber and a halogenated butyl rubber in combination in this manner, workability can be improved. In addition, due to the difference in vulcanization speed of these rubbers, physical properties such as viscosity and elasticity differ depending on the part of the sealant composition (sealant layer) after vulcanization, resulting in good sealability and moderate fluidity. It is advantageous to achieve both in a well-balanced manner.

In the present invention, the cross-linking agent preferably contains a sulfur component. As a result, the reactivity between the rubber component (halogenated butyl rubber) and the cross-linking agent (sulfur) or organic peroxide is increased, and the workability of the sealant material composition can be improved.

In the present invention, it is preferable that 50 to 400 parts by mass of the liquid polymer is blended with 100 parts by mass of the rubber component. At this time, the liquid polymer is preferably paraffin oil. Furthermore, it is preferable that the molecular weight of the paraffin oil is 1000 or more. This makes it possible to impart a moderately high viscosity to the rubber component, which is advantageous for improving sealing properties.

In the present invention, it is preferred that a vulcanization accelerator is included. At this time, the vulcanization accelerator is preferably a thiuram-based vulcanization accelerator. Thereby, the vulcanization speed can be increased and the productivity can be improved.

In the pneumatic tire provided with the sealant layer composed of the sealant material composition of the present invention described above, the excellent physical properties of the sealant material composition make it possible to achieve a good balance between ensuring sealing performance and suppressing flow of the sealant. .

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a meridian sectional view showing an example of a self-sealing pneumatic tire to which the present invention is applied;

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

In the sealant composition of the present invention, the rubber component necessarily comprises non-halogenated butyl rubber. Non-halogenated butyl rubbers include unmodified butyl rubbers commonly used in sealant compositions, such as BUTYL-065 manufactured by JSR and BUTYL-301 manufactured by LANXESS. The content of the non-halogenated butyl rubber is more than 10% by mass, preferably 10% by mass or more and 50% by mass or less in 100% by mass of the rubber component. By using a non-halogenated butyl rubber in this way, the rubber component and the cross-linking agent and the organic peroxide described later react well, which is advantageous in ensuring both sealing performance and suppressing the flow of the sealant. .

In the sealant material composition of the present invention, it is not necessary that the entire amount of the rubber component is non-halogenated butyl rubber, and one or more other rubbers selected from natural rubber, halogenated butyl rubber, butadiene rubber, and styrene-butadiene rubber are used. They can also be used in combination. Among these, it is particularly preferable to use halogenated butyl rubber together. Halogenated butyl rubbers include those commonly used in sealant compositions, such as chlorinated butyl rubbers and brominated butyl rubbers. By using the halogenated butyl rubber in this manner, the reactivity between the rubber component and the cross-linking agent and the organic peroxide described later is increased, which is advantageous for ensuring both sealing performance and suppressing flow of the sealant. In addition, the workability of the sealant material composition can be improved.

When a rubber other than the non-halogenated butyl rubber is used in combination, the amount of the other rubber is less than 90% by mass, preferably 30% by mass or more and 80% by mass or less in 100% by mass of the rubber component. In particular, when halogenated butyl rubber is used in combination, the halogenated butyl rubber preferably contains chlorinated butyl rubber, and 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. should be

In the sealant material composition of the present invention, it is preferable to use two or more rubbers in combination. That is, it is preferable to use halogenated butyl rubber (for example, chlorinated butyl rubber or brominated butyl rubber) in combination with non-halogenated butyl rubber. Since these rubbers have different vulcanization speeds, by using at least two types in combination, the viscosity and viscosity of the sealant composition (sealant layer) after vulcanization may vary depending on the part of the sealant composition (sealant layer) after vulcanization due to the difference in vulcanization speed. A difference occurs in physical properties such as elasticity. As a result, the fluidity is suppressed in the relatively hard portion, and the sealing performance is exhibited in the relatively soft portion, which is advantageous in 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 other than the organic peroxide. sulfur), amine (amine vulcanization), quinone dioxime, and the like. 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 appropriate cross-linking for ensuring both sealing performance and preventing flow of the sealant. The amount of the cross-linking agent is 0.1 to 40 parts by mass, preferably 0.5 to 10 parts by mass, per 100 parts by mass of the rubber component. The amount of the organic peroxide compounded is 1 to 40 parts by mass, preferably 10 to 20 parts by mass, per 100 parts by mass of the rubber component. If the amount of the cross-linking agent is less than 0.1 parts by mass, it is equivalent to not containing the cross-linking agent, and appropriate cross-linking cannot be achieved. If the amount of the cross-linking agent exceeds 40 parts by mass, the cross-linking of the sealant material composition progresses too much and the sealability deteriorates. If the amount of the organic peroxide to be blended is less than 1 part by mass, it is equivalent to substantially not containing the organic peroxide, and appropriate cross-linking cannot be performed. If the amount of the organic peroxide is more than 40 parts by mass, the sealant composition will be crosslinked too much and the sealability will deteriorate.

When a cross-linking agent and an organic peroxide are used in combination in this way, the ratio A/B of the amount A of the cross-linking agent and the amount B of the organic peroxide is preferably 5/1 to 1/200, or more. It is preferably 1/10 to 1/20. By setting it as such a compounding ratio, it becomes possible to balance securing of a sealing property and prevention of a sealant flow.

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

The sealant composition of the present invention can contain a liquid polymer. By blending the liquid polymer in this manner, the viscosity of the sealant material composition can be increased to improve the sealability. The amount of the liquid polymer compounded is preferably 50 to 400 parts by mass, more preferably 100 to 200 parts by mass, per 100 parts by mass of the rubber component. If the 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 capable of co-crosslinking with the rubber component (butyl rubber) in the sealant material composition. . Among these, paraffin oil is preferably used from the viewpoint of keeping the temperature dependence of the physical properties of the sealant material composition low. When paraffin oil is used, its molecular weight is preferably 1000 or more, more preferably 1200 or more and 3000 or less. By using a compound having a large molecular weight in this manner, it is possible to prevent the oil content 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 adding a vulcanization accelerator, the vulcanization speed can be increased, and the productivity of the sealant material composition can be increased. The amount of the vulcanization accelerator compounded is preferably 0.1 to 10.0 parts by mass, more preferably 1.0 to 5.0 parts by mass with respect to 100 parts by mass of the rubber component. .

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

The sealant material composition of the present invention contains at least a non-halogenated butyl rubber, thereby imparting a moderately high viscosity to the rubber component and cross-linking with a combination of a cross-linking agent and an organic peroxide. While securing sufficient viscosity to obtain good sealing properties, it is possible to obtain appropriate elasticity that does not flow during running, and achieve both of these properties in a well-balanced manner. Therefore, if it is used in the sealant layer of a self-sealing pneumatic tire, which will be described later, the sealant layer does not flow during running, and good sealing performance can be exhibited. In addition, since the non-halogenated butyl rubber having low reactivity is contained, deterioration due to oxidation is suppressed and the sealability is maintained, so that good sealability can be exhibited over a long period of time.

Furthermore, outside air (particularly oxygen) may flow into the tire during the period from when a foreign object such as a nail is stuck in the tire until the sealant flows into the through-hole, and the puncture seal is performed once by the sealant layer. In the tire, the sealant layer may be more susceptible to oxidative deterioration due to the oxygen that has flowed into the tire. On the other hand, the sealant material composition of the present invention, as described above, contains a non-halogenated butyl rubber to suppress the progress of oxidative deterioration, thereby maintaining the sealing performance. Even if a foreign object such as a nail or the like is stuck in another part of the tire after the tire is sealed, the excellent sealing performance can be continuously exhibited.

A self-sealing pneumatic tire to which the present invention is applied comprises, for example, as shown in FIG. and a pair of bead portions 3 arranged inside the sidewall portion 2 in the tire radial direction. In FIG. 1, symbol CL indicates the tire equator. Although FIG. 1 is a meridional sectional view and is not depicted, the tread portion 1, the sidewall portion 2, and the bead portion 3 each extend in the tire circumferential direction and form an annular shape. A toroidal basic structure is constructed. Further, unless otherwise specified, other tire constituent members in meridional cross-sectional views also extend in the tire circumferential direction and form an annular shape.

In the example of FIG. 1, a carcass layer 4 is mounted between a 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 vehicle inner side to the outer side 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 the main portion and the folded portion of the carcass layer.

A plurality of (two layers in FIG. 1) belt layers 7 are embedded in the outer peripheral side of the carcass layer 4 in the tread portion 1 . Among these multiple belt layers 7, the layer with the smallest belt width is called the smallest belt layer 7a, and the layer with the largest belt width is called the largest belt layer 7b. Each belt layer 7 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to cross each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set, for example, in the range of 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: a full cover layer that covers the entire width of the belt layer 7 and an edge cover layer that is arranged further on the outer peripheral side of the full cover layer and covers only the ends of the belt layer 7. ing. The belt reinforcing layer 8 includes organic fiber cords oriented in the tire circumferential direction, and the angles of the organic fiber cords with respect to the tire circumferential direction are set to, for example, 0° to 5°.

An inner liner layer 9 is provided along the carcass layer 4 on the inner surface of the tire. This 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 air permeation prevention performance. Alternatively, it can 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 a thermoplastic resin matrix.

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 this sealant layer 10 . The sealant layer 10 is adhered to the inner surface of the pneumatic tire having the basic structure described above. For example, when a foreign object such as a nail pierces the tread portion 1, the sealant layer 10 forms the through hole. The inflow of the sealant material suppresses the decrease in air pressure, making 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 running while ensuring good sealing performance. In addition, workability is improved when the sealant layer 10 is adhered to the inner surface of the tire. When the thickness of the sealant layer 10 is less than 0.5 mm, it becomes difficult to ensure sufficient sealing performance. When 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 the average thickness.

The sealant layer 10 can be formed by attaching it to the inner surface of the vulcanized pneumatic tire later. For example, a sheet-shaped sealant material made of the sealant material composition described later is 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 in the shape of a string or band. can be spirally attached to the inner surface of the tire to form the sealant layer 10 . Moreover, at that time, by heating the sealant material composition, variations in performance of the sealant material composition can be suppressed. 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 that has good sealing properties when punctured and that prevents the sealant from flowing.

EXAMPLES The present invention will be further described with reference to examples below, 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. Tires of Comparative Examples 1 to 4 and Examples 1 to 17 prepared as shown in Table 1 were produced (Example 6, which does not contain halogenated butyl rubber together with non-halogenated butyl rubber, is a reference example. ) .

These test tires were evaluated for sealability (initial performance and after oxidative degradation acceleration treatment) and fluidity of the sealant material by the following test methods, and the results are also shown in Tables 1 and 2.

Sealability (initial performance)
Each test tire was mounted on a wheel with a rim size of 20 x 9J and mounted on a test vehicle, with an initial air pressure of 250 kPa and a load of 8.5 kN. The air pressure was measured after the tire was left at rest for 1 hour. The evaluation results were shown in the following three grades.
○: The air pressure after standing is 230 kPa or more and 250 kPa or less △: The air pressure after standing is 200 kPa or more and less than 230 kPa ×: The air pressure after standing is less than 200 kPa

Sealability (after oxidation deterioration acceleration treatment)
Each test tire was mounted on a wheel with a rim size of 20 x 9J, mounted on a test vehicle, and left at 80°C for 4 days (96 hours) while being filled with oxygen at an air pressure of 220 kPa to accelerate oxidation deterioration. rice field. Then, for each test tire after the accelerated oxidation deterioration treatment, the initial air pressure was set to 250 kPa, the load was set to 8.5 kN, and a nail with a diameter of 4 mm was driven into the tread portion. The air pressure after placing was measured. The evaluation results were shown in the following three grades.
○: The air pressure after standing is 230 kPa or more and 250 kPa or less △: The air pressure after standing is 200 kPa or more and less than 230 kPa ×: The air pressure after standing is less than 200 kPa

Fluidity of sealant The test tire is assembled on a wheel with a rim size of 20 × 9J and mounted on a drum tester, the air pressure is set to 220 kPa, the load is set to 8.5 kN, and the sealant after running is run for 1 hour at a running speed of 100 km / h. We investigated the flow state of The evaluation results were obtained by drawing a line of 20 x 40 squares with a 5 mm square ruled line on the surface of the sealant layer before running, counting the number of squares with a distorted shape after running, and if no sealant flow was observed (distorted squares 0) is indicated by "○", the case where the number of distorted squares is less than 1/4 of the total is indicated by "△", and the number of distorted squares 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.
- Non-halogenated IIR: BUTYL065 manufactured by JSR
Halogenated IIR1: chlorinated butyl rubber, CHLOROBUTYL1066 manufactured by JSR
Halogenated IIR2: Brominated butyl rubber, BROMOBUTYL2222 manufactured by JSR
・NR: Natural rubber, natural rubber manufactured by SRI TRANG ・Organic peroxide: Dibenzoyl peroxide, Niper NS manufactured by NOF Corporation (1 minute half-life temperature: 133 ° C.)
・Crosslinking agent: Sulfur, Hosoi Chemical Co., Ltd. Small lump sulfur ・Vulcanization accelerator 1: Thiuram-based vulcanization accelerator, Ouchi Shinko Kagaku Kogyo Co., Ltd. Noxceler DM-PO
・ Vulcanization accelerator 2: Guanidine-based vulcanization accelerator, Noccellar 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, Diana Process PW-380 manufactured by Idemitsu Kosan Co., Ltd. (molecular weight: 1500)
・ Liquid polymer 3: paraffin oil, Diana Process K-350 manufactured by Idemitsu Kosan Co., Ltd. (molecular weight: 800)

As is clear from Tables 1 and 2, the pneumatic tires of Examples 1 to 17 exhibited excellent sealing properties while suppressing sealant flow. In particular, even after the oxidative degradation acceleration treatment, good sealing performance could be exhibited.

On the other hand, in Comparative Examples 1 and 2, since the amount of the non-halogenated butyl rubber compounded was small, sufficient sealing properties could not be obtained after the oxidative degradation acceleration treatment. In Comparative Example 3, since the amount of the organic peroxide compounded was small, the sealability deteriorated both at the initial stage and after the oxidation deterioration acceleration treatment. Since Comparative Example 4 did not contain a cross-linking agent, the fluidity of the sealant deteriorated.

1 tread portion 2 sidewall portion 3 bead portion 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 belt reinforcing layer 9 inner liner layer 10 sealant layer CL tire equator

Claims (8)

A sealant material composition that constitutes a sealant layer disposed on the inner surface of a pneumatic tire, wherein organic peroxide is added to 100 parts by mass of a rubber component containing more than 10% by mass of non-halogenated butyl rubber and halogenated butyl rubber. A sealant composition characterized by containing 1 to 40 parts by mass of an oxide and 0.1 to 40 parts by mass of a cross-linking agent. 2. The sealant composition of claim 1 , wherein said cross-linking agent comprises a sulfur component. 3. The sealant material composition according to claim 1, wherein 50 to 400 parts by mass of the liquid polymer is blended with 100 parts by mass of the rubber component. 4. The sealant composition of claim 3 , wherein said liquid polymer is paraffin oil. 5. The sealant material composition according to claim 4 , wherein the paraffin oil has a molecular weight of 1000 or more. 6. The sealant material composition according to any one of claims 1 to 5 , further comprising a vulcanization accelerator. 7. The sealant material composition according to claim 6 , wherein the vulcanization accelerator is a thiuram-based vulcanization accelerator. A pneumatic tire comprising the sealant layer made of the sealant material composition according to any one of claims 1 to 7 .

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