JP2021046488A - Sealant material composition - Google Patents

Abstract

To provide a sealant material composition that makes it possible to exhibit excellent sealability while suppressing the flow of a sealant material during driving.SOLUTION: As a sealant material composition constituting a sealant layer disposed on the inner surface of a pneumatic tire, used is one in which an adhesion to vulcanized rubber is 0.20 N/mm or more and an adhesion to metal is 0.05 N/mm or more and 0.15 N/mm or less.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 (hereinafter, may be simply referred to as "foreign substance") pierces the tread portion, the sealant material constituting the sealant layer flows into the through hole, thereby causing the sealant material to flow into the through hole. It is possible to suppress the decrease in air pressure and maintain running.

In the self-sealing type pneumatic tire described above, if the viscosity of the sealant material is low, the sealant material can be expected to improve the sealing property in that the sealant material easily flows into the through hole. If the sealant material flows toward the tire center side due to the influence, and as a result, the through hole deviates from the tire center region, the sealant material may be insufficient and sufficient sealing property may not be obtained. On the other hand, if the viscosity of the sealant material is high, the above-mentioned flow of the sealant material can be prevented, but the sealant material is less likely to flow into the through hole, and the sealing property may be deteriorated. Therefore, the sealant material composition constituting the sealant material is required to balance the suppression of the flow of the sealant material with running and the securing of good sealing property in a well-balanced manner.

Further, considering the behavior of the foreign matter when the through hole is formed, the foreign matter itself seals the through hole in the state where the foreign matter remains stuck in the tread portion, so that the centrifugal force while the foreign matter is traveling and the centrifugal force It is effective to ensure that the sealant material seals the through hole when it comes off due to vibration in order to maintain running. Therefore, as a sealant material, while it appropriately adheres to foreign matter stuck in the tread portion, it is easily peeled off from the foreign matter when the foreign matter comes off, and further, it has good adhesiveness to the inner surface of the tire. It would be preferable to have complex properties.

Japanese Unexamined Patent Publication No. 2006-152110

An object of the present invention is to provide a sealant material composition capable of exhibiting excellent sealing properties while suppressing the flow of the sealant material during running.

The sealant material composition of the present invention that achieves the above object is a sealant material composition that constitutes a sealant layer arranged on the inner surface of a pneumatic tire, and has an adhesive force to vulcanized rubber of 0.20 N / mm or more. Moreover, the adhesive force to the metal is 0.05 N / mm or more and 0.15 N / mm or less.

The sealant material composition of the present invention has the above-mentioned properties, and when used in the sealant layer of a pneumatic tire, exhibits appropriate adhesiveness and peelability to foreign substances such as nails made of metal. .. That is, it can be appropriately adhered to a foreign substance such as a nail stuck in the tread portion, and can exhibit good sealing performance in that state. On the other hand, when a foreign substance such as a nail falls off the tire, the sealant material is surely peeled off from the foreign substance and remains in the tire. Can be done. At this time, since it has good adhesiveness to the inner surface of the tire made of vulcanized rubber, it is possible to suppress the flow during traveling and to reliably seal the through holes.

The sealant material composition of the present invention preferably has an adhesive force of 0.20 N / mm or more with respect to the vulcanized rubber containing butyl rubber. Since the innermost layer (inner liner layer) of a pneumatic tire often contains butyl rubber mainly, having such physical properties can improve the adhesiveness to the inner surface of the tire.

The sealant composition of the present invention preferably has an adhesive force of 0.05 N / mm or more and 0.15 N / mm or less with respect to a metal selected from iron, stainless steel, or aluminum. Foreign substances such as nails that may damage the tire during running are mainly composed of iron, stainless steel, or aluminum. Therefore, having such physical properties should improve the adhesiveness to foreign substances such as nails. This is advantageous for improving the sealing property.

The sealant composition of the present invention has 5 parts by mass to 20 parts by mass of an organic peroxide, 0.1 parts by mass to 40 parts by mass of a cross-linking agent, and 0 parts by mass of a cross-linking aid with respect to 100 parts by mass of a rubber component containing butyl rubber. It is preferable that more than 1 part by mass and less than 1 part by mass are blended. With such a composition, it is advantageous to achieve both the adhesiveness to the vulcanized rubber and the adhesiveness to the metal in the above-mentioned balance. Further, by performing cross-linking by using a cross-linking agent and an organic peroxide in combination in this way, it is possible to obtain appropriate elasticity that does not flow during traveling while ensuring sufficient viscosity to obtain good sealing properties. It is also possible to achieve a good balance of performance.

At this time, the one-minute half-life temperature of the organic peroxide is preferably 100 ° C. to 200 ° C. By using an organic peroxide having such characteristics, it is advantageous to achieve both the adhesiveness to vulcanized rubber and the adhesiveness to metal in the above-mentioned balance.

The sealant composition of the present invention preferably contains butyl rubber in an amount of 80% by mass or more as a rubber component. Further, it is preferable that the butyl rubber contains chlorinated butyl rubber and the blending amount of the chlorinated butyl rubber is 5% by mass or more with respect to 100% by mass of the rubber component. With such a composition, the adhesiveness to the inner surface of the tire can be improved.

In the sealant material composition of 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 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 sealant material composition of the present invention, the blending amount of the cross-linking aid is preferably 50% by mass to 400% by mass of the blending amount of the cross-linking agent. As a result, the balance between the cross-linking agent and the cross-linking aid is improved, thermal deterioration can be suppressed, and good sealing properties can be maintained for a long period of time.

In the sealant material composition of the present invention, the cross-linking aid is preferably a thiazole-based compound or a thiuram-based compound. As a result, the vulcanization rate can be increased and the productivity can be increased. On the other hand, it is possible to suppress thermal deterioration more than other cross-linking aids, and it is possible to maintain good sealing properties for a long period of time.

In the sealant material composition of 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. Further, it is preferable that the liquid polymer is at least one selected from paraffin oil, polybutene oil, polyisoprene oil, polybutadiene oil, and aroma oil. By using the liquid polymer in this way, the temperature dependence of the physical properties of the sealant material composition can be lowered, and the sealing property in a low temperature environment can also be improved. Further, when the molecular weight of the liquid polymer is 800 or more, 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.

In a pneumatic tire provided with a sealant layer made of the above-mentioned sealant material composition of the present invention, excellent sealing properties are exhibited while suppressing the flow of the sealant during running due to the excellent physical properties of the above-mentioned sealant material composition. can do. In particular, when the vulcanized rubber located on the innermost surface of the tire and forming the rubber layer adjacent to the sealant layer contains butyl rubber, excellent sealing properties can be effectively exhibited.

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.

The self-sealing type pneumatic tire in which the sealant material composition of the present invention is used has, for example, as shown in FIG. 1, a tread portion 1 extending in the tire circumferential direction and forming an annular shape, and both sides of the tread portion 1. A pair of sidewall portions 2 arranged in the tire and a pair of bead portions 3 arranged inside the sidewall portion 2 in the tire radial direction are provided. In FIG. 1, the 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, unless otherwise specified, other tire components in the meridian cross-sectional view extend in the tire circumferential direction to form an annular shape.

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. However, in relation to the physical properties of the sealant material composition of the present invention described later, the inner liner layer 9 located on the innermost surface of the tire and adjacent to the sealant layer is composed of a rubber composition containing butyl rubber (additional rubber composition). In the tire after vulcanization, the vulcanized rubber constituting the inner liner layer 9 contains butyl rubber).

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. In particular, the sealant layer 10 is provided on the inner surface of the tire corresponding to the area where foreign matter such as a nail may pierce during traveling, that is, the ground contact area of the tread portion 1. In particular, it is preferable to provide the sealant layer 10 in a range wider than the width of the minimum belt layer 7a. 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. By inflowing the sealant material and sealing the through hole, it is possible to suppress the decrease in air pressure and maintain the 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. Further, 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 weight of the tire 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 material composition of the present invention is used, for example, in the sealant layer 10 of the self-sealing type pneumatic tire described above, but the basic structure of the pneumatic tire and the structure of the sealant layer 10 are not limited to the above examples.

The sealant composition of the present invention has an adhesive force to vulcanized rubber of 0.20 N / mm or more, preferably 0.2 N / mm to 0.5 N / mm, and an adhesive force to metal of 0.05 N / mm or more. It is 0.15 N / mm or less, preferably 0.075 N / mm to 0.125 N / mm. When used in the sealant layer 10 of a pneumatic tire, the sealant material composition having such characteristics exhibits appropriate adhesiveness and peelability to foreign substances such as nails, which are generally made of metal. To do. That is, it can be appropriately adhered to a foreign substance such as a nail stuck in the tread portion, and can exhibit good sealing performance in that state. On the other hand, when a foreign substance such as a nail falls off the tire, the sealant material is surely peeled off from the foreign substance and remains in the tire. Can be done. At this time, since it has good adhesiveness to the inner surface of the tire made of vulcanized rubber, it is possible to suppress the flow during traveling and to reliably seal the through holes. If the adhesive force to the vulcanized rubber is less than 0.20 N / mm, the tire does not sufficiently adhere to the inner surface of the tire, and the effect of suppressing the flow and the effect of improving the sealing property cannot be obtained. If the adhesive force to the metal is less than 0.05 N / mm, it becomes difficult to sufficiently secure the sealing property in a state where a foreign substance such as a nail is stuck in the tread portion. If the adhesive force to the metal exceeds 0.15 N / mm, when foreign matter such as nails falls off the tire, a part of the sealant material will fall off from the tire while adhering to the foreign matter, and the through hole will be securely sealed. There is a risk that it will not be possible. The "adhesive strength" is the adherend adjusted to a width of 25 mm and a length of 250 mm (an object for measuring the adhesive strength with the sealant material, in this case vulcanized rubber or metal) and the sealant material. , JIS Z0237, the force required for peeling (peeling 180 °) at an angle of 180 ° at a tensile speed of 500 mm / min was measured as an adhesive force.

The innermost layer (inner liner layer 9) of the pneumatic tire often contains butyl rubber mainly from the viewpoint of air permeation prevention performance. In view of this, it is preferable that the sealant material composition of the present invention has an adhesive force to the vulcanized rubber containing butyl rubber in an appropriate range, not an adhesive force to the vulcanized rubber in general. Specifically, the adhesive force to the vulcanized rubber containing butyl rubber is preferably 0.20 N / mm or more, more preferably 0.2 N / mm to 0.5 N / mm. By having such physical properties, the adhesiveness to the inner surface of the tire can be effectively enhanced.

Similarly, foreign objects such as nails that can damage tires during travel are primarily composed of iron, stainless steel, or aluminum. In view of this, it is preferable that the sealant composition of the present invention has an appropriate range of adhesive strength to a metal selected from iron, stainless steel, or aluminum, rather than adhesiveness to metals in general. Specifically, the adhesive force to a metal selected from iron, stainless steel, or aluminum is 0.05 N / mm or more and 0.15 N / mm or less, more preferably 0.075 N / mm to 0.125 N / mm. Good. Having such physical properties makes it possible to improve the adhesiveness to foreign substances such as nails, which is advantageous for improving the sealing property.

As long as the sealant material composition of the present invention has the above-mentioned physical characteristics, the specific formulation thereof is not particularly limited. However, in order to surely obtain the above-mentioned physical properties, for example, it is preferable to adopt the formulation described later.

In the sealant material composition of the present invention, the rubber component may include a butyl rubber. The ratio of the butyl rubber to the rubber component is preferably 80% by mass or more, more preferably 85% by mass to 95% by mass. By including the butyl rubber in this way, good adhesiveness to the inner surface of the tire can be ensured. If the proportion of the butyl rubber is less than 80% by mass, sufficient adhesiveness to the inner surface of the tire cannot be ensured.

In the sealant material composition of the present invention, it is preferable to include halogenated butyl rubber as the butyl rubber. Examples of the halogenated butyl rubber include chlorinated butyl rubber and brominated butyl rubber, and chlorinated butyl rubber can be particularly preferably used. When chlorinated butyl rubber is used, the ratio of chlorinated butyl rubber to 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass to 85% by mass. By including halogenated butyl rubber (chlorinated butyl rubber), the reactivity of the rubber component with the cross-linking agent and organic peroxide described later is enhanced, which is advantageous for both ensuring the sealing property and suppressing the flow of the sealant. Become. In addition, the processability of the sealant material composition can be improved. If the proportion of chlorinated butyl rubber is less than 5% 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 total amount of butyl rubber does not have to be halogenated butyl rubber (chlorinated 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, BUTYL-301 manufactured by LANXESS Corporation, and the like. 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 together as the butyl rubber. 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 (brominated butyl rubber), and non-halogenated butyl rubber are different from each other, if at least two types are used in combination, the difference in vulcanization rate is caused. , The physical properties (viscosity, elasticity, etc.) of the sealant composition after vulcanization are not uniform. That is, due to the distribution (variation in concentration) of rubbers having different vulcanization rates in the sealant material composition, a relatively hard portion and a relatively soft portion are mixed in the vulcanized sealant layer. 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.

In the sealant material composition of the present invention, a diene rubber other than the butyl rubber can be blended as a rubber component. Other diene rubbers include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), and chloroprene. Rubber generally used for sealant composition such as rubber (CR) and acrylonitrile butadiene rubber (NBR) can be used. These other diene rubbers can be used alone or as any blend.

In the sealant material composition of the present invention, it is preferable to add a cross-linking agent and an organic peroxide. The "crosslinking agent" in the present invention is a crosslinking agent excluding organic peroxides, and examples thereof include sulfur, zinc oxide, cyclic sulfide, resin (resin vulcanization), and amine (amine vulcanization). be able to. As the cross-linking agent, 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. Further, it is advantageous to achieve both the adhesiveness to the vulcanized rubber and the adhesiveness to the metal in the above-mentioned balance. The blending amount of the cross-linking agent is preferably 0.1 part by mass to 40 parts by mass, and more preferably 0.5 part 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 preferably 5 parts by mass to 20 parts by mass, and more preferably 10 parts by mass to 15 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 that the cross-linking agent is not contained, and appropriate cross-linking cannot be performed. If the blending amount of the cross-linking agent exceeds 40 parts by mass, the sealant material composition is cross-linked too much and the sealing property is deteriorated. If the blending amount of the organic peroxide is less than 5 parts by mass, the amount of the organic peroxide is too small to sufficiently carry out cross-linking, and the desired physical properties cannot be obtained. If the amount of the organic peroxide compounded exceeds 20 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 mass 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. More preferably, it is 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. By using an organic peroxide having such characteristics, it is advantageous to achieve both the adhesiveness to vulcanized rubber and the adhesiveness to metal in the above-mentioned balance. If the 1-minute half-life temperature deviates from the above range, there is a risk that the effect of achieving both the adhesiveness to the vulcanized rubber and the adhesiveness to the metal in the above-mentioned balance cannot be sufficiently obtained. In the present invention, the "1 minute half-life temperature" generally adopts the value described in "Organic Peroxide Catalog 10th Edition" of Nippon Oil & Fats Co., Ltd., 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.

It is preferable to add a cross-linking aid to the sealant composition of the present invention. The cross-linking aid is a compound that acts as a cross-linking reaction catalyst when blended with a cross-linking agent containing a sulfur component. By blending the cross-linking agent and the cross-linking aid, the vulcanization rate can be increased and the productivity of the sealant material composition can be increased. The blending amount of the cross-linking aid is preferably more than 0 parts by mass and less than 1 part by mass, and more preferably 0.1 parts by mass to 0.9 parts by mass with respect to 100 parts by mass of the above-mentioned rubber component. By suppressing the blending amount of the cross-linking aid in this way, it is possible to suppress the deterioration (heat deterioration) of the sealant material composition while promoting the cross-linking reaction as a catalyst. If the blending amount of the cross-linking aid is 1 part by mass or more, the effect of suppressing thermal deterioration cannot be sufficiently obtained. Since the cross-linking aid acts as a cross-linking reaction catalyst by blending with the cross-linking agent containing a sulfur component as described above, the cross-linking reaction catalyst can be coexisted with an organic peroxide instead of the sulfur component. As a result, a large amount of cross-linking aid must be used, which accelerates thermal deterioration.

The blending amount of the cross-linking aid is preferably 50% by mass to 400% by mass, more preferably 100% by mass to 200% by mass, based on the blending amount of the above-mentioned cross-linking agent. By appropriately blending the cross-linking aid with the cross-linking agent in this way, the function of the cross-linking aid as a catalyst can be satisfactorily exhibited, and both ensuring the sealing property and preventing the flow of the sealant are achieved at the same time. Will be advantageous to. If the blending amount of the cross-linking aid is less than 50% by mass of the blending amount of the cross-linking agent, the fluidity decreases. If the blending amount of the cross-linking aid exceeds 400% by mass of the blending amount of the cross-linking agent, the deterioration resistance is lowered.

Examples of the cross-linking aid include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamate-based, aldehyde-amine-based, aldehyde-ammonia-based, imidazoline-based, and xanthate-based compounds ( A vulcanization accelerator) can be exemplified. Among these, thiazole-based, thiuram-based, guanidine-based, and dithiocarbamate-based vulcanization accelerators can be preferably used. Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole and dibenzothiazyl disulfide. Examples of the thiuram-based vulcanization accelerator include tetramethylthiuram monosulfide and tetramethylthiuram disulfide. Examples of the guanidine-based vulcanization accelerator include diphenylguanidine and dioltotrilguanidine. Examples of the dithiocarbamate-based vulcanization accelerator include sodium dimethyldithiocarbamate and sodium diethyldithiocarbamate. In particular, in the present invention, it is preferable to use a thiazole-based or thiuram-based vulcanization accelerator, and variations in the performance of the obtained sealant material composition can be suppressed.

A compound that actually functions as a cross-linking agent, such as quinonedioxime, may be referred to as a cross-linking aid for convenience. Since it is a compound that functions as a cross-linking aid, quinonedioxime does not fall under the cross-linking aid in the present invention.

The sealant composition of the present invention preferably contains 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, for example, paraffin oil, polybutene oil, polyisoprene oil, polybutadiene oil, polyisobutene oil, aroma oil, polypropylene glycol and the like. Can be mentioned. From the viewpoint of keeping the temperature dependence of the physical properties of the sealant composition low and ensuring good sealing properties in a low temperature environment, among these, paraffin oil, polybutene oil, polyisoprene oil, polybutadiene oil, aroma oil, polypropylene Glycol is preferable, and paraffin oil is particularly preferable. The molecular weight of the liquid polymer is preferably 800 or more, more preferably 1000 or more, and further 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.

The sealant composition composed of the above-mentioned composition is good by cross-linking with a cross-linking agent and an organic peroxide while imparting an appropriately high viscosity to the rubber component by containing at least a butyl rubber. It is possible to obtain an appropriate elasticity that does not flow during traveling while ensuring sufficient viscosity to obtain a good sealing property, and to achieve both of these performances in a well-balanced manner. Further, when an appropriate amount of an organic peroxide having a half-life temperature of 1 minute in an appropriate range is blended, an effect can be expected to achieve both the adhesiveness to vulcanized rubber and the adhesiveness to metal in the above-mentioned balance. Therefore, it can be suitably used for the sealant layer 10 (sealant material) of a self-sealing type pneumatic tire, and it is possible to exhibit excellent sealing performance while sufficiently exhibiting the basic performance as a sealant material. ..

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 8 and Examples 1 to 20 in which the composition and physical properties (adhesive strength) of the above were set as shown in Tables 1 to 3 were produced.

The adhesive strength was adjusted to a width of 25 mm and a length of 250 mm (natural rubber or butyl rubber was used as the vulcanized rubber, and iron, stainless steel, and aluminum were used as the metal) and the sealant material was attached to JIS Z0237. According to this, the force required to peel off (peel 180 °) at an angle of 180 ° at a tensile speed of 500 mm / min was measured as the adhesive force. In the table, columns are provided for each material used as the adherend, and the values are shown for each.

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 also shown in Tables 1 to 3.

Sealability Each test tire is attached to a wheel with a rim size of 20 x 9J and mounted on a test vehicle. Under the conditions of initial air pressure of 250 kPa and load of 8.5 kN, a nail with a diameter of 4.0 mm (metal when the adhesive strength is tested) After driving a nail made of a material corresponding to the type of tire into the tread portion, the air pressure was measured after the tire was allowed to stand for 1 hour with the nail removed. The evaluation results are shown in the following five stages. It should be noted that if the score of the evaluation result is "2" or more, sufficient sealing property is exhibited, and the larger the score, the better the sealing property is exhibited.
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 215 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 215 kPa 1: Air pressure after standing is less than 200 kPa

Sealant fluidity test The tire was assembled to a wheel with a rim size of 20 x 9J, mounted on a drum tester, and ran for 1 hour under the conditions of air pressure 220 kPa, load 8.5 kN, and running speed 80 km / h, and the sealant flow after running. I checked the condition. 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 the sealant is observed (distorted squares). The number of distorted cells is 0) is indicated by "○", the number of distorted cells is less than 1/4 of the total, 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 to 3 are shown below.
Butyl rubber 1: Chlorinated butyl rubber, JSR CHLOROBUTYL 1066
-Butyl rubber 2: Brominated butyl rubber, BROMOBUTYL2222 manufactured by JSR Corporation
-Natural rubber: Natural rubber / organic peroxide manufactured by SRI TRANG 1: Dikmyl peroxide, Park mill D-40 manufactured by Nippon Yushi Co., Ltd. (1 minute half-life temperature: 179 ° C)
-Organic peroxide 2: Dibenzoyl peroxide, NOF NS manufactured by NOF CORPORATION (1 minute half-life temperature: 133 ° C)
-Organic peroxide 3: Diisobutyryl peroxide, NOF Corporation Perloyl IB (1 minute half-life temperature: 85 ° C)
・ Cross-linking agent 1: Sulfur, small-lump sulfur manufactured by Hosoi Chemical Industry Co., Ltd. ・ Cross-linking agent 2: Quinone dioxime, Barnock GM manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
・ Cross-linking aid: Thiazole-based vulcanization accelerator, Noxeller MZ manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
-Liquid polymer 1: Paraffin oil, HYCOAL K-350 manufactured by Kaneda (molecular weight: 850)

As is clear from Tables 1 to 3, the pneumatic tires of Examples 1 to 20 exhibited good fluidity and good sealing performance, and achieved both of these performances in a well-balanced manner. On the other hand, in all of Comparative Examples 1 to 8, sufficient sealing properties could not be obtained.

1 Tread part 2 sidewall 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 (15)

A sealant material composition constituting a sealant layer arranged on the inner surface of a pneumatic tire, having an adhesive force to vulcanized rubber of 0.20 N / mm or more and an adhesive force to metal of 0.05 N / mm or more. A sealant material composition characterized by being 0.15 N / mm or less. The sealant composition according to claim 1, wherein the adhesive force to the vulcanized rubber containing butyl rubber is 0.20 N / mm or more. The sealant composition according to claim 1 or 2, wherein the adhesive force to a metal selected from iron, stainless steel, or aluminum is 0.05 N / mm or more and 0.15 N / mm or less. 5 parts by mass to 20 parts by mass of organic peroxide, 0.1 parts by mass to 40 parts by mass of cross-linking agent, and more than 0 parts by mass of cross-linking aid and less than 1 part by mass are blended with respect to 100 parts by mass of the rubber component containing butyl rubber. The sealant material composition according to any one of claims 1 to 3, wherein the sealant material composition has been obtained. The sealant material composition according to claim 4, wherein the organic peroxide has a half-life temperature of 100 ° C. to 200 ° C. for 1 minute. The sealant composition according to claim 4 or 5, wherein the content of the butyl rubber with respect to 100% by mass of the rubber component is 80% by mass or more. The sealan material composition according to any one of claims 4 to 6, wherein the butyl rubber contains chlorinated butyl rubber, and the blending amount of the chlorinated butyl rubber is 5% by mass or more with respect to 100% by mass of the rubber component. .. The sealant composition according to any one of claims 4 to 7, wherein the cross-linking agent contains a sulfur component. The sealant material composition according to any one of claims 4 to 8, wherein the blending amount of the cross-linking aid is 50% by mass to 400% by mass of the blending amount of the cross-linking agent. The sealant composition according to any one of claims 4 to 9, wherein the cross-linking aid is a thiazole-based compound or a thiuram-based compound. The sealant material composition according to any one of claims 4 to 10, wherein 50 parts by mass to 400 parts by mass of a liquid polymer is blended with respect to 100 parts by mass of the rubber component. The sealant composition according to claim 11, wherein the liquid polymer is at least one selected from paraffin oil, polybutene oil, polyisoprene oil, polybutadiene oil, and aroma oil. The sealant composition according to claim 11 or 12, wherein the liquid polymer has a molecular weight of 800 or more. A pneumatic tire provided with the sealant layer comprising the sealant material composition according to any one of claims 1 to 13. The pneumatic tire according to claim 14, wherein the vulcanized rubber located on the innermost surface of the tire and forming a rubber layer adjacent to the sealant layer contains butyl rubber.

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