JP2007216961A - Inner lining for pneumatic tire and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inner lining for a pneumatic tire capable of significantly improving the internal pressure holding performance after running without increasing the weight of the tire by improving the technology for holding the internal pressure of an inner lining, etc., and a pneumatic tire using the same. <P>SOLUTION: The inner lining for the pneumatic tire comprises a layer (A) made of a polyvinyl alcohol polymer and a layer (B) with which diene elastomer is blended. The layer A is adhered to the layer B, and the layer A is crosslinked, and further comprises an inner lining. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inner liner for a pneumatic tire and a pneumatic tire including the inner liner, and more particularly to a technique for improving internal pressure retention without increasing the tire weight.

  Conventional tubeless pneumatic tires include an inner liner as an air-impermeable layer for maintaining the internal pressure of the tire, and butyl rubber, halogenated butyl rubber, or the like is used as a main raw material of the inner liner. However, since the rubber composition containing these materials has low air impermeability, the inner liner needs to have a thickness of about 1 mm. To improve the internal pressure retention, the inner liner is made thicker. In this case, there is a problem that the weight of the tire increases.

  By the way, there are many thermoplastic resins as materials having lower air permeability than butyl rubber and halogenated butyl rubber. For example, air permeability of nylon or the like is 1/10 or less compared to butyl rubber and halogenated butyl rubber. However, since nylon has a high modulus of elasticity, the inner liner made of nylon cannot follow the deformation at the time of rolling of the tire, causing cracks and the like, causing air leakage from the cracks, and cannot maintain the internal pressure.

  A pneumatic tire provided with an air impermeable layer made of polyvinyl alcohol or ethylene-vinyl alcohol copolymer has been proposed. However, the air-impermeable layer easily breaks and cracks due to bending deformation at the time of rolling of the tire, and further, the generated cracks are easily extended. There is a problem that it falls. In addition, the ethylene-vinyl alcohol copolymer has a relatively low melting point and melts at the time of vulcanization of the tire, and a uniform air-impermeable layer may not be obtained. Polyvinyl alcohol is easily affected by humidity. Even if the physical properties of the molecular design are sufficient, the strength may be lowered at the vulcanization temperature.

  On the other hand, polyvinylidene chloride (PVDC) is also known as an air-impermeable resin, and if this resin is used, the thickness necessary for maintaining the internal pressure can be reduced. However, since polyvinylidene chloride has poor adhesion to the adjacent rubber member, in the unlikely event that the air-impermeable layer made of polyvinylidene chloride breaks, there is a problem that the air-impermeable layer easily peels from the adjacent rubber member. is there.

  An object of the present invention is a pneumatic tire that solves the above-described problems of the prior art, improves internal pressure retention technology such as an inner liner, and can significantly improve internal pressure retention after running without increasing the weight of the tire. An inner liner for use and a pneumatic tire using the same are provided.

Means for solving the problems are as follows. That is,
(1) An inner liner for a pneumatic tire comprising a layer (A) comprising a polyvinyl alcohol polymer and a layer (B) comprising a diene elastomer, wherein the layer (A) comprises An inner liner for a pneumatic tire characterized in that it is bonded to B) and the layer (A) is crosslinked.
(2) The inner liner for a pneumatic tire according to (1), wherein the layer (A) is crosslinked by an electron beam.
(3) The inner liner for a pneumatic tire according to (1), wherein an adhesive is used between the layer (A) and the layer (B).
(4) The inner liner for a pneumatic tire according to (3), wherein the adhesive is a chlorinated rubber-isocyanate adhesive.

(5) A pneumatic tire comprising the inner liner for a pneumatic tire according to any one of (1) to (4).
(6) The pneumatic tire according to (5), wherein the layer (B) is disposed between a carcass and the layer (A).

The present invention is described in detail below.
The inner liner for a pneumatic tire of the present invention includes a layer (A) made of a polyvinyl alcohol polymer as an air impermeable layer and a layer (B) formed by blending a diene elastomer as an auxiliary layer. The pneumatic tire of the present invention includes the inner liner. Here, examples of the gas filled in the tire include air or an inert gas such as nitrogen.

  Examples of the polyvinyl alcohol polymer used for the layer (A) made of the polyvinyl alcohol polymer according to the present invention include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. The molar ratio of ethylene to vinyl alcohol in the ethylene-vinyl alcohol copolymer is not particularly limited, and can be set as appropriate according to the purpose. For example, by increasing the number of ethylene units, a stronger air impervious layer can be obtained, and by increasing the number of vinyl alcohol units, air impermeability can be increased.

  The layer (A) made of the polyvinyl alcohol polymer of the present invention is preferably crosslinked. When the layer (A) is cross-linked, it will not melt even if heat is applied during vulcanization molding of the tire. In addition, no reduction in strength or the like occurs even at the vulcanization temperature. The crosslinking method is not particularly limited, and an electron beam irradiation method that can directly act on the produced air-impermeable layer is preferable.

  The polyvinyl alcohol polymer is very effective for reducing the air permeability. For example, the air permeability coefficient of the polyvinyl alcohol polymer is 1/100 or less of the air permeability coefficient of butyl rubber such as butyl rubber or halogenated butyl rubber. Accordingly, the thickness required for maintaining the internal pressure almost equal to that of the conventional inner liner using the butyl rubber composition is less than 1/100.

  In addition to the polyvinyl alcohol polymer of the present invention, there are many resins having a smaller air permeability coefficient than butyl rubber. For example, a resin whose air permeability is about 1/10 that of butyl rubber was used. The air-impermeable layer has a thickness of about 1 mm for the conventional inner liner using a butyl rubber composition. 1 / 10th or more). However, when the thickness of the air-impermeable layer is 100 μm or more, there is a problem that the air-impermeable layer breaks due to bending deformation during rolling of the tire. On the other hand, when a polyvinyl alcohol polymer is used as the air impermeable layer, a thickness of 50 μm or less is sufficient for the air impermeable layer in order to obtain an effect of improving the internal pressure retention, and 50 μm or less. If it is thick, even if it undergoes bending deformation during rolling of the tire, it is difficult to break. The minimum thickness for obtaining the desired internal pressure retention is 5 μm.

Examples of the diene elastomer used in the layer (B) formed by blending the diene elastomer according to the present invention include natural rubber and butadiene rubber. The layer (B) formed by blending the diene elastomer further contains an additive usually used in the tire industry.
The layer (B) formed by blending the diene elastomer of the present invention and the layer (A) are preferably adjacent to each other. As described above, even if the thickness of the air-impermeable layer is 50 μm or less, pinholes, cracks, and the like may occur due to bending deformation during tire rolling. On the other hand, by arranging the layer (B) formed by blending the diene elastomer adjacent to the layer (A) between the layer (A) and the carcass located outside the layer (A), growth of cracks and the like is achieved. Can be suppressed.

The tensile stress at 300% elongation of the layer (B) formed by blending the diene elastomer of the present invention is preferably 8 MPa or less. If the tensile stress at 300% elongation of the layer (B) is 8 MPa or less, the occurrence and growth of cracks and the like in the layer (A) can be suitably suppressed. The tensile stress was measured according to JIS K 6251-1993.
The thickness of the layer (B) formed by blending the diene elastomer of the present invention is preferably 50 to 1000 μm. If the thickness of the layer (B) is less than 50 μm, the production is difficult, and if it exceeds 1000 μm, the weight of the tire increases.

  The layer (A) comprising the polyvinyl alcohol polymer of the present invention and the layer (B) comprising the diene elastomer are preferably adhered. Since the polyvinyl alcohol-based polymer of the layer (A) has an —OH group, adhesion to an adjacent rubber member such as the layer (B) can be secured relatively easily. For example, if a chlorinated rubber-isocyanate adhesive is used, sufficient adhesion with the diene rubber composition used in the tire can be ensured. For this reason, even if the air-impermeable layer breaks, the air-impermeable layer is difficult to peel from the adjacent rubber member.

  When layer (A) is firmly adhered to the surface of layer (B), even if cracks occur in layer (A), layer (A) is difficult to peel off from layer (B), so most layers The layer (A) is present as it is on the surface of (B), which is preferable because it continues to exhibit the internal pressure maintaining function.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited by these examples.

Examples 1-5 and Comparative Examples 1-3
Using an ethylene-vinyl alcohol copolymer (EVOH), polyvinyl alcohol (PVA), and 6-nylon (PA6), air-impermeable layers having the thicknesses shown in Tables 1 and 2 were formed. Using the rubber compositions 1 and 2 having the above composition, an auxiliary layer having a thickness described in Tables 1 and 2 is provided, and an air-impermeable layer and the auxiliary layer are bonded to each other with an adhesive (Metaloc R30M, manufactured by Toyo Chemical Laboratory). ) To produce an inner liner, and a passenger car tire (195 / 65R15) was manufactured using the inner liner.
The air impermeable layers used in the examples were all crosslinked by electron beam irradiation, and the treatment conditions were an acceleration voltage of 300 kV and an irradiation energy of 20 Mrad.

Each test tire was filled with an air pressure of 250 kPa, allowed to stand at room temperature for 3 months, the air pressure after 3 months was measured, the reciprocal of the amount of air leakage was taken, and Comparative Example 1 was taken as 100, and displayed as an index. The results are shown in Tables 1 and 2. In addition, a result is so favorable that a table value becomes large.
Further, the appearance of the inner liner of each tire was visually observed to examine the state of cracking and peeling, and the results are also shown in Tables 1 and 2.

  Compared with the tire of Comparative Example 1, the tire of Example 1 greatly improved the internal pressure retention after running. In the tires of Examples 2 and 3 in which the auxiliary layer was thicker than the tire of Example 1, the internal pressure retention was further improved as compared with the tire of Example 1, and the air-impermeable layer after running had no cracks. The tire of Example 4 has a thicker air-impermeable layer than the tire of Example 3, but the internal pressure retention is inferior to the tire of Example 3, but the internal pressure retention than the tire of Comparative Example 1. Was greatly improved. The tire of Example 5 was obtained by changing the material of the air-impermeable layer to PVA in the tire of Example 2, but the internal pressure retention was slightly inferior to the tire of Example 2 using EVOH, but Comparative Example 1 The internal pressure retention was significantly improved compared to the tires.

The tire of Comparative Example 2 uses an air-impermeable layer and does not use an auxiliary layer, but the internal pressure retention after running is equivalent to that of Comparative Example 1, and the air-impermeable layer cracks after running. Was big. From this, it can be seen that an auxiliary layer is necessary to maintain the internal pressure after running and to suppress the growth of cracks.
Comparative Example 3 is a case where PA6 is used for the air-impermeable layer and an auxiliary layer is also used. However, as with the tire of Comparative Example 2, the internal pressure retention after running is equivalent to that of Comparative Example 1, and after running The cracks in the air-impermeable layer were large. This shows that a polyvinyl alcohol polymer is suitable as a material for the air impermeable layer.

  As described above, if the inner liner of the present invention is used, the internal pressure retention after running can be greatly improved without increasing the weight of the tire.

Claims (6)

An inner liner for a pneumatic tire comprising a layer (A) comprising a polyvinyl alcohol polymer and a layer (B) comprising a diene elastomer,
The layer (A) is bonded to the layer (B),
An inner liner for a pneumatic tire, wherein the layer (A) is crosslinked.   The inner liner for a pneumatic tire according to claim 1, wherein the layer (A) is crosslinked by an electron beam.   The inner liner for a pneumatic tire according to claim 1, wherein an adhesive is used between the layer (A) and the layer (B).   The inner liner for a pneumatic tire according to claim 3, wherein the adhesive is a chlorinated rubber-isocyanate adhesive.   A pneumatic tire comprising the inner liner for a pneumatic tire according to any one of claims 1 to 4.   The pneumatic tire according to claim 5, wherein the layer (B) is disposed between a carcass and the layer (A).