JP2648332B2 - Method for manufacturing pneumatic tire having sound absorbing layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to disposing a foamed rubber composition in an innermost layer of a tire to cause vibration mainly caused by road surface irregularities during running of a vehicle under rolling of a tire wheel. The present invention relates to a method for manufacturing a pneumatic radial tire in which the noise inside the vehicle is significantly reduced.

(Prior Art) As a method of reducing the noise of a conventional vehicle, for example, Japanese Patent Publication No. 58-53221 discloses a method in which a dynamic damper is provided on the outer periphery of a vehicle rim and its longitudinal and lateral resonance frequencies are respectively measured by the tire vibration. Disclosed to be tuned to the frequency,
Also, U.S. Pat. No. 4,392,522 discloses a method for reducing noise by providing a noise absorbing means made of an open-cell material disposed in the whole or a part of the inner surface of a cavity filled with internal pressure air of a tire. . However, according to the conventional method, the tire weight becomes extremely heavy and the rolling resistance deteriorates, and the effect of reducing the durability and noise vibration characteristics of the tire is not sufficient. For this reason, the present applicant has filed Japanese Patent Application No. 61-301745.
No. (JP-A-63-154410) proposed a pneumatic tire with reduced noise and a method for producing the same. This tire has a pair of sidewall portions, a bead portion, and a tread portion located between the sidewalls, and a carcass layer composed of at least one cord in which these are arranged in parallel in a substantially radial plane, and an inner layer in a radial plane. In a low-noise pneumatic radial tire having a liner and reinforced by a belt portion disposed between the carcass layer tread portions, a foamed rubber having a foaming rate of 150% or more is formed inside the radial surface of the inner liner and the innermost layer of the tire. The composition is disposed, and the rubber foamed composition is mainly composed of a rubber containing 30 parts by weight or more of a polyisobutylene rubber derivative, and 1.1 ≦ A ² xB A of the following formula: Tire inner surface coverage of the foamed rubber composition B: By satisfying the average thickness of the foamed rubber composition, a passenger pneumatic radial tire with unsprung resonance corresponding to a peak of around 10 Hz and road noise near 260 Hz which could not be solved until now. The two vibration characteristics that impair the ride comfort of the car have been successfully reduced while slightly suppressing the increase in tire weight.

(Problems to be Solved by the Invention) However, in the method of manufacturing a tire disclosed in Japanese Patent Application No. 61-301745, a foamed rubber composition is formed into a sheet shape similar to a normal rubber composition, and is applied in a tire manufacturing process. I have
As described above, the compound Mooney viscosity of the foamed rubber composition is increased so that there is no problem until the normal tire molding operation (ML
_{(1 + 4} ≧ 30,130 ° C.), and it is extremely difficult for the foaming rate in the ordinary vulcanization step to exceed 150%. If the compound Mooney viscosity is less than 30, the tire molding operation becomes extremely inefficient due to problems such as sticking of the sheet. On the other hand, when the foamed rubber composition is pasted, not only the adhesiveness to the inner liner is lowered, but also the foamed rubber composition is significantly deteriorated due to high heat during vulcanization. In addition, there is a problem that when sticking to a tire after vulcanization, complete manual work is required and a great deal of labor is required.

Therefore, an object of the present invention is to provide a method for manufacturing a pneumatic tire by efficiently forming a sound-absorbing layer made of a foamable rubber composition on the inner surface of a rubber tire without applying much labor in the tire manufacturing process. And

(Means for Solving the Problems) As a result of various studies on the sound absorbing layer provided on the inner surface of the pneumatic tire, the present inventors have found that a composition A containing a polymer and a vulcanizing agent and a vulcanizing accelerator and a foaming agent are contained. It has been found that the above object can be achieved by forming a sound-absorbing layer using a foamable rubber composition prepared by previously mixing the composition B to be obtained, and the present invention has been accomplished.

Therefore, the method for manufacturing a pneumatic tire having a sound absorbing layer according to the present invention is suitable for manufacturing a pneumatic tire having a sound absorbing layer made of a foamable rubber composition having a foaming ratio of 150% or more on the inner surface of a rubber tire having a hollow toroidal shape. After preliminarily mixing the composition A containing the polymer and the vulcanizing agent with the composition B containing the vulcanization accelerator and the foaming agent to form the foamable rubber composition, Before the vulcanization reaction and the foaming reaction proceed, the foamable rubber composition is applied or sprayed to a predetermined portion on the inner surface of the vulcanized tire to form a sound absorbing layer.

In the method for producing a tire according to the present invention, the composition A containing a polymer and a vulcanizing agent prior to forming the sound absorbing layer.
And a composition B containing a vulcanization accelerator and a foaming agent to form a foamable rubber composition having a foaming ratio of 150%. Foaming rate 150
The reason why the ratio is limited to not less than 150% is that if it is less than 150%, the effect of absorbing sound is small and the effect of reducing noise cannot be expected so much. In order to expect a sufficient effect, foaming rate
It is better to make it 250% or more.

The foaming rate V _S of the foamed rubber is represented by the following equation: V _S = {(ρ ₀ −ρ ₉ ) / (ρ ₁ −ρ ₉ ) −1} × 100 (%) (1) ₁ is the density of the foamed rubber (g / cm ³ ), ρ ₀ is the density of the rubber solid phase of the foamed rubber (g / cm ³ ), and ρ ₉ is the density of the gas part in the foamed rubber bubbles (g / cm ³ ). ³ ).

Composition A used to form the foamable rubber composition
Examples of the polymer which is an essential component of natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, ethylene-propylene-diene terpolymer rubber (EPDM), acrylonitrile-butadiene rubber (NBR), Isobutene-isoprene rubber (IIR) and its derivatives, polyisobutylene rubber and urethane rubber
There are species or blends of two or more.

Examples of the vulcanizing agent include sulfur, morpholine disulfide (manufactured by Ouchi Shinko Chemical Co., Ltd., trade name: Barnock R) and alkylphenol disulfide (manufactured by Penwald, trade name: Baltac 5).

Next, the vulcanization accelerator and the foaming agent used in the composition B are those which start the reaction at a temperature of normal temperature or higher. As the vulcanization accelerator, a super accelerator, for example, di-n-butyl-
Zinc dithiocarbamate (Ouchi Shinko Chemical Co., Ltd., trade name: Noxeller BZ), zinc zinc dithiocarbamate (Ouchi Shinko Chemical Co., Ltd., trade name: Noxeller EZ),
It is preferable to use zinc dimethyl dithiocarbamate (trade name: Noxeller PZ, manufactured by Ouchi Shinko Chemical Co., Ltd.) and the like, and furthermore, a quasi-super accelerator such as an n-butyraldehyde-aniline condensate (Ouchi Shinko Chemical) Co., Ltd., trade name: Noxeller 8), butyraldehyde-acetaldehyde-butylideneaniline reactant (manufactured by Monsanto, trade name: A-100), butyraldehyde-monobutylamine condensate (manufactured by DuPont, trade name: Accelerator 83
3) etc. should be used together.

As foaming agents, ammonium bicarbonate, a combination of ammonium carbonate and magnesium carbonate, sodium bicarbonate
50% mineral oil dispersion (Unicell S, Unicell SX manufactured by DuPont)
Etc.) and a paste of sodium bicarbonate (Ouchi Shinko Chemical Co., Ltd. Sponge Paste No. 2) is used as appropriate.

In the present invention, the composition A and the composition B are mixed in advance to prepare a foamable rubber composition, and the composition is subjected to a predetermined portion of the inner surface of the pneumatic tire before the vulcanization reaction and the foaming reaction proceed. Then, in a vulcanization reaction which is usually provided by coating or spraying and then simultaneously with foaming, co-vulcanization with the inner liner layer is performed, and the foamable rubber composition layer is adhered to the tire body to form a sound absorbing layer.

1 (a), 1 (b) and 1 (c) are cross-sectional views showing an example of a tire wheel manufactured by the method of the present invention, in which 1 is a rubber tire, 2 is a tread, 3 is a rim, 4
Is a sound absorbing layer provided on the inner surface of the tread 2 over the circumference thereof. FIG. 1 (a) shows an example in which the radial end of the sound absorbing layer is disposed inside the tread end, and FIG. 1 (b) shows that the radial end of the sound absorbing layer extends outside the tread end. It is a figure showing an example. In these examples, the first
Since the sound absorbing layer of the tire of FIG. 1B is more easily peeled off than the sound absorbing layer of the tire of FIG. 1A, it is preferable to arrange the sound absorbing layer at the position shown in FIG. Further, in addition to the sound absorbing layer shown in FIG. 2 (a), the sound absorbing layer may be provided on the inner surface of the bead portion as shown in FIG. 2 (c).

The bubbles in the sound-absorbing layer are preferably open cells, because if they are closed cells, the film on the surface of the bubbles reflects sound and a sufficient sound-absorbing effect cannot be expected.

The thickness of the sound absorbing layer is preferably 1.5 to 50.0 mm, but this is 1.5
If it is less than 5 mm, a sufficient sound absorbing effect cannot be expected.If it exceeds 50.0 mm, on the other hand, the rolling resistance is increased or the sound absorbing layer is partially destroyed due to the heat stored on the inner surface of the sound absorbing layer, and the uniformity is reduced. This is because it may cause a decrease.

If the volume of the sound absorbing layer made of the foamable rubber composition is more than 80% of the volume of the air inside the tire, the stored heat is liable to cause a failure such as breaking of the cord of the shoulder portion, which is not preferable.

As described above, the vulcanization accelerator and the foaming agent contained in the liquid of the composition B must start the reaction at room temperature or higher. This is characterized in that both liquids of the products A and B are applied or sprayed, so that if the vulcanized tire is exposed to a high temperature, it deteriorates, which is not preferable. If you use one that starts the reaction at room temperature, it is applied or sprayed on the tire,
Since foaming occurs and is stabilized during standing for several hours to several days, no trouble is required after coating or spraying. In addition, since the pressure is not increased as compared with the vulcanization, the foaming ratio is easily increased.

The main polymer contained in the composition A liquid is co-vulcanized with the inner liner layer in a vulcanization reaction that occurs simultaneously with foaming, and the foamable rubber composition layer is bonded to the tire body.

In the present invention, the composition A is defined to be composed of a main polymer, a vulcanizing agent and the like, and the composition B is composed of a vulcanization accelerator and a foaming agent. Since the reaction only needs to be started after the composition is mixed, other components may be freely converted as long as the vulcanizing agent and the vulcanization accelerator are in another liquid.

Further, since the present invention is characterized in that the composition is applied or sprayed on the inner surface of the tire, the compositions A and B are prepared by diluting with a solvent, emulsifying, latex-like, or liquid (viscous) polymer. , The viscosity must be reduced to such an extent that there is no problem in operation.

(Examples) The present invention will be described in detail based on examples and comparative examples.

 The tire size of each example tire is as follows.

Tire size: 215 / 60R15 Example 1 Compositions A and B of Table 1 were mixed at the position shown in FIG. 1 (a) on the inner surface of a tire molded and vulcanized by a usual method, and immediately applied. Then, it was left at room temperature for one day to obtain the tire of Example 1.

Comparative Example 1 A tire molded and vulcanized by an ordinary method was used as a tire of Comparative Example 1.

Comparative Example 2 A tire manufactured in the same manner as in Example 1 except that the amount of the foaming agent in Composition B in Table 1 was changed to 2 parts by weight was used as a tire of Comparative Example 2.

Example 2 A tire manufactured in the same manner as in Example 1 except that the amount of the foaming agent in the composition B in Table 1 was 20 parts by weight was used as a tire of Example 2.

Example 3 A tire manufactured in the same manner as in Example 1 except that the polymer in the composition A of Table 1 was changed to styrene-butadiene latex (0561 manufactured by Nippon Synthetic Rubber Co., Ltd.) and rubber volatilization was omitted. The tire of Example 3 was used.

Table 2 below shows the foaming ratios of the sound absorbing layers of the tires of the above Examples and Comparative Examples.

Car interior noise tests were performed on the tires manufactured in Examples 1 to 3 and Comparative Examples 1 and 2, and the obtained results are shown in FIGS. 2 (a) to 2 (e). FIG. 2A shows the first embodiment and the second embodiment.
2 (b) shows the results of Comparative Example 1, FIG. 2 (c) shows the results of Comparative Example 2, FIG. 2 (d) shows the results of Example 2, and FIG. 2 (e) shows the results of Example 3. The vehicle interior noise test was performed on road noise roads.
The sound at the left ear of the driver during steady running at 40 km / hr was measured (internal pressure of tire: 1.8 kg / cm ² ).

(Effect of the Invention) As described above, according to the present invention, the sound absorbing layer is formed using the foaming composition comprising the compositions A and B and having a foaming ratio of 150% or more, so that the sound absorbing layer can be easily formed. became. Also, in the case of pneumatic radial tires for passenger cars, road noise peaks often appear at around 250 Hz, which significantly impairs the vibration riding comfort. On the other hand, in the case of tires obtained by the method of the present invention, FIGS. 2 (a) to 2 (e) are shown. As shown in (1), the effect of suppressing noise in the frequency range of 230 to 280 Hz is obtained.

[Brief description of the drawings]

1 (a), (b) and (c) are cross-sectional views of an example tire manufactured by the method of the present invention, respectively, and FIGS. 2 (a) to (e) are Example 1, Comparative Example 1 and Comparative Example, respectively. An example
2 is a graph showing the results of a vehicle interior noise test of the tires manufactured in Examples 2 and 3. 1 ... rubber tire, 2 ... tread 3 ... rim, 4 ... sound absorbing layer

Claims (1)

(57) [Claims] 1. A composition comprising a polymer and a vulcanizing agent for producing a pneumatic tire having a sound absorbing layer made of a foamable rubber composition having a foaming ratio of 150% or more on the inner surface of a rubber tire having a hollow toroidal shape. A is preliminarily mixed with the composition B containing a vulcanization accelerator and a foaming agent to form the foamable rubber composition, and before the vulcanization reaction and the foaming reaction of the foamable rubber composition progress. A method for producing a pneumatic tire having a sound absorbing layer, wherein the foamable rubber composition is applied or sprayed onto a predetermined portion of an inner surface of a vulcanized tire to form a sound absorbing layer.