JPH0292701A - Low-noise pneumatic tire - Google Patents

Abstract

PURPOSE:To lower the noise of a tire while rolling and improve driving stability while keeping the balance of the functions thereof by controlling the visco- elasticity of the rubber composition of an inner liner. CONSTITUTION:In a pneumatic tire having a tread, side walls and beads, the product of the dynamic modulus of elasticity (stored elasticity) G' and loss factor tandelta of the rubber of the inner liner thereof, i.e., the loss elasticity G'' is set to be, G'' = G' X tandelta > 8.00 X 10<6>dyne/cm<2>, or preferably, G'' = G' Xtandelta > 1.25 X 10<7>dyne/cm<2> (values in a measuring condition at: temperature = 50 deg.C, shearing strain = 1%, frequency = 15Hz). Thereby, a noise level can be lowered while improving driving stability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic tire for passenger cars that reduces noise level and improves handling stability without impairing air permeation resistance and crack growth resistance, which are the basic characteristics of the inner liner. .

BACKGROUND OF THE INVENTION In recent years, there has been an increasing demand for reducing noise levels, especially in tires for large passenger cars. Although various studies have been made in response to this request, a sufficiently low noise level has not yet been achieved.

For example, JP-A-59-124411, JP-A-60-18
No. 9611, JP-A-61-229602, JP-A-61
285105, the dynamic elastic modulus (storage elastic modulus) and loss tangent of the tread portion and side portion of the tire are generally defined. It is true that the tread and side portions account for a large proportion of the total tire volume, and while it is possible to reduce tire noise to a relatively large extent by changing their viscoelasticity, it may also worsen handling stability.
There were problems such as a decrease in lifespan due to wear and tear, and damage to the side part's traumatic properties. However, as will be discussed later, the inner liner, which is a member installed inside the tire to retain air especially in tubeless tires, has a large effect on noise reduction even though it occupies a small proportion of the total tire volume. is currently unknown, and there are no reports or patent documents related to it.

Further, for example, Japanese Patent Publication No. 58-53221 discloses that a dynamic bumper is provided on the outer periphery of a vehicle rim so that its longitudinal and lateral resonance frequencies are tuned to the vibration frequency of the tire, and US Pat. No. 4,392,522 discloses The document discloses a method for reducing noise by providing a noise absorbing means made of an open cell material disposed entirely within the internal air filling cavity of a tire or partially within the inner surface thereof.

Problems to be Solved by the Invention However, although the method described above is effective in reducing noise, it not only deteriorates the rolling resistance due to the significant increase in tire weight or reduces the high-speed durability of the tire, but also makes it difficult to manufacture the tire. The law was complicated and there were problems with its practical implementation.

The present invention was made against the background of the above-mentioned conventional technical problems, and it does not impair air permeation resistance and crack growth resistance, which are the basic required characteristics of inner liners, and also improves the tread resistance and abrasion resistance. The purpose is to reduce the noise level without impairing rolling resistance, crack propagation properties on the sides, etc., and at the same time improve handling stability.

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention have noticed that the inner liner has a significantly large effect on noise reduction, and have arrived at the invention shown below. That is, in the present invention, in a pneumatic tire equipped with a tread, sidewalls, and beads, the product of the dynamic elastic modulus (storage elastic modulus) G' of the rubber for the inner liner and the loss tangent tan δ, that is, the loss elastic modulus G # is G#= G'X tanδ) ao OX 10'
dyne/MP preferably 01==C)'X tanδ) 1.25X10'
dyne/J (measurement conditions: temperature 50°C, shear strain 1%, frequency 15Hz).

The rubber for the inner liner that satisfies the above-mentioned loss modulus OI is preferably polyisoprene (including natural rubber) (
A) and/or isobutylene-isoprene copolymer (including halogen-modified butyl rubber) (B),
Polyisoprene (C) containing micro short fibers and/or micro fibers? A AIR-containing isobutylene-isoprene copolymer (D) is completely blended, and the blending ratio is (A) to (
(A) and/or for 1 ootit part of the rubber component in D)
or (B) 50-90 area, (C) and/or (D
) rubber component 1 (11 to 50 parts by weight), (C) and/or (D) fiber component 1 to 5 to 25 parts by weight (i.e., (
15 to 75 parts by weight of C) and/or (D) are obtained from the composition.

As the rubbers (A) and (B) above, polybutadiene rubber, styrene-butadiene copolymer rubber, ethylene-propylene-diene ternary copolymer rubber, acrylonitrile-butadiene copolymer rubber, etc. may also be used. Can be done.

The micro-short Aam-containing rubber mentioned here is used to strengthen the rubber and reduce loss, and it is better suited for this purpose than a normal car pump hook. These micro short fibers are generally micro organic short fibers, and the average short fiber length is Q, 8 to 30 μm.
, the average short fiber diameter is 1 pm or less, preferably Q, 02~
[1L is 8 μm, and the ratio L/D of average short fiber length to average short fiber diameter is 8 or more, preferably in the range of 8 to 400. Examples of the short fiber include nylon, syndiotactic-1,2-polybutadiene, polyvinylidene chloride, polyvinylidene fluoride, poly-p-t
ert-butylstyrene, p-chlorostyrene, dichlorostyrene, poly-α-methylstyrene, poly-2-methylstyrene, poly-2,5-dimethylstyrene, polytrimethylstyrene, isotactic polypropylene, etc. Those described in Japanese Patent No. 42956 can be used. These microshort fibers are generally blended as a microshort fiber-containing resin, but they can be directly added to the above (A).
, (B). Examples of the microshort fiber-containing rubber include (1) nylon reinforced natural rubber (FRB) manufactured by Ube Industries, Ltd., and (2) syndiotactic-z2-polybutadiene-containing rubber also manufactured by Ube Industries.

In particular, the FRB of the present invention is desirable because the reinforcing effect is large.

In addition, the present composition desirably contains 60 parts by weight or more, particularly 60 to 130 parts by weight, of car pump hooks per 100 parts by weight of rubber, and optionally contains softeners, anti-aging agents, vulcanizing agents, etc.
A vulcanization accelerator, a vulcanization accelerating aid, etc. can be blended. Mica may also be added to improve air permeability. Furthermore, patent application No. 1983-78258, patent application No. 1983
It is known that placing foam rubber as proposed in No. 501745 has a sound reduction effect, but by adding a foaming agent and a foaming aid to the composition and foaming the inner liner, Furthermore, it is also possible to reduce the sound.

The inventor of the present invention was researching the contribution rate of each tire component to tire noise, and found that the inner liner, although its volume accounts for a small proportion of the total tire volume, causes noise. It was found that the contribution to the noise reduction was unusually large, and that the inner liner's viscoelastic control μ provided a significant noise improvement effect. That is, Ooi #: loss modulus of conventional rubber C) Ii':
Loss modulus of elasticity of improved rubber V and volume of member 1: Number of member, 1 = 1 to n, n is the total number of members k
: If it is taken as a constant, the noise improvement effect S can be roughly expressed as: The tread, side, rubber, ply rubber, bead filler, etc. show roughly the same S value, but only the inner liner has an abnormal S value. I noticed that it takes a large value.

Upon further consideration, it was found that the loss tangent or loss modulus under compression takes a very large value compared to that measured under normal no-load conditions. In other words, when considering deformation due to inflation or deformation under load in a tire, if the ply is set as the neutral axis, the side rubber will move a few percent toward the tension side.
However, the inner liner is deformed on the compression side. Under such circumstances, the inner liner exhibits a large loss modulus. Therefore, if a rubber composition with a large loss modulus is used in the inner liner, the difference will be further emphasized on the compression side, and the contribution rate to the sound reduction effect will be higher than that of other members.

EXAMPLE Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples in any way as long as the gist thereof is not exceeded.

In the examples, loss tangent, storage modulus (dynamic modulus), and loss modulus were measured using a viscoelasticity measuring device manufactured by Rheometrics. Measurement was performed at a temperature of 50° C.), a shear strain of 1%, and a frequency of 15 Hz. In addition, the vulcanization physical properties are JIS
Measured according to K6301. The tire size of the tires in each example was f65SR13.

In addition, in the vehicle interior noise test, the road noise level was 6 ok/km/h.
The sound near the left ear of the driver was measured when passing the vehicle at 100 Hz, the sound pressure level between 10 Hz and 500 Hz was integrated with respect to the frequency, and the average value was obtained by dividing by the frequency. The sound pressure level was expressed as the difference spectrum μ between the test tire and the control tire. Steering stability is evaluated as an overall score based on the feeling of grip during cornering on dry and wet circuit roads, response during acceleration and braking, sharpness when following low rudder, and controllability at the limit. expressed. Wear resistance was measured by running a taxi on a fire truck, and measuring the distance traveled in groove 1 to 2 by measuring the groove depth, and expressed as the distance traveled per 1 inch groove of the test tire and the distance traveled per 1 inch groove of the control tire. .

Air permeability resistance is initially set to an internal pressure of 7-00 kg/yt.
”, and the internal pressure was measured after standing still for 3 months.

The value obtained by dividing the internal pressure of the test tire by the internal pressure of the control tire was taken as an index of air permeability resistance. 1) Crack resistance is determined by measuring the wear on the taxi tires.
The value of Σ (crack length x number of cracks) was measured on the circumference, and the value obtained by dividing the value of the control tire by the value of the test tire was used as the index of crack resistance.

Table 1. Rubber composition A for inner filler
B C natural rubber 50
30 30 chlorinated buty μ rubber”)so
5(+50F RR(*2)-3030 Carb/Black FEF60 100
75 Naftenitskuoi / I / 3 4
0 15 stearic acid 1
1 Magnesium monooxide 115
0゜50.5 Zinc oxide 5 5 3 Accelerator N0BS (*5) α5 1. O1
,7/l DM(*4)Cl3 0.5 0
．． 8 Sulfur ts ts 2.5 [Note] (*1) Chlorobutyl 1068 (trade name) manufactured by Nippon Butyl Co., Ltd. (*2) Nylon short fiber reinforced natural rubber manufactured by Ube Industries.

Contains 100 parts by weight of natural rubber and 50 parts by weight of short nylon fibers.

(*3) N-oxydiethylene-2-benzothiazo-
μsulfenamide (N-Oxydiethylene)
-2-benzothiazole sul-fen
amide) (*Dibenzoazil disulfide)
thiazyldisulfids) Table 2 Loss tangent and storage modulus of control tires <! tiI
The product of 4.82 x 10' dyne/
cs", and in Example 1 it is 1.71 x 10' d
yne/J.

In Example 2, 1.92 x 10' dyne/ca
t”.

As is clear from Table 2, compared to Comparative Example 1, which is a conventional tire, Examples 1 and 2 have significantly greater reductions in noise Vbeμ without impairing other performances, and at the same time have improved handling stability. It has been improved.

Table 4 Natural Rubber Chlorinated Butyl Rubber (*1) FRR (*2) Carbon Black FEF 7 Tennic Oil Stearate Oxidized Magnesilla!・Zinc oxide accelerator N0BS") DM (*4) Sulfur In order to control the viscoelasticity of the composition, it is possible to reduce the noise caused by tire rolling while maintaining the puffiness of the tire, which has been difficult with conventional technology (for example, controlling the viscoelasticity of tread rubber). It can be achieved that the steering stability is reduced and at the same time also the handling stability is improved.

Claims (4)

[Claims] (1) In a pneumatic tire equipped with a tread, a sidewall, and a bead, the product of the dynamic elastic modulus (storage elastic modulus) G' of the inner liner rubber and the loss tangent tan δ, that is, the loss elastic modulus G'' is G″=G′tanδ>8.00×10^6(dyne/
cm^2) (Measurement conditions: temperature 50°C, shear strain 1%, frequency 15Hz) A pneumatic tire for a passenger car. (2) The rubber for the inner liner is polyisoprene (A)
and/or a composition comprising a rubber consisting of an isobutylene-isoprene copolymer (B) and a polyisoprene containing microshort fibers (C) and/or an isobutylene-isoprene copolymer containing microshort fibers (D) A pneumatic tire for a passenger car as described in Scope 1. (3) Polyisoprene (A) and/or isobutylene
50 to 90 parts by weight of the rubber made of isoprene copolymer (B), and 10 to 50 parts by weight of the rubber component of polyisoprene containing microshort fibers (C) and/or isobutylene-isoprene copolymer (D) containing microshort fibers. 3. The pneumatic tire for a passenger car according to claim 2, wherein the short micro fiber component is 5 to 25 parts by weight. (4) The pneumatic tire for a passenger car according to claim 2, wherein the composition further contains 60 parts by weight or more of carbon black per 100 parts by weight of rubber.