JPH01234441A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To obtain the subject tire having good durability to heat-generation and steerability on snow-covered or frozen road, by using a rubber layer having low glass transition temperature and compounded with a specific amount of microencapsulated oil having a specific particle diameter as a surface layer of a tread covering the crown part of a tire case. CONSTITUTION:The objective pneumatic tire 1 is provided with a tire case 2 and a tread 3 covering the crown part 2a of the case 2. In the above tire, the case 2 is composed of a carcass part 6 consisting of a pair of bead parts 5 and a rubberized cord radially disposed between the bead parts, a belt part disposed on the crown part in the circumferential direction of the tire, and a side wall 8 covering both sides in the direction of the tire axis. The tread 3 on the surface layer 3a accounts for >=10% of the total volume of the tread and the crown part 2a of the case 2 is covered with a rubber layer 4 obtained by compounding 100 pts.wt. of a rubber component composed of a polymer having a glass transition temperature of <=-60 deg.C with 5-40 pts.wt. of a microencapsulated oil having an average particle diameter of 5-150mum.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a pneumatic tire, specifically, a pneumatic tire that has sufficient wear resistance for practical use without impairing summer handling performance and heat generation durability, and that can be used on icy and snowy roads. This invention relates to a pneumatic tire that has significantly improved driving performance, braking performance, and maneuverability.

(Conventional technology and its problems) In the past, spike bins were driven into the tread surface in order to ensure driving performance, braking performance, and maneuverability (hereinafter simply referred to as ice and snow performance) when driving on icy and snowy roads. Spiked tires are often used.

However, today, dust pollution caused by the scattering of these fine powders due to wear of spike bins and road abrasion, and damage to roads caused by spike bins have become major social problems. In order to cope with these problems, studies have been made on regulating the protrusion amount of the spike bottle, the number of spikes, and the material of the spike bottle, but the fundamental solution to the above social problem has not yet been reached.

On the other hand, the tire tread pattern and tread rubber quality have also been studied for so-called studless tires that do not use spike bins, but such tires have the problem that they do not have the same ice and snow performance as spiked tires. In particular, for the tread rubber, a polymer with a low glass transition point is used to ensure rubber elasticity at low temperatures, and a softener with a low melting point is used to ensure a coefficient of friction with the road surface at low temperatures. However, there is still the problem that the ice and snow performance is not sufficient.

In addition, attempts have been made to improve the slipperiness on icy and snowy roads by mixing granular materials such as sand, gilt bronze sand, carborundum, and metal particles into the tread rubber, but the slipperiness is poor unless a large amount of granular materials are mixed in. However, if a large amount is mixed in, there is a problem that the abrasion properties will be significantly deteriorated.

Furthermore, in order to improve braking performance on ice, efforts have been made to lower the hardness of tread rubber. In other words, efforts have been made to reduce the amount of reinforcing agent, reduce the crosslinking density of rubber, and increase the amount of oil softener. There are problems such as setting (permanent deformation) and increasing the amount of oil and softener increases changes in the hardness of the rubber during running and long-term use.

As mentioned above, conventional spiked tires and studless tires have various problems, and the reality is that no technology has yet been found that can solve all of these problems.

On the other hand, the present applicant has previously developed a tread with a rubber component having a predetermined glass transition temperature and a bracket tread having a specific foamed rubber layer, which was developed with the aim of solving the problems of the above-mentioned conventional technology. A patent application was filed for a pneumatic tire (Japanese Unexamined Patent Publication No. 62-283001). This pneumatic tire was able to improve its ice and snow performance, including braking performance, driveability, and maneuverability on ice and snow road surfaces, to the point where it can be put to practical use, without impairing wear resistance and heat generation durability.

Incidentally, tires using closed-cell rubber for the tread have been proposed in Japanese Patent Publication No. 40-4641, US Pat. However, in Japanese Patent Publication No. 40-4641, synthetic rubber with a large hysteresis loss, such as high styrene rubber, is used for the tread, so the glass transition temperature of the rubber increases, the hardness of the rubber at low temperatures increases, and ice and snow This was not desirable in terms of ensuring performance.

Further, in U.S. Pat. No. 4,249,588, a tread rubber having bubbles is prepared at a temperature of 25° C. and a compressive strain of 5.
Compressive property (stress) at 0% is 0.070 to 56.2 kg
/c+n” (1 to 800p3i),
Tread rubber for pneumatic automobile tires must be at least 28.1 kg/am" (400 psi) or higher to be of practical use in terms of steering response.

Furthermore, in Japanese Patent Application Laid-Open No. 56-154304, a lightweight tire is made by using foamed rubber to obtain the same hardness as non-foamed rubber, but this does not improve ice and snow performance.

The purpose of the present invention is to further improve the ice and snow performance of the tire based on the pneumatic tire technology related to the above patent application by the present applicant.
In addition to achieving both abrasion resistance, handling performance, and heat generation durability, the tire's coefficient of friction on ice, especially on wet ice near the temperature O''CC, has been improved, making it more practical than pneumatic tires using foam rubber. An object of the present invention is to provide a pneumatic tire that is durable enough for use.

(Means for Solving the Problems) The present inventors have developed a pneumatic tire that has even better ice and snow performance and wear resistance than the previously developed pneumatic tire (Japanese Unexamined Patent Publication No. 62-283001). As a result of various studies to develop the tread, we found that by using a polymer with a low glass transition point in the rubber layer of the tread and containing microencapsulated oil inside the rubber brackets, we could develop a tread without reducing the crosslinking density of the rubber itself. It has been found that the hardness of the entire rubber, ie the entire composite of rubber and microencapsulated oil, can be reduced. In addition, it has been found that by blending microencapsulated oil with rubber having a high modulus of elasticity, appropriate hardness of the tread rubber can be obtained due to the softening effect of the microencapsulated oil. Furthermore, the use of a small amount of low-temperature softener in the tread rubber together with microencapsulated oil can adjust the dynamic modulus and internal loss of the tread, and reduce the change in hardness of the rubber during long-term use, thus reducing the It has been found that the coefficient of friction on water surfaces increases, and the braking performance, driving performance, and cornering performance of the tire on wet and icy surfaces are improved. Based on these facts, and as a result of further studies from the structural aspect, the present invention was completed.

That is, the present invention provides a pneumatic tire comprising a tire case and a tread covering the crown portion of the case, in which the tread has a total volume of at least 10% or more of the total volume of the tread on its surface layer side. a microencapsulated oil-blended rubber layer having a glass transition temperature of -6.
consisting of a polymer having a temperature of 0°C or less, and in an amount of 5 to 40 parts by weight based on 100 parts by weight of the rubber component, and an average particle size of 5 to 150 μm.
This invention relates to a pneumatic tire characterized by containing microencapsulated oil of m.

The rubber component in the microencapsulated oil-blended rubber layer is a polymer having a glass transition temperature of -60°C or lower, such as natural rubber, polyisopropylene rubber, polybutadiene rubber,
Butyl rubber, low styrene-containing styrene-butadiene copolymer rubber alone, or a mixture of two or more of these polymers. In the present invention, the reason why the glass transition temperature of the rubber component is limited as described above is to ensure that the tread has sufficient rubber elasticity even at low temperatures.

The microencapsulated oil used in the present invention can be produced by a known production method, specifically, "Production method of containing polyester cells" (Kyokata, "Microcapsules", Nikkan Kogyo Shimbunsha (1970); IBM Company, B,
P, 950.443 (1964); Fr, P
, 1.278°621 (1961)) and “Production of polyphenyl ester microcapsules” (Y. Wakamak, M. Koishi and T. Kondo Chem.
PharmBull, 22(6) 1319 (19
74)).

In addition, acid dichloride and bisphenol as membrane materials that can be used in the latter "method for producing polyphenyl ester microcapsules" include those shown in Table 1 below.

Table 1 Oils to be encapsulated in microcapsules are not particularly limited, such as natural mineral oils, animal oils, vegetable oils, and synthetic oils, but preferably have a freezing point of 15°C or less, more preferably 12°C or less.
Use one with a temperature below 0°C. Specifically, the following can be used.

(1) Monoolefins, diolefins and acetylenes octene-1, cis-octene-2, trans-octene-3, cis-octene-4, trans-octene-4
, 2-methylhebutene-1,2,3-dimethylhexane-2,2,3,3-trimethylpentene-L 2,4.
4-trimethylpentene-L 2,4.4-)IJ/Tylpentene-2, nonene-L 2,3-dimethylhebutene-2,2-methylhexazine-284,2,4-dimethylpentazine-1,3 , octadine-2,6,3-methylhebutazine-1,5,2,5-dimethylhexazine-1,5,2,6-dimethylhebutazine-1,5,2-
Methyl-3-ethylhexazine-1,5,3,7-dimethyloctadine-1.6, octyne-1, octyne-2
, octyne-3, octyne-4, nonine-1, (2) vegetable oil tung oil, corn oil, (3) saturated fatty acid butyric acid, caproic acid, enanthic acid, (4) nitrile amide capronitrile, enantonitrile, cabrilonitrile , Belargonitrile, Caprinitrile, (5) Pilgrimage X > 4
鉦Z Hexylamine, heptylamine, dihexylamine,
Trioctylamine, N,N-dimethyl-laurylamine, (6) Ester diptyl phthalate, diheptyl phthalate, dioctyl phthalate, diisononyl phthalate, diptyl maleate,
Dioctyl maleate, dioctyl fumarate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, diisodecyl adipate, dioctyl azelaate, diptyl sebacate, dioctyl sebacate, methyl butyrate, ethyl butyrate, propyl butyrate, butyric acid Butyl, isobutyl acetate, amyl butyrate, isoamyl butyrate,
Hexyl butyrate, heptyl butyrate, benzyl butyrate, octyl butyrate, decyl butyrate, methyl caproate, ethyl caproate, propyl caproate, isopropyl caproate, allyl caproate, butyl caproate, acyl caproate, hexyl caproate, heptyl caproate , octyl caproate, nonyl caproate, decyl caproate, undecyl caproate, dodecyl caproate, methyl enanthate, ethyl enanthate, propyl enanthate, butyl enanthate, amyl enanthate, hexyl enanthate, heptyl enanthate, enanthate Octyl caprylate, methyl caprylate, ethyl caprylate, vinyl vinyl caprylate, propyl caprylate, isopropyl caffrylate, butyl caprylate, amyl caprylate, hexyl caprylate, hebutyl caprylate, octyl caprylate, methyl pelargonate , ethyl pelargonate, vinyl pelargonate, propyl pelargonate, butyl pelargonate, amyl pelargonate, heptyl pelargonate, methyl caprate, ethyl caprate, butyl caprate, hexyl caprate, heptyl caprate, (7) Process oil Aromatic process oil, naphthenic process oil, paraffin process oil.

In the present invention, the microencapsulated oil-blended rubber layer is required to have a volume of at least 10% or more of the total volume of the tread, preferably 10 to 70%, and more preferably 40 to 60%. The reason why the microencapsulated oil-blended rubber layer is required to account for at least 10% of the total tread volume is that if it is less than 10%, the effect of improving ice and snow performance is small.

Note that the entire tread may be made of a microencapsulated oil-blended rubber layer.

The proportion of microencapsulated oil in the microencapsulated oil-containing rubber layer (parts by weight relative to 100 parts by weight of the rubber component) is required to be within the range of 5 to 40 parts by weight; however, if it is less than 5 parts by weight, the temperature If the amount exceeds 40 parts by weight, the abrasion resistance will decrease and the abrasion resistance will be insufficient for practical use on dry roads other than icy and snowy roads and wet roads. be. Preferably, the blending ratio is within the range of 5 to 20 parts by weight.

In addition, the average particle size of the microencapsulated oil in the compounded rubber is 5
~150 pm, which is 5 μm
If it is less than 150 μm, the effect of improving ice and snow performance is small;
Exceeding this will significantly reduce the wear resistance, and furthermore, the distortion recovery power of the compounded rubber will decrease, resulting in a decline in so-called fatigue resistance, which may cause deformation of the tire block and clogging of the sipes during driving, resulting in poor performance on snow. This is because the cut resistance also decreases, leading to increased block chipping, and furthermore, it becomes difficult to obtain a stable shape during manufacturing. Preferably, the average particle size is within the range of 10 to 100 μm.

Incidentally, as a method for blending the microencapsulated oil into the rubber component, the usual Banbury mixing method or latex mixing method can be adopted. Furthermore, compounding agents commonly used in the rubber industry, such as sulfur, vulcanization accelerators, softeners, and anti-aging agents, can be appropriately blended into the rubber component.

(Example) Next, the present invention will be explained by examples.

First, a method for preparing microencapsulated oil used in the following Examples and Comparative Examples will be explained.

100 g of dibutyl phthalate and 200 g of terephthaloyl chloride in 5% bicarbonate of soda 20! and then add 25% ethylene glycol 20
1 was added, and a homomixer manufactured by Chuo Rika Co., Ltd. (AM-HM) was added.
-1 type) at a stirring intensity of 900 rpm. As the mixture was stirred, a polyester film was formed around the microdroplets of dibutyl phthalate.

After the film was formed, it was collected by centrifugation and used as microcapsule type A.

Microcapsule type B was obtained as described above, except that the particle size was changed by changing the stirring intensity to 600 rpm.

In addition, dibutyl phthalate was used instead of dibutyl phthalate, and the stirring intensity was 6000 rl 1 m, respectively.
Microcapsule types C, D and E were obtained as described above except that the speeds were 2000 rpm and 8000 rpm.

The characteristics of these microcapsules, such as capsule diameter, are shown in Table 2 below.

Examples 1 to 5, Comparative Examples 1 to 3 Various rubbers containing microencapsulated oil were prepared at the blending ratios (parts by weight) shown in Table 3 below (in Comparative Example 1, no microencapsulated oil was blended as a control). . For these rubbers, the coefficient of friction on ice, especially the coefficient of friction on ice in a wet state around 0°C, was measured. The measurement is performed when the surface temperature is -0
, the surface roughness of the sample was measured on ice at 5°C (sample dimensions: length 10 mm, width 10 mm, thickness 5 mm) was brought into contact with the ice, and a dynamic/static friction coefficient meter manufactured by Kyowa Interface Science Co., Ltd. was used. This was done using Load 2kg/Cl11 as measurement conditions
2. A sliding speed of 10 mm/sec, an ambient temperature of -2° C., and a surface condition similar to a mirror surface were selected.

The obtained results are also listed in Table 3.

Next, a pneumatic tire having a tire size of 165 SR13 as shown in FIG. 1 was manufactured using the microencapsulated oil-blended rubber.

This tire l has a tire case 2 and a tread 3 covering a crown portion 2a of the case 2. Case 2
consists of a pair of bead portions 5, a carcass portion 6 consisting of a rubberized cord disposed approximately radially between the bead portions 5, a belt portion 7 disposed approximately in the circumferential direction of the tire at the crown portion of the carcass portion 6, and a carcass portion 6. sidewall rubber 8 covering both sides of the tire in the axial direction.

The tread 3 has a micro-encapsulated oil compounded rubber layer 4 (indicated by black dots in the figure) between both shoulder parts on the surface part 3a side of the tread 3, and this rubber layer has a total volume V of the tread 3. It has a volume of at least 10% or more, and in this embodiment, it has a volume of 100%, which is the same as the total volume of the tread. The rubber components of the rubber layer 4 are as shown in Table 3 below. (Glass Transition Temperature -100°C)) 7, to which were added conventional compounding agents and microencapsulated oil, and molded according to a conventional tire manufacturing method.

The tread surface heat generation temperature, wear resistance performance, and braking performance on ice of the various test pneumatic tires obtained were evaluated as follows.

(a) Tread surface heat generation temperature test After filling the tire with the normal internal pressure, the drum outer diameter was 1.7
m normal indoor drum testing machine with a speed of 100 kg/hour,
The tread was pressed under a regular load and run for 3 hours, and the surface temperature at the center of the tread was measured.

(b) Wear resistance performance Two tires for each test were attached to the drive shaft of a passenger car with a displacement of 1500 cc, and the tires were run on the concrete road surface of a test course at a predetermined speed. The amount of change in groove depth was measured and expressed as an index with the tire of Comparative Example 1 set as 100. The larger the value, the better the wear resistance performance.

(c) Braking performance on ice Four test tires of each type were mounted on a passenger car with a displacement of 1500 cc, and the braking distance was measured on ice at an outside temperature of -5°C. The tire of Comparative Example 1 was set as 100 and expressed as an index. The larger the value, the better the braking.

The obtained evaluation results are also listed in Table 3.

The following was confirmed from Table 3.

Comparative Example 2 contained 15 parts by weight of microencapsulated oil, but the diameter of the microcapsules was as small as 2 μm, so the tread rubber's coefficient of friction on ice and the tire's braking ability on ice were insufficient. Furthermore, in Comparative Example 3, the amount of microencapsulated oil blended was too small, so the friction coefficient on ice and the braking ability on ice were not sufficient.

The coefficient of friction on ice of a tire is particularly important in a wet state at a temperature around 0°C, but the tread rubber and tires using the compounded rubbers of Examples 1 to 5 have a lower coefficient of friction on ice than Comparative Examples 1 and 2.3. The coefficient and ice braking performance are clearly improved.

Examples 6 and 7, Comparative Examples 4 and 5 Tread rubbers were prepared in the same manner as above using the compounding ratios (parts by weight) shown in Table 4 below, and the hardness (0°C) and change in rubber hardness of these rubbers were measured. and wear resistance was evaluated.

The hardness of the rubber was measured in accordance with JIS K 6301.

The abrasion resistance was tested using the usual Lambourn abrasion test a (slip 25%) and expressed as an index, with the test result of Comparative Example 4 set as 100.

The obtained results are also listed in Table 4.

Next, various test tires were manufactured in the same manner as above using the above tread rubber. The on-ice braking performance of these test tires was evaluated in the same manner as in the above-mentioned on-ice braking test.The on-ice braking performance near O''CC and around -20°C was evaluated.This evaluation was performed using an index display using the tire of Comparative Example 4 as a control. I see that the performance is good.

The obtained results are also listed in Table 4.

As is clear from Table 4, Comparative Example 4.5 is a blending system in which only the blended number of low-temperature softener was changed without blending microencapsulated oil, whereas Example 6.7 is a blended system containing microencapsulated oil along with a small amount of low-temperature softener. Compared to Comparative Examples 6 and 7, Examples 6 and 7, in which microencapsulated oil was blended with a small amount of low-temperature softener, had little change in hardness during long-term use, and could be used on ice while maintaining sufficient wear resistance for practical use. Braking performance has been significantly improved.

Examples 8-10, Comparative Examples 6-8 Comparative Examples 6-8 at the blending ratios (parts by weight) shown in Table 5 below
In Examples 8 to 10 (same as Examples 3 to 5), tread rubbers containing encapsulated oil were prepared.

The coefficient of friction on ice was measured for these tread rubbers in the same manner as described above. The obtained results are also listed in Table 5.

Next, various test tires were manufactured in the same manner as above using the above tread rubber, and the wear resistance performance and on-ice braking performance of these tires were evaluated in the same manner as above. These evaluations were performed using index display using the tire of Comparative Example 6 as a control. The larger the number, the better the performance.

The obtained results are listed in Table 5, and the relationship between the wear resistance and the braking performance on ice in tires using a foaming agent and tires using microencapsulated oil is shown in comparison in FIG.

As is clear from Table 5 and FIG. 2, the tires using microencapsulated oil were relatively superior in wear resistance and braking performance on ice compared to the tires using foaming agents. This is considered to be because the microencapsulated oil has a more uniform diameter than the foaming agent bubbles, and as a result, a better edge effect was exhibited.

(Effects of the invention) As explained above, in the pneumatic tire of the present invention,
It has sufficient abrasion resistance for practical use without compromising handling performance and heat generation durability, and has improved driving performance, braking performance, and maneuverability on icy and snowy roads compared to tires using foam rubber. As a result, it can be said that the tire fully meets expectations as an alternative to spiked tires.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a pneumatic tire as an example of the present invention, and FIG. 2 is a graph showing the relationship between wear resistance and braking performance on ice in tires using a foaming agent and tires using microencapsulated oil. 1... Pneumatic tire 2... Case 2a...
Case crown part 3-h Red 3a... Tread surface part 4... Microencapsulated oil blended rubber layer 5... Bead part 6... Carcass part 7... Belt part 8... Side wall Rubber patent applicant Akihide Sugimura, patent attorney representing Brideston Co., Ltd.

Claims (1)

[Scope of Claims] 1. A pneumatic tire comprising a tire case and a tread covering the crown of the case, wherein the tread has at least 10% or more of the total volume of the tread on its surface layer side. a microencapsulated oil-blended rubber layer having a volume of
The average particle size is 5 to 1 in the range of 5 to 40 parts by weight to 0 parts by weight.
A pneumatic tire characterized by containing 50 μm micro-encapsulated oil.