JP2006240470A - Checking method of hollow particle for safety tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply and correctly check presence/absence of occurrence of volumetric expansion of hollow particles filled in a safety tire under the pressure, and the degree of occurrence thereof. <P>SOLUTION: In a safety tire in which a large number of thermally expandable hollow particles 4 consisting of continuous phases made of resin and closed cells surrounded thereby are sealed in a tire air chamber 3 demarcated by the tire 1 and a rim 2 while the tire 1 is mounted on the rim 2, hollow particles 4 in a tire before travel and in a used tire are respectively sampled, the particle size distribution of the hollow particles 4 of the predetermined amount is measured, the results of measurement is compared with each other, and acceptance/rejection of the hollow particles 4 in the used tire is determined. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  This invention is still in a puncture state due to trauma, etc., and can continue to travel safely over the required distance, and has excellent durability, riding comfort, etc. in steady running before breakage, In order to check whether hollow particles applied to a safety tire that is mounted on a general-purpose rim and used without damaging the productivity of the tire can sufficiently exhibit the function as a safety tire. The present invention relates to an inspection method for hollow particles for safety tires.

  A large number of bubble-containing particles consisting of a continuous phase made of resin and closed cells held at a pressure higher than atmospheric pressure are enclosed in a space defined by the tire and the rim under the mounting posture of the tire on the rim. The safety tire formed is described in, for example, Patent Document 1 related to the applicant's previous proposal.

  In this safety tire, when the tire is damaged and the internal pressure starts to decrease, the bubble-containing particles seal the damaged portion, and while a rapid decrease in the internal pressure is suppressed, the amount of deflection of the tire is reduced as the tire internal pressure decreases. As the tire volume increases and the volume inside the tire decreases, the bubble-containing particles themselves will bear the load directly, maintaining the minimum tire pressure required for subsequent driving, and before being damaged. The bubble internal pressure in the closed cells of the bubble-containing particles that existed under the tire internal pressure was maintained at the pressure corresponding to the tire internal pressure even after the damage, in other words, the total volume of the bubble-containing particles before the damage. Since it will be present in the tire as it is held, the rolling of the tire will cause the bubble-containing particles themselves to bear the load while the bubbles-containing particles themselves bear a load, causing self-heating. As a result, the temperature of the bubble-containing particles in the tire rises rapidly, and when the temperature exceeds the softening temperature of the resin forming the continuous phase of the bubble-containing particles, the pressure in the bubbles in the closed cells of the bubble-containing particles is reduced before being damaged. In addition to the pressure according to the tire internal pressure, since the bubble internal pressure further increases due to the rapid increase in the temperature of the bubble-containing particles, the bubble-containing particles expand in volume at a stretch, and the tire internal pressure reaches a pressure close to the state before the damage. Suppose that it will be revived.

  In addition, as a safety tire according to the applicant's recent proposal, for example, as disclosed in Japanese Patent Application No. 2004-329301, a tire is mounted on a rim, and a continuous tire made of resin is provided in a tire chamber partitioned by the tire and the rim. Filled with thermally expandable hollow particles composed of phases and closed cells at a filling rate of 5 vol% or more and 80 vol% or less, and filled with a gas whose humidity at 30 ° C. under atmospheric pressure was adjusted to 70% or less. There is something.

Also with this safety tire, the wound of the tire damage part is closed with hollow particles, and the hollow particles in the tire chamber are thermally expanded with the load rolling of the tire to increase the volume. By recovering the indoor pressure, it is possible to ensure continued safe driving over the required distance.
JP 2003-118312 A

  However, the “bubble-containing particles” in Patent Document 1 and the “hollow particles” in the proposed technology are both filled into a tire chamber partitioned by a tire and a rim under pressure. Before the tire becomes punctured due to trauma, etc., there is a risk of causing unexpected breakage, volume expansion, etc., and particles that caused such unexpected volume expansion are no longer in the damaged tire, Since the required internal pressure recovery function cannot be achieved, when many of the filled particles undergo volume expansion, etc., the safety tire cannot perform the inherent function described above. It becomes.

  Therefore, in this type of safety tire, the soundness of the packed particles is checked, for example, every predetermined time interval or every predetermined traveling distance, in a state where steady running is possible, and volume expansion, etc. When there are so many hollow particles that exceed the allowable limit, replenishment or replacement of the filler particles is necessary to ensure that safety tires always perform their original functions. It becomes important in.

  Therefore, the present invention simply and accurately checks the presence or absence and the degree of occurrence of volume expansion, etc., in the hollow particles containing bubble-containing particles, which are filled in this type of safety tire under pressure. A method for inspecting hollow particles for a safety tire that can be provided is provided.

  According to the method for inspecting a hollow particle for a safety tire according to the present invention, one or a plurality of small chambers made of a resin are provided in a tire chamber partitioned by a tire and a rim under the mounting posture of the tire on the rim. In a safety tire in which a large number of thermally expandable hollow particles consisting of a continuous phase and one or a plurality of closed cells surrounded by it are sealed under pressure, in the tire before running or the same as that The hollow particles under the above conditions and the hollow particles in the used tire were collected, and the particle size distribution of each predetermined amount of the hollow particles was measured, and the measurement results were compared with each other. It is to determine the suitability of the hollow particles.

In this case, preferably, the suitability of the hollow particles in the used tire is determined by a change in the average particle diameter.
In other words, when the average particle size of the tire after use changes by more than ± 10% with respect to the average particle size before use, the hollow particles are broken or expanded, and the desired performance cannot be exhibited. It can be judged.

The definition of the average particle diameter here is a particle diameter corresponding to R = 50% obtained from the upper curve, and is also called a median diameter, median diameter, or 50% particle diameter, and is represented by D50.
In addition, when the measured particle size distribution is determined to be a substantially normal distribution, the average particle size may be the maximum frequency diameter obtained from the peak of the frequency distribution curve.

According to another inspection method of the present invention, the tire is composed of a continuous phase made of resin and closed cells surrounded by the tire in a tire chamber partitioned by the tire and the rim under the mounting posture of the tire on the rim. In a safety tire formed by enclosing a large number of thermally expandable hollow particles under pressure,
Obtain the total volume of the hollow particles in the tire before running and the hollow particles in the used tire, and determine the suitability of the hollow particles in the used tire based on the rate of change of the total volume. It is in.
In this case, for example, when the filling rate after use changes beyond the range of −15% to + 5% with respect to the filling rate before use, it is determined that the performance deterioration of the hollow particles has occurred. can do.
Here, “total volume” means the total volume of all hollow particles.

In addition, when judging by such a change amount of the filling rate of the volume, the judgment criterion is limited to “−15% to + 5%” and an unbalanced range as the safety tire is used. This is because the internal volume of the tire chamber itself increases.
In other words, the inner volume of a tire that has received a running input shows an increasing tendency of about + 5% with respect to the inner volume of the tire when the tire is new. Even if the volume of the hollow particles does not change, it seems as if the volume has decreased. This is because data including errors is obtained.
By the way, the rate of increase of the tire internal volume referred to here varies depending on the structure of the tire and the usage environment, so it is difficult to define it as a general percentage.

  Preferably, the suitability of the hollow particles in the used tire is determined in consideration of the amount of hollow particles broken in the tire and / or the color tone change accompanying the use of the hollow particles.

In the former inspection method according to the present invention, the hollow particles in the tire before running, or the hollow particles placed under the same conditions as in the tire before running, and the hollow particles taken out from the used tire, respectively. By measuring the particle size distribution and comparing the results with each other, it is possible to easily and accurately grasp the relative volume expansion state of the hollow particles in the used tire.
Therefore, based on the particle size distribution, for example, when the average particle size has changed by ± 10% or more, the hollow particles cannot be said to be in a healthy state, that is, the hollow particles are broken or expanded. Judgment is made and prompt replacement of the packed particles is performed.

  In the latter inspection method according to the present invention, the suitability of the hollow particles in the used tire is determined based on the filling rate of the hollow particles. For example, the change rate of the filling rate is -15% to + 5%. When exceeding the range, it can be said that the hollow particles are not in a healthy state, that is, it is judged that the hollow particles are broken or expanded, and the filled particles are promptly replaced.

  Furthermore, considering the amount of hollow particles broken in the tire, for example, when the proportion of the broken particles in a specific amount of hollow particles exceeds 1%, the hollow particles in the tire When it is determined that the particles are inappropriate and are exchanged, etc., even if the volume expansion of the hollow particles is only appropriate, the hollow particles are relatively Therefore, it is possible to grasp the tendency to be easily broken and take more sufficient measures.

In addition, it is possible to take more sufficient measures in the same manner by determining the suitability in consideration of the color tone change of the hollow particles.
For example, when the b * value measured with a color difference meter changes by 3 or more, it can be considered that a thermal history that is suspicious about the soundness of the hollow particles has been received. It is determined that it is a thing, and those are replaced.

The “L * value, a * value, and b * value” referred to here are numerical values representing the color tone. The color is decomposed, the lightness is the L * value, the redness is the a * value, and the yellowness is b. * It will be quantified as a value.
If we take hollow particles based on acrylonitrile copolymer as an example, the one that was initially white to cream colored will change its color tone by receiving a heat history, and will change from orange to brown. The change can be easily grasped by the b * value, and can be applied as a material for judging the soundness of the hollow particles.

  Further, depending on the structure of the tire, the inner surfaces of the tires rub against each other during run-flat running, so the inner liner may become powdery and be released into the tire. This powder is black because carbon black is mixed. In other words, the hollow particles in the tire that has run flat run can be easily detected by the color difference meter because an extreme change in color appears regardless of the material.

  The ratio of the broken particles or the change in the color tone of the hollow particles due to the use described above is a numerical value that does not depend on the particle size distribution, average particle size, or volume change of the hollow particles. In other words, if the breakage and expansion of the hollow particles occur at the same time, they may not be reflected in the particle size distribution, average particle size, or volume change rate. Judgment is possible.

FIG. 1 is a cross-sectional view in the width direction illustrating a safety tire that can be an inspection object of the present invention.
In the illustrated safety tire, a tire 1 is mounted on a rim 2, and a hollow particle 4 composed of a continuous phase made of resin and closed cells is thermally expandable in a tire chamber 3 defined by the tire 1 and the rim 2. Are arranged under pressure.
Here, the structure of the tire 1 is not particularly limited as long as it is various automobile tires according to the standard, for example, a tire for trucks and buses, a tire for passenger cars, and the like. That is, the present invention is a technique that can be applied to all safety tires that are an assembly of a tire and a rim, and the illustrated tire has a radius at the crown portion of the carcass 6 that extends in a toroid shape between a pair of bead cores 5. This is a general automobile tire in which a belt 7 and a tread 8 are sequentially arranged outward in the direction.
In the figure, reference numeral 9 denotes an inner liner layer, reference numeral 10 denotes a void around the hollow particle 4, and 11 denotes a side portion.

The hollow particles 4 have closed cells surrounded by a continuous phase of a substantially spherical resin, for example, a hollow body having a particle size distribution in the range of about 10 μm to 500 μm, or a small chamber made of closed cells. It is a spongy structure containing a large number of. That is, the hollow particle 4 is a particle that encloses closed closed cells that do not communicate with the outside, and the number of closed cells may be singular or plural. In this specification, the “inside of closed cells of the hollow particle group” is generically expressed as “hollow part”.
In addition, the fact that the particles have closed cells means that the particles have a “resin shell” for enclosing the closed cells in a sealed state. It refers to the “continuous phase on the component composition constituting the shell”. The composition of the resin shell is as described later.

The hollow particle group, which is a large number of the hollow particles 4, is disposed inside the tire chamber 3 together with the high-pressure gas, and thus partially bears the “internal pressure” of the tire under normal use conditions. At the time of injury, it becomes a source for expressing the function of restoring the pressure lost in the tire chamber 3. This “internal pressure restoration function” will be described later.
Here, “internal pressure” refers to “a tire chamber pressure value (gauge pressure value) for each mounting position specified by an automobile manufacturer for each vehicle”.

By the way, the hollow particles are obtained by heating and expanding “expandable resin particles” that are raw materials, that is, particles encapsulated in a resin using a gas component as a foaming agent in a liquid state. Ts1 exists.
Further, when the hollow particles obtained by this thermal expansion are heated again from room temperature, the hollow particles start to expand further, and there exists the expansion start temperature Ts2 of the hollow particles. As a result of producing hollow particles from many expandable resin particles and studying them, the inventors have used Ts1 as an index of expansion characteristics. However, Ts2 is appropriate as an index of expansion characteristics of hollow particles. I came to find out.

That is, when observing the expansion behavior when the expandable resin particles are heated and expanded, the expandable resin particles are in a stage before expansion, so the particle size is extremely small compared to the state of the hollow particles, Therefore, the rigidity as a microcapsule is high. Therefore, even if the continuous phase of the resin shell exceeds the glass transition point in the process of thermal expansion, the expansion force of the internal gas overcomes the rigidity of the shell until the shell is softened to some extent by further heating. I can't. Therefore, Ts1 shows a higher value than the actual glass point transfer of the shell.
On the other hand, when the hollow particles are heated and expanded again, the thickness of the shell of the hollow particles is extremely thin and the rigidity of the hollow body is low. Therefore, since the continuous phase of the shell exceeds the glass transition point in the process of thermal expansion, expansion starts at the same time, so Ts2 is positioned lower than Ts1.

Therefore, in the illustrated safety tire, further expansion characteristics of the hollow particles once expanded are utilized. In this case, Ts2 of the hollow particles is preferably 90 ° C or higher and 200 ° C or lower.
That is, if the Ts2 of the hollow particles is less than 90 ° C., there is a risk of expansion in the temperature environment of the tire chamber during normal running, while if it exceeds 200 ° C., the run flat running after puncture damage However, Ts2 may not be reached even if a sudden temperature rise due to frictional heat generation of the hollow particles occurs, and thus the intended “internal pressure restoration function” may not be sufficiently developed. is there.

Next, as a gas constituting the hollow part (closed cell) of the hollow particles, nitrogen, air, linear and branched aliphatic hydrocarbons having 2 to 8 carbon atoms and fluorinated products thereof, and having 2 carbon atoms are used. To 8 alicyclic hydrocarbons and their fluorinated products, and the following general formula (I):
R ¹ —O—R ² ... (I)
(Wherein R ¹ and R ² are each independently a monovalent hydrocarbon group having 1 to 5 carbon atoms, and part of the hydrogen atoms of the hydrocarbon group may be replaced by fluorine atoms) And at least one selected from the group consisting of ether compounds.
The gas filled into the tire chamber may be air. However, when the gas in the particles is not a fluorinated product, a gas not containing oxygen, such as nitrogen or an inert gas, is preferable from the viewpoint of safety.

The method for obtaining hollow particles having closed cells is not particularly limited, but a general method is to produce “expandable resin particles” using a foaming agent and to heat and expand them.
Examples of the foaming agent include a method utilizing vapor pressure such as high-pressure compressed gas and liquefied gas, and a method utilizing a thermally decomposable foaming agent that generates gas by thermal decomposition.

  Many of the latter thermally decomposable foaming agents are characterized by generating nitrogen, and the particles obtained by appropriately controlling the reaction of the expandable resin particles obtained by foaming by these have mainly nitrogen in the bubbles. It will be a thing. Although it does not specifically limit as this thermally decomposable foaming agent, Dinitroso pentamethylenetetramine, azodicarbonamide, para-toluene sulfonyl hydrazine and its derivative (s), and oxybisbenzene sulfonyl hydrazine can be mentioned suitably.

Next, a technique for obtaining “expandable resin particles” that become hollow particles by utilizing the vapor pressure of the former high-pressure compressed gas and liquefied gas will be described.
When polymerizing a continuous phase of the resin forming the hollow particles, linear and branched aliphatic hydrocarbons having 2 to 8 carbon atoms and fluorinated products thereof, alicyclic hydrocarbons having 2 to 8 carbon atoms And its fluorinated products, and the following general formula (II):
R ¹ —O—R ² ... (II)
(Wherein R ¹ and R ² are each independently a monovalent hydrocarbon group having 1 to 5 carbon atoms, and part of the hydrogen atoms of the hydrocarbon group may be replaced by fluorine atoms) In this method, at least one selected from the group consisting of ether compounds represented by the following formula is liquefied under high pressure as a blowing agent and dispersed in a reaction solvent, followed by emulsion polymerization. As a result, “expandable resin particles” in which the gas component shown above is contained in the liquid continuous phase as a foaming agent in a liquid state can be obtained, and desired hollow particles can be obtained by heating and expanding the particles. I can do it.

  The surface of the “expandable resin particles” is coated with an anti-blocking agent such as silica particles, carbon black fine powder, antistatic agent, surfactant, etc., and then heated and expanded to obtain the desired hollow particles. be able to.

Here, in the state where the tire chamber pressure is reduced due to the damage, in order to apply the minimum necessary internal pressure by the hollow particles, the gas sealed at the predetermined pressure in the hollow portion of the hollow particles leaks to the outside of the particles. In other words, it is important that the continuous phase of the resin corresponding to the shell part of the hollow particles has a property that gas is difficult to permeate.
That is, the resin constituting the continuous phase is made of a material having low gas permeability, specifically, at least one of an acrylonitrile copolymer, an acrylic copolymer, and a vinylidene chloride copolymer. It is preferable. These materials are particularly effective when applied to safety tires because they have flexibility as hollow particles with respect to input due to tire deformation.

  In particular, it is preferable to apply any one of an acrylonitrile polymer, an acrylic polymer, and a vinylidene chloride polymer to the continuous phase of the hollow particles. More specifically, the polymer constituting the polymer is a polymer selected from acrylonitrile, methacrylonitrile, methyl methacrylate, methacrylic acid, and vinylidene chloride, preferably an acrylonitrile / methacrylonitrile / methyl methacrylate terpolymer, Each of at least one selected from acrylonitrile / methacrylonitrile / methacrylic acid terpolymer is advantageously suitable. Since all of these materials have a small gas permeability coefficient and are difficult for gas to permeate, the gas in the hollow part of the hollow particles hardly leaks to the outside, and the pressure in the hollow part can be appropriately maintained.

Further, the continuous phase of the hollow particles has a gas permeability coefficient at 30 ° C. of 300 × 10 ⁻¹² (cc · cm / cm ² · s · cmHg) or less, preferably a gas permeability coefficient at 30 ° C. of 20 × 10 ⁻¹² ( ^{cc · cm / cm 2 · s} · cmHg) or less, it is recommended and further preferably the gas permeability coefficient at 30 ° C. is ^{2 × 10 -12 (cc · cm} / cm 2 · s · cmHg) or less.
This is because normal performance gas permeability coefficient of the inner liner layer in the pneumatic tire of ^{300 × 10 -12 (cc · cm} / cm 2 · s · cmHg) In the following levels have sufficient internal pressure retaining function In view of the above, the gas permeation coefficient at 30 ° C. was set to 300 × 10 ⁻¹² (cc · cm / cm ² · s · cmHg) or less for the continuous phase of the particles. However, at this gas permeation coefficient level, it is necessary to replenish the internal pressure once every 3 to 6 months. From the standpoint of maintainability, 20 × 10 ⁻¹² (cc · cm / cm ² · s · cmHg) or less, more preferably 2 × 10 ⁻¹² (cc · cm / cm ² · s · cmHg) or less is recommended.

In the safety tire that is an assembly of the tire 1 and the rim 2 in which the hollow particles that can be manufactured as described above are arranged in the tire chamber, when the tire 1 is damaged, the voids between the hollow particles 4 are interspersed. The existing high pressure gas in the tire chamber 3 leaks to the outside of the tire, and along with this, many of the hollow particles 4 that are accompanied by the outflow of the high pressure gas block the wounded part, and a sudden air chamber pressure is generated. Suppresses the decline.
In other words, the wound of the damaged part becomes a flow path through which gas in the tire chamber leaks, but the hollow particles can enter the flow path in a “consolidated” state and clog the flow path with a large number of hollow particles. .

Furthermore, when the pressure inside the tire chamber is increased from the atmospheric pressure by the internal pressure restoration mechanism described later, tension is applied to the tire frame, so that the inner diameter of the wound is reduced so as to be narrowed down. A compressive force that is squeezed from the tire side acts on the hollow particle group that has entered the compacted state due to the pressure increase in the tire chamber. In this case, since the hollow part has a high hollow part pressure, the reaction force based on the hollow part pressure can be generated with respect to the compressive force to increase the degree of consolidation. The wound can be closed to such an extent that the gas in the air chamber hardly leaks out.
Therefore, the wound that caused the puncture is instantly and reliably blocked by the hollow particles.

  On the other hand, when the amount of tire deflection increases as the air chamber pressure decreases and the air chamber volume decreases, the hollow particles disposed in the air chamber are sandwiched between the tire inner surface and the rim inner surface. However, it receives compression and shear input. According to this, since the hollow particles rub against each other and self-heat, the temperature of the hollow particles in the tire chamber rises rapidly, When the thermal expansion start temperature Ts2 (corresponding to the glass transition temperature of the resin) of the resin continuous phase as a part is exceeded, the shell of the particles starts to soften.

  At this time, in addition to the pressure in the hollow part of the hollow particles being a high pressure corresponding to the working internal pressure of the tire, the pressure in the hollow part is further increased due to the sudden rise in the temperature of the hollow particles, so that the hollow particles are rapidly increased in volume. It expands and compresses the void gas around the particles, and the pressure of the tire chamber can be restored to at least the tire chamber pressure at which the side portion of the tire does not come into contact with the ground. A vehicle equipped with the vehicle can continue to travel safely over a required distance.

The inspection of the hollow particles according to the present invention for the safety tire as described above is performed under a predetermined amount collected from the safety tire before use, for example, the hollow particles 4 having a predetermined mass, or under the same setting conditions as in the tire. The particle size distribution of each of the collected predetermined amount of hollow particles 4 and, for example, the predetermined amount of hollow particles 4 collected from within the safety tire that has been traveled for a certain period of time or a certain traveling distance is measured. This is performed by comparing the results of the particle size distribution measurement with each other and determining the suitability of the hollow particles 4 in the used tire.
Here, this determination can be made based on the particle size distribution, for example, by determining that the hollow particles are not in a healthy state when the average particle size has changed by ± 10% or more.

  In such a determination, when the hollow particles in the used tire are still sufficiently durable, for example, the hollow particles are continuously used as they are until the next inspection. If the hollow particles are inappropriate, for example, the filler particles are replaced quickly.

  Further, the other inspection of the hollow particles according to the present invention is performed based on the change rate of the total volume of the hollow particles, in other words, the change rate of the filling rate. According to this, the particle size distribution is directly determined. Compared to the previous case, the suitability of hollow particles can be determined by a relatively inexpensive and simple measuring device.

    By the way, this judgment based on the rate of change of the filling rate is, for example, hollow when the filling rate in the used tire exceeds the range of −15% to + 5% with respect to the filling rate before use. This can be done by judging that the performance of the particles has deteriorated.

The determination of the suitability of the hollow particles can be made in consideration of at least one of the determinations based on the average particle diameter and the rate of change of the filling rate, and taking into account the amount of hollow particles broken in the used tire.
In this case, for example, the non-destructive particles and the destructive particles are discriminated by dispersing the hollow particles in the liquid and allowing the broken hollow particles to settle, and the ratio of the destructive particles in the hollow particles having a specific mass. For example, when it reaches 1%, it is judged that the deterioration of the hollow particles is progressing as a whole, and all of the hollow particles are unconditionally regardless of the average particle diameter, the volume change rate, etc. By exchanging, it is possible to effectively eliminate the risk of unexpected inaction of the hollow particles when the tire 1 is punctured.

  The determination of the suitability of the hollow particles can be made by taking into account the change in the color tone of the used hollow particles as well as at least one of the determinations based on the average particle diameter and the change rate of the filling rate. According to this, for example, in the color tone of the hollow particles after use, when the b * value has changed by 3 or more, the hollow particles are unconditionally regardless of the average particle diameter, the volume change rate, etc. By exchanging all of the above, it is possible to effectively eliminate the possibility of unexpected inaction of the hollow particles during puncture or the like.

(Particle size distribution, average particle size)
The hollow particles collected from the tires before and after running are dispersed in n-hexane, and the broken hollow particles are allowed to sink.
The particle size distribution of a predetermined mass (3 g) of each non-destructive hollow particle floating in the hexane was measured with the following apparatus.
Instrument: Sympatec GmbH, Laser diffraction particle size distribution analyzer HELOS & RODOS system Measurement conditions: 2S-100ms / DRY
Dispersion pressure: 2.00 bar, feed: 50.00%, rotation 60.00%, shape factor: 1.00

The measurement results are shown as a graph in FIG.
The phantom lines in FIG. 2 indicate the particle size distribution after the tire internal pressure is once set to atmospheric pressure and the hollow particles exhibit the internal pressure recovery function, and the solid line and the broken line are before and after use, respectively. Shows the particle size distribution.
Each figure is a prototype hollow particle of Matsumoto Yushi Seiyaku Co., Ltd. The representative physical properties are shown in Table 1.

260 g of Prototype 1 was loaded into a 225 / 45R18 size tire mounted on a 7.5-18 wheel, and was run at a speed of 320 km / h for 60 minutes on a drum tester.
The particle size distribution before and after the running is shown by a solid line and a broken line in FIG.
Furthermore, after the running, the tire was mounted on a 3.0-liter class sedan type passenger car (front wheel drive), the internal pressure was removed from the valve core, the valve core was returned, and run flat running was started from 0 kPa. The particle size distribution after the run-flat running is shown by imaginary lines on FIG. This run-flat running was performed by cruising the test course circuit of 4 km per cycle for 30 minutes at a speed of 90 km / h. The mounting wheel is the left front wheel, and the vehicle weight applied to the wheel is 550 kgf.

On the other hand, 145 g of prototype 2 was loaded in a 195 / 65R15 size tire mounted on a 6.0-15 wheel, and mounted on a 1.5-liter class passenger car (front wheel drive) for actual driving. The total travel distance is 16,000 km. The particle size distribution before and after traveling is shown by a solid line and a broken line in FIG.
Further, after the running, the tire was mounted on a passenger car of the same class, and run-flat running was performed as described above. The particle size distribution after the run-flat running is shown by an imaginary line in FIG. At this time, the vehicle weight applied to the wheel is 390 kgf.

  Here, as can be seen from FIG. 2A, the particle size distribution is shifted to the large particle size side by traveling. This is because the hollow particles were slightly expanded by the tire that generated heat under the severe input condition of 320 km / h. On the other hand, according to FIG. 2B, it can be seen that the shift of the particle size distribution hardly occurs when the actual driving level is input, which is the normal use range.

  Moreover, the particle size distribution after the run flat is further shifted to the large particle size side. The large shift seen here indicates that the potential of the hollow particles has been released, and is a level sufficient to determine that it cannot withstand subsequent use.

From the particle size distribution thus determined, the particle size of the peak portion showing the maximum frequency is shown as an average particle size in Table 2 and the figure. When the suitability was judged from the average particle size, the change before and after running in FIG. 2B was less than 10%, whereas in FIG. 2A, a change of 10% or more was observed. Although it was at a level that does not hinder subsequent run-flat running, replacement of hollow particles is desired from the rate of change in particle size. Further, after run flat, an increase in average particle size exceeding 10% was observed in both FIGS. 2 (a) and 2 (b). Therefore, it can be determined that the hollow particles after run-flat are not applicable.

(Volume change rate)
Create a three-pronged jig that can be attached to a tire valve. One of the remaining two halves is a tire valve that can be filled with air and adjusted for internal pressure. The remaining one is led to a volumetric flow meter by a pressure hose or the like via a ball valve that can be opened and closed. After filling the tire with 200 kPa of air at a gauge pressure, the ball valve is opened, and the volume of discharged air is measured by a volume flow meter, whereby the hollow particle volume can be determined.
For example, when the filled air discharged from an empty tire is 60 liters, the internal volume of the tire is 30 liters. Similarly, when hollow particles are enclosed in the tire, the hollow particles are not discharged out of the tire, that is, if only the filled air is discharged and the discharged amount is reduced to 40 liters, the tire is filled. It can be seen that the total volume of the hollow particles was 10 liters.

Equipment: DRY TEST GAS METER DC-2C, manufactured by Shinagawa Co., Ltd.
Measurement conditions: 25 ° C., flow rate of 2 liters / minute or less, and air is used for filling.
Emissions from tire pressure 200 kPa to 0 kPa are measured and converted to hollow particle volume.

Tables 3 and 4 show the measurement results for the respective tires described in Example 1.

  As described above, the volume change of the hollow particles before and after use thus obtained includes an error of change in the tire internal volume accompanying use, but is relatively inexpensive and simple compared to the particle size distribution measurement. It is possible to detect the breakage and expansion of the hollow particles by the apparatus, and the change in the filling rate exceeds the range of −15% to + 5%. The hollow particles after the run flat running are determined to be inapplicable.

(Broken particle amount)
The hollow particles having a specific mass (10 g) collected from the used tire were dispersed in n-hexane, and the mass of the subsidence broken particles was measured. Thereafter, the ratio of the mass of broken particles to the total mass of hollow particles filled before traveling was calculated.
Tables 5 and 6 show the measurement results for the respective tires described in Example 1.

  The accuracy of the determination of suitability can be improved by considering the amount of broken particles after use obtained in this way together with the determination of at least one of the average particle diameter and the volume change rate.

(Color change)
An appropriate amount of hollow particles collected from the used tire was transferred to a transparent bag such as PE and shaped flat, and then a color difference meter was applied from the outside of the bag to quantify the color tone of the hollow particles.

Equipment: CHROMA METER (color difference meter) CR-200 made by MINOLTA

Tables 7 and 8 show the measurement results for the respective tires described in Example 1.

  The change in color tone after use thus obtained can be taken into consideration together with at least one determination of the average particle diameter and the volume change rate, and the accuracy of the suitability determination can be improved.

1 is a cross-sectional view in the width direction illustrating a safety tire that can be an inspection target of the present invention. It is a graph which shows the measurement result of a particle size distribution.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Rim 3 Tire air chamber 4 Hollow particle 5 Bead core 6 Carcass 7 Belt 8 Tread 9 Inner liner layer 11 Side part

Claims (5)

A large number of thermally expandable hollow particles composed of a continuous phase made of resin and closed cells surrounded by a tire chamber defined by the tire and the rim, with the tire mounted on the rim. In safety tires that are sealed under pressure,
Collect the hollow particles in the tire before running or under the same conditions and the hollow particles in the used tire and measure the particle size distribution of each hollow particle in a predetermined amount, In contrast, a method for inspecting hollow particles for safety tires that determines the suitability of hollow particles in a used tire.   The method for checking the hollow particles for a safety tire according to claim 1, wherein the suitability of the hollow particles in the used tire is determined by a change in average particle diameter. A large number of thermally expandable hollow particles composed of a continuous phase made of resin and closed cells surrounded by a tire chamber defined by the tire and the rim, with the tire mounted on the rim. In safety tires that are sealed under pressure,
Obtain the total volume of the hollow particles in the tire before running and the hollow particles in the used tire, and determine the suitability of the hollow particles in the used tire based on the rate of change of the total volume. Inspection method for hollow particles for safety tires.   The inspection method of the hollow particle for safety tires in any one of Claims 1-3 which determine the suitability of a hollow particle also considering the quantity of the hollow particle destroyed in the tire. The inspection method of the hollow particle for safety tires in any one of Claims 1-4 which judge the suitability of a hollow particle also considering the color tone of the hollow particle in the used tire.

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