JP5567295B2 - Puncture sealant - Google Patents

Description

The present invention relates to a puncture sealing agent in which the viscosity of a sealing liquid at a low temperature is improved in a puncture treatment system in which a puncture sealing agent and high-pressure air are sequentially injected into a tire from an air valve of a tire wheel during tire puncture.

As a treatment system for repairing a punctured tire as an emergency, for example, using a pressure vessel containing a puncture sealant and a high-pressure air source such as a compressor, the sealant is injected into the tire via an air valve, and subsequently There has been known one that continuously injects high-pressure air and pumps up the tire to a pressure capable of running (hereinafter sometimes referred to as an integral type) (see FIG. 1 of Japanese Patent Laid-Open No. 2001-199886).

As such a puncture sealing agent, a natural rubber latex described in Patent Documents 1 to 4 is blended with a resin-based adhesive and an antifreezing agent such as propylene glycol. However, since these puncture sealants have a high viscosity at low temperatures, it may be difficult to inject the sealant from the air valve in a very low temperature environment, and further improvement is desired. Here, it is possible to increase the fluidity of the sealing agent by reducing the content of the rubber particles and the tackifying resin, which are solid components, but the puncture sealing performance is deteriorated.

JP 2002-294214 A JP 2001-198986 A JP 2000-272022 A Patent 4074073

The present invention solves the above problems, and provides a tire puncture sealing agent that can reduce the viscosity at low temperature and improve the injectability at low temperature while exhibiting excellent initial seal performance and seal retention performance. Objective.

The present invention relates to a puncture sealant for a tire containing a dephosphorized natural rubber latex having a phosphorus content relative to a rubber solid content of 200 ppm or less and an antifreezing agent.

The dephosphorized natural rubber latex is obtained by saponifying natural rubber latex, and the gel content measured as a toluene insoluble content is preferably 20% by mass or less.

The antifreezing agent is preferably 1,3-propanediol.

The present invention also relates to a tire puncture sealing agent having a phosphorus content relative to rubber solid content of 200 ppm or less.

According to the present invention, since the dephosphorized natural rubber latex having a phosphorus content with respect to the rubber solid content of 200 ppm or less is used, the initial seal performance and the seal retention performance of the puncture sealant are exhibited, and the viscosity at low temperature is reduced. Can improve the injection property at low temperature. For this reason, in the integrated type puncture treatment system, when the puncture sealing agent and air are injected from the valve core, clogging in the valve core can be prevented even at a low temperature.

The tire puncture sealant of the present invention includes a dephosphorized natural rubber latex having a phosphorus content with respect to rubber solid content of 200 ppm or less and an antifreezing agent.

In the present invention, the sealing agent can be smoothly injected into the tire, the sealing agent quickly enters the puncture hole by running, and solidifies and seals the puncture hole by receiving mechanical stimulation due to deformation of the tire (initial sealing performance). From the viewpoint of performance such as that the sealability is maintained up to a certain travel distance (seal retention performance), a sealant mainly composed of dephosphorized natural rubber latex is used.

The phosphorus content relative to the rubber solid content in the dephosphorized natural rubber latex (hereinafter also referred to as saponified natural rubber latex) of the present invention is 200 ppm or less, preferably 100 ppm or less. If it exceeds 200 ppm, the viscosity of the puncture sealant at low temperatures may not be sufficiently reduced. The phosphorus content can be measured by a conventional method such as ICP emission analysis. Phosphorus is derived from phospholipids.

20 mass% or less is preferable and, as for the gel content rate in the natural rubber contained in the dephosphorized natural rubber latex of this invention, 10 mass% or less is more preferable. If it exceeds 20% by mass, the processability tends to decrease, for example, the Mooney viscosity increases. The gel content means a value measured as an insoluble content with respect to toluene which is a nonpolar solvent, and may be simply referred to as “gel content” or “gel content” below. The measuring method of the content rate of a gel part is as follows. First, the natural rubber sample contained in the dephosphorized natural rubber latex is immersed in dehydrated toluene, light-shielded in a dark place and left for 1 week, and then the toluene solution is centrifuged at 1.3 × 10 ⁵ rpm for 30 minutes to insoluble. The gel and toluene-soluble components are separated. Methanol is added to the insoluble gel and solidified, and then dried, and the gel content is determined from the ratio between the mass of the gel and the original mass of the sample.

In the dephosphorized natural rubber latex of the present invention, the nitrogen content relative to the rubber solid content is preferably 0.3% by mass or less, and more preferably 0.15% by mass or less. When the nitrogen content exceeds 0.3% by mass, the viscosity of the puncture sealing agent at low temperature may not be sufficiently lowered. The nitrogen content can be measured by a conventional method such as Kjeldahl method. Nitrogen is derived from protein.

The dephosphorized natural rubber latex of the present invention can be produced, for example, by saponifying a natural rubber latex with an alkali, saponifying, and then concentrating by centrifugation. The saponification treatment is performed by adding an alkali and, if necessary, a surfactant to natural rubber latex and allowing to stand at a predetermined temperature for a predetermined time. In addition, you may perform stirring etc. as needed. According to this method, since the phosphorus compound separated by saponification is washed away, the phosphorus content of natural rubber can be suppressed. Moreover, since the protein in natural rubber is decomposed by the saponification treatment, the nitrogen content of the natural rubber can be suppressed. In the present invention, saponification is performed by adding alkali to natural rubber latex, but there is an effect that saponification treatment can be efficiently performed by adding it to natural rubber latex.

Natural rubber latex is collected as sap of heavy trees and contains rubber, water, proteins, lipids, inorganic salts, etc., and the gel content in rubber is thought to be based on the complex presence of various impurities. . In the present invention, raw latex produced by tapping a heavy tree or purified latex (high ammonia latex or the like) concentrated by a centrifugal separation method or the like is used.

Examples of the alkali used for the saponification treatment include sodium hydroxide, potassium hydroxide, calcium hydroxide, and an amine compound. From the viewpoint of the effect of the saponification treatment and the influence on the stability of the natural rubber latex, it is particularly hydroxylated. Sodium or potassium hydroxide is preferably used.

The amount of alkali added is not particularly limited, but the lower limit is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and the upper limit is 10 parts by mass or less with respect to 100 parts by mass of the solid content of natural rubber latex. Is preferable, and 7 mass parts or less are more preferable. If the amount of alkali added is less than 0.1 parts by mass, saponification may take time. Conversely, if the amount of alkali added exceeds 10 parts by mass, the natural rubber latex may become unstable.

As the surfactant, at least one of an anionic surfactant, a nonionic surfactant and an amphoteric surfactant can be used. Among these, examples of the anionic surfactant include carboxylic acid-based, sulfonic acid-based, sulfate ester-based and phosphate ester-based anionic surfactants. Examples of the nonionic surfactant include nonionic surfactants such as polyoxyalkylene ester, polyoxyalkylene ester, polyhydric alcohol fatty acid ester, glycolipid ester, and alkylpolyglycoside. Examples of the amphoteric surfactant include amphoteric surfactants such as amino acid type, betaine type, and amine oxide type.

The addition amount of the surfactant is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the solid content of the natural rubber latex, the lower limit is 0.1 parts by mass, and the upper limit is 3.5 parts by mass. More preferred. If the addition amount is less than 0.01 parts by mass, the natural rubber latex may become unstable during the saponification treatment. On the other hand, if the amount added exceeds 5 parts by mass, the natural rubber latex may become too stable and coagulation may become difficult.

The temperature of the saponification treatment can be appropriately set within the range where the saponification reaction with alkali can proceed at a sufficient reaction rate and the natural rubber latex does not cause alteration such as coagulation, but is usually 20 to 70 ° C. Preferably there is. Further, the treatment time is 3 to 48 hours in consideration of both sufficient treatment and productivity improvement, depending on the treatment temperature when the treatment is performed with natural rubber latex standing. Is preferred.

After completion of the saponification reaction, washing is performed as necessary to remove excess alkali. Moreover, as a washing | cleaning method, the rubber part is diluted with water, for example, after washing | cleaning, the method of taking out a rubber part by performing a centrifugation process is mentioned. When centrifuging, it is first diluted with water so that the rubber content of the natural rubber latex is 5 to 40% by mass, preferably 10 to 30% by mass. Then, it may be centrifuged at 5000 to 10,000 rpm for 1 to 60 minutes.

After washing, if necessary, a surfactant and water as an emulsifier are added, and the proportion of rubber solids in the latex is adjusted to about 60% by mass to obtain a dephosphorized natural rubber latex. The obtained dephosphorized natural rubber latex is obtained by emulsifying and dispersing rubber solids in an aqueous medium containing a small amount of a surfactant as an emulsifier.

In addition, if necessary, natural rubber latex other than dephosphorized natural rubber latex (saponified natural rubber latex), butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, ethylene-acetic acid. Synthetic rubber latex such as vinyl rubber, chloroprene rubber, vinyl pyridine rubber and butyl rubber may be blended.

From the viewpoint of initial seal performance and seal retention performance, the blending amount A of the dephosphorized natural rubber latex (rubber solid content) with respect to 100% by mass of the total mass of the puncture sealant is preferably in the range of 15 to 40% by mass. The lower limit of the amount A is more preferably 35% by mass or more, and the upper limit is more preferably 18% by mass or less.

In the present invention, since the dephosphorized natural rubber latex having a phosphorus content with respect to the rubber solid content of 200 ppm or less is used, the viscosity of the sealing agent at a low temperature can be reduced, and the injectability at a low temperature can be improved. For this reason, the operating temperature range of the sealing agent can be expanded to the low temperature side, and clogging in the valve core can be prevented when the sealing agent and air are injected from the valve core even at a low temperature in the integral type puncture treatment system. This is presumably because the stability of the colloid (latex) in the sealing agent is increased by using the dephosphorized natural rubber latex.

The puncture sealing agent of the present invention preferably contains a tackifier. The tackifier is used to improve the adhesion between the dephosphorized natural rubber latex and the tire and improve the puncture sealing performance. For example, the tackifier resin is finely divided in an aqueous medium containing a small amount of an emulsifier. An emulsified and dispersed tackifying resin emulsion (oil-in-water emulsion) is used. As the tackifier resin which is a solid content of the tackifier resin emulsion (tackifier), those which do not coagulate the rubber latex, for example, terpene resins, phenol resins and rosin resins can be preferably used. Other preferred resins include polyvinyl ester, polyvinyl alcohol, and polyvinyl pyrrolidine.

As for the compounding quantity B of tackifying resin (solid content of a tackifier), 2-20 mass% is preferable in 100 mass% of total mass of a puncture sealing agent. The lower limit of the amount B is more preferably 3% by mass or more, and the upper limit is more preferably 15% by mass or less.

In addition, when the compounding amount A of the rubber solid content is less than 15% by mass and the compounding amount B of the tackifying resin is less than 2% by mass, the puncture sealing performance and the seal holding performance may be insufficient. On the contrary, if the blending amounts A and B exceed 40% by mass and 20% by mass, respectively, the storage performance is impaired such as rubber particles are likely to be aggregated during storage, and the viscosity increases and the air valve of the puncture sealing agent increases. May make it difficult to inject. Therefore, it is preferable that the sum of the blending amounts A and B (A + B (solid content)) is in the range of 20 to 50% by mass with respect to 100% by mass of the total mass of the puncture sealing agent. The lower limit of the blending amount A + B (solid content) is more preferably 25% by mass or more, and the upper limit is more preferably 45% by mass or less.

As the emulsifier for the rubber latex and the emulsifier for the tackifying resin emulsion, for example, a surfactant such as an anionic surfactant, a nonionic surfactant, and a cationic surfactant can be preferably used. The total amount of the emulsifier is about 0.4 to 2.0% by mass with respect to 100% by mass of the total mass of the puncture sealing agent.

The antifreezing agent used in the present invention is not particularly limited, and ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol and the like can be used. When ethylene glycol is used as an antifreeze, the stability of rubber particles may deteriorate and may aggregate, but when propylene glycol or 1,3-propanediol is used as an antifreeze, it may be stored for a long time. Even so, rubber particles and pressure-sensitive adhesive particles can be prevented from aggregating near the surface and transforming into a cream-like substance, and excellent storage performance (storage stability) can be exhibited. Preference is given to using 3-propanediol. Furthermore, when propylene glycol is used as an antifreeze, the viscosity may increase at low temperatures, but when 1,3-propanediol is used as the antifreeze, an increase in viscosity at low temperatures can be suppressed. It is more preferable to use 1,3-propanediol because the injection property of the sealing agent at a low temperature can be improved. When 1,3-propanediol is used, the operating temperature range of the sealing agent can be expanded to the low temperature side. In an integrated type puncture treatment system, when the sealing agent and air are injected from the valve core even at low temperatures, the valve core is clogged. Can be prevented. This is because in 1,3-propanediol, the hydroxyl group (—OH) is bonded to positions 1 and 3 of the carbon atom, but “1,3-” is more bipolar than “1,2-”. Since the child moment is reduced, it is assumed that the hydrogen bonding force is reduced and the viscosity can be reduced.

As explained above, the use of 1,3-propanediol can achieve both storage stability and low temperature characteristics in a well-balanced manner. Such an effect is obtained when 1,3-propanediol is used, and when other compounds such as butadiol are used as an antifreeze agent, the viscosity increases. I can't expect it.

Further, by using 1,3-propanediol, a good antifreezing effect can be obtained. Furthermore, the amount used can be minimized, and adverse effects on various performances such as puncture sealing performance by the antifreezing agent can be prevented.

The blending amount C of the antifreeze agent with respect to 100% by mass of the total mass of the puncture sealing agent is preferably 20 to 64% by mass. If the blending amount C is less than 20% by mass, the increase in viscosity at a low temperature increases, and conversely if it exceeds 64% by mass, the solid content in the sealing agent decreases and the puncture sealing property may be deteriorated. The lower limit of the amount C is more preferably 25% by mass or more, and the upper limit is more preferably 40% by mass or less.

The puncture sealing agent of the present invention preferably contains a nonionic surfactant. In a puncture sealing agent in which propylene glycol or 1,3-propanediol is blended with natural rubber latex and tackifier, clogging may occur during use at high temperatures. This clogging at high temperature is caused by high pressure air injection following sealing agent injection, and the sealing agent adhering to the inner wall of the bottle or hose comes into contact with warm air and becomes dry and rubberized to narrow parts of the flow path (valve core, valve This is caused by clogging of the flow path. In the present invention, by adding a nonionic surfactant, the injection property at high temperature can be improved and clogging at high temperature can be prevented. This is because the non-ionic surfactant is adsorbed on the natural rubber particles dispersed by the ionic repulsion of the anionic surfactant, so that the interparticle potential energy in the vicinity of the particles can be increased, thus improving the thermal stability. Inferred. Such an effect is exhibited when a nonionic surfactant is used, and when a cationic surfactant or an anionic surfactant is added, thickening of the sealing agent is observed.

Further, by using a nonionic surfactant, excellent initial seal performance, seal retention performance, and storage stability can be obtained.

The polyoxyalkylene alkyl ether and the polyoxyalkylene alkenyl ether preferably have an ethylene oxide structure and / or a propylene oxide structure. Those having an ethylene oxide structure and / or a propylene oxide structure as the hydrophilic group can enhance the compatibility with propylene glycol. Especially, what has an ethylene oxide structure is preferable. Moreover, when it has an ethylene oxide structure and / or a propylene oxide structure, the average addition mole number of ethylene oxide (EO) and propylene oxide (PO) (total of the average addition mole number of EO and PO) may be 10 or more. Preferably, it is 13 or more. The average added mole number is preferably 60 or less, more preferably 40 or less. In this case, the compatibility is enhanced and the high temperature injection property can be improved.

The carbon number of the alkyl group in the polyoxyalkylene alkyl ether and the carbon number of the alkenyl group in the polyoxyalkylene alkenyl ether are preferably 10 or more, preferably 12 or more, and more preferably 15 or more. preferable. The carbon number is preferably 20 or less, more preferably 18 or less. In this case, the high temperature injection property can be effectively improved.

Examples of the polyoxyalkylene alkyl ether and the polyoxyalkylene alkenyl ether include compounds represented by the following formula (1). The use of the compound improves the high temperature injectability and also provides excellent initial seal performance, seal retention performance, and storage stability.
R ¹ —O— (AO) _n —H (1)
(In the formula (1), R ¹ represents an alkyl group having 4 to 24 carbon atoms or an alkenyl group having 4 to 24 carbon atoms. The average added mole number n represents 1 to 80. AO may be the same or different and the number of carbon atoms. Represents 2 to 4 oxyalkylene groups.)

R ¹ preferably has 8 or more carbon atoms, more preferably 10 or more, still more preferably 12 or more, and most preferably 15 or more. The number of carbon atoms in R ¹ is preferably 22 or less, more preferably 20 or less, and still more preferably 18 or less.

n is preferably 10 or more, more preferably 13 or more. N is preferably 60 or less, more preferably 50 or less, and still more preferably 40 or less.

AO is preferably an oxyalkylene group having 2 to 3 carbon atoms (oxyethylene group (EO), oxypropylene group (PO)). (AO) When _n contains two or more oxyalkylene groups, the arrangement of the oxyalkylene groups may be block or random. When R ¹ and n are in the above ranges, or when AO is EO and PO, the above effects are exhibited well.

As the polyoxyalkylene alkyl ether and polyoxyalkylene alkenyl ether, a compound represented by the following formula (2) is preferably used.
R ² —O— (EO) _x (PO) _y —H (2)
(In Formula (2), R ² represents an alkyl group having 8 to 22 carbon atoms or an alkenyl group having 8 to 22 carbon atoms. EO represents an oxyethylene group, PO represents an oxypropylene group. The average added mole number x is 1-60, the average added mole number y is 0-20.)

The preferable numerical range of the carbon number of R ² is the same as that of R ¹ described above. R ² may be linear or branched, but is preferably a linear alkyl group or alkenyl group. x is preferably 10 or more, more preferably 13 or more. X is preferably 50 or less, more preferably 40 or less. y is preferably 10 or less, more preferably 4.5 or less, and still more preferably 2.0 or less. Moreover, y may be 0. When R ² , x, and y are in the above ranges, the above effects are exhibited well.

The arrangement of EO and PO may be block or random. When the arrangement of EO and PO is a block, the number of EO blocks and the number of PO blocks may each be one or more as long as the average added mole number is within the above range. When the number of EO blocks is two or more, the number of EO repetitions in each block may be the same or different. When the number of PO blocks is two or more, the number of PO repetitions in each block may be the same or different. When the arrangement of EO and PO is random, EO and PO may be arranged alternately or randomly as long as each average added mole number is within the above range.

As the nonionic surfactant in the present invention, polyoxyethylene alkyl ether and polyoxyethylene alkenyl ether (for example, a compound of y = 0 in the formula (2)) are preferably used from the viewpoint of high temperature injectability. In this case, preferable average added mole number of EO, alkyl group, and alkenyl group are the same as described above.

As polyoxyalkylene alkyl ether and polyoxyalkylene alkenyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene cetyl ether, polyoxyethylene myristyl ether, polyoxyethylene lauryl ether, polyoxyethylene polyoxypropylene Examples include stearyl ether, polyoxyethylene polyoxypropylene oleyl ether, polyoxyethylene polyoxypropylene cetyl ether, polyoxyethylene polyoxypropylene myristyl ether, and polyoxyethylene polyoxypropylene lauryl ether. Of these, polyoxyethylene stearyl ether and polyoxyethylene oleyl ether are preferred from the viewpoint of high temperature injection.

The HLB value (calculated by the Griffin method) of a nonionic surfactant such as polyoxyalkylene alkyl ether and polyoxyalkylene alkenyl ether is preferably 12 or more, more preferably 13 or more. The HLB value is preferably 19 or less, more preferably 17 or less. In this case, the compatibility is enhanced and the stability at high temperature is improved, so that the storage performance and the high temperature injection property are improved, and excellent puncture sealing performance, seal holding performance, and low temperature characteristics are also obtained.

Commercially available nonionic surfactants include Emulgen 320P (formula (2): R ² = stearyl group, x = 13, y = 0), Emulgen 420 (formula (2): R ² = oleyl group, x = 20, y = 0), Emulgen 430 (Formula (2): R ² = oleyl group, x = 30, y = 0), Emulgen 150 (Formula (2): R ² = Lauryl group, x = 40, y = 0), Emulgen 109P (Formula (2): R ² = Lauryl group, x = 9, y = 0), Emulgen 120 (Formula (2): R ² = Lauryl group, x = 12, y = 0), Emulgen 220 (formula (2): R ² = cetyl group, x = 12, y = 0) and the like (all are manufactured by Kao Corporation).

As for the compounding quantity D of nonionic surfactant with respect to 100 mass% of total mass of a puncture sealing agent, 1-12 mass% is preferable. If the blending amount D is less than 1% by mass, the effect of preventing clogging at high temperatures may be insufficient. On the other hand, if it exceeds 12% by mass, the sealing property becomes insufficient and the viscosity at room temperature may increase. The lower limit of the amount D is more preferably 1.5% by mass or more, and the upper limit is more preferably 10% by mass or less.

The blending amount D ′ of the nonionic surfactant with respect to 100% by mass of the surfactant contained in the puncture sealing agent is preferably 30% by mass or more, more preferably 40% by mass or more. Thereby, high temperature injection | pouring property can be improved effectively.

In addition, ensuring a good balance between the freezing temperature and the effect of suppressing the increase in viscosity at low temperatures, extending the operating temperature range to the low temperature side, increasing high-temperature injection properties, and ensuring the stability of the sealing agent Therefore, the sum (C + D) of the blending amounts C and D is preferably 34 to 65% by mass. The lower limit of the amount C + D is more preferably 36% by mass or more, and the upper limit is more preferably 62% by mass or less.

The puncture sealing agent of the present invention may further contain other components as long as the effects of the present invention are not impaired.
The puncture sealant of the present invention is produced by a general method. That is, it can be produced by mixing each of the above components by a known method.

The phosphorus content relative to the rubber solid content in the puncture sealing agent of the present invention is 200 ppm or less, preferably 100 ppm or less. If it exceeds 200 ppm, the viscosity of the puncture sealant at low temperatures may not be sufficiently reduced.

20 mass% or less is preferable and, as for the gel content rate in the rubber solid content in the puncture sealing agent of this invention, 10 mass% or less is more preferable. If it exceeds 20% by mass, the processability tends to decrease, for example, the Mooney viscosity increases.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Production Example 1
(Preparation of saponified natural rubber latex (dephosphorized natural rubber latex))
After adjusting the field latex obtained from the farm to a solid content concentration (DRC) of 30% (w / v), 10 g of Emal-E (manufactured by Kao Corporation) and NaOH (manufactured by Wako Pure Chemical Industries) are used for 1000 g of natural rubber latex. ) 10g was added and saponification reaction was performed at 70 degreeC for 24 hours. Water was added to the obtained latex to dilute to DRC 15% (w / v), and then formic acid was added with slow stirring to adjust the pH to 4.0 to 4.5 to cause aggregation. The agglomerated rubber was pulverized and washed repeatedly with 1000 ml of water. Next, the washed latex was concentrated by centrifugation and adjusted to DRC 60% (w / v) to obtain a saponified natural rubber latex (dephosphorized natural rubber latex).

Production Example 2
(Preparation of saponified natural rubber latex (dephosphorized natural rubber latex))
After adjusting the field latex obtained from the farm to a solid content concentration (DRC) of 30% (w / v), 10 g of Emal-E (manufactured by Kao Corporation) and NaOH (manufactured by Wako Pure Chemical Industries) are used for 1000 g of natural rubber latex. ) 20g was added and saponification reaction was performed at 70 degreeC for 48 hours. Water was added to the obtained latex to dilute to DRC 15% (w / v), and then formic acid was added with slow stirring to adjust the pH to 4.0 to 4.5 to cause aggregation. The agglomerated rubber was pulverized and washed repeatedly with 1000 ml of water. Next, the washed latex was concentrated by centrifugation and adjusted to DRC 60% (w / v) to obtain a saponified natural rubber latex (dephosphorized natural rubber latex).

Production Example 3
(Preparation of saponified natural rubber latex (dephosphorized natural rubber latex))
After adjusting the field latex obtained from the farm to a solid content concentration (DRC) of 30% (w / v), 10 g of Emal-E (manufactured by Kao Corporation) and NaOH (manufactured by Wako Pure Chemical Industries) are used for 1000 g of natural rubber latex. ) 10g was added and saponification reaction was performed at room temperature for 24 hours. Water was added to the obtained latex to dilute to DRC 15% (w / v), and then formic acid was added with slow stirring to adjust the pH to 4.0 to 4.5 to cause aggregation. The agglomerated rubber was pulverized and washed repeatedly with 1000 ml of water. Next, the washed latex was concentrated by centrifugation and adjusted to DRC 60% (w / v) to obtain a saponified natural rubber latex (dephosphorized natural rubber latex).

Each natural rubber latex of Production Examples 1 to 3 and a commercially available natural rubber latex (HA-type natural rubber latex from Malaysia) were dried at 110 ° C. for 120 minutes to obtain a solid rubber. The phosphorus content of each solid rubber obtained was measured by the method shown below.
-Measurement of phosphorus content The phosphorus content of raw rubber was determined using an ICP emission spectrometer (ICPS-8100, manufactured by Shimadzu Corporation).
The phosphorus content of each natural rubber latex of Production Examples 1 to 3 and commercially available natural rubber latex was 98 ppm, 64 ppm, 120 ppm, and 560 ppm, respectively, with respect to the rubber solid content.

Examples and Comparative Examples Using the natural rubber latex of Production Examples 1 to 3 and a commercially available natural rubber latex, a puncture sealant was prototyped based on the specifications in Table 1.

In addition, the following were used for the tackifier and surfactant.
Tackifier: terpene resin emulsion (solid content: about 50% by mass)
Emulgen 320P: polyoxyethylene stearyl ether (formula (2), R ² = stearyl group, x = 13, y = 0, HLB value = 13.9, manufactured by Kao Corporation)
Emulgen 430: polyoxyethylene oleyl ether (formula (2), R ² = oleyl group, x = 30, y = 0, HLB value = 16.2, manufactured by Kao Corporation)

About each obtained puncture sealing agent, low temperature characteristic (viscosity at -30 degreeC), puncture seal performance, seal retention performance, storage performance (storage stability), high temperature pouring property, and gel content rate are evaluated by the following methods. The results are shown in Table 1.

(1) Low temperature characteristics (viscosity at −30 ° C.):
Using a B-type viscometer (Brookfield viscometer), the viscosity of the puncture sealant at −30 ° C. was measured.

(2) Punk seal performance:
A tire having a tire size of 185 / 65R14 was drilled with a nail having a diameter of 4.0 mm, and after removing the nail, 500 ml of a puncture sealing agent was injected, and the air was pressurized to 200 kpa. Thereafter, the drum was rotated at a load (3.5 kN) on the drum, the time until the puncture hole was sealed was judged by the amount of air leakage, and the index evaluation was performed in five stages, where the conventional product was 3. The higher the value, the better.

(3) Seal retention performance:
The tire was used to measure whether or not there was an air leak from a puncture hole before traveling 100 km after being sealed, and was evaluated in two stages: no air leak ... ○, air leak ... ×.

(4) Storage performance (storage stability):
500ml of puncture sealant is stored in a bottle-shaped container, and the amount of cream-like substance produced after standing still in an oven at 80 ° C for 2 months is measured, and the mass ratio to the whole puncture sealant (%).

(5) High temperature injection property:
Puncture sealant was injected using an integrated type puncture treatment system in an atmosphere of 50 ° C., and it was judged whether the tire pressure increased to a predetermined pressure. Evaluation was made in two stages: things ... x.
(6) Gel content in rubber solids:
The puncture sealant was dried at 110 ° C. for 120 minutes to obtain a solid rubber. 70.00 mg of a sample obtained by cutting each solid rubber obtained into 1 mm × 1 mm was weighed, 35 mL of toluene was added thereto, and the mixture was allowed to stand in a cool dark place for 1 week. Subsequently, centrifugation was performed to precipitate a gel component insoluble in toluene, the soluble component of the supernatant was removed, and only the gel component was solidified with methanol, and then dried and the mass was measured. The gel content (%) was determined by the following formula.
Gel content (mass%) = [mass mg after drying / mg of initial sample] × 100

As shown in Tables 1 and 2, the sealants of the examples using saponified natural rubber latex (dephosphorized natural rubber latex) greatly increase the viscosity at low temperatures while ensuring puncture seal performance, seal retention performance, and storage performance. It was able to drop to. Therefore, the integrated type can be suitably used in a low temperature range. On the other hand, in the comparative example using a commercially available natural rubber latex, the viscosity at low temperature was inferior.

Claims (5)

A tire puncture sealing agent comprising a dephosphorized natural rubber latex having a phosphorus content with respect to a rubber solid content of 200 ppm or less and an antifreezing agent ,
A tire puncture sealing agent in which the blending amount of the dephosphorized natural rubber latex (rubber solids) is 15 to 40% by mass and the antifreezing agent is 20 to 64% by mass with respect to 100% by mass of the puncture sealing agent . 2. The tire puncture sealing according to claim 1, wherein the dephosphorized natural rubber latex is obtained by saponifying natural rubber latex, and the gel content measured as a toluene insoluble content is 20% by mass or less. Agent. The tire puncture sealing agent according to claim 1 or 2, wherein the antifreezing agent is 1,3-propanediol. The puncture sealing agent for a tire according to any one of claims 1 to 3, comprising a nonionic surfactant. The tire puncture sealant according to claim 4, wherein the nonionic surfactant has an ethylene oxide structure and / or a propion oxide structure.