Patent Description:
Known systems for temporarily repairing a punctured tire include, for example, a system in which a pressure-proof container containing a puncture sealant and a high pressure air source such as a compressor are used to inject the sealant into a tire through the air valve, followed by continuously injecting high-pressure air until the tire is pumped up to a sufficient pressure for driving (hereinafter also referred to as the integrated system) (see, for example, Fig. <NUM> of <CIT>).

In general, a puncture sealant is provided inside a car or in the trunk room or the like and is used only when a puncture occurs. Thus, it is necessary to reduce deterioration of the puncture sealant until use. However, it is known that when a puncture sealant based on synthetic rubber is stored for a long time, the synthetic rubber undergoes gelation, resulting in a deterioration in puncture repair performance. The gelation of the synthetic rubber has been reduced by adding an antioxidant such as a monophenolic antioxidant (see Patent Literature <NUM>).

<CIT> describes a tire puncture sealant containing a natural rubber latex (A) and a VEVA copolymer resin emulsion (B), wherein the solid content mass of the natural rubber latex (A)/solid content mass of the VEVA copolymer resin emulsion (B) is between <NUM>/<NUM> and <NUM>/<NUM>.

Patent Literature <NUM> discloses only a puncture sealant based on synthetic rubber and does not examine any puncture sealant based on natural rubber. We therefore conducted studies on deterioration of a puncture sealant based on natural rubber latex and found that the puncture sealant causes the following problem that is different from that with synthetic rubber: when the puncture sealant is stored in a resin bottle for a long time, the oxygen permeated through the resin bottle degrades the natural rubber so that it has a reduced molecular weight and may not solidify during puncture repairing, resulting in difficulty in sufficient repairing and thus a reduction in puncture seal durability (the ability of the long-term stored puncture sealant to reduce a decrease in tire pressure after puncture repairing).

Natural rubber proteins, which, for example, can act as allergens, are usually not considered as favorable components. Thus, a person skilled in the art generally tends to decompose the proteins, e.g., by adding a proteolytic enzyme. However, the present inventors have focused on the fact that the proteins in a puncture sealant based on natural rubber latex can act to protect dispersion and improve adhesive strength. Thus, we have changed the mindset and have conceived the idea that the performance can be enhanced by intentionally protecting the proteins. Then, we have found that by adding a protease inhibitor or phosphatase inhibitor to the puncture sealant to protect the proteins, it is possible to reduce age deterioration of the puncture sealant and prevent a reduction in puncture seal durability. This finding has led to the completion of the present disclosure.

The present disclosure aims to solve the above problem and provide a tire puncture sealant having excellent puncture seal durability.

The present disclosure relates to a puncture sealant, containing:.

The puncture sealant of the present disclosure contains at least one natural rubber latex, at least one antioxidant, at least one antifreezing agent, and at least one selected from the group consisting of protease inhibitors and phosphatase inhibitors and thus has excellent puncture seal durability.

The puncture sealant of the present disclosure contains at least one natural rubber latex, at least one antioxidant, at least one antifreezing agent, and at least one selected from the group consisting of protease inhibitors and phosphatase inhibitors. Since deterioration of the puncture sealant, even when stored for a long time, is reduced, even the stored puncture sealant can provide good puncture repairing. Thus, even the long-term stored puncture sealant can prevent a decrease in tire pressure after puncture repairing, resulting in excellent puncture seal durability.

The present disclosure uses a puncture sealant containing one or more natural rubber latexes as main components to provide the following properties: for example, the sealant can be smoothly injected into a tire; the sealant can rapidly fill a puncture hole during driving and then can solidify in response to the mechanical stimuli due to the deformation of the tire to seal the puncture hole (initial sealing performance); and the sealant can maintain the sealing performance during driving a certain distance (seal retention performance).

The natural rubber latexes may further be blended with synthetic rubber latexes such as polybutadiene rubbers, styrene-butadiene rubbers, acrylonitrile-butadiene rubbers, ethylene-vinyl acetate rubbers, chloroprene rubbers, vinylpyridine rubbers, and butyl rubbers, as needed.

The term "rubber latex" refers to one in which fine particles of rubber solids are emulsified and dispersed in an aqueous medium containing a small amount of a surfactant as an emulsifier. The rubber latex to be used is usually adjusted to have a rubber solid content of approximately <NUM>% by mass.

From the standpoints of initial sealing performance and seal retention performance, the amount of the natural rubber latexes (in terms of rubber solids) is in the range of <NUM> to <NUM>% by mass based on <NUM>% by mass of the total puncture sealant. The lower limit of the amount is more preferably <NUM>% by mass or more, still more preferably <NUM>% by mass, while the upper limit is more preferably <NUM>% by mass or less, still more preferably <NUM>% by mass or less. With an amount not lower than the lower limit, good puncture sealing performance and seal retention performance tend to be obtained. Conversely, with an amount not higher than the upper limit, good storability, such as reduced agglomeration of rubber particles during storage, tends to be obtained, and an increase in viscosity tends to be reduced to ensure injectability of the puncture sealant through the air valve.

The puncture sealant contains at least one antioxidant. This tends to provide a good sealing effect in puncture repairing after long-term storage.

The antioxidant may be any antioxidant, including those which may be used to prevent deterioration of crosslinked rubbers. Suitable examples include phenolic antioxidants (e.g., monophenolic antioxidants, bisphenolic antioxidants, and polyphenolic antioxidants) and amine antioxidants. Phenolic antioxidants are preferred among these, with polyphenolic antioxidants being more preferred. These antioxidants may be used alone or in combinations.

Examples of the monophenolic antioxidants include styrenated phenol, <NUM>,<NUM>-di-tert-butyl-<NUM>-methylphenol, <NUM>-tert-butyl-<NUM>,<NUM>-dimethylphenol, <NUM>,<NUM>-di-tert-butyl-<NUM>-ethylphenol, <NUM>,<NUM>-di-tert-butyl-<NUM>-n-butylphenol, <NUM>,<NUM>-di-tert-butyl-<NUM>-isobutylphenol, <NUM>,<NUM>-dicyclopentyl-<NUM>-methylphenol, <NUM>-(α-methylcyclohexyl)-<NUM>,<NUM>-dimethylphenol, <NUM>,<NUM>-dioctadecyl-<NUM>-methylphenol, <NUM>,<NUM>,<NUM>-tricyclohexylphenol, <NUM>,<NUM>-di-tert-butyl-<NUM>-methoxymethylphenol, branched nonylphenols (e.g., <NUM>,<NUM>-di-nonyl-<NUM>-methylphenol), <NUM>,<NUM>-dimethyl-<NUM>-(<NUM>'-methylundec-<NUM>'-yl)phenol, <NUM>,<NUM>-dimethyl-<NUM>-(<NUM>'-methylheptadec-<NUM>'-yl)phenol, and <NUM>,<NUM>-dimethyl-<NUM>-(<NUM>'-methyltridec-<NUM>'-yl)phenol.

Examples of the bisphenolic antioxidants include <NUM>,<NUM>'-methylenebis(<NUM>-tert-butyl-<NUM>-methylphenol), <NUM>,<NUM>'-methylenebis(<NUM>-tert-butyl-<NUM>-ethylphenol), <NUM>,<NUM>'-methylenebis[<NUM>-methyl-<NUM>-(α-methylcyclohexyl)phenol], <NUM>,<NUM>'-methylenebis(<NUM>-methyl-<NUM>-cyclohexylphenol), <NUM>,<NUM>'-methylenebis(<NUM>-nonyl-<NUM>-methylphenol), <NUM>,<NUM>'-methylenebis(<NUM>,<NUM>-di-tert-butylphenol), <NUM>,<NUM>'-ethylidenebis(<NUM>,<NUM>-di-tert-butylphenol), <NUM>,<NUM>'-ethylidenebis(<NUM>-tert-butyl-<NUM>-isobutylphenol), <NUM>,<NUM>'-methylenebis[<NUM>-(α-methylbenzyl)-<NUM>-nonylphenol], <NUM>,<NUM>'-methylenebis[<NUM>-(α,α-dimethylbenzyl)-<NUM>-nonylphenol], <NUM>,<NUM>'-methylenebis(<NUM>,<NUM>-di-tert-butylphenol), <NUM>,<NUM>'-methylenebis(<NUM>-tert-butyl-<NUM>-methylphenol), <NUM>,<NUM>-bis(<NUM>-tert-butyl-<NUM>-hydroxy-<NUM>-methylphenyl)butane, <NUM>,<NUM>-bis(<NUM>-tert-butyl-<NUM>-methyl-<NUM>-hydroxybenzyl)-<NUM>-methylphenol, <NUM>,<NUM>,<NUM>-tris(<NUM>-tert-butyl-<NUM>-hydroxy-<NUM>-methylphenyl)butane, <NUM>,<NUM>-bis(<NUM>-tert-butyl-<NUM>-hydroxy-<NUM>-methylphenyl)-<NUM>-n-dodecylmercaptobutane, ethylene glycol bis[<NUM>,<NUM>-bis(<NUM>'-tert-butyl-<NUM>'-hydroxyphenyl)butyrate], bis(<NUM>-tert-butyl-<NUM>-hydroxy-<NUM>-methylphenyl)dicyclopentadiene, bis[<NUM>-(<NUM>'-tert-butyl-<NUM>'-hydroxy-<NUM>'-methylbenzyl)-<NUM>-tert-butyl-<NUM>-methylphenyl]terephthalate, <NUM>,<NUM>-bis(<NUM>,<NUM>-dimethyl-<NUM>-hydroxyphenyl)butane, <NUM>,<NUM>-bis(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl)propane, <NUM>,<NUM>-bis(<NUM>-tert-butyl-<NUM>-hydroxy-<NUM>-methylphenyl)-<NUM>-n-dodecylmercaptobutane, and <NUM>,<NUM>,<NUM>,<NUM>-tetrakis(<NUM>-tert-butyl-<NUM>-hydroxy-<NUM>-methylphenyl)pentane.

Examples of the polyphenolic antioxidants include <NUM>,<NUM>-di-t-butylhydroquinone, tetrakis[methylene-<NUM>-(<NUM>',<NUM>'-dit-butyl-<NUM>'-hydroxyphenyl)propionate]methane, and flavonoids (e.g., catechin, anthocyanin, flavone glycosides, isoflavone glycosides, flavan glycosides, flavanone, and rutin glycosides).

Examples of the amine antioxidants include amides of β-(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl)propionic acid, such as N,N'-bis(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl propionyl)hexamethylenediamine, N,N'-bis(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl propionyl)trimethylenediamine, N,N'-bis(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl propionyl)hydrazine, N,N'-bis[<NUM>-(<NUM>-[<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl]propionyloxy)ethyl]oxamide, and <NUM>,<NUM>'-bis(α,α-dimethylbenzyl)diphenylamine.

The amount of the antioxidants is not limited, but it is preferably <NUM> to <NUM> parts by mass per <NUM> parts by mass of the solids in the natural rubber latexes. The lower limit of the amount is more preferably <NUM> parts by mass or more, still more preferably <NUM> parts by mass or more, while the upper limit is more preferably <NUM> parts by mass or less, still more preferably <NUM> part by mass or less. With an amount not lower than the lower limit, a decrease in the molecular weight of the natural rubbers tends to be reduced so that good puncture sealing performance can be maintained. With an amount not higher than the upper limit, an economic advantage tends to be obtained.

The amount of the antioxidants based on <NUM>% by mass of the total puncture sealant is <NUM> to <NUM>% by mass. The lower limit of the amount is more preferably <NUM>% by mass or more, still more preferably <NUM>% by mass or more, while the upper limit is more preferably <NUM>% by mass or less, still more preferably <NUM>% by mass or less. With an amount not lower than the lower limit, a decrease in the molecular weight of the natural rubbers tends to be reduced so that good puncture sealing performance can be maintained. With an amount not higher than the upper limit, an economic advantage tends to be obtained.

The antioxidants are preferably dispersed in the natural rubber latexes. The antioxidants can be dispersed in any way and may be dispersed in water using a surfactant and then in the natural rubber latexes.

The present disclosure may use any antifreezing agent and examples include ethylene glycol, propylene glycol (<NUM>,<NUM>-propanediol), and <NUM>,<NUM>-propanediol. These may be used alone or in combinations.

The use of ethylene glycol may deteriorate the stability of rubber particles and cause their agglomeration. On the other hand, the use of propylene glycol or <NUM>,<NUM>-propanediol can inhibit the rubber particles and tackifier particles from agglomerating around the surface and changing into a creamy substance, even after long-term storage. Thus, excellent storability (storage stability) can be provided. Moreover, the use of propylene glycol may cause an increase in viscosity at low temperatures, whereas the use of <NUM>,<NUM>-propanediol can reduce an increase in viscosity at low temperatures, thus improving injectability at low temperatures. The use of <NUM>,<NUM>-propanediol can increase the operating temperature range of the sealant to a lower temperature. Thus, clogging of the valve core can be prevented during the injection of the sealant and air through the valve core in an integrated puncture repair system, even at low temperatures.

The amount of the antifreezing agents based on <NUM>% by mass of the total puncture sealant is <NUM> to <NUM>% by mass. With an amount not lower than the lower limit, an increase in viscosity at low temperatures tends to be reduced, while with an amount not higher than the upper limit, good puncture sealing performance tends to be obtained. The lower limit of the amount is more preferably <NUM>% by mass or more, while the upper limit is more preferably <NUM>% by mass or less.

The amount of the antifreezing agents based on <NUM>% by mass of the liquid components of the puncture sealant is preferably <NUM> to <NUM>% by mass. With an amount not lower than the lower limit, an increase in viscosity at low temperatures tends to be reduced, while with an amount not higher than the upper limit, good injectability tends to be obtained. The lower limit of the amount is more preferably <NUM>% by mass or more, still more preferably <NUM>% by mass or more, while the upper limit is more preferably <NUM>% by mass or less. The liquid components herein refer to water and antifreezing agents. Thus, the amount means the amount calculated from the equation: (mass of antifreezing agents)/(combined mass of water and antifreezing agents) × <NUM> (% by mass).

The puncture sealant contains at least one selected from the group consisting of protease inhibitors and phosphatase inhibitors. This can reduce deterioration of natural rubber proteins and provide a good sealing effect in puncture repairing, even after long-term storage.

The protease inhibitors may be any one having a protease inhibitory effect, and examples include serine protease inhibitors, cysteine protease inhibitors, and metal protease inhibitors. These protease inhibitors may be used alone or in admixture of two or more. Preferred among these are metal protease inhibitors.

The serine protease inhibitors may be any one having a serine protease inhibitory effect. Examples include <NUM>-(<NUM>-aminoethyl)benzenesulfonyl fluoride (AEBSF), benzamidine, aprotinin, bestatin, E-<NUM> (Cayman Chemical), leupeptin, pepstatin A, inhibitor cocktails (Thermo Shientific) which are mixtures of the foregoing, a trypsin inhibitor (derived from soybean), phenylmethylsulfonyl fluoride (PMSF), and tosyllysine chloromethyl ketone (TLCK).

The cysteine protease inhibitors may be any one having a cysteine protease inhibitory effect. Examples include cysteine protease inhibitors such as iodine acetamide, iodoacetic acid, and E-<NUM>. Other examples include cysteine protease inhibitors such as TPCK (N-tosyl-L-phenylalanylchloromethyl ketone) and aspartic acid and salts thereof.

The metal protease inhibitors may be any one having a metal protease inhibitory effect (any inhibitor that can inhibit the activity of a metal protease by sequestering the metal ions). Examples include chelating agents and <NUM>,<NUM>-phenanthroline. The chelating agents may be any known one, and examples include dibasic acids such as oxalic acid, adipic acid, and succinic acid; tribasic acids such as citric acid; polyphenols such as catechin, epigallocatechin, and tannic acid; and phytic acid and ethylenediaminetetraacetic acid and/or salts thereof. Preferred among these are dibasic acids, tribasic acids, ethylenediaminetetraacetic acid and/or salts thereof, and <NUM>,<NUM>-phenanthroline, with ethylenediaminetetraacetic acid and/or salts thereof or <NUM>,<NUM>-phenanthroline being more preferred. The ethylenediaminetetraacetic acid and/or salts thereof are referred to as edetic acid or ethylenediaminetetraacetic acid (EDTA), and examples include disodium edetate, trisodium edetate, tetrasodium edetate dihydrate, and tetrasodium edetate tetrahydrate.

The phosphatase inhibitors may be any one having a phosphatase inhibitory effect. Examples include phosphatase inhibitors such as sodium orthovanadate and sodium fluoride. Other examples include inhibitors of serine or threonine phosphatases (e.g., PPP family or PPM family) and inhibitors of tyrosine phosphatases (PTP family). Preferred among these is sodium orthovanadate.

The combined amount of the protease inhibitors and the phosphatase inhibitors is not limited, but it is preferably <NUM> to <NUM> parts by mass per <NUM> parts by mass of the solids in the natural rubber latexes. The lower limit of the combined amount is more preferably <NUM> parts by mass or more, still more preferably <NUM> parts by mass or more, while the upper limit is more preferably <NUM> parts by mass or less, still more preferably <NUM> parts by mass or less. With a combined amount not lower than the lower limit, a decrease in the molecular weight of the natural rubbers tends to be reduced so that good puncture sealing performance can be maintained. With a combined amount not higher than the upper limit, an economic advantage tends to be obtained. It should be noted that the amount of the protease inhibitors or phosphatase inhibitors alone is suitably in the same range as indicated above.

The combined amount of the protease inhibitors and the phosphatase inhibitors based on <NUM>% by mass of the total puncture sealant is <NUM> to <NUM>% by mass. The lower limit of the combined amount is more preferably <NUM>% by mass or more, still more preferably <NUM>% by mass or more, while the upper limit is more preferably <NUM>% by mass or less, still more preferably <NUM>% by mass or less. With a combined amount not lower than the lower limit, a decrease in the molecular weight of the natural rubbers tends to be reduced so that good puncture sealing performance can be maintained. With a combined amount not higher than the upper limit, an economic advantage tends to be obtained. It should be noted that the amount of the protease inhibitors or phosphatase inhibitors alone is suitably in the same range as indicated above.

The puncture sealant preferably contains one or more tackifiers. The tackifiers refer to materials used to increase adhesion between the rubber latex and the tire and thereby improve puncture sealing performance. For example, a tackifying resin emulsion (oil-in-water emulsion) may be used in which fine particles of a tackifying resin are emulsified and dispersed in an aqueous medium containing a small amount of an emulsifier. The tackifying resin, which corresponds to the solids in the tackifying resin emulsion, may preferably be one that does not coagulate the rubber latex, such as a terpene resin, a phenolic resin, or a rosin resin. Other preferred examples of the resin include polyvinyl esters, polyvinyl alcohol, and polyvinyl pyrrolidine.

The amount of such tackifying resins (the solids in the tackifiers) based on <NUM>% by mass of the total puncture sealant is preferably <NUM> to <NUM>% by mass. The lower limit of the amount is more preferably <NUM>% by mass or more, while the upper limit is more preferably <NUM>% by mass or less. With an amount not lower than the lower limit, good puncture sealing performance and seal retention performance tend to be obtained. With an amount not more than the upper limit, good storability, such as reduced agglomeration of rubber particles during storage, tends to be obtained, and an increase in viscosity tends to be reduced to ensure injectability of the puncture sealant through the air valve.

The sum (in terms of solids) of the amount of the natural rubber latexes (in terms of rubber solids) and the amount of the tackifying resins (the solids in the tackifiers) based on <NUM>% by mass of the total puncture sealant is preferably in the range of <NUM> to <NUM>% by mass. The lower limit of the sum is more preferably <NUM>% by mass or more, still more preferably <NUM>% by mass or more, while the upper limit is more preferably <NUM>% by mass or less, still more preferably <NUM>% by mass or less.

The puncture sealant preferably contains one or more surfactants.

Examples of the surfactants include anionic surfactants, nonionic surfactants, and cationic surfactants. Preferred among these are nonionic surfactants.

Polyoxyalkylene alkyl ethers and/or polyoxyalkylene alkenyl ethers are preferred as the nonionic surfactants.

The nonionic surfactants (e.g., polyoxyalkylene alkyl ethers and polyoxyalkylene alkenyl ethers) preferably have an ethylene oxide structure and/or a propylene oxide structure, more preferably an ethylene oxide structure. In the nonionic surfactants having an ethylene oxide structure and/or a propylene oxide structure, the average number of moles of ethylene oxide (EO) and propylene oxide (PO) added (the sum of the average numbers of moles of EO and PO added) is preferably <NUM> or greater, more preferably <NUM> or greater, but is preferably <NUM> or smaller, more preferably <NUM> or smaller, still more preferably <NUM> or smaller.

The number of carbon atoms of the alkyl groups in the polyoxyalkylene alkyl ethers and the number of carbon atoms of the alkenyl groups in the polyoxyalkylene alkenyl ethers are each preferably <NUM> or greater, more preferably <NUM> or greater, but are each preferably <NUM> or smaller, more preferably <NUM> or smaller.

Examples of the polyoxyalkylene alkyl ethers and the polyoxyalkylene alkenyl ethers include compounds represented by the following formula (<NUM>):.

wherein R<NUM> represents a C4-C24 alkyl group or a C4-C24 alkenyl group; the average number n of moles of AO added is <NUM> to <NUM>; and each AO is the same or different and represents a C2-C4 oxyalkylene group.

The number of carbon atoms of R<NUM> is preferably <NUM> or greater, more preferably <NUM> or greater, still more preferably <NUM> or greater, but is preferably <NUM> or smaller, more preferably <NUM> or smaller, still more preferably <NUM> or smaller.

The average number n is preferably <NUM> or greater, more preferably <NUM> or greater, but is preferably <NUM> or smaller, more preferably <NUM> or smaller, still more preferably <NUM> or smaller.

AO is preferably a C2-C3 oxyalkylene group (an oxyethylene group (EO) or oxypropylene group (PO)). When the (AO)n includes two or more types of oxyalkylene groups, the oxyalkylene groups may be arranged blockwise or randomly. When R<NUM> and n are within the above respective ranges or when AO is EO or PO, the advantageous effect can be well achieved.

Suitable examples of the polyoxyalkylene alkyl ethers and the polyoxyalkylene alkenyl ethers include compounds represented by the following formula (<NUM>):.

wherein R<NUM> represents a C8-C22 alkyl group or a C8-C22 alkenyl group; EO represents an oxyethylene group; PO represents an oxypropylene group; the average number x of moles of EO added is <NUM> to <NUM>; and the average number y of moles of PO added is <NUM> to <NUM>.

The preferred range of the number of carbon atoms of R<NUM> is as described for R<NUM>. R<NUM> may be either linear or branched and is preferably a linear alkyl or alkenyl group. The average number x is preferably <NUM> or greater, more preferably <NUM> or greater, but is preferably <NUM> or smaller, more preferably <NUM> or smaller. The average number y is preferably <NUM> or smaller, more preferably <NUM> or smaller, still more preferably <NUM> or smaller, and may be <NUM>. When R<NUM>, x, and y are within the above respective ranges, the advantageous effect can be well achieved.

EO and PO may be arranged blockwise or randomly. When EO and PO are arranged blockwise, the number of EO blocks and the number of PO blocks may each be one or two or more as long as the average numbers of moles of EO or PO added are within the above respective ranges. Moreover, when the number of EO blocks is two or more, the numbers of repeating EO units in the blocks may be the same as or different from each other. Also, when the number of PO blocks is two or more, the numbers of repeating PO units in the blocks may be the same as or different from each other. When EO and PO are arranged randomly, EO and PO may be arranged alternately or disorderly as long as the average numbers of moles thereof are within the above respective ranges.

Polyoxyethylene alkyl ethers and polyoxyethylene alkenyl ethers such as the compounds of formula (<NUM>) where y is <NUM> are suitable as the nonionic surfactants. In this case, the average number of moles of EO added, the type of alkyl group, and the type of alkenyl group are preferably as described above.

Specific examples of the polyoxyalkylene alkyl ethers and the polyoxyalkylene alkenyl ethers include polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene cetyl ether, polyoxyethylene myristyl ether, polyoxyethylene lauryl ether, polyoxyethylene polyoxypropylene stearyl ether, polyoxyethylene polyoxypropylene oleyl ether, polyoxyethylene polyoxypropylene cetyl ether, polyoxyethylene polyoxypropylene myristyl ether, and polyoxyethylene polyoxypropylene lauryl ether. Preferred among these are polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, and polyoxyethylene lauryl ether.

The HLB value (calculated by Griffin's method) of the nonionic surfactants (e.g., polyoxyalkylene alkyl ethers and polyoxyalkylene alkenyl ethers) is preferably <NUM> or greater, more preferably <NUM> or greater, but is preferably <NUM> or smaller, more preferably <NUM> or smaller.

Commercial products of the nonionic surfactants include EMULGEN 320P (formula (<NUM>): R<NUM> = stearyl group, x = <NUM>, y = <NUM>), EMULGEN <NUM> (formula (<NUM>): R<NUM> = oleyl group, x = <NUM>, y = <NUM>), EMULGEN <NUM> (formula (<NUM>): R<NUM> = oleyl group, x = <NUM>, y = <NUM>), EMULGEN <NUM> (formula (<NUM>): R<NUM> = lauryl group, x = <NUM>, y = <NUM>), EMULGEN 109P (formula (<NUM>): R<NUM> = lauryl group, x = <NUM>, y = <NUM>), EMULGEN <NUM> (formula (<NUM>): R<NUM> = lauryl group, x = <NUM>, y = <NUM>), and EMULGEN <NUM> (formula (<NUM>): R<NUM> = cetyl group, x = <NUM>, y = <NUM>) all available from Kao Corporation.

The amount of the surfactants based on <NUM>% by mass of the rubber solids in the natural rubber latexes is preferably <NUM> to <NUM>% by mass, more preferably <NUM> to <NUM>% by mass, still more preferably <NUM> to <NUM>% by mass, from the standpoints of injectability at low temperatures and heat resistance.

The amount of the surfactants based on <NUM>% by mass of the total puncture sealant is preferably <NUM> to <NUM>% by mass. With an amount not lower than the lower limit, good injectability tends to be obtained, while with an amount not higher than the upper limit, good sealing performance tends to be obtained. The amount is more preferably <NUM> to <NUM>% by mass, still more preferably <NUM> to <NUM>% by mass.

The puncture sealant of the present disclosure may further contain other components as long as the advantageous effect is not inhibited. The puncture sealant of the present disclosure can be prepared by common methods. Specifically, it may be prepared, for example, by mixing the above-described and other components by a known technique.

The present disclosure will be specifically described by reference to, but not limited to, examples.

The following collectively describes the chemicals used in the examples and comparative examples.

The antioxidants were mixed with water and the antifreezing agents to prepare antioxidant dispersions. Each of the antioxidant dispersions was mixed with the other materials according to the recipe shown in Table <NUM> to prepare puncture sealants.

A low-density polyethylene bottle was filled with each of the puncture sealants and then stored at an ambient temperature of <NUM> for <NUM> days. After the storage, the puncture seal durability of each puncture sealant was evaluated as follows. The results are shown in Table <NUM>.

A hole was made in a tread portion of a tire of size <NUM>/65R15 using a nail having a diameter of <NUM>. After removal of the nail, <NUM> of the puncture sealant was injected into the punctured tire and the tire pressure was increased to <NUM> kPa. Then, the tire was run at a speed of <NUM> to <NUM>/h for <NUM> minutes while a load of <NUM> kN was applied to the tire. Thereafter, the repaired tire was stored in a <NUM> environment for two hours, and the tire pressure was adjusted to <NUM> kPa. Then, the tire pressure was measured after a lapse of <NUM> hours, and the puncture seal durability was evaluated according to the following criteria:.

Claim 1:
A puncture sealant, comprising:
at least one natural rubber latex;
at least one antioxidant;
at least one antifreezing agent; and
at least one selected from the group consisting of protease inhibitors and phosphatase inhibitors;
wherein the puncture sealant comprises, based on <NUM>% by mass of the total puncture sealant, <NUM> to <NUM>% by mass of the at least one natural rubber latex in terms of rubber solids, <NUM> to <NUM>% by mass of the at least one antioxidant, <NUM> to <NUM>% by mass of the at least one antifreezing agent, and <NUM> to <NUM>% by mass in total of the at least one selected from the group consisting of protease inhibitors and phosphatase inhibitors.