JP2005120273A - Puncture sealing agent for tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the formation of creamy substances during storage without detriment to various performances including puncture sealing performances. <P>SOLUTION: The puncture sealing agent for tires comprises a natural rubber latex, a tackifier resin emulsion, and an antifreezing agent comprising glycols, where the natural rubber latex contains fine rubber particles having a particle size of at most 0.5 μm in the rubber particles and the number of the fine rubber particles is at least 55% of the total number of the rubber particles. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tire puncture sealant that suppresses the formation of a cream-like substance during long-term storage and has improved storage performance (stability over time).

  When a puncture occurs in a tire, a natural rubber latex is combined with an antifreezing agent consisting of glycol and a natural rubber latex as a puncture sealant that repairs a puncture hole by injecting it into the tire through an air valve. What was done is used a lot.

  However, when this type of puncture sealing agent is stored for a long period of time, the rubber particles therein tend to aggregate near the surface and transform into a creamy substance, which tends to lower the puncture sealing performance.

  In addition, the generation | occurrence | production mechanism of this cream-like substance is estimated as follows. In other words, the puncture sealant is an emulsion in which rubber particles and tackifying resin particles are repelled by ionic repulsion and suspended in an aqueous solution of an antifreeze glycol (eg, ethylene glycol). Since the specific gravity of the particles is smaller than that of the aqueous glycol solution, which is the dispersion medium, the rubber particles gradually rise in the dispersion medium due to the action of gravity, and this creates a concentrated layer near the surface, producing a cream-like substance. Guessed.

  Therefore, for example, by increasing the viscosity of the dispersion medium by adding a thickener (see Patent Document 1), it has been proposed to suppress the rising speed of the rubber particles and suppress the formation of a cream-like substance.

JP 2002-294214 A

  However, the means for increasing the viscosity has a problem that it becomes difficult to inject the puncture sealant into the tire.

  Therefore, the present invention activates the Brownian motion of rubber particles based on the use of natural rubber latex containing rubber particles containing fine rubber particles having a particle size of 0.5 μm or less in a predetermined ratio. By increasing dispersibility, the floating and aggregation of rubber particles in the dispersion medium can be suppressed, and the generation of cream-like substances during storage is suppressed to a low level without impairing the puncture sealing performance and causing the above problems. An object of the present invention is to provide a tire puncture sealant that can be used.

In order to achieve the above object, the invention of claim 1 of the present application is a tire puncture sealing agent comprising a natural rubber latex, a tackifying resin emulsion, and an antifreezing agent comprising glycol,
The natural rubber latex is characterized in that the rubber particles contain fine rubber particles having a particle size of 0.5 μm or less, and the number of fine rubber particles is 55% or more of the total number of rubber particles.

  The invention according to claim 2 is characterized in that the natural rubber latex is deproteinized rubber latex.

  The invention of claim 3 is characterized in that the antifreezing agent is ethylene glycol or propylene glycol and is contained in an amount of 20 to 35% by weight based on the total weight of the puncture sealing agent.

  Since the present invention is configured as described above, the activation of the Brownian motion of the rubber particles can prevent the rubber particles from floating and agglomerating in the dispersion medium, and the puncture sealing performance is not impaired. It becomes possible to suppress the production | generation of the creamy substance in low.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The tire puncture sealant of the present invention comprises at least rubber latex, a tackifying resin emulsion, and an antifreezing agent composed of glycol.

  As the rubber latex, natural rubber latex having high sealing performance is used in the present invention. In particular, so-called deproteinized natural rubber latex obtained by removing protein from natural rubber latex can suppress spoilage with less ammonia. Therefore, the steel cord can be more preferably employed from the viewpoint of preventing corrosion damage to the steel cord caused by ammonia and generation of an irritating odor.

  Here, the natural rubber latex is a suspension in which rubber solids are dispersed in the form of rubber particles in an aqueous medium (dispersion medium) containing a small amount of a surfactant as an emulsifier, as is well known. In order to quickly enter the puncture hole, close the puncture hole, and maintain the puncture sealing performance up to a certain travel distance, the blending amount A with respect to the total weight of the puncture sealing agent of the rubber solid content is 25 to 40% by weight. It is preferable to be in the range. In order to secure the blending amount A within the above range, a concentrated natural rubber latex having a rubber solid content in the natural rubber latex increased to about 60% by weight is used.

  Next, the tackifying resin emulsion is an oil-in-water emulsion in which the tackifying resin is dispersed in the form of fine particles in an aqueous medium containing a small amount of an emulsifier, like rubber latex, and the tackifying resin is a solid content thereof. For example, those that do not coagulate the natural rubber latex, such as terpene resins, phenol resins, and rosin resins, can be preferably used. Other preferred resins include polyvinyl esters, polyvinyl alcohol, and polyvinyl pyrrolidine.

  This tackifying resin is used for enhancing the adhesion between the natural rubber latex and the tire and improving the puncture sealing performance, and its blending amount B is 10-30 with respect to the total weight of the puncture sealing agent. % By weight is preferred. In addition, when the compounding amount A of the rubber solid content is less than 25% by weight and the compounding amount B of the tackifying resin is less than 10% by weight, the puncture sealing performance and the performance of retaining it (seal retaining performance) are insufficient. On the other hand, if the blending amounts A and B exceed 40% by weight and 30% by weight, respectively, the storage performance is impaired such as the rubber particles tend to aggregate during storage, and the viscosity increases and the air valve of the puncture sealant increases. Makes injection difficult. Therefore, it is also preferable to regulate the sum (A + B) of the blending amounts A and B to 35 to 60% by weight with respect to the total weight of the puncture sealing agent.

  As the emulsifier for the natural rubber latex and the emulsifier for the tackifying resin emulsion, various surfactants 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 weight with respect to the total weight of the puncture sealing agent.

  Next, as the antifreezing agent, for example, glycols (dihydric alcohols) such as ethylene glycol, diethylene glycol, propylene glycol, and triethylene glycol can be used. Of these, ethylene glycol and propylene glycol, which are excellent in antifreezing effect, can be used in a minimum amount, and are preferable for preventing adverse effects on various properties such as puncture sealing performance by the antifreezing agent.

  When ethylene glycol and propylene glycol are used as antifreeze agents, the blending amount C with respect to the total weight of the puncture sealing agent is preferably in the range of 20 to 35% by weight, whereby the freezing temperature of the puncture sealing agent is reduced. Can be lowered to a low temperature of, for example, −30 ° C. or lower.

  In the present invention, when the puncture sealant is stored for a long period of time, in order to prevent the rubber particles from agglomerating to produce a cream-like substance, the natural rubber latex has a particle diameter of 0.5 μm in the rubber particles. Fine rubber latex containing 55% or more of the following fine rubber particles with respect to the total number of rubber particles is employed. The ratio of the number of fine rubber particles to the total number of rubber particles may be referred to as the number of particles% for convenience. The particle size of the rubber particles dispersed in the rubber latex and the particle size distribution can be measured using a light scattering photometer. From the measurement results, the fine rubber having a particle size of 0.5 μm or less is used. The number% of particles can be determined.

  Here, as a result of the study by the present inventor, fine rubber particles having a particle size of 0.5 μm or less have high dispersibility due to active Brownian motion. In particular, the number of particles is 55% or more, preferably 60%. When the amount is increased as described above, the other rubber particles are also affected by the fine rubber particles, so that the overall dispersibility can be improved. It has been found that the production can be suppressed.

  In the rubber particles, when the number of particles of rubber fine particles having a particle diameter of 0.5 μm or less is less than 55%, it is difficult to sufficiently increase the dispersibility of the entire rubber particles, and the production of creamy substances is suppressed. I can't do that. The upper limit value of the number of particles of rubber fine particles having a particle diameter of 0.5 μm or less in the rubber particles is not specified, but if the percentage of the number of fine particles is too high, it is disadvantageous for production efficiency and production cost. There is a problem that the viscosity increases at a high solid content. Therefore, the upper limit of the number% of particles of 0.5 μm or less in the rubber particles is preferably 75% or less.

  Here, according to the inventor's investigation, the field rubber latex collected from the rubber tree generally contains fine rubber particles having a particle diameter of 0.5 μm or less of 60% or more of the total number of rubber particles. In the concentrated latex having a rubber solid content of about 60% by weight obtained by concentrating the field rubber latex, it was found that the number of fine rubber particles was reduced to 55% or less. The cause is the concentration method of field rubber latex. That is, for the concentration of the field rubber latex, a centrifugal separation method is usually employed. In this centrifugal separation method, most of the fine rubber particles remain in the serum without being separated, and in the separated concentrated latex. Reduces fine rubber particles.

Therefore, the fine particle rubber latex used in the present invention is not particularly restricted, for example,
(1) Concentrate the field rubber latex by a concentration method other than the centrifugation method; or (2) Collect fine rubber particles from the serum obtained at the time of centrifugation, and use this to collect the concentrated latex in the centrifugation or other concentrated latex. Added;
Can be formed.

An example of purifying concentrated fine particle rubber latex that has been deproteinized using the methods (1) and (2) will be described below.
First, a deproteinized rubber latex is formed by adding a proteolytic enzyme to a field rubber latex (solid content: 30% by weight) to decompose proteins. The enzyme for proteolysis may be any of, for example, those derived from bacteria, those derived from filamentous fungi, those derived from yeasts, and is not particularly limited. preferable. Such a degradation treatment with a proteolytic enzyme is usually carried out by adding 0.01 to 10% by weight of the proteolytic enzyme to the field rubber latex and allowing it to stand or stir for several hours to one week. it can. Proteolytic treatment is suitably performed at a temperature of 5 to 90 ° C, preferably 20 to 60 ° C.

  The deproteinized rubber latex obtained above is concentrated by a rotary flat membrane separation method using a rotary flat membrane separator described in JP-A-7-238102. As a result, a concentrated fine rubber latex having a solid content of about 60% by weight can be obtained while maintaining a high content of fine rubber particles.

  Alternatively, the deproteinized rubber latex obtained above is concentrated by a creaming separation method using a creaming agent described in JP-A-11-106405, so that the content of the fine rubber particles is kept high. Thus, a concentrated fine rubber latex having a solid content of about 60% by weight can be obtained. At this time, as a creaming agent, for example, sodium alginate (sodium alginate), ammonium alginate, konjac paste (mannan), tragagant gum (tragacanth), etc., and the creaming agent is added to the deproteinized rubber latex by 0. Add 1-1 phr. Thereby, substantially all rubber particles can be separated from the serum as a cream layer without transferring the fine rubber particles to the serum side.

  Next, a method using the serum obtained at the time of centrifugation will be described. First, the deproteinized rubber latex obtained above is concentrated by a conventional centrifugation method. At this time, most of the fine rubber particles remain in the serum without being separated. Therefore, concentrated fine rubber particles having a high content of fine rubber particles can be obtained by concentrating the fine rubber particles contained in the serum and returning to the concentrated latex of the centrifugal separation. In the initial field rubber latex, when the number of fine rubber particles is less than 55%, fine rubber particles concentrated from the serum are obtained by the rotary flat membrane separation method and the creaming separation method. By adding to the fine rubber latex, the number of fine rubber particles can be set to 55% or more.

  As the serum concentration method, the rotary flat membrane separation method and the creaming separation method are suitable. Centrifugation may also be employed, but in this case, in order to ensure the separation effect, it is necessary to add a water-soluble compound having a high specific gravity (for example, glycols) to the serum, and this water-soluble compound is added to the rubber. In order to suppress mixing, it is preferable to increase the rotation speed and lengthen the residence time during centrifugation.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, it is not limited to the above-mentioned embodiment, It can deform | transform and implement in a various aspect.

  While producing a puncture sealant on the basis of the specifications in Table 1, the puncture seal performance, seal retention performance, and storage performance of each sample were measured, and compared with Conventional Examples 1 and 2, and the results are shown in Table 1. .

In Table 1, each rubber latex Ga to Ge (solid content 60% by weight) was formed by the following method.
The rubber latex Ga was formed by concentrating field rubber latex (solid content 30% by weight) using a centrifugal separation method.
The rubber latex Gb is obtained by adding a bacterial protease derived from the field rubber latex (solid content 30% by weight) and leaving it at 40 ° C. for 24 hours to decompose the protein, thereby obtaining a deproteinized rubber latex. This deproteinized rubber latex was formed by concentrating using a centrifugation method.
The rubber latex Gc was formed by concentrating a deproteinized rubber latex obtained by the same method as described above using a rotary flat membrane separation method.
The rubber latex Gd was formed by concentrating the deproteinized rubber latex obtained by the same method as described above using a creaming separation method (adding 0.5 phr of sodium alginate as a creaming agent).
The rubber latex Ge is obtained by concentrating the deproteinized rubber latex obtained by the same method as described above by using a centrifugal separation method, concentrating fine rubber particles in the serum, and forming the rubber latex of the centrifugal separation. Formed by returning.

  In each rubber latex Ga to Ge, the number% of fine rubber particles having a particle diameter of 0.5 μm or less was measured using a light scattering photometer.

(1) Punk seal performance:
A tire having a tire size of 185 / 65R14 was drilled with a nail having a diameter of 4.0 mm, the nail was pulled out, 500 ml of a puncture sealant was injected, and the air pressure was increased to 200 kpa. Thereafter, the drum was rotated at a load (3.5 kN) on the drum, and the time until the puncture hole was sealed was judged based on the amount of air leakage. The higher the value, the better.

(2) 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 ... ×.

(3) Storage performance (stability over time):
The cream substance produced when the prototype puncture sealing agent was allowed to stand under the conditions of a period (10 days) and temperature (70 ° C.) was taken out using a filter and indicated by volume ratio with respect to the whole puncture sealing agent. In the parentheses, the volume ratio is shown as a value with the conventional example 1 being 100. The smaller the value, the better.

  As shown in the table, it can be confirmed that the puncture sealing agents of the examples can suppress the formation of cream substance and improve the storage performance (stability over time) while maintaining the puncture sealing performance and seal retention performance.

Claims (3)

A tire puncture sealing agent comprising a natural rubber latex, a tackifying resin emulsion, and an antifreezing agent comprising glycol,
The natural rubber latex includes fine rubber particles having a particle diameter of 0.5 μm or less in rubber particles, and the number of fine rubber particles is 55% or more of the total number of rubber particles. Puncture sealant.   The tire puncture sealing agent according to claim 1, wherein the natural rubber latex is a deproteinized rubber latex.   3. The tire puncture sealing agent according to claim 1, wherein the antifreezing agent is ethylene glycol or propylene glycol and is contained in an amount of 20 to 35% by weight based on the total weight of the puncture sealing agent.