JP6092030B2 - Release agent for tire vulcanization molding and method for producing the same - Google Patents

Description

  The present invention relates to a release agent for tire vulcanization molding and a method for producing the same.

  In general, vulcanization molding of a pneumatic tire is performed by installing a rubber bag called a bladder inside a raw tire mounted in a vulcanization mold, and the bladder is heated by a high-temperature and high-pressure heating and pressing medium such as steam. By inflating, the outer surface of the green tire is heated while being pressed against the vulcanization mold. At that time, in order to improve the lubricity between the raw tire and the bladder, exhaust the air that has entered between the raw tire and the bladder, and improve the releasability of the bladder from the tire after vulcanization A release agent is applied in advance to the inner surface (inner liner surface) of the raw tire.

  In view of the required performance of lubricity (smoothness), air permeability and releasability, such a release agent for tire vulcanization molding, an oil-in-water emulsion of silicones imparting releasability, and A mixed composition with a solid particle suspension imparting smoothness and air permeability is generally used (see Patent Documents 1 and 2).

JP 2012-228783 A JP 2005-193448 A

  Since the release agent for tire vulcanization molding is a suspension containing inorganic powder, the inorganic powder generally tends to settle over time, and improvement in dispersion stability is required. Moreover, since it apply | coats by spraying with a spray gun etc. with respect to the inner surface of a green tire, the improvement of spray workability | operativity, such as improving the clogging property of a sprayer, is calculated | required. Furthermore, in order to improve tire productivity, it is required to shorten the drying time of the applied release agent.

  In view of the above points, an object of the present invention is to provide a release agent for tire vulcanization molding that is excellent in dispersion stability with time and excellent in spray workability and drying property.

The release agent for tire vulcanization molding according to the present invention is a release agent applied to the inner surface of a raw tire at the time of tire vulcanization molding, an inorganic component made of mica and / or talc powder, a silicone component, And a surfactant and water, the average particle size of the dispersoid is 0.1 to 7 μm, and the viscosity at 23 ° C. is 1000 mPa · s or less.

  The production method according to the present invention is a method for producing the release agent for tire vulcanization molding, wherein the mixed solution containing the inorganic component, the silicone component, the surfactant, and water is mixed with a high-speed shearing stirrer. Stirring while cooling to below ℃.

  The tire vulcanization mold release agent according to the present invention is a suspension because it has a very small average particle diameter of 0.1 to 7 μm and a viscosity of 1000 mPa · s or less. Nevertheless, the dispersion stability is good, clogging at the time of spraying with a sprayer is eliminated, and the drying time can be shortened.

  Moreover, since it is stirred using the high-speed shearing type stirrer in the production method according to the present invention, a release agent having a small particle size can be obtained while shortening the stirring process time. Further, by stirring while cooling, the increase in viscosity can be suppressed, and spraying workability and drying property can be improved.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The release agent for tire vulcanization molding according to the present embodiment (hereinafter sometimes simply referred to as a release agent) includes an inorganic component made of powder, a silicone component, a surfactant, and water. .

  The inorganic component composed of the above powder (hereinafter sometimes simply referred to as “inorganic component”) is not particularly limited. For example, smectite such as montmorillonite, saponite, and stevensite; bentonite; vermiculite; kaolin such as halloysite and kaolinite; Phyllosilicates such as talc, pyrophyllite, mica (mascobite, sericite), muscovite, biotite, phlogopite, etc .; jamonite such as antigolite; Carbonates such as calcium carbonate, magnesium carbonate and barium carbonate; sulfates such as calcium sulfate and barium sulfate; metal oxides such as silica, alumina, magnesium oxide, antimony trioxide, titanium oxide and iron oxide; aluminum hydroxide , Gold such as magnesium hydroxide and iron hydroxide Hydroxides; red iron oxide; diatomaceous earth; aluminum silicate; carbon black; graphite, and the like, these may be alone or in combination of two or more either. As the inorganic component, mica and / or talc is preferable.

  The silicone component is a general term for organopolysiloxanes and includes silicone oil, silicone rubber, and silicone resin. Examples of the organopolysiloxane include dialkylpolysiloxanes such as dimethylpolysiloxane, diethylpolysiloxane, and methylisopropylpolysiloxane; alkylphenylpolysiloxanes such as methylphenylpolysiloxane and dimethylsiloxane / methylphenylsiloxane copolymer; Alkylethyl) polysiloxane, alkyl (aralkylpropylsiloxane) such as methyl (phenylpropyl) polysiloxane; 3,3,3-trifluoropropylmethylpolysiloxane, etc., and these may be used alone or in combination of two or more. May be. As the silicone component, silicone oil is preferable from the viewpoint of releasability.

  Examples of the surfactant include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. Among these, nonionic surfactants and / or anionic surfactants are included. Activators are preferred. When both are used in combination, the mass ratio is not particularly limited, but the nonionic surfactant / anionic surfactant is preferably 75/25 to 99/1. The nonionic surfactant is not particularly limited, but polyoxyalkylene such as polyoxyethylene alkyl ether and polyoxypropylene alkyl ether is preferable. The anionic surfactant is not particularly limited, and examples thereof include carboxylic acid type anionic surfactants such as polyoxyethylene alkyl ether carboxylates; sulfonic acid type anionic surfactants such as alkylbenzene sulfonates, These may use any 1 type (s) or 2 or more types together.

  Examples of the water include, but are not limited to, distilled water, ion exchange water, tap water, and industrial water.

  The mass ratio of the inorganic component, the silicone component and the surfactant contained in the release agent is not particularly limited, but the inorganic component is 15 to 90% by mass and the silicone component is 5 to 75% by mass with respect to the total amount. %, And the surfactant is preferably 1 to 10% by mass. More preferably, the inorganic component is 55 to 70% by mass, the silicone component is 10 to 40% by mass, and the surfactant is 2 to 5% by mass. Moreover, although content of water is not specifically limited, It is preferable that it is 35-90 mass% with respect to the whole mold release agent, More preferably, it is 45-60 mass%.

  The mold release agent according to the present embodiment may contain additives such as a colorant, a rust inhibitor, a preservative, and a metal salt of a higher fatty acid, if necessary, in addition to the above components.

  The release agent according to the present embodiment can be prepared using a high-speed shearing stirrer. In other words, the premixed liquid containing the inorganic component, the silicone component, the surfactant, and water (that is, the mixed liquid) is stirred using a high-speed shearing stirrer, thereby releasing the mold according to the present embodiment. An agent is obtained. By using a high-speed shearing type stirrer, it is possible to shorten the stirring process time as compared with a conventional propeller type stirrer, and to obtain a mold release agent having a small particle diameter, which is less likely to cause lumps. Here, it is preferable that it is 3000 rpm or more as rotation speed in the stirring process by a high-speed shearing type stirrer, More preferably, it is 5000 rpm or more. The higher the number of revolutions, the better. Therefore, the upper limit is not particularly limited, but is usually 8000 rpm or less.

  The high-speed shearing stirrer is not particularly limited as long as it can exert a large fluid shearing action by rotating at a high speed, but a rotor / stator mixer is preferable. The rotor / stator mixer is composed of a fixed stator and a rotor that rotates at a high speed with a small clearance inside, and a large peripheral speed at the tip of the rotor and liquid is discharged outside through the stator. The effect of both the high velocity liquid flow and the time creates a large fluid shearing action. Such a rotor / stator type high-speed shearing stirrer itself is known and commercially available ones can be used.

  Further, as the high-speed shearing type stirrer, it is preferable to use an inline type shearing stirrer having a circulation path, more preferably an inline type rotor / stator type shearing stirrer. Here, the in-line type is a type in which a stirrer is installed in the middle of the circulation path to continuously stir the passing liquid. Therefore, in this case, the high-speed shearing stirrer usually circulates the liquid by connecting the reservoir tank, the inline shearing stirrer that stirs the liquid flowing out of the reservoir tank, and the reservoir tank and the inline shearing stirrer. It is equipped with a circulation path and is stirred while circulating the mixed solution.

  With such an in-line type shear stirrer, since air is not embraced, foaming can be prevented. Further, since the mixed liquid can be passed through the slit of the stator 100% and a shearing action can be applied, the uniformity is excellent and the processing time can be greatly shortened. Furthermore, by providing a cooling device in the reservoir tank or the circulation path, it is possible to cool the mixed solution, and the cooling efficiency is excellent.

  In this embodiment, it is preferable to use a high-speed shearing stirrer and stir while cooling so that the liquid temperature is 60 ° C. or lower. More preferably, it is cooling to 50 ° C. or lower. In general, in a high-speed shear type stirrer, the temperature of the mixed solution rises due to stirring, and in the release agent, the viscosity increases as the temperature increases. On the other hand, by stirring while cooling, an increase in temperature of the mixed solution can be suppressed and an increase in viscosity can be suppressed. In addition, the lower limit of the stirring temperature (liquid temperature) is not particularly limited, and the room temperature may be maintained as it is. However, since there is usually a slight temperature increase due to stirring, it is, for example, 30 ° C. or higher.

  As described above, by stirring with cooling using a high-speed shearing stirrer, a release agent having an average particle size of dispersoid of 0.1 to 7 μm is obtained. Here, the dispersoid is fine particles dispersed in water as a dispersion medium, and includes the inorganic component, the silicone component, and the like. The average particle size of the dispersoid is more preferably 0.1 to 5 μm.

  Moreover, the mold release agent whose viscosity in 23 degreeC is 1000 mPa * s or less is obtained by stirring while cooling using a high-speed shear type stirrer as mentioned above. The viscosity of the release agent is more preferably 500 Pa · s or less. The lower the viscosity, the better, so the lower limit is not particularly limited, but it is usually 100 Pa · s or higher.

  Thus, since it is the mold release agent which concerns on embodiment, since a particle diameter is very fine and it is low viscosity, the following effect is show | played. That is, since the particles are fine, the dispersion stability over time is good despite the suspension. Further, since the particle size is small and the viscosity is low, clogging at the time of spraying with a spray gun or the like is improved, the spraying workability is excellent, and the drying time can be shortened.

The mold release agent according to the present embodiment is used by being applied to the inner surface of a green tire (also referred to as a green tire or an unvulcanized tire) during tire vulcanization formation. As an embodiment, after forming a green tire according to a conventional method, a release agent is applied to the inner surface (inner liner surface) using a sprayer such as a spray gun. The coating amount is not particularly limited, but is preferably 5 to 50 g / m ² in terms of mass after drying. After drying the mold release agent, place the raw tire in a vulcanizing mold, press the bladder from the inside with hot steam and press it against the mold, and the final tire shape and tread pattern Vulcanize to Thereafter, the bladder is shrunk, peeled off from the inner surface of the tire, and removed from the vulcanization mold to obtain a pneumatic tire.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

[Preparation of mold release agent]
47 parts by weight of a commercially available inner surface mold release agent for tires ("RA-365P" manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) in which necessary components as a release agent are mixed in advance, such as mica, talc, and silicone emulsion, are 48 parts by weight of water. 5 parts by weight of carbon black (Mitsubishi Chemical Corporation “Mitsubishi Carbon Black MA-600”) is added as a colorant for the purpose of blackening the release agent, and a lab-scale inline rotor / stator type Using a shear stirrer ("High Shear Mixer Model L4RT" manufactured by SILVERSON), a release agent was prepared by uniformly dissolving and dispersing. The rotational speed of the stirrer was 6000 rpm, and the treatment time was as shown in Table 1. In Comparative Example 4, the cooling device was not operated, and in the other examples, the cooling device provided in the reservoir tank and the circulation path was operated and stirred while cooling. In Comparative Example 5, a conventional general propeller stirrer (rotation speed = 300 rpm) was used for stirring. Table 1 shows the liquid temperature of each release agent after the stirring treatment.

[Physical properties and evaluation of release agents]
About the obtained mold release agent, the average particle diameter and viscosity of the dispersoid were measured. Each mold release agent was used to evaluate dispersion stability, spray gun clogging, and drying properties. Each measurement / evaluation method is as follows.

-Average particle size: measured by laser diffraction / scattering method. Specifically, using a red semiconductor laser (wavelength 680 nm) as a light source, the particle size distribution of the dispersoid contained in the release agent is measured by a laser diffraction particle size distribution measuring device “SALD-2200” manufactured by Shimadzu Corporation. The average value of the obtained particle size distributions (the value of 10 ^μ where μ is the average value of the particle size distribution (volume basis) on the logarithmic scale) was defined as the average particle size.

Viscosity: Measured with a BL type viscometer manufactured by Toki Sangyo Co., Ltd. (rotor # 2, 12 rpm).

-Dispersion stability: The prepared release agent was allowed to stand at room temperature for 10 hours, and the precipitation of inorganic components was observed. “○” indicates that there is no sedimentation (good dispersibility stability), and “x” indicates that there is sedimentation (poor dispersion stability).

Clogging property of spray gun (spraying workability): A release agent was sprayed for 5 seconds using a spray gun, and this was repeated 20 times to check the discharge amount. The discharge amount stability (no clogging) is indicated by “◯”, and the discharge amount reduction (clogging) is indicated by “×”.

And drying properties: a release agent unvulcanized rubber sheet, after drying the mass was coated with a 10 g / m ^2, was confirmed time to take the drying by natural drying. A time until drying was within 10 minutes was indicated by “◯” (good drying property), and a time until drying exceeding 10 minutes was indicated by “x” (poor drying property).

  The results are as shown in Table 1. In Comparative Examples 1 and 2, since the stirring treatment time was short, the dispersion was insufficient and the average particle size was large, so that the dispersion stability, spray workability and drying properties were improved. It was inferior. In Comparative Example 3, since the treatment time was too long, an increase in viscosity due to an increase in the liquid temperature was observed even though the cooling device was operated. Therefore, the spray workability and the drying property were inferior. In Comparative Example 4, since stirring was performed without cooling, reaggregation of particles occurred due to an increase in the liquid temperature, the average particle size was larger than specified, and the spraying workability and the drying property were poor. Moreover, since the general propeller stirrer like the comparative example 5 had low stirring ability and the dispersion process was inadequate, it was inferior to dispersion stability, spray workability | operativity, and drying property.

  On the other hand, in Examples 1 to 3, since the mixture was appropriately stirred while being cooled using a high-speed shearing stirrer, a release agent having a small particle size and a low viscosity was obtained. It was excellent in all properties, spray workability and drying properties.

Claims (3)

A mold release agent applied to the inner surface of the raw tire during tire vulcanization molding,
It contains an inorganic component consisting of mica and / or talc powder, a silicone component, a surfactant, and water, the average particle size of the dispersoid is 0.1 to 7 μm, and the viscosity at 23 ° C. is 1000 mPa · A release agent for tire vulcanization molding, characterized by being s or less. A method for producing a release agent for tire vulcanization molding according to claim 1,
A method for producing a release agent for tire vulcanization molding, comprising stirring a mixed solution containing the inorganic component, a silicone component, a surfactant, and water while cooling to 60 ° C. or lower using a high-speed shearing stirrer. .   3. The method for producing a release agent for tire vulcanization molding according to claim 2, wherein the high-speed shear type stirrer is an in-line type shear stirrer having a circulation path, and the mixed liquid is stirred while being circulated.