Mold release agent composition for vulcanized rubber and its use

Abstract

To provide a mold release agent composition for vulcanized rubber which has excellent release properties, dispersion stability and redispersibility.SOLUTION: A mold release agent composition for vulcanized rubber comprises an inorganic component (A) and a hydrophobic silicone (B), wherein a weight ratio of crystalline silica to the nonvolatile content of the mold release agent composition for vulcanized rubber is 2 wt.% or less. The inorganic component (A) preferably comprises mica (a1). The weight ratio of the mica (a1) to the inorganic component (A) is preferably 0.1 to 50 wt.%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a release agent composition for vulcanized rubber and its use. [Background technology]

[0002] When molding rubber or resin products, a release agent is required between the raw polymer and the mold (rubber, resin, metal) that comes into contact with the raw polymer. Without a release agent, molding defects can occur, significantly reducing productivity. For example, in the case of rubber products, a rubber bag called a bladder or air bag (hereinafter sometimes referred to as a bladder) is inserted inside the raw rubber, which is the rubber product before molding and vulcanization, and high-temperature, high-pressure gas (e.g., steam at approximately 180°C) or liquid is introduced into the bladder to expand it, and the raw rubber is pressed against a mold to be heated and pressurized, and molded and vulcanized to produce the rubber product. When the rubber product is a tire, a bladder is inserted inside the tire before molding and vulcanization (hereinafter sometimes referred to as a green tire), the bladder is inflated, and the green tire is pressed against a mold, heated and pressurized, and molded and vulcanized. In this case, because both the bladder and the inner surface of the green tire are made of rubber, a release agent is required between the two.

[0003] Conventionally, in the process of molding vulcanization, for example, a method has been used in which a release agent is applied in advance to the inner liner surface of a green tire (hereinafter referred to as the green tire inner surface) during the tire manufacturing process. In this case, the release agent must have the ability to provide good lubrication between the green tire inner surface and the bladder (smoothness), the ability to allow air that has entered the bladder and the green tire inner surface to escape and to adhere to each other (air permeability), and the ability to smoothly separate the bladder and the green tire inner surface when the bladder is deflated after vulcanization (releasability).

[0004] Such release agents are mainly composed of compositions consisting of an aqueous emulsion of silicone and inorganic powder such as mica or talc, and Patent Document 1 proposes a release agent for tire vulcanization molding characterized by containing inorganic powder including at least mica in an aqueous emulsion of silicone, with the average particle size of the mica being in the range of 55 μm to 95 μm. Also, Patent Document 2 proposes a release agent for the inner surface of rubber containing an inorganic substance, hydrophobic silicone, a surfactant, and graphite. However, the release agents disclosed in Patent Documents 1 and 2 have the problem of insufficient processability during tire manufacturing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-193448 [Patent Document 2] Japanese Patent Application Publication No. 2022-93966 Summary of the Invention [Problem to be solved by the invention]

[0006] It has been found that the reason for the decrease in processability during the production of molded, vulcanized rubber such as tires is that the degree of adhesion between the green tire, which is unvulcanized rubber, and the bladder, which is the mold frame, becomes too great, and that the releasability of conventional release agents such as those disclosed in Patent Documents 1 and 2 is insufficient. Furthermore, when the release agent is used, it is dispersed in water in a dedicated tank and stored as an aqueous dispersion for several days to several weeks. After storage, the aqueous dispersion of the release agent is redispersed and used. Therefore, the aqueous dispersion of the release agent needs to have high dispersion stability and redispersibility. It has also been found that the release agents disclosed in Patent Documents 1 and 2 lack dispersion stability and redispersibility. Therefore, an object of the present invention is to provide a release agent composition for vulcanized rubber which has excellent release properties, dispersion stability and redispersibility. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have found that the above object can be achieved by using a release agent composition for vulcanized rubber containing specific components. That is, the present invention provides a release agent composition for vulcanized rubber, which comprises an inorganic component (A) and a hydrophobic silicone (B), wherein the weight ratio of crystalline silica to the non-volatile content of the release agent composition for vulcanized rubber is 2% by weight or less.

[0008] The release agent composition for vulcanized rubber of the present invention comprises the following components: <1> ~ <5> It is preferable that at least one of the following conditions is satisfied. <1> The inorganic component (A) includes mica (a1). <2> The weight ratio of the mica (a1) to the inorganic component (A) is 0.1 to 50% by weight. <3> The content of the hydrophobic silicone (B) is 1 to 30 parts by weight relative to 100 parts by weight of the inorganic component (A). <4> It further contains a surfactant (C). <5> The content of the surfactant (C) is 0.1 to 10 parts by weight relative to 100 parts by weight of the inorganic component (A).

[0009] The aqueous dispersion of the release agent composition for vulcanized rubber of the present invention contains the above-mentioned release agent composition for vulcanized rubber and water.

[0010] The method for producing a vulcanized rubber according to the first aspect of the present invention comprises a step of heating and vulcanizing the unvulcanized rubber in a state in which the above-mentioned mold release agent composition for vulcanized rubber adheres to the interface between the unvulcanized rubber and a mold.

[0011] The method for producing vulcanized rubber according to the second aspect of the present invention comprises step 1 of applying the aqueous dispersion of the above-mentioned mold release agent composition for vulcanized rubber to at least one of the surface of unvulcanized rubber and the surface of a mold form, and volatilizing the water, and step 2 of heating the unvulcanized rubber to vulcanize it after step 1. [Effects of the Invention]

[0012] The release agent composition for vulcanized rubber of the present invention has excellent release properties, and when dispersed in water, it has excellent dispersion stability and redispersibility. The aqueous dispersion of the release agent composition for vulcanized rubber of the present invention contains the above-mentioned release agent composition for vulcanized rubber, and is excellent in dispersion stability and redispersibility. The method for producing vulcanized rubber according to the first aspect of the present invention uses the above-mentioned mold release agent composition for vulcanized rubber, and can efficiently produce vulcanized rubber. The method for producing vulcanized rubber according to the second embodiment of the present invention uses the aqueous dispersion of the release agent composition for vulcanized rubber, and can efficiently produce vulcanized rubber. DETAILED DESCRIPTION OF THE INVENTION

[0013] The release agent composition for vulcanized rubber of the present invention (hereinafter sometimes simply referred to as the release agent composition) contains an inorganic component (A) and a hydrophobic silicone (B), and the weight ratio of crystalline silica to the non-volatile content of the release agent composition for vulcanized rubber is 2% by weight or less. First, each component constituting the release agent composition will be described in detail.

[0014] [Inorganic component (A)] The release agent composition of the present invention contains an inorganic component (A) (hereinafter, sometimes simply referred to as component (A)). Component (A) is a component that imparts smoothness and air permeability.

[0015] Component (A) is not particularly limited, and examples thereof include smectites such as montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite; bentonite; vermiculites such as di-vermiculite and tri-vermiculite; kaolins such as halloysite, kaolinite, endelite, dickite, nacrite, and chrysotile; phyllosilicates such as talc, pyrophyllite, mica (muscovite, sericite), margarite, clintite, muscovite, biotite, phlogopite, synthetic mica, fluorine mica, paragolite, phlogopite, lepidolite, tetrasilylic mica, and taeniolite. ; jamonite such as antigorite; chlorite such as dompatite, suzukiite, kukkaite, clinochlore, chamosite, chlorite, nanite, etc.; piolites-palygorskites such as sepiolite and palygorskite; (heavy) carbonates such as calcium carbonate, magnesium carbonate, barium carbonate; sulfates such as calcium sulfate, barium sulfate; metal oxides such as silica, alumina, magnesium oxide, antimony trioxide, titanium oxide, iron oxide; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, iron hydroxide; red iron oxide; diatomaceous earth; aluminum silicate; carbon black; graphite, etc., and one or more of these may be used in combination.

[0016] If component (A) contains mica (a1), it is preferable in that releasability is improved. The weight proportion of mica (a1) in component (A) is not particularly limited, but is preferably 0.1 to 50% by weight, more preferably 1 to 49% by weight, even more preferably 3 to 45% by weight, and particularly preferably 5 to 40% by weight.

[0017] The component (A) may contain a fibrous inorganic powder (a2), which is preferable in that the component (A) contains a fibrous inorganic powder (a2), since this improves the releasability. Examples of the fibrous inorganic powder (a2) include sepiolite, attapulgite, attapulgous clay, wallathite, palygorskite, and the like, and one or more of these may be used in combination.

[0018] The average fiber length of the fibrous inorganic powder (a2) is not particularly limited, but is preferably 0.5 to 50 μm, more preferably 1 to 30 μm. The average fiber diameter of the fibrous inorganic powder (a2) is not particularly limited, but is preferably 0.01 to 50 μm, more preferably 0.05 to 30 μm. The average fiber length and average fiber diameter of the fibrous inorganic powder (a2) are values ​​obtained by randomly selecting 10 fibrous inorganic powders (a2) from an electron microscope image, measuring the length and diameter of each primary particle, and calculating the average value.

[0019] The weight proportion of the fibrous inorganic powder (a2) in component (A) is not particularly limited, but is preferably 0.1 to 10% by weight, more preferably 0.2 to 8% by weight, even more preferably 0.3 to 6% by weight, and particularly preferably 0.5 to 4% by weight.

[0020] The average particle size of component (A) is not particularly limited, but is preferably 1 to 100 μm, more preferably 3 to 75 μm, and even more preferably 5 to 60 μm. When the average particle size of component (A) is 1 μm or more, air permeability tends to be improved. When the average particle size of component (A) is 100 μm or less, smoothness tends to be improved. The average particle size of component (A) is determined from the particle size value at 50% by weight of the cumulative amount (median particle size D50) read from a cumulative particle size distribution curve measured on a volume basis using a laser particle size distribution analyzer in accordance with JIS R 1629. An example of a laser particle size distribution analyzer that can be used for measurement is the "LA920" manufactured by Horiba, Ltd.

[0021] Component (A) may contain crystalline silica, but since crystalline silica has low hydrophilicity and poor dispersibility, its content is preferably low. Examples of crystalline silica include quartz, cristobalite, tridymite, coesite, and stachobalite. The weight proportion of the crystalline silica in component (A) is not particularly limited, but is preferably 4% by weight or less, more preferably 3% by weight or less. If the weight proportion exceeds 4% by weight, the dispersion stability and redispersibility of the release agent composition may decrease. The weight ratio of the crystalline silica in the mica (a1) is not particularly limited, but is preferably 10% by weight or less, more preferably 5% by weight or less. If the weight ratio exceeds 10% by weight, the dispersion stability and redispersibility of the release agent composition may decrease.

[0022] [Hydrophobic silicone (B)] The release agent composition of the present invention contains a hydrophobic silicone (B) (hereinafter, sometimes referred to as component (B)). Component (B) is a component that imparts release properties and lubricity. Examples of component (B) include organopolysiloxanes, which include at least one selected from silicone oil, silicone rubber, silicone oligomer, and silicone resin.

[0023] Examples of component (B) include dialkylpolysiloxanes such as dimethylpolysiloxane, diethylpolysiloxane, methylisopropylpolysiloxane, and methyldodecylpolysiloxane; alkylphenylpolysiloxanes such as methylphenylpolysiloxane, dimethylsiloxane-methylphenylsiloxane copolymer, and dimethylsiloxane-diphenylsiloxane copolymer; alkylaralkylpolysiloxanes such as methyl(phenylethyl)polysiloxane and methyl(phenylpropyl)polysiloxane; and 3,3,3-trifluoropropylmethylpolysiloxane, and the like. These may be used alone or in combination of two or more. When component (B) is used in producing the release agent composition of the present invention, an emulsion of component (B) may be used. When an emulsion of component (B) is used, the surfactant contained in the emulsion may be component (C) described below, and the content of the surfactant is included in the content of component (C).

[0024] Component (B) is not particularly limited, but from the viewpoint of releasability, it is preferable that the molecular structure is linear and that it has the fluidity of a liquid or paste at room temperature (25°C), and silicone oil is preferable. The kinematic viscosity of component (B) at 25°C is not particularly limited, but is preferably 100 to 1,000,000 mm 2 / s, more preferably 1,000 to 500,000 mm 2 / s, and more preferably 5,000 to 100,000 mm 2 / s. The kinematic viscosity is 100mm 2 When the kinematic viscosity is 1,000,000 mm / s or more, the mold releasability tends to be improved. 2 When the viscosity is 1 / s or less, the stability of the release agent composition tends to be improved. The kinematic viscosity of component (B) at 25°C is measured in accordance with JIS K2283 using a Cannon-Feske viscometer.

[0025] [Surfactant (C)] In addition to the above-described components (A) and (B), the release agent composition of the present invention preferably further contains a surfactant (C) (hereinafter, sometimes simply referred to as component (C)) in order to improve the wettability of the release agent composition. Improved wettability reduces the occurrence of liquid repellency when the release agent composition is applied, thereby improving the release properties. Furthermore, the dispersibility of component (A) can be improved, and the dispersion stability and redispersibility of the release agent composition can also be improved.

[0026] Component (C) may be at least one selected from nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants, and is preferably at least one selected from nonionic surfactants and anionic surfactants.

[0027] The nonionic surfactant is not particularly limited, and examples thereof include polyoxyalkylene alkyl ethers such as polyoxyethylene cetyl ether and polyoxyethylene lauryl ether; polyoxyalkylene alkylphenyl ethers such as polyoxyethylene nonylphenyl ether and polyoxyethylene octylphenyl ether; polyoxyalkylene fatty acid esters such as polyoxyethylene monolaurate and polyoxyethylene monooleate; polyoxyalkylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monostearate and polyoxyethylene sorbitan monooleate; polyoxyalkylene hydrogenated castor oil; polyoxyalkylene sorbitol fatty acid esters; polyglycerin fatty acid esters; alkyl glycerin ethers; polyoxyalkylene cholesteryl ethers; alkyl polyglucosides; sucrose fatty acid esters; polyoxyalkylene alkylamines; oxyethylene-oxypropylene block polymers, and the like, and one or more of these may be used in combination.

[0028] The anionic surfactant is not particularly limited, and examples thereof include fatty acid salts such as sodium oleate, potassium palmitate, and triethanolamine oleate; alkyl sulfates such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium stearyl sulfate, and sodium cetyl sulfate; polyoxyalkylene alkyl ether acetates such as sodium polyoxyethylene tridecyl ether acetate; alkyl benzene sulfonates such as sodium dodecyl benzene sulfonate; polyoxyalkylene alkyl ether sulfates; sodium stearoyl methyl taurate, sodium lauroyl methyl taurate, sodium myristoyl methyl taurate, and palmitoyl methyl taurine. alkyl phosphates such as sodium monostearyl phosphate; polyoxyalkylene alkyl ether phosphate esters such as polyoxyethylene oleyl ether sodium phosphate and polyoxyethylene stearyl ether sodium phosphate; long-chain sulfosuccinates such as sodium di-2-ethylhexyl sulfosuccinate and sodium dioctyl sulfosuccinate; long-chain N-acyl glutamates such as sodium monosodium N-lauroyl glutamate and disodium N-stearoyl-L-glutamate; and the like, and one or more of these may be used in combination.

[0029] Examples of cationic surfactants include alkyltrimethylammonium salts such as stearyltrimethylammonium chloride, lauryltrimethylammonium chloride, and cetyltrimethylammonium bromide; dialkyldimethylammonium salts; trialkylmethylammonium salts; and alkylamine salts, and these may be used alone or in combination of two or more. Examples of amphoteric surfactants include imidazoline-based amphoteric surfactants such as 2-undecyl-N,N-(hydroxyethylcarboxymethyl)-2-imidazoline sodium and 2-cocoyl-2-imidazolinium hydroxide-1-carboxyethyloxy disodium salt; betaine-based amphoteric surfactants such as 2-heptadecyl-N-carboxymethyl-N-hydroxyethylimidazolium betaine, lauryldimethylaminoacetic acid betaine, alkyl betaine, amido betaine, and sulfobetaine; and amino acid-based amphoteric surfactants such as N-laurylglycine, N-lauryl-β-alanine, and N-stearyl-β-alanine, and these may be used alone or in combination.

[0030] The HLB value of component (C) is not particularly limited, but is preferably 6 to 16. When the HLB value is within the above range, the wettability of the release agent composition improves and it tends to be possible to apply it more uniformly. The HLB value is a number from 1 to 20 that indicates the degree of affinity of the surfactant for water and oil, with a smaller number indicating higher lipophilicity and a larger number indicating higher hydrophilicity. The HLB value of the component (C) can be calculated by the Griffin method (HLB value=20×sum of molecular weights of hydrophilic groups / molecular weight).

[0031] [Water-soluble polymer (D)] The release agent composition of the present invention may further contain a water-soluble polymer (D) (hereinafter, sometimes simply referred to as component (D)) in addition to the above-mentioned components (A) and (B). When the release agent composition contains component (D), it is preferable in that dispersion stability and redispersibility are improved.

[0032] Component (D) is not particularly limited, and examples thereof include starches such as oxidized starch, starch acetate, starch phosphate, carboxymethyl starch, carboxyethyl starch, hydroxyethyl starch, cationic starch, cyanoethylated starch, and dialdehyde starch; mannan; alginic acids such as alginic acid, sodium alginate, propylene glycol alginate, triethanolamine alginate, and ammonium alginate; methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, and hydroxyethylcellulose; Examples of suitable water-soluble polymers include cellulose ethers such as ethylmethyl cellulose, hydroxyethyl ethyl cellulose, and carboxymethyl cellulose; natural gums such as taracant gum, gum arabic, guar gum, xanthan gum, British gum, glucomannan, gellan gum, tara gum, locust bean gum, and carrageenan; sodium polyacrylate; polyvinyl alcohol; polyethylene glycol; polyethylene oxide; water-soluble acrylic resins; water-soluble urethane resins; water-soluble melamine resins; water-soluble epoxy resins; water-soluble butadiene resins; and water-soluble phenolic resins, and these may be used alone or in combination.

[0033] In addition to the above components, the release agent composition of the present invention may contain other components such as polyhydric alcohols, metal soaps, waxes, antifoaming agents, preservatives, and water. The polyhydric alcohol is not particularly limited, and examples thereof include glycerin, 1,3-butanediol, propylene glycol, dipropylene glycol, pentylene glycol, neopentyl glycol, hexylene glycol, polyethylene glycol, erythritol, pentaerythritol, dipentaerythritol, trimethylolethane, trimethylolpropane, ditrimethylolpropane, xylitol, sorbitol, mannitol, maltitol, maltotriose, glucose, sucrose, fructose, and maltose, and one or more of these may be used in combination.

[0034] The metal soap is not particularly limited, and examples thereof include magnesium laurate, calcium laurate, zinc laurate, magnesium myristate, calcium myristate, zinc myristate, magnesium palmitate, calcium palmitate, zinc palmitate, magnesium stearate, calcium stearate, zinc stearate, aluminum stearate, aluminum trioctadecanoate, aluminum dioctadecanoate, aluminum monooctadecanoate, calcium octadecanoate, zinc octadecanoate, magnesium octadecanoate, and barium octadecanoate, and one or more of these may be used in combination.

[0035] The waxes are not particularly limited, and examples thereof include vegetable waxes such as candelilla wax, carnauba wax, rice wax, Japan wax, jojoba oil, sugar wax, bayberry wax, oculist wax, and esparto wax; animal waxes such as beeswax, lanolin, spermaceti, insect wax, and shellac wax; mineral waxes such as montan wax, ozokerite, and ceresin; and hydrocarbon waxes such as polyethylene wax, modified polyethylene wax, polypropylene wax, paraffin wax, microcrystalline wax, petrolatum, Fischer-Tropsch wax, and polyethylene wax. Waxes include hydrogenated waxes such as hydrogenated castor oil, 12-hydroxystearic acid, 12-hydroxystearic acid amide, N-hydroxyethyl-12-hydroxystearylamide, N,N'-ethylene-bis-12-hydroxystearylamide, N,N'-hexamethylene-bis-12-hydroxystearylamide, N,N'-xylylene-bis-12-hydroxystearylamide, methyl-12-hydroxystearate, propylene glycol-mono-12-hydroxystearate, and ethylene glycol-mono-12-hydroxystearate, and one or more of these may be used in combination.

[0036] [Mold release agent composition for vulcanized rubber and method for producing the same] The release agent composition for vulcanized rubber of the present invention contains the above-mentioned component (A) and component (B), and the weight ratio of crystalline silica to the nonvolatile content of the release agent composition is 2% by weight or less. The release agent composition of the present invention has excellent releasability between vulcanized rubber and a mold, and is also excellent in dispersion stability and redispersibility.

[0037] The weight percentage of crystalline silica in the nonvolatile content of the release agent composition of the present invention is 2% by weight or less. If the weight percentage exceeds 2% by weight, the release properties, dispersion stability, and redispersibility decrease. The weight percentage is preferably (1) 1.5% by weight or less, (2) 1.0% by weight or less, (3) 0.7% by weight or less, (4) 0.5% by weight or less, (5) 0.3% by weight or less, and (6) 0.1% by weight or less (the larger the number in parentheses, the more preferable it is). The lower limit of the weight percentage is preferably 0% by weight. The nonvolatile content of the release agent composition of the present invention is the residue remaining when the release agent composition is heated at 110° C. and the weight of the composition becomes constant. The weight proportion of crystalline silica in the nonvolatile components of the release agent composition, the weight proportion of crystalline silica in the entire component (A), and the weight proportion of crystalline silica in each of the raw materials constituting component (A) (for example, mica (a1)) are measured by powder X-ray diffraction.

[0038] The weight proportion of component (A) in the nonvolatile content of the release agent composition is not particularly limited, but is preferably 50 to 95% by weight, more preferably 60 to 92.5% by weight. When this weight proportion is 50% by weight or more, the release properties and smoothness tend to be improved. When this weight proportion is 95% by weight or less, the dispersion stability and redispersibility tend to be improved.

[0039] The amount of component (B) contained in the release agent composition is not particularly limited, but is preferably 1 to 30 parts by weight, more preferably 5 to 20 parts by weight, per 100 parts by weight of component (A). When the amount is 1 part by weight or more, dispersion stability and redispersibility tend to be improved. When the amount is 30 parts by weight or less, releasability tends to be improved.

[0040] The weight proportion of component (B) in the nonvolatile content of the release agent composition is not particularly limited, but is preferably 1 to 30% by weight, more preferably 5 to 20% by weight. When this weight proportion is 1% by weight or more, dispersion stability and redispersibility tend to be improved. When this weight proportion is 30% by weight or less, release properties tend to be improved.

[0041] When the release agent composition contains component (C), the amount of component (C) is not particularly limited, but is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, per 100 parts by weight of component (A). When the amount is 0.1 part by weight or more, dispersion stability and redispersibility tend to be improved. When the amount is 10 parts by weight or less, releasability tends to be improved.

[0042] The weight proportion of component (C) in the nonvolatile content of the release agent composition is not particularly limited, but is preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight. When this weight proportion is 0.1% by weight or more, dispersion stability and redispersibility tend to be improved. When this weight proportion is 10% by weight or less, release properties tend to be improved.

[0043] When the release agent composition contains component (D), the amount of component (D) is not particularly limited, but is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, relative to 100 parts by weight of the content of component (A). When the content is 0.1 part by weight or more, dispersion stability and redispersibility tend to be improved. When the content is 10 parts by weight or less, dispersion stability and redispersibility tend to be improved.

[0044] The weight proportion of component (D) in the nonvolatile content of the release agent composition is not particularly limited, but is preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight. When the content is 0.1% by weight or more, dispersion stability and redispersibility tend to be improved. When the weight proportion is 10% by weight or less, dispersion stability and redispersibility tend to be improved.

[0045] The pH of an aqueous dispersion of the release agent composition of the present invention having a nonvolatile content of 1% by weight at 25°C is not particularly limited, but is preferably 7.0 to 10.5. When the pH is 7.0 or higher, the adhesion of the release agent composition tends to improve. When the pH is 10.5 or lower, the workability tends to improve.

[0046] The release agent composition of the present invention may be in a powder form, which is preferable in terms of storage stability and preservation efficiency. The release agent composition may be in the form of a particulate or granules. If the release agent composition is in the form of a particulate or granules, scattering can be suppressed when preparing an aqueous dispersion of the release agent composition for vulcanized rubber, which will be described later.

[0047] The weight percentage of water in the release agent composition of the present invention is not particularly limited, but is preferably 2 to 25% by weight, more preferably 5 to 15% by weight. If the water content is 2% by weight or more, scattering tends to be suppressed, and if it is 25% by weight or less, aggregation of the release agent composition tends to be suppressed when it is used.

[0048] Examples of methods for producing the release agent composition of the present invention include a method of mixing component (A) and component (B), and, if necessary, component (C) and other components. In the method for producing the release agent composition, the mixing order and the like are not particularly limited, and all components may be mixed simultaneously, or the components may be mixed in order, or some components may be mixed in advance, and the remaining components or a mixture thereof may be added to the obtained mixture, mixed, and dispersed. The mixing method is not particularly limited, and can be performed using an apparatus equipped with an extremely simple mechanism such as a container and a stirring blade. Examples of the mixing apparatus include a Nauta mixer, a V-type mixer, a conical blender, a ribbon mixer, a high-speed mixer, a homomixer, a homogenizer, a colloid mill, and a line mixer.

[0049] When the release agent composition is in a powder form, the release agent composition in powder form may be pulverized with a feather mill, a hammer mill, etc., and then sieved. By adjusting the particle size to a certain value by such a method, the powder becomes easier to handle when measuring it. When the release agent composition is produced in the form of a granule or particulate material, a binder component such as water or a water-soluble polymer compound may be added and then a granulator such as a dish granulator or an extrusion granulator may be used.

[0050] [Method for producing vulcanized rubber] The method for producing vulcanized rubber according to the first aspect of the present invention is a method comprising the step of vulcanizing unvulcanized rubber in a state in which the above-mentioned mold release agent composition for rubber vulcanization adheres to the interface between the unvulcanized rubber as a raw material and a mold for molding.

[0051] The mold used in producing vulcanized rubber is not particularly limited, but it is preferable that it has a fixed mold and a movable mold. The movable mold moves to the fixed mold, or the movable mold changes shape by expanding or the like, and unvulcanized rubber is pressed against the fixed mold, and the unvulcanized rubber is further heated and vulcanized to produce vulcanized rubber. When the vulcanized rubber is a tire, an example of the movable mold is a bladder. The above mold can also be used in the production method of vulcanized rubber of the second aspect of the present invention described below.

[0052] When the mold has a fixed mold and a movable mold, the release agent composition may adhere to at least one of the surface of the fixed mold that comes into contact with the unvulcanized rubber and the surface of the movable mold that comes into contact with the unvulcanized rubber. The position where the release agent composition is to be applied is not particularly limited, but is preferably at least one of the surface of the unvulcanized rubber and the surface of the movable mold that comes into contact with the unvulcanized rubber, more preferably the surface of the unvulcanized rubber, and even more preferably the surface of the unvulcanized rubber that comes into contact with the movable mold. When the movable mold is a bladder and the resulting vulcanized rubber is a tire, the surface of the unvulcanized rubber that comes into contact with the movable mold becomes the inner surface of the tire.

[0053] (Aqueous dispersion of release agent composition for vulcanized rubber) When the release agent composition for vulcanized rubber is adhered to the interface between the unvulcanized rubber and the mold, an aqueous dispersion containing the above-mentioned release agent composition and water (hereinafter, sometimes simply referred to as an aqueous dispersion of the release agent composition) may be adhered to at least one of the surface of the unvulcanized rubber and the surface of the mold. The use of an aqueous dispersion of the release agent composition is preferred because it allows the release agent composition to be adhered uniformly to the object.

[0054] The water used to prepare the aqueous dispersion of the release agent composition may be tap water, ion-exchanged water, distilled water, or the like. The weight proportion of water in the aqueous dispersion of the release agent composition is not particularly limited, but is preferably more than 25% by weight and not more than 75% by weight, more preferably 35 to 70% by weight, and even more preferably 45 to 60% by weight.

[0055] The viscosity of the aqueous dispersion of the release agent composition at 20° C. is not particularly limited, but is preferably 100 to 50,000 mPa·s, and more preferably 150 to 30,000 mPa·s. The viscosity of the aqueous dispersion of the release agent composition at 20° C. can be measured using a B-type rotational viscometer.

[0056] The aqueous dispersion of the release agent composition can be produced using an apparatus equipped with a very simple mechanism such as a container and a stirring blade. Examples of such an apparatus include a homomixer, a homogenizer, a colloid mill, and a line mixer.

[0057] Examples of methods for attaching the aqueous dispersion of the release agent composition to an object include a method of spraying the composition with a spray gun to form a mist, a method of applying the composition to the surface of the object with a brush, etc. Another example is a method of immersing the raw materials for the movable mold of the mold frame or unvulcanized rubber in the aqueous dispersion of the release agent composition.

[0058] The method for producing a vulcanized rubber according to the second aspect of the present invention includes step 1 of applying the aqueous dispersion of the above-mentioned mold release agent composition to at least one of the surface of an unvulcanized rubber and the surface of a mold form and volatilizing the water, and step 2 of heating the unvulcanized rubber to vulcanize it after step 1. Step 1 allows the release agent composition to adhere to the interface between the unvulcanized rubber and the mold. In the case of the method for producing a vulcanized rubber according to the second embodiment of the present invention, the position where the aqueous dispersion of the mold release agent composition is applied is not particularly limited, but is preferably at least one of the surface of the unvulcanized rubber and the surface of the movable mold that comes into contact with the unvulcanized rubber, more preferably the surface of the unvulcanized rubber, and even more preferably the surface of the unvulcanized rubber that comes into contact with the movable mold. When the movable mold is a bladder and the resulting vulcanized rubber is a tire, the surface of the unvulcanized rubber that comes into contact with the movable mold becomes the inner surface of the tire.

[0059] The temperature at which water is evaporated is not particularly limited, but is preferably 20 to 120°C, more preferably 20 to 100°C, and even more preferably 25 to 100°C. The period for volatilizing water is not particularly limited, but is preferably 0.1 to 10 hours, more preferably 0.3 to 8 hours, and even more preferably 0.5 to 5 hours.

[0060] In the method for producing vulcanized rubber of the present invention, the amount of the release agent composition applied varies depending on the application and size of the vulcanized rubber, but is preferably 10 to 50 g / m 2 It is preferable that the coating amount is 10 g / m 2 If the amount is more than 50 g / m, sufficient releasability tends to be obtained. 2 If it is less than this, there is a tendency for the pollution of the working environment to be reduced.

[0061] In the method for producing vulcanized rubber of the present invention, it is preferable that the mold is heated when the unvulcanized rubber is heated to vulcanize it. The temperature of the heated mold is not particularly limited, but is preferably 100 to 300°C, more preferably 110 to 260°C, even more preferably 120 to 220°C, and particularly preferably 130 to 180°C. When the mold has a fixed mold and a movable mold, it is preferable that at least one of the fixed mold and the movable mold is heated to a temperature within the above range.

[0062] When the mold has a fixed mold and a movable mold, the movable mold moves to the fixed mold and presses the unvulcanized rubber on the side that is not in contact with the movable mold against the inner surface of the fixed mold. At this time, at least one of the fixed mold and the movable mold is heated, so that the unvulcanized rubber is heated and vulcanized. Furthermore, if the movable mold is a bladder, it is preferable because unvulcanized rubber can be produced efficiently. When using a bladder to heat and vulcanize unvulcanized rubber, high-temperature, high-pressure gas (e.g., steam at about 180°C) or liquid is introduced into the bladder to expand it and press the unvulcanized rubber against the fixed mold, whereby the unvulcanized rubber is heated and vulcanized. The shape of the bladder is not particularly limited, and examples thereof include a sheet, a film, a hose, a tube, a sponge, a packing, a belt, etc. The bladder may also have grooves for allowing air to escape when vulcanizing the unvulcanized rubber.

[0063] Products obtainable by the method for producing vulcanized rubber of the present invention are not particularly limited, but examples thereof include tires, hoses, anti-vibration rubber, automobile belts, seals, fenders, conveyor belts, elastic sleepers, rubber pads, rubber mats, seismic isolation rubber, sealing materials, waterproofing agents, rubber electric wires, rubber cables, condoms, rubber gloves, rubber balloons, gaskets, packing, and rubber balls, with tires being preferred among these. Examples of tires include automobile tires for passenger cars, automobile tires for trucks and buses, automobile tires for sports cars, racing car tires, aircraft tires, motorcycle tires, bicycle tires, buggy tires, agricultural tires, rubber crawlers, etc. [Example]

[0064] The present invention will be specifically described below with reference to examples and comparative examples. The present invention is not limited to these examples. In the following examples and comparative examples, "parts" means "parts by weight" unless otherwise specified. Furthermore, hereinafter, the release agent composition for vulcanized rubber may be referred to as the "release agent composition" for simplicity. In the following examples and comparative examples, the physical properties were measured and evaluated as follows.

[0065] <Measurement of the weight ratio of crystalline silica> The weight percentage of crystalline silicic acid in each sample was measured by powder X-ray diffraction. When the measured value was below the detection limit, it was taken as 0% by weight.

[0066] <Evaluation of dispersion stability> 10 mL of the prepared aqueous dispersion of the release agent composition was placed in a 15 mL centrifuge tube (made of polypropylene) and allowed to stand at 40°C for one week. After standing, the ratio of the volume of the transparent supernatant to the total volume of the sample liquid in the centrifuge tube was measured visually and defined as the water synergy rate (vol %) of the aqueous dispersion of the release agent composition. From the obtained water synergy rate, the dispersion stability of the release agent composition was evaluated using the following index. ○: Syneresis rate is 2% or less △: Syneresis rate is over 2% and 5% or less ×: Syneresis rate is over 5%

[0067] <Evaluation of redispersibility> 10 mL of the prepared aqueous dispersion of the release agent composition was placed in a 15 mL centrifuge tube (made of polypropylene), and the weight (W1) of the aqueous dispersion of the release agent composition that had been placed was measured. Next, the centrifuge tube containing the aqueous dispersion of the release agent composition was left standing at 40°C for one week. After being left standing, the centrifuge tube was shaken up and down 20 times to redisperse the sample, and a sample was then taken out. After the sample was taken out, the weight (W2) of the residue remaining in the centrifuge tube was measured. The redispersibility of the release agent composition was evaluated using the following index based on the ratio of the weight (W2) of the residue to the weight (W1) of the aqueous dispersion of the release agent composition that had been placed (residue ratio, 100 × (W2 / W1) wt%). ◎: Residue rate is 20% by weight or less ○: Residue rate is more than 20% by weight and 25% by weight or less △: Residue rate is over 25% by weight and 30% by weight or less ×: Residue rate exceeds 30% by weight

[0068] <Evaluation of releasability> An unvulcanized rubber test piece measuring 4 cm in width, 7 cm in length, and 0.5 cm in thickness was prepared. The aqueous dispersion of the release agent composition prepared was applied to only one of the horizontal and vertical surfaces of this unvulcanized rubber test piece using a sprayer, and then dried at 25°C until the amount of adhesion after drying was 20 g / cm. 2 An unvulcanized rubber specimen for evaluation was obtained. Next, a piece of unvulcanized rubber measuring 4 cm wide x 7 cm long x 0.5 cm thick, intended to be a bladder, was placed on the coated surface of the unvulcanized rubber for evaluation, and the unvulcanized rubber for evaluation was vulcanized by pressing at a temperature of 160°C and a pressure of 2 MPa for 20 minutes. After vulcanization was complete, the releasability of the vulcanized rubber from the intended bladder rubber was evaluated. The evaluation criteria were as follows: The vulcanized rubber and the rubber intended for the bladder were peeled off at an angle of 180 degrees, and the peel load required for this was measured using a tensile tester. The releasability was evaluated according to the following criteria. A rating of ○ or higher was considered a pass. ◎: Peeling load is 20N or less ○: Peel load is over 20N and 25N or less △: Peel load is over 25N and 30N or less ×: Peel load exceeds 30N

[0069] Example 1 20 parts of mica 1, 69.7 parts of talc 1, and 0.3 parts of carboxymethylcellulose sodium (CMC-Na) were placed in a 200 L ribbon blender and mixed for 30 minutes. The resulting mixture was then transferred to a 200 L Nauta mixer, and while mixing, 10 parts of silicone 1 were gradually added, and mixed for 60 minutes after the addition. The mixture was then crushed and classified using a sieve to obtain a powdery release agent composition. 50 parts of the obtained release agent composition were placed in a 200 L stainless steel cylinder, and 50 parts of tap water were added thereto. The mixture was dissolved and dispersed for 30 minutes at a rotation speed of 3,000 rpm using a homodisper to obtain an aqueous dispersion of the release agent composition. The dispersion stability, redispersibility, and releasability of the obtained aqueous dispersion of the release agent composition were evaluated by the methods described above. The evaluation results, as shown in Table 1, showed that the dispersion stability, redispersibility, and releasability were all good.

[0070] (Examples 2 to 17, Comparative Examples 1 to 6) In Examples 2 to 17 and Comparative Examples 1 to 6, powdery release agent compositions and aqueous dispersions thereof were obtained and evaluated in the same manner as in Example 1, except that the raw materials and their blending amounts were changed as shown in Tables 1 and 2. The evaluation results are shown in Tables 1 and 2. The details of the compounds shown in Tables 1 and 2 are as follows: In the compounds shown in Tables 1 and 2, POE means polyoxyethylene, and the number in parentheses following POE indicates the average number of moles of oxyethylene added. Mica 1: average particle size 10 μm, weight percentage of crystalline silica 0% by weight Mica 2: average particle size 25 μm, weight ratio of crystalline silica 1% by weight Mica 3: average particle size 25 μm, weight percentage of crystalline silica 5% by weight Talc 1: Average particle size 8 μm, weight percentage of crystalline silica 0% by weight Talc 2: average particle size 25 μm, weight percentage of crystalline silica 0% by weight Sepiolite: crystalline silica weight percentage 1% by weight Bentonite: 7% by weight of crystalline silica Clay: crystalline silica weight ratio 1% by weight Silicone 1: Dimethyl silicone oil, viscosity 10,000 mm 2 / s Silicone 2: Dimethyl silicone oil, viscosity 100,000 mm 2 / s Silicone 3: Dimethyl silicone oil, viscosity 100mm 2 / s CMC-Na: Sodium carboxymethylcellulose

[0071] [Table 1]

[0072] [Table 2]

[0073] As can be seen from Examples 1 to 17, it has been confirmed that the object of the present invention can be achieved by using a release agent composition containing an inorganic component (A) and a hydrophobic silicone (B) in which the weight ratio of crystalline silica to the nonvolatile content of the release agent composition is 2% by weight or less. On the other hand, when the inorganic component (A) was not included (Comparative Example 5), when the hydrophobic silicone (B) was not included (Comparative Example 6), or when the weight ratio of crystalline silica exceeded 2% by weight (Comparative Examples 1 to 4), the problem of the present application could not be solved.

Claims

1. A release agent composition for vulcanized rubber, comprising an inorganic component (A) and a hydrophobic silicone (B), A release agent composition for vulcanized rubber, wherein the weight ratio of crystalline silica to the nonvolatile content of the release agent composition for vulcanized rubber is 2% by weight or less.

2. 2. The mold release agent composition for vulcanized rubber according to claim 1, wherein the inorganic component (A) comprises mica (a1).

3. 3. The release agent composition for vulcanized rubber according to claim 2, wherein the weight ratio of the mica (a1) to the inorganic component (A) is 0.1 to 50% by weight.

4. 4. The mold release agent composition for vulcanized rubber according to claim 1, wherein the content of the hydrophobic silicone (B) is 1 to 30 parts by weight per 100 parts by weight of the inorganic component (A).

5. The release agent composition for vulcanized rubber according to any one of claims 1 to 3, further comprising a surfactant (C).

6. 6. The mold release agent composition for vulcanized rubber according to claim 5, wherein the content of the surfactant (C) is 0.1 to 10 parts by weight based on 100 parts by weight of the inorganic component (A).

7. 4. An aqueous dispersion of a release agent composition for vulcanized rubber, comprising the release agent composition for vulcanized rubber according to claim 1 and water.

8. 4. A method for producing vulcanized rubber, comprising a step of heating and vulcanizing unvulcanized rubber in a state in which the mold release agent composition for vulcanized rubber according to claim 1 is adhered to the interface between the unvulcanized rubber and a mold.

9. Step 1: Applying the aqueous dispersion of the mold release agent composition for vulcanized rubber according to claim 7 to at least one of the surface of unvulcanized rubber and the surface of a mold, and volatilizing the water; A method for producing vulcanized rubber, comprising, after step 1, step 2 of heating the unvulcanized rubber to vulcanize it.

Images