Process oil for rubber

Abstract

Provided is a process oil for rubber, said process oil containing at least 25 mass% of an ester compound (A), wherein the ester compound (A) has a dynamic viscosity of 5.0 mm2 / s or higher at 100°C and a hydroxyl value of 5.0 mgKOH / g or less. The ester compound (A) preferably has an iodine value of less than 2.5 g I2 / 100g. Furthermore, the ester compound (A) preferably has a (poly)glycerin skeleton.

Description

Rubber processing oil

[0001] This invention relates to a process oil for rubber.

[0002] Rubber compositions undergo various processing steps to become molded articles, depending on the intended use and required properties of the final product. Process oils are added to improve the processability of the rubber composition. Various process oils using mineral oil have been proposed (see, for example, Patent Document 1).

[0003] Japanese Patent Publication No. 2009-013421

[0004] In recent years, from the perspective of moving away from fossil fuels, there has been a desire for the creation of process oils containing lubricants that can replace or partially replace petroleum-derived mineral oils. However, currently, sufficient research has not been conducted on process oils that can impart good viscoelastic properties to rubber compositions while suppressing bleeding and stickiness.

[0005] Therefore, the object of the present invention is to provide a process oil for rubber that can impart good viscoelastic properties to a rubber composition while suppressing bleeding and stickiness of the rubber composition.

[0006] The present invention provides the following [1] to [4]: ​​[1] A compound containing 25% by mass or more of an ester compound (A), wherein the kinematic viscosity of the ester compound (A) at 100°C is 5.0 mm ２ [2] A rubber process oil having a hydroxyl value of 5.0 mg KOH / g or less of the ester compound (A). [3] A rubber composition containing the rubber process oil described in [1] above. [4] A method for producing a rubber process oil, comprising the step of blending ester compound (A) at a rate of 25% by mass or more on a total basis of the rubber process oil, wherein the kinematic viscosity of ester compound (A) at 100°C is 5.0 mm ２A method for producing a rubber process oil, wherein the hydroxyl value of the ester compound (A) is 5.0 mg KOH / g or less, and the hydroxyl value of the ester compound (A) is 5.0 mg KOH / g or less. [4] A method for producing a rubber composition, comprising the step of mixing the rubber process oil described in [1] above with rubber.

[0007] According to the present invention, it is possible to provide a process oil for rubber that can impart good viscoelastic properties to a rubber composition while suppressing bleeding and stickiness of the rubber composition.

[0008] The upper and lower limits of the numerical ranges described herein can be combined in any way. For example, if the numerical ranges "A to B" and "C to D" are described, the numerical ranges "A to D" and "C to B" are also included within the scope of the present invention. Furthermore, unless otherwise specified, the numerical ranges "lower limit to upper limit" described herein mean greater than or equal to the lower limit and less than or equal to the upper limit.

[0009] [Description of the rubber process oil] The rubber process oil of this embodiment contains 25% by mass or more of ester compound (A). Ester compound (A) has a kinematic viscosity of 5.0 mm at 100°C. ２ The kinematic viscosity is 5.0 mg KOH / g or more, and the hydroxyl value is 5.0 mg KOH / g or less. As a result of diligent research by the inventors, the kinematic viscosity at 100°C is 5.0 mm ２ We discovered that by using a process oil containing 25% by mass or more of an ester compound (A) having a hydroxyl value of 5.0 mgKOH / g or less and a hydroxyl value of 0.0 mgKOH / g or less, it is possible to impart good viscoelastic properties to the rubber composition while suppressing bleeding and stickiness. After further investigations, we completed the present invention.

[0010] Hereinafter, the components constituting the process oil for rubber of the present embodiment, the physical properties of the process oil for rubber, the production method of the process oil for rubber, the uses of the process oil for rubber, and the production method of the rubber composition will be described in detail. In addition, in this specification, the "ester compound (ester compound (A) and ester compound (B))" means an ester that is a dehydration condensate of an alcohol and a carboxylic acid. Here, in the present embodiment, the ester compound (ester compound (A) and ester compound (B)) is preferably a non-aromatic ester. By the ester compound being a non-aromatic ester, it becomes possible to prevent the scattering of aromatic components into the working environment and provide a process oil for rubber with excellent working environmental properties.

[0011] <Ester Compound (A)> The process oil for rubber of the present embodiment contains an ester compound (A).

[0012] (Kinematic Viscosity of Ester Compound (A) at 100 °C) In the present embodiment, the ester compound (A) requires a kinematic viscosity at 100 °C of 5.0 mm ２ / s or more. When the kinematic viscosity of the ester compound (A) at 100 °C is 5.0 mm <00000​​​​​​​​​​​​​２ / s or less, more preferably 18.0 mm ２ It is less than or equal to / s. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, 8.0 mm is preferred. ２ / s ~ 30.0 mm ２ / s, more preferably 10.0 mm ２ / s ~ 25.0 mm ２ / s, more preferably 12.0 mm ２ / s ~ 20.0 mm ２ / s, more preferably 14.0 mm ２ / s ~ 18.0 mm ２ The value is / s. In this specification, kinematic viscosity at 100°C means the value measured in accordance with JIS K2283:2000.

[0013] (Hydroxyl value of ester compound (A)) In this embodiment, ester compound (A) is required to have a hydroxyl value of 5.0 mgKOH / g or less. By having a hydroxyl value of 5.0 mgKOH / g or less of ester compound (A), good viscoelastic properties can be imparted to the rubber composition while suppressing bleeding and tackiness of the rubber composition. Herein, from the viewpoint of making it easier to further improve the effects of the present invention, the hydroxyl value of ester compound (A) is preferably 4.0 mgKOH / g or less, more preferably 3.0 mgKOH / g or less, and even more preferably less than 3.0 mgKOH / g. In this specification, the hydroxyl value means the value measured in accordance with JIS K 0070:1992.

[0014] (Iodine value of ester compound (A)) In this embodiment, ester compound (A) has an iodine value of 2.5 gI ２ It is preferable that the iodine value of the ester compound (A) is less than 100g. ２ If the amount is less than 100g, the effects of the present invention can be more easily improved. Here, from the viewpoint of further improving the effects of the present invention, the iodine value of the ester compound (A) is more preferably 0.5gI ２ / 100g to 2.0g ２ / 100g, more preferably 0.8g ２ / 100g to 1.7g２ / 100 g, more preferably 1.0 g I ２ / 100 g to 1.5 g I ２ / 100 g. In this specification, the iodine value means a value measured in accordance with JIS K 0070:1992.

[0015] (Structure of the ester compound (A)) In the present embodiment, the ester compound (A) preferably has a (poly)glycerol skeleton. In other words, the ester compound (A) is preferably an ester of (poly)glycerol, which is a polyhydric alcohol, and a carboxylic acid. By the ester compound (A) having a (poly)glycerol skeleton, it is easier to further improve the effects of the present invention. In this specification, “(poly)glycerol” means glycerol or polyglycerol. Polyglycerol means a multimer of glycerol, preferably a dimer to decamer of glycerol, more preferably a dimer to hexamer of glycerol, still more preferably a dimer to tetramer of glycerol, and even more preferably a dimer of glycerol (that is, diglycerol).

[0016] Further, the carboxylic acid constituting the ester compound (A) is preferably a fatty acid having 12 to 24 carbon atoms. By the carboxylic acid constituting the ester compound (A) being a fatty acid having 12 to 24 carbon atoms, it is easier to further improve the effects of the present invention. The fatty acid may be a straight-chain fatty acid or a branched fatty acid, and may be a saturated fatty acid or an unsaturated fatty acid, but from the viewpoint of further easily improving the effects of the present invention, it is preferably a saturated branched fatty acid. Further, from the viewpoint of further easily improving the effects of the present invention, the number of carbon atoms of the fatty acid is more preferably 14 to 22, still more preferably 16 to 20, and even more preferably 18.

[0017] In this embodiment, a preferred ester compound (A) is an ester of diglycerin and isostearic acid (an ester of diglycerin and isostearic acid containing polyglyceryl-2 tetraisostearate, which is a full ester). Here, from the viewpoint of providing a rubber process oil with a high biomass content, it is preferable that the ester compound (A) is an ester compound having biomass-derived carbon. Specifically, examples include ester oils synthesized from vegetable oils such as palm oil, coconut oil, soybean oil, rapeseed oil, and mixtures thereof. Commercially available ester compounds (A) can also be used. Examples of commercially available products include Cosmoll 44V (manufactured by Nisshin Oillio Co., Ltd.). One type of ester compound (A) may be used alone, or two or more types may be used in combination.

[0018] (Content of ester compound (A)) In this embodiment, the content of ester compound (A) must be 25% by mass or more based on the total amount of rubber process oil. By having a content of ester compound (A) of 25% by mass or more based on the total amount of rubber process oil, it is possible to impart good viscoelastic properties to the rubber composition while suppressing bleeding and stickiness of the rubber composition. Herein, from the viewpoint of making it easier to further improve the effects of the present invention, the content of ester compound (A) is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass, based on the total amount of rubber process oil.

[0019] Here, the rubber process oil of this embodiment preferably contains ester compound (B), described later, together with ester compound (A), from the viewpoint of imparting good viscoelastic properties to the rubber composition. When the rubber process oil of this embodiment further contains ester compound (B), the content of ester compound (A) is preferably 25% by mass or more, more preferably 30% by mass or more, even more preferably 35% by mass or more, even more preferably 40% by mass or more, and still more preferably 43% by mass or more, based on the total amount of the rubber process oil, from the viewpoint of making it easier to further improve the effects of the present invention (particularly from the viewpoint of imparting good viscoelastic properties to the rubber composition). Also, from the same viewpoint, it is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, the amount is preferably 25% to 60% by mass, more preferably 30% to 60% by mass, even more preferably 35% to 55% by mass, even more preferably 40% to 55% by mass, and still more preferably 43% to 50% by mass.

[0020] <Ester compound (B)> The rubber process oil of this embodiment preferably contains, together with ester compound (A), ester compound (B) having a hydroxyl value of more than 5.0 mg KOH / g and 15.0 mg KOH / g or less. By containing ester compound (B) together with ester compound (A) in the rubber process oil of this embodiment, it is possible to suppress bleeding and stickiness of the rubber composition while making it easier to impart good viscoelastic properties to the rubber composition. Here, the hydroxyl value of ester compound (B) is preferably 6.0 mg KOH / g to 15.0 mg KOH / g, more preferably 7.0 mg KOH / g to 13.0 mg KOH / g, and even more preferably 8.0 mg KOH / g to 11.0 mg KOH / g, from the viewpoint of making it easier to further improve the effects of the present invention (particularly from the viewpoint of imparting good viscoelastic properties to the rubber composition).

[0021] (Iodine value of ester compound (B)) In this embodiment, ester compound (B) has an iodine value of 30 gI ２Preferably, the iodine value of the ester compound (B) is 30 gI. ２ If the amount is 100g or more, the effects of the present invention can be more easily improved. Here, from the viewpoint of further improving the effects of the present invention, the iodine value of the ester compound (B) is more preferably 30gI ２ / 100g~60gI ２ / 100g, more preferably 40g ２ / 100g~55gI ２ / 100g, more preferably 45g ２ / 100g~50gI ２ It is / 100g.

[0022] (Kinematic viscosity of ester compound (B) at 100°C) In this embodiment, the kinematic viscosity of ester compound (B) at 100°C is preferably 15.0 mm, from the viewpoint of making it easier to improve the effects of the present invention and from the viewpoint of improving the friction suppression effect during the kneading process when manufacturing rubber compositions. ２ / s ~ 60mm ２ / s, more preferably 20.0 mm ２ / s ~ 50mm ２ / s, more preferably 25.0 mm ２ / s ~ 45mm ２ / s, more preferably 30.0 mm ２ / s ~ 40mm ２ It is / s.

[0023] (Preferred Embodiment of Ester Compound (B)) In this embodiment, preferred ester compound (B) is an ester of a fatty acid mainly composed of a polymer of trimethylolpropane (TMP) and a saturated fatty acid having 10 carbon atoms (preferably containing 50% or more by mass of saturated fatty acids having 10 carbon atoms based on the total amount of fatty acids). Here, from the viewpoint of providing a rubber process oil with a high biomass content, ester compound (B) is preferably an ester compound having biomass-derived carbon. Specifically, examples include ester oils synthesized from vegetable oils such as palm oil, coconut oil, soybean oil, rapeseed oil, and mixtures thereof. Commercially available ester compound (B) can also be used. Examples of commercially available products include Priolubé 2088 (manufactured by Cargill). Ester compound (B) may be used alone or in combination of two or more types.

[0024] (Total content of ester compound (A) and ester compound (B)) When the rubber process oil of this embodiment contains ester compound (A) and ester compound (B), the total content of ester compound (A) and ester compound (B) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 99% by mass or more, and still more preferably 100% by mass, based on the total amount of the rubber process oil, from the viewpoint of making it easier to further improve the effects of the present invention.

[0025] (Content of ester compound (B)) When the rubber process oil of this embodiment contains ester compound (A) and ester compound (B), the content of ester compound (B) is preferably 40% by mass or more, more preferably 45% by mass or more, and even more preferably 50% by mass or more, based on the total amount of the rubber process oil, from the viewpoint of making it easier to improve the effects of the present invention (particularly from the viewpoint of imparting good viscoelastic properties to the rubber composition). Also from the same viewpoint, it is preferably 75% by mass or less, more preferably 70% by mass or less, even more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, and even more preferably 57% by mass or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 40% by mass to 75% by mass, more preferably 40% by mass to 70% by mass, even more preferably 45% by mass to 65% by mass, even more preferably 45% by mass to 60% by mass, and even more preferably 50% by mass to 57% by mass. Furthermore, when the rubber process oil of this embodiment contains ester compound (A) and ester compound (B), the content of ester compound (A) is as previously described.

[0026] (Ratio of ester compound (A) and ester compound (B)) When the rubber process oil of this embodiment contains ester compound (A) and ester compound (B), the ratio of ester compound (A) to ester compound (B) [(A) / (B)] is preferably 25 / 75 to 60 / 40 by mass, more preferably 30 / 70 to 60 / 40, even more preferably 35 / 65 to 55 / 45, even more preferably 40 / 60 to 55 / 45, and still more preferably 43 / 57 to 50 / 50, from the viewpoint of making it easier to further improve the effects of the present invention (particularly from the viewpoint of imparting better viscoelastic properties to the rubber composition).

[0027] <Other Components> The rubber process oil of this embodiment may contain other components besides ester compound (A) and ester compound (B), to the extent that they do not significantly impair the effects of the present invention. Examples of other components include other base oil components other than ester compound (A) and ester compound (B). Examples of other base oil components include mineral oil and ester compound (C) other than ester compound (A) and ester compound (B). However, from the viewpoint of improving the effects of the present invention, it is preferable that the mineral oil content be low. Specifically, the mineral oil content is preferably less than 50% by mass, more preferably less than 30% by mass, even more preferably less than 10% by mass, even more preferably less than 1% by mass, and even more preferably no mineral oil at all, based on the total amount of rubber process oil. Furthermore, from the viewpoint of improving the effects of the present invention, it is preferable that the ester compound (C) content be low. Specifically, the content of ester compound (C) is preferably less than 50% by mass, more preferably less than 30% by mass, even more preferably less than 10% by mass, even more preferably less than 1% by mass, and even more preferably no ester compound (C) at all, based on the total amount of rubber process oil. It is preferable that ester compound (C) is a non-aromatic ester. If ester compound (C) is an aromatic ester, from the viewpoint of improving the working environment, the content of ester compound (C) is preferably less than 3% by mass, more preferably less than 1% by mass, and even more preferably no ester compound (C) at all, based on the total amount of rubber process oil.

[0028] <Physical Properties of Rubber Process Oil> From the viewpoint of improving the effects of the present invention, it is preferable that the rubber process oil of this embodiment satisfies the following physical properties.

[0029] (Kinematic viscosity at 100°C) The rubber process oil of this embodiment preferably has a kinematic viscosity at 100°C of 10.0 mm. ２ / s ~ 50.0 mm ２ / s, more preferably 15.0 mm ２ / s ~ 40.0 mm ２ / s, more preferably 20.0 mm ２ / s ~ 35.0 mm２ The value is / s. Furthermore, by having a kinematic viscosity at 100°C that is above the above lower limit, a good friction suppression effect is exhibited during the kneading process when manufacturing the rubber composition, and effects such as suppression of heat generation and adverse effects on the kneading equipment are also exhibited.

[0030] (Acid Value) The rubber process oil of this embodiment has an acid value of preferably 0.10 mg KOH / g to 0.80 mg KOH / g, more preferably 0.15 mg KOH / g to 0.60 mg KOH / g, and even more preferably 0.20 mg KOH / g to 0.50 mg KOH / g. In this specification, the acid value is a value measured in accordance with JIS K2501-7:2003.

[0031] (Base Number) The rubber process oil of this embodiment has a base number of preferably less than 0.1 mg KOH / g, more preferably less than 0.05 mg KOH / g, and even more preferably less than 0.01 mg KOH / g. In this specification, the base number is a value measured by the hydrochloric acid method in accordance with JIS K2501-8:2003.

[0032] (Saponification Value) The rubber process oil of this embodiment has a saponification value of preferably 150 mg KOH / g to 300 mg KOH / g, more preferably 180 mg KOH / g to 270 mg KOH / g, and even more preferably 200 mg KOH / g to 250 mg KOH / g. In this specification, the saponification value is a value measured in accordance with JIS K 2503:2010.

[0033] (Hydroxyl value) The rubber process oil of this embodiment has a hydroxyl value of preferably 9.0 mgKOH / g or less, more preferably 3.0 mgKOH / g to 8.5 mgKOH / g, and even more preferably 4.0 mgKOH / g to 8.0 mgKOH / g.

[0034] (Iodine value) The rubber process oil of this embodiment preferably has an iodine value of 0.1 gI ２ / 100g to 45.0g ２ / 100g, more preferably 10.0g ２ / 100g to 42.0g ２ / 100g, more preferably 20.0g２ / 100g to 40.0g ２ This is per 100g. In this specification, the iodine value is the value measured in accordance with JIS K 0070:1992.

[0035] (Density at 15°C) The rubber process oil of this embodiment preferably has a density of 0.920 g / cm³ at 15°C. ３ ~0.955g / cm ３ , more preferably 0.930 g / cm³ ３ ~0.952g / cm ３ More preferably 0.940 g / cm³ ３ ~0.950g / cm ３ In this specification, the density at 15°C is the value measured in accordance with JIS K 2249-1:2011 (Crude oil and petroleum products - Method for determining density - Part 1: Vibration method).

[0036] (Flash point by Cleveland Open Method) The rubber process oil of this embodiment has a flash point by the Cleveland Open Method preferably between 260°C and 290°C, more preferably between 262°C and 285°C, and even more preferably between 265°C and 280°C. In this specification, the flash point is a value measured by the Cleveland Open Method (COC) in accordance with JIS K 2265-4:2007.

[0037] [Method for Manufacturing Rubber Process Oil] The method for manufacturing the rubber process oil of this embodiment is not particularly limited. For example, the method for manufacturing the rubber process oil of this embodiment includes a step of blending ester compound (A) at a rate of 25% by mass or more based on the total amount of rubber process oil. Ester compound (A) has a kinematic viscosity of 5.0 mm at 100°C. ２The hydroxyl value is 5.0 mgKOH / g or less, and the hydroxyl value is 5.0 mgKOH / g or less. Furthermore, the process may further include a step of incorporating ester compound (B) as needed, and a step of incorporating other components. The preferred embodiments of ester compound (A), ester compound (B), and other components are as previously described. The amounts and ratios of ester compound (A), ester compound (B), and other components are preferably those corresponding to the preferred content and ratio of ester compound (A), ester compound (B), and other components described above.

[0038] [Applications of the rubber process oil] The rubber process oil of this embodiment can suppress bleeding and stickiness of rubber compositions, and can also improve the viscoelastic properties of rubber compositions. Therefore, the rubber process oil of this embodiment can be suitably used as a process oil for various products containing rubber compositions, such as in molding applications for tires.

[0039] [Rubber Composition] The rubber composition of this embodiment contains the rubber process oil of this embodiment, and therefore bleed and stickiness are suppressed, and it has good viscoelastic properties. Here, it is preferable that the rubber composition of this embodiment satisfies the following physical properties.

[0040] <Bleed suppression> In the evaluation of bleed suppression of the rubber composition containing the rubber process oil of this embodiment, it is preferable that no oil stains are observed on the release paper according to the method described in the examples below.

[0041] <Adhesion Suppression> In the rubber composition containing the rubber process oil of this embodiment, it is preferable that, in the evaluation of adhesiveness by the method described in the examples below, no elongation due to adhesive force is observed when the rubber composition is peeled off.

[0042] <Viscoelastic properties 1: Breaking stress> The rubber composition containing the rubber process oil of this embodiment has a breaking stress, as measured by the method described in the examples below, preferably 8.0 MPa or higher, more preferably 9.0 MPa or higher, even more preferably 9.3 MPa, even more preferably 9.6 MPa or higher, and still more preferably 10.0 MPa or higher. Having a breaking stress within the above range provides the rubber composition with good tensile strength.

[0043] <Viscoelastic properties 2: Fracture strain> The rubber composition containing the rubber process oil of this embodiment has a fracture strain, as measured by the method described in the examples below, preferably 500% or more, more preferably 560% or more, even more preferably 600% or more, even more preferably 630% or more, and still more preferably 700% or more. The fracture strain being within the above range gives the rubber composition good flexibility.

[0044] [Method for Manufacturing the Rubber Composition] The method for manufacturing the rubber composition of this embodiment is not particularly limited as long as it is a manufacturing method using the rubber process oil of this embodiment, but for example, it includes a step of mixing the rubber process oil of this embodiment with rubber.

[0045] <Rubber> In the method for producing the rubber composition of this embodiment, examples of rubber include styrene-butadiene rubber (hereinafter also referred to as "SBR"), butadiene rubber, isoprene rubber, butyl rubber, halogenated butyl rubber, ethylene propylene diene rubber, butadiene acrylonitrile copolymer rubber, chloroprene rubber, and natural rubber. Among these, SBR is preferred.

[0046] <Additives> In the method for producing the rubber composition of this embodiment, additives may be further added to the rubber composition. Examples of additives to be added to the rubber composition include one or more general-purpose additives for rubber compositions, such as antioxidants, ultraviolet absorbers, lubricants, flame retardants, antistatic agents, fillers, and foaming agents.

[0047] <Manufacturing Conditions> In the method for manufacturing the rubber composition of this embodiment, the mixing conditions of the rubber process oil and the rubber are not particularly limited, and the usual conditions for compounding and mixing (kneading) rubber with process oil can be used. In addition, in the method for manufacturing the rubber composition of this embodiment, the amount of process oil compounded with the rubber is preferably 10 to 100 parts by mass, more preferably 20 to 80 parts by mass, and even more preferably 30 to 60 parts by mass, per 100 parts by mass of rubber.

[0048] <Molding Process> The method for producing the rubber composition of this embodiment may further include a molding process for obtaining a molded product. The molding method for obtaining the molded product is not particularly limited and includes, for example, extrusion molding, injection molding, blow molding, and calendering.

[0049] [One aspect of the present invention provided] According to one aspect of the present invention, the following [1] to

[11] are provided. [1] A compound containing 25% by mass or more of an ester compound (A), wherein the kinematic viscosity of the ester compound (A) at 100°C is 5.0 mm ２ A rubber process oil having a value of 1 / s or more, and the hydroxyl value of the ester compound (A) being 5.0 mg KOH / g or less. [2] A rubber process oil having an iodine value of 2.5 gI ２[1] above, the rubber process oil, wherein the amount is less than 100 g. [3] The rubber process oil, wherein the ester compound (A) has a (poly)glycerin skeleton, wherein the rubber process oil, wherein the ester compound (A) is composed of a fatty acid having 12 to 24 carbon atoms, wherein the rubber process oil, wherein the carboxylic acid constituting the ester compound (A) is a fatty acid having 12 to 24 carbon atoms, wherein the rubber process oil, wherein the hydroxyl value of the rubber process oil is 9.0 mg KOH / g or less, wherein the rubber process oil, wherein the rubber process oil, wherein the hydroxyl value of the rubber process oil is 9.0 mg KOH / g or less, wherein the rubber process oil, wherein the rubber process oil, wherein the hydroxyl value of the ester compound (B) is greater than 5.0 mg KOH / g and 15.0 mg KOH / g or less, wherein the rubber process oil, wherein the total content of the ester compound (A) and the ester compound (B) is 80% by mass or more on a total basis of the rubber process oil, wherein the rubber process oil, wherein the rubber process oil, wherein the total content of the ester compound (A) and the ester compound (B) is 80% by mass or more, based on the total amount of the rubber process oil. [8] The rubber process oil according to [7], wherein the content of the ester compound (A) is 40% by mass or more on a total basis of the rubber process oil. [9] A rubber composition containing the rubber process oil according to any one of the above items [1] to [8].

[10] A method for producing a rubber process oil, comprising the step of blending the ester compound (A) at a rate of 25% by mass or more on a total basis of the rubber process oil, wherein the kinematic viscosity of the ester compound (A) at 100°C is 5.0 mm. ２ A method for producing a rubber process oil, wherein the hydroxyl value of the ester compound (A) is 5.0 mg KOH / g or less, and the hydroxyl value of the ester compound (A) is 5.0 mg KOH / g or less.

[11] A method for producing a rubber composition, comprising the step of mixing the rubber process oil described in any one of [1] to [8] above with rubber.

[0050] The present invention will be specifically described by the following examples, but the present invention is not limited to the following examples.

[0051] [Preparation of Process Oil] The raw materials for process oil are as follows. <Ingredients> ・"Ester A1": Cosmol 44V (manufactured by Nisshin Oillio, ester of diglycerin and isostearic acid (contains polyglyceryl-2 tetraisostearate, a full ester, ester of diglycerin and isostearic acid)) ・"Ester B1": Priolubé 2088 (manufactured by Cargill, ester of trimethylolpropane (TMP) polymer and saturated fatty acid (mainly saturated fatty acid with 10 carbon atoms)) ・"Ester C1": Synative ES 1200 (manufactured by BASF, complex ester) ・"Ester C2": Priolubé 2087 (manufactured by Cargill, complex ester) ・"Ester C3": Priolubé 1847 (manufactured by Cargill, complex ester) • "Ester C4": Synative ES 3101 (BASF, complex ester) • "Ester C5": Synative ES 3100 (BASF, synthetic high-performance ester) • "Ester C6": Ngelb HFP-600B (Shin Nippon Rika Co., Ltd., complex ester) • "Ester C7": Cosmoll 43V (Nisshin Oillio Co., Ltd., ester of diglycerin and isostearic acid (ester of glycerin and isostearic acid containing diglyceryl triisostearate, a triester)) • "Ester C8": Cosmoll 42V (Nisshin Oillio Co., Ltd., ester of diglycerin and isostearic acid (ester of glycerin and isostearic acid containing diglyceryl diisostearate, a diester)) • "Ester C9": Cosmol 41V (manufactured by Nisshin Oillio, an ester of diglycerin and isostearic acid (an ester of glycerin and isostearic acid containing diglyceryl diisostearate, which is a monoester)) • "Mineral oil": Diana Process NH-70S (manufactured by Idemitsu Kosan, mineral oil)

[0052] <Measurement of various physical properties of process oil> Process oil was prepared according to the formulation shown in Table 1 (unit: mass%), and various physical properties of the process oil were measured by the following methods. (1) Kinematic viscosity at 100°C Measured in accordance with JIS K2283:2000. (2) Acid value Measured in accordance with JIS K2501-7:2003. (3) Base number Measured by hydrochloric acid method in accordance with JIS K2501-8:2003. (4) Saponification value Measured in accordance with JIS K 2503:2010. (5) Hydroxyl value Measured in accordance with JIS K 0070:1992. (6) Iodine value Measured in accordance with JIS K 0070:1992. (7) Density (15°C) was measured in accordance with JIS K 2249-1:2011 (Crude oil and petroleum products - Method for determining density - Part 1: Vibration method). (8) Flash point was measured in accordance with JIS K 2265-4:2007 using the Cleveland Open-Cold (COC) method.

[0053] Table 1 shows each process oil and its physical properties. The kinematic viscosity at 100°C, iodine value, and hydroxyl value of process oils 2a and 3a were calculated based on the kinematic viscosity at 100°C, iodine value, and hydroxyl value of process oil 1a (Cosmol 44V) and process oil 6b (Priolube 2088), and the blending amounts of Cosmol 44V and Priolube 2088 in process oils 2a and 3a. The above calculations were performed assuming that the hydroxyl value of process oil 1a (Cosmol 44V) is 0 mgKOH / g.

[0054]

[0055] Based on the physical properties shown in Table 1, ester A1 is an ester corresponding to ester compound (A), and ester B1 is an ester corresponding to ester compound (B).

[0056] [Examples 1-3, Comparative Examples 1-10, and Reference Examples] Rubber compositions were produced using the methods described in Examples 1-3, Comparative Examples 1-10, and Reference Examples, and the evaluations described below were carried out.

[0057] <Raw Materials> Details of the raw materials used in Examples 1-3, Comparative Examples 1-10, and the Reference Example are shown below. In Examples 1-3, Comparative Examples 1-10, and the Reference Example, the blending ratio (unit: mass%) of each raw material was as shown in Table 2 below. ・"SBR": SBR1500 (ENEOS Material Co., Ltd.) ・"Carbon Black": Asahi #60U (Asahi Carbon Co., Ltd.) ・"Zinc Oxide": Zinc Oxide Type 2 (Seido Chemical Industry Co., Ltd.) ・"Stearic Acid": Lunac S-70V (Kao Corporation) ・"Sulfur": Fine Sulfur Powder (Hosoi Chemical Industry Co., Ltd.) ・"Vulcanization Accelerator": Noxellar CZ (Ouchi Shinko Chemical Industry Co., Ltd.)

[0058] <Example 1> A mixture of carbon black, zinc oxide, zinc stearate, and process oil 1a was prepared. Then, SBR was placed in a Banbury mixer and kneaded for 1 minute, after which the mixture was placed in the Banbury mixer and kneaded for 4 minutes to obtain a first knead. Sulfur and a vulcanization accelerator were added to the obtained first knead, and rubber kneading was performed at 50°C using two rolls to prevent vulcanization from progressing, to obtain a second knead in which sulfur and vulcanization accelerator were uniformly mixed in the first knead. Then, the second knead was placed in a mold measuring 250 mm × 150 mm × 2 mmt and pressed at a pressure of 20 MPa and a temperature of 145°C for 60 minutes to obtain rubber composition 1a.

[0059] <Examples 2-3> Process oil 1a was changed as follows, and rubber compositions 2a-3a were obtained in the same manner as in Example 1. • Example 2 (rubber composition 2a): Changed to process oil 2a • Example 3 (rubber composition 3a): Changed to process oil 3a

[0060] <Comparative Examples 1-10> Process oil 1a was changed as follows, and rubber compositions 1b-10b were obtained in the same manner as in Example 1. • Comparative Example 1 (rubber composition 1b): Changed to process oil 1b • Comparative Example 2 (rubber composition 2b): Changed to process oil 2b • Comparative Example 3 (rubber composition 3b): Changed to process oil 3b • Comparative Example 4 (rubber composition 4b): Changed to process oil 4b • Comparative Example 5 (rubber composition 5b): Changed to process oil 5b • Comparative Example 6 (rubber composition 6b): Changed to process oil 6b • Comparative Example 7 (rubber composition 7b): Changed to process oil 7b • Comparative Example 8 (rubber composition 8b): Changed to process oil 8b • Comparative Example 9 (rubber composition 9b): Changed to process oil 9b • Comparative Example 10 (rubber composition 10b): Changed to process oil 10b

[0061] <Reference Example> Process oil 1a was changed to process oil c, and rubber composition c was obtained in the same manner as in Example 1. • Reference Example (Rubber Composition c): Changed to process oil c

[0062] [Evaluation] The rubber compositions 1a to 3a obtained in Examples 1 to 3, rubber compositions 1b to 10b obtained in Comparative Examples 1 to 10, and rubber composition c obtained in the Reference Example were evaluated according to the following evaluations 1 to 4.

[0063] <Evaluation 1: Evaluation of Bleed Inhibition> The rubber composition was sandwiched between two release papers (manufactured by Maru Adhesive Co., Ltd., model number "G73AN44") and left to stand at room temperature (23°C) for one week, and the appearance was visually evaluated. In this example, evaluation A was considered acceptable. - Evaluation A: No oil stains on the release paper. - Evaluation B: Oil stains covering less than 50% of the area of ​​the release paper. - Evaluation C: Oil stains covering 50% or more of the area of ​​the release paper.

[0064] <Evaluation 2: Evaluation of Adhesion Inhibition> The rubber composition was cut into JIS-3 dumbbell shapes, stacked in three layers, and stored in a submerged environment at room temperature (23°C) for 17 days. Subsequently, when the three stacked rubber compositions were peeled apart, if the rubber compositions could be peeled apart without stretching due to adhesive force, it was evaluated as evaluation A (no adhesiveness). If adhesive force acted between the stacked rubber compositions when peeling them apart, requiring enough force to stretch the rubber compositions, it was evaluated as evaluation B (adhesion present). In this example, evaluation A was considered acceptable.

[0065] <Evaluation 3: Evaluation of Viscoelastic Properties 1 (Breaking Stress)> The rubber composition was cut into a JIS-3 dumbbell shape, and the breaking stress was measured using an INSTRON 68TMR (manufactured by INSTRON) under the following measurement conditions. (Measurement conditions) ・Temperature: Room temperature (23℃) ・Tensile speed: 500 mm / min ・Chuck distance: 70 mm The higher the breaking stress, the less likely the rubber composition is to break. In this example, a breaking stress of 8.00 MPa or higher was considered acceptable.

[0066] <Evaluation 4: Evaluation of Viscoelastic Properties 2 (Fracture Strain)> The rubber composition was cut into a JIS-3 dumbbell shape, and the fracture strain was measured using an INSTRON 68TMR (manufactured by INSTRON). Specifically, while the rubber composition was being stretched, the distance between the chucks was detected, and the difference from the initial value of the distance between the chucks was defined as ΔL (mm). The tensile nominal strain ε was then calculated as ε = ΔL / 20 × 100 (%), and the tensile nominal strain at the time of fracture was defined as the fracture strain. The greater the fracture stress, the more flexible the rubber composition is. In this example, a fracture strain of 500% or more was considered acceptable.

[0067] The results are shown in Table 2.

[0068]

[0069] From Table 2, the following can be seen: The rubber compositions 1a to 3a of Examples 1 to 3, which used process oils 1a to 3a, are excellent in terms of bleed suppression, adhesion suppression, and viscoelastic properties. In contrast, the rubber compositions 1b to 10b of Comparative Examples 1 to 10, which used process oils 1b to 10b, are inferior in either bleed suppression, adhesion suppression, or viscoelastic properties.

Claims

1. Contains 25% by mass or more of ester compound (A), and the kinematic viscosity of the ester compound (A) at 100°C is 5.0 mm. ２ A rubber process oil having a value of 0.0 mgKOH / g or more, and the hydroxyl value of the ester compound (A) being 5.0 mgKOH / g or less.

2. The iodine value of the ester compound (A) is 2.5 gI ２ The rubber process oil according to claim 1, wherein the amount is less than 100g.

3. The rubber process oil according to claim 1 or 2, wherein the ester compound (A) has a (poly)glycerin skeleton.

4. The rubber process oil according to any one of claims 1 to 3, wherein the carboxylic acid constituting the ester compound (A) is a fatty acid having 12 to 24 carbon atoms.

5. The rubber process oil according to any one of claims 1 to 4, wherein the hydroxyl value of the rubber process oil is 9.0 mgKOH / g or less.

6. The rubber process oil according to any one of claims 1 to 5, further comprising an ester compound (B) having a hydroxyl value greater than 5.0 mg KOH / g and less than or equal to 15.0 mg KOH / g.

7. The rubber process oil according to claim 6, wherein the total content of the ester compound (A) and the ester compound (B) is 80% by mass or more based on the total amount of the rubber process oil.

8. The rubber process oil according to claim 7, wherein the content of the ester compound (A) is 40% by mass or more based on the total amount of the rubber process oil.

9. A rubber composition containing the rubber process oil described in any one of claims 1 to 8.

10. A method for producing a rubber process oil, comprising the step of blending an ester compound (A) at a concentration of 25% by mass or more based on the total amount of the rubber process oil, wherein the kinematic viscosity of the ester compound (A) at 100°C is 5.0 mm². ２ A method for producing rubber process oil, wherein the hydroxyl value of the ester compound (A) is 5.0 mg KOH / g or less, and the hydroxyl value of the ester compound (A) is 5.0 mg KOH / g or less.

11. A method for producing a rubber composition, comprising the step of mixing rubber process oil according to any one of claims 1 to 8 with rubber.

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