Title of Invention	PROCESS OIL AND RUBBER COMPOSITION
Abstract	A process oil of the present invention has properties of: (a) flash point of 250 °C or higher; (b) Saybolt color of + 28 or higher; and (c) ultraviolet absorptivity (198nm) of 1.7 or lower.

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1 DESCRIPTION PROCESS OIL AND RUBBER COMPOSITION TECHNICAL FIELD [0001] The present invention is related to a process oil and a rubber composition formed by applying the process oil to a natural rubber and a synthetic rubber. BACKGROUND ART [0002] A rubber used in various fields such as for mechanical and electric products typically contains a process oil to enhance mechanical property and processability. The process oil is used as constituents of a plasticizer for a thermoplastic resin and a printing ink and as a lubricant or solvent component used for a softener or the like for a recycled asphalt, as well as being added to a rubber material such as a natural rubber and a synthetic rubber. [0003] In recent years, there have been increasing demands for a rubber composition using an EPDM (Ethylene-Propylene-Diene Monomer), an olefinic thermoplastic elastomer, a styrenic thermoplastic elastomer or the like, the rubber composition being used as automobile interior parts. Since the rubber composition is required to have thermal stability and sunlight stability to be used as the automobile interior parts, a white paraffinic process oil with high purity is usually employed. For instance, there has been known a process oil having the following properties: kinematic viscosity at 40 °C = 95 to 300 mm2/s; distillation temperature at 5 vol% in distillation = 445 °C or higher; and color (Saybolt color) = +15 or higher (see, for instance, Patent Document 1). [0004] [Patent Document 1] JP-A- 2000-302919 DISCLOSURE OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION [0005] 2 However, the process oil disclosed in Document 1 does not have sufficient sunlight stability, so that in applications such as the automobile interior parts, which are exposed to the direct sunlight for a long time, the process oil might cause discoloration of a rubber material. [0006] An object of the present invention is therefore to provide a process oil capable of exhibiting properties similar to conventional process oils as well as having excellent thermal stability and sunlight stability, and to provide a rubber composition using the process oil. MEANS FOR SOLVING THE PROBLEMS [0007] A process oil according to an aspect of the present invention has properties of: (a) flash point of 250 °C or higher; (b) Saybolt color of+28 or higher; and (c) ultraviolet absorptivity (198nm) of 1.7 or lower. [0008] According to the aspect of the present invention, since the process oil has the flash point of 250 °C or higher and volatility is low, when being added to and kneaded with a rubber material, little oil vapor is generated, resulting in excellent workability. Further, since the process oil has the ultraviolet absorptivity (198nm) of 1.7 or lower, a rubber composition containing the process oil exhibits excellent sunlight stability. Meanwhile, the present invention was achieved as a result of discovery of which the sunlight stability of a white process oil depends on a trace concentration of an aromatic component contained in the oil. That is, it has been found out that the white process oil with significantly improved sunlight stability can be obtained by controlling the trace amount of the aromatic component to be substantially equal to or lower than a predetermined amount that is set using the ultraviolet absorptivity as an indication. [0009] A rubber composition according to another aspect of the present invention 3 contains the above-described process oil of the present invention. According to the aspect of the present invention, since the rubber composition employs the process oil having the properties as described above, the rubber composition shows excellent workability with little generation of the oil vapor when the process oil is added to and kneaded with the rubber material. Further, since the process oil has the Saybolt color of+28 or higher and the ultraviolet absorptivity (198nm) of 1.7 or lower, the rubber composition containing the process oil also has a sufficient sunlight stability. [0010] In the rubber composition according to the aspect of the present invention, the rubber material is preferably at least one component selected from the group consisting of an EPDM, an olefinic thermoplastic elastomer and a styrenic elastomer. With the arrangement, since the rubber composition is provided with enhanced sunlight stability while employing the widely-used rubber material such as the EPDM, the olefinic thermoplastic elastomer and the styrenic elastomer, a technical value especially in an automobile interior part field can further be enhanced. BEST MODE FOR CARRYING OUT THE INVENTION [0011] A process oil of the present invention has properties of (a) to (c) as shown below: (a) flash point of 250 °C or higher; (b) Saybolt color of+28 or higher; and (c) ultraviolet absorptivity (198nm) of 1.7 or lower. [0012] (a) Flash Point The flash point of the process oil of the present invention should be 250 °C or higher, and preferably 260 °C or higher. When the process oil has the flash point of below 250 °C, amount of evaporation during kneading with a rubber material becomes large, thus resulting in lowering workability. Incidentally, the flash point of the process oil may be measured in compliance with ASTM D 92. 4 [0013] (b) Saybolt Color The Saybolt color of the process oil of the present invention should be +28 or higher, and preferably +30 or higher. When the Saybolt color is below +28, concentration of aromatic component becomes large, which adversely affects the sunlight stability. Incidentally, the Saybolt color may be measured in compliance with ASTM D 1500. [0014] (c) Ultraviolet Absorptivity (198nm) The ultraviolet absorptivity of the process oil of the present invention should be 1.7 or lower, and preferably 1.6 or lower. The ultraviolet absorptivity exceeding 1.7 indicates that there is contained large amount of the aromatic component that adversely affects the sunlight stability, thus degrading the sunlight stability. Note that the ultraviolet absorptivity may be measured in compliance with JIS K 0115. Specifically, the ultraviolet absorptivity is measured as follows: 2.00 gram of a sample is diluted with a hexane to be 50 ml, which is then placed in 1 mm cell and irradiated with the wavelength of 198 nm for measurement. The hexane was provided as a blank in the measurement. [0015] An example of a procedure to manufacture the process oil of the present invention will be described below in detail. [Manufacturing of Vacuum Gas Oil (Manufacturing Step of Vacuum Gas Oil)] In a manufacturing step of a vacuum gas oil, vacuum distillation is performed on an atmospheric residue that is obtained by performing atmospheric distillation on a crude oil, in order to obtain a vacuum gas oil. Here, in order to perform the atmospheric distillation on the crude oil, a conventional atmospheric distillation device and a conventional distillation condition can be used. Specifically, for instance, the crude oil such as a paraffinic crude oil or a naphthenic crude oil, which is an object to be refined, is heated to about 350 °C in a 5 heating furnace or the like and sent out to an atmospheric distillation column, which is then turned into a petroleum vapor in the atmospheric distillation column. After cooling, the petroleum vapor is sequentially fractionated into fractions in the ascending order of boiling points. [0016] Next, further distillation (vacuum distillation) under reduced pressure is performed on the obtained atmospheric residue. The vacuum distillation may be performed using a conventional vacuum distillation device and a conventional operating condition, and the vacuum distillation fractionates the atmospheric residue into fractions such as a vacuum naphtha, a vacuum gas oil and a vacuum residue, from which the vacuum gas oil is obtained. [0017] [Manufacturing of Deasphalted Oil (Manufacturing Step of Deasphalted Oil)] The vacuum residue obtained in the above-described step is separated into an oil component (deasphalted oil) and an asphalt component using a solvent such as a liquefied propane (or a combined solvent of the liquefied propane and a butane). Deasphalting using the liquefied propane is performed by, for instance, adding the liquefied propane to the vacuum residue by an amount of 4.5 to 6 times as large as that of the vacuum residue and setting extraction temperature to 85-95 °C (column top) / 60-75 °C (column bottom ) to extract the deasphalted oil. [0018] [Hydrocracking Step] The vacuum gas oil, the deasphalted oil obtained in each step described above or a mixed oil thereof is hydrocracked under the following conditions. There may be preferably used a catalyst formed of one or more members selected from the group consisting of Ni, Mo, W and Co that is supported by an alumina or a silica as a carrier or a catalyst formed of a noble metal such as Pt and Pd that is supported by a zeolite. The hydrocracking temperature is preferably 300 to 450 °C, more preferably 350 6 to 400 °C. The hydrogen/raw oil ratio is preferably 500 to 10000 Nm3/KL, more preferably 800 to 2000 Nm3/KL. The LHSV is preferably 0.1 to 10 Hr"1, more preferably 0.5 to 2.0 Hr"'. The hydrogen pressure is preferably 10 to 25 MPa, more preferably 15 to 20 MPa. [0019] [Hydrofinishing Step] A hydrocracked oil obtained in the hydrocracking step described above is fractionated into two or more types of distillate oils, each having a specified viscosity, by the vacuum distillation. Then, the distillate oils are further refined under the following conditions to obtain a refined oil having a trace concentration of the aromatic component. There may be preferably used a catalyst formed of one or more members selected from the group consisting of Ni, Mo, W and Co that is supported by an alumina or a silica as a carrier or a catalyst formed of a noble metal such as Pt and Pd that is supported by a zeolite. [0020] The finishing temperature is preferably 200 to 350 °C, more preferably 220 to 320 °C. The hydrogen/raw oil ratio is preferably 500 to 10000 Nm /KL, more preferably 500 to 1000 Nm3/KL. The LHSV is preferably 0.1 to 10 Hr"1, more preferably 0.5 to 2.0 Hr"1. The hydrogen pressure is preferably 10 to 25 MPa, more preferably 15 to 20 MPa. With such conditions for hydrofinishing, the Saybolt color and the ultraviolet absorptivity can be adjusted. [0021] Although the product obtained in the hydrofinishing step described above may be used in situ as a process oil, it is further subjected to vacuum distillation to remove a light component as needed, so that the flash point can be adjusted to be 250 °C or lower. [0022] Since the process oil of the present invention which is obtained as described above has the properties of (a) to (c) described above, the process oil with low volatility and excellent sunlight stability can be realized. 7 By adding the process oil to the rubber material which is at least one component selected from the group consisting of the EPDM, the olefinic thermoplastic elastomer and the styrenic elastomer, various rubber compositions can be properly provided. The obtained rubber compositions can be properly used especially as the automobile interior parts which require sunlight stability. [0023] When a rubber (rubber composition) is manufactured using the process oil of the present invention, the process oil may be added by, for instance, 10 to 50 parts by mass, preferably 20 to 40 parts by mass relative to 100 parts by mass of a rubber material. Also, in order to manufacture the rubber composition, reinforcers such as a carbon black and a silica, a vulcanizing agent, a vulcanizing accelerator, a filler, an antidegradant such as waxes, a softener or a plasticizer, etc. other than the process oil of the present invention, which are generally used in the rubber industry, may appropriately be added, in addition to the process oil of the present invention and the rubber material. [0024] Incidentally, the embodiment described above is only an embodiment illustrating the present invention, and the present invention is not limited to the embodiment but includes modifications and improvements as long as the object and the advantages of the present invention can be achieved. Specific structure and shape of the components in the present invention may be designed in any manner as long as the object and the advantages of the present invention can be achieved. For instance, as long as the process oil has the properties of (a) to (c), the procedure to obtain the process oil may appropriately be adjusted. [Example] [0025] Now, the present invention will be described in more detail with examples and comparisons, the description of which by no means limits the present invention. [Example 1 and 2] (Vacuum Gas Oil Manufacturing Step) 8 By performing the atmospheric distillation on a middle-east crude oil to obtain a fuel oil such as a kerosene and a gas oil and further performing the vacuum distillation on an atmospheric residue from a distillation column bottom to obtain a vacuum gas oil. [0026] (Deasphalting Step) Deasphalting was performed, using a propane as a solvent, on a vacuum residue that was obtained after fractionating the vacuum gas oil in the above-described step to obtain a deasphalted oil. [0027] (Mixing Step) The vacuum gas oil and the deasphalted oil obtained in the above-described steps were mixed by a volume ratio of 60/40 to obtain a mixed oil. (Hydrocracking Step) Using a catalyst having Ni and W supported by an alumina, the hydrocracking was performed on the mixed oil under the following conditions: reaction pressure = 200 Kg/cm ; reaction temperature = 384 °C; LHSV = 1.0 Hr" ; and mixing ratio of hydrogen/mixed oil = 1000 Nm3/KL. A product obtained by the hydrocracking was subjected to the vacuum distillation and fractionated into four types of viscosity fractions, from which heavy fractions having viscosity at 40°C of 94 mm /s and 430 mm /s were sent to a hydrofinishing step. [0028] (Hydrofinishing Step) The hydrofinishing was performed on the two types of fractions described above using the catalyst having Ni and W supported by the alumina under the following conditions: reaction temperature that causes the ultraviolet absorptivity of the product to be 1.7 or lower; reaction pressure = 20 MPa; LHSV = 0.5Hr_1; and mixing ratio of hydrogen/mixed oil = 1000 Nm /KL. Finally, a product having viscosity at 40°C of 92 mm /s was obtained from the fraction having viscosity at 40°C of 94 mm Is, while a product having viscosity at 40°C of 380 mm2/s was obtained from the fraction having 9 viscosity at 40°C of 430 mm /s. The obtained products were respectively provided as process oils of Examples 1 and 2. [0029] [Comparison 1 and 2] Hydrofmishing was performed under the same conditions as the hydrofinishing step for the Examples 1 and 2, except that the reaction temperature was lowered by 10 °C. As a result, products respectively having the ultraviolet absorptivity of 1.8 and 2.0 were obtained. The obtained products were respectively provided as Comparisons 1 and 2. [0030] [Comparison 3] A fraction having viscosity at 40°C of 32 mm Is (a light fraction in the four types of viscosity fractions obtained in Example 1) that has been subjected to hydrofinishing so as to have the ultraviolet absorptivity of 1.2 was mixed with the product having higher viscosity (viscosity at 40°C of 380mm Is) that is obtained in the hydrofinishing step in Example 2, in order to obtain a product with viscosity at 40°C of 95 mm2/s. The obtained product was provided as a process oil of Comparison 3. [0031] [Comparison 4] The product having high viscosity (430 mm2/s) obtained in the hydrocracking step of Example 2 was subjected to sulfuric acid treatment and white clay treatment to be purified, by which a white product having the Saybolt color of +30 was obtained. The obtained product was provided as a process oil of Comparison 4. [0032] [Comparison 5] Hydrofinishing was performed under the same conditions as the hydrofinishing step for Example 1, except that the reaction temperature for the fraction having the viscosity at 40 °C of 94 mm Is was lowered by 5 °C. As a result, a product having the ultraviolet absorptivity of 1.79 was obtained. The obtained product was provided as a process oil of Comparison 5. 10 [0033] [Test Example 1] For the process oils of Examples 1 and 2 and Comparisons 1 to 4, the Saybolt colors after the resistance tests were measured. In addition, volatility of the process oils were also evaluated. Properties and the test results of the process oils are shown in Table 1. Note that the following test method and evaluation method were employed. [0034] (Sunlight Stability Test) The process oils were irradiated by a xenon lamp at 65 °C for 8 hours to measure coloring (Saybolt color) of the process oils. Note that the time corresponds to a condition in which the process oils are exposed outdoors for one month in summer. A process oil having excellent sunlight stability shows almost no coloring, while a process oil with poor sunlight stability shows significant coloring even after several hours. [0035] (Volatility) Measurement was conducted in compliance with JIS K 2540 "Petroleum products-Lubricating oils-Determination of thermal stability". Specifically, 10 gram of a sample process oil was placed in a predetermined container, heated at 200 °C for one hour. Mass loss at this time was evaluated in accordance with the following criteria. A: mass loss of 0.2 mass% or smaller B: mass loss of above 0.2 mass% to 0.3 mass% C: mass loss of above 0.3 mass% 11 [0036] [Table 1] Example 1 Example 2 Comparison 1 Comparison 2 Comparison 3 Comparison 4 Comparison 5 Viscosity at 40°C (mm2/s) 92 380 91.5 381 95 392 96.8 Saybolt color (Initial) +30 +30 +27 +25 +30 +30 +30 Flash point(°C) 258 310 256 310 242 308 274 UV absorptivity 1.45 1.52 1.81 2.05 1.37 >10 1.79 Saybolt color (after sunlight stability test) +22 (not colored) +25 (not colored) -10 (colored) -5 (colored) +24 (not colored) Notably colored -8 (colored) Volatility A A A A B A A [0037] (Result) From Table 1, it was verified that the process oils of Examples 1 and 2 had high flash points and thus had excellent volatility. In addition, the process oils of Examples 1 and 2 showed the ultraviolet absorptivities of 1.7 or lower, which indicated that the contents of the aromatic component having an adverse effect on the sunlight stability were small. Owing to this, the Saybolt colors after the sunlight stability tests showed no coloring, so that it was verified that the process oils of Examples 1 and 2 had excellent sunlight stability. On the other hand, all of the process oils of Comparisons 1, 2 and 4 showed the ultraviolet absorptivity of above 1.7, which indicated that they had poor sunlight stability, so that all of them showed coloring after the sunlight stability test. Especially, since the process oil of Comparison 4 showed the ultraviolet absorptivity of 10 or higher, which was quite high, the coloring was significant. Although the process oil of Comparison 3 showed no coloring, the flash point was below 250 °C, which indicated that it had poor (high) volatility and would show poor operability when being kneaded with rubbers. Although the process oil of Comparison 5 showed the Saybolt color of +30, since the 12 ultraviolet absorptivity exceeded 1.7, coloring after the sunlight stability test was observed. [0038] [Test Example 2] Using the process oils obtained in Examples 1 and 2 and Comparisons 1 to 5 described above, styrenic rubbers were manufactured as described below. 100 parts by mass of a styrenic thermoplastic elastomer ("Kraton G 1652" manufactured by KRATON Polymers, Japan) and 70 parts by mass of the process oil were kneaded and milled by two rolls into a sheet, which was then molded with a die at 200 °C to obtain a rubber sheet with 2 mm thick. The sunlight stability tests with two different irradiation times (24 hours and 78 hours) were conducted on the obtained rubber sheet under the same conditions as Test Example 1, and presence of discoloration (coloring) of the rubber was visually evaluated in accordance with the following criteria. The results are shown in Table 2. A: Not colored B: Slightly colored C: Discolored to yellow D: Discolored to brown [0039] [Table 2] Example 1 Example 2 Comparison 1 Comparison 2 Comparison 3 Comparison 4 Comparison 5 Acceleration time (sunlight stability test) 24 78 24 78 24 78 24 78 24 78 24 78 24 78 Coloring A B A B B C B C A B D - B C [0040] (Result) From Table 2, it was verified that the rubbers of Examples 1 and 2 showed almost no coloring even after the 78-hour sunlight stability test. On the other hand, all the rubbers 13 of Comparisons 1, 2 and 5 discolored into yellow after 78 hours. Especially, the rubber of Comparison 4 showed significant discoloration, the sunlight stability test was discontinued at 24 hours. INDUSTRIAL APPLICABILITY [0041] The process oil according to the present invention can be properly used as a process oil for a rubber composition used as automobile interior parts. 14 CLAIMS [1] A process oil, comprising properties of: (a) flash point of 250 °C or higher; (b) Saybolt color of+28 or higher; and (c) ultraviolet absorptivity (198nm) of 1.7 or lower. [2] A rubber composition, comprising the process oil according to claim 1. [3] The rubber composition according to claim 2, wherein a rubber material of the rubber composition is at least one component selected from the group consisting of an EPDM, an olefinic thermoplastic elastomer and a styrenic elastomer. A process oil of the present invention has properties of: (a) flash point of 250 °C or higher; (b) Saybolt color of + 28 or higher; and (c) ultraviolet absorptivity (198nm) of 1.7 or lower.

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