Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-02-08
2002-06-04
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S575500, C524S848000, C524S474000, C524S484000, C585S002000
Reexamination Certificate
active
06399697
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to process oil, a process for producing the same, and a rubber composition containing the process oil or the process oil obtained by the process. More specifically, it relates to process oil in which a content of polycyclic aromatic compounds (PCA) is less than 3% by weight and which maintains an ordinary performance, a process for producing the same, and a rubber composition.
The present invention further relates to rubber process oil which is process oil used in rubber processing, and a rubber composition. More specifically, it relates to rubber process oil having a reduced content of polycyclic aromatic compounds (PCA) and having an excellent performance, and a rubber composition containing the same.
2. Description of the Related Art
Process oil is used as oil for processing a natural rubber or a synthetic rubber, an extender thereof, a plasticizer of a thermoplastic resin, a solvent of printing ink or a softening agent of regenerated asphalt. Accordingly, process oil having specific properties such as a viscosity, a density, a volatility and a compatibility with a rubber according to each use has been in demand. For example, when process oil is used for a rubber (namely, as rubber process oil), it has been deemed good that process oil is good in a compatibility with a rubber for improvement of the processability, has a viscosity according to the use and is excellent in a durability. For this reason, an extract with a high aromatic content which is formed as a by-product in producing a lubricant fraction (raffinate) by solvent extraction from feedstock free of residue such as vacuum distillate or deasphalted oil has been used.
The toxicity of polycyclic aromatic compounds (PCA) has been recently a problem. Since especially process oil used for automobile tire involves the environmental pollution as tire dust, it has been required to reduce PCA in process oil. However, large amounts of the polycyclic aromatic compounds are contained in an extract with the high aromatic content produced by the process. Accordingly, process oil with PCA reduced and a process for producing the same have been in urgent demand.
Therefore, the development of process oil with PCA reduced has proceeded. For example, International Patent Publication No. 505524/1994 discloses a rubber composition using process oil with low PCA. The process oil disclosed therein is produced using deasphalted oil as feedstock, and it has a high viscosity. Accordingly, its use is limited.
Further, EP 417980A1 discloses a process for producing process oil with low PCA and high aromatic hydrocarbon by a two-step extraction process using a polar solvent. This process has however suffered problems that a density of a primary extract, a raw material, of an extraction at a second stage, is close to that of a polar solvent and an affinity for a polar solvent is strong so that it is quite difficult to set extraction conditions and an extraction efficiency is poor (according to Examples, a maximum yield is 51%).
As a process similar to,this process, EP 0839891A2 discloses a process for producing process-oil in which a PCA content is less than 3% by weight. It describes that process oil is obtained in which a kinematic viscosity at 100° C. is in a wide range of 2 to 70 cSt and a total amount of an aromatic hydrocarbon and a polar substance is 40% by weight or more, the polar substance being not higher than 10% by weight. With respect to a process for producing the process oil, an extract formed as a by-product in producing a lubricant fraction (raffinate) by solvent extraction using vacuum distillate and/or deasphalted oil as feedstock is further extracted to provide the process oil. The process is intricate, and a yield of the process oil is low as a whole.
Further known as a related art are a process in which a non-carcinogenic bright stock extract and/or deasphalted oil is produced from atmospheric residue feedstock (International Patent Publication No. 501346/1995), a process in which a mutagenicity of polycyclic aromatic compounds is reduced through alkylation (International Patent Publication No. 503215/1996), a rubber composition using aromatic oil of low polycyclic aromatic compounds (PCA) obtained by treating a vacuum distillate (350 to 600° C.) of crude oil from the Middle East (International Patent Publication No. 505524/1994 and WO 92/14479), and a process for producing low PCA process oil made of a mononuclear or dinuclear aromatic hydrocarbon compound (EP 0489371B1 and DE 4038458C2).
As stated above, rubber process oil is a type of process oil, and is blended for improving a processability by increasing a plasticity of a rubber or decreasing a hardness of a vulcanized rubber. For the rubber process oil, a compatibility with a rubber is required.
A safety of a product is, as described above, also required for the rubber process oil, and the use of highly refined mineral oil in which the content of the polycyclic aromatic compound is less than 3% by weight is requested. However, the use of ordinary mineral oil which is refined such that the content of the polycyclic aromatic compound is adjusted to less than 3% by weight is problematic in that a compatibility with an aromatic rubber is poor and that when a rubber is blended with this oil, oil is bled in a vulcanized rubber to decrease heat aging properties of the vulcanized rubber. Further, from the aspect of a workability, it is required that a viscosity is kept to be as low as that of ordinary oil. Accordingly, rubber process oil in which the content of the polycyclic aromatic compound is less than 3% by weight, the viscosity of current oil is maintained and a compatibility with an aromatic rubber is excellent has been in demand.
SUMMARY OF THE INVENTION
The present invention aims to provide process oil in which PCA is reduced and properties required for current process oil, such as a processability and a bleed resistance of a rubber, are excellent, a process for efficiently producing the process oil using residual oil as feedstock, and a rubber composition containing the process oil or the process oil obtained by the process.
The present invention further aims to provide process oil in which a PCA content is less than 3% by weight, a viscosity of ordinary oil is maintained and a compatibility with an aromatic rubber is excellent, and a rubber composition in which bleeding does not occur in a vulcanized rubber containing the same and heat aging properties are excellent.
The present inventors have assiduously conducted investigations, and have consequently found that residual oil is mixed with lubricant base oil and the mixture is extracted with a solvent to obtain excellent process oil with a low PCA content that satisfies the aims. This finding has led to the completion of the present invention.
The present inventors have further assiduously conducted investigations, and have consequently found that oil having specific properties becomes excellent rubber process oil that satisfies the aims. This finding has led to the completion of the present invention.
That is, the gist of the present invention is as follows. (1) Process oil which satisfies requirements that (a) a content of a polycyclic aromatic compound is less than 3% by weight, (b) a content of an aromatic hydrocarbon is 18% by weight or more, (c) a content of a polar compound is between 11 and 25% by weight, (d) a kinematic viscosity at 100° C. is between 10 and 70 mm
2
/s, and (e) a flash point is 210° C. or more; (2) a process for producing process oil having a content of a polycyclic aromatic compound of less than 3% by weight, which comprises extracting mixed oil made of 20 to 90% by volume of residual oil and 10 to 80% by volume of lubricant base oil with a polar solvent; (3) the process for producing process oil as recited in (2), wherein the process oil further satisfies requirements that (b) a content of an aromatic hydrocarbon is 18% by weight or more, (c′) a content of a polar compound is 25% by weight or less
Anzai Hisao
Endo Chisato
Nakamura Masashi
Takasaki Masami
Tanaka Meishi
Egwim Kelechi
Idemitsu Kosan Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Wu David W.
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