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
2001-01-16
2004-01-27
Harlan, Robert Deshon (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...
C524S546000, C524S545000
Reexamination Certificate
active
06683127
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a clean crosslinkable elastomer composition being capable of providing a sealing material to be used for sealing of semi-conductor production apparatuses and a carbon black filler which is added to the composition and has a reduced content of impurity metals.
BACKGROUND ART
In producing semiconductor elements, very high cleanliness is required, and the requirements for high cleanliness range over not only management of a production process of semiconductors but also semiconductor production apparatuses and parts thereof. If the parts of semiconductor production apparatuses are cleaned after built in the apparatuses, a degree of possible cleanliness is limited. Such parts are required to have been cleaned highly before built in the apparatuses. In production of semiconductors, there are problems with contamination, particularly micro particles so-called particles, organic additives and elution of metals, which have an adverse effect on accurate etching treatment.
Also cleanliness is required similarly in a sealing material for semiconductor production apparatuses which the present invention can be particularly suitably applied to. The applicant of the present invention has attained high cleanliness of the sealing material itself by employing a special method of cleaning the sealing material after molding (Japanese Patent Application No. 77781/1998).
Such a sealing material has been produced by crosslinking and molding a crosslinkable elastomer composition such as a rubber, and in order to impart mechanical properties, there is a case where a carbon black is added to the composition as a filler.
For cleaning a sealing material containing a carbon black as a filler, particularly for removing impurity metals, the above-mentioned method of extraction of impurity metals by washing the sealing material after molding with an acid, or the like and a method of adding a filler cleaned by washing with an acid can be considered. The present invention relates to the latter method of cleaning a filler itself. In that case, after adding the filler to an elastomer composition, the composition has to be crosslinked and molded. However when usual fillers obtained by cleaning with an acid was used, peroxide crosslinking which was a generally employed crosslinking method could not be carried out. Namely when the peroxide crosslinking is tried, those fillers cause crosslinking failure which not only lower mold-processability but also has an adverse effect on properties of molded article such as compression set, tensile strength and modulus.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a carbon black filler which has a reduced content of impurity metals and does not cause crosslinking failure even if not only radiation crosslinking but also peroxide crosslinking is carried out.
Also an object of the present invention is to provide a crosslinkable elastomer composition which contains the carbon black filler and can be subjected to not only radiation crosslinking but also peroxide crosslinking.
Further the present invention relates to a sealing material obtained by crosslinking and molding the above-mentioned composition.
Namely the carbon black filler of the present invention has a content of impurity metals of not more than 300 ppm. Preferably pH is adjusted to 5.0 to 11.0.
The carbon black filler having a reduced content of impurity metals can be obtained by extraction treatment of a starting carbon black filler with an acid to reduce a content of impurity metals in the filler and then treatment with an alkali to neutralize the remaining acid.
The crosslinkable elastomer composition obtainable by adding the carbon black filler of the present invention to a fluorine-containing elastomer component or silicone-based elastomer component can be crosslinked and molded without causing a crosslinking failure and can give a sealing material having excellent mechanical properties. Then the sealing material is subjected to treatment by a special cleaning method described in the above-mentioned Japanese Patent application No. 77781/1998, namely a cleaning method with ultra pure water, a method of cleaning with a clean organic compound in the form of liquid at a washing temperature or a clean inorganic aqueous solution, a cleaning method by dry etching or an extraction cleaning method, and thereby a highly cleaned sealing material for semi-conductor production apparatuses can be obtained.
BEST MODE FOR CARRYING OUT THE INVENTION
For the carbon black in the present invention, various grades of carbon blacks produced by various methods can be used. For example, there are SAF, ISAF, HAF, MAF, FEF, SRF, FT, MT, and the like. Among them, particularly suitable are carbon black having a specific surface are of not less than 3 m
2
/g and DBP absorption of not less than 15 cm
3
/100 g from the viewpoint of processability. Examples thereof are, for instance, N990, N550, N330, N220, and the like.
An average particle size of the carbon black filler of the present invention is from about 10 &mgr;m to about 600 &mgr;m.
A content of impurity metals of the carbon black filler of the present invention is not more than 300 ppm, preferably not more than 100 ppm, further preferably not more than 10 ppm. Reduction of impurity metals may be carried out by treating a starting carbon black with an acid such as sulfuric acid, nitric acid, hydrofluoric acid or hydrochloric acid to extract impurity metals.
Impurity metals contained particularly in a large amount are, for example, alkali metals such as Na, K and Li; alkaline earth metals such as Ca, Mg and Ba; Fe, Cu, Cr, Ni, Al, etc. which become a problem.
In the present invention, not to cause a crosslinking failure even if a carbon black is mixed to a crosslinkable elastomer composition, the carbon black is subjected to not only acid treatment but also treatment for neutralizing the acid being present on the acid-treated carbon black since the acid causes a peroxide crosslinking failure. The neutralizing treatment may be carried out by using an alkali. It is preferable to avoid use of an alkali containing metals from the viewpoint of reduction of contamination sources. Examples of the preferred alkali are, for instance, aqueous ammonia, basic amines such as triethanolamine, triethylamine and diethylamine, ammonia gas, and the like. Particularly from the viewpoint of handling property, separation and removal, aqueous ammonia having a concentration of 1 to 28% by weight is preferable. By the neutralizing treatment, a pH value which is 3.0 to 4.5 after the acid treatment is increased to 5.0 to 11.5. A preferred pH is 5.0 to 11.0.
The neutralizing treatment is easily carried out by dipping in an alkaline solution. Also a method of spraying an alkaline solution may be used.
It is further preferable that after the neutralizing treatment, washing with a clean chemical solution such as ultra pure water is carried out to remove generated salt and remaining micro particles.
The carbon black filler subjected to neutralizing treatment and washing is separated and dried. It is preferable to carry out the drying in a clean atmosphere such as a clean gas. Examples of the preferably used clean gas are, for instance, high purity inert gases such as nitrogen gas, helium gas and argon gas. It is preferable that the drying is carried out by pre-drying at 50° to 150° C. for 5 to 24 hours and further heating at 200° to 300° C. for 1 to 24 hours.
In addition to the above-mentioned neutralizing method, the neutralizing treatment may be carried out by a method of merely washing with a clean chemical solution such as ultra pure water or a method of exposing to ammonia gas. Examples of the clean chemical solution to be used preferably are ultra pure water which has a metal content of not more than 1.0 ppm and does not contain micro particles of not less than 0.2 &mgr;m in an amount of more than 300 per 1 ml and an organic compound in the form of liquid at a washing temperature or inorganic aqueous solution which has a metal content of
Hasegawa Masanori
Noguchi Tsuyoshi
Tanaka Hiroyuki
Daikin Industries Ltd.
Harlan Robert Deshon
Sughrue & Mion, PLLC
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