Mineral oils: processes and products – Asphalts – tars – pitches and resins; making – treating and...
Reexamination Certificate
1999-04-16
2001-08-07
Lovering, Richard D. (Department: 1712)
Mineral oils: processes and products
Asphalts, tars, pitches and resins; making, treating and...
C208S022000, C208S045000, C252S299010, C252S299200, C264S029200
Reexamination Certificate
active
06270652
ABSTRACT:
FIELD OF THE INVENTION
The present invention resides in metals-containing carbon fibers and an improved process for producing a soluble, aromatic-organometallic-compound-containing mesophase pitch which is suitable for carbon fiber manufacture. More particularly, the invention relates to a process for making high strength carbon fibers which exhibit superior oxidative stabilization characteristics, tensile strength and modulus properties. The process comprises adding a soluble, aromatic-organometallic compound to a graphitizable, carbonaceous feedstock or adjusting the concentration of an aromatic-organometallic compound in a graphitizable, carbonaceous feedstock and heat soaking said carbonaceous feedstock to produce an isotropic pitch product containing mesogens and metals from the organometallic compound. The resulting pitch product is solvent fractionated using solvents near atmospheric pressure. Next, the metals-containing mesogens are heated to a temperature sufficient to cause fusion to produce a metals-containing mesophase pitch. The resulting metals-containing mesophase pitch is suitable for melt spinning into a fiber artifact.
In another method, the carbonaceous feedstock is heat soaked to produce an isotropic pitch product containing mesogens. High molecular weight, soluble aromatic organometallic compounds are then added to this isotropic pitch product and the resulting mixture is solvent fractionated to separate metals-containing mesogens.
Alternatively, the isotropic pitch product containing metals from either of the foregoing methods can be solvent fractionated at supercritical extraction conditions to produce a metals-containing mesophase pitch. When supercritical extraction is used, conditions are such that fused mesophase pitch is obtained directly making the mesogen fusion step unnecessary.
THE PRIOR ART
Processes for producing metals-containing pitches and/or carbon fibers are known and are currently practiced commercially. For example, U.S. Pat. No. 3,258,419, issued Aug. 16, 1977 relates to the use of a phosphoric acid and metal catalyst to promote air blowing of asphalts. The catalyst consists of phosphoric acid which contains dissolved metals.
U.S. Pat. No. 3,385,915, issued May 28, 1968, discloses a process for producing metal oxide fibers which consists of impregnating a preformed organic polymeric material with a metal. Cellulose and rayon are described as suitable organic polymeric materials.
U.S. Pat. No. 4,042,486, issued Aug. 16, 1977 relates to a process for converting pitch to a crystalloid which consists of coating solid amorphous pitch particles with a metal or metal salt prior to gas sparging and heat soaking to produce a mesophase pitch.
U.S. Pat. No. 4,554,148, issued Nov. 19, 1985 relates to a process for the preparation of carbon fibers which consists of subjecting a raw material oil to thermal cracking conditions to obtain a pitch product containing at least 5 weight percent mesophase. A substantially mesophase free pitch is obtained by removing mesophase of a particular particle size from the pitch product. The raw material oil is derived from a napthene base or intermediate base petroleum crude and contains metals.
U.S. Pat. No. 4,600,496, issued Jul. 15, 1986, discloses a process for converting pitch into mesophase in the presence of catalytically effective amounts of oxides, diketones, carboxylates and carbonyls of certain metals. The mesophase pitch obtained is described as suitable for use in the production of carbon fibers.
U.S. Pat. No. 4,704,333 relates to a process for the formation of carbon fibers produced from the pitch described in U.S. Pat. No. 4,600,496 above. The process consists of extruding said mesophase to form fibers, cooling the extruded fibers and subjecting the fibers to elevated temperature to carbonize said fibers.
As can readily be determined from the above references, there is an ongoing research effort to determine new and more advanced processes and methods of producing various pitches and carbon fibers.
SUMMARY OF THE INVENTION
The present invention resides in metals-containing carbon fibers, metals-containing mesophase pitch and in a process for producing said metals-containing mesophase pitch which is readily spinnable into carbon fibers. The process for producing the metals-containing mesophase pitch herein comprises adding a soluble, aromatic-organometallic compound to a graphitizable carbonaceous feedstock. The metals-containing carbonaceous feedstock is heat soaked to produce an isotropic pitch product containing mesogens and soluble, aromatic-organometallic compounds. The resulting pitch product is solvent fractionated to separate metals-containing mesogens from the isotropic oil fraction. Thereafter, the mesogens are heated to a temperature that is sufficient to cause the mesogens to fuse and form a mesophase pitch which contains from about 50 PPM to about 20,000 PPM metals from the organometallic compounds.
In another method, the graphitizable carbonaceous feedstock is heat soaked to produce an isotropic pitch product containing mesogens, and a high molecular weight, soluble, aromatic-organometallic compound is added to the pitch product prior to solvent fractionation. Thus, the organometallic compounds herein may be added to the carbonaceous feedstock either prior to or after the heat soak step.
Solvent fractionation is conducted with solvents or solvent mixtures so as to isolate the desired mesophase formers (mesogens) from isotropic oils and particulate contaminants. Solvent fractionation is performed with liquid solvents at or near atmospheric pressure. Alternatively, the isotropic pitch product containing metals can be solvent fractionated at supercritical extraction conditions to produce a metals-containing mesophase pitch. When supercritical extraction is used, conditions are such that fused mesophase pitch is obtained directly making the mesogen fusion step unnecessary.
The present invention provides for a metals-containing, mesophase pitch which is readily spinnable into a carbon artifact or fiber. The metals-containing mesophase pitch herein provides fibers having enhanced oxidative stabilization, tensile strength and modulus properties.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the present invention a soluble, aromatic-organometallic compound is added to a carbonaceous feedstock. The metals-containing carbonaceous feedstock is heat soaked to produce an isotropic pitch product containing mesogens and a soluble, aromatic-organometallic compound. The resulting pitch product is solvent fractionated to separate metals-containing mesogens. Thereafter, the metals-containing mesogens are heated to a temperature sufficient to produce mesophase pitch which contains metals from the soluble, aromatic-organometallic compound.
It should be noted that some carbonaceous feedstocks may contain minor or trace amounts of a metal compound therein. Whenever this occurs, it is desirable to adjust the metal content of the carbonaceous feedstock to the desired concentration. This is accomplished by adding the soluble, aromatic-organometallic compounds herein to the carbonaceous feedstock thereby adjusting said metals content of the carbonaceous feedstock to the desired concentration.
In another method, the carbonaceous feedstock may be heat soaked to produce an isotropic pitch product which contains mesogens. High molecular weight, soluble aromatic-organometallic compounds are then added to the pitch product prior to solvent fractionation. The organometallic compounds may be added to the carbonaceous feedstock either prior to or after the heat soak step.
Solvent fractionation is conducted with solvents or solvent mixtures so as to isolate the desired mesophase formers (mesogens) from isotropic oils and particulate contaminants. Solvent fractionation is performed with liquid solvents at or near atmospheric pressure. Alternatively, the solvent fractionation is conducted under supercritical extraction conditions of temperature and pressure to produce a mesophase pitch containing organometallic co
McConaghy, Jr. James R.
Rodgers John A.
Romine H. Ernest
Conoco Inc.
Hall William D.
Lovering Richard D.
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