Bleaching and dyeing; fluid treatment and chemical modification – Cleaning or laundering – Dry cleaning
Reexamination Certificate
1999-11-10
2001-11-06
Einsmann, Margaret (Department: 1751)
Bleaching and dyeing; fluid treatment and chemical modification
Cleaning or laundering
Dry cleaning
C210S690000, C210S916000, C556S466000
Reexamination Certificate
active
06312476
ABSTRACT:
TECHNICAL FIELD
The present invention is directed to a process, more specifically, to a process for removing malodorous elements from silicone dry cleaning solvents.
BACKGROUND
Current dry cleaning technology uses perchloroethylene (“PERC”) or petroleum-based materials as the cleaning solvent. PERC suffers from toxicity and odor issues. The petroleum-based products are not as effective as PERC in cleaning garments. Volatile siloxanes are being introduced into the dry cleaning industry as an alternative to PERC. However, undesirable odors are sometimes carried over with the siloxane solvent, so there exists a need to remove the odor from the siloxane solvent.
Methods for the purification of organopolysiloxanes have previously been reported as utilizing elemental metals (see U.S. Pat. No. 5,245,067). Other patents disclose the purification of polyether silicones by contacting with an aqueous acid and removing the malodorous materials formed (see U.S. Pat. No. 5,118,764), or the reaction with hydrogen and a hydrogenation catalyst (see U.S. Pat. No. 5,225,509). Hexamethyldisiloxane has been purified by successive treatments with a condensation catalyst, washing with water, separating the phases, distilling the siloxane, treating with acid clay and then treating with activated carbon (see U.S. Pat. No. 4,774,346). Siloxanes have also been purified by contacting with steam and distilling out the impurities (see EP 543 665). A deodorization method utilizing active carbon to which a functional group has been fixed through a silanol bond has been reported (see U.S. Pat. No. 5,238,899). Finally, a method was reported for purifying silicone oil by adding a drying agent and an adsorption agent to silicone and passing a low water vapor inert gas through the system (see U.S. Pat. No. 4,661,612).
There is a need for a method for removing unwanted odors in a volatile siloxane used in dry cleaning applications.
SUMMARY OF THE INVENTION
In a first aspect, the present invention is directed to a method for removing malodorous elements from silicone dry cleaning solvents, comprising contacting the silicone solvent with adsorbent to remove the malodorous elements, and separating the silicone solvent.
The process of the present invention is effective in removing or reducing malodorous elements, such as for example, propionic acid, propionaldehyde, butyric acid and butyraldehyde, from the silicone solvent.
DETAILED DESCRIPTION OF THE INVENTION
Preferably, the first preferred embodiment of the method of the present invention comprises, contacting a silicone dry cleaning solvent that may contain malodorous elements with an adsorbent, removing the malodorous elements, and separating the silicone solvent. Preferably, the silicone dry cleaning solvent is a volatile linear, branched, cyclic or a combination thereof, siloxane.
Compounds suitable as the adsorbent are those that effectively remove the malodorous components of the siloxane solvent. Examples of adsorbents suitable for use include, but are not limited to, silica gel, fullers earth, alumina, diatomaceous earth, magnesium silicate, granular activated carbon, molecular sieves, powdered decolorizing charcoal, magnesium sulfate, corn cob powder, zeolites, and clays. Preferably, the adsorbent is granular activated carbon, 4A molecular sieves, or 13X molecular sieves.
Compounds suitable as the linear or branched, volatile siloxane solvent of the present invention are those containing a polysiloxane structure that includes from 2 to 20 silicon atoms. Preferably, the linear or branched, volatile siloxanes are relatively volatile materials, having, for example, a boiling of below about 300° C. point at a pressure of 760 millimeters of mercury (“mm Hg”).
In a preferred embodiment, the linear or branched, volatile siloxane comprises one or more compounds of the structural formula (I):
M
2+y+2z
D
x
T
y
Q
z
(I)
wherein:
M is R
1
3
SiO
1/2
;
D is R
2
2
SiO
2/2
;
T is R
3
SiO
3/2
;
and Q is SiO
4/2
R
1
, R
2
and R
3
are each independently a monovalent hydrocarbon radical; and
x and y are each integers, wherein 0≦×≦10 and 0 ≦y≦10 and 0 ≦z≦10.
Suitable monovalent hydrocarbon groups include acyclic hydrocarbon radicals, monovalent alicyclic hydrocarbon radicals, monovalent and aromatic hydrocarbon radicals. Preferred monovalent hydrocarbon radicals are monovalent alkyl radicals, monovalent aryl radicals and monovalent aralkyl radicals.
As used herein, the term “(C
1
-C
6
)alkyl” means a linear or branched alkyl group containing from 1 to 6 carbons per group, such as, for example, methyl, ethyl, propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, hexyl, preferably methyl.
As used herein, the term “aryl” means a monovalent unsaturated hydrocarbon ring system containing one or more aromatic rings per group, which may optionally be substituted on the one or more aromatic rings, preferably with one or more (C
1
-C
6
)alkyl groups and which, in the case of two or more rings, may be fused rings, including, for example, phenyl, 2,4,6-trimethylphenyl, 2-isopropylmethylphenyl, 1-pentalenyl, naphthyl, anthryl, preferably phenyl.
As used herein, the term “aralkyl” means an aryl derivative of an alkyl group, preferably a (C
2
-C
6
)alkyl group, wherein the alkyl portion of the aryl derivative may, optionally, be interrupted by an oxygen atom, such as, for example, phenylethyl, phenylpropyl, 2-(1-naphthyl)ethyl, preferably phenylpropyl, phenyoxypropyl, biphenyloxypropyl.
In a preferred embodiment, the monovalent hydrocarbon radical is a monovalent (C
1
-C
6
)alkyl radical, most preferably, methyl.
In a preferred embodiment, the linear or branched, volatile siloxane comprises one or more of, hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, dodecamethylpentasiloxane, tetradecamethylhexasiloxane or hexadecamethylheptasiloxane or methyltris(trimethylsiloxy)silane. In a more highly preferred embodiment, the linear or branched, volatile siloxane of the present invention comprises octamethyltrisiloxane, decamethyltetrasiloxane, or dodecamethylpentasiloxane or methyltris(trimethylsiloxy)silane. In a highly preferred embodiment, the siloxane component of the composition of the present invention consists essentially of decamethyltetrasiloxane.
Suitable linear or branched volatile siloxanes are made by known methods, such as, for example, hydrolysis and condensation of one or more of tetrachlorosilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, or by isolation of the desired fraction of an equilibrate mixture of hexamethyldisiloxane and octamethylcyclotetrasiloxane or the like and are commercially available.
Compounds suitable as the cyclic siloxane component of the present invention are those containing a polysiloxane ring structure that includes from 2 to 20 silicon atoms in the ring. Preferably, the linear, volatile siloxanes and cyclic siloxanes are relatively volatile materials, having, for example, a boiling point of below about 300° C. at a pressure of 760 millimeters of mercury (“mm Hg”).
In a preferred embodiment, the cyclic siloxane component comprises one or more compounds of the structural formula (II):
wherein:
R
5
, R
6
, R
7
and R
8
are each independently a monovalent hydrocarbon group; and
a and b are each integers wherein 0≦a≦10 and 0≦b≦10, provided that 3≦(a+b)≦10.
In a preferred embodiment, the cyclic siloxane comprises one or more of, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, tetradecamethylcycloheptasiloxane. In a more highly preferred embodiment, the cyclic siloxane of the present invention comprises octamethylcyclotetrasiloxane or decamethylcyclopentasiloxane. In a highly preferred embodiment, the cyclic siloxane component of the composition of the present invention consists essentially of decamethylcyclopentasiloxane.
Suitable cyclic siloxanes are made by known methods, such as, for example, hydrolysis and condensation of dimethyldichlorosilane and are commercially available.
Dorn Steven B.
Kilgour John A.
Perry Robert J.
Einsmann Margaret
General Electric Company
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