CA1199250A

CA1199250A - Organic gels

Info

Publication number: CA1199250A
Application number: CA000419207A
Authority: CA
Inventors: Robert J. Purinton, Jr.
Original assignee: Dow Chemical Co
Current assignee: Hydrochem LLC
Priority date: 1982-01-12
Filing date: 1983-01-11
Publication date: 1986-01-14
Also published as: EP0083957A1; JPS58125798A; EG16021A; NO830061L; BR8300155A; NO164041C; NO164041B; DE3377771D1; US4537700A; JPS624436B2; EP0083957B1; OA07389A; US4473408A

Abstract

ABSTRACT OF THE DISCLOSURE

Organic gels are described which comprise (a) a nonpolar, liquid, organic solvent and (b) a gelling amount of a mixture of (1) an alkyl oleyl phosphate and (2) an alkali metal aluminate. The gels have many uses, one of which is as a gelled pig for pipeline cleaning.

Description

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ORGANIC GELS

This invention pertains to novel organic gels and to their uses. In particular, this invention pextains to organic gels of nonpolar li~uid organic solvents ~P.g. perchlorinated alphatic hydrocarbons of one to two carbon atoms, such as perchloroethylene).
This invention also pertains to the use of such organic gels as gelled pigs in pipeline cleaning.

Pipeline efficiency in volume can be lost by scale buildup in -the interior lining of the pipe.
Mechani~al pigs and/or gelled chemical pigs have been used to remove scale. The mechanical pigs are normally solid bullet-shaped devices which have wire brushes or abrasive surfaces to physically abrade the scale interior of the pipe. The gelled chemical pigs on the other -15 hand, remove the surface deposits by dissolution and/or by picking up loose debris as they pass through the plpel lne .

A method for cleaninq ~i~eline using an : aqueous gel of a different type is disclosed by Scott 28,163-F -1-~.

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ln IJSP 4,216,026. Sco-tt alleges that plugs of Blngham plastic fluids are effectlve in picking up loose debris and minor amounts of liquids as the plug moves through the pipeline. The plug is used ln combination with mechanical scrapers.

A method of removing flulds and solids from a pipelirle is described in USP 4,003,393 using an organic liquid gel with a metal salt of an aliphatic ester of orthophosphoric acid.

While the aforementioned aqueous gels have many desirable properties, certain types of scale or scale components are effectively removed on].y by an organic solvent. In most instances, a "fill and soak"
type treatment with a liquid solvent is no-t practical due to the volume of solvent required. Waste disposal of such a large volume of material is also a commercial problem. Applicant conceived that these problems could be solved by a gelled organic pig if a gel of suitable stability could be found.

There are, of course, many organic gels described in the literature. For example, Monroe in USP 3,505,374 described the use of magnetite salts of alkyl oleyl orthophosphate as gelling agents for hydro-carbons and halogenaked hydrocarbon liquids. Crawford et al. (USP 3,757,864) taught that the pressure drop of a confined nonpolar organic li~uid in motion due to friction is lessened by a~m'xing with the liquid one or more aluminum salts of an aliphatic orthophosphate ester. Crawford et al. also taught that such esters can gel the liquids. Dickerson (USP 3,219,619) disclosed the idea of thickened hydrocarbons with t-butylstyrene 28,163-F -2-~ .3~

interpolymers con-taining metal carboxylate groups.
Haigh et al. (USP 3,527,582) formed reversible gels of liquid hydrocarbons using a crosslinked latex polymer of an alkyl styrene. But, as Monroe illustrates, thickened organic fluids are not -the same as organic gels. With organic gels, the gel consistency ~ill not disappear on dissolution of the gel. With sufficient dissolution, the solvent swollen gelling agent will appear as a distinct phase ln suspension. Moreover, the gel structure has a viscosity profile that is quite different from liquids tha-t are merely thickened but not gelled. If a gel is to be used as a pipeline pig, the rheology and chemical and physical properties of the gel must meet certain demands. For example, the lS gel must be viscoelastic and self-sustaining so that it will not break -up as it is being forced through a pipeline under pressure, It is also desirable for the gel to have the capacity to retain suspended solids and the ability to sustain a gel/liquid interface. This later capability is needed because in many instances it is desirable to displace a fluid with the gelled pig and/or to drive the pig directly with a fluid ~a gas) under pressure. Also, it is desirable in many instances to use a pig train which will have one or more chemical pig segments and the gelled segments desirably have a structure that would prohibi-t or substantially inhibit comingling of liquids in front of and/or behind the gelled pig (some-times called fluid by-pass).

It has now been discovered that organic gels comprising: (a) a non-polar, liquid, organic solvent and (b) a gelling amount of a mixture of (1) an alkyl oleyl phosphate and (2~ an alkali metal aluminate, have very desirable properties. These organic gels can be 28,163-F ~3-~ 3~

used as gelled pigs to remove organic soluble scale or scale contaminants from a pipeline and can also be used in a varie-ty of other ways.
Non-polar, liquid, organic solvents form a known class of organic compounds, essentially any member of which can be used herein. This class includes, for example, normally liquid aromatic hydrocarbons (e.y. benzene, toluene, 1,4-dimethyl~
benzene, 1,3,5-trimethylbenzene, etc.), aliphatic hydrocarbons (e.g. kerosene, gasoline, petroleum ether, etc.), chloxina-ted hydrocarbons ~e.g. carbon tetra-chloride, perchloroethylene, 1,4-dichlorobenzene, etc.), and the like. Of these organic solvents, gels prepared from kerosenes, toluene, or perchlorinated alphatic hydrocarbons of one to two carbons atoms are preferred based on the commercial availability of the solvents and their excellent solvent properties. Gels prepared from perchloroethylene are most preferred.

The gelling agent is a mixture of (1) an alkyl oleyl phosphate and (2) an alkali metal aluminate.

The alkyl oleyl phosphates constitute a known class of compounds having many members. Of these, the (C1-C4) alkyl oleyl phosphates are preferred, and ethyl oleyl phosphate is most preferred. There are a variety of known chemical reactions which can be used to prepare the alkyl oleyl phosphates.

However, it should be noted that the presence of a monoester phosphoric acid reduces the effectiveness of the alkyl oleyl phosphate as a gelling agent. So, reaction processes which maximize the formation of the 28,163-F -4~

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desired alkyl oleyl phosphate a-t -the expense of the monoester are preferred.

The alkali metal aluminates are likewise a known class of compounds. Of these, sodium aluminate and potassium aluminate are preferred, and sodlum aluminate is mos-t preferred.

The ratio o alkyl oleyl phosphate to alkali metal aluminate can be varied. A preferred ratio, however, is from 7 to 12 volumes of alkyl oleyl phosphate per volume of alkali metal aluminate. More preferably, a ra-tio of from 9 to 10 volumes of alkyl oleyl phosphate per volume of alkali metal aluminate.

The mixture of alkyl oleyl phosphate and alkali metal aluminate is added to the organic solvent in an amount sufficient to cause gellation. This amount will vary depending upon the selection of a particular organic solvent. Typically, however, amounts of from 1.5 to 5 weight percent lbased on the weight of the solvent) of gelling agent is sufficien-t.

The gels are conveniently prepared by dis-solving an appropriate amount of alkyl oleyl phosphate in the organic solvent and subsequently adding the alkali metal aluminate to the mixture with thorough mlxlng .

~5 The gel formulations have a variety of use~.
One such use is as a gelled pig in cleaning pipelines.
For such particular use, the gel can be mixed external to the pipeline and pumped into place. Alternatively the components can be blended "on the fly" and the gel 28,163-F ~5-3 ~, formed in situ. The gel is then forced through the pipeline by a 1uid (either CJas or liquid) under pres-sure. If a gas is ~lsed as the driving force, a swab or squeegee pig (i.e. a foamed polymer plug, such as a polyurethane foam plug) is used behind the gel to assist in preventing fluid bypass. The gelled pigs oE
the present invention are usually used as one segment or element of a pig train containing other chemical pigs of the same or different composition. For example, one could have segments in the pig train of liquid or gelled acid, a desiccating alcohol ~e.g. methanol or isopropanol) in liquid or gelled form, an aqueous gel containing a bactericide, an aqueous gel to suspend and carry solids or to separate liquids, etc. In these pig trains, one might find it advantageous to include one or more mechanical piys. For example, it is convenient in many instances to insert a squeegee pig or scraper pig in the pig train to restrict fluid bypass, to physically separate chemical segments of the train, to abrade the walls of the pipeline, etc. The number of combinations and permutations in staging a pig train are limited only by the skilled artisan's imagirlation and need at the time.

The following examples will further illustrate the invention.

Experimental Preparation of the alkyl oleyl phosphate:
the phosphate ester was prepared in a two stage reaction.
First, substantially equal molar amounts of triethyl phosphate and phosphorus pentoxide (P205) were blended together in a mixed aromatic solvent and warmed at 70C
for one hour. Then, a stoichiometric amount of oleyl 28,163-F -6-alcohol was added and the reaction mixture heated to a tempera-ture of 90C for two hours. The reaction product thus produced was a dark liquld (75 percent sollds) having only minor amounts of mono-alkyl ester by-product with the remainder being the desired ethyl oleyl phos-phate (greater than 90 percent of theoretlcal yleld).
This reaction mixture was used without further purifica-tion as the gelling agent to gel kerosene, perchloro-ethylene and a mixed aromatic solvent which is pre dominantly toluene. In each instance, the ethyl oleyl phosphate mixture was dissolved in the organic solvent and aqueous sodium aluminate (38 percen-t solids in water) was added subsequently with vigorous stirring.
The shear strength of the gel was measured at the end of one hour after mixing an~ then again at the end of a 21-24 hour period using a model BAROIDTM SHEAROMETER
TUBE. The data are summarized in Table I.

TABLE I
Shear Shear Strength Gelling Agent Strength ~1-hr 21-24 hr.
Solvent (lit/100 lit) lbs/100 ft.2) (lb/100 ft2) Kerosene 25 17.0 146 41.3 207 96.7 211 50 218.4 398 Mix~d Aromatics ~5 9.0 31.8 13.3 36.0 ~0 19.8 57.3 ~5.7 86.3 Perchloro-ethylene 25 10.9 45.5 18.1 89.6 ~4.0 93.8 34.4 158.7 28,163-F -7-These data show the effectiveness of the gelling agents in gelllng a variety of organic liquids and the data also show that the gel. strength improves upon standing. For these reasons, it may be desirable to batch mix the gels prior to their use, depending upon the chosen utility.

Claims

1. An organic gel comprising: (a) a non-polar, liquid, organic solvent, and (b) a gelling amount of a mixture of (1) an alkyl oleyl phosphate and (2) an alkali metal aluminate.

2. The gel defined by Claim 1 wherein (1) is ethyl oleyl phosphate.

3. The gel defined by Claim 1 wherein (2) is sodium aluminate.

4. The gel defined by Claim 1 wherein (a) is a normally liquid aromatic or aliphatic hydrocarbon or a chlorinated derivative thereof.

5. The gel defined by Claim 4 wherein (a) is a perchlorinated aliphatic hydrocarbon of 1 to 2 carbon atoms.

6. The gel defined by Claim 5 wherein (a) is carbon tetrachloride, or perchloroethylene, and (b) is a mixture of (1) ethyl oleyl phosphate and (2) sodium aluminate.

7. A method of cleaning the interior of a pipeline comprising the step of passing through said pipeline a gelled pig which comprises (a) a nonpolar, liquid, organic solvent, and (b) a gelling amount of a mixture of (1) an alkyl oleyl phosphate and (2) an alkali metal aluminate.

8. The method defined by Claim 7 wherein said gelled pig is a segment of a pig train.

9. The method defined by Claim 8 wherein said pig train contains a plurality of chemical pig segments.

10. The method defined by Claim 8 wherein said pig train additionally contains at least one mechanical pig.

11. The method defined by Claim 10 wherein at least one of said mechanical pigs is a foamed polyurethane swab included as the last segment of the pig train, and wherein said pig train is driven by an inert gas or liquid under pressure.