FOAM FORMULATION AND ITS USE IN TEMPORARY PIPE PLUGGING

Abstract

The present specification refers to a patent of invention for a foam formulation and its use in the temporary plugging of pipes, where the foam has volumetric and time stability, is prepared from a solution containing surfactant, co-surfactant, alkaline substance and LDH nanoparticles, is able to have its viscosity increased over time and remain intact for 8 hours or more even under pressure differences of up to 0.1 bar and a temperature of 60° C. and then it is able to disperse simply by using water or even the fluid transported in the pipeline. The LDH nanoparticle reinforced foam of the present invention can be applied in pipes that need to be plugged when they are undergoing maintenance, either to prevent incandescent soldering splashes from coming into contact with an explosive atmosphere or to avoid contamination in the pipe interior, among other applications. The present invention belongs to (but is not limited to) the field of plugs for pipes with explosive atmospheres and can be applied in systems that require temporary plugs that can be easily remover by using water or another solvent.

Claims

1. A foam formulation characterized in that it comprises a surfactant or a mixture of surfactants, a co-surfactant or a mixture of co-surfactants, a base or a mixture of bases and LDH nanoparticles.

2. The foam formulation according to claim 1 characterized in that the surfactant belongs to the class of fatty acids of the C.sub.mH.sub.nCOOH type, where 15≤m≤17 and 31≤n≤33, such as palmitic acid, stearic acid, linoleic acid, oleic acid and linolenic acid, or a mixture thereof or other equivalent substances.

3. The foam formulation according to claims 1 and 2 characterized in that the fatty acid preferably has a concentration between 0.09 and 0.54 mol.Math.L.sup.−1, more preferably between 0.15 and 0.40 mol.Math.L.sup.−1, most preferably between 0.20 and 0.30 mol.Math.L.sup.−1.

4. The foam formulation according to claim 1 characterized in that the co-surfactant belongs to the class of ethoxylated lauryl ether alcohols or glycolic acids of the R.sub.1C.sub.xH.sub.y(C.sub.2H.sub.4O).sub.zR.sub.2 type, where 12≤x≤16, 27≤y≤31, 10≤z≤21, R.sub.1 being H or O and R.sub.2 being the alcohol, carboxylic acid or ether function (—CH.sub.2OH, —CH.sub.2COOH or —OC.sub.2H.sub.5), such as Laureth-11, Brij-58, Brij-56, Laureth-23, a mixture thereof or similar.

5. The foam formulation according to any one of claims 1 to 4 characterized in that the co-surfactant ethoxylated hydrocarbon alcohol or acid has a concentration preferably between 0.001 and 0.060 mol.Math.L.sup.−1, more preferably between 0.005 and 0.020 mol.Math.L.sup.−1, most preferably between 0.008 and 0.012 mol.Math.L.sup.−1.

6. The foam formulation according to claim 1 characterized in that the base is a strong, moderately strong or weak base, such as sodium hydroxide, ammonium hydroxide or triethanolamine, or a mixture thereof or the like.

7. The foam formulation according to any one of claims 1 to 6 characterized in that the base has a concentration preferably between 0.009 and 0.84 mol.Math.L.sup.−1, more preferably between 0.018 and 0.36 mol.Math.L.sup.−1, most preferably between 0.02 and 0.30 mol.Math.L.sup.−1.

8. The foam formulation according to claim 1 characterized in that the nanoparticles belong to the class of lamellar double hydroxides, which can be made of lamellae of a mixture of aluminum oxyhydroxide, zinc oxyhydroxide and their counterions or they can also be composed of a mixture of aluminum, nickel and magnesium oxyhydroxide, or any other LDH-forming mixtures whose lamellae surface has a positive charge.

9. The foam formulation according to any one of claims 1 to 8 characterized in that the LDH concentration ranges, preferably from 0.5 to 3% (w/w), more preferably from 1 to 2%, most preferably from 1.25 to 1.75%.

10. Use of foam for temporary plugging pipes, characterized in that the foam has a composition according to any one of claims 1 to 9.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0029] To obtain a full and complete visualization of the object of the present invention, figures containing references are presented, as follows.

[0030] FIGS. 1A-1C schematically show the preparation of the foam forming liquid (FFL) (FIG. 1A), the preparation of LDH (FIG. 1B) and the preparation of FFL with LDH foam (FIG. 1C).

[0031] FIGS. 2A and 2B show the variation in foam volume and drainage over time for samples prepared with surfactant ammonium palmitate, ethoxylated ammonium lauryl ether glycolate and LDH nanoparticles (FIG. 2A) and with surfactant SDS, ethoxylated ammonium lauryl ether glycolate and LDH nanoparticles (FIG. 2B). All components of the sample of FIG. 2B are at the same concentration as the components of the sample of FIG. 2A.

[0032] FIG. 3 shows the progression with time of the elastic modulus G′, the loss modulus G″ and the viscosity for the sample containing surfactant ammonium palmitate, ethoxylated ammonium lauryl ether glycolate and LDH nanoparticles.

[0033] FIGS. 4A and 4B shows the SAXS diagrams of the intercalation kinetics of palmitate ion between the LDH lamellae (FIG. 4A) 3D graph (FIG. 4B) 2D graph.

[0034] FIGS. 5A and 5B shows the structural stability and plugging ability of the foam made of the formulation containing triethanolammonium palmitate, ethoxylated triethanolammonium lauryl ether glycolate kept at 60° C.: (FIG. 5A) after foam formation, (FIG. 5B) after 1 h.

[0035] FIGS. 6A, 6B, and 6C show the sequence of application of the foam plug in the steel pipe, with one side of the pipe having an explosive atmosphere generated by a mixture of volatile hydrocarbons and the other side of the pipe being hydrocarbon-free.

[0036] FIG. 7 shows the flammability test on the pipe side with no explosive atmosphere.

[0037] FIGS. 8A-8F show the sequence of flame propagation in the flammability test on the side of the pipe containing an explosive atmosphere. Exposure to flame (FIG. 8A), occurrence of explosion (FIGS. 8B and 8C), termination of explosion (FIGS. 8D and 8E), foam after explosion (FIG. 8f). The sequence has a time interval of about 0.2 s.

DETAILED DESCRIPTION OF THE INVENTION

[0038] Embodiments of the foam for temporarily plugging pipes will be presented below and then the mode of preparation of the foam forming liquid (FFL), LDH and foam formation will be described, in addition to its use as a plug in pipes, the foam formulation and its use being a temporary plug for pipes, which are the objects of the present patent of invention. It is noteworthy that for formulating the foam, there is proposed a pathway for preparing FFL with different formulations and then a pathway for forming the foam. The formulations result in foam capable of plugging the pipe for over 8 h with resistance to pressure differences of up to 0.1 bar.

Preparation of the Foam Forming Liquid (FFL)

[0039] In one embodiment, the method of preparing the foam forming liquid (FFL) consisted of the following steps (FIG. 1A): [0040] a) Adding 7.9% (w/w) (0.26 mol) palmitic acid under stirring to a container containing 86.4% (864 mL) distilled water at 85° C.; [0041] b) Stirring for 5 min keeping the temperature at 85° C.; [0042] c) Adding 0.8% (w/w) (0.01 mol) ethoxylated lauryl ether glycolic acid co-surfactant (Laureth-11), stirring for 5 min while keeping the temperature at 85° C.; [0043] d) Adding 4.9% (w/w) (0.27 mol) triethanolamine base under stirring and agitate for 15 min. [0044] e) Allowing to cool and storing in a closed glass vessel.

[0045] In another embodiment, the method of preparing the foam forming liquid (FFL) consisted of the following steps: [0046] a) Adding 7.9% (w/w) (0.26 mol) palmitic acid under stirring to a container containing 86.4% (864 mL) distilled water at 85° C.; [0047] b) Stirring for 5 min, keeping the temperature at 85° C.; [0048] c) Adding 0.8% (w/w) (0.01 mol) ethoxylated lauryl ether glycolic acid co-surfactant (Laureth-11), stirring for 5 min while keeping the temperature at 85° C.; [0049] d) Adding 4.9% (w/w) (0.06 mol) ammonium hydroxide base under stirring and agitate for 15 min. [0050] e) Allowing to cool and storing in a closed glass vessel.

[0051] In another embodiment, the method of preparing the foam forming liquid (FFL) consisted of the following steps: [0052] a) Adding 7.9% (w/w) (0.26 mol) palmitic acid under stirring to a container with 86.4% (864 mL) distilled water at 85° C.; [0053] b) Stirring for 5 min, keeping the temperature at 85° C.; [0054] c) Adding 0.8% (w/w) (0.01 mol) ethoxylated lauryl ether glycolic acid co-surfactant (Laureth-11), stirring for 5 min while keeping the temperature at 85° C.; [0055] d) Adding 4.9% (w/w) (0.02 mol) sodium hydroxide base under stirring and agitate for 15 min. [0056] e) Allowing to cool to room temperature and storing in a closed vial.

[0057] In another embodiment, the method of preparing the foam forming liquid (FFL) consisted of the following steps: [0058] a) Adding 7.9% (w/w) (0.26 mol) palmitic acid under stirring to a container with 86.4% (864 mL) distilled water at 85° C.; [0059] b) Stirring for 5 min while keeping the temperature at 85° C.; [0060] c) Adding 0.8% (w/w) (0.01 mol) BRIJ-56 co-surfactant, stirring for 5 min while keeping the temperature at 85° C.; [0061] d) Adding 4.9% (w/w) (0.26 mol) triethanolamine base under stirring and agitate for 15 min. [0062] e) Allowing to cool and storing in a closed glass vessel.

[0063] In another embodiment the method of preparing FFL consisted of the following steps: [0064] a) Adding 0.26 mol soy fatty acid under stirring to a flask containing 845 mL distilled water at 85° C.; [0065] b) Stirring for 5 min while keeping the temperature at 85° C.; [0066] c) Adding 0.01 mol BRIJ-56 co-surfactant and stir for 5 min while keeping the temperature at 85° C.; [0067] d) Under stirring, add 0.26 mol triethanolamine, stir for 15 min. [0068] e) Allowing to cool and storing in a closed glass vessel.

[0069] In another embodiment the method of preparing FFL consisted of the following steps: [0070] a) Adding 0.26 mol soy fatty acid under stirring to a flask containing 845 mL distilled water at 85° C.; [0071] b) Stirring for 5 min while keeping the temperature at 85° C.; [0072] c) Adding 0.01 mol BRIJ 56 co-surfactant and stir for 5 min while keeping the temperature at 85° C.; [0073] d) Under stirring, adding 0.03 mol NH.sub.4OH and 0.23 mol triethanolamine and stir for 15 min. [0074] e) Allowing to cool and storing in a closed glass vessel.

[0075] Further fatty acids may be added in place of palmitic acid, such as linoleic, oleic or stearic acids, or a mixture thereof (distilled soy fatty acid) or the like.

[0076] The co-surfactant Laureth-11 can be replaced by polyethylene glycol hexadecyl ether (BRIJ-58), polyoxyethylene (10)cetyl ether (BRIJ-56), polyoxyethylene (23)lauryl ether (Laureth-23) or a mixture thereof or the like.

[0077] Other bases can be added in place of triethanolamine such as sodium or ammonium hydroxides or the like, or a mixture of these bases.

Preparation of LDH Sol

[0078] In one embodiment, the method of preparing lamellar double hydroxides (LDH) consisted of the following steps (FIG. 1B): [0079] a) Adding a mixture of zinc chloride (342 mg, 2.5 mmol) and aluminum chloride (302 mg, 1.25 mmol) in 2.5 mL water/ethanol solution at a 1:1.5 ratio (v/v) in order to obtain a cations concentration of 1.0 mol.Math.L.sup.−1. [0080] b) Adding 131 μL (1.25 mmol) acetylacetone (acac) under mechanical stirring and then; [0081] c) 1.31 mL (18.75 mmol) propylene oxide (PO) under stirring for another 1 min. [0082] d) Closing the reaction flask and keeping the sample for 72 h at 25° C. The concentrated nanoparticle suspension contains about 10% (m/v) LDH.

[0083] In another embodiment, the method of preparing lamellar double hydroxides (LDH) consisted of the following steps: [0084] a) Adding a mixture of nickel nitrate (1.5 mmol), magnesium nitrate (1.0 mmol) and aluminum nitrate (1.25 mmol) in 2.5 mL of a water/ethanol solution at a 1:1 ratio, 5 (v/v) in order to achieve a cation concentration of 1.0 mol.Math.L′.sup.1. [0085] b) Adding 131 μL (1.25 mmol) acetylacetone (acac) under mechanical stirring and then; [0086] c) 1.31 mL (18.75 mmol) propylene oxide (PO) under stirring for another 1 min. [0087] d) Closing the reaction flask and keeping the sample for 72 h at 25° C. The concentrated nanoparticle suspension contains about 10% (m/v) LDH.

[0088] Other metallic salts can be used, such as zinc, copper, tin nitrates, or chlorides of these metals, or other equivalents. Preparation of foam with LDH

[0089] In one embodiment, the method of preparing the LDH-containing foam consists of the following steps (FIG. 1C): [0090] a) Adding 83.8 mL FFL in a flask: [0091] b) Adding, under magnetic stirring, 16.2 mL of a LDH suspension; [0092] c) Stirring for another 1 min; [0093] d) Adding the mixture to the foam forming system.
The resulting mixture has 1.5% (w/w) nanoparticles.

[0094] In another embodiment, a foam solution having a nanoparticle concentration of 0.5% was prepared, according to the following steps: [0095] a) Adding 83.8 mL FFL to a flask; [0096] b) Adding, under magnetic stirring, 10.8 mL of distilled water; [0097] c) Adding, under magnetic stirring, 5.4 mL of a LDH suspension; [0098] d) Stirring for another 1 min; [0099] e) Adding the mixture to the foam forming system.

Foam Formulation Compositions

[0100] The present invention is characterized by being made of a surfactant or a mixture of surfactants, a co-surfactant or a mixture of co-surfactants, a base or a mixture of bases and LDH nanoparticles (of inverse surface charge to that of the surfactant ion) responsible for the programmed increase in viscosity and elastic modulus of the initial liquid foam.

[0101] The invention consists of formulating a foam containing fatty acid preferably at a concentration between 0.09 and 0.54 mol.Math.L.sup.−1, more preferably at a concentration between 0.15 and 0.40 mol.Math.L.sup.−1, most preferably at a concentration between 0.20 and 0.30 mol.Math.L.sup.−1. The foam further contains acid or ethoxylated hydrocarbon alcohol, preferably at a concentration between 0.001 and 0.060 mol.Math.L.sup.−1, more preferably at a concentration between 0.005 and 0.020 mol.Math.L.sup.−1 and most preferably at a concentration between 0.008 and 0.012 mol.Math.L.sup.−1. The foam further contains a base that acts to form the ionic surfactant (and co-surfactant) that is present in a concentration that ranges preferably between 0.009 and 0.84 mol.Math.L.Math..sup.−1, more preferably between 0.018 and 0.36 mol.Math.L.sup.−1, most preferably between 0.02 and 0.30 mol.Math.L.sup.−1. Finally, foam precursor solutions having LDH concentrations preferably ranging between 0.5 and 3% (w/w), more preferably between 1 and 2%, most preferably between 1.25 and 1.75% can be prepared.

[0102] The surfactant precursor is from the class of fatty acids of the C.sub.mH.sub.nCOOH type, with 15≤m≤17 and 31≤n≤33, such as palmitic acid, linoleic acid, oleic acid and linolenic acid, or a mixture thereof. The co-surfactant belongs to the class of alcohols or glycolic acids of the ethoxylated lauryl ether type or a mixture thereof, of the R.sub.1C.sub.xH.sub.y(C.sub.2H.sub.4O).sub.zR type, where 12≤x≤16, 27≤y≤31, 10≤z≤21, R.sub.1 being H or O and R.sub.2 being the alcohol, carboxylic acid or ether function (—CH.sub.2OH, —CH.sub.2COOH or —OC.sub.2H.sub.5), such as Laureth-11, Brij-58, Brij-56 or Laureth-23. The pH adjusting agent is a (strong or weak) base, such as sodium hydroxide, ammonium hydroxide or triethanolamine, or a mixture thereof. The nanoparticles are double lamellar hydroxides, in this instance, made of lamellae of a mixture of aluminum oxyhydroxide and zinc oxyhydroxide. LDH nanoparticles can also be made of a mixture of aluminum, nickel and magnesium oxyhydroxide, or any other LDH-forming mixtures, whose surface has a positive charge or a charge that i inverse to that of the surfactant ion in solution.

Features of the New LDH-Containing Foam Formulation

[0103] The use of fatty acid as a surfactant plays an important role in lowering the surface tension of the liquid and accordingly increasing the foam volume and stability as compared, for example, with the surfactant sodium dodecyl sulfate (SDS), as seen in FIGS. 2A and 2B, which compares the stability of foams made of SDS with those made of palmitic acid. Stability of the foam volume increases with time and there is also less drainage of the liquid phase for samples whose formulations differ only by the nature of the surfactant.

[0104] The better performance of the palmitic acid containing formulation is explained by the gradual increase in viscosity and elastic modulus (FIG. 3) over time, which contributes to a greater stabilization of the foam. Viscosity of the sample reaches a plateau after about 6 h.

[0105] FIGS. 4A and 4B show the X-ray diffraction patterns monitored by SAXS (in 3D and 2D) for the foam formulation containing palmitate ion and LDH. Two peaks at q(Å.sup.−1)=0.175 and 0.165 Å.sup.−1 are seen, where intensity of the first peak decreases over time while that of the second peak increases. The initial peak position matches the distance between the LDH lamellae intercalated with counterions (Cl.sup.− or NO.sub.3.sup.−), on the other hand, values of the peak of increasing intensity match the distance between the lamellae containing an intercalated double layer of the palmitate ion. Progression of such an ion exchange process asymptotically tends to a steady state after 6 h, which is very close to the equilibrium reached by viscosity (FIG. 3). Therefore, the increased viscosity can be explained by the expansion of the volume of LDH particles caused by the ion exchange of Cl.sup.− and/or NO.sub.3.sup.− ions initially present with fatty acid ions. Such a substitution does not happen with the formulation containing SDS surfactant. This specific stabilization behavior of the foam containing both LDH and surfactant based on fatty acid demonstrates the inventive step and novelty of the present invention.

Temperature Stability Test of the LDH Containing Foam

[0106] A foam sample made with palmitic acid, Laureth-11, triethanolamine and 1.5% LDH was applied in a thermostat glass tube, which allowed to assess foam stability as a function of time and temperature. The images in FIGS. 5A and 5B illustrate stability of the foam kept at 60° C. for 8 h, demonstrating its potential as a pipe plugging device during hot maintenance work.

Plugging Capacity and Flammability Test

[0107] The foam of the present invention was applied to the central part of a steel tube of 1 m in length and 4″ in diameter (FIGS. 6A to 6C), forming a block of 15 cm in length (approximately), having on one side of the tube an inert atmosphere and on the other side an explosive atmosphere with application on the tube walls of a mixture of gasoline and diesel (ratio 1:1). The tube ends were sealed and after 1 h the seals were removed and the (supposedly) inert tube end was exposed to the flame (FIG. 7). In this procedure, no occurrence of fire or explosion was seen. Then, the end contaminated with the explosive atmosphere was also exposed to the flame, causing the explosive atmosphere to fire (FIGS. 8A to 8F) without flame propagation through the foam plug, proving its ability to plug an explosive atmosphere.

[0108] An advantage of the foam of the present invention is its ease of application, as seen in FIGS. 6A to 6C.

[0109] Another great advantage of this foam is its plugging ability, separating the inert atmosphere (FIG. 7) from the explosive atmosphere (FIGS. 8A to 8F), resistance to pressure differences of up to 0.1 bar and resistance to explosions, as seen in FIGS. 8A to 8F, where the foam remains intact after the explosion.

[0110] The scope and contents of the present invention are not construed to be limited by the aforementioned applications, but by the terms defined in the claims and equivalents thereof.