FOR GAS PIPELINE COATING

FIELD

[0001] The present disclosure relates to compositions suitable for coating gas pipelines and methods of applying such compositions. The compositions and methods are particularly suited for use in the in situ rehabilitation of gas lines such as natural gas main and service pipes.

SUMMARY

[0002] Briefly, in one aspect, the present disclosure provides a gas pipeline coating composition comprising a Part A and a Part B. Part A comprises at least one polyamine that is a liquid at 25 °C; at least one polyol having a hydroxyl functionality of greater than 2; at least one diol; and a first thixotropic agent. Part B comprises at least one polyisocyanate; and a second thixotropic agent. Generally, the first and second thixotropic agents may be the same or different thixotropic agents.

[0003] In some embodiments, the polyamine comprises an aromatic diamine, e.g., an aromatic, secondary diamine. In some embodiments, the polyol is selected form the group consisting of castor oil, synthetic castor oil, and combinations thereof. In some embodiments, the polyol has a functionality of less than 3. In some embodiments, the diol is an aliphatic diol having 3 to 10 carbon atoms. In some embodiments, the diol is a branched aliphatic diol.

[0004] In some embodiments, the polyisocyanate has an isocyanate functionality of greater than 2, e.g., in some embodiments the polyisocyanate has an isocyanate functionality of 3.

[0005] In some embodiments, the composition comprises at least 0.7 and no greater than 3 pbw of the thixotropic agent. In some embodiments, the ratio of low shear rate viscosity to high shear rate viscosity (Ratio 1 rpm/50 rpm) is at least 3, e.g., at least 5, as measured according to the Viscosity Procedure.

[0006] In some embodiments, the composition is substantially free of aspartic acid esters.

[0007] In another aspect, the present disclosure provides a method of applying a coating on an internal surface of a gas pipeline comprising: a) providing the coating composition according to any of the compositions of the present disclosure; b) combining Part A and Part B to form a liquid mixture; c) applying the liquid mixture to the internal surface of the gas pipeline; and d) allowing the liquid mixture to set forming a cured coating. In some embodiments, the cured coating comes in contact with natural gas.

[0008] In some embodiments, step c) comprises applying the liquid mixture to the internal surface of the gas pipeline having a length of at least 20 meters. In some embodiments, step c) comprises applying the liquid mixture in situ to the internal surface of the gas pipeline, wherein the gas pipeline is buried underground.

[0009] In some embodiments, the cured coating has a flexural strength of at least 8 MPa and a flexural modulus of at least 350 MPa, as measured according to the Flexural Properties Procedure. In some embodiments, the cured coating is resistant to immersion in n-hexane for 14 days as measured according to the Immersion Test Procedure .

[0010] The above summary of the present disclosure is not intended to describe each embodiment of the present invention. The details of one or more embodiments of the invention are also set forth in the description below. Other features, objects, and advantages of the invention will be apparent from the description and from the claims. DETAILED DESCRIPTION

[0011] Aging infrastructure is a critical issue facing many governments and communities. For example, there is a significant need for materials and methods useful for the rehabilitation of existing pipelines. In particular, there is a need for in situ rehabilitation solutions that can be more cost effective and less disruptive than removing and replacing existing systems.

[0012] U.S. Patent No. 7, 189,429 ("Method for Renovating Pipelines") describes a method of forming a coating on the internal surface of a drinking water pipeline. The method includes the steps of: a) providing a liquid, two-part coating system; b) mixing together the first part and the second part to form a mixture, and c) applying the mixture as a coating to said surface so as to form, at high cure rate, a monolithic lining which exhibits high strength and flexibility. Preferably the two parts of the system are applied through heated airless spray equipment. Such equipment may, for example, include a centrifugal spinning head or a self-mixing spray gun assembly.

[0013] International Publication Number WO 2010/120617 A2 ("Method and Composition Suitable for Coating Drinking Water Pipelines") describes a method of forming a coating on the internal surface of a drinking water pipeline. The coating composition comprises a first part comprising at least one polyisocyanate and a second part comprising at least one aspartic acid ester and, optionally, at least one aromatic amine that is a solid at 25 °C.

[0014] U.S. Patent Application Publication Number US 2011/0070387 Al ("Polyurea

Composition") describes a two-component coating system containing (A) a polyisocyanate prepolymer having polyether groups bonded through allophanate groups and (B) a mixture of polyamines in which at least 75 mole % of all NH groups originate from an amino-functional polyaspartic acid ester.

[0015] Numerous problems arise when trying to use coatings and methods developed for water pipes to rehabilitate gas pipes. For example, twenty-meter application distances are common for gas pipes, while shorter application distances are more common for water pipes. Also, significantly lower pressures are used in gas service lines compared to drinking water pipes. Therefore, thinner, more uniform coat weights are more critical to minimize pressure drops in gas lines. In addition, coatings are applied to water pipes to act as a simple barrier to prevent the existing pipes (often made from lead) from contaminating the drinking water; thus, thin, nonuniform coatings can be tolerated. For natural gas pipe rehabilitation, the applied coating is often designed to replace the structural integrity of the existing service lines. Thus, coatings having at least a minimum, preferably uniform thickness may be preferred. Also, the coating may provide the desired mechanical properties to serve as the structural element of the service line. Finally, the coatings may need to be selected to resist degradation in the presence of the gas, e.g., natural gas.

[0016] In some cases, the requirements for gas pipelines lead to conflicting product requirements. For example, slow curing, low viscosity compositions may be better suited to meet the need for long application distances. In contrast, fast curing, high viscosity coatings may be required to achieve uniform coating thicknesses. Also, thicker coatings might be more suitable to provide the required structural integrity, yet such thicker coatings could result in unacceptable increases in pressure drop as the flow diameter is reduced.

[0017] The present inventors have discovered coating compositions and application methods that meet some or all of these competing requirements. In general, the coating compositions result from combining two parts. The first part comprises at least one polyamine and at least one polyol. The second part comprises a polyisocyanate that reacts with the polyamine to form urea linkages and with the polyol to form urethane linkages resulting in a cured or set composition. At least one part, and in some embodiments, both parts further comprise a thixotropic agent ("thixotrope"). In some embodiments, the compositions also include one or more optional components such as catalysts, fillers, pigments, and the like.

[0018] The first part (sometimes referred to as "Part A") of the coating composition is the amine- and hydroxyl-group containing portion. Part A comprises at least one polyamine. As used herein, polyamine refers to compounds having at least two amine groups, each containing at least one active hydrogen (N-H group). In some embodiments, a polyamine may include primary amines, secondary amines, or a combination thereof. [0019] In some embodiments, suitable polyamines include cycloaliphatic and aromatic diamines. In some embodiments, secondary cycloaliphatic or aromatic diamines may be preferred. In some embodiments, the cycloaliphatic or aromatic diamines may be solid at 25 °C. However, such solid materials may be difficult to fully dissolve. Also, when solid materials are dissolved, the resulting effects on the viscosity may interfere with the desired rheological behavior of the coating composition. Thus, in some embodiments, cycloaliphatic or aromatic diamines that are liquid at 25 °C may be preferred. Exemplary diamine curatives that are liquid at 25 °C include those available under the tradenames ETHACURE from Albamarle Corp.; U ILINK from Dorf Ketal, LLC; and LONZACURE from Lonza Group Ltd.

[0020] In some embodiments, at least one polyamine may be an aspartic acid ester. Preferred aspartic acid ester amines have the following Formula I

Formula I wherein R ¹ is a divalent organic group (up to 40 carbon atoms), and each R ² is independently an organic group inert toward isocyanate groups at temperatures of 100°C or less.

[0021] In some embodiments, R ¹ is an aliphatic group (preferably, having 1-20 carbon atoms), which can be branched, unbranched, or cyclic. In some embodiments, R ¹ is selected from the group of divalent hydrocarbon groups obtained by the removal of the amino groups from 1,4- diaminobutane, 1,6-diaminohexane, 2,2,4- and 2,4,4-trimethyl- 1,6-diaminohexane, l-amino-3,3,5- trimethyl-5-aminomethyl-cyclohexane, 4,4'-diamino-dicyclohexyl methane or 3, 3 -dimethyl -4,4'- diamino-dicyclohexyl methane. In some embodiments, R ¹ preferably comprises a dicyclohexyl methane group or a branched C4 to C12 group. R ² is typically independently a lower alkyl group (having 1-4 carbon atoms). Exemplary aspartic acid esters are commercially available under the tradename DESMOPHEN from Bayer Corp., including DESMOPHEN NH 1220 and

DESMOPHEN NH 1420.

[0022] However, the present inventors have discovered that the cure properties of compositions prepared with aspartic acid esters may be undesirable in some gas pipeline applications. For example, the compositions tend to cure from the surface, which can lead to a skinning effect. This can contribute to long cure times or poor cure. This skinning may also result in significant thickness variations. Therefore, in some embodiments, aspartic acid esters present in the composition provide no greater than 0.05 equivalents of amine per equivalent of isocyanate groups, e.g., no greater 0.02 equivalents of amine per equivalent of isocyanate groups. In some embodiments, the composition is substantially free of aspartic acid esters (e.g., no greater 0.01 or even no greater than 0.005 equivalents of amine from aspartic acid esters per equivalent of isocyanate groups), or even free of aspartic acid esters.

[0023] The first part of the coating composition also comprises at least one polyol. Generally, the use of at least one diol may be preferred making it easier to control the overall rheological properties of Part A and the resulting composition. Exemplary diols include linear and branched, aliphatic diols. In some embodiments, low molecular weight diols, for example, low molecular weight aliphatic diols may be preferred. In some embodiments, the low molecular weight diols comprise 3 to 10 carbon atoms, for example, 3 to 8, 4 to 8, or even 4 to 6 carbon atoms.

[0024] In some embodiments, branched diols may be preferred. The present inventors discovered that such branched diols can help retain the desired low viscosity in solution similar to straight chain diols but, surprisingly, they can also provide enhanced mechanical properties in the cured composition. For example, the use of branched diols was found to reduce the flexibility of the cured composition compared to similar compositions using a linear diol. Suitable diols include 2 -Methyl- 1,3 -Propanediol and 1,5-pentanediol.

[0025] In some embodiments, Part A comprises a polyol with more than two hydroxyl groups, for example, a triol or a tetraol. As used herein, "higher-functional polyol" refers to polyols having a functionality greater than 2. In some embodiments, the composition comprises at least one higher-functional polyol having a functionality of at least 2.1, e.g., at least 2.2, or even at least 2.3. In some embodiments, if the functionality is too high, the degree of crosslinking may lead to poorer properties for example, excessively high viscosities. In some embodiments, the composition comprises at least one higher-functional polyol having a functionality of no greater than 3, e.g., no greater than 2.9, or even no greater than 2.7. In some embodiments, at least one higher-functional polyol has a functionality of 2.1 to 2.9, e.g., 2.2 to 2.8, or even 2.3 to 2.7.

[0026] Generally, the higher-functional polyols have a higher molecular weight than the diols. In some embodiments, the higher-functional polyols may have at least 15 carbon atoms, e.g., at least 30 carbon atoms, or even at least 50 carbon atoms.

[0027] Higher functional polyols include polyether polyols, polyester polyols, and

polyether/polyester polyols. In some embodiments, the polyol may be castor oil. Generally, castor oil primarily contains a triglyceride based on ricinoleic acid, an 18-carbon fatty acid that has a hydroxyl functional group on the twelfth carbon atom. In some embodiments, synthetic polyols based on castor oil may be used, including, e.g., those available under the tradename ALBIDUR from Alberdingk Boley (e.g., ALBIDUR 901, 903, 904, 912, and 921). [0028] Such higher-functional polyols may be used alone or in combination with one or more diols. In some embodiments, Part A includes at least one low molecular weight diol (e.g., an aliphatic diol with no greater than 10 carbon atoms) and at least one higher-functional polyol. In some embodiments, the low molecular weight diol is a branched aliphatic diol and the higher- functional polyol has a functionality of 2.1 to 2.9 (e.g., certain synthetic castor oils).

[0029] The second part (sometimes referred to as "Part B") of the composition is the isocyanate-group containing portion of the composition. Part B comprises at least one polyisocyanate. As used herein, "polyisocyanate" refers to any organic compound that has two or more reactive isocyanate groups (R-N=C=0) in a single molecule.

[0030] Generally, when Parts A and B are mixed, at least some of the isocyanate groups react with the amine groups to form urea linkages (-NR-C(O) -NR-). Also, at least some of the isocyanate groups react with the hydroxyl groups to form urethane linkages (-NR-C(O)O -NR-). When the two-part coating composition comprises other isocyanate reactive or amine reactive components, the reacted coating may comprise other linkages as well. Generally, these curing or setting reactions can proceed at ambient conditions. That is, no heat or actinic radiation is required to cure the compositions. Thus, the coatings are suitable for in situ applications.

[0031] Suitable polyisocyanates include, for example, diisocyanates, triisocyanates, tetraisocyanates, etc., and mixtures thereof. Cyclic and/or linear polyisocyanates may be employed. In some embodiments, aliphatic polyisocyanates may be preferred. Suitable aliphatic polyisocyanates include derivatives of hexamethylene-l,6-diisocyanate; 2,2,4- trimethylhexamethylene diisocyanate; isophorone diisocyanate; and 4,4'-dicyclohexylmethane diisocyanate. Alternatively, reaction products or prepolymers of aliphatic polyisocyanates may be used. Preferred aliphatic polyisocyanates are solvent-free and are substantially free of isocyanate monomer, i.e. less than 0.5 % and more preferably no greater than 0.3 % as measured according to DIN EN ISO 10 283.

[0032] In some embodiments, at least one polyisocyanate comprises one or more derivatives of hexamethylene-l,6-diisocyanate (HDI), e.g., an uretdione of HDI, a biuret of HDI, a isocyanurate of HDI, and combinations thereof. In some embodiments, higher-functional isocyanates (i.e., isocyanates having a functionality of greater than 2) may be useful to enhance the crosslinking and resultant mechanical properties of the cured coating. In some embodiments, the higher-functional isocyanates have a functionality of greater than 2.2, e.g., greater than 2.5. For example, in some embodiments, trimers and tetramers may be preferred.

[0033] In some embodiments, polyisocyanates having a low viscosity at room temperature (20 to 25 °C) may be preferred to aide in controlling the overall rheological properties of the parts and the composition (e.g., no greater than 5000 milliPascal'seconds (mPa ^« s) at 25 °C, no greater than 3000 mPa ^« s at 25 °C, or even no greater than 1500 mPa ^« s at 25 °C). One type of HDI uretdione polyisocyanate is available under the trade designation DESMODUR N 3400 from Bayer Corporation. This material is reported to have a viscosity of about 140 mPa ^« s at 25 °C. Another low viscosity polyisocyanate HDI trimer, reported to have a viscosity of about 1100 mPa ^« s at 23 °C, is available under the trade designation DESMODUR N 3600 from Bayer Corp.

[0034] Generally, the relative amounts of the polyols and amines in Part A compared to the amount of isocyanates in Part B are selected to achieve a stoichiometric ratio of reactive groups. In some embodiments, an excess of isocyanate groups may be used. Generally, the molar ratio of the equivalents of isocyanate groups (Eq-NCO) over the sum of equivalents of hydroxyl groups

(Eq-OH) and equivalents of amine groups (Eq-NH) is at least one. In some embodiments, the ratio of (Eq-NCO) / [(Eq-OH) + (Eq-NH)] is at least 1.02, e.g., at least 1.05, or even at least 1.1. In some embodiments, the ratio of (Eq-NCO) / [(Eq-OH) + (Eq-NH)] is no greater than 1.2, e.g., no greater than 1.15. If other materials that are reactive with the hydroxyl groups, the amine groups, or the isocyanate groups are present, these ratios should be adjusted. For example, if additional hydroxyl or amine reactive materials are present, the above ratios should be adjusted to account for only the hydroxyl and amine groups available to react with the isocyanate. Similarly, if additional isocyanate reactive materials are present, the above ratios should be adjusted to account for only those isocyanate groups available for reaction with the hydroxyl or amine groups.

[0035] As is understood by one of ordinary skill in the art, the amount of equivalents of a particular reactive group available for reaction may be less than the theoretical amount based on chemical structure. For example, manufacturing variations, steric hindrance, and other known factors may limit the number of functional groups readily capable of reacting. The above ratios may be adjusted to account for only available reactive groups. The theoretical values may be useful as a starting point. However, many commercially available materials have reported numbers of equivalents, which may be a better starting point. In addition, methods such as titration may be used to determine the available equivalents, with further refinements made by routine experimentation.

[0036] The present inventors discovered that the addition of a thixotropic agent (thixotrope) to one or both of Parts A and B resulted in compositions that upon mixing have a suitably low viscosity at the high shear rates associated with typical application procedures such as spray or air vortex delivery and yet a suitably high viscosity at the low shear rates associated with the coating once applied. Low viscosities during high shear application aide in applying the coating over long distances, e.g., at least 20 meters. High viscosities at low shear aide minimizing flow of the coating once it is applied to the pipe walls prior to cure.

[0037] Generally, a thixotrope or thixotropic agent is a material that when added to a composition results in the composition having a shear dependent viscosity, where the viscosity generally decreases as the shear rate increases. Thixotropic agents should be distinguished from fillers that may increase the composition viscosity uniformly over the range shear rates of interest, but do not result in any significant shear thinning behavior. For example, untreated metal oxides (e.g., silicon dioxide) and carbonates (e.g., calcium carbonate and dolomite) are common fillers that can increase the viscosity of compositions but do not result in any significant shear thinning behavior. In contrast, surface-treated silica, e.g., hydrophobic, fumed silica can provide excellent shear thinning behavior in some embodiments of the present disclosure. Suitable thixotropic agents include hydrophobic fumed silicas available under the tradename CAB-O-SIL available from Cabot Corporation (e.g., TS-710 and TS-720 surface-treated silicas). Other suitable thixotropic agents include those available under the trade name AEROSIL from Evonik Industries.

[0038] The total amount of thixotropic agent is generally determined by the total composition and the desired shear rate dependent viscosity of the final mixture. Generally, the ratio of low shear rate viscosity to high shear rate viscosity should be controlled. In some embodiments, the ratio of low shear rate viscosity to high shear rate viscosity is at least 3, e.g., at least 5. For example, in some embodiments, the viscosity may be measured according the Viscosity Procedure described herein. The resulting ratio of the viscosity measured at 25 °C using a number 6 spindle at 1 rpm (low shear rate) over the viscosity measured at 25 °C using a number 6 spindle at 50 rpm (high shear rate) will be at least 3, e.g., at least 5.

[0039] In some embodiments, the final composition (i.e., the mixture of Parts A and B) comprises at least 0.7, e.g., at least 0.9, or even at least 1.0 pbw of the thixotropic agent. In some embodiments, the final composition comprises no greater than 3, e.g., no greater than 2, or even no greater than 1.5 pbw of the thixotropic agent.

[0040] If the viscosities of Parts A and B are too dissimilar during mixing, it may be difficult to achieve proper mixing. Therefore, in order to aide in mixing Parts A and B, it can be desirable to include a portion of the thixotropic agent in both Parts A and B. The amounts of the thixotropic agent in each part depends on the composition of each part and the effect the thixotropic agent has on the viscosity of each part. In some embodiments, Part A (the amine- and polyol-containing component) comprises at least 0.4 pbw of the thixotropic agent, with the remainder in Part B. For example, in some embodiments, Part A comprises at least 0.6, at least 1.0, or even at least 1.2 pbw of the thixotropic agent. In some embodiments, Part A comprises no greater than 3, e.g., no greater than 2, or even no greater than 1.5 pbw of the thixotropic agent.

[0041] Generally, one or more thixotropic agents may used. In some embodiments, the same thixotropic agent(s) will be used in Parts A and B. In some embodiments, different thixotropic agents may be used.

[0042] Generally, the compositions of the present disclosure may include one or more optional additives to achieve known benefits. Examples include, but are not limited to pigments, dyes, fillers, defoamers, water scavengers, and molecular sieves. In some embodiments, additional resins may be included, e.g., epoxy resins. For example, in some embodiments, such resins may assist in compounding certain additives such as pigments into the system. In some embodiments, catalysts may be used, e.g., to enhance the rate of the isocyanate - hydroxyl reaction. Suitable catalysts include, e.g., metal catalysts such as those available under the trade names FOMREZ from Momentive Performance Materials, Inc., and DABCO from Air Products. In some embodiments, tin catalysts such as dimethyltin dineodecanoate may be used.

[0043] Although a primer may be used, the coating composition is typically applied directly to the internal surfaces of a pipe without a primer layer applied to the surface. The composition may be applied by any of various known coating application systems as described in the art. The composition may be formed when the pipeline is initially laid, or after a period of use when the pipeline itself begins to deteriorate. In some embodiments, the coating compositions may be applied in situ to pipelines buried underground.

[0044] In some embodiments, the same systems and general procedures used to apply coatings to drinking water pipes may be used. For example, United States Patent Number 7, 189,429 describes a method of forming a coating on the internal surface of a drinking water pipeline, the method comprising the steps of: a) providing a liquid, two-part coating system; b) mixing together the first part and the second part to form a mixture, and c) applying the mixture as a coating to said surface so as to form, at high cure rate, a monolithic lining which exhibits high strength and flexibility. In some embodiments, the two parts of the system are applied through heated airless spray equipment. Such equipment may, for example, include a centrifugal spinning head or a self- mixing spray gun assembly.

[0045] In some embodiments, the compositions of the present disclosure may be applied using an apparatus that allows the two parts to combine immediately prior to exiting the apparatus. For example, the first and second parts of the system may be fed independently, e.g. by flexible hoses, to a spraying apparatus capable of being propelled through an existing pipeline to be renovated. In some embodiments, the composition may be mixed and blown down the length of the pipeline. In some embodiments, the apparatus may heat one or both parts of the composition pipeline and mixes the two parts immediately before applying the mixture to the interior surface of the pipeline. The mixture of the two parts cures on the interior surface of the pipeline to form a (e.g. monolithic) lining.

[0046] In some embodiments, an airless spray apparatus, such as a centrifugal spinning head is employed. An airless, impingement mixing spray system generally includes the following components: a proportioning section which meters the two components and increases the pressure to above about 10 MPa (e.g., above about 1500 psi); optionally, a heating section to raise the temperatures of the two parts (preferably, independently) to control viscosity; and an impingement spray gun which combines the two parts and allows mixing just prior to atomization. In other embodiments, an air vortex can be used to propel the liquid coating along the pipe.

[0047] Generally, the compositions generally cure at ambient conditions. Curing can begin as soon as Parts A and B are mixed and continues for some time after the coating has been applied to the walls of the pipe.

Table 1: Summary of materials used in the preparation of the examples.

Name Description Trade Name and Source

(yellow pigment) BASF , Germany rutile titanium dioxide TIONA 595

Pigment-W

(white pigment) Cristal, Belgium

Bisphenol A CHS Epoxy 520

Epoxy

(mixed with Pigment W) Spolchemie, Czech Republic dimethyltin dineodecanoate FOMREZ UL28

Catalyst

Momentive, Germany

polydimethylsiloxane LA-E 450

Defoamer

Evonik, Germany

[0048] Application Procedure. The coating compositions were mixed and applied using SERLINE forced air vortex technology available from Whirlwind Utilities Company, UK.

[0049] Viscosity Procedure. Viscosity was measured using a Model DV-I+ viscometer from Brookefield Viscometers Ltd. with a Number 6 spindel at 20 °C. The LUBRIZOL TEST

PROCEDURE TP-AATM-105A-b, Edition: October 12, 2006, was followed.

[0050] Sagging Resistance Procedure. The sagging resistance of the compositions was evaluated according to ISO 16862:2003 (Paints and Varnishes - Evaluation of Sag Resistance").

[0051] Tensile Properties Procedure. The tensile strength and elongation at break were determined according to ASTM D638-08 "Tensile Properties of Plastics." The test specimens were Type IV with a thickness of 1.2 mm +/- 0.2 mm. The samples were cut from a free film that had been allowed to cure for seven days. The samples were tested at 50 mm/minute on a Lloyd Instruments LR30K testing machine with a 5 kN load cell using NEXYGEN software.

[0052] Flexural Properties Procedure. Flexural properties were tested according to ASTM D790-07 ("Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials"). The test specimens were 165 mm x 12.7 mm x 6 mm molded bars. The samples were formed with a steel mold and allowed to cure for seven days. The samples were tested at 3.5 mm/minute on a Lloyd Instruments LR30K testing machine with a 5 kN load cell using

NEXYGEN software.

[0053] The composition of Part B was the same for each sample and is summarized in Table 2. Table 2: Composition of Part B in parts by weight (pbw).

[0054] Sample EX-1 was prepared based on a commercially available coating for water pipes. A yellow pigment was added, as this color is common in gas pipe applications. The resulting composition of Part A is summarized in Table 3.

Table 3: Composition of Part A in parts by weight (pbw).

[0055] The Application Procedure was used to mix 100 parts by weight of Part A with 60 parts by weight of Part B and apply the resulting composition to the interior of a pipe having an interior diameter of 19 millimeters. The mixing ratio resulted in a ratio of isocyanate equivalents to the sum of hydroxyl and amine equivalents of 1.06. This coating had a good travel time of 7 minutes, but the travel distance was only 12 meters, well below the target distance of 20 meters. Also, there were significant coating variations with application thicknesses ranging from 200 to 1000 microns. The variation in application thickness was caused by gravitational flow of the applied coating prior to cure. Attempts to reduce gravitational flow by increasing the amount of thixotrope led to even shorter travel distances.

[0056] Two samples were prepared, replacing the solid amine curative with liquid amine curatives. The compositions of Part A are summarized in Table 4A. The Application Procedure was used to mix 100 parts by weight of Part A with 60 parts by weight of Part B and apply the resulting compositions to the interior of a pipe having an interior diameter of 19 millimeters.

[0057] Sample EX-2 had a travel distance of 20 meters and a travel time of 5 minutes.

Although Sample EX-3 had a travel distance of 22 meters, the travel time was 11 minutes, which may be too long for some applications. In addition, upon examining the cured coating of EX-3, significant non-uniformities were detected. The coating appeared to cure from the surface down, resulting in poor cure and a rippled surface. The use of aspartic acid amine curatives contributes to this surface curing affect. Table 4A: Composition of Part A for Samples EX-2, EX-3, and EX-4 (pbw).

[0058] Sample EX-4 was a further modification of Sample EX-2, replacing the

polyether/polyester resin with castor oil. The composition of Part A is summarized in Table 4A. The Application Procedure was used to mix 100 pbw of Part A with 60 pbw of Part B and to apply the resulting compositions to the interior of a pipe having an interior diameter of 19 millimeters. Sample EX-4 had a travel distance of 20 meters and a travel time of 5 minutes.

[0059] Samples EX- 1 to EX-4 were evaluated using the Viscosity Procedure and the Sagging Resistance Procedure. The results are summarized in Table 4B.

Table 4B: Summary of Samples EX-1 to EX-4.

[0060] Samples EX-2 and EX-4 showed the best combination of properties including travel time, travel distance, sagging resistance, and cure behavior - including surface uniformity. The amount of thixotrope in these samples was increased resulting in the viscosity behavior summarized in Table 5A. The increased amount of thixotrope was offset by a corresponding decrease in the amount of filler. All other components of Parts A and B were unchanged.

Table 5A: Summary of modifications to Samples EX-2 and EX-4.

[0061] The samples with Polyol-B (castor oil) showed significantly greater thixotropic behavior that the samples with Polyol-A (polyether/polyester polyol). The ratio of low shear rate viscosity to high shear rate viscosity (Ratio 1 rpm/50 rpm) was only about 2 to 2.5 when using Polyol-A. With Polyol-B, this viscosity ratio was greater than 5 (about 6 to 13).

[0062] The cured coatings of gas pipelines may have structural requirements that water pipeline coatings do not. For example, in some embodiments, the in situ formed cured coating may need to perform even in the absence of the host pipe. The physical properties of cured Samples EX- 1 and EX-4b were measured according to the Tensile Properties Procedure and Flexural Properties Procedure. The results for three replicates are summarized in Table 5B.

Table 5B: Physical properties Samples EX-2 and EX-4.

[0063] Both sample formulations may be too flexible for use as a structural replacement in the rehabilitation of gas pipe service lines. In some embodiments, a Flexural Strength of at least 8 MPa, e.g., at least 9 or even at least 10 MPa is desired. In some embodiments, a Flexural Modulus of at least 350 MPa, e.g., at least 400, or even at least 500 MPa is desired. In some embodiments, meeting both of these flexural strength requirements is desired.

[0064] Two approaches were taken to improve the physical properties. First, in Samples EX-5 and EX-6, a portion of the polyol curative (Polyol-B) was replaced with an aspartic acid ester curative (Amine-D). Amine-D (DESMOPHEN NH1420) is slower curing that Amine-C

(DESMOPHEN NH1220). The resulting blend of Amine-B and Amine-C was used in an attempt to reduce or eliminate the undesirable skinning (surface curing) effect noted with Sample EX-3, while obtaining enhanced physical properties. Second, in Samples EX-6 and EX-7, a short chain branched diol (DIOL-B) was substituted for the short chain linear diol (DIOL-A). The compositions are summarized in Table 6A. The composition of Sample EX-4b is included for comparison.

[0065] The mix ratio for Samples EX-5, EX-6 and EX-7 were 100 pbw Part A to 70 pbw Part B, resulting in 1.45 pbw of the thixotrope in the final mixture. The physical properties of cured Samples EX-5, EX-6, and EX-7 were measured according to the Tensile Properties Procedure and the Flexural Properties Procedure. The results for three replicates are summarized in Table 6B.

Table 6A: Composition of Part A in parts by weight (pbw).

Table 6B: Physical properties Samples EX-5, EX-6, and EX-7.

Tensile Young' Elongation Flexural Flexural

Strength Modulus at break Strength Modulus

(MPa) (MPa) (%) (MPa) (MPa)

18.1 163 55 10.7 479

EX-5 18.2 268 50 10.4 472

18.4 168 55 9.8 440 Tensile Young' Elongation Flexural Flexural

Strength Modulus at break Strength Modulus

(MPa) (MPa) (%) (MPa) (MPa)

19.2 215 60 12.9 607

EX-6 17.2 203 40 11.2 550

17.0 173 40 12.6 615

14.6 58 75 5.1 178

EX-7 14.7 49 75 5.1 148

14.0 59 65 5.2 158

[0066] Samples EX-5 and EX-6, which included the aspartic acid curative (Amine-D), had improved flexural properties suitable for structural rehabilitation of gas lines. The replacement of the linear diol (Diol-A) with the branched diol (Diol-B) improved the properties of aspartic acid containing sample (compare EX-6 with EX-5). However, such replacement of the diol had a smaller affect in the samples without the aspartic acid curative (compare EX-7 with EX-4b).

[0067] Further testing of Samples EX-5 and EX-6 was performed to determine resistance to natural gas using a liquid simulant. The Immersion Test Procedure followed ASTM D6943-15 ("Standard Practice for Immersion Testing of Industrial Protective Coatings and Linings"). The samples were immersed in n-hexane for 14 days. The samples were then examined and assessed for signs of blistering and softening. Both samples using the aspartic acid ester (Samples EX-5 and EX-6) exhibited blistering and softening. The aspartic acid esters in these samples contributed 0.09 equivalents of amine groups per equivalent of isocyanate groups. Therefore, in some embodiments, low levels of aspartic acid esters may be preferred. For example, in some embodiments, aspartic acid esters present in the composition provide no greater than 0.05 equivalents of amine per equivalent of isocyanate groups, e.g., no greater 0.02 equivalents of amine per equivalent of isocyanate groups. In some embodiments, the composition is substantially free of aspartic acid esters (e.g., no greater 0.01 or even no greater than 0.005 equivalents of amine from aspartic acid esters per equivalent of isocyanate groups), or even free of aspartic acid esters.

[0068] Despite the inferior physical properties of Sample EX-7, further modifications were made in an attempt to improve these properties without resorting to the use of aspartic acid esters. Sample EX-8 was identical to Sample EX-7 except the Polyol-B (castor oil) was replaced with Polyol-C (synthetic castor oil). Polyol-B had an OH-functionality of 2, while Polyol-C had an OH-functionality of 2.4.

[0069] The mixing ratio of Part A to Part B was adjusted to 100:80 to achieve a ratio of (Eq- NCO)/[(Eq-OH)+(Eq-NH)] of 1.04. The resulting mixture contained 1.45 pbw of the Thixotrope. The physical properties of cured Sample EX-8 were measured according to the Tensile Properties Procedure and the Flexural Properties Procedure. The results for three replicates are summarized in Table 7. Table 7: Physical properties Samples EX-8.

[0070] Not only are the physical properties of Sample EX-8 superior to those of Sample EX-7, they are comparable to the properties of Samples EX-5 and EX-6, without the need for an aspartic acid ester. These properties are also suitable for structural rehabilitation of gas lines.

[0071] Sample EX-8 was tested to determine resistance to natural gas using a liquid simulant. The samples were examined after 14 days immersion in n-hexane. In contrast to the samples containing aspartic acid esters, no adverse effects were detected with Sample EX-8.

[0072] Using the Application Procedure, samples EX-5 and EX-6 achieved a twenty meter application distance. Sample EX-8 achieved a 22 meter application distance, producing a uniform 2 mm thick coating. The rheology of Samples EX-6, EX-7, and EX-8 were measured using the Viscosity Procedure. The results are summarized in Table 8.

Table 8: Summary of properties of Samples EX-5, EX-6, and EX-8.

[0073] The effect of mix ratio for Sample EX-8 was evaluated by preparing Sample EX-8A. Sample EX-8 had a volumetric mix ratio of Part A:Part B of 1.1 : 1 (corresponding to a mass mixing ration of 100:80). Sample EX-8A had a volumetric mix ratio of Part A:Part B of 1 : 1, which is more easily achieved with conventional application equipment (corresponding to a mass mixing ration of 100:88). The physical properties measured according to the Tensile Properties Procedure were compared by taking the average values for five replicates of each Sample. These results are summarized in Table 9. Table 9: Tensile properties for Sample EX-8 and two mixing ratios.

[0074] In some embodiments, a useable life time of at least 4 minutes, e.g., at least 5 minutes may be desired to provide a coating which can be applied over the desired application distance of 20 meters. However, slowing the cure to achieve a longer useable life also increases the time to cure the system sufficiently to withstand damage. In some embodiments, damage resistance times of no greater than 90 minutes, e.g., no greater than 80 minutes, or even no greater than 70 minutes are desired. The level of catalyst in Sample EX-8 was 0.05 pbw in Part A, and 0.03 pbw for the overall mixture of Parts A and B. Using Sample EX-8 as the base formulation, the level of catalyst was varied from 0.03 pbw to 0.08 pbw in Part A. The resulting useable life and damage resistance times are summarized in Table 10.

Table 10: Effect of catalyst level.

[0075] In some embodiments, using the formulation of Example 8, catalyst levels of 0.04 to 0.07, e.g., 0.05 to 0.07, or even 0.05 to 0.06 in Part A may be preferred. In some embodiments, using the formulation of Example 8, catalyst levels of 0.02 to 0.04, e.g., 0.025 to 0.04, or even 0.025 to 0.035 in total composition (mixture of Parts A and B) may be preferred. The catalyst levels for other formulations and other catalysts may be determined in a similar manner.