WO2019003190A1

WO2019003190A1 - Composition comprising high creep rupture strength and methods of coating drinking water pipelines

Info

Publication number: WO2019003190A1
Application number: PCT/IB2018/054827
Authority: WO
Inventors: Chad M. AMB; Saswata CHAKRABORTY; Zai-Ming Qiu; Alexander J. KUGEL
Original assignee: 3M Innovative Properties Company
Priority date: 2017-06-30
Filing date: 2018-06-28
Publication date: 2019-01-03

Abstract

A method of forming a coating on a surface of a pipeline comprises the steps of: a) providing a coating composition comprising a first part comprising at least one polyisocyanate, and a second part comprising at least 20 wt.-% of aliphatic cyclic polyamine wherein the aliphatic cyclic polyamine is not an aspartic ester amine; b) combining the first part and the second part to form a liquid mixture; c) applying the liquid mixture to internal surfaces of the pipeline; and d) allowing the mixture to set forming a cured coating.

Description

COMPOSITION COMPRISING HIGH CREEP RUPTURE STRENGTH

AND METHODS OF COATING DRINKING WATER PIPELINES

BACKGROUND

Trenchless methods for structural renovation of drinking water pipelines include the pipe in pipe method, pipe bursting method, and polyethylene thin wall lining method. As described in U.S. Patent No. 7,189,429, these methods are disadvantaged by their inability to deal with multiple bends in a pipeline and the fact that lateral connection pipes to customers' premises are disconnected and then reinstated after execution of the renovation process.

Various compositions have been described that are suitable to form a coating on the internal surface of a drinking water pipeline. See for example U.S. Patent No.

7,189,429; U.S. Patent No. 6,730,353; WO2010/120617; US2014/0010956;

US2014/0014220; and US2007/0043197.

SUMMARY

Industry would find advantage in methods and compositions suitable to form a coating on the internal surface of a drinking water pipeline having improved properties.

In one embodiment, a method of forming a coating on a surface of a pipeline is described. The method comprises the steps of: a) providing a coating composition comprising a first part comprising at least one polyisocyanate, and a second part comprising at least 20 wt.-% of aliphatic cyclic polyamine wherein the aliphatic cyclic polyamine is not an aspartic ester amine; b) combining the first part and the second part to form a liquid mixture; c) applying the liquid mixture to internal surfaces of the pipeline; and d) allowing the mixture to set forming a cured coating.

In one embodiment, the components of the first and second part are selected such that the cured coating has a calculated 50 year creep rupture tensile strength of at least 8, 9 or lO MPa.

In one embodiment, the liquid mixture comprises less than 15% filler by volume, a polyether content ranging from 0 to 22 wt-%, and an average functionality of at least 2.35.

Also described are reactive two-part coating compositions and a method of determining the calculated 50 year tensile creep rupture tensile strength. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 depicts a perspective view of a pipe comprising a coating of a caliper of at least 5 mm.

FIG. 2 depicts a perspective view of a pipe comprising a coating not having a caliper of at least 5 mm.

Fig. 3 depicts a plot of stress versus time for various samples.

DETAILED DESCRIPTION

The present invention provides a two-part coating system that can be applied to internal pipeline surfaces so as to form, at a high cure rate, an impervious lining suitable for contact with drinking water. By virtue of its rapid setting characteristics and insensitivity to moisture, the system of the present invention is particularly useful as an "in-situ" applied lining for refurbishment of existing drinking water pipelines.

The first part of the two-part coating composition generally comprises at least one polyisocyanate and the second part comprises at least one polyamine. After application and curing, the coating composition comprises the reaction product of such first and second components. The reacted coating comprises urea groups (- R-C(O)- R-).

Polymers containing urea groups are often referred to as polyureas. When the two-part coating composition comprises other isocyanate reactive or amine reactive components, the reacted coating may comprise other groups as well.

The reactive components such as the polyisocyanate and polyamine can be characterized based on their functionality. Functionality may be calculated by dividing the molecular weight by the equivalent weight. The equivalent weight of isocyanate end groups can be determined by titration procedures with, for example ASTM D 2572-97. The equivalent weight of amine end groups can be determined by titration procedures with, for example ASTM D 2074-92. In the case of polyisocyanates, the average functionality is the average number of isocyanate (-NCO) groups of a polyisocyanate. In the case of polyamines, the average functionality is the average number of amine groups of a polyamine. The functionality is typically reported by the supplier. For example, Covestro, Leverkusen, Germany, reports the average functionality of their polyisocyanates. An average functionality is often reported when the material comprises a mixture of compounds. However, when the material is substantially a single compound, the material may be reported as difunctional (e.g. diamine) or trifunctional (e.g. triamine).

The first part of the two-part coating comprises one or more polyisocyanates.

"Polyisocyanate" refers to any organic compound that has two or more reactive isocyanate (-NCO) groups in a single molecule such as diisocyanates, triisocyanates, tetraisocyanates, etc., and mixtures thereof. Cyclic and/or linear polyisocyanate molecules may usefully be employed. The polyisocyanate(s) of the isocyanate component are preferably aliphatic. In typical embodiments, the (e.g. aliphatic) polyisocyanates are selected such that the total composition is substantially free of isocyanate monomer (e.g. less than 0.5%).

Suitable aliphatic polyisocyanates include derivatives of hexamethylene-1,6- diisocyanate; 2,2,4-trimethylhexamethylene diisocyanate; isophorone diisocyanate; and 4,4'-dicyclohexylmethane diisocyanate. Alternatively, reaction products or prepolymers of aliphatic polyisocyanates may be utilized.

The first part generally comprises at least one aliphatic polyisocyanate. Such aliphatic polyisocyanate typically comprises one or more derivatives of hexamethylene- 1,6-diisocyanate (HDI). In some embodiments, the aliphatic polyisocyanate is a derivative of isophorone diisocyanate. The aliphatic polyisocyanate may comprise an uretdione, biuret, and/or isocyanurate of HDI.

In some embodiments, the first part comprises at least one solvent-free aliphatic polyisocyanate(s) that is substantially free of isocyanate (HDI) monomer, i.e. less than 0.5 % and more preferably no greater than 0.3 % as measured according to DIN EN ISO 10 283. Various solvent-free aliphatic polyisocyanate(s) are available. One type of HDI uretdione polyisocyanate, reported to have an isocyanate content of 21.8 and a viscosity of 150 mPa- s at 23°C is available from Covestro under the trade designation "Desmodur N

3400". Another HDI polyisocyanate is a trimer, reported to have a viscosity of about 1200 mPa- s at 23°C is available from Covestro under the trade designation "Desmodur N 3600". Such polyisocyanates typically have an isocyanate content of 20-25%. Another polyisocyanate is an aliphatic prepolymer resin comprising ether groups, based on HDI is available from Covestro under the trade designation "Desmodur XP 2599". Yet another aliphatic HDI polyisocyanate is a trimer is available from Covestro under the trade designation "Desmodur N3800". This material has an NCO content of 11% and a viscosity of 6,000 mPa s at 23°C. Yet another aliphatic HDI polyisocyanate is a trimer is available from Covestro under the trade designation "Desmodur N3300". This material has an NCO content of 21.8% and a viscosity of 3,000 mPa s at 23 °C. Yet another aliphatic polyisocyanate resin based on HDI and isophorone diisocyanate is available from Covestro under the trade designation "Desmodur XP2838". This material has an NCO content of 20% and a viscosity of 3,000 mPa s at 23 °C. One type of HDI biuret polyisocyanate, is available from Covestro under the trade designation "Desmodur N 3200". This material has an NCO content of 20-25%) and a viscosity of 2,500 mPa- s at 23°C.

In some embodiments, the first part comprises a single aliphatic polyisocyanate based on hexamethylene-l,6-diisocyanate (HDI). In this embodiment, the first part may comprise 100 wt-%> of a single aliphatic polyisocyanate based on hexamethylene-1,6- diisocyanate (HDI). In some embodiments, the single aliphatic polyisocyanate has a viscosity of no greater than 1,500 mPa s at 23°C and a functionality ranging from about 2.8 to 3.5, such as "Desmodur N 3600". In typical embodiments, the first part further comprises additives, as will subsequently be described, such that the first part comprises less than 100 wt-%> of polyisocyanate.

In some embodiments, the first part comprises a mixture of aliphatic

polyisocyanates based on hexamethylene-l,6-diisocyanate (HDI). In one embodiment, the first part comprises a first aliphatic polyisocyanate having a viscosity of no greater than 1,500 mPa s at 23°C and a functionality ranging from about 2.8 to 3.5, such as "Desmodur N 3600," and a second aliphatic polyisocyanate having a functionality greater than the first aliphatic polyisocyanate. In some embodiments, the second aliphatic polyisocyanate has an average functionality of at least 3.6, 3.7, 3.8, 3.9, or 4.0 and typically no greater than 4, 5, or 6. In some embodiments, the second aliphatic polyisocyanate may have a higher viscosity than the first polyisocyanate. In some embodiments, the second aliphatic polyisocyanate has a viscosity of at least 1,600; 1,700; 1,800; or 1,900 mPa s at 23°C and typically no greater than 5,000; 4,500; 4,000; 3,500; or 3,000 mPa s at 23°C, such as "Desmodur XP 2599".

In this embodiment, the amount of first aliphatic polyisocyanate is typically at least 70, 75, or 80 wt.% and in some embodiments at least 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95 wt.%> or greater of the first part. In this embodiment, the amount of second aliphatic polyisocyanate is typically at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 wt.% or greater of the first part. Various other mixtures of aliphatic polyisocyanates based on hexamethylene-1,6- diisocyanate (HDI) can be used. In some embodiments, the mixtures comprise three or four different polyisocyanates.

In some embodiments, the first part is substantially free of other "amine reactive resin(s)" i.e. a resin containing functional groups capable of reacting with primary or secondary amines. For example, the first part is typically free of aromatic amine reactive resins. The first part may also be free of epoxy functional compounds and compounds containing unsaturated carbon-carbon bonds capable of undergoing "Michael Addition" with polyamines, (e.g. monomelic or oligomeric polyacrylates). The first part may optionally comprise non-reactive resins or the composition may be free of non-reactive resins.

The second part of the two-part coating comprises one or more polyamines. As used herein, polyamine refers to compounds having at least two amine groups, each containing at least one active hydrogen (N-H group) selected from primary amine or secondary amine. In some embodiments, the second component comprises or consists solely of one or more (e.g. secondary) polyamines.

In a preferred coating composition, as described herein the amine component comprises at least one aliphatic cyclic secondary polyamine (e.g. diamine). As described for example in US 6,005,062, aspartic ester amines react with isocyanates to form urea- diester linkages. However, urea-diester linkages are reportedly unstable, typically forming the hydantoin and an alcohol as a by-product. Hydantoin formation can cause dimensional changes of the polymer. Unlike aspartic ester amine, the amine component comprises at least one aliphatic cyclic secondary polyamine (e.g. diamine) that is not an aspartic ester amine. Therefore, such polyamine comprises secondary amine substituents, yet the polyamine lacks ester groups and specifically diester moieties.

In one embodiment, the second part comprises one or more aliphatic cyclic secondary diamines that comprise two, optionally substituted, hexyl groups bonded by a bridging group. Each of the hexyl rings comprise a secondary amine substituent.

The aliphatic cyclic secondary diamine typically has the general structure:

(Formula 1) wherein Ri and R2 are independently linear or branched alkyl groups, having 1 to 10 carbon atoms. Ri and R2 are typically the same alkyl group. Representative alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, secondary butyl, tertiary butyl, and the various isomeric pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups. The symbol "S" in the center of the hexyl rings indicates that these cyclic groups are saturated. The preferred Ri and R2 contain at least three carbons, and the butyl group is particularly favored, such as a sec-butyl group. R3, R4, R5 and R₆ are independently hydrogen or a linear or branched alkyl group containing 1 to 5 carbon atoms. R3, and R₄ are typically the same alkyl group. In some embodiments, R5 and R₆ are hydrogen. Further, in some embodiments, R3, and R₄ are methyl or hydrogen.

The substituents are represented such that the alkylamino group may be placed anywhere on the ring relative to the CR5R6 group. Further, the R3 and R₄ substituents may occupy any position relative to the alkylamino groups. In some embodiments, the alkylamino groups are at the 4,4'-positions relative to the CR5R6 bridge. Further, the R3 and R₄ substituents typically occupy the 3- and 3'-positions.

Commercially available aliphatic cyclic secondary diamines having this structure include:

"Clearlink 3000"

(Dorf Ketal 3,3'-dimethylcyclohexanamine,

Chemicals LLC, 4,4'-methylenebis(N-(l-

Stafford, TX) methylpropyl)-

In another embodiment, the second part comprises one or more aliphatic cyclic secondary diamines that comprise a single hexyl ring. The aliphatic cyclic secondary diamine typically has the general structure:

(Formula 2) wherein R₇ and Rs are independently linear or branched alkyl groups, having 1 to 10 carbon atoms or an alkylene group terminating with a -CN group. R7 and Rs are typically the same group. Representative alkyl groups include the same as those described above for Ri and R2. In one embodiment, R7 and Rs are alkyl groups having at least three carbons, such as isopropyl. In another embodiment, R7 and Rs are short chain (e.g. Cl- C4) alkylene groups, such as ethylene, terminating with a -CN group.

R9, Rio and R11 are independently hydrogen or a linear or branched alkyl group having 1 to 5 carbon atoms. R9, Rio and R11 are typically the same alkyl group. In some embodiments, R9, Rio and R11 are methyl or hydrogen. In one embodiment R9, Rio and R11 are methyl groups.

The substituents are represented such that the alkylamino group may be placed anywhere on the ring relative to the -NRs group. In some embodiments, the alkylamino group is 2 or 3 positions away from the -NRs. The preferred alkylamine group is two positions away from the -NRs group on the cyclohexyl ring.

In some embodiments, the aliphatic cyclic secondary diamine is prepared by the reaction product of (1 equivalent of) isophorone diamine and (2 equivalents of) a Michael acceptor group that reduces the nucleophilicity of the resulting secondary amine groups. Representative Michael acceptors include acrylonitrile and α,β-unsaturated carbonyl compounds, with acrylonitrile typically preferred. In some embodiments, the alkylene group between the terminal -CN group and the amine group has at least two carbon atoms.

Commercially available aliphatic cyclic secondary polyamines (e.g. diamines) having this structure include:

In some embodiments, the isocyanate-reactive component of the second part may include a single aliphatic cyclic secondary diamine comprising two hexyl rings bonded by a bridging group, such as a species according to Formula 1. In some embodiments, the isocyanate-reactive component of the second part comprises two or more aliphatic cyclic secondary diamines comprising two hexyl rings bonded by a bridging group, such as two or more species according to Formula 1. In some embodiments, the isocyanate-reactive component of the second part may include a single aliphatic cyclic secondary diamine comprising a single hexyl ring, such as a species according to Formula 2. In some embodiments, the isocyanate-reactive component of the second part comprises two or more aliphatic cyclic secondary diamines comprising a single hexyl ring, such as two or more species according to Formula 2. In yet other embodiments, the isocyanate-reactive component of the second part may include at least one aliphatic cyclic secondary diamine comprising two hexyl rings bonded by a bridging group (e.g. a specie or species according to Formula 1) and at least one aliphatic cyclic secondary diamine comprising a single hexyl ring (e.g. a specie or species according to Formula 2).

The second part typically comprises at least 20, 21, 22, 23, 24 or 25 wt.-% of aliphatic cyclic secondary polyamine(s) (e.g. diamine(s)). In some embodiments, the second part comprises at least 30, 35, 40, 45 or 50 wt.-% of aliphatic cyclic secondary polyamine(s) (e.g. diamine(s)). The amount of aliphatic cyclic aliphatic cyclic secondary polyamine(s) (e.g. diamine(s)) can range up to 100%. However, in typical embodiments, the second part further comprises a polyether polyamine and fillers, such as a thixotrope. Thus, the amount of aliphatic cyclic secondary polyamine(s) (e.g. diamine(s)) is less than 100%. In some embodiments, the second part comprises up to 70, 75, 80, 85, 90, or 95 wt.-% of aliphatic cyclic aliphatic cyclic secondary polyamine(s) (e.g. diamine(s)).

In typical embodiments, the liquid mixture of the first and second part further comprises a polyether component. In some embodiments, the polyether component may be an isocyanate functional polyether, such as Desmodur XP 2599. The polyether component may also be an isocyanate-functional prepolymer, where an alcohol or amine functional polyether is added to a large molar excess of isocyanate compound. The polyether component may also be an amine- functional prepolymer, where an isocyanate functional polyether is added to a large molar excess of polyamine.

In typical embodiments, the polyether component comprises one or more amine functional polyethers, such as the JEFF AMINE series of polyether amines. Common types of amine functional polyethers include for example amine-terminated polypropylene oxide, amine-terminated polyethylene oxide (PEG), amine-terminated polytetramethylene oxide, etc.

The polyether amines may be either primary or secondary and are available in various molecular weights and functionality. In typical embodiments, the molecular weight is at least 100, 150, or 200 g/mol. In typical embodiments, the molecular weight is no greater than about 10,000; 9,000; 8,000; 7,000; 6,000 or 5,000 g/mol.

Commercially available (e.g. primary and secondary) polyether amines include the following:

Chemical Tradename

Chemical Structure (Major Component)

(Supplier, Location)

In some embodiments, the polyether component is amine functional polyether(s) or a combination of at least one isocyanate functional polyether and at least one amine functional polyether. In this embodiment, the coating composition may contain little or no glycols, such as polyethylene glycol.

In some embodiments, the first and/or second part comprises one or more polyether components such that the polyether content of the total composition (i.e. liquid mixture of first and second part) is at least 1, 1.5, 2, or 2.5 wt.%. In some embodiments, the total polyether content is at least 3, 3.5, 4, 4.5, 5, 5.5, 6. 6,5. 7, 7.5, 8, 8.5, 8, 9.5 or 10 wt.-%. In other embodiments, the total polyether content is at least 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5 or 15 wt.-%. The polyether content of the total composition (i.e. liquid mixture of first and second part) is preferably less than 25, 24, 23, 22 or 21 wt.-%. When the second part consists of aliphatic cyclic secondary diamine comprising a single hexyl ring, the concentration of polyether amine is typically no greater than 15, 14, 13, 12, 11, or 10 wt.-%.

The inclusion of one or more polyether components can increase the elongation while maintaining a calculated 50 year tensile creep rupture strength of at least 8, 9, or 10 MPa, under water saturated conditions as would be expected in a drinking water pipeline. As used herein, the calculated 50 year creep rupture strength refers to the value obtained according to the test method described in the examples. Such test method is believed to correspond with the value obtained when determining the 50 year creep rupture tensile strength according to ASTM D-2990-17, using the same sample conditioning method described in the examples and keeping the sample specimens saturated throughout the test. Thus, when a composition exhibits a calculated 50 year creep rupture tensile strength of at least 10 MPa according to the test method described in the examples it will also exhibit a calculated 50 year creep rupture tensile strength of at least 10 MPa according to ASTM D- 2990-17. The difference between the average values obtained by these methods is generally within the statistical standard deviation of such tests, meaning the average values are statistically the same.

In some embodiments, the calculated 50 year creep rupture tensile strength is at least 11, 12, 13, 14, 15, or 16 MPa. In typical embodiments, the calculated 50 year creep rupture tensile strength is no greater than 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, or 17 MPa. The calculated 50 year creep rupture tensile strength is determined according to the test method described in the examples. In some embodiments, the elongation is at least 4, 5, 6, or 7%. In typical embodiments, the elongation is no greater than 25% or 20% and in some embodiments, no greater than 19, 18, 17, 16 or 15%.

In some embodiments, the aliphatic cyclic secondary polyamine (e.g. diamine) is combined with one or more secondary aliphatic polyamine (including other cycloaliphatic polyamines) having a different structure than Formulas 1 and 2. The other secondary aliphatic polyamine may include aspartic acid ester, such as described in

US2010/0266762; incorporated herein by reference.

Preferred aspartic ester amines have the following formula:

Formula

wherein R12 is a divalent organic group (up to 40 carbon atoms), and each R13 is independently an organic group inert toward isocyanate groups at temperatures of 100°C or less.

In the above formula, preferably, Rms an aliphatic group (preferably, having 1-20 carbon atoms), which can be branched, unbranched, or cyclic. More preferably, R12 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-l,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, R12 preferably comprises a dicyclohexyl methane group or a branched C4 to C12 group. R13 is typically independently a lower alkyl group (having 1-4 carbon atoms).

Suitable aspartic acid esters are commercially available from Bayer Corp. under the trade designations "Desmophen NH 1420", "Desmophen NH 1520" and "Desmophen NH 1220".

Desmophen NH 1220 is substantially composed of the following compound Formula IV;

wherein Et is ethyl. Formula The inclusion of aspartic acid esters according to Formula 3, wherein R¹ is a branched or unbranched group lacking cyclic structures and having less than 12, 10, 8, or 6 carbon atoms, such as depicted in Formula 4, is typically preferred for faster film set times of 2 to 5 minutes. The inclusion of an aspartic acid ester according to Formula 3, wherein R¹ is comprises unsubstituted cyclic structures can be employed to extend the film set time to 5 to 10 minutes. The inclusion of an aspartic acid ester according to Formula 3, wherein R¹ comprises substituted cyclic structures, (e.g. Formula III of US 2010/0266764, can even further extend the film set time). Typically, such aspartic acid esters are employed at only small concentrations in combination with another aspartic acid ester that provides faster film set times, as just described.

In other embodiments, the second part may further comprise acyclic aliphatic linear or branched polyamines (i.e. that lacks a cyclic group).

One suitable commercially available aliphatic acyclic secondary diamine includes the following:

In favored embodiments, the other aliphatic secondary diamine components are utilized at a lower concentration than the aliphatic cyclic secondary diamine (e.g. of Formula 1 and/or 2). Depending on the amount of aliphatic cyclic secondary diamine (e.g. of Formula 1 and/or 2) the concentration of such other aliphatic secondary diamine (e.g. aspartic ester amine) is typically no greater than 40, 35, 30, 25, 20, 15, 10 or 5 wt.-% of the first part (or less than 25, 20, 15, 10, or 5 wt.-% of the total coating composition).

When present the optional other amine components are chosen to dissolve in the liquid aliphatic cyclic secondary diamine (e.g. of Formula 1 and/or 2).

In some embodiments, the total composition (i.e. first and second part) is substantially free of aromatic components, such that the composition meets the NSF/ANSI Standard. In some embodiments, the total composition typically comprises less than 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 or 0.5 wt.-% of aromatic components. The total composition can be free of hydroxyl-functional components and thus may be free of polyurethane moieties.

The average functionality (favg) of the reactive components (e.g. polyisocyanates, polyamines, etc.) of the total composition can be calculated using Equation 1, where Ni is the number of moles of a given reactant, and is the functionality of that reactant. The functionality of the reactant can be obtained by division of the molecular weight of the reactant by the equivalent weight of the reactant. It is appreciated that fillers (inclusive of pigments and dessicants, thixotropes), and other additives are not reactive components and are excluded for the calculation of favg.

Equation 1. Calculation of average functionality It has been found that increasing the average functionality can contribute to increasing the calculated 50 year creep rupture tensile strength. In some embodiments, the average functionality is at least 2.30, 2.31, 2.32, 2.33, 2.34, 2.35, 2.36, 2.37, 2.38, 2.39, or 2.40. In other embodiments, the average functionality is at least 2.41, 2,42, 2.43, 2.44, 2.45, 2.46, 2.47, 2.48, 2.49, or 2.50. In typical, embodiments, the average functionality is less than 2.65, 2.64, 2.63, 2.62, 2.61, or 2.60.

In some embodiments, the above functionality is achieved utilizing one or more polyisocyantes each having a functionality greater than 2. However, the above functionality can also be achieved by utilizing a polyisocyanate having a functionality of 2 in combination with a second polyisocyante having a functionality greater than 2.

The first and/or second part may comprise a filler. A filler is a solid, insoluble particulate material often employed to add bulk volume or to extend the pigment capabilities without impairing the reactive chemistry of the coating mixture. Many fillers are natural inorganic minerals such as talc, clay (e.g. kaolin), calcium carbonate (e.g. whiting), dolomite (calcium magnesium carbonate), and siliceous fillers including silica (e.g. particle size greater than 1 micron).

Pigments, such as titanium dioxide, can concurrently function as a colorant and filler. Further, molecular sieves (e.g. aluminosilicate) can concurrently function as a desiccant and a filler. Inorganic thixotropes, such as fumed silica, can concurrently function as a thixotrope and a filler. Other thixotropes comprise an organic material such as polyamides, waxes, castor oil derivatives, and others, as described for example in US 4,923,909 and US 5,164,433. These may be soluble and/or semisoluble in the resin and are not considered "fillers".

Other fillers include ceramic microspheres, hollow polymeric microspheres such as those available from Akzo Nobel, Duluth, GA, (under the trade designation "Expancel 551 DE"), and hollow glass microspheres (such as those commercially available from 3M Company, St. Paul, MN. under the trade designation "K37"). Hollow glass microspheres are particularly advantageous because they demonstrate excellent thermal stability and a minimal impact on dispersion viscosity and density. Other fillers can be solid insoluble particulates comprised of insoluble organic matter. Exemplary fillers of this type could include nylon, polyethylene, polypropylene, polyamides, etc.

In some embodiments, the filler may further comprise a surface treatment compound. In some embodiments, the surface treatment compound may be non-reactive with respect to the reactive components (e.g. amine(s) and isocyanate) of the first and second part. For example, polydimethylsiloxane, as can be present as a surface treatment compound on the fumed silica thixotrope, is an example of a non-reactive surface treatment compound.

To avoid applying multiple coating layers, it is advantageous to apply a coating at a thickness or caliper greater than 5 mm. In order to apply a caliper of at least 5 mm in a single pass, the composition typically comprises thixotrope filler, other fillers, or a combination thereof. Thixotropes often can provide a suitable viscosity at lower concentrations than other types of filler and therefore can be advantageous for reducing the filler concentration.

With reference to FIG. 1, pipe 100 illustrates the polyurea coating composition 150, as described herein, having a caliper of at least 5 mm. In contrast, with reference to FIG. 2, pipe 200 illustrates the polyurea coating composition (250 and 260) not having a caliper of at least 5 mm. When the viscosity of the liquid mixture is too low, the coating sags such that portion 250 may have a thickness greater than 5 mm. However, portions 260 have a caliper significantly less than 5 mm.

Surprisingly, it has been found that even though high filler concentrations can contribute to high tensile strength, high filler concentrations can result in lower tensile creep rupture strength. Thus, filler is preferably employed in the coating composition (i.e. liquid mixture of first and second part) at a concentration no greater than 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2% or 1% by volume.

In some embodiments, the second part comprises at least 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5 wt.-% or greater of thixotrope in order that a coating of sufficient caliper can be applied in a single pass. The concentration of thixotrope in the second part is typically no greater than 30 wt.-%. The first part may also comprise thixotrope. The concentration of thixotrope in the first part can be less than the second part depending on the viscosity (e.g. molecular weight) of polyisocyanate(s). In some embodiments, the amount of thixotrope of the first part in is the same range as just described for the first part. In other embodiments, the second part comprises up to 1, 1.5, 2, 2.5, or 3 wt.-% of thixotrope. In some embodiments, the amount of thixotrope employed in the coating composition (i.e. liquid mixture of first and second part) is at least 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 wt.-%. In some embodiments, the concentration of thixotrope employed in the coating composition (i.e. liquid mixture of first and second part) is no greater than 30, 25, 20, 15% or 10 wt.-%.

The first and/or second part may comprise various additives as are known in the art, provided the inclusion of such is permitted with the requirements of the NSF/ANSI Standard. For example, dispersing and grinding aids, water scavengers, defoamers, etc., can be added to improve the manufacturability, the properties during application, and/or the shelf life. The stoichiometry of the polyurea reaction is based on a ratio of equivalents of isocyanate (e.g. modified isocyanate and excess isocyanate) of the first component to equivalents of amine of the second component. The first and second components are reacted at a stoichimetric ratio of at least about 1 : 1. Preferably, the isocyanate is employed in slight excess, such that the first part is combined with the second part at a ratio of 1.1 to 1.4 equivalents isocyanate to amine.

To simplify application in typical embodiments, the first and second part are formulated such that the stoichiometric ratio is obtained at a volume ratio of 1 : 1.

However, other volume ratios can be employed, typically ranging from 1 :3 to 3 :2. When the first and second part are combined at a particular volume ratio (e.g. 1 : 1) the weight percent of each of the components in the total coating composition (i.e. liquid mixture of first and second part) can be calculated based of the wt.-% of the part and the density of the component. Typical amounts of each of the components in the total coating composition are set forth in the following table. Other specific amounts can be derived from the wt.-% of the part as previously described and the density of a particular component as described in Table 1 of the examples.

The first and second parts are preferably each liquids at temperatures ranging from 5°C to 25°C, 30°C, 35°C, or 40°C. In view of the confined spaces within the pipeline and the resultant lack of suitable outlet for vapor, both the first part and the second part are substantially free of any volatile solvent. That is to say, solidification of the system applied to the pipeline interior is not necessitated by drying or evaporation of solvent from either part of the system. To further lower the viscosity, one or both parts can be heated. Further, the coating composition has a useful shelf life of at least 6 months, more preferably, at least one year, and most preferably, at least two years.

Although a wide range of formulations are possible, such as exemplified in the forthcoming examples, the coating compositions described herein are particularly suitable for water distribution pipes, typically having a diameter > 3 inches (7.6 cm) up to about 36 inches (91 cm). It is generally desired that the cured coating has sufficient long term strength (i.e. 50 year creep rupture tensile strength) and ductility (i.e. flexibility as characterized by elongation at break) to remain continuous in the event of a subsequent circumferential fracture of a partially deteriorated (e.g. cast iron) pipe, such that the cured coating continues to provide a water impervious barrier between the flowing water and internal surfaces of the pipe. The following table describes typical and preferred properties of cured coating compositions for water distribution pipes as determined by the test methods described in the examples.

Preferred Performance Ranges for Structural Coatings

The coating compositions described herein advantageously provide these desired properties while complying with NSF/ANSI Standard 61-2008, (i.e. the standard for the United States) and are also believed to comply with Regulation 31 of the Water Supply (Water Quality) Regulations (i.e. the standard for the United Kingdom).

The coating composition is typically applied directly to the internal surfaces of a pipe without a primer layer applied to the surface. This can be done using various spray coating techniques. Typically, the amine component and the isocyanate component are applied using a spraying apparatus that allows the components to combine immediately prior to exiting the apparatus. In carrying out the method of the invention, the first and second parts of the system are fed independently, e.g. by flexible hoses, to a spraying apparatus capable of being propelled through an existing pipeline to be renovated. For example, a remote-controlled vehicle, such as described in US 2006/0112996, may enter the pipeline to convey the spraying apparatus through the pipeline. The apparatus preferably heats the two parts of the system prior to application to the pipeline interior 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) water impervious lining. Such linings may be formed when the pipeline is initially laid, or after a period of use when the pipeline itself begins to deteriorate. Thus, the pipeline is typically buried underground at the time the coating composition is applied. The liquid mixture can be applied at various thickness. In some embodiments, the coating is present at a caliper ranging from about 1 to 15 mm. Multiple coating layers can be applied to obtain the desired caliper. Notably, the composition described herein can be applied at a caliper of at least 5 mm in a single pass forming a cured continuous lining.

A variety of spray systems may be employed as described in the art. In some embodiments, a heated airless spray apparatus, such as a centrifugal spinning head is employed. In another embodiment, an airless, impingement mixing spray system is employed and generally includes the following components: a proportioning section which meters the two components and increases the pressure to above about 1500 psi (10.34 MPa); a heating section to raise the temperatures of the two components (preferably, independently) to control viscosity; and an impingement spray gun which combines the two components and allows mixing just prior to atomization. In other embodiments, the liquid mixture (e.g. coating composition is a heated and applied with an (e.g. air vortex) spray apparatus.

In some embodiments and in particular when the liquid mixture is applied by spraying, the first and second part typically each have a (Brookfield) viscosity ranging from about 5,000 centipoise (cps) to about 60,000 cps (using spindle 6 with a spindle speed of 20 revolutions per minute (RPM)) at the temperature at which the liquid mixture is applied. The temperature at which the liquid mixture is applied typically ranges from about 15°C to 50°C.

Viscosity behavior of each of the two components is important for two-part spray - coating processes. With impingement mixing, the two parts should be as close as possible in viscosity at high shear rates to allow adequate mixing and even cure. The plural component static mix/spray system appears to be more forgiving of viscosity differences between the two components. Characterization of viscosities as functions of shear rate and temperature can help with decisions as to starting points for temperatures and pressures of the coatings in the two part spray equipment lines.

Advantages and embodiments of this disclosure are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention. In these examples, all percentages, proportions and ratios are by weight unless otherwise indicated.

These abbreviations are used in the following examples: s = seconds, min = minute, ppb = part per billion, hr = hour, L = liter, mL = milliliter; wt = weight, gpm = gallons per minute, V = volts, cP = centipoise, MPa = megapascals, RPM = revolutions per minute, HP = horsepower, and Mw = molecular weight.

Materials and methods Table 1. List of Materials used.

OMYCARB 5- A benefi dated calcium 2.7 Omya Inc., Filler

FL carbonate with an Proctor, VT

intermediate and closely

sized particle distribution

MESAMOLL A phthalate-free mixture of 1.06 Laxness, Plasticizer

C10-C18 alkylsulphonic Leverkusen, esters of phenol Germany

CAB-O-SIL Medium surface area 2.2 Cabot Thixotrope

TS-720 fumed silica which has Corporation,

been surface modified with Bilerica, MA

polydimethylsiloxane

(thixotrope)

BAYFERROX Synthetic black iron oxide 4.6 Lanxess, Filler/colorant

318M pigment Pittsburg, PA

TIONA 595 Titanium dioxide pigment 4.1 Cristal Global, Filler/colorant

Australind,

WA

MICRODOL 5.5 micron average size 2.85 Bentley Filler

H600 dolomite filler Chemicals,

Kidderminster,

Worcestershire,

UK

PURMOL 3 ST Aluminosilicate molecular 2.1 Zeochem, Filler/desiccan sieve powder, 3 A pore size Louisville, KY t

PV FAST Phthalocyanine blue 1.61 Clariant, Filler/colorant

BLUE A4R pigment Charlotte, NC

General method for preparation of resin mixtures

Two part cartridges were acquired: 1) Sulzter Mixpac 1 : 1 cartridges (Sulzer Mixpac EAAC400-01-10-01, 400 mL 1 to 1 Cartridge Assembly Kit available from Ellsworth Adhesives, Germantown, WI), or 2) Plas-Pak Industries Inc. 3 :2 cartridges (Cartridge package 3 :2 Ratio (150 x 100 mL), Norwich, CT).

Resin formulations of the first and second part were separately blended using a 3 horse power (HP), high dispersion Ross Mixer (Charles Ross and Son Company, St. Charles, IL) equipped with a vacuum attachment. Liquid formulation components were charged into a mixing vessel equipped with a Cowles mixing blade and vacuum was applied to the mixing vessel. The components mixed for 15 min at 1200 revolutions per minute (RPM). The first and second part compositions were then loaded into opposite sides of the two-part cartridges.

General method for preparation of molded samples The cartridges were dispensed at 40°C (except for Ex-12, which was dispensed at room temperature, and for Ex- 19, which was dispensed at -5°C was used due to the extremely high rate of cure when at room temperature or higher) using a pneumatic cartridge dispenser or mechanically driven cartridge dispensing system through a 32 element static mixer. A Sulzer Mixpac Static Mixer MCQ 08-32T was used for low viscosity materials, and a Sulzer Mixpac Static Mixer MCH 10-32T was used for materials containing CAB-O-SIL TS-720 (both mixers were obtained from Brandywine Materials, LLC, Burlington, MA). The materials were injected into a closed

polytetrafluoroethylene (PTFE) mold (ASTM D638-08 Type IV dogbone, ~ 2 mm thickness). The parts were then demolded and stored in a desiccator for greater than 7 days prior to testing. Tags/molding excess on the samples were sanded smooth using 400 grit sandpaper. Tensile strength and elongation measurements

Samples were stored for at least seven days in a dessicator prior to measurements (except for Ex-12, which was stored in a dessicator for 3 days). Tensile strength and elongation were measured from the molded samples according to ASTM D-638-14 using either a MTS 880 servohydraulic load frame or a Sintech 10/D electromechanical load frame. Strain was measured by means of an extensometer with 25.4 mm gage length for both load frames. Test control and data acquisition was performed using TestWorks 4.0 software (MTS Corp., Eden Prairie, MN).

50 year tensile creep rupture strength determination

The above molded 2 mm thick Type IV dogbone samples were allowed to condition for 7 days in a dessicator, then soaked in deionized water for at least 10 days at room temperature (20±2°C) to allow complete water saturation to simulate long-term conditions inside a water pipe. Before testing, the narrow portion of the dogbone was wrapped in a wet paper towel to keep samples saturated during the testing period, and the wet paper towel was taped over using 3M SCOTCH 3750 packaging tape to prevent cooling due to water evaporation. Creep rupture strength was determined by using an Instron model 55R1122 universal load frame to apply a fixed level of stress to a sample specimen, and time to failure (i.e. when the sample breaks) was recorded. The temperature during testing was 20±2°C. A minimum of five specimens per formulation were tested, with all five of such specimens failing in more than 0.1 hours, at least 3 samples failing in more than 1 hour, and at least one sample failing in more than 10 hours. The applied stress for each specimen was held constant, but differed from another specimen by at least 1 MPa. Samples with visible defects (such as bubbles and/or voids) were discarded. The measured values were plotted on a stress versus time plot (see Fig. 3) and fit using a power function (i.e. y =mx^b , where y = applied stress and x = time to failure, and m and b are fitting parameters). The 50 year creep rupture tensile strength was extrapolated (i.e. calculated) from the fit and all R² values were greater than 0.85. An example of the fitting is shown below.

CE- 1

General method for spraying formulations on PVC pipes

Cartridges (Sulzer Mixpac EAAC400-01-10-01) filled with the first part and the second part of resin formulations were heated to 40°C and dispensed using a variable speed screw driven plunger apparatus. Plunger speeds were set to 18 inches/min (46 cm/min). When spraying formulations on PVC pipes, the blended resin is dispensed through a static mixer (Sulzer statomix MC-18) into a centrifugul spinning cone head, the spinning cone is placed onto a translational stage that moves within the pipe interior at a fixed speed. The volumetric rate of the resin in the spinning cone is determined to coincide with the translational speed of the spinning cone relative to the interior of the pipe, thus it is possible to achieve a determined coating thickness. In this case the translational speed was set to approximately 12 inches/min (30.5 cm/min), thus targeting a thickness of 8.3 mm. After the spraying, the coated pipe was left to stand over night at room temperature. Post-lining coating measurements were taken by cutting cross-sections of the coated pipes using a band saw and measuring with a ruler. Example preparation

All inventive, control, and comparative examples were generated using the general procedure described above. Formulation CE-1 is Ex. 1 of US 2014/0010956, CE-2 is Ex. 9 of US 2014/0010956 (with the minor substitution of colorant in the first side), CE-3 is Ex. 5 of US 2007/0043197, CE-4 is Ex. 6 of US 2007/0043197, and CE-5 is Ex. 10 of US 2007/0043197. The values described are weight percent for each side of the two-part formulations. All formulations were dispensed using 1 : 1 volume ratio cartridges unless otherwise noted. Weight percent in the following tables describe the weight percent of the first and second parts before mixing.

Formulations Comparative Examples 1 to 5 (CE-1 to CE-5) First Part

Second Part

Formulations Examples Ex-1 to Ex-7

First Part

Formulations Ex-8 and Ex-9 First Part

Formulations Ex-10 to Ex-14

First Part

Second Part

MATERIAL Ex-10 Ex-11 Ex- 12 Ex- 13 Ex-14

CLEARLINK 1000 77.25 77.2 85.9 54.5 72.6

JEFF AMINE T-5000 22.75 22.8 15.9 20.4

DESMOPHEN NH1220 14.1

CAB-O-SIL TS-720 5.0 6.5

MICRODOL H600 24.1

Formulations Ex-15 and Ex-16

First Part

*Denotes a volume mixing ratio of 3 :2 for First Part: Second Part

Second Part

*Denotes a volume mixing ratio of 3 :2 for First Part: Second Part Formulations Ex-17 and Control-1 (CT-1)

First Part

Weight percent (volume % in parenthesis) in the tables below are of the total composition (liquid mixture of first and second part)

Formulations CE-1 to CE-5

Formulations Examples Ex-1 to Ex-7

Formulations Ex-8 and Ex-9

MATERIAL Ex-8 Ex-9

DESMODUR N 3600 56.6 55.4 (50.0)

CLEARLINK 1000 24.5 (28.8)

JEFFLINK 754 33.4

JEFF AMINE T-5000 10.0

JEFF AMINE SD-231 8.9 (10.5)

Formulations Ex-10 to Ex-14

Formulations Ex-15 and Ex-16

*Denotes a volume mixing ratio of 3 :2 for A:B

Formulations Ex-17 and Control-1 (CT-1)

Table 2. Compositional Criteria and Test Results

*Denotes data quoted from reference. US 2007/0043197 reported max elongation, not average. Ex = Example #. % wt PE = weight % polyether in total formulation. % vol fill = volume % filler in total formulation (includes all non-soluble solids). f_avg = average functionality in total formulation. % E = % tensile elongation at break. Thix = thixotrope TS = Tensile strength. Creep Str. = calculated 50 year creep rupture tensile strength. NM = not measured.

Claims

What is claimed is:

1. A method of forming a coating on a surface of a pipeline the method comprising the steps of: a) providing a coating composition comprising

a first part comprising at least one polyisocyanate, and

a second part comprising at least 20 wt-% of aliphatic cyclic polyamine wherein the aliphatic cyclic polyamine is not an aspartic ester amine;

b) combining the first part and the second part to form a liquid mixture wherein the mixture comprises less than 15% filler by volume, a polyether content ranging from 0 to 22 wt.-%, and an average functionality of at least 2.35;

c) applying the liquid mixture to internal surfaces of the pipeline; and

d) allowing the mixture to set forming a cured coating.

2. The method of claim 1 wherein the cured coating has a calculated 50 year water saturated creep rupture tensile strength of at least 10 MPa.

3. The method of claim 1 wherein the second part comprises one or more of the aliphatic cyclic secondary diamine(s) in an amount ranging from 25 wt-% to 100 wt-% of the second part.

4. The method of claim 1 wherein the polyether content is at least 2.5 wt-%.

5. The method of claim 1 wherein the polyether content is derived at least in part from a polyether polyamine, a polyisocyanate, or a combination thereof.

6. The method of claim 1 wherein the second part comprises an aliphatic cyclic secondary diamine comprising two hexyl rings bonded by a bridging group.

7. The method of claim 6 wherein the aliphatic cyclic secondary diamine has the general formula:

wherein Ri and R₂ are independently alkyl groups, having 1 to 10 carbon atoms and R3, R4, R5 and R5 are independently hydrogen or alkyl groups having 1 to 5 carbon atoms.

8. The method of claim 7 wherein Ri and R2 are independently alkyl groups comprising at least 2 carbon atoms, R3 and R4 are methyl or hydrogen, and R5 and R5 are hydrogen.

9. The method of claim 1 wherein the second part comprises an aliphatic cyclic secondary diamine comprising a single hexyl ring.

10. The method of claim 9 wherein the aliphatic cyclic secondary diamine has the general formula:

wherein R7 and Rs are independently linear or branched alkyl groups having 1 to 10 carbon atoms, or an alkylene group terminating with a -CN group; and R9, Rio and Rn are independently hydrogen or alkyl groups containing 1 to 5 carbon atoms.

11. The method of claim 10 wherein R7 and Rs are independently alkyl groups comprising at least 3 carbon atoms and R9, Rio and Rn are independently hydrogen, methyl or isopropyl.

12. The method of claim 1 wherein the second part comprises at least one aliphatic cyclic secondary diamine comprising two hexyl rings bonded by a bridging group and at least one aliphatic cyclic secondary diamine comprising a single hexyl ring.

13. The method of claim 1 wherein the second part comprises an aspartic ester amine in an amount less than 20 wt.% of the first part.

14. The method of claim 1 wherein the liquid mixture is applied at a caliper ranging from about 1 to 15 mm.

15. The method of claim 14 wherein the liquid mixture is applied at a caliper of at least 5 mm in a single pass.

16. The method of claim 1 wherein the pipeline is a drinking water pipeline and the cured coating contacts drinking water.

17. The method of claim 16 wherein the aliphatic isocyanate is a derivative of hexamethylene diisocyanate, a derivative of isophorone diisocyanate, a derivative of hexamethylene diisocyanate and isophorone diisocyanate, or a mixture thereof.

18. The method of claim 1 wherein the first part is combined with the second part at a ratio of 1 : 1 to 1 :4 equivalents isocyanate to amine.

19. The method of claim 1 wherein the first part is combined with the second part at a volume ratio of about 1 : 1 ranging to about 1.5: 1.

20. A method of forming a coating on a surface of a pipeline the method comprising the steps of: a) providing a coating composition comprising

a first part comprising at least one component comprising polyisocyanate, and a second part comprising at least one component comprising at least 20 wt-% of aliphatic cyclic polyamine wherein the aliphatic cyclic polyamine is not an aspartic ester amine;

b) combining the first part and the second part to form a liquid mixture;

c) applying the liquid mixture to internal surfaces of the pipeline; and

d) allowing the mixture to set forming a cured coating;

wherein the components of the first and second part are selected such that the cured coating has a calculated 50 year creep rupture tensile strength of at least 10 MPa.

21. A reactive two-part coating composition, comprising:

a first part comprising at least one polyisocyanate, and

a second part comprising at least 20 wt-% of aliphatic cyclic polyamine wherein the aliphatic cyclic polyamine is not an aspartic ester amine; and

wherein upon combining the first and second part the coating composition comprises less than 15% filler by volume, a polyether content ranging from 0 to 22 wt.-%, and an average functionality of at least 2.35.

22. The reactive coating composition of claim 21 wherein the coating composition is further characterized by any one or combination of claims 2-19.

23. A reactive two-part coating composition, comprising: a first part comprising at least one polyisocyanate, and

a second part comprising at least 20 wt-% of aliphatic cyclic secondary diamine comprising secondary amine substituents that lack diester groups; and

wherein the two-part composition comprises at least 3 wt.-% of thixotrope.

24. The reactive two-part coating composition of claim 23 wherein upon combining the first and second part the coating composition comprises less than 15% filler by volume.

25. The reactive two-part coating composition of claims 23 or 24 wherein upon combining the first and second part the coating composition comprises a polyether content ranging from 2.5 to 20 wt.-%.

26. The reactive two-part coating composition of claim 23 wherein upon combining the first and second part the coating composition comprises an average functionality of at least 2.35.

27. The reactive coating composition of claim 23 wherein the coating composition is further characterized the method of claim 2.