RAPID-SET EPOXY RESIN SYSTEMS AND PROCESS OF COATING PIPELINES USING THE EPOXY RESIN SYSTEM

Abstract

Rapidly gelling epoxy resin systems include an epoxy resin, certain acrylate-functional compounds, and a curing agent mixture that includes a thiol curing agent and an amine curing agent. Gel times well less than 1 minute can be obtained. The ratio of acrylate-functional compound to thiol curing agent can be varied to adjust the gel time to precise values within a broad range.

Claims

1. An epoxy resin system comprising an A-side and a B-side, the A-side including: A-1) an epoxy resin having an average of 2 to 6 epoxy groups per molecule and an epoxy equivalent weight of 150 to 300; A-2) 3 to 20 parts by weight, per 100 parts by weight of component A-1) of a polyacrylate having an average of 2 to 8 acrylate groups per molecule and an equivalent weight per acrylate group of 80 to 250; and A-3) 0 to 10 parts by weight, per 100 parts by weight of component A-1) of a polymethacrylate having an average of 2 to 8 methacrylate groups per molecule and an equivalent weight per methacrylate group of 95 to 265; and the B-side including: B-1) an amine curing agent having an average of 2 to 8 amine hydrogens per molecule and an amine hydrogen equivalent weight of 15 to 100 and B-2) a thiol curing agent having an average of 2 to 8 thiol groups per molecule and an equivalent weight per thiol group of 50 to 300; wherein the proportions of the A-side and B-side are such that (i) the A-side contains 0.3 to 2 equivalents combined of acrylate and methacrylate groups per equivalent of thiol groups in the B-side and (ii) the B-side contains from 0.75 to 1.5 equivalents of thiol groups and amine hydrogens combined per combined equivalents of epoxy, acrylate and methacrylate groups in the A-side.

2. A method of forming a cured thermoset polymer comprising: 1. forming a reaction mixture by combining A-1) an epoxy resin having an average of 2 to 6 epoxy groups per molecule and an epoxy equivalent weight of 150 to 300; A-2) 3 to 20 parts by weight, per 100 parts by weight of component A-1) of a polyacrylate having an average of 2 to 8 acrylate groups per molecule and an equivalent weight per acrylate group of 80 to 250; and A-3) 0 to 10 parts by weight, per 100 parts by weight of component A-1) of a polymethacrylate having an average of 2 to 8 methacrylate groups per molecule and an equivalent weight per methacrylate group of 95 to 265; B-1) an amine curing agent having an average of 2 to 8 amine hydrogens per molecule and an amine hydrogen equivalent weight of 15 to 100 and B-2) a thiol curing agent having an average of 2 to 8 thiol groups per molecule and an equivalent weight per thiol group of 50 to 300; wherein the proportions of the ingredients A-1, A-2, A-3, B-1 and B-2 are such that (i) 0.3 to 2 equivalents combined of acrylate and methacrylate groups are provided to the reaction mixture per equivalent of thiol groups and (ii) 0.75 to 1.5 equivalents of thiol groups and amine hydrogens combined are provided to the reaction mixture per combined equivalents of epoxy, acrylate and methacrylate groups in the A-side; and 2. curing the reaction mixture to form the cured thermoset polymer.

3. A method for lining the internal surface of a pipe with a cured thermoset resin, comprising: 1. forming a reaction mixture by combining A-1) an epoxy resin having an average of 2 to 6 epoxy groups per molecule and an epoxy equivalent weight of 150 to 300; A-2) 3 to 20 parts by weight, per 100 parts by weight of component A-1) of a polyacrylate having an average of 2 to 8 acrylate groups per molecule and an equivalent weight per acrylate group of 80 to 250; and A-3) 0 to 10 parts by weight, per 100 parts by weight of component A-1) of a polymethacrylate having an average of 2 to 8 methacrylate groups per molecule and an equivalent weight per methacrylate group of 95 to 265; B-1) an amine curing agent having an average of 2 to 8 amine hydrogens per molecule and an amine hydrogen equivalent weight of 15 to 100 and B-2) a thiol curing agent having an average of 2 to 8 thiol groups per molecule and an equivalent weight per thiol group of 50 to 300; wherein the proportions of the ingredients A-1, A-2, A-3, B-1 and B-2 are such that (i) 0.3 to 2 equivalents combined of acrylate and methacrylate groups are provided to the reaction mixture per equivalent of thiol groups and (ii) 0.75 to 1.5 equivalents of thiol groups and amine hydrogens combined are provided to the reaction mixture per combined equivalents of epoxy, acrylate and methacrylate groups in the A-side; 2. applying the reaction mixture to an internal surface of the pipe; and 3. curing the reaction mixture in contact with the internal surface of the pipe to form a coating of the cured thermoset polymer thereon.

4. The process of claim 2 wherein step a) is performed at a temperature of 15 to 40° C. and step b) is performed without applying heat until at least the reaction mixture has gelled.

5. The process of claim 2 wherein the reaction mixture is cured at an elevated temperature after it has gelled.

6. The process of claim 2 wherein component A-2 has an equivalent weight of 100 to 175 and component B-2 has an equivalent weight of 65-200.

7. The process of claim 6 wherein component B-2 has an average of 3.5 to 8 thiol groups per molecule, and the proportions of the ingredients A-2, A-3 and B-2 are such that (i) 0.4 to 1.4 equivalents combined of acrylate and methacrylate groups are provided to the reaction mixture per equivalent of thiol groups.

8. The process of claim 7 wherein component B2 is a curing agent prepared by coupling a polythiol compound having 3 or 4 thiol groups with an epoxy resin having 2 to 3 epoxy groups per molecule.

9. The process of claim 6 wherein component B-2 has an average of 2 to 3.4 thiol groups per molecule, and the proportions of the ingredients A-2, A-3 and B-2 are such that (i) 0.8 to 1.25 equivalents combined of acrylate and methacrylate groups are provided to the reaction mixture per equivalent of thiol groups.

10. The process of claim 9 wherein component B-2 is one or more of 1,2-ethane dithiol, 1,2-propane dithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,6-hexanedithiol, 1,2,3-trimercaptopropane, 1,2,3-tri(mercaptomethyl)propane, 1,2,3-tri(mercaptoethyl)ethane, (2,3-di((2-mercaptoethyl)thio)1-propanethiol and a mercaptoacetate or mercaptopropionate esters of a low molecular weight polyols having 2 to 8 hydroxyl groups and an equivalent weight of up to about 75, in which ester all of the hydroxyl groups are esterified with the mercaptoacetate and/or mercaptopropionate.

11. The process of claim 9 wherein the reaction mixture is devoid of a basic catalyst.

12. The process of claim 2 wherein the reaction mixture contains at least one basic catalyst.

Description

EXAMPLE 1

[0083] An A-side mixture is prepared by charging 10 g (0.056 epoxy equivalents) of Epoxy Resin 1 and 1.11 g (0.01 acrylate equivalents) of 1,6-hexanediol diacrylate (HDODA) into a high-speed laboratory mixer, where they are mixed at high speed until thoroughly blended. Separately, a B-side is prepared by combining 0.85 g (0.01 thiol equivalents) of 2,3-bis[(2-mercaptoethyl)thio]-1-propanethiol (DMPT) with 2.39 g (0.056 amine hydrogen equivalents) of isophorone diamine (IPDI). The B-side is added to the laboratory mixer and is stirred at room temperature into the A-side mixture at high speed for one minute.

[0084] In the foregoing formulation, the equivalent ratio of acrylate groups to thiol groups is 1:1. To study the effect of the amount of thiol on gel time, Example 1 is duplicated several times, in each case changing the proportions of DMPT and IPDA in the B-side. The amount of DMPT is decreased or increased relative to the Example 1 formulation, in each case increasing the amount of IPDA a corresponding amount so the total amine plus thiol equivalents in the B-side remains constant.

[0085] Gel times for each of these formulations are measured as described above.

[0086] Results for the Example 1 series of experiments are as indicated in Table 1:

TABLE-US-00001 TABLE 1 Gel Time, s Example 1A 1B 1C 1D 1E 1F Meq. Epoxy 56 56 56 56 56 56 Meq. Acrylate 10 10 10 10 10 10 Meq. DMPT 20 16.7 13.3 11.1 10 8.7 Meq. IPDA 46 49.3 52.7 54.9 56 57.3 Acrylate:DMPT 0.5:1 0.6:1 0.75:1 0.9:1 1:1 1.15:1 eq. ratio DMPT:IPDA 0.43 0.34 0.25 0.20 0.18 0.15 eq. ratio Eq.-% DMPT 33% 37.5% 42.9% 47.3% 50% 53.5% in B-side Gel time, s >120 >120 30 20 25 110

[0087] The data in Table 1 demonstrates a large and unexpected effect of the amount of thiol curing agent on gel time. As the data shows, gel time reduces drastically as the amount of thiol increases from 37.5% to 42.9% of the total equivalents of the B-side, and then increases equally dramatically as the amount of thiol increases from 50% to 53.5%, on the same basis. The same trend is seen when the amount of thiol is expressed in relation to the amount of acrylate; cure time drops sharply as the acrylate:DMPT ratio decreases from 0.34 to 0.25, and increases sharply as this ratio decreases further from 0.18 to 0.15.

[0088] Plaques are prepared by spraying the formulation of Example 1E into an open mold. The A- and B-sides are loaded into disposable cartridges of a Ratio-Pak HSS Spray Gun. This spray gun is a low-pressure air-assisted spraying device equipped with a spray nozzle assembly that includes a bell house type 48-element static mixer. 339 g of the A-side and 99 g of the B-side are dispensed into and through the spray nozzle and onto an open mold. Gel time from the time of dispensing is measured using a wood stick as before. After gel time is measured, the coated mold is cured for 3 hours at 100° C. and glass transition temperature is measured by DMA as before.

[0089] The sprayed formulation has a gel time of 30 seconds, which is almost unchanged from that of the cast formulation (25 seconds). The glass transition temperature also is essentially changed by spraying, being 107° C. versus 105° C. for the cast plaque.

EXAMPLE 2

[0090] Example 2 is prepared and tested for gel time in the same manner as Example 1. The A-side mixture is the same as Example 1. The B-side mixture is 1.303 g (10 thiol equivalents) of trimethylolpropane tri(3-mercaptoproprionate) (TMPMP) and 1.334 g (56 amine hydrogen equivalents) of triethylenetetramine (TETA).

[0091] Example 2 is duplicated several times, in each case adjusting the ratio of TMPMP and TETA so the total amine plus thiol equivalents in the B-side remain constant.

[0092] Table 2 shows the corresponding data for the Example 2 series of experiments:

TABLE-US-00002 TABLE 2 Gel Time, s Example 2A 2B 2C 2D 2E 2F 2G 2H 2I Meq. Epoxy 56 56 56 56 56 56 56 56 56 Meq. Acrylate 10 10 10 10 10 10 10 10 10 Meq. TMPMP 20 16.7 14.2 13.3 10 8.3 7.1 6.7 6.3 Meq. TETA 46 49.3 51.8 52.7 56 57.3 58.9 59.9 60.3 Acrylate:TMPMP 0.5 0.6 0.7 0.75 1.0 1.2 1.4 1.5 1.6 eq. ratio TMPMP:TETA 0.43 0.34 0.27 0.25 0.18 0.14 0.12 0.11 0.10 eq. ratio Eq.-% TMPMP 30% 25% 21.5% 20.1% 15% 12.6% 10.7% 10.1% 9.5% in B-side Gel time, s ≧120 ≧120 30 20 20 20 30 ≧120 ≧120

[0093] These results again show the variability of gel time with ratio of acrylate to thiol groups. The gel time reaches a minimum when this ratio falls within the range of 0.7:1 to 1.4:1. Outside of this range, gel time increases very rapidly.

EXAMPLES 3-8

[0094] Example 3: An A-side mixture is prepared by charging 10 g (56 epoxy milliequivalents) of Epoxy Resin 1 and 1.11 g (10 acrylate milliequivalents) of HDODA into a high-speed laboratory mixer, where they are mixed at high speed until thoroughly blended. Separately, a B-side is prepared by combining 1.303 g (10 thiol milliequivalents) of TMPMP 2,3-bis[(2-mercaptoethyl)thio]-1-propanethiol (DMPT) with 2.39 g (56 amine hydrogen milliequivalents) of isophorone diamine. The B-side is added to the laboratory mixer and is stirred at room temperature into the A-side mixture at high speed for one minute. The resulting reaction mixture is dispensed into a vertical mold and cured at 80° C. for 16 hours to produce plaques for property testing. Tensile strength, elongation, tensile modulus and glass transition temperature are evaluated as before.

[0095] Example 4 is made the same way as Example 3, except the amount of HDODA is reduced to 1 g and 0.11 of trimethyolpropane trimethacrylate (TMPTMA) is added to the A-side. The weight ratio of HDODA to TMPTMA is about 9:1. The amount of thiol curing agent is adjusted slightly to maintain the same ratio of acrylate and methacrylate groups combined to thiol groups.

[0096] Examples 5-8 are made the same way as Example 4, further reducing the amount of HDODA and increasing the amount of TMPTMA to produce weight ratios of HDODA to TMPTMA of 8:2, 6:4, 4:6 and 2:8. The amount of thiol curing agent is again adjusted slightly in each case.

[0097] Gel times are measured for each of Examples 3 and 5-8. Results are as follows:

TABLE-US-00003 TABLE 3 Ex. No. HDODA/TMPTMA weight ratio Gel time, seconds 3 HDODA only, no TMPTMA <20 5 8:2 <20 6 6:4 About 240 7 4:6 About 480 8 2:8 >1500 

[0098] These results indicate the effect of replacing acrylate groups with methacrylate groups. The equivalent weights of HDODA and TMPTMA are very similar, so the weight ratios closely approximately the mole ratios of acrylate and methacrylate groups. Replacing up to about 20% of the acrylate groups with methacrylate groups has little effect on gel time, but replacing a greater proportion leads to a large increase. These results indicate that varying the ratio of acrylate to methacrylate groups is a useful means to “tune” the gel time of the system to a desired value.

[0099] Physical properties and glass transition temperature are measured for Examples 3, 4 and 5, as follows. A portion of the reaction mixture is dispensed into a vertical mold and cured at 80° C. for 16 hours to produce plaques. Dog-bone samples are cut from the cured plaques and tensile strength, elongation and tensile modulus are evaluated according to ASTM D638. Shore D hardness is measured according to ASTM D 2240.

[0100] Glass transition temperature is measured by dynamic mechanical analysis. Rectangular bars 47.5 mm in length and 7 mm wide are cut from the plaques. Dynamic mechanical analysis (DMA) is performed in a torsion mode using a strain-controlled ARES rheometer. The temperature is ramped from −100° C. to 200° C. at a rate of 3° C./minute. Strain frequency is 1 Hz and strain amplitude is 0.05%.

[0101] Results are as in Table 4. For comparison, those of commercially available polyurea spray-in-place (SIP) and epoxy cure-in-place (CIP) systems are provided.

TABLE-US-00004 TABLE 4 Designation Polyurea Epoxy Property Ex. 3 Ex. 4 Ex. 5 SIP CIP Tensile Str. (MPa) 86 73 48 39 72 Elongation, % 4.5 6.8 14 5 5 Tensile Modulus (MPa) 3300 3300 2250 N.D. 3300 Hardness (Shore D) 87 85 83 87 N.D. T.sub.g (° C.) 105-110 105 102 96 85

[0102] Examples 3-5 have physical properties very comparable to the cure-in-place epoxy system, with a significantly higher glass transition temperature. Examples 4 and 5 show the effect of the increasing amount of TMPTMA at the expense of HDODA—the TMPTMA reduces tensile properties and increases elongation, each of which is consistent with a plasticization effect. The tensile strength of Examples 3-5 is generally superior to that of the polyurea spray-in-place formulation.

EXAMPLES 9-11

[0103] 1.27 mg of a 33% triethylene diamine catalyst solution is added dropwise to 80 g of Epoxy Resin 1 and mixed at high speed for 2 minutes. 150 g of DMPT is separately heated to 80° C. under nitrogen. 77.7 g of the epoxy resin/catalyst mixture is added to the heated DMPT and the resulting mixture is heated at 80° C. for six hours. The product is a coupled thiol-epoxy resin adduct having a calculated thiol equivalent weight of 176 g/mol and approximately 4 thiol groups per molecule. This is designated Thiol Adduct 1.

[0104] Thiol Adduct 2 is made in the same manner except only 62.2 g of the epoxy resin/catalyst mixture is added to the DMPT. The thiol-epoxy resin adduct (Thiol Adduct 2) has a calculated thiol equivalent weight of 154 g/mol and approximately 4 thiol groups per molecule.

[0105] Examples 9-11 are made in the same general manner as the earlier Examples. The formulations are as indicated in Table 5. TMPTA is trimethylolpropanetriacrylate.

TABLE-US-00005 TABLE 5 Parts By Weight (millequivalents) Ingredient Ex. 9 Ex. 10 Ex. 11 Epoxy Resin 1 10 (56) 10 (56) 10 (56) HDODA 1.11 (10) 1.11 (10) 0 (0) TMPTA 0 (0) 0 (0) 1.11 (11) Thiol Adduct 1 1.95 (11) 0 (0) 0 (0) Thiol Adduct 2 0 (0) 1.51 (10) 2.05 (13) IPDA 2.334 (54) 2.39 (56) 2.23 (53) Equivalent Ratio, 0.88 1.0 0.84 acrylate:thiol

[0106] All of Examples 9-11 gel within 20 seconds on the foregoing test.

[0107] Each of Examples 9-11 is repeated several times, changing the proportions of DMPT and IPDA in the B-side. The amount of DMPT is decreased or increased relative to the Example 9, 10 or 11 formulation, in each case increasing the amount of IPDA a corresponding amount so the total amine plus thiol equivalents in the B-side remains constant. This has the effect of increasing or decreasing the acrylate/thiol equivalent ratio. When gel times are measured, it is seen that very fast gelation is obtained in across a wider range of acrylate/thiol equivalent weight ratios that is seen for Examples 1-3. For Example 9, gelation is ≦20 seconds across an acrylate/thiol ratio of about 0.5 to 1.2. For Example 10, gelation is ≦20 seconds across an acrylate/thiol ratio of about 0.56 to 1.20. And for Example 11, gelation is ≦20 seconds across an acrylate/thiol ratio of about 0.40 to well above 1.0.

EXAMPLES 12-16

[0108] Examples 12-16 are made in the same general manner as the earlier Examples. The formulations are as indicated in Table 6.

TABLE-US-00006 TABLE 6 Parts By Weight (Milliequivalents) Ingredient Ex. 12 Ex. 13 Ex. 14 Ex. 15 Ex. 16 Epoxy 10 (56) 10 (56) 10 (56) 10 (56) 10 (56) Resin 1 TMPTA 1.1 (11) 0.7 (7) 0.6 (6) 0.5 (5) 0.4 (4) Thiol 4.1 (27) 2.7 (18) 2 (13) 1.5 (10) 0.8 (5) Adduct 2 IPDA 1.7 (40) 2.0 (46) 2.1 (49) 2.2 (51) 2.4 (56) Equivalent 0.42 0.40 0.46 0.52 0.78 Ratio, acrylate:thiol

[0109] Example 16, with only 4 parts of acrylate compound per 100 parts epoxy resin, gels very slowly. However, by adding more Thiol Adduct 2 to the formulation to increase the acrylate:thiol equivalent ratio, a gel time of <20 seconds is easily achieved.

[0110] Examples 12-15, which have more of the acrylate compound exhibit gel times of <20 seconds despite the low acrylate:thiol equivalent ratios.

[0111] Example 12 is repeated, reducing the acrylate to thiol ratio to 0.337; no gelation occurs. By adding 15 mg of 1,8-diazabicyclo[5.4.0]undec-7-ene to that formulation, however, rapid gelation takes place despite the low acrylate to thiol ratio, accompanied by an exotherm to 140° C.