Thiol-functional compound

Abstract

The invention relates to a thiol-functional organic compound having on average at least 3.1 thiol groups per molecule, and having carbon atoms, oxygen atoms, and sulfur atoms, and optionally further heteroatoms, and wherein the ratio of the number of carbon atoms (C) to the sum of the number of heteroatoms (HA), (C/HA) is at least 2.0, and wherein the thiol groups are derived from 2-mercapto acetic acid, 2-mercapto propionic acid, or 3-mercapto propionic acid, or esters thereof; and to a liquid coating composition comprising the thiol-functional compound and a thiol-reactive crosslinker.

Claims

1. A thiol-functional organic compound comprising on average at least 3.1 thiol groups per molecule, and comprising carbon atoms, oxygen atoms, and sulfur atoms, and optionally further heteroatoms, and wherein the ratio of the number of carbon atoms (C) to the sum of the number of heteroatoms (HA), (C/HA) is at least 2.0, and wherein the thiol functionality is provided by a group selected from 2-mercapto acetyl, 2-mercapto propionyl, 3-mercapto propionyl, and combinations thereof, and wherein the compound further additionally comprises one or more hydroxyl groups, and wherein the thiol-functional compound is obtained by reaction of a part of the thiol groups of a thiol-functional precursor compound with an epoxide-functional or acryloyl-functional compound.

2. The thiol-functional compound according to claim 1, wherein the compound is liquid at 23 C.

3. The thiol-functional compound according to claim 2, wherein the compound has a viscosity at 23 C. in the range of 2 to 100 Pas.

4. The thiol-functional compound according to claim 1, wherein the compound has on average at most 7 thiol groups per molecule.

5. The thiol-functional compound according to claim 1, wherein the thiol-functional compound has a surface tension of at most 45 dyne/cm.

6. A liquid coating composition comprising the thiol-functional compound according to claim 1 and a thiol-reactive crosslinker.

7. The coating composition according to claim 6, wherein the thiol-reactive crosslinker is a polyisocyanate.

8. The coating composition according to claim 6, wherein the coating composition is a non-aqueous coating composition.

9. The coating composition according to claim 1, wherein the coating composition is a non-aqueous coating composition.

10. The thiol-functional compound according to claim 2, wherein the compound has on average at most 7 thiol groups per molecule.

11. The thiol-functional compound according to claim 3, wherein the compound has on average at most 7 thiol groups per molecule.

12. The thiol-functional compound according to claim 4, wherein the thiol-functional compound has a surface tension of at most 45 dyne/cm.

13. The thiol-functional compound according to claim 1, wherein the thiol-functional compound has a surface tension of at most 45 dyne/cm.

Description

EXAMPLES

Raw Materials Used

(1) ACE (reaction product of acrylic acid and Cardura E10) and Cardura E10 were obtained from Momentive.

(2) Trimethylolpropane trimethacrylate was obtained from Aldrich.

(3) Perkadox AMBN was obtained from AkzoNobel.

(4) CGI277 is a photobase from BASF.

(5) Dipentaerythritol, with the quality name di-penta 93, was obtained from Perstorp polyols.

(6) Pentaerythritol was obtained from Perstorp polyols.

(7) Setalux 1753, 1157, 1160: acrylic polyol resins solutions ex Nuplex Resins

(8) Setalux 2120: thermoplastic acrylic resin ex Nuplex Resins

(9) Vikoflex: epoxidized soybean oil ex Arkema

(10) CAB381, CAB551: cellulose acetate/butyrate ex Eastman

(11) Laropal A81: aldehyde resin ex BASF

(12) Pentaerythritol tetra 3-mercaptopropionate (PTMP) and dipentaerythritol hexa 3-mercaptopropionate ex Bruno Bock

(13) Tolonate HDT-LV: polyisocyanate ex Perstorp

(14) Vestanat T1890: polyisocyanate ex Evonik

(15) DOT: dioctyltin dilaurate

(16) Pripol 1009: Dimer fatty acid ex Croda

Example 1

Preparation of a Thiol-Functional Compound

(17) 1 mole of di-pentaerythritol hexa(3-mercapto propionate) and 2 moles of versatic acid glycidyl ester (Cardura E10) were charged into a 2,000 ml four-necked round-bottomed flask equipped with mechanical stirrer, heating mantle, thermocouple, reflux cooler, and nitrogen inlet. The batch was made inert by breaking a vacuum 3 times with a nitrogen flow. The reaction mixture was heated to 150 C. and kept at this temperature until the epoxy value was 8 mg KOH/g, determined according to ISO 3001. The reaction time was about 10 hours. Thereafter, the reaction mixture was cooled to room temperature. GPC (PLmix column) showed an Mn of 1,184 and an Mw of 1,887. A viscosity of 17 Pa.Math.s were measured using cone number 6 @ 100 rpm. A total surface tension of 33.5 mN/m was measured.

(18) The material has a theoretical molecular formula C.sub.54H.sub.94O.sub.19S.sub.6 and C/HA=2.16 and a theoretical average SH-functionality of 4.0.

Example 2

Compatibility Tests

(19) The improved compatibility of the compound according to the invention was shown by preparing mixtures of commercial binders with either pentaerythritol tetra(3-mercaptopropionate) or the material from Example 1, and judging the compatibility of the mixtures visually. Table 1 summarizes the results obtained when binders were mixed in a 1:1 weight ratio with the thiol-functional compounds. Table 2 summarizes results wherein binders were mixed with the thiol-functional compound in a 2:1 weight ratio.

(20) Compatibility:

(21) +=completely miscible,

(22) +/=borderline,

(23) =immiscible.

(24) TABLE-US-00001 TABLE 1 PTMP Example 1 Binder C/HA = 1.42 C/HA = 2.16 Setalux 1753 +/ + Setalux 1160 + Vikoflex +

(25) TABLE-US-00002 TABLE 2 PTMP Example 1 Binder C/HA = 1.42 C/HA = 2.16 CAB 381 +/ + CAB 551 + Seta lux 2120 +/ Laropal A81 +/ +

(26) It can be inferred from Tables 1 and 2 that the thiol-functional compound of Example 1 according to the invention has a better compatibility and miscibility with commercial binders of variable structure than the known thiol-functional compound PTMP.

Example 3

Preparation of a Thiol-Functional Compound

(27) Into a 2-liter four-necked round-bottomed flask equipped with mechanical stirrer, thermocouple, distillation equipment, and nitrogen inlet the following materials were charged: dipentaerythritol (343.97 grams), isononanoic acid (427.89 grams), and 3-mercaptopropionic acid (574.07 grams). The batch was made inert by breaking a vacuum 3 times with a nitrogen flow. Then methanesulfonic acid (1.06 grams) was added. The batch was slowly heated to 150 C. The distillation of reaction water started at 133 C. The mixture was kept at 150 C. and a reduced pressure of about 200 mbar was applied. Two further portions of 1.06 grams of methanesulfonic acid were added during the reaction. The reaction was continued until an acid value of 10 mg KOH/gram was obtained (about 20 hours). GPC (Oligopore column) showed an Mn of 917 and an Mw of 1,037.

(28) The material has a theoretical molecular formula C.sub.40H.sub.70O.sub.13S.sub.4 and C/HA=2.35 and a theoretical average SH-functionality of 4.0. A viscosity of 2.4 Pa.Math.s was measured using cone #3 @ 200 rpm.

Example 4

Preparation of a Thiol-Functional Compound

(29) Into a 1-liter four-necked round-bottomed flask equipped with mechanical stirrer, thermocouple, distillation equipment, and nitrogen inlet the following materials were charged: dipentaerythritol (138.35 grams), 12-hydroxystearic acid (326.9 grams), and 3-mercaptopropionic acid (230.89 grams). The batch was made inert by breaking a vacuum 3 times with a nitrogen flow. Then methanesulfonic acid (0.43 gram) was added. The batch was slowly heated to 150 C. The distillation of reaction water started at 123 C. The mixture was kept at 150 C. and a reduced pressure of about 200 mbar was applied. The reaction was continued until an acid value of 5 mg KOH/gram was obtained (about 12 hours). GPC (Mixed C column) showed an Mn of 1,646 and an Mw of 2,973.

(30) The material has a theoretical molecular formula C.sub.50H.sub.106O.sub.15S.sub.4 and C/HA=2.63 and a theoretical average SH-functionality of 4.0. A viscosity of 5.1 Pa.Math.s was measured using cone #3 @ 200 rpm.

Example 5

Preparation of a Thiol-Functional Compound

(31) 266.07 grams of pentaerythritol tetrakis 3-mercaptopropionate (PTMP) were pre-charged into a 1-liter four-necked round-bottomed flask equipped with mechanical stirrer, thermo couple, reflux condenser, and nitrogen inlet. The batch was made inert by breaking a vacuum 3 times with a nitrogen flow and is slowly heated to 80 C. Then a mixture of ACE (acrylic acidCardura E10) (172.53 grams), trimethylolpropane trimethacrylate (61.37 grams), and 1,000 ppm of Perkadox AMBN was dosed in 2.5 hours to the round-bottomed flask at a temperature of 80 C. The batch was stirred for 2 hours more at this temperature as a post-reaction. NMR showed that the acrylic double bonds had fully reacted. GPC (Polypore column) showed an Mn of 1,499 and an Mw of 3,927. A viscosity of 56 Pa.Math.s was measured using cone #6 @ 50 rpm.

(32) A total surface tension of 36.2 mN/m was measured. The material has an Mn of 1,385, an Mw of 3,632, a theoretical molecular formula C.sub.120H.sub.198O.sub.47S.sub.12 and C/HA=2.03, and a theoretical average SH-functionality of 6.0.

Example 6

Preparation of Clear Coating Compositions According to the Invention and Comparative Compositions

(33) For each composition the A, B, and C components were prepared individually by mixing the ingredients indicated in Table 3 below. Before application the A, B, and C components were mixed together, adjusted to a viscosity of 16 seconds DIN cup 4 with butyl acetate, and applied on door panels over a basecoat (Autowave MM VWLY9Z ex AkzoNobel), using a SATA RP 4000 1.3 spray gun. Clear coats were applied in two layers, with a flash-off of 2 minutes between layers. On one side of the panel an additional layer was sprayed, in order to judge sagging. After another 2 minutes of flash-off UV exposure was carried out with a Panacol handheld Lamp 400 W. This was done two to three times as if spraying at a distance of 20-30 cm from the panel. During application, sprayability, wetting, flow, and sagging on vertical parts were evaluated. After these evaluations EHO (Enamel Hold Out), clearness, gloss, craters, and pinholes were evaluated. This was done on the same day and the next. The touch dry time was evaluated immediately after UV-exposure.

(34) In Comparative Examples 6ac and 6bc a thiol-functional polyester was used in combination with PTMP. Clear films were obtained, but the sprayability, wetting, flow, and sagging were at best borderline. However, when the PTMP was replaced with the compound of Example 1, clear films with good application properties were obtained (Example 6ci).

(35) When the thiol-functional polyester in Comparative Examples 6ac and 6bc was replaced with an OH-functional acrylic (Comparative Examples 6dc and 6fc), the application properties were good, but no clear films were obtained. However, when in these formulations PTMP was replaced with the thiol-functional compounds of Examples 1, 3, 4, and 5, respectively, (Examples 6ei, 6gi, 6hi, 6ii, and 6ji) compositions were obtained which both gave clear films and had excellent application properties.

(36) In Comparative Example 6kc an acrylic was combined with the SH-functional polyester. Clear films were obtained, but due to the high viscosity of the polyester the VOC level at spraying viscosity was high. Moreover, due to the relatively low SH-functionality of the polyester the touch dry time was long.

(37) TABLE-US-00003 TABLE 3 Example 6 ac bc ci dc ei fc gi hi ii ji kc A Component Thiol polyester 56.9 28.4 28.4 86.5 Setalux 1157 XS54 58.3 58.3 Setalux 1753 XS70 48.1 48.1 48.1 48.1 48.1 48.1 PTMP 24.6 32.8 32.8 32.8 Example 1 55.0 55.0 50.1 Example 3 54.2 Example 4 55.5 Example 5 65.5 Byk 306 1.1 1.1 1.1 1.1 1.1 1.7 1.7 1.7 1.7 1.7 1.9 Byk 355 Tinuvin 400 2.0 2.0 2.2 2.0 2.3 2.2 2.2 2.3 2.0 2.4 2.4 Tinuvin 123 0.8 0.7 0.8 0.7 0.8 0.8 0.8 0.8 0.8 0.8 0.9 11.8% DOT 3.3 3.3 3.3 3.3 3.3 3.3 4.2 4.3 3.9 4.6 4.6 in butyl acetate B Component Butyl Acetate 50.0 50.0 50.0 50.0 50.0 41.4 41.4 41.4 41.4 41.4 41.4 Tolonate HDT LV 100.0 100.0 100.0 100.0 100.0 77.6 77.6 77.6 77.6 77.6 77.6 Vestanat T1890E 12.0 12.0 12.0 12.0 12.0 12.0 C Component Xylene 9.0 9.0 9.9 9.9 9.9 9.9 9.9 9.9 9.9 9.9 10.9 CGI277 1.0 1.0 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.2 Butyl acetate 13.2 13.2 23.3 23.3 29.3 43.3 48.3 38.3 38.3 23.3 53.2 VOC@16 s DC4 320 320 410 340 410 420 420 390 380 370 460 (gram/liter) Application/ Coating Results Clearness ++ ++ ++ ++ ++ ++ ++ ++ ++ Sprayability/ +/ + + ++ + ++ ++ ++ ++ n.d. Wetting Flow/Sagging + + ++ + ++ ++ ++ ++ n.d. Touch dry time 10 5 10 5 10 5 10 10 10 10 45 (minutes)

Comparative Thiol-Functional Polyester

(38) The thiol-functional polyester used in Examples 6ac, bc, ci and kc was prepared in a two-step process.

(39) In the first step a polyester polyol was prepared from the following components:

(40) TABLE-US-00004 Hexahydrophthalic anhydride 203.76 g Trimethylol propane 264.60 g Isononanic acid 97.35 g Dimethylolcyclohexane 5.21 g Adipic acid 5.77 g Aqueous solution of 85% phosphoric acid 0.49 g

(41) The components were placed in a 2-liter glass 4-necked reactor equipped with stirrer, packed column, condenser, heating mantle, thermocouple, temperature controls, vacuum line, and nitrogen inlet. The reaction mixture was heated under a nitrogen stream. The temperature of the mixture was gradually raised to 240 C. The reaction water was distilled off at such a rate that the temperature at the top of the packed column did not exceed 103 C. Finally, vacuum of 200 mbar was applied while maintaining the nitrogen stream, and the reaction was run at 240 C. for one hour until an acid value below 5 mg KOH/g is reached. The mixture was cooled to about 100 C.

(42) In the second step the hydroxyl-functional polyester polyol was esterified with 3-mercaptopropionic acid to form thiol-functional polyester. 211 g 3-mercaptopropionic acid were added at atmospheric pressure. The esterification reaction was carried out at 150 C. for 2-3 hours under vacuum (maintaining the nitrogen flow) until an acid value of approx. 80 mg KOH/g was reached. Then 0.26 g of methane sulfonic acid was added and the esterification was continued to an acid value between 25-30 mg KOH/g. Another portion of 0.26 g of methane sulfonic acid was added and the esterification was continued until an acid value of <10 mg KOH/g was reached. High vacuum was applied for two hours, using the column bypass, with a gentle nitrogen flow. The reaction mixture was cooled to 130 C. and diluted with 177.5 g n-butyl acetate. The product was cooled to 50-60 C. and filtered over 10 microns filter cloth. A thiol-functional polyester was obtained. The thiol-functional polyester did not contain residual methane sulfonic acid catalyst (<20 ppm detection limit). GPC showed an Mn of 1,122 and an Mw of 2,663. The polyester had a C/HA of 2.59 and a theoretical SH-functionality of 3.0.

(43) A small amount of resin was evaporated to dryness and a viscosity of 211 Pa.Math.s was measured for this dried sample, using cone #6 @ 20 rpm.

Example 7

Preparation of a Thiol-Functional Compound

(44) In a 2-liter four-necked round-bottomed flask equipped with mechanical stirrer, thermocouple, Vigreux column, distillation equipment and nitrogen inlet the following materials were charged: pentaerythritol (175.26 gram), Pripol 1009 (370.98 gram), 3-mercapto propionic acid (273.56 gram), triphenyl phosphite (1.63 gram) and xylene (160 gram). The batch was made inert by breaking a vacuum with a nitrogen flow. This was repeated 3 times. Batch temperature was set to 150 C. If necessary more xylene was added to maintain a gentle reflux. The reaction water was distilled off. When 67% of the theoretical amount of water had been distilled off, 0.8 grams of methane sulfonic acid were added. When necessary another 0.8 grams of methane sulfonic acid were added.

(45) The reaction was continued until an acid value of less than 3 mg KOH/gram was obtained. The xylene was then distilled off using a vacuum. The residue was a liquid having a viscosity of 40 Pa.Math.s at 23 C.

(46) Assuming that Pripol 1009 is the dimer of the C.sub.18 fatty acid, the material has a theoretical thiol functionality of 4, a theoretical molecular formula C.sub.58H.sub.104O.sub.14S.sub.4 and a C/HA of 3.22.