FLUOROCOPOLYMERS FOR COATING APPLICATIONS

Abstract

Disclosed are copolymers formed by copolymerization of: (1) one or more hydrofluoroolefin monomer(s) such as hydrofluoropropenes, (2) one or more of an alkyl vinyl ether monomer(s) that are not substituted with a reactive group, and (3) one or more reactive group substituted, lower alkyl vinyl ether monomer(s) wherein the copolymer has a MWn of from about 1000 to about 6000 grams/mole and other advantageous properties.

Claims

1. A fluorocopolymer formed by copolymerization of: (1) one or more hydrofluoroolefin monomer(s) in an amount of from about 40 mole % to about 70 mole % based on all of the monomers in the copolymer (2) one or more of an alkyl vinyl ether monomer(s) that are not substituted with a reactive group in an amount of from about 20 mole % to about 40 mole % weight based on all of the monomers in the copolymer, (3) one or more reactive group substituted, lower alkyl vinyl ether monomer(s) in an amount of from about 5 mole % to about 20 mole % based on all of the monomers in the copolymer, and (4) optionally one or more of an alkyl vinyl ester monomer in an amount, when present, of not greater than about 20 mole % based on all of the monomers in the copolymer, wherein the copolymer has a MWn of from about 1000 to about 6000 grams/mole.

2. The fluorocopolymer of claim 1 wherein said one or more hydrofluoroolefin monomer(s) is selected from the group consisting of hydrofluoroethylenes, hydrofluoropropenes, hydrofluorobutenes, hydrofluoropentenes and combinations of these.

3. The fluorocopolymer of claim 1 wherein said one or more hydrofluoroolefin monomer(s) is selected from 2,3,3,3-tetrafluoropropene and 1,3,3,3-tetrafluoropropene.

4. The fluorocopolymer of claim 3 wherein said one or more hydrofluoroolefin monomer(s) consists essentially of trans-,3,3,3-tetrafluoropropene.

5. The fluorocopolymer of claim 1 wherein said one or more of an alkyl vinyl ether monomer(s) that are not substituted with a reactive group consist essentially of lower alkyl vinyl ethers.

6. The fluorocopolymer of claim 4 wherein said one or more of an alkyl vinyl ether monomer(s) that are not substituted with a reactive group consist essentially of lower alkyl vinyl ethers.

7. The fluorocopolymer of claim 1 wherein said one or more of a reactive group substituted, lower alkyl vinyl ether monomer(s) comprises a hydroxyl substituted lower alkyl vinyl ether.

8. The fluorocopolymer of claim 6 wherein said one or more of a reactive group substituted, lower alkyl vinyl ether monomer(s) comprises a hydroxyl substituted lower alkyl vinyl ether.

9. The fluorocopolymer of claim 1 having a hydroxyl value of from about 50 to about 150 a viscosity of from about 4000 mPas to about 12000 mPas at an 80% solids content in butyl acetate.

10. A coating composition comprising a carrier and a fluorocopolymer of claim 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0090] As described above, preferred aspects of the present invention involve coating methods that provide reduced VOC emissions while at the same time providing effective and efficient protective coatings on substrates. As those skilled in the art will appreciate, the quality of a protective coating applied to a substrate can be measured by a variety of coating properties that, depending on the particular application, are important for achieving a commercially successful coating on a given substrate. These properties include but are not limited to: (1) viscosity, (2) color retention and (3) substrate adhesion.

[0091] Viscosity as used herein is measured according the ASTM Standard Test Method for Measuring Solution Viscosity of Polymers with Differential Viscometer, Designation D5225-14. According to this method as used herein, the viscometer used is a Brookfield viscometer (DV-II+Pro) using spindles S18/S31 using torque values from between 40% and 80% at room temperatures of about 23±2° C. If a solvent is used for the measurements, it is butyl acetate.

[0092] The QUV-A is measured as indicated above according to ASTM D 7251, which is QUV Accelerated Weathering Tester Operating Procedure by which accelerated testing is performed in an accelerated testing cabinet sold under the trade mark QUV® manufactured by Q-Lab Corporation of Cleveland Ohio. Two lamps are used in this testing cabinet: “A” lamps (UVA-340) have a normal output of 0.69 W/m.sup.2@340 nm m and a maximum output of 1.38 W/m.sup.2@340 nm m; and “B” lamps (UVA-313) have a normal output of 0.67 W/m.sup.2@310 nm 0.67 and a maximum output of 1.23 W/m.sup.2@310 nm m. As used herein, the designation QUV-A refers to tests using the A lamps and QUA-B refers to tests using the B lamps. The procedure is accomplished using the following steps: [0093] 1. Measure the initial gloss of the coating film three times and obtain the average of the measurements, which is designated in the following calculations as “A.” [0094] 2. Place the test plate containing the coating in the panel holder in the cabinet and power the cabinet on. [0095] 3. Set the PROGRAM button in the control panel and select the desired program operation. [0096] 4. Engage the RUN button to start test. [0097] 5. Record down the exposure time indicated on the led panel [0098] 6. Stop the machine after the indicated hours, remove the test plate, and measure the gloss three times to get an average result for the indicated exposure time, and record this value as “B” for use in the calculation below. [0099] 7. Determine Gloss retention using the formula Gloss Retention=B/A

[0100] In preferred embodiments, the polymers of the present invention have a hydroxyl value of greater than about 70, and in other preferred embodiments have a hydroxyl value of greater than about 90. As mentioned above, the ability to achieve such a method resides, in part, on the judicious selection of the type and the amounts of the various components that are used to form the fluoropolymer and the coating compositions of the present invention.

[0101] In preferred embodiments, the polymers of the present invention have a fluorine content of from about 35% to about 50% by weight, or a fluorine content of from about 40% to about 45% by weight.

MONOMERS

Hydrofluoroolefins

[0102] The hydrofluoroolefin monomers according to the methods of the present invention can include in certain preferred embodiments hydrofluoroethylene monomer, that is, compounds having the formula CX.sup.1X.sup.2=CX.sup.3X.sup.4; wherein X′, X.sup.2, X.sup.3, X.sup.4 are each independently selected from H or F or Cl atom, but at least one of them is a hydrogen atom. Examples of hydrofluoroethylene monomers include, among others: [0103] CH.sub.2═CHF, [0104] CHF═CHF, [0105] CH.sub.2═CF.sub.2, and [0106] CHF═CF.sub.2.

[0107] The hydrofluoroolefin monomers according to certain preferred aspects of the methods of the present invention include, and preferably consists essentially of or consist of hydrofluoropropenes having the formula CX.sup.5X.sup.6=CX.sup.7CX.sup.8X.sup.9X.sup.10; wherein X.sup.5, X.sup.6, X.sup.7, X.sup.8, X.sup.9 and X.sup.10 are independently selected from H or F or Cl atom, but at least one of them is a hydrogen atom and another is a fluorine atom. Examples of hydrofluoro-propene monomers include, among others: [0108] CH.sub.2═CFCF.sub.3 (HFO-1234yf), [0109] trans-CHF═CHCF.sub.3 (trans-HFO-1234ze), [0110] CHCl═CFCF.sub.3 and [0111] CH.sub.2═CHCF.sub.3.

[0112] In preferred embodiments, the hydrofluoroolefin comprises, consists essentially of or consist of HFO-1234yf and/or HFO-1234ze. In preferred embodiments, the hydrofluoroolefin comprises, consists essentially of or consist of HFO-1234ze, with said HFO-1234ze preferably comprising, consisting essentially of or consisting of trans- HFO-1234ze.

[0113] The hydrofluoroolefin monomers according to certain preferred aspects of the methods of the present invention include, hydrofluorobutene according to the following formula: CX.sup.11X.sup.12=CX.sup.13CX.sup.14X.sup.15CX.sup.16X.sup.17X.sup.18; wherein X.sup.11, X.sup.12, X.sup.13, X.sup.14, X.sup.15, X.sup.16, X.sup.17 and X.sup.18 are independently selected from H or F or Cl atom, but at least one of them is a hydrogen atom and at least one is a fluorine atom. Examples of hydrofluorobutene include, among others, CF.sub.3CH═CHCF.sub.3.

Vinyl Esters

[0114] The copolymers in accordance with the present invention can optionally include vinyl ester monomer units, preferably in amounts of from greater than 0 mol % to not greater than about 20 mol %. In preferred embodiments the vinyl ester monomer(s) when present are represented by the formula CH.sub.2═CR.sup.1—O(C═O).sub.XR.sup.2, wherein x is 1 and wherein R.sup.1 is either hydrogen or a methyl group, and wherein R.sup.2 is selected from the group consisting of a substituted or unsubstituted, preferably unsubstituted, straight-chain or branched-chain, preferably branched chain, alkyl group having 5 to 12 carbon atoms, more preferably having from 5 to 10 carbon atoms, and even more preferably 8 to 10 carbon atoms. In preferred embodiments the alkyl group includes at least one tertiary or quaternary carbon atom. In highly preferred embodiments, the vinyl ester includes at least one quaternary carbon according to the following formula:

##STR00001##

where each of R.sup.7 and R.sup.8 are alkyl groups, preferably branched alkyl groups, that together contain from 5 to about 8, more preferably from 6 to 7, carbon atoms.

[0115] Examples of vinyl ester monomers that are preferred according to certain preferred embodiments include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl capronate, vinyl laurate, VEOVA-9 (vinyl versatate ester formed from a C9 carbocylic acid, produced by Momentive), VEOVA-10 (vinyl versatate ester formed from a C10 carbocyclic acid, produced by Momentive) and vinyl cyclohexanecarboxylate. Each of VEOVA-9 and VEOVA-10 contain at least one quaternary carbon according to Formula A above. According to preferred embodiments, the vinyl ester comprises vinyl versatate ester having from 11 to 12 carbon atoms in the molecule, preferably with at least one quaternary carbon according to Formula A above.

Vinyl Ethers

[0116] The copolymers in accordance with the present invention preferably are also formed from vinyl ether monomer units, preferably in amounts of from about 20 mol % to about 40 mol %, more preferably from about 25 mol % to about 40 mol. In preferred embodiments the vinyl ester monomer(s) are represented by the formula CH.sub.2═CR.sup.3—OR.sup.4, wherein R.sup.3 is independently either hydrogen or a methyl group and wherein R.sup.4 is selected from the group consisting of a substituted or unsubstituted, preferably unsubstituted, straight-chain or branched-chain, preferably straight chain, alkyl group having 1 to 5 carbon atoms, more preferably 1 to 3 carbon atoms. Examples of vinyl ether monomers that are preferred according to certain preferred embodiments include alkyl vinyl ethers such as methyl vinyl ether, ethyl, propyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, hexyl vinyl ether, octyl vinyl ether, decyl vinyl ether and lauryl vinyl ether. Vinyl ethers including an alicyclic group can also be used, for example, cyclobutyl vinyl ether, cyclopentyl vinyl ether and cyclohexyl vinyl ether. According to preferred embodiments the vinyl ether comprises, consists essentially of, or consists of ethyl vinyl ether.

Hydroxy Vinyl Ethers

[0117] The copolymers in accordance with the present invention preferably are also formed from hydroxyl vinyl ether monomer units, preferably in amounts of from about 3 mol % to about 20 mol % of hydroxy vinyl ether monomer, preferably in an amount of from about 5 mol % to about 15 mol %, more preferably from about 5 mol % to about 10 mol %. In preferred embodiments the hydroxyl vinyl ether monomer(s) are represented by the formula represented by formula CH.sub.2═CR.sup.3—O—R.sup.5—OH, where R.sup.3 is as defined above, preferably hydrogen, and where R.sup.5 is selected from the group consisting of a C2 to C6 substituted or unsubstituted, preferably unsubstituted, straight-chain or branched- chain, preferably straight chain, alkyl group. Examples of preferred hydroxyalkyl vinyl ether monomers include hydroxyl-ethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxypentyl vinyl ether and hydroxyhexyl vinyl ether. In certain embodiments, the copolymer is formed from about 5 mol % to about 20 mol % of hydroxyalkyl vinyl ether monomers, based on the total weight of the monomer.

CoPolymer Formation Methods

[0118] It will be appreciated by those skilled in the art, based on the teachings contained herein, that copolymers of the present invention may be formed to achieve the preferred characteristics described herein using a variety of techniques, and all such techniques are within the scope of the present invention.

[0119] In preferred embodiments, the fluorocopolymer is preferably produced in a polymerization system that utilizes a carrier for the monomer/polymer during and/or after formation. According to one preferred embodiment the carrier acts as a solvent and/or dispersant for the monomer and/or polymer, and such operations include dispersion, emulsion and solution polymerization. Examples of carriers in such systems, including preferably solvents for solution polymerization, include: esters, such as methyl acetate, ethyl acetate, propyl acetate and butyl acetate; ketones, such as acetone, methyl ethyl acetone and cyclohexanone; aliphatic hydrocarbons, such as hexane, cyclohexane, octane, nonane, decane, undecane, dodecane and mineral spirits; aromatic hydrocarbons, such as benzene, toluene, xylene, naphthalene, and solvent napthta; alcohols, such as methanol, ethanol, tert-butanol, iso-propanol, ethylene glycol monoalkyl ethers; cyclic ethers, such as tetrahydrofuran, tetrahydropyran, and dioxane; fluorinated solvents, such as HCFC-225 and HCFC-141b; dimethyl sulfoxide; and the mixtures thereof.

[0120] It is contemplated that the temperature conditions used in the polymerization process of the present invention can be varied according to the particular equipment and applications involved and all such temperatures are within the scope of the present invention. Preferably, the polymerization is conducted at a temperature in a range of from about 30° C. to about 150° C., more preferably from about 40° C. to about 100° C., and even more preferably from about 50° C. to about 70° C., depending on factors such as the polymerization initiation source and type of the polymerization medium.

[0121] In certain preferred embodiments, it is preferred that the solution polymerization is conducted under conditions under which the total amount of the solvent used in the copolymerization process, based on the weight of the solvent and monomer in the solution, is from about 10 wt % to about 40 wt %, more preferably in amounts of from about 10 wt % to about 30 wt %, and more preferably in certain embodiments in an amount of from about 15% to about 25%. In certain of such embodiments, the solvent used in the solution copolymerization process comprises, preferably consists essentially of, and more preferably in certain embodiments consists essentially of C2-C5 alkyl acetate, and even more preferably butyl acetate.

[0122] In preferred embodiments, the copolymer as formed in accordance with the preferred methods described herein is prepared by copolymerizing those monomers under conditions effective to achieve a copolymer having a number average molecular weight of 5000 to 50,000, or is some embodiments 1000 to 6,000 as measured by gel phase chromatography (“GPC”) according to the method described in Skoog, D. A. Principles of Instrumental Analysis, 6th ed.; Thompson Brooks/Cole: Belmont, Calif., 2006, Chapter 28, which is incorporated herein by reference. In certain embodiments, the copolymer has a number average molecular weight that is greater than about 6,000, and even more preferably from 4,000 to about 6,000. According to certain preferred embodiments, the copolymer has a molecular weight distribution of 1.5 to about 3, more preferably 1.9 to about 3, and most preferably 1.9 to about 2.5. Applicants have found that in certain embodiments the use of copolymers having a molecular weight properties as disclosed herein with and exceptional and unexpected ability to provide high solid content, low viscosity coating compositions that also unexpectedly possess desirable levels of gloss and gloss durability.

Coating Composition Formation Methods

[0123] The copolymers as formed in accordance with the procedures described herein may then be used to form various coating compositions that have the substantial advantages described above. For example, various solvents can be used for the preparation of solution-type paints or coatings by adding those solvents to the fluorocopolymer of the present invention formed as described herein. In certain embodiments, preferred solvents for formation of the coating composition include aromatic hydrocarbons such as xylene and toluene; alcohols such as n-butanol; esters such as butyl acetate; ketones such as methyl isobutyl ketone, and glycol ethers such as ethyl cellusolve and various commercial thinners.

[0124] In certain embodiments, the coating composition of the present invention has a solid content of from about 70% to about 90% by weight based on the total weight of the coating composition, and more preferably in certain embodiments from about 75% go about 85% by weight of solids. In certain preferred embodiments, the solids comprise and preferably consist essentially of the copolymers of the present invention and/or cross-linked copolymers formed using the copolymers of the present invention. Although it is contemplated that those skilled in the art will be able to form coatings using the present compositions according to anyone of known methods, in preferred embodiment the coating is formed by brushing, a rolling, air spraying, airless spraying, flow coating, roller coating, a spin coating, and the like and any combination of these may be used. Furthermore, the coating can be applied on various substrates. The coating film can be formed directly on a substrate or via a primer or if necessary, via an undercoating layer. Although all thicknesses are within the scope of the present invention, in preferred embodiments the outermost cured coating film layer has a layer thickness of from about 20 to about 30 μm.

EXAMPLES

Example 1—Fluoropolymer Preparation

[0125] A solution polymerization operation is carried out by charging into a 1 liter stainless steel autoclave equipped with a stirrer the components as indicated in the following Table 1 in accordance with the procedure descried thereafter:

TABLE-US-00001 TABLE 1 COMPONENT Weight, TYPE NAME grams Solvent butyl acetate 54 Hydrohaloolefin trans-1,3,3,3- 287 Monomer tetrafluoropropene (trans-HFO-1234ze) Alkyl vinyl ether EVA 85 monomer HBVE 50 Catalyst Zinc oxide (ZnO) 25 Initiator tertbutylperoxypivalate 20 Chain transfer Methanol 80

[0126] The ZnO was added to the autoclave, and then the autoclave vacuumed and sealed. The butyl acetate, EVE and HBVE were then charged into the autoclave. Then, the trans-HFO-1234ze were added in the reaction mixture in the autoclave, and the autoclave was gradually heated to about 87° C. with agitation of about 400 revolutions per minute (rpm). When the temperature reached 87° C., the tert-butyl peroxypivalate was added into the autoclave and 20 g of methanol was fed into the autoclave during the course of the next 1 hour, and then the remaining 60.0 g methanol was added into the autoclave and the temperature was increased from 87° C. to 130° C. and then the autoclave was maintained at 130° C. for 3 hrs. The autoclave was then cooled to room temperature, the unreacted monomers were purged, and the autoclave was opened. Excess solvent was removed via evaporation and a polymer solution with 80 wt % solid content and a viscosity of 3,600 cps was obtained. The final fluorocopolymer (without solvent) was tested and found to have: a number average molecular weight (Mn) of about 4,500 and a Mw/Mn of 1.89; a hydroxyl value of 90 mg KOH/g; a Fluorine content of 44 wt %. The yield of cofluoropolymer was about 87%.

[0127] The result reported in Example 1 above indicates that the fluorocopolymer according to the present invention is capable of forming formulations for protective coatings, and accordingly the present fluorocopolymer has excellent usefulness in the formation of protective coatings in conjunction with a wide variety of materials that may be used, for example, as supplemental carriers in such coating compositions.

Example 2—Fluoropolymer Preparation

[0128] A solution polymerization operation is carried out by charging into a 1 liter stainless steel autoclave equipped with a stirrer the components as indicated in the following Table 2 in accordance with the procedure descried thereafter:

TABLE-US-00002 TABLE 2 COMPONENT Weight, TYPE NAME grams Solvent butyl acetate 110 Hydrohaloolefin trans-1,3,3,3- 287 Monomer tetrafluoropropene (trans-HFO-1234ze) Alkyl vinyl ether EVA 100 monomer HBVE 40 Catalyst Zinc oxide (ZnO) 25 Initiator Tertbutyl peroxypivalate 20 Chain transfer Methanol 30

[0129] The ZnO was added to the autoclave, and then the autoclave vacuumed and sealed. The butyl acetate, EVE and HBVE were then charged into the autoclave. Then, the trans-HFO-1234ze were added in the reaction mixture in the autoclave, and the autoclave was gradually heated to about 87° C. with agitation of about 400 revolutions per minute (rpm). When the temperature reached 87° C., the tert-butyl peroxypivalate was added into the autoclave. After being maintained for 3 hours at 87° C., the methanol was added into the autoclave and the temperature was increased from 87° C. to 130° C. After the autoclave reached 130° C., it was maintained at this temperature for 3 hours. The autoclave was cooled to room temperature, the unreacted monomers were purged, and the autoclave was opened. Excess solvent was removed via evaporation and a polymer solution with 80 wt % solid content and a viscosity of 7,600 cps was obtained. The final fluorocopolymer (without solvent) was tested and found to have: a number average molecular weight (Mn) of about 5,300 and a Mw/Mn of 2.24; a hydroxyl value of 90 mg KOH/g; a Fluorine content of 43 wt %. The yield of cofluoropolymer was about 89%.

[0130] The ZnO The result reported in Example 2 above indicates that the fluorocopolymer according to the present invention is capable of forming formulations for protective coatings, and accordingly the present fluorocopolymer has excellent usefulness in the formation of protective coatings in conjunction with a wide variety of materials that may be used, for example, as supplemental carriers in such coating compositions.

Example 3—Fluoropolymer Preparation

[0131] A solution polymerization operation is carried out by charging into a 1 liter stainless steel autoclave equipped with a stirrer the components as indicated in the following Table 3 in accordance with the procedure descried thereafter:

TABLE-US-00003 TABLE 3 COMPONENT Weight, TYPE NAME grams Solvent butyl acetate 110 Hydrohaloolefin trans-1,3,3,3- 287 Monomer tetrafluoropropene (trans-HFO-1234ze) Alkyl vinyl ether EVA 100 monomer HBVE 40 Catalyst Zinc oxide (ZnO) 25 Initiator Tertbutyl peroxypivalate 20 Chain transfer Methanol 30

[0132] The ZnO was added to the autoclave, and then the autoclave vacuumed and sealed. The butyl acetate, EVE and HBVE were then charged into the autoclave. Then, the trans-HFO-1234ze were added in the reaction mixture in the autoclave, and the autoclave was gradually heated to about 87° C. with agitation of about 400 revolutions per minute (rpm). When the temperature reached 87° C., the tert-butyl peroxypivalate was added into the autoclave. After being maintained for 3 hours at 87° C., the methanol was added into the autoclave and the temperature was increased from 87° C. to 150° C. After the autoclave reached 150° C., it was maintained at this temperature for 3 hours. The autoclave was cooled to room temperature, the unreacted monomers were purged, and the autoclave was opened. Excess solvent was removed via evaporation and a polymer solution with 80 wt % solid content and a viscosity of 9,600 cps was obtained. The final fluorocopolymer (without solvent) was tested and found to have: a number average molecular weight (Mn) of about 4,600 and a Mw/Mn of 2.13; a hydroxyl value of 65 mg KOH/g; a Fluorine content of 44 wt %. The yield of cofluoropolymer was about 93%.

Example 4—Coating Composition and Coating Properties

[0133] A coating composition in the form of a white paste is formed using the polymer composition formed in Example 1 hereof. The white paste is formed by adding 310.9 grams of copolymer composition formed in Example 1 hereof, and the other ingredients identified in Table 4 below in the amounts indicated, into a 1,500 ml can. 300 grams of glass beads are then added as grinding medium into the can and the contents are milled at 3000 rpm for 1 hour or until the fines reaches 10 um.

TABLE-US-00004 TABLE 4A White Paste COMPONENT Weight, TYPE NAME grams Resin Example 1 copolymer 310.9 (80% solids and viscosity of 3600 cPs) Pigment Titanium oxide 500 (Ti-Pure R960) Dispersant BYK 180 10 Solvent butyl acetate 58.4

[0134] The glass beads are removed from the white paste so produced, and then the white paste without the glass beads is introduced, together with curing agent and other additives, into a new can, and stirred at 1500 rpm for about 15 minutes or until a uniform solution is achieved. This pigment paste is combined with additional resin as indicated in Table 4B below to produce the Let Down (Main Package).

TABLE-US-00005 TABLE 4B Let Down (Main Package) COMPONENT Parts by TYPE NAME weight Pigment paste Example 4 white paste 73.4 as per above Additional resin Example 1 copolymer 26.6 (80% solids and viscosity of 3600 cPs) Solvent butyl acetate 0 Total 100 Solids (%) 84.5

[0135] A series of samples formed by taking a portion of the material as formed in this Example in Table 4B a diluting the sample with butyl acetate to the solids content as indicated in Table 4C below and the viscosity of each sample is measured by Sheen Ref. 480 (expressed as KU in the table):

TABLE-US-00006 TABLE 4C Sample # Solids KU 1 83% 118.2 2 80% 86.4 3 78% 70.1 4 76% 62.8 5 73% 59.5 6 71% 56.7

[0136] A commercial fluorocoplymer product based on fluroethylene/vinyl ether is tested using the same viscosity versus solids content test described in connection with Table 4C, and the results of this test are reported in Example 4D below:

TABLE-US-00007 TABLE 4D FEVE Sample Solids KU 1 75% 106.1 2 73% 88.1 3 71% 77.0 4 69% 69.0 5 67% 63.9 6 65% 61.0 7 63% 57.9 8 61% 55.8 9 60% 53.6 10 58% 52.7 11 57% 51.3

[0137] The viscosity results are reported herein are illustrated in FIG. 1 hereof. As can be seen from these results and as illustrated in FIG. 1, the present invention provides copolymers, coating compositions and coating methods which have the advantage of providing a high solids content at a much lower viscosity than competitive materials. As those skilled in the art will appreciate, this is an unexpected by highly important advantage.

[0138] In addition, the coatings of the present invention are capable of being formed with very low VOC levels. In particular, the density and solids are determined for the Let-Down material using each of 20S (using T-4 cup viscosity, which is used for viscosity in air pressure spraying) and using 70 KU (which is used for viscosity in airless spraying), and based on this information the VOCs (volatile organic compounds) are calculated using the equation VOCs=1000*(1-Solids) *density (unit being g/L), and this information is provided in Table 4E below:

TABLE-US-00008 TABLE 4E VOC 1 (20 s), g/L 430 2 (70 KU), g/L 360

[0139] In addition, an equivalent curing agent (—NCO:—OH=1.05:1) is added into the Let Down of Table 4B to form a white paint, and this white paint is then applied to a hot dipped galvanized steel (HDG) substrate. The thickness of the substrate was about 0.3 mm. The substrate was sanded by 400 mesh sandpaper. The coated panel was placed in oven set at a temperature of about 80° C. for 24 hours, which produces a fully cured dry film topcoat. The dry film thickness of the topcoat was about 35±5 um and was found to have the properties in Table 4F below:

TABLE-US-00009 TABLE 4F Property Test Method Results Gloss ASTM D 523 60° 72.3 Pencil hardness ASTM D 3363 Scratch HB Flexibility GB/T 6742 2 mm pass Dry adhesion ASTM D 3359 Cross-hatch 5B Acid resistance GB/T 9274 5% H.sub.2SO.sub.4*10 No blistering, days no color change

[0140] The UV exposure conditions are provided in Table 4G below:

TABLE-US-00010 TABLE 4G Typical Approximate Lamp Irradiance Wavelength Exposure Cycle UVB- 0.49 310 nm 8 h UV at 70 (±3) ° C. 313 W/m2/nm Black Panel Temperature; 4 h Condensation at 50 (±3) ° C. Black Panel Temperature

[0141] The results of this durability performance test are illustrated in FIG. 2 and show that the present invention is able to provide a highly durable coating having a initial durability of about 100% and remaining at about 100% after about 1500 hours and decreasing only slightly and remaining at about 90% or greater up to about 3000 hours. This results are illustrated in FIG. 2, together with the results from a competitive material which shows a durability that declines much more rapidly than the paint according to the present invention.

Example 5—Coating Composition and Coating Properties

[0142] Example 4 is repeated except that the copolymer produced in Example 2 is used instead of the copolymer of Example 1. Similar advantageous and unexpected results are achieved.

Example 6—Coating Composition and Coating Properties

[0143] Example 4 is repeated except that the copolymer produced in Example 3 is used instead of the copolymer of Example 1. Similar advantageous and unexpected results are achieved.