WO1983000155A1 - Thermosetting powder coating compositions - Google Patents
Thermosetting powder coating compositions Download PDFInfo
- Publication number
- WO1983000155A1 WO1983000155A1 PCT/GB1982/000189 GB8200189W WO8300155A1 WO 1983000155 A1 WO1983000155 A1 WO 1983000155A1 GB 8200189 W GB8200189 W GB 8200189W WO 8300155 A1 WO8300155 A1 WO 8300155A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- polyester
- acid
- moieties
- coating
- powder
- Prior art date
Links
- 239000000843 powder Substances 0.000 title claims abstract description 28
- 229920001187 thermosetting polymer Polymers 0.000 title claims description 15
- 239000008199 coating composition Substances 0.000 title abstract description 6
- 229920000728 polyester Polymers 0.000 claims abstract description 49
- 239000000203 mixture Substances 0.000 claims abstract description 36
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 claims abstract description 30
- 125000002887 hydroxy group Chemical group [H]O* 0.000 claims abstract description 15
- 239000002253 acid Substances 0.000 claims abstract description 12
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 12
- XXMIOPMDWAUFGU-UHFFFAOYSA-N hexane-1,6-diol Chemical group OCCCCCCO XXMIOPMDWAUFGU-UHFFFAOYSA-N 0.000 claims abstract description 10
- QQVIHTHCMHWDBS-UHFFFAOYSA-N isophthalic acid Chemical group OC(=O)C1=CC=CC(C(O)=O)=C1 QQVIHTHCMHWDBS-UHFFFAOYSA-N 0.000 claims abstract description 10
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 6
- 239000003054 catalyst Substances 0.000 claims abstract description 6
- 239000000155 melt Substances 0.000 claims abstract description 5
- 229920006395 saturated elastomer Polymers 0.000 claims abstract description 3
- 238000000576 coating method Methods 0.000 claims description 44
- 239000011248 coating agent Substances 0.000 claims description 24
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 15
- 239000012948 isocyanate Substances 0.000 claims description 10
- 150000002513 isocyanates Chemical class 0.000 claims description 10
- WERYXYBDKMZEQL-UHFFFAOYSA-N butane-1,4-diol Chemical compound OCCCCO WERYXYBDKMZEQL-UHFFFAOYSA-N 0.000 claims description 8
- SLCVBVWXLSEKPL-UHFFFAOYSA-N neopentyl glycol Chemical compound OCC(C)(C)CO SLCVBVWXLSEKPL-UHFFFAOYSA-N 0.000 claims description 5
- 150000002334 glycols Chemical class 0.000 claims description 4
- 229920005862 polyol Polymers 0.000 claims description 4
- 150000003077 polyols Chemical class 0.000 claims description 4
- 150000007519 polyprotic acids Polymers 0.000 claims description 4
- YIMQCDZDWXUDCA-UHFFFAOYSA-N [4-(hydroxymethyl)cyclohexyl]methanol Chemical compound OCC1CCC(CO)CC1 YIMQCDZDWXUDCA-UHFFFAOYSA-N 0.000 claims description 3
- 239000003377 acid catalyst Substances 0.000 claims description 2
- SRPWOOOHEPICQU-UHFFFAOYSA-N trimellitic anhydride Chemical compound OC(=O)C1=CC=C2C(=O)OC(=O)C2=C1 SRPWOOOHEPICQU-UHFFFAOYSA-N 0.000 claims description 2
- ARCGXLSVLAOJQL-UHFFFAOYSA-N trimellitic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C(C(O)=O)=C1 ARCGXLSVLAOJQL-UHFFFAOYSA-N 0.000 claims 2
- 238000004132 cross linking Methods 0.000 abstract description 4
- 229920005989 resin Polymers 0.000 description 22
- 239000011347 resin Substances 0.000 description 22
- 238000009472 formulation Methods 0.000 description 21
- 238000001723 curing Methods 0.000 description 13
- 230000000704 physical effect Effects 0.000 description 13
- 230000004927 fusion Effects 0.000 description 12
- 238000000034 method Methods 0.000 description 9
- 229920001634 Copolyester Polymers 0.000 description 8
- 229920006038 crystalline resin Polymers 0.000 description 8
- 229920000642 polymer Polymers 0.000 description 7
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 6
- WOZVHXUHUFLZGK-UHFFFAOYSA-N dimethyl terephthalate Chemical compound COC(=O)C1=CC=C(C(=O)OC)C=C1 WOZVHXUHUFLZGK-UHFFFAOYSA-N 0.000 description 6
- 239000003431 cross linking reagent Substances 0.000 description 5
- 239000004014 plasticizer Substances 0.000 description 5
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- OFOBLEOULBTSOW-UHFFFAOYSA-N Malonic acid Chemical compound OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 4
- 229920000877 Melamine resin Polymers 0.000 description 4
- WNLRTRBMVRJNCN-UHFFFAOYSA-N adipic acid Chemical compound OC(=O)CCCCC(O)=O WNLRTRBMVRJNCN-UHFFFAOYSA-N 0.000 description 4
- 150000002148 esters Chemical class 0.000 description 4
- 239000000945 filler Substances 0.000 description 4
- 150000007974 melamines Chemical class 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 125000001931 aliphatic group Chemical group 0.000 description 3
- 125000004432 carbon atom Chemical group C* 0.000 description 3
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 3
- 238000000151 deposition Methods 0.000 description 3
- 230000008021 deposition Effects 0.000 description 3
- 150000002009 diols Chemical class 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 3
- 239000000049 pigment Substances 0.000 description 3
- 239000004408 titanium dioxide Substances 0.000 description 3
- 239000004971 Cross linker Substances 0.000 description 2
- 229920003270 Cymel® Polymers 0.000 description 2
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 2
- ZJCCRDAZUWHFQH-UHFFFAOYSA-N Trimethylolpropane Chemical compound CCC(CO)(CO)CO ZJCCRDAZUWHFQH-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- -1 aliphatic dicarboxylic acids Chemical class 0.000 description 2
- 229920006127 amorphous resin Polymers 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- JGFBRKRYDCGYKD-UHFFFAOYSA-N dibutyl(oxo)tin Chemical compound CCCC[Sn](=O)CCCC JGFBRKRYDCGYKD-UHFFFAOYSA-N 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000003607 modifier Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- BDJRBEYXGGNYIS-UHFFFAOYSA-N nonanedioic acid Chemical compound OC(=O)CCCCCCCC(O)=O BDJRBEYXGGNYIS-UHFFFAOYSA-N 0.000 description 2
- CXMXRPHRNRROMY-UHFFFAOYSA-N sebacic acid Chemical compound OC(=O)CCCCCCCCC(O)=O CXMXRPHRNRROMY-UHFFFAOYSA-N 0.000 description 2
- 239000003381 stabilizer Substances 0.000 description 2
- JOXIMZWYDAKGHI-UHFFFAOYSA-N toluene-4-sulfonic acid Chemical compound CC1=CC=C(S(O)(=O)=O)C=C1 JOXIMZWYDAKGHI-UHFFFAOYSA-N 0.000 description 2
- IUYYVMKHUXDWEU-UHFFFAOYSA-N 2,2,4-trimethylpentane-1,1-diol Chemical compound CC(C)CC(C)(C)C(O)O IUYYVMKHUXDWEU-UHFFFAOYSA-N 0.000 description 1
- NGNBDVOYPDDBFK-UHFFFAOYSA-N 2-[2,4-di(pentan-2-yl)phenoxy]acetyl chloride Chemical compound CCCC(C)C1=CC=C(OCC(Cl)=O)C(C(C)CCC)=C1 NGNBDVOYPDDBFK-UHFFFAOYSA-N 0.000 description 1
- FBPFZTCFMRRESA-FSIIMWSLSA-N D-Glucitol Natural products OC[C@H](O)[C@H](O)[C@@H](O)[C@H](O)CO FBPFZTCFMRRESA-FSIIMWSLSA-N 0.000 description 1
- FBPFZTCFMRRESA-JGWLITMVSA-N D-glucitol Chemical compound OC[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-JGWLITMVSA-N 0.000 description 1
- VOWAEIGWURALJQ-UHFFFAOYSA-N Dicyclohexyl phthalate Chemical compound C=1C=CC=C(C(=O)OC2CCCCC2)C=1C(=O)OC1CCCCC1 VOWAEIGWURALJQ-UHFFFAOYSA-N 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
- 239000013032 Hydrocarbon resin Substances 0.000 description 1
- ORLQHILJRHBSAY-UHFFFAOYSA-N [1-(hydroxymethyl)cyclohexyl]methanol Chemical compound OCC1(CO)CCCCC1 ORLQHILJRHBSAY-UHFFFAOYSA-N 0.000 description 1
- UKLDJPRMSDWDSL-UHFFFAOYSA-L [dibutyl(dodecanoyloxy)stannyl] dodecanoate Chemical compound CCCCCCCCCCCC(=O)O[Sn](CCCC)(CCCC)OC(=O)CCCCCCCCCCC UKLDJPRMSDWDSL-UHFFFAOYSA-L 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 239000001361 adipic acid Substances 0.000 description 1
- 235000011037 adipic acid Nutrition 0.000 description 1
- 125000003545 alkoxy group Chemical group 0.000 description 1
- 150000008064 anhydrides Chemical class 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 125000002843 carboxylic acid group Chemical group 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000012975 dibutyltin dilaurate Substances 0.000 description 1
- 150000001991 dicarboxylic acids Chemical class 0.000 description 1
- 150000005690 diesters Chemical class 0.000 description 1
- 125000000118 dimethyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 238000002845 discoloration Methods 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004924 electrostatic deposition Methods 0.000 description 1
- 230000032050 esterification Effects 0.000 description 1
- 238000005886 esterification reaction Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 235000011187 glycerol Nutrition 0.000 description 1
- 125000003055 glycidyl group Chemical group C(C1CO1)* 0.000 description 1
- 125000003827 glycol group Chemical group 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229920006270 hydrocarbon resin Polymers 0.000 description 1
- 238000013035 low temperature curing Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- IRIAEXORFWYRCZ-UHFFFAOYSA-N n-butyl benzyl phthalate Natural products CCCCOC(=O)C1=CC=CC=C1C(=O)OCC1=CC=CC=C1 IRIAEXORFWYRCZ-UHFFFAOYSA-N 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- WXZMFSXDPGVJKK-UHFFFAOYSA-N pentaerythritol Chemical compound OCC(CO)(CO)CO WXZMFSXDPGVJKK-UHFFFAOYSA-N 0.000 description 1
- DOIRQSBPFJWKBE-UHFFFAOYSA-N phthalic acid di-n-butyl ester Natural products CCCCOC(=O)C1=CC=CC=C1C(=O)OCCCC DOIRQSBPFJWKBE-UHFFFAOYSA-N 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000003755 preservative agent Substances 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000600 sorbitol Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- LXEJRKJRKIFVNY-UHFFFAOYSA-N terephthaloyl chloride Chemical compound ClC(=O)C1=CC=C(C(Cl)=O)C=C1 LXEJRKJRKIFVNY-UHFFFAOYSA-N 0.000 description 1
- QXJQHYBHAIHNGG-UHFFFAOYSA-N trimethylolethane Chemical compound OCC(C)(CO)CO QXJQHYBHAIHNGG-UHFFFAOYSA-N 0.000 description 1
- JNXDCMUUZNIWPQ-UHFFFAOYSA-N trioctyl benzene-1,2,4-tricarboxylate Chemical compound CCCCCCCCOC(=O)C1=CC=C(C(=O)OCCCCCCCC)C(C(=O)OCCCCCCCC)=C1 JNXDCMUUZNIWPQ-UHFFFAOYSA-N 0.000 description 1
- 238000000214 vapour pressure osmometry Methods 0.000 description 1
- 239000003039 volatile agent Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/40—High-molecular-weight compounds
- C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
- C08G18/4205—Polycondensates having carboxylic or carbonic ester groups in the main chain containing cyclic groups
- C08G18/4208—Polycondensates having carboxylic or carbonic ester groups in the main chain containing cyclic groups containing aromatic groups
- C08G18/4211—Polycondensates having carboxylic or carbonic ester groups in the main chain containing cyclic groups containing aromatic groups derived from aromatic dicarboxylic acids and dialcohols
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
- C08G63/16—Dicarboxylic acids and dihydroxy compounds
- C08G63/18—Dicarboxylic acids and dihydroxy compounds the acids or hydroxy compounds containing carbocyclic rings
- C08G63/181—Acids containing aromatic rings
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
- C08G63/16—Dicarboxylic acids and dihydroxy compounds
- C08G63/20—Polyesters having been prepared in the presence of compounds having one reactive group or more than two reactive groups
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G2150/00—Compositions for coatings
- C08G2150/20—Compositions for powder coatings
Definitions
- thermosetting polyester compositions especially adapted for use as powder coatings.
- Thermosetting polyesters have long been used in surface coatings. Hydroxyl and carboxyl groups are most frequently utilised to impart reactive functionality to these resins.
- hydroxyl-functional polyesters are usually cured using alkoxymelamine, anhydride or blocked isocyanate crosslirikers.
- Typical of the hydroxylated polyesters known for use in coating formulations are those derived from various combinations of terephthalic acid, neopentyl glycol, cyclohexanedimethanol, and polyols such as trimethylolprcpane.
- Such polyesters are generally amorphous and have relatively high melt viscosities at fusion temperatures. These resins, at a typical fusion temperature of 160°C., have melt viscosities in excess of about 6500 cps, and often in excess of 10,000 cps.
- copolyesters however, have a relatively high molecular weight and a relativelyhigh melt viscosity, which satisfies the requirements for the intended purpose i.e., a fusion adhesive.
- the high melt viscosity tends to limit the flow of the molten coating and hence adversely affects the smoothness and gloss of the finished coating.
- a linear saturated crystalline polyester of an acid component and a dihydric alcohol component at least 40 mole per cent of the acid component being a terephthalic or isophthalic acid moiety and at least 40 mole per cent of the dihydric alcohol component being a 1,6-hexanediol moiety, the polyester having a number average molecular weight of 700 to 3000, a melt viscosity of 50-3000 cP at 160°C and a hydroxyl number of 30-160.
- the preferred molecular weight range is 1000-2000 and the preferred range of hydroxyl number is 50-125.
- the crystalline polyesters described herein have several advantageous properties which render then superior to the conventional amorphous themoset polyesters currently used in powder coatings, e.g.,
- the crystalline nature of the resins enhances their anti-blocking properties at room temperature. Amorphous resins having similar molecular weight distribution to the crystalline copolyesters would be expected to undergo more pronounced blocking on storage at ambient conditions.
- the crystalline polymers impart a more rapid build-up of physical properties to the coatings during fusion compared to currently used commercial resins.
- the composition of the inherent low viscosity of the crystalline resins and the high level of physical properties they impart to the final coating, enables significantly higher filler concentrations to be used in formulations based on crystalline resins compared to formulations containing amorphous resins of similar molecular weight distribution.
- the present invention provides copolyesters particularly useful in thermosetting compositions, more particularly, thermosetting powder coating compositions such as might be used as automobile coatings.
- polyesters described herein have the unique ability to form thermosetting powder coatings which have low melt viscosities, thereby allowing the powder to flow out to form a smooth coating prior to setting up.
- the powder is more resistant to caking than amorphous polyesters of similar molecular weight distribution.
- the copolyesters of the invention contain terephthalic or isophthalic acid moieties. These moieties can be supplied by the usual terephthalic or isophthalic moiety sources, e.g., terephthalic acid, terephthaloyl chloride and the mono- and dialkyl esters of terephthalic acid. Thus, the term "terephthalic moiety” or “terephthalic acid moiety” is to be considered as including those moieties supplied by- the acid chloride or a mono- or diester.
- the polyester contains terephthalic or isophthalic acid in an amount of at least 40 mole %, based upon the acid moieties.
- the copolyester of the invention is a terephthalic or isophthalic acid copolyester in which from 1 to 60 mol percent of terephthalic or isophthalic acid moieties are replaced, if desired, by a second acid moiety. If a portion of the terephthalic or isophthalic acid moiety is replaced by a second acid moiety, it is replaced by a saturated aliphatic dicarboxylic acid having terminal carboxylic acid groups having from 4 to about 34 carbon atoms between the two carboxyl groups. Preferably, the saturated aliphatic dicarboxylic acid contains between 4 and 8 carbon atoms between the carboxyl groups.
- the diol component of the copolyesters of the invention preferably comprises one or more glycols selected from ethylene glycol, 1,4-butanediol, neopentyl glycol, or 1,4-cyclohexanedimethanol and 1,6-hexanediol where the combined quantities of these diols constitute all of the diol component.
- polyester forming derivatives can be used in the preparation of the polyester, especially the mono- or dialkyl esters of the named dicarboxylic acids, especially C 1 -C 4 mono- or dialkyl esters, particularly the dimethyl esters.
- part of the dicarboxylic acid or glycol moieties of the polyester are replaced by polyols or polybasic acids (having three or more functional groups) to enhance crosslinking.
- the preferred polyfunctional material is trimethylolpropane.
- suitable polyols include trimethylolethane, pentaerythritol, glycerine, sorbitol, etc.
- Suitable polybasic acids include trimellitic anhydride. If such polyfunctional materials are used, it is preferred that they be used in amounts of between about 0.1 and about 12 mole percent.
- polyesters according to this invention are prepared using conventional esterification techniques well known in the art. Some excess glycol is used, and the reaction is such that the polymer is of a relatively low molecular weight, i.e., about 700-3000. The excess glycol and low molecular weight provide for the functional hydroxyl groups in the polymer for crosslinking, thereby making the polymer thermosetting.
- Suitable curing or crosslinking agents for use with thermosetting resins containing functional hydroxyl groups are well known in the art.
- Such curing agents include blocked isocyanates, melamines and polyfunctional epoxy compounds containing at least two glycidyl groups.
- An example of a preferred isocyanate is Huls B1530 (trade mark) a caprolactam-blocked polyfunctional isocyanate.
- Suitable melamines include alkoxymelamine wherein the alkoxy group contains 1 to 8 carbon atoms. Specific examples are Cymel 300 and Cymel 303 (trade marks) hexamethoxymethyl melamines.
- the curing agents are used in amounts of between about 10% and 40%, preferably 15-30%, based on the weight of polyester.
- blocked curing agents it is meant that the curing agent is temporarily deactivated or neutralized so as to allow the powder to flow out and form a smooth coating prior to crosslinking.
- Blocked curing agents and catalysts are well known in the art, e.g., U.S. Patent 3,842,021. In any case, it is preferred that the curing agent be blocked, so as to allow complete flow-out of the powder to eliminate or reduce orangepeel and thereby produce a smooth coating prior to the coating setting up.
- thermosetting composition containing the polyester and curing agen ⁇ has been found to cure without the use of a catalyst at temperatures as low as about 150°C., it is sometimes desirable to use a catalyst Suitable caxalysts are well known in the art and include acid catalysts such as p-toluenesulfonic acid for melamines and dibutyl tin dilaurate for isocyanates.
- the thermosetting composition may also contain a suitable plasticizer.
- the plasticizer must be sufficiently compatible to avoid a sticky formulation. Suitable plasticizers include cioctyl phthalate, dibutyl phthalate, butyl benzyl phthalate, dicyclohexyl phthalate, 2,2,4-trimethylpentanediol-
- 1,3-monoisobutyrate monobenzoate 1,3-monoisobutyrate monobenzoate, trioctyl trimellitate , an ester derived from neopentyl glycol and adipic acid, or the like.
- Conventional stabilizers such as Irganox 1093 (trade mark), a product of Ciba-Geigy, may be used in small amounts to prevent discoloration, etc.
- conventional dyes or pigments such as R-100 titanium dioxide pigment marketed by Du Pont may be used.
- Conventional flow aids, fillers, preservatives, etc. may also be used.
- the components of the composition according to this invention may be mixed by dry blending in a mixer or blender (e.g., a Waring Blender), followed by compounding in a Buss Ko-Kneader, Wearner and Pfleiderer (trade marks) or similar extrusion mixing machine at 90-140°C. and 30-100 r.p.m., granulating, grinding and then screening to obtain a 150 mesh powder for coating.
- a mixer or blender e.g., a Waring Blender
- the polyester pigment and stabilizer if used, may be extruded at about 200°C., then mixed with the crosslinking agent, catalyst, and plasticizer (if used) in a Banbury mixer, a combination of a Banbury mixer and roll mill, or roll mill alone or an extruder at a temperature of between about 90°C. and 150°C.
- all the components may be dissolved in a solvent such as methylene chloride (at about 20 weight percent solids) and spray dried at a chamber temperature of about
- the povrdered composition may be deposited on the substrate by use of a powder gun, by electrostatic deposition or by deposition from a fluidized bed or by other well-known methods of powder deposition. After deposition the powder is heated to a temperature sufficient to cause its particles to flow and thus fuse together to form a smooth, uniform, continuous, uncratered coating on the substrate surface.
- a powder gun by electrostatic deposition or by deposition from a fluidized bed or by other well-known methods of powder deposition. After deposition the powder is heated to a temperature sufficient to cause its particles to flow and thus fuse together to form a smooth, uniform, continuous, uncratered coating on the substrate surface.
- the softening of the coating caused by acetone being applied to the surface is determined.
- the orange peel effect is rated on a scale from 1 (severe orange peel) to 8 (no orange peel) using a set of standard panels for comparison. At the lower levels of orange peel, in the range of ratings 7 to 8, a set of ten standard panels is used to give more accurate assessment, and panels in this range are rated to an accuracy of two figures, e.g., 7.1, 7.5, etc. Imnact Strength
- Impact strength is determined by using a Gardner Laboratory, Inc., Impact Tester. A weight is dropped within a slide tube from a specified height to hit a punch having a 5/8 inch diameter hemispherical nose which is driven into the front (coated face) or back of the panel. The highest impact which does not crack the coating is recorded in inch-pounds, front and reverse. Flexibility
- test panel is bent over a period of 15 seconds, using a Gardner Laboratory, Inc., conical mandrel of specified size, according to ASTM D-522. A pass or fail is recorded. Gloss
- Twen ⁇ y degree and sixty degree gloss are measured using a gloss meter (Gardner Laboratory, Inc., Model GG-9095) according to ASTM D-523.
- Pencil Hardness The pencil hardness of a coating is that cf the hardest pencil that will not cut into the coating. The procedure for preparing the truncated cons pencil lead and carrying out the test is given in the National Coil Coaters Association Technical Bulletin No. II (Aug. 12, 1968). Results are expressed according to the following scale:
- Test panels are placed in a Gallenkamp forced air oven and fused at a specified temperature for a specified time. The fused coatings are then hung on a bar to cool at room temperature.
- Example 1 illustrate typical techniques for forming the polyesters- according to this invention.
- Example 1 illustrate typical techniques for forming the polyesters- according to this invention.
- the properties of the crystalline resins make them particularly suited for use in powder coatings, both in high filler content auto primer surfacer formulations and high gloss top coat formulations for a wide variety of metal products, e.g., appliances, furniture, cycles, etc.
- the performance of representative resins in powder primer surfacers is shown in Examples 13-56. Included for comparison is the performance of fcrmulations based on a commercial polyester.
- the crosslinking agent used in all cases is a caprolactum-blocked polyfunctional isocyanate. I y x> I
- Example 8 and Example 11 Two of the crystalline polyesters (Example 8 and Example 11) give high gloss coatings of excellent physical properties even on curing at 180°C. for 5 minutes. Under these cure conditions, the commercial resin gives low gloss finishes having poor physical properties.
- Examples 13-56 are examples of physical properties of Formulations A-F in a coating. Fusion time is 45 minutes. The following table applied to these examples.
- the crystalline polymers impart a more rapid build-up of mechanical properties to the coatings during fusion compared to currently used commercial resins. They also tend to give higher physical properties in thicker films, as shown in the following examples:
- the polyester is derived from terephthalic acid.
- the glycols are 1,6-hexanediol and as indicated.
- thermoset polyesters For comparison, three commercial thermoset polyesters have the following properties:
- the following formulations G, H and I are polyesters of terephthalic acid and 1 ,6-hexanediol, containing respectively as a second glycol 22 mole % 1,4-cyclohexanedimethanol, 25 mole % neopentyl glycol and 25 mole % ethylene glycol.
- the molecular weights of the resins used in Formulations G, H and I are
- Fusion time is 45 minutes and the fusion temperature is 163°C.
- Formulation G is used; in Examples 77-80, Formulation H is used; and in Examples 81-83, Formulation I is used.
- Examples 84-96 demonstrate the coating properties of powder top coats based on crystalline polyesters. Fusion time and temperature for
- Examples 84-88, 89-92 and Examples 93-96 are 20 minutes, 163°C.; 5 minutes, 180°C. and 10 minutes,
- the crystalline polyesters When used in powder topcoat formulations, cured for 20 min. at 163°C., the crystalline polyesters, gave coatings having excellent physical properties, low orange peel and a significantly higher gloss than that obtained for the commercial resins. The same pattern is maintained on cure at 180°C./10 min.
- the high gloss finish characteristic of the crystalline resins is believed to be due to their outstanding flow properties, imparted to the coatings by virtue of the low melt viscosity of these polymers.
- Hydroxyl number is a conventional, well- known term, meaning the number in terms of milligrams of potassium hydroxide per gram of sample, over and above the amount required to neutralize any acid groups that are present.
- Number average molecular weight (used herein) is also a conventional term, and is determined by the well-known technique of vapor pressure osmometry.
- Viscosity is determined in centipoises at specified temperatures using a conventional Shirley-Ferranti Viscometer at a shear rate of 563 sec -1 . Unless otherwise specified, all parts, percentages, ratios, etc., are by weight.
Abstract
A linear saturated crystalline polyester comprising an acid component containing at least 40 mole per cent of terephthalic or isophthalic acid moieties and a dihydric alcohol component containig at least 40 mole per cent of 1,6-hexanediol moieties, and having a number average molecular weight of 700 to 3000, a melt viscosity of 50-3000 cP at 160oC and a hydroxyl number of 30 to 160 is very suitable for use in powder coating compositions. These compositions contain a curing agent to crosslink the polyester and may contain an acid crosslinking catalyst.
Description
THERMOSETTING POWDER COATING COMPOSITIONS
This invention relates to thermosetting polyester compositions especially adapted for use as powder coatings. Thermosetting polyesters have long been used in surface coatings. Hydroxyl and carboxyl groups are most frequently utilised to impart reactive functionality to these resins. In the area of powder coatings, hydroxyl-functional polyesters are usually cured using alkoxymelamine, anhydride or blocked isocyanate crosslirikers. Typical of the hydroxylated polyesters known for use in coating formulations are those derived from various combinations of terephthalic acid, neopentyl glycol, cyclohexanedimethanol, and polyols such as trimethylolprcpane. Such polyesters are generally amorphous and have relatively high melt viscosities at fusion temperatures. These resins, at a typical fusion temperature of 160°C., have melt viscosities in excess of about 6500 cps, and often in excess of 10,000 cps.
The high melt viscosity tends to limit the flow of the molten coating and hence adversely affects the smoothness and gloss of the finished coating. Cure speed of these resins depends upon the type of crosslinking agent used, but to resin is recommended for use at cure schedules less than 160°C. for 35 minutes. Below these recommended temperatures, the coatings generally have a poor appearance and poor physical properties are obtained. U.S. Patent No. 4,094,721 describes copolyesters of terephthalic acid, 1,4-butanediol and 1,6- hexanediol. These copolyesters, however, have a relatively high molecular weight and a relativelyhigh melt viscosity, which satisfies the requirements for the intended purpose i.e., a fusion adhesive.
The high melt viscosity tends to limit the flow of the molten coating and hence adversely affects the smoothness and gloss of the finished coating.
According to the present invention there is provided a linear saturated crystalline polyester of an acid component and a dihydric alcohol component, at least 40 mole per cent of the acid component being a terephthalic or isophthalic acid moiety and at least 40 mole per cent of the dihydric alcohol component being a 1,6-hexanediol moiety, the polyester having a number average molecular weight of 700 to 3000, a melt viscosity of 50-3000 cP at 160°C and a hydroxyl number of 30-160.
The preferred molecular weight range is 1000-2000 and the preferred range of hydroxyl number is 50-125.
The crystalline polyesters described herein have several advantageous properties which render then superior to the conventional amorphous themoset polyesters currently used in powder coatings, e.g.,
(a) The crystalline polyesters of a given molecular weighx tend to have lower melt viscosities than those normally associated with the amorphous polyesters of similar molecular weight which are currently used in powder coatings. This means that powder coatings based on these crystalline, thermoset polyesters generally flow better on fusion, resulting in less orange peel and smooth coatings having high gloss.
(b) The crystalline polyesters react more rapidly with the blocked isocyanate cross- linker than would be expected. This results in coating formulations which can cure at temperatures as low as 150°C. With suitable
curing agents, even lower curing temperatures might be achieved.
(c) The crystalline polyesters, when incorporated into powder formulations cured with blocked isocyanate crosslinker, give finished coatings having outstanding physical properties.
(d) The crystalline nature of the resins enhances their anti-blocking properties at room temperature. Amorphous resins having similar molecular weight distribution to the crystalline copolyesters would be expected to undergo more pronounced blocking on storage at ambient conditions. (e) The crystalline polymers impart a more rapid build-up of physical properties to the coatings during fusion compared to currently used commercial resins. (f) The composition of the inherent low viscosity of the crystalline resins and the high level of physical properties they impart to the final coating, enables significantly higher filler concentrations to be used in formulations based on crystalline resins compared to formulations containing amorphous resins of similar molecular weight distribution. The present invention provides copolyesters particularly useful in thermosetting compositions, more particularly, thermosetting powder coating compositions such as might be used as automobile coatings.
The polyesters described herein have the unique ability to form thermosetting powder coatings which have low melt viscosities, thereby allowing the powder to flow out to form a smooth coating
prior to setting up. On the other hand, the powder is more resistant to caking than amorphous polyesters of similar molecular weight distribution.
The copolyesters of the invention contain terephthalic or isophthalic acid moieties. These moieties can be supplied by the usual terephthalic or isophthalic moiety sources, e.g., terephthalic acid, terephthaloyl chloride and the mono- and dialkyl esters of terephthalic acid. Thus, the term "terephthalic moiety" or "terephthalic acid moiety" is to be considered as including those moieties supplied by- the acid chloride or a mono- or diester. The polyester contains terephthalic or isophthalic acid in an amount of at least 40 mole %, based upon the acid moieties. Stated differently, the copolyester of the invention is a terephthalic or isophthalic acid copolyester in which from 1 to 60 mol percent of terephthalic or isophthalic acid moieties are replaced, if desired, by a second acid moiety. If a portion of the terephthalic or isophthalic acid moiety is replaced by a second acid moiety, it is replaced by a saturated aliphatic dicarboxylic acid having terminal carboxylic acid groups having from 4 to about 34 carbon atoms between the two carboxyl groups. Preferably, the saturated aliphatic dicarboxylic acid contains between 4 and 8 carbon atoms between the carboxyl groups. Examples of aliphatic dicarboxylic acids contemplated include adipic, azelaic or sebacic acid or mixtures thereof. The diol component of the copolyesters of the invention preferably comprises one or more glycols selected from ethylene glycol, 1,4-butanediol, neopentyl glycol, or 1,4-cyclohexanedimethanol and 1,6-hexanediol where the combined quantities of these diols constitute all of the diol component.
With respect to the aliphatic or the aromatic dicarboxylic acids, polyester forming derivatives can be used in the preparation of the polyester, especially the mono- or dialkyl esters of the named dicarboxylic acids, especially C1-C4 mono- or dialkyl esters, particularly the dimethyl esters.
In a preferred embodiment of the invention, part of the dicarboxylic acid or glycol moieties of the polyester are replaced by polyols or polybasic acids (having three or more functional groups) to enhance crosslinking. The preferred polyfunctional material is trimethylolpropane. Other suitable polyols include trimethylolethane, pentaerythritol, glycerine, sorbitol, etc. Suitable polybasic acids include trimellitic anhydride. If such polyfunctional materials are used, it is preferred that they be used in amounts of between about 0.1 and about 12 mole percent.
The polyesters according to this invention are prepared using conventional esterification techniques well known in the art. Some excess glycol is used, and the reaction is such that the polymer is of a relatively low molecular weight, i.e., about 700-3000. The excess glycol and low molecular weight provide for the functional hydroxyl groups in the polymer for crosslinking, thereby making the polymer thermosetting.
Suitable curing or crosslinking agents for use with thermosetting resins containing functional hydroxyl groups, i.e., the polyester disclosed herein, are well known in the art. Such curing agents include blocked isocyanates, melamines and polyfunctional epoxy compounds containing at least two glycidyl groups. An example of a preferred isocyanate is Huls B1530 (trade mark) a caprolactam-blocked polyfunctional isocyanate. Suitable melamines
include alkoxymelamine wherein the alkoxy group contains 1 to 8 carbon atoms. Specific examples are Cymel 300 and Cymel 303 (trade marks) hexamethoxymethyl melamines. The curing agents are used in amounts of between about 10% and 40%, preferably 15-30%, based on the weight of polyester. By blocked curing agents, it is meant that the curing agent is temporarily deactivated or neutralized so as to allow the powder to flow out and form a smooth coating prior to crosslinking. Blocked curing agents and catalysts are well known in the art, e.g., U.S. Patent 3,842,021. In any case, it is preferred that the curing agent be blocked, so as to allow complete flow-out of the powder to eliminate or reduce orangepeel and thereby produce a smooth coating prior to the coating setting up.
Although the thermosetting composition containing the polyester and curing agenτ has been found to cure without the use of a catalyst at temperatures as low as about 150°C., it is sometimes desirable to use a catalyst Suitable caxalysts are well known in the art and include acid catalysts such as p-toluenesulfonic acid for melamines and dibutyl tin dilaurate for isocyanates. The thermosetting composition may also contain a suitable plasticizer. The plasticizer must be sufficiently compatible to avoid a sticky formulation. Suitable plasticizers include cioctyl phthalate, dibutyl phthalate, butyl benzyl phthalate, dicyclohexyl phthalate, 2,2,4-trimethylpentanediol-
1,3-monoisobutyrate monobenzoate, trioctyl trimellitate , an ester derived from neopentyl glycol and adipic acid, or the like.
Conventional stabilizers, such as Irganox 1093 (trade mark), a product of Ciba-Geigy, may be used in small amounts to prevent discoloration, etc. Also, conventional dyes or pigments such as R-100 titanium dioxide pigment marketed by Du Pont may be used. Conventional flow aids, fillers, preservatives, etc., may also be used.
The components of the composition according to this invention may be mixed by dry blending in a mixer or blender (e.g., a Waring Blender), followed by compounding in a Buss Ko-Kneader, Wearner and Pfleiderer (trade marks) or similar extrusion mixing machine at 90-140°C. and 30-100 r.p.m., granulating, grinding and then screening to obtain a 150 mesh powder for coating. Also, the polyester pigment and stabilizer, if used, may be extruded at about 200°C., then mixed with the crosslinking agent, catalyst, and plasticizer (if used) in a Banbury mixer, a combination of a Banbury mixer and roll mill, or roll mill alone or an extruder at a temperature of between about 90°C. and 150°C. Alternately, all the components may be dissolved in a solvent such as methylene chloride (at about 20 weight percent solids) and spray dried at a chamber temperature of about 50°C. by well-known techniques.
The povrdered composition may be deposited on the substrate by use of a powder gun, by electrostatic deposition or by deposition from a fluidized bed or by other well-known methods of powder deposition. After deposition the powder is heated to a temperature sufficient to cause its particles to flow and thus fuse together to form a smooth, uniform, continuous, uncratered coating on the substrate surface.
The following Examples are sumbitted for a better understanding of the invention. In the Examples, the physical properties of the coatings are determined as follows: Peel Adhesion
Because powder coatings generally have superior adhesion properties to wet paints, the adhesion tape test commonly used for wet systems is often abandoned in favor of the more demanding peel adhesion test. In this test a scalpel is used to cut two intersecting lines, each about 2 cm. long, at about 60° to one another. The tip of the scalpel is used to try to lift the coating from the substrate. If the coating can be removed easily, the test result is rated as "fail". If the coating cannot be removed from the substrate, except by scraping, then a "pass" is recorded. Acetone Resistance
The softening of the coating caused by acetone being applied to the surface is determined. Caking Test
100 mis of powder are poured into a 27 mm diameter measuring cylinder which is then placed in a forced air oven at a constant temperature of 40°C. The powder is examined for loss of free-flowing properties after 24, 48, 72, 96 and 168 hours. Orange Peel
The orange peel effect is rated on a scale from 1 (severe orange peel) to 8 (no orange peel) using a set of standard panels for comparison. At the lower levels of orange peel, in the range of ratings 7 to 8, a set of ten standard panels is used to give more accurate assessment, and panels in this range are rated to an accuracy of two figures, e.g., 7.1, 7.5, etc.
Imnact Strength
Impact strength is determined by using a Gardner Laboratory, Inc., Impact Tester. A weight is dropped within a slide tube from a specified height to hit a punch having a 5/8 inch diameter hemispherical nose which is driven into the front (coated face) or back of the panel. The highest impact which does not crack the coating is recorded in inch-pounds, front and reverse. Flexibility
The test panel is bent over a period of 15 seconds, using a Gardner Laboratory, Inc., conical mandrel of specified size, according to ASTM D-522. A pass or fail is recorded. Gloss
Twenτy degree and sixty degree gloss are measured using a gloss meter (Gardner Laboratory, Inc., Model GG-9095) according to ASTM D-523. Pencil Hardness The pencil hardness of a coating is that cf the hardest pencil that will not cut into the coating. The procedure for preparing the truncated cons pencil lead and carrying out the test is given in the National Coil Coaters Association Technical Bulletin No. II (Aug. 12, 1968). Results are expressed according to the following scale:
(softest) 63, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H (hardest) Coating Thickness The coating thickness is determined using a Fischer Instrumentation (GB) Ltd. Permascope Model ES 8e 3K 4. Fusion of the Coating
Test panels are placed in a Gallenkamp forced air oven and fused at a specified temperature
for a specified time. The fused coatings are then hung on a bar to cool at room temperature.
Examples 1 and 2 which follow illustrate typical techniques for forming the polyesters- according to this invention. Example 1
Two thousand thirty seven g. (10.5 moles) of dimethyl terephthalate, 1062 g (9 moles) of 1,6- hexanediol, 270 g (3 moles) of 1,4-butanediol and 2 g of dibutyl tin oxide are heated under nitrogen in a conventional single stage reaction. Cook log is shown below.
Process Time (Hr) Temp. °C. Distillate (ml)
6 0-200 approx 2 200-225 820 (Theory = 840 )
Resin Properties
Molecuϊar Wt. = 1,338
Hydroxyl No. = 88
Acid No. = < 1
Melt viscosity at 160°C. = 215 cp
Examole 2
Seventeen hundred g. of dimethyl terephthalate, 1216 g. 1,6-hexanediol, 48 g trimethylol propane and 3 g of dibutyl tin oxide are heated under nitrogen in a conventional single stage process according to the following cook log. Process Time
(Hr) Temp. (°C) Distillate (ml)
0 22 —
1.25 140 100
1.5 165 310
2.0 195 630
2.5 200 670
3.5 200 680
6.5 180 680 (Theory = 710)
Resin Properties
Hydroxyl No. = 81
Acid No. = <1
Molecular Wt. = 1200 (Theory = 1500) Other resins prepared in a conventional manner, similar to Examples 1 and 2, are given in Table 1, Examples 3-12 and 75-82. Dimethyl terephthalate is used in all examples as the dicarboxylic acid. 1,6-Hexanediol is used with other glycols as noted.
I y ro
Direct comparison of the melt viscosities at 160°C. of selected crystalline resins relative to currently used commercial resins (R, S and T) of comparable molecular weight and hydroxyl number is made in Table 2. These results clearly show the very low melt viscosity of the crystalline resins relative to the conventional polymers.
Table 2
Molecular Hydroxyl Melt Viscosity Resin Wt No. (cps at 160°C.)
From Ex. 4 2100 62 362
From Ex. 12 2200 81 906
R 2400 56 >10,000
S 1850 59 6,700 T 2700 62 >10,000
The properties of the crystalline resins make them particularly suited for use in powder coatings, both in high filler content auto primer surfacer formulations and high gloss top coat formulations for a wide variety of metal products, e.g., appliances, furniture, cycles, etc. The performance of representative resins in powder primer surfacers is shown in Examples 13-56. Included for comparison is the performance of fcrmulations based on a commercial polyester. The crosslinking agent used in all cases is a caprolactum-blocked polyfunctional isocyanate.
I y x> I
All of the primer surfacer formulations readily cured at 163°C for 45 minutes to give finishes having low orange peel. However, the formula tions-based on the crystalline resins gave physical properties superior to those obtained using the commercial resin. Furthermore, the crystalline polyester-based formulations maintained their high performance even on curing at 150°C. for 45 minutes. On the other hand, the control primers completely lost their physical properties on curing at this lower temperature. This clearly demonstrates the novel low temperature cure properties of the crystalline polyesters.
Two of the crystalline polyesters (Example 8 and Example 11) give high gloss coatings of excellent physical properties even on curing at 180°C. for 5 minutes. Under these cure conditions, the commercial resin gives low gloss finishes having poor physical properties. Examples 13-56 are examples of physical properties of Formulations A-F in a coating. Fusion time is 45 minutes. The following table applied to these examples.
Examples Fusion Temperature Formulation
13-15 163 A
16-19 163 B
20-24 163 C
25-29 163 D
30-33 163 E
34-36 163 F
37-33 150 A
39-42 150 B
43-45 150 C
46-50 150 D
51-53 150 E
The crystalline polymers impart a more rapid build-up of mechanical properties to the coatings during fusion compared to currently used commercial resins. They also tend to give higher physical properties in thicker films, as shown in the following examples:
It can be seen that the formulation according to this invention achieves maximum physical properties between 15-30 minutes, while that based on the commercial resin only gives maximum properties after 45 min.
In the following examples, the polyester is derived from terephthalic acid. The glycols are 1,6-hexanediol and as indicated.
I ro ro
I
For comparison, three commercial thermoset polyesters have the following properties:
Melt Viscosity Ex. Resin Molecular Wt. Hydroxyl No. (cps at 160°C) 71 X 2,400 56 >10,000
72 Y 1,850 59 6,700
73 Z 2,700 62 >10,000
The following formulations G, H and I are polyesters of terephthalic acid and 1 ,6-hexanediol, containing respectively as a second glycol 22 mole % 1,4-cyclohexanedimethanol, 25 mole % neopentyl glycol and 25 mole % ethylene glycol. The molecular weights of the resins used in Formulations G, H and I are
970, 960 and 1800 respectively. Crystalline Resins in Primer Surfacer Formulations
Parts by Weight
G H I
Resin From Ex. 67 74.3 Resin From Ex. 65 - 76.4 -
Resin From Ex. 68 - - 85.0
Caprolactam-Blocked Isocyanate 25.7 23.6 15.0
Filler 90.0 90.0 90.0 Polymerized Debutanized Hydrocarbon Resin 5.0 5.0 5.0
Flow Modifier 1.0 1.0 1.0
Volatiles Release Agent 0.5 0.5 0.5
Titanium Dioxide 10.0 10.0 10.0 In the following examples, Formulations G,
H and I are used in primer surface application.
Fusion time is 45 minutes and the fusion temperature is 163°C. In Examples 74-76, Formulation G is used; in Examples 77-80, Formulation H is used; and in Examples 81-83, Formulation I is used.
Examples 84-96, based on the formulations given in the following table, demonstrate the coating properties of powder top coats based on crystalline polyesters. Fusion time and temperature for
Examples 84-88, 89-92 and Examples 93-96 are 20 minutes, 163°C.; 5 minutes, 180°C. and 10 minutes,
180°C., respectively.
PIGMENTED POWDER TOPCOAT FORMULATIONS BASED ON CRYSTALLINE THERMOSET POLYESTERS
Parts by Weight
Component J K L M
Resin Y 80 - - -
From Ex. 4 - 76.7 - -
From Ex. 8 - - 76.7 -
From Ex. 11 - - - 71.4
Plasticizer 5 5 5 5
Flow Modifier 1 1 1 1
Volatile Release Agent 0.5 0.5 0.5 0.5
Titanium Dioxide 50 50 50 50
Crosslinking Agent 20 23.3 23.3 28.6
When used in powder topcoat formulations, cured for 20 min. at 163°C., the crystalline polyesters, gave coatings having excellent physical properties, low orange peel and a significantly higher gloss than that obtained for the commercial resins. The same pattern is maintained on cure at 180°C./10 min. The high gloss finish characteristic of the crystalline resins is believed to be due to their outstanding flow properties, imparted to the coatings by virtue of the low melt viscosity of these polymers.
Hydroxyl number is a conventional, well- known term, meaning the number in terms of milligrams of potassium hydroxide per gram of sample, over and above the amount required to neutralize any acid groups that are present.
Number average molecular weight (used herein) is also a conventional term, and is determined by the well-known technique of vapor pressure osmometry.
Viscosity is determined in centipoises at specified temperatures using a conventional Shirley-Ferranti Viscometer at a shear rate of 563 sec-1 . Unless otherwise specified, all parts, percentages, ratios, etc., are by weight.
Claims
1. A linear saturated crystalline polyester of an acid component and a dihydric alcohol component, at least 40 mole per cent of the acid component being a terephthalic or isophthalic acid moiety and at least 40 mole per cent of the dihydric alcohol component being a 1,6-hexanediol moiety, the polyester having a number average molecular weight of 700 to 3000, a melt viscosity of 50-3000 cP at 160°C and a hydroxyl number of 30-160.
2. A polyester according to claim 1 having a number average molecular weight of 1000-2000.
3. A polyester according to claim 1 or 2 having a melt viscosity of 50 to 100 cP.
4. A polyester according to any of the preceding claims having a hydroxyl number of 50-125.
5. A polyester according to any of the preceding claims wherein the dihydric alcohol component contains moieties of at least one of the glycols : ethylene glycol, 1,4-butanediol, neopentyl glycol and 1,4-cyclohexanedimethanol.
6. A polyester according to any of the preceding claims which comprises moieties of a polyol.
7. A polyester according to any of the preceding claims which comprises moieties of a polybasic acid.
8. A polyester according to claim 7 wherein the polybasic acid is trimellitic acid, the moieties being derived from trimellitic anhydride.
9. A thermosetting composition which contains a polyester according to any of the preceding claims and a curing agent which is reactive with hydroxyl groups to crosslink the polyester.
10. A composition according to claim 9 wherein the curing agent is a blocked isocyanate or a melaπine.
11. A composition according to claim 9 or 10 which contains a catalyzing amount of an acid catalyst.
12. A composition according to claim 11 wherein the weight of the catalyst present is from 0.01 to 5% of the weight of the polyester.
13. A composition according to any of claims
9 to 12 which is in particulate form of a size suitable for coating as a powder.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US278,228810629 | 1981-06-29 | ||
US06/278,228 US4387214A (en) | 1981-06-29 | 1981-06-29 | Thermosetting powder coating compositions |
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WO1983000155A1 true WO1983000155A1 (en) | 1983-01-20 |
Family
ID=23064190
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PCT/GB1982/000189 WO1983000155A1 (en) | 1981-06-29 | 1982-06-28 | Thermosetting powder coating compositions |
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EP (1) | EP0070118A1 (en) |
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US3907733A (en) * | 1974-01-08 | 1975-09-23 | Eastman Kodak Co | Hot melt adhesive compositions |
DE2435863C3 (en) * | 1974-07-25 | 1983-02-24 | Dynamit Nobel Ag, 5210 Troisdorf | Linear, saturated, semi-crystalline copolyesters |
US4197353A (en) * | 1978-04-14 | 1980-04-08 | Mobil Oil Corporation | Thermosetting powder coating polyesters |
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1981
- 1981-06-29 US US06/278,228 patent/US4387214A/en not_active Expired - Lifetime
-
1982
- 1982-06-28 WO PCT/GB1982/000189 patent/WO1983000155A1/en unknown
- 1982-06-28 EP EP82303382A patent/EP0070118A1/en not_active Withdrawn
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DE2837522B1 (en) * | 1978-08-28 | 1979-04-26 | Huels Chemische Werke Ag | Liquid coating agents |
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Title |
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Cited By (3)
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EP0512335A2 (en) * | 1991-05-07 | 1992-11-11 | Bayer Ag | Polyesterpolyols and their use as adhesion promoter for polymeric systems and as polymeric plasticizer |
EP0512335A3 (en) * | 1991-05-07 | 1993-02-03 | Bayer Ag | Polyesterpolyols and their use as adhesion promoter for polymeric systems and as polymeric plasticizer |
US5243013A (en) * | 1991-05-07 | 1993-09-07 | Bayer Aktiengesellschaft | Polyester polyols and their use as anchoring agents for polymer systems and as polymeric plasticizers |
Also Published As
Publication number | Publication date |
---|---|
US4387214A (en) | 1983-06-07 |
EP0070118A1 (en) | 1983-01-19 |
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