GB2102009A

GB2102009A - Coating compositions containing catalyst

Info

Publication number: GB2102009A
Application number: GB08121158A
Authority: GB
Inventors: Stephen John Thomas; Raymond Stanley Stewart
Original assignee: PPG Industries Inc
Current assignee: PPG Industries Inc
Priority date: 1981-07-08
Filing date: 1981-07-09
Publication date: 1983-01-26
Also published as: DE3129230A1; FR2510130A1; AU529874B2; AU7265381A; DE3129230C2

Abstract

Coating compositions comprise film forming components (a) consisting essentially of (i) a polyepoxide having a 1,2-epoxy functionality greater than 1.0 and a molecular weight below about 6000 and (ii) an amine-containing vinyl addition interpolymer wherein the weight ratio of (i) to (ii) is from 1:19 to 19:1, (b) as catalyst a soluble salt of a Group II A metal in amount of 0.1 parts to 5 parts per 100 parts of the film- forming components, and (c) organic solvent.

Description

SPECIFICATION Coating compositions containing catalyst The subject invention relates to organic solvent based coating compositions. More particularly, the invention relates to coating compositions especially useful for the refinishing of automobiles.

Automobiles when first manufactured are typically painted with several layers of paint. The paint provides aesthetic as well as protective features to the automobile. While the paints provide long lasting protection, it is occasionally necessary to repaint an automobile. Typically, however, the repainting of automobiles is done in facilities wherein high curing temperatures are not available and the equipment used to apply the paint is not equivalent to automotive manufacturers' equipment. A coating composition intended for use in the refinishing of automobiles should be quick-drying at a low cure temperature as well as provide features typically expected of a paint, e.g., durability, good appearance and adhesion. The characteristics expected of an automotive paint include the following: organic solvent resistance, gasoline resistance, humidity resistance and chip resistance.Many compositions are available in the prior art which have been used for refinishing of automobiles. Such prior art compositions can be improved upon.

There have now be discovered coating compositions which possess all the attributes expected of a refinishing paint for automotive use. Additionally, the compositions are capable of curing at a low temperature in a short period oftime.

As used herein, all percents, parts and ratios are by weight unless otherwise indicated.

Organic solvent based coating compositions of the invention especially useful for refinishing automobiles consist essentially of (a) film-forming components of polyepoxide resin and amine-containing vinyl addition interpolymer and (b) catalyst. The polyepoxide resins have a 1,2-epoxy functionality of greater than 1.0 and a molecular weight of below about 6000. In a preferred embodiment, the polyepoxide resins are selected from the group consisting of polyglycidyl ethers of saturated polyphenols, polyglycidyl ethers of polyhydric alcohols and polyglycidyl ethers of nitrogencontaining ring compounds.The addition interpolymer can be derived from ethylenically unsaturated carboxylic acid monomers and other copolymerizable ethylenically unsaturated mono merswherein from about 5 percent to about 100 percent of the pendent carboxyl groups are iminated with an alkylenimineorfrom polyamines having aliphatic amine groups on polycarboxyl-containing materials. The catalyst is a soluble salt of Group IIA of the Periodic Chart of the Elements.

According to the present invention there is provided a coating composition characterised in consisting essentially of film forming components, catalyst and organic solvent, wherein: (a) the flIt n- forming component is (i) a polyepoxide having a 1,2-epoxy functionality greater than 1.0 and a molecular weight below about 6000 and (ii) an amine-containing vinyl addition interpolymer wherein the weight ratio of (i) to (ii) is from about 1:19 to about 19:1 and (b) the catalyst is a soluble salt of a Group II A metal with the level of catalyst ranging from about 0.1 parts to about 5 parts per 100 parts of the film-forming components.

The subject invention relates to organic solvent based coating compositions. The compositions consist essentially of (a) a polyepoxide resin and addition interpolymers and (b) catalysts. The following paragraphs described the essential components in more detail as well astheirformulation in the coating compositions.

The polyepoxide resin has a 1,2-epoxy functionality of above 1.0 and a molecular weight of below about 6000. Preferred polyepoxides have a molecular weight below about 4000. One class of suitable polyepoxides is the polyglycidyl ethers of polyhydric alcohols. The polyhdric alcohols can be ethylene glycol, diethylene glycol, triethylene glycol, 1,2- propylene glycol, 1,4-butylene glycol, 1,5-pentane diol, 1,2,6-hexanetriol, and glycerol.

Another class of useful polyepoxides is the polyglycidyl ethers of saturated polyphenols. These products are available commercially or can be manufactured from the reaction product of an appropriate biphenyl compound and epihalohydrin followed by hydrogenation of the aromatic ring. Examples of biphenyl compounds are bis (4-hydroxyphenyl) methane, i.e., bisphenol F; 1,1-bis (4-hydroxyphenyl) ethane; 2,2-bis (4-hydroxyphenyl) propane, i.e., bisphenol A; and 1,1 -bis (4-hydroxyphenyl) butane. The 2,2- bis (4-hydroxyphenyl) propane is preferred.

Suitable epihalohydrins include epichlorohydrin and epibromohydrin. Suitable catalysts for use in the reaction of the diphenyl compound with the epihalohydrin are the tertiary amines, quaternary ammonium hydroxides, quaternary ammonium halides, alkali halides, and hydrazines with a tertiary nitrogen atom. As a general rule, the reaction of the diphenyl compound with epihalohydrin occurs at elevated temperatures, for example, from about 60"C to about 200"C. Agents for splitting off hydrogen halide are as a rule strong alkalis such as anhydrous sodium hydroxide or concentrated sodium hydroxide solution. The above described reaction products are made in a manner as illustrated in U. S. Patent 3,336,241, issued August 15, 1967.The disclosure of this patent is herein incorporated by reference.

Other polyepoxide resins which are used include the polyglycidyl ethers of nitrogen-containing ring compounds. Such resins are commercially available or can be made by the reaction of a N-heterocyclic compound and an epihalohydrin. Suitable N-heterocyclic compounds are 2,4 imidazolidinedione (hydantoin); 5 - methyl - 2,4- imidazolidinedione; 5,5 - dimethyl - 2,4 imidazolidinedione; 5 - methyl - ethyl - 2,4 imidazolidinedione; 5 - ethyl - 5 - amyl - 2,4 imidazolidinedione; 5 - isopropyl - 2,4 imidazolidinedione; and 5,5 - pentamethylene - 2, imidazolidinedione. Epichlorohydrin and epibromohydrin are examples of epihalohydrins com monly used. U. S. Patents 3365471,3391097, 3450711,3503979 and British Patent No. 1172916 contain further illustrations of this class of polyepox ides.These patents are herein incorporated by refer ence.

One class of an amine-containing vinyl addition interpolymer is derived from an ethylenically unsaturated carboxylic acid monomer and at least one copolymerizable ethylenically unsaturated monomer. Examples of the ethylenically unsaturated carboxylic acids are acrylic acid and methacrylic acid. The copolymerizable ethylenically unsaturated monomers include the alkyl acrylates e.g., methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate and isobutyl acrylate; the alkyl methacrylates e.g., methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate and isobutyl methacrylate; and a styrene e.g., styrene, alpha methyl styrene, and the halo-substituted styrenes.

The interpolymer is formed from about 5 percent to about30 percent, preferably from about 10 percent to about 25 percent of the ethylenically unsaturated carboxylic acid monomer and from about 70 percent to about 95 percent, preferably from about 75 percent to about 90 percent of the copolymerizable ethylenically unsaturated monomers.

Ordinarily, the above-described monomer mixture is polymerized in a solvent medium and in the presence of a suitable catalyst. The reaction occurs usually under controlled elevated temperature with agitation. Various modifications commonly used in solution polymerization reactions such as stepwise addition of the monomer mixture during polymerization, incremental addition of catalysts, polymerization under an inert atmosphere and continuous or batch polymerization techniques may be employed.

Usually an organic solvent is included in the reaction mixture to facilitate handling. Many different solvents can be used including alcohols such as propanol, butanol, and other lower alcohols, ketones such as methyl ethyl ketone; aromatic hydrocarbons such as xylene and toluene; and esters such as butyl acetate. Mixtures of the solvents can also be used.

The above-described interpolymers are iminated by reacting the interpolymer with an alkylenimine in a sufficient amount to iminate from about 5 mole percent to about 100 mole percent of the pendent carboxyl groups. The amount of imination preferably ranges from about 50 mole percentto about 95 mole percent. It has been found that the aforementioned levels of imination are important to achieving a fast, low temperature curing coating composition.

High levels of imination e.g. 200 mole percent give a composition having a reduced cure response as well as lesser physical properties.

Alkylenimines which are used in the imination reaction include ethyleneimine, 1,2-propyleneimiple, 1 ,3-propyleneimine, 1,1 -dimethylethyleneimine, phenylethyleneimi ne, tolylethyleneminine, benzyl ethyleneimine, 1 ,2-diphenylethyleneimine, hydrox- yethyl ethylenemine, aminoethyl ethylenimine, 2-methyl propyleneimine, p-chlorophenylethylenimine, ethoxyethyl ethylenimine, N-ethyl ethylenimine and N-butylethylenimine. The preferred alkylenimines are ethylenimine and 1,2-propylenimine.

Another class of amine-containing vinyl addition interpoiymers is prepared by reacting a polyamine containing aliphatic amine groups and having at least one ether group with a polycarboxyl-containing material. These interpolymers are described in copending application No.8037831. The backbone of the plycarboxyl-containing materials include acryl ics, polyesters and polyamides.

Acrylic polymers as described above can be used as the backbone. Saturated polyester resins having pendent carboxyl groups can also form the backbone of the resins of this invention. The saturated polyesters are derived from saturated polycarboxylic acids, preferably dicarboxylic acids, and mixtures of polyhydric alcohols having an average functionality greater than 2. As used herein, aromatic polycarboxylic acids having unsaturation only in the aromatic ring are considered saturated since the aromatic double bonds do not react by addition. Examples of such acids include phthalic acid, isophthalic acid, adipic acid, azelic acid, sebacic acid and their anhydrides where they exist. Commonly used polyhydric alcohols are ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, butylene glycol, glycerol, trimethylol propane, pentaerythritol and sorbitol.

Other useful polycarboxyl-containing materials are the polyamide class of resins. The polyamide resins are made by condensing a diamine with a dibasic carboxylic acid. They are characterized by recurring amide groups, -CONH-, as an integral part of the main polymer chain. Examples of diamines used in making the polyamide resins are ethylenediamine, diethylenetriamine, and hexamethylenediamine. The dicarboxylic acids used in the reaction are those listed above in connection with the production of the polyester resins with the preferred acids being adipic acid, sebacic acid, succinic acid, glutaric acid and azelaic acid. The equivalent ratio of diamine to dicarboxylic acid in the polyamide resins ranges from about 1.5:1 to about 1:2. Known procedures are used for making the resins.

The carboxyl content of preferred polycarboxyl containing material ranged from about 0.5 milliequivalents to about 12 milliequivalents of carboxyl per gram. The more preferred carboxyl content ranges from about 1 milliequivalent to about lamilliequi- valents of carboxyl per gram.

The ungelled amidation products ofthe invention are prepared by reacting the above-described materials containing pendent carboxyl groups with a polyamine containing aliphatic amine groups and having at least one ether linkage One class of polyamines has the formula: H2N - (CnRaH2n - aO)x - R'Nl'l2 where n is from 2 to 6, a is from 0 to 2, R is H, CH3 or C2Hs, x is from 1 to 60 and R' is an alkylene group having from 2 to 6 carbon atoms. Preferably, x ranges from 1 to 40.Examples of suitable polyamines are as follows: H2N ~ C2H40 ~ C2H4 ~ NH2 H2N - (C2H4O)16 - C2H4 - NH2 H2N - (C2H40)25 - C2H4 - NH2 H2N - CH(CH3) CH2O - - CH2CH(CH3) - NH2 H2N - CH(CH3)CH20 6 - CH2CH (CH3)- NH2 H2N - CH(CH3) CH2O 33- - CH2CH (CH3)- NH2 H2N - (C4H8O)3 C4H3 - NH2 H2N - (C3H60)3 - CH2C(CH3)2CH20 - C3H6 - NH2 H2N -C3H60 -C4H80 -C3He- NH2 Another class of polyamines useful herein the formula:: [H2N- (Cn RaH2n-ao)x]y - Z where n is from 2 to 4, a is from 0 to 2, R is H, CH2 or C2Hs, xis from 1 to 60, y is 2 or 3 and Z is an alkyl, aryl or alkylaryl group. Preferably, x ranges from 1 to 40 and the alkyl and alkylaryl groups contain from about 1 to about 20 carbon atoms. A specific example of such a polyamine is:

Other polyamines useful in the above described reaction are the polyamines resulting from the ring opening reaction of a polyepoxide containing ether groups with ammonia. Such ungelled reaction products are referred to herein as ammonia defunctionalized epoxide resins. A suitable class of polyepoxides is the polyglycidyl ethers of polyphenols, such as bisphenol-A.These are produced by etherification of a polyphenol with epichlorohydrin in the presence of an alkali. The phenolic compound can be 1,1-bis (4-hydroxyphenyl) ethane; 1,1-bis (4-hydroxyphenyl) isobutane; 2,2-bis (4hydroxytertiarybutylphenyl) propane; bis (2hydroxynaphthyl) methane; 1,5 - dihydroxynaph- thalene; and 1,1-bis (4- hydroxy- 3- allylphenyl) ethane. Another useful class of polyepoxides is produced similarly from polyphenol resins. Also suitable are the similar polyglycidyl ethers of polyhydric alcohols which are derived from such polyhydric alcohols as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1 ,5-pentanediol, 1 2,6-hexanetriol, glycerol, and 2,2-bis (4-hydroxycyclohexyl) propane.The above-described polyepoxide resins are reacted with ammonia. This reaction involves a simple ring opening reaction where the resultant ungelled product is the amine terminated product of the polyepoxide resin. The ammonia used can be an aqueous solution or anhydrous ammonia. It is desired that substantially all of the 1,2-epoxy groups in the polyepoxide resin react with the ammonia. Thus, a molar excess of the ammonia to expoxy groups is used in the reaction. Molar excesses of the ammonia of up to 10:1 or even higher can be used, with the unreacted excess ammonia being later removed.The reaction of the polyepoxide resin with the ammonia occurs over a range of temperatures, preferably from about 30"C. to about 100"C. The time of the reaction varies according to the temperature used, but general I / ranges from about 2 to 5 hours. The aforedescribed conditions are necessary to minimize further reaction of the produced primary amine with expoxy groups to form a highly polymerized or gelled product.

The equivalent ratio of the above described materials containing pendent carboxyl groups and polyamines is important to obtaining an ungelled product. The equivalent ratio of the polyamine to the carboxyl-containing polymer ranges from about 3:1 to about 1:4, preferably from about 1.5:1 to about 1:1.5. The reaction temperatures and time can vary considerably; however, it is preferred that a temperature of from about 25"C. to about 250"C., preferably from about 85"C. to about 195"C., is used with a reaction time ranging from about 0.1 hours to about 48 hours, preferably from about 0.5 hours to about 8 hours.

The resultant reaction product is an ungelled amidation polymer which is storage stable for substantial lengths oftime. The ungelled amidation product contains primary amine groups, secondary amine groups, or a mixture thereof and carboxyl groups.

The amidation products have an acid number of at least 5, preferably from a bout 10 to about 500, more preferably from about 15 to about 300 and amine equivalent values of from about 100 to about 5000, preferably from 200 to about 2000. The products can be stored for at least one year at 50"C.

Coating compositions ofthis invention contain the aforedescribed polyepoxide resins and aminecontaining vinyl addition interpolymers. The coating compositions are organic solvent based wherein the film-former consists essentially of the polyepoxide resin and the addition interpolymer in a ratio of about 1:19 to about 19:1, preferably from about 1:5 to about 5:1.

The level of organic solvent in the compositions ranges up to about 90 percent and is preferably present at a level of from about 60 percent to about 80 percent. Suitable solvents include the alkanes, toluene, xylene, naphthas, mineral spirits alkylene glycol monoalkyl ethers, e.g., ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether and propylene glycol monobutyl ether; the dialkylene glycol monoalkyl ethers, e.g. diethylene glycol monoethyl ether and dipropylene glycol monobutyl ether; lower alcohols, e.g., ethanol, isopropanol and butanol; esters, e.g.

butyl acetate, ethyl acetate, ethylene glycol monoethyl ether acetate; and mixtures thereof.

The soluble salt of a Group II A metal catalyst is included in the compositions at a level of from about 0.1 parts to about 5 parts, preferably from about 1 part to about 3 parts per 100 parts of the film-forming components. Higher levels of catalyst can be used, but are generally not since no increased catalytic effect is seen. Characteristics offllms formed from the compositions using the higher levels can also be adversely affected, e.g. the film's humidity resistance decreases with high levels of catalyst. Examples of suitable catalysts include magnesium nitrate, calcium nitrate, strontium nitrate, barium nitrate, magnesium chloride, calcium chloride, strontium fluoride and barium chloride. Magnesium nitrate and calcium nitrate are preferred with magnesium nitrate being most preferred. It has been found the Group II A nitrate or halide catalyst is particularly suitable for use with the film-formir,a components of this invention to provide a low temperature cure coating composition.

Various other common additives including pigments, dyes, fillers, antioxidants, flow control agents, surfactants, thickeners and otherformulating additives are included.

The compositions are preferably applied over automotive bodies. However, they can be used for the coating of other substrates including wood, cement and plastics. Generally, the compositions are applied by spraying, though other conventional methods including brushing, rolling, dipping, tlow coating and roll coating can be used.

Compositions ofthis invention can be cured at air temperature within about 36 hours. If desired, however, elevated temperatures can be used to speed up the cure time.

The following examples illustrate this invention.

Example I The following compositions are formulated to show the advantages in cure time achieved using the compositions of this invention.

Components IO/oJ A B C D E F Diglylcidyl ether of 2,2-bis 8.3 8.3 8.3 8.3 8.3 8.3 (4-hydroxycyclohexyl) propane (1) Addition interpolymer (2) 15.5 15.5 15.5 15.5 15.5 15.5 Pigment (non-leafing aluminum flake) 1.0 1.0 1.0 1.0 1.0 1.0 Ethylene glycol monoethyl ether 15.2 15.2 15.2 15.2 15.2 15.2 Naphtha 40.0 40.0 40.0 40.0 40.0 40.2 Toluene 9.0 9.0 9.0 9.0 9.0 9.0 Xylene 10.8 10.8 10.8 10.8 10.8 10.8 Magnesium nitrate 0.2 Calcium nitrate - 0.2 - - - - Magnesium chloride - - 0.2 - - Calcium chloride - - - 0.2 - Magnesium bromide - - - - 0.2 (1) Available from Shell Chem.Co. as DRH 151 (2) The interpolymer is derived from 53.3% butyl methacrylate, 26.7% styrene and 20.0% methacrylic acid. Propylenimine is used to iminate 95 molar per cent of the carboxyl groups. The interpolymer has an acid number of 29 and an amine equivalent weight of 515.

The compositions are separately applied to metal panels to form dry films ranging from 1.8 to 2.1 mils.

The coatings are then tested to determine the times needed to form a tack-free and tape-free surface (a tape-free surface is when application and removal of tape leaves no marks). Pencil hardness, gasoline resistance and toluene double rubs of the coatings are also determined after different cure time intervals. The gasoline resistance is measured by soaking the coated panel in gasoline for thee minutes and then visually grading the coating for dullness and softening on a scale of 1 to 4 with 1 being the more resistant. The results from the tests are tabulated below: Composition A B C D E F Tack-free (min.) 50 40 40 40 40 45 Tape-free (hrs.) 24 24 24 24 24 48 Pencil hardness (24 hrs. cure) 2B 2B 2B 2B 3B 4B (168 hrs. cure) H H H H H F Gasoline resistance (48 hrs. 1 1 1 1 3 3 cure) (168 hrs. cure) 1 1 1 1 1 1 Toluene double rubs (168 hrs. cure) 30 30 35 30 20 15 The above results show the compositions of this invention i.e.: Compositions A-E cure to a tape-free state fasterthan the control while being comparable or better in all other tests.

Claims

1. A coating composition characterised in consisting essentially of film forming components, catalyst and organic solvent, wherein: (a) the film- forming component is (i) a polyepoxide having a 1,2-epoxy functionality greater than 1.0 and a molecular weight below about 6000 and (ii) an amine-containing vinyl addition interpolymer wherein the weight ratio of (i) to (ii) is from about 1:19 to about 19:1 and (b) the catalyst is a soluble salt of a Group II A metal with the level of catalyst ranging from about 0.1 parts to about 5 parts per 100 parts ofthefilm-forming components.

2. A coating composition as claimed in claim 1 characterised in that the polyepoxide is selected from polyglycidyl ethers of saturated polyphenols, polyglycidyl ethers of polyhydric alcohols, polyglycidyl ethers of nitrogen-containing ring compounds, and mixtures thereof.

3. A coating composition as claimed in claim 1 or 2 characterised in that the amine-containing vinyl interpolymer is formed from about 5 percent to about 30 percent of an ethylenically unsaturated carboxylic acid monomer and from about 70 percent to about 95 percent of at least one copolymerizable ethylenically unsaturated monomer selected from the group consisting of alkyl acrylates, alkyl methacrylates, styrene, and mixtures thereof and further characterized by having from about 5 mole percent to about 100 mole percent of carboxyl groups pendent from the interpolymer iminated with an alkyleneimine.

4. A coating composition as claimed in claim 3 characterised in that the ethylienically unsaturated carboxylic acid monomer is acrylic acid, methacrylic acid or a mixture thereof.

5. A coating composition as claimed in claim 3 or 4 characterised in that the alkyl acrylates and alkyl methacrylates contain from 1 to 20 carbon atoms in the alkyl groups.

6. A coating composition as claimed in any of claims 3 to 5 characterised in that the interpolymer is comprised of about 10 percent to about 25 percent of the ethylenically unsaturated carboxylic acid monomer and from about 75 percent to about 90 percent ofthe copolymerizable ethylenically unsaturated monomers.

7. A coating composition as claimed in any of claims 3 to 6 characterised in that the alkylenimine is propylenimine, ethylenimine or a mixture thereof and from about 50 mole percent to about 95 mole percent of the carboxyl groups are iminated.

8. A coating composition as claimed in claim 1 or 2 characterised in that the amine-containing interpolymer is an ungelled reaction product of a polyamine containing aliphatic amine groups and having at least one ether group with a polycarboxyl-containing material.

9. A coating composition as claimed in claim 8 characterised in that the polyamine has the formula: H2N - (CnRaH2n - aO)x - - NH2 where n is from 2 to 6, a is from 0 to 2, R is H, CH3 or C2Hs, xis from 1 to 60, and R' is an alkylene group having from 2 to 6 carbon atoms.

10. A coating composition as claimed in claim 8 characterised in that the polyamine is an ammonia defunctionalized epoxide resin.

11. A coating composition as claimed in any of claims 8, 9 or 10 wherein the polycarboxylcontaining material is an acrylic resin, polyester resin, polyamide resin or a mixture thereof.

12. A coating composition as claimed in claim 1 wherein the polyepoxide resin is a polyglycidyl ether of saturated polyphenols.

13. A coating composition as claimed in any of claims 1 to 12 characterised in that the organic solvent content of the composition ranges from about 60 percent to about 80 percent.

14. A coating composition as claimed in any of claims 1 to 13 characterised in that the catalyst is magnesium nitrate, calcium nitrate or a mixture thereof.

15. A coating composition as claimed in any of claims 1 to 14 wherein the ratio of polyepoxide to addition interpolymer ranges from about 1:5 to about 5:1.

16. A coating composition as claimed in claim 1 substantially as hereinbefore described in any one of the Examples.

17. A coating composition as claimed in any of the preceding claims characterised in that the composition is a two-package polymeric composition with the polyepoxide forming one package, addition interpolymerforming a second package and the catalyst in either package.