LACTIDE

This invention relates to alkyd resins.

Alkyd resins are a class of branched polyesters. They are reaction products of reactants that include a dicarboxylic acid or anhydride (almost always an aromatic type), a polyol such as neopentyl glycol, glycerin or pentaerythritol, and an unsaturated fatty acid (which is generally supplied as a mixture of fatty acids obtained from a plant source). A short-chain monocarboxylic acid such as benzoic acid is usually included in the reaction mixture to help control crosslinking and reduce gelation.

Alkyd resins are used as the resin phase of oil-based paints. They are soluble in a variety of organic solvents. An oil-based paint therefore typically includes a solution of the alkyd resin in such a solvent, together with a drier and typically with one or more pigments. When formed into a coating, the solvent evaporates and the alkyd resin cures via a crosslinking reaction whereby unsaturation introduced with the fatty acids react in the presence of oxygen. The paint formulation may contain one or more catalysts to promote the crosslinking reaction.

Apart from the fatty acids, the raw materials used in making alkyd resins tend to be produced industrially from fossil carbon sources such as petroleum. As with many other chemical products that have traditionally been produced from petroleum, there is a desire to produce alkyd resins using starting materials derived from annually renewal resources. There is also a desire to reduce the carbon footprint associated with the production of alkyd resins.

To this end, it has been suggested to replace a portion of the starting materials with L-lactide. See, e.g., van Leeuwen et al., "Improved Saturated Polyester and Alkyd Coatings", Paint & Coatings Industry, March 2013, pp. 32-41 and Michel, "Reducing the Environmental Footprint of Coatings with Lactide Technology", Paint & Coatings Industry, May 2016. These articles report positive but modest benefits on various properties such as lower viscosity of the resin and on adhesion and impact resistance of the cured coating when an L-lactide-modified alkyd resin is used in a "medium oil" alkyd resin paint formulation. Further improvements in properties such as adhesion and impact resistance are desired, while retaining the benefit of low viscosity. These benefits should be obtained without sacrificing other desired attributes of the coating.

The invention is in one aspect an alkyd resin comprising i) 5 to 50 weight percent polymerized lactide residues based on the weight of the alkyd resin, wherein 10 to 90% of the polymerized lactide residues are meso-lactide residues and correspondingly 90 to 10% of the polymerized lactide residues are L-lactide and/or D- lactide residues, and ii) fatty acid residues such that the alkyd resin has an oil content of at least 20% by weight.

In particular embodiments, the alkyd resin of the invention includes A) residues of at least one polybasic carboxylic acid, B) 5 to 50 weight percent, based on the weight of the alkyd resin, of the polymerized lactide residues, C) residues of at least one polyol, and D) residues of at least one fatty acid, wherein the residues A), B), C) and D) form ester linkages with adjacent residues and the alkyd resin has an oil content of at least 20% by weight.

The invention is in other aspects a lacquer comprising solution of the alkyd resin in an organic solvent and a coating composition comprising such a lacquer and at least one drier. The coating composition may be, for example, an enamel or "paint" composition that may include, in addition to the lacquer of the invention, various components such as pigments, aluminum silicates, fumed silica, colorants and other functional fillers and extenders to provide further utility in the targeted coating application.

The invention is also a crosslinked polymer formed by crosslinking the alkyd resin.

The invention is in yet another aspect a method for making an alkyd resin, comprising reacting in one or more steps A) at least one polybasic carboxylic acid and/or anhydride of a polybasic carboxylic acid, B) a mixture of 10 to 90% by weight meso-lactide and correspondingly 90 to 10% by weight L- and/or D-lactide; and C) either or both of C- l) at least one polyol and at least one fatty acid and C-2) a mono-, di- or triglyceride of at least one fatty acid to produce the alkyd resin, the alkyd resin containing 5 to 50 weight percent, based on the weight of the alkyd resin, of polymerized lactide residues and having an oil content of at least 20% by weight.

The alkyd resin of the invention, when formed into a coating and cured, forms coatings that have unexpectedly good impact resistance. Compared to an otherwise like alkyd resin coating made using only L-lactide (rather than a mixture of meso- and L- and/or D-lactide as in this invention), very significant increases in impact strength are seen, as measured according to ISO 6272.

The alkyd resin in some embodiments contains residues of at least one p cid. Such residues have the structure I:

(I), wherein R is an organic linking group and x is independently in each occurrence of a polybasic acid residue at least 1 and y is independently in each occurrence of a polybasic acid residue zero or greater, provided that x + y > 2. Structure I corresponds to the structure of a polybasic acid having the structure R-(COOH) _x + _y after removal of a -OH from at least one of the carboxylic acid groups of the polybasic acid, x + y may be, for example, 2, 3, 4, 5 or 6 and is preferably 2 or 3. The polybasic carboxylic acid residues are produced from one or more polybasic carboxylic acids and/or their corresponding anhydrides that are included in the synthesis of the alkyd resin, as described below.

R may contain, for example, at least 2 carbon atoms, at least 3 carbon atoms or at least 6 carbon atoms, and may contain, for example, up to 20 carbon atoms, up to 16 carbon atoms, up to 12 carbon atoms or up to 8 carbon atoms. R may be aliphatic, aromatic, or araliphatic. If aliphatic, R may be linear, branched and/or cyclic. If araliphatic, the aliphatic portion may be linear, branched and/or cyclic. R may contain one or more heteroatoms or may be hydrocarbyl. R in some embodiments has a weight of up to 200 g/mol, up to 125 g/mol, up to 100 g/mol or up to 80 g/mol.

In some embodiments, the polybasic carboxylic acid residues correspond to residues, after removal of an -OH from at least one carboxyl group, of one or more of phthalic acid, isophthalic acid, terephthalic acid, succinic acid, maleic acid, fumaric acid, butane- 1,4-dicarboxylic acid, adipic acid, sebacic acid, cyclohexane- 1,2- dicarboxylic acid, cyclohexane-l,3-dicarboxylic acid, cyclohexane- 1,4-dicarboxylic acid, citric acid, isocitric acid, benzene- 1,3, 5-tricarboxylic acid, propane- 1,2, 3-tricarboxylic acid or mellitic acid.

Meso-lactide is a cyclic diester corresponding to the condensation product of a molecule of L-lactic acid (S-lactic acid) with a molecule of D-lactic acid (R-lactic acid) with the loss of two molecules of water. It has the chemical structure: . In the formation of the alkyd resin of the invention, it ring-opens to form meso-lactide residues. The meso-lactide residues consist of two adjacent lactic (-0-C(CH3)-C(0)-) residues, one of which is an L-lactic residue and one of which i meso-lactic residues therefore take either of the forms:

or, depending upon at which ester group the meso-lactide ring opens as it reacts.

L-lactide (S,S-lactide) is the cyclic diester corresponding to the condensation of two molecules of L-lactic acid (S-lactic acid). It has the structure:

and reacts in the formation of the alkyd resin to form L-lactide residues that consist of two L-lactic residues. The L-lactide residues take the form:

Similarly, D-lactide (R,R-lactide) corresponds to the condensation of two molecules of D-lactic acid (R- lactic acid) and has the structure:

It reacts to form D-lactide residues that have the structure:

In some embodiments, the alkyd resin contains polyol residues. The polyol residues have the structure II: ( _HO -)-R ^l -(-0-)

y

(Π)

wherein R ¹ is an organic linking group, x' is independently in each occurrence of a polyol residue at least 1, y' is independently in each occurrence of a polyol residue zero or a positive number, and x' + y' > 2 and preferably > 3. x' + y' may be, for example, 2, 3, 4, 5 or 6.

The polyol residues correspond to the structure of a polyol having the structure R'-(OH)x+ _y ' after removal of one or more hydroxyl hydrogen atoms from the polyol. R' may contain, for example, at least 2 carbon atoms, at least 3 carbon atoms or at least 4 carbon atoms, and may contain, for example, up to 20 carbon atoms, up to 16 carbon atoms, up to 12 carbon atoms, up to 8 carbon atoms or up to 5 carbon atoms. R' may be aliphatic, aromatic, or araliphatic, but is preferably aliphatic. If aliphatic, R may be linear, branched and/or cyclic. If araliphatic, the aliphatic portion may be linear, branched and/or cyclic. R may contain one or more heteroatoms or may be hydrocarbyl. R in some embodiments has a weight of up to 150 g/mol, up to 100 g/mol or up to 75 g/mol.

In some embodiments, the polyol residues correspond to residues, after removal of at least one hydroxyl hydrogen, of one or more of ethylene glycol, 1,2- propanediol, 1,3-propanediol, 1,4-butane diol, 1,2-butane diol, 1,3-butane diol, 1,5- pentane diol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol, 1, 10-decanediol, 1,2- dodecanediol. Preferred polyol compounds have more than 2 active hydroxyl groups. Among these are glycerin, trimethylolpropane, trimethylolethane, erythritol, pentaerythritol, mannitol, sucrose and sorbitol.

The fatty acid residues have the structure: , wherein R ³ is independently in each occurrence a straight- chain or branched acyclic hydrocarbyl group having at least 7 carbon atoms. R ³ may have, for example, at least 9 or at least

11 carbon atoms and may have, for example, up to 23, up to 21, up to 19 or up to 17 carbon atoms. R ³ may independently in each occurrence be saturated or unsaturated. When unsaturated, each R ³ independently may contain, for example, 1, 2 or 3 carbon- carbon double bonds. If more than one carbon-carbon double bond is present, they may be conjugated or non- conjugated. It is preferred that at least a portion of the fatty acid residues are unsaturated, and more preferred that at least a portion of the fatty acid residues contain 2 or more non- conjugated double bonds.

A portion of the fatty acid residues may be saturated and another portion may be unsaturated. The fatty acid residues may be residues of fatty acid mixtures obtained from a plant oil or animal fat. Such fatty acid mixtures may contain, for example, a quantity of unsaturated fatty acids, a quantity of monounsaturated fatty acids and a quantity of polyunsaturated fatty acids. The fatty acid residues may be residues of the constituent fatty acids from a plant oil or animal fat characterized in having a "drying index" of at least 50 or at least 70, wherein "drying index" is equal to the weight percentage of linolenic acid plus twice the weight percentage of linoleic acid in the constituent fatty acids.

The fatty acid residues may be, for example, residues of linseed oil fatty acids, tung oil fatty acids, sunflower oil fatty acids, safflower oil fatty acids, walnut oil fatty acids, soybean oil fatty acids, canola oil fatty acids, corn oil fatty acids, dehydrated castor oil fatty acids or tall oil fatty acids, or a mixture of any two or more thereof.

The alkyd resin may also contain residues of other monoiunctional carboxylic acids, which are produced from monocarboxylic acids (other than fatty acids) that are optionally present in one or more of the reaction steps that produce the alkyd resin. The presence of monoiunctional acids during the synthesis of the alkyd resin permits higher molecular weight alkyds to be produces without gelation. Representative of these monofunctional organic carboxylic acids are aliphatic carboxylic acids having up to 7 carbon atoms (such as acetic acid, butanoic acid or hexanoic acid) or aromatic monocarboxylic acids such as benzoic acid. An advantage of this invention, however, is that the inclusion of lactide in the synthesis of the alkyd resin also allows for high molecular weight alkyds (such as at least 1500 molecular weight) to be manufactured with minimal gelation. Accordingly, monofunctional acids can be omitted from the synthesis of the alkyd resin of the invention if desired.

The polybasic carboxylic acid residues may constitute, for example, at least 5%, at least 8%, at least 10% or at least 12% of the total weight of the alkyd resin and may constitute, for example up to 40%, up to 35%, up to 30%, up to 25% or up to 20% thereof.

The alkyd resin of the invention contains at least 5 weight percent of lactide residues. It may contain at least 10, at least 12, at least 15 or at least 20 weight percent lactide residues. It may contain up to 50 weight percent, up to 40 weight percent, up to 35 weight percent, up to 30 weight percent, up to 25 weight percent or up to 20 weight percent lactide residues. In each case, the weight of the lactide residues is based on the total weight of the alkyd resin.

10 to 90% of the lactide residues are meso-lactide residues. For example, at least 15%, at least 20% or at least 25% of the lactide residues may be meso-lactide residues. For example, up to 70%, up to 65%, up to 60%, up to 55% or up to 50% of the lactide residues may be meso-lactide residues. The remaining lactide residues may be L-lactide residues, D-lactide residues or a mixture of L-lactide residues and D-lactide residues. At least 95% of remaining lactide residues preferably are L- lactide residues, on the basis of lower cost due to plentiful and inexpensive commercial sources of L-lactide.

The polyol residues may constitute, for example, at least 5%, at least 10%, or at least 12% of the total weight of the alkyd resin and may constitute, for example, up to 25%, up to 20% or up to 18% thereof.

The amount of fatty acid residues is typically expressed as "oil content" . When the precursor to the fatty acid residues is a plant oil or animal fat, the "oil content" is calculated as:

weight o f the oil

Oil Content = 100% x weight of all ingredients -weight of water evolved .

When the precursor to the fatty acid residues is a fatty acid or fatty acid mixture, the oil content is calculated as

1.04 x weiqht of the fatty acids

Oil Content = 100% x

weight of all ingredients— weight of water evolved

In some embodiments, the oil content is at least 20% but less than 40%. Such an alkyd resin is generally described in the art as a "short oil" resin. In other embodiments, the oil content is 40 to 60%. Such an alkyd resin is generally described in the art as a "medium oil" resin. In still other embodiments the alkyd resin is a "long oil" resin having an oil content greater than 60%, such as 61 to 75%.

The amount of each of the monol residues and other monocarboxylic acids, if present at all, preferably is no greater than 10 weight percent or no greater than 5 weight percent, based on the weight of the alkyd resin.

The alkyd resin preferably is non-crosslinked and therefore is soluble in at least one of hexane and mineral spirits, and typically is soluble in a wide range of organic solvents as indicated below. The alkyd resin is considered to be soluble in a particular solvent if soluble therein to the extent of at least one part by weight per part by weight solvent, at 23°C.

The alkyd resin may have a number average molecular weight (by gel permeation chromatography against a polystyrene standard) of at least 1000, at least 1500, at least 2000 or at least 2400 g/mol. The number average molecular weight may be, for example, up to 25,000, up to 20,000, up to 15,000, up to 10,000, up to 7, 500 or up to 5,000 g/mol. The polydispersity may be at least 2, at least 3 or at 4 and may be, for example, up to 12, up to 10, up to 8 or up to 6.

The alkyd resin may have an acid value as small as zero. If non-zero, the acid value may be, for example, at least 2, at least 4 or at least 6 mg KOH/g and may be, for example, up to 30, up to 20, up to 15, up to 12 or up to 10 mg KOH/g. The alkyd resin may have a hydroxyl value of, for example, at least 10, at least 25, at least 50 or at least 75 mg KOH/g and may have a hydroxyl value of, for example, up to 250, up to 200, up to 150, up to 125 or up to 100. Acid and hydroxyl values can be measured according to ISO 2114 and DIN 53240, respectively.

The alkyd resin may have a viscosity of 500 to 10,000, preferably 1000 to 4000 and especially 1500 to 3000 mPa-s at 95°C, as measured on a Brookfield Model 2000+ cone-and-plate rheometer using a #5 cone spindle at 300 rpm.

The alkyd resin of the invention can be produced by reacting, in one or more steps, ingredients that include A) at least one polybasic carboxylic acid or anhydride of a polybasic carboxylic acid, B) a mixture of 10 to 90% by weight meso-lactide and correspondingly 90 to 10% by weight L- and/or D-lactide; and C) either or both of C- l) at least one polyol and at least one fatty acid and C-2) a mono-, di- or triglyceride of at least one fatty acid.

Useful polybasic carboxylic acids are as described above. Useful anhydrides are anhydrides of polybasic carboxylic acids as described above.

Ingredient C) can include a polyol, which upon reaction gives rise to polyol residues as described above, plus at least one fatty acid that gives rise to fatty acid residues as describe above. Alternatively or in addition, ingredient C may include C- 2) a mono-, di- or triglyceride of at least one fatty acid. In case C-2, the glycerin portion of the fatty acid glyceride functions as a precursor for at least part of the polyol residues, and the fatty acid portion of the fatty acid glyceride functions as a precursor for at least part of the fatty acid residues. It is preferred to provide an excess of hydroxyl groups over carboxyl and/or anhydride groups.

The reactions are conveniently performed at elevated temperature, such as 60 to 250C. A preferred temperature is at least 100°C and a more preferred temperature is at least 180° C. Pressures are sufficient to maintain the starting materials as liquids at the reaction temperature while allowing water to volatilize. The reactions can be performed in any suitable solvent for the starting materials, if desired. Examples of useful solvents include those described below in connection with the preparation of lacquers.

It is generally preferable to perform the reactions in the presence of an esterification catalyst, i.e., a catalyst that promotes the reaction of an alcohol with a carboxylic acid and/or carboxylic acid anhydride group. Examples of esterification catalysts are very well known and include, for example, strong acids such as sulfuric acid, sulfonic acids and hydrochloric acid; alkali metal hydroxides; aluminum alkoxides, zinc carboxylates such as zinc acetate; other metal carboxylates, and the like.

The reaction is a condensation reaction that produces water as a by-product. Because the reaction is an equilibrium reaction, completion is favored by removing water as it forms. Water is conveniently removed by applying a vacuum and/or by establishing a flow of a gas through the headspace of the reactor to sweep out volatized water from the headspace. Water may be removed as an azeotrope in cases in which the reaction solvent forms an azeotrope with water. Xylene can be used as a solvent for this purpose, in which case water is removed as a xylene-water azeotrope.

If the fatty acid residues are produced from one or more fatty acids or a mono- or diglyceride thereof (rather than a triglyceride), the alkyd resin-forming reaction can be performed in one step by combining all ingredients, bringing them to the appropriate reaction temperature and continuing the reaction until the desired product is formed. The reaction can be followed by measuring the acid number of the product, the reaction being continued until the acid number falls to a predetermined value. Alternatively, the reaction can be continued until a predetermined amount of water has evolved, or until the product has attained a desired molecular weight.

An alternative process is performed in multiple steps, using a triglyceride as the fatty acid source. The triglyceride is reacted in a first step with glycerin to form a mixture of mono- and di- triglycerides, which mixture is then reacted in a subsequent step with the lactides and polybasic acid (or anhydride) to form the alkyd resin.

In another alternative process, again using a triglyceride as the fatty acid source, the triglyceride is reacted with the polybasic acid (or anhydride) in a first step to replace at least one of the fatty acids with the polybasic acid. This intermediate is subsequently reacted with the lactides and polyol to form the alkyd resin.

Lacquers according to the invention include a solution of the alkyd resin of the invention in an organic solvent. Examples of suitable organic solvents include aliphatic hydrocarbons having for example, 4 to 16 carbon atoms, including the various acyclic or cyclic isomers of a Ce-Cw alkane such as hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane and the like. Other suitable solvents include aromatic hydrocarbons such as xylene, benzene and toluene, as well as various alkylcarboxylate (ester) solvents such as ethyl acetate, butyl acetate, hexyl acetate, butyl propionate, hexyl propionate, and the like. Various commercially available solvent mixtures such as turpentine, naphtha, Stoddard's solvent, white spirit type 0, white spirit type 1, white spirit type 2, white spirit type 3, Coleman fuel, the various solvents sold by Exxon under the Varsol® brand including Varsol® 40 and Varsol® 60, and the like are also useful solvents. A mixture of any two or more of the foregoing can be used.

The lacquer of the invention may contain 1 to 95% of the alkyd resin, based on the combined weight of the alkyd resin and the solvent(s). An advantage of this invention is that the viscosity of the alkyd resin and therefore the lacquer (at a given solids level) tends to be low; this allows higher concentrations of the alkyd resin to be present in the coating composition at a given viscosity, which has the further advantage of reducing the quantity of volatile organic compounds (VOCs). Thus, for example, the solids (alkyd resin) content in some embodiments is at least 40%, at least 50%, at least 60% or at least 70% and, for example, up to 90% or up to 85%, the percentages representing the weight of the alkyd resin based on the combined weight of solvent and alkyd resin.

A coating composition of the invention includes a lacquer as just described, in which the alkyd resin is a drying type, i.e., at least some of the fatty acid residues contain carbon-carbon double bonds capable of reacting with atmospheric oxygen to form crosslinks. Such a coating composition further includes at least one drier. A "drier" is a catalyst for one or more of the sequence of reactions that leads to the formation of such crosslinks. Driers are typically metal salts that are soluble in the lacquer. They include, for example, metal carboxylate salts, particularly in which the carboxylate contains 6 to 20 carbon atoms, such as, for example, 2-ethylhexanoate, neo-decanoate, naphthenate and the like. The metal may be one or more of, for example, magnesium, cobalt, iron, calcium, zirconium, barium, strontium, and cerium. Combinations of two or more driers can be present. Suitable driers are described, for example, by Uninski, M., Paints and Coatings Magazine, Sept. 1, 2011.

In addition, the coating composition may contain one or more anti-skinning agents, which function to inhibit the premature occurrence of the crosslinking reaction as may occur, for example, in the packaged coating composition during storage and/or transportation. Examples of anti-skinning agents include various oxime compounds such as methylethylketoxime and various phenolic and/or amine compounds.

The coating composition may contain one or more pigments. The pigment(s) may be naturally occurring and/or synthetic types. Examples include various titanium, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury and zinc pigments; carbon pigments such as carbon black and ivory black; clay earth pigments such as yellow ochre, raw sienna, burnt sienna, raw umber and burnt umber; ultramarine pigments, alizarin, alizarin crimson, gamboge, cochineal red, rose madder, indigo, Indian yellow, Tyrian purple, quinacridone, magenta, phthalo green, phthalo blue, pigment red 170 and diarylide yellow.

The coating composition may in addition contain other additives as may be beneficial, including for example rheology modifiers such as thickeners and thixotropic agents, water scavengers; pigment dispersants, crosslinkers and other polymers.

The following examples are provided to illustrate the invention, but not to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated. Examples 1-3 and Comparative Samples A-C

Alkyd resin Examples 1-3 and Comparative Samples A-C are made from the ingredients listed in Table 1. In each case, the resins are made in a one-step process in which all ingredients are combined at once and reacted in 3 to 5% xylene (based on total weight). The reactants are heated to 220 to 235°C with removal of a xylene/water azeotrope until the measured acid value is reduced to approximately 8 mg KOH/g.

Table 1

*Not an example of this invention. Calculated as (100% x 1.04 x fatty acid weight) ÷ 100. ² Based on total weight of lactides charged to the reaction, ³ Brookfield cone-and- plate viscosity at 95°C, 300 rpm, cone spindle #5. ⁴ Molecular weights are by GPC relative to polystyrene standards. Each of Examples 1-3 and Comparative Samples A-C are mixed with varying amounts of a 4: 1 by volume mixture of Varsol® 40 white spirits and xylene to produce a viscosity vs. alkyd resin concentration curve. In each case, the solids content of a lacquer having a target Brookfield Model 2000+ cone-and-plate viscosity (23°C, 100 rpm, Spindle #4) of 3000 to 4000 mPa-s at 23°C is reported in Table 2, as is the estimated viscosity of a 60% solids solution (as estimated from the viscosity/solids concentration curves). Table 2

weight of resin plus Varsol™ 40/xylene 4: 1 by weight. ² Brookfield 2000+ cone-and- plate at 23°C, 300 rpm, cone spindle #4, estimated from viscosity curve data.

Coating compositions are prepared from each of the lacquers described in Table 2 by adding 4.1 parts, per 100 parts of alkyd resin, of a cobalt/calcium/zirconium drier composition (Nuodex Combi HS, from Huntsmann). The resulting coating compositions are separately applied to glass and steel panels for evaluation of Persoz Pendulum Hardness (ISO 1522), adhesion (cross-cut test, ISO 2409), mechanical bending resistance (ISO 1519), cupping resistance (ISO 1520) and both front and reverse impact resistance (ISO 6272). Results are as indicated in Table 3.

Table 3

*Not an example of this invention.

Example 4 and Comparative Sample D and E

Alkyd resin Example 4 and Comparative Samples D and E are made from the ingredients listed in Table 4, following the same general procedure described before. The result alkyd resins are made into lacquers and coating compositions in the general manner described in the foregoing examples. In each case, the solids content of a lacquer having a target Brookfield cone-and-plate viscosity (23°C, #4 cone spindle, 100 rpm) of 3000 to 4000 mPa-s at 23°C is reported in Table 5, as is the estimated viscosity of a 60% solids solution (as estimated from the viscosity/solids concentration curves). Coatings are evaluated as in the previous examples with results are as indicated in Table 6.

Table 4

÷ resin weight. ² Based on total weight of lactides charged to the reaction. ³ Brookfield cone-and-plate viscosity at 95°C, 35 cone spindle, 300 rpm. ⁴ Molecular weights are by GPC relative to polystyrene standards.

Table 5

weight of resin plus Varsol™ 40/xylene 4: 1 by weight. ² Brookfield cone-and-plate at 23°C, #4 cone spindle, 300 rpm, estimated from viscosity curve data. Table 6

*Not an example of the invention.

Coating Evaluations

Coating Examples 2 and 4 and Comparative Samples A, B and C are subjected to Taber abrasion testing according to ASTM D4060, using a Teledyne Taber Model 5130 apparatus with a CS-10 wheel. The applied load on the wheels is 1000 g and the force on the abrasive disk is 9.81 N. The number of wear cycles is 1000. Panels are tested in duplicate with the results averaged. Turntable speed is 60 rpm.

In each case, the coatings are applied to R-T-44 (Q-Lab Corporation) steel panels having dimensions of 102 x 102 x 0.8 mm, with a central hole of diameter 6.35 mm. The coatings are cured and conditioned at 3°C and 50% relative humidity for 15 days. Dried film thickness is approximately 90 μπι.

Prior to testing, the surface of each sample is pre-abraded with 20 wear cycles in order to align the sample. After each weighing, the sample surface is activated by 20 cycles of sandpaper S-l l (Teledyne Taber Inc., USA).

Results are as indicated in Table 7.

Table 7

*Not an example of this invention. Examples 2 and 4 each exhibit markedly better abrasion resistance than the control (Comp. A). The results for Example 4 are especially remarkable, as they demonstrate a very significant improvement over the other coatings.

Three layers each of a coating Examples A-C, 2 and 4 are applied to separate oak wooden panels having dimensions 200 mm x 130 mm x 18 mm. Adhesion is measured according to ISO 4624. Results are as indicated in Table 8.

Table 8

*Not an example of the invention. ¹ A=substrate cohesive failure; A/B = adhesion failure between substrate and first coat.

The examples of the invention exhibit markedly better adhesive strength than the control (Comp. Ex. A). Example 4, in turn, exhibits markedly better adhesion than do any of the other samples. Alkyd Enamel Preparation and Testing

Alkyd enamels are made from each of Comparative Lacquer Sample A and lacquer Example 4. In each case, the ingredients are the lacquer, titanium dioxide particles at a pigment volume concentration of 20%, a dispersing and wetting additive, an anti-skinning additive and the Nuodex Combi HS drier described before.

This cone-and-plate viscosity of the enamels are measured at 23°C. The enamel made from Comparative lacquer A has a viscosity of 5150 mPa-s at a nonvolatile content of 71.2%. The enamel made from lacquer Example 3 has a slightly higher non-volatile content (72.4%) yet has a viscosity of only 4060 mPa-s, or about 20% lower than that of the control.

The enamel prepared from lacquer Example 4 is applied to glass and steel panels for evaluation of Persoz Pendulum Hardness (ISO 1522), adhesion (cross-cut test, ISO 2409), mechanical bending resistance (ISO 1519), cupping resistance (ISO 1520) and both front and reverse impact resistance (ISO 6272). Results are as indicated in Table 9. Table 9