WO1994002553A1 - Thermosetting powder coating compositions - Google Patents

Abstract

Provided are certain oligomeric liquid-crystalline diols which are useful as plasticizers in thermosetting powder coating compositions. The plasticizers of the present invention are copolymerizable, and upon curing of the composition, enhance the flow of the powder thereby providing a markedly improved coating appearance. Preferred plasticizers include those comprised of residues of terephthalic acid, p-hydroxy benzoic acid, and 'end-capped' with simple straight chain alkyl diols.

Description

THERMOSETTING POWDER COATING COMPOSITIONS

This invention belongs to the field of organic chemistry. More particularly, this invention relates to thermosetting powder coating compositions which contain certain plasticizer materials which have improved flow properties, thus improving the resulting coating's appearance.

Plastic materials used in the manufacture of powder coatings are classified broadly as either thermosetting or thermoplastic. In the application of thermoplastic powder coatings, heat is applied to the coating on the substrate to melt the particles of the powder coating and thereby permit the particles to flow together and form a smooth coating.

Thermosetting coatings, when compared to coatings derived from thermoplastic compositions, generally are tougher, more resistant to solvents and detergents, have better adhesion to metal substrates and do not soften when exposed to elevated temperatures. However, the curing of thermosetting coatings has created problems in obtaining coatings which have, in addition to the above- stated desirable characteristics, good smoothness and flexibility. Coatings prepared from thermosetting powder compositions, upon the application of heat, may cure or set prior to forming a smooth coating, resulting in a relatively rough finish referred to as an "orange peel" surface. Such a coating surface or finish lacks the gloss and luster of coatings typically obtained from thermoplastic compositions. The "orange peel" surface problem has caused thermosetting coatings to be applied from organic solvent systems which are inherently undesirable because of the environmental and safety problems that may be occasioned by the evaporation of the solvent system. Solvent-based coating compositions also suffer from the disadvantage of relatively poor percent utilization, i.e., in some modes of application, only 60 percent or less of the solvent-based coating composition being applied contacts the article or substrate being coated. Thus, a substantial portion of solvent-based coatings can be wasted since that portion which does not contact the article or substrate being coated obviously cannot be reclaimed.

In addition to exhibiting good gloss, impact strength and resistance to solvents and chemicals, coatings derived from thermosetting coating compositions must possess good to excellent flexibility. For

example, good flexibility is essential for powder coating compositions used to coat sheet (coil) steel which is destined to be formed or shaped into articles used in the manufacture of various household appliances and automobiles wherein the sheet metal is flexed or bent at various angles.

The concept of plasticizers in the plastics industry is well-known. Plasticizers are generally used to improve the melt flow during the extrusion and to modify the properties of the resulting plastic. In powder coating applications, plasticizers have been found to improve melt flow and thus improve appearance of the coating but they also lower the powder stability which is essential for a powder coating composition.

Plasticizers are also known to migrate (i.e., "bloom") to the surface of the coating thereby causing a milky temporary thin film. Thus, the blooming phenomenon limits the usefulness of known plasticizers in powder coating compositions.

Roviello and Sierger, J. Poly. Sci., Polym. Lett. Ed.. 13, 455 (1975), teach polymeric substances which exhibit melt anisotropic phases with optical properties appearing very similar to conventional, monomeric thermotropic liquid crystals. Others have synthesized a variety of polymers from novel monomers capable of forming liquid crystalline structures. In turn, these polymers have been evaluated to characterize the unique chemical and mechanical properties of polymer fibers, films, and molded articles fabricated from them. These unique properties have been attributed to the rigid rod-like structure of the monomers which imparts a collinear geometry to the mesogenic polymer repeating groups.

Increased thermal stability, higher stiffness (modulus), and improved chemical resistance are obtained from the close packing of these polymer units in this stable mesophase, or liquid crystalline form.

Unless these rigid-rod polymers are modified structurally, they are generally insoluble, infusible (not melt processable) and otherwise intractable. For example, poly(p-phenylene terephthalate) and poly(p-phenylene trans-1,4-cyclohexanedicarboxylate) are mesomorphic rigid polyesters with melting

temperatures above 500°C. (See Agculeia and Ludewald, Makromol. Chem.. 179. 2817 (1978) and Kircheldorf and Schwarg, Makromol. Chem., 188. 1281 (1987)). Alteration of the polymer structure by copolymerization with a non-linear or "kink-inducing" monomer such as isophthalic acid and/or a "flexible spacer" like 1,10-decanediol has been found to depress the melting point. (See Gladge, J. Appl. Polv. Sci.. 37, 1579). Further, Delvin and Ober, Polymer Bull., 20. 45 (1988) report that the solubility of the stiff polymer so modified can be significantly improved.

Many of these liquid crystalline polymers (LCP's) have found commercial application as fibers, films, and plastics. The improvements which this class of polymers provide include high strength and modulus down to

-195°C; excellent oxygen and water barrier properties; non-dripping; no nitrous oxides or cyanides upon

burning; dimensional stability up to 200-300°C;

coefficient of thermal expansion equal to glass;

transparent to microwave radiation; no effect of humidity after 200 h at 120°C; very low moisture

absorption; dielectric properties as good as high performance plastics; excellent stain resistance; low or no odor; and higher filler loading ability.

It has also been demonstrated in theory (see

Warner, Gelling, and Vilgis, J. Chem. Phys., 88, 4008 (1988)) and in practice (see Barclay, et al.

Proceedings of the ACS Division of Polymeric Materials: Science and Engineering, 63, 356, (1990)) that thermo-tropic LCP mesophases can be "locked" into polymeric network by cross-linking reaction. Their work supports the idea of applying LCP in coatings technology. Low molecular weight, soluble, and cross-linkable LCPs may be prepared and formulated into enamels. The cured (or cross-linked) films of enamels would have LC

characteristics, and therefore improve the coating properties. Only recen tly, this concept has been explored.

A linear oligoester diol modified with p- ydroxybenzoic acid (PHBA) was reported by Jones,

EP-A-287233, for use in surface coatings. The oligomers having number average molecular weight of 830-1400 and weight average molecular weight of 1400-2400 were synthesized by reacting an excess of neopentyl glycol with phthalic anhydride and adipic acid in the presence of the solvent, "Aromatic 150", and a catalyst,

p-toluenesulfonic acid, to yield an oligoester diol, which was subsequently reacted with PHBA to form

mesogens, i.e., repeating p-oxybenzoyl groups, in the oligomer chain ends. The resulting oligomer was then dissolved in dichloromethane and purified by repeated extraction with water before used as a binder in surface coatings. Jones also describes a method for grafting oligomeric mesogens, i.e., repeating p-oxybenzoyl groups, into polymer chain ends of carboxyl functional alkyd polyesters or acrylics. These reactions generally involved the use of a dehydrating agent, dicyclohexyl-carbodiimide, in the solvent, pyridine, and repeated purification steps which are all not favored for large-scale industrial production. (See also Jones et al, "Liquid Crystalline Polymers as Binders for Coatings", Fifteenth International Conference in Organic Coatings Science and Technology. Athens, July 10-14, 1989; and Wang, D. and Jones, F. N., "Synthesis of Cross-Linkable Heterogeneous Oligoester Diols by Direct Esterification with p-Hydroxybenzoic Acid", Ch. 23 of Cross-Linked Polymers. pp. 335-248.)

JP 02,245,068 discloses liquid-crystalline

polyester compositions for powder coating. Eur. Pat. Appl. EP 312,331 discloses liquid crystalline thermosetting polyesters containing polyphenyldicarboxylic acids for use in powder coatings. See also, "Model Crosslinkable Liquid Crystal Oligoester Diols as

Coatings Binders", Dimian, A.F.; Jones, F.N., Polym. Mater. Sci. Eng., 56, 640-4 (1987).

The present invention provides certain cross-linkable liquid crystalline diols which are useful as plasticizers in thermosetting powder coating compositions. The compositions which contain these plasticizer materials generally flow better upon fusion and thus the physical appearance of the coating is markedly improved. Because the plasticizer is crosslinked into the

polymeric matrix of the coating, a significant amount, i.e., greater than or equal to 20 percent of total binder can be used; also, the problem associated with classical plasticizers "blooming" to the surface of the coating is overcome.

The present invention provides a liquid-crystalline oligomeric plasticizer of the formula

wherein R is a divalent C₂-C₁₀ alkyl group;

M is a divalent group selected from the list consisting of ;

,

wherein A is halogen, C ₁-C₆ alkyl, or phenyl; ;

; and

; and

wherein R¹ is hydrogen, halo, hydroxy, cyano, nitro, or C₁-C₆ alkyl. The amount of the plasticizer used in the

formulation is dependent on characteristics of each polyester component, crosslinker, pigment loading, and end use of the desired coating. The plasticizer may be present in an amount of as high as 40 weight percent. Preferably, the plasticizer will be present in a

concentration of about 1 to about 20 weight percent. The resulting powder coating compositions of the present invention plasticizes, because once melted during curing, has a melt viscosity approximately 1/20 of that of typical polyesters used in powder coatings. The plasticizer then crosslinks into the matrix after it serves its role as a plasticizer.

In a preferred embodiment of the present invention, the liquid crystalline oligomeric plasticizer of the present invention is comprised of residues of 4-hydroxy benzoic acid and residues of terephthalic acid. An especially preferred oligomer has the formula

wherein M is a residue of p-hydroxy benzoic acid, and R¹ is hydrogen.

As a further embodiment of the present invention, there is provided a thermosetting powder coating

composition, which comprises (a) a liquid-crystalline oligomeric plasticizer of the formula

wherein R is a divalent C₂-C₁₀ alkyl group;

M is divalent group selected from the list

consisting of ;

,

wherein A is halogen, C₁-C₆ alkyl, or phenyl; ;

; and

; and

wherein R¹ is hydrogen, halo, hydroxy, cyano, nitro, or C₁-C₆ alkyl; (b) a hydroxyl-functional amorphous polyester; and

(c) an effective amount of a crosslinking agent. In the above plasticizers (component (a)),

preferred C₂-C₁₀ divalent alkyl groups correspond to the alkyl portions of diols selected from the list

consisting of ethylene glycol, propylene glycol, 1,3-propanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobuty1-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, thiodiethanol, 1,2-, 1,3- and 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 1,4-xylylenediol and the like.

Especially preferred C₂-C₁₀ divalent alkyl groups include ethylene, 1,3-propylene, 1,4-butylene, 1,5-pentylene,and 1,6-hexylene.

The most highly preferred mesogen-inducing hydroxyacid is p-hydroxy benzoic acid.

The hydroxyl-functional amorphous polyester useful in the compositions of the present invention may be produced using well known polycondensation procedures. As used herein, the term "amorphous" refers to a polyester which exhibits no, or only a trace of,

crystallization or melting point as determined by differential scanning calorimetry (DSC).

The preferred amorphous polyester component of the composition provided by this invention has a glass transition temperature (Tg) greater than 55°C, a

hydroxyl number in the range of about 25 to 80, an acid number of not more than 15 and an inherent viscosity of about 0.15 to 0.4.

The amorphous polyester may be produced using well-known polycondensation procedures employing an excess of glycol to obtain a polymer having the specified hydroxyl number. The glycol residues of the amorphous polyester may be derived from a wide variety and number of

aliphatic, alicyclic and alicyclic-aromatic glycols or diols containing from 2 to about 10 carbon atoms.

Examples of such glycols include ethylene glycol, propylene glycol, 1,3-propanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, thiodiethanol, 1,2-, 1,3- and 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 1,4-xylylenediol and the like.

The dicarboxylic acid residues of the amorphous polyester component may be derived from various

aliphatic, alicyclic, aliphatic-alicyclic and aromatic dicarboxylic acids containing about 4 to 10 carbon atoms or ester-forming derivatives thereof such as dialkyl ester and/or anhydrides. Succinic, glutaric, adipic, azelaic, sebacic, fumaric, maleic, itaconic, 1,3- and 1,4-cyclohexanedicarboxylic, phthalic, isophthalic and terephthalic are representative of the dicarboxylic acids from which the diacid residues of the amorphous polyester may be derived. A minor amount, e.g., up to 10 mole percent, of the glycol and/or diacid residues may be replaced with branching agents, e.g., tri-functional residues derived from trimethylolethane, trimethylolpropane and trimellitic anhydride.

The preferred amorphous polyester component of the composition provided by this invention has a Tg greater than 55°C, a hydroxyl number in the range of about 25 to 80, an acid number of not more than 15 and an inherent viscosity of about 0.15 to 0.4. The amorphous polyester component (1) (a) preferably is comprised of (1) diacid residues of which at least 50 mole percent are terephthalic acid residues, (2) glycol residues of which at least 50 mole percent are derived from 2,2-dimethyl-1,3-propanediol (neopentyl glycol) and (3) up to 10 mole percent, based on the total moles of (2) and (3), of trimethylolpropane residues. These preferred amorphous polyesters are commercially available, e.g., under the names AZS 50 Resin, RUCOTE 107 and CARGILL Resin 3000, and/or can be prepared according to the procedures described in U.S. Patent Nos. 3,296,211, 3,842,021, 4,124,570 and 4,264,751 incorporated herein by

reference, and Published Japanese Patent Applications (Kokai) 73-05,895 and 73-26,292. The most preferred amorphous polyester consists essentially of terephthalic acid residues, 2,2-dimethyl-1,3-propanediol residues and up to 10 mole percent, based on the total moles of 2,2-dimethyl-1,3-propanediol residues, of trimethylolpropane residues, and possesses a Tg of about 50° to 65°C, a hydroxyl number of about 35 to 60, an acid number of less than 10 and an inherent viscosity of about 0.1 to 0.25.

The most readily-available, and thus the preferred, blocked polyisocyanate cross-linking agents or compounds are those commonly referred to as ∈-caprolactam-blocked isophorone diisocyanate, e.g., those described in U.S. Patent NOS. 3,822,240, 4,150,211 and 4,212,962,

incorporated herein by reference. However, the products marketed as ∈-caprolactam-blocked isophorone diisocyanate may consist primarily of the blocked,

difunctional, monomeric isophorone diisocyanate, i.e., a mixture of the cis and trans isomers of 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate, the blocked, difunctional dimer thereof, the blocked, trifunctional trimer thereof or a mixture of the monomeric, dimeric and/or trimeric forms. For example, the blocked polyisocyanate compound used as the cross-linking agent may be a mixture consisting primarily of the ∈-caprolactam-blocked, difunctional, monomeric isophorone diisocyanate and the ∈-caprolactam-blocked, trifunctional trimer of isophorone diisocyanate. The reaction of the isocyanato groups with the blocking compound is reversible at elevated temperatures, e.g., normally about 150°C, and above, at which temperature the isocyanato groups are available to react with the hydroxyl groups present on the free hydroxy groups of the polyester to form

urethane linkages.

Alternatively, the blocked isocyanate may be a cross-linking effective amount of an adduct of the 1,3-diazetidine-2,4-dione dimer of isophorone diisocyanate and a diol having the structure

wherein

R¹ is a divalent 1-methylene-1,3,3-trimethyl-5- cyclohexyl radical, i.e., a radical having the structure

R² is a divalent aliphatic, cycloaliphatic,

araliphatic or aromatic residue of a diol; and X is a 1,3-diazetidine-2,4-dionediyl radical, i.e., a radical having the structure

wherein the ratio of NCO to OH groups in the formation of the adduct is about 1:0.5 to 1:0.9, the mole ratio of diazetidinedione to diol is from 2:1 to 6:5, the content of free isocyanate groups in the adduct is not greater than 8 weight percent and the adduct has a molecular weight of about 500 to 4000 and a melting point of about 70 to 130°C.

The adducts of the 1,3-diazetidine-2,4-dione dimer of isophorone diisocyanate and a diol are prepared according to the procedures described in U.S. Patent 4,413,079, incorporated herein by reference, by reacting the diazetidine dimer of isophorone diisocyanate, preferably free of isocyanurate trimers of isophorone

diisocyanate, with diols in a ratio of reactants which gives as isocyanto:hydroxyl ratio of about 1:0.5 to 1:0.9, preferably 1:0.6 to 1:0.8. The adduct preferably has a molecular weight of 1450 to 2800 and a melting point of about 85 to 120°C. The preferred diol reactant is 1,4-butanediol. Such an adduct is commercially available under the name Hüls BF1540.

Alternatively, the crosslinking agent may be a glycouril type. In general, such crosslinking agents possess a plurality of -N-CH₂OR groups with R = C₁-C₈ alkyl, such as one sold by American Cyanamid as

POWDERLINK 1174:

The amount of the cross-linking compound present in the compositions of this invention can be varied

depending on several factors such as those mentioned hereinabove relative to the amount of components (a) and (b) which are utilized. Typically, the amount of cross-linking compound which will effectively cross-link the polymers to produce coatings having a good combination of properties is in the range of about 5 to 30 weight percent, preferably 15 to 25 weight percent, based on the total weight of components (a) and (b).

The powder coating compositions of this invention may be prepared from the compositions described herein by dry-mixing and then melt-blending components (a) and (b), and (c), and preferably along with a cross-linking catalyst, e.g., dibutyltindilaurate along with other additives commonly used in powder coatings, and then grinding the solidified blend to a particle size, e.g., an average particle size in the range of about 10 to 300 microns, suitable for producing powder coatings. For example, the ingredients of the powder coating composition may be dry blended and then melt blended in a

Brabender extruder at 90° to 130°C, granulated and finally ground. The melt blending should be carried out at a temperature sufficiently low to prevent the unblocking of the polyisocyanate cross-linking compound and thus avoiding premature cross-linking.

Typical of the additives which may be present in the powder coating compositions include benzoin, flow aids or flow control agents which aid the formation of a smooth, glossy surface, stabilizers, pigments and dyes.

In the above powder coating compositions the plasticizer (a) acts as a flow aid, but it may be desirable to utilize in addition, a conventional flow aid, also referred to as flow control or leveling agents, to enhance the surface appearance of cured coatings of the powder coating compositions. Such flow aids typically comprise acrylic polymers and are available from several suppliers, e.g., MODAFLOW from

Monsanto Company and ACRONAL from BASF. Other flow control agents which may be used include MODAREZ MFP available from Synthron, EX 486 available from Troy Chemical, BYK 360P available from BYK Mallinkrodt and PERENOL F-30-P available from Henkel. An example of one specific flow aid is an acrylic polymer having a

molecular weight of about 17,000 and containing 60 mole percent 2-ethylhexyl methacrylate residues and about 40 mole percent ethyl acrylate residues. The amount of flow aid present may preferably be in the range of about 0.5 to 4.0 weight percent, based on the total weight of the resin component, and the cross-linking agent.

The powder coating compositions may be deposited on various metallic and non-metallic (e.g., thermoplastic or thermoset composite) substrates by known techniques for powder deposition such as by means of a powder gun, by electrostatic deposition or by deposition from a fluidized bed. In fluidized bed sintering, a preheated article is immersed into a suspension of the powder coating in air. The particle size of the powder coating composition normally is in the range of 60 to 300 microns. The powder is maintained in suspension by passing air through a porous bottom of the fluidized bed chamber. The articles to be coated are preheated to about 250° to 400°F (about 121° to 205°C) and then brought into contact with the fluidized bed of the powder coating composition. The contact time depends on the thickness of the coating that is to be produced and typically is from 1 to 12 seconds. The temperature of the substrate being coated causes the powder to flow and thus fuse together to form a smooth, uniform,

continuous, uncratered coating. The temperature of the preheated article also effects cross-linking of the coating composition and results in the formation of a tough coating having a good combination of properties. Coatings having a thickness between 200 and 500 microns may be produced by this method.

The compositions also may be applied using an electrostatic process wherein a powder coating composition having a particle size of less than 100 microns, preferably about 15 to 50 microns, is blown by means of compressed air into an applicator in which it is charged with a voltage of 30 to 100 kV by high-voltage direct current. The charged particles then are sprayed onto the grounded article to be coated to which the particles adhere due to the electrical charge thereof. The coated article is heated to melt and cure the powder particles. Coatings of 25 to 120 microns thickness may be obtained.

Another method of applying the powder coating compositions is the electrostatic fluidized bed process which is a combination of the two methods described above. For example, annular or partially annular electrodes are mounted in the air feed to a fluidized bed so as to produce an electrostatic charge such as 50 to 100 kV. The article to be coated, either heated, e.g., 250° to 400°F, or cold, is exposed briefly to the fluidized powder. The coated article then can be heated to effect cross-linking if the article was not preheated to a temperature sufficiently high to cure the coating upon contact of the coating particles with the article.

The powder coating compositions of this invention may be used to coat articles of various shapes and sizes constructed of heat-resistance materials such as glass, ceramic and various metal materials. The compositions are especially useful for producing coatings on articles constructed of metals and metal alloys, particularly steel articles. Thus, as a further aspect of the present invention there is provided a shaped or formed article coated with the cured thermosetting powder coating composition of the present invention as

illustrated herein.

Further examples of formulation methods, additives, and methods of powder coating application may be found in User's Guide to Powder Coating. 2nd Ed., Emery

Miller, editor, Society of Manufacturing Engineers, Dearborn, (1987).

Experimental Section

The inherent viscosity (I.V.), in dl/g are

determined in phenol/tetrachloroethane ( 60640 w/w ) at a concentration of 0.5 g/100 ml. The resin melt

viscosity, in poise, are determined using an ICI melt viscometer at 200°C. The acid number and hydroxyl number are determined by titration and reported as mg of KOH consumed for each gram of resin. The weight average molecular weight (Mw) and number average molecular weight (Mn) are determined by gel permeation

chromatography in tetrahydrofuran (THF) using

polystyrene standard and a UV detector. Impact

strengths are determined using a Gardner Laboratory, Inc., impact tester per ASTM D 2794-84.

Pencil hardness is determined using ASTM D 3363-74. The hardness is reported as the hardest pencil which will not cut into the coating. The results are expressed according to the following scale: (softest)

6B,5B,4B,3B,2B,B,HB,F,H,2H,3H,4H,5H,6H (hardest).

The conical mandrel is performed using a Gardener

Laboratory Inc., conical mandrel of specified size according to ASTM-522. The 20 and 60 degree gloss are measured using a gloss meter (Gardener Laboratory, Inc. Model GC-9095) according to ASTM D-523. The flexibility of coating is tested by bending panel back with panels inserted between the two halves and pressurized with hydraulic jack to 10,000 psi. The coating capable of bending without cracks or popping with the least numbers of panels (X) in between the bend is called to have passed XT bend.

Preparation of plasticizers A. Preparation of

In a three-neck round bottom flask equipped with a mechanic stirrer, a thermocouple and a solid addition funnel was added pentanediol (2 kg) and methyl

4-hydroxybenzoate (152.2 g). The mixture was kept at 10°C in an ice bath and was stirred for five minutes. Sodium methoxide (26 g) was added over 5 minutes with stirring and the mixture was heated to 160°C. Once the methyl 4-hydroxybenzoate was consumed, part of the excess pentanediol was distilled off. The cooled mixture was poured, with vigorous stirring, into water (5 L) containing cone. HCl (25 ml). A white precipitate fell out of the aqueous solution. The pH of the solution was adjusted to between 2.0 and 3.0. After stirring for 30 minutes, it was filtered and the solid was washed with water till the pH of the filtrate was neutral. The solid was determined by GC and ¹H NMR to be free of pentanediol. It was dried in a vacuum oven (using house vacuum) at 45°C overnight to afford the product 220 g (98 % yield).

B. Preparation of LQ5

To the above solid (220 g) in acetone 2 L was added over 20 minutes a solution of NaOH (39.8 g) in a mixture of water/acetone (200 ml/400 ml). The temperature was kept at around 10°C. After stirring for 5 minutes, a solution of terephthaloyl chloride (99.8 g) in acetone (1 L) was added over a period of 30 minutes. A white solid precipitate appeared immediately. The mixture was stirred for 4 hours. It was filtered and the solid was washed with water and then dried in a vacuum oven at 65°C overnight to afford the diol (220 g, 77 %). m.p. 150° +/- 10°C. Examples for LQ4 and LQ6

The title plasticizers were prepared by the same procedure as the above example except that butanediol or hexanediol was used instead of pentanediol. The

products had a melting point of 150° +/- 10°C.

Powder formulation and film properties:

RUCOTE 107 406 g 288.75 g 342.85 g 320 g

LQ-5 150 g 72.2 g 38.10 g

HULS-1530 244 g 139.05 g 119.05 g 80 g

Benzoin 8 g 5 g 5 g 4 g

MODAFLOW III 8 g 7.5 g 7.5 g 4 g

DBTDL¹ 8 g 5 g 5 g 4 g

R900(TiO₂) 320 g 200 g 200 g 160 g bake time/temp.

15/375 15/375 15/375 15/375 thickness 2.1 1.9 1.7 1.9 gloss 20°/60° 64.7/87 77/91 54/87 82/91.9 impact F/R 160/160 160/160 160/160 160/160

Pencil Hardness F F HB H

T bend 6 T 2 T 1 T 6 T

MEK rubs 200 200 200 200 surface

appearance* 7 6 5 3

1 Dibutyltin dilaurate

* Surface smoothness was judged by visual

inspection of the panel to determine the amount of orange peel. Nine scales were used to describe the amound of orange peel.

0 = very heavy

1 = heavy

2 = moderate-heavy

3 = moderate

4 = slight-moderate

5 = slight

6 = very slight

7 = trace

8 = none

Claims

Claims I claim:

1. A liquid-crystalline oligomeric plasticizer of the formula

wherein R is a divalent C₂-C₁₀ alkyl group;

M is a divalent group selected from the list consisting of ;

,

wherein A is halogen, C₁-C₆ alkyl, or phenyl; ;

; and

; and

wherein R¹ is hydrogen, halo, hydroxy, cyano, nitro, or C₁-C₆ alkyl.

2. The plasticizer of claim 1, wherein M is a group of the formula ;

3. The plasticizer of claim 1 or 2, wherein R¹ is hydrogen.

4. The plasticizer of any one of claims 1 to 3, wherein R is a group of the formula -(CH₂)_n- , wherein n is an integer from 2 to 6.

5. A thermosetting powder coating composition, which comprises

(a) a liquid-crystalline oligomeric plasticizer of the formula

wherein R is a divalent C₂- C₁₀ alkyl group; M is divalent group selected from the list

consisting of ;

,

wherein A is halogen, C₁-C₆ alkyl, or phenyl; ;

; and

; and

wherein R¹ is hydrogen, halo, hydroxy, cyano, nitro, or C₁-C₆ alkyl;

(b) a hydroxyl-functional amorphous polyester; and

(c) an effective amount of a crosslinking agent.

6. The composition of claim 5, wherein M is a group of the formula ;

7. The composition of claim 5, wherein R¹ is hydrogen.

8. The composition of claim 5, wherein R is a group of the formula -(CH₂)_n- , wherein n is an integer from 2 to 6.

9. The composition of claim 5, wherein the cross-linking agent is selected from the list consisting of ∈-caprolactam blocked isophoronediisocyanate,

tetraalkoxymethyl glycoluril, ∈-caprolactam blocked toluenediisocyanate, and ∈-caprolactam blocked m-tetramethylxylene diisocyanate.

10. The composition of claim 5, wherein the crosslinking agent is an adduct of the 1,3-diazetidine-2,4-dione dimer of isophorone diisocyanate and a diol having the structure

wherein

R¹ is a divalent 1-methylene-1,3,3-trimethy1-5- cyclohexyl radical, i.e., a radical having the structure

R² is a divalent aliphatic, cycloaliphatic,

araliphatic or aromatic residue of a diol; and X is a 1,3-diazetidine-2,4-dionediyl radical, i.e., a radical having the structure

wherein the ratio of NCO to OH groups in the formation of the adduct is about 1:0.5 to 1:0.9, the mole ratio of diazetidinedione to diol is from 2:1 to 6:5, the content of free isocyanate groups in the adduct is not greater than 8 weight percent and the adduct has a molecular weight of about 500 to 4000 and a melting point of about 70 to 130°C.

11. The composition of claim 5, wherein the crosslinking agent is a compound having a plurality of -N-CH₂OR groups wherein R is C₁-C₈ alkyl.

12. The composition of claim 5, wherein the crosslinking agent is a compound of the formula

13. A shaped or formed article coated with the cured composition of claim 5.