KR20010020186A - Epoxidized polyester-based powder coating compositions - Google Patents

Abstract

Curable epoxidized polyesters useful in powder coating applications include (i) tetrahydrophthalic acid or anhydride, (ii) at least one cycloaliphatic polyol, (iii) at least one saturated polycarboxylic acid and (iv) optionally at least one other alcohol. Provided by epoxidizing a polyester having a melting point of at least 90 ° C. and a viscosity of up to 50 poise at 200 ° C., prepared by reacting under conditions effective to obtain a solid polyester having a melting point of at least 90 ° C. A curable coating powder is obtained that contains an epoxidized polyester and a solid carboxylic acid curing agent having an acid equivalent in the range of 100-1500.

Description

Epoxidized Polyester-Based Powder Coating Composition {EPOXIDIZED POLYESTER-BASED POWDER COATING COMPOSITIONS}

Thermosetting powder coatings with some external durability can be prepared from polyester and acrylic base resins in combination with suitable co-reactants. Examples of currently available external grade epoxy group containing materials are triglycidyl isocyanurate (TGIC) and glycidyl methacrylate (GMA) containing acrylic resins. However, TGIC-based powder coatings do not have sufficient weather resistance as evidenced by gloss loss and discoloration. Although acrylic materials generally have good weather resistance, they are known to have poor physical properties (eg, flexibility and impact resistance) and cause film scratches when present as contaminants in other powder coating materials. Other solid epoxy resins such as EPON Resin 2002, 2003 and 2004 (Epon Resin is a trademark) are available, but they do not provide external durability as they consist of aromatic subunits. Thus, there is a need for improved low aromatic or non-aromatic solid epoxy resins that can react with low aromatic or non-aromatic acrylic resins and polyesters to produce durable powder coatings.

The present invention relates to a powder coating composition. In one aspect, the present invention relates to an epoxidized solid resin composition useful for powder coating.

According to the invention,

(a) (i) tetrahydrophthalic acid or anhydride,

(ii) at least one cycloaliphatic polyol,

(iii) optionally at least one saturated polycarboxylic acid, and

(iv) optionally at least one other alcohol having an acid to hydroxyl equivalent ratio of 0.8 to 1 to 0.96 to 1 and an equivalent ratio of (i) to (iii) of 100: 0 to 1: 4 and (ii) to (iv) By epoxidizing a polyester having a melting point of at least 90 [deg.] C. prepared by reacting a mixture comprising a molar ratio of (i) :( ii) :( iii) :( iv) such that the equivalent ratio is from 100: 1 to 4: 1 Produced solid epoxidized polyester, and

(b) A curable coating powder composition is provided comprising a solid carboxylic acid component having an acid equivalent in the range of 100 to 1500.

This coating powder provides a cured powder coating having hydrolysis and good resistance to ultraviolet light.

Epoxidized polyesters must be abrasive and non-sintered to be useful in powder coating applications. The polyester sinters when it aggregates (attaches together) within one week at room temperature and cannot be easily redispersed. Solid epoxidized polyesters preferably have a melting point of at least 100 ° C. in order to obtain good performance.

Solid epoxidized polyesters useful for powder coating applications are preferably prepared by epoxidizing polyesters having a Tg of at least 50 ° C., a melting point of at least 90 ° C. and a viscosity of up to 50 poise at 200 ° C. (ICI Cone & Plate viscosity). Turned out to be. Such polyesters can be prepared by reacting the components (i) to (iv) described herein in the molar ratios described herein. Preferably the total acid to hydroxyl equivalent ratio is from 0.85 to 1 to about 0.95 to 1, the equivalent ratio of (i) to (iii) is from 4: 1 to 1: 4 and more preferably from about 2: 1 to 1: 2 And the equivalent ratio of (ii) to (iv) is from 100: 0 to 12.5: 1. In a preferred embodiment, it is preferred that components (i) to (iii) have a 2: 1 to 1: 2 equivalent ratio to obtain a good weather resistant formulation.

The reaction is typically carried out by heating the mixture at a temperature in the range of 150 ° C., preferably 170 ° C. to 240 ° C., preferably 230 ° C., until the acid value of the reaction mixture reaches 5 or less, preferably 2 or less. . Preferably water and / or other condensation products formed during the reaction are removed continuously. The reaction mixture may also contain inert organic solvents such as ketones such as 2-butanone, 4-methyl-2-pentanone and hydrocarbons such as xylene and toluene. A catalyst can be added to facilitate the completion of the reaction. Such catalysts include, for example, those made from titanium, zirconium, tin and antimony, and other conventional catalysts used in the polyesterification reaction. The resulting solid polyester resin can be recovered by conventional methods.

The alcohol is preferably a polyhydric alcohol having 5 to 50 carbon atoms and 2 to 4 hydroxyl groups per molecule. If present, small amounts, up to 15 equivalents, preferably up to 10 equivalents, of the total hydroxyl content of polyhydric alcohols or monohydric alcohols having up to 4 carbon atoms may also be present in the reaction mixture.

Examples of tetrahydrophthalic acid or anhydrides thereof useful for preparing solid polyesters include cyclohex-4-ene-1,2-dicarboxylic anhydride, 3-methylcyclohex-4-ene-1,2-dicarboxylic anhydride, 4- Methylcyclohex-4-ene-1,2-dicarboxylic acid anhydride, cyclohex-4-ene-1,2-dicarboxylic acid, 3-methylcyclohex-4-ene-1,2-dicarboxylic acid, 4-methyl Cyclohex-4-ene-1,2-dicarboxylic acid and mixtures thereof. Alicyclic polyols useful for preparing solid polyesters include cyclohexanedimethanol and hydrogenated bisphenol A and mixtures thereof. Examples of saturated polycarboxylic acids useful for preparing solid polyesters include hexahydrophthalic anhydride, hexahydrophthalic acid, 1,4-cyclohexanedicarboxylic acid, dimethyl esters of cyclohexanedicarboxylic acid, and mixtures thereof. Examples of the polyhydric alcohol component (iv) include trimethylolpropane, neopentyl glycol, trimethylolethane, pentaerythritol and mixtures thereof. Examples of polyhydric alcohols having up to 4 carbon atoms include ethylene glycol, 1,3-propanediol, 1,4-butanediol. Examples of monohydric alcohols include butanol, 2-ethyl-1-hexanol and cyclohexanol.

Solid polyesters may be epoxidized by conventional epoxidation methods described in US Pat. Nos. 5,244,985, 3,493,631 and 2,928,805. For example, the solid polyester may contain a sufficient amount of base, such as sodium carbonate, sodium bi, to neutralize the strong acid contained at a temperature in the range of 0 ° C., preferably 20 ° C. to 70 ° C., preferably 40 ° C. A mixture of performic or molybdic acid and hydrogen peroxide produced individually or in situ in the presence of a strong acid or acidic resin from an acid solution such as peracetic acid, formic acid and hydrogen peroxide in the presence of carbonate or disodium hydrogen phosphate By treatment with a furnace. The resulting epoxidized solid polyester preferably has a WPE (weight per epoxy functional group equivalent) in the range from 350 to 1500. Solid, wear-resistant epoxidized polyester is recovered by conventional methods.

Carboxylic acid curing agents must also be solid and wear resistant to be useful in powder coating applications. These carboxylic acid components useful as hardeners for powder coating applications have been found to have acid equivalents in the range of 100 to 1500, preferably 110 to 900. Such carboxylic acids preferably have an average of 10 to 100 carbon atoms and 2 to 4 carboxyl groups, more preferably 2 carboxyl groups per molecule, provided they have an acid equivalent in the range of 100 to 1500.

Examples of polycarboxylic acids include linear or branched solids, preferably crystalline alkanoic acids such as dodecanedioic acid and sebacic acid. Other preferred polycarboxylic acids include 2: 1, preferably 1.2: 1 to 2: 1, preferably at least one cycloaliphatic dicarboxylic acid or anhydride in the acid and at least one polyhydric alcohol having 5 to 50 carbon atoms. It can be prepared by reacting a mixture comprising an acid to hydroxyl equivalent ratio of 1.4: 1. Mixtures of one or more polyhydric alcohols are preferred in order to obtain optimum performance and ease of processing. Examples of cycloaliphatic dicarboxylic acids or anhydrides and polyhydric alcohols are listed above.

The curable coating powder composition comprises (a) a solid epoxidized polyester and (b) an acid functional component. The amounts of (a) and (b) will generally be within ± 35% of the stoichiometric amount. The ratio can be adjusted to compensate for the catalyst type, curing conditions and desired coating properties. Ratios outside the range can produce low molecular weight, poorly cross-linked products having sub-optimal properties. Conventional powder coating additives such as flow regulators, anti-popping agents, powder flow materials, fillers and pigments may also be included. The curable coating powder composition may be prepared by increasing the crosslinking ratio of the coating composition depending on the desired application, such as catalysts such as phosphonium salts (eg ethyltriphenylphosphonium iodide), imidazole and tin salts (eg For example, dibutyltin oxide) may be further included in a small percentage.

Thermosetting coating powder compositions can be prepared by various methods known in the powder coating industry: dry blending, two-roll mills or melt compounding by extruder and spray drying. A method typically used is a melt compounding method wherein the components are dry blended in a planetary mixer and then the melt blended in the extruder at a temperature in the range of 80 ° C to 130 ° C. The extrudate is then cooled and triturated into a granular blend.

The thermosetting coating powder composition can then be applied directly to the substrate of the metal, such as steel or aluminum. Non-metallic substrates such as plastics and composites can also be used. Application can be by electrostatic spraying or the use of a fluidized bed. Electrostatic spraying is the preferred method. The coating powder may be applied in a single sweep or multiple passes to provide a film thickness after curing of 2.0-15.0 mils.

The substrate may optionally be preheated prior to application of the coating powder composition to promote uniform and thicker powder deposition. After application of the coating powder, the powder coated substrate is typically at a time sufficient to cure the powder coating composition at 120 ° C., preferably 150 ° C. to 205 ° C., typically 1 minute to 60 minutes, preferably 10 to 30 minutes. Bake for minutes.

The coating powder composition may be applied to the raw metal or plastic or composite (eg, untreated and unprimed steel) directly or on a pretreated surface (eg, phosphated and unprimed steel). The powder coating composition may also be applied to phosphated steel with a thin (0.8 mil to 2 mil) layer of electrodeposited primer or as a top coating layer on the chip-resistant coating layer, either uncured or not before application of the coating powder composition. Examples of chip-resistant layers are described, for example, in US Pat. Nos. 5,115,029 and 5,264,503. The electrodeposited primer coating on the metal substrate can be, for example, a negative electrodeposition primer composition. In one aspect of the invention, it is contemplated that the coating powder composition may be applied directly to an uncured electrodeposition primer coating and the coating powder may be cured together by heating for 10 to 30 minutes at a temperature in the range of 150 ° C to 180 ° C.

The powder coating composition of the present invention exhibits good UV resistance and good chemical resistance which can be observed by good retention of gloss at 60 ° and is used for automobiles and for general metal surfaces such as wheel covers and for building materials such as window frames It has good flow under curing conditions useful for exterior durable powder coatings. The powder coating compositions of the present invention are preferred for conventional liquid systems as they have essentially no volatile organic content.

The following illustrative embodiments are described for the novel epoxy resin compositions of the present invention and are provided for illustrative purposes and are not intended to limit the present invention.

Tetrahydrophthalic anhydride is obtained from Janssen Chemical. Hexahydrophthalic anhydride and hydrogenated bisphenol A are obtained by Milliken Chemical. 1,4-cyclohexane is Aldrich Chemical Co. Or from Eastman Chemical Co. 1,4-cyclohexane dicarboxylic acid is provided from Eastman Chemical Co. The trimethylolpropane mentioned in the examples below is obtained from Aldrich Chemical Co. Tin catalyst (Fascat 4100) is obtained from Elf Atochem. Equilibrium peracetic acid (35%) is available from Aldrich Chemical Co.

Example 1-8

Preparation of Solid Hydroxyl-functional Polyesters

Solid polyesters containing multiple sites of olefinic unsaturation may contain various amounts of reactants (CHDA = cyclohexanedicarboxylic acid; THPA = tetrahydrophthalic anhydride; HHPA = hexahydrophthalic anhydride; CHDM = 1,4-cyclohexane Dimethylethanol; HBPA = hydrogenated bisphenol A; TMP = trimethylolpropane). Both procedures are used to add reagents.

In one procedure, the acid-functional reactant, HBPA and toluene are placed in a 5.0 liter flask equipped with a Dean-Stark trap and condenser, thermocouple and overhead stirrer assembly. After the flask and contents have been purged with nitrogen for a while, the static pressure of nitrogen is maintained until sparging starts. The component is heated to reflux and maintained for 1 hour. Then a solution of 2-butanone (800 g) and the remaining hydroxyl component is added and the solvent is removed continuously. In another procedure, cyclohexanedimethanol is added with other reactants before heating.

The reaction mixture is slowly warmed to 200 ° C. and the solvent and byproducts are removed if necessary. The reaction mixture is kept at reflux to promote the removal of water until the rate of release of water is reduced. Fascat 4100 (butylated tin oxide) is added at the beginning of the reaction or all at once after the initial release of condensation water has slowed down. After holding for 1-2 hours at a temperature of 200 ° C., the reaction mixture is further warmed to 220 ° C. and sparged with nitrogen. This is maintained until the acid value of resin becomes 1 or less. The acid value is determined by titration of a 50:50 (w / w) toluene / isopropanol solution of the resin with 0.1 N ethanol potassium hydroxide. The flask contents are transferred to an aluminum pan to separate the resulting polyester resin.

The properties of the resulting solid polyesters are listed in Table 2. Viscosity was measured by ICI Cone & Plate at 200 ° C unless otherwise noted. Mettler melting point (M.P. (° C)) and final acid value are listed.

Table 1 ¹

Example CHDA THPA HHPA CHDM HBPA TMP Acid / OH ² One 10.1 8.6 16.7 3.3 0.935 / 1 2 1.19 1.81 3.02 0.24 0.92 / 1 3 1.9 1.66 0.34 0.95 / 1 4 2.4 4.48 0.54 / 1 5 0.86 1.01 1.67 0.33 0.935 / 1 6 5.16 6.06 10.4 2.06 0.9 / 1 7 9.35 8.35 1.65 0.935 / 1 8 10.1 8.6 16.7 3.35 0.3 0.92 / 1 1) The value represents the equivalent used: Molecular equivalent ---------------------------- CHDA 86THPA 76HHPA 77CHDM 72HBPA 120TMP 44.72) Based on the equivalent used.

Example Acid M.P. (℃) Melt Viscosity (Poise / ° C) Olefin Functionality ¹ Mn ² One 0.88 101.7 21/20080/175 7.7 4400 2 0.43 107.5 75/175 6.6 4768 3 1.9 138.1 ＞ 250/200 19 5752 4 5.1 66.6 13/150 4.1 1231 5 1.5 108 52/175 7.8 4400 6 0.5 90.8 22/175 4.9 2827 7 0.9 103 14/20047/175 14.4 4386 8 0.9 104.3 29/175 7.5 4246 1) Functionality is theoretical. 2) Mn is the theoretical number average molecular weight.

As can be seen from the above table, the polyesters of Examples 1-2 and Examples 5-8 have a melting point of 90 ° C. or higher and a viscosity measurement of 50 poise or less at 200 ° C. Example 4 serves as a comparative example with a too low melting point. Example 3 serves as a comparative example with too high a viscosity. The acid to OH ratio of Example 7 is to obtain a low viscosity value suitable for processing in powder coating applications.

Examples 9-13

Preparation of Solid Epoxidized Polyester

The polyester obtained above is dissolved in toluene or methylene chloride (25 / 75-40 / 60 w / w) and reacted with equilibrium 35% peracetic acid at 25-40 ° C. for 2-3 hours. The reaction mixture is treated with sufficient sodium carbonate to neutralize the sulfuric acid contained in peracetic acid. Following the reaction, the epoxidized polyester is separated in one of two ways. In one method (Method A), the reaction mixture is condensed under reduced pressure to remove water, unreacted hydrogen peroxide, peracetic acid and acetic acid and the desired solvent. The residue is diluted to 25% solids with toluene or methylene chloride and filtered or washed 4 to 5 times to remove solid impurities. The resin solution is then condensed by distillation of the volatiles at elevated temperature (up to 200 ° C.) under reduced pressure. The residue is optionally sparged with nitrogen to remove the final small amount of volatiles such that the product is more acceptable as a coating powder vehicle.

In another method (method B), after completion of the epoxidation reaction the reaction mixture is diluted to 25% as above and then filtered; The mixture is then washed 4-5 times with water and condensed by distillation and sparging as above.

WPE (weight per epoxy functional equivalent), Mettler melting point (M.P. (° C.)) and ICI Cone & Plate viscosity at 200 ° C. are listed in Table 3. WPE is measured by titrating a dichloromethane / acetic acid solution of resin and tetraethylammonium bromide to a crystalline purple end point with standardized 0.1 N perchloric acid in acetic acid.

Example Polyester produced in the examples WPE Melt Viscosity (Poise / ° C) Mettler M.P. (° C) 9 2 852 142/175 107.7 10 5 783 69/175 107.7 11 6 721 68/175 105.3 12 7 490 - - 13 8 682 36/175 112

Example 14-17

Preparation of Acid Functional Ingredients

The acid functional component (polyester curing agent) was prepared in various amounts (equivalent) of reagents listed in Table 4 (CHDA = cyclohexane dicarboxylic acid; HHPA = hexahydrophthalic anhydride; CHDM = 1,4-cyclohexanedimethanol; TMP = trimethyl Olpropane) is prepared by reacting in a manner similar to that used to make the polyesters in Tables 1 and 2. All reagents are placed in a four neck flask equipped with an overhead stirring assembly, thermocouple, Dean-Stark trap and condenser, and nitrogen source. Xylene is optionally added to the reaction to serve as a carrier for the water to be formed. After the flask and contents have been purged with nitrogen for a while, static pressure of nitrogen is applied and the mixture is heated to reflux or 150 ° C. if xylene is used. In Examples 15-17, 0.1-0.2 wt% Fascat 4100 catalyst is added. After 1 hour at this temperature, the mixture is warmed to 175 ° C. and maintained at this temperature until about 75% of water is released. The mixture is then warmed to 200 ° C. After the water release is slowed down again, the mixture is sparged with nitrogen until the theoretical acid value is achieved or exceeded. The total acid / OH ratio and melting point of each product are listed in Table 4.

Table 4 ¹

Example CHDA HHPA CHDM TMP Acid / hydroxyl equivalent ratio Acid equivalent Melting Point (℃) Melt Viscosity (Poise / ° C) 14 6 3 2.0 197.6 94.3 25/150 15 1.85 1.6 1.16 1064 93.5 115/150 16 2.0 1.48 0.26 1.15 1017 106.8 165/175 17 2.0 1.03 0.48 1.32 503 99.5 50/175 1) The value represents the equivalent used.

Examples 18 and 19

Preparation of Powder Coating Compositions and Properties of Curing Products

Example 18 Example 19

Example 13, Oxirane Component 395

Example 17, Cured Co-Reactant 296

Polyester resin ^A , DSM P-3900 ---- 596

TGIC ^B ---- 45

Modaflow Powder III ^C 7 6

Benzoin ---- 3

Ethyltriphenylphosphonium iodide 2 ----

Titanium Dioxide (External Grade) 300 350

Total 1000 1000

A: Acid functional polyester resin from DSM. Acid number = 32-38.

B: Araldite PT 810 from Ciba-Geigy.

C: acrylate copolymer of Monsanto.

Manufacturing method

The composition is processed using a typical method for preparing the coating powder: strong premix, high shear melt compounding (extrusion), grinding and siving through a 200 mesh screen.

Powder coating performance

The coating is applied and cured to a "Type S" Q-panel about 2 mil cured film thickness as follows.

Example 18 Example 19

Cure Cycle 20 minutes, 250 ° F 10 minutes, 400 ° F

Gel time ^A seconds @ 175 ℃ 97 ----

Second @ 200 ℃ 45 220

Gardner Shock ^B (Inch Pounds)

Direct pass 50 ----

Reverse fail 10 fail 10

Flexible ^C , 1/8 inch through conical mandrel ----

Pencil Hardness ^D (Gouge Hardness) 2H -4H ----

MEK resistant ^E , double friction pass 100 pass 50

Glossiness ^F ,% @ 20 degrees 73 61

60 degrees 91 91

Color ^G , 20 minutes at 350 ° F L 94.6 91.5

a -0.92 -1.03

b -0.24 0.23

Smoothness ^H , PCI Standard 6

Weathering Test ^I

QUV-B 60。 Glossy retention 97%, 1000 hours 30%, 200 hours

Yellowing, △ b 0.15, 1000 hours 3.0,200 hours

EMMAGUA 60。 Glossy retention 65-85%, 5 years 50%, 3 years

No yellowing Severe

A Powder Coatings Association (PCI) Test Procedure # 6.

B ASTM D2794

C ASTM D522

D ASTM D3363

E PCI # 8.

F ASTM D523

G ASTM D2244

H PCI # 20

I ASTM D4141

As can be seen from above, Example 18, which is a powder coating of the present invention, has excellent weather resistance and at least other performance properties equivalent to Example 19, which is a typical TGIC-polyester powder. The 60 ° gloss retention is 97% after 1000 hours for the present invention versus 30% after 200 hours for the TGIC-polyester powder.

Claims (10)

(a) (i) tetrahydrophthalic acid or anhydride, (ii) at least one cycloaliphatic polyol, (iii) optionally at least one saturated polycarboxylic acid, and (iv) optionally having at least one polyhydric alcohol having 5 to 50 carbon atoms with an acid to hydroxyl equivalent ratio of 0.8 to 1 to 0.96 to 1 and an equivalent ratio of (i) to (iii) of 100: 1 to 1: 4 Wherein the acid value of the reaction mixture is 5 or less in a reaction mixture comprising a molar ratio of (i) :( ii) :( iii) :( iv) such that the equivalent ratio of (ii) to (iv) is from 100: 0 to 4: 1 Solid epoxidized polyester prepared by epoxidizing a polyester having a melting point of at least 90 ° C. and a viscosity of at most 50 poises at 200 ° C., prepared by reacting until (b) a curable coating powder composition comprising a solid carboxylic acid component having an acid equivalent in the range of from 100 to 1500. The method of claim 1, wherein the tetrahydrophthalic acid or anhydride is cyclohex-4-ene-1,2-dicarboxylic acid anhydride, 3-methylcyclohex-4-ene-1,2-dicarboxylic acid anhydride, 4-methylcyclohex 4-ene-1,2-dicarboxylic acid anhydride, cyclohex-4-ene-1,2-dicarboxylic acid, 3-methylcyclohex-4-ene-1,2-dicarboxylic acid, 4-methylcyclohex- Curable coating powder composition selected from the group consisting of 4-ene-1,2-dicarboxylic acid and mixtures thereof. The curable coating powder composition of claim 2 wherein component (ii) is selected from the group consisting of cyclohexanedimethanol and hydrogenated bisphenol A and mixtures thereof. 4. The curable coating powder composition of claim 3 wherein component (iii) is selected from the group consisting of hexahydrophthalic anhydride, hexahydrophthalic acid, 1,4-cyclohexanedicarboxylic acid, dimethyl ester of cyclohexane dicarboxylic acid, and mixtures thereof. . The curable coating powder composition of claim 4, wherein component (iv) is selected from the group consisting of trimethylolpropane, neopentyl glycol, trimethylolethane, pentaerythritol, and mixtures thereof. 5. The curable coating powder composition of claim 1 wherein the acid to hydroxyl equivalent ratio of (i) :( ii) :( iii) :( iv) is in the range of 0.90 to 1 to 0.96 to 1. 6. A cured powder coating composition obtained by curing the composition according to claim 1. (a) (i) tetrahydrophthalic acid or anhydride, (ii) at least one cycloaliphatic polyol, (iii) optionally at least one saturated polycarboxylic acid, and (iv) optionally having at least one polyhydric alcohol having 5 to 50 carbon atoms with an acid to hydroxyl equivalent ratio of 0.8 to 1 to 0.96 to 1 and an equivalent ratio of (i) to (iii) of 100: 1 to 1: 4 And the molar ratio of (i) :( ii) :( iii) :( iv) such that the equivalent ratio of (ii) to (iv) is from 100: 0 to 4: 1 until the acid value of the reaction mixture is 5 or less Thereby producing a solid polyester having a melting point of at least 100 ° C .; (b) epoxidizing the solid polyester to produce a solid epoxidized polyester; (c) A process for producing a solid epoxidized polyester having a melting point of at least 100 ° C. comprising recovering the epoxidized polyester. 9. The process according to claim 8, wherein component (ii) is selected from the group consisting of cyclohexanedimethanol and hydrogenated bisphenol A and mixtures thereof. 10. The process of claim 9, wherein component (iii) is selected from the group consisting of hexahydrophthalic anhydride, hexahydrophthalic acid, 1,4-cyclohexane dicarboxylic acid, dimethyl ester of cyclohexane dicarboxylic acid, and mixtures thereof.