Unsaturated polyester composition with improved adhesion to metal substrates for vehicle body repair

Abstract

A vehicle body repair formulation is provided that includes a polyester resin having an unsaturation of between 25 and 100 molecular percent based on the total acid and anhydride content. The polyester resin is dissolved or suspended in a monomer reactive diluent. Microellipsoids are provided to enhance the grindability of the cured formulation. An initiator package is also provided. The reactive diluent / monomer may be selected to be non-styrene type to improve performance attributes. A method for repairing a vehicle body is provided that utilizes environmental conditions alone or in combination with a heat source to facilitate curing after application to a vehicle body in need of repair.

Description

[0001] This application is a divisional application of the patent application for invention titled "Unsaturated Polyester Composition with Improved Adhesion to Metal Substrates for Body Repair", with the filing date of July 7, 2017, international application number PCT / US2017 / 041245, and national application number 201780055374.5.

[0002] Cross - Reference to Related Applications

[0003] This application claims the benefit of priority to U.S. Provisional Patent Applications 62 / 361,672 and 62 / 363,019, filed on July 13, 2016, and July 15, 2016, respectively, the contents of which are incorporated herein by reference. Technical Field

[0004] The present invention generally relates to unsaturated polyester compositions and, in particular, to a polyester composition that can strongly adhere to metal substrates present on body panels and bumpers without the aid of styrene monomers. Background Art

[0005] Unsaturated polyester resins have been used in various applications, such as in polyester body filler systems and glass - reinforced polyester body filler systems used in the field of automotive body repair. Electroplated (corrosion - resistant) coatings inherently interfere with the curing and adhesion at the interface of all materials cured by free - radical polymerization, including polyester resin formulations. It has been known that the adhesion of polyester to metal can be improved by using adhesion promoters, using low - molecular - weight polymers with reduced monomer content, using metal pretreatment, or by accelerating the cross - linking reaction. Unfortunately, a highly flexible polymeric mastic that can be easily sanded and does not require the expensive use of pretreatment or adhesion promoters has not been available; the present invention overcomes this defect.

[0006] In the case of electroplated substrates, the problem of poor adhesion is more severe due to the fact that electroplating (zinc) delays the curing of the resin system, delays sanding and further processing of the filler, and may, in some cases, prevent complete curing. In addition, as vehicle bodies are increasingly made of lighter - weight aluminum, high - strength steel, composites, and thermoplastics, there is a need to develop body fillers that can adhere to substrates with a wide range of surface energies.

[0007] Another trend in the automotive refinish aftermarket industry is the increasing regulation of the use of styrene. Unsaturated polyester resins are condensation products of dibasic carboxylic acids or anhydrides and bifunctional or polyfunctional alcohols that have traditionally been dissolved in styrene as a reactive diluent. Although unsaturated polyesters have been developed in the past, as detailed, for example, in US 6,268,464, these polyesters have been found unacceptable as body fillers due to brittleness and excessive hardness.

[0008] Accordingly, there is a need for a polyester resin that can provide adhesion to automotive body panels of metal without the aid of using a pretreatment or adhesion promoter. There is a further need for such a polyester resin formulation that is free of styrene. SUMMARY OF THE INVENTION

[0009] There is provided a body repair formulation comprising a polyester resin having an unsaturation between 25 and 100 mole percent based on the total acid and anhydride monomer content. The polyester resin is dissolved or suspended in a monomer reactive diluent. Microspheroids are provided to enhance the sandability of the cured formulation. A separately stored initiator package is also provided. The monomer can be selected to be non-styrene type to improve performance attributes.

[0010] There is provided a method for repairing a body, which includes mixing a polyester resin formulation Part A comprising a polyester resin having an unsaturation between 25 and 100 mole percent based on the total acid and anhydride monomer content with a Part B initiator package. At least one of Part A or the Part B contains microspheres to form a curable mixture. The mixture is applied to a substrate of a body to be repaired. The mixture allowed to contact the substrate is cured at ambient conditions (7 to 49 °C) or exposed to a heat source (37 - 82 °C) to promote curing of the mixture. The mixture is cured to form a filler to repair the body. DETAILED DESCRIPTION

[0011] The present invention has utility as a polyester resin that can adhere to electroplated steel substrates without the aid of using a pretreatment or adhesion promoter. There is also provided a formulation of the polyester resin that does not contain styrene monomer in the uncured formulation.

[0012] It is to be understood that in instances where a numerical range is provided, the range is intended to cover not only the end point values of the range but also the intermediate values of the range, the intermediate values of the range being expressly included within the range and varying with the last significant digit of the range. For example, the recited range of 1 to 4 is intended to include 1 - 2, 1 - 3, 2 - 4, 3 - 4, and 1 - 4.

[0013] One innovative aspect of the present invention lies in the unsaturation of the polyester, which, although traditionally may be overly reactive, resulting in a brittle matrix with high shrinkage rate, poor adhesion and being too hard for manual sanding, is unexpectedly very suitable for application to electroplated steel substrates. In addition to the adhesion to electroplated steel substrates, the polyester of the present invention provides desired properties when applied to other substrates that are problematic in terms of adhesion. These other substrates exemplarily include stainless steel and aluminum. By selecting vinyltoluene as the sole reactive diluent, it has been found that, as compared with styrene as the reactive diluent, the dimensional stability is improved, making the polyester composition of the present invention suitable for the automotive body repair industry and providing excellent adhesion to metal substrates such as zinc alloy panels and / or zinc - aluminum alloy panels, electrocoated (e - coated) (primer - precoated) steel, cold - rolled steel and aluminum.

[0014] In certain embodiments, the polyester resin formulation of the present invention comprises a polyester resin that has fully reacted with a non - styrene - type molecule as the sole diluent. The polyester formulation is modified with dedicated additives to control free - radical polymerization, thereby minimizing exothermic heating and shrinkage. To further maximize the toughness and adhesion of the resulting cured polyester composite, in some embodiments of the present invention, a thermoplastic filler is also added.

[0015] As used herein, with respect to the cured formulation of the present invention, "sandable" is defined as having limited clogging of sandpaper and being able to form a smooth and unbroken featheredge with 60 - to 180 - grit sandpaper in less than 20 minutes at 25 °C. When external heat is applied, sanding can be carried out in less than 10 minutes.

[0016] As used herein, with respect to the cured formulation of the present invention, "non - brittle" is defined as not cracking or crazing due to thermal expansion / contraction between 34 and 65 degrees Celsius during 20 cycles measured in accordance with ASTM D6944 - 03 and ASTM D522 - 13.

[0017] The polyester resin of the present invention has an ethylenic unsaturation between 25 and 100 mole percent of the dicarboxylic acids and acid anhydrides in the polyester resin, representing the reactivity towards free - radical polymerization within the polyester resin backbone. For calculating the monomer percentage, the reactive diluent is ignored.

[0018] Suitable unsaturated acids or acid anhydrides for the embodiments of the polyester resin of the present invention include maleic anhydride, maleic acid, fumaric acid, itaconic acid, and related derivatives retaining ethylenic unsaturation, and any combination of the foregoing. These are present in a molar percentage of 25 to 100 of the non-alcohol monomers. In some embodiments of the present invention, they are present in a monomer percentage of 50 to 100.

[0019] Saturated polyfunctional carboxylic acids or acid anhydrides that can be used herein include, by way of example, phthalic acid, isophthalic acid, terephthalic acid, hexahydrophthalic acid, tetrahydrophthalic acid, cyclohexanedicarboxylic acid, adipic acid, succinic acid, malonic acid, 5-norbornene-2,3-dicarboxylic acid (nadic acid), trimellitic acid, pyromellitic acid, the acid anhydrides of any of the foregoing acids, and any combination thereof. Saturated monofunctional carboxylic acids that can be used herein in the polyester resin formulations according to the present invention include, by way of example, benzoic acid, 2-ethylhexanoic acid, lauric acid, and any combination thereof. In some embodiments of the present invention, the total saturated carboxylic acid and acid anhydride monomer content is 0 to 10 molar percentage.

[0020] In some embodiments of the present invention, only maleic acid is present, resulting in 100% unsaturation. In still other embodiments, 5-norbornene-2,3-dicarboxylic acid and phthalic acid are used, resulting in 50% unsaturation.

[0021] React any combination of the dicarboxylic acids and acid anhydrides with monofunctional, difunctional, or polyfunctional alcohols. Monofunctional alcohols that can be used herein include, by way of example, benzyl alcohol, 2-ethylhexanol, lauryl alcohol, cyclohexanol, and any combination thereof. Difunctional and polyfunctional alcohols that can be used herein include, by way of example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, neopentyl glycol, butanediol, butylethylpropanediol, trimethylolpropane, hexanediol, cyclohexanedimethanol, glycerol, pentaerythritol, polyether polyols, and any combination thereof. The total amount of alcohols in the polyester resin of the present invention is in the range of about 100 to about 120 molar percentage relative to the total carboxylic acid and acid anhydride content.

[0022] In some embodiments of the present invention, propylene glycol is used as the alcohol, and in still other embodiments, propylene glycol is condensed with maleic acid or with a combination of 5-norbornene-2,3-dicarboxylic acid and phthalic acid to produce 50% unsaturation. In still other embodiments of the present invention, propylene glycol and diethylene glycol are used in a molar ratio between 0.1 - 10:1, and in still other embodiments, propylene glycol and diethylene glycol are condensed with maleic acid or with a combination of 5-norbornene-2,3-dicarboxylic acid and phthalic acid to produce 50% unsaturation. In still other embodiments, propylene glycol and diethylene glycol are condensed with monomers to form a polyester having hydroxyl and amine side group functional groups.

[0023] The unsaturated portions in the polyester backbone react with vinyl and allyl groups of non-styrene type molecules by free radical polymerization.

[0024] In some embodiments, exemplary molecules that end-functionalize the unsaturated polyester resin of the present invention include allyl glycidyl ether, glycidyl methacrylate, trimethylolpropane diallyl ether, allyl pentaerythritol, or polymeric allyl glycidyl ether. The typical amount of the end-functionalizing molecule ranges from 1 to 3 mole percent relative to the total carboxylic acid and anhydride monomer content.

[0025] The unsaturated polyester of the present invention is readily formed in a single-stage or multi-stage reaction. The typical reaction temperature range is from 130 - 240 °C, and in some embodiments, in the range of 180 to 230 °C. Conventional esterification catalysts are present and are exemplarily acids, transition metal catalysts, and organotin compounds. The typical catalyst dosage ranges from 0.01 to 1 weight percent of the reactants.

[0026] The reactive polyester resin for use in a body filler formulation has an average molecular weight in the range of 500 to 3000 by average weight, and in additional other embodiments, 1000 to 2000.

[0027] To form the body filler formulation, the resulting reactive polyester resin is dissolved in a non-styrene type reactive diluent. The non-styrene type diluent is present in an amount of 20 to 100 weight percent relative to the unsaturated polyester.

[0028] Reactive diluents that can be used herein include acrylics, acrylates, and methacrylates, such as methyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxypropyl methacrylate, hydroxyethyl methacrylate, lauryl acrylate, stearyl methacrylate, lauryl methacrylate, butanediol diacrylate, ethylene glycol dimethacrylate, ethylene glycol-DCPD methacrylate, ethyl (meth)acrylate and n-butyl (meth)acrylate and isobutyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, butanediol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, propylene glycol dimethacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, and trimethylolpropane triacrylate or DCPD diacrylate; ether monomers having the structure (C1-C6 alkyl)-O-(C2-C6 alkene) such as vinyl ethyl ether or vinyl methyl ether; vinyl toluene, allyl-substituted benzene, divinylbenzene, bifunctional and trifunctional acrylates (commercially available, such as and products), acrylonitrile, monovinyl-capped polydimethylsiloxane, and any combination of any of the foregoing. It should be understood that phenyl rings having two groups in the foregoing list are intended to include ortho isomers, para isomers, meta isomers, and mixtures of their respective isomers.

[0029] In some embodiments, the reactive diluent is a non-styrene-based aryl monomer. A non-styrene-based aryl monomer is herein defined as any aromatic molecule having a vinyl functional group. In a particularly useful embodiment, the reactive diluent is vinyl toluene, as it retains the accelerated sanding time and performance of conventional formulations using styrene as a reactive diluent, with the added benefit of reducing environmental pollution and the risk of employee exposure to styrene.

[0030] Additives are present in the unsaturated polyester formulations of the present invention to improve at least one property of performance, storage stability, cure rate, sandability, or substrate adhesion. Exemplary additives include at least one of a thixotropic agent, pigment, dye, suppressant, filler, accelerator, inhibitor, leveling agent, or wetting agent.

[0031] Thixotropic agents useful in the present invention include, by way of example, calcined silica, organic clay, inorganic clay, and precipitated silica. Polyfunctional alcohols are often used to enhance the thixotropic properties. The thixotropic agent is present in an amount of 0.1 - 3.0 weight percent. The thixotropic agent is typically present in an amount of 0.5 to 2 total weight percent of the complete formulation applied to the substrate.

[0032] Pigments or dyes useful in the present invention include, by way of example, titanium dioxide, carbon black, iron oxides, phthalocyanine blue, and other colorants. These pigments and dyes can be dissolved or suspended in a reactive diluent. The pigment or dye is present in an amount of 0 to 10 total weight percent of the complete formulation applied to the substrate.

[0033] Inhibitors reduce vapor emissions and, in some embodiments, increase the cure time. Inhibitors useful in the present invention include, by way of example, waxes, polyethers, polysiloxanes, and various block copolymers. The inhibitor is present in an amount of 0 to 5 total weight percent of the complete formulation applied to the substrate.

[0034] Fillers useful in the present invention include, by way of example, talc, mica, aluminum trihydrate, calcium sulfate, calcium carbonate, magnesium sulfate, magnesium carbonate, barium sulfate, microspheres, and the like. The filler is present in an amount of 0 to 70 percent of the complete formulation applied to the substrate.

[0035] As used herein, microspheres are defined to include hollow microspheres having an aspect ratio between two normal maximum linear dimensions between 1 and 1.6. Typically, ellipsoidal particles are formed of glass or a thermoplastic material. In some embodiments of the present invention, the microellipsoids are within 10 percent of the linear dimensions of a sphere and are formed of glass. The microspheres typically have a longest linear dimension between 20 and 150 microns to improve sandability and reduce density. Thermoplastic microellipsoids are formed, by way of example, of acrylonitrile, polymethyl methacrylate (PMMA), phenolic resin, and wax having a melting point higher than that which would prevent melting upon curing of the formulation.

[0036] Levelling agents useful in the present invention include, by way of example, acrylic resins, fluorocarbons, fluoropolymers, and silicones. The levelling agent is present in an amount of 0 to 2 total weight percent of the complete formulation applied to the substrate.

[0037] Wetting agents useful in the present invention include, by way of example, borate esters, phosphate esters, fatty acid salts, and polyethers. The wetting agent is present in an amount of 0 to 2 total weight percent of the complete formulation applied to the substrate.

[0038] An accelerator is present to accelerate curing. Cure accelerators that can be used herein include tertiary amines such as dimethylaniline (all anilines) (DMAs), diethylaniline (DEA), dimethyl-p-toluidine (DMPT) (all toluidines), dihydroxy-p-toluidine (DHPT), monohydroxy-p-toluidine (MHPT), and any combination thereof. The cure accelerator is present in an amount of 0.0005 to 1 total weight percent of the complete formulation applied to the substrate.

[0039] The polymerization inhibitor is present to extend shelf life and to extend the curing time. Cure inhibitors that can be used herein include, for example, hydroquinone; p-benzoquinone; methylhydroquinone; substituted quinones such as NQ or TMHQ; 4-tert-butylcatechol; and metal naphthenates. The cure inhibitor is present in an amount of 0.0005 to 1 total weight percent of the complete formulation applied to the substrate.

[0040] The resin formulation is typically stored as Part A, which includes all components except the initiator package, and Part B, which includes the initiator package, which is mixed with Part A immediately before application to the vehicle body substrate. Part B typically includes a peroxide, a stabilizer, and a plasticizer. It should be understood that in certain embodiments, other components in addition to the polyester resin are present in the initiator package. Thus, the weight ratio of Part A: Part B is 1-100: 1 or 1 to 4 total weight percent catalyst to total weight percent filler.

[0041] Resin combination of the present invention is crosslinked with reactive diluent by using a variety of free radical initiators, including organic peroxides, azo initiators, electron beams, ultraviolet (UV) light, and any combination thereof. Peroxide initiators that can be used here illustratively include diacyl peroxides, hydroperoxides, ketone peroxides, peroxyesters (peroxyesters), peroxyketals (peroxyketals), dialkyl peroxides, peracid alkyl esters and percarbonates. Azo initiators that can be used here illustratively include azobisisobutyronitrile (AIBN). Chemical initiators are usually present in 1 to 3 total weight percentages of the polyester resin formulation that is fully mixed and applied. These resin combinations can optionally be cured by UV or electron beam.

[0042] In some embodiments of the present invention, after mixing Part A and Part B and applying to the substrate, the polyester resin formulation is heated to promote faster curing. For example, the temperature of the polyester resin formulation is raised to a temperature between 37 and 82° C. using induction heating, infrared lamps, forced hot air, and any combination thereof.

[0043] Whether or not the specific polyester resin formulation of the present invention is heated during curing, the curing time is generally between 5 and 60 minutes, and in other embodiments of the present invention, the curing time is between 10 and 20 minutes. This curing time range is manifested as a "dry to sand" (DTS) time between 5 and 30 minutes. At DTS, the resulting filler has sufficient adhesion strength to the substrate to become a "thin edge", meaning there is no tearing or peeling at the perimeter edge of the filler.

[0044] The present invention is further described by the following non-limiting examples. These examples are intended to exemplify specific formulations according to the present invention and should not be construed as limiting the scope of the present invention.

[0045] Example 1

[0046] A first set of body fillers was prepared having the components detailed in Table 1.

[0047] Table 1. Body filler formulations of the present invention, where weight percentages are percentages by total weight.

[0048]

[0049]

[0050] The appropriate resin was added to a mixing container and placed under a high-torque mixer equipped with shear blades. At slow rpm, any required "additives", inhibitors, and rheological additives were slowly added until uniformly dispersed. The mixer rpm was increased to about 2500 and the blend was sheared for 3 minutes. The fillers were added one by one and then the entire mixture was sheared for an additional 5 minutes. The shear blades were now replaced with blending blades. Then the microspheres were added and mixed at medium rpm for 3 minutes. The mixture was then adjusted as needed to meet viscosity and gel time specifications.

[0051] Example 2

[0052] A second set of body fillers was prepared having the components detailed in Table 2.

[0053] Table 2. Body filler formulations of the present invention, where weight percentages are percentages by total weight.

[0054]

[0055]

[0056] Add the appropriate resin to a mixing vessel and place it under a high-torque mixer equipped with shear blades. At slow rpm, slowly add any required "additives", inhibitors, and rheological additives until uniformly dispersed. Increase the mixer rpm to approximately 2500 and shear the blend for 3 minutes. Add the fillers one by one and then shear the entire mixture for an additional 5 minutes. Now replace the shear blades with blending blades. Then add the microspheres and mix at medium rpm for 3 minutes. Then adjust the mixture as needed to meet the viscosity and gel time specifications.

[0057] Example 3

[0058] Test the lap shear strength of various embodiments of the filler formulations of the present invention on various substrates according to ASTM 1002-10. Make lap shear measurements at 20 minutes after catalysis, which is typically the time for hand sanding and is well correlated with the "thin edge", the time when the filler has sufficient adhesion to form a seamless edge with no signs of flaking or delamination. For body shop technicians, this is the most critical part of the repair process because sanding cannot be done until this cure strength is reached.

[0059] Table 3. Lap shear strength of the body filler formulations of the present invention on various substrates relative to comparative conventional fillers 1-5. The formulation of Example 1 was tested according to ASTM 1002-10.

[0060]

[0061] Example 4

[0062] Repeat the process of Example 3 with the formulation of Example 2, which has an overall saturation of 79% by blending resin A and resin D. The resulting formulation achieves adhesion results comparable to those of Example 1, as detailed in Table 3.

[0063] Properties relative to comparative examples

[0064] Compare the properties of the present invention with the prior art formulations given in Table 4.

[0065] Table 4. Comparison of the body repair formulations of the present invention with prior art filler compositions

[0066]

[0067]

[0068]

[0069] As those skilled in the art will recognize from the foregoing detailed description and claims, modifications and changes can be made to the preferred embodiments of the present invention without departing from the scope of the present invention as defined in the following claims.

Claims

1. A vehicle body repair preparation, comprising: a polyester resin having an unsaturation between 25 and 100 mole percent based on the total acid and anhydride monomer content; a monomer reactive diluent in which the polyester resin is dissolved or suspended; thermoplastic microellipsoids; and an initiator package.

2. The preparation according to claim 1, wherein the unsaturation is 100 mole percent.

3. The preparation according to claim 1, wherein the unsaturation is between 50 and 100 mole percent.

4. The preparation according to claim 1, wherein the total acid and anhydride content is only maleic acid.

5. The preparation according to claim 1, wherein the total acid and anhydride content comprises at least two of 5-norbornene-2,3-dicarboxylate, 5-norbornene-2,3-dicarboxylic acid, and phthalic acid.

6. The preparation according to claim 5, wherein the unsaturation is between 40 and 100 mole percent.

7. The preparation according to claim 1, wherein the monomer reactive diluent is a non-styrene-based aryl monomer having a vinyl functional group.

8. The preparation according to claim 1, wherein the monomer reactive diluent comprises vinyltoluene.

9. The preparation according to claim 1, wherein the monomer reactive diluent is one or more of the following: methyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxypropyl methacrylate, hydroxyethyl methacrylate, lauryl acrylate, stearyl methacrylate, lauryl methacrylate, butanediol diacrylate, ethylene glycol dimethacrylate, ethylene glycol-DCPD methacrylate, (meth)acrylic acid ethyl ester, (meth)acrylic acid n-butyl ester, and (meth)acrylic acid isobutyl ester, (meth)acrylic acid cyclohexyl ester, (meth)acrylic acid isobornyl ester, (meth)acrylic acid benzyl ester, butanediol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, propylene glycol dimethacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, and trimethylolpropane triacrylate, DCPD diacrylate, an ether monomer having the structure (C1-C6 alkyl)-O-(C2-C6 alkene), vinyltoluene, allyl-substituted benzene, divinylbenzene, and difunctional and trifunctional acrylates.

10. The preparation according to claim 1, wherein the longest linear dimension of the microellipsoids is from 20 to 150 microns.

11. The preparation according to claim 1, wherein the microellipsoids are hollow.

12. The preparation according to claim 1, wherein the microellipsoids are present in an amount of 0.50 to 2.0 total weight percent.

13. A method for repairing a vehicle body, comprising: Mix a polyester resin formulation part A with a part B initiator package to form a curable mixture, wherein the part A comprises a polyester resin having an unsaturation between 25 and 100 mole percent based on the total acid and anhydride monomer content, and at least one of the part A or the part B contains thermoplastic microellipsoids; Apply the mixture to the substrate of the vehicle body to be repaired; Expose the mixture either alone to environmental conditions or in combination with a heat source to promote curing of the mixture; and Cure the mixture to form a filler for repairing the vehicle body.

14. The method according to claim 13, wherein the curing occurs within 60 minutes of forming the mixture.

15. The method according to claim 13, the method further comprising sanding the filler.

16. The method according to claim 15, wherein the sanding occurs within 30 minutes of forming the mixture.

17. The method according to claim 13, wherein the heat source is present and is an infrared lamp.

18. The method according to claim 13, wherein the exposure raises the temperature of the mixture to a temperature between 37 °C and 82 °C.

19. A vehicle body repair formulation, comprising: A polyester resin having an unsaturation between 25 and 100 mole percent based on the total acid and anhydride monomer content; A monomer reactive diluent in which the polyester resin is dissolved or suspended; Thermoplastic microellipsoids; and An initiator package, wherein the monomer reactive diluent consists only of vinyltoluene.

20. A vehicle body repair formulation for strongly adhering to metal substrates present on vehicle body panels and bumpers, comprising: A polyester resin having an unsaturation between 25 and 100 mole percent based on the total acid and anhydride monomer content; A monomer reactive diluent in which the polyester resin is dissolved or suspended; Thermoplastic microellipsoids; and An initiator package.

21. A method for repairing a vehicle body, comprising: Mix a polyester resin formulation part A with a part B initiator package to form a curable mixture, wherein the part A comprises a polyester resin having an unsaturation between 25 and 100 mole percent based on the total acid and anhydride monomer content, and at least one of the part A or the part B contains thermoplastic microellipsoids; Apply the mixture to the metal substrate of the vehicle body to be repaired; Expose the mixture either alone to environmental conditions or in combination with a heat source to promote curing of the mixture; and Cure the mixture to form a filler for repairing the vehicle body.

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