WO2019023301A1

WO2019023301A1 - Powder primeable thermoset resins and articles formed therefrom

Info

Publication number: WO2019023301A1
Application number: PCT/US2018/043608
Authority: WO
Inventors: James Hutchinson; Michael J. HILTUNEN; Michael J. Siwajek
Original assignee: Continental Structural Plastics, Inc.
Priority date: 2017-07-27
Filing date: 2018-07-25
Publication date: 2019-01-31

Abstract

A conductive molding compound is provided that is amenable to receiving a highly uniform automotive surface skin quality surface gloss paint coating via electrostatic painting techniques without resort to a conductive priming step. A low density molding compound formulation is provided that includes a thermoset cross-linkable unsaturated polyester, a low profile additive package containing a maleic anhydride copolymer, microspheroids, and an amount of between 0.3 and 3 weight percent of the formulation exclusive of fiber filler of high surface area conductive carbon black particulate. The carbon black is dispersed in at least one of the unsaturated polyester and the low profile additive to produce a cured panel having a surface resistivity value of between 1x105Ω and 1x108Ω, and a Diffracto analysis D number of less than 100 when cured against a mold platen having a Diffracto analysis D number of 25. A process for producing a panel is provided.

Description

POWDER PRIMEABLE THERMOSET RESINS AND ARTICLES FORMED

THEREFROM

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority of United States Provisional Patent Application Serial No. 62/537,852 filed July 27, 2017, which is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention in general relates to electrically conductive polyester molding compound and methods of forming the same and in particular to dispersion of conducting particulate in the curable unsaturated polyester resin component of a molding compound containing a maleic anhydride copolymer as part of a low profile additive package to provide a high gloss article amenable to powder priming to enhance uniform paint coating receipt to achieve a surface finish suitable for automotive skin panels.

BACKGROUND OF THE INVENTION

[0003] Electrostatic painting of various vehicle components presents an attractive and cost effective scheme as compared to usage of a conventional paint line. Electrostatic painting of vehicle parts, such as doors, hoods, quarter panels, and other vehicle skin parts can be routinely performed. Owing to the high visibility and environmental exposure encountered by such vehicle parts, a high quality paint finish surface is demanded with a high degree of reflectivity and a surface free of visual defects. Electrostatic painting requires the part to be electrically conductive and support an electrical potential on the part needed to attract oppositely charged paint aerosol droplets to the part. Early attempts at producing inexpensive molding compound components amenable to electrostatic painting involved the application of an electrically conductive primer. With the primer application adding considerable cost and the primer application defects being manifest in the resulting painted article. As a result, these previous attempts to make sheet molding compound conductive articles were relegated to vehicle portions other than the vehicle skin, such as radiator brackets and wheel wells.

[0004] The development of an inherently conductive sheet molding compound obviates the need for the application of a conductive primer coat. Such a conductive sheet molding compound (SMC) is detailed in U.S. Pat. No. 6,001 ,919. As tolerances for the acceptable amount of SMC article shrinkage relative to mold specifications decreases, as well as increased demands as to painted surface finish attributes, low profile additives are increasingly found in SMC. Representative of these high-performance SMC formulations inclusive of low profile additives are those currently marketed by Continental Structural Plastics under the trade name TCA®. The inclusion of low profile additives is compatible with a conductive particulate to render an SMC article amenable to electrostatic painting, however, the inclusion of loadings of conductive particulate necessary to make an article sufficiently conductive, modifies the flow properties of the molding compound resins, leading to inhomogeneous molded articles, degrades the surface finish, and the higher viscosity forces molding filling conditions that degrade the conductivity of a given volume of conductive filler. While US 7,655,297 details a formulation that achieves automotive surface high gloss finishes, however, with low density formulations loaded with glass hollow microspheroids surface finish degrades with the inclusion of conducting particulate.

[0005] Thus, there exists a need for a molding compound composition that is conductive to provide a high quality paint finish provided through electrostatic painting that has handling properties allowing mold filling without damaging the delicate structure of high surface area conductive particles.

SUMMARY OF THE INVENTION

[0006] A conductive molding compound is provided that is amenable to receiving a highly uniform automotive surface skin quality surface gloss paint coating via electrostatic painting techniques without resort to a conductive priming step. A low density molding compound formulation is provided that includes a thermoset cross-linkable unsaturated polyester, a low profile additive package containing a maleic anhydride copolymer, microspheroids, and an amount of between 0.3 and 3 weight percent of the formulation exclusive of fiber filler of high surface area conductive carbon black particulate. The carbon black is dispersed in at least one of the unsaturated polyester and the low profile additive to produce a cured panel having a surface resistivity value of between 1χ10⁵Ω and 1χ10⁸Ω, and a Diffracto analysis D number of less than 100 when cured against a mold platen having a Diffracto analysis D number of 25.

[0007] A process for producing a finished panel with the conductive molding a panel is provided. The molding compound formulation is cured into a shape and a surface having a surface resistivity. A paint coating is applied to the surface to yield a surface finish. The surface finish being of a highly uniform automotive surface skin quality.

DESCRIPTION OF THE INVENTION

[0008] The present invention has utility as a conductive molding compound amenable to receiving a highly uniform paint coating via electrostatic painting techniques. A low density molding compound formulation is provided that includes a thermoset cross-linkable unsaturated polyester, a low profile additive package containing a maleic anhydride copolymer, microspheroids, and an amount of between 0.3 and 3 weight percent of the formulation exclusive of fiber filler of high surface area conductive carbon black particulate. The carbon black is dispersed in at least one of the unsaturated polyester and the low profile additive to produce a cured panel having a surface resistivity value of between 1χ10⁵Ω and 1χ10⁸Ω, and a Diffracto analysis D number of less than 100 when cured against a mold platen having a Diffracto analysis D number of 25. A process for producing such a molding compound panel includes mixing through rotary mechanical stirring the high surface area conductive carbon black particulate into one side of the molding compound formulation under conditions that satisfy: ln(viscosity)≤-0.82{ln(RPM) 1+12.734 (I) where viscosity is in Centipoise and RPM denotes revolutions per minute. Upon combining the side with other sides of the molding compound formulation and fiber filler, a fully formulated molding compound is obtained. Flowing the fully formulated molding compound having a molding viscosity, of between 30 and 50 million Centipoise is especially desirous, into the panel mold and curing the unsaturated polyester yields the panel having a surface resistivity of less than 1χ10⁸Ω and a Diffracto analysis D number of less than 100 when the mold platen having a Diffracto analysis D number of 25. The resulting panel is amenable to direct electrostatic painting without resort to a conductive priming step to achieve an automotive surface skin quality surface gloss on an overpainted article produced according to the present invention.

[0009] As used herein, "molding compound" refers to both sheet molding compound (SMC) and bulk molding compound (BMC).

[0010] As used herein, "panel" refers to planar and three dimensionally contours articles and especially those formed as vehicle skin parts.

[0011] The present invention achieves superior paint finish properties to a panel molded from a conductive molding compound through the recognition that controlling the viscosity of molding compound components is essential to retain the conductivity properties of high surface area conductive carbon black particulate. Accordingly, the distribution of high surface area conductive carbon black particulate occurs within a molding compound portion such that the mixing into that portion satisfies the expression (I): ln(viscosity)≤-0.82{ln(RPM) 1+12.734 (I) where viscosity is in Centipoise and RPM denotes revolutions per minute of the component side to which the high surface area conductive carbon black particulate is added. To assure the radiative structures of the high surface area conductive carbon black particulate are maintained a fully formulated molding compound has a molding viscosity in the range of 30 to 50 million Centipoise.

[0012] In certain inventive embodiments, the high surface area conductive carbon black particulate is dispersed in liquid unsaturated polyester resin of a molding compound that is segregated from the resin A side components of the molding compound to avoid exceeding the conditions of expression (I). It is appreciated that high surface area conductive carbon black particulate is added to other components of a molding compound other than or in combination with the unsaturated polyester resin so long as expression (I) is satisfied and the molding viscosity is maintained in the range of 30 to 50 million Centipoise. Representative are other liquid bases amenable to receiving as a dispersal high surface area conductive carbon black particulate low profile additive and unsaturated monomer components. As used herein, "the total weight percent" is intended to define a fully loaded molding compound inclusive of fillers and fibers.

[0013] As used herein, "unsaturated" refers to covalent bond attachment to the carbon atoms of a carbon-carbon bond being less than a maximal complement of bonding carbon or hydrogen atoms, namely the carbon-carbon bond is a double or triple bond.

[0014] A base conductive SMC formulation that benefits from incorporation of conductive particulate into the low profile additive phase includes a wide variety of thermoset, and thermoplastic SMC components. While a variety of base SMC formulations are known such as those described in U.S. Pat. Nos. 4,260,538; 4,643,126; 5,100,935; 5,268,400; 5,854,317; 6,001,919; and 6,780,923; and all of these formulation benefit from the inventive process of high surface area conductive carbon black particulate dispersion, a new formulation is required to attain the maximal benefits of the present invention as to molded panel conductivity and surface finish. The typical amounts of components in an inventive composition are provided below in Table 1 ; however, to achieve a satisfactory degree of low surface resistivity of less than or equal to lxl0⁹ Ohms (Ω/sq) and preferably between lxl0⁵ Q/sq and lxl0⁸ Q/sq simultaneous with a surface finish to a molded panel having Diffracto analysis D number of less than 100 when the panel is cured against a mold platen having a surface with a Diffracto analysis D number of 25, dispersing the high surface area conductive carbon black particulate dispersion must satisfy expression (I) and yield a molding viscosity of between 30 and 50 million Centipoise. This is accomplished with a quantities of carbon black of between 0.3 and 3 composition weight percent exclusive of fiber filler and preferably with between 0.4 and 1 composition weight percent exclusive of fiber filler. Accordingly, Table 2 shows the segregation of components between A, B, C, and D sides to achieve a high performance molding compound.

[0015] The required degree of surface resistance in an automotive skin panel is dependent more on the shear forces that high surface area conductive carbon black particulate dispersion is exposed to during molding compound mixing and molding as compared to total quantity of the high surface area conductive carbon black particulate dispersion present. Without intending to be bound by a particular theory, damage to the dendritic and other structures extending from high surface area conductive carbon black particulate lessens the effective electrically conductivity diameter of a particle thereby increasing the effective separation distance between such high surface area conductive carbon black particles. [0016] Table 1. Components as Percentages of Fully Formulated Inventive Molding Compound

Preferred

Typical Total

Total

Weight

Weight Percent

Percent

Reactants

Cross-linkable unsaturated polyester 6-60 8-40

prepolymer

Ethylenically unsaturated monomer 4-50 6-30

(e.g. styrene)

Reaction Kinetic Modifiers

Free radical initiation (e.g. peroxide/ 0-3 0.1 -1

peroxy ketals, or azo cmpds)

Polymerization inhibitor (e.g., 0-2 0.1 -1

hydroquinone)

Additives

Mold release (e.g., stearate additive) 0-5 0.2-1

Plasticizer 0-3 0.1 -0.5

Flame retardant 0-3 0.1 -0.7

Thickeners 0-5 0.5-2.5

Colorants 0-3 0.1 -1

Fillers

Particulate filler (e.g., calcium

0-80 15-50

carbonate

or alumina)

Glass microspheroids 2-20 5-15

Fiber fillers (e.g., glass) 0-80 5-60

high surface area conductive carbon 0.3-1 .4 0.4-0.8

black particulate dispersion

Low Profile Additive (LPA) Package

Total amount 5-40 7-20

Maleated copolymer 0.1 -8 1 -3

Ethlyeneically saturated polyester 0-20 2-15

Polyvinyl acetate (PVAc) 0.1 -20 1 -4

Copolymers of polyvinyl acetate

Styrene Butadiene rubber 0.1 -20 1 -4

Polystyrene 0.1 -20 1 -4 [0017] Table 2. Distribution of conductive particulate among MC composition (components in parts per hundred with the exception of fiber filler)

Typical parts per Preferred hundred (phr) phr

A side

Saturated polyester 5-50 20-40 Ethylenically unsaturated monomer 2-25 3-15 (e.g. styrene, divinyl benzene, etc.)

Stryrene butadiene rubber (LPA) 0.1 -15 2-8 Polystyrene (LPA) 0.1 -15 2-8 PVAc (LPA) 0.1 -15 1 -6

Maleated copolymer (LPA) 0.1 -8 1 -3 Free radical initiation (e.g., 0.1 -2.0 0.5-1.5 peroxide/peroxy ketals, or azo cmpds)

Polymerization inhibitor (e.g., 0.1 -2.0 0.5-1.5 hydroquinone)

Mold release (e.g., stearate additive) 0-5 0.5-2.5

Flame retardant 0-5 0.5-2.5

Colorants 0-5 0.5-2.5

Particulate filler/microsheroids (e.g., calcium carbonate 0-350 100-250 Alumina, hollow glass microspheres)

B side

3-10 (0.5- saturated polyester + (alkali earth oxide 1 -15 (0.1 -3)

1.5) or hydroxide thickener)

C side

Isocyanate terminated polyurethane 0-20 2-14 D side

Curable ethylenically unsaturated 30-140 40-120 polyester resin

unsaturated monomer 0.5-20 1 -15

High Surface area carbon 0.8-13.0 1.4-4.0

(dispersed in resin)

Fiber reinforcement

Fiber fillers (e.g., glass) 0-40 total 25-35 SMC wt percent 5-40 BMC [0018] A principal component of a mold compound formulation is an unsaturated polyester resin cross-linkable polymer resin. The prepolymer polymeric resin has a molecular weight on average of typically between 400 and 100,000 Daltons. The polyester prepolymer resins typically represent condensation products derived from the condensation of unsaturated dibasic acids and/or anhydrides with polyols. It is appreciated that the saturated di- or poly-acids are also part of the condensation process to form polyester prepolymers with a lesser equivalency of reactive ethylenic unsaturation sites. Unsaturated polyester resins disclosed in U.S. Pat. No. 6,780,923 are preferred for use with the present invention, however these polyester resins in contrast to the prior art are separated, along with an optional portion of viscosity reducing athletically unsaturated monomer to form a side D in which high surface area conductive carbon black particulate is dispersed to satisfy the mechanical mixing requirements of expression (I).

[0019] The polymeric resin prepolymer is suspended, and preferably dissolved, in an ethylenically unsaturated monomer that copolymerizes with the resin during the thermoset process. It is appreciated that more than one type of monomer can be used in a molding compound. The monomer provides benefits including lower prepolymer viscosity and thermosetting without formation of a volatile byproduct. Ethylenically unsaturated monomer operative herein illustratively includes styrene, alpha-methylstyrene, vinyltoluene, chlorostyrene, (meth)acrylic acid, alkyl (methyl)acrylates, acrylonitrile, vinyl acetate, allyl acetate, triallyl cyanurate, triallyl isocyanurate, and acrylamide. Styrene and methyl methacrylate are especially preferred. A normally solid polymerizable monomer such as diacetone acrylamide is optionally used as a solution in one of the above- recited normally liquid polymerizable monomer.

[0020] A typical molding compound includes a free radical initiator to initiate cross-linking between the polymeric prepolymer resin with itself or with ethylenically unsaturated monomer, if present. A free radical initiator is typically chosen to preclude significant cross-linking at lower temperature so as to control the thermoset conditions. Conventional free radical polymerization initiators contain either a peroxide or azo group. Peroxides operative herein illustratively include benzoyl peroxide, cyclohexanone peroxide, ditertiary butyl peroxide, dicumyl peroxide, tertiary butyl perbenzoate and l,l-bis(t-butyl peroxy) 3,3,5- trimethylcyclohexane. Azo species operative herein illustratively include azobisisobutyronitrile and t-butylazoisobutyronitrile. While the quantity of free radical polymerization initiator present varies with factors such as desired thermoset temperature and decomposition thermodynamics, an initiator is typically present from 0.1 to 3 total weight percent. In order to lessen cross-linking at temperatures below the desired thermoset temperature, a polymerization inhibitor is often included in base molding formulations. Hydroquinone and t-butyl catechol are conventional inhibitors. An inhibitor is typically present between 0 and 1 total weight percent.

[0021] The inventive molding compound preferably includes a nonconductive particulate filler. Non-conductive particulate fillers operative in such molding compounds illustratively include hollow glass microspheroids, calcium carbonate, calcium silicate, alumina, alumina trihydrate (ATH), silica, talcs, dolomite, vermiculite, diatomaceous earth, kaolin clay, and combinations thereof. Factors relevant in the choice of a particulate filler illustratively include filler cost, resultant viscosity of flow properties, resultant shrinkage, surface finish weight, flammability, and chemical resistance of the thermoset formulation. Typical filler sizes are from 0.1 to 50 microns. It is appreciated that glass microspheres are preferable surface derivatized in applications where high performance is required. Surface derivatized microspheroids are detailed in US 7,700,670; and US Patent Publication 20150376350 Al.

[0022] In some inventive embodiments, the surface activating agent molecules covalently bonded to the microspheroid surface have a terminal reactive moiety adapted to bond to a surrounding resin matrix during cure. Without intending to be bound to a particular theory, covalent bonding between a cured resin matrix and the microspheroid increases the delamination strength of the resulting SMC or BMC in tests such as ASTM D3359. As used herein, the weight percent of a microspheroid covalently bonded to a surface activating agent is intended to include the weight of the surface activating agent.

[0023] A terminal reactive moiety that is reactive with an SMC or BMC resin during cure illustratively includes a tertiary amine-; hydro xyl-; imine-; an ethylenic unsaturation, such as an allyl- or acryl-; or cyano-moiety. It is appreciated that matrix cure can occur through mechanisms such as free radical cure, moisture cure, and combinations thereof.

[0024] Tertiary amine terminated thermoplastic are readily prepared. D. H. Richards, D. M. Service, and M. J. Stewart, Br. Polym. J. 16, 117 (1984). A representative tertiary amine terminated thermoplastic is commercially available under the trade name ATBN 1300 X 21 from Noveon. [0025] A surface activating agent molecule that bonds to a glass microspheroid is an alkoxysilane where the silane is reactive with the silica surface of the microspheroid. Representative alkoxysilane surface activating agents for the microspheroid illustratively include: 3-aminopropyltrimethoxysilane, 3- aminopropyltriethoxysilane,

3 -glycidoxypropyltrimethoxysilane, 3 -glycidoxypropyltriethoxysilane,

(3-glycidoxypropyl) bis(trimethylsiloxy)methylsilane, (3- glycidoxypropyl)methyldiethoxysilane, (3-glycidoxypropyl) dimethylethoxysilane,

(3-glycidoxypropyl)methyldimethoxysilane,

methacryloxymethyltriethoxysilane,

methacryloxymethyltrimethoxysilane,

methacryloxypropyldimethylethoxysilane,

methacryloxypropyldimethylmethoxysilane, methacryloxypropyltrimethoxysilane ethacryloxypropylmethyldimethoxysilane,

methacryloxypropyltriethoxysilane, methoxymethyltrimethylsilane, 3- methoxypropyltrimethoxysilane, 3-methacryloxypropyldimethylchlorosilane, methacryloxypropylmethyldichlorosilane, methacryloxypropyltrichlorosilane, 3 - isocyanatopropyldimethylchlorosilane, 3-isocyanatopropyltriethoxysilane, bis(3-triethoxysilylpropyl)tetrasulfide, and combinations thereof. In certain inventive embodiments, the alkoxysilane surface activating agent includes an ethylenically unsaturated moiety that is reactive under free radical cross-linking conditions so as to covalently bond the microspheroid surface to the surrounding resin matrix. [0026] Alternatively, it is appreciated that microspheroid surface activating agent is readily mixed into the pre-cured SMC or BMC formulation and hollow glass microspheres added thereto to induce microsphere activation prior to initiation of matrix cure. Typically, the surface activating agent is present in concentrations of about 0.05 to 0.5 grams of surface activating agent per gram of microspheroids.

[0027] A fiber filler is typically added to provide strength relative to a particulate filler. Fiber fillers operative herein illustratively include glass, carbon, polyimides, polyesters, polyamides, and natural fibers such as cotton, silk, and hemp. Preferably, the fiber filler is glass fiber in the form of chopped glass strands. More preferably, chopped glass strands are provided in lengths ranging from 5 to 50 millimeters.

[0028] A mold release agent is typically provided to promote mold release. Mold releases include fatty acid salts illustratively including oleates-, palmitates-, stearates- of metal ions such as sodium, zinc, calcium, magnesium, and lithium. A mold release is typically present from 0 to 5 total weight percent.

[0029] A low profile additive is optionally provided to improve surface properties and dimensional stability of a resulting molded product. In contrast to US 7,655,297; low profile additives of polyethylene, polyacrylates are preferential replaced entirely or at least 50% by weight is with LPAs that illustratively include thermoplastics such as polystyrene, polycarbonate, or combinations thereof; and copolymers including butadiene, acrylonitrile, and vinyl chloride and specifically include styrene butadiene rubbers. Preferably, a mixture of thermoplastic and elastomeric LPAs are present. It is appreciated that the present invention optionally also incorporates additional additives illustratively including flame retardants, plasticizers, colorants, and other processing additives conventional to the art.

[0030] A maleated polymer is present in an inventive composition as part of the LPA package and is characterized by a graft polymer in which maleic anhydride is graft copolymerized with a polymer. Maleated polymers operative in the present invention illustratively include a maleic anhydride grafted copolymer of styrene, polypropylene, maleated polyethylene, maleated copolymers or terpolymers of propylene containing acrylate and maleate, maleic anhydride grafted polystyrene, and combinations thereof. In some inventive embodiments, the degree of maleation is between 0.1 and 5 maleic anhydride content as weight percent of the maleated polymer. In other inventive embodiments, the degree of maleation is between 1 and 4 weight percent of the maleated polymer and most preferably between 1 and 2 weight percent. Typically, a maleated polymer is present in an inventive formulation in an amount of between 0.1 and 8 total weight percent and preferably between 1 and 3 total weight percent.

[0031] For molding compounds of the present invention to be well suited for the rapid production of molded composite articles that have a high gloss finish as measured by ASTM D523 inclusive of an electrostatic paint coating, a high surface area conductive carbon black particulate is mixed into a single side or multiple side of a compound formulation under conditions that satisfy expression (I) and upon mixing all the side and fiber filler results in a molding viscosity of between 30 and 50 million Centipoise.

[0032] According to an inventive process, the total quantity of high surface area conductive carbon black particulate needed to form an electrostatically paintable molding compound panel is determined based on factors such as particle dimensions, intrinsic conductivity, and particle surface area. It is appreciated that high surface area conductive carbon black particulate loadings while essential to the electrostatic properties of the resulting articles tend to increase the viscosity of the fully formulated molding composition and compensating for this viscosity increase by reducing other fillers tends to decrease the physical performance characteristics of the resulting panel.

[0033] The high surface area conductive carbon black particulate fillers operative herein have high surface area of greater than 500 meters squared per gram and specifically excludes acetylenic carbon black that common to the art. Illustrative high surface area conductive carbon blacks include Ketjen EC 300J, Ketjen EC 600 J (Akzo Nobel) Black Pearls 2000 (Cabot), Vulcan XC 72R (Cabot), Denlca Black, Denka Black AB 18 (Denko Kogyo) and those disclosed in WO/2007/013678.

[0034] The isocyanate terminated urethane is operative as a thickener and becomes covalently bonded to the polyester resin matrix of the polyester resin product. The isocyanate terminated urethane prepolymer of the present invention is made in a one-step process and has an NCO/OH ratio of approximately 1.2/1 to approximately 5/1, and preferably an NCO/OH ratio of 1.8 to 3 and is made by combining one equivalent of a polyol, preferably polyether polyol having a molecular weight of approximately 600 to 4,000 and a functionality of approximately 2 to 6, and preferably 2 to 3, and most preferably 2, with two equivalents of a polyisocyanate and preferably a di-isocyanate and 0 to 1 % of any conventional urethane catalyst, such as stannous octoate, dibutyltin dilaurate (and the like). Such isocyanate terminated urethanes are known to the art as exemplified in U.S. Pat. No. 4,535,110.

[0035] The present invention is particularly well suited for the production of a variety of panel products illustratively including bumper beams, fenders, vehicle door panel components, automotive floor components, spoilers and hoods; and various industrial and consumer product housings.

[0036] The present invention is further detailed with respect to the following non- limiting examples. These examples are not intended to limit the scope of the appended claims.

EXAMPLES

Control

[0037] To test the properties of the present invention, SMC formulas were prepared by mixing an A-side paste, a filler, a B-side solution, an isocyanate- terminated urethane prepolymer, and 1 " chopped glass fiber according to the following recipe: A-side Paste Components (by phr): 26 low profile additive, 1.5 divinylbenzene, 4.5 styrene, 4 styrene butadiene rubber, 3.5 polyvinyl acetate solution polyester, polymethylmetaacrylate, 1.5 viscosity reducer, 1.04 p- benzoquinone inhibitor, 1.5 stearic acid 2.2 catalyst, 2.5 mold release agent, and 200 calcium carbonate filler.

[0038] B-side solution (by phr): 5.2 magnesium oxide dispersion (25% by wt.) in saturated polyester.

[0039] C-side solution (by phr): 8 isocyanate-terminated urethane [0040] D-side solution (by phr): 70 curable unsaturated polyester, 5 styrene, and containing 1.9 800 square meters per gram of conductive carbon black particulate mixed tlierein with mechanical stirring to maintain the natural log, In of the viscosity, ln(viscosity)<-0.8193 (ln(RPM) throughout the dispersion process.

[0041] 27.50% by total weight 1 " chopped glass fiber and 6 total weight percent of 3-isocyanatopropyltriethoxysilane surface modified 16 micron hollow glass microspheroids are combined with sides A-D resulting in a molding viscosity of 38 million Centipoise. A total of 0.45% carbon black particulate of is present. Upon cure of to form a 10 centimeter square flat planar panel through contact with a mold platen having a Diffracto analysis D number of 25, a panel was obtained having a Diffracto analysis D number of 95. The surface resistivity of this panel had an average value of 1.13xl0⁶ Q/sq with a small variation across an array of 35 equally spaced radially points.

Example 1.

[0042] Surface finish visual evaluations of applied paint were conducted on panels formed using embodiments of the inventive formulations. Table 3 provides a summary of the sample formulations for the panels used in the surface finish visual evaluations relative to the Control were portions not detailed below are the same as the Control.

[0043] Table 3. Inventive test formulations

Styrene butadiene Polyvinyl acetate

rubber (SBR) 39.87 2,472 (PVAc) 7.97 494

Divinyl benzene

(63.5% in diluent) 2.27 141 Polystyrene (PS) 7.97 494

Styrene butadiene

Styrene 5.83 361 rubber 23.92 1,483

Divinyl benzene

Saturated polyester 7.35 456 (63.5% in diluent) 2.27 141

Dispersant 2.03 126 Styrene 8.05 499

Dibutylhydroxytoluene 0.04 2.48 Saturated polyester 7.35 456

Catalyst 1.52 94 Dispersant 2.03 126

Cure inhibitor 0.08 4.96 Dibutylhydroxytoluene 0.04 2.48

Water 0.58 36 Catalyst 1.52 94

Myristic acid 1.43 89 Cure inhibitor 0.08 4.96

Calcium Stearate 1.56 97 Water 0.58 36

Glass microspheres 35.61 2,208 Myristic acid 1.43 89

CaC0₃ 27.47 1,703 Calcium Stearate 1.56 97

A-SIDE TOTAL 177.67 11 ,016 Glass microspheres 35.61 2,208

CaC0₃ 27.47 1,703

Styrene/Maleic acid

B-side 5.85 362.70 copolymer 2.67 165

Carbon black 5.81 360.22

Acid group free

polyester resin 0.04 2.48 A-SIDE TOTAL 182.55 11 ,318

B-side 5.85 362.70

Carbon black 5.81 360.22

Acid group free

polyester resin 0.04 2.48

[0044] Table 4 is a table summarizing prior art Hansen polarity and hydrogen bonding values for various thermoplastics and elastomeric low profile additives.

[0045] Table 4. Conventional Hansen Polarity and hydrogen bond values for various thermoplastic and elastomeric low profile additives.

PS 5.8 4.3

PM MA 10.1 5.4

PVAc 11.3 9.7

PE 17.4 4.2

approximate values

[0046] Table 5 is a key providing definitions used for abbreviations used in the example tables to follow.

[0047] Table 5. Abbreviation Key

Key

Brad Rating Visual rating - higher is better

LTW Diffracto - long term waviness - lower is better

STW Diffracto - short term waviness - higher is better

SMA Styrene maleic anhydride variant

WA 24 hour water absorption mean

GM G M composite Wavescan

Ford Ford composite Wavescan

[0048] Table 6 provides means of surface values for the sample formulations.

[0049] Table 6. Surface Value Means

Emb Emb

Method Value Control Metal

1 2

Visual Brad Rating N/A 8.7 9.0 10.0

Diffracto LTW 17.0 Bad 19.8 N/A

Diffracto STW 28.9 Bad 31.6 N/A

Wavescan GM N/A 4.9 5.2 5.5

Wavescan Ford N/A 51.2 52.4 52.0

[0050] Table 7 provides powder capable ratings after powder coat at ACT

[0051] Table 7. Powder Capable Ratings Powder Capable Ratings

Conditioning

time

0 Days 8 Days 10 Days 12 Days 15 days (pre e-coat)

(80F/80%

RH)

Emb 1 Emb 2 Emb 1 Emb2 Emb 1 Emb 2 Emb 1 Emb 2 Emb 1 Emb 2 Metal

1 9 9 9 9 9 9 9 9 10 10 10

2 9 10 9 9 9 9 8 7 10 10 10

3 9 10 9 9 9 9 7 9 9 10 10

4 9 10 9 9 7 9 7 8 9 9 10

5 9 9 9 9 9 9 8 9 9 10 10

6 9 Lost Lost 9 9 9 7 8 9 10 N/A

AVG. 9.0 9.6 9.0 9.0 8.7 9.0 7.7 8.3 9.3 9.8 10.0

Example 2

[0052] Comparisons were conducted on panel formulations using various base materials and subjected to various other factors for use in surface painting evaluations. Table 8 summarizes the material and other factors. The solids content (ratio of polymer to monomer in resin blends) was held constant by varying the level of free monomer added to the formulation. This allowed our total resin PHR and total solids PHR to remain constant.

[0053] Table 8.

Example 3

[0054] Visual ratings for a series of samples at five days, ten days, and 12 days following ten days of conditioning and an applied powder coat are provided in Table 9. 2"x2" x.100" samples submerged in water for 24 hours. Water gain is by weight %. [0055] Table 9. Visual ratings as a function of time in which 10 is a maximal result and percent water

Example 4

[0056] Measurements were obtained of the amount of water gained in a sample formulation as a function of the type of stryenic maleic anhydride (SMA) present. A control of Embodiment 2 lacking SMA was compared to a first grade having a styrene/MA molar ratio of 2:1, a hydrophilic lipophilic balance (HLB) of 16.5 and a molecular weight, Mn of 3000 with a second grade having a styrene/MA molar ratio of 3 :1, HLB of 12.3 and a molecular weight, Mn of 3800, a third maleated polymer based on polybutadiene (PMA) with 5-20% maleic functional and a molecular weight, Mn of 4,700-5,600; each alone along with other additives. The percent water gain was measured as above and the results are summarized in Table 10.

[0057] . Table 10. Percent water gained versus the amount of additive in a SMA or PMA variant sample formulations. Description of additional LPA % water gain

Emb 1 0.194

Emb 2 0.194

Emb 2+14.02 PHR PVAc, 2^nd SMA 0.258

Emb 2+2.66 PHR 3^rd polybutadiene maleate 0.220

Emb 2+2.66 PHRl^st SMA 0.206

Emb 2 +2.66 PHR2^nd SMA 0.176

[0058] Patent documents and publications mentioned in the specification are indicative of the levels of those skilled in the art to which the invention pertains. These documents and publications are incorporated herein by reference to the same extent as if each individual document or publication was specifically and individually incorporated herein by reference.

Claims

1. A molding compound formulation comprising:

a thermoset cross-linkable unsaturated polyester;

a isocyanate terminated polyurethane;

an alkali metal oxide or an alkali metal hydroxide;

hollow glass microspheroids;

a low profile additive package comprising a maleated copolymer; and a high surface area conductive carbon black particulate in an amount of between 0.3 and 3 weight percent of the molding compound formulation exclusive of fiber filler, said high surface area conductive carbon black particulate dispersed in at least one of said unsaturated polyester and said low profile additive to produce a cured panel having a surface resistivity value of between 1χ10⁵Ω and 1χ10⁸Ω, and a Diffracto analysis D number of less than 100 when cured against a mold platen having a Diffracto analysis D number of 25.

2. The formulation of claim 1, wherein said high surface area conductive carbon black particulate has a surface area of greater than 500 square meters per gram.

3. The formulation of claim lwherein said hollow glass microspheroids further comprise a silane surface derivative.

4. The formulation of any one of claims 1 to 3 wherein said hollow glass microspheroids are present from 5 to 15 total weight percent.

5. The formulation of any one of claims 1 to 3 wherein said low profile additive package further comprises polystrene.

6. The formulation of any one of claims 1 to 3 wherein said low profile additive package further comprises styrene-butadiene rubber.

7. The formulation of any one of claims 1 to 3 wherein said low profile additive package further comprises a polyvinyl acetate.

8. The formulation of any one of claims 1 to 3 wherein said low profile additive package is devoid of polyethylene.

9. The formulation of any one of claims 1 to 3 wherein said high surface area conductive carbon black particulate is dispersed only in a side comprising said unsaturated polyester.

10. The formulation of any one of claims 1 to 3 further comprising a water content of less than 0.25 total weight percent.

11. A panel comprising; a cured molding compound formulation of claim 1 having a shape and a surface having the surface resistivity; and

a paint coating applied to the surface to yield a surface finish.

12. The panel of claim 11 wherein the surface finish has a Diffracto analysis D number of less than 100.