WO1993007216A1

WO1993007216A1 - Thermosetting polyester plastic compositions containing blocked polyisocyanate and isocyanate-reactive material

Info

Publication number: WO1993007216A1
Application number: PCT/US1992/008158
Authority: WO
Inventors: Kenneth Earl Atkins; Gary C. Rex
Original assignee: Union Carbide Chemicals & Plastics Technology Corporation
Priority date: 1991-09-30
Filing date: 1992-09-30
Publication date: 1993-04-15
Also published as: EP0559888A1; CA2097330A1; JPH06504087A

Abstract

A thermosetting molding composition which affords molded products having improved strength and surface smoothness, a method for making the same, and products made with the composition. The composition includes a) an unsaturated polyester resin; an olefinically unsaturated monomer; a thermoplastic low profile additive; a reinforcing filler; and additionally includes a blocked polyisocyanate and an isocyanate-reactive material different from the unsaturated polyester resin.

Description

THERMOSETTING POLYESTER PLASTIC COMPOSITIONS

CONTAINING BLOCKED POLYISOCYANATE AND

ISOCYANATE-REACTIVE MATERIAL

This application is a continuation-in-part of Application Serial No. 07/767,498 filed September 30, 1991.

Field of the Invention

This application relates to reinforced thermosetting polyester compositions, and more particularly, to such compositions containing blocked polyisocyanates plus isocyanate-reactive material.

Backαround of the Invention

Reinforced thermosetting polyester-based molding compositions in the form of sheet molding compound (SMC) and bulk molding compound (BMC) have been known for many years. These materials are based on unsaturated polyester resins produced from a reaction between a polyol having at least 2 hydroxyl groups, and a mixture of saturated and unsaturated dicarboxylic acids (or their

anhydrides). The initially formed unsaturated polyester resin is blended with one or more monomers capable of crosslinking with the unsaturated in the polyester, a peroxide catalyst, and a reinforcing material such as fiberglass, then heated to

decompose the peroxide and cause the crosslinking reaction between the monomer and the unsaturation in the polyester molecule to occur. The resulting product is a composite of the reinforcing material and the crosslinked polyester. For many applications, an alkaline

earth-containing thickener such as magnesium oxide is added to the composition before crosslinking is initiated. This is thought to complex with residual carboxyl groups of the polyester molecules, thereby increasing the viscosity of the mixture and aiding achievement of uniform distribution of reinforcing filler as the mixture is caused to flow into its final shape during processing. In addition to the materials mentioned thus far, the molding

compositions also frequently contain various other fillers, mold release agent, and other additives to be discussed below.

A great variety of properties may be achieved in the cured composite by appropriate selection of the identities and amounts of the starting diacids, polyols, crosslinking monomers, catalysts, other additives, etc. used in the

preparation. As a result, these materials have wide applicability in the manufacture of strong

relatively light weight plastic parts.

Historically, molding composite materials based on thermosetting polyester resins suffered from the difficulties that 1) the surfaces of molded parts were poor, and included fiber patterns which required costly sanding operations for painted applications and precluded use of such materials in high appearance internally pigmented applications; 2) parts could not be molded to close tolerances because of warpage; 3) molded parts contained

internal cracks and voids, particularly in thick sections; and 4) molded parts had notable

depressions or "sinks" on surfaces opposite

reinforcing ribs and bosses. The cause of these problems was believed to be a high degree of shrinkage during

copolymerization of the unsaturated polyester resin with the crosslinking monomer. Such shrinkage during the crosslinking reaction causes the polymer to pull away from the surfaces of the mold and the fiberous reinforcements. This reduces accuracy of mold surface reproduction and leaves fiber patterns at the surface of the molded parts. The stresses created by nonuniform shrinkage cause warpage, internal cracks, and poor reproduction of mold dimensions in finished molded parts. It has been shown that curing of typical unsaturated polyester resin results in volumetric shrinkage of

approximately 7%.

The above-discussed difficulties have been addressed in practice by adding certain

thermoplastic materials to the molding composite. The presence of these thermoplastics in the

composition reduces shrinkage of the part during cure, or in some cases causes a small amount of expansion, thereby providing molded parts which more accurately reflect the molds in which they were made, and which have relatively smooth surfaces.

The surface smoothness of a molded part is gauged by measuring its surface profile by means of a suitable surface analyzer. A rough surface exhibits a high surface profile, while a smooth surface exhibits a low surface profile. As the addition of thermoplastic materials to the

polyester-based molding composite results in

smoother surfaces in the molded part, relative to the case without such thermoplastic materials present, these thermoplastics are called "low profile additives".

A number of thermoplastics have been found to give varying levels of shrinkage control.

Examples are:

a) poly(vinyl acetates). See, for

example, US Patents 3,718,714; 4,284,736;

4,288,571; and 3,842,142.

b) polymethylmethacrylates and copolymers with other acrylates. See, for example, US Patents 3,701,748; 3,722,241; 4,463,158; 4,020,036; and 4,161,471.

c) copolymers of vinyl chloride and vinyl acetate. See, for example, US Patents 4,284,736 and 3,721,642.

d) polyurethanes. See, for example, US Patents 4,035,439 and 4,463,158; British Patent 1,451,737; and European Patent 074,746.

e) styrene-butadiene copolymers and other elastomers. See, for example, US Patents 4,042,036; 4,161,471; and 4,160,759.

f) polystyrene and certain copolymers of certain monomers. See, for example, US Patents 3,503,921 and 3,674,893; Netherlands Patent

70-15386; and German Patent 2,252,972.

g) polycaprolactones. See, for example, US Patents 3,549,586 and 3,688,178.

h) cellulose acetate butyrate. See, for example, US Patent 3,642,672.

i) saturated polyesters and various blends of saturated polyesters with poly(vinyl chloride). See, for example, US Patents 3,489,707; 3,736,728; and 4,263,199; Japanese Patent 4,601,783; and

Netherlands Patent 70-14568.

These polymers, when blended in appropriate ratios with unsaturated polyester resins and

comonomers result in shrinkage control under both standard compression and injection molding

conditions. For optimum shrinkage control and hence mold reproduction in particular systems, the

combinations of structures and molecular weights of the unsaturated polyester resin and the

thermoplastic low profile additive are selected on the basis of simple trials.

A wide variety of unsaturated polyester resin structures has been reported in the

literature. The most commonly used polyester resins, however, are those based on the condensation of 1.0 mole of maleic anhydride with a slight excess of propylene glycol, and similar resins in which up to 0.35 moles of the maleic anhydride is replaced with orthophthalic anhydride or isophthalic acid. The comonomer is almost always styrene.

This approach to shrinkage control can also be applied in the case of vinyl ester resins. See for example, US Patent 3,674,893.

Progress in overcoming the above-discussed problems of shrinkage of molded polyester-based composite material during cure has occurred in stages over approximately the past twenty-five years. The successive improvements have been quantified by determining the linear shrinkage of parts and/or measuring their surface smoothness. The first generation of low profile additives were materials such as polystyrene and polyethylene. Molded parts incorporating such additives were found to exhibit shrinkage of about 2 mils per inch (0.2%), in contrast to shrinkages of 4 to 5 mils per inch (0.4-0.5%) found for composites lacking these additives. The resulting composites were found to accept internal pigments well, but the surface quality of the parts was poor and the degree of shrinkage, although improved relative to that of composites containing no low profile additive, was still objectionably high for many applications.

The second generation of low profile additives were acrylic-based polymers such as polymethylmethacrylate, which when employed with specific unsaturated polyester resins prepared by condensation of maleic anhydride with propylene glycol, gave composite materials which exhibited shrinkage of about 0.5 mils per inch (0.05%). These materials were found to have poor pigmentability and poor surface smoothness by current standards.

The third generation of low profile additives were the poly(vinyl acetate) polymers.

Such additives can be used in a wide range of

unsaturated polyester resin materials, and the molded parts exhibit essentially no shrinkage.

Compositions containing poly(vinyl acetate) low profile additives have poor pigmentability, but the molded parts have very good dimensional stability and surface smoothness. As a result, these

materials are widely used. The fourth generation of low profile additives are materials which cause unsaturated polyester resin composite materials containing them to tend to expand slightly during cure, thereby reproducing the surface of the mold with great accuracy. At room temperature, products made with these additives generally are 0.3 to 0.4 mils per inch larger than the room temperature dimensions of the mold. The surface smoothness of parts made with these low profile additives equals or exceeds the smoothness of automotive grade steel.

There are several varieties of fourth generation low profile additives:

1) a poly(vinyl acetate) or other thermoplastic polymer, plus at least one shrinkage control "synergist". Examples of shrinkage control synergists are a) epoxide-containing materials such as epoxidized octyl tallate, b) secondary monomers such as vinyl acetate monomer, which are more reactive with themselves than with styrene, c) mixtures of such epoxides and secondary monomers, d) lactones such as caprolactone, e) siloxane-alkylene oxide polymers, and f) fatty acid esters.

2) certain modified poly(vinyl acetate) polymers which are employed with specially selected unsaturated polyester resins.

3) a standard low profile additive such as poly(vinyl acetate), preferably acid-containing, plus an isocyanate prepolymer resulting from

reaction of a polyether polyol and a diisocyanate, which provides a dual thickening mechanism. Despite the substantial improvements in physical properties which have been achieved in reinforced polyester-based composite materials by use of low profile additives, further improvement in properties such as flexural strength, impact

strength, and surface smoothness are still very desirable. Additives providing one or more of these improvements are the subject of the present

application.

Summary

It has been found that addition of a blocked polyisocyanate and an isocyanate-reactive material to a thermosetting polyester-based molding composition containing a low profile additive results in final molded parts having significantly enhanced strength, particularly flex strength, as well as well as excellent shrinkage control and superior surface smoothness, relative to parts made from such polyester-based molding compositions not containing these additives.

The thermosetting molding composition of the invention comprises an unsaturated polyester, an olefinically unsaturated monomer, a thermoplastic low profile additive, a reinforcing filler, and further includes a blocked polyisocyanate, and an isocyanate-reactive material which is different from the unsaturated polyester employed in the

composition. An example is a material which

contains active hydrogen atoms, such as a polyol.

A process for preparing a reinforced thermoset molded composite includes the steps of preparing the thermosetting molding composition of the invention, forming this composition into a desired shape, and heating the shaped composition to cure it.

Molded articles made using the composition and process of the invention are also aspects of the invention.

Detailed Description

The unsaturated polyesters which are employed in the invention are materials which are well known to the art. Each is the reaction product of a polyol and at least one olefinically

unsaturated dicarboxylic acid or anhydride, and may also include residues of saturated and/or aromatic dicarboxylic acids or anhydrides. The olefinic unsaturation is preferably in the β position

relative to at least one of the carbonyl groups of the dicarboxylic acid or anhydride. The unsaturated polyester typically has a molecular weight in the range of 1,000 to 2,000, and contains residual carboxyl and hydroxyl groups as well as olefinic unsaturation.

Examples of suitable unsaturated

dicarboxcyclic acids and anhydrides useful in preparation of the polyesters are materials such as maleic acid or anhydride, fumaric acid,

tetrahydrophthalic acid or anhydride,

hexachloroendomethylene tetrahydrophthalic anhydride ("chlorendic anhydride"), itaconic acid, citraconic acid, mesaconic acid, and Diels Alder adducts of maleic acid or anhydride with compounds having conjugated olefinic unsaturation, such adducts being exemplified by bicyclo[2.2.1]hept-5-en3-2,3- dicarboxylic anhydride, methyl maleic acid, and itaconic acid. Maleic acid or anhydride and fumaric acid are the most widely used commercially.

Examples of saturated or aromatic dicarboxycyclic acids or anhydrides which may be used in the preparation of the polyesters are materials such as phthalic acid or anhydride, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid or anhydride, adipic acid, isophthalic acid, sebacic acid, succinic acid, and dimerized fatty acids.

Polyols useful in the preparation of the polyesters are materials such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butylene glycols, neopentyl glycol, 1,3- and

1,4-butane diols, 1,5-pentane diol, 1,6-hexanediol, glycerol, 1,1,1-trimethylolpropane, bisphenol A, and hydrogenated bisphenol A. It is also possible to employ the corresponding oxides, such as ethylene oxide and propylene oxide, etc. Generally no more than about 20% of the polyols employed in the

preparation of a polyester are triols.

In addition to the above esters, one may also use dicyclopentadiene-modified unsaturated polyester resins described in U.S. Patents 3,986,922 and 3,883,612.

Another type of unsaturated polyester useful for preparation of polyester-based molding compositions is the group of materials known as vinyl esters. These are reaction products of saturated polyesters possessing secondary hydroxyl functionalities with vinyl group-containing acids or anhydrides such as acrylic acid or methacrylic acid. An example is the reaction product of an epoxy resin based on bis-phenol A with an

unsaturated carboxylic acid such as methacrylic acid. Vinyl esters and their preparation are disclosed in US Patent 3,887,515.

The unsaturated polyester is generally employed in the composition at a level of between 20 and 50%, preferably 36% to 45%, by weight based on the weight of polyester, monomer, and low profile additive employed. In practice, it is usually employed as a 60-65% by weight solution in the olefinically-unsaturated monomer used for

crosslinking.

The olefinically unsaturated monomer employed in the molding composition of the invention is a material which is copolymerizable with the unsaturated ester to cause crosslinking which effects the curing of the polyester. The monomer also serves the function of dissolving the

polyester, thereby facilitating its interaction with the other components of the composition. Sufficient monomer is employed to provide convenient

processing, but a large excess beyond that required is to be avoided since too much monomer may have an adverse effect on properties of the final composite material.

The monomer is generally employed in the composition at a level of between 30 and 70%, preferably 40 to 55%, by weight based on the weight of polyester, monomer, and any low profile additive employed.

By far the most commonly employed olefinically unsaturated monomer is styrene, although other monomers such as vinyl toluene isomers, methyl methacrylate, acrylonitrile, and substituted styrenes like chlorostyrene and

alpha-methyl styrene may also be employed.

Another component of the compositions of the invention is a thermoplastic low profile additive, preferably a ρoly(vinyl acetate).

Suitable vinyl acetate polymer low profile additives are poly(vinyl acetate) homopolymers and

thermoplastic copolymers containing at least 50% by weight of vinyl acetate. Such copolymers include, for example, carboxylated vinyl acetate polymers which are copolymers of vinyl acetate and

ethyleπically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid and the like or anhydrides such as maleic anhydride; vinyl acetate/vinyl chloride/ maleic acid terpolymer, and the like; etc.

Reference is made to US Patents 3,718,714 and

4,284,736, and British Patent 1,361,841 for

descriptions of some suitable vinyl acetate polymer low profile additives.

The useful vinyl acetate polymer low profile additives ordinarily have molecular weights within the range from 10,000 to 250,000, preferably from 25,000 to 175,000. They are usually employed in the composition at a level of 5 to 25 percent by weight, preferably 10 to 20 percent by weight, based on the total weight of polyester resin, low profile additive, and monomer.

Other thermoplastic low profile additives besides poly(vinyl acetate)s should also serve in the compositions of the invention. Examples of such materials are: poly(methyl methacrylate),

polystyrene, polyurethanes, saturated polyesters, and ground polyethylene powder.

Yet another component of the compositions of the invention is a reinforcing filler such as glass fibers or fabrics, carbon fibers and fabrics, asbestos fibers or fabrics, various organic fibers and fabrics such as those made of polypropylene, acrylonitrile/vinyl chloride copolymer, and others known to the art. Such materials are generally employed at a level between 5 and 75 % by weight of the total composition, preferably 15 to 50 % by weight.

Also included in the compositions of the invention is a blocked polyisocyanate, which is generally employed at a level of 1-20 parts per hundred, and preferably 1-10 parts per hundred, based on the total weight of the resin, the monomer, and the low profile additive.

A blocked isocyanate is an adduct of an isocyanate and an isocyanate-reactive material, this adduct being stable at room temperature where processing takes place, but dissociating to regenerate the isocyanate functionality at some temperature above room temperature, usually between 120°C and 250°C.

The regenerated isocyanate is then free to react with compounds containing active hydrogen to form more thermally stable units such as urethane

(hydroxyl+isocyanate) or urea (amine+isocyanate) linkages.

where X = N, O, or S

Examples of polyisocyanates which may be used as starting materials for the blocked

isocyanates which are useful in the compositions of the invention are materials such as tetramethylene diisocyanate, hexamethylene diisocyanate (HMDI), 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, isophorone diisocyanate (IPDI), xylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, and straight or branched urethane polymers

containing multiple isocyanate substituent groups, these polymers being synthesized from a simple polyisocyanate and at least one polyol having at least two active hydrogen atoms. Examples of the latter materials are isocyanate-containing

prepolymers prepared by reaction of a toluene diisocyanate (TDI), or a methylenediphenylene diisocyanate (MDI) or polymeric form thereof

(polymeric MDI), with a polyalkylene oxide diol such as polypropylene oxide diol. Materials having three isocyanate groups may also be employed.

Materials which may be used as blocking groups are compounds having a single active hydrogen atom. Examples of blocking agents for isocyanates are:

phenols; for example, nonyl phenol, resorcinol, cresols, and bisphenol A.

imidazoles; for example, imidazole, 1- or 2- methylimidazole, 4-phenylimidazole, 2,4,5-triphenylimidazole, 2,2'-bis(4,5-dimethylimidazole, and 4 , 5-diphenylimidazole.

pyrazoles; for example, pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole, and

3/ 5-pyrazoledicarboxylic acid.

oximes; for example, 2-butanone oxime, dimethyl glyoxime, cyclohexanone oxime,

p-benzoquinone dioxime, pinonic acid oxime,

benzophenone oxime, and 4-biphenylcarboxaldehyde oxime.

materials having acidic hydrogen attached to carbon, such as acid esters, diketones, and beta-dicarbonyl compounds generally; for example, dialkyl malonates, 2,4-pentanedione, and ethyl acetoacetate. amides; for example, caprolactam.

hydroxamic esters; for example, benzyl methacrylohydroxamate (BMH), and acetohydroxamic acid.

triazoles; for example, benzotriazole, methylbenzotriazole, and 1,2,4-triazole.

alcohols; for example, benzyl alcohol, ethanol, and butanol.

carbodiimides; for example, carbodiimide reacts with isocyanate to form uretonimine.

furazon N-oxides; which react by opening the heterocyclic ring to form isocyanates.

Methods for synthesizing blocked isocyanates are well known to those skilled in the art. Typically, stoichiometrically equivalent amounts of the isocyanate compound and the blocking material are dissolved in separate portions of a suitable solvent, and one is added dropwise to the other with stirring and heating under an inert atmosphere. A catalyst may be employed, but is not always necessary. See, for example, Anagnostou and Jaul, Journal of Coatings Technology, 533 35 (1981); the review articles by Z.W. Wicks in Progress in Organic Coatings, 9, 3 (1981), and 3, 73 (1975) also provide references to the original literature.

The dissociation temperature of a blocked isocyanate is generally a function of the structure of the blocking group, with alcohols > lactams > phenols > oximes > active methylene compounds.

Aromatic blocked isocyanates usually dissociate at lower temperatures than their aliphatic counterparts. Blocked isocyanate compounds have been used in the coatings and related industries for many years. However, most blocked isocyanates have been marketed with solvents present. These solvent- containing materials are not suitable for use in the molding process for fiber reinforced plastic since this process cannot tolerate the presence of

non-reactive solvents.

Blocked isocyanates apparently have seldom been employed in polyester-based plastic

compositions. Several references in which they have been used are discussed below.

U.S. Patent 4,542,177 of Kriek et al.

discloses a thermoplastic polyester molding

composition comprising a blend of a thermoplastic polyester and a prepolymer derived from reaction of an organic polyisocyanate with an organic compound containing at least two isocyanate-reactive groups, this prepolymer containing blocked isocyanate groups. This molding composition is not based on an unsaturated polyester resin, does not employ an olefinically unsaturated monomer or a low profile additive, and does not contain an isocyanate-reactive material as used in the present invention. Products produced using this molding composition are stated to have improved impact performance.

Japanese Kokai Patent No. 57-3819 discloses a thermosetting polyester resin molding composition comprising an unsaturated polyester resin and blocked isocyanate. This molding composition does not include an isocyanate-reactive material

different from the unsaturated polyester resin, and does not necessarily contain low profile additive or reinforcing filler. Products made from the molding composition are stated to have excellent strength.

Japanese Kokai Patent No. 56-155216

discloses thermosetting polyester molding

compositions comprising an unsaturated polyester and a low molecular weight olefinically unsaturated blocked isocyanate crosslinker. Molded products made from the composition are stated to have

improved strength.

The isocyanate-reactive materials which are useful in the thermosetting molding composition of the invention are materials which contain active hydrogen atoms, such as polyether polyols, polyester polyols different from the unsaturated polyester resin (including those derived from polylactones), hydroxyl group-containing vinyl polymers,

amine-terminated polyols, diamines, and polyamines. In these materials primary hydroxyl groups and primary amino groups are preferred. The

isocyanate-reactive materials are employed at levels between 1 and 20 parts per hundred, preferably 1 to 10 pph, based on the total weight of the resin, the monomer, and the low profile additive.

Polyols are the preferred isocyanate-reactive materials. Examples of suitable polyols are: hydroxyl-containing vinyl based polymers such as copolymers of vinyl acetate or other vinyl esters with hydroxyl containing unsaturated monomers, terpolymers of vinyl chloride and vinyl acetate (or other vinyl esters) with hydroxyl containing

unsaturated monomers, and also, hydrolyzed versions of vinyl ester containing polymers; polyester polyols, diols, and triols, such as DEG/adipate, ethylene-butylene/adipate, condensation products of diols with dicarboxylic acids having more than 6 carbon atoms, and lactone polyols such as

polycaprolactones; polyether polyols, diols, and triols, such as polypropylene oxide and ethylene oxide capped PPO (which yields primary hydroxyls); and amine-terminated polyols such as amino

terminated polypropylene oxide or polypropylene oxide/polyethylene oxide polyethers.

The molding compositions of the invention may also contain one or more conventional additives, which are employed for their known purposes in the usual amounts. The following are illustrative of such additives:

1. Polymerization initiators such as t-butyl hydroperoxide, t-butyl perbenzoate, benzoyl peroxide, t-butyl peroctoate, cumene hydroperoxide, methyl ethyl ketone peroxide, and others known to the art, to catalyze the reaction between the olefinically unsaturated monomer and the

olefinically unsaturated polyester. The

polymerization initiator is employed in a

catalytically effective amount, such as from about 0.3 to about 2 to 3 weight percent, based on the total weight of the polyester, monomer, and low profile additive;

2. Fillers such as clay, alumina trihydrate, silica, calcium carbonate, and others known to the art; 3. Mold release agents or lubricants, such as zinc stearate, calcium stearate, and others known to the art; and

4. Rubbers or elastomers such as: a) homopolymers or copolymers of conjugated dienes containing from 4 to 12 carbon atoms per molecule (such as 1,3-butadiene, isoprene, and the like), the polymers having a weight average molecular weight of 30,000 to 400,000 or higher, as described in US Patent 4,020,036; b) epihalohydrin homopolymers, copolymers of two or more epihalohydrin monomers, or a copolymer of an epihalohydrin monomer(s) with an oxide monomer(s) having a number average molecular weight (M_n) which varies from 800 to 50,000 as described in US Patent 4,101,604; c) chloroprene polymers including homopolymers of chloroprene and copolymers of chloroprene with sulfur and/or with at least one copolymerizable organic monomer wherein chloroprene constitutes at least 50 weight percent of the organic monomer make-up of the copolymer, as described in US Patent 4,161,471; d) hydrocarbon polymers including ethylene/propylene dipolymers and copolymers of ethylene/propylene and at least one nonconjugated diene, such as ethylene/propylene/ hexadiene terpolymers and ethylene/propylene/

1,4-hexadiene/norbornadiene, as described in US Patent 4,161,471; e) conjugated diene butyl

elastomers, such as copolymers consisting of from 85 to 99.5 percent by weight of a C₄-C₇ olefin combined with 15 to 0.5 percent by weight of a conjugated multi-olefin having 4 to 14 carbon atoms, and

copolymers of isobutylene and isoprene where a major portion of the isoprene units combined therein have conjugated diene unsaturation, as described in US Patent 4,160,759.

Thickening agents are also frequently employed in the compositions of the invention.

These materials are known in the art, and include the oxides and hydroxides of the metals of Groups I, II, and III of the Periodic Table. Specific

illustrative examples of thickening agents include magnesium oxide, calcium oxide, zinc oxide, barium oxide, calcium hydroxide, magnesium hydroxide, and mixtures thereof. Thickening agents are normally employed in proportions of from about 0.1 to about 6 percent by weight, based on the total weight of the polyester resin, monomer, and low profile additive.

Glossary of Terms and Definitions of Materials

Alumina Trihydrate a commercially-available

filler.

BMC bulk molding compound.

Camel white Calcium carbonate filler

available from GenStar Stone Products.

CaSt calcium stearate.

Desmocap 11a a branched aromatic urethane polymer with ether groups, containing 2.4% blocked NCO content. This is a solid material available from Mobay Corporation. Desmocap 12a a linear aromatic urethane polymer with ether groups, containing 1.7% blocked NCO content. This is a solid material available from

Mobay Corporation.

Gamma Plas Calcium carbonate filler available from Georgia

Marble.

JM 615G 1" fiberglass from Manville

Corp.

LP-40A Acid-modified poly(vinyl acetate), 40% in styrene.

LPS-40AC Solid acid-modified

poly(vinyl acetate).

MDI methylene diphenylene

diisocyanate.

Microthene Cryogenically ground

polyethylene powder

available from USI, Quantum

Corp.

Millicarb Calcium carbonate filler from Omya.

Mod E 5% parabenzoquinone solution in diallyl phthalate.

MR-13017 Isophthalic acid modified polyester resin available from Aristech Chemical, containing about 35 weight percent styrene. MR-13031 Orthophthalic acid modified polyester resin available from Aristech Chemical, containing about 35 weight percent styrene.

Palapreg P-18 Maleic anhydride/propylene glycol polyester resin containing about 35 weight percent styrene and

available from BASF.

PBQ parabenzoquinone.

PDO 50% t-butyl peroctoate

available from Lucidol Corp.

PG-9033 MgO (35% dispersion)

available from Plasticolors,

Inc.

PPG-3029 fiberglass reinforcement

(1/2") from PPG Industries.

SMC sheet molding compound.

tBPB t-butyl perbenzoate.

TONE 0301 polycaprolactone triol

available from Union Carbide

Chemicals and Plastics Co,

Inc.

Trigonox 29B75 a peroxy ketal available

from Akzo Corp.

UCAR^® VYES-4 a terpolymer that contains approximately 29% primary hydroxyls, available from

Union Carbide Chemicals and

Plastics Co., Inc. ZMC unthickened injection

molding compound similar to unthickened BMC, with a glass content of 20% by weight.

ZnSt zinc stearate.

XLP-4022 a 37 weight percent acid

modified poly(vinyl acetate) solution in styrene,

available from Union Carbide Chemicals and Plastics Co., Inc.

Experimental

Procedure for Nonyl Phenol Blocking of an MDI Terminated Polvoxyalkylene Glycol.

Nonyl phenol (I) was obtained as a 99% mixture of monoalkyl phenols. The MDI terminated polyoxyalkylene glycol (II) was obtained as a 75% solution in styrene. The isocyanate content of (II) was determined by the method given by Siggia in

"Quantitative Organic Analysis via Functional

Groups," John Wiley and Sons, 1962, p559. One mole of (I) was taken to react with each mole of

isocyanate present in (II). The quantity of (I) needed to cap all of the isocyanate groups present in (II), where (II) was MDI terminated

polyoxypropylene glycol, was calculated as shown below.

g(I) = g(II) × g isocyanate × 1 g●mole × 220 g●g^-1●mol^-1

100 g(II) 42 g isocyanate Because nonyl phenol is an inhibitor of peroxide initiators found in the molding compound (BMC), g(I) was multiplied by a factor of 0.98 to insure no free nonyl phenol at end of reaction.

A weighed amount of (II) was placed in a three neck reactor of appropriate size, then 100 ppm of parabenzoquinone and 100 ppm of triethylene diamine were added. The reaction mixture was blanketed by a 4% oxygen/96% nitrogen mixture, then heated to 60ºC under constant agitation, and this temperature was maintained throughout the reaction. The phenol (I) was then diluted with styrene to give a 50% solution and added dropwise to the reactor. Beginning at four hours, specimens were taken for determination of free isocyanate content as

referenced above. When the free isocyanate content had dropped to <0.1%, l-butanol was added in slight excess to react with any remaining isocyanate. At 0.0% isocyanate the reactor was cooled and dumped. The product was used as made.

Blocked isocyanates synthesized in this work are discussed below. Each was composed of MDI, nonyl phenol (as the blocker), and varied by the molecular weight of propylene glycol polyol. No free

isocyanate was present due to blocking with nonyl phenol.

Example 1

Preparation of Blocked Isocyanate A

Following the procedure given above, a blocked isocyanate was prepared from a 75% solution in styrene of an isocyanate prepolymer based on MDI and a 2000 molecular weight polypropylene oxide diol. The free NCO content of this prepolymer solution was 2.4 % before blocking.

Example 2

Preparation of Blocked Isocyanate B

Following the procedure above a blocked isocyanate was prepared from a 50% solution in styrene of an isocyanate prepolymer based on MDI and a 2000 molecular weight polypropylene oxide diol. The free NCO content of this prepolymer solution was 0.5% before blocking.

Preparation of the Molding Compositions

The compositions of the invention are prepared by mixing the components in a suitable apparatus such as a Hobart mixer, at temperatures on the order of about 20°C to about 50°C. The

components may be combined in any convenient order. Generally, it is preferable that the thermosetting resin and the low profile additive are added in liquid form by preparing a solution of these

materials in styrene or some other liquid

copolymerizerable monomer. All the liquid

components, including the blocked isocyanate and the isocyanate-reactive material (preferably a primary polyol), are usually mixed together before adding fillers and the thickening agent. The fiberglass is added after the thickening agent. Once formulated. the compositions can be molded into thermoset articles of desired shape, particularly thermoset articles such as automobile body parts. The actual molding cycle will depend upon the particular composition being molded as well as upon the nature of the cured product desired. Suitable molding cycles are conducted on the order of about 100°C to about 182°C for periods of time ranging from about 0.5 minutes to about 5 minutes. This depends on the particular peroxide catalyst employed.

General Recipe for Bulk Molding

Compound (BMC) Compositions

Material PBWW

Unsaturated polyester

(60-65 weight % in styrene) 60

Low profile additive

(33-40% in styrene) 40

Recipe for BMC, continued

Blocked isocyanate 1-10

Reactive coupling material

(e.g., polyol) 2-5

Peroxide catalyst

(t-bu perbenzoate) 1.5

5% pBQ 0.4 Mold release

(zinc stearate) 4

Filler (calcium carbonate) 230

Fiberglass (as a percentage

of the total composition) 15.0 weight percent

* Amounts given in parts per hundred, based on the total weight of the resin, the monomer, and the low profile additive, except as otherwise noted.

General Procedure for Preparation of Bulk Molding

Compound (BMC) Formulations

All the liquid components were weighed individually into a Hobart mixing pan placed on a balance. The pan was attached to a Model C-100 Hobart mixer located in a hood. The agitator was started at slow speed, then increased to maximum speed to completely mix the liquids over a period of 3-5 minutes. The agitator was then stopped and the internal mold release agent was next added to the liquid. The mixer was restarted and the mold release was mixed with the liquid until it was completely wet out. The filler was next added to the pan contents with the agitator off, then mixed using a medium to high speed until a consistent paste was obtained. The mixer was again stopped, a weighed amount of thickening agent was added, and then this was mixed into the paste using a slow to medium speed over a period of 2-3 minutes. The mixer was stopped again and about 175 grams of the paste were removed from the pan using a large spatula, and transferred to a wide-mouth 4 oz bottle. The bottle was capped, and the paste sample was stored in the capped bottle at room temperature and viscosity was measured periodically using a model HBT 5X Brookfield Synchro-Lectric Viscometer on a Helipath.

After removal of the paste sample, the composition was reweighed and styrene loss was made up, and chopped glass fibers were added slowly to the pan with the mixer running on slow speed. The mixer was then run for about 30 seconds after all the glass was in the paste. This short mixing time gave glass wet-out without degradation of the glass. The pan was then removed from the mixer and separate portions of the BMC mix of about 1200 grams each were removed using a spatula and were

transferred to aluminum foil sheets lying on a balance pan. Each portion of the mix was tightly wrapped in the aluminum foil (to prevent loss of styrene via evaporation) and stored at room

temperature until the viscosity of the retained paste sample reached an appropriate molding

viscosity. The weight of the BMC added to the foil varies with the molding application.

General Procedure for Preparation of Sheet Molding

Compound (SMC) Formulations

All the liquid components were weighed individually into a five gallon open top container on a Toledo balance. The contents of the container were then mixed in a hood with a high speed Cowles type dissolver. The agitator was started at a slow speed, then increased to maximum speed to completely mix the liquids over a period of 2-3 minutes. The mold release agent, if one is desired, was next added to the liquids and mixed until completely dispersed. The filler was next added gradually from a tared container until a consistent paste was obtained, and the contents were further mixed to a minimum temperature of 90°F. The thickener, if used, was next mixed into the paste over a period of 2-3 minutes, the mixer was stopped and about 175 grams of paste were removed from the container and transferred to a wide mouth 4 oz bottle. This paste sample was stored in the capped bottle at room temperature and its viscosity was measured

periodically using a model HBT 5X Brookfield

Synchro-Letric Viscometer on a Helopath Stand. The remainder of the paste was next added to the doctor boxes on the SMC machine where it was further combined with fiber glass (about 1 inch fibers). The sheet molding compound (SMC) was then allowed to mature to molding viscosity and was then molded into the desired articles.

Apparatus and Process for Preparation of Molding Test Panels

Flat panels for surface evaluation were molded on a 200 ton Lawton press containing a matched dye set of 18"×l8" chrome plated molds. The female cavity is installed in the bottom and the male portion is at the top. Both molds are

electrically heated and are controlled on separate circuits so that they can be operatded at different temperatures. For the present molding, the top and bottom temperatures were 295-305 °F, 1200g samples of molding compound were employed, and the molded part thickness was 0.120". The molding pressure, which can be varied from 0 to 1000 psi, was run at maximum pressure. The panels were laid on a flat surface, weighted to keep them flat, and allowed to cool overnight. The molded panels were measured with a micro caliper from corner to corner in all four directions to determine shrinkage, which is an average of the four readings. These panels were used for surface smoothness determinations.

Shrinkage Measurement

18"×18"×1/8" flat panels were molded in a highly polished chrome plated matched metal die mold in a 200 ton Lawton press, as described above. The exact dimensions of the four sides of this mold were measured to ten-thousandths of an inch accuracy, at room temperature. The exact lengths of the four sides of the flat molded panels were determined to the same degree of accuracy. These measurements were substituted into the equation below:

(a-b)/a = inch/inch shrinkage where a = the sum of the lengths of the four sides of the mold, and b = the sum of the lengths of the four sides of the molded panels. The shrink control test compares the perimeter of a cold panel to the perimeter of the cold mold. A positive number indicates an expansion and vice-versa for a negative number as compared to the cold mold. The units mil/inch indicate the amount of expansion (+) or contraction (-) in mils per inch of laminate (or panel perimeter).

Evaluation of Surface Smoothness

The faithful reproduction of a reflection of a light grid's 1" × 1" squares on the surface of a molded panel gave a visual picture of the surface smoothness. A quantitative evaluation of surface quality was obtained by comparing two panels

simultaneously and picking the panel with the best reproduction of the reflected squares. This

technique was repeated until the surface of every panel in the series was compared to all other

panels. Surface smoothness was measured as a

frequency, or number of times that a panel was picked as being the best in surface quality.

Therefore, the highest number denotes the best panel; the lowest number, the worst panel.

BMC RESULTS

Bulk molding compositions were prepared with and without Desmocap 11A to test the effects of the presence of a blocked polyisocyanate in such

compositions. The ingredients and their amounts are listed in Table I below. Table I

Effect of Blocked Isocyanate in Bulk Molding Compositions

Component Example Numbers

#3 #4

Palapreg P-18 53 53

LP-40A 42 41

Desmocap 11A x 1

Styrene 5 5 tBPB 1.5 1.5

PDO 0.25 0.25

Mod E 0.4 0.4

Ca St 2 2

Zn St 2 2

Camel white 230 230

PPG-3029 fiberglass, 20% by wt. in each composition

Flexural Properties: #3 #4

Flex Modulus (mpsi) 2.02 1.99

Flex Strength (psi) 12760 15200

Est. Energy at Break (in-lbs) 3.2 4.5

The results shown in Table I demonstrate that a blocked polyisocyanate can lead to an increase in flexural properties of the resulting composite relative to the composite lacking this additive. The control formula, Example #3, gives a laminate about 20% lower in flex strength and about 40% lower in break energy than the material containing blocked isocyanate, Example #4. The greater increase in break versus flex strength reveals that Example #4 not only achieves higher loads but also a greater amount of deflection before failure. Furthermore this improvement was obtained at the relatively low level of 1 phr of additive.

Additional experimental bulk molding compositions were prepared, in which the amounts of the blocked polyisocyanate and styrene monomer were varied, and in one of these trials (Example #8) the additional reactive polyol UCAR VYES-4 was included. The compositional makeup and test results relating to these composites are shown in Table II below.

TABLE II

Blocked Isocyanate Effects

Component Example Numbers

#5 #6 #7 #8 #9

NR-13031 53 53 53 53 53

LP-40A 42.3 42.3 42.3 42.3 42.3

Desmocap 11A x 1.4 2.8 1.4 x

Styrene 4.7 3.3 1.9 0.9 4.7

Table II, continued

UCAR VYES-4 x x x 2.4^a x tBPB 1.5 1.5 1.5 1.5 1.5

PDO 0.25 0.25 0.25 0.25 0.25

Ca St 2 2 2 2 2

2n St 2 2 2 2 2

Millicarb 230 230 230 230 230

PPG-3029 fiberglass 20% by wt.

Flexural Properties: #5 #6 #7 #8 #9

Flex Modulus (mmpsi) 2.38 2.51 2.35 2.53 2.32

Flex Strength (psi) 12960 16280 16370 18600 11510

Est. Energy at Break (in-lbs) 2.8 3.7 4.3 4.2 2.1

Surface Properties: #5 #6 #7 #8 #9

Surface Smoothness (freq) 11 9 12 17 7 Shrink Control (mil/in) -0.041 0.166 0.222 0.166 0.027

a) This material was predissolved in the LP-40A before addition to the formulation. The results shown in Table II are further evidence that a blocked polyisocyanate provides increased flexural strength and break energy. The control materials #5 and #9 containing no blocked polyisocyanate were approximately 33% lower in strength and about 60% lower in break energy than test composites #6 and #7, which contained blocked polyisocyanate. Again, these results were achieved at relatively low levels of blocked polyisocyanate. Example #8, which contained reactive polyol UCAR VYES-4 in addition to blocked polyisocyanate, exhibited an increase in flex strength over the composites of trials #6 and #7.

Table II also includes an evaluation of the surface properties, surface smoothness, and shrink control of the test composites. The blocked

polyisocyanate provided a minor but positive

contribution to shrink control. More noticeably, the addition of reactive polyol UCAR^® VYES-4 in Example #8 substantially improves the surface quality of the composite.

Several test compositions based on a ZMC formulation were prepared, each containing one of two blocked polyisocyanates, and three containing an additional reactive polyol. The styrene level was also varied. These compositions and amounts of ingredients are listed in Table III below. TABLE III

Blocked Isocyanates with Various Polyols

Component Example Numbers

#10 #11 #12 #13 #14

MR-13031 53 53 53 53 53

Table III, continued

LP-40A 42.3 42.3 42.3 42.3 42.3

Desmocap 11A 2.35 x 2.35 2.35 x

Desmocap 12A x Z.35 x x x

UCAR VYES-4^a x x 2.35 x x

TONE 0301 x x x 2.35 x

Styrene 2.35 2.35 x x 4.7 tBPB 1.5 1.5 1.5 1.5 1.5

PDO 0.25 0.25 0.25 0.25 0.25

Mod E 0.4 0.4 0.4 0.4 0.4

Ca St 2 2 2 2 2

Zn St 2 2 2 2 2

Milllicarb 230 230 230 230 230

PPG-3029 fiberglas 20% by weight in all samp!es

Flexural Properties: #10 #11 #12 #13 #14

Flex Modulus (mpsi) 1.85 1.83 1.92 1.54 1.81

Flex Strength (psi) 10850 17340 17150 14420 11260

Est. Energy at Break

(in-lbs) 2.9 6.5 6.5 5.4 3.4

Flex Prop., postbaked: #10 #11 #12 #13 #14

Flex Modulus (mpsi) 1.78 2.1 1.89 1.72 1.89 Flex Strength (psi) 11150 17000 16930 14420 11380 Est. Energy at Break

(in-lbs) 3.1 6.2 6.1 5.7 3.2 Table III, continued

Surface Properties: #10 #11 #12 #13 #14

Surface Smoothness 10 15 22 27 9

(freq.)

Shrink Control (mil/in) 0.263 0.361 0.333 0.374 0.182

a) This material was predissolved in the LP-40A before introduction into the formul ati on.

In Table III the blocked polyisocyanates Desmocap 11A and 12A were evaluated in a polyester resin based ZMC formulation with respect to surface quality, shrink control, and flex properties.

Desmocap 11A was also compounded with polyisocyanate reactive polyols such as UCAR^® VYES-4 and TONE 0301. The control formulation contained LP-40A.

In the surface quality evaluation virtually all of the compositions containing blocked

polyisocyanate outperformed the control composition lacking these additives. Further, the panels that contained the reactive polyols UCAR^® VYES-4 and TONE 0301 had shrink control values >+0.300 and had excellent surface quality with good gloss. These were the best panels of the surface quality

evaluation.

In the flex property evaluation study, the control laminate #14, containing only LP-40A, attained slightly higher than typical BMC flex strength of approximately 11,000 psi and an energy to break of about 3.4 in-lb. Composition #12,

containing both Desmocap 11A and the polyol coupling agent UCAR^® VYES-4, had the highest flex strength and break energy of all the compositions containing

Desmocap 11A, namely, 17,150 psi and 6.5 in-lb, respectively. However, in composition #10, Desmocap 11A alone failed to confirm previous results of a significant increase in flex properties, showing a flex strength of 10,850 psi and an energy at break of 2.9 in-lb. It appears that to obtain a consistent increase in flex performance from a blocked

polyisocyanate the addition of a reactive polyol such as the UCAR^® VYES-4 is required.

To ascertain if there was any residual unreacted polyisocyanate in these laminates they were postbaked at 300°F for 20 minutes. Comparing the flex results of baked versus unbaked laminates, it can be seen that there is very little difference between the two. Therefore, it would appear that most of the blocked polyisocyanate is reacted during the molding step.

Further trial compositions to evaluate the effects of other blocked polyisocyanates in the presence of the primary polyol UCAR^® YVES-4 were prepared in the same manner as those discussed

above. The ingredients and their amounts are listed in Table IV below. TABLE IV

Blocked Isocyanates With a Primary Polyol

Component Example Numbers

#15 #16 #17 #16 #19 #20 #21 #22 #23

MR-13031 53 53 53 53 53 53 53 53 53

LPS-40AC^a 16.8 16.8 16.8 16.8 16.8 16.8 16.8 16.8 16.8

UCAR VYES-4³ 2.3 2.3 2.3 2.3 2.3 2.3 x 2.33 2.3

Styrene^a 23.2 23.2 23.2 25.6 25.6 25.6 30.2 27.9 27.9

Blocked isocyanate A 4.7 x x 2.3 x x x x x

Blocked isocyanate B x 4.7 x x 2.3 x x x x

Desmocap 12A x x 4.7 x x 2.3 x x x tBPB 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

PDO 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25

Ca St 2 2 2 2 2 2 2 2 2

Zn St 2 2 2 2 2 2 2 2 2

Millicarb 230 230 230 230 230 230 230 230 230

PPG-3029 fiberglass 20% by weight in each sample.

Flexural Properties: #15 #16 #17 #18 #19 #20 #21 #22 #23

Flex Modulus (mpsi) 2.8 2.1 1.78 2.05 1.97 1.96 2.1 2.1 1.85

Flex Strength (psi) 17420 17900 13185 18570 20145 16730 14580 12180 11180

Est. Energy at Break

(in-lbs.) 6.9 7.2 5.1 8.1 9.4 6.7 4.5 3.3 3.2

Impact Properties: #15 #16 #17 #18 #19 #20 #21 #22 #23

Unnotched Izod

(in-lb/in) 10.2 10.5 9.1 12 12.2 13.1 8.6 7 9

Notched Izod (in-lb/in) 8.9 10.3 7.3 8.7 7.4 8.8 8.6 7.22 10.2

Surface Propertiesi #15 #16 #17 #18 #19 #20 #21 #22 #23

Surface Smoothness

(freq.) 6 10 12 16 18 12 12 x x

Shrink Control (mil/in) 0.337 0.324 0.445 0.311 0.351 0.405 0.202 0.324 0.216

* Amounts given in parts per hundred, based on the total weight of the resin, the monomer, and the low profile additive, except as otherwise noted,

a) The LPS-40AC, UCAR VES-4, and styrene were predissolved together before

introduction to the formulation.

These experiments indicate that the

synthesized blocked isocyanates perform well when combined with the reactive polyol. The reactive polyol without blocked isocyanate yields poor results.

A sheet molding formulation was made up with and without the blocked polyisocyanate Desmocap 12A and polyol UCAR^® VYES-4 in the manner described above, to test the effects of these additives in sheet molding compositions. The ingredients and amounts are given in Table V below.

TABLE V

Corroborating Evidence in SMC

Example Numbers

#24 #25

MR-13017 63.9 63.9

LP-40A 32.5 36.1

UCAR VYES-4^a 1.8 x

Desmocap 12A 1. 8 x

Styrene 5 5

Trigonox 29B75 1.1 1.1

Mod E 0.3 0.3

Microthene 4 4

Zn St 5.6 5.6

Pigment 14.1 14.1

Alumina Trihydrate 33.3 33.3

Gamma Plas 133.3 133.3

JM 615G, 1" fiberglass 14% by wt. 14% by wt.

PG-9033 1.5 1.5

Flexural Properties: #24 #25

Flex Modulus (mpsi) 1.53 1.35

Flex Modulus (psi) 17950 11300

Est. Energy at Break

(in-lbs) 10.2 5.7

Impact Properties: #24 #25

Notched Izod 10.6 7.6

Unnotched Izod 10.8 9

Amounts given in parts per hundred, based on the total weight of the resin, the monomer, and the low profile additive, except as otherwise noted,

a) This material was predissolved in the LP-40A before introduction into the formulation.

Table V shows the increase in physical properties in sheet molding compound as a result of adding a blocked polyisocyanate and additional polyol to the formulation. Increases of approximately 55% and 75% are seen in flex strength and break energy, respectively, over the LP-40A control. Izod impact results, though not as dramatic, are also higher than the control.

Other embodiments of the invention will be apparent to the skilled in the art from a

consideration of this specification or practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

Claims

We claim:

1. A thermosetting molding composition, comprising:

a) an unsaturated polyester resin;

b) an olefinically unsaturated monomer; c) a thermoplastic low profile additive; d) a reinforcing filler; and further including:

e) a blocked polyisocyanate; and f) an isocyanate-reactive material

different from said unsaturated polyester resin.

2. The molding composition of claim 1, wherein said blocked polyisocyanate is the blocked form of a polyisocyanate selected from the group consisting of tetramethylene diisocyanate, hexamethylene

diisocyanate (HMDI), 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, isophorone diisocyanate (IPDI), xylene diisocyanate, 4,4'-diphenylmethanediisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, and isocyanate-containing prepolymers prepared by reaction of a toluene diisocyanate (TDI) or a methylenediphenylene diisocyanate (MDI) or polymeric form thereof (polymeric MDI) with a

polyalkylene oxide diol.

3. The molding composition of claim 1, wherein said isocyanate-reactive material is selected from the group consisting of polyether polyols, polyester polyols different from said unsaturated polyester resin, hydroxyl group-containing vinyl polymers, amine-terminated polyols, diamines, and polyamines.

4. A thermosetting molding composition, comprising the following materials, the amount of each being given in parts per hundred based on the total amount of polyester resin, monomer, and low profile additive except for the reinforcing filler:

a) from 20 to 50 pph of an unsaturated polyester resin;

b) from 30 to 70 pph of an olefinically unsaturated monomer;

c) from 5 to 25 pph of a poly(vinyl acetate) thermoplastic low profile additive;

d) from 5 to 75 % by weight, based on the total composition, of a reinforcing filler;

e) from 1 to 20 pph of a blocked polyisocyanate which is the blocked form of a polyisocyanate selected from the group consisting of isocyanate-containing prepolymers prepared by reaction of a toluene diisocyanate (TDI), or a methylenediphenylene diisocyanate (MDI) or polymeric form thereof (polymeric MDI), with a polyalkylene oxide diol; and

f) from 1 to 20 pph of a polyol selected from the group consisting of polyether polyols, polyester polyols different from said unsaturated polyester resin, and hydroxyl group-containing vinyl polymers, each of these materials containing primary hydroxyl groups.

5. A process for preparing a reinforced thermoset molded composite, comprising the following steps :

A. preparing a thermosetting molding composition comprising:

a) an unsaturated polyester resin;

e) a blocked polyisocyanate; and f) an isocyanate-reactive material

different from said unsaturated

polyester resin;

B. forming said molding composition into a desired shape; and

C. heating the shaped molding composition to cure it.

6. The process of claim 5, wherein said blocked polyisocyanate is the blocked form of a

polyisocyanate selected from the group consisting of tetramethylene diisocyanate, hexamethylene

diisocyanate (HMDI), 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, isophorone diisocyanate (IPDI), xylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, and isocyanate-containing prepolymers prepared by reaction of a toluene diisocyanate (TDI) or a methylenediphenylene diisocyanate (MDI) or polymeric form thereof (polymeric MDI) with a

polyalkylene oxide diol.

7. The process of claim 5, wherein said isocyanate-reactive material is selected from the group consisting of polyether polyols, polyester polyols different from said unsaturated polyester resin, hydroxyl group-containing vinyl polymers, amine-terminated polyols, diamines, and polyamines.

8. A molded reinforced thermoset product made with the composition of claim 1.

9. A molded reinforced thermoset product made by the process of claim 5.