WO1998021021A1

WO1998021021A1 - Composition and method for producing a reinforced polymeric article by pultrusion molding

Info

Publication number: WO1998021021A1
Application number: PCT/US1997/016917
Authority: WO
Inventors: Michele Ceh Johnson
Original assignee: Aztec Peroxides, Inc.
Priority date: 1996-11-12
Filing date: 1997-09-23
Publication date: 1998-05-22

Abstract

The invention is directed to a curing agent composition for the preparation of cured, reinforced polymeric articles and includes a mixture of a peroxybenzoate component, a ketone peroxide component, and a promoter component. The promoter component includes a multi-valent transition metal or a tertiary amine, or a combination thereof. The curing agent composition is preferably storable and transportable at room temperature without undergoing substantial decomposition. The invention is further direct to the use of a curing agent composition in a method for the production of a cured, reinforced polymeric article by a pultrusion process.

Description

COMPOSITION AND METHOD FOR PRODUCING A REINFORCED POLYMERIC ARTICLE BY PULTRUSION MOLDING

BACKGROUND OF THE INVENTION

A. Field of the Invention The present invention relates to a curing agent composition including one or more peroxides for use in producing cured polymeric articles. This invention also relates to a method for producing reinforced polymeric products employing a pultrusion process.

B. Background

Pultrusion processing, first developed several decades ago, is now a well-known process for the fabrication of reinforced plastic articles. Generally, pultrusion methods and apparatus involve continuously pulling a reinforcement material, e.g., in the form of continuous webs or strands, from a supply station through a bath of catalyzed resin so as to impregnate the reinforcement material with the resin. The impregnated material is then pulled through a heated forming die in which the resin is polymerized to form a cured composite article or product having a uniform cross section and the shape of the forming die.

A puller mechanism is a component of a pultrusion apparatus that engages the cured composite article after the article leaves the die so as to pull the materials through the apparatus. This operation includes pulling the reinforcement material from the supply station and through the resin bath and the die. Pultrusion is an effective system for the continuous production of solid or hollow articles that have a constant cross-sectional shape, for example, I-beams, rods, and the other products described below. The continuous cured reinforced plastic article can be cut into selected lengths by a cutting device, such as a saw, located downstream of the puller mechanism.

As mentioned above, the reinforcing materials used in a composite made with pultrusion apparatus are continuously pulled through the heated die by the puller mechanism located downstream of the die. This requires that the reinforcing material employed in a pultruded composite article be supplied in the form of continuous webs or strands that can be engaged and pulled by the puller mechanism of the pultrusion apparatus. The reinforcing materials typically employed are referred to as unidirectional, bidirectional and multidirectional materials. Most commonly, filamentary reinforcing materials are used in the forms of: rovings, tows, mats, or cloth, including combinations of these forms.

Continuous strand fiberglass rovings are an example of unidirectional reinforcement materials.

Rovings are made from strands that include a number

(e.g., 50 or more) of continuous filaments (or bundles of continuous filaments) that are gathered together without mechanical twist and wound onto a cylindrical package or spool . Many pultruded fiber-reinforced plastic products include a substantial percentage of rovings, which provide for axial reinforcement and tensile strength of the finished product.

In order to form a multidirectional reinforcing material, resinous binders are generally used to hold strands together to form a continuous mat or web. Such mats are available in various weights, for example in the range of about 7/8 to 4 ounces per square foot. One specific type of multidirectional mat is a very lightweight mat (e.g., about 1/2 ounce per square foot or less) known as a "surfacing mat" or a "veil." This type of mat is used to provide a resin-rich surface that enhances the surface finish of the article.

Bidirectional reinforcing materials include woven fabrics having spaced fibers or rovings that are woven or knit at right angles to one another or at other selected angles such as 30°, 45°, and 60°, for example. This form of reinforcement material generally includes elements that provide axial reinforcement, as well as elements at angles to one another to provide for transverse reinforcement.

In pultrusion, the reinforcing material may be made from any filamentary material having a suitable strength, such as glass fibers, aramid fibers, polyester fibers, nylon fibers, boron fibers or graphite fibers.

Glass fibers are the most widely used reinforcement material for pultruded plastic products.

Because pultrusion incorporates continuous strands of reinforcing material, it produces a product much stronger and more flexible than those products produced by extrusion processes, which can only utilize discontinuous lengths of reinforcing filament material. Because of these characteristics, pultrusion will often be used whenever high-strength products having the customary properties of polyester resins are desired, such as corrosion resistance, electrical resistance or light weight. The sizes and shapes of products capable of being produced by pultrusion are widespread, as for example, I-beams, channel, wide-flange beams, solid bars and rods, plates, round and square tubing, rectangular beams, angles, and flat sheets. The thickness of these parts can range from as little as about 1/8 inch up to about three inches, for example.

Typically, products having a thickness of about 0.25-0.375 inch (about 6.35-9.5 mm) made with relatively fast-curing polyester resins can be pultruded at speeds of up to about 10 feet per minute with fairly smooth surfaces. In pultrusion, a high activity curing agent, generally including a peroxide, is required in order to provide for relatively fast cure rates. Products having a thickness of about 0.375 to 0.675 inch made with an intermediate reactivity resin can generally be pultruded at speeds up to 6 feet per minute with only mildly abraded surfaces. Thick products over 0.67 inches (17.0 mm) in thickness and made with medium reactivity resins are generally limited to speeds of about 0.5 to about 5 feet (about 15 to about 152 cm) per minute, depending on thickness . Pultrusion processes generally use thermosetting resins. Unsaturated polyester resins and vinyl ester resins are the resins most widely used in the pultrusion process. Resins including epoxy functionality can be used. Some thermoplastic resins can be used for some end applications. Numerous types of polyester resins are suitable for pultrusion and are commercially available. Polyester resins can be mixed with a styrene monomer which acts as a cross-linking agent for curing the polyester into a hard rigid mass. Thus, the resin bath for a pultrusion apparatus can typically include an unsaturated polyester, styrene monomer and catalyst, together with filler, additives, mold release agents, and pigments .

Because the pultrusion process requires that the curing take place over a short period of time (as well as taking place over limited distance along the production line) , pultrusion presents particular demands on the curing agent. For example, the curing agent used in a pultrusion process must be able to provide very short curing times (generally on the order of about 0.5 to about 10 seconds, for example, one second) . For this reason, in pultrusion processing, it has generally necessary to use high activity curing agents. Commercially-available high activity curing agents typically have a substantial disadvantage in that they require refrigeration both during transportation and storage. Refrigeration adds substantial cost and complication to the manufacturing process, particularly since the curing agent is generally utilized in a location different from the location in which the curing agent is prepared.

In addition to the need for fast cure times, the pot life of the curing agent used in pultrusion processes is important, because the liquid resin is being held in a tank (a resin bath) , through which the reinforcing material is pulled to achieve impregnation thereof. A batch of resin must generally have a pot life of at least about eight hours (equivalent, for example, to one manufacturing shift or one working day) and up to twelve hours. If the resin begins to cure in the resin bath (and the viscosity rises too much) , the impregnation of the reinforcement material (which is taking place immediately prior to curing) will not be satisfactory, resulting in an unsatisfactory final product. As a result, the curing agents used in pultrusion have to allow for a satisfactory level of resin stability at temperatures typically encountered in a resin bath, e.g., room temperature and above. However, it has been difficult to provide pultrusion curing agents with a pot life of eight hours. Further, many of the resins used in pultrusion (e.g., those including epoxy functionalities) are more difficult to cure than in other processes.

Other processes for producing composite reinforced articles can differ significantly from pultrusion. In sheet molding compound ("SMC") processes, reinforcements, fillers, resin, and a thickener (e.g., magnesium oxide) are formed into a sandwich. This sandwich is stored for several days in a maturation room wherein the filaments become wetted by the resin and the resin becomes somewhat thickened. The sheets, or sandwiches, can later be used in injection molding or compression molding, for example. Thus, processes using sheet molding compound (injection molding or compression molding, for example) generally require a resin and curing agent combination that is stable (i.e., usable in its formulated form under reasonable ambient conditions) for a matter of days (e.g., about thirty days), and does not require a curing agent that can provide curing in such a short period of time as required in pultrusion. SMC and bulk molding compound (BMC) molding differ from pultrusion in that in the former, the resinous material goes into the mold having a very high viscosity (e.g, in the millions of centipoises) in the form of a log or a sheet, for example. When heated, the material loses viscosity to become liquidous, thus filling a mold cavity. As curing proceeds, the viscosity will climb again as crosslinking reactions occur.

The end uses of products made by pultrusion processes also generally differ from the end uses of products made by other types of molding, such as resin transfer molding, injection molding, and methods using sheet molding compounds. The products made by pultrusion processes are generally employed where superior chemical and high temperature resistance are required.

It would therefore be beneficial to provide a curing agent composition for use in pultrusion processing that has the following properties: (1) the ability to provide the fast cure required by pultrusion; (2) the ability to be transported and stored at room temperature;

(3) the ability to provide a high degree of cure in pultrusion, even during short cure times; (4) safe for storage and use; and (5) economy for use in commercial operations . Various methods for producing molded articles, along with useful promoters, are disclosed in U.S. Patent No. 3,988,290, the disclosure of which is hereby incorporated herein by reference.

More specific information concerning pultrusion is available from various technical publications, such as Handbook of Pul trusion Technology, R. W. Meyer (Chapman & Hall 1985) . Various molding processes, including pultrusion, are described in Modern Plastics Mid-October Encyclopedia Issue, Vol. 86, No. 11, pages 310-317 (McGraw-Hill, Inc. 1989) . The disclosures of these publications are hereby incorporated herein by reference in their entireties. SUMMARY OF THE INVENTION

It is an object of the invention to overcome one or more of the problems described above.

It has been unexpectedly discovered that the use of the curing agent composition of the invention has the ability to provide extensive cure even at relatively low temperatures. See, for example, Experiments I and II below. It has also been discovered that the curing agent compositions of the invention can be stored and transported at room temperature without undergoing substantial decomposition. The ability to avoid having to refrigerate the curing agent compositions is a substantial advantage of the invention. This stability is also advantageous in the inventive pultrusion process itself, since the liquid resin is held in a vessel while a reinforcing material is pulled through the same.

Accordingly, in a first aspect, the invention provides a curing agent composition that facilitates the preparation of cured polymeric articles by pultrusion techniques. The curing agent composition includes a mixture of a peroxybenzoate component, ketone peroxide component, and a promoter component. The promoter component includes a multi-valent transition metal or tertiary amine, including combinations thereof. The curing agent composition of the present invention is advantageously storable and transportable at room temperature, e.g., about 20°C, without undergoing substantial decomposition. According to another aspect of the invention, the inventive curing agent composition is utilized in method for the production of a reinforced, cured polymeric article by a pultrusion technique. The process includes first providing a reinforcement material and a resin bath comprising a polymerizable organic resin and a curing agent composition. The curing agent composition includes a mixture of a peroxybenzoate, a ketone peroxide, and a promoter comprising a multi-valent transition metal and/or tertiary amine. The reinforcement material is at least substantially continuously pulled through the bath so as to impregnate the reinforcement material with resin. The resin- impregnated reinforcement material is then pulled through a heated pultrusion die, to polymerize the organic resin in the resin-impregnated reinforcement material to form a cured reinforced polymeric article. The method provides substantially complete cure over relatively short curing times and relatively low curing temperatures. The curing agent composition preferably includes a perbenzoate compound, such as t-butyl peroxybenzoate ("TBPB"), preferably present in an amount of about 0.5 to about 10.0 weight percent based on the weight of the organic resin, more preferably about 0.5 to about 5.0 weight percent, and most preferably between about 1.0 and about 1.5 weight percent. The curing agent composition also preferably includes a ketone peroxide, such as acetylacetone peroxide, preferably present at about 0.1 to about 6.0 weight percent based on the weight of the resin, more preferably about 0.1 to about 0.6 weight percent, and most preferably about 0.3 to about 0.5 weight percent. The curing agent composition preferably includes a promoter component including a multi-valent transition metal or a tertiary amine, including mixtures thereof. The promoter component of the curing agent composition of the invention is preferably utilized at about 0.001 to about 10 weight percent based on the weight of the organic resin, more preferably about 0.1 to about 1.5 weight percent, and most preferably about 0.25 to about 0.9 weight percent.

Other objects and advantages of the invention will be apparent to those skilled in the art from the following detailed description, taken in conjunction with the appended claims.

DETAILED DESCRIPTION

The present invention is directed to a curing agent composition and method for producing a cured reinforced polymeric article which includes the use of Applicant's curing agent composition in a pultrusion process. The present invention is also directed to a reinforced polymeric article produced by a pultrusion process employing one or more of the curing agent compositions of the invention. The term "pultrusion, " as used herein, refers to a technique, as described above, wherein reinforcement materials, e.g., in the form of continuous webs or strands, are substantially continuously pulled from a supply station or location through a bath of catalyzed resin. The reinforcement material is impregnated with resin in the resin bath. The impregnated materials are then pulled through a heated forming die in which the resin is polymerized to form a cured article or product, typically having a uniform cross sectional shape of the forming die.

In pultrusion, a high activity curing agent is required in order to provide for relatively fast cure rates. However, as discussed above, this frequently provides catalyst compositions that need refrigeration, or resin batches that have a short batch life. The curing agent composition of the present invention solves these problems and comprises a perbenzoate compound, a ketone peroxide, and optionally one or more of the following: a promoter, a multi-valent transition metal ion, an accelerator, and/or an inhibitor.

Thus, in one aspect, the invention provides a curing agent composition comprising: (A) a perbenzoate compound; (B) a ketone peroxide; and (C) a promoter selected from the group consisting of a multi-valent transition metal ion, a tertiary amine, and mixtures thereof; wherein the weight ratio of A:B:C is about 0.5 to about 10: about 0.1 to about 6.0: about 0.001 to about 10. The weight ratio of A:B:C is more preferably about 0.5 to about 5 : about 0.1 to about 0.6: about 0.1 to about 1.5. The weight ratio of A:B:C is most preferably about 0.5 to about 1.5: about 0.3 to about 0.5: about 0.25 to about 0.9. In another aspect, the invention provides a curing agent composition consisting essentially of the above described components, i.e., (A) a perbenzoate compound, (B) a ketone peroxide, and (C) a promoter selected from a multi-valent transition metal ion, a tertiary amine, and mixtures thereof, in the above described ratios.

The first component of the curing agent composition is the perbenzoate compound (also known as a peroxybenzoate compound) . The perbenzoate compound is preferably utilized at about 0.5 to about 10.0 weight percent based on the weight of the resin, more preferably between about 0.5 and about 5.0 weight percent, and most preferably between about 1.0 and about 1.5 weight percent. At levels below about 0.5 weight percent, the amount and speed of cure is generally unsatisfactory, and levels above about 5.0 weight percent are generally undesirable, typically because they add additional cost without providing commensurate benefits in cure rates.

A highly preferred perbenzoate compound is t- butyl perbenzoate (also known as tertiarybutyl peroxybenzoate, referred to as "TBPB"). T-butyl perbenzoate can be supplied as a 98 weight percent liquid or in 50 weight percent solution in dimethyl phthalate. T-butyl perbenzoate is soluble in alcohols, esters, ethers, ketones, and has the following structure:

The perbenzoate compound or component used in the curing agent composition of the invention provides high activity. Due to its high reactivity, this compound should be stored separately from incompatible materials such as oxidizers and reducing agents, as well as any other material capable of inducing decomposition of the compound through a redox reaction. However, perbenzoate compounds such as TBPB, are stable at room temperature, which is a major advantage in the composition of the invention.

The perbenzoate compound is useful mainly at relatively high temperatures, for example at least about 100°F (about 37.7°C), and more preferably at least about

150°F (about 65.5°C). In the invention, this compound can be "activated" by the elevated temperatures produced by the exothermic decomposition of one of the ketone peroxide component of the inventive curing agent composition, as described below.

The curing agent composition preferably includes an additional peroxide component in the form of a ketone peroxide. The ketone peroxide is preferably utilized at about 0.1 to about 6.0 weight percent based on the weight of the resin, and more preferably between about 0.1 to about 0.6 weight percent, and most preferably about 0.3 to about 0.5 weight percent. The ketone peroxide can be supplied with one or more organic solvents and/or phlegmatisers .

A highly preferred ketone peroxide is acetylacetone peroxide ("AAP"), which has the following structure:

0

I I II

Acetylacetone peroxide is preferred because it provides faster curing than other ketone peroxides, and one function of the ketone peroxide component is to provide fast cure of the resin at relatively low temperatures . Further, acetylacetone peroxide is stable at room temperature, which is an important advantage for the reasons described above, particularly for the pultrusion process of the present invention.

The pultrusion process of the present invention is preferably accomplished by employing activators or promoters which cause the above-described peroxide (s), particularly the ketone peroxide component, to decompose into free radicals, according to the following reaction:

RO:OR > RO- + -OR

The generated free radicals initiate the curing of the resin at either room temperature or elevated temperatures, depending upon the resin, the particular curing agents, and the presence of other components. The above-described reaction is exothermic, thereby producing heat that will raise the ambient temperature of the curing reaction to a level that activates the previously- described perbenzoate component of the curing agent composition.

Thus, another preferred component of the curing agent composition of the invention is a promoter. The promoter preferably includes one or more multi-valent transition metals or tertiary amines, including mixtures thereof. The multi-valent transition metal or tertiary amine chemically promotes decomposition of the peroxide components through the oxidation-reduction mechanism mentioned above.

Generally, only a very small amount of promoter decomposes a substantial amount of ketone peroxide, since many of the metals used as the preferred promoters of the invention are capable of promoting peroxide decomposition in more than one valence state. Therefore, this component of the curing agent composition is generally included in the range of about 0.001 to about 10 parts per 100 parts by weight (i.e., weight percent) of the organic resin. More preferably, this component is included in the range of about 0.1 to about 1.5 weight percent, and most preferably about 0.25 to about 0.9 weight percent (for example about 0.5 weight percent). It is possible to "kill" a cure by overpromoting with excess levels of metal or amine, therefore this component should generally be included only in the required amount.

In such cases, the produced free radicals are undesirably converted into ions, which cannot initiate curing of the resin. Moreover, radicals cannot be regenerated from ions. In another aspect of the invention, the weight ratio of the promoter to the ketone peroxide is preferably about 100:1 or less, more preferably about 6:1 or less, even more preferably about 3:1 or less, and most preferably about 1:1. Multi-valent transition metal ions useful with the invention include, for example, ions of copper, cobalt, iron, and vanadium cations. Cobalt is the preferred transition metal. Examples of useful compositions containing cobalt ions include cobalt salts of monocarboxylic acids, such as cobaltic acetate, cobaltic decanoate, cobaltic neodecanoate, cobaltic octanoate, and cobaltic napthenate . Useful cobaltic compounds also include inorganic salts, such as cobaltic fluoride, cobaltic hydroxide, cobaltic oxide, cobaltic chloride, cobaltic sulfate and cobaltic salts of diketones, such as cobaltic acetyl- acetonate and cobaltic acetonylacetonate . The ions of the promoter are preferably in a plus three valence state, but can be in a plus two valence state or mixtures of two or more valence states. Ions, such as copper, are limited to having plus two and plus one oxidation states.

A suitable cobaltic promoter is sold under the trade designation C-101 by Borchers France of Castres, France. C-101 is a cobalt octoate solution in phthalate having about 1 weight percent cobalt. Other commercially available cobalt promoters are also sold by Borchers under the trade designations COB-6 (cobalt octoate solution in xylene with about 6 weight percent cobalt) , and COB-10 (cobalt octoate solution in xylene with about 10 weight percent cobalt) .

One preferred cobalt/amine promoter includes a mixture of the following (percentages are by weight) : 10% dimethylaniline ("DMA") (tertiary amine promoter)

2% cobalt ion (e.g., as provided by cobalt octoate)

0.8% di (t-butyl) p-cresol (stabilizer, anti- oxidant ) 0.04% copper (as Cu⁺² ion) balance di-n-butylphthalate ("DBP") (solvent/ diluent)

Other preferred cobaltic promoters are sold by

Air Products and Chemicals, Inc. of Allentown, Pennsylvania as the "PEP^®" product line of promoters.

The PEP^® promoters are organometallic compounds based on cobalt. These promoters are advantageous because they are not active in their supplied state, and are made active by altering the valence state of cobalt through the addition of heat. This facilitates safe storage of the promoter and curing agent composition. More specifically, such promoters are sold under the names, for example, PEP® 100, PEP^® 176, and PEP^® 308 by Air Products and Chemicals, Inc., the product bulletins of which are hereby incorporated herein by reference.

Preferred tertiary amine promoters include dimethyl toluidine and dimethyl aniline. A suitable amine is sold under the trade designation A-302 by Biesterfeld Graen of Munich, Germany. A-302 is a 10% dimethyl p-toluidine solution in a phthalate solvent. Other amines are also sold by Biesterfeld Graen under the trade designations A-305 (10% dimethyl aniline solution in a phthalate solvent) and A-311 (10% diethyl aniline solution in a phthalate solvent) .

If a promoter is used in the inventive method, the particular promoter to be selected depends upon the processing conditions, and more particularly, upon the curing conditions. The organocobalt promoter PEP^® 308, for example, is a preferred promoter because it provides good results even at low curing temperatures. Generally, however, the higher the cure temperature, the less important is the type and activity of the promoter, since peroxides can generate free radicals themselves at elevated temperatures. One advantage of the invention is that it provides advantageous results even at relatively low cure temperatures, as described in greater detail below.

The curing agent composition of the invention can also include an accelerator, which facilitates the redox activation of the peroxide components described above, e.g., acetylacetone peroxide. The accelerator component of the invention increases the speed of the curing agent composition by facilitating the formation of free-radicals by the above-described mechanism. More specifically, the accelerator can act upon the promoter to enhance the promoter's effects, usually by facilitating the formation of a complex between the cobalt metal and the peroxide linkage, for example. A preferred accelerator is acetylacetone. Other suitable accelerators are known in the art. The accelerator is preferably present at about 0.1 to about 0.5 weight percent, and more preferably about 0.2 to about 0.4 weight percent, based on the weight of the resin.

The inventive curing agent composition can also include one or more inhibitors present at about 0.01 to about 5.0 weight percent, and more preferably about 0.05 to about 0.5 weight percent, based on the weight of the resin. Inhibitors can avoid a premature start of the curing reaction, and can provide increased storage life. Suitable inhibitors such as Inhibitor TC-510 and Inhibitor BC-500 are available from Biesterfeld Graen. The TC-510 inhibitor is a 10 percent solution of t-butyl catechol in styrene; the BC-500 inhibitor is a 40 percent solution of di (t-butyl) -p-cresol in xylene. Finally, the inventive curing agent composition can also include a relatively small amount (e.g., about 10 to about 35 weight percent of the weight of the peroxide initiator (s) of one or more diluents or solvents which have no substantive effect on the curing reaction. Diluents, such as water and diacetone alcohol, are generally present in the peroxide formulations of the invention for safety reasons. These components can stabilize the system and absorb heat produced during the exothermic decomposition of peroxides (e.g., acetylacetone peroxide) .

The curing agent composition of the invention can be employed in any amount which is effective to cure of the stabilized thermosettable unsaturated resins. The curing agent composition (including the various components described above) can be used, for example, in amounts of from about 0.1 to about 5.0 weight percent based upon total weight of resin, and more preferably about 0.5 to about 2.5 weight percent.

The inventive pultrusion process may in some cases use a greater amount of curing agent composition than that disclosed above, in order to reduce the required cure time of the organic resin. For example, in practice, as little as 0.1 weight percent peroxide initiator (e.g., TBPB) based upon weight of resin can sometimes be sufficient to initiate polymerization if a high enough temperature is used. However, to increase the speed of the resin's cure, the peroxide initiator can be increased to about 0.5% to about 1.5% of the weight of the selected resin, for example. It is understood that the optimum level of curing agent composition will vary depending upon the particular curing agent components and the resin being employed, as well as upon the conditions under which the pultrusion operation is being carried out.

The curing agent composition of the invention is typically soluble in the polyester resin systems described above. Because the curing agent compositions are liquids, it is typically not difficult to disperse the curing agent composition in the resin to provide a homogeneous distribution of curing agent composition in the resin. On the other hand, other known curing agents that are solids can make satisfactory dispersion of the curing agent difficult to achieve.

In its second aspect, the present invention is also directed to a process for producing a reinforced resin. In particular, the process of the present invention comprises the steps of:

(a) providing a reinforcement material and a resin bath comprising a polymerizable organic resin and a curing agent composition, the curing agent composition comprising a mixture of a peroxybenzoate compound, a ketone peroxide, and a promoter selected from the group consisting of a multi-valent transition metal ion, a tertiary amine, and mixtures thereof;

(b) pulling the reinforcement material through the resin bath at least substantially continuously to provide a resin-impregnated reinforcement material;

(c) pulling the resin-impregnated reinforcement material through a heated forming die; and

(d) polymerizing the polymerizable organic resin in the resin-impregnated reinforcement material as it is pulled through the forming die to form a cured reinforced polymeric article.

The first step in the method of the present invention comprises providing a reinforcing material. Any of the known reinforcing materials suitable for use in a pultrusion process can be used in accordance with the present invention. Suitable materials include glass fibers, aramid fibers, polyester fibers, nylon fibers, boron fibers, and graphite fibers. Glass fibers are preferred. Beneficial reinforcing materials can be provided in the shapes and styles described above.

The method of the invention includes at least substantially continuously pulling the reinforcing material from a supply station. As used herein, the phrase "at least substantially continuously" means that the pulling, or "feeding," of the reinforcing material is either continuous or intermittent. The pulling preferably is continuous, particularly on commercial scales of production. If the pulling is intermittent, the intermittency is preferably at regular intervals ("periodic") . As will be understood by those of skill in the art, pultrusion processes can involve other insignificant delays or stoppages in the pulling of the reinforcing material which will not negatively affect the final product or the overall efficiency of the process. Such processes are also within the scope of the invention. The reinforcing material is pulled into and through a bath comprising an organic resin and an effective amount of a curing agent composition that can initiate polymerization of the organic resin. As discussed above, the curing agent composition preferably includes a perbenzoate compound, such as t-butyl peroxybenzoate ("TBPB"), preferably present in an amount of about 0.5 to about 10.0 weight percent based on the weight of the organic resin, and more preferably between about 0.5 and about 5.0 weight percent, and most preferably about 1.0 and about 1.5 weight percent. The curing agent composition also preferably includes a ketone peroxide, such as acetylacetone peroxide, preferably present at about 0.1 to about 6.0 weight percent based on the weight of the resin, more preferably about 0.1 to about 0.6 weight percent, and most preferably about 0.3 to about 0.5 weight percent. The curing agent composition also includes a promoter component including a multi-valent transition metal or a tertiary amine, including mixtures thereof. The promoter component of the curing agent composition of the invention is preferably utilized at about 0.001 to about 10 weight percent based on the weight of the organic resin, more preferably about 0.1 to about 1.5 weight percent, and most preferably about 0.25 to about 0.9 weight percent, for example about 0.5 weight percent.

Organic resins suitable for use with the invention, as well as their sources, are well known to those skilled in the art. Any resin that is capable of providing beneficial characteristics in a cured polymeric article is suitable for use in the present invention.

Resins used with the invention are preferably of the thermosetting type. Thermosetting resins which can be employed with the invention preferably include ethylenically unsaturated groups. For example, suitable resins include polyester resins (particularly unsaturated polyester resins) , vinyl ester resins, vinyl urethane resins, and combinations thereof. Resins including epoxy functionality can be used.

A substantial number of well known polyester resins are useful in accordance with the invention. Polyester resins are generally a reaction product of at least one dicarboxylic acid, or anhydride thereof, with at least one polyfunctional alcohol (also referred to as a polyhydric alcohol or "polyol"). The dicarboxylic acids or anhyrides that are employed to produce the polyester should contain olefinic or ethylenic unsaturation. An ethylenically unsaturated polyester is the reaction product of at least one ethylenically unsaturated dicarboxylic acid with at least one polyol.

Preferably, the ethylenic unsaturation of the dicarboxylic acid is alpha, beta to at least one of the carboxylic acid groups. Such acids include, for example, aleic acid or anhydride, fumaric acid, chloromaleic acid, methyl maleic acid, and itaconic acid. Maleic acid or anhydride and fumaric acid are the most widely used commercially. Aromatic dicarboxylic acids or anhydrides can also be employed in producing the polyester. Such acids include phthalic acid or anhydride (such as ortho phthalic acid, or "OPA"), endomethylene- tetrahydrophthalic acid, terephthalic acid, tetrachlorophthalic acid, hexachloroendomethylene- tetrahydrophthalic acid, adipic acid, sebacic acid, hexahydrophthalic acid, isophthalic acid, and "dimer" acids (i.e., dimerized fatty acids). Useful low molecular weight aliphatic dicarboxylic acids include succinic acid, diglycolic acid, or their anhydrides.

As stated above, a polyol is generally also employed with the resin component, in order to produce a polyester through a reaction with the aforementioned dicarboxylic acid or anhydride. The polyol preferably contains about 4 to about 9 carbon atoms. Exemplary of the polyols that can be used to form the polyester compositions include aliphatic glycols, such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, butane diols, hexane diol, neopentyl glycol, glycerol, 1, 1, 1-trimethylol-propane, and mixtures thereof. Preferably, not more than about 20 mole percent of the polyol will be a triol, with the remainder being one or more diols.

Suitable methods for preparation of polyester resins are disclosed in U.S. Patent Nos . 3,775,513; 3,883,612; and 3,901,953, the disclosures of which are all hereby incorporated herein by reference. Many commonly-used vinyl ester resins are also suitable for use with the invention.

Suitable vinyl ester resins can be prepared, for example, by reacting a polyepoxide with an unsaturated monocarboxylic acid. The polyepoxide and unsaturated monocarboxylic acid can be reacted, for example, in amounts which provide a ratio of carboxyl groups per epoxide group of from about 0.9:1 to about 1.1:1, and more particularly, from about 0.95:1 to about 1.05:1. Suitable vinyl ester resins and methods for their preparation are disclosed, for example, in U.S. Patent

Nos. 3,887,515; 4,213,837; 4,407,991; 4,594,398; and

5,382,626, the disclosures of which are all hereby incorporated herein by reference.

The vinyl ester resins can be modified with any modifier known by those in the art. For example, it may be advantageous for some end applications to use rubber or elastomer modifiers. Suitable rubbers or elastomers include, for example, carboxyl-containing rubbers or elastomers, copolymers of alkyl acrylates or methacrylates or alkyl esters of other alpha-alkyl rubber particles characterized by having a rubbery core and a grafted polymer shell which is compatible with vinyl ester resins.

If desired, any of the thermosetting unsaturated resins disclosed above can be diluted or blended with a polymerizable, ethylenically unsaturated monomer. Suitable monomers include, for example, vinyl aromatic compounds, saturated or unsaturated aliphatic or cycloaliphatic esters of ethylenically unsaturated monocarboxylic acids (e.g., wherein the ester portion of the monomer contains from 1 to about 20 carbon atoms, and the acid portion of the monomer contains from about 3 to about 10 carbon atoms), and combinations thereof.

Suitable polymerizable ethylenically unsaturated monomers are disclosed in U.S. Patent Nos. 3,892,819 and 4,594,398, the disclosures of which are hereby incorporated herein by reference. Particular examples include ethylene, propylene, styrene, alpha- methylstyrene, p-methylstyrene, chlorostyrenes such as dichlorostyrene, bromostyrenes, vinyl benzyl chloride, vinylpyridine, vinyl naphthalene, vinyl toluene, divinylbenzene, vinyl acetate, vinyl benzoate, vinyl chloroacetate, unsaturated esters such as esters of acrylic and methacrylic acid, vinyl propionate, and vinyl laurate. Useful diolefins include 1, 2-butadiene, isoprene, chloroprene, and methylpentadiene . Other useful compounds include unsaturated acids such as, for example, acrylic acid, alpha alkylacrylic acid, butenoic acid, allylbenzoic acid, vinylbenzoic acid, as well as unsaturated organic halides (such as tetrafluoroethylene, hexafluoropropylene, chlorotrifluorethylene, vinyl chloride, and vinylidene chloride) ; esters and amides, such as acrylic acid anhydride; nitriles such as acrylonitrile and methacrylonitrile; esters of polycarboxylic acids such as diallyl phthalate, divinyl succinate, diallyl maleate, divinyl adipate, and dichloroallyl tetrahydrophthalate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and n-butyl vinyl ether; and suitable ketones such as methyl vinyl ketone.

Any combinations of two or more of the above monomers can also be used.

As mentioned above, such monomers can function as cross-linking agents for providing three-dimensionally crosslinked products with exceptionally good mechanical and thermal properties. Polyester thermosets can be made by curing an unsaturated polyester resin and a polymerizable monomer with an organic peroxide curing agent or catalyst. In many applications, it may be advantageous to include a small quantity of a thermoplastic material, preferably a resin, as a low profile additive (known as an "LPA") in order to add dimensional stability to molded parts. Thermosetting resins can sometimes tend to shrink or warp upon curing. The addition of a thermoplastic resin, which does not undergo any chemical reaction in the molding process, acts to reduce and/or prevent shrinkage or warping.

Other fillers, as known in the art, can be added to the polymerizable composition. Examples include calcium carbonate, calcium sulfate, various types of clay, wollastinite, and glass spheres. Ingredients such as aluminum trihydrate, a flame retardant, can also be included. As stated above, in addition to the organic resin, a curing agent composition is provided in the resin bath of the inventive pultrusion process. Although the peroxide catalyst composition of the invention may be referred to herein as a "catalyst" (as in industry) , it is understood that these compositions are not true catalysts. Using the strict definition of catalysts as components that are added in very small quantities to speed up the rate of reaction and which do not undergo any permanent changes to their chemical structure as the result of the reaction, organic peroxides are not catalysts. The peroxides used in accordance with the invention are actually free radical initiators. As stated above, the method of the present invention includes providing the above resin and curing agent composition in a resin bath. The method includes the step of pulling the impregnated reinforcement material through a heated forming die, in which the resin is polymerized. Because the present invention includes the step of at least substantially continuously pulling the reinforcing material through the resin bath, it may be advantageous, particularly for commercial operations, to have the ability to continuously or intermittently re- supply materials to the resin bath.

The resin and curing agent composition remain in the resin bath throughout the duration of the pultrusion run or runs, and the reinforcing material is pulled through the resin bath in order to impregnate the reinforcing material. On a commercial scale, the bath should remain usable throughout at least an eight-hour period (e.g., an eight-hour work shift). Therefore, because the liquid resin is being held in the resin bath, the pot life of the curing agent used in pultrusion processes is particularly crucial (more so than in processes using SMC) . If the resin begins to cure and the viscosity rises too much, the impregnation of the reinforcement material will not be satisfactory, and, as a result, the final molded article will not perform satisfactorily.

The final step of the method of the present invention includes at least substantially continuously withdrawing the cured article or product from the heated forming die. As discussed above, the phrase "at least substantially continuously" refers to both continuous and intermittent withdrawal of the cured article, depending upon the particular production requirements . Although the polymerization is typically performed at temperatures greater than about 150°F (about 65°C) , such as in the

range of about 175OF (about 80oC) to about 400OF (about

204°C) and more preferably in the range of about 180°F

(about 820C) to about 275°F (about 135oc) . However, it is also within the scope of the present invention to perform the polymerization at lower temperatures such as room temperature.

EXPERIMENT I

In order to demonstrate the curing ability of the curing agent composition of the invention, there was provided a curing agent composition, referred to herein as Curing Agent A, containing the ingredients shown in Table I below. TABLE I - CURING AGENT A

Component Weight % t-Butylperoxybenzoate (TBPB) (initiator) 90 n-Methyl pyrrolidone (solvent/diluent) 1.5

Acetylacetone peroxide (initiator) 3.4

Diacetone alcohol (solvent, phlegmatiser) 3.9

Water (solvent) 1.2

Another preferred curing agent, referred to herein as Curing Agent B, is identified below.

TABLE II - CURING AGENT B

Component Weight % t-Butylperoxybenzoate (TBPB) (initiator) 55 n-Methyl pyrrolidone (solvent/diluent) 3.75

Acetylacetone peroxide (initiator) 8.5

Diacetone alcohol (solvent, phlegmatiser) 9.75 Water (solvent) 3 Acetylacetone (2, 4-pentanedione) (accelerator) 20

In order to test the activity of curing agent compositions according to the invention, Curing Agent A was mixed with various promoters to produce several samples. These samples are identified as Samples 3-9 in

Table III below.

Two controls, identified as Samples 1 and 2 in Table III, utilized t-butylperbenzoate in combination with a commercially available peroxide initiator (BCHPC) . Sample 1 included an additional commercially-available, low-temperature active peroxide ("TBPEH"). Each of the curing agents of the control samples requires refrigeration.

All of the samples were mixed with a commercially-available high activity resin. The resin included about 65 weight percent ortho-phthalic acid (OPA) and about 35 weight percent styrene. Typically, commercial mixtures include about 25 to about 50 weight percent of cross-linking monomer, such as styrene.

The catalyzed shelf life (hours) at 23°C of each of the curing agent compositions/resin mixtures was determined. These values are also shown in Table III.

TABLE III - FORMULATIONS OF SAMPLES 1-9

Refrigeration required.

The amounts shown in Table III are based on weight. Samples 3-9 included 1.5 weight parts of Curing Agent A per 100 weight parts resin. Thus, for Samples 3-

9, the following amounts of the ingredients of Curing

Agent A were included for every 100 parts of resin:

TABLE IV - Samples 3-9 Amounts of Each Component of Curing Agent A,

Based on 100 Parts Resin

Weight Per Component 100 Parts Resin t-Butylperoxybenzoate 1.35 (90% x 1.5%) (initiator) n-Methyl pyrrolidone 0.225

Acetylacetone peroxide 0.51 (initiator)

Diacetone alcohol 0.585

Water 0.18

Each of the resin and curing agent compositions represented by Samples 1-9 was utilized to make two glass-reinforced laminates.

In order to produce each laminate, a layer of catalyst resin was laid down at a thickness of about 5mm, along with commercially-available glass reinforcements. A thermocouple was embedded in the laminate in order to determine degree of cure of the composition and exotherm temperature during curing. This procedure is similar to the standardized SPI "Procedure For Running Exotherm Curves - Using Thermocouple Needle (SPI Gel Time I8O0F) , " the data sheet for which is hereby incorporated herein by reference.

In order to determine the effect of curing temperatures, for each sample, one of the laminates was cured at 80°C and one of the laminates was cured at

lOOoc.

Residual styrene content of each cured laminate was also determined. The results are reported below in Tables V and VI.

TABLE V - Curing of 5mm Laminates @ IQQoC

TABLE VI - Curing of 5mm Laminates @ 8Q C

10

Table V reflects that when Samples 1-9 were cured at lOOoc, the cure times provided by the curing agent compositions of the invention are equal to or somewhat above those of the control curing resins, with the best result in this regard being produced by Sample 6. More importantly, the residual styrene percent for the samples of the invention (Samples 3-9) were all at or below those provided by control Samples 1 and 2. Those skilled in the art recognize that the minimization of styrene monomer (and other resin monomers) in products intended to contact food is particularly important.

Table VI reflects that when the same Samples 1-

9 were cured at 80°C, several of the samples using the curing agent compositions of the invention (particularly, Samples 4-6) provided residual styrene amounts of 0.01%, which were substantially lower than the 1.3% and 4.2% residual styrene provided by control Samples 1 and 2, respectively. Thus, the curing agent compositions of the present invention are capable of providing excellent curing at lower temperatures than the compositions of the prior art. In addition, the compositions of the present invention further provide (a) an advantageously high pot life and (b) the ability to be stored at temperatures at

(and in some cases above) room temperature.

EXPERIMENT II Another experiment was performed in order to determine what effects, if any, might be produced on the present curing agent-resin composition by adding thereto other components typically provided in commercial pultruded products, such as fillers, preservatives, low profile additives, and fire retardants. Those samples more closely approximate commercial molding formulations.

Four samples were made according to the formulation in

Table VII. In the experiment, curing agent compositions were varied according to the formulations in Table VIII below. TABLE VII

Ingredient (function) Weight Percent

Calcium carbonate 26.0 (filler)

Aluminum trihydrate 34.8

(flame retardant) Atomite (clay filler) 2.4

Zinc stearate 1.1

(internal lubricant) Zinc sulfate 4.8

(white pigment)

Barium sulfate/Zinc 0.54 sulfate mixture (white pigment) styrene 0.12

(cross-linking monomer) Butylated hydroxy toluene (BHT) 0.01 (anti-oxidant stabilizer)

Hydroquinone - 20% solution 0.01

(inhibitor/stabilizer)

Commercial Isophthallic 24.1 acid-based polyester resin

Polystyrene 3.8 (low profile additive)

Powdered polyethylene 2.4

(flow modifier and surface modifier) TABLE VIII

Each composition was used to make the following: (1) a 4 gram tablet (no reinforcements), and (2) a laminate (with reinforcements) having a thickness of about 2mm. The reinforcements of the laminates were glass chip reinforcements. All of the samples were cured at 150°C for about 30 seconds. Tables IX and X below show the curing data for all of the samples.

TABLE IX TABLETS

TABLE X - CURE TIME FOR LAMINATES

"Tgel" is the gel time, defined as the time elapsed until the resinous material reaches a no-flow state. A resin will gel before it cures, and the Tgel value is a convenient manner to measure cure. "Tmax" is the maximum or peak exotherm temperature reached by the system as cure progresses. As those of skill in the art will understand, higher degrees of cure are generally achieved when higher Tmax temperatures are encountered.

For both the tablets and the laminates of Experiment II, the curing agent compositions of the invention were able to produce peak exotherm temperatures, peak exotherm times, and gel times similar to those of both Control A and Control B. Further, the residual styrene content for laminate Sample 1 and laminate Sample 2 of the invention were better than for each of Control A and Control B.

Shown below in Table XI are data that indicate the stability of various known curing agents in comparison to the stability of the curing agent compositions of the invention. The 10 hour half-life temperature is the temperature at which 50% of the peroxide is consumed during a 10-hour period. Both of the values in Table XI are measures of stability of the peroxide. Higher half-lives and higher maximum storage temperatures are highly advantageous properties for a commercially-useful curing agent. As those of skill in the art will appreciate, since acetylacetone peroxide (AAP) is available only as an oligomer, it is not possible to calculate a "10 Hour Half-Life" value. However, as shown below, AAP can be stored at relatively high temperatures .

TABLE XI - Stability of Curing Agent Components

10 Hour Maximum

Curing Agent Half-Life Storage Temp.

BCHPC 4loc 68oF (20oc)

(prior art) (needs refrigerated storage)

TBPEH 74oc 60oF (15.50C)

(prior art) (needs refrigerated storage)

Thus, the above data show that the curing agent compositions of the invention can provide similar results to, and in some cases substantially better results than, the control curing agents. Moreover, the curing agent compositions of the present invention provide the additional advantage over the control curing agents that the inventive curing agent compositions are storable at room temperature, e.g., at about 20oc. Still further, the curing agent compositions of the invention can be supplied in liquid form, which improves their dispersibility in the liquid resin mixture.

Further, because the curing agent compositions of the invention provide even greater improvement over the control resins when curing is performed at the lower temperature of 80oc, the resins allow for faster mold cycles and/or lower temperature mold cycles than could previously be used with commercially-available curing agents .

The foregoing description is given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications within the scope of the invention will be apparent to those skilled in the art.

Claims

What is claimed is:

1. A process for producing a cured, reinforced polymeric article by a pultrusion molding technique, comprising the steps of:

(a) providing a reinforcement material and a resin bath comprising a polymerizable organic resin and a curing agent composition, said curing agent composition comprising a mixture of a peroxybenzoate compound, a ketone peroxide, and a promoter selected from the group consisting of a multi-valent transition metal ion, a tertiary amine, and mixtures thereof;

(b) pulling the reinforcement material through said resin bath at least substantially continuously to provide a resin-impregnated reinforcement material;

(c) pulling said resin-impregnated reinforcement material through a heated forming die; and

(d) polymerizing said polymerizable organic resin in said resin-impregnated reinforcement material as it is pulled through said forming die to form a cured reinforced polymeric article.

2. The process of claim 1 wherein: said curing agent composition comprises t-butyl peroxybenzoate and acetylacetone peroxide.

3. The process of claim 1, wherein said curing agent composition comprises: (1) a peroxybenzoate compound present in an amount of about 0.5 weight percent to about 10.0 weight percent based on weight of the resin;

(2) a ketone peroxide present in an amount of about 0.1 to about 6.0 weight percent based on weight of the resin; and

(3) a promoter selected from the group consisting of a multi-valent transition metal ion, a tertiary amine, and mixtures thereof, said promoter being present in an amount of about 0.001 to about 10 weight percent based on weight of the resin.

4. The process of claim 1, wherein said curing agent composition comprises: (1) a peroxybenzoate compound present in an amount of about 1.0 to about 5.0 weight percent based on weight of the resin;

(2) a ketone peroxide present in an amount of about 0.1 to about 0.6 weight percent based on weight of the resin; and

(3) a promoter selected from the group consisting of a multi-valent transition metal ion, a tertiary amine, and mixtures thereof, said promoter being present in an amount of about 0.1 to about 1.5 weight percent based on weight of the resin.

5. The process of claim 1, wherein said curing agent composition comprises:

(1) a peroxybenzoate compound present in an amount of about 1.0 to about 1.5 weight percent based on weight of the resin;

(2) a ketone peroxide present in an amount of about 0.3 to about 0.5 weight percent based on weight of the resin; and

(3) a promoter selected from the group consisting of a multi-valent transition metal ion, a tertiary amine, and mixtures thereof, said promoter being present in an amount of about 0.25 to about 0.9 weight percent based on weight of the resin.

6. The process of claim 1 wherein said heated forming die is at a temperature in a range of about 1750F

(about 80oc) to about 400OF (about 204oc) .

7. The process of claim 1, wherein said reinforcing material comprises a material selected from the group consisting of glass fibers, aramid fibers, polyester fibers, nylon fibers, boron fibers, and graphite fibers.

8. The process of claim 1, wherein said resin bath comprises a mixture of one or more unsaturated carboxylic acids and styrene.

9. The process of claim 1, wherein said resin comprises (1) a first resin selected from the group consisting of polyester resins, vinyl ester resins, and vinyl urethane resins and (2) a second, thermoplastic resin, and wherein said curing agent composition is soluble in the resin.

10. The process of claim 1, wherein said promoter comprises a multi-valent transition metal ion selected from the group consisting of a cation of copper, cobalt, iron, and vanadium.

11. The process of claim 1, wherein said curing agent composition further comprises an accelerator present in an amount of about 0.1 to about 0.5 weight percent, based on weight of the resin.

12. The process of claim 1, wherein the curing agent composition does not undergo substantial decomposition at temperatures between about 25°C and 30oc.

13. A process for producing a cured, reinforced polymeric article by a pultrusion molding technique, comprising the steps of:

(a) providing a reinforcement material and a resin bath comprising a polymerizable organic resin and a curing agent composition, said curing agent composition comprising:

(1) t-butyl peroxybenzoate present in an amount of about 0.5 to about 5.0 weight percent based on weight of the resin; (2) a ketone peroxide present in an amount of about 0.1 to about 0.6 weight percent based on weight of the resin;

(3) a promoter comprising a cobalt ion present in an amount of about 0.1 to about 1.5 weight percent based on weight of the resin; and

(4) an inhibitor present in an amount of about 0.01 to about 5.0 weight percent based on the weight of the resin;

(b) pulling said reinforcement material through said resin bath at least substantially continuously to provide a resin-impregnated reinforcement material;

(c) pulling said resin-impregnated reinforcement material through a heated forming die having a temperature in a range of about 175°F (about

80oc) to about 400OF (about 204oc) ; and

(d) polymerizing said polymerizable organic resin in said resin-impregnated reinforcement material as it is passed through said forming die to form a cured, reinforced polymeric article having a uniform cross section and a shape of the forming die.

14. A cured, reinforced polymeric article produced by a pultrusion molding technique, comprising the steps of:

(b) pulling said reinforcement material through said resin bath at least substantially continuously to provide a resin-impregnated reinforcement material; (c) pulling said resin-impregnated reinforcement material through a heated forming die; and

(d) polymerizing said polymerizable organic resin in said resin-impregnated reinforcement material in said forming die to form a cured reinforced polymeric article.

15. The article of claim 14, wherein said curing agent composition comprises:

(1) a peroxybenzoate compound present in an amount of about 0.5 weight percent to about 10.0 weight percent based on weight of the resin;

16. The article of claim 14, wherein said perbenzoate comprises t-butyl peroxybenzoate and said ketone peroxide comprises acetylacetone peroxide.

17. A curing agent composition, comprising: (A) a peroxybenzoate compound;

(B) a ketone peroxide; and

(C) a promoter selected from the group consisting of a multi-valent transition metal ion, a tertiary amine, and mixtures thereof; and wherein the weight ratio of A:B:C is about 0.5 to about 10: about 0.1 to about 6.0: about 0.001 to about 10.

18. The curing agent composition of claim 17, wherein: the weight ratio of A:B:C is about 0.5 to about 5 : about 0.1 to about 0.6: about 0.1 to about 1.5.

19. The curing agent composition of claim 17, wherein: the weight ratio of A:B:C is about 0.5 to about 1.5: about 0.3 to about 0.5: about 0.25 to about .9.

20. A curable composition, comprising:

(A) a reinforcement material;

(B) a polymerizable organic resin; and

(C) a curing agent composition, comprising: (1) a peroxybenzoate compound present in an amount of about 0.5 to about 5.0 weight percent based on weight of the resin;

21. The curable composition of claim 20, wherein said curing agent composition comprises:

22. The curable composition of claim 20, wherein said curing agent composition comprises:

(1) a peroxybenzoate compound present in an amount of about 1.0 to about 1.5 weight percent based on weight of the resin; (2) a ketone peroxide present in an amount of about 0.3 to about 0.5 weight percent based on weight of the resin; and

23. The curable composition of claim 20, wherein the curing agent composition does not undergo substantial decomposition at temperatures between about

24. The curable composition of claim 20, wherein the curing agent composition has a 10-hour half- life of greater than about 75°C.

25. The curable composition of claim 20, wherein the curing agent composition has a 10-hour half- life of greater than about 95oc.

26. The curable composition of claim 20, wherein said curing agent composition comprises a liquid mixture of t-butyl peroxybenzoate and acetylacetone peroxide.

27. The curable composition of claim 20, wherein said resin comprises a mixture of a carboxylic acid and styrene.

28. The curable composition of claim 20, wherein said resin comprises (1) a first resin selected from the group consisting of polyester resins, vinyl ester resins, and vinyl urethane resins and (2) a second, thermoplastic resin, and wherein said curing agent composition is soluble in the resin.

29. The curable composition of claim 20, wherein said promoter comprises a multi-valent transition metal ion selected from the group consisting of a cation of copper, cobalt, iron, and vanadium.

30. The curable composition of claim 20, wherein said curing agent composition further comprises an accelerator present in an amount of about 0.1 to about 0.5 weight percent, based on the weight of the resin.

31. A curable composition, comprising: (A) a polymerizable organic resin; and (B) a curing agent composition, comprising:

(1) t-butyl peroxybenzoate present in an amount of about 1.0 to about 1.5 weight percent based on weight of the resin;

(2) acetylacetone peroxide present in an amount of about 0.1 to about 0.6 weight percent based on weight of the resin; and

(3) a promoter comprising a cobalt ion present in an amount of about 0.1 to about 1.5 weight percent based on weight of the resin.