FOR USING SAME

This invention relates to the use of inorganic peroxygen compositions as initiators for the curing of unsaturated polyester resins. 5 Unsaturated polyester resin syrups formulated according to the present invention may be employed in the production of coatings, molded or cast, spray-layup and hand-layup products such as flat and profiled building sheets, automobile fenders and other shaped components, furniture, plumbing fixtures such as tub and shower inserts, duct work, 0 boats, electrical component housings, electrical circuit boards, and the like. Unsaturated polyester resins may additionally be used as adhesives, potting compounds, moldings and composites reinforced with fibrous fillers. Such reinforcing materials may include fibers of graphite, glass, aramid and blends. Furthermore, the resins may be extended with inert particuiate 5 fillers and aggregates such as wood flour, silica, glass beads, clay, calcium carbonate and the like. See Bjorksten et al., Polyesters and Their Applications. (Reinhold Publishing Corporation, New York 1960). Unsaturated polyester resins are customarily produced by polyesterification of polycarboxylic acids or polycarboxylic acid anhydrides o and polyols, particularly glycols. The polyester contains at least one ethylenic unsaturation which is customarily present due to the polycarboxylic acid.

Unsaturated polyester resins, such as polyethylene maleate may be cured, or cross-linked, by mixing the polyester with a suitable vinyl 5 monomer such as styrene. On heating in the presence of an initiator, polymerization takes place so that the vinyl monomer polymerizes at the site of the polyester double bonds and a cross-linked network of polyester chains is produced thereby. The rate of such addition polymerization may be accelerated as explained herein by the addition of promoters such as o organic metal complexes, for example, cobalt napthenate, vanadium octoate, or lithium napthenate and/or amines, for example, phenoidiethanoiamine or triethanolamine.

Typical prior art initiators for curing unsaturated polyester resin syrups include the organic peroxygen compounds, of which 5 methylethylketone peroxide and benzoyl peroxide are the most widely

used. Other known initiators for curing unsaturated polyester resins include lauroyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, hydroheptyl peroxide, succinic acid peroxide, butyl peroctoate, df-t-butyl peroxide, di-t-butyl perbenzoate, isopropyl procarbonate, t-butyl 5 perbenzoate, acetyl peroxides, t-butyf peracetate, t-butyl hydroperoxides, di-t-butyl diperphthalate, benzoin, cumene hydroperoxide, cyclohexanone peroxide, the ozonides including di-isopropylene ozonide, and di- isobutylene ozonide, 2,5-dimethyl hexane-2,5-dimethyl-diper-2-ethyl hexoate and various other organic peroxygen compounds. o Such initiators have generally been employed as a paste-like mixture of a plastϊcizer and initiator. Additionally, a finely divided, partially soluble, thermoplastic such as polystyrene or polymethylmethacrylate may be added thereto to reduce shrinkage during polymerization, thus resulting in a smoother composite surface. 5 The initiator and a promoter, if any, are selected so that the initiation of polymerization of the unsaturated polyester resin syrup can be controlled by the operator. The initiator must be compatible with the promoter and the unsaturated polyester resin to be cured.

The nature of the polyester resin and the processing system will o dictate the promoter, or accelerator, and the particular catalyst, or initiator, that will be used. Cure times may be adjusted, for example, from 72 hours to 10 seconds by proper selection of the types and amounts of various promoters. Gel times may be adjusted, for example, from 24 hours to 3 seconds, depending entirely on the temperature, the reactivity of the resin, 5 and promoter selection.

As mentioned above, known initiators for unsaturated polyester resin syrups have generally been limited to organic peroxygen compounds such as benzoyl peroxide. One such organic peroxide composition is disclosed in U.S. Patent No.4,917,816 to Self as an aqueous organic o peroxide dispersion for use as a catalyst for unsaturated polyester resin syrups. Various other examples of and processes for using organic peroxides to initiate unsaturated polyester resin syrups are discussed in the '816 patent which is incorporated herein by reference.

Although organic peroxides have been employed as initiators for 5 unsaturated polyester resin syrups, inorganic peroxides have not been so

used. Inorganic peroxides, such as the peroxydisulphates (also known as persulphates) perborate tetrahydrates (also known as perborates), carbonate peroxyhydrates (also known as percabonates), and other inorganic peroxides such as zinc peroxide and calcium peroxide have, 5 however, been widely used as initiators for emulsion polymerizations of monomers such as vinyl acetate. Other examples of polymers which have been made using emulsion polymerization techniques employing inorganic peroxygen compounds as initiators include the polyvinylacetates, poly- styrenebutydienes, polymethylmethacrylates, polyvinylchlorides, and 0 polyacrylonitriles, acrylics, polystyrenes, and neoprenes.

Prior to the present invention, the inorganic peroxides have not been used to cure unsaturated polyester resins. Moreover, prior to the present invention, it was not known in the art that inorganic peroxygen compounds could be combined with organic peroxygen compounds. 5 Although some initial investigations into combining organic and inorganic peroxygen compounds was done during the 1960's relative to solid rocket fuels research, such combinations generally failed due to their highly explosive nature and incompatability.

It is an advantage of the present invention to provide an initiator for o curing unsaturated polyester resins.

Another advantage of the present invention is to provide an initiator for curing unsaturated polyester resins wherein an inorganic peroxygen composition is utilized.

Yet another advantage of the present invention is to provide an 5 initiator for unsaturated polyester resins comprising inorganic and organic peroxygen compounds.

Still another advantage of the present invention is to provide a method for using an inorganic peroxygen composition as an initiator for curing unsaturated polyester resins. o Still another advantage of the present invention is to provide a method for curing unsaturated polyester resins wherein an organic peroxygen composition and an inorganic peroxygen composition are used. Yet another advantage of the present invention is to provide articles made by curing polyester resins with an inorganic peroxygen initiator.

Another advantage of the present invention is to provide an article containing a polyester resin that has been cured by the combination of an inorganic peroxygen composition and an organic peroxygen composition.

Generally speaking, initiators for curing unsaturated polyester resins 5 according to teachings of the present invention comprise an inorganic peroxygen composition. The inorganic peroxygen composition may either be in a solid or anhydrous form, or be an aqueous dispersion. An organic peroxygen compound or dispersion may be added to the inorganic peroxygen composition to form the initiator. Like the inorganic peroxygen o composition, the organic peroxygen composition may be in a solid, or anhydrous form, or be an aqueous dispersion.

More specifically, inorganic peroxygen compositions such as the peroxy disulfates, the perborates, the percarbonates, the perphosphates and other inorganic peroxides such as zinc and calcium peroxides may be 5 added alone or in the presence of other components, including organic peroxygen compositions, to cure polyester resins. The peroxygen compounds may be added in the presence of a number of further ingredients to permit utilization for particular end uses and to impart certain desirable characteristics thereto. Examples of such ingredients include o defoamers, water soluble inorganic salts, blowing agents, acidic inorganic salts, fire retardants, wetting agents, any of the various promotors previously described or similar thereto, various fillers and piastfcizers. The various inorganic peroxygen initiators of the present invention may be used to initiate cross-finking of any unsaturated polyester resin mixes and may 5 be added thereto according to well-known methods of initiating such cross- linking.

Exemplary inorganic peroxygn compositions useful as initiators for curing unsaturated polyester resins according to the present invention include the persulfates, perborates, percarbonates, perphosphates and the o peroxides, and specifically sodium persulfate, ammonium persulfate, potassium sulfate, sodium perborate, sodium percarbonate, zinc peroxide, and calcium peroxide. In certain particular embodiments of the present invention, the inorganic peroxygen initiator is present with respect to said unsaturated polyester resin in an amount of from about 0.1 % weight to 5 about 4.0% weight.

Initiators according to the present invention may be employed in a number of different environments, realizing improvement in each due to the nature and characteristics of the composition. As previously mentioned, inorganic peroxygen compounds are well known as catalysts for emulsion 5 polymerizations but have not been utilized in the free radical polymerication involved in curing unsaturated polyester resin syrups. The organic peroxygen compounds have been the initiator of choice for such systems.

Most inorganic peroxygen compounds, as opposed to organic o oxygen compounds have the characteristic of being very stable. Inorganic peroxygn compounds generally do not deteriorate under normal storage conditions over prolonged periods of time if they are kept dry in closed containers. Moreover, inorganic peroxygen compounds are much less costly than the organic peroxygens, sometimes costing as much as two to 5 three times less per pound than the organics. A further advantage over organic oxygen compounds is the ability of inorganic peroxygen compounds to decompose harmlessly over a period of time, unlike organic peroxygen compounds which must be carefully disposed of using hazardous waste disposal techniques. In addition, inorganic peroxygen o compounds are generally non-flammable, unlike the normally highly flammable organic peroxygen compounds. Moreover, it is generally thought that organic peroxygens, particularly methylethylketone peroxide and the phthalates are carcinogens.

Although inorganic peroxygen compounds may be employed as 5 initiators without further constituents, the initiator of the present invention preferably utilizes an admixture of an inorganic peroxygen compound and organic peroxygen compound. Using this combination of inorganic and organic initiators results in the ability to control the curing of unsaturated polyester resins within a precise, predetermined time. Although use of an o inorganic peroxygen compound alone as the initiator for such systems is part of the present invention and will result in the successful curing of unsaturated polyester resins, curing times for such systems are harder to predict..

The peroxygen compounds, whether inorganic and/or organic, may 5 be dispersed in the polyester resin in the anhydrous form or may

alternatively be first formed into an aqueous solution and then dispersed in the resin. Accordingly, dry inorganic and dry organic peroxygen compounds may be utilized in the present invention.

The dispersion methods disclosed herein are not necessarily critical to the preparation of the initiators of the present invention. However, as explained below, methods utilizing a Kady Mill and/or Eppenbach Mixer are preferred in making the present initiators.

When used according to the present method, the inorganic peroxygen compounds utilized herein are generally soluble in the organic peroxide dispersions. However, when used alone as the initiator, the inorganic peroxygen compounds are generally insoluble in the unsaturated polyester resins. The organic peroxygen compounds used alone are, however, soluble in such resins. When the inorganic peroxygen compounds are dissolved in water and the water solution is dispersed in the unsaturated polyester resin, an aqueous emulsion is formed thereby. In employing the inorganic initiators of the present invention, the preferred range of inorganic peroxide relative to the amount of polyester resin cured thereby is at least 0.1%, and preferably, between about 0.2% and about 4.0%. If lesser amounts of the inorganic initiator are employed, curing of the polyester resins may be incomplete, thus resulting in a rubbery and soupy laminate. Likewise, if more than about 4% by weight of the initiator is used relative to the weight of the polyester resin, the resins will not cure optimally and will result in a rubbery, undesirable laminate. In addition to inorganic peroxygen compounds, with or without organic peroxygen compounds, other constituents may be added to the initiator systems of the present invention for curing unsaturated polyester resins.

Byway of example, a defoamer may be included to reduce foaming. Further, a water soluble inorganic salt may be included to render the suspension or dispersion stable and retain the peroxides in suspension. Such salts, which must be stable to the peroxides, may include sodium chloride, potassium chloride, calcium chloride and most other chloride salts except those of the transition metals which may cause the peroxide to decompose. Also, the soluble phosphate and sulfate salts of the group I and II metals are also generally acceptable.

Carbonate or bicarbonate salts of the Group I or II metals may also be included in the systems of the present invention so that a variance of the amount of initiator employed will produce a low density foamed or a high density polymer product. The carbonate or bicarbonate salts liberate carbon dioxide which serves as a blowing agent to foam the polyester.

Acidic inorganic salts may also be included in the dispersion, attributing a number of beneficial aspects thereto. Specifically, such salts, exemplified by NaH2Pθ4, Na2HPθ4, NaHSθ4 and AICI3, increase specific gravity of the water phase and thereby decrease settling propensity of the peroxide, act as a fire retardant for the peroxide in suspension, serve as a humectant whereby the rate of water evaporation from the dispersion is reduced, and retain the water of hydration after drying of the dispersion to negate any fire hazard that may be experienced with the dry organic peroxides used in the system. As to the particular inorganic salts, sodium dihydrogen phosphate and sodium hydrogen phosphate are particularly beneficial for serving as natural buffers for the system and for maintaining pH in a range of from about 3 to about 8. Such inorganic salts act as sequesterants to reduce the likelihood of decomposition of the peroxide due to transition metal ions. Additionally, fire retardants and fillers may be employed in the initiator systems. Examples of such compounds include alumina trihydrate, gypsum, borax, magnesium sulfate and tri-sodium polyphosphate.

Various accelerators, or promotors, may also be employed in the curing of polyester resins, especially when curing is to occur at room temperature. Accelerators may generally be divided into three classes- metal compounds (primarily the organic cobalts), amines, and sulfur compounds, with the cobalt compounds and amines being the most widely used. Examples of known promoters include stannous octoate, amines such as dimethylaniline and diethylaniline, mercaptans such as lauroyl percaptan and dodecyl mercaptan, organic cobalts such as cobalt naphthenate and cobalt octoate, manganese octoate, zirconium naphthenate, dimethyl paratoludene and other known promoters.

The polyester resin systems may further include inhibitors such as hydroquinone, p-tert-butylcatechol, pyrogallol, chloranil, picric acid, and

quϊnones, to inhibit polymerization and/or reduce the peak exotherm temperatures involved.

Plasticizers may also be employed to disperse the initiator into a paste-like state. Examples of such plasticizers include butyl 5 benzolphthalate, dioctyl maleate, isopropyl phenyl phosphate, and other plasticizers.

Other ingredients, including curing agents, foaming agents, and additives that improve adhesion to fillers and fibers may also be used therein. 0 The initiators of the present invention are generally produced according to the teachings U. S. Patent No.4,917,816 ("the '816 patent") which was issued to the inventor of the present subject matter on April 17, 1990. That patent is incorporated herein by reference. As disclosed therein, the mixture of dispersion constituents, including a compound that 5 produces an ionic region about the dispersed peroxygen particles and permits viscosity control, is subjected to a low shear, attrition-type dispersion mill for a predetermined period of time and is then degassed. More specifically, the dispersion constituents other than the peroxygen compounds are preferably first blended in a low shear mixer after which the o blend is added to a low shear attrition-type dispersion mill. The particular peroxide is then added to the blend in the dispersion mill and the mill is operated for a predetermined time to produce the desired dispersion. Thereafter, the dispersion is removed from the dispersion mill and is preferably degased and filtered. 5 By utilization of the low shear, attrition-type dispersion mill, preferably a Kady Mill, as described in the '816 patent, viscosity can be controlled from a very low viscosity, for example, about 100 centiposies to a very high viscosity, for example, 15,000 ceηtiposies or greater. At the low viscosities, the initiator is sprayable in conventional spray equipment o without damage or fouling while at the higher viscosities a thick paste results. For both types of applications, as well as others in medium viscosity ranges, any of the additional constituents previously mentioned may be added to the dispersions to stabilize same, reduce the flammable and explosive nature of the peroxides, for foaming ofthe polymer, and the 5 like.

Alternatively, the dispersions according to the present invention may be provided by blending all of the constituents in a low shear mixer, and subjecting the mixture to a high shear dispersion mill for a predetermined period of time. Thereafter, the dispersion is removed from the dispersion 5 mill and is preferably degased and filtered. Such high shear dispersion mills, such as a Cowles Mill or, more preferably, an Eppenbach Mill, yield an acceptable dispersion in accordance with the present invention.

The inorganic peroxygen compounds that may be suitably employed according to the present invention include any of the various 0 inorganic peroxides and, particularly, those which have been heretofore used as catalysts for emulsion polymerizations. Exemplary inorganic peroxides include persulfates such as sodium persulfate, ammonium persulfate, and potassium persulfate, the perborates such as sodium perborate, the percarbonates such as sodium percarbonate, and other 5 inorganic peroxides such as zinc peroxide and calcium peroxide.

Organic peroxides that may be suitably employed according to teachings of the present invention include solid peroxides dispersible in an aqueous medium as exemplified by benzoyl peroxide, lauroyl peroxide, di- cumyl peroxide, and di-cetyl peroxydicarbonate. Benzoyl peroxide is the o preferred organic peroxide when an organic peroxide is used in the present invention. However, care must be taken when handling the organic peroxygen, particularly the dry form of benzoyl peroxide. Benzoyl peroxide's highly flammable and explosive nature makes it an extremely dangerous compound which should be used in small amounts. 5 Dispersions or suspensions of the peroxides may range from very low viscosity, sprayable compositions for catalysis of unsaturated polyester resin syrups, to very viscous dispersions in virtually paste form which likewise would be suitable for catalysis but are employed in molding operations, mine bolt securement, repair of structured elements where the o materials are poured or spread by hand or the like. Additionally, present compositions may be provided in which the peroxide is present in very finely divided powder form.

Unsaturated polyester resin syrups which may be catalyzed by the inorganic peroxide compositions of the present invention include 5 unsaturated polyester resins having a copolymerizable monomer

containing a terminal vinyl group. The unsaturated polyester resin may be derived from the polyesterifrcation of a polycarboxylic acid or a polycarboxylic acid anhydride with a polyol according to techniques well known to those skilled in the art. Because the polyester resin to be produced is unsaturated, the polycarboxylic acid or anhydride, the polyol, or both, must contain at least one ethylenicly unsaturated bond. Exemplary of polycarboxylic acids and anhydrides which are suitable for use in production of the unsaturated polyesters include, without limitation, phthalic acid, isopthalic acid, terephthalic acid, adipic acid, succinic acid, tetrahydrophthalic acid, tetrabromophthalic acid, maleic acid, fumaric acid, the anhydride of any of the aforementioned acids, and combinations thereof. Polyols suitable for use in preparation of the unsaturated polyester resins are exemplified by ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, diethylene glycol, dipropylene gfycol, polyethylene glycol, polypropylene glycol, trimethylol ethane, trfmethylo! propane, pentaerythritol, hydroxy-alkyl esters of polycarboxylic acids and combinations thereof. As is well known to those skilled in the art, a slight stoichoimetric excess of polyol is generally employed in preparation of the polyester resin to facilitate reaction between the polycarboxylic acid or anhydride and the polyol and to reduce the viscosity of the formed polyester resin.

A copolymerizable monomer is combinable with the unsaturated polyester resins to yield a resin syrup containing a terminable vinyl group. Such monomers are exemplified by styrene, alpha-methyl styrene, o- chlorostyrene _t vinyl toluene, acrylic acid, methacrylic acid, alkyl acrylates, alkyl methacrylates, divinyl benzene, diacrylates, dimenthacrylates, triacrylates, trimefhacrylates and combinations thereof. In general, the monomer may be present in an amount of from about 20 to about 40% of the total weight of the polyester resin syrup, that is, the unsaturated polyester resin comprises from about 90 to about 60% of the total weight. When reacted with the unsaturated polyester resins, monomer produces a crosslinked polymer structure. Further suitable copolymerizable monomers for the resin syrup include the reaction products of polyepoxides with acrylic or methacrylic acids for example the reaction products of a polyol such as 2,2-bis (4-hydroxypheπyl) propane with a glycidyl acrylate or

methacrylate. If employed, this particular type of copolymerizable monomer replaces a portion of the unsaturated polyester resin.

Products according to the present invention may be employed without danger of fire or explosive hazard in spray up systems as catalysts 5 for resin syrups, as thickened pastes in curing of resin syrups or pastes in mine bolt-applications, in repair of structured elements or the like, as active ingredients in dermicidal and other pharmaceutical compositions, and the like.

The present invention may be better understood by reference to the 0 following examples.

To determine whether inorganic peroxygen compounds, affect the cure rate of unsaturated polyester resins with various promoters, a general purpose unsaturated polyester resin designed for a filled system and formulated to cure with benzoyl peroxide was acquired from Cargil Resin 5 Division of Atlanta, Georgia. The resin was formulated by mixing

1500 parts by wt. resin with 1500 parts by wt. CaC0 ₃ (100 mesh; 150 μ sieve size) material.

ASTM Standard E11-87 is used herein for sieve size description. Such designations shall include mesh size and the equivalent sieve size in o the following format: (mesh size; sieve size).

EXAMPLES 1-8 Two hundred gram samples of the resin were initiated using various activator systems employing benzoyl peroxide (BPO) alone and in 5 combination with sodium persulfate (SPS) (which is technically known as sodium peroxydisulfate). These peroxygen compounds were added to the resins as a 40% water dispersion solution made according to the low shear, attrition-type process employing a Kady Mill as described above and in the '816 patent. In Examples 4 and 5, triethanolamine was used as a o promoter; in Example 6, phenyl diethanolamine was used as a promoter; in

Example 7, thiourea dioxide was used as a promoter; and in Example 8, erythorbic acid was used as a promoter. In Examples 5-8, a wetting agent obtained from Dow Corning and identified as DC193 was employed. The resin systems were allowed to cure in a paper cup and a one gallon paint 5 can lid.

Table 1 shows the amounts of constituents employed in the various initiator systems studied and the gel times therefor. "Gelling" of a resin generally occurs when the liquid resin changes from a liquid to a colloidal semi-solid state indicating that cross-linking of the polyesters is about 5% 5 complete.

Table 1

0

5

Table 1 , and particularly a comparison of Example 1 with Example 3, shows that the addition of an inorganic peroxygen compound to an unsaturated polyester resin system decreases the gelling time required o for the resin. Moreover, the addition of a wetting agent in Examples 5-8 indicated that wetting agents also increase the rate of gelling when used with the peroxygen initiators. Furthermore, Table 1 shows the effects of various promotors with respect to the geling time of the resins.

5 EXAMPLES 9-14

The following examples show the effect of several different inorganic peroxygen compounds on the gelling time of polyester resins when the inorganic peroxygen compounds are added in combination with various organic peroxygen compounds. The polyester resin used in o Examples 1-8 was promoted with dimethylaniline and cobalt naphthenate.

Into 200 gram samples of the resin, two grams of the following inorganic peroxygen compounds - ammonium persulfate, sodium persulfate, potassium persulfate, sodium perborate (technically, sodium perborate tetrahydrate), and sodium percarbonate (technically, sodium carbonate 5 peroxyhydrate) - and two grams of the following organic peroxygen

compounds - BPO, methylethyl ketone (MEKP), di (4-t-butyl-cyclohexyl) peroxydicarbonate (DBCPOC), 2,4-pentanedione peroxide (PDPO) and cyclohexanone peroxide (CHPO) - were dispersed as described in Examples 1-8. The gel times for the various inorganic initiator systems as well as the gel time for a standard system employing only the various organic peroxygen compounds (Example 9) are shown in Table 2.

CHPO

Ex.13 NaB0 ₃ x4H ₂ 0 11 17 13.5 9 11 Ex.14 2Na ₂ Cθ3x3H ₂ 0 ₂ 8 15.5 10 8.5 8

As seen in Table 2, each of the various inorganic peroxygen initiators tested resulted in a reduction of the polyester resin gelling time as compared to initiation with only the organic peroxygen compounds.

Particularly note in Example 14 the substantial decrease in gelling time when sodium percarbonate was employed.

In addition, calcium peroxide and zinc peroxide were used as inorganic peroxygen initiators in combination with benzoyl peroxide and hydrogen peroxide was used as an initiator alone. The curing of the unsaturated polyesters initiated thereby was comparable to curing in the above-described systems.

EXAMPLES 15-21 In order to determine the effect of sodium persulfate on the increase in resin hardness as compared to resins initiated with benzoyl peroxide, the following tests were conducted. Resin systems as described in Examples 1 -8 were prepared. As in Examples 1 -8, benzoyl peroxide was used as an organic peroxygen initiator alone and in combination with sodium persulfate as an inorganic peroxygen initiator. The peroxygen

compounds were employed as 40% water dispersion solutions made as described in Examples 1-8. The systems in Examples 16 and 17 were promoted with triethanolamine; in Example 18, with phenyl diethanolamine; in Example 19, with thiourea dioxide; and in Example 20 with erythorbic acid. The DC193 wetting agent previously described was employed in Examples 17-21.

The gel times and rate of hardness increase during curing of 200 gram samples in one gallon paint can lids were measured. The well-known Barcole hardness test was employed according to American Society Testing Materials Standard C581-74. The results are shown in Table 3. A "-" indicates no dial deflection and a "+" indicates some dial deflection after 45 minutes of curing. The hardness increase was measured after one hour of curing and is shown in Barcole units.

Table 3

Hardness Increase 15-20 20-30 25-35 20-30 15-20 15-25 20-30

As seen in Table 3, the increase in hardness of the resin initiated by employing inorganic and organic peroxygen initiators in combination, was comparable to or better than the rate of hardness increase in resin systems employing benzoyl peroxide alone.

EXAMPLES 22-31 To determine the chemical and physical stability, or shelf life, of initiator systems of the present invention employing an inorganic peroxygen compound, such as sodium persulfate, in combination with various known additives, the formulations described below were prepared. In each example, the listed amount of benzoyl peroxide (a 50% water dispersion made as described in the '816 patent with the exception of omitting the monosodium phosphate as a salt) was combined with the listed additive(s). The pH of each sample was adjusted to between about 7 and about 9 with NaOH, if needed. All formulations were stored at lab conditions for 120 days.

Ex.22

500 gms. benzoyl peroxide

221 gms. alumina trihydrate (400 mesh; 38μm sieve size) (a flame retardant and filler)

and pH adjuster) 25 gms. water

An active oxygen analysis was performed to compare day 1 with day 120. After being stored for 120 days, each of the samples separated to some extent, but none had caked in the bottom of their storage containers. Mixing restored all samples to their original viscosity. Each of the samples was employed to initiate curing of the unsaturated polyester resin described in Examples 1 -8. The times for and extent of curing on day 120 were comparable to those when curing occurred immediately with the initiator systems employed in Examples 1-8.

EXAMPLES 32-42

In order to determine the performance of the inorganic peroxygen initiators in the absence of water, the following examples were directed to the use of dry initiator systems. One hundred gram samples of the unsaturated polyester resin system described in Examples 1 -8 were initiated with initiator systems employing dry materials as opposed to the water-dispersed peroxygen compounds used in the previous examples. The gel time in minutes for the various inorganic peroxygen systems employed in various amounts are shown in Table 4. As indicated, certain of the following examples employed peroxygen compounds that were finely ground using a mortar and pestil.

Table 4

EXAMPLE 43 In order to determine the gelling time of an inorganic/organic peroxygen initiator in conjunction with a plasticizer, the following system was utilized. One hundred grams of benzoyl peroxide was dispersed in 300 grams butyl benzyl phthalate by the mechanical methods described above wherein the constituents are subjected to a high-shear dispersion mill process utilizing an Eppenbach Mill after being subjected to the low-shear, attrition-type methods used for Examples 1-8. Butyl benzyl phthalate is a known plasticizer often employed in such initiator systems. One hundred grams of spray-dried fine particles of calcium peroxide were blended into the mix. The resulting low viscosity fluid contained 20% benzoyl peroxide, 20% calcium peroxide and 60% butyl benzyl phthalate plasticizer. Two grams of the initiator system was added to a 100 gram sample of the unsaturated polyester resin employed in Examples 1-8. The resin gelled in 15.0 minutes. Further testing was conducted on the system employing ethylene diamine as a promoter which resulted in faster gel times. The utilization of a plasticizer in which the organic and inorganic peroxygen compounds are dispersed does not decrease the performance of the initiator systems.

Examples 44-48 describe the use of different unsaturated polyester resin and the effects of promoting same with various inorganic peroxygen initiators without the addition of an organic peroxygen initiator. As can be seen in the Examples, the various inorganic peroxygen compounds affect gel times differently depending on the promotor employed.

EXAMPLE 44 A 100 gram sample of a dicyclopentadiene-based resin acquired from Cargil Resin Division was promoted with 0.1 gram of 12% cobalt naphthenate and initiated by dispersing sodium perborate in the resin according to the methods described in Example 43. The gel time was 90 minutes.

EXAMPLE 45 A 100 gram sample of the resin used in Example 44 was promoted with 0.1 gram of 12% cobalt naphthenate and initiated with calcium peroxide. The gel time was 45 minutes.

EXAMPLES 46-52 The following constituents were added to the dicyclopentadiene- based resin used in Example 44: 0.1% diethyl aniline, 0.1% N-N dimethyl paratoludene, and 0.1 % cobalt naphthenate. One hundred gram samples of the modified resin were initiated with various inorganic peroxygen compounds and the gel time results are shown below.

lithium persulfate (1g) - 7 min.

In addition to the specifically described examples, various ^" combinations of inorganic initiators and inorganic/organic combination

initiator systems were tested for their capability to cure unsaturated polyester resins. Each of the systems which employed inorganic peroxygens such as sodium perborate, sodium percarbonate, sodium persulfate, calcium peroxide, and zinc peroxide in combination with various plasticizers including butyl benzoyl phalate plasticizer (also known as Sanitizer 160), Kronitex 50 a dioctylmaleate plasticizer, isopropylphenyl phenyl phosphate plasticizer Kronitex 50 is a registered trademark of FMC Corporation for its , isopropylene plasticizer, in combination with various promoters including diethylaniline, N,N-dimethyl paratoludene, and cobalt napthanate showed effective gelling of various unsaturated polyester resins.

To determine various characteristics of laminates formed using certain inorganic/organic peroxygen initiator systems, the laminates of Examples 53-56 were formed. The results of the various strength, modulus, and elongation tests indicate that the inorganic peroxygen initiator systems of the present invention are comparable to the previously- known organic peroxygen initiator systems when employed to cure particular unsaturated polyester resins.

EXAMPLES 53-56

A dicyclopentadiene-based resin having 70% solids was diluted with styrene to 50% solids and filled to 50% by weight with a 80/20 calcium sulfate dihydrate/calcium carbonate blend.

Portions of this mix were then promoted and initiated with the initiators in the amounts listed in Table 13 below and then made into approximately .001" thick laminates containing 2 to 2 1/2 ounces of chopped strand mats. In Table 13, n-dimethyl paratoludene is DMPT, diethylaniline is DEA, triethanolamine is TEA, and cobalt naphthenate is CN.

Table 13

0

5

56 D .1% CN 1.25% methyl ethyl ketone in plasticizer

Each of the cured laminates was tested according to accepted o ASTM standards. The results of the tests for each of these laminates are shown below in Table 14 (numbers are shown in psi).

Table 14 5 B D

14,313

0 1,449,390

7,736 5

1 ,404,952

.984%

Although preferred embodiments of the invention have been described using specific terms, devices, concentrations, and methods, such description is for illustrative purposes only. The words used are words of description rather than of limitation. It is to be understood that changes and variations may be made without departing from the spirit or the scope of the following claims.