CA1211590A - Room temperature crosslinking unsaturated polyester resins - Google Patents

Abstract

- I -ABSTRACT
The crosslinking of unsaturated polyester resins at room temperature in the presence of a peroxyester initiator is accelerated by a mercapto compound and a metal salt wherein the metal is selected from the group consisting of copper, and iron, or a mixture of the metal salts.

Description

ROOM TEMPERATURE C~OSSL:L~IKING
, _ UNSATURATED POLYESTER RESINS
SIR 2579) . BACKGROUND OF rye INVENTION
The present- invention pertains to the room temperature crossl~nking of unsaturated polyester resin and more particularly, Jo accelerating the room temperature cross linking of such polyester resins with an organosulfur compound and metal salt.
Organo~ulur compounds and metal salts are known in the prior art for accelerating (also called promoting the room temperature cross linking of unsaturated polyester resins in the presence of a organic peroxide. US. Patent No. 2~946J770 discloses the use of an organic sulphoni~m compound in combination with a quate~nary ammonium compound end a copper or iron salt Jo accelerate toe polymerization time. US.
Patent No. 3,333,021 teaches thy use of mercap~ans in combination with vanadium salts as an accelerator system. British Pun No. 1,170,983 discloses the use of a 2wmercapto-alcohol in combination with a cobalt or vanadium salt as an accelerator. None of these patents teaches the present invert SUMMARY OF Lowe. INVENTION
The present invention it directed to a process of cro~slinking an unsaturated polyester resin comprising admixing to said unsaturated resin a) an initiating amount of a peroxyester, by at least one Merritt compound, and c) an inorganic metal salt wherein the metal is elected from the group consisting of iron and copper or 2 mixture of the metal salts, and cross linking the admixture at room temperature.

DETAILED DESCRIPTION OF _ E INVENTION
It has now been found that unsaturated polyester resins cay be crosslinkled (also called cured) rapidly and thoroughly at room temperature using a peroxyes~er initiator and an accelerator system of a Marquette compound and inorganic metal salts.
The unstirred polyester resins used in this invention are reactive resins dissolved in a polymerizable monomer or mixture of monomers.
These reactive no ins are formed by condensing a saturated dicar~ox~lic acid or android and an unworried dicarboxylic acid or android with a dodder alcohol. Examples of these polyester resins are the products of the reaction of a saturated dicarboxylic acid or android ego.
phthalic adored, isophthalic acid, tet~ahydrophthalic android, hexahydrophthalic android, endomethylene ~e~rahydrophthalic android, tetrachloroph~halic android 9 hexachloroendo~ethylene ~etrahydrophthalic acid, succinic acid, glu~aric acid, adipic acid, pimelic acid, sub Eric acid azelaic acid or sebacic acid) and a Imsaturated dicarboxylic acid or android (e g., malefic android, fumaric acid, chl.oromaleic acid; laconic acid, citraco~lic acid or mesa conic acid) with a dihydric alcohol (e.g., ethylene glycol, propylene glycol, battalion glycol, diethylene glycol, triethylene glycol or neopentyl glycol). Small amounts of a polyhydric alcohol (e.g., glycerol, pentaery~hritol, ~rimethylopropane or sourball) may be used in combination with the glycol.
A three-dimensional structure is produced by reacting the unsaturated polyester through the unsaturated acid component with an unsaturated monomer which is capable of reacting with the polyester resin Jo form cross-linkages. Suitable unsaturated monomers include styrenes methylstyrene, dimethylstyrene, vinyltoluene, divinylbenzene, dichlorostyrene, methyl acryla~e, ethyl a relate, methylacrylat~, Delilah phLhalate, vinyl acetate, triallyl sonority, acryloni~rile, acrylamide and mixtures thereof. The relative amounts of the unsaturated polyester resin and the unwatered monomer in the composition may be varied over a wide range.
The unsaturated polyester resin compositions generally contain 2Q% to 80% by weight of the monomer, the monomer content preferably being in the range prom 30% to 70% by weight.
:

Also included among useful reactive resins are those resins which are terminated by polymerizable unsaturated ester functions but wherein the polymer repeating unit may or may not S be of the polyester type, for example, polyethers terminated with acrylic acid ester groups, blended with suitable copol~merizable monomers. A typical series of such resins are commercially available from Dow Chemical Corp. under the trademark "Darken" resins and generally comprise polyethers prepared from an epoxide (e.g., glycidol) and a bisphenol ego.,

2,2-di(4-hydroxyphenyl) propane or bisphenol A
which are terminated by acrylic acid ester functions and blended with Syrian. A more detailed description of vinyl ester resins may be found in "Unsaturated Polyester Technology", Gordon and Breach Science Publishers, New York 1976, p 315 and in Developments in Reinforced Pluses - 1 edited by G. Pritchard, published by Applied Science Publishers Ltd., England 1980.
To simplify discussion in the remainder of this text the term pulse resin will be used to describe both unsaturated polyester resins and polyether resins with terminal unsa~uration (Darken types).

In the practical utilization of polyester resins, i c is common to incoxpora'~e fillers and reinforcements. Fillers are substances added to poultry resin before curing to enhance various properties of the final product or to reduce its cost. Bulk fillers such as carbonates and clays are used to decrease the cost of the final precut to give better flow- characteristics to the resin, and to provide a smoother surface on the finished Lomb. nether advantage of bulk fillers is that they absorb some of the exothermic heat of the curing reaction. This lessens internal strain and reduces thermal expansion and shrinkage. Other filler such as hydrated alumina increase fire Ritz of the final products Reinforcing fillers include such fibrous materials as glass, quartz, cotton, nylon, asbestos and sisal. They are usually incorporated into the resin to improve strength, particularly impact and flexural strengths.
A wide variety of fullers and reinforcement have been found to be compatible with the curing process of this invention.
To utilize the many advantages of the process of this invention, an number of a variety of methods known to Whose skilled in the art may be used to convert the reactive liquid resin into a useful thermoses solid. The process of this invention is particularly suited to such known methods as spray-up t hand lay-up, resin injection, centrifugal casting filament winding wet compression molding, continuous laminating, casting and encapsulation.
The peroxidic compounds of this invention ware the peroxyesters. Peroxyesters are widely used as initiators for free radical polymerization and cross linking a elevated taperers (>150F). A
detailed description of peroxy~sters and their use in curing unsaturated polyester resins may be found in the following reference, V. R. Kamath and R. B. Killer "Initiator Systems for Unsaturated Puller Resins", Developments in Reinforced Plastics - I, published by Applied Science Publishers Ltd., England 1980, pup 121-144.
Peroxyesters have the general structure I
(R3x(OOC)y(Rl)z wherein x, y and z are 1 or 2 with the provisos that when x, y and z are 1, R is selected from the group consisting of a substituted or unsubsti.t~l~ed terti.ary-alkyl of-4 to 8 carbons, tertiary-alkynyl of 5 Jo 8 carbons, tertiary-cycloa~lkyl of 6 to 10 carbons and tertiary-aralkyl of 9 to 12 carbons, and Al is selected from the group consisting of hydrogen, a subs~iLuted or llnsubst:ituted primary, squanderer ter~iary-alkyl of Jo 20 carbons, alkenyl of 2 to 20 carbons, alkynyl of Jo 20 carbons, cycloalkyl of 5 to lo cartons, arzLkyL of 7 to 14 carbons, aureole of 6 Jo lo carbons, alkoxy of 1 to 20 carbons, cycloalkoxy of S to 10 carbons 0 or aralkoxy of 7 to 12 carbons when x and y are 2 and z is 1, R is the-same as defined above, and R1 is selected from the group consisting of a substituted or unsubstituted alkaline diradical of 1 Jo 10 carbons, alkynelene I diradical of 2 to 10 carbons, alkenylene diradical of 2 to 10 carbons, cycloalkylene diradical of 5 to 10 carbons, Arlene diradical of 6 Jo 10 carbons, alkylenedioxy di~adical of 2 to 10 carbons, oxyalkylenedioxy ox 4 to 10 carbons, and 0 cycloalkylenedioxy of 5 to 10 carbons, and when y and z are 2 and x is 1, R is selected from the group consisting of a substituted or unsubstituted di~tertlary alkaline diradical of 7 Jo 10 carbons, di-tertiary-alkynelene diradical of 8 to 10 carbons, di-te~tiary~cycloalkylene diradical of 7 to-12 carbons t and di-ter~iary~aralkylene diradical of 12 to 18 carbons, and Al is the same as when x, y and z are 1, .
the substituents for R and Al being lower alkyd of l to 4 carbons, Of, F, Bra cyan, car boxy, lower alkoxycarbonyl, lower acyloxy, airlocks of 7 to lo carbons, lower alkoxy and C~3 wherein R2 is the same a defined above for R when X 9 y and z are 1.
Specific expels of particularly preferred peroxyesters of this invention are t-butyl peroxybenzoate, t-butyl peroxyac~tate, t-butyl peroxyisobutyrate, t-butyl porks ethylhexanoa~e J bottle peroxypivalate, timely peroxypivala~e, t-butyl peroxyneodecanoate, t-butyl peroxymaleio acid di-t-butyl I diperoxyphthalate, 00-t bottle 0-isopropyl peroxycarbonate, 2,5~dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane,, 2-5-dimethyl-2,5~bi~benzoylperoxy)hexane, timely peroxy-2-ethyl-hexanoate, timely peroxybenzoate, US 00-t bottle 0-2-ethylhexyl monoperoxycarbonate, Diablo diperoxya~elate, and OO-t-~nyl 0-2 ethylhexyl monoperoxycarbonate.
In activated cure systems, activity is independent of half-life temperatures of peroxides. Therefore, the preferred peroxyester is one which exhibits good thermal stability and ease of handling. In this respect, t-butyl peroxybenzoate is a preferred initiator. In this invention one can use mixtures of two or more peroxides wherein at least one of the peroxides is a peroxyester as defined above. These types of mixtures are useful for obtaining specific processing or economic advantages. Thus, a mixture of t-butyl peroxybenzoate sod cumin hydroperoxide leads to rapid gel times and fully cured resin even in thin layer. This mixture would have the added advantage of being less expensive. Along similar lives, one can use a mixture of t-butyl peroxybenzoate and I l,l-di(~-butylperoxy) cyclohexane might be used to cure the resin at ambient temperatures. The undecomposed peroxyKetal could then be thermally activated by post curing the part a elevated temperatures. Cured resin with low residual monomer content could then be obtained more rapidly than in the absence of the peroxyke~al In practicing the process of this invention, an amount of peroxye.ster effective for providing an optimum cure rate is added Jo the unsaturated polyester resin. Generally, the peroxyester compound is added in a proportion to provide from about 0.1 to ablate 5 . O parts, and preferably about OHS to 2.0 parts peroxyester per 100 parts by weight of the polyester no in (phi) includillg unsaturated monomer The amount of peroxyester can be varied within this particular range depending on the no cult desired.
When a mixture of peroxides is used, the total concentration of initiator would be preferably about 0.5 to 2.0 parts by weight per 100 parts by weight of the polyester resin including unsaturated monomer s ) . In this case, the concentration of pero~yester(s) would be a least about 0.1 to 1.0 pa by weight per 100 parts by weight of polyester resin.
The Marquette compounds which are used in this inventiorl are those which contain the markup to radical or metal salt fumed therefrom and have the general s true lure (R )m(S)n~M)~S' where I and n are 1, 2 or 3 and an is 1 or 2, with the provisos that when m, n, and are l, M is hydrogen and R3 is selected from the group consisting of a substituted or unst~bstitu~ed alkyd of 1 to 18 carbons, aureole of 6 to 14 cartons, cycloalkyl of 5 to 10 carbons, aralkyl of 7 to 14 carbons, if -R2 (Al) 2N-C---- , heterocyclic of 2 Lo 10 carbons and 1 to 3 nitrogen, sulfur or oxygen atoms, wherein Al and R2 are independently selected from the group consisting of hydrogen, lower alkyd of 1 to 4 cartons, aureole of 6 to 12 carbons and cycloalkyl of 5 to 10 carbons, and when m and n are 2 or 3, Crisp 1, M is selected from the group consisting of copper and iron, and R3 is the same as mentioned above, and when n and are 2 and m is 1, M is hydrogen and R3 is selected from the group consisting of a substituted or unsubs~ituted alkaline diradical of 2 to 20 carbons, cycloalkylene diradical o f 5 to lo carbons, Arlene diradical of 6 to 14 carbons, and a heterocyclic diradical of 2 to 10 carbons and 1 to 3 nitrogen 9 slur or oxygen atoms, and wherein substations for R3 being selected from lower alkyd of 1 to 4 carbons F, C1, Bra cyan, alkoxycarbonyl of -l to 6 carbons, acyloxy ox 1 to 20 carbons, airlocks of 7 to 10 cartons and a~koxy of 1 to 6 carbons.
Compounds in which the Marquette grout can exist in equilibrillm with another chemical structure are useful. For example, in the case of Thor or substituted Theresa the Marquette radical can exist in equilibrium SAC HS-C
~NH2 NH2 Thor Isothiourea Examples of the variety of Marquette compounds which can be used in this invention are as follows: 2-mercaptobenzothiazole (MET), n-dodecylmercaptan, n-octadecylmercaptan, d-limonene dimercaptan, methyl-3-mercaptopropionate, Marquette ethyl palpitate, dibutyl mercaptosuccinate, isothiourea, ethylene isothiourea, ferrous mercaptobenzothiazolate, and cupric mercaptobenzo-thiazolate.
One of the preferred Marquette compounds is2-mercaptobenzothiazole (MET). This compound is preferred because it produces significant acceleration, has essentially no odor, and is available commercially in large quantities.

Mixtures of Marquette compounds can also be used in this invention. Such mixtures allow one to regulate the rate of cure and, thus, obtain better processing control. In addition mixtures 5 of markup compounds may also be used to improve the extent of cure , i . e ., reduce surface tackiness especially in thin molded samples.
Generally the amount of Marquette compound required is from about 0.05 Jo 5.0 parts and I preferably from about O .1 kiwi 2 . 5 parts Marquette compound per 100 parts by weight of the polyester rouser (phi) including unsoured monomer. The amount of markup compound can be varied within this particular range dependirlg on the result lo de trod.
Organic salts of transition metals such as cobalt and vanadium are commonly used as accelerators (promoters. Off the polyester resin is prepromoted so thaw the fabricator needs only to add the required peroxide. Keeping this in mind, we have found that inorganic salts of metals such as copper and iron are particularly preferred as accelerators in our invention. These inorganic salts include hydrated salts of copper and iron. Specific examples include cuprous chloride, cupric chloride, ferris chloride anal - 15 - .

ferrous chloride. These salts act as good accelerators and in addition provide long shelf-life to the prepromo~ed resin, which is very desirable.
S Salts of cobalt and vanadium have the added disadvantage of giving a strong color (pink or green respectively) lo> the cured piece. This is especially undesirable it clear gel coat applications. Using halide salts of copper and iron as accelerators in this invention overcomes this disadvantage.
Specific examples of useful metal salts include cuprous chloride, cupric chloride 9. ferris chloride, ferrous chloride, and their hydrated salts.
An essential compound of this invention is cupric chloride, since it is effective at extremely low concentrations. A particularly preferred mixture of metal compounds is thaw of cupric chloride and ferris chloride, since this mixture offers Improved reactivity as compared to the use of a single metal compound while providing increased shelf life of the prepromoted resin.
For example, when the accelerator system consists of a combination of a mercaptan, such as mercaptobenzothiazole (MET), and a metal salt, i such as cupric chloride, the shelf-life of the resin is less than eight hours. However, when ferris chloride is added in addition to cupric chloride, the shelf-1ife is greater Han 2 months S and, ion addition 9 the cure activity is increased.
To facilitate mixing of the metal compound with the resin, it is preferable to first dissolve the metal compound. Suitable solvents would include, Tulane, zillion, dimethylformamide, lo mineral spirits, dim ethyl sulfoxide, water, methanol, diethyleneglycol, ethylene chloride, methyl ethyl kitten, ethyl acetate, hexane, Delilah phthalate and Sterno.
Generally the optimum amount of metal compound(s) used is dependent upon the specific metal compound and is influenced by compound characteristics such as volubility and compatibility in the system. Generally 0~00001 to 0.50 part and preferably from about Oily to 0.05 29 part of metal per 100 parts by weight of the polyester resin (phi) including unsaturated monomer.
It is well known to those skilled in the art aye organic peroxides and accelerators (promoters) should not be mixed together directly.
Such direct contact between peroxides and I

promoters can result in hazardous decomposition of the peroxide. To avoid such contact the reactive ingredients are preferably added to the resin in the following order: metal solutes Marquette compounds peroxyester(s). Each ingredient should be thoroughly mixed into the resin before adding the next ingredient. The peroxyester may also be added as- a second component in the processes (ego spray-up) where the equipment it designed to dispense a mixture of resin and promoters as one coupon and peroxide as a separate component.

EXAMPLES
The following examples are provided Jo illustrate preferred embodiments of the invention and are not intended to restrict the scope thereof. All parts are parts by weight and all percentages are expressed a weight percentages.

EXAMPLE I
Into a g oz. waxed paper cup was weighed 100 grams of Laminac 4123 resin followed by 0.3 grams of merc~p~obenzothiazole. After mixing thoroughly, 0.0003 grams of cupric chloride was added as a 5% solution in methanol. After mixing thoroughly, lo gram of t bottle peroxybenzoate was added Jo the resin. A timer was started and the peroxide was mixed thoroughly and uniformly into the resin with a go ass stirring rod. The resin mixture was poured into a 4 oz. glass jar which was immersed in a 30C constant temperature water bath to the level of the resin. A thermocouple was located at the center of the resin mass to record exotherm temperature. The time when the resin golfed was recorded as the gel time. The - resin was Conrad golfed when inserting a stirring rod and raising a portion of the rev n out of the jar resulted in a string of resin that would snap instead of stretch elastically. The time a which the peak temperature was reached was recorded as the cure time. The peak exo~herm temperature way also recorded. The Berkeley hardness was measured aver Z4 his. at room temperature. The range of 10 hardness readings was recorded, it 40-45.
Parts by weight Laminac 41~3 (a) 100 100 100 t-Butyl Peroxybenzoate 1.0 1.0 1.0 Mercaptobenzothia~le - 0.3 0.3 Cupric Chloride D - - 0.0003 Gel Time (mint) 200 hrs.240 min. 16. min.
Cure Time (min.) - - 34 min.
Peak Exotherm Ç~ - - 155 Berkeley Hurriedness his.) - 40-45 (a) Orthophthalic type resin, USES. Chemicals (b) added as a 5% solution ox Quickly in methanol (c) Measured after 24 his. a room temperature using Berkeley impresser (yodel 934-1), Barber-Colman Co.

EXAMPLE II
The following experiments (1-:12) illustrate the variety Go peroxyesters which may be effectively used in this invention. The procedllre used was that defined in.Ex~mple I. The resin formulation is shown below:
Parts by Wt.
Resin (OF Eye) 100.0 Mercap~obenzothiazole 0.40 5% Curl OH O in methanol 0.03 50% Fake OWE in water 0.03 Peroxide (a shown in table) Peroxyest~rGel Cure Peak Bar-Expel Perox~esters C got 1 t-Butyl Peroxybenzoate 1.0 . 1 .0 2 t-Butyl Peroxy-2-ethyl-hexanoate 1.0 6.5 14.5 204 30-35

3 2,5 Dimethyl-2,5-bis(2-ethylhexa~oylperoxy~-hexane 0.5 12.5 23.0 188 25-30

4 t-Butyl Peroxyi~obutyrate 1.0 6.0 14.0 208 30-35 S OO-t-Butyl O-Isopropyl Monoperoxycarbonate 1.0 10.0 21.0 236 30-40 6 t-Butyl Peroxyace~ate 1.0 8.0 .17.0 209 30-40 I 7 Di-~-Butyl Diperoxyaz~la~e 0.5 10.0 21.0 193 25-40 8 2,5-Dimethyl-2,5-bis~b~n-zoylperoxy)h~xane 0.5 11.0 24.0 184 20-35 hexanoate 1.0 6.0 14.0 205 30-40 10 D -t~But~Jl Diperoxy- 16.0 195 35-40 11 t-butyl perox~maleic acid 1.0 7.5 19.0 199 30-40 Yeroxyest:er Gel Cure Peak Bar-Jo Peroxyesters Conc.(phr) (mix) (mix) C got ._ .
12 timely peroxybenzoate 1.0 7.5 18.0 205 35-40 13 bottle 0-2 ethylhexyl- 1.0 11.5 22.0 201 30-40 peroxycarbonate Lo timely 0-2-ethylhexyl- 1.0 12.0 23.0 197 30 40 peroxycarbonate teakettle peroxyneo- 1.0 14.0 Z2.5 191 30-40 hexanoate (a) Isophthalic polyester resin containing approximately 45% by weight styrenes monomer.
Resin solids have an acid value of lo.
available from Owens Corning Fiberglass.

I

SAMPLE III
The following experiments compare the cure activity obtained using the process of this invention to the cure activity obtained with a S common (standard) cure system.
To facilitate addition of the promoter to the resin a solution of the mercaptans and metal salts was prepared as a master batch using dim ethyl formamide as the solvent.

10 Promoter Solution A
Ingredient Wt.%
Marquette benzothiazole 48.1 Quill 2H2 0.10 Focal 2.75 lo n-dodecylmercaptan 1.72 N,N-dimethyl formamide 47.3 Promoter solution A was added to the polyester resin (OSSIFY) and after mixing thoroughly t-butyl peroxybenzoate was added. The "standard" cure system used for comparison consists of cobalt neodecanoate (6%) and a commercial methyl ethyl kitten peroxide containing 9% active oxygen (sold under the trademark LEPROUSLY DDM-9). Concentrations and cure activity are shown in the hollowing table. The resin was cured in a 5.5" diameter plastic mold. Thickness a I., of the cured resin was approximately 0.23".
Initial resin temperature was 22C.

Experiment # 1 2 OF Resin Eye (g) 100 100 S Promoter Solution A (g) 1.46 t-butyl peroxybenzoate (g) 0.50 6%-Cobalt neodecanoa~e (g) - 0.80 Leprously DDM-9 (go 1.2 Cure Active 10 Gel Time (mint I 5.0 Time to peck . 21.0 22.0 exotherm (mix) Peak Exotherm (C) 116 43 Surface Tackiness none sticky 15 48 ho Berkeley Hardness:
top 30-40 bottom 35 40 0 This example demonstrates what this invention gives good cures at much lower peroxide concentrations than are possible with a standard cure system.

EXAMPLE IV
EFFECT OF VARIOUS MARQUETTE COMBO W DO
_ _ This example illustrates the variety of mercap~an compounds which have been found useful

5 in this invention.

Grams Laminac 4123 100 5% CuC12(C~ 0-007 50% Fake 0.025 10 t-bu~yl peroxybenzoate 1.0 (c) Solvent is methanol (d) Solvent is dimethylformamide Results:
EYE 0.2 Phi merca~tan 30C Gel Mooney) 1. Control (no mercaptan) >500 2. n-Octadecyl mercaptan 1.0 3. d-limonene dimercaptan 1.0 4. Methyl-3-mercaptopropionate 0.5 S. erect ethyl palm 35.0

6. Dibutyl mercapto~uccinate I

EXAMPLE V
EFFECT OF VARIOUS COPPER SALTS

The following results indicate that both organic and inorganic salts of copper are useful in this invention.
Parts by Weight Item 1_ 2 3 Laminac 4123 100 100 10V
t-Butyl peroxybenzoate1.0 1.0 1.0 -Mercap~ob~nzo~hi~zole0.3 0.3 0.3 8% Copper naphthenate0.24 - -Copper swept - 0.10 Cupric chloride - - 0.0003 Gel time (mint 16 24 16 Cure time (mix) 28 38 34 Peak Exotherm (C) 163 157 155 Berkeley Hardness (24 hr)40-45 40-45 40-45 SAMPLE VI
effect Of Quick Concentration on Cure Activity]
This example illustrates the effect of the concentration of cupric chloride on the cure S characteristics of an orthophthalic type unsaturated polyester resin at 30C. Gel time, cure time, and peal exotherm temperature were determi~cd using thy standard SPY procedure Cupric chloride was added to the following resin 10 formulation.
Grams Laminac 4123 100 Mercaptobenzothiazole 0.2 t-Butyl peroxybenzoate 1.0 15 5% Quick (as in table below) Results:
OWE CuC12~g) Conc.(ppm) Gel (mix) cure (mix) Peacock) (24 ho 0 007 1.6 36 156 40-45 0 013 3.3 8 22 157 40-45 ~.025 6.0 3 15 158 40-45 0 Q3~ 8.0 1 12 lS8 40-45 0 047 11.0 1 11 157 ~-45 0.~72 ~7.0 I 12 146 30-40 0.~2 . 28 ~0.5 I 126 0-30 . Results indicate that cure time goes through a minimum in rheology of 10 15 Pam copper and thaw high levels of copper, for example 28 Pam, can cause slower reactivity and result in poor cures.

(a) SPY test procedure reference" Thea Annual Technical conference 1969 Reinforced Plastics/Composites Division, The Society of the Plastics Industry.
by 5% Quickly in methanol.

EXAMPLE YIP
This example illustrates the present mention (Experiment I and also illustrates the fact that initiators other Loan peroxyesters do not function. Experiment Nos. 1 and 2 illustrate the dramatic effect of Fake on eke shelf Experiment No. 4, 6 and 9 illustrate thaw peroxyket~ls, dozily peroxides and dialkyl peroxides respectively do not function in the present invention.
Experiment No. 10 illustrates that qua ternary minim compounds asp a necessary part of the accelerator system for dozily peroxides such as bouncily peroxide USA US. 2,946,770).

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EXAM YE VI I I
This example illustrates the use of metal salts of Marquette compounds as accelerators for persisters .

1 2 3_ 4 Laminac 4123 100 100 100 100 Cupric mereaptobenzo-thia:zolate - 1. 5 0 .1 0 .1 Ferrous mercaptoc~enzo-thiazolate - - 0 . 4 Mercaptobenzo~hiazole - - - 0 . 4 Tuttle peroa~ybenzoate 1. 0 1. 9 1. 0 1. 0 Room tempt gel time (Mooney 56 21 13 EXPEL IX
This example illustrates the use of peroxide mixtures.

S Resin OF Eye 100 100 100 Mercaptobenzo-thiazole 0.70 0.70 0.70 Dodecyl mercaptan 0.02 0.02 0.02 5% Quick in dim ethyl formamide 0.02 0.02 0.02 50% Fake in water 0.04 0.04 0.04 t-Butyl proxy-Bassett 1.0 0.5 0.6 t-Butyl proxy 2-e~hylhexanoate - 0.5 1,1-Bis(t-butylperoxy~
3,3,5-trimethyl cycle-hexane - - 0.4 Room tempt Mel time Mooney) 10 10 11 experiment No. 2 illustrates the use of a mixture of two peroxyesters while experiment No. 3 illustrates the use of a mixture consisting of a peroxyester in combination with a peroxyketal.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE
IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process of crosslinking an unsaturated polyester resin comprising admixing to said unsaturated resin (a) an initiating amount of at least one peroxyester, (b) mercaptobenzothiazole, and (c) an inorganic metal salt wherein the metal is selected from the group consisting of iron, copper and a mixture of the metal salt, and crosslinking the admixture at room temperature.

2. The process of claim 1 wherein the peroxyester is used in the amount of from about 0.1 to about 5.0 parts by weight.

3. The process of claim 1 wherein the mercapto compound is used in the amount from about 0.05 to 5.0 parts per 100 parts by weight of the polyester resin.

4. The process of claim 1 wherein the copper salt and additional metal salt together are used in the amount from about 0.00001 to about 0.50 part of metal per 100 parts by weight of the polyester resin.

5. The process of claim 1 wherein the ingredients are added to the unsaturated polyester resin in the order of metal salts, mercapto compounds, and finally the peroxyester, wherein each ingredient is thoroughly mixed into the unsaturated polyester resin before the next ingredient is added.

6. The process of claim 1 wherein the unsaturated polyester resin is a polyester containing 20 to 80% by weight of a monomer.

7. The process of claim 6 wherein the monomer is styrene.

8. The process of claim 7 wherein the peroxyester is t-butyl peroxybenzoate, the copper salt is cupric chloride, and the additional metal salt is ferric chloride.

9. The process of claim 1 wherein the peroxyester is selected from the group consisting of t-butyl, peroxybenzoate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-amyl perbenzoate, t-amyl peroxy-2-ethylhexanoate, and di-t-butyl diperoxyazelate.

10. The process of claim 1 where an additional mercapto compound is present selected from the group consisting of n-dodecylmercaptan, n-octadecylmercaptan, d-limonene dimercaptan, methyl-3-mercaptopropionate, 2-mercapto ethyl palmitate, dibutyl mercaptosuccinate, isothiourea, ethylene isothiourea, ferrous mercaptobenzothiazolate, and cupric mercaptobenzothiazolate.