Patent Description:
It is well known to react a polyepoxide with a polyisocyanate, in the presence of a catalyst, to form an oxazolidone-containing polymer or polyoxazolidone polymer. The oxazolidone-containing polymer is also referred to, by those skilled in the art, as a "prepolymer" or "polymer precursor" because after the oxazolidone-containing polymer or polyoxazolidone polymer precursor is produced, the precursor can be subsequently used to prepare a final product such as polyurethane films, elastomers, structural foams, rigid foams, flexible foams and the like when the precursor is an isocyanate-terminated prepolymer. Or, the precursor can be subsequently used to prepare a final product such as epoxy coating, resins, adhesives and the like when the precursor is an epoxy-terminated oxazolidone pre-polymer. Any of the conventional techniques for preparing polyurethanes and/or epoxy resins are used with the known precursors. Thus, processes of the prior art include, as a first step, producing a pre-polymer by reacting a polyepoxide and polyisocyanate in the presence of a catalyst to form a polyoxazolidone pre-polymer followed by curing the pre-polymer to form a final oxazolidone structure-containing curable polymer resin composition product for subsequent use in an application. The use of such known pre-polymers can add complexity and cost to the known processes.

Therefore, it would be an advantage to eliminate the use of a pre-polymer in the production of an oxazolidone structure-containing curable polymer resin composition. In addition, it would be beneficial to provide an oxazolidone structure-containing curable polymer resin composition that does not require the use of a pre-polymer and still maintains excellent mechanical properties including tensile strength, flex and impact resistance as well as high glass transition temperature (Tg). Furthermore, it would be an advancement in the art to provide a formulation that includes a catalyst system that can catalyze the reaction with a fast curation rate and higher Tg, while maintaining a high oxazolidone content and a long shelf life at low temperatures.

<CIT> discloses a thermosetting epoxy resin composition comprising (a) a polyisocyanate compound, (b) a polyepoxide compound, (c) a radical polymerizable compound selected from the group consisting of a vinyl aromatic monomer and a (meth)acrylate represented by CH<NUM>=CR<NUM>-CO-OR<NUM> wherein Ri represents a hydrogen atom o r a methyl group, R<NUM> represents an aliphatic group having <NUM> to <NUM> carbon atoms, an alicyclic group or an aromatic group, (d) a specific oxazolidone-forming catalyst, and (e) a radical polymerization initiator; the polyisocyanate compound (a) and polyepoxide compound (b) being present in a functional group equivalent ratio of isocyanate group:epoxy group within the range of <NUM>:<NUM> t o <NUM>:<NUM> and the radical polymerizable compound (c) being present in an amount of about <NUM> to <NUM> parts by weight based on the total amount of the polyisocyanate compound (a) and the polyepoxide compound. The present invention also provides a cured article obtained from the thermosetting resin composition of the present invention.

<CIT> discloses a process for preparing polyisocyanurate-based polyoxazolidone polymers by reacting a polyepoxide and a polyisocyanate in the presence of a catalytic amount of organoantimony iodide catalyst. While the above patent discloses a process, the patent reference is silent on the physical or mechanical performance or the shelf stability of the reacted compositions. The above patent is not directed to producing reactive composition with (<NUM>) a final oxazolidone/isocyanurate ratio content of <NUM> or more, (<NUM>) an improved shelf stability, and/or (<NUM>) a glass transition temperature (Tg) (following curing of the compositions) of greater than <NUM>. These performance properties are all important properties for providing a composition that can be successfully used in an application process.

One embodiment of the present invention is directed to a process for preparing a curable resin composition comprising admixing (a) at least one polyepoxide compound; and (b) at least one polyisocyanate compound in the presence of (c) a catalyst system; wherein the catalyst system comprises at least one organoantimony catalyst, at least one nitrogen-containing catalyst, and at least one iodide catalyst added in a sequence in the order of first the organoantimony catalyst, then the nitrogen-containing catalyst, and last the iodide catalyst; wherein the organoantimony catalyst is triphenyl antimony and wherein the iodide catalyst is iodine; wherein the ratio of the at least one polyepoxide compound to the at least one polyisocyanate compound is from <NUM> to <NUM>; and wherein the composition has an oxazolidone/isocyanurate ratio of greater than <NUM>. The process can be used to prepare an in situ curable polymer resin formulation or composition that is free of solvent; and that surprisingly achieves a high oxazolidone/isocyanurate ratio content (greater than <NUM>) simultaneously during the curation process.

Therefore, one objective of the present invention is to provide a polyisocyanurate-based polyoxazolidone polymer that: (<NUM>) is made without using a pre-polymer; (<NUM>) has a high ratio of oxazolidone/isocyanurate (> <NUM>); and (<NUM>) is in situ curable in the absence of a solvent, i.e., there is no solvent introduced or needed in the formulation to dissolve the catalyst. Solvents tend to generate bubbles during the cure process of the formulation. Therefore, there is an advantage in using a solventless formulation. There is also a cost advantage for using an in situ cure process of the present invention which does not require a pre-polymer.

Another embodiment of the present invention includes a process for preparing a cured thermoset resin polymer product made from the above polyisocyanurate-based polyoxazolidone polymer which; after curing the polymer, the in-situ cured polymer resin exhibits excellent properties such as a high glass transition temperature (Tg) (e.g., greater than (>) <NUM>); a high impact strength (e.g., > <NUM> kJ/m2); a high tensile strength (e.g., > <NUM> MPa); a high flex strength (e.g., > <NUM> MPa); and an increased pot stability (e.g., > <NUM> hours (hr) at RT (room temperature, approximately (~) <NUM>)). These performance properties are comparable to, or exceed, conventional products made from conventional oxazolidone-containing pre-polymers.

The beneficial results obtained by the in-situ cure oxazolidone chemistry of the present invention disclosed above are achieved by using the proper polymer having a high oxazolidone content in the formulation and by selecting the proper reactants including the polyepoxide compound, polyisocyanate compound, catalyst system; and the proper dosages of the reactants, proper catalyst ratios, and proper cure temperatures.

Also disclosed herein but not part of the claimed invention, another objective is to provide a catalyst system that can catalyze the reactions with a fast curation rate and a high Tg, while maintaining the high oxazolidone content and a long shelf life of a formulation, which are important for a successful application process.

The catalyst system with the desired properties may include, for example, a combination of at least one primary catalyst (e.g., Ph<NUM>Sb plus I<NUM>) and at least one secondary catalyst (e.g., DBU or EMI). In addition, the present invention includes the discovery of a beneficial narrow concentration range of the secondary catalyst. It is known that the secondary catalyst can also catalyze side reaction for isocyanurate. Thus, it has been discovered that the maximum loading for the secondary catalyst can be up to <NUM> wt % so as to keep the oxazolidone content of the formulation at a high level.

It was found that the sequence of the catalyst loading affects the results of the catalyst activity. For example, the following sequence: Ph<NUM>Sb→DBU→I<NUM>, demonstrates all of the beneficial properties such as a high Tg, a high oxazolidone content, and a fast reactivity while maintaining the formulation stability at a lower temperature (e.g., <NUM>). It is hypothesized that when Ph<NUM>Sb, a Lewis acid, when combined first with DBU, can react with DBU to form catalyst-blocking, whereas when Ph<NUM>Sb is paired up with I<NUM> first, the resulting Ph<NUM>SbI<NUM> once formed can no longer react with DBU.

In a broad embodiment, the present invention includes a neat, solventless (i.e., free of solvent) curable thermoset polymer resin composition which is adapted for in situ curing. For example, the resin composition includes: (a) at least one epoxy resin compound such as D. <NUM> and 127E; (b) at least one isocyanate compound such as MDI or pMDI; and (c) a catalyst system including a combination of at least a first catalyst and a second catalyst; wherein the first catalyst includes (ci) at least one antimony catalyst that is Ph<NUM>Sb; and wherein the second catalyst includes (cii) an iodine (I<NUM>) catalyst.

The epoxy resin component (a) useful for preparing the thermoset resin polymer composition of the present invention may include for example a single epoxy resin or a mixture of two or more different epoxy resins. The epoxy resin component (a) may be solid or liquid at room temperature (about <NUM>). If a solid, the polyepoxide may be heat softenable at an elevated temperature of between <NUM>. and <NUM>° C. Mixtures of solid and liquid (at room temperature) polyepoxides can be used. The polyepoxide or a mixture thereof suitably has an average epoxide equivalent weight (EEW) of from <NUM> to <NUM>, from <NUM> to <NUM> and/or from <NUM> to <NUM>. Individual polyepoxides contained in a mixture may have EEWs outside of that range. A wide variety of polyepoxide compounds, such as cycloaliphatic epoxides, epoxidized novolac resins, epoxidized bisphenol A or bisphenol F resins can be used, but may be preferred on the basis of cost and availability are liquid or solid glycidyl ethers of a bisphenol such as bisphenol A or bisphenol F. Halogenated, particularly brominated, polyepoxides can be used to impart flame retardant properties if desired. Polyepoxides of particular interest are polyglycidyl ethers of bisphenol A or bisphenol F having an EEW of <NUM> to <NUM>. Blends of one or more polyglycidyl ethers of bisphenol A or bisphenol F. The epoxy resin may be halogenated (in particular, brominated) if desired in order to impart flame resistance.

Suitable polyepoxides useful in the present invention can include commercially available polyepoxides. Among these polyepoxides are liquid polyepoxides such as D. <NUM> and D. <NUM>; solid polyepoxides such as D. R <NUM>, D. <NUM>-<NUM>, D. <NUM>-<NUM>, D. <NUM>-<NUM>, D. 669E and D. R <NUM>; brominated polyepoxides such as D. <NUM> and D. <NUM>; epoxy novolac resins such as D. N <NUM>; D. <NUM>; and 127E; and mixtures thereof; all of which are available from Olin.

In an exemplary embodiment, the epoxy compounds useful for preparing the thermoset resin polymer composition can include, for example, brominated aromatic epoxy resins, non-brominated epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins, biphenyl epoxy resins, naphthalene epoxy resins, divinylbenzene dioxide, and mixture thereof.

In general, the concentration of the epoxy resin component (a) used in the present invention may range generally from about <NUM> weight percent (wt %) to about <NUM> wt % in one embodiment, and from about <NUM> wt % to about <NUM> wt % in another embodiment, based on the total weight of all components in the composition.

The resin composition or formulation of the present invention includes at least one isocyanate component, as component (b), of the formulation, i.e., the isocyanate component useful in the present invention may include one or more isocyanate-containing components. For example, the resin composition may include for example a single polyisocyanate or a mixture of two or more different polyisocyanates.

In general, suitable polyisocyanate compounds useful in the present invention can include aromatic, aliphatic and cycloaliphatic polyisocyanates. For example, polyisocyanate compounds may include m-phenylene diisocyanate; <NUM>,<NUM>-and /or <NUM>,<NUM>-toluene diisocyanate (TDI); the various isomers of diphenylmethanediisocyanate (MDI); the so-called polymeric MDI products (pMDI); carbodiimide modified MDI products; hexamethylene-<NUM>,<NUM>-diisocyanate; tetramethylene-<NUM>,<NUM>-diisocyanate; cyclohexane-<NUM>,<NUM>-diisocyanate; hexahydrotoluene diisocyanate; hydrogenated MDI; naphthylene-<NUM>,<NUM>-diisocyanate; isophorone diisocyanate (IPDI) and mixtures thereof. Suitable examples of commercially available MDI or pMDI may include for example OP50 and PAPI27; and mixtures thereof.

The polyisocyanate component (b) can have an average functionality of isocyanate groups of, for example, from <NUM> to <NUM> in one embodiment, and from <NUM> to <NUM> in another embodiment.

Generally, the amount of polyisocyanate component (b) used in the resin formulation of the present invention can be generally for example from <NUM> wt % to <NUM> wt % in one embodiment, and from <NUM> wt % to <NUM> wt % in another embodiment, based on the total weight of all components in the formulation.

The catalyst system component (c) useful in the present invention includes a combination of (ci) a catalytic amount of at least one primary catalyst that is, an organoantimony iodide (Ph<NUM>Sb and I<NUM>); and (cii) a catalytic amount of at least one secondary catalyst for example <NUM>,<NUM>-diazabicyclo[<NUM>. <NUM>]undec-<NUM>-ene (DBU) and/or <NUM>-ethyl-<NUM>-methylimidazole (EMI) catalyst or <NUM>- methylimidazole; or mixtures thereof.

The primary catalyst includes, a first catalyst and a second catalyst; wherein the first catalyst includes at least one antimony catalyst that is triphenyl antimony (Ph<NUM>Sb) with iodine (I<NUM>); and wherein the second catalyst includes (cii) a nitrogen-containing catalyst.

The secondary catalyst can include, for example, a third catalyst and optionally a fourth catalyst; wherein the third catalyst includes for example, DBU catalyst; and wherein the optional fourth catalyst may include EMI catalyst.

In addition, a variety of other known catalysts can be optionally added to the catalyst system component (c) of the present invention. For example, the optional catalyst useful in the present invention may include tertiary amines such as trimethylamine, triethylamine, N-methylmorpholine, N-ethylmorpholine, N,N-dimethylbenzylamine, N,N-dimethylethanolamine, N,N,N',N'-tetrsmethyl-<NUM>,<NUM>-butanediamine, N,N-dimethylpiperazine, bis(dimethylaminoethyl) ether and triethylenediamine; tertiaery phosphines such as trialkylphosphines and dialkylbenzylphosphines; chelates of various metals such as those which can be obtained from acetyl acetone, benzoylacetone, trifluoroacetyl acetone, ethyl acetoacetate and the like, with metals such as Be, Mg, Zn, Cd, Pd, Ti, Zr, Sn, As, Bi, Cr, Mo, Mn, Fe, Co and Ni; acidic metal salts of strong acids such as ferric chloride, stannic chloride; salts of organic acids with variety of metals, such as alkali metals, alkaline earth metals, Aal, Sn, Pb, Mn, Co, Ni and Cu; and mixtures thereof. In another embodiment, organometallic derivatives of tetravalent tin, trivalent and pentavalent As, Sb and Bi and metal carbonyls of iron and cobalt; and mixtures thereof, can also be used in the present invention. In still another embodiment, tertiary amine catalysts such as N,N,N-trimethyl-N-hydroxyethyl-bis(aminoethyl) ether, dimethyl <NUM>-<NUM>(<NUM>-aminoethoxy) ethanol and the like; and mixtures thereof, can also be used in the present invention.

In the formulation of the present invention, the equivalent NCO and equivalent epoxy mole ratio: (mass of isocyanate* epoxy equivalent weight of epoxy resin) / (mass of epoxy resin * NCO equivalent weight of isocyanate) ranges from <NUM> to <NUM> in one embodiment and from <NUM> to <NUM> in another embodiment.

The total mass of Ph<NUM>Sb and I<NUM> in the formulation of the present invention can be from <NUM> wt % to <NUM> wt % in one embodiment, from <NUM> wt % to <NUM> wt % in another embodiment, and from <NUM> wt % to <NUM> wt %. The mass ratio between Ph<NUM>Sb and I<NUM> can range from <NUM> to <NUM>.

When the DBU catalyst and/or the EMI catalyst is used as the secondary catalyst component, the secondary catalyst can be used in a beneficial narrow concentration range with a maximum loading value (e.g., up to <NUM> wt %). It is important to have a maximum loading for the secondary catalyst to keep the oxazolidone content of the formulation at a high level. For example, the range of the secondary catalyst can be less than or equal to <NUM> wt % in one embodiment; and from <NUM> wt % to <NUM> wt % in another embodiment. It is known that the secondary catalyst can catalyze side reaction for isocyanurate which can deleteriously affect the oxazolidone content of the formulation. Thus, the maximum loading for the secondary catalyst should be kept at the narrow range of from <NUM> wt % to <NUM> wt %.

The two chemicals are mixed sequentially, with either the polyepoxide component or with the polyisocyanate component, in solid form without a solvent.

According to the invention, the catalyst system includes a nitrogen-containing catalyst, such as DBU or EMI, and the adding sequence of the catalysts to the polyepoxide component is as follows: Ph<NUM>Sb→nitrogen-containing catalyst e.g. DBU/EMI→I<NUM>.

The advantage of using a low amount of secondary catalyst is that a high oxazolidone content of final product can be maintained by accelerating the reaction speed. The ratio of Ph<NUM>Sb and I<NUM> is also important as Ph<NUM>SbI<NUM> or Ph<NUM>SbI<NUM> can catalyze the reaction much faster than Ph<NUM>Sb alone. And, the novel catalyst loading sequence is likewise important because either Ph<NUM>SbI<NUM> or Ph<NUM>SbI<NUM> alone is insoluble in epoxy resin; however, the combination of Ph<NUM>Sb and I<NUM> can be dissolved in epoxy resin below <NUM>. In addition, once I<NUM> is added to the epoxy resin, I<NUM> can react with Ph<NUM>Sb and thereafter the secondary catalyst cannot form an acid:base pair with Ph<NUM>Sb. Therefore, the sequence of adding the catalyst system to the epoxy resin is in the order of: first Ph<NUM>Sb, then secondary catalyst, and last I<NUM>. The above novel sequence of addition is preferred to achieve the benefit of long pot life and fast reaction.

A variety of other optional conventional components can be added to the polymer resin formulation of the present invention. Suitable optional compounds or additives useful for the resin composition are well known in the art and can include, for example, molecular sieve for moisture adsorption; mold releasing agents; surfactants; toughening agents, flow modifiers, adhesion promoters, diluents, stabilizers, plasticizers, catalyst de-activators, flame retardants, liquid nucleating agents, solid nucleating agents, Ostwald ripening retardation additives, and mixtures thereof.

Any suitable combination of the above optional additives and additive amounts, as well as the method of incorporating the optional additive(s) into the resin composition can be carried out. Typically, each of the above optional additives, if used in the resin composition, does not exceed <NUM> wt % based on total composition weight; and are advantageously used in the range of generally from <NUM> wt % to <NUM> wt %, preferably from <NUM> wt % to <NUM> wt %, more preferably from <NUM> wt % to <NUM> wt %, even more preferably from <NUM> wt % to <NUM> wt %, and most preferably from <NUM> wt % to <NUM> wt %.

In one broad embodiment, the process for making the reactive thermoset resin composition of the present invention includes admixing components (a)-(c) described above. Then one or more additional optional components may be added to the formulation as desired. Generally, the preparation of the resin composition includes mixing of the components at a temperature of from <NUM> to <NUM> in one embodiment; and from <NUM> to <NUM> in another embodiment. The order of mixing of the ingredients is not critical and two or more compounds can be mixed together followed by addition of the remaining ingredients. The ingredients that make up the resin composition may be mixed together by any known mixing process and equipment. The conventional process and equipment to make the polymer resin composition may include for example a bench top mixer.

In a preferred embodiment, the process for preparing a polyoxazolidone product by reacting (a) at least one polyepoxide compound; and (b) at least one polyisocyanate compound in the presence of (c) a catalyst system. The process includes for example the sequential steps of: (I) allowing the polyepoxide compound to react for a predetermined time in presence of the catalyst system at a temperature of at least greater than or equal to <NUM> to form a polyepoxide reaction mixture; and (II) after step (I), adding the polyisocyanate compound to the polyepoxide reaction mixture of step (I) and allowing the polyisocyanate compound to react with the polyepoxide reaction mixture of step (I) for a predetermined time in the presence of the catalyst system at an temperature of less than <NUM> to form a polyoxazolidone material having an oxazolidone/isocyanurate ratio of greater than <NUM>. Following the process steps above, a polymer resin composition and a cured product made from the resin composition having improved properties can be obtained as described herein.

In another embodiment, the reaction temperature of step (I) of the above process can be, for example, from <NUM> to <NUM>; and the reaction temperature of step (II) can be, for example, from <NUM> to <NUM>.

In still another embodiment, the process of the present invention can include, after step (II), the step of (III) degassing the polyoxazolidone material, for a predetermined amount of time under vacuum, any bubbles formed in the reaction.

The polymer resin composition of the present invention produced by the process of the present invention has several advantageous properties and benefits compared to conventional formulations. According to the invention, the resin has a desired high content of oxazolidone at an oxazolidone/isocyanurate ratio of > <NUM>. The oxazolidone/isocyanurate ratio of the composition is important because high oxazolidone provide better mechanical strength and high isocyanurate provides high glass transition temperature and flame-retardant properties.

Another beneficial property exhibited by the composition of the present invention can include a long shelf stability or pot life of the composition which can be > <NUM> hr below <NUM> in one embodiment, and from <NUM> hr to <NUM> hr in another embodiment. "Shelf stability" or "pot life", with reference to a resin composition, herein means the viscosity draft after mixing. Shelf stability or pot life" can be measured according to the time while viscosity of the formulation is below <NUM> Pa. s at a defined temperature (e.g. <NUM>). The long shelf life of the composition is advantageous at low temperatures including for example from -<NUM> to <NUM> in one embodiment; and from <NUM> to <NUM> in another embodiment. A long pot life of the composition is beneficial because a long pot life provides a long window of operation time which, in turn, allows a material to be prepared prior to curing the material without requiring in-line mixing equipment.

Gel time is another advantageous property exhibited by the composition of the present invention. For example, the gel time of the composition can be from <NUM> seconds (s) to <NUM> in one embodiment; and from <NUM> to <NUM> in another embodiment. A short gel time of the composition, as described above, can lead to high productivity and fast curing.

Generally, after the reactive resin composition is prepared as described above, the composition can be in situ cured at a temperature of from <NUM> to <NUM> in one embodiment; from <NUM> to <NUM> in another embodiment; and from <NUM> to <NUM> in still another embodiment.

The formulation of the present invention also includes a catalyst system that can catalyze the reaction with a fast curation rate. For example, the cure time of the composition in <NUM> can be from <NUM> to <NUM> in one embodiment; and from <NUM> to <NUM> in another embodiment. The cure time of the composition can determine the minimal heating time or processing time needed for sufficient curation.

The thermoset cured product made in accordance with the present invention advantageously has several advantageous properties and benefits compared to conventional polymer resins made from prepolymers. For example, the in situ cured polymer resin product produced from the resin composition of the present invention surprisingly and unexpectedly exhibits excellent properties including, for example, a glass transition temperature (Tg) of > <NUM> in one embodiment; a Tg of from > <NUM> to <NUM> in another embodiment; and a Tg of from <NUM> to <NUM> in still another embodiment. A proper Tg of the thermoset demonstrates the thermostability of the material and the Tg can be correlated to a maximum temperature for the thermoset to maintain its mechanical strength.

In addition, the impact resistance strength property of the thermoset product as measured and determined by the procedure described in ISO179 can be, for example, > <NUM> kJ/m<NUM> in one embodiment; and from > <NUM> kJ/m<NUM> to <NUM> kJ/m<NUM> in another embodiment. The impact resistance property of the thermoset can demonstrate the toughness of the material.

Also, the tensile strength property of the thermoset product as measured and determined by the procedure described in ISO527 can be can be, for example, > <NUM> MPa in one embodiment; and from > <NUM> MPa to <NUM> MPa in another embodiment. The tensile strength property of the thermoset can demonstrate the toughness of the material.

Another advantageous property of the thermoset product is its flex strength. The flex strength property of the thermoset product as measured and determined by the procedure described in ISO178 can be, for example, > <NUM> MPa in one embodiment, > <NUM> MPa in another embodiment, and from > <NUM> MPa to <NUM> MPa in still another embodiment. The flex strength property of the thermoset can also demonstrate the toughness of the material.

The thermoset product made in accordance with the present invention can be useful in a variety of applications including, for example, for composite applications; coating applications; and adhesive applications. In a preferred embodiment, the thermosets of the present invention may be used for composite applications.

The following examples are presented to further illustrate the present invention in detail but are not to be construed as limiting the scope of the claims. Unless otherwise stated all parts and percentages are by weight.

Various raw materials used in the examples which follow are explained hereinbelow in Table I.

The compositions for testing described in Table II were prepared according to the general procedure described herein below; and the results of testing the formulations prepared according to the procedure are also found in Table II.

The compositions for testing described in Table II were prepared according to the following general procedure:.

The results of testing the formulations prepared according to the above procedure are also found in Table II.

The results described in Table II show that, when the formulations of Inv. <NUM>-<NUM> are compared to the three control samples (Comp. <NUM>-<NUM> demonstrate a higher oxazolidone selectivity, represented by the high ratio of oxazolidone/isocyanurate content. The results in Table II also show that catalyst selectivity has a significant impact on an in-situ cure process. In addition, the difference in the Tg for Inv. <NUM> and Inv. <NUM> demonstrates the impact of isocyanate functionality on Tg. And, the difference in Tg and oxazolidone functionality for Inv. <NUM> and Inv. <NUM> demonstrates the impact of the NCO/epoxy ratio on the Tg and oxazolidone functionality of the formulations.

For the sample formulations described in Table II above having a high oxazolidone/isocyanurate ratio, the mechanical properties including tensile strength, impact strength and flex strength, are all better than the sample formulations having a low oxazolidone/isocyanurate ratio. It is theorized the better mechanical properties of the present invention formulation is based on the impact of oxazolidone. This data described in Table II generally shows that a higher oxazolidone content (e.g., from <NUM> to <NUM>) is desired to obtain a resin product with excellent mechanical properties.

In general, known oxazolidone-containing solutions include either a pre-polymer solution or a foaming process, which cannot generate a clear casting with neat epoxy resin and diisocyanate or pMDI. Several of the unique steps in the method of the present invention include (<NUM>) in situ catalyst formation in epoxy resin, (<NUM>) catalyst dosage, and (<NUM>) cure temperature. The process or operation range of the present invention can enable the in-situ oxazolidone formation simultaneous with the curation process, providing excellent mechanical properties for the resin products produced by the compositions of the present invention compared to resin products produced using oxazolidone prepolymers (e.g. VORAFORCE <NUM> series products available from The Dow Chemical Company). Due to the high viscosity of an oxazolidone-containing polymer, the desired epoxy/NCO mole ratio should be far from <NUM> to avoid a high degree of polymerization; and therefore, a high viscosity which naturally limits the oxazolidone content of the polymer. Another benefit of the in situ cure process of the present invention is that the raw materials used to form the solventless, in situ, curable reaction composition of the present invention do not contain oxazolidone; and thus, the viscosity of the original composition of the present invention is lower than prior art oxazolidone prepolymers. Therefore, the low viscosity composition of the present invention can be favorably used in many applications such as coating applications or composite applications.

The data in the above Table II demonstrates the impact of cure temperature of a final product. The data shows that there is a positive impact of temperature on oxazolidone selectivity when the temperature is above <NUM>. However, under <NUM>, even the selectivity is not changed from <NUM>, as the Tg significantly decreases. These results indicate the initial cure temperature desired is above <NUM> and more preferable above <NUM> to obtain a resin with a high Tg (e.g., > <NUM>).

The data in the above Table II illustrates that catalyst level is another important parameter to obtain a proper composition. When the results of testing the formulations of Inv. Ex-<NUM>, Inv. <NUM>, and Comp. E, are compared, the data in Table II shows that the catalyst loading for Ph<NUM>SbI<NUM> beneficially can be above <NUM> wt % to maintain a Tg above <NUM>.

The compositions for testing described in Table III were prepared according to the general procedure described above; and the results of testing the formulations prepared according to the above procedure are also found in Table III.

The data described in Table III shows that the example formulations using a primary catalyst (e.g., Ph<NUM>Sb and I<NUM>) in combination with a secondary catalyst (e.g., DBU or EMI) at a low loading (e.g., lower than <NUM> wt %), the Tg for the resulting resin product is higher than the example formulations using only the primary catalyst of Ph<NUM>Sb and I<NUM>. At the same time, the oxazolidone selectivity (Oxazolidone/Isocyanurate ratio), for example formulations using the primary and secondary catalyst, is much higher than for example formulations using a secondary catalyst only. Therefore, use of a low concentration of secondary catalyst provides a resin product having the benefits of a high Tg and concurrently a high oxazolidone content.

The data described in Table III also shows that a formulation including a secondary catalyst exhibits a good performance in reaction rate. As shown in Table III, the gel time results for Comp. J, which uses a catalyst combination of Ph<NUM>Sb and I<NUM> catalyst, is higher than Inv. The gel time on curing temperature, e.g. <NUM>, as well as in lower temperatures such as <NUM> or <NUM>, was significantly reduced (e.g., <NUM> % to <NUM> % reduction), after introducing a secondary catalyst into a formulation. This reduction in gel time indicates an increase in reactivity across all of the above conditions.

Claim 1:
A solventless, in situ, curable reaction composition having an oxazolidone and isocyanurate structure comprising the reaction product of: (a) at least one polyepoxide compound; and (b) at least one polyisocyanate compound in the presence of (c) a catalyst system; wherein the catalyst system comprises at least one organoantimony catalyst, at least one nitrogen-containing catalyst, and at least one iodide catalyst added in a sequence in the order of first the organoantimony catalyst, then the nitrogen-containing catalyst, and last the iodide catalyst; wherein the organoantimony catalyst is triphenyl antimony and wherein the iodide catalyst is iodine; wherein the ratio of the at least one polyepoxide compound to the at least one polyisocyanate compound is from <NUM> to <NUM>; and wherein the composition has an oxazolidone/isocyanurate ratio of greater than <NUM>.