阅读说明：本技术 聚异氰脲酸酯基聚合物和纤维增强复合材料 (Polyisocyanurate-based polymer and fiber-reinforced composite material ) 是由 H·A·金纳多 于 2019-12-11 设计创作，主要内容包括：本发明涉及一种反应混合物,其包括一或多种多官能异氰酸酯,使得该混合物的平均异氰酸酯官能度大于2.1,和包括至少一种三聚催化剂和至少一种环氧基团的催化剂组合物；和将反应混合物固化以得到由异氰酸酯与其自身反应产物组成的固化聚合物组合物。(The present invention relates to a reaction mixture comprising one or more polyfunctional isocyanates such that the mixture has an average isocyanate functionality of greater than 2.1, and a catalyst composition comprising at least one trimerisation catalyst and at least one epoxy group; and curing the reaction mixture to obtain a cured polymer composition consisting of the reaction product of the isocyanate with itself.)

1. A method for preparing an isocyanurate-based polymer, comprising the steps of:

providing a liquid aromatic polyisocyanurate;

providing a catalyst composition; and

the aromatic polyisocyanurate comprises a combination of methylene diphenyl diisocyanate (MDI) and polymeric methylene diphenyl diisocyanate (pMDI), provides an average functionality of greater than 2 to the aromatic polyisocyanurate forming a reaction mixture, and the catalyst composition comprises a trimerization catalyst and at least one monofunctional or polyfunctional epoxide, and cures the reaction mixture to produce a polymer composition comprising two or more isocyanate reaction products.

2. The method set forth in claim 1 wherein said step of providing said aromatic polyisocyanurate having a functionality of greater than 2 is further defined as providing said aromatic polyisocyanurate having an average functionality of greater than about 2.5.

3. The method of claim 1 further comprising the step of providing an aliphatic polyisocyanate of hexamethylene diisocyanate comprising at least one of a uretdione, isocyanurate, biuret, allophanate, or iminooxadiazinedione.

4. The process of claim 1, wherein the catalyst composition comprises up to about 7 weight percent of a monofunctional or multifunctional epoxide based on the total reaction mixture.

5. The method of claim 1, wherein the epoxide is present in an amount of about 3% by weight of the total reaction mixture.

6. The method of claim 1, wherein the reaction mixture is substantially free of active hydrogen and the cured composition is substantially free of urethane groups and amide groups.

7. The method as set forth in claim 1 wherein the reaction mixture is further defined as an isocyanate terminated prepolymer comprising at least one of urethane groups, amide groups, urea groups, uretdione groups, biuret groups, allophanate groups, isocyanurate groups, or carbodiimide groups.

8. The method of claim 1, wherein the reaction mixture comprises 5-20% by weight of at least one of uretdione of hexamethylene diisocyanate and trimer of hexamethylene diisocyanate.

9. The method of claim 1, wherein the polymer composition post-cures in one of a humid environment or an aqueous solution providing a glass transition temperature greater than 300 ℃.

10. The method of claim 1, further comprising the step of aging the polymer composition at ambient temperature and pressure and in an environment comprising atmospheric moisture to provide the polymer composition with a glass transition temperature of greater than about 300 ℃.

11. The method of claim 1, wherein the polymer composition achieves a glass transition temperature of greater than about 350 ℃ after ambient aging.

12. The method of claim 1, further comprising the steps of providing a fibrous material and injecting a reaction mixture into the fibrous material after catalyzing the reaction mixture and then heating the reaction mixture to cure the fiber reinforced composite reaction mixture.

13. The method of claim 1, wherein the at least one epoxide is mixed into the reaction mixture prior to providing the trimerization catalyst, thereby forming a storage-stable mixture for future catalysis with the trimerization catalyst.

14. The process of claim 1, wherein the reaction product comprises greater than about 0.5MPa-m according to ASTM standard D5045^1/2Fracture toughness of (3).

15. The method as set forth in claim 1 wherein the step of curing the reaction product is further defined as thermally curing the reaction mixture in less than 10 minutes.

16. The method as set forth in claim 1 wherein the step of curing the reaction product is further defined as thermally curing the reaction mixture in less than 5 minutes at less than 120 ℃.

17. The method as set forth in claim 1 wherein the step of curing the reaction product is further defined as thermally curing the reaction mixture in less than 2 minutes at less than 170 ℃.

18. The method as set forth in claim 1 wherein the step of curing the reaction product is further defined as thermally curing the reaction product in less than 1 minute at less than 170 ℃.

19. The process of claim 1 wherein the liquid aromatic polyisocyanurate comprises a viscosity of less than 1500mPa s.

20. The process of claim 1 wherein the liquid aromatic polyisocyanurate comprises a viscosity of less than 300mPa s.

21. The method set forth in claim 1 wherein the step of providing a fibrous material is further defined as providing at least one of: unidirectional glass fibers, woven glass fibers, non-crimped glass fibers, non-woven glass fibers, unidirectional carbon fibers, woven carbon fibers, non-crimped carbon fibers, non-woven carbon fibers, unidirectional basalt fibers, woven basalt fibers, non-crimped basalt fibers, non-woven basalt fibers, and equivalents.

22. A method of producing an isocyanurate polymeric material, comprising the steps of:

providing an aromatic polyisocyanate comprising methylene diphenyl diisocyanate (MDI) and polymeric methylene diphenyl diisocyanate (pMDI);

mixing a catalytic amount of an epoxy resin with the aromatic polyisocyanate to prepare a reaction mixture;

after preparing the reaction mixture, a catalyst is mixed with the reaction mixture to initiate polymerization of the isocyanurate polymer material and the reaction mixture is heated to less than about 170 ℃ for less than five minutes, thereby curing the isocyanurate polymer material.

23. A method as set forth in claim 22 wherein the step of mixing a catalyst with the reaction mixture is further defined as mixing a trimerization catalyst into the reaction mixture.

24. A process as set forth in claim 23 wherein said step of combining a catalyst into said reaction mixture is further defined as combining at least one of bis- (2-dimethylaminoethyl) ether (BDMAEE) or 1, 4-diazabicyclo [2.2.2] octane (DABCO) dissolved in a suitable solvent into a reaction mixture.

25. The method set forth in claim 22 wherein said step of mixing a catalytic amount of epoxy resin with said aromatic polyisocyanurate is further defined as mixing less than about 10 weight percent epoxy resin with said aromatic polyisocyanurate.

26. The method of claim 22, further comprising the steps of providing a fibrous material and injecting the catalyzed reaction mixture into the fibrous material prior to heating the reaction mixture.

27. The method set forth in claim 26 wherein the step of providing a fibrous material is further defined as providing at least one of: unidirectional glass fibers, woven glass fibers, non-crimped glass fibers, non-woven glass fibers, unidirectional carbon fibers, woven carbon fibers, non-crimped carbon fibers, non-woven carbon fibers, unidirectional basalt fibers, woven basalt fibers, non-crimped basalt fibers, non-woven basalt fibers, and equivalents.

28. The method of claim 22 wherein the polyisocyanurate polymer is further defined as being substantially free of active hydrogens, urethane groups, and amide groups.

29. The method set forth in claim 22 wherein the step of heating the reaction mixture is further defined as heating the reaction mixture to less than 120 ℃ for less than five minutes to cure the isocyanurate polymer material.

30. The method of claim 22, wherein the polymer composition achieves a glass transition temperature of greater than 300 ℃ after aging at ambient temperature and pressure.

Technical Field

The present invention broadly relates to reaction mixtures that are primarily isocyanates. More particularly, the present invention relates to a predominantly isocyanate reaction mixture comprising polymeric methylene diphenyl diisocyanate (pMDI) which, upon curing, produces a polymer having high strength, high strain-to-failure, high fracture toughness and high glass transition temperature.

Background

Isocyanurates are formed by trimerization of three isocyanates and have been widely used for decades to improve the thermal stability of polyurethanes, epoxies and polyureas. Isocyanurates are also widely used in the production of foams due to their excellent flame retardancy, but the use of high density polymers based essentially only on polyisocyanates without forming additional segments that increase the toughness of the polymer has not been found. To overcome the well-known disadvantage of friable or brittle polyisocyanurate foams, the polyisocyanurate foam needs to contain a high percentage of reactants that consume isocyanate groups and limit the proportion of isocyanurate in the polymer. For example, U.S. patent 4568701A describes the use of "a surface active organosilicone compound characterized by having active hydrogen functional groups and a hydroxyl number greater than about 50 and an equivalent weight less than about 2000, and a plasticizing amount of a non-volatile organic plasticizer" at 4-20% by weight of the foam formulation to reduce the friability of the foam. U.S. patent 3676380A describes the use of 1-10% aliphatic diols to form polyurethane segments that increase the elasticity of the polymer. U.S. patent 3793236 describes trimerization of isocyanate-terminated polyoxazolidone prepolymers by means of a trimerization catalyst such as a tertiary amine. The inventors describe that the resulting polymer exhibits low brittleness and high flame retardancy due to the incorporation of oxazolidinone linkages. Chinese patent application publication No. 103012713a discloses that foams with high crosslink density pure polyisocyanurate have very brittle characteristics and are "of no practical value", the inventors using 10-50% epoxy resin to achieve brittleness reduction.

When polyisocyanurate is used to produce dense plastics with low void volume, it is well known that the materials are brittle if no linear bond, chain extender or flexible group for toughness is introduced, i.e. oxazolidinones as disclosed in us patent nos. 3793236, 8501877, 2010/0151138a1, urethanes as disclosed in (european patent No.226176B1, EP 0643086a1, us patent No.9334379) and ureas as disclosed in us patent No.6617032B2 and chinese patent No. 103568337B. For example, U.S. Pat. No.4564651 teachesIt is led that cured isocyanate/epoxy mixtures with an epoxy resin to isocyanate ratio of less than 1:5 are very brittle and get worse with increasing concentration of diphenylmethane diisocyanate (MDI), and us patent No.5036135 teaches that polyisocyanurate polymers exhibit poor mechanical properties when they comprise less than 20% epoxy resin. Both of these patents teach that it is not possible to obtain polymers with high strength and toughness as a result of the reaction of the isocyanate and the epoxy resin at high temperatures with less than 20% epoxy resin or less than 20% oxazolidone. European patent application No.3189088A1 further teaches that "materials known to contain polyisocyanates are very difficult to toughen, and some may be too brittle to toughen effectively" and "past attempts to increase fracture toughness have generally been to alter (typically lower) the modulus and lower thermal properties such as glass transition temperature (T.sub.T.) (T.sub._g) At the expense of unacceptable limitations on the suitability of the resulting composite. "

U.S. patent application No.2018/0051119a1 teaches that the molar ratio of the at least one epoxy resin to the at least one isocyanate resin should be at least 0.4:1 and most preferably 1:1, which ratio results in "particularly advantageous properties with respect to glass transition temperature, elastic modulus and impact resistance. These preferred ratios far exceed the catalytic amount of the epoxy resin to achieve the desired results of tensile strength, tensile stiffness and tensile failure strain. Furthermore, the above patents clearly teach that polymers and foams composed primarily of polyisocyanurate exhibit a high degree of brittleness.

U.S. patent No.4070416 discloses a process for the manufacture of oxazolidinone/isocyanurate polymers having an epoxy resin to isocyanate ratio of less than 1 and indicates that high glass transition temperatures and good mechanical properties are obtained at the most advantageous epoxy resin to isocyanate ratio in the range of 0.29 to 0.5. U.S. Pat. No.4070416 discloses that "since an isocyanurate bond moiety having a high crosslinking density and a relatively flexible epoxy-based resin moiety coexist with a sufficient balance between the two moieties, a cured product having excellent mechanical properties can be obtained. The inventors claim that when the polyfunctional organic isocyanate is in an amount of 5 equivalents or more, the properties of the cured product tend to become significantly brittle. In particular, when the polyfunctional organic isocyanate is used in the range of 2 to 3.5 equivalents, good results are obtained in terms of both thermal stability and mechanical properties. "U.S. Pat. No.4564651 discloses that the inventors evaluated the results for polymers of the epoxy resin to isocyanate ratio range specified in U.S. Pat. No.4070416 and found" given the crosslinking conditions, very brittle oxazolidinone/isocyanurate molding materials are obtained with increasingly poorer mechanical properties with increasing diphenylmethane diisocyanate (MDI) concentration ". The inventors assert that 1-5 times the amount of epoxy resin should be mixed with the isocyanate to obtain a polymer with good mechanical properties. This publication refutes the idea that a large fraction of oxazolidinone is required to obtain polymers with high strength, high strain to failure, high fracture toughness and high glass transition temperature, indicating that cured compositions consisting essentially of isocyanurate cross-links can provide excellent mechanical properties when polymeric methylene diphenyl diisocyanate (pMDI) is included in the reaction mixture with catalytic amounts of epoxy resin.

Although oxazolidinones have found widespread use due to their high thermal stability, the formation of oxazolidinones requires high temperatures, typically greater than 150 ℃, and is therefore unsuitable for all applications. Polyurethanes are common chemicals in the development of coatings, adhesives, sealants and elastomers (CASE), as well as rigid plastics, and are formed by the reaction of hydroxyl groups with isocyanates, with most polymers being formed from diols or polyols with diisocyanates or polyisocyanates. When trimerization is desired, such chemicals are typically used to form a prepolymer or added to the reaction mixture, thereby reducing the weight percent of isocyanate (expressed as NCO) in the reaction mixture and the cured composition exhibits improved elasticity and toughness, but typically at the expense of young's modulus and glass transition temperature (Tg). U.S. Pat. No. 9816008B2 teaches that it is generally preferred to effect curing in the presence of one or more polyols wherein the upper limit of the isocyanate to polyol ratio is 10:1 or in other words the isocyanate index is 10. U.S. patent No.6294117 discloses the use of polymeric MDI with a novolac resin in a concentration ratio of 2:1 to 10:1, preferably 3:1 to 7:1, to produce a formaldehyde free wood adhesive. U.S. patent No.6294117 teaches that pMDI requires a high percentage of novolac resin to form a high strength polymer with high toughness. Each of these patents teaches that urethane linkages are required to obtain cured compositions with acceptable mechanical properties.

Many patents focus on forming oligomeric prepolymers with terminal isocyanate groups that can subsequently be reacted with active hydrogen containing molecules to form dense polymers. U.S. patent No.4382125 describes the prepolymerization reaction of MDI isomers with an isocyanate mixture of polymeric MDI to form a partially trimerized isocyanurate polymer, and then it is reacted with a polyol to reduce the brittleness of the isocyanurate foam. U.S. Pat. No.6515125 discloses a storage-stable, liquid, partially trimerized polyisocyanate having an NCO group content of 24 to 40% by weight, containing 20 to 88% by weight of TDI and 12 to 80% by weight of MDI. U.S. patent No.4518761 discloses a method of preparing a mixed trimer by at least partially trimerizing the isocyanate groups of two isocyanate components having different reactivity (for trimerization) in the presence of a trimerization catalyst, and the mixed trimer prepared by the method. U.S. Pat. No.4456709 describes storage-stable liquid polyisocyanates having an NCO group content of 36.5 to 45% and prepared by mixing 25 to 70 parts of partially trimerized 2,4-TDI with 75 to 30 parts of unmodified 2, 4-and/or 2, 6-TDI. While these references disclose a number of processes for producing aromatic, aliphatic, and mixed aromatic and aliphatic structured isocyanurate prepolymers, no curing compositions prepared by the reaction of substantially isocyanate are disclosed.

Another method of preparing polyisocyanurate polymers exhibiting improved fracture toughness is to prepare prepolymers comprising amide, imide, urea, urethane, allophanate or biuret linkages and subsequently trimerize the isocyanate-terminated prepolymers. U.S. Pat. Nos. 6028158 and 6063891 disclose allophanate-modified toluene diisocyanurate with an NCO group content of about 15-42%. These compositions are prepared by reacting A) toluene diisocyanate and B) an organic compound containing at least one hydroxyl group in the presence of a catalytic amount of C) at least one allophanate-trimer catalyst or allophanate-trimer catalyst system. These compositions contain both isocyanurate groups and a high percentage of allophanate groups as well as urethane groups. However, these patents do not teach the subsequent reaction of the allophanate-modified toluene diisocyanurate with itself or with other isocyanate-terminated monomers, oligomers or prepolymers or polymers to form a cured composition.

U.S. patent nos. 4359550, 3817939, and 4359541 describe the formation of trimeric prepolymers followed by the reaction of residual free isocyanate with monofunctional active hydrogen compounds or mixtures thereof to produce polyurethanes containing isocyanurate trimers. While there is a great deal of literature on the formation of isocyanurate-containing prepolymers which are subsequently reacted with active hydrogen-containing molecules or the trimerization of isocyanate-terminated prepolymers prepared using urethane, urea, allophanate, amide, biuret or oxazolidone, each reaction mixture requires an active hydrogen compound to form a cured composition, thus utilizing the urethane, amide, urea, biuret or allophanate reaction products to form a cured composition. A curable composition is produced from a reaction mixture consisting essentially of isocyanate-terminated monomers, oligomers or prepolymers or polymers to form a curable composition.

European patent No.226176B1 describes a composite material based on polyisocyanurate and containing a reinforcing filler, in which the polyisocyanurate matrix is derived from isocyanurate repeating structural units of the formula

Wherein at least one group X represents a group-R₁-NCO and at least one group X represents a group-R₁-NH-CO-OR₂-(-OCO-NH-R₁-NCO)_nWherein n is an integer of 1 to 8, preferably1 to 3, R₁Is an aliphatic, cycloaliphatic, aromatic or mixed radical containing up to 20 carbon atoms, and R₂And R is_lIdentical or different, are aliphatic, cycloaliphatic, aromatic or mixed radicals containing up to 20 carbon atoms, or may also be carbon-based, siloxane, silane or corresponding mixed radicals; wherein the composite material is obtainable by the process specified below. According to a preferred embodiment, in the recurring structural unit of formula (I), on average two groups X represent a group-R₁NCO and the third group X represents a group-R₁-NH-CO-OR₂-(-OCO-NH-R₁-NCO)_n. The prepolymer thus formed is a polyurethane prepolymer in which at least 33% of the chain members are polyurethane chains. The inventors also claim that "one of the essential features of the composites of the invention is the process for obtaining them, including the use of specific prepolymers, prepared by partial addition of polyisocyanates and polyols which remain fluid at room temperature", thus clearly describing isocyanurate-modified polyurethanes. European patent No.226176B1 does not teach a cured composition consisting essentially of an isocyanurate or a cured composition containing a reinforcing filler.

U.S. patent No.9334379 relates to a fiber composite part produced by impregnating fibers with a reaction resin mixture of a polyisocyanate, a polyol, a trimerization catalyst and optionally additives, and a method for producing the same. The inventors teach that the ratio of the number of isocyanate groups to the number of OH groups is from 1.6 to 6.0 and in particular from 2.1 to 3.5. U.S. patent No.9334379 also discloses that the preferred reaction mixture does not include epoxy resins and does not teach polymers consisting essentially of the reaction product of an isocyanate with itself, i.e., an isocyanurate, a uretdione, a carbodiimide, and an open structure.

U.S. patent application publication No. US2005/0038222a1 discloses that thermoset resins based on polyisocyanate and polyurethane chemistry have not been widely used for filament winding because they are mixed reactive components and require the exact combination of two or more chemical precursors such as polyisocyanate and polyol in well-defined stoichiometry. The problem with mixing active components is that it is difficult to control the reaction, as the reaction can occur on contact, even without a catalyst at ambient temperature, making the rate of reaction difficult to control.

While the above prior art references disclose various efforts to improve physical properties of polyisocyanurate-containing polymers through the reaction of various active hydrogen-containing molecules, they do not provide cured compositions prepared by reaction of reaction products that are substantially free of these moieties (moieties) and provide the high strength, high stiffness, high strain-to-failure, high toughness and high glass transition temperatures required for modern polymers, fiber-reinforced polymers and adhesives.

Summary of The Invention

In one embodiment, a process for making an isocyanurate polymer provides a mixed liquid aromatic polyisocyanurate and less than about 10 weight percent epoxy resin is mixed into the liquid polyisocyanurate. In another embodiment, the liquid aromatic polyisocyanurate is mixed with the catalyst composition after providing less than about 10 weight percent epoxy resin. The aromatic polyisocyanurate comprises polymeric methylene diphenyl diisocyanate (pMDI) that provides the aromatic polyisocyanurate with an average functionality of greater than 2 to form a reaction mixture. In one embodiment, the pMDI comprises a mixture of MDI and higher functionality pMDI. The mixture is cured at a temperature greater than about 70 ℃ to produce a polymer composition comprising the reaction product of two or more isocyanates. In another embodiment, the mixture is aged at ambient temperature and pressure to provide enhanced performance results.

The prior art literature indicates that the use of high percentages of pMDI or other aromatic polyisocyanurate reaction mixtures results in poor performing polymers, which are generally too brittle for any practical application. The chemical composition of the present invention demonstrates that these assertions are erroneous and achieve unexpected performance results over all other polyisocyanurate blends. Notably, the glass transition temperature of the resulting thermoset polymer is well above 300 ℃, a level not previously achieved with polyisocyanurates.

Notably, it was found that aging of the polymer in an atmospheric pressure and temperature environment containing moisture resulted in isocyanurate polymers having greatly increased glass transition temperatures (Tg). In addition, the presence of aliphatic isocyanurates (trimers) or uretdiones (dimers) in the reaction mixture was shown to result in more complete cure and a reduction in the temperature required to obtain high strength polymers. The present invention also found that the polymers can be cured in less than 5 minutes to achieve mechanical properties comparable to polymers with longer cure times at elevated temperatures.

Brief description of the drawings

Other advantages of the present invention will be more readily and better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1: example 10 DMA measurement profile after thermal curing and after leaving the sample at ambient temperature, pressure and humidity for 90 days;

FIG. 2 shows a diagram of DMA measurements of example 21 after 60 days of aging at ambient temperature and humidity in a climate controlled laboratory;

FIG. 3: example 12 DMA measurement chart after thermal curing and after placing the cured sample in a 100% humidity environment at 40 ℃ for 72 hours;

FIG. 4: example 9 DMA measurement chart after thermal curing and immersion of the cured sample in water at 80 ℃ under atmospheric pressure for 24 hours; and;

figure 5 shows a graph of DMA measurements of example 24 carbon fiber composite after 65 days of aging in a climate controlled laboratory at ambient temperature and humidity.

Detailed Description

It has been found in the present invention that the polymerization of a liquid reaction mixture comprising polymeric methylene diphenyl diisocyanate (pMDI) results in a cured composition having high strength, glass transition, young's modulus and toughness, while the reaction mixture is substantially free of chemicals such as oxazolidinones, amides, carbamates and ureas which can lead to chain extenders in the curing process. As will be further explained below, selection of a suitable catalyst further enables the cured compositions of the present invention to be obtained at 120 ℃ in less than 5 minutes and above 140 ℃ in less than 2.5 minutes, providing results not previously achievable. In the present invention, the dense polymer is a substantially void-free polymer having a void content of less than10%, or even less than 2%. The present invention achieves high toughness (greater than 0.5MPa m) by polymerization of a reaction mixture comprising polymeric methylene diphenyl diisocyanate and a catalytic amount of an epoxy resin substantially free of active hydrogen moiety-containing molecules such as hydroxyl, primary and secondary amines, carboxylic acids, thiols, and others known to those skilled in the art^1/2) High breaking strain (greater than 3%), high glass transition temperature (greater than 160 ℃), high tensile strength (greater than 60 MPa). The present invention further demonstrates the unexpected result that the presence of an aliphatic uretdione, aliphatic trimer or aliphatic iminooxadiazinedione as a reaction product of two or three aliphatic isocyanates accelerates the polymerization reaction, enabling higher isocyanate conversion and improved mechanical strength at lower curing temperatures.

The present invention provides a method of preparing a cured polymer composition by polymerization of isocyanate groups, which in one embodiment comprises the steps of:

(1) providing a liquid reaction mixture comprising:

A) at least one liquid aromatic polyisocyanate; and

B) optionally at least one liquid aliphatic polyisocyanate

C) A catalyst composition comprising a metal oxide having a metal oxide,

wherein the at least one aromatic polyisocyanate comprises polymeric methylene diphenyl diisocyanate (pMDI) such that the at least one aromatic polyisocyanate has a functionality of greater than 2, particularly at least 2.2, or at least 2.5, even greater than 2.65. Furthermore, the reactive composition comprises at least one epoxide, which may be monofunctional or polyfunctional, in a proportion of up to 7.5% by weight, in particular from 0.01% to 5%, in another embodiment from 0.5% to 4%, in another embodiment between 1.0% and 3%, in another embodiment 2%, of the total reaction mixture.

(2) Curing the reaction mixture by self-reaction of the isocyanate groups to obtain a cured polymer composition comprising the structure of the reaction product of isocyanate and itself.

In another aspect, the present invention relates to a cured composition comprising a filler to improve the mechanical properties of the cured composition, in one embodiment the filler is continuous fibers or in another embodiment discontinuous fibers.

As used herein, "at least one" refers to 1 or more, for example 1,2, 3, 4,5, 6, 7, 8, 9 or more. With respect to the components of the catalyst compositions described herein, this information does not refer to the absolute amount of molecules, but rather to the type of component. Thus, "at least one epoxy resin" for example means one or more different epoxy resins, i.e. one or more different types of epoxy resins. If together with a quantity, the quantity refers to the total amount of the respective identified type component that has been defined.

As used herein, "liquid" refers to a composition that is capable of flowing at room temperature (20 ℃) and atmospheric pressure (1013 mbar).

When referring to a chemical moiety (moiey), "substantially free" means that the mole fraction of molecules comprising the specified moiety in the reaction mixture or the cured composition is less than 7.5%. In some instances, "substantially free" means that the mole fraction of molecules comprising the specified moiety in the reaction mixture or cured composition is less than 5%. In contrast, "substantially" and "essentially" mean that the specified moiety is present in a molecular mole fraction greater than 92.5% of the reaction mixture or cured composition. In some instances, "substantially" and "essentially" means that the specified moiety is included in a molar fraction of molecules greater than 95% of the reaction mixture or cured composition.

The viscosity of the liquid composition described herein is particularly low enough that the composition is pumpable and capable of wetting and impregnating fibrous materials such as those used for fiber reinforced plastic parts. In various embodiments, the reaction mixture has a viscosity of <2500mPa s at room temperature and <150mPa s at a temperature of 50 ℃. To determine the viscosity, the resin mixture was produced at room temperature using a suitable mixer and the viscosity was measured on a rotor rheometer.

The present invention provides a cured composition having high strength, high fracture toughness and high glass transition temperature by curing a reaction mixture consisting essentially of a polyisocyanateWherein at least one polyisocyanate is polymeric methylene diphenyl diisocyanate (pMDI) such that the reaction mixture has a functionality of greater than 2, particularly at least 2.2, and in another embodiment at least 2.5 and in yet another embodiment greater than 2.7. Upon curing of the reaction mixture using a trimerization catalyst comprising at least one epoxy resin, a rigid polymer is obtained and this substantially isocyanurate polymer exhibits a high tensile strength (greater than 50MPa), a high toughness (greater than 0.5 MPa-m)^1/2) High strain to failure (greater than 3%) and high glass transition temperature (greater than 160 ℃). In preparing the substantially polyisocyanurate cured compositions, the fracture toughness and strength are insufficient without using polymeric methylene diphenyl diisocyanate (pMDI) as part of the reaction mixture to produce isocyanate functionalities greater than 2, particularly at least 2.2, more preferably at least 2.5 and even more preferably greater than 2.65. Although epoxy resins are known in the prior art to improve the fracture toughness of polymers, the amount of epoxy resin included in the present invention is representative of the amount of catalyst and therefore does not significantly affect the material properties.

Oligomeric MDI in the sense of the present application means polyisocyanate mixtures of the higher nuclear homologues of MDI having at least 3 aromatic nuclei and at least 3 functionalities. In the context of the present invention, the terms "polymeric diphenylmethane diisocyanate", "polymeric MDI", "oligomeric MDI" or pMDI refer to a mixture of oligomeric MDI and optionally monomeric MDI. Generally, the monomer content of the polymeric MDI is in the range of 25 to 85 wt%, based on the total mass of the pMDI, so that the average functionality is greater than about 2.1.

In addition to pMDI, the isocyanate mixture in step 1) may comprise monomeric or oligomeric isocyanates or prepolymer isocyanates. Monomeric isocyanates include conventional aliphatic, cycloaliphatic and aliphatic di-and/or polyisocyanates, especially the aromatic isocyanates well known from polyurethane chemistry. Aromatic isocyanates, in particular the MDI series (monomeric MDI) and TDI isomers, are particularly advantageous.

Isocyanates useful in embodiments disclosed herein may include isocyanates, polyisocyanates, isocyanate carbodiimides, uretdiones, and trimers composed of such isocyanates. Suitable polyisocyanates include any of the known aromatic, aliphatic, cycloaliphatic and araliphatic di-and/or polyisocyanates. Variants such as uretdiones, isocyanurates, carbodiimides, iminooxadiazinediones, etc., which are produced by reaction between isocyanates, are also included in these isocyanates.

Suitable aromatic diisocyanate compounds may include, for example, xylene diisocyanate, m-xylene diisocyanate, tetramethylxylene diisocyanate, toluene diisocyanate, 4 '-diphenylmethane diisocyanate, 1, 5-naphthalene diisocyanate, 1, 4-naphthalene diisocyanate, 4' -toluidine diisocyanate, 4 '-diphenyl ether diisocyanate, m-or p-phenylene diisocyanate, 4' -biphenyl diisocyanate, 3 '-dimethyl-4, 4' -biphenyl diisocyanate, bis (4-isocyanatophenyl) -sulfone, isopropylidene bis (4-phenylisocyanate), and the like. Polyisocyanates having three or more isocyanate groups per molecule may include, for example, triphenylmethane-4, 4',4 "-triisocyanate, 1,3, 5-triisocyanatobenzene, 2,4, 6-triisocyanatotoluene, 4' -dimethyldiphenylmethane-2, 2',5,5' -tetraisocyanate, and the like. The aliphatic polyisocyanate may include hexamethylene diisocyanate, 1, 4-diisocyanatobutane, 1, 8-diisocyanatooctane, m-xylylene isocyanate, p-xylylene isocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, lysine diisocyanate, etc., and uretdione type adducts, carbodiimide adducts and isocyanurate ring adducts of these polyisocyanates. The alicyclic diisocyanate may include isophorone diisocyanate, 4' -methylenebis (cyclohexyl isocyanate), methylcyclohexane-2, 4-or-2, 6-diisocyanate, 1, 3-or 1, 4-bis (isocyanatomethyl) cyclohexane, 1, 4-cyclohexane diisocyanate, 1, 3-cyclopentane diisocyanate, 1, 2-cyclohexane diisocyanate, and the like, and uretdione-type adducts, carbodiimide adducts and isocyanurate ring adducts of these polyisocyanates.

In a further embodiment of the invention, the reaction mixture comprises 15-85% polymeric MDI, 15-85% diphenylmethane diisocyanate isomers and homologues. In other embodiments of the present invention, the reaction mixture comprises 15 to 85% polymeric MDI, 25 to 65% diphenylmethane diisocyanate isomers and homologues and 2 to 20% uretdione of hexamethylene diisocyanate. In another embodiment of the invention, the reaction mixture comprises 15 to 85% polymeric MDI, 25 to 65% diphenylmethane diisocyanate isomers and homologues and 2 to 20% hexamethylene diisocyanate trimer.

Surprisingly, the cured compositions formed in step 2) of the present invention achieve higher isocyanate conversions when the reaction mixture comprises aliphatic uretdiones, aliphatic isocyanurates or aliphatic iminooxadiazinediones, enabling the cured compositions to achieve high mechanical properties at lower reaction temperatures than they would otherwise be. This result is unexpected, since aliphatic isocyanates are known to react more slowly than aromatic isocyanates, but in the reaction mixture of step 1), the reactivity is enhanced. Uretdiones, isocyanurates, carbodiimides, and iminooxadiazinediones are the reaction products of 2 or 3 isocyanates as shown below, where x, x', and x "can be the same or different aliphatic segments having isocyanate end groups.

It is of course also possible to use mixtures of any of the isocyanates listed above. Furthermore, there are many different orders of contacting or combining the desired compounds in making the reaction mixtures of the present invention including the polyisocyanurates, and one skilled in the art will recognize that it is within the scope of the present invention to mix or vary the order of addition of the compounds.

Catalyst composition

The reaction mixture is cured by a catalyst composition capable of initiating a trimerization reaction of the polymer. Trimerization catalysts may include amine catalysts such as N, N-dimethylbenzylamine (BDMA), 4-Dimethylaminopyridine (DMAP), 2-dimethylaminopyridine (2-DMAP), 1, 4-diazabicyclo [2.2.2] octane (DABCO), bis- (2-dimethylaminoethyl) ether (BDMAEE), 1, 8-diazabicyclo [5.4.0] undec-7-ene (DBU), 1, 5-diazabicyclo [4.3.0] non-5-ene (DBN), N-alkylmorpholines, N-alkylalkanolamines, tris (dimethylaminopropyl) hexahydrotriazine, N-dialkylcyclohexylamine, and alkylamines where the alkyl is methyl, ethyl, propyl, butyl and isomeric forms thereof, and heterocyclic amines. Amine catalysts also include quaternary ammonium hydroxides and salts, such as benzyltrimethylammonium hydroxide, benzyltrimethylammonium chloride, benzyltrimethylammonium methoxide, ammonium (2-hydroxypropyl) trimethylisooctanoate, ammonium (2-hydroxypropyl) trimethylammonium formate, and the like. In one embodiment BDMA and in another embodiment BDMAEE and in another embodiment DABCO are dissolved in a suitable solvent such as benzene, benzonitrile, tetrahydrofuran, nitrobenzene, or other suitable solvents known to those skilled in the art, used in the catalyst composition at a weight between 0.001 to 10 wt%, more preferably between 0.1 to 3 wt%. In another embodiment, the catalyst may be used as a solvent for DABCO, and suitable catalyst solvents include BDMA, imidazoles, organometallic compounds, or other catalysts known to those skilled in the art that solubilize DABCO, used in the catalyst composition at a weight between 0.001 and 10 wt%, more preferably between 0.1 and 3 wt%.

Non-amine catalysts may also be used. Organometallic compounds of bismuth, lead, tin, potassium, lithium, sodium, titanium, iron, antimony, uranium, cadmium, cobalt, thorium, aluminum, mercury, zinc, nickel, cerium, molybdenum, vanadium, copper, manganese and zirconium may be used. Illustrative examples include potassium acetate, potassium naphthol, potassium octoate, potassium 2-ethylhexanoate, bismuth nitrate, lead 2-ethylhexanoate, lead benzoate, ferric chloride, antimony trichloride, stannous acetate, stannous octoate, and stannous 2-ethylhexanoate.

In other embodiments, suitable catalysts may include imidazole compounds, including compounds having one imidazole ring per molecule, such as imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-phenyl-4-benzylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-isopropylimidazole, 1-cyanoethyl-2-phenylimidazole, 2, 4-diamino-6- [2 '-methylimidazolyl- (l)' ] -ethyl-s-triazine, 2, 4-diamino-6- [2 '-ethyl-4-methylimidazolyl- (l)' ] -ethyl-s-triazine, 2, 4-diamino-6- [2 '-undecylimidazolyl- (l)' ] -ethyl-s-triazine, 2-methylimidazolium-isocyanuric acid adduct, 2-phenylimidazolium-isocyanuric acid adduct, l-aminoethyl-2-methylimidazole, 2-phenyl-4, 5-dimethylolimidazole, and dimethylolimidazole, and dimethylolimidazole, and dimethylolimidazole, 2-2, and dimethyloliminiumsubm-bis-2, and dimethyloliminiumsubm-2-bis-2, and optionally, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4-benzyl-5-hydroxymethylimidazole, and the like; and compounds having 2 or more imidazole rings per molecule, obtained by dehydrating the above-mentioned hydroxymethyl-containing imidazoles such as 2-phenyl-4, 5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole and 2-phenyl-4-benzyl-5-hydroxymethylimidazole and condensing them by a dealdehyding reaction, for example, 4' -methylene-bis- (2-ethyl-5-methylimidazole) and the like.

Optionally, latent catalysts as described in U.S. patent No.9334379 may be used to delay the curing reaction. Such latent catalysts are known to the person skilled in the art and are generally used for the preparation of prepregs, Sheet Moulding Compounds (SMC) and Bulk Moulding Compounds (BMC). In one embodiment not disclosed in the prior art 2- (dimethylamino) pyridine acts as a latent catalyst.

In other embodiments of the present invention, the catalyst comprises at least one co-catalyst for the epoxy resin. The cocatalyst behaviour of epoxy resins has been reported in U.S. Pat. No. 2979485. Epoxy resins may include epoxy-containing monomers, prepolymers, and polymers, and mixtures thereof, and are also referred to hereinafter as epoxides or epoxy-containing resins. Suitable epoxy-containing resins are specific resins containing 1 to 10, or 1 to 2 or 1 epoxy groups per molecule. As used herein, "epoxy group" means a1, 2-epoxy group (oxirane). Preferably, the at least one epoxide is added to the reaction mixture in an amount of 0.1 to 10% by weight or 0.5 to 3% by weight of the reaction mixture. The epoxy resin acts as a co-catalyst but may be added to the reaction mixture separately from the trimerisation catalyst. In one embodiment, the epoxy resin is mixed with the substantially isocyanurate reaction mixture to form a mixture that is storage stable and can be catalyzed in the future.

The reaction mixture is mixed with a catalyst composition and cured by trimerization to form a catalyst composition consisting essentially of polyisocyanurate and having a density of 500 or more, preferably 1000kg/m or more³The cured composition of (1). The curing reaction is preferably carried out at an elevated temperature of 50-200 ℃ or at 75-170 ℃ or further between 80-150 ℃. In one embodiment of the invention, the reaction mixture is mixed with a catalyst composition and cured to form a cured composition consisting essentially of the reaction product of two or more isocyanates, including imides.

Trimerization of isocyanurates is known to be a slow process, especially in the absence of solvents, however, the present invention can cure surprisingly rapidly. The present inventors have shown that the reaction mixture can be cured at 120 ℃ for less than 5 minutes or at a temperature above 140 ℃ for less than 2.5 minutes, while achieving mechanical properties (see examples 17-23) comparable to those of long cure times (see example 11). High volume industrial production of polymers requiring rapid curing, such as the automotive industry, requires polymerization in less than 10 minutes. The unexpectedly fast cure further achieves high strength, stiffness and toughness. In one embodiment of the invention, the reaction mixture may be cured in less than 2 minutes, while in another embodiment, the reaction mixture may be cured in 90 seconds or less. In another embodiment of the present invention, the reaction mixture may be cured in less than 60 seconds. The reaction rate is controlled by the catalyst concentration and is greatly accelerated by the reaction of the epoxy or epoxide included as a co-catalyst with the trimerization catalyst to form a complex. As the ratio of epoxy resin to trimerization catalyst increases, the polymerization rate increases. It has surprisingly been found that the reaction mixture according to the invention remains stable for a considerable period of time until rapid curing takes place after the temperature has risen to 70 ℃ or more. Furthermore, the reaction is less exothermic than other fast curing resins (e.g., vinyl esters, epoxies, polyesters, etc.), and thus thick materials can be processed.

Unexpectedly, the cured composition continues to cure over time and, optionally, in the presence of humidity or moisture surrounding the sample, is able to achieve a glass transition temperature of greater than 250 ℃, or greater than 300 ℃, or greater than 325 ℃, or greater than 340 ℃. This final cure reaction rate is determined by the temperature and humidity of the environment surrounding the cured composition. When the cured composition is at a humidity level typical of climate controlled buildings, for example 20% to 70% relative humidity at 22 ℃, the final reaction will be complete over 2 to 12 weeks or 4 to 8 weeks. Fig. 1 shows the storage modulus and tan delta measured by dynamic thermomechanical analyzer (DMA) of example 10 after 90 days of aging, showing a substantial increase in glass transition temperature. Fig. 2 shows the storage modulus and tan delta measured by dynamic thermomechanical analyzer (DMA) of example 21 after aging for 60 days in ambient environment, showing a large increase in glass transition temperature, from 195.5 ℃ after curing to 354.2 ℃ after standing for 60 days under ambient atmospheric conditions. Figure 2 shows that the samples cured within 5 minutes exhibited the same unexpected increase in Tg as the longer cured samples. However, as shown by the DMA measurements of FIG. 3, 100% relative humidity at 40 ℃ and atmospheric pressure will complete the reaction within 24-72 hours or 24 hours. The aging reaction conditions change with increasing humidity and temperature to achieve faster curing. Referring to fig. 1, the DMA measurement plot of example 10, as explained further below, after thermal curing and after the sample was left at ambient temperature, pressure and humidity for 90 days, the glass transition temperature (Tg) increased from 196 ℃ to 356 ℃ after the aging period. This result is completely unexpected based on the teaching of the prior art. Further, referring to fig. 3, the DMA measurement profile of example 12, as further explained below, after thermal curing and after placing the cured sample in an environment of 40 ℃ at 100% humidity for 72 hours. The glass transition temperature (Tg) increased from 185 ℃ to 345 ℃, another unexpected result.

In further embodiments, the cured composition may be immersed in water to complete the reaction to achieve a glass transition temperature above 250 ℃, or above 300 ℃, or above 325 ℃, or above 340 ℃. The reaction rate is believed to be determined by the temperature and pressure of the water. For example, immersion of the sample at 80 ℃ will result in complete curing in less than 48 hours or less than 24 hours. The thermomechanical properties measured by a dynamic thermomechanical analyzer (DMA) are shown in fig. 4, measured after thermal curing of example 9 and after immersing the cured sample in water at 80 ℃ under atmospheric pressure for 24 hours. The glass transition temperature (Tg) is measured from the peak of the Tan delta curve and shows an increase in Tg from 240 ℃ to 374 ℃ after immersion in water. Most polymers undergo a decrease in glass transition temperature after moisture absorption, however the present invention shows a significant improvement in glass transition temperature. Referring to fig. 4, DMA measurement profile of example 9, as will be further explained below, after thermal curing and measurement after immersing the cured sample in water at 80 ℃ under atmospheric pressure for 24 hours. After immersion in water, the glass transition temperature (Tg) increased from 240 ℃ to 374 ℃.

In one embodiment of the invention, the reaction mixture is blended with continuous or discontinuous reinforcing fibers and cured with a trimerization catalyst composition to form a fiber-reinforced molded part. The molded parts can be used in the manufacture of automobiles, wind turbines, sporting goods, aerospace structures, pressure vessels, building materials, and printed circuit boards. However, the end use of the fiber reinforced plastic molded part may be applied to other applications known to those of ordinary skill in the art.

Known high strength fibrous materials suitable as a fibrous component of the fiber reinforced curing composition include, for example, carbon fibers, glass fibers, synthetic fibers such as polyester fibers, polyethylene fibers, polypropylene fibers, polyamide fibers, polyimide fibers, polyoxazolo fibers, polyhydroquinone-diimidazole pyridine fibers or aramid fibers, boron fibers, oxidized or unoxidized ceramic fibers such as alumina/silica fibers, silicon carbide fibers, metal fibers such as made of steel or aluminum, or natural fibers such as flax, hemp or jute. These fibers may be introduced in the form of mats, wovens, knits, flat scrims, nonwovens, or rovings. Two or more of these fibrous materials may also be used in the form of a mixture. Such high strength fibers, flat skips, woven fabrics, and rovings are known to those of ordinary skill in the art.

In particular, the fibre composite comprises more than 25 vol% of fibres, alternatively more than 50 vol%, alternatively between 50 and 70 vol%, based on the total fibre composite, in order to achieve excellent mechanical properties.

The reactive mixture may be blended with the reinforcing fibers by known methods, such as Resin Transfer Molding (RTM), Vacuum Assisted Resin Transfer Molding (VARTM), injection molding, high pressure reaction injection molding (HP-RIM), wet layup, pultrusion, or prepreg techniques. Since the present invention is a room temperature liquid, the present invention is particularly useful for the introduction process.

In various embodiments of the present invention, the reaction mixture is applied to a substrate, for example when used as an adhesive, or loaded into a molding tool when used as a molding compound for producing plastic parts, depending on the desired use. In one embodiment, the process is a Resin Transfer Molding (RTM) process and the reaction mixture is a reactive injection resin. The term "reactive" as used herein refers to the fact that the injected resin can be chemically cross-linked. In the RTM process, providing a reaction mixture, step (1) of the process, may comprise loading, in particular injecting, an injection resin into a mold. The described method and reaction mixture are particularly suitable when producing fiber-reinforced plastic parts, where the fiber or semifinished fiber product (pre-woven fabric/preform) can be placed in a mold before injection. The fibres and/or semifinished fibre products used may be materials known in the art to be useful for the present application, in particular carbon fibres.

In one embodiment of the invention, the reaction mixture is injected into a mold containing continuous or discontinuous fibers by resin transfer molding and cured within 5 minutes. In another embodiment of the invention, the reaction mixture is injected into a mold containing continuous or discontinuous fibers by resin transfer molding and cured in less than 2 minutes. In another embodiment of the invention, the reaction mixture is injected into a mold containing continuous or discontinuous fibers by resin transfer molding and cured in less than 1 minute.

In one embodiment of the invention, the reaction mixture is injected into a wind turbine blade mould comprising continuous or discontinuous fibres by resin transfer moulding and cured at a temperature below 95 ℃. In another embodiment of the invention, the reaction mixture is applied to the continuous fibers by direct injection, or placed in a resin bath and pultruded by a heated die. In any of these embodiments, the catalyst is mixed into the reaction mixture prior to processing. It should also be understood that the compositions of the present invention are particularly suitable for pultrusion because they can be rapidly cured in less than 5 minutes or in another embodiment in less than 2 minutes.

Like the cured compositions, fiber reinforced composites prepared with the cured compositions also exhibit an increase in Tg with ambient aging. FIG. 5 shows the storage modulus and tan delta of example 24 after 65 days of aging as measured by dynamic thermomechanical analyzer (DMA), showing a substantial improvement in the increase in glass transition temperature from 209.3 ℃ to 335.1 ℃, a level previously thought unattainable.

In one embodiment of the invention, the reaction mixture includes sufficient adherence to function as an adhesive. The reaction mixture can be mixed with fillers known for use in adhesives, such as fumed silica, glass beads, ceramic particles, nanowires, nanorods, nanoparticles, Carbon Nanotubes (CNTs), synthetic particles such as rubber, elastomers or thermoplastics.

In yet another embodiment of the present invention, the cured composition is flame retardant. In another embodiment of the present invention, the cured composition is non-flammable.

The present invention achieves a cured composition consisting essentially of isocyanurate crosslinks having excellent mechanical properties without the need for high curing temperatures or expensive chemicals. The invention further provides polymers having an incredibly high glass transition temperature. Furthermore, the present invention demonstrates that the presence of aliphatic uretdiones, aliphatic trimers, or aliphatic iminooxadiazinediones in the reaction mixture accelerates the trimerization reaction, resulting in higher isocyanate conversion, whereas the presence of aliphatic components has conventionally been predicted to reduce reactivity. The present invention further shows that the polymerization reaction can be completed within a few minutes, making the polymer suitable for large scale production.

Examples

Polyisocyanurate (polyisocyanurate)The polymer was prepared by the following method. The monomeric MDI used was a liquid mixture of methylene diphenyl diisocyanate (MDI) isomers from Covestro under the trade name MONDOUR MLQ and LUPRANATE MI from BASF, where the mixture essentially comprised 50/50 mixtures of 4,4'-MDI and 2,4' -MDI. Polymeric methylene diphenyl diisocyanate (pMDI) from BASF under the trade name LUPRANATE M20, was prepared from the material MSDS<55% of oligomeric MDI and 38% of monomeric 4-4 diphenylmethane diisocyanate and<10% MDI isomer composition and an average isocyanate functionality of 2.7. Polymeric methylene diphenyl diisocyanate (pMDI) with the trade name MONDUR MR Light was purchased from Covestro and consisted of 58% oligomeric MDI and 38% monomeric 4-4 diphenylmethane diisocyanate and 3.8% 2,4'-MDI and 0.2% 2,2' -MDI and an average isocyanate functionality of 2.8, depending on the MSDS of the material. HDI uretdione is obtained from Covestro under the trade name DESMODUR N3400 and HDI trimer is obtained from Wanhua under the trade name Wannate HT-100. Technical grade toluene diisocyanate (80% toluene-2, 4-diisocyanate) was purchased from Sigma Aldrich at 80% purity and all chemicals were used as received. Hexion is under the trade name EPON^TM828 sold undiluted difunctional bisphenol A/epichlorohydrin derived liquid epoxy resins and EPON from Hexion^TM862 diglycidyl ether of bisphenol F and purity obtained from TCI America>99% of the monofunctional reactive diluent Glycidyl Phenyl Ether (GPE) and glycidyl ether (CGE) available from Evonik under the trade name EPODIL 742. Purity of>98% N-phenyldimethylamine (BDMA) was obtained from Alfa Aesar in purity>98% of 1, 4-diazabicyclo [ 2.2.2%]Octane (DABCO) was obtained from TCI Chemicals, bis- (2-dimethylaminoethyl) ether (BDMAEE) was obtained from Huntsman International under the trade name ZF-20, and stannous octoate of 92.5-100.0% purity was obtained from Sigma Aldrich. No special storage or handling procedures were used, nor were any of these reagents subjected to any further purification procedures.

Preparation of pure resin sample: selected isocyanates of the selected formulations were mixed using vortex mixer mixing and a catalytic epoxy resin was added to the solution. The mixture was further mixed for 1 minute using a Fisher vortex mixer.The catalyst was then added to the mixture at the desired concentration and mixed for 1 minute with a vortex mixer. The solution was then centrifuged using a centrifuge at 5000rpm for 2 minutes to remove air introduced during mixing. Other common methods of sample degassing (i.e., vacuum pressure, sonication) may also be used. This solution was then carefully added to the solution supplied by Ellsworth AdhesivesRTV-4230-E silicon rubber suite. The mold containing the reaction mixture was placed in an autoclave and pressurized to 100psig, then heated to the desired temperature and held at that temperature for the specified period of time before cooling to room temperature. The cured sample was cooled under pressure until the autoclave temperature dropped below 80 c and the cured polymer was removed from the autoclave. Samples were prepared that cured within 10 minutes, the silicone rubber mold was heated prior to addition of the catalytic reaction mixture and then placed in an autoclave which was rapidly closed, pressurized and vented to allow the cured polymer to be removed from the autoclave for the designated cure time. The sample was immediately removed from the mold.

Fracture toughness: samples for measuring fracture toughness of neat resins were prepared according to ASTM standard D5045-polymer plane strain toughness test method, specifically following a "notched beam" geometry. A Buehler ECOMET 3 variable speed grinding polisher was used to remove surface defects and ensure that the specimens met the geometric tolerances defined by the test standards. The pre-splitting was performed using a slitting saw on a numerically controlled milling machine, and then the split tips were sharpened by sliding the sample at least 10 times over a fixed and unused razor blade. The blade was replaced after each test piece and a fixture was used to ensure uniform sharpening of the tip of the crack. The presplit samples were loaded into a 3-point bend test apparatus attached to an Instron 3367 test stand with a 30kN load cell. The maximum load before the crack propagates in the specimen is recorded and used for fracture toughness calculation. The calculation of the mean and standard deviation is based on a sample set of at least 5 samples.

Stretching a sample: samples for measuring tensile strength and stiffness of neat resin were prepared according to ASTM standard D638, specifically using type IV geometry. The samples were removed from the silicone rubber mold and polished to compliance using a Buehler ECOMET 3 variable speed grinder polisher. The sides were hand polished using commercial grade sandpaper and finally final polished using 1500 grit wet/dry sandpaper. The samples were mounted in an Instron 50kN wedge clamp attached to a 30kN load cell of an Instron 3367 test rig. The failure mode was analyzed to confirm the correct and expected failure of the material during the test and to ensure within the track gauge section of the failure. The maximum load was recorded during the test and used to calculate the tensile strength, the initial slope of the stress-strain curve was used to calculate the tensile modulus, and the crosshead extension was used to calculate the failure strain for each specimen. The mean and standard deviation were calculated based on a sample set of at least 5 samples.

Water bath treatment: pure resin samples were prepared according to the previous procedure. After removal from the autoclave and demolding, the sample was immersed in a RO filter water bath. The bath was loosely covered with a lid and placed in an oven at 80 ℃ for 24 hours. The water bath was then removed from the oven and the sample removed from the water bath once cooled. The samples for testing were then prepared according to the respective sample preparation steps.

And (3) moisture treatment: the pure resin samples prepared according to the previous procedure, after removal from the autoclave and demoulding, were placed in an environment of saturated humidity. This environment was created by placing an excess of liquid water in a Pyrex bakeware in a laboratory vacuum oven. The oven was heated to 40 ℃ and completely sealed from the outside environment, allowing water to evaporate into the air and remain there. The oven was maintained at about 100% humidity. The sample was left in this environment for 24-72 hours. Similar tests were conducted in a controlled laboratory environment at atmospheric pressure with a relative humidity between 20% and 70% at 22 ℃.

And (3) aging of atmosphere: the samples were aged in a laboratory with climate control. The relative humidity was not controlled.

Dynamic thermomechanical analysis. The glass transition temperature (Tg) of the cured polymer and fiber reinforced polymer composite was measured using a dynamic thermomechanical analyzer (DMA), where Tg is designated as the peak of Tan δ cure.

Some comparative examples have been prepared to demonstrate some embodiments of the invention. Tables 1,3 and 4 provide the composition of the reaction mixture and the reaction conditions. The reactants of all examples were prepared according to the pure resin test sample procedure.

Examples 1 to 9

Table 1 gives the formulations and cure conditions for examples 1-9 and table 2 provides the corresponding material properties for all examples, using type IV geometry to obtain tensile strength, tensile stiffness and strain to failure according to ASTM D638, while using single-edge notched beam specimens to measure fracture toughness according to ASTM 5045. Comparative examples 1-9 demonstrate cure conditions at 180 ℃ for 12 hours and show that various combinations of reactants are used to obtain polymers with high mechanical strength, stiffness and toughness. Table 2 shows the glass transition temperature of the samples after 12 weeks of aging under ambient conditions and demonstrates that very high Tg's can be obtained.

TABLE 1

TABLE 2

Examples 10 to 23

The formulations and curing conditions for examples 10-16 are given in Table 3, and the formulations and curing conditions for examples 17-22 are given in Table 4. Table 5 provides the corresponding material properties for all examples. Tensile strength, tensile stiffness and failure strain were obtained using type IV geometry according to ASTM D638 and fracture toughness was measured using single-edge notched beam specimens according to ASTM 5045. Comparative examples 10-16 demonstrate that cured compositions can be obtained by low temperature curing conditions, and comparative examples 17-22 demonstrate that cured compositions with high performance characteristics can be obtained in less than 5 minutes. Comparative example 10 includes the isocyanate of hexamethylene diisocyanate (Wannate HT-100), while comparative example 11 includes the uretdione of hexamethylene diisocyanate (DESMODUR N3400) cured at 85 ℃ for 2 hours and shows that excellent mechanical properties can be obtained, but comparative example 12 does not include an aliphatic component and gives a brittle polymer with limited strength under the same curing conditions. Aliphatic isocyanates are known to be less reactive than aromatic isocyanates and therefore the presence of aliphatic components in the reaction mixture would be expected to slow the reaction. This comparative example illustrates that, contrary to expectations, the presence of an aliphatic component can cause the polymer to cure at a lower temperature. The results are further demonstrated by examples 13 and 14 cured for 2h at 110 ℃ and 120 ℃ respectively, and show that the mechanical properties increase with increasing reaction temperature, and similar properties can be obtained at 120 ℃ without aliphatic isocyanate in the reaction mixture. Comparative example 15 shows that DABCO dissolved in BDMA in a weight ratio of 1:5 is used as a catalyst, while comparative example 16 shows that increasing the curing temperature can further improve the mechanical properties. Comparative examples 17 and 18 show that the reaction mixtures of the invention can be cured in as little as 5 minutes while achieving similar mechanical properties as reaction mixtures cured at lower temperatures for longer periods of time. Examples 19-23 used DABCO catalyst solutions dissolved in appropriate solvents. Examples 19-23 used solutions of DABCO to benzonitrile in a 1:3 weight ratio. Comparative examples 19 and 20 show that the reaction mixture of the present invention can be cured in as little as 3 minutes while achieving similar mechanical properties as the reaction mixture cured at lower temperatures for longer times. Example 21 demonstrates that the reaction mixture of the present invention can be cured at 160 ℃ for as little as 2 minutes while achieving similar mechanical properties as the reaction mixture cured at a lower temperature for a longer period of time. Example 22 demonstrates that the reaction mixture can be cured at 120 ℃ for 5 minutes and example 23 demonstrates that the reaction mixture can be cured at 130 ℃ for 3 minutes, while achieving similar mechanical properties as the reaction mixture cured at higher temperatures.

Example 24

The reaction mixture was injected into the fiber reinforcement and displayed by preparing a fiber reinforced composite sample. The reaction mixture of example 20 was injected into an 8-ply 12k Mitsubishi Grafil carbon fiber unidirectional carbon tape with an overhead weight of 373gsm using Vacuum Assisted Resin Transfer Moulding (VARTM). The VARTM process was allowed to complete in 2-10 minutes, and the panels were then cured in a l00psi autoclave at 170 ℃ for 3 minutes or in a 170 ℃ hot press for 3 minutes. After the composite was inserted into the autoclave, it was sealed and pressurized to l00psi immediately after about 90 seconds of adding the vacuum bagged composite, then held under pressure for about 15 seconds, then vented so that the autoclave door could be opened and the composite removed after 180 seconds at this temperature. Immediately after removal from the autoclave, the cured composite was removed from the plate and vacuum bag and then cured under ambient conditions. This procedure was intended to simulate the high pressure resin transfer molding (HP-RTM) process and show that cold resin cures in 3 minutes, while the high pressure injection system allows the resin to be heated before introduction into the mold, which greatly accelerates the curing reaction. The short beam strength of the composite was tested according to ASTM 2344 and was as high as 69.0 ± 3.68 MPa.

TABLE 3

TABLE 4

TABLE 5

In one embodiment of the invention, there is a large increase in the glass transition temperature when the cured composition is aged or immersed in water in the presence of atmospheric moisture. Table 6 shows the glass transition temperature (Tg) of selected examples before and after aging at ambient pressure and humidity, after aging at elevated temperature and elevated humidity, and after immersion in hot water. In each example, the results show that the cured composition experienced a substantial improvement in glass transition temperature. The prior art polymers exhibit predominantly a reduction in the glass transition temperature when exposed to moisture. However, the glass transition temperature of the cured compositions of the present invention increased significantly after this moisture history, as shown in Table 6 below. The results are quite clearly contrary to conventional teachings.

TABLE 6

Obviously, many modifications and variations of the present invention are possible in light of the above teachings, and the foregoing invention has been described in accordance with the relevant legal standards; accordingly, the description is to be regarded as illustrative in nature and not as restrictive. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and fall within the scope of the invention. Accordingly, the scope of legal protection given to this invention can only be determined by studying the following claims.