All-liquid, unfilled, halogen-free, flame-retardant thermosetting compositions

Abstract

This paper reports a series of all-liquid, unfilled, halogen-free, flame-retardant thermosetting resins. These compositions offer good physical and mechanical performance while providing inherent non-flammability. The resin systems are designed to eliminate exposure to toxic gases, such as halogen halides, that are typically produced during combustion. Furthermore, due to their mechanical properties, these materials are capable of superior performance in high-pressure and high-temperature environments, such as those found in battery enclosures during runaway reactions. Overall, these compositions provide novel flame-retardant resins that can reduce the hazards associated with fires and their by-products without compromising their usefulness and performance.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This non-provisional application claims the benefit of priority under 35 U.S.C. §119 to U.S. patent application Ser. No. 63 / 416,287, filed October 14, 2022, the entirety of which is incorporated herein by reference.

[0002] The present invention relates to all-liquid, unfilled, halogen-free, flame-retardant thermosetting compositions. More particularly, the present invention relates to the use of such thermosetting compositions for mass transit and related applications. Similarly, the present invention also relates to methods for the preparation of these resin compositions. [Background technology]

[0003] Currently, the majority of flame-retardant thermosetting resins rely on the use of halogen-based materials and / or inert fillers, such as alumina trihydrate, to perform satisfactorily. Unfortunately, these materials present challenges, such as the generation of highly toxic gases during combustion. For example, these materials may have reduced processability, which precludes their use in many applications or processes. For example, halogen-based thermosetting resins derived from tetrachlorophthalic anhydride, tetrabromophthalic anhydride, chlorendic anhydride, dibromoneopentyl glycol, and tetrabromobisphenol A have excellent flame-retardant properties but produce corrosive hydrogen halide gases upon combustion. Apart from that, many prior art resins have limited light stability and high specific gravity, which are disadvantageous in construction applications. Overall, these challenges prevent the use of these resins in mass transportation and other applications.

[0004] The primary fillers used in prior art flame-retardant thermosetting resins based on inert fillers include alumina trihydrate, melamine, calcium sulfate, and / or calcium carbonate. The major disadvantages of these materials are the high specific gravity and high viscosity exhibited by resins incorporating these materials. This is undesirable from a processing standpoint, as it limits the types of processes in which these resins can be employed. As with halogen-based resins, highly filled prior art systems also generally suffer from limited light stability and weathering defects.

[0005] Separately, existing thermosetting resins with flame-retardant properties belong to a class known as intumescent resins. Intumescent materials are materials that expand in volume when heated above a certain temperature. An insulating layer is formed on the intumescent material during the combustion process, thereby preventing further heat transfer to the composite part. It is well recognized that there is a need for this subclass of flame-retardant materials that function as intended components. One of these components is a polyhydroxy material (or derived therefrom), such as sugars, trimethylolpropane, and pentaerythritol, among others. These materials generally need to be capable of dehydrating to produce a carbonaceous layer.

[0006] Another component required for the expanding resin is a phosphorus compound that can generate phosphoric acid upon heating. Phosphoric acid is a strong dehydrating agent, which will eventually interact with the polyhydroxy materials. Finally, the expanding resin system requires a nitrogen-containing material that will contribute to the expanding gas during its decomposition.

[0007] Exemplary prior art expandable resin compounds rely on significant amounts of fillers and therefore suffer from the aforementioned drawbacks of high specific gravity, high viscosity, limited light stability, and weathering failure. For example, PCT Publication WO 97 / 31056 ("Weil") proposes the use of unsaturated polyester resins in combination with solid melamine and phosphorus compounds to exhibit self-extinguishing properties and low smoke generation. However, the compounds disclosed by Weil rely on significant amounts of melamine combined with ammonium polyphosphate as a flame retardant, both of which are fillers that suffer from some of the drawbacks discussed above. PCT Publication WO 2020 / 025845 ("Nogues") also demonstrates that the use of compositions derived from unsaturated polyester resins and vinyl ester resins combined with gel coats using ammonium polyphosphate (APP) and melamine can provide significant fire protection. The composition disclosed by Nogues also contains pentaerythritol, which serves as a source of carbonaceous material.

[0008] Therefore, a halogen-free, flame-retardant thermosetting resin that does not rely on the use of fillers to limit the generation of corrosive and / or toxic gases, including halogen halides, during combustion would be an improvement over the prior art. Furthermore, a halogen-free, flame-retardant thermosetting resin that does not rely on the use of fillers would also have the advantages of lower specific gravity and viscosity, and would have improved light stability, enabling their use in construction, transportation, and similar applications. Summary of the Invention

[0009] The present invention is a series of novel all-liquid, unfilled, halogen-free, flame-retardant thermosetting resins for general composite applications, particularly those related to mass transportation. The invention includes a series of resin compositions explicitly composed of unsaturated polyester resins, urethane (meth)acrylate resins, liquid oligomeric phosphonates, reactive liquid melamine derivatives, mobile liquid polyurethanes, and combinations of vinyl and (meth)acrylate reactive monomers.

[0010] It is therefore an object of the present invention to provide a (a) all-liquid, (b) unfilled, and (c) halogen-free thermosetting resin composition with mechanical and physical characteristics that make it suitable for use in general composite applications.

[0011] Another object of the present invention is to provide a thermosetting resin that can be cured using thermal initiation at both low and high temperatures.

[0012] Another object of the present invention is to provide a thermoset resin backbone that is capable of providing fire protection by using various sources of nitrogen materials, such as urethane (meth)acrylates and liquid melamine derivatives, among others.

[0013] Another object of the present invention is to provide a flame retardant thermoset resin that is capable of passing stringent tests such as Docket 90, which includes, among others, the ASTM E-162 flame spread test, the ASTM E-662 smoke generation test, and the BSS 7239 gas toxicity test.

[0014] Another object of the present invention is to provide a flame retardant thermoset resin that is capable of meeting the requirements of UL 2596, as they relate to the thermal and mechanical performance of battery enclosure materials.

[0015] These and other objects, features and advantages of the present invention will become apparent with reference to the following embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0016] As noted above, the present invention is a class of resin compositions, which in preferred embodiments comprise or consist essentially of one or more of the following elements: (A) unsaturated polyester resin, (B) urethane (meth)acrylate resin, (C) liquid oligomeric phosphonate, (D) reactive liquid melamine derivative, (E) mobile liquid polyurethane, and (F) one or more reactive monomers, such as vinyl-reactive monomer (F1), (meth)acrylate ester-reactive monomer (F2), or a combination of both (F1) and (F2). The compositions of the present invention may also utilize one or more optional additives.

[0017] In embodiments, the compositions of the present invention utilize either (A) an unsaturated polyester resin, or (B) a urethane resin, or both an unsaturated polyester resin and a urethane resin, in combination with one or more of the other components listed above. In embodiments, the total amount of resin in the compositions of the present invention ranges from 0 to 35% or from 10 to 35%. In some embodiments, the total amount of resin in the compositions of the present invention ranges from 15 to 33.6%.

[0018] In embodiments, the unsaturated polyester resin (A) used in the compounds of the present invention may be a dicyclopentadiene (DCPD) modified unsaturated polyester resin. In some preferred embodiments, the unsaturated polyester resin (A) is made from a DCPD-terminated unsaturated polyester resin used in combination with a nitrogen-rich compound and a liquid phosphorus compound.

[0019] As used herein, the term urethane (meth)acrylate refers to the product of the reaction of an isocyanate with a possible acrylic acid ester and / or methacrylic acid ester moiety. In an embodiment, the urethane (meth)acrylate resin (B) used in the composition of the present invention may be the product of the reaction of an aromatic difunctional isocyanate with a hydroxy-functionalized (meth)acrylic acid ester. In an embodiment, the urethane (meth)acrylate resin (B) used in the composition of the present invention may be a urethane methacrylate derived from methylene diphenyl diisocyanate (MDI).

[0020] Also in some preferred embodiments, the liquid phosphorus component (C) of the compounds of the present invention is an oligomeric phosphonate and / or polyphosphonate. In an embodiment, component (C) is selected from the group consisting of phosphonic acid, methyl-(5-ethyl-2-methyl-2-oxido-1,3,2-dioxophospho), phosphonic acid, P-methyl-, diphenyl ester polymer with 4,4'-(1-methylethylidene)bis[phenol], and bis[(5-ethyl-2-methyl-2,2-dioxido-1,3,2-dioxaphosphorinan-5-yl)methyl](methyl)phosphonic acid with (5-ethyl-2-methyl-2-oxido-1,3,2-dioxaphosphorinan-5-yl)methylmethyl methylphosphonate. The liquid oligomeric phosphonate (C) may be one or more compounds selected from the list including bis[(5-ethyl-2-methyl-2,2-dioxido-1,3,2dioxaphosphorinan-5-yl)methyl]ester). In embodiments, the total amount of liquid oligomeric phosphonate (C) in the compositions of the present invention ranges from 3 to 15%. In some embodiments, the total amount of liquid oligomeric phosphonate (C) in the compositions of the present invention ranges from 4 to 12%. Percentages of each component referenced herein are understood to represent the weight percent of each component in the formulation.

[0021] Also as used herein, the term reactive liquid melamine derivative refers to a melamine-derived material containing covalently bonded vinyl and / or (meth)acrylic acid ester groups that render it copolymerizable with the aforementioned resins. In some embodiments, the reactive liquid melamine derivative component (D) can be a melamine acrylate and / or a melamine triacrylate. In embodiments, the amount of reactive liquid melamine derivative (D) in the compositions of the present invention can range from 0 to 50%. In some embodiments, the amount of reactive liquid melamine derivative (D) in the compositions of the present invention can range from 0 to 45% or from 40 to 45%.

[0022] The mobile liquid polyurethane (E) used in accordance with the present invention can be a compound such as, for example, an aliphatic urethane trifunctional acrylate oligomer composition. In some embodiments, the amount of mobile liquid polyurethane (E) in the composition of the present invention can range from 10 to 40%. In some embodiments, the amount of mobile liquid polyurethane (E) in the composition of the present invention can range from 15 to 35%.

[0023] As used herein, the term (meth)acrylate ((meth)acrylic acid ester) refers to reactive diluents such as acrylic acid esters and methacrylic acid esters with various degrees of functionalization. In certain embodiments, the vinyl and / or (meth)acrylic acid ester reactive monomers (F) according to the present invention may include methyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, trimethylolpropane triacrylate (TMPTA), and / or a combination of tris(2-hydroxyethyl)isocyanurate triacrylate and trimethylolpropane triacrylate. In embodiments, the total amount of vinyl and (meth)acrylic acid ester reactive monomers (F) in the compositions of the present invention may range from 30 to 40%. In some embodiments, the total amount of vinyl and (meth)acrylic acid ester reactive monomers (F) in the compositions of the present invention may range from 34 to 36%.

[0024] In embodiments, the compounds of the present invention may employ additives such as defoamers, degassing additives, binders or coupling agents including silane coupling agents such as trimethoxyvinylsilane, preservatives such as copper naphthenate 8%, and other additives known in the art.

[0025] In embodiments, the compounds of the present invention may also employ one or more reactive diluents, such as cyclohexanedicarboxyimide ethyl acrylate, which is preferred in certain embodiments due to its nitrogen content. The inventors have discovered that nitrogen- and phosphorus-containing materials provide better flame retardancy in combination with other components in the formulations of the present invention when compared to other materials in this class.

[0026] Furthermore, it will be understood that the relative amounts of a particular class of material recited for the formulations of the present invention may not encompass that amount of that class of composition in the base resin formulation or in another component listed separately in the exemplary formulation. For example, the DCPD unsaturated polyester used in exemplary formulations 1 and 2 below may contain 28% styrene, and the urethane methacrylate component may contain 15% methyl methacrylate (MMA) and 15% 2-hydroxyethyl methacrylate (HEMA).

[0027] While all formulations containing one or more of the compounds or classes of compounds described above fall within the scope of the present invention, preferred embodiments of the present invention include three major classes of materials, each in combination with one or more of the other classes of materials and / or one or more additives. The major classes of materials included in each of the preferred embodiments of the present invention are as follows:

[0028] (1) Polyphosphonates (C), such as liquid oligomeric phosphonates;

[0029] (2) reactive polyurethanes (E), such as mobile liquid polyurethanes, and

[0030] (3) at least one reactive monomer (F) of the vinyl or (meth)acrylic acid ester type;

[0031] The inventors have discovered that a surprising positive flame retardant effect is achieved by each of these three major components in the formulation.

[0032] In particular, the inventors have discovered that a surprising positive flame retardant effect is achieved when the total percentage of reactive monomers (F) in the formulation is between 34 and 36% or between 34.11 and 35.34%. In preferred embodiments, the at least one reactive monomer in the formulation includes 2-hydroxyethyl methacrylate (HEMA). In some preferred embodiments, the at least one reactive monomer in the formulation includes a combination of HEMA and trimethylolpropane triacrylate (TMPTA). In other preferred embodiments, the at least one reactive monomer in the formulation includes HEMA, methyl methacrylate (MMA), TMPTA, and tris(2-hydroxyethyl)isocyanurate triacrylate.

[0033] Furthermore, the inventors have discovered that a surprising positive flame retardant effect is achieved when the amount of polyphosphonate (C) is 4-10% or 4.87-10%. In a preferred embodiment, the polyphosphonate (C) used in the formulations of the present invention comprises a compound formed from the reaction of phosphonic acid and methyl-(5-ethyl-2-methyl-2-oxido-1,3,2-dioxophospho).

[0034] Furthermore, the inventors have discovered that a surprising positive flame retardant effect is achieved when the ratio of component (C) to component (F) in the formulation, i.e., the ratio of polyphosphonate to reactive monomer, is between 1:3 and 1:8, or between 1:3.5 and 1:7.17.

[0035] Furthermore, the inventors have discovered that when the formulations of the present invention contain reactive polyurethane (E) in an amount of 16 to 35% or 17.04 to 34.5%, a surprisingly positive flame retardant effect is achieved.

[0036] Exemplary Formulations

[0037] Without limiting the foregoing summary, exemplary formulations are provided in Tables 1-3 to illustrate specific embodiments of the present invention. [Table 1] [Table 2] [Table 3]

[0038] Results: Flame retardancy testing of formulations of the present invention

[0039] Exemplary formulations 1-3 of the present invention described above were tested for flame, smoke, and toxicity performance according to the known Docket 90 test protocol (to demonstrate the safety of materials in transportation applications with respect to flammability and smoke generation characteristics), which included the ASTM E-162 Flame Spread Test, the ASTM E-662 Smoke Generation Test, and the BSS 7239 Gas Toxicity Test.

[0040] As can be seen from the remaining results presented in Tables 4-6 below, the compositions of the present invention, shown here as Exemplary Formulations 1-3, each demonstrated good physical and mechanical performance while providing inherent non-flammability. In particular, the mechanical performance demonstrated by the compounds of the present invention makes them suitable for high-pressure, high-temperature environments, such as those found in battery enclosures during runaway reactions. The ability of the compounds of the present invention to be used in such applications represents a distinct improvement over prior art flame-retardant compositions. Furthermore, the present invention is particularly novel in that it is an all-liquid, halogen-free, resinous composition that has passed the UL 2596 test protocol (Test Method for Thermal and Mechanical Performance of Battery Enclosure Materials), demonstrating that the compositions of the present invention can be used in battery enclosures and are safe during a thermal runaway event.

[0041] Generally, the compositions of the present invention provide novel flame-retardant resins capable of reducing the risks associated with fires and their by-products without compromising their usefulness and performance. The results shown below for all three exemplary formulations demonstrate that the resins passed each of the tests in the Docket 90 protocols (ASTM E-162 Flame Spread Test, ASTM E-662 Smoke Emission Test, and BSS 7239 Gas Toxicity Test), and the bottom half of each of Tables 4-6 reports the amount of gas released in the BSS 7239 Gas Toxicity Test (all within acceptable limits). [Table 4] [Table 5] [Table 6]

[0042] Results: Thermal and mechanical performance of battery enclosure materials

[0043] To further illustrate the novel and improved features of the formulations of the present invention over the prior art, the exemplary formulation 2 disclosed above was next tested in a thermal runaway box using the UL 2596 test protocol. This test simulates a battery enclosure containing 25 electrochemical cells subjected to a violent reaction; i.e., the battery enclosure must remain intact throughout the process. The test protocol requires the assembly to have a 16 mm pinhole, which allows the runaway reaction to reach a specific pressure and temperature. For this test, a laminate with 67% glass content and 3.75 mm was fabricated using formulation 2. This laminate was then placed on the surface of the electrochemical cells to simulate the enclosure. Finally, the electrochemical cells were intentionally heated, placing them in an unstable state where they would enter a self-heating thermal runaway reaction. Thermal runaway occurs when the cells generate heat faster than they can dissipate it, which can lead to flames, explosions, and gas release. To the inventor's knowledge, no other liquid, unfilled, halogen-free thermosetting resins have successfully passed the UL 2596 testing protocol.

[0044] As shown in Table 7 below, enclosures containing compositions of the present invention exhibited acceptable suppression of runaway reactions while maintaining physical and mechanical performance in a manner not possible using known prior art flame-retardant resins. In particular, battery enclosures incorporating exemplary Formulation 2 met the requirements of UL 2596 without resorting to fillers or halogen-containing materials, while exhibiting flame retardancy such that it was commensurate with the thermal and mechanical performance of the battery enclosure material. [Table 7]

[0045] This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles, and this application is intended to cover such departures from the present disclosure as come within known practice or custom in the art to which this invention pertains. [Industrial Applicability]

[0046] Statement of Industrial Applicability The present invention embodies a class of thermosetting compositions having mass transit and related applications. In particular, the present invention relates to one or more thermosetting compositions that embody novel flame-retardant resins that can reduce the hazards associated with fires and their by-products without compromising their utility and performance.

Claims

1. 1. An unfilled, halogen-free, flame-retardant thermoset resin comprising essentially: one or more resins, liquid oligomeric phosphonates, reactive liquid melamine derivatives, a mobile liquid polyurethane, and An unfilled, halogen-free, flame-retardant thermosetting resin comprising one or more monomers selected from the group consisting of vinyl and (meth)acrylic acid ester reactive monomers.

2. 10. The unfilled, halogen-free, flame-retardant thermoset resin of claim 1, wherein the one or more resins include unsaturated polyester resins and urethane (meth)acrylate resins.

3. 10. The unfilled, halogen-free, flame-retardant thermoset resin of claim 1, wherein said one or more resins comprise an unsaturated polyester resin.

4. 10. The unfilled, halogen-free, flame-retardant thermoset resin of claim 1, wherein the one or more resins comprise a urethane (meth)acrylate resin.

5. 10. The unfilled, halogen-free, flame-retardant thermoset resin of claim 1 further comprising one or more additives.

6. 10. The unfilled, halogen-free, flame retardant thermoset resin of claim 1, wherein the one or more resins are present in the flame retardant thermoset resin in the range of 10-20%.

7. 10. The unfilled, halogen-free, flame retardant thermoset of claim 1, wherein the liquid oligomeric phosphonate is present in the flame retardant thermoset in the range of 3 to 15%.

8. 10. The unfilled, halogen-free, flame retardant thermoset resin of claim 1, wherein the reactive liquid melamine derivative is present in the flame retardant thermoset resin in the range of 40-45%.

9. 10. The unfilled, halogen-free, flame retardant thermoset resin of claim 1, wherein the one or more monomers are present in the flame retardant thermoset resin in the range of 30-40%.

10. The resin is polyphosphonates, reactive polyurethanes, and 10. The unfilled, halogen-free, flame-retardant thermoset resin of claim 1, comprising at least one reactive monomer selected from the group consisting of vinyl and (meth)acrylic acid ester reactive monomers.

11. 11. The unfilled, halogen-free, flame-retardant thermoset resin of claim 10, wherein the at least one reactive monomer comprises 2-hydroxyethyl methacrylate (HEMA).

12. 11. The unfilled, halogen-free, flame-retardant thermoset of claim 10, wherein the at least one reactive monomer in the formulation comprises a combination of 2-hydroxyethyl methacrylate (HEMA) and trimethylolpropane triacrylate (TMPTA).

13. 11. The unfilled, halogen-free, flame-retardant thermoset of claim 10, wherein the at least one reactive monomer comprises a combination of 2-hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), trimethylolpropane triacrylate (TMPTA), and tris(2-hydroxyethyl)isocyanurate triacrylate.

14. 11. The unfilled, halogen-free, flame-retardant thermoset resin of claim 10, wherein the total weight percent of the at least one reactive monomer is 34% to 36%.

15. 11. The unfilled, halogen-free, flame-retardant thermoset of claim 10, wherein the amount of polyphosphonate is 4 wt% to 10 wt%.

16. 16. The unfilled, halogen-free, flame-retardant thermoset of claim 15, wherein the polyphosphonate comprises a compound formed from the reaction of phosphonic acid and Methyl-(5-Ethyl-2-Methyl-2-Oxido-1,3,2-Dioxophospho).

17. 11. The unfilled, halogen-free, flame-retardant thermoset of claim 10, wherein the ratio of polyphosphonate to reactive monomer in the formulation is from 1:3 to 1:

8.

18. 16. The unfilled, halogen-free, flame-retardant thermoset of claim 15, wherein the ratio of polyphosphonate to reactive monomer in the formulation is from 1:3 to 1:

8.

19. 11. The unfilled, halogen-free, flame-retardant thermoset of claim 10, wherein the amount of reactive polyurethane is 16 wt% to 35 wt%.

20. 11. The unfilled, halogen-free, flame-retardant thermoset of claim 10, wherein the reactive polyurethane is an aliphatic trifunctional urethane acrylate.

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