Epoxy resin composition and composite material thereof

Abstract

A halogen-free, antimony-free, phenolic-free thermoset epoxy resin composition is provided. The halogen-free, antimony-free, phenolic-free epoxy resin composition includes an epoxy resin, a curing agent, a catalyst, and a flame retardant additive. When the epoxy resin composition is impregnated into a fabric (e.g., a fiberglass fabric) and molded into a panel, the panel has an OSU two-minute total heat release of less than 40 kW-min / m 2 and an OSU peak heat release rate of less than 40 kW / m 2 . The epoxy resin composition can be combined with a fabric (e.g., a fiberglass fabric) to form a prepreg. The prepreg can be cured when in contact with at least one honeycomb structure to form a composite material, including a panel for aerospace interior applications.

Description

Related applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 607,894, filed December 8, 2023, entitled “Epoxy Resin Compositions and Composites thereof,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The embodiments disclosed herein relate to epoxy resin compositions and composites thereof, and more specifically to epoxy resin compositions and composites having a low heat release rate and a low total heat release during combustion. Background Technology

[0003] The following paragraphs do not imply an admission that anything discussed herein is prior art or part of the knowledge of someone skilled in the art.

[0004] Composite materials can be used to manufacture components in a variety of industries, such as structural panels for aircraft interiors. The manufacture of these structural panels typically involves the use of an intermediate material called a thermosetting prepreg, in which structural fibers (such as carbon fibers, glass fibers, and aramid fibers) are impregnated within a thermosetting resin (such as epoxy or phenolic resins). This intermediate material, composed of fibers and resin, can be molded into a rigid structure by applying heat and / or pressure.

[0005] Composite materials used in aircraft interior applications must meet very stringent fire, smoke, and toxicity (FST) requirements to protect aircraft passengers in the event of an accident and / or fire. Generally, composites made from phenolic resins exhibit better FST performance than those made from epoxy resins, while composites made from epoxy resins offer better mechanical properties than those made from phenolic resins. Therefore, a common practice among composite material manufacturers is to maximize the use of phenolic resins in composites intended for applications with acceptable lower mechanical properties, and to maximize the use of epoxy resins in composites intended for applications requiring higher mechanical properties.

[0006] Flame retardant (FR) additives can be added to phenolic and epoxy resins to improve the FST (Flame Stem Strength) properties of the resulting composites; however, these additives are typically toxic and can only be used in small quantities. Furthermore, global compliance standards (such as the EU regulation REACH, adopted to improve protection of human health and the environment from the potential risks of chemicals) have phased out the use of potentially toxic chemicals in aircraft interior applications, including the use of halogen and antimony compounds as FR additives. The use of phenolic resins in aircraft interior applications is also expected to be phased out in the near future.

[0007] In the absence of effective FR additives and phenolic resins, the composites manufacturing industry faces significant challenges in producing acceptable composites for aircraft interior applications that comply with current and anticipated regulatory compliance. Summary of the Invention

[0008] This article describes a halogen-free, antimony-free, and phenol-free thermosetting epoxy resin composition. This halogen-free, antimony-free, and phenol-free epoxy resin composition comprises an epoxy resin, a curing agent, a catalyst, and a flame-retardant additive. When the epoxy resin composition is impregnated into a fabric (e.g., fiberglass fabric) and molded into a sheet, the sheet exhibits a power output of less than 40 kW-min / m². 2 The total heat release of the OSU in two minutes is less than 40 kW / m². 2 The peak heat release rate of the OSU.

[0009] Depending on some aspects of the epoxy resin composition, the epoxy resin can be a biphenyl-type epoxy resin, a naphthalene-type epoxy resin, or an aralkyl-type epoxy resin. Furthermore, the amount of epoxy resin in the composition can be 30 to 70% by weight of the total weight of the epoxy resin composition.

[0010] Depending on some aspects of the epoxy resin composition, the amount of curing agent is 3 to 10% by weight of the total weight of the epoxy resin composition.

[0011] Depending on some aspects of the epoxy resin composition, the amount of catalyst is 1 to 10% by weight of the total weight of the epoxy resin composition.

[0012] Depending on some aspects of the epoxy resin composition, the amount of flame retardant additive is less than 40% by weight of the total weight of the epoxy resin composition.

[0013] Depending on some aspects of the epoxy resin composition, the epoxy resin composition may also contain a toughening agent.

[0014] According to some aspects of the epoxy resin composition, the epoxy resin composition also contains non-reactive additives. Furthermore, according to some of the aforementioned aspects, the amount of non-reactive additives and flame-retardant additives is less than 40% by weight of the total weight of the epoxy resin composition.

[0015] According to some aspects of the epoxy resin composition, when the epoxy resin composition is impregnated into a fabric (e.g., a glass fiber fabric) and molded into a sheet, the sheet has a power of less than 35 kW-min / m. 2 The total heat release of the OSU in two minutes is less than 30kW / m 2 The peak heat release rate of the OSU.

[0016] Depending on other aspects, the epoxy resin composition can be bonded to fabrics (such as fiberglass fabrics) to form a prepreg. When in contact with at least one honeycomb structure, the prepreg can be cured to form a composite material, including sheets for aerospace interior applications.

[0017] Other aspects and features will become apparent to those skilled in the art after reading the following description of some exemplary implementations. Attached Figure Description

[0018] The accompanying drawings included herein are used to illustrate examples of the various articles, methods, and apparatus described in this specification. In the drawings: Figure 1 This is a flowchart of a method for preparing an epoxy resin composition according to one embodiment; and Figure 2 This is a flowchart of a method for preparing a composite material from an epoxy resin composition according to one embodiment. Detailed Implementation

[0019] Various apparatuses or methods are described below to provide examples of each claimed embodiment. The embodiments described below are not intended to limit any claimed embodiment, and any claimed embodiment may cover processes or materials different from those described below. Claimed embodiments are not limited to materials or processes having all the characteristics of any one of the materials or processes described below, nor are they limited to features common to many or all of the materials described below. The materials or processes described below may not be covered by any claimed embodiment. Any embodiments described below not claimed in this document may be the subject of other protective documents (e.g., continuation patent applications), and the applicant, inventor, or owner does not intend to waive, deny, or contribute to the public by virtue of the disclosure of any such embodiments in this document.

[0020] In this document, the term "epoxy resin" or "epoxy resin" refers to a compound having an epoxy group in its molecule; the term "epoxy resin composition" or more simply "epoxy composition" refers to an uncured composition comprising an epoxy resin, a component for curing the epoxy resin (commonly referred to as a "curing agent," "curing catalyst," or "curing accelerator"), and optionally one or more additives or modifiers (e.g., plasticizers, toughening agents, dyes, organic pigments, inorganic fillers, polymer compounds, antioxidants, UV absorbers, coupling agents, surfactants, or other suitable compounds); and the term "epoxy resin composite" or "epoxy composite" refers to a cured product obtained by curing an epoxy resin composition.

[0021] Epoxy Resin Composition The epoxy resin compositions of the composite materials described herein contain epoxy resin. In some examples, the epoxy resin is a halogen-free, antimony-free, and phenol-free thermosetting epoxy resin that can be cured into a solid, infusible matrix surrounding reinforcing fibers in the composite material.

[0022] Typical examples of epoxy resins include non-halogenated epoxy resins, such as bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenolic varnish type epoxy resins, cresol phenolic varnish type epoxy resins, bisphenol A phenolic varnish type epoxy resins, trifunctional phenolic type epoxy resins, tetrafunctional phenolic type epoxy resins, naphthalene type epoxy resins, biphenyl type epoxy resins, aralkyl type epoxy resins, alicyclic epoxy resins, polyol type epoxy resins, compounds obtained by epoxidizing double bonds (e.g., glycidylamine, glycidyl ester, and butadiene), and compounds obtained by reacting hydroxyl-containing silicone resins with epichlorohydrin.

[0023] Among the epoxy resins mentioned above, naphthalene-containing epoxy resins, biphenyl-type epoxy resins, and aralkyl-type epoxy resins generally offer heat resistance and flame retardancy compared to the other resins mentioned above.

[0024] In the epoxy resin composition of the embodiments of the present invention, the content of epoxy resin can be 10 to 90 weight percent of the total epoxy resin composition, particularly 30 to 70 weight percent. When the content of epoxy resin is within the above range, the resulting composite material exhibits heat resistance and flame retardancy.

[0025] The epoxy resin compositions of the composite materials described herein may also contain toughening agents. In some instances, the toughening agents in the epoxy resin compositions described herein can improve the toughness (e.g., fracture toughness, or the ability of cracked materials to resist fracture) of the composite materials obtained therefrom without impairing mechanical properties. The toughening agents can also improve the adhesion between the reinforcing fibers and the epoxy resin in the resulting composite material without affecting heat resistance.

[0026] Toughening agents may include elastomers, such as carboxyl-terminated butadiene-acrylonitrile (CTBN) and amino-terminated butadiene-acrylonitrile (ATBN); inorganic particles, such as clay particles and carbon nanotubes; core-shell toughening agents, such as Kaneka KaneAce; block copolymers, such as Arkema Nanostrength; thermoplastic resins, such as polypropylene, polybutylene terephthalate, ABS, polyamide, polyethylene terephthalate, polymethacrylate, polyvinyl acetal, polyacetal, polycarbonate, polyimide, polyphenylene ether, polyetherketone, polysulfone, polyphenylene sulfide, polyamide-imide, polyethersulfone, polyetheretherketone, and polyetherimide; etc.

[0027] The epoxy resin compositions of the composite materials described herein also include curing agents. The term "curing agent" refers to polymerization accelerators, co-curing agents, catalysts, initiators, or other additives intended to participate in or promote the curing of thermosetting epoxy resin compositions. For thermosetting resin formulations containing epoxy resins, such curing agents include polymerization accelerators and catalysts, such as acid anhydrides, amines, imidazoles, amides, thiols, carboxylic acids, phenols, dicyandiamide, urea, hydrazine, acylhydrazine, aminoformaldehyde resins, melamine-formaldehyde resins, amine-boron trihalide complexes, quaternary ammonium salts, quaternary phosphonium salts, triarylsulfonium salts, diaryliodonium salts, diazonium salts, etc., and any combination of two or more of them, optionally also including transition metal complexes.

[0028] In one embodiment, the curing agent is a dicyandiamide curing agent, such as micronized dicyandiamide, dicyandiamide, or cyanoguanidine (e.g., Alzchem's Dyhard® 100S or CVC Chemical's Omicure® DDA 10).

[0029] In the epoxy resin composition of the embodiments of the present invention, the content of the curing agent can vary depending on the presence of reactive functional groups, optional co-reactants, etc. Typically, the amount of curing agent will fall in the range of about 1 to 20 weight percent of the total epoxy resin composition, particularly in the range of 3 to 10 weight percent.

[0030] The epoxy resin composition of the composite material described herein also contains a catalyst. The catalyst in the resin composition is preferably, but not limited to, a curing accelerator.

[0031] Examples of catalysts used include, but are not particularly limited to: substituted urea compounds, imidazole compounds; organometallic salts, such as zinc naphthenate, cobalt naphthenate, tin octoate, cobalt octoate, bis(acetylacetone)cobalt(II) and tri(acetylacetone)cobalt(III); tertiary amines, such as triethylamine, tributylamine and diazabicyclo[2,2,2]octane; phenolic compounds, such as phenol, bisphenol A and nonylphenol; organic acids, such as acetic acid, benzoic acid, salicylic acid and p-toluenesulfonic acid; and mixtures thereof. These compounds, including their derivatives, can be used alone or in combination of two or more as curing accelerators.

[0032] In the resin composition of the embodiments of the present invention, the content of the catalyst can be 1 to 50 weight percent of the total resin composition, particularly 1 to 10 weight percent. When the epoxy resin content is within the above range, the catalyst can increase the speed of the curing process and reduce the processing time in the composite material manufacturing process.

[0033] The epoxy resin composition of the composite material described herein also contains one or more flame retardant additives. The flame retardant additives in the compositions described herein are halogen-free additives. In some instances, the flame retardant additives are phosphorus-based additives, as phosphorus-based additives typically provide flame retardant properties to the resulting composite material.

[0034] Examples of nonhalogenated flame retardant additives include phosphorus compounds, including inorganic phosphorus compounds such as red phosphorus, ammonium phosphate and metal salts of hypophosphite, semi-organic phosphorus compounds such as amine salts and melamine salts of phosphate, metal salts and phosphonium salts of organic hypophosphite, and phosphate esters and phosphonates; mineral filler flame retardants, such as aluminum(III) hydroxide and magnesium hydroxide, zinc borate, zinc stannate, zinc hydroxystannate, molybdate; nitrogen-based flame retardants, such as ammonium salts, melamine salts, melamine cyanurate, melamine phosphate, phosphazenes, phosphamidons and phosphorus oxynitrides; cyanuric acid-based compounds; silicone-based flame retardants; and boron-based flame retardants.

[0035] In the epoxy resin compositions described herein, the content of flame retardant additives may be in the range of about 1 to 50 weight percent of the total epoxy resin composition, particularly in the range of 10 to 40 weight percent.

[0036] The epoxy resin compositions described herein may also contain rheology modifiers. Examples of rheology modifiers include common additives and auxiliaries, such as, but not limited to, fumed silica.

[0037] The epoxy resin compositions described herein may also contain solvents to provide dissolution of one or more components in the resin composition. Examples of such solvents include acetone, methyl ethyl ketone (MEK), tetrahydrofuran (THF), dimethylformamide (DMF), methanol, ethanol, and glycol ethers.

[0038] refer to Figure 1 The illustration shows a method 100 for preparing an epoxy composition according to one embodiment. Method 100 provides an epoxy composition for producing molded parts of composite materials that can be used in various structural applications. For example, some structural applications may include aircraft structural panels or amusement materials.

[0039] In one embodiment of method 100, in step 102, the epoxy resin (as described above) may be dissolved in a solvent (also as described above). It should be noted that step 102 is an optional step, as the resin can also be formulated without a solvent (e.g., as a solvent-free hot-melt epoxy system).

[0040] In step 104, other components are added to the epoxy resin to form an epoxy composition. These other components may include, but are not limited to, one or more curing agents; catalysts; flame retardant additives, toughening agents, rheology modifiers, or other non-reactive compounds.

[0041] In step 106, the composition is mixed at a temperature and time sufficient to distribute the components within the epoxy composition.

[0042] In an alternative embodiment, the epoxy resin may be part of a solvent-free "hot melt" system. In this embodiment, the epoxy resin can be melted by applying heat to it, and other components (e.g., but not limited to) can then be added to the melted epoxy resin, and the resulting composition can be mixed to form a substantially homogeneous epoxy composition.

[0043] Composite materials refer to Figure 2 The illustration shows a method 200 for preparing a composite material according to one embodiment. Method 200 manufactures molded parts of the composite material that can be used in various structural applications. For example, some structural applications may include aircraft structural panels or amusement materials.

[0044] At 202, long-fiber thermosetting reinforced composites are selected, cut, and stacked (at 204) into one or more layers. The fibers are long because they are typically continuous along the length and / or width of the layer, or at least along most of its length and / or width. Long fibers are not chopped fibers or SMC. Short-fiber composites or SMC have a higher resin content, making it easier for internal release agents to migrate.

[0045] In some instances, long-fiber thermosetting reinforced composites may include an intermediate material called a prepreg. The prepreg comprises high-performance fibers pre-impregnated with a bulk resin. The bulk resin may be an uncured thermosetting resin, such as epoxy resin. The prepreg may contain fibers in a linear (unidirectional) or braided form. The fibers may be, for example, carbon fiber, glass fiber, Kevlar fiber, or any other high-performance fiber with the properties required for the application.

[0046] In some embodiments, the fiber may be a high-performance fiber, such as aramid fiber, long-chain polyethylene fiber and / or poly(p-phenylene-2,6-benzobisoxazole) (PBO) fiber. Other exemplary fibers may include aramid and copolyaramid fibers, such as fibers commercially produced by DuPont (Kevlar®), Teijin (Twaron®), Kolon (Heracron®), and Hyosung Aramid; modified para-aramid fibers (e.g., Rusar®, Autex®); ultra-high molecular weight polyethylene (UHMWPE) commercially produced by Honeywell, DSM, and Mitsui under the trade names Spectra®, Dyneema®, and Tekmilon® (and Pegasus® yarn), respectively; poly(p-phenylene-2,6-benzobisoxazole) (PBO) (produced by Toyobo under the trade name Zylon®); and / or polyester-polyaryl yarns (e.g., liquid crystal polymers produced by Kuraray under the trade name Vectran®).

[0047] The amount of strength provided by the fibers will depend on the amount and specific type of reinforcing fibers used, as well as the orientation of the fibers relative to the stresses the composite will withstand. Based on the total weight of the reinforcing fiber and epoxy resin composition, reinforcing fibers can be used in amounts from about 20% to about 80% by weight. When weight is a primary consideration, the amount of reinforcing fibers used will preferably be close to the lower limit of the disclosed range. When strength, rather than weight, is a primary consideration, the amount of reinforcing fibers used will generally be close to the upper limit of the disclosed range.

[0048] At 206, the stacked prepreg is placed into a mold to prepare a molded part. Heat and / or pressure are applied to the mold for an appropriate period of time to cure the resin in the composite material. The resin can be cured using processes such as autoclaves, compression molding, vacuum bags, and ovens. Typically, the surface film is compatible with the bulk resin of the composite material and can be cured in the same or similar manner. At 208, the cured composite molded part is removed from the mold.

[0049] FST properties of composite materials Several properties can be used to measure the FST (Flame-Standing Test) performance of composite materials. These properties include vertical burning, heat release, smoke density, and smoke toxicity. In particular, heat release performance is a difficult metric to meet. Composite materials used in aerospace interior applications typically have their heat release performance measured using equipment developed by Ohio State University (OSU). This test is commonly referred to as the OSU heat release test. Typical flame-retardant epoxy prepreg specifications are set at a maximum of 65 kW / m². 2 Peak value and 65 KW·min / m2 Total heat release, while the specifications for flame-retardant phenolic prepreg are set at a maximum of 30-45 KW / m. 2 Peak value and 30-45 KW·min / m 2 Total heat release.

[0050] The composite material formed using the epoxy resin composition and reinforcing fibers described herein meets the Ohio State University (OSU) heat release value: 40 KW / m². 2 The peak value is or lower, and 40 KW·min / m 2 The total heat release is lower, while keeping the proportion of non-reactive additives below 40%.

[0051] Example A prepreg was formed by impregnating it with an epoxy resin composition comprising a naphthalene-type epoxy resin, a curing agent, a catalyst, and a phosphorus-based additive. Test samples were manufactured by bonding a 3 pcf phenolic resin-coated aramid honeycomb core to prepreg sheets on both sides and curing in a press. The substrate reinforcement fabric used was a 7781 type glass fiber fabric with a resin content of 40%.

[0052] The formulations of the components of the resin composition are provided in Table 1.

[0053] Table 1: Exemplary epoxy resin compositions.

[0054]

[0055] These composite materials are prepared by sandwiching a honeycomb core material between one or more layers of prepreg on each side. The composite material is then molded in a press.

[0056] The resin composition was cured into a composite material at 130°C and 90 psi for 40 minutes. The FST properties of the composite materials cured according to the formulation in Table 1 are provided in Table 2 below.

[0057] The Ohio State University-developed thermal testing method (called the OSU flammability test) is used to determine whether the polymer composition meets U.S. government airworthiness standards. The OSU test measures the total heat release (“2-minute THR”) and peak heat release rate (“maximum HRR”) over the first five minutes of flammability testing under OSU conditions, expressed in kilowatt-minutes per square meter of surface area (kW-min / m²). 2 ) and kilowatts per square meter of surface area (kW / m 2(This is indicated by the symbol ). More precisely, the heat release properties of the polymer composition were evaluated according to Part IV of Annex F, FAR 25-83, Amendment 25-83. The sample was mounted vertically in a closed chamber and exposed to a flame via multiple igniters mounted at the top and bottom of the sample holder. The sample was simultaneously exposed to 3.5 W / cm². 2 Radiative heat flux and 85 ft 3 The airflow rate is 1 / min. The heat released during combustion is determined by measuring the temperature difference between the exhaust air and the intake air.

[0058] Table 2: FST properties of composite materials prepared using the epoxy resin compositions in Table 1.

[0059]

[0060] Data shows that, compared with industry standards, composite materials formed from the epoxy resin compositions in Table 1 exhibit lower levels of heat release rate and total heat release.

[0061] While the foregoing description provides examples of one or more devices, methods, or systems, it should be understood that other devices, methods, or systems may also fall within the scope of the appended claims, as will be understood by those skilled in the art.

Claims

1. A halogen-free, antimony-free, and phenol-free thermosetting epoxy resin composition, comprising: a) Epoxy resin; b) Curing agent; c) Catalysts; and d) Flame retardant additives; e) wherein, when the epoxy resin composition is impregnated into a fabric such as a glass fiber fabric and molded into a sheet, the sheet has a strength of less than 40 kW-min / m 2 The total heat release of the OSU in two minutes is less than 40 kW / m². 2 The peak heat release rate of the OSU.

2. The epoxy resin composition according to claim 1, wherein the epoxy resin is a biphenyl-type epoxy resin.

3. The epoxy resin composition according to claim 2, wherein the epoxy resin is a naphthalene-type epoxy resin.

4. The epoxy resin composition according to claim 1, wherein the epoxy resin is an aralkyl type epoxy resin.

5. The epoxy resin composition according to claim 1, wherein the amount of the epoxy resin is 30 to 70% by weight of the total weight of the epoxy resin composition.

6. The epoxy resin composition according to claim 1, wherein the amount of the curing agent is from 3% to 10% by weight of the total weight of the epoxy resin composition.

7. The epoxy resin composition according to claim 1, wherein the amount of the catalyst is from 1% to 10% by weight of the total weight of the epoxy resin composition.

8. The epoxy resin composition according to claim 1, wherein the amount of the flame retardant additive is less than 40% by weight of the total weight of the epoxy resin composition.

9. The epoxy resin composition according to claim 1, further comprising a toughening agent.

10. The epoxy resin composition according to claim 1, further comprising a non-reactive additive.

11. The epoxy resin composition according to claim 9, wherein the amount of the non-reactive additive and the flame retardant additive is less than 40% by weight of the total weight of the epoxy resin composition.

12. The epoxy resin composition according to claim 1, wherein the sheet has a strength of less than 35 kW-min / m 2 The total heat release of the OSU in two minutes is less than 30 kW / m². 2 The peak heat release rate of the OSU.

13. A prepreg comprising a fabric, such as a fiberglass fabric, impregnated with a halogen-free, antimony-free, phenol-free thermosetting epoxy resin composition, said epoxy resin composition comprising: a) Epoxy resin; b) Curing agent; c) Catalysts; and d) Flame retardant additives; e) Wherein, When the prepreg is molded into a sheet, the sheet has a strength of less than 40 kW-min / m. 2 The total heat release of the OSU in two minutes is less than 40 kW / m². 2 The peak heat release rate of the OSU.

14. The prepreg of claim 13, wherein the sheet has a strength of less than 35 kW-min / m 2 The total heat release of the OSU in two minutes is less than 30 kW / m². 2 The peak heat release rate of the OSU.

15. A composite material comprising a prepreg in contact with at least one honeycomb structure, the prepreg comprising a fabric, such as a fiberglass fabric, impregnated with a halogen-free, antimony-free, phenol-free thermosetting epoxy resin composition, the epoxy resin composition comprising: a) Epoxy resin; b) Curing agent; c) Catalysts; and d) Flame retardant additives; e) Wherein, When the composite material is molded into a sheet, the sheet has a strength of less than 40 kW-min / m. 2 The total heat release of the OSU in two minutes is less than 40 kW / m². 2 The peak heat release rate of the OSU.

16. The composite material according to claim 15, wherein the sheet has a strength of less than 35 kW-min / m 2 The total heat release of the OSU in two minutes is less than 30 kW / m². 2 The peak heat release rate of the OSU.

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