Latent amine compositions for flame resistant epoxy systems

Abstract

The present disclosure provides latent amine compositions for use as curing agents for flame-resistant epoxy systems, amine-epoxy resin compositions, and cured products from the amine-epoxy compositions.

Description

[Technical field]

[0001] The present invention relates to a latent amine composition used as a hardener for flame-resistant epoxy systems, an amine-epoxy resin composition, and a cured product from the amine-epoxy composition. One-part epoxy systems are preferred over traditional two-part epoxy systems because they are free of misformulation and can be used continuously. One-part epoxy systems require a latent curing agent that does not react with the epoxy compound at room temperature but reacts with the epoxy upon heating to bring about curing.

[0002] Background technology Fiber-reinforced composite materials are used in a wide variety of applications due to their low density and high strength. One such application is in the automotive industry, where there is a desire to save fuel by reducing vehicle weight. Fiber-reinforced composite materials offer a material with lower density while retaining mechanical performance comparable to steel and aluminum.

[0003] The demands of the automotive industry require that the preparation of molded parts be completed with the speed and automation typically found in automotive sites. As a result, epoxy formulations for use in preparing molded parts must have relatively fast cure rates and be capable of being processed in automated systems.

[0004] Fiber reinforced composites include a resin matrix reinforced with fibers, which is typically an epoxy resin. Fiber reinforced composites are prepared in a process where chopped fibers are impregnated in resin to form a so-called sheet molding compound (SMC). SMC is generally described as a reinforced composite that includes chopped fibers impregnated in resin in an uncured or partially cured state. The SMC can then be molded into a final or semi-final molded part by subjecting it to conditions that will cure the resin. Heat is used to cure the SMC in the mold, at a temperature sufficient to cure the resin, and for a time sufficient to cure the resin.

[0005] Examples of articles being evaluated for production from epoxy resin systems include sheet molding compound (SMC) composites. There are many requirements for effective production, especially when complex manufacturing processes are used. These processes include composite applications such as SMC, prepreg, high pressure resin transfer molding, and filament winding.

[0006] US Pat. No. 9,862,798 discloses an epoxy liquid hardener composition comprising dicyandiamide and at least one polyamine.

[0007] CN112063118 discloses a low-density flame-retardant epoxy resin composition with no VOC emission for preparing sheet molding compounds.

[0008] There is a need in the art for epoxy systems with good flame retardancy and high curing efficiency. Epoxy systems used in composites in the transportation and automotive industries must achieve flame retardancy requirements. In such industries, flame retardants such as ammonium polyphosphate are used to meet the fire resistance requirements due to their high flame retardancy and cost-effectiveness.

[0009] Another need in the art is fast curing of epoxy systems at high temperatures. According to the processing characteristics of SMC composites, the epoxy system should gel in 100 seconds and cure in 10 minutes at 150-160°C. Fast curing of epoxy systems is highly desirable as it reduces the production cycle of composite parts and allows for improved production efficiency. Flame retardants such as ammonium polyphosphate will reduce the reactivity of amine-based epoxy systems, especially dicyandiamide cured systems. Therefore, a higher ratio of accelerators is used to meet the fast curing speed requirement. A higher ratio of accelerators will also reduce the Tg and latency of the composites.

[0010] Another need in the art is good latency of epoxy systems at ambient temperature. Epoxy systems used in SMC composites should have a shelf life of more than 30 days at ambient temperature. According to the processing characteristics of SMC, the material should reach B-stage after the maturation process and keep relatively stable properties such as Tg and gel time for 30 days to meet production requirements.

[0011] Therefore, there is a need in the art for improved curing agents to produce epoxy resin systems with good flame resistance, fast cure at high temperatures, and good latency at ambient temperatures, while maintaining desirable mechanical properties and good processing properties. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] U.S. Pat. No. 9,862,798 [Patent Document 2] China Patent Application Publication No. 112063118 Summary of the Invention

[0013] The present disclosure includes a hardener composition comprising dicyandiamide, at least one cycloaliphatic amine, at least one additive, at least one urea accelerator, and at least one inorganic alkali used as a reaction accelerator. There are several advantages associated with the hardener composition of the present invention. These advantages include (i) being able to be formulated with liquid bisphenol A diglycidyl ether (DGBPA) epoxy resin and flame retardant, (ii) fast curing at high temperature, (iii) having stable latency at room temperature, (iv) having good mechanical performance and heat resistance, and (v) having excellent flame resistance performance and good processing properties. Another advantage includes that the latent epoxy system can be used for fiber reinforcement of composite materials.

[0014] Another embodiment of the present disclosure includes an epoxy system prepared from at least one epoxy resin and a hardener composition including dicyandiamide, at least one cycloaliphatic amine, at least one additive, at least one urea accelerator, and at least one inorganic alkali. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention relates to a curing agent composition of the present invention, comprising dicyandiamide (A), at least one alicyclic amine (B), at least one additive (C), at least one urea accelerator (D), and at least one inorganic alkali (E) and additive (F).

[0016] The particle size of the dicyandiamide in the curing agent composition must be sufficiently small with a narrow particle size distribution. Preferred examples of particle sizes of dicyandiamide that can be used in the composition include D90<10 micrometers, 10 <D90<35マイクロメートル、35<D90<100マイクロメートル、およびD90> In a preferred embodiment, the particle size of the dicyandiamide is D90<10 micrometers.

[0017] Preferably, the at least one cycloaliphatic amine is selected from the group consisting of metaxylylenediamine (MXDA), 1,3-cyclohexanedimethylamine, N-aminoethylpiperazine (NAEP), isophoronediamine (IPD), methylcyclohexanediamine, cyclohexylpropylenediamine, bis(aminocyclohexyl)methane, 1,2-cyclohexanediamine, 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, other cycloaliphatic amines, and combinations thereof. In a preferred embodiment, the cycloaliphatic amine is isophoronediamine. In this system, polyetherdiamines, aliphatic amines, aromatic amines, and amidoamines can also be used in combination with the cycloaliphatic amines. Preferred polyetheramines include Jeffamine® D230, D400, D2000 available from Huntsman under the tradenames. Although not specifically mentioned, other polyetheramines available from Huntsman under the tradename Jeffamine® D and T series, or polyetheramines of the same grade from other manufacturers, could also be used. Preferred aliphatic amines include triethylenetetramine (TETA), diethylenetriamine (DETA), tetraethylenepentamine (TEPA), other aliphatic amines, and combinations thereof. Preferred aromatic amines include 4,4'-methylenedianiline (MDA), Preferred amidoamines include those available from Evonik under the tradename Ancamide® 502, 503, 504, 505, 506, other aromatic amines, and combinations thereof.

[0018] Preferably, the at least one additive is selected from the group consisting of mold release agents, antifoam agents, leveling agents, coupling agents, other additives, and combinations thereof.

[0019] Preferably, the at least one urea accelerator is selected from the group consisting of 1-phenyl-3,3,dimethylurea, 1,1'-(4-methyl-m-phenylene)bis(3,3-dimethylurea), 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(4-chlorophenyl)-1,1-dimethylurea, 4,4'-methylenebis(phenyldimethylurea), or urea accelerators, and combinations thereof. In a preferred embodiment, the urea accelerator is 4,4'-methylenebis(phenyldimethylurea). In this system, imidazoles and blocked amines can be preferably used in combination with the urea accelerator. Preferred imidazoles include those available from Ajinomoto under the tradenames Ajicure® PN-23, PN-40, PN-40J, other modified imidazoles, and combinations thereof. Preferred blocked amines include those available from Evonik under the tradename Ancamine® 2014FG, 2337S, 2014AS, 2441, other blocked amines, and combinations thereof.

[0020] Preferably, the at least one inorganic alkali is selected from the group consisting of calcium carbonate, calcium oxide, calcium hydroxide, magnesium hydroxide, barium hydroxide, potassium hydroxide, magnesium oxide, barium oxide, potassium oxide, sodium hydroxide, other inorganic alkalis, and combinations thereof. In a preferred embodiment, the inorganic alkali is calcium hydroxide.

[0021] In a preferred embodiment, the weight percentages in the curing agent composition of the present invention are 1-50% dicyandiamide, 1-50% alicyclic amine, 1-50% additive, 1-30% urea accelerator, and 1-30% inorganic alkali. In another preferred embodiment, the weight percentages in the curing agent composition of the present invention are 10-30% dicyandiamide, 25-40% alicyclic amine, 15-30% additive, 5-15% urea accelerator, and 5-15% inorganic alkali.

[0022] Another embodiment of the present disclosure includes an epoxy system prepared from at least one epoxy resin, at least one flame retardant, and a curing agent composition including dicyandiamide, at least one cycloaliphatic amine, at least one additive, at least one urea accelerator, and at least one inorganic alkali.

[0023] Preferably, the at least one epoxy resin is selected from the group consisting of liquid bisphenol A diglycidyl ether, liquid bisphenol F diglycidyl ether, phenol novolac epoxy resin, and multifunctional epoxy resin. In a preferred embodiment, the epoxy resin is liquid bisphenol A diglycidyl ether. Preferred multifunctional epoxy resins include trifunctional epoxy resins based on para-aminophenol, meta-aminophenol, methylene dianiline, tetrafunctional epoxy resins based on methylene dianiline, other multifunctional epoxy resins, and combinations thereof. In a preferred embodiment, multifunctional epoxy resins are used in combination with liquid bisphenol A diglycidyl ether to improve heat resistance performance.

[0024] Preferably, the at least one flame retardant is selected from the group consisting of ammonium polyphosphate, aluminum hydroxide, tributyl phosphate, tris(2-ethylhexyl) phosphate, tris(2-chloroethyl) phosphate, tricresyl phosphate, triphenyl phosphate and 2-ethylhexyldiphenyl phosphate.

[0025] In another embodiment, the epoxy system further comprises at least one epoxy reactive diluent. Preferably, the at least one epoxy reactive diluent is an alkyl (C 12 ~C 14) glycidyl ether, p-tert-butylphenol glycidyl ether, cresyl glycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexanedimethylol diglycidyl ether, resorcinol diglycidyl ether, trimethylolpropane triglycidyl ether, glycerol triglycidyl ether, and neopentyl glycol diglycidyl ether. In a preferred embodiment, the epoxy reactive diluent is 1,4-butanediol diglycidyl ether.

[0026] Preferably, the mixing ratio of the at least one epoxy resin to the at least one epoxy reactive diluent is 50-99% to 1-50% by weight. In a preferred embodiment, the mixing ratio is 75%-95% to 5-25% by weight.

[0027] Preferably, the mixing ratio of the hardener composition to the at least one epoxy resin is 1-40% to 60-95% by weight. In a preferred embodiment, the mixing ratio is 10-25% to 75-90% by weight. The ratio of the hardener composition to the at least one epoxy resin is preferably stoichiometric.

[0028] The hardener composition can be produced with other fillers and additives. The epoxy system can also be produced with other fillers and additives. The hardener composition and at least one epoxy resin are mixed for testing and composite fabrication. Additives include mold release agents, defoamers, leveling agents, coupling agents, other additives, and combinations thereof. In one embodiment, additives will be premixed into the epoxy resin or hardener or matrix to improve performance.

[0029] In another embodiment, the epoxy system further comprises reinforcing fibers. Preferred examples of reinforcing fibers that can be used in the epoxy system include, but are not limited to, glass fibers, carbon fibers, ceramic fibers, polymer fibers, polyester fibers, polyamide fibers, aramid fibers, and the like.

[0030] The fiber reinforced composite material of the present invention comprises an epoxy system reinforced with fibers. The fiber reinforced composite material is prepared in a process in which chopped fibers are impregnated into an epoxy system to form a sheet molding compound (SMC). Preferably, the reinforcing fibers are present in the SMC in an amount ranging from about 10 to 60% by weight. In one preferred embodiment, the reinforcing fibers are present in the SMC in an amount ranging from about 20 to 40%. EXAMPLES

[0031] These examples are provided to demonstrate certain aspects of the invention and are not intended to limit the scope of the appended claims.

[0032] The following epoxy systems were formed by blending the epoxy resin and hardener in a mixing device. The epoxy resin and hardener can be prepared as a one-part pack.

[0033] Various terms and nomenclature used in the examples below are explained and described in Table 1 as follows: [Table 1-1] [Table 1-2]

[0034] Definitions and Test Methods: -EEW is the epoxy equivalent weight. -AHEW is the amine hydrogen equivalent weight. -PHR is the level of hardener used per 100 parts of resin. - The stoichiometric point is the ratio of the AHEW of the hardener to the EEW of the epoxy resin. - Viscosity was measured by Brookfield viscometer according to ASTM D445-83. -Glass transition temperature (Tg) The glass transition temperature, also called Tg, is measured by differential scanning calorimetry (DSC) according to ASTM D 3418-82, with the test examples being from 0 to 250°C at a heating rate of 10°C / min. The midpoint of the steep part of the cure curve was taken as the Tg. The DSC instrument used was a TA Instruments DSC model Q2000. Tg wet was determined on the second scan curve of the wet mixture. -Gel time test A hot plate with a metal surface capable of controlling the surface temperature to within ±1°C of the set point. The hot plate was set to 150°C for 30 minutes and allowed to stabilize. 1 ml of the prepared sample was removed and placed on the plate, a timer was immediately started, and strokes were immediately initiated with a wooden spatula. Strokes were made by gently pushing the resin over an area of ​​approximately 7 cm x 7 cm. The resin gradually became more viscous. The resin eventually formed strings and then quickly turned into a rubbery gel that adhered to the spatula. At this point the timer was stopped and the gel time was recorded.

[0035] Example 1: Curing of SMC formulations with ammonium polyphosphate and accelerators Resin NPEL 127, hardeners Dicyanex 1400F and IPD, imidazole accelerator Curezol 2MZ-Azine, reaction accelerator, and ammonium polyphosphate were mixed in a high-speed mixer to obtain a homogeneous resin varnish formulation. The gel time of the SMC formulation required before aging should be less than 140 seconds, and after aging should be in the range of 60-90 seconds. At least 6% flame retardant should be used compared to liquid epoxy resin to keep good flame resistance of SMC material when used in automotive or transportation industry. The formulation is shown in Table 2 below. From Table 2, ammonium polyphosphate reduced the reactivity of epoxy SMC sample (SAH-2), and the addition of calcium hydroxide showed the best acceleration effect and good latency compared to other accelerators. [Table 2]

[0036] Example 2 In epoxy SMC formulations, diamines are used as thickeners to react with liquid epoxy resins to increase the viscosity of the matrix during the maturation process. The epoxy SMC formulations will reach a stable B-stage with a viscosity range that meets storage and transportation requirements. As Table 3A shows, Vestamin IPD showed a good balance between efficiency and latency of maturation when combined with liquid epoxy resins, DICY, Curezol 2MZ-Azine, and calcium hydroxide. As Table 3B shows, different ratios of IPD will affect the reactivity and latency of epoxy SMC formulations when stored at room temperature for 30 days. For good handling, the epoxy SMC formulation should have a flexible state. [Table 3A] [Table 3B]

[0037] Example 3 In epoxy SMC formulations, accelerators are used to lower the curing temperature and increase the curing speed of DICY-based epoxy systems. Meanwhile, it will also affect the latency and heat resistance performance. As shown in Table 4A, Amicure UR-M has the best balance of reactivity and latency during room temperature storage compared with other accelerators, and Amicure UR-M at a ratio of 2% compared with epoxy resin remains flexible after 30 days of room temperature storage. [Table 4A] [Table 4B]

[0038] Example 4 Optimization of hardener composition for requirements of fast cure, good latency, high heat resistance and mechanical properties. During SMC production, high curing efficiency is crucial, especially in the automotive industry. The gel time required during the molding process ranges from 60 to 90 seconds at 150°C, depending on the design of the production parts. Meanwhile, SMC is a two-step process for composite materials, and the SMC material should have a latency of 30 days at room temperature to meet the daily production requirements, and the gel time after 30 days should be within the range of 60 to 90 seconds. For the special requirements for the automotive and transportation industries, the glass transition temperature (Tg) should be higher than 120°C and the mixed viscosity at 30°C should be less than 2500cps for good handling. As shown in Table 5, SAH-28 exhibits good handling (mixed viscosity and Tg after curing) and meets the curing speed and latency requirements. [Table 5] [Table 6]

[0039] As shown in Table 6, in the example of the epoxy resin composition of the present invention, the release effect is improved by adding the additives. Furthermore, the heat resistance performance and mechanical performance are improved when the multifunctional epoxy resin is combined with the bisphenol A diglycidyl ether resin.

Claims

1. A curing agent composition comprising dicyandiamide, at least one cycloaliphatic amine, at least one additive, at least one urea accelerator, and at least one inorganic alkali.

2. 2. The hardener composition of claim 1, wherein the at least one alicyclic amine is selected from the group consisting of metaxylylenediamine, 1,3-cyclohexanedimethylamine, N-aminoethylpiperazine, isophoronediamine, methylcyclohexanediamine, cyclohexylpropylenediamine, bis(aminocyclohexyl)methane, 1,2-cyclohexanediamine, and 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, and combinations thereof.

3. 3. The hardener composition of claim 1 or claim 2, wherein the at least one additive is selected from the group consisting of mold release agents, antifoam agents, leveling agents, coupling agents, other additives, and combinations thereof.

4. 4. The hardener composition of any one of claims 1 to 3, wherein the at least one urea accelerator is selected from the group consisting of 1-phenyl-3,3,dimethylurea, 1,1'-(4-methyl-m-phenylene)bis(3,3-dimethylurea), 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(4-chlorophenyl)-1,1-dimethylurea, 4,4'-methylenebis(phenyldimethylurea), and combinations thereof.

5. 5. The hardener composition of any one of claims 1 to 4, wherein the at least one inorganic alkali is selected from the group consisting of calcium carbonate, calcium oxide, calcium hydroxide, magnesium hydroxide, barium hydroxide, potassium hydroxide, magnesium oxide, barium oxide, potassium oxide, sodium hydroxide, and combinations thereof.

6. An epoxy system prepared from at least one epoxy resin, at least one flame retardant, and the hardener composition of any one of claims 1 to 5.

7. 7. The epoxy system of claim 6, wherein the at least one epoxy resin is selected from the group consisting of liquid bisphenol A diglycidyl ether, liquid bisphenol F diglycidyl ether, phenol novolac epoxy resins, multifunctional epoxy resins, and combinations thereof.

8. 8. The epoxy system of claim 7, wherein the multifunctional epoxy resin is selected from the group consisting of trifunctional epoxy resins based on para-aminophenol, meta-aminophenol, or methylene dianiline, tetrafunctional epoxy resins based on methylene dianiline, and combinations thereof.

9. Epoxy system according to any one of claims 6 to 8, wherein the at least one flame retardant is selected from the group consisting of ammonium polyphosphate, aluminum hydroxide, tributyl phosphate, tris(2-ethylhexyl) phosphate, tris(2-chloroethyl) phosphate, tricresyl phosphate, triphenyl phosphate and 2-ethylhexyldiphenyl phosphate.

10. Alkyl (C １２ ~C １４ 9. The epoxy system of any one of claims 6 to 8, further comprising at least one epoxy reactive diluent selected from the group consisting of butyl ether, p-tert-butylphenol glycidyl ether, cresyl glycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexanedimethylol diglycidyl ether, resorcinol diglycidyl ether, trimethylolpropane triglycidyl ether, glycerol triglycidyl ether, and neopentyl glycol diglycidyl ether.

11. 11. The epoxy system of claim 10, wherein the mixing ratio of said at least one epoxy resin to said at least one epoxy reactive diluent is 50-99% to 1-50% by weight.

12. Epoxy system according to any one of claims 6 to 11, wherein the mixing ratio of the hardener composition to the at least one epoxy resin is 1-40% to 60-95% by weight.

13. Epoxy system according to any one of claims 6 to 12, further comprising reinforcing fibers.

14. 14. The epoxy system of claim 13, wherein the reinforcing fibers are selected from the group consisting of glass fibers, carbon fibers, ceramic fibers, polymer fibers, polyester fibers, polyamide fibers, aramid fibers, and the like.

Images