WO2020252681A1

WO2020252681A1 - Flame retardant composition

Info

Publication number: WO2020252681A1
Application number: PCT/CN2019/091841
Authority: WO
Inventors: Bin Cao; Huan CHEN; Xiaolin Huang
Original assignee: Dow Global Technologies Llc
Priority date: 2019-06-19
Filing date: 2019-06-19
Publication date: 2020-12-24

Abstract

A high pressure resin transfer molding composition and a composite is provided. The high pressure resin transfer molding composition has a viscosity <30mP·s (100℃), Tg>95℃, and 1mm UL94 V0 flame resistance.

Description

FLAME RETARDANT COMPOSITION

FIELD OF THE INVENTION

The present disclosure relates to a flame retardant composition, in particular a flame retardant composition for battery shell.

INTRODUCTION

Battery is a key part of the EV car. For safety consideration, the shell of the battery should have mechanical strength and heat/fire resistance. Typically, the shell of the battery is made by a metal such as steel or aluminum alloy, which has high weight.

There is a need to replace the metal shell with a composite. High pressure resin transfer molding (HPRTM) is a process for producing a composite by injecting a resin composition under high pressure into a mold with preformed fiber. Generally, the HPRTM composition need low viscosity such as <30mP·s (100℃) due to fluidity.

For battery-related composites, flame resistance is needed. Some composites also require 1mm UL94 V0 performance. Traditional HPRTM resin composition can’t provide flame resistance performance.

There is a need to provide a HPRTM composition with a viscosity <30mP·s (100℃) , Tg>95℃, and 1mm UL94 V0 flame resistance.

SUMMARY OF THE INVENTION

The inventor have unexpectedly found that a HPRTM composition comprising a liquid epoxy resin, a brominate epoxy resin and a flame retardant can achieve the above requirements, i.e., the HPRTM composition can have a viscosity <30mP·s (100℃) , Tg>95℃, and 1mm UL94 V0 flame resistance.

The present disclosure provides a high pressure resin transfer molding composition comprising:

(a) 40-70wt%of a liquid epoxy resin, based on the total weight of the composition;

(b) 30-50wt%of a brominated epoxy resin, based on the total weight of the composition; and

(c) 5-20 wt%of a flame retardant, based on the total weight of the composition,

wherein the weight ratio of the brominated epoxy resin and the flame retardant is 2.5: 1 or greater.

On another aspect, the present disclosure provides a composite formed from a high pressure resin transfer molding composition comprising:

(c) 5-20 wt%of a flame retardant, based on the total weight of the composition,

On another aspect, the present disclosure provides a battery comprising a shell made from a high pressure resin transfer molding composition comprising:

(c) 5-20 wt%of a flame retardant, based on the total weight of the composition,

DETAILED DESCRIPTION OF THE INVENTION

As disclosed herein, the term "composition" , "formulation" or "mixture" refers to a physical blend of different components, which is obtained by mixing simply different components by a physical means.

As disclosed herein, the term "glass transition temperature" or "Tg" is determined by differential scanning calorimetry (DSC) .

As disclosed herein, all the percentages and parts of all components of the composition refer to the weight. All the percentages of all components of the composition are calculated based on the total weight of the composition. The sum of the percentages of all the components of the composition is 100%.

On one aspect, the present disclosure provides a high pressure resin transfer molding composition comprising:

(c) 5-20 wt%of a flame retardant, based on the total weight of the composition,

The composition according to the present disclosure generally comprises 40-70wt%, typically 45-65wt%, more typically 45-55wt%, of a liquid epoxy resin, based on the total weight of the composition.

The composition according to the present disclosure comprises a liquid epoxy resin. By "liquid epoxy resin" is meant an epoxy resin that is liquid at room temperature, for example, liquid at 25℃, 15℃ or 5℃.

Typically, the liquid epoxy resin is also referred to as polyepoxide. Polyepoxides useful herein can be monomeric (for example, the diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, digylcidyl ether of tetrabromobisphenol A, novolac-based epoxy resins, and tris-epoxy resins) , higher molecular weight resins (for example, the diglycidyl ether of bisphenol A advanced with bisphenol A) or polymerized unsaturated monoepoxides (for example, glycidyl acrylates, glycidyl methacrylate, allyl glycidyl ether, etc. ) to homopolymers or copolymers. Most desirably, epoxy resins contain, on the average, at least one pendant or terminal 1, 2-epoxy group (that is, vicinal epoxy group) per molecule. For example, a preferred epoxy resin is diglycidyl ether of bisphenol A. Some preferred liquid epoxy resins include DER 330, DER 331 and DER 332, commercially available from Olin. One preferable epoxy resin has general formula:

where n is generally in the range of 0 to about 25. Some basic liquid resins, for example, D.E.R. 331, can have epoxy equivalent weights in the range of about 180 to 195 g/mol. Others, such as D.E.R. 332, can have epoxy equivalent weights in the range of about 170 to 175 g/mol. D.E.R. 330 can have epoxy equivalent weights in the range of about 176 to 185 g/mol.

In one embodiment of the present disclosure, the liquid epoxy resin may include, but not limited to, NPEL-127, NPEL-127E, NPEL-128 (commercially available from Nanya) , DER383 (commercially available from Blue Cube) , BE-188EL (commercially available from Chuangchun Group) , and TTA21 (commercially available from TetraChem) .

Typically, the liquid epoxy resin has a viscosity of from about 100mP·s to about 20,000 mP·s (100℃) , more typically from about 500 mP·s to about 15,000 mP·s (100℃) , most typically from about 500 mP·s to about 5,000 mP·s (100℃) .

Typically, the liquid epoxy resin has an epoxy equivalent weight (EEW) of <190, more typically <100.

The composition according to the present disclosure may include 30-50wt%, typically 32-48wt%, more typically 35-45wt%, of a brominated epoxy resin, based on the total weight of the composition.

The composition according to the present disclosure may include a brominated epoxy resin. The brominated epoxy resin according to the present disclosure may be any brominated epoxy resin well known in the art. Examples of the bromine containing epoxy resins include tetrabromo bisphenol A, diglycidyl ether of tetrabromo bisphenol A, and other brominated epoxies such as those commercially available from The Dow Chemical Company under the trademarks D.E.R. 560, D.E.R 542, D.E.R 592, D.E.R 593, D.E.R 530 and D.E.R 538; those commerically avaiable from Nanya under the trademarks NPEB-400, NPEB-340, BEB350, BEB400, EPON 1163, YDB-400; and mixtures thereof. A preferred epoxy resin containing bromine used in the present disclosure includes NPEB-400.

The composition according to the present disclosure may contain one or more brominated epoxy resins. Two or more different brominated epoxy resins may be blended together to make up the brominated epoxy resin component of the present disclosure. The bromine content of the brominated epoxy resin may be from about 5 wt percent (wt%) to about 50 wt%, preferably from about 10 wt%to about 25 wt %, and more preferably from about 18 wt%to about 21 wt%.

The composition according to the present disclosure may comprise 5-20 wt%, typically 8-15wt%, more typically 8-12wt%, of a flame retardant, based on the total weight of the composition.

The composition according to the present disclosure may include a flame retardant. This flame retardant may typically be a liquid flame retardant with viscosity of <50 mPa·s at 25℃ and a phosphorus content of >15wt%. Typically, the flame retardant according to the present disclosure is an organic phosphate flame retardant.

Typically, the organic phosphate flame retardant useful in the practice of this disclosure includes both aromatic and aliphatic phosphate esters and their polymers. Examples of aliphatic phosphate ester flame retardants include trimethyl phosphate, tributyl phosphate, tri (2-ethylhexyl) phosphate, triethyl phosphate, tris- (2-chloroethyl) phosphate, tris- (2-chloroisopropyl) phosphate, tributoxyethyl phosphate, monoisodecyl phosphate and 2-acryloyloxyethylacid phosphate. Examples of aromatic phosphate esters include trixylenyl phosphate, tris (phenylphenyl) phosphate, trinaphthyl phosphate, cresyldiphenyl phosphate, xylenyldiphenyl phosphate, isopropylated triphenyl phosphate and dipheny-2-methacryloyloxyethyl phosphate. Examples of aromatic bis (phosphate esters) include resorcinol bis (diphenyl phosphate) (RDP) , resorcinol bis (dixylenyl phosphate) , resorcinol bis (dicresylphosphate) , hydroquinone bis (dixylenyl phosphate) , bisphenol-A bis (diphenyl phosphate) (BPADP) and tetrakis (2, 6-dimethyl-phenyl) -1, 3-phenylene bisphosphate. These organic phosphate esters can be used alone or in combination with one another. Preferred organic phosphate flame retardants are liquid under ambient conditions (23℃ and atmospheric pressure) .

Generally, the weight ratio of the brominated epoxy resin and the flame retardant is 2.5: 1 or greater, preferably 3.0: 1 or greater, more preferably 2.5: 1 to 10: 1, even more preferably 2.5: 1 to 6: 1, most preferably 3: 1 to 5: 1.

The composition according to the present disclosure may further include a hardener. In general, the hardener may be any conventional amine curing agent known in the art. The hardener may include, for example, an aliphatic amine, a cycloaliphatic amine, an aromatic amine, a polycyclic amine, or a mixture thereof. The hardener may have a viscosity of ＜30 mPa·s (100℃) , and can be cured within 120s under 120 to 140℃.

In one embodiment, the hardener may be selected from aliphatic amines, polyether amines, aromatic amines, cycloaliphatic amines, piperazines, and mixtures thereof.

In another embodiment, the hardener can be an aliphatic polyamine including for example, an aliphatic diamine such as methylene diamine, ethylenediamine, 1, 2-diaminopropane, 1, 3-diaminopropane, 1, 4-diaminobutane, 1, 5-diamino pentane, 1, 6-diamino hexane, 1, 7-diamino heptane, 1, 8-diamino octane, 1, 9-diamino nonane, 1, 10-diamino decane, o-xylylene diamine, m-xylylene diamine, p-xylylene diamine or mixtures thereof; a tetra- (aminomethyl) methane such as diethylenetriamine, dipropylene triamine, triethylenetetramine, tripropylene tetramine, tetraethylenepentamine, tetrapropylenepentamine, penta ethylene hexamine, nonaethylene decamine; or mixtures thereof; a trimethyl hexamethylenediamine; tetrakis (2-aminoethylaminomethyl) methane; an aliphatic triamine such as 1, 3-bis (2'-amino ethyl amino) propane, triethylene-bis (trimethylene) hexamine, bis (3-amino ethyl) amine, bis-hexamethylene triamine or mixtures thereof; 1, 4-cyclohexanediamine; 4, 4'-methylene his cyclohexylamine; an alicyclic diamine such as 4, 4'-isopropylidene biscyclo hexylamine, norborna diamine, bis (aminomethyl) cyclohexane, diamino dicyclo hexylmethane, isophorone diamine, menthen diamine or mixtures thereof; bis (aminoalkyl) benzene; bis (aminoalkyl) naphthalene; bis (cyanoethyl) diethylenetriamine; phenylenediamine; naphtylene diamine; diamino diphenylmethane; diamino diethyl phenylmethane; 2, 2-bis (4-aminophenyl) propane; 4, 4'-diamino diphenylether; 4, 4'-diamino benzophenone; 4, 4'-diamino diphenylether; 4, 4'-diaminodiphenyl sulfone; a 2, 2'-dimethyl-4, 4'-diamino diphenylmethane; 2, 4'-diamino biphenyl; 2, 3'-dimethyl-4, 4'-diamino biphenyl; 3, 3'-dimethoxy-4, 4'-diamino biphenyl; an aromatic diamine such as bis (aminomethyl) naphthalene, bis (amino ethyl) naphthalene or mixtures thereof; N-methyl piperazine; morpholine; 1, 4-bis (8-aminopropyl) -piperazine; a heterocyclic diamine such as piperazine-1, 4-diaza cycloheptane, 1- (2'-amino ethyl piperazine) , 1- [2'- (2”-aminoethylamino) ethyl] piperazine, 1, 11-diazacycloeicosane, 1, 15-diazacyclo octacosane or mixtures thereof; or any combination of two or more of the above aliphatic polyamines. The hardener may be those commercially available from Dow Chemical under the trademark name VORAFORCE 5350, ARALDITE XB3458, EPIKURE 05443.

The composition according to the present disclosure may comprise 0-20 wt%, typically 1-20wt%, more typically 5 to 15 wt%, most typically 8 to 12 wt%of a hardener, based on the total weight of the composition.

The composition according to the present disclosure may also contain other optional components such as impact modifiers, internal mold release agents (IMR) , pigments, antioxidants, preservatives, reinforcing fibers short (up to about 6 inches (15.24 cm) in length, preferably up to 2 inches (5.08 cm) in length, more preferably up to about 1/2 inch (1.27 cm) in length) , non-fibrous particulate fillers including micron-and nanoparticles, wetting agents, internal mold release agents and the like. An electroconductive filler may be present in the composition.

Suitable impact modifiers include natural or synthetic polymers having a Tg of lower than -40℃. These include natural rubber, styrene-butadiene rubbers, polybutadiene rubbers, isoprene rubbers, polyethers such as poly (propylene oxide) , poly (tetrahydrofuran) and butylene oxide-ethylene oxide block copolymers, core-shell rubbers, mixtures of any two or more of the foregoing, and the like. The rubbers are preferably present in the form of small particles that become dispersed in the composition.

It is generally preferred to cure the composition in the presence of an internal mold release agent. Such an internal mold release agent may constitute up to 5%, more preferably up to about 1%of the total weight of the composition. Suitable internal mold release agents are well known and commercially available, including those marketed as Marbalease. TM. by Rexco-USA, Mold-Wiz. TM. by Axel Plastics Research Laboratories, Inc., Chemlease. TM. by Chem-Trend, PAT. TM. by Wurtz GmbH, Waterworks Aerospace Release by Zyvax and Kantstik. TM. by Specialty Products Co. In addition to (or instead of) adding the internal mold release agent during mixing, it is also possible to combine such an internal mold release agent into the epoxy component and/or the hardener component before the epoxy component and the hardener component are brought together.

Suitable particulate fillers have an aspect ratio of less than 5, preferably less than 2, and do not melt or thermally degrade under the curing conditions. Suitable fillers include, for example, glass flakes, aramid particles, carbon black, carbon nanotubes, various clays such as montmorillonite, and other mineral fillers such as wollastonite, talc, mica, titanium dioxide, barium sulfate, calcium carbonate, calcium silicate, flint powder, carborundum, molybdenum silicate, sand, and the like. Some fillers are somewhat electroconductive, and their presence in the composition can increase the electroconductivity of the composition. Conductive fillers of this type include metal particles (such as aluminum and copper) , carbon black, carbon nanotubes, graphite and the like.

The composition according to the present disclosure generally has a viscosity of less than 30mP·s (100℃) and a EEW (epoxy equivalent weight) /AHEW (Active hydrogen equivalent weight) molar ratio of from 0.5 to 1.5, preferably 0.8 to 1.0.

(c) 5-20 wt%of a flame retardant, based on the total weight of the composition,

Typically, the composite according to the present disclosure is produced by a high pressure transfer resin molding (HPTRM) process. The HPTRM process is conventional in the art, such as those as disclosed in US9,868,831B, which is incorporated herein by reference.

In one embodiment, according to the general procedure of HPTRM process, after one or more fabric layers have been inserted into the mold half, the mold is closed with an opposite half of the mold, a reduced pressure may be generated in the mold, and then the composition is introduced under pressure. If necessary, what are called flow aids (for example in the form of pressure-stable but resin-permeable mats) can be introduced between the mold halves and the fabric material, and these can be removed again after the curing.

In one embodiment, the composite according to the present disclosure comprise a fabric layer. Typically, the fabric layer is made from a synthesized fiber such as a polyester fiber, glass fiber and carbon fiber; and a natural fiber such as cotton fiber.

(c) 5-20 wt%of a flame retardant, based on the total weight of the composition,

EXAMPLES

Raw materials:

Ingredients	Suppliers
NPEL-127E	Nanya
NPEB-400	Nanya
Triethyl phosphate	Jiangsu Yarui Chemical
VORAFORCE 5350	Dow Chemical

Measure of UL 94 V0

The method of flame resistance of vertical burning test is according to UL 94 Standard for Safety-Test for Flammability of Plastic Materials for Parts in Devices and Appliances.

Measure of Tg

The glass transition temperature (Tg) was determined with a DSC (Differential Scanning Calorimetry) apparatus of TA Q2000. Samples of 5 mg to 10 mg of the cured epoxy resins were weighed and carefully placed in non-hermetic closed aluminum pan. Scaning was performed at a heating rate of 20℃/min under nitrogen. Two scanning cycles were conducted and Tg was determined by the mid-point method from the second cycle. The first cycle was used to to enable polymer chains relaxation and release any potential residual thermal stress of the curing reaction.

Measure of viscosity

Dynamic viscosity was measured by using ARES-G2 rheometer from TA. A small amount of sample (around 0.5 ml) was used. The measurement was done in the steady flow mode by using 25 mm parallel disposable aluminum plates. The measurement was done at different temperature with a shear rate of 10s ^-1.

EEW/AHEW

The EEW is tested by method according to ASTM D-1652. The hydrogen equivalent is the calculation of the molecular weight of the amine divided by the amount of the active hydrogen atom. Active hydrogen atom is the hydrogen which is connected with a nitrogen. If the amine molecular weight is W, the hydrogen atom number connected with nitrogen is N, AHEW=W/N. Usually this number is calculated by materials vender based on composition’s structure. If it’s a mixture amine, AHEW=Total weight of the amine/ (wt%of part A/AHEW of part A + wt%of part B/AHEW of part B) .

Examples

NPEL-127E, NPEB-400, Triethyl phosphate were premixed under 100℃ to form resin pre-mixture. The pre-mixture was preheated, mixed and degased in a mixing tank. VORAFORCE 5350 was preheated and degased in another mixing tank. The pre-mixture was then mixed with VORAFORCE 5350 by static mixing head to form a resin composition. The resin composition is then high pressure injected to glass fabric (Owenscorning,

SE1200 600TEX) in vacuum mold by using HPRTM machine (KraussMaffei) . The resultant composite has a thickness of 1mm, with fabric weight loading of 70wt%. The composite was fast cured in 3min and de-molded.

The components and their amounts were listed in Table 1 below. The results were also listed in Table 1 below.

The viscosity of inventive example1 was about 27 mPa·s at 100℃. The viscosity is very suitable for HPRTM injection.

Claims

A high pressure resin transfer molding composition comprising:

(a) 40-70wt%of a liquid epoxy resin, based on the total weight of the composition;

(b) 30-50wt%of a brominated epoxy resin, based on the total weight of the composition; and

(c) 5-20 wt%of a flame retardant, based on the total weight of the composition,

wherein the weight ratio of the brominated epoxy resin and the flame retardant is 2.5: 1 or greater.
The composition of claim 1, wherein the liquid epoxy resin is diglycidyl ether of bisphenol A.
The composition of claim 1, wherein the liquid epoxy resin has a viscosity of from about 100mP·sto about 20, 000 mP·s (100℃) and/or an epoxy equivalent weight (EEW) of <190.
The composition of claim 1, wherein the brominated epoxy resin includes tetrabromo bisphenol A or diglycidyl ether of tetrabromo bisphenol A.
The composition of claim 1, wherein the bromine content of the brominated epoxy resin is from about 5 wt percent (wt%) to about 50 wt%.
The composition of claim 1, wherein the flame retardant is a liquid flame retardant with viscosity of <50 mPa·sat 25℃ and a phosphorus content of >15wt%.
The composition of claim 1, wherein the flame retardant is an organic phosphate flame retardant selected from the group consisting of aromatic phosphate esters, aliphatic phosphate esters and their polymers.
The composition of claim 1, further comprising a hardener.
The composition of claim 1, wherein the compsotion has a viscosity of less than 30mP·s (100℃) and a EEW/AHEW molar ratio of from 0.5 to 1.5.
A composite formed from a high pressure resin transfer molding composition comprising:

(a) 40-70wt%of a liquid epoxy resin, based on the total weight of the composition;

(b) 30-50wt%of a brominated epoxy resin, based on the total weight of the composition; and

(c) 5-20 wt%of a flame retardant, based on the total weight of the composition,

wherein the weight ratio of the brominated epoxy resin and the flame retardant is 2.5: 1 or greater.
The composite according to claim 10, wherein the composite is produced by a high pressure transfer resin molding (HPTRM) process.
A battery comprising a shell made from a high pressure resin transfer molding composition comprising:

(a) 40-70wt%of a liquid epoxy resin, based on the total weight of the composition;

(b) 30-50wt%of a brominated epoxy resin, based on the total weight of the composition; and

(c) 5-20 wt%of a flame retardant, based on the total weight of the composition,

wherein the weight ratio of the brominated epoxy resin and the flame retardant is 2.5: 1 or greater.