EPDM RUBBER

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Patent Application Serial No. 62/988,558, of same title, filed March 12, 2020; the entire disclosure of which is incorporated herein by reference in its entirety for all purposes.

TECHNICAL FIELD

[0002] The disclosure herein relates to ethylene propylene diene monomer (EPDM) rubber. More specifically, the present disclosure relates to fire-resistant EPDM rubber. In one embodiment, the fire-resistant EPDM rubber is used for weatherproofing buildings, in particular as a membrane for facade application.

BACKGROUND

[0003] Ethylene propylene diene monomer (EPDM) rubber has many remarkable properties such as heat resistance, chemical resistance, low electrical conductivity, stability at temperatures ranging from -50°F to 350°F, flexibility at low temperatures, and weather resistance, to name a few. EPDM is cost effective and can be fabricated in a variety of ways including custom molding and extruding. EPDM has numerous applications in the automotive industry (e.g., hoses, seals, O-rings, gaskets, accumulator bladders, wire and cable connectors and insulators, diaphragms, and weather stripping); construction (e.g., roofing and waterproofing); HVAC (e.g., compressor grommets, tubing, gaskets, and seals); and many other industries.

[0004] The main drawback to EPDM rubber is its flammability. In the construction industry, fire resistance is generally achieved through two different methods, the first is the addition of an external retardant and the second is the use of a ballasted roof system. Accordingly, there is a need for a fire-resistant EPDM rubber. SUMMARY

[0005] The disclosure herein is directed to fire-resistant EPDM rubber. In one embodiment, the EPDM includes ethylene propylene diene monomer (EPDM) polymer, aluminum hydroxide, tris(2-ethylhexyl) phosphate, expendable graphite, and a maleic anhydride adduct of polybutadiene; wherein the composition does not contain mineral oil. The foregoing composition can also include a curing agent such as sulfur or a sulfur releasing compound. The foregoing composition can also include activators and/or accelerators such as zinc oxide, steric acid, tetrabenzyl thiuram disulfide. In one embodiment, the composition is halogen free. In one embodiment, the composition is antimony trioxide free. In one embodiment, the composition is halogen free and antimony trioxide free.

[0006] A non-limiting example of a fire-resistant EPDM formulation is sulfur, tetrabenzyl thiuram disulfide, N-cyclohexyl-2-benzothiazylesulphenamide, zinc oxide, stearic acid, a maleic anhydride adduct of polybutadiene, expandable graphite, carbon black N550, tris(2- ethylhexyl) phosphate, and aluminum hydroxide. In one embodiment, the composition does not include mineral oil. In one embodiment, the composition may be halogen free. In one embodiment, the composition may be antimony trioxide free. In one embodiment, the composition may be both halogen free and antimony trioxide free.

[0007] In another aspect of the invention there is provided a method for making an EPDM roofing membrane comprising the steps of: processing a homogeneous mixture of the composition of any one of the previous embodiments using either calendaring or a roller die extruder; and heat curing the membrane with or without pressure.

DETAILED DESCRIPTION

[0008] Ethylene propylene diene monomer (EPDM) rubber is a synthetic rubber compound made from ethylene, propylene, and diene monomers that can be crosslinked via sulfur vulcanization. Because EPDM is purely a hydrocarbon, it can easily catch fire. This disclosure is directed to an EPDM rubber that is fire-resistant. In particular, this disclosure is directed to an EPDM rubber that meets the European Classification for building materials EN 13501-1 class B. Definitions

[0009] In the description that follows, a number of terms are extensively utilized. The following non-limiting definitions provide a clear and consistent understanding of the specification and claims, including the exemplary scope to be given such terms.

[0010] When the terms “one,” “a,” or “an” are used in this disclosure, they mean “at least one” or “one or more,” unless otherwise indicated.

[0011] The terms “invention” or “present invention” as used herein are intended to be non limiting and are not intended to refer to any single embodiment of the particular invention but encompasses all possible embodiments as described in the specification and the claims and their equivalents.

[0012] When proportions of constituent ingredients are expressed in percentages, they should be understood to be expressed as parts per hundred rubber (PHR).

Composition

[0013] EPDM rubber compounds generally include an EPDM polymer, (providing waterproof and elastic properties) and one or more of the following: (1) oil extenders; (2) crosslinkers/curing agents; (3) processing aids; (4) accelerators (which assist the vulcanization process); (5) antioxidants (for weather resistance); (6) antiozonants (for ozone resistance); (7) softeners and plasticizers (which improve pliability); (8) fillers, reinforcing (which increase moduli of elasticity and toughness) and/or non-reinforcing; (9) flame retardants; and (10) other agents.

[0014] Various diene monomers can be used in the formation of the EPDM polymer. Non limiting examples of suitable diene monomers include ethylidene norbomene, dicyclopentadiene, vinyl norbomene, alkyldicyclopentadiene, 1 ,4-pentadiene, 1 ,4-hexadiene, 1,5-hexadiene, 1,4-heptadiene, 2-methyl- 1,5-hexadiene, cyclooctadiene, 1,4-octadiene, 1,7- octadiene, 5-ethylidene-2-norbomene, 5-n-propylidene-2-norbomene, and 5-(2-methyl-2- butenyl)-2-norbomene, and mixtures thereof.

[0015] In certain embodiments, the oils may be halogenated.

[0016] Non-limiting examples of suitable crosslinkers/curing agents include peroxides such as alpha-cumyl hydroperoxide, methylethylketone peroxide, hydrogen peroxide, acetylacetone peroxide, t-butyl hydroperoxide, t-butyl peroxybenzoate, 2,5-bis(t- butylperoxy)-2,5-dimethylhexene, lauryl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, dibenzoyl peroxide, bis(p-monomethylene-benzoyl) peroxide, bis(p-nitrobenzoyl peroxide, phenylacetyl peroxide, p-quinone dioxime, lead peroxide, zinc peroxide, barium peroxide, copper peroxide, potassium peroxide, silver peroxide, sodium peroxide, calcium peroxide, metallic peroxyborates, peroxychromates, peroxydicarbonates, peroxydiphosphates, peroxydisulfates, peroxygermanates, peroxymolybdates, peroxynitrates, magnesium peroxide, sodium pyrophosphate peroxide, and mixtures thereof. Other non-limiting examples of crosslinkers/curing agents include sulfur with accelerators, resins, and radiation. [0017] Non-limiting examples of suitable processing aids include hydrocarbon resins, fatty acid soaps, fatty acid esters, paraffins, polyethylene waxes, EVA waxes, phenolic resins, poly(ethylene-co-acrylic acid), and mixtures thereof.

[0018] Non-limiting examples of suitable accelerators include sulfur, mercaptans, benzothiazoles, thiurams, zinc oxide, stearic acid, benzothiazolesulfenamides, dithiocarbamates, thioureas, N-cyclohexyl-2-benzothiazolesulfenamide (CBS), N-tert-butyl- 2-benzothiazolesulfenamide (TBBS), 2,2'-dithiobis(benzothiazole) (MBTS), tetramethyl thiuram disulfide (TMTD), tetramethyl thiuram monosulfide (TMTM), zinc dibutyl dithiocarbamate (ZDBC), zinc dimethyl dithiocarbamate (ZDM), tetrabenzyl thiuram disulfide (TBzTD), di-o-tolylguanidine (DOTG), diphenylguanidine (DPG), 4,4'- dithiodimorpholine (DTDM), hexamethylenetetramine (HMTA), mercaptobenzothiazole (MBT), nickel dibutyl dithiocarbamate (NDBDC), /V-(cyclohcxylthio) phthalimide (PVI), copper dialkyl dithiophosphate (CUT), dithiocaprolactam, zinc amine-dithiophosphate (ZAT), tetrabutyl thiuram disulfide (TBTS), zinc dibenzyl dithiocarbamate (ZBEC), zinc dialkyl dithiophosphate (ZDDP), zinc diethyl dithiocarbamate (ZDEC), zinc ethyl phenyl dithiocarbamate (ZEPD), dipentamethylene thiuram tetrasulfide (DPTT), 2- mercaptobenzothiazoles; 2,2’-dithiobenzothiazole, N-cycohexylbenzothiazole-2-sulfenamide, N-tert-butylbenzothiazole-2-sulfenamide, tetramethyl thiuram disulfide, tetramethyl thiuram monosulfide, tetrabutyl thiuram disulfide, tetraethyl thiuram monosulfide, dipentamethylene thiuram hexasulfide, N,N-dibutyl thiourea, N,N-diethyl thiourea, sulfur donor-type accelerators, other organic accelerators, and mixtures thereof.

[0019] Non-limiting examples of suitable softeners and plasticizers include paraffinic oils, naphthenic oil, diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), dioctyl phthalate (DOP), di-n-hexyl phthalate, isodecyl diphenyl phosphate (e.g., Santicizer® 148), tris(2- ethylhexyl) phosphate (TEHP), and mixtures thereof.

[0020] Non-limiting examples of suitable fillers include carbon black, clay, talc, ground coal, silicas, mica, calcium carbonate, other organic materials, and mixtures thereof.

[0021] Non-limiting examples of suitable flame retardants include aluminum hydroxide (also referred to as aluminum trihydroxide), magnesium hydroxide, expandable graphite, zinc borate, ammonium polyphosphate, melamine polyphosphate, antimony oxide, and mixtures thereof.

[0022] Non-limiting examples of other suitable agents include a maleic anhydride adduct of polybutadiene, anti-degradants (e.g., waxes and paraffinic products), poly(l,2-dihydro-2,2,4- trimethylquinoline (TMQ), methyl-2-mercaptobenzimidazole (MMBI), N-isopropyl-N'- phenyl- 1 ,4-phenylenediamine (IPPD), N-(l,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), butylated hydroxytoluene (BHT)), and mixtures thereof

[0023] In certain embodiments, the EPDM rubber compound includes a flame retardant. In such embodiments, the amount of flame retardant can be from about 2% to about 90%. In certain embodiments, the flame retardant is aluminum hydroxide, expandable graphite, or both. In such embodiments, the amount of aluminum hydroxide can be from about 10% to about 90%, and the amount of expandable graphite can be from about 2% to about 25%. [0024] In certain embodiments, the EPDM rubber compound includes a crosslinker. In such embodiments, the amount of cross linker can be from about 1% to about 10%. In certain embodiments, the crosslinker can be a maleic anhydride adduct of polybutadiene. In such embodiments, the amount of maleic anhydride adduct of polybutadiene can be from about 1 % to about 10%.

[0025] In certain embodiments, the EPDM rubber compound includes a plasticizer. In such embodiments, the amount of plasticizer can be from about 1% to about 60%. In certain embodiments, the plasticizer is not mineral oil. In certain embodiments, the plasticizer is tris(2-ethylhexyl) phosphate. In such embodiments, the amount of tris(2-ethylhexyl) phosphate can be from about 1% to 25%.

[0026] In certain embodiments, the EPDM rubber compound includes fillers. In such embodiments, the amount of fillers can be from about 1% to about 50%. In certain embodiments, the filler can be carbon black. In such embodiments, the amount of carbon black can be from about 1% to about 50%.

[0027] In certain embodiments, the EPDM rubber compound includes a curing agent. In such embodiments, the amount of curing agent can be from about 1% to about 5%. In certain embodiments, the curing agent is sulfur. In such embodiments, the amount of sulfur can be from about 1% to about 3%.

[0028] In certain embodiments, the EPDM rubber compound includes an accelerator. In such embodiments, the amount of accelerator can be from about 1% to about 10%. In certain embodiments, the accelerator is tetrabenzyl thiuram disulfide, zinc oxide, steric acid, or combinations thereof. In such embodiments, the amount of tetrabenzyl thiuram disulfide can be from about 1% to about 8%, the amount of zinc oxide can be from about 1% to about 10%, and the amount of steric acid can be from about 1% to about 5%.

[0029] In certain embodiments, the EPDM rubber compound includes EPDM, aluminum hydroxide, expendable graphite, and a maleic anhydride adduct of polybutadiene. In one embodiment, the compound does not contain mineral oil. In one embodiment, the compound is halogen free. In one embodiment, the compound is antimony trioxide free. In one embodiment, the compound is both halogen and antimony trioxide free.

[0030] In certain embodiments, the EPDM rubber compound includes EPDM, sulfur, tetrabenzyl thiuram disulfide, N-cyclohexyl-2-benzothiazylesulphenamide, zinc oxide, stearic acid, a maleic anhydride adduct of polybutadiene, Carbofoil L-120, carbon black n550, tris(2- ethylhexyl) phosphate; and aluminum hydroxide. In one embodiment, the compound does not contain mineral oil. In one embodiment, the compound is halogen free. In one embodiment, the compound is antimony trioxide free. In one embodiment, the compound is both halogen and antimony trioxide free.

Methods

[0031] Making the EPDM rubber products generally involves two steps, processing a mixture into a product, and then curing the product. To form a homogenous mixture, the ingredients may be blended together using a high-shear mixing machine such as an internal mixer. Non limiting examples of suitable mixers include Banbury mixers, which are internal mixers or mills or extruders. During the processing step, the homogenous mixture may be formed into its final shape using molding, calendaring, or extruding (e.g., a roller die). Curing may be done using various methods including heating (with or without pressure) and radiation (with or without pressure).

[0032] In one embodiment, the EPDM rubber compounds described herein may be processed into roofing material, specifically an EPDM membrane for facade application. The membranes are generally about 0.5 millimeters (mm) thick to about 3 mm thick. The membranes are generally made of one layer of EPDM rubber or two or more layers of EPDM rubber that may be calendared or laminated together. In some embodiments, the membranes can include a fabric layer in or laminated on one or both sides. In some embodiments, the membranes can include a glass scrim layer adhered to one or both sides. EXAMPLES

Example 1 - EPDM Rubber Formula

[0033] In this example, various fire-resistant EPDM rubber membranes were made using the following formulas.

* PHR = Parts per Hundred Rubber

[0034] The materials in the amounts listed above were added to a Banbury mixer, and mixed for 5 minutes reaching a final temperature of 135 “C. The mixture was dropped onto a sheeting mill and formed into slabs 8 millimeters thick. The slabs were processed into sheets 1.0 and 1.2 millimeters thick. Optionally, two thinner sheets may be laminated into one membrane of the same thickness. A polyamide liner was applied, and the membranes were placed on rolls. The rolls were loaded into a hot air oven to cure under heat.

Example 2 - Open Flame Test

[0035] In this example, the EPDM membrane of Example 1 was evaluated by direct contact with a single flame. Flame from a torch was held to the membrane for 30 seconds, single frame source test EN 11925-2 class B, C, or D. The membrane glowed red where the flame touched it. However, once the flame was removed, the embers were extinguished immediately. The membrane revealed a bum spot of roughly 10 millimeters by 20 millimeters. Example 3 - Single Burning Item Test

[0036] The EPDM membrane of Example 1 was evaluated using the Single Burning Item (SBI) test (EN 13823). The SBI test measures lateral flame spread, rate of heat release, propensity for the production of flaming drips, and rate of smoke production. A sample of the EPDM membrane was mounted to a vertical surface and placed in a hood. After collecting baseline data, a 30 KW flame impinged on the membrane for 21 minutes. The performance of the membrane was evaluated over a 20 minute period on the factors listed above.

Example 4 - Additional EPDM Rubber Formulas

[0037] Additional EPDM rubber formulas are shown in the tables below. The amounts are based on parts per hundred rubber (PHR).

Example 5 - Evaluation of the Formulations

[0038] Select formulations from Example 4 were evaluated for physical properties and preliminary flame resistance testing. The results are summarized in the tables below (“MR” is the minimum requirement).

[0039] The examples set forth above are provided to give those of ordinary skill in the art a complete disclosure and description of how to make and use various embodiments of the compositions, and are not intended to limit the scope of what the inventors regard as their invention. Modifications of the above-described modes for carrying out the invention that are obvious to persons of skill in the art are intended to be within the scope of the following claims. All publications, patents and patent applications cited in this specification are incorporated herein by reference as if each such publication, patent or patent application were specifically and individually indicated to be incorporated herein by reference.