Antioxidant blends for emulsion polymerized rubbers

Abstract

The present invention relates to a stabilizing composition, in particular a stabilizing composition useful for stabilizing elastomeric materials such as rubber and / or butadiene-based elastomers. The stabilizing composition comprises: a first stabilizing component comprising at least one phosphite antioxidant; a second stabilizing component comprising at least one amine antioxidant; and a third stabilizing component comprising at least one phenolic antioxidant. Also disclosed herein are uses of the stabilizing composition for stabilizing an elastomeric material, stabilized compositions comprising an elastomeric material and the above stabilizing composition, and useful articles comprising the stabilizing composition.

Description

[0001] This application is a divisional application of the invention patent application entitled “Antioxidant Blend for Emulsion Polymerized Rubber” filed on May 22, 2020 and application number 202080038313.X.

[0002] This application claims priority to UK patent application No. GB1907363.4 filed on May 24, 2019, which is incorporated herein by reference in its entirety.

[0003] The present invention relates to stabilizing compositions. More particularly, but not exclusively, the present invention relates to stabilizing compositions for stabilizing polymers, especially stabilizing elastomers such as rubber and / or butadiene based elastomers.

[0004] Polymers are used in many applications. Elastomers are a class of polymers with a variety of structures, properties, and applications. They all exhibit a certain degree of viscoelasticity and can be made from natural or synthetic polymers. Elastomers are used in many applications such as tires, pipes, gaskets, and seals because of their unique properties such as high elasticity, durability, and high strength.

[0005] Elastomers are susceptible to physical and visual degradation over time, which results in poor performance and reduced service life. Factors such as exposure to heat, oxygen, ozone, and radiation (e.g., light) can cause elastomers to degrade and result in significant changes in their mechanical properties; for example, due to softening or hardening of the elastomer. Thus, the viscosity of the rubber can change significantly with degradation. Most commonly, the elastomeric structure degrades through chain scission and / or crosslinking. Undesirable odors, discoloration, and fading of elastomers due to degradation may also be observed.

[0006] Polybutadiene and its copolymers, which contain fewer reactive double bonds, are more susceptible to degradation due to chain crosslinking. Elastomers with larger groups or electron-donating groups, such as natural rubber, polyisoprene, and isobutylene isoprene rubber, are more susceptible to degradation via chain scission.

[0007] The Mooney viscosity value is widely used to evaluate the ability of an elastomer to flow and retain its shape. It is important to ensure that the Mooney viscosity value does not drift and fluctuate over a long period of time to ensure that the elastomer properties are maintained.

[0008] Therefore, it is important to maintain the Mooney viscosity of the elastomeric material to minimize the degradation effects of chain scission and / or cross-linking. Discoloration of the elastomer due to degradation can also be observed; therefore, minimizing color change is also important.

[0009] For many elastomeric applications, it is desirable for the elastomer to maintain certain properties during storage, handling, and subsequent applications. More specifically, it is desirable for the elastomer to maintain its melt flow properties, Mooney viscosity, and have good color stability during storage, even during prolonged or repeated exposure to temperature fluctuations during storage.

[0010] To help maintain elastomeric properties such as Mooney viscosity (M at 100°C) L (1+4)) and color stability (according to the yellowness index), it is known to add different types of additives to elastomers, in particular, it is known to add antioxidants.

[0011] US9309379 describes a composition comprising a degradable latex crude rubber, synthetic latex or natural rubber latex and a stabilizer comprising a mixture selected from a specific group of alkylthiomethylphenol compounds and styrenated diphenylamine.

[0012] US4489099 describes a chewing gum rubber composition (gum base) using a combination of dilauryl thiodipropionate and at least one ingredient selected from tert-butylhydroquinone (TBHQ) and vitamin E as an antioxidant stabilizer system.

[0013] EP2980146 describes an elastomeric composite material comprising a diene-based elastomer containing an antioxidant. The antioxidant comprises a combination of tris(nonylphenyl)phosphite (TNPP) and tetramethylethylenediamine (TMEDA), and the weight ratio of TNPP to TMEDA ranges from 4 / 1 to 50 / 1. In addition, a rubber composition comprising such an elastomeric composite material, an article such as a tire comprising such an elastomeric composite material or a rubber composition, and a method for manufacturing the same are disclosed.

[0014] EP2159264 describes an acrylic rubber composition and a vulcanized rubber, which ensure the heat resistance of the vulcanized rubber, especially the elongation at break (EB) and hardness of the vulcanized rubber under heating conditions. An acrylic rubber composition, which comprises a carboxyl group-containing acrylic rubber and 10 to 100 parts by mass of carbon black per 100 parts by mass of the carboxyl group-containing acrylic rubber, 0.1 to 15 parts by mass of at least one primary antioxidant selected from amine antioxidants and phenolic antioxidants, and 0.1 to 15 parts by mass of at least one auxiliary antioxidant selected from phosphorus antioxidants and sulfur antioxidants.

[0015] WO2015114131 discusses a composition for stabilizing an organic polymer, especially a natural rubber or a synthetic rubber, against oxidative degradation and damage, comprising a) poly(dicyclopentadiene-co-p-cresol) (Formula I); b) a sterically hindered phenol of Formula II; and c) an alkylthiophenol of Formula III.

[0016]

[0017] WO2018041649 describes a liquid antioxidant composition for raw rubber, comprising: a) 5 wt % to 30 wt % of at least one aromatic amine-based antioxidant; b) 20 wt % to 70 wt % of at least one hindered phenol-based antioxidant; c) 0 wt % to 40 wt % of at least one phosphite-based antioxidant; and d) 20 wt % to 40 wt % of at least one solvent having a boiling point above 185° C. and a freezing point below −10° C. at 101.325 kPa, the weight percentages of components a), b), c) or d) being based on the total weight of the antioxidant composition, wherein a mixture of components a), b) and c) is liquid at 25° C. at 101.325 kPa.

[0018] WO2007050991 describes a composition comprising: an antioxidant; and at least one additive selected from the group consisting of: a phosphorus stabilizer, an acid stabilizer, and a co-stabilizer.

[0019] GB2322374 describes a composition comprising: an organic material which is subject to oxidative, thermal or light-induced degradation; at least one compound of the benzofuran-2-one type; at least one compound selected from organic phosphites or phosphonites; at least one compound selected from phenolic antioxidants; and at least one compound selected from sterically hindered amines.

[0020] JP2018070747 describes a polyolefin resin material stabilized with a phenolic antioxidant, a phosphorus-based antioxidant and a hindered amine light stabilizer.

[0021] JP2003012900 describes a composition comprising an antioxidant based on an aromatic amine, a hindered phenolic antioxidant, a sulfur-based antioxidant and a phosphorus-based antioxidant.

[0022] US20070254990 describes a pipe coating resin composition having an oxidative induction time of more than five minutes, wherein the composition comprises: a thermoplastic ethylene-alpha olefin copolymer composition having a melt index of 1 to 10 g / 10 min and a molecular weight distribution of 2.0 to 3.0 as determined by ASTM D1238; and an antioxidant system comprising 250 to 2500 ppm of a hindered phenol, a secondary antioxidant which is a phosphorus (III) compound, and a hindered amine light stabilizer.

[0023] There is a continuing need in the industry for an improved stable composition that does not suffer from discoloration, Mooney viscosity changes, and undesirable odors, particularly when exposed to temperature fluctuations during storage for prolonged or repeated periods of time.

[0024] According to a first aspect of the present invention, there is provided a stabilizing composition for an elastomer, comprising:

[0025] a. a first stabilizing component comprising at least one phosphite antioxidant;

[0026] b. a second stabilizing component comprising at least one aminic antioxidant; and

[0027] c. A third stabilizing component comprising at least one phenolic antioxidant.

[0028] The inventors of the present invention surprisingly found that the stabilizing composition according to the present invention results in superior property retention compared to compositions conventionally used in the art and is very effective in stabilizing articles made with elastomers, in particular butadiene based elastomers.

[0029] The elastomer may be butadiene-based. In this article, "butadiene-based" means that the elastomer contains butadiene or butadiene derivatives such as chloroprene as monomer base units. For example, the elastomer may contain polybutadiene (BR), nitrile rubber (NBR), styrene-butadiene (SBR), polychloroprene (CR) and / or compatible mixtures of two or more thereof.

[0030] It has been unexpectedly discovered that elastomeric materials incorporating the stabilizing composition of the present invention outperform the industry benchmark, 4,6-bis(octylthiomethyl)-o-cresol (LOWINOX TM 520-CAS110553-27-0) stabilizes the properties of the same elastomeric material and has a lower overall odor. Therefore, the stabilizing composition of the present invention can be used to replace conventional additives.

[0031] Without wishing to be bound by theory, it is believed that the antioxidants of the present invention exhibit a synergistic effect on the stabilized composition or article, such as elastomeric materials and articles made therefrom. This synergistic blend is important in significantly improving Mooney viscosity retention and color retention during heat aging and providing lower initial color.

[0032] The stabilizing composition of the present invention, when added to an elastomer, may cause the Mooney viscosity of the elastomer (measured according to ASTM D1646) to fluctuate less during six days of heat aging at 100°C than the Mooney viscosity of the same elastomer to which an equivalent weight / weight amount of the same stabilizing composition in the absence of any amine component has been added.

[0033] This accelerated heat aging test uses high temperature (100°C) to simulate several months under different storage and transportation conditions. It is a widely accepted standard quality control test for elastomers. This accelerated heat aging test is used to predict the long-term thermal and storage stability of elastomers.

[0034] The maximum percent fluctuation (measured as the percentage difference between the starting Mooney viscosity and the highest and / or lowest Mooney viscosity measured) may result in the viscosity of the elastomer (measured according to ASTM D1646) fluctuating by less than 30%, less than 25%, less than 20%, less than 16%, or less than 10% over a six day period.

[0035] The stabilizing composition of the present invention, when added to an elastomer, can provide the elastomer with an initial Yellowness Index value (Day 0) (measured according to ASTM E313) of less than about 15, less than about 10, less than about 8.

[0036] The stabilizing composition of the present invention, when added to an elastomer, can provide the elastomer with a Yellowness Index value (measured according to ASTM E313) of less than 45, less than 40, less than 37, less than 35, less than 30 after a period of four days.

[0037] In the following paragraphs, the product name AMINOX TM ANOX TM 、BLE TM 、DURAZO NE TM 、FLEXZONE TM LOWINOX TM 、NAUGALUBE TM NAUGARD TM NAUGAWHITE TM 、NOVAZONE TM 、OCTAMINE TM 、WESTON TM The indicated compounds are available from USAA, LLC, 4 Mountainview Terrace, Suite 200, Danbury, CT 06810.

[0038] The phosphite antioxidant may be a liquid at ambient conditions. The amine antioxidant may be a liquid at ambient conditions. Preferably, both the phosphite antioxidant and the amine antioxidant are liquid at ambient conditions. However, in some cases, it is possible to produce a stable composition according to the present invention that is liquid at ambient conditions by blending a liquid phosphite antioxidant with a solid amine antioxidant.

[0039] It is also possible to produce a stable composition according to the invention that is liquid under ambient conditions by blending a solid phosphite antioxidant with a liquid amine antioxidant.

[0040] "Ambient conditions" refers to preferably a temperature of 50°C or less, more preferably a temperature of 30°C or less, most preferably a temperature of 25°C or less, and atmospheric pressure, i.e., 101.325 kPa. For example, "ambient conditions" may refer to a temperature of 25°C and atmospheric pressure.

[0041] Preferably, the stabilizing composition is liquid at ambient conditions.

[0042] As described above, the phosphite antioxidant provided in the stabilizing composition of the present invention is selected so that the stabilizing composition is liquid at ambient conditions. Often this will be achieved by selecting a single phosphite antioxidant component that is itself liquid at ambient conditions.

[0043] The phosphite antioxidant may include an organic phosphite antioxidant.

[0044] The phosphite antioxidant may include triaryl phosphites, trialkyl phosphites, and / or alkylaryl phosphites.

[0045] The phosphite antioxidant may include a triaryl phosphite, optionally triphenyl phosphite.

[0046] The phosphite antioxidant may include one or more triaryl phosphites of Formula I:

[0047]

[0048] wherein R1, R2 and R3 are independently selected alkylated aryl groups of formula II:

[0049]

[0050] wherein R4, R5 and R6 are independently selected from hydrogen and C1 to C 20 Alkyl, provided that at least one of R4, R5 and R6 is not hydrogen.

[0051] R4, R5 and R6 can be independently selected from hydrogen and C1 to C 10 Alkyl, provided that at least one of R4, R5 and R6 is not hydrogen.

[0052] R4, R5 and R6 may be independently selected from hydrogen and C1 to C6 alkyl, provided that at least one of R4, R5 and R6 is not hydrogen.

[0053] The C1 to C6 alkyl group may be selected from methyl, ethyl, propyl, butyl, pentyl, hexyl and / or isomers thereof, such as isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, tert-pentyl and / or neopentyl.

[0054] At least one of R4, R5 and R6 may be selected from tert-butyl and / or tert-pentyl.

[0055] The one or more triaryl phosphites may have the structure of formula (III):

[0056]

[0057] wherein R7, R8 and R9 are independently selected from methyl and ethyl groups, and wherein n is 0, 1, 2 or 3.

[0058] The one or more triaryl phosphites may be independently selected from tris(4-tert-butylphenyl) phosphite; tris(2,4-di-tert-butylphenyl) phosphite; bis(4-tert-butylphenyl)-2,4-di-tert-butylphenyl phosphite; bis(2,4-di-tert-butylphenyl)-4-tert-butylphenyl phosphite; tris(4-tert-amylphenyl) phosphite; tris(2,4-di-tert-amylphenyl) phosphite; bis(4-tert-amylphenyl)-2,4-di-tert-amylphenyl phosphite; bis(2,4-di-tert-amylphenyl)-4-tert-amylphenyl phosphite; and / or blends thereof.

[0059] The one or more triaryl phosphites may be independently selected from tris(4-tert-pentylphenyl) phosphite; tris(2,4-di-tert-pentylphenyl) phosphite; bis(4-tert-pentylphenyl)-2,4-di-tert-pentylphenyl phosphite; bis(2,4-di-tert-pentylphenyl)-4-tert-pentylphenyl phosphite; and / or blends thereof.

[0060] The phosphite antioxidant may comprise a blend of triaryl phosphites as previously described. Preferably, the phosphite antioxidant comprises a blend of at least two different triaryl phosphites, at least three different triaryl phosphites, or at least four different triaryl phosphites.

[0061] Particularly preferred phosphite antioxidants according to the present invention comprise a mixture of 2,4-bis(1,1-dimethylpropyl)phenyl phosphite and 4-(1,1-dimethylpropyl)phenyl phosphite (WEST TM 705-CAS 939402-02-5).

[0062] The inventors of the present invention have found that when the phosphite antioxidant includes one or more triaryl phosphites, certain advantages are achieved. Specifically, it has been found that, compared with other known phosphite antioxidants, particularly alkyl aryl phosphites such as tetra-C12-15-alkyl (propane-2,2-diylbis (4,1-phenylene)) bis (phosphites) (CAS 96152-48-6), when combined with elastomers and under elastomer processing conditions, triaryl phosphites are much more stable and less prone to hydrolysis. In WO2018041649, the key component of the antioxidant composition is a solvent, which is used to ensure that the antioxidant, especially the phosphite antioxidant, is not hydrolyzed during the preparation of raw rubber. On the contrary, the stabilized composition of the present invention is stable under elastomer processing conditions, and can therefore be formulated in the absence of any solvent.

[0063] The phosphite antioxidant may be an antioxidant that does not contain a nonylphenyl group.

[0064] Phosphite antioxidants may include trialkyl phosphites, such as DOVERPHOS TM LGP-11 (available, for example, from Dover Chemicals).

[0065] The phosphite antioxidant may include an alkyl aryl phosphite, such as tri(tridecyl) phosphite (WESTON TM TTDP-CAS25488-25-3).

[0066] As a specific and non-limiting example, the phosphite antioxidant may, for example, include one or more of the following: a mixed 2,4-bis(1,1-dimethylpropyl)phenyl phosphite and 4-(1,1-dimethylpropyl)phenyl phosphite (WESTON TM 705 (CAS 939402-02-5); tris(nonylphenyl) phosphite (WESTON TM TNPP-CAS26523-78-4); tridecyl phosphite (WESTON TM TTDP-CAS25488-25-3); Trilauryl phosphite (WESTON TM TLP-CAS 3076-63-9); triisodecyl phosphite (WESTON TM TDP-CAS25448-25-3; Phenyl diisodecyl phosphite (WESTON TM PDDP-CAS 25550-98-5); diphenyl isodecyl phosphite (WESTON TMDPDP-CAS26544-23-0); tri-isooctyl phosphite (TOP-CAS25103-12-52); tri(2-ethylhexyl) phosphite (CAS78-42-2); mixed 2-ethylhexylphenyl phosphite (WESTON TM EHDP-CAS 15647-8-2); tri(dipropylene glycol) phosphite (WESTON TM 430-CAS 36788-39-3); Poly 4,4'-isopropylidene diphenol C12-15 alcohol phosphite (WESTON TM 439-CAS 96152-48-6); polymeric liquid phosphites (DOVERPHOS TM LGP-11, available, for example, from Dover Chemicals); 4,4'-butylene-bis(3-methyl-6-tert-butylphenyl)alkyl(C13) phosphite; and / or compatible mixtures of two or more thereof.

[0067] The phosphite antioxidant may comprise a mixture of 2,4-bis(1,1-dimethylpropyl)phenyl phosphite and 4-(1,1-dimethylpropyl)phenyl phosphite (WESTON TM 705-CAS 939402-02-5) and / or tri(tridecyl) phosphite (WESTON TM TTDP-CAS 25488-25-3).

[0068] The phosphite antioxidant may comprise a mixture of 2,4-bis(1,1-dimethylpropyl)phenyl phosphite and 4-(1,1-dimethylpropyl)phenyl phosphite (WESTON TM 705-CAS 939402-02-5).

[0069] The phosphite antioxidant can be present in an amount of about 20 wt % to about 95 wt % of the stabilizing composition, about 25 wt % to about 90 wt % of the stabilizing composition, about 30 wt % to about 85 wt % of the stabilizing composition, about 35 wt % to about 70 wt % of the stabilizing composition, or about 50 wt % to about 65 wt % of the stabilizing composition.

[0070] Preferably, the phosphite antioxidant is present in an amount greater than about 40% by weight of the stabilized composition. For example, the phosphite antioxidant may be present in an amount greater than about 40% by weight up to about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90% or about 95% by weight of the stabilized composition.

[0071] Phosphite antioxidant can be present in an amount of about 41 % by weight, about 42 % by weight, about 45 % by weight or about 50 % by weight to about 60 % by weight, about 65 % by weight, about 70 % by weight, about 75 % by weight, about 80 % by weight, about 85 % by weight, about 90 % by weight or about 95 % by weight of the stabilizing composition. For example, phosphite can be present in an amount of about 42 % by weight to about 75 % by weight of the stabilizing composition, about 45 % by weight to about 70 % by weight of the stabilizing composition or about 50 % by weight to about 65 % by weight of the stabilizing composition.

[0072] The phosphite antioxidant may be liquid at a temperature of 50°C or less, optionally 30°C or less, optionally 25°C or less, and at atmospheric pressure, i.e., 101.325 kPa. The phosphite antioxidant may be liquid at a temperature of 25°C and atmospheric pressure, i.e., 101.325 kPa.

[0073] The stabilizing component (b) comprises one or more aminic antioxidants.

[0074] As a specific and non-limiting example, the amine antioxidant may include, for example, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (NAUGARD TM 445-CAS10081-67-1); mixed butylated diphenylamine, octylated diphenylamine (NAUGARD TM PS30-CAS 68411-46-1); Octylated diphenylamine (OCTAMINE TM -CAS101-67-7; Nonylated diphenylamine (NAUGALUBE TM 438L-CAS122-39-4); polymerized 1,2-dihydro-2,2,4-trimethylquinoline (NAUGARD TM Q-CAS 26780-96-1); N,N-bis-(1,4-dimethylpentyl)-p-phenylenediamine (FLEXZONE TM 4L-CAS 3081-14-9); Acetone diphenylamine (AMINOX TM -CAS 68412-48-6); reaction products of diphenylamine and acetone (BLE TM -CAS 112-39-4); 1,4-phenylenediamine, N,N'-mixed phenyl and tolyl derivatives (NOVAZONE TM AS-CAS 68953-84-4); N-phenylaniline, reaction products with 2,4,4-trimethylpentene (IRGANOX TM 5057-CAS 68411-46-1 (available, for example, from BASF); N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (SANTOFLEXTM 6PPD-CAS 793-24-8 (e.g. available from Eastman); N,N'-diphenyl-p-phenylenediamine (DPPD-CAS 74-31-7); N-isopropyl-N'-phenyl-1,4-phenylenediamine (IPPD-CAS 101-72-4); 2,4,6-tris-(N-1,4-dimethylpentyl-p-phenylenediamine)-1,3,5-triazine (DURAZONE TM 37-CAS121246-28-4); N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (SANTOFLEX TM 77PD-CAS 3081-14-9 (available, for example, from Eastman); and / or compatible mixtures of two or more thereof.

[0075] Amine antioxidants may include 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (NAUGARD TM 445-CAS10081-67-1) and / or mixed butylated diphenylamine, octylated diphenylamine (NAUGARD TM PS30-CAS 68411-46-1).

[0076] Amine antioxidants may include mixed butylated diphenylamine, octylated diphenylamine (NAUGARD TM PS30-CAS68411-46-1).

[0077] Mixed butylated diphenylamine, octylated diphenylamine (NAUGARD TM PS30 - CAS 68411-46-1) is a liquid amine antioxidant which is particularly useful in producing liquid blends according to the present invention.

[0078] The amine antioxidant can be present in an amount of about 1 wt % to about 40 wt % of the stabilizing composition, about 1 wt % to about 30 wt % of the stabilizing composition, about 5 wt % to about 25 wt % of the stabilizing composition, or about 7 wt % to about 20 wt % of the stabilizing composition.

[0079] The amine antioxidant may be a secondary amine.

[0080] The amine antioxidant may be an aromatic amine.

[0081] Amine antioxidants may have the general formula -R-NH-R', optionally wherein the R and / or R' groups are aromatic. R and R' may be the same or different.

[0082] Amine antioxidants may have the general formula R-NH-R'-NH-R, optionally wherein R' is aromatic and / or the R groups are aromatic and / or alkyl. R and R' may be the same or different.

[0083] The amine antioxidant may contain at least one aromatic group, or at least two aromatic groups.

[0084] The aminic antioxidant may comprise a single compound or a blend of two or more compounds.

[0085] The aminic antioxidant may have a total nitrogen content of at least 3.5% or at least 4% weight / weight.

[0086] The stabilizing component (c) comprises one or more phenolic antioxidants.

[0087] The phenolic antioxidant may comprise a single compound or a blend of two or more compounds.

[0088] The phenolic antioxidants may optionally be substituted.

[0089] The phenolic antioxidants may include semi-hindered and / or hindered phenolic antioxidants.

[0090] The phenolic antioxidant may include a hindered phenolic antioxidant.

[0091] In this specification, "hindered" preferably means that the phenolic antioxidant comprises substituted hydrocarbyl groups in both positions ortho to the phenolic -OH group, each of those substituted groups being branched at the C1 and / or C2 position relative to the aromatic ring, preferably at the C1 position.

[0092] In the present specification, "semi-hindered" preferably means that the phenolic antioxidant comprises at least one substituted hydrocarbyl group adjacent to the phenolic -OH group, only one or each of the substituted groups being branched at the C1 and / or C2 position relative to the aromatic ring, preferably at the C1 position.

[0093] The phenolic antioxidant may comprise a phenol group which is substituted, preferably twice, preferably in that case in an ortho position to the -OH group in the phenol.

[0094] The or each substituent on the phenolic group may comprise an alkyl group, optionally a branched alkyl group, optionally a tert-butyl group.

[0095] Phenolic antioxidants can be further substituted at the meta and para positions of the -OH group in the phenol.

[0096] Phenolic antioxidants may contain multiple phenolic groups.

[0097] As specific and non-limiting examples, phenolic antioxidants may include: C13-C15 linear and branched alkyl esters of 3-(3',5'-di-tert-butyl-4-hydroxyphenyl) propionate (ANOX TM 1315-CAS 171090-93-0); 3-(3',5'-di-tert-butyl-4-hydroxyphenyl) propionate (ANOX TM PP18-CAS2082-79-3); 3-(3',5'-di-tert-butyl-4-hydroxyphenyl) propionate (NAUGARD TM PS48-CAS125643-61-0); 3-(3',5'-di-tert-butyl-4-hydroxyphenyl) propionate (CAS 6386-38-5); pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (ANOX TM 20-CAS 6683-19-8); Butylated hydroxytoluene (BHT-CAS 128-37-0); Butylated hydroxyethylbenzene (BHEB-CAS4130-42-1); Butylated octylated phenol (ANOX TM T-CAS12674-05-4; Styrenated phenol (NAUGARD TM SP-CAS 61788-44-1); Styrenated p-cresol (NAUGARD TM 431-CAS1817-68-1); 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxyphenylpropionic acid C7-C9 branched alkyl ester (IRGANOX TM 1135-CAS125643-61-0 (e.g. available from BASF)); 2,2-methylenebis(6-nonyl-p-cresol) (NAUGAWHITE TM -CAS 7786-17-6); 4-sec-butyl-2,6-di-tert-butylphenol (CAS 17540-75-9); 2-tert-butyl-4,6-dimethylphenol (LOWINOX TM 624-CAS 1879-09-0); Mixed tert-butylphenol (ISONOX TM133-CAS 60083-44-5 (e.g. available from SI Group, Inc., 2750 Balltown Road, Schenectady, NY 12301, US); 4,4'-methylenebis(2,6-di-tert-butylphenol) (CAS 118-82-1); methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (PP-CAS 6386-38-5); 2,4-dimethyl-6-(1-methylpentadecyl)-phenol (CAS 134701-20-5); and / or compatible mixtures of two or more thereof.

[0098] Phenolic antioxidants may include C13-C15 linear and branched alkyl esters of 3-(3',5'-di-tert-butyl-4-hydroxyphenyl) propionate (ANOX TM 1315-CAS171090-93-0) and / or 3-(3',5'-di-tert-butyl-4-hydroxyphenyl) propionate (NAUGARD TM PS48-CAS125643-61-0).

[0099] The phenolic antioxidant can be present in an amount from about 5 wt % to about 70 wt % of the stabilizing composition, from about 10 wt % to about 60 wt % of the stabilizing composition, from about 15 wt % to about 55 wt % of the stabilizing composition, from about 20 wt % to about 50 wt % of the stabilizing composition, or from about 20 wt % to about 40 wt % of the stabilizing composition.

[0100] The phenolic antioxidant may be selected to be liquid at 50°C or less, optionally 30°C or less, optionally 25°C or less, at atmospheric pressure, i.e. 101.325 kPa. The phenolic antioxidant may be liquid at 25°C at atmospheric pressure, i.e. 101.325 kPa.

[0101] The ratio of phosphite antioxidant to amine antioxidant to phenolic antioxidant in the stabilizing composition can be: (about 35 to about 70): (about 1 to about 30): (about 15 to about 35); (about 45 to about 65): (about 5 to about 25): (about 15 to about 30); or (about 50 to about 65): (about 7 to about 20): (about 20 to about 30).

[0102] Additional antioxidants, such as hydroxylamine or its precursors, lactone radical scavengers, acrylate radical scavengers, UV absorbers and / or chelating agents, may be included in the stabilizing composition.

[0103] The stabilizing composition according to the invention is particularly effective in stabilizing elastomeric materials.Elastomeric materials may be stabilized against, for example, oxidation, heat and / or radiation (eg light) induced degradation.

[0104] The stabilizing composition according to the invention may additionally comprise a fourth stabilizing component comprising at least one sulfur-containing antioxidant.

[0105] For example, a stabilizing composition may comprise:

[0106] a. a first stabilizing component comprising at least one phosphite antioxidant;

[0107] b. a second stabilizing component comprising at least one aminic antioxidant; and

[0108] c. a third stabilizing component comprising at least one phenolic antioxidant; optionally,

[0109] d. A fourth stabilizing component comprising at least one sulfur-containing antioxidant.

[0110] The sulfur-containing antioxidant may contain one or more thioether groups.

[0111] The sulfur-containing antioxidant may contain one or more thioester groups.

[0112] The sulfur-containing antioxidant may include a sulfur-containing phenolic antioxidant.

[0113] Sulfur-containing antioxidants may be liquids at ambient conditions.

[0114] As a specific and non-limiting example, the sulfur-containing antioxidant may include: 4,6-bis(octylthiomethyl)-o-cresol (LOWINOX TM 520-CAS110553-27-0); 2,2'-thiodiethylenebis[3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate](ANOX TM 70-CAS 41484-35-9); Dilauryl thiodipropionate (NAUGARD TM DLTDP-CAS123-28-4; Distearyl thiodipropionate (NAUGARD TM DSTSP-CAS 693-36-7); di(tridecyl)thiodipropionate (NAUGARD TM DTDTDP-CAS10595-72-9); Pentaerythritol tetra(β-laurylthiopropionate) (NAUGARD TM 412S-CAS29598-76-3); 2,4-bis(dodecylthiomethyl)-6-methylphenol (IRGANOX TM 1726-CAS110675-26-8 (available, for example, from BASF)); and / or compatible mixtures of two or more thereof.

[0115] The sulfur-containing antioxidant may include 4,6-bis(octylthiomethyl)-o-cresol (LOWINOX TM 520-CAS110553-27-0) and / or di(tridecaproyl)thiodipropionate (NAUGARD TM DTDTD P-CAS10595-72-9).

[0116] The sulfur-containing antioxidant can be present in an amount of about 0 wt % to about 50 wt % of the stabilizing composition, about 1 wt % to about 40 wt % of the stabilizing composition, about 2 wt % to about 30 wt % of the stabilizing composition, about 2 wt % to about 20 wt % of the stabilizing composition, or about 2 wt % to about 10 wt % of the stabilizing composition.

[0117] The ratio of phosphite antioxidant to amine antioxidant to phenolic antioxidant to sulfur-containing antioxidant in the stabilizing composition may be:

[0118] (about 35 to about 70):(about 1 to about 30):(about 15 to about 35):(about 0 to about 20);

[0119] (about 45 to about 65):(about 5 to about 25):(about 15 to about 30):(about 1 to about 15); or

[0120] (about 50 to about 65):(about 7 to about 20):(about 20 to about 30):(about 1 to about 5).

[0121] According to a second aspect of the present invention, there is provided use of the stabilizing composition for stabilizing an elastomeric material.

[0122] Elastomers are amorphous polymers with a glass transition temperature below ambient temperature, preferably below the temperature of use. Due to their low glass transition temperature, elastomers have excellent viscoelastic properties such as high elasticity, excellent impact resistance, etc.

[0123] Elastomers may be thermoplastic or thermoset, vulcanized or unvulcanized.

[0124] Elastomeric materials may include natural rubber, synthetic rubber, and / or blends of plastics with elastomers such as high impact polystyrene (HIPS) or acrylonitrile butadiene styrene (ABS).

[0125] The elastomer may be butadiene-based. As mentioned above, in this context, "butadiene-based" means that the elastomer contains butadiene or a butadiene derivative such as chloroprene as a monomer base unit. For example, the elastomer may contain polybutadiene (BR), nitrile rubber (NBR), styrene-butadiene (SBR), polychloroprene (CR) and / or a compatible mixture of two or more thereof.

[0126] According to a third aspect of the present invention, there is provided a stabilized elastomer composition comprising:

[0127] a. Elastomer materials

[0128] b. Stable compositions according to the invention.

[0129] The stabilized elastomeric composition may be suitable for stabilizing elastomeric materials such as rubber.

[0130] The rubber may include natural rubber, synthetic rubber, and / or combinations thereof.

[0131] The elastomeric material may be the product of emulsion polymerization or solution polymerization.

[0132] After incorporation of the above-mentioned stabilizers in the end use, the elastomeric material may or may not be cross-linked.

[0133] The stabilized elastomeric composition may further comprise any material suitable for combination with the elastomeric material and the stabilizing composition of the present invention.

[0134] As specific and non-limiting examples, the elastomer may include natural polyisoprene (cis-1,4-polyisoprene, natural rubber (NR)); gutta-percha (trans-1,4-polyisoprene); synthetic polyisoprene; polybutadiene (butadiene rubber (BR)); polychloroprene (CR); butyl rubber (copolymer of isobutylene and isoprene, IIR); halogenated butyl rubber; styrene-butadiene (copolymer of styrene and butadiene, SBR), nitrile rubber (Buna-N rubber (NBR)); hydrogenated nitrile rubber (HNBR) and / or compatible mixtures of two or more thereof.

[0135] The elastomer may be derived from an emulsion polymerization comprising at least one of styrene-butadiene (SBR); nitrile rubber (NBR); polybutadiene (BR); polychloroprene (CR).

[0136] The elastomer may comprise butadiene as one of the structural units. Other suitable structural unit comonomers may be styrene, acrylonitrile, ethylene or propylene.

[0137] Elastomers can use different catalyst systems, including metallocenes.

[0138] The present invention is also directed to useful articles comprising the stabilized elastomeric compositions described herein.

[0139] The stabilizing composition according to the present invention may be added to the elastomeric material in an amount of about 0.01 to about 5% w / w, about 0.05 to about 3% w / w, about 0.1 to about 2% w / w, or about 0.2 to about 1% w / w.

[0140] This percentage of the stable composition is important to provide the desired protection for the stabilized elastomeric composition during storage and transportation. A storage stable composition requires as little change in Mooney viscosity as possible during long storage periods, for example up to one year at 40°C.

[0141] The stabilizing composition can be added during or after the polymerization.

[0142] Preferably, the stabilizing composition is added after polymerization.

[0143] According to a fourth aspect of the present invention, there is provided a method for stabilising an article made using an elastomeric material, comprising incorporating or applying the stabilising composition of the present invention into or to the elastomeric material.

[0144] For the avoidance of doubt, all features relating to the stabilised composition of the present invention also relate where appropriate to the stabilised elastomeric composition, the stabilised article and the method of stabilising an article, and vice versa.

[0145] The present invention will now be described in more detail with reference to the following non-limiting examples. Example

[0146] Table 1 summarizes the details concerning the different stabilizing components used in the stabilizing compositions. In the following, the stabilizing components will be referred to simply using the names given in the "Abbreviation" column.

[0147]

[0148]

[0149] Key to Table 1:

[0150] Component A Phosphite Antioxidant

[0151] Component B Amine antioxidant

[0152] Component C Phenolic antioxidant

[0153] Component D: Sulfur-containing antioxidant

[0154] It will be apparent to the skilled person that certain materials (such as LOWINOX TM 520-CAS110553-27-0) may belong to one or more of the component categories A, B, C, and D defined as essential components of the present invention. LOWINOX TM 520 may therefore be regarded as component C and / or component D according to the present invention.

[0155] Table 2 shows the various stabilizing compositions prepared. The % amounts shown in the table are % by weight of the total stabilizing composition, and the dosage of the stabilizing composition is in parts per hundred parts of rubber (phr).

[0156]

[0157] Examples A, B, C and D are comparative examples in the absence of any amine component, with Example D representing an industry benchmark. Examples 1 to 10 are in accordance with the present invention.

[0158] Sample preparation

[0159] Various antioxidant mixtures were prepared according to the compositions outlined in Table 2. The antioxidant blends (about 60 g) for each example were melted and mixed together. The mixture was then heated to 70° C. and oleic acid was dosed and mixed together. KOH solution (13.3% w / w) (about 48 g) was then slowly dosed to the mixture and stirred at high speed to ensure homogeneous mixing and emulsion formation. The mixing speed was then reduced and approximately 152 g of hot deionized water was added. The resulting antioxidant emulsion had a solid content of about 20% w / w.

[0160] The examples show the stability that can be obtained by using various stabilizing compositions in ESBR.

[0161] The antioxidant emulsion was dosed to the ESBR latex. After stirring, the ESBR latex sample was coagulated using a standard hydrochloric acid coagulation system. More specifically, the sample was coagulated with 2% calcium chloride. The latex was then dropped into a 2% calcium chloride solution and the rubber was transferred to fresh water. The rubber was washed 3 times under squeezing. The rubber was then dried in a vacuum oven at 50°C for 16 hours. The HAAKE TM Internal mixer for 2 minutes to remove any residual water. Use a two-roll mill to make the elastomer more homogeneous.

[0162] The elastomers were oven aged at 100°C and measurements were recorded every 24 hours for a duration of 4 days (yellowness index) and 6 days (Mooney viscosity).

[0163] Test conditions

[0164] Color stability

[0165] First, the sample is placed in a compression mold at 100 ° C for 5 minutes, and the resulting ESBR sheet is 1 mm thick. Use a colorimeter to measure the discoloration with a yellowness index (YI). Each YI measurement takes about 4 grams of elastomer. Take the YI value at 0 hour and every 24 hours thereafter, and measure as defined in ASTM E313. Take the average value of 5 measurements. The lower the YI value, the less discoloration of the composition. The results are shown in Table 3.

[0166] Table 3

[0167]

[0168] Stabilized compositions A and B represent comparative examples without the use of an amine antioxidant. Example D represents an industry benchmark, including L520.

[0169] From the results it can be seen that the ESBR samples stabilized with the stabilizing composition according to the present invention (Examples 1-6) showed less discoloration than the industry standard.

[0170] The ESBR samples stabilized with the stabilizing composition according to the present invention showed a lower initial yellowness index at day 0 and a lower yellowness index value at day 4.

[0171] Thus, the ESBR samples using the stabilizing composition according to the present invention provided better color retention, allowing for longer storage without color change.

[0172] Mooney viscosity

[0173] For each of the examples described, approximately 20 g of sample was taken for Mooney viscosity testing. Mooney viscosity was measured using standard method ASTM D1646 (1+4) T 100° C. Mooney viscosity values ​​were taken at 0 hours and every 24 hours thereafter.

[0174]

[0175] *The day ESBR started crosslinking. When degradation via crosslinking dominates over chain scission, an overall increase in Mooney viscosity is expected. Degradation of ESBR is primarily dominated by crosslinking.

[0176] Elastomer structures degrade primarily through two different degradation mechanisms: chain scission and crosslinking. Chain scission behavior generally occurs earlier in the degradation process and may result in a decrease in Mooney viscosity. Crosslinking generally occurs later in the process and results in an increase in Mooney viscosity. In theory, Example 8 exhibits higher initial chain scission than the other examples compared to the comparative examples, but then exhibits relatively low Mooney viscosity fluctuations, as witnessed from day 2 to day 6.

[0177] Small fluctuations in Mooney viscosity values ​​over time indicate the structural integrity of the elastomer and show minimal degradation.

[0178] Examples according to the invention exhibited better Mooney viscosities than the comparative examples at equivalent loadings, and were equivalent to or better than the comparative examples at lower loading levels.

[0179] Therefore, the examples comprising the stable compositions according to the present invention clearly show superior Mooney viscosity retention and outperform Comparative Examples A to D. These stable compositions will have better storage stability and better physical property retention.

[0180] The examples according to the present invention showed a lower degree of Mooney viscosity fluctuation from day 0 to day 6. From the results, it can be seen that the maximum fluctuation percentage of the examples according to the present invention is significantly lower than that of the comparative examples.

[0181] Thus, the Examples comprising the stable compositions according to the present invention clearly show greater Mooney viscosity retention and less Mooney viscosity drift, and outperform Comparative Examples A-D.

[0182] Mooney viscosity testing was performed on the samples of Examples 9 and 10. Mooney viscosity values ​​were measured using standard method ASTM D1646 (1+4) T 100° C. Mooney viscosity values ​​were taken at 0 hours and thereafter at 12, 24, 36 and 72 hours.

[0183]

[0184] Examples 9 and 10 both comprise stable compositions according to the invention. Example 10 shows a considerably lower degree of Mooney viscosity fluctuation from 0 to 72 hours.

[0185] As can be seen from the results, adding component D to the stable composition significantly improves stability and reduces Mooney viscosity fluctuations. Therefore, the example (Example 10) containing a four-component stable composition according to the present invention clearly shows greater Mooney viscosity retention and less Mooney viscosity drift. The stable composition will have better storage stability and better physical property retention.

[0186] Elastomer converters typically standardize processing conditions for elastomers for large-scale production, so a drift in Mooney viscosity will result in fluctuations in the properties of the final article and lead to inconsistent quality. This is undesirable.

[0187] Accelerated heat aging testing simulates the change in Mooney viscosity under various storage and shipping conditions. This gives elastomer manufacturers an indication of how stable their elastomers will be.

[0188] Thus, the increased stability and reduced Mooney viscosity fluctuations when using the stabilizing compositions according to the present invention are beneficial to the customer and result in greater consistency in product quality.

Claims

1. A stabilizing composition for an elastomer, comprising: a. a first stabilizing component comprising at least two different triaryl phosphites, each of the at least two different triaryl phosphites having a structure of formula (III), wherein R7, R8 and R9 are independently selected from methyl and ethyl groups, and n is 0, 1, 2 or 3; b. a second stabilizing component comprising at least one aminic antioxidant, wherein the aminic antioxidant comprises at least one aromatic group; and c. A third stabilizing component comprising at least one phenolic antioxidant.

2. The stabilized composition of claim 1, wherein the phosphite antioxidant comprises at least three different triaryl phosphites.

3. The stabilized composition of claim 1, wherein the phosphite antioxidant comprises at least four different triaryl phosphites.

4. The stabilized composition of claim 1, wherein the phosphite antioxidant is a nonylphenyl-free antioxidant.

5. The stabilizing composition of claim 1, wherein the at least two different triaryl phosphites are tris(4-tert-amylphenyl) phosphite; tris(2,4-di-tert-amylphenyl) phosphite; bis(4-tert-amylphenyl)-2,4-di-tert-amylphenyl phosphite; bis(2,4-di-tert-amylphenyl)-4-tert-amylphenyl phosphite; or mixtures thereof.

6. The stabilizing composition of claim 1, which, when added to an elastomer, causes the Mooney viscosity of the elastomer, as measured in accordance with ASTM D1646, to fluctuate less during six days of heat aging at 100°C than the Mooney viscosity of the same elastomer to which an equivalent weight / weight amount of the same stabilizing composition in the absence of any amine component has been added.

7. The stabilized composition of claim 1 further comprising a fourth stabilizing component comprising at least one sulfur-containing antioxidant.

8. The stable composition of claim 7, wherein the sulfur-containing antioxidant comprises one or more sulfur-containing phenolic antioxidants.

9. The stabilizing composition according to claim 8, wherein the sulfur-containing phenol antioxidant is 4,6-bis(octylthiomethyl)-o-cresol; 2,2'-thiodiethylenebis[3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; 2,4-bis(dodecylthiomethyl)-6-methylphenol; or a mixture thereof.

10. The stable composition of claim 1, wherein the stable composition is formulated in the absence of any solvent.

11. The stable composition of claim 1, wherein the phenolic antioxidant comprises a hindered phenolic antioxidant.

12. The stable composition of claim 1, wherein the phenolic antioxidant is present in the stable composition in an amount of 5% to 70% by weight of the stable composition.

13. The stable composition of claim 1, wherein the aminic antioxidant is a secondary amine.

14. The stabilizing composition of claim 1, wherein the aminic antioxidant comprises 4,4'-bis(α,α-dimethylbenzyl)diphenylamine) and / or a mixed butylated diphenylamine, octylated diphenylamine.

15. The stabilized composition of claim 1, wherein the aminic antioxidant is present in the stabilized composition in an amount of 1 wt% to 40 wt% of the stabilized composition.

16. The stabilized composition of claim 1, wherein the ratio of phosphite antioxidant to amine antioxidant to phenolic antioxidant is: (35 to 70):(1 to 30):(15 to 35).

17. The stabilizing composition according to claim 16, wherein the ratio of the phosphite antioxidant to the amine antioxidant to the phenolic antioxidant to the sulfur-containing antioxidant in the stabilizing composition is: (35 to 70):(1 to 30):(15 to 35):(0 to 20).

18. The stabilizing composition of claim 1, which, when added to an elastomer, causes the Mooney viscosity of the elastomer measured according to ASTM D1646 to have a maximum percent fluctuation over a six day period of less than 30%.

19. The stabilizing composition of claim 1, which, when added to an elastomer, causes the elastomer to have a Yellowness Index value of less than 45 as measured according to ASTM E313 after a period of four days.

20. Use of the stabilizing composition according to any one of claims 1 to 19 for stabilizing elastomeric materials.

21. A stabilized elastomeric composition comprising: a. Elastomeric materials; and b. A stable composition according to any one of claims 1 to 19.

22. The stabilized elastomeric composition according to claim 21, wherein the elastomeric material comprises natural rubber and / or synthetic rubber; and / or wherein the elastomeric material is the product of emulsion polymerization.

23. The stabilized elastomeric composition of claim 21, wherein the elastomeric material comprises a butadiene-based elastomer.

24. The stabilized elastomeric composition of claim 23, wherein the butadiene-based elastomer comprises at least one of styrene-butadiene, polybutadiene, nitrile rubber, or polychloroprene.

25. The stabilized elastomeric composition of claim 21, wherein the stabilizing composition is added to the elastomeric material in an amount of 0.01 to 5% weight / weight.

26. A useful article comprising the stabilized elastomeric composition of any one of claims 21 to 25.

27. A method for stabilizing an article made using an elastomeric material, comprising incorporating or applying the stabilizing composition of any one of claims 1 to 19 to the elastomeric material.

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