WO2019083387A1

WO2019083387A1 - A composition of dynamically vulcanized thermoplastic elastomer

Info

Publication number: WO2019083387A1
Application number: PCT/RU2017/000774
Authority: WO
Inventors: Alexey Mikhailovich VOLKOV; Irina Gennadievna RYZHIKOVA; Yury Mikhailovich KAZAKOV
Original assignee: Public Joint Stock Company "Sibur Holding"
Priority date: 2017-10-23
Filing date: 2017-10-23
Publication date: 2019-05-02
Also published as: RU2759148C1; CN111315815B; CN111315815A

Abstract

The present invention relates to compositions combining properties of vulcanized elastomers at operation and thermoplasts during processing and also to a method of producing such compositions and articles based thereupon. In particular, the invention relates to a dynamically vulcanized thermoplastic elastomer composition comprising: 5 to 50 wt% polypropylene and/or copolymer of polypropylene with olefins having 2 to 6 carbon atoms, 30 to 85 wt% nitrile-containing rubber, 2 to 40 wt% polymer compatibilizers, 0 to 40 wt% polymeric elasticizing agents and 0 to 30 wt% ester plasticizers and 1 to 13 wt% vulcanizing system. The said composition comprises a vulcanizing system comprising 0.7 to 23 wt% peroxide initiator, 7.5 to 76.9% vulcanization co-agent, 0.7 to 38.5% polyatomic phenols, 0 to 23 wt% monofunctional monomers. The present subject matters also are: a method for producing a dynamically vulcanized thermoplastic elastomer composition, an industrial article made by said method or comprising a composition according to the invention. The obtainable dynamically vulcanized thermoelastoplasts are suitable for producing articles for automotive, cable, electrotechnical, footwear industry, in the production of industrial rubber articles, in household commodity industry.

Description

A COMPOSITION OF DYNAMICALLY VULCANIZED THERMOPLASTIC

ELASTOMER

Technical field

The invention relates to polymer composite materials that combine properties of vulcanized elastomers at operation and thermoplasts during processing as well as to a method for producing such compositions and articles based thereon. In particular, the invention relates to dynamically vulcanized thermoplastic elastomers based on nitrile butadiene rubber (NBR) and polypropylene (PP) and also to method for producing thereof. The obtained dynamically vulcanized thermoplastic elastomers (TPVs) can be used for producing articles in automotive, cable, electrotechnical, footwear industry, in production of industrial rubber articles, household commodity industry.

State of the art

The main problem emerging at production of TPV based on polymers of various natures is absence of their composite compatibility, which is as higher as the difference of solubility parameters of hydrocarbon solvents of polymers forming a composition is higher. For a composition comprising polymers strongly differing in polarity such as polypropylene (PP) and nitrile-containing rubber (e.g. NBR) the problem of composite incompatibility is especially important. A known approach for solving the said problem is use of vulcanizing systems in the TPV production, in particular sulfur-containing ones [CN 1252419, M. Hernandez, J. Gonzales, C.Albano, M. Ichago, D. Lovera. Thermal and mechanical characterization of PP/NBR blends.// Rev. Fac. Ing. UCV, 2006.- V.21.- n.l., 140., RU 2312872], phenol formaldehyde ones (phenolic or resin) [US4355139, CN1880366, JP4476713], peroxide systems [CN101205331, CN1128842, JP3985547].

The drawbacks of dynamically vulcanized thermoplastic elastomers (TPV) obtained using sulfur-containing vulcanizing systems is low fluidity and unpleasant acute odor manifested at melt processing, which significantly degrades technological working and sanitary-hygienic qualities of the thermoplastic elastomers and also reduces quality of articles based thereon.

Use of phenolic or so-called resinous vulcanizing systems, as a rule, comprised of resol phenol-formaldehyde resins (PFR) or resorcinol formaldehyde resins (RFR) is described, e.g. in the patent US4355139 wherein alkyl phenol formaldehyde resin (SP- 1045 trademark) is used as vulcanizing system. In order to improve the efficiency of vulcanizing system effect vulcanization accelerators are used: Friedel-Crafts catalysts, as which the tin chloride SnCb or zinc chloride ZnCl₂ is used. The TPV composition disclosed in US4355139 also comprises a polymer compatibilizing agent (compatibilizer), as which a mixture of maleinized PP and liquid nitrile-containing rubber (NBR) with grafted amino groups is used. The composition obtained according to US4355139 is characterized by breaking strength in the range of 17 to 23 MPa, tensile strain at break of 330 to 500%. The disadvantages of the obtained composition are: low fluidity (The MFIi9o°c 2. i6kg is less than 1 g/10 min), high hardness and rigidity (Shore A hardness is over 80 units, flexural modulus is over 800 MPa) and also low elasticity: the relative residual elongation (s_res.ioo%) is 30 to 50% depending on surface hardness parameter.

From CN 1880366 use of an ester plasticizer for increasing elasticity of a TPV- based composition is known. JP4476713 describes use of an oil of non-aromatic nature as a plasticizer. However, no significant improvement of physical and mechanical TPV properties is thus achieved. Thus, TPV of JP4476713 has low Shore A hardness ranges of 75 to 76 units and breaking strength of no more than 2.6 to 2.9 MPa. The TPV of CN1880366 is characterized by low elasticity- tensile strain at break is from 254 to 325%.

Use of a mixed vulcanizing system comprised of peroxide and phenol formaldehyde resin for producing TPV is also known from the art. For example, in the patent EP 1226932 a mixture of peroxide and resorcinol formaldehyde resin formed in situ by reaction of resorcinol and melamine formaldehyde oligomer is used for vulcanization of a composition comprised of ethylene and propylene copolymers and at least one triple copolymer, e.g. ethylene, propylene and diene (EPDM). Use of resorcinol instead of usual phenol in the composition of vulcanizing system allows for significantly increasing adhesion of vulcanization products to polar polyamide support due to presence of two hydroxyl groups in the resorcinol structure.

However, it should be noted that the known vulcanizing system, comprising phenol formaldehyde resin is characterized by a number of non-removable disadvantages, firstly associated with high toxicity of phenol formaldehyde resins which drastically decreases ecological and sanitary-hygienic safety of the obtained TPV. Moreover, for the phenol formaldehyde vulcanizing system a relatively low optimal temperature mode of effective operation in the presence of known vulcanization accelerators is known: from 150 to 170 °C, which hinders extrusion processing of PP with a melting point of 163 to 165 °C.

Use of peroxide vulcanizing systems allows for carrying out vulcanization at higher temperatures which are 200 °C and above, following from the decomposition temperature of organic peroxide. A disadvantage of the known peroxide vulcanizing system is an ability to accelerate radical chain processes of destruction of PP macro chains during its melt treatment, which can adversely affect the complex of properties of the obtained TPV. The said problem can be solved by combined use in the TPV production process of peroxides and vulcanization co-agents - polyfunctional vinyl monomers of various nature- facilitating crosslinking the polymer macro chains. Polar functional groups comprised in the vulcanization co-agent improve interaction of polymers with different polarity such as PP and NBR.

In the patent CN1128842 for production of TPV based on the mixture of nitrile- containing rubber (NBR) and PP a peroxide vulcanizing system is used in a combination with compatibilizer obtained by grafting acrylic acids and diamines to PP. A disadvantage of the obtained TPV composition is a low range of the Shore A hardness from 80 to 90 units and insufficiently high elasticity: tensile strain at break is not more than 480%.

JP3985547 outlines a TPV composition comprising a nitrile-containing rubber (NBR) with a special structure formed by partial hydration of double bonds of butadiene links and/or incorporation of third co-monomer links in the structure of the NBR molecule during polymerization of monomers in the reactor. As a result more flexible

NBR chains are formed having at least two glass transition points. Also, the TPV composition may comprise a low molecular weight softener, as which one can use mineral or naphthene oils and also ester plasticizers such as: phthalates, adipates, sebacates and combinations thereof. The TPV compositions obtained in a presence of peroxide vulcanizing system and vulcanization co-agent, phenylene bis-maleimide are characterized by improved softness and high fluidity. The disadvantages of the TPV composition disclosed in JP3985547 are insufficiently high strength and strength elastic characteristics: Shore A hardness is from 77 to 83 units, the breaking strength is 5.5 to 7.6 MPa and tensile strain at break is 230 to 250%. The disadvantages also are: low wear resistance of the surface of articles made out of the TPV due to insufficient compatibility (compatibilization) of PP and NBR: alteration of the sample volume in oil at 120 °C for 70 hours is from 27 to 40 units which is unacceptable for use of such a material, e.g. at manufacturing cables of oil immersion pumps.

The analogous peroxide vulcanizing system in combination with vulcanization co-agent - phenylene bis-maleimide - is used in the invention described in CN101205331. Thereby, from 5 to 15 wt% of chlorinated PP or polyethylene (PE) is used as compatibilizer. The TPV composition obtained according to the invention of CN101205331 is characterized by breaking strength of 11.5 to 12.3 MPa, Shore A surface hardness of 83 to 96 units and also low elasticity: tensile strain at break is from 160 to 410%. Moreover, the TPV composition has a high melt viscosity and limited temperature processing range, which, it their turn, limit its use.

From KR100554822 a TPV composition is known based on PP and NBR obtained in a presence of a peroxide vulcanizing system in an amount of 0.5 to 3.5 wt% and vulcanization co-agent, zinc dimethyl acrylate, in an amount of 1 to 5 wt%. Additionally the composition comprises 5 to 10 wt% chlorinated PE. The composition obtained by this method is characterized by Shore A hardness of 70 to 85 units, breaking strength of up to 6 MPa and tensile strain at break not above 250%.

According to RU2269549, in particular, ester derivatives of acrylic, methacrylic acids, vinyl butyrate are used as co-agents for peroxide vulcanization of TPV based on PP and NMR. Low viscosity high pressure polyethylene (HPPE) is introduced into the TPV composition as softeners, together with mineral oil. In order to increase abrasion resistance and decrease scratching of the articles 0.4 to 5.0 wt% mineral filers (mixture of CaC0₃ and S1O2) is introduced into the composition. Disadvantages of the obtained TPV compositions are low fluidity values (MFI₂3₀°c/2.i6kg is less than 0.9 g/10 min) and also low physical and mechanical characteristics of TPV with Shore A hardness of below 65 units: breaking strength is less than 5.2 MPa, tensile strain at break is less than 210%.

The patent US8779060 outlines a composition (A)+(B)+(C) wherein (A) is 10 to 90 wt% olefin thermoplastic polymer; (B) is 90 to 10 wt% elastomer comprising unsaturated double bonds and capable of interacting with the crosslinking or vulcanizing agent; (C) is up to 100 wt% based on (A) + (B), of a grafted copolymer comprising polyamide blocks. Ethylene, propylene, butene (co)polymers etc. are used as olefin thermoplastic polymer (A). Triple copolymers of ethylene, propylene and diene (EPDM), styrene and butadiene copolymers, butadiene and acrylonitrile copolymers are used as elastomer (B). Compounds obtained by reacting an amide- terminal polyamide with unsaturated monomer grafted to polyolefin are used as component (C). A disadvantage of the composition is absence in its contents of plasticizers and polymeric elasticizing agents which limits highly elastic properties of the obtained TPV. Use of a copolymer having polyamide blocks as compatibilizer limits resistance of such TPV composition to aggressive chemicals such as hot alkali and acids, present, e.g. in raw oil or in formation fluid.

The closest to the claimed invention in essence is the method for producing a TPV composition disclosed in the patent JP4125576 and selected as a prototype of the present invention. The main difference of the method for dynamic peroxide vulcanization in the mixture of PP and NBR outlined in JP4125576 is contents of the vulcanization co-agents. Together with the system of polar and polyfunctional vinyl monomers (triple mixture of trimethylol propane triacrylate (TMPTA), glycidyl methacrylate (GMA) and methacrylate (MA)) the TPV composition is additionally charged with a co-agent which is an oligomeric polybutadiene (PB) with hydroxyl functional groups. Is presence in contents of the vulcanization co-agents improves physical and mechanical parameters of the obtained TPV compositions: the Shore A hardness range is 66 to 84 units, the breaking strength is in the range of 3 to 9 MPa. Presence of hydroxyl groups in the structure of the oligomeric PB possibly increases chemical interaction with nitrile groups of NBR during dynamic vulcanization of this system.

Another feature of the method for dynamic vulcanization of the mixture of PP and NBR claimed in JP4125576 is a mandatory presence of a polymeric elasticizing agent, as which the copolymer of ethylene, propylene and diene (EPDM) is used. For further increase in softness of the TPV compositions low molecular weight (paraffin oils, ester plasticizers) and polymeric (styrene-ethylene-butylene-styrene rubber, SEBS) softeners are used. Moreover, the composition comprises stabilizers, antioxidants, mineral fillers and further components.

Despite all of the advantages, the composition disclosed in JP4125576 has a number of disadvantages, in particular:

1) high activity of polyfunctional monomers, co-agents of dynamic rubber vulcanization in particular TMPTA facilitates excessive crosslinking of the NBR and

EPDM unsaturated monomers used in the compositions;

2) low PP content in the TPV composition, especially, in the case of TPV with Shore A hardness of below 70 units. The PP concentration at a level of 9.2 wt% leads to unsatisfactory distribution of elastomeric phase in the PP matrix;

3) use of EPDM as a elasticizing component that is thermodynamically incompatible with PP leads to predominant localization of EPDM in the NBR matrix and/or in the interphase space;

4) use of the oligomeric hydroxylated polybutadiene as a vulcanization co-agent that has an insignificantly high chemical activity associated e.g. with its reduced mobility in the diffusion processes of oligomeric molecules in the substrate melt relatively large in volume.

The aforesaid circumstances adversely affect the physical properties of the obtained compositions, in particular the TPV compositions obtainable according to prototype are characterized by high melt viscosity (low

the ranges of 0.01 to 1.03 g/ 10 min) and low elasticity parameters (tensile strain at break of 280 to 350%); for the TPV with Shore A hardness of 66 units the tensile strain at break is 230%.

Therefore, the methods known from the art do not allow for producing TPV compositions with a required complex of technological and working characteristics. In this connection further improvement in the field of producing TPV compositions with a complex of properties allowing for significantly expanding field of the application are of the great importance and are desirable.

SUMMARY OF THE INVENTION

The aim of the present invention is to improve technological and working characteristics of dynamically vulcanized thermoplastic elastomers (TPV) by improving composition compatibility of polymer different in polarity comprised in the composition.

The technical result of the present invention consists in producing a dynamically vulcanized thermoplastic elastomers composition using a peroxide vulcanizing system having improved technological and working characteristics, in particular, high swelling resistance in oil products at elevated temperature (up to 100 °C and above) exceeding the composition obtained of JP4125576 of more than 90%.

The said technical result is achievable due to use of peroxide vulcanizing system in a combination with vulcanization co-agent which is a half-ester of polyhydric alcohol and polybasic unsaturated acid during production of a TPV peroxide composition. Use in the vulcanizing system of aromatic system of the aromatic phenol series also leads to improvement of composition compatibility. The technical result is achievable also owing to use of elasticizing polymer agent with certain microstructure of chains comprising preferably propylene links in contents of TPV compositions.

DESCRIPTION OF THE INVENTION

The present invention relates to a composition of dynamically vulcanized thermoplastic elastomers (TPVs) which comprises the following components, based on 100 wt% of the composition:

- 5 to 50 wt% polypropylene and/or copolymers of propylene with olefins comprising 2 to 6 carbon atoms;

- 30 to 85 wt% nitrile-containing rubber;

- 2 to 40 wt% polymer compatibilizer which is a maleinized product based on polypropylene, ethylene and propylene and/or butadiene-styrene comonomers;

- 0 to 40 wt% polymeric elasticizing agent;

- 0 to 30 wt% ester plasticizer;

- 1 to 13 wt% vulcanizing system. The said vulcanizing system comprises, based on 100 wt% vulcanizing system:

- 0.7 to 23 wt% peroxide initiator;

- 7.5 to 76.9 wt% vulcanization co-agent;

- 0.7 to 38.5 wt% polyatomic phenol;

- 0 to 23 wt% polyfunctional monomer.

According to the present invention the polypropylene, or copolymers of propylene with olefins comprising 2 to 6 carbon atoms is selected from propylene homopolymer or propylene and ethylene, butene-1 copolymers, in particular, from block copolymers of propylene and ethylene. Preferably, the said poly- and/or copolymer is selected from the groups comprising isotactic polypropylene (PPH), random copolymer of propylene with ethylene (PPR), block copolymer of propylene with ethylene (PPB) or mixtures thereof.

The said polypropylene or its copolymer is characterized by the value of MFI₂₃o°c/2.i6kg in the range of 0.3 to 30 g/10 min, preferably, 3 to 8 g/10 min.

The polypropylene and/or its copolymers are comprised in the TPV compositions in an amount of 2 to 50 wt%, preferably 5 to 50 wt%, more preferably 7 to 40 wt%, even more preferably 7 to 20 wt%. The said range of the polypropylene content in the composition of the present invention allows for varying the properties of the final product depending on the requirements of the articles wherein the TPV composition is used. The polypropylene contents of about 50 wt% provides for strength and gasoline- and oil stability of TPV whereas the polypropylene content close to 5 wt% leads to increase in product elasticity. The polypropylene content outside of the said range would significantly later the properties of the final thermoplastic elastomers and would lead to distortion of the hardness-elasticity complex.

The nitrile-containing rubber, as implied in the present invention, is a rubber comprising a functional nitrile group and it is, in particular, selected from a copolymer of conjugated diene and acrylonitrile, partially or fully hydrogenated copolymer of substituted diene and acrylonitrile, copolymers of conjugated diene, acrylonitrile and other monomers. In particular, the nitrile-containing rubber of the present invention is a hydrogenated butadiene-nitrile rubber, non-hydrogenated butadiene nitrile rubber, a copolymer of butadiene and acrylonitrile (NBR, perbunane, CBN, BNR, BNCS), a triple copolymer of butadiene, acrylonitrile and acrylic acid, triple copolymer of butadiene, acrylonitrile and vinylidene chloride. The most preferable is butadiene nitrile rubber. In the compositions of the present invention any commercially available nitrile- containing rubber can be used comprising both trademarks with relatively high nitrile links content and the trademarks with relatively butadiene links content such as e.g. BNR- 18 and also trademarks comprising third polar copolymer, e.g. links of (met)acrylic acid comprising carboxyl groups. Such wide selection of nitrile-containing rubber trademarks suitable for TPV production allows for making TPVs with optima properties, e.g. use of nitrile-containing rubber with increased content of butadiene links allows for further improving frost resistance of TPV. More preferably, in the composition of the present invention, the nitrile- containing rubber is a butadiene nitrile rubber (NBR) based on the copolymer of butadiene and acrylonitrile. Most preferably, NBR with acrylonitrile content of 17 to 40 w% and Mooney viscosity of ML(₁+₄)ioo°c from 40 to 120 conditional units is used as nitrile-containing rubber.

In order to improve chemical and thermal stability of the TPV compositions one can use instead of NBR, partially or completely, its carboxylated and/or hydrogenated analogues (HNBR) represented, e.g. by Lanxess production (Germany) as the Therban trademark, or Zeon Chemicals (Japan) as the Zetpol trademark.

The content of the nitrile-containing rubber in the TPV composition is from 30 to 85 wt%, preferably from 35 to 80 wt%, more preferably from 40 to 70 wt%.

The polymeric compatibilizers of polypropylene and nitrile-containing rubber comprised in the TPV compositions are maleinized products based on polypropylene, copolymer of ethylene and propylene, copolymer of butadiene and styrene. Thereby, content of chemically grafted maleic anhydride groups in said polymeric compatibilizers is from 0.1 to 5%. In particular, commercially available products Bondyram, Fusabond, Polybond can be used as compatibilizers in the compositions of the present invention. Also, use of any other compatibilizer classes based on polypropylene and/or copolymers of ethylene with propylene and/or higher a-olefin modified by grafting of the polar groups is possible. The content of compatibilizers in the TPV composition of the present invention is 2 to 40 wt%, preferably, from 5 to 30 wt%.

The polymeric elasticizing agents comprised in the claimed composition are amorphous copolymers of propylene, in particular, copolymers of propylene with ethylene with ethylene contents in the range of 8 to 16 wt% and also terpolymers of propylene with ethylene and butene-1. Preferably, copolymers of propylene with the MFl2₃₀°c/2.i6kg parameter of 3 to 18 g/10 min are used. For example, Vistamaxx propylene copolymers made by ExxonMobil Chemical can be selected as said elasticizing agents. An example of terpolymer of propylene with ethylene and butene-1 are the Vestoplast products made by Degussa. It is also possible to use of any other commercially available trademarks of propylene copolymers. The content of the elasticizing agents in the TPV composition is 0 to 40 wt%, preferably 0 to 30 wt%, and preferably 12 to 27 wt%.

The polymeric elasticizing agents based on propylene copolymers provide for the best compatibility of the polymeric components in the TPV compositions. Moreover, the elasticizing agents based on propylene compared to the elasticizing agents based on ethylene allow for controlling the macrochain destruction and crosslinking processes occurring under exposure to peroxide vulcanizing system, which in combination with the structure of vulcanization co-agent provides for a possibility of significantly improving and widely varying such technological and working qualities of the products as melt viscosity, surface hardness, tensile strain at break, surface smoothness, appearance of the obtained articles.

The present inventors have unexpectedly found that the TPV compositions comprising the said polymeric elasticizing agents have better swelling resistance in the hydrocarbon media compared to analogous TPV compositions comprising elasticizing agents of another nature (such as e.g. EPDM which comprises predominantly ethylene - see JP4125576). Without being bound by theory, the inventors believe that reason of this is different compatibility of elasticizing agents of various natures with polymeric components of the TPV composition. The elasticizing agent based on propylene copolymers used in the present invention is most compatible with the PP matrix comprised in the composition. The elasticizing agents of another nature, e.g. EPDM are compositionally incompatible with polypropylene, which leads to the fact that upon introduction of such elasticizing agents in the composition their distribution (localization) occurs predominantly in the nitrile-containing rubber phase. Such distribution (localization) of elasticizing agents (e.g. EPDM) loosens the structure of the nitrile-containing rubber and also the interphase region, which can somewhat affect decrease of diffusion barrier provided mainly by polar rubber to the TPV swelling processes in the hydrocarbon media.

In order to reduce the TPV swelling degree in hydrocarbon media even more one can use ester plasticizers, both separately and in mixtures with each other. Examples of ester plasticizers include but not limited to, e.g. phthalic, terephthalic acid esters with aliphatic alcohols, trioctyl trimellitate (TOTM), dioctyl adipate (DO A), dioctyl sebacinate (DOS), aromatic and semi-aromatic esters of phosphoric acid. The content of plasticizers in the TPV composition is 0 to 30 wt%, preferably 0 to 22 wt%, most preferably 0 to 18 wt%.

The components of the compositions are subjected to vulcanization using a vulcanizing system which comprises, according to the present invention, a peroxide initiator, a vulcanization co-agent, and also a polyatomic phenol and, optionally a polyfunctionality monomer.

As the said peroxide initiator, organic peroxides are used with a half-life of up to 0.1 h in the temperature range of 150 to 210 °C, preferably from 170 to 200 °C. Non- limiting examples of peroxides are l,3-l,4-bis(tert-butylperoxyisopropyl)benzene, 2,5- dimethyl-2,5-di-(tert-butylperoxy)-hexane, 3,6,9-triethyl-3,6,9-trimethyl-l,4,7- triperoxynonane. The content of peroxide initiator in the vulcanizing system is from 0.5 to 23 wt%, preferably from 0.7 to 15 wt%, most preferably about 1.5 wt%.

According to the present invention, improvement of technological and working characteristics of the TPV composition is provided at using a vulcanization co-agent together with a peroxide initiator, in contents of a vulcanizing system. Esters, half- products of condensation of polyhydric alcohol and polybasic unsaturated acid having at least one ester bond and one free acid group are used as said vulcanization co-agent. The "ester bond" means a chemical bond between carbon (C-) of the carboxyl group (- COOH) of the carboxylic acid and oxygen (-0) of a polyhydric alcohol in an ester group.

Presence of no more than one double bond in the vulcanization co-agent molecule somewhat facilitates decrease in excessive crosslinking of nitrile-containing rubber macromolecules to each other at dynamic vulcanization in the melt of PP and nitrile-containing rubber. The absence of excessive crosslinking of nitrile-containing rubber allows for producing higher fluidity products with improved tensile strain at break.

The preferable vulcanization co-agents are selected from glycol mono esters, preferably, ethylene glycol (EG) ones and unsaturated aliphatic dibasic acids, preferably, maleic acid, comprising one ester bond. The content of the vulcanization co- agent in the vulcanizing system is 7.5 to 76.9 wt%, preferably from 20 to 60 wt%.

Further prevention of excessive crosslinking of nitrile-containing rubber is allowed by use in the vulcanizing group of aromatic compounds from the group of polyatomic phenols which are mono- or polycyclic aromatic compounds comprising 2 or more hydroxyl groups. The resultant complex of the polyatomic phenol with the vulcanization co-agent has a selective impact on the kinetic and mechanism of radical chain processes of dynamic vulcanization. This impact is expressed in somewhat inhibiting of the crosslinking process of nitrile-containing rubber macromolecules in double bonds.

Preferably, during production of TPV a preliminary mixing of the vulcanization co-agent and polyatomic phenol is carried out prior to full dissolution of the polyatomic phenol. The weight ratio of polyatomic phenol and the vulcanization co-agent is 1 :1 to 1 :20, preferably 1 :2 to 1 :12, most preferably 1 :3 to 1 :10.

As polyatomic phenol at least one of such compounds is used as cyclic aromatic compound, e.g. pyrocatechol, resorcinol, hydroquinone, pyrogallol, oxyhydroquinone, phloroglucine, hexahydroxybenzene, polycyclic aromatic compound of fused structure, e.g. 1 ,2,4-trihydroxynaphthalene, 2,6,9, 10-tetrahydroxyanthracene, polyhydric aromatic compound of isolated structure with aromatic cycles linked by no more than one single C-C bond, e.g. 4,4'-dihydroxhybiphenyl. It is more preferable to use a polyatomic phenol, in particular, hydroquinone (HQ).

In order to increase activity and efficacy of the vulcanizing system of the present invention monofunctional monomers with terminal vinyl groups incapable of chemical interaction with the co-agent molecules and intermediate complexes formed during vulcanization process are optionally used. A monofunctional monomer in the present invention is a polar compound, preferably selected from acrylic and methacrylic ester derivatives with C₄-C₁₈ aliphatic alcohols, preferably with C₈-C₁₂ alcohols. Content of such polar compound in the claimed vulcanizing system should not exceed the amount equimolar to the main vulcanization co-agent. The "equimolar amount" term means amount of components providing for equimolar ratio. The "equimolar ratio" term means 1 : 1 molar ratio of the components.

In order to stabilize the TPV composition phenolic, aramine, phosphite stabilizers, stearates or hydrotalcites are additionally used. For example, pentaerithrite- tetrakis-(3-(3,5-di-tert-butyl-4-oxyphenyl)-propionate), tris-(2,4-di-tert- butylphenyl)phosphite, calcium stearate are related to such compounds. Also, light stabilizers, antistatics, nucleating agents, fillers such as talc, calcium carbonate, kaolin, pigments, technical carbon and other additives can be further used. According to the present invention, the weight ratio of the used vulcanizing system to the composition content, i.e. the sum of weights of the polypropylene and/or copolymer of polypropylene with olefins having 2 to 6 carbon atoms, nitrile-containing rubber, polymer compatibilizer and optionally polymeric elasticizing agent and ester plasticizer is 1 :99 to 13:87, preferably from 2:98 to 10:90, most preferably from 2.5:97.5 to 8:92.

The present invention also relates to the method of producing the said TPV composition comprising:

a) producing a homogenous melt comprising from 5 to 50 wt% polypropylene and/or copolymer of propylene with olefins having 2 to 6 carbon atoms, from 30 to 85 wt% nitrile-containing rubber, from 2 to 40 wt% polymer compatibilizers, from 0 to 40 wt% polymeric elasticizing agents and from 0 to 30 wt% ester plasticizers;

b) vulcanization of the melt obtained at step a) using from 1 to 13 wt% vulcanizing system which comprises (based on 100%): from 0.7 to 23 wt% peroxide initiator, from 7.5 to 76.9% vulcanization co-agent, from 0.7 to 38.5% polyatomic phenols, from 0 to 23 wt% monofunctional monomers.

The TPV composition obtained according to the present invention can be used for producing articles based thereupon using known molding and processing methods such as: extrusion, injection molding, hot pressing, melt blowing.

In particular, at step a) a homogenous melt is obtained at stirring and mixing of the components of the claimed composition. The stirring is carried out in equipment known from the art, e.g. in such mixing equipment as rollers, Banbury mixers, Brabender mixers, single-screw or double-screw extruder.

In one embodiment of the invention, the components are added to the mixing equipment in the following order: nitrile-containing rubber - polypropylene (PP) or a copolymer of propylene with olefins comprising from 2 to 6 carbon atoms - polymer compatibilizer - polymeric elasticizing agent - ester plasticizer. Preferably, the components are introduced in this order: nitrile-containing rubber - a complex of vulcanization co-agent with polyatomic phenol - polypropylene or a copolymer of propylene with olefins comprising from 2 to 6 carbon atoms - polymer compatibilizer - polymeric elasticizing agent - ester plasticizer.

The temperature of mixing the composition components is defined by the melting point of the polymers used. The mixing time is determined in such a way so to provide for homogenizing of the melt and is about 1 to 30 minutes, preferably from 2 to 20 minutes.

At step b) after the homogenous melt of polymers at step a) is obtained, vulcanization process is carried out by introducing the vulcanizing system in the melt of components. The components are introduced in the following order: vulcanization co- agent together with the polyatomic phenol and then peroxide initiator is added.

The vulcanization is carried out at the temperature of 150 to 210 °C, preferably from 170 to 200 °C. The duration of the vulcanization process is 1 to 30 minutes.

The TPV composition obtained according to the present invention is a polymeric product and it is characterized by the following properties: melt index up to 40- 50 g/10 min at 190°C and 5 kg load, Shore A hardness from 50 to 97 units, breaking strength is from 3.5 to 11.5 MPa, tensile strain at break is up to 650%, including the compositions with increased softness of the surface. Moreover, separate variants of the compositions are characterized by high swell resistance in oil products at elevated temperature (145- 150 °C).

The TPV composition obtained according to the present invention can be subjected to molding resulting in article. The method for producing an article according to the present invention comprises the steps (a) and (b) described above:

step a): producing a homogenous polymer melt;

step b): vulcanization and production of TPV composition,

after which steps c) and d) are carried out:

step c): molding of the vulcanized melt of the TPV composition obtained at step b) resulting in a mold composition in granulated or finely milled form; and

step d) producing an article from the mold composition obtained at step c).

At step d) the mold composition obtained at step c) is subjected to processing in order to obtain various industrial articles by all available methods known for processing thermoplastic polymers, in particular, extrusion, injection casting, hot pressing, melt blowing.

The present invention also relates to an industrial article comprising said composition, and to the industrial article obtained by the aforesaid method. In particular, such industrial article is, but not limited to, a molded construction element of a vehicle, housing part, packing, insulating or industrial rubber article. This invention is described in more detail with a reference to the Examples outlined below. These examples are outlined only for illustrative purposes of the present invention and do not limit thereof.

Invention examples

Production of the compositions of the present invention was carried out using a batch cycle mixing equipment as which the laboratory "Brabender" rotary type mixer was used with a mixing chamber volume of 350 cm³. The temperature of mixing chamber was set to 150 °C. The mixing time in the melt was 2.5- 3.5 minutes, rotation rate of the mixer rotors was 100 rpm. The composition after unloading from the mixer and cooling was milled using a cutting mill, the milled material was used for making test samples.

Assessment of the physical and mechanical properties and oil and gasoline resistance of the compositions was carried out using samples made by the injection molding method.

The melt flow index of the compositions was determined according to ASTM D

1238, diameter of the capillary was (2.095 ± 0.005) mm, temperature was 190°C, load was 5 kg.

The compositions of the present invention were obtained using the starting components described below.

The following were selected as polymer base:

1. Polypropylene

- propylene homopolymer of the PPH030GP trademark: MFl23o°c/2.i₆kg = 3.0 g/10 min, made by "Tomskneftekhim" LLC (Russia);

- Random copolymer of propylene of the PPR015BM trademark: MFl230°c/2.i6kg = 1.2-1.8 g/10 min, made by "Tomskneftekhim" LLC (Russia);

- block copolymer of propylene and ethylene of the BC 22015 trademark.

2. Nitrile-containing rubber (NBR)

- copolymer of butadiene and acrylic acid nitrile of the BNCS-28AMN trademark, weight percentage of the acrylic acid nitrile was 27- 30%, Mooney viscosity was ML(i+₄)ioo°c was 50-70 conditional units, made by "Krasnoyarsk Synthetic Rubber

Plant" Co. (Russia);

- copolymer of butadiene and acrylic acid nitrile of the BNCS-18AMN trademark, weight percentage of the acrylic acid nitrile was from 17 to 20%, Mooney viscosity was ML(i+₄)ioo°c was from 40 to 60 conditional units, made by "Krasnoyarsk Synthetic Rubber Plant" Co. (Russia);

- hydrogenated butadiene nitrile rubber Therban 3467.

3. Polymeric compatibilizers:

- homopolypropylene of the Bondyram 1101 trademark modified by maleic anhydride: d = 0.900 g/cm³.

4. Polymeric elasticizing agents:

- Copolymer of propylene and ethylene of the Vistamaxx6202 trademark: MFI^o-c^iekg = 9.1 g/10 min, ethylene content 15%, made by ExxonMobil (USA);

- Copolymer of propylene and ethylene of the Vistamaxx6102 trademark: MFIi90°c/2.i6kg = 1.4 g/10 min, ethylene content 16%, made by ExxonMobil (USA);

- amorphous polyolefin of the Vestoplast EPX35 trademark: MFI₂3₀°c/2.i6kg = 138 g/10 min, made by Evonik (Germany);

- copolymer of ethylene, propylene and diene (EPDM) Vistalon 2502X: Mooney viscosity was ML(i+4)i25°c was 26 conditional units, ethylene content was 49.0 wt%, ethylidene norbornene content was 4.2 wt%, made by ExxonMobil (USA);

- polybutadiene with hydroxyl terminal groups of the R-45HT trademark, made by Cray Valley (USA);

- Epoxidized oligomeric polybutadiene;

- Styrene-ethylene-butylene-styrene rubber of the G 1643 trademark, MFl230°c/2.i6kg = 18 g/10 min, styrene:rubber ratio was 20/80.

5. Peroxide initiator:

- l,3/l,4-bis(tert-butylperoxy-isopropyl)benzene of the LUPEROX F40 trademark, self-accelerating decomposition temperature was 70 °C, made by Arkema

(France).

6. Vulcanization co-agent:

- Ethylene glycol and maleic acid monoester (MEG);

- Trimethylolpropane triacrylate (TMPTA);

- Maleic anhydride (MA);

- Iso-decyl methacrylate;

- Oxyethylmethacrylate. 7. Polyatomic phenols:

- Pyrocatechol;

- Resorcinol;

- Hydroquinone (HQ);

- Pyrogallol;

- Oxyhydroquinone;

- 1,2,4-trihydroxynaphthalene;

- 4,4'-dihydroxybiphenyl.

8. Monofunctional monomer:

- Glycidyl methacrylate (GMA);

-Iso-decyl methacrylate;

- Oxyethylmethacrylate.

9. Target and technological additives

- Talc of the A20 trademark, made by Luzenac (France);

- Mineral oil PW-90;

- Mixture of antioxidants, Irgaphos 1010 and Irgaphos 168 (1 :1 ratio);

- Kaolin MIKAO 98-02;

- Dioctyl adipate (DOA);

- Trioctyl trimellitate (TOTM);

- Triphenyl phosphate (TPP).

Methods of studying the compositions:

Determination of the melt flow index was carried out at a temperature of 190 °C and load of 2.16 N according to National State Standard 11645.

Determination of the tensile yield at break, breaking strength and relative deformation at break was carried out according to National State Standard 11262 at the test rate of 500 mm/min.

Determination of elasticity modulus at bending was carried out according to ASTMD 790, test type was three-point bend, test rate was 1.3 mm/min.

Determination of Shore A/1 hardness was carried out according to GOST 24621.

Determination of Vicat temperature (10N) was carried out according to ASTM

1525.

Determination of resistance to liquid aggressive media was carried out according to National State Standard 9.030-74.

Contents and properties of the TPV compositions are outlined in Table 1 comprising examples 1-42.

Table 1. Polymeric consents and contents of the vulcanizing TPV system and properties of the obtained TPV

t

Table 1 (continued 1)

t

Table 1 (continued 2)

t

* MPC-4 is an experimental sample of PP modified by grafting of 3% MEG in the presence of 0.1% Luperox F-40 on a double-screw extruder LTE-20-44. PP was pre- mixed in the melt with 10-% EPDM (Royalene 563) and 24% Butyl Rubber (BR- 1675N) in the Brabender mixer.

σ_ρρ - tensile yield, MPa

ε_ρ - tensile strain at break, %

σιοο%, - breaking strength, MPa

eres.ioo% - residual elongation of the sample after its 100% elongation with subsequent stress removal, %

Am - alteration of the sample weight at exposure to oil, %

Examples 1 and 2 (Table 1) outline contents and test results for the TPV compositions characterized by improved properties such as tensile strain at break and melt flow index of the compositions without significant decrease in strength parameters owing to use of the diphenol, hydroquinone (HQ) in contents of the TPV vulcanizing system.

Examples 2 to 6 and 11 (Table 1) demonstrate effect of the nature of polypropylene and/or copolymers of propylene with olefins having 2 to 6 carbon atoms and a polymeric elasticizing agent on the main properties of the TPV composition. The advantages of the properties of the TPV According to the present invention are seen compared to the analogous compositions represented in the Prototype (see data on the prototype in Table 1, Examples 7 comp., 8 comp. and data of Examples 1, 2).

The Comparative Example 10 demonstrates negative alterations in the fluidity and other TPV properties at using the vulcanizing system according to the Prototype compared to the properties of the TPV composition obtained according to the invention (Example 6).

Examples 31 and 30 Comp. (Table 1, Continued 2) demonstrate advantages of the vulcanizing system according to the present invention using a complex of MEG and HQ in the part of providing a TPV with improved resistance to exposure to hot oil products (135 °C).

Examples 32 comp. and 33 (Table 1, continued 2) demonstrate the advantages of the vulcanizing system of the invention using a complex of MEG and HQ in the part of providing a TPV with increased surface softness. Data of Examples 34-42 (Table 1, continued 2) demonstrate new possibilities of improving the resistance of the claimed TPV to exposure to oil products in the wide temperature range due to partial or full replacement of a polymeric elasticizing agent (Vistamax, Vestoplast) in contents of the TPV compositions with PVC plasticizers such as DOA, TOTM and TPP at various combination variants thereof.

Therefore, from the obtained experimental data it is obvious to the one skilled in the art that the TPV composition of the present invention has improved properties, in particular, oil and gasoline resistance compared to the prototype compositions. Moreover, according to the present invention producing of the TPV compositions is provided with wide Shore A hardness (from 50 to 97 units), MFI (up to 50 g/10 min), breaking strength (from 3.5 to 11.5 MPa) ranges and high elasticity characterized by tensile strain at break up to 650% including for the compositions with increased surface softness.

Claims

WHAT IS CLAIMED IS:

1. A composition of dynamically vulcanized thermoplastic elastomer which comprises the following components, based on 100 wt% of the composition:

from 5 to 50 wt% polypropylene and/or copolymers of propylene with olefins comprising 2 to 6 carbon atoms;

from 30 to 85 wt% nitrile-containing rubber;

from 2 to 40 wt% polymer compatibilizer which is a maleinized product based on polypropylene, ethylene and propylene and/or butadiene-styrene copolymers;

from 0 to 40 wt% polymeric elasticizing agent;

from 0 to 30 wt% ester plasticizer;

from 1 to 13 wt% vulcanizing system, wherein said vulcanizing system comprises, based on 100 wt% of the vulcanizing system:

from 0.7 to 23 wt% peroxide initiator;

from 7.5 to 76.9 wt% vulcanization co-agent;

from 0.7 to 38.5 wt% polyatomic phenol;

from 0 to 23 wt% polyfunctional monomer.

2. A composition of claim 1 wherein the said polypropylene, and/or polypropylene comonomer with olefins comprising from 2 to 6 carbon atoms is selected from propylene or copolymers of propylene with ethylene, butene-1, preferably, from homopolypropylene or propylene and ethylene copolymer.

3. A composition of claim 1 wherein the said polypropylene, and/or copolymers of propylene with olefins comprising from 2 to 6 carbon atoms is characterized by the value of MFl2_30°c/2. i6kg in the range of 0.3 to 30 g/10 min, preferably, from 3 to 8 g/10 min.

4. A composition of claim 1 wherein the nitrile-containing rubber is selected from hydrogenated butadiene-nitrile rubber, non-hydrogenated butadiene nitrile rubber, triple copolymers of butadiene, acrylonitrile and other monomers, e.g. from triple copolymer of butadiene, acrylonitrile and acrylic acid, triple copolymer of butadiene, acrylonitrile and vinylidene chloride, more preferably, from nitrile butadiene rubber.

5. A composition of claim 4 wherein the said nitrile-containing rubber is a nitrile butadiene rubber with acrylonitrile content of 17 to 40 wt% and Mooney viscosity of ML(₁+₄)₁₀₀°c from 40 to 120 conditional units.

6. A composition of claim 1 wherein the said polymeric compatibilizers are selected from a group of polypropylenes modified by chemically grafted maleic anhydride groups.

7. A composition of claim 6 wherein the content of chemically grafted maleic anhydride groups in 0.1 to 5%.

8. A composition of claim 1 wherein the said polymeric elasticizing agents are selected from amorphous copolymers of propylene.

9. A composition of claim 8 wherein the said amorphous copolymers of propylene are copolymers of propylene with ethylene with ethylene contents in the range of 8 to 16 wt% or terpolymers of propylene with ethylene and butene-1.

10. A composition of claim 8 wherein the said amorphous copolymers of propylene have the MFI₂₃₀»c/_{2 1}6kg parameter of 3 to 18 g/10 min.

11. A composition of claim 1 wherein the content of polymeric elasticizing agents is from 0 to 30 wt%.

12. A composition of claim 1 wherein the said ester plasticizers are selected from a group comprising phthalic, terephthalic acid esters with aliphatic alcohols trioctyl trimellitate (TOTM), dioctyl adipate (DOA), dioctyl sebacinate (DOS) aromatic and semi-aromatic phosphoric acid esters.

13. A composition of claim 1 wherein the content of said ester plasticizers is from 0 to 22 wt%, more preferably from 0 to 18 wt%.

14. A composition of claim 1 wherein the said peroxide initiator of the vulcanizing system is an organic peroxide with a half-life of up to 0.1 h in the temperature range of 150 to 210 °C, preferably from 170 to 200 °C.

15. A composition of claim 14 wherein the organic peroxide is selected from a group consisting of l,3-l,4-bis(tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di-

(tert-butylperoxy)-hexane, 3,6,9-triethyl-3,6,9-trimethyl-l,4,7-triperoxynonane.

16. A composition of claim 1 wherein content of peroxide initiator in the vulcanizing system is from 0.7 to 15 wt%.

17. A composition of claim 1 wherein said vulcanization co-agent is a half-ester of polyhydric alcohol and polybasic unsaturated acid.

18. A composition of claim 17 wherein the vulcanization co-agent is a monoester of ethylene glycol and maleic acid.

19. A composition of claim 1 wherein the said polyatomic phenol is a mono- or polycyclic aromatic compounds comprising 2 or more hydroxyl groups.

20. A composition of claim 19 wherein said polyatomic phenol is selected from a group comprising at least one of the polycyclic aromatic compounds, e.g. such as pyrocatechol, resorcinol, hydroquinone, pyrogallol, oxyhydroquinone, phloroglucine, hexahydroxybenzene, polycyclic aromatic compound of fused structure, such as 1,2,4- trihydroxynaphthalene, 2,6,9, 10-tetrahydroxyanthracene, polyhydric aromatic compound of isolated structure with aromatic cycles linked by no more than one single C-C bond, such as 4,4'-dihydroxhybiphenyl.

21. A composition of claim 19 wherein said polyatomic phenol is a monocyclic phenol, preferably hydroquinone.

22. A composition of claim 1 wherein said monofunctional monomers are monomers with terminal vinyl groups incapable of chemical interaction with the co- agent molecules and intermediate complexes formed during vulcanization process.

23. A composition of claim 22 wherein said monofunctional monomers are polar compounds, preferably selected from acrylic and methacrylic ester derivatives with C₄- Ci8 aliphatic alcohols, preferably with C₈-Ci₂ alcohols.

24. A composition of claim 1 wherein the weight ratio of the used vulcanizing system to the total amount of the polypropylene and/or copolymer of polypropylene with olefins having from 2 to 6 carbon atoms, nitrile-containing rubber, polymer compatibilizer and polymeric elasticizing agent and ester plasticizer is from 1 :99 to 13:87, preferably from 2:98 to 10:90, most preferably, from 2.5:97.5 to 8:92.

25. A method of producing a dynamically vulcanized thermoplastic elastomer composition of claims 1-24 comprising:

a) producing a homogenous melt comprising from 5 to 50 wt% polypropylene and/or copolymer of propylene with olefins having from 2 to 6 carbon atoms, from 30 to 85 wt% nitrile-containing rubber, from 2 to 40 wt% polymer compatibilizers, from 0 to 40 wt% polymeric elasticizing agents and from 0 to 30 wt% ester plasticizers;

26. A method of claim 25 wherein at step a) the components are introduced in the following order: nitrile-containing rubber - polypropylene and/or a copolymer of propylene with olefins comprising from 2 to 6 carbon atoms - polymer compatibilizer - polymeric elasticizing agent - ester plasticizer.

27. A method of claim 25 wherein at step a) the components are introduced in the following order: nitrile-containing rubber - a complex of vulcanization co-agent with polyatomic phenol - polypropylene or a copolymer of propylene with olefins comprising from 2 to 6 carbon atoms - polymer compatibilizer - polymeric elasticizing agent - ester plasticizer.

28. A method of claim 25 wherein the vulcanization is carried out at the temperature from 150 to 210 °C, preferably from 170 to 200 °C.

29. A method of claim 25 wherein the duration of the vulcanization process is from 1 to 30 min.

30. A method of claim 25 wherein the components of the vulcanizing system are introduced in the following order: vulcanization co-agent together with the polyatomic phenol and then the peroxide initiator.

31. A method of producing an article based on the composition of claims 1-24 comprising:

b) vulcanization of the melt obtained at step a) using from 1 to 13 wt% vulcanizing system which comprises (based on 100%): from 0.7 to 23 wt% peroxide initiator, from 7.5 to 76.9% vulcanization co-agent, from 0.7 to 38.5% polyatomic phenols, from 0 to 23 wt% monofunctional monomers;

c) molding of the vulcanized melt of the TPV composition obtained at step b) resulting in a mold composition;

d) producing an article from the mold composition obtained at step c).

32. A method of claim 31 wherein at step c) the molding is carried out by extrusion, injection molding, hot pressing or melt blowing.

33. An article obtained by a method of claim 31.

34. An article comprising a composition of any one of claims 1- 24.