FIELD OF THE INVENTION

The present invention relates to novel thermoplastic materials based on polyamides and nitrile rubbers containing polar termonomers, new vulcanizates based on such mixtures and a process for preparing such vulcanizates.

BACKGROUND OF THE INVENTION

Blends of polyamides (PA) and aciylonitrile-butadiene based polymers ("NBR") are possible materials for flexible oil resistant articles based on thermoplastic elastomers.

For several reasons, including processing difficulties and basic material properties, blends of polyamides and acrylonitrile-butadiene-copolymers are not yet in industrial use.

Typically the polyamide component represents the continuous phase in blends based on polyamides and rubbers. Therefore the resulting blends are too hard and not flexible. Hence, such materials are not suited for flexible articles with a requested Shore A hardness (at 23 °C according to DIN 53505) in the range of from 60 to 95.

Fundamental facts are known since more than thirty years, particularly since the work of A.Y. Coran and R, Patel was issued in 1980 in Rubber Chemistry and Technology, Vol 53, 781ff (1980) titled "Rubber Thermoplastic Compositions: Part I; NBR-Nylon Thermoplastic Elastomeric Compounds". In such work the basic variables have been varied, especially the ratio of the blend components (using NBR in a range of 60 to 80% by weight), the types of polyamide (all polyamides PA6 of different origin) and the aciylonitrile content of NBR (using up to 41 % by weight of aciylonitrile). It is reported that the hardness of the materials vaiy between 28 to 33 Shore D, which is equivalent to 80 to 85 Shore A hardness.

A.Y, Coran and R. Patel distinguished between so-called "self-curing" and "non-self-curing" NBR polymers, the definition of which was based on a high temperature test. "Self-curing" polymers were found more active than "non-self-curing" types. The blends were manufactured in a brabender mixer. In order to improve the properties m-phenylene-bismaleimide was added a cross- linking agent which leads to a significant increase of hardness and elongation at break.

Gherasim and Schuster transferred these findings to hydrogenated nitrile rubbers ("HNBR") ("Thermoplastische Vulkanisate auf Basis Polyamid", DKG Bezirkstagung Bad Neuenahr 2004) in Journal of Applied Polymer Scinece 123 (3072-3080) (2012) further work by Enio C. M. Faguendes and Marly A. Maldaner Jacobi is reported, in particular in order to optimize the curing system. They describe thermoplastic vulcanizates (TPV) as consisting of a thermoplastic polymer matrix and a crosslinking rubber that are cured during melt-blending, resulting in a fine dispersion of micro-size rubber particles in the continuous thermoplastic matrix. The stress-strain behaviour found for various TPVs is shown in Figure 2 of the article. These curves show the typical behaviour for blends with rubber particles in the continuous thermoplastic matrix, comprising a first part of the curve at lower strain being typical for energy elastic materials which then passes into a second part of the curve at higher strain being typical for plastic deformation.

Neither Coran and Patel nor their successors investigated blends on the basis of NBR-based terpolymers.

In Journal of Applied Polymer Science, Vol 100, 1008-1012 (2006) it is reported by R. Chowdliury, M. S. Banerji, and . Shivakumar that additional work was carried out by including carboxylated nitrile rubber (sometimes also referred to as "XNBR") into the investigations to find terpolymers having a better compatibility with polyamides than simple nitrile rubbers representing copolymers of an α,β-unsaturated nitrile and a conjugated diene. As materials Krynac ^® XI .46 (33% by weight of acrylonitrile ("ACN"); 1% by weight of carboxylic acid; Mooney viscosity ML (1+4) at 100°C of 45) and Krynac ^® X7.50 (27% by weight of CAM; 7% by weight of carboxylic acid; Mooney viscosity ML (1+4) at 100°C of 47) were used. It was shown that tensile strenght, hardness and the compression set properties were ail improved. The degree of improvement increased with the degree of carboxylation and depending on the ratio of the components in the blend. This effect was explained by a new quality of the phase distribution evidenced by microscopic analysis resulting from an interfacial chemical reaction between the carboxylic acid groups of the XNBR component and the poiyamide to form amides. Because water is generated simultaneously further hydrolysis of poiyamide groups occurs and gives rise to the formation of additional block-polymers as shown in principle in the following Scheme 1. Scheme 1 : Compatibilizing PA and XNBR during processing

carboxylated acrylonitrile-butadiene rubber polyamide

to initiate hydrolysis of amide groups to form additional end groups

In Journal of Applied Polymer Science Vol. 104, 372-377 (2007) it is further reported by R. Chowdhury, M. S. Banerji, and K. Shivakumar that appropriate blends of that kind have been produced in a twin-screw-extruder,

The aforesaid represented the state of the art when blends of polyamides and NBR-based terpolymers containing a polar termonomer were picked up by the inventors of the present invention with the objective to find systems that can be applied in oil resistant thermoplastic applications and which may be processed like thermoplasts and nevertheless show a rubber-like stress-strain behaviour.

This object has now been solved by providing specific thermoplastic materials based on polyamides and nitrile rubbers representing terpolymers with repeating units of at least one polar termonomer,

SUMMARY OF THE INVENTION

The present invention therefore relates to thermoplastic materials based on

(i) one or more polyamide(s) and

(ii) one or more nitrile rubber(s) comprising repeating units derived from at least one ,β unsaturated nitrile, at least one conjugated diene and one or more further copolymerizable polar monomers,

wherein the weight ratio of the polyamide (i) to the nitrile rubber (ii) is (10-50):(90-50), preferably (20-40):(80-60), more preferably (25-35);(75-65), based on the total weight of the polyamide (i) and the nitrile rubber (ii) characterized in that the nitrile nibber(s) represents) the continuous phase.

The present invention further relates to a process for preparing such thermoplastic materials by mixing one or more poiyamide(s) (i) and one or more nitrile rubbers (ii) in a mixing device wherein the nitrile rubber(s) comprise(s) repeating units derived from at least one α,β unsaturated nitrile, at least one conjugated diene and one or more further copolymerizable polar monomers and wherein the weight ratio of the polyamide (i) to the nitrile rubber (ii) as fed to the mixing device is (10- 50):(90-50), preferably (20-40):(80-60), more preferably (25-35);(75-65), based on the total weight of the polyamide(s) (i) and the nitrile rubber(s) (ii).

BRIEF DESCRIPTION OF THE FIGURES

The above and other aspects, features and advantages of the invention will become apparent from the following detailed description of the invention and the examples in conjunction with the accompanying drawings:

Figure 1 shows the stress-strain curve as measured for Examples 1 to 3.

Figure 2 shows the granules obtained in Example 2 (non-inventive).

Figure 3 shows the stress-strain curve as measured for Examples 4 to 6.

Figure 4 shows the sheet obtained after the milling step in Example 5 (inventive).

Figure 5 shows the AFM reproduction for Example 2 (non-inventive; ratio of Durethan ^® B29 to Krynac ^® X740 = 40:60) and Example 5 (inventive; ratio of Durethan ^® B29 to Krynac ^® X740 = 40:60)

Figure 6 shows the stress-strain curve as measured for Example 7a (inventive; mixing time 6 minutes) and Example 7b (inventive, mixing time 10 minutes).

Figure 7 shows the the AFM reproduction for Example 7a.

Figure 8 shows the the AFM reproduction for Example 7b.

DETAILED DESCRIPTION OF THE INVENTION

The term "substituted" used for the purposes of the present patent application means that a hydrogen atom on an indicated radical or atom has been replaced by one of the groups indicated in each case, with the proviso that the valency of the atom indicated is not exceeded and the substitution leads to a stable compound.

For the purposes of the present patent application and invention, all the definitions of moities, parameters or explanations given above or below in general terms or in preferred ranges can be combined with one another in any way, i.e. including combinations of the respective ranges and preferred ranges. In this application the term „blend(s) ^f< is used synonymously to the term thermoplastic materials)". The thermoplastic materials according to the present invention are based on

(i) one or more polyamide(s) and

(ii) one or more nitrile rubber(s) comprising repeating units derived from at least one α,β unsaturated nitrile, at least one conjugated diene and one or more further copolymerizable polar monomers, wherein the weight ratio of the polyamide (i) to the nitrile rubber (ii) is (10-50):(90-50), preferably (20-40):(80-60), more preferably (25-35):(75-65), based on the total weight of the polyamide (i) and the nitrile rubber (ii) characterized in that the nitrile rubber(s) represent(s) the continuous phase in the thermoplastic material.

Typically the thermoplastic materials according to the present invention have a Shore A hardness at 23 °C in tiie range of from 65 to 95, preferably in the range of from 65 to 90, more preferably in the range of from 65 to 80 and even more preferably in the range of 65 to 70, Such Shore A hardness is determined at 23°C in accordance with DIN 53505.

The thermoplastic materials provided by the present invention are advantageously flexible, relatively "soft" and dispose of an excellent oil-resistance. Importantly the materials provided by the present invention show a morphology in which the nitrile rubber(s) represents the continuous phase while the polyamide(s) (i) are the discontinuous phase. The polyamide(s) have a reinforcing effect. The blend according to the present invention shows a stress-strain behaviour which is quasi elastomeric or "rubber-like". They can be re-milled and processed to produce rubber-like articles. Such blends may be typically used in a temperature range between the glass transition temperature of the nitrile rubber component(s) (ii) and the melting temperature of the polyamide component(s) (i), i.e. typically between -5°C and about 260°C, preferably between 20°C and 1 0°Ο. Depending on the composition excellent levels of properties can be obtained like e.g. a tensile strength of 13 MPa, an elongation at break of 100 to 400% depending on the hardness, and a compression set at room temperature (after 70 hours) of 50%. Since the base polymers (i) and (ii) show high swelling resistance in oil and similar fluids, the blends are extremely oil resistant as already mentioned above. Due to the acceptable costs of the base polymers (i) and (ii) the blends are fairly economic. Polyamide component (0:

The polyamide component (i) in the inventive blend comprises one or more polyamide(s) which means it is possible to use an individual thermoplastic or else a combination of various thermoplastics.

Polyamides are thermoplastic polymers and well-known to any artisan. The polyamides used according to the invention can be prepared by various processes well-known and synthesized from a wide variety of monomers. They can be used alone or else in the form of polyamide moulding compositions, i.e. in combination with processing aids, stabilizers, or else reinforcing materials (e.g. mineral fillers or glass fibres) for purposes of specific adjustment of combinations of properties,

There is a wide variety of procedures known for the preparation of polyamides, and different monomer units are used here as a function of the desired final product, as also are various chain regulators to set a desired molecular weight, or else monomers having reactive groups for post- treatments subsequently envisaged.

The industrially relevant processes for preparation of polyamides mostly proceed by way of polycondensation in the melt. The hydrolytic polymerization of lactams is also understood to be polycondensation for these purposes.

Particularly preferred polyamides are semici stall ine polyamides which can be prepared stalling from diamines and dicarboxylic acids and/or from lactams having at least five ring members or from corresponding amino acids.

Monomers that can be used are firstly aliphatic and/or aromatic dicarboxylic acids, e.g. adipic acid, 2,2,4- and 2,4,4-trimethyladipic acid, azelaic acid, sebacic acid, isophthalic acid or terephthalic acid. Other monomers that can be used are aliphatic and/or aromatic diamines, e.g. tetramethylenediamine, hexamethylenediamine, 1,9-nonanediamine, 2,2,4- and 2,4,4- trimethylhexamethylenediamine, the isomeric diaminodicyclohexylmethanes, diaminodicyclohexylpropanes, bisaminomethylcyclohexane, phenylenedi amines, xylylenediamines, aminocarboxylic acids, e.g. aminocaproic acid, or the corresponding lactams. Copolyamides composed of more of the monomers mentioned are included. For tiie inventive multicomponent systems it is particularly preferable to use polyamides based on caprolactams, in particular ε-caprolactam, PA6, PA66, and other aliphatic and/or aromatic polyamides and, respectively, copolyamides having from 3 to 11 methylene groups in the polymer chain for each polyamide repeating unit,

The semicrystalline polyamides to be used according to the invention can also be used in a mixture with other polyamides and/or with further polymers. However, it is also possible to only use one or more polyamide(s) as component (i) without any further additives.

If so desired, but not mandatorily, conventional additives can be admixed in the melt with the polyamides or applied to the surface.

Examples of conventional additives are stabilizers (e.g. UV stabilizers, heat stabilizers or gamma radiation stabilizers), antistatic agents, flow aids, mould-release agents, flame-retardant additives, emiilsifiers, nucleating agents, plasticizers, lubricants, dyes, pigments, and also additives for increasing electrical conductivity. The additives can be used alone in a mixture or in the form of masterbatches.

Examples of stabilizers that can be used are metal salts, in particular copper compounds, sterically hindered phenols, hydroquinones, aromatic secondary amines, e.g. diphenylamines, substituted resorcinols, salicylates, benzotriazoles and benzophenones, and also various substituted representatives of these groups and their mixtures.

Examples of flow aids that can be used are low-molecular-weight compounds or branched, highly branched or dendritic polymers whose polarity is similar to that of the polymer resin, or else copolymers of olefins with methacrylic or aciylic esters of aliphatic alcohols, the MFI (melt flow index) of these being not less than 50 g/10 min,

Examples of pigments or dyes that can be used are titanium dioxide, zinc sulphide, ultramarine blue, iron oxide, carbon black, phthalocyanines, quinacridones, perylenes, nigrosin or anthraquinones.

Examples of nucleating agents that can be used are sodium phenylphosphinate or calcium phenylphosphinate, aluminium oxide, silicon dioxide, and also preferably talc.

Examples of lubricants and mould-release agents that can be used are ester waxes, pentaerythritol tetrastearate (PETS), long-chain fatty acids (e.g. stearic acid or behenic acid) and esters, their salts (e.g. Ca stearate or Zn stearate), and also amide derivatives (e.g. ethylenebisstearylamide) or montan waxes (mixtures composed of straight-chain, saturated carboxylic acids whose chain lengths are from 28 to 32 carbon atoms), and also low-molecular-weight polyethylene waxes and low-molecular-weight polypropylene waxes.

Examples of plasticizers that can be used are dioctyl phthalate, dibenzyJ phthafate, butyl benzyl phthalate, hydrocarbon oils, N-(n-butyI)benzenesulphonamide.

Additives that can be added to increase electrical conductivity are carbon blacks, conductive carbon blacks, carbon fibrils, nanoscale graphite fibres, nanoscale carbon fibres, graphite, conductive polymers, metal fibres, and also other conventional additives for increasing electrical conductivity.

Nanoscale fibres that can be used with preference are "single wall carbon nanotubes" or "multiwall carbon nanotubes" (e.g. from Hyperion Catalysis).

There can be a filler or reinforcing material present in the polyamides to be used according to the invention. The filler or reinforcing material used can also comprise a mixture composed of two or more different fillers and/or reinforcing materials, e.g. based on talc, mica, silicate, quartz, titanium dioxide, woilastonite, kaolin, amorphous silicas, magnesium carbonate, chalk, feldspar, barium sulphate, glass beads and/or fibrous fillers and/or reinforcing materials based on carbon fibres and/or glass fibres.

It is preferable to use particulate mineral fillers based on talc, mica, silicate, quartz, titanium dioxide, woilastonite, kaolin, amorphous silicas, magnesium carbonate, chalk, feldspar, barium sulphate and/or glass fibres. It is particularly preferable to use particulate mineral fillers based on talc, woilastonite, kaolin and/or glass fibres.

The filler and/or reinforcing material can, if appropriate, have been surface-modified, e.g. with an adhesion promoter or with an adhesion-promoter system, e.g. based on silane. However, the pretreatment is not absolutely essential. Particularly when glass fibres are used, it is also possible to use polymer dispersions, film formers, branching agents and/or glass fibre processing aids, in addition to silanes.

Appropriate glass fibres to be used in the thermoplastic material, whose fibre diameter is generally from 7 to 18 μιη, preferably from 9 to 15 μιη, are added in the form of continuous -filament fibres or in the form of chopped or ground glass fibres. The fibres can have been modified with a suitable sizing system and with an adhesion promoter or, respectively, adhesion-promoter system, e.g. based on silane. Examples of silane-based adhesion promoters commonly used for pretreatment are silane compounds of the general formula (I) (X-(CH ₂ ) _q )k-Si-(0-C _r H2r+i)4-k wherein

X is NH ₂ - _> HO- or ^Ηϊ ° H

q is a whole number from 2 to 10, preferably from 3 to 4,

r is a whole number from 1 to 5, preferably from 1 to 2 and

k is a whole number from 1 to 3, preferably 1.

Preferred adhesion promoters are silane compounds from the group of aminopropyl- trimethoxysilane, aminobutyltrimethoxysilane, aminopropyltriethoxysilane, aminobutyltriethoxy- silane, and also the corresponding silanes which contain a glycidyl group as substituent X.

The amounts generally used of the silane compounds for surface-coating for modification of the fillers is from 0.05 to 2% by weight, preferably from 0.25 to 1.5% by weight and in particular from 0.5 to 1% by weight, based on the mineral filler.

The thermoplastic component features high dimensional stability even at high temperatures, together with high flowability. The plastics component moreover has high oil resistance in commonly used engine oils, and also in industrial fluids and in fluids commonly used in motor vehicles.

Component (ii) (nitrite rubber component :

The nitrile rubber component (ii) in the inventive thermoplastic material comprises one or more nitrile rubber(s) which represent terpolymers comprising repeating units based on at least one α,β- unsaturated nitrile, at least one conjugated diene, and of one or more other copolymerizable polar monomers.

The conjugated diene can be of any type. It is preferable to use GpCe conjugated dienes. Particular preference is given to 1,3-butadiene, isoprene, 2,3-dimethylbutadiene, piperylene or a mixture thereof. Particular preference is given to 1,3-butadiene and isoprene or a mixture thereof. 3 ,3-butadiene is very particularly preferred.

The α,β-unsaturated nitrile used can be any known α,β-unsaturated nitrile, and preference is given to C3-C5 α,β-unsaturated nitriles, such as aciylonitrile, methacrylonitrile, ethacrylonitrile or a mixture of these. Aciylonitrile is particularly preferred. Alongside the one or more , β -unsaturated nitrile(s) and the one or more conjugated diene(s) the nitrile rubber (ii) comprises repeating units of at least one or more other copolymerizable polar termonomers. Appropriate polar termonomers are monomers either containing carboxyl groups or derivatives thereof or termonomers having at least one epoxy group.

As termonomers containing carboxyl groups or derivatives thereof α,β-unsaturated moiiocarboxyiic acids, their esters, their amides, α,β-unsaturated dicarboxylic acids, their monoesters, their diesters, their corresponding anhydrides or amides are preferred. More preferably α,β-unsaturated monocarboxylic acids or α,β-unsaturated dicarboxylic acids are used as polar termonomers.

As α,β-unsaturated monocarboxylic acids it is possible with preference to use acrylic acid and methacrylic acid.

It is also possible to employ esters of the α,β-unsaturated monocarboxylic acids, preferably their alkyl esters and alkoxyalkyl esters. Preference is given to the alkyl esters, especially CpC^ alky] esters, of the ,β-unsaturated monocarboxylic acids. Particular preference is given to alkyl esters, especially C Cig alkyl esters, of aciylic acid or of methacrylic acid, more particularly methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, n-dodecyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and 2-ethylhexyl methacrylate. Also preferred are alkoxyalkyl esters of the α,β-unsaturated monocarboxylic acids, more preferably alkoxyalkyl esters of aciylic acid or of methacrylic acid, more particular C ₂ -C} ₂ alkoxyalkyl esters of aciylic acid or of methacrylic acid, veiy preferably methoxymethyl acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate and methoxymethyl (meth)acrylate. Use may also be made of mixtures of alkyl esters, such as those mentioned above, for example, with alkoxyalkyl esters, in the form of those mentioned above, for example. Use may also be made of cyanoalkyl acrylates and cyanoatkyl methacrylates in which the C atom number of the cyanoalkyl group is 2-12, preferably -cyanoethyl acrylate, β-cyanoethyl acrylate and cyanobutyl methacrylate, Use may also be made of hydroxyalkyl aciylates and hydroxyalkyl methacrylate in which the C atom number of the hydroxyalkyl groups is 1-12, preferably 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate and 3-hydroxypropyl acrylate; use may also be made of fluorine- substituted benzyl-group-containing acrylates or methacrylates, preferably fluorobenzyl acrylates, and fluoroben2yl methacrylate. Use may also be made of acrylates and methacrylates containing fluoroalkyl groups, preferably trifluoroethyl acrylate and tetrafluoro ropyl methacrylate. Use may also be made of α,υβ-unsaturated carboxylic esters containing amino groups, such as dimethylaminomethyl acrylate and diethyl amino ethyl acrylate.

In the alternative it is possible to use α,β-unsaturated dicarboxylic acids, preferably maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid and inesaconic acid as copolymenzable polar termonomers.

Use may be made, furthermore, of α,β-unsaturated dicarboxylic anhydrides, preferably maleic anhydride, itaconic anhydride, citraconic anhydride and mesaconic anhydride.

It is possible, furthermore, to use nionoesters or diesters of α,β-uiisaturated dicarboxylic acids.

These α,β-unsaturated dicarboxylic monoesters or diesters may be, for example, alkyl esters, preferably Ci-Ci ₀ alkyl, more particularly ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl or n-hexyl esters, alkoxyalkyl esters, preferably C2-C12 alkoxyalkyl, more preferably C _, i-Cg- alkoxyalkyl, hydroxyalkyl, preferably Ci-C ₁₂ hydroxyalkyl, more preferably C ₂ -C ₈ hydroxyalkyl, cycloalkyl esters, preferably C ₅ -C ₁₂ cycioalkyl, more preferably C ₆ -C] ₂ cycloalkyl, alkylcyclo alkyl esters, preferably C ₆ -C _n alkylcycloalkyl, more preferably C ₇ -C ₁₀ alkylcycloalkyl, aryl esters, preferably Ce-C^ aryl esters, these esters being monoesters or diesters, and it also being possible, in the case of the diesters, for the esters to be mixed esters,

Particularly preferred alkyl esters of α,β-unsatu rated monocarboxylic acids are methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)aci l te, octyl (meth)acry!ate, 2-propyI- heptyl aciylate and lauryl (meth)aciylate. More particularly, n-butyl actylate is used.

Particularly preferred alkoxyalkyl esters of the α,β-unsaturated monocarboxylic acids are metlioxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate and methoxymefhyl (meth)acrylate. More particularly, metlioxyethyl aciylate is used.

Particularly preferred hydroxyalkyl esters of the α,β-unsaturated monocarboxylic acids are hydroxyethyl (liieth)acrylate, hydroxypropyl (meth)aciylate and hydroxybutyl (meth)actylate. Other esters of the α,β-unsaturated monocarboxylic acids that are used are additionally, for example, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, glycidyl (meth)acrylate, epoxy (meth)aciylate, N-(2-hydroxyethyl)acrylamides, N-(2-hydroxy- methyl)aciylamides and urethane (meth)acrylate.

Examples of α,β-unsaturated dicarboxylic monoesters encompass

e maleic acid monoalkyi esters, preferably monomethyl maleate, monoethyl maleate, monopropyl maleate and mono-n-butyl maleate; • maleic acid monocycloalkyl esters, preferably monocyclopentyl maleate, monocyclohexyl male ate and monocycloheptyl maleate;

« maleic acid monoalkyl cycloalkyl esters, preferably monomethyl cyclopentyl maleate and monoethyl cyclohexyl maleate;

maleic acid monoaryl esters, preferably monophenyl maleate;

• maleic acid monobenzyl esters, preferably monobenzyl maleate;

fumaiic acid monoalkyl esters, preferably monomethyl fumarate, monoethyl f marate, monopropyl fumarate and mono-n-butyl fumarate;

» fumaric acid monocycloalkyl esters, preferably monocyclopentyl fumarate, monocyclohexyl fumarate and monocycloheptyl fumarate;

« fumaric acid monoalkyl cycloalkyl esters, preferably monomethyl cyclopentyl fumarate and monoethyl cyclohexyl fumarate;

® fumaric acid monoaryl esters, preferably monophenyl fumarate;

« fumaric acid monobenzyl esters, preferably monobenzyl fumarate;

» citraconic acid monoalkyl esters, preferably monomethyl citraconate, monoethyl citraconate, monopropyl citraconate and mono-n-butyl citraconate;

» citraconic acid monocycloalkyl esters, preferably monocyclopentyl citraconate, monocyclohexyl citraconate and monocycloheptyl citraconate;

« citraconic acid monoalkyl cycloalkyl esters, preferably monomethyl cyclopentyl citraconate and monoethyl cyclohexyl citraconate;

• citraconic acid monoaryl esters, preferably monophenyl citraconate;

© citraconic acid monobenzyl esters, preferably monobenzyl citraconate;

• itaconic acid monoalkyl esters, preferably monomethyl itaconate, monoethyl itaconate, monopropyl itaconate and niono-n-biityl itaconate;

• itaconic acid monocycloalkyl esters, preferably monocyclopentyl itaconate, monocyclohexyl itaconate and monocycloheptyl itaconate;

® itaconic acid monoalkyl cycloalkyl esters, preferably monomethyl cyclopentyl itaconate and monoethyl cyclohexyl itaconate;

• itaconic acid monoaryl esters, preferably monophenyl itaconate;

® itaconic acid monobenzyl esters, preferably monobenzyl itaconate.

« Mesaconic acid monoalkyl esters, preferably mesaconic acid monoethyl esters;

As α,β-unsaturated dicarboxylic diesters it is possible to use the analogous diesters based on the abovenientioned monoester groups, and the ester groups may also be chemically different groups.

It is further possible, as further copolymerizable polar termonomers, to use compounds which contain per molecule two or more olefinic double bonds. Examples of such di- or polyunsaturated compounds are di- or polyunsaturated acrylates, methacrylates or itaconates of polyols, such as, for example, 1 ,6-hexanediol diacrylate (HDODA), 1 ,6-hexanediol dimethac ylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate (EGDMA), diethylene glycol dimethacrylate, triethylene glycol diacrylate, butane- 1,4-diol diacrylate, propane- 1 ,2-diol diacrylate, butane-l,3-diol dimethaciylate, neopentylglycol diacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, trimethylolethane diaciylate, trimetlvylolethane dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate (TMPTMA), glyceryl diaciylate and triacrylate, pentaerythritol di-, tri- and tetraacrylate or -methacrylate, dipentaerythritol tetra-, penta- and hexa- aciylate or -metliaciylate or -itaconate, sorbitol tetraaciylate, sorbitol hexamethaciylate, diacrylates or dimethaciylates or 1 ,4-cyclohexanediol, 1,4-dimethylolcyclohexane, 2,2-bis(4- hydroxyphenyl)propane _} of polyethylene glycols or of oligoesters or oligourethanes having terminal hydroxy! groups. As polyunsaturated monomers it is also possible to use aciylamides, such as, for example, methylenebisacrylamide, hexamethylene-l ,6-bisacrylamide, diethylenetriaminetrismet acjylamide, bis(methacrylamidopropoxy)ethane or 2-acrylamidoethyl acrylate. Examples of polyunsaturated vinyl compounds and allyl compounds are divinylbenzene, ethylene glycol divinyi ether, diallyl phthalate, allyl metliaciylate, diallyl maleate, triallyl isocyanu ate or triallyl phosphate.

In an alternative embodiment it is possible to use a copolymerizable polar tennonomer having at least one epoxy group. Appropriate and viable examples of such copolymerizable polar termonomer having at least one epoxy group are chosen from the group consisting of 2- ethylgtycidyl acrylate, 2-ethylglycidyl methacrylate, 2-(n-propyl)glycidyl acrylate, 2-(n- propyl)glycidyl metliaciylate, 2-(n-butyl)glycidyl aciylate, 2-(n-butyl)glycidyl metliaciylate, glycidyl metliaciylate, glycidy! methyl metliaciylate, glycidyl aciylate, (3 ',4'-epoxyhepty1)-2-ethyl acrylate, (3 ',4 ^' -epoxyheptyl)-2-ethyl methacrylate, 6',7 ^' -epoxyheptyl acrylate, 6',7'-epoxyheptyl methacrylate, allyl glycidyl ether, allyl 3,4-epoxyheptyl ether, 6,7-epoxyheptyl allyl ether, vinyl glycidyl ether, vinyl 3,4-epoxyheptyl ether, 3,4-epoxyheptyl vinyl ether, 6,7-epoxyheptyl vinyl ether, o-vinylbenzyi glycidyl ether, m-vinylbenzyl glycidyl ether, p-vinylbenzyl glycidyl ether, 3- vinylcyclohexene oxide. In such alternative embodiment the polar termonomer having at least one epoxy group is preferably a glycidyl(alkyl) aciylate. Particular preference is given to using glycidyl aciylate or glycidyl methacrylate.

Proportions of the monomers in the niti ile rubber component (ii)

The proportions of repeating units of the three different monomers types, i.e, the α,β-unsaturated nitriie(s), the conjugated diene(s), and the copolymerizable polar termonomer(s) in the nitrile rubber component (ii) can vaty widely. Typically the nitrile rubber component (ii) is based on

10 to 60 % by weight of one or more α,β-unsaturated nitrile(s),

39.9 to 89.9 % by weight of one or more conjugated diene(s), and

0.1 to 30 % by weight, preferably 0.1 to 20 % by weight, more preferably 0.1 to 10 % by weight of one or more copolymerizable polar termonomers,

wherein the proportions of all monomers gives a total of 100% by weight.

In another embodiment the nitrile rubber component (ii) is based on

25 to 50 % by weight of one or more α,β-unsaturated nitrile(s),

49.9 to 74.9 % by weight of one or more conjugated diene(s), and

0.1 to 30 % by weight, preferably 0.1 to 20 % by weight, more preferably 0.1 to 10 % by weight of one or more copolymerizable polar termonomers,

wherein the proportions of all monomers gives a total of 100% by weight.

The aforementioned % by weight refer to the repeating units of the respective monomer being present in the nitrile rubber component (ii).

The preparation of the nitrile rubbers (i) via polymerization of the abovementioned monomers is well known to the person skilled in the art. It is typically performed by emulsion polymerisation as extensively described in the literature (e.g. Houben-Weyl, Methoden der Organischen Chemie [Methods of organic chemistry], Vol. 14/1 , Georg Thieme Verlag Stuttgart 1961). In the alternative it is also possible to prepare such nitrile rubbers (i) via solution polymerization as also sufficiently described e.g. in EP-A-2 385 074.

Nitrile rubbers which can be used for the purposes of the invention as nitrile rubber component (ii) are available commercially, e.g. as products from the product range marketed under the trademark rynac ^® from Lanxess Deutschland GmbH. A particularly preferred nitrile rubber (ii) is a terpolymer based on aciylonitrile, 1,3-butadiene and one further copolymerizable polar termonomer selected from the group consisting of α,β- unsaturated monocarboxylic acids, their esters, their amides, ,β-unsaturated dicarboxylic acids, their monoesters, their diesters, their corresponding anhydrides, and their amides. More preferably the nitrile rubber (ii) is a terpolymer based on acrylonitrile, 1,3-butadiene and one further copolymerizable polar termonomer selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic acid, methyl acrylate, ethyl acrylate, propyl acrylate, n- butyl acryiate, teit-butyl acrylate, 2-ethylhexyl acrylate, n-dodecyl acrylate, methyl methactylate, ethyl methacrylate, butyl metliaciyiate and 2-ethylhexyl methaciylate.

Even more preferably the nitrile rubber (ii) is a terpoiymer based on acrylonitrile, 1,3-butadiene and one further copolymerizable polar termonomer selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, and maieic acid.

In a preferred embodiment of the present invention the thermoplastic materials are thus based on (i) one or more polyamide(s), more preferably polyamide 6, and

(ii) one or more nitrile rubber(s) based on

25 to 50 % by weight of repeating units of one or more α, β -unsaturated nitrile(s),

49.9 to 74.9 % by weight of repeating units of one or more conjugated diene(s), and 0.1 to 30 % by weight, more preferably 0.1 to 20 % by weight, and most preferably 0.1 to 10% by weight of repeating units of one or more copolymerizable polar termonomers, wherein the proportions of all monomers gives a total of 100% by weight.

wherein the weight ratio of the polyamide(s) (i) to the nitrile rubber(s) (ii) is (10-50):(90-50), preferably (20-40):(80-60), more preferably (25-35):(75-65), based on the total weight of the polyamide (i) and the nitrile rubber (ii) characterized in that the nitrile rubber(s) represent(s) the continuous phase.

An alternative particularly preferred nitrile rubber (ii) is a terpoiymer based on acrylonitrile, 1,3- butadiene and one further copolymerizable polar termonomer having at least one epoxy group.

As even more preferred alternative embodiment the nitrile rubber (ii) is a terpoiymer based on acrylonitrile, 1 ,3-butadiene and one further copolymerizable polar termonomer having at least one epoxy group chosen from the group consisting of 2-ethylglycidyl acrylate, 2-ethylg!ycidyI methacrylate, 2-(n-propyl)glycidyl acrylate, 2-(n-propyl)glycidyl methacrylate, 2-(n-butyl)glycidyl acrylate, 2-(n-butyi)glycidyl methacrylate, glycidyl methacrylate, glycidylmethyl methaciylate, glycidyl acrylate, (3 ',4'-epoxyheptyl)-2-ethyl acrylate, (3 ',4'-epoxyheptyl)-2-ethyl methaciylate, 6',7 ^' -epoxyheptyl acrylate, 6',7'-epoxyheptyl methaciylate, allyl glycidyl ether, allyl 3,4- epoxyheptyl ether, 6,7-epoxyheptyl allyl ether, vinyl glycidyl ether, vinyl 3,4-epoxyheptyl ether, 3,4-epoxyheptyl vinyl ether, 6,7-epoxyheptyl vinyl ether, o-vinylbenzyl glycidyl ether, m- vinylbenzyl glycidyl ether, p-vinylbenzyl glycidyl ether, and 3-vinylcyclohexene oxide. Particularly preferred is a terpoiymer comprising repeating units of acrylonitrile, 1,3-butadiene and a glycidyl(alkyl) acrylate. Most preferred is a terpoiymer comprising repeating units of acrylonitrile, 1,3-butadiene and glycidyl acrylate or glycidyl methaciylate. In an alternative embodiment it is also possible to use the partially liydrogenated derivatives of the above defined nitrile rubber components (i). In such partially liydrogenated derivatives the C=C double bonds of the diene repeating units incorporated into the terpolymer have been liydrogenated to some extent. The degree of hydrogenation of the diene units incorporated into the polymer is usually in the range from 50 to 99%, preferably in the range from 75 to 98.5%, more preferably in the range from 80 to 98%, and particularly preferably in the range of from 85 to 96%..

Said partially liydrogenated nitrile rubbers which can be used for the purposes of the invention as nitrile rubber component (ii) are also available commercially, e.g. as products from the product range with trademarks Therban® from Lanxess Deutschland GmbH, e.g. from the Therban®LT range from Lanxess Deutschland GmbH, e.g. Therban®LT 2157, and also Therban®VP KA 8882. An example of carboxylated liydrogenated nitrile rubbers is the Therban®XT range from Lanxess Deutschland GmbH. Examples of liydrogenated nitrile rubbers with low Mooney viscosities and therefore with improved processability are products from the Therban® AT range, e.g. Therban AT VP KA 8966.

Mooney viscosity:

The Mooney viscosity (ML 1+4 @ 100°C) of the nitrile rubbers or liydrogenated nitrile rubbers respectively, to be used according to the invention is in the range from 1 to 120 Mooney units (MU), preferably in the range from 5 to 80 MU, particularly preferably in the range from 10 to 70 ML ¹ . The Mooney viscosity is determined according to ASTM D1646.

Mw and Mn:

The nitrile rubbers that can be used in the thermoplastic materials pursuant to the invention usually have a number-average molecular weight M _n in the range from 35 000 to 300 000, preferably in the range from 60 000 to 300 000 and particularly preferably in the range from 60 000 to 250 000 and very particularly preferably in the range from 80 000 to 200 000 and most preferably in the range from 70 000 to 200 000. They moreover have a polydispersity index D = M„M„ in the range from 1.5 to 6, preferably in the range from 1.8 to 5.5, particularly preferably in the range from 2 to 5 where M _w is the weight-average molecular weight and M _n is the number-average molecular weight.

In a preferred embodiment the thermoplastic material according to the invention additionally contains

(iii) at least one antioxidant. Appropriately bisphenolic antioxidants may be used, more preferably sterically hindered polynuciear phenols which are e.g. commercially available as Vulkanox SKF from Lanxess Deutschland GmbH. In the alternative diphenylamines like 4,4'~bis(l,l-dimethylbenzyl)- diphenylamine can be used (e.g. sold as Luvomaxx CDPA by Lehmann&Voss).

Such antioxidant is typically used in an amount of 0.1 to 10 parts by weight, preferably in an amount of 0.25 to 5 parts by weight and more preferably in an amount of 0.5 to 2.5 parts by weight, based on the 100 parts of polyamide(s) and nitrile rubber(s) (ii) In the alternative to the bisphenolic antioxidant oligomerized 2,2,4-trimethyl-l _J 2-dihydroquinoline (TMQ), styrenated diphenylamine (DDA), octylated diphenylamine (OCD) or the zinc salt of 4- and 5-methylmercaptobenzimidazole (ZMB2) may also be used. It is also possible to use combinations of the antioxidants mentioned.

In an alternative embodiment the thermoplastic material according to the invention additionally contains

(iv) at least one cross-linking agent, more preferably a cross-linking agent based on a phenol- formaldehyde based resin, even more preferably a halogene activated octylphenole- formaldehyde resin. As halogene activated octylphenole formaldehyde resin Resin SP 1055 sold by SI Group Inc. Shenectady, NY, U.S.A. may for example be used. Other typical cross-linkers or crosslinking systems may also be used, however, phenolic resins have proven to give an appropriate cross- linking density on the one hand and still allow re-processing during further handling steps on the other hand.

Such cross- 1 inking agent is typically used in an amount of 0.1 to 15 parts by weight, preferably in an amount of 0,5 to 10 parts by weight and more preferably in an amount of 1 to 8 parts by weight, and most preferably 1 to 2 parts by weight, based on the 100 parts of polyamide(s) and nitrile nibber(s) (ii).

The amount has to be chosen in a way so that the cross-linking agents cause dynamic cross-linking of the remaining double bonds in the nitrile rubber component (ii) during the mixing process on the one hand but the resulting thermoplastic vulcanizate shall still meet the requirement of being re- processable. Adding 1 to 2 parts by weight of the cross-linking agent advantageously results in an increase of Shore A hardness of e.g. 83 to approximately 88. In an alternative embodiment the thermoplastic material according to the invention additionally contains

(v) at least one pfasticizer, preferably an N-(hydroxyalkyl)benzenesulfonainide-type plasticizer, more preferably N-(2-hydroxypropyl) benzenesulphonamide.

In principle plasticizers may be used which are compatible with the nitrile rubber component (ii) as well as the polyamide component (i) and, in addition, are non-volatile to overcome operating temperatures of su tp 260°C.

The preferred plasticizer N-(2-hydroxypropyl) benzenesulphonamide may e.g. be purchased as Proviplast 2102 from Proviron or as Unite 225 from Lanxess Corporation.

Such plasticizer is ty ically used in an amount of 0.1 to 20 parts by weight, preferably in an amount of 0.5 to 15 parts by weight and more preferably in an amount of 0.1 to 1 0 parts by weight, based on the 100 parts of polyamide(s) and nitrile rubber(s) (ii).

In view of the above a preferred embodiment relates to a thermoplastic material containing the defined polyamide(s) (i) and nitrile rubber(s) (ii) as mentioned above and comprises additionally

(iii) at least one antioxidant, more preferably one antioxidant which is a bisphenolic antioxidant, even more preferably a sterically hindered polynuclear phenol,

(iv) at least one cross-linking agent, more preferably one cross-linking agent based on a phenol- formaldehyde based resin, even more preferably octyiplienole-formaldehyde resin, and

(v) at least one plasticizer, preferably an alkylenebzenesulfonamide-type plasticizer.

Apart from the above mentioned additional components the thermoplastic mateiral may contain by way of example, further additives like fillers, filler activators, accelerators, antiozonants, processing aids, extender oils, reinforcing materials, mould-release agents, and also scorch inhibitors.

Examples of fillers that can be used are carbon black, silica, barium sulphate, titanium dioxide, zinc oxide, calcium oxide, calcium carbonate, magnesium oxide, aluminium oxide, iron oxide, aluminium hydroxide, magnesium hydroxide, aluminium silicates, diatomaceous earth, talc, kaolins, bentonites, carbon nanotubes, Teflon (the latter preferably in powder form), or silicates.

Particular filler activators that can be used are organic silanes, e.g. vinyltrimethyloxysilane, vinyldimethoxymethylsilane, vinyitriethoxysilane, vinyltris(2~methoxyethoxy)silane,

^" N-cyclohexyl-3 -aminopiOpyltrimethoxysilane, 3-aminopropyltrimethoxysilane, methyltrimethoxy- silane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethyl- ethoxysilane, isooctyltrimethoxysilane, isooctyltriethoxysilane, hexadecylti'imethoxysilane or (octadecyl)methyldimethoxysilane. Examples of other filler activators are substances with surface activity, e.g, triethanolamine and ethylene glycols whose molar masses are from 74 to 10 000 g/mol. The amount of filler activators is usually from 0 to 10 phr, based on 100 phr of the elastomers in the rubber component 2).

Examples of mould-release agents that can be used are: saturated and partially unsaturated fatty and oleic acids and their derivatives (fatty acid esters, fatty acid salts, fatty alcohols, fatty acid amides), these preferably being used as a constituent of a mixture, and also products that can be applied to the mould surface, e.g. products based on !ow-molecular-weight silicone compounds, products based on fluoropolymers, and also products based on phenolic resins.

The amount used of the mould-release agents as constituent of a mixture is from about 0 to 10 partx by weight, preferably from 0.5 to 5 parts by weight, based on the 100 parts of polyamide(s) and nitrile rubber(s) (ii)

Preparation process:

The thermoplastic materials in accordance with the present invention can be prepared by mixing one or more polyamide(s) (i) and one or more nitrile rubbers (ii) in a mixing device at a temperature which lies above the melting temperature of the polyamide and up to 350°C, wherein the nitrile rubbers) comprise(s) repeating units derived from at least one ,β unsaturated nitrile, at least one conjugated diene and one or more further copolymerizable polar monomers and wherein the weight ratio of the polyamide (i) to the nitrile rubber (ii) as fed to the mixing device extruder is (10-50):(90-50), preferably (20-40):(80-60), more preferably (25-35):(75-65), based on the total weight of the polyamide(s) (i) and the nitrile rubber(s) (ii).

In such process the mixing takes place until the nitrile rubber (ii) represents the continuous phase in the thermoplastic material.

To the extent further components are added mentioned above as components (in) to (v) and else, these are also fed into the mixing device.

Preferably the temperature which shall be kept in the above mentioned range for the whole dui'ation of the mixing process lies in a range of from 170°C to 260°C, under the proviso that it has to be chosen above the melting temperature of the polyamide(s) used. The mixing is carried out for a sufficient duration to ensure that the nitrile rubber component (i) is present as continuous phase (matrix). Such process may be carried out continuously or discontinuously (the latter meaning "batch-wise").

Continuous process (extruder + mill-mixing)

In one embodiment the process is carried out continuously in a two-step process comprising

(1 ) as first step feeding and processing one or more polyamide(s) (i) and one or more nitrile rubbers (ii) in an extruder as a first mixing device at a temperature which lies above the melting temperature of the polyamide(s) and up to 350°C, wherein the nitrile rtibber(s) comprise(s) repeating units derived from at least one α,β unsaturated nitrile, at least one conjugated diene and one or more further copolymerizable polar monomers and wherein the weight ratio of the polyamide (i) to the nitrile rubber (ii) as fed to the extruder is (10- 50):(90-50), preferably (20-40):(80-60), more preferably (25-35):(75-65), based on the total weight of the polyamide(s) (i) and the nitrile rubber(s) (ii), and

(2) subjecting to and processing the material obtained in step (1 ) in a mill.

To the extent further components are added mentioned above as components (iii) to (v) and else, these are also fed into the extruder in step (1). It is also possible to prepare a premix of the nitrile rubber component (ϋ) and the optional stabilizer (iii) before feeding the extruder in order to avoid further mixing steps during the mixing

Discontinuous process (internal mixer);

In an alternative embodiment the process is carried out discontinuously or in other words batch- wise by feeding one or more polyamide(s) (i) and one or more nitrile rubbers (ii) to an internal mixer as mixing device wherein the nitrile rubber(s) comprise(s) repeating units derived from at least one α,β unsaturated nitrile, at least one conjugated diene and one or more further copolymerizable polar monomers and wherein the weight ratio of the polyamide (i) to the nitrile rubber (ii) as fed to the internal mixer is (10-50):(90-50), preferably (20-40):(80-60), more preferably (25-35):(75-65), based on the total weight of the polyamide(s) (i) and the nitrile rubber(s) (ii).

Again the mixing is performed to assure that the nitrile rubber (ii) represents the continuous phase in the thermoplastic material.

To the extent further components are added mentioned above as components (iii) to (v) and else, these are also fed into the internal mixer, too. Such internal mixers allow both to transfer large quantities of (shear) energy into the mixture and to control the process at high temperatures needed to melt the polyamide. Hence such internal mixer is well-suited to prepare the thermoplastic materials according to the invention, essentially controlled by a fluid temperature being set to the maximum permitted level and by a flexile rotor equipment that allows to keep the mixture temperature at 220°C to 260°C.

Internal mixers are well-known in the art and are commercially available. A suitable internal mixer is e.g. a G 5E intermeshing internal mixer, enabling high rotation speeds (> 150rRpm) and high temperatures (>2BB°C)

The invention also relates to the use of the inventive thermoplastic materials as thermoplastic elastomers or thermoplastic vtilcanizates for the manufacture of rubber based articles requiring good abrasion- and wear-resistance such as hard rollers and rubber-based articles requiring good resistance against fuels and low fuel permeation properties,

Examples:

The following substances were used in the following examples:

Krynac ^® X 740 "XNBR" rubber, namely a terpolymer of aciylonitrile, 1,3- butadiene, and a carboxylic acid

Aciylonitrile content (wt %) 26.5 +/- 1.5

Mooney viscosity (ML (1+4) at 100 °C) 38 +/- 4

Carboxylic acid content (wt %) 7

Durethan ^® B 29 polyamide 6 without any reinforcing or modifying additives

Examples 1-3 (comparative examples ^' ):

At a temperature of 230°C to 260°C, i.e. above the melting temperature of polyamide 6 a two- component blend of Krynac ^® X740 and Durethan ^® B 29 has been processed in a twin-screw co- rotating extruder (ZS type extruder with gravimetric feeding) plus accessory equipment. During the process a rope having a diameter of ca. 5 mm of a transparent, opake material could be produced which was chopped to form hard, brownish granules. The polymer ratio was varied as shown in Table 1.

A stress-strain test according to DIN 53505 and a micro-optical investigation applying Atomic Force Microscopy ("AFM") the latter used in order to visualize the phase distribution and morphology gave both evidence that the polyamide represents the continuous phase after extrusion. The results of the stress-strain test are shown in Figure 1. These curves in Figure 1 show the typical behaviour for blends with rubber particles in the continuous thermoplastic matrix, comprising a first part of the curve at lower strain being typical for energy elastic materials which then passes into a second part of the curve at higher strain being typical for plastic deformation. A photograph of the granules obtained for Example 2 is shown in Figure 2. The respective micro-optical investigation of Example 2 applying AFM is shown in Figure 5, The hard phase of Durethan ^® B 29 occurs as light areas and the soft phase of Krynac ^® X740 occurs as dark areas. Examples 4-6 (examples according to the invention);

The blends obtained in Examples 1 to 3 after the processing step via the twin-screw extruder were additionally subjected to a milling step on a hot mill,

The material obtained after this milling step was also subjected to the stress-strain test according to DIN 53505, The resulting curves are shown in Figure 3. A photograph of the sheet obtained for Example 5 is shown in Figure 4, The respective micro-optical investigation applying AFM is shown in Figure 5.

Differently to the curves in Figure 1 the curves of the inventive materials in this Figure 3 show a behaviour for blends with thermoplastic particles in a continuous nitrile rubber matrix, showing a curve illustrating an entropy elastic behaviour. The curves in Figure 3 do not show the first part at lower strain which is typical for energy elastic materials nor do they show a second part at higher strain being typical for plastic deformation, Example 7a and 7b (examples according to the invention :

Polyamide 6 and Krynac X740 were mixed in an internal mixer with a flexible rotor equipment in a weight ratio of 30:70 while keeping the temperature in a range of 215°C to 230°C, After a mixing time of 6 minutes (Example 7a) and 10 minutes (Example 7b) the material was dumped and also subjected to the stress-strain test according to DIN 53505 and the respective micro-optical investigation applying AFM. The stress-strain curves are depicted in Figure 6 and the AFM photographs in Figure 7 (Example 7a) and 8 (Example 7b). Both, the stress-strain curve as well as the AFM records show that the phase distribution and the basic properties are influened by the mixing efficiency, hence by the mixing time. The following values for tensile strength ("TS") _> elongation at break ("EB"), hardness ("H'VShore A) and compression ("CS"; %) were obtained as shown in Tabie 2:

Table 2:

Mixing time 6 min 10 min

TS MPa 14,3 12.6

EB % 120 140

H Shore A 80 83

Com pression Set (CS) at 70h/RT

CS % 58