KR20010020282A - Polyamide composition for method of manufacturing articles by extrusion blow-moulding, and articles obtained - Google Patents

Abstract

The present invention relates to polyamide compositions having rheological properties in the molten state and improved flexibility at low temperatures, for example, which are compatible with molding processes by extrusion blow molding. The composition contains a polyamide thermoplastic polymer based matrix and at least one impact strength modifier present at a concentration of 10-50% by weight of the composition, wherein the composition has an elastic modulus of less than 1500 MPa. The invention also relates to a first part (1) obtained by extrusion blow molding a rigid polyamide, likewise a second part (2) obtained by extrusion blow molding a hard polyamide composition and a polyamide composition corresponding to Example 1 A product in the form of a tube consisting of a hollow third part 3 made by extrusion blow molding. Extrusion of each part takes place continuously.

Description

POLYAMIDE COMPOSITION FOR METHOD OF MANUFACTURING ARTICLES BY EXTRUSION BLOW-MOULDING, AND ARTICLES OBTAINED}

The present invention relates to a thermoplastic composition having properties suitable for use in a method of manufacturing a part or an article by extrusion blow molding.

It is more particularly directed to thermoplastic polyamide based compositions having a low modulus of elasticity which allows for the manufacture of parts or articles having flexible or at least flexible portions.

Polyamide based compositions have long been used as raw materials for the manufacture of parts or products molded according to various molding techniques. Among these techniques, extrusion blow molding is used for the production of hollow articles such as bottles, tubes, tanks, hoses and pipes. The use of polyamide compositions in such molding techniques is making significant progress.

However, the rheological properties in the molten state of the polyamide based composition must be improved for the implementation of extrusion blow molding techniques. Therefore, a number of solutions, such as increasing the degree of polymerization or adding a bifunctional chain extender to increase the molecular weight of the polyamide, have already been proposed to improve the rheological properties.

It is also proposed to add ionomer elastomers or crosslinkers, as in patent applications WO93 / 04129, WO90 / 07556 and WO90 / 07555.

However, it is not possible with these compositions to produce products or parts with sufficient flexibility particularly required in certain parts of a heat engine, such as those that require a particular flexibility and high impact resistance.

In fact, these parts are often tense during assembly, or during operation of the engine or vehicle, which can cause the engine or vehicle to break immediately or in the course of aging, or wholly interfere with their installation. Component flexibility should not be affected by temperature. In fact, air and water pipes in heat engines can reach up to 130 ° C if they are installed in a cold place and the engine is running. To avoid any deterioration of these tubes, the flexibility of the parts must be adequate between cold and elevated temperatures (about 150 ° C).

Moreover, known compositions are not suitable for the manufacture of parts such as tubes, hoses and tubes with flexible parts associated with hard parts. Therefore, there is a need to manufacture the part in the form of a large number of components that are assembled into a mechanical connection or system such as a color or a gasket. In such a system, the soft portion is typically made of an elastomeric material, such as a thermoplastic rubber.

One of the objects of the present invention is to provide a polyamide-based composition having rheological properties in the molten state and improved flexibility at low temperatures, for example, which is compatible with molding methods by extrusion blow molding.

Another object of the present invention is to provide a composition which enables the production of parts consisting of interconnected soft and hard parts. Such parts can advantageously be produced by continuous extrusion blow molding techniques.

To this end, the present invention provides a thermoplastic composition comprising a matrix based on a thermoplastic polyamide polymer and at least one impact modifier present at a concentration of 10 to 50% by weight of the composition, the modulus of elasticity of such a composition Is less than 1500 MPa.

According to another preferred property of the invention, the composition contains a plasticizer for the polyamide matrix, which is present at a concentration of 5 to 20% by weight of the polyamide matrix.

As another part, the composition advantageously contains a chain extender for the polyamide matrix, which is present at a concentration of 0.05 to 5% by weight of the polyamide matrix.

The thermoplastic composition of the invention advantageously has an elastic modulus of less than 1000 MPa.

Thus, the compositions of the present invention allow for the manufacture of parts such as tubes, hoses and tubes that have a degree of flexibility sufficient to be easily installed in a heat engine, for example, without the need for molding with complex profiles.

Further, the polyamide based thermoplastic composition can be combined with a conventional thermoplastic polyamide composition to produce a part including hard powder and soft portions interconnected to each other. In other words, the connection between each of these parts is obtained by the compatibility of the matrix constituting the composition used without the use of external fixation or binding means. The manufacture of such parts is obtained, in particular, using continuous injection, extrusion or molding techniques.

Advantageously, the soft part of the part has an expanded shape that can further enhance the flexibility of the tube or tube. This kind of form for the part is obtained in particular by the practice of the technique of extrusion blow molding.

According to one preferred feature of the invention, the thermoplastic composition has a melt flow index of 0.5 g / 10 minutes to 8 g / 10 minutes. This index is measured by applying a 5 kg load at 275 ° C. This melt index range makes the composition usable particularly in molding methods utilizing the techniques of extrusion blow molding.

Furthermore, the composition according to the invention advantageously has a notched IZOD impact strength (measured at 23 ° C.) of at least 800 J / m.

Thermoplastic polyamide matrices suitable for the present invention include in particular semicrystalline polyamides.

The term semicrystalline polyamide suitable for the invention refers to saturated aliphatic dicarboxylic acids and primary diamines, such as, for example, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, fatty acids such as dimers of fatty acids or mixtures thereof. Is a polymer obtained by polycondensing linear or branched saturated aliphatic primary diamines having 4 to 12 carbon atoms, such as hexamethylenediamine, trimethylhexamethylenediamine, tetramethylenediamine, m-xylenediamine or mixtures thereof; Containing hydrocarbon chains of 4 to 12 carbon atoms Polyamides obtained by direct monocondensation of aminoalkanoic acids or by hydrolytic opening and polymerization of lactams derived from said acids; Copolyamides obtained from the original monomers of the aforementioned polyamides, or with other monomers such as terephthalic acid and / or isophthalic acid; Diamines comprising polyethylene glycol or polypropylene glycol chains as organic radicals; It means the said mixture of the said polyamide or its copolymer.

Examples of polyamides obtained by polycondensation of diacids and diamines include the following:

Nylon 4,6 (polymer of tetramethylenediamine and adipic acid),

Nylon 6,6 (polymer of hexamethylenediamine and adipic acid),

Nylon 6,9 (polymer of hexamethylenediamine and azelaic acid),

Nylon 6,10 (polymer of hexamethylenediamine and sebacic acid),

Nylon 6,12 (polymer of hexamethylenediamine and dodecanedioic acid), and

Nylon 12,12 (polymer of dodecanediamine and dodecanedioic acid),

Examples of polyamides obtainable by homopolycondensation of lactams or α, ω-amino acids which may be suitable include the following:

Nylon 4 (4-aminobutanoic acid or Polymers of butyrolactam),

Nylon 5 (polymer of 5-aminopentanoic acid or δ-amylolactam),

Nylon 6 (polymer of ε-caprolactam),

Nylon 7 (polymer of 7-aminoheptanoic acid),

Nylon 8 (polymer of capryllactam),

Nylon 9 (polymer of 9-aminononanoic acid),

Nylon 10 (polymer of 10-aminodecanoic acid),

Nylon 11 (polymer of 11-aminoundecanoic acid),

Nylon 12 (polymer of 12-aminododecanoic acid or lauryllactam).

Copolyamides include the following:

Nylon 6,6 / 6,10 (copolymer of hexamethylenediamine, adipic acid and sebacic acid),

Nylon 6,6 / 6 (copolymer of hexamethylenediamine, adipic acid and caprolactam),

Nylon 6/12,

Nylon 6/11,

Nylon 6/6, 36.

Preferred polymers are nylon 6,6, nylon 6 or copolymers thereof, mixtures of these polyamides with other polyamides such as PA 6 / 6,36.

The polyamide is advantageously present in the composition at a weight concentration of 55% to 70%.

The impact modifier of the composition is advantageously a compound having a Tg of less than 0 ° C, preferably less than -20 ° C. Moreover, in order to obtain compositions having very low modulus, such as less than 1000 MPa, these compounds advantageously have modulus of less than 200 MPa.

Preferred modifiers of the present invention are polyolefins with or without elastomeric properties.

According to one preferred property of the invention, at least some elastomeric compounds of the composition have a polar functional group capable of reacting with the polyamide. Such polar functional groups can be, for example, acids, anhydrides, acrylics, methacryl or epoxy functional groups.

Such functional groups are typically grafted into the macromolecular chains of the compound.

Suitable polyolefins for the present invention include copolymers of ethylene and α-olefins, such as polyethylene, polypropylene, polybutylene or ethylene / propylene diene and ethylene-propylene copolymers.

Very particularly preferred polymers include ultra low density polyethylene known as ULDPE. These compounds have 4 to 10 carbon atoms, melt flow index (index measured under 2.16 kg load at 190 ° C. according to standard ASTM D 1238) 0.5 to 7 g / 10 min, preferably less than 1 g / min, and density 0.9 g / cm Less than ³ , advantageously from 0.86 to 0.90 g / cm ³ of a-olefin and a copolymer of ethylene.

Advantageously, the ULDPE polyethylene comprises grafted polar functional groups such as acid or anhydride functional groups such as maleic anhydride functional groups. The weight concentration of the polar functional group in the ULDPE polyethylene can vary very widely. For example, the concentration may be 0.01 to 0.8% by weight relative to polyethylene. Such ULDPE copolymers have been known for many years because of their preparation. It is especially marketed by the company ENICHEM under the trade name "Clearflex CH GO".

Grafts and copolymers with polar functional groups such as maleic anhydride are also known and are described in particular in European patent applications 581360 and 0646247.

The concentration (or elastic modifier) of the impact modifier in the composition depends in particular on the level of impact strength desired. This concentration is preferentially 10 to 50% by weight, preferably 20 to 40% by weight of the polyamide matrix.

According to another feature of the invention, the thermoplastic composition may contain a plasticizer for the polyamide matrix. Such plasticizers are advantageously present at a concentration of 5 to 20% by weight relative to the weight of the polyamide matrix.

Examples of suitable plasticizers include sulfonamides such as o, p-toluenesulfonamide, N-ethyl-o, p-toluenesulfonamide, N-butylbenzenesulfonamide, alkyl parahydroxybenzoates of 1 to 20 carbon atoms, polyethylene Glycols and polypropylene glycols.

According to another feature of the invention, this is more particularly preferred when the thermoplastic composition is shaped by extrusion blow molding techniques and the chain extender for the polyamide matrix is present at a weight concentration of 0.05 to 5% by weight of the polyamide matrix.

The polymer-chain extender increases the molecular weight of the polyamide matrix to obtain rheological properties in the molten state of the composition which can be compatible with the method of extrusion blow molding while retaining the specific flexibility of the resulting product, ie the low modulus of the composition. can do.

As the chain extender compound, mention may be made of compounds containing at least two functional groups capable of reacting with terminal amines or acid functional groups of the polyamide. Preferred functional groups of the present invention are epoxy, anhydride or isocyanate functional groups.

Compounds of this kind are described in numerous documents such as US Pat. Nos. 4,433,116, 4,417,031 and 4,417,032 and European 0 295 905.

Thus, epoxy compounds are preferred difunctional compounds of the present invention. Examples of the epoxy compound include diepoxypolyglycol, diepoxybisphenol A, triglycidyl ether, diglycidyl ether and diepoxysphenol F. Such epoxy compounds advantageously have a molecular weight of at least 1000 g.

The composition of the present invention may also contain one or more other components. Such components are additives that enhance their properties against heat or light stability or withdrawal of molded articles without modifying the basic properties of the composition.

Thus, examples include heat stabilizers such as alkali metal halides, light stabilizers such as amines and containment phenols, lubricants such as waxes and nucleating agents.

The composition of the present invention may, of course, contain pigments or dyes, and other additives commonly used.

The composition of the present invention can be prepared by mixing various components. This mixing operation is advantageously usually carried out in a single screw or twin screw extruder. The mixture is then extruded in strand form and cut into granules.

The granules thus obtained are fed in units for molding by molding, injection, extrusion or grinding.

The compositions of the invention are more particularly suitable for the practice of molding techniques by extrusion blow molding, such as continuous extrusion blow molding, 2D or 3D extrusion blow molding.

Indeed, the compositions of the present invention have physical or rheological properties that make them particularly suitable for the manufacture of parts such as hollow parts, such as, for example, air tubes for fuel engines, fuel tubes or cooling systems.

In detail, the advantages and objects of the present invention will become more apparent from the following examples to illustrate the present invention and from a single view showing an overview of the parts composed of hard and soft parts.

The percentages shown in the examples below are given in weight relative to the total composition, unless otherwise indicated.

The properties of the composition are measured according to the standards indicated above. Melt viscosity index (MFI) is measured at 275 ° C under a load of 5000 g.

The relative viscosity (η _rel ) of polyamide 6 is measured according to standard methods (ISO 307, 1984) with a 1 wt% solution of polyamide in 95.7 wt% sulfuric acid.

Example 1

The composition according to the invention is obtained by mixing the respective components described below with a twin screw extruder of type W & P ZSK 40 at a feed rate of 30 kg / h and a rotary screw speed of 270 revolutions per minute at a temperature of 270 ° C.

Polyamide 6 (η _rel = 4.8): 58.0%

Impact modifier: 40.0%

(PRIMEFLEX (trademark) AFG4W)

-Chain Extender: 0.80%

(ARALDITE (trademark) GT7071)

Pigment (Carbon Black): 0.90%

Lubricant (calcium stearate): 0.30%

The composition has the following properties:

Melt Viscosity Index (MFI): 0.9 g / 10 min

Elastic modulus: 1300 MPa

-IZOD impact strength: 900 J / m

Impact modifier is a ULDPE polyethylene sold by Encheme under PRIMEFLEX® AFG4W. The compound has a density of 0.885 g / cm ³ , a melt viscosity index of 0.7-0.8 g / 10 min and a Tg of -45 ° C. measured at 190 ° C. under a load of 2.16 kg.

The chemical reagent used as the chain extender is a compound containing an epoxy functional group (epoxy equivalent of 1.90 to 2.0 eq / kg) sold by ARALDITE® GT7071.

The black pigment used is mineral carbon black or a mixture of mineral carbon black and nigrosine.

Example 2

A new composition was prepared according to the method of Example 1 at a mixing temperature of 250 ° C.

The compounding ratio of this composition is as follows:

Polyamide 6 (η _rel = 3.8): 33.60%

Copolyamide 6 / 6-36: 30.0%

(NYCOA (registered trademark) 2012)

Impact modifier: 35.0%

(PRIMEFLEX (trademark) AFG4W)

-Chain Extender: 0.80%

(ARALDITE (trademark) GT7071)

Antioxidant: 0.30%

Lubricant (calcium stearate): 0.30%

The composition has the following properties:

Melt Viscosity Index (MFI): 1.2 g / 10 min

Elastic modulus: 1300 MPa

-IZOD impact strength: 1000 J / m

Example 3

According to the method of Example 2, a composition according to the present invention having the following compounding ratio was prepared.

Polyamide 6 (η _rel = 3.8): 20.1%

Copolyamide 6 / 6-36: 48.5%

(NYCOA (registered trademark) 2012)

Impact modifier: 30.0%

(PRIMEFLEX (trademark) AFG4W)

Chain extender: 0.8%

(ARALDITE (trademark) GT7071)

Antioxidant: 0.30%

Lubricant (calcium stearate): 0.30%

The composition has the following properties:

Melt Viscosity Index (MFI): 1.9 g / 10 min

Elastic modulus: 1300 MPa

-IZOD impact strength: 1000 J / m

Example 4

According to the method of Example 2, a composition according to the present invention having the following compounding ratio was prepared.

Polyamide 6 (η _rel = 3.8): 18.6%

Copolyamide 6 / 6-36: 45.0%

(NYCOA (registered trademark) 2012)

Impact modifier: 35.0%

(PRIMEFLEX (trademark) AFG4W)

-Chain Extender: 0.80%

(ARALDITE (trademark) GT7071)

Antioxidant: 0.30%

Lubricant (calcium stearate): 0.30%

The composition has the following properties:

Melt Viscosity Index (MFI): 1.5 g / 10 min

Elastic modulus: 1200 MPa

-IZOD impact strength: 1000 J / m

Example 5

According to the method of Example 2, a composition according to the present invention having the following compounding ratio was prepared.

Polyamide 6 (η _rel = 3.8): 17.1%

Copolyamide 6 / 6-36: 41.5%

(NYCOA (registered trademark) 2012)

Impact modifier: 40.0%

(PRIMEFLEX (trademark) AFG4W)

-Chain Extender: 0.80%

(ARALDITE (trademark) GT7071)

Antioxidant: 0.30%

Lubricant (calcium stearate): 0.30%

The composition has the following properties:

Melt Viscosity Index (MFI): 1.2 g / 10 min

Modulus of elasticity: 900 MPa

-IZOD impact strength: 1100 J / m

Example 6

According to the method of Example 2, a composition according to the present invention having the following compounding ratio was prepared.

Copolyamide 6 / 6-36: 63.6%

(NYCOA (registered trademark) 2012)

Impact modifier: 35.0%

(PRIMEFLEX (trademark) AFG4W)

-Chain Extender: 0.80%

(ARALDITE (trademark) GT7071)

Antioxidant: 0.30%

Lubricant (calcium stearate): 0.30%

The composition has the following properties:

Melt Viscosity Index (MFI): 2.2 g / 10 min

Elastic modulus: 1000 MPa

-IZOD impact strength: 1100 J / m

Example 7

According to the method of Example 2, a composition according to the present invention having a blending ratio of 260 ° C. was prepared.

Polyamide 6 (η _rel = 4.8): 64.4%

Impact modifier: 28.0%

(PRIMEFLEX (trademark) AFG4W)

Plasticizer: 7.0%

(N-BBSA or N-butylbenzenesulfonamide)

Antioxidant: 0.30%

Lubricant (calcium stearate): 0.30%

The composition has the following properties:

Melt Viscosity Index (MFI): 2.2 g / 10 min

Modulus of elasticity: 800 MPa

-IZOD impact strength: 1200 J / m

Example 8

According to the method of Example 2, a composition according to the present invention was prepared having the following blending ratio at a mixing temperature of 260 ° C.

Polyamide 6 (η _rel = 4.8): 64.7%

Impact modifier: 28.0%

(PRIMEFLEX (trademark) AFG4W)

Plasticizer: 7.0%

(Polyethylene glycol of molecular weight 200)

Antioxidant: 0.30%

Lubricant (calcium stearate): 0.30%

The composition has the following properties:

Melt Viscosity Index (MFI): 6.0 g / 10 min

Elastic modulus: 500 MPa

-IZOD impact strength: 1100 J / m

Example 9

According to the method of Example 2, a composition according to the present invention having the following compounding ratio was prepared.

Polyamide 6 (η _rel = 3.8): 22.1%

Copolyamide 6 / 6,6: 35.0%

(NYCOA (registered trademark) 2062)

Impact modifier: 30.0%

(PRIMEFLEX (trademark) AFG4W)

Plasticizer: 10.0%

(N-BBSA or N-butylbenzenesulfonamide)

-Pigment (Carbon Black): 0.9%

Antioxidant: 2.0%

Lubricant (calcium stearate): 0.30%

The composition has the following properties:

Melt Viscosity Index (MFI): 4.2 g / 10 min

Elastic modulus: 300 MPa

-IZOD impact strength: 1200 J / m

Example 10

According to the method of Example 2, a composition according to the present invention having the following compounding ratio was prepared.

Polyamide 6 (η _rel = 3.8): 21.1%

Copolyamide 6 / 6,6: 35.0%

(NYCOA (registered trademark) 2062)

Impact modifier: 30.0%

(PRIMEFLEX (trademark) AFG4W)

Chain Extender: 1.0%

(ARALDITE (trademark) GT7071)

Plasticizer: 10.0%

(N-BBSA or N-butylbenzenesulfonamide)

-Pigment (Carbon Black): 0.9%

Antioxidant: 2.0%

Lubricant (calcium stearate): 0.30%

The composition has the following properties:

Melt Viscosity Index (MFI): 1.0 g / 10 min

Elastic modulus: 300 MPa

-IZOD impact strength: 1200 J / m

Example 11

According to the method of Example 2, a composition according to the present invention having the following compounding ratio was prepared.

Polyamide 6 (η _rel = 5.2): 61.8%

Copolyamide 6 / 6-36: 30.0%

(NYCOA (registered trademark) 2012)

Impact modifier: 28.0%

(EXXELOR (trademark) VA1801)

Plasticizer: 7.0%

(N-BBSA or N-butylbenzenesulfonamide)

-Pigment (Carbon Black): 0.9%

Antioxidant: 2.0%

Lubricant (calcium stearate): 0.30%

The composition has the following properties:

Melt Viscosity Index (MFI): 5.0 g / 10 min

Elastic modulus: 700 MPa

-IZOD impact strength: 1200 J / m

Example 12

According to the method of Example 2, a composition according to the present invention having the following compounding ratio was prepared.

Polyamide 6 (η _rel = 5.2): 39.8%

Copolyamide 6 / 6-9: 30.0%

(NYCOA (registered trademark) 2047)

Impact modifier: 20.0%

(EXXELOR (trademark) VA1801)

Plasticizer: 7.0%

(o, p-toluenesulfonamide)

-Pigment (Carbon Black): 0.9%

Antioxidant: 2.0%

Lubricant (calcium stearate): 0.30%

The composition has the following properties:

Melt Viscosity Index (MFI): 7.0 g / 10 min

Elastic modulus: 1400 MPa

-IZOD impact strength: 1000 J / m

Example 13

Articles of the type shown in the accompanying figures were prepared by extrusion blow molding in a sequential extrusion manner.

The article was manufactured by a sequential coextrusion apparatus under the trademark BATTENFELD 2D, which was equipped with two single screw extrusion facilities and a coextrusion die. Each extrusion facility has a storage facility.

The diameter of the extrusion plant is 60 mm, the length / diameter ratio is 20 in the first plant and 24 in the second plant. The storage capacity is 0.7 liters for the first plant and 1 liter for the second.

The diameter of the extrusion die is 32 mm and the pressing force is 25 tons.

The article shown in the figure comprises a first part (1) obtained by extrusion blow molding of hard polyamide, a second part (2) obtained by extrusion blow molding of hard polyamide composition, and a polyamide according to Example 1 A tube containing the third intermediate portion 3 in the foam form produced by extrusion blow molding of the composition. Extrusion of each part was performed sequentially

Claims (18)

A matrix based on a thermoplastic polyamide polymer and at least one impact modifier present at a concentration of 10 to 50% by weight of the composition, wherein the composition has an elastic modulus of less than 1500 MPa. A composition according to claim 1, which contains a plasticizer for the polyamide matrix, which is present at a concentration of 5 to 20% by weight of the polyamide matrix. The composition according to claim 1 or 2, which contains a chain extender for the polyamide matrix, which is present at a concentration of 0.05 to 5% by weight of the polyamide matrix. The composition according to claim 1, having a melt flow index of 0.5 g / 10 min to 8 g / 10 min when measured under 5 kg load at a temperature of 275 ° C. 5. The composition according to any one of claims 1 to 4, having an elastic modulus of less than 1000 MPa. The composition according to any one of claims 1 to 5, having a notched IZOD impact strength (23 ° C.) of at least 800 J / m. The composition of claim 1, wherein the impact modifier is selected from the group consisting of compounds having a Tg of less than 0 ° C. and a modulus of elasticity of less than 200 MPa. 8. The composition of claim 7, wherein the impact modifier is a compound selected from the group of polyolefins. 9. The composition of claim 8, wherein at least some of the impact modifiers contain polar functional groups capable of reacting with the polyamide matrix. 10. The composition of claim 9, wherein the polar functional group is selected from the group consisting of acid, anhydride, acrylic, methacryl and epoxy functional groups. The impact modifier of claim 7, wherein the impact modifier has a melt flow index of 0.5 to 7 g / 10 minutes, preferably 1 g / 10 minutes, and a density of less than 0.9 as measured at 190 ° C. under a 2.16 kg load. Ultra Density Polyethylene (ULDPE). The plasticizer according to any one of claims 2 to 11, wherein the plasticizer is o, p-toluenesulfonamide, N-ethyl-o, p-toluenesulfonamide, N-butylbenzenesulfonamide, alkyl parahydric having 1 to 20 carbon atoms. A composition characterized in that it is selected from the group consisting of sulfonamides such as oxybenzoate, polyethylene glycol and polypropylene glycol. The composition according to any one of claims 3 to 12, wherein the chain extender is an organic diepoxy, dianhydride or diisocyanate compound. 14. The polyamide resin according to any one of claims 1 to 13, wherein the polyamide resin is PA6, PA6.6, copolymers thereof, PA6 / 6.36, PA6 / 6-9, PA6.10, PA6.12, PA6.36, PA6.11 / 6.12 or a mixture thereof. 15. An article obtained by molding the composition according to any one of claims 1-14. At least one soft portion obtained by molding the composition according to any one of claims 1 to 14 and a matrix-based composition of thermoplastic material compatible with the polyamide of the flexible composition, which is obtained and molded in connection with the soft portion. A product comprising at least one hard part. 17. The article of claim 16, wherein the thermoplastic matrix of the composition forming the hard portion is a polyamide resin. 18. The product of claim 16 or 17, wherein the soft portion has an expanded form.