Mixture of copolymers grafted with polyamide blocks and elastomers formulated with a cross-linking or vulcanisation system

Abstract

The mixture of the invention contains, for 100 parts by weight: (A) 10 to 90 parts in weight of at least one copolymer grafted to polyamide blocks, said copolymer comprising a polyolefin trunk and at least 1.3 polyamide grafts on said trunk in average, and having a nanostructured organization, wherein said grafts are attached to the trunk by the rest of an unsaturated monomer (X) having a function capable of reacting with a polyamide with an amine end; the rest of said monomer (X) being attached on the trunk by grafting or copolymerization from its double bond thereof, (A) optionally including at least one non-grafted polyolefin in a proportion such that the nano-structured organization of the compound (A) is preserved; and (B) 90 to 10 parts in weight of a formulation of at least one elastomer having unsaturated double bonds and capable of reacting with a crosslinking or vulcanization agent, said formulation containing a crosslinking or vulcanization system of said elastomer(s), at least one plasticizer and the standard additives present in elastomer formulations.

Claims

1. A mixture comprising, per 100 parts by weight: (A) 10 to 90 parts by weight of at least one graft copolymer having polyamide blocks, said copolymer being composed of a polyolefin backbone and of on average at least 1.3 polyamide grafts on said backbone, and having a nanostructured organization, where said grafts are attached to the backbone by the residues of an unsaturated monomer (X) having a function capable of reacting with an amino-terminal polyamide; and the residues of said unsaturated monomer (X) being attached to the backbone by grafting or copolymerization from its double bond, optionally said constituent (A) comprises at least one ungrafted polyolefin in a proportion such that the nanostructured organization of said component (A) is not lost; and (B) 90 to 10 parts by weight of a formulation of at least one elastomer which has unsaturated double bonds and is capable of reacting with a crosslinking or vulcanizing agent, said formulation including a system for crosslinking or vulcanizing of said elastomer or elastomers, at least one plasticizer, and other additives.

2. The mixture as claimed in claim 1, wherein the proportion of constituent (A) is from 15 to 75 parts by weight for, respectively, 85 to 25 parts by weight of the constituent (B).

3. The mixture as claimed in claim 1, wherein X is an unsaturated carboxylic acid anhydride.

4. The mixture as claimed in claim 3, wherein the polyolefin backbone comprising X is selected from ethylene-maleic anhydride and ethylene-alkyl (meth)acrylate-maleic anhydride copolymers.

5. The mixture as claimed in claim 1, wherein there are on average 1.3 to 10 moles of X, attached to the polyolefin backbone of the constituent (A).

6. The mixture as claimed in claim 1, wherein the grafts are homopolymers composed of residues of caprolactam, of 11-aminoundecanoic acid or of dodecalactam or are copolyamides composed of residues selected from at least two of the three aforementioned monomers.

7. The mixture as claimed in claim 1, wherein the grafts have a weight-average molar mass of less than 5000 g/mol.

8. The mixture as claimed in claim 1, wherein the polyolefin of the backbone of the graft copolymer of the constituent (A) or forming part of the composition of the constituent (A) is selected from ethylene homopolymers, propylene homopolymers, copolymers of ethylene with C.sub.3-C.sub.8 alpha-olefins, copolymers of ethylene with esters of (meth)acrylic acid and copolymers of ethylene C.sub.1-C.sub.8 alcohols and with vinyl acetate.

9. The mixture as claimed in claim 1, wherein the copolymer having polyamide blocks exhibits a nanostructured organization with polyamide lamellae with a thickness of between 10 and 50 nanometers, or with an elastic modulus, measured by thermomechanical analysis to a frequency of 1 Hz on a Rheometrics dynamic rheometer, of more than 0.5 MPa at the center of the range between the melting point of the polyolefin backbone and the melting point of the polyamide graft, when the melting point of the polyolefin backbone is lower by at least 40 C. than that of the polyamide graft.

10. The mixture as claimed in claim 1, wherein the graft copolymer having polyamide blocks represents more than 50% by weight of the constituent (A).

11. The mixture as claimed in claim 1, wherein the unsaturated elastomer of the constituent (B) is selected from: terpolymers of ethylene, propylene, and a diene (EPDM); elastomers based on butadiene, natural (NR) or synthetic, and styrene-butadiene copolymers (SBR); copolymers of butadiene with acrylonitrile (NBR); partially hydrogenated copolymers of butadiene with acrylonitrile (HNBR); elastomers based on isoprene (IR); and acrylic elastomers.

12. The mixture as claimed in claim 1, wherein the crosslinking or vulcanizing system is selected from the group consisting of vulcanizing agents based on sulfur, peroxide, phenolic resin on azo maleimido, quinoid, and urethane compounds, for the diene elastomers; from agents based on polyfunctional amines, hexamethylenediamine carbamate, and on diisocyanates, for the acrylic elastomers having acid groups; and from agents based on ammonium salts, 2-methylimidazole and the molecules of polyfunctional acids, for the acrylic elastomers having an epoxide group.

13. The mixture as claimed in claim 1, wherein the crosslinking or vulcanizing system represents 1 to 20 phr of the constituent (B).

14. The mixture as claimed in any claim 1, wherein the plasticizer or plasticizers represent 5 to 200 phr of the constituent (B), being selected from oils composed of mixtures of aliphatic, naphthenic or aromatic hydrocarbons for the elastomers having unsaturated double bonds, and polar oils based on esters of phthalic acid for the acrylic elastomers.

15. The mixture as claimed in claim 1, wherein the additives are selected from the group consisting of pulverulent inorganic fillers, zinc oxides and titanium oxides, carbon blacks, kaolins, silicas, pigments, coupling agents, antidegradants, processing additives, stearates, and waxes, and represent 10 to 150 phr of the constituent (B).

16. A mixture comprising, per 100 parts by weight: (A) 10 to 90 parts by weight of the precursors adapted to form at least one graft copolymer having polyamide blocks, said copolymer being composed of a polyolefin backbone and of on average at least 1.3 polyamide grafts on said backbone, and having a nanostructured organization, where said grafts are attached to the backbone by the residues of an unsaturated monomer (X) having a function capable of reacting with an amino-terminal polyamide; and the residues of said unsaturated monomer (X) being attached to the backbone by grafting or copolymerization from its double bond, optionally said constituent (A) comprises at least one ungrafted polyolefin in a proportion such that the nanostructured organization of said component (A) is not lost; and (B) 90 to 10 parts by weight of a formulation of at least one elastomer which has unsaturated double bonds and is capable of reacting with a crosslinking or vulcanizing agent, said formulation including a system for crosslinking or vulcanizing of said elastomer or elastomers, at least one plasticizer, and other additives, wherein the precursors comprise a mixture of polyolefinic backbone+amino-terminal polyamide grafts.

17. The mixture as claimed in claim 1, wherein the grafts have a number-average molar mass of less than 5000 g/mol.

18. A crosslinked or vulcanized thermoplastic composition it is formed from the mixture as defined in claim 1, wherein the elastomer of the constituent (B) has been crosslinked or vulcanized in the course of mixing with the constituent (A).

19. A process for preparing the composition as defined in claim 18, comprising the step of milling the formulation of the constituent (B) with the constituent (A) at a sufficient temperature and for a sufficient period of time to crosslink or vulcanize the elastomer of the constituent (B).

20. The process as claimed in claim 19, wherein the milling is carried out at a temperature of between 150 and 240 C. and for a time of between 3 and 15 minutes.

21. A finished article comprising the composition as defined in claim 18 formed by a technique selected from the group consisting of extrusion, coextrusion, extrusion coating, injection molding, compression molding, calendering, deposition on cable, deposition of powders after grinding, electrostatic spraying, fluidized bed dipping, laser prototyping, rotor molding or slush molding, wherein said finished article comprises skins for dashboards, door panels or consoles.

Description

EXAMPLE 1

Comparative

(1) The reference is a thermoplastic elastomer composed of 35% of a polypropylene with an MFI of 2 g/10 min (at 230 under 2.16 kg) (A1) and of 65% of a formulated EPDM (B1), crosslinked with a system based on phenolic resin and comprising 150 phr of aliphatic oil.

(2) Composition of (B1)

(3) TABLE-US-00001 EPDM 100 phr Polyphenolic crosslinking agent with a 12 phr degree of polymerization of between 4 and 5 Zinc oxide accelerator 12 phr Aliphatic plasticizer 150 phr Kaolin 40 phr Titanium oxide pigment 10 phr

(4) This thermoplastic elastomer has a Shore A hardness of 65 and a compression set, measured at 80 C., of 35%.

(5) Its creep resistance at 150 C. on an injection-molded bar subjected to a stress of 4.910.sup.4 Pa (0.5 kg/cm.sup.2) can no longer be measured, since the test specimens rapidly break.

(6) Its elastic modulus at 150 C., measured with a Rheometrics dynamic rheometer at a frequency of 1 Hz, is less than 0.1 MPa.

EXAMPLE 2

(7) On a Brabender mixer rotating at 80 rpm, in 8 minutes with a regulated temperature of 180 C., we produced an alloy composed of 35% by weight of a graft copolymer having polyamide blocks (A2) and of 65% by weight of a formulated EPDM elastomer (B1) of Comparative Example 1, comprising a crosslinking system based on phenolic resin and 150 phr of aliphatic oil.

(8) The thermoplastic elastomer obtained has a Shore A hardness of 55 and a compression set at 80 C. of 38%.

(9) Its creep resistance at 150 C. on an injection molded bar subjected to a stress of 4.910.sup.4 Pa (0.5 kg/cm.sup.2) is 25% after 15 minutes.

(10) The elastic modulus of this composition, measured with a Rheometrics dynamic rheometer at a frequency of 1 Hz, is greater than 1 MPa.

(11) Composition of (A2): Graft Polymer Having PA Blocks

(12) The copolymer having PA blocks (A2) was produced by the process described in WO 02/28959, and is composed of 80% of an ethylene/ethyl acrylate/maleic anhydride terpolymer, in an amount by weight of 80/17/3, and of 20% of polyamide 6 grafts having a weight-average molar mass of 3000 g/mol.

EXAMPLE 3

Comparative

(13) On a Buss co-kneader with a diameter of 40 mm, equipped with a pelletizing extruder having a thermal profile of between 160 C. and 250 C., we produced an alloy composed of 60% by weight of a high-viscosity polyamide 6 for extrusion (A3) and of 40% by weight of a formulated acrylic elastomer (B3).

(14) B3 is composed of a copolymer with butyl acrylate, comprising acid functions for crosslinking, which is formulated in a Brabender mixer regulated at 80 C. with 5 phr of hexamethylenediamine carbamate.

(15) This thermoplastic elastomer possesses a Shore D hardness of 60.

(16) It is subsequently extruded in the form of a tube of 18/20 mm in diameter.

(17) This tube is subsequently subjected to a test which is carried out in the automotive industry to test its resistance to an aggressive medium:

(18) It is bent at 180 as per FIAT method 9.0213701, the radius of bending being equal to approximately 5 times the outer diameter of the tube, and is partly immersed at 23 C. in a 50% by weight aqueous zinc chloride solution.

(19) After 200 hours, it is found that the test specimens have broken, since the PA6 in the composition is not resistant to stress cracking in this medium.

EXAMPLE 4

(20) On a Buss co-kneader with a diameter of 40 mm, equipped with a pelletizing extruder having a thermal profile of between 160 C. and 250 C., we produced an alloy composed of 60% by weight of a graft copolymer having polyamide blocks (A2) of Example 2 and of 40% by weight of a formulated acrylic elastomer (B3) of Example 3.

(21) This thermoplastic elastomer possesses a Shore D hardness of 25.

(22) It is subsequently extruded in the form of a tube of 18/20 mm in diameter and is subjected to the test of Example 3.

(23) This tube does not break in this test.