WO2006095094A1

WO2006095094A1 - Nanostructured dual-phase material comprising a polyamide matrix and elastomeric nodules

Info

Publication number: WO2006095094A1
Application number: PCT/FR2006/000527
Authority: WO
Inventors: Fernand Pla; Christian Fonteix; Sandrine Hoppe; Rabih Rached
Original assignee: Centre National De La Recherche Scientifique
Priority date: 2005-03-10
Filing date: 2006-03-09
Publication date: 2006-09-14
Also published as: FR2883001A1

Abstract

The invention concerns a polyamide-based material, having improved impact and crack propagation resistance. The material is a nanostructured dual phase polymer material comprising a polyamide matrix consisting of recurrent units derived from one or more monomers selected among cyclic lactams polymerizable by anionic process and elastomeric nodules dispersed on nanometric scale and uniformly in the polyamide matrix. The material is obtained by a method which consists in extruding a mixture comprising the elastomer for forming the nodules, one or more precursor monomers of the polyamide matrix, a co-activator, a macroactivator, and an anionic polymerization catalyst of the precursor monomers.

Description

Nanostructured two-phase material comprising a polyamide matrix and elastomer nodules

The present invention relates to a reinforced polyamide, and a process for its preparation.

Polyamides are polymers widely used in industry because of their good mechanical properties (toughness, wear resistance) combined with good resistance to heat, abrasion and chemicals. However, their resistance to shocks and crack propagation, especially at low temperatures, is insufficient. It has been proposed in the prior art to overcome these disadvantages by preparing a material by a process of mixing a polyamide with an elastomer having the properties lacking polyamide. The mixture may be a simple mechanical mixture (Chang Hyung Lee, Yong Moo Lee, Hyeong Ki Choi, Shin Horiuchi, Takeshi Kitano, Polymer, 40, 6321-6327 (1999). Alternatively, mixing is carried out in the presence of a compatibilizer (third component such as a copolymer comprising polyamide blocks and elastomer blocks [Gonzalez-Montiel A, Keskkula H., Paul DR, Polymer, 36, 4621-4637 (1995)]. According to another variant, the mixing is carried out by causing a chemical reaction at the polyamide / elastomer interface [Kelar K., Jurkowski B., Polymer, 41, 1055-1062, (2000)]. a material consisting of a polyamide matrix in which elastomer nodules of micrometric size are dispersed The impact resistance is certainly improved, but it remains at levels that are insufficient for certain applications Examples of impact resistance properties are given s by Tjong S. C KeY. C., [Eur. Polym. J., (1998), 34, 1565-1570] and by DM Laura [Polymer (2003), 44, 3347-3361] especially for the following mixtures, in which "polyamide-6" refers to a polyamide obtained from ε -caprolactam: The polyamide-β mixed with 15% EPDM (terpolymer of ethylene, propylene, diene monomer) has a resistance of 20 kJ / m ² ;

Polyamide-6 mixed with 15% EPDM and 40% PPE (Ethylene Propylene Copolymer) has a strength of 24 kJ / m ² ;

- Polyamide-6 / EPR (ethylene-propylene elastomer) / EPR-MA (maleic anhydride) has a resistance of the order of 600 J / m (Izod test); - The polyamide-β / SEBS (styrene ethylene butadiene elastomer) / SEBS-MA blend has a resistance of the order of 900 J / m (Izod test).

Reactive extrusion processes are also known which are used on an industrial scale, in particular for the modification of polyolefins (KR-2001.003567 or JP-5179138) or the mixture of polyolefins with other polymers (DE -4141577 or US-5,369,168).

The inventors have found that, surprisingly, the production by reactive extrusion of a material constituted by a polyamide matrix and elastomer particles made it possible to obtain a material which has the good properties inherent to the polyamide, but also a resistance shock and crack propagation sufficient in a wide range of temperature (-50 ⁰ C to 150C °). The object of the present invention is to provide a polyamide-based polymer material which has the good properties inherent in conventional polyamides, but also a high resistance to shocks and crack propagation, and a process for its preparation. The material according to the present invention is a nanostructured biphasic polymer material comprising:

a polyamide matrix consisting of repeating units which come from one or more monomers chosen from cyclic lactams capable of polymerizing anionically;

nodules of an elastomer dispersed at nanometric scale and uniformly in the polyamide matrix. The elastomer may be chosen from polyisoprene, polybutadiene, butadiene copolymers (for example a butadiene-nitrile acrylic copolymer), copolymers based on ethylene and propylene (EPR), and ethylene-propylene-diene terpolymers ( EPDM), polyurethanes, polyacrylates functionalized with chlorine, ethylene-vinyl acetate-acrylic acid copolymers in which the ethylene unit may optionally be grafted with a maleic anhydride, and silicones [for example, poly (dimethylsiloxane) PDMS].

The anionically polymerizable cyclic lactams are lactams in which the ring-forming linkage with the -NH-O- group comprises at least two carbon atoms. As examples, mention may be made of ε-caprolactam (ε-CL) and lauryllactam (LL), which respectively give a repeating unit of the polyamide -NH- (CH ₂ ) ₅ -C (= O) - and -NH- ( CH ₂ ) ₁₁ -C (= O) -. In addition, mention may be made of the lactams indicated in the following table, which also gives the repeating unit of the corresponding polyamide:

Generally, a content of 2 to 20% by weight of elastomer substantially improves the impact resistance. For example, for a material constituted by a matrix of polyamide 12 (LL polymer) and nodules of PDMS, the untagged test pieces are unbreakable between -50 ^° C. and 150 ^° C., and their impact strength, measured according to the ISO 179 / leC standard, is greater than 60 kJ / m ² at room temperature and 20 kJ / m ² at -40 ^° C., for an elastomer content greater than 10%.

The process according to the invention for producing a material comprising a matrix of polyamide and elastomer nodules, is characterized in that it consists in extruding a mixture comprising the elastomer intended to form the nodules, one or more precursor monomers of the polyamide matrix, a coactivator, a macroactivator, and an anionic polymerization catalyst of the precursor monomers. The coactivator is obtained by reacting a diisocyanate with a lactam monomer. The macroactivator is obtained by modification under an inert atmosphere of the elastomer so as to provide it with terminal functions capable of reacting with the monomer (s) precursor (s) of the polyamide to form a polyamide-elastomer-polyamide triblock copolymer.

In the process of the invention, the polyamide is formed in situ anionically, by successive additions of lactam monomer molecules at the ends of the coactivator. Simultaneously, a compatibilizing agent is formed anionically, by successive additions of lactam monomer molecules at the ends of the macroactivator.

The method of the present invention is thus distinguished from the processes of the prior art, in which the material is obtained by mixing a polyamide previously formed optionally in the presence of a compatibilizer also formed beforehand. The method of the invention thus makes it possible to disperse the elastomer at the nanometric scale in the polyamide matrix during the formation of said matrix.

The catalyst is an anionic polymerization catalyst, chosen, for example, from strong bases such as alkali metal salts. As examples, we can mention sodium caprolactamate, alkali metal hydrides or organometallic compounds. There may be mentioned in particular the compound (CH ₃ OCH ₂ CH ₂ O) ₂ AlH ₂ ] Na.

In a particular embodiment, the process for producing the material according to the invention comprises:

a preliminary step consisting in firstly preparing a macroactivator by modifying the elastomer in an inert atmosphere so as to provide it with terminal functions capable of reacting with the monomer (s) precursor (s) of the polyamide to form a polyamide-elastomer-polyamide triblock copolymer, and on the other hand a coactivator by reaction of a polyamide precursor monomer with a diisocyanate using a slight excess of monomer, at a temperature above the precursor monomer melting temperature ;

a step during which a mixture consisting of the precursor monomer (s) of the polyamide, the elastomer, the macroactivator and the coactivator is prepared at a temperature above the melting point of the precursor monomer;

a step during which is introduced into a twin-screw extruder simultaneously on the one hand said mixture and on the other hand an anionic polymerization catalyst, the screw of the extruder having a profile adapted to perform the mixing and conveying reagents so that the residence time in the extruder is sufficient to achieve maximum conversion, and the extrusion is carried out at a temperature above the precursor monomer melting temperature, the feed rates of the mixture and the catalyst being selected such that the formation rate of the triblock copolymer from the macroactivator is at least as fast as the rate of homopolymerization of the polyamide precursor or copolymerization of the polyamide precursors.

A macroactivator may be prepared, for example, by reaction of an elastomer carrying OH or NH groups with a diisocyanate to form a macrodiisocyanate, then by reaction of the macrodiisocyanate with the lactam monomer.

The polyamide-elastomer-polyamide triblock copolymer which is formed from the macroactivator during the extrusion process acts as a compatibilizer.

The precursor monomer of the polyamide is a cyclic lactam capable of anionic polymerization, chosen for example from ε-caprolactam and lauryllactam.

The elastomer may be chosen from the elastomers indicated above in the definition of the material.

The determination of the specific conditions for each polyamide / elastomer pair and depending on the desired impact resistance is within the abilities of those skilled in the art. It can be carried out by implementing the method of the invention for a given cyclic lactam and a given elastomer, and by carrying out a series of experiments according to a simple experimental plan, provided for example by the software marketed by the company. Stat Soft under the name Statistica. For each experiment, the impact resistance of the resulting material is measured.

For example, the determination of the specific conditions can be carried out according to the following procedure: in a first step, a mixture (A) of the precursor amide monomer of the matrix, the elastomer, the macroactivator and the coactivator is prepared in a stirred tank at a temperature above the melting point of the monomer and with a stirring speed of 300 rpm; in a second step, the mixture A is introduced at the same time as the catalyst in a twin-screw extruder having a suitable profile and a sheath temperature greater than the melting point of the polyamide. For example, if a BC21 extruder marketed by Clextral is used, the following operating parameters must be retained:

• speed of rotation of the screws, between 50 and 150 revolutions / minute • feed rate of the mixture (A), between 10 and 50 grams per minute

The number-average molar mass of the elastomer of between 5000 and 70000 grams per mole, and the mass fraction of this same elastomer, of between 2% and 20%.

The set of results obtained by the series of tests thus carried out for a given monomer / amide / elastomer pair makes it possible to optimize the parameters of the process. The present invention is illustrated by the examples described below, to which it is however not limited. The following starting materials were used:

An α, ω-dihydroxy poly (dimethylsiloxane) PDMS (hereinafter referred to as PDMS-3100) which has been dried under vacuum at 70 ^° C. for 6 hours before use, and whose molecular mass determined by ¹ H NMR is 3100 g / mol;

An α, ω-dihydroxy poly (dimethylsiloxane) PDMS (hereinafter referred to as PDMS-28000) whose molecular mass determined by ¹ H NMR is 28,000 g / mol; An α, ω-dihydroxy-poly (dimethylsiloxane) PDMS (hereinafter referred to as PDMS-62700) whose molecular mass determined by ¹ H NMR is 62700 g / mol;

Lauryllactam (LL) and ε-caprolactam (ε-CL), dried under vacuum at 70 ^° C. for 24 hours before their use;

Sodium hydride-bis- (2-methoxyethoxy) aluminum;

• 4,4'-diphenylmethane diisocyanate (MDI);

Toluene, cyclohexane, tetrahydrofuran and acetone. All products are marketed by Aldrich, with the exception of α, ω-dihydroxy-poly (dimethylsiloxane) which are marketed by ABCR.

A co-rotating BC 21 twin-screw extruder sold by the company Clextral was used. The catalyst was prepared according to the following procedure. To 2 ml of a solution containing 5.10 ^{~ 4} mol of ε-CL to room temperature, was added drop by drop 5.10 ^{~ 4} mol of sodium hydride bis (2-methoxyethoxy) aluminum hydride. The end of the reaction is marked by stopping the evolution of hydrogen.

The co-activator was prepared according to the following reaction scheme:

A slight excess of ε-CL is mixed with the diisocyanate

MDI at 100 ^° C. After 6 hours of reaction, the product is dissolved in acetone and then precipitated in distilled water. The MDI dicaprolactam recovered by filtration is dried under vacuum at 60 ^° C. for 3 days.

Example 1

Synthesis of the macroactivator

The macroactivator α, ω-dicarbamoyloxy caprolactam PDMS is prepared according to the following reaction scheme:

During a preview ^st step, reacting PDMS-3100 (1 eq.) With the diisocyanate MDI (2.1 eq.) At 9O ⁰ C under nitrogen atmosphere, in the presence of dibutyltin diacetate as a catalyst.

In a ^2nd stage, reacting the cyanate macrodiiso- formed with ε-CL to obtain the macroactivateur Sou Haite, which is then characterized by IR, ¹ H NMR and by elemental analysis.

Figure 1 shows the infrared spectrum of the macroactivator. The absorbance A is indicated on the ordinate, and the wavelength L (in cm ^-1 ) is indicated on the abscissa, revealing the presence of a large peak (vibration at 3333 cm ^-1 ) corresponding to the NH function. The characteristic vibrations of Amide I and Amide II are located at 1713 and 1537 cm- ¹ and are clear evidence of urethane groups, Figure 1 shows that the absorption band of the amide I and the amide II of the terminal imide function is probably masked by that of the urethane group, but, as expected for this macroactivator of high molar mass (M _n = 3100 g / mol), the low intensity bands characteristic of the function imide (v CO = 1770 cm ^-1 ; v CN ≤ 1380 cm ^-1 and y CO s 725 cm ^-1 ) could not be identified using the infrared spectrum.

Figure 2 shows the ¹ H NMR spectrum. It has shown that the peak at 11.25 ppm is characteristic of the hydrogen of the NH group in the α position of the terminal imide group. The methylen protons of ε-CL are easily identified at 1.78, 2.76 and 3.89 ppm. In contrast, the broad peak at 6.89 corresponds to the urethane group. The complete assignment of the protons of the macroactivator is presented in Table 1 below. Table 1

The macroactivator was characterized by an elementary analysis:

- experimental: Si, 30.05; C, 39.95; H, 7.95; N, 2.15;

- theoretical: Si, 30.23; C, 39.52; H, 7.66; N, 2.26. Preparation of the composite material

3.1 kg of LMS monomer, 0.245 kg of PDMS-28000, 0.155 kg of the macroactivator and 0.0187 of the coactivator as prepared above were introduced into a reactor, and the mixture was stirred at 18 ^° C. at 300 rpm.

In a twin-screw extruder, the mixture contained in the reactor and, secondly, the catalyst were continuously introduced simultaneously. The flow rate of the mixture was 30 g / min and the catalyst flow rate was 0.48 g / min. the temperature of the barrel of the extruder was maintained at 200 ^° C. and the rotational speed of the screws of the extruder was 150 rpm.

FIG. 3 represents a view obtained by scanning electron microscopy (SEM) of the composite material obtained. The scale index at the bottom right represents 5.00 μm.

The material was subjected to a shock test, which showed an impact strength of 45 kJ / m ² at room temperature

Comparative example

A sample of composite material was prepared with the same starting materials as in Example 1 and in using the same proportions. The addition of the catalyst to the mixture comprising the lactam monomer, the elastomer, the coactivator and the macroactivator, however, was carried out in a kneader and not in an extruder. The obtained material has an impact resistance, determined by a shock test, of 20 kJ / m ² at ambient temperature.

FIG. 4 represents a view obtained by scanning electron microscopy (SEM) of the composite material obtained. The scale index at the bottom right represents 5.00 μm

Figure 5 shows the size distribution of elastomer nodules for the material according to the invention of Example 1 (solid line), and for the material given for comparison in the present example (dotted line). The frequency F (in number) is given on the ordinate, and the diameter D (in nm) is given on the abscissa.

Example 2

Synthesis of the macroactivator

The macroactivator α, ω-dicarbamoyloxy caprolactam PDMS is prepared according to the procedure of Example 1. Preparation of the composite material

3.3 kg of LL monomer, 0.116 kg of PDMS-62700, 0.07 kg of the macroactivator and 0.0199 of co-activator were introduced into a reactor, and the mixture was stirred at 180 ^° C. at 300 ^° C. min. In a twin-screw extruder, the mixture contained in the reactor and, secondly, the catalyst were continuously introduced simultaneously. The flow rate of the mixture was 50 g / min and the catalyst flow rate was 0.8 g / min. the temperature of the barrel of the extruder was maintained at 200 ^° C. and the rotational speed of the screws of the extruder was 150 rpm.

FIG. 6 represents a view obtained by scanning electron microscopy (SEM) of the composite material obtained. In the left view, the scale index at the bottom right is 5.00 μm. The view on the right is a view enlarged from the framed area of the left view, and the scale index at the bottom right is 2.00 μm.

Figure 7 shows the size distribution of the elastomer nodules in the material. The frequency F (in number) is given on the ordinate, and the diameter D (in nm) is given on the abscissa. The average diameter of the nodules is

120 nm.

The material was subjected to a shock test, which showed an impact strength of 23 kJ / m ² at room temperature.

Example 3

Synthesis of the macroactivator

The macroactivator α, ω-dicarbamoyloxy caprolactam PDMS is prepared according to the procedure of Example 1.

Preparation of the composite material 3.05 kg of monomer LL was introduced into a reactor,

0.28 kg of PDMS-62700, 0.168 kg of the macroactivator and 0.0184 of the coactivator, and the mixture was stirred at 180 ^° C.

300 rpm.

In a twin-screw extruder, the mixture contained in the reactor and, secondly, the catalyst were continuously introduced simultaneously. The flow rate of the mixture was 45 g / min and the flow rate of the catalyst was

0.715 g / min. the temperature of the barrel of the extruder was maintained at 200 ^° C. and the speed of rotation of the screws of the extruder was 100 rpm.

FIG. 8 represents a view obtained by scanning electron microscopy (SEM) of the composite material obtained.

The scale index at the bottom right represents 5.00 μm.

Figure 9 shows the size distribution of the elastomer nodules in the material. The frequency F (in number) is given on the ordinate, and the diameter D (in μm) is given on the abscissa. The average diameter of the nodules is

210 nm.

The material was subjected to a shock test, which showed an impact strength of 37 kJ / m ² at room temperature. Example 4

Synthesis of the macroactivator

Preparation of the composite material 3.39 kg of LL monomer were introduced into a reactor,

0.07 kg of PDMS-28000, 0.042 kg of the macroactivator and 0.0204 of the co-activator, and the mixture was stirred at 180 ^° C.

300 rpm.

In a twin-screw extruder, the mixture contained in the reactor and, secondly, the catalyst were continuously introduced simultaneously. The flow rate of the mixture was 10 g / min and the flow rate of the catalyst was

0.16 g / min. the temperature of the barrel of the extruder was maintained at 200 ^° C. and the speed of rotation of the screws of the extruder was 133.3 rpm.

FIG. 10 represents a view obtained by scanning electron microscopy (SEM) of the composite material obtained.

In both views, the scale index at the bottom right is 5.00 μm. Figure 11 shows the size distribution of the elastomer nodules in the material. The frequency F (in number) is given in ordinate, and the diameter D (in nrri) is given in abscissa. The average diameter of the nodules is

168 nm. The material was subjected to a shock test, which showed an impact strength of 30 kJ / m ² at room temperature.

Claims

claims

A nanostructured biphasic polymer material comprising:

nodules of an elastomer dispersed at nanometric scale and uniformly in the polyamide matrix.

2. Material according to claim 1, characterized in that the elastomer is chosen from polyisoprene, polybutadiene, butadiene copolymers, copolymers based on ethylene and propylene, ethylene-propylene-diene terpolymers, polyurethanes. , polyacrylates functionalized with chlorine, ethylene-vinyl acetate-acrylic acid copolymers in which the ethylene unit may optionally be grafted with a maleic anhydride, and silicones.

3. Material according to claim 1, characterized in that recurring units derived from cyclic lactams are -NH- (CH ₂ ) ₅ -C (= O) - or -NH- (CH ₂ ) uC (= O) - .

4. Material according to claim 1, characterized in that the recurring units derived from cyclic lactams are NH- (CH ₂ ) ₃ -C (= O) -, -NH-CH ₂ -C (CH ₃ ) (C) units. ₄ H ₉₎ -C (= 0) -,

-NH-CH ₂ -C (CH ₃ ) ₂ -C (= O) -, -NH-C (CH ₃ ) ₂ -CH ₂ -C (= O) -, or

5. Material according to claim 1, characterized in that the elastomer content is 5 to 15% by weight.

6. Process for producing a material comprising a matrix of polyamide and elastomer nodules, characterized in that: it consists in extruding a mixture comprising the elastomer intended to form the nodules, one or more precursor monomers; of the polyamide matrix, a coactivator, a macroactivator, and an anionic polymerization catalyst of the precursor monomers; the coactivator is obtained by reaction of a diisocyanate with a lactam monomer; the macroactivator is obtained by modification under an inert atmosphere of the elastomer so as to provide it with terminal functions capable of reacting with the monomer (s) precursor (s) of the polyamide to form a polyamide-elastomer-polyamide triblock copolymer .

7. Method according to claim 6, characterized in that the precursor monomer of the polyamide is a cyclic lactam capable of polymerizing anionically.

8. Process according to claim 7, characterized in that the cyclic lactam is ε-caprolactam or lauryllactam.

9. Process according to claim 6, characterized in that the cyclic lactam is chosen from α-pyrrolidone, 3-butyl-3-methyl-2-azetidinone and 8-oxa-6-azabicyclo- [3.2.1] octan-7-one, 3,3-dimethyl-2-azetidinone and 4,4-dimethyl-2-azetidinone.

10. The method of claim 6, characterized in that the catalyst is selected from strong bases.

11. The method of claim 10, characterized in that the catalyst is an alkali metal salt.

12. The method of claim 11, characterized in that the catalyst is selected from alkali metal hydrides or organometallic compounds.

13. The method of claim 11, characterized in that the catalyst is sodium caprolactamate or the compound (CH ₃ OCH ₂ CH ₂ O) ₂ AlH ₂ ] Na.

14. The method of claim 6, characterized in that it comprises: a preliminary step of preparing on the one hand a macroactivator by modification in an inert atmosphere of the elastomer so as to provide terminal functions capable of reacting with the monomer (s) precursor (s) of the polyamide to form a polyamide-elastomer-polyamide triblock copolymer, and secondly a co-activator by reacting a polyamide precursor monomer with a diisocyanate using a slight excess of monomer at a temperature above the melting temperature of the monomer; a step during which a mixture consisting of the precursor monomer (s) of the polyamide, the elastomer, the macroactivator and the coactivator is prepared at a temperature above the melting temperature of the monomer ; a step during which is introduced into a twin-screw extruder simultaneously on the one hand said mixture and on the other hand an anionic polymerization catalyst, the screw of the extruder having a profile adapted to perform the mixing and conveying of reagents so that the residence time in the extruder is sufficient to achieve maximum conversion, and the extrusion is carried out at a temperature above the melting temperature of the precursor monomer, the feed rates of the mixture and the catalyst being chosen so that the rate of formation of the triblock copolymer from the macroactivator is at least as fast as the rate of homopolymerization of the polyamide precursor or the copolymerization of the polyamide precursors.

15. The method of claim 6, characterized in that the macroactivator is prepared by reaction of an elastomer carrying OH or NH groups with a diisocyanate to form a macrodiisocyanate, then by reaction of the macrodiisocyanate with the lactam monomer.

Process according to Claim 6, characterized in that the proportion of elastomer introduced into the extruder is from 5 to 15% by weight of the total amount of the mixture subjected to the extrusion.