FR2934867A1 - Use of a composition comprising carbon nanotubes and copolyamide obtained from different starting product of e.g. lactams and amino carboxylic acids as electrically conductive adhesive composition - Google Patents

Abstract

Use of a composition comprising (a) a conductive amount of carbon nanotubes and (b) an adhesive amount of at least one copolyamide capable of being obtained from at least two different starting products of (i) lactams, (ii) amino carboxylic acids and (iii) equimolar quantities of diamines and dicarboxylic acids, as electrically conductive adhesive composition, is claimed. An independent claim is included for the use of a dispersion of carbon nanotubes, in such a copolyamide, in order to produce the electrically conductive adhesive composition.

Description

1

Use of a dispersion of carbon nanotubes in a copolyamide as a conductive adhesive composition

The present invention relates to the use, as an electrically conductive adhesive composition, of a composition containing carbon nanotubes, and at least one copolyamide.

It is known that certain copolyamides have adhesive properties making it possible to envisage their use in the manufacture of hot melt adhesives having good resistance to hot water and dry cleaning, in particular for the heat-sealing of low temperature textiles (US Pat. No. 5,459,230). FR 2 228 813, FR 2 228 806, US 2002/0022670) or at high temperature (DE 1 594 233).

For some industrial applications, it may be advantageous to give these adhesives electrical dissipation properties to prevent the accumulation of electrostatic charges, which may cause safety problems or even attract dust.

A solution conventionally used to impart conductive properties to polymeric materials consists in dispersing conductive fillers such as carbon black in quantities generally ranging from 7 to 30% by weight and, more specifically, in quantities ranging from 7 to 30% by weight. at 20% by weight for highly structured carbon blacks and from 15 to 30% by weight for loosely structured carbon blacks.

However, it appeared to the Applicant that the introduction of such amounts of carbon black in some 2

copolyamides increased the flexural modulus of these materials and reduced their adhesion properties.

It is the merit of the Applicant to have identified another solution to increase the conductivity of these copolyamides while retaining adhesion properties, and to provide a composition based on copolyamide, used as a conductive adhesive.

The subject of the present invention is therefore the use, as an electrically conductive adhesive composition, of a composition containing (a) carbon nanotubes and (b) at least one copolyamide obtainable from at least one minus two different starting materials selected from: (i) lactams, (ii) aminocarboxylic acids and (iii) equimolar amounts of diamines and dicarboxylic acids.

The present invention also relates to the use of a dispersion of said nanotubes in said copolyamide to manufacture an electrically conductive adhesive composition.

In the preamble, it is specified that the expression "included (e) between" used in the rest of this description should be understood as including the limits cited.

The constituents of the composition used according to the invention will now be described in detail.

Copolyamide 3

The composition used according to the invention comprises, as a first component, a copolyamide which can be formed from any monomers, provided that it has adhesive properties, in particular in hot welding operations.

This copolyamide preferably has a melting point between 40 and 150 ° C, preferably between 70 and 140 ° C. Particularly advantageously, the number-average molecular weight of this copolyamide may be between 5,000 and 15,000 g / mol.

According to a preferred variant, one will choose a relatively fluid copolyamide. For example, in the particular case of the copolyamide marketed under the trade name Platamid H106 by the company Arkema, the melt flow index (hereinafter MFI), which reflects this fluidity character, will be at least 10, preferably at least 15 g / 10 min and more preferably at least 20 g / 10 min, at 130 ° C under a load of 2.16 kg.

Polyamide copolymers, also referred to as copolyamides, can be obtained from various starting materials: lactams, aminocarboxylic acids or equimolar amounts of diamines and dicarboxylic acids. Obtaining a copolyamide requires choosing at least two different starting materials from those mentioned above. The copolyamide then comprises at least these two units. It can thus be a lactam and an aminocarboxylic acid having a different number of carbon atoms, or two lactams having different molecular weights, or a lactam combined with 4

an equimolar amount of a diamine and a dicarboxylic acid.

The copolyamide used according to the invention may for example be obtained from (i) at least one lactam chosen from lauryllactam and / or caprolactam, preferably a combination of these two lactams, and at least one other precursor of polyamide selected from (ii) aminocarboxylic acids and (iii) equimolar amounts of diamines and dicarboxylic acids.

The aminocarboxylic acid is advantageously chosen from α,--amino carboxylic acids, such as 11-aminoundecanoic acid or 12-aminododecanoic acid.

For its part, the precursor (iii) may in particular be a combination of at least one aliphatic, cycloaliphatic or aromatic C 6 -C 36 carboxylic acid diacid, such as adipic acid, azelaic acid, sebacic acid, brassylic acid, n-dodecanedioic acid, terephthalic acid, isophthalic acid or 2,6-naphthalene dicarboxylic acid with at least one aliphatic, cycloaliphatic, arylaliphatic or aromatic C4-C22 diamine, such as hexamethylene diamine, piperazine, 2-methyl-1,5-diaminopentane, m-xylylene diamine or p-xylylene diamine; it being understood that said diacid (s) carboxylic (s) and diamine (s) are used, when present, in equimolar amount.

The copolyamide according to the invention may advantageously comprise precursors derived from resources derived from renewable raw materials, that is to say containing organic carbon of renewable origin determined according to the ASTM D6866 standard. Among these monomers derived from renewable raw materials, there may be mentioned 9-aminonanoic acid, 10-aminodecanoic acid, 12-aminododecanoic acid and 11-aminoundecanoic acid and its derivatives, especially N-acid. -heptyl-11-aminoundecanoic acid, as well as the diamines and diacids explained in application PCT / FR2008 / 050251. In particular, it is possible to envisage: the diamines chosen from butanediamine (z = 4), pentanediamine (z = 5), hexanediamine (z = 6), heptanediamine (z = 7), nonanediamine; (z = 9), decanediamine (z = 10), undecanediamine (z = 11), dodecanediamine (z = 12), tridecanediamine (z = 13), tetradecanediamine (z = 14), hexadecanediamine (z = 16), octadecanediamine (z = 18), octadecenediamine (z = 18), eicosanediamine (z = 20), docosanediamine (z = 22) and diamines obtained from fatty acids and the diacids chosen from succinic acid (w = 4), adipic acid (w = 6), heptanedioic acid (w = 7), azelaic acid (w = 9), acid sebacic acid (w = 10), undecanedioic acid (w = 11), dodecanedioic acid (w = 12), brassylic acid (w = 13), tetradecanedioic acid (w = 14), acid hexadecanedioic acid (w = 16), octadecanoic acid (w = 18), octadecenoic acid (w = 18), eicosanedioic acid (w = 20), docosanedioic acid (w = 22) ) and fatty acid dimers containing 36 carbons.

It is preferred to use as polyamide precursors a combination of adipic acid and hexamethylene diamine and / or 11-aminoundecanoic acid. 6

Examples of copolyamides that may be used in the context of the present invention are, for example, copolyamides 6 / 6.6 / 6.10, 6 / 6.6 / 6.12, 6 / 6.6 / 6.36 or else 6 / 6.6 / 10.10.

It is furthermore preferred that the proportion of aromatic diacids does not exceed 10 mol% relative to the total weight of the copolyamide precursors.

According to a particularly preferred embodiment of the invention, the copolyamide can be obtained from caprolactam, adipic acid, hexamethylenediamine, 11-aminoundecanoic acid and lauryllactam. In this embodiment, it can for example be obtained from 25 to 35% by weight of caprolactam, from 20 to 40% by weight of 11-aminoundecanoic acid, from 20 to 30% by weight of lauryllactam and from 10 to 25% by weight of an equimolar mixture of adipic acid and hexamethylenediamine.

These copolymers can be prepared by polycondensation, according to methods well known to those skilled in the art. They are also commercially available from ARKEMA under the trade name PLATAMID ° and in particular PLATAMID H106.

The copolyamide preferably represents from 100 to 95% by weight, and more preferably from 100 to 96% by weight, relative to the total weight of the composition used according to the invention.

nanotubes

In the composition used according to the invention, the copolyamide is associated with carbon nanotubes (hereinafter, CNT).

The nanotubes that can be used according to the invention can be single-walled, double-walled or multi-walled. The double-walled nanotubes can in particular be prepared as described by FLAHAUT et al in Chem. Com. (2003), 1442. The multi-walled nanotubes may themselves be prepared as described in WO 03/02456. They are preferred for use in the present invention.

The nanotubes usually have a mean diameter ranging from 0.1 to 200 nm, preferably from 0.1 to 100 nm, more preferably from 0.4 to 50 nm and better still from 1 to 30 nm and advantageously a length of from 0 to 100 nm. , 1 to 10} gym. Their length / diameter ratio is preferably greater than 10 and most often greater than 100. Their specific surface area is for example between 100 and 300 m 2 / g and their apparent density may especially be between 0.05 and 0.5. g / cm 3 and more preferably between 0.1 and 0.2 g / cm 3. The multiwall nanotubes may for example comprise from 5 to 15 sheets and more preferably from 7 to 10 sheets.

An example of crude carbon nanotubes is in particular commercially available from ARKEMA under the trademark Graphistrength C100. 7 8

These nanotubes can be purified and / or treated (for example oxidized) and / or milled and / or functionalized before being used in the process according to the invention.

The grinding of the nanotubes may in particular be carried out cold or hot and be carried out according to known techniques used in devices such as ball mills, hammers, grinders, knives, gas jet or any other system. grinding capable of reducing the size of the entangled network of nanotubes. It is preferred that this grinding step is performed according to a gas jet grinding technique and in particular in an air jet mill.

The purification of the crude or milled nanotubes can be carried out by washing with a sulfuric acid solution, so as to rid them of any residual mineral and metallic impurities originating from their preparation process. The weight ratio of the nanotubes to the sulfuric acid may especially be between 1: 2 and 1: 3. The purification operation may also be carried out at a temperature ranging from 90 to 120 ° C, for example for a period of 5 to 10 hours. This operation may advantageously be followed by rinsing steps with water and drying the purified nanotubes.

The oxidation of the nanotubes is advantageously carried out by putting them in contact with a solution of sodium hypochlorite containing from 0.5 to 15% by weight of NaOCl and preferably from 1 to 10% by weight of NaOCl, for example in a weight ratio of nanotubes to sodium hypochlorite ranging from 1: 0.1 to 1: 1. The oxidation is advantageously carried out at a temperature below 9

60 ° C and preferably at room temperature for a period ranging from a few minutes to 24 hours. This oxidation operation may advantageously be followed by filtration and / or centrifugation, washing and drying steps of the oxidized nanotubes.

The functionalization of the nanotubes can be carried out by grafting reactive units such as vinyl monomers on the surface of the nanotubes. The material constituting the nanotubes is used as a radical polymerization initiator after having been subjected to a heat treatment at more than 900 ° C., in an anhydrous and oxygen-free medium, which is intended to eliminate the oxygenated groups from its surface. It is thus possible to polymerize methyl methacrylate or hydroxyethyl methacrylate on the surface of carbon nanotubes.

Crude nanotubes, optionally milled, that is to say nanotubes that are not oxidized, purified or functionalized and have undergone no other chemical treatment, are preferably used in the present invention.

The nanotubes may represent from 0.1 to 5% by weight, preferably from 0.5 to 4% by weight, and even more preferably from 1 to 3% by weight, relative to the weight of the composition used according to the invention. .

According to an advantageous version of the invention, it is possible to use nanotubes made from resources derived from renewable raw materials, that is to say containing organic carbon of renewable origin determined according to the ASTM D6866 standard. Such a method of 10

manufacturing has been described by the Applicant in the patent application EP 08103248.4.

More preferably, the composition used according to the invention may comprise nanotubes and / or copolyamide precursors derived in whole or in part from resources derived from renewable raw materials within the meaning of ASTM D6866.

It is preferred that the nanotubes and the copolyamide be compounded by conventional devices such as twin-screw extruders or co-kneaders. In this process, the copolyamide is typically melt blended with the nanotubes, either in a single step or in two stages where the first step is the making of a masterbatch and the second step is mixing or diluting the masterbatch with the copolyamide. A masterbatch formed of copolyamide and nanotubes may comprise from 10 to 30% by weight, advantageously from 15 to 25% by weight, of nanotubes.

Alternatively, the nanotubes may be dispersed by any suitable means in the copolyamide in solution in a solvent. In this case, the dispersion can be improved, according to an advantageous embodiment of the present invention, by the use of dispersion systems, such as ultrasounds or rotor-stator systems, or of particular dispersing agents.

A rotor-stator system is marketed by SILVERSON under the trademark Silverson L4RT. Another type of rotor-stator system is 11

marketed by IKA-WERKE under the trade name Ultra-Turrax.

Other rotor-stator systems still consist of colloid mills, deflocculating turbines and high-shear mixers of the rotor-stator type, such as the apparatus marketed by the company IKA-WERKE or the company ADMIX.

The dispersing agents may in particular be chosen from plasticizers which may themselves be chosen from the group consisting of: alkyl esters of phosphates or of hydroxybenzoic acid (the alkyl group of which, preferably linear, contains from 1 to 20 carbon atoms ) phthalates, in particular dialkyl or alkylaryl, in particular alkylbenzyl, alkyl groups, linear or branched, independently containing 1 to 12 carbon atoms, adipates, especially dialkyls, sulfonamides, in particular aryl sulphonamides, the aryl group of which is optionally substituted by at least one alkyl group containing from 1 to 6 carbon atoms, such as benzene sulphonamides and toluene sulphonamides, which may be N-substituted or N, N-disubstituted with at least one alkyl group, preferably linear, containing from 1 to 20 carbon atoms, and - mixtures thereof.

Alternatively, the dispersing agent may be a copolymer comprising at least one hydrophilic anionic monomer and at least one monomer including at least one aromatic ring, such as the copolymers described in document FR-2 766 106, the weight ratio of the nanotube dispersing agent preferably ranging from 0.6: 1 to 1.9: 1. In another embodiment, the dispersing agent may be a vinylpyrrolidone homo- or copolymer, the ratio by weight of the nanotubes to the dispersing agent preferably ranging from 0.1 to less than 2. Alternatively, the mixture of carbon nanotubes and copolyamide can be obtained by diluting a commercial masterbatch such as Graphistrength C M2-20 available from ARKEMA.

The adhesive composition used according to the invention may be in solid form, especially in the form of powder, granules, sheets, threads, filaments, netting, etc., or in liquid or semi-liquid form, advantageously in the form of an aqueous dispersion, solution or emulsion.

In addition to the copolyamide and the nanotubes described above, as well as the possible plasticizers mentioned above, it may contain at least one adjuvant chosen from the chain limiters, the anti-oxygen stabilizers, the light stabilizers, the dyes, the anti-shock agents, antistatic agents, flame retardants, lubricants, and mixtures thereof.

The composition used according to the invention is more particularly used as a hot-melt glue, for welding together identical or different materials chosen in particular from: wood; paper ; cardboard ; metal ; glass ; synthetic or natural textiles; leather ; sheets of polymeric material such as polyesters, polyolefins or polyamides; and self-adhesive cables for deflection coils for cathode ray tubes.

Specifically, the adhesive composition may be in the form of monofilaments, multifilaments, canvas, veil or films. This adhesive composition can also be applied to the materials to be welded using dough coating, powder coating or two-point coating techniques, well known to those skilled in the art. This composition can thus be deposited either on the entire surface of the materials to be welded, or only on distinct areas thereof, then the laminate obtained can be compressed at high temperature, typically at 80-150 ° C, and then cooled to ambient temperature. Subsequent stages of drying and / or evaporation of solvents are generally not necessary.

The invention will now be illustrated by the following examples, which are given for purposes of illustration only and are not intended to limit the scope of the invention defined by the appended claims.

EXAMPLES Example 1: Preparation of an adhesive composition 14

Multilayered carbon nanotubes (Graphistrength C100 from ARKEMA) were added to a 6 / 6.6 / 11/12 copolyamide having a melting temperature of 118 ° C. and an MFI of 22 g / 10 min at 130 ° C. under a load of 2.16 kg (Platamid H106 from ARKEMA). The nanotubes were added at a rate of 20% by weight to form a masterbatch which was then diluted in a matrix consisting of the same copolyamide, using a DSM twin-screw micro-extruder equipped with a flat die, the extrusion parameters being as follows: temperature: 225 ° C .; rotational speed: 150 rpm; mixing time: 30 minutes. Composite films having 3% by weight of nanotubes having a thickness of 500 μm and a width of 30 mm were thus obtained. These were cooled at the outlet of die with the aid of an air knife.

Example 2: Electrical and Adhesive Properties

The resistive and adhesive properties of a film according to Example 1 (hereinafter, film A-NTC) were evaluated by comparison with similar films based on Platamid H106 containing 22% by weight of carbon black (Ensaco 250G of TIMCAL) (hereinafter, film A-NC) and with a film of Platamid H106 free of conductive fillers (hereinafter, film A).

The surface resistances were measured using the Sefelec M1500P device equipped with electrodes, under the following conditions: applied voltage: 100 V charging time before reading: 15 seconds electrode length: 30 mm distance between electrodes: 50 mm. 15

The adhesion properties were measured after application of each of the films tested, on the one hand, on a sheet of PET 350} thick gym and, on the other hand, between two sheets of PET 170} gym 'thickness. The corresponding bilayer and trilayer structures were obtained by hot pressing of these laminates under the conditions below. - temperature of the heating plates: 150 ° C - hold time between trays: 5 min - holding pressure: low. These structures were subjected to a peel test on a DY30 dynamometer, using a free geometry method, using a crosshead speed of 50 mm / min and a 100 N test cell.

The results of these tests are summarized in Table 1 below.

Table 1 Film A Film A- Film A- NC NTC Resistivity (ohm) 1x1012 <1x10 <1x10 Adhesion to PET - 6 0 1 Bilayer structure (N / 15 mm) Adhesion to PET - 8 0 2 Three-layer structure (N / 15 mm ) It appears from this table that the film consisting of the composition according to the invention (film A-NTC) is also 16

conductive as the A-NC film while exhibiting much better adhesion properties.

Example 3: Preparation of an adhesive composition A film similar to that of Example 1 was made on a micro-extruder operating at 240 ° C (the other extrusion parameters being in accordance with Example 1), except that it contained 2% by weight of carbon nanotubes.

Example 4: Peel test

The adhesion properties of the film obtained in Example 3 (hereinafter, B-NTC film) were compared with those of an identical film but not containing carbon nanotubes (hereinafter, film B). after each of these films was applied between two 175 μm thick PET sheets and the resulting laminates were pressed as indicated in Example 2.

The three-layer structures thus obtained were subjected to a peel test on a DY30 dynamometer, using a free geometry method (90 ° angle), using a crosshead speed of 50 mm / min and a test cell of 100 N. The test was performed in duplicate.

The average of the maximum peel forces measured in these tests is: - for film B: 11.5 N / 15 mm - for film B-NTC: 9.5 N / 15 mm. 17

The peel forces observed for the film consisting of the composition according to the invention are therefore similar to those measured for the comparative film. However, the film B-NTC is conductive, while the film B is an insulator.

In this regard, it was verified that the surface resistance of the B-NTC film was less than or equal to 1x106 ohm, while that of the film B was of the order of 1x1012 ohm.

These examples thus demonstrate that carbon nanotubes make it possible to obtain a compromise of adhesive properties and conduction properties.

Claims (9)

REVENDICATIONS1. Use, as an electrically conductive adhesive composition, of a composition containing: (a) carbon nanotubes and (b) at least one copolyamide obtainable from at least two different starting materials selected from (i) lactams, (ii) aminocarboxylic acids and (iii) equimolar amounts of diamines and dicarboxylic acids. 2. Use according to claim 1, characterized in that the copolyamide is obtainable by polycondensation of (i) at least one lactam chosen from lauryllactam and / or caprolactam, preferably a combination of these two lactams, and at least one other polyamide precursor selected from (ii) aminocarboxylic acids and (iii) equimolar amounts of diamines and dicarboxylic acids. 3. Use according to claim 1 or 2, characterized in that said copolyamide has a melting temperature between 40 and 150 ° C, preferably between 70 and 140 ° C. 4. Use according to any one of claims 1 to 3, characterized in that the aminocarboxylic acid is selected from α, β-amino carboxylic acids such as 11-aminoundecanoic acid or 12-aminododecanoic acid. 5. Use according to any one of claims 1 to 4, characterized in that the precursor 19 (iii) is a combination of at least one aliphatic, cycloaliphatic or aromatic dicarboxylic acid C6-Cm, such as adipic acid , azelaic acid, sebacic acid, brassylic acid, n-dodecanedioic acid, terephthalic acid, isophthalic acid or 2,6-naphthalene dicarboxylic acid with at least one aliphatic, cycloaliphatic diamine arylaliphatic or aromatic C4-C22, such as hexamethylenediamine, piperazine, 2-methyl-1,5-diaminopentane, m-xylylene diamine or p-xylylenediamine; it being understood that said diacid (s) carboxylic (s) and diamine (s) are used, when present, in equimolar amount. 6. Use according to claim 5, characterized in that said precursor (iii) comprises a combination of adipic acid and hexamethylenediamine. 7. Use according to any one of claims 1 to 6, characterized in that said aminocarboxylic acid is 11-aminoundécanoïque acid. 8. Use according to any one of claims 1 to 7, characterized in that said copolyamide is obtainable from caprolactam, adipic acid, hexamethylenediamine, 11-aminoundecanoic acid and lauryllactam . 9. Use of a dispersion of carbon nanotubes in a copolyamide according to any one of claims 1 to 8 for producing an electrically conductive adhesive composition.