U.S. patent application number 10/567915 was filed with the patent office on 2007-08-30 for electrostatic composition based on a polyamide matrix.
Invention is credited to Gerard Bradley, Nicolangelo Peduto.
Application Number | 20070203282 10/567915 |
Document ID | / |
Family ID | 34073105 |
Filed Date | 2007-08-30 |
United States Patent
Application |
20070203282 |
Kind Code |
A1 |
Bradley; Gerard ; et
al. |
August 30, 2007 |
Electrostatic Composition Based On A Polyamide Matrix
Abstract
The invention relates to a composition based on a polyamide
matrix comprising electrically conductive charges and antistatic
agents. This composition makes it possible to obtain plastic
articles, for example, body parts used in the automobile industry
that are well-suited for painting by means of an electrostatic
paint deposition process.
Inventors: |
Bradley; Gerard; (Saronno,
IT) ; Peduto; Nicolangelo; (Cesano Maderno,
IT) |
Correspondence
Address: |
Jean- Louis Seugnet;Rhodia Inc - Legal Department
8 Cedar Brook Drive
CN 7500
Cranbury
NJ
08512-7500
US
|
Family ID: |
34073105 |
Appl. No.: |
10/567915 |
Filed: |
August 3, 2004 |
PCT Filed: |
August 3, 2004 |
PCT NO: |
PCT/FR04/02077 |
371 Date: |
October 31, 2006 |
Current U.S.
Class: |
524/439 ;
524/495 |
Current CPC
Class: |
C08L 77/06 20130101;
C08L 77/02 20130101; C08L 77/00 20130101; C08L 77/02 20130101; C08L
77/00 20130101; C08L 77/02 20130101; C08L 77/00 20130101; C08L
77/00 20130101; C08L 2666/04 20130101; C08L 2666/04 20130101; C08K
3/04 20130101; C08L 2666/20 20130101; C08L 2666/04 20130101; C08L
2666/20 20130101; C08L 2666/20 20130101; C08L 77/06 20130101; C08L
77/06 20130101; B60R 13/08 20130101; C08K 3/04 20130101 |
Class at
Publication: |
524/439 ;
524/495 |
International
Class: |
C08K 3/08 20060101
C08K003/08; C08K 3/04 20060101 C08K003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 2003 |
FR |
0309782 |
Claims
1-19. (canceled)
20. A composition comprising a polyamide matrix, comprising: at
least 2% by weight of electrically conductive fillers; and at least
1% by weight of antistatic agents; the percentages by weight being
expressed with respect to the total weight of the composition.
21. The composition as claimed in claim 20, exhibiting a surface
resistivity of between 10.sup.5 .OMEGA. and 10.sup.11 .OMEGA.,
measured according to Standard IEC 61340-4-1.
22. The composition as claimed in claim 20, having a discharge time
of greater than or equal to 10 seconds, measured according to
Standard IEC 61340-5-1.
23. The composition as claimed in claim 20, having from 2 to 50% by
weight of electrically conductive fillers, with respect to the
total weight of the composition.
24. The composition as claimed in claim 20, wherein the
electrically conductive fillers are a carbon black, a metal, a
graphite, a conductive polymer, a glass or an inorganic filler
coated with a metal layer.
25. The composition as claimed in claim 20, having from 2 to 10% by
weight of carbon black as electrically conductive fillers, with
respect to the total weight of the composition.
26. The composition as claimed in claim 20, having from 1 to 30% by
weight of antistatic agents, with respect to the total weight of
the composition.
27. The composition as claimed in claim 20, wherein the antistatic
agents are a polyetheramide, a sodium alkylsulfonate, an
alkylbenzenesulfonate, primary, secondary or tertiary amines, an
ethoxylated amine, an ethoxylated alcohol, glyceryl monostearates,
distearates or tristearates.
28. The composition as claimed in claim 20, wherein the antistatic
agent is a polyetheramide represented by the formula (I): ##STR4##
in which: n is an integer between 5 and 50; X represents an oxygen
atom or an NH group; PAO represents a poly(alkylene oxide) block;
PA represents a polyamide block, the repeat unit of which is
represented by either of the formulae (IIa) or (IIb): ##STR5## in
which: R.sup.1, R.sup.2 and R.sup.3 are aromatic or aliphatic
radicals having 4 to 36 carbon atoms.
29. The composition as claimed in claim 28, wherein the radical
R.sup.1 is a linear divalent pentyl radical.
30. The composition as claimed in claim 28, wherein the PAO block
is a poly(ethylene oxide) block.
31. The composition as claimed in claim 20, wherein the polyamide
matrix is composed of at least one (co)polyamide which is:
(co)polyamide 6; 4; 11; 12; 4,6; 6,6; 6,9; 6,10; 6,12; 6,18; 6,36;
6(T); 9(T); 6(I); MXD6; their copolymers or their blends.
32. The composition as claimed in claim 20, wherein the composition
further comprises at least one modifier of the impact strength
chosen from the group consisting of: ethylene-propylene (EP)
optionally grafted with maleic anhydride, ethylene-propylene-diene
(EPDM) terpolymer optionally grafted with maleic anhydride,
styrene-maleic anhydride (SMA), ultra-low-density polyethylene
(ULDPE), linear low density polyethylene (LLDPE), styrene-butadiene
(SBS and SBR) compounds, styrene-ethylene-butadiene-styrene (SEBS)
compounds, polypropylene (PP), acrylic elastomers, copolymers and
terpolymers of ethylene with acrylic or methacrylic derivatives
and/or with vinyl acetate, ionomers,
acrylonitrile-butadiene-styrene (ABS) terpolymer and
acrylic-styrene-acrylonitrile (ASA) terpolymer.
33. A process for the preparation of a polyamide composition as
claimed in claim 20, comprising the step of blending at least 2% by
weight of electrically conductive fillers and at least 1% by weight
of antistatic agents with a polyamide matrix, optionally in the
molten state.
34. A process for the preparation of a polyamide composition as
claimed in claim 20, comprising the step of blending the polyamide
matrix with: a concentrated blend based on a thermoplastic matrix
comprising at least 20% by weight of electrically conductive
fillers, and at least 1% by weight of antistatic agents.
35. The process as claimed in claim 34, wherein the thermoplastic
matrix is chosen from the group consisting of: the (co)polyamide,
ethylene-vinyl acetate (EVA) copolymer, ethylene-acrylic acid
(EAA), polyethylene (PE), polypropylene (PP), their copolymers and
their blends.
36. A process for the manufacture of an article by forming a
composition as claimed in claim 20 by an extrusion process, a
molding process or an injection process.
37. An article obtained by forming a composition as claimed in
claim 20.
38. The article as claimed in claim 37, painted by a process of
applying a paint by electrostatic deposition.
Description
[0001] The present invention relates to a composition based on a
polyamide matrix comprising electrically conductive fillers and
antistatic agents. The forming of this composition makes it
possible to obtain plastic articles, such as, for example, bodywork
components in the motor vehicle field, having a good ability to be
painted by a process for the electrostatic deposition of the
paint.
PRIOR ART
[0002] There exists a high demand in numerous industries for
components made of polyamide materials. This is because these
components are light and can be conceived and designed more easily
than components made of steel or aluminum, in particular in the
field of the motor vehicle industry.
[0003] However, plastic components present problems when it is
desired to paint them.
[0004] Thus, for example, in the field of motor vehicles, there
exist in particular three main methods for painting
electrostatically, that is to say by movement of the particles
under the influence of an electric current. The first, referred to
as "inline" process, refers to a process according to which the
component made of plastic is assembled on the vehicle after the
latter has been subjected to degreasing and electroplating stages,
followed by a drying stage. The component made of plastic and the
vehicle are subsequently painted and dried by heating. The second,
referred to as "online" process, refers to a process according to
which the component made of plastic is assembled on the vehicle at
the beginning of the process mentioned above. The plastic
components are thus subjected to degreasing, electroplating and
drying stages at temperatures which can exceed 200.degree. C.
Consequently, for this type of process, it is necessary for the
components made of plastic to be able to withstand higher
temperatures. In a third process, referred to as "offline" process,
the component made of plastic is first painted in order to be
subsequently assembled on the vehicle.
[0005] When processes for painting by electrostatic deposition are
used, poor adhesion of the paint to conventional plastic components
is obtained. Specifically, the paint easily comes away and does not
adhere or only slightly adheres to the plastic components.
[0006] In order to render plastic components suitable for being
painted by a process for the electrostatic deposition of the paint,
it is known to add conductive fillers to the thermoplastic matrix.
However, the incorporation of these fillers has a negative effect
on some properties of the plastics, such as the mechanical
properties. Furthermore, the incorporation of conductive fillers
significantly increases the melt viscosity of the thermoplastic
matrices, rendering them unsuitable for use in certain processes
for the forming of these matrices.
[0007] Thus, there exists a need to manufacture and use plastic
components exhibiting excellent mechanical properties, such as good
impact strength, and a good ability to be painted by a process for
the electrostatic deposition of the paint.
INVENTION
[0008] The Applicant Company has demonstrated a composition based
on a polyamide matrix comprising electrically conductive fillers
and antistatic agents.
[0009] This polyamide composition makes possible the forming of
articles exhibiting a good balance in mechanical properties,
thermal properties and properties with regard to the ability to be
painted, in particular by deposition of paint by an electrostatic
process.
[0010] The plastic components according to the invention also
exhibit a suitable linear thermal expansion coefficient (LTEC), in
particular for the field of the motor vehicle industry. The plastic
components according to the invention furthermore have a good
temperature stability, a good surface appearance and a good
propensity for molding.
[0011] These plastic components are thus very well suited to
processes for painting by electrostatic deposition, such as the
"inline", "online" and "offline" processes used in particular in
the motor vehicle industry.
[0012] Moreover, it is apparent that the composition based on a
polyamide matrix according to the invention has a significantly
lower melt viscosity, in comparison with a polyamide composition
comprising solely conductive fillers, which is in particular
advantageous for certain processes for the manufacture of
components, such as injection molding.
DETAILED ACCOUNT OF THE INVENTION
[0013] A first subject matter of the present invention is a
composition comprising at least one polyamide matrix:
[0014] at least 2% by weight of electrically conductive fillers;
and
[0015] at least 1% by weight of antistatic agents; the percentages
by weight being expressed with respect to the total weight of the
composition.
[0016] This composition can comprise one or more types of
electrically conductive fillers and one or more types of antistatic
agents.
[0017] Preferably, the composition according, to the invention is a
composition which dissipates static electricity and which exhibits
a surface resistivity of between 10.sup.5 .OMEGA. and 10.sup.11
.OMEGA., according to Standard IEC 61340-4-1.
[0018] The composition according to the present invention can also
exhibit a discharge time of greater than or equal to 10 seconds,
preferably of greater than or equal to 30 seconds, more preferably
of greater than or equal to 50 seconds, measured according to
Standard IEC 61340-5-1. The discharge time can, for example, be
measured on a sheet (for example having the following dimensions:
200.times.150.times.3 mm) obtained from the composition according
to the invention, to which a charge of 1000 volts (V) is applied.
The discharge time corresponds to the time necessary for the
electrical voltage at the surface of the sheet to change from 1000
V to 100 V.
[0019] The parameters of surface resistivity and of discharge time
of the composition of the invention are highly appropriate in
particular for the production of articles which are highly suitable
for painting and which have a good compromise in mechanical
properties.
[0020] The composition according to the invention can comprise from
2 to 50% by weight of electrically conductive fillers, with respect
to the total weight of the composition, preferably from 2 to 30% by
weight, more preferably still from 2 to 10% by weight, particularly
from 2 to 5% by weight.
[0021] The electrically conductive fillers are preferably chosen
from the group consisting of: a carbon black, a metal, a graphite,
a conductive polymer, a glass and/or an inorganic filler coated
with a metal layer, and/or their mixture.
[0022] The glass and/or the inorganic fillers can be coated with a
layer of metal, such as nickel, aluminum, silver, iron, chromium
and/or titanium, for example.
[0023] The electrically conductive fillers can be in the form of
spheres, such as, for example, in the form of microspheres and/or
nanospheres; of tubes, such as, for example, in the form of
microtubes and/or nanotubes; and/or of fibers, such as, for
example, in the form of microfibers and/or nanofibers. These fibers
can be cut up and/or ground.
[0024] Use may be made, as conductive polymer, for example, of
polyaniline, polypyrrole, polythiophene and/or poly-acetylene.
[0025] Preferably, the conductive filler according to the invention
is carbon black.
[0026] The conductive carbon black is described in particular in
Carbon Black, Second Edition, Revised and Expanded, Science and
Technology, edited by J. B. Donnet, R. C. Bansal and M. J. Wang,
Marcel Dekker Inc., pages 271-275. Preferably, the composition
according to the invention comprises from 2 to 10% by weight of
carbon black, preferably from 2 to 5% by weight, particularly from
2 to 4% by weight, as electrically conductive fillers, with respect
to the total weight of the composition.
[0027] The antistatic agents used according to the present
invention can also be referred to as "dissipating electrostatic
agents".
[0028] Preferably, the composition according to the invention
comprises from 1 to 30% by weight of antistatic agents, with
respect to the total weight of the composition, more preferably
still from 5 to 20% by weight.
[0029] The antistatic agents can be chosen, for example, from the
group consisting of polyetheramides, sodium alkyl-sulfonates,
alkylbenzenesulfonates, primary, secondary or tertiary amines,
ethoxylated amines, ethoxylated alcohols, glyceryl monostearates,
distearates or tristearates, and their mixtures.
[0030] The term "polyetheramides" is understood to mean various
types of polymers comprising one or more polyamide blocks and one
or more poly(alkylene oxide) blocks.
[0031] Preferably, the polyetheramide is a block polymer compound
represented by the formula (I): ##STR1## in which:
[0032] n is an integer between 5 and 50;
[0033] X represents an oxygen atom or an NH group;
[0034] PAO represents a poly(alkylene oxide) block;
[0035] PA represents a polyamide block, the repeat unit of which is
represented by either of the formulae (IIa) or (IIb): ##STR2## in
which: R.sup.1, R.sup.2 and R.sup.3 are aromatic or aliphatic
radicals comprising 4 to 36 carbon atoms.
[0036] The block copolymer represented by the formula (I) is a
polyether-block-amide or a polyetheresteramide. Such compounds are
sold in particular by Atofina under the name of Pebax.RTM. and Ciba
under the name of Irgastat. They comprise polyamide blocks and
poly(alkylene glycol) blocks. The number of blocks of each nature
is between 3 and 50. It is preferably between 10 and 15. The number
of blocks is represented by the integer n in the formula (I).
[0037] The polyamide blocks can be represented by either of the
formulae (IIa) or (IIb) represented above. The blocks of formula
(IIa) are polyamides of the type of those obtained by
polymerization starting from lactams and/or amino acids. The
processes for the polymerization of such compounds are known:
mention is made, inter alia, of anionic polymerization or melt
polycondensation, for example in a VK tube. The (IIb) blocks are of
the type of those obtained by polycondensation of dicarboxylic
acids with amines.
[0038] Preferably, X represents an oxygen atom, the formula (I)
thus being as follows: ##STR3##
[0039] According to the embodiment where the polyamide block is
represented by the formula (IIa), the radical R.sup.1 is
advantageously chosen from the following radicals:
[0040] the linear divalent pentyl radical: the polyamide block is
then a polyamide 6 block;
[0041] the unbranched divalent decyl radical (10 carbon atoms): the
polyamide block is then a polyamide 11 block;
[0042] the unbranched divalent undecyl radical (11 carbon atoms):
the polyamide block is then a polyamide 12 block.
[0043] According to the embodiment where the polyamide block is
represented by the formula (IIb), the pairs of radicals R.sup.2 and
R.sup.3 are advantageously chosen from the following pairs:
[0044] R.sup.2=linear divalent butyl radical, R.sup.3=linear
divalent hexyl radical: polyamide 6,6 block;
[0045] R.sup.2=linear divalent butyl radical, R.sup.3=linear
divalent butyl radical: polyamide 4,6 block;
[0046] R.sup.2=linear divalent octyl radical, R.sup.3=linear
divalent hexyl radical: polyamide 6,10 block.
[0047] The poly(alkylene oxide) block can be chosen from
poly(ethylene oxide), poly(trimethylene oxide) or
poly(tetramethylene oxide) blocks. In the case where the block is
based on poly(ethylene oxide), it can comprise propylene glycol
units at the ends of the block.
[0048] The average molecular weights of each of the blocks are
independent of one another. However, it is preferable for them to
be close to one another. The average molecular weight of the PAO
blocks is preferably between 1000 and 3000 g/mol. The average
molecular weight of the PA blocks is advantageously between 1000
and 3000 g/mol.
[0049] The compound of formula (I) can be obtained by catalyzed
reaction between polyamide macromolecular chains, the end
functional groups of which are carboxylic acid functional groups,
and polyetherdiol chains, that is to say poly(alkylene oxide)
macromolecular chains, the end functional groups of which are
alcohol functional groups. They are, for example, poly(ethylene
glycol) chains comprising alcohol endings.
[0050] The reaction between the end functional groups of the blocks
can be catalyzed by tetraalkyl orthotitanates or zirconyl
acetate.
[0051] According to a specific embodiment of the invention, the
modifying compounds of formula (I) have a melting point of greater
than 150.degree. C., preferably of between 150 and 250.degree.
C.
[0052] The polyamide matrix according to the invention is generally
composed of at least one (co)polyamide chosen from the group
consisting of: (co)polyamide 6; 4; 11; 12; 4,6; 6,6; 6,9; 6,10;
6,12; 6,18; 6,36; 6(T); 9(T); 6(I); MXD6; their copolymers and/or
blends.
[0053] Mention may be made, for example, of semicrystalline or
amorphous polyamides, such as aliphatic polyamides, semiaromatic
polyamides and more generally linear polyamides obtained by
polycondensation between an aliphatic or aromatic saturated diacid
and an aromatic or aliphatic saturated primary diamine, polyamides
obtained by condensation of a lactam or of an amino acid, or linear
polyamides obtained by condensation of a mixture of these various
monomers. These copolyamides can, for example, be
poly(hexamethylene adipamide), the polyphthalamides obtained from
terephthalic and/or isophthalic acid, the copolyamides obtained
from caprolactam, and from one or more monomers generally used for
the manufacture of polyamides, such as adipic acid, terephthalic
acid and/or hexamethylenediamine.
[0054] Polyamide 6(T) is a polyamide obtained by polycondensation
of terephthalic acid and hexamethylenediamine. Polyamide 9(T) is a
polyamide obtained by polycondensation of terephthalic acid and a
diamine comprising 9 carbon atoms. Polyamide 6(I) is a polyamide
obtained by polycondensation of isophthalic acid and
hexamethylenediamine. Polyamide MXD6 is a polyamide obtained by
polycondensation of adipic acid and meta-xylylenediamine.
[0055] The composition can comprise one or more (co)polyamides
obtained as a blend or as a copolymer, for example.
[0056] The polyamide matrix can in particular be a polyamide
comprising star or H macromolecular chains and, if appropriate,
linear macromolecular chains. The polymers comprising such star or
H macromolecular chains are disclosed, for example, in the
documents FR 2 743 077, FR 2 779 730, U.S. Pat. No. 5,959,069, EP 0
632 703, EP 0 682 057 and EP 0 832 149.
[0057] According to another specific alternative form of the
invention, the polyamide matrix of the invention can be a polymer
of random tree type, preferably a copolyamide exhibiting a random
tree structure. These copolyamides of random tree structure and the
process for the preparation thereof are disclosed in particular in
document WO 99/03909. The thermoplastic matrix of the invention can
also be a composition comprising a linear thermoplastic polymer and
a star, H and/or tree thermoplastic polymer as described above. The
thermoplastic matrix of the invention can also comprise a
hyperbranched copolyamide of the type of those disclosed in the
document WO 00/68298. The thermoplastic matrix of the invention can
also comprise any combination of linear, star, H or tree
thermoplastic polymer or hyperbranched copolyamide as described
above.
[0058] According to a specific characteristic of the invention, the
polyamide matrix of the composition is composed of a blend of a
polyamide with one or more other polymers, preferably of
(co)polyamide type. A blend of (co)polyamide with at least one
polymer chosen from the group consisting of: polyphenylene ether
(PPE), poly(vinyl chloride) (PVC), the
acrylonitrile-butadiene-styrene (ABS) polymer, polyethylene (PE),
polypropylene (PP), poly(ethylene terephthalate) (PET) and/or
poly(butylene terephthalate) (PBT), can also be envisaged.
[0059] The polyamide composition according to the invention can
comprise reinforcing and/or bulking fillers preferably chosen from
the group consisting of fibrous fillers, such as glass fibers,
metal fibers or carbon fibers; inorganic fillers, such as clays,
kaolin, wollastonite, mica, talc and glass beads; finely
dispersible reinforcing nanoparticles, such as montmorillonite; or
made of thermosetting material. The level of incorporation of these
fillers is in accordance with the standards in the field of
composite materials. The level of filler can, for example, be from
1 to 70% by weight, preferably from 10 to 60% by weight, with
respect to the total weight of the composition.
[0060] The polyamide composition according to the invention can
also comprise at least one agent which modifies the impact strength
chosen, for example, from the group consisting of:
ethylene-propylene (EP) optionally grafted with maleic anhydride,
ethylene-propylene-diene (EPDM) terpolymer optionally grafted with
maleic anhydride, elastomeric copolymers, such as styrene-maleic
anhydride (SMA), for example, ultra-low-density polyethylene
(ULDPE), linear low density polyethylene (LLDPE), styrene-butadiene
(SBS and SBR) compounds, styrene-ethylene-butadiene-styrene (SEBS)
compounds, polypropylene (PP), acrylic elastomers (such as
polyacrylate elastomers), copolymers and terpolymers of ethylene
with acrylic or methacrylic derivatives and/or with vinyl acetate,
ionomers, acrylonitrile-butadiene-styrene (ABS) terpolymer and
acrylic-styrene-acrylonitrile (ASA) terpolymer. The modifiers of
the impact strength can optionally comprise grafted groups, such as
maleic anhydride, for example. The modifiers of the impact strength
according to the invention can also be combinations, blends,
homopolymers, copolymers and/or terpolymers of the compounds
mentioned above. The modifiers of the impact strength are chosen by
a person skilled in the art for their compatibility with the
polyamide matrix.
[0061] The polyamide composition according to the invention can
additionally comprise one or more additives commonly used by a
person skilled in the art in thermoplastic compositions used in
particular for the manufacture of molded articles. Mention may thus
be made, as example of additives, of heat stabilizers, flame
retardants, molding agents, such as calcium stearate, UV
stabilizers, antioxidants, lubricants, abrasion reducers, pigments,
dyes, plasticizers, laser marking promoters, waxes or agents which
modify the impact strength. By way of examples, the antioxidants
and heat stabilizers are, for example, alkaline halides, copper
halides, sterically hindered phenolic compounds, organic phosphites
and aromatic amines.
[0062] The present invention also relates to a process for the
preparation of a polyamide composition as defined above in which at
least 2% by weight of electrically conductive fillers and at least
1% by weight of antistatic agents are blended with a polyamide
matrix, optionally in the molten state.
[0063] The blending can be carried out in the molten state, for
example in a single- or twin-screw extruder, or by blending without
conversion to the molten state, for example in a mechanical mixer.
The compounds can be introduced simultaneously or successively. Any
means known to a person skilled in the art relating to the
introduction of the various compounds of a thermoplastic
composition can be used. Use is generally made of an extrusion
device in which the material is heated, subjected to a shear force
and conveyed. Such devices are fully known to a person skilled in
the art.
[0064] The composition according to the invention, when it is
prepared using an extrusion device, can be put into the form of
granules.
[0065] The electrically conductive fillers and antistatic agents
can be blended beforehand, for example by continuous or batchwise
mixing. To do this, use may be made, for example, of a Banbury
mixer.
[0066] A concentrated blend, preferably based on polyamide,
comprising the electrically conductive fillers and/or the
antistatic agents, for example prepared according to the method
described above, can also be added to the polyamide matrix. This
masterblend can, for example, be prepared by preblending the
various compounds.
[0067] Thus, the present invention also relates to a process for
the preparation of a polyamide composition as described above in
which at least one polyamide matrix is blended with:
[0068] a concentrated blend based on a thermoplastic matrix
comprising at least 20% by weight of electrically conductive
fillers, and
[0069] at least 1% by weight of antistatic agents.
[0070] The masterblend can comprise, for example, from 20 to 50% by
weight of electrically conductive fillers, such as carbon
black.
[0071] This masterblend is based on a thermoplastic matrix, for
example chosen from the group consisting of: a (co)polyamide, an
ethylene-vinyl acetate (EVA) copolymer, an ethylene-acrylic acid
(EAA), a polyethylene (PE), a polypropylene (PP), their copolymers
and/or blends.
[0072] It should be noted that the masterblend can also comprise
antistatic agents according to the invention.
[0073] Numerous methods for blending the (co)polyamides of the
invention with the reinforcing and/or bulking fillers, agents which
modify the impact strength and/or additives can be envisaged. For
example, these can be introduced as a blend with the (co)polyamide
in the molten state before the manufacture of granules. Some of
these fillers, agents and/or additives can also be added during the
polymerization of the (co)polyamide.
[0074] The present invention also relates to a process for the
manufacture of an article by forming a composition according to the
invention by a process chosen from the group consisting of an
extrusion process, such as the extrusion of thin sheets and films,
a molding process, such as compression molding, and an injection
process, such as injection molding.
[0075] The articles according to the invention can, for example, be
automobile components, in particular bodywork components, pipes
intended for the transportation of liquids or gases, tanks,
coverings, films and/or covers made of plastic for tanks.
[0076] The present invention also relates to a process for the
application of paint by electrostatic deposition on an article,
characterized in that an article of the invention as described
above is used in this process. The paint can be applied to the
article, for example, by spraying or immersion. Generally, a
process for the application of paint by electrostatic deposition on
an article comprises at least the following stages: cataphoresis
treatment of the article at temperatures of between 150 and
250.degree. C., application of a primer by electrostatic spraying
and application of the paint by electrostatic spraying. Each
spraying stage can be followed by stage(s) of heating at
temperatures of between 100 and 200.degree. C. and by stage(s) of
cooling.
[0077] The present invention also relates to an article painted by
a process for the application of paint by electrostatic
deposition.
[0078] Other details or advantages of the invention will become
more clearly apparent in the light of the examples given below
solely by way of indication.
Experimental Part
Materials Used:
[0079] PA 6,6: polyamide 6,6 with a relative viscosity of 2.7
(according to Standard ISO 307 using sulfuric acid as solvent) sold
by Rhodia Engineering Plastics under the name Techny.RTM. 27
A00.
[0080] PA 6: polyamide 6 with a relative viscosity of 2.7
(according to Standard ISO 307 using sulfuric acid as solvent) sold
by Rhodia Engineering Plastics under the name ASN 27 S.
[0081] Elastomer: EPR-g-MA: ethylene-propylene copolymer comprising
grafted maleic anhydride, with a density of 0.87 g/ml (measured
according to ASTM D792) and an MFR of 23 (measured according to
ASTM D1238 at 280.degree. C./2.16 kg).
[0082] Conductive carbon black: sold by Akzo under the name Ketjen
Black 600.RTM..
[0083] Polyetheramide: multisegmented block copolymer comprising
50% by weight of polyamide 6 blocks and 50% by weight of
polyethylene glycol blocks, X corresponding to an oxygen atom, the
average molecular weight of each block of which is approximately
1500 g/mol. Melting point: 204.degree. C. according to Standard
ASTM D3418.
[0084] Wollastonite: calcium silicate having a particle size of
less than 10 .mu.m and an aspect ratio of 5, surface treatment with
a coupling agent.
[0085] Mica: mica of ground muscovite type having an average
particle size, expressed as D.sub.50, of less than or equal to 40
.mu.m and a bulk density of 450 g/l.
[0086] Others: corresponds to a blend of color stabilizer and of
lubricants (calcium stearate).
[0087] Masterblend MB: blend based on EVA comprising 30% of
conductive carbon black Ketjen Black 300.RTM., sold by Iridi Color
Srl under the name MBUN NIRO N129.
EXAMPLE 1
Preparation of Compositions
[0088] Polyamide-based compositions are manufactured by blending
various compounds mentioned below via a twin-screw extruder. The
compositions, the compounds used and their amounts are given in
table 1: TABLE-US-00001 TABLE 1 Formulations A B C D E F G 1 2 PA
6,6 (%) 54.5 56.5 58.5 59.8 60.5 55.5 50.5 58.5 57.5 PA 6 (%) 10 10
10 10 0 0 0 0 0 Elastomer (%) 12 12 12 12 12 12 12 12 12 Mica (%)
15 15 15 15 15 15 15 15 15 Others (%) 2.5 2.5 2.5 2.5 2.5 2.5 2.5
2.5 2.5 Polyetheramide (%) 0 0 0 0 10 15 20 10 10 Carbon black (%)
6 4 2 1 0 0 0 2 3 Adhesion of the paint + + - - - - - + + Surface
resistivity (.OMEGA.) n 5 .times. 10.sup.5 7 .times. 10.sup.11
insulator 25 .times. 10.sup.9 25 .times. 10.sup.9 25 .times.
10.sup.9 16 .times. 10.sup.9 5 .times. 10.sup.9 MFI (g/10 min) 0
0.1 5.1 8.5 14 15 17 12 10 Notched Charpy impact 5.4 5.6 5.9 6.9
8.3 8.5 9 7.5 7 (kJ/m.sup.2) Elongation at break (%) 5.7 7.7 12.1
11.1 18 21 23 12.5 11 Tensile modulus (N/mm.sup.2) 3540 3700 3530
3510 3210 3250 2910 3100 3210 HDT (.degree. C.) 200 201 206 208 205
202 192 205 205
[0089] The percentages of the various components are expressed by
weight, with respect to the total weight of the composition.
[0090] The properties are measured in the following way:
[0091] MFI (melt flow index), according to Standard ISO 1133 at
275.degree. C. with a load of 5 kg.
[0092] Notched Charpy impact according to Standard ISO 179/1 eA at
23.degree. C.
[0093] Elongation at break, according to Standard ISO 527 at
23.degree. C.
[0094] Tensile modulus, according to Standard ISO 527 at 23.degree.
C.
[0095] HDT (heat deflection temperature), according to Standard ISO
75Be with a load of 0.45 N/mm.sup.2.
[0096] Surface resistivity, according to Standard IEC 61340-4-1.
Measurement is carried out on an injection-molded sheet
(200.times.150.times.3 mm) by placing the probes of a device for
measuring the resistance (Metriso 2000 ESD) at a distance of 1 cm
from one another. A voltage of 100 volts is applied and the surface
resistivity of the sheet is measured. The measurement is carried
out in a room at a temperature of 23.degree. C. approximately and a
relative humidity of 50%.
[0097] Adhesion of the paint by electrostatic deposition: a sheet
is injection-molded from the above compositions. The paint is
applied to the sheets by an "online" process for painting by
cataphoresis in seven stages: stage 1: e-coat simulation
(cataphoresis treatment) at 185.degree. C. for 30 minutes. Stage 2:
cooling for 20 minutes. Stage 3: application of the primer, BASF
PMR82, by electrostatic spraying. Stage 4: heating at 160.degree.
C. for 30 minutes. Stage 5: cooling for 20 minutes. Stage 6:
application of a white paint by electrostatic spraying. Stage 7:
cooling for 20 minutes. Poor adhesion of the paint by electrostatic
deposition (recorded as-in the above table) is recorded if an
orangepeel appearance, a lack of paint and/or poor adhesion of the
paint to the sheet are observed. In the contrary case, good
adhesion of the paint (recorded as+in the above table) is
observed.
In the above table, n means not measured.
EXAMPLE 2
Preparation of Compositions
[0098] Polyamide-based compositions are manufactured by blending
various compounds mentioned below via a twin-screw extruder. The
compositions, the compounds used and their amounts are given in
table 2: TABLE-US-00002 TABLE 2 Formulations 3 4 PA 6,6 (%) 46.95
43.95 Elastomer (%) 7 7 Wollastonite (%) 26 26 Others (%) 2.05 2.05
Polyetheramide (%) 11 10 Masterblend MB (%) 7 11 Adhesion of the
paint + + Surface resistivity (.OMEGA.) 45 .times. 10.sup.9 3
.times. 10.sup.9 MFI (g/10 min) 23.5 18.7 Notched Charpy impact
(kJ/m.sup.2) 9.2 8 Elongation at break (%) 12.8 10.8 Tensile
modulus (N/mm.sup.2) 2730 2570 HDT (.degree. C.) 206 206
[0099] The percentages of the various components are expressed by
weight, with respect to the total weight of the composition.
* * * * *