U.S. patent application number 12/527014 was filed with the patent office on 2010-05-27 for polyamide-based thermoplastic polymer compositions.
Invention is credited to Marco Amici, Cesare Guaita.
Application Number | 20100130677 12/527014 |
Document ID | / |
Family ID | 38535647 |
Filed Date | 2010-05-27 |
United States Patent
Application |
20100130677 |
Kind Code |
A1 |
Amici; Marco ; et
al. |
May 27, 2010 |
POLYAMIDE-BASED THERMOPLASTIC POLYMER COMPOSITIONS
Abstract
Polyamide-based thermoplastic polymer compositions that exhibit
a good balance among the properties thereof, in particular their
mechanical properties, and a high fluidity in the molten state;
such compositions contain at least one high-fluidity polyamide and
a shock modification agent having functional groups that react with
the polyamide.
Inventors: |
Amici; Marco; (Perugia,
IT) ; Guaita; Cesare; (Tradate, IT) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Family ID: |
38535647 |
Appl. No.: |
12/527014 |
Filed: |
February 21, 2008 |
PCT Filed: |
February 21, 2008 |
PCT NO: |
PCT/EP08/52134 |
371 Date: |
January 20, 2010 |
Current U.S.
Class: |
524/606 ;
525/178; 525/184; 525/420 |
Current CPC
Class: |
C08L 33/20 20130101;
C08L 23/0884 20130101; C08L 77/06 20130101; C08L 2666/04 20130101;
C08L 2666/06 20130101; C08L 2666/06 20130101; C08L 2666/04
20130101; C08L 35/00 20130101; C08L 77/02 20130101; C08L 77/06
20130101; C08L 23/0869 20130101; C08L 77/06 20130101; C08L 77/02
20130101; C08L 77/02 20130101; C08L 33/08 20130101 |
Class at
Publication: |
524/606 ;
525/178; 525/184; 525/420 |
International
Class: |
C08L 77/06 20060101
C08L077/06; C08L 23/06 20060101 C08L023/06; C08L 23/12 20060101
C08L023/12 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 23, 2007 |
FR |
0701302 |
Claims
1.-13. (canceled)
14. A polymer composition comprising at least: a) a polyamide 6 or
66 obtained via a process of polymerization of the polyamide 6 or
66 monomers in the presence of monofunctional and/or difunctional
compounds comprising carboxylic acid or amine functional groups,
said polyamide having a melt flow index of greater than or equal to
10 g/10 min. according to the ISO1133 standard measured at a
temperature of 275.degree. C. with a load of 325 g; and b) an
impact modifier comprising functional groups that react with the
polyamide a).
15. The polymer composition as defined by claim 14, wherein the
molecular weight Mn of the polyamide ranges from 3,000 to 25,000
g/mol.
16. The polymer composition as defined by claim 14, wherein the
polydispersity index of the polyamide is less than or equal to
2.
17. The polymer composition as defined by claim 14, wherein the
polyamide is obtained by adding, at the beginning, during or at the
end of polymerization, aliphatic or aromatic, monocarboxylic or
dicarboxylic acids and/or aliphatic or aromatic, monoamines or
diamines.
18. The polymer composition as defined by claim 14, wherein the
polyamide has a melt flow index ranging from 10 to 50 g/10 min.
19. The polymer composition as defined by claim 14, wherein the
polyamide has a melt flow index ranging from 20 to 40 g/10 min.
20. The polymer composition as defined by claim 14, wherein the
impact modifiers are oligomeric or polymeric compounds comprising
at least one of the following monomers, or a mixture thereof:
ethylene, propylene, butene, isoprene, diene, acrylate, butadiene,
styrene, octene, acrylonitrile, acrylic acid, methacrylic acid,
vinyl acetate, vinyl esters such as acrylic and methacrylic esters,
and glycidyl methacrylate.
21. The polymer composition as defined by claim 14, wherein the
impact modifiers comprise an elastomeric base selected from the
group consisting of polyethylenes, polypropylenes, polybutenes,
polyisoprenes, ethylene-propylene rubbers (EPRs),
ethylene-propylene-diene rubbers (EPDMs), ethylene butene rubbers,
ethylene acrylate rubbers, butadiene styrene rubbers, butadiene
acrylate rubbers, ethylene octene rubbers, butadiene acrylonitrile
rubbers, ethylene acrylic acids (EAAs), ethylene vinyl acetate
(EVAs), ethylene acrylic esters (EEAs),
acrylonitrile-butadiene-styrene (ABS) copolymers,
styrene-ethylene-butadiene-styrene (SEBS) block copolymers,
styrene-butadiene-styrene (SBS) copolymers, core-shell elastomers
of methacrylate-butadiene-styrene (MBS) type, or blends of at least
two of the elastomers listed above.
22. The polymer composition as defined by claim 14, wherein the
functional groups of the impact modifier, that are capable of
reacting chemically with the polyamide a) are selected from the
group consisting of acids, carboxylic acids, salified acids,
esters, acrylates and methacrylates, ionomers, glycidyl groups,
epoxy groups, glycidyl esters, anhydrides, maleic anhydrides,
maleimides, and mixtures thereof.
23. The polymer composition as defined by claim 14, wherein the
impact modifiers are selected from the group consisting of
ethylene/acrylic ester/glycidyl methacrylate terpolymers,
ethylene/butyl ester acrylate copolymers, ethylene/n-butyl
acrylate/glycidyl methacrylate copolymers, ethylene/maleic
anhydride copolymers, maleic anhydride-grafted styrene/maleimide
copolymers, copolymers of styrene/ethylene/butylene/styrene
modified with maleic anhydride, maleic anhydride-grafted
styrene/acrylonitrile copolymers, maleic anhydride-grafted
acrylonitrile/butadiene/styrene copolymers, and hydrogenated
congeners thereof.
24. The polymer composition as defined by claim 14, wherein the
proportion of impact modifiers present therein ranges from 0.1% to
10% by weight.
25. The polymer composition as defined by claim 14, comprising at
least one reinforcing and/or bulking filler.
26. A method for producing a polymer composition as defined by
claim 14, comprising melt blending said polyamide a) and said
impact strength modifiers b).
27. The polymer composition as defined by claim 14, comprising at
least one polyamide 6.
28. The polymer composition as defined by claim 14, comprising at
least one polyamide 66.
29. A shaped article product of reaction between the polyamide and
the impact modifier as defined by claim 14.
30. A shaped article product of reaction between the constituents
of the polymer composition as defined by claim 14.
Description
[0001] The present invention relates to a polyamide-based
thermoplastic polymer composition that exhibits a good balance
between its properties, in particular its mechanical properties,
and a high melt flow. The invention relates in particular to a
composition comprising at least one high-fluidity polyamide and an
impact modifier comprising functional groups that react with the
polyamide, and to a method for preparing such a composition.
PRIOR ART
[0002] Among the properties that it is often desired to control in
the case of a thermoplastic intended to be formed by techniques
such as injection molding, gas injection molding, extrusion and
extrusion-blow molding, mention may be made of stiffness, impact
strength, dimensional stability, in particular at a relatively high
temperature, low post-forming shrinkage, a capacity for coating by
various processes, surface appearance and density. These properties
can be controlled, within certain limits, through the choice of a
polymer or through the addition to the polymer of compounds of
various natures. In the latter case, the term polymeric
compositions is used. The choice of a material for a given
application is generally guided by the required level of
performance with respect to certain properties and by its cost. The
aim is always to obtain new materials that can meet a specification
in terms of performance and/or cost. Polyamide is, for example, a
material that is widely used, in particular in the sector of the
automobile industry.
[0003] Polyamide is a polymer which is chemically resistant, which
is stable at high temperatures and which can be mixed with other
types of polymers in order to modify the properties thereof. It is,
for example, possible to improve its resilience by adding an
elastomeric polymer.
[0004] There are at least three major properties that it is desired
to obtain for these polyamide-based compositions, in particular
when they are used in these conversion processes.
[0005] The first of these properties lies in the fact that these
thermoplastic compositions used should be characterized, in the
melting state, by a fluidity and a rheological behavior compatible
with the forming processes of interest, such as injection molding.
Specifically, these thermoplastic compositions should be
sufficiently fluid, when they are molten, for it to be possible to
easily and rapidly convey and manipulate them in certain forming
devices, such as, for example, injection molding devices.
[0006] It is also sought to increase the mechanical properties of
these compositions. These mechanical properties are in particular
the impact strength, the flexural or tensile modulus, the flexural
strength or tensile strength, inter alia. Reinforcing fillers, such
as glass fibers, are generally used to this effect.
[0007] Finally, in the case of components molded from these
thermoplastic compositions, a clean and uniform surface appearance
is desired. This constraint becomes a problem which is difficult to
solve, particularly when a thermoplastic composition with a high
load of glass fibers is used, these glass fibers detrimentally
affecting the surface appearance of the molded components. It is
known practice, in order to obtain an acceptable surface
appearance, to use thermoplastic compositions that exhibit a high
fluidity. However, this increase in fluidity results in a decrease
in the mechanical properties of the articles obtained.
[0008] The result is thus that it is difficult to obtain these
various properties for the same polyamide-based thermoplastic
composition.
INVENTION
[0009] The applicant has developed a polyamide composition that
exhibits an increased melt flow and equivalent or superior
mechanical properties, in comparison with conventional polyamide
compositions, and that makes possible the preparation of articles
having an excellent surface appearance, in particular when they
comprise a high level of fillers.
[0010] The subject of the invention is thus a composition
comprising at least:
[0011] a) a polyamide of type 6 or 66 obtained by means of a
process of polymerization of the monomers of the polyamide 6 or 66
in the presence, in addition, of monofunctional and/or difunctional
compounds comprising carboxylic acid or amine functions; said
polyamide having a melt flow index of greater than or equal to 10
g/10 min. according to the ISO1133 standard measured at a
temperature of 275.degree. C. with a load of 325 g; and
[0012] b) an impact modifier comprising functional groups that
react with the polyamide a).
DETAILED DISCLOSURE OF THE INVENTION
[0013] The polyamide a) may be a thermoplastic polyamide of type
66, i.e. a polyamide obtained at least from adipic acid and
hexamethylenediamine, which may optionally comprise other polyamide
monomers.
[0014] The term "polyamide of type 66" is intended in particular to
mean a polyamide comprising at least 80 mol %, preferably at least
90 mol % of adipic acid and hexamethylenediamine monomer
residues.
[0015] The polyamide a) may be a thermoplastic polyamide of type 6,
i.e. a polyamide obtained at least from caprolactam, which may
optionally comprise other polyamide monomers.
[0016] The term "polyamide of type 6" is intended in particular to
mean a polyamide comprising at least 80 mol %, preferably at least
90 mol % of caprolactam monomer residues.
[0017] Preferably, the polyamide according to the invention has a
molecular weight Mn of between 3000 and 25000 g/mol, more
preferably between 5000 and 15000. It may have a polydispersity
index (D=Mw/Mn) of less than or equal to 2.
[0018] The polymerization of the polyamide of the invention is in
particular carried out according to the conventional operating
conditions for the polymerization of polyamides, continuously or
batchwise.
[0019] Such a polymerization process may comprise, briefly: [0020]
heating the mixture of monomers and water, with stirring and under
pressure; and [0021] maintaining the mixture at this temperature
for a given period of time, followed by decompression and
maintaining, for a given period of time, at a temperature above the
melting point of the mixture, in particular under nitrogen or under
vacuum, so as to thus continue the polymerization by removal of the
water formed.
[0022] At the end of polymerization, the polymer can be cooled
advantageously with water, and extruded in the form of rods. These
rods are cut up so as to produce granules.
[0023] According to the invention, the polyamide is produced by
adding during polymerization, in particular at the beginning of the
polymerization, monomers of the polyamides 6 or 66, in the
presence, in addition, of difunctional and/or monofunctional
compounds. These difunctional and/or monofunctional compounds have
amine or carboxylic acid functions capable of reacting with the
polyamide monomers. The difunctional compounds may have the same
amine or carboxylic acid functionality.
[0024] The difunctional and/or monofunctional compounds used are
agents for modifying the chain length of polyamides of type 6 or 66
and make it possible to obtain polyamides having a melt flow index
of greater than or equal to 10 g/10 min. according to the ISO1133
standard measured at a temperature of 275.degree. C. with a load of
325 g.
[0025] The polyamide-6 monomers are in particular adipic acid and
hexamethylenediamine, or hexamethylenediamine adipate, also called
nylon salt or N salt. The polyamide-6 monomers are caprolactam or
derivatives thereof.
[0026] It is possible to use, at the beginning, during or at the
end of polymerization, aliphatic or aromatic, monocarboxylic or
dicarboxylic acids of any type or aliphatic or aromatic, monoamines
or diamines of any type. It is in particular possible to use, as
monofunctional compound, n-hexadecylamine, n-octadecylamine and
n-dodecylamine, acetic acid, lauric acid, benzylamine and benzoic
acid. It is in particular possible to use, as difunctional
compound, succinic acid, terephthalic acid, isophthalic acid,
sebacic acid, azelaic acid, dodecanoic acid, fatty acid diamers,
di(.beta.-ethylcarboxy)cyclohexanone, 5-methyl
pentamethylenediamine, metaxylylenediamine, isophorone diamine and
1,4-cyclohexanediamine.
[0027] It is also possible to use an excess of adipic acid or an
excess of hexamethylenediamine for the production of a polyamide of
type 66 that exhibits a high melt flow.
[0028] Preferably, the proportion of acid end groups is different
than the proportion of amine end groups, in particular at least
twice as many or half as many. The amounts of amine and/or acid end
groups are determined by potentiometric assays after dissolution of
the polyamide. A method is, for example, described in "Encyclopedia
of Industrial Chemical Analysis", volume 17, page 293, 1973.
[0029] Preferably, the polyamide according to the invention has a
melt flow index, according to the ISO1133 standard measured at a
temperature of 275.degree. C. with a load of 325 g, of between 10
and 50 g/10 min., more preferably between 20 and 40 g/10 min.
[0030] According to the invention, the term "impact modifier" is
intended to mean a compound capable of modifying the impact
strength of a polyamide composition. These impact-modifier
compounds comprise functional groups that react with the polyamide
a).
[0031] According to the invention, the expression "functional
groups that react with the polyamide a)" is intended to mean groups
capable of reacting or of interacting chemically with the acid or
amine functions of the polyamide, in particular by covalence, ionic
or hydrogen interaction or van der Walls bonding. Such reactive
groups make it possible to provide good dispersion of the impact
modifiers in the polyamide matrix. Good dispersion in the matrix is
generally obtained with impact-modifier particles having a size of
between 0.1 and 1 .mu.m.
[0032] The impact modifiers may very well comprise, in themselves,
functional groups that react with the polyamide a), for example as
regards ethylene acrylic acid (EAA).
[0033] It is also possible to attach thereto functional groups that
react with the polyamide a), generally by grafting or
copolymerization, for example for ethylene-propylene-diene (EPDM)
grafted with maleic anhydride.
[0034] According to the invention, use may be made of the impact
modifiers, which are oligomeric or polymeric compounds, comprising
at least one of the following monomers, or a mixture thereof:
ethylene, propylene, butene, isoprene, diene, acrylate, butadiene,
styrene, octene, acrylonitrile, acrylic acid, methacrylic acid,
vinyl acetate, vinyl esters such as acrylic and methacrylic esters,
and glycidyl methacrylate.
[0035] The compounds according to the invention may also comprise,
in addition, monomers other than those mentioned above.
[0036] The base of the impact-modifier compound, optionally
referred to as elastomeric base, can be chosen from the group
comprising: polyethylenes, polypropylenes, polybutenes,
polyisoprenes, ethylene-propylene rubbers (EPRs),
ethylene-propylene-diene rubbers (EPDMs), ethylene butene rubbers,
ethylene acrylate rubbers, butadiene styrene rubbers, butadiene
acrylate rubbers, ethylene octene rubbers, butadiene acrylonitrile
rubbers, ethylene acrylic acids (EAAs), ethylene vinyl acetate
(EVAs), ethylene acrylic esters (EEAs),
acrylonitrile-butadiene-styrene (ABS) copolymers,
styrene-ethylene-butadiene-styrene (SEBS) block copolymers,
styrene-butadiene-styrene (SBS) copolymers, core-shell elastomers
of methacrylate-butadiene-styrene (MBS) type, or blends of at least
two elastomers listed above.
[0037] In addition to the groups listed above, these impact
modifiers may also comprise, generally grafted or copolymerized,
functional groups that react with the polyamide a), such as, in
particular, functional groups as follows: acids, such as carboxylic
acids, salified acids, esters, in particular acrylates and
methacrylates, ionomers, glycidyl groups, in particular epoxy
groups, glycidyl esters, anhydrides, in particular maleic
anhydrides, maleimides, or mixtures thereof.
[0038] Such functional groups on the elastomers are, for example,
obtained by using a comonomer during the preparation of the
elastomer.
[0039] As impact modifiers comprising functional groups that react
with the polyamide a), mention may in particular be made of
ethylene/acrylic ester/glycidyl methacrylate terpolymers,
ethylene/butyl ester acrylate copolymers, ethylene/n-butyl
acrylate/glycidyl methacrylate copolymers, ethylene/maleic
anhydride copolymers, maleic anhydride-grafted styrene/maleimide
copolymers, copolymers of styrene/ethylene/butylene/styrene
modified with maleic anhydride, maleic anhydride-grafted
styrene/acrylonitrile copolymers, maleic anhydride-grafted
acrylonitrile/butadiene/styrene copolymers, and hydrogenated
versions thereof.
[0040] The proportion by weight of the elastomers b) of the
invention in the total composition is in particular between 0.1%
and 50%, preferably between 0.1% and 20%, in particular between
0.1% and 10%, in particular the values 1, 2, 3, 4, 5, 6, 7, 8, 9 or
10 or any ranges composed of said values, in particular between 1%
and 6%.
[0041] In order to improve the mechanical properties of the
composition according to the invention, it may be advantageous to
add thereto at least one reinforcing and/or bulking filler
preferably chosen from the group comprising fibrous fillers such as
glass fibers, inorganic fillers such as clays, kaolin, or
reinforced nanoparticles or nanoparticles made of thermosetting
material, and powder fillers such as talc. The degree of
incorporation of reinforcing and/or bulking filler is in accordance
with the standards in the composite material field. It may, for
example, be a degree of filler of from 1% to 50% by weight,
relative to the total weight of the composition.
[0042] The composition may comprise, in addition to the modified
polyamide of the invention, one or more other polymers, preferably
polyamides or copolyamides.
[0043] The composition according to the invention may also comprise
additives normally used for the production of polyamide
compositions. Thus, mention may be made of lubricants, flame
retardants, plasticizers, nucleating agents, catalysts, agents for
improving impact strength, such as optionally grafted elastomers,
light and/or heat stabilizers, antioxidants, antistatics,
colorants, mattifying agents, molding aids or other conventional
additives.
[0044] These fillers and additives can be added to the modified
polyamide by standard means suited to each filler or additive, such
as, for example, during melt blending or polymerization.
[0045] The thermoplastic compositions are generally obtained by
mixing the various compounds that go to make up the composition,
the thermoplastic compounds being in molten form. The process is
carried out at more or less high temperature, and at more or less
high shear force depending on the nature of the various compounds.
The compounds can be introduced simultaneously or successively. An
extrusion device in which the material is heated, subjected to a
shear force and conveyed along, is generally used. Such devices are
entirely known to those skilled in the art.
[0046] According to a first embodiment, all the compounds are melt
blended during a single operation, for example during an extrusion
operation. It is, for example, possible to blend granules of the
polymeric materials, and to introduce them into the extrusion
device in order to melt them and to subject them to a more or less
large shear stress.
[0047] According to particular embodiments, it is possible to
prepare pre-blends, which may or may not be melt pre-blends, of
some of the compounds before preparation of the final
composition.
[0048] The composition according to the invention, when it is
prepared using an extrusion device, is preferably conditioned in
the form of granules. The granules are intended to be formed by
means of processes involving melting so as to obtain articles. The
articles are thus made up of the composition. According to one
customary embodiment, the modified polyamide is extruded in the
form of rods, for example in a twin-extrusion device, and said rods
are then cut into granules. The molded components are then prepared
by melting the granules produced above and feeding the molten
composition into injection molding devices.
[0049] The use of the compositions according to the invention is
particularly advantageous in the context of the electrical
industry, in particular for the molding of components of large
sizes or with a complex geometry.
[0050] Specific terms are used in the description in such a way as
to facilitate understanding of the principle of the invention. It
should nevertheless be understood that no limitation of the scope
of the invention is envisioned with the use of these specific
terms. The term "and/or" includes the meanings and, or, and also
all the other possible combinations of elements connected to this
term.
[0051] Other details or advantages of the invention will emerge
more clearly in view of the examples below, given only by way of
indication.
EXPERIMENTAL SECTION
[0052] The following compounds are used: [0053] PA1: Polyamide 66
having an MFI of 2.7 g/10 minutes (according to the ISO1133
standard measured at 275.degree. C. with a load of 325 g) and an IV
of 140. Contents of following end groups: amine end groups=40
meq/kg, carboxylic end groups=60 meq/kg. [0054] PA2: Polyamide 66
having an MFI of 30 g/10 minutes (according to the ISO1133 standard
measured at 275.degree. C. with a load of 325 g) and an IV of 98.
Contents of following end groups: amine end groups=28 meq/kg,
carboxylic end groups=90 meq/kg. Obtained by adding 0.7 mol % of
benzoic acid at the beginning of polymerization. [0055] Glass
fibers: Vetrotex 99B. [0056] E1: ethylene/acrylicester/glycidyl
methacrylate terpolymer elastomer (8% by weight of glycidyl
methacrylate), sold under the name Lotader.RTM. AX8900 by the
company Arkema. [0057] E2: ethylene/butyl ester acrylate copolymer
elastomer, sold under the name Lotryl.RTM. 30 BA 02 by the company
Atofina. [0058] E3: ethylene/n-butyl acrylate/glycidyl methacrylate
copolymer elastomer, sold under the name Elvaloyl.RTM. PTW by the
company DuPont. [0059] E4: ethylene/maleic anhydride copolymer
elastomer, sold under the name Exxelor.RTM. VA 1840 by the company
Exxon Mobil. [0060] E5: ethylene/maleic anhydride copolymer
elastomer, sold under the name Fusabond.RTM. N MN493D by the
company DuPont. [0061] E6: ethylene/acrylic acid copolymer
elastomer, sold under the name Primacor.RTM. EAA 449 by the company
Dow. [0062] E7: ethylene/vinyl acetate copolymer elastomer, sold
under the name Escorene.RTM. UL 02528 by the company Exxon Mobil.
[0063] Additives: EBS wax, and nigrosine sold under the name
54/1033 by the company Ferroplast.
[0064] The compositions are prepared by melt blending, using a
Werner and Pfleiderer ZSK twin-screw extruder, the polyamides, 5%
by weight of elastomers, 30% by weight of glass fibers, and 1.3% by
weight of additives. The extrusion conditions are the following:
temperature: between 240 and 280.degree. C., rotation speed:
between 200 and 300 rpm, flow rate between 25 and 60 kg/hour.
[0065] The various compositions prepared are shown in Table 1:
TABLE-US-00001 TABLE 1 Unnotched Spiral Charpy test impact Examples
Polymer Elastomer (cm) (KJ/m.sup.2) C1 PA1 -- 25 86.3 C2 PA1 E1 24
89.7 C3 PA2 -- 46 58.2 1 PA2 E1 47 82.2 2 PA2 E3 45 84.4 3 PA2 E4
45 88.1 4 PA2 E5 44 88.8 5 PA2 30% E1 + 45 86.8 70% E2 6 PA2 15% E1
+ 46 80.8 85% E2 7 PA2 E6 41 78.8 8 PA2 E7 46 79.7 The unnotched
Charpy impact strength is measured according to ISO standard
179/1eU.
[0066] The spiral test makes it possible to quantify the fluidity
of the compositions by melting the granules and injecting them into
a spiral-shaped mold with a semicircular cross section of thickness
2 mm and of width 4 cm, in a BM-Biraghi 85T press at a barrel
temperature of 275.degree. C. and a mold temperature of 80.degree.
C. and with a maximum injection pressure of 130 bar, which
corresponds to an injection time of approximately 0.4 seconds (the
result is expressed as length of mold correctly filled by the
composition).
[0067] It is thus observed that the compositions obtained exhibit
excellent compatibilization between the polyamide of the invention
and the grafted elastomers, thereby resulting in the obtaining of
articles having an excellent balance between mechanical properties
and melt flow. It is, moreover, observed that the articles of
Examples 1-8 exhibit a good surface appearance.
* * * * *