Note: Descriptions are shown in the official language in which they were submitted.
. CA 02243288 1998-09-02
METHOD FOR MAKING METALLIC-EFFECT POLYAMIDES WITH IMPROVED
5COLOR DEVELOPMENT AND BRIGHTNESS
Field of the Invention
The present invention relates to a method of improving
the metallic appearance of nylon materials and the nylon
materials produced by this method. In particular, the
invention relates to a process in which aluminum pigment is
added as a hot feed to molten nylon compositions and then
extruded, molded, or otherwise shaped into a desired article.
B~ckgrol~nd ~n~ Sllmm~ry of the Invention
Nylon resins are employed to manufacture many different
products for which good physical properties such as tensile
strength, stiffness, and the ability to withstand high
temperatures are important. In many of these articles,
aesthetic or design aspects are also of great importance.
While polyamides have displaced metallic materials in many
applications because of the good physical properties and the
comparatively light weight and ease of fabrication of nylon
materials, there continues to be a reluctance to employ
polyamides in other applications due to the difference in
appearance of the polyamide and metal materials. For example,
automotive parts exposed to high temperatures in the engine
~ CA 02243288 1998-09-02
.
compartment of motor vehicles, such as intake manifolds,
cylinder head caps, and motor compartment covers, may
advantageously be made of polyamides materials, especially
reinforced polyamide materials. The visual difference between
the natural polyamide materials and the metals from which such
parts have been made in the past, however, presents a drawback
in terms of design.
In the past, providing articles with a metallic
appearance has involved tedious, time-consuming, and/or
expensive methods of treating articles after the molding,
extrusion, or other forming step. For example, molded or
extruded polyamide parts have been painted or metallized to
produce a metal-like appearance. In addition, methods such as
painting or metallizing require specialized equipment and may
produce unwanted regulated emissions. It would thus be
desirable to provide a metallic-appearance polyamide material
that would provide a part with metal-like visual appearance
without any aftertreatment.
In an improved process, nylons with a metal effect
prepared by blending nylon pellets with a metallic effect
pigment, preferably al~lmlnllm glitter, and then feeding the
blend into a screw extruder or a Brabender mixer to produce a
uniform composition. The resulting compounded material can be
molded or shaped into parts that have a metallic look. The
CA 02243288 1998-09-02
.,
disadvantage of this method is that the composition are
generally limited to dark blue gray colors as a consequence of
a substantial generation of broken and bent aluminum flakes
during the compounding operation. Addition of white or yellow
pigments produces slightly lighter colors; however,
substantial additions of pigments attenuates the glitter
effect by producing more opaque materials. The parts made
with this material thus tend to be too dark and have too
strong of a blue color component for many applications where a
light metallic appearance or a colored metallic look is
desirable.
S~mm~ry of the Invention
It has now been discovered a method of improving both the
brightness and the metallic effect of nylon materials can be
achieved by substantially melting the nylon resin component
prior to addition of a metallic-effect flake pigment in a
process that will be termed in this specification as "hot
feedingN the metallic-effect flake pigment. In a preferred
embodiment, the process of the invention includes a step of
adding the metallic-effect flake pigment directly into a
substantially melted nylon material, for example through a
port in the melt zone of a compounding extruder. The invention
further provides a nylon material with improved metallic
' CA 02243288 1998-09-02
appearance and lightness that includes a nylon resin and a
metallic effect flake appearance produced according to the
method of the invention that has unexpectedly improved
brightness and color. The nylon materials of the invention
S have a more pronounced metallic effect, even at a lower
content of the metallic-effect flake pigment, than materials
produced by cold feed of metallic effect pigment and the nylon
materials of the invention can be modified with small amounts
of other pigments to achieve light-colored metallic appearance
materials which have not been obtainable by previous methods.
Detailed Description
The present invention provides a process for preparing a
metallic-look polyamide (nylon) material with superior
brightness and color development. The metallic-look polyamide
materials of the present invention include a polyamide resin,
a metallic-effect flake pigment, andL optionally, a mineral
reinforcing agent or other additives. According to the method
of the invention, the polyamide resin is substantially melted,
and optionally mixed with one or more additives, and then the
flake pigment, optionally together with one or more mineral
reinforcing agents i8 a mixed into the melt. The term
"substantially melted" is used to describe the polyamide resin
in a state in which about three-fourths or more of the solid
CA 02243288 1998-09-02
resin has melted so that the melt forms a substantially
continuous phase. The compounded polyamide material with the
metallic-effect pigment is then formed into a desired shape.
Metallic-effect flake pigments that are useful in the
S methods and materials of the invention include metallic and
pearlescent flake pigments. Useful metallic flake pigments
include alllm;~l~m.c, copper, nickel, magnesium, zinc, brass, and
bronze metals and alloys of these. Important types of
pearlescent pigments that are useful as the flake pigments of
the invention are metal oxide-coated micas, such as titanium
dioxide- and/or iron oxide-coated micas, and bismuth
oxychoride pigments.
In general, relatively large metallic-effect flake
pigments are preferred, and these flake pigments may be up to
about 1.0 mm in a longest dimension. The metallic-effect
flake pigments preferably have a size distribution in which
about 90% of the material is less than about 0.5 mm and 50~ of
the material is less than about 0.3 mm as measured for the
longest dimension. Preferably, the metallic-effect flake
pigments are at least about 0.05 mm as measured for the
longest dimension. While the metallic-effect flake pigments
may be of irregular shapes, especially for sheet molding or
for polyamide compounds that will be used to form other such
simple shapes, pigments with regular shapes, which are
CA 02243288 1998-09-02
commonly referred to as nglitter, n preferably square and/or
rectangular flake shapes, are preferred for polyamide
compounds that will be used to form more complicated shapes.
Glitter generally refers to metallic particles produced
by cutting or stamping of uncoated or transparently coated
metal films. Stamped metallized plastic films or other
metallized carrier materials can also be used. Preferred
glitter materials are coated or uncoated aluminum, copper, and
steel bronze. The glitter is preferably rectangular or
square, with an edge length of at least about 0.01 mm,
preferably at least about 0.05 mm, or an edge length of up to
about 1 mm, preferably up to about 0.4 mm. Square-shaped
flakes of about 0.1 mm on a side are particularly preferred.
It is also highly preferred to use flake pigments that
have substantially uniform sizes, that is, that have
relatively narrow size distributions. Regular shapes and
narrow size distributions are thought to minimize the
occurrence of flow lines or weld marks in forming articles
having complicated shapes. One important criteria of a narrow
size distribution is that there is a minimum amount of
"fines," the material of the smallest size. The metallic-
effect flake pigment preferably contains less than about 1% by
weight of material that has a length of less than about 50
microns. The fines content of the particles may be determined
' CA 02243288 1998-09-02
by sieving, as per ISO method 787/7. The amount of fines may
be determined by the fraction not retained on a screen of a
specified mesh size.
Pearlescent pigments should have an average particle size
of at least about 50 microns, preferably at least about 100
microns.
The surfaces of metal flakes that tend to oxidize
readily, such as aluminum, are preferably coated by a method
known in the art. Aluminum flakes or glitter preferably has a
polymeric coating, such as a polyurethane coating, although
pastes of aluminum flakes in plasticizer~ such as dioctyl
phthalate or diisononyl phthalate may be useful for certain
applications. Aluminum glitter having a polyurethane coating
is particularly preferred. The alllmlntlm may also be added as
a color concentrate pellet of alllminllm in polyethylene wax. A
typical pellet has from 80 to 90% metallic pigment by weight,
up to about 5% polyethylene wax, and the balance dispersion
agents or other ingredients.
Metallic-effect flake pigments are widely available
commercially from, for example, The Mearl Corporation,
Briarcliff Manor, NY under the tradenames MEARLIN~ and
MEARLITE~; EM Industries, Inc., Hawthorne, NY under the
trademark AFFLAIR~; Obron Atlantic Corp., Painesville, OH,
under the trademarks STANDART~, STAPA~, AND MASTERSAFE~;
' CA 02243288 1998-09-02
~,
Transmet Corp., Columbus OH; Glitterex Corp., Cranford, NJ,
under the tra~en~me Alu*Flake WSR~; Silberline, Tamaqua, PA;
Alllm;nllm Company of America, Pittsburgh, PA; Reynold Metals
Company, Richmond, VA; and Toyo Aluminum KK, Higashiku, Osaka,
Japan.
In general, the polyamides included in the polyamide
compounds according to the invention have a viscosity of
preferably at least about 90, more preferably at least about
100 mL/g, as determined in accordance with ISO method 307 for
a 0.5% by weight solution in 96 weight percent sulfuric acid
at 25~C. Semicrystalline and amorphous polyamides are
preferred, particularly those having a weight average
molecular weight of at least 5000, such as those described in
U.S. Patents No. 2,071,250, 2,071,251, 2,130,523, 2,130,948,
2,241,322, 2,312,966, 2,512,606, and 3,393,210, each of which
is incorporated herein by reference.
Illustrative examples of suitable polyamides include
those derived from lactams with 7- to 13-membered rings, such
as polycaprolactam, polycaprylyl lactam, and polylauryl
lactam, as well as polyamides obtained by a reaction of a
polycarboxylic acid, preferably a dicarboxylic acid, with a
polyamine, preferably a diamine. Examples of suitable
polyacids include, without limitation, alkanedicarboxylic
acids having at least about 6 carbon atoms and up to about 12,
CA 02243288 1998-09-02
preferably up to about 10, carbon atoms; and aromatic
dicarboxylic acids. Particular examples include adipic,
azelaic, sebacic, dodecanedicarboxylic, terephthalic,
phthalic, and isophthalic acids and anhydrides and mixtures of
these. Suitable polyamines include, without limitation,
alkanediamines having at least about 6 carbon atoms and
alkanediamines having up to about 12, preferably up to about
8, carbon atoms. Particular examples of useful polyamines are
m-xylylenediamine, di-(4-aminophenyl)methane, di-(4-
aminocyclohexyl)methane, 2,2-di-(4-aminophenyl)propane, 2,2-
di-(4-aminocyclohexyl)propane, and mixtures of these.
Examples of nylons (polyamides) that may be used in the
processes and compounds of the invention include, without
limitation, nylon-6, nylon-6,6, nylon-6,10, nylon-4,6, nylon-
6,12, nylon-11, nylon-12, and nylon 6/66, particular with from
about 5 to about 95% by weight caprolactam units; partially
aromatic nylon copolymers such as nylon-6/6,T, nylon-
6,6/6,I/6,T; and so on, and mixtures and blends of these.
Suitable nylons are available from BASF Corporation, Mt.
Olive, NJ under the tr~pn~mp ULTRAMID . Preferred among these
are nylon-6 and nylon-6,6. The nylons that are used in the
invention have number average molecular weights of preferably
at least about 10,000 and more preferably at least about
15,000. The number average molecular weights of preferred
' CA 02243288 1998-09-02
nylons may be up to about 40,000 and particularly up to about
20,000. The nylon resins used to prepare the metallic-look
nylons of the invention preferably have a polydispersity of
less than about 4 and more preferably less than about 2.5.
The nylon resin may be included in the nylon material in
an amount of at least about 40%, preferably at least about
50%, and even more preferably at least about 60%, based on the
weight of the compounded nylon material. The nylon resin may
also included in the nylon material in an amount of up to
about 99%, preferably up to about 90%, more preferably up to
about 80%, and even more preferably up to about 70%, based on
the weight of the compounded nylon material.
The metallic-effect flake p$gment may be included in the
nylon compound in an amount of at least about 0.1~, preferably
at least about 0.5%, more preferably at least about 1%, and
particularly preferably at least about 1.5~ by weight. In
addition, the metallic-effect flake pigment may also be
included in the nylon compound in an amount of up to about 5%,
preferably up to about 3%, and particularly preferably up to
about 2.5% by weight. Because the compositions of the
invention have a more pronounced metallic effect as compared
to compositions produced according to other methods, it is
usually possible to include the metallic effect flake pigment
CA 02243288 1998-09-02
at lower concentrations to produce the desired metallic
effect.
Heat stabilizers should be hi~ered phenols and
phosphites, copper iodide or other stabilizers that would
color the materials are not preferred.
In a preferred embodiment of the invention, one or more
stabilizers such as heat stabilizers or antioxidants are
included in the compounded nylon materials. It is usually
preferred to include colorless stabilizers so that the
addition of stabilizer does not shift the intended color of
the composition. Particularly useful stabilizers include
sterically hindered phenolic compounds, phosphorus acid,
hypophosphite~, and combinations of these.
Useful sterically hin~ered phenolic compounds include,
without limitation, compounds derived from substituted
benzenecarboxylic acid and the hindered phenols described in
U.S. Patent No. 4,360,617, incorporated herein by reference.
Specific examples include, without limitation, 2,2~-
methylenebis-(4-methyl-6-tert-butylphenol), 1,6-hexanediolbis-
[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate],
pentaerythrityl tetrakis-[3-(3,5-di-tert-butyl-4-
hydroxyphenyl)propionate], distearyl 3,5-di-tert-butyl-4-
hydroxybenzyl phosphonate, 2,6,7-trioxa-1-
phosphabicyclo[2.2.2]oct-4-ylmethyl-3,5-di-tert-butyl-4-
' CA 02243288 1998-09-02
hydroxyc;~n~mAte, 3,5-di-tert-butyl-4-hydroxyphenyl-3,5-
distearylthiotriacylamine, 2-(2i-hydroxy-3i-hydroxy-3i,5i-di-
tert-butylphenyl)-5-chlorobenzotriazole, 2,6-di-tert-butyl-4-
hydroxymethylphenol, l,3,5-trimethyl-3,4,6-tris-(3,5-di-tert-
butyl-4-hydroxybenzyl-benzene, 4,4'-methylenebis-(2,6-di-tert-
butylphenol), 3,5-di-tert-butyl-4-hydoxybenzyldimethylamine,
N,N'-hexamethylenebis-3,5-di-tert-butyl-4-hydroxycinn~m;de,
and combinations thereof. Useful sterically hindered phenolic
compounds are available under the trademark Irganox~ from
Ciba-Geigy Corp., Tarrytown, NY; under the trademark Lowinox
from Great Lakes Chemical, West Lafayette, IN; and Hostanox,
Hoechst AG. Particularly preferred are N,N'-hexamethylenebis-
3,5-di-tert-butyl-4-hydroxyc;nn~m;de, pentaerythrityl
tetrakis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], n-
octadecanoyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,
bis-[3,3-bis-(4'-hydroxy-3'-tert-butylphenyl)butanoic acid
amide] glycol ester or mixtures thereof, available
commercially under the traden~mps Irganox~ 1098 (Ciba-Geigy),
Lowinox~ HD 98 (Great Lakes Chemical), Irganox~ 1010 (Ciba-
Geigy), Hostanox~ 010 (Hoechst), Irganox~ 1076 (Ciba-Geigy),
and Hostanox~ 03 (Hoechst).
The sterically hindered phenolic compounds are included
in amounts of at least about 0.05% by weight, preferably at
least about 0.1% by weight, and even more preferably at least
'' CA 02243288 1998-09-02
about 0.2% by weight. The sterically hindered phenolic
compounds are also included in amounts of up to about 2% by
weight, preferably up to about 1~ by weight, and particularly
preferably up to about 0.6~ by weight.
Preferred compositions of the invention include one or
more phosphorus-containing heat stabilizers, preferably one or
more compounds selected from phosphorus acid and esters of
phosphoruQ acid, hypophosphites, and mixtures of these. The
phosphorus may be in a valence state of +l or +3. The heat
stabilizers are included in amounts of at least about 0.05% by
weight, and also preferably included in amount of up to about
2~ by weight, preferably up to about 1% by weight, and
particularly preferably up to about 0.5% by weight. Specific
examples of useful compounds in which the phosphorus has a
valence state of +1 include, without limitation, salts such as
alkali metal hypophosphites including sodium hypophosphite,
calcium hypophosphite, magnesium hypophosphite, and amine
salts such as melamine hypophosphite; double, complex, or
organic hypophosphites such as cellulose hypophosphite esters,
esters of hypophosphorus acids and diols such as 1,10-
dodecanediol; substituted phosphinic acid and anhydrides such
as diphenenylphosphinic acid, di-p-tolylphosphinic acid,
dicresylphosphinic anhydride, bis-(diphenylphosphinic acid)
esters of hydroquinone, ethylene glycol, or other polyols; and
CA 02243288 1998-09-02
aryl(alkyl)phosphin~m;des such as diphenylphosphinic
dimethylamide and sulfonamidoaryl(alkyl)phosphinic acid
derivatives such as p-tolylsulfonamidodiphenylphosphinic acid.
Specific examples of useful compounds in which the phosphorus
S has a ~alence state of +3 include, without limitation, cyclic
phosphonates derived from pentaerythritol, neopentyl glycol,
and pyrocatechol; triaryl(alkyl)phosphites such as triphenyl
phosphite, tri-(4-decylphenyl)phosphite, tri-(2,4-di-tert-
butylphenyl)phosphite, and phenyl-di-decyl phosphite;
diphosphites such as propylene glycol 1,2-bis-(diphosphite);
cyclic phosphites; and ester derivatives of phosphorous acid
such as 2-{[2,4,8,10-tetrakis(1,1-
dimethylethyl)dibenzo[D,F][1,3,2]-dioxaphosphepin-6-yl]oxy~-
N,N-bis-(2-{[2,4,8,10-tetrakis(1,1-
dimethylethyl)dibenzo[D,F][1,3,2]-dioxaphosphepin-6-yl]oxy}-
ethyl)eth~ne~m;ne and tris-2,4-di-tert-butylphenyl)phosphite.
Preferred among these are alkali metal hypophosphites,
particularly sodium hypophosphitei 2-{[2,4,8,10-tetrakis(1,1-
dimethylethyl)dibenzo[D,F][1,3,2]-dioxaphosphepin-6-yl]oxy}-
N,N-bis-(2-{[2,4,8,10-tetrakis(1,1-
dimethylethyl)dibenzo[D,F][1,3,2]-dioxaphosphepin-6-yl]oxy}-
ethyl)ethaneamine and tris-2,4-di-tert-butylphenyl)phosphite.
Such stabilizers are commercially available under the
tradenames Irgafos~ from Ciba-Geigy and Hostanox~ from Hoechst
CA 02243288 1998-09-02
AG. Preferred materials are Irgafos~ 12, Irgafos~ 168, and
Hostanox~ PAR 24. The phosphorus-containing heat stabilizers
are included in amounts of at least about O.OS~ by weight.
The phosphorus-containing heat stabilizers are also included
in amounts of up to about 2~ by weight, preferably up to about
1% by weight, and particularly preferably up to about 0.5% by
weight.
The nylon material of the invention may also comprise a
reinforcing agent that may be a fibrous material or,
preferably, a mineral reinforcing agent. Useful fiber
reinforcements include, without limitation, glass fibers,
especially E glass fibers, carbon and graphite fibers,
polymeric fibers including aramide fibers, boron filaments,
ceramic fibers, metal fibers, asbestos fibers, potassium
titanate fibers, beryllium fibers, silica fibers, silicon
carbide fibers, and so on. The fibers may be surface-treated,
for example with a silane, for better compatibility with the
nylon resin. The fibers may be conductive and such conductive
fibers, for example conductive carbon fibers or metal fibers,
may be used to produce articles for conductive or static
charge dissipative applications or EMI shielding. Among
these, glass fibers, carbon fibers, and aramide fibers are
preferred. Methods of preparing thermoplastic resins that
include such fibers are well-known in the art. Rovings or
CA 02243288 1998-09-02
16
chopped fibers may be used. In one method, chopped glass
fiber bundles are fed into the melting zone of the extruder
that is being used to form the metallic-effect nylon material.
Alternatively, the fiber is introduced as a continuous tow or
bundle into a port in the extruder.
The reinforcing agent of the invention preferably
comprises a mineral reinforcing agent. Suitable mineral
reinforcing agents include, without limitation, wollastonite,
micas, glass beads (solid or hollow), kaolin, calcined kaolin,
chalk, and talc. Micas and other reinforcing agents may be
treated, for example with coupling agents such as silanes to
improve mechanical properties or with a nickel coating for
special applications. Preferred mineral reinforcing agents
are wollastonites, micas, kaolins, and talc. Mineral
reinforcing agents are typically incorporated into the resin
by feeding through a hopper into a melt zone of the extruder.
In a particularly preferred embodiment of the invention,
the metallic effect pigment is blended with mineral filler
before addition to the substantially melted polyamide resin.
Blen~ng with a mineral filler is useful for dilution of the
metallic effect pigment, for example when small amount of the
metallic effect pigment would otherwise be difficult to
accurately meter into the polyamide melt, and/or to prevent
agglomeration of the metallic effect pigment in the addition
CA 02243288 1998-09-02
equipment. Blending with a mineral filler is particularly
useful for pearlescent pigments because the blending tends to
make the low density, fluffy pearlescent pigments easier to
handle. Blending of a mineral filler and the metallic effect
pigment may be accomplished, for example, by dry mixing, for
example in a drum blender by tumbling until uniform.
The reinforcing agent may be, and in many cases is
preferred to be, a combination of reinforcing fibers and
reinforcing minerals. For example, in one preferred
embodiment the reinforcing agent is a combination of glass
fibers and wollastonite. The reinforcing agent or agents are
included in amounts of at least about 1%, preferably at least
about 5%, more preferably at least about 15%, and even more
preferably at least about 25%, based on the weight of the
compounded resin. The reinforcing agent or agents are
included in amounts of up to about 70~, preferably up to about
60%, and even more preferably up to about 50~, based on the
weight of the compounded resin. Typically, about 25% to about
60% reinforcing agent is included in the compounded nylon.
The nylon materials may also include at least one further
additive. Examples of suitable additives include, without
limitation, plasticizers; thixotropes; optical brighteners;
antioxidants; W stabilizers, including resorcinols,
slicylates, benzophenones, hindered amine light stabilizers
CA 02243288 1998-09-02
18
such as benzotriazoles, and hindered amide light stabilizers;
flame retardants; pigments and colorants; processing aids such
as lubricants, mold release agents, and slip agents;
fragrances; antifoaming agents; antioxidants such as
hydroquinone, aromatic secondary amines, and derivatives of
these; antistatic agents; antimicrobials; biocides; and so
forth. Impact modifiers such as ionomers, maleated
elastomers, and natural and synthetic rubber particles and
other materials that would tend to form discreet phases may be
included in relatively minor amounts to obtain good metallic
appearance. Processing aids such as polytetrafluoroethylene
homopolymers and copolymers may be included.
The nylon composition may include one or more pigments or
colorants in addition to the flake pigment. Preferably, the
pigment is present in an amount of up to about 4% by weight,
and especially up to about 2~ by weight, based on the weight
of the resin. Suitable pigments are black, white, or color
pigments. Examples of useful pigments include, without
limitation, titanium dioxide, zinc oxide, zinc sulfide carbon
black, black iron oxide, copper chromite black, yellow iron
oxides, red iron oxides, brown iron oxides, ocher, sienna,
umber, hematite, limonite, mixed iron oxides, chromium oxide,
Prussian blue (ammonium ferrocyanide), chrome green, chrome
yellow, manganese violet, cobalt phosphate, cobalt lithium
CA 02243288 1998-09-02
19
phosphate, ultramarines, blue and green copper
phthalocyanines, metallized and nonmetallized azo reds, gold,
red, and purple quinacridones, mono-and diarylide yellows,
naphthol reds, pyrrolo-pyrroles, anthraquinones, thioindigo,
flavanthrone, and other vat pigments, benzimidazolone-based
pigments, dioxazine, perylenes, carbazole violet, perinone,
isoindoline, and so on.
Dyes may employed instead of a pigment or in addition to
a pigment. For example, a dye may be used to produce a
brighter color than would otherwise be obtained with a
composition containing only pigments. Examples of useful dyes
include, without limitation, azo dyes, such as Solvent Yellow
14 and Metanil Yellow; anthraquinone dyes, such as Solvent Red
111, Solvent Blue 56, and Solvent Green 3; xanthene dyes, such
as Rhodamine B, Sulfo Rhodamine, Sovent Green 4, Acid Red 52,
Basic Red 1, and Sovent Orange 63; azine dyes, such as
induline and nigrosines; fluorescent dyes, Brilliant
Sulfoflavine (Acid Yellow 7), Sovent Orange 60 (a perinone
dye), basic triphenylmethane dyes, such as methyl violets and
victoria Blue B, and quinoline yellows.
Conductive materials include conductive pigments, such as
certain grades of carbon black and graphite. The carbon black
may function as both a conductive material and a colorant.
Such conductive materials may be incorporated into the coating
'' CA 02243288 1998-09-02
composition according to usual methods of incorporating
fillers or pigments, which will now be generally described
with particular reference to pigments.
The dry pigment may be added, preferably along with the
resin, during compounding of the metallic-effect nylon
material, or may be pre-dispersed in a carrier resin before
compounding. The pigment may be dispersed in a carrier resin
component, which is preferably a hydrophobic resin component,
by a two-step process. In a first step, the pigment
agglomerates are broken into smaller particles. In a second
step, the air at the surface of the pigment particles is
displaced with resin to ~wet out" the pigment and thereby
fully develop its color shade and strength. One method of
dispersing the pigment in the carrier resin component is to
first tumble the pigment with granules of the resin and then
obtain a intimate mixture by processing the tumbled blend in a
roller mill, Banbury mixer, intensive mixer, or single- or
twin-screw extruder. The resin component is advantageously
selected for its ability to disperse a high loading of pigment
and for easy handling.
The dispersed colorant may be, for example, a
conventional color concentrate or a liquid color. Typical
color concentrates may include one or more thermoplastic
resins and one or more pigments. Examples of suitable
CA 02243288 1998-09-02
21
thermoplastic resins include, without limitation, waxes,
polyolefins, nylon homopolymers and copolymers, and styrene-
based polymers. Suitable waxes include naturally occurring
waxes such as animal waxes, vegetable waxes, mineral waxes,
and petroleum waxes, as well as synthetic waxes. Preferred
among these are hydrocarbon waxes, such as paraffin waxes;
polyalkylene homopolymers and copolymers, especially
polyethylene, polypropylene, and copolymers of alkenes having
from 2 to 10 carbon atoms, particularly copolymers of ethylene
with alkenes having from 3 to 10 carbon atoms, especially
copolymers with propylene or butylene; microcrystalline waxes;
carnuba waxes; montan waxes; Fischer-Tropsch waxes; fatty
alcohols; derivatives of fatty acids, especially those having
from about 12 to about 18 carbon atoms, including stearic
acid, palmitic acid, lauric acid, myristic acid, oleic acid,
linoleic acid, and tall oil fatty acid, such derivatives
including fatty amides and esters of fatty acids; hydrogenated
oils, such as hydrogenated castor oil; polyethers, including
polyalkylene glycols such as polyethylene glycol,
polypropylene glycol, and block copolymers of these;
polytetrahydrofuran; and mixtures of these. Particularly
preferred waxes are polyethylene waxes having molecular
weights of preferably at least about 2000 and preferably below
about 12,000; carnuba waxes; esters of fatty acids; montan
CA 02243288 1998-09-02
waxes, and mixtures of these. The pigment may be any of those
known in the art, such as those listed hereinabove, and
mixtures of such pigments. Conventional color concentrates
may be in the form of pellets, cubes, beads, wafers, or micro-
beads. Color concentrates may have a pigment loading of fromabout 10% by weight to about 80% by weight, typically from
about 30% by weight to about 60% by weight, based upon the
weight of the color concentrate. Preferably, the color
concentrate has a pigment loading of up to about 80% by
weight, and preferably at least about 50% by weight, based
upon the weight of the color concentrate. The pigment
concentration will vary, depending upon the selection of
pigment and carrier. Liquid colors typically have pigment
loadings of from about 10% up to about 80%.
Alternatively, two or more color concentrates or pigments
may be added to the metallic-effect nylon material during
compounding to obtain the desired color. Pigments and color
concentrates are readily commercially available from a number
of companies, including BASF Corporation, Mt. Olive, NJ; Cabot
Corporation, Waltham, MA; Degussa AG, Frankfurt, Germany;
ReedSpectrum, Holden, MA; Unifor Color Company, Holland, MI;
Americhem Inc., Cuyahoga Falls, OH; and Holland Colors
Americas Inc., Richmond, IN.
CA 02243288 1998-09-02
23
According to the process of the invention, the nylon
material, optionally a reinforcing agent, and any additional
materials including, without limitation, the additives, color
pigments, color concentrates, dyes, or plasticizers, discussed
S above, are added to an apparatus to substantially melt the
nylon material and blend the nylon with the other components.
Preferably, apparatus is a single- or twin-screw extruder,
such as a 40 mm twin-screw extruder. In a preferred
embodiment the extruder has a melt zone temperature of about
270~C and a throughput rate of about 60 kg/min. The nylon
resin is preferably added as a pellet. Thermoplastic resins
are customarily manufactured as pellets for later processing
or compounding. The nylon resin may also be added to the
compounding apparatus as a melt. The nylon resin, along with
optional materials such as one or more additives such as W
stabilizers or processing aids, is charged to a hopper and fed
into a single-screw or twin-screw extruder. A heat stabilizer
such as a hindered phenol and an organic or inorganic
phosphorus-containing stabilizer may be included. Dry pigment
or color concentrate, if used, should be charged along with
the nylon resin to ensure homogeneous mixing. A hot feed of
the reinforcing agent, particularly fiber reinforcing agents,
and, optionally, impact modifier may be introduced into the
extruder melt zone.
' CA 02243288 1998-09-02
~4
The flake pigment and optionally, as described above,
mineral reinforcing agent, i9 added as a hot feed at a point
when the nylon is substantially melted. The hot compounding
melt is then mixed for an additional time necessary to achieve
a relatively uniform distribution of the flake pigment in the
polyamide matrix. In a preferred embodiment, the metallic
effect flake pigment is dry blended with a mineral reinforcing
agent, in particular with wollastonite, mica, solid glass
beads, or hollow glass beads, and then this blend is used as a
hot feed as described above. Blending of the metallic effect
flake pigment and the mineral reinforcing agent is preferably
carried out under low ~hear conditions, for example by
tumbling in a drum blender, to avoid as much as possible
bending or breaking the flake pigment pieces. Bl~n~1n~ with
the mineral reinforcing agent is useful in cases in which the
flake pigment, such as aluminum pigment, would tend to bridge
or clump in the feeding hopper, as the mineral reinforcing
agent tends to improve the flowability of the feed. It is
also beneficial to blend the metallic effect pigment with a
mineral reinforcing agent when it would otherwise be difficult
to meter in a proper amount of the flake pigment due to the
low amount of flake pigment used, for example when
conventional auger-type feeding equipment is used. The
metallic effect flake pigment may be added at a side port past
'' CA 02243288 1998-09-02
the initial kneading blocks in the melting zone of the
extruder.
The extrudate from the die may be cooled, for example in
a water bath, and then pelletized according to customary
methods. In the case of a nylon resin that is susceptible to
yellowing, the extrudate is preferably quickly cooled to a
temperature below the melting point range, preferably to a
temperature below about 150~C. The pellet may then be used to
form a final article by any method known in the art for
forming thermoplastic resins. The term "pellets'~ is
understood and used herein to encompa6s various geometric
forms, such as squares, trapezoid~, cylinders, lenticular
shapes, cylinders with diagonal faces, flakes, chunks, and
substantially spherical shapes including a particle of powder
or a larger-size sphere.
Alternatively, the hot compounding melt may be directly
formed into the desired article following the addition of the
metallic-effect flake pigment. For example, the melt may be
extruded as a sheet instead of as the strands that are
pelletized. The compol~n~i ng melt may also blended in a heated
apparatus and then introduced into a mold of the desired shape
to cool and solidify into the desired shape.
The method of the invention provides a metallic-effect
nylon material with improved metallic appearance and lightness
CA 02243288 1998-09-02
26
as compared to materials that can be produced by previously-
known methods. Moreover, when glitter (that is, metallic-
effect flake pigment of substantially uniform size and shape)
is employed, the metallic-effect polyamide materials of the
invention may be molded into complex shapes that have a bright
and uniform metallic effect. The metallic-effect nylon
material of the invention may be formed into articles
according to any of the methods known in the art for thermal
melt processing of thermoplastic resin compositions. For
example, compression molding, vacuum molding, injection
molding, thermoforming, blow molding, calendering, casting,
extrusion, filament winding, laminating, rotational or slush
molding, transfer molding, lay-up or contact molding,
stamping, and combinations of the~e methods may be used with
the metallic-effect nylon materials formed by the present
methods.
The metallic-effect nylon materials of the invention may
be formed into any of the articles generally made with
thermoplastic resins. Among the many possibilities are,
without limitation, chair bases, automotive components
including door handles, air intake manifolds, cylinder head
caps, motor compartment covers, mirror housings, decorative
auto parts, power tool housings; and extruded sheets that may
be used, for example, for packaging or thermoforming.
CA 02243288 1998-09-02
power tool bases, automotive engine covers, toys, and cosmetic
containers.
The invention is further described in the following
examples. The examples are merely illustrative and do not in
any way limit the scope of the invention as described and
claimed. All parts are parts by weight unless otherwise
noted.
Examples 1 and 2 of the invention are prepared according
to the following Method of the Invention using the amounts of
materials shown in Table I.
Metho~ I: Method of the Inv~ntio~
The nylon-6, chopped glass fiber, Irganox 1098, Irgafos
168, sodium hypophosphite, and colorants are blended and fed
lS into an open port at the beginning of a twin-screw extruder.
The Alu*Flake alnmin-lm pigment and wollastonite mineral are
dry blended under low shear conditions and charged to a
feeding hopper of an auger-type feeding apparatus attached to
a side port past the initial kneading blocks in the melting
zone of the extruder. The aluminum pigment blend is then
metered into the melted nylon blend in the melt zone. The
extrudate is cooled and pelletized.
CA 02243288 1998-09-02
28
Comparative Examples A - C are prepared according to the
following Comparative Method using the amounts of materials
shown in Table I.
Metho~ A: ComD~rative Metho~
The nylon-6 and Alu*Flake alllm;nllm pigment are dry
blended under low shear conditions, using a little mineral oil
to make the pigment stick to the nylon pellets. The nylon-
alllm;nll~ pigment blend, chopped glass fiber, Irganox 1098,
Irgafos 168, sodium hypophosphite, and colorants are then
blended and fed into an open port at the beginning of a twin-
screw extruder. The extrudate is cooled and pelletized.
~valll~tion of the Com~ounded Mate~ials
Compounded nylon materials prepared according to the
above methods were molded on a 100-ton Engel molding machine
at 275~C into test plaques of about 4.3 cm x 9 cm x 2 cm. A
Byk-Gardner color-view~ Spectrophotometer was used to
determine the color according to the L*,a*,b* (CIELAB) color
scale using D-65 illumination. The results are shown in the
Table I.
CA 02243288 1998-09-02
29
Table I.
Al 1 ingredi en t arnoun ts 1 i s ted are parts by weigh t .
INGREDIENTS Example 1 Example 2 Comparative
Example A
nylon 6 tbalance)
chopped glass 15 15 15
fibers2
wollastonite 2 2 0
mineral3
Irganox 10984 0.3 0.3 0.3
Irgafos 168~ 0.1 0.1 0.1
sodium 0.05 0-05 0-05
hypophosphite
Kronos 2220 0 0.3 0
Filamid Yellow R 0 0.014 0
Filamid Red GR 0 0.003 0
Alu*Flake .004~ 2 2 2
Method I (hot feed) I (hot feed) A (cold feed)
TEST RESULTS
L~,a*,b* 50.9, -0.8, 0.8 54.9, 0.6, 43.6, -0.9, -0.7
12.8
Appearance light gray color khaki brown dark blue gray
with pronounced color with color with
metallic glitter medium glitter medium-to-
effect, well- effect, well- pronounced metal
defined metal defined metal effect and
flake pattern flake pattern somewhat
irregular metal
flake pattern
1. Ultramid~ B3, available from ~SF Corporation, Mt. Olive,
NJ
2. PPG 3540, available from PPG Corp., Pittsburgh, PA
3. 10 Wollastocoat, available from Nyco Minerals, Inc.,
Willsboro, NY
4. phenolic antioxidant available form Ciba-Geigy
Corporation, Tarrytown, New York
5. phosphite costabilizer available form Ciba-Geigy
Corporation, Tarrytown, New York
6. available from Glitterex Corp., Cranford, NJ
CA 02243288 1998-09-02
As illustrated by the Examples, unexpected and
significant improvements in brightnes~ and metallic color
appearance are obtained using the method of the invention.
The invention has been described in detail with reference
to preferred embodiments thereof. It should be understood,
however, that variations and modifications can be made within
the spirit and scope of the invention and of the following
claims.
