Note: Descriptions are shown in the official language in which they were submitted.
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MASTERBATCH COMPOSITION HAVING A
HIGH POLYMER PROCESSING AID
FIELD OF THE INVENTION
[0001] The present invention relates in general to masterbatch compositions
having a
colorant, a processing aid, and optionally one or more additives, and a
process for making the
same.
BACKGROUND OF THE INVENTION
[0002] Colorants such as pigment preparations are often produced for
masterbatches. A
masterbatch is a granular, dust-free concentrate of a plastomeric or
elastomeric polymer
comprising a fraction of a colorant. Masterbatches are used to color plastics,
being added to
the plastic to be colored prior to or during processing. Masterbatches are
used because they
provide better colorant dispersion than neat colorant.
[0003] A variety of processes for producing masterbatches are known and the
following
processes are standard in the production of the masterbatches: a) the mixing
of a suitable
matrix (polymers) with the colorant; b) extrusion and kneading with subsequent
grinding of
the colorant concentrate; or c) extrusion and subsequent fine spraying, hot
chopping, or
strand pelletizing.
[0004] Known masterbatches generally include a colorant, a dispersant, a
thermoplastic
polymer, and optionally one or more additives. The thermoplastic polymer is
commonly
referred to as a "carrier." A typical commercial formulation of a masterbatch
includes about
30% by weight of colorant, about 5% by weight of dispersant, about 10% by
weight of
additive, and about 55% by weight of a carrier.
[0005] Unfortunately, known masterbatches have a relatively low colorant
concentration.
Thus, it has been found that many known masterbatches have insufficient
brilliance for high-
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quality applications. Larger proportions of colorant cannot be used in known
masterbatches
due to insufficient dispersion. Insufficient dispersion of the colorant
particles can lead to a
decrease in physical and mechanical properties of the end product, such as
tensile strength,
flexural modulus, elongation, and impact strength. Additional problems due to
insufficient
dispersion include thread breakage during spinning and clogging filters of
melt spinning
equipment. Accordingly, colorant concentrations have been limited in
conventional
masterbatches.
[0006] Another deficiency in known masterbatch compositions is the inability
to include
relatively significant amounts of additives such as ultraviolet light
absorbers, light stabilizers,
antioxidants, and blowing agents. Generally, additives are added only if
desired and then in
small amounts. Otherwise, it is believed that the processability of the
masterbatch would be
impaired.
[0007] Yet another deficiency in known masterbatch compositions is the
inability to
significantly improve the processability of the masterbatch itself and of the
end product. For
example, the melt extrusion of thermoplastics into shaped structures is
generally
accomplished by well-known procedures such as a reciprocating screw, injection
molding,
blow molding, compression molding, sheet extrusion, and fiber spinning.
[0008] The present assignee owns U.S. Patent No. 7,442,742 to Smink, et at.,
which is
incorporated by reference in its entirety. The `742 patent teaches a
substantially amorphous
metallocene polypropylene as a processing aid in the production of color
masterbatches
containing high loadings of colorants and, optionally, additives. While the
substantially
amorphous metallocene polypropylene processing aid is very effective and
provides
numerous advantages over conventional compositions, it has a relatively low
molecular
weight and viscosity, which may in some instances limit the capability of the
masterbatch
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composition in certain fabrication processes.
[0009] Accordingly, it is desirable to provide a masterbatch composition with
improved
processability that increases extrusion rates of the masterbatch composition
as well as the end
product without raising the melt temperature, while producing articles having
smoother
surfaces, and better physical and mechanical properties than with known
masterbatches while
reducing the amount of thermoplastic carrier.
[0010] It is also desirable to provide a masterbatch composition of colorants
and optionally
additives that produces better coloration of the end product while reducing
the amount of
thermoplastic carrier.
[0011] The present application, as described and claimed herein, addresses the
deficiencies of
prior art masterbatches.
SUMMARY OF THE INVENTION
[0012] In one aspect, the present invention is directed to a masterbatch that
includes a
colorant, a thermoplastic carrier, a high polymer processing aid, and
optionally an additive.
The high polymer processing aid can have a melt flow of less than about 200
g/l0min (ISO
Condition 1133) and can be selected from the group consisting of a polybutene
polymer, a
polybutene copolymer, and an olefin block copolymer.
[0013] In another aspect, the present invention is directed to a process for
making a
masterbatch that includes mixing a colorant, a thermoplastic carrier, a high
molecular weight
polymer processing aid, and optionally an additive, and applying heat and
shear to the
mixture to form the masterbatch. The high polymer processing aid can have a
melt flow less
than about 200 g/l0min (ISO Condition 1133) and can be selected from the group
consisting
of a polybutene polymer, a polybutene copolymer, and an olefin block
copolymer.
[0014] In a further aspect, the present invention is directed to a process for
making a
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colorized polymer that includes introducing a highly-loaded masterbatch
composition to a
melt-processible polymer to form a melt processable polymer composition,
wherein the
masterbatch comprises a colorant, a thermoplastic carrier, a high polymer
processing aid, and
optionally an additive, and extruding the polymer composition to form the
colorized polymer.
The high polymer processing aid is selected from the group consisting of a
polybutene
polymer, a polybutene colpolymer, and an olefin block copolymer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] While the present invention is described with reference to embodiments
described
herein, it should be clear that the present invention is not limited to such
embodiments.
Therefore, the description of the embodiments herein is merely illustrative of
the present
invention and will not limit the scope of the invention as claimed.
[0016] A masterbatch composition having a colorant, a high polymer processing
aid, and
optionally one or more additives is provided. This composition allows the use
of standard
plastic processing equipment to make relatively highly loaded color
concentrates and
additives. The composition including the high molecular weight polymer
processing aid,
exhibits excellent colorant dispersability, coloring properties, increased
additive
concentrations, as well as improved handleability, so that the colored end
product has
excellent physical and mechanical strength as well as excellent coloration.
The compositions
provided generally include a colorant, a thermoplastic carrier, a high polymer
processing aid,
and optionally additives such as antioxidants, ultraviolet light absorbers,
and light stabilizers.
[0017] The present masterbatch composition includes a high molecular weight
polymer
processing aid that substantially eliminates many of the practical problems
and limitations
encountered in the current art. The high polymer processing aid is superior
over conventional
masterbatch compositions because it is compatible with various carrier resins,
allows for
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decreasing the amount of conventional carrier resin, and provides better
mechanical and
physical properties of the end products. The masterbatch composition that
includes the high
polymer processing aid also allows for two to three times of increased
concentration or
loading of the colorants and additives. It also improves the colorant
dispersion as well as the
physical and mechanical properties of the end products. As the concentration
of colorants and
additives is increased, the amount of the masterbatch composition required to
achieve the
desired end product properties can be appreciably lower than conventional
masterbatch
compositions.
[0018] The high polymer processing aid also improves the handleability of the
masterbatch
composition. The masterbatch composition including the high polymer processing
aid melts
at lower temperatures that allow it to "wet out" or distribute more
efficiently to provide better
processability and increased throughput than conventional compositions.
[0019] The high polymer processing aid works in conjunction with the polymeric
carrier to
allow the masterbatch composition to include a relatively large amount of
colorant that can be
evenly dispersed in the presence of a high additive concentration, giving the
end product
excellent coloration as well as better physical and mechanical properties.
Accordingly, the
composition can provide molded or extruded articles having excellent
mechanical strength.
[0020] Accordingly, the high polymer is a desirable processing aid in a
masterbatch
composition because it has a relatively low melt point and good binding
capability. The
melting point of the polymer ranges preferably from about 80 C to about 125 C.
The density
of the polymer may be about 0.86 to about 0.92 g/cm3. The high polymer may be
present in
the masterbatch composition up to about 20%, preferably from about 4% to about
12%.
[0021] The high polymer processing aid exhibits a melt flow (ISO 1133) of less
than about
200 g/l0min. The relatively high molecular weight and viscosity of the high
polymer
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processing aid is greater than, for example, the metallocene polymer
processing aid taught in
U.S. Patent No. 7,442,742, which is owned by the present assignee. The
relatively high
molecular weight and viscosity of the high polymer processing aid may provide
a
masterbatch composition superior properties in certain fabrication processes
where the
processing aid of U.S. Patent No. 7,442,742 may exhibit a measurable weight
loss or "bum
off' at higher temperatures. Therefore, the masterbatch composition including
a high polymer
processing aid may have broader applicability than other known masterbatch
compositions.
[0022] Furthermore, the high polymer processing aid may exhibit a melting
temperature no
more than the melting temperature of the thermoplastic carrier. For example,
if the
thermoplastic carrier is high density polyethylene, which typically has a
melting point in its
commercial form of about 120-130 C, then the high polymer processing aid may
have a
melting point of no more than about 120 C. The high polymer processing aid
having a
melting temperature of no more than about the melting temperature of the
thermoplastic
carrier provides the masterbatch composition with desirable binding properties
to a polymer
to be colored by the compositions. Also, this feature provides desirable
processing
characteristics when coloring a polymer with the masterbatch composition.
[0023] The high polymer processing aid may be a polybutene. Polybutene is a
high molecular
weight, isotactic, semi-crystalline thermoplastic. Polybutene combines the
typical
characteristics of polyolefins with a unique property mix of high flexibility
and outstanding
creep resistance over a wide temperature range. Due to a similar molecular
structure,
polybutene is very compatible with polypropylene and propylene-based
thermoplastic
elastomers. It is easily dispersible in polyethylene notwithstanding its
limited molecular
compatibility. Polybutene can be a homopolymer or a copolymer of a polybutene
with one or
more olefins or grafted with other polymers, such as polymerization of butene-
1 and
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ethylene, and/or propylene comonomers. The Mõ for a polybutene homopolymer may
be
greater than about 30,000. Copolymers of polybutene with ethylene are
preferred. The
ethylene or propylene content of the copolymers is from about 2% to about 20%.
The melting
point of the polybutene homopolymer and copolymer is about 80-125 C.
[0024] Alternatively, the high polymer processing aid may be an olefin block
copolymer. The
olefin block copolymer may be a polyethylene copolymer produced via dual
metallocene
catalysts. Olefin block copolymers exhibit desirable properties including
improved balance of
flexibility and high temperature resistance, faster set-up in processing due
to higher
crystallization temperature, better elastic recovery and compression set
properties at both
ambient and elevated temperatures, and improved abrasion resistance. The
melting point of
the olefin copolymer is about 118 C - 122 C.
[0025] The high polymer processing aid is highly compatible with various
carrier resins.
Illustrative examples of thermoplastic carriers are homopolymers or copolymers
of high and
low density polyethylene, high and low density polypropylene, polystyrene,
polyoxymethylene, polyethylene terephthalate, polybutylene terephthalate,
polymethyl
methacrylate, polyether sulfones, polysulfones, polyether ketones, polystyrene
copolymers,
acrylonitrile-butadiene-styrene terpolymers, polyamides such as nylon-6 or
nylon-6,6,
polyvinyl chloride and copolymers of ethylene with 0.1-20 mol % of 1-butene, 1-
pentene, 1-
hexene, 4-methyl-l-pentene, 1-octene, 1-decene, 1-undecene, other impact
modified alloys,
or mixtures thereof. The polymer to be and the carrier polymer of the
masterbatch can be, but
do not have to be, the same.
[0026] Colorants added to the masterbatch may comprise pigments, single
pigment
dispersions, dyes, talc filled resins, nano composites, coated micas, powdered
aluminum and
other metals, optical brighteners, fluorescents, phosphorescents, or mixtures
thereof.
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Pigments may be at least one or a combination of organic pigments and
inorganic pigments,
and there is no particular limitation. When organic pigments are used, the
organic pigments
may be present up to about 50% by weight of the masterbatch composition. In a
preferred
embodiment, the organic pigments are present in a range from about 10 to about
40% by
weight of the masterbatch composition. If inorganic pigments are used, the
inorganic
pigments may be present up to about 75% by weight of the masterbatch
composition. In a
preferred embodiment, the inorganic pigments are present in a range from about
15% to
about 75% by weight of the masterbatch composition. In another embodiment,
both organic
and inorganic pigments are used, and the organic pigments may be present up to
about 20%
and the inorganic pigments may be present up to about 60%. In one embodiment,
the organic
pigment is present from about 3% to about 20% and the inorganic pigment is
present from
about 10% to about 60%.
[0027] Illustrative examples of the organic pigments include azo and disazo
pigments such as
azo and disazo lake, Hansas, benzimidazolones, diarylides, pyrazolones,
yellows and reds;
polycyclic pigments such as phthalocyanines, quinacridones, perylenes,
perinones,
dioxazines, anthraquinones, isoindolins, thioindigo, diaryl or quinophthalone
pigment,
Aniline Black, or mixtures thereof. Illustrative examples of the inorganic
pigments include
inorganic pigments such as titanium oxide, titanium yellow, iron oxide,
ultramarine blue,
cobalt blue, chromic oxide green, Lead Yellow, cadmium yellow and cadmium red,
carbon
black pigments, and mixtures thereof. The organic and inorganic pigments can
be used singly
or in combination. These pigments may be in any form of a dry powder, single
pigment
dispersions made conventionally or according to this process, or mixtures
thereof.
[0028] Optionally, the masterbatch composition may also comprise an additive.
Illustrative
examples are ultraviolet light absorbers, light stabilizers, antioxidants,
flame-retardants,
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antibacterial agents, surface tension reducers, deodorizing agents, anti-
static agents, anti-
blocking agents, plasticizer agents, blowing agents, fillers, and other known
additives, or
mixtures thereof.
[0029] Ultraviolet light absorbers (UVA) shield the polymer from UV light by
absorbing
light energy and releasing the absorbed light energy harmlessly as heat
energy. Hindered
amine light stabilizers (HALS) scavenge radical intermediates formed in the
photo-oxidation
process. The higher the concentration of UVA and/or HALS, the greater the
protection of the
polymer (both the masterbatch carrier and the end product) from degradation
and the color
from fading. UVAs and HALS can be added up to about 45% by weight of the
masterbatch.
Preferred UVAs and HALS include those of the TINUVIN grades from BASF.
Illustrative
examples of UVA's and HALS include salicylic acid derivatives such as phenyl
salicylate, p-
t-butyl salicylate, etc., benzophenone system such as 2,4-dibydroxy
benzophenone, 2-
hydroxy-4-methoxybenzophenone, etc., benzotriazole system such as 2-(2'-
hydroxy-3',5'-di-t-
butylphenyl)benzotriazo le, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-
chlorobenzotriazole,
etc., hindered amine system such as bis(2,2,6,6-tetramethyl-4-piperidyl)
sebacate, dimethyl
succinate-l-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethyl piperidine
condensation product,
2-hydroxybenzophenones, e.g. 2,4-dihydroxybenzophenone, 2-hydroxy-4-
methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 5,5'-methylene bis(2-
hydroxy-4-methoxybenzophenone); 2-(2'-hydroxyphenyl)benzotriazoles, e.g. 2-(2'-
hydroxy-
5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole, 2-
(2'-hydroxy-
3',5'-di-t-butylphenyl)benzotriazo le, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-
chlorobenzotriazo le, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-
chlorobenzotriazole, 2-(2'-
hydroxy-3',5'-dicumylphenyl)benzotriazo le, and 2,2'-methylene bis(4-t-octyl-6-
benzotriazolyl)phenol; benzoates, e.g. phenylsalicylate, resorcinol
monobenzoate, 2,4-di-t-
butylphenyl-3',5'-di-t-butyl-4'-hydroxybenzoate, and hexadecyl-3,5-di-t-butyl-
4-
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hydroxybenzoate; substituted oxanilides, e.g. 2-ethyl-2'-ethoxyoxanilide and 2-
ethoxy-4'-
dodecyloxanilide; cyanoacrylates, e.g. ethyl-a-cyano-(3,(3-diphenylacrylate
and methyl-2-
cyano-3-methyl-3-(p-methoxyphenyl)acrylate, and any other known UVA, or
mixtures
thereof.
[0030] Additional illustrative examples of HALS include 2,2,6,6-tetramethyl-4-
piperidylstearate, 1,2,2,6,6-pentamethyl-4-piperidylstearate, 2,2,6,6-
tetramethyl-4-
piperidylbenzoate, bis(2,2,6,6-tetramethyl-4-piperidylsebacate, bis(1,2,2,6,6-
pentamethyl-4-
piperidyl)sebacate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3, 4-butane
tetracarboxylate,
tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-buta ne tetracarboxylate,
bis(1,2,2,6,6-
pentamethyl-4-piperidyl)-di(tridecyl)- 1,2,3,4-butane tetracarboxylate,
bis(1,2,2,6,6-
pentamethyl-4-piperidyl)-2-butyl-2-(3',5'-di-t-butyl-4-hydro
xybenzyl)malonate, 1-(2-
hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol/diethyl succinate
polycondensate, 1,6-
bis(2,2,6,6-tetramethyl-4-piperidylamino) hexane/dibromoethane polycondensate,
1,6-
bis(2,2,6,6-tetramethyl-4-piperidylamino)hexane/2,4-dichloro-6-t-octyl amino-s-
triazine
polycondensate, 1,6-bis(2,2,6,6-tetramethyl-4-piperidylamino)hexane/2,4-
dichloro-6-
morphol ino-s-triazine polycondensate, and the like, or mixtures thereof.
[0031] Antioxidants, including processing stabilizers, can be added to the
masterbatch
composition up to about 15% by weight of the masterbatch. Peroxide polymer
degradation
generally occurs during processing (due to heat or shear), or at the time of
light exposure.
Peroxide radicals may be formed during this period, which in turn may lead to
the formation
of hyperoxides. Antioxidants are incorporated into polymers to stabilize
peroxide radicals to
prevent degradation. Optimal polymer stability is achieved when the initial
molecular weight
and/or the initial color of the polymer is maintained. Therefore, the present
masterbatch
composition provides a higher degree of protection by achieving higher
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concentrations without sacrificing colorant concentration. In one embodiment,
both UVAs
(and/or HALS) and an antioxidant may be added up to about 60% by weight of the
masterbatch. It is preferred in such embodiments that the UVAs (and/or HALS)
are added up
to about 45% by weight of the masterbatch, and the antioxidant is added up to
about 15% by
weight of the masterbatch. Sterically hindered phenols or HALS are preferred
antioxidants,
particularly sterically hindered phenols of the Irganox grades from BASF.
Other illustrative
examples of antioxidants include a phenol system such as 2,6-di-t-butyl-p-
Cresol,
pentaerythritol-tetrakis-(3,5-di-t-butyl-4-hydroxyphenyl) propionate methyl
phenol,
octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate, etc., phosphorus
system such as
tris(2,4-di-t-butylphenyl)phosphate, distearylpnetaerythritol diphophate,
tetrakis (2,4-di-t-
butylphenyl)-4,4'-biphenylene phosphonate, etc., sulfur system such as
distearyl-3,3'-
thiodipropionate, pentaerythritol-tetrakis-(3-laurylthiopropionate), hindered
phenol type
antioxidants and peroxide decomposers, HALS (as set described above), or
mixtures thereof.
[0032] Illustrative examples of hindered phenol type antioxidants are 2,6-di-t-
butyl-4-
methylphenol, styrenated phenol, n-octadecyl-3-(3,5-di-t-butyl-4-
hydroxylphenyl)
propionate, 2,2'-methylene bis(4-methyl-6-t-butylphenol), 2-t-butyl-6-(3-t-
butyl-2-hydroxy-5-
methylbenzyl)-4-methylphenylacrylate, 2-[l-(2-hydroxy-3,5-di-t-
pentylphenyl)ethyl]-4,6-di-
t-pentylphenyl acrylate, 4,4'-butylidene bis(3-methyl-6-t-butylphenol), 4,4'-
thio-bis(3-methyl-
6-t-butylphenol), alkylated bisphenol, tetrakis[methylene-3-(3,5-di-t-butyl-4-
hydroxyphenyl)-
proprionate] methane, 3,9-bis[2-{3-(3-t-butyl-4-hydroxy-5-methylphenyl)-
propionyloxy}-
1,1-dimethylethyl] -2,4,8, 1 0-tetraoxyspiro [5.5 ]undecane, or mixtures
thereof.
[0033] Illustrative examples of peroxide decomposers are organic phosphorus
type peroxide
decomposers, such as trisnonylphenylphosphite, triphenylphosphite and tris(2,4-
di-t-
butylphenyl)phosphite; and organic thio type peroxide decomposers, such as
dilauryl-3,3'-
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thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-
thiodipropionate,
pentaerythrityltetrakis(3-laurylthiopropionate), ditridecyl-3,3'-
thiodipropionate and 2-
mercaptobenzimidazo le, or mixtures thereof.
[0034] Illustrative examples of flame-retardants are phosphoric acid systems
such as allkyl
diallyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate,
triallyl phosphate,
tributyl phosphate, triphenyl phosphate, tris((3-chloroethyl) phosphate,
tris(dichloropropyl)
phosphate, tris(2,3-dibrompropyl) phosphate, tris(bromo-chloropropyl)
phosphate, etc.,
chlorine system such as chlorinated paraffin, chlorinated polyphenyl,
perchloropentacyclodecane, etc., bromine system such as tetrabromoethane,
tetrabromobutane, hexaborombenzene, decabromodiphenyloxide,
polydibrornophenyloxide,
bis(tribromophenoxy)ethane, ethylene bisbromonorbomane dicarboxyimide,
ethylene
bistetrabromophthalimide, etc. reaction type such as chlorendic acid
anhydride, tetrabromo
phthalic anhydride, tetrabromo bisphenol A, dietoxy-bis-(2-hydroxyethyl)-
aminomethyl
phosphate, dibormcresyl alycidyl ether, etc, or mixtures thereof.
[0035] Illustrative examples of antibacterial agents include, phenol ether
based antibacterial
agents, such as those having the phenol group in the intramolecular skeleton,
for example, 10,
10'-oxybisphenoxa arsine, etc.; natural antibacterial agents, such as those
having tropolone as
a central skeleton, for example, hinokitiol, (3-dolabulin, etc., as glycerol
ester of fatty acid,
lower fatty acid monoglycerol ester, sucrose fatty acid ester, polyglycerol
fatty acid ester, for
example, monoglyceride caprylate, monoglyceride caprate, lauric acid
monoglyceride, Sugar-
ester palpitate, decaglycerol monocaprate, hexaglycerol caprylate, etc.,
zeolite-based
compounds, part or whole of ion-exchangeable ion in zeolite-based compounds,
for example,
part or whole of sodium ion, calcium ion, potassium ion, magnesium ion, iron
ion, etc. is
substituted with ions with antibacterial property, such as silver ion, copper
ion, zinc ion,
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ammonium ion, etc. can be exemplified. These compounds can be used singly or
two or more
kinds of them can be used in combination.
[0036] Fillers are typically inexpensive particulate materials that do not
contribute to the
color. Illustrative examples of fillers include, among others, talcs, micas,
clays, nano-clays,
silicas, or mixtures thereof.
[0037] The masterbatch composition described herein may contain other
additives or
ingredients and should not be limited to the stated formulations. In one
embodiment, a
dispersion package can be added to the masterbatch composition in an amount up
to about
25% by weight of the masterbatch. In another embodiment, the dispersion
package is added
in an amount from about 2% to about 8% based on the weight of the masterbatch.
The
dispersion package can be waxes, metal salts, surfactants, coupling agents,
organometallic
compounds, and mixtures thereof. Illustrative examples include conventional
polyethylene
and polypropylene waxes and derivatives thereof such as acid-modified products
and metal
salts of acid-modified products, as well as zinc stearate, magnesium stearate,
aluminium
stearate, calcium stearate and ethylene bisteramide, and mixtures thereof.
[0038] Before actual mixing of the masterbatch, the components can be premixed
if desired,
for which drum or tumbler mixers may be used. In the actual mixing process,
the mixing is
generally performed in a high intensity mixer. In one embodiment, the
masterbatch is
prepared by mixing the components in a Henschel-type mixer for up to 30
minutes,
preferably for 4 to 10 minutes. It is understood that the masterbatch
components may be
added together and mixed, or added individually at any point during the mixing
process.
Actual dispersion generally takes place in a single-screw or twin-screw
extruder; however,
any equipment known in the art may be used. Illustrative examples include Buss
kneaders,
planetary roll extruders, open double-trough kneaders, rapid stirrers,
internal fluxing mixers
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such as Banbury mixers and Farrel continuous mixers, or the like.
[0039] The masterbatch may be introduced to any compatible polymer and
processed. It is
understood that the masterbatch composition of the present invention can be
used for coloring
polymers formed into various shapes, such as sheet, film, tube, bottles,
containers, molded
products and other molded articles. The term processing is used herein to
describe the
conversion of polymers into articles of a desired shape. Illustrative examples
of processing
are extrusion molding, injection molding, blow molding, compression molding
and
calendering. The term processable is used herein to mean capable of
processing. The
addition of the masterbatch to the melt-processible polymer can be
accomplished by any
means known in the art. It is possible to use the same methods as for
preparing the
masterbatch itself. It is understood that the masterbatch carrier polymer can
be the same or
different than the melt-processible polymer. The masterbatch composition may
be introduced
and processed via a batch or continuous process. In one illustrative
embodiment, the
masterbatch may be introduced to the melt-processible polymer and processed on
a rubber
compounding mill, simple kneader, or in a Banbury or other internal mixer or
in a mixing
extruder. Alternatively, the masterbatch can be metered to the feed section of
an extruder by
appropriate devices. Continuous processes can be carried out, for example, in
rapid mixers,
single-screw extruders, twin-screw extruders, Buss kneaders, planetary roll
extruders, open
double-trough kneaders or rapid stirrers. Continuous processes are preferred.
EXAMPLES
[0040] The following masterbatch examples set forth in Table 1 below were
prepared in
accordance with the invention and are intended to illustrate the invention
without, however,
limiting it. The percentages shown in Table 1 below are percent by weight of
the total
masterbatch composition.
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Materials Example 1 Example 2
Carrier Resin 11.0% (Linear Low Density 15.7% (High Density
Polyethylene) Polyethylene)
Processing Aid 7.0% 6.0%
Colorant 80.0% (TiO2) 39.5%
UV Stabilizer -- 31.5% (Tinuvin)
Anti-Oxidant -- 5.3% (Irganox)
Dispersion 2.0% (Zn Stearate) 2.0% (Zn Stearate)
Package
[0041] Table 1 above demonstrates that addition of the high polymer processing
aid to the
masterbatch composition allows for a higher colorant and additive
concentration with a lower
carrier concentration than conventional masterbatches. Example 1 shows a
masterbatch
composition having a high concentration of pigment. Example 2 shows a
masterbatch
composition having a high concentration of pigment and additives. The
masterbatch
compositions in Examples 1-2 were processed on standard laboratory and
commercial scale
extrusion equipment to yield fully compounded pellets. In both examples the
following
processing aids were used with substantially the same results: (1) a
homopolymer polybutene
resin with melt flow of 200 g/l0min and melt point of about 124 C, (2) a
copolymer
polybutene resin with > 10% ethylene comonomer that has a melt flow of about
40 g/l0min
and a melt point of about 81 C, (3) and a olefin block copolymer of
polyethylene made by
shuttling the chain between two catalysts and having a melt flow of about 15
g/l0min and a
melt point of about 120 C.
[0042] The resulting pellets formed from the masterbatch compositions in
Examples 1-2
were evaluated for pigment dispersion quality and pellet integrity. Dispersion
was assessed
visually using thin, pressed-out films of the masterbatch composition. Pellet
integrity was
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evaluated by applying pressure to individual pellets. The pellets deformed
rather than break
apart.
[0043] The invention has been described above and, obviously, modifications
and
alternations will occur to others upon a reading and understanding of this
specification. The
claims as follows are intended to include all modifications and alterations
insofar as they
come within the scope of the claims or the equivalent thereof.
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