U.S. patent application number 13/908105 was filed with the patent office on 2013-10-10 for polyolefin dispersion technology used for porous substrates.
The applicant listed for this patent is Dow Global Technologies LLC. Invention is credited to Gert J. Claasen, Martin Pavlik, Miguel A. Prieto.
Application Number | 20130267138 13/908105 |
Document ID | / |
Family ID | 40580325 |
Filed Date | 2013-10-10 |
United States Patent
Application |
20130267138 |
Kind Code |
A1 |
Claasen; Gert J. ; et
al. |
October 10, 2013 |
POLYOLEFIN DISPERSION TECHNOLOGY USED FOR POROUS SUBSTRATES
Abstract
A method of forming an article that includes applying an aqueous
dispersion to a porous substrate, wherein the aqueous dispersion
includes a thermoplastic polymer, a dispersing agent, and water.
The method includes removing at least a portion of the water, to
result in an article formed that is breathable.
Inventors: |
Claasen; Gert J.;
(Richterswil, ZA) ; Prieto; Miguel A.;
(Richterswil, CH) ; Pavlik; Martin; (Wadenswil,
CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dow Global Technologies LLC |
Midland |
MI |
US |
|
|
Family ID: |
40580325 |
Appl. No.: |
13/908105 |
Filed: |
June 3, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12739623 |
Apr 23, 2010 |
8475878 |
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PCT/US2008/079815 |
Oct 14, 2008 |
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13908105 |
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60982653 |
Oct 25, 2007 |
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Current U.S.
Class: |
442/59 |
Current CPC
Class: |
D06N 2209/121 20130101;
D06N 7/00 20130101; Y10T 442/20 20150401; D04H 13/00 20130101; D06N
3/045 20130101; D06N 2209/123 20130101; D06N 2205/023 20130101;
D06N 2203/042 20130101 |
Class at
Publication: |
442/59 |
International
Class: |
D04H 13/00 20060101
D04H013/00 |
Claims
1.-13. (canceled)
14. A breathable article, comprising: a non-woven substrate and an
applied compound, wherein the applied compound, at the time of
application, comprised an aqueous dispersion, wherein the aqueous
dispersion comprised a thermoplastic polymer, a dispersing agent,
and water.
Description
BACKGROUND OF INVENTION
[0001] 1. Field of the Invention
[0002] Embodiments disclosed herein relate generally to methods for
forming breathable articles, and breathable articles formed using
those methods.
[0003] 2. Background
[0004] Coverings, such as gloves, mitts, socks, shoes, or boots,
long have been used to protect hands and feet from environmental or
work conditions. Depending on the type of environment, nature of
work, or desired properties, these type of coverings have been made
from a variety of materials, which have included woven cloth
fabrics, leather, natural latex or synthetic polymer elastomeric
materials, or combinations of such materials. These articles
typically have been designed for durable use.
[0005] The vast majority of gloves or foot covers, typically, have
been made from either woven cloth fabrics, suede, or leather.
Gloves made of woven fabrics generally allow the skin of the wearer
to breathe through the spaces between the individual strands of
woven fabric material, and any perspiration from the hand or foot
is wicked away by the fabric. Leather tends not to fit as
comfortably as cloth or fabric-lined articles, nor is it as
flexible, or permits the skin to breathe as easily. Moreover,
leather, while resilient, typically is not as good of a barrier
against prolonged exposure to wetness or hazards as polymeric
elastomer materials.
[0006] For applications that require greater protection against
fluids, chemicals, or microscopic pathogens, such as found in
laboratory, healthcare and clinical, or other work settings, the
protective articles--gloves in particular--traditionally have
incorporated a barrier layer that is impervious to the undesirable
substances. Surgical, examination, or work gloves, for example,
typically are made using natural or synthetic rubber latex or other
elastic polymer membranes, which generally exhibit good barrier
properties. Unfortunately, the good barrier properties of such
materials may create a harsh environment for the wearer's skin,
which is bad for skin/hand health.
[0007] For example, wearing a glove made from an elastic polymer
latex for prolonged periods can trap perspiration in the article
because the wearer's skin is not able to adequately breathe, making
the glove uncomfortable to wear. As perspiration accumulates, the
moist environment within the article may become a potential source
or incubator for the growth of fungi or yeast, as well as bacterial
or viral contamination, which can exacerbate skin problems.
[0008] People have tried to solve these problems in a variety of
ways, for instance, by combining woven and elastomeric materials. A
common practice has been to unite a woven or cloth-like material as
an underlayer with an elastomeric membrane or film as a barrier
overcoat, for a strong and resistant article (e.g., as described in
U.S. Pat. No. 2,060,961, or 5,246,658, or U.S. Patent Publication
No. 2004/0139529). Manufacturers have used knit, woven, or
non-woven fabrics as liners in a variety of durable industrial
gloves that can have a relatively long work life. Such gloves can
be made in a variety of ways. For instance, as described in the
patent examples, gloves are fabricated by providing a hand-shaped
block mould or former, applying or fitting a woven or knit
glove-shaped liner, then dipping into a polymer solution, such as
latex or nitrile, to cover the glove liner.
[0009] Typically, the liners for such gloves are generally thick,
hence gloves made from this type of processes usually have poor
flexibility and fit loosely to the hand. In some other cases,
fabrics are first laminated to a polymer layer and then sealed
under harsh conditions to form an air and water-proof seam, such as
described in U.S. Pat. No. 5,981,019, which discloses an air and
liquid-proof protective cover for use in harsh environments.
Furthermore, the configuration of the human hand is such that the
thumb projects considerably beyond the palm, and the thumb and
other four fingers can move relatively freely in relation to each
other to perform any desired task.
[0010] Gloves that are made according to conventional methods are
often made on a flat hand-shaped dipping mould or a last. Since a
hand or foot has three-dimensionality, gloves or foot covers that
are made in largely flat moulds do not fit the hand or foot well
when worn and feel uncomfortable, which can be cumbersome when
working.
[0011] According to other approaches, manufacturers fabricate
elastomeric articles reinforced with fibers. Common work gloves,
such as for housework or industrial uses, are examples of this
latter design. Manufacturers of fiber-reinforced gloves incorporate
an internal lining composed of fibrous material, such as cotton
flock (e.g., U.S. Pat. No. 4,918,754, 4,536,890, or 5,581,812).
Typically, flock is composed of finely divided, short, ground,
fibrous particles, which can be applied as a lining by spraying the
flock particles onto an adhesive-covered backing (e.g., the
external shell of a glove). An inner glove lining of flock provides
a smooth, comfortable feeling, cushions the hands, absorbs
perspiration and keeps the hands dry, insulates against moderate
heat and cold without being bulky, makes the glove easier to put on
and take off, and has other advantageous characteristics. Gloves
with such characteristics are favored by workers and have become
common articles for various heavy-duty industrial applications.
[0012] The disadvantages, however, of a glove having an internal
lining composed of cotton flock or other similar fibrous material
are many. First, for instance, fibers and particles can become
detached from the internal lining over time through abrasion with
either the glove wearer's hand or the surface of the sleeve of a
garment worn by the wearer. The detached particles can migrate out
of the glove, particularly when the glove is being donned or
removed from the wearer's hand.
[0013] Second, fibers, like short cotton fibers, typically are not
elastomeric, which makes them difficult to coat onto glove skins
made of latex or nitrile materials, etc. The current commercial
flocking process uses glue to make the short cotton fibers stick.
Flocking is essentially a batch process, and fibers can not be
embedded into the polymer layers effectively.
[0014] Like in elastomeric articles, current-commercial flocked
gloves, in some cases, use powder, such as cornstarch or calcium
carbonate powders, to enhance the donning and comfort. The presence
of powders may help absorb some of the perspiration moisture and
alleviate some of the problems the wearer faces. The use of powder,
however, was only partially successful, as the powder particles
could absorb only a limited amount of the moisture. Additionally,
powders are not well accepted among consumers because of allergy
and health concerns of small particles, or for certain uses, such
as in clean-room type applications and during surgical procedures,
powders may not be used at all.
[0015] Aside from industrial-type gloves with cotton liners or
fabric liners, currently very few examples of disposable gloves
exist that incorporate coated fibers, which can provide qualities
such as comfort, good fit with flexibility, easy donning or
insertion of the hand, being powder-free, allergy prevention, skin
protection, and moisture absorption. For disposable latex gloves,
the challenge is to create an elastomeric fiber-layer without
limiting the fiber length and size to make economically viable
flexible, fiber-lined, disposable gloves. Unfortunately, current
technologies for durable industrial gloves cannot satisfy this
challenge.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 shows SEM images in accordance with one disclosed
embodiment.
SUMMARY OF INVENTION
[0017] In one aspect, the present invention relates to a method of
forming an article comprising applying an aqueous dispersion to a
porous substrate, wherein the aqueous dispersion comprises a
thermoplastic polymer, a dispersing agent, and water; and removing
at least a portion of the water; wherein the article formed is
breathable.
[0018] Other aspects and advantages of the invention will be
apparent from the following description and the appended
claims.
DETAILED DESCRIPTION
[0019] The present inventors have advantageously discovered that by
coating porous (e.g., nonwoven substrates) with aqueous polyolefin
dispersions, breathable structures can be achieved. These
structures have a unique morphology with a controllable porosity
and mechanical properties that can be controlled by judicious
manipulation of the following parameters: [0020] Composition of the
dispersion [0021] Viscosity [0022] Neutralization type [0023]
Drying temperature [0024] Drying time [0025] Multi layer structures
[0026] Crosslinking
[0027] Briefly, then, embodiments disclosed herein provide for the
fabrication of breathable coated articles that are moisture
resistant. By starting with an aqueous dispersion, as opposed to
traditional manufacturing techniques, the present inventors are
able to employ a larger range of coating techniques such as curtain
coating, spraying, casting, dipping, rotational coating, and other
standard coating techniques available for dispersions, which are
not available to the current breathable backsheet producers.
[0028] Before describing the present invention in detail, the
terminology used herein is for the purpose of describing particular
embodiments only, and is not intended to be limiting. The invention
should not necessarily be limited to specific compositions,
materials, designs or equipment, as such may vary. All technical
and scientific terms used herein have the usual meaning
conventionally understood by persons skilled in the art to which
this invention pertains, unless context defines otherwise. As used
in this specification and the appended claims, the singular forms
"a," "an," and "the" include plural referents unless the context
clearly dictates otherwise.
[0029] The term "biconsfituent fibers" (sometimes also referred to
as "multiconstituent fibers") as used herein refers to filaments or
fibers that have been formed from at least two polymers, or the
same polymer with different properties or additives, extruded from
the same extruder as a blend. Biconstituent fibers do not have the
various polymer components arranged in relatively constantly
positioned distinct zones across the cross-sectional area of the
fiber and the various polymers are usually not continuous along the
entire length of the fiber, instead usually forming fibrils or
protofibrils which start and end at random. Fibers of this general
type are discussed in, for example, U.S. Pat. Nos. 5,108,827 and
5,294,482, to Gessner. Biconstituent fibers are also discussed in
the textbook POLYMER BLENDS AND COMPOSITES by John A. Manson and
Leslie H. Sperling, Plenum Press, a division of Plenum Publishing
Corporation of New York, IBSN 0-306-30831-2, pp. 273-277, .COPYRGT.
1976.
[0030] The term "breathable" as used herein refers to materials
that are pervious to water vapor and gases. In other words,
"breathable barriers" and "breathable films" allow water vapor to
pass through, but still protect the users skin from microbes or
other infectious agents. For example, "breathable" can refer to a
film or laminate having a moisture vapor transmission rate (MVTR)
of at least about 300 g/m.sup.2 per 24 hours measured using ASTM
Standard E96-80, upright cup method.
[0031] The term "conjugate fibers" as used herein refers to fibers
that have been formed from at least two polymers extruded from
separated extruders but spun together to form one fiber. Conjugate
fibers are also sometimes referred to as multicomponent or
bicomponent fibers. The polymers are usually different from each
other though conjugate fibers may be monocomponent fibers. The
polymers are arranged in substantially instantly positioned
distinct zones across the cross-section of the conjugate fibers and
extend continuously along the length of the conjugate fibers. The
configuration of such a conjugate fiber may be, for example, a
sheath/core arrangement, wherein one polymer is surrounded by
another or may be a side by side arrangement, a pie arrangement or
an "islands-in-the-sea" arrangement. Conjugate fibers are taught by
U.S. Pat. No. 5,108,820 to Kaneko et al., U.S. Pat. No. 4,795,668
to Krueger et al., and U.S. Pat. No. 5,336,552 to Strack et al.
Conjugate fibers are also taught in U.S. Pat. No. 5,382,400 to Pike
et al. and may be used to produce crimp in the fibers by using the
differential rates of expansion and contraction of the two (or
more) polymers. Crimped fibers may also be produced by mechanical
means and by the process of German Patent DE 25 13 251A1. For two
component fibers, the polymers may be present in ratios of 75/25,
50/50, 25/75, or any other desired ratios. The fibers may also have
shapes, such as those described in U.S. Pat. No. 5,277,976 to Hogle
et al., U.S. Pat. No. 5,466,410 to Hill, and U.S. Pat. Nos.
5,069,970 and 5,057,368 to Largman et al., which describe fibers
with unconventional shapes.
[0032] The term "continuous" or "substantially continuous" with
respect to a filament or fiber refers a filament or fiber having a
length much greater than its diameter, for example having a
diameter to length ratio of about 1 to 2,000 or 3,000, or greater,
desirably in excess of about 1 to 5,000, 15,000 or 25,000.
[0033] The term "disposable article" refers to a single or limited
use article that is made from relatively inexpensive materials that
make the article cost effective to fabricate. The technical,
material, and economical problems associated with disposable
articles are different from articles that can be used multiple
times or reused, and as such have been constructed from relatively
expensive materials.
[0034] The term "machine direction" or MD means the length of a web
in the direction in which it is produced. The term "cross machine
direction" or CD means the width of fabric, i.e. a direction
generally perpendicular to the MD.
[0035] The terms "elastic" and "elastomeric" as used herein are
interchangeable and generally refer to materials that, upon
application of a deforming stress or force, are stretchable in at
least one direction (e.g., CD direction), and which upon release of
the force returns to approximately its original size and shape. For
example, a stretched material having a stretched length which is at
least 5-20% greater than its relaxed unstretched length, and which
will recover to within at least 5-20% of its original length upon
release of the stretching, biasing force.
[0036] The term "filament" as used herein refers to a generally
continuous strand that has a large ratio of length to diameter,
such as, for example, a ratio of about 1 to 500-1000 or more.
[0037] The term "laminate" or "lamination" as used herein refers to
a composite structure of two or more sheet material layers that
have been adhered through a bonding step, such as through adhesive
bonding, thermal bonding, point bonding, pressure bonding,
extrusion coating, or ultrasonic bonding.
[0038] The term "meltblown fibers" refers to fibers formed by
extruding a molten thermoplastic material through a plurality of
fine, usually circular, die capillaries as molten threads or
filaments into converging high velocity, usually hot, gas (e.g.
air) streams which attenuate the filaments of thermoplastic
material to reduce their diameter, which may be to microfiber
diameter. Thereafter, the meltblown fibers are carried by the high
velocity gas stream and are deposited on a collecting surface to
form a web of randomly disbursed meltblown fibers. Such a process
is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin et
a. Meltblown fibers are microfibers which may be continuous or
discontinuous, are generally smaller than about 8-10 microns
(.mu.m) in average diameter, and are generally tacky when deposited
on a collecting surface.
[0039] As used herein, the term "microporous film" or "microporous
filled film" means films which contain filler material which
enables development or formation of micropores in the film during
stretching or orientation of the film.
[0040] The term "monolithic" is used to mean "non-porous,"
therefore a monolithic film is a non-porous film. Rather than holes
produced by a physical processing of the monolithic film, the film
has passages with cross-sectional sizes on a molecular scale formed
by a polymerization process. The passages serve as conduits by
which water molecules (or other liquid molecules) can disseminate
through the film. Vapor transmission occurs through a monolithic
film as a result of a concentration gradient across the monolithic
film. This process is referred to as activated diffusion. As water
(or other liquid) evaporates on the body side of the film, the
concentration of water vapor increases. The water vapor condenses
and solubilizes on the surface of the body side of the film. As a
liquid, the water molecules dissolve into the film. The water
molecules then diffuse through the monolithic film and re-evaporate
into the air on the side having a lower water vapor
concentration.
[0041] A "moisture bather" refers to any material that is
relatively impermeable to the transmission of liquid fluids, i.e. a
fabric having a moisture barrier can have a blood strikethrough
ratio of about 1.0 or less according to ASTM test method 22.
[0042] The term "nonwoven web" or "nonwoven fabric" refers to a web
having a structure of individual fibers or threads which are
interlaid, but not in an identifiable manner as in a knitted
fabric. Nonwoven webs or fabrics have been formed from many
processes, such as, for example, meltblowing processes, spunbonding
processes, and bonded carded web processes. The basis weight of
nonwoven fabrics is usually expressed in ounces of material per
square yard (osy) or grams per square meter (gsm) and the fiber
diameters are usually expressed in microns. (Note that to convert
from osy to gsm, multiply osy by 33.91). Nonwoven webs or fabrics
may be used interchangeably and are distinguishable from flocking
or other collection of individual fibers that do not form a unitary
structure.
[0043] In one aspect, breathable articles disclosed herein can be
formed from a variety of materials. Exemplary breathable articles
include diaper backsheets, protective clothing (such as gloves,
mitts, socks, shoes, or boots), and packing materials.
[0044] As an exemplary embodiment, a glove can be formed as a
unitary structure from a base web. Alternatively, a glove can be
formed from two sections made from the same or different base webs.
A base web, as used herein, refers to a substrate that includes one
or more layers of fibrous materials. For most applications, gloves
made according to embodiments disclosed herein are constructed for
nonwoven webs containing an elastic component referred to herein as
an "elastic nonwoven." An elastic nonwoven is a nonwoven material
having non-elastic and elastic components or having purely elastic
components. The elastic component can form a separate section of
the glove. For example, the glove can be made from two or more
sections of material that includes a first section made from a
non-elastic material and a second section made from an elastic
material. Alternatively, the glove can be made from a single piece
of material that contains an elastic component. For example, the
elastic component can be a film, strands, non-woven webs, or
elastic filament incorporated into a laminate structure.
[0045] Non-elastic materials used in the present invention
typically include nonwoven webs or films. The nonwoven webs, for
instance, can be meltblown webs, spunbond webs, carded webs, and
the like. The webs can be made from various fibers, such as
synthetic or natural fibers. For instance, in one embodiment,
synthetic fibers, such as fibers made from thermoplastic polymers,
can be used to construct the glove of the present invention. For
example, suitable fibers could include melt-spun filaments, staple
fibers, melt-spun multicomponent filaments, and the like.
[0046] Synthetic fibers or filaments used in making the nonwoven
materials of the base web have any suitable morphology, which may
include hollow or solid, straight or crimped, single component,
conjugate or biconstituent fibers or filaments, and blends or
mixtures of such fibers and/or filaments, as are well known in the
art.
[0047] The synthetic fibers used in disclosed embodiments may be
formed from a variety of thermoplastic polymers where the term
"thermoplastic polymer" refers to a long chain polymer that
repeatedly softens when exposed to heat and substantially returns
to its original state when cooled to ambient temperature. As used
herein, the term "polymer" generally includes, but is not limited
to, homopolymers, copolymers, such as for example, block, graft,
random, and alternating copolymers, terpolymers, etc., and blends
and modifications thereof. As used herein, the term "blend" means a
mixture of two or more polymers. Furthermore, unless otherwise
specifically limited, the term "polymer" shall include all possible
geometrical configurations of the molecule. These configurations
include, but are not limited to, isotatic, synditatic, and random
symmetries.
[0048] Exemplary thermoplastics include, without limitation,
poly(vinyl) chlorides, polyesters, polyamides, polyfluorocarbons,
polyolefins, polyurethanes, polystyrenes, poly(vinyl) alcohols,
caprolactams, and copolymers of the foregoing, and elastomeric
polymers such as elastic polyolefins, copolyether esters, polyamide
polyether block copolymers, ethylene vinyl acetates (EVA), block
copolymers having the general formula A-B-A' or A-B like
copoly(styrene/ethylene-butylene),
styrene-poly(ethylene-propylene)-styrene,
styrene-poly(ethylene-butylene)-styrene,
polystyrene/poly(ethylene-butylene)/polystyrene,
poly(styrene/ethylene-butylene/styrene), A-B-A-B tetrablock
copolymers and the like.
[0049] Dispersions
[0050] Dispersions used in accordance with embodiments disclosed
herein include a base polymer, a stabilizing agent, water, and,
optionally, a filler.
[0051] Base Polymer
[0052] The base polymer resin(s) contained within the dispersion
composition may vary depending upon the particular application and
the desired result. In one embodiment, for instance, the base
polymer may be a thermoplastic resin. In particular embodiments,
the thermoplastic resin may be an olefin polymer. As used herein,
an olefin polymer, in general, refers to a class of polymers formed
from hydrocarbon monomers having the general formula
C.sub.nH.sub.2n. The olefin polymer may be present as a copolymer,
such as an interpolymer, a block copolymer, or a multi-block
interpolymer or copolymer.
[0053] In one particular embodiment, for instance, the olefin
polymer may comprise an alpha-olefin interpolymer of ethylene with
at least one comonomer selected from the group consisting of a
C.sub.3-C.sub.20 linear, branched or cyclic diene, or a vinyl
compound, such as vinyl acetate, and a compound represented by the
formula H.sub.2C.dbd.CHR wherein R is a C.sub.1-C.sub.20 linear,
branched or cyclic alkyl group or a C.sub.6-C.sub.20 aryl group.
Examples of comonomers include propylene, 1-butene,
3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene,
1-heptene, 1-hexene, 1-octene, 1-decene, and 1-dodecene.
[0054] In other embodiments, the thermoplastic resin may be an
alpha-olefin interpolymer of propylene with at least one comonomer
selected from the group consisting of ethylene, a C.sub.4-C.sub.20
linear, branched or cyclic diene, and a compound represented by the
formula H.sub.2C.dbd.CHR wherein R is a C.sub.2-C.sub.20 linear,
branched or cyclic alkyl group or a C.sub.6-C.sub.20 aryl group.
Examples of comonomers include ethylene, 1-butene,
3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene,
1-heptene, 1-hexene, 1-octene, 1-decene, and 1-dodecene. In some
embodiments, the comonomer is present at about 5% by weight to
about 25% by weight of the interpolymer. In one embodiment, a
propylene-ethylene interpolymer is used.
[0055] Other examples of thermoplastic resins which may be used in
the present disclosure include homopolymers and copolymers
(including elastomers) of an olefin such as ethylene, propylene,
1-butene, 3-methyl-1-butene, 4-methyl-1-pentene,
3-methyl-1-pentene, 1-heptene, 1-hexene, 1-octene, 1-decene, and
1-dodecene as typically represented by polyethylene, polypropylene,
poly-1-butene, poly-3-methyl-1-butene, poly-3-methyl-1-pentene,
poly-4-methyl-1-pentene, ethylene-propylene copolymers,
ethylene-1-butene copolymers, and propylene-1-butene copolymers;
copolymers (including elastomers) of an alpha-olefin with a
conjugated or non-conjugated diene as typically represented by
ethylene-butadiene copolymers and ethylene-ethylidene norbornene
copolymers; and polyolefins (including elastomers) such as
copolymers of two or more alpha-olefins with a conjugated or
non-conjugated diene as typically represented by
ethylene-propylene-butadiene copolymers,
ethylene-propylene-dicyclopentadiene copolymers,
ethylene-propylene-1,5-hexadiene copolymers, and
ethylene-propylene-ethylidene norbornene copolymers; ethylene-vinyl
compound copolymers such as ethylene-vinyl acetate copolymers with
N-methylol functional comonomers, ethylene-vinyl alcohol copolymers
with N-methylol functional comonomers, ethylene-vinyl chloride
copolymers, ethylene acrylic acid or ethylene-(meth)acrylic acid
copolymers, and ethylene-(meth)acrylate copolymers; styrenic
copolymers (including elastomers) such as polystyrene, ABS,
acrylonitrile-styrene copolymers, methylstyrene-styrene copolymers;
and styrene block copolymers (including elastomers) such as
styrene-butadiene copolymer and hydrates thereof, and
styrene-isoprene-styrene triblock copolymers; polyvinyl compounds
such as polyvinyl chloride, polyvinylidene chloride, and vinyl
chloride-vinylidene chloride copolymers, polymethyl acrylate, and
polymethyl methacrylate; polyamides such as nylon 6, nylon 6,6, and
nylon 12; thermoplastic polyesters such as polyethylene
terephthalate and polybutylene terephthalate; polycarbonates,
polyphenylene oxides, and the like. These resins may be used either
alone or in combinations of two or more.
[0056] In particular embodiments, polyolefins such as
polypropylene, polyethylene, and copolymers thereof and blends
thereof, as well as ethylene-propylene-diene terpolymers may be
used. In some embodiments, the olefinic polymers include
homogeneous polymers described in U.S. Pat. No. 3,645,992 by
Elston; high density polyethylene (HDPE) as described in U.S. Pat.
No. 4,076,698 to Anderson; heterogeneously branched linear low
density polyethylene (LLDPE); heterogeneously branched ultra low
linear density (ULDPE); homogeneously branched, linear
ethylene/alpha-olefin copolymers; homogeneously branched,
substantially linear ethylene/alpha-olefin polymers which can be
prepared, for example, by a process disclosed in U.S. Pat. Nos.
5,272,236 and 5,278,272, the disclosure of which process is
incorporated herein by reference; heterogeneously branched linear
ethylene/alpha olefin polymers; and high pressure, free radical
polymerized ethylene polymers and copolymers such as low density
polyethylene (LDPE).
[0057] In another embodiment, the thermoplastic resin may include
an ethylene-carboxylic acid copolymer, such as, ethylene-vinyl
acetate (EVA) copolymers, ethylene-acrylic acid (EAA) and
ethylene-methacrylic acid copolymers such as, for example, those
available under the tradenames PRIMACOR.TM. from the Dow Chemical
Company, NUCREL.TM. from DuPont, and ESCOR.TM. from ExxonMobil, and
described in U.S. Pat. Nos. 4,599,392, 4,988,781, and 5,384,373,
each of which is incorporated herein by reference in its entirety.
Exemplary polymers include polypropylene, (both impact modifying
polypropylene, isotactic polypropylene, atactic polypropylene, and
random ethylene/propylene copolymers), various types of
polyethylene, including high pressure, free-radical LDPE, Ziegler
Nana LLDPE, metallocene PE, including multiple reactor PE ("in
reactor") blends of Ziegler-Natta PE and metallocene PE, such as
products disclosed in U.S. Pat. Nos. 6,545,088, 6,538,070,
6,566,446, 5,844,045, 5,869,575, and 6,448,341. Homogeneous
polymers such as olefin plastomers and elastomers, ethylene- and
propylene-based copolymers (for example polymers available under
the trade designation VERSIFY.TM. available from The Dow Chemical
Company and VISTAMAXX.TM. available from ExxonMobil) may also be
useful in some embodiments. Of course, blends of polymers may be
used as well. In some embodiments, the blends include two different
Ziegler-Natta polymers. In other embodiments, the blends may
include blends of a Ziegler-Natta and a metallocene polymer. In
still other embodiments, the thermoplastic resin used herein may be
a blend of two different metallocene polymers.
[0058] In one particular embodiment, the thermoplastic resin may
comprise an alpha-olefin interpolymer of ethylene with a comonomer
comprising an alkene, such as 1-octene. The ethylene and octene
copolymer may be present alone or in combination with another
thermoplastic resin, such as ethylene-acrylic acid copolymer. When
present together, the weight ratio between the ethylene and octene
copolymer and the ethylene-acrylic acid copolymer may be from about
1:10 to about 10:1, such as from about 3:2 to about 2:3. The
polymeric resin, such as the ethylene-octene copolymer, may have a
crystallinity of less than about 50%, such as less than about
25%.
[0059] Embodiments disclosed herein may also include a polymeric
component that may include at least one multi-block olefin
interpolymer. Suitable multi-block olefin interpolymers may include
those described in U.S. Provisional Patent Application No.
60/818,911, for example. The term "multi-block copolymer" refers to
a polymer comprising two or more chemically distinct regions or
segments (referred to as "blocks") preferably joined in a linear
manner, that is, a polymer comprising chemically differentiated
units which are joined end-to-end with respect to polymerized
ethylenic functionality, rather than in pendent or grafted fashion.
In certain embodiments, the blocks differ in the amount or type of
comonomer incorporated therein, the density, the amount of
crystallinity, the crystallite size attributable to a polymer of
such composition, the type or degree of tacticity (isotactic or
syndiotactic), regio-regularity or regio-irregularity, the amount
of branching, including long chain branching or hyper-branching,
the homogeneity, or any other chemical or physical property. The
multi-block copolymers are characterized by unique distributions of
polydispersity index (PDI or M.sub.w/M.sub.n), block length
distribution, and/or block number distribution due to the unique
process making of the copolymers. More specifically, when produced
in a continuous process, embodiments of the polymers may possess a
PDI ranging from about 1.7 to about 8; from about 1.7 to about 3.5
in other embodiments; from about 1.7 to about 2.5 in other
embodiments; and from about 1.8 to about 2.5 or from about 1.8 to
about 2.1 in yet other embodiments. When produced in a batch or
semi-batch process, embodiments of the polymers may possess a PDI
ranging from about 1.0 to about 2.9; from about 1.3 to about 2.5 in
other embodiments; from about 1.4 to about 2.0 in other
embodiments; and from about 1.4 to about 1.8 in yet other
embodiments.
[0060] One example of the multi-block olefin interpolymer is an
ethylene/.alpha.-olefin block interpolymer. Another example of the
multi-block olefin interpolymer is a propylene/.alpha.-olefin block
interpolymer. The following description focuses on the interpolymer
as having ethylene as the majority monomer, but applies in a
similar fashion to propylene-based multi-block interpolymers with
regard to general polymer characteristics.
[0061] The ethylene/.alpha.-olefin multi-block interpolymers may
comprise ethylene and one or more co-polymerizable .alpha.-olefin
comonomers in polymerized form, characterized by multiple (i.e.,
two or more) blocks or segments of two or more polymerized monomer
units differing in chemical or physical properties (block
interpolymer), preferably a multi-block interpolymer. In some
embodiments, the multi-block interpolymer may be represented by the
following formula:
(AB).sub.n
where n is at least 1, preferably an integer greater than 1, such
as 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, or
higher; "A" represents a hard block or segment; and "B" represents
a soft block or segment. Preferably, A's and B's are linked in a
linear fashion, not in a branched or a star fashion. "Hard"
segments refer to blocks of polymerized units in which ethylene is
present in an amount greater than 95 weight percent in some
embodiments, and in other embodiments greater than 98 weight
percent. In other words, the comonomer content in the hard segments
is less than 5 weight percent in some embodiments, and in other
embodiments, less than 2 weight percent of the total weight of the
hard segments. In some embodiments, the hard segments comprise all
or substantially all ethylene. "Soft" segments, on the other hand,
refer to blocks of polymerized units in which the comonomer content
is greater than 5 weight percent of the total weight of the soft
segments in some embodiments, greater than 8 weight percent,
greater than 10 weight percent, or greater than 15 weight percent
in various other embodiments. In some embodiments, the comonomer
content in the soft segments may be greater than 20 weight percent,
greater than 25 eight percent, greater than 30 weight percent,
greater than 35 weight percent, greater than 40 weight percent,
greater than 45 weight percent, greater than 50 weight percent, or
greater than 60 weight percent in various other embodiments.
[0062] In some embodiments, A blocks and B blocks are randomly
distributed along the polymer chain. In other words, the block
copolymers do not have a structure like:
AAA-AA-BBB-BB
[0063] In other embodiments, the block copolymers do not have a
third block. In still other embodiments, neither block A nor block
B comprises two or more segments (or sub-blocks), such as a tip
segment.
[0064] The multi-block interpolymers may be characterized by an
average block index, ABI, ranging from greater than zero to about
1.0 and a molecular weight distribution, M.sub.w/M.sub.n, greater
than about 1.3. The average block index, ABI, is the weight average
of the block index ("BI") for each of the polymer fractions
obtained in preparative TREF from 20.degree. C. and 110.degree. C.,
with an increment of 5.degree. C.:
ABI=.SIGMA.(w.sub.iBI.sub.i)
where BI.sub.i is the block index for the i.sup.th fraction of the
multi-block interpolymer obtained in preparative TREF, and w.sub.i
is the weight percentage of the i.sup.th fraction.
[0065] Similarly, the square root of the second moment about the
mean, hereinafter referred to as the second moment weight average
block index, may be defined as follows:
2 nd moment weight average B I = ( w i ( B I i - A B I ) 2 ) ( N -
1 ) w i N ##EQU00001##
[0066] For each polymer fraction, BI is defined by one of the two
following equations (both of which give the same BI value):
B I = 1 / T X - 1 / T XO 1 / T A - 1 / T AB or ##EQU00002## B I = -
LnP X - LnP XO LnP A - LnP AB ##EQU00002.2##
where T.sub.X is the analytical temperature rising elution
fractionation (ATREF) elution temperature for the i.sup.th fraction
(preferably expressed in Kelvin), P.sub.X is the ethylene mole
fraction for the i.sup.th fraction, which may be measured by NMR or
IR as described below. P.sub.AB is the ethylene mole fraction of
the whole ethylene/.alpha.-olefin interpolymer (before
fractionation), which also may be measured by NMR or IR. T.sub.A
and P.sub.A are the ATREF elution temperature and the ethylene mole
fraction for pure "hard segments" (which refer to the crystalline
segments of the interpolymer). As an approximation or for polymers
where the "hard segment" composition is unknown, the T.sub.A and
P.sub.A values are set to those for high density polyethylene
homopolymer.
[0067] T.sub.AB is the ATREF elution temperature for a random
copolymer of the same composition (having an ethylene mole fraction
of P.sub.AB) and molecular weight as the multi-block interpolymer.
T.sub.AB may be calculated from the mole fraction of ethylene
(measured by NMR) using the following equation:
LnP.sub.AB=.alpha./T.sub.AB+.beta.
where .alpha. and .beta. are two constants which may be determined
by a calibration using a number of well characterized preparative
TREF fractions of a broad composition random copolymer and/or well
characterized random ethylene copolymers with narrow composition.
It should be noted that .alpha. and .beta. may vary from instrument
to instrument. Moreover, one would need to create an appropriate
calibration curve with the polymer composition of interest, using
appropriate molecular weight ranges and comonomer type for the
preparative TREF fractions and/or random copolymers used to create
the calibration. There is a slight molecular weight effect. If the
calibration curve is obtained from similar molecular weight ranges,
such effect would be essentially negligible. In some embodiments,
random ethylene copolymers and/or preparative TREF fractions of
random copolymers satisfy the following relationship:
LnP=-237.83/T.sub.ATREF+0.639
[0068] The above calibration equation relates the mole fraction of
ethylene, P, to the analytical TREF elution temperature,
T.sub.ATREF, for narrow composition random copolymers and/or
preparative TREF fractions of broad composition random copolymers.
T.sub.XO is the ATREF temperature for a random copolymer of the
same composition and having an ethylene mole fraction of P.sub.X.
T.sub.XO may be calculated from LnP.sub.X=.alpha./T.sub.XO+.beta..
Conversely, P.sub.XO is the ethylene mole fraction for a random
copolymer of the same composition and having an ATREF temperature
of T.sub.X, which may be calculated from Ln
P.sub.XO=.alpha./T.sub.X+.beta..
[0069] Once the block index (BI) for each preparative TREF fraction
is obtained, the weight average block index, ABI, for the whole
polymer may be calculated. In some embodiments, ABI is greater than
zero but less than about 0.4 or from about 0.1 to about 0.3. In
other embodiments, ABI is greater than about 0.4 and up to about
1.0. Preferably, ABI should be in the range of from about 0.4 to
about 0.7, from about 0.5 to about 0.7, or from about 0.6 to about
0.9. In some embodiments, ABI is in the range of from about 0.3 to
about 0.9, from about 0.3 to about 0.8, or from about 0.3 to about
0.7, from about 0.3 to about 0.6, from about 0.3 to about 0.5, or
from about 0.3 to about 0.4. In other embodiments, ABI is in the
range of from about 0.4 to about 1.0, from about 0.5 to about 1.0,
or from about 0.6 to about 1.0, from about 0.7 to about 1.0, from
about 0.8 to about 1.0, or from about 0.9 to about 1.0.
[0070] Another characteristic of the multi-block interpolymer is
that the interpolymer may comprise at least one polymer fraction
which may be obtained by preparative TREF, wherein the fraction has
a block index greater than about 0.1 and up to about 1.0 and the
polymer having a molecular weight distribution, M.sub.w/M.sub.n,
greater than about 13. In some embodiments, the polymer fraction
has a block index greater than about 0.6 and up to about 1.0,
greater than about 0.7 and up to about 1.0, greater than about 0.8
and up to about 1.0, or greater than about 0.9 and up to about 1.0.
In other embodiments, the polymer fraction has a block index
greater than about 0.1 and up to about 1.0, greater than about 0.2
and up to about 1.0, greater than about 0.3 and up to about 1.0,
greater than about 0.4 and up to about 1.0, or greater than about
0.4 and up to about 1.0. In still other embodiments, the polymer
fraction has a block index greater than about 0.1 and up to about
0.5, greater than about 0.2 and up to about 0.5, greater than about
0.3 and up to about 0.5, or greater than about 0.4 and up to about
0.5. In yet other embodiments, the polymer fraction has a block
index greater than about 0.2 and up to about 0.9, greater than
about 0.3 and up to about 0.8, greater than about 0.4 and up to
about 0.7, or greater than about 0.5 and up to about 0.6.
[0071] Ethylene .alpha.-olefin multi-block interpolymers used in
embodiments of the invention may be interpolymers of ethylene with
at least one C.sub.3-C.sub.20 .alpha.-olefin. The interpolymers may
further comprise C.sub.4-C.sub.18 diolefin and/or alkenylbenzene.
Suitable unsaturated comonomers useful for polymerizing with
ethylene include, for example, ethylenically unsaturated monomers,
conjugated or non-conjugated dienes, polyenes, alkenylbenzenes,
etc. Examples of such comonomers include C.sub.3-C.sub.20
.alpha.-olefins such as propylene, isobutylene, 1-butene, 1-hexene,
1-pentene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene,
1-decene, and the like. 1-Butene and 1-octene are especially
preferred. Other suitable monomers include styrene, halo- or
alkyl-substituted styrenes, vinylbenzocyclobutane, 1,4-hexadiene,
1,7-octadiene, and naphthenics (such as cyclopentene, cyclohexene,
and cyclooctene, for example).
[0072] The multi-block interpolymers disclosed herein may be
differentiated from conventional, random copolymers, physical
blends of polymers, and block copolymers prepared via sequential
monomer addition, fluxional catalysts, and anionic or cationic
living polymerization techniques. In particular, compared to a
random copolymer of the same monomers and monomer content at
equivalent crystallinity or modulus, the interpolymers have better
(higher) heat resistance as measured by melting point, higher TMA
penetration temperature, higher high-temperature tensile strength,
and/or higher high-temperature torsion storage modulus as
determined by dynamic mechanical analysis. As compared to a random
copolymer containing the same monomers and monomer content, the
multi-block interpolymers have lower compression set, particularly
at elevated temperatures, lower stress relaxation, higher creep
resistance, higher tear strength, higher blocking resistance,
faster setup due to higher crystallization (solidification)
temperature, higher recovery (particularly at elevated
temperatures), better abrasion resistance, higher retractive force,
and better oil and filler acceptance.
[0073] Other olefin interpolymers include polymers comprising
monovinylidene aromatic monomers including styrene, o-methyl
styrene, p-methyl styrene, t-butylstyrene, and the like. In
particular, interpolymers comprising ethylene and styrene may be
used. In other embodiments, copolymers comprising ethylene, styrene
and a C.sub.3-C.sub.20 .alpha.-olefin, optionally comprising a
C.sub.4-C.sub.20 diene, may be used.
[0074] Suitable non-conjugated diene monomers may include straight
chain, branched chain or cyclic hydrocarbon dienes having from 6 to
15 carbon atoms. Examples of suitable non-conjugated dienes
include, but are not limited to, straight chain acyclic dienes,
such as 1,4-hexadiene, 1,6-octadiene, 1,7-octadiene, 1,9-decadiene,
branched chain acyclic dienes, such as 5-methyl-1,4-hexadiene;
3,7-dimethyl-1,6-octadiene; 3,7-dimethyl-1,7-octadiene and mixed
isomers of dihydromyricene and dihydroocinene, single ring
alicyclic dienes, such as 1,3-cyclopentadiene; 1,4-cyclohexadiene;
1,5-cyclooctadiene and 1,5-cyclododecadiene, and multi-ring
alicyclic fused and bridged ring dienes, such as tetrahydroindene,
methyl tetrahydroindene, dicyclopentadiene,
bicyclo-(2,2,1)-hepta-2,5-diene; alkenyl, alkylidene, cycloalkenyl
and cycloalkylidene norbornenes, such as 5-methylene-2-norbornene
(MNB); 5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene,
5-(4-cyclopentenyl)-2-norbornene, 5-cyclohexylidene-2-norbornene,
5-vinyl-2-norbornene, and norbornadiene. Of the dienes typically
used to prepare EPDMs, the particularly preferred dienes are
1,4-hexadiene (HD), 5-ethylidene-2-norbornene (ENB),
5-vinylidene-2-norbornene (VNB), 5-methylene-2-norbornene (MNB),
and dicyclopentadiene (DCPD).
[0075] One class of desirable polymers that may be used in
accordance with embodiments disclosed herein includes elastomeric
interpolymers of ethylene, a C.sub.3-C.sub.20 .alpha.-olefin,
especially propylene, and optionally one or more diene monomers.
Preferred .alpha.-olefins for use in this embodiment are designated
by the formula CH.sub.2.dbd.CHR*, where R* is a linear or branched
alkyl group of from 1 to 12 carbon atoms. Examples of suitable
.alpha.-olefins include, but are not limited to, propylene,
isobutylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and
1-octene. A particularly preferred .alpha.-olefin is propylene. The
propylene based polymers are generally referred to in the art as EP
or EPDM polymers. Suitable dienes for use in preparing such
polymers, especially multi-block EPDM type polymers include
conjugated or non-conjugated, straight or branched chain-, cyclic-
or polycyclic-dienes comprising from 4 to 20 carbons. Preferred
dienes include 1,4-pentadiene, 1,4-hexadiene,
5-ethylidene-2-norbornene, dicyclopentadiene, cyclohexadiene, and
5-butylidene-2-norbornene. A particularly preferred diene is
5-ethylidene-2-norbornene.
[0076] The polymers (homopolymers, copolymers, interpolymers and
multi-block interpolymers) described herein may have a melt index,
I.sub.2, from 0.01 to 2000 g/10 minutes in some embodiments; from
0.01 to 1000 g/10 minutes in other embodiments; from 0.01 to 500
g/10 minutes in other embodiments; and from 0.01 to 100 g/10
minutes in yet other embodiments. In certain embodiments, the
polymers may have a melt index, I.sub.2, from 0.01 to 10 g/10
minutes, from 0.5 to 50 g/10 minutes, from 1 to 30 g/10 minutes,
from 1 to 6 g/10 minutes or from 0.3 to 10 g/10 minutes. In certain
embodiments, the melt index for the polymers may be approximately 1
g/10 minutes, 3 g/10 minutes or 5 g/10 minutes.
[0077] The polymers described herein may have molecular weights,
M.sub.w, from 1,000 g/mole to 5,000,000 g/mole in some embodiments;
from 1000 g/mole to 1,000,000 in other embodiments; from 10,000
g/mole to 500,000 g/mole in other embodiments; and from 10,000
g/mole to 300,000 g/mole in yet other embodiments. The density of
the polymers described herein may be from 0.80 to 0.99 g/cm.sup.3
in some embodiments; for ethylene containing polymers from 0.85
g/cm.sup.3 to 0.97 g/cm.sup.3. In certain embodiments, the density
of the ethylene/.alpha.-olefin polymers may range from 0.860 to
0.925 g/cm.sup.3 or 0.867 to 0.910 g/cm.sup.3.
[0078] In some embodiments, the polymers described herein may have
a tensile strength above 10 MPa; a tensile strength .gtoreq.11 MPa
in other embodiments; and a tensile strength .gtoreq.13 MPa in yet
other embodiments. In some embodiments, the polymers described
herein may have an elongation at break of at least 600 percent at a
crosshead separation rate of 11 cm/minute; at least 700 percent in
other embodiments; at least 800 percent in other embodiments; and
at least 900 percent in yet other embodiments.
[0079] In some embodiments, the polymers described herein may have
a storage modulus ratio, G'(25.degree. C.)/G'(100.degree. C.), from
1 to 50; from 1 to 20 in other embodiments; and from 1 to 10 in yet
other embodiments. In some embodiments, the polymers may have a
70.degree. C. compression set of less than 80 percent; less than 70
percent in other embodiments; less than 60 percent in other
embodiments; and, less than 50 percent, less than 40 percent, down
to a compression set of 0 percent in yet other embodiments.
[0080] In some embodiments, the ethylene/.alpha.-olefin
interpolymers may have a heat of fusion of less than 85 .mu.g. In
other embodiments, the ethylene/.alpha.-olefin interpolymer may
have a pellet blocking strength of equal to or less than 100
pounds/foot.sup.2 (4800 Pa); equal to or less than 50 lbs/ft.sup.2
(2400 Pa) in other embodiments; equal to or less than 5
lbs/ft.sup.2 (240 Pa), and as low as 0 lbs/ft.sup.2 (0 Pa) in yet
other embodiments.
[0081] In some embodiments, block polymers made with two catalysts
incorporating differing quantities of comonomer may have a weight
ratio of blocks formed thereby ranging from 95:5 to 5:95. The
elastomeric interpolymers, in some embodiments, have an ethylene
content of from 20 to 90 percent, a diene content of from 0.1 to 10
percent, and an .alpha.-olefin content of from 10 to 80 percent,
based on the total weight of the polymer. In other embodiments, the
multi-block elastomeric polymers have an ethylene content of from
60 to 90 percent, a diene content of from 0.1 to 10 percent, and an
.alpha.-olefin content of from 10 to 40 percent, based on the total
weight of the polymer. In other embodiments, the interpolymer may
have a Mooney viscosity (ML (1+4) 125.degree. C.) ranging from 1 to
250. In other embodiments, such polymers may have an ethylene
content from 65 to 75 percent, a diene content from 0 to 6 percent,
and an .alpha.-olefin content from 20 to 35 percent.
[0082] In certain embodiments, the polymer may be a
propylene-ethylene copolymer or interpolymer having an ethylene
content between 5 and 20% by weight and a melt flow rate
(230.degree. C. with 2.16 kg weight) from 0.5 to 300 g/10 min. In
other embodiments, the propylene-ethylene copolymer or interpolymer
may have an ethylene content between 9 and 12% by weight and a melt
flow rate (230.degree. C. with 2.16 kg weight) from 1 to 100 .mu.l
0 min.
[0083] In some particular embodiments, the polymer is a
propylene-based copolymer or interpolymer. In certain embodiments,
the propylene-based copolymer may be a propylene-.alpha. olefin
copolymer. In some embodiments, a propylene/ethylene copolymer or
interpolymer is characterized as having substantially isotactic
propylene sequences. The term "substantially isotactic propylene
sequences" and similar terms mean that the sequences have an
isotactic triad (mm) measured by .sup.13C NMR of greater than about
0.85, preferably greater than about 0.90, more preferably greater
than about 0.92 and most preferably greater than about 0.93.
Isotactic triads are well-known in the art and are described in,
for example, U.S. Pat. No. 5,504,172 and WO 00/01745, which refer
to the isotactic sequence in terms of a triad unit in the copolymer
molecular chain as determined by .sup.13C NMR spectra. In other
particular embodiments, the ethylene-.alpha. olefin copolymer may
be ethylene-butene, ethylene-hexene, or ethylene-octene copolymers
or interpolymers. In other particular embodiments, the
propylene-.alpha. olefin copolymer may be a propylene-ethylene or a
propylene-ethylene-butene copolymer or interpolymer.
[0084] The polymers described herein (homopolymers, copolymers,
interpolymers, and multi-block interpolymers) may be produced using
a single site catalyst and may have a weight average molecular
weight of from about 15,000 to about 5 million, such as from about
20,000 to about 1 million. The molecular weight distribution of the
polymer may be from about 1.01 to about 80, such as from about 1.5
to about 40, such as from about 1.8 to about 20.
[0085] The resin may also have a relatively low melting point in
some embodiments. For instance, the melting point of the polymers
described herein may be less than about 160.degree. C., such as
less than 130.degree. C., such as less than 120.degree. C. For
instance, in one embodiment, the melting point may be less than
about 100.degree. C.; in another embodiment, the melting point may
be less than about 90.degree. C.; less than 80.degree. C. in other
embodiments; and less than 70.degree. C. in yet other embodiments.
The glass transition temperature of the polymer resin may also be
relatively low. For instance, the glass transition temperature may
be less than about 50.degree. C., such as less than about
40.degree. C.
[0086] In some embodiments, the polymer may have a Shore A hardness
from 30 to 100. In other embodiments, the polymer may have a Shore
A hardness from 40 to 90; from 30 to 80 in other embodiments; and
from 40 to 75 in yet other embodiments.
[0087] The olefin polymers, copolymers, interpolymers, and
multi-block interpolymers may be functionalized by incorporating at
least one functional group in its polymer structure. Exemplary
functional groups may include, for example, ethylenically
unsaturated mono- and di-functional carboxylic acids, ethylenically
unsaturated mono- and di-functional carboxylic acid anhydrides,
salts thereof and esters thereof. Such functional groups may be
grafted to an olefin polymer, or it may be copolymerized with
ethylene and an optional additional comonomer to form an
interpolymer of ethylene, the functional comonomer and optionally
other comonomer(s). Means for grafting functional groups onto
polyethylene are described for example in U.S. Pat. Nos. 4,762,890,
4,927,888, and 4,950,541, the disclosures of which are incorporated
herein by reference in their entirety. One particularly useful
functional group is maleic anhydride.
[0088] The amount of the functional group present in the functional
polymer may vary. The functional group may be present in an amount
of at least about 1.0 weight percent in some embodiments; at least
about 5 weight percent in other embodiments; and at least about 7
weight percent in yet other embodiments. The functional group may
be present in an amount less than about 40 weight percent in some
embodiments; less than about 30 weight percent in other
embodiments; and less than about 25 weight percent in yet other
embodiments.
[0089] Stabilizing Agent
[0090] Embodiments disclosed herein may use one or more stabilizing
agents to promote the formation of a stable dispersion or emulsion.
In some embodiments, the stabilizing agent may be a surfactant,
dispersing agent, emulsifier, or a polymer (different from the base
polymer detailed above), or mixtures thereof. In certain
embodiments, the polymer may be a polar polymer, having a polar
group as either a comonomer or grafted monomer. In preferred
embodiments, the stabilizing agent comprises one or more polar
polyolefins, having a polar group as either a comonomer or grafted
monomer. Typical polymers include ethylene-acrylic acid (EAA) and
ethylene-methacrylic acid copolymers, such as those available under
the trademarks PRIMACOR.TM. (trademark of The Dow Chemical
Company), NUCREL.TM. (trademark of E.I. DuPont de Nemours), and
ESCOR.TM. (trademark of ExxonMobil) and described in U.S. Pat. Nos.
4,599,392, 4,988,781, and 5,938,437, each of which is incorporated
herein by reference in its entirety. Other polymers include
ethylene ethyl acrylate (EEA) copolymer, ethylene methyl
methacrylate (EMMA), and ethylene butyl acrylate (EBA). Other
ethylene-carboxylic acid copolymers may also be used. Those having
ordinary skill in the art will recognize that a number of other
useful polymers may also be used.
[0091] In general, any suitable stabilizing agent can be used. In
one embodiment, for instance, the stabilizing agent comprises at
least one carboxylic acid, a salt of at least one carboxylic acid,
or carboxylic acid ester or salt of the carboxylic acid ester.
Examples of carboxylic acids useful as a dispersant comprise fatty
acids such as montanic acid, stearic acid, oleic acid, and the
like. In some embodiments, the carboxylic acid, the salt of the
carboxylic acid, or at least one carboxylic acid fragment of the
carboxylic acid ester or at least one carboxylic acid fragment of
the salt of the carboxylic acid ester has fewer than 25 carbon
atoms. In other embodiments, the carboxylic acid, the salt of the
carboxylic acid, or at least one carboxylic acid fragment of the
carboxylic acid ester or at least one carboxylic acid fragment of
the salt of the carboxylic acid ester has 12 to 25 carbon atoms. In
some embodiments, carboxylic acids, salts of the carboxylic acid,
at least one carboxylic acid fragment of the carboxylic acid ester
or its salt has 15 to 25 carbon atoms are preferred. In other
embodiments, the number of carbon atoms is 25 to 60. Some examples
of salts comprise a cation selected from the group consisting of an
alkali metal cation, alkaline earth metal cation, or ammonium or
alkyl ammonium cation.
[0092] Other surfactants that may be used include long chain fatty
acids or fatty acid salts having from 12 to 60 carbon atoms. In
other embodiments, the long chain fatty acid or fatty acid salt may
have from 12 to 40 carbon atoms.
[0093] If the polar group of the polymer is acidic or basic in
nature, the stabilizing polymer may be partially or fully
neutralized with a neutralizing agent to form the corresponding
salt. In certain embodiments, neutralization of the stabilizing
agent, such as a long chain fatty acid or EAA, may be from 25 to
200% on a molar basis; from 50 to 110% on a molar basis in other
embodiments. For example, for EAA, the neutralizing agent is a
base, such as ammonium hydroxide or potassium hydroxide, for
example. Other neutralizing agents may include lithium hydroxide or
sodium hydroxide, for example. Those having ordinary skill in the
art will appreciate that the selection of an appropriate
neutralizing agent depends on the specific composition formulated,
and that such a choice is within the knowledge of those of ordinary
skill in the art.
[0094] Additional surfactants that may be useful in the practice of
the present invention include cationic surfactants, anionic
surfactants, zwitterionic, or non-ionic surfactants. Examples of
anionic surfactants include sulfonates, carboxylates, and
phosphates. Examples of cationic surfactants include quaternary
amines. Examples of non-ionic surfactants include block copolymers
containing ethylene oxide and silicone surfactants. Surfactants
useful in the practice of the present invention may be either
external surfactants or internal surfactants. External surfactants
are surfactants that do not become chemically reacted into the
polymer during dispersion preparation. Examples of external
surfactants useful herein include salts of dodecyl benzene sulfonic
acid and lauryl sulfonic acid salt. Internal surfactants are
surfactants that do become chemically reacted into the polymer
during dispersion preparation. An example of an internal surfactant
useful herein includes 2,2-dimethylol propionic acid and its
salts.
[0095] In particular embodiments, the stabilizing agent or
stabilizing agent may be used in an amount ranging from greater
than zero to about 60% by weight based on the amount of base
polymer (or base polymer mixture) used. For example, long chain
fatty acids or salts thereof may be used in an amount ranging from
0.5 to 10% by weight based on the amount of base polymer. In other
embodiments, ethylene-acrylic acid or ethylene-methacrylic acid
copolymers may be used in an amount from 0.5 to 60% by weight based
on the amount of base polymer. In yet other embodiments, sulfonic
acid salts may be used in an amount from 0.5 to 10% by weight based
on the amount of base polymer.
[0096] The type and amount of stabilizing agent used may also
affect end properties of the article formed incorporating the
dispersion. For example, articles having improved oil and grease
resistance might incorporate a surfactant package having
ethylene-acrylic acid copolymers or ethylene-methacrylic acid
copolymers in an amount from about 10 to about 50% by weight based
on the total amount of base polymer. A similar surfactant package
may be used when improved strength or softness is a desired end
property. As another example, articles having improved water or
moisture resistance might incorporate a surfactant package
utilizing long chain fatty acids in an amount from 0.5 to 5%, or
ethylene-acrylic acid copolymers in an amount from 10 to 50%, both
by weight based on the total amount of base polymer. In other
embodiments, the minimum amount of surfactant or stabilizing agent
must be at least 1% by weight based on the total amount of base
polymer.
[0097] In other embodiments, the stabilizing agent is selected from
alkyl ether carboxylates, petroleum sulfonates, sulfonated
polyoxyethylenated, alcohol, sulfated or phosphated
polyoxyethylenated alcohols, polymeric ethylene oxide/propylene
oxide/ethylene oxide stabilizing agents, primary and secondary
alcohol ethoxylates, alkyl glycosides and alkyl glycerides.
[0098] When ethylene-acrylic acid copolymer is used as a
stabilizing agent, the copolymer may also serve as a thermoplastic
resin. In one particular embodiment, the aqueous dispersion
contains an ethylene and octene copolymer, ethylene-acrylic acid
copolymer, and a fatty acid, such as stearic acid or oleic acid.
The stabilizing agent, such as the carboxylic acid, may be present
in the aqueous dispersion in an amount from about 0.1% to about 10%
by weight.
[0099] Additives
[0100] Additives may be combined with the dispersion, or with the
base polymer, stabilizing agent, or filler used in the dispersion,
without deviating from the scope of the present invention. For
example, additives may include a wetting agent, fire retardants,
surfactants, anti-static agents, antifoam agent, anti block,
wax-dispersion, pigments, a neutralizing agent, a thickener, a
compatibilizer, a brightener, a rheology modifier, a biocide, a
fungicide, reinforcing fibers, and other additives known to those
skilled in the art. While optional for purposes of the present
invention, other components may be highly advantageous for product
stability during and after the manufacturing process.
[0101] Additives and adjuvants may be included in any formulation
comprising the above described polymers, copolymers, interpolymers,
and multi-block interpolymers. Suitable additives include fillers,
such as organic or inorganic particles, including clays, talc,
titanium dioxide, zeolites, powdered metals, organic or inorganic
fibers, including carbon fibers, silicon nitride fibers, steel wire
or mesh, and nylon or polyester cording, nano-sized particles,
clays, and so forth; tackifiers, oil extenders, including
paraffinic or napthelenic oils; and other natural and synthetic
polymers, including other polymers according to embodiments of the
invention. Thermoplastic compositions according to other
embodiments of the invention may also contain organic or inorganic
fillers or other additives such as starch, talc, calcium carbonate,
glass fibers, polymeric fibers (including nylon, rayon, cotton,
polyester, and polyaramide), metal fibers, flakes or particles,
expandable layered silicates, phosphates or carbonates, such as
clays, mica, silica, alumina, aluminosilicates or
aluminophosphates, carbon whiskers, carbon fibers, nanoparticles
including nanotubes, wollastonite, graphite, zeolites, and
ceramics, such as silicon carbide, silicon nitride, or titania.
Silane-based or other coupling agents may also be employed for
better filler bonding.
[0102] Polymers suitable for blending with the above described
polymers include thermoplastic and non-thermoplastic polymers
including natural and synthetic polymers. Exemplary polymers for
blending include ethylene-vinyl acetate (EVA), ethylene/vinyl
alcohol copolymers, polystyrene, impact modified polystyrene, ABS,
styrene/butadiene block copolymers and hydrogenated derivatives
thereof (SBS and SEBS), and thermoplastic polyurethanes.
[0103] Suitable conventional block copolymers which may be blended
with the polymers disclosed herein may possess a Mooney viscosity
(ML 1+4 @ 100.degree. C.) in the range from 10 to 135 in some
embodiments; from 25 to 100 in other embodiments; and from 30 to 80
in yet other embodiments. Suitable polyolefins especially include
linear or low density polyethylene, polypropylene (including
atactic, isotactic, syndiotactic and impact modified versions
thereof) and poly(4-methyl-1-pentene). Suitable styrenic polymers
include polystyrene, rubber modified polystyrene (HIPS),
styrene/acrylonitrile copolymers (SAN), rubber modified SAN (ABS or
AES) and styrene maleic anhydride copolymers.
[0104] The blend compositions may contain processing oils,
plasticizers, and processing aids. Rubber processing oils having a
certain ASTM designation and paraffinic, napthenic or aromatic
process oils are all suitable for use. Generally from 0 to 150
parts, more preferably 0 to 100 parts, and most preferably from 0
to 50 parts of processing oils, plasticizers, and/or processing
aids per 100 parts of total polymer are employed. Higher amounts of
oil may tend to improve the processing of the resulting product at
the expense of some physical properties. Additional processing aids
include conventional waxes, fatty acid salts, such as calcium
stearate or zinc stearate, (poly)alcohols including glycols,
(poly)alcohol ethers, including glycol ethers, (poly)esters,
including (poly)glycol esters, and metal salts, especially Group 1
or 2 metal or zinc salts and derivatives thereof.
[0105] For conventional TPO, TPV, and TPE applications, carbon
black is one additive useful for UV absorption and stabilizing
properties. Representative examples of carbon blacks include ASTM
N110, N121, N220, N231, N234, N242, N293, N299, S315, N326, N330,
M332, N339, N343, N347, N351, N358, N375, N539, N550, N582, N630,
N642, N650, N683, N754, N762, N765, N774, N787, N907, N908, N990
and N991. These carbon blacks have iodine absorptions ranging from
9 to 145 g/kg and average pore volumes ranging from 10 to 150
cm.sup.3/100 g. Generally, smaller particle sized carbon blacks are
employed, to the extent cost considerations permit. For many such
applications the present polymers and blends thereof require little
or no carbon black, thereby allowing considerable design freedom to
include alternative pigments or no pigments at all.
[0106] Compositions, including thermoplastic blends according to
embodiments of the invention may also contain anti-ozonants or
anti-oxidants that are known to a rubber chemist of ordinary skill.
The anti-ozonants may be physical protectants such as waxy
materials that come to the surface and protect the part from oxygen
or ozone or they may be chemical protectors that react with oxygen
or ozone. Suitable chemical protectors include styrenated phenols,
butylated octylated phenol, butylated di(dimethylbenzyl) phenol,
p-phenylenediamines, butylated reaction products of p-cresol and
dicyclopentadiene (DCPD), polyphenolic anitioxidants, hydroquinone
derivatives, quinoline, diphenylene antioxidants, thioester
antioxidants, and blends thereof. Some representative trade names
of such products are WINGSTAY.TM. S antioxidant, POLYSTAY.TM. 100
antioxidant, POLYSTAY.TM. 100 AZ antioxidant, POLYSTAY.TM. 200
antioxidant, WINGSTAY.TM. L antioxidant, WINGSTAY.TM. LHLS
antioxidant, WINGSTAY.TM. K antioxidant, WINGSTAY.TM. 29
antioxidant, WINGSTAYT.TM. SN-1 antioxidant, and IRGANOX.TM.
antioxidants. In some applications, the anti-oxidants and
anti-ozonants used will preferably be non-staining and
non-migratory.
[0107] For providing additional stability against UV radiation,
hindered amine light stabilizers (HALS) and UV absorbers may be
also used. Suitable examples include TINUVINT.TM. 123, TINUVINT.TM.
144, TINUVIN.TM. 622, TINUVIN.TM. 765, TINUVIN.TM. 770, and
TINUVIN.TM. 780, available from Ciba Specialty Chemicals, and
CHEMISORBT.TM. T944, available from Cytex Plastics, Houston, Tex.,
USA. A Lewis acid may be additionally included with a HALS compound
in order to achieve superior surface quality, as disclosed in U.S.
Pat. No. 6,051,681. Other embodiments may include a heat
stabilizer, such as IRGANOX.TM. PS 802 FL, for example.
[0108] For some compositions, additional mixing processes may be
employed to pre-disperse the heat stabilizers, anti-oxidants,
anti-ozonants, carbon black, UV absorbers, and/or light stabilizers
to form a masterbatch, and subsequently to form polymer blends
therefrom.
[0109] Suitable crosslinking agents (also referred to as curing or
vulcanizing agents) for use herein include sulfur based, peroxide
based, or phenolic based compounds. Examples of the foregoing
materials are found in the art, including in U.S. Pat. Nos.
3,758,643, 3,806,558, 5,051,478, 4,104,210, 4,130,535, 4,202,801,
4,271,049, 4,340,684, 4,250,273, 4,927,882, 4,311,628, and
5,248,729.
[0110] When sulfur based curing agents are employed, accelerators
and cure activators may be used as well. Accelerators are used to
control the time and/or temperature required for dynamic
vulcanization and to improve the properties of the resulting
cross-linked article. In one embodiment, a single accelerator or
primary accelerator is used. The primary accelerator(s) may be used
in total amounts ranging from about 0.5 to about 4, preferably
about 0.8 to about 1.5 phr, based on total composition weight. In
another embodiment, combinations of a primary and a secondary
accelerator might be used with the secondary accelerator being used
in smaller amounts, such as from about 0.05 to about 3 phr, in
order to activate and to improve the properties of the cured
article. Combinations of accelerators generally produce articles
having properties that are somewhat better than those produced by
use of a single accelerator. In addition, delayed action
accelerators may be used which are not affected by normal
processing temperatures yet produce a satisfactory cure at ordinary
vulcanization temperatures. Vulcanization retarders might also be
used. Suitable types of accelerators that may be used in the
present invention are amines, disulfides, guanidines, thioureas,
thiazoles, thiurams, sulfenamides, dithiocarbamates, and xanthates.
Preferably, the primary accelerator is a sulfenamide. If a second
accelerator is used, the secondary accelerator is preferably a
guanidine, dithiocarbamate, or thiuram compound. Certain processing
aids and cure activators such as stearic acid and ZnO may also be
used. When peroxide based curing agents are used, co-activators or
coagents may be used in combination therewith. Suitable coagents
include trimethylolpropane triacrylate (TMPTA), trimethylolpropane
trimethacrylate (TMPTMA), triallyl cyanurate (TAC), and triallyl
isocyanurate (TAIC), among others. Use of peroxide crosslinkers and
optional coagents used for partial or complete dynamic
vulcanization are known in the art and disclosed, for example, in
"Peroxide Vulcanization of Elastomer," Vol. 74, No 3, July-August
2001.
[0111] When the polymer composition is at least partially
crosslinked, the degree of crosslinking may be measured by
dissolving the composition in a solvent for specified duration, and
calculating the percent gel or unextractable component. The percent
gel normally increases with increasing crosslinking levels. For
cured articles according to embodiments of the invention, the
percent gel content is desirably in the range from 5 to 100
percent.
[0112] In some embodiments, additives may also include perfumes,
algae inhibitors, anti-microbiological and anti-fungus agents,
flame retardants and halogen-free flame retardants, as well as slip
and anti-block additives. Other embodiments may include PDMS to
decrease the abrasion resistance of the polymer. Adhesion of the
polymer may also be improved through the use of adhesion promoters
or functionalization or coupling of the polymer with organosilane,
polychloroprene (neoprene), or other grafting agents.
[0113] Overall Dispersion Characteristics/Properties
[0114] In addition to the above components, the aqueous dispersion
also contains water. Water may be added as deionized water, if
desired. The pH of the aqueous dispersion is generally less than
about 12, such as from about 5 to about 11.5, such as from about 7
to about 11. The aqueous dispersion may have a solids content of
less than about 75%, such as less than about 70%. For instance, the
solids content of the aqueous dispersion may range from about 5% to
about 60%. In general, the solids content can be varied depending
upon the manner in which the additive composition is applied or
incorporated with the particulate substrate.
[0115] Aqueous dispersions, for example, may be formed using a base
polymer, as described above, a stabilizing agent, and water. Froths
and foams comprising the polymers may also be formed, as disclosed
in PCT Application No. PCT/US2004/027593, filed Aug. 25, 2004, and
published as WO2005/021622. The polymers may also be crosslinked by
any known means, such as the use of peroxide, electron beam,
silane, azide, gamma irradiation or other cross-linking techniques.
The polymers may also be chemically modified, such as by grafting
(for example by use of maleic anhydride (MAH), silanes, or other
grafting agent), halogenation, amination, sulfonation, or other
chemical modification.
[0116] Dispersions formed in accordance with embodiments disclosed
herein may include: a base polymer, which may comprise at least one
olefin polymer; and a stabilizing agent, which may comprise at
least one polar polyolefin. The olefin polymer, in some
embodiments, may be a propylene-based homopolymer, copolymer,
interpolymer, or multi-block interpolymer. In other embodiments,
the olefin polymer may be an ethylene-based homopolymer, copolymer,
interpolymer, or multi-block interpolymer. In other embodiments,
the olefin polymer may be a combination of one or more olefin
polymers described herein.
[0117] With respect to the base polymer and the stabilizing agent,
in some embodiments, the base polymer may comprise between about 30
percent to about 99 percent by weight of the total amount of base
polymer and stabilizing agent in the composition. In other
embodiments, the base polymer may comprise between about 50 percent
and about 90 percent of the total amount of base polymer and
stabilizing agent in the composition. In yet other embodiments, the
one or more base polymers may comprise between about 60 percent and
about 80 percent of the total amount of base polymer and
stabilizing agent in the composition.
[0118] The one or more olefin resins may be contained within the
aqueous dispersion in an amount from about 1 percent by weight to
about 96 percent by weight. In some embodiments, the olefin polymer
may be present in the aqueous dispersion in an amount from about 10
percent by weight to about 80 percent by weight. In other
embodiments, the olefin polymer may be present in an amount from
about 20 percent to about 70 percent by weight; and, from about 30
percent to about 60 percent by weight in yet other embodiments.
[0119] Dispersions formed in accordance with embodiments disclosed
herein may include: a base polymer, which may include at least one
olefin polymer as described above; a secondary polymeric component,
which may include at least one thermoplastic polyolefin; and a
stabilizing agent. The at least one olefin polymer, in some
embodiments, may comprise from about 30 percent to 95 percent by
weight of the total amount of base polymer, secondary polymer, and
stabilizing agent in the composition. In other embodiments, the at
least one olefin polymer may comprise between about 50 percent and
about 80 percent by weight; and, between about 60 percent to about
70 percent by weight in yet other embodiments. In some embodiments,
the secondary polymeric component may comprise from 1 to 48 percent
by weight of the total amount of base polymer, secondary polymer,
and stabilizing agent in the composition. In other embodiments, the
secondary polymeric component may comprise from 5 to 30 percent by
weight; and from 10 to 25 percent by weight in yet other
embodiments.
[0120] Benefits derived from an olefin polymer may also be realized
where the polymer is used as a minority component in a dispersion.
Accordingly, dispersions formed in accordance with other
embodiments disclosed herein may include: a base polymer, which may
include at least one thermoplastic polyolefin; a secondary
polymeric component, which may include at least one olefin polymer
or interpolymer as described above; and a stabilizing agent. The
base polymer, in some embodiments, may comprise from about 30
percent to 95 percent by weight of the total amount of base
polymer, olefin polymer or interpolymer, and stabilizing agent in
the composition. In other embodiments, the base polymer may
comprise between about 50 percent and about 80 percent by weight;
and, between about 60 percent to about 70 percent by weight in yet
other embodiments. In other embodiments, the olefin polymer
component may comprise from 1 to 48 percent by weight of the total
amount of base polymer, olefin polymer, and stabilizing agent in
the composition. In other embodiments, the olefin polymer component
may comprise from 5 to 30 percent by weight; and from 10 to 25
percent by weight in yet other embodiments.
[0121] With respect to the filler, typically, an amount greater
than about 0 to about 1000 parts per hundred of the polymer
(polymer meaning here the base polymer combined with the
thermoplastic polymer (if any) and the stabilizing agent) is used.
In selected embodiments, between about 50 to 250 parts per hundred
are used. In other selected embodiments, between about 10 to 500
parts per hundred are used. In still other embodiments, from
between about 20 to 400 parts per hundred are used. In other
embodiments, from about 0 to about 200 parts per hundred are
used.
[0122] The solid materials (base polymer plus thermoplastic polymer
(if any) plus stabilizing agent) are preferably dispersed in a
liquid medium, which in preferred embodiments is water. In
preferred embodiments, sufficient neutralization agent is added to
neutralize the resultant dispersion to achieve a pH range of
between about 4 to about 14. In preferred embodiments, sufficient
base is added to maintain a pH of between about 6 to about 11; in
other embodiments, the pH may be between about 8 to about 10.5.
Water content of the dispersion is preferably controlled so that
the solids content is between about 1% to about 74% by volume. In
another embodiment, the solids content is between about 25% to
about 74% by volume. In particular embodiments, the solids range
may be between about 10% to about 70% by weight. In other
particular embodiments, the solids range is between about 20% to
about 60% by weight. In particularly preferred embodiments, the
solids range is between about 30% to about 55% by weight.
[0123] Dispersions formed in accordance with embodiments of the
present invention are characterized in having an average particle
size of between about 0.1 to about 5.0 microns. Broadly speaking,
however, they may have a dispersed particle size of greater than
about 0 to about 10 microns. In other embodiments, dispersions have
an average particle size of from about 0.5 .mu.m to about 2.7
.mu.m. In other embodiments, from about 0.8 .mu.m to about 1.2
.mu.m. By "average particle size," the present invention means the
volume-mean particle size. In order to measure the particle size,
laser-diffraction techniques may be employed for example. A
particle size in this description refers to the diameter of the
polymer in the dispersion. For polymer particles that are not
spherical, the diameter of the particle is the average of the long
and short axes of the particle. Particle sizes may be measured on a
Beckman-Coulter LS230 laser-diffraction particle size analyzer or
other suitable device. The particle size distribution of the
polymer particles in the dispersion may be less than or equal to
about 2.0, such as less than 1.9, 1.7 or 1.5.
[0124] In addition, embodiments of the present invention optionally
include a filler wetting agent. A filler wetting agent generally
may help make the filler and the polyolefin dispersion more
compatible. Useful wetting agents include phosphate salts, such as
sodium hexametaphosphate. A filler wetting agent may be included in
a composition of the present invention at a concentration of at
least about 0.5 parts per 100 parts of filler, by weight.
[0125] Furthermore, embodiments of the present invention may
optionally include a thickener. Thickeners may be useful in the
present invention to increase the viscosity of low viscosity
dispersions. Thickeners suitable for use in the practice of the
present invention may be any known in the art such as for instance
polyacrylate type or associated non ionic thickeners such as
modified cellulose ethers. For example, suitable thickeners include
ALCOGUM.TM. VEP-II (trademark of Alco Chemical Corporation),
RHEOVIS.TM. and VISCALEX.TM. (trademarks of Ciba Ceigy), UCAR.RTM.
Thickener 146, ETHOCEL.TM., or METHOCEL.TM. (trademarks of the The
Dow Chemical Company), PARAGUM.TM. 241 (trademarks of Para-Chem
Southern, Inc.), BERMACOL.TM. (trademark of Akzo Nobel),
AQUALON.TM. (trademark of Hercules), and ACUSOL.RTM. (trademark of
Rohm and Haas). Thickeners may be used in any amount necessary to
prepare a dispersion of desired viscosity.
[0126] The ultimate viscosity of the dispersion is, therefore,
controllable. Addition of the thickener to the dispersion including
the amount of filler may be done with conventional means to result
in viscosities as needed. Viscosities of the dispersions may reach
+3000 cP (Brookfield spindle 4 with 20 rpm) with moderate thickener
dosing (up to 4%, preferably below 3%, based on 100 phr of polymer
dispersion). The starting polymer dispersion as described has an
initial viscosity prior to formulation with fillers and additives
between 20 and 1000 cP (Brookfield viscosity measured at room
temperature with spindle RV3 at 50 rpm). Still more preferably, the
starting viscosity of the dispersion may be between about 100 to
about 600 cP.
[0127] Also, embodiments of the present invention are characterized
by their stability when a filler is added to the
polymer/stabilizing agent. In this context, stability refers to the
stability of viscosity of the resultant aqueous polyolefin
dispersion. In order to test the stability, the viscosity is
measured over a period of time. Preferably, viscosity measured at
20.degree. C. should remain +/-10% of the original viscosity over a
period of 24 hours, when stored at ambient temperature.
[0128] Examples of aqueous dispersions that may be incorporated
into embodiments of the present disclosure are disclosed, for
instance, in U.S. Patent Application Publication No. 2005/0100754,
U.S. Patent Application Publication No. 200510192365, PCT
Publication No. WO 20051021638, and PCT Publication No. WO
2005/021622, which are all incorporated herein by reference.
[0129] Dispersion Formation
[0130] Dispersions used in embodiments disclosed herein may be
formed by any number of methods recognized by those having skill in
the art. In selected embodiments, the dispersions may be formed by
using techniques, for example, in accordance with the procedures as
described in WO2005021638, which is incorporated by reference in
its entirety.
[0131] While any method may be used to produce the aqueous
dispersion, in one embodiment, the dispersion may be formed through
a melt-kneading process. For example, the kneader may comprise a
BANBURY.RTM. mixer, single-screw extruder, or a multi-screw
extruder. The melt-kneading may be conducted under the conditions
which are typically used for melt-kneading the one or more
thermoplastic resins.
[0132] In one particular embodiment, the process includes
melt-kneading the components that make up the dispersion. The
melt-kneading machine may include multiple inlets for the various
components. For example, the extruder may include four inlets
placed in series. Further, if desired, a vacuum vent may be added
at an optional position of the extruder.
[0133] In a specific embodiment, a base polymer, a stabilizing
agent, and optionally a filler are melt-kneaded in an extruder
along with water and a neutralizing agent, such as ammonia,
potassium hydroxide, or a combination of the two to form a
dispersion. Those having ordinary skill in the art will recognize
that a number of other neutralizing agents may be used. In some
embodiments, the filler may be added after blending the base
polymer and stabilizing agent. In some embodiments, the dispersion
is first diluted to contain about 1 to about 3% by weight water and
then, subsequently, further diluted to comprise greater than about
25% by weight water.
[0134] Any melt-kneading means known in the art may be used. In
some embodiments, a kneader, a BANBURY.RTM. mixer, single-screw
extruder, or a multi-screw extruder is used. A process for
producing the dispersions in accordance with the present invention
is not particularly limited. One preferred process, for example, is
a process comprising melt-kneading the above-mentioned components
according to U.S. Pat. No. 5,756,659 and U.S. Pat. No.
6,455,636.
[0135] An extrusion apparatus that may be used in embodiments of
the invention may be described as follows. An extruder, in certain
embodiments a twin screw extruder, is coupled to a back pressure
regulator, melt pump, or a gear pump. Embodiments also provide a
base reservoir and an initial water reservoir, each of which
includes a pump. Desired amounts of base and initial water are
provided from the base reservoir and the initial water reservoir,
respectively. Any suitable pump may be used, but in some
embodiments a pump that provides a flow of about 150 cc/min at a
pressure of 240 bar is used to provide the base and the initial
water to the extruder. In other embodiments, a liquid injection
pump provides a flow of 300 cc/min at 200 bar or 600 cc/min at 133
bar. In some embodiments, the base and initial water are preheated
in a preheater.
[0136] Polymer resin(s), in the form of pellets, powder, or flakes,
for example, is fed from the feeder to an inlet of the extruder
where the resin is melted or compounded. In some embodiments, the
stabilizing agent is added to the resin through and along with the
resin and in other embodiments, the stabilizing agent is provided
separately to the twin screw extruder. The resin melt is then
delivered from the mix and convey zone to an emulsification zone of
the extruder where the initial amount of water and base from the
reservoirs is added through the inlet. In some embodiments,
stabilizing agent may be added additionally or exclusively to the
water stream.
[0137] In some embodiments, the emulsified mixture is further
diluted with additional water inlet from the reservoir in a
dilution and cooling zone of the extruder. Typically, the
dispersion is diluted to at least 30 weight percent water in the
cooling zone. In addition, the diluted mixture may be diluted any
number of times until the desired dilution level is achieved. In
some embodiments, water is not added into the twin screw extruder
but rather to a stream containing the resin melt after the melt has
exited from the extruder. In this manner, steam pressure build-up
in the extruder is eliminated.
[0138] In particular embodiments, it may be desired to utilize the
dispersion in the form of foam. When preparing foams, it is often
preferred to froth the dispersion. For example, froths and foams
may be prepared as described in WO2005021622, which is fully
incorporated herein by reference. Preferred in the practice of this
invention is the use of a gas as a frothing agent. Examples of
suitable frothing agents include: gases and/or mixtures of gases
such as, air, carbon dioxide, nitrogen, argon, helium, and the
like. Particularly preferable is the use of air as a frothing
agent. Frothing agents are typically introduced by mechanical
introduction of a gas into a liquid to form a froth. This technique
is known as mechanical frothing. In preparing a frothed dispersion,
it is preferred to mix all components and then blend the air or gas
into the mixture, using equipment such as an OAKES, MONDO, or
FIRESTONE frother.
[0139] Surfactants useful for preparing a stable froth are referred
to herein as foam stabilizers. Foam stabilizers are useful in the
practice of the present invention. Those having ordinary skill in
this field will recognize that a number of foam stabilizers may be
used. Foam stabilizers may include, for example, sulfates,
succinamates, and sulfo succinamates.
[0140] Articles
[0141] Final articles formed using the dispersions disclosed above
can take a number of forms, and employ a number of components. They
may also include a number of other layers, but generally include a
nonwoven layer as a substrate. In a glove or foot wear, for
instance, the nonwoven layer may serve as either an underglove or a
lining for barrier layer and elastomeric overcoat. The nonwoven
fiber layer web separates and keeps the elastomeric material away
from skin. A common problem associated with the wearing of articles
or garments made from natural rubber latex over enclosed skin is
the development of various skin allergies (e.g., irritant
dermatitis, delayed cutaneous hypersensitivity (Type IV allergy),
and immediate reaction (Type I allergy)) that are believed to be
caused by proteins in the rubber latex. By using a non-woven liner,
such allergy reactions can be minimized and/or eliminated by
avoiding direct contact of skin with latex. Instead of being in
contact with the latex rubber, a barrier will protect the wearer's
skin, which will touch an inner surface that has a non-woven layer
of long continguous fiber strands.
[0142] The non-woven liner can provide a soft cloth or
"cotton-like" feel that is significantly more comfortable for the
wearer than direct skin contact with latex or plastic films. A
nonwoven liner also provides additional advantages over unlined or
naked latex gloves by absorbing moisture, and eliminating the
convention requisite for specialized donning coats. Since a
nonwoven fabric has a lower coefficient of friction relative to
plastic films or latex membranes, a glove with an inner lining of
nonwoven fabric can facilitate donning or doffing of the glove,
permitting the user to easily slip a hand in or out of the
glove.
[0143] Various types of polymer-based materials from the art may be
used to make cloth-like non-woven fabrics. A foundational substrate
or base nonwoven fiber web can be formed from materials that may
include, for instance, synthetic fibers, pulp fibers,
thereto-mechanical pulp, or mixtures of such materials such that
the web has cloth-like properties. A flexible sheet material can be
used to form the non-woven webs. Non-woven web materials suitable
for use in the invention may be, for example, selected from a group
consisting of spunbond, meltblown, spunbond-meltblown-spunbond
laminates, coform, spunbond-film-spunbond laminates, bicomponent
spunbond, bicomponent meltblown, biconstituent spunbond,
biconstituent meltblown, bonded carded bicomponent web, crimped
fibers, airlaid, and combinations thereof.
[0144] The base web can also include various elastomeric
components, such as elastic laminates or film laminates. For
example, suitable elastic laminates can include stretch-bonded and
neck-bonded laminates. Alternatively, fibrous nonwoven webs formed
by extrusion processes such as spunbonding and meltblowing, and by
mechanical dry-forming process such as air-laying and carding, used
in combination with thermoplastic film or microfiber layers, may be
utilized as components. Since the materials and manufacture of
these components of the present invention are often inexpensive
relative to the cost of woven or knitted components, the products
can be disposable.
[0145] Films in general and elastic layers in particular, whether a
film sheet layer or a microfiber layer, often have unpleasant
tactile aesthetic properties, such as feeling rubbery or tacky to
the touch, making them unpleasant and uncomfortable against the
wearer's skin. Fibrous non-woven webs, on the other hand, have
better tactile, comfort and aesthetic properties.
[0146] An article formed in accordance with embodiments disclosed
herein may include an elastic component, such as to provide a glove
or foot covering with form-fitting properties. For instance, a
glove formed with an elastic component can snuggly fit onto a
person's hand so that the glove can more effectively remain on the
hand. The barrier film is adapted to remain "breathable" to aid in
a person's comfort during use, while also remaining capable of
substantially inhibiting the transfer of liquids from the outer
surface of the glove to the person's hand.
[0147] The barrier layer can include a moisture barrier that is
incorporated into or applied to the foundational substrate or base
nonwoven web. In general, a moisture barrier refers to any barrier,
layer or film that is relatively liquid-impervious. In particular,
the moisture barrier of the present invention can prevent the flow
of liquid through the glove so that the hand inserted therein
remains dry when the glove is being used. In some embodiments, the
moisture barrier can remain breathable, i.e., permeable to vapors,
such that the hand within the glove is more comfortable. Examples
of suitable moisture barriers can include films, fibrous materials,
laminates, and the like. In particular, a layer of film or
microfibers may be used to impart liquid barrier properties, and an
elastic layer (e.g., elastic film or elastic microfibers) may be
used to impart additional properties of stretch and recovery.
[0148] The tactile aesthetic properties of elastic films can be
improved by forming a laminate of an elastic film with one or more
non-elastic materials, such as fibrous non-woven webs, on the outer
surface of the elastic material. Fibrous non-woven webs formed from
non-elastic polymers, such as, for example polyolefins, however,
are generally considered non-elastic and may have poor
extensibility, and when non-elastic non-woven webs are laminated to
elastic materials the resulting laminate may also be restricted in
its elastic properties. Therefore, laminates of elastic materials
with non-woven webs have been developed wherein the non-woven webs
are made extensible by processes such as necking or gathering.
[0149] In accordance with the present invention, the non-woven
fiber web can be porous and its fiber surface can be further
modified to have a variety of different surface functionalities.
For example, pores associated with the fiber web can be used as a
carrier for a variety of treatments in which various additives can
be applied, if desired, to the whole or part of the glove before
use. When used as a protection garment for dry skin, wounds, cuts,
bruises, blisters, odor control, keeping hand or foot warm, etc.,
various additives can be applied to the glove to aid for
therapeutic purposes. Examples of such articles may include
disposable, exam, surgical, clean room, work, and/or industrial
protection gloves where added strength, comfort, skin protection,
and powder-free aspects are desirable characteristics. For example,
an article of the present invention can generally include additives
such as antibiotics, anti-microbial agents, anti-inflammatory
agents, NEOSPORIN, moisturizing agents, cationic polymers, and the
like. In addition, when used as a glove for treating other
ailments, such as arthritis, "black toe," "trigger finger," or
jammed, sprained, hyper-extended, dislocated, or broken appendages,
a glove of the present invention can generally include various
other additives, such as topical analgesics (e.g. BEN-GAY.RTM.),
anti-inflammatory agents, vasodilators, corticosteroids, dimethyl
sulfoxide (DMSO), capsaicin, menthol, methyl salicylate,
DMSO/capsaicin, cationic polymers, anti-fungal agents, and the
like.
[0150] Additives can be applied to a glove of the present invention
in the form of an aqueous solution, non-aqueous solution (e.g.,
oil), lotions, creams, suspensions, gels, etc. When utilized, the
aqueous solution can, for example, be coated, sprayed, saturated,
or impregnated into the glove. In some embodiments, the additives
can be applied asymmetrically. Moreover, in some instances, it may
be desired that the additives comprise less than about 100% by
weight of the glove, and in some embodiments, less than about 50%
by weight of the glove and particularly less than 10% by weight of
the glove, and in some embodiments, less than about 5% by weight of
the glove, and in some embodiments, less than about 1% by weight of
the glove. It should be noted that any given range presented herein
in intended to include any and all lesser included ranges. For
example, a range from 45 to 90 would also include 50 to 90; 45.5 to
80; 75-89 and the like. In some embodiments, the glove may be
treated with above said additives to only certain areas,
particularly in areas that are desired to be treated. For example,
a glove can have additives in only finger areas for being used as a
finger appendage.
[0151] The non-woven web materials are preferably formed with
polymers selected from the group including: polyolefins,
polyamides, polyesters, polycarbonates, polystyrenes, thermoplastic
elastomers, fluoropolymers, vinyl polymers, and blends and
copolymers thereof. Suitable polyolefins include, but are not
limited to, polyethylene, polypropylene, polybutylene, and the
like; suitable polyamides include, but are not limited to, nylon 6,
nylon 6/6, nylon 10, nylon 12 and the like; and suitable polyesters
include, but are not limited to, polyethylene terephthalate,
polybutylene terephthalate and the like. Particularly suitable
polymers for use in the present invention are polyolefins including
polyethylene, for example, linear low density polyethylene, low
density polyethylene, medium density polyethylene, high density
polyethylene and blends thereof; polypropylene; polybutylene; and
copolymers as well as blends thereof. Additionally, the suitable
fiber forming polymers may have thermoplastic elastomers blended
therein.
[0152] Non-woven fabrics which are used in such laminates, prior to
conversion into such laminates, desirably have a basis weight
between about 10 g/m.sup.2 and 50 g/m.sup.2 and even more desirably
between about 12 g/m.sup.2 and 25 g/m.sup.2. In an alternative
embodiment such non-woven fabrics have a basis weight between about
15 g/m.sup.2 and 20 g/m.sup.2.
[0153] Another flexible sheet material that may be used include
polymeric films, which provide a barrier to fluids while remaining
flexible. The films can be either micro-porous or monolithic.
Micro-porous or monolithic films can be combined in the
construction of the present protective articles. For instance,
depending on the desired properties or use, one part of a gloves or
foot cover can be made with micro-porous films (e.g., back of the
hand of a glove, or upper body of a foot cover) while another part
can be made with a monolithic film (e.g., palm and fingers, or foot
sole), since each respective area of the article will have
different demands place on its function and it may come in contact
with different environmental conditions. In certain variations, to
illustrate, often the palm and finger areas of a glove, like the
sole of a foot covering, will be exposed to much wear and tear
against abrasion or hard surfaces, as well as chemical or
biological hazards, hence they need to be both resilient and
impermeable to protect the wearer. In contrast, the back of the
hand and upper body of a foot cover are relatively sheltered from
harsh use of treatment, hence a more breathable films is more
suited. Examples of such films are described in WO 96/19346 to
McCormack et al., incorporated herein by reference in its entirety.
Also because of the exposure to abrasion, the palm and fingers of a
glove can have a further elastomeric polymer overcoat to strength
the barrier layers or protect the underlying nonwoven-laminate body
of the glove or foot cover.
[0154] While it should be recognized that flexible sheet materials
can be chosen from a broad spectrum of materials, non-woven webs
and polymeric films are used hereunder for illustrative purposes.
When a machine direction tension force is applied to an elastic
film sheet, the force will cause the elastic film sheet to be
stretched or elongated in the machine direction. Because the film
sheet is elastic, when the tension is removed or relaxed the film
will retract toward its original machine direction length. When the
film retracts or becomes shorter in the machine direction, first
fibrous nonwoven web and/or second fibrous nonwoven web which are
bonded to the side or sides of the elastic film will buckle or form
gathers. The gathers can be applied to form a cuff around an open
end of the present protective articles. The resulting elastic
laminate material is stretchable in the machine direction to the
extent that the gathers or buckles in the fibrous nonwoven web or
webs can be pulled back out flat and allow the elastic film to
elongate.
[0155] Formulation Characteristics
[0156] In accordance with embodiments disclosed herein, the present
inventors have discovered that the type of polyolefin used in the
aqueous dispersion may be significant in the end breathability of
the article. Specifically, higher MFI polymers can be more easily
spread over the whale substrate surface at the drying temperature,
forming a compact homogeneous layer and reducing the breathability.
Moreover, the type of polyolefin used in the aqueous dispersion may
have an effect on the MVTR, as higher crystallinity polymers are
expected to improve the MVTR. Similarly, higher MFI polymers are
expected to have less of a tendency to form "pinholes," or to form
excessive pores during drying, leading to a more uniform coating.
Obviously, those of ordinary skill in the art will appreciate that
the type of polymer selected will determine the temperature at
which a stable, breathable structure can be created.
[0157] The present inventors have also advantageously found that
the type of base used in neutralization of the dispersion may be
significant. Residual non-volatile base can increase the articles
breathability.
[0158] As noted above, because embodiments disclosed herein employ
an aqueous dispersion, the coating of a non-woven substrate may be
achieved in a number of different manners. For example, an
industrial curtain coating method may be used that allows for the
coating of substrates at high speeds (100-1100 m/min). As an
alternative method, a film transfer technique, which may include a
first film fabrication on a flat, non-porous substrate, subsequent
film transfer, and lamination to a final substrate may be
employed.
[0159] Multi-coating (i.e., repeating coating of the same substrate
with the dispersion, or with different materials) can help overcome
difficulties with covering either rough or large pore substrates.
These techniques may also introduce new functions to the coating,
such as color, adhesion to another substrate, soft touch, odor
acceptance, etc.
[0160] As noted above, inorganic or organic fillers (e.g., calcium
carbonate) may be employed as a co-component in the aqueous
dispersion, or as a major component of a primer layer applied below
the dispersion coating to smooth the substrate. A crosslinking
agent may be added to provide partial or complete crosslinking of
one or more of the polymers in the aqueous dispersion. Crosslinking
one or more of the polymers may have the effect of improving the
MVTR of the article.
[0161] In addition, the substrate may be functionalized in order to
tailor the end use article. For example, the substrate may be
subjected to corona treatment, (i.e., subjected to an electrical
discharge), which may improve the coating quality.
EXAMPLES
Aqueous Dispersions
[0162] Dispersion 1:
[0163] POD 1 is an aqueous polyolefin dispersion DPOD 8501
(Developmental Polyolefin Dispersion) batch UJ2655WC30 available
from The Dow Chemical Company. POD 1 is formed using a
ethylene-octene copolymer (ENGAGE.TM. 8200, available from The Dow
Chemical Company, having a I.sub.2 of 5.0 dg/min (190.degree. C.,
2.16 kg, ASTM D 1238) and a density of 0.870 glee). The surfactant
system used is PRIMACOR.TM. 59801 (an ethylene acrylic acid
copolymer available from The Dow Chemical Company). PRIMACOR.TM. is
used at a loading of 30 weight percent based on the weight of the
ethylene-octene copolymer.
[0164] POD 1 (DPOD 8501, batch UJ2655WC30) is a large scale market
development sample product produced by Dow Material Transforamtion
Group (MTG) Process Development Center (PDC) in Weston Canal, USA,
using standardized procedure, common manufacturing documentation
and the following manufacturing hardware and setups: Twin Screw
Extruder (TSE) Coperion Werner & Pfleiderer ZSK-58 (250 bhp
motor, 1200 rpm max speed, 12 barrels, Screw 009), Two (2) ITT
shell and tube heat exchangers (Model No. 5-160-03-036-005, 11 ft2
surface area; 3 inch by 36 inch)-56 tubes, 1/4 inch OD stainless
steel tubes (wall thickness 0.022 inch), four (4) pass with narrow
baffle spacing on shell side, process connected in series, cooling
water connected in parallel, Rosedale Model 6 Basket Strainer and
Bag Filter, stainless steel construction Model No. MC6181P
150SVPBD, polyester filter bag with 300 micron rating.
[0165] The POD batch used has a solids content of 44.4 weight
percent (determined by DOWM 102168-E06A), a pH of 9.7 (determined
by DOWM 102159-E05A), and a Brookfield viscosity of 199 centipoise
(Spindle 1 @ 20 rpm; determined by DOWM 102166-E05A). The dispersed
polymer phase particle average volume diameter is 1.1 microns
(measured by DOWM 102167-E06A).
[0166] Dispersion 2:
[0167] POD 2 is formed in accordance with the procedures as
described in WO2005021638 using an ethylene-octene copolymer
(ENGAGE.TM. 8200, available from The Dow Chemical Company, having a
I.sub.2 of 5.0 dg/min and a density of 0.870 glee). The surfactant
system used is PRIMACOR.TM. 5980I (as described above).
PRIMACOR.TM. is used at a loading of 30 weight percent based on the
weight of the ethylene-octene interpolymer.
[0168] The ethylene-octene copolymer is dry blended with the
surfactant. The mixture is then extruded at 76.6 g/min using a
Berstorff ZE25 (36 L/D, 458 rpm) and a Schenck Mechatron
loss-in-weight feeder. An ISCO dual-syringe pump meters a 28-30%
(w/w; .about.14.8 Normal) ammonium hydroxide solution directly from
the stock bottle at 3.99 cc/min, while ISCO dual-syringe pumps
meter in the Initial Water at 22 cc/min (blended with the base
solution before entering the initial aqueous (IA) injector) and
Dilution water at 60 cc/min. Each aqueous stream is pumped into the
twin-screw extruder though a tappet style injector designed by the
Dow Material Engineering Center. The Initial water stream is
pre-heated to 25.degree. C. through a pre-heater consisting of (2)
sections each comprising 30'' of 1/4''OD stainless steel tubing
wrapped with 72'' of 1/2'' wide electric heat tape ("Omegalux
STH051-060") providing 470 watts of heating. The pre-heater is
controlled by an Omron E5CK temperature controller with a separate
over-temperature cut-off controller. Control thermocouple is placed
in the liquid flow at the pre-heater outlet and the
over-temperature thermocouple is placed between the heat tape and
the tubing wall for safety at no-flow conditions. The dilution
stream is pre-heated to 24.degree. C. with a similar setup
containing 3 sections. After the extruder, two devices are
installed to allow control of back-pressure on the barrel while
allowing polymer to exit when dispersion is not being made. The
larger device, a 1/2'' NuPro spring-loaded check valve with 1/2''
NPT connections, is set to open at 350-700 psi depending on the
spring tension adjustment. For liquid dispersion, a GO BP60
Back-Pressure Regulator (BPR) is installed and adjusted for no
back-pressure initially, then set to maintain about 17.2 barg (250
psig) upstream pressure mid-run when dispersion is being made.
[0169] The dispersion product is collected directly after the
back-pressure regulator, allowed to cool, filtered, and analyzed
for particle size, pH, solids content, and viscosity. The aqueous
dispersion produced has a solids content of 50.0 weight percent, a
pH of 10.0, and a viscosity (RV-3 spindle, 22.6.degree. C., 50 rpm)
of 444 centipoise. The dispersed polymer phase is measured by a
Coulter LS230 particle analyzer consisting of an average volume
diameter particle size of 1.86 microns and a particle size
dispersity of 18.1.
[0170] After forming the dispersions, a series of breathable
laminates are prepared using POD1 and POD 2 in the following
manner. An appropriate amount of the POD is transferred to an A4
glass plate (which is well cleaned with water and
methylethylketone) with a pipette to form a bubble-free continuous
line across the substrate. The POD is then spread by rolling a fine
screw steel roller caster for latex with a defined coating
thickness yield (12, 20, or 36 microns) over the substrate to
generate a continuous thin layer. The layer is then partly dried
for one minute at room temperature. The partially dried layer is
then over layered by a homo-poly(propylene) 20 g/m.sup.2 spun bond
nonwoven fabric fabricated out of H502-25RG resin with a melt flow
rate (230.degree. C., 2.16 kg) of 25 g/10 min and density of 0.9
g/cm.sup.3 (available from The Dow Chemical Company), over rolled
by the same, but clean, fine screw steel latex caster as above to
ensure proper contact and left for drying at (a) room temperature
for 2 hours. After 2 hours, the sheets are moved to a Heraeus UT
5050 hot air oven at 80.degree. C. for 10 minutes, or at
100.degree. C. for 10 minutes. In the case of multilayer coatings,
this whole procedure is repeated using in the previous step already
pre-coated nonwoven laminate as a starting substrate.
[0171] Table I below summarizes the moisture vapor transmission
rates (MVTTR) and selected water column data on the samples
described above.
TABLE-US-00001 TABLE 1 Coating Water Column Drying Thickness MVTR
(mm) (28 cm.sup.2, POD Sample Temp (.degree. C.) (.mu.m)
(g/m.sup.2/day) 600 mm/min) POD1 80 12 3930 110 POD1 80 20 4011 100
POD1 80 36 4042 60 POD1 100 12 3885 260 POD1 100 20 3794 240 POD1
100 36 4030 220 POD2 Room 20 5645 15 POD2 Room 36 4956 100 POD2 80
12 5288 130 POD2 80 20 3891 160 POD2 80 36 4643 160 POD2 100 12
1886 180 POD2 100 20 1763 140 POD2 100 36 3411 170
[0172] As Table 1 shows, the laminates varied in performance under
various conditions. POD2, because of the ammonium hydroxide
neutralization, led to useful coating films at room temperature.
The coatings formed with POD2 dried at room temperature exhibited
the highest MVTR values among all of the samples. Drying
temperature had a significant influence on the MVTR value of the
POD2 coatings. FIG. 1 includes several SEM images illustrating the
drying temperature impact on the coating structure. As seen in FIG.
1, as higher temperatures are employed, smoother surfaces result.
From Table 1 and FIG. 1, an evident trend of dropping MVTR in POD2
coated articles is seen with increasing drying temperature. Without
being bound to any scientific theory, the present inventors believe
that this can be related to the smoothening of the film structure
due to softening and melting effects, causing reordering of
dispersion phases. Such a macroscopic smoothening is apparent from
the micrographs in FIG. 1.
[0173] Nevertheless, in terms of MVTR values, such a treatment in
POD1 did not lead (in contrast to POD2) to considerable changes or
trends. Without being bound to any theory, the present inventors
believe that this may because POD1 maintained effective porosity
(permeability channels), while having a surface smoothing in
macroscopic scale (micron resolution).
[0174] Another example is a repetitive coating of 20 g/m.sup.2 spun
bond nonwoven fabric fabricated out of H502-25RG
homo-poly(propylene), with a melt flow rate (230.degree. C., 2.16
kg) of 25 g/10 min and density of 0.9 g/cm.sup.3 (available from
The Dow Chemical Company), at speed of 450 m/min on a Papageno Lab
Coater (curtain coater). The substrate has been coated with 10
g/m.sup.2 of POD 8501 (preparation described in [paragraph [00156])
in one or two or three consecutive coating steps, with each of them
followed by an on-line inter-drying step at 60.degree. C. Then all
the monolayer 10 g/m.sup.2 (S1), doublelayer 20 g/m.sup.2 (S2), and
triple layer 30 g/m.sup.2 (S3) coated samples were treated off-line
at 100.degree. C. for 10 min in a Heraeus UT 5050 conventional
oven. So prepared samples were then examined on a water column
tester TEXTEST FX3000, equipped with 28 cm.sup.2 head, at 60
Bar/min pressure increase setup, and exhibited water column
performance summarized in Table 2.
TABLE-US-00002 TABLE 2 Coating Gauge Water Column (mm) Sample
(g/m.sup.2) (28 cm.sup.2, 600 mm/min) S1 10 90 S2 20 400 S3 30
960
[0175] In another example, a series of breathable laminates are
fabricated using the dispersions described above, using the
following general procedure. A4 polypropylene nonwoven sheets are
coated with the dispersions on a pilot curtain coater. The A4
sheets are stuck to a continuous carrier paper band and compactly
coated with 6-14 g/m.sup.2 coatings. A repetitive coating with
inter-drying is possible as well. The reachable coating speed
applied is up to about 1100 m/min.
[0176] In another example, a series of breathable laminates are
fabricated using the dispersions described above, using the
following general procedure. A4 polypropylene nonwoven sheets are
coated with the dispersions on a pilot curtain coater. The A4
sheets are stuck to a continuous carrier paper band and compactly
coated with 6-14 g/m.sup.2 coatings. A repetitive coating with
inter-drying is possible as well. The reachable coating speed
applied is up to about 1100 m/min.
[0177] Advantageously, therefore, polyolefin dispersions as
described herein may be useful in the manufacturing of breathable
backsheets for the hygiene market, breathable clothing, breathable
packaging, and breathable construction membranes. Specifically, in
one or more embodiments, the techniques described above may provide
cost savings, as the film/coating may be formed directly onto a
final substrate (e.g., a nonwoven textile) allowing a manufacturer
to skip a separate film extrusion, masterbatch addition,
stretching, and lamination steps. Further, overall manufacturing
may be simplified as the coating process may be integrated into a
nonwoven manufacturing line, and be adapted to the same line speed
as the nonwoven production (which can be 100 m/min to 1100 m/min).
Still further, the breathability and MVTR can be finally controlled
by various independent manufacturing parameters.
[0178] While the invention has been described with respect to a
limited number of embodiments, those skilled in the art, having
benefit of this disclosure, will appreciate that other embodiments
can be devised which do not depart from the scope of the invention
as disclosed herein. Accordingly, the scope of the invention should
be limited only by the attached claims.
[0179] All priority documents are herein fully incorporated by
reference for all jurisdictions in which such incorporation is
permitted. Further, all documents cited herein, including testing
procedures, are herein fully incorporated by reference for all
jurisdictions in which such incorporation is permitted to the
extent such disclosure is consistent with the description of the
present invention.
* * * * *