U.S. patent application number 13/949277 was filed with the patent office on 2013-11-21 for multicomponent biodegradable filaments and nonwoven webs formed therefrom.
This patent application is currently assigned to Kimberly-Clark Worldwide, Inc.. The applicant listed for this patent is Kimberly-Clark Worldwide, Inc.. Invention is credited to Aimin He, Doris Palfery, Vasily A. Topolkaraev, James H. Wang, Gregory J. Wideman.
Application Number | 20130309932 13/949277 |
Document ID | / |
Family ID | 49581672 |
Filed Date | 2013-11-21 |
United States Patent
Application |
20130309932 |
Kind Code |
A1 |
He; Aimin ; et al. |
November 21, 2013 |
Multicomponent Biodegradable Filaments and Nonwoven Webs Formed
Therefrom
Abstract
A biodegradable, substantially continuous filament is provided.
The filament contains a first component formed from at least one
high melting polyester and a second component formed from at least
one low melting polyester. The low melting point polyester is an
aliphatic-aromatic copolyester formed by melt blending a polymer
and an alcohol to initiate an alcoholysis reaction that results in
a copolyester having one or more hydroxyalkyl or alkyl terminal
groups. By selectively controlling the alcoholysis conditions
(e.g., alcohol and copolymer concentrations, catalysts,
temperature, etc.), a modified aliphatic-aromatic copolyester may
be achieved that has a molecular weight lower than the starting
aliphatic-aromatic polymer. Such lower molecular weight polymers
also have the combination of a higher melt flow index and lower
apparent viscosity, which is useful in the formation of
substantially continuous filaments.
Inventors: |
He; Aimin; (Appleton,
WI) ; Wang; James H.; (Appleton, WI) ;
Topolkaraev; Vasily A.; (Appleton, WI) ; Wideman;
Gregory J.; (Menasha, WI) ; Palfery; Doris;
(Neenah, WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kimberly-Clark Worldwide, Inc. |
Neenah |
WI |
US |
|
|
Assignee: |
Kimberly-Clark Worldwide,
Inc.
Neenah
WI
|
Family ID: |
49581672 |
Appl. No.: |
13/949277 |
Filed: |
July 24, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12668255 |
Nov 22, 2010 |
8518311 |
|
|
13949277 |
|
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Current U.S.
Class: |
442/415 ;
428/373; 525/437 |
Current CPC
Class: |
Y10T 442/697 20150401;
D04H 1/4382 20130101; Y10T 428/2929 20150115; D01F 8/14 20130101;
D04H 3/153 20130101; D04H 3/147 20130101 |
Class at
Publication: |
442/415 ;
428/373; 525/437 |
International
Class: |
D01F 8/14 20060101
D01F008/14; D04H 1/4382 20060101 D04H001/4382 |
Claims
1. A biodegradable, substantially continuous multicomponent
filament comprising a first component and a second component, the
first component containing a first polyester having a melting point
of from about 150.degree. C. to about 250.degree. C. and the second
component containing a second polyester, wherein the second
polyester is an aliphatic-aromatic copolyester terminated with an
alkyl group, hydroxyalkyl group, or a combination thereof, the
aliphatic-aromatic copolyester having a melt flow index of from
about 5 to about 200 grams per 10 minutes, determined at a load of
2160 grams and temperature of 190.degree. C. in accordance with
ASTM Test Method D1238-E.
2. The biodegradable filament of claim 1, wherein the melt flow
index of the copolyester is from about 15 to about 50 grams per 10
minutes.
3. The biodegradable filament of claim 1, wherein the copolyester
has a number average molecular weight of from about 10,000 to about
70,000 grams per mole and a weight average molecular weight of from
about 20,000 to about 125,000 grams per mole.
4. The biodegradable filament of claim 1, wherein the copolyester
has a number average molecular weight of from about 20,000 to about
60,000 grams per mole and a weight average molecular weight of from
about 30,000 to about 110,000 grams per mole.
5. The biodegradable filament of claim 1, wherein the copolyester
has a melting point of from about 50.degree. C. to about
150.degree. C.
6. The biodegradable filament of claim 1, wherein the copolyester
has a glass transition temperature of about 0.degree. C. or
less.
7. The biodegradable filament of claim 1, wherein the copolyester
has the following general structure: ##STR00003## wherein, m is an
integer from 2 to 10, in some embodiments from 2 to 4, and in one
embodiment, 4; n is an integer from 0 to 18, in some embodiments
from 2 to 4, and in one embodiment, 4; p is an integer from 2 to
10, in some embodiments from 2 to 4, and in one embodiment, 4; x is
an integer greater than 1; y is an integer greater than 1; and
R.sub.1 and R.sub.2 are independently selected from hydrogen;
hydroxyl groups; straight chain or branched, substituted or
unsubstituted C.sub.1-C.sub.10 alkyl groups; and straight chain or
branched, substituted or unsubstituted C.sub.1-C.sub.10 hydroxalkyl
groups.
8. The biodegradable filament of claim 7, wherein m and n are each
from 2 to 4.
9. The biodegradable filament of claim 7, wherein the copolyester
is derived from polybutylene adipate terephalate.
10. The biodegradable filament of claim 1, wherein the first
polyester is polylactic acid.
11. The biodegradable filament of claim 1, wherein the filament has
a sheath/core or side-by-side configuration.
12. A nonwoven web comprising the biodegradable filament of claim
1.
13. An absorbent article comprising an absorbent core positioned
between a substantially liquid-impermeable layer and a
liquid-permeable layer, wherein the substantially
liquid-impermeable layer contains the nonwoven web of claim 12.
14. The absorbent article of claim 13, wherein the substantially
liquid-impermeable layer forms an outer cover of the absorbent
article.
15. The absorbent article of claim 14, wherein the nonwoven web is
laminated to a breathable film.
16-37. (canceled)
Description
BACKGROUND OF THE INVENTION
[0001] Biodegradable nonwoven webs are useful in a wide range of
applications, such as in the formation of disposable absorbent
products (e.g., diapers, training pants, sanitary wipes, feminine
pads and liners, adult incontinence pads, guards, garments, etc.)
and/or health care products (e.g., surgical gowns, drapes, etc.).
To facilitate formation of the nonwoven web, a biodegradable
polymer should be selected that is melt processable, yet also has
good mechanical and physical properties. Biodegradable
aliphatic-aromatic copolyesters have been developed that possess
good mechanical and physical properties. Unfortunately, the high
molecular weight and viscosity of aliphatic-aromatic copolyesters
has generally prevented their use in certain fiber forming
processes. For example, conventional aliphatic-aromatic
copolyesters are not typically suitable for meltblowing processes,
which require a low polymer viscosity for successful microfiber
formation. As such, a need currently exists for a biodegradable
aliphatic-aromatic copolyester that exhibits good mechanical and
physical properties, but which may be readily formed into a
nonwoven web using a variety of techniques (e.g., meltblowing).
SUMMARY OF THE INVENTION
[0002] In accordance with one embodiment of the present invention,
a biodegradable, substantially continuous multicomponent filament
is disclosed that comprises a first component and a second
component. The first component contains a first polyester having a
melting point of from about 150.degree. C. to about 250.degree. C.
and the second component contains a second polyester. The second
polyester is an aliphatic-aromatic copolyester terminated with an
alkyl group, hydroxyalkyl group, or a combination thereof. The
aliphatic-aromatic copolyester has a melt flow index of from about
5 to about 200 grams per 10 minutes, determined at a load of 2160
grams and temperature of 190.degree. C. in accordance with ASTM
Test Method D1238-E.
[0003] In accordance with another embodiment of the present
invention, a method for forming biodegradable, substantially
continuous multicomponent filaments is disclosed. The method
comprises forming a first thermoplastic composition that contains a
first polyester having a melting point of from about 150.degree. C.
to about 250.degree. C. and forming a second thermoplastic
composition by melt blending a precursor aliphatic-aromatic
copolyester with at least one alcohol so that the copolyester
undergoes an alcoholysis reaction. The alcoholysis reaction results
in a modified copolyester having a melt flow index that is greater
than the melt flow index of the precursor copolyester, determined
at a load of 2160 grams and temperature of 190.degree. C. in
accordance with ASTM Test Method D1238-E. The first thermoplastic
composition and the second thermoplastic composition are
co-extruded to form substantially continuous filaments.
[0004] Other features and aspects of the present invention are
discussed in greater detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] A full and enabling disclosure of the present invention,
including the best mode thereof, directed to one of ordinary skill
in the art, is set forth more particularly in the remainder of the
specification, which makes reference to the appended figures in
which:
[0006] FIG. 1 is a schematic illustration of a process that may be
used in one embodiment of the present invention to form a
continuous filament web;
[0007] FIG. 2 is a graph depicting apparent viscosity versus
various shear rates for the extruded resins of Example 1;
[0008] FIG. 3 is a graph depicting apparent viscosity versus
various shear rates for the extruded resins of Example 3; and
[0009] FIG. 4 is a graph depicting apparent viscosity versus
various shear rates for the extruded resins of Example 4.
[0010] Repeat use of references characters in the present
specification and drawings is intended to represent same or
analogous features or elements of the invention.
DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS
[0011] Reference now will be made in detail to various embodiments
of the invention, one or more examples of which are set forth
below. Each example is provided by way of explanation of the
invention, not limitation of the invention. In fact, it will be
apparent to those skilled in the art that various modifications and
variations may be made in the present invention without departing
from the scope or spirit of the invention. For instance, features
illustrated or described as part of one embodiment, may be used on
another embodiment to yield a still further embodiment. Thus, it is
intended that the present invention covers such modifications and
variations as come within the scope of the appended claims and
their equivalents.
DEFINITIONS
[0012] As used herein, the term "biodegradable" or "biodegradable
polymer" generally refers to a material that degrades from the
action of naturally occurring microorganisms, such as bacteria,
fungi, and algae; environmental heat; moisture; or other
environmental factors. The biodegradability of a material may be
determined using ASTM Test Method 5338.92.
[0013] As used herein, the term "continuous filament web" generally
refers to a nonwoven web containing substantially continuous
filaments. The filaments may, for example, have a length much
greater than their diameter, such as a length to diameter ratio
("aspect ratio") greater than about 15,000 to 1, and in some cases,
greater than about 50,000 to 1.
[0014] As used herein, the term "nonwoven web" refers to a web
having a structure of individual threads (e.g., fibers or
filaments) that are randomly interlaid, not in an identifiable
manner as in a knitted fabric. Nonwoven webs include, for example,
meltblown webs, spunbond webs, carded webs, wet-laid webs, airlaid
webs, coform webs, hydraulically entangled webs, etc. The basis
weight of the nonwoven web may generally vary, but is typically
from about 5 grams per square meter ("gsm") to 200 gsm, in some
embodiments from about 10 gsm to about 150 gsm, and in some
embodiments, from about 15 gsm to about 100 gsm.
[0015] As used herein, the term "meltblown web" generally refers to
a nonwoven web that is formed by a process in which a molten
thermoplastic material is extruded through a plurality of fine,
usually circular, die capillaries as molten fibers into converging
high velocity gas (e.g. air) streams that attenuate the fibers of
molten 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 dispersed meltblown
fibers. Such a process is disclosed, for example, in U.S. Pat. No.
3,849,241 to Butin, et al., which is incorporated herein in its
entirety by reference thereto for all purposes. Generally speaking,
meltblown fibers may be microfibers that are substantially
continuous or discontinuous, generally smaller than 10 micrometers
in diameter, and generally tacky when deposited onto a collecting
surface.
[0016] As used herein, the term "spunbond web" generally refers to
a web containing small diameter substantially continuous filaments.
The filaments are formed by extruding a molten thermoplastic
material from a plurality of fine, usually circular, capillaries of
a spinnerette with the diameter of the extruded filaments then
being rapidly reduced as by, for example, eductive drawing and/or
other well-known spunbonding mechanisms. The production of spunbond
webs is described and illustrated, for example, in U.S. Pat. Nos.
4,340,563 to Appel, et al., 3,692,618 to Dorschner, et al.,
3,802,817 to Matsuki, et al., 3,338,992 to Kinney, 3,341,394 to
Kinney, 3,502,763 to Hartman, 3,502,538 to Levy, 3,542,615 to Dobo,
et al., and 5,382,400 to Pike, et al., which are incorporated
herein in their entirety by reference thereto for all purposes.
Spunbond filaments are generally not tacky when they are deposited
onto a collecting surface. Spunbond filaments may sometimes have
diameters less than about 40 micrometers, and are often between
about 5 to about 20 micrometers.
[0017] As used herein, the term "multicomponent" refers to
filaments formed from at least two polymer components (e.g.,
bicomponent filaments).
DETAILED DESCRIPTION
[0018] The present invention is directed to a substantially
continuous filament that is biodegradable. The filament contains a
first component formed from at least one high melting polyester and
a second component formed from at least one low melting polyester.
The first and second components may be arranged in any desired
configuration, such as sheath-core, side-by-side, pie,
island-in-the-sea, and so forth. Regardless, the low melting point
polyester is an aliphatic-aromatic copolyester formed by melt
blending a polymer and an alcohol to initiate an alcoholysis
reaction that results in a copolyester having one or more
hydroxyalkyl or alkyl terminal groups. By selectively controlling
the alcoholysis conditions (e.g., alcohol and copolymer
concentrations, catalysts, temperature, etc.), a modified
aliphatic-aromatic copolyester may be achieved that has a molecular
weight lower than the starting aliphatic-aromatic polymer. Such
lower molecular weight polymers also have the combination of a
higher melt flow index and lower apparent viscosity, which is
useful in the formation of substantially continuous filaments.
I. First Component
[0019] As stated, the first component of the multicomponent
filaments is formed from one or more "high melting point"
biodegradable polyesters. The melting point of such polyesters is
from about 150.degree. C. to about 250.degree. C., in some
embodiments from about 160.degree. C. to about 240.degree. C., and
in some embodiments, from about 170.degree. C. to about 220.degree.
C. Various "high melting point" polyesters may be employed in the
present invention, such as polyesteramides, modified polyethylene
terephthalate, polylactic acid (PLA), terpolymers based on
polylactic acid, polyglycolic acid, polyalkylene carbonates (such
as polyethylene carbonate), polyhydroxyalkanoates (PHA),
polyhydroxybutyrates (PHB), polyhydroxyvalerates (PHV), and
polyhydroxybutyrate-hydroxyvalerate copolymers (PHBV). The term
"polylactic acid" generally refers to homopolymers of lactic acid,
such as poly(L-lactic acid), poly(D-lactic acid), poly(DL-lactic
acid), mixtures thereof, and copolymers containing lactic acid as
the predominant component and a small proportion of a
copolymerizable comonomer, such as 3-hydroxybutyrate, caprolactone,
glycolic acid, etc. One particularly suitable polylactic acid
polymer that may be used in the present invention is commercially
available from Biomer, Inc. (Germany) under the name Biomer.TM.
L9000. Still other suitable polylactic acid polymers are
commercially available from Natureworks, LLC of Minneapolis,
Minn.
[0020] Although not required, the high melting point polyesters
typically constitute the principal ingredient of the first
component. That is, the polyesters may constitute at least about 80
wt. %, in some embodiments at least about 90 wt. %, and in some
embodiments, at least about 95 wt. % of the first component. In
such embodiments, the characteristics of the first component (e.g.,
melting point) will be substantially the same as the
characteristics of the polyesters employed. For example, the
melting point of the first component may range from about
150.degree. C. to about 250.degree. C., in some embodiments from
about 160.degree. C. to about 240.degree. C., and in some
embodiments, from about 170.degree. C. to about 220.degree. C.
II. Second Component
[0021] The second component is formed from one or more "low melting
point" biodegradable aromatic-aliphatic copolyesters. Such
copolyesters have a melting point of from about 50.degree. C. to
about 150.degree. C., in some embodiments from about 80.degree. C.
to about 140.degree. C., and in some embodiments, from about
90.degree. C. to about 130.degree. C. Moreover, the melting point
is also typically at least about 30.degree. C., in some embodiments
at least about 40.degree. C., and in some embodiments, at least
about 50.degree. C. less than the melting point of the "high
melting point" polyesters. In addition, they are generally softer
to the touch than most "high melting point" polyesters. The glass
transition temperature ("T.sub.g") of the low melting point
copolyesters may also be less than that of the high melting point
polyesters to improve flexibility and processability of the
polymers. For example, the low melting point copolyesters may have
a T.sub.g of about 25.degree. C. or less, in some embodiments about
0.degree. C. or less, and in some embodiments, about -10.degree. C.
or less. Such a glass transition temperature may be at least about
5.degree. C., in some embodiments at least about 10.degree. C., and
in some embodiments, at least about 15.degree. C. less than the
glass transition temperature of the high melting point polyesters.
As discussed in more detail below, the melting temperature and
glass transition temperature may be determined using differential
scanning calorimetry ("DSC") in accordance with ASTM D-3417.
[0022] Generally speaking, the aliphatic-aromatic copolyesters are
formed by melt blending a polymer an alcohol to initiate an
alcoholysis reaction that results in a copolyester having one or
more hydroxyalkyl or alkyl terminal groups. Various embodiments of
the alcoholysis reaction components and techniques will now be
described in more detail below.
III. Reaction Components
[0023] A. Aliphatic-Aromatic Copolyester
[0024] The aliphatic-aromatic copolyester may be synthesized using
any known technique, such as through the condensation
polymerization of a polyol in conjunction with aliphatic and
aromatic dicarboxylic acids or anhydrides thereof. The polyols may
be substituted or unsubstituted, linear or branched, polyols
selected from polyols containing 2 to about 12 carbon atoms and
polyalkylene ether glycols containing 2 to 8 carbon atoms. Examples
of polyols that may be used include, but are not limited to,
ethylene glycol, diethylene glycol, propylene glycol,
1,2-propanediol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol,
1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol,
1,5-pentanediol, 1,6-hexanediol, polyethylene glycol, diethylene
glycol, 2,2,4-trimethyl-1,6-hexanediol, thiodiethanol,
1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol,
2,2,4,4-tetramethyl-1,3-cyclobutanediol, cyclopentanediol,
triethylene glycol, and tetraethylene glycol. Preferred polyols
include 1,4-butanediol; 1,3-propanediol; ethylene glycol;
1,6-hexanediol; diethylene glycol; and
1,4-cyclohexanedimethanol.
[0025] Representative aliphatic dicarboxylic acids that may be used
include substituted or unsubstituted, linear or branched,
non-aromatic dicarboxylic acids selected from aliphatic
dicarboxylic acids containing 2 to about 12 carbon atoms, and
derivatives thereof. Non-limiting examples of aliphatic
dicarboxylic acids include malonic, succinic, oxalic, glutaric,
adipic, pimelic, azelaic, sebacic, fumaric, 2,2-dimethyl glutaric,
suberic, 1,3-cyclopentanedicarboxylic, 1,4-cyclohexanedicarboxylic,
1,3-cyclohexanedicarboxylic, diglycolic, itaconic, maleic, and
2,5-norbornanedicarboxylic. Representative aromatic dicarboxylic
acids that may be used include substituted and unsubstituted,
linear or branched, aromatic dicarboxylic acids selected from
aromatic dicarboxylic acids containing 1 to about 6 carbon atoms,
and derivatives thereof. Non-limiting examples of aromatic
dicarboxylic acids include terephthalic acid, dimethyl
terephthalate, isophthalic acid, dimethyl isophthalate,
2,6-napthalene dicarboxylic acid, dimethyl-2,6-naphthalate,
2,7-naphthalenedicarboxylic acid, dimethyl-2,7-naphthalate,
3,4'-diphenyl ether dicarboxylic acid, dimethyl-3,4'diphenyl ether
dicarboxylate, 4,4'-diphenyl ether dicarboxylic acid,
dimethyl-4,4'-diphenyl ether dicarboxylate, 3,4'-diphenyl sulfide
dicarboxylic acid, dimethyl-3,4'-diphenyl sulfide dicarboxylate,
4,4'-diphenyl sulfide dicarboxylic acid, dimethyl-4,4'-diphenyl
sulfide dicarboxylate, 3,4'-diphenyl sulfone dicarboxylic acid,
dimethyl-3,4'-diphenyl sulfone dicarboxylate, 4,4'-diphenyl sulfone
dicarboxylic acid, dimethyl-4,4'-diphenyl sulfone dicarboxylate,
3,4'-benzophenonedicarboxylic acid,
dimethyl-3,4'-benzophenonedicarboxylate,
4,4'-benzophenonedicarboxylic acid,
dimethyl-4,4'-benzophenonedicarboxylate, 1,4-naphthalene
dicarboxylic acid, dimethyl-1,4-naphthalate, 4,4'-methylene
bis(benzoic acid), dimethyl-4,4'-methylenebis(benzoate), etc., and
mixtures thereof.
[0026] The polymerization may be catalyzed by a catalyst, such as a
titanium-based catalyst (e.g., tetraisopropyltitanate,
tetraisopropoxy titanium, dibutoxydiacetoacetoxy titanium, or
tetrabutyltitanate). If desired, a diisocyanate chain extender may
be reacted with the copolyester to increase its molecular weight.
Representative diisocyanates may include toluene 2,4-diisocyanate,
toluene 2,6-diisocyanate, 2,4'-diphenylmethane diisocyanate,
naphthylene-1,5-diisocyanate, xylylene diisocyanate, hexamethylene
diisocyanate ("HMDI"), isophorone diisocyanate and
methylenebis(2-isocyanatocyclohexane). Trifunctional isocyanate
compounds may also be employed that contain isocyanurate and/or
biurea groups with a functionality of not less than three, or to
replace the diisocyanate compounds partially by tri- or
polyisocyanates. The preferred diisocyanate is hexamethylene
diisocyanate. The amount of the chain extender employed is
typically from about 0.3 to about 3.5 wt. %, in some embodiments,
from about 0.5 to about 2.5 wt. % based on the total weight percent
of the polymer.
[0027] The copolyesters may either be a linear polymer or a
long-chain branched polymer. Long-chain branched polymers are
generally prepared by using a low molecular weight branching agent,
such as a polyol, polycarboxylic acid, hydroxy acid, and so forth.
Representative low molecular weight polyols that may be employed as
branching agents include glycerol, trimethylolpropane,
trimethylolethane, polyethertriols, glycerol, 1,2,4-butanetriol,
pentaerythritol, 1,2,6-hexanetriol, sorbitol,
1,1,4,4,-tetrakis(hydroxymethyl)cyclohexane,
tris(2-hydroxyethyl)isocyanurate, and dipentaerythritol.
Representative higher molecular weight polyols (molecular weight of
400 to 3000) that may be used as branching agents include triols
derived by condensing alkylene oxides having 2 to 3 carbons, such
as ethylene oxide and propylene oxide with polyol initiators.
Representative polycarboxylic acids that may be used as branching
agents include hemimellitic acid, trimellitic
(1,2,4-benzenetricarboxylic) acid and anhydride, trimesic
(1,3,5-benzenetricarboxylic) acid, pyromellitic acid and anhydride,
benzenetetracarboxylic acid, benzophenone tetracarboxylic acid,
1,1,2,2-ethane-tetracarboxylic acid, 1,1,2-ethanetricarboxylic
acid, 1,3,5-pentanetricarboxylic acid, and
1,2,3,4-cyclopentanetetracarboxylic acid. Representative hydroxy
acids that may be used as branching agents include malic acid,
citric acid, tartaric acid, 3-hydroxyglutaric acid, mucic acid,
trihydroxyglutaric acid, 4-carboxyphthalic anhydride,
hydroxyisophthalic acid, and 4-(beta-hydroxyethyl)phthalic acid.
Such hydroxy acids contain a combination of 3 or more hydroxyl and
carboxyl groups. Especially preferred branching agents include
trimellitic acid, trimesic acid, pentaerythritol, trimethylol
propane and 1,2,4-butanetriol.
[0028] The aromatic dicarboxylic acid monomer constituent may be
present in the copolyester in an amount of from about 10 mole % to
about 40 mole %, in some embodiments from about 15 mole % to about
35 mole %, and in some embodiments, from about 15 mole % to about
30 mole %. The aliphatic dicarboxylic acid monomer constituent may
likewise be present in the copolyester in an amount of from about
15 mole % to about 45 mole %, in some embodiments from about 20
mole % to about 40 mole %, and in some embodiments, from about 25
mole % to about 35 mole %. The polyol monomer constituent may also
be present in the aliphatic-aromatic copolyester in an amount of
from about 30 mole % to about 65 mole %, in some embodiments from
about 40 mole % to about 50 mole %, and in some embodiments, from
about 45 mole % to about 55 mole %.
[0029] In one particular embodiment, for example, the
aliphatic-aromatic copolyester may comprise the following
structure:
##STR00001##
[0030] wherein,
[0031] m is an integer from 2 to 10, in some embodiments from 2 to
4, and in one embodiment, 4;
[0032] n is an integer from 0 to 18, in some embodiments from 2 to
4, and in one embodiment, 4;
[0033] p is an integer from 2 to 10, in some embodiments from 2 to
4, and in one embodiment, 4;
[0034] x is an integer greater than 1; and
[0035] y is an integer greater than 1. One example of such a
copolyester is polybutylene adipate terephthalate, which is
commercially available under the designation ECOFLEX.RTM. F BX 7011
from BASF Corp. Another example of a suitable copolyester
containing an aromatic terephtalic acid monomer constituent is
available under the designation ENPOL.TM. 8060M from IRE Chemicals
(South Korea). Other suitable aliphatic-aromatic copolyesters may
be described in U.S. Pat. Nos. 5,292,783; 5,446,079; 5,559,171;
5,580,911; 5,599,858; 5,817,721; 5,900,322; and 6,258,924, which
are incorporated herein in their entirety by reference thereto for
all purposes.
[0036] The aliphatic-aromatic polyester typically has a number
average molecular weight ("M.sub.n") ranging from about 40,000 to
about 120,000 grams per mole, in some embodiments from about 50,000
to about 100,000 grams per mole, and in some embodiments, from
about 60,000 to about 85,000 grams per mole. Likewise, the polymer
also typically has a weight average molecular weight ("M.sub.w")
ranging from about 70,000 to about 240,000 grams per mole, in some
embodiments from about 80,000 to about 190,000 grams per mole, and
in some embodiments, from about 100,000 to about 150,000 grams per
mole. The ratio of the weight average molecular weight to the
number average molecular weight ("M.sub.w/M.sub.n"), i.e., the
"polydispersity index", is also relatively low. For example, the
polydispersity index typically ranges from about 1.0 to about 3.0,
in some embodiments from about 1.2 to about 2.0, and in some
embodiments, from about 1.4 to about 1.8. The weight and number
average molecular weights may be determined by methods known to
those skilled in the art.
[0037] The aromatic-aliphatic polyester may also have an apparent
viscosity of from about 100 to about 1000 Pascal seconds (Pas), in
some embodiments from about 200 to about 800 Pas, and in some
embodiments, from about 300 to about 600 Pas, as determined at a
temperature of 170.degree. C. and a shear rate of 1000 sec.sup.-1.
The melt flow index of the aromatic-aliphatic polyester may also
range from about 0.1 to about 10 grams per 10 minutes, in some
embodiments from about 0.5 to about 8 grams per 10 minutes, and in
some embodiments, from about 1 to about 5 grams per 10 minutes. The
melt flow index is the weight of a polymer (in grams) that may be
forced through an extrusion rheometer orifice (0.0825-inch
diameter) when subjected to a load of 2160 grams in 10 minutes at a
certain temperature (e.g., 190.degree. C.), measured in accordance
with ASTM Test Method D1238-E.
[0038] B. Alcohol
[0039] As indicated above, the aliphatic-aromatic copolyester may
be reacted with an alcohol to form a modified copolyester having a
reduced molecular weight. The concentration of the alcohol reactant
may influence the extent to which the molecular weight is altered.
For instance, higher alcohol concentrations generally result in a
more significant decrease in molecular weight. Of course, too high
of an alcohol concentration may also affect the physical
characteristics of the resulting polymer. Thus, in most
embodiments, the alcohol(s) are employed in an amount of about 0.1
wt. % to about 10 wt. %, in some embodiments from about 0.1 wt. %
to about 4 wt. %, and in some embodiments, from about 0.2 wt. % to
about 1 wt. %, based on the total weight of the starting
aliphatic-aromatic copolyester.
[0040] The alcohol may be monohydric or polyhydric (dihydric,
trihydric, tetrahydric, etc.), saturated or unsaturated, and
optionally substituted with functional groups, such as carboxyl,
amine, etc. Examples of suitable monohydric alcohols include
methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol,
1-pentanol, 2-pentanol, 3-pentanol, 1-hexanol, 2-hexanol,
3-hexanol, 1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol,
1-octanol, 2-octanol, 3-octanol, 4-octanol, 1-nonanol, 2-nonanol,
3-nonanol, 4-nonanol, 5-nonanol, 1-decanol, 2-decanol, 3-decanol,
4-decanol, 5-decanol, allyl alcohol, 1-butenol, 2-butenol,
1-pentenol, 2-pentenol, 1-hexenol, 2-hexenol, 3-hexenol,
1-heptenol, 2-heptenol, 3-heptenol, 1-octenol, 2-octenol,
3-octenol, 4-octenol, 1-nonenol, 2-nonenol, 3-nonenol, 4-nonenol,
1-decenol, 2-decenol, 3-decenol, 4-decenol, 5-decenol,
cyclohexanol, cyclopentanol, cycloheptanol, 1-phenylhyl alcohol,
2-phenylhyl alcohol, 2-ethoxy-ethanol, methanolamine, ethanolamine,
and so forth. Examples of suitable dihydric alcohols include
1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,
1,7-heptanediol, 1,8-octanediol, 1,2-cyclohexanedimethanol,
1,3-cyclohexanedimethanol,
1-hydroxymethyl-2-hydroxyethylcyclohexane,
1-hydroxy-2-hydroxypropylcyclohexane,
1-hydroxy-2-hydroxyethylcyclohexane,
1-hydroxymethyl-2-hydroxyethylbenzene,
1-hydroxymethyl-2-hydroxypropylbenzene,
1-hydroxy-2-hydroxyethylbenzene, 1,2-benzylmethylol,
1,3-benzyldimethylol, and so forth. Suitable trihydric alcohols may
include glycerol, trimethylolpropane, etc., while suitable
tetrahydric alcohols may include pentaerythritol, erythritol, etc.
Preferred alcohols are dihydric alcohols having from 2 to 6 carbon
atoms, such as 1,3-propanediol and 1,4-butanediol.
[0041] The hydroxy group of the alcohol is generally capable of
attacking an ester linkage of the aliphatic-aromatic copolyester,
thereby leading to chain scission or "depolymerization" of the
copolyester molecule into one or more shorter ester chains. The
shorter chains may include aliphatic-aromatic polyesters or
oligomers, as well as minor portions of aliphatic polyesters or
oligomers, aromatic polyesters or oligomers, and combinations of
any of the foregoing. Although not necessarily required, the short
chain aliphatic-aromatic polyesters formed during alcoholysis are
often terminated with an alkyl and/or hydroxyalkyl groups derived
from the alcohol. Alkyl group terminations are typically derived
from monohydric alcohols, while hydroxyalkyl group terminations are
typically derived from polyhydric alcohols. In one particular
embodiment, for example, an aliphatic-aromatic copolyester is
formed during the alcoholysis reaction that comprises the following
general structure:
##STR00002##
[0042] wherein,
[0043] m is an integer from 2 to 10, in some embodiments from 2 to
4, and in one embodiment, 4;
[0044] n is an integer from 0 to 18, in some embodiments from 2 to
4, and in one embodiment, 4;
[0045] p is an integer from 2 to 10, in some embodiments from 2 to
4, and in one embodiment, 4;
[0046] x is an integer greater than 1;
[0047] y is an integer greater than 1; and
[0048] R.sub.1 and R.sub.2 are independently selected from
hydrogen; hydroxyl groups; straight chain or branched, substituted
or unsubstituted C.sub.1-C.sub.10 alkyl groups; straight chain or
branched, substituted or unsubstituted C.sub.1-C.sub.10 hydroxalkyl
groups. Preferably, at least one of R.sub.1 and R.sub.2, or both,
are straight chain or branched, substituted or unsubstituted,
C.sub.1-C.sub.10 alkyl or C.sub.1-C.sub.10 hydroxyalkyl groups, in
some embodiments C.sub.1-C.sub.8 alkyl or C.sub.1-C.sub.8
hydroxyalkyl groups, and in some embodiments, C.sub.2-C.sub.6 alkyl
or C.sub.2-C.sub.6 hydroxyalkyl groups. Examples of suitable alkyl
and hydroxyalkyl groups include, for instance, methyl, ethyl,
iso-propyl, n-propyl, n-butyl, isobutyl, sec-butyl, tert-butyl,
n-pentyl, n-hexyl, n-heptyl, n-octyl, n-decyl, 1-hydroxyethyl,
2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl, and
5-hydroxypentyl groups. Thus, as indicated, the modified
aliphatic-aromatic copolyester has a different chemical composition
than an unmodified copolyester in terms of its terminal groups. The
terminal groups may play a substantial role in determining the
properties of the polymer, such as its reactivity, stability,
etc.
[0049] Regardless of its particular structure, a new polymer
species is formed during alcoholysis that has a molecular weight
lower than that of the starting polyester. The weight average
and/or number average molecular weights may, for instance, each be
reduced so that the ratio of the starting copolyester molecular
weight to the new molecular weight is at least about 1.1, in some
embodiments at least about 1.4, and in some embodiments, at least
about 1.6. For example, the modified aliphatic-aromatic copolyester
may have a number average molecular weight ("M.sub.n") ranging from
about 10,000 to about 70,000 grams per mole, in some embodiments
from about 20,000 to about 60,000 grams per mole, and in some
embodiments, from about 30,000 to about 55,000 grams per mole.
Likewise, the modified copolyester may also have a weight average
molecular weight ("M.sub.w") of from about 20,000 to about 125,000
grams per mole, in some embodiments from about 30,000 to about
110,000 grams per mole, and in some embodiments, from about 40,000
to about 90,000 grams per mole.
[0050] In addition to possessing a lower molecular weight, the
modified aliphatic-aromatic copolyester may also have a lower
apparent viscosity and higher melt flow index than the starting
polyester. The apparent viscosity may for instance, be reduced so
that the ratio of the starting copolyester viscosity to the
modified copolyester viscosity is at least about 1.1, in some
embodiments at least about 2, and in some embodiments, from about
10 to about 40. Likewise, the melt flow index may be increased so
that the ratio of the modified copolyester melt flow index to the
starting copolyester melt flow index is at least about 1.5, in some
embodiments at least about 3, in some embodiments at least about
10, and in some embodiments, from about 20 to about 200. In one
particular embodiment, the modified copolyester may have an
apparent viscosity of from about 10 to about 500 Pascal seconds
(Pas), in some embodiments from about 20 to about 400 Pas, and in
some embodiments, from about 30 to about 250 Pas, as determined at
a temperature of 170.degree. C. and a shear rate of 1000
sec.sup.-1. The melt flow index (190.degree. C., 2.16 kg) of the
modified copolyester may range from about 5 to about 200 grams per
10 minutes, in some embodiments from about 10 to about 100 grams
per 10 minutes, and in some embodiments, from about 15 to about 50
grams per 10 minutes. Of course, the extent to which the molecular
weight, apparent viscosity, and/or melt flow index are altered by
the alcoholysis reaction may vary depending on the intended
application.
[0051] Although differing from the starting polymer in certain
properties, the modified copolyester may nevertheless retain other
properties of the starting polymer to enhance the flexibility and
processability of the polymers. For example, the thermal
characteristics (e.g., T.sub.g, T.sub.m, and latent heat of fusion)
typically remain substantially the same as the starting polymer,
such as within the ranges noted above. Further, even though the
actual molecular weights may differ, the polydispersity index of
the modified copolyester may remain substantially the same as the
starting polymer, such as within the range of about 1.0 to about
3.0, in some embodiments from about 1.1 to about 2.0, and in some
embodiments, from about 1.2 to about 1.8.
[0052] Typically, modified aliphatic-aromatic copolyesters
constitute the principal ingredient of the second component. That
is, the modified copolyesters may constitute at least about 90 wt.
%, in some embodiments at least about 92 wt. %, and in some
embodiments, at least about 95 wt. % of the second component. In
such embodiments, the characteristics of the second component
(e.g., melting point) will be substantially the same as the
characteristics of the modified copolyesters employed.
[0053] C. Catalyst
[0054] A catalyst may be employed to facilitate the modification of
the alcoholysis reaction. The concentration of the catalyst may
influence the extent to which the molecular weight is altered. For
instance, higher catalyst concentrations generally result in a more
significant decrease in molecular weight. Of course, too high of a
catalyst concentration may also affect the physical characteristics
of the resulting polymer. Thus, in most embodiments, the
catalyst(s) are employed in an amount of about 50 to about 2000
parts per million ("ppm"), in some embodiments from about 100 to
about 1000 ppm, and in some embodiments, from about 200 to about
1000 ppm, based on the weight of the starting aliphatic-aromatic
copolyester.
[0055] Any known catalyst may be used in the present invention to
accomplish the desired reaction. In one embodiment, for example, a
transition metal catalyst may be employed, such as those based on
Group IVB metals and/or Group IVA metals (e.g., alkoxides or
salts). Titanium-, zirconium-, and/or tin-based metal catalysts are
especially desirable and may include, for instance, titanium
butoxide, titanium tetrabutoxide, titanium propoxide, titanium
isopropoxide, titanium phenoxide, zirconium butoxide, dibutyltin
oxide, dibutyltin diacetate, tin phenoxide, tin octylate, tin
stearate, dibutyltin dioctoate, dibutyltin dioleylmaleate,
dibutyltin dibutylmaleate, dibutyltin dilaurate,
1,1,3,3-tetrabutyl-1,3-dilauryloxycarbonyldistannoxane,
dibutyltindiacetate, dibutyltin diacetylacetonate, dibutyltin
bis(o-phenylphenoxide), dibutyltin bis(triethoxysilicate),
dibutyltin distearate, dibutyltin
bis(isononyl-3-mercaptopropionate), dibutyltin bis(isooctyl
thioglycolate), dioctyltin oxide, dioctyltin dilaurate, dioctyltin
diacetate, and dioctyltin diversatate.
[0056] D. Co-Solvent
[0057] The alcoholysis reaction is typically carried out in the
absence of a solvent other than the alcohol reactant. Nevertheless,
a co-solvent may be employed in some embodiments of the present
invention. In one embodiment, for instance, the co-solvent may
facilitate the dispersion of the catalyst in the reactant alcohol.
Examples of suitable co-solvents may include ethers, such as
diethyl ether, anisole, tetrahydrofuran, ethylene glycol dimethyl
ether, triethylene glycol dimethyl ether, tetraethylene glycol
dimethyl ether, dioxane, etc.; alcohols, such as methanol, ethanol,
n-butanol, benzyl alcohol, ethylene glycol, diethylene glycol,
etc.; phenols, such as phenol, etc.; carboxylic acids, such as
formic acid, acetic acid, propionic acid, toluic acid, etc.;
esters, such as methyl acetate, butyl acetate, benzyl benzoate,
etc.; aromatic hydrocarbons, such as benzene, toluene,
ethylbenzene, tetralin, etc.; aliphatic hydrocarbons, such as
n-hexane, n-octane, cyclohexane, etc.; halogenated hydrocarbons,
such as dichloromethane, trichloroethane, chlorobenzene, etc.;
nitro compounds, such as nitromethane, nitrobenzene, etc.;
carbamides, such as N,N-dimethylformamide, N,N-dimethylacetamide,
N-methylpyrrolidone, etc.; ureas, such as
N,N-dimethylimidazolidinone, etc.; sulfones, such as dimethyl
sulfone, etc.; sulfoxides, such as dimethyl sulfoxide, etc.;
lactones, such as butyrolactone, caprolactone, etc.; carbonic acid
esters, such as dimethyl carbonate, ethylene carbonate, etc.; and
so forth.
[0058] When employed, the co-solvent(s) may be employed in an
amount from about 0.5 wt. % to about 20 wt. %, in some embodiments
from about 0.8 wt. % to about 10 wt. %, and in some embodiments,
from about 1 wt. % to about 5 wt. %, based on the weight of the
reactive composition. It should be understood, however, that a
co-solvent is not required. In fact, in some embodiments of the
present invention, the reactive composition is substantially free
of any co-solvents, e.g., less than about 0.5 wt. % of the reactive
composition.
[0059] E. Other Ingredients
[0060] Other ingredients may of course be utilized for a variety of
different reasons. For instance, a wetting agent may be employed in
some embodiments of the present invention to improve
hydrophilicity. Wetting agents suitable for use in the present
invention are generally compatible with aliphatic-aromatic
copolyesters. Examples of suitable wetting agents may include
surfactants, such as UNITHOX.RTM. 480 and UNITHOX.RTM. 750
ethoxylated alcohols, or UNICID.TM. acid amide ethoxylates, all
available from Petrolite Corporation of Tulsa, Okla. Other suitable
wetting agents are described in U.S. Pat. No. 6,177,193 to Tsai, et
al., which is incorporated herein in its entirety by reference
thereto for all relevant purposes. Still other materials that may
be used include, without limitation, melt stabilizers, processing
stabilizers, heat stabilizers, light stabilizers, antioxidants,
pigments, surfactants, waxes, flow promoters, plasticizers,
particulates, and other materials added to enhance processability.
When utilized, such additional ingredients are each typically
present in an amount of less than about 5 wt. %, in some
embodiments less than about 1 wt. %, and in some embodiments, less
than about 0.5 wt. %, based on the weight of the aliphatic-aromatic
copolyester starting polymer.
IV. Reaction Techniques
[0061] The alcoholysis reaction may be performed using any of a
variety of known techniques. In one embodiment, for example, the
reaction is conducted while the starting polymer is in the melt
phase ("melt blending") to minimize the need for additional
solvents and/or solvent removal processes. The raw materials (e.g.,
biodegradable polymer, alcohol, catalyst, etc.) may be supplied
separately or in combination (e.g., in a solution). The raw
materials may likewise be supplied either simultaneously or in
sequence to a melt-blending device that dispersively blends the
materials. Batch and/or continuous melt blending techniques may be
employed. For example, a mixer/kneader, Banbury mixer, Farrel
continuous mixer, single-screw extruder, twin-screw extruder, roll
mill, etc., may be utilized to blend the materials. One
particularly suitable melt-blending device is a co-rotating,
twin-screw extruder (e.g., ZSK-30 twin-screw extruder available
from Werner & Pfleiderer Corporation of Ramsey, N.J.). Such
extruders may include feeding and venting ports and provide high
intensity distributive and dispersive mixing, which facilitate the
alcoholysis reaction. The raw materials (e.g., polymer, alcohol,
catalyst, etc.) may be fed into the extruder from a hopper. The raw
materials may be provided to the hopper using any conventional
technique and in any state. For example, the alcohol may be
supplied as a vapor or liquid. Alternatively, the
aliphatic-aromatic copolyester may be fed to the hopper, and the
alcohol and optional catalyst (either in combination or separately)
may be injected into the copolyester melt in the extruder
downstream from the hopper.
[0062] Regardless of the particular melt blending technique chosen,
the raw materials are blended under high shear/pressure and heat to
ensure sufficient mixing for initiating the alcoholysis reaction.
For example, melt blending may occur at a temperature of from about
50.degree. C. to about 300.degree. C., in some embodiments, from
about 70.degree. C. to about 250.degree. C., and in some
embodiments, from about 90.degree. C. to about 220.degree. C.
Likewise, the apparent shear rate during melt blending may range
from about 100 seconds.sup.-1 to about 10,000 seconds.sup.-1, in
some embodiments from about 500 seconds.sup.-1 to about 5000
seconds.sup.-1, and in some embodiments, from about 800
seconds.sup.-1 to about 1200 seconds.sup.-1. The apparent shear
rate is equal to 4Q/.pi.R.sup.3, where Q is the volumetric flow
rate ("m.sup.3/s") of the polymer melt and R is the radius ("m") of
the capillary (e.g., extruder die) through which the melted polymer
flows.
V. Substantially Continuous Filaments
[0063] Any of a variety of known techniques may be employed to form
substantially continuous filaments in accordance with the present
invention. A modified aliphatic-aromatic copolyester may be
initially formed and then fed to an extruder in a filament
formation line (e.g., extruder 12 of a spinning line).
Alternatively, the modified aliphatic-aromatic copolymer may be
directly formed into a filament. Referring to FIG. 1, for example,
one embodiment of a process 10 for forming a substantially
continuous filament in accordance with the present invention is
shown. As illustrated, the process 10 of this embodiment is
arranged to produce a bicomponent, continuous filament web,
although it should be understood that other embodiments are
contemplated by the present invention. The process 10 employs a
pair of extruders 12a and 12b for separately extruding a first
component A (e.g., high melting point polymer component) and a
second component B (e.g., low melting point polymer component). The
relative amount of the components A and B may generally vary based
on the desired properties. For example, the first component A
normally constitutes from about 5 wt. % to about 95 wt. %, in some
embodiments from about 10 wt. % to about 90 wt. %, and in some
embodiments, from about 15 wt. % to about 85 wt. % of the
multicomponent filaments. Likewise, the second component B normally
constitutes from about 5 wt. % to about 95 wt. %, in some
embodiments from about 10 wt. % to about 90 wt. %, and in some
embodiments, from about 15 wt. % to about 85 wt. % of the
multicomponent filaments.
[0064] The first component A is fed into the respective extruder
12a from a first hopper 14a and the second component B is fed into
the respective extruder 12b from a second hopper 14b. The
components A and B are fed from the extruders 12a and 12b
("co-extruded") through respective polymer conduits 16a and 16b to
a spinneret 18. Spinnerets for extruding multicomponent filaments
are well known to those of skill in the art. For example, the
spinneret 18 may include a housing containing a spin pack having a
plurality of plates stacked one on top of each other and having a
pattern of openings arranged to create flow paths for directing
polymer components A and B separately through the spinneret 18. The
spinneret 18 also has openings arranged in one or more rows. The
openings form a downwardly extruding curtain of filaments when the
polymers are extruded therethrough. The spinneret 18 may be
arranged to form sheath/core, side-by-side, pie, or other
configurations.
[0065] The process 10 also employs a quench blower 20 positioned
adjacent the curtain of filaments extending from the spinneret 18.
Air from the quench air blower 20 quenches the filaments extending
from the spinneret 18. The quench air may be directed from one side
of the filament curtain as shown in FIG. 1 or both sides of the
filament curtain. A fiber draw unit or aspirator 22 is positioned
below the spinneret 18 and receives the quenched filaments. Fiber
draw units or aspirators for use in melt spinning polymers are
well-known in the art. Suitable fiber draw units for use in the
process of the present invention include a linear fiber aspirator
of the type shown in U.S. Pat. Nos. 3,802,817 and 3,423,255, which
are incorporated herein in their entirety by reference thereto for
all relevant purposes. The fiber draw unit 22 generally includes an
elongate vertical passage through which the filaments are drawn by
aspirating air entering from the sides of the passage and flowing
downwardly through the passage. A heater or blower 24 supplies
aspirating air to the fiber draw unit 22. The aspirating air draws
the filaments and ambient air through the fiber draw unit 22.
Thereafter, the filaments are formed into a coherent web structure
by randomly depositing the filaments onto a forming surface 26
(optionally with the aid of a vacuum) and then bonding the
resulting web using any known technique.
[0066] To initiate filament formation, the hoppers 14a and 14b are
initially filled with the respective components A and B. Components
A and B are melted and extruded by the respective extruders 12a and
12b through polymer conduits 16a and 16b and the spinneret 18. Due
to the relatively low apparent viscosity of the modified
aliphatic-aromatic copolyesters used in the present invention,
lower extrusion temperatures may be employed. For example, the
extruder 12b for Component B may employ one or multiple zones
operating at a temperature of from about 120.degree. C. to about
200.degree. C., and in some embodiments, from about 145.degree. C.
to about 195.degree. C. Likewise, the extruder 12a for Component A
may employ one or multiple zones operating at a temperature of from
about 160.degree. C. to about 250.degree. C., and in some
embodiments, from about 190.degree. C. to about 225.degree. C.
Typical shear rates range from about 100 seconds.sup.-1 to about
10,000 seconds.sup.-1, in some embodiments from about 500
seconds.sup.-1 to about 5000 seconds.sup.-1, and in some
embodiments, from about 800 seconds.sup.-1 to about 1200
seconds.sup.-1.
[0067] As the extruded filaments extend below the spinneret 18, a
stream of air from the quench blower 20 at least partially quenches
the filaments. Such a process generally reduces the temperature of
the extruded polymers at least about 100.degree. C. over a
relatively short time frame (seconds). This will generally reduce
the temperature change needed upon cooling, to preferably be less
than 150.degree. C. and, in some cases, less than 100.degree. C.
The ability to use relatively low extruder temperature in the
present invention also allows for the use of lower quenching
temperatures. For example, the quench blower 20 may employ one or
more zones operating at a temperature of from about 20.degree. C.
to about 100.degree. C., and in some embodiments, from about
25.degree. C. to about 60.degree. C. After quenching, the filaments
are drawn into the vertical passage of the fiber draw unit 22 by a
flow of a gas such as air, from the heater or blower 24 through the
fiber draw unit. The flow of gas causes the filaments to draw or
attenuate which increases the molecular orientation or
crystallinity of the polymers forming the filaments. The filaments
are deposited through the outlet opening of the fiber draw unit 22
and onto a foraminous surface 26. Due to the high strength of the
filaments of the present invention, high draw ratios (e.g., linear
speed of the foraminous surface 26 divided by the melt pump rate of
the extruders 12a and 12b) may be employed in the present
invention. For example, the draw ratio may be from about 200:1 to
about 6000:1, in some embodiments from about 500:1 to about 5000:1,
and in some embodiments, from about 1000:1 to about 4000:1.
[0068] The desired denier of the filaments may vary depending on
the desired application. Typically, the filaments are formed to
have a denier per filament of less than about 6, in some
embodiments less than about 3, and in some embodiments, from about
0.5 to about 3. In addition, the filaments generally have an
average diameter not greater than about 100 microns, in some
embodiments from about 0.5 microns to about 50 microns, and in some
embodiments, from about 4 microns to about 40 microns. The ability
to produce such filaments may be facilitated in the present
invention through the use of a modified copolyester having the
desirable combination of low apparent viscosity and high melt flow
index.
[0069] If desired, an endless foraminous forming surface 26 may be
positioned below the fiber draw unit 22 and receive the filaments
from an outlet opening. The forming surface 26 travels around guide
rollers 28. A vacuum 30 positioned below the forming surface 26 to
draw the filaments against the forming surface 26 and consolidate
the unbonded nonwoven web. The web may then be compressed by a
compression roller 32. Once formed, the nonwoven web may be bonded
using any conventional technique, such as with an adhesive or
autogenously (e.g., fusion and/or self-adhesion of the filaments
without an applied external adhesive). Autogenous bonding, for
instance, may be achieved through contact of the filaments while
they are semi-molten or tacky, or simply by blending a tackifying
resin and/or solvent with the aliphatic polyester(s) used to form
the filaments. Suitable autogenous bonding techniques may include
ultrasonic bonding, thermal bonding, through-air bonding, and so
forth.
[0070] In FIG. 1, for instance, the web passes through a nip formed
between a pair of rolls 34 prior to being wound onto a roll 42. One
or both of the rolls 34 may be heated to melt-fuse the filaments
and/or contain intermittently raised bond points to provide an
intermittent bonding pattern. The pattern of the raised points may
be selected so that the nonwoven web has a total bond area of less
than about 50% (as determined by conventional optical microscopic
methods), and in some embodiments, less than about 30%. Likewise,
the bond density is also typically greater than about 100 bonds per
square inch, and in some embodiments, from about 250 to about 500
pin bonds per square inch. Such a combination of total bond area
and bond density may be achieved by bonding the web with a pin bond
pattern having more than about 100 pin bonds per square inch that
provides a total bond surface area less than about 30% when fully
contacting a smooth anvil roll. In some embodiments, the bond
pattern may have a pin bond density from about 250 to about 350 pin
bonds per square inch and a total bond surface area from about 10%
to about 25% when contacting a smooth anvil roll. Exemplary bond
patterns include, for instance, those described in U.S. Pat. No.
3,855,046 to Hansen et al., U.S. Pat. No. 5,620,779 to Levy et al.,
U.S. Pat. No. 5,962,112 to Haynes et al., U.S. Pat. No. 6,093,665
to Sayovitz et al., U.S. Design Pat. No. 428,267 to Romano et al.
and U.S. Design Pat. No. 390,708 to Brown, which are incorporated
herein in their entirety by reference thereto for all purposes.
[0071] Due to the particular rheological and thermal properties of
the components used to form the multicomponent filaments, the web
bonding conditions (e.g., temperature and nip pressure) may be
selected to cause the low melting point, modified copolyester to
melt and flow without substantially melting the high melting point
polyester. For example, the bonding temperature (e.g., the
temperature of the rollers 34) may be from about 50.degree. C. to
about 160.degree. C., in some embodiments from about 80.degree. C.
to about 160.degree. C., and in some embodiments, from about
100.degree. C. to about 140.degree. C. Likewise, the nip pressure
may range from about 5 to about 150 pounds per square inch, in some
embodiments, from about 10 to about 100 pounds per square inch, and
in some embodiments, from about 30 to about 60 pounds per square
inch.
[0072] When bonded in this manner, the low melting point, modified
copolyester may thus form a matrix within the compacted area that
substantially surrounds the high melting point polymer. Because the
high melting point polymer does not substantially melt, however, it
retains a substantially fibrous form. The high melting point
polymer is also generally oriented within the compacted area in two
or more directions due to the random manner in which the filaments
are deposited. One polymer, for instance, may be oriented from
about 60.degree. to about 120.degree., and in some cases, about
90.degree., relative to another polymer within a compacted area. In
this manner, the high melting point polymer may impart enhanced
strength and toughness to the resulting web. For example, the
nonwoven web may exhibit a relatively high "peak load", which
indicates the maximum load to break as expressed in units of
grams-force per inch. The MD peak load of the web may, for
instance, be at least about 3000 grams-force per inch
("g.sub.f/in"), in some embodiments at least about 3500 g.sub.f/in,
and in some embodiments, at least about 4000 g.sub.f/in. The CD
peak load may also be at least about 1200 grams-force per inch
("g.sub.f/in"), in some embodiments at least about 1500 g.sub.f/in,
and in some embodiments, at least about 2500 g.sub.f/in.
[0073] In addition to contributing to the overall strength of the
web, the selected bond conditions may also improve other mechanical
properties of the web. For example, although retaining its fiber
form within a compacted area, the high melting point polymer will
normally release or separate from the compacted area upon the
application of strain, rather than fracture. By releasing under
strain, the polymer may continue to function as a load bearing
member even after the web has exhibited substantial elongation. In
this regard, the nonwoven web is capable of exhibiting improved
"peak elongation" properties, i.e., the percent elongation of the
web at its peak load. For example, the nonwoven web may exhibit a
machine direction ("MD") peak elongation of at least about 10%, in
some embodiments at least about 20%, and in some embodiments, at
least about 35%. The nonwoven web may also exhibit a cross-machine
direction ("CD") peak elongation of at least about 35%, in some
embodiments at least about 45%, and in some embodiments, at least
about 50%. Of course, in addition to possessing good mechanical
properties, the nonwoven web is also soft, drapable, and tactile.
Further, the nonwoven web possesses good water absorption
characteristics, which facilitates its ability to be used in
absorbent articles.
[0074] The filaments of the present invention may constitute the
entire fibrous component of the nonwoven web or blended with other
types of fibers (e.g., staple fibers, continuous filaments, etc).
When blended with other types of fibers, it is normally desired
that the filaments of the present invention constitute from about
20 wt % to about 95 wt. %, in some embodiments from about 30 wt. %
to about 90 wt. %, and in some embodiments, from about 40 wt. % to
about 80 wt. % of the total amount of fibers employed in the
nonwoven web. For example, additional monocomponent and/or
multicomponent synthetic fibers may be utilized in the nonwoven
web. Some suitable polymers that may be used to form the synthetic
fibers include, but are not limited to: polyolefins, e.g.,
polyethylene, polypropylene, polybutylene, and so forth;
polytetrafluoroethylene; polyesters, e.g., polyethylene
terephthalate and so forth; polyvinyl acetate; polyvinyl chloride
acetate; polyvinyl butyral; acrylic resins, e.g., polyacrylate,
polymethylacrylate, polymethylmethacrylate, and so forth;
polyamides, e.g., nylon; polyvinyl chloride; polyvinylidene
chloride; polystyrene; polyvinyl alcohol; polyurethanes; polylactic
acid; etc. If desired, biodegradable polymers, such as
poly(glycolic acid) (PGA), polylactic acid) (PLA),
poly(.beta.-malic acid) (PMLA), poly(s-caprolactone) (PCL),
poly(p-dioxanone) (PDS), poly(butylene succinate) (PBS), and
poly(3-hydroxybutyrate) (PHB), may also be employed. Some examples
of known synthetic fibers include sheath-core bicomponent fibers
available from KoSa Inc. of Charlotte, N.C. under the designations
T-255 and 1-256, both of which use a polyolefin sheath, or T-254,
which has a low melt co-polyester sheath. Still other known
bicomponent fibers that may be used include those available from
the Chisso Corporation of Moriyama, Japan or Fibervisions LLC of
Wilmington, Del. Synthetic or natural cellulosic polymers may also
be used, including but not limited to, cellulosic esters;
cellulosic ethers; cellulosic nitrates; cellulosic acetates;
cellulosic acetate butyrates; ethyl cellulose; regenerated
celluloses, such as viscose, rayon, and so forth.
[0075] The filaments of the present invention may also be blended
with pulp fibers, such as high-average fiber length pulp,
low-average fiber length pulp, or mixtures thereof. One example of
suitable high-average length fluff pulp fibers includes softwood
kraft pulp fibers. Softwood kraft pulp fibers are derived from
coniferous trees and include pulp fibers such as, but not limited
to, northern, western, and southern softwood species, including
redwood, red cedar, hemlock, Douglas fir, true firs, pine (e.g.,
southern pines), spruce (e.g., black spruce), combinations thereof,
and so forth. Northern softwood kraft pulp fibers may be used in
the present invention. An example of commercially available
southern softwood kraft pulp fibers suitable for use in the present
invention include those available from Weyerhaeuser Company with
offices in Federal Way, Wash. under the trade designation of
"NB-416." Another suitable pulp for use in the present invention is
a bleached, sulfate wood pulp containing primarily softwood fibers
that is available from Bowater Corp. with offices in Greenville,
S.C. under the trade name CoosAbsorb S pulp. Low-average length
fibers may also be used in the present invention. An example of
suitable low-average length pulp fibers is hardwood kraft pulp
fibers. Hardwood kraft pulp fibers are derived from deciduous trees
and include pulp fibers such as, but not limited to, eucalyptus,
maple, birch, aspen, etc. Eucalyptus kraft pulp fibers may be
particularly desired to increase softness, enhance brightness,
increase opacity, and change the pore structure of the sheet to
increase its wicking ability.
[0076] Nonwoven laminates may also be formed in which one or more
layers are formed from the multicomponent filaments of the present
invention. In one embodiment, for example, the nonwoven laminate
contains a meltblown layer positioned between two spunbond layers
to form a spunbond/meltblown/spunbond ("SMS") laminate. If desired,
one or more of the spunbond layers may be formed from the filaments
of the present invention. The meltblown layer may be formed from
the modified copolyester, other biodegradable polymer(s), and/or
any other polymer (e.g., polyolefins). Various techniques for
forming SMS laminates are described in U.S. Pat. Nos. 4,041,203 to
Brock et al.; 5,213,881 to Timmons, et al.; 5,464,688 to Timmons,
et al.; 4,374,888 to Bornslaeger; 5,169,706 to Collier, et al.; and
4,766,029 to Brock et al., as well as U.S. Patent Application
Publication No. 2004/0002273 to Fitting, et al., all of which are
incorporated herein in their entirety by reference thereto for all
purposes. Of course, the nonwoven laminate may have other
configuration and possess any desired number of meltblown and
spunbond layers, such as spunbond/meltblown/meltblown/spunbond
laminates ("SMMS"), spunbond/meltblown laminates ("SM"), etc.
Although the basis weight of the nonwoven laminate may be tailored
to the desired application, it generally ranges from about 10 to
about 300 grams per square meter ("gsm"), in some embodiments from
about 25 to about 200 gsm, and in some embodiments, from about 40
to about 150 gsm.
[0077] If desired, the nonwoven web or laminate may be applied with
various treatments to impart desirable characteristics. For
example, the web may be treated with liquid-repellency additives,
antistatic agents, surfactants, colorants, antifogging agents,
fluorochemical blood or alcohol repellents, lubricants, and/or
antimicrobial agents. In addition, the web may be subjected to an
electret treatment that imparts an electrostatic charge to improve
filtration efficiency. The charge may include layers of positive or
negative charges trapped at or near the surface of the polymer, or
charge clouds stored in the bulk of the polymer. The charge may
also include polarization charges that are frozen in alignment of
the dipoles of the molecules. Techniques for subjecting a fabric to
an electret treatment are well known by those skilled in the art.
Examples of such techniques include, but are not limited to,
thermal, liquid-contact, electron beam and corona discharge
techniques. In one particular embodiment, the electret treatment is
a corona discharge technique, which involves subjecting the
laminate to a pair of electrical fields that have opposite
polarities. Other methods for forming an electret material are
described in U.S. Pat. Nos. 4,215,682 to Kubik. et al.; 4,375,718
to Wadsworth; 4,592,815 to Nakao; 4,874,659 to Ando; 5,401,446 to
Tsai, et al.; 5,883,026 to Reader, et al.; 5,908,598 to Rousseau,
et al.; 6,365,088 to Knight, et al., which are incorporated herein
in their entirety by reference thereto for all purposes.
[0078] The nonwoven web or laminate may be used in a wide variety
of applications. For example, the web may be incorporated into a
"medical product", such as gowns, surgical drapes, facemasks, head
coverings, surgical caps, shoe coverings, sterilization wraps,
warming blankets, heating pads, and so forth. Of course, the
nonwoven web may also be used in various other articles. For
example, the nonwoven web may be incorporated into an "absorbent
article" that is capable of absorbing water or other fluids.
Examples of some absorbent articles include, but are not limited
to, personal care absorbent articles, such as diapers, training
pants, absorbent underpants, incontinence articles, feminine
hygiene products (e.g., sanitary napkins), swim wear, baby wipes,
mitt wipe, and so forth; medical absorbent articles, such as
garments, fenestration materials, underpads, bedpads, bandages,
absorbent drapes, and medical wipes; food service wipers; clothing
articles; pouches, and so forth. Materials and processes suitable
for forming such articles are well known to those skilled in the
art. Absorbent articles, for instance, typically include a
substantially liquid-impermeable layer (e.g., outer cover), a
liquid-permeable layer (e.g., bodyside liner, surge layer, etc.),
and an absorbent core. In one embodiment, for example, a nonwoven
web formed according to the present invention may be used to form
an outer cover of an absorbent article. If desired, the nonwoven
web may be laminated to a liquid-impermeable film that is either
vapor-permeable or vapor-impermeable.
[0079] The present invention may be better understood with
reference to the following examples.
Test Methods
[0080] Molecular Weight:
[0081] The molecular weight distribution of a polymer was
determined by gel permeation chromatography ("GPC"). The samples
were initially prepared by adding 0.5% wt/v solutions of the sample
polymers in chloroform to 40-milliliter glass vials. For example,
0.05.+-.0.0005 grams of the polymer was added to 10 milliliters of
chloroform. The prepared samples were placed on an orbital shaker
and agitated overnight. The dissolved sample was filtered through a
0.45-micrometer PTFE membrane and analyzed using the following
conditions: [0082] Columns: Styragel HR 1, 2, 3, 4, & 5E (5 in
series) at 41.degree. C. [0083] Solvent/Eluent: Chloroform @1.0
milliliter per minute [0084] HPLC: Waters 600E gradient pump and
controller, Waters 717 auto sampler [0085] Detector: Waters 2414
Differential Refractometer at sensitivity=30, at 40.degree. C. and
scale factor of 20 [0086] Sample Concentration; 0.5% of polymer "as
is" [0087] Injection Volume: 50 microliters [0088] Calibration
Standards Narrow MW polystyrene, 30-microliter injected volume.
[0089] Number Average Molecular Weight (MW.sub.n), Weight Average
Molecular Weight (MW.sub.w) and first moment of viscosity average
molecular weight (MW.sub.z) were obtained.
[0090] Apparent Viscosity:
[0091] The rheological properties of polymer samples were
determined using a Gottfert Rheograph 2003 capillary rheometer with
WinRHEO version 2.31 analysis software. The setup included a
2000-bar pressure transducer and a 30/1:0/180 roundhole capillary
die. Sample loading was done by alternating between sample addition
and packing with a ramrod. A 2-minute melt time preceded each test
to allow the polymer to completely melt at the test temperature
(usually 160 to 220.degree. C.). The capillary rheometer determined
the apparent viscosity (Pas) at various shear rates, such as 100,
200, 500, 1000, 2000, and 4000 s.sup.-1. The resultant rheology
curve of apparent shear rate versus apparent viscosity gave an
indication of how the polymer would run at that temperature in an
extrusion process.
[0092] Melt Flow Index:
[0093] The melt flow index is the weight of a polymer (in grams)
forced through an extrusion rheometer orifice (0.0825-inch
diameter) when subjected to a load of 2160 grams in 10 minutes,
typically at 190.degree. C. Unless otherwise indicated, the melt
flow index was measured in accordance with ASTM Test Method
D1238-E.
[0094] Thermal Properties:
[0095] The melting temperature ("T.sub.m"), glass transition
temperature ("T.sub.g"), and latent heat of fusion
(".DELTA.H.sub.f") were determined by differential scanning
calorimetry (DSC). The differential scanning calorimeter was a
THERMAL ANALYST 2910 Differential Scanning calorimeter, which was
outfitted with a liquid nitrogen cooling accessory and with a
THERMAL ANALYST 2200 (version 8.10) analysis software program, both
of which are available from T.A. Instruments Inc. of New Castle,
Del. To avoid directly handling the samples, tweezers or other
tools were used. The samples were placed into an aluminum pan and
weighed to an accuracy of 0.01 milligram on an analytical balance.
A lid was crimped over the material sample onto the pan. Typically,
the resin pellets were placed directly in the weighing pan, and the
fibers were cut to accommodate placement on the weighing pan and
covering by the lid.
[0096] The differential scanning calorimeter was calibrated using
an indium metal standard and a baseline correction was performed,
as described in the operating manual for the differential scanning
calorimeter. A material sample was placed into the test chamber of
the differential scanning calorimeter for testing, and an empty pan
is used as a reference. All testing was run with a 55-cubic
centimeter per minute nitrogen (industrial grade) purge on the test
chamber. For resin pellet samples, the heating and cooling program
was a 2-cycle test that began with an equilibration of the chamber
to -50.degree. C., followed by a first heating period at a heating
rate of 10.degree. C. per minute to a temperature of 200.degree.
C., followed by equilibration of the sample at 200.degree. C. for 3
minutes, followed by a first cooling period at a cooling rate of
10.degree. C. per minute to a temperature of -50.degree. C.,
followed by equilibration of the sample at -50.degree. C. for 3
minutes, and then a second heating period at a heating rate of
10.degree. C. per minute to a temperature of 200.degree. C. For
fiber samples, the heating and cooling program was a 1-cycle test
that began with an equilibration of the chamber to -50.degree. C.,
followed by a heating period at a heating rate of 10.degree. C. per
minute to a temperature of 200.degree. C., followed by
equilibration of the sample at 200.degree. C. for 3 minutes, and
then a cooling period at a cooling rate of 10.degree. C. per minute
to a temperature of -50.degree. C. All testing was run with a
55-cubic centimeter per minute nitrogen (industrial grade) purge on
the test chamber.
[0097] The results were then evaluated using the THERMAL ANALYST
2200 (version 8.10) analysis software program, which identified and
quantified the glass transition temperature of inflection, the
endothermic and exothermic peaks, and the areas under the peaks on
the DSC plots. The glass transition temperature was identified as
the region on the plot-line where a distinct change in slope
occurred, and the melting temperature was determined using an
automatic inflection calculation. The areas under the peaks on the
DSC plots were determined in terms of joules per gram of sample
(J/g). For example, the heat of fusion of a resin or fiber sample
was determined by integrating the area of the endothermic peak. The
area values were determined by converting the areas under the DSC
plots (e.g. the area of the endotherm) into the units of joules per
gram (Jig) using computer software.
[0098] Fiber Tenacity:
[0099] Individual fiber specimens were carefully extracted from an
unbonded portion of a fiber web in a manner that did not
significantly pull on the fibers. These fiber specimens were
shortened (e.g. cut with scissors) to 38 millimeters in length, and
placed separately on a black velvet cloth. 10 to 15 fiber specimens
were collected in this manner. The fiber specimens were then
mounted in a substantially straight condition on a rectangular
paper frame having external dimension of 51 millimeters.times.51
millimeters and internal dimension of 25 millimeters.times.25
millimeters. The ends of each fiber specimen were operatively
attached to the frame by carefully securing the fiber ends to the
sides of the frame with adhesive tape. Each fiber specimen was then
be measured for its external, relatively shorter, cross-fiber
dimension employing a conventional laboratory microscope, which has
been properly calibrated and set at 40.times. magnification. This
cross-fiber dimension was recorded as the diameter of the
individual fiber specimen. The frame helped to mount the ends of
the sample fiber specimens in the upper and lower grips of a
constant rate of extension type tensile tester in a manner that
avoided excessive damage to the fiber specimens.
[0100] A constant rate of extension type of tensile tester and an
appropriate load cell were employed for the testing. The load cell
was chosen (e.g. 10N) so that the test value fell within 10-90% of
the full scale load. The tensile tester (i.e., MTS SYNERGY 200) and
load cell were obtained from MTS Systems Corporation of Eden
Prairie, Mich. The fiber specimens in the frame assembly were then
mounted between the grips of the tensile tester such that the ends
of the fibers were operatively held by the grips of the tensile
tester. Then, the sides of the paper frame that extended parallel
to the fiber length were cut or otherwise separated so that the
tensile tester applied the test force only to the fibers. The
fibers were then subjected to a pull test at a pull rate and grip
speed of 12 inches per minute. The resulting data was analyzed
using a TESTWORKS 4 software program from the MTS Corporation with
the following test settings:
TABLE-US-00001 Calculation Inputs Test Inputs Break mark drop 50%
Break sensitivity 90% Break marker elongation 0.1 in Break
threshold 10 g.sub.f Nominal gage length 1 in Data Acq, Rate 10 Hz
Slack pre-load 1 lb.sub.f Denier length 9000 m Slope segment length
20% Density 1.25 g/cm.sup.3 Yield offset 0.20% Initial speed 12
in/min Yield segment length 2% Secondary speed 2 in/min
[0101] The tenacity values were expressed in terms of gram-force
per denier.
Example 1
[0102] An aliphatic-aromatic copolyester resin was initially
obtained from BASF under the designation ECOFLEX.RTM. F BX 7011.
The copolyester resin was modified by melt blending with a reactant
solution. For Samples 1 and 4 (see Table 1), the reactant solution
contained 89 wt. % 1,4-butanediol and 11 wt. % acetone. For Samples
2, 3, 5, and 6 (see Table 1), the reactant solution contained 87
wt. % 1,4-butanediol, 11 wt. % acetone, and 2 wt. % dibutyltin
diacetate (the catalyst). The solution was fed by an Eldex pump to
a liquid injection port located at barrel #4 of a co-rotating,
twin-screw extruder (USALAB Prism H16, diameter: 16 mm, L/D of
40/1) manufactured by Thermo Electron Corporation. The resin was
fed to the twin screw extruder at barrel #1. The screw length was
25 inches. The extruder had one die opening having a diameter of 3
millimeters. Upon formation, the extruded resin was cooled on a
fan-cooled conveyor belt and formed into pellets by a Conair
pelletizer. Reactive extrusion parameters were monitored on the
USALAB Prism H16 extruder during the reactive extrusion process.
The conditions are shown below in Table 1.
TABLE-US-00002 TABLE 1 Reactive Extrusion Process Conditions for
modifying Ecoflex F BX 7011 on a USALAB Prism H16 Sample
Temperature (.degree. C.) Screw Speed Resin Rate Reactant No. Zone
1, 2, 3-8, 9, 10 (rpm) (lb/h) (% of resin rate) F BX 7011 90 125
165 125 110 150 2.6 0 1 90 125 165 125 110 150 2.6 4 (No catalyst)
2 90 125 165 125 110 150 2.6 4 3 90 125 180 125 110 150 2.6 4 4 90
125 190 125 110 150 2.6 4 (No catalyst) 5 90 125 190 125 110 150
2.6 4 6 90 125 200 125 110 150 2.6 4
[0103] The melt rheology was studied for the unmodified
ECOFLEX.RTM. F BX 7011 and Samples 1-6 (modified with 1,4
butanediol). The measurement was carried out on a Goettfert
Rheograph 2003 (available from Goettfert of Rock Hill, S.C.) at
170.degree. C. with a 30/1 (Length/Diameter) mm/mm die. The
apparent melt viscosity was determined at apparent shear rates of
100, 200, 500, 1000, 2000 and 5000 s.sup.-1. The apparent melt
viscosities at the various apparent shear rates were plotted and
the rheology curves were generated as shown in FIG. 2. As
illustrated, the apparent viscosity of the control sample
(unmodified ECOFLEX.RTM. resin) was much higher than the apparent
viscosities of Samples 1-6. The melt flow indices of the samples
were also determined with a Tinius Olsen Extrusion plastometer
(170.degree. C., 2.16 kg). Further, the samples were subjected to
molecular weight (MW) analysis by GPC with narrow MW distribution
polystyrenes as standards. The results are set forth below in Table
2.
TABLE-US-00003 TABLE 2 Properties of modified Ecoflex F BX 7011 on
a USALAB Prism H16 Apparent Viscosity Melt Flow (Pa s at rate
apparent (g/10 min Average Mol. Poly- Sample shear rate at
170.degree. C. Wt (g/mol) dispersity No. of 1000/s) and 2.16 kg) Mw
Mn (Mw/Mn) F BX 7011 498 1.65 125206 73548 1.7 1 365 9.6 114266
67937 1.68 2 51 230 77391 41544 1.86 3 37 377 71072 39767 1.79 4
241 14 109317 66507 1.64 5 38 475 65899 35529 1.85 6 22 571 56809
29316 1.94
[0104] As indicated, the melt flow indices of the modified resins
(Samples 1-6) were significantly greater than the control sample.
In addition, the weight average molecular weight (M.sub.w) and
number average molecular weight (M.sub.n) were decreased in a
controlled fashion, which confirmed that the increase in melt flow
index was due to alcoholysis with butanediol. The resulting
modified aliphatic-aromatic copolyesters had hydroxybutyl terminal
groups.
Example 2
[0105] The modification of ECOFLEX.RTM. F BX 7011 by monohydric
alcohols was demonstrated with 1-butanol, 2-propanol, and
2-ethoxy-ethanol as examples of monohydric alcohols. The
experimental set-up was the same as described in Example 1. The
process conditions are shown in Table 3. Dibutyltin diacetate was
the catalyst used. As shown in Table 3, the torque decreased as
monohydric alcohol was fed to the extruder. The torque was further
decreased as monohydric alcohol and catalyst were both fed to the
extruder.
TABLE-US-00004 TABLE 3 Reactive Extrusion Conditions for modifying
Ecoflex F BX 7011 on a USALAB Prism H16 with monohydric alcohols
Sample Temperature ( .degree. C.) Screw Speed Resin Rate Reactant
Catalyst Torque I.D. Zone 1, 2, 3-8, 9, 10 (rpm) (lb/h) (% of resin
rate) (% of resin rate) (%) F BX 7011 90 125 180 125 110 150 2.5 0
0 >100 7 90 125 180 125 110 150 2.5 3.4%, 2-Propanol 0 90 8 90
125 180 125 110 150 2.5 3.4%, 2-Propanol 0.1 80 9 90 125 180 125
110 150 2.5 3.6%, 1-Butanol 0 72 10 90 125 180 125 110 150 2.5
3.6%, 1-Butanol 0.1 54 11 90 125 180 125 110 150 2.5 4%,
2-Ethoxy-ethanol 0 64 12 90 125 180 125 110 150 2.5 4%,
2-Ethoxy-ethanol 0.1 58
[0106] The apparent viscosity and molecular weight were determined
for each sample as described in Example 1. The results are shown
below in Table 4.
TABLE-US-00005 TABLE 4 Properties of modified Ecoflex F BX 7011
with monohydric alcohols on a USALAB Prism H16 Apparent Viscosity
(Pa s at Average Mol. Sample apparent shear Wt (g/mol)
Polydispersity I.D. rate of 1000 1/s) Mw Mn (Mw/Mn) F BX 7011 376
128100 77200 1.66 7 364 120800 71800 1.68 8 273 115000 69400 1.66 9
292 115900 70800 1.64 10 126 89800 51000 1.76 11 324 116800 71000
1.64 12 215 104100 60500 1.72
[0107] As indicated, Samples 7-12 had lower apparent viscosities
and molecular weights over the entire range of shear rates than the
control sample. The resulting modified copolyesters had alkyl
terminal groups that are compositionally different than the
unmodified copolyester.
Example 3
[0108] Modification of ECOFLEX.RTM. F BX 7011 with 1,4-butanediol
was performed as described in Example 1 using titanium propoxide
("Ti-P"), titanium butoxide ("Ti-B") and titanium isopropoxide
("Ti-IsoP") catalysts. During the reactive extrusion process, the
torques of the extruder were moderately decreased with the addition
of only 1,4-butanediol, and further decreased with the addition of
the titanium catalysts. The process conditions are shown in Table
5. The resulting modified copolyesters have hydroxybutyl terminal
groups.
TABLE-US-00006 TABLE 5 Reactive Extrusion Process Conditions for
modifying Ecoflex F BX 7011 on a USALAB Prism H16 with
1,4-butanediol and titanium catalysts Sample Temperature ( .degree.
C.) Screw Speed Resin Rate 1,4-butanediol Catalyst Torque I.D. Zone
1, 2, 3-8, 9, 10 (rpm) (lb/h) (% of resin rate) (ppm of resin rate)
(%) F BX 7011 95 145 180 130 100 150 3 0 0 >100 13 95 145 180
130 100 150 3 2 0 85 14 95 145 180 130 100 150 3 3.5 0 75 15 95 145
180 130 100 150 3 2 400, TI-P 69 16 95 145 180 130 100 150 3 3.5
700, Ti-P 48 17 95 145 180 130 100 150 3 2 400, Ti-B 76 18 95 145
180 130 100 150 3 3.5 700, Ti-B 55 19 95 145 180 130 100 150 3 2
400, Ti-IsoP 79 20 95 145 180 130 100 150 3 3.5 700, Ti-IsoP 64
[0109] The apparent viscosity and molecular weight were determined
for each sample as described in Example 1. The results are shown in
FIG. 3 and Table 6.
TABLE-US-00007 TABLE 6 Properties of modified Ecoflex F BX 7011
with monohydric alcohols on a USALAB Prism H16 Apparent Viscosity
(Pa s at Average Mol. Sample apparent shear Wt (g/mol)
Polydispersity I.D. rate of 1000 1/s) Mw Mn (Mw/Mn) F BX 7011 376
128100 77200 1.66 13 297 112800 71000 1.7 14 219 102000 60100 1.83
15 198 97050 57050 1.74 16 60 69100 37600 1.67 17 218 103700 61800
1.6 18 95 89900 51600 1.7 19 243 110200 64100 1.68 20 87 100300
59900 1.72
[0110] As shown in FIG. 3, the viscosity of Sample 16 (titanium
propoxide catalyst) was significant lower than Sample 14 (no
catalyst) over the entire range of shear rates. In addition, the
molecular weights of Samples 13-20 were less than the control
sample.
Example 4
[0111] An aliphatic-aromatic copolyester resin was obtained from
BASF under the designation ECOFLEX.RTM. F BX 7011. A reactant
solution contained 87.5 wt. % 1,4-butanediol, 7.5 wt. % ethanol,
and 5 wt. % titanium propoxide was made. A co-rotating, twin-screw
extruder was employed (ZSK-30, diameter of 30 millimeters) that was
manufactured by Werner and Pfleiderer Corporation of Ramsey, N.J.
The screw length was 1328 millimeters. The extruder had 14 barrels,
numbered consecutively 1-14 from the feed hopper to the die. The
first barrel (#1) received the ECOFLEX.RTM. F BX 7011 resin via a
volumetric feeder at a throughput of 30 pounds per hour. The fifth
barrel (#5) received the reactant solution via a pressurized
injector connected with an Eldex pump at a final rate of 0 to 1 wt.
% 1,4-butanediol and 0 to 700 parts per million ("ppm") titanium
propoxide, respectively. The screw speed was 150 revolutions per
minute ("rpm"). The die used to extrude the resin had 4 die
openings (6 millimeters in diameter) that were separated by 3
millimeters. Upon formation, the extruded resin was cooled on a
fan-cooled conveyor belt and formed into pellets by a Conair
pelletizer. Reactive extrusion parameters were monitored during the
reactive extrusion process. The conditions are shown below in Table
7.
TABLE-US-00008 TABLE 7 Process Conditions for Reactive Extrusion of
Ecoflex F BX 7011 with 1,4-Butanediol on a ZSK-30 Extruder Resin
Reactants Extruder Samples feeding rate Butanediol Titanium speed
Extruder temperature profile (.degree. C.) Torque No. (lb/h) (%)
Propoxide (ppm) (rpm) T.sub.1 T.sub.2 T.sub.3 T.sub.4 T.sub.5
T.sub.6 T.sub.7 T.sub.melt P.sub.melt (%) F BX 7011 30 0 0 150 160
170 185 185 185 185 100 116 400 >100 21 30 1 0 150 160 171 184
185 185 185 100 108 300 >100 22 30 0.75 375 150 160 170 185 185
185 185 100 110 70 85-90 23 30 1 700 150 160 170 185 185 185 185
100 110 30 66-72
[0112] As indicated, the addition of 1 wt. % butanediol alone
(Sample 21) did not significantly decrease the torque of the
control sample, although the die pressure did drop from 300 to 130
pounds per square inch ("psi"). With the addition of 1 wt. %
1,4-butanediol and 700 ppm titanium propoxide (Sample 23), both the
torque and die pressure decreased significantly to 66-72% and 30
psi, respectively. The torque and die pressure could be
proportionally adjusted with the change of reactant and
catalyst.
[0113] Melt rheology tests were also performed with the control
sample and Samples 21-23 on a Goettfert Rheograph 2003 (available
from Goettfert in Rock Hill, S.C.) at 180.degree. C. and
190.degree. C. with 30/1 (Length/Diameter) mm/mm die. The apparent
melt viscosity was determined at apparent shear rates of 100, 200,
500, 1000, 2000 and 4000 s.sup.-1. The results are shown in FIG. 4.
As indicated, Samples 21-23 had much lower apparent viscosities
over the entire range of shear rates than the control sample. The
melt flow index of the sample was determined by the method of ASTM
D1239, with a Tinius Olsen Extrusion Plastometer at 190.degree. C.
and 2.16 kg. Further, the samples were subjected to molecular
weight (MW) analysis by GPC with narrow MW polystyrenes as
standards. The results are set forth below in Table 8.
TABLE-US-00009 TABLE 8 Properties of unmodified and modified
Ecoflex F BX 7011 on a ZSK-30 Apparent Viscosity (Pa s Melt at
apparent Flow rate shear rate (g/10 min Average Mol. Poly- Sample
of 1000/s at at 190.degree. C. Wt (g/mol) dispersity No.
180.degree. C.) and 2.16 kg) Mw Mn (Mw/Mn) F BX 7011 321 4.5 125200
73500 1.7 Control 294 6.8 117900 72100 1.64 21 182 24 100400 60500
1.66 22 112 68 82800 46600 1.78 23 61 169 68900 37600 1.83
[0114] As indicated, the melt flow indices of the modified resins
(Samples 21-23) were significantly greater than the control sample.
In addition, the weight average molecular weight (M.sub.w) and
number average molecular weight (M.sub.n) were decreased in a
controlled fashion, which confirmed that the increase in melt flow
index was due to alcoholysis with butanediol catalyzed. Table 9,
which is set forth below, also lists the data from DSC analysis of
the control sample and Samples 21-23.
TABLE-US-00010 TABLE 9 DSC Analysis Glass transition Melting Peak
Enthalpy temperature, T.sub.g Temperature, T.sub.m of melting
Sample (.degree. C.) (.degree. C.) (J/g) Ecoflex .RTM. F BX 7011
-30.1 123.3 11.7 Control -31.5 123.5 10.1 21 -35.1 127 10.7 22
-32.5 124.7 11.6 23 -34.2 125.1 12
[0115] As indicated, Samples 22 and 23 (modified with
1,4-butanediol) exhibited little change in their T.sub.g and
T.sub.m compared with the control samples.
Example 5
[0116] As described in Example 4, a ZSK-30 extruder was used to
form various samples (Samples 24-28). For Sample 24, the first
barrel (#1) received 90 wt. % ECOFLEX.RTM. F BX 7011 resin via a
volumetric feeder, and the seventh barrel (#7) received 10 wt. %
boron nitride via a side feeder, at a total throughput of 20 pounds
per hour. For Sample 25, the first barrel (#1) received 80 wt. %
ECOFLEX.RTM. F BX 7011 resin and 20% EnPol.RTM. polybutylene
succinate G-4500 via two volumetric feeders, at a total throughput
of 20 pounds per hour. For Sample 26, the first barrel (#1)
received 90 wt. % ECOFLEX.RTM. F BX 7011 resin and 10 wt. %
ENMAT.RTM. polyhydroxybutyrate-co-valerate via two volumetric
feeders, at a total throughput of 30 pounds per hour. For Sample
27, the first barrel (#1) received 85 wt % ECOFLEX.RTM. F BX 7011
resin and 10 wt. % Biomer.RTM. polyhydroxybutyrate P-226 via two
volumetric feeders, and seventh barrel (#7) received 5% (w/w) boron
nitride via a side feeder, at a total throughput of 20 pounds per
hour. Finally, for Sample 28, the first barrel (#1) received 90 wt.
% ECOFLEX.RTM. F BX 7011 resin and 10 wt. % Sample 27 via two
volumetric feeders at a total throughput of 30 lb/h, and the fifth
barrel (#5) received a reactant solution via a pressurized injector
connected with an Eldex pump at a final rate of 0.5 wt. %
1,4-butanediol and 350 parts per million ("ppm") titanium
propoxide, respectively.
[0117] The die used to extrude the resins had 4 die openings (6
millimeters in diameter) that were separated by 3 millimeters. Upon
formation, the extruded resin was cooled on a fan-cooled conveyor
belt and formed into pellets by a Conair pelletizer. Reactive
extrusion parameters were monitored and recorded. The conditions
are shown below in Table 10.
TABLE-US-00011 TABLE 10 Process Conditions on a ZSK-30 Extruder
Resin Reactants Extruder Samples feeding rate Butanediol Titanium
speed Extruder temperature profile ( .degree. C.) Torque No. (lb/h)
(%) Propoxide (ppm) (rpm) T.sub.1 T.sub.2 T.sub.3 T.sub.4 T.sub.5
T.sub.6 T.sub.7 T.sub.melt P.sub.melt (%) 24 20 N/A N/A 150 150 160
180 180 180 175 170 192 120 95 25 20 N/A N/A 150 150 155 170 170
170 170 160 180 220 85 26 30 N/A N/A 150 150 180 180 185 180 180
165 181 95 75 27 20 N/A N/A 160 130 180 180 180 180 180 115 127 180
90 28 30 0.5 350 160 150 190 190 190 190 190 125 137 70 88
Example 6
[0118] As described in Example 1, a USALAB Prism H16 extruder was
used to prepare various samples (Samples 29-32) for evaluating
their fiber spinning capacity. For Sample 29, ECOFLEX.RTM. F BX
7011 resin was fed into extruder at Barrel #1, and a reactant
solution of 2.7 wt. % of 1,4-butanediol and 700 ppm of titanium
propoxide (TP) was injected into the extruder by an Eldex pump via
a liquid injection port located at Barrel #4, at a total throughput
of 3 pounds per hour. For Sample 30, ECOFLEX.RTM. F BX 7011 resin
was fed into the extruder at Barrel #1 and a reactant solution of
2.7 wt. % of 1-butanol and 700 ppm of dibutylene diacetate (DBDA)
was injected into the extruder by an Eldex pump via a liquid
injection port located at barrel #4, at a total throughput of 3
pounds per hour. For Sample 31, a dry blend of 90 wt. %
ECOFLEX.RTM. F BX 7011 and 10 wt. % Sample 24 was fed into the
extruder at Barrel #1, and a reactant solution of 2.7 wt. % of
1,4-butanediol and 700 ppm of dibutylene diacetate (DBDA) was
injected into the extruder by an Eldex pump via a liquid injection
port located at Barrel #4, at a total throughput of 3 pounds per
hour. For Sample 32, a dry blend of 90 wt. % ECOFLEX.RTM. F BX 7011
and 10 wt. % Sample 26 was fed into the extruder at Barrel #1, and
a reactant solution of 2.7 wt. % of 1,4-butanediol and 700 ppm of
dibutylene diacetate (DBDA) was injected into extruder by an Eldex
pump via a liquid injection port located at Barrel #4, at a total
throughput of 3 pounds per hour. The extruder profiles were
monitored and recorded. The conditions are shown below in Table
11.
TABLE-US-00012 TABLE 11 Reactive extrusion process conditions for
producing modified Ecoflex BFX 7011 Sample Temperature (.degree.
C.) Screw Speed Resin Rate Reactant Catalyst Torque I.D. Zone 1, 2,
3-8, 9, 10 (rpm) (lb/h) % of resin rate (ppm) (%) 29 95 125 180 125
100 150 3 2.7%, 1,4-butanediol 700, DBDA 64 30 95 125 180 125 100
150 3 2.7%, 1-butanol 700, DBDA 61 31 95 125 180 125 100 150 3
2.7%, 1,4-butanediol 700, DBDA 59 32 95 125 180 125 100 150 3 2.7%,
1,4-butanediol 700, TP 64
Example 7
[0119] Fiber spinning was conducted with a pilot Davis Standard
fiber spinning line consisting of two extruders, a quench chamber
and a godet with a maximal speed of 3000 m/min. The spinning die
plate used for these samples was a 16 holes plate with each hole
with a diameter of 0.6 mm. Sample 29-32 were pre-dried at
70.degree. C. before fiber spinning. Unmodified Ecoflex.RTM. F BX
7011 was also spun at an extruder speed of 5 rpm and 150.degree. C.
Extruder pressure rose quickly above 3650 psi and shut off. No
fiber was collected. Unmodified Ecoflex.RTM. F BX 7011 preblended
with 20% PBS (Sample 25) was also spun at an extruder speed of 5
rpm, pressure of 2500 psi and temperature of 160.degree. C. Fibers
could only be drawn up to 200 m/min before break up. Fiber samples
were analyzed on a MTS Synergie 200 tensile tester. The fiber
spinning conditions and resulting fiber properties are shown in
Table 12.
TABLE-US-00013 TABLE 12 Fiber spinning conditions and fibers
properties of modified Ecoflex resins Godet Ext. Ext. Ext. Spin Die
Peak Peak Strain at Samples speed Temp speed press. Temp Diameter
Load Stress Break No. m/min .degree. C. rpm Psi .degree. C. micron
gf Mpa % Denier Tenacity 29 1500 145 10 2225 135 24.3 4.12 88 104
5.3 0.8 30 1500 160 5 1300 160 16.8 2.4 105.4 103.1 2.5 0.96 31
2200 150 5 990 150 12.8 1.47 112.3 29.5 1.45 1.02 32 1500 160 10
2060 150 24.9 4.48 89.6 166.2 5.51 0.81
Example 8
[0120] Bicomponent fibers with modified Ecoflex.RTM. F BX 7011
(Sample 28) as sheath and NatureWorks PLA 6201D as the core were
also spun using the fiber spinning line of Example 7. The
sheath/core ratios of the resulting bicomponent fibers for Sample
33 and Sample 34 were 20/80 and 30/70, respectively. Fiber spinning
conditions are listed in Table 13.
TABLE-US-00014 TABLE 13 Fiber spinning conditions for making
modified Ecoflex/PLA bicomponent fibers Temperature (.degree. C.)
Pressure Melt Pump Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Zone 7
Psi rpm Extruder 1 160 170 170 180 180 180 180 140 1-1.5 Extruder 2
195 205 215 220 220 225 225 105 3.5-4 Lower SP Upper SP Chimney
Spinbeam Quench Setpoints (.degree. C.) / / 100 240 Lower Mid-Lower
Mid-Upper Upper Lower Air Upper Air Quench Readings (.degree. C.)
25 28 27 28 390 432 Godet Speed (m/min) 2500
[0121] The resulting fibers were analyzed on a MTS Synergie 200
tensile tester. The properties are listed as in Table 14.
TABLE-US-00015 TABLE 14 Properties of modified Ecoflex and PLA
bicomponent fibers Samples Sheath Core Diamter (micron) Peak load
(gf) Peak Stress (Mpa) Strain at Break (%) Denier Tenacity No. (%)
(%) Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD 33 20 80 10.5 1
2.1 0.2 242 49 67.2 12.4 0.98 0.19 2.2 0.44 34 30 70 11 0.88 2 0.28
208 29 65.9 8.9 1.1 0.17 1.9 0.26
[0122] While the invention has been described in detail with
respect to the specific embodiments thereof, it will be appreciated
that those skilled in the art, upon attaining an understanding of
the foregoing, may readily conceive of alterations to, variations
of, and equivalents to these embodiments. Accordingly, the scope of
the present invention should be assessed as that of the appended
claims and any equivalents thereto.
* * * * *