U.S. patent application number 09/814032 was filed with the patent office on 2002-11-21 for compositions for enhanced thermal bonding.
Invention is credited to Aroch, Maya, Day, Bryon P., Griffith, Nina Cecilia, Ning, Xin.
Application Number | 20020172823 09/814032 |
Document ID | / |
Family ID | 25214028 |
Filed Date | 2002-11-21 |
United States Patent
Application |
20020172823 |
Kind Code |
A1 |
Griffith, Nina Cecilia ; et
al. |
November 21, 2002 |
COMPOSITIONS FOR ENHANCED THERMAL BONDING
Abstract
A composition including an aromatic polyester and a copolyester
having a lower melting point than the aromatic polyester. The
aromatic polyester and the copolyester can be blended together to
form fibers and fibrous webs. The composition can be thermally
bonded at a temperature below the melting point of the aromatic
polyester.
Inventors: |
Griffith, Nina Cecilia;
(Atlanta, GA) ; Ning, Xin; (Alpharetta, GA)
; Day, Bryon P.; (Canton, GA) ; Aroch, Maya;
(Atlanta, GA) |
Correspondence
Address: |
Pauley Petersen Kinne & Fejer
Suite 365
2800 W. Higgins Road
Hoffman Estates
IL
60195
US
|
Family ID: |
25214028 |
Appl. No.: |
09/814032 |
Filed: |
March 21, 2001 |
Current U.S.
Class: |
428/373 ;
442/401; 525/437 |
Current CPC
Class: |
Y10T 428/2929 20150115;
C08L 67/02 20130101; Y10T 428/2967 20150115; D01F 8/14 20130101;
Y10T 428/2931 20150115; Y10T 442/681 20150401; D01F 6/92 20130101;
Y10T 428/29 20150115; Y10T 428/2913 20150115; Y10T 442/60 20150401;
C08L 67/02 20130101; C08L 2666/18 20130101 |
Class at
Publication: |
428/373 ;
525/440 |
International
Class: |
D02G 003/00; C08F
020/00 |
Claims
We claim:
1. A composition comprising: between 5 and 50 wt % of a
copolyester; and between 50 and 95 wt % of an aromatic polyester;
wherein the copolyester has a lower melting point than the aromatic
polyester.
2. The composition of claim 1, wherein the copolyester comprises an
aliphatic copolyester.
3. The composition of claim 1, wherein the copolyester comprises an
aromatic copolyester.
4. The composition of claim 1, wherein the copolyester comprises an
aromatic copolyester selected from the group consisting of a
semicrystalline copolyethylene ester and an amorphous
copolyethylene ester.
5. The composition of claim 1, wherein the aromatic polyester is
selected from the group consisting of polyethylene terephthalate,
polytrimethylene terephthalate, and polybutylene terephthalate, and
combinations thereof.
6. The composition of claim 1, further comprising between 10 and 40
wt % of the copolyester and between 60 and 90 wt % of the aromatic
polyester.
7. The composition of claim 1, further comprising between 15 and 30
wt % of the copolyester and between 70 and 85 wt % of the aromatic
polyester.
8. The composition of claim 1, wherein the copolyester has a
melting point about 100 to 175 degrees Fahrenheit lower than the
aromatic polyester.
9. The composition of claim 1, wherein the copolyester has a
melting point about 110 to 170 degrees Fahrenheit lower than the
aromatic polyester.
10. The composition of claim 1, wherein the copolyester has a
melting point about 115 to 165 degrees Fahrenheit lower than the
aromatic polyester.
11. A fiber comprising the composition of claim 1.
12. A multi-fiber yarn comprising the composition of claim 1.
13. A woven fabric comprising the composition of claim 1.
14. A nonwoven web comprising the composition of claim 1.
15. A fiber comprising a blend of an aliphatic copolyester and an
aromatic polyester on an outer surface of the fiber; wherein the
aliphatic copolyester has a lower melting point than the aromatic
polyester.
16. The fiber of claim 15, further comprising a first component and
a second component in a side-by-side arrangement, wherein the first
component includes the aliphatic copolyester and the aromatic
polyester and the second component includes a polymer.
17. The fiber of claim 15, further comprising: a core; and a sheath
including between 50 and 95 wt % of the aromatic polyester and
between 5 and 50 wt % of the aliphatic copolyester.
18. The fiber of claim 17, wherein the core comprises a polymer
selected from the group consisting of polyamides, polyesters, and
polyolefins.
19. The fiber of claim 17, wherein the core comprises an aromatic
polyester.
20. A fiber comprising a blend of an aromatic copolyester and an
aromatic polyester on an outer surface of the fiber; wherein the
aromatic copolyester has a lower melting point than the aromatic
polyester.
21. The fiber of claim 20, further comprising a first component and
a second component in a side-by-side arrangement, wherein the first
component includes the aromatic copolyester and the aromatic
polyester and the second component includes a polymer.
22. The fiber of claim 20, further comprising: a core; and a sheath
including between 50 and 95 wt % of the aromatic polyester and
between 5 and 50 wt % of the aromatic copolyester.
23. The fiber of claim 22, wherein the core comprises a polymer
selected from the group consisting of polyamides, polyesters, and
polyolefins.
24. The fiber of claim 22, wherein the core comprises an aromatic
polyester.
Description
FIELD OF THE INVENTION
[0001] This invention is directed to compositions that can be
thermally bonded at relatively low temperatures.
BACKGROUND OF THE INVENTION
[0002] Aromatic polyesters, such as polyethylene terephthalate
(PET), polytrimethylene terephthalate (PTT), and polybutylene
terephthalate (PBT), are widely used in fiber forming applications.
However, the use of aromatic polyesters in nonwoven applications
has been hindered by the inability of aromatic polyesters to be
thermally bonded at relatively moderate bonding temperatures, such
as those used for polypropylene, because polyesters have relatively
high melting points.
[0003] Aliphatic copolyesters, which may or may not have an
aromatic structure, typically have much lower melting points than
aromatic polyesters. The melting points of aliphatic copolyesters
are in about the same range as those of polyolefins. Similarly,
aromatic copolyesters also melt at lower temperatures than typical
aromatic polyesters. However, aliphatic copolyesters and aromatic
copolyesters typically have less desirable fiber forming properties
than aromatic polyesters.
[0004] There is a need or desire for compositions having favorable
fiber forming properties as well as the ability to be thermally
bonded at relatively moderate bonding temperatures.
SUMMARY OF THE INVENTION
[0005] The present invention is directed to fiber forming
compositions made from aliphatic copolyesters blended with aromatic
polyesters, and to fibrous webs made from these compositions. The
present invention is also directed to fiber forming compositions
made from aromatic copolyesters blended with aromatic polyesters,
and to fibrous webs made from these compositions.
[0006] Fibrous webs made from the compositions of the invention can
be thermally bonded to other fibrous webs, and/or to each other, at
substantially lower temperatures than the aromatic polyesters
themselves. The fiber forming capability of base polymers is
maintained in the compositions despite the presence of the
aliphatic copolyesters or aromatic copolyesters.
[0007] The blending of these compositions can be achieved with a
twin-screw extruder or a single screw extruder, for example.
Furthermore, the compositions can have as little as 5 wt % of
aliphatic copolyester or aromatic copolyester for detectable
beneficial reduction in bonding temperature.
[0008] The compositions of the invention can be in the form of
fibers, including nonwoven fibers.
[0009] With the foregoing in mind, it is a feature and advantage of
the invention to provide compositions having favorable fiber
forming properties as well as the ability to be thermally bonded at
relatively moderate bonding temperatures.
DEFINITIONS
[0010] Within the context of this specification, each term or
phrase below will include the following meaning or meanings.
[0011] "Aliphatic compounds" are organic compounds characterized by
a straight or branched-chain arrangement of the constituent carbon
atoms. Aliphatic hydrocarbons include three subgroups. The first
subgroup is paraffins (alkanes) which are saturated and
comparatively unreactive. The second subgroup is olefins (alkenes
or alkadienes), which are unsaturated and quite reactive. The third
subgroup is acetylenes (alkynes), which contain a triple bond and
are highly reactive.
[0012] "Aliphatic copolyesters" are copolymers of aliphatic
compounds and polyesters. These include copolymers of aliphatic
compounds with aromatic polyesters, as well as copolymers of
aliphatic compounds with polyesters that are not aromatic.
[0013] "Amorphous copolyethylene ester" is a type of copolyester
that lacks a distinct crystalline structure.
[0014] "Aromatic compounds" are cyclic hydrocarbons containing one
or more rings, typified by benzene, each ring having six carbon
atoms and three double bonds.
[0015] "Aromatic copolyesters" are copolymers of aromatic compounds
and polyesters. These include copolymers of aromatic compounds with
aromatic polyesters, as well as copolymers of aromatic compounds
with polyesters that are not aromatic.
[0016] "Aromatic polyesters" are polyesters containing at least one
aromatic molecule or compound. Aromatic polyesters include, for
instance, polyethylene terephthalate (PET), polytrimethylene
terephthalate (PTT), polybutylene terephthalate (PBT), and their
copolymers and the like.
[0017] "Polyesters" are a group of synthetic resins that are
polycondensation products of dicarboxylic acids with dihydroxy
alcohols.
[0018] "Polymers" include, but are not limited to, homopolymers,
copolymers, such as for example, block, graft, random and
alternating copolymers, terpolymers, etc. and blends and
modifications thereof. Furthermore, unless otherwise specifically
limited, the term "polymer" shall include all possible geometrical
configurations of the material. These configurations include, but
are not limited to isotactic, syndiotactic and atactic
symmetries.
[0019] "Semicrystalline copolyethylene ester" is a type of
copolyester that includes about 40 to 60% crystalline matter and
about 40 to 60% amorphous matter.
[0020] "Spunbonded fiber" refers to small diameter fibers which are
formed by extruding molten thermoplastic material as filaments from
a plurality of fine capillaries of a spinnerette having a circular
or other configuration, with the diameter of the extruded filaments
then being rapidly reduced as by, for example, in U.S. Pat. No.
4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to Dorschner
et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S. Pat. Nos.
3,338,992 and 3,341,394 to Kinney, U.S. Pat. No. 3,502,763 to
Hartmann, U.S. Pat. No. 3,502,538 to Petersen, and U.S. Pat. No.
3,542,615 to Dobo et al., each of which is incorporated herein in
its entirety by reference. Spunbond fibers are quenched and
generally not tacky when they are deposited onto a collecting
surface. Spunbond fibers are generally continuous and often have
average deniers larger than about 0.3, more particularly, between
about 0.6 and 10.
[0021] These terms may be defined with additional language in the
remaining portions of the specification.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0022] The compositions of the invention include a blend of an
aliphatic copolyester and an aromatic polyester. As a result, the
compositions can be bonded to fabrics at relatively low
temperatures, and can have relatively good fiber forming
capabilities. In the case of fibrous webs made from the
compositions of the invention, the fibers can also be more easily
thermally bonded to each other, for example, in a spunbonding
process.
[0023] In general, aliphatic copolyesters have lower melting points
than aromatic polyesters. In fact, the melting points of aliphatic
copolyesters are in the same range as the melting points of
polyolefins. However, the fiber forming capabilities of aliphatic
copolyesters do not even come close to the excellent fiber forming
capabilities of aromatic polyesters. By blending an aliphatic
copolyester with an aromatic polyester, the resulting compositions
can be bonded at substantially lower temperatures than the aromatic
polyester and can maintain the fiber forming capability of the
aromatic polyester. Furthermore, beneficial reduction in bonding
temperature can be exhibited when as little as 5 wt % of aliphatic
copolyester is present in the composition.
[0024] Suitable aromatic polyesters for use in this invention
include, without limitation, polyethylene terephthalate (PET),
polytrimethylene terephthalate (PTT), polybutylene terephthalate
(PBT), and combinations thereof. These aromatic polyesters are
widely used in fiber forming applications.
[0025] Suitable aliphatic copolyesters can be prepared by reacting
diols and diacids (or diesters or anhydrides) at temperatures from
about 150 degrees Celsius to about 300 degrees Celsius in the
presence of polycondensation catalysts such as titanium
tetrachloride, manganese diacetate, antimony oxide, dibutyl tin
diacetate, zinc chloride, or combinations thereof. The catalysts
are typically employed in amounts between 10 to 1000 ppm, based on
total weight of the reactants. The final stages of the reaction are
generally conducted under high vacuum (<10 mm Hg) in order to
produce a high molecular weight polyester.
[0026] Suitable aliphatic copolyesters can also be prepared using
(as the aliphatic component) aliphatic polyhydric alcohol,
aliphatic polycarboxylic acid and hydroxycarboxylic acid. Examples
of aliphatic polyhydric alcohols that can be used include ethylene
glycol, diethylene glycol, triethylene glycol, polyethylene glycol,
propylene glycol, dipropylene glycol, 1,3-butanediol,
1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol,
1,9-nonanediol, neopentyl glycol, polytetramethylene glycol,
1,4-cyclohexanedimethanol, 1,4-benzenedimethanol,
trimethylolpropane, trimethylolethane, trimethylolheptane,
1,2,4-butanetriol and 1,2,6-hexanetriol, and combinations thereof.
Examples of aliphatic polycarboxylic acids that can be used include
oxalic acid, malonic acid, succinic acid, glutaric acid, adipic
acid, pimelic acid, suberic acid, azelaic acid, sebacic acid,
undecanoic diacid, dodecanoic diacid and tricarballylic acid, and
combinations thereof.
[0027] A specific example of a suitable aliphatic copolyester is
available under the trade name BOSTIK.RTM. 4178, available from
Bostik of Middleton, Mass. The blends of aliphatic copolyester and
aromatic polyester can be readily formed into fibrous nonwoven
webs.
[0028] Alternatively, in another embodiment of the invention,
aromatic copolyester can be used in place of the aliphatic
copolyester in a nonwoven fabric. Instead of forming a nonwoven web
from a polymer blend of an aliphatic copolyester and an aromatic
polyester, the nonwoven web can contain an aromatic copolyester
blended with an aromatic polyester. Although they may have an
aromatic structure, copolyesters, such as copolyethylene
terephthalate, melt at lower temperatures than typical aromatic
polyester fibers, such as polyethylene terephthalate, and provide
adequate bonding both to the aromatic polyester fibers and to a
web. Examples of suitable aromatic copolyesters include amorphous
copolyethylene esters such as EASTAR.RTM. polyethylene
terephthalate glycol (PETG), available from Eastman Chemical
Company of Kingsport, Tenn., and semicrystalline copolyethylene
esters such as Copolyester 21398, also available from Eastman
Chemical Company.
[0029] In any case, the copolyester in the compositions of the
invention, whether an aliphatic copolyester or an aromatic
copolyester, has a lower melting point than the aromatic polyester
in the compositions. Suitably, the melting point of the copolyester
is about 100 to 175 degrees Fahrenheit lower than the melting point
of the aromatic polyester. For example, the melting point of the
copolyester can be about 110 to 170 degrees Fahrenheit lower than
the melting point of the aromatic polyester. As another example,
the melting point of the copolyester can be about 115 to 165
degrees Fahrenheit lower than the melting point of the aromatic
polyester.
[0030] The compositions of the invention can be formed into fibers
including sheath/core or side-by-side bicomponent fibers, as well
as monocomponent fibers. The fibers may be nonwoven fibers, such as
spunbond fibers, meltblown fibers, air-laid fibers, and staple
fibers. The resulting fibers can be used to make multi-fiber yarn
and woven fabrics, as well as nonwoven webs.
[0031] The compositions of the invention can have as little as 5 wt
% of the copolyester for detectable beneficial reduction in bonding
temperature. The composition suitably includes between about 5 and
about 50 wt % of the copolyester polymer. The composition also
includes between about 50 and about 95 wt % of the aromatic
polyester polymer. For example, the composition can include between
about 10 and about 40 wt % of the copolyester and between about 60
and 90 wt % of the aromatic polyester. As another example, the
composition can include between about 15 and about 30 wt % of the
copolyester and between about 70 and 85 wt % of the aromatic
polyester.
[0032] The polymer blend compositions can be made in a variety of
ways including, for example, using a twin-screw extruder or a
single screw extruder. The polymer blend compositions are then
formed into fibrous webs using conventional fiber-spinning
techniques. Any type of fiber including the polymer blend
composition of the invention suitably has a blend of the
copolyester and the aromatic polyester at least on an outer surface
of the fibers.
[0033] In one embodiment, the polymer blend composition is used as
the sheath component for sheath/core bicomponent fibers. A
sheath/core fiber including the composition of the invention
suitably includes between about 50 and 95 wt % of the aromatic
polyester and between about 5 and 50 wt % of the copolyester in the
sheath. For example, the sheath/core fiber can include between
about 60 and 95 wt % of the aromatic polyester and between about 5
and 40 wt % of the copolyester in the sheath. As another example,
the sheath/core fiber can include between about 70 and 95 wt % of
the aromatic polyester and between about 5 and 30 wt % of the
copolyester in the sheath. The core of the sheath/core fiber can be
made of any suitable polymer. For example, the core can include a
thermoplastic polymer selected from polyamides, polyesters, and/or
polyolefins (e.g. polyethylene, polypropylene, polybutene, ethylene
copolymers, propylene copolymers, or butene copolymers). Each of
the sheath and core should constitute about 10 to 90 wt % of the
fiber, or about 20 to 80 wt %, or about 30 to 70 wt %.
[0034] As mentioned, the composition can be in the form of
side-by-side bicomponent fibers, each fiber having a first side
composed of a blend of the copolymer and the aromatic polyester and
a second side composed of any suitable polymer. For example, the
second side of each fiber can include a thermoplastic polymer
selected from polyamides, polyesters, and/or polyolefins (e.g.
polyethylene, polypropylene, polybutene, ethylene copolymers,
propylene copolymers, or butene copolymers). When the composition
is in the form of side-by-side bicomponent fibers, the overall
weight percentages of the aromatic polyester and the copolyester in
the fibers should be the same as if the composition were in the
form of a polymer blend.
[0035] Conventional bicomponent spinning processes can be used for
making the composition of the invention in the form of sheath/core
or side-by-side bicomponent fibers. For example, PET-1N211 (0.55
intrinsic viscosity), available from NanYa in Lake City, S.C., is a
suitable aromatic polyester that can be used to form the core of a
sheath/core fiber or one side of a side-by-side fiber. Bicomponent
fibers can be produced by bicomponent spunbonding processes which
are well known in the art. These processes generally use an
extruder to supply the molten polymers to a spinnerette where the
polymers are fiberized in a sheath/core or side-by-side
arrangement. The fibers can then be drawn, usually pneumatically,
and deposited on a foraminous mat or belt to form a nonwoven
fabric, for example. Fibers produced in the spunbond process are
generally in the range of from about 1 to about 50 microns in
diameter, depending on process conditions and the desired end use
for the fabrics to be produced from such fibers.
[0036] The copolyester can be combined with the aromatic polyester
to form, for example, a 30% blended sheath of copolyester and
polyester/70% PET core, or a 20% blended sheath/80% PET core, or a
40% blended sheath/60% PET core. In terms of a semicrystalline
copolyester versus an amorphous copolyester, the semicrystalline
copolyester appears to perform better in terms of experiencing less
on-line shrinkage and the resulting material being stronger, softer
and bonded more evenly than when an amorphous copolyester is
used.
[0037] Once a dimensionally stable fibrous web is made using the
composition of the invention, its thermal bonding temperature to a
fibrous web can be determined and optimized. When bonding the
layers, the set bonding temperature and the actual bonding
temperature of both a top calender roll and a bottom calender roll
through which the layers are bonded can be recorded using a
thermocouple.
[0038] With an aliphatic copolyester and PET blend (having a lower
melting temperature) on the sheath and polypropylene in the core of
bicomponent fibers, a dimensionally stable web can be formed by
bonding the fibers to each other well below the polyester's melting
temperature. An example of the inter-fiber bonding temperature of
one composition of the invention compared to the bonding
temperature of a 100% polypropylene sample is described below.
EXAMPLE
[0039] In a spunbond trial, a first composition including 30% blend
of copolyester and polyethylene terephthalate (PET) and 70%
polypropylene (PP) was spun in a sheath/core configuration, with a
95% PET and 5% BOSTIK.RTM. 4178 copolyester blend on the sheath and
the PP in the core. A second composition included 100% PP
monofilament as a control. Each of the two fabrics was bonded at a
bond roll temperature of 277.degree. Fahrenheit (136.degree.
Celsius). The bonding temperature was 250.degree. Fahrenheit
(121.degree. Celsius). When 100% PET was used as the sheath the
fabrics could not be bonded in any meaningful sense at temperatures
under 390.degree. Fahrenheit (199.degree. Celsius).
1TABLE 1 Comparison of Material Properties Based on Fabric
Composition Bonding Basis MD MD MD CD CD CD Temp. Weight Tensile
Strain Energy Tensile Strain Energy Composition (.degree. F.) (osy)
(lbs.) (%) (In-lb) (lb) (%) (In-lb) 30% Blend 250 1.24 9.4 36.8 6.9
9.8 53.2 9.34 70% PP 100% PP 277 1.27 22.2 62.2 26.11 21.7 63.0
25.6
[0040] As can be seen in Table 1, the PET/PP composition had
inferior material properties compared to the PP composition, but
was at least able to bond at a moderate bonding temperature. The
inclusion of the copolyester as a bonding agent demonstrates that a
PET web can be bonded on systems primarily designed to process
olefin based materials.
[0041] The compositions of the invention can be incorporated into
disposable absorbent articles. Examples of such suitable articles
include diapers, training pants, feminine hygiene products,
incontinence products, other personal care or health care garments,
including medical garments, or the like. Furthermore, the
compositions of the invention can also be used for printing or
medical applications.
[0042] It will be appreciated that details of the foregoing
embodiments, given for purposes of illustration, are not to be
construed as limiting the scope of this invention. Although only a
few exemplary embodiments of this invention have been described in
detail above, those skilled in the art will readily appreciate that
many modifications are possible in the exemplary embodiments
without materially departing from the novel teachings and
advantages of this invention. Accordingly, all such modifications
are intended to be included within the scope of this invention,
which is defined in the following claims and all equivalents
thereto. Further, it is recognized that many embodiments may be
conceived that do not achieve all of the advantages of some
embodiments, particularly of the preferred embodiments, yet the
absence of a particular advantage shall not be construed to
necessarily mean that such an embodiment is outside the scope of
the present invention.
* * * * *