Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2001-03-21
2002-11-05
Edwards, Newton (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S374000, C525S444000
Reexamination Certificate
active
06475618
ABSTRACT:
FIELD OF THE INVENTION
This invention is directed to compositions that can be thermally bonded at relatively low temperatures.
BACKGROUND OF THE INVENTION
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.
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.
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
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.
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.
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.
The compositions of the invention can be in the form of fibers, including nonwoven fibers.
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
Within the context of this specification, each term or phrase below will include the following meaning or meanings.
“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.
“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.
“Amorphous copolyethylene ester” is a type of copolyester that lacks a distinct crystalline structure.
“Aromatic compounds” are cyclic hydrocarbons containing one or more rings, typified by benzene, each ring having six carbon atoms and three double bonds.
“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.
“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.
“Polyesters” are a group of synthetic resins that are polycondensation products of dicarboxylic acids with dihydroxy alcohols.
“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.
“Semicrystalline copolyethylene ester” is a type of copolyester that includes about 40 to 60% crystalline matter and about 40 to 60% amorphous matter.
“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.
These terms may be defined with additional language in the remaining portions of the specification.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
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.
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.
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.
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 polyeste
Aroch Maya
Day Bryon P.
Griffith Nina Cecilia
Ning Xin
Edwards Newton
Kimberly--Clark Worldwide, Inc.
Pauley Petersen Kinne & Erickson
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