Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2003-02-06
2004-03-16
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S027000, C528S038000, C528S272000, C528S288000, C528S297000, C528S300000, C528S302000, C528S306000, C528S308000, C528S308600, C524S188000, C524S196000
Reexamination Certificate
active
06706842
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a crosslinked polyester copolymer, to a composition that can be used to produce the copolymer, to a process for producing the composition and the crosslinked copolyester.
BACKGROUND OF THE INVENTION
Polyesters are widely used to manufacture textile fibers, containers, and packaging materials. Polyesters can be manufactured by combining a glycol, such as ethylene glycol, and a carbonyl compound, such as dimethyl terephthalate (DMT) or terephthalic acid (TPA). In the DMT route, DMT reacts with the glycol to form a bis-glycolate ester of terephthalate (“monomer”) in an ester exchanger column. The monomer is then polymerized by condensation reactions in one or two prepolymerizers and then a final polymerizer or finisher.
In the TPA route, TPA is combined with the glycol to form a slurry at 60° C. to 100° C. followed by injecting the slurry into an esterifier. A linear oligomer with a degree of polymerization 5 to 10 is formed in one or two esterifiers at temperatures from 240° C. to 290° C. The oligomer is polymerized in one or two prepolymerizers and then in a final polymerizer at temperatures from 250° C. to 300° C. Water is a byproduct of the TPA esterification and polycondensation process.
A problem associated with polyester fibers is their tendency to pill. Pilling is a defect in fabric caused when fibers are rubbed or pulled out of yarns and entangled with intact fibers, forming soft, fizzy balls on the fabric surface. One of the most common commercial practices to produce pilling resistant fibers is to make lower molecular weight polyester. Unfortunately, spinning is very difficult or impossible with lower molecular weight polyester fibers. A temporary crosslinker or brancher can be used to increase molecular weight and polymer strength for better spinning performance. After spinning, the temporary crosslinks or branches hydrolyze in water. Tetraethoxysilane (TEOS) has been used commercially in DMT process to produce pilling resistance fibers. TPA process, however, has byproduct water, TEOS forms rocks or sands in the recycle glycol of TPA process.
The dilemma is that the temporary crosslinker or brancher must hydrolyze after spinning, but it must not hydrolyze in TPA polymerization process where there is water. U.S. Pat. No. 6,407,194 discloses a temporary crosslinker 3-Glycidoxypropyltrimethoxysilane (GTMS) to improve the pilling resistant of polyester fibers, which does not form solids in the TPA process. The spinning performance of polyester containing GTMS, however, is not as good as the polyester containing TEOS, because GTMS forms permanent crosslinks or branches due to the hydrophilic epoxy group in addition to the temporary crosslinks or branches, resulting in excessive crosslinks or branches in the polyester. According to the invention, GTMS is merely dissolved in the glycol solution before injection, most methanol byproduct from GTMS emits in the TPA polymerization process.
Most new polyester plants built in the world are based on the newer TPA process. Therefore, there is an increasing need to develop a polyester polymer having lower molecular weight that is crosslinked with a temporary crosslinker to increase molecular weight for spinning, which does not form solids in TPA process.
An additional consideration for producing polyester polymers is the rate of crystallization of partially oriented yarn (POY) during spinning. Normal spinning speeds are typically in the order of 3000-3500 m/min for POY. At higher spinning spuds, such as 4000-5000 m/min, crystallization of the POY can occur too fast, resulting in low orientation in fibers and deteriorates physical properties such as tenacity, elongation, and shrinkage. Further, the draw texturing speed of POY is normally about 900 m/min. Higher draw texturing speed such as 1000 m/min requires POY with lower crystallization.
Also, for container and packaging materials, polyethylene terephthalate (PET) are often modified with a comonomer such as isophthalic acid (IPA) and diethylene glycol (DEG) to reduce the crystallization rate during injection or extrusion blow molding. However, the resulting products have lower strength due to these additives.
Normal PET fibers require disperse dye at temperature 120 to 140 degree C. under high pressure. PET copolymer containing additives such as polyethylene glycol can be dyed at temperature 100 degree C. or lower under atmospheric pressure, but its melt strength is low and spinning is more difficult. PET copolymer containing IPA 15% to 40% by mole has been commercially produced for binder fibers, this copolymer can be difficult to spin because the melt strength is low.
Accordingly, there is a desire to decrease the crystallization rate of the polyester polymer during spinning without adversely altering the physical properties of the polyester polymer fiber, to develop a polyester composition and process suitable for injection and extrusion blow molding for container and packaging materials, which has low rate of crystallization, good heat resistance, high strength and clarity; and to develop a polyester copolymer with higher melt strength for fiber products such as binder fibers, biodegradable fibers, atmospherically dyeable fibers.
SUMMARY OF THE INVENTION
The present invention comprises a glycol-organosilane composition that comprises or is produced by combining (a) a glycol and (b) an organosilane comprising D
m
SiX
n
Z
p
, where D is a halogen, a hydrogen, or a hydrocarbon oxygen group; X is a hydrocarbon or a hydrocarbon oxygen group; Z is a reactive hydrophobic group or a hydrophilic group; m and n are each about 1 to about 3; and p is 1 to 20. This composition is preferably substantially soluble in glycol and water.
The invention also comprises a polyester copolymer composition and a process to produce the composition. The composition comprises repeat units derived from (a) a carbonyl compound or its oligomer, (b) a glycol, (c) a crosslinker, and (d) optionally a comonomer. A preferred process for producing the polyester copolymer comprises contacting a crosslinker, and optionally a comonomer, with a polymerization mixture comprising or consisting essentially of a glycol and either a carbonyl compound or its oligomer. The process can be used for increasing the rate of polymerization, for increasing the pill resistance or strength of a polyester copolymer, or for decreasing the crystallization rate during object forming process such as spinning of fibers or injection and extrusion blow molding and stretching of containers and packaging materials.
DETAILED DESCRIPTION OF THE INVENTION
The terms “crosslinked polyester polymer” and “crosslinked polyester copolymer” are alternatively used herein referring polyester polymer containing temporary or permanent crosslinker or brancher, with or without a comonomer.
The term “temporary crosslinker” herein refers to a composition that temporary crosslinks or branches polyester molecules, and thereby increases the molecular weight of the polyester polymer and melt viscosity. The bonds of the branches or crosslinks (Si—O) formed by the crosslinker can be broken down after spinning by hydrolysis in water, moisture, an alcohol, a weak acid, or a weak base.
The term “permanent crosslinker” herein refers to a composition that permanently crosslinks or branches polyester molecules. The bonds of the crosslinks and branches do not break down in water, an alcohol, a weak acid, or a weak base.
The term “glycol-organosilane composition” and “glycol-organosilane” as used herein refers to a product produced from a glycol and an organosilane, preferably it is a reaction product produced by partially reacting an organosilane with a glycol. By partially reacting or reacted, it is meant that about 20% to about 99%, preferably 50% to 95%, even more preferably 60% to 90%, by mole, of all reactive functional groups in the organosilane molecule that can react with a glycol are reacted with the glycol. The term “reactive functional groups” refers to those functional groups that can react with a glycol. The ter
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