Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1998-11-03
2001-11-27
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S493000
Reexamination Certificate
active
06323271
ABSTRACT:
FIELD OF THE INVENTION
This invention is directed to polyester resins containing fumed silica to improve the processability of the resins in the production of articles of manufacture. In particular, the invention is directed to polyester resins containing fumed silica, which resins are suitable for the productions of beverage bottles. This application is related to an application titled “Poly(Terephthalic Acid Diester)-Poly(Isophthalic Acid Diester) Resin Formulations Having Improved Gas Barrier Properties”, application Ser. No. 09/185,237, which was filed concurrent with this application and whose teaching are incorporated herein.
BACKGROUND OF THE INVENTION
The use of polyester compositions as a packaging material, particularly, compositions comprising polyethylene terephthalate, generally referred to as “PET”, in the form of films, plastic bottles and other containers is well known. Plastic bottles are used for containing pressurized fluids such as carbonated drinks, e.g., soft drinks or mineral waters, as well as for non-carbonated, non-pressurized drinks. To form plastic bottles, the polymer is extruded and then formed into chips. The chips are employed to make a bottle preform by injection molding as is well known in the industry. The preform is then reheated and blown into a mold which provides the final shape of the bottle.
During the manufacture of bottles, one problem often encountered is that of “stickiness”, wherein the newly formed bottles or bottle preforms have a tendency to stick to surfaces, including each other. This can give rise to problems during the conveying and palletizing of the bottles which disrupt operations. While various approaches to solving this bottle problem have been tried, none have been satisfactory until the invention disclosed herein, particularly under economic considerations which require high production rates.
The approach to solving the stickiness problem disclosed herein is to increase the surface roughness of the bottles by the addition of particulate matter to the resin prior to using the resin to form bottles. With increased roughness, bottle-to-bottle or bottle-to-other-surface contact will be minimized, or the bottles will have a lesser tendency to stick to each other and will thus not cause interruptions in operations. While a variety of substances have been evaluated for reducing stickiness, including fumed silica (sometimes called pyrogenic silica), colloidal silica and silica beads, it has been determined that amorphous and fumed silicas are most advantageous for reducing stickiness.
Silica has been used in the production of polyester films for a variety of uses. For example, U.S. Pat. Nos. 5,384,191 and 5,266,397 to Ogawa et al. describe the preparation of an amorphous silica filler and its incorporation into a film resin to improve, among other things, the scratch resistance properties of the surface of films prepared using such resin; U.S. Pat. No. 5,281,379 to Noguchi et al. describes a process for producing thermoplastic resin compositions which includes adding fine particles, including silica, of less than 10 &mgr;m particle size to a variety of polymer resins, including polyester resins. Other U.S. Patents teaching polyester resins suitable for the production of films and including, among other things, silica in combination with a polyester resin, are U.S. Pat. No. 5,475,046 to Son et al. (polyester with macro particles of silica and aluminum oxide); U.S. Pat. No. 5,382,651 to Kim et al (polyester with silica produced from an ethylene glycol silica sol); U.S. Pat. No. 5,336,709 (undrawn polyester yarns containing fumed silica); U.S. Pat. Nos. 5,278,221 and 5,278,205 (polyester film containing glass beads and fumed silica); and U.S. Pat. No. 4,029,289 (polyester film resin containing pyrogenic aluminum and pyrogenic silica). While film resins have incorporated various silicas for a variety of reasons, similar teachings have not been found in the art related to polyester resins suitable for use in the production of containers, particularly bottles. This is most likely due to the fact that incorporation of particulates into bottle resins causes haziness, making the resins unsuitable for many bottle uses.
Therefore, it is a object of the invention to describe polyester resins incorporating, among other things, fumed silica, colloidal silica, precipitated silica and silica beads, and a process for producing such resins. Fumed silicas are preferred.
A further object of this invention is to describe polyester resins suitable for the production of containers which incorporate, among other things, fumed silica to improve the processing characteristics of such resins and the products made therefrom, and a process for producing such resins.
An additional object of this invention is to describe polyester resins comprising, among other things, polyethylene terephthalate, and similar terephthalate polyesters, and fumed silica, and a process for making same.
A further object of the invention is to describe a resin comprising, among other things, polyethylene terephthalate and fumed silica which is suitable for the production of beverage containers and which has improved handling characteristics during the production of same.
SUMMARY OF THE INVENTION
The invention is directed to a polyester resin suitable for the production of containers and particularly beverage containers including clear polyester bottles; such resins containing, among other things, polyethylene terephthalate and a siliceous substance, particularly about 50 to about 2500 ppm by weight fumed silica of particle size of about 0.1 &mgr;m to about 30 &mgr;m, preferably about 0.1 &mgr;m to about 5 &mgr;m, and more preferably from about 0.1&mgr;m to about 3 &mgr;m, and most preferably from about 0.1 &mgr;m to about 1.5 &mgr;m.
The invention is further directed to a process for producing a polyester resin suitable for the production of containers, particularly beverage containers, such process having, among other steps:
(a) a step of mixing together, among other things, at least one polycarboxylic acid substance or diester thereof suitable for the production of a polyester resin and a polyol suitable for the production of a polyester resin;
(b) heating the mixture of step (a);
(c) removing from the product of step (b) excess or unreacted glycol or water present or produced; and
(d) optionally, solid stating the product of step (c) to produce a silica-containing polyester resin suitable for the production of containers;
wherein fumed silica or other siliceous substance is added to the process at any of steps (a), (b), (c) and (d) to produce said polyester-silica resin.
In an alternate embodiment of the invention fumed silica is added to a polyester resin in a vessel, or a mixture of polyesters and other resins as described herein, and the resulting mixture is heated and mixed to a temperature at or above the melting point of the polyester. The silica can be added before or after the polyester has reached its melting point. The vessel can be any vessel suitable for accomplishing the mixing, for example, a resin bottle or an extruder.
DETAILED DESCRIPTION OF THE INVENTION
The term “polyester” as used herein means any substance formed by the reaction between at least one polyhydric alcohol (a polyol, a substance containing two or more hydroxyl groups) and a dicarboxylic acid or a mono- or diester of a dicarboxylic acid. In the preferred embodiments of the invention, the preferred dicarboxylic acids and esters thereof are those in which two carboxylic acid groups (—COOH), are attached to the same or different aromatic or saturated rings, be such rings fused or bonded together. Examples include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid (fused aromatic rings), 4,4′-biphenyl dicarboxylic acid (aromatic rings bonded at 1,1′ positions), 4,4′-bicyclohexane dicarboxylic acid (saturated ring bonded at the 1,1′ position), and similar substances, including mono- and diesters, known to those skilled in the art. When using mono- or diesters
Caldwell Sarah E.
King Jennifer
Schwietert Jim
Woodward John
Wu Audrey C.
Arteva North America S.a.r.l.
Cain Edward J.
Clements Gregory N.
Wyrozebski Katarzyna Lee
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