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
2001-06-04
2002-10-22
Sanders, Kriellion A. (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...
C524S413000
Reexamination Certificate
active
06469083
ABSTRACT:
FIELD OF INVENTION
The present invention provides a master batch for use with polyester resins that does not need to be dried prior to use.
BACKGROUND OF THE INVENTION
Master batch systems, which are sometimes referred to as concentrates or additive packages, can be letdown at controlled ratios to deliver predetermined amounts of colorants, light stabilizers, heat stabilizers, flame retardants, antioxidants, lubricants, anti-stats, biocides, fillers, and/or other process aids into host polymer resins. A number of master batch systems are known. One type, which is sometimes referred to as a liquid color system or a liquid color concentrate, consist of various colorants and/or other additives dispersed in a hydrophobic liquid carrier that is typically mixed with host polymer resin during thermal processing (e.g., molding or extrusion) to impart color and/or other desirable properties to the polymeric article being formed.
Liquid color concentrates, while effective with many host polymer resins, do present some limitations and/or disadvantages when used with polyester resins such as, for example, polyethylene terephthalate (hereinafter “PET”), polybutylene terephthalate (hereinafter “PBT”), and polyethylene naphthalate (hereinafter “PEN”). For example, it is known that liquid color concentrates containing high colorant loadings can sometimes adversely affect physical properties of the host polyester resin including degrading the molecular weight of the polymer. Molecular weight is typically monitored by measuring the solution intrinsic viscosity (hereinafter “SIV”) of the polymer. Additionally, the liquid carriers in liquid color concentrates can sometimes act as lubricants and thereby promote screw slippage during thermal processing, which adversely affects production speed and efficiency.
Another type of master batch system commonly used to deliver additives to polymer resins is sometimes referred to as a wax-based master batch system. One example of a wax-based system is described in Bes et al., U.S. Pat. No. 4,988,477. In wax-based systems, colorants and/or other additives are dispersed in a wax-like carrier that is generally a solid at ambient temperatures. The wax-like carrier melts at a temperature well below the melt temperature of the host polymer resin into which the master batch is being added. Typically, wax-based systems are added to polymer resins as solid granules or beads using special cooled feeders that prevent the wax-based carrier from melting prematurely.
Wax-based systems, while effective for delivering colorants and/or other additives to some polymer resins, also present some limitations and disadvantages when used with polyester resins. For example, it is very difficult, if not impossible, to obtain a high loading of various additives in wax-based systems (e.g., it is usually not possible to obtain additive loadings higher than 50% by weight). This necessitates the use of relatively larger volumes of the wax-based master batch systems, which can result in a degradation of the physical properties of the host polymer resin. Furthermore, the melted waxes tend to act as lubricants and thus contribute to significant screw slippage during thermal processing.
Another form of master batch system commonly used to deliver additives to polymer resins is sometimes referred to as an olefin-based system. In olefin-based systems, colorants and/or other additives are dispersed in olefin polymers such as, for example, polymers and copolymers of ethylene. One example of an olefin-based system is disclosed in Phillips et al., U.S. Pat. No. 5,686,515. Again, while olefin-based systems can be used successfully with many polymer resins, such systems do have some limitations and/or disadvantages when used with polyester resins. For example, because olefin-based systems are not wholly compatible with polyester resins, they tend to “plate out” or form deposits on molds and/or other thermal processing equipment over time.
Attempts have been made in the past to form master batch systems using polyester resin carriers to deliver the additives to host polyester resins. Unfortunately, these attempts have met with very little success. One problem with such systems is that polyester resins, which are hygroscopic, must generally be dried before they are melt processed in order to inhibit the degradation of molecular weight of the polymer. Accordingly, such prior polyester resin based master batch systems required the installation and use of costly driers.
A master batch is needed for use in polyester resins that facilitates a high loading of colorants and/or other additives. Such a master batch should be compatible with the polyester resins in which it is used, and should not “plate out” on processing equipment. Moreover, it should not require drying prior to use. In addition, such a master batch should preferably not cause any screw slippage or adversely affect the physical properties of the polyester resin such as, for example, molecular weight as measured by SIV. Moreover, such a master batch should not require the use of special equipment or processing conditions in order to be used with conventional polyester resin thermal processing equipment and should be acceptable for use in food contact applications. Ideally, the master batch should not adversely affect the clarity of the host polyester resin where the maintenance of clarity is important.
SUMMARY OF INVENTION
The present invention provides a master batch for use with polyester resins. The master batch according to the present invention comprises an additive package dispersed in a carrier. The additive package comprises one or a combination of additives such as, for example, colorants, light stabilizers, heat stabilizers, flame retardants, antioxidants, lubricants, anti-stats, biocides, fillers, and/or other process aids. The carrier comprises an intimate mixture of from about 10 to about 25 percent by weight of one or more polyhydric alcohol esters of wood and/or gum rosin, from about 5 to about 35 percent by weight of one or more core-shell polymers, and from about 25 to about 70 percent by weight of one or more thermoplastic polyesters compatible with the polyester resin. Preferably, the additive package comprises at least about 5 percent by weight, and more preferably at least about 50 percent by weight, of the master batch.
The master batch according to the invention is compatible with polyester resins such as PET, PBT, PEN, and copolyesters of PET and PEN. It does not need to be dried prior to use. It does not cause any screw slippage, nor does it adversely affect the molecular weight of the host polyester resin. When necessary, the master batch according to the present invention can be formed so as to maintain the clarity of the host polyester resin. It is acceptable for use in food contact applications. Furthermore, the master batch according to the invention does not “plate out” on processing equipment.
The present invention also provides a method of forming a polyester article. The method comprises letting down a master batch according to the invention into a polyester resin, heating the master batch and the polyester resin to form a melt, and processing the melt to form the polyester article. The method can be used to form a variety of polyester articles such as, for example, blow molded bottles, extrusion blow molded bottles, injection molded bottles, extruded film sheets, and drawn fibers. It will be appreciated that the method can also be used to form preforms (parisons).
The foregoing and other features of the invention are hereinafter more fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the present invention may be employed.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention provides a master batch for polyester resins such as, for example, PET, PBT, PEN, and copolyesters of PET and PEN. The po
Ferro Corporation
Rankin, Hill Porter & Clark LLP
Sanders Kriellion A.
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