Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-06-12
2003-01-14
Mullis, Jeffrey (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S064000, C525S070000, C525S074000, C525S401000, C525S222000, C525S227000, C525S231000, C525S239000, C525S298000, C525S302000, C524S502000
Reexamination Certificate
active
06506835
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the use of polyvinyl butyral as a component for alloying into blends of polyvinyl chloride and ethylene copolymers, and compositions and shaped articles formed therefrom.
BACKGROUND OF THE INVENTION
Plasticized polyvinyl butyral (PVB) is a resinous material used in large quantities as an interlayer in laminated safety glass for windows in buildings and windshields in automobiles. The glass from these safety glasses can be recovered by conventional techniques such as grinding, crushing, and milling the scrap glass to recover the glass cullet to the glass manufacturer, while the PVB is disposed of in landfills or incinerators. It is estimated that the supply of post-consumer PVB waste and scrap is between 35 to 45 MM pounds a year.
U.S. Pat. No. 5,380,794 suggests an approach to recycle or recover PVB, by using the material as tackifier in the manufacture of resilient flooring material. The PVB provides a tackiness, or sticky property, to the surface of a polyvinyl chloride (PVC) composition. However, it is suggested that PVB be used in a limited amount of 0.5 to 4% by weight and preferably about 0.75% to 1.25% by weight in a composition comprising PVC and inorganic fillers.
It has been known in the art to add plasticizers to PVC to improve its flexibility. U.S. Pat. No. 3,780,140 discloses the use of an ethylene copolymer as an effective plasticizer for PVC. Considering the abundant amount of post-consumer PVB available for recycling, it would be desirable to replace some of the ethylene copolymer plasticizers with PVB to give flexibility and elastomeric property to PVC. There would be a desirable side effect of addressing industrial and environmental concerns by finding a way to efficiently and economically recover PVB.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a novel composition comprising a high percentage of virgin, recycled or recovered polyvinyl butyral (PVB), from about 5-95 weight percent (wt. %) PVB, 5-95 wt. % polyvinyl chloride (PVC), 1-50 wt. % of a high-molecular weight solid ethylene-containing plasticizer, 0-90 wt. % inorganic fillers, and 0-50 wt. % of a low-molecular weight liquid plasticizer, whereby the weight percent totals 100. The high-molecular weight solid ethylene-containing plasticizer is selected from the group consisting of: a) an ethylene/alkyl acrylate copolymer; b) an ethylene/alkyl acrylate/carbon monoxide copolymer; c) an ethylene/alkyl acrylate/carbon monoxide copolymer grafted with carboxylic acid anhydride groups; d) an ethylene/alkyl acrylate/mono methyl maleate copolymer; e) an ethylene/alkyl acrylate copolymer grafted with carboxylic acid anhydride groups; f) an ethylene/vinyl acetate copolymer; g) an ethylene/vinyl acetate copolymer grafted with carboxylic acid anhydride groups; h) an ethylene/vinyl acetate/carbon monoxide copolymer; and i) an ethylene/vinyl acetate/carbon monoxide copolymer grafted with carboxylic acid anhydride groups.
There is also provided a process for preparing a novel composition comprising a large amount of virgin, recycled or recovered polyvinyl butyral of up to 95 wt. % PVB, 5-95 wt. % PVC, 1-50 wt. % a high-molecular weight solid ethylene-containing plasticizer, 0-90 wt. % inorganic fillers, and 0-50 wt. % a low-molecular weight liquid plasticizer, whereby the weight percent totals 100.
DETAILED DESCRIPTION OF THE INVENTION
The composition of the present invention provides a new utility for polyvinyl butyral (PVB) in a blend of polyvinyl chloride (PVC) and a plasticizer as a compatibilizer.
The polyvinyl chloride in this disclosure can be a homopolymer of vinyl chloride or a copolymer of vinyl chloride with a small amount, e.g., up to 20 weight percent, of another copolymerizable monomer well-known commercially (such as vinyl acetate) which does not change the essential character of the homopolymer. The term PVC is used generally to mean the polymer alone which is a stiff, somewhat brittle polymer. The PVC will generally have a glass transition temperature (T
g
) of about 80° C. and will normally be melt processed by itself at a temperature of 180-200° C.
The polyvinyl butyral in accordance with this invention may be virgin vinyl butyral, that is PVB which has not been used previously. However, it is preferred that the PVB be recovered or recycled to provide a lower cost but equally high quality raw material for the blend. The kind of recovered or recycled PVB is not critical to the working of the invention. It has been found that recovered or recycled PVB of different kinds and from different manufacturing origins, as well as mixtures of different kinds of PVB, are suitable for use in accordance to this invention. The recovered or recycled PVB can contain common additives and contaminants such as plasticizers, sand, and fine glass particles and still acceptable for use in the invention.
PVB is a complex resin which may be manufactured, depending upon the desired application, with large variations in respect to structural features and composition. Acetals, such as polyvinyl butyral, are formed by the well-known reaction between aldehydes and alcohols. The addition of one molecule of an alcohol to one molecule of an aldehyde produces a hemiacetal. Hemiacetals are rarely isolated, because of their inherent instability, but rather, are further reacted with another molecule of alcohol to form a stable acetal. Polyvinyl acetals are prepared from aldehydes and polyvinyl alcohols. Polyvinyl alcohols are high molecular weight resins containing various percentages of hydroxyl and acetate groups produced by hydrolysis of polyvinyl acetate. The conditions of the acetal reaction and the concentration of the particular aldehyde and polyvinyl alcohol used are closely controlled to form polymers containing predetermined proportions of hydroxyl groups, acetate groups and acetal groups. The primary differences between different types of polyvinyl butyral relate to differences in molecular weight, differences in the content of hydroxyl, butyral and residual ester groups, and differences in the type and content of other additives. A typical polyvinyl butyral resin may have a molecular weight range, according to the Staudinger equation, of from about 30,000 to about 600,000, a range of from about 12% to about 20% by weight of hydroxyl groups calculated as the polyvinyl alcohol, and a range of from 0% to about 3% by weight residual ester groups calculated as polyvinyl acetate.
A third component of the melt blend of the present invention is an ethylene polymer with carboxyl and/or carbon monoxide functionalities as a solid plasticizer. Plasticizers of the type can be prepared by well-known methods of free-radical, high-pressure polymerization as described in U.S. Pat. No. 3,780,140 entitled “Ethylene/Carbon Monoxide Polymer Composition.” Examples of this ethylene polymer plasticizer includes: a) ethylene terpolymers of the general formula E/X/CO where E is the ethylene, X is a “softening” monomer such as, for example, vinyl acetate or an acrylic ester, and CO is the carbon monoxide functionality; b) ethylene carbon monoxide-functional copolymer that is anhydride modified in the form of E/X/CO/grafted MAH, e.g., obtained by grafting reaction between the preformed copolymer with maleic acid or maleic anhydride; c) ethylene copolymers of the general formula E/X, including copolymers of ethylene with methyl acrylate, butyl acrylate, and; d) ethylene terpolymers of the formula E/X/grafted MAH, e.g., containing carboxylic acid anhydride groups pendant from the polymer backbone.
Examples of carboxyl-functionalized ethylene polymer “E/X” are copolymers of ethylene with C3-C12 ethylenically unsaturated monocarboxylic acids, C1-C18 alkyl esters of ethylenically unsaturated C3-C12 monocarboxylic acids, and vinyl esters of C3-C18 saturated carboxylic acids. More specific examples include ethylene/vinyl acetate copolymer and ethylene/alkyl (meth)acrylic acid copolymer, wherein the alkyl group contains 1 to 8 carbon atoms. Such ethylene polymers include copolymer
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