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...
Patent
1998-03-06
1999-09-07
Hoke, Veronica P.
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...
524227, 524386, 524389, 524399, C08K 520
Patent
active
059488484
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a biodegradable plastics material and to a method for its manufacture. In particular, the invention relates to a biodegradable plastics material comprising a polyvinylacetate/polyvinylalcohol copolymer.
Commercially available biodegradable plastics do not fully degrade in the environment and retain a high degree of toxicity when partially degraded. Furthermore, such materials are expansive and generally only used for niche markets.
The use of polyvinylacetate/polyvinylalcohol (PVA) copolymers for the manufacture of biodegradable plastics materials is described in WO92/01556. By layering or surrounding PVA which is water soluble at 20.degree. C. with a thin layer of a PVA which is water insoluble at 20.degree. C., an article which is protected from dissolution by water until its waterproofing, insoluble layer is breached may be manufactured. The PVA's are co-extruded as a laminate or may be moulded, with or without an intervening filler layer. Water soluble PVA dissolves readily in water and is broken down in the environment within a relatively short time to carbon dioxide and water.
The Hoescht AG Resins specialty print (1991), "Plastic Films Formed From Polyvinyl Alcohol" by Albrecht Harricus et al, discloses that in order to process PVA plastics material on standard processing apparatus such as profile extruding machines, blown film extruders or injection moulding machines, undesirable thermal decomposition of the products occurs at temperatures above 150.degree. C. and must be prevented by external plasticising of granular plastics material. The plastics material is plasticized by mixing with a suitable plasticizer for 15-30 mins. at a temperature of up to 110.degree. C. This plasticized PVA can be injection moulded and extruded under the following conditions: heating the material to a temperature in the range 145-190.degree. C. and at an injection pressure of 100-130 bar.
While PVA is known as a biodegradable material, its use in the manufacture of plastic articles has up to now been limited as it is technically difficult to work with this material and to produce an acceptable product, therefore it is costly and commercially unsuccessful.
The present invention seeks to provide an improved plastics material comprising a PVA copolymer which can readily be worked by known processes such as blow moulding, injection moulding, cast extrusion, etc. and which is suitable for the manufacture of biodegradable articles.
The term PVA as used herein refers to a polyvinylacetate polymer which has been partially hydrolysed to convert a proportion of the acetate groups to the corresponding alcohol. Therefore, the term refers to a polyvinylacetate/polyvinylalcohol copolymer. The solubility of the PVA is dependent, inter alia, on the degree to which the PVA is hydrolysed. "Cold soluble" PVA denotes a copolymer which is generally referred to as "partially hydrolyzed" polyvinylacetate. Typically, the partially hydrolyzed copolymer comprises 70 to 85 wt % of the alcohol, with the remainder comprising residual acetate, and this material is soluble in "cold" water. It is generally readily soluble in water at 20.degree. C. Further hydrolysis of the PVA to levels at which the alcohol comprises about 96 mol % or greater (usually referred to as "fully hydrolyzed" polyvinylalcohol, results in a marked decrease in solubility. While the fully hydrolyzed polymer is usually thought of as insoluble, it is in fact soluble in water at a temperature of about 50.degree. C. or greater. Such material is referred to herein as "hot soluble" PVA. Both hot and cold soluble PVA's, once dissolved, are fully biodegradable in nature to CO.sub.2 and H.sub.2 O. The undegraded copolymers and their partially degraded derivatives are non-toxic.
The present invention provides a method of manufacturing a biodegradable plastics material comprising mixing partially hydrolysed, water soluble polyvinyl alcohol (PVA) co-polymer with a plasticizer and stabiliser at a temperature in the range of between 106 to 140.degree. C., whe
REFERENCES:
patent: 2948697 (1960-08-01), Robertson
patent: 3066999 (1962-12-01), Nakajo et al.
patent: 3287313 (1966-11-01), Imoto
patent: 3397162 (1968-08-01), Takigawa et al.
patent: 3769151 (1973-10-01), Knutson et al.
patent: 3886112 (1975-05-01), Watson et al.
patent: 3997489 (1976-12-01), Coker
patent: 4323492 (1982-04-01), Zimmerman et al.
patent: 4469837 (1984-09-01), Cattaneo
patent: 4529666 (1985-07-01), Salzburg et al.
patent: 4536532 (1985-08-01), Miller et al.
patent: 4542178 (1985-09-01), Zimmerman et al.
patent: 4656216 (1987-04-01), Muller et al.
patent: 4753760 (1988-06-01), Kawaguchi et al.
patent: 5102950 (1992-04-01), Terada et al.
patent: 5110859 (1992-05-01), Flesher et al.
patent: 5206278 (1993-04-01), Famili et al.
patent: 5322866 (1994-06-01), Mayer et al.
patent: 5349000 (1994-09-01), Robeson et al.
patent: 5462981 (1995-10-01), Bastioli et al.
patent: 5489638 (1996-02-01), Burdick
patent: 5583187 (1996-12-01), Sharak et al.
Hoechst Resins Special Print, "Plastic Films Formed From Polyvinyl Alcohol", by Dr. Albrecht Harreus, et al., Company brochure Hoechst AG 1991.
Hoke Veronica P.
Solplax Limited
LandOfFree
Biodegradable plastic material and a method for its manufacture does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Biodegradable plastic material and a method for its manufacture, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Biodegradable plastic material and a method for its manufacture will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1805135