U.S. patent application number 11/167970 was filed with the patent office on 2005-12-01 for biodegradable polymers.
This patent application is currently assigned to University of Massachusetts a Massachusetts corporation. Invention is credited to Ching Ku, Man, Morelli, Alessandra, Warner, John C..
Application Number | 20050266546 11/167970 |
Document ID | / |
Family ID | 29586511 |
Filed Date | 2005-12-01 |
United States Patent
Application |
20050266546 |
Kind Code |
A1 |
Warner, John C. ; et
al. |
December 1, 2005 |
Biodegradable polymers
Abstract
The invention relates to methods of solubilizing and recycling
polymers using irradiation, wherein the polymers comprise
photoreactive moieties. These polymers have many applications
including use in disposable consumer products such as beverage
bottles, eating utensils and diapers.
Inventors: |
Warner, John C.; (Quincy,
MA) ; Morelli, Alessandra; (Edinburgh, GB) ;
Ching Ku, Man; (Boston, MA) |
Correspondence
Address: |
FISH & RICHARDSON PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
University of Massachusetts a
Massachusetts corporation
|
Family ID: |
29586511 |
Appl. No.: |
11/167970 |
Filed: |
June 28, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11167970 |
Jun 28, 2005 |
|
|
|
10295729 |
Nov 15, 2002 |
|
|
|
6946284 |
|
|
|
|
60333816 |
Nov 16, 2001 |
|
|
|
Current U.S.
Class: |
435/262 |
Current CPC
Class: |
C12N 13/00 20130101;
C12P 1/00 20130101 |
Class at
Publication: |
435/262 |
International
Class: |
C07C 001/00 |
Claims
1-11. (canceled)
12. A product in the form of a beverage bottle, eating utensil,
dish, bag, or diaper, the product comprising a crosslinked polymer,
wherein the cross-links are formed through [2+2] reactions between
photoreactive moieties of the polymer and the polymer is capable of
being solubilized using an enzyme that recognizes [2+2] reaction
products.
13. A method of recycling a polymer, the method comprising; (a)
obtaining a water-soluble polymer comprising photoreactive moieties
capable of participating in [2+2] cross-linking reactions; (b)
irradiating the polymer for a time sufficient to cross-link the
polymer, thereby making the polymer water-insoluble; (c) contacting
the cross-linked polymer with an enzyme that recognizes [2+2]
cyclization products to form a polymer-enzyme mixture; and (d)
irradiating the polymer-enzyme mixture for a time sufficient to
render the polymer water-soluble.
14. The method of claim 13, wherein the photoreactive moieties are
thymine.
15. The method of claim 13, wherein the photoreactive moieties are
uracil.
16. The method of claim 13, wherein the photoreactive moieties of
the polymer comprise about 3%-50% by weight of the polymer.
17. The method of claim 13, wherein the polymer is irradiated for
the first time with UV light.
18. The method of claim 13, wherein the polymer is irradiated with
UV light of 285 nm.
19. The method of claim 13, wherein the polymer-enzyme mixture is
irradiated with UV light.
20. The method of claim 13, wherein the polymer-enzyme mixture is
irradiated with visible light.
21. The method of claim 13, wherein the enzyme is DNA photolyase.
Description
CROSS-REFERERENCE TO RELATED APPLICATION
[0001] This application claims priority from U.S. Provisional
Patent Application Ser. No. 60/333,816, filed on Nov. 16, 2001,
which is incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] The invention relates to methods of reprocessing
polymers.
BACKGROUND
[0003] Polymers have broad commercial applications ranging from use
in consumer products such as diapers and beverage bottles, to
industrial applications such as photoresists, stencils, and films.
Typical polymers are made from organic solvent-dependent monomers
that undergo polymerization upon irradiation. These often-toxic
monomers are recollected in a step that involves an organic wash
and therefore requires strict monitoring of waste and solvent
evaporation.
[0004] Although many polymers are insoluble in water, thymine
polymers are generally water-soluble, unless treated. For example,
one can cross-link the thymine moieties in the polymer chains to
cause the polymer to become insoluble. This cross-linking can be
accomplished, for example, by irradiating the polymer at the proper
wavelength. The irradiation causes the thymine moieties to undergo
a [2+2] photoreaction (a cyclization between two thymine moieties),
which connects them to form four-membered rings. The cross-linking
causes the polymers to become insoluble and stable to various
environmental conditions. The physical characteristics of theses
polymers can be controlled by the quantity of the thymine moieties
used as co-monomers in the synthesis of the polymer. Once
crosslinked, these thymine polymers are fairly resilient.
SUMMARY
[0005] The invention is based on the discovery that irradiation of
[2+2] photo cross-linked polymers in the presence of the proper
enzymes, such as DNA photolyase, reverses the cross-linking and
causes the polymers to become water-soluble, provided the polymers
were originally water-soluble prior to cross-linking. Prior methods
of degrading these cross-linked polymers, such as
photo-dissociation, have required harsh conditions. Additionally,
these methods resulted in dissociation of the polymer chain itself
as opposed to the selective reaction with the photolyase of only
reversing the [2+2] cross-links by reversing the formation of the
four membered rings.
[0006] In general, the invention features a method of solubilizing
a cross-linked polymer. The method includes obtaining a
cross-linked polymer, wherein the cross-links are formed by [2+2]
cyclization reactions between photoreactive moieties of the
polymer. The polymer is then contacted with an enzyme that
recognizes [2+2] cyclization products, forming a polymer-enzyme
mixture. The mixture is then irradiated for a time sufficient to
solubilize the polymer. In these methods, the photoreactive
moieties can be thymine or uracil and can be present in the polymer
at from 3%-50% by weight. The polymer can be irradiated with broad
UV light, UV light at specific wavelengths, such as 285 nm, or
visible light. The enzyme can be DNA photolyase.
[0007] In another embodiment, the invention features products made
of cross-linked polymers, wherein the cross-links are formed by
[2+2] reactions between photoreactive moieties of the polymer. The
polymers can be solubilized using enzymes that recognize [2+2]
reaction products. Examples of products include beverage bottles,
eating utensils, dishes, bags, or diapers, i.e., any product
typically made of polymers and that are desirably recycled.
[0008] The invention also features a method of recycling a polymer.
The method includes obtaining a water-soluble polymer made from
photoreactive moieties capable of participating in [2+2]
cross-linking reactions. The water-soluble polymer is then
irradiated for a time sufficient to cross-link the polymer, making
the polymer water-insoluble. In this way, the polymer can be used
in a variety of products including beverages bottles and infant
diapers. The cross-linked polymer is contacted with an enzyme that
recognizes [2+2] cyclization products, forming a polymer-enzyme
mixture. Then, the polymer-enzyme mixture is irradiated for a time
sufficient to render the polymer water-soluble. The polymer can be
irradiated with UV light, e.g., at a wavelength of 285 nm, to
become water-insoluble.
[0009] Unless otherwise defined, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs. Although
methods and materials similar or equivalent to those described
herein can be used in the practice or testing of the present
invention, suitable methods and materials are described below. All
publications, patent applications, patents, and other references
mentioned herein are incorporated by reference in their entirety.
In case of conflict, the present specification, including
definitions, will control. In addition, the materials, methods, and
examples are illustrative only and are not intended to be
limiting.
[0010] The new methods of degrading [2+2] cross-linked polymers
achieve the goal of creating a polymer that is robust and resistant
to water and exposure to air and sunlight until a time when it is
to be recycled, at which point it can easily be made water-soluble
and biodegradable. Under both economical and environmentally
friendly conditions, the polymer can be selectively degraded and
subsequently either removed with water, recycled into a new
product, or both.
[0011] The details of one or more embodiments of the invention are
set forth in the accompanying drawings and the description below.
Other features, objects, and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
DETAILED DESCRIPTION
[0012] Typical plastic materials are made from organic
solvent-dependent, water-insoluble monomers that undergo
polymerization upon irradiation. Thymine-based polymers, on the
other hand, can be water-soluble. However, these polymers can
undergo a photoreaction, initiating a cross-linking mechanism,
where neighboring polymer strands are "tied" together. This
formation of cross-links makes the polymers water-insoluble and
able to withstand a variety of environmental conditions. These
characteristics are required for a number of useful applications of
these polymers.
[0013] Reversal of the cross-links causes the polymers to again
become water-soluble. The invention provides simple and economical
methods to achieve reprocessing of these polymers, thus making them
easily recyclable. Irradiation of these cross-linked polymers in
the presence of certain enzymes, such as DNA photolyase effectively
reverses the photocross-linking in an efficient manner under mild
conditions. Creating more environmentally friendly polymer products
is a goal of many corporations and research institutions. The new
methods make considerable progress in reaching this goal.
[0014] General Methodology
[0015] In one embodiment, the invention provides a method of
recycling a polymer. A water-soluble polymer incorporating
photoreactive moieties capable of participating in [2+2]
cyclization reactions is synthesized using methods known in the
art. Examples of the photoreactive moieties include thymine (e.g.,
benzyl thymine), uracil, and other organic molecules capable of
participating in [2+2] cyclization reactions in polymer chains. The
photoreactive moieties of the polymer comprise about 3%-50% by
weight of the polymer, e.g., 4, 5, 7, 10, 12, 15, 20, 25, 30, 35,
40, or 45% by weight.
[0016] Such polymers can include multi-functional vinylbenzyl and
vinylphenyl pendant thymine (and/or uracil) groups, and are
described, for example, in U.S. Pat. Nos. 5,708,106 and 5,455,349.
Such monomers, and polymers made from such monomers, are
commercially available. The water-soluble polymer is then
irradiated for a time sufficient to cross-link the polymer. Broad
UV light or actinic radiation, e.g., UV light at specific
wavelengths, such as 285 nm, can be used to cause cross-linking of
the polymer. Irradiation of the polymer initiates the [2+2]
cyclization reaction between the photoreactive moieties, which
causes the polymer to become insoluble as well as to become stable
to other environmental conditions (e.g., air and light).
[0017] The water-insoluble, cross-linked polymer is then contacted
with an enzyme that recognizes [2+2] cyclization products, forming
an enzyme-polymer mixture. The enzyme is a photolyase, such as DNA
and other photolyases from various bacteria (such as E. coli, in
which DNA photolyase is encoded by the phr gene) and other
organisms (e.g., fish and frogs). Only catalytic amounts of the
enzyme are required (e.g., 0.1% to 1% by weight). The resulting
polymer-enzyme mixture is irradiated, e.g., with UV or actinic
radiation, for a time sufficient to solubilize the polymer (e.g.,
less than 5 minutes). The enzyme can be recycled and used over and
over again (e.g., by repeating the methodology described above),
adding to the economic and environmental advantages.
[0018] In another embodiment, the invention provides methods of
solubilizing polymers. A polymer that is cross-linked through [2+2]
cyclization reactions between photoreactive moieties of the polymer
chain is contacted with an enzyme that recognizes [2+2] cyclization
products, forming a polymer-enzyme mixture. The resulting
polymer-enzyme mixture is then irradiated (treated with a
sufficient amount of radiation) under conditions sufficient to
solubilize the polymer.
[0019] In another embodiment, the invention is a product comprised
of a polymer cross-linked through [2+2] cyclization reactions,
capable of being solubilized using an enzyme that recognizes [2+2]
reaction products.
[0020] Applications
[0021] Consumers consistently choose products that are disposable.
While these products are popular because they are convenient, they
often end up in landfills, causing harm to the environment.
Although there has recently been an increased awareness of the
importance of preserving our land resources, disposable consumer
products remain popular due to their low cost and their
convenience. Polymers have a broad array of applications and are
used in the manufacture of many disposable consumer products.
[0022] The new economic and environmentally friendly methods of
recycling polymeric products will have a significant positive
impact on the environment. These new methods provide a means of
reducing the number of consumer products that are currently
disposed in landfills. In addition, they will reduce the air and
water pollution involved in recycling traditional polymers by
providing a non-toxic recycling method that does not require
organic solvents or harsh conditions. All that is needed in the new
recycling method is a source of irradiation, water, and a catalytic
amount of an enzyme, which itself can be recycled and reused
repeatedly. These advantages provide producers of consumer products
a viable, more environmentally friendly alternative to
manufacturing and recycling than what is currently available,
without increasing cost to consumers or sacrificing convenience of
the products.
[0023] Examples of products that can by recycled using the new
method include beverage bottles, dishes, eating utensils, bags, and
diapers, and any other products, such as consumer products, made of
polymers. For these products, the polymers described herein can
include various additives, such as colorants or pigments, fillers,
and other additives, as long as they do not interfere with the new
methods.
EXAMPLES
[0024] The invention is further described in the following
examples, which do not limit the scope of the invention described
in the claims.
Example 1
Formation and Solubilization of a Polymer Product
[0025] A copolymer of 1-[4-vinylbenzyl]thymine and
[4-vinylbenzyl]trimethy- lammonium chloride in a 1:4 ratio was
synthesized using free radical polymerization. The polymer was
dissolved in water to form a 10% solution and cast on a
polyethylene terphtalate ("PET") support with a #3 gauge coating
rod. Regions of the polymer film were selectively exposed to broad
UV light for 50 seconds, thereby cross-linking the exposed regions.
The film was washed with water, and the non-irradiated, still
soluble, polymer was removed. The regions where the polymer was
irradiated with UV light became insoluble and remained on the
support.
[0026] Some samples of the residual polymer were visualized by
toning with an anionic dye to verify crosslinking.
[0027] DNA photolyase and reaction buffer solution (PharMingen
Int., Becton Corp.) were applied to regions by covering a portion
of the previously exposed films with a small volume of an enzyme
solution by spraying. Control regions were treated with water by
soaking in a solution not containing the enzyme.
[0028] The polymer in the regions of the films that had the DNA
photolyase applied was solubilized and removed by the process. No
effect was seen in the controls.
[0029] The residual polymer was visualized by toning with an
anionic dye.
Example 2
Recycling of a Polymeric Beverage Container
[0030] An appropriately clean bottle, made from an organic polymer
containing cross-linked photoreactive moieties, is placed in a vat
containing an aqueous solution of DNA photolyase (PharMingen Int.,
Becton Corp.). The entire vat is irradiated with broad UV light for
a time sufficient to reverse the cross-linking of the organic
polymer. The enzyme-containing solution is then separated from the
polymer mixture. The remaining polymer mixture is dried and used in
a mold or dye, forming a new polymer product. Alternatively, the
polymer mixture can be used without evaporation of the solvent, and
directly applied to a dye, mold, or cast.
Other Embodiments
[0031] It is to be understood that while the invention has been
described in conjunction with the detailed description thereof, the
foregoing description is intended to illustrate and not limit the
scope of the invention, which is defined by the scope of the
appended claims. Other aspects, advantages, and modifications are
within the scope of the following claims.
* * * * *