U.S. patent application number 14/167738 was filed with the patent office on 2014-05-29 for release coating.
This patent application is currently assigned to Sustainable Fiber Solutions, LLC. The applicant listed for this patent is Sustainable Fiber Solutions, LLC. Invention is credited to John KOKOSZKA, Robert Scott VONFELDEN.
Application Number | 20140148542 14/167738 |
Document ID | / |
Family ID | 45928110 |
Filed Date | 2014-05-29 |
United States Patent
Application |
20140148542 |
Kind Code |
A1 |
VONFELDEN; Robert Scott ; et
al. |
May 29, 2014 |
RELEASE COATING
Abstract
Described herein is the use of a modified PET in combination
with a vinyl addition silicone water-based release coating to
provide performance equivalent to the silicone by itself at a lower
cost than the silicone by itself and resulting in a release backing
paper that can be repulped and recycled in conventional recycled
paper mills avoiding the additional cost of sending the scrap paper
to landfill.
Inventors: |
VONFELDEN; Robert Scott;
(Concord, CA) ; KOKOSZKA; John; (Atlanta,
GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sustainable Fiber Solutions, LLC |
San Juan Capistrano |
CA |
US |
|
|
Assignee: |
Sustainable Fiber Solutions,
LLC
San Juan Capistrano
CA
|
Family ID: |
45928110 |
Appl. No.: |
14/167738 |
Filed: |
January 29, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13252983 |
Oct 4, 2011 |
8663743 |
|
|
14167738 |
|
|
|
|
61390088 |
Oct 5, 2010 |
|
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Current U.S.
Class: |
524/386 ;
524/539 |
Current CPC
Class: |
C09D 167/08 20130101;
C09J 7/401 20180101; C09J 2400/283 20130101; C09J 2467/005
20130101; C08L 83/06 20130101; C09J 2483/005 20130101; C09D 167/08
20130101 |
Class at
Publication: |
524/386 ;
524/539 |
International
Class: |
C09J 7/02 20060101
C09J007/02 |
Claims
1. A release coating for a pressure sensitive adhesive product
comprising: 60-90% polyethylene terephthalate modified by the
addition of carboxyl functional fatty acids and 10-40% water
dispersible or emulsifiable silicone.
2. The release coating according to claim 1 comprising 65-90%
modified polyethylene terephthalate and 10-35% water dispersible or
emulsifiable silicone.
3. The release coating according to claim 1 wherein the carboxyl
functional fatty acid is selected from the group consisting of
trimellitic acid, trimellitic anhydride, maleic acid, maleic
anhydride, fumaric acid and isophthalic acid.
4. The release coating according to claim 1 wherein the water
dispersible or emulsifiable silicone comprises an aqueous emulsion
of polyorganosiloxanes and an aqueous emulsion catalyst.
5. The release coating according to claim 4 wherein the aqueous
emulsion catalyst is a platinum catalyst.
6. The release coating according to claim 4 wherein the aqueous
emulsion of polyorganosiloxanes includes propylene glycol and
polydimethyl (methyl hydrogen) siloxane.
7. The release coating according to claim 4 wherein the aqueous
emulsion catalyst comprises an emulsifying agent, propylene glycol
and a platinum complex.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional application of U.S. patent
application Ser. No. 13/252,983, filed Oct. 4, 2011, which claims
the benefit of U.S. Provisional Application No. 61/390,088 filed on
Oct. 5, 2010, the contents of which are hereby incorporated by
reference herein in their entirety for all purposes.
BACKGROUND OF THE INVENTION
[0002] Silicone-based release coatings are useful in applications
where relatively non-adhesive surfaces are required. For example,
pressure sensitive adhesive labels may have a backing sheet that
has applied thereto a silicone-based coating to retain the labels
without affecting the adhesive properties of the labels.
[0003] For example, for the preparation of pressure sensitive
adhesive labels, a paper layer such as glassine, wood free paper or
kraft paper, is coated with a silicone-based film. The silicone
film is then adhered to by the adhesive material of the label
stock. The silicone-based release film allows the adhesive material
of the label stock to be easily removed and for the label stock to
still retain its adhesive characteristics.
[0004] The typical methods for providing release papers for
adhesives is based on three chemistries: silicone, chrome complex
and polyethylene (PE). None of these treatments allow the backing
paper to be recycled.
[0005] In addition, there are three different silicone types:
solvent based, solventless or water-based. Solvent based technology
requires a solvent recovery system so that the solvent does not
escape to the environment causing pollution and to make the process
economical. Solventless technology is expensive and the catalyst
can be easily inactivated by minor contaminants. Solvent-based and
solventless technologies both produce a backing paper which is not
repulpable or recyclable. Water-based silicone technology can
provide performance for a broad range of adhesives, but the
resulting backing paper is not repulpable or recyclable. The chrome
complexes, some of which can be considered as having non-objection
status from the FDA for food contact, still represent a potential
environmental hazard because of their chromium content.
[0006] PE is not recyclable and like the chrome complex, does not
provide performance to a broad range of adhesives, especially the
more aggressive types.
[0007] Published PCT Application WO2008/019953 teaches a
polyorganosiloxane based release coating composition which can be
used to coat polyester films.
[0008] Published PCT Application WO 2010/012787 teaches a liquid
silicone composition for coating a number of substrates, including
polyethylene terephthalate type polymer films.
SUMMARY OF THE INVENTION
[0009] According to a first aspect of the invention, there is
provided a release coating for a pressure sensitive adhesive
product comprising:
[0010] 60-90% polyethylene terephthalate modified by the addition
of carboxyl functional fatty acids and 10-40% water dispersible or
emulsifiable silicone.
[0011] According to a second aspect of the invention, there is
provided a method of applying a release coating onto a pressure
sensitive adhesive product comprising:
[0012] mixing 10-40% water dispersible or emulsifiable silicone
with 60-90% polyethylene terephthalate modified by the addition of
carboxyl functional fatty acids in the presence of a suitable
catalyst, thereby producing a release coating; and
[0013] applying the release coating to a suitable support.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which the invention belongs. Although
many methods and materials similar or equivalent to those described
herein can be used in the practice or testing of the present
invention, the preferred methods and materials are now described.
All publications mentioned hereunder are incorporated herein by
reference.
[0015] Described herein is the use of a modified PET in combination
with a vinyl addition silicone water-based release coating to
provide performance equivalent to silicone coatings at a lower cost
than the silicone by itself and resulting in a release backing
paper that can be repulped and recycled in conventional recycled
paper mills, thereby avoiding the additional cost of sending the
scrap paper to landfill.
[0016] According to a first aspect of the invention, there is
provided a release coating for a pressure sensitive adhesive
product comprising:
[0017] 60-90% polyethylene terephthalate modified by the addition
of carboxyl functional fatty acids and 10-40% water dispersible or
emulsifiable silicone.
[0018] According to a second aspect of the invention, there is
provided a method of applying a release coating onto a pressure
sensitive adhesive product comprising:
[0019] mixing 10-40% water dispersible or emulsifiable silicone
with 60-90% polyethylene terephthalate modified by the addition of
carboxyl functional fatty acids in the presence of a suitable
catalyst, thereby producing a release coating; and
[0020] applying the release coating to a suitable support.
[0021] In other embodiments of the invention, the mixture may be
65-90% modified polyethylene terephthalate and 10-35% water
dispersible or emulsifiable silicone.
[0022] Polyethylene terephthalate (PET) is used in most plastic
beverage bottles. The coatings described herein employ a modified
PET that it is dispersible in water so that it can be applied using
conventional coating equipment as discussed herein. A method for
preparing such a water-dispersible PET is described in U.S. Pat.
No. 5,858,551 which is incorporated herein by reference in its
entirety, particularly the sections describing the preparation of
the water-dispersible PET. The modifications also affect the
polymer properties such that it can be repulped when applied to
paper packaging.
[0023] As discussed in U.S. Pat. No. 5,858,551, the carboxy
functional compound preferably has at least two carboxyl groups. In
preferred embodiments, the carboxy functional compound is selected
from the group consisting of trimellitic acid, trimellitic
anhydride, maleic acid, maleic anhydride, fumaric acid and
isophthalic acid.
[0024] Typical water-based silicone release coatings contain a
reactive polymer dispersed in water; this polymer may contain
another reactive polymer that will crosslink with the first polymer
or the crosslinking polymer may be incorporated in a second
material, for example, a catalyst, which is added to the reactive
polymer prior to usage. The mixture of reactive polymer, reactive
crosslinking polymer and catalyst are typically applied to the
paper substrate using a paper coater. The resulting film is then
dried and cured using ovens and/or IR heaters. It is noted that
such water-based silicone release coatings are well known in the
art. Exemplary examples are described in a number of patents,
including but by no means limited to U.S. Pat. No. 5,138,012; U.S.
Pat. No. 6,734,217; U.S. Pat. No. 2,606,510; U.S. Pat. No.
2,462,242; U.S. Pat. No. 4,448,815; U.S. Pat. No. 4,576,999; U.S.
Pat. No. 5,108,782; U.S. Pat. No. 4,423,095 and U.S. Pat. No.
4,454,266.
[0025] As will be apparent to one of skill in the art, water based
silicone coatings are preferred within the invention because the
water based silicone coatings are miscible with the
water-dispersible PET described above.
[0026] Preferably, the water-based silicone release coating is an
aqueous emulsion of polyorganosiloxanes and an aqueous emulsion
catalyst, for example, a platinum catalyst. More preferably, the
aqueous emulsion of polyorganosiloxanes is a mixture of
polyorganosiloxanes, water, propylene glycol and polydimethyl
(methyl hydrogen) siloxane and the aqueous emulsion catalyst is a
mixture of polyorganosiloxanes, water, an emulsifying agent,
propylene glycol and a platinum complex.
[0027] As noted above, the modified PET is a PET-containing polymer
that has been chemically modified with the addition of carboxyl
functional fatty acids. Specifically, the modified PET is a water
dispersible and redispersible hydrophilic polyester resin derived
from PET or recycled PET and has improved hydrophobicity and/or
non-polar characteristics, as described in U.S. Pat. No. 5,858,551.
As discussed therein, the polyester resins have a general formula
of: I.sub.n-P-A.sub.m wherein I is the ionic group, n is an integer
of 1-3, P is a polyester backbone, A is an aliphatic group and m is
an integer of 3-8. PET content can vary from 30-80% though 40-60%,
50-60% or 40-50% is preferred. Due to the carboxyl functionality on
the modified PET, the modified PET is self emulsifying when it is
mixed with water that contains a base. Various bases can be used,
but ammonia is preferred because it is fugitive; i.e., when the
coating is heated, the ammonia vaporizes leaving a durable surface
that is not easily adhered to by adhesives.
[0028] For use, the catalyst is mixed with the silicone water-based
coating. To this mixture the modified PET is added with agitation
in the desired ratio to blend the two materials. This mixture is
then applied to a paper surface or other suitable support using
similar techniques known in the art for silicone coatings.
[0029] Silicone paper coatings are very expensive; however, by
virtue of using a mixture of silicone and PET, there is a
significant reduction in the cost of the release coating. In
addition, the coated paper can be repulped and recycled, resulting
in a significant income stream to the converter rather than a cost
for sending the material to a landfill.
[0030] The instant invention is designed to replace the alternative
methods known in the art by providing performance to aggressive and
standard adhesives while having the added advantage of being
repulpable and recyclable. Adhesive strength is determined by
measuring the force in Win required to remove the adhesive backed
pressure sensitive label or decorative top sheet. It is of note
that `prime` release is considered to require 5-15 g/in, `medium`
release requires 15-150 g/in while `high` release requires 150-500
g/in.
[0031] Pressure sensitive adhesives are used in a number of
applications. For example, they are used in applications such as
name tags that utilize adhesives that are temporary and/or don't
have strong adhesive characteristics. They can also be used with an
adhesive that will have to permanently bond to the substrate once
the protective backing paper is removed. Each application may
require a different release surface in order to maximize
performance economically. These categories are typically known as
Repositionable, Reusable or Permanent Labels.
[0032] It is known in the industry that the typical coatings (e.g.,
silicone, chrome complex or PE) that are used in the various
applications are not repulpable or recyclable. The current
manufacturers and users have to send cut waste/matrix from the
manufacturing process and used backing paper to landfill or to an
incinerator to dispose of them.
[0033] In some embodiments, the modified PET has a recycled plastic
content of 40-45% and a renewable content (i.e., non-petroleum
based) of 20-25%.
[0034] A non-recyclable backing paper has a significant cost: the
backing paper has to be sent to landfill or be incinerated; this
becomes a cost to the producer of the backing paper and the user of
the final sandwich of backing paper, release coating, adhesive and
label stock; this additional cost will ultimately be reflected in
the cost of the end product that utilizes the backing paper. If the
backing paper can be sent back to a recycled paper mill, the
producer of the scrap would be paid for this product.
[0035] As will be apparent to one knowledgeable in the art, there
are a wide range of adhesives that utilize a release backing paper,
depending on the application. The release coating described herein
will provide performance that will be acceptable from a release
perspective for all adhesive classes, but also provide a backing
paper that can be repulped and recycled.
[0036] A suitable silicone catalyst is also added. It is noted that
such catalysts are well known in the art. In a preferred
embodiment, the catalyst is platinum or platinum-based. Exemplary
examples of such catalysts include but are by no means limited to
those described in U.S. Pat. No. 3,159,602; U.S. Pat. No.
3,220,972; European Patent 0,057,459; European Patent 0,188,978;
and European Patent 0,190,530.
[0037] It has been found that when the modified PET as described
above is mixed with a commercially available water-based silicone
release coating based on rare metal (e.g., platinum complex)
addition catalysts as discussed above, release equivalent to that
obtained with silicone, PE or chrome complex can be achieved when
using 10-40% by weight of the silicone (on a dry basis) and 90-60%
of the modified PET (on a dry basis). It is believed that other
silicone cure chemistries will exhibit the same performance when
utilized with the modified PET described above. In addition, these
mixtures, unlike the pure silicone, will be repulpable and
recyclable.
[0038] While not wishing to be bound to a particular hypothesis or
theory, it is believed that the fatty acid modified PET orients at
the surface of the paper so that the fatty acid faces away from the
paper providing a low surface energy film to which the adhesive
can't adhere. The modified PET is compatible with the water-based
silicone, as discussed above.
[0039] The invention described herein is directed to release
backings for various pressure sensitive release applications.
Pressure sensitive release papers are used in a number of
applications. These include the simple and non-demanding
applications such as name labels that are individually removed and
applied by an individual. A more demanding application would be the
labels that are used to attach, for example, a FedEx or UPS label
to the box or the plastic covers that are removed to close the box.
The most complex applications are those in which the face or
printed papers are removed by a robot and stuck to a surface. An
example of this would be medallions and other paraphernalia that
are applied to various consumer products such as autos, appliances
and other commercial items.
[0040] As discussed herein, the described coating will perform
equally to the prior art silicone coatings but also provide a
backing paper that can be recycled and repulped.
[0041] In some embodiments, a base coat, for example, a typical
pigment (for example but by no means limited to kaolin clay or
other such inorganic material typically used in the paper industry)
plus binder (for example a styrene-butadiene latex) is applied to
the surface to be coated prior to the application of the
PET/silicone coating. The ratio of pigment to binder can vary
depending on substrate and performance requirements. In preferred
embodiments, the ratio is between 3:1 and 1:3 pigment to latex
solids.
[0042] In use, a commercially available silicone release emulsion
and its catalyst are mixed together in the desired ratios. To this
is added a prescribed amount of the modified PET as described
above. This mixture of silicone and PET is then pumped to a coating
station where it is applied to a paper substrate. In some
embodiments, depending on the substrate, a basecoat such as the one
described above is applied to the substrate prior to applying the
mixture of modified PET and catalyzed silicone release coating. In
some embodiments, the coated paper is dried and cured, for example,
such that the coated surface achieves a temperature of about 100C
(min); it then must be cooled for example to about <45C before
it is taken to the reel. It is noted that these temperatures are
intended for illustrative purposes and that other suitable
temperatures will be readily apparent to one of skill in the art
through routine experimentation.
[0043] This paper is then sent to a converting operation where an
adhesive is applied to the back of a decorative face sheet which is
then combined with the coated backer sheet. This operation results
in some amounts of scrap paper or cut waste that can now be sent to
a recycled mill rather than being burned or sent to landfill. As
the product approaches the end market or ultimate user, waste from
the processing or the remaining backing paper that can recovered
from the process can also go to the recycle mill who will pay for
this fiber source rather than going to landfill where the owner
will have to pay to have it disposed of.
[0044] It is our understanding that typical silicone, QUILON.TM.
(chrome complex--DuPont) or PE backing papers cannot be recycled.
For the silicone, when recycled they may cause spots on the
resulting paper and/or build up on the paper machine. QUILON.TM.
could be a problem because of its chromium content; certain
oxidative states of chromium are highly toxic and a paper mill
would not want to introduce this potential hazard into its process.
PE laminated backing papers not repulpable; if a PE film is used as
the backing, it could be recycled into plastic film. The
above-described PET/silicone combinations are fully repulpable and
recyclable.
[0045] While the preferred embodiments of the invention have been
described above, it will be recognized and understood that various
modifications may be made therein, and the appended claims are
intended to cover all such modifications which may fall within the
spirit and scope of the invention.
* * * * *