U.S. patent application number 09/330923 was filed with the patent office on 2002-08-22 for adhesives for use on fluorine-containing or polycarbonate surfaces.
Invention is credited to AELING, ELLEN O., EVERAERTS, ALBERT I., PELOQUIN, RICHARD L..
Application Number | 20020115808 09/330923 |
Document ID | / |
Family ID | 23291884 |
Filed Date | 2002-08-22 |
United States Patent
Application |
20020115808 |
Kind Code |
A1 |
PELOQUIN, RICHARD L. ; et
al. |
August 22, 2002 |
ADHESIVES FOR USE ON FLUORINE-CONTAINING OR POLYCARBONATE
SURFACES
Abstract
Adhesives useful in applying articles, such as tapes, labels,
signs, decals, emblems, car moldings, protective or optical films,
etc., to surfaces to which articles normally do not adhere well,
such as surfaces containing fluorine and polycarbonate, for
example. The adhesives include a copolymer of one or more
monoethylenically unsaturated alkyl (meth)acrylate monomers, one or
more monoethylenically unsaturated secondary or tertiary
amide-functional monomers, and optionally one or more acidic
monomers.
Inventors: |
PELOQUIN, RICHARD L.;
(MAPLEWOOD, MN) ; EVERAERTS, ALBERT I.; (BELGIUM,
DE) ; AELING, ELLEN O.; (ST PAUL, MN) |
Correspondence
Address: |
MUETING RAASCH & GEBHARDT PA
PO BOX 581415
MINNEAPOLIS
MN
55458
|
Family ID: |
23291884 |
Appl. No.: |
09/330923 |
Filed: |
June 11, 1999 |
Current U.S.
Class: |
526/307.7 ;
428/522; 522/126; 522/168; 522/171; 522/173; 522/180; 522/182;
526/287; 526/303.1; 526/310; 526/312; 526/317.1; 526/318.3 |
Current CPC
Class: |
C09J 133/062 20130101;
C09J 2301/302 20200801; B32B 7/12 20130101; B32B 27/365 20130101;
C09J 2301/304 20200801; B32B 27/30 20130101; B32B 2369/00 20130101;
Y10T 428/31935 20150401; B32B 27/08 20130101; C09J 2433/00
20130101; C09J 7/385 20180101 |
Class at
Publication: |
526/307.7 ;
526/310; 526/312; 526/317.1; 526/303.1; 526/318.3; 526/287;
522/126; 522/168; 522/171; 522/173; 522/180; 522/182; 428/522 |
International
Class: |
C08F 218/02 |
Claims
What is claimed is:
1. A pressure sensitive adhesive having a Tg of at least about
-20.degree. C. comprising a copolymer comprising: at least one
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester comprising an alkyl group having at least 4 carbons on
average; at least one copolymerized monoethylenically unsaturated
(meth)acrylic acid ester comprising an alkyl group having less than
4 carbons on average; and greater than 10 parts by weight, based on
the total weight of monomers, of at least one copolymerized
monoethylenically unsaturated monomer having a secondary or
tertiary amide group of the formula -C(O)NR.sup.1R.sup.2 wherein
R.sup.1 and R.sup.2 are each independently H or a saturated or
unsaturated hydrocarbon moiety, which optionally forms a ring with
the carbonyl carbon (--C(O)) of the amide group.
2. The pressure sensitive adhesive of claim 1 wherein the
monoethylenically unsaturated (meth)acrylic acid ester comprising
an alkyl group having at least 4 carbons has a Tg of less than
about 0.degree. C. as a homopolymer, and the monoethylenically
unsaturated (meth)acrylic acid ester comprising an alkyl group
having less than 4 carbons has a Tg of less than about 50.degree.
C. as a homopolymer.
3. The pressure sensitive adhesive of claim 1 wherein a 50-micron
thick polymeric plasticized vinyl film having a 35-micron thick
layer of the adhesive disposed thereon has a 180.degree. peel
adhesion value of no greater than about 35 N/100 mm, measured at a
30.5 cm per minute peel rate, from a surface comprising an 80/20
polyvinylidenefluoride/polymethy- lmethacrylate blend after contact
for 24 hours at 22.degree. C.
4. The pressure sensitive adhesive of claim 3 wherein a 50-micron
thick polymeric plasticized vinyl film having a 35-micron thick
layer of the adhesive disposed thereon has a 180.degree. peel
adhesion value of at least about 70 N/100 mm, measured at a 30.5 cm
per minute peel rate, from a surface comprising an 80/20
polyvinylidenefluoride/polymethylmethacryla- te blend after contact
for 7 days at 66.degree. C.
5. The pressure sensitive adhesive of claim 1 wherein the amount of
copolymerized monethylenically unsaturated (meth)acrylic acid ester
comprising an alkyl group having at least 4 carbon atoms on average
is at least about 5 parts to no greater than about 95 parts by
weight, based on the total weight of monomers.
6. The pressure sensitive adhesive of claim 1 wherein the amount of
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester comprising an alkyl group having less than 4 carbon atoms on
average is no greater than about 90 parts, based on the total
weight of monomers.
7. The pressure sensitive adhesive of claim 1 wherein the amount of
copolymerized monoethylenically unsaturated monomer having a
secondary or tertiary amide group is no greater than about 50 parts
by weight, based on the total weight of monomers.
8. The pressure sensitive adhesive of claim 1 wherein the copolymer
further comprises at least one copolymerized acidic monomer.
9. The pressure sensitive adhesive of claim 1 which is coated on at
least one surface of a film or a foam.
10. An adhesive having a Tg of at least about -20.degree. C.
comprising a copolymer comprising: at least one copolymerized
monoethylenically unsaturated (meth)acrylic acid ester comprising
an alkyl group having at least 4 carbons on average; at least one
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester comprising an alkyl group having less than 4 carbons on
average; and greater than 10 parts by weight, based on the total
weight of monomers, of at least one copolymerized monoethylenically
unsaturated monomer having a secondary or tertiary amide group of
the formula --C(O)NR.sup.1R.sup.2 wherein R.sup.1 and R.sup.2 are
each independently H or a saturated or unsaturated hydrocarbon
moiety, which optionally forms a ring with the carbonyl carbon
(--C(O)) of the amide group; wherein all of the copolymerized
monoethylenically unsaturated (meth)acrylic acid esters of the
copolymer have a Tg of less than about 50.degree. C. as a
homopolymer.
11. The adhesive of claim 10 wherein the adhesive is a pressure
sensitive adhesive.
12. The adhesive of claim 10 wherein the adhesive is a heat
activatable adhesive.
13. A pressure sensitive adhesive having a Tg of at least about
-20.degree. C. comprising a copolymer comprising: about 10 parts to
about 70 parts by weight, based on the total weight of monomers, of
at least one copolymerized monoethylenically unsaturated
(meth)acrylic acid ester comprising an alkyl group having at least
4 carbons on average; about 20 parts to about 80 parts by weight,
based on the total weight of monomers, of at least one
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester comprising an alkyl group having less than 4 carbons on
average; and greater than 10 parts and up to about 50 parts by
weight, based on the total weight of monomers, of at least one
copolymerized monoethylenically unsaturated monomer having a
secondary or tertiary amide group of the formula
--C(O)NR.sup.1R.sup.2 wherein R.sup.1 and R.sup.2 are each
independently H or a saturated or unsaturated hydrocarbon moiety,
which optionally forms a ring with the carbonyl carbon (--C(O)) of
the amide group.
14. A pressure sensitive adhesive having a Tg of at least about
-20.degree. C. comprising a copolymer comprising: at least one
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester comprising an alkyl group having at least 4 carbons on
average and which as a homopolymer has a Tg of less than about
0.degree. C.; at least one copolymerized monoethylenically
unsaturated (meth)acrylic acid ester comprising an alkyl group
having less than 4 carbons on average and which as a homopolymer
has a Tg of less than about 50.degree. C.; and greater than 10
parts by weight, based on the total weight of monomers, at least
one copolymerized monoethylenically unsaturated monomer having a
secondary or tertiary amide group of the formula
--C(O)NR.sup.1R.sup.2 wherein R.sup.1 and R.sup.2 are each
independently H or a saturated or unsaturated hydrocarbon moiety,
which optionally forms a ring with the carbonyl carbon (--C(O)) of
the amide group; wherein a 50-micron thick polymeric plasticized
vinyl film having a 35-micron thick layer of the pressure sensitive
adhesive disposed thereon has a 180.degree. peel adhesion value of
no greater than about 35 N/100 mm, measured at a 30.5 cm per minute
peel rate, from a surface comprising an 80/20
polyvinylidenefluoride/polymethylmethacrylate blend after contact
for 24 hours at 22.degree. C., and after 7 days at 66.degree. C.
has a 180.degree. peel adhesion value of at least about 70 N/100
mm, measured at a 30.5 cm per minute peel rate.
15. An article comprising a substrate surface comprising a
nonperfluorinated fluoropolymer derived from at least one
hydrofluoro monomer, and an adhesive-coated article adhered
thereto, wherein the adhesive-coated article comprises a backing,
which has disposed on at least one major surface thereof an
adhesive which is adhered to the substrate surface; wherein the
adhesive comprises a copolymer comprising: at least one
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester; and at least one copolymerized monoethylenically unsaturated
monomer having a secondary or tertiary amide group.
16. The article of claim 15 wherein the substrate surface
comprising a nonperfluorinated fluoropolymer derived from at least
one hydrofluoro monomer further comprises polymethylmethacrylate
blended therewith.
17. The article of claim 15 wherein the copolymer comprises: at
least one copolymerized monoethylenically unsaturated (meth)acrylic
acid ester comprising an alkyl group having less than 4 carbon
atoms on average; at least one copolymerized monoethylenically
unsaturated (meth)acrylic acid ester comprising an alkyl group
having at least 4 carbon atoms on average; and at least one
copolymerized monoethylenically unsaturated monomer having a
secondary or tertiary amide group.
18. The article of claim 17 wherein the copolymer further comprises
at least one copolymerized acidic monomer.
19. The article of claim 15 wherein the backing is in the form of a
film or a foam.
20. The article of claim 15 wherein the adhesive is a pressure
sensitive adhesive.
21. An article comprising a substrate surface comprising a
polycarbonate and an adhesive-coated article adhered thereto,
wherein the adhesive-coated article comprises a backing, which has
disposed on at least one major surface thereof an adhesive which is
adhered to the substrate surface; wherein the adhesive comprises a
copolymer comprising: at least one copolymerized monoethylenically
unsaturated (meth)acrylic acid ester; and at least one
copolymerized monoethylenically unsaturated monomer having a
secondary or tertiary amide group of the formula
--C(O)NR.sup.1R.sup.2 wherein R.sup.1 and R.sup.2 are each
independently H or a saturated or unsaturated hydrocarbon moiety,
which optionally forms a ring with the carbonyl carbon (--C(O)) of
the amide group.
22. The article of claim 21 wherein the copolymer comprises: at
least one copolymerized monoethylenically unsaturated (meth)acrylic
acid ester comprising an alkyl group having less than 4 carbon
atoms on average; at least one copolymerized monoethylenically
unsaturated (meth)acrylic acid ester comprising an alkyl group
having at least 4 carbon atoms on average; and at least one
copolymerized monoethylenically unsaturated monomer having a
secondary or tertiary amide group of the formula
--C(O)NR.sup.1R.sup.2 wherein R.sup.1 and R.sup.2 are each
independently H or a saturated or unsaturated hydrocarbon moiety,
which optionally forms a ring with the carbonyl carbon (--C(O)) of
the amide group.
23. The article of claim 22 wherein the copolymer further comprises
at least one copolymerized acidic monomer.
24. The article of claim 21 wherein the backing is in the form of a
film or a foam.
25. The article of claim 21 wherein the adhesive is a pressure
sensitive adhesive.
26. An article comprising a substrate surface comprising
plasticized polymer, and an adhesive-coated article adhered
thereto, wherein the adhesive-coated article comprises a backing,
which has disposed on at least one major surface thereof an
adhesive which is adhered to the substrate surface; wherein the
adhesive has a Tg of at least about -20.degree. C. and comprises a
copolymer comprising: at least one copolymerized monoethylenically
unsaturated (meth)acrylic acid ester comprising an alkyl group
having less than 4 carbon atoms on average; at least one
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester comprising an alkyl group having at least 4 carbon atoms on
average; at least one copolymerized monoethylenically unsaturated
monomer having a secondary or tertiary amide group; and at least
one acidic monomer; wherein all of the copolymerized
monoethylenically unsaturated (meth)acrylic acid esters of the
copolymer have a Tg of less than about 50.degree. C. as a
homopolymer.
27. A method of adhering an article to a substrate surface
comprising a nonperfluorinated fluoropolymer derived from at least
one hydrofluoro monomer, the method comprising applying to the
substrate surface an adhesive-coated article, which comprises a
backing and an adhesive disposed on at least one major surface
thereof, such that the adhesive is adhered to the substrate
surface, wherein the adhesive comprises a copolymer comprising: at
least one copolymerized monoethylenically unsaturated (meth)acrylic
acid ester; and at least one copolymerized monoethylenically
unsaturated monomer having a secondary or tertiary amide group.
28. The method of claim 27 wherein the backing comprises a film or
a foam.
29. A method of adhering an article to a substrate surface
comprising a polycarbonate, the method comprising applying to the
substrate surface an adhesive-coated article, which comprises a
backing and an adhesive disposed on at least one major surface
thereof, such that the adhesive is adhered to the substrate
surface, wherein the adhesive comprises a copolymer comprising: at
least one copolymerized monoethylenically unsaturated (meth)acrylic
acid ester; and at least one copolymerized monoethylenically
unsaturated monomer having a secondary or tertiary amide group of
the formula --C(O)NR.sup.1R.sup.2 wherein R.sup.1 and R.sup.2 are
each independently H or a saturated or unsaturated hydrocarbon
moiety, which optionally forms a ring with the carbonyl carbon
(--C(O)) of the amide group.
30. A method of adhering an article to a substrate surface
comprising a plasticized polymer, the method comprising applying to
the substrate surface an adhesive-coated article, which comprises a
backing and an adhesive disposed on at least one major surface
thereof, such that the adhesive is adhered to the substrate
surface, wherein the adhesive has a Tg of at least about
-20.degree. C. and comprises a copolymer comprising: at least one
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester comprising an alkyl group having less than 4 carbon atoms on
average; at least one copolymerized monoethylenically unsaturated
(meth)acrylic acid ester comprising an alkyl group having at least
4 carbon atoms on average; at least one copolymerized
monoethylenically unsaturated monomer having a secondary or
tertiary amide group; and at least one acidic monomer; wherein all
of the copolymerized monoethylenically unsaturated (meth)acrylic
acid esters of the copolymer have a Tg of less than about
50.degree. C. as a homopolymer.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to adhesives, particularly
adhesives that are useful on fluorine-containing or polycarbonate
surfaces and, more specifically, to pressure sensitive adhesives
that include a copolymer of one or more alkyl (meth)acrylate
monomers, one or more amide-functional monomers, and optionally one
or more acidic monomers.
BACKGROUND
[0002] Graphic marking films or labels that include vinyl films
coated with acrylic pressure sensitive adhesives (PSAs) are
well-known in the art. Such films are typically applied to
plasticized polyvinylchloride substrates which may have a thin
dirt- and chemical-resistant top coating. Such clear top coatings
include fluorine-containing polymers, for example. One such product
includes a clear top surface containing a blend of
polymethylmethacrylate (PMMA) and a copolymer of vinylidenefluoride
(VDF) and chlorotrifluoroethylene (CTFE). Typically, the higher the
fluoropolymer content of such surfaces, the better the dirt
repellancy. As long as this clear top surface includes a major
amount of PMMA, adequate bond formation of a vinyl marking film is
obtained using an acrylic PSA containing a copolymer of an
alkylacrylate and acrylic acid (AA). This adhesive, however, does
not work effectively on clear top surfaces that include a major
amount of fluorine-containing polymer and a minor amount of PMMA or
no PMMA. In general, the ability to provide such label and graphic
marking films, or other articles, with high bonding strength to
surfaces containing fluorine has not been generally possible
without surface treatment of the substrate (e.g., chemical
priming).
[0003] Similarly, it is difficult to adhere articles to substrate
surfaces that include polycarbonates, or plasticized polymers such
as polyvinylchloride. There are a limited number of known
adhesives, many of which are based on acrylate chemistry, that can
be used, however. For example, U.S. Pat. No. 5,612,136 (Everaerts
et al.) discloses acrylate-based (i.e., acrylic) pressure sensitive
adhesive compositions that adhere well to acidic surfaces. The
adhesive is prepared from an alkyl acrylate, wherein the alkyl
group includes four or more carbon atoms, which is copolymerized
with basic monomers, such as dialkyl substituted amides. Lower
(less than C4) alkyl acrylates can be copolymerized with such
monomers provided that the glass transition temperature (Tg) of the
resultant polymer is below about -20.degree. C. U.S. Pat. No.
5,905,099 (Everaerts et al.) discloses heat-activatable adhesive
compositions prepared from a low Tg (homopolymer Tg of no greater
than about 0.degree. C.) alkyl acrylate, wherein the alkyl group
includes two or more carbon atoms, a high Tg acrylate (homopolymer
Tg of at least about 50.degree. C.), such as a cycloalkyl or
aromatic acrylate, and a polar functional monomer such as a
carboxylic acid, an N-substituted amide, an N-substituted amine,
and a carbamate. Weakly basic monomers, such as N,N-dimethyl
acrylamide and N-vinyl pyrrolidone are disclosed as enhancing
adhesion to plasticized and rigid polyvinylchloride. Acidic
functional monomers, such as acrylic acid, are disclosed as
enhancing adhesion to polar surfaces such as glass, metals, paint,
and basic surfaces.
[0004] U.S. Pat. No. 4,985,488 (Landin) discloses a
plasticizer-resistant acrylate-based adhesive prepared from
nitrogen-containing alkyl acrylate monomers, wherein the alkyl
group includes four or more carbon atoms. U.S. Pat. No. 5,334,686
(Ando et al.) discloses acrylate-based adhesives prepared from
alkyl acrylates, wherein the alkyl group includes four or more
carbon atoms, dialkyl-substituted acrylamides, and acids. JP
8-143843 (Nitto) discloses removable acrylate-based adhesives
prepared from alkyl acrylates, wherein the alkyl group includes two
or more carbon atoms, N,N-dialkyl acrylamides, and carboxylic
acids. U.S. Pat. No. 4,605,592 (Paquette et al.) discloses
plasticizer-resistant acrylate-based pressure sensitive adhesive
compositions prepared from alkyl acrylates, wherein the alkyl group
includes four or more carbon atoms, to prevent vinyl decorative
graphics from wrinkling. JP 06-108025A (Nippon) discloses
acrylate-based adhesives for bonding cellulose to glass without
appearance defects. One example includes a copolymer of, for
example, n-butyl acrylate, methyl acrylate, acrylic acid, and an
amide such as N,N-dimethyl acrylamide, wherein the amide monomer is
present in an amount of 0.3-10 weight percent of the copolymer.
[0005] There is still a need in the art for other adhesives that
can be used to adhere articles to surfaces such as
fluorine-containing or polycarbonate surfaces that do not typically
demonstrate particularly good adhesion.
SUMMARY
[0006] This invention relates generally to adhesives useful for
adhering articles to fluorine-containing or polycarbonate surfaces,
for example. Preferably, adhesives of the present invention have an
initial level of adhesion that allows an article to be removable
and/or repositionable, but which builds to a greater level of
permanency with time, heat, and/or pressure, for example. The
adhesive may be pressure sensitive or heat activatable.
[0007] In one embodiment, a pressure sensitive adhesive (PSA)
having a Tg of at least about -20.degree. C. is provided. The PSA
includes a copolymer comprising: at least one copolymerized
monoethylenically unsaturated (meth)acrylic acid ester comprising
an alkyl group having at least 4 carbons on average; at least one
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester comprising an alkyl group having less than 4 carbons on
average; and greater than 10 parts by weight, based on the total
weight of monomers, of at least one copolymerized monoethylenically
unsaturated monomer having a secondary or tertiary amide group of
the formula --C(O)NR.sup.1R.sup.2 wherein R.sup.1 and R.sup.2 are
each independently H or a saturated or unsaturated hydrocarbon
moiety, which optionally forms a ring with the carbonyl carbon
(--C(O)) of the amide group.
[0008] In another embodiment, the present invention provides an
adhesive (which can be a pressure sensitive or heat activatable
adhesive) having a Tg of at least about -20.degree. C. that
includes a copolymer comprising: at least one copolymerized
monoethylenically unsaturated (meth)acrylic acid ester comprising
an alkyl group having at least 4 carbons on average; at least one
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester comprising an alkyl group having less than 4 carbons on
average; and greater than 10 parts by weight, based on the total
weight of monomers, of at least one copolymerized monoethylenically
unsaturated monomer having a secondary or tertiary amide group of
the formula --C(O)NR.sup.1R.sup.2 wherein R.sup.1 and R.sup.2 are
each independently H or a saturated or unsaturated hydrocarbon
moiety, which optionally forms a ring with the carbonyl carbon
(--C(O)) of the amide group. In this embodiment, all of the
copolymerized monoethylenically unsaturated (meth)acrylic acid
esters of the copolymer have a Tg of less than about 50.degree. C.
as a homopolymer. Preferably, the copolymer further includes at
least one copolymerized acidic monomer.
[0009] Preferably, a 50-micron thick polymeric plasticized vinyl
film having a 35-micron thick layer of the adhesive disposed
thereon has a 180.degree. peel adhesion value of no greater than
about 35 N/100 mm, measured at a 30.5 cm per minute peel rate, from
a surface comprising an 80/20
polyvinylidenefluoride/polymethylmethacrylate blend after contact
for 24 hours at 22.degree. C. Preferably, if stored for 7 days at
66.degree. C., the 180.degree. peel adhesion value is at least
about 70 N/100 mm.
[0010] In yet another embodiment, the present invention provides a
pressure sensitive adhesive having a Tg of at least about
-20.degree. C. The PSA includes a copolymer comprising: at least
one copolymerized monoethylenically unsaturated (meth)acrylic acid
ester comprising an alkyl group having at least 4 carbons on
average and which as a homopolymer has a Tg of less than about
0.degree. C.; at least one copolymerized monoethylenically
unsaturated (meth)acrylic acid ester comprising an alkyl group
having less than 4 carbons on average and which as a homopolymer
has a Tg of less than about 50.degree. C.; and greater than 10
parts by weight, based on the total weight of monomers, at least
one copolymerized monoethylenically unsaturated monomer having a
secondary or tertiary amide group of the formula
--C(O)NR.sup.1R.sup.2 wherein R.sup.1 and R.sup.2 are each
independently H or a saturated or unsaturated hydrocarbon moiety,
which optionally forms a ring with the carbonyl carbon (--C(O)) of
the amide group; wherein a 50-micron thick polymeric plasticized
vinyl film having a 35-micron thick layer of the pressure sensitive
adhesive disposed thereon has a 180.degree. peel adhesion value of
no greater than about 35 N/100 mm, measured at a 30.5 cm per minute
peel rate, from a surface comprising an 80/20
polyvinylidenefluoride/polymethylmethacrylate blend after contact
for 24 hours at 22.degree. C., and after 7 days at 66.degree. C.
has a 180.degree. peel adhesion value of at least about 70 N/100
mm, measured at a 30.5 cm per minute peel rate.
[0011] The present invention also provides an article comprising a
substrate surface comprising a nonperfluorinated fluoropolymer
derived from at least one hydrofluoro monomer, and an
adhesive-coated article adhered thereto, and a method of adhering.
The adhesive-coated article comprises a backing (e.g., a film or a
foam), which has disposed on at least one major surface thereof an
adhesive which is adhered to the substrate surface; wherein the
adhesive comprises a copolymer comprising at least one
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester (preferably, at least one copolymerized monoethylenically
unsaturated (meth)acrylic acid ester comprising an alkyl group
having less than 4 carbon atoms on average, and at least one
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester comprising an alkyl group having at least 4 carbon atoms on
average) and at least one copolymerized monoethylenically
unsaturated monomer having a secondary or tertiary amide group.
Preferably, the substrate surface further includes a
polymethylmethacrylate blended with the nonperfluorinated
fluoropolymer derived from at least one hydrofluoro monomer. In
certain embodiments the copolymer further includes at least one
copolymerized acidic monomer.
[0012] A further embodiment of the present invention is an article
comprising a substrate surface comprising a polycarbonate and an
adhesive-coated article adhered thereto, and a method of adhering.
The adhesive-coated article comprises a backing (e.g., a film or a
foam), which has disposed on at least one major surface thereof an
adhesive which is adhered to the substrate surface; wherein the
adhesive comprises a copolymer comprising: at least one
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester (preferably, at least one copolymerized monoethylenically
unsaturated (meth)acrylic acid ester comprising an alkyl group
having less than 4 carbon atoms on average, and at least one
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester comprising an alkyl group having at least 4 carbon atoms on
average); and at least one copolymerized monoethylenically
unsaturated monomer having a secondary or tertiary amide group of
the formula --C(O)NR.sup.1R.sup.2 wherein R.sup.1 and R.sup.2 are
each independently H or a saturated or unsaturated hydrocarbon
moiety, which optionally forms a ring with the carbonyl carbon
(--C(O)) of the amide group. In certain embodiments the copolymer
further includes at least one copolymerized acidic monomer.
[0013] A still further embodiment of the present invention is an
article comprising a substrate surface comprising a plasticized
polymer and an adhesive-coated article adhered thereto, and a
method of adhering. The adhesive-coated article comprises a backing
(e.g., a film or a foam), which has disposed on at least one major
surface thereof an adhesive which is adhered to the substrate
surface; wherein the adhesive has a Tg of at least about
-20.degree. C. and comprises a copolymer comprising: at least one
copolymerized monoethylenically unsaturated (meth)acrylic acid
ester comprising an alkyl group having less than 4 carbon atoms on
average; at least one copolymerized monoethylenically unsaturated
(meth)acrylic acid ester comprising an alkyl group having at least
4 carbon atoms on average; at least one copolymerized
monoethylenically unsaturated monomer having a secondary or
tertiary amide group; and at least one acidic monomer. In this
embodiment, all of the copolymerized monoethylenically unsaturated
(meth)acrylic acid esters of the copolymer have a Tg of less than
about 50.degree. C. as a homopolymer.
[0014] Methods of adhering an article to a substrate surface are
also provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic representation of the cross-section of
a vinyl film label or graphic applied to a plasticized vinyl
substrate which has a dirt and chemical resistant top coating.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0016] This invention relates broadly to adhesives that are useful
in applying articles, such as tapes, labels, signs, decals,
emblems, car moldings, protective or optical films, etc., to
surfaces to which articles normally do not adhere well. Typically
and preferably, such surfaces contain fluorine, particularly
nonperfluorinated fluoropolymers derived from monomers, at least
one of which is a hydrofluoro monomer (i.e., a monomer of the
formula (H)(X)C.dbd.C(Y)(Z) wherein at least one of X, Y, and Z is
F, and otherwise is H, an alkyl, a perfluoroalkyl, or another
halogen), optionally blended with another polymer such as
polymethylmethacrylate. Another preferred surface to which it is
difficult to adhere articles is polycarbonate. Alternatively, such
surfaces may contain plasticized polymers, such as polyvinyl
chloride, although this is not a preferred surface.
[0017] The adhesives of the present invention include a copolymer
of one or more monoethylenically unsaturated alkyl (meth)acrylate
monomers, one or more monoethylenically unsaturated secondary or
tertiary amide-functional monomers, and optionally one or more
acidic monomers. Such copolymers may or may not be crosslinked.
Preferably, they form an adhesive that has a glass transition
temperature (Tg) of at least about -20.degree. C. Preferably, they
are generally optically clear (i.e., able to be seen through
without significant optical distortion) as well as removable and/or
repositionable within an initial period of time, preferably within
about 24 hours. As used herein, a "removable" adhesive is one that
can be adhered to a substrate surface and the adhesive and backing
can be simultaneously removed from the substrate without bond
failure between the adhesive and the backing. A "repositionable"
adhesive is one that can be applied and adhered to a substrate
surface and then removed (generally within about 24 hours) and
reapplied without distorting, defacing, or destroying the backing,
adhesive, or substrate. The adhesion properties of the adhesives of
the present invention preferably build with time, heat, and/or
pressure such that they are capable of providing high levels of
adhesion once the adhesive-coated article is in position.
[0018] Preferred adhesives are pressure sensitive, although
heat-activatable adhesives are also possible. A pressure sensitive
adhesive is conventionally understood to refer to an adhesive that
displays aggressive tackiness to a wide variety of substrates after
applying only light pressure. In contrast, heat-activatable
adhesives may be applied to a substrate by simple heating of the
adhesive at or above its Tg to make the bond. An accepted
quantitative description of a pressure sensitive adhesive is given
by the Dahlquist criterion, which indicates that materials having a
storage modulus (G') of less than about 4.0.times.10.sup.5 Pascals
(measured at room temperature) have pressure sensitive adhesive
properties while materials having a G.sup.40 in excess of this
value do not.
[0019] Preferred adhesive compositions and articles coated with
such adhesive compositions of the invention provide relatively low
initial adhesion but show acceptable levels of adhesion build such
that the articles are initially removable and/or repositionable but
become permanent (typically showing adhesion greater than about 90
N/100 mm for an indefinite period of time) once in position on a
substrate surface. This adhesion build can result from the passage
of time, the application of pressure, and/or the application of
heat, for example.
[0020] Preferably and advantageously, adhesives of the present
invention that have a generally smooth (i.e., nontextured) surface
(which typically occurs upon coating the adhesive on a
silicone-coated release liner, for example) when disposed at a
thickness of about 35 microns on a 50-micron thick polymeric
plasticized vinyl film display a 180.degree. peel adhesion value of
no greater than 35 N/100 mm, when measured at a 30.5 cm per minute
peel rate from an 80/20 PVDF/PMMA substrate (i.e., a blend of 80
weight percent PVDF and 20 weight percent PMMA), after having been
applied to the PVDF/PMMA substrate with a rubber roll laminator and
stored for 24 hours at 22.degree. C. For purposes of this peel
adhesion test, the polymeric plasticized vinyl film has an
elongation of 100% to 200% and a tensile strength of 22 Newtons to
35 Newtons per 2.54-cm width as measured by an Instron tensile
tester. Although typically under such conditions preferred
adhesives display a peel adhesion value of no greater than about 35
N/100 mm, certain preferred adhesives may exhibit a "shocky" or
"slip/stick" peel phenomenon that result in measured average peel
adhesion values greater than 35 N/100 mm yet still are removable
and/or repositionable. It has been observed that adhesives with a
glass transition temperature (Tg), as calculated by the Fox
Equation (T. G. Fox, Bull. Amer. Phys. Soc., Series 2, 1, 123
(1956), and Satas, Handbook of Pressure Sensitive Adhesive
Technology, 2.sup.nd Edition, Van Nostrand Reinhold), of about
-20.degree. C. or greater are preferred. Significantly, adhesive
articles of the present invention, which have been applied to the
PVDF/PMMA substrate and aged for 7 days in an oven at 66.degree.
C., can provide a final 180.degree. peel adhesion of preferably at
least about 70 N/100 mm, more preferably, at least about 100 N/100
mm, most preferably, at least about 150 N/100 mm, and often even
higher, measured at a 30.5 cm per minute peel rate under the same
test conditions described above. As used herein, a "24-hour" peel
adhesion is determined after 24 hours at 22.degree. C. and 50%
relative humidity, and a "final" peel adhesion is determined after
7 days of storing in an oven at 66.degree. C.
[0021] When adhered to a substrate that includes a plasticized
polymer layer, such as a polyvinyl chloride, preferred adhesives of
the present invention display a T-peel adhesion value of at least
about 35 N/100 mm (measured at a 30.5 cm per minute peel rate),
when a 35 micron thick adhesive layer coated onto a 50-micron thick
polymeric plasticized vinyl film (as described above for the
180.degree. peel test) is applied to a polyvinyl chloride substrate
(available under the trade designation Duraskin 070 Blue PVC Coated
Polyester Style #B129334 from Verseidag of Krefeld, Germany and
stored for 24 hours at 22.degree. C. Such preferred adhesives of
the present invention substantially retain, if not further
increase, their T-peel adhesion values over a period of at least
about 7 days, and more preferably, at least about 3 weeks of
storing in an oven at 66.degree. C.
[0022] Preferably and advantageously, adhesive articles of the
present invention can provide good shear resistance, as
demonstrated by film shrinkage of less than 250 microns as measured
by the test method listed in the Testing Protocol.
[0023] Highly preferred embodiments of the invention exhibit these
attributes to several, and most preferably, to all of the substrate
surfaces mentioned above.
[0024] Amide-functional Adhesives
[0025] Adhesive compositions useful in the invention comprise and,
more preferably, consist essentially of, a copolymer of (i.e., a
copolymer derived from) at least two different types of
monoethylenically unsaturated monomers, at least one of which
includes secondary or tertiary amide functionality. The copolymer
is preferably a copolymer of at least one type of copolymerizable
acrylate monomer and at least one type of copolymerizable secondary
or tertiary amide-functional monomer. The copolymer is more
preferably a copolymer of at least two different types of
copolymerizable acrylate monomers and at least one type of
copolymerizable secondary or tertiary amide-functional monomer.
Optionally, the copolymer is also derived from a copolymerizable
acidic monomer.
[0026] Thus, a "copolymer," as used herein, includes a polymer of
two or more types of polymerizable monomers, and therefore includes
terpolymers, tetrapolymers, etc. This can include random
copolymers, block copolymers, or sequential polymers.
[0027] The monomers can include (A) a monoethylenically unsaturated
(meth)acrylic ester wherein the alkyl group has at least 4 carbons
(on average), (B) a monoethylenically unsaturated (meth)acrylic
ester wherein the alkyl group has less than 4 carbons (on average),
(C) a monoethylenically unsaturated monomer having a secondary or
tertiary amide group, and (D) an acidic monomer. Various
combinations of these four types of monomers can be used as long as
monomer C and at least one of monomer A or B is present. For
example, polymers can be made from A, B, and C, or A and C, or B
and C, or A, B, C, and D, or A, C, and D, or B, C, and D. In
preferred embodiments, when monomer D is present, monomer C is
present in a molar excess relative to monomer D.
[0028] Preferably, the monomers include:(A) a monoethylenically
unsaturated (meth)acrylic acid ester (i.e., an alkyl acrylate or
alkyl methacrylate), wherein the alkyl group has at least 4 carbon
atoms (on average) and which as a homopolymer has a Tg of less than
about 0.degree. C.; (B) a monoethylenically unsaturated
(meth)acrylic ester, wherein the alkyl group has less than 4 carbon
atoms (on average) and which as a homopolymer has a Tg of less than
about 50.degree. C.; (C) a monoethylenically unsaturated monomer
having a secondary or tertiary amide group; and (D) an acidic
monomer.
[0029] Monomer A is a monoethylenically unsaturated (meth)acrylic
acid ester (i.e., an alkyl acrylate or methacrylate), wherein the
alkyl group has at least 4 carbon atoms (on average). Preferably,
the alkyl group of the (meth)acrylate has about 4 to about 14
carbon atoms (on average). The alkyl group can optionally contain
heteroatoms and can be linear or branched. Preferably, when
homopolymerized, these monomers yield inherently tacky polymers
with glass transition temperatures which are typically less than
about 0.degree. C. Preferred such (meth)acrylate monomers have the
following general formula: 1
[0030] wherein R.sup.1 is H or CH.sub.3, the latter corresponding
to where the (meth)acrylate monomer is a methacrylate monomer, and
R.sup.2 is broadly selected from linear or branched organic groups
optionally including one or more heteroatoms. The number of carbon
atoms in the R.sup.2 group is preferably about 4 to about 14, and
more preferably about 4 to about 8.
[0031] Examples of monomer A include, but are not limited to,
2-methylbutyl acrylate, isooctyl acrylate, isooctyl methacrylate,
lauryl acrylate, 4-methyl-2-pentyl acrylate, isoamyl acrylate,
sec-butyl acrylate, n-butyl acrylate, n-hexyl acrylate,
2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-octyl acrylate,
n-octyl methacrylate, 2-methoxy-ethyl acrylate, 2-ethoxy-ethyl
acrylate, n-decyl acrylate, isodecyl acrylate, isodecyl
methacrylate, and isononyl acrylate. Preferred (meth)acrylates that
can be used as monomer A include isooctyl acrylate, 2-ethyl hexyl
acrylate, 2-methylbutyl acrylate, and n-butyl acrylate.
Combinations of various monomers categorized as an A monomer can be
used to make the copolymer of the present invention.
[0032] Monomer B is a monoethylenically unsaturated (meth)acrylic
acid ester (i.e., an alkyl acrylate or methacrylate), wherein the
alkyl group has less than 4 carbon atoms (on average). Preferably,
the alkyl group of the (meth)acrylate has about 1 to about 2 carbon
atoms (on average). The alkyl group can optionally contain
heteroatoms and can be linear or branched. Preferably, when
homopolymerized, these monomers yield essentially non-tacky
polymers with a Tg of less than about 50.degree. C. Preferred
(meth)acrylate monomers have the following general formula: 2
[0033] wherein R.sup.1 is H or CH.sub.3, and R.sup.2 is broadly
selected from linear or branched hydrocarbon groups and optionally
including one or more heteroatoms. The number of carbon atoms in
the R.sup.2 group is preferably 1 or 2.
[0034] Examples of monomer B include, but are not limited to,
methyl acrylate, ethyl acrylate, propyl acrylate, and
propylmethacrylate. Preferred (meth)acrylates that can be used as
monomer B include methyl acrylate and ethylacrylate. Combinations
of various monomers categorized as a B monomer can be used to make
the copolymer of the present invention.
[0035] Monomer C is a monoethylenically unsaturated monomer having
a secondary or tertiary amide group, preferably, a secondary or
tertiary amide group of the formula --C(O)NR.sup.1R.sup.2 wherein
R.sup.1 and R.sup.2 are each independently H or a saturated or
unsaturated hydrocarbon moiety (i.e., a group that includes only
carbon and hydrogen and not nitrogen or oxygen, for example), which
optionally can form a ring with the carbonyl carbon (--C(O)) of the
amide group.
[0036] Examples of monomer C include, but are not limited to:
N-alkylated (meth)acrylamides, such as, N-methyl acrylamide,
N-ethyl acrylamide, N,N-dimethyl acrylamide, N,N-dimethyl
methacrylamide, N,N-diethyl acrylamide, N,N-diethyl methacrylamide,
N-isopropyl acrylamide, t-butyl acrylamide, N-octyl acrylamide,
4-(N,N-dimethylamido) butylacrylate; N-vinyl lactams, such as,
N-vinyl pyrrolidone, N-vinyl caprolactam; and N-vinyl formamide.
Preferred monomers that can be used as monomer C are N,N-dimethyl
acrylamide, N,N-diethyl acrylamide, N-vinyl pyrrolidone, and
N-vinyl caprolactam. Combinations of various monomers categorized
as a C monomer can be used to make the copolymer of the present
invention.
[0037] Monomer D is preferably a copolymerizable acidic monomer
selected from the group of ethylenically unsaturated carboxylic
acids, ethylenically unsaturated sulfonic acids, and ethylenically
unsaturated phosphonic acids. Examples include, but are not limited
to, acrylic acid, methacrylic acid, itaconic acid, fumaric acid,
crotonic acid, citraconic acid, maleic acid, beta-carboxyethyl
acrylate, 2-sulfoethyl methacrylate, and vinyl phosphonic acid.
Preferred monomers that can be used as monomer D include acrylic
acid, methacrylic acid, and beta-carboxyethyl acrylate.
Combinations of various monomers categorized as a D monomer can be
used to make the copolymer of the present invention.
[0038] Monomers A, B, C, and D can be used in amounts to produce a
copolymer having properties as defined above. Preferably, when
adhesive removability and/or repositionability is desired, monomer
B is used as part of the composition. All parts referred to herein
are weight percent of the total weight of the monomers, unless
otherwise specified.
[0039] Preferably, monomer A is present in an amount of at least
about 5 parts by weight, and more preferably, at least about 10
parts, based on the total weight of monomers in a copolymerizable
mixture. Preferably, it is present in an amount of no greater than
about 95 parts, more preferably no greater than about 80 parts, and
most preferably, no greater than about 70 parts, based on the total
weight of monomers in a copolymerizable mixture.
[0040] Preferably, monomer B is present in an amount of no greater
than about 90 parts by weight, and more preferably, no greater than
about 80 parts, based on the total weight of monomers in a
copolymerizable mixture. Preferably, it is present in an amount of
at least about 20 parts, and more preferably, greater than about 20
parts, based on the total weight of monomers in a copolymerizable
mixture.
[0041] Preferably, monomer C is present in an amount of no greater
than about 50 parts by weight, more preferably, no greater than
about 40 parts, and most preferably, no greater than about 25
parts, based on the total weight of monomers in a copolymerizable
mixture. Preferably, monomer C is present in an amount of at least
about 5 parts, more preferably, at least about 10 parts, and most
preferably, greater than about 10 parts, based on the total weight
of monomers in a copolymerizable mixture.
[0042] Preferably, monomer D is present in an amount of no greater
than about 10 parts by weight, and more preferably, no greater than
about 5 parts, based on the total weight of monomers in a
copolymerizable mixture. If monomer D is present, it is preferably
present in an amount of at least about 2 parts, based on the total
weight of monomers in a copolymerizable mixture.
[0043] In particularly preferred embodiments, the monomers can be
used in amounts of about 5 parts to about 80 parts of monomer A,
greater than 20 parts to about 90 parts of monomer B, about 10
parts to about 50 parts of monomer C, and about 0 parts to about 10
parts of monomer D.
[0044] For preferred compositions having desired removability
and/or repositionability, the amounts of these monomers are
selected to provide a composition having a glass transition
temperature (Tg) of at least about -20.degree. C. Such compositions
typically include monomer C in an amount of greater than 10 parts
to about 25 parts, and monomer D in an amount of about 2 parts to
about 5 parts, with the balance being monomer A and/or B selected
to provide a Tg of at least about -20.degree. C. The glass
transition temperatures of the homopolymers and copolymer are
typically accurate to within .+-.5.degree. C. and are measured by
differential scanning calorimetry.
[0045] For certain other preferred compositions, monomers A, B, and
C are present, with monomer C being present in an amount of greater
than 10 parts. In still other embodiments, the monomers can be used
in amounts of about 10 parts to about 70 parts of monomer A, about
20 parts to about 80 parts of monomer B, greater than 10 parts to
about 40 parts of monomer C, and about 2 parts to about 5 parts of
monomer D.
[0046] In order to improve shear or cohesive strength, control
elastic modulus, and preadhesion tack, for example, of the
adhesives of the present invention, the copolymers can be
crosslinked. Preferably, the crosslinking agent is one that is
copolymerized with the monomers. The crosslinking agent may produce
chemical crosslinks (e.g., covalent bonds). Alternatively, it may
produce physical crosslinks that result, for example, from the
formation of reinforcing domains due to phase separation or acid
base interactions. Suitable crosslinking agents are disclosed in
U.S. Pat. Nos. 4,379,201 (Heilman), 4,737,559 (Kellen), 5,506,279
(Babu et al.), and 4,554,324 (Husman). Combinations of various
crosslinking agents can be used to make the copolymer used in
making the fibers of the present invention. It should be
understood, however, that such crosslinking agents are
optional.
[0047] Such crosslinking agents also include thermal crosslinking
agents such as a multifunctional aziridine, for example. One
example is 1,1'-(1,3-phenylene dicarbonyl)-bis-(2-methylaziridine),
referred to herein as "bisamide." Such chemical crosslinkers can be
added into solvent-based adhesives containing acid functionality
after polymerization and activated by heat during oven drying of
the coated adhesive.
[0048] Other suitable crosslinking agents include chemical
crosslinkers that rely upon free radicals to carry out the
crosslinking reaction. Reagents such as peroxides, for example,
serve as a precursor of free radicals. When heated sufficiently,
these precursors will generate free radicals that bring about a
crosslinking reaction of the polymer chains. A common free radical
generating reagent is benzoyl peroxide. Free radical generators are
required only in small quantities, but generally require higher
temperatures to complete the crosslinking reaction than those
required for the bisamide reagent.
[0049] Still other suitable crosslinking agents include
photosensitive crosslinkers that are activated by high intensity
ultraviolet (UV) light. Two examples are benzophenone and
4-acryloxybenzophenone, the latter being a monomer which is
copolymerized into the adhesive copolymer. Another
photocrosslinker, which can be post-added to a solution polymer and
activated by UV light is a triazine, such as, for example,
2,4-bis(trichloromethyl)-6-(4-methoxy-phenyl)-s-triazine. These
crosslinkers are activated by UV light generated from artificial
sources such as medium pressure mercury lamps.
[0050] Aside from thermal or photosensitive crosslinkers,
crosslinking may also be achieved using high energy electromagnetic
radiation such as gamma or e-beam radiation, for example.
[0051] A physical crosslinking agent may also be used. In one
embodiment, the physical crosslinking agent is a high Tg macromer
such as those based upon polystyrene and polymethylmethacrylate.
Such vinyl-terminated polymeric crosslinking monomers are sometimes
referred to as macromolecular monomers (i.e., "macromers"). Such
monomers are known and may be prepared by the methods disclosed in
U.S. Pat. Nos. 3,786,116 (Milkovich et al.) and 3,842,059
(Milkovich et al.), as well as Y. Yamashita et al., Polymer
Journal, 14, 255-260 (1982), and K. Ito et al., Macromolecules, 13,
216-221 (1980). Typically, such monomers are prepared by anionic
polymerization or free radical polymerization.
[0052] Diisocyanates and moisture activated crosslinkers, such
copolymerizable alkoxysilanes, may also be used as crosslinking
agents. The adhesives may be crosslinked before or after bonding of
the article to a substrate.
[0053] If used, the crosslinking agent is used in an effective
amount, by which is meant an amount that is sufficient to cause
crosslinking of the pressure sensitive adhesive to provide adequate
cohesive strength to produce the desired final adhesion properties
to the substrate of interest. Preferably, if used, the crosslinking
agent is used in an amount of about 0.1 part to about 10 parts,
based on 100 parts of monomers.
[0054] Optionally, the compositions of the present invention can
include plasticizers, tackifiers, antioxidants, UV light absorbers,
fillers, colorants, etc.
[0055] Backings
[0056] In one embodiment of the present invention, backings of
plasticized, flexible polyvinylchloride films are used to form
decorative films, labels or graphic marking films. These films may
be made by casting from organosol solutions or calendered from an
extrudable PVC resin.
[0057] Other backings of interest include, but are not limited to,
polyesters, polyolefins, papers, foils, poly(meth)acrylates,
polyurethanes, perfluoropolymers, polycarbonates, ethylene vinyl
acetates, and the like. These backings may be primed (e.g.,
chemical coating, corona, flame, etc.) prior to application of the
adhesive. Woven and nonwoven sheets, woven and nonwoven fabrics,
foams (e.g., acrylic or polyethylene foams), and the like, are
intended to be included. Preferably, the backing is a film (i.e., a
thin, flexible, single- or multi-layer polymeric sheet) or a
foam.
[0058] The adhesives of the current invention may also be coated on
release liners, such as siliconized paper or polymeric film. These
adhesives can be transferred to any desired surface for subsequent
bond making between two substrates.
[0059] Method of Making Adhesives
[0060] The adhesive can be polymerized by a wide variety of
conventional free radical polymerization methods, including
solution, emulsion, bulk, and suspension processes.
[0061] In one solution polymerization method, the alkyl
(meth)acrylate monomers, amide-functional monomers, and optional
acidic monomers, along with a suitable inert organic solvent, and
free radically copolymerizable crosslinker, if used, are charged
into a four-neck reaction vessel which is equipped with a stirrer,
a thermometer, a condenser, an addition funnel, and a temperature
controller. After this monomer mixture is charged into the reaction
vessel, a concentrated thermal free radical initiator solution is
added to the addition funnel. The whole reaction vessel and
addition funnel and their contents are then purged with nitrogen to
create an inert atmosphere. Once purged, the solution within the
vessel is heated to decompose the added thermal initiator, and the
mixture is stirred during the course of the reaction. A conversion
of about 98 percent to about 99 percent is typically obtained in
about 20 hours. If desired, solvent can be removed to yield a hot
melt coatable adhesive.
[0062] Another polymerization method is the ultraviolet (UV)
radiation initiated photopolymerization of the monomer mixture.
This composition, along with suitable photoinitiator and
crosslinker, is coated onto a flexible carrier web and polymerized
in an inert, i.e., oxygen-free, atmosphere, such as a nitrogen
atmosphere, for example. A sufficiently inert atmosphere can be
achieved by covering a layer of the photoactive coating with a
plastic film that is substantially transparent to ultraviolet
radiation, and irradiating through that film in air using
fluorescent-type ultraviolet lamps that generally give a total
radiation dose of about 500 milliJoules/cm.sup.2.
[0063] Solventless polymerization methods, such as the continuous
free radical polymerization in an extruder described in U.S. Pat.
Nos. 4,619,979 (Kotnour, et al.) and 4,843,134 (Kotnour, et al.);
the essentially adiabatic polymerization methods using a batch
reactor described in U.S. Pat. No. 5,637,646 (Ellis); and, the
methods described for polymerizing packaged pre-adhesive
compositions described in U.S. Pat. No. 5,804,610 (Hamer, et al.)
may also be utilized to prepare the polymers.
[0064] Initiators such as free radical initiators and
photoinitiators can be used. Suitable thermal free radical
initiators that can be utilized include, but are not limited to,
those selected from the group consisting of azo compounds such as
2,2'-azobis(isobutyronitrile), hydroperoxides such as tert-butyl
hydroperoxide, and peroxides such as benzoyl peroxide and
cyclohexanone peroxide. Suitable photoinitiators that are useful
according to the invention include, but are not limited to, those
selected from the group consisting of the benzoin ethers such as
benzoin methyl ether or benzoin isopropyl ether, substituted
benzoin ethers such as anisole methyl ether, substituted
acetophenones such as 2,2-diethoxyacetophenone and
2,2-dimethoxy-2-phenyl acetophenone, substituted alpha-ketols such
as 2-methyl-2-hydroxy propiophenone, aromatic sulfonyl chlorides
such as 2-naphthalene sulfonyl chloride, and photoactive oximes
such as 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl)- -oxime. For
both thermal and radiation induced polymerizations, the initiator
is present in an amount of about 0.05 percent by weight to about
0.5 percent by weight based upon the total weight of the
monomers.
[0065] Suitable inert organic solvents, if required, may be any
organic liquid which is inert to the reactants and product and will
not otherwise adversely affect the reaction. Such solvents include
ethyl acetate, acetone, methyl ethyl ketones, and mixtures thereof.
The amount of solvent is generally about 30 percent by weight to
about 80 percent by weight based on the total weight of the
reactants (monomer, crosslinker, initiator) and solvent.
[0066] The adhesive compositions of the present invention may then
be applied to a backing by a variety of coating methods brush,
roll, spray, spread, wire, gravure, transfer roll, air knife, or
doctor blade coating.
[0067] If the composition includes a solvent or water, it is then
dried at a temperature (e.g., about 65.degree. C. to about
120.degree. C.) and a time (e.g., several minutes to about one
hour) so as to provide an adhesive tape, for example. The thickness
of the layer of adhesive may vary over a broad range of about 10
microns to several hundred microns (e.g., about 200 microns).
[0068] The adhesives may be applied by hot-melt coating the
adhesive onto a sheet material or another suitable substrate. The
adhesives can be hot melt coated by using a heated extruder, bulk
tank melter, melt-on-demand equipment, or a hand-held hot melt
adhesive gun. The hot melt adhesive can be delivered out of a film
die and subsequently coated by contacting the drawn adhesive with a
moving plastic web or other suitable substrate. A related coating
method involves extruding the adhesive and a coextruded backing
material from a film die and cooling the layered product to form a
pressure sensitive adhesive tape. Other forming methods involve
directly contacting the hot melt adhesive to a rapidly moving
plastic web or other suitable preformed substrate. Using this
method, the adhesive is applied to the moving preformed web using a
die having flexible die lips, such as a rotary rod die. After
forming by any of these continuous methods, the adhesive films or
layers can be solidified by quenching using both direct methods
(e.g., chill rolls or water baths) and indirect methods (e.g., air
or gas impingement).
[0069] Once the adhesive composition has been coated, and
optionally crosslinked, the adhesive surface of the article may,
optionally, be protected with a temporary, removable release liner
(i.e., protective liner) such as a polyolefin (e.g., polyethylene
or polypropylene) or polyester (e.g., polyethylene terephthalate)
film, or a plastic film. Such films may be treated with a release
material such as silicones, waxes, fluorocarbons, and the like.
[0070] Film Constructions
[0071] The present invention has particular applicability in
connection with vinyl films for graphic marking film and labels,
although other adhesive articles are also possible, such as foam
tapes, and the like. In one embodiment of a graphic marking film or
label, the vinyl film can be an extendible polyvinylchloride
backing for use in decorative labels and graphic marking films.
[0072] A typical applied film construction is shown in FIG. 1 in
which the film 1 comprises a film layer, such as a 2 mil (0.05 mm)
vinyl film, which can be a decorative film, having an adhesive of
the present invention 2 applied to one surface thereof. The
adhesive 2 is applied to a substrate containing two layers, one of
which is a fluoropolymer-containing top layer 3, such as a
PVDF/PMMA blend, which can provide stain and/or chemical resistance
and may also act as a barrier for plasticizer migration, and the
other is a support layer 4, such as a plasticized vinyl film.
Alternatively, the substrate may be a polycarbonate sheet or panel,
replacing both the fluoropolymer top layer 3 and the plasticized
vinyl support layer 4.
[0073] Graphic film constructions of the type depicted in FIG. 1
are useful in many outdoor applications including, but not limited
to, architectural flexible and rigid signs.
[0074] Furthermore, the adhesives described herein can be used in
such constructions as well as in retroreflective sheeting, light
management films such as light enhancement films and privacy films.
Also, when microreplicated film with optical properties such as
that described in U.S. Pat. No. 4,775,219 (Appledorn et al.) is
laminated, for example, adhesives of the present invention can be
used in the lamination as they are optically clear so as to leave
the microreplicated films with the intended optical quality. The
adhesive may also be used to securely adhere articles against
hydrofluoropolymers (and blends thereof with other polymers) as
used in dirt repellant or chemically resistant surfaces used in
artistic coatings, automotive paints, hoses, and the like.
[0075] The adhesives of the current invention may also be useful in
applications requiring high adhesion to polycarbonate. These may
include bonding of digital video disks (DVD), application of labels
thereto, and application of dirt-repellant or other overlay films
to polycarbonate panels and sheets. These overlay films may provide
additional functionality to the underlaying polycarbonate, such
anti-dew properties, resistance to graffiti, enhanced resistance to
scratching or impact, and the like.
EXAMPLES
[0076] The invention will be more fully appreciated with reference
to the following non-limiting examples. The examples were evaluated
with respect to certain test methods that are described below. All
dimensions given in the test methods and the examples are nominal
dimensions. The abbreviations used herein are set for the in Table
1.
1TABLE 1 Abbreviations and Sources of Reagents IOA Isooctyl
acrylate Sartomer, Exton, PA PMMA Polymethylmethacrylate Zeneca
Resins, Wilmington, MA 2-MBA 2-methylbutyl acrylate Aldrich
Chemical, PANAFLEX 930 Flexible sign substrate 3M, St Paul, MN
Milwaukee, WI MA Methyl acrylate Aldrich Chemical PANAFLEX 945
Flexible sign substrate 3M, St Paul, MN EA Ethyl acrylate Aldrich
Chemical DURASKIN 070 Blue PVC Coated Style Verseidag, #B129334
Krefeld, Germany, BA n-butyl acrylate Aldrich Chemical FEP
Fluoroethylenepropylene Dyneon, Oakdale, polymer MN NOAcm N-octyl
acrylamide National Starch & ETFE Ethylenetetrafluoroethylene
Dyneon Chemical, Salisbury, polymer NC NNDMA N,N-dimethyl
acrylamide Aldrich Chemical TFE Tetrafluoroethylene Dyneon polymer
NVP N-vinyl pyrrolidone Aldrich Chemical TEDLAR Polyvinylfluoride
Dupont, Wilmington, DE NVC N-vinyl caprolactam Aldrich Chemical
LEXAN Polycarbonate GE Plastics, Schenectady, NY AA Acrylic acid
Aldrich Chemical ABP 4-acryloxybenzophenone CTH Constant
temperature humidity PVDF Polyvinylidenefluoride Ausimont USA, Tg
Glass transition temperature Thorofare, NJ HYLAR Vinylidene
fluoride Ausimont USA N/dm Newtons per decimeter FXH
hexafluoropropylene copolymer
[0077] Preparation of Adhesives
[0078] A 250 milliliter (ml) round bottom flask was equipped with a
stirrer, a condenser, and an addition funnel. A 40 gram (g) monomer
mix consisting of the desired monomer ratios, listed as Examples C
and 1-14 in the tables below, 0.04 gram ABP photocrosslinker, 0.04
gram isooctylthioglycolate (chain-transfer agent), and 50 grams of
ethyl acetate were charged into this flask and a solution of 0.12
gram of VAZO 64 (2,2'-azobis(isobutyronitrile), an initiator
commercially available from DuPont, Willmington, Del.) in 10 grams
ethyl acetate was added to the addition funnel. This reaction
apparatus was then inerted with nitrogen and the flask contents
were heated to 55.degree. C. The initiator solution was added to
the flask and the temperature was maintained at 55.degree. C. for
about 20 hours. The sample was allowed to cool to room temperature.
The cooled solution was then coated to form a dry coating thickness
of about 35 microns on a siliconized release liner (POLYSLIK liner
available from Rexam, South Hadley, Mass.) and oven dried for 10
minutes at 66.degree. C. The adhesive of Example 15 was prepared
according to the procedure of Example 1 in U.S. Pat. No. 4,364,972
(Moon) except 68/32 IOA/NVC was substituted for 70/30 IOA/NVP. The
adhesive was subsequently laminated to a 50 micron vinyl film
backing having an elongation of 100% to 200% and a tensile strength
of 22 Newtons to 35 Newtons per 2.54-cm width as measured on an
Instron tensile tester at 23.degree. C. and 50% relative humidity
using a crosshead speed of 30.5 cm/minute. Adequate shear
performance, as measured by applied film shrinkage, was obtained by
exposing adhesive samples, containing 4-acryloxybenzophenone
crosslinker, to 500 milliJoules/cm.sup.2 UV energy from a medium
pressure mercury lamp.
[0079] Preparation of Test Substrate
[0080] The PVDF/PMMA powder coated test surfaces in Table 3 were
made as described in Example 11 of U.S. Pat. No. 5,827,608
(Rinehart, et al.).
[0081] Test substrates (layers 3 and 4 in FIG. 1) in Tables 4 and 5
were prepared by extruding, using a twin-screw extruder, at
temperature of approximately 200.degree. C., an 80:20 PVDF/PMMA
polymer blend onto a casting liner to a film thickness of 5 microns
to 10 microns. The casting liner had a 60.degree. gloss of about 12
to about 20 measured according to ASTM D523-85 using a BYK Gardner
Glossgard II gloss meter (Rivershank, Ill.). The extruded film was
subsequently hot laminated to 3M PANAFLEX 930 film at a temperature
of 175.degree. C., a pressure of 525 Newtons per centimeter, and a
line speed of 4 meters per minute.
[0082] Testing Protocols
[0083] 180.degree. Peel Adhesion PSTC-1:
[0084] The data in Tables 1-7 was based on Pressure Sensitive Tape
counsel (PSTC) test standard. In this test, a 2.54 centimeter (cm)
wide strip of PSA-coated 50-micron thick polymeric plasticized
vinyl was laminated to the PVDF/PMMA test substrate described
above, a fluoropolymer panel, or polycarbonate panel using a 2
kilogram rubber covered roller. The test specimens were backed with
a standard 35-micron thick psa coated 50-micron thick polymeric
plasticized vinyl film (having an elongation from 100% to 200% and
a tensile from 22 Newtons to 35 Newtons per 2.54 cm width as
measured by an Instron tensile tester) for reinforcement. The
applied test specimen was allowed to equilibrate for 24 hours at
22.degree. C. and 50% relative humidity and also oven aged at 7
days at 66.degree. C. The test sample was then peeled at an angle
of 180.degree. and at a speed of 30.5 centimeters per minute using
a Instron peel test machine. The peel adhesion measurement was
reported in Newtons per 100 millimeters width (N/100 mm).
[0085] T-peel Adhesion:
[0086] For the data in Table 8, a 2.54 cm wide strip of PSA-coated
50-micron thick polymeric plasticized vinyl was laminated to a
non-rigid or flexible test substrate (Duraskin 070 Blue PVC Coated
Polyester Style #B129334 from Verseidag of Krefeld, Germany) using
2 firm swipes of a PA-1 squeegee available from 3M Company. The
applied test specimen was allowed to equilibrate for 24 hours at
22.degree. C. and 50% relative humidity and also oven aged at 7
days at 66.degree. C. One end of the PSA coated film sample was
clamped into the upper jaw of an Instron peel test machine and one
end of the flexible substrate was clamped in the lower jaw. The
test sample was then peeled at an angle of 180.degree. and at a
speed of 30.5 centimeters per minute using a Instron peel test
machine. The peel adhesion measurement was reported in Newtons per
100 millimeters width (N/100 mm).
[0087] Film Shrinkage:
[0088] This test is used to measure internal adhesive or shear
strength. It relates directly to actual product use conditions.
This test measures the ability of the adhesive to "hold the vinyl
film in place" or to resist the shinkage forces imparted by the
vinyl film. A 6.35 cm by 10.2 cm adhesive coated 50 micron vinyl
film sample (as described in the 180 peel adhesion test) sample was
applied to an ED-2.75.times.11 aluminum panel from Q-Panel Lab
Products, Cleveland, Ohio. The applied vinyl film sample was slit
with a razor blade in both the crossweb and machine direction and
was conditioned at 65.5.degree. C. for 24 hours. Measurements in 25
micron increments of the razor cut openings were recorded. The
razor slit tends to separate or widen for adhesives with poor
internal or cohesive strength. Generally a gap opening of 250
microns or greater indicates that the adhesive has poor shear
strength while adhesives that have good shear or cohesive strength
will show small gap openings, less than 250 microns, and will hold
the vinyl film in place.
EXAMPLES
[0089] Table 2 compares 1800 peel adhesion values for 24-hour
constant temperature and constant humidity aged (CTH at 22.degree.
C./50% R.H.) samples and 7-day heat aged (66.degree. C.) samples of
the control adhesive (Example C) compared to the new adhesive
composition (Example 1) on surfaces comprised of a blend of an
acrylic polymer and a fluoropolymer. Comparison between aging
conditions shows that Example 1 has low adhesion, measured after 24
hour at 22.degree. C., for good fabrication characteristics, and
substantially builds and maintains adhesion on the acrylic
polymer/fluoropolymer blend surface. Adhesion values denoted with
"s" indicate shocky or slip/stick peel behavior as described in
Satas, Handbook of Pressure Sensitive Adhesive Technology, 2.sup.nd
Edition, Van Nostrand Reinhold page 68.
2TABLE 2 180.degree. Peel Adhesion to substrates with Fluoropolymer
Containing Top Surfaces 24 Tg Hour 1 Week Ex. Adhesive Test
Substrate .degree. C. CTH 66.degree. C. C 90/10 2-MBA/AA 3M
PANAFLEX -20 25 69 945 C 90/10 2-MBA/AA 3M SCOTCHCAL -20 61s 73
3640 1 52/26/20/2 3M PANAFLEX -15 51 211 EA/BA/NNDMA/AA 945 1
52/26/20/2 3M SCOTCHCAL -15 35s 163 EA/BA/NNDMA/AA 3640 All
adhesions at 180.degree. angle, 30.5 cm/minute rate, units of N/100
mm.
[0090] Table 3 illustrates the difference in adhesion performance
between the control adhesive (Example C) and the new adhesive
(Example 1) on the PVDF/PMMA surface which has been powder coated
(U.S. Pat. No. 5,827,608, Rinehart, et al.) onto a plasticized
vinyl substrate at varying levels of PVDF content in the PVDF/PMMA
polymer blend. Note that the control samples show the expected
decrease in 1 week 66.degree. C. adhesion as the amount of
fluoropolymer increases in the blend. Surprisingly, the adhesives
of the current invention show an increase in 1 week 66.degree. C.
adhesion values as the amount of the PVDF polymer is increased in
the blend.
[0091] Table 4 shows that the 66.degree. C. heat age adhesion
values decrease as the level of NNDMA is decreased in the adhesive
composition. Thus, surprisingly, as the amount of NNDMA increased
the ultimate level of adhesion increased.
3TABLE 3 180.degree. Peel Adhesion to Powder-coated PVDF/PMMA Top
Surface 24 Hour 1 Week Ex. Adhesive Fluoropolymer Top Surface Tg
.degree. C. CTH 66.degree. C. C 90/10 2-MBA/AA 100/0 HYLAR FXH/PMMA
Blend -20 23s 55 C 90/10 2-MBA/AA 90/10 HYLAR FXH/PMMA Blend -20
23s 55 C 90/10 2-MBA/AA 80/20 HYLAR FXH/PMMA Blend -20 26s 63 C
90/10 2-MBA/AA 70/30 HYLAR FXH/PMMA Blend -20 28s 63 1 52/26/20/2
EA/BA/NNDMA/AA 100/0 HYLAR FXH/PMMA Blend -15 <10 211 1
52/26/20/2 EA/BA/NNDMA/AA 90/10 HYLAR FXH/PMMA Blend -15 7s 192 1
52/26/20/2 EA/BA/NNDMA/AA 80/20 HYLAR FXH/PMMA Blend -15 17s 153 1
52/26/20/2 EA/BA/NNDMA/AA 70/30 HYLAR FXH/PMMA Blend -15 30 123 All
adhesions at 180.degree. angle, 30.5 cm/minute rate, units of N/100
mm. Adhesion values with "s" denote "shocky" or slip/stick peel
behavior.
[0092]
4TABLE 4 180.degree. Peel Adhesion to Plasticized Vinyl Substrate
with 80/20 PVDF/ PMMA Top Surface Adhesives with different amounts
of NNDMA 1 24 Week % Tg Hour 66.degree. Ex. Adhesive NNDMA .degree.
C. CTH C. 1 52/26/20/2 EA/BA/NNDMA/AA 20 -15 12s 184 2 62/26/10/2
EA/BA/NNDMA/AA 10 -23 88 107 3 67/26/5/2 EA/BA/NNDMA/AA 5 -27 88
102 4 76/26/2 EA/BA/AA 0 -30 81 104 5 30/50/18/2 MA/BA/NNDMA/AA 18
-15 83s 211 6 20/60/18/2 MA/BA/NNDMA/AA 18 -22 93 123 7 30/55/13/2
MA/BA/NNDMA/AA 13 -21 90 112 8 38/50/10/2 MA/BA/NNDMA/AA 10 -19 88
112 All adhesions at 180.degree. angle, 30.5 cm/minute rate, units
of N/100 mm. Adhesion values with "s" denote "shocky" or slip/stick
peel behavior.
[0093] Adhesive were made with other amide functional monomers
besides N,N-dimethylacrylamide (NNDMA). These included N-vinyl
pyrollidone (NVP) and N-octylacrylamide (NOAcm). The adhesion
values are listed in Table 5. The highly preferred adhesive
composition contains the tertiary amide NNDMA.
5TABLE 5 180.degree. Peel Adhesion to Plasticized Vinyl Substrate
with 80/20 PVDF/PMMA Top Surface Adhesives with different amide
functional monomers Tg Ex. Adhesive .degree. C. 24 Hr CTH 1 Wk
66.degree. C. 1 52/26/20/2 EA/BA/NNDMA/AA -15 12s 184 9 78/20/2
BA/NNDMA/AA -32 74 100 10 52/26/20/2 EA/BA/NVP/AA -15 12s 165 11
78/20/2 BA/NVP/AA -33 79 104 12 85/10/5 BA/NVP/AA -39 72s 79 13
85/10/5 2-MBA/NVP/AA -17 72s 84 14 52/26/20/2 EA/BA/NOAcm/AA -36
21s 109 All adhesions at 180.degree. angle, 30.5 cm/minute rate,
units of N/100 mm. Adhesion values with "s" denote "shocky" or
slip/stick peel behavior.
[0094] Table 6 shows adhesion values of the NNDMA containing
adhesive to various fluoropolymers (substituting for layers 3 and 4
in FIG. 1). The Dyneon THV 500 fluoropolymer contains less
vinylidene fluoride monomer and more perfluorinated monomer than
the Dyneon THV 200 fluoropolymer, hence, lower heat age or ultimate
adhesion build. The Dyneon FEP T-100 is a plastic consisting of
100% perfluoroinated monomers and the ETFE is a copolymer of
ethylene and perfluorinated monomer (tetrafluoroethylene). There
was little or no adhesion build against both polymers which are not
derived from hydrofluorinated monomers. Again, against the TEDLAR
plastic, which is a hydrofluoropolymer, high adhesion build was
obtained when heat aged.
6TABLE 6 180.degree. Peel Adhesion to Various Fluoropolymer
Containing Plastics 24 Hour 1 Week Ex. Adhesive Plastic CTH
66.degree. C. 1 52/26/20/2 Dyneon THV <10 70 EA/BA/NNDMA/AA 500
1 52/26/20/2 Dyneon THV <10 130 EA/BA/NNDMA/AA 200 1 52/26/20/2
Dyneon FEP T- <10 <10 EA/BA/NNDMA/AA 100 1 52/26/20/2 Dyneon
6235J <10 <10 EA/BA/NNDMA/AA ETFE 1 52/26/20/2 TEDLAR 30 160
EA/BA/NNDMA/AA All adhesions at 180.degree. angle, 30.5 cm/minute
rate, units of N/100 mm. Adhesion values with "s" denote "shocky"
or slip/stick peel behavior.
[0095] Besides adhesion to hydrofluoropolymer surfaces, and blends
of these with other polymers, the NNDMA adhesives exhibit a high
bonding affinity to polycarbonate plastics. Polycarbonate is
classically not defined as a low energy surface, but does exhibit
such qualities when acrylic PSA's are applied to this type of
plastic. The data in Table 7 illustrates the difference in
adhesion, especially upon heat aging, between adhesives with amide
functional monomers and the control sample having only acid
functionality. Again, the linear, tertiary amides, such as NNDMA,
are highly preferred, but secondary and cyclic amides, such as NVP,
NOAcm, and NVC, are also useful.
7TABLE 7 180.degree. Peel Adhesion to Polycarbonate Plastic Exam-
24 Hour 1 Week ple Adhesive Tg .degree. C. CTH 66.degree. C. C
90/10 2-MBA/AA -20 51s 79 1 52/26/20/2 EA/BA/NNDMA/AA -15 46s 211 3
67/26/5/2 EA/BA/NNDMA/AA -27 77 158 5 30/50/18/2 MA/BA/NNDMA/AA -15
74 211 8 38/50/10/2 MA/BA/NNDMA/AA -19 92 211 9 78/20/2 BA/NNDMA/AA
-32 106 139 11 78/20/2 BA/NVP/AA -33 125 118 12 85/10/5 BA/NVP/AA
-33 67 113 14 52/26/20/2 EA/BA/NoAcm/AA -36 120 130 15 68/32
IOA/NVC -24 113 121 All adhesions at 180.degree. angle, 30.5
cm/minute rate, units of N/100 mm. Adhesion values with "s" denote
"shocky" or slip/stick peel behavior.
[0096] Table 8 shows that the EA/BA/NNDMA/AA adhesive also
maintains an adhesive bond to highly plasticized substrates such
Duraskin 070 Blue PVC Coated Polyester Style #B129334 from
Verseidag of Krefeld, Germany.
8TABLE 8 T-Peel Adhesion to Duraskin 070 Blue PVC Coated Style
#B129334 24 Hour 1 Week 3 Weeks Example Adhesive CTH 66.degree. C.
66.degree. C. 1 52/26/20/2 2.3 2.5 3.3 EA/BA/NNDMA/AA All adhesions
measured by T-Peel Method, 30.5 cm/minute rate, units of N/100
mm.
[0097] Each of the patents, patent applications, and publications
cited herein are incorporated herein by reference, as if
individually incorporated. Various modifications and alterations of
this invention will become apparent to those skilled in the art
without departing from the scope and spirit of the invention. It
should be understood that this invention is not limited to the
illustrative embodiments set forth herein.
* * * * *