U.S. patent application number 13/917113 was filed with the patent office on 2013-11-07 for adhesion promotion to difficult substrates for hot melt adhesives.
The applicant listed for this patent is HONEYWELL INTERNATIONAL INC.. Invention is credited to MICHAEL JABLON, NATALIE A. MERRILL, THOMAS QUINN.
Application Number | 20130295380 13/917113 |
Document ID | / |
Family ID | 39885597 |
Filed Date | 2013-11-07 |
United States Patent
Application |
20130295380 |
Kind Code |
A1 |
MERRILL; NATALIE A. ; et
al. |
November 7, 2013 |
ADHESION PROMOTION TO DIFFICULT SUBSTRATES FOR HOT MELT
ADHESIVES
Abstract
Hot melt adhesive compositions which have enhanced adhesion to
difficult substrates, particularly at refrigerator/freezer
temperatures or at elevated temperatures. The inventive
compositions require a base polymer comprising at least one
metallocene ethylene-containing polymer or at least one
non-metallocene, amorphous, propylene containing polymer; a
tackifier; an optional wax; and an adhesion promoting additive
comprising at least one semi-crystalline polymer having a weight
average molecular weight of about 30,000 daltons or less. It has
been found that the adhesion promoting additive of this invention
enhances the adhesion properties of a hot melt adhesive composition
having a metallocene ethylene-containing base polymer or
non-metallocene, amorphous, propylene containing base polymer,
particularly at elevated temperatures or at low refrigerator and
freezer temperatures where other conventional adhesives have been
unsuccessful.
Inventors: |
MERRILL; NATALIE A.; (Gig
Harbor, WA) ; QUINN; THOMAS; (St. Paul, MN) ;
JABLON; MICHAEL; (Ramsey, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HONEYWELL INTERNATIONAL INC. |
Morristown |
NJ |
US |
|
|
Family ID: |
39885597 |
Appl. No.: |
13/917113 |
Filed: |
June 13, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11789306 |
Apr 24, 2007 |
8475621 |
|
|
13917113 |
|
|
|
|
Current U.S.
Class: |
428/348 ;
428/349 |
Current CPC
Class: |
C08L 23/0869 20130101;
C09J 123/10 20130101; C09J 123/10 20130101; C09J 151/06 20130101;
C08F 210/16 20130101; C08L 91/06 20130101; Y10T 428/2822 20150115;
C08L 23/04 20130101; C08F 210/16 20130101; C09J 123/04 20130101;
C08L 2666/02 20130101; C09J 151/06 20130101; Y10T 428/2826
20150115; C09J 123/0815 20130101; C09J 123/04 20130101; C08L 53/02
20130101; C08L 23/10 20130101; C09J 123/00 20130101; C08L 23/0853
20130101; C09J 123/0815 20130101; C08L 2314/06 20130101; C09J
123/04 20130101; C09J 123/10 20130101; C08F 2500/12 20130101; C08L
2666/02 20130101; C08L 91/06 20130101; C08F 2500/23 20130101; C08L
2666/02 20130101; C08F 2500/02 20130101; C08L 91/06 20130101; C08F
2500/17 20130101; C08F 210/06 20130101; C08L 2666/02 20130101; C08L
2666/02 20130101 |
Class at
Publication: |
428/348 ;
428/349 |
International
Class: |
C09J 123/00 20060101
C09J123/00 |
Claims
1-30. (canceled)
31. An article comprising: one or more substrate materials; and a
hot melt adhesive composition comprising: i) a base polymer
comprising at least one metallocene ethylene-containing polymer or
at least one non-metallocene, amorphous, propylene containing
polymer wherein the metallocene ethylene-containing polymer
comprises at least one polymer selected from the group consisting
of a metallocene ethylene-octene polymer, a metallocene
ethylene-butene polymer, and a metallocene ethylene-hexene
copolymer; and wherein the non-metallocene, amorphous, propylene
containing polymer comprises at least one polymer selected from the
group consisting of a non-metallocene amorphous propylene-butene
copolymer, a non-metallocene amorphous propylene-ethylene
copolymer, and a non-metallocene amorphous
propylene-butene-ethylene terpolymer, wherein the base polymer is
provided in an amount of from about 20% to about 80% by weight of
the hot melt adhesive composition; ii) a tackifier which comprises
an aliphatic or aromatic modified cycloaliphatic hydrocarbon resin
or a polyterpene, wherein the tackifier is provided in an amount of
from about 15% to about 70% by weight of the hot melt adhesive
composition; iii) an optional wax; and iv) an adhesion promoting
additive provided in an amount of from about 1% to about 17% by
weight of the hot melt adhesive composition comprising at least one
semi-crystalline polymer having an average weight average molecular
weight of about 30,000 daltons or less and, which is selected from
the group consisting of a polypropylene polymer, a maleated
polypropylene polymer, a maleated polyethylene polymer, and
copolymers thereof.
32. The article of claim 31, wherein the substrate material
comprises a packaging material.
33. The article of claim 31, wherein the substrate material is
selected from the group consisting of plastic films, plastic
sheets, metal sheets, lacquer coated papers, polypropylene, wood,
paper, cellulosics, corrugated cardboard, coated board, coated
carton stock composites, aluminum, glass, steel, rebar, and
combinations thereof
34. The article of claim 31, wherein the substrate material
comprises a polyolefin film.
35. The article of claim 31, wherein the substrate material
comprises a vinyl film.
36. The article of claim 31, wherein the substrate material
comprises a metal sheet.
37. The article of claim 31, wherein the substrate material is
selected from the group consisting of a plastic film, a metal
sheet, and combinations thereof.
38. The article of claim 31, wherein the substrate material
comprises a plastic film.
39. The article of claim 31, wherein the substrate material
comprises acrylic coated paperboard and the base polymer comprises
at least one metallocene ethylene-containing polymer.
40. The article of claim 31, wherein the substrate material is
selected from the group consisting of steel, wood, plastic films,
plastic sheets, and combinations thereof and the base polymer
comprises at least one amorphous, propylene containing polymer.
41. The article of claim 31, wherein the hot melt adhesive
composition demonstrates improved adhesiveness to the substrate at
temperatures of greater than or equal to 60.degree. C., as compared
to a composition lacking the adhesion promoting additive, when the
base polymer includes at least one non-metallocene, amorphous,
propylene containing polymer, and the hot melt adhesive composition
demonstrates improved adhesiveness to a substrate at temperatures
of less than or equal to 5.degree. C., as compared to a composition
lacking the adhesion promoting additive, when the base polymer
includes at least one metallocene ethylene-containing polymer.
42. The article of claim 31, wherein the adhesion promoting
additive comprises a maleated polymer having a percent bound of
about 50% or greater.
43. The article of claim 31, wherein the adhesion promoting
additive has a Mettler drop point of from about 100.degree. C. to
about 170.degree. C.
44. The article of claim 31, wherein the adhesion promoting
additive has a viscosity, based on Brookfield viscometer
measurement at 190.degree. C., of from about 100 cps to about 5000
cps.
45. The article of claim 31, wherein the metallocene
ethylene-containing polymer has a melt index of from about 200 to
about 2000.
46. The article of claim 31, wherein the metallocene
ethylene-containing polymer has a melt index of from about 400 to
about 1200.
47. The article of claim 31, wherein the metallocene
ethylene-containing polymer has a specific gravity of about 0.90 or
below.
48. The article of claim 31, wherein the base polymer comprises at
least one metallocene-ethylene containing polymer, and wherein the
optional wax is present.
49. The article of claim 31, wherein the base polymer comprises at
least one non-metallocene amorphous propylene containing polymer,
and wherein the optional wax is not present.
50. The article of claim 31, wherein the base polymer comprises a
metallocene ethylene-octene copolymer.
51. The article of claim 31, wherein the base polymer comprises a
metallocene ethylene-hexene copolymer.
52. The article of claim 31, wherein the base polymer comprises a
non-metallocene amorphous poly-alpha-olefin.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to hot melt adhesive
compositions. More particularly, the invention relates to hot melt
adhesives which exhibit improved adhesion to difficult substrates,
particularly at very low or very high temperatures.
[0003] 2. Description of the Related Art
[0004] Hot-melt adhesives are thermoplastic materials which are
typically solid at room temperature, and are denoted by the
abbreviation HMA (hot-melt adhesives). Hot melt adhesives are
widely used in industry for various applications such as product
assembly, packaging, hygiene and elastic attachment, lamination,
case and carton sealing, bookbinding and applications in the
construction bonding, furniture, and textile industries, profile
wrapping, and the like.
[0005] Various HMA's have different weaknesses relating to adhesion
to certain substrates and adhesion at different temperatures. For
instance, hot melt adhesives based on metallocene ethylene octene
copolymers, or "mEO" adhesives, which are advantageous for their
low odor, high clarity, and ease of use, often exhibit poor
adhesion to difficult substrates, particularly at low temperatures
such as refrigerator or freezer temperatures. This can be a problem
in applications relating to corrugated and/or coated carton stock
for food packaging and the like. Conversely, hot melt adhesives
based on amorphous poly-alpha-olefins, known as "APAO" adhesives,
often suffer from poor adhesion to difficult substrates,
particularly at elevated temperatures, as well as difficulty in
viscosity control while maintaining adhesive and cohesive
properties required for performance. This can be a problem with
applications such as film laminating, woodworking, profile
wrapping, PVC edge banding, and other adhesion applications with
wood, steel, and wrapping films.
[0006] It is highly undesirable for materials to lose adhesion due
to an adhesive that either lacks cold temperature resistance and
becomes brittle, or lacks high temperature resistance and softens.
However, in achieving high temperature resistance, cold temperature
resistance is often sacrificed, and vice versa. In addition, an
increase in adhesion may result in a decrease in cohesion between
component parts of a composition. It would therefore be desirable
to formulate a hot melt adhesive composition having improved
cohesion properties in addition to improved adhesion performance to
difficult substrates, particularly at elevated or low temperatures.
Such compositions would exhibit improved adhesion to difficult
substrates at elevated and/or low temperatures, as compared to
conventional hot melt adhesives. Further, certain compositions
would exhibit an increase in both cohesion and adhesion when
considering both shear adhesion failure temperature (SAFT) and peel
adhesion failure temperature (PAFT).
SUMMARY OF THE INVENTION
[0007] The invention provides a hot melt adhesive composition which
comprises: [0008] a) a base polymer comprising at least one
metallocene ethylene-containing polymer or at least one
non-metallocene, amorphous, propylene containing polymer; [0009] b)
a tackifier; [0010] c) an optional wax; and [0011] d) an adhesion
promoting additive comprising at least one semi-crystalline polymer
having a weight average molecular weight of about 30,000 daltons or
less.
[0012] The invention also provides a process for forming a hot melt
adhesive composition which comprises combining: [0013] a) a base
polymer comprising at least one metallocene ethylene-containing
polymer or at least one non-metallocene, amorphous, propylene
containing polymer; [0014] b) a tackifier; [0015] c) an optional
wax; and [0016] d) an adhesion promoting additive comprising at
least one semi-crystalline polymer having a weight average
molecular weight of about 30,000 daltons or less.
[0017] The invention further provides a process for forming an
adhesive substrate which comprises: [0018] I) forming a hot melt
adhesive composition by combining: [0019] a) a base polymer
comprising at least one metallocene ethylene-containing polymer or
at least one non-metallocene, amorphous, propylene containing
polymer; [0020] b) a tackifier; [0021] c) an optional wax; and
[0022] d) an adhesion promoting additive comprising at least one
semi-crystalline polymer having a weight average molecular weight
of about 30,000 daltons or less; [0023] II) heating the hot melt
adhesive composition to a temperature at or above the melting point
of the hot melt adhesive composition; and [0024] III) applying the
heated hot melt adhesive composition to a substrate.
[0025] The invention still further provides a process for adhering
an article to an adhesive substrate which comprises: [0026] I)
forming a hot melt adhesive composition by combining: [0027] a) a
base polymer comprising at least one metal locene
ethylene-containing polymer or at least one non-metallocene,
amorphous, propylene containing polymer; [0028] b) a tackifier;
[0029] c) an optional wax; and [0030] d) an adhesion promoting
additive comprising at least one semi-crystalline polymer having a
weight average molecular weight of about 30,000 amu or less; [0031]
II) heating the hot melt adhesive composition to a temperature at
or above the melting point of the hot melt adhesive composition;
[0032] III) applying the heated hot melt adhesive composition to a
substrate, to thereby form an adhesive substrate; and [0033] IV)
contacting the adhesive substrate with an article, such that the
article adheres to the adhesive substrate via the hot melt adhesive
composition.
DETAILED DESCRIPTION OF THE INVENTION
[0034] The present invention provides hot melt adhesive
compositions which exhibit improved adhesion to difficult
substrates, particularly at low or high temperatures. Temperatures
considered "low" are those temperatures at which foods are
refrigerated or frozen. Refrigerator temperatures typically range
from about 33.degree. F. (0.56.degree. C..) to about 40.degree. F.
(4.4 .degree. C..). Freezer temperatures typically range from about
32.degree. C.. (0.degree. C.) and below. Particularly low
temperatures are those at which frozen foods are stored, for
instance about -4.degree. F. (-20.degree. C.). Temperatures
considered "high" are those at temperatures above the DOT
(Department of Transportation) temperature test requirement for
adhesives, which is about 60.degree. C. Temperatures above this,
and particularly those at about 65.degree. C. or higher, would be
considered "high" for adhesives. The term "difficult substrate" is
herein defined as those substrates which typically exhibit poor
adhesion to hot melt adhesives, or which exhibit poor adhesion to
other substrates or articles via such hot melt adhesives. Examples
of difficult substrates at low temperatures include food packaging
materials such as acrylic coated paperboard. Examples of difficult
substrates at high temperatures include vinyl and wood.
[0035] The invention provides a hot melt adhesive composition which
comprises: [0036] a) a base polymer comprising at least one
metallocene ethylene-containing polymer or at least one
non-metallocene, amorphous, propylene containing polymer; b) a
tackifier; c) an optional wax; and d) an adhesion promoting
additive comprising at least one semi-crystalline polymer having a
weight average molecular weight of about 30,000 daltons or
less.
[0037] The base polymer is defined herein as being the polymer
component of the highest molecular weight in the overall hot melt
adhesive composition. The base polymer according to this invention
comprises at least one metallocene ethylene-containing polymer, or
at least one non-metallocene, amorphous, propylene containing
polymer. As used herein, the term "polymer" is meant to include
homopolymers, copolymers, terpolymers, interpolymers, or
combinations thereof. The base polymer component is preferably
present in the hot melt adhesive composition in an amount ranging
from about 5% by weight to about 95% by weight, more preferably
from about 20% by weight to about 80% by weight, and most
preferably from about 40% to about 75% by weight of the overall
composition.
[0038] The metallocene ethylene-containing polymer is defined for
purposes of this invention as a base polymer which comprises
ethylene polymerized by a catalyst. The catalyst may be referred to
as a metallocene, single site, constrained geometry, or
"post-metallocene" catalyst. Examples of suitable metallocene
ethylene-containing polymers nonexclusively include: metallocene
ethylene-octene copolymers, metallocene ethylene-hexene copolymers,
ethylene-butene, and terpolymers which comprise a mixture of
alpha-olefin or cyclic comonomers. In one preferred embodiment, the
metallocene ethylene-containing polymer comprises a metallocene
ethylene-hexene copolymer. In another preferred embodiment, the
metallocene ethylene-containing polymer comprises a metallocene
ethylene-octene copolymer.
[0039] As mentioned previously, hot melt adhesives which are based
on metallocene ethylene-octene copolymers are known in the art as
"mEO" adhesives. These adhesives are advantageous for their low
odor, high clarity, and ease of use. However, they have been known
to exhibit poor adhesion to difficult substrates, such as acrylic
coated paperboard, particularly at low temperatures such as
refrigerator or freezer temperatures. It has now been unexpectedly
found that mEO adhesive compositions which are formed according to
the present invention exhibit improved adhesion to difficult
substrates at low temperatures, particularly due to the adhesion
promoting additive. The unexpected findings of improved adhesion,
in terms of percent fiber tear of the substrate, are shown in the
data of Table 2, below, as well as in Examples 12-24. An increase
in percent fiber tear of 50% or more is considered a significant
improvement. The data shows that the inventive hot melt adhesives
of Examples 13-24 all exhibited increases in percent fiber tear
versus the "control" adhesive of Example 12 at 0.degree. C.
Significant increases of 50% or greater were shown in eleven out of
twelve of these trials at 0.degree. C. for corrugated board stock,
and at 35.degree. C. for coated carton stock in the form of a bacon
carton. These results were unexpected because the control adhesive
is exemplary of conventionally known and used hot melt adhesives,
which have presumably been optimized over time by those skilled in
the art. Commercially available metallocene ethylene-octene
copolymers useful for this invention nonexclusively include
Affinity.TM. GA-1950 and Affinity.TM. GA-1900, available from Dow
Global Technologies Inc., of Midland, Mich.
[0040] The metallocene ethylene-containing polymer preferably has a
specific gravity of about 0.90 or below, and more preferably from
about 0.88 or below. The specific gravity may be determined using
ASTM procedure D1238-04c, "Standard Test Method for Melt Flow Rates
of Thermoplastics by Extrusion Plastometer."
[0041] The metallocene ethylene-containing polymer preferably has a
melt index of from about 5 to about 3000, more preferably from
about 200 to about 2000, and most preferably from about 400 to
about 1200. In one specific embodiment, a preferred metallocene
ethylene-containing polymer has a melt index of about 500. In
another specific embodiment, a preferred metallocene
ethylene-containing polymer has a melt index of about 1000.
[0042] In a specific embodiment of the invention, the metallocene
ethylene-containing polymer comprises a metallocene polyethylene
copolymer, which is defined herein as including at least one linear
or substantially linear interpolymer of ethylene and at least one
C.sub.3-C.sub.20 alpha olefin comonomer, prepared with a
metallocene catalyst, or constrained geometry as described above.
The interpolymer preferably has a polydispersity of about 2.5 or
less, and a density of from about 0.850 g/cm.sup.3 to about 0.886
g/cm.sup.3. Polydispersity is defined herein as the ratio of the
weight-average molecular weight to the number average molecular
weight, or Mw/Mn. Polydispersity is an indicator of molecular
weight variation. A lower polydispersity corresponds to a narrow
molecular weight range, which is indicative of improved
performance, especially over a range of temperatures.
[0043] Regarding the non-metallocene, amorphous, propylene
containing polymer, suitable examples nonexclusively include:
amorphous poly-alpha-olefins, propylene alpha-olefin interpolymers,
propylene-butene copolymers, and amorphous terpolymers of ethylene,
propylene and 1-butene monomers. In a preferred embodiment, the
non-metallocene, amorphous, propylene containing polymer comprises
an amorphous poly-alpha-olefin or "APAO." Examples of suitable
commercially available APAO polymer materials include Huntsman's
REXtac.RTM. materials and Degussa's Vestoplast.RTM. materials, as
well as the Eastman Eastoflex.RTM. materials. Typical molecular
weight ranges for these APAO base polymers usually range from about
30,000 to about 110,000 or more.
[0044] APAO adhesives are often used in film laminating,
woodworking profile wrapping, wood edgebanding, and other adhesion
applications with wood, steel, and wrapping films. Conventional
APAO adhesives typically exhibit poor peel adhesion to these
substrates, particularly at high temperatures such as those
discussed above, and the viscosity of APAO formulations has been
difficult to control while maintaining both adhesive and cohesive
properties. A well known trade-off in the formation of hot melt
adhesives is that cohesion tends to suffer as viscosity is reduced.
It has now been unexpectedly found that APAO adhesives formed
according to the present invention exhibit improved adhesion to
these substrates, even at elevated temperatures. These unexpected
findings, in terms of PAFT, SAFT, and polypropylene (PP) lap shear,
are shown in the data of Table 1 below, as well as in Examples
1-11. An increase in PAFT of 50.degree. F. (10.degree. C.) or
greater, or an increase in SAFT of 25.degree. F. or greater is
considered a significant improvement. An increase in polypropylene
(PP) lap shear of 50 psi or greater is considered a significant
improvement. The data shows that the inventive hot melt adhesives
of Examples 2-11 each exhibited increases in PP lap shear versus
the "control" adhesive of Example 1. In nine out of ten of these
trials, significant improvements in lap shear were shown. The data
also shows that each of Examples 2-11 exhibited increases in PAFT,
with seven out of ten of these trials showing significant
improvements. Furthermore, nine out of ten of these trails also
exhibited increases in SAFT, with six out of ten of these trials
showing significant improvements. These results were unexpected
because the control adhesive is exemplary of conventionally known
and used hot melt adhesives, which have presumably been optimized
over time by those skilled in the art. Commercially available
non-metallocene, amorphous, propylene containing polymers useful
for this invention nonexclusively include Vestoplast.RTM. 828,
available from Degussa Corporation of Parsippany, N.J.
[0045] The present inventive compositions further comprise a
tackifier. The tackifier gives tack to the adhesive, and may also
lower viscosity. Lower viscosity improves application flow
characteristics, allowing for easier processing, lower energy
requirements, and lower processing temperatures. Lower viscosity
also helps the adhesive to "wet out," or to substantially uniformly
coat the surface and penetrate the substrate. Tack is required in
most adhesive formulations to allow for proper joining of articles
prior to solidification of the hot melt adhesive. Any
conventionally known tackifier, which is suitable for use in
formulating hot melt adhesives, may be used in the present practice
of the invention. Examples of suitable tackifiers nonexclusively
include glycerol and pentaerythritol esters of natural and
chemically modified rosins; naturally occurring and chemically
modified resins, such as wood rosin, gum rosin, tall oil rosin,
distilled rosin, and rosins modified by processes such as
polymerization, hydrogenation, esterification and dimerization;
thermal oligomerization and aromatic modification; polyterpene
resins; modified terpene resins, such as chlorinated terphenyl
resins and phenolic-modified terpene resins; aliphatic petroleum
hydrocarbon resins, such as those resulting from polymerization of
olefin and diolefin monomers, cyclopentadiene or dicyclopentadiene,
piperylene, oligomers of the same, or combinations thereof. A
preferred tackifier comprises an aromatic modified cycloaliphatic
hydrocarbon resin. Commercially available tackifiers which are
suitable for this invention nonexclusively include Escorez.RTM.
5637 and Escorez.RTM. 2596, available from Exxon Mobil Corporation
of Irving, Tex.
[0046] The tackifier is preferably present in the inventive hot
melt adhesive composition in an amount ranging from about 2% by
weight to about 75% by weight, more preferably from about 15% by
weight to about 70% by weight, and most preferably from about 20%
to about 40% by weight of the overall composition.
[0047] The inventive compositions may optionally further comprise a
wax. Waxes serve to reduce the overall viscosity of the adhesive,
thereby allowing it to liquefy and allowing for the proper
application or coating of the hot melt adhesive onto an intended
substrate. The type and melting point of a wax controls the open
time and setting speed of the adhesive. Open time is known in the
art as being the amount of time for an adhesive to wet out and bond
to a substrate after application. Any conventionally known wax,
which is suitable for use in formulating hot melt adhesives, may be
used in the practice of the invention. Examples of suitable waxes
nonexclusively include polar waxes, paraffin waxes, polyolefin
waxes, Fischer-Tropsch waxes, petroleum waxes, synthetic waxes,
vegetable waxes, microcrystalline waxes, ethylene vinyl acetate
waxes, polyethylene waxes, slack wax, byproduct or degraded waxes
derived from polymerization or refinery processes, oxidized waxes,
ethylene acrylic acid copolymer waxes, or combinations thereof. One
commercially available wax that is suitable for this invention is
Sasol.RTM. H-I, available from Sasol Wax Americas, Inc. of Shelton,
Conn.
[0048] In one preferred embodiment, where the base polymer
comprises at least one metallocene ethylene-containing polymer, the
optional wax is present. In other preferred embodiment, where the
base polymer comprises at least one non-metallocene amorphous
propylene containing polymer, the optional wax is not present. The
wax, if present in the inventive hot melt adhesive composition, is
preferably present in an amount ranging from about 4% by weight to
about 85% by weight, more preferably from about 10% by weight to
about 60% by weight, and most preferably from about 15% to about
35% by weight of the overall composition.
[0049] Another component of the present hot melt adhesive
compositions is the adhesion promoting additive. The adhesion
promoting additive comprises at least one semi-crystalline polymer
having a weight average molecular weight of about 30,000 daltons or
less, preferably from about 8,000 daltons to about 25,000 daltons,
and more preferably from about 12,000 daltons to about 22,000
daltons. Using semi-crystalline polymers having a weight average
molecular weight of about 30,000 daltons or less enhances the
adhesion promoting additive's compatibility with the higher
molecular weight base polymer. Examples of suitable
semi-crystalline polymers for the adhesion promoting additive
nonexclusively include: propylene-containing polymers, maleated
propylene-containing polymers, maleated ethylene-containing
polymers, or combinations thereof Specific examples include
maleated propylene-ethylene copolymer, maleated ethylene copolymers
propylene-ethylene copolymer, and propylene homopolymer. A
preferred semi-crystalline polymer for this invention comprises
maleated propylene-ethylene copolymer. Commercially available
adhesion promoting additives useful for this invention
nonexclusively include certain Honeywell A-C.RTM. additives, such
as A-C.RTM. 925, A-C.RTM. 573, A-C.RTM. 575, A-C.RTM. 596, A-C.RTM.
597, A-C.RTM. 1325, and A-C.RTM. 1089, A-C.RTM. 1660 and A-C.RTM.
1172 additives, which are available from Honeywell International
Inc., of Morristown, N.J.
[0050] In a preferred embodiment, the adhesion promoting additive
comprises a semi-crystalline polymer, as described above, which
comprises a maleated polymer having a percent bound of about 50% or
greater. The term "percent bound" (i.e. percent grafted) is defined
herein as the weight ratio of bound maleic anhydride to the total
maleic anhydride of a maleated polymer. The total maleic anhydride
includes both bound and unbound maleic anhydride. The term "bound
maleic anhydride" is defined as the maleic anhydride which has
reacted with the polymer chain, and is thus bound or grafted
thereto. The term "unbound maleic anhydride" describes both
unreacted maleic anhydride and unbound maleic anhydride-containing
oligomers. Maleated polymers having a percent bound of 50% or
greater nonexclusively include: A-C.RTM. 925, A-C.RTM. 1325,
A-C.RTM. 596 and A-C.RTM. 597, available from Honeywell
International, Inc. of Morristown, N.J..
[0051] In a preferred embodiment, the adhesion promoting additive
comprises a semi-crystalline polymer, as described above, which has
a Mettler drop point of from about 100.degree. C. to about
170.degree. C. Mettler drop point is determined by a Mettler drop
point apparatus, which is well-known in the art. The Mettler drop
point is the point where a molten polymeric material "drops" past
an electric eye, and is recorded in terms of the temperature of the
dropping point, generally in degrees Celsius or Fahrenheit. Mettler
drop point of the adhesion promoting additive is a function of its
crystallinity, which contributes to the heat resistance, process
temperature, and application performance of the final adhesive. In
a further embodiment, an ethylene-based adhesion promoting additive
has a viscosity, based on Brookfield viscometer measurement at
140.degree. C., of from about 100 cps to about 5000 cps. In another
embodiment, a adhesion promoting additive comprising propylene has
a viscosity, based on Brookfield viscometer measurement at
190.degree. C., of from about 100 cps to about 5000 cps, due to the
melting point of propylene. The viscosity may be determined using
ASTM procedure D3236.
[0052] The adhesion promoting additive is preferably present in the
hot melt adhesive composition in an amount of from about 1% to
about 25% by weight of the composition, more preferably from about
3% to about 19% by weight of the composition, and most preferably
from about 7% to about 14% by weight of the composition.
[0053] It has been unexpectedly found that the adhesion promoting
additive of this invention enhances the adhesion properties of a
hot melt adhesive composition having a metallocene
ethylene-containing base polymer at low temperatures, such as
refrigerator and freezer temperatures, where other conventional
adhesives have suffered. Comparative Example 12 shows the low
adhesion results, based on the percent of substrate fiber tear, for
a conventional mEO adhesive which does not contain the additive of
the present invention. Based on the results of Comparative Example
12, the benefits resulting from a combination of the adhesion
promoting additives of the present invention with a metallocene
ethylene-containing base polymer was surprising and unexpected as
shown in Examples 13-24 which show increases in percent of
substrate fiber tear with the addition of the inventive adhesion
promoting additive.
[0054] It has also been unexpectedly found that the adhesion
promoting additive of this invention enhances the adhesion
properties of a hot melt adhesive composition having a
non-metallocene, amorphous, propylene containing base polymer,
particularly at elevated temperatures such as those above
60.degree. C. as stated above, where other conventional adhesives
have suffered. Comparative Example 1 shows the low PAFT, SAFT, and
polypropylene (PP) lap shear strength results from a conventional
APAO adhesive which does not contain the additive of the present
invention. Based on the results of Comparative Example 1, the
benefits resulting from a combination of the adhesion promoting
additives of the present invention with an amorphous, propylene
containing base polymers was surprising and unexpected, as shown in
Examples 2-11 which show increases in PAFT and SAFT with the
addition of the inventive adhesion promoting additive.
[0055] The present results were further unexpected based on
Comparative Examples 25-37 showing either poor results or no
significant improvements in adhesion of a hot melt adhesive formed
with an ethylene vinyl acetate (EVA) base polymer, based on percent
of substrate fiber tear, even though this EVA adhesive included the
adhesion promoting additive of the present invention. Specifically,
for instance, Comparative Example 25 shows a 0% adhesion (fiber
tear) to a bacon carton at 35.degree. F. (1.7.degree. C.). With the
addition of the inventive adhesion promoting additive in Examples
26-37, each of these trials still exhibit 0% adhesion (fiber tear)
to a bacon carton at 35.degree. F. (1.7.degree. C.). Thus, improved
adhesion properties were only shown in hot melt adhesive
compositions which contained the selected adhesion promoting
additives of the present invention, in combination with the
selected base polymers of the present invention.
[0056] The inventive hot melt adhesive compositions may further
comprise other additives such as stabilizers, plasticizers,
antioxidants, fillers, colorants, diluents such as oils, talcs such
as silica, minerals such as clays, or other additives deemed
suitable by those skilled in the art, and combinations thereof.
These may include functional additives which may add a specific
physical or chemical property that impacts the characteristics of
the adhesive in manufacturing or use, and not necessarily related
to the adhesion character of the adhesive. In formulating
adhesives, all of the ingredients should be compatible, so the
formulation does not separate when heated or melted. Separation
would result in the inability to apply the adhesive, as well as
poor adhesive performance.
[0057] The hot melt adhesive compositions of the present invention
are particularly useful in packaging applications and in the
formation of packaging materials, such as food packaging materials.
The hot melt adhesive compositions are also particularly useful in
applications such as film laminating, woodworking profile wrapping,
wood edge banding, and other adhesion applications with wood,
steel, and wrapping films.
[0058] The invention further provides a process for forming the
inventive hot melt adhesive compositions. The process comprises
combining the above-described components of the inventive hot melt
adhesive compositions, namely: a) a base polymer comprising at
least one metallocene ethylene-containing polymer or at least one
non-metallocene, amorphous, propylene containing polymer; b) a
tackifier; c) an optional wax; and d) an adhesion promoting
additive comprising at least one semi-crystalline polymer having a
weight average molecular weight of about 30,000 daltons or
less.
[0059] The combining of these components may be done using any
suitable conventional method such as mixing, extrusion, and the
like. In one embodiment, the combining step comprises forming a
substantially homogeneous admixture of components (a)-(d). In
another embodiment, the combining comprises extruding components
(a)-(d). Any conventional extrusion method may be used, such as
melt extrusion, coextrusion, solid extrusion, master batching, melt
blending, batch mixing, and the like.
[0060] The invention further provides a process for forming an
adhesive substrate. In this process, a hot melt adhesive
composition is formed as described above. That is, components
(a)-(d) are combined. The resulting hot melt adhesive composition
is then heated to a temperature at or above the melting point of
the overall hot melt adhesive composition. This heated hot melt
adhesive composition is then applied to a substrate, using any
suitable conventional technique, to thereby form an adhesive
substrate. In certain embodiments, this process further comprises
the subsequent step of bringing the hot melt adhesive composition
to a temperature below the melting point of the composition, to at
least partially solidify the hot melt adhesive composition. The
substrate may comprise any suitable material which is to be made
adhesive. Particularly desirable substrates include those suitable
in forming packaging materials for packaging applications, such as
food packaging. Suitable substrate materials nonexclusively include
plastic films and sheets, metal sheets, lacquer coated papers,
polypropylene, wood, paper, cellulosics, corrugated, cardboard,
coated board, coated carton stock, composites, aluminum, glass,
steel and rebar and the like. In one preferred embodiment, the
substrate comprises a polyolefin film. In another preferred
embodiment, the substrate comprises a metal sheet.
[0061] In a further process, the formed adhesive substrate is
contacted with an article, such that the article adheres to the
adhesive substrate via the hot melt adhesive composition. In
certain embodiments, this process further comprises the subsequent
step of bringing the hot melt adhesive composition to a temperature
below the melting point of the composition. As stated above, this
preferably least partially solidifies the hot melt adhesive
composition. The article may comprise any suitable material which
is capable of adhering to the adhesive substrate. Particularly
desirable articles include those suitable for use in forming
packaging materials for packaging applications, such food
packaging. The article may or may not comprise substantially the
same material as that used for the aforementioned adhesive
substrate. Suitable article materials nonexclusively include
plastic films and sheets, metal sheets, paper, corrugated board,
wood, coated carton stock and the like. In one preferred
embodiment, the substrate comprises a polyolefin film. In another
preferred embodiment, the substrate comprises a vinyl film. In
another preferred embodiment, the substrate comprises a metal
sheet.
[0062] The above described processes are particularly suitable in
packaging applications including food packaging applications. In
one preferred embodiment a material to be packaged, such as a food
product or the like, is placed between the adhesive substrate and
the article. The material to be packaged is preferably placed
between the adhesive substrate and the article such that, when the
article adheres to the adhesive substrate via the hot melt adhesive
composition, the material to be packaged is present between the
adhesive substrate and the article.
[0063] In accordance with the present invention, it is preferred
that the article which adheres to the adhesive substrate via the
hot melt adhesive composition maintains adhesion to the adhesive
substrate at elevated temperatures and/or at refrigerator and/or
freezer temperatures, as described above. In one preferred
embodiment, the article maintains adhesion to the adhesive
substrate at temperatures of about 60.degree. C. or above. In
another preferred embodiment, the article maintains adhesion to the
adhesive substrate at refrigerator or freezer temperatures, such as
temperatures of about 5.degree. C. or below. Tables 1 and 2, below,
show specific data relating to adhesion properties of the inventive
hot melt adhesive compositions.
[0064] The following non-limiting examples serve to illustrate the
invention. It will be appreciated that variations in proportions
and alternatives in elements of the components of the invention
will be apparent to those skilled in the art and are within the
scope of the present invention.
EXAMPLE 1 (COMPARATIVE)
[0065] The data for Examples 1-11 correspond to trials 1-11 of
Table 1, below.
[0066] An APAO hot melt adhesive composition was formed with the
following formulation: 100 parts Vestoplast.RTM. 828 base polymer,
35 parts Escorez.RTM. 2596 tackifier, no wax, and no adhesion
promoting additive. The resulting hot melt adhesive composition
exhibited a PAFT of 116.degree. F. (46.7.degree. C.), and a SAFT of
241.degree. F. (116.1.degree. C.). This adhesive composition
exhibited a lap shear strength of 98 psi to a polypropylene
substrate. PAFT and SAFT test procedures were conducted using ASTM
D4498 testing methods.
EXAMPLE 2
[0067] An APAO hot melt adhesive composition was formed with the
following formulation: 100 parts Vestoplast.RTM. 828 base polymer,
35 parts Escorez.RTM. 2596 tackifier, no wax, and 10 parts of a
conventional maleated polypropylene compatibilizer. The resulting
hot melt adhesive composition exhibited a PAFT of 197.degree. F.
(91.7.degree. C.), and a SAFT of 266.degree. F. (130.degree. C.).
This shows a significant improvement in both PAFT and SAFT over the
composition of Comparative Example 1. This adhesive composition
exhibited a lap shear strength of 124 psi to a polypropylene
substrate, which shows an increase over Comparative Example 1.
EXAMPLE 3
[0068] An APAO hot melt adhesive composition was formed with the
following formulation: 100 parts Vestoplast.RTM. 828 base polymer,
35 parts Escorez.RTM. 2596 tackifier, no wax, and 10 parts of
Honeywell's A-C.RTM. 596 as an adhesion promoting additive. The
resulting hot melt adhesive composition exhibited a PAFT of
179.degree. F. (81.7.degree. C.), and a SAFT of 236.degree. F.
(113.3.degree. C.). This shows a significant improvement in PAFT
over the composition of Comparative Example 1.
[0069] The SAFT temperature in this case was the only trial where
the SAFT decreased, and the decrease was so minor (.about.5.degree.
F.) that it is likely the result of experimental error. This
adhesive composition exhibited a lap shear strength of 162 psi to a
polypropylene substrate, which is a significant improvement over
Comparative Example 1.
EXAMPLE 4
[0070] An APAO hot melt adhesive composition was formed with the
following formulation: 100 parts Vestoplast.RTM. 828 base polymer,
35 parts Escorez.RTM. 2596 tackifier, no wax, and 10 parts of
Honeywell's A-C.RTM. 1325 as an adhesion promoting additive. The
resulting hot melt adhesive composition exhibited a PAFT of
164.degree. F. (73.3.degree. C.), and a SAFT of 255.degree. F.
(123.9.degree. C.). This shows improvements in both PAFT and SAFT
over the composition of Comparative Example 1. This adhesive
composition exhibited a lap shear strength of 176 psi to a
polypropylene substrate, which is a significant improvement over
Comparative Example 1.
EXAMPLE 5
[0071] An APAO hot melt adhesive composition was formed with the
following formulation: 100 parts Vestoplast.RTM. 828 base polymer,
35 parts Escorez.RTM. 2596 tackifier, no wax, and 10 parts of
Honeywell's A-C.RTM. 925 as an adhesion promoting additive. The
resulting hot melt adhesive composition exhibited a PAFT of
231.degree. F. (110.6.degree. C.), and a SAFT of 271.degree. F.
(132.2.degree. C.). This shows a significant improvement in both
PAFT and SAFT over the composition of
[0072] Comparative Example 1. This adhesive composition exhibited a
lap shear strength of 174 psi to a polypropylene substrate, which
is a significant improvement over Comparative Example 1.
EXAMPLE 6
[0073] An APAO hot melt adhesive composition was formed with the
following formulation: 100 parts Vestoplast.RTM. 828 base polymer,
35 parts Escoree 2596 tackifier, no wax, and 10 parts of
Honeywell's A-C.RTM. 1172 as an adhesion promoting additive. The
resulting hot melt adhesive composition exhibited a PAFT of
120.degree. F. (48.9.degree. C.), and a SAFT of 245.degree. F.
(118.3.degree. C.). This shows an improvement in both PAFT and SAFT
over the composition of Comparative Example 1. This adhesive
composition exhibited a lap shear strength of 162 psi to a
polypropylene substrate, which is a significant improvement over
Comparative Example 1.
EXAMPLE 7
[0074] An APAO hot melt adhesive composition was formed according
to Example 2, except that instead 20 parts of the conventional
maleated polypropylene compatibilizer was added. The resulting hot
melt adhesive composition exhibited a PAFT of 217.degree. F.
(101.1.degree. C.), and a SAFT of 273.degree. F. (133.9.degree.
C.). This shows a significant improvement in PAFT and SAFT over the
composition of Comparative Example 1. This adhesive composition
exhibited a lap shear strength of 256 psi to a polypropylene
substrate, which is a significant improvement over Comparative
Example 1.
EXAMPLE 8
[0075] An APAO hot melt adhesive composition was formed according
to Example 3, except that instead 20 parts of Honeywell's A-C.RTM.
596 was added as the adhesion promoting additive. The resulting hot
melt adhesive composition exhibited a PAFT of 206.degree. F.
(96.7.degree. C.), and a SAFT of 249.degree. F. (120.6.degree. C.).
This shows a significant improvement in PAFT and an increase in
SAFT over the composition of Comparative Example 1. This adhesive
composition exhibited a lap shear strength of 196 psi to a
polypropylene substrate, which is a significant improvement over
Comparative Example 1.
EXAMPLE 9
[0076] An APAO hot melt adhesive composition was formed according
to Example 4, except that instead 20 parts of parts of Honeywell's
A-C.RTM. 1325 was added as the adhesion promoting additive. The
resulting hot melt adhesive composition exhibited a PAFT of
198.degree. F. (92.2.degree. C.), and a SAFT of 275.degree. F.
(135.degree. C.). This shows a significant improvement in both PAFT
and SAFT over the composition of Comparative Example 1. This
adhesive composition exhibited an excellent lap shear strength of
260 psi to a polypropylene substrate, which is a significant
improvement over Comparative Example 1.
EXAMPLE 10
[0077] An APAO hot melt adhesive composition was formed according
to Example 5, except that instead 20 parts of Honeywell's A-C.RTM.
925 was added as the adhesion promoting additive. The resulting hot
melt adhesive composition exhibited a PAFT of 224.degree. F.
(106.7.degree. C.), and a SAFT of 272.degree. F. (133.3.degree.
C.). This shows a significant improvement in both PAFT and SAFT
over the composition of Comparative Example 1. This adhesive
composition exhibited a lap shear strength of 244 psi to a
polypropylene substrate, which is a significant improvement over
Comparative Example 1.
EXAMPLE 11
[0078] An APAO hot melt adhesive composition was formed according
to Example 6, except that instead 20 parts of Honeywell's A-C.RTM.
1172 was added as the adhesion promoting additive. The resulting
hot melt adhesive composition exhibited a PAFT of 129.degree. F.
(53.9.degree. C.), and a SAFT of 282.degree. F. (138.9.degree. C.).
This shows an increase in PAFT and a significant improvement in
SAFT over the composition of Comparative Example 1. This adhesive
composition exhibited a lap shear strength of 280 psi to a
polypropylene substrate, which is a significant improvement over
Comparative Example 1.
TABLE-US-00001 TABLE 1 Trial No. (Compar.) 1 2 3 4 5 6 7 8 9 10 11
Additive (in wt. %): no additive 0 maleated 6.9 12.9 polypropylene
A-C .RTM.596 6.9 12.9 A-C .RTM.1325 6.9 12.9 A-C .RTM.925 6.9 12.9
A-C .RTM.1172 6.9 12.9 Base Polymer 74.1 69 69 69 69 69 64.5 64.5
64.5 64.5 64.5 (Vestoplast .RTM. 828) Tackifier 25.9 24.1 24.1 24.1
24.1 24.1 22.6 22.6 22.6 22.6 22.6 (Escorez .RTM. 2596) Adhesion
(psi) PP Lap Shear 98 124 162 176 174 162 256 196 260 244 280 SD+/-
10 9.8 12.8 10.4 12.4 18.8 25.6 26.4 14 32.8 12.4 Heat Resistance
(.degree. F.) PAFT 116 197 179 164 231 120 214 206 198 224 129 SAFT
241 266 236 255 271 245 273 249 275 272 282
EXAMPLE 12 (COMPARATIVE)
[0079] The data for Examples 12-23 correspond to trials 1-13 of
Table 2, below.
[0080] A mEO hot melt adhesive composition was formed with the
following formulation: 40 wt % of Affinity.RTM. GA-1900 base
polymer, 30 wt % of Escorez.RTM. 5637 tackifier, 30 wt % of
Sasol.RTM. H-1 wax, and no adhesion promoting additive. The
resulting hot melt adhesive composition exhibited an adhesion level
(in % fiber tear) of 0% at 0.degree. F. (-17.8.degree. C.) for
inland board stock, and 0% at 35.degree. F. (1.7.degree. C.) for a
bacon carton.
[0081] EXAMPLE 13
[0082] A mEO hot melt adhesive composition was formed with the
following formulation: 40 wt % of Affinity.RTM. GA-1950 base
polymer, 30 wt % of Escorez.RTM. 5637 tackifier, 25 wt % of
Sasol.RTM. H-1 wax, and 5 wt% of a conventional maleated
polypropylene compatibilizer. The resulting hot melt adhesive
composition exhibited an adhesion level (in % fiber tear) of 50% at
0.degree. F. (-17.8.degree. C.) for inland board stock, which is a
significant improvement in low-temperature adhesion at freezer
temperatures over Comparative Example 12. In addition, an adhesion
level of 100% at 35.degree. F. (1.7.degree. C.) was shown for a
bacon carton. This is also a significant improvement in
low-temperature adhesion at refrigerator temperatures over the
composition of Comparative Example 12.
EXAMPLE 14
[0083] A mEO hot melt adhesive composition was formed with the
following formulation: 40 wt % of Affinity.RTM. GA-1950 base
polymer, 30 wt % of Escorez.RTM. 5637 tackifier, 25 wt % of
Sasol.RTM. H-1 wax, and 5 wt % of Honeywell's A-C.RTM. 596 as an
adhesion promoting additive. The resulting hot melt adhesive
composition exhibited an adhesion level (in % fiber tear) of 50% at
0.degree. F. (-17.8.degree. C.) for inland board stock, which is a
significant improvement in low-temperature adhesion at freezer
temperatures over Comparative Example 12. In addition, an adhesion
level of 100% at 35.degree. F. (1.7.degree. C.) was shown for a
bacon carton. This is also a significant improvement in
low-temperature adhesion at refrigerator temperatures over the
composition of Comparative Example 12.
EXAMPLE 15
[0084] A mEO hot melt adhesive composition was formed with the
following formulation: 40 wt % of Affinity.RTM. GA-1950 base
polymer, 30 wt % of Escorez.RTM. 5637 tackifier, 25 wt % of
Sasol.RTM. H-1 wax, and 5 wt % of Honeywell's A-C.RTM. 1325 as an
adhesion promoting additive. The resulting hot melt adhesive
composition exhibited an adhesion level (in % fiber tear) of 50% at
0.degree. F. (-17.8.degree. C.) for inland board stock, which is a
significant improvement in low-temperature adhesion at freezer
temperatures over Comparative Example 12. In addition, an adhesion
level of 100% at 35.degree. F. (1.7.degree. C.) was shown for a
bacon carton. This is also a significant improvement in
low-temperature adhesion at refrigerator temperatures over the
composition of Comparative Example 12.
EXAMPLE 16
[0085] A mEO hot melt adhesive composition was formed with the
following formulation: 40 wt % of Affinity.RTM. GA-1950 base
polymer, 30 wt % of Escorez.RTM. 5637 tackifier, 25 wt % of
Sasol.RTM. H-1 wax, and 5 wt % of Honeywell's A-C.RTM. 925 as an
adhesion promoting additive. The resulting hot melt adhesive
composition exhibited an adhesion level (in % fiber tear) of 100%
at 0.degree. F. (-17.8.degree. C.) for inland board stock, which is
a significant improvement in low-temperature adhesion at freezer
temperatures over Comparative Example 12. In addition, an adhesion
level of 100% at 35.degree. F. (1.7.degree. C.) was shown for a
bacon carton. This is also a significant improvement in
low-temperature adhesion at refrigerator temperatures over the
composition of Comparative Example 12.
EXAMPLE 17
[0086] A mEO hot melt adhesive composition was formed with the
following formulation: 40 wt % of Affinity.RTM. GA-1950 base
polymer, 30 wt % of Escorez.RTM. 5637 tackifier, 25 wt % of
Sasol.RTM. H-1 wax, and 5 wt % of Honeywell's A-C.RTM. 1172 as an
adhesion promoting additive. The resulting hot melt adhesive
composition exhibited an adhesion level (in % fiber tear) of 100%
at 0.degree. F. (-17.8.degree. C.) for inland board stock, which is
a significant improvement in low-temperature adhesion at freezer
temperatures over Comparative Example 12. In addition, an adhesion
level of 50% at 35.degree. F. (1.7.degree. C.) was shown for a
bacon carton. This is also a significant improvement in
low-temperature adhesion at refrigerator temperatures over the
composition of Comparative Example 12.
EXAMPLE 18
[0087] A mEO hot melt adhesive composition was formed with the
following formulation: 40 wt% of Affinity.RTM. GA-1950 base
polymer, 30 wt% of Escorez.RTM. 5637 tackifier, 25 wt% of
Sasol.RTM. H-1 wax, and 5 wt% of Honeywell's A-C.RTM. 573 as an
adhesion promoting additive. The resulting hot melt adhesive
composition exhibited an adhesion level (in % fiber tear) of 50% at
0.degree. F. (-17.8.degree. C.) for inland board stock, which is a
significant improvement in low-temperature adhesion at freezer
temperatures over Comparative Example 12. In addition, an adhesion
level of 100% at 35.degree. F. (1.7.degree. C.) was shown for a
bacon carton. This is also a significant improvement in
low-temperature adhesion at refrigerator temperatures over the
composition of Comparative Example 12.
EXAMPLE 19
[0088] A mEO hot melt adhesive composition was formed according to
Example 13 except that instead 10 wt % of the conventional maleated
polypropylene compatibilizer was added to the composition. The
resulting hot melt adhesive composition exhibited an adhesion level
(in % fiber tear) of 20% at 0.degree. F. (-17.8.degree. C.) for
inland board stock, which showed an improvement in low-temperature
adhesion at freezer temperatures over Comparative Example 12. In
addition, an adhesion level of 100% at 35.degree. F. (1.7.degree.
C.) was shown for a bacon carton. This also a significant
improvement in low-temperature adhesion at refrigerator
temperatures over the composition of Comparative Example 12.
EXAMPLE 20
[0089] A mEO hot melt adhesive composition was formed according to
Example 14 except that instead 10 wt % of Honeywell's A-C.RTM. 596
was added to the composition. The resulting hot melt adhesive
composition exhibited an adhesion level (in % fiber tear) of 50% at
0.degree. F. (-17.8.degree. C.) for inland board stock, which is a
significant improvement in low-temperature adhesion at freezer
temperatures over Comparative Example 12. In addition, an adhesion
level of 25% at 35.degree. F. (1.7.degree. C.) was shown for a
bacon carton. This is an improvement in low-temperature adhesion at
refrigerator temperatures over the composition of Comparative
Example 12.
EXAMPLE 21
[0090] A mEO hot melt adhesive composition was formed according to
Example 15 except that instead 10 wt % of Honeywell's A-C.RTM. 1325
was added to the composition. The resulting hot melt adhesive
composition exhibited an adhesion level (in % fiber tear) of 100%
at 0.degree. F. (-17.8.degree. C.) for inland board stock, which is
a significant improvement in low-temperature adhesion at freezer
temperatures over Comparative Example 12. In addition, an adhesion
level of 50% at 35.degree. F. (1.7.degree. C.) was shown for a
bacon carton. This is also a significant improvement in
low-temperature adhesion at refrigerator temperatures over the
composition of Comparative Example 12.
EXAMPLE 22
[0091] A mEO hot melt adhesive composition was formed according to
Example 16 except that instead 10 wt % of Honeywell's A-C.RTM. 925
was added to the composition. The resulting hot melt adhesive
composition exhibited an adhesion level (in % fiber tear) of 100%
at 0.degree. F. (-17.8.degree. C.) for inland board stock, which is
a significant improvement in low-temperature adhesion at freezer
temperatures over Comparative Example 12. In addition, an adhesion
level of 100% at 35.degree. F. (1.7.degree. C.) was shown for a
bacon carton. This is also a significant improvement in
low-temperature adhesion at refrigerator temperatures over the
composition of Comparative Example 12.
EXAMPLE 23
[0092] A mEO hot melt adhesive composition was formed according to
Example 17 except that instead 10 wt % of Honeywell's A-C.RTM. 1172
was added to the composition. The resulting hot melt adhesive
composition exhibited an adhesion level (in % fiber tear) of 100%
at 0.degree. F. (-17.8.degree. C.) for inland board stock, which is
a significant improvement in low-temperature adhesion at freezer
temperatures over Comparative Example 12. In addition, an adhesion
level of 100% at 35.degree. F. (1.7.degree. C.) was shown for a
bacon carton. This is also a significant improvement in
low-temperature adhesion at refrigerator temperatures over the
composition of Comparative Example 12.
EXAMPLE 24
[0093] A mEO hot melt adhesive composition was formed according to
Example 18 except that instead 10 wt % of Honeywell's A-C.RTM. 573
was added to the composition. The resulting hot melt adhesive
composition exhibited an adhesion level (in % fiber tear) of 100%
at 0.degree. F. (-17.8.degree. C.) for inland board stock, which is
a significant improvement in low-temperature adhesion at freezer
temperatures over Comparative Example 12. In addition, an adhesion
level of 100% at 35.degree. F. (1.7.degree. C.) was shown for a
bacon carton. This is also a significant improvement in
low-temperature adhesion at refrigerator temperatures over the
composition of Comparative Example 12.
TABLE-US-00002 TABLE 2 Trial No. (Compar.) 1 2 3 4 5 6 7 8 9 10 11
12 13 Additive (in wt. %): no additive 0 maleated 5 10
polypropylene A-C .RTM.596 5 10 A-C .RTM.1325 5 10 A-C .RTM.925 5
10 A-C .RTM.1172 5 10 A-C .RTM.573 5 10 Wax (Sasol .RTM. H-1) 30 25
25 25 25 25 25 20 20 20 20 20 20 Tackifier 30 30 30 30 30 30 30 30
30 30 30 30 30 (Escorez .RTM. 5637) Base Polymer 40 40 40 40 40 40
40 40 40 40 40 40 40 (Affinity .RTM. GA-1950) Adhesion (% fiber
tear) Inland Board Stock 0.degree. F. (-17.8.degree. C.) 0% 50% 50%
50% 100% 100% 50% 20% 50% 100% 100% 100% 100% 35.degree. F.
(1.7.degree. C.) 100% 100% 100% 100% 100% 100% 100% 100% 100% 100%
100% 100% 100% Bacon carton 35.degree. F. (1.7.degree. C.) 0% 100%
100% 100% 100% 50% 100% 100% 25% 50% 100% 100% 100%
EXAMPLES 25-37 (COMPARATIVE)
[0094] The data for Examples 25-37 correspond to trials 1-13 of
Table 3, below.
[0095] The procedures of Examples 12-24 were repeated using an
ethylene vinyl acetate (EVA) base polymer (28VA-200MI), and except
that Examples 15 and 20 were conducted with Honeywell's A-C.RTM.
415 as the adhesion promoting additive rather than A-C.RTM. 573.
Results from Examples 25-37 were poor as compared to Examples
12-24, particularly where adhesion to the bacon package at
35.degree. F. remained at 0% for all trials. Further, six out of 12
trials remained at 0% for the board stock at 0.degree. C. These
results show that the improvements exhibited in Examples 12-24 were
unexpected and dramatic.
TABLE-US-00003 TABLE 3 Trial No. (Compar.) 1 2 3 4 5 6 7 8 9 10 11
12 13 Additive (in wt. %): no additive 0 maleated 5 10
polypropylene A-C .RTM.596 5 10 A-C .RTM.1325 5 10 A-C .RTM.925 5
10 A-C .RTM.1172 5 10 A-C .RTM.415 5 10 Wax (Sasol .RTM. H-1) 30 25
25 25 25 25 25 20 20 20 20 20 20 Tackifier 30 30 30 30 30 30 30 30
30 30 30 30 30 (Escorez .RTM. 5637) Base Polymer 40 40 40 40 40 40
40 40 40 40 40 40 40 (28VA, 400MI) Adhesion (% fiber tear) Inland
Board Stock 0.degree. F. (-17.8.degree. C.) 0% 50% 50% 0% 0% 0% 0%
100% 50% 50% 0% 100% 0% 35.degree. F. (1.7.degree. C.) 100% 100%
100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% Bacon carton
35.degree. F. (1.7.degree. C.) 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 0%
0%
[0096] While the present invention has been particularly shown and
described with reference to preferred embodiments, it will be
readily appreciated by those of ordinary skill in the art that
various changes and modifications may be made without departing
from the spirit and scope of the invention. It is intended that the
claims be interpreted to cover the disclosed embodiment, those
alternatives which have been discussed above and all equivalents
thereto.
* * * * *