U.S. patent application number 10/866541 was filed with the patent office on 2005-12-15 for lidstock material having improved sealability and peelability to wide classes of materials.
Invention is credited to Stevenson, James A..
Application Number | 20050276940 10/866541 |
Document ID | / |
Family ID | 35460881 |
Filed Date | 2005-12-15 |
United States Patent
Application |
20050276940 |
Kind Code |
A1 |
Stevenson, James A. |
December 15, 2005 |
Lidstock material having improved sealability and peelability to
wide classes of materials
Abstract
A material that can be used as a lid (12) on a container (14,
40), the lid containing a solid substrate (30) and a peelable and
heat sealable film (32) which contains a mixture of at least
aliphatic-aromatic copolyester, inorganic filler, butene-1 polymer
and ethylene-vinyl acetate copolymer, where the substrate (30) is
preferably made of aluminum.
Inventors: |
Stevenson, James A.;
(Pittsburgh, PA) |
Correspondence
Address: |
ECKERT SEAMANS CHERIN & MELLOTT, LLC
ALCOA TECHNICAL CENTER
100 TECHNICAL DRIVE
ALCOA CENTER
PA
15069-0001
US
|
Family ID: |
35460881 |
Appl. No.: |
10/866541 |
Filed: |
June 10, 2004 |
Current U.S.
Class: |
428/35.7 |
Current CPC
Class: |
B32B 27/20 20130101;
B32B 27/10 20130101; B32B 27/36 20130101; B32B 15/08 20130101; B32B
15/20 20130101; Y10T 428/1352 20150115; B32B 27/306 20130101; B32B
1/02 20130101; B32B 2435/02 20130101; B32B 27/08 20130101; B32B
27/06 20130101 |
Class at
Publication: |
428/035.7 |
International
Class: |
B65D 001/00 |
Claims
What is claimed is:
1. A peelable and heat sealable material suitable for bonding to a
wide variety of substrates, comprising a solid substrate joined to
a film, the film comprising: a.) aliphatic-aromatic copolyester;
b.) particulate inorganic filler; c.) butene-1 polymer; and d.)
ethylene-vinylacetate copolymer.
2. The material of claim 1, wherein, said substrate material is a
lidstock material and comprises at least one material selected from
metal foil, plastic, and paper.
3. The material of claim 1, wherein said substrate comprises
aluminum foil.
4. The material of claim 1, wherein said inorganic filler comprises
talc, silica, or alumina.
5. The material of claim 1, wherein said material is bondable to
all of PVC, PET and PVDC.
6. The material of claim 1, wherein said film comprises about 25
wt. % to about 50 wt. % of aliphatic-aromatic copolyester.
7. The material of claim 1, wherein said film comprises at least
about 5 wt. % of both butene-1 polymer and ethylene-vinyl acetate
copolymer.
8. The material of claim 1, wherein said film comprises from about
10 wt. % to about 30 wt. % of butene-1 polymer and from about 10
wt. % to about 30 wt. % of ethylene-vinyl acetate copolymer.
9. The lidstock material of claim 1, wherein said film comprises
about 20-30 wt. % of the inorganic filler.
10. The lidstock material of claim 1, wherein said filler has a
particle size of from about 0.5 micrometer to 10 micrometer and
contains from about 0.5 wt. % to 5 wt. %, based on the weight of
the filler, of a carboxylic acid.
11. The material of claim 1, wherein said material is bondable to
PS, PP and PE as well as PVC, PET and PVDC.
12. The material of claim 9, wherein said filler is selected from
the group consisting of talc, alumina, silica and mixtures thereof
talc having an average particle size of from 0.5 micrometers to 10
micrometers.
13. A lid for a plastic container comprising the lidstock material
of claim 2.
14. A container comprising a plastic body having an edge defining
an opening and a flange extending radially outwardly of said
opening, and a lid comprising the lidstock material of claim 2 heat
sealed to said flange.
15. The container of claim 13, wherein said substrate comprises
aluminum foil.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a lidstock material
suitable for making lids to be sealed over plastic containers such
as pharmaceutical blisters.
BACKGROUND OF THE INVENTION
[0002] Many products are placed in containers covered by a lidstock
material and such products can range from yogurt to disposable
contact lenses. Such lidstocks must be sealable to a very wide
class of materials, peelable and resistant to both hot and cold
temperatures.
[0003] Many pharmaceuticals and disposable contact lenses are
packaged in blister packages consisting of 2 pieces: a base and a
lid. The base is an injection molded plastic shaped to include a
bowl-shaped or rectangular recess for receiving the contents. In
the case of contact lenses, each blister pack generally contains a
contact lens and enough solution to prevent drying and to maintain
the contact lens ready for use.
[0004] The lid covering the base is heat sealed over the recess
containing the contents of the blister package. The lid must be
easily peelable from the base in order to provide easy access
without spilling the contents. Also the lid must be seal compatable
with a wide variety of materials. These containers are described,
for example, in U.S. Pat. Specification Nos. 4,691,820; 4,810,541;
5,061,532; 5,626,929 and 5,958,531. (Martinez, Newman et al.,
Yamada, Stevenson and Stevenson, respectively) as well as in U.S.
Ser. No. 10/388,001 filed on Mar. 12, 2003 (Docket No. 02-1312,
Stevenson) and "Excitement In Plastics" Packaging Digest, September
2003 pp. 13-15, at
http://www.packagingdigest.com/articles200309/48.html Martinez U.S.
Pat. No. 4,691,820 suggests a polypropylene base and cover of
polypropylene film/aluminum foil laminate. Yamada in U.S. Pat. No.
5,061,532 suggests a thermoplastic rim and a lid made of the same
material as the rim. Stevenson in U.S. Pat. No. 5,626,929 suggests
a lidstock material containing a mixture of butene-1 and ethylene
copolymer, an ethylene homopolymer or copolymer, an inorganic
filler and optionally a propylene homopolymer or copolymer
laminated to a metal or polymer substrate. Stevenson in U.S. Pat.
No. 5,958,531 suggests a lidstock material containing a mixture of
ethylene-carboxylic acid copolymer, polybutylene and an inorganic
filler laminated to a metal or polymer substrate. Packaging Digest
describes a lidstock containing a type ethylene acid copolymer
which replaces adhesive-mounted versions having high peel strengths
making them somewhat difficult to wpen with an extrusion mounted
version.
[0005] U.S. Pat. Specification Nos. 4,665,130; 4,886,849; and
4,916,190 (Hwo, Hwo et al., and Hwo respectively) relate to use of
butene-1 polymers or coplymers with other mateials such as
propylene and polyethylene to provide film and sheet with
peelability and also moldable articles such as containers. Other
patents in this area include U.S. Pat. Specification Nos.
4,876,156; 5,066,543; and 5,106,917 (Hwo, Hwo and Lee et al.
respectively).
[0006] Lidstock materials suitable for covering openings in
packages for contact lenses and foods are known in the prior art.
However, there are still needs in this area. The prior art lidstock
materials generally suffer from one or more serious disadvantages
making them less than entirely suitable for their intended purpose,
including compatibility with an extensive class of substrate or
blister package sealing lids, for example compatibility with
polystyrene ("PS"), polypropylene ("PP"), polyethylene ("PE") and
with all three of polyvinyl chloride ("PVC"), polyethylene
terepthalate ("PET"), and polyvinylidene chloride ("PVDC").
[0007] Recently, biodegradable polyesters have been developed for
packaging, such as sandwich wrap, produce and meat trays, seedling
bags, lawn and garden bags, and hot/cold cups, and the like;
featuring aromatic-aliphatic copolyesters, as described in
"Biodegradable Polyesters: Packaging Goes Green" Plastics
Technology pp. 1-8, found at
http://www.plasticstechnologv.com/articles/200209 fa.3.html, Jun.
6, 2003 and "Next Generation of Biodegradable Plastic Introduced by
Eastman", Analytica & Chemie. DE News, p. 1 of 1, found at
http://www.chemie.de/cus-
tomers/analytica/news/details.php3?cmid=9487 & lang=en, Jun. 6,
2003. These polyester resins appear to be further described in U.S.
Pat. Specification Nos. 5,292,783; 5,446,079; and 6,342,304B1 (all
Buchanan et al.) for possible use as fibers, molded objects and
films. Also, Mueller, in U.S. Pat. Specification No. 6,503,549B1,
teaches polyethylene terephthalate (PET) tray typed packages with
lidding films directly sealable to the tray where the films include
glycol-modified polyethylene terephthalate sealant layers.
[0008] A principal objective of the present invention is to provide
a lidstock material for lids having excellent burst strength, good
cohesive peel properties, acceptable heat resistance and excellent
compatibility with all of PVC, PET and PVDC, as well as with PS, PP
and PE.
[0009] Additional objectives and advantages of the present
invention will become apparent from the following detailed
description of some preferred embodiments.
SUMMARY OF THE INVENTION
[0010] The above needs are solved and objects accomplished by
providing, in accordance with the present invention, a peelable and
heat sealable material suitable bonding to a wide variety of
substrates, comprising a solid substrate joined to a film
comprising aliphatic-aromatic copolyester, particulate inorganic
filler, butene-1 polymer, and ethylene-vinyl acetate copolymer. The
invention also consists essentially of and consists of such
components. The copolyester can include a biodegradable component.
The particle size of the filler is very important and ranges from
0.5 micrometer (micron) to 10.0 micrometer. Preferably the film
contains from about 25 wt. % to about 50 wt. % copolyester,
preferably a butene-1 homopolymer, and from about 15 wt. % to about
30 wt. % filler with the remainder containing at least 5 wt. % of
both butene-1 polymer and ethylene-vinyl acetate copolymer.
[0011] The substrate can be, for example, metal foil, plastic or
paper but the preferred substrate is aluminum foil. The preferred
range is from about 10 wt. % to about 30 wt. % of butene-1 polymer
and about 10 wt. % to about 30 wt. % ethylene-vinyl acetate
copolymer. The above composition/substrate provides excellent
bonding sealing and cohesive peeling to all of PVC, PET and PVDC as
well as more easily bondable packaging such as PS, PP and PE.
[0012] Plastic and metal substrates are easily bonded to films of
this material. These materials are particularly useful as a
"peelable" "heat sealable" "lidstock material" for containers.
[0013] As used herein, the term "lidstock material" refers to a
metal, polymer, or paper substrate laminated with a heat seal layer
or film. Lidstock material of the present invention is made into
container lids by cutting the material into desired shapes such as
circles or rectangles. As used herein, the term "heat sealable"
refers to the ability to form a bond between a plastic container
and its lid when heat and pressure are applied locally for a
sufficient time. The bond is gas-tight and preferably has
sufficient burst strength to resist separation of the lid from the
container body, even when the sealed container is retorted at an
elevated temperature.
[0014] As used herein, the term "peelable" refers to the ability of
a sealed lid to separate and to release from sealed engagement with
a container body while both the lid and the body substantially
retain their integrity. Such separation and release are achieved by
manually applying a separating force to an outer edge portion of
the lid.
[0015] The lidstock material of the invention preferably a
substrate laminated with a film comprising a polymer mixture of
this invention. The substrate can be an aluminum foil having a
thickness of about 0.25 mil to 3.0 mils (0.00025 inch to 0.003 inch
(6.35 to 76.2 micrometers). Aluminum foil provides an excellent
barrier against penetration of gases and moisture. Aluminum foil
also protects the package contents from ultraviolet light and has
an aesthetically pleasing appearance. A particularly preferred
aluminum foil substrate has a thickness of about 2 mils (0.002
inch-50.8 micrometers). Other preferred suitable materials for the
substrate include biaxially oriented polyethylene terephthalate
(PET), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC),
nylon, paper, and combinations thereof.
[0016] The substrate is preferably coated with a print primer. The
print primer facilitates application of printed labeling on the
substrate. A particularly preferred print primer has a coating
weight of about 0.4 to 0.9 pound per 3000 square feet (0.6-1.4
g./sq meter).
[0017] The peelable and heat sealable film has a total weight of
about 17 lb per 3000 square feet (27 g/sq meter). The filler
enhances peelablity of the coating by assisting the seal failure
upon peeling from adhesive failure at the container-coating layer
interface to cohesive failure in the coating layer itself. The
filler preferably is selected from at least one of talc, silica or
alumina and comprises at least about 15 wt. % of the coating,
preferably about 15 wt. % to 30 wt. %, more preferably about 20 wt.
% to 30 wt. %. The filler is preferably a powder having an average
particle size of about 0.5-10 micrometers (microns). Talc having an
average particle size of about 12 0.5 to 10 micrometers is
particularly preferred. The talc or other filler is preferably
provided with a surface coating comprising about 0.5 wt. % to about
5 wt. % of the filler, preferably about 1 wt. %. A carboxylic acid
surface coating is particularly preferred. The surface coating
contributes to talc dispersion and adhesion within the polymer. The
carboxylic acid in the surface coating may be a mono or
dicarboxylic acid or a mixture of such acids. Some preferred acids
include stearic acid and isostearic acid, which is a liquid mixture
of mostly C.sub.1-8 saturated fatty acids having the general
formula C.sub.17H.sub.35COOH. Other saturated C.sub.10-C.sub.20
carboxylic acids or mixtures thereof may also be useful.
[0018] A particularly preferred butene-1 polymer is sold by Basell
Polyolefins under the Trademane "PB 1710 M" and has a density of
0.908; a melt flow rate of 1.0 min by ASTM D 1238; and a melting
point of 241.degree. F. (116.degree. C.).
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a top plan view of one embodiment of a container,
here a blister pack, which might be made with the present
invention;
[0020] FIG. 2 is a side elevational view of the blister pack of
FIG. 1 with the lid partially peeled back;
[0021] FIG. 3 is an enlarged fragmentary, cross-sectional view of
the lid of the blister pack shown in FIG. 2, and
[0022] FIG. 4 is a perspective view of a food container which might
be made with the present invention; and
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0023] In FIGS. 1 and 2 there is shown one type of many varieties
of containers that are useful with the lidstock material of this
invention; a blister pack 10 made in accordance with the present
invention, with a lid 12 partially peeled back to reveal its
contents. While the present invention will be described with a
blister pack this is in no way to be taken as limiting. The pack 10
comprises an injection molded plastic container body 14 heat sealed
to the lid 12. The body 14 defines a bowl-shaped recess 16 having a
diameter of about 2 cm. and a depth of about 0.5 cm. A flange 18
extending around the recess 16 includes a tapered curled lip 20
spaced apart from the recess 16.
[0024] The recess 16 here houses a contact lens 22 and a saline
solution 24. The recess 16 is circumscribed by a seal area 26 which
is part of the flange 18. The lid 12 is preferably attached to the
body 14 by heat sealing in the seal area 26. Other suitable means
for attaching the lid 12 to the body 14 include induction sealing
and sonic welding. The total interior volume defined by the recess
16 and the lid 12 is preferably less than 1 milliliter. The body 14
is preferably made from a plastic material which can be shaped by
injection molding or thermoforming. The plastic material for the
body is preferably polypropylene but may also be other plastic
materials having similar properties, such as polyethylene,
polyethylene-polypropylene mixtures, polyethylene-polypropylene
copolymers, polybutylene, polyesters (e.g. PET), polycarbonates,
and other thermoplastics. Plastics having low vapor transmission
rates are most preferred. Plastics such as PVC, PET and PVDC are
also bondable with the lidstock material of this invention.
[0025] Referring now to FIG. 3, the lid 12 is made from lidstock
material comprising substrate 30, preferably aluminum foil, having
a polyurethane adhesive layer 31 joining a film 32 to the substrate
30. An exterior side of the substrate 30 displays graphic matter
(not shown) printed over a print primer 33. The substrate 30 has a
thickness of about 2 mils. (0.002 inch-50.8 micrometers). The print
primer 33 has a weight of about 0.4 to 0.9 pounds per 3000 square
feet. The film 32 has a thickness of about 25 micrometers (1 mil.),
corresponding to a weight of about 17 pounds per 3000 square feet.
The lid 12 includes only a single layer of the film 32.
[0026] FIG. 4 shows another type container that might use the
lidstock material of this invention. The container 40 has a cavity
42 within the body for containing food such as prepared cake,
frosting, pudding, yogurt, cream cheese, or apple sauce, juice,
coffee and the like with a lip/flange 44 extending radially outware
from the body 46 and a lid 12 made from lidstock material having
the same configuration as FIG. 3.
[0027] The preferred blister pack 10 shown in FIGS. 1 to 3 has a
lid 12 heat sealed to an injection molded polypropylene body 14.
The film 32 on the lid 12 may have the compositions as follows:
1 Film Composition Component Range wt. % Preferred Range wt. %
Aliphatic-Aromatic Copolyester 25 to 50 20 to 40 Particulate
Inorganic Filler 15 to 30 20 to 30 Butene-1 polymer >5 10 to 30
Ethylene-Vinyl Acetate >5 10 to 30 Copolymer
[0028] Preferably, the copolyester is a mixture of
aliphatic-aromatic copolyester and a biodegradable component
selected from the group consisting of cellulose, cellulose
monoacetate, starch and mixtures thereof making up from 0.5 wt. %
to 10 wt. %, based on the weight of the copolyester. The preferred
range of copolyester is from about 20 wt. % to 40 wt. %.
[0029] Preferably the inorganic filler is selected from the group
consisting of talc, silica, alumina, alumina trihydrate, and
mixtures thereof.
[0030] Having described the presently preferred embodiments, it is
to be understood that the invention may be otherwise embodied
within the scope of the appended claims.
* * * * *
References