U.S. patent application number 14/005016 was filed with the patent office on 2014-01-02 for partially crystalized polyester containers.
The applicant listed for this patent is Eugenio Longo. Invention is credited to Eugenio Longo.
Application Number | 20140001074 14/005016 |
Document ID | / |
Family ID | 44650674 |
Filed Date | 2014-01-02 |
United States Patent
Application |
20140001074 |
Kind Code |
A1 |
Longo; Eugenio |
January 2, 2014 |
Partially Crystalized Polyester Containers
Abstract
A clear polyester container (1.0) comprising a base and upwardly
extending side walls terminating in a continuous flange projecting
from the side walls is described. Said multilayer container
comprises an inner layer (1.1) in amorphous phase and an outer
layer comprising a nucleating agent in the polymer composition in
order to be crystallized in at least one portion of the flange.
Inventors: |
Longo; Eugenio; (Rho,
IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Longo; Eugenio |
Rho |
|
IT |
|
|
Family ID: |
44650674 |
Appl. No.: |
14/005016 |
Filed: |
March 12, 2012 |
PCT Filed: |
March 12, 2012 |
PCT NO: |
PCT/EP12/54216 |
371 Date: |
September 13, 2013 |
Current U.S.
Class: |
206/524.2 ;
493/52 |
Current CPC
Class: |
B32B 2439/06 20130101;
B29C 51/002 20130101; B29K 2067/003 20130101; B65D 77/2024
20130101; B65D 85/72 20130101; B32B 27/36 20130101; B65D 2577/2025
20130101; B29C 51/14 20130101; B29C 51/04 20130101; B32B 2307/412
20130101; B32B 27/08 20130101 |
Class at
Publication: |
206/524.2 ;
493/52 |
International
Class: |
B65D 85/72 20060101
B65D085/72 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2011 |
EP |
11158187.2 |
Claims
1) A clear multilayer polyester container comprising a base and
upwardly extending side walls terminating in a continuous flange
projecting from the side walls, said multilayer container
comprising at least an inner layer of an amorphous polyester and a
bulk outer layer comprising a polyester in admixture with a
nucleating agent, said bulk outer layer being crystallized in at
least one portion of said flange.
2) The container according to claim 1 wherein said bulk outer layer
is continuously crystallized all along the flange.
3) The container according to claim 1 wherein the polyester is
selected among polyethylene terephthalate, polylactic acid, and
polyethylene terephthalate-glycol.
4) The container according to claim 3 wherein the polyester is
polyethylene terephthalate or polyethylene
terephthalate-glycol.
5) The container according to claim 1 having two or three layers of
polyester film.
6) The container according to claim 1 wherein the flange has a
thickness of from 100 .mu.m to 1000 .mu.m.
7) The container according to claim 1 wherein the percentage of
crystallization of the crystallized portion of the flange is equal
to or higher than about 10%.
8) The container according to claim 1 wherein the crystallization
of the flange is obtained by heating at least one portion of said
flange at a temperature of from 270.degree. C. to 300.degree. C.
for a time from 5 seconds to 10 seconds.
9) The container according to claim 1 wherein the nucleating agent
is selected among alkali metal salts of organic acids; lithium or
sodium salts of aliphatic, cycloaliphatic, aromatic carboxylic
acids or heterocyclic polycarboxylic acids, containing up to 20
carbon atoms; DBS-Dibenzylidene Sorbitol; trygliceride oil and
triglyceride oil in combination with organic acid metal salts or
chemically bonding to organic metal salts.
10) A package comprising a container according to claims 1,
including a product loaded into said container and a lid sealed
onto the flange of said container.
11) The package according to claim 10 wherein the container and the
lid are made of polyesters.
12) The package according to claim 10 wherein said lid is made of a
shrinkable film.
13) The package according to claim 10 having one or more films
covering it.
14) Use of a container according to claim 1 for tray lidding
applications.
15) A process for manufacturing a container, comprising the steps
of: a) providing a multilayer polyester sheet comprising an inner
amorphous polyester layer and a bulk outer layer comprising a
polyester in admixture with a nucleating agent; b) pre-heating said
multilayer polyester sheet at a temperature between 90 and 120
.degree. C.; and c) forming said pre-heated polyester sheet in a
mold suitable for inducing crystallization of the bulk outer layer
in at least one portion of the flange.
Description
[0001] The present invention relates to packages for products,
preferably food products, comprising in particular clear polyester
containers having a crystallized portion of the flange with good
sealability to a top web.
[0002] The resultant package has a neat, clear appearance which is
more attractive to the final consumer.
[0003] Commercially sold packages usually have a product support
member, i.e. a container or a tray, with a cavity formed therein to
accomodate the product and a flange around the perimeter of the
member to be lidded, and the tray and the lid are not made by the
same material causing recycling problems.
[0004] A generally known process to form a polyester tray includes
extruding a polyester sheet in amorphous phase and subsequently
crystallizing the whole tray by using a two stage mold, one hot for
crystallization and the other cold for cooling down the
article.
[0005] This kind of process results suitable to make mono-layer PET
trays able to withstand the shrink of a lid without giving
container distortion but the same process of crystallization makes
the tray opaque and significantly reduces the rate of production
due to thermoforming cycles.
STATE OF THE ART
[0006] U.S. Pat. No. 4,374,800 relates to a PAT (Polyalkylene
terephthalate) container including a body portion of at least 20%
of crystallinity, a flange having a crystallinity lower than that
of the body, adjoined to the body portion.
[0007] EP 0 605 081 relates to a food package, comprising a
crystalline opaque or colored tray thermoformed from a nucleated
PET sheet which remains rigid at elevated temperature, and a
transparent cover in an amorphous state connected to the tray.
[0008] GB 2 205 063 relates to a PET container having different
degrees of crystallization in different regions of the article to
ensure best functionality, the different degree of crystallization
of the tray is obtained using a special mold at different heating
region without using nucleating agents.
[0009] US 2007/0082151 relates to a polyester container with a
flange with a projecting portion, which exhibits low-temperature
heat sealability.
[0010] There is still the need of a clear polyester container with
a flange showing good sealability and with a sufficient mechanical
resistance to withstand the shrink force exerted by a shrinking
lid.
[0011] We have now found that a clear polyester container with a
good sealability on the flange and good mechanical properties can
be obtained by crystallizing only a portion of the flange. The
resultant container remains transparent while increasing the
rigidity of the flange which can withstand the shrink of the lid
and shows good sealability.
DESCRIPTION OF THE INVENTION
[0012] Therefore object of the present invention is a clear
multilayer polyester container comprising a base and upwardly
extending side walls terminating in a continuous flange projecting
from the side walls, said multilayer container comprising at least
an inner layer of an amorphous polyester and a bulk outer layer
comprising a polyester in admixture with a nucleating agent, said
bulk outer layer being crystallized in at least one portion of said
flange.
[0013] For the purpose of the present invention the term "inner
layer" means the layer of the container that will be in contact
with the content of the container or in alternative that part of
the container that comes in contact with the forming plug of the
mold; in FIG. 1 the "inner layer" is indicated by (1.1), the
crystallized portion of the flange and the bulk outer layer are
indicated by (1.2) and (1.3), respectively.
[0014] For the purpose of the present description and of the claims
which follow, except where otherwise indicated, all numbers
expressing amounts, quantities, percentages, and so forth, are to
be understood as being modified in all instances by the term
"about". Also, all ranges include any combination of the maximum
and minimum points disclosed and include any intermediate ranges
therein, which may or may not be specifically enumerated herein
[0015] A container according to the present invention wherein said
bulk outer layer is continuously crystallized all along the flange
is particularly preferred.
[0016] In a preferred embodiment of the present invention the
container is a double-layer or tri-layer container. In a
double-layer container, the inner layer is in the amorphous phase
and the crystallized portion of the flange is in the other outer
layer. In a tri-layer container, the inner layer is in the
amorphous phase and the crystallized portion of the flange is
preferably in the intermediate bulk layer. In a tri-layer container
according to the present invention the third outermost layer is
preferably amorphous, being the nucleating agent preferably in the
second layer. In the preferred embodiment only the portion of the
bulk outer layer of the flange is crystallized while the other
parts of the same, i.e. of the side walls and of the bottom part of
the container, remain in amorphous phase, i.e. with a crystallinity
percentage lower than 10%.
[0017] The polymers used in the present invention are clear
amorphous thermoplastic polymers that can be injection molded or
sheet extruded.
[0018] In particular the polymers used in the present application
are polyesters, such as, for example polyethylene terephthalate
(PET), polylactic acid (PLA), polyethylene terephthalate--glycol
(PETG).
[0019] In a preferred embodiment the polymer used in the present
invention is PET or PETG.
[0020] The inner layer remains amorphous during the crystallization
of the flange so it can easily seal to a top lid using conventional
sealing system, such as sealing bars. The bulk outer layer(s)
comprising the nucleating agent can be crystallized in the flange
part of the container, for example by using the mold showed in FIG.
2.
[0021] The nucleating agent used to promote crystallization is
contained in the bulk outer layer of the container and preferably
only the flange portion is crystallized.
[0022] Examples of nucleating agents which can be used in the
container according to the present application and nucleating agent
known in the art and commercially available, are: [0023] (i) alkali
metal salts of organic acids, e.g. carboxylic acid; sodium,
lithium, potassium benzoates (see D. Garcia, Heterogeneous
nucleation of PET, J. of Polymer Science--Polymer physics edition,
Vol 22, 2063-2072, 1984 and R. Legras, C. Bailly, M. Daumerie, V.
Zichy and others, Chemical nucleation, a new concept applied to
mechanism of action of organic acid salts on the crystallization of
PET and bisphenol-A-polycarbonate, Polymer, Vol 25, 835-844, 1984)
or sodium salts of substituted benzoic acids which contain at least
one nitro, halogen, hydroxyl, phenyl or oxyphenyl substituent, and
salts of alkali metals including phenolic, phosphonic, phosphinic
and sulfonic (see EP 0 021 648); [0024] (ii) lithium and/or sodium
salts of aliphatic, cycloaliphatic, aromatic carboxylic acids or
heterocyclic polycarboxilic acids, containing up to 20 carbon atoms
(see U.S. Pat. No. 3,761,450); [0025] (iii) DBS-dibenzylidene
sorbitol (see J. of Applied Polymer Science, Vol 36, 387-402,
1988); [0026] (iv) trygliceride oil and triglyceride oil in
combination with/or chemically bonding to organic acid metal salts
(see U.S. Pat. No. 5,356,972)
[0027] The nucleating agent preferably used in the present
invention is commercially available as Tna S471 by Sukano.RTM..
[0028] The amount of nucleating agent generally depends on the type
of polyester used. According to the conventional practice, the
nucleating agent is generally used in an amount of from 2% to 5%,
more preferably from 2.5% to 4%, even more preferably of 3%.
[0029] Preferably the nucleating agents have a particle size not
higher than 10 microns.
[0030] The containers object of the present invention can be
manufactured, for example, according to a process comprising the
following steps: [0031] a) providing a multilayer polyester sheet
comprising an inner amorphous polyester layer and a bulk outer
layer comprising a polyester in admixture with a nucleating agent;
[0032] b) pre-heating said multilayer polyester sheet at a
temperature between 90.degree. and 120 .degree. C. [0033] c)
forming said preheated polyester sheet in a mold suitable for
inducing crystallization of the bulk outer layer in at least one
portion of the flange.
[0034] The crystallization of the flange is therefore selectively
guaranteed by the heating provided on the flange using, for
instance, a mold similar to the mold showed in FIG. 2.
[0035] The heating can be provided using a mold at different
heating zones in order to crystallize only a portion of the flange
or preferably the entire flange. The percentage of crystallization
in the bulk outer layer outside the flange remains lower than the
percentage of crystallization of the flange or portions of the
flange.
[0036] The crystallization of flange may take place, preferably, in
a forming mold but also outside a mold.
[0037] The percentage of crystallization of the flange or portion
of the flange is equal to or higher than about 10%, preferably
higher than 12%, more preferably higher than 15%. The
crystallization of the flange takes place by heating the bulk outer
layer generally at a temperature of from 270.degree. C. to
300.degree. C., preferably at 275.degree. C. for a time comprised
between 5 seconds and 10 seconds, preferably between 6 seconds and
8 seconds. The heat transfer takes place by conduction, induction
or convection systems. The flange, after heating, can be cooled if
needed.
[0038] The flange has a thickness ranging from 100 .mu.m to 1000
.mu.m, preferably from 200 .mu.m to 700 .mu.m, more preferably from
300 .mu.m to 600 .mu.m.
[0039] Furthermore the container object of the present invention,
having the nucleating agent contained into the whole bulk outer
layer, can also be crystallized if needed, in other portions but
preferably only the flange is crystallized, thus providing the
optical and mechanical properties needed i.e. more rigidity of the
flange, transparency of the container and good sealability to the
top lid.
[0040] The container of the present invention with the crystallized
flange withstands the force imparted by the shrinking of lidding
films and resists to deformations . However the present container
is also suitable for tray lidding applications with non shrinkable
films.
[0041] The container according to the present invention can be
loaded with the product and then closed with a suitable top web by
using a lidding machine which is characterized by a sealing bar
operating at adequate temperature to get the seal. The temperature
of the sealing bar depends on the type of lidding film used and the
sealing operation can be carried out both under clean and
contaminated conditions.
[0042] The packages so obtained, further object of the present
invention, have a particularly good appearance. Moreover said
packages, having the container and the lid the same polymeric
composition, are really advantageous in the step of recycling.
Furthermore it is possible to manufacture them by using recycled
polyester.
EXAMPLES
[0043] A three-layer container (sample 1) in which the flange has a
total thickness of 520 .mu.m is formed using a mold as showed in
FIG. 2.
[0044] The inner layer is made of 100% PETG 6763 by Eastman
Chemical and has a thickness of 100 .mu.m.
[0045] The second layer is made of 97% PETG Ramapet 9921W by
Indorama and 3% of nucleating agent Tna S471 by Sukano.RTM. and has
a thickness of 320 .mu.m.
[0046] The third layer is made of 97% PETG Ramapet 9921W by
Indorama and 3% of nucleating agent Tna S471 by Sukano.RTM. and has
a thickness of 100 .mu.m.
[0047] Sample 1 is tested in order to evaluate the variability of
crystallinity and is tested after flange conditioning at different
temperatures for different times.
[0048] The areas of the flange were selected and submitted to the
thermal analysis that showed 12% of crystallinity, by conditioning
the sample at 275.degree. C. for 6 seconds.
[0049] The crystallinity of the flange is higher than the
crystallinity of the container which is 2.45%.
DESCRIPTION OF THE DRAWINGS
[0050] FIG. 1 represents a two layers container (1.0) according to
the present invention. The inner layer (1.1) is in the amorphous
phase while the bulk outer layer has two portions at different
degrees of crystallization: the area of the crystallized flange
(1.2) and the remaining area of the polyester in the amorphous
state (1.3).
[0051] FIG. 2 represents the forming process used to provide the
container according to the present invention.
[0052] The polyester film (2.1) is inserted into the female mold
which comprises the cooled part (2.3) and the heated part (2.2)
where the crystallization of the flange occurs.
[0053] The polyester film (2.1) adheres to the female mold due to
the vacuum applied (2.5), while the forming plug (2.4) pushes the
polyester film (2.1) in the female mold, providing the final
container.
* * * * *