U.S. patent application number 17/231844 was filed with the patent office on 2021-07-29 for heat shrinkable film and method for reproducing polyester container using same.
The applicant listed for this patent is SKC CO., LTD., SKC INC.. Invention is credited to Eugene JUNG, Yongdeuk KIM, Jung Kyu LEE, Daeyong SHIN, Jaehyong SON.
Application Number | 20210230392 17/231844 |
Document ID | / |
Family ID | 1000005520242 |
Filed Date | 2021-07-29 |
United States Patent
Application |
20210230392 |
Kind Code |
A1 |
SHIN; Daeyong ; et
al. |
July 29, 2021 |
HEAT SHRINKABLE FILM AND METHOD FOR REPRODUCING POLYESTER CONTAINER
USING SAME
Abstract
Embodiments relate to a heat shrinkable film and a process for
regenerating a polyester container using the same. The heat
shrinkable film comprises a copolymerized polyester resin
comprising a diol component and a dicarboxylic acid component and
has a heat shrinkage rate of 30% or more in the main shrinkage
direction upon thermal treatment at a temperature of 80.degree. C.
for 10 seconds and a melting point of 190.degree. C. or higher as
measured by differential scanning calorimetry. It not only solves
the environmental problems by improving the recyclability of the
polyester container, but also is capable of enhancing the yield and
productivity.
Inventors: |
SHIN; Daeyong; (Sugar Hill,
GA) ; KIM; Yongdeuk; (Jeollanam-do, KR) ; LEE;
Jung Kyu; (Seoul, KR) ; SON; Jaehyong;
(Snellville, GA) ; JUNG; Eugene; (Lawrenceville,
GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SKC INC.
SKC CO., LTD. |
Covington
Gyeonggi-do |
GA |
US
KR |
|
|
Family ID: |
1000005520242 |
Appl. No.: |
17/231844 |
Filed: |
April 15, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
16687357 |
Nov 18, 2019 |
11008434 |
|
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17231844 |
|
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|
16355483 |
Mar 15, 2019 |
10800897 |
|
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16687357 |
|
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|
|
62664543 |
Apr 30, 2018 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08J 2367/02 20130101;
B29C 61/02 20130101; B29B 17/04 20130101; C08G 63/183 20130101;
B29B 9/04 20130101; C08J 11/12 20130101; B29L 2009/00 20130101;
C08J 5/18 20130101; C08J 2367/03 20130101; C08G 63/672 20130101;
C08G 2390/00 20130101 |
International
Class: |
C08J 11/12 20060101
C08J011/12; C08J 5/18 20060101 C08J005/18; C08G 63/183 20060101
C08G063/183; C08G 63/672 20060101 C08G063/672; B29B 9/04 20060101
B29B009/04; B29B 17/04 20060101 B29B017/04; B29C 61/02 20060101
B29C061/02 |
Claims
1. A container comprising: a polyester container, and a heat
shrinkable film, which is provided at the polyester container;
wherein the heat shrinkable film is shrunk by steam or hot air to
wrap the outer surface of the polyester container, wherein the heat
shrinkable film comprises a copolymerized polyester resin
comprising a diol component and a dicarboxylic acid component and
has a heat shrinkage rate of 30% or more in the main shrinkage
direction upon thermal treatment at a temperature of 80.degree. C.
for 10 seconds and a melting point of 190.degree. C. or higher as
measured by differential scanning calorimetry, wherein when a
plurality of flakes are thermally treated at a temperature of
200.degree. C. to 220.degree. C. for 60 minutes to 120 minutes, the
clumping fraction is 5% or less, wherein the flakes are formed by
crushing the polyester container and the heat shrinkable film.
2. The container of claim 1, wherein the crystallization
temperature of the resin is not measured or is 70.degree. C. to
95.degree. C. by differential scanning calorimetry.
3. The container of claim 1, wherein the diol component is at least
one selected from the group consisting of ethylene glycol,
diethylene glycol, neopentyl glycol, and cyclohexanedimethanol.
4. The container of claim 1, wherein the copolymerized polyester
resin comprises neopentyl glycol in an amount of 5 to 35% by mole
based on the total number of moles of the diol component.
5. The container of claim 1, wherein the copolymerized polyester
resin comprises ethylene glycol in an amount of 55 to 93% by mole
based on the total number of moles of the diol component.
6. The container of claim 1, which has a heat shrinkage rate of 5%
to 55% in the main shrinkage direction upon thermal treatment at a
temperature of 70.degree. C. for 10 seconds, wherein the rate of
increase in the heat shrinkage rate in the main shrinkage direction
in the temperature range of 0.35.times.Tm.degree. C. to
0.40.times.Tm.degree. C. is 2.5%/.degree. C. to 4.0%/.degree. C.,
and the rate of increase in the heat shrinkage rate in the main
shrinkage direction in the temperature range of
0.45.times.Tm.degree. C. to 0.50.times.Tm.degree. C. is
0.1%/.degree. C. to 1.0%/.degree. C.
7. A container comprising: a polyester container, and a heat
shrinkable film, which is provided at the polyester container;
wherein the heat shrinkable film is shrunk by steam or hot air to
wrap the outer surface of the polyester container, wherein the heat
shrinkable film comprises a copolymerized polyester resin
comprising a diol component and a dicarboxylic acid component and
has a heat shrinkage rate of 30% or more in the main shrinkage
direction upon thermal treatment at a temperature of 80.degree. C.
for 10 seconds and wherein the crystallization temperature of the
heat shrinkable film is not measured or is 70.degree. C. to
95.degree. C. by differential scanning calorimetry, wherein when a
plurality of flakes are thermally treated at a temperature of
200.degree. C. to 220.degree. C. for 60 minutes to 120 minutes, the
clumping fraction is 5% or less, wherein the flakes are formed by
crushing the polyester container and the heat shrinkable film.
8. The container of claim 7, wherein the heat of crystallization of
the heat shrinkable film at the crystallization temperature is not
measured or is 0.01 to 50 J/g.
9. The container of claim 7, which has a heat shrinkage rate of 5%
to 55% in the main shrinkage direction upon thermal treatment at a
temperature of 70.degree. C. for 10 seconds, wherein the rate of
increase in the heat shrinkage rate in the main shrinkage direction
in the temperature range of 0.85.times.Tc.degree. C. to
1.00.times.Tc.degree. C. is 2.5%/.degree. C. to 4.0%/.degree. C.,
and the rate of increase in the heat shrinkage rate in the main
shrinkage direction in the temperature range of
1.12.times.Tc.degree. C. to 1.27.times.Tc.degree. C. is
0.11%/.degree. C. to 1.0%/.degree. C.
10. A process for regenerating the container according to claim 1;
crushing the polyester container provided with the heat shrinkable
film to obtain the flakes; and thermally treating the flakes to
produce regenerated polyester chips, wherein the flakes comprise
first flakes obtained by crushing the container and second flakes
obtained by crushing the heat shrinkable film.
11. The process for regenerating a polyester container of claim 10,
wherein the flakes are thermally treated at a temperature of
200.degree. C. to 220.degree. C. for 60 minutes to 120 minutes, and
the clumping fraction is 5% or less.
12. A process for regenerating the container according to claim 7;
crushing the container provided with the heat shrinkable film to
obtain the flakes; and thermally treating the flakes to produce
regenerated polyester chips, wherein the flakes comprise first
flakes obtained by crushing the container and second flakes
obtained by crushing the heat shrinkable film.
13. The process for regenerating a polyester container of claim 12,
wherein the flakes are thermally treated at a temperature of
200.degree. C. to 220.degree. C. for 60 minutes to 120 minutes, and
the clumping fraction is 5% or less.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/687,357 filed on Nov. 18, 2019, which is a
division of U.S. patent application Ser. No. 16/355,483 filed on
Mar. 15, 2019 and issued as U.S. Pat. No. 10,800,897 on Oct. 13,
2020, which claims the benefit of U.S. Patent Application Ser. No.
62/664,543 filed on Apr. 30, 2018. The disclosure of each of the
foregoing application is incorporated herein by reference in its
entirety.
TECHNICAL FIELD
[0002] Embodiments relate to a heat shrinkable film and a process
for regenerating a polyester container using same, which not only
solve the environmental problems by improving the recyclability of
the polyester container, but also are capable of enhancing the
yield and productivity.
BACKGROUND ART OF THE INVENTION
[0003] As concerns about environmental problems have increased in
recent years, there is a demand for addressing the recycling issues
of products fabricated using thermoplastic polymers. In particular,
polyethylene terephthalate, a thermoplastic resin having excellent
properties in terms of thermal resistivity, processability,
transparency, and non-toxicity, has been widely used for producing
a wide range of products such as films, fibers, bottles,
containers, and the like, and efforts have been made to improve the
regeneration rate thereof.
[0004] In general, a polyolefin stretch film or the like is
attached to a container produced from polyethylene terephthalate.
Thus, once a container recycled from the consumers is washed and
crushed, it is then subjected to liquid specific gravity
separation, dehydration, drying, and/or wind specific gravity
separation in order to remove a large amount of films contained in
the crushed product and then to such an additional step as
pelletization to obtain regenerated chips. However, there has been
a disadvantage in that the regenerated chips are colored or clumped
during the thermal treatment of the regenerated chips due to the
inks and the films that have not been removed even after the above
steps. Thus, in order to increase the regeneration rate of
containers, it is important to prevent inks and films from being
adulterated in the regenerated chips.
[0005] Accordingly, a method of using a film made of a low specific
gravity polymer such as polystyrene, polyethylene, polypropylene,
and the like has been proposed in order to readily carry out the
specific gravity separation. However, the low specific gravity
thereof cannot be effectively achieved due to the influence of the
ink layer, which makes it difficult to completely separate the
film, and the problem that the residual ink colors the regenerated
chips cannot be solved.
DISCLOSURE OF THE INVENTION
Technical Problem to be Solved
[0006] Accordingly, embodiments aim to provide a heat shrinkable
film capable of effectively separating inks and films during a
regeneration process, thereby improving the recyclability of a
polyester container, and a process for regenerating a polyester
container using the same.
Solution to the Problem
[0007] According to an embodiment, there is provided a heat
shrinkable film, which comprises a copolymerized polyester resin
comprising a diol component and a dicarboxylic acid component and
has a heat shrinkage rate of 30% or more in the main shrinkage
direction upon thermal treatment at a temperature of 80.degree. C.
for 10 seconds and a melting point of 190.degree. C. or higher as
measured by differential scanning calorimetry.
[0008] According to an embodiment, there is provided a heat
shrinkable film, which comprises a copolymerized polyester resin
comprising a diol component and a dicarboxylic acid component and
has a heat shrinkage rate of 30% or more in the main shrinkage
direction upon thermal treatment at a temperature of 80.degree. C.
for 10 seconds, wherein the crystallization temperature of the
resin is not measured or is 70.degree. C. to 95.degree. C. by
differential scanning calorimetry.
[0009] According to an embodiment, there is provided a process for
regenerating a polyester container, which comprises preparing the
polyester container provided with the heat shrinkable film;
crushing the container provided with the heat shrinkable film to
obtain flakes; and thermally treating the flakes to produce
regenerated polyester chips, wherein the flakes comprise first
flakes obtained by crushing the container and second flakes
obtained by crushing the heat shrinkable film.
Advantageous Effects of the Invention
[0010] The heat shrinkable film according to an embodiment improves
the recyclability of a polyester container, thereby solving the
environmental problems and enhancing the yield and
productivity.
[0011] In addition, the process for regenerating a polyester
container according to an embodiment does not require a separate
step of separating the polyester container and a film, thereby
saving time and cost.
BRIEF DESCRIPTION OF THE DRAWING
[0012] FIG. 1 schematically depicts a process for regenerating a
polyester container according to an embodiment.
[0013] FIG. 2 shows the heat shrinkage rates of the heat shrinkable
films of Examples 1 to 4 and Comparative Example 1.
[0014] FIG. 3 shows the results of DSC (differential scanning
calorimeter) measurement of the heat shrinkable film of Example
1.
[0015] FIG. 4 shows the results of DSC measurement of the heat
shrinkable film of Example 2.
[0016] FIG. 5 shows the results of DSC measurement of the heat
shrinkable film of Example 3.
[0017] FIG. 6 shows the results of DSC measurement of the heat
shrinkable film of Example 4.
[0018] FIG. 7 shows the results of DSC measurement of the heat
shrinkable film of Comparative Example 1.
DETAILED DESCRIPTION FOR CARRYING OUT THE INVENTION
[0019] Hereinafter, the present invention will be described in
detail with reference to embodiments. The embodiments are not
limited to those described below. Rather, they can be modified into
various forms as long as the gist of the invention is not
altered.
[0020] Throughout the present specification, when a part is
referred to as "comprising" an element, it is understood that other
elements may be comprised, rather than other elements are excluded,
unless specifically stated otherwise.
[0021] All numbers and expressions relating to quantities of
components, reaction conditions, and the like used herein are to be
understood as being modified by the term "about" unless
specifically stated otherwise.
[0022] Heat Shrinkable Film
[0023] According to an embodiment, there is provided a heat
shrinkable film, which comprises a copolymerized polyester resin
comprising a diol component and a dicarboxylic acid component and
has a heat shrinkage rate of 30% or more in the main shrinkage
direction upon thermal treatment at a temperature of 80.degree. C.
for 10 seconds and a melting point of 190.degree. C. or higher as
measured by differential scanning calorimetry.
[0024] According to an embodiment, there is provided a heat
shrinkable film, which comprises a copolymerized polyester resin
comprising a diol component and a dicarboxylic acid component and
has a heat shrinkage rate of 30% or more in the main shrinkage
direction upon thermal treatment at a temperature of 80.degree. C.
for 10 seconds, wherein the crystallization temperature of the
resin is not measured or is 70.degree. C. to 95.degree. C. by
differential scanning calorimetry.
[0025] According to an embodiment, the copolymerized polyester
resin comprises a diol component and a dicarboxylic acid
component.
[0026] The diol component is composed of a linear or branched
C.sub.2 to C.sub.10 diol. That is, the diol component does not
comprise an alicyclic diol or an aromatic diol. For example, the
linear or branched C.sub.2 to C.sub.10 diol may comprise a
derivative of ethylene glycol, diethylene glycol, neopentyl glycol,
1,3-propanediol, 1,2-octanediol, 1,3-octanediol, 2,3-butanediol,
1,3-butanediol, 1,4-butanediol, 1,5-pentanediol,
2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,5-pentanediol,
2,4-diethyl-1,5-pentanediol, 3-methyl-1,5-pentanediol,
1,1-dimethyl-1,5-pentanediol, 1,6-hexanediol,
2-ethyl-3-methyl-1,5-hexanediol, 2-ethyl-3-ethyl-1,5-hexanediol,
1,7-heptanediol, 2-ethyl-3-methyl-1,5-heptanediol,
2-ethyl-3-ethyl-1,6-heptanediol, 1,8-octanediol, 1,9-nonanediol,
1,10-decanediol, or a combination thereof. But it is not limited
thereto.
[0027] According to an embodiment, the diol component may comprise
at least one selected from the group consisting of ethylene glycol,
diethylene glycol, cyclohexanedimethanol (CHDM), propanediol
unsubstituted or substituted with an alkyl group, butanediol
unsubstituted or substituted with an alkyl group, pentanediol
unsubstituted or substituted with an alkyl group, hexanediol
unsubstituted or substituted with an alkyl group, octanediol
unsubstituted or substituted with an alkyl group, and a combination
thereof.
[0028] According to an embodiment, the diol component may comprise
ethylene glycol, diethylene glycol, 1,4-cyclohexanedimethanol,
1,3-propanediol, 1,2-octanediol, 1,3-octanediol, 2,3-butanediol,
1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol,
2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,5-pentanediol,
2,4-diethyl-1,5-pentanediol, 3-methyl-1,5-pentanediol,
1,1-dimethyl-1,5-pentanediol, or a combination thereof.
[0029] According to an embodiment, the diol component may be at
least one selected from the group consisting of ethylene glycol,
diethylene glycol, neopentyl glycol, and cyclohexanedimethanol.
[0030] The dicarboxylic acid component may be selected from the
group consisting of an aromatic dicarboxylic acid such as
terephthalic acid, dimethylterephthalic acid, isophthalic acid,
naphthalene dicarboxylic acid, orthophthalic acid, and the like; an
aliphatic dicarboxylic acid such as adipic acid, azelaic acid,
sebacic acid, decanedicarboxylic acid, and the like; an alicyclic
dicarboxylic acid; an ester thereof; and a combination thereof.
Specifically, the dicarboxylic acid component may be composed of
terephthalic acid, dimethyl terephthalic acid, isophthalic acid,
naphthalene dicarboxylic acid, orthophthalic acid, or a combination
thereof.
[0031] According to an embodiment, the dicarboxylic acid component
may comprise an aromatic dicarboxylic acid. For example, the
dicarboxylic acid component may comprise at least 80% by mole, at
least 90% by mole, or at least 95% by mole of terephthalic acid,
based on the total number of moles of the dicarboxylic acid
component.
[0032] According to an embodiment, the copolymerized polyester
resin may comprise neopentyl glycol in an amount of 5 to 35% by
mole based on the total number of moles of the diol component. For
example, the copolymerized polyester resin may comprise neopentyl
glycol in an amount of 5 to 30% by mole, 7 to 30% by mole, 10 to
25% by mole, or 10 to 20% by mole, based on the total number of
moles of the diol component. If the above range is satisfied, a
heat shrinkable film having a heat shrinkage rate in the direction
perpendicular to the main shrinkage direction that is not high even
at a high temperature can be prepared. In particular, if the
content of neopentyl glycol exceeds the above range, the film may
excessively expand in the direction perpendicular to the main
shrinkage direction, so that wrinkles or deformation may occur when
the film is applied to a container. In addition, if the content of
neopentyl glycol is less than the above range, the amorphous region
is unnecessarily large, whereby the expansion coefficient would be
increased due to low shrinkage characteristics in the direction
perpendicular to the main shrinkage direction although the
shrinkage characteristics in the main shrinkage direction could be
improved.
[0033] According to an embodiment, the copolymerized polyester
resin may comprise ethylene glycol in an amount of 55 to 93% by
mole based on the total number of moles of the diol component. For
example, the copolymerized polyester resin may comprise ethylene
glycol in an amount of 60 to 90% by mole, 70 to 90% by mole, or 75
to 85% by mole, based on the total number of moles of the diol
component. If the above range is satisfied, the heat shrinkage rate
can be enhanced, and the clumping fraction can be reduced.
[0034] According to an embodiment, the copolymerized polyester
resin may comprise diethylene glycol in an amount of 0 to 20% by
mole based on the total number of moles of the diol component. For
example, the copolymerized polyester resin may comprise diethylene
glycol in an amount of 0 to 15% by mole, 1 to 13% by mole, 1 to 10%
by mole, or 2 to 10% by mole, based on the total number of moles of
the diol component. If the above range is satisfied, the heat
shrinkage rate can be enhanced, and the clumping fraction can be
reduced.
[0035] According to an embodiment, the copolymerized polyester
resin may comprise cyclohexanedimethanol in an amount of 0 to 30%
by mole based on the total number of moles of the diol component.
For example, the copolymerized polyester resin may comprise
cyclohexanedimethanol in an amount of 10 to 30% by mole, 20 to 30%
by mole, or 22 to 30% by mole, based on the total number of moles
of the diol component.
[0036] According to an embodiment, the polyester resin comprises a
dicarboxylic acid component and a diol component, wherein the
dicarboxylic acid component may be composed of terephthalic acid,
and the diol component may be composed of (i) neopentyl glycol and
(ii) ethylene glycol, diethylene glycol, or a combination thereof.
Specifically, the dicarboxylic acid component may be composed of
terephthalic acid, and the diol component may be composed of (i)
neopentyl glycol and (ii) ethylene glycol. Alternatively, the
dicarboxylic acid component may be composed of terephthalic acid,
and the diol component may be composed of neopentyl glycol.
[0037] If the dicarboxylic acid component in the polyester resin is
composed of a terephthalic acid and if the diol component therein
is composed of (i) neopentyl glycol and (ii) ethylene glycol,
diethylene glycol, or a combination thereof, the polyester resin
may have a reduced whitening phenomenon and a low haze of 15% or
less and is excellent in dimensional stability.
[0038] The diol component may further comprise a monohydric
alcohol. For example, it may further comprise isopropyl alcohol.
Specifically, the copolymerized polyester resin may comprise a
monohydric alcohol in an amount of 15 to 30% by mole, 18 to 25% by
mole, or 20 to 25% by mole, based on the total number of moles of
the diol component. But it is not limited thereto.
[0039] The dicarboxylic acid and the diol as described above are
subjected to a transesterification reaction and then polymerization
to thereby form a copolymerized polyester resin. Specifically, at
least one catalyst selected from manganese acetate, calcium
acetate, and zinc acetate may be used as a catalyst for the
transesterification reaction. The content of the catalyst may be
0.02 to 0.2% by weight based on the total weight of the
dicarboxylic acid compound. Upon completion of the
transesterification reaction, at least one additive selected from
silica, potassium, and magnesium; a stabilizer such as trimethyl
phosphate; a polymerization catalyst selected from antimony
trioxide and tetrabutylene titanate; and the like may be
selectively added to carry out the reaction, to thereby prepare a
copolymerized polyester resin composition.
[0040] According to an embodiment, the heat shrinkable film has a
heat shrinkage rate of 30% or more in the main shrinkage direction
upon thermal treatment at a temperature of 80.degree. C. for 10
seconds. For example, the heat shrinkable film may have a heat
shrinkage rate of 40% or more, 45% or more, 50% or more, 30% to
85%, 40% to 80%, or 50% to 80%, in the main shrinkage direction
upon thermal treatment at a temperature of 80.degree. C. for 10
seconds Specifically, if the above range is satisfied, it is easy
to attach and label the heat shrinkable film on the surface of a
container.
[0041] According to an embodiment, the heat shrinkable film has a
melting point of 190.degree. C. or higher as measured by
differential scanning calorimetry. For example, the heat shrinkable
film may have a melting point of 185.degree. C. or higher,
180.degree. C. or higher, 175.degree. C. or higher, as measured by
differential scanning calorimetry. Specifically, if the above range
is satisfied, the clumping fraction can be effectively reduced in
the subsequent process.
[0042] According to an embodiment, the crystallization temperature
of the heat shrinkable film is not measured or is 70.degree. C. to
95.degree. C. by differential scanning calorimetry. For example,
the crystallization temperature of the heat shrinkable film may be
70.degree. C. to 93.degree. C., 75.degree. C. to 93.degree. C., or
75.degree. C. to 90.degree. C. by differential scanning
calorimetry. In such event, the clumping fraction can be
effectively reduced in the subsequent process.
[0043] According to an embodiment, the heat of crystallization of
the heat shrinkable film may not be measured or may be 0.01 to 50
J/g by differential scanning calorimetry. For example, the heat of
crystallization of the heat shrinkable film may be 0.01 to 40 J/g,
0.05 to 30 J/g, 0.1 to 20 J/g, 0.1 to 10 J/g, 0.1 to 8 J/g, or 0.1
to 5 J/g by differential scanning calorimetry. In such event, the
clumping fraction can be effectively reduced in the subsequent
process.
[0044] Specifically, if the melting point of the heat shrinkable
film is 190.degree. C. or higher and if the crystallization
temperature and the heat of crystallization are not measured by
differential scanning calorimeter, the effect of reducing the
clumping fraction may be the most excellent.
[0045] According to an embodiment, the heat shrinkable film may
have a haze of 10% or less. For example, the heat shrinkable film
may have a haze of 8% or less, 7% or less, or 5% or less.
[0046] According to an embodiment, the heat shrinkable film may
have a thickness of 30 to 100 .mu.m. For example, the heat
shrinkable film may have a thickness of 30 to 95 .mu.m or 35 to 90
.mu.m. If the above range is satisfied, the shrinkage uniformity is
excellent.
[0047] Process for Preparing a Heat Shrinkable Film
[0048] A heat shrinkable film may be prepared from the
copolymerized polyester resin composition.
[0049] Specifically, the copolymerized polyester resin composition
is melt-extruded at 260.degree. C. to 300.degree. C. or 270.degree.
C. to 290.degree. C. through a T-die and then cooled to obtain an
unstretched sheet. The unstretched sheet is passed through rolls
while it is conveyed at a speed of 10 m/min to 110 m/min or 50
m/min to 90 m/min, preheated, and then the stretched to obtain a
stretched sheet, which is thermally treated to prepare a heat
shrinkable film.
[0050] The preheating may be carried out at 90.degree. C. to
120.degree. C. for 0.01 to 1 minute. For example, the preheating
temperature (T1) may be 95.degree. C. to 115.degree. C. or
97.degree. C. to 113.degree. C., and the preheating time may be
0.05 to 0.5 minute or 0.08 to 0.2 minute. But it is not limited
thereto.
[0051] The stretching may be carried out at a temperature lower
than the preheating temperature (T1) by at least 20.degree. C. in a
first direction or in a second direction perpendicular to the first
direction by 3 to 5 times. For example, the stretching may be
carried out at a stretching temperature of 60.degree. C. to
90.degree. C., 70.degree. C. to 90.degree. C., or 80.degree. C. to
90.degree. C., in a first direction or in a second direction
perpendicular to the first direction by 3 to 4.5 times, 3.5 to 4.5
times, or 4 to 4.5 times. But it is not limited thereto.
[0052] In this specification, the first direction may be the
longitudinal direction, and the second direction may be the
transverse direction. Alternatively, the first direction may be the
transverse direction, and the second direction may be the
longitudinal direction.
[0053] The thermal treatment may be carried out at 70.degree. C. to
95.degree. C. for 0.01 to 1 minute. For example, the thermal
treatment temperature (T2) may be 70.degree. C. to 90.degree. C.,
70.degree. C. to 85.degree. C., or 70.degree. C. to 80.degree. C.,
and the thermal treatment time may be 0.05 to 0.5 minute or 0.08 to
0.2 minute. But it is not limited thereto.
[0054] According to an embodiment, the preheating temperature
(T1)-the thermal treatment temperature (T2) may be 10 to 40.degree.
C. For example, T1-T2 may be 13.degree. C. to 35.degree. C.,
11.degree. C. to 34.degree. C., 15.degree. C. to 34.degree. C., or
20.degree. C. to 34.degree. C. If the above range is satisfied, the
shrinkage rate in the main shrinkage direction and the heat
shrinkage rate in the direction perpendicular to the main shrinkage
direction may be effectively controlled.
[0055] Process for Regenerating a Polyester Container
[0056] According to an embodiment, there is provided a process for
regenerating a polyester container, which comprises preparing the
polyester container provided with the heat shrinkable film;
crushing the container provided with the heat shrinkable film to
obtain flakes; and thermally treating the flakes to produce
regenerated polyester chips, wherein the flakes comprise first
flakes obtained by crushing the container and second flakes
obtained by crushing the heat shrinkable film.
[0057] FIG. 1 schematically depicts a process for regenerating a
polyester container according to an embodiment. Specifically, FIG.
1 illustrates (1) preparing a polyester container provided with a
heat shrinkable film; (2) crushing the container provided with the
heat shrinkable film to obtain flakes; and (3) thermally treating
the flakes to produce regenerated polyester chips.
[0058] Step (1)
[0059] In step (1), a polyester container provided with a heat
shrinkable film is prepared. Specifically, in step (1), a waste
polyester container provided with a heat shrinkable film is
prepared.
[0060] The description on the heat shrinkable film is as described
above.
[0061] In the polyester container provided with the heat shrinkable
film, the heat shrinkable film may be provided on the outer surface
of the polyester container. Specifically, the outer surface of the
container is covered with the heat shrinkable film, and the heat
shrinkable film may be shrunk by steam or hot air to wrap the outer
surface of the container. In such event, the heat shrinkable film
may have an ink layer formed by a process such as printing before
the heat shrinkage.
[0062] According to an embodiment, the container may comprise at
least 90% by weight of the polyester resin based on the total
weight of the container. Specifically, the container may be a
container that comprises polyethylene terephthalate and may
comprise polyethylene terephthalate in an amount of 90% by weight
or more, 95% by weight or more, or 99% by weight or more, based on
the total weight of the container.
[0063] In general, recycled waste products are intermingled with
containers, metals, glass, and plastics. Once the waste products
are washed, polyester containers are classified. Then, the
container may be subject to a process in which the film covering
the container is mechanically torn or cut to be removed. In such
event, the quality of the regenerated polyester chips to be
produced may be deteriorated due to the residual film and the ink
layer formed on the residual film.
[0064] In contrast, it is possible to produce regenerated polyester
chips from a container provided with a heat shrinkable film
according to the embodiment even without an additional process of
removing a film Thus, time and cost are saved.
[0065] Step (2)
[0066] In step (2), the container provided with the heat shrinkable
film is crushed to obtain flakes. The polyester container
classified in the above step (1) comprises a heat shrinkable film,
which may be crushed to obtain flakes. In such event, the flakes
comprise first flakes obtained by crushing the container and second
flakes obtained by crushing the heat shrinkable film.
[0067] According to an embodiment, the particle size of the first
flakes may be 0.1 to 20 mm, and the particle size of the second
flakes may be 0.1 to 20 mm. For example, the particle size of the
first flakes may be 0.5 to 15 mm, 1 to 15 mm, or 2 to 10 mm, and
the particle size of the second flakes may be 0.5 to 15 mm, 1 to 15
mm, or 2 to 10 mm.
[0068] According to an embodiment, the flakes may be washed with a
0.5% to 3% aqueous solution of NaOH at 80.degree. C. to 97.degree.
C. for 5 minutes to 30 minutes. A part or all of the ink layer
remaining in the flakes may be removed by carrying out the
washing.
[0069] According to an embodiment, the flakes may be dried at
60.degree. C. to 175.degree. C. for 10 minutes to 30 minutes after
the washing step.
[0070] Step (3)
[0071] In step (3), the flakes are thermally treated to produce
regenerated polyester chips.
[0072] The thermal treatment may be carried out at 200.degree. C.
to 220.degree. C. for 60 minutes to 120 minutes. For example, it
may be carried out at 200.degree. C. to 215.degree. C. or
205.degree. C. to 220.degree. C. for 70 minutes to 120 minutes or
80 minutes to 120 minutes.
[0073] Regenerated polyester chips that comprise the flakes may be
obtained after the thermal treatment step. Specifically,
regenerated polyester chips that comprise the first flakes and the
second flakes may be obtained. For example, the flakes may be
melt-extruded and cut to obtain regenerated polyester chips.
[0074] Regenerated Polyester Chips
[0075] According to an embodiment, the regenerated polyester chips
may have an intrinsic viscosity (IV) of 0.60 dl/g or more. For
example, the regenerated polyester chips may have an intrinsic
viscosity (IV) of 0.63 dl/g or more, 0.65 dl/g or more, 0.70 dl/g
or more, 0.75 dl/g or more, 0.60 to 3.00 dl/g, 0.60 to 2.0 dl/g, or
0.65 to 1.0 dl/g.
[0076] According to an embodiment, when the flakes are thermally
treated at a temperature of 200.degree. C. to 220.degree. C. for 60
minutes to 120 minutes, the clumping fraction may be 5% or less.
For example, when the flakes are thermally treated at a temperature
of 200.degree. C. to 220.degree. C. for 60 minutes to 120 minutes,
the clumping fraction may be 3% or less, 2.5% or less, 2% or less,
or 1% or less. Specifically, the clumping fraction refers to the
fraction of aggregates based on the total weight of the flakes. For
example, the flakes may be passed through a sieve and thermally
treated. Then, the aggregates, which are entangled flakes, may be
passed through a sieve again to be separated. In such event, the
sieves used can be the same size. That is, the clumping fraction
can be measured as a percentage of the aggregate content based on
the thermally treated flakes.
[0077] In addition, the higher the value of the crumbling fraction
is, the more the first flakes and the second flakes are entangled
together to lower the quality of the regenerated chips. For
example, the size of the aggregates may be at least three times the
particle size of the flakes. The second flakes are obtained by
crushing the heat shrinkable film according to the embodiment,
thereby effectively reducing or preventing the clumping phenomenon
and enhancing the quality of the regenerated polyester chips.
[0078] According to an embodiment, the regenerated polyester chips
may comprise first flakes that comprise polyethylene terephthalate
and second flakes that comprise a copolymerized polyester
resin.
[0079] According to an embodiment, the regenerated polyester chips
may comprise 70 to 99% by weight of polyethylene terephthalate and
1 to 30% by weight of a copolymerized polyester resin based on the
total weight of the regenerated polyester chips. For example, the
regenerated polyester chips may comprise 80 to 99% by weight, 90 to
99% by weight, or 95 to 99% by weight of polyethylene terephthalate
and 1 to 28% by weight or 3 to 25% by weight of a copolymerized
polyester resin based on the total weight of the regenerated
polyester chips.
[0080] According to an embodiment, the copolymerized polyester
resin may comprise neopentyl glycol in an amount of 5 to 35% by
mole based on the total number of moles of the diol component and
terephthalic acid in an amount of at least 90% by mole based on the
total number of moles of the dicarboxylic acid component. For
example, the copolymerized polyester resin may comprise neopentyl
glycol in an amount of 5 to 30% by mole, 10 to 30% by mole, or 10
to 25% by mole, based on the total number of moles of the diol
component and terephthalic acid in an amount of at least 93% by
mole, at least 95% by mole, at least 98% by mole, or at least 99%
by mole, based on the total number of moles of the dicarboxylic
acid component.
[0081] According to an embodiment, the copolymerized polyester
resin may comprise ethylene glycol in an amount of 55 to 93% by
mole and diethylene glycol in an amount of 2 to 10% by mole based
on the total number of moles of the diol component. For example,
the copolymerized polyester resin may comprise ethylene glycol in
an amount of 60 to 90% by mole, 65 to 90% by mole, or 65 to 85% by
mole and diethylene glycol in an amount of 2 to 8% by mole or 3 to
8% by mole based on the total number of moles of the diol
component.
[0082] Hereinafter, the present invention will be described in more
detail with reference to the following examples. However, these
examples are set forth to illustrate the present invention, and the
scope of the present invention is not limited thereto.
EXAMPLE 1
[0083] <Preparation of a Copolymerized Polyester Resin
[0084] A stainless steel autoclave equipped with a stirrer, a
thermometer, and a partial reflux condenser was charged with 100%
by mole of dimethyl terephthalate (DMT), 80% by mole of ethylene
glycol (EG), 15% by mole of neopentyl glycol (NPG), and 5% by mole
of diethylene glycol (DEG). Then, 0.05% by mole (based on the acid
component) of zinc acetate as a transesterification catalyst was
added thereto. The transesterification reaction was carried out
while methanol was being distilled off Thereafter, 0.025% by mole
(based on the acid component) of antimony trioxide as a
polycondensation catalyst was added, and the polycondensation
reaction was carried out under a reduced pressure of 26.6 Pa (0.2
Torr) at 280.degree. C. to obtain a copolymerized polyester
resin.
[0085] <Preparation of a Heat Shrinkable Film>
[0086] The copolymerized polyester resin was fed to an extruder and
then melt-extruded at 280.degree. C. through a T-die. Thereafter,
it was wound around a rotating metal roll whose surface temperature
was cooled to 30.degree. C. to obtain an unstretched film having a
thickness of 204 .mu.m. Here, the take-up speed (rotation speed of
the metal roll) of the unstretched film was 54 m/min.
[0087] The unstretched film was continuously wound around a
plurality of rotating rolls heated to 60.degree. C. and preheated.
The longitudinally stretched film was stretched 5 times in the
transverse direction at 96.degree. C.
[0088] Thereafter, the film was annealed in the second direction
while it was heated to 81.degree. C. using an infrared heater to
obtain a heat shrinkable film having a thickness of 41 .mu.m.
[0089] <Preparation of a Container Provided with a Heat
Shrinkable Film>
[0090] The outer surface of a polyethylene terephthalate container
(PET container, 30 g) was wrapped with the heat shrinkable film (1
g) prepared above. The heat shrinkable film was shrunk in hot air
at a temperature of 90.degree. C. to obtain a container provided
with a heat shrinkable film
[0091] <Process for Regenerating a Container>
[0092] The container provided with the heat shrinkable film was
crushed with a crusher to obtain flakes. The flakes were washed
with water and then washed for 15 minutes with a corrosion washing
solution (a mixture of a solution of 0.3% by weight of Triton X-100
and a solution of 1.0% by weight of NaOH) stirred in a water bath
at 85.degree. C. to 90.degree. C. at 880 rpm.
[0093] Thereafter, the flakes were washed with water at room
temperature to remove the residual corrosion washing solution,
dried at 160.degree. C. for 20 minutes, and then thermally treated
at 210.degree. C. to produce regenerated polyester chips.
Examples 2 to 4 and Comparative Example 1
[0094] Regenerated polyester chips were prepared in the same manner
as in Example 1, except that the components, contents, and
heat-setting temperature were changed as shown in Table 1
below.
TABLE-US-00001 TABLE 1 Stretching Heat- temperature in setting DMT
EG NPG DEG CHDM the transverse temper- (% by (% by (% by (% by (%
by direction ature mole) mole) mole) mole) mole) (.degree. C.)
(.degree. C.) Ex. 1 100 80 15 5 -- 96 81 Ex. 2 100 70 25 5 -- 96 81
Ex. 3 100 70 25 5 -- 96 78 Ex. 4 100 70 25 5 -- 96 75 C. Ex. 1 100
70 -- 5 25 96 81 * CHDM: cyclohexanedimethanol
Evaluation Example 1: Evaluation of Heat Shrinkage Rates
[0095] The heat shrinkable films prepared above (300 mm.times.15
mm) were immersed in a water bath heated to 80.degree. C. and
90.degree. C. for 10 seconds, respectively. After water was removed
at room temperature, the heat shrinkage rate was calculated by the
following equation.
Heat shrinkage rate (%)=[(300-length of film sample upon thermal
treatment (mm)/300].times.100
Evaluation Example 2: Evaluation of Tg, Tc, Tm, and Heat of
Crystallization
[0096] The endotherm and exotherm of the heat shrinkable films (10
mg) prepared above were each measured with Differential Scanning
calorimetry-Mettler Toledo DSC 1 while the temperature was raised
at a rate of 10.degree. C./min from 30.degree. C. to 250.degree. C.
The first endothermic temperature was a glass transition
temperature (Tg), the exothermic temperature measured after the Tg
was a crystallization temperature (Tc), and the endothermic
temperature measured after the Tc was a melting point (Tm) in the
measurement result. The integral at Tc was calculated as the heat
of crystallization. The larger the value of the heat of
crystallization, the faster the crystallization rate and the higher
the transfer rate to a crystalline phase.
Evaluation Example 3: Evaluation of Clumping
[0097] The flakes prepared above were passed through a
0.625''-sieve. 1 kg of the flakes thus sieved was exposed in an
oven at 210.degree. C. for 90 minutes without pressure. They were
cooled to room temperature and passed through a 0.625''-sieve. The
weight of the aggregates thus filtered was measured and calculated
as a percentage of the total weight of the flakes.
Evaluation Example 4: Evaluation of Intrinsic Viscosity
[0098] The regenerated polyester chips prepared above were
dissolved in ortho-chlorophenol at 100.degree. C., and the
intrinsic viscosity (IV) was measured with an Ostwald viscometer at
35.degree. C. in a thermostatic bath by measuring the time for the
sample to drop.
[0099] The results of Evaluation Examples 1 to 4 are shown in Table
2 below.
TABLE-US-00002 TABLE 2 Heat Heat shrinkage shrinkage rate in the
rate in the Heat of Intrin- transverse transverse Tm crystalli-
Clump- sic direction direction Tc (.degree. C.) zation ing viscos-
(80.degree. C.) (90.degree. C.) (.degree. C.) (J/g) (%) (dl/g) ity
Ex. 1 58% 70% -- 199 -- 0.02 0.76 Ex. 2 65% 78% -- 171 -- 1.3 0.78
Ex. 3 62% 79% 90 171 0.3 0.5 0.79 Ex. 4 67% 79% 78 -- 1.2 0 0.76 C.
Ex. 1 68% 78% 82 166 0.1 9.7 0.76
[0100] As shown in Table 2, the heat shrinkable films prepared in
the Examples and the regenerated polyester chips prepared by the
process for regenerating a polyester container using the same had a
low clumping fraction and were excellent in all of the heat of
crystallization and intrinsic viscosity characteristics.
* * * * *