Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2~0~37~j,
PHOTODEGRADATION AND HEAT-SEAL AGENTS
FOR POLYMERIC MATRIX MATERIALS
_
The photodegradability and/or heat-seal range
of polymeric matrix materials is controllably enhanced
by incorporating therein TiO2 and ethylene copolymers
which have pendent carbonyl groups along the copolymer
chain.
Photodegradation is the process whereby the
ultraviolet radiation in sunlight attacks the chemical
bonds in a chemical structure, such as plastics and
polymers, thereby breaking the structure into smaller
segments. This causes the structure to lose its
physical strength, especially its ability to flex or
stretch. The degradation proQess can continue the
embrittlement and produce smaller and smaller pieces.
The photodegradation tendency of ethylene
copolymers containing carbonyl groups (>C-O) is known
and it is also known that the blending of such
copolymers with other resins can cause the other resins
to have a greater tendency to degrade by the effects of
sunlight. A copolymer prepared by polymerizing ethylene
with carbon monoxide is a well-known and preferred
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example of a copolymer containing carbonyl groups; these
copolymers have the >C=0 groups directly in the polymer
chain. The ethylene/carbon monoxide copolymers include
those which have other copolymerizable monomers
contained in the polymer, such as acrylic acid,
methacrylic acid, vinyl alkylates, alkyl acrylates, and
even minor amounts of lower olefins, such a~ propylene
or butylene. Patents showing the preferred method o~
- making C0-containing ethylene copolymers include U.S.
Patent 4,600,614 and U.S. Patent 4,601,948.
A European Patent Application published July
~ ~ 29, 1987 as European Patent No. 0230143 discloses that a
photodegrading agent comprising a heavy metal
dithiocarbamate or heavy metal dithiophosphate together
with an ethylene/carbon monoxide polymer is useful for
enhancing the photodegradation of an ethylene polymer,
such as a linear low density polymer.
Another type of copolymer whioh has carbonyl
oxygen groups, but which is less pre~erred in the
present invention, is one prepared by copolymerizing
ethylene with an alkyl vinyl ketone, such as methyl
vinyl ketone, ethyl vinyl ketone, propyl vinyl ketone,
or an alkyl isopropenyl ketone and the like; these
copolymers have the carbonyl groups pendent from one of
the carbons of the vinyl group which LS directly in the
polymer "backbone" chain. The location of the carbonyl
groups in this type of copolymer chain structure can be
3 illustrated generally by the following:
~'
-(-CH2-C-CH2-CH2-)n-
C=O
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R where n is a plural number, R' is
hydrogen or alkyl group~ and where R
is the alkyl group of the alkyl vinyl
ketone or alkyl isopropenyl ketone,
with the >C=0 group connected
directly to one of the carbon atoms
of the vinyl group which is
polymerized to become part of the
chain.
For conciseness, the expression "C0-containing
polymer", when used in this disclosure, is a reference
to poly~ers which have >C=0 groups along the polymer
chain, whether it is directly in the chain or is
connected to a carbon atom which is directly in the
~ ~ chain unless it is specifically identified as being one
or the other.
The photodegradation properties of olefin
polymers which contain carbonyl groups along the chain
are disclosed in U.S. Patent 3,676,401 and U.S. Patent
3,860,538.
It is known that the anatase form of TiO2 will
accelerate the photodegradation of polyethylene and
polypropylene. The rutile form of Ti~2 is relatively
inactive with respect to the photodegradation of
polymers to which it may be added, but it may be
employed for other purposes, such as for pigmentation or
thermal activity.
There is a recognized need for materials,
especially packaging resins, which are more readily
decomposed by sunlight. This includes such items as
disposable diaper materials, trash bags, garbage bags~
grocery bags, food wraps, beverage cartons, beverage can
"loop holders", portions of sanitary napkins, disposable
gloves, wiping rags, and other discardable products.
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For purposes of distinguishing between (1) the
polymers or copolymers used herein as part of the
photodegradating agents or and (2) the polymeric matrix
materials into which the photodegrading a~ents are
added, the latter will be referred to herein as "matrix
resins". Thus unless otherwise identified, the term
"polymers or copolymers" refers herein to portions oP
the photodegradating agents, and which are also useful
in enhancing the photodegradation of the matrix resins.
A first aspect of the invention is a
photodegrading agent comprising a blend of anatase TiO2
~ - and at least one photodegrading polymer containing
carbonyl C0 groups along the polymer chain.
A second aspect o~ the invention is a process
of synergistically enhancing the photodegradation rate
of photodegradation polymers containing carbonyl groups
along the polymer chain; the said process comprising
incorporating the anatase form of TiO2 therein.
It has now been found, unexpectedly, that there
is a synergistic effect in the combined use of a C0-
containing polymer and anatase titanium oxide~ TiO2~ as
an agent for the photodegradation of matrix resins. The
combination exhibits accelerated rates of
photodegradation. When the combination is added, for
example as a masterbatch, to a matrix resin the
photodegradation of the matrix resin is desirably
accelerated. It has also been found that by employing
various predetermined amounts of the C0-containing
polymer, anatase Ti02, rutile Ti02, and U~J stabilizers
which are added to resins, one can exercise appreciable
control on the amount of pigmentation, and
photodegradation rate of various formulations. T~e have
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not found the rutile form o~ TiO2 to exhibit the
enhancement of photodegradation that is exhibited by the
anatase form o~ TiO2 and we have determined that one can
use predetermined mixtures of anatase TiO2 and rutile
TiO2 to achieve various degrees of pigmentation having
various degrees of photosensitivity.
Furthermore, we have also found that the heat-
seal range of the matrix resin is beneficially broadened
by the presence therein of the above TiO2/C0-containing
polymer agents; in heat-sealing using radiant and or
conduction heat it does not matter (vis-a-vis the heat
- _ seal range) whether the TiO2 is rutile or anatase,
though it does matter i~ heating is being done using RF
energy, especially MW energy, to cause heating of the
material.
The present invention involves the following
listed related, identifiable aspects or embodiments:
1. A blend containing anatase TiO2 and at least
one C0-containing polymer, said blend having a
beneficial rate o~ photodegradation. An ethylene
copolymer containing copolymerized carbon monoxide (C0)
in the polymer chain backbone is the preferred type of
C0-containing polymer.
2. A blend containing predetermined amounts of
anatase TiO2~ at least one C0-containing polymer, and
optionally rutile TiO2 and/or UV stabilizer, said blend
exhibiting a predetermined regulated rate of
3 photodegradation.
3. A blend of a matrix resin which contains
anatase TiO2 and at least one C0-containing polymer.
4. A blend of a matrix resin which contains
predetermined amounts of anatase TiO2, at least one C0-
containing polymer, and optionally rutile TiO2 and~or UV
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stabilizer.
5. A process of synergistically enhancing the
photodegradation rate of CO-containing polymers by
incorporating the anatase form of TiO2 therein.
6. A process of accelerating the photodegrada-
tion rate of a matrix resin, said process comprising
incorporating into the matrix resin 2 photodegrading
composition (or "agent") comprising anatase TiO2 and at
least one CO-containing polymer.
7. A process of providing a predetermined
regulated rate of photodegradation to a matrix resin,
said process comprising blending the matrix resin with
predetermined amounts of anatase TiO2~ at least one CO-
containing polymer and optionally rutile TiO2, and/or a
U~ stabilizer.
The photodegradation rate of CO-containing
polymers is synergistically accelerated by the addition
thereto of the anatase form of TiO2 and is not merely a
numerically additive effect of the two ingredients.
That, in itself, is beneficial in the preparation of
articles which can be made directly from an anatase
TiO2/polymer blend and relatively fast photodegradation
is desirably obtained~
The mixture of anatase TiO2/CO-containing
polymer is also used as an agent to provide a faster
photodegradation rate to articles such as resin films,
filaments, fibers, sheets, slabs, containers or other
3 configurations prepared from matrix resins. The agent
may, as a "masterbatch" of TiO2/CO-containing polymer,
be blended with the matrix resin in which the
accelerated rate of photodegradation is desired. The
carbonyl-containing polymer and the TiO2 can be added
separately to the matrix resin, but are beneficially and
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preferably mixed together to form a photodegrading agent
which is then added to the resin. Optionally, other
additives and/or degradation accelerators and/or
photostabilizers and/or photosensitizers may also be
employed along with the agent of this invention either
by way of having the photodegradation agent added to
matrix resins which contain the said optional
ingredients, or by way of adding the optional additives
to matrix resins which contain the photodegradation
agents, or by adding them to the matrix resin at
substantially_the same time.
~ ~ Within the ambit of the present invention the
matrix resins to which a photodegrading property are
desired to be imparted or accelerated may be resins
which are used in making packaging materials, especially
those which are usually intended to be discarded after
their first use. Examples of matrix resins are
polyolefins, polyesters, polyurethanes, polyamides,
polyepo~ides, polyacrylates and plolycarbonates. Such
articles as garbage bags, grocery bags, tampon-type
applicators, wipe-cloths, hygiene products~ disposable
diapers, sanitary napkins, food-wrapping, food cartons,
can holders, beverage overwraps, beverage containers~
beer can "loop carriers", and the like, often comprise
or include resins which can be caused to be more rapidly
photodegraded by sunlight. Of special interest in this
re~ard are those resins which are prepared from olefin
monomers and/or vinyl monomers, such as ethylene,
propylene, butene, styrene, vinyl acetate, vinyl halide,
and derivatives of these or other such monomers which
are used in making plastics and which are often used as
discardable packaging materials. Resins prepared from
olefins and mixtures of olefins, such as low density
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branched polyethylene (LDPE), linear low density
polyethylene (LLDPE) and high density linear
polyethylene (HDPE) as well as styrene polymers and
copolymers are of particular interest as the matrix
resins in this invention. LLDPE resins are of special
interest considering, among other things, the strength
and i~pact resistance they exhibit which makes them
popular in the making of garbage bags and trash bags.
Compositions comprising HDPE are particularly useful ~or
preparing discardable molded articles. Compositions
comprising LLDPE or LDPE are particularly useful for
preparing discardable melt-extruded films. Compositions
comprising styrenic polymers or copolymers are
particularly useful for preparing discardable foams.
The titanium oxide, Ti02, which exhibits a
synergistic effect when combined with C0-containing
polymers is of the crystalline form known as anatase.
Throughout this disclosure the TiO2 is the anatase form
unless stated otherwise.
The C0-containing polymer used as a
photodegrading agent, in conjunction with the Ti02, may
be any thermoplastic polymer which has carbonyl groups
along the polymer chain and which is either compatible
with, or can be compatibilized with, the resin lnto
which it is to be blended. Compatibilizing may be
accomplished, e.g., by the addition o~ a compatibilizer
or by special blending techniques while the
3 polymers/resins are in solution or are molten.
Preferably the C0-containing polymer is an ethylene
copolymer, especially a binary or ternary polymer, which
is prepared using carbon monoxide as one of the
monomers. The preparation of such ethylene/carbon
monoxide polymers is known in the art of making ethylene
36,15~-F -8-
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copolymers. Less preferred are those polymers wherein
the carbonyl groups are supplied to the polymer chain by
the presence of an alkyl vinyl ketone polymerized into
the chain.
The C0 containing polymer usually contains an
amount of the >C=0 groups (or "C0") along the polymer
chain to provide at leas~ 0.2 percent by weight of the
total polymer, preferably at least 0.5 percent by
weight, and can be as much as 50 percent or more of the
total polymer. Below 0.2 percent the effect o~ the C0-
containing polymer is not very likely to provide an
~ - appreciably significant effect on the photodegradation
of the resin. Above 50 percent, the polymer which
contains the C0 groups may not exhibit the physical
properties needed for attaining the initial strength or
other properties desired in the resin article of which
it is to be a part. A preferred range is 1 percent to
30 percent by weight, more preferably 2 percent to 20
percent by weight.
The amount of the C0-containing polymer used in
the matrix resin usually is an amount in the range of
~.05 percent to 50 percent of the total weight of the
formulation. The amount of the anatase TiO2 used in the
matrix resin usually is an amount in the range of 0.05
percent to 25 percent of the total ~eight of the
formulation. Within those ranges, the ratio of the C0-
containing polymer to the anatase TiO2 usually is in the
3 range of 99.9/0.1 to 0.3/99.7, preferably in the range
of 99.8/0.2 to 0.5/99.5, most preferably in the range of
99~7/0.3 to 1~99.
In those instances where it is desired to
produce articles from resins which contain the rutile
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2006376
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form of TiO2 as a white pigment and/or opacifier and
which sometimes also contain a UV stabilizer or other
filler or pigment or opacifier such as SiO2 and/or CaC03
(used, e.g., as an antiblock), one may employ slip
agents such as erucylamides or oleamides, or
antioxidants or UV stabilizers, such as compounds sold
under the following names (some of which are proprietary
formulations):
Irganox 1010 --- Tetrakis [methylene 2-(3',5'-di-tert-
butyl-4'hydroxylphenol) propionate] methane,
Irganox 1076 --- Octadecyl 3-(3,5-di-t-butyl-4-
hydroxyphenyl)propionate or Octadecyl 3,5-di-t-butyl-4-
hydroxyhydrocinnamate,
BHT ---2 ,6-di-t-butyl-p-cresol,
Mark 2047 --- a thiodipropionate ester complex,
Cyasorb UV 531 --- substituted 2-hydroxybenzophenones,
Tinuvin 770 --- hindered piperidines,
Tinuvin 328 --- a benzotria~ole, and
Cyasorb UV 5411 --- a benzotriazole.
Some compounds or families of UV stabilizers
are, e.g., as follows:
Hindered amines light stabilizers,
Substituted hindered amine light stabilizers,
Hindered piperidines,
Dithiolate metal complexes (e.g. Ni, Co. Cu),
Phosphite esters,
Salicylaldehyde oximes,
Thiobisphenolates,
Hydroxy-benzyl phosphonates,
Substituted 2-hydroxybenzophenones,
2-hydroxyphenyl benztriazoles,
Metal dithiocarbamates,
Metal acetyl acetonates,
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Hindered phenols,
Metal dithiophosphate,
Hindered aliphatic amine,
Metal salicylaldehyde oximes,
Peroxydienones,
Thioglycolate 2-hydroxybenzophenones, and
Metal disulfides.
It is within the ambit of the present inventive
concept to provide foaming agents, to cause foaming of
the matrix resin and produce lightweight articles,
and/or add other polymers to the C0-containing
~ ~ polymer/TiQ2 compositions, thus preparing an appreciable
variety o~ final products having an enhanced tendency to
degrade under the influence of actinic radiation,
especially UV.
The following embodiments are for illustration
purposes, but the invention is not limited to the
particular embodiments illustrated. All parts and
percentages are by weight unless otherwise indicated.
The expression "LLDPE" is an acronym, widely accepted
and recognized in the art, for linear low density
polyethylene which is actually an ethylene~1-alkene
copolymer prepared by using a coordination catalyst,
such as a Ziegler catalyst or the like. The melt flow
rate (MFR) of the polymers is measured in accordance
with ASTM D-1238 (190~2.16) unless specified otherwise;
the MFR is often called melt index (MI) when applied to
3 polyethylene homopolymer.
The following listed ingredients are used in
various following examples:
In~redient Descri~tion of In~redients
36,159-F _11_
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20(~63~
LLDPE-1 Ethylene/octene copolymer,
density o~ 0.941 g/cc and MFR
o~ 40 g/10 min.
LLDPE-2 Ethylene/octene copolymer, density of
0.920 g/cc and MFR of 10 g/10 min.
LDPE~1 Branched homopolymer of ethylene, 0.922
g/cc density, MI o~ 20 g/10 min.
10 ECO-1 Copolymer of ethylene/carbon monoxide,
containing 1.9 percent CO, MFR 10 g/10
min, density of 0.935 g/cc.
ECO-2 Copolymer of ethylene/carbon monoxide,
containing 10 p~orcent CO, MFR 10 g/10 min.
TiO2 Titanium oxide, indicated as the anatase
crystal ~orm or the rutile crystal form,
or in some instances it can be either one~
0 Concentrate #1 Equal parts of ECQ-1 and anatase TiO2,
prepared on a Banbury intensive mixer
then cooled and ground into small
granular pieces.
5 Concentrate #2 Equal parts of ECO-2 and anatase TiO2,
prepared on a Banbury intensive mixer
then cooled and ground into small
granular pieces.
Concentrate #3 Equal parts o~ LDPE and rutile TiQ2,
prepared on a Banbury intensive mixer
then cooled and ground into small
granular pieces.
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Concentrate #4 Equal parts of LDPE and anatase TiO2,
prepared on a Banbury intensive mixer
then cooled and ground into small
granular pieces.
Concentrate #5 Equal parts of ECO-2 and rutile TiOz,
prepared on a Banbury intensive mixer
then cooled and ground into small
granular pieces.
0 Concentrate #6 Equal parts of ECO-1 and rutile TiO2,
prepared on a Banbury intensive mixer
_ then cooled and ground into small
granular pieces.
5 Example 1:
A composite blend is prepared by blending 9.9
parts of LLDPE-1, 0.3 parts of LLDPE-2, and 4.8 parts of
Concentrate ~'~1. The components are tumble dry blended
prior to being fabricated into cast film at 550F (288C)
of 1.2 mil (30 micrometers) thickness. Strips of film,
1-inch by 8-inch (2.5 cm by 20 cm) are cut from the cast
film and subjected to outside weathering in accordance
with ASTM D-1435-85. By analyses of the parameters of
interest, average tensile, average yield and percent
elongation at break are determined and analyzed in
accordance with ASTM D-882. The brittle point is
determined to be that point where the tensile at break
and yield strength values were identical and the film
samples demonstrated brittleness when handled. The data
for the outside weathering are shown in TABLE I.
Example 2:
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In similar manner to Example 1, a composite
blend is prepared consisting of 9.9 parts of LLDPE-1,
0.3 parts of LLDPE-2, and 4.8 parts of Concentrate #2.
The composite is tested by outside weathering and the
data are shown in Table I.
Example 3-6:
In similar manner to the foregoing descriptions
and examples, other tests are made using various combi-
nations to make composites, holding the LLDPE-1 and
LLDPE-2 content~constant, using different concentrates
_ (some of which are not examples of the invention, but
are for comparison purposes to illustrate the synergism
of the EC0/anatase TiO2 combination) are shown in Table
I.
36,159-F _14_
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-15-
Table I
% Elon~ation/Elasticit~
Example Concentrate
0 days 17 da~s
1 (Comp.) #1 497/ductile 4/brittle
2 (Comp.) #2 456/ductile 5/brittle
3* #3 447/ductile 534/ductile
4~ #4 412/ductile 439/ductile
5* ~5 505/ductile 453/ductile
- - 6~ #6 445/ductile 697/ductile
*Example not of the invention, but for comparison
The data in Table I indicate that the
syner~istic mixture of EC0/anatase TiO2 (concentrates #1
& #2) causes a very rapid embrittlement of the LLDPE
film in only 17 days of exposure, a remarkable amount of
embrittlement when compared to the other examples which
were tested in the same manner. The comparison examples
which retained a high degree of elongation/elasticity
(i.e. they remained ductile) indicated that the use of
rutile alone, or rutile/EC0 combinations, or
anatase/LDPE combinations had no noticeable e~fect on
embrittlement during the 17 day test.
The following are preferred ranges and rakios
for the practice of the above embodiments:
3 For the ratio of EC0/anatase TiO2 in the
concentrate, the range of 1/99 to 99/1 is believed to be
operable, preferably 40/60 to 90/10, most preferably
50/50 to 80/20.
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Example 9 Heat Seal Range Compared With Prior Art
Hot tack tests are performed on a "Pack Forsk"
instrument which is fully automated and is equipped with
an Instron type seal strength testing device. The dwell
time is set at 0.5 seconds. The delay time (between the
formation of seal and the strength) is set at 0.2
seconds. The film samples are 1-inch (2.5 cm) wide
strips of uniform thickness. Each data point is
calculated from an average of at least 3 measurements.
The tear resistance is measured by Elmendorf
- _ tear test type B, which is ASTM # D-1922. Each data
point is an aYerage of four measurements.
Films from which testing samples are taken are
prepared by dry blending the components for 1 hour and
then extruding the well-mixed ingredients through a
1-inch (2.5 cm) 24/1 L/D MPM extruder and fabricated
into cast film (film gauge of 2.5 to 2.7 mils~ i.e.
about 63 to 69 micrometers, under the following
conditions:
Extruder Location Temperatures
Zone 1 370F/188C
Zone 2 430F/221C
Zone 3 450F/232C
Gate 450F/232~C
Adapter 450F/232C
Feed Block 450F/232C
90 Adapter 450F/232C
Die #1 450F/232C
Die #1 450F/232~C
Chill Roll 59F/15C
36,159-F -16-
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A typical prior art composite contains about 73
percent LLDPE, about 25 percent LDPE, and about 2
percent TiO2. The heat seal temperature range and the
tear strength of this currently used composite, when
fabricated into a cast film without the TiO2, are 225F
to 275F (107C to 135C) and 200 grams, respectively.
~ith the TiO2 added to the LDPE/LLDPE formulation, the
heat seal temperature range and tear strength become
reduced to 230F to 265F (110C to 129C) and 146 grams,
respectively.
When an ethylene/carbon monoxide (ECO)
~ copolymer is used with the LLDPE in place of the LDPE,
and without the TiO2, the heat seal temperature range
and tear resistance is 225F to 280F and 592 grams,
respectively. Then when TiO2 is added to the LLDPE/ECO
blend, the heat seal temperature and tear strength is
235F to 295F and 606 grams, respectively. ~e believe
that an acid-base interaction between TiO2 ~acidic
surface) and ECO (basic carbonyl) contributes to better
dispersion of TiO2 in the polymer matrix which is
essentially non-polar. For this heat seal effect the
TiO2 can be either anatase or rutile or any variety
having an acid surface. Other particulate solid
compounds having acid surfaces ma~ be employed in place
of, or alon~ with, the TiO2 and the CO-containing olefin
polymer.
Example 10
The use of ECO/TiO2 in place of LDPE/TiO2 is
found to result in widening the heat seal temperature
range o~ a wide variety of polymers into which the
ECO/TiO2 is incorporated, especially olefin polymers and
copolymers such as LLDPE, HDPE, and LDPE and the like.
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The benefits of the ECO/TiO2 additives are found in
blown films as well as cast films.
For the purposes of improving the heat seal
range of the preferred LLDPE the following amounts are
preferred:
Component* Operative wt. % Preferred wt. %
LLDPE 20 to 99 30 to 95
10 ECO 0.5 to 60 1.0 to 30
TiO2 1 to 30 1 to 20
*The ECO copolymer usually contains 1 to 50 weight
percent CO. The LLDPE usually contain any one or more
alkene comonomers in the C3-C10 range.
3o
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