The photodegradability and/or heat-seal range of polymeric matrix materials is controllably enhanced by incorporating therein Tiθ2 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 process can continue the embrittlement and produce smaller and smaller pieces.

The photodegradation tendency of ethylene copolymers containing carbonyl groups (>C=0) 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

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 as propylene or butylene. Patents showing the preferred method of making CO-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 which has carbonyl oxygen groups, but which is less preferred 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 is directly in the polymer "backbone" chain. The location of the carbonyl groups in this type of copolymer chain structure can be illustrated generally by the following:

-(-CH2-C r-CH2-CH2-)n-

/ C=0 /

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 "CO-containing polymer", when used in this disclosure, is a reference to polymers which have >C=0 groups along the polymer 0 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. 5 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. 0 It is known that the subpigmentary form of anatase Tiθ2 having a particle size from about 0.01 to 0.15 microns will accelerate the photodegradation of polyethylene and polypropylene up to two or three times c faster than the use of commercial anatase grade Tiθ2 _> as disclosed in Canadian Patent 1,073 _» 581 and in Research Disclosure No. 15661 (April 1977). The rutile form of Tiθ2 is relatively inactive with respect to the photodegradation of polymers to which it may be added, 0 but it may be employed for other purposes, such as for pigmentation or thermal activity. The latter utility may be demonstrated, for example, by Material Safety Data Sheet No. HM88143 for a degradable polyethylene based white concentrate trademarked SPECTRATECH™ HM88143 by Quantum Chemical Corporation and described as

50 blend of polyethylene modified to be degradable and 50 of titanium dioxide (CAS RN: 13463-67-1); this Chemical Abstracts Service Registry Number is generic to Tiθ2-

It is known that the anatase form of Tiθ2 will accelerate the photodegradation of polyethylene and polypropylene. The rutile form of Tiθ2 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.

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 agents 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 of the photodegradating agents, and which are also useful in enhancing the photodegradation of the matrix resins.

Various broad aspects of the invention are given in the independent claims hereinafter.

A first aspect of the invention is a photodegrading agent comprising a blend of anatase Tiθ2

and at least one photodegrading polymer containing carbonyl CO groups along the polymer chain.

A second aspect of 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 Tiθ2 therein.

It has now been found, unexpectedly, that there is a synergistic effect in the combined use of a CO- containing polymer and anatase titanium oxide, Tiθ2, 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 CO-containing polymer, anatase Tiθ2 _> rutile Tiθ2, and UV stabilizers which are added to resins, one can exercise appreciable control on the amount of pigmentation, and photodegradation rate of various formulations. We have not found the rutile form of Tiθ2 to exhibit the enhancement of photodegradation that is exhibited by the anatase form of Tiθ2 and we have determined that one can use predetermined mixtures of anatase Tiθ2 and rutile Tiθ2 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 Tiθ2/CO-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 Ti0 ₂ is rutile or anatase, though it does matter if 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 Tiθ2 and at least one CO-containing polymer, said blend having a beneficial rate of photodegradation. An ethylene

10 copolymer containing copolymerized carbon monoxide (CO) in the polymer chain backbone is the preferred type of CO-containing polymer.

2. A blend containing predetermined amounts of ■,_- anatase Tiθ2» at least one CO-containing polymer, and optionally rutile Tiθ2 and/or UV stabilizer, said blend exhibiting a predetermined regulated rate of photodegradation.

3. A blend of a matrix resin which contains 20 anatase Tiθ2 and at least one CO-containing polymer.

4. A blend of a matrix resin which contains predetermined amounts of anatase Tiθ2» at least one CO- containing polymer, and optionally rutile Tiθ2 and/or UV stabilizer.

25 5. A process of synergistically enhancing the photodegradation rate of CO-containing polymers by incorporating the anatase form of Tiθ2 therein.

6. A process of accelerating the photodegrada¬

30 tion rate of a matrix resin, said process comprising incorporating into the matrix resin a photodegrading composition (or "agent") comprising anatase Tiθ2 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 Tiθ2, at least one CO- containing polymer and optionally rutile Tiθ2 _> and/or a UV stabilizer.

The photodegradation rate of CO-containing polymers is synergistically accelerated by the addition thereto of the anatase form of Tiθ2 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 Tiθ2/polymer blend and relatively fast photodegradation is desirably obtained.

The mixture of anatase Tiθ2/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 configurations prepared from matrix resins. The agent may, as a "masterbatch" of Ti02/C0-containing polymer, be blended with the matrix resin in which the accelerated rate of photodegradation is desired. The carbonyl-containing polymer and the Tiθ2 can be added separately to the matrix resin, but are beneficially and 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, polyepoxides, 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 regard 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 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 impact resistance they exhibit which makes them popular in the making of garbage bags and trash bags. Compositions comprising HDPE are particularly useful for

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, Tiθ2 _> which exhibits a synergistic effect when combined with CO-containing polymers is of the crystalline form known as anatase. Throughout this disclosure the Tiθ2 is the anatase form

10 unless stated otherwise. Anatase Ti02 having a size range of between about 0.5 microns and about 3.5 microns is preferred, and the pigmentary grade of anatase Ti02 having a particle size of about 2 microns is especially -c preferred.

The CO-containing polymer used as a photodegrading agent, in conjunction with the Tiθ2 _» may be any thermoplastic polymer which has carbonyl groups _Q along the polymer chain and which is either compatible with, or can be compatibilized with, the resin into which it is to be blended. Compatibilizing may be accomplished, e.g., by the addition of a compatibilizer or by special blending techniques while the 5 polymers/resins are in solution or are molten.

Preferably the CO-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 0 monoxide polymers is known in the art of making ethylene 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 CO-containing polymer usually contains an amount of the >C=0 groups (or "CO") along the polymer chain to provide at least 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 of the CO- 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 CO 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 CO-containing polymer used in the matrix resin usually is an amount in the range of 0.05 percent to 50 percent of the total weight of the formulation. The amount of the anatase Tiθ2 used in the matrix resin usually is an amount in the range of 0.05 percent to 25 percent of the total weight of the formulation. Most often it is used in an amount in the range of 5 to 10 weight percent. Within those ranges, the ratio of the CO-containing polymer to the anatase Tiθ2 usually is in the 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 form of Tiθ2 as a white pigment and/or opacifier and which sometimes also contain a UV stabilizer or other filler or pigment or opacifier such as Siθ2 and/or CaCθ3 (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- hydroxyphenyDpropionate 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 benzotriazole, 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, 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 CO-containing polymer/Tiθ2 compositions, thus preparing an appreciable variety of 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 polyethylene homopolymer.

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 copolτmer 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 polyethylene homopolymer.

The following listed ingredients are used in various following examples:

Ingredient Description of Ingredients

LLDPE-1 Ethylene/octene copolymer, density of 0.941 g/cc and MFR of 4 g/10 min.

LLDPE-2 Ethylene/octene copolymer, density of 0.920 g/cc and MFR of 1 g/10 min.

LDPE-1 Branched homopolymer of ethylene, 0.922 g/cc density, MFR of 2 g/10 min.

ECO-1 Copolymer of ethylene/carbon monoxide, containing 1.95- CO, MFR 0.5 g/10 min, density of 0.935 g/cc.

ECO-2 Copolymer of ethylene/carbon monoxide, containing 10 CO, MFR 1.5 g/10 min, density of 0.97 g/cc.

Tiθ2 Titanium oxide, indicated as the anatase crystal form or the rutile crystal form, or in some instances it can be either one. Unless indicated otherwise, the Tiθ2 used is pigment grade Tiθ2 (particularly that available as Mobay ^® Type A-X).

Concentrate #1 Equal parts of EC0-1 and anatase Tiθ2 _> prepared on a Banbury intensive mixer

then cooled and ground into small granular pieces.

Concentrate #2 Equal parts of ECO-2 and anatase Ti02, prepared on a Banbury intensive mixer then cooled and ground into small granular pieces.

Concentrate #3 Equal parts of LLDPE-2 and rutile Tiθ2» prepared on a Banbury intensive mixer then cooled and ground into small granular pieces.

Concentrate #4 Equal parts of LLDPE-2 and anatase Ti02, prepared on a Banbury intensive mixer then cooled and ground into small granular pieces.

Concentrate #5 Equal parts of EC0-1 and rutile Tiθ2» prepared on a Banbury intensive mixer then cooled and ground into small granular pieces.

Concentrate #6 Equal parts of ECO-2 and rutile Ti02, prepared on a Banbury intensive mixer then cooled and ground into small granular pieces.

Example 1 :

A composite blend is prepared by blending 9.9 parts of LLDPE-1 , 0.3 parts of LLDPE-2, 4.2 parts of EC0-1 and 0.6 parts of Concentrate #1. The components are tumble dry blended prior to being fabricated into cast film at 550°F (288°C) of 1.2 mil thickness. Strips of film, 1-inch by 8-inch (2.54cm by 20.32cm) 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:

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, 4.2 parts of ECO-2 and 0.6 parts

15 of Concentrate #2. The composite is tested by outside weathering and the data are shown in TABLE I.

Example 3s

In similar manner to Example 1, a composite

20 blend is prepared consisting of 9.9 parts of LLDPE-1, 4.5 parts of LDPE-1 and 0.6 parts of Concentrate #3. The composite is tested by outside weathering and the data are shown in TABLE I.

- _c Example 4:

In similar manner to Example 1, a composite blend is prepared consisting of 9.9 parts of LLDPE-1, 4.5 parts of LDPE-1 and 0.6 parts of Concentrate #4. The composite is tested by outside weathering and the

30 data are shown in TABLE I.

Example 5:

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, 4.2 parts of EC0-1 and 0.6 parts

of Concentrate #5. The composite is tested by outside weathering and the data are shown in TABLE I.

Example 6:

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, 4.2 parts of ECO-2 and 0.6 parts of Concentrate #6. The composite is tested by outside weathering and the data are shown in TABLE I.

TABLE I

% Elongation/Elasticity

*Example not of the invention, but for comparison **A=Anatase Tiθ2» R=Rutile Tiθ2

The data in Table I indicate that the synergistic mixture of ECO/anatase Tiθ2 (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/ECO combinations, or anatase/LDPE combinations had no noticeable effect on embrittlement during the 17 day test.

The following are preferred ranges and ratios for the practice of the above embodiments:

For the ratio of ECO/anatase Tiθ2 in the concentrate, the range of about 1/99 to about 99/1 is believed to be operable, preferably about 40/60 to about 90/10, most preferably about 50/50 to about 80/20.

Example 7 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 (2.54 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 average 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 24/1 L/D MPM extruder and fabricated into cast film (film gauge of 2.5 to 2.7 mils, i.e. about 0.0635 to 0.06858 mm), under the following conditions:

Extruder Location Temperatures

Zone 1 370°F/188°C

Zone 2 430°F/221°C Zone 3 450°F/232°C

Gate 450°F/232°C

Adapter 450°F/232°C

Feed Block 450°F/232°C

90° Adapter 450°F/232°C

Die #1 450°F/232°C

Die #2 450°F/232°C

Chill Roll 59°F/15°C

A typical prior art composite contains about 73% LLDPE, about 25% LDPE, and about 2% Ti0 ₂ . The heat

seal temperature range and the tear strength of this currently used composite, when fabricated into a cast film without the Ti0 ₂ » are 225°F to 275°F and 200 grams, respectively. With the Ti0 ₂ added to the LDPE/LLDPE formulation, the heat seal temperature range and tear strength become reduced to 230°F to 265°F and 146 grams, respectively.

When about 25% of ethylene/carbon monoxide (ECO) copolymer is used with about 75% of LLDPE, without the LDPE, and without the Ti0 ₂ » the heat seal temperature range and tear resistance is 225°F to 280°F and 592 grams, respectively. Then when about 2% TiU2 (either rutile or anatase) is added to the blend such that the LLDPE is about 73% and the ECO copolymer is about 25% of the total, the heat seal temperature and tear strength is 235°F to 295°F and 606 grams, respectively. We believe that an acid-base interaction between Tiθ2 (acidic surface) and ECO (basic carbonyl) contributes to better dispersion of Tiθ2 in the polymer matrix which is essentially non-polar. For this heat seal effect the Tiθ2 can be either anatase or rutile or any variety having an acid surface. Other particulate solid compounds having acid surfaces may be employed in place of, or along with, the Ti02 and the CO-containing olefin polymer.

The use of EC0/Ti0 ₂ in place of LDPE/Ti0 ₂ is found to result in widening the heat seal temperature range of a wide variety of polymers into which the ECO/Tiθ2 is incorporated, especially olefin polymers and copolymers such as LLDPE, HDPE, and LDPE and the like. The benefits of the ECO/Tiθ2 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:

*The ECO copolymer can contain 1 to 50 weight % CO. The LLDPE can contain any one or more alkene comonomers in the C3-C10 range.