WO1996031563A1

WO1996031563A1 - Modified polyolefins

Info

Publication number: WO1996031563A1
Application number: PCT/EP1996/001504
Authority: WO
Inventors: Wai Keung Wong; Stefan Bertil Ohlsson
Original assignee: Exxon Chemical Patents Inc
Current assignee: ExxonMobil Chemical Patents Inc
Priority date: 1995-04-07
Filing date: 1996-04-09
Publication date: 1996-10-10
Anticipated expiration: 1997-10-07
Also published as: GB9507321D0

Abstract

This invention relates to a method to reduce gels in polyolefins and a method to introduce long chain branching in an olefin polymer by blending the polyolefin with a reactive co-agent having two or more functional groups capable of irreversibly reacting with free radicals on the polyolefin back bone under conditions of heat and/or shear. This invention also provides a method to reduce blocking force in polyolefin films.

Description

Title: Modified Polyolefins

Field of the Invention

This invention relates to a method to provide a polyolefin composition having improved melt processing characteristics. This invention also relates to a method which provides a polyolefin composition having a reduced number of gels. This invention further realtes to a method to reduce blocking force in polyolef in f ilms .

Background of the Invention

Polymer processors face numerous problems in

transforming olefinic polymer feedstock, generally in the form of granules or pellets, into useful final articles. Among these challenges, the converter must be concerned about power consumption. Such concern arises from the fact that power is an expense in the processing but, at least as importantly, as a general principle the greater the power consumption for polymer processing machinery, the greater is the wear on the machine itself as well as on attached or downstream forming tooling. Generally, reduction in power consumption means not only direct savings in energy coses, but also noticeable diminishment in capital expense and maintenance costs downstream.

Other problems are encountered at the point of forming the molten plasticized polymer material into an intermediate or final product. In the case of film production for example, where molten polymer is forced through a die and then blown, expanded or drawn into a film, the fluidity of the molten plastic, its tenacity, and its melt strength must be balanced to achieve useful products and achieve good processing speeds. Prior to solidification, the melt must be fluid enough to pass through the forming die, yet must be strong enough to hold itself together while being subjected to the stresses of formation. Methods to address this concern encompass a number of options for increasing the melt properties of the polymer. Introducing long chain branching into the polymer is one favored method to address this concern. Such introduction is typically attempted in the reactor by manipulating the monomers or by simply grafting a branch onto an existing polymer. For example, U.S. Patents 5,272,236 and 5,278,272, suggest producing a long chain branched polymer by polymerizing in the solution phase with an expensive metallocene/non-coordinationg anion catalyst system. The polymer so produced is alleged to demonstrate enhanced melt properties through the inclusion of some level of side chain branching. Likewise , grafting methods to introduce long chain branches are costly, cumbersome and also tend to produce negative side effects such as gels in the final polymer product. Thus, a need exists in the art to provide elegant, less expensive means to introduce effective amounts of branching into olefin polymers without the unwanted side effect of gels.

Another problem faced by film manufacturers is that of gel formation due to crosslinked polymer within the extrudate as a consequence of adding crosslinking and/or other modifying agents to improve the polyolefin

properties. U.S. 4,737,547, attempts to solve this problem and exemplifies a melt blending technique useful for reducing gels in polyethylene compositions modified with organic peroxides and optional cocuring agents such as triallyl cyanurate, triallylisocyanurate or 1,2 polybutadiene or modifying agents of unsaturated organic acids. Note that the films and molded items made in U.S. Patent 4,737,547 using the melt blending technique have no gel, while the films and items made not using the melt blending technique have gel . Note also that in the instances where triallylcyanurate or maleic anhydride was used in the examples, it was present as a coagent in addition to the peroxide.

Finally, South African Patent Application O. Z .00503/43314 (No. 934261) discloses partially crosslinked ethylene polymers obtained by crosslinking with a bismaleimido compound in the absence of a free radical initiator. The concentration of bismalemido compound in the examples indicates however that gels would most likely be produced in this process. Summary of the Invention

This invention provides, inter alia, a means of introducing branching into an olefin polymer while also reducing the number and/or size of resultant gels in the final product. In particular the invention relates to a process for modifying polymer which comprises:

a) subjecting an olefin polymer to heat and/or shear;

b) contacting the olefin polymer, in the

substantial absence of a free radical generating initiator, with a reactive co-agent having at least two functional groups capable of irreversibly

reacting with free radicals on the polymer backbone; and

c) obtaining an olefin polymer with a melt index at least 10 % below that of the starting polymer.

Detailed Description

In preferred embodiments this invention relates to a process for lowering the melt index (MI, as measured by ASTM 1238 condition E) of an olefin polymer. While application of this invention is useful for all

polyolefins, preferred polymers include those comprising ethylene and/or propylene monomers. For example, this class includes but is not limited to, homopolyethylenes and copolymers of ethylene and any linear, cyclic or branched C₃ to C₃₀ α-olefin, such as propylene, butene, isobutene, pentene, isopentene, hexene, 4 -methyl -hexene- 1, 3-methyl-hexene -1, heptene, octene, nonene, decene, dodecene, heptadecene, 3 , 5 , 5-trιmethylhexene-1, cyclopentene , cyclohexene , norbornene, ethylidene norbornene, cyclooctene and the like. Likewise this invention is also useful for polymers of propylene, including homopolypropylene and copolymers of propylene one or more of ethylene and any linear, cyclic or branched C₄ to C₃₀ α-olefin. Examples include copolymers of propylene and one or more of ethylene, butene, isobutene, pentene, isopentene, hexene, 4 -methyl-hexene- 1, 3-methyl-hexene-1, heptene, octene, nonene, decene, dodecene, heptadecene, 3, 5, 5-trimethylhexene-1,

cyclopentene, cyclohexene, norbornene, ethylidene norbornene, cyclooctene and the like. This invention is also particularly useful for modifying that class of polymers having a narrow molecular weight distribution (Mw/Mn), i.e. Mw/Mn of 4 or less, preferably 3 or less, even more preferably 2 or less, preferably 1.5 or less and/or a composition distribution breadth index (CDBI) over 50%, preferably at or over 60%, even more preferably at or over 70%, even more preferably at or over 80%.

CDBI is defined and explained in WO 9303093, published February 18, 1993, which is incorporated by reference herein for the purposes of U.S. law. Catalyst systems that produce polymers having narrow molecular weights and/or high CDBI's are well described in the art and commercially available products that fall within this category are sold under the trade name EXACT™ by Exxon Chemical Company in Houston, Texas, U.S.A. Likewise, catalyst systems and processes that produce polymers having narrow molecular weights and/or high CDBI's are also described in WO 94/26816, published November 24, 1994.

Additional preferred polymers that may be modified according to this invention include all commercially available substantially linear ethylene polymers, including linear low density polyethylenes (LLDPE), high density polyethylenes (HOPE), very low density

polyethylenes (VLDFE) and all ethylene based polymers having a density (as measured by ASTM 792 ) of between 0.88 and 0.97 g/cm³. Substantially linear polymer is defined to be a polymer having no long chain branching or a polymer having a rheologically insignificant amount of long chain branching. Branching becomes rheologically significant when shear thinning occurs.

In a preferred embodiment one or more of the olefin polymers described above is combined under conditions of heat and/or shear with a reactive co-agent having at least two functional groups capable of irreversibly reacting with free radicals on the polymer backbone. For the purposes of this invention and the claims thereto a reactive co-agent is defined to be an agent having two or more sites capable of irreversibly reacting with free radicals on the olefin polymer backbone and "capable of ireversibly reacting" is defined to mean forming covalent bonds stable under the extrusion and processing

conditions typically used in the art, particularly those conditions described below. While not wishing to be bound by any theory, it is believed that in a preferred embodiment, the reactions with the two or more sites form bridges between polymer chains. In a preferred

embodiment the free radicals on the polymer backbone are alkyl or alkoxy free radicals. In preferred embodiments the reactive co-agent is any electrcphillic composition that is more reactive with the free radicals on the polymer backbone than the polymer backbone is reactive with the free radicals. Such compositions include any compound having two or more vinyl unsaturations or other groups capable of irreversibly reacting with a free radical. In a preferred embodiment the reactive co-agent is a diene, an acrylic acid, an ester of an acrylic acid, a C₁ -C₃₀ alkyl acrylic acid, such as methacrylic acid, ethacrylic acid and the like, an ester of a C₁ -C₃₀ alkyl acrylic acid, and/or an allyl containing composition and is not a peroxide. These reactive co-agent having two or more active sites, preferably have three or more active sites. Preferred species of the reactive co-agent include but are not limited to: trimerhylolpropane trimethacrylate, ethylene glycol dimethacrylate,

polyethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, triallyl cyanurate, norbornadiene, pentadiene, hexadiene, 1,3- butylene

glycoldimethacrylate, 1,6-hexanediol diacrylate,

tripropylene glycol diacrylate, trimethyolpropane- triacrylate, allyl methacrylate, and the like.

In a preferred embodiment the free radicals on the polymer backbone are alkyl or alkoxy radicals. Likewise in a preferred embodiment, the free radicals are

generated on the polymer backbone by heat and/or shear. In a preferred embodiment the polymer is heated to a molten state or more and/or is subjected to shear sufficient to evenly distribute the reactive co-agent into the polymer or more to generate the free radicals on the polymer back bone.

In a preferred embodiment the reactive co-agents are used in the substantial absence of an initiator which generates free radicals. Such initiators are well known in the art and comprise the well known organic peroxides, such as all the peroxides available under the LUPERSOL™ and VULCUP^™ trade names from the Lucidol division of Pennwalt Corp and Herculues Incorporated, respectively. For the purposes of this invention and the claims thereto, the tern substantial absence means that the peroxide or other free radical generating initiator is present at less than 0.5 weight percent, based upon the weight of the copolymer, preferably at 0.1 weight percent, even more preferably less than 0.05 weight percent, even more preferably less than 0 01 weight percent. In a particularly preferred emDodiment the free radical generating initiator is not present. Likewise, in another emoodiment this invention is practiced with neat polyolefins and/or unstabilized polyolefins. For Durposes of tnis invention and the claims thereto, a neat polyolefin is a polyolefin that nas nad no additives or additive packages combined with the polymer prior to the treatment with the reactive co-agent. Likewise, an unstabilized polyolefin is a polyolefin that may have one or more additives combined therein but none of which compete for the free radicals along the backbone of the polymer being modified. When additives are included in the blend that do compete for the free radicals on the polymer backbone, one should compensate for the effect. For example, one might compensate for the presence of peroxide by adding more of the reactive co-agent.

Likewise one might compensate for the presence of an antioxidant by adding more of the reactive co-agent and increasing the heat and/or shear to promote the formation of free radicals. Examples of non-competitive additives include well known fillers such as silica, oil, talc, carbon black and the like.

This invention may also be practiced with

commercially available polymer that have had additive packages, such as stabilization packages, blended in. One must consider the effect of additives, however when choosing the amount of reactive co-agent to use.

Inclusion of commercial free radical -scavenging

antioxidants, such as IRGANOX^™ IR1010 or IRGANOX™ IR1076, available from Ciba-Geigy will likely tend to compete wi th the react ive co- agents modif iers for react ion with the free radicals, as induced by heat or irradiation or some other action, of the base polymer chains. Therefore the effectiveness of the reactive co-agents as chain- extending agents may be diminished. Preferably, the modification will be made and the reaction will be completed prior to the inclusion of anti-oxidants. If antioxidants are added prior to completion of the

reactive co-agent- induced chain-extension, then more than the small amounts of reactive co-agents may be needed to accomplish the desired ends. In a preferred embodiment the antioxidant is added after the reaction of the polyolefin with the reactive co-agent.

The reactive co-agent may be used alone or in combination with another reactive co-agent and the reactive co-agent (s) is typically used in amounts as small as 10 parts per million (ppm) up to amounts of 750 ppm based upon the weight of the copolymer. In a preferred embodiment the reactive co-agent is used in amounts of 100 ppm to 600ppm, based upon the weight of the copolymer, preferably from 200 ppm to 550 ppm.

The polyolefin and the reactive co-agent may be combined by any method known in the art, however melt blending techniques are preferred. Any extruder can be used to combine the polyolefin and the reactive co-agent. In a preferred embodiment the polymer is heated to a temperature high enough to melt the polymer or more and subjected to shear. The reactive co-agent may be added after the polymer has been heated and subjected to shear or may be added at any point prior to or after that .

Once the polymer and the reactive co- agent are combined the heat and shearing stresses are preferably maintained but may be increased, decreased or stopped altogether as desired. Typical temperatures that will for melt

blending the polymer and the reactive co-agent include those temperatures above the polyolefin's melting

temperature (as measured by differential scanning

calorimetry, second peak, heat rate of 5°C/mιn),

preferably those temperatures at or above 150º C,

preferably at or above 200º C, even more preferably at: or above 230 °C, even more preferably at or above 250 °C, even more preferably at or above 270 °C. In a preferred embodiment the polyolefin is heated to a molten state, subjected to shear and combined with the reactive co- agent.

Furthermore, typical shear rates for the known blending and extrusion machines are useful in the

practice of this invention. In particular, a preferred shear rate is aoout 50 sec^-1 or greater, preferably about 100 sec^-1 or σreater. One of many non-limiting examples of how to combine the polymer and the reactive co-agent is, in a Brabender extruder, heating a linear low density ethylene-butene copolymer having a density of about 0.918 to about 0.92 g/cm³ to a temperature of 230ºC or more and subjecting the heated polymer before, during and/or after heating, to a shear rate of 50 sec^-1or more. Thereafter blending between 10 ppm to 2 weight % of tetrahydrofurfuryl methacrylate, trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate), and/or tetraethylene glycol dimethacrylate into the molten polyolefin.

One of the substantial benefits of this invention is that the melt index of the polyolefin (as measured by ASTM 1238, condition D) is decreased by at least 10 %, preferably by at least 15 %, even more preferably at least 20 % as compared to the same polyolefin prior to modification.

Likewise this method modifies the polymer so as to improve processability, as measured by MI for example, without substantially increasing specific energy

consumption (power/kg/hr). Specific energy consumption is a measure of the force needed to push the polymer through a machine Thus a reduction in energy consumption is desirable, while maintaining the polymer's melt strength and other melt properties. In a preferred embodiment the energy consumption in a given system for a given

polyolefin not substantially increased, more preferably the specific energy consumption is reduced by 20% or more, preferably reduced by 30% or more, preferably by 40% or more. Without wishing to be bound by theory, it is believed that the modified polyolefins exhibit reduced shear viscosity at typical extrusion-processing shear rates thereby reducing specific energy consumption.

Furthermore, as added benefit, the number and size of gels in films and molded articles made from polyolefin modified as disclosed herein is significantly reduced. In a preferred embodiment the number of gels of the size of 0.1mm² or less is 75 or less per square meter of film, even more preferably 50 or less, even more preferably 40 or less. Gel measurements are taken using an on-line flow-vision camera. This camera scans the film surface at 2,000 lines per second and each measurement includes eleven scanned intervals of 500 cm each.

Additionally the reactive co-agents also appear to serve as anti-oxidants by efficiently scavenging alkyl or alkoxy radicals which may be formed in the polyolefin polymer upon mild oxidation or oxidative chain scission. The reactive co-agents of this invention, therefore, appear to be effective anti-oxidants which will stabilize the polymer resin against oxidation and prevent or minimize the typical discoloration or yellowing which accompanies such oxidative degradation

Likewise the modified polymers of this invention show enhanced physical properties compared to peroxide treated polyolefins. When a polyolefin is treated with a

peroxide the strength of that polyolefin is typically reduced in the transverse direction (TD) while the

physical properties in the machine direction (MD) are not as severely affected. In the practice of this invention, however the reactive co-agent modified polyolefins do not exhibit the same loss of properties. In fact the MD and TD strength properties of the modified polyolefin are comparable to the properties of the polymer prior to modification with the reactive co-agent

The modified polymers of this invention can be used in any typical extrusion, molding, spinning, film forming or other application. For example one can blow or cast films of the modified polymer. Preferred processes include extrusion, film casting, film blowing, melt spinning, injection molding, melt blowing or combinations thereof. Useful articles will include extrudates, pellets, films, and fibers including strands, webs and filaments.

Branching

Another benefit of this invention is that it may be used to cause chain extension, otherwise called long chain branching in a polyolefin by blending the polymer and the reactive co- agent under conditions of heat and/or shear as described above. One may determine the level of long chain branching introduced by this method by determining the affect on the radius of gyration. By substituting the intrinsic viscosity and weight average molecular weight data of the polymer prior to

modification and the polymer after modification into the following equation on can determine the affect on the radius of gyration:

[η₁]/[η₂] = (R_Θ12)^3/2/(R_Θ22)^3/2 (MW²/MW¹)

such that [η] is the intrinsic viscosity, Mw is the average molecular weight and the subscripts 1 and 2 designate the unmodified polymer and the modified polymer respectively and R_Θ is the radius of gyration of the coil in the Θ state.

Intrinsic viscosity numbers are determined according to well- known techniques such as that described by P. A. Lovell in

"Dilute Solution Viscometry", Comprehensive Polymer Science, C. Booth & C. Price, ed., Pergamon, vol. 1, pg, 173 (1989). The viscosity numbers measured herein were measured with a

Ubbelohde viscometer with a 0.46 mm capillary; the viscometer was placed in an oil bath maintained at 135°C +0.1°. The solvent used was trichlorobenzene (TCB).

The average molecular weight is determined by gel

permeation chromatography using a low-angle LASER light

scattering detector (GPC-LALLS). These measurements are obtained by the general methods as described by W.W. Yaw, et al., Modern Size-Exclusion Liquid Chromatography, Wiley

Interscience, John Wiley & Sons, New York (Page 156 +) and J. Mitchell, ed., Applied Polymer Analysis and Characterization, Hanser Publishers, New York (page 260+) . The measurements made herein were made using a Waters 150 °C instrument, 4 Shodex column, with trichlorobenzene as the solvent using a Wyatt LALLS detector. Chain extentsion or long chain brancning will cause a net reduction in the radius of gyration.

An example calculating the values follows:

Two samples were tested for intrinsic viscosity numbers and Mw under the procedures described above. Sample A is neat Polymer A as described below. Sample C is Polymer A blended with 2500 ppm of ATM 3 at 250 ºC and 50 rpm and extruded three times in the extruder described in the Examples below. Sample A has an intrinsic viscosity of 107.5 cm³/g and an Mw of 69,700. Sample C has an intrinsic viscosity of 96.7 cm³/g and an Mw of 73,100. By substituting the intrinsic viscosity and weight average molecular weight data into the previous equation the following (R_Θ1 )/(R_Θ2) values were obtained: Sample A/Sample C = 1.02.

Since the value is greater than 1, it indicates the presence of long chain branching. In a preferred embodiment the (R_Θ2 )/(R_Θ2) is greater than or equal to 1.01, more preferably greater than or equal to 1.015, even more preferably greater than or equal to 1.02, even more preferably greater than or equal to 1.025 In addition, shear thinning behavior of the modified polyolefin as compared to the neat polymer is also evidence of long chain branching being present.

Another property helpful in determining the presence of long chain branching is tne activation energy of flow

(Ea) . The Ea for a given polyolefin modified according to this invention is higher than the Ea for the

unmodified polyolefin In a preferred embodiment the Ea of the modified polymer is 5% or more higher than the Ea of tne unmodified polymer, preferably 10 % or more

higher, even more preferably 20% or more higher, even

more preferably 30 % or more higher. Ea is preferabLy

measured by the procedure set out in Polym. Eng. & Sci.

mid-Dec. 1992, Vol. 32, no 23 page 1778 - 1791.

Although, since the Ea values are relative to eacn other for the modified and unmodified polymer, any method to

measure Ea may oe used as long as tne same method is jsed for both polymers. Examples

Five different compounds were used in this series of experiments, they were:

1. tetrahydrofurfuryl methacrylate (ATM 1);

2. trimethylolpropane trimethacrylate (ATM 11);

3. ethylene glycol dimethacrylate (ATM 3 );

4. tetraethylene glycol dimethacrylate (ATM 4); and

5. triallyl cyanurate (TAC).

The polymers used were:

Polymer A is neat ESCORENE LL 3003™, An ethylene-hexene copolymer having a melt index (MI) of 3.2 and a density of 0.9175 g/cm³.

Polymer B is ESCORENE LL 3001™ an ethylene-hexene copolymer having an MI of 1 g/10 min and a density of

0.917 g/cm³.

Polymer C is ECD 103™ an ethylene-hexene copolymer having a Mw/Mn of less than 3, an MI of 1.2 g/10 min and a density of about 0.917 to about 0.918 g/cm³, and 2.75 mole % hexene.

Polymer D is ESCORENE LL 1001 XV™ an ethylene-butene copolymer having an MI=1 g/10 min and density = 0.91B g/cm³ stabilized with 800 ppm of IRGAFOS 168™, 200 ppm of

IRGANOX 1076™, 200 ppm of polyethylene glycol and 500 ppm of zinc sterate.

Polymer E is ESCORENE LL 6301RQ™ an ethylene-butene ccpolymer having an MI= 5 g/10 min and density = 0.935 g/cm³ stabilized with 200 ppm of IRGANOX 1076™.

Polymer F is ESCORENE LL 1002 XV™ an ethylene-butene copolymer having an MI= 2 g/10 min and density = 0.918 g/cm³ stabilized with 800 ppm of IRGAFOS 168™, 200 ppm of

IRGANOX 1076™, 200 ppm of polyethylene glycol and 500 ppm of zinc sterate.

Polymer G is ESCORENE LL 1004RQ™ an ethylene-butene copolymer having an MI= 2.8 g/10 min and density = 0.913 g/cm³ stabilized with 200 ppm of IRGANOX 1076™.

Polymer H is ESCORENE LL 1030XV^™ which is a linear low density polyethylene copolymer of ethylene and butene having an MI of 0.5 g/10 min and a density of 0.918 g/cm² stabilized with 800 ppm of IRGAFOS 168™, 200 ppm of

IRGANOX 1076™, 200 ppm of polyethylene glycol and 500 ppm of zinc sterate.

Polymer I is an LLDPE copolymer of ethylene and 3.2 mole

% of hexene, having an MI of 0.8 g/10 min and a density of 0.924 g/cm³.

Polymer J is an ethylene/hexene copolymer having 3.3 mole

% hexene, an MI of 3.2 g/10 min, an MWD of less than 3, and a density of 0.917 g/cm³.

Polymer K is an ethylene hexene copolymer having an MI of

2.8 g/ 10 min and a density of 0.918 g/cm³.

TRIG B is TRIGANOX B™ (di-tert-butyl-peroxide), a commercially available peroxide sold by AKZO Chemicals.

B900 is a mixture of IRGANOX 1076™ and IRGAFOS 168™ in a

1:4 ratio, typically used at 800ppm in the examples.

IRGANOX 1010™ is tetrakis [methylene (3, 5-di-t-butyl-4- hydroxyhydrocinnamate)] methane.

IRGANOX 1076™ is octadecyl-3,5-di-t-butyl-4-hydroxy cinnamate.

Example 1

Five 500 gram samples of Polymer A were melt blended at 250-255-255-260°C at 80 rpm in Brabender Plasticorder PL 2000 with one of 4 different reactive co-agents or a comparative agent and then subjected to multiple

extrusion passes through a Brabender Plasticorder PL 2000 laboratory single-screw extruder with a 25/1 L/D ratio and compression ratio of 4/1. The screw also includes a mixing zone. The extruder has 3 heating zones and was fitted with a round capillary die a diameter of 3 mm; made by Brabender in Duisburg, Germany. Melt index (MI) measurements were carried out with a Davenport Solo 2 melt indexer available from Daventest, Welwyn Garden City, England according to ASTM D-1238 using a preextrusion weight with a mass of 2.16 kg, pre-extrusion time of five minutes, with the barrel temperature set at 190°C, and a cut-off time cf one minute. The conditions and data are reported in Table 1

Table 1

MI = melt index (g/10 min)

The co-agents were added as liquid to the polymer in granular form and tumble blended for five minutes prior to being introduced into the extruder feed. The amount of each added was determined in a manner such that the number of methacrylate end groups present were equivalent among all test samples. A neat sample of Polymer A was run as a control.

Example 2

The procedure of experiment 1 was repeated with, except as noted. The data are reported in table 2.

Example 3

500 grams of Polymer B or Polymer C were blended as described in example 1 with 1,000 ppm of ATM 11 and extruded in pellet form from a Brabender single screw laboratory extruder, with a temperature profile of 250°C - 255°C - 255° - 260°C. Polymer without ATM 11 was run as a control. The melt tensile strength was measured using a Göttfert Rheograph 2002 capillary rheometer, having a capillary L/D ratio of 30/2 coupled with a Rheotens.

These measurements were made at 170°C with steady piston speed (0.915 mm/sec.) and extrusion at a temperature of 170°C. Samples of the neat polymer were also extruded as a control. The results are reported in Table 3 for samples extruded at both 40 and 80 rpm using the

Brabender single-screw laboratory extruder The melt Tensile strengths were recorded with the Rheotens at an elongation ratio of 8. (Polymer C had a melt tensile strength of 4.4 CN with 0 ppm of ATM 11 and 7.2 CN with 1000 ppm of ATM 11.)

Example 4

Polymers C and E were blended with additives and different amounts of ATM 11 and then cast into films using a Collins film casting line with an L/D ratio of 25/1 and a compression ratio of 3/1 under a temperature profile of 160°C-170ºC-180ºC-210ºC-230°C-230ºC-230ºC-230°C with a screw speed of 60 rpm. Gel measurements were taken using an on-line flow-vision camera This camera scanned the film surface at 2,000 lines per second. Each measurement includes eleven scanned intervals of 500 cm each The data and test conditions appear in Table 4 N* = number of gels per square meter, #long gels = the number of gels per square meter 1 cm or longer and 0 2 mm wide or wider, a = first run; b = second run.

Example 5

500 gram samples of neat Polymer B and Polymer B were blended with 1,000 ppm of ATM 11 in a Brabender

Plasticorder PL 2000 laboratory mixer 200 °C and 50 rpm under nitrogen. Additionally 1,000 ppm of an inert

mineral oil, Marcol 82 as obtained from Exxon Chemical

Europe, was added to another sample of Polymer B. ATM 11 has a Mw of 338.4 and viscosity at 25°C of 40 cSt. The

Marcol 62, having Mw of 360 and viscosity of 36 cSt at 20 °C was thought to be a reasonable non-reactive match for the ATM 11. Torque was measured at 200°C while mixing at 50 rpm under nitrogen in the Brabender mixer. Table 5

displays the three-way comparison.

Example 6

Three 50 gram samples of Polymer B and varying

concentrations of ATM 11 were mixed in the Brabender described above for six minutes at SC rpm and at 270°C, under nitrogen or oxygen-containing atmospheres. The data are reported in Table 6

Example 7

Polymers C, G and F were blended with peroxide or ATM 11, formed into films following the procedure described above and tested and tested for physical properties according to the following tests:

1. Elmendorf Tear Strength (both machine and transverse directions) was tested according to ASTM 1922. (The specimen is held on one side by a pendulum and on the other side by a stationary member. The pendulum swings through an arc tearing the specimen from a precut slit. The loss in energy by the pendulum is indicated by a pointer on a scale of 0 to 100. The instrument is a 1600 gforce instrument.);

2. Shrinkage was tested on a Shrinkage Tester Betex a temperature of 150 °C on samples of 5 cm diameter disks of polymer molten on a silicon oil layer on top of an aluminum plate, the shrinkage ratio is the final dimension in the transverse direction divided by the final dimension in the machine direction); and

3. DYNA impact was measured according to DIN 53373. (sample holder = 40 mm diameter, velocity of 4.5 m/s as sample strikes hemisphere. The results are reported in Tables 7a- 7c.

Example 8

Table 8, below, presents comparison of specific energy consumption of Polymer C, Polymer C + 250 ppm ATM 11, and Polymer H blended in the brabender described above at 250-255-255-260 °C at 80 rpm then cast on a Collins film casting line under a temperature profile of 160-170-180-210-230-230-230-230 °C with a screw speed of 65 rpm as described above.

Example 9.

Polymer J, Polymer K and Polymer G were extruded upon a Leistritz twin screw extruder having an 1/d ratio of 36 and a die diameter of 34mm . The barrell temperature ran through ten zones beginning at about 170 ºC and ending at about 260 °C. The extrusion conditions and the data are reported in Table 9.

All polymers had 800ppm of B900. Polymers marked with the # sign also had 750 ppm of Carbowax 3400. Polymers marked with the * sign also had the antioxidant added at the vent zone. Polymers with no * had the antioxidant aided at the hopper. Polymer G was used neat without the 200 ppm of IRGANOX 1076 mentioned in the definition of polymer G above. "TM" = Thermal modification occurs when the unstabilized resin is heated and exposed to shear causing chain scission and free radical generation.

Films were made from the samples by film blowing using a Doln line Film blowing line consisting of a single screw extruder (60 mm diameter, 1/d = 20, temp. 160-180 °C.) Haze of the film was measured according to ASTM D 1003. Gloss of the film was measured according Lo ASTM D 2457 at 60°. Blocking Force was measured according to ASTM D 3354. MD and TD tear strength were measured according to ASTM 1822. Dart drop impact strength was measured according to DIN 53373

Example 10

Polymer C was combined with 500 ppm of ATM 11 in a pilot scale Werner and Pfeiderer twin screw extruder at a melt temperature of 290 °C and having an 1/d of 20 and 5 barrel. Polymer I was not combined with any modifiers but was otherwise treated the same . Films were blown from the sample prepared as in example 9. The samples were tested for blocking force according to ASTM D 3354. The data are reported in Table 10.

Another advantage to the invention described herein is that it also has the benefit of reducing blocking force, even in the absence of anti -block agents, typically by at least 30 %, even more preferably by about 50 % or more.

For the purposes of U.S. law all references, testing procedures and priority documents are incorporated by reference herein. As is apparent from the foregoing general description and the specific embodiments, while forms of the invention have been illustrated and

described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited thereby.

Claims

1. A process for providing an olefin polymer coposition having improved melt processing which comprises:

a) subjecting an olefin polymer to heat and/or shear b) contacting the olefin polymer, in the substantial absence of a free radical generating initiator, with a reactive co-agent having at least two functional groups capable of irreversibly reacting with free radicals on the polymer backbone, and

2. The process of claim 1 wherein a film formed of the modified olefin polymer has 75 or less gels of a size less than 0.1 mm² per square meter of film.

3. The method of claim 1 or 2 wherein the free radical generating initiator is present at less than 0.01 weight percent base dupon the weight of the copolymer.

4. The method of any of the avbove claims wherein the free radical generating initiator is not present.

5. The process of any of the above claims wherein the reactive co-agent is present at an amount of 10 ppm to 750 ppm, based upon the weight of the copolymer.

6. The process of any of the above claims wherein the reactive co-agent is present at an amount of 100 ppm to 600 ppm, based upon the weight of the copolymer.

7. The process of any of the above claims wherein the olefin polymer is an ethylene homopolymer or copolymer, preferably a copolymer of ethylene and a linear , cyclic or branched C₃ to C₂₀ α-olefin.

6. The process of any of the above claims wherein the olefin polymer has an Mw/ Mn of 4 or less and/or has a composition distribution breadth index of 60% or greater.

9. The process of any of the above claims wherein the olefin polymer has a composition distribution breadth index of 70% or greater, and a density between 0.901 and 0.92 g/cm³.

10. The process of any of the above claims wherein the reactive co-agent is an electrophilic composition that is more reactive with the free radicals on the polymer backbone than the polymer backbone is reactive with the free radicals on the backbone.

11. The process of any of the above claims wherein the reactive co-agent has three functional groups capable of irreversibly reacting with free radicals on the polymer backbone.

12. The process of any of claims 1 to 9 wherein the reactive co-agent is an acrylic acid, an ester of an acrylic acid, a C₁ -C₃₀alkyl acrylic acid, such as methacrylic acid, ethacrylic acid, an ester of a C₁ - C₃₀alkyl acrylic acid, and/or an allyl containing

composition.

13. The process of claim 1 or 2 wherein the reactive coagent is one or more of trimethylolpropane

trimethacrylate, ethylene glycol dimethacrylate,

polyethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, triallyl cyanurate, norbornadiene, pentadiene, hexadiene, 1,3- butylene glycoldimeth- acrylate, 1, 6-hexanediol diacrylate, tripropylene glycol diacrylate, trimethyolpropane-triacrylate, allyl

methacrylate, or allyl methacrylate.

14. The process of any of the above claims wherein the modified polyolefin has a (R_Θ1)/(R_Θ2) greater than 1.

15. The use of a reactive co-agent to reduce the number of gels in a polyolefin film.

16 . The use of a reactive co -agent to increase the Ea of a polyolefin.

17. The use of a reactive co-agent to increase the melt processability and/or melt strength of a polyolefin.

19. A method to introduce branching into a polyolefin comprising combing the polyolefin with a reactive coagent under conditions of heat and/or shear.

20. A method to provide a polymer composition having a decreased melt index comprising:

a) subjecting an olefin polymer to heat and/or shear, b) contacting the olefin polymer, in the substantial absence of a free radical generating initiator, with a reactive co-agent having at least two functional groups capable of irreversibly reacting with free radicals on the polymer backbone, and

21. A method to reduce blocking force in a polyolefin film comprising:

a) subjecting an olefin polymer to heat and/or shear, b) contacting the olefin polymer, in the substantial absence of a free radical generating initiator, with a reactive co-agent having at least two functional groups capable of irreversibly reacting with free radicals on the polymer backbone,

c) obtaining an olefin polymer with a melt index at least 10 % below that of the starting polymer; and d) forming a film from the olefin polymer obtained in step c) .