Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G81/00—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers
  • C08G81/02—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers at least one of the polymers being obtained by reactions involving only carbon-to-carbon unsaturated bonds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/04—Homopolymers or copolymers of ethene
  • C08L23/06—Polyethene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/04—Homopolymers or copolymers of ethene
  • C08L23/08—Copolymers of ethene
  • C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing four or more carbon atoms
  • C08L23/0815—Copolymers of ethene with unsaturated hydrocarbons only containing four or more carbon atoms with aliphatic 1-olefins containing one carbon-to-carbon double bond
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
  • C08L2666/02—Organic macromolecular compounds, natural resins, waxes or and bituminous materials
  • C08L2666/04—Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof

Definitions

• the subject invention pertains to heteromorphic olefin polymers.
• the subject invention pertains to olefin polymers comprising a homogeneously branched linear or substantially linear ethylene/ ⁇ -olefin interpolymer backbone, and a higher density ethylene homopolymer or ethylene/ ⁇ -olefin interpolymer long chain branch appending from the interpolymer backbone.
• Homogeneous ethylene/ ⁇ -olefin interpolymers are characterized by narrow molecular weight distributions and narrow short-chain branching distributions. Further, homogeneous ethylene interpolymers containing long-chain branches, known as "substantially linear" ethylene polymers, are disclosed and claimed in U.S. 5,272,236 and in U.S. 5,278,272.
• homogeneous linear and substantially linear ethylene polymers lack the highly linear fraction characteristic of heterogeneously branched polyethylene (and thus the high crystalline melting peak), homogeneous linear and substantially linear ethylene polymers tend to have a poorer high temperature resistance, especially when the polymer density is less than 0.920 g/crn ⁇ , than heterogeneously branched polymers of the same density.
• homogeneous linear and substantially linear elastomers may lose their strength at 60°C or less. This has been attributed to the fact that such low density polymers have a molecular structure which is characterized by the presence of fringed micelles, and typically lacks higher melting point lamellar structures. While the differential is less pronounced, even higher density homogeneous linear and substantially linear ethylene polymers which have lamellae structures, generally melt at lower temperatures than their heterogeneously branched counterparts. Regardless of polymerization catalyst, polyethylenes face a practical use limitation above their crystalline melting point, which does not exceed approximately 140°C.
• U.S. Patent No. 5,530,072 discloses polymers exhibiting long chain branching formed by self-grafting a linear polyethylene using a free radical initiator. While such self-grafting serves to increase the molecular weight of the polyethylene and to improve the melt strength, it does not affect the crystallinity of the polyethylene, and thus does not affect the high temperature resistance of the polyethylene.
• U.S. Patent No. 5,346,963 discloses graft modified substantially linear ethylene polymers, which are optionally blended with thermoplastic polymers, such as high density polyethylene, linear low density polyethylene, and low density polyethylene.
• Such enhanced high temperature performance may show advantage, for instance, in shoe soles which better withstand the heat of a clothes dryer.
• such enhanced high temperature performance may show advantage, for instance, in pressure sensitive adhesives which exhibit reduced creep resistance.
• polymer means a compound prepared by polymerizing monomers, whether of the same or a different type.
• the generic term polymer thus embraces the term “homopolymer”, usually employed to refer to polymers prepared from only one type of monomer, and the term “inte ⁇ olymer”, as defined hereinafter.
• inte ⁇ olymer means polymers prepared by the polymerization of at least two different types of monomers.
• the generic term “inte ⁇ olymer” thus includes the term “copolymers”, which is usually employed to refer to polymers prepared from two different monomers, as well as to polymers prepared from more than two different types of monomers.
• the subject invention is in a unique polymer composition
• a unique polymer composition comprising: (A) a homogeneous linear or substantially linear ethylene/ ⁇ -olefin inte ⁇ olymer backbone; and (B) an ethylene homopolymer or an ethylene/ ⁇ -olefin inte ⁇ olymer which is appended from the inte ⁇ olymer backbone and which has a density which is at least 0.004 g/cm 3 greater than that of the first inte ⁇ olymer backbone.
• Such polymer compositions will resist deformation under high temperatures better than a comparative physical blend or in-reactor blend of the first and second inte ⁇ olymers.
• the material science principle used to improve the high temperature performance of homogeneous linear or substantially linear elastomers is illustrated in Figure 1.
• the elastomer acts as a soft segment to provide flexibility at room temperature of the heteromo ⁇ hic polymer composition.
• the branch may have many forms, of which certain exemplary forms are as shown in Figure 2.
• Figure 2-1 shows a substantially linear copolymer backbone with three different forms of connection of the polymer branch.
• Figure 2- 1(a) illustrates the branch resulting from an "H-link" with the backbone polymer. This could, for example, be introduced by randomly crosslinking the backbone polymer and the precursor polymer to the heteromo ⁇ hic long chain branch.
• Figure 2- 1 (b) illustrates a long-chain branch linking to the backbone polymer at two (or more) positions.
• Figure 2- 1(c) illustrates the formation of a "T" with the backbone polymer. This could, for example, result from grafting a reactive endgroup of a heteromo ⁇ hic long-chain branch precursor polymer with the backbone polymer, or could result from copolymerization of a reactive endgroup such as vinyl with the monomers during polymerization of the backbone polymer (in this case, of course, the "backbone polymer” is just a concept and is not substantially present in pure form).
• Figures 2-2 illustrates an example of the variation where a linear copolymer (2-2) backbone polymer has "T" type heteromo ⁇ hic long-chain branches such as resulting from copolymerization or grafted endgroups.
• the ethylene/ ⁇ -olefin inte ⁇ olymer (A) which constitutes the backbone of the heteromo ⁇ hic olefin polymer of the invention will be either a homogeneous linear or substantially linear ethylene/ ⁇ -olefin inte ⁇ olymer, both of which are described in greater detail below.
• the density of the backbone polymer depends on the type and amount of comonomer used.
• the density may be controlled according to methods known to those skilled in the art, in order to control the softness of the polymer over the range from highly amo ⁇ hous, elastomeric grades to highly crystalline, nonelastomeric grades.
• the choice of backbone polymer density will depend on the requirements of each application according to the performance requirements known to those skilled in the art. Typically, however, the density of the backbone polymer will be less than 0.920 g/cm 3 , preferably less than 0.900 g/cm 3 , more preferably less than 0.880 g/cm 3 .
• the density of the backbone polymer will be less than 0.870 g/cm 3 , preferably less than 0.865 g/cm 3 , with densities as low as 0.850 g/cm 3 being achievable.
• the molecular weight of the backbone polymer may likewise vary according to each system.
• the branch polymer When the branch polymer is attached to the backbone polymer by crosslinking or grafting, it may be preferred to reduce the molecular weight of the backbone inte ⁇ olymer to reduce gelation, particularly if the branch polymer is high molecular weight or multifunctional in reactive sites. It is an aspect of this invention that excellent physical properties may be obtained even with relatively low molecular weight backbone polymers due to the optimized connectivity afforded by the heteromo ⁇ hic character of the compositions of the invention. Thus, it is possible to obtain good physical properties and good processability simultaneously.
• the backbone polymer will have a melt index (I 2 ) of from 0.01 to 10,000 g/10 min., and preferably from 0.01 to 1,000 g/10 min. Especially preferred melt indices are greater than 10 g/10 min., more preferably greater than 20 g/10 min. Note that for low molecular weight polymers, that is, polymers having a melt index greater than 1000 g/10 min., molecular weight may be indicated rather by measuring the melt viscosity of the polymer at 350°F. The melt viscosities at 350°F of polymers having melt indices of 1000 g/10 min. and 10,000 g/ 10 min., as measured by the technique set forth in the Test Procedures section below, are approximately 8200 and 600 centipoise respectively.
• the branch polymer (B) which appends from polymer backbone (A) may be any polymer that can be copolymerized with the monomers during production of the backbone polymer, or that may be grafted or crosslinked with the backbone polymer, and that has a density which is at least 0.004 g/cm 3 , preferably at least 0.006 g/cm 3 , more preferably at least 0.01 g/cm 3 greater than that of the backbone polymer.
• the branch polymer (B), in its pure state will have a glass transition temperature (Tg) or crystalline melting point (Tm) which is at least 10°C, preferably 20°C, and most preferably at least 50°C higher than the Tg or Tm (whichever is higher) of the backbone polymer in its pure state.
• Tg glass transition temperature
• Tm crystalline melting point
• the term "grafting” means linking one endgroup of the branch polymer to the backbone polymer
• crosslinking means, in a limited fashion, connecting via one or more linkages elsewhere along the long-chain branch precursor (that is, not an endgroup) to form the heteromo ⁇ hic long chain branched composition rather than a crosslinked network.
• heteromo ⁇ hic long-chain branch materials include heterogeneously and homogeneously branched linear ethylene homopolymers and ethylene/ ⁇ -olefin inte ⁇ olymers, as well as substantially linear ethylene homopolymers and ethylene/ ⁇ -olefm inte ⁇ olymers, each of which is described in more detail below.
• Such branch polymers may further optionally be functionalized.
• a suitable branch polymer for one backbone polymer might not be suitable for another backbone polymer.
• a suitable branch polymer for a homogeneous linear or substantially linear ethylene/octene inte ⁇ olymer having a density of 0.865 g/cm 3 would be an ethylene/octene inte ⁇ olymer having a density of 0.900 g/cm 3 .
• the same branch polymer would not be suitable for use in conjunction with a polymer backbone which is a homogeneous linear or substantially linear ethylene/octene inte ⁇ olymer having a density of 0.920 g/cm 3 , as the Tm of the former is not at least 10°C greater than the Tm bf the latter (and in fact is significantly lower).
• the heteromo ⁇ hic long-chain branch will further be of sufficient molecular weight to be able to cocrystallize or form a phase with other branch polymer molecules or additionally added polymer.
• the heteromo ⁇ hic long-chain branch will have a weight average molecular weight (M w ) of at least 1000, preferably at least 3000, as measured in accordance with the procedure set forth in the Test Methods section below.
• the amount of backbone polymer should be sufficient to make it the continuous or co-continuous phase in the mixture of backbone polymer and heteromo ⁇ hic long-chain branch polymer.
• the ratio by weight of backbone polymer to branch polymer will generally be greater than 1 :3, preferably at least 1 :2, and most preferably greater than 1 :1.
• the optimum ratio will vary with application and resultant changes in preferences for elastomer properties, high temperature properties, modulus/stiffness, etc.
• the average number of heteromo ⁇ hic long chain branches per polymer backbone molecule will be sufficient to provide to the final polymer composition an improvement in temperature resistance as measured by RSA and/or an improvement in tensile strength that is greater than that provided by a simple physical blend of comparable polymers without copolymerization, grafting, or crosslinking.
• the compositions of the invention will exhibit a temperature resistance as measured by RSA of at least 10°C, preferably at least 15°C greater than that of a physical blend of comparable polymers.
• compositions of the invention will exhibit an ultimate tensile strength which is at least 70 percent that of the physical blend of comparable polymers, more preferably at least 85 percent, most preferably which equals or exceeds that of the physical blend of comparable polymers, with ultimate tensile strengths which are 120 percent of the physical blend of comparable polymers being easily attained.
• the composition of the invention will preferably exhibit a percent elongation which is at least 40 percent, more preferably which is at least 50 percent, even more preferably which is at least 60 percent that of the blend of comparable polymers, with compositions exhibiting percent elongations which equal or exceed that of the comparable blend being easily achieved.
• the ethylene polymers useful as the polymer backbone (A) and the heteromo ⁇ hic long chain branch (B) can independently be inte ⁇ olymers of ethylene and at least one ⁇ -olefin.
• Suitable ⁇ -olefins are represented by the following formula:
• R is a hydrocarbyl radical.
• the comonomers which form a part of backbone polymer (A) may be the same as or different from the comonomers which form the heteromo ⁇ hic long chain branch (B).
• R generally has from one to twenty carbon atoms.
• Suitable ⁇ -olefins for use as comonomers in a solution, gas phase or slurry polymerization process or combinations thereof include the C 3 -C 20 ⁇ -olefins, styrene, tetrafluoroethylene, vinyl benzocyclobutane, 1 ,4-hexadiene, 1 ,7-octadiene, and cycloalkenes, for example cyclopentene, cyclohexene, cyclooctene, norbomene (NB), and ethylidene norbomene (ENB).
• Preferred C 3 -C 20 ⁇ -olefins include 1-propylene, 1-butene, 1 -isobutylene, 1- pentene, 1-hexene, 4-methyl-l-pentene, 1-heptene and 1-octene, as well as other monomer types such as).
• the ⁇ -olefin will be 1-butene, 1-pentene, 4- methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, NB or ENB, or mixtures thereof. More preferably, the ⁇ -olefin will be 1-hexene, 1-heptene, 1-octene, or mixtures thereof. Most preferably, the ⁇ -olefin will be 1-octene.
• Ethylene/ ⁇ -olefin/diene te ⁇ olymers may also be used as elastomeric polymers in this invention.
• Suitable ⁇ -olefins include the ⁇ -olefins described above as suitable for making ethylene ⁇ -olefin copolymers.
• the dienes suitable as monomers for the preparation of such te ⁇ olymers are typically non-conjugated dienes having from 6 to 15 carbon atoms.
• suitable non-conjugated dienes that may be used to prepare the te ⁇ olymer include:
• branched chain acyclic dienes such as 5-methyl-l, 4-hexadiene, 3,7- dimethyl-l-6-octadiene, and 3,7-dimethyl-l,7-octadiene, and 1,9- decadiene;
• multi-ring alicyclic fused and bridged ring dienes such as dicyclopentadiene; alkenyl, alkylidene, cycloalkenyl and cycloalkylidene norbomenes such as 5-methylene-2-norbornene, 5- methylene-6-methyl-2-norbornene, 5-methylene-6, 6-dimethyl-2- norbomene, 5-propenyl-2-norbornene, 5-(3-cyclopentenyl)-2- norbomene, 5-ethylidene-2-norbornene, 5-cyclohexylidene-2- norbomene, etc.
• the preferred dienes are selected from the group consisting of 1 ,4-hexadiene, dicyclopentadiene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 7-methyl- 1, 6-octadiene, 4-vinylcyclohexene, etc.
• a suitable conjugated diene is piperylene.
• the preferred te ⁇ olymers for the practice of the invention are te ⁇ olymers of ethylene, propylene and a non-conjugated diene (EPDM). Such te ⁇ olymers are commercially available.
• the homogeneous polyethylenes that can be used as components (A) and (B) of this invention fall into two broad categories, the linear homogeneous polyethylenes and the substantially linear homogeneous polyethylenes. Both are known.
• Homogeneous polymers are ethylene inte ⁇ olymers in which any comonomer is randomly distributed within a given inte ⁇ olymer molecule and substantially all of the inte ⁇ olymer molecules have the same ethylene/comonomer ratio within that inte ⁇ olymer.
• Homogeneous polymers generally are characterized as having a single melting peak between -30°C and 150°C, as determined by differential scanning calorimetry (DSC). The single melting peak is determined using a differential scanning calorimeter standardized with indium and deionized water. The method involves 3-7 mg sample sizes, a "first heat" to about 180°C which is held for 4 minutes, a cool down at 10°C/min.
• the single melting peak may show, depending on equipment sensitivity, a "shoulder or a "hump" on the low melting side that constitutes less than 12 percent, typically, less than 9 percent, and more typically less than 6 percent of the total heat of fusion of the polymer.
• Such an artifact is also observable for homogeneous linear polymers such as ExactTM resins (available from Exxon Chemical Company), and is discerned on the basis of the slope of the single melting peak varying monotonically through the melting region of the artifact.
• Such an artifact occurs within 34°C, typically within 27°C, and more typically within 20°C of the melting point of the single melting peak.
• the heat of fusion attributable to an artifact can be separately determined by specific integration of its associated area under the heat flow versus temperature curve.
• the homogeneity of the polymers is typically described by the CDBI (Composition Distribution Branch Index) and is defined as the weight percent of the polymer molecules having a comonomer content within 50 percent of the median total molar comonomer content.
• the CDBI of a polymer is readily calculated from data obtained from techniques known in the art, such as, for example, temperature rising elution fractionation (abbreviated herein as "TREF") as described, for example, in Wild et al, Journal of Polymer Science, Poly. Phys. Ed., Vol. 20, p. 441 (1982), in U.S. Patent 4,798,081 (Hazlitt et al), or in U.S. Patent 5,089,321 (Chum et al.).
• the CDBI for the homogeneous linear and for the substantially linear ethylene/ ⁇ -olefm polymers used in the present invention is preferably greater than 50 percent, more preferably greater than 70 percent.
• Homogeneous polymers will also typically have a molecular weight distribution, M w /M n , less than or equal to 3 (when the density of the inte ⁇ olymer is less than about 0.960 g/cm 3 ), preferably less than or equal to 2.5.
• M w /M n molecular weight distribution polystyrene standards
• the SLEPs are analyzed by gel permeation chromatography (GPC) on a Waters 150 C high temperature chromatographic unit equipped with differential refractometer and three columns of mixed porosity.
• the columns are supplied by Polymer Laboratories and are commonly packed with pore sizes of 10 3 , 10", 10 5 and 10 6 .
• the solvent is 1 ,2,4-trichlorobenzene, from which 0.3 percent by weight solutions of the samples are prepared for injection.
• the flow rate is 1.0 ml/min, unit operating temperature is 140 C, and the injection size is 100 microliters.
• and M f are the weight fraction and molecular weight, respectively, of the i tn fraction eluting from the GPC column.
• homogeneous linear ethylene polymers have long been commercially available.
• homogeneous linear ethylene polymers can be prepared in conventional polymerization processes using Ziegler-type catalysts such as, for example, zirconium and vanadium catalyst systems.
• U.S. Patent No. 4,937,299 to Ewen et al. and U.S. Patent No. 5,218,071 to Tsutsui et al. disclose the use of metallocene catalysts, such as catalyst systems based on zirconium and hafnium, for the preparation of homogeneous linear ethylene polymers.
• Homogeneous linear ethylene polymers are typically characterized as having a molecular weight distribution, M w /M n , of about 2.
• Commercially available examples of homogeneous linear ethylene polymers include those sold by Mitsui Petrochemical Industries as TafmerTM resins and by Exxon Chemical Company as ExactTM resins.
• SLEPs are homogeneous polymers having long chain branching. They are disclosed in U.S. Patent Nos. 5,272,236 and 5,278,272. SLEPs are made by the InsiteTM Process and Catalyst Technology, and are available from The Dow Chemical Company as AffinityTM polyolefin plastomers (POPs) and from DuPont Dow Elastomers, LLC as EngageTM polyolefin elastomers (POEs).
• POPs AffinityTM polyolefin plastomers
• POEs EngageTM polyolefin elastomers
• SLEPs can be prepared via the solution, slurry, or gas phase, preferably solution phase, polymerization of ethylene and one or more optional ⁇ -olefin comonomers in the presence of a constrained geometry catalyst, such as is disclosed in European Patent Application 416,815-A.
• substantially linear means that, in addition to the short chain branches attributable to homogeneous comonomer inco ⁇ oration, the ethylene polymer is further characterized as having long chain branches, such that the polymer backbone is substituted with an average of 0.01 to 3 long chain branches/1000 carbons.
• Preferred substantially linear polymers for use in the invention are substituted with from 0.01 long chain branch/1000 carbons to 1 long chain branch/1000 carbons, and more preferably from 0.05 long chain branch/1000 carbons to 1 long chain branch/1000 carbons.
• LLB Long chain branching
• deGroot and Chum found that the presence of octene does not change the hydrodynamic volume of the polyethylene samples in solution and, as such, one can account for the molecular weight increase attributable to octene short chain branches by knowing the mole percent octene in the sample. By deconvoluting the contribution to molecular weight increase attributable to 1 -octene short chain branches, deGroot and Chum showed that GPC-DV may be used to quantify the level of long chain branches in substantially linear ethylene/octene copolymers.
• the long chain branch is longer than the short chain branch that results from the inco ⁇ oration of the ⁇ -olefin(s) into the polymer backbone.
• the empirical effect of the presence of long chain branching in the substantial linear ethylene/ ⁇ -olefin inte ⁇ olymers used in the invention is manifested as enhanced rheological properties which are quantified and expressed herein in terms of gas extrusion rheometry (GER) results and/or melt flow, I 10 I 2 , increases.
• GER gas extrusion rheometry
• linear means that the polymer lacks measurable or demonstrable long chain branches, that is, the polymer is substituted with an average of less than 0.01 long chain branch/1000 carbons.
• a gas extrusion rheology such that the critical shear rate at onset of surface melt fracture for the SLEP is at least 50 percent greater than the critical shear rate at the onset of surface melt fracture for a linear ethylene polymer, wherein the SLEP and the linear ethylene polymer comprise the same comonomer or comonomers, the linear ethylene polymer has an I 2 , MJM Block and density within ten percent of the SLEP and wherein the respective critical shear rates of the SLEP and the linear ethylene polymer are measured at the same melt temperature using a gas extrusion rheometer, and
• GER gas extrusion rheometer
• the PI is the apparent viscosity (in kpoise) of a material measured by GER at an apparent shear stress of 2.15 x 10 6 dyne/cm 2 (0.215 MPa).
• the substantially linear ethylene polymers for use in the invention includes ethylene inte ⁇ olymers and have a PI in the range of 0.01 kpoise to 50 kpoise (0.01 to 50 kg/cm-sec), preferably 15 kpoise (15 kg/cm-sec) or less.
• the substantially linear ethylene polymers used herein have a PI less than or equal to 70 percent of the PI of a linear ethylene polymer (either a Ziegler polymerized polymer or a linear uniformly branched polymer as described by Elston in US Patent 3,645,992) having an I 2 , MJM n and density, each within ten percent of the substantially linear ethylene polymers.
• the rheological behavior of substantially linear ethylene polymers can also be characterized by the Dow Rheology Index (DRl), which expresses a polymer's
• DRl values range from 0 for polymers which do not have any measurable long chain branching (such as, TafmerTM products available from Mitsui Petrochemical Industries and ExactTM products available from Exxon Chemical Company) to about 15 and are independent of melt index.
• DRl provides improved correlations to melt elasticity and high shear flowability relative to correlations of the same attempted with melt flow ratios.
• DRl is preferably at least 0.1, and especially at least 0.5, and most especially at least 0.8.
• DRl can be calculated from the equation:
• n is the power law index of the material
• ⁇ and ⁇ are the measured viscosity and shear rate, respectively.
• Baseline determination of viscosity and shear rate data are obtained using a Rheometric Mechanical Spectrometer (RMS-800) under dynamic sweep mode from 0.1 to 100 radians/second at 160 C and a Gas Extrusion Rheometer (GER) at extrusion pressures from 1,000 psi to 5,000 psi (6.89 to 34.5 MPa), which corresponds to shear stress from 0.086 to 0.43 MPa, using a 0.0754 mm diameter, 20:1 length to diameter die at 190 C.
• Specific material determinations can be performed from 140 to 190 C as required to accommodate melt index variations.
• the onset of surface melt fracture is characterized at the beginning of losing extrudate gloss at which the surface roughness of the extrudate can only be detected by 40 times magnification.
• the critical shear rate at the onset of surface melt fracture for the substantially linear ethylene polymers is at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear ethylene polymer having essentially the same I 2 and M M n .
• Gross melt fracture occurs at unsteady extrusion flow conditions and ranges in detail from regular (for instance, alternating rough and smooth or helical) to random distortions. For commercial acceptability to maximize the performance properties of films, coatings and moldings, surface defects should be minimal, if not absent.
• the critical shear stress at the onset of gross melt fracture for the substantially linear ethylene polymers, especially those having a density greater than 0.910 g/cm 3 , used in the invention is greater than 4 x 10 6 dynes/cm 2 (0.4 MPa).
• substantially linear ethylene polymers are known to have excellent processability, despite having a relatively narrow molecular weight distribution (that is, the M M_ ratio is typically less than 2.5). Moreover, unlike homogeneously and heterogeneously branched linear ethylene polymers, the melt flow ratio (I 10 /I 2 ) of substantially linear ethylene polymers can be varied independently of the molecular weight distribution, MJM n . Accordingly, the polymer backbone (A) of the heteromo ⁇ hic polymer compositions of the invention is preferably a substantially linear ethylene polymer.
• heterogeneous polyethylenes that can be used as the heteromo ⁇ hic long chain branch (B) in the practice of this invention fall into two broad categories, those prepared with a free radical initiator at high temperature and high pressure, and those prepared with a coordination catalyst at high temperature and relatively low pressure.
• the former are known generally as low density polyethylenes (LDPE) and are characterized by branched chains of polymerized monomer units pendant from the polymer backbone.
• LDPE polymers generally have a density between 0.910 and 0.935 g/cm 3 .
• Ethylene polymers and copolymers prepared by the use of a coordination catalyst, such as a Ziegler or Phillips catalyst, are generally known as linear polymers because of the substantial absence of branch chains of polymerized monomer units pendant from the backbone.
• High density polyethylene (HDPE) generally having a density of about 0.941 to about 0.965 g/cm 3 , is typically a homopolymer of ethylene or a copolymer of ethylene and low levels of a comonomer, and it contains relatively few branch chains relative to the various linear copolymers of ethylene and an ⁇ -olefin.
• HDPE is well known, commercially available in various grades, and may be used in this invention.
• Linear copolymers of ethylene and at least one ⁇ -olefin of 3 to 12 carbon atoms, preferably of 4 to 8 carbon atoms, are also well known and commercially available.
• the density of a linear ethylene/ ⁇ -olefin copolymer is a function of both the length of the ⁇ -olefm and the amount of such monomer in the copolymer relative to the amount of ethylene, the greater the length of the ⁇ -olefin and the greater the amount of ⁇ -olefin present, the lower the density of the copolymer.
• the densities of these linear polymers generally range from 0.87 to 0.91 g/cm 3 .
• Heterogeneous linear ethylene polymers are available from The Dow Chemical Company as DowlexTM LLDPE and as AttaneTM ULDPE resins. Heterogeneous linear ethylene polymers can be prepared via the solution, slurry or gas phase polymerization of ethylene and one or more optional ⁇ -olefin comonomers in the presence of a Ziegler- Natta catalyst, by processes such as are disclosed in U.S. Patent No. 4,076,698 to Anderson et al.
• Heterogeneous ethylene polymers are typically characterized as having molecular weight distributions, MJM n , in the range of from 3.5 to 4.1. Relevant discussions of both of these classes of materials, and their methods of preparation are found in U.S. Patent No. 4,950,541 and the patents to which it refers.
• Heterogenous polymers are ethylene/ ⁇ -olefin inte ⁇ olymers characterized as having a linear backbone and a differential scanning calorimetry (DSC) melting curve having a distinct melting peak greater than 115°C attributable to a high density fraction.
• Heterogeneous inte ⁇ olymers will typically have an M w /M n greater than 3 (when the density of the inte ⁇ olymer is less than 0.960 g/cm 3 ), and will typically have a CDBI less than or equal to 50, indicating that such inte ⁇ olymers are a mixture of molecules having differing comonomer contents and differing amounts of short chain branching.
• the crystallinity in reference to an ethylene polymer is a well known property of ethyl leennee ppoollyymmeerrss.
• Various techniques have been developed to measure ethylene polymer crystallinity
• the crystallinity can be determined from the density of the polymer using the following equation:
• percent C is the percent crystallinity of the ethylene polymer
• pa is the density of an ethylene polymer which has 0 percent crystallinity (that is, which is 100 percent amo ⁇ hous) at room temperature (0.852 g/cm 3 .)
• pc represents the density of an ethylene polymer at 100 percent crystallinity at room temperature (1.000 g/cm 3 .)
• p represents the density of the polymer for which the percent crystallinity is being determined. Density may be determined according to ASTM D792 in which the samples are annealed at ambient temperature for 24 hours before the measurement is taken.
• under load service temperature (ULST), also referred to as “softening point under load” or “SPUL” means the temperature at which probe penetration of 1 mm into the polymer is achieved using a device capable of applying a constant force of 1 N to a flat tip probe having a diameter of 1 mm while raising the temperature of the polymer from 25 C at a rate of 5 C/minute under a nitrogen atmosphere.
• ULST under load service temperature
• SPUL softening point under load
• the higher density branch-forming polymer (B) can be of a broad range of molecular weights.
• the branch polymer On the low molecular weight side, the branch polymer will have an Mn of at least 2000, preferably at least 3000.
• the branch polymer On the higher molecular weight side, the branch polymer will have an I 2 of at least 0.05 g/cm 3 .
• Typical melt indices for the branch polymer range from 0.05 to 40 g/10 min.
• the decreased number of branch polymer chains will require the presence of a higher concentration of the branch polymer, that is, amounts greater than 20 weight percent (or the use of higher levels of free radical initiator, that is, amounts greater than 0.5 weight percent) to yield a given increase in under load service temperature.
• a lower molecular weight branch polymer when a lower molecular weight branch polymer is used, the presence of an increased number of shorter chains (which are preferably vinyl terminated) will cause an increase in under load service temperature, despite the use of relatively small amounts of the branch polymer, that is, amounts as low as 5 weight percent.
• heteromo ⁇ hic compositions of the invention can be envisioned by those skilled in the art of polymer science.
• the higher crystallinity branch polymer and the lower crystallinity backbone polymer will be prepared by reacting previously prepared and isolated polymer reactants.
• the higher crystallinity branch polymer will react to form a T-link (by grafting) or an H-link (by light crosslinking) with the lower crystallinity backbone polymer. This reaction may be accomplished by methods of known to those skilled in the art.
• hydrogen will be abstracted from the polymer backbone, and will react with the branch polymer.
• Methods for abstracting hydrogen from the polymer backbone include but are not limited to reaction with free radicals which are generated by homolytically cleaving molecules (for instance, peroxide-containing compounds, or azo-containing compounds) or by radiation.
• the presence of olefinic unsaturation on the backbone polymer or branch polymer can help control the location of the grafting/crosslinking sites.
• peroxide decomposition in the presence of a major fraction of a saturated backbone polymer and a minor fraction of vinyl-terminated branch polymer will tend to graft the branch polymer onto the backbone polymer, whereas a vinyl-free branch polymer can undergo hydrogen abstraction to produce a radical which will react with that of the backbone polymer to form H-links.
• Vinyl-terminated branch polymers are prepared by adjusting reactor conditions such that the polymerizing chains are terminated by beta-hydride elimination, rather than being hydrogen terminated.
• coagents such as mono-, di- or tri-allyl functional molecules (for instance, triallyl cyanurate) may be used to further control the free radical processes.
• grafting is preferred over light crosslinking, since more heteromo ⁇ hic long-chain branches may be inco ⁇ orated without gelation.
• ⁇ , ⁇ -dienes as a comonomer in the formation of the higher branch- forming polymer or in the backbone-forming polymer will increase the reactivity of that polymer component.
• Suitable ⁇ , ⁇ -dienes include 1 ,7-octadiene and 1 ,9 decadiene. When inco ⁇ orated, such dienes will typically be present in an amount less than 2 per polymer chain.
• the crosslinking or grafting reactions may be carried out in a solution of the two polymers in an appropriate solvent or in a melt blend of the polymer components.
• the latter is the preferred method.
• Melt blending can be done in a batch mixer such as a Brabender mixer, Banbury mixer, roll mill, or in a continuous mixer such as a Farrell Continuous Mixer, or in a single or twin screw extruder. It is also possible to form a mixture of the polymers, then irradiate or imbibe with reactive solution (such as peroxide) and heat. However, melt or solution blending is preferred over these approaches.
• compositions of the invention may be prepared by copolymerizing the branch polymer with monomers that make the backbone polymer.
• the backbone polymer and the subject composition that is, the heteromo ⁇ hic polymer composition
• This method has the advantage of minimizing phase-out of high Tg/Tm polymer in a relatively cold reactor.
• compositions of the invention may be produced in a series dual reactor arrangement whereby the branch polymer is made in the first reactor and then fed into a second reactor where it is copolymerized with the monomers which form the backbone polymer to make the subject composition.
• the second reactor should be maintained at a temperature which is greater than that at which the higher crystallinity branch polymer would phase separate from the lower crystallinity backbone polymer.
• the reactor in which the copolymerization takes place be a reactor with a high polymer (“solids") concentration, such as a loop reactor, to maximize the concentration of polymerizable higher crystallinity branch polymer in the reactor.
• a single site catalyst will be employed to copolymerize higher crystallinity branch polymers with ethylene and octene to produce ethylene/octene elastomers having HDPE side-chain branches.
• Single site catalysts particularly constrained geometry catalysts, are advantageous, in that they have a higher acceptance of high molecular weight monomers than traditional Ziegler catalysts or non-constrained geometry single site catalysts. Unlike crosslinking, copolymerization avoids gelation even at relatively high heteromo ⁇ hic long-chain branch contents, since only one site on the long chain branch is reactive.
• the high Tm or Tg heteromo ⁇ hic long chain branch precursor monomer be of relatively low molecular weight and have at least one olefin endgroup per chain to aid in the copolymerization and the dissolution of the monomer in the process solvent and/or diffusion to the catalyst site.
• a diene or polyene may be used as a comonomer in one or both polymers to improve the rate of inco ⁇ oration/linkage during the copolymerization.
• an ethylene-diene or propylene-diene copolymer could be produced in one reactor, then fed to a second reactor where it is copolymerized with ethylene and octene or ethylene and propylene.
• the level of diene is relatively low, gelation may be avoided while increasing the rate of copolymerization of heteromo ⁇ hic branch precursor polymer and the monomers of the backbone polymer.
• a diene or polyene when a diene or polyene is utilized as a comonomer, it will be constitute less than 20 weight percent, more preferably less than 10 weight percent of the composition of the invention.
• the heteromo ⁇ hic polymer composition may be blended with one or more additional polymers that are of similar structure to the branch polymer or that can form a high Tm or Tg phase with it via solid solution or cocrystallization.
• additional polymers that are of similar structure to the branch polymer or that can form a high Tm or Tg phase with it via solid solution or cocrystallization.
• One example of such a blend component is high density polyethylene.
• An excess of the higher crystallinity polymer will usefully cocrystallize with the higher crystallinity branches of the heteromo ⁇ hic polymer compositions, serving to increase the thickness of the lamella, which will tend to increase the crystalline melting temperature of the polymer composition. Further, such an excess of the higher crystallinity polymer will serve to bridge two separate higher crystallinity branches, which will raise the overall crystallinity of the heteromo ⁇ hic polymer composition, which will increase the under load service temperature.
• a preferred way to introduce the additional polymer is to simply add an excess of the branch polymer to the reactor or melt blender so that as the copolymerization or grafting or crosslinking takes place, excess unreacted branch polymer remains unreacted and is available for cocrystallization or phase formation with the heteromo ⁇ hic long-chain branches.
• compositions of the invention may be used in blends with other polymers.
• the compositions of the invention may be blended with other polyolefms, such as heterogeneously branched linear ethylene/ ⁇ - olefin inte ⁇ olymers, homogeneously branched linear ethylene/ ⁇ -olefin inte ⁇ olymers, substantially linear ethylene/ ⁇ -olefin inte ⁇ olymers, ethylene/vinyl acetate copolymers, styrene block copolymers, and amo ⁇ hous polyolefms (such as polypropylene and polybutene).
• polyolefms such as heterogeneously branched linear ethylene/ ⁇ - olefin inte ⁇ olymers, homogeneously branched linear ethylene/ ⁇ -olefin inte ⁇ olymers, substantially linear ethylene/ ⁇ -olefin inte ⁇ olymers, ethylene/vinyl acetate copolymers, styrene block
• the heteromo ⁇ hic polymer composition will include at least one component which contains polar moieties. That is, either the backbone polymer or the branch polymer will preferably be functionalized by grafting of a polar moiety thereto.
• any unsaturated organic compound containing at least one site of ethylenic unsaturation for example, at least one double bond
• at least one carboxyl group -COOH
• carboxyl group includes carboxyl groups per se and derivatives of carboxyl groups such as anhydrides, esters and salts (both metallic and nonmetallic).
• the organic compound contains a site of ethylenic unsaturation conjugated with a carboxyl group.
• Representative compounds include maleic, acrylic, methacrylic, itaconic, crotonic, ⁇ -methyl crotonic, and cinnamic acid and their anhydride, ester and salt derivatives, and fumaric acid and its ester and salt derivatives.
• Maleic anhydride is the preferred unsaturated organic compound containing at least one ethylenic unsaturation and at least one carboxyl group.
• the unsaturated organic compound content of the grafted backbone polymer or branch polymer is preferably at least 0.01 wt percent, and more preferably at least 0.05 wt percent, based on the combined weight of the polymer and the organic compound.
• the maximum amount of unsaturated organic compound content can vary to convenience, but typically it does not exceed 10 wt percent, preferably it does not exceed 5 wt percent, and more preferably it does not exceed 2 wt percent of the grafted polymer.
• the unsaturated organic compound can be grafted to the desired or branch polymer by any known technique, such as those taught in USP 3,236,917 and USP 5,194,509.
• the polymer is introduced into a two-roll mixer and mixed at a temperature of 60 C.
• the unsaturated organic compound is then added along with a free radical initiator, such as, for example, benzoyl peroxide, and the components are mixed at 30 C until the grafting is completed.
• a free radical initiator such as, for example, benzoyl peroxide
• the hetermo ⁇ hic polymer compositions will have less than 30 percent gel, more preferably less than 10 percent gel, more preferably less than 5 percent gel, and most preferably less than 2 percent gel. Most preferably, the heteromo ⁇ hic polymer compositions will be substantially free of gels.
• the heteromo ⁇ hic polymers of the invention may optionally include antioxidants, fillers, extender oils, ultraviolet light stabilizers, slip and antiblocking agents, pigments, dyes, or blowing agents, according to the practices of those skilled in the art of polymer formulation.
• the antioxidant is typically present in an amount less than 0.5 weight percent, preferably less than 0.2 weight percent, based on the total weight of the composition.
• compositions of the invention may usefully be employed in hot melt adhesive and pressure sensitive adhesive formulations.
• the compositions of the invention may be admixed with suitable amounts of one or more tackifiers, one or more waxes, and/or one or more plasticizers.
• tackifier means any of several hydrocarbon based compositions useful to impart tack to the hot melt adhesive composition.
• tackifiers include aliphatic C5 resins, polyte ⁇ ene resins, hydrogenated resins, mixed aliphatic-aromatic resins, rosin esters, and hydrogenated rosin esters.
• the tackifier employed will typically have a viscosity at 350°F (177°C) , as measured using a Brookfield viscometer, of no more than 300 centipoise (300g/cm-sec), preferably no more than 150 centipoise (150 g/cm-sec), and most preferably of no more than 50 centipoise (50 g/cm-sec).
• the tackifier employed will typically have a glass transition temperature greater than 50 °C.
• Exemplary aliphatic resins include those available under the trade designations EscorezTM, PiccotacTM, MercuresTM, WingtackTM, Hi-RezTM, QuintoneTM, TackirolTM, etc.
• Exemplary polyte ⁇ ene resins include those available under the trade designations NirezTM, PiccolyteTM, WingtackTM, ZonarezTM, etc.
• Exemplary hydrogenated resins include those available under the trade designations EscorezTM, ArkonTM, ClearonTM, etc.
• Exemplary mixed aliphatic-aromatic resins include those available under the trade designations EscorezTM, RegaliteTM, HercuresTM, ARTM, ImprezTM, NorsoleneTM M, MarukarezTM, ArkonTM M, QuintoneTM, etc.
• Other tackifiers may be employed, provided they are compatible with the homogeneous linear or substantially linear ethylene/ ⁇ -olefin inte ⁇ olymer and the optional wax.
• the tackifier will typically be present in the hot melt adhesives of the invention in an amount less than 70 weight percent, preferably less than 50 weight percent.
• the tackifier will be typically present in the hot melt adhesives of the invention in an amount of at least 5 weight percent, preferably at least 10 weight percent.
• the term "wax" is used to refer to paraffinic or crystalline ethylene homopolymer or inte ⁇ olymer or homogeneous ethylene polymers, which have a number average molecular weight less than 6000. Exemplary polymers falling within this category include ethylene homopolymers available from Petrolite, Inc.
• PolywaxTM 2000 has a molecular weight of approximately 2000, an M w /M n of approximately 1.0, a density at 16°C of about 0.97 g/cm.3, and a melting point of approximately 126°C.
• CP Hall 1246 paraffinic wax is available from CP Hall (Stow, OH). CP Hall 1246 paraffinic wax has a melting point of 143°F (62°C), a viscosity at 210°F (99°C) of 4.2 centipoise (4.2 g/cm-sec), and a specific gravity at 73°F (23°C) of 0.915.
• Preferred waxes will be prepared using a constrained geometry catalyst.
• Such polymers will be either ethylene homopolymers or iinte ⁇ olymers of ethylene and a comonomer such as is set forth above with respect to polymer one, for instance, C3-C20 ⁇ -olefins, styrene, alkyl-substituted styrene, tetrafluoroethylene, vinylbenzocyclobutane, non-conjugated dienes, and naphthenics.
• Such polymers in contrast to traditional waxes, will have an MJM n of from 1.5 to 2.5, preferably from 1.8 to 2.2.
• Such polymers are disclosed and claimed in U.S. Patent Application Serial No. 784,683, filed on January 22, 1997 (WO 97/01181).
• the wax will have a number average molecular weight less than 6000, preferably less than 5000. Such waxes will typically have a number average molecular weight of at least 800, preferably at least 1300.
• the wax useful in the hot melt adhesives of the invention when it is an ethylene homopolymer (either a traditional ethylene homopolymer wax or an ethylene homopolymer prepared with a constrained geometry catalyst) or an inte ⁇ olymer of ethylene and a comonomer selected from the group consisting of C3-C20 ⁇ -olefins, non-conjugated dienes, and naphthenics, will have a density of at least 0.910 g/cm- ⁇ Such second polymers will have a density of no more than 0.970 g/cm- , preferably no more than 0.965 g/c ⁇
• the heteromo ⁇ hic polymer compositions of the invention are usefully employed in pressure sensitive adhesive formulations, in that the higher crystallinity branch polymer serves to improve the close time of the adhesive. As the adhesive cools, the branch polymer crystallizes while the polymer backbone remains soft and/or flowable. This imparts strength to the adhesive during the setting process and decreases the
• the hot melt adhesive may further comprise an oil or other plasticizer, such as an amo ⁇ hous polyolefin.
• Oils are typically employed to reduce the viscosity of the hot melt adhesive. When employed, oils will be present in an amount less than 25, preferably less than 15, and more preferably less than 10 weight percent, based on the weight of the hot melt adhesive.
• Exemplary classes of oils include white mineral oil (such as KaydolTMoil (available from Witco), and ShellflexTM 371 naphthenic oil (available from Shell Oil Company). To the extent that the oil decreases the adhesion character of the hot melt adhesive to levels detrimental for the contemplated use, they should not be employed.
• the hot melt adhesives of the invention may be prepared by standard melt blending procedures.
• heteromo ⁇ hic polymer composition, optional tackifier, optional wax, and optional plasticizer may be melt blended at an elevated temperature (from 150 to 200°C) under an inert gas blanket until a homogeneous mix is obtained. Any mixing method producing a homogeneous blend without degrading the hot melt components is satisfactory, such as through the use of a heated vessel equipped with a stirrer.
• the heteromo ⁇ hic polymer composition, optional wax, optional tackifier, and optional plasticizer may be provided to an extrusion coater for application to the substrate.
• Suitable pressure sensitive adhesives will exhibit a probe tack of at least 200 grams, more preferably at least 300 grams, and most preferably at least 350 grams. Suitable pressure sensitive adhesives will further exhibit a heat resistance which is at least 10°C, preferably at least 15°C, and more preferably at least 20°C greater than that of pressure sensitive adhesives in which the branch polymer and backbone polymer are employed as a blend rather than in the form of the heteromo ⁇ hic polymer compositions of the invention.
• Suitable adhesives will be of a low enough viscosity to permit facile application on the desired substrate.
• hot melt adhesives will have a melt viscosity at 350°F (177°C) which is less than 50,000 centipoise (50,000 g/cm-sec), with lower viscosities being typically more preferred.
• heteromo ⁇ hic polymer compositions of this invention will further include, but are not limited to, gaskets such as those in automobile windows, sealants, adhesive, flexible molded goods such as shoes soles, wire and cable insulation and jacketing, roofing membranes, floor coverings, hoses, boots, automobile parts, and other parts known to the industry to require elastomeric materials with adhesion to polar substrates.
• gaskets such as those in automobile windows, sealants, adhesive, flexible molded goods such as shoes soles, wire and cable insulation and jacketing, roofing membranes, floor coverings, hoses, boots, automobile parts, and other parts known to the industry to require elastomeric materials with adhesion to polar substrates.
• Polymer Al a substantially linear ethylene octene copolymer prepared in accordance with the teachings of U.S. 5,278,236, which had a measured I 2 of 0.94 g/10 min. and density of 0.869 g/cm 3 .
• Polymer A4-- a substantially linear ethylene/octene copolymer prepared in accordance with the teachings of U.S. 5,278,236, which had an I 2 of 30 g/10 min. and density of 0.870 g/cm 3 .
• Polymer A6 a substantially linear ethylene octene copolymer prepared in accordance with the teachings of U.S. 5,278,236, which had a measured I 2 of 1 g/10 min. and density of 0.855 g/cm 3 .
• Polymer A7 ⁇ is a substantially linear ethylene/ 1 -octene copolymer prepared in accordance with the teachings of U.S. 5,278,236, which had a density of 0.855 g/cm3 and a melt index of 30g/10min.
• Polymer A8 ⁇ is an ultralow molecular weight ethylene/ 1 -octene copolymer prepared in accordance with the teachings of U.S. Patent Application serial No.
• Polymer A9— is a substantially linear ethylene/ 1 -octene copolymer prepared in accordance with the teachings of U.S. 5,278,236, which had a density of 0.855 g/cm 3 and a melt index of 0.5 g/1 Omin.
• Polymer A10 ⁇ is a substantially linear ethylene/ 1 -octene prepared in accordance with the teachings of U.S. 5,278,272, which had a density of 0.870 g/cm ⁇ and a melt index of 30 g/10 min.
• Polymer B3 DowlexTM 25355 high density polyethylene having a density of 0.955 g/cm 3 and an I 2 of 25 g/10 min.
• Polymer B4-- DowlexTM 25455 high density polyethylene having a density of 0.955 g/cm 3 and an I 2 of 25 g/10 min.
• Polymer B5 a substantially linear ethylene/ 1 -octene copolymer prepared in accordance with the teachings of U.S. 5,278,236, which has a density of 0.902 g/cm 3 and a melt index of 30 g/10 min.
• Polymer B7 AttaneTM 6152 ultralow density polyethylene, a heterogeneous linear ethylene/ 1 -octene copolymer having a density of 0.904 g/cm 3 and a melt index of 0.5 g/10 min.
• Polymer B 8 Ultralow molecular weight ethyl ene/1 -octene copolymer prepared in accordance with the teachings of U.S. Patent Application Serial No. 784,683, filed January 22, 1997 (WO 87/01181) having a density of 0.955 g/cm 3 and a melt viscosity at 350°F (177°C) of 5000 centipoise (5000g/cm-sec).
• Polymer B9 ⁇ Dow high density polyethylene HDPE 12165 having a density of 0.955 g/cm 3 and a melt index of 1.0 g/cm 3 .
• Polymer C an in-reactor polymer mixture prepared in accordance with the procedure of WO 94/17112, which has as its targeted composition: 68.5 wt. percent of a substantially linear ethylene/octene copolymer having a density of 0.861 g/cm 3 and an I 2 of 0.29 g/10 min. and 31.5 wt. percent of a high density polyethylene having a density of 0.946 g/cm 3 and an I 2 of 370 g/10 min.
• Polymer D a maleic anhydride grafted high density polyethylene having a density of 0.953 g/cm 3 , a melt index of 9 g/ 10 min, and 1.2 weight percent maleic anhydride prepared by reactive extrusion of high density polethylene having a density of 0.953 g/cm.3 with maleic anhydride.
• Lupersol 500R 99 percent pure dicumylperoxide, available from Elf Atochem.
• Lupersol -130 90 - 95 percent of 2,5-dimethyl-2,5-di(t- butylperoxy)hexyne-3, available from Elf Atochem).
• Lupersol-101 2,5-dimethyl-2,5- di(t-butylperoxy)hexane (available from Elf Atochem).
• Under load service temperature (ULST) is measured using a thermomechanical analyzer (TMA). The penetration versus temperature was measured. Temperature at the probe penetration of 1 mm is taken as under load softening temperature. A heating rate of 5°C/min and a load of 102 g was used.
• a Rheometrics Solids Analyzer Model RSAII was used to determine the change in modulus with respect to temperature. Samples were compression molded into approx. 0.25 mm thick films by holding at 1500 psi (10.3 MPa) and 350°F (177°C) for 5 minutes, then cooling at 27°F/min (-2.8°C/min) until 90°F (32°C). Samples were held at 90°F (32°C) for 1 minute and then removed from the press. A specimen of approx.
• 0.25 x 4.4 x 22 mm was cut, then tested under the following conditions: 10 rad/sec frequency in torsion rectangular test, beginning at -145°C and increasing to 120°C or 150°C or 270°C at a 5°C step size with a 30 second soak time for each step, in nitrogen atmosphere.
• Hardness shore A is measured in accordance with ASTM D2240.
• Melt viscosity is determined in accordance with the following procedure using a Brookfield Laboratories DVII+ Viscometer in disposable aluminum sample chambers.
• the spindle used is a SC-31 hot-melt spindle, suitable for measuring viscosities in the range of from 10 to 100,000 centipoise (10 to 100,000 g/cm-sec).
• a cutting blade is employed to cut samples into pieces small enough to fit into the 1 inch (2.5 cm) wide, 5 inches (12.5 cm) long sample chamber.
• the sample is placed in the chamber, which is in turn inserted into a Brookfield Thermosel and locked into place with bent needle-nose pliers.
• the sample chamber has a notch on the bottom that fits the bottom of the Brookfield Thermosel to ensure that the chamber is not allowed to turn when the spindle is inserted and spinning.
• the sample is heated to 350°F (177°C), with additional sample being added until the melted sample is about 1 inch (2.5 cm) below the top of the sample chamber.
• the viscometer apparatus is lowered and the spindle submerged into the sample chamber. Lowering is continued until brackets on the viscometer align on the Thermosel.
• the viscometer is turned on, and set to a shear rate which leads to a torque reading in the range of 30 to 60 percent. Readings are taken every minute for about 15 minutes, or until the values stabilize, which final reading is recorded.
• a Haake Rheocord System 40 torque rheometer with a Rheomix 600 mixer and roller style mixing blades was used to prepare the compositions of these Examples. Blends were prepared by mixing the components at 75 revolutions per minute at 145°C. The compositions of Polymers A2, A3, and B are set forth above. Lupersol 500 (99 percent pure dicumyl peroxide, available from Elf Atochem) was added in the indicated amount and the resultant mixture was mixed for approximately 1 minute at 145°C, the temperature was raised to 175°C, and the sample mixed for a total of 15 minutes. Samples were placed on a cool compression molding platen while still hot and compressed to a thin film for FTIR analysis of vinyl content.
• Lupersol 500 99 percent pure dicumyl peroxide, available from Elf Atochem
• the reduction in vinyl endgroup concentration may be considered an indication of the extent to which "T" links formed. Since hydrogen extractability from the Polymer A2 and A3 can be assumed to be of approximately equal probability as hydrogen extractability from Polymer Bl, since most of the vinyl groups are on the lower molecular weight Polymer B 1 than on the higher molecular weight Polymers A2 and A3 (given that a 50:50 blend of the polymer components was used), it may be assumed that approximately 50 percent of the "T” links formed were due to grafting of Polymer Bl to Polymers A2 and A3. The strong reduction in vinyl concentration shown in Table One is further evidence of the formation of "T" links. The appending of the higher crystallinity polymer Bl onto the backbone is supported by the dramatic improvement in temperature resistance as described in the following examples.
• Examples and Comparative Examples 4-18 Improvement in Temperature Resistance Exhibited by Heteromo ⁇ hic Polvmer Compositions of the Invention
• the mixer speed was raised to approximately 160 revolutions per minute to rapidly mix in the peroxide, thereby causing a viscous heating effect, which, over the course of 1-2 minutes, raised the temperature of the mixture to approximately 190°C, causing the decomposition of the peroxide.
• the mixer speed was reduced to 60 revolutions per minute for an additional minute. Following mixing, the mixer was stopped and the sample removed and allowed to cool. The chunks of polymer were then granulated.
• Table Two shows that the blend of Comparative Example 15, that is, the blend which was not subjected to peroxide treatment, failed at approximately 70°C. Due to the melting of the crystallites of Polymer A3, the blend did not have sufficient strength to maintain its integrity in the RSA test and the sample specimen broke. In contrast, the heteromo ⁇ hic polymer composition of Example 15, that is, the composition which was subjected to peroxide treatment, maintained its integrity up to 130°C, which is approximately the melting point of Polymer Bl.
• Table Two summarizes the results for a series of comparative blend compositions (prepared without peroxide treatment) and a series of heteromo ⁇ hic polymer compositions of the invention (prepared with peroxide treatment).
• Table Two shows that the heteromo ⁇ hic compositions of the invention had significantly improved temperature resistance as compared to the comparative blends.
• Table Two shows that the pure Polymers Al, A2, and A3, which were treated with peroxide, additionally failed at relatively low temperatures.
• the substantial improvement in temperature resistance for the heteromophic polymer compositions of the invention cannot be attributed to the formation of a crosslinked network, but is rather attributable to the appending of the high melting point Polymer Bl branches onto the backbone formed by Polymers Al, A2, and A3.
• heteromo ⁇ hic polymer compositions of the Comparative Examples and Examples 19-23 were prepared in accordance with the procedures set forth above in Examples 1-4.
• the compositions of the heteromo ⁇ hic polymer compositions and comparative blends, and the resultant properties are set forth in the following Table Three.
• Example 19-21 Discussion of Examples 19-21. With respect to Examples 19-21 , as the amount of peroxide was increased, the under load service temperature likewise increased, by 27°C in the case of Example 20, and 47°C in the case of Example 21.
• Table Three show that the heteromo ⁇ hic polymer compositions of the invention of Examples 20 and 21 have a much higher heat resistance than the corresponding comparative blend of Comparative Example 19. This is set forth in Figure 3, which shows that the heteromo ⁇ hic polymer compositions of Examples 20 and 21 withstand a temperature before the hardness shore A drops below 45 than does Comparative Example 19. This is further shown in Figure 4, which shows that the heteromo ⁇ hic polymer compositions of Examples 20 and 21 undergo 1mm probe penetration at higher temperatures than does Comparative Example 19.
• heteromo ⁇ hic polymer compositions have tensile properties at elevated temperatures which exceed those of the comparative blends of Comparative Example 19. For instance, the blend of Comparative Example 19 lost most of its tensile strength at 70°C. In contrast, the heteromo ⁇ hic polymer compositions of Examples 20 and 21 exhibited a tensile strength at 100°C of 250 psi (1.72 MPa) and 180 psi (1.24 MPa), respectively.
• the gel contents of the heteromo ⁇ hic polymer compositions of Examples 20-21 are less than that of partially crosslinked blends of the prior art, see, for instance, U.S. 3,806,558, which discloses a gel content of greater than 30 percent. It is su ⁇ rising that the heteromo ⁇ hic polymer compositions exhibit such a large improvement in high temperature properties without a large reduction in flexibility and softness, and without the formation of significant amounts of a crosslinked network structure.
• Examples 21-23 With respect to Examples 21 -23, the under load service temperature increased as the concentration of the higher crystallinity branch-forming polymer increased. It is interesting to note that as between Examples 23 and 21, an increase in the amount of the higher crystallinity material from 20 to 25 weight percent yielded an increase in under load service temperature of 40°C.
• Examples 24 and 25 illustrate the fact that in-reactor produced mixtures of the higher crystallinity polymer and the lower crystallinity polymer can beneficially be made into heteromo ⁇ hic compositions of the invention. It is noted that the heteromo ⁇ hic polymer composition of Example 25 exhibited an under load service temperature which was 40°C greater than that of the non-reacted in-reactor mixture of Comparative Example 24.
• heteromo ⁇ hic polymer compositions and comparative blends were compression molded to disks with dimensions of 1 inch (2.5 cm) inner diameter and 1/16 inch (0.16cm) thickness at a molding temperature of 177°C, then cooled to 22°C at a rate of 15°C/minute before demolding.
• Thin strips of the compression molded samples were embedded in Epofix (Struer's epoxy based embedding kit) at room temperature. After trimming the blocks, these were stained in a mixture of mthenium trichloride and CloroxTM bleach for two hours at room temperature. Ultrathin sections of approximately 1000 angstroms in thickness were collected at room temperature using a Reichert-Jung Ultracut E mcrotome. The sections were placed on formvar coated copper grids. The sections were viewed using a JEOL 2000FX TEM operated at 100 kV accelerating voltage and a magnification of 30,000 times.
• the digital image analyzer measured eight diameters on each dispersed phase and total area fraction from the binaries. Statistical diameters were calculated from the average diameter of each dispersed phase. These statistical diameters convey information about the phase size and breadth of the size distribution. The volume weighted mean diameter emphasized the presence of large features, while the harmonic mean diameter emphasized small features.
• the TEM image of Comparative Example 19 is shown in Figures 5, at 30,000 times magnification.
• the micrograph shows a two phase mo ⁇ hology consisting of dispersed higher density polyethylene domains in a continuous matrix of the elastomer phase attributable to Polymer A3.
• the domains attributable to the higher density polyethylene component of Polymer B2 are distinguished by their lamellar mo ⁇ hology both within and radiating outwards into the matrix.
• the elastomer phase attributable to the lower density polyethylene component of Polymer A3 shows the characteristic granular mo ⁇ hology of fringed micelle crystallites.
• the TEM image of heteromo ⁇ hic polymer composition of Example 20 is shown in Figure 6, at 30,000 times magnification.
• the volume fraction of the dispersed high density polyethylene phase was determined by digital image analysis.
• the volume and size of the high density polyethylene dispersed phase in the comparative blends and in the heteromo ⁇ hic polymer compositions is set forth in the following Table Four:
• the heteromo ⁇ hic polymer compositions of Example 20 of the invention exhibited over 50 percent fewer higher crystallinity islands (as evidenced by a significantly lower volume percent) than the unreacted blends of Comparative Examples 19.
• the heteromo ⁇ hic polymer compositions of Example 25 of the invention exhibited 67 percent fewer higher crystallinity islands (as evidenced by a significantly lower volume percent) than the unreacted blends of Comparative Examples 24. This suggests that the heteromo ⁇ hic compositions of the invention in fact comprise elastomer backbones to which the higher density polymer component has been grafted.
• An average of the volume percent of Comparative Examples 19 and 24 is 22.1 percent.
• the average of the volume percent of Examples 20 and 25 is 8. On this basis, it is estimated that 64 percent of the total high density polyethylene is grafted onto the elastomer backbone.
• Samples were prepared by melt blending Polymers A6 and D in the indicated amounts in a Haake Rheocord System 40 torque rheometer with a Rheomix 3000E mixer and roller style mixing blades at 60 to 75 revolutions per minute and approximately 145°C for approximately 4 minutes.
• LupersolTM 101 available from Elf Atochem
• the mixer speed was raised to approximately 160 revolutions per minute to rapidly mix it in and to cause a viscous heating effect, and over the course of 1 -2 minutes, raising the temperature to approximately 190°C to decompose the peroxide.
• the mixer speed was reduced to 60 revolutions per minute for an additional minute. Following mixing, the mixer was stopped and the sample removed and allowed to cool. The chunks of polymer were then granulated.
• the resultant heteromo ⁇ hic polymers and a comparative polymer blend were tested for performance as a pressure sensitive adhesive for tape.
• the following adhesive formulations were employed: 100 phr resin, 220 phr Escorez 1310 LC tackifier, and 1 phr IrganoxTM 1010.
• the formulation components were melt blended at 130°C in a Haake. Upon achieving a uniform mixture, 80 phr Kaydol oil was added via a syringe.
• the tape samples were prepared by compression molding the formulated adhesives between MylarTM film and a release sheet at 170°C under
• the resultant thickness of the adhesive was about 2 mil (0.05mm).
• Heat resistance of the formulated adhesive was measured using a Rheometrics, Inc., RDA-II dynamic mechanical spectrometer.
• the temperature at which the storage modulus (G') of the rabber plateau decreased suddenly was taken as the heat resistance temperature.
• a temperature sweep was ran from approximately -70°C to 200°C at 5°C/step with 30 seconds equilibration delay at each step.
• the oscillatory frequency was 1 radian second with an autostrain function of 0.1 percent strain initially, increasing in positive 100 percent adjustments whenever the torque decreased to 4 gram-centimeters.
• the maximum strain was set at 26 percent.
• the 7.9 mm parallel plates fixtures were used with an initial gap of 1.5 mm at 160°C (the sample was inserted into the RDA-II at 160°C).
• the "HOLD" function was engaged at 160°C and the instrument was cooled to -70°C and the test started, which corrects for the thermal expansion or contraction as the test chamber is heated or cooled. A nitrogen environment was maintained
• Probe tack was measured in accordance with ASTM D-2979-71, using a dwell time of 10 seconds and a probe separation rate of 1 cm/sec.
• Viscosity at 177°C was measured in accordance with the following procedure using a Brookfield Laboratories DVII+ Viscometer in disposable aluminum sample chambers.
• the spindle used is SC-31 hot melt spindle.
• the samples were cut into pieces small enough to fit into the 1 inch (2.5 cm) wide, 5 inches (12.5 cm) long sample chamber.
• the sample was heated to 177°C, with the melted sample is about 1 inch (2.5 cm) below the top of the sample chamber.
• the viscometer apparatus is lowered and the spindle submerged into the sample chamber.
• the viscometer was turned on, and set to a shear rate which leads to a torque reading in the range of 30 to 60 percent. Readings were taken every minute for about 15 minutes, or until the values stabilize, which final reading is recorded.
• heteromo ⁇ hic polymer compositions and comparative polymers, properties thereof, and performance as pressure sensitive adhesive formulations is set forth in Tables Five through Seven.
• the heteromo ⁇ hic polymers can be used as a pressure sensitive adhesive: the sample has an acceptable processability, probe tack (comparable with commercially available Scotch Magic Tape), and higher service temperature than the comparative blend.
• the TMA data set forth in Table Seven suggests that the upper service temperature of the heteromo ⁇ hic polymer compositions is higher than the comparative non-grafted samples. Compare, for instance, Examples 21-2 to 21-3, and 21-4 to 21-5.
• the probe tack results suggest that the compositions of the invention have acceptable tackiness, that is, probe tack values of at least 200 grams, more preferably at least 300 grams, and most preferably at least 380 grams.
• the G' and Tg data suggest that the heteromo ⁇ hic polymer compositions may be utilized in pressure sensitive adhesive formulations, that is, they are characterized as having a G' of 10 5 to 10 6 dynes/cm 2 and a Tg of from -10 to 10°C.
• the Examples of Table Seven show the flexibility of the technology of this invention, that is, the molecular weight and density of the backbone polymer and branching polymer may changed to make the compositions suitable for use in a variety of pressure sensitive adhesive applications.
• Samples were prepared by reactive extrusion of Polymers AlO and B4 (in the case of Example 40) and Polymer AlO and D (in the case of Example 41).
• the mixture of the polymer reactants was imbibed with the peroxide, and the imbibed sample was extruded in a twin screw extruder at 210°C.
• the resultant compositions were evaluated for upper service temperature, lap shear adhesion, and T-peel shear adhesion.
• T-Peel Shear Adhesion was determined as follows. Glass slides (dimensions: 3 x 1 x 0.05 inches (7.6 x 2.5 x 0.12 cm) from Fisher Scientific) were bonded to cold rolled steel strips (CRS, dimensions: 6 x 1 x 0.032 inches (15 x 2.5 x 0.08) from Q- Panel Company) using Loctite Depend Adhesive (Item No 00206, from the Loctite Co ⁇ oration) by placing a surface activator on the CRS strip and the adhesive resin on the glass slide. Sufficient mixing of the adhesive occurred when the glass slide and CRS were place together. These bonded joints were held together with a 10 pound (22 kg) weight for 10 minutes. The CRS/glass strips were placed on a hot plate
• the HDPE-g-EO test polymers and second metal strip were placed onto the CRS/glass strips residing on the hot plate. They were heated until the polymer sample had melted. Then they were cooled to room temperature. These test specimens were tested 24 hours after preparation.
• the nominal stress-strain diagrams were generated using an Instron 4204 Materials Testing System according to ASTM method D 1876-72. The distance between the grips was 2 inches (5 cm), and the crosshead speed was 10 inches/min (25 cm/min).
• heteromo ⁇ hic polymer compositions and the resultant properties are set forth in the following Table Eight.
• the adhesion to glass of the heteromo ⁇ hic polymer composition significantly increases when MAH-g-HDPE is used instead of HDPE as the branch polymer.
• the results in Table Eight show that the MAH-g-HDPE grafted heteromo ⁇ hic composition has much higher lap shear adhesion and T-peel shear Adhesive to glass than the non-functionalized heteromo ⁇ hic polymer composition.
• maleic acid functionalized heteromo ⁇ hic polymer compositions may be usefully employed in pressure sensitive adhesive formulations.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)
• Other Resins Obtained By Reactions Not Involving Carbon-To-Carbon Unsaturated Bonds (AREA)
• Sealing Material Composition (AREA)
• Graft Or Block Polymers (AREA)
• Paints Or Removers (AREA)
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• 1998
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