Process for making ethylenic polymer foam structures

IS 2 145 133 T3

DESCRIPTION

Procedure for manufacturing ethylene polymer foam structures.

This invention relates to an ethylene polymer foam structure having improved toughness and elasticity and to a process for making the foam.

Commercially available ethylenic polymer foam structures are made topically with conventional highly branched low density polyethylene (LDPE) resins made by high pressure processes. LDPE resin foam structures have been found to be suitable for cushion packaging and other applications.

There is a need for an ethyloenic polymer foam structure that has better toughness and elastic characteristics than the foam structures of LDPE resins. Such tougher and more elastic foam structures would be very useful in sports and leisure applications as well as cushion packaging applications.

One means of making a more tough and more elastic ethyloenic polymer foam structure is to use conventional heterogeneously branched linear low density polyethylene (LLDPE) resins as the primary or secondary resin in the foam. Unfortunately, LLDPE resins have undesirable extrusion foaming characteristics.

It would be desirable to have an ethyloenic polymer foam that has foamability similar to LDPE foams and toughness and elasticity similar to LLDPE foams.

According to the present invention, there is an ethyloenic polymer foam structure comprising an ethyloenic polymer material. The ethylenic polymer material comprises a substantially linear ethylone polymer having: a) a melt flow ratio, I₁₀/ I₂,> 5.63; b) a molecular weight distribution, M_w/ M_n, defined by the equation M_w/ M_n <(I₁₀/ I₂) - 4.63; and c) a chromic shear rate at the beginning of surface fracture of the melt of at least 50 percent greater than the crotic shear rate at the beginning of surface fracture of the melt of a linear olephonic polymer having approximately the same I2 and Mw / Mn. .

Maós according to the present invention, there is a process to manufacture an ethyloenic polymer foam structure. The process comprises: a) heating the ethylene polymeric material described above to form a molten polymeric material; b) incorporating into the molten polymeric material, at high pressure, an expanding agent; and c) expanding the foamable gel under reduced pressure to form the foam structure.

In accordance with the present invention, there is a process for manufacturing an ethyloenic polymer foam structure in the form of a foam bead. The process comprises: a) forming a suspension of discrete particles of the ethyloenic polymeric material described above in a liquid in which it is substantially insoluble and at elevated temperature and pressure; b) impregnating a blowing agent into the discrete particles at elevated temperature and pressure; and c) discharging the discrete particles in a reduced pressure atmosphere to form the foam beads.

Elastic, substantially linear ethyloenic polyomers have unusual properties, including an unusual combination of properties, leading to improved processability of the new polymers. Substantially linear ethyloenic polyomers have processability similar to highly branched low-density polyethylene, but strength and toughness similar to linear low-density polyethylene.

Substantially linear ethyloenic polyomers have a critical shear rate at the beginning of melt surface fracture of at least 50 percent greater than the chromic shear rate at the beginning of melt surface fracture of a linear ethyloenic polyomer having approximately the same I2 yMw / Mn.

Elastic, substantially linear ethyloenic polyomers also have a processing index (PI) less than or equal to about 70 percent of the PI of a comparative linear ethyloenic polymer at about the same I2 and Mw / Mn.

The substantially linear and elastic ethylenic polyomers also have a melt flow ratio, I10 / I2> 5.63, and a molecular weight distribution, Mw / Mn, defined by the equation: Mw / Mn

ES 2 145 133 T3 <(I10 / I2) - 4.63.

Especially preferred are substantially linear and elastic ethylenic polymers comprising homopolymers of ethylene or a copolymer of ethylene with at least one C3-C20 α-olefinic (alpha-olefin) comonomer.

Other properties of substantially linear polymers include: a) a density preferably from 0.85 grams / cubic centimeter (g / cm³) up to 0.97 g / cm³; and b) a melt index, I2, preferably from 0.01 grams / 10 minutes to 1000 grams / 10 minutes.

Preferably, the melt flow ratio, I10 / I2, is from 7 to 20.

The molecular weight distribution (Mw / Mn) is preferably 3.5 or less, more preferably 1.5 to 2.5, and most preferably 1.7 to 2.3.

Throughout this description the "melt index" or "I2" is measured according to ASTM D-1238 (190 ° C / 2.16 kg); "I₁₀”Is measured according to ASTM D-1238 (190 ° C / 10 kg).

The melt tensions of these new polymers are also surprisingly good, for example, as high as 2 grams or more, especially for polymers that have a very narrow molecular weight distribution (i.e., Mw / Mn from 1.5 to 2, 5).

US Patent 4,649,001 describes a process for producing polyethylene foams that comprises melting and kneading, with a foaming agent, a linear low-density polyethylene having a density of 0.920 to 0.940 g / cm³, a melt flow rate of 0.3 to 10 g / 10 minutes and a ratio of M_w/ M_n > 4 between a weighted average molecular weight, M_w, and a number average molecular weight, Mn, and extruding and foaming it.

The substantially linear polymers useful for the present invention may be homopolymers of ethylene (polyethylene) or may be copolymers of ethylene with at least one C3-C20 α-olefinic compound and / or C2-C20 acetylenically unsaturated compounds and / or diolephenic comoneomers. of C4C18 and / or other unsaturates. Useful comonomers include ethylenically unsaturated comonoimers, conjugated or unconjugated dienes and polyenes. Preferred monomers include the C3-C10 α-olefinics, especially 1-propene, isobutylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Other useful comonomers include styrene, alkyl- or halogen-substituted styrene, tetrafluoroethylene, vinylbenzocyclobutane, 1,4-hexadiene, and naphthenics (eg, cyclopentene, cyclohexene, and cyclooctene).

The expression "substantially linear polymers" means that the main chain of the polymer is substituted with 0.01 long chain side chains / 1000 carbons up to 3 long chain side chains / 1000 carbons, mine preferably from 0.01 long chain side chains / 1000 carbons up to 1 long chain side chain / 1000 carbons and especially from 0.05 long chain side chains / 1000 carbons to 1 long chain side chain / 1000 carbons.

The expression "linear ethylenic polymers" means that the ethylenic polymer does not have long chain branching. That is, the linear ethylene polymer is absent of long chain branching, such as, for example, linear low-density polyethylene polymers or conventional linear high-density polyethylene polymers made using Ziegler's polymerization processes (e.g., patents from United States n^° 4,076,698 or 3,645,992). The term "linear ethylene polymers" does not refer to high pressure branched polyethylene, ethylene / vinyl acetate copolymers, or ethylene / vinyl alcohol copolymers which are known to those skilled in the art to have numerous long chain side chains.

Long chain branching is defined in this invention as a chain length of at least 6 carbons, above which the length cannot be distinguished using nuclear magnetic resonance (NMR) spectroscopy. ¹³C. The long chain side chain can be as long as about the same length as the length of the polymer backbone.

Long-chain branching is determined using spectroscopy of ¹³C NMR and quantified using Randall's method (Rev. Macromol. Chem. Phys., C29 (2 and 3), pages 285-297).

Excellent teachings regarding polymers are seen in US Patent Numbers 5,278,272, filed September 2, 1992, and 5,272,236, filed October 15, 1991.

ES 2 145 133 T3 substantially linear ethylenics and to the processes for making them.

The "melt tension" is measured by a specially designed pulley transducer in conjunction with the melt indexer. The melt tension is the load that the extrudate or filament exerts while passing over the pulley that rotates at the standard speed of 30 rpm. The melt tension measurement is similar to the "Melt Tension Tester" made by Toyoseiki and is described by John Delay in Rheometers for Molten Plastics, published by Van Nostrand Reinhold Co. (1982) at pages 250-251.

The SCBDI (Short Chain Branch Distribution Index) or the CDBI (Composition Distribution Branch Index) is defined as the amount by weight percent of the polymer molecules having a comonomer content within 50% of the average total molar comonomer content. The CDBI of a polymer is easily calculated from data obtained from techniques known in the art, such as, for example, fractionation by elution by temperature rise (abbreviated in this invention as "TREF") as described, by For example, in the work of Wild et al., Journal of Polymer Science, Poly. Phys. Ed., Volume 20, page. 441 (1982), or in US Patent No.^° 4,798,081. The SCBDI or CDBI for the substantially linear ethylene polymers of the present invention is preferably greater than about 30 percent, especially greater than about 50 percent. Therefore, substantially linear polymers are homogeneously branched.

A unique feature of the presently claimed polymers is a highly unexpected flow property where the I10 / I2 value is essentially independent of the polydispersity index (ie Mw / Mn). This is in contrast to conventional polyethylene resins which have rheological properties such that as the polydispersity index increases, so does the value of

I10 / I2.

The density of substantially linear ethylene or ethylene / α-olefinic polymers is measured in accordance with ASTM D-792 and is generally from 0.85 g / cm³ up to 0.97 g / cm³ and preferably from 0.87 g / cm³ up to 0.95 g / cm³.

The molecular weight of the ethylene or ethylene / α-oleinic substantially linear ethylenic polymers in the present invention is conveniently indicated using a Melt Index measurement in accordance with ASTM D-1238, Condition 190^°C / 2.16 kg (formally known as “Condition (E)”, and also known as I2). The melt index is inversely related to the molecular weight of the polymer. Therefore, the higher the molecular weight, the lower the melting index, although the relationship is not linear. The melt index for the ethylene or ethylene / aolephene substantially linear ethylene polymers used in this invention is generally from 0.01 grams / 10 minutes (g / 10 min) to 1000 g / 10 min, preferably from 0.05 g / 10 min to 100 g / 10 min, and especially from 0.1 g / 10 min to 20 g / 10 min.

Additives such as antioxidants (eg, hindered phenolic compounds (eg, Irganox¹® 1010), phosphites (for example, Irgafos¹® 168)), and pigments, to the extent that they do not interfere with the improved properties discovered by applicants.

Possible ethylene polymeric materials are mixtures of the substantially linear ethylene polymer and an appropriate different ethylene polymer or other natural or synthetic polymers. Suitable different ethylene polymers include low (LDPE), medium (MDPE) and high (HDPE) density polyethylenes (for example, those made using Ziegler catalysts as in US Patent No.^° 4,076,698), ethylene / ether copolymers, ethylene / vinyl acetate copolymers, ethylene-ethylenically unsaturated carboxylic acid copolymers, α-ethylenic homo- and copolymers. Other suitable polymers include polystyrene (including high impact polystyrene), styrene-butadiene block copolymers, polyisoprene, and other rubbers. Blends comprising a higher proportion of the resin having the higher melting point are preferred. Regardless of composition, the ethylene polymeric material preferably comprises greater than 50 percent, and most preferably greater than 70 percent, by weight of ethylene monomeric units. The ethylene polymeric material can be partially or totally composed of ethylene monomeric units. Preferred blends are those with the substantially linear ethylene polymer and other conventional ethylene polymers, such as LDPE, HDPE, ethylene / acrylic acid copolymer (EAA), and LLDPE.

Substantially improved elasticity and melt processability of polymers

Linear ES 2 145 133 T3 according to the present invention are obtained as a result, it is believed, of its production method. Polymers can be produced by means of a continuous (compared to batch) process of controlled polymerization using at least one reactor, but can also be produced using multiple reactors (for example, using a multiple reactor setup as described in US Patent No. 3,914,342) at a polymerization temperature and pressure sufficient to produce polyomers having the desired properties. In accordance with one embodiment of the present process, the polyomers are produced in a continuous process, as compared to a batch process. Preferably, the polymerization temperature is from 20^°C up to 250^°C, using constrained geometry catalyst technology. If a polymer with a narrow molecular weight distribution (Mw / Mn from 1.5 to 2.5) is desired that has a higher I10 / I2 ratio (for example, I10 / I2 of 7 or more, preferably 8 or more, more preferably 9 or more), the ethylene concentration in the reactor is preferably no more than about 8 weight percent of the reactor content, especially no more than 4 weight percent of the reactor content. Preferably, the polymerization is carried out in a solution polymerization process. Generally, the manipulation of I10 / I2 while keeping Mw / Mn relatively low to produce the novel polymers described in this invention is a function of reactor temperature and / or ethylene concentration. A lower ethylene concentration and higher temperature generally produce higher I10 / I2.

The molecular weight distribution (Mw / Mn) of the individual polymer samples is analyzed by gel permeation chromatography (GPC) on a Waters 150 chromatographic unit.^°High temperature C equipped with three mixed porosity columns (Polymers Laboratories 10³, 10⁴, 10⁵ y10⁶), which operates at a system temperature of 140^°C. The solvent is 1,2,4-trichlorobenzene, from which 0.3 weight percent solutions of the injection samples are prepared. The flow rate is 1.0 milliliters / minute and the injection volume size is 200 microliters.

Molecular weight determination is deduced using narrow molecular weight distribution polystyrene standards (from Polymer Laboratories) in conjunction with their elution volumes. The equivalent polyethylene molecular weights are determined using the appropriate Mark-Houwink coefficients for polyethylene and polystyrene (as described by Williams and Word in Journal of Polymer Science, Polymer Letters, volume 6, (621) -1968) to derive the following equation: M_polyethylene = a * (M_polystyrene)^b. In this equation, a = 0.4316 and b = 1.0. The weight average molecular weight, Mw, is calculated in the usual way according to the following formula: M_w = Σw_i * M_i, where w_i and M_i are the weight fraction and molecular weight, respectively, of the th fraction eluted from the GPC column.

The processing rheology (PI) onyx is measured by a gas extrusion rheoometer (GER). The GER is described by M. Shida, RN Shroff and LV Cancio in Polym. Eng. Sci., Volume 17, n^°11, page 770 (1977) and in Rheometers for Molten Plastics by John Dealy, published by Van Nostrand Reinhold Co. (1982) at pages 97-99. The processing onyx is measured at a temperature of 190^°C, at 17.340 MPa nitrogen pressure using a 0.752 mm diameter 20: 1 L / D nozzle that has an inlet angle of 180^°. The GER processing index is calculated in millipoise units from the following equation:

PI = 2.15x10⁶ dynes / cm²/ (1000 x shear rate), where:

2.15 x 10⁶ dynes / cm² is the shear stress at 17,237 MPa, and the shear rate is the shear rate in the wall, represented by the following equation:

Q '/ (60 s / min) (0.745) (Diameter x 2.54 cm / inch)³, in which:

Q 'is the extrusion speed (g / min)

0.745 is the density of the polyethylene melt (g / cm³) ^Y

Diameter is the diameter of the capillary hole (inches).

PI is the apparent viscosity of a material measured at apparent shear stress of 2.15 x

IS 2 145 133 T3

10⁶ dynes / cm².

For the substantially linear ethylenic polymers described in this invention, the PI is less than or equal to 70 percent that of a comparative linear ethylenic polymer at about the same I₂and Mw / Mn.

The constrained geometry catalysts suitable for use in this invention preferably include the constrained geometry catalysts described in US Patent Nos. 5,703,187, filed July 3, 1990; 5,064,802 and 5,132,38θ, filed on September 12, 1991; and 5,721,185 filed June 24, 1991. The monocyclopentadienyl transition metal ethylene polymerization catalysts shown in US Patent No. 5,026,798 are also suitable for use in preparing the polymers of the present invention.

The constrained geometry catalysts useful for making the substantially linear ethylenic polymer comprise a metal complex and a cocatalyst.

The metal complexes correspond to Formula (I):

(I)

<img file="ES2145133T3_D0001.tif" />

Z - Y

Cp * - M

<img file="ES2145133T3_D0002.tif" />

(X) n in which:

M is selected from the group consisting of groups 3-10 or the Lanthanide series of the Periodic Table of the Elements;

Cp * is selected from the group consisting of indenyl, tetrahydroindenyl, fluorenyl, octahydrofluorenyl, tetrahydrofluorenyl, cyclopentadienyl, and R-substituted cyclopentadienyl linked in the η bond mode⁵to M;

X is, independently in each case, an anionic ligand group selected from the group consisting of hydride, halide, alkyl of up to 30 carbon atoms, alkoxy having up to a total of 30 carbon and oxygen atoms, cyanide, azide, acetylacetonate, aryl of up to 30 carbon atoms, aryloxy having up to a total of 30 carbon and oxygen atoms, norbornyl and benzyl;

n is 0, 1, 2, 3 or 4 and is 2 less than the valence of M;

Y is NR ", PR", O or S;

Z is CR *, CR2CR2, SiR *, SiR * SiR *;

R is selected from the group consisting of alkyl having 1 to 20 carbon atoms, cyano, norbornyl, benzyl, aryl having up to 20 carbon atoms, (R ')₃Yes, and (R ')₃Ge;

R 'is selected from the group consisting of C alkyl₁-C₂₀ and aryl of up to 20 carbon atoms;

R "is selected from the group consisting of C alkyl₁-C₂₀, aryl of up to 20 carbon atoms, benzyl, haloaryl having up to a total of 20 atoms than carbon and halogen, 2-methoxyphenyl, 4-methoxyphenyl, and norbornyl; Y

R * is selected from the group consisting of hydrogen, C₁-C₂₀, haloalkyl having up to a total of 20 carbon and halogen atoms, aryl having up to 20 carbon atoms, and haloaryl having up to a total of 20 carbon and halogen atoms.

M is titanium, zirconium, or hafnium;

X, independently at each occurrence, is selected from the group consisting of halide, alkyl of up to 30 carbon atoms, aryl of up to 30 carbon atoms, and benzyl;

ES 2 145 133 T3 nes1o2;

YesNR ";

Z is CR2CR * or SiR2;

R is selected from the group consisting of alkyl having 1 to 20 carbon atoms, benzyl, aryl of up to 20 carbon atoms, and (R ') 3Si;

R 'is selected from the group consisting of C1-C20 alkyl and aryl of up to 20 carbon atoms;

R "is selected from the group consisting of C1-C20 alkyl, aryl of up to 20 carbon atoms, and benzyl; Y

R * is selected from the group consisting of hydrogen, C₁-C₂₀ and aryl of up to 20 carbon atoms.

It should be noted that the complex may exist as a larger or larger oligéomer. Most preferably, at least one of R, Z or R "is an electron donating moiety. Therefore, most preferably Y is a nitrogen or phosphorus containing group corresponding to the formula -NR "or -PR" -, where R "is C1-C20 alkyl, that is, an alkylamido group or alkylphosphide.

The most highly preferred complex compounds are amidosilane or amidoalkanediyl compounds corresponding to Formula (II):

(II)

<img file="ES2145133T3_D0003.tif" />

in which:

M is titanium, zirconium, or hafnium, attached in an η-bond mode⁵ to the cyclopentadienyl group;

R ', at each occurrence, is independently selected from the group consisting of hydrogen, silyl, alkyl, aryl and combinations thereof, said R' having up to 10 carbon or silicon atoms;

E is silicon or carbon;

X, independently at each occurrence, is hydride, halo, alkyl, aryl, aryloxy or alkoxy, said X having up to 10 carbon atoms;

mes1o2; and nes1o2.

Examples of the most highly preferred metal coordination compounds include compounds in which the R 'on the amido group is methyl, ethyl, propyl, butyl, pentyl, hexyl, (including

ES 2 145 133 T3 isomers), norbornyl, benzyl or phenyl; the cyclopentadienyl group is cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl, or octahydrofluorenyl; R 'on the above cyclopentadienyl groups, in each case, is hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, (including isomers), norbornyl, benzyl or phenyl; and X is chlorine, bromine, iodine, methyl, ethyl, propyl, butyl, pentyl, hexyl, (including isomers), norbornyl, benzyl, or phenyl.

Specific compounds include: (tert-butylamido) dichloride (tetramethyl-n⁵-cyclopentadienyl) 1,2-ethanediyl zirconium, (tert-butylamido) (tetramethyl-n⁵-cyclopentadienyl) -1,2-ethanediyl titanium, (methylamido) (tetramethyl-n dichloride⁵-cyclopentadienyl) -1,2-ethanediyl zirconium, (methylamido) (tetramethyl-n dichloride⁵-cyclopentadienyl) -1,2-ethanediyl titanium, (ethylamido) (tetramethyl-n dichloride⁵cyclopentadienyl) -methylene titanium, (tert-butylamido) dibenzyl (tetramethyl-n⁵-cyclopentadienyl) silane zirconium dibenzyl, (benzylamido) dimethyl (tetramethyl-n dichloride⁵-cyclopentadienyl) silane titanium, (phenylphosphido) dimethyl (tetramethyl-n⁵-cyclopentadienyl) silane zirconium dibenzyl, and (tert-butylamido) dimethyl (tetramethyl-n⁵cyclopentadienyl) dimethyl titanium silane.

The complexes can be prepared by contacting a metal derivative, M, and a Group I metal derivative or Grignard derivative of the cyclopentadienyl compound in a solvent, and removing the by-product salt. Suitable solvents for use to prepare the metal complexes are aliphatic or aromatic liquids, such as cyclohexane, methylcyclohexane, pentane, hexane, heptane, tetrahydrofuran, dietary ether, benzene, toluene, xylene, ethylbenzene, or mixtures thereof.

In a preferred embodiment, the metal compound is MX_n+₁, that is, M is in a lower oxidation state than in the corresponding compound, MX_n+₂ and the oxidation state of M in the final desired complex. A non-interfering oxidizing agent can then be used to raise the oxidation state of the metal. The oxidation is carried out simply by contacting the reactants using solvents and reaction conditions used in the preparation of the complex itself. By the term "non-interfering oxidizing agent" is meant a compound that has sufficient oxidation potential to increase the oxidation state of the metal without interfering with the formation of the desired complex or subsequent polymerization processes. A particularly suitable non-interfering oxidizing agent is AgCl or an organic halide such as methylene chloride. The above techniques are described in US Patent Nos. 5,703,187, filed July 3, 1990, and US-SN 702,475, filed May 20, 1991 abandoned in favor of US-SN 967,365.

Additionally, the complexes can be prepared in accordance with the teachings of the United States Document Serial No. 778,433, pending, entitled: "Preparation of Metal Coordination Complex (I)", filed in the name of Peter Nickias and David Wilson, the October 15, 1991, and United States Document Serial No. 778,432, pending, entitled: "Preparation of Metal Coordination Complex (II)", presented on behalf of Peter Nickias and David Devore, on October 15, 1991, both being abandoned.

Suitable cocatalysts for use in this invention include polymeric or oligomeric aluminoxanes, especially methylaluminoxane, as well as compatible, non-coordinating, inert, ion-forming compounds. The so-called modified methylaluminoxane (MMAO) is also suitable for use as a cocatalyst. A technique for preparing such modified aluminoxane is described in US Patent No. 5,041,584. Aluminoxanes can also be manufactured as described in US Patent Nos. 5,542,199, 4,544,762, 5,015,749, and 5,041,585. Preferred catalysts are inert, non-coordinating boron compounds.

The ionic active catalytic species that can be used to polymerize the polymers described in this invention correspond to Formula (III):

(III)

<img file="ES2145133T3_D0004.tif" />

Cp * - M \

A (X) n-1 in which:

M, Cp *, X, Y and Z are as defined for Formula (I) above;

ES 2 145 133 T3 n is 1, 2, 3 or 4, and is 2 less than the oxidation state of M; Y

A- is a non-coordinating and compatible anion.

As used in this invention, the expression "non-coordinating and compatible anion" means an anion that either does not coordinate with the cation containing the substituted monocyclopentadienyl or monocyclopentadienyl group or that was only weakly coordinated with said cation thus remaining, weak enough to be displaced by a neutral Lewis base. A non-coordinating and compatible anion specifically refers to a compatible anion which, when functioning as a charge balancing anion in the catalytic system of this invention, does not transfer an anionic substituent or fragment thereof to said cation, thereby forming , a neutral tetracoordinated metallocene and a neutral metal by-product. "Compatible anions" are those anions that do not degrade to neutrality when the initially formed complex decomposes and are non-interfering with the desired subsequent polymerization or other uses of the complex.

One method of making the ionic catalytic species that can be used to make the polyomers of the present invention involves combining: a) at least one first component that is a mono (cyclopentadienyl) derivative of a metal of Group 3-10 or of the Lantoanide Series of the Periodic Table of the Elements that contains at least one substituent that will combine with the cation of a second component (described later), which first component is capable of forming a cation that formally has a coordination number that is one less than its valence; and b) at least one second component that is a salt of a Bronsted acid and a non-coordinating and compatible anion.

More in particular, the non-coordinating and compatible anion of the Bronsted acid salt may comprise a uonic coordination complex comprising a charge-bearing metal or metalloid nucleus, which anion is both bulky and non-nucleophilic. The term "metalloid" as used in this invention includes non-metals such as boron, phosphorus, and the like that exhibit semi-metallic characteristics.

Illustrative, but not limiting, examples of monocyclopentadienyl metal components (first components) that can be used to prepare the cationic complexes are derivatives of titanium, zirconium, vanadium, hafnium, chromium and lanthanum. The preferred components are titanium or zirconium compounds. Examples of suitable monocyclopentadienyl metal compounds are hydrocarbyl-substituted monocyclopentadienyl metal compounds such as (tert-butylamido) (tetramethyln⁵-cyclopentadienyl) -1,2-ethanediyl zirconium dimethyl, (tert-butylamido) (tetramethyl-n⁵-cyclopentadienyl) -1,2ethanediyl titanium dimethyl, (methylamido) (tetramethyl-n⁵-cyclopentadienyl) -1,2-ethanediyl zirconium dibenzyl, (methylamido) (tetramethyl-n⁵-cyclopentadienyl) -1,2-ethanediyl titanium dimethyl, (ethylamido) (tetramethyl-n⁵-cyclopentadienyl) -methylene titanium dimethyl, (tert-butylamido) dibenzyl (tetramethyl-n⁵-cyclopentadienyl) silane zirconium dibenzyl, (benzylamido) dimethyl (tetramethyl-n⁵-cyclopentadienyl) silane titanium diphenyl and (phenylphosphido) dimethyl (tetramethyl-n⁵-cyclopentadienyl) silane zirconium dibenzyl.

Such components are easily prepared by combining the corresponding metal chloride with a dilithium salt of the substituted cyclopentadienyl group, such as a cyclopentadienyl-alkanediyl compound, cyclopentadienyl silane amide, or cyclopentadienyl phosphide. The reaction is carried out in an inert liquid such as tetrahydrofuran, C5-10 alkanes, toluene, etc. using conventional prosthetic procedures. Additionally, the first components can be prepared by reacting a group II metal derivative of the cyclopentadienyl compound in a solvent and removing the by-product salt. Magnesium derivatives of cyclopentadienyl compounds are preferred. The reaction can be carried out in an inert solvent such as cyclohexane, pentane, tetrahydrofuran, diethyl ether, benzene, toluene, or mixtures of the like. The resulting metal cyclopentadienyl halide complexes can be rented using various techniques. Generally, metal cyclopentadienyl alkyl or aryl complexes can be prepared by alkylating the metal cyclopentadienyl halide complexes with alkyl or aryl derivatives of Group I or Group II metals. Preferred alkylating agents are alkyl lithium and Grignard derivatives using conventional synthetic techniques. The reaction can be carried out in an inert solvent such as cyclohexane, pentane, tetrahydrofuran, diethyl ether, benzene, toluene, or mixtures of the like. A preferred solvent is a mixture of toluene and tetrahydrofuran.

The compounds useful as a second component to prepare the ionic catalysts useful in this invention will comprise a cation, which is a Bronsted acid capable of giving a protoon, and a compatible non-coordinating anion. Preferred anions are those that contain a uonic coordination complex comprising a charge-bearing metal or metalloid nucleus, which anion is relatively large (bulky), capable of stabilizing the active catalytic species (the Group 3-10 cation Or the

IS 2 145 133 T3

Lanthanide series) that is formed when the two components combine and labile enough to be displaced by ethylanic, diethienic and acetylanically unsaturated substrates or other neutral Lewis bases, such as ethers, nitriles and the like. Suitable metals, therefore, include, but are not limited to, aluminum, gold, platinum, and the like. Suitable metalloids include, but are not limited to, boron, phosphorus, silicon, and the like. Anion-containing compounds comprising coordination complexes containing a metal or metalloid atom atom are, of course, well known and many, particularly such compounds which contain a boron atom at the anion part, are commercially available. In view of this, salts containing anions comprising a coordination complex containing a boron atom are preferred.

The second highly preferred component useful for preparing the catalysts of this invention can be represented by the following general formula:

(LH)⁺ [TO]^- in which:

L is a neutral Lewis base;

(LH)⁺ it is a Bronsted acid; Y

[TO]^- it is a compatible and non-coordinating anion.

More preferably [A]^- corresponds to the faormula:

[M'Qq]^- in which:

M 'is a metal or metalloid selected from Groups 5-15 of the Periodic Table of the Elements;

Q, independently in each case, is selected from the group consisting of hydride, dialkylamido, halide, alkoxide, aryloxide, hydrocarbyl and substituted hydrocarbyl radicals of up to 20 carbons, provided that in no more than one case Q is halide; and q is one more than the valence of M '.

The second boron-comprising components, which are particularly useful in preparing the catalysts of this invention, can be represented by the following general formula:

(LH)⁺ [BQ4]^- in which:

L is a neutral Lewis base;

(LH)⁺ it is a Bronsted acid;

B is boron in a valence state of 3; Y

Q is as previously defined.

Illustrative, but not limiting, examples of boron compounds that can be used as a second component to prepare the improved catalysts of this invention are trialkyl substituted ammonium salts such as triethylammonium tetraphenylborate, tripropylammonium tetraphenylborate, tris (n-butyl tetraphenylborate). ) ammonium, trimethylammonium tetrakis (p-tolyl) borate, tributylammonium tetrakis (penta-fluorophenyl) borate, tripropylammonium tetrakis (2,4-dimethylphenyl) borate, tributylammonium tetrakis (3,5-dimethylphenyl) borate, triethylammonium tetrakis (3,5-di-trifluoromethylphenyl) borate, and the like. Also suitable are N, N-dialkylanilinium salts such as N, N-dimethylanilinium tetraphenylborate, N, N-diethylanilinium tetraphenylborate, N, N-dimethyl-2,4,6-trimethylanilinium tetraphenylborate and the like; dialkylammonium salts such as di- (i-propyl) ammonium tetrakis (pentafluorophenyl) borate, dicyclohexylammonium tetraphenylborate and the like; and triarylphosphonium salts such as triphenylphosphonium tetraphenylborate, tri (ethylphenyl) phosphonium tetrakis (pentafluorophenyl) borate and tri (dimethylphenyl) phosphonium tetraphenylborate.

IS 2 145 133 T3

Preferred ionic catalysts formed in this way are those having a separate charge limiting structure corresponding to Formula (IV):

(IV)

<img file="ES2145133T3_D0005.tif" />

Z - Y

Cp * - M

<img file="ES2145133T3_D0006.tif" />

XA * (X) n-1 in which:

M is titanium, zirconium, or hafnium;

Cp *, X and Z are as defined for Formula (I); n is 1, 2, 3 or 4 and is 2 less than the oxidation state of M; and XA * - is -XB (C6F5) 3.

This class of cationic complexes can be conveniently prepared by contacting a metal compound corresponding to Formula (V):

(V)

<img file="ES2145133T3_D0007.tif" />

Z - Y

Cp * - M

<img file="ES2145133T3_D0008.tif" />

(X) n in which:

Cp *, M and n are as previously defined for Formula (IV), with the cocatalyst tris (pentafluorophenyl) borane under condition is to produce the abstraction of X and the formation of the anion -XB (C6F5) 3.

Preferably, X, in the ionic catalyst above, is C hydrocarbyl₁-C₁₀, most preferably methyl.

Formula (V) is called a separate load limiting structure. However, it is also to be understood that, particularly in solid form, the catalyst may not be completely charge-separated. That is, the group X can retain a partial covalent bond towards the metal atom, M. Therefore, the catalysts can be alternatively drawn as having in Formula (VI):

(SAW)

Z - Y

Cp * - M..X..A \

(X) n-1

The catalysts are preferably prepared by contacting the Group 4 metal derivative or Lanthanide with the tris (pentafluorophenyl) borane in an inert diluent such as an organic liquid. Tris (pentafluorophenyl) borane is a commonly available Lewis acid that can be easily prepared according to known techniques. The compound is described in the work of Marks et al. J. Am. Chem. Soc., 1991, 113, 3623-3625, for use in abstracting alkyl from zirconocenes.

Any reference to the Periodic Table of the Elements in this invention shall refer to the Periodic Table of the Elements published and copyrighted by CRC Press, Inc., 1989. Also, any reference to a Group or Groups shall be to the Group or Groups reflected in this Periodic Table of the Elements using the IUPAC system to number the groups.

IS 2 145 133 T3

Other compounds that are useful in the catalytic compositions of this invention, especially compounds containing metals other than Group 4 or Lantoanides, will, of course, be apparent to those skilled in the art.

The polymerization conditions for making the polyomers of the present invention are generally those useful in solution polymerization processes, although the application of the present invention is not limited to them. Suspension and gas phase polymerization processes are also believed to be useful, provided appropriate catalysts and polymerization conditions are employed.

Multi-reactor polymerization procedures, such as those described in US Patent No. 3,914,342, are also useful in the present invention. The multiple reactors can be operated in series or in parallel, with at least one constrained geometry catalyst employed in at least one of the reactors.

In general, continuous polymerization according to the present invention can be carried out under conditions well known in the prior art for polymerization reactions of the ZieglerNatta or Kaminsky-Sinn type, i.e. temperatures from 0^°C up to 250^°C, and pressures from atmospheric to 100 MPa. If desired, suspension, solution, suspension, gas phase or other process conditions may be employed. A support may be employed but preferably the catalysts are used homogeneously (ie soluble). It will of course be taken into account that the active catalyst system is formed in situ if the components of the catalyst and the cocatalyst thereof are added directly to the polymerization process and an appropriate solvent or diluent, including monoomer, is used in said polymerization process. condensed. However, it is preferred to form the active catalyst in a separate step in an appropriate solvent before adding it to the polymerization mixture.

Excellent teachings for procedures for making and processing ethylene polymer foam structures are seen in CP Park's work, "Polyolefin Foam," Chapter 9, Handbook of Polymer Foams and Technology, edited by D. Klempner and KC Frish, Hanser Publishers, Munich, Vienna, New York, Barcelona (1991).

The present foam structure can be manufactured by a conventional extrusion foaming process. The framework is generally prepared by heating an ethylogenic polymeric material to form a plasticized or molten polymeric material, incorporating an expanding agent into it to form a foamable gel, and extruding the gel through a die to form the foamed product. Before mixing with the blowing agent, the polymeric material is heated to a temperature at or above its vitreous transition temperature or melting point. The blowing agent can be incorporated or mixed into the molten polymeric material by any means known in the art, such as with an extruder, mixer, or blender. The blowing agent is mixed with the molten polymeric material at a high pressure sufficient to prevent substantial expansion of the molten polymeric material and to generally disperse the blowing agent homogeneously in the oil. Optionally, a nucleator can be blended into the molten polymer or dry blended with the polymeric material prior to plasticizing or melting. The foamable gel is topically cooled to a lower temperature to optimize the phosphoric characteristics of the foam structure. The gel is then extruded or passed through a die in the desired shape to a zone of reduced or lower pressure to form the foam structure. The lower pressure zone was at a lower pressure than that in which the foamable gel is maintained prior to extrusion through the die. The lower pressure can be super-atmospheric or sub-atmospheric (vacuum), but it is preferably at an atmospheric level.

The present foam structure can be formed into a bonded base wire formed by extruding the ethylogenic polymeric material through a multi-hole die. The holes are arranged so that contact between adjacent streams of molten extrudate occurs during the foaming process and the surfaces in contact adhere to one another with sufficient adhesion to result in a unitary foam structure. The molten extrudate streams exiting the die take the form of base wires or profiles that desirably foam, bond and adhere to one another to form a unitary structure. Desirably, the bonded individual base yarns or profiles should remain adhered in a unitary structure to prevent delamination of the base yarn under the stresses encountered in preparing, shaping and using the foam. Apparatus and methods for producing bonded core strand foam structures are seen in US Patent Nos. 3,573,152 and 4,824,720.

IS 2 145 133 T3

The present foam structure can also be formed by a build-up extrusion process, as seen in U.S. Patent No.^° 4,323,528. In this procedure, low-density foam structures having large lateral cross-sectional areas are prepared by: 1) forming under pressure a gel of the ethylene polymeric material and a blowing agent at a temperature at which the viscosity of the gel is sufficient to retain the blowing agent when the gel is allowed to expand; 2) Extrude the gel in a retention zone maintained at a temperature and pressure that does not allow the gel to foam, the retention zone having an outlet nozzle that defines a building opening in a lower pressure zone than the foam gel, and an openable hatch that closes the mouthpiece orifice; 3) periodically open the gate; 4) apply, substantially concurrently, mechanical pressure by means of a mobile plunger on the gel to expel it from the retention zone through the nozzle orifice to the zone of lower pressure, at a speed greater than that at which it occurs. substantial foaming in the nozzle orifice and less than that at which substantial irregularities occur in cross-sectional area or shape; and 5) allowing the ejected gel to expand unrestricted in at least one dimension to produce the foam structure.

The present foam structure can also be formed into non-crosslinked foam beads suitable for molding into articles. To make the foam beads, discrete resin particles, such as granulated resin pellets: are suspended in a liquid medium in which they are substantially insoluble, such as water; they are impregnated with a blowing agent by introducing the blowing agent into the liquid medium at an elevated pressure and temperature in an autoclave or other pressure vessel; and, quickly, they are discharged to the atmosphere or a zone of reduced pressure to expand until they form the foam beads. This procedure is well taught in US Patent Nos. 4,379,859 and 4,464,484.

In a derivative of the above process, styrene monomer can be impregnated into the suspended pellets prior to impregnation with the expanders to form a graft interpolymer with the ethylene polymeric material. The polyethylene / polystyrene interpolymer beads are cooled and discharged from the container substantially unexpanded. The beads are then expanded and molded by the conventional extended polystyrene bead molding process. Procedure for manufacturing polyethylene / polystyrene interpolymer beads is described in US Patent No.^° 4.168.353.

The foam beads can then be molded by any means known in the art, such as loading the foam beads into the mold, pressing in-mold to compress the beads, and heating the beads such as with steam to effect bonding and bonding. welding the beads to form the article. Optionally, the beads can be impregnated with air or other blowing agent at elevated pressure and temperature prior to loading into the mold. In addition, the beads can heat up before charging. The foam beads can then be molded into blocks or shaped articles by an appropriate molding method known in the art. (Some of the methods are taught in US Patent Nos. 3,504,068 and 3,953,558). Excellent teachings of the above molding procedures and methods are seen in the previous CP Park publication, page 191, pp. 197-198 ypéags. 227-229.

Useful blowing agents to make the present foam structure include inorganic agents, organic blowing agents, and decomposable chemical blowing agents. Suitable inorganic blowing agents include carbon dioxide, nitrogen, argon, water, air, and helium. Organic blowing agents include aliphatic hydrocarbons having 1-6 carbon atoms, aliphatic alcohols having 1-3 carbon atoms, and fully and partially halogenated aliphatic hydrocarbons having 1-4 carbon atoms. Aliphatic hydrocarbons include methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, and neopentane. Aliphatic alcohols include methanol, ethanol, n-propanol, and isopropanol. Fully and partially halogenated aliphatic hydrocarbons include fluorocarbons, chlorocarbons, and chlorofluorocarbons. Examples of fluorocarbons include methyl fluoride, perfluomethane, ethyl fluoride, 1,1-difluoroethane (HFC-152a), 1,1,1-trifluoroethane (HFC143a), 1,1,1,2-tetrafluoroethane (HFC-134a) , pentafluoroethane, difluomethane, perfluoroethane, difluoropropane, such as 2,2-difluoropropane, 1,1,1-trifluoropropane, perfluoropropane, dichloropropane, perfluobutane and perfluorocyclobutane. Partially chlorinated and chlorofluorinated hydrocarbons for use in this invention include methyl chloride, methylene chloride, ethyl chloride, 1,1,1-trichloroethane, 1,1-dichloro-1-fluoethane (HCFC141b), 1-chloro-1 , 1-Difluoroethane (HCFC-142b), 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123) and 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124). Fully chlorofluorinated hydrocarbons include trichloromonofluomethane (CFC-11), dichlorodifluomethane (CFC-12), trichlorotrifluoroethane (CFC-113), dichlorotetrafluoroethane (CFC-114), chloroheptafluoropropane, and dichlorohexafluoropropane. Chemical blowing agents include

ES 2 145 133 T3 azodicarbonamide, azodiisobutyronitrile, benzenesulfonhydrazide, 4,4-oxybenzenesulfonyl semicarbazide, ptoluenesulfonyl semicarbazide, barium azodicarboxylate, N, N'-dimethyl-N, N'-dinitrosoterephrazine- triamine. Preferred blowing agents include isobutane, HFC-152a, and mixtures of the foregoing.

The amount of blowing agent incorporated into the polymer melt to make a foam-forming polymer gel is from 0.2 to 5.0, preferably from 0.5 to 3.0, and most preferably from 1, 0 to 2.50 gram-mole per kilogram of polymer.

Various additives, such as stability control agents, nucleating agents, inorganic fillers, pigments, antioxidants, acid scavengers, UV absorbers, flame retardants, processing aids, can be incorporated into the present foam structure. and extrusion aids.

A stability control agent can be added to the present foam to improve dimensional stability. Preferred agents include amides and esters of C10-24 fatty acids. Such agents are seen in US Patent Nos. 3,644,230 and 4,214,054. The most preferred agents include stearyl stearamide, glycerol monostearate, glycerol monobehenate, and sorbitol monostearate. Typically, such stability control agents are employed in an amount ranging from about 0.1 to about 10 parts per hundred parts of the polymer.

The present foam structure exhibits excellent dimensional stability. Preferred foams recover 80 or more percent of their initial volume within a month with the initial volume being measured within 30 seconds after foam expansion. Volume is measured by an appropriate method such as a cubic water displacement.

In addition, a nucleating agent can be added in order to control the size of the foam cells. Preferred nucleating agents include inorganic substances such as calcium carbonate, talc, clay, titanium oxide, silica, barium sulfate, diatomaceous earth, and mixtures of citric acid and sodium bicarbonate. The amount of nucleating agent employed can range from about 0.01 to about 5 parts by weight per hundred parts by weight of a polymeric resin.

The present foam structure is substantially uncrosslinked or uncrosslinked. The alkenylaromaetic polymeric material comprising the foam structure is substantially free of crosslinking. Foam structure contains 5 percent or less gel per ASTM D-2765-84 Method

A. The slight degree of crosslinking that occurs naturally without the use of crosslinking agents or radiation is allowable.

The present foam structure has a density less than 250, more preferably less than 100, and most preferably from 10 to 70 kilograms per cubic meter. The foam has an average cell size from 0.05 to 5.0, more preferably from 0.2 to 2.0 and most preferably 0.3 to 1.8 millimeters, according to ASTM and D3576.

The present foam structure can take any physical configuration known in the art such as sheet, bar, board and extruded profiles. The foam structure can also be formed by molding expandable beads into any of the above configurations or any other configuration.

The present foam structure can be closed cell or open cell. Preferably, the present foam contains 80 percent or more closed cells in accordance with ASTM D2856-A.

The following are examples of the present invention, and should not be construed as limiting. Unless otherwise indicated, all percentages, parts or proportions are by weight relative to total weight.

Table A represents the physical properties of certain substantially linear low-density polyethylene resins (CGCT resins), a conventional LLDPE resin, and a conventional ultra-low-density linear resin (ULLDPE resin). The CGCT resins were prepared in a continuous polymerization process with a constrained geometry catalyst as set forth in U.S. Patent No.^° 5,272,236. CGCT resins are indicated by "CG", and LLDPE and ULLDPE resins are indicated by the prefixes "ZN" in the resin designation. The foams were prepared in the

ES 2 145 133 T3 following examples and comparative examples with CGCT resins and ULLDPE and LLDPE resins. TABLE A

Physical properties of CGCT resins and LLDPE resin

<td>Resin name</td><td>ME (dg / min)¹</td><td>Mw / Mn</td><td>Density (g / cm³)²</td><td>I10 / I2</td><td>Tf (° C)³</td><td>Melt Tension (g)⁴</td>

<td>CG1</td><td> 1,06</td><td> 2,090</td><td> 0,9018</td><td> 7,61</td><td> 95,3</td><td> 1,46</td>

<td>CG2</td><td> 0,87</td><td> 1,884</td><td> 0,9394</td><td> 8,55</td><td> 126,6</td><td> 1,88</td>

<td>CG3</td><td> 0,57</td><td> 1,903</td><td> 0,8730</td><td> 7,22</td><td> 55,5</td><td> 3,17</td>

<td>CG4</td><td> 2,00</td><td> 1,793</td><td> 0,9014</td><td> 6,45</td><td> 95,6</td><td> 0,71</td>

<td>CG5</td><td> 5,17</td><td> 1,900</td><td> 0,8732</td><td> 7,65</td><td> 60,6</td><td> 0,35</td>

<td>CG6</td><td> 0,98</td><td> 2,190</td><td> 0,9016</td><td> 8,80</td><td> 95,3</td><td> 1,90</td>

<td>ZN1⁵</td><td> 0,80</td><td> 4,25</td><td> 0,9050</td><td> 8,70</td><td> 121,3</td><td> 1,32</td>

<td>ZN2⁶</td><td> 1,00</td><td> -</td><td> 0,9350</td><td> -</td><td> 128,0</td><td> -</td>

^{1 or}Melt index of the resin, in decigrams per minute, determined according to ASTM 1238 in the Condition

AND.

² Resin density, in grams per cubic centometer ³ Melting point of the resin, in degrees Celsius, determined by DSC (Differential Scanning Calorimetry) (endotherm peak while heating at a rate of 10^°C / min).

⁴ Tension of the resin melt, in grams ⁵ ZN1 is a ULLDPE (Attane 4203 from The Dow Chemical Company) ⁶ ZN2 is an LLDPE (Dowlex 2038 from The Dow Chemical Company)

Example 1 and Comparative Example 1

The ethylenic polymer foams of the present invention were prepared from CG1 and CG2 resins. They were compared to determine extrudability and phosphoric properties with ethylenic polymer foams prepared with conventional LLDPE resin (ZN1 and ZN2).

The equipment used in this example was a 25 millimeter (mm) screw type extruder that had additional mixing and cooling zones at the end of the normal sequential feed, metering and mixing zones. An opening for the blowing agent is provided on the extruder drum between the dosing and mixing zones. At the end of the cooling zone, a nozzle orifice having a rectangular shaped opening was attached. The height of the opening, hereinafter called the nozzle opening, was adjustable while its width was fixed at 3.68mm.

The granular resins were fed into the extruder hopper, and extruded at a uniform rate of 1.8 kilograms per hour (kg / hr) by adjusting the rotational speed of the screw. In the trial

1.1, where a lower density resin was tested, two parts of stearyl stearamide were added per hundred parts of the polymer to improve dimensional stability. The stearyl stearamide was Kemamide S-180 from Witco Corporation. The stearyl stearamide was previously mixed with the resin granules. The temperatures maintained in the extruder zones were 175^°Cenlazonade feeding, 180^°C in the fusion zone, 190^°C in the dosing area, and 210^°C in the mixing zone.

IS 2 145 133 T3

The blowing agent HCFC-142b was injected into the injection port at a predetermined rate. The temperature of the cooling zone and the opening of the nozzle were adjusted in each test to obtain the best foam.

As shown in Table B, the CGCT resins provided good quality foams having relatively large cell size and cross sectional size. The resins could be foamed at a relatively low temperature for those polymer densities.

The CGCT resin foams exhibited good dimensional stability. The foam from Test 1.1 had a relatively low open cell content (24 percent), and initially shrunk to some degree but recovered to over 90 percent of the initial volume during aging. The foam in Trial 1.2 shrunk by no more than 4 percent during aging.

In contrast, the foams prepared in Trials 1.3 and 1.4 from conventional LLDPE resins were unsatisfactory due to smaller cell size and cross-sectional size. The foam from Trial 1.3 was partially flattened, and had a high level of open cells (70 percent). The relatively high foaming temperature (115^°C) of the resin affected its foamability. The higher density LLDPE resin in Test 1.4 expanded to a foam that had a relatively low open cell content, but exhibited flow instability, resulting in uneven foam skins.

TABLE B

CGCT resin foams and LLDPE resins

<td>Test No.</td><td>Resin used¹</td><td>AE level²</td><td>Temp. of the₃foam³</td><td>Size of the₄foam⁴</td><td>Density of the₅foam⁵</td><td>Cell size⁶</td><td>Cell open⁷</td><td>Foam quality⁸</td>

<td> 1.1</td><td>CG1</td><td> 1,9</td><td> 98</td><td> 0,84</td><td> 41</td><td> 0,74</td><td> 24</td><td>B</td>

<td> 1.2</td><td>CG2</td><td> 1,7</td><td> 120</td><td> 0,48</td><td> 38</td><td> 0,34</td><td> 55</td><td>B</td>

<td> 1.3*</td><td>ZN1</td><td> 1,9</td><td> 115</td><td> 0,14</td><td> 46</td><td> 0,15</td><td> 70</td><td>PA</td>

<td> 1.4*</td><td>ZN2</td><td> 1,7</td><td> 123</td><td> 0,36</td><td> 32</td><td> 0,15</td><td> 20</td><td>FF</td>

^* It is not an example of the present invention.

Refer to Table A for the characteristics of the resins

Gram-mole of blowing agent mixed per kilogram of polymer (mpk)

The optimum melting temperature that provides the best foam, in degrees Celsius

TO^and Foam body cross-sectional area, in square centimeters

Density of a one-month-old body of foam, in kilograms per cubic meter

Cell size, in millimeters, determined according to ASTM D3576

Open cell content, in percent, determined according to ASTM 2856-A

Foam body quality: B = good; E = excellent; S = satisfactory; M = poor quality foam that has hard skins that result from crushing surface cells; PA = partially crushed foam; FF = uneven foam core yarn due to melt fracture.

Example 2

An ethylene polymer foam of the present invention was prepared using CG3 resin.

IS 2 145 133 T3

The experimental equipment and procedure employed were substantially the same as in Example 1, except for the stability control agent, the extruder zone temperatures, and the level of blowing agent. Glycerol monostearate (GMS) was used as a stability control agent at a level of 2 parts per hundred parts resin (ppc). The temperatures maintained in the extruder zones were 120 ° C in the feeding zone, 160 ° C in the melting zone, 180 ° C in the dosing zone, and 195 ° C in the mixing zone. The HCFC-142b blowing agent was injected uniformly into the injection port at a rate of 2.2 gram-mole per kilogram of resin (mpk). The melt was cooled to approximately 66^°C before extrusion through the die.

Satisfactory foam of 1.4 cm was achieved² cross section, 45 kg / m³ density, 1.2 mm cell size and 49 percent open cell content. The foam was dimensionally stable, very soft and elastic.

Example 3

An ethylenic polymer foam of the present invention was prepared using CG4 resin.

The experimental equipment and procedure employed were substantially the same as in Example 1, except for the stability control agent, the extruder zone temperatures, and the level of blowing agent. The temperatures maintained in the extruder zones were 120^°C in the feeding zone, 165^°C in the fusion zone, 190^°C in the dosing zone, and 195^°C in the mixing zone. Glycerol monostearate (GMS) was used as a stability control agent at a level of 2 phr. In the tests of this example, two types of blowing agent were used: HCFC-142b and an 80/20 mole mixture of HFC-152a and ethanol (EtOH).

Excellent quality foams were produced when the melt was cooled to approximately 93^°C before extrusion through the die. As seen in Table C, both blowing agents extended the resin to low density foams that had large cross sections and low open cell contents. The dimensional stability of the resins was excellent. The open cell contents of the foams are comparable to those of foams prepared from conventional highly branched low density polyethylene (LDPE) on the same foam extrusion apparatus.

TABLE C

CGCT resin foams

<td>Test No.</td><td>Kind of AE¹</td><td>AE level²</td><td>Temp. of the₃foam³</td><td>Size of the₄foam⁴</td><td>Density of the₅foam⁵</td><td>Cell size⁶</td><td>Cell open⁷</td><td>Foam quality⁸</td>

<td> 3.1</td><td>HCFC-142b</td><td> 1,7</td><td> 93</td><td> 1,40</td><td> 25</td><td> 1,16</td><td> 10</td><td>AND</td>

<td> 3.2</td><td>HFC-152a / EtOH</td><td> 1,7</td><td> 93</td><td> 1,35</td><td> 27</td><td> 0,44</td><td> 7</td><td>AND</td>

¹ Types of blowing agent used. The molar ratio of the mixture of HFC-152a and EtOH was 80/20^2-8 Same as in Table B.

Example 4 and Comparative Example 4

Ethylene polymer foams were prepared in accordance with the present invention with a mixture of a conventional CGCT resin and a conventional highly branched low density polyethylene (LDPE) resin. That foam was compared with a foam prepared with a mixture of conventional LLDPE resin (ZN1) and the LDPE resin.

Each of the CG1 and ZN1 resins were mixed with the LDPE resin in a 50/50 weight ratio. The LDPE resin was of the type prepared by a high pressure process and had a melt index of 1.8 and a density of 0.923 g / cm.³. Two ppc of stearyl stearamide were added for foam stability.

IS 2 145 133 T3

The equipment and the operating procedure were substantially the same as in Example 1. HCFC-142b was used as the blowing agent at a level of 1.5 mpk. In Test 4.1 a small amount of talc (0.05 phr) was added to reduce the calula size of the foam produced. In Test 4.2 no talc was necessary since the size of the cell was desirably small without it.

As seen in Table D, the CG1 / LDPE blend produced a substantially closed cell foam of satisfactory quality. The mixture foamed at a temperature that foams composed only of LDPE resin typically foamed (106 ° C). The ZN1 / LDPE mixture foams at the same temperature as the ZN1 resin foams (115 ° C). The ZN1 / LDPE blend produced a foam that had all the undesirable characteristics: smaller cross-sectional size, higher density, smaller cell size without nucleator, and more open cells.

TABLE D

Resin Blend Foams

<td>Test No.</td><td>Resin type¹</td><td>Relationship from mix²</td><td>Temp. of the₃foam³</td><td>Size of the₄foam⁴</td><td>Density of the₅foam⁵</td><td>Cell size⁶</td><td>Calula open⁷</td><td>Foam quality⁸</td>

<td> 4.1</td><td>CG1 / LDPE</td><td> 50/50</td><td> 106</td><td> 0,85</td><td> 56</td><td> 0,68</td><td> 15</td><td>S</td>

<td> 4.2*</td><td>ZN1 / LDPE</td><td> 50/50</td><td> 115</td><td> 0,46</td><td> 61</td><td> 0,36</td><td> 51</td><td>M</td>

* Not an example of the present invention ¹ Refer to Table A for the characteristics of the resins ² Weight ratio of the two polymers ^3-8 Same as in Table B.

Example 5

Ethylene polymer foams were prepared according to the present invention with a mixture of a CGCT and LLDPE and a mixture of a CGCT resin (CG1 resin) and ethylene-acrylic acid (EAA) resin. They were compared to an ethylanic polymer foam prepared with a blend of a conventional LLDPE resin (ZN1) and each of the CG1 and EAA resins.

The equipment and operating procedure were substantially the same as in Example

Four. The LDPE resin used was the same as in Example 4 and the EAA resin was PRIMACOR® 1410 resin (The Dow Chemical Company). The EAA resin has 9 weight percent acrylic acid copolymerized in it and a melt index of 1.4. Different mixing ratios were used than in Example 4. Isobutane was used as the blowing agent at a level of 1.5 mpk, and 0.01 phr of talc was added for scale size control. For dimensional stability, two ppc of stearyl stearamide were added. The data is summarized in Table E.

CGCT (CG1) resin blends made better foams than corresponding blends with conventional LLDPE (ZN1) resins. The CG1 / EAA foam was soft and flexible. CG1 / EAA foam can find applications in sports and leisure as well as in padded packaging.

IS 2 145 133 T3

TABLE E

Resin Blend Foams

<td>Test No.</td><td>Resin type¹</td><td>Relationship from mix²</td><td>Temp. of the₃foam³</td><td>Size of the 4 foam⁴</td><td>Density of the₅foam⁵</td><td>Cell size⁶</td><td>Cell open⁷</td><td>Foam quality⁸</td>

<td> 5.1</td><td>CG1 / LDPE</td><td> 20/80</td><td> 107</td><td> 0,77</td><td> 39</td><td> 1,08</td><td> 13</td><td>S</td>

<td> 5.2</td><td>CG1 / EAA</td><td> 20/80</td><td> 99</td><td> 0,61</td><td> 66</td><td> 0,85</td><td> 32</td><td>S</td>

<td> 5.3*</td><td>ZN1 / LDPE</td><td> 20/80</td><td> 112</td><td> 0,62</td><td> 49</td><td> 0,68</td><td> 22</td><td>M</td>

<td> 5.4*</td><td>ZN1 / EAA</td><td> 20/80</td><td> 107</td><td> 0,60</td><td> 80</td><td> 0,45</td><td> 71</td><td>M</td>

^* It is not an example of the present invention. ¹ Refer to Table A for the characteristics of the resins ² Weight ratio of the two polymers ^3-8 Same as in Table B.

Example 6

Ethylene polymer foams of the present invention were prepared with a 20/80 by weight mixture of CGCT resin (CG2 resin) and an intermediate density polyethylene (IDPE) resin prepared by the high pressure process.

The equipment and operating procedure were substantially the same as in Example 1. The IDPE resin had a melt index of 6.0, density of 0.930 g / cm³ and frothed 112^°C in the extrusion equipment. GMS (2 phr) and talc (0.1 phr) were added to control dimensional stability and cell size, respectively. The mixture was expanded with 1.5 mpk of isobutane.

The mixture foamed well at 114^°C, which is much lower than the foaming temperature of CG2 resin alone (120^°C). The foam was of satisfactory quality with a cross section of 0.89 cm², a density of 35 kg / m³, and an open cell content of 21 percent.

Example 7

Ethylene polymer foams of the present invention were prepared with two additional CGCT resins, CG5 and CG6.

The foaming equipment and procedure were substantially the same as in Example 1. 1.8 phr of GMS was added for foam dimensional stability, and 0.05 phr of talc was added for cell size control. A mixture of blowing agents of 75/25 in moles of isobutane / n-butane was used. The temperatures maintained in the extruder zones up to the dosing zone were the same in both tests: 150^°C in the feeding area, 160^°C in the fusioén area and 180^°C in the dosing zone. Good foams were made when the melts were cooled to the seventh temperatures in both tests.

As shown in Table F, the foams were relatively large in size and of good quality. The foams initially shrunk to some degree, but recovered well. The foam made in Test 7.2 showed excellent quality and satisfactory dimensional stability. The foam recovered to 89 percent of the initial volume within two weeks after extrusion.

IS 2 145 133 T3

TABLE F

<td>Test No.</td><td>Resin used¹</td><td>AE level²</td><td>Temp. of the₃foam³</td><td>Size of the₄foam⁴</td><td>Density of the₅foam⁵</td><td>Cell size⁶</td><td>Cell open⁷</td><td>Foam quality⁸</td>

<td> 7.1</td><td>CG5</td><td> 1,7</td><td> 54</td><td> 1,01</td><td> 53</td><td> 1,35</td><td> 43</td><td>B</td>

<td> 7.2</td><td>CG6</td><td> 1,7</td><td> 96</td><td> 0,89</td><td> 36</td><td> 0,65</td><td> 17</td><td>AND</td>

^1-8 Same as in Table B.

Example 8

Ethylene polymer foams of the present invention were prepared from a CGCT resin (CG6) and a mixture with an LDPE resin.

The apparatus was a 45mm screw type extruder having substantially the same configuration as that of Example 1. This larger extruder has an additional zone between the feed and melt zone, such as a transition zone, and is equipped with a Adjustable aperture nozzle having a width of 12.7mm. The operating procedure was substantially the same as that of Example 1.

The CG6 resin was foamed alone in Test 8.1 and in an 80/20 by weight mixture of CG6 / LDPE in Test 8.2. The blowing agent was a 75/25 mole mixture of isobutane and normal butane. The LDPE resin was the same as in Example 4. For comparison, the LDPE resin was also foamed in Example 8.3. The blowing agent level was 1.7 mpk in Test 8.1 and 1.5 mpk in both Tests 8.2 and 8.3. GMS was used at 1.8 ppc to control the dimensional stability of the foam. The nucleating agent of the brand HYDROCEROL (registered trademark of Boehringer Ingelheim KG, Germany) CF-20 of the citric acid / sodium bicarbonate type was used at 0.4 ppc in Test 8.1 and at 0.3 ppc in Tests 8.2 and 8.3 to control cell size. The temperatures maintained in the extruder zones throughout the tests were 100^°C in the feeding area, 135^°Cen the transition zone, 165^°C in the fusion zone and 185^°C in the dosing area. The temperatures in the mixing and cooling zones were varied from trial to trial to effect optimal foam expansion. The temperature maintained in the mixing zone was 180^°C in Test 8.1 and 165^°Cen both Essays 8.2 and 8.3.

Excellent foams were produced from both CGCT resin and the 80/20 LDPE / CG6 blend. All foams exhibited excellent dimensional stability. The characteristics of the foams produced in this example are represented in Table G.

The foam from Test 8.1 was very soft due to its high level of open cells. The foam squeezed easily due to its very low compressive strength. The foam recovered somewhat slowly from a compression flexion. This kind of foam can be useful in certain applications such as earplugs. The results indicated that a CGCT resin foam could easily be made into an open cell foam as well as closed cell foam as in Test 7.2 of Example 7. In both Tests 8.2 and 8.3 substantially closed cell foams were achieved which they had good cellular integrity.

Foam made of LDPE / CG6 showed advantages in both skin quality and properties over a foam made of LDPE resin, which is evident from Table G. Incorporating 20 percent by weight of CGCT LLDPE resin in An LDPE resin resulted in a foam about 3 times harder than a 100 percent LDPE resin foam, and it also improved the skin quality of the foam. Such a hard foam is expected to die better and be durable in repeated use packaging material.

IS 2 145 133 T3

TABLE G

<td>Test No.</td><td>Temp. of the foam¹</td><td>Size of the₂foam²</td><td>Densid. of the₃foam³</td><td>Cell size⁴</td><td>Cell open</td><td>Skin quality⁶</td><td>Resist to 7 compression⁷</td><td>Resist to traction⁸</td><td>Elongation at traction⁹</td>

<td> 8.1</td><td> 98</td><td> 13,6</td><td> 28</td><td> 1,98</td><td> 78</td><td>AND</td><td> 7,6</td><td> 121</td><td> 261</td>

<td> 8.2</td><td> 107</td><td> 6,1</td><td> 24</td><td> 1,22</td><td> 8</td><td>AND</td><td> 62,7</td><td> 231</td><td> 182</td>

<td> 8.3*</td><td> 112</td><td> 5,6</td><td> 25</td><td> 1,32</td><td> 10</td><td>P</td><td> 71,0</td><td> 210</td><td> 66</td>

^* It is not an example of the present invention. ¹ Optimal melting temperature that provides the best foam, in degrees Celsius ² TO^and Foam body cross-sectional area, in square centimeters ³ Density of a one-month-old body of foam, in kilograms per cubic meter ⁴ Cell size in, millimeters, determined according to ASTM D3576 ⁵ Open cell content, in percent, determined according to ASTM 2856-A ⁶ Foam skin quality: E = excellent, P = hairy with nozzle shedding (undesirable) ⁷ Average of 3 directional compressive strength at 25% flexion, in kilopascals, determined according to ASTM D3575 ⁸ Tensile strength, in kilopascals, determined according to ASTM D412 ⁹ Tensile elongation, in percent, determined according to ASTM D412

Although the embodiments of the foam and the process for making it of the present invention have been shown in relation to specific details, it will be noted that, depending on the manufacturing process and the wishes of the manufacturer, the present invention can be modified by various means. changes although still fully within the scope of the novel teachings and principles set forth in this invention.