MXPA99007983A - Filled polyethylene compositions - Google Patents

Abstract

The subject invention is directed to a polyethylene composition comprising from 5 to 70 weight percent of a homogeneous ethylene/&agr;-olefin interpolymer, from 30 to 95 weight percent of at least one filler, and from 0.1 weight percent to less than 10 weight percent of at least one functionalized polyethylene. The polyethylene compositions of the present invention exhibit high tensile strength, high indentation resistance and filler holding capacity, and are especially useful for floor tile and sheeting applications.

Description

FILLED POLYETHYLENE COMPOSITIONS The present invention relates to polyethylene compositions. In particular, the present invention relates to polyethylene compositions highly mineral-filled. Heretofore, polyvinyl chloride (PVC) resin has been commonly used as a base resin for resin compositions containing mineral filler, due to its ability to accept higher levels of this filler. For example, compositions comprising polyvinyl chloride and a mineral filler, such as Si02, BaSO4, and CaCO3, have been used in tile and floor tile applications, due to the high impact strength, abrasion resistance, and flexibility of polyvinyl chloride, coupled with the lower cost associated with increasing filler loads. However, polyvinyl chloride has come under increasing scrutiny for several reasons. For example, the presence of the chloride atom in the base structure of polyvinyl chloride makes it difficult to melt, re-extrude, and recycle, and leads to poor heat stability. In addition, when burned, polyvinyl chloride tends to inconveniently release harmful substances such as hydrochloric acid. In addition, polyvinyl chloride typically contains a plasticizer to improve flexibility, which plasticizer can leach out of polyvinyl chloride from landfills, and cause soil and / or water contamination. In addition, polyvinyl chloride is inconvenient because it is thermally sensitive, and therefore, requires closer temperature control in the molding processes than non-halogen-containing polymers. In view of the above shortcomings, the industry would find advantage in a replacement of halogen-free polyvinyl chloride that is more easily recyclable, but does not sacrifice physical properties. U.S. Patent No. 4,847,317 (Dokurno et al.) Discloses filled thermoplastic compositions comprising: (a) from 30 to 90 parts of ethylene polymer, (b) from 10 to 60 parts of modified ethylene polymer with graft, and (c) from 20 to 70 weight percent filler, based on the amount of (a) and (b). Those in the industry would find advantage in compositions that tolerate filler levels greater than 70 weight percent. Those in the industry would further find advantage in compositions that achieve the desired performance, but utilize less than 10 weight percent functionalized polyethylene, more preferably less than 3 weight percent functionalized polyethylene. U.S. Patent No. 4,379,190 (Schenck I) teaches filled thermoplastic compositions comprising: (a) from 5 to 60 weight percent of a mixture of at least two ethylene copolymers, having comonomer contents specified polar, (b) from 40 to 90 weight percent filler, and (c) from 0 to 15 weight percent plasticizer. When the filler is present in an amount greater than 75 weight percent, Schenck requires that the plasticizer be present in an amount of at least 1 weight percent, with plasticizer levels being preferred between 3 and 10 percent by weight. weight, and more plasticizer levels are preferred between 4 and 8 weight percent. U.S. Patent No. 4,403,007 (Coughlin) discloses a filled thermoplastic composition comprising: 5 to 55 weight percent of a copolymer of ethylene with a functionalized comonomer, 1 to 15 weight percent of plasticizer, and 40 to 90 weight percent filler. U.S. Patent No. 4,438,228 (Schenck II) discloses a filled thermoplastic composition useful, for example, as a sound absorbing coating for automotive carpet, comprising: (a) from 5 to 55 percent by weight of an ethylene / α-olefin copolymer, (b) from 2 to 12 percent of a plasticizer, and (c) from 40 to 90 percent filler.

PCT Publication Number WO 96/04419 discloses the use of substantially linear ethylene polymers in floor covering materials. Although the TCP Publication recognizes the potential use of substantially linear ethylene polymers in coating materials comprising up to 85 percent by weight filler, it uses no more than 65 percent filler in the examples. In contrast to the teaching of Schenck I and Schenck II, and Coughline, those in the industry would also find advantage in a thermoplastic, plasticizer-free, filled composition, ie, a thermoplastic composition containing less than 3 weight percent, especially less of 1 weight percent plasticizer. However, the compositions of the above references do not teach or disclose plasticizer-free, highly-filled, substantially halogen-free plasticizer-based compositions that achieve high flexibility. One aspect of the present invention is a plasticizer free of plasticizer characterized in that it comprises: (A) from 5 weight percent to 50 weight percent of at least one homogeneous ethylene / c-olefin interpolymer having: ( i) a density of 0.85 grams / cubic centimeter to 0.92 grams / cubic centimeter, (ii) a molecular weight distribution (Mw / Mn) less than 3.5, (iii) a melt index (I2) of 0.1 grams / 10 minutes at 175 grams / 10 minutes, (iv) a CDBI greater than 50 percent; (B) from 30 weight percent to 95 weight percent of at least one filler; and (C) from 0.1 weight percent to less than 10 weight percent of at least one functionalized polyethylene. All percentages used herein are by weight, based on the weight of the total formulation. Preferably, the homogeneous ethylene / c-olefin interpolymer used in the polyethylene compositions of the present invention is a substantially linear ethylene polymer, more preferably a substantially linear interpolymer of ethylene and Al-olefin of 3 to 20 carbon atoms. carbon. The polyethylene compositions of the present invention can be usefully employed in tile applications for floors and coatings, due to their good abrasion resistance, indentation resistance, flexibility, impact resistance, and ability to contain filler. In addition, the polyethylene compositions of the present invention are substantially free of halogen, and do not require the presence of plasticizer to achieve the above-mentioned advantages. The homogeneous ethylene / c-olefin useful in the formation of polyethylene compositions of the present invention is a homogeneously branched interpolymer. That is, the α-olefin comonomer of the interpolymer is randomly distributed within each given interpolymer molecule, such that substantially all of the interpolymer molecules have the same ethylene / comonomer ratio. The homogeneous ethylene / c-olefin interpolymers used to form the polyethylene compositions of the present invention essentially lack a non-short chain branching polymer fraction that can be measured as a "high density" fraction by the fractionation by elution with elevation of temperature (TREF). The homogeneity of the ethylene / α-olefin interpolymers is typically described by the SCBDI (Short Chain Branching Distribution Index) or CDBI (Amplitude Index / Composition Distribution Branch), and is defined as the percentage in Weight of the polymer molecules having a comonomer content with 50 percent 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 with elevation of temperature (abbreviated herein as "TREF") as described, for example. , in Wild et al., Journal of Polymer Science, Poly. Phys. Ed., Volume 20, page 41 (1982), in the Patent of the United States of America Number 4,798,081 (Hazlitt et al.), In the Patent of the United States of America Number 5,008,204 (Stehling), in the Patent of the United States of America. U.S. Patent No. 5,246,783 (Spenadel et al.), In the U.S. Pat.

North America Number 5,322,728 (Davey et al.), In the Patent of the United States of America Number 4,798,081 (Hazlitt et al.), Or in United States Patent No. 5,089,321 (Chum et al.). The SCBDI or CDBI for the homogeneous ethylene / α-olefin interpolymers used for the polyethylene composition of the present invention is greater than 50 percent, preferably greater than 70 percent, especially greater than 90 percent. The density of the homogeneous ethylene / α-olefin interpolymer used to form the composition of the present invention (measured according to ASTM D-792) is generally at least 0.85 grams / cubic centimeter, preferably at least 0.86 grams / cubic centimeter . The density of the homogeneous ethylene / α-olefin interpolymer in the same manner is typically less than 0.95 grams / cubic centimeter, preferably less than 0.92 grams / cubic centimeter, more preferably less than 0.91 grams / cubic centimeter, and most preferably less than 0.905 grams / cubic centimeter. The molecular weight of the homogeneous ethylene / α-olefin interpolymer useful in the polyethylene compositions of the present invention is conveniently indicated using the melt index measurement according to ASTM D-1238, condition 190 ° C / 2.16 kg (previously known as "condition (E)", and also known as I2). The melt index is inversely proportional to the molecular weight of the polymer, although the relationship is not linear. The melt index of the homogenously branched ethylene / α-olefin interpolymer is generally at least 0.1 grams / 10 minutes (g / 10 min), preferably at least 1 gram / 10 minutes. The melt index of the homogenously branched ethylene / c-olefin interpolymer is typically less than 175 grams / 10 minutes, preferably less than 100 grams / 10 minutes. The homogeneous ethylene / c-olefin interpolymers can be analyzed by molecular weight distribution by gel permeation chromatography (GPC) in a Waters high temperature chromatographic unit at 150 ° C equipped with columns of mixed porosity, operating at a temperature of the 140 ° C system. The solvent is 1,2,4-trichlorobenzene, from which 0.3 percent by weight solutions of the samples for injection are prepared. The flow rate is 1.0 milliliters / minute, and the injection size is 100 microliters. The molecular weight determination is deduced by using polystyrene standards of a narrow molecular weight distribution (from Polymer Laboratories) in conjunction with their elution volumes. Equivalent polyethylene molecular weights are determined using appropriate Mark-Houwink coefficients for polyethylene and polystyrene (as described by Williams and Ward in Journal of Polvmer Science, Polymer Letters, Volume 6, (621) 1968) to derive the following equation: M_ol,; ißetti;, le -._ no = a * (Mnnopli "es5tirrPennno) ' In this equation, a = 0.4316 and b = 1.0. The weight average molecular weight, Mw, and the number average molecular weight, Mn, are calculated in the usual manner according to the following formula: M: = (S j (Mjj)); where w, is the weight fraction of molecules with a molecular weight M, which is eluted from the column of gel permeation chromatography in fractions i and j = 1 when Mw is calculated, and j = -1 when calculated Mn. The molecular weight distribution (Mw / Mn) of the homogeneous ethylene / α-olefin interpolymer is less than 3.5, preferably less than 2.8, and more preferably less than 2. 2. The molecular weight distribution (Mw / Mn) of the homogeneous ethylene / α-olefin interpolymer is typically at least 1.8, preferably at least 1.9. More preferably, the molecular weight distribution (Mw / Mn) of the homogeneous ethylene / c-olefin interpolymer is about 2. The homogeneous ethylene / α-olefin interpolymer can be a homogeneously branched linear polymer., or a substantially linear polymer, with substantially linear polymers being preferred. Homogeneously branched linear / α-olefin interpolymers are described in U.S. Patent No. 3,645,992 (Elston), and are commercially available from Exxon Chemical Company under the trademark Exact, and at Mitsui Petrochemical Company under the trademark. commercial Tafmer. The substantially linear ethylene / α-olefin interpolymers are disclosed and are claimed in U.S. Patent Nos. 5,272,236 (Lai et al.) And 5,278,272 (Lai et al.), And are available from The Dow Chemical Company under the Affinity trademark. The "substantially linear" ethylene / α-olefin interpolymers are not a "linear" polymer in the traditional sense of the term, as used to describe linear low density polyethylene (linear low density polyethylene (LLDPE) polymerized with Ziegler). Neither the term "substantially linear" interpolymers is used to describe highly branched polymers, such as low density polyethylene (LDPE). The substantially linear ethylene / α-olefin interpolymers ("SLEP") are characterized by having a base structure which is substituted with 0.01 long chain branches / 1000 carbon atoms to 3 long chain branches / 1000 carbon atoms, more preferably of 0.01 long chain branches / 1000 carbon atoms to 1 chain branch / 1000 carbon atoms, and especially 0.05 long chain branches / 1000 carbon atoms to 1 long chain branch / 1000 carbon atoms. The long chain branching is defined herein as a chain length of at least 6 carbon atoms, above which the length is not distinguished using nuclear magnetic resonance C (NMR) spectroscopy. The long chain branching may be as long as about the same length as the length of the polymer base structure.

The long chain branching can be determined by i3C nuclear magnetic resonance spectroscopy, and is encoded using the Randall method (Rev. Macromol.

Chem. Phys., C29 (2 and 3), pages 282-297). As a practical matter, current C nuclear magnetic resonance spectroscopy can not determine the length of a long chain branch greater than 6 carbon atoms. However, there are other useful techniques for determining the presence of long chain branches in ethylene polymers, including ethylene / l-octene interpolymers. Two of these methods are gel permeation chromatography coupled with a low angle laser light scattering detector (GPC-LALLS), and gel permeation chromatography coupled with a differential viscometer detector (GPC-DV). The use of these techniques for the detection of long chain branching and the underlying theories have been well documented in the literature. See, for example, Zimm, G.H. and Stockmayer, W.H., J. Chem. Phys., 17, 1301 (1949), and Rudin, A., Modern Methods of Polymer Characterization, John Wiley & Sons, New York (1991) pages 103-112. A. Willen deGroot and P. Steven Chum, both of The Dow Chemical Company, at the October 4, 1994 conference of the Federation of the Society of Analytical Chemistry and Spectroscopy (FACSS) in St. Louis, Missouri, presented data that demonstrate that GPC-DV is a useful technique for quantifying the presence of long chain branches in substantially linear ethylene / α-olefin interpolymers. In particular, deGroot and Chum found that the level of long chain branches in homogeneous substantially linear ethylene / α-olefin interpolymer samples, measured using the Zimm-Stockmayer equation, correlated well with the level of long chain branches. measurements using nuclear magnetic resonance 13c In addition, deGroot and Chum discovered that the presence of octene does not change the hydrodynamic volume of the polyethylene samples in solution, and as such, one can count the increase in molecular weight attributable to the short chain branches of octene, on knowing the mole percentage of octene in the sample. By deconvolution of the contribution to the molecular weight increase attributable to the short chain branches of 1-octene, deGroot and Chum showed that GPC-DV can be used to quantify the level of long chain branches in the ethylene / octene copolymers substantially linear. deGroot and Chum also showed that a Log plot (I2, Fusion index) as a function of Log (Average molecular weight in GPC weight), determined by GPC-DV, illustrates that the long chain branching aspects (but not the long branch extension) of the SLEPs, are comparable with those of high-density, high-branched, high-pressure polyethylene (LDPE), and are clearly distinct from ethylene polymers produced using Ziegler-type catalysts, such as titanium and ordinary catalysts to make homogeneous polymers, such as hafnium and vanadium complexes. For the ethylene / α-olefin interpolymers, the long chain branching is longer than the short chain branching resulting from the incorporation of the α-olefins into the polymer backbone. The empirical effect of the presence of the long chain branching on the substantially linear ethylene / α-olefin interpolymers used in the invention manifests itself as the improved rheological properties which are quantified and are expressed herein in terms of rheometry results of gas extrusion (GER) and / or increases in the flow of fusion, IIQ / I. In contrast to the term "substantially linear", the term "linear" means that the polymer lacks measurable or demonstrable long chain branches, i.e. the polymer is substituted with an average of less than 0.01 long chain branches / 1000 atoms of carbon. SLEPs are further characterized by having: (a) a melt flow rate, T-? O ^ 2 > 5.63, (b) a molecular weight distribution, Mw / Mn, determined by gel permeation chromatography, defined by education:(Mw / Mn = < (I10 / I2) "4.63, (c) a gas extrusion rheology such that the critical tear rate at the establishment of the surface melt fracture for the SLEP is at least 50 percent greater than the tear rate critical to the establishment of the surface melt fracture for a linear ethylene polymer, wherein SLEP and the linear ethylene polymer comprise the same comonomer or comonomers, the linear ethylene polymer has a 12, one Mw / Mn, and a density within 10 percent of the SLEP, and where the respective critical tear rates of the SLEP and the linear ethylene polymer are measured at the same melting temperature, using a gas extrusion rheometer, and (d) a single melting peak in the differential scanning calorimetry, DSC, of between 30 ° C and 150 ° C. The determination of the critical tear index and the critical tear stress with respect to the melt fracture, as well as other rheology properties, such as the rheological processing index (PI), is performed using a gas extrusion rheometer ( GER). The gas extrusion rheometer is described by M. Shida, R.N. Shroff and L.V. Cancio in Polymer Engineering Science, volume 17, number 11, page 770 (1977), and in "Rheometers for Molten Plastics" by John Dealy, published by Van Nostrand Reinhold Co. (1982) on pages 97-99. The experiments of the gas extrusion rheometer are performed at a temperature of 190 ° C, at nitrogen pressures between 250 and 5500 psig (from 1.7 to 38 MPa) using a diameter of 0.0754 millimeters, a die of 20: 1 of the length to diameter (L / D) with an entry angle of 180 °. For the substantially linear ethylene polymers described herein, the rheological processing index is the apparent viscosity (in kpoise) of a material measured by a gas extrusion rheometer, with an apparent tear stress of 2.15 x 10 dynes / centimeter. square (0.21 MPa). The substantially linear ethylene polymers for use in the invention include ethylene interpolymers, and have a rheological processing index in the range of 0.01 kpoise to 50 kpoise, preferably 15 kpoise or less. The substantially linear ethylene polymers used herein, have a rheological processing index less than, or equal to, 70 percent of the rheological processing index of a linear ethylene polymer (either a polymer polymerized with Ziegler, or a uniformly branched linear polymer as described by Elston in U.S. Patent Number 3,645,992), having an I2, an Mw / Mn, and a density, each within 10 percent of substantially linear ethylene polymers . The rheological behavior of substantially linear ethylene polymers can also be characterized by the Dow Rheology Index (DRI), which expresses the "normalized relaxation time of a polymer as the result of long chain branching". (See, S. Lai and G.W. Knight, ANTEC '93 Proceedings, INSITEMR Technology Polyolefins (SLEP) - New Rules in the Structure / Rheology Relationship of Ethylene to-Olefin Copolymers, New Orleans, La., May 1993. The values of the Dow Rheology Index are from 0 for polymers that do not have a chain branching long measurable (such as the Tafmer products available from Mitsui Petrochemical Industries, and the Exact products available from Exxon Chemical Company) to approximately 15, and are independent of the melt index. In general, for medium pressure low pressure ethylene polymers (particularly at lower densities), the Dow Rheology index provides better correlations with the elasticity of the melt and the high fluidity to tearing in relation to the correlations of the same tried with proportions of fusion flow. For the substantially linear ethylene polymers useful in this invention, the Dow Rheology index is preferably at least 0.1, and especially at least 0.5, and more especially at least 0.8. The Dow Rheology index can be calculated from the equation: DRI = (3652879 * ro 1.00649 / .7 0-1) / lO where to is the characteristic relaxation time of the material, and? 0 is the zero tear viscosity of the material. Both tQ and? Q are the values of the "best fit" for the Cross equation, that is, ? /? 0 = 1 / (1 (7 r0) 1-n ' where n is the index of the power law of the material, and? and r are the measured viscosity and tear index, respectively. The determination of the base line of the viscosity and the tear index data are obtained using a Rheometric Mechanical Spectrometer (RMS-800) under the dynamic scan mode of 0.1 to 100 radians / second at 160 ° C, and a Rheometer Gas Extrusion (GER) at extrusion pressures of 1000 psi to 5,000 psi (from 6.89 to 34.5 MPa), which corresponds to the tear stress of 0.086 to 0.43 MPa, using a diameter of 0.0754 millimeters, a die of 20: 1 of the length to the diameter L / D at 190 ° C. Specific determinations of the material can be made from 140 ° C to 190 ° C, as required to accommodate variations in the melt index. A graph of apparent tear stress versus apparent tear rate is used to identify melt fracture phenomena and to quantify the critical tear index and critical tear stress of ethylene polymers. According to Ramamurthy in the Journal of Rheology, 30 (2), 337-357, 1986, above a certain critical flow velocity, the irregularities observed in the extrudate can be broadly classified into two main types: fracture by surface fusion and fracture by coarse melting. Surface melt fracture occurs under seemingly continuous flow conditions, and is detailed from the loss of specular film gloss, to the more severe form of "shark skin". At present, as determined using the Gas Extrusion Rheometer described above, the establishment of the surface melt fracture (OSMF) is characterized at the beginning of the loss of gloss of the extrudate, where the surface roughness of the extrudate can only be detect by a 40-fold amplification. The critical tear rate at the establishment of the surface melt fracture for substantially linear ethylene polymers is at least 50 percent greater than the tear rate critical to the establishment of the surface melt fracture of a linear ethylene polymer that have essentially the same The coarse melt fracture occurs under non-continuous extrusion flow conditions, and is in detail from regular (alternating rough and smooth, helical, etc.) to random distortions. For commercial acceptability, in order to maximize the operating properties of the films, coatings, and mounds, surface defects must be minimal, if not absent. The critical tear stress at the setting of the surface melt fracture for substantially linear ethylene polymers, especially those having a density greater than 0.910 grams / cubic centimeter, used in the invention, is greater than 4 x 10 dynes / square centimeter (0.4 MPa). It is known that substantially linear ethylene polymers have excellent processability, despite having a relatively narrow molecular weight distribution (ie, the Mw / Mn ratio is typically less than 2.5). Moreover, unlike homogeneously branched and heterogeneously branched linear ethylene polymers, the melt flow ratio (IJQ / I2) of the substantially linear ethylene polymers can be varied independently of the molecular weight distribution, Mw / Mn. In accordance with the above, the polymer (A) of the polymeric compositions of the invention is preferably a substantially linear ethylene polymer. The homogeneous ethylene / α-olefin interpolymer useful in the formation of the polyethylene composition of the present invention, is typically an interpolymer of ethylene and at least one α-olefin of 3 to 20 carbon atoms, and / or a diolefin of 4 to 18 carbon atoms, and is preferably an interpolymer of ethylene and at least one α-olefin from 3 to 20 carbon atoms, more preferably a copolymer of ethylene and an α-olefin of 4 to 8 carbon atoms, and most preferably a copolymer of ethylene and 1-octene. The term "interpolymer" is used herein to mean a copolymer, or a terpolymer, or the like. That is, at least one other comonomer is polymerized with ethylene to make the interpolymer. Preferred comonomers include the o-olefins of 3 to 20 carbon atoms, especially propylene, isobutylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, and 1-decene, more preferably 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene, and more preferably 1-hexene, 4-methyl-1-pentene, and 1-octene, and most preferably l-octene. The amount of the ethylene / α-olefin interpolymer used in the polyethylene compositions of the present invention will depend on the desired physical properties of the resulting composition, and on the amount of functionalized polyethylene included in the composition. However, typically, the compositions of the invention will comprise at least 5 percent by weight, preferably at least 10 percent by weight of the homogeneous ethylene / α-olefin interpolymer. Typically, the compositions of the invention will comprise no more than 70 weight percent, preferably no more than 50 weight percent, and more preferably no more than 30 weight percent of the homogeneous ethylene / α-olefin interpolymer. The polyethylene compositions of the present invention comprise a filler. The type of filler used will be selected based on the desired physical properties of the final product. Exemplary fillers include calcium carbonate, barium sulfate, barite, glass fiber and powder, alumina metal powder, hydrated alumina, clay, magnesium carbonate, calcium sulfate, silica or glass, vaporized silica, talc, black smoke or graphite, fly ash, cement powder, feldspar, nepheline, magnesium oxide, zinc oxide, aluminum silicate, calcium silicate, titanium dioxide, titanates, glass microspheres, chalk and mixtures thereof. Preferred fillers are calcium carbonate, barium sulfate, talc, silica / glass, alumina, and titanium dioxide, and mixtures thereof. The most preferred filler is calcium carbonate, which is available in the industry as limestone and rock dust. In the same way, the filler may belong to the class of fillers known as ignition-resistant fillers. Exemplary ignition-resistant fillers include antimony oxide, decabromobiphenyl oxide, alumina trihydrate, magnesium hydroxide, borates, and halogenated compounds. Of these ignition-resistant fillers, alumina trihydrate and magnesium hydroxide are preferred. Other miscellaneous fillers include wood fibers / flours / chips, ground rice husks, cotton, starch, glass fibers, synthetic fibers (such as polyolefin fibers), and carbon fibers. The amount of filler present in the polyethylene compositions of the present invention will be selected based on the requirement of the final application. Typically, the polyethylene compositions of the invention will comprise at least 30 percent by weight, preferably at least 50 percent by weight, more preferably at least 70 percent, and most preferably more than 75 percent by weight of filling. Typically, the polyethylene compositions of the invention will comprise no more than 95 weight percent, preferably no more than 90 weight percent filler. The polyethylene compositions of the present invention withstand high levels of filler without suffering a corresponding sacrifice of physical properties. The polyethylene composition of the present invention further comprises at least one functionalized polyethylene. The term "functionalized polyethylene" herein means a polyethylene incorporating at least one functional group in its polymer structure. The example functional groups can include, for example, mono- and di-functional ethylenically unsaturated carboxylic acids, ethylenically unsaturated mono- and difunctional carboxylic acid anhydrides, salts thereof and esters thereof. These functional groups may be grafted onto an ethylene homopolymer or an ethylene / α-olefin interpolymer, or may be copolymerized with ethylene and an optional additional comonomer, to form an interpolymer of ethylene, the functional comonomer, and optionally other comonomers. In general, examples of this functionalized polyethylene may include: copolymers of ethylene and ethylenically unsaturated carboxylic acid, such as acrylic acid and methacrylic acid; ethylene copolymers and carboxylic acid esters, such as vinyl acetate; polyethylene grafted with an unsaturated carboxylic acid or with a carboxylic acid anhydride, such as maleic anhydride. Specific examples of this functionalized polyethylene may include ethylene / vinyl acetate copolymer (EVA), ethylene / acrylic acid copolymer (EAA), ethylene / methacrylic acid copolymer (EMAA), salts thereof (ionomers), different polyethylenes grafted with maleic anhydride (MAH), such as low-density and high-pressure polyethylene grafted with maleic anhydride, homogenously branched linear ethylene / α-olefin interpolymers (which have been commonly referred to as linear low density polyethylene and ultra-high polyethylene). low density), homogenously branched linear ethylene / α-olefin interpolymers, substantially linear ethylene / α-olefin interpolymers, and high density polyethylene (HDPE). Means for grafting functional groups onto polyethylene are described, for example, in U.S. Patent Nos. 4,762,890; 4,927,888, or 4,950,541. Two preferred functionalized polyethylenes used to form the compositions of the present invention are copolymers of ethylene / acrylic acid and polyethylene grafted with maleic anhydride. The most preferred functionalized polyethylenes are ethylene / acrylic acid copolymers, substantially linear ethylene / α-olefin interpolymers grafted with maleic anhydride, and high density polyethylene grafted with maleic anhydride.

The amount of the functional group present in the functional polyethylene will vary. Typically, the functional group will be present in a graft-type functionalized polyethylene (e.g., the content of maleic anhydride in a polyethylene grafted with maleic anhydride) at a level that is preferably at least 0.1 weight percent, more preferably at least 0.5 percent by weight. The functional group will typically be present in a graft-type functionalized polyethylene in an amount of less than 10 percent by weight, more preferably less than 5 percent by weight, and most preferably less than 3 percent by weight. In contrast, the functional group will typically be present in a copolymer-type functionalized polyethylene (e.g., the content of acrylic acid in an ethylene-acrylic acid copolymer) will be at least 1.0 percent by weight, preferably at least 5 percent by weight, and more preferably at least 7 percent. The functional group will typically be present in a copolymer-type functionalized polyethylene in an amount of less than 40 percent by weight, preferably less than 30 percent by weight, and more preferably less than 25 percent by weight. The melt index (I2) of the functionalized polyethylene can be varied, except to the extent that the processability of the composition of the invention and the physical properties of the final product are unacceptably affected. In general terms, the functionalized polyethylene has a melt index of at least 0.1 grams / 10 minutes, preferably at least 0.2 grams / 10 minutes. In general, the functionalized polyethylene has a melt index no greater than 500 grams / 10 minutes, more preferably no greater than 350 grams / 10 minutes. The functionalized polyethylene will typically be present in the polyethylene composition of the invention in an amount of at least 0.1 percent by weight, preferably at least 0.5 percent by weight, and more preferably at least 1.0 percent by weight. The functionalized polyethylene will typically be present in the polyethylene composition of the invention in an amount of not more than 10 percent by weight, preferably not more than 5 percent by weight, and more preferably not more than 3 percent by weight. The polyethylene composition of the present invention may comprise any known additives, to the extent that they do not interfere with the improved formulation properties discovered by the applicants. Any additives commonly used in polyolefin compositions, for example, crosslinking agents, antioxidants (eg, calcium stearates, hindered phenols such as Irganox MR 1010 made by Ciba Geigy Corp., phosphites such as Irgafos) may be included in the composition. R 168, also by Ciba Geigy Corp.), fire retardants, heat stabilizers, ultraviolet absorbers, antistatic agents, slip agents, glidants, waxes, oils, process aids, foaming agents, dyes, pigments and the like. Preferred additives include, for example, calcium stearate, Irgafos 168, and Irgafos ™ 1010. The polyethylene compositions of the present invention can be formed by any convenient method, such as mixing the individual components, and subsequently melting mixture, or by premixing in a separate extruder (for example, a Banbury mixer, a Haake mixer, an internal Brabender mixer, or a twin screw extruder). The polyethylene compositions of the present invention can be formed easily in the desired configuration, by using any apparatus commonly available in the industry. For example, the polyethylene composition can be fed to an apparatus for the manufacture of articles, employing unit operations such as compression molding, injection molding, sheet extrusion, web compression, roll rolling, and / or calendering step. , to produce sheet or mosaic structures.

The following examples are for illustrative purposes only, and should not be taken to limit the scope of the specification or the claims. Unless otherwise reported, all percentages and parts are by weight. The polymeric components indicated in Table 1 are used in the Examples.

Table 1 In Table 1, CaSt refers to calcium stearate, Irganox 1076 is a hindered phenolic stabilizer available from Ciba Geigy, and PEPQ refers to tetrakis diphosphonium (2,4-dibutyl-tertiary-phenyl) -4,4'-biphenylene (available from Clariant Corporation). In the case of sample I, the polymer was produced by grafting 1.2 percent maleic anhydride onto a linear high density polyethylene having a density of 0.955 grams / cubic centimeter, an I2 of 25 grams / 10 minutes, and an I? g / I of 6.5. In the case of sample J, the polymer was produced by grafting 1.2 percent maleic anhydride onto a substantially linear ethylene / octene copolymer, having a density of 0.871 grams / cubic centimeter, an I2 of 1 gram / 10 minutes, and an II / I2 of 7.6.

Comparative Example 1 15 weight percent of Polymer A, a copolymer of ethylene and octene-1, having a density of 0.902 grams / cubic centimeter, a melt index (I2) of 1.0 grams / 10 minutes, is added. molecular weight distribution (Mw / Mn) of 2.0, and 85 weight percent CaC03 type filler (this filler comprising a mixture of equal weight proportions of Pfizer ATF-40 Limestone, and Georgia Marble Rock Dust ) to a Banbury type mixer (Farrel Banbury BR mixer, with a 1573 cubic centimeter chamber), and mixed with a rotor operation at the speed of 300 to 350 ° F (149 to 177 ° C) temperature in the chamber for 2 minutes. The mixing material is then removed from the Banbury mixer, and fed to a roller mill having a diameter of 6 inches (15 centimeters) and a width of 12 inches (30 centimeters) set at a surface temperature of 350 ° F ( 177 ° C). A sheet is removed after a 180 ° wrap, or allowed to wrap 540 ° before being released. The sheet is then cut and compression molded into plates that have a thickness of 0.125 inches (0.318 centimeters), a width of 12 inches (30.5 centimeters), and a length of 12 inches (30.5 centimeters), by using a Hydraulic press manufactured by Pasadena Hydraulics Incorporated (PHI). The press is operated at 400 ° F (204 ° C) in a preheat mode, at a minimum pressure for 3 minutes, and then pressurized to 15 tons (81.36 x 10 kg) for 2 minutes. The plates are then removed from the heat, and cooled to 15 tons (1.36 x 10 kg) for 3 minutes. The tensile properties are measured in accordance with ASTM D-638, Type C. The Shore A and Shore D hardness of compression molded plates is measured using a Hardness Tester in accordance with ASTM D-2240. The tensile properties and hardness data are summarized in Table 2. A mandrel test is conducted for the compression molded plates, using the following procedure. The plates are cut into strips that have a width of 2 inches (5.1 centimeters), and a length of 6 inches (15.2 centimeters). The strips are folded over a succession of tubes of different diameter, or mandrels, until the strip breaks. The diameter corresponding to the failure is recorded as the mandrel bending, or the flexibility evaluation. The flexibility data are summarized in Table 2. In the table, "no" breakage means that no breakage is experienced, even when bent at 180 °. An indentation test is conducted on the strips, using the following procedure. A weight of 140 pounds (63.6 kilograms) is applied to the strips by means of a cylindrical leg of 0.178 inches (0.7 millimeters) in diameter, for 10 minutes, and the initial indentation is measured. The residual indentation is measured after 60 minutes. Indentation depths are measured to the nearest thousandth (0.001 inches (0.03 millimeters)). For residual indentation, the sample is given an evaluation of failure if the cylindrical indentation leg cuts and permanently damages the surface. The results are summarized in Table 2.

Comparative Examples 2 to 7 Substantially the same procedure as described with Comparative Example 1 is repeated, using copolymers of ethylene and octene with the melt indexes and the densities referenced in Table 1 and mentioned in Table 2. The results are summarized in Table 2. These examples are for comparison, and are not claimed.

Table 2 Ex. Comp. No .: Comparative Example MI Number: Fusion Index (grams / 10 minutes) Dens: Density (grams / cubic centimeter) Final Traction: Final Traction Force (kg / cm) Elongation: Final Elongation (%) Initial Indentation: Initial Indentation (0.001 inches (mm)) Residual Indentation: Residual Indentation (0.001 inches (mm)). Examples 8-13 Substantially repeats the process of Comparative Example 1, except that the 15 percent polymer A used is replaced by a 10 percent by weight mixture of linear high density polyethylene grafted with maleic anhydride (MAH) having, before grafting, a melt index (I2) of 25 grams / 10 minutes, a density of 0.955 grams / cubic centimeter, and a maleic anhydride content of 1.0 percent by weight (based on the weight of linear high density polyethylene), and 90 percent in weight of a substantially linear ethylene / l-octene copolymer, having melt indexes and densities referenced in Table 1, and mentioned in Table 3. The results are summarized in Table 3. Example 14 The process of Example 1, except that the 15 percent polymer A used, is replaced by a 20 percent by weight mixture of a linear high density polyethylene grafted with maleic anhydride that has, before grafting, an index e of melting (I2) of 25 grams / 10 minutes, a density of 0.955 grams / cubic centimeter, and a content of maleic anhydride of 1.0 weight percent (based on the weight of linear high density polyethylene), and 80 percent by weight of a substantially linear ethylene / l-ketene copolymer, having melt indexes and densities referenced in Table 1 and mentioned in Table 3. The results are summarized in Table 3. Example 15 Substantially The process of Example 1, except that the 15 percent polymer A used, is replaced by a 20 percent by weight blend of a substantially linear ethylene / l-cytene copolymer grafted with maleic anhydride (ie, a substantially linear polyethylene). which has, before grafting, a melt index (I2) of 0.4 grams / 10 minutes, a density of 0.871 grams / cubic centimeter, and a maleic anhydride content of 1.0 percent by weight), and 80 percent in weight of a substantially linear ethylene / l-octene copolymer, having the melt indexes and the densities referenced in Table 1 and mentioned in Table 3. The results are summarized in Table 1.

Table 3 Examples 16 to 21 The procedure of Comparative Example 1 is substantially repeated except that 15 percent of the Polymer A used is replaced with a mixture of 10 percent by weight of ethylene / l-octene copolymer substantially linearly grafted with maleic anhydride. , which has, before grafting, a melt index of 0.4 grams / 10 minutes, a density of 0.871 grams / cubic centimeter, and a content of maleic anhydride of 1.0 weight percent, and 90 weight percent of copolymer of ethylene and octene, which has the melt indexes and densities referenced in Table 1. The results are summarized in Table 4.

Table 4 * The abbreviations are the same as indicated in Table 1 Examples 22 to 33 The procedure of Example 1 is substantially repeated, except that the mixture is of a copolymer of ethylene and acrylic acid, and copolymers of ethylene and octene, having the melt indexes and the densities referenced in Table 1 and mentioned in Table 5, which are used in place of the ethylene and octene copolymer. The results are summarized in Table 5.

Table 5 * The abbreviations are the same as indicated in Table 1, As indicated above, the polyethylene compositions of the present invention have superior physical properties, such as tensile properties, indentation resistance, and ability to contain filler, with a simple formulation, making them particularly useful in flooring applications, especially mosaic for floors and coatings for floors. In particular, the above examples illustrate that the polyethylene compositions of the invention exhibit good filler containment, ie, more than 75 percent filler. The polyethylene compositions of the invention also exhibit residual indentation values less than 20 thousandths (0.5 millimeters), preferably less than 10 thousandths (0.25 millimeters), and more preferably less than 5 thousandths (0.13 millimeters). The polyethylene compositions of the invention also exhibit ultimate tensile strengths greater than 50 kg / cm ~, preferably greater than 60 kg / cm, and more preferably greater than 100 kg / cm. The polyethylene compositions of the invention further have a good flexibility of a mandrel bending diameter of less than 15 centimeters, preferably less than 10 centimeters, and more preferably less than 5 centimeters.

Claims (11)

1. A polyethylene composition free of plasticizer characterized in that it comprises: (A) from 5 weight percent to 50 weight percent of at least one homogeneous ethylene / o-olefin interpolymer having: (i) a density of 0.85 grams / cubic centimeter to 0.92 grams / cubic centimeter, (ii) a molecular weight distribution (Mw / Mn) less than 3.5, (iii) a melt index (I2) of 0.1 grams / 10 minutes at 175 grams / 10 minutes, (iv) a CDBI greater than 50 percent; (B) from 30 weight percent to 95 weight percent of at least one filler; and (C) from 0.1 weight percent to less than 10 weight percent of at least one functionalized polyethylene, selected from the group consisting of linearly heterogeneously branched functionalized polyethylene, functionalized linear ethylene homopolymer, linearly homogenously branched functionalized polyethylene , functionalized substantially linear polyethylene, and ethylated / saturated carboxylic acid interpolymers.

2. The polyethylene composition of claim 1, wherein the ethylene / c-olefin interpolymer is a substantially linear ethylene polymer.

3. The polyethylene composition of claim 1, wherein the ethylene / v-olefin is further characterized by having an I10 / I2 of 7 to 16.

The polyethylene composition of claim 1, wherein the ethylene interpolymer / c-olefin is a copolymer of ethylene and a cx-olefin of 3 to 10 carbon atoms.

5. The polyethylene composition of any of the preceding claims, wherein the functionalized polyethylene is a polyethylene modified by grafting thereto to an unsaturated carboxylic acid or an unsaturated carboxylic acid anhydride.

6. The polyethylene composition of claim 5, wherein the polyethylene is a homopolymer of ethylene, a copolymer of ethylene and α-olefin of 3 to 20 carbon atoms.

The polyethylene composition of any of the preceding claims, wherein the functionalized polyethylene is a substantially linear ethylene polymer modified by grafting thereto to an unsaturated carboxylic acid or an unsaturated carboxylic acid anhydride.

8. The polyethylene composition of any of the preceding claims, wherein the functionalized polyethylene is a substantially linear copolymer of ethylene and l-octene modified by grafting thereto maleic acid or maleic anhydride.

The polyethylene composition of claim 1, wherein the functionalized polyethylene is a copolymer of ethylene and a comonomer selected from the group consisting of unsaturated carboxylic acids and salts and esters thereof.

10. A floor structure characterized in that it comprises a polyethylene composition of any of the preceding claims.

11. The floor structure of claim 10, wherein the floor structure is in the form of a mosaic or a covering.