MXPA98002561A - Compositions poliolefi - Google Patents

Abstract

Described polyolefin compositions, articles made from said compositions, and processes for making said compositions having good level of processability and rapid curing index are described. The degradable polyolefin compositions are preferably bi-dispersed mixtures of ethylene polymers of the same polymer family having different average molecular weights which is obtained by deconvolution wherein Mn1 / Mn2 > 5, Mn2 > 3000 and 0.7 > / - (A1 / (A1 + A2)) > / - 0.15, where Mn1 represents the number average molecular weight of the first component Mn2 represents the number average molecular weight of the second component A1 and A2 are the relative proportions of the first component and the second component. These degradable polyolefin compositions are useful for the manufacture of numerous articles, such as cable coatings, weather strips and seals, gaskets, articles made with foam and / or sponge-type polyolefins of open or closed cell structure and / or combinations thereof, hollow containers, hollow tanks, medical elements, upholstery and coverings, health and personal hygiene elements, fibers, tapes, tubes, pipes and hoses, bellows, boots, gaiters and shoes

Description

POLYOLEPHIN COMPOSITIONS The present invention relates to polyolefins. In one aspect, the invention relates to degradable polyolefin compositions, particularly to polyethylene compositions, which have a good level of processability as well as rapid rates of curing. In another aspect, the invention relates to degradable, bi-dispersed polyolefin compositions of the same family that differ in average molecular weight numbers that are useful in a wide variety of manufacturing technologies, for example, wire and cable extrusion, rotomolded, profile extrusion, formwork or injection molding, extrusion blow molding, injection blow molding, thermoforming, top forming, pressure blow molding, die extrusion, die extrusion sheets (sheet die extrusion), blown film extrusion and powder coatings. In another aspect, the invention relates to a process for improving the processability of the polyolefin compositions while at the same time maintaining a relatively fast curing index. In another aspect, the invention relates to numerous articles of manufacture, for example, wire and cable coatings, weather strips and seals, gaskets, articles made with degradable sponge and / or foam polyolefins of open or closed cell structure and / or combinations thereof, hollow containers, hollow tanks, medical devices, upholstery articles and linings, health and personal care items, fibers, tapes, tubes, pipes and hoses, bellows, boots, leggings, footwear, all of them made with degradable polyolefin compositions. The polyolefin compositions can be processed to obtain articles using various technologies. For many end uses, the items must be degradable. Degradation usually occurs during the processing step or later. Generally, such polyolefin compositions should be processed relatively easily and should be degraded or cured relatively quickly. The index or speed of curing, that is to say, the time necessary to achieve a certain state or optimal curing, depends in general on several factors. It is generally accepted that the higher the curing temperature or the higher the molecular weight, the higher the curing speed. Short curing times are required since they improve productivity and reduce the so-called "work in progress inventory". On the other hand, less stringent curing conditions (eg, lower temperature) are required to reduce energy consumption or facilitate the handling of manufactured or semi-finished parts. Another important aspect is the processability of the composition. Various indices have been proposed as a measure of the processability of a polymer composition. Among the most well known are the Melt index, also called I2, measured according to ASTM D-1238 (Condition 190 / 2.16), formerly known as Condition E.) The Melt index is a useful processability indicator when comparing polymers within the same family. In general, the lower the value of said index, the more difficult it will be to process the polymer. High molecular weight polyolefins usually have a Melt index that is lower, and therefore, these high molecular weight polyolefins are more difficult to process. For example, during injection molding, low melt index values translate into higher pressure requirements to fill the mold cavities, and in the case of excessively low melt index values, it may be impossible to completely fill the cavity of the mold, in addition to consuming an unnecessary amount of energy to make the polymer flow. Another measure of processability is the cutting index (or shear stress) at which the polyolefin composition presents a mass fracture during the process. It is preferable that the cutting index (or cutting force) at which the mass fracture occurs is as high as possible in order to enable high rates of manufacture of finished or semi-finished articles. As usual, it is considered that for a given molecular weight distribution, the cutting index corresponding to the start of the mass fracture is reduced while increasing the average molecular weight of a polyolefin composition. John Dealy in "Melt Rheology and Its Role in Plastics Processing" published by Van Nostrand Reinhold Co in 1990 reveals on page 597 that the measurement of the Melt index according to ASTM D-1238, using different charges will give an estimate of dependence of the cutoff index of the mass viscocity, which is sensitive to the weight average molecular weight (Mw) and the number average molecular weight (M "). Commonly, the melt index ratio at 190 ° C measured under 10 kg is used with the index measured under 2.16 kg as a measure of sensitivity to cut refinement. This relationship is known as I? I2 Stehling et al. demonstrate in U.S. Patents 5,387,630 and 5,382,631 (corresponding to WO 90/03414) that specific mixtures of linear low density polyethylenes and narrow molecular weight distribution, essentially characterized by a polydispersity index (Mw). / Mn) of the mixture exceeding a value of 3, provided that the value of Mw / Mn for each of the components of the mixtures is less than 3, have better resistance to tearing and lower "extractability" compared with previous compositions. This publication does not describe the degradation of these compositions. The industry has identified that a polyolefin composition that possesses a rapid curing index and excellent level of processability is a desired product and, in light of the contradictory requirements of low molecular weight (to improve processability) and high molecular weight (to improve the curing index) an attempt has been made to find a balance between the two opposing requirements, or to optimize the processing machinery given the operating conditions so as to minimize the disadvantages or find an alternative method to solve this drawback. Those who process degradable polyolefin compositions devote great efforts, for example, to choosing the exact and precise dimensions of the tools so that the pressure drops are not so harmful when the polymer is forced to flow through the matrices, which allows the use of polyolefins of higher molecular weight and at the same time achieve the benefits of shorter curing time as a result. However, the optimal tool and the optimal design of the matrix for a polyolefin composition is not necessarily advantageous for another polyolefin composition, therefore, it is necessary to modify and change the circulation path and the design of the matrix with each change of production , and in any case the benefits are not too many if the initial design is adapted to good industrial practice. Various forms of "processing aids" have been proposed. Among them, for example, calcium stearate, zinc stearate, magnesium stearate, mineral oils of various viscosity indexes (between 50 and 150 centistokes), microcrystalline paraffin wax, and polyethylene glyols either by themselves or in combination. Varrall et al. in WO 91/08262 describe the addition of 10% polyethylene wax to LLDPE for the purpose of improving the processability of degradable silane LLDPEs which are used in the manufacture of coatings, coatings and cable insulation elements. In general, it is desired to reduce the friction between the polymer mass and the internal surfaces of the matrix and associated flow passages. In general, the additive migrates at least partially, from the molten polymer composition to the interface with the matrix, and thus lubricates said interface. It is common for these lubricants to disappear from the polymer / metal interface during their use, and so they must be replaced regularly by the addition of the active process additive. This makes the cost of the processing operation greater. Since the lubricant element rarely remains in the mass or stuck to the processed polymer surface, this causes a lack of purity that represents a serious problem in the use and useful life of the manufactured article, such as the properties of inferior sealing, greater difficulty to print on the surface, less electrical properties. One method for improving the processability of narrow molecular weight distribution polyethylenes such as LLDPE is that suggested by Varrall et al. in WO 91/08262. Varrall et al. suggest using mixtures of LDPE with LLDPE for degradable silane compositions to be employed for cable insulation and coatings, to thereby improve the extrudability of the LLDPE compositions. An alternative approach is to use mixtures of high molecular weight polyethylene with low molecular weight polyethylenes. For example, Varrall et al. mention in WO 91/08262 that a mixture of a first LLDPE with a Melt index of between 0.2 and 10 and a second LLDPE with a Melt index of between 20 and 50, more preferably in proportions of between 30 and 70% of the first component and 70 to 30% of the second component will result in a good balance of curing speed and processability for the degradable silane systems for the manufacture of coatings and cable insulation. However, they do not mention any example of said composition. Another example of an attempt to define proportions of optimal mixtures and composition appears in Wong et al. in EP 584927, in which they describe that the addition of a small amount of an "auxiliary" polymer component that is co-crystallizable with a "major" polymer component derived from ethylene and optionally at least one higher alpha-olefin will reduce the time necessary to obtain an optimum level of curing without affecting the processability in a significant way. However, they also explain that it is preferable to add a polymeric processing element in the form of a fluorinated polymer and / or a polymer derived from ethylene and optionally at least one olefinically unsaturated co-monomer having a Melt index of at least 5%. grams / 10 minutes greater than the "main" component. Despite several attempts, there is a need to provide degradable polyethylene compositions which possess a good degree of processability and a good curing index. The present invention describes compositions that possess an improved combination of both elements. The polyolefin compositions of the invention consist of at least one olefin polymer, preferably an ethylene polymer, said composition fulfills the following conditions: Mn 1 / Mn2 > 5. Mn2 > 3000 and 0.7 > / - (A, / ^ + A2)) > - 0.15 wherein AL A2 l Mn 1, Mn 2 are derived from the molecular weight distribution of the composition that is obtained through gel penetration chromatography (GPC) by taking the relative response (RR) as a function of molecular weight (MW ) to adapt the RR and MW to the next function which is a heavy sum of two logarithmic normal distribution functions: RR = - ^ expí-í - ¡- f) + - exp (- < -fez)) using a non-linear regression technique to obtain values for A,, A2, μ,, R2, d, and d2, where: MW is the molecular weight value of GPC: RR is the relative response that for individual RR / MW is: RR [i] = normalized height [i] / (log (MW [i-1] -log (MW [i] )) where the normalized height [i] is the GPC output for the corresponding MW (i); μi and d2 represent the mean and standard deviation of the first logarithmic normal distribution; Mn1 = 10 μ1 exp (-0.5 (1n (10) x d,) 2) and Mn2 = 70 μ2 exp (-0.5 (1n (10) x d2) 2).

The present invention further discloses a process for making polyolefin compositions consisting of: a) preparing a first olefin polymer and a second olefin polymer; b) mixing the first and second olefin polymer so that they are homogeneously mixed to obtain a polyolefin composition that meets the following conditions: Mn1 / Mn2 > 5. Mn2 > 3000 and 0.7 > / - (A ^ I (A + A2)) > - 0.15 where Ai, A2, M "?, Mn2 are derived from the molecular weight distribution of the composition that is obtained through gel penetration chromatography (GPC) by unlocking the relative response (RR) as a function of molecular weight (MW) to adapt the RR and MW to the following function, which is a heavy sum of two logarithmic normal distribution functions: A,, b. gíMWYμ,, A2. , -bg (MW) -μ2, A using a non-linear regression technique to obtain values for A1t A2, μ1, μ2 'd1 and d2, where: MW is the molecular weight value of GPC: RR is the relative response that for individual RR / MW is: RR [i ] = normalized height [i] / (log (MW [i-1] -log (MW [i])) where the normalized height [i] is the GPC output for the corresponding MW (i); μ! and d2 represent the mean and standard deviation of the first logarithmic normal distribution; Mn1 = 10 μ1 exp (-0.5 (1n (10) x d1) 2) and Mn2 = 70 μ2 exp (-0.5 (1n (70) x d2) 2). Another aspect of the present invention is an article consisting of a degradable polyolefin composition that is obtained by curing a degradable polyolefin composition of the present invention. Another aspect of the present invention is a process for degrading said degradable composition. Figure 1 illustrates a gel penetration chromatogram for the Tafmer ™ P0480 polyethylene of the prior art. Figure 2 illustrates a gel penetration chromatogram for the polyethylene of the prior art having a total Mn of 1 9,400, a total Mw of 64,100 and a polydispersity index of 3.3. Figure 3 illustrates a gel penetration chromatogram of a modeled olefin composition according to the present invention corresponding to Example 2 having a total Mn of 29,900, a total Mw of 124,000 and a polydispersity index of 4.1.1. The bi-dispersed nature of the molecular weight distribution is clearly observable. Figure 4 illustrates a gel penetration chromatogram for another model olefin composition according to the invention corresponding to Example 3 having a total Mn of 6950; a total Mw of 85,000; and a polydispersity index of 1 2.2. Figure 4 represents an extreme case of bi-dispersity. Figure 5 represents the cutoff index at which the onset of the mass fracture occurs as a function of the Mn for the polymer composition of Table IV. Figure 6 shows the viscosity of the mass as a function of total Mn for the compositions of Table V. Figure 7 shows the variation of curing time for the series of degradable peroxide compositions of Table VI as a function of total Mn. Figure 8 shows the variation of hot cure time to 175 percent for the series of air-cured degradable silane compositions detailed in Table VII as a function of total Mn. Figure 9 shows the influence of Mn on the hot cure time at 175 percent for the series of degradable silane compositions cured in water at 60 ° C as detailed in Table VII I. The data representing the present invention are indicated by arrows. Figure 10 graphically illustrates the difference between the prior art compositions and the present invention based on the deconvolution parameters M "?, Mn2, Ai, and A2 presented in Table IX. When the terms M "and Mw are used as terms Mn total and Mw total, these refer to the number average molecular weight and the weight average molecular weight respectively of the total polyolefin composition, as opposed to Mm and Mn2 representing characteristics of the composition polyolefin obtained by the conventional method of deconvolution. In accordance with the present invention it is surprisingly established that the compositions of the invention demonstrate an improved combination of processability and curing speed compared to prior art compositions of a similar Mn and similar density. The inventors of the present have discovered that said improved characteristics and properties refer to specific molecular weight parameters as explained in greater detail below. The parameters An, A2, Mn 1 and Mn2 used to describe the polyolefin compositions herein are derived from the GPC analysis of samples of these compositions. Figures 1 and 2 are representative of the GPC curves of polyolefin compositions of prior art, Figures 3 and 4 are representative of the GPC curves of polyolefin compositions according to the present invention. The samples are analyzed by gel penetration chromatography in a Waters chromatographic unit of 150 ° C high temperature equipped with three mixed 10 μm pl-gel columns% operating at a temperature of 140 ° C. The solvent is 1, 2,4-trichlorobenzene with which solutions for injection of 0.2% by weight of the samples are prepared. The circulation index is 1.0 milliliters / minute and the injection size is 200 microliters. The molecular weight determination is deduced using standard polyethylenes of narrow molecular weight distribution (from Polymer Laboratories) together with their effusion volumes. The equivalent molecular weights are determined using appropriate Mark-Houwink coefficients for polystyrenes and polyethylenes (as described by Williams and Ward in the Journal of Polymer Science, Polymer Letters, Vol. 6, (621) 1968) to derive the following equation: " polyethylene = a * (Mpolystyrene) 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: Mw = S wi * Mi, in which Wi and Mi are the fraction of weight and molecular weight, respectively, of the fraction i that eludes from the GPC column When subjecting the GPC curves to deconvolution by non-linear regression based on the distribution function Log-normal dual that is detailed above, the values of Ai, A2, di, μ and μ2 can be calculated for each gel penetration chromatogram.The values of μ1 and d2, respectively μ2 and d2 are used to calculate the values of Mn 1 and Mn2. The previous deconvolution provides two normal logarithmic-normal distributions, each of which is characterized by the values of Mm, dj and μj. The benefits of the present invention were observed when Mm and Mn2 complied with the ratio specified above. It can be considered that Mn 1 represents the average molecular weight number of the logarithmic normal distribution that corresponds to the highest molecular weight fractions, as obtained by the specified deconvolution method. In an analogous way, it can be considered that Mn2 represents the weight average molecular weight of the logarithmic normal distribution corresponding to the lower molecular weight fractions, as calculated by the specified method. The greater the ratio of M "? with respect to Mn2, the greater the processability of the polyolefin composition. However, to maintain the desired curve of the composition the value of Mn 1 / Mn 2 must be greater than 5, preferably greater than 6.5 and more preferably greater than 7.0. If the ratio is less than 5, the cure index improvement will not be obtained. In accordance with the present invention, it is preferable that the composition contains a mixture of components chosen from the families of a linear homogeneous PE, or from the family of substantially linear ethylene polymers. The compositions obtained from two SLPEDs are preferred. The value of Mn2 is greater than 3,000 and is preferably greater than 4,000. In addition, the relation A? / (A? + A2), which can be considered as the relative contribution of the first logarithmic normal distribution (characterized by μ1 and d1) to the heavy sum of the first and second logarithmic normal distributions that are obtained by applying the function of dual normal deconvolution described above to the gel penetration chromatogram of the composition, must fit within certain limits. The ratio between A1 and (Ai + A) must be greater than or equal to 0, 15, and preferably greater than or equal to 0.2 and more preferably greater than or equal to 0.25. Also, the ratio of A i to (A i + A2) must be less than or equal to 0.7, preferably less than or equal to 0.65, and more preferably less than or equal to 0.6. If the ratio does not oscillate between 0.7 and 0.15, the curing index will be less than necessary, and the cutting refining effect associated with the bimodal molecular weight distribution polymers will decrease, which will affect processability. The values for Ai, A2, M "? , and Mn2 result from the application of the non-linear analysis "least squares" of a series of data points generated by the GPC expressed in the form of logarithmic MW versus relative response. The true increased relative response (Relative response [i]), corresponding to a logarithmic MW [i] is expressed by the formula: normalized height [i] Relative response [i] = log (MW [i-1] -log (MW [i]) where the normalized height (i) and MW [i-1] and MW [i] are obtained from the GPC data For i equals 1, the relative response is zero The sum of all the normalized heights [i] is equal to 1. The numerical method used to adapt the curve is the method of Choleski decomposition with derivatives determined in numerical form with errors in all the variables as detailed in Technical University of Eindhoven (Netherlands) PP- 5.3, non-linear regression without limits, 1989 TU E-RC 68438 and in "An Introduction to Numerical Analysis" by KE Atkinson, published by John Wiley & amp; amp;; Sons, Inc. in 1978. This numerical analysis can be performed using software that is available on the market such as RR Graph ™ from the Reactor Research Foundation, which is registered with the Chamber of Commerce of Delft, the Netherlands, with the number of record S145980. This analysis applies the function of logarithmic normal distribution to a series of data represented by logarithm (MW [i]) versus Relative response [i] to determine the values A, A2, di, d2, μ1 t μ2 that provide the best fit ("fit") for the log (MW [i] versus relative response [i] .The start values for the parameters Ai, A2 (equal 1 - A ^, μ μ ?, d 1, and d2 are based on knowledge of the opposition and / or shape of the GPC curve The initial values that have resulted in accepted deviations are: AT = 0.4 to 0.6, μ of approximately 5; μ2 of approximately 4; di and d2 each If the deconvolution is not successful, the initial values can be adjusted in view of the shape of the GPC curve The values Ai, A2, M "? and Mn2 calculated as detailed above can be obtained from the composition and may not coincide, in the case of a real mixture, with the indices of the actual mixture pectiva and the average molecular weights number of the components of the mixture. Thus, the relation of A, with (+ A2) does not necessarily correspond to the indices of the actual mixture in the case that the composition is made with the mixture of two or more polymeric components. The values of M "? and Mn2 also do not necessarily correspond to the actual values of Mn that would have been obtained by gel permeation chromatography of the components of the mixture separately before mixing. The compositions herein may have one or more olefin polymer components especially when prepared by mixing, so long as the total composition meets the conditions detailed above. The polyolefin compositions of the present invention are generally obtained by mixing two or more polyolefins which are preferably selected from the same family. As such, the polyolefin compositions of the present invention include mixtures of two or more linear PEs, or mixtures of two or more LDPE, or two or more SLEP, but not mixtures of linear PE and LDPE. Low density polyethylene (LDPE) is usually made at high pressure using free radical initiators, and usually has a density that ranges from 915 to 940 kilograms per cubic meter (kg / m3). LDPE is also known as "branched" polyethylene because of the relatively large number of long chain branches extending from the main column of the polymer. The LDPE consists of ethylene and may optionally contain small amounts (e.g., up to 5 percent by weight) of comonomers such as propylene, buten-1, vinyl acetate and butyl acrylate. Ethylene polymers and copolymers prepared by the use of a coordination catalyst, such as the Ziegler or Philips catalyst, are known as linear polyethylene ("linear PE") given the substantial absence of branched chains of polymerized monomer units depending on the spine. Linear PEs include LDPE and LLDPE; The latter include ULDPE and VLDPE. High density polyethylene (ßHDPE "), which usually has a density of 941 to 967 kg / m3, is a linear ethylene homopolymer or an interpolymer of ethylene and a small amount of high-olefin and contains relatively few chains or branches with respect to the various linear ethylene interpolymers and an alpha olefin As used herein, "interpolymer" means a polymer of two or more comonomers, for example, a copolymer or terpolymer. LLDPE ") is usually an interpolymer of ethylene and an alpha olefin of 3 to 12 carbon atoms, preferably from 4 to 8 carbon atoms (for example, 1-butene, or 1-ketene), which has sufficient alpha-olefin content to reduce the density of the interpolymer in relation to that of the LDPE. The LLDPE is a member of the linear PE family. When the interpolymer contains even higher-olefin, the density will decrease below 910 kg / m3 and these interpolymers are known as ultra-low density polyethylene ("ULDPE") or very low density polyethylene ("VLDPE"). .

The densities of these linear polymers usually range between 865 and 910 kg / m3. VLDPEs and ULDPEs are members of the family of linear PEs. The linear ethylene interpolymers comprise the homogeneously branched and the homogeneously branched. The latter generally have a very broad and non-uniform distribution of comonomer content, ie some molecules have a relatively high content of alpha olefin comonomer while others have a relatively low content. In general, polymer molecules with low comonomer content are relatively more crystalline and have a high melting temperature, while polymer molecules with a high comonomer content are more amorphous and melt at a lower temperature. Homogeneously branched linear polyethylenes which can be employed in the practice of the present invention (also referred to as homogeneous linear polyethylenes or homogeneous linear PEs or homogeneous LLDPE) are known, and their method of preparation is described in US Patent 3,645,992. . Examples of the homogeneous LLDPE include Tafmer ™ polymers (Mitsui trademark), and Exact ™ polymers (Exxon trademark). A family other than olefin polymers is that of substantially linear olefin polymers. These polymers, and more particularly the substantially linear ethylene polymers (SLEP) and the method of their preparation are described in U.S. Patent Nos. 5,272,236; 5,278,272 and 5,380,810. SLEPs are marketed by DuPont Dow Elastomers L. L.C. with the name of Engage® polyolefin elastomers and by The Dow Chemical Company with the name of AffinityR polyolefin elastomers. As used herein, the term "substantially linear" means that the bulk polymer has an average of between 0.01 long chain / 1000 carbon and 3 long chain / 1000 carbon, preferably 0, branches. 01 and 1 long chain branch / 1000 carbons, and more preferably between 0.05 and 1 long chain branches / 1000 carbons. By contrast, "linear simply means that the column of the polymer is substituted with less than 0.01 long chain / 1000 carbon branches." The term "bulk polymer" as used herein means the resulting polymer. of the polymerization process and, for the substantially linear polymers, includes the molecules without long chain branching, as well as the molecules with long chain branching Thus, a "bulk polymer" includes all the molecules that are formed during the polymerization It is known that for substantially linear polymers, not all molecules possess long chain branching, but many do possess it, so that the average long chain branching content of the bulk polymer positively affects the smelting rheology (ie the properties of mass fracture) In the present, the long chain branching (LCB) is described as the length of ac at least 1 carbon less than the number of carbons in the comonomer, while the short chain branching (SCB) is defined herein as the chain length of the same number of carbons in the comonomer residue after It is incorporated into the polymer column. For example, a substantially linear ethylene / polymer of 1-octene possesses columns with long chain branches of at least 7 carbons in length, but also possesses short chain branches of only 6 carbons in length. The long chain branching can be differentiated from the short chain branching using 13C nuclear magnetic resonance (NMR) spectroscopy and to a certain extent, for example, for ethylene homopolymers, it can be quantified using Randall's method (Re. Chem Phys. C29 (2 &3), pp. 285-297). However, in the practical field, said spectroscopy can not determine the length of a long chain branch of more than 6 carbon atoms and as such, this analytical technique can not differentiate between a branch of 7 carbons and a branch of 70 carbons. . The long chain branch may have the same length or almost the same length as the polymer column.

U.S. Patent 4,500,648 discloses that the long chain branching frequency (LCB) can be represented by the equation LCB = b / Mw where is the average weight number of long chain branches per molecule, and M is the average molecular weight weight. The molecular weight averages and the characteristics of long chain branches are determined by gel penetration chromatography and intrinsic viscosity methods. As used herein, the term "homogeneously branched" means that the comonomer is randomly distributed within a given molecule and that substantially the total number of the copolymer molecules possesses the same ethylene / comonomer ratio. The distribution or homogeneity of comonomer branches for substantially linear ethylene interpolymers and homopolymers are characterized by their SCBDI (short chain branch distribution index) or CDBI (composition distribution index), and is defined as the percentage by Weight of the polymer molecules having a comonomer content within 50 percent of the average total molar content. The CDBI of a polymer is easily calculated from data obtained from conventional techniques, such as, for example, the so-called TREF ("temperature rising elution fractionation", described by Wild et al (Journal of Polymer Science, Poly. Phys. Ed. Vol 20, p 441 (1982) or in U.S. Patent 4,798,081 The SCDBI or CDBI for homogeneously branched substantially linear interpolymers in the preferred compositions according to the present invention generally exceeds 30% by weight. %, preferably exceeds 50%, and especially exceeds 80% The homogenously branched linear polymers and SLEPs used in the invention have a single melting peak, as measured by DSC (differential scanning calorimetry), compared to heterogeneously branched linear ethylene polymers that have two or more melting peaks due to their wide branching distribution. SLEP is a surprisingly high circulation property in which the I10 I2 value of the polymer is essentially independent of the poiidispersity index (ie, Mw / Mn) of the polymer. This contrasts with homogeneously branched linear and heterogeneously branched linear polyethylene resins possessing Theological properties such that to increase the I10 / I2 value the polydispersity index must also be increased. Preferably, the mass circulation velocity, measured as I? 0 / I2 (ASTM D-1238), is greater than or equal to 5.63, and preferably is 6.5, more preferably at least 7 and may be up to 20, preferably up to 15, and more preferably up to 10. These unique SLEPs are prepared using catalysts of limited geometry (CGC) and are characterized by a narrow molecular weight distribution, and if it is an interpolymer, by a distribution of comonomers homogeneous or narrow. The molecular weight distribution (M / Mp), measured by gel permeation chromatography (GPC) is preferably defined by the equation: Mw / Mn < / - (I10 / 12) -4, 63 and is generally less than 5, preferably between 1, 5 and 2.5, and especially ranges between 1, 7 and 2.3. The ideal melt index, measured as I2 (ASTM D-1238), condition 190/2, 16 (formerly known as condition E), ranges from 0.1 g 10 minutes to 100 g / 10 minutes, more preferably 1 to 20 g / 10 minutes. In general, the substantially linear ethylene polymers that are employed in the practice of the present invention are homogeneously branched and do not possess any measurable high density fraction (ie, as measured by Temperature Rising Elution Fractionation), for example, they do not contain fraction of polymer that has a degree of branching less than or equal to 2 methyl / 1000 carbons. Other basic characteristics of substantially linear ethylene polymers is a low residual content (ie, low concentrations in the substantially linear ethylene polymer of the catalyst used to prepare the polymer, the non-reactive comonomers, if any, and the low molecular weight oligomers made during the polymerization), and a controlled molecular architecture that provides a good level of processability although the molecular weight distribution is narrow with respect to conventional olefin polymers. The substantially linear olefin polymers used to make the polymer compositions of the present invention preferably include substantially linear ethylene polymers, both interpolymers and homopolymers. The substantially linear ethylene polymers contain between 95 and 50 percent by weight of ethylene and between 5 and 50 percent by weight of at least one alpha olefin comonomer, more preferably between 10 and 25 percent by weight of at least one comonomer alpha olefin. The percentage of comonomers is measured by infrared spectroscopy in accordance with ASTM D-2238 Method B. Typically, these substantially linear ethylene polymers, as well as homogeneous linear polyethylenes, are copolymers of ethylene and an alpha-olefin comonomer of 3 to 20 carbon atoms (for example, propylene, 1-butene, 1-hexane, 4-methyl-1-pentene, 1-heptene, 1-ketene and styrene) with a density of 850 to 967 kg / m 3, preferably 865 a 960 kg / m3. Preferably, the comonomer is an alpha olefin containing between 4 and 10 carbon atoms, more preferably between 5 and 10 carbon atoms. The ideals are 4-methyl-pentene-1, 1-hexane and 1-ketene. For substantially linear ethylene polymers, the I? 0 / I2 indices indicate the degree of long-chain branching, that is, the higher the index, the greater the branching of the polymer. The "Theological processing index" (Pl) is the apparent viscosity (expressed in kpoise) of a polymer measured with a gas extrusion rheometer (GER). This rheometer is described by M. Shida, R. N. Shroff and L. V. Cancio in Polymer Engineering Science, vol. 17, no. 1 1, p. 770 (1977), and in "Rheometers for Molten Plastics" by John Dealy, published by Van Nostrand Reinhold Co. (1982) on p. 97 to 99. The experiments with G ER are carried out at a temperature of 1 90 ° C, with a nitrogen pressure between 250 and 5500 psig using a matrix of 7.54 m in diameter, 20: 1 L / D with an entrance angle of 180 ° C. For the substantially linear ethylene polymers described herein, Pl is the apparent viscosity (expressed in kpoise) of a material measured with a GER with an apparent shear stress of 2.15 x 106 dynes / cm2. These substantially linear ethylene interpolymers and homopolymers have a Pl ranging from 0.01 kpoise to 50 kpoise, preferably 15 kpoise or less, which is less than or equal to 70% of the Pl of a comparative ethylene polymer (either a polymer or a polymer). polymerized with Ziegler or a linearly branched polymer as described by Elston in U.S. Patent 3,645,992) with approximately the same I2 and Mw / Mn. A graph is used showing the apparent shear stress versus the cut index to identify the mass fracture phenomenon. According to Ramamurthy in the Journal of Rheology, 30 (2), 337-357, 1 986, above a critical circulation index, the irregularities of the stranded can be classified into two large groups: surface mass fracture and total mass fracture. The first one is produced in constant circulation conditions and covers the loss of film thickness to the most severe forms of "sharkskin" (shark skin). In this disclosure, the beginning of the surface fracture (OSMF) is characterized in that the rough surface has the appearance of an extrudate through the capillary rheometer. The critical cutoff index at the beginning of the surface fracture of the substantially linear ethylene interpolymers and homopolymers that are employed in the present invention is at least 50 percent greater than that of the start of the surface fracture of a comparative linear ethylene polymer. which has the same I2 and Mw / Mn. The total mass fracture occurs in unstable circulation conditions and ranges from regular distortions (for example, alternating between smooth and rough distortions or helices) to random distortions. For the purposes of commercial acceptance (for example, in blown films and bags made with such material) surface defects must be minimal or non-existent to achieve good properties and quality in the article. The critical cutoff index at the start of the total mass fracture for the substantially linear ethylene interpolymers and homopolymers employed to make the compositions of the present invention should be greater than 4 x 106 dynes. cm2. The critical cutoff index at the beginning of the surface mass fracture (OSMF) and the start of the total mass fracture (GFMO) will be used here based on the changes that occur in the surface roughness and the configurations of the extrudates extracted by the G ER.

The rheological behavior of substantially linear ethylene polymers is also characterized by the Dow Rheology Index (DRI) which expresses the normalized relaxation time as a result of the long chain branching of a polymer, (see, S. LAi and GW Knight ANTEC) 93 Proceedings: "I NSITE Technology Polyolefins (ITP) - New Rules in the Structure / Rheology Relationship of Ethylene Alpha-Olefin Copolymer", New Orleans, La., May 1993.) DRI values range from 0 for polymers that they do not possess measurable long chain branching (for example, Tafmer ™ products marketed by Mitsui Petrochemical Industries and Exact ™ products marketed by Exxon Chemical Company at 15 and is independent of the mass index.) In general, for low ethylene polymers medium pressure (particularly at low densities) the DRI provides an improved ratio with respect to the elasticity of the mass and a circulation of c orte high with respect to the correlations of the same mass circulation indexes. For the substantially linear ethylene polymers which are useful in the present invention, the DRI is preferably at least 0.1, and more preferably at least 0.5, and more preferably at least 0.8. The DRI can be calculated from equation 1: Equation 1: - DRI (3652879 t0 1 00649 / No - 1) / 10 where t0 is the characteristic relaxation time of the material and N0 is the zero viscosity of the material. Both are the "best fit" values determined by non-linear regression of the experimental data of the crossed equation (see equation 2), that is, Equation 2: - -N / N0 = 1 / (1 + (t X t0) n) where n is the power index index of the material, ynyt is the viscosity and the cut index measured (rad sec "1), respectively The base determination of the data corresponding to the viscosity and the cut index are obtained using Rheometrics Mechanial Spectometer (RMS-800) in the dynamic sweep mode between 0, 1 and 100 radians / second at 1 90 ° C and a Gas Extrusion Rheometer (G ER) at extrusion pressures ranging from 1 000 psi to 5000 psi (6, 89 to 34, 5 MPa), corresponding to a shear stress ranging between 0.086 and 0.43 MPa, using a 0.754 cm diameter die, 20: 1 L / D at 1 90 ° C. Specific determinations of the material can be made between 1 40 and 1 90 ° C as necessary to adapt the variations of the mass index. The mixtures can be prepared by physically mixing two or more polyolefins or by mixing in the reactor. The first method includes dry mixing, mixing the dough and mixing the solution, i.e., dissolving one or both of the components in a suitable solvent such as, for example, a hydrocarbon, or combining the components to then remove the solvent or the solvents. Mixing in the reactor usually means mixing the components in the polymerization reactor, during or after the preparation of one or both components. Both types of mixing, i.e. physical mixing and mixing in the reactor, are conventional methods. Preferably, the compositions herein are prepared by the process of mixing in the reactor using two reactors either in series or in parallel, or employing two or more catalysts in a single reactor or combinations of multiple catalysts in several reactors. The general principle for making polymer blends by mixing in the reactor using two or more catalysts in a single reactor or combinations of several catalysts and several reactors is described in WO 93/13143, EP-A-619827 and in the patent of the United States 3,914,342. The polyolefin compositions herein can be prepared by selecting the catalyst and the appropriate process conditions to obtain the characteristics of the final composition. The polyolefin composition of the present invention can be degraded or cured according to any conventional method to degrade saturated polyolefin compositions. Suitable techniques for introducing degradations between the different molecular chains of a saturated polymer such as polyethylene include various mechanisms such as the reaction with the polyethylene of a peroxide or other free radical generator, and optionally a suitable coagent / or catalyst and / or mixed activator and / or accelerator and / or promoter such as triallyl cyanurate or elemental sulfur. The reaction usually starts when heating the formed article. Generally, the desired mass index will depend on the desired end use of the article manufactured with the composition and method of making it from the degradable composition and can range between 0.01 and 100 grams / 10 minutes. For example, a mass index value of between 0.2 and 5 grams / 10 minutes is preferred for those articles that will be made by extrusion processes such as the blown film technique. In general, a lower value of mass index will be associated with items that require greater resistance to abuse or those subject to cracks and environmental stress. The articles that are made by injection molding will be made with compositions of the invention of a mass index of 4 to 100 grams / 10 minutes, and more preferably between 5 and 25 grams / 10 minutes. Those skilled in the art will apply the usual rules to determine the most appropriate value of mass index for the determined use of the composition. The compositions of the present invention preferably have a total density of at least 0.850 g / cm 3, preferably at least 0.855 g / cm 3, more preferably at least 0,860 g / cm 3. The total densities are generally less than 0.907 g / cm 3, preferably less than 0.900 g / cm 3, more preferably less than 0,890 g / cm 3, more preferably less than 0,885 g / cm 3. Compositions with densities of less than 0.900 g / cm3 are very suitable for insulation and cable coatings, especially those of the flexible type. In the patent British Patent No. 1,286,460 (corresponding to United States Patent 3,646,155) Scott discloses that chemically reactive compounds can be added as a graft to the polymer column so that subsequent reactions between the compounds can be carried out. grafted adhered to the different polymer molecular chains in such a way that degradations are formed between said polymer chains. An example of such a method is the so-called "silane degradation process" in which unsaturated silanes are grafted onto a polymer; said silanes may in turn react with the moisture in the presence of a catalyst to form degradations between the polymer chains. Unsaturated silanes suitable for performing said grafts in a base polymer include silanes of the general formula: R 'O CH2 = C- (C-O) x (CnH2n) and SiR3 where R "represents a hydrogen atom or a methyl group, x and y are 0 or 1 with the proviso that when x is 1, y is equal to 1; n is an integrator of between 1 and 12 inclusive, preferably between 1 and 4 and each R independently represents a hydrolysable organic group such as an alkoxy group having between 1 and 12 carbon atoms (eg, methoxy, ethoxy, or butoxy), an aryloxy group (eg, phenoxy), raloxy (e.g. , benzyloxy), an aliphatic acyloxy group having between 1 and 12 carbon atoms (for example, formyloxy, acetyloxy or propanoyloxy), or substituted or substituted amine groups (alkylamino or arylamino) or a lower alkyl group having between 1 and 6 atoms carbon atoms are also included, with the proviso that no more than one of the three R groups is an alkyl.These silanes can be grafted onto the olefin compositions either before or during the molding operation.The silane can be grafted to the polymer by any method conventional, generally in the presence of a free radical initiator for example, an organic initiator of ionizing radiation. Organic initiators, such as organic peroxides, are preferred, for example, dicumyl peroxide, t-butyl perbenzoate, benzoyl peroxide, eumeno hydroperoxide, t-butyl peroctoate, or methyl ethyl ketone peroxide. The amount of initiator may vary but is generally present in an amount of at least 0.04 parts per cent based on the olefin composition (phr), preferably at least 0.06 phr. In general, the amount of initiator does not exceed 0.15 phr and preferably does not exceed about 0.10 phr. The ratio of silane to initiator can vary significantly, but the ratio Silane: "typical initiator ranges from 10: 1 to 30: 1, preferably between 18: 1 and 24: 1. The degradation of the composition with silane graft is effected by placing in contact said composition with water or other active compound of hydrogen.The water or the compound penetrates the polymer from the atmosphere or from a water bath or "sauna" or by incorporating a substance in the polymer that can release water in suitable conditions, for example, by heating a polymer containing a hydrated filler such as aluminum trihydroxide.The degradation reaction requires a catalyst, which may in turn contain a degrading agent, activator or promoter and / or accelerator, and combinations These catalysts generally include organic bases, carboxylic acids, and organometallic compounds including organic titanates and complexes or carboxylates of lead, cobalt, iron, nickel, zinc and tin; dibutyltin dilaurate, dioctyltin maleate, dibutyltin diacetate, dibutyltin diocteate, stannous acetate, stannous octoate, lead naphthenate, zinc caprylate, and cobalt naphthenate. Tin carboxylate, especially dibutyltin dilaurate and dioctyltin meleate are particularly effective for this invention. The catalyst (or mixture of catalysts) is present in a catalytic amount, between 0.01 and 1.0, preferably between 0.015 and 0.10 parts by weight per 100 parts by weight of resin, ie, parts per cent resin. Other degradation methods may be employed for the polyolefin compositions of the present invention, For example, a combination of electron beam and a multifunctional comonomer or degradation promoter such as ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, trimethylene propane trimethacrylate, may be used. , trimethylolpropane triacrylate, diethylene glycol diacrylate, diallyl phthalate, triallyl cyanurate or pentaerythritol tetraacrylate, to degrade the products of the invention In the text "Radiation Processing of Polymers" published by Hanser Publishers, Munich, Vienna, New York and Barcelona and edited by A Singh and J. Silverman include details of the radiation degradation technology. The aforementioned methods are illustrative. The phase of the process during which the degradations between the different polymeric molecular chains are obtained are commonly known as the curing phase ", and the process is known as "curing". The present olefin composition may contain additional additives, such as for example heat stabilizers, radiation stabilizers such as UV stabilizers, pigments, dyes, extenders, fillers and additional process elements. These must be incorporated before the degradation step.

The compositions of the present invention can be used in a wide variety of applications, and are particularly useful in those applications where a short curing time is required. Illustrative applications include films, laminated and extrusion coated foils, extruded and calendered sheets and foils, cable coatings, weather strips and seals, gaskets, articles made with foam or sponge degraded polyolefins, open or closed cell structure and / or combinations thereof, hollow containers, hollow tanks, medical devices, molded cups, upholstery and coverings, health and personal hygiene elements, fibers, tapes, tubes, pipes and hoses, bellows, boots, leggings, footwear, soles and shoe shoes. The compositions of the present invention can be converted into finished articles or component parts used for the manufacture of other articles by conventional methods such as cable extrusion, rotomolding, profile extrusion, injection molding, compression molding, transfer molding, extrusion by overmolded, blow molded, injection blow molded, thermoformed, top forming, pressure blown, die extrusion, sheet extrusion, foam extrusion, blow extrusion, mono and monofilament extrusion and powder coating .

EXAMPLES The following examples are illustrative of certain specific embodiments of the invention. Unless otherwise indicated, all parts and percentages are expressed by weight. A series of SLEP was manufactured in a solution process miniplant equipped with two reactors, called "primary reactor" and "secondary reactor", connected in series. The primary reactor was used to continuously polymerize a feed mixture containing a mixture of ethylene / 1-octene / solvent and hydrogen gas in the presence of a metallocene catalyst as described in U.S. Patents 5,272,236, 5,278. .272 and 5,380,810. The partially reacted product of the primary reactor was continuously brought to the secondary reactor through the series connection between these reactors, where the product was reacted with additional ethylene, again in the presence of the same metallocene catalyst, under reaction conditions that gave a polymer with different Mn, generally a lower one, than that of the polymer produced under the conditions of the primary reactor. These conditions consisted of operating the secondary reactor at a higher temperature than the primary reactor. The polymer blends corresponding to Examples 1 to 4 were obtained by manipulating the reaction parameters of the primary and secondary reactors. Example 1, for example, is prepared by introducing into the primary reactor a mixture consisting of ethylene (C2), 1-octene (C8) and hydrogen gas (H2) in the following indices: Mixture of the primary reactor for Example 1 SCMH = standard cubic meters per hour (that is, the index in cubic meters at standard temperature and pressure). The primary reactor was maintained at a temperature of 70 ° C; the product was transferred from the primary reactor to the secondary reactor at a rate of 223.6 kg / hr along with 7.71 kg / hr of ethylene; the second reactor was maintained at a temperature of 120 ° C to produce the final product at a rate of 36.5 kg / hr. Comparative Examples C-1 to C-14 are examples of comparative SLEPs, C-15 is an example of a homogeneous polyethylene polymer, C-16 to C-19 are examples of comparative LLDPE polymers and C-20 and C-21 are examples of comparative VLDPE polymers. Comparative Examples C-1 1 to C-20 are ethylene polymers obtainable in the market. The EngageR Poiyolefin Elastomer and the AffinityR Poiyolefin Plastomer are both SLEP. Dowlex®, and Attane® are LLDPE and VLDPE resins, respectively manufactured and marketed by The Dow Chamical Company. Tafmer ™ is a homogeneous linear polyethylene interpol sold by Mitsui (Japan). further, the comparative examples DR-A to DR-M were elaborated with pairs of SLEP in mixing to drum and then extruding the mixture. The extrudate was cooled and pelletized, and then reactive silane extrusion with said pellets was carried out. The characterization of the samples of the two-component mixture appears in Table III below. Each polymer mixture, when subjected to GPC analysis before degradation, produced a dual peak chromatogram. The results and the corresponding characterization appear in Tables I to II I and IX below.

J or TABLE I OR TABLE H • F- Ln O TABLE II (continued) • f- J o TABLE m The data in Table IV show that the processability of the degradable polyethylene composition refers to the average moment of the total number of its molecular weight M "- The cutoff index at which the onset of the surface fracture occurs is a function of the total M for a series of substantially linear ethylene polymer compositions that appear in Table IV. Figure 5 illustrates the dependence of the onset of said fracture on a total Mn for the series of substantially linear ethylene polymer compositions (SLEP) that appear in Table IV.

Table IV Start of the surface fracture as a function of Mp (capillary rheology: cut index - I gave the viscosity curves in a range of 1 to 22,000 sec "1 in a reograph instrument 2000 at 220 ° C using a capillary matrix of 30 / 1 mm).

Table V shows the dependency of the mass viscosity measured at 220 ° C to 1800 sec "1 of the polymer of the prior art and the examples of the invention on the total Mn Figure 6 illustrates this dependence and clearly demonstrates that the viscosity of the mass depends essentially on the total Mn.

Table V: Viscosity of polymer mass in Pa * s as a function of Mn (capillary rheology: cut index - viscosity curves were measured in a range of 1 to 22,000 sec. "1 on a 200 ° reagent instrument at 220 ° C. using a capillary matrix of 30/1 mm).

Examples Cured to Peroxide The compositions listed in Table VI were made with degradable compounds according to Recipe 1 by the following procedure; 85 percent by weight of the polymer was added to an internal Farrel 89 < 5030 and mixed until the temperature of the mixture reached 80 ° C (about 2 minutes). A total batch weight of 1335 grams was used. Then, the remaining ingredients were added and mixed for an additional period until the total cycle time reached 5 minutes; then the mixer batch was removed. The temperature of the discharge was between 100 and 1 10 ° C. The mixture was then ground in a Farrel two-roll mixer at 6"x 13" for two minutes at 60 ° C using a friction index of 1.5 to 1 between the speeds of the front and rear roller and a hole around 0.5mm, before removing a 4mm sheet that was allowed to stand for two hours at 20 ° C before submitting it to the test.

Recipe 1 * Perkadox 14/40 K is 40 percent active bis (tert-butylperoxyisopropyl) benzene peroxide, marketed by Akzo Chamical International B .V. Amersfoort, The Netherlands.

** Rhenofit TAC / S is 70 percent Triallylcyanurate / 30 percent silicon co-agent marketed by Rhein Chmeie Rheinau GmbH, Mannheim, Germany. *** Vulkanox HS / LG is a polymerized antioxidant 2,2,4-trimethyl-1,2-dihydro-quinoline marketed by Bayer AG, LeverEusen, Germany. The time to achieve the optimum cure for the degradable peroxide formulations was determined at 160 ° C using a Zwick Oscillating Disk 4308 rheometer (rotor angle of 1 o and frequency of 100 min "1) .The optimum curing time, expressed in T90 l was calculated directly with software model Zwick ODR 7049 3-2, version 06.07.89 / 07 / 07.89 according to the procedure described in DIN 53529 / T2 Table VI shows the time dependence with respect to optimum curing as determined with the oscillating disc rheometer using the method described above as a function of the total Mn for a series of peroxide degradable SLEP compositions as described in Recipe 1. Samples were identified by reference to the raw polymer in The raw material with which the degradable compositions were prepared, Figure 7 illustrates this dependence and clearly shows the curing speed higher than that estimated for the compositions of the tion with respect to their number average molecular weights. For example, Example 2 cures in 46.2 minutes at 160 ° C against an estimated time of about 54 minutes based on its number average molecular weight. Similarly, Example 3 cures in 47.3 minutes at the same temperature against an estimated time of more than 60 minutes, and Example 1 cures in 48 minutes against an estimated time of 56 minutes at 160 ° C. The estimated curing times were calculated on the basis of the extrapolation of the data for the prior art compositions, ie, on the basis of the extrapolation of the curing time against the total Mn ratios of prior art compositions.

Table VI: SLEP compositions cured with peroxide Examples degraded with silane A reaction was carried out with a series of polyethylene resins and substantially linear ethylene polymers with a graft pack of 1519 weight percent vinyl trimethoxy silane, 0.075 weight percent dicumyl peroxide as the graft initiator, and 0.025 percent by weight dibutyl tin laurate as a catalyst based on the weight of the polyethylene resin of the substantially linear ethylene polymer. To prepare the graft pack, 10 cm3 of Dynasylan Silfin 12 was mixed with 92.5 percent vinyl trimethoxysilane and 7.5 percent dicumyl peroxide with 6.67 cm3 of Dynasylan Silfin 21 containing 96.2 percent of vinyl trimethoxy Silane and 3.8 percent dibutyl tin laurate (Dynasylan Silfin 12 and Dynasylan Silfin 21 are products marketed by Hüls). That mixture was added to 985 grams of the polymer sample in a closed drum. The content was mixed for one hour and then transferred to a 16 mm single screw extruder (single screw) of L / D - 28/1, equipped with a 2.5: 1 compression bolt, and with a "Cavity" matrix Transfer Mixer ". Said equipment is manufactured by Extrusion Center, Plasticisers Engineering Ltd. (United Kingdom) . It is also possible to measure the premixed mixture of silane / peroxide / catalyst directly in the mouth of the extruder (hopper throat), although for the purposes of the present study this method was not used. The rpm of the extruder was such that the residence time ranged between 3 and 7 minutes and the melting temperature of the resin was about 220 ° C. With this procedure, all the resins were grafted in the same degree. The extruded strands were cut with an air knife ("air knife") using a burst of compressed air to prevent premature curing upon contact with moisture. The compression molded plates of the strudates were obtained by taking the dry granules and placing them in a mold of nominal dimensions of 160 mm x 160 mm x 2 mm in width at a temperature of 180 ° C, heating the mold to 190 ° C, pressurizing the mold to 15 bars for 6 minutes, then increase the pressure to 150 bars for 3 minutes and then lowering the temperature to 20 ° C at a rate of cooling of 15 ° C / minute with a hydraulic press, type Platen Presse 200 manufactured by Collins. Then, the molded plates were cured at 23 ° C in air containing 80 percent relative humidity or cured by placing them in a thermostated water bath heated to 60 ° C. The rate of degradation was followed by removing the plate periodically and taking a dog-bone sample for hot analysis. This analysis consisted of placing the sample of ASTM dimensions in an oven at 200 ° C and adding equivalent weights at an effort of 20 N / cm2 to the sample. The resulting elongation of the sample was recorded. As the curing state of the sample increased, the measured elongation decreased. The decrease in elongation is therefore a measure of the rate or rate of cure. The method is described in detail in Publication 81 1 -2-1 of the International Electrotechnical Commision Standard published in 1986. According to these industry guidelines, it is considered that a satisfactory curing state has been achieved if the elongation to a determined temperature of the sample does not exceed 175 percent after 15 minutes under a load of 20 Ncm "2. To determine the cure time corresponding to this hot-set value of 175 percent after 15 minutes under a load of 20Ncm" 2 to 200 ° C, the hot-set is measured using a different dog-bone sample for each curing time and the resulting hot-set is plotted against time on logarithmic graph paper. With very short curing times, the hot-set value can be very high and the sample can be broken before 15 minutes. In this case, elongation under load was measured just before the sample broke. A line was drawn (best line) joining the data points and the intersection with the hot-set value of 175 percent and thus the desired curing time for the effects of the evaluation was obtained. Table VII includes the time dependency for a series of prior art LLDPEs (including VLDPE and LDPE), and the comparative SLEPs as a function of number average molecular weight when degraded in air containing 80 percent relative humidity. 23 according to the procedure detailed above. Figure 8 illustrates this dependence and clearly shows that the desired curing time increased significantly at the time that the Mn decreased for the LLDPE and SLEP. Similar curing can be obtained for other kinds of polyolefins.

Table VII Desired cure time as a function of Mn for degradable silane compositions cured with air based on SLEP and LLDPE above.

An additional series of compositions degradable with silane was prepared according to the methods described above, with the difference that the compositions were degraded leaving the plates molded in water at 60 ° C. The series included compositions based on substantially linear ethylene polymers, mixtures thereof and conventional homogeneous polyethylene.

Table VI II shows the dependence of time with respect to the desired curing time for this series of polymer compositions as a function of Mn when degraded with silane using water at 60 ° C according to the procedure described above.

HIV TABLE: Desired cure time for homogeneous polyethylene compositions and substantially linear degradable ethylene polymer comparative with silane cured in a 60248 C water bath and examples of the invention.

Table VIII (continued) On the other hand figures 5 and 6 show that the processability was improved while the Mn of the polyethylene was reduced; Figures 8 and 9 clearly demonstrate that the desired cure time for the silane degraded compositions according to the prior art increased significantly when the primary Mn of the polyethylene sample decreased. Figure 9 also demonstrates that the formulations proposed by Wong et al. they follow the same structure as would be expected from the values of M ". Table VI II also details the dependence of the cure time for the inventive samples of the present disclosure as a function of the number average molecular weight, and hence the processability, compared to the curing time of the corresponding formulations of the prior art. . Figure 9 shows the examples of the invention as boxes marked with arrows. The axis corresponding to the "desired cure time" scale is logarithmic to more clearly illustrate the surprising and significant improvement in curing time performance that can be obtained without loss of processability by the application of this invention. For example, the composition based on Example 1 cured in 2.79 hours vs. 31, 35 hours for comparative example DR-B and 104.3 hours for comparative example C-14, of similar average molecular weight; Example 2 cured in water at 60 ° C in 3.67 hours vs. a curing time of 9.82 hours under the same conditions for the comparative composition DR-C of similar average molecular weight. Example 3 cured under the same conditions in 17.43 hours vs. a desired curing time of more than 1000 hours; Example 4 cured in 31, 16 hours vs. an expected time of more than 1000 hours. Example 1, which cured at 2.79 hours, can be compared with compositions DR-F and DR-E that cured at 3.67 and 2.40 hours respectively. Example 1 had a mass viscosity of 1800 sec "1 at 220 ° C of 1 12 Pa * s for DR-F and 185 Pa * s for DR-E. Similarly, the processability of Example 4 which cured in , 16 hours can be compared with the processability of the DR-B composition that also cured in 31, 35 hours The mass viscosity at 1800 sec "1 at 220 ° C for Example 4 was 44 Pa * s vs. 72 Pa * s for DR-B, and considerably better for the composition of the invention. Table XI shows a summary of Mn 1 / Mn2 and + A2) for the compositions of the invention and the comparatives. Figure 1 1 details the same data in graphical form and illustrates the combinations of the parameters Mn 1 / Mn2 and A T / ÍA, + A2) that provide the benefits of the present invention.

While the present invention has been described in detail through the specific embodiments set forth above, said embodiments serve merely by way of illustration. Variations and modifications may be made without departing from the essence and scope of the present invention.

Claims (10)

1. A polyolefin composition containing at least one olefin polymer, said composition fulfills the following conditions: Mn2 > 3000 and 0.7 > / - (A, / (A? + A2)) > - 0.15, where AL A2, Mn? and M "2 are derived from the molecular weight distribution of the composition that is obtained through gel penetration chromatography (GPC) by unblocking the relative response (RR) as a function of molecular weight (MW) to adapt the RR and the MW to the following function which is a heavy sum of two functions of logarithmic normal distribution: using a non-linear regression technique to obtain values for A1t A2, μ1t μ2, b and d2; where MW is the GPC molecular weight value; RR is the relative response that for an individual data set RR / MW is: normalized height [i] Relative response [i] = - log (MW [i-1] -log (MW [y]) where the normalized height [i] is the corresponding GPC output for MW (y); μn and di represent the standard deviation and normal of the first logarithmic normal distribution; μ2 and d2 represent the standard normal deviation of the second logarithmic normal distribution; Mn1 = 10 μ1 exp (-0.5 (1n (10) x d,) 2) and Mn2 = 70 μ2 exp (-0.5 (1n (10) x d2) 2), said composition having a total density lower than 0.907 g / cm3.

2. The composition of claim 1 wherein the total density is less than 0.900 g / cm

3. 3. The composition of claim 1 or 2 wherein Mn2 is greater than 4,000.

4. The composition of claims 1 to 3 wherein + A2) is less than or equal to 0.6

5. 5. The composition of any of claims 1 to 4 wherein AT / AI + A2) is greater than or equal to 0.2. The composition of any of claims 1 to 5 containing ethylene polymer components. The composition of claim 6 wherein the two ethylene polymer components are selected from substantially linear ethylene polymers. The composition of claim 7 wherein the substantially linear ethylene polymers contain ethylene and an alpha-olefin comonomer containing between 4 and 10 carbon atoms. The composition of claim 8 wherein each of the substantially linear ethylene polymers possesses a molecular weight distribution (M / Mn) defined by the formula: Mw / M "< (I? O / I2) -4.63 in which the mass circulation ratio (o / l2) is greater than or equal to 5.63. 10. The composition of claim 7 having a density ranging between 0.850 and 0.900 g / cm3. 1 1. A degradable composition of claim 1 further comprising a degraded agent, promoter activator or accelerator. 12. The composition of claim 1 wherein the degrading agent is an unsaturated silane grafted into the composition. The composition of claim 12 wherein the unsaturated silane is represented by the formula: R 'O I I I C H2 = C- (C-0) x (CnH2n) and SiR3 where R 'represents a hydrogen atom or a methyl group; x and y are 0 or 1 with the proviso that when x is 1, y equals 1; n is an integrator of between 1 and 12 inclusive, preferably 1 to 4; and each R independently represents a hydrolyzable organic group, such as an alkoxy group having between 1 and 12 carbon atoms, an aryloxy group, araloxy, an aliphatic acyloxy group with between 1 and 1 2 carbon atoms, or aximum or substituted amino groups , or a lower alkyl group with between 1 and 6 carbon atoms inclusive, with the proviso that not more than one of the three R groups is an alkyl. 14. A composition according to claim 1 wherein Mn2 is greater than 4000, and A? / (A? + A2) is greater than or equal to 0.2 and less than or equal to 0.65. 5. An article containing a degraded polyolefin composition obtained by curing the composition of claim 11. 1

6. An article containing a degraded polyolefin composition obtained by curing the composition of claim 14. 1

7. A process for making a polyolefin composition consisting of: a) preparing a first olefin polymer and a second olefin polymer; b) mixing the first and second olefin polymer so that they are mixed homogeneously to provide a polyolefin composition that meets the following conditions: Mn, / Mn2 > 7, Mn2 > 3000 and 0.7 > (A ^ A, + A2)) > 0.15, where Mn 1, Mn2 A1 f and A2, are derived from the molecular weight distribution of the composition that is obtained through gel penetration chromatography (GPC) by unblocking the relative response (RR) as a function of molecular weight (MW ) to adapt the RR and the MW to the next function that is a sum posada of two functions of logarithmic normal distribution: A,, log (MW) -μ,, A2,, -bg (M Tμ2, A RR- _L_ exp (- (- ^ = -)) + - == P < - < -j > > using a non-linear regression technique to obtain values for Ai, A2 l μ,, μ2, di and d2; where MW is the GPC molecular weight value; RR is the relative response that for an individual RR / MW data set is: normalized height [i] Relative response [i] = log (MW [i- 1] -log (MW [i]) where the normalized height [i] is the corresponding output G PC for MW (i); μ, and di represent the standard and standard deviation of the first logarithmic normal distribution; μ2 and d2 represent the normal and standard deviation of the second logarithmic normal distribution; Mn 1 = 10 μ1 exp (-0.5 (1 n (10) xd,) 2) and Mn2 = 70 μ2 exp (-0.5 (1 n (10) x d2) 2), said composition having a l density less than 0.907 g / cm3. 1

8. The process of claim 17 wherein the first olefin polymer is an ethylene polymer that is prepared in the first reactor, and the second olefin polymer is an ethylene polymer that is prepared in the second reactor. The process of claim 18 wherein the first ethylene polymer prepared in the first reactor is transferred to the second reactor where the second ethylene polymer is prepared in the presence of the first ethylene polymer. 20. The process of claim 18 or 19 carried out in a suspension phase, solution phase or gas phase. twenty-one . The process of any of claims 17 to 20 further comprising adding a degradation agent to the composition. 22. A process for degrading the degradable composition of claim 1 which consists in subjecting the degradable composition to degradation conditions. 23. The process of claim 22 wherein the degradable composition is subjected to degradation conditions during or after the step of processing the composition to make the article.