CS214804B2 - Method of making the extrudate from the quick melting polymere of ethylene - Google Patents

Abstract

The invention relates to a process for producing an extrudate, preferably in the form of a polymer film ethylene, which rapidly melts in extrusion machine and exhibits slow attenuation at shear stress at which it is stated the polymer is extruded in an extruder with auger oi length to diameter ratio v ranges from 15: 1 to 21: 1.

Description

The present invention relates to a process for the production of an extrudate, preferably in the form of a film of ethylene polymer, which melts rapidly in an extrusion machine and exhibits a slow shear attenuation in which the polymer is extruded in a screw extruder having a length to diameter ratio of about 15 : 1 to 21: 1.

The bulk of low-density industrially produced polyethylene is produced by polymerization in thick-walled autoclaves or in tubular reactors at pressures up to 344 MPa and temperatures up to 300 ° C. The molecular structure of low-density high-density polyethylene is very complex. The permutations in the arrangement of its simple building blocks are essentially endless. High-pressure resins are characterized by complex, branched architecture with long side chains. These long branches have a marked effect on the theological properties of the resin melt. Low-density high-density polyethylene resins also contain a spectrum of short side chains, generally having 1 to 6 carbon atoms, which have an effect on crystallinity (density). The frequency distribution of these short branches is such that on average most chains contain the same number of branches. The short side chain distribution, which is a characteristic of low density high pressure polyethylene, can be considered narrow.

Low density polyethylene can exhibit many good properties. It is flexible and has a good balance of mechanical properties such as tensile strength, impact strength, tear strength and tear strength. In addition, it maintains its strength up to relatively low temperatures. Some resins do not brittle at temperatures up to -70 ° C. Low density polyethylene has good chemical resistance. It is relatively inert to acids and bases and inorganic solutions. However, it is sensitive to hydrocarbons, halogenated hydrocarbons and oils and fats. Low density polyethylene has excellent dielectric strength.

More than 50% of all low density polyethylene is processed into films. The films are mainly used in packaging, for example for packaging meat, crops, frozen food, for making ice bags, sachets that can be cooked, for wrapping textile and paper products and hangers, for making liners (for example, crates), shipping sacks and shrink films for packaging pallets of goods. Large amounts of thick film are used in construction and agriculture.

Most low density polyethylene films are made by extrusion blow molding in the form of hoses or sleeves. The diameter of the hoses produced varies. The narrowest hoses have a diameter of 5 µm or less and are used to make bags, and the largest hoses can be up to 6 m in diameter (when the hose is cut longitudinally, the strip width is 12 m).

Polyethylene can also be produced under low to medium pressure by homopolymerization of ethylene or copolymerization of ethylene with various α-olefins, using heterogeneous transition metal catalysts of different valency. These resins usually contain few long side chains, if any, and the only side chains are short side chains. The length of the side-chains depends on the type of cotaonomer. The frequency of the side chains is dependent on the concentration of the comonomer or comonomers used during copolymerization. The side chain frequency distribution depends on the type of transition metal catalyst used during copolymerization. The distribution of short side chains characteristic of low density polyethylene produced using transition metals as catalysts can be very broad.

U.S. Patent Application No. 892,325, filed Mar. 21, 1978, and re-filed July 27, 1979 under No. 014,414 (FJ Karol et al.: Preparation of Ethylene Copolymers in a Fluid Bed Reactor) discloses that ethylene copolymers having a density of 910-960 kg / m ³ , a melt flow rate (MFR) of 32 and MFR g 22 having a relatively low catalyst residue content can be produced as a granulate at a relatively high productivity by polymerizing the monomer or monomers by a low pressure gas phase process. using a specific high-performance magnesium and titanium complex catalyst mixed with an inert carrier.

United States Patent Application No. 892,322, filed March 31, 1978, and filed February 16, 1979 under No. 012,720 (GL Goeke et al., Impregnated Polymerization Catalyst, Process for its Preparation, and its Use for Ethylene Colpolymerization) discloses that ethylene copolymers having a density of 910 to 960 kg / m ³ , a melt flow rate (MFR) of 32 š MFR g 22 having a relatively low catalyst residue content can be produced as a granulate at relatively high productivity by polymerizing the monomer or monomers by low pressure a gas-phase process using a specific high-performance magnesium-titanium complex catalyst impregnated in a porous inert support.

U.S. Patent Application No. 892,037, filed Mar. 31, 1978, and re-filed on Feb. 27, 1979 under No. 014,412 (E. E. Wagner et al., Polymerization Catalyst, Process for its Preparation and its Use for Homopolymerization of Ethylene) discloses that ethylene homopolymers having a density of about 958 to 972 kg / m ³ (including limit values and a melt flow rate (MFR) of 32 and MFR gg 22 having a relatively low residual catalyst content of 14804 can be produced as a granulate at relatively high productivity so The process according to claim 1, wherein the ethylene is homopolymerized by a low pressure gas phase process using a highly efficient complex catalyst comprising magnesium and titanium mixed with an inert carrier.

Polymers produced according to these US patent applications (hereafter referred to as the aforementioned earlier US applications), when used in an extruder, have the property of melting rapidly and exhibiting a slow attenuation when subjected to shear stress.

Polymers such as those produced according to the cited US applications using complex catalysts containing magnesium and titanium have a narrow molecular weight distribution with an Mw / Mn ratio of 2.7 g Mw / Mn g of 3.6 and preferably 2.8 w Mw / Mn g 3.4.

The rheological properties of polymeric substances largely depend on their molecular weight and molecular weight distribution. When extruding foils, two aspects of Theological Behavior are important, namely in shear and stretching. In the extruder and extruder die, the polymer melt is subject to severe deformation due to shear stress. When the melt is pumped through the extruder screw to the die and the forming die, the melt is within a wide range of shear deformation rates. It is believed that in most film extrusion processes, the melt is subjected to shear at a deformation rate of 100 to 5000 s ^-1 . Polymeric melts, as is known, exhibit a weakening, i.e., non-Newton flow properties, under shear stress. As the shear rate increases, the viscosity decreases (the ratio of shear stress τ to shear rate y 'j. The degree of viscosity drop depends on the molecular weight, molecular weight distribution and molecular configuration, i.e. on the long side chains of the polymeric material. High-density low density polyethylenes typically have a broad molecular weight distribution and exhibit increased shear attenuation within the shear rate range common to film extrusion. The narrow molecular weight resins of the present invention exhibit reduced shear attenuation. Due to these differences, resins with narrow molecular weight distribution require the use of more energy and higher energy. extrusion pressures than low density, high density polyethylene resins having a broad molecular weight distribution having the same average molecular weight.

The rheological properties of polymeric substances are usually studied by shear deformation. At pure shear, the velocity gradient of the deforming resin is perpendicular to the flow direction. This deformation method is experimentally suitable, but does not provide the important information needed to understand the reaction of the material in the production of the films.

Like shear viscosity, it can be defined by shear stress and shear rate

7jstrih - τ12 / χ (lj where shear represents shear viscosity in Pa.s, τΐ2 represents shear stress in Pa and y shear rate vs ^_1 , Isé stretching viscosity defined by normal stress and strain rate at tensile stress by formula 2 rjext - τ / ε (2) where

Tjext represents the stretching viscosity in Pa.s, τΐΐ represents the normal stress in Pa and ε represents the strain rate under tensile stress vs ^_1 .

At a purely longitudinal flow, unlike the shear stress flow, the velocity gradient is parallel to the flow direction. Industrial extrusion processes include both shear and tensile deformations. When extruding films (slot extrusion and hose blowing), the rheological properties of the resin during stretching are extremely important. They may actually be decisive in the process.

The stretching viscosity can be measured by a number of experimental techniques (see, for example, JL White, Report No. 104 of the Polymer Science and Engineering., Univ. Of Tenn., Knoxvillej.). The ends of the molten polymer ring immersed in a silicone oil bath are withdrawn at increasing velocity according to the following formula 3

L (t) = L _o exp (ε ie where

Lt is the jaw distance at time t

L _o is the initial jaw distance, ε is the tensile strain rate (s ~ 'j - constant, t is time).

The deformation load is measured by a force converter. The stretching viscosity is calculated by dividing the stress by the strain rate at tensile and determined as a function of displacement or time during deformation (temperature ~ 150 ° Cj.

When deformed according to equation 3, high pressure low density polyethylene, it is found that the stretching viscosity increases exponentially with the logarithm of time. This behavior is illustrated in Fig. 1 for the case of high pressure low density polyethylene having a melt index of 0.65 g / 10 min and a density of 922 kg / m ³ . This property is referred to as melt solidification under deformation. Deformation solidification intensifies as the rate of deformation increases. In some cases, the melt may exhibit unrestricted stress growth.

The ethylene polymers produced by the processes of the aforementioned US applications usually do not exhibit unlimited voltage growth. Some resins with a broad molecular weight distribution solidify under deformation, but their elongation viscosity increases linearly with the logarithm of time (see Fig. 2j. Certain narrow molecular weight resins described in the aforementioned US applications show little deformation solidification when Figure 3 shows that deformation solidification intensifies at a higher strain rate, but not to the degree seen with high-density low density polyethylene or ethylene-hydrocarbon copolymers with a broad molecular weight distribution.

High-pressure low density polyethylene can be considered soft in shear and stretch in comparison with ethylene-hydrocarbon copolymers with a narrow molecular weight distribution. Copolymers of ethylene with hydrocarbons of narrow molecular weight distribution exhibit opposite theological properties. They are rigid in shearing and soft in stretching. The terms "soft" and "rigid" as used herein refer to the relative magnitude of the shear viscosity and elongation viscosity when comparing the theology of the high-density low-density polyethylene and the narrow-molecular-weight ethylene polymers of the invention.

High density low density polyethylene is typically processed to melt films by a screw extruder having a length to diameter ratio greater than 21: 1. In the industrial production of low density polyethylene films, the extrusion screw has a length to diameter ratio (L). (D) 24: 1 or greater. These long extrusion screws use mixing devices to achieve maximum production speed and acceptable film quality (homogeneous melt temperature distribution). When an extruder screw with a length to diameter ratio of 15: 1 to 21: 1 is used to extrude low density polyethylene low density polyethylene, the film quality is not acceptable due to the uneven temperature distribution. The quality of the film can be improved by using an extruder screw with a length to diameter ratio of 15: 1 to 21: 1 when the extruder screw is cooled. However, cooling the extruder screw is not suitable from an industrial point of view since it greatly reduces the production rate and increases the energy consumption per kilogram of resin. This can be illustrated by the data given in the following table (for the case of film production by blow molding hoses):

Table

Extrusion screw (L / D) ³ 'Film Quality Maximum extruder speed at full speed Consumption energy Consumption Cooling Type of polyethylene limited by fiefs with low • per 1 kg speed density 20: 1 or> 20: 1 + 1.0 1.0 1.00 • 1.0 high pressure 15: 1 - 21: 1 - 0.80 0.70 0.88 1.1 high pressure 15: 1 - 21: 1 + 0.50 0.80 1.60 1.0 high pressure (cooling) 15: 1 - 21: 1 ^b ' + 0.95 1.0 1.00 1.0 low pressure

aj Film quality marked - means that the film shows an uneven temperature distribution bj The low density resins described in the substrates provide an extrusion screw with an L / D ratio of 15: 1 to 21: 1 providing satisfactory melt quality defined by variations in head pressure extruder.

The unique Theological behavior of low molecular weight polyethylene resins produced, for example, by the methods of the aforementioned US applications, manifests itself in blow molding of the extruded hose in several ways. When these resins are processed in a commercially available machine, i.e. in a screw extruder having a length ratio greater than 21: 1, in particular 24: 1, the energy consumption is high and the melt temperature is also high. This causes the production speed to be limited either by the extruder power or by cooling the blown bag to a value that is lower than in the case of processing high-pressure low density polyethylene resins.

However, when used in an extruder to extrude films of these ethylene polymers with a narrow molecular weight distribution of an extruder screw having a length to diameter ratio in the range of about 15: 1 to 21: 1, energy consumption and melt temperature are reduced and the film is obtained. good quality.

Films suitable for packaging must balance certain key features to meet the operational requirements important for broad end-user availability. These properties are optical properties such as haze, gloss and transparency, and mechanical properties include tear resistance, tensile strength, impact strength, stiffness and tear strength. When packaging products that can go bad, water vapor and gas permeability are important characteristics. The performance of the packaging and the like is influenced by such properties of the film as the coefficient of friction, gluing, heat weldability and resistance to bending. Low-pressure high-density polyethylene is widely used for the production of packaging both inside and outside the food industry. For example, low density polyethylene is commonly used to make sacks that are useful as transport bags, textile packaging, launder and clean garment packaging in laundries and dry cleaners, and garbage bags. Low density polyethylene foil can be used to unload barrels for various liquid and solid chemicals and as a filler material in wood lattice crates. Low density polyethylene films can be used in a variety of agricultural and horticultural applications, such as plant and crop protection, for example, silencing and fruit and vegetable storage. Furthermore, low density polyethylene films can be used in the construction industry as barriers to moisture or water vapor. Low density polyethylene films can also be coated and printed and can be used in the production of newspapers, books, etc.

Due to the unique combination of the above characteristics, the low density polyethylene films are the most important of the thermoplastic packaging films. In packaging, they account for about 50% of the total consumption of these films. The films of the ethylene polymers, in particular the ethylene-hydrocarbon copolymers of the present invention, have an improved combination of user properties and are particularly suitable for many of the applications where hitherto used low pressure high density polyethylene.

. Improving any of the film properties or improving the extrusion properties of the film or improving the film extrusion process itself is of great importance in many end-use applications, such films can be used to replace low-density polyethylene films.

Figures 1, 2 and 3 show a plot of the elongation viscosity versus the logarithm of time for three types of low density polyethylene.

Figure 4 shows a fluidized bed reactor in which ethylene and hydrocarbon copolymers can be produced.

Giant. 5 shows a diagram of an extruder screw extruder cylinder according to the invention.

Figures 8 and 7 illustrate the slow attenuation of the two low pressure ethylene polymers of the invention under shear compared to two high pressure polyethylene resins of comparable density and melt index.

According to the invention, it has been found that in the production of an extrudate, preferably in the form of a film of ethylene polymer, which melts rapidly in the extruder and exhibits slow shear weakening by extruding the polymer from the melt using an extruder having a length to diameter ratio ranging from about 15: 1 to 21: 1, the energy consumption and melt temperature of the polymer are reduced compared to extrudate production using an extruder screw having a length to diameter ratio greater than 21: 1.

Using an extruder screw having a length to diameter ratio in the range of about 15: 1 to 21: 1 for extruding these ethylene polymers from the melt also achieves higher machine productivity compared to the extruder screw having a ratio of In addition, an acceptable, homogeneous temperature distribution is achieved using an extruder screw having a length to diameter ratio of about 15: 1 to 21: 1.

As ethylene polymers applicable in this invention, homopolymers of ethylene or copolymers containing a prevailing molar proportion of (i 90%) of ethylene and a minor mole percent (SLO ° / o) one or more C ₃ to C ₈ α-olefins which should not contain any branching on any of its carbon atoms that is closer to the copolymer backbone than the fourth carbon atom. Preferred n-olefins are propylene, 1-butene, 1-hexene, 4-methyl-1-pentent and 1-iocene.

The ethylene polymers have a melt flow rate ratio of 18 to 32, preferably from 22 to 32, including limit values. The melt flow rate ratio is another way of characterizing the molecular weight distribution of a polymer. The melt flow rate (MFR) of 22 to 32 (including limit values) corresponds to a Mw / Mn in the range of about 2.7 to 4.1. The polymers used according to the invention have an Mw / Mn value ranging from about 2.2 to 4.1.

Homopolymers have a density of from about 958 to 972, preferably from 961 to 968 kg / m ³ , including limit values.

The ethylene copolymers have a density of about 910 to 960, preferably 917 to 955 kg / m ^3, and most preferably about 917 to 935 kg / m ³ , including limit values. At a given melt index, the copolymer density can be controlled primarily by the amount of C ₃ to C ₈ comonomers to be copolymerized with ethylene. In the absence of a comonamer, ethylene homopolymer would be present with the catalyst of the present invention to form homopolymers having a density of about g 0.96. The introduction of increasing amounts of comonomers into the polymers results in a gradual decrease in the density of the copolymer. Under the same reaction conditions, the amount of each of the various C ₃ to C ₈ kiomonomers needed to achieve the same result varies from comonomer to comonomer.

Increasing molar amounts of comonomers in the series C ₃ > C ₄ > C ₃ >> C ₇ > Cg are needed to achieve the same results, i.e. the same density at a certain melt index.

The melt index of homopolymers or copolymers is a reflection of its molecular weight. The relatively high molecular weight polymers have a relatively low melt index. Ultra high molecular weight ethylene polymers have a high load melt index (HLMI) of about 0.0, and very high molecular weight polymers have a high load melt index of about 0.0 to about 1.0 g / 10 min. The polymers of the invention have a melt flow index at normal load (MI) ranging from g of 0.0 to about 50, preferably ranging from about 0.5 to 35, and a melt flow index at higher load (HLMI of from about 11 to about 950) The melt index of the polymers used in the process of the invention is dependent on the combination of polymerization reaction temperature, copolymer density, and hydrogen / monomer ratio in the reaction system The melt index increases with increasing polymerization temperature and / or decreasing polymer density or / and increasing the hydrogen / monomer ratio.

The polymers contain 1, and usually 0.1 to 0.3, C-C double bonds per 1000 carbon atoms and have a cyclohexane extractable component content of less than about 3, and preferably less than about 2% by weight.

The polymers contain as catalyst residues of the order of at most 20 ppm Ti inclusive at a productivity of 50,000 or more and at most 10 ppm Ti inclusive at a productivity of 100,000 or more and at most 3 ppm inclusive at a productivity of 300,000 or more. When polymers have been produced using halogen-containing catalysts where halogen is chlorine, they have a chlorine residue content of not more than 140 ppm inclusive at a productivity of 50,000 or more, not more than 70 ppm inclusive at a productivity of 100,000 or more . Ethylene polymers are readily produced at productivity rates of up to about 300,000.

The copolymers are granules of a substance having a mean particle size of the order of about 0.127 to about 1.524 mm and preferably about 0.5 to about 1 mm. The particle size is important for the easy fluidization of the polymer particles in the fluidized bed reactor as described below. The copolymers have a bulk density after settling of from about 243.2 to about 518.7 kg / m ³ .

Homopolymers and copolymers are suitable for the production of films.

For the production of films, it is preferable to use those copolymers having a density of about 917 to 924, including limit values, a molecular weight distribution of 0.2 g Mw / Mn g of 3.6, preferably 2.8 g Mw / Mn g of 3.1 and standard melt index (MFI) 0.5 <MFI g 5.0, preferably about 1.0 g MFI g 4.0. The films have a thickness of 0 to 0.25 mm, preferably 0.12 mm.

Compounds used to prepare a highly active catalyst that is used to produce polymers include at least one titanium compound, at least one magnesium compound, at least one electron donor compound, at least one activating compound, and at least one inert substance as a carrier. The individual components are defined below.

The titanium compound has a structure corresponding to the general formula

Ti (OR) _and X _b where

R is a C ₁ to C ₁₄ aliphatic or aromatic hydrocarbon radical or a radical of formula COR ', wherein R' is a C 1 to C 14 aliphatic or aromatic hydrocarbon radical,

X is chlorine, bromine, iodine, or a mixture thereof, and is an integer of 0 or 1, b is an integer of 2 to 4, inclusive, wherein the sum of a b is 3 or 4.

The titanium compounds can be used singly or in mixtures and include compounds of the formulas

T1C1 _3, TiCl _4, Ti (OCH ₃₎ Cl _3, Ti (OC ₆ H ₅₎ Cl _3, Ti (OCOCH ₃₎ Cl ₃ and Ti (OCOC ₆ H ₅₎ C1 _third

The magnesium compound has a structure corresponding to the general formula

MgX ₂ where

X represents chlorine, bromine or iodine.

These magnesium compounds can be used singly or in combination and include compounds of the formulas MgCl ₂ , MgBr ₂ and Mg ₁₂ . Of the magnesium compounds, anhydrous magnesium chloride is particularly preferred.

In the preparation of the catalysts, about 0.5 to 56, preferably at least 1 to 10 mol, of the magnesium compound are used per mole of titanium compound.

The titanium compound and the magnesium compound are conveniently used in a form which facilitates their dissolution in the electron donor compound as described below.

The electron donor compound is an organic compound that is liquid at 25 ° C and in which the titanium compound and the magnesium compound are partially or fully soluble. The electron donor compounds are known either under this name or under the name. Lewls bases.

By electron donor compounds are meant such compounds as alkyl esters of aliphatic and aromatic carboxylic acids, aliphatic ethers, cyclic ethers and aliphatic ketones. Of these electron donor compounds, C 1 to C ₄ alkyl esters of saturated aliphatic carboxylic acids, C ₇ to C ₈ aromatic carboxylic acid alkyl esters, C ₂ to C _8, and preferably C ₃ to C ₄ aliphatic ethers, C ₃ to C ₄ cyclic ethers and preferably C ₄ cyclic mono- or dietberům, C ₃ to C _Fi, and preferably _C3 to _C4 aliphatic ethers. Most preferred of these electron donor compounds are methyl formate, ethyl acetate, butyl acetate, ethyl ether, hexyl ether, tetrahydrofuran, dioxane, acetone and methyl isohutyl ketone.

The electron donor compounds can be used singly or in mixtures.

About 2 to 85 and preferably about 3 to 10 moles of the electron-morphine compound are used per mole of titanium.

The activating compound has a structure corresponding to the general formula

Al (R ') _c X _d ' H _c where

X * represents chlorine or a group of the formula OR '‘and each of the symbols

R "and R '" are the same or different and are _C} to _C14 saturated hydrocarbon radicals, d is 0 to 1.5, e is 1 or 0, with the proviso that the sum c + d + e value 3.

The activating compounds may be used singly or in combination and exemplified by compounds of the formula

A1 (C ₂ H _{5) 3,} A1 _{(C2 H5) 2,} C1, A1 (i-C ₄ H _{9) 3,} A1 ₂ (C ₂ H _{5) 3} C 1 _3, A1 (i-C ₄ H ₉ ) ₂ H, A1 (C ₆ H ₁₃ ) _3i A1 (C ₈ H ₁₇ ) ₃ , A1 (C ₂ H _s ) ₂ H and

A1 (C ₂ H _{5) 2} (OC ₂ H _5).

About 10 to 400, and preferably about 10 to 100 moles of activating compound per mole of titanium compound are used to activate the catalysts.

The substances used as carriers are particulate solids which are inert to the other components of the catalyst composition and to the other active components of the reaction system. Such carriers include inorganic materials such as silica and alumina and molecular sieves and organic materials such as polyolefins such as polyethylene. The carriers are used in the form of dry powders having a mean particle size of about 10 to 250, preferably about 50 to 150 μΐη. These substances are preferably also porous and have a specific surface area of at least 3 and preferably at least 50 m ² / g. The carrier should be dry, ie not contain absorbed water. This is normally done by heating or drying the support with a dry inert gas prior to use. The inorganic carrier can also be further activated by treating it with about 1 to 8% by weight of one or more of the alkyl aluminum compounds described above.

The catalyst is prepared by first preparing a precursor from a titanium compound, a magnesium compound and an electron donor compound as follows. The carrier can then be impregnated with a precursor and then treated with the activating compound in one or more stages as described below. Alternatively, the precursor may be treated with the carrier and the activating compound in one or more steps, as described below.

The precursor is prepared by dissolving the titanium compound and the magnesium compound in the electron donor compound at a temperature from about 20 ° C to about the boiling point of the electron donor compound. The titanium compound may be added to the electron donor compound before or after or simultaneously with the addition of the magnesium compound. The dissolution of the titanium compound and the magnesium compound may be aided by stirring and, in some cases, heating the two compounds in the electron donor compound to reflux. After dissolution of the titanium compound and the magnesium compound, the precursor is isolated by crystallization or precipitation of a C ₅ to C ₈ aliphatic or aromatic hydrocarbon such as hexane, isopentane or benzene.

The crystallized or precipitated precursor is isolated in the form of fine, free-flowing particles having a mean size of about 10 to 100% and a bulk density of about 292 to about 535 kg / m ³ (after settling).

The precursor thus prepared has a composition corresponding to the general formula

Mg _m Ti ₁ (OR j _n X _p [ED j _q where

ED represents an electron donor compound, m represents a number from 0.5 to 56, preferably from 1.5 to 5 including limit values, n represents a number · 0, 1 or 2, p represents a number o <d 2 to 116, preferably from 6 days 14, including the limit values, q represents a number from 2 to 85, preferably from 4 to 11, including the limit values,

R represents a C 1 to O 2 aliphatic or aromatic hydrocarbon radical or a radical of formula COR ¹ , wherein R 1 is C 1-6; to Civ; an aliphatic or aromatic hydrocarbon residue; and

X represents chlorine, bromine or iodine or a mixture thereof.

The carrier can then be impregnated with a carrier in a weight ratio of about 0.033 to 1 and preferably 0.1 to 0.33 parts of precursor per part of carrier.

Impregnation of the dried (activated) carrier with the precursor can be carried out by dissolving the precursor in an electron donor compound and then mixing the resulting solution with the carrier. When the carrier is impregnated with the precursor, the solvent is evaporated by drying at a temperature of up to 70 ° C.

The carrier may also be impregnated with the precursor by adding to the expansion of the feedstocks used to prepare the precursor in the electron donor compound. In this case, the precursor is not isolated from the solution. Excess electron-donor compound is then removed by drying at a temperature of up to 70 ° C.

Alternatively, the precursor may be diluted with the carrier.

Dilution of the precursor may be performed before or simultaneously with the activation of the precursor as described below. Dilution of the precursor is accomplished by mechanical agitation or mixing of about 0.033 to 1 and preferably about 0.1 to 0.33 parts of the precursor with 1 part by weight of carrier.

In order to use it, the precursor must be fully or partially activated, i.e. it must be treated with a sufficient amount of the activating compound to bring the titanium atoms contained in the precursor to active state.

In the preparation of the useful catalyst, it is necessary to carry out the activation such that at least the last activation stage is carried out in the absence of a solvent, so that the fully active catalyst does not need to be dried to remove the solvent. Two activation procedures are described below, namely activation of the 18 released precursor (procedure A) and activation of the precursor diluted with the carrier.

In process A), the activation is carried out in at least two stages. In the first step, the precursor impregnated in silica is partially activated by partial reduction with an amount of activating compound to obtain a partially activated precursor in which the molar ratio of activator to titanium is up to about 10: 1 and preferably about 4 to 8: 1. This partial activation is preferably carried out in a hydrocarbon solvent suspension. The resulting product is then dried to remove the solvent at a temperature of 20 to 80, preferably 50 to 70 ° C. In this partial activation, the activating compound can be used in absorbed form on a carrier used as a precursor carrier. The resulting product has the character of a free-flowing particulate material and can be readily introduced into the polymerization reactor. The partially activated impregnated precursor is preferably poorly effective as a polymerization catalyst in the process of the invention. In order to activate the partially activated precursor for ethylene polymerization, an additional activator must be introduced into the polymerization reactor. This completes the activation of the precursor in the reactor. The additional activator compound and the partially activated impregnated precursor are preferably fed to the reactor via separate lines. The additional activating compound may be injected into the reactor as a solution in a hydrocarbon solvent such as isopentane, hexane or mineral oil. This solution typically contains about 2 to 30% by weight of the activating compound. The additional activating compound is added to the reactor in an amount such that, together with the amount of activating compound and titanium compound given in the form of a partially activated precursor of a total Al / Ti molar ratio of about 10 to 400 and preferably about 15 to 60 are present in the reactor. the activator compound introduced into the reactor reacts with the 'partially activated impregnated precursor and' completes the activation of the titanium compound directly in the reactor.

Two variants have been developed for the Bj procedure, i.e. activation of the precursor diluted with the carrier:

According to a first variant, the precursor is completely activated outside the reactor in the absence of solvent by mixing the precursor dry with the activating compound. In this dry mixing, the activating compound is preferably used in the soaked state in the carrier. However, this process has the disadvantage that the resulting fully activated catalyst is pyrophoric when it contains above 10% by weight of the activating compound.

According to a second preferred variant, the precursor is partially activated outside the polymerization reactor. This partial activation is carried out in a hydrocarbon solvent suspension. The resulting product was then dried to remove solvent. The partially activated precursor is fed to a polymerization reactor in which activation with the additional activator is completed.

In the preparation of the catalyst by dry blending, the solid particulate precursor is uniformly mixed with the solid particles of the porous carrier in which the activating compound is absorbed. The activator compound is absorbed into the carrier from its solution in the hydrocarbon solvent such that 10 to 50% by weight of the activator is stored at 90 to 50% by weight of the carrier. The amount of precursor, activator and carrier is selected so as to achieve the desired Al / Ti molar ratio and to provide the resulting catalyst with a precursor to carrier weight ratio of less than about 0.50, preferably less than about 0.33. This amount of support provides the necessary dilution of the activated catalyst to allow desired control of the polymerization activity of the catalyst in the reactor. When the final catalyst contains more than 10% by weight of the activator, it is pyrophoric. During dry mixing, which can be carried out at ambient temperature (25 ° C) or below, the dry mixture is well mixed to prevent heat build-up on subsequent activation, which is initially exothermic. This gives a catalyst that is fully reduced and activated and can be used as such in a polymerization reactor. It is a free-flowing (loose) substance.

According to a second preferred variant of the process, the catalyst is activated in at least two stages. In the first step, the solid particulate precursor diluted with the carrier is partially activated by reacting with an amount of activating compound to give a partially activated precursor in which the molar ratio of activator to titanium is about 1 to 10: 1 and preferably about 4 to 8:

1. This partial reduction is preferably carried out in a hydrocarbon solvent suspension. The resulting product is then dried to remove the solvent, at a temperature of 20 to 80, preferably 50 to 70 ° C. In this partial activation, the activating compound can be used in absorbed form on a carrier used to dilute the activating compound. The resulting product has the character of a free-flowing particulate matter and can be readily introduced into the polymerization reactor. The partially activated precursor is preferably poorly effective as a polymerization catalyst in the process of the invention. In order to activate the partially activated precursor for ethylene polymerization, an additional activator must be introduced into the polymerization reactor. This completes the activation of the precursor in the reactor. The additional activating compound and the partially activated precursor are preferably fed to the reactor through separate lines. The additional activating compound can be injected into the reactor as a solution in a hydrocarbon solvent such as isopentane, hexane or mineral oil. This solution typically contains about 2 to 30% w / w of the activating compound. The activator can also be added to the reactor in solid form, absorbed in the carrier. The carrier usually contains 10 to 50% by weight of activator. The additional activator compound is added to the reactor in an amount such that, together with the amount of activator compound and titanium compound present in the form of the partially activated precursor, a total Al / Ti molar ratio of about 10 to 400 and preferably about 15 to 60 is achieved. the amount of activating compound introduced into the reactor reacts with the partially activated precursor and completes the activation of the titanium compound directly in the reactor.

In a continuous gas phase process such as the fluidized bed process described below, separate batches of partially or fully activated precursor are continuously introduced into the reactor during polymerization, or • separate batches of partially activated precursor impregnated in the carrier, optionally with simultaneous introduction. separate doses of additional activating compound needed to complete activation of the partially activated precursor and thus replace the active sites of the catalyst that were consumed during the reaction.

The polymerization is carried out by contacting the stream of aionomers in the gas phase, for example in the fluidized bed process described below, substantially in the absence of catalytic poisons such as moisture, oxygen, carbon monoxide, carbon dioxide and acetylene, with a catalytically effective amount. a fully activated precursor (catalyst), optionally impregnated on a support, at a pressure and temperature sufficient to initiate the polymerization.

In order to achieve the desired density range of the copolymers, it is necessary to copolymerize with ethylene sufficient comonomers with a carbon chain of 3 or more carbon atoms to have a C content; ₅ to ₈ comonomers in copolymers 0 to 10 mol%. The amount of comonomer required to achieve this result depends on the particular comonomer or comonomers used.

The following table lists several different comonomers that must be used for copolymerization with ethylene to produce polymers having a density within the desired range at any given melt index. The table shows, on the one hand, the molar amounts of these comonomers in the polymer and, on the other hand, the relative molar ratio of these comonomers to ethylene, which must be kept in the recycled monomer gas stream under equilibrium reaction conditions in the reactor.

Comonomer propylene

1-butene

1-pen-ten

1-hexene

4-Methyl-1-pente n

1-Hepten

1-okten

The comonomer / / ethylene gas phase molar ratio under equilibrium conditions

0.2. up to 0,9 0,1 to 0,5 0,05 to 0,2 0,02 to 0,15 0,02 to 0,15 0,017 to 0,10 0,015 to 0,03

Comonomer / / ethylene molar ratio in the polymer

0.01 to 0.09 0.006 to 0.08 0.005 to 0.07 0.004 to 0.06 0.004 to 0.06 0.003 to 0.04 0.003 to 0.04

In order to maintain said ratio during the reaction, the hamonomers are fed to the reactor at a higher ratio than their necessary gas phase concentration.

A fluidized bed reaction system that can be used is illustrated in FIG. 4. The reactor 10 consists of a reaction zone 12 and a speed reducing zone 14.

Reaction zone 12 comprises a bed of growing polymer particles, formed polymer particles, and a minor amount of catalyst fluidized by the continuous flow of polymerizable and modifying gaseous components formed by the make-up gas and the gas recycled to the reaction zone. To maintain the fluidized bed in a fluidized state, the gas mass flow rate through the bed must be greater than the minimum flow rate required for fluidization. Preferably, the gas mass flow rate through the bed is 1.5 to about 10 times higher, preferably about 3 to 6 times higher than the minimum gas flow rate required for fluidization (Gmf). The Gmf designation for the minimum gas mass flow rate required to achieve fluidization was suggested by C. Y. Wen and Y.H. Yu, "Mechanics of Fluidization," Chemical Engineering Progress Symposium Series, Vol. 62, pp. 100-111 (1966).

It is important that the bed always contain particles that prevent "hot spots" and that trap and distribute the pulverulent catalyst in the reaction zone. Upon commencement of operation, polymeric particles are usually introduced as a basis into the reaction zone before the gas stream is introduced. These particles may be identical to the polymer formed or may be different. When different, they are drawn off with the resulting polymer particles as a leading product. Finally, the fluidized bed of the desired polymer particles displaces the starter bed.

The partially or fully activated precursor (catalyst) used in the fluidized bed is preferably stored in a standby container 32 under an atmosphere of an inert gas such as nitrogen or argon.

Fluidization is achieved by a high rate of gaseous, recycled through and through the bed, which is typically of the order of about 50 times higher than that of the make-up gas. The fluidized bed usually looks like a dense mass of moving particles flowing in the free vortex created by the passage of gas through the bed. The pressure drop across the bed is equal to or somewhat higher than the weight of the bed divided by the cross-section of the bed and is therefore dependent on the reactor geometry.

The make-up gas is introduced into the bed at the same rate as the withdrawal rate of the polymer product particles. The composition of the make-up gas is determined by an analyzer 16 located above the bed. The gas analyzer determines the loss of components in the gas to be recycled and the composition of the make-up gas is adjusted accordingly to keep the composition of the gaseous mixture substantially steady state in the reaction zone.

In order to ensure complete fluidization, the recycle gas and possibly part of the make-up gas is fed into the reactor via an inlet 18 under the bed. Above the inlet 18 is a gas distribution plate 20 which assists fluidization of the bed.

The portion of the gaseous stream which does not react in the lozenge is recycled gas, which is preferably discharged in the polymerization zone by passing through a zone 14 located above the bed in which the velocity is reduced and the entrained particles fall back into the bed. Particle separation may be aided by the inclusion of a cyclone 22, which may either be part of or outside the speed reducing zone 14. If necessary, the recycle gas can then be passed through a filter 24 which is adapted to separate small particles therein at high flow rates to prevent dust from depositing on the heat transfer surface and on the compressor sheets. .

The recycle gas is then compressed in a compressor 25 and passed through a heat exchanger 26 where it is stripped of the reaction heat before returning to the bed. By constantly removing the reaction heat, there is no appreciable temperature gradient in the upper part of the bed. A temperature gradient exists in the lower 152 to 304 mm bed, between the inlet gas temperature and the bed rest temperature. It has been observed that the bed almost immediately adapts the temperature of the recycle gas above this bed to the bed zone temperature so that the bed temperature is substantially constant under steady state conditions. The recycled gas is fed to the bottom of the reactor via the inlet 18-a into the fluidized bed through the distributor plate 20. The compressor 25 may also be placed upstream of the heat exchanger 26 in the direction of flow.

The monomers in the reactor include a feed line 18. To avoid condensation in particular C ₅ to C ₈ comonomer in the reaction system is suitably C ₅ to C ₈ comonomers used in the gas mixture. The temperature of the gaseous mixture in the reaction system must be above the dew temperature of the mixture. This is achieved in particular by keeping the temperature of the gas mixture at least about 3 to 10 ° C above the dew temperature by appropriately adjusting the coolant temperature in the heat exchanger 26. If any of the Cr, up to C ₈ comonomers condense on the cooled surface the heat exchanger 26, these comonomers are easily re-evaporated by contacting part or all of the recycle gas stream which is maintained at a temperature above the dew temperature.

The distributor plate 20 plays an important role in the operation of the reactor. The fluidized bed contains both growing and formed polymer particles and catalyst particles. Since the polymeric particles are hot and possibly active, they must be prevented from settling, since if any calm mass were formed, the active catalyst contained in these particles could cause the reaction to continue and the particles would melt due to the heat generated. It is therefore important that the recycle gas is passed through the bed at a rate sufficient to fluidize the particles at the bottom of the bed. The bottom of the bed is formed by a separating plate 20 and may be a sieve, a plate with slits, a perforated plate, a plate with caps (analogous to distillation column trays) and the like. All parts of the plate may be stationary or of a movable type Like any plate described in U.S. Patent No. 3,298,792, Whatever the plate design, the plate must disperse the recycled gas between the particles at the bottom of the bed and keep them in fluidized state. The movable portions of the plate may be used to extrude polymer particles retained on or within the plate.

Hydrogen can be used as the chain transfer agent. The hydrogen / ethylene molar ratio that can be used is in the range of about 0 to about 2.0 moles of hydrogen per mole of monomer in the gas stream.

Any gas inert to the catalysts and reactants may also be present in the gas stream. The activator compound is preferably added to the gas recycle system in its hottest part. Preferably, therefore, the activator is fed into the recycle line downstream of the heat exchanger, such as a container 27 through line 27A.

In addition to the catalysts, in addition to hydrogen, compounds of the formula I may be used as molecular weight control agents, i.e. as chain transfer agents.

Zn (R _and J (R _b) wherein

R _a and R _b are identical or different C _L to C ₁₄ aliphatic or aromatic hydrocarbon radicals.

This further increases the melt index values of the produced copolymers. About 0 to 50, and preferably about 20 to 30 moles of zinc compound (calculated as Zn) per mole of titanium compound (calculated as Ti) may be added to the reactor gas feed into the reactor. The zinc compound may preferably be introduced into the reactor in the form of a dilute solution (2 to 30% by weight of JV hydrocarbon solvent or · absorbed on a solid, a diluent such as silica described above · type, in an amount from about 10 to 50 ^'%! weight. These compositions tend to be pyrophoric The zinc compound may be introduced either alone or optionally together with an activating compound from a dosing device, not shown in the figure, and which may be placed adjacent to the dosing device 27. It is indicated near the hottest part of the gas recycle system.

The fluidized bed reactor must operate at a temperature below the sintering temperature of the polymer particles. In order to prevent sintering of the particles, the working temperature must be below the sintering temperature. The production of ethylene copolymers is preferably carried out at a temperature of about 30 to about 115 ° C, most preferably at a temperature of about 75 to 95 ° C. A temperature of about 75 to 95 ° C is used to produce products with a density of about 910 to 920 kg / m ³ and a temperature of about 80 to 100 ° C is used to produce products with a density of about 920 to 940 kg / m ³ and 90 to 115 ° C is used for the preparation of products with a density above 940 kg / m ³ .

The fluidized bed reactor is operated at a pressure of up to about 6.87 MPa, preferably at a pressure of about 1.03 to 2.41 MPa, and when operating at higher pressures within this range, heat transfer is facilitated because the pressure increase results in increase in unit volume heat capacity of gas.

The partially or fully activated precursor is injected into the bed at a rate equal to the rate at which it is consumed by an inlet 30 located above the manifold plate 20. Preferably, the catalyst is injected at a location located about 6.35 to 19.05 mm above the manifold plate. An important feature is that the catalyst is injected at a point above the manifold plate. Since the catalysts used are highly active, injection into the space below the manifold plate could result in initiation of polymerization at this point, which could eventually lead to clogging of the manifold plate. Injection of the catalysts into the fluidized bed, on the other hand, helps to distribute the catalyst in the bed and prevents the formation of sites with high catalyst concentrations that could lead to hot spots.

A gas inert to the catalyst, such as nitrogen or argon, is used to introduce the partially or fully reduced precursor and the optional activating compound or transfer agent, not gaseous, into the bed.

Bed productivity is controlled by catalyst injection rate. Bed productivity can simply be increased by increasing the catalyst injection rate and reduced by reducing the catalyst injection rate.

Since any change in catalyst injection rate results in a change in reaction heat evolution rate, the temperature of the recycle gas is adjusted up or down to accommodate the heat evolution rate. This ensures a substantially constant temperature in the bed. both the fluidized bed and the recycle gas cooling system must, of course, be equipped with appropriate devices for detecting temperature changes in the bed and the cooling system so that the operator can appropriately adjust the recycle gas temperature.

Under a certain combination of operating conditions, the fluidized bed is maintained at substantially the same height by withdrawing a portion of the bed as the product at the same rate as the particle formation rate of the polymer product. Since the rate of heat evolution is directly proportional to product formation, the measurement of the increase in gas temperature along the reactor (i.e. the temperature difference between the inlet gas temperature and the outlet gas temperature) determines the rate of polymer particle formation at a constant gas velocity.

Preferably, the polymer product particles are collected continuously through a conduit 34 or near the distributor plate 20. The particles are collected in the form of a suspension with a portion of the gaseous stream vented prior to settling to prevent further polymerization and caking before the particles reach the zone where are gathering. Suspension gas can also be used to transfer the product from one reactor to another.

The polymer product particles are expediently and preferably removed by means of two sequentially operated time-adjusted valves 38 and 38, between which a separation zone 40 is arranged. When the valve 38 is closed, the valve 36 is opened so that the gas / product mixture passes through zone 40. valve 38 opens to transfer the product to the outer insulation zone. The valve 38 is then closed and closed until the product is removed.

Finally, the fluidized bed reactor is equipped with a suitable venting system that allows venting of the bed during start-up and shutdown. The reactor does not require the use of any mixing devices and / or wall scraping devices.

The high-activity supported catalyst system provides a fluidized bed product with a mean particle size of about 0.127 to about 0.127

1.32 mm, preferably between about 0.50 to 1.0 mm.

The feed monomer feed stream, optionally with inert gaseous diluents, is fed into the reactor at a rate to provide a space and time yield of about 32.4 to about 162.2 kg / hr / m ³ bed volume.

As used herein, the term "crude resin" or polymer refers to a polymer in granular form as obtained from a polymerization reactor.

The films produced by the process of the invention have a thickness of from about 0.00254 mm to about 0.508 mm, preferably from about 0.00254 to about 0.254 mm, and most preferably from about 0.00254 to about 0.1016 mm. Films having a thickness of 0.00254 to 0.1524 mm have the following characteristics: tear resistance greater than about 31.17 J / mm, elongation greater than about 400%, thermal shrinkage of less than 3% when heated to 105-110 degrees Celsius, and cooling to room temperature, an impact strength of about 41.5 to about 166.77 J / cm ^3, and a tensile strength of about 13.74 to about 48.09 MPa.

Various conventional additives such as glidants, sticking agents and antioxidants can be added to the films in accordance with conventional practice.

Foils can be produced by extrusion blow molding. In this process, the molten ethylene and hydrocarbon copolymer with a narrow molecular weight distribution is extruded by means of an extruder screw having a length to diameter ratio in the range of 15: 1 to 21: 1, preferably 15: 1 to 18: 1, most preferably 18 1. The extrusion screw comprises a metering, intermediate and metering zone. The extruder screw optionally comprises a mixing zone, such as that described in U.S. Patent No. 3,486,192, 3,730,492, 3,756,574. The mixing zone is preferably located at the end of the screw.

For example, an Egan 24/1 machine can be used as an extruder. The extruder typically comprises a length to diameter screw of 24: 1. The screw of the invention can be directly replaced by an extruder screw with an L / D 2 &apos; 4 / l ratio. The space left in the extruder barrel after the auger can be replaced, for example if an 18/1 auger is used instead of an L / D 24/1 extruder, may be partially filled with various inserts, torpedoes or stops to reduced the residence time of the polymer melt. Also, the extruder cylinder can be directly matched to an extruder screw having a length / diameter ratio of 18/1.

FIG. 5 is a schematic diagram of an extruder barrel comprising an extruder screw that can be used in the method of the invention. The extruder barrel 2 comprises an extruder screw 3 and has a mixing head 4. The extruder screw has a length A and a diameter B. The ratio of the extruder screw to diameter is in the range of about 15: 1 to 21: 1. The hopper 1 and the breather plate 6 are also shown.

The molten polymer can be extruded through an annular die having a slot wider than about 1.27 mm and narrower than about 3.05 mm as described in U.S. Patent Application Serial No. 892,324 filed Mar. 31, 1978 and re-filed 16. 2. 1979 under No. 012 795 (WA Fraser et al., Method for making a film of low density ethylene-hydrocarbon copolymer).

The polymer is extruded at a temperature of about 163 to about 260 ° C in the form of a hose vertically from the bottom up. However, it can also be extruded from top to bottom or sideways. After the molten polymer is extruded through the annular die, the hose is blown to the desired size, cooled or allowed to cool, and the bag is compressed. Pressing the deflated bag is performed by guiding the bag by flattening the frame and a series of pressure rollers. These rollers are driven to ensure that the tubular film is pulled away from the annular nozzle.

Inside the cylindrical bag a pressure of gas, for example air or nitrogen, is maintained. As is known from conventional film production, the gas pressure is adjusted to achieve the desired degree of bag expansion. The degree of expansion is defined as the ratio of the circumference of the fully inflated ¹ bag to the circumference of the annular nozzle and is in the range of 1/1 to 6/1 and preferably 1/1 to 4/1. The hoses are cooled in a conventional manner, for example by cooling with air, water or a cooling mandrel.

The stretching properties of the ethylene-hydrocarbon copolymer are excellent. The draw ratio, defined as the ratio between the slit width and between the product of the film thickness and the blow ratio, is maintained in the range of about 2 to 250, and preferably about 25 to 150. if the copolymer is highly contaminated with foreign particles and / or gel. Thin films with a thickness of more than 0.0127 mm may have elongation in the longitudinal direction of from about 400 to about 700% and in the transverse direction of from about 500 to about 700%. In addition, the films obtained are not cleavable. "Splitting" is a qualitative property describing the tearing behavior of a notched film at high strain rate. The fracture rate reflects the crack propagation rate. It is a custom property of a certain type of film and does not follow from the basic knowledge in this field.

As the ethylene-hydrocarbon copolymer exits the annular die, it begins to cool, its temperature decreases below the melting point, and the polymer solidifies. The optical properties of the extruded polymer vary with crystallization and a solidification line is formed. The position of the solidification line above the annular die is a measure of the cooling rate of the copolymer film. The cooling rate has a very significant effect on the optical properties of the film.

The films can also be produced by slot extrusion. This method of film extrusion is well known and is carried out by extruding a sheet of molten polymer through a flat slit die and then cooling the extruded sheet with, for example, a cooled roller or water bath. In the cooling roll process, the film can be extruded horizontally and guided to the top of the cooling roll or vertically downwards and guided to the bottom of the cooling roll. The rate of cooling of the extruded mass during slot extrusion is very high. Cooling with a cooling roller or water bath is so fast that, as the extruded mass cools below its melting point, the crystallites nucleate very rapidly, • the supermolecular structures have a short time to grow and the size of the spherulites is therefore very small. The optical properties of the sheets produced by slit extrusion are much better than the properties of films obtained using lower extrusion blow-cooling rates. The extrusion temperature of the slot extrusion is usually much! higher than the typical temperatures used in the manufacture of an extruded hose. The melt strength is not a limiting factor in this extrusion process. Both shear viscosity and elongation viscosity are lower. Films can usually be extruded at a higher speed than blow molding. Higher temperatures reduce shear stress in the die and allow increased performance without melt fracture.

In the slot extrusion of high-pressure polyethylene at a high draw ratio, the melt property of the high-pressure low density polyethylene, referred to as deformation solidification, causes considerable molecular orientation. Low-density polyethylene films made in this manner can have very unbalanced mechanical properties. The narrow molecular weight ethylene and hydrocarbon copolymers used according to the invention, as mentioned above, show less solidification of the melt during deformation. As in the production of blow-out hoses, these can also be extruded in the slot extrusion at a higher draw ratio without causing excessive orientation of the molecules. The equilibrium of the mechanical properties of these films does not change substantially as the drawing ratio increases.

The properties of the polymers produced in the examples were measured using the following test methods:

Density:

For substances with a density below 940 kg / m ³ , the ASΓΜ-1505 procedure is used, the plate being tempered for 1 hour at 100 ° C to approach the equilibrium crystalline state. For substances with a density of 940 kg / m ³ and above, a modified procedure is used in which the test plate is tempered for 1 hour at 12 ° C to approach equilibrium crystallinity and then rapidly cooled to room temperature. All density data are in kg / m ³ . All measurements were performed in a density gradient column.

Melt Flow Index (MI)

ASTM D-1238-Condition E measurements are performed at 190 ° C, g data per 10 minutes.

Flow rate (melt flow index at higher load) (HLMI)

ASTM D — 1238 — Condition F

The measurement is performed using a 10-fold load than when measuring the melt index, data are in g / 10 min.

Flow rate ratio = flow rate_ melt index Productivity

A sample of the resin product is ashed and the weight% ash is determined, since the ash is essentially a catalyst. The productivity is therefore expressed in kg of polymer produced per kg of total catalyst consumed. The amount of titanium, magnesium and chlorine in the ash is determined by elemental analysis.

Substances extractable with n-hexane (FDA-test used for polyethylene films intended to come into contact with food). A film sample of 0.038 mm thickness and an area of 1290 cm ² is cut into 2.54 x 15.24 cm strips and weighed to the nearest 0.1 mg. The strips were placed in a flask and extracted with 300 ml of n-hexane at 50 + 1 ° C for 2 hours. The extract is then decanted into a balanced culture dish. After drying the extract in a vacuum desiccator, the culture dish is weighed to the nearest 0,1 mg. The amount of extract calculated on the original sample weight is then reported as the mass fraction of the n-hexane extractable substances.

Density

The resin is poured into a 100 ml graduated cylinder through a funnel with a 9.5 mm stem diameter up to the 100 ml mark. Do not shake the cylinder during filling. The weight difference is determined by weighing.

Molecular weight distribution (Mw / / Mn)

It is determined by gel chromatography, in the case of resins with a density below 940 kg / m ^3. E Magnesium and titanium still exist in the form of compounds used as a stationary phase of Styrogel with a pore size sequence ΙΟ ⁶ , ΙΟ ⁴ , 10 ³ , 10 ² and 6 nm and as perchlorethylene solvent, operating at 117 ° C. In the case of resins with a density of 940 kg / m ³ or higher, Styrogel is used with a pore size sequence ΙΟ ⁶ , ΙΟ ⁵ ,, ⁴ , 10 ^θ , β nm. o-dichlorobenzene at 135 ° C is used as solvent. Detection is performed in all cases by infrared radiation at 3.45 μνη.

The following examples illustrate the process of the invention but do not limit its scope in any way.

Example I a

Preparation of impregnated precursor

A 12 L flask equipped with a mechanical stirrer was charged with 41.8 g (0.439 mol) of anhydrous magnesium chloride and 2.5 L of tetrahydrofuran (THF). To this mixture was added dropwise 27.7 g (0.184 mol) of titanium tetrachloride over 1/2 hour. It may be necessary to heat the mixture at 60 ° C for about 1/2 hour to completely dissolve the substance.

To the above solution was added 500 grams of porous silica and the mixture was stirred for 1/4 hour. The mixture was purged with nitrogen at 60 ° C for about 3-5 hours. A dry, free-flowing powder is obtained having a particle size equal to the silica particles used. The absorbed precursor has a composition corresponding to the formula

TiM _{G3 0 10} Cl (THF) _{6 7} Example I b

Preparation of the impregnated precursor from a preformed precursor.

In a 12 L flask equipped with a mechanical stirrer, dissolve 146 g of the precursor in; 2.5 L of dry THF. The solution may be heated to 60 ° C to facilitate dissolution. When; 500 g of porous silica are added and the mixture is stirred for 1/4 hour. The mixture is then dried by flushing with a nitrogen stream at a temperature of not more than 60 for about 3 to 5 hours. A dry free mobile powder is obtained which has a particle size equal to that of the silica particles.

The precursor used in Procedure Ib was obtained f / j in the same manner as in Example Ia, except that it was isolated from solution in tetrahydrofuran by crystallization or precipitation. The precursor can be analyzed at this stage for the magnesium and titanium content, since a certain amount of the magnesium compound or / and the titanium may be lost in the isolation of the precursor. The empirical formulas used herein to characterize the precursor composition are derived on the assumption that the valuables that were originally added to the electron donor compound. The amount of electron donor compound is determined by chromatography.

Example II

Activation procedure

The desired weight of impregnated precursor and activating compound is placed in a mixing drum together with a sufficient amount of an anhydrous aliphatic hydrocarbon diluent such as isopentane to form a suspension.

The activator compound and the precursor are used in amounts to obtain a partially activated precursor having an Al / Ti ratio greater than 0 but less than or equal to 10. A preferred polymer is 4 to 8: 1.

The suspension is stirred vigorously at room temperature and at atmospheric pressure for 1/4 to 1/2 hour. The resulting suspension is dried with a stream of dry inert gas such as nitrogen or argon at atmospheric pressure and at a temperature of 65 + 10 ° C to remove the hydrocarbon diluent. This usually takes about 3 to 5 hours. The resulting catalyst is in the form of a partially activated precursor impregnated into the pores of silica. The substance is in the form of a freely movable powdered material. The particles correspond to the size and shape of the silica particles. The product is not pyrophoric when its aluminum alkyl content is not more than 10% by weight. It is kept under a dry inert gas such as nitrogen or argon until use. It is ready for introduction into the polymer eye reactor, where complete activation is then performed.

When an additional activating compound is introduced into the polyreration reactor to complete activation of the precursor, the de reactor is metered in the form of a dilute solution in a hydrocarbon solvent such as isopentane. These dilute solutions contain about 5 to about 30% v / v of the activating compound.

The activator compound is introduced into the polymerization reactor in an amount such that the Al / Ti ratio in the reactor is maintained at from 10 to 400: 1, preferably from 15 to 60: 1.

Example III

Preparation of precursor

In a 51 liter flask equipped with a mechanical stirrer, 16.0 g (0.163 mol) of anhydrous magnesium chloride was mixed with 850 ml of pure tetrahydrofuran under nitrogen. The mixture was stirred at room temperature (about 25 ° C) and 13.05 g (0.069 mol) of titanium tetrachloride was added dropwise. At the end of the addition, the contents of the flask were refluxed for 1/2 hour to 1 hour to dissolve the solids. The system is cooled to room temperature and then 3 liters of n-hexane are slowly added over 1/4 hour. A yellow solid precipitated. The supernatant was decanted and the solid was washed three times with one liter of n-hexane. The solids are then filtered off and dried on a rotary evaporator at 40 to 60 ° C. 55 g of a solid precursor are obtained.

The precursor can be analyzed for magnesium and titanium at this point, since certain amounts of the magnesium and / or titanium compound may have been lost in the isolation of the precursor. The empirical formulas used herein to characterize precursor reduction are derived provided that magnesium and titanium still exist in the form of compounds that were originally added to the electron donor compound and that the remaining weight of the precursor is the electron donor compound.

Analysis of solids revealed Mg composition:

6.1%, Ti: 4.9%, which corresponds to the formula: o .., !! i ikj. ,,.

where

THE represents tetrahydrofuran.

Example 1 I d

Activation procedures

Procedure

This activation process involves a multi-step activation of the precursor. The activation is carried out in such a way that the precursor is only partially reduced before being introduced into the polymerization reactor and the reduction is completed in the reactor.

The required weight of dry inert carrier is placed in a mixing vessel or drum. In the examples described herein, about 500 g of silica or about 1000 g of polyethylene carrier are used as carriers. The inert carrier is then mixed with a sufficient amount of an anhydrous aliphatic hydrocarbon diluent, such as isopentane, to form a suspension. Usually about 4 to 7 ml of diluent per g of inert carrier is required. The desired weight of the precursor is then placed in a mixing vessel and thoroughly mixed with the suspension. In the cases disclosed herein, about 80 to 135 grams of precursor containing 1 + 0.1 mmol of titanium per gram of precursor are used to produce the catalysts.

The required amount of activator needed to partially activate the precursor is added to the contents of the mixing vessel. The amount of activator used is such that the Al / Ti ratio in the partially reduced precursor is up to 10: 1, and preferably 4 to 8: 1. The activator is added to the mixing drum in the form of a solution containing about 20% by weight of activator (triethyl aluminum in these examples). ) in an inert aliphatic, hydrocarbon solvent (in these examples, breath of hexane). Activation is accomplished by thoroughly mixing and contacting the activator with the precursor. All operations described above are carried out at room temperature and at atmospheric pressure under an inert atmosphere.

The resulting suspension is dried under a stream of dry inert gas, such as nitrogen or argon, at atmospheric pressure and at a temperature of not more than 60 ° C to remove the hydrocarbon diluent. This usually takes about 3 to 5 hours. The substance is in the form of a free-flowing powder-yellow material consisting of a uniform mixture of activated precursor with an inert carrier. The dried, non-pyrophoric product is stored under an inert gas.

When the additional activator of Process A is introduced into the polymerization reactor to complete activation of the precursor, the activator may first be absorbed in an inert nasal, such as silica gel or polyethylene, but most preferably the activator is introduced into the reactor as a dilute solution in a hydrocarbon solvent such as isopentane. .

When the activator is to be absorbed in a silica gel carrier, the two substances are mixed together in a container containing about 4 ml of isopentane per gram of carrier. The resulting suspension is then dried for about 3-5 hours under a stream of nitrogen at atmospheric pressure at 65 + 10 ° C to remove the hydrocarbon diluent.

When the activator is injected into the polymerization system as a dilute solution, a concentration of about 5 to 10% by weight is preferably used.

Regardless of the method of introducing the activator into the polymerization reactor to complete activation of the precursor, the activator is used in an amount such that the Al / Ti ratio in the polymerization reactor is maintained at from 10 to 400: 1 and preferably from 10 to 100: 1. .

The silica is dried at least 600 ° C for at least 4 hours before use. Procedure B

In this procedure, the complete activation of the precursor is accomplished by contacting the precursor with the activator absorbed in the inert carrier during mixing.

The activator is absorbed in the inert carrier by suspending it together with the carrier in an inert hydrocarbon solvent and then drying the suspension to remove the solvent. The mixture obtained contains about 10 to 50% by weight of activator. Thus, 500 g of silica (previously dried at 800 degrees Celsius for 4 hours) are introduced into a mixing vessel. The required amount of activator in the form of a 20% by weight solution in a hydrocarbon solvent such as hexane is then added to the mixing vessel and the mixture is mixed, suspended with an inert carrier at room temperature and atmospheric pressure. Then the solvent is evaporated by drying the resulting suspension at 65 + 10 ° C for about 3-5 hours at atmospheric pressure with a stream of dry inert gas such as nitrogen. The dried composition is in the form of particulate particles having the same size as the particles of the carrier used.

Approximately 500 g of dried silica on which the activator is applied (in a 50/50 ratio by weight) is placed in a mixing vessel and the required weight of precursor (80 to 100 g) is added. The substances are mixed thoroughly for 1 to 3 hours at room temperature; atmospheric pressure under a dry inert gas such as nitrogen or argon. The resulting mixture takes the form of a physical mixture of bulk particles having a size of the order of 10 to 150 μΐη. During mixing, the activator on the carrier comes into contact with the precursor and activates it completely. During the exothermic reaction that occurs, the temperature of the catalyst should not exceed 50 ° C to prevent any catalyst deactivation. The resulting activated catalyst has an Al / Ti ratio of about 10 to 50 and, if it contains more than 10% by weight of the activator, may be pyrrolidic. It is stored under a dry inert gas such as nitrogen or argon before being introduced into the reactor.

Example 1

Preparation of copolymers

Ethylene is copolymerized with propylene or 1-butene (in Examples 1 to 2 with propylene and in Examples 3 to 14 with 1-butene). In all examples, a catalyst prepared as described above and activated by activation process A is used. Polymers having a density of 940 kg / m ³ or less are produced. In all cases, the partially activated precursor has an Al / T1 molar ratio of 4.4 to 5.8. The activation of the precursor in the polymerization reactor is accomplished with triethylaluminum, which is used either in the form of a 5% by weight isopentane solution (examples 1 to 3 and 4 to 14) or in absorbed form on 50/50 silica (Examples 4 and 5). in an amount such that a fully activated catalyst with an Al / Ti molar ratio of about 29 to 140 is obtained in the reactor.

Each of the reactions is carried out continuously in a fluidized bed reaction system for at least 1 hour after reaching equilibrium at a pressure of 2.06 MPa at a gas velocity of about five to six times the Gmf value and a space and time yield of 48.7 to 97 3 kg / m ² / h. The reaction system described above is used. Its lower part is 3.05 m high and its inner diameter is 0.343 m. The upper part is 4.88 m high and its inner diameter is 0.597 m.

In several examples, diethylzinc (as a 2.6% by weight solution in isopentane) is added during the reaction to maintain a constant Zn / Ti molar ratio. When diethylzinc was used, triethyl aluminum was also added in the form of an isopentane solution with a concentration of 2.6% by weight.

The following Table A lists the different operating conditions used in Examples 1 to 14, i.e. the precursor content of the precursor / silica mixture (% by weight); the Al / Ti ratio in the partially activated precursor, the Al / Ti ratio maintained in the reactor; polymerization temperature; ethylene content in the reactor (% by volume); hydrogen / ethylene molar ratio; the molar ratio of comonomer (C _x ) to ethylene (C ₂ ) in the reactor, the catalyst productivity, and the molar ratio of Zn / Ti.

Table B lists the properties of the granular raw resins produced in Examples 1-14, i.e. density, melt index (MI), melt flow rate (MFR), bulk density, average particle size, ash content in% by weight, and titanium content. (ppm).

Table A

The reaction conditions in Examples 1 to 14

Example Content prekursc ru [% weight] Al / Ti molar ratio in partially ac- tivovaný precursor Al / Ti molar ratio in the reactor Temperature PC] Content Molar Mo- Molar Mo- of ethylene, measure H ₂ / [% v / v] / ethylene comonomer / / ethylene 1 8.3 5.8 40.5 90 41.7 0.492 0.486 2 8.3 5.8 50.8 90 39.7 0.566 0.534 3 20.1 4.50 88.3 85 56.3 0.148 0.450 4 19.8 4.40 26.7 85 54.1 0.350 0.350 5 19.8 4.40 26.7 80 54.1 0.157 0.407 6 6.9 5.08 42.0 85 49.2 0,209 · 0.480 7 6.9 5.08 33.6 85 46.5 0.208 0.482 8 6.9 5.08 28.8 85 42.1 0,206 0.515 10 8.3 5.8 124.6 90 45.1 0.456 0.390 11 8.3 5.8 80.8 90 42.7 0.365 0.396 12 8.3 5.8 52.0 90 48.4 0.350 0.397 13 8.3 5.8 140.1 90 42.6 0.518 0.393 14 8.3 5.8 63.5 90 40.8 0.556 0.391 Table l B Properties of polymers produced in Examples 1 to 14 Example Density Flow index Speed ratio Bulk Medium size [kg / m ^! ] melt melt flow mass [mm] [g / 10 min) [kg / m ^! ] 1 927 22.0 24.4 272.5 0.58 2 929 24.0 23.4 283.8 0.58 3 925 0.61 27.1 272.5 0.76 4 931 12.0 26.7 272.5 0.70 5 923 1.47 28.2 253.0 1.03 6 919 3.41 25.9 272.5 1.40 7 925 2.90 24.5 283.8 1.50 8 919 3.10 24.6 262.8 1.45 10 929 16.0 24.1 280.6 0.58 11 929 15.3 24.0 269.2 0.59 12 928 11.5 24.1 270.9 0.63 13 929 20.7 24.3 280.6 0.65 14 929 29.2 26.1 272.5 0.52

Example 1 and cl 2

An ethylene-1-butene copolymer prepared according to Example 1 having a density of 920 kg / m @ 2 ^. and a melt index of 2 g / 10 min is processed on a 0.038 mm thick film by blowing out the extruded hose using a 24/1 extruder with a 63.5 mm extruder screw and an L / D ratio of 18: 1. length 317.5 mm, transition zone ¹ of length

190.5 mm, 508 mm measuring zone and 127 mm mixing zone. The mixing part is grooved and has the following characteristics: 63.5 mm diameter, 76.2 mm channels, 13.74 mm channel radius, 6.35 mm thread mixing field width, 5.08 mm thread wiping field width and mixing plug length 114 , 3 mm. The void in the cylinder is filled with a 63.25 mm diameter insert with a length of 279.4 mm, which includes a stopper with a length of 228.6 mm and a diameter of 25.4 mm.

The temperature in the extruder barrel is about 177 ° C. A 20/60/20 meshes screen and an extrusion die are used to produce films with a diameter of 152.4 mm with a spiral of 1 and 1 hunters with a needle. The nozzle temperature is set to about 177 ° C. The production rate is 21.79 kg / h. The pressure roller height is about 4.57 au. Cooling is carried out using a Venturi-type air ring. All films are produced at a blow ratio of 2: 1 (bag circumference to die circumference ratio). Extruder screw speed [min ^-1 ], power in kg / h per revolution, shaft power in kW, efficiency in kWh / kg and extrudate temperature are given in Table I.

Example 3

The procedure of Example 2 is repeated in all details, except that the production rate is 31.78 kg / h. The results are shown in Table I.

Example 4

The procedure of Example 2 is repeated in all details, except that the production rate is 43.58 kg / h. The results are shown in Table I.

Example 2

Production speed [kg / h] 21.79

Speed [min ^-1 ] 30

Power at one revolution [kg / h / rev. 0.73

Shaft power [kW] 2,39

Efficiency [kWh / kg] 0.110

Temperature [° C] 196.3

Example 5

The procedure of Example 2 is repeated exactly, except that the production rate is

31.78 kg / h and a 24: 1 L / D extrusion screw is used instead of extrusionTable II

Example 3

L / D extrusion screw ratio Production speed [kg / h]

Speed [min ^-1 ]

Power speed [kg / h / rev] Shaft power [kW]

Efficiency [kWh / kg]

Temperature [° C]: 1 31,78 44 0,73 4,39 0,136 221,3

31.78 43.58

60

0.73 0.73

4.25 6.56

0,133 0,151

The 210.2 220.2 auger with an L / D ratio of 18: 1. The results using this production speed and the extrusion screw are compared to Example 3, in which the production speed is 31.78 kg / h and the extruder used has an L / D ratio D 18: 1. The results are shown in Table II.

: 1

31,78 41

0.75

4.71

0.151

235.2

The data presented in Table II show the advantages achieved by using an 18: 1 L / D extrusion screw, ie lower energy demand at the same production rate, better energy use (as shown by lower kWh / kgj values and lower extrudate temperature.

Fast melting in extrusion machines

A shear melting mechanism is accepted as the melting mechanism for all crystalline and vitreous thermoplastic polymers.

Shear melting can be described as a thin film heat generation mechanism that occurs between the non-molten solid polymer and the extruder barrel. The film formed in the extruder duct is typically 0.381 to 0.508 mm thick, and in a thin melt film, a shear rate of up to 5000 s ^-1 can occur. As the channel progresses to the extruder exit port, the amount of solid polymer in the channel decreases due to heating and melting in a thin film that is shear stressed. For high-pressure polyethylene, this melting continues along 50 to 80% of the length of the extruder. For the polymers used according to the invention, in the series of tests described below, this slow melting mechanism occurring in high-pressure polyethylene was not observed.

The melting mechanism of the polymers used according to the invention is faster, which translates into less than 40 why. screw length (which has a length to diameter ratio of 15: 1 to 21: 1). In some cases, the melting takes place only in the length of 2 to 5 worm diameters from where the melting started.

The differences between fast melting and slow melting high-pressure polyethylene resins are threefold:

1) Melting is much faster

2) Melting is not limited to a thin film between the solid polymer and the roll

3) The melt tends to form at the trailing edge instead of at the leading edge of the extruder screw

The melting mechanism described above, referred to as the so-called rapid melting, applies as has been shown in the pellet and granulate feedstock.

Fast melting is responsible for the ability of the short worm to provide a quality melt at short length and at high film extrusion speeds. The quality, ie uniform temperature distribution, is important in the extrusion of films. To achieve this uniform temperature distribution, melt tempering is required. In the case of a short auger, it melts rapidly and tempering occurs over the remaining length of the auger.

Method of determining the melting rate

A 2.5-inch extruder (63.5 mm) is used, with the possibility of rapidly cooling or warming the cylinder, i.e. with the possibility of heating to 150 ° C to room temperature (about 25 ° C at a rate of about 15 ° C / imine). a cooling channel embedded in the extruder barrel, which can be programmed to continuously feed cold water through the cooling channel, high-intensity heaters are used in combination with steam through the cooling channel for rapid heating.

At the rear of the extruder is a large air cylinder, which is used to exert a large force on the extruder screw (about 549.6 kPa per 304.8 mm piston, which corresponds to a total force of about 39 240 N.

The melting rate is determined by freezing the molten polymer in the extruder barrel and punching the frozen sample out.

The frozen sample is obtained as follows:

The polymer-filled extruder is allowed to run under the desired conditions (i.e. 60 rpm, cylinder temperature 149 ° CJ, then cooling water is turned on suddenly and the speed is reduced to zero. Wait until the polymer is at room temperature, which usually takes at least 4 hours, and then the electrical heater is turned on and steam is introduced into the cylinder to quickly release the liner. at intervals of 3 to 10 minutes, the screw is punched out of the extruder by applying a force to the back of the screw, heating to melt as little polymer as possible at the cylinder wall. at the ratio of the screw length to the diameter to determine the relative amount of molten polymer compared to the molten polymer under extrusion conditions CONTRARY TO existing at the time of cooling.

A fast-melting polymer is one which, when passed through the extrusion process described above, completely melts within a screw length corresponding to 2 to 5 screw diameters from the start of melting. Slow attenuation during shear

By slow attenuation is meant that when the shear strain rate of the test polymer is measured in a capillary plastometer at 204.7 ° C within the shear strain rate of 1 to 5000 s ^-1 , the viscosity of the test polymer measured by Pa decreases. s (lb.s / in ² ) consistently within the test range, but is always higher than the viscosity of the high-pressure ethylene homopolymer having the same density (+5 kg / m ³ ) and the same melt flow index (+ 0) throughout the test range 3 g / 10 min}.

A comparison made to the shear deformation rate of two such groups of polymers is made in Figures 6 and 7. 6 shows a comparison between the shear strain rate of a low pressure ethylene-1-butene copolymer used in the process of the invention (low pressure polyethylene) whose melt index is 1 dg / min with a high pressure ethylene homopolymer (high pressure polyethylene) having a melt index of 0.7 dg / min The two polymers tested have a density of 920 kg / m 2 ^: The curves for the individual resins will be substantially the same regardless of the density of the polymers (in the range of about 910 to 960 kg / m ³ ). As the melt index of the test polymer changes, as the flow index increases, the curves are plotted above.

Figure 7 shows a comparison between the shear deformation rate of the low pressure ethylene-1-butene copolymer used in the process. of the process according to the invention (low-pressure ethylene poles) having a melt flow index of 2.0 dg / min with a high-pressure ethylene homopolymer (high-pressure polyethylene) which also has a melt flow index of 2.0 dg / min. m ³ .

Although the extrusion process described in these documents has been explained in the case of polymers made according to the earlier U.S. patents mentioned above, it is not limited to the use of these polymers. Other ethylene polymers (homopolymers and copolymers with one or more C ₃ to C ₈ comonomers) which melt rapidly and exhibit a slow shear attenuation regardless of the molecular weight distribution of the polymers may also be used in the extrusion process of the invention. the polymers may therefore have a relatively wide range of molecular weights of about 2 to 10, and preferably about 2 to 4.

The process of the invention is generally applicable to resins having a melt index in the range of about 0.1 to 10 dg / min, preferably in the range of about 0.1 to 5 dg / min. These resins should also have a density of about 910 to 940 kg / m ³ .

Claims (1)

A method for producing an extrudate from a fast melting ethylene polymer that exhibits a slow shear attenuation by melt extrusion in an extrusion BACKGROUND OF THE INVENTION A machine comprising an extruder screw, characterized in that an extruder screw having a length to diameter ratio in the range of 15: 1 to 21: 1 is used.