JPS6215327B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of forming a film from a low density ethylene hydrocarbon copolymer, a method of controlling the properties of the film, and a film containing said low density ethylene hydrocarbon copolymer. Films produced in this manner are substantially free from melt failure. Most commercially available low density polyethylenes are polymerized in thick-walled autoclaves or tubular reactors at pressures as high as 50,000 psi and temperatures up to 300°C. The molecular structure of high-pressure low-density polyethylene is very complex. The transformations of the arrangement of its simple building blocks are essentially infinite. High-pressure resins are characterized by having complex long-chain branched molecular structures. These long chain branchings have a large influence on the melt rheology of the resin. High pressure low density polyethylene resins also have a short chain branching range, generally from 1 to 6 carbon atoms in length, which controls the crystallinity (density) of the resin. The frequency distribution of these short chain branches is such that, on average, most chains have the same average number of branches. The short chain branching distribution that characterizes high pressure low density polyethylene can be considered narrow. Low density polyethylene can also be produced at low to moderate pressures by copolymerizing ethylene with various α-olefins using heterogeneous catalysts based on transition metal compounds of variable valence. These resins generally have little if any long chain branching, and the branching is short chain branching. Branch length is controlled by the type of comonomer. The frequency of branching is controlled by the concentration of comonomer used during the copolymerization. The frequency distribution of branching is influenced by the nature of the transition metal catalyst used during the copolymerization process. The short chain branching distribution that characterizes transition metal catalyzed low density polyethylene is very broad. As discussed below, films formed from certain ethylene hydrocarbon copolymers by the present method exhibit new and novel combinations of optical, mechanical, and shrinkage properties. Low density polyethylene exhibits a variety of properties. This polyethylene is flexible and exhibits a good balance of mechanical properties such as tensile strength, impact resistance, burst strength and tear strength. In addition, this type of polyethylene retains its strength up to relatively low temperatures. Some resins do not become brittle at temperatures as low as -70°C. Low density polyethylene has good chemical resistance. That is, it is relatively inert to acids, alkalis, and inorganic solutions. On the other hand, it is sensitive to hydrocarbons, halogenated hydrocarbons and oils and greases. Low density polyethylene has excellent dielectric strength. Over 50% of all low density polyethylene is processed into film. This film mainly consists of
Meat products, frozen foods, ice bags, boilable bags, textile and paper products, shelf goods, industrial liners,
It is used in the field of packaging such as transport sacks, stretch pallets and shrink wraps. Large amounts of wide and thick films are used in construction and agrochemicals. Most low density polyethylene films are manufactured by tubular blown film extrusion. Products range from 2in or smaller film tubes used as sleeves or pouches to giant valves offering 20ft fold diameters (the latter exhibiting a 40ft width when cut along the edges). First, the rheology of low density polyethylene will be explained. The rheology of polymeric materials is highly dependent on molecular weight and molecular weight distribution. Studies of high pressure low density polyethylene have also shown the importance of long chain branching. Two aspects of rheological properties are important in film extrusion: shear and elongation. Within the film extruder and extrusion die, the polymerized melt undergoes severe shear deformation. As the extrusion screw draws the melt into the film die, the melt is subjected to shear over a wide range of shear rates. In most film extrusion methods, the melt is 100-
It is thought that shearing will occur at a shear rate in the range of 5000 sec ^-1 . Polymer melts are known to exhibit a property generally referred to as shear thinning or non-Newtonian flow. As the shear rate increases, the viscosity (ratio of shear stress τ to shear rate γ)
decreases. The degree of viscosity reduction depends on the molecular weight, its distribution and molecular conformation, ie, the long chain branching of the polymeric material. Short chain branching has only a small effect on shear viscosity. Generally, broad molecular weight distribution resins exhibit improved shear thinning over the shear rate range common to film extrusion. Narrow molecular weight distribution resins exhibit reduced shear thinning at extrusion grade shear rates. As a result of these differences, narrow distribution resins require more power and generate higher pressure during extrusion than equivalent average molecular weight broad molecular weight distribution resins. The rheology of polymeric materials is traditionally studied under shear deformation. In pure shear, the velocity profile of the deformed resin is perpendicular to the flow direction. Although this deformation mode is convenient experimentally, it does not provide essential information for understanding the response of materials in the film manufacturing process. Shear viscosity can be defined in terms of shear stress and shear rate. That is, ηshear=τ12/γ〓 (1) Here, ηshear=shear viscosity (poise) τ12=shear stress (dyne/cm ² ) γ=shear rate (sec ^-1 ) Extensional viscosity is determined by normal stress and strain. It can be defined by speed. That is, ηext=σ11/ε〓 (2) ηext= extensional viscosity (poise) σ11=normal stress (dyne/cm ² ) ε==strain rate (sec ^-1 ) In pure extensional flow, unlike shear flow, The velocity gradient is parallel to the flow direction. Extrusion methods used commercially involve both shear and elongation deformation. In film extrusion (tubular inflation and slot casting), the extensional rheological properties of the resin are extremely important. These are what actually govern the method. Extensional viscosity can be measured by a number of experimental techniques (e.g. University of Tennessee Polymer Science and Department Report No. 104).
(see G.L. White's paper). The method used here is the constant strain rate method. Briefly, the method uses a servo-controlled Instron tensile testing machine. The ends of a molten ring of polymer immersed in a silicone oil bath are separated at an accelerated rate according to the following relationships: L(t) = Loexp(εt) (3) Here, L(t) = Jaw separation at time t Lo = Initial jaw separation ε = Strain rate (sec ^-1 ), constant t = Time Force transducer is deforming Measure the load. The extensional viscosity is calculated by dividing the stress by the strain rate and is determined as a function of displacement or time during deformation (temperature approximately 150 °C). When a high pressure low density polyethylene melt is deformed according to equation (3), the extensional viscosity is observed to increase at an accelerating rate with respect to logarithmic time. This embodiment is illustrated in FIG. 1 for high pressure polymerized low density polyethylene having a melt index of 0.65 and a density of 0.922. In this case, the melt is said to be strain hardened. This strain hardening increases as the strain rate increases. In some cases, the melt may exhibit infinite stress growth. Transition metal catalyzed ethylene hydrocarbon copolymers generally do not exhibit infinite stress growth. Although certain broad molecular weight distribution resins are strain hardening, their elongational viscosity appears to increase linearly with logarithmic time (see Figure 2). Certain narrow molecular weight distribution resins, such as those described below, exhibit little strain hardening at low strain rates. FIG. 3 shows that strain hardening increases at high strain rates, but not to the extent observed with high pressure low density polyethylene or ethylene hydrocarbon copolymers with broad molecular weight distributions. High pressure low density polyethylene is considered "soft" in shear and "hard" in elongation compared to narrow molecular weight distribution ethylene hydrocarbon copolymers.
Ethylene hydrocarbon copolymers with narrow molecular weight distributions have the opposite rheology. These are considered "hard" in shear and "soft" in extension. The terms "soft" and "hard" as used herein refer to the relative magnitude of shear and extensional viscosity when comparing high pressure low density polyethylene and narrow molecular weight distribution ethylene hydrocarbon copolymers.
An improved method for extruding films from molten ethylene hydrocarbon copolymers with narrow molecular weight distributions has been developed as described below. Next, film extrusion of low density polyethylene will be explained. Low density polyethylene is extruded into a film using conventional film extrusion techniques such as blown film extrusion and slot cast extrusion. The die cap of an extrusion equipment die used to extrude film from high-pressure low-density polyethylene is
Generally narrow and kept in the 1545mil range. These narrow die gaps accommodate the "soft" shear and "hard" elongation rheology of these resins. In narrow die gear blown film extrusion, the MD drawdown ratio, the ratio of die gap to final film product thickness and blowup ratio, is kept relatively low. This is done so as to reduce the amount of gauge reduction that must be performed in elongation. As previously mentioned, high pressure low density polyethylene melts can exhibit infinite stress growth during elongation deformation. High pressure low density polyethylene melts are said to exhibit good melt strength. In blown film extrusion, this property gives good "bubble stability" to the process, but limits the level of drawdown that can be achieved. When the extrudate is deformed in elongation, the melt stress increases, producing oriented and unbalanced film properties. If the deformation is excessive, i.e. done at high strain rates, this melt stress can cause melt strength;
The extrudate is destroyed. High pressure low density polyethylene resins can only obtain high drawdown ratios under carefully controlled conditions. The resin generally has a high melt index and must be extremely clean.
Contaminants such as foreign particles of any kind, inhomogeneous melts, high molecular weight gels, crosslinked gels, etc. act as stress concentration points, causing blowholes to form and the tubular bubbles to collapse. In slot cast extrusion, the melt temperature is considerably higher (100-200°) than the melt temperature used in blown film extrusion. A higher withdrawal ratio can be obtained. On the other hand, the elongation deformation rates used in this film extrusion method are generally much higher than those used in blown film extrusion. The strain hardening extensional rheology of high pressure low density polyethylene is manifested in this process as an effect on the mechanical properties of slot cast high pressure low density polyethylene films. High deformation rate slot extrusion using high pressure low density polyethylene resins produces films with highly unbalanced properties. The strength in the machine direction increases with drawdown ratio, but the strength properties in the transverse direction decrease sharply. The ultimate elongation of the film in the machine direction (MD) can be very small. The Elmendorf tear strength in the transverse direction (TD) can also be quite low. Narrow molecular weight distribution, transition metal catalyzed ethylene hydrocarbon copolymers can also be extruded into films by conventional techniques such as blown film extrusion and slot cast extrusion. On the other hand, these resins generate very high extrusion head pressures when extruded through narrow gap dies. The shear stress becomes high and the extrudate tends to melt and fail. These shear-related problems severely limit the extrusion speed of the extruder. When the die gap of the extrusion equipment used to extrude films from these resins is greater than about 50 mils,
It has been found that the extrusion speed can be increased considerably. By implementing the present invention, drawdown ratios can be significantly increased. Head pressure, shear stress within the die, and the tendency of the resin to melt fracture are all reduced. Melt fracture refers to a phenomenon in which a resin extrudate becomes coarse and non-uniform due to melt turbulence in the polymer flow. When the polymer extrudate is in the form of a film,
Surface strains induced by melt fracture can "freeze" as the extrudate cools and solidifies. These surface strains can severely reduce the mechanical strength of the film. Increasing the die gap of the extrusion equipment can reduce shear stress and eliminate melt fracture at a given extrusion speed. By implementing the present invention, withdrawal rates can be increased considerably. Essentially, extensional deformation replaces shear deformation. This method is thus compatible with the shear "hard", extensional "soft" rheology of these narrow molecular weight distribution ethylene hydrocarbon copolymers. Furthermore, the large elongation deformations used in the present method can be accomplished without highly orienting the film. The resins defined herein exhibit excellent drawdown properties. Melt stress does not occur to the extent experienced with high pressure low density polyethylene. Very high deformation rates and/or drawdown rates are required before the melt stress exceeds the extrudate strength. High draw rate films can be produced with wide processing latitude. Contamination is not a problem.
Foreign particles do not act as stress concentration points. The lack of flow holes in blown film extrusion is greatly improved. Very thin films, for example 0.1 mil thick, can be made with an excellent balance of optical and mechanical properties. It is a very thin film with relatively balanced mechanical properties and relatively low thermal shrinkage. In slot cast extrusion, films can be produced that are relatively insensitive to drawdown. The drawdown rate at the slot is defined as die gap/film gauge. Tensile strength and ultimate elongation are only slightly influenced by drawdown rate. Elmendorf's tear strength can be maintained at acceptable levels for both MD and TD. Next, the interaction between the structure and properties of low density polyethylene and process will be explained. Tubular blown film extrusion method is 20
It existed for over a year. The influence of extrusion variables on the optical and mechanical properties of high-pressure low-density polyethylene tubular blown films is
It is discussed in detail in the paper by ND Hook and PL Kretz (SPE Transactions, pp. 121-132, published in 1961). The optical properties of high pressure low density polyethylene films, namely haze and gloss, are dominated to a large extent by surface irregularities caused by melt flow phenomena and crystallization behavior. In tubular blown, high pressure low density polyethylene films, the most important light scattering surface irregularities are extrusion defects resulting from complex elastic melt flow regimes in the extrusion die itself. A second source of light scattering is surface irregularities resulting from crystallite growth and pseudocrystallization at or near the surface of the film. This distorts the surface of the film, and the magnitude of the effect depends on the rate of crystallite nucleation and growth during cooling. Crystalline
Changes in refractive index at amorphous phase boundaries also scatter light. Because extrusion defects are a major cause of poor optical properties in tubular blown high pressure low density polyethylene films, special operating procedures have been developed to control the optical properties of films with these materials. In some tubular blown ethylene hydrocarbon copolymer films, the most important irregularities that scatter light are defects introduced by crystallization. The film of the present invention is
It is extruded from an ethylene hydrocarbon copolymer with a very broad short chain branching distribution. These materials can develop very large spherulites during cooling. To control the optical properties of blown films with these transition metal contact resins, a completely different operating procedure is required than that performed with high pressure low density polyethylene. These operating procedures constitute another aspect of the present invention. Films suitable for the packaging field must have a good balance of important properties to meet the essential performance requirements for a wide range of end uses and wide commercial acceptance. These properties include the optical properties of the film, such as haze, gloss and transparency. Mechanical strength properties such as fracture resistance, tensile strength, impact strength, stiffness and tear resistance are also important. Vapor permeability and gas permeability also
This is a consideration when packaging perishable items. The performance of film flipping and packaging equipment is
It is influenced by film properties such as coefficient of friction, tack, thermal stability and resistance to bending. High resistance low density polyethylene has a wide range of uses, such as in the food packaging and non-food packaging areas. Bags made from low-density polyethylene generally include
There are transport sacks, textile bags, washing and dry cleaning bags, and garbage bags. Low-density polyethylene film can be used as drum liners for many liquid and solid chemicals and as a protective wrap inside wooden crates. Low density polyethylene films can be used in various agricultural and horticultural fields such as plant and crop protection such as mulch, fruit and vegetable storage. Additionally, low density polyethylene films can be used in architectural applications such as moisture or water vapor barriers. Low density polyethylene films can be coated and printed for use in newspapers, books, etc. This film is the subject of a U.S. patent application filed March 31, 1978 in the name of T. E. Norlin et al. entitled Electrical Apparatus Using Dielectric Film of Ethylene Hydrocarbon Copolymer.
Used in capacitors as described in No. 892125. Low density polyethylene films can be thermoformed or laminated. The film can be laminated on itself or on other materials to form a series of layers by methods well known in the art. High pressure low density polyethylene is an important component of thermosetting packaging films because it has a unique combination of the properties described above. Its amount accounts for about 50% of the total usage of this type of film in packaging. The ethylene hydrocarbon copolymer films of the present invention offer an improved combination of end use properties and are particularly suitable for many areas where high pressure low density polyethylene is already utilized. Improvements in any of the properties of the film, or in the extrusion properties of the resin or in the film extrusion process itself, are critical to the acceptance of the film as a replacement for high pressure low density polyethylene in many end use areas. be. Thin films with a combination of properties such as improved fracture resistance, high ultimate elongation, low heat shrinkage and significant impact strength and virtual absence of melt fracture have been produced from low density ethylene hydrocarbon copolymers. It has been found that the polymer is formed by extruding it through an extrusion die having a gap greater than about 50 mils. It is therefore an object of the present invention to provide an improved method of extruding a narrow molecular weight distribution ethylene hydrocarbon copolymer film by extruding the copolymer film through an extrusion die having a gap of greater than about 50 mils. That's true. The present invention applies only to narrow molecular weight distribution ethylene hydrocarbons as described herein. This improved film extrusion method eliminates melt fracture in the copolymer, and because of its rheological properties, the increased drawdown rate associated with the practice of the present invention does not induce excessive molecular orientation. , therefore no unacceptable directionally unbalanced properties are induced. Another object of the present invention is to improve the optical performance of blown films extruded from molten ethylene hydrocarbon copolymers by controlling the cooling rate and by adding certain heterogeneous nucleating additives. The objective is to provide a method for improving properties. Yet another object of the invention is to provide a film comprising a blend of ethylene hydrocarbon copolymer and high pressure low density polyethylene. Yet another object of the present invention is to improve the processability and properties of films extruded from molten ethylene hydrocarbon copolymers by adding high pressure low density polyethylene. Yet another object of the present invention is to provide approximately 7.0 in-lb/mil
The purpose of the present invention is to provide ethylene hydrocarbon copolymer films with thicknesses as low as approximately 0.10 mils while retaining a fracture resistance of . Preferred embodiments of the present invention will be described below. (1) Low Density Ethylene Hydrocarbon Copolymer The low density ethylene hydrocarbon copolymer from which the film of the present invention is extruded has a molecular weight distribution Mw/Mn of about 2.7 to 4.1, preferably about 2.8 to 3.4. The copolymer has a molecular weight of about 22 to 32, preferably 25
It has a melt flow ratio of ~32. Thus,
The melt flow ratio range of 22-32 is approximately 2.7-3.6
Corresponding to the Mw/Mn value range, the melt flow ratio range of 25-32 corresponds to the Mw/Mn range of approximately 2.8-3.6. These ethylene hydrocarbon copolymers also contain about 0.1 to 0.3 C═C per 1000 carbon atoms,
Preferably they have a total unsaturation content of about 0.14 to 0.24 C=C per 1000 carbon atoms. The low density ethylene hydrocarbon copolymer from which the films of the present invention are extruded is characterized as a copolymer of ethylene and at least one _C3 to _C8 olefin, and is No. 892,325, filed in the name of F. G. Karol et al.
and U.S. Pat. No. 892,325, issued March 31, 1978, entitled "Impregnated Polymerization Catalysts, Method of Preparation, and Utilization in Ethylene Copolymerization Ratios," issued in the name of G. L. Gauk et al. It can be produced according to the method and method for producing ethylene hydrocarbon copolymers having the properties as described above. The copolymer contains a large mole percent (90%) of ethylene and a small mole percent (10%) of one or more _C3
It is a copolymer of ~C ₈ α-olefin. _C8 - _C8 α-olefins include propylene, butene-1, pentene-1, heptene-1, 4-methylpentene-1, heptene-1 and octene-1.
Contains 1. The copolymer has a density of about 0.912 to 0.940, preferably about 0.916 to 0.928, and about 0.05
It has a volatile content (TEA, heat release analysis) of ~0.38% by weight. In addition, the copolymer is 0.1~
5.0, preferably about 0.5 to 4.0. The copolymers used in the present invention are prepared by polymerizing the monomer charge under specific operating conditions as described below and in the presence of specific highly active catalysts, also described below. can be easily produced in a low pressure gas phase fluidized bed reactor as described below. Highly active catalyst The compounds used to form the highly active catalyst used in the present invention include at least one titanium compound, at least one magnesium compound, at least one electron donor compound, at least It consists of one activator compound and at least one inert carrier material. _The titanium compound _{has the} structure _{Ti (} OR) _a is a hydrocarbon), and X is
selected from the group consisting of Cl, Br, I or mixtures thereof, a is 0 or 1, b is 2 to 4, and a+b=3 or 4. Titanium compounds can be used separately or in their mixed forms, including TiCl ₃ , TiCl ₄ , Ti
( _OCH3 ) _Cl3 ,Ti( _OC6H5 ) _{Cl3 ,} Ti
( _OCOCH3 ) _Cl3 and Ti _{( OCOC6H5} ) _Cl3 are included. Magnesium compounds have the structure MgX ₂ , where X is selected from the group consisting of Cl, Br, I, or mixtures thereof. Such magnesium compounds can be used individually or in mixtures thereof and include MgCl ₂ , MgBr ₂ and MgI ₂ . Anhydrous _MgCl2 is a particularly preferred magnesium compound. In producing the catalyst used in the present invention, the amount of magnesium compound used is about 0.5 to 56 mol, preferably about 1 to 10 mol, per mol of titanium compound. The titanium and magnesium compounds should be used in a form in which they are readily soluble in the electron donor compound. The electron donor compound will be explained below. The electron donor compound is an organic compound that is liquid at 25° C. in which the titanium and magnesium compounds are partially or completely soluble. Electron donor compounds are known per se and are otherwise known as Lewis bases. Electron donor compounds include alkyl esters of aliphatic and aromatic carboxylic acids, aliphatic ethers,
Included are cyclic ethers and aliphatic ketones.
Preferred examples of such electron donor compounds are:
Alkyl esters of _C1 - _C4 saturated aliphatic carboxylic acids, alkyl esters of _C7 - _C8 aromatic carboxylic acids, _C2 - _C8 , preferably _C3 - _C4 aliphatic ethers, _C3 - _C4 cyclic Ethers, preferably C ₄ cyclic mono- or diethers, C ₃ -C ₆ , preferably C ₃
~ _C4 aliphatic ketone. Most preferred electron donor compounds include methyl formate, ethyl acetate, butyl acetate, ethyl ether, hexyl ether,
Included are tetrahydrofuran, dioxane, acetone and methyl isobutyl ketone. Electron donor compounds can be used individually or in their mixed form. The amount of electron donor compound used is about 2 to 85 moles, preferably about 3 to 10 moles per mole of Ti. The _{activator compound} has _the structure Al(R _″ ) _c Yes, d is 0 to 1.5, e is 1 or 0,
and c+d+e=3). Such activator compounds can be used individually or in mixtures thereof, including Al
(C ₂ H ₅ ) ₃ , Al (C ₂ H ₅ ) ₂ Cl, Al (iso-C ₄ H ₉ ) ₃ , Al ₂
(C ₂ H ₅ ) ₃ Cl ₃ , Al(iso-C ₄ H ₉ ) ₂ H, Al(C ₆ H ₁₃ ) ₃ ,
Al( _C8H17 ) ₃ , Al( _C2H5 ) _2H and _{Al ( C2H5 ) 2}
(OC ₂ H ₅ ) is included. To activate the catalyst used in the present invention, the amount of activator compound used per mole of titanium compound is approximately 10
~400 moles, preferably about 10-100 moles. The support material is a solid particulate material that is inert with respect to the other components of the catalyst composition and other active components of the reaction system. These carrier materials include inorganic materials such as silicon and aluminum oxides and molecular sieves, and organic materials such as olefin polymers such as polyethylene. The carrier material is about 10-250μ, preferably about 50-150μ
It is used in the form of a dry powder with an average particle size of . These materials are also preferably porous and have a surface area of 3 m ² /g, preferably 50 m ² /g. The carrier material should be dry, ie should not contain occluded water. this is,
This is usually done by heating or pre-drying the carrier material with a dry inert gas before use. The inorganic support may also be treated with about 1-8% by weight of one or more aluminum alkyl compounds to further activate it. Preparation of Catalyst The catalyst used in the present invention is prepared by first preparing a precursor composition from a titanium compound, a magnesium compound, and an electron donor as described below, and then adding this precursor composition to a carrier material and an activator compound as described below. It is manufactured by processing in one or more steps such as. The precursor composition is formed by dissolving the titanium compound and the magnesium compound in the electron donor compound at a temperature ranging from about 20° C. to the boiling point of the compound. The titanium compound can be added to the electron donor compound before, after, or simultaneously with the addition of the magnesium compound. Dissolution of the titanium and magnesium compounds can be promoted by stirring and, in some cases, by refluxing both of these compounds in an electron donor compound. After the titanium and magnesium compounds are dissolved, the precursor composition is separated by precipitation or crystallization with a _C5 - _C8 aliphatic or aromatic hydrocarbon such as hexane, isopentane or benzene. The precipitated or crystallized precursor composition is isolated in the form of fine, free-flowing particles with an average particle size of about 10-100 microns and a bulk density of about 18-33 lb/ ^ft3 . A particle size of 100μ is preferred for use in fluidized bed processes. The particle size of the isolated precursor composition can be controlled by the crystallization or precipitation rate. When the precursor composition is prepared as described above, it has the formula Mg _n Ti′(OR) _o X _p [ED] _q [where ED is an electron donor compound and m is
0.5-56, preferably 1.5-5.0, n is 0-1, p is 6-116, preferably 6-14, q is 2-85, preferably 4-11, R is a _C1 - _C14 aliphatic or aromatic hydrocarbon group or COR' (where R' is a _C1 - _C14 aliphatic or aromatic hydrocarbon group), and X is Cl, Br, I or a mixture thereof selected from the group consisting of]. The letter written at the bottom right of the element titanium (Ti) is the Arabic numeral 1. The polymerization activity of a fully activated catalyst is so high in the process of the invention that it is necessary to dilute the precursor composition with a support material in order to effectively control the reaction rate. Dilution of the precursor composition can be accomplished before the precursor composition is partially or fully activated, or in parallel with such activation, as described below. The dilution of the precursor composition is from about 0.033 to 1 part, preferably about 0.1 part.
This is accomplished by mechanically mixing or blending ~0.33 parts by weight of the precursor composition with 1 part by weight of the carrier material. For use in the method of the invention, the precursor composition must be fully or completely activated. That is, it is the Ti of the precursor composition.
It must be treated with sufficient activator compound to convert the atoms to the active state. However, it has been found that even when an inert support is present, the method of activating the catalyst is very critical in order to obtain active substances. For example, a method similar to that described in U.S. Pat. Activation of the catalyst was attempted by adding it to the composition and subsequently removing the solvent by drying this slurry at a temperature between 20 and 80 °C to facilitate the use of the catalyst in gas phase processes. For commercial purposes, the gas phase fluidized bed process described below resulted in a product that was not sufficiently active. In order to prepare useful catalysts, this activation requires that at least the final activation step be carried out in the absence of solvent so that no further removal of solvent is required to obtain a sufficiently active dry catalyst. It was found that it was necessary to implement the project in a certain manner. Two methods have been developed to achieve such results. In one method, the precursor composition is fully activated in the absence of a solvent by dry blending the precursor composition and an activator compound outside the reactor.
In this dry blending method, the active agent compound is used while being absorbed into a carrier material. However, this process had the disadvantage that the resulting fully activated dry catalyst was pyrophoric if it contained >10% by weight of activator compound. In another preferred method of catalyst activation, the precursor composition is partially activated with an activator compound in a hydrocarbon slurry outside the polymerization reactor, the hydrocarbon solvent is removed by drying, and The partially activated precursor composition is fed to a polymerization reactor where activation is completed with additional activator compound. Thus, in dry blending catalyst preparation methods, a solid particulate precursor composition is added to solid particles of a porous carrier material, homogeneously blended therewith, and the activator compound is absorbed. The activator compound, from its hydrocarbon solvent solution,
It is adsorbed onto the carrier material to give a coverage of about 10 to 50% by weight of active agent relative to the weight % of the carrier material. The amounts of precursor composition, activator compound, and carrier material used are such as to provide the desired Al/Ti molar ratio and have a weight ratio of precursor composition to carrier material of no more than about 0.50, preferably no more than about 0.33. The amount is such as to give the final composition. The amount of support material thus provides the necessary dilution of the activated catalyst to provide the desired control of the polymerization activity of the catalyst in the reactor. If the final compositions contain about 10% by weight of activator compound, they are pyrophoric. During the dry blending operation (which may be carried out at ambient temperature (25 °C) or lower), the dry mixture is initially exothermic to avoid heat accumulation during the subsequent reduction reaction. Stir thoroughly. The resulting catalyst is thus completely reduced and activated and can be fed to the polymerization reactor and used therein as is. It is a free-flowing particulate material. In a second preferred method of catalyst activation, activation is carried out in at least two stages. In a first step, a solid particulate precursor composition diluted with a carrier material is partially reduced having an activator compound/Ti molar ratio of about 1 to 10:1, preferably about 4 to 8:1. It is reacted with sufficient activator compound to provide a precursor composition and partially reduced. This partial activation reaction is preferably carried out in a slurry of hydrocarbon solvent, and the solvent is then removed by drying the resulting mixture at a temperature of 20-80<0>C, preferably 50-70<0>C. In this partial activation method, the activator compound can be used while being absorbed into the carrier material used to dilute it. The resulting product is a free-flowing solid particulate material that can be easily fed to a polymerization reactor. However, partially activated precursor compositions, at best, are poorly active as polymerization catalysts in the process of the present invention. To make this partially activated precursor composition active for ethylene polymerization, an additional amount of activator compound is added to the polymerization reactor to complete activation of the precursor composition in the reactor. I have to let it happen.
Additional activator compound and partially activated precursor composition are preferably fed to the reactor by separate feed lines. Additional activator compounds may be sprayed into the reactor as a solution in a hydrocarbon solvent such as isopentane, hexane or mineral oil.
This solution typically contains about 2-30% by weight of activator compound. The activator compound may also be added to the reactor in solid form by absorption onto a carrier material. For this purpose the carrier material is usually 10
Contains ~50% by weight of active agent. The additional activator compound increases the total Al/Ti molar ratio in the reactor from about 10 to 400, preferably about 15 when the activator compound and titanium compound are fed to the partially activated precursor composition. ~60% to the reactor. The additional amount of activator compound added to the reactor reacts with the titanium compound within the reactor to complete activation. In continuous gas phase processes, such as the fluidized bed process described below, a partially or fully activated precursor composition is continuously fed into the reactor in fixed quantities and then during the continuous polymerization process. The additional activator compound necessary to complete activation of the partially activated precursor composition is delivered in portions to restore active catalyst sites consumed during the reaction process. do. Polymerization Reaction The polymerization reaction is carried out at a temperature sufficient to initiate the polymerization reaction by a gas phase process such as that found in fluidized beds as described below, in the virtual absence of moisture, oxygen, carbon monoxide, carbon dioxide, and catalyst poisons such as acetylene. and pressures by contacting the monomer stream with a catalytically effective amount of a fully activated precursor composition (catalyst). In order to obtain the desired density range of the copolymer, the proportion of _C3 to _C8 comonomer in the copolymer should be adjusted to 1 to 10 mol%.
It is necessary to copolymerize enough C ₃ comonomer and ethylene to give ethylene. The amount of comonomer required to achieve such results will vary depending on the type of comonomer used. The table below lists the amounts (in moles) of various comonomers that must be copolymerized with ethylene to obtain a polymer having the desired density range at a given melt index. This table also lists the relative molar concentrations of comonomer/ethylene that must be present in the monomer gas stream fed to the reactor.

[Table] A fluidized bed reaction system that can be used in carrying out the present invention is illustrated in FIG. To explain this, the reactor 10 consists of a reaction zone 12 and a moderation zone 14. Reaction zone 12 contains growing polymer particles and product polymer particles fluidized by continuous passage of polymerizable and modifying gas components in the form of make-up feeds and recycle gas through the reaction zone, and a small amount of polymerizable polymer particles. Consists of a bed with catalyst particles. To maintain an active fluidized bed, the mass flow rate of gas into the bed must exceed the minimum flow rate required for fluidization, preferably from about 1.5 to Gmf.
10 times, more preferably about 3 to 6 times. As used herein, Gmf means the minimum mass flow rate of gas required to achieve fluidization [CYWen & Y.H.
Yu, “Mechanics of Fluidization”, Chemical
Engineering Progress Symposium Series,
Vol.62, p100-111 (1966)]. The bed always contains particles to prevent the formation of local "hot spots" and to confine the particulate catalyst to the reaction zone, yet distribute it throughout the zone. To begin operation, the reaction zone is typically charged with a particulate polymeric paste material before the gas flow.
Such particulate polymers may be the same or different in type from the polymer to be produced. When the type is different, it is removed together with the desired polymer particles to be formed as the initial product. in the end,
The starting bed is replaced by a fluidized bed of the desired polymer particles. The partially or fully activated precursor composition (catalyst) used in the fluidized bed is preferably stored in a gas-sealed reservoir 32 in preparation for use. Thus, the gas should be inert to the storage material, such as nitrogen or argon. Fluidization is accomplished by a high flow rate (typically on the order of about 50 times the flow rate of the make-up gas feed) of circulating gas entering and passing through the bed. The fluidized bed is
It presents the appearance of a dense body of lively particles in a flow-like manner without the possible vortices created by percolation of gas into the bed. The pressure drop across this bed is equal to or slightly greater than the mass of the bed divided by its cross-sectional area. It thus depends on the geometry of the reactor. Makeup gas is supplied to the bed at a flow rate equal to the flow rate at which particulate polymer product is removed. The makeup gas composition is measured by a gas analyzer 16 located above the bed. This device measures the composition of the gas that is to be recycled. Accordingly, the makeup gas composition is adjusted to maintain an essentially steady state gas composition within the reaction zone. To ensure complete fluidization, the recycle gas and, if desired, a portion of the make-up gas are returned into the reactor at a point 18 located below the fluidized bed. Thus, a gas distribution plate 20 is present above the return point 18 to aid fluidization of the bed. The portion of the gas stream that does not react in the bed constitutes the recycle gas. This is preferably removed from the polymerization zone by passing it through a moderation zone 14 located above the bed, where the entrained particles are given the opportunity to fall back to the bed below. The return of particles may be assisted by a cyclone 22 which may form part of the deceleration zone or be located outside of it. If desired, the circulating gas can be passed through a filtration system 2 designed to remove small particles at high gas flow rates to prevent fines from contacting heat transfer surfaces or compressor plates.
4 can be passed. The circulating gas is then compressed in a compressor 25 and passed through a heat exchanger 26 where the heat of reaction is removed and then returned to the bed. Due to the constant removal of the heat of reaction, there appears to be no noticeable temperature gradient in the upper part of the bed. Approximately 6 to 12 inches at the bottom of the bed, a temperature gradient exists between the inlet gas temperature and the temperature of the remainder of the bed. The bed thus almost instantly adjusts the temperature of the circulating gas that has come above this bottom layer of the bed zone to bring it in line with the temperature of the rest of the bed, thereby keeping it essentially isothermal at steady-state conditions. was observed to have an effect on
The recycle then enters the vessel from the base 18 of the reactor and is returned to the fluidized bed through the distribution plate 20. Compressor 25 can also be installed upstream of heat exchanger 26. The role played by the distribution plate 20 in operating the reactor is important. The fluidized bed contains growing and forming particulate polymer and catalyst particles. Since polymer particles can be hot and active, their settling must be prevented. This is because if a stationary body is present, the active catalyst contained therein can continue to react and cause melting. It is therefore important to diffuse the circulating gas into the bed at a flow rate sufficient to maintain fluidization at the base of the bed. The distribution plate 20 serves this purpose; it can be a screen, a slotted plate, a perforated plate, a bell-shaped plate, etc. All members of the distribution plate may be fixed or of the movable type as disclosed in US Pat. No. 3,298,792. Whatever the design of the distribution plate, it must disperse the circulating gas into the particles at the base of the bed to keep them in a fluid state and keep the resin flowing when the reactor is not in operation. It must function to support a stationary layer of particles. The movable member of the distribution plate can be used to dislodge and displace any polymer particles that become trapped within or deposited on the distribution plate. In the polymerization reaction of the present invention, hydrogen can be used as a chain transfer agent. The hydrogen/ethylene ratio used is between about 0 and 2.0 moles of hydrogen per mole of ethylene monomer in the gas stream. Any gas that is inert to both the catalyst and the reactants can also be present in the gas stream. The activator compound is preferably added to the reaction system in the hottest part of the gas, usually downstream of a heat exchanger.
Therefore, the activator is transferred from dispenser 27 to line 2.
7A to the gas circulation system. In order to increase the melt index value of the copolymer to be produced, the structure Zn(R _a )(R _b ) (where R _a and R _b are the same or different C ₁ to _C14 aliphatic or aromatic hydrocarbon groups) can be used together with hydrogen with the catalyst of the invention. this
The Zn compound is added to the gas flow in the reactor from about 0 to 1 mole of titanium compound (as Ti) in the reactor.
50 moles, preferably about 20-30 moles (as Zn)
used in quantity. In addition, this Zn compound is
It is preferably introduced into the reactor as a dilute solution (2-10% by weight) in a hydrocarbon solvent or adsorbed at about 10-50% by weight on a solid diluent such as silica of the type described above. The zinc compound can be added by itself or with an additional portion of activator compound added to the reactor from a feeder (not shown). This feeder could thus be located adjacent to the dispenser 27 in the vicinity of the hottest part of the gas circulation system. It is essential to operate the fluidized bed reactor at a temperature below the sintering temperature of the polymer particles. Thus, operating temperatures below the sintering temperature are desirable to ensure that sintering does not occur. To produce ethylene copolymers by the method of the present invention, approximately 30 to
A working temperature of 115°C is preferred, and a temperature of about 75-95°C is most preferred. Temperatures of about 75-90°C are used to make products with densities of about 0.91-0.92, and temperatures of about 80-100°C are used to make products with densities of about >0.92-0.94. . Fluidized bed reactors operate at pressures up to about 1000 psi, preferably from about 150 to 350 psi. Heat transfer is enhanced by using higher pressures within this range. This is because an increase in pressure increases the unit volume heat capacity of the gas. The partially or fully activated precursor composition is injected into the bed from a point 30 located above the distribution plate 20 at a flow rate equal to its consumption. Injecting the catalyst above the distribution plate is an important feature of the invention. Because the catalyst used in the practice of this invention is highly active, if a fully activated catalyst is injected into an area below the distribution plate, polymerization will begin there and eventually cause clogging of the distribution plate. I will do it. Instead, active bed injection tends to help distribute the catalyst throughout the bed and eliminate the formation of localized areas of high catalyst concentration that can also cause the formation of "hot spots." A catalyst inert gas such as nitrogen or argon is used to convey the partially or fully activated precursor composition and any required additional amount of activator compound or non-gaseous chain transfer agent into the bed. Gas is used. The bed formation rate is controlled by the catalyst injection rate. Production rates can be increased simply by increasing the catalyst injection rate, and can be decreased by simply decreasing the catalyst injection rate. Since changing the catalyst injection rate also changes the amount of reaction heat generated, the temperature of the circulating gas is adjusted up or down to adjust this amount of heat. Thus, an essentially constant temperature is thereby ensured within the bed. Also, complete mechanization of the fluidized bed and circulating gas cooling system is of course required to be able to detect any temperature changes within the bed so that the operator can adjust the temperature of the circulating gas accordingly. Under certain combined operating conditions, the fluidized bed is maintained at an essentially constant height by withdrawing a portion of the bed as product at a rate equal to the production rate of particulate polymer product. There is a direct relationship between the rate of heat generation and the rate of product formation, so when the gas velocity is held constant,
By measuring the temperature rise of the gas across the reactor (the difference between the temperature of the incoming gas and the temperature of the outgoing gas), the rate of formation of particulate polymer is determined. The particulate polymer product is preferably evacuated from a point 34 at or near the distribution plate 20 before it settles out to prevent the particles from reaching their final collection zone and further polymerizing and sintering. is continuously removed in suspension by a portion of the gas flow. This floating gas can also be used to transport product from one reactor to another, as described above. Preferably, particulate polymer product is continuously withdrawn by continuous operation of a pair of timing valves 36 and 38 defining separation zone 40. While valve 38 is closed, valve 36 is open and valve 36 and zone 40
Plug flow of gas and product to and from zone 40
and then valve 36 is closed. Valve 38 is then opened to transport the product to an external collection zone. Valve 38 is then closed in preparation for the next product recovery operation. Eventually, the fluidized bed will be equipped with a suitable drainage system to evacuate the bed during start-up and shutdown. This reactor thus does not require the use of stirring and/or wall scraping means. The supported highly active catalyst system of the present invention has approximately 0.005
It is believed to result in a fluidized bed product having an average particle size of from about 0.07 inches, preferably from about 0.02 to about 0.04 inches. The feed stream of gaseous monomer, with or without an inert gas diluent, is approximately 2 to 10 lb/min.
It is fed to the reactor with a space-time yield of hr/ft ³ (bed volume). As used herein, virgin resin or polymer refers to the particulate form of the polymer recovered from the polymerization reactor. (2) Film The thickness of the film produced by the method of the present invention ranges from about 0.10 mil to about 20 mil, preferably about
0.10 mil to about 10 mil, most preferably about
It should range from 0.10 mils to approximately 6.0 mils. 0.10～
The properties of the 6.0 mil thick film are as follows. Fracture resistance: Approximately 7.0in.lbs/mil or more Ultimate elongation rate: Approximately 400% or more Heat shrinkage rate: 3% or less when cooled to room temperature after heating to 105~110℃ Impact tensile strength: Approximately 400~ Approx. 2000ft.lbs/in ³ Tensile strength: Approx. 2000 to approx. 7000psi This film contains slip agents, anti-stick agents,
Various conventional additives such as antioxidants can be added according to conventional techniques. Also, as discussed below, a particularly desirable processing aid for increasing bubble stability in the blown film extrusion process is a blend of ethylene hydrocarbon copolymer and 1-20% by weight high pressure low density polyethylene. Additionally, heterogeneous nucleating agents can be added to the copolymers of the present invention to enhance the optical properties of films formed from the copolymers. Unlike high pressure low density polyethylene, whose optical properties are primarily dominated by rheological factors, the optical properties of the ethylene hydrocarbon copolymers of the present invention are controlled by crystallization effects. That is, the heterogeneous nucleating agent provides additional sites for crystallization to occur within the ethylene hydrocarbon copolymers of the present invention, increasing the crystallization, nucleation rate and crystallization temperature, and increasing the spherulite size. Reduction is achieved. Heterogeneous nucleating agents include high surface area silica,
Examples include carbon black, phthalocyanine green, and phthalocyanine blue pigments. These additives are used at a rate of about 2.5 ppm to about 2000 ppm. (3) Blown film extrusion molding The film of the present invention can be extruded by a tubular blown film extrusion method. In this method, a molten ethylene hydrocarbon copolymer of narrow molecular weight distribution is extruded using an annular die having a die cap of from about 50 mils to about 120 mils, preferably from about 50 mils to about 100 mils. . The copolymer is extruded in a vertically upward direction in the form of a tube at a temperature of about 325° to about 500°. (It may also be extruded downward or sideways). After extruding the molten polymer through an annular die, the tubular film formed is expanded to the desired degree, cooled actively or simply allowed to cool, and flattened. The tubular film is flattened by passing the film through a crushing frame and a set of nip rolls. These nip rolls are driven to pull out the tubular film from the annular die. The pressure of a gas such as air or nitrogen is maintained within the tubular bubble. As is well known in the conventional film processing art, this gas pressure is controlled to provide the desired degree of expansion to the tubular film. The degree of expansion is preferably between 1/1 and 6/1 when expressed as a ratio of the fully expanded circumference of the die ring to the circumference of the die ring.
It ranges from 1/1 to 4/1. The tubular extrudate is cooled by conventional techniques such as air cooling, water quenching, or mandrel cooling. The draw-down properties of the ethylene hydrocarbon copolymer of the present invention are very excellent. The drawdown ratio, ie, the ratio of die gap to the product of film thickness and blowup ratio, is from about 2 to about 250, preferably from about 25 to about
Up to 150. The ethylene hydrocarbon copolymer of the invention, even if it is heavily contaminated with foreign particles and/or gels,
Extremely high films can be produced even at high draw down ratios. For thin films of about 0.5 mil or greater, they can be processed to exhibit ultimate longitudinal elongation of about 400% to about 700% and ultimate transverse elongation of about 00% to about 700%. Moreover, these films do not fall into the category of "tear easily". "Tearability" is a qualitative term that describes the notched tear response of a film at high deformation rates.
That is, "tearability" refers to the rate of crack growth. This is a characteristic of a certain type of film at the time of final use, and is difficult to estimate from basic factors. When the ethylene hydrocarbon copolymer is extruded as an extrudate through an annular die, it is cooled, the temperature is lowered to below its melting point, and the copolymer solidifies. The optical properties of the extrudate change when crystallization occurs, resulting in the formation of frost lines. When the film is extruded upward through an annular die, the height of this frost line, ie, the distance from the die to the frost line, is a measure of the cooling rate of the copolymer film. This cooling rate has a very significant effect on the optical properties of the ethylene hydrocarbon copolymer films produced according to the present invention. As mentioned above, crystallization effects govern the optical properties of the ethylene hydrocarbon copolymer films of the present invention. The processing parameters of blown films have a significant effect on the optical properties of the film. A special blown film processing methodology was devised to control the optical properties of the ethylene hydrocarbon copolymer films used in the present invention.
That is, the 45° (specular) specular gloss of these blown films can be controlled by operating the film extrusion process according to the following relationship. 45゜Specular gloss = 336.4φ ^-664 φ is the cooling rate parameter φ=τ (MI) ^0.29 [(Tm-Tc)/Tm] ^-1 where, Tc = Resin crystallization ^temperature (〓) Tm = Compound temperature Temperature (〓) MI = Melt index of the resin (g/10min) τ = Residence time of the extrudate from the die to the frost line (sec) τ is the elongation of the extrudate from the die to the height of the frost line is calculated assuming that it approximates a deformation with constant skewness. τ=FLH/V ₁ -V ₀ inV ₁ /V ₀ where, FLH = height of frost line (cm) V ₁ = linear velocity of niproll (cm/
sec) V ₀ = Average linear velocity of the extrudate at the die exit (cm/sec) V ₀ is calculated according to the formula below. V ₀ = Q/ρmπDG Where, Q = Extrusion rate of extruder (g/sec) ρm = Melt density D = Die diameter (cm) G = Die gap (dice gap)
(cm) The 45° specular gloss as a function of the parameter φ is:
It is shown in FIG. This data ranges from 0.5 to 3.1
The data was obtained when a 1.5 mil thick film was prepared at a 2:1 blow-up ratio from an ethylene hydrocarbon copolymer over a melt index range of g/10 min. The solid line in FIG. 5 represents 45° specular ^{gloss = 336φ -0.66 .} As shown in Figure 5, the 45° specular gloss can be achieved by adjusting the parameter φ by adjusting the temperature and/or rate of the air used to cool the bubbles, thereby controlling the cooling rate of the extrudate. It can be adjusted accordingly. The ethylene hydrocarbon copolymers of the present invention exhibit low melt strength during the tubular blown film extrusion process. This can lead to "bubble stability" problems if the melt index of the resin is low or if the temperature of the extrusion compound is too high. However, if a small amount of high-pressure low-density polyethylene of about 1 to 20% by weight with a melt index of about 0.1 to about 6.0 g/10 min is added to the ethylene hydrocarbon copolymer, the "bubble stability" can be increased. , thus allowing high throughputs. What is “bubble stability”?
It refers to the processing stability of extruded products during the tubular blown film extrusion process. Poor bubble stability is due to the fact that the bubbles are blown by turbulent air from an air injection ring onto the tubular bubbles to cool the extrudate and control the height of the frost line. It is manifested by causing "chatter" (chattering vibration phenomenon). The addition of the high pressure low density polyethylene may be done as a separate high temperature compounding step prior to the film extrusion step, or simply added when the ethylene monohydrogen copolymer is charged into the hopper of the film extruder. It can also be carried out by dry blending high pressure low density polyethylene with the copolymer. The high pressure low density polyethylene resin can also serve as a masterbatch carrier for, for example, slip agents, anti-stick compounds, colorants, antioxidants, stabilizers, fillers, nucleating agents, etc. Such high pressure low density polyethylene additives often also function to improve the optical and mechanical properties of the film. The preferred range of melt index for high pressure low density polyethylene is from about 0.2 to about 5.0, and the preferred loading is from about 2 to about 12% by weight. (4) Slot Cast Film Extrusion This film extrusion process is well known in the art and consists of extruding a sheet of molten polymer through a slot die and then quenching the extrudate using a chilled cast roll or water bath. In the chill roll method, the film may be extruded horizontally and extended along the top surface of the chill roll, or the film may be extruded downward and pulled through the bottom surface of the chill roll. The cooling rate of the extrudate in the slot casting method is very fast. The speed of chill roll or water bath quenching is so fast that as the extrudate cools below its melting point, microcrystals are bound to rapidly nucleate and supramolecular structures grow;
Spherulites are kept to a very small size. The optical properties of slot cast films are significantly improved over those of films formed using tubular film extrusion processes, which have relatively slow cooling rates. In general, the compound temperature for slot cast film extrusion is much higher than for tubular blown film. In this slot cast film extrusion method, melt strength is not a limiting factor in processing. Both shear viscosity and extensional viscosity are reduced. The extrusion speed of the film can be faster than in the blown film process. The high compound temperature reduces shear stress in the die and increases the extrusion rate upper limit for melt failure. In slot cast film processes, the drawdown ratio is defined as the ratio of die gap to film thickness. The distance from the extrusion die lip to the point at which the extrudate solidifies is called the drawdown span. This distance defines the length of the section in which drawdown, ie, elongation deformation occurs. The drawdown span controls the strain rate of the elongation deformation. When the draw span is shortened, the strain rate increases, and when the draw span is lengthened, the strain rate decreases. The drawdown span is the section where molecular blending is performed. In slot cast film extrusion of high pressure low density polyethylene, the strain hardening properties of the polyethylene melt result in excessive molecular orientation within the film when extruded at high draw down ratios. Slot cast films of high pressure low density polyethylene can exhibit highly imbalanced mechanical properties. However, as mentioned above, the strain hardening behavior of the narrow molecular weight distribution ethylene hydrocarbon copolymer used in the present invention in its met state is small. Therefore, in the slot cast film extrusion method as well, as in the case of the blown film extrusion method, the above material can be extruded at a high draw-down ratio without causing excessive molecular orientation. The balance of mechanical properties of these films does not change significantly with increasing draw down ratio. (5) Extrusion Coating The ethylene hydrocarbon copolymers of the present invention can be directly extruded onto various supports to form composite sheets by methods well known in the art. As a support (base material), polyethylene,
Materials include paper and aluminum foil. The coating equipment may have a single extrusion line, or may include a single extrusion line for coating multiple substrate layers.
Alternatively, it may have two or more extrusion lines in order to bond a plurality of base material layers together. (6) Properties of copolymer and film The properties of the ethylene hydrocarbon copolymer and the film produced therefrom were measured by the following method. Density…ASTM D-1505: Condition a plaque (thin flat plate) at a temperature of 100℃ for 1 hour,
Close to equilibrium crystallinity. Recorded as g/ ^cm3 . Melt index (MI)…ASTM D-1238,
Condition E: Measured at a temperature of 190°C.
The number of grams per 10 minutes was recorded. Flow index (HLMI)…ASTM D-
1238, Condition F: Measurement was performed using a sample 10 times the weight of the sample used for the above melt index measurement. g (grams) per 10 minutes
The number was recorded. Melt flow ratio (MFR)...flow index/melt index molecular weight distribution Mw/Mn...gel permeation chromatography method; the pore diameter of the styrogel packing material is 10 ⁷ ,
10 ⁵ , 10 ⁴ , 10 ³ , and 60 Å. Solvent temperature is 117℃
of perchlorethylene; Detection method: Infrared unsaturation degree of 3.45μ: Infrared spectrophotometer (PerkinElmer
21 type). 25 mil thick pressing was used. Characteristic absorption is 10.35μ for trans vinylene and 11.0 for terminal vinyl
μ, side chain vinylidene was observed at 11.25μ. The amount of absorption per mil at each wavelength is proportional to the product of the unsaturated concentration absorption rate. The absorption rate is J.Poly.
RJ in Sci Part B, 2 , 339 (1964)
The literature values described by Mr. dekock and Mr. P. Hol were adopted. TEA volatile content…This measurement was performed with a DuPont Model 916 Thermal Release Analyzer (TEA) and approximately
Measure the percentage of volatiles present in a sample with a molecular weight below 500. 5 mg of the sample is heated to 300°C at a rate of 32°C per minute in the presence of nitrogen and kept at constant temperature for 20 minutes. As the sample is heated, the gas generated is swept by nitrogen to the flame ionization detector. _C20
By calibrating with a standard, the output of the measuring device can be converted into the weight of volatile matter. Calculate the weight of volatile matter per unit weight of the sample and multiply by 100 to get the weight% of volatile matter.
is obtained. Film Haze…ASTM D-1003-61: Percentage of transmitted light scattered beyond 2.5° from a normally incident beam. Expressed as % haze. Specular gloss at 45° ASTM D-2457-70: Gloss measurement was performed using a Gardner UX-6 gloss meter. 45° specular gloss refers to the luminous specular reflectance of a film sample when the incident beam is incident on the sample surface at an angle of 45° from the vertical, and the receiver is placed at the specular reflection position of the optical axis of the incident beam. Specular gloss at 60° C. ASTM D-2457-70: Gloss measurement was performed using a Gardner UX-6 gloss meter. What is 60° mirror gloss (polished)?
This is the luminous specular reflectance of a film sample when the incident beam is incident on the sample surface at an angle of 60 degrees from the vertical, and the receiver is placed at a position where the optical axis of the incident beam is specularly reflected. Breaking resistance...A measured film of a certain thickness
Support on a 3.25 inch diameter ring and attach the ring to an Instron tensile tester. 0.75in through the ring that supported this film
A rounded end plunger with a hemispherical diameter head is pressed at a speed of 20 in/min. The energy required to deform the film to breakage was determined as a value per unit thickness of the film and was recorded as in·lb/mil. ASTM D-1922: This is a notched tear test. Elmendorf Tear Strength: A 2 1/2 inch x 3 1/2 inch piece of film is subjected to a "pant leg" tear test. This is a pendulum impact test,
Measure the force required to propagate the tear. Tear strength was measured in grams and the resulting data was expressed as a value per unit thickness of film and was reported as g/mil. Tensile strength and elongation rate...ASTM D-882: Clamp a 1in x 5in film piece with a gauge length of 2in,
Deform at a Jio pull-off speed of 20 in/min. This tensile strength is the engineering stress that occurs at the point of break. Elongation at break is measured by the separation of 1 inch gauge marks on the film sample and is expressed as a percentage. Tensile impact strength...This is a pendulum impact test,
A test piece according to ASTM test method D1822 is used.
Multiple films are stacked to obtain a minimum specimen thickness of 15 mils, thereby bringing the fracture energy to a measurable value. The resulting pendulum impact energy is measured per unit volume of the sample and is recorded as ft.lbs/in ³ . Secant modulus...ASTM D-882: 10in x 0.5in
A piece of film is clamped with a gauge length of 5 inches and deformed at a Jio pull-off speed of 0.5 inches/min. Measure the footprint of applied extension. The secant modulus is the slope of the secant drawn from the origin to the load point at a 1% deformation rate. The rate of deformation is measured by the position of the crosshead. The secant modulus is the value per unit cross-sectional area of the sample when it is not deformed,
Expressed in psi. Film Grading: Film samples are viewed with the naked eye and examined for size and distribution of gel or other foreign particles relative to standard film samples. In this way, the appearance of the film tested by comparing it with the standard product was -100%
Grades are given on a scale from (extremely poor) to +100 (excellent). Crystallization temperature Tc...PerkinElmer DSC-2 type differential scanning calorimeter was used. Samples 10-12 mils thick were heated to 150°C in a nitrogen atmosphere, incubated for 3 minutes, and then heated to 10°C/
Cooled at a rate of min. Crystallization temperature refers to the temperature at which the resin begins to generate a crystallization exotherm. Drop impact strength...ASTM-1709: A single layer film is gripped by a 5 inch diameter ring clamp,
1 A spear with a hemispherical head of 1/2 inch diameter.
Drop from a height of 26 inches. Film breakage is recorded when a true break is observed as a result of spear thrust. Weights are added and removed from the spear in 15 gram increments to record the breaking weight grossly. The exam is 30
Repeat several times. Breaking weight is the weight of the spear when 50% of the film span breaks. For illustrative purposes, the breaking weight is the value per unit thickness of the film;
Expressed as g/mil. Melt fracture...As mentioned above, melting is a phenomenon in which a resin extrudate becomes irregular and non-uniform on its surface due to instability of the melt during polymer flow. Such surface distortions may remain "frozen" within the polymer film and are visible to the naked eye. Melting failure of the film is detected by visually observing such surface irregularities. Bulk Density: Pour the resin through a 3/8 inch diameter funnel into a 100 ml graduated cylinder without shaking the cylinder to the 100 ml graduation line and measure the difference in weight. The above examples are intended to illustrate the method of the invention and are not intended to limit the scope of the invention. Example I Preparation of Precursor Composition 16.0 g in a 5 l flask equipped with a mechanical stirrer
(0.168 mol) of anhydrous _MgCl2 under nitrogen atmosphere
ml of pure tetrahydrophthane. This mixture was stirred at room temperature (~25<0>C) while 13.05 g (0.069 mol) of _TiCl4 was added dropwise thereto. _TiCl4
After complete addition, the contents of the flask were heated for about 1/2 to 1 hour until reflux occurred to dissolve the solids. The system was then cooled to room temperature and 3 l
of pure n-hexane was slowly added over 1/4 hour. As a result, a yellow solid was precipitated. The supernatant was decanted and washed three times with 1 liter of n-hexane. The solid was then filtered and dried in a rotary evaporation flask at a temperature of 40-60°C to form 55 g of solid precursor composition. During the isolation of this precursor composition Mg and/or
Analyze the Mg and Ti content of the precursor composition at this point, as some of the Ti compounds may have been lost. The empirical formula used in this example to record these precursor compositions is that the Mg and Ti are present in the form of the compounds as they were originally added to the electron donor, and the precursor It was derived by assuming that all other residual weight in the body composition is due to the electron donor compound. The results of solid analysis are Mg: 6.1%, Ti: 4.9
It was %. This is TiMg2.45, Cl8.9 (THF)
Equivalent to 7.0. THF stands for tetrahydrofuran. Activation Operation Drying A: This operation relates to a multi-step activation process of the precursor composition. According to this operation, the precursor composition is only partially reduced before it is introduced into the polymerization reactor, and activated so that the remaining reduction process is completed after it is introduced into the reactor. I do. Charge the desired weight of dry inert carrier into a mixing vessel or tank. In the examples described herein, the amount of inert support is about 500 g for silica and about 1000 g for polyethylene support.
It is g. This inert carrier is then mixed with a sufficient amount of anhydrous aliphatic hydrocarbon diluent, such as isopentane, to form a slurry system. To make a slurry, usually 1 g of inert carrier
Approximately 4-7 ml of diluent is required per serving. Next, charge the desired weight of the precursor composition into a mixing vessel;
Mix thoroughly into slurry system. The amount of precursor composition used in this activation operation to prepare the catalysts in the examples described herein ranges from about 80 to 135 g.
It is. The precursor composition has an elemental titanium content of 1±0.1 mmol/g. The desired amount of activator compound necessary to partially activate the precursor composition is added to the contents of the mixing vessel to partially activate the precursor composition. The amount of activator compound used here is such that the Al/Ti ratio in the partially reduced precursor composition is >
The amount is 0 to 10:1, preferably 4 to 8:1. The activator compound is dissolved in an inert aliphatic hydrocarbon solvent (hexane in the examples described herein) at about
It is added to the mixing tank in the form of a solution containing 20% by weight of the activator compound (triethylaluminum in the example described). Activation is accomplished by mixing and contacting the activator compound with the precursor composition. All of the above operations were performed at room temperature, and
Carry out at atmospheric pressure in an inert atmosphere. The slurry thus obtained is dried to remove the hydrocarbon diluent at atmospheric pressure and a temperature of 60° C. under a dry inert purging gas such as nitrogen or argon. This process usually takes about 3~
It takes 5 hours. The resulting product is in the form of dry, free-flowing granules in which the activated precursor composition is homogeneously blended with the inert carrier. The dried non-pyrophoric product is stored under an inert gas atmosphere. If additional activator compound is to be fed to the polymerization reactor in this step A to complete activation of the precursor composition, it is preferred to first adsorb the activator onto an inert support such as silica or polyethylene. Most preferably, however, the activator is injected into the reaction zone as a dilute solution in a hydrocarbon solvent such as isopentane. If the activator compound is to be absorbed onto a silica support, the two materials should be mixed at approximately 4 ml per gram of support.
of isopentane. The resulting slurry is then dried to remove the hydrocarbon diluent at a temperature of 65±10° C. for about 3 to 5 hours under a purge nitrogen atmosphere at atmospheric pressure. When the activator compound is injected into the polymerization reaction system as a dilute solution, a solution having a concentration of about 5 to 10% by weight is preferred. Regardless of the method used to introduce the activator into the polymerization reactor to complete the activation of the precursor composition, the activator must be present within the reactor.
Al/Ti ratio of 10-400:1, preferably 10-400:1
Add in proportions to maintain a 100:1 level. The silica is dried at 200° C. for 4 hours before being used in the present invention. Procedure B: In this drying step, complete activation of the precursor composition is achieved by combining and contacting the precursor composition with an activator compound absorbed on an inert carrier. The activator compound is absorbed onto the inert carrier by slurrying it with the carrier in an inert hydrocarbon solvent and then drying the slurry to remove the solvent, thereby leaving about 10-50% by weight of the activator. A composition containing the compound is prepared. That is, in advance
500 g of silica, which has been dehydrated for 4 hours at a temperature of 800° C., is charged into the mixing vessel. The desired amount of activator compound is then added to the mixing vessel as a 20% by weight solution in a hydrocarbon solvent such as hexane and mixed (slurried) with the inert carrier at room temperature and atmospheric pressure. ). The solvent is then removed by drying the resulting slurry in a flowing stream of dry inert gas, such as nitrogen, at atmospheric pressure and a temperature of 65±10° C. for about 3 to 5 hours. The dried composition is in the form of free-flowing particles having the dimensions of the carrier material. Next, approximately 500 g of dry silica-supported activator (50/50
% silica/activator) into a mixing vessel.
The desired weight of precursor composition (80-100 g) is also added into the mixing vessel. These materials are thoroughly mixed under a dry inert gas such as nitrogen or argon at atmospheric pressure and room temperature for about 1 to 3 hours. The resulting composition is a physical mixture of dry, free-flowing particles having a particle size on the order of 10-150 microns. During this mixing operation, the activator contacts the precursor composition and fully activates it. During the resulting exothermic reaction, the temperature of the catalyst should not exceed 50°C to avoid significant deactivation of the catalyst composition.
The activated composition thus obtained has a ratio of approximately 10:50
It may be pyrophoric if it has an Al/Ti ratio and contains >10% by weight of activator. The composition is kept under a dry inert gas such as nitrogen or argon until it is injected into the reactor. Example 1 In this series of experiments, the catalyst produced as described above and activated by activation procedure A was used to convert ethylene to propylene or butene-1.
(propylene in experiments 1 and 2, experiment 3
~14, copolymerized with butene-1),
A polymer with a density of 0.940 was produced. In each case, the Al/Ti molar ratio of the partially activated precursor composition was between 4.4 and 5.8. Completion of activation of the precursor composition in the polymerization reactor was accomplished using triethylaluminum (as a 5 wt% solution in isopentane in runs 1-3 and 6-14,
and 5 as adsorbed on silica at a 50/50 wt% ratio) to produce a fully activated catalyst with an Al/Ti molar ratio of about 29-140 in the reactor. . The polymerization reaction for each experiment was carried out in a fluidized bed reactor at a pressure of about 300 psig and a gas velocity of about 5 to 6 times Gmf for >1 hour after equilibrium was reached in the bed space.
It was run continuously at a space-time yield of about 3-6 lbs/hr/ft ³ . The reactor system, as shown in Figure 4, has a lower section 10 feet high and 13 1/2 inches inside diameter and an upper section 16 feet high and 23 1/2 inches inside diameter. In some experiments, diethylzinc was added as a 2.6% by weight solution in isopentane during the reaction run to maintain a constant Zn/Ti molar ratio. When diethylzinc was used, triethylaluminum was also added as 2.6% by weight of isopentane. Table A below shows the following operating conditions used for Experiments 1-14. the weight percent of the precursor composition in the blend of silica and precursor composition; the Al/Ti ratio of the partially activated precursor composition; the Al/Ti ratio maintained within the reactor; the polymerization temperature; Volume % of ethylene in the reactor; _H2 /ethylene molar ratio;/comonomer (Cx)/ _C2 molar ratio in the reactor; catalyst productivity and Zn/Ti molar ratio. Table B shows the properties of the granular virgin resins produced in Experiments 1 to 14, namely density, melt index (MI); melt flow ratio (MFR); weight % ash content; Ti content (ppm); bulk density. ; and the average particle size is shown.

【table】

【table】

【table】

[Table] Examples 2 to 9 Ethylene-butene-1 copolymers produced under the conditions of Example 1 (Examples 2 to 3), prior art ethylene-butene-1 copolymers (Examples 4 to 7), and high pressure and low Density polyethylene (Union Carbide DYNH,
The properties of Examples 8 to 9) are shown in the following table.

[Table] These resins have a diameter of 2 1/2 inches and a length/diameter ratio.
A 1.5 mil thick film was formed by blown film extrusion using a 24:1 extruder.
A polyethylene extrusion screw with a screw mixing head was used. The mixing section of this machine has a diameter
Grooved with the characteristics of 2.5in, groove length 3.0in, groove radius of curvature 0.541in, width of mixing obstruction land 0.25in, width of purification obstruction land 0.20in, and length of mixing obstruction part 4.5in. This is a mixed section. Also, a 20/60/20 mesh screen stack and a 6 inch diameter spiral pin type blown film extrusion die were used. The temperature of the die was set at 400-430°C. The extrusion speed was 70 lbs/hr. The height of Nitzprol was approximately 15ft. Cooling was achieved using a bench lily air injection ring. Any film,
Molding was performed at a blow-up ratio (ratio of bubble circumference to die circumference, hereinafter referred to as BUR) of 2:1. The extrusion die die gap, compound temperature and pressure in the mixing head are as listed in the table. Breaking resistance of the produced film,
Elmendorf tear strength, tensile strength, elongation, yield strength, tensile impact strength, and melt fracture were measured. Their characteristics are listed in the table.

【table】

[Table] The table shows melt index 1.7, density 0.920;
and three types of ethylene-butene-1 copolymers (Examples 2 to 7) with a melt index of 0.9 and a density of 0.919; and a melt index of 2.4 produced in a tube reactor,
This figure compares the extrusion performance of high-pressure, low-density branched long-chain polyethylene resins (Examples 8 to 9) with a density of 0.918 using a wide die gap. 30 Dai Gap
When increasing to ~61 mil, the mix head pressure decreased by 1275 psi for the narrow molecular weight distribution ethylene-butene-1 copolymer (Examples 2-3), compared to the control sample high pressure low density polyethylene resin (Examples 2-3). Example 8
~9), the drop is only 400 psi. By keeping the melt temperature and extrusion speed constant and widening the die gap, shear stress within the extrusion die is reduced. Under the extrusion conditions used here, increasing the die gap from 30 to 61 mils eliminates melt failure in Examples 2 and 3. In other words, the upper limit of extrusion speed in terms of melt failure is increased by extruding the film through a wide die gap. The gist of the invention is demonstrated by the film property data in the table. For film extrusion with a wide die gap die, increasing the die gap width from 30 mils to 61 mils effectively doubles the drawdown ratio of the extruded film from 10 to 20, assuming constant film thickness and blow-up ratio. This increase in draw down ratio has a significant effect on the mechanical properties of the high pressure low density polyethylene films (Examples 8-9). That is, the Elmendorf tear strength in the machine direction (MD) increases, but the tear strength in the transverse direction decreases. Tensile strength also shows the same tendency. However, the ultimate elongation rate decreases in the machine direction and increases in the transverse direction. On the other hand, ethylene-butene-1 copolymer exhibits the opposite behavior to the polyethylene described above. The longitudinal Elmendorf tear strength of the conventional copolymers (Examples 4-7) is very low. Also,
Prior art ethylene-butene-1 copolymer films also fall into the category of "tear-prone" in the machine direction. Wide die gap extrusion further exacerbates this problem. The lateral tear strength increases with increasing drawdown ratio. Examples 2 and 3
An ethylene-butene-1 copolymer with a narrow molecular weight distribution can be extruded through a wide die gap.
It is unique in that longitudinal Elmendorf tear strength is maintained at a significant level. it is,
It is not "tearable" and its tensile strength increases with increasing drawdown ratio, both in the machine direction and in the transverse direction. The longitudinal elongation rate shows almost no change with increasing drawdown ratio. (When using a 61 mil die gap, it exceeded 630%.) The break resistance of these films is extremely high. Examples 10-18 Ethylene-butene-1 copolymer prepared according to the conditions of Example 1 and a commercially available high-pressure low-density polyethylene resin (Union Carbide's DFDA-0154,
The properties of Example 18) are as shown in the table below.

[Table] The above film is manufactured using a 1 inch diameter spiral pin type blown film extrusion die with a 3 inch diameter spiral pin type blown film extrusion die.
A film of a constant thickness was formed in the same manner as in the table using a 1/2 inch extruder with an L/D ratio of 18:1.
The die gap was set to 50mil. A 20/60/20 mesh screen stack was used. The extrusion rate was approximately 27 lbs/hr. Examples 10-17 use a blow-up ratio (BUR) of 3:1;
In 18, a 2:1 BUR was used. Compound temperatures are as indicated in the table.
Properties such as film thickness and draw-down ratio, film grade, haze, 45° specular gloss, fracture resistance, Elmendorf tear strength, tensile strength, elongation, tensile impact strength, and secant modulus are listed in the table. It is shown.

【table】

TABLE The data in the table illustrates that ultrathin films can be readily produced from the ethylene hydrocarbon copolymers used in the present invention. These ethylene hydrocarbon copolymers can withstand very high elongation deformations without causing fracture in the extrudate. These ultra-thin films are
Although extrusion molding was performed using highly impure resin (film grade -50), there was no problem at all with the blow extrusion operation. No blowholes caused by gale were observed. Moreover, these films retain good properties. The fracture resistance value is extremely high, and the ultimate elongation rate remains above 300% even at very high drawdown ratios. Ethylene hydrocarbon copolymers with a relatively high melt index retain even higher elongation rates even at such high drawdown ratios. The tensile impact strength of such copolymers exceeds that of high pressure low density polyethylene. The Elmendorf tear strength decreases in the machine direction but increases in the transverse direction with increasing drawdown ratio. Although it is difficult to measure the Elmendorf tear strength of ultra-thin films, even the thinnest films did not feel "tearable". The ethylene hydrocarbon copolymer used in this invention allows extremely thin films to be formed at extremely high draw down ratios due to its unique rheological strain softening elongation properties. When the drawdown ratio is maximized, the film begins to exhibit a fairly high level of orientation and exhibits unbalanced properties, but in general the lateral properties of the film still do not lose their overall commercial utility. maintains a fairly high level. Examples 19-25 An ethylene-butene-1 copolymer with a melt index of 2.0 and a density of 0.922, prepared according to the conditions of Example 1, was mixed with two commercially available high-pressure low-density polyethylene resins, namely Resin A (Union Carbide Co., Ltd.).
DYNH, melt index 2.0, density 0.918)
and resin B (DYNK manufactured by Union Carbide,
(melt index 2.0, density 0.920) in a Banbury mixer at a temperature of approximately 140°C. The blended resin was extruded into a 1.5 mil thick film using a 1 1/2 inch diameter, 18:1 L/D ratio extruder equipped with a 3 inch diameter spiral pin blown film extrusion die. Molded.
The die gap was set to 50mil. 20/60/20
A mesh screen stack was used. The extrusion rate was approximately 18 lbs/hr. The blow-up ratio was 2:1. The height of the frost line is approximately 7
Maintained at ~9in. The types of high pressure low density polyethylene resins and their concentrations are listed in the table. The haze, 45° specular gloss, fracture resistance, Elmendorf tear strength, tensile strength, elongation, tensile impact strength, and secant modulus of the film were measured and listed in the table. As mentioned earlier, strain-softening polymer melts are
It is recognized as having low melt strength. This causes a reduction in "bubble stability" if the temperature is too high or the melt index of the resin is too high in the tubular blown film extrusion process. Addition of a small amount of high-pressure low-density polyethylene, which is strain-hardened when stretched as a melt, can increase "bubble stability" and further improve the balance of film properties. Example 19 shows the properties of a heavily modified, ie, additive-free, ethylene-butene-copolymer film with a melt index of 2.0 and a narrow molecular weight distribution with a density of 0.922. Examples 19-24 illustrate the effect of adding 1-20% by weight of high pressure low density branched long chain polyethylene resin (melt index 2.4, density 0.918) on film properties. Examples 25-28 illustrate the effect on film properties of adding 1-20% by weight of high pressure low density branched long chain resin with a melt index of 0.2 and a density of 0.920. Ethylene-butene-1 by addition of a small amount (less than 50% by weight) of high-pressure low-density polyethylene resin.
It is observed that the properties of the copolymer are enhanced.
In the case of high-pressure resins with a melt index of 2.4, their addition in proportions up to 1-2% by weight has the effect of additively improving the optical properties of the film, namely haze and gloss, at any proportion. show. In the case of high-pressure resins with a melt index of 0.2, additions of up to 10% by weight have the effect of improving optical properties. Data on mechanical properties show that longitudinal Elmendorff tear strength increases with the addition of high-pressure low-density polyethylene (concentration).
It increases as the amount is decreased, and decreases as the amount added increases. On the other hand, the tear strength in the transverse direction is generally
It increases as the amount added increases. The tensile strength of the film shows an unexpected additive increase with increasing loading of high pressure low density polyethylene resin with a melt index of 2.4. The elongation rate is maintained at over 600% in both the longitudinal and transverse directions. It seems that tensile impact strength is better balanced with other mechanical properties when the amount of high-pressure low-density polyethylene added is at a lower concentration. The tensile impact strength in the machine direction (ie, machine direction) generally decreases with increasing loading, while the tensile impact strength in the transverse direction increases. This effect persists up to a loading of 5% by weight in both cases of the two high pressure low density resins. The secant modulus also shows a additive increase with the addition of small amounts of high pressure low density polyethylene.

【table】

[Table] Examples 29-34 Ethylene-butene-1 copolymers prepared according to the conditions of Example 1 (Examples 29-30) and ethylene-butene-1 copolymers of the prior art (Examples 31-32) , high-pressure low-density polyethylene resin (Union Carbide DYNH, Examples 33-34) having the melt index, MFR and density listed in the table, respectively, with a 6 inch diameter spiral pin type blown film extrusion die. 2 1/2in in diameter, L/
A 1.5 mil thick film was extruded using an extruder with a D ratio of 24/1. A 20/60/20 mesh screen stack was used. The extrusion speed is approximately
70lbs/hr., die temperature is Example 29, 30, 33, 34
For Examples 31 and 32, it was set to 400〓, and for Examples 31 and 32 it was set to 430〓. Blow up ratio is 2:1
And so. The degree of shrinkage was measured using a Birkin Elmer Model TMS-1 thermomechanical analyzer (TMA). This measuring instrument uses a linear variable differential transformer to measure minute changes in the length of a sample. A sample piece of 1/16 inch x 3/16 inch is fixed, and an oven set at a predetermined temperature is placed surrounding it. Sample length can be tracked as a function of time. The specimen was kept in the oven until its dimensions reached a stable state, then removed and allowed to cool to room temperature. After this heating/cooling cycle, the degree of shrinkage was recorded. The table provides longitudinal shrinkage data for several film specimens tested at two different oven temperatures. From the data in the table, it has a melt index of 1.7 and a density of 0.922. It can be seen that the narrow molecular weight distribution ethylene-butene-1 copolymer exhibits almost no shrinkage at a temperature of 117°C, even when extruded using a 61 mil die gap. Conventional copolymers exhibit slight shrinkage at a temperature of 105°C, and the degree of shrinkage increases at 117°C. High pressure low density polyethylene resin exhibits slight shrinkage at a temperature of 105°C when extruded through a 30 mil die gap. The shrinkage of this resin is
If extruded using a 60 mil die gap, this increases considerably.

【table】

[Table] Examples 35-45 Ethylene-butene-1 copolymer (Examples 35-41) as a base resin prepared according to the conditions of Example 1,
Prior art ethylene-butene-1 copolymer (Example 42
and 43) and high-pressure low-density polyethylene (DYNH manufactured by Union Carbide, Examples 44 and 45),
Each was extruded into a 1.5 mil thick film. The melt index, MFR and density of these resins are shown in the table. The copolymers of Examples 36 to 39 were made of high-pressure low-density polyethylene (DYNH manufactured by Union Carbide, melt index 2.4,
MFR50, density 0.918 g/cm ³ ), i.e. blended with Resin C in the proportions shown in the table, the copolymer of Example 41 was produced using a high pressure low density resin (Union Carbide Co., Ltd.).
DFD-0600, melt index 0.7, density 0.922
g/cm ³ ), i.e. resin D and the proportions shown in the table.
Blend according to the procedure given in 19-25. These resins were extruded into a 11/2 inch diameter, L/D ratio, with a 3 inch diameter spiral pin blown film extrusion die with the gap shown in the table.
It was extruded into a film using an 18/1 extruder. A 20/60/20 mesh screen stack was used. The extrusion rate was approximately 27 lbs/hr. and the die temperature was maintained at 400°C. The blow-up ratio is 2:
It was set to 1. The degree of shrinkage of the film was measured according to the following procedure. That is, a 3-inch square film sample was immersed in an oil bath whose temperature was controlled at 135°C for 60 seconds, taken out, and left to cool to room temperature. (%). As can be seen from the data in the table, the degree of shrinkage of these example narrow molecular weight distribution unmodified ethylene hydrocarbon copolymer films increases significantly at 135°C, compared to high pressure low density polyethylene films or conventional It is smaller than the ethylene-butene-1 copolymer film. Examples 36-39 show that the shrinkage behavior of narrow molecular weight distribution ethylene hydrocarbon copolymer films can be conveniently controlled by adding a small amount of high pressure low density branched long chain polyethylene. I understand. The narrow molecular weight distribution ethylene hydrocarbon copolymers used in the present invention, due to their unique rheological strain-softening elongation properties, make it possible to produce films with a limited degree of orientation. do. The degree of orientation and therefore the degree of shrinkage can be controlled by adding a small amount of high pressure low density polyethylene which is strain hardened during elongation deformation.

【table】

[Table] Examples 46 to 51 Ethylene-butene with melt index 1.7 g/cm ³ , density 0.922 g/cm ³ , MFR 26 and TEA volatile content 0.1% by weight, prepared according to the conditions of Example 1.
1 copolymer into a 1 1/2 diameter extrusion die equipped with a 3 inch diameter spiral pin blown film extrusion die.
In, extrusion molding was performed by a blown film extrusion method using an extruder with an L/D ratio of 18/1. 20／
A 60/20 screen stack was used. The extrusion speed was approximately 27 lbs/hr. and the die gap was 50 mil. The film has a blow-up ratio of 2:1.
It was formed to a thickness of 1.5 mil. Those in examples 50 and 51 are
It was extruded using a 2 1/2 inch diameter, 24/1 L/D ratio extruder equipped with a 6 inch diameter spiral pin die. The screen stack used was a combination of 20/60/20 mesh. The extrusion speed is approximately
68lbs/hr., and the die gap was set to 61mil. The film has a blow-up ratio of 2:1.
It was formed to a thickness of 1.5 mil. Die diameter, die gap and compound temperature are listed in the table. Extrusion speed, frost line height, extrudate residence time from die to frost line, cooling rate parameters, film haze, 60° and 45° specular gloss are also listed in the table.

[Table] The table shows the optical properties of a blown film extruded from a narrow molecular weight distribution ethylene-butene-1 copolymer with a melt index of 1.7 and a density of 0.922, with a frost line height and thus a cooling rate. Show the impact on The data in the table illustrate the very unique characteristics of the narrow molecular weight distribution ethylene-butene-1 copolymers used in the present invention. From the optical properties of 20% haze and 45° specular gloss, to 7% haze and 45° specular gloss.
Blown films with various optical properties up to 70% were able to be produced from the same base resin by controlling the cooling rate. High pressure low density polyethylene and prior art ethylene hydrocarbon copolymers do not exhibit such extreme sensitivity to cooling rate or frost line height. The ethylene hydrocarbon copolymer used in this invention has a very broad short chain branching distribution, and upon cooling, compared to the spherulites that occur in high pressure low density polyethylene resins of similar melt index and density. produces much larger spherulites. It has been found that by carefully controlling the cooling rate of the extrudate during the blown film extrusion process, it is possible to produce films with a very wide range of optical properties from the same base resin. Examples 52-54 Prepared according to the conditions of Example 1. Ethylene with a melt index of 1.7 g/cm ³ and a density of 0.9200 g/cm ³
A butene-1 copolymer was extruded using a 6 inch diameter spiral pin type blown film extrusion die. It was extruded by blown film extrusion using an extruder with a diameter of 2 1/2 inches and an L/D ratio of 18/1. The extrusion screw of the extruder has a 12.5in long feed section,
7.5in long transition section, 20in long metering section, 5in long
It had a long mixed section. The mixing section is 2.5in in diameter, 3.0in in groove length, and the radius of curvature of the groove.
The grooved mixing section has a width of 0.541in, a width of the mixing obstruction land of 0.20in, a width of the purification obstruction land of 0.20in, and a length of the mixing obstruction part of 4.5in. The cavity inside the barrel has a length
9.0in diameter, encompassing 1.0in diameter static mixer
2.496, a plug with a length of 11.0in was inserted. The screen stack was a 20/60/20 mesh combination. The extrusion speed was approximately 60 lbs/hr. and the die gap was set at 60 mil. The film is 2:
It was formed to a thickness of 1.5 mil with a blow-up ratio of 1. Example 53
, 2.5 ppm of phthalocyanine green pigment was added to the copolymer in a high-pressure, low-density concentrate (1/4%
It was added as a concentrated liquid). In Example 54, 1.5 ppm of phthalocyanine green pigment was added to the copolymer as a high pressure low density concentrate (1.5% concentrate). This concentrated liquid is made of 99.9% by weight high-pressure low-density polyethylene (DYNH manufactured by Union Carbide).
and 0.1% phthalocyanine green pigment at high temperature. This concentrated liquid was dry blended with a particulate copolymer resin and extruded into a film. As shown in the table, when the proportion of high-pressure low-density polyethylene in the ethylene-butene-1 copolymer is 1.5% or less, the effect on the optical properties of the film is negligible. The frost line height, 45° specular gloss, and film haze are shown in the table.

[Table] Examples 55-56 Ethylene with a melt index of 1.35 g/cm ³ and a density of 0.921/g cm ³ prepared according to the conditions of Example 1.
The spherulite size of the butene-1 copolymer was measured. example
In No. 56, the spherulite size of the above ethylene-butene-1 copolymer to which 2.5 ppm of phthalocyanine pigment was added by high temperature compounding was measured. The size of the spherulites was measured as follows. That is, a micrograph of the spherulites was taken using a 45X polarizing microscope. Place a small amount of resin between a glass slide and a coverslip and place it on a slide warmer for 200-220 hr.
Heated for about 20 seconds at a temperature of °C. During this time, a pressing force was applied to the molten resin to form a film approximately 10 μm thick. The slide was then removed and rapidly cooled while applying pressure. The sample is heated for about 3 to 5 seconds.
It was cooled from 210°C to 50°C. The results of this experiment are listed in the table below. Table Example of the effect of homogeneous nucleation on spherulite size Spherulite size (μ) 55 5 to 10 56 to 1 Example 57 Prepared according to the conditions of Example 1, melt index 0.5 to 5.6, density 0.921 to 0.925 g /cm ³ , MFR approximately 26 ethylene-butene-1 copolymer was extruded into a 1-diameter extrusion die equipped with a 3-inch spiral pin type extrusion die.
It was extruded by a blown film extrusion method using a 1/2 inch extruder with an L/D ratio of 18/1. 20/
A 60/20 mesh screen stack was used.
The extrusion rate was approximately 27 lbs/hr. and a 1.5 mil thick film was formed with a 2:1 blow up ratio. For the first extrusion, a 30 mil die gap was used and the die temperature was 400 °C. The dart drop test data, measured in accordance with ASTM Test Method 1709 and calculated as a value per unit film thickness, was plotted against the melt index of the resin as shown in FIG. This data is approximately
It shows a remarkable maximum value at a melt index of 1.5. This maximum value is due to the melt fracture phenomenon. Using the blown film extrusion conditions previously described, the ethylene-butene copolymer resins of the present invention melt-ruptured when their melt index was less than about 1.5. The rheological distortion of the film surface caused by this phenomenon serves as a stress concentration point during testing of the final properties. Such distortion is a macroscopic defect and causes premature film breakage. If the above blown film extrusion was performed using a 50 mil die gap, approximately 1.5
No melt failure was observed for resins with smaller melt indexes. The falling spear test data calculated as the value per unit film thickness did not show the maximum value of the characteristics as seen in FIG.
As described above, the wide die gap extrusion according to the present invention avoids melt fracture and increases the drop strength of the extruded low melt index ethylene-butene-1 copolymer.

[Brief explanation of the drawing]

Figures 1-3 are extensional viscosity-logarithmic time plots for three types of low-density polyethylene;
Figure 4 shows a fluidized bed reactor capable of producing ethylene hydrocarbon copolymer, Figure 5 shows the 45° specular gloss as a function of the parameter φ (cooling rate parameter), and Figure 6 shows the resin melt index. It is a figure which shows the falling spear data plotted against. 10: Reactor, 12: Reaction zone, 14: Deceleration zone, 16: Gas analyzer, 20: Distribution plate, 22: Cyclone, 24: Passage device, 25: Compressor, 2
6: Heat exchanger.

Claims (1)

[Scope of Claims] 1 Consisting of a copolymer of 90 mol% ethylene and 10 mol% of one or more C ₃ to C ₈ α-olefins and having a molecular weight distribution of about 2.7 to 4.1.
A method of forming a film from a molten ethylene hydrocarbon copolymer having a Mw/Mn comprising extruding the copolymer through an extrusion die having a gap greater than about 50 mils. 2. In the method described in claim 1,
A film forming method, wherein the film is formed by a blown film forming method.