JPH01172408A - Manufacture of ethylene copolymer - Google Patents

Abstract

PURPOSE:To produce an ethylene copolymer which hardly forms fish eyes, is excellent in mechanical properties, moldability, transparency, etc., and has a desired molecular weight in a wide range, by using a dialkylzinc instead of hydrogen as a molecular weight modifier in the manufacture of an ethylene copolymer by the solution polymerization method. CONSTITUTION:Ethylene and an alpha-olefin other than ethylene are polymerized in an inert solvent in the presence of not only a catalyst obtained from a magunesium compound, a titanium compound and an organic aluminum compound but also a dialkylzinc as molecular weight modifier and in the absence of hydrogen at a temperature ranging 120-300 deg.C. As the dialkylzinc, one which has alkyl groups with 1-3 carbon atoms is preferred, with diethylzinc being most preferred.

Description

[Detailed description of the invention]

[Industrial Application Field] This invention relates to a method for producing an ethylene copolymer consisting of a copolymer of ethylene and other α-olefins, and more specifically, it has few fish eyes, good mechanical properties, good moldability, This invention relates to a method for producing an ethylene copolymer that has excellent properties such as transparency. [Prior art and its problems] Conventionally, as a method for producing ethylene copolymers such as linear low-density polyethylene (LLIIPE), catalysts obtained from organomagnesium compounds, titanium compounds, organoaluminum compounds, and organohalogen compounds have been used. A method is known in which solution polymerization is carried out at high temperature in the presence of a compound (Japanese Unexamined Patent Application Publication No. 2003-120002). However, the ethylene copolymer obtained by this method has many fish eyes and has insufficient transparency. In addition, methods for producing ethylene copolymers by adding various activators to catalysts consisting of organomagnesium compounds, titanium compounds, and organoaluminum compounds (Japanese Patent Publication No. 4-13133σ, Japanese Patent Publication No. 48-31888
Although the transparency of this copolymer was still far from being sufficient, the transparency of this copolymer was also known. New linear low density polyethylene (LLDPF: ')
17) Although a production method is disclosed in Japanese Patent Publication No. 59-528343, the copolymer obtained by this method is also not satisfactory in terms of fish eyes and transparency. Furthermore, a method for producing high-density polyethylene in the presence of hydrogen using a catalyst containing a zinc compound is disclosed in JP-A-57-1.
Although the method described in Japanese Patent No. 00106 is known, the resulting polymer has a wide molecular weight distribution and has an insufficient mechanical strength. The present inventors first produced LLDPE by solution polymerization, and discovered a method of polymerizing in the absence of hydrogen (Japanese Patent Application No.
No. 180385) was completed, but the molecular weight of the polymer that could be produced was limited to a certain range and narrow. [Object of the invention] The object of the invention is to reduce the number of fish eyes. The present invention provides a method for producing an ethylene copolymer that has excellent physical properties such as mechanical properties, moldability, and transparency, and has a desired molecular weight within a wide range. [Means for Solving the Problems] As a result of extensive research in order to solve the above-mentioned problems, the inventors found that in producing LLDPE by solution polymerization,
By using dialkylzinc instead of hydrogen as a molecular weight agent, the molecular weight distribution of the resulting ethylene copolymer is not broadened, resulting in improved transparency while retaining mechanical properties, and significantly reduces fish eyes. They found that it is possible to reduce the amount of carbon dioxide, and based on this knowledge, they have completed the present invention. That is, the constitution of the present invention for achieving the above object is as follows. This is a method for producing an ethylene copolymer, which comprises polymerizing ethylene and an α-olefin other than ethylene at a temperature of 120 to 300°C in the absence of ethylene. The above-mentioned magnesium compound has the linear formula % formula % (wherein 1111 is an alkyl group having carbons a1 to 18, an alkoxyl group, a cycloargyl group, an alkylaryl group, an aryl group, an aryloxy group, an aralkyl group, or an arylalkoxyl group). , X represents a halogen atom, and n means a real number satisfying 0≦n≦2). Examples of the magnesium compound include methylmagnesium chloride, ethylmagnesium chloride,
Alkylmagnesium halides such as ethylmagnesium bromide, propylmagnesium chloride, isopropylmagnesium chloride, butylmagnesium chloride, butylmagnesium bromide, nidoxymagnesium chloride, ethoxymagnesium bromide, inpropoxymagnesium chloride. Flukoxymagnesium halides such as butoxymagnesium chloride, aryloxymagnesium halides such as phenoxymagnesium chloride, dichlorofurkylmagnesium halides such as cyclopentylmagnesium chloride, 7-aryl magnesium halides such as phenylmagnesium halide, alkylaryls such as ethylphenylmagnesium chloride. Magnesium halide, dialkylmagnesium such as diethylmagnesium, dipropylmagnesium, diisopropylmagnesium, diisobutylmagnesium, diakylmagnesium, dioctylmagnesium, ethylmethylmagnesium, ethylisopropylmagnesium, ethyl-n-butylmagnesium, jetoxymagnesium, diisopropoxymagnesium , dialkoxymagnesium such as dibutoxymagnesium, and magnesium halides such as anhydrous magnesium chloride and anhydrous magnesium bromide. Among the various magnesium compounds represented by the above formula, anhydrous magnesium chloride, ethyl-n-butylmagnesium, etc. are preferred, and ethyl-n-butylmagnesium, etc. are particularly preferred. Note that these various magnesium compounds may be used alone or in combination by mixing or compounding two or more types. As the organoaluminum compound, there are various compounds, but usually a compound having at least one aluminum-carbon bond in the molecule can be used, for example, the following formula, R23-pA standing X1, R23-LA l (OR3) XI, R23A12X
3 (However, in the formula, 1li2, l (3 is 1 to 2 carbon atoms
0 alkyl group or aryl group, X is the same as above, p is 0.1 or 2, and t is O or 1). Examples of such organoaluminum compounds include:
Examples include diethylaluminum monochloride, diisopropylaluminium monochloride, diisobutylaluminum monochloride, dioctylaluminum monochloride, ethylaluminum dichloride, isopropylaluminum monochloride, and ethylaluminum sesquichloride. Among these, organic aluminum represented by R23A12X3 is preferred, and ethylaluminum sesquichloride is particularly preferred. The titanium compound has a linear formula% formula% (wherein, R4 has 1 to 10 carbon atoms, preferably 1
~6 alkyl group, cycloalkyl group, aryl group, or aralkyl group, X is the same halogen atom as above, and 1m is usually an integer of 0.1 to 4, but is not necessarily an integer and can be various is a real number that satisfies O≦m≦4 as the average value of a mixture of titanium compounds. ) can be used. As the titanium compound, for example, general formula Ti (OR2) such as tetramethoxytitanium, tetraethoxytitanium, tetra-n-propoxytitanium, tetraisopropoxytitanium, tetra-n-butoxytitanium, tetraisobutoxytitanium, tetraphenoxytitanium, etc. 4, a tetraalkoxytitanium represented by TiCl4. TiBr4.
Tetrahalogenated titanium such as TiI4, (CH30)TiC3, (C2I50)TiCl3, (C3H+ O)TiC3, (n-C4890)TiC1a, (C2Is0)TiBr3. Tri/\Rogenated alkoxytitanium, (CH30) 2 T i 0 sentence 2,
(C2I50) 2 T i 0 sentence 2, (C3I70)
2 T i C12, (n-C4)fq O)2 TiCl2, (C3870
) dihalogenated titanium such as 2 T i B r2,
(CH30) 3 T i C, (C2Hs O)3
Ti0 sentence, (C3I70)3 TiC1, (n-C4I90) 3 T i C1, (C2I50
)3 Examples include TiBr, etc.\titanium chloride. Among these, the above-mentioned formula T i (OR') a
Tetraalkoxytitanium represented by is preferred, and tetra-■-butoxytitanium is particularly preferred. These various titanium compounds may be used alone or in combination of two or more. Further, the polymerization catalyst can be obtained by preparing the magnesium compound, the aluminum compound, and the titanium compound. There are no particular restrictions on the method for preparing the catalyst; for example, the magnesium compound, the organic aluminum compound, and the titanium compound may be separately added to a polymerization reaction vessel containing monomers and then mixed. A preferred method for preparing the catalyst includes, for example, a method in which the magnesium compound and the organoaluminum compound are reacted, and the resulting reaction product is mixed with the titanium compound. This method will be explained in further detail as follows. That is, the magnesium compound and the organoaluminum compound are added to an inert solvent, and the temperature is, for example, θ to
The contact reaction is carried out at 240° C., for example, for up to 1 hour, with stirring. Examples of the inert solvent used in this case include aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons having 5 to 1 B carbon atoms, and specifically, normal or iso-hydrocarbons. Pentane, hexane, heptane, octane, decane, dodecane. Examples include tetradecane or cyclohexane, as well as benzene, toluene, and xylene. Further, the ratio of the magnesium compound and the organoaluminum compound added here is not particularly limited, and may be appropriately adjusted within a range that provides the ratio of each metal component in the catalyst described later. There is no particular restriction on mixing the reaction product of the magnesium compound and the organoaluminum compound with the titanium compound. However, when mixing, the proportion of each metal component in the catalyst is
Magnesium/titanium (atomic ratio) = 0.1-200. In particular, it is preferably within the range of 0.5 to 30, and aluminum/titanium (atomic ratio) is preferably within the range of 1 to 200, particularly 2 to 10G. Magnesium/titanium is outside the above range. If the aluminum/titanium ratio is less than 1, the catalyst activity decreases, and even if the aluminum/titanium ratio is greater than 200, the corresponding catalytic activity may not be obtained. Furthermore, if the magnesium/titanium or aluminum/titanium ratio is outside the above range, the physical properties of the obtained polymer, particularly the film formability, may deteriorate, which is not preferable. In addition, during the polymerization, the catalyst is further added with a known activator,
For example, it can be used as a polymerization catalyst system in the presence of a halide of an element belonging to Group 1 of the periodic table, and it is also possible to further enhance the activity in this way. Examples of the activator include halides of carbon, silicon, germanium, tin, lead, etc.
Specifically, for example, carbon halides such as methyl chloride, methyl iodide, methylene chloride, inpropyl chloride, t-butyl chloride, carbon tetrachloride, silicon halides such as tetrachlorosilane, tin tetrachloride, etc. Examples include tin halides and lead halides such as lead tetrachloride. Among these various halides, carbon halides, n-propyl chloride, isopropyl chloride, n-butyl chloride, inbutyl chloride, te
rt-butyl chloride, 5ec-butyl chloride, etc. can be suitably used. In addition, even if one of these activators is used alone,
It is also possible to use a combination of two or more types, such as by mixing or combining them. There are no particular restrictions on the procedure for blending the activator and polymerization catalyst prior to polymerization; for example, (1) ffi
The magnesium compound, the organoaluminum compound, the titanium compound, and the activator may be separately supplied into the reaction vessel. Alternatively, (3) the activator may be added to any of the magnesium compound, organoaluminum compound, and titanium compound during catalyst preparation. The remaining amount of the activator may be added to any one of the magnesium compound, organoaluminium compound, and titanium compound when a portion of the activator is mixed and then other components of the catalyst are mixed and prepared. The proportion of the catalyst to be supplied to the polymerization reaction should be appropriately set in consideration of the type and composition of the catalyst used, the type of monomer, the physical properties of the desired polymer, and various other factors such as those mentioned above. The catalyst concentration in the system is 0, oot to 10 mmol/Jl as a titanium concentration, preferably 0.001-1.0 mm! It is preferable to set it to about j%le/l. Further, the conversion amount of the activator is usually Ova≦5.0, preferably 0, when the molar ratio of activator/An is a.
．． It may be set within the range of O1≦a≦1.0. In the method of the present invention, ethylene and α-olefin are copolymerized at a predetermined temperature in an inert solvent in the presence of the catalyst and dialkylzinc as a molecular weight regulator and in the absence of hydrogen gas. The inert solvent in the method of the present invention is a so-called substantially inert hydrocarbon solvent with respect to the polymerization reaction system, such as aliphatic saturated hydrocarbons having 5 to 16 carbon atoms, alicyclic hydrocarbons, aromatic hydrocarbons, etc. Examples include hydrocarbons. Specific examples include alkanes such as n-pentane, impentane, hexane, inhexane, neohexane, heptane, inhebutane, octane, isooctane, nonane, isononane, decane, isodecane, undecane, dodecane, tetradecane, and hexadecane. ; Cycloalkanes such as cyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane and dimethylcyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene. Among these, for example, n-pentane, impentane, n-hexane, isohexane, n-heptane, isoheptane, n-octane, isooctane, n-decane, indecane, cyclohexane, benzene, toluene, xylene, etc. Preferred, particularly n-hexane. In addition, these may be used individually by 1 type, or may be used in combination of 2 or more types. Examples of the dialkylzinc include dimethylzinc,
Diethylzinc, dipropylzinc, dibutoxyzinc, methylethylzinc, methylpropylzinc, ethylpropylzinc, and other dialkylzincs can be used. Among these various alkyl zincs, 7. nR (wherein R is dialkylzinc having 1 to 3 carbon atoms) is preferred, and diethylzinc is particularly preferred. In the present invention, it is important to carry out the monopolymerization reaction in the absence of hydrogen as a molecular weight regulator. If hydrogen as a molecular weight regulator is present in the polymerization reaction system, many fish eyes will occur in the resulting ethylene copolymer molded product. The α-olefin is not particularly limited as long as it is an α-olefin other than ethylene; for example, the α-olefin has 4 to 2 carbon atoms.
0, preferably 4 to 8 can be suitably used. The α-olefin may be used alone or in combination of two or more types. The α-olefins include butene-1, pentene-1,
Examples include 1,4-methyl-1-pentene, hexene-1, heptene-1, octene-1, decene-1, undecene-1, and the like. The ratio of the ethylene (A) to the α-olefin (B) may be selected to various values depending on the type and characteristics of the desired ethylene copolymer.1 For example,
When the total of (A) and (B) used is too mol%, (A) is usually set in the range of 60 to 95 mol%, preferably (^) is set in the range of 70 to 88.5 mol%. By carrying out this process, the ethylene copolymer of the present invention can be suitably produced. In the present invention, it is important to set the reaction temperature during the polymerization reaction within the range of 120 to 300°C. Within this temperature range, a temperature range 1 in which the produced polyE melts, for example, a temperature range of about 150 to 250°C is preferable. The reaction pressure is preferably set to usually 10 to 150 kg/cm2G, preferably 20 to 90 kg/cm2G. In addition, the average residence time of the polymerization reaction mixture in the polymerization container depends on the type and composition of the catalyst used, the 7-mer 1 solvent, etc.
It cannot be uniformly defined because it varies depending on various other conditions such as reaction temperature. That is, this average residence time may be appropriately selected so as to obtain a sufficient conversion rate, but it is usually within a suitable range, for example, from 0.1 to 100 minutes, preferably from 0.5 to 100 minutes. The range for BO can be exemplified. According to the method of this invention, there are fewer fish eyes,
Ethylene copolymers with excellent mechanical properties, moldability, and transparency can be produced. An example of a suitable ethylene copolymer obtained by the method of the present invention is one in which the content of α-olefin units having 4 to 2 carbon atoms is 3 to 40% by weight, preferably 5 to 40% by weight.
30% by weight, and the intrinsic viscosity

[η] is 0.5~5d/
g, especially 1 to 3 d/g, and its density is 0JOO~
0.940 g1cm3, especially 0.905-0.
940 g/cm3, and its highest melting point range is 1
10 to 130°C, especially 112 to 128°C,
The ratio (Mw/Mu) of the weight average molecular weight (My) to the number average molecular ffi (Ml) is 2.0 to 5.0.
It is preferably 2.2 to 4.0, and the entire chromatogram reflecting the molecular weight distribution measured by gel permeation chromatography (GPC)/low angle laser light scattering photometer (LALLSS measurement method (GPC-LALLS method) The ratio of the peak area corresponding to the ultra-high molecular weight component to the area (γLA
LLS ) is 0.1 or less, particularly 0.08 or less. If the content of the α-olefin units other than ethylene is less than 3% by weight, the transparency and mechanical strength of the ethylene copolymer will be insufficient, and if it is more than 40% by weight, the molded product of the ethylene copolymer will be insufficient. The surface may become sticky. Therefore, it is preferable to adjust the content of α-olefin units within the above range depending on the intended use of the ethylene copolymer. The intrinsic viscosity is the viscosity measured in decalin at 135°C. If the intrinsic viscosity [η1] is less than 0.5 dm/g, the mechanical strength of the ethylene copolymer will be insufficient;
If it is more than dll/g, the moldability of the ethylene copolymer may be poor. If the density is less than 0.900 g/cm3, the surface of the ethylene copolymer molded product tends to become sticky;
If it is more than 9401/cm2, the transparency and mechanical strength of the ethylene copolymer may become insufficient. Note that the density can be measured in accordance with the density gradient tube method of JIS K7112. When the maximum melting point of the ethylene copolymer is below 110°C, the ethylene copolymer loses practical heat resistance;
If the maximum melting point exceeds 130° C., when the ethylene copolymer is formed into a film, the heat sealing temperature will be high, making it impractical. The highest melting point here is determined based on differential scanning calorimetry (DSC). That is, according to ASTM D3418, the ethylene copolymer Iong was held at 200°C for 5 minutes, cooled to 50°C at a rate of 10°C/min, held for 5 minutes, and then heated at a rate of 10°C/min. record the endothermic curve, and then calculate the Δ corresponding to the peak that appears on the highest temperature side.
It's temperature. If the M w / M n ratio is less than 2.0, the moldability and transparency of the ethylene copolymer will be insufficient. If it exceeds 5.0, the mechanical strength may be insufficient. The ethylene copolymer obtained by the method of this invention and having the above-mentioned characteristic has an extremely low content of ultra-high molecular weight components, and the ultra-high molecular weight components herein refer to those having an ffi weight average molecular weight of 106 or more. . If the ratio (γ(^113)) is larger than 0.1, fish eyes will increase and it will not be suitable for practical use. (GPC-
LALLS method) This is a recently developed method for measuring the molecular weight of polymers. This GPC-LALLS method measures the molecular weight of a polymer using a device incorporating a low-angle laser light scattering photometer as a GPC detector. In this case, the GPC-LALLS measurement is performed using a sample of 1.2.
4-) Dissolved in dichlorobenzene at 150"0 over 2 hours, filtered while hot using a membrane filter with a pore size of 0.45 ILm, and then dissolved using LALLS at a temperature of 140 °C, a wavelength of 833 nm, and a scattering angle. This can be carried out by measuring the intensity of scattered light at a temperature of 6 to 7°C.The ethylene copolymer obtained by the method of the present invention and having the above-mentioned properties has an ultra-high molecular weight component, that is, a weight average molecular weight of 106 or more. Therefore, it is an ethylene copolymer with very few fish eyes and has particularly excellent mechanical properties, moldability, and transparency. etc., and its commercial value is even higher. [Examples] Next, the present invention will be explained in more detail by showing examples and comparative examples of the present invention. (Examples) 1) In the continuous polymerization reaction vessel ii, 7.5 Jl/hour of dehydrated n-hexane, 3.3 layers of ethylaluminum sesquichloride and 0.68 layers of ethyl-n-butylmagnesium were added. on/h and tetrabutoxytitanium at a rate of 0.17 g/h, while simultaneously feeding ethylene at 700 g/h and l-octene at 700 g/h.
g/hour and diethylzinc per mole of ethylene 8
Continuously supplied at a ratio of X10-4 mol, one reaction temperature 185℃
A polymerization reaction was carried out for 0.11 hours under the conditions of 1 reaction pressure cuff of 0 kg/c and 2 G to obtain ethylene-1-octene copolymer 75.
Obtained 0g. The polymerization conditions and polymerization results at this time are shown in Table 1. Note that the density, fisheye, haze, and film impact strength were each evaluated as follows. Density: Measured according to JIS K7112 density gradient tube method. Fish eye: A film with a thickness of 25 #Lm was produced by using an extrusion molding machine with a diameter of 20 mm under the conditions of a die width of 170 mm and a Glylip of 0.5 mm. Fish eyes were visually evaluated. Haze: Measured in accordance with JIS K7105. Film impact strength, measured in accordance with ASTN 03420. (Comparative Example 1) The same operations as in Example 1 were repeated, except that H2 was used instead of diethylzinc, and the results shown were obtained. (Examples 2 to 5) In Example 1, the diethylzinc/ethylene molar ratio (ZnEt2/C2) was
The results were obtained by repeating the same operation as in Example 1, except that the diethylzinc/ethylene molar ratio (Z!l/C2) and the amount of α-olefin were changed as shown in Table 1 in each example. I got it. (Comparative Examples 2 to 5) In Example 1, hydrogen/ethylene molar ratio (12102), diethylzinc/
The same operation as in Example 1 was repeated, except that the ethylene molar ratio (ZnEt2/C2) and the amount of α-olefin were changed, and the results shown were obtained. (Example 5) The same operation as in Example 1 was repeated one time, except that dipropylzinc was used instead of diethylzinc, and the results were obtained. (Margins below this page) [Effects of the invention] According to the invention, a high-quality linear low-density product with significantly less occurrence of fish eyes and excellent properties such as mechanical properties, moldability, and transparency. Ethylene copolymers such as polyethylene can be provided.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the procedure for preparing a catalyst in this invention. Patent applicant: Idemitsu Petrochemical Co., Ltd. Agent
Patent attorney Naoki Fukumura

Claims (1)

[Claims] (1) In an inert solvent, in the presence of a catalyst obtained from a magnesium compound, a titanium compound and an organoaluminium compound, and in the presence of dialkylzinc as a molecular weight regulator and in the absence of hydrogen, at a temperature of 120 to 300 °C.
1. A method for producing an ethylene copolymer, which comprises polymerizing ethylene and an α-olefin other than ethylene.