JPS5880309A - Production of polyethylene by multi-stage polymerization - Google Patents

Abstract

PURPOSE:To obtain polyethylene having a wide MW distribution and a constant MW, by polymerizing ethylene in a three-stage polymerization ethylene in a three-stage polymerization reactor in such a way that part of the polymer is recycled from the third reactor to the second reactor. CONSTITUTION:Ethylene, alone or together with alpha-olefin is slurry-polymerized by using three consecutive polymerization reactors. Part of the produced polyethylene slurry is recycled from the third to the second polymerization reactor. It is preferred that the operation of the first stage polymerization reactor is controlled so that the polymer produced therein can have an intrinsic viscosity of 0.3-1 and a melt index of 100-3,000. Next, the polymerization conditions in the second and third stage polymerization reactors are preferably controlled so that intrinsic viscosities of the polymers produced in the reactors lie in the ranges of 0.6-3.0 and of 0.6-8.5, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyethylene by multistage polymerization, and specifically, slurry polymerization of ethylene or ethylene and α-olefin using a three-stage multi-containing reactor,
This invention relates to a method for producing polyethylene that has a wide molecular weight distribution and a constant molecular weight regardless of the powder particle size by recycling a polymer slurry from the third stage to the second stage polymerization reactor.

Generally, when polyethylene is produced using a highly active catalyst,
Since polyethylene with a relatively narrow molecular weight distribution can be obtained, multi-stage polymerization is required to produce polyethylene with a wide molecular weight distribution.

However, polyethylene produced by the above-mentioned multi-stage polymerization tends to have a non-uniform powder, resulting in the problem of gel formation, and this gel does not disappear completely even if it is vigorously kneaded in a kneader.

In order to solve this problem, 4Ii! Introduction 52-1
An attempt has been made to make the intrinsic viscosity of the produced polymer powder uniform by the sequential two-stage circulation polymerization method disclosed in Japanese Patent No. 9788. However, since this method circulates high-molecular polymers and low-molecular polymers, it is impossible to control the molecular weight of the produced polymer in each O2 bath, and as a result, it is difficult to control the molecular weight distribution. The drawback is that it cannot be done.

The present inventors have overcome the drawbacks of the above-mentioned prior art and have
-0 We conducted extensive research to find a method that would allow us to control the molecular weight distribution and at the same time make the intrinsic viscosity (or molecular weight) constant for each particle size of the powder. As a result, ethylene was polymerized at 3RWII, and 3
It has been found that the objective can be achieved by recycling the polymer slurry from the first stage to the second stage polymerization reactor. The present invention was completed based on this knowledge.

That is, the present invention provides a method for producing polyethylene by slurry polymerizing ethylene or ethylene and α-olefin using three successive stages of polymerization reactors, from the third stage polymerization reactor to the second stage polymerization reactor. The present invention provides a method for producing polyethylene by multistage polymerization, which is characterized by recycling a portion of remer slurry.

The method of the present invention is to produce polyethylene or an ethylene copolymer by polymerizing ethylene or ethylene and α-olefin (hereinafter simply referred to as E-ethylene) in three stages as described above. In the polymerization reactor, the polymerization conditions may be appropriately selected depending on the purpose, but it is preferable to adjust the polymer produced here to have an intrinsic viscosity of 0.3 to 1 and a melt index of lOθ to 3000. In the method of the present invention, since po-9-r- is not recycled to the first-stage polymerization reactor, it is easy to set the polymerization conditions for the first-stage polymerization reactor.

In addition, the amount of ethylene to be polymerized in this 1 jaiIO polymerization reactor is preferably 40 to 60% of the amount of ethylene polymerized in the entire first to third stage polymerization reactors.
Preferably, the range is within the weight arc.

Next, the polymerization conditions in the second and third stage polymerization reactors may be determined as appropriate, but preferably the 12th stage is the polymerization condition produced in the second stage Ojusha reactor. - The intrinsic viscosity of Ink should be in the range of 0.6 to 3, and 3
The stages should be adjusted so that the intrinsic viscosity of the polymer produced in the third stage polymerization reactor is in the range of 6 to 8.50.

Furthermore, in the method of the present invention, it is necessary to recycle a part of the polyester slurry in the third-stage polymerization reactor to the second-stage polymerization reactor, and the amount of recycling is limited to the O polymerization reaction IIO of each stage. Although it may be determined depending on the polymerization conditions or the physical properties of the polymer to be produced, it is preferably 0.1 to 2 times, particularly preferably 0.5 to 1 times, the amount of polymer extracted from the third stage polymerization reactor. Should. 0.1
If it is less than 2, the resulting polymer will have a large gel content, while if it exceeds 2, power consumption will increase and this is not practical.

As described above, by polymerizing K and ethylene in three stages and recycling a part of the polymer slurry from the third stage to the second stage polymerization reactor, the molecular weight of the polymer is controlled and the molecular weight distribution is adjusted to the desired range K11liil. death,
At the same time, the O molecular weight can be made uniform for each particle size of the polymer powder.

The reason why the method of the present invention achieves the effects mentioned in -E is as follows.

In general, polyethylene has excellent physical properties such as impact resistance and environmental stress crack resistance, as well as good moldability such as high-speed moldability, and its molecular weight is within a certain range. It is necessary that it is widely distributed in 1IIC. If! fK
Since the physical properties of the polyethylene as a whole are greatly affected by the molecular weight of the low molecular weight polyethylene, it is especially important to accurately control the molecular weight of the low molecular weight Ill.

Therefore, it is effective to produce K, which produces polyethylene with a wide molecular weight distribution, by multi-stage polymerization as described above, but if only multi-stage polymerization is carried out, the polyethylene powder obtained will be non-uniform and a gel will not form. This is easy to occur, and there is a large difference in O molecular weight for each powder particle size, causing various problems. For example, if a large gel is formed, the quality of the product will deteriorate, and if there is a large difference in the molecular weight of each powder particle size, the powder may be classified during the compounding stage of various additives, storage, or transportation. Because the physical properties of each type are different, there are problems such as unstable product quality. In order to eliminate such interlayer points in multi-stage polymerization, it is possible to circulate the produced polymer of at, as in the method shown in the above-mentioned ll1W/a bulletin No. 19788-1988, but in this method, the molecular weight Precise control of distribution is not possible. This will be explained by taking as an example a two-stage circulation overlap as shown in FIG. The symbol used here is the following togin.

[w, intrinsic viscosity of the polymer produced in the 1-1st stage.

[η−]・−゛Intrinsic viscosity of the polymer produced in the second stage.

[η. ]...Intrinsic viscosity of the 11th step polymer.

[ηb]...Intrinsic viscosity of the polymer at the second stage exit.

Ordinary... Recycled amount (polymer weight 1197 hours) a
- Ethylene supply amount to the first stage (~/hour) b -...
Ethylene supply amount to the second stage (J9/hour) First, from the additivity of the intrinsic viscosity in the first stage polymerization reactor 1, aCIF〕+N*b〕=(a + R) CW&)
holds true.

Similarly, in the second stage polymerization reactor 2, from the additivity of the intrinsic viscosity, (a + R) [v,) + b (η,) = (a + b + R
) rvb] holds true.

・・・　・－（phantom becomes.

This is 5k, (11j (from formula 21 [da,], [da,]
is calculated, and it seems possible to control the molecular weight, but considering the difference between the actual measurement membranes, accurate control is impossible. Here, considering that the actual measurement error of intrinsic viscosity is approximately 0.18 degrees, [9,]
= 1.9~10, (Wb) = 3.2~3.
3 and a/R=1, and when calculating the above equation (1), [:1Fa) = 1.9, Cηb] = 3.
3, (w*)=0.5, and [η,)=2.0. When [ηb] = 3.2, [ηl
] = 0.11, and the calculated [vl)0 hip difference is 0.
3, the error is too large for the [ma,]k that should be set, and in practice it becomes impossible to control the molecular weight, and as a result, it becomes impossible to control the molecular weight distribution. . 41V - Relatively low molecular weight poly! - generates 1
Because it is difficult to control the inside of the heavy metal reactor in the first stage,
The impact on product quality is significant.

On the other hand, in the case of the method of the present invention as shown in FIG. 2, the following O is obtained. The symbols used here have the following meanings.

[Da,], [ηself], [η1], [η,], R, a, b
,,・Same as above.

[η,]・−・ Intrinsic viscosity of the polymer produced in the third stage.

[ηC] - Intrinsic viscosity of the polymer at the third stage exit.

c -... Amount of ethylene supplied to the third stage (in kgZ)
.

First, in the first stage polymerization reactor 1, since there is no circulation of polymer, [η1]=[Misaki,]・−・−1 (3) holds true.

In addition, in the second stage polymerization reactor 2, due to the additivity of the intrinsic viscosity, a[v,) + b(Da11 + RITη.) =
(a + b + R) Cqb] holds true.

Furthermore, in the third stage polymerization reactor 3, due to the additivity of the resin viscosity, (a + b + R) (4b) + c Cη, ) = (
a+b+c+R) Cη. ] holds true.

−・−(51 becomes.

Here [da. ]2053-0.63. (ηb)=1.8
5-195. cη. ') = 3.1 to 3.2 and a = b = R. From equation (3), [η,) = o, s3 to 0.63, and the error range is small. Therefore, the molecular weight on the low molecular weight side can be accurately controlled. On the other hand, ['F*
) 'ic is (from formula 4, [maa) = 0.53° [ηb1 = 1.85. When (da.)=3.2, [η
,]=1.82, [η,'1=0.63. rηb')=1.95. [η.

``When l = 3.1, K[η*) = 2.12.

In other words, [:17m) = 1-82 to 2.12, which is a fairly large error range. However, even if the [η,] of a medium molecular weight changes somewhat, it does not cause much difference in the molecular weight distribution and does not change the physical properties. As mentioned above.

Poly! Regarding the physical properties of -, that is, the breadth of the molecular weight distribution, the molecular weight on the low molecular weight side is an extremely important factor, and the molecular weight on the intermediate molecular weight side has almost no effect. Therefore, like the method of the present invention, it is a multi-stage polymerization, the polymer produced in each stage is recycled, and the intrinsic viscosity [η1] of the polymer produced in the first stage, that is, the molecular weight of the low molecular weight polymer, can be precisely controlled. According to the possible method,
The molecular weight is within the desired range and is distributed over a wide range,
In addition, polyethylene with extremely excellent physical properties is produced, with less gel and the like and a uniform molecular weight for each powder particle size.

Therefore, according to the method of the present invention, the gel content is low;
Furthermore, it is possible to produce polyethylene products with excellent moldability, stable quality, and extremely high utility value.

In addition, examples of the α-olefin used together with ethylene in the present invention include propylene, butene-1, and the like. Further, the catalyst used in the present invention contains a reaction product of a magnesium compound and a titanium halide and an organoaluminum compound as components. Here, a titanium compound is supported on a reaction product of a magnesium compound and a titanium halide and a &i magnesium compound, and there are various types of magnesium compounds. For example, magnesium chloride, bromide! Gnesium, magnesium iodide, magnesium fluoride, magnesium hydroxide. can be exemplified by mixtures thereof.

These magnesium compounds may be produced by any method and may contain other metals or electron donors.

Moreover, as a halogenated titanium compound, it is tetravalent.

Achieved with trivalent or divalent titanium compounds containing nitrogen.
t % IICs+ II kt tx squid, ff
i Formula xqTi(OR'')a-q C In the formula, ] Preferred are compounds represented by (specific examples) i Tie/
4. C,)1,0TiCj, , (CJ(,0)
.

Methods for producing these halogenated titanium compounds, including TiCz, , (C,H,O), T, Cz, etc., are described in Japanese Patent Publication No. 46-34092 and Japanese Patent Application Laid-Open No. 55-729.
Publication No.

The method described in JP-A-55-13709 and the like can be used.

On the other hand, as organoaluminum compounds, the general formula Fe,
At, R%AzX, R-Al, X,, R4A
lOR'C In the formula, R/ and R# represent an alkyl group or an aryl group having 1 to 6 carbon atoms, and X represents a halogen atom]
Compounds represented by the following are preferred; specific examples include trimethylalkenium, triethylaluminum, triisobutylaluminum, triisobutylaluminum,
Examples include diethylaluminium monochloride, diisopropylaluminium monochloride, diisobutylaluminum monochloride, diethylaluminum ethoxide, and ethylaluminum sesquichloride.

Next, the present invention will be explained in more detail based on examples.

Example 1 a) Preparation of titanium-supported magnesium compound n-Hef I
750 at Mg(QC,H,), 1 fl
(8,8j mol) and commercially available anhydrous Mg8041.0
69 (8,8Z IJ mol) was suspended, 35.2 mmol of ethanol was further added, and the reaction was carried out at 80° C. for 1 hour. Next, this KTi(J, 5 m (45 mmol)) was added and reacted at 98°C for 3 hours. After the reaction was completed, the temperature was lowered, and the mixture was allowed to stand still, and the supernatant liquid was removed.

The operation of adding fresh Kn-hebutane lO-, stirring, and standing still, and then removing the supernatant liquid was repeated three times.

Further, 200 d of n-hebutane was added to obtain a dispersion of the solid catalyst component. The amount of titanium supported on this solid catalyst component was determined by a colorimetric method and was found to be 142 inches per gram of support.

b) Polymerization of ethylene A first stage polymerization reactor with a capacity of 200 g as shown in Figure 4
Ethylene 6jlt/hr, hexyl 7j7'
hr.

Hydrogen was continuously supplied at a rate of 0.1 Nsm"/hr, and the supported catalyst was supplied at a rate of 1 mm"/hr calculated by T1 atoms.
hr and triethylalyl elum 25 mmol envy/hr
and a total pressure of 7119/a11" at 90°C,
Polymerization was carried out under conditions of a residence time of 3 hours, and the contents of the reactor were led to the second stage reactor 2 at a predetermined rate. In the second stage polymerization reactor 2, 1.2"9/hr of ethylene and hexay
4//hr, add 0.0 I Nm"/br of hydrogen, 8
Polymerization was carried out continuously under conditions of a total pressure of 211 t/ell and a residence time of 2 hours at 0°Cm. The obtained hexane suspension containing polyethylene was introduced into the hydrogen degassing tank 4 at the same temperature, and after separating hydrogen, the entire amount was directly introduced into the third stage polymerization reactor 3. In addition, ethylene 4.2 J9/hr and hexane 121/hr were added to the third stage polymerization reactor 3.
r, Buchi 7-1 230g/hr, hydrogen 0.005N heat/hr supplied at a total pressure of 2k at 70"C
q/cm! Polymerization was carried out continuously under conditions of 1.5 hours. Further, a suspension solution containing the same amount of polyethylene as the amount flowing out from the third-stage polymerization reactor was recycled to the second-stage polymerization reactor 2.

Table 1 shows the intrinsic viscosity of the ethylene polymer produced in each stage and the physical properties of the ethylene polymer as a final product. In addition, the intrinsic viscosity for each particle size of the final product, ethylene polymer, is
Shown in the table.

Examples 2 to 8 In the method of Example 10, the ratio of the polymerization amount in the first stage to the polymerization amount in the second stage, the ratio of the polymerization amount in the first stage to the polymerization amount in the third stage, the molecular weight of K produced, and the recycle Varying the amount,
An ethylene polymer composition was obtained in the same manner as in Example 1. When the obtained ethylene polymer was molded into a 9 μ film, the gel was 5 in 100 OCIII.
The film moldability was also excellent.

Table 1 shows the results obtained.

Comparative Example 1 @3 Ethylene 6 #q/hr e Hexane 171/br in the 200J@01st stage polymerization reactor as shown in the figure
.

Hydrogen 0. The same catalyst as in Example 1 was introduced at a rate of 1 mmol/hr and triethylaluminum at a rate of 25 electrmol/hr, and the total pressure was 7 kI/cam at 90°C. The contents of the polymerization vessel were continuously introduced at a predetermined speed into the water bulk degassing tank 4, and after separating the hydrogen into layers, the entire amount was directly transferred to the second stage polymerization reactor. In addition, 5.1 kg/hr of ethylene and 1 s of hexane were added to the 2RID polymerization vessel.
j/hr ebuti 7-1 2209/hr, hydrogen 0,0
Polymerization was carried out under conditions of a total pressure of 2 kI/ls and a residence time of 1.5 hours at 70"C. The physical properties of the ethylene polymer discharged from the second stage reactor are shown in Table 1.2.

Comparative Example 2 The same operation as in Comparative Example 1 was carried out, except that in Comparative Example I, the same amount of the effluent from the second-stage polymerization reactor 2 was cycled through the 1&IO polymerization reactor KVt. The results are shown in Table 1.2.

Comparative Example 3 The same operation as in Example 1 was carried out except that in Example I, the hexane suspension containing polyethylene was not recycled from the third-stage polymerization reactor 3 to the second-stage O polymerization reaction-2. . The results are shown in Table 1.2.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the material balance at each stage of the conventional method.
Diagram 2 is an explanatory diagram showing the material balance at each stage of the method of the present invention. Further, FIG. 3 is an explanatory diagram of the apparatus used in Comparative Example 1.2, and FIG. 4 is an explanatory diagram of the apparatus used in Examples 1 to 3 and Comparative Example 3. 1.--1st stage polymerization reactor, 2-.2nd stage polymerization reactor, 3.-.3rd stage polymerization reactor, 4.-.Hydrogen degassing tank. Patent applicant: Idemitsu Petrochemical Co., Ltd. Figure 1 Figure 2 R] η, l Figure 3

Claims (1)

[Scope of Claims] +11 In producing polyethylene by slurry polymerizing ethylene or ethylene and α-olefin using three successive stages of polymerization reactors, the polymerization reaction from the third stage polymerization reactor to the second stage polymerization reaction A method for producing polyethylene by multi-stage polymerization, characterized by recycling a portion of a polymer slurry. (2) The polymer produced in the first stage polymerization reactor has an intrinsic viscosity of 0.3 to 1 and a melt index of lOO to 3.
2. A method according to claim 1, in which the temperature is adjusted to a range of 0.000. (3) The intrinsic viscosity of the polymer produced in the 1st, 2nd, and 3rd stage polymerization reactions INK is set to 0.3 to 1.0.6 to 3.0, respectively.
The method according to claim 1, wherein the temperature is adjusted to a range of 6 to 8.5. (4) Adjust the amount of polymer slurry recycled from the third-stage polymerization reactor to the second-stage polymerization reactor to be 0.1 to 2 times the amount of polymer slurry extracted from the third-stage polymerization reactor. A method according to claim 1. ψThe amount of ethylene polymerized in the 11th stage polymerization reactor is 1 to 1.
The amount of ethylene polymerized in the entire third stage polymerization reactor is 40~
The method according to claim 1, wherein the weight is adjusted to a range outside of 60% by weight.俤) The method according to claim 1, wherein the α-olefin is butene-1.