JPS6364448B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a propylene-ethylene block copolymer having improved impact whitening resistance and impact strength. More specifically, the present invention relates to an improved method for producing a heteroblock copolymer in which a propylene-ethylene copolymer is block copolymerized onto a polypropylene main chain in multiple stages. Polypropylene has excellent mechanical properties and is therefore used in a wide range of industrial fields. especially,
Propylene-ethylene block copolymers have both high impact strength and rigidity, and are therefore widely used in injection molded products. However, on the other hand, such block copolymers generally have the disadvantage that the gloss of molded products is poor, and that transparency decreases in areas that receive stress when subjected to impact or bending, which is a so-called impact whitening phenomenon. Depending on the purpose of the molded product, this can significantly reduce the product value. Methods considered to be aimed at improving the impact whitening resistance mentioned above include Japanese Patent Publication No. 44-19540, Japanese Patent Publication No. 55
-58245, in which a propylene copolymer containing a small amount of ethylene (8% by weight or less) is produced in the first stage, and a propylene copolymer containing a larger amount of ethylene is produced in a second stage, and in some cases A method has been proposed in which polyethylene is further added to the block copolymer. These methods are excellent methods for improving impact whitening resistance, but the first
Since polypropylene already contains a small amount of ethylene at this stage, it is not possible to sufficiently maintain the original rigidity of polypropylene.
This method has the disadvantage that it is not possible to completely avoid an excessive decrease in the rigidity of the block copolymer as a whole. Furthermore, JP-A No. 55-104333 describes a method of adding polyethylene to a block copolymer consisting of polypropylene and a propylene-ethylene copolymer, but this method is also effective as a method for improving impact whitening resistance. is not enough. On the other hand, when producing a block copolymer by carrying out propylene homopolymerization and propylene-ethylene copolymerization in two stages using a continuous polymerization method, the resulting block copolymer is generally A problem arises in that a large amount of white or opaque gel-like material (hereinafter simply referred to as "gel") appears in the molded product, which significantly impairs the value of the product. this is,
Catalyst components that deviate short-circuit from the polymerization reactor as a complete mixing tank with statistical probability flow into the second stage polymerization tank without producing a sufficient amount of propylene homopolymer, and the compatibility with polypropylene is increased. This is believed to be due to producing a composition with an abnormally high content of propylene-ethylene copolymer component. Therefore, if such short-circuit escape of the catalyst components from the complete mixing tank can be completely or largely avoided, it is possible to eliminate the appearance of gel. Based on this perspective, various measures have been taken to prevent gel formation. For example, a method of carrying out propylene homopolymerization and/or propylene-ethylene copolymerization in multiple stages is as follows:
Special Publication No. 49-12589, Special Publication No. 25585-1977, Publication No.
49-53990, and a method for chemically preferentially deactivating short-circuited catalysts is described in JP-A-55-115417. However, these methods require many reaction vessels, which is economically disadvantageous, and there are problems in that the selectivity of chemical catalyst deactivation is insufficient, so they cannot necessarily be said to be advantageous methods. . In addition, among the polymer particles generated during slurry polymerization, the particle size and density of the short-circuit catalyst component are relatively small, so that preferential separation and recovery of the short-circuit catalyst using a hydrocyclone and subsequent polymerization are possible. A method for producing a high quality block copolymer by recycling to a tank is described in JP-A-51-135987 and US Pat. No. 4,199,546. However, even with these methods, preferential separation of short-circuit catalysts cannot necessarily be said to be sufficient. The present inventors have succeeded in improving the above-mentioned impact whitening resistance and further improving the block copolymer by a continuous polymerization method, while maintaining high impact resistance and high rigidity, which are the original characteristics of the propylene-ethylene block copolymer. As a result of extensive research in order to develop a method that would almost or completely eliminate the gel appearance during polymer production, we conducted polymerization of propylene in liquid propylene, followed by propylene-ethylene copolymerization.
In conducting the process in stages, two types of propylene-ethylene copolymers with high molecular weight and low molecular weight are produced by appropriately controlling the amount of hydrogen added in each stage, and as a result, a block copolymer consisting of three components is produced. By producing a polymer, the problems of impact whitening resistance and gel formation in continuity can be solved without impairing the original physical properties of the propylene-ethylene block copolymer, and it is also industrially and economically viable. We were able to arrive at the present invention which has excellent properties. That is, the feature of the method of the present invention is that the amorphous propylene-ethylene copolymer in the propylene-ethylene block copolymer, which conventionally consisted of only one component, is made of two types, a high molecular weight component and a low molecular weight component. The reason is that a copolymer consisting of In general, the impact resistance of a block copolymer made of two components, a propylene homopolymer and a propylene-ethylene copolymer, is controlled by the composition, molecular weight, and other properties of the propylene-ethylene copolymer. The greater the ethylene copolymer content, the greater the effect. However, in that case, at the same time, undesirable phenomena such as a decrease in impact whitening resistance and the appearance of fish eyes or gels in the molded product occur. This is because, in the block copolymer, there is insufficient compatibility at the interface between the propylene homopolymer matrix and the propylene-ethylene copolymer as finely dispersed domains within the matrix, and therefore, due to external pressure etc. It is thought that the whitening phenomenon occurs due to the formation of voids between interfaces or the formation of so-called "microcracks" in the matrix. On the other hand, for gel expression, by increasing the compatibility between the domain and the matrix,
It should have the effect of eliminating or preventing gelation. However, on the other hand, it is difficult to impart sufficient impact resistance to the block copolymerization using only low molecular weight components. Therefore, by introducing a high molecular weight component in an appropriate composition, it is possible to simultaneously satisfy the physical properties of the block copolymer and the elimination of gel. The gist of the invention is to use stereoregular catalysts to
In producing a propylene-ethylene block copolymer by polymerization or copolymerization in stages, in the first stage, the melt flow index is 1 g/10 min to 100 g/10 min in liquefied propylene, and the propylene content is 95 wt. % or more of propylene polymer (A) is produced from 60% to 95% by weight, and then the second
In the presence of liquefied propylene or in the substantial absence of liquid hydrocarbons in the step and third step, the concentration of propylene relative to the sum of propylene and ethylene in the gas phase is 40
Propylene and ethylene are copolymerized under conditions of mol% to 90 mol%, and the propylene-ethylene copolymer (B) is made such that the ethylene content in the total polymer is 2% to 30% by weight. 5% to 40% by weight
In the method for producing, a high molecular weight propylene-ethylene copolymer (H) is produced in one of the second stage and the third stage, and a low molecular weight propylene-ethylene copolymer (L) is produced in the other, ) The ratio of the melt flow index MFI (A) of the propylene polymer (A) to the melt flow index MFI (A + B) of the entire polymer is MEI (A) / MFI (A + B) = 1.5 to 10 (Ro ) The melt flow index MFI (L) of the low molecular weight propylene-ethylene block copolymer (L) in the propylene-ethylene copolymer (B) is the same as the melt flow index MFI (L) of the propylene-ethylene copolymer (B). The present invention relates to a method for producing a propylene-ethylene block copolymer, characterized in that, for (B), MEI(L)/MFI(B)=10 to 1000. To explain the present invention in detail, the stereoregular catalyst is not particularly limited as long as it has sufficient activity to polymerize propylene, but typically a catalyst containing a transition metal halide and an organoaluminum compound. system is used. Various halides can be used as the transition metal halide as the first component of the catalyst, but titanium trichloride or a eutectic or mixed crystal of titanium trichloride and other metal halides, and pulverized titanium halides are preferred. powder, a mixture of two or more, a mixture with other organic compounds, or a complex compound, etc. Furthermore, it is supported on a suitable carrier, for example, a Mg-based carrier such as magnesium halide, titanium tetrachloride and a suitable There is no problem even if it supports an electron-donating compound. Particular preference is given to using certain solid titanium trichloride-based catalyst complexes which are highly active catalysts. Such a solid titanium trichloride-based catalyst complex was disclosed in Japanese Patent Application Laid-Open No. 1986-
No. 34478, No. 48-64170, No. 50-112289, No. 50
- No. 143790, No. 51-16297, No. 51-16298, No.
51-76196, 51-123796, etc., the aluminum content is 0.15 or less in terms of the atomic ratio of aluminum to titanium, preferably 0.1 or less, more preferably 0.02 or less,
And it contains a complexing agent. Although various organoaluminum compounds can be used as the second component of the catalyst, particularly preferred are alkyl aluminum and alkyl aluminum halide.
In addition to these two components, the catalyst also contains N, O, P or Si.
A third component such as various compounds including esters, unsaturated hydrocarbon compounds, etc. may also be added. Particularly preferred catalysts for application of the present invention are so-called high-activity catalysts, which have a catalytic efficiency (number of grams of polymer produced per gram of catalyst) of 5,000 or more, preferably 8,000 or more, and more preferably 15,000 or more. . The transition metal halide used as a catalyst may be used in the polymerization as it is, but it is preferably used after being pretreated with a small amount of olefin, such as propylene or ethylene, in the presence of an organoaluminum compound. This pretreatment is effective in improving the physical properties of the polymer slurry, such as bulk density. Pretreatment is performed at a temperature lower than the polymerization temperature, generally from 20℃
At 60°C, polymer generated by pretreatment/transition metal halide = 0.1 to 50/1 (weight ratio), usually 1
It is done so that the ratio is ~20/1. In the method of the present invention, when producing a propylene-ethylene block copolymer using the stereoregular catalyst as described above, the polymerization is carried out in three stages as follows. First, in the first step, propylene is polymerized in the presence of liquefied propylene to produce a propylene polymer (A) having a propylene content of 95% by weight or more. That is, a propylene homopolymer may be produced, or a propylene-ethylene copolymer having an ethylene unit content of 5% by weight or less, preferably 3% by weight or less may be produced by copolymerizing, for example, in the presence of ethylene. In order to supply the stereoregular catalyst into the polymerization tank, inert liquid hydrocarbons such as aliphatic hydrocarbons such as hexane and heptane, alicyclic hydrocarbons such as cyclohexane, and aromatic hydrocarbons such as benzene and toluene are used. It is preferred to use these as diluents, and it is therefore within the scope of the invention for trace amounts of these inert liquid hydrocarbons to coexist with the liquefied propylene. The polymerization temperature and polymerization time are selected so that the amount of propylene polymer (A) is 60 to 95% by weight of the total amount of polymer produced. Polymerization temperature is usually 30~
The temperature is selected from the range of 100°C, preferably from 55 to 80°C.
The polymerization pressure is the sum of the vapor pressure of liquefied propylene determined by the polymerization temperature, the pressure of hydrogen used as a molecular weight regulator, and the vapor pressure of a small amount of the inert liquid hydrocarbon used as a diluent for the catalyst component.
It is 30-40Kg/ ^cm2 . The melt flow index of the propylene polymer obtained in the first stage (extrusion rate g/10 min at 230°C and load 2.16 kg,
According to ASTMD1238-70. In the following, it will be abbreviated as MFI. ) is 1 to 100 g/10 min, select the polymerization temperature and amount of molecular weight regulator. Examples of the molecular weight modifier include hydrogen, dialkylzinc, etc., but hydrogen is preferred. Typically, the hydrogen concentration in the gas phase is about 1 to 30 mole percent. Next, in the second and third stages, polymerization is carried out in the presence of the polymer produced in each previous stage, but both may be carried out in the presence of liquefied propylene, or one stage can be carried out in the presence of liquefied propylene. The other step can also be carried out in the substantial absence of a liquid hydrocarbon, such as liquefied propylene. Polymerization in the presence of liquefied propylene is carried out using the usual slurry polymerization method;
Polymerization in the substantial absence of liquid hydrocarbons such as inert hydrocarbon solvents is carried out by a gas phase polymerization method in which the catalyst is brought into direct contact with propylene or ethylene gas. Gas phase polymerization may be carried out in either the second or third stage, but it is industrially advantageous to carry out in the third stage. The concentration of propylene relative to the sum of propylene and ethylene in the gas phase (hereinafter simply referred to as "gas phase propylene concentration") is 40 to 90 mol%, preferably 50 to 90%.
It is preferred that either the second or third stage is selected from a range of 50 to 85 mol %. Here, the gas phase propylene concentration is 50~
85 mol% is the condition where the amount of by-product of the amorphous polymer is maximized, but on the other hand, it is the condition where the impact strength of the final polymer is improved the most. Therefore, the second
Gas phase propylene concentration is 85 mol% in both stage and 3rd stage.
A block copolymer endowed with sufficient impact strength cannot be obtained under conditions exceeding this range. In addition,
Although the gas phase propylene concentrations in the second and third stages may be the same or different, this does not impede the effects of the present invention; however, if the concentrations are outside the above range, the impact strength will not be improved sufficiently and is therefore not preferred. do not have. When polymerization is carried out at a gas phase propylene concentration of 50 to 85 mol%, the resulting propylene-ethylene copolymer contains 30 to 70% by weight (22 to 61 mol%) of propylene. The polymerization temperature and time are selected so that the total amount of propylene-ethylene copolymer obtained in the second and third stages is 5 to 40% by weight of the total amount of polymer produced. If this amount is less than 5% by weight, the effect of improving impact strength etc. will be small, and if it exceeds 40% by weight, the bulk density and free flow properties will deteriorate, the rigidity and transparency will be greatly reduced, and the shrinkage rate of the molded product will also increase, which is preferable. do not have. Furthermore, the gas phase propylene concentration, polymerization temperature and polymerization time are selected such that the total reaction amount of ethylene used in the second and third stages is between 2% and 30% by weight, based on the total polymer. Here, the total reaction amount of ethylene, that is, the ethylene content in the total polymer is 2% by weight.
If the content is less than 30% by weight, the brittle point temperature will increase and the properties of the propylene-ethylene block copolymer will be lost, and if the content of ethylene units exceeds 30% by weight, sufficient impact strength will not be obtained. In the second and third stages, the propylene-ethylene copolymer (B) is converted into a high molecular weight propylene-ethylene copolymer (H) (hereinafter abbreviated as high molecular weight component (H)).
When producing low molecular weight propylene-ethylene copolymer (L) (hereinafter abbreviated as low molecular weight component (L)), the ratio of propylene-ethylene copolymer (B) to MFI of low molecular weight component (L) is determined. Letting the former be MFI(L) and the latter MFI(B), the ratio of MFI is MFI(L)/
MFI (B) = 10 to 1000, and the MFI of the propylene polymer produced in the first step and the MFI of the entire polymer
Assuming that the ratio of the former is MFI(A) and the latter is MFI(A+B), it is necessary to determine the MFI and polymerization amount of each component so that the ratio is MFI(A)/MFI(A+B) = 1.5 to 10. be. However, the implementation of copolymerization requires that the high molecular weight component (H)
and low molecular weight component (L), whichever comes first has no effect on the physical properties of the final product. When the present invention is carried out with the MFI ratio exceeding the above range, an increase in impact strength is observed, but not only does the effect of improving impact whitening resistance, which is a feature of the present invention, decrease significantly, but also the continuous When polymerization is carried out, the effect on gel resolution is also significantly reduced. Furthermore, the balancing effect during injection molding becomes large, resulting in poor dimensional stability and rough skin in the molded product, and in some cases, the compatibility between the components in the propylene-ethylene block copolymer decreases. This may even lead to a decrease in impact strength. On the other hand, when the present invention is carried out with the MFI ratio below the above range, the compatibility between the components in the block copolymer is greatly improved,
Although the effects of the present invention on impact whitening resistance and anti-gelling properties are significantly increased, and both are not a problem at all, the fluidity of the molten polymer during injection molding is not fully satisfactory, and the resulting product However, a disadvantage arises in that sufficient impact strength cannot be imparted to the material. Thus, when the MFI ratio is within the above range, the components constituting the block copolymer have sufficient compatibility, have sufficient impact strength, and have very well-balanced physical properties. Polymers can be obtained. The proportion of the low molecular weight component (L) in the propylene-ethylene copolymer (B) is 20 to 80% by weight, preferably
A range of 40 to 70% by weight is selected, but above this range the resulting final product will not have sufficient impact strength;
Further, below this range, the effects on impact whitening resistance and gel elimination are unsatisfactory. The polymerization temperature in the second and third stages is usually 0~
The temperature is selected from the range of 100°C, but in the case of polymerization in liquefied propylene, the temperature is selected from the range of 25 to 70°C, preferably 25 to 65°C. If the temperature exceeds 70°C, the resulting propylene-ethylene block copolymer will have poor free flow properties and agglomeration between polymer particles will occur, which is unfavorable in terms of slurry properties. On the other hand, in the case of gas phase polymerization, the temperature is selected from the range of 60 to 90°C. The polymerization pressure is usually 1 to 50 kg/cm ² . Polymerization may be carried out in a continuous or batchwise manner, but the effects of the method of the present invention are particularly exhibited when carried out in a continuous manner. In the continuous system, each stage uses a separate polymerization vessel, the transfer of the polymer slurry or polymer powder between the polymerization vessels being conveniently carried out by means of a pressure difference. Therefore, it is preferable to determine the polymerization pressure so that the pressure in the polymerization tank is such that the pressure in the polymerization tank is in the range of first stage>second stage>third stage. It is also possible to increase the pressure in the first stage by adding an inert gas such as nitrogen or argon. The propylene-ethylene block copolymer obtained by the method of the present invention has high impact resistance, high rigidity, excellent impact whitening resistance, and has almost no gel component. Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, the meanings of the abbreviations in the examples and various measurement methods are as follows. Catalytic efficiency CE (g/g) is the amount of polymer produced in grams per gram of titanium trichloride. Isotactic Index II (%) is the residual amount (% by weight) after extraction with boiling n-heptane for 6 hours in a modified Soxhlet extractor.
Since the amorphous polymer is soluble in boiling n-heptane, II (%) indicates the yield of the crystalline polymer. The bulk density ρ _B (g/cc) was based on JIS-6721. Ethylene content in copolymer [E] _IR (wt%)
was determined using the absorbance at 720 cm ^-1 of the infrared absorption spectrum of a 0.2 mm thick press sheet. Melt flow index MFI (g/10min)
According to ASTM D1238-70, 230℃, load 2.16Kg
It shows the amount of polymer extruded when . Density ρ (g/cc) was determined at 20°C by the density gradient tube method in accordance with ASTM-D1505. The first yield strength YS (Kg/cm ² ) is ASTM D638-72
It was determined by a tensile test of a dumbbell piece punched from a press sheet with a thickness of 1.0 mm in accordance with the above. Unless otherwise specified, values are measured at 20°C. Izotsu impact strength (Kg-cm/cm) is according to ASTM D256,
Measurements were made on a strip cut out from a 5.0 mm thick press sheet with a notch in it. Unless otherwise specified, values are at 20°C. The elongation at break of the weld portion (%) was determined by making a 3 mm thick two-point gate dumbbell piece using a 1-ounce injection molding machine and performing a tensile strength test. This is a measure of the strength of the weld portion. The embrittlement temperature Tb (°C) was determined according to ASTM D746 for a test piece punched from a 2.0 mm thick flat plate made using a 1 oz injection molding machine. The tensile impact strength was measured according to ASTM D1822. The degree of whitening was measured as follows and was used as a measure of impact whitening resistance. First, after measuring the light transmittance (To) of a 1 mm thick injection piece according to JIS K6714,
For the same test piece, a 1.5Kg heavy hammer was dropped from a height of 50cm in the same manner as the measurement of the falling hammer impact strength, and after 4 days, the light transmittance (Tw) of the whitened area was the same as that of the test piece before whitening treatment. Measure by method. Then, the degree of whitening is calculated according to the following formula. Degree of whitening = To - Tw / To × 100 (%) The degree of gel development was evaluated by measuring the number of gels that could be visually confirmed in a 4 cm ² area of a 1 mm thick press piece, and dividing it into the following three stages. .

[Table] Gas phase propylene concentration is expressed as the ratio of propylene to the sum of propylene and ethylene in the gas phase in mol%, and gas phase hydrogen concentration is the ratio of hydrogen to the sum of propylene and ethylene in the gas phase. The ratio was expressed in mol%. Catalyst production example 1 (Preparation of highly active purple titanium trichloride catalyst) 150 ml of purified toluene, 85 mmol of di-n-butyl ether, and 90 mmol of titanium tetrachloride were placed in a 500 ml three-necked flask whose interior was purged with argon.
45 mmol of diethylaluminum monochloride was added with electromagnetic stirring at room temperature, held for 30 minutes, heat treated at 50℃ for 60 minutes and 90℃ for 60 minutes, and washed with 100ml of toluene 5 times to form a purple precipitate. 13.8 g of titanium trichloride was obtained. Catalyst production example 2 (Preparation of highly active purple titanium trichloride catalyst) Into a 300 ml three-necked flask whose interior was purged with argon, 75 ml of n-heptane, 45 mmol of di-n-octyl ether, and 45 mmol of titanium tetrachloride were placed.
15 mmol of diethylaluminum monochloride was added with electromagnetic stirring at room temperature, held for 30 minutes, and then heat treated at 50°C for 60 minutes and at 90°C for 60 minutes. The precipitate formed five times was washed with 100 ml of n-heptane to obtain 4.2 g of purple titanium trichloride. Example 1 An induction-stirred autoclave with a capacity of 2 and equipped with a built-in anchor-type stirring blade was thoroughly dried, and the autoclave was vacuumed and replaced with nitrogen gas, and then replaced with propylene gas. 2.0 mmol of di-n-propyl aluminum monochloride was charged into the autoclave. . hydrogen gas
After charging 2.9 kg/cm ² and then charging 700 g of liquefied propylene, the temperature of the autoclave was raised. When the internal temperature of the autoclave reached 70° C., 4.0 ml of toluene slurry of the solid titanium trichloride catalyst complex (containing 20 mg of TiCl ₃ ) obtained in Catalyst Production Example 1 was introduced under pressure with nitrogen gas while stirring. This time is the first
The polymerization reaction was continued at 70° C. for 3.5 hours under stirring, which was the start of a stepwise polymerization reaction. The total pressure was 33.3 kg/cm ² gauge pressure. After 3.5 hours, the liquefied propylene and hydrogen gas were purged, the pressure inside the autoclave was set to 0 kg/ ^cm2 , and a siphon was attached under nitrogen gas. The Ti content was measured by
I asked for MFI. Next, hydrogen gas was charged and liquefied propylene 500
Immediately after charging the autoclave, the internal temperature is 50%.
℃, and 6.1 Kg/cm ² of ethylene gas was charged.
This time is considered the start of the second stage polymerization reaction, and the temperature is set at 50℃.
The polymerization reaction was continued under stirring for 0.2 hours. During this time, ethylene gas was continuously charged so that the ethylene partial pressure was 6.1 Kg/cm ² . The total pressure was 27.7 kg/cm ² gauge pressure. The propylene concentration in the gas phase is the average
The hydrogen concentration was 75 mol%, and the average hydrogen concentration was 5.3 mol%. After 0.2 hours, the liquefied propylene, ethylene gas, and hydrogen gas were purged and the autoclave internal pressure was set to 0 kg/cm ² gauge pressure, and several grams of powdered propylene-ethylene block copolymer was added in the same manner as at the end of the first stage. The Ti content was measured using preparative fluorescent X-rays, and the yield of the polymer in the second stage was determined. Next, the third stage copolymerization was carried out in exactly the same manner as the second stage, except that hydrogen gas was charged so that the gas phase hydrogen concentration was 1.8 mol% on average, and propylene-ethylene copolymerization was carried out at 50°C for 0.5 hours. I went. The total polymerization pressure was 27.2 kg/cm ² gauge pressure. After 0.5 hours, the liquefied propylene-ethylene gas and hydrogen gas were purged, and 476 g of a white powdery propylene-ethylene block copolymer with high free-flowing properties and no agglomerates was taken out from the autoclave. Polymerization conditions and various measurement results are shown in Table 1. In the table, MFI (A) / MFI (A + B) is the MFI of the first stage polypropylene (A) and the total polymer (A + B).
MFI(L)/MFI(B) is the ratio of MFI of low molecular weight propylene-ethylene copolymer (L) to MFI of total propylene-ethylene copolymer (B),
The former is an actual value, and the latter is a value determined by measuring the MFI of a propylene-ethylene copolymer separately polymerized under exactly the same polymerization conditions as in the second and third stages. All values of MFI(L)/MFI(B) shown in the following Examples and Comparative Examples are values measured in this way. The bulk density ρ _B of the copolymer powder is 0.43 g/cc,
II was 95.2%, but these values are based on ρ _B = ρ of the propylene homopolymer extracted at the end of the first stage.
It was 0.47g/cc, which was close to II=97.4%. On the other hand, in terms of physical properties, even without removing the amorphous polymer, both the first yield strength and the Izot impact strength were high, and the embrittlement temperature was low. Catalyst efficiency CE is
23800, and the amount of Ti remaining in the copolymer is
The amount was 13.1 ppm, which was sufficiently low that there was no need to remove it. In addition, the tensile impact strength is 953Kg・
cm/cm, and the degree of whitening, which is a measure of impact whitening resistance, was as low as 11%, and the degree of whitening was extremely low. Examples 2 to 5 Polymerization was carried out in the same manner as in Example 1, except that the propylene concentration, hydrogen concentration, polymerization temperature, and polymerization time in the gas phase at each polymerization stage were changed as shown in Table 1. A block copolymer was obtained. The various measurement results are shown in Table 1, and it can be seen that the degree of whitening was low in all Examples, indicating that the impact whitening resistance was sufficiently improved. Example 6 In Example 1, the polymerization conditions of the second and third stages were reversed, and a high molecular weight propylene-ethylene copolymer was produced in the second stage as shown in Table 1.
Polymerization was then carried out in the same manner except that a low molecular weight copolymer was produced in the third step to obtain a propylene-ethylene block copolymer. The various measurement results are shown in Table 1. In terms of physical properties, there were no major differences from those obtained in Example 1, and in particular, the degree of whitening was as low as 12%. This indicates that the polymerization order of high molecular weight components and low molecular weight components does not have a direct effect on the effect of improving impact whitening resistance. Comparative Example 1 In Example 1, the propylene concentration, hydrogen concentration, and polymerization temperature and time in the gas phase at each polymerization stage are shown.
Polymerization was carried out in the same manner except for the changes shown in 1 to obtain a propylene-ethylene block copolymer. The various measurement results are shown in Table-1. Physical properties such as first yield strength and Izot impact strength were good, but MFI(L)/MFI(B) was high at 4300 and whitening degree was 61.
%, and the improvement in whitening property was insufficient. Comparative Example 2 In Comparative Example 1, the hydrogen concentrations in the gas phase in the second and third stages were set to 25.3 mol% and 14.9 mol%, respectively.
Polymerization was carried out in the same manner except that the percentage was changed to obtain a propylene-ethylene block copolymer. The various measurement results are shown in Table-1. Whitening degree is 10%
Although the impact whitening resistance was sufficiently improved, the Izot impact strength was as low as 9.8 kg·cm/cm, which was insufficient.

【table】

[Table] Comparative Example 3 In Example 1, the third step was performed without performing the second step.
A propylene-ethylene block copolymer was obtained in the same manner, except that the polymerization was carried out in two stages under the conditions shown in Table 2. The various measurement results are shown in Table 2. When the low molecular weight propylene-ethylene copolymer was not included, the degree of whitening was as high as 46%, and the whitening was higher than that of the block copolymer obtained in Example 1. I can see that it is getting easier. Examples 7 and 8 In Example 1, instead of the solid titanium trichloride catalyst complex obtained in Catalyst Production Example 1, Catalyst Production Example 2 was used.
Polymerization was carried out in the same manner using the catalyst obtained in Example 1, except that the hydrogen and propylene concentrations in the gas phase were changed as shown in Table 2. The various measurement results are shown in Table 2. Catalyst production example 1
Similarly to the catalyst obtained in Catalyst Production Example 2, the catalyst obtained showed excellent performance, and a polymer powder with excellent free-flowing properties and no agglomerates was obtained. Even without removing the polymer, both the first yield strength and the isot impact strength were high, and the impact whitening resistance was also improved.

[Table] Example 9 A continuous polymerization experiment was carried out using a three-tank series-coupled polymerization tank equipped with a blade-type stirring blade. There are 3 polymerization tanks
Both tanks have a pressure resistance of 40Kg/cm ² and an internal volume of 200. (1) First stage: The internal temperature of the first reactor filled with liquefied propylene is
The toluene slurry of the titanium trichloride catalyst complex prepared by the same method as in Catalyst Production Example 1 was maintained at 70°C, and 0.4 g/hour of titanium trichloride, 1.9 g/hour of di-n-propyl aluminum monochloride, and liquefied propylene were added every hour. 18.8Kg was pumped into the first reactor. Further, hydrogen was supplied at a concentration adjusted to 4.9 mol % relative to propylene in the gas phase. The total polymerization pressure at this time was 31.6 Kg/cm ² . Further, the liquid level was adjusted so that the average residence time was 5 hours, and the produced polypropylene was transferred to the next second reactor as a liquefied propylene slurry. A portion of the slurry transfer pipe from the first reactor to the second reactor was extracted to sample polypropylene, and the Ti content was measured using fluorescent X-rays to determine the yield and MFI in the first stage. As a result, the polypropylene yield was 7.5Kg/hour and the MFI was 7.0.
g/10min. (2) Second stage A liquefied propylene slurry containing polypropylene was supplied from the first reactor to the second reactor through the connecting pipe. At this time, the internal temperature of the second reactor was maintained at 50°C, and ethylene and propylene were supplied so that the concentration of propylene in the gas phase was 75 mol%, and the concentration of hydrogen in the gas phase was 5.3 mol%. It was adjusted to be %. The total polymerization pressure at this time was 26.2Kg/
It was warm in ^cm2 . Further, the liquid level was adjusted so that the average residence time was 0.5 hours, and the produced propylene-ethylene birock copolymer was further transferred to a third reactor as a liquefied propylene slurry. In the same manner as in the first stage polymerization, a part of the block copolymer was extracted from the transfer pipe to the third reactor, and the Ti content was measured using fluorescent X-rays. The total yield was determined. As a result, the yield of block copolymer was 8.1 kg/hour. The extracted block copolymer powder was a white powder with excellent free-flowing properties and no agglomerates. (3) Third stage In the second stage above, the concentration of hydrogen in the gas phase
The polymerization was carried out in exactly the same manner as the second stage, except that the polymerization concentration was adjusted to 1.8 mol %, the liquid level was adjusted so that the average residence time was 1.5 hours, and polymerization was carried out continuously. The total polymerization pressure at this time was 25.3 Kg/cm ² . The final product in the form of white powder was obtained at 8.8Kg per hour,
It is a free-flowing, spherical powder, and
MFI was 3.3g/10min. The bulk density ρ _B of the copolymer powder is 0.44 g/cc, and II
was 95.0%, but these values are based on ρ _B =0.48 of the propylene homopolymer extracted at the end of the first stage.
g/cc, II=97.3%, the decrease was extremely small. The composition of the block copolymer is the weight ratio of 1st stage: 2nd stage: 3rd stage = 85:8:7
The ethylene content [E] _IR was 3.9% by weight. Also, propylene homopolymer and total polymer
The ratio of MFI, MFI(A)/MFI(A+B) is 2.12,
Ratio of MFI of the propylene-ethylene copolymer obtained in the second stage and the total propylene-ethylene copolymer obtained in the second and third stages, MFI(L)/
MFI (B) was estimated and determined from the MFI of each propylene-ethylene copolymer obtained by separate batch polymerization under the same conditions as in the second and third stages. The result is MFI(L)/MFI(B)=32
It was hot. On the other hand, in terms of physical properties, the first yield strength is 258 Kg/cm ² even without removing the amorphous polymer, and the Izot impact strength is 17.5, similar to the batch method described above.
The temperature was as high as Kg·cm/cm and the embrittlement temperature was sufficiently low at -22°C. In addition, the tensile impact strength is 864Kg・cm/
Even when compared with 953 kg·cm/cm of the batch system of Example 1, it was sufficiently satisfactory. Furthermore, the degree of whitening, which is a measure of impact whitening resistance, was as low as 12%, and the degree of whitening was extremely low. Furthermore, when the degree of gel development was visually compared with that of the block copolymer obtained in Comparative Example 6 using a 1 mm thick pressed piece, it was found that there was no difference between the two and that the copolymer had a satisfactory appearance. Comparative Example 4 After carrying out the first stage polymerization in exactly the same manner as the first stage of Example 9, the second stage polymerization was performed except that the liquid level was adjusted so that the average residence time was 2 hours. Continuous polymerization was carried out in two stages in exactly the same manner as in the third stage of Example 9, and 8.8 kg of propylene-ethylene block copolymer was obtained per hour. The MFI of the final product is 1.8 g/10 min, and it is a spherical white powder with rich free-flowing properties, and its composition is 1st stage: 2nd stage = 85:15 by weight.
Ethylene content [E] _IR was 4.0% by weight. In addition, the bulk density ρ _B of the polymer powder is 0.44 g/cc, and II
was 95.1%, which was not much different from the polymer obtained in Example 9. On the other hand, in terms of physical properties, similar to the polymer obtained in Example 9, the first yield point strength was 256 Kg/cm ² ,
The Izotsu impact strength was 16.8Kg・cm/cm, which was high and satisfactory, but the tensile impact strength was 216Kg・cm/cm.
cm/cm. Furthermore, the degree of whitening was as high as 58%, and the impact whitening resistance was poor.Also, the observation results regarding gel development in a pressed piece with a thickness of 1 mm could not be compared with the polymer obtained in Example 9, and there were many large and small particles. The expression of gel was observed. Comparative Example 5 Comparative Example 4 was performed except that the polymerization was carried out in two stages in batch mode using two autoclaves.
A propylene-ethylene block copolymer was produced under the same conditions as described above. The various measured values are shown in Table 3, and both the first yield strength and the isot impact strength were high, and the tensile impact strength was particularly high at 918 Kg·cm/cm. Also,
Visual observation of the pressed piece with a thickness of 1 mm revealed that no gel was present at all. The whitening level is 44
It was as high as %.

[Table] Example 10 The first and second stage polymerizations were carried out in the same manner as in Example 1, except that the polymerization conditions were as shown in Table 4. Next, the third stage of polymerization was carried out as follows. That is, after the second stage polymerization was completed, the liquefied propylene, ethylene gas, and hydrogen gas were purged to bring the gauge pressure to 0 Kg/cm ² , and then the internal temperature of the autoclave was adjusted to 70°C, and then 14.1 kg of propylene gas was immediately added. /cm ² , ethylene gas was charged at 2.45Kg/cm ² , and the hydrogen concentration in the gas phase was further increased.
Hydrogen gas was charged so that the concentration was 0.2 mol%. This time is the start of the third stage polymerization reaction, and 1
The polymerization reaction was continued under stirring for an hour. During this time, ethylene gas was continuously charged so that the ethylene partial pressure was 2.45 Kg/cm ² , and propylene gas was continuously charged so that the propylene partial pressure was 14.1 Kg/cm ² . The total pressure is
The pressure was 17.5Kg/cm ² gauge. The propylene concentration in the gas phase was 85 mol%. After 1 hour, the propylene, ethylene and hydrogen gases were purged and 482 g of a free-flowing white powdery propylene-ethylene block copolymer without any agglomerates was taken out from the autoclave. Polymerization conditions and various measurement results are shown in Table 4. Copolymer bulk density ρ _B
was 0.43 g/cc and II was 94.6%, these values were extracted at the end of the first stage. The decrease was smaller than that of propylene homopolymer with ρ _B =0.47 g/cc and II =97.4%. On the other hand, in terms of physical properties, even without removing the amorphous polymer, both the first yield strength and the Izot impact strength were high, and the embrittlement temperature was sufficiently low. In addition, the tensile impact strength is 931Kg・cm/
cm, and the degree of whitening was low at 19%, and the effect of improving impact whitening resistance was sufficient. In addition, the catalyst efficiency CE is
24100 and the amount of Ti remaining in the copolymer is
The amount was 12.9 ppm, which was sufficiently low that there was no need to remove it. Examples 11 and 12 Polymerization was carried out in the same manner as in Example 10 except that the polymerization conditions in the first to third stages were changed as shown in Table 4 to obtain a propylene-ethylene block copolymer. Various measurement results are shown in Table 4. In all examples, the degree of whitening was low;
It can be seen that the impact whitening resistance has been improved. Comparative Example 6 Polymerization was carried out in the same manner as in Example 12, except that the hydrogen concentration in the third stage was reduced to 0.08 mol% to produce a higher molecular weight propylene-ethylene copolymer. I got it. The various measurement results are shown in Table 4, and the MFI(L)/MFI(B) at this time was as high as 3990. The first yield strength and Izot impact strength were relatively high, but the tensile impact strength was 412
Kg·cm/cm, which was insufficient, and the degree of whitening was particularly high at 62%, making it easy to whiten. Furthermore, rough skin was observed in the molded product, and it was found that it had a great balancing effect.

【table】

Claims (1)

[Scope of Claims] 1 In producing a propylene-ethylene block copolymer by polymerization or copolymerization in three stages using a stereoregular catalyst, in the first stage, the melt flow index is measured in liquefied propylene. is 1g/
Propylene polymer (A) having a propylene content of 95% or more is produced at a rate of 10min to 100g/10min at 60% to 95% by weight, and then in the second and third stages in the presence of liquefied propylene or in a liquid state. In the substantial absence of hydrocarbons, the propylene concentration relative to the sum of propylene and ethylene in the gas phase ranges from 40 mol % to 90 mol %.
Copolymerize propylene and ethylene under conditions of mol%, and add 5% by weight of propylene-ethylene copolymer (B) so that the ethylene content in the total polymer is 2% to 30% by weight. In the method of producing ~40% by weight, one of the second and third stages produces a high molecular weight propylene-ethylene copolymer (H), and the other produces a low molecular weight propylene-ethylene copolymer (L). (a) The ratio of the melt flow index MFI (A) of the propylene polymer (A) to the melt flow index MFI (A + B) of the entire polymer is MFI (A) / MFI (A + B) = 1.5 to 10. Yes, (b) The melt flow index MFI (L) of the low molecular weight propylene-ethylene copolymer (L) in the propylene-ethylene copolymer (B) is the melt flow index of the propylene-ethylene copolymer (B). index
A method for producing a propylene-ethylene block copolymer, characterized in that the relationship between MFI(B) and MFI(L)/MFI(B) is 10 to 1000. 2. The method for producing a block copolymer according to claim 1, wherein the copolymerization of propylene and ethylene in the second and third stages is carried out in the presence of liquefied propylene. 3 Of the copolymerization of propylene and ethylene in the second and third stages, one is carried out in the presence of liquefied propylene, and the other is carried out in the substantial absence of liquid hydrocarbons, as set forth in claim 1. Method for producing block copolymer.