JPS58189250A - Production of modified block copolymer - Google Patents

Abstract

PURPOSE:To obtain the titled copolymer which scarcely forms fish eye when molded into a film, by heat-treating in the presence of an org. peroxide a propylene/ethylene block copolymer obtd. by a continuous process. CONSTITUTION:Propylene is polymerized in the presence of a catalyst in a first stage. In a second stage ethylene and propylene are copolymerized in the presence of the catalyst/polymer system obtd. in the first stage to obtain a block copolymer. The polymn. is carried out by a continuous process such that the melt flow index of each of the polymer and the block copolymer obtd. in each stage becomes 0.3 or below. The block copolymer is heat-treated at 170-300 deg.C, pref. 180-250 deg.C in the presence of an org. peroxide to obtain the titled polymer. The org. peroxide is used in an amount of 0.01-1wt%, pref. 0.01-0.5wt% based on that of the block copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a continuous polymerization method to achieve excellent impact resistance, and even when processed into a film, it has no fish-like properties.
The present invention relates to a method for producing a modified block copolymer with extremely low eyes.

Conventionally, various methods for polymerizing propylene have been proposed. However, polypropylene does not have sufficient impact resistance, especially at low temperatures. For this reason, methods for producing propylene-ethylene block copolymers have attracted attention and have been adopted industrially. The block copolymer usually comprises a first step of first polymerizing propylene in the presence of a catalyst, and a second step of copolymerizing ethylene and propylene in the presence of a polymer containing the catalyst obtained in the first step. It is obtained by the following polymerization method. The above polymerization method is generally carried out in the first step in the presence of a molecular weight regulator in a hydrogen tank, and in the second step, the introduction of the molecular weight regulator is suppressed as much as possible and polymerization is carried out in a low concentration range. That is, in the first step, the melt flow index (hereinafter referred to as MFI) of the obtained block copolymer is appropriately adjusted by controlling the molecular weight, and in the second step, the melt flow index (hereinafter referred to as MFI) of the block copolymer obtained is adjusted appropriately by controlling the molecular weight. The aim is to improve the impact resistance of block copolymers produced by

On the other hand, the above polymerization methods include a batch method in which copolymerization in the second step is carried out after completing the polymerization in the first step, and a batch method in which the polymerization product in the first step is continuously supplied to the second step. It can be roughly divided into two methods: continuous method, which copolymerizes ethylene, and propylene. If a block copolymer is obtained by the batch method, a product with physical properties such as impact resistance and rigidity can be obtained, but the product cost will only increase due to operational deficiencies and increased equipment costs. It is rarely used industrially because it is unsuitable for mass production. On the other hand, the continuous method, which is the complete opposite of the batch method, is widely adopted as an industrially superior technology, but it has inferior impact resistance compared to the batch method, and when processed into a film, it is prone to・There are defects such as the formation of eyes, which limits the use and causes dissatisfaction with the physical properties.

Therefore, establishing a technology for manufacturing products equivalent to batch-type products using a continuous method is a major challenge in the field of this application.

Conventionally, in a method for obtaining block copolymers in a continuous manner, as a technique to homogenize the obtained block copolymer and prevent fish eyes that occur when processed into a film, a step is carried out following the first step. By controlling the concentration of the molecular weight modifier in the second step as well, the difference in intrinsic viscosity between the polymer obtained in the first step and the polymer produced in the second step is reduced, resulting in a block copolymer having an appropriate MFI. A method to obtain coalescence has been proposed. However, the block copolymer obtained by the above method has the disadvantage that impact resistance decreases as the fish eyes decrease.

The present inventors have discovered that the block copolymer obtained by the continuous method can be processed into a film with extremely low occurrence of fish eyes by simply giving it almost the same physical properties as those obtained by the batch method. Moreover, we have been conducting intensive research with the aim of developing technology that is industrially satisfactory. As a result, a block copolymer was obtained by carrying out the polymerization in the first step and the second step so that the MFI of the polymer and block copolymer obtained respectively became a specific value. By heat treatment in the presence of
The inventors have discovered that the object can be achieved and have completed the present invention.

The present invention comprises a first step of polymerizing propylene in the presence of a catalyst, and a second step of copolymerizing ethylene and propylene in the presence of the catalyst-polymer obtained in the first step. The process is carried out in a continuous manner so that the melt flow index of the polymer and block copolymer obtained is 0.6 or less, and the block copolymer obtained from the second step is heat treated in the presence of an organic peroxide. A method for producing a modified block copolymer characterized by the following.

(5) In the present invention, MFI refers to a value measured according to ASTM D 1238.

In the present invention, when producing a block copolymer, the first
The M F17 of the polymer obtained in the step and the block copolymer obtained in the second step is 0.6 or less, preferably 0.
．． Setting the value to 2 or less, more preferably 0, improves the impact resistance of the modified block copolymer obtained through the heat treatment described below, and the effect of preventing the occurrence of fish eyes when processed into a film. It is extremely important to perform to the best of your ability. The method of conducting polymerization so that the MFI becomes the above value is generally performed in the absence of a molecular weight regulator such as hydrogen, or by restricting the amount of the molecular weight regulator so that the MFI becomes the above value. Bye. As in the conventional continuous production method of block copolymers described above, in the first step of polymerizing propylene and the second step of copolymerizing ethylene and propylene, the molecular weight of the polymer produced in the first step is When controlled using a molecular weight regulator, the molecular weight of the block copolymer produced in the second step is increased, that is, the MFI is decreased. , when processed into a film as mentioned above, the occurrence of fish eyes is significant.
Impact resistance is also not sufficient. Even if the block copolymer is heat-treated with an organic peroxide, the above-mentioned drawbacks cannot be improved much. Furthermore, if a molecular weight regulator is used to control the MFI to an appropriate level so that there is no large difference in the molecular weight of the polymers produced in both processes, fish eyes will be significantly reduced when the block copolymer is processed into a film. On the other hand, impact resistance decreases.

If this is further heat-treated, the impact resistance will further decrease.

The catalyst used in the present invention is not particularly limited, and any catalyst that can polymerize propylene or propylene and other olefins can be used as necessary. Generally, industrially, it is preferable to employ a binary catalyst of titanium trichloride and an organoaluminum compound, or a ternary catalyst in which a third component is added as an electron donor to the binary catalyst. Various methods of manufacturing titanium trichloride have been proposed, but they can be used in the present invention without any particular limitations. Especially, when the polymerization rate of the catalyst is 2
Highly active titanium trichloride with a 50Of.polymer/2.TICLs of 71 hours or more is preferred. The method for producing highly active titanium trichloride is described, for example, in JP-A-47-34478 and JP-A-50-1.
No. 2659 [].

No. 50-114394, No. 50-93888.

No. 50-123091, No. 50-74594.

No. 50-74595, No. 50-104191.

No. 50-98489, No. 51-92885.

No. 51-1 '56625, No. 52-30888.

It is preferable to use the one described in Japanese Patent No. 52-35283. The organic aluminum compound generally used in the polymerization of propylene in combination with titanium trichloride can be used without particular limitation. For example, trialkyl aluminum, sialgyl aluminum monochloride,
Examples include alkyl aluminum sesquichloride, alkyl aluminum dichloride, and dialkyl aluminum monohalides such as diethyl aluminum monochloride are particularly suitable.

Further, as the electron donor used as the sixth component of the catalyst, any known electron donor may be used without particular limitation.

For example, nitrogen-containing compounds and phosphorus-containing compounds as shown in JP-A-50-123182.

Ether compounds etc. can be suitably employed.

In the first step of the present invention, propylene is used in an amount that does not adversely affect the block copolymer obtained.
For example, it may contain ethylene, butene, etc. In general, the other olefins mentioned above are less than 6% by weight, preferably 3% by weight.
It is preferable to limit the proportion to less than % by weight. The polymerization in the first step may be carried out in the presence of the above-mentioned catalyst in an inert solvent such as heptane, hexane, petroleum ether, etc., or using the above-mentioned pro(9)pyrene itself as a solvent. Known conditions are appropriately applied to the polymerization conditions. Generally, the polymerization temperature is 40~
The temperature is preferably 80°C, preferably 50 to 70°C, and the shorter the polymerization time, the better. Generally, 30 minutes to 6 hours is preferable.
.

The polymer obtained in the first step may be taken out in the form of a slurry containing the catalyst (1) and continuously fed to the second step as it is or after removing unreacted monomers by, for example, flanshing. Of course, it is preferable to take out the catalyst-polymer composition in the first step so that the liquid level in the polymerization tank does not fluctuate, and the taken-out catalyst-polymer composition maintains a constant slurry concentration. It is preferable to supply it to the second step so that it does. For example, when the first step is a polymerization operation using propylene as a substantial solvent, it is generally adopted to remove unreacted monomers by flashing them in a flash tank, but the resulting polymer containing catalyst is It is also possible to add the required amount of the above-mentioned inert solvent and supply it to the second step as a slurry having a constant concentration of (10).

The addition or mixing ratio of each catalyst component used in the first step of the present invention is not particularly limited, and a suitable ratio may be determined in advance from known ratios.

In general, the molar ratio of organoaluminum compound to titanium trichloride, that is, organoaluminum compound/titanium trichloride (
The molar ratio) is preferably in the range of 1 to 30, preferably 3 to 20. In particular, when the highly active titanium trichloride is used as titanium trichloride, the molar ratio of organoaluminum compound/titanium trichloride is preferably in the range of 5 to 20. In addition, when an electron donor, that is, a third component is used as a catalyst component, the third component is
Since there are differences depending on the type of component, it is better to determine the appropriate usage amount in advance according to the type of third component.In general, the electron donor/titanium trichloride (molar ratio) is
A range of o o i to 1 is preferably used.

Further, in the present invention, pretreatment of the catalyst to be supplied to the first step is not particularly limited. As the pretreatment, it is preferable to adopt a means of preliminarily polymerizing a small amount of olefin with a catalyst containing titanium trichloride and an organoaluminum compound. For example, titanium trichloride and an organoaluminum compound, if necessary, an electron donor are mixed in an inert solvent such as heptane, hexane, petroleum ether, etc., and an olefin such as propylene, ethylene, butene-1, or a mixture thereof is supplied. All it has to do is polymerize. This pretreatment is generally referred to as prepolymerization, and known prepolymerization conditions can be used as they are. For example, '50~70c
Preferably, it is generally carried out at a temperature range of 40 to 60°C. In addition, the polymerization degree of prepolymerization is determined by the T of the catalyst used.
The higher the iCl3 unit weight, the more preferable it is, but from an equipment or economic point of view, it is generally 1 to 100 f/f-
T1CLs or so are most commonly employed.

The second step of the present invention is a step of copolymerizing propylene and ethylene in the presence of the catalyst-containing polymer obtained in the first step so that the MFI of the resulting block copolymer has the above value. . Although the copolymerization can be carried out using the monomer itself as a solvent, it is generally preferable to carry out the copolymerization in an inert solvent as described above.

The mixing ratio of propylene and ethylene to be supplied to the second step of the present invention depends on the physical properties required of the finally obtained modified block copolymer, the copolymerization conditions in the second step,
It varies depending on the polymerization conditions in the first step, etc., but cannot be definitively defined, but generally the ethylene/propylene molar ratio is 1.
The range of /9 to 8/2, preferably 2/8 to 515, is most widely adopted. Moreover, the content of ethylene contained in the block copolymer obtained in the second step is generally widely used in the range of 2 to 20% (by weight).

The copolymerization conditions in the second step of the present invention are not particularly limited (13) and may be selected from known operating conditions, but generally a range of 30 to 70°C, preferably 40 to 60°C is suitable, It is common to react for 60 minutes to 3 hours. In addition, in the second step, a small amount of an organoaluminum compound is added. , it is also possible to measure the improvement of polymerization activity. In this case, it is preferable to use an amount of 0.1 to 4.0 times the mole of titanium trichloride.b0 The block copolymer obtained in the second step of the present invention is usually The slurry is removed continuously to maintain a constant surface. The slurry is continuously transferred to a flash tank, and unreacted monomers are purged and separated to obtain a block copolymer. Alternatively, if necessary, a block copolymer can be obtained by adding alcohol to deactivate the catalyst and performing a deashing operation to separate the alcohol and drying. Any known method (14) may be used to separate the block copolymer from the slurry taken out from the second step.

The devices, reactors, etc. used to carry out the present invention are not particularly limited and can be used, and the type, system, attached equipment, etc. can be determined as necessary. In addition, operations such as carrying out the second step of the present invention in two parts, or carrying out the first and second steps of the present invention repeatedly as one unit may be adopted as necessary. I can do it.

In the present invention, the block copolymer obtained by the method described above is heat-treated in the presence of an organic peroxide. By the above heat treatment, a modified block copolymer whose MFI is adjusted to an arbitrary value can be obtained. The modified block copolymer has extremely good impact resistance and an effect of reducing fish eyes when processed into a film, compared to block copolymers obtained by various conventional continuous methods. It has almost the same physical properties as a block copolymer obtained by a batch process.

The mixing method of the block copolymer and the organic peroxide is not particularly limited as long as the organic peroxide is present when the block copolymer is heat-treated. For example, a method of mechanically mixing using a mixer such as a blender, a method of dissolving an organic peroxide in a suitable solvent, adhering it to the block copolymer, and drying the solvent. be. Further, the heat treatment temperature is a temperature higher than the melting temperature of the block copolymer and higher than the decomposition temperature of the organic peroxide. However, if the heat treatment temperature is too high, thermal deterioration of the block copolymer will result. Generally, the heat treatment temperature is 170 to 600°C, particularly 180 to 250°C.
It is preferable to set it within the range of .

Known organic peroxides are generally used in the present invention. Typical organic peroxides include ketone peroxides such as methyl ethyl ketone peroxide, methyl imbutyl ketone peroxide, and imbutyl ketone peroxide.
J k Bar oxide, diacyl peroxide such as acetyl peroxide: diimprobylbenzene hydroperoxide, other hydroperoxides: 2,5-dimethyl 2,5-di(1-butylperoxy)hexane, 1,3 -Dialkyl peroxides such as -bis-(t-butylperoxyinpropyl)benzene; 111-di-t-butylperoxy-cyclohexane and other peroxyketals: t-butylperoxyacetate.

Alkyl peresters such as t-butylperoxybenzoate; t-butylperoxyinpropyl carbonate, other percarbonates, and the like. The amount of the organic peroxide to be used varies depending on the set value of MFI of the modified block copolymer obtained, and cannot be determined unconditionally, but it is preferably 0.001 to 1.0% by weight, preferably 1% by weight based on the block copolymer. The amount is generally 0.01 to 0.5% by weight.

(17) The modified block copolymer obtained by the method of the present invention can be processed into an excellent impact-resistant film, etc., as described above.
Although it is not clear why the fish-eye reduction effect is achieved in the case of 100 mm, the inventors of the present invention assume the following. That is, a high molecular weight propylene polymer is produced in the first step, and a high molecular weight copolymerized portion of ethylene and propylene is produced in the second step. It is thought that the polymer produced in the first step, while exhibiting good compatibility, receives preferential molecular weight reduction action and improves the MFI of the block copolymer.

EXAMPLES Hereinafter, Examples will be shown to explain the present invention more specifically, but the present invention is not limited to these Examples.

The method of measuring the physical properties used in the same example is as follows.

(1) The C2H4 content in the polymer was determined by infrared absorption spectrum analysis.

(18) (2) The number of fish eyes was measured as follows.

Using the obtained modified block copolymer as a raw material, a blown film is formed by a water-cooling method using a 65 mm diameter extruder. The number of fish eyes in 100 ml of film formed was calculated visually.

(3) Flexural modulus was measured according to ASTM D-790.

(4) Izod (Izod) shock value is ASTMD
-256.

Example 1 Brown titanium trichloride obtained by reducing titanium tetrachloride with diethylaluminum monochloride in an inert solvent was treated with about an equimolar amount of diynamyl ether at room temperature, and then
The brown titanium trichloride was chemically treated with a 65° C. hexane solution containing 1.5 times the molar amount of titanium tetrachloride to obtain titanium trichloride.

Using this catalyst, polymerization was carried out according to the following procedure. Namely, an autoclave (4), a flash tank (B), and a slurry tank (C) each weighing 300 tons.

Autoclave (D), flash tank (E),
Using a polymerization device with washing tanks (F) arranged in series, the first
The process is a so-called solvent-free method using propylene itself as a solvent.
In the process, propylene-ethylene copolymerization was carried out continuously by a so-called solvent method using hebutane as a solvent.

First, titanium trichloride, diethylaluminum monochloride, and liquid propylene were continuously supplied to a polymerization tank set at a temperature of 65°C. The amount of liquid propylene supplied and the amount of produced propylene homopolymer withdrawn were set so that the average residence time of the catalyst was 4 hours.

In this way, the propylene homopolymer slurry produced is continuously transferred to the flash tank (B) so as not to fluctuate the liquid level as much as possible, and after purging unreacted monomers there, the polymer is transferred to a rotary feeder. The mixture was continuously transferred to a slurry tank (C'l). Along with the supply of the polymer, heptane was supplied to this tank at a rate of 40 t/hour, and the mixture was made into a uniform slurry while stirring.

Subsequently, the polymer slurry was continuously transferred to an autoclave (D) set at 50°C, and ethylene gas,
Propylene gas was fed continuously. Autoclave (
The amount of polymer slurry supplied and withdrawn to D) is set so that the average residence time of the polymer slurry is 2 hours,
The supply of ethylene gas and propylene gas was controlled by gas chromatography so that the molar ratio of ethylene/propylene in the gas phase region was as shown in Table 1.

The block copolymer slurry produced in this way is
It was continuously transferred to a flash tank (E), and after purging unreacted monomers, it was transferred to a washing tank (F). Subsequently, the catalyst was treated by adding a predetermined amount of alcohol, and then the solid and liquid were separated using a centrifuge.

(21) The solid thus obtained was dried for 6 hours to obtain a white granular polymer.

Note that no molecular weight regulator was used during the polymerization in the first and second steps. As a result, the MF of the propylene homopolymer and the white granular polymer obtained in the first step was
When I was measured, it showed no fluidity at all (MFI
−〇). The ethylene content in the white fruit granular polymer is shown in Table-
It was like 1.

2,5-dimethyl-2,5-di(t-butylperoxy)-hexane (
MBH) in the proportions shown in Table 1, an antioxidant, a heat stabilizer, and a lubricant were further added and mixed in a Henschel mixer.

Next, Nakatani Machinery'VSK40 with vent 40■φ
The polymer was extruded using an extruder while controlling the resin temperature at the die outlet to 260° C. to obtain a pellet-like polymer. The MFL, Izod impact strength 2 flexural modulus, and number of fish eyes of the polymer were measured. The results are also shown in Table-1.

(22) Comparative Example 1 Polymerization was carried out using the same catalyst composition and equipment as in Example 1, but at that time, hydrogen gas was introduced into the autoclave in the first and second steps to adjust the molecular cap. . The concentration of hydrogen gas (gas phase) was checked by gas chromatography and was controlled to be constant during polymerization. The other polymerization conditions were exactly the same as in Example 1 to obtain a white granular polymer. Next, an antioxidant, a heat stabilizer, and a lubricant were added to the polymer, mixed in a Henschel mixer, and passed through an extruder in the same manner as in Example 1 to obtain a pellet-shaped polymer.

Table 2 shows the hydrogen concentration (gas phase) during the polymerization in the first step, the MFI of the polymer sampled at the end of the first step, the hydrogen concentration (gas phase) during the polymerization in the second step, and the pellet-shaped polymer. The MFI, ethylene content, isot impact strength, flexural modulus, and number of fish eyes are listed from 1 to 1.

(23) (25)　　　　　　　　　　-347-(24)

Claims (1)

[Claims] 1. A first step of polymerizing propylene in the presence of a catalyst;
The second step is to copolymerize ethylene and propylene in the presence of the catalyst-polymer obtained in the first step to obtain a block copolymer.
Steps are carried out in a continuous manner so that the melt flow index of the polymer and block copolymer obtained in each step is 0.3 or less, and the block copolymer obtained in the second step is treated with an organic peroxide. A method for producing a modified block copolymer, the method comprising heating in the presence of. 2. The method according to claim 1, wherein the amount of organic peroxide used is 0.01 to 1% by weight based on the block copolymer.