JPS584725B2 - Purification method for highly crystalline polyolefin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying a polyolefin containing a halogen-containing metal catalyst residue, such as a highly crystalline polyolefin obtained by polymerization using a Ziegler-Natsuta type catalyst.

More specifically, the present invention involves deactivating a catalyst in a highly crystalline polyolefin obtained by polymerization using a so-called Ziegler-Natsuta type catalyst using a deactivating agent, and then subjecting the catalyst residue to a water extraction treatment. After that, in the process of drying the polyolefin separated from water and the hydrocarbon medium, the polyolefin is brought into contact with a gas of a specially selected alcohol to inactivate and remove acidic substances derived from catalyst residues contained in the polyolefin. The present invention relates to a method for purifying a highly crystalline polyolefin.

Conventionally, methods for producing highly crystalline polyolefins using Ziegler-Natsuta type catalysts are known.

That is, polyolefin is produced by polymerizing α-olefin in the presence of a catalyst consisting of a halogen compound of a transition metal such as titanium halide and an organoaluminium compound, or a catalyst system in which a third catalyst component is added as necessary. can be obtained.

Therefore, the resulting polymer contains these catalyst residues.

This catalyst residue destabilizes the polymer mainly due to the acidic substances derived therefrom (typical examples include free hydrochloric acid and halogen ions bonded to catalyst metal atoms in an extremely unstable state). This not only significantly reduces product value but also causes corrosion problems for process equipment.

In order to avoid these problems, various polyolefin purification methods have been proposed.

For example, a method in which a polymer obtained by solvent polymerization is treated with a chelating agent such as an alcohol or a diketone to solubilize and purify the catalyst component (Japanese Patent Publication No. 35-12593, Japanese Patent Publication No. 34-346); is a method of re-extracting the solubilized catalyst components with water after these treatments (Japanese Patent Publication No. 1973-
No. 941).

However, even with such treatment, the catalyst residue could not be sufficiently reduced to a level that does not cause the above-mentioned problems.

On the other hand, a method has been proposed in which the purification of the polymer is omitted by using a highly active catalyst to relatively reduce the amount of catalyst residue in the polymer (Japanese Patent Publication No. 46-6986, Japanese Patent Publication No. 46-16891, etc.). ) However, in this case as well, there is a small amount of catalyst residue containing acidic substances in the polyolefin, so it was necessary to perform some kind of stabilization treatment to obtain a high-quality product.

Furthermore, a method has been proposed for purifying polyolefin by bringing it into contact with a mixed gas of alkylene oxide and water (Japanese Patent Laid-Open No. 139883).

However, since this method contains halogen components and moisture in the system, it poses a serious problem of corrosion of the equipment.

Alkylene oxide is convenient as a scavenger for acidic substances such as hydrogen halides, and is also attracting attention as a processing agent for gas-phase treatment of polyolefins (Japanese Patent Publication No. 32313/1983, etc.).

However, since this agent is highly reactive, it also reacts with water and alcohol at high temperatures, resulting in considerable waste and resulting in an expensive product.

In this sense, in Japanese Patent Publication No. 49-32313, the catalyst residue is not eluted and removed in advance, and it is essential to carry out steam treatment at a later stage, so it is an economically extremely disadvantageous process.

In addition, even when this agent is used in the drying step of the water extraction process as seen in the above-mentioned Japanese Patent Publication No. 35-941, waste of this agent due to reaction with moisture accompanying the polyolefin is a problem. .

Furthermore, alkylene chlorohydrin, which is a reaction product between alkylene oxide and an acidic substance such as hydrogen chloride, has a low vapor pressure and is difficult to remove from polyolefin, which is an inconvenient property for obtaining high-quality products. There is.

Also, technology to bring alcohol into contact with vapor phase
No. 32313) requires a subsequent steam treatment, which also necessitates additional drying treatment, which is considered to be an economically extremely disadvantageous process.

The object of the present invention is to stabilize polyolefin containing catalyst residue using an extremely simple method, and in particular to inactivate and remove acidic substances such as hydrogen halides that cause corrosion and quality deterioration, thereby obtaining high-quality polyolefin. There is a particular thing.

In view of the above-mentioned problems, the inventors of the present invention have conducted intensive studies from various angles with the aim of realizing the present problem.
This has led to the completion of the present invention.

That is, the catalyst in the polyolefin produced using the Ziegler-Natsuta type catalyst is deactivated using a deactivating agent, the catalyst residue is then extracted with water, and the polyolefin separated from water and the hydrocarbon medium is dried. In the step of converting the polyolefin to 2-methyl-2-propanol (referred to as the alcohol).

), the amount of acidic substances such as hydrogen halides contained in the polyolefin is significantly reduced and the catalyst residue is stabilized, resulting in extremely high quality products and solving the corrosion problem of manufacturing equipment. I found out what I can do.

The Ziegler-Natsuta type catalyst used in the present invention is: a)
It is composed mainly of a halogenated titanium compound and b) an organoaluminum compound.

Specifically, titanium trichloride and titanium tetrachloride are used as component a).

In the case of titanium trichloride, titanium tetrachloride reduced with hydrogen, metal aluminum, or an organoaluminum compound to be highly activated is used.

Furthermore, titanium halides and the like containing other metal compounds are also used as carriers.

Component b) is typically an alkyl aluminum or an alkyl aluminum halide.

Examples include triethylaluminum, diethylaluminum chloride, and ethylaluminum sesquichloride.

In addition, in addition to these a) and b) components, oxygen nitrogen,
Also included are compounds in which a compound containing an electron donating group such as phosphorus is added as a third component.

The relationship between the alcohol used in the present invention and the alcohol for deactivating or decomposing the catalyst component in the polyolefin slurry after polymerization and solubilizing it in the solvent (referred to as deactivated solubilizing alcohol) is as follows. It seems so.

That is, the alcohol used as the deactivated solubilizing alcohol is selected from among those that are compatible with the polyolefin.

If the compatibility is insufficient, the rate of deactivation and solubilization of the catalyst component in the polyolefin will be insufficient, making it industrially meaningless.

Therefore, primary alcohols are selected as the most suitable deactivated solubilizing alcohols, and tertiary alcohols are not effectively used and are therefore not practically used industrially.

The present inventors have also experimentally confirmed that 2-methyl-2-propanol is practically ineffective as a deactivated solubilizing alcohol in a temperature range of at least 80° C. or lower.

In this way, it is inauspicious to use it as a deactivated solubilizing alcohol (therefore, it is unlikely that it will be used as a deactivated solubilizing alcohol, which may inevitably be entrained even in small amounts in the drying process of polyolefin after water extraction). 2-methyl-2-propanol is deactivated,
80% in the drying process of polyolefin after water extraction treatment
When brought into contact with a dry polyolefin in a gaseous state at a temperature exceeding ℃, acidic substances originating from catalyst residues in the polyolefin are inactivated and removed at a speed and degree sufficiently high for industrial use. It was revealed for the first time in the present invention that a high quality polyolefin could be produced by using the same method, and this was a surprising achievement.

The catalytic conditions using the alcohol in the present invention are as follows.

That is, the alcohol only needs to be in a gaseous state when it comes into contact with the polyolefin, but it does not necessarily have to be a single gas, and it can be diluted with an inert gas, such as nitrogen gas, argon gas, hydrocarbon gas, etc. The method used can be used to advantage.

The highly crystalline polyolefin to be subjected to the contact treatment in the present invention is produced using a Ziegler-Natsuta type catalyst, and may be an α-olefin homopolymer.
Further, it may be a copolymer of two or more types of α-olefins, and is not particularly limited, even if it is a copolymer mainly composed of α-olefins and other comonomers that can be copolymerized.

In addition, whether produced by a solvent polymerization method or a bulk polymerization method, after polymerization, the catalyst in the polyolefin is deactivated using a deactivating agent, and then the catalyst residue is extracted with water. After treatment, polyolefins separated from water and hydrocarbon media are considered.

The contact time of the polyolefin with the alcohol gas (either alone or diluted with the gas mentioned above, hereinafter referred to as treatment agent gas), the contact temperature, the treatment agent gas composition, the amount used relative to the polyolefin, etc. Although it varies depending on the type and amount of the catalyst residue contained in the highly crystalline polyolefin and cannot be absolutely limited, the generally applicable ranges are as follows.

The contact time may advantageously be 1 minute or more and 5 hours or less, particularly preferably 5 minutes or more and 1 hour or less.

Contact temperature is 40℃ or higher and 10℃ above the melting point of polyolefin.
Preferably a 20°C lower temperature is used, particularly preferably above 80°C and below 150°C for polypropylene, above 80°C and below 110°C for polyethylene, and particularly preferably above 80°C and below 110°C for copolymers of propylene and ethylene. If the temperature exceeds 80°C, the temperature used is 10°C, preferably 20°C lower than the melting point of the copolymer selected from the range of 110 to 150°C.

The amount of alcohol used is usually in the range of 10 ppm (w/w) to 10% by weight based on the highly crystalline polyolefin, particularly preferably 30 ppm to 500% by weight.
A range of 0 ppm (w/w) may be advantageously used.

Further, there is no problem as long as the composition of the processing agent gas can be controlled so that the concentration of the alcohol gas in the total processing agent gas is not less than 10 ppm (W/W).

A known apparatus for contacting the highly crystalline polyolefin and the processing agent gas in the present invention is used, but the processing agent gas is supplied from the lower part of the apparatus, the highly crystalline polyolefin is supplied from the upper part or the side part of the apparatus, The most common method is a fluidized dryer, which involves contact in a fluidized state, but other commonly used drying devices such as a powder stirring type (commonly known as a paddle dryer) and a cylindrical rotary dryer may also be used.

In addition, a certain amount of polyolefin is stored in a silo-like, rigid cylindrical storage tank, and processing agent gas is supplied from the bottom or side of the storage tank, highly crystalline polyolefin is supplied from the top of the storage tank, and high-crystalline polyolefin is supplied from the bottom of the storage tank. A pull-out type contact device (Japanese Patent Application No. 52-1184325) can also be used advantageously.

In the present invention, a method of separating by evaporation is generally adopted as a method for separating the processing agent gas brought into contact with the highly crystalline polyolefin and the reaction product of the alcohol and the acidic substance derived from the catalyst residue from the highly crystalline polyolefin. .

That is, a method may be adopted in which the highly crystalline polyolefin after treatment is brought into contact with a purified inert gas, such as nitrogen gas, for cleaning. This is not particularly necessary when using a processing agent gas.

In purifying the processing agent gas after the contact treatment with the highly crystalline polyolefin in the present invention, a reaction product of the alcohol and an acidic substance derived from the contact residue is separated from the processing agent gas in a conventional purification column. Alternatively, the reaction product can be easily purified and recycled by removing the reaction product from the processing agent gas by bringing it into contact with an alkali-containing aqueous solution and/or an alkali-containing hydrocarbon solution.

Next, the main effects of the present invention will be listed.

The first main effect of the present invention is that by contacting a highly crystalline polyolefin containing a metal halogen tower compound as a catalyst residue with a gas consisting of the alcohol, acidic substances originating from the catalyst residue in the highly crystalline polyolefin can be removed. can be inactivated and converted into a harmless form.

The second main effect of the present invention is that the reaction product produced when acidic substances are inactivated as described above has a relatively low boiling point, making it difficult to evaporate and separate it from highly crystalline polyolefin. It is the intention.

The third main effect of the present invention is that the concentration of acidic substances in the drying air stream can be reduced by contacting the highly crystalline polyolefin with the treatment gas of the present invention as described above in the normal drying process of highly crystalline polyolefin. As a result, corrosion of equipment around or after the drying process can be sufficiently suppressed.

The fourth main effect of the present invention is that the concentration of acidic substances derived from catalyst residues in highly crystalline polyolefin can be significantly reduced, resulting in the occurrence of cooling roll deposits during extrusion film forming (normal roll fouling). ), and the workability of film forming operations can be significantly improved.

The fifth main effect of the present invention is that the concentration of acidic substances in polyolefin can be significantly reduced, and as a result, the hue of polyolefin molded products is improved, and when a stretched film is produced, a film with extremely excellent transparency can be obtained. It is possible to obtain the following.

The transparency of a stretched film depends on the amount of microbubbles, usually called voids, in the film.

This relationship is shown in Table 1 and the Examples below.

The measurement of the number of voids in Table 1 was carried out in the same manner as in Example 1.

A commercially available film was used.

As can be seen from Table 1, there is a good correlation between the transparency of the stretched film and the number of voids.

Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not unduly restricted thereto.

Examples 1-3 Comparative Examples 1-4 Heptane 16 as solvent! Using 5 g of commercially available titanium trichloride and 6 g of diethylaluminum chloride as catalysts, 550 ml of hydrogen was charged into a 50 L autoclave at 6 k9/cm2G as a molecular weight regulator, and propylene was introduced at 70 C and 9 kg/cm2 G for 6 hours. A butane slurry was obtained by polymerizing polypropylene.

Next, 16 liters of pure water was added to the heptane slurry of polypropylene obtained by adding 500 ml of 1-butanol and stirring at 70°C for 15 hours to deactivate the catalyst, followed by stirring at 60°C for 2 hours.

When left to stand, the upper layer was a polypropylene Hepkun slurry and the lower layer was separated into two layers, an upper and lower layer, consisting of an aqueous phase.

After separating the lower layer, 11 liters of pure water was added again and the mixture was heated to 0.5 liters at 60°C.
Stir for hours.

Separate the aqueous phase and then separate the heptane phase containing the soluble polypropylene into a polypropylene-hebutane cake of about 4
I got kg.

0.65 kg of this polypropylene cake (polypropylene powder containing about 30% hebutane) was placed in a 50 cm long
It was placed in a fluidized dryer with a width of 50 cr and a height of 50 cr, and after contact treatment at a predetermined temperature for a predetermined time with a processing agent gas having the composition shown in Table 2, it was dried under reduced pressure at 50° C. to obtain crystalline polypropylene powder. was recovered.

The intrinsic viscosity of this polypropylene powder measured in tetralin at 135°C was 2.1 and the isotactic part was 9.
It was 8%.

To 100 g of this crystalline polypropylene powder, 0.29 g of 2,6-di-t-butyl-4-methylphenol and 0.19 g of calcium stearate were added as antioxidants, and the mixture was thoroughly mixed with a mixer. (roller cross line type, volume 60ml) at temperature 1
After mixing for 5 minutes at 90° C. and 5 orpm, the melt was cut and allowed to cool to obtain polypropylene pellets.

The obtained pellets were hot pressed (pressing temperature 220℃
) to a thickness of 300 μm (referred to as press sheet A) and a thickness of 2 mm (referred to as press sheet B), and then rapidly cooled at 40° C. to create press sheets.

A circular sample with a diameter of 50 mm was punched out from press sheet B and subjected to a fluorescent X-ray analyzer to measure the residual chlorine concentration in the polypropylene (referred to as FX analysis), and the results are shown in Table 2.

Next, press sheet A was used as a stretched original fabric, and stretched at a stretching temperature of 120°C and a stretching ratio of 4×4 using a research biaxial stretching machine manufactured by Iwamoto Seisakusho.
A stretched film with a thickness of about 15 μm was prepared by simultaneous biaxial stretching at a double speed.

The number of poids with a diameter of 10 μm or more per 1 cm 2 of this stretched film was counted by the phase contrast method (bright contrast, magnification: 100 times) using an optical microscope, and the results were calculated per 15 μm thickness, and the results are shown in Table 2.

Next, press sheet B was punched out to a size of 50 mm as a sample, and the hue was measured using a color difference meter manufactured by Nippon Denshoku Kogyo KK).

The hue of polypropylene can be represented by the degree of yellow coloring, and the b value is a measure of this, and the higher the value, the more intense the coloring, and the lower the value, the less colored it is, and it can be said that it is close to colorless. .

The results are shown in Table 2.

On the other hand, a part of the pellet was crushed and extracted with n-hebutane,
The amount of stearic acid produced by decomposition of calcium stearate was measured using gas chromatography and was used as a measure of the remaining active chlorine.

The results are shown in Table 2. Examples 4-6 Comparative Examples 5-8 Using heptane 16l as a solvent, 5 g of commercially available titanium trichloride and 6 g of diethylaluminium chloride as a catalyst, and hydrogen as a molecular weight regulator at 6 kg/cn2G, 550 ml was charged into a 501 autoclave. , propylene and ethylene (ethylene is 60°G, 9k9/cm2G
The amount introduced is controlled on average so that the total amount introduced under pressure is 5 liters.

) was introduced at 60° C. under 9 kg/cm 2 G for 6 hours to obtain polymerized heptane 7J of propylene-ethylene copolymer.

Next, 500 ml of 1-butanol was added, and 1.
After stirring for 5 hours to deactivate the catalyst, pure water 16! was added, stirred at 60°C for 2 hours, left to stand, then separated the lower aqueous phase, added 16 liters of pure water again, stirred at 60°C for 0.5 hours, left to stand, then separated the lower aqueous phase. did.

The heptane phase containing the soluble polypropylene is then separated to form a heptane cake of propylene-ethylene copolymer.
I got kg.

This heptane cake (contains about 40% hebutane) 0.
7kg was placed in a fluidized dryer measuring 50cr in length, 50cm in width, and 50cl in height, and after contact treatment with a treatment gas having the composition listed in Table 3 at a sufficient temperature for a predetermined period of time, it was dried under reduced pressure at 50°C. A propylene-ethylene copolymer powder was recovered.

135% of this propylene-ethylene copolymer powder
When measured in tetralin at ℃, the intrinsic viscosity was 2.6 and the isotactic part was 92%, and the ethylene content obtained as a result of analysis by infrared absorption spectroscopy was 4.
．． It was 0% by weight.

Table 3 below shows the results of evaluation by performing the same treatments as in Examples 1 to 3 and Comparative Examples 1 to 4.

Claims (1)

[Claims] 1. A catalyst in a polyolefin produced using a Ziegler-Natsuta catalyst is deactivated using a deactivating agent, and then the catalyst residue is extracted with water, and then mixed with water and a hydrocarbon medium. A method for purifying a highly crystalline polyolefin, which comprises bringing the polyolefin into contact with a processing gas consisting of 2-methyl-2-propanol in the step of drying the separated polyolefin. 2. The method for purifying a highly crystalline polyolefin according to claim 1, which comprises contacting the processing agent gas with an alkali-containing aqueous solution and/or an alkali-containing hydrocarbon solution after the contact treatment with the polyolefin.