KR20010062882A - Process for producing hiperpure polypropylene - Google Patents

Abstract

PURPOSE: Provided is a method for preparing hyperpure polypropylene using magnesium supported catalyst. The process is characterized in that alcohols are used to make magnesium complexes with the remaining catalyst, and the product is washed with liquid propylene to eliminate the complexes and low molecular weight substances in the polymer. Previously, the catalyst residues in hexane slurry are eliminated by washing with alcoholic (isopropanol) NaOH, thereby complicated after-treatment such as neutralization, washing and drying are needed and a large amount of wastewater is produced. The product manufactured by this process has low content of catalyst and low molecular residues and therefore it is used in dielectric film in condense, bottle for explosives, packaging film for semiconductor or hard disk and film for less corona aging. CONSTITUTION: The process comprises the following steps of: introducing polypropylene powder with 50-150ppm catalyst residue into a washing column of which ends is attached to 10u stainless steel filter; setting the column temperature at 30-80deg.C and pressure under 20-60 atm.; pouring 1:1 - 1:10 weight of alcohol; flowing liquid propylene into the column at 2.5ml/min. for 5-10 min. and finally washing down with liquid propylene alone at 2.5ml/min. for 10-40 min. to eliminate remaining residue.

Description

Production method of ultrapure polypropylene {PROCESS FOR PRODUCING HIPERPURE POLYPROPYLENE}

The present invention relates to a method of preparing ultrapure polypropylene that can be applied when using a magnesium-supported catalyst system, and more specifically, to form a trace residue of a catalyst contained in a polypropylene prepared by a magnesium-supported catalyst system with a catalyst residue. After reacting with alcohols, the present invention relates to a method for producing ultrapure polypropylene (Hiperpure PP) having a low content of catalyst residue and low molecular weight by washing the complex and the low molecular weight contained in the polypropylene with liquid propylene.

When polypropylene is polymerized using a supported catalyst system, a small amount of catalyst residue and low molecular weight are contained in the polymer. Catalyst residues vary in type and content depending on the method of polymerization of polypropylene. However, the catalyst residue contains about 200 ppm of catalyst residue in a high-activity polypropylene polymerization method using a magnesium supported catalyst. In addition, the polypropylene polymer polymerized using a Ziegler-Natta supported catalyst by a bulk or vapor phase polymerization reaction includes not only catalyst residues but also a small amount of low molecular weight bodies. Such a general polypropylene product is not known to be applicable to such products because it cannot satisfy the electric conductivity and stability required for a product having a condensation dielectric film and a chemical storage bottle.

In order to produce a product for this purpose, it is necessary to reduce the catalyst residue which may affect the properties of the product to 20 ppm or less, and at the same time, there should be little low molecular sieve that can leak to the surface during long-term use. Therefore, polypropylene for this purpose is called ultrapure polypropylene unlike general polypropylene.

The general method for producing ultrapure polypropylene is known as the deliming process of the slurry process. The catalyst residue contained in the polypropylene powder contained in the hexane slurry is replaced with sodium hydroxide (NaOH) and isopropanol (IPA). This method is a method that separates using a solution dissolved in), and a large amount of wastewater is generated during the manufacturing process and complicated post-treatment process (neutralization, washing, drying) requires a lot of manufacturing costs, and the existing gas phase Or it is difficult to apply in the plant that was polymerized in a bulk reactor because the investment cost must be newly entered.

US Pat. Nos. 3,271,380 and 3,356,669, etc., present a basic concept of removing catalyst residues into coordination ligands using compounds such as diketones or epoxides as methods that can be used during bulk polymerization, and US Pat. Nos. 4,053,697 Ho, etc. invented a method that can effectively apply the above process. However, the above method was found to be ineffective when applied to the polymerization of polypropylene by magnesium-supported catalyst system.

An object of the present invention is to improve the above problems, and to provide a method for producing ultrapure polypropylene having low catalyst residue and low molecular weight which can be applied during polypropylene polymerization by using a magnesium-supported catalyst system.

The method for preparing ultrapure polypropylene of the present invention is characterized in that ultrapure polypropylene is prepared by a process of washing alcohol with polypropylene prepared by a magnesium-supported catalyst system and then washing with liquid propylene.

The present inventors recognize that a new deliming method should be developed in a polyolefin polymerization process using a magnesium-supported catalyst system, and an organic magnesium complex (ML) is formed by reacting an organic substance to a magnesium catalyst residue (M) as shown in Equation 1 below. We have developed a process for the production of ultrapure polypropylene that can be applied to magnesium complex-based catalysts using the complex and the low-molecular weight of the low molecular weight contained in the polymerization process.

M (catalyst residue) + L (organic residue) ------> M-L (organic catalyst residue complex) .... Equation 1

The organic compound (L) used here should be capable of reacting with magnesium to form an organic magnesium complex (M-L) well, and the complex (M-L) should be a compound having a property of being well soluble in liquid propylene. To this end, in the present invention, alcohols may be used as the organic substance (L), preferably methanol, ethanol, propanol, or the like.

In the present invention, the reaction with alcohols and washing with liquid propylene may be performed by putting polypropylene into a refining machine, first flowing a mixture of alcohols and liquid propylene into the refining machine, and then sequentially flowing only liquid propylene. Can be.

In the bulk or gas phase process using a magnesium-supported high activity catalyst system, there is no residue about 200 ppm in the powder after polymerization unless there is a special deliming process. The present invention relates to a deliming process that can be used in a polypropylene process prepared using a magnesium-supported high activity catalyst system, wherein the polypropylene powder in the present invention refers to a powder obtained immediately after polymerization.

In a preferred embodiment of the method for producing ultrapure polypropylene of the present invention, a polypropylene powder (residual content of 50 to 150 ppm) synthesized using a Ziegler-Natta type high active magnesium supported catalyst system is placed in a purifier in a temperature of 30 to 80 ° C. and a pressure of 20 After setting to -60 atm, the amount of alcohols and liquid propylene is 1: 1 to 1:10, and 2.5 ml per minute is used for 2.5-10 minutes per minute to remove the remaining residues. Flow for 10-40 minutes.

Experimental apparatus for the implementation of the results of the production method of the ultrapure water polypropylene of the present invention can be used as a continuous type of the device of the type introduced in US Pat. No. 4,053,697 or a device modified from such a device, the practice of the present invention In the example, the following apparatus was manufactured and used.

The apparatus used in the embodiment of the present invention is a diameter (1/2 inch) X length (15 cm), filled with a polypropylene powder in a washing column with a 10 μ stainless steel filter (10 u SS Frit) attached to both sides, and Install a Piston Pump (HP, USA) and Syringe Pump (Havad, USA) to add alcohol, and back pressure regulator and valve at the end of the purifier. The pressure of the purifier was settable by the installation, and the temperature of the purifier was designed to be controlled by putting the purifier into an oven.

The present invention can be understood in more detail through the following examples and comparative examples, the following examples and comparative examples are not intended to limit the scope of the present invention but are described for illustrative purposes.

Experimental Example (Selection of Organic Matter)

Table 1 shows the results of investigating the solubility of the catalyst after the hexane slurry of a commercially supported magnesium supported catalyst was blown with hexane under a nitrogen atmosphere and an organic solvent (organic substance) was added in an amount of 10 times the amount of the catalyst. In Table 1, the generation of smoke (solubility: indicated as ◎) means that the metal oxide formed by the metal oxide and hydrochloric acid (vapor) by the reaction of the organic material and the catalyst cannot be washed away with liquid propylene. No dissolution (solubility: denoted by X) means no role.

Table 1.

Organic water Melting degree Remarks Kinds Product Name Magnesium Supported Catalyst TiCl _3- based catalyst Aqueous solution Distilled water ◎ ◎ Solvents applied to deliming process of slurry process 1% hydrochloric acid ◎ ◎ Alcohol ethanol O ◎ Isopropanol O ◎ Issuru Dioxane X O Dimethyls X O Ketones Acetone X O Solvent applied to deliming process of TiCl ₃ catalyst 2,4-pentadione X O Acetate Acetate X O

※ <Solubility> ◎: Steam generation (remains as metal oxide), O: Dissolution (in M-L state of Formula 1)

Present), X: undressed (remains catalyst)

As shown in Table 1, unlike the titanium trichloride (TiCl ₃ ) -based catalysts applied in the US Pat. have.

Example

10 g of polypropylene powder (MI = 2.0, catalyst residue content = 120ppm, low molecular weight content = 680ppm) produced using a Ziegler-Natta type high activity magnesium supported catalyst was placed in a reactor, and the temperature was set to 40 ° C., and the pressure was 40 The pressure was set. First, a piston pump and a syringe pump were used. The amount of ethanol and liquid propylene was adjusted to 2:10, and flowed for 10 minutes at a rate of 2.5 ml per minute, followed by 30 minutes at a rate of 2.5 ml per minute with liquid propylene alone.

After drying the polypropylene powder through this process it is shown in Table 2 to evaluate the content of catalyst residue and low molecular weight body. The content of catalyst residue was measured by weight change after burning for 2 hours at 800 ° C using an electric furnace, and the low molecular weight content was collected after volatile matter was collected at 180 ° C using gas chromatography equipped with a head space sampler. The low molecular weight content, which was analyzed by the flame ionization detector, was evaluated based on the content of n-Nonane. The low molecular weight analyzed in this way refers to the total amount of the wax or liquid compound having 30 or less carbon atoms in the polypropylene.

Comparative example

The same procedure as in Example was conducted except that 2,4-pentadione was used instead of ethanol.

TABLE 2

division Purified solvent Evaluation Item Catalyst residue (ppm) Low molecular weight (ppm) Before removal - 120 680 Example Ethanol / propylene 18 <1 Comparative example 2,4-pentadione / propylene 110 <1

According to Table 2, it can be seen that the polypropylene prepared through the example is ultrapure polypropylene in which the catalyst residue is more than five times higher than the conventional one and the low molecular weight is not included at all.

The 2,4-pentadione used in the comparative example did not play any role in removing the catalyst residue from the polypropylene synthesized with the magnesium carrier, and instead, only the low molecular weight removal effect by the liquid propylene was shown.

As can be seen from the above, the ultrapure water polypropylene prepared according to the method of the present invention has a very low content of catalyst residue (<20 ppm) and a low molecular weight content (<1 ppm) that can be volatilized at a high temperature. It can be used for applications requiring higher physical properties, such as films for use, chemical storage bottles, films for precision electronics such as semiconductor or hard disk packaging films, coronas that can be stored at high temperatures for a long time, or films with little change over time.

Claims (3)

A method for producing ultrapure polypropylene, characterized in that the polypropylene prepared on a magnesium-supported catalyst system is poured into a refiner, and after flowing a mixture of alcohols and liquid propylene, only liquid propylene is passed back into the refiner. The method of claim 1, wherein the mixture of alcohols and liquid propylene is a mixture of alcohols and liquid propylene in a weight ratio of 1: 1 to 1:10. The method for producing ultrapure polypropylene according to claim 1, wherein the alcohols are methanol, ethanol or propanol.