JPH05239149A - Production of highly fluidic polypropylene resin for injection molding - Google Patents

Abstract

PURPOSE:To obtain the subject resin with high elongation at break, suitable for injection molding by multistage polymerization of propylene using a stereoregular catalyst with the respective stages differing in hydrogen concentration from one another. CONSTITUTION:The objective resin can be obtained by (A) multistage polymerization using a stereoregular catalyst with the respective stages differing in hydrogen concentration from one another, (B) polymerization using a catalyst with solid catalytic component being a Ti compound treated with a halogenated compound (pref. a carbon halide), or (C) polymerization under addition of an oxygen-contg. compound (pref. organic acid ester). This resin has the following characteristics: (1) melt flow index: >=10; and (2) in the molecular weight distribution curve determined by gel permeation chromatography (GPC) expressed by rectangular coordinates with the ordinate representing elution and the abscissa with natural logarithm of molecular weight, the curve is divided into high- molecular weight, low-molecular weight, and medium molecular weight regions around its peak and Mw/Mn in the high-molecular weight region approximated by Gaussian distribution from this distribution is >=6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polypropylene resin for injection molding which has a high melt flow index of 10 or more and has a high elongation at break.

[0002]

2. Description of the Related Art Polypropylene has been used in many applications because of its excellent rigidity and light weight. In recent years, high fluidity of resin and thin wall molding have been attempted to save resources and energy. There is.

It is most convenient to lower the molecular weight in order to make the polypropylene resin highly fluid, and when the propylene is polymerized to obtain polypropylene, a chain transfer agent such as hydrogen is added to lower the molecular weight, or It is known that high fluidity is achieved by a method of heating and mixing with a radical generator such as an organic peroxide to lower the molecular weight.

However, if the polypropylene resin is made highly fluid by simply lowering the molecular weight by the above-mentioned method, the elongation at break of the obtained resin becomes extremely small,
Therefore, the practical strength of the molded product is inferior.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a polypropylene resin having high fluidity and large elongation at break.

[0006]

The present invention provides a titanium compound obtained by carrying out polymerization in multiple stages using a stereoregular catalyst and varying the hydrogen concentration in each stage of the polymerization, or by treating with a halogen compound. The polymer has a melt flow index (MFI) of 10 or more, which is obtained by polymerizing using a catalyst having a solid catalyst component, or by adding an oxygen-containing compound during the polymerization, and gel permeation chromatography. Measured by (GPC), the vertical axis is the elution amount, and the horizontal axis is the natural logarithm of the molecular weight.
The present invention relates to a method for producing a highly fluid polypropylene resin having a large elongation at break, which has Mw / Mn of 6.0 or more when a high molecular weight region is approximated by a Gaussian distribution.

As the method for producing the polypropylene resin of the present invention, the molecular weight distribution of polypropylene obtained by polymerizing at a constant concentration under ordinary polymerization conditions, that is, with a constant hydrogen concentration in the gas phase is measured, and the molecular weight is determined by the method described below. The distribution curve is divided into three to obtain the molecular weight at the boundary point on the high molecular weight side, and the polymerization conditions are set so as to obtain polypropylene having a molecular weight such that the molecular weight distribution curve has a peak in the molecular weight range higher than the molecular weight. Usually, the conditions of the hydrogen concentration in the gas phase and the polymerization temperature may be set. The polypropylene resin of the present invention is subjected to two-stage polymerization in which the two conditions of hydrogen concentration and polymerization temperature thus determined (additional conditions for obtaining a higher molecular weight polypropylene) are used in the same polymerization system, for example, the hydrogen concentration is changed. It is obtained by doing. As a guide, the ratio of higher molecular weight polypropylene to the total polymer is 30.
Polymerization is carried out so as to be less than wt%, usually 30 wt% to 5 wt%.

Another preferred method is to use a catalyst system which gives a polymer with a large molecular weight distribution in the high molecular weight range. Although many excellent catalyst systems are already known, the molecular weight distribution of the polypropylene obtained for each catalyst system is unknown, so it cannot be clarified for all catalyst systems, but it is relatively high. As a catalyst system which gives a polypropylene having a wide molecular weight distribution in the molecular weight range, when a solid catalyst component obtained by treating a titanium compound with a halide, particularly a halogenated hydrocarbon is used as a titanium component, or when an oxygen-containing compound, particularly an organic compound, is used during polymerization. The reason for using an acid ester or a ketone compound is not clear, but a polymer having a wide molecular weight distribution in a high molecular weight region tends to be obtained. Particularly, an active titanium catalyst obtained by supporting titanium halide on a carrier obtained by treating magnesium halide with a halogenated hydrocarbon and an oxygen-containing compound as a catalyst system which gives a polymer having a wide molecular weight distribution in a high molecular weight range, A catalyst system consisting of an organoaluminum compound and an organic acid ester may be mentioned. When a catalyst system that gives a polymer having a wide molecular weight distribution in a relatively high molecular weight range as described above is used, the polymerization is carried out while maintaining constant polymerization conditions such as hydrogen concentration in the gas phase and polymerization temperature. However, the intended polypropylene resin can be obtained by the production method of the present invention.

In short, the method for producing a polypropylene resin according to the present invention comprises (i) a multi-step polymerization using a stereoregular catalyst, and different steps of hydrogen concentration for each step, or (ii) a halide. The treated titanium compound is polymerized using a catalyst having a titanium component, (iii) the polymerization is performed by adding an oxygen-containing compound during the polymerization, or (iv) magnesium halide is a halogenated hydrocarbon or oxygen-containing compound. A polymer having a melt flow index (MFI) of 10 was obtained by polymerizing using an active titanium catalyst obtained by supporting a titanium halide on a carrier obtained by treating with a compound, and a catalyst system consisting of an organic aluminum compound and an organic acid ester. The above is the peak position of the molecular weight distribution curve measured by gel permeation chromatography (GPC), in which the vertical axis represents the elution amount and the horizontal axis represents the natural logarithm of the molecular weight. High molecular weight region,
This is a method for producing a high-fluidity polypropylene resin having a large elongation at break, which has a Mw / Mn of 6.0 or more when a high molecular weight region is approximated to a Gaussian distribution by dividing it into a low molecular weight region and an intermediate region.

The polypropylene resin produced by the present invention is required to be a polypropylene having a relatively high stereoregularity because of the high rigidity which is the original characteristic of the polypropylene resin. The degree of stereoregularity is, for example, when a powder state before granulation is extracted with boiling n-heptane using a Soxhlet extractor for 10 hours. It is preferable that the boiling n-heptane extraction residual rate (II) calculated in step 7 is 70% or more and less than 98.0% of polypropylene or a copolymer of propylene and a small amount of ethylene, butene-1, or hexene-1. .. Above 98.0%,
The impact resistance is poor, which is not preferable.

In the present invention, MFI is ASTM D1.
Measured at 230 ° C according to 238 and expressed in units of g / 10 min. When MFI is 10 or less, the flowability is poor, and the effect of energy saving such as shortening of the molding cycle during injection molding and lowering of injection pressure. Cannot be realized. MF
The range of I is preferably 15-100.

In the present invention, GPC at 135 ° C.
The elution amount is measured as a difference in refractive index, using 2,4-trichlorobenzene as a solvent, for example, a column in which two Shodex A-80M (trade name) manufactured by Showa Denko KK is connected.

Mw / Mn in the present invention is calculated as follows. As shown in FIG. 1, the molecular weight distribution curve in which the horizontal axis is the natural logarithm of the molecular weight and the vertical axis is the elution amount is divided into three parts, and the molecular weight distribution curve in the high molecular weight range is approximated to a Gaussian distribution.

A method for approximating the molecular weight distribution by a Gaussian distribution is described in, for example, Journal of Chromatographic Science vol. 20 Ju
See ne 1982, 252 for more details. That is, the molecular weight distribution curve is approximated by the following formula: Y = Ym · exp [− (X−Xm) ² / 2S ² ] Y: height at natural logarithm (ln (molecular weight)) X of Ym: Natural logarithm of peak molecular weight (ln (peak molecular weight))
Peak height calculated so as to correspond to the height at Xm or the boundary point when dividing into three, S = √ (ln (weight average molecular weight / number average molecular weight)) By the above, the weight average molecular weight / number average molecular weight, That is, Mw
/ Mn is calculated.

In the present invention, it is necessary that Mw / Mn in the high molecular weight region measured and calculated by the above-mentioned measurement method is 6.0 or more in order to keep the elongation at break large, and if it is less than 6.0, for example, ASTM. The elongation at break as measured by D 638-64T is 200% or less, and particularly the high stereoregular polypropylene having II of 90% or more is 100% or less, which is not preferable. FIG. 2 shows how Mw / Mn in the high molecular weight range has a great influence on the elongation at break. MF is shown in FIG.
It has been shown that for polypropylene with I of 17 to 20 and II of 96% (propylene homopolymerized), the elongation at break changes significantly at Mw / Mn of 6.

[0016]

EXAMPLES The present invention will be further described below with reference to examples. Physical properties in Examples and Comparative Examples are values measured by the following methods: MFI (g / 10 min) ASTM D12
38 Tensile Yield Strength (kg / cm ² ) ASTM D63
8-64T Elongation at break (%) ASTM D63
8-64T Flexural Rigidity (kg / cm ² ) ASTM D74
7-63 Izod Impact Strength (With Notch) ASTM D25
6-56 MFI is 230 ℃, other properties are 8cm by injection molding machine.
An injection-molded sheet of x16 cm x 2 mm was produced and measured at 23 ° C.

Examples 1-3 and Comparative Examples 1-2 The catalysts used in the Examples and Comparative Examples were as follows: Catalyst (A): 20 g magnesium chloride, 1 ml ethyl orthoacetate and 1,2-dichloroethane. An active titanium catalyst obtained by contacting titanium tetrachloride with 4 ml of co-pulverized powder and then washing with n-heptane three times; Catalyst (B): Commercially available highly active titanium trichloride catalyst, Marubeni Solvay The company's TBN-05 (lot number) is used as it is.

The polymerization conditions used in the examples and comparative examples were as follows: Polymerization conditions (i): 2 g of the above active titanium catalyst (A), 6 ml of triethylaluminum, 8.5 ml of diethylaluminum chloride and p-toluyl. In the bulk polymerization method using propylene itself as a medium and using a catalyst composed of 4 ml of methyl acid, the hydrogen concentration was kept constant at 7.0 vol% in Example 1 and 10.1 vol% in Example 2. (Table 1
It is described in the section of the first-stage polymerization in the above.) Polymerization was carried out at 75 ° C. using a 1 m ³ polymerization machine, and then the catalyst was deactivated with isopropanol, followed by washing with propylene 3 times at 40 ° C. to obtain polypropylene. It was The yield of polypropylene was about 20000 g / g of activated titanium catalyst.

Polymerization conditions (ii): 100 g of the activated titanium catalyst (B) and diethylaluminum chloride 8
Polymerization was carried out at a total pressure of 10 kg / cm ² · gauge and 70 ° C. using n-heptane as a medium, using a catalyst consisting of 00 ml. At this time, in Comparative Example 1, the hydrogen concentration was kept constant at 21.0 vol% (described in the column of the first-stage polymerization in Table 1), and Example 3 was used.
Then, in the first-stage polymerization, the hydrogen concentration was 3.0 vol% and the total polymer amount was 8%.
Polymerization of 2% by weight, hydrogen concentration of 25.0 vol% in the second stage polymerization
92% by weight of the total polymer was polymerized with
In the first-stage polymerization, the hydrogen concentration was 15.0 vol% and 20% by weight of the total amount of the polymer was polymerized.
80% by weight of the total polymer was polymerized with ol%, the catalyst was deactivated with methanol after polymerization for 2 hours, and then repeatedly washed with water, and the n-heptane layer was removed by filtration to obtain polypropylene. ..

After drying the powder obtained under the above polymerization conditions (i) and (ii), a phenolic antioxidant (0.2% based on the weight of the powder) and calcium stearate (0.2% based on the weight of the powder). 1%) was added and granulated, then an injection-molded sheet was prepared and the physical properties were measured. The results are shown in Table 1.

[0021]

[Table 1]

[0022]

Industrial Applicability The polypropylene resin obtained by the production method of the present invention has excellent fluidity at the time of molding as polypropylene for injection molding, and has excellent characteristics that the obtained molded article has a large elongation at break. Yes, it is of industrial value.

[Brief description of drawings]

FIG. 1 is a drawing showing a molecular weight distribution curve and its dividing method, where a is a high molecular weight region, b is an intermediate molecular weight region, and c is a low molecular weight region.

FIG. 2 is a graph showing the relationship between Mw / Mn in the high molecular weight region and elongation at break, where Mw / Mn = 6.0 is indicated by a broken line.

Claims (1)

[Claims] 1. A catalyst comprising a titanium compound as a solid catalyst component, which is obtained by performing polymerization in multiple stages using a stereoregular catalyst and varying the hydrogen concentration in each stage of the polymerization, or treating with a halogen compound. The polymer has a melt flow index (MFI) of 10 or more when polymerized by using or by adding an oxygen-containing compound at the time of polymerization, and the melt flow index (MFI) is measured by gel permeation chromatography (GPC). Mw when the high molecular weight region is approximated by a Gaussian distribution by dividing the high molecular weight region, the low molecular weight region, and the intermediate region around the peak position of the molecular weight distribution curve where the axis is the elution amount and the horizontal axis is the natural logarithm of the molecular weight. A method for producing a high-fluidity polypropylene resin having a large elongation at break with / Mn of 6.0 or more.