JPH0549689B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polypropylene resin which is excellent in processability and has good physical properties in molded products obtained by stretching. Polypropylene has good rigidity, and especially when stretched, it has excellent tensile strength, so it is widely used in applications such as films and tapes. However, in order to obtain good strength, especially tensile strength, polypropylene with a relatively low melt flow index is usually selected, so a relatively large amount of energy is required when molding it, and from the point of view of energy saving. A propylene resin with good physical properties and excellent processability is desired. As a result of various studies, the present invention was completed by discovering that polypropylene having specific properties has good processability and also has good physical properties of stretched molded products. An object of the present invention is to provide a polypropylene resin which is excellent in processability and has good physical properties in molded products obtained by stretching. The present invention is based on (a) a high molecular weight region, a low molecular weight region, an intermediate molecular weight region, centered on the peak position of a molecular weight distribution curve measured by gel permeation chromatography, and the vertical axis is the elution amount and the horizontal axis is the natural logarithm of the molecular weight. Mw/Mn is 8 or more on the high molecular weight side and 10 or less on the low molecular weight side when approximated by a Gaussian distribution for each weight range, (b) Isotactic pentad fraction measured by ¹³ C-NMR is 0.95 That's all,
Melt flow index measured at 230℃ is 0.2
The present invention relates to a polypropylene resin for stretching that has good processability of 20 to 20. The polypropylene resin of the present invention has high stereoregularity, and the isotactic pentad fraction measured by ¹³ C-NMR (400MHz) is A Zambelli.
Assigned by Macromolecules 8 687
(1975), and is a value determined by the area ratio of each peak of methyl carbon. If the pentad fraction is less than 0.95, the polypropylene resin will lack rigidity and tensile strength, which is not preferable. The preferred range is about 0.95 to 0.99. The molecular weight distribution of the polypropylene of the present invention is a value measured as follows. Measured by gel permeation chromatography (e.g. Shodex A-column at 135°C with 1,2,4-trichlorobenzene as the mobile phase).
Measured using two 80M wires. ) Using a chromatograph, as shown in the figure, the molecular weight distribution curve, where the horizontal axis is represented by the natural logarithm of the molecular weight and the vertical axis is represented by the elution amount, is divided into three parts, and Gaussian is calculated for the high molecular weight side peak and the low molecular weight side, respectively. Obtained by approximating the distribution. The method of approximating the molecular weight distribution with a Gaussian distribution is described, for example, in the Journal of Chromatographic Science.
It is explained in detail in Vol20 June 1982 252. That is, the molecular weight distribution curve is approximated by the following formula. Y=Ym・exp [−(X−Xm) ² /2S ² ] Y: Height when natural logarithm of molecular weight (1n (molecular weight)) X. Ym: The height when the natural logarithm of the peak molecular weight (1n (peak molecular weight)) Xm or the peak height calculated to match the boundary point when divided into three. S=√1 (weight average molecular weight number average molecular weight) Accordingly, weight average molecular weight/number average molecular weight, ie, Mw/Mn is calculated. Among the above ratios determined in this way, it is the value on the high molecular weight side that has a large effect on processability, 8
It needs to be more than that. Preferably, it is 8 to 25; if it is less than 8, the improvement in workability is insufficient;
Above this, a decrease in physical properties can be seen. The ratio on the low molecular weight side has a great effect on the appearance of the molded product, and if it is more than 10, the surface condition will be poor and undesirable. The preferred range is 4-10. The resin of the present invention is preferably used for drawing, and is suitably used as film grade and flat yarn grade. The polypropylene resin of the present invention can be produced by various methods, but one example is a highly stereoregular catalyst system consisting of a titanium tetrachloride catalyst supported on various known magnesium chlorides and an organoaluminum compound. It is preferable to use a catalyst system that provides polypropylene, and in some cases, an ester compound is added to form a catalyst system that provides highly stereoregular polypropylene. This is a bulk polymerization method using the above catalyst system and using propylene itself as a liquid medium, and it is also performed at relatively high temperatures, i.e. 65
It is obtained by polymerizing propylene at a temperature of ~80°C and then removing the propylene-soluble, low stereoregular polypropylene with a low boiling hydrocarbon such as propylene. The polypropylene resin of the present invention can be used as a resin for stretching films, flat yarns, etc.
The resulting molded product has high rigidity and tensile strength, requires less energy during molding, and surprisingly can be stretched even with relatively low molecular weight polypropylene (those with a high melt flow index). This is a matter of extremely high industrial objection. EXAMPLES The present invention will be explained in more detail with reference to Examples below. Example 1 1 Synthesis of catalyst A vibratory mill equipped with four crushing pots each having an internal volume of 4 and containing 9 kg of steel balls with a diameter of 12 mm was prepared. 300 g of magnesium chloride in each pot under nitrogen atmosphere,
60 ml of tetraethoxysilane and 45 ml of α, α, α-trichlorotoluene were added and pulverized for 40 hours. Add 3 kg of the above-mentioned pulverized material and 20 kg of titanium tetrachloride to a fully dried autoclave with a nitrogen atmosphere.
After stirring at 80°C for 120 minutes, the supernatant liquid was removed by standing still, and then 35% of n-heptane was added, stirred at 80°C for 15 minutes, left standing, and the washing operation to remove the supernatant liquid was performed for 7 days.
After repeating this process several times, 20 ml of n-heptane was further added to form a solid catalyst slurry. A portion of the solid catalyst slurry was sampled, n-heptane was evaporated, and analysis revealed that the solid catalyst contained 1.9 wt% titanium. 2. Polymerization Reaction 25 kg of propylene was charged into a jacketed autoclave which had been sufficiently dried, purged with nitrogen, and further purged with propylene. On the other hand, 500 ml of n-heptane, 2.6 ml of diethylaluminum chloride, 1.4 ml of methyl p-toluate and 1 g of the above solid catalyst were placed in flask 1, stirred at room temperature for 1 minute, and then 0.5 ml of triethylaluminum was added. Pressed into autoclave. After charging hydrogen, run hot water into the jacket to bring up the internal temperature.
Polymerization was continued at 75°C while charging hydrogen so that the gas phase hydrogen concentration was 4 vol%. On the other hand, 3.5 ml of triethylaluminum dissolved in 56.5 ml of n-heptane was dissolved at 0.5 ml/min, and propylene was dissolved at 125 g/min.
Polymerization was continued for 2 hours while being continuously pressurized into the autoclave at a rate of min. After 2 hours, add 10ml of diethylene glycol monoisopropyl ether and stir at 60℃ for 30 minutes.Then, the inner diameter of the thin part is 10cm, the inner diameter of the upper thick part is 30cm, the length of the thinner part is 10m, and the upper thick part is 10cm long. 30 kg/h of slurry is poured into the top of a 2 m long countercurrent cleaning tower, and a cleaning solution with a composition of 95% propylene and 5% propane is poured from the bottom.
Introduce the cleaning solution at a rate of 40Kg/h, and pour the cleaning liquid from the top at 44kg/h.
Kg/h, slurry washed from the bottom 26Kg/h
The slurry was taken out through a double tube with an inner diameter of 3/4 inch and a length of 60 m, and then discharged into a cyclone maintained at atmospheric pressure to separate the polymer. The obtained polymer was further dried at 20 mmHg and 80°C for 4 hours to obtain 12 kg of powder. The obtained powder was evaluated by the method shown below. Evaluation was performed by using an extruder to form a film using a 40mm downward die (extrusion temperature 250℃, thickness 750μm)
Then, heat it at 150℃ for 60 seconds using a biaxial stretching machine manufactured by TM Long Co., Ltd. to obtain a stretching ratio (MD x TD) = 5 x 7.
The film was formed at a rate of 10 cm/sec and its physical properties were determined by the following method.・ Melt flow index (230℃, 2.16Kg)
(g/10min) JIS K7210 ・Haze (%) ASTM D1003 ・Young's modulus (Kg/mm) ASTM D882 ・Tensile strength (Kg/mm) ASTM D638 ・Heat shrinkage rate (%) Each at 120℃ x 15min according to ASTM D1206 It was measured. The results are shown in Table 1. Comparative Example 1 Commercially available highly active titanium trichloride catalyst 1.5
1 using g and 10 ml of diethylaluminum chloride.
The flask was charged with 500 ml of n-heptane and stirred, and then 10 g of propylene was charged and stirred for 1 hour. Next, 1 ml of diethylene glycol monoisopropyl ether was added and stirred, and then propylene 25
Kg in an autoclave and set the polymerization temperature to 60
11 kg of powder was obtained in the same manner as in Example 1, except that the temperature, hydrogen concentration was 5.5 vol%, and the polymerization time was 4 hours. Table 1 shows the results of a similar evaluation of this powder. Comparative Example 2 12 kg of powder was obtained by polymerization without using diethylene glycol monoisopropyl ether. The results of the similar evaluation are shown in Table 1. Example 2 15 kg of powder was obtained in the same manner as in Example 1, except that the amount of methyl toluate used was 1.2 ml. Table 1 shows the results of the same evaluation. Example 3 The procedure of Example 1 was repeated except that the polymerization temperature was changed to 72°C, and 10 kg of powder was obtained. A flat yarn was formed using this powder and its physical properties were measured. The flat yarn is 112mmφ (L/D) manufactured by Nippon Steel Corporation.
= 28), the original fabric was formed into a film using a 1700 mm downward T-die (extrusion temperature: 250°C, thickness: 160 μm), made into a 6 mm width using a slitter, and then stretched to a specified temperature at 100°C to 100 to 150°C. After annealing, the yarn was wound to form a yarn of approximately 1,100 denier and a width of 2.4 mm, and its physical properties were measured.
Measurement is strength (g/d) and elongation (%) is JIS L1073
I went to bed. The resin temperature of the extruder and the current of the main motor were set so that the molding speed was the same, and are shown in Table 2. Comparative Example 3 The same procedure as in Example 3 was carried out, except that the powder obtained in the same manner as in Comparative Example 1 was used, except that the polymerization temperature was 65° C. and the polymerization time was 3 hours. The results are shown in Table 2. Comparative Example 4 The same procedure as in Example 3 was carried out except that a powder obtained in the same manner as in Comparative Example 3 but without using a countercurrent washing tower was used. The results are shown in Table 2. Example 4 Example 3 except that the powder obtained in Example 1 was used.
It was evaluated in the same manner. The results are shown in Table 2. Comparative Example 5 Example 3 except that the powder obtained in Comparative Example 1 was used.
Table 2 shows the results of the same evaluation. Comparative Example 6 Polypropylene powder was obtained in the same manner as in Example 1, except that the polymerization temperature was 60° C. and the gas phase hydrogen concentration was 8 vol%. Table 1 shows the results of the same evaluation.
As shown in the table, there is no major difference in physical properties, but the surface of the stretched film is whitish and the surface condition is poor. Comparative Example 7 Evaluation was carried out in the same manner as in Example 3, except that the polypropylene powder obtained in Comparative Example 6 was used. The results are shown in Table 2. Although there was no significant difference in physical properties, the surface of the flat yarn was white and the surface condition was poor.

【table】

[Table] * Based on known methods

[Table] * Based on known methods

[Brief explanation of drawings]

The figure shows a molecular weight distribution curve measured by gel permeation chromatography and its three-division state, where the horizontal axis shows the molecular weight expressed in natural logarithm, and the vertical axis shows the elution amount. The left side of the horizontal axis is high molecular weight, and the right side is low molecular weight. a represents 1/3 of the high molecular weight range, b represents 1/3 of the intermediate weight range, and c represents 1/3 of the low molecular weight range.
3, the solid line shows the measured molecular weight distribution curve, the broken line shows the extrapolation to the peak of the approximate molecular weight distribution curve, the vertical axis shows the elution amount (height), and the horizontal axis shows the high molecular weight side on the left and the high molecular weight side on the right. The scale is 1n (molecular weight) on the low molecular weight side, and o indicates the peak and boundary point, respectively.

Claims (1)

[Claims] 1. A high molecular weight region and a low molecular weight region centered on the peak position of a molecular weight distribution curve measured by gel permeation chromatography, with the vertical axis representing the elution amount and the horizontal axis representing the natural logarithm of the molecular weight. When approximated by Gaussian distribution, Mw/Mn is 8 or more on the high molecular weight side and 10 or less on the low molecular weight side, and the isotactic pentad fraction measured by ¹³ C-NMR is A polypropylene resin for stretching that has a melt flow index of 0.95 or more and a melt flow index of 0.2 to 20 measured at 230°C and has good processability.