JPS6053510A - Polypropylene resin for drawing - Google Patents

Abstract

PURPOSE:Polypropylene resin for drawing, consisting of polypropylene having specific properties, having improved processability, capable of giving molded articles having good physical properties, and useful for films and tapes such as film grade, flat yarn grade, etc. CONSTITUTION:Polypropylene resin, obtained by polymerizing propylene in the presence of (A) titanium tetrachloride catalyst supported on magnesium chloride, and having >=8MW/MN on the high-molecular weight side and <=10MW/MN on the low-molecular weight side, obtained by measuring the molecular weight by gel permeation chromatography, and approximating the molecular weight from the molecular weight distribution curve, prepared by plotting the amount eluted versus the molecular weight expressed in natural logarithm with the peak position as a center, and dividing the curve into the high-molecular weight, low- molecular weight and medium-molecular weight regions using the Gaussian distribution and >=0.95 isotactic pentad measured by <13>C NMR. EFFECT:Even low-molecular weight polypropylene can be drawn.

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, and therefore a relatively large amount of energy is required during the molding process. A propylene resin with good physical properties and excellent processability is desired.

As a result of various studies, the present invention was completed after discovering that polypropylene having specific properties has good processability and also has good physical properties of stretched molded products.

The object of the present invention is to measure polypropyl resin roughy, which has good physical properties of molded products obtained by stretching and is characterized by its additive properties, and the vertical axis represents the elution amount, and the horizontal axis represents the natural logarithm of the molecular weight. High molecular weight region centered around the peak position of the molecular weight distribution curve,
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 Gaussian distribution for each of the low molecular weight range and intermediate weight range. The present invention relates to a polypropylene resin for stretching that has excellent processability and is characterized by having a polypropylene resin of 0.95 or more.

The polypropylene resin of the present invention has high stereoregularity, and the isotactic bentanod fraction measured by 6ONMR (400MH2) was assigned by A Zambcil et al.
87 (1975), N M i (
, 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. 1.2 at 1358C).
4 to 5 as a column with trichlorobenzene as a mobile phase
Measured using two hodeX A-80'M.

) Using Chromadog 27, as shown in the figure, the molecular weight distribution curve, in which 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 a Gaussian distribution is created around the peak on the high molecular weight side and on the low molecular weight side, respectively. Approximate it.

For example, the method of approximating the molecular weight distribution with a Gaussian distribution is as follows:
urnal of chromatographic
5ciencevol 20 June 198225
2 is explained in detail.

That is, the molecular weight distribution curve is approximated by the following formula.

Y = Ym, exp (-(X-XnJ/2FfEY
;Natural logarithm of molecular weight (In (molecular weight))
The peak height calculated to match the height at m or the boundary point when divided into three. )S-1l] (Weight molecular weight -7
-17 number (noteable molecular weight), weight average molecular weight/number average molecular weight, ie, Mw/MH is calculated. Of the above ratios thus determined, it is the value on the high molecular weight side that has a large effect on processability, and must be 8 or more.

Preferably, it is 8 to 25; if it is less than 8, the improvement in processability is insufficient, and if it is more than 25, a decrease in physical properties is observed.

The ratio of low molecular weight side has a great influence on the appearance of the molded product.
If it is 0 or less, the surface condition is poor and undesirable. The preferred range is 4-10.

The resin of the present invention is preferably used for stretching, 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 to give an example, the polypropylene resin with high stereoregularity is used among the catalyst systems consisting of a titanium tetrachloride catalyst supported on magnesium chloride and an organoaluminum compound. It is preferable to use a catalyst system that provides polypropylene with high stereoregularity, and in some cases, an ester compound is added to form a catalyst system that provides polypropylene with high stereoregularity.

This is a bulk polymerization method using propylene itself as a liquid medium using the above catalyst system, in which propylene is polymerized at a relatively high temperature, that is, 65°C to 80°C, and then a low boiling point hydrocarbon such as propylene is used to polymerize propylene. Obtained by removing stereoregular polypropylene.

The polypropylene resin of the present invention can be used as a resin for stretching films or flat yarns, etc., so that the resulting molded products have high rigidity and tensile strength, require less energy during molding, and surprisingly have a relatively low molecular weight. This is of extremely high industrial significance as it is possible to stretch even polypropylene (with a high melt flow index).

EXAMPLES The present invention will be explained in more detail with reference to Examples below.

Example 1.2 and Comparative Example 1.2 Biaxially stretched films were formed using the polypropylene resins shown above, and their physical properties were measured.

4. The biaxially stretched film was produced using a biaxially stretched machine manufactured by TM Long Co., Ltd. Q m/m Form the original fabric into a film with a downward die (extrusion temperature 250°C, thickness 750μ) L Heating at 150°C for 60 seconds, stretching ratio (MDxTD) = 5 X7 Film forming at a drawing speed of 10 cm/sec Physical properties The value was measured by the following method.

Melt flow index, 9-/I Qtnin 2
Measured at 30°C2, 16kg load JISK7210 haze, ASTM D1003% Young's modulus,
ASTM I) 882 kg/in♂ tensile strength,
AS'l"M I) 638 k!//++ui' Heat shrinkage rate, 120°CX15 according to ASTM 1) 1206
The results are shown in Table 1.

Example 3.4 and Comparative Examples 3 to 5 Poor 1-h cow A flat yarn was formed using the polyglobint r1 fat shown in Table 2, and its physical properties were measured.

The flat yarn is 112mmφ (L/■) manufactured by Nippon Steel Corporation.
-28) Extruder with a 1700 x 1700 x 100mm downward die to form a film (thickness: 160μ at extrusion temperature of about 250°C)
After cutting the yarn to a width of 6 mm using a slitter, it was stretched to a specified temperature at 100°C, annealed at 100 to 150°C, and then wound to form a yarn of approximately 1100 denier and a width of 2.4 mm.
Physical properties were measured. ■ No Uta Tsuji 1 strength, JIS L-10739/d elongation, JIS L-1073% initial resistance, strength at elongation 5 The conditions were set so that the molding speed was the same, and the respective values are shown in Table 2.

It can be seen that although the conditions were relatively low temperature and low extrusion power, in the examples, products with good physical properties were obtained.

[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. On the left side of the horizontal axis, high molecular weight cloth has low molecular weight. a represents 1/3 of the high molecular weight region, b represents 1/3 of the intermediate weight region, C represents 1/3 of the low molecular weight region, the solid line is the measured molecular weight distribution curve, and the broken line is 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 low molecular weight side on the right (scaled by molecular weight, O shows the peak and boundary point, respectively.

Claims (1)

[Claims] b) Divided into high molecular weight range, low molecular weight range, and intermediate weight range around the peak position of the molecular weight distribution curve measured by Köl permeation chromatography and showing the elution amount on the vertical axis and the natural logarithm of the molecular weight on the horizontal axis. The isotactic pentad fraction measured by NMR must be 0.95 or more. Polypropylene resin for stretching with good processability.