JPS58173141A - Production of polypropylene resin composition for extrusion/stretching - Google Patents

Abstract

PURPOSE:To produce the titled compsn. having excellent extrudability and stretchability, by polymerizing two kinds of propylene polymers having different melt flow in dexes (MFI) in two or more stages. CONSTITUTION:Propylene and not more than 7wt% ethylene are polymerized in the presence of a catalyst consisting of an org. Al compd. an electron-donating compd. and a solid catalyst composed mainly of TiCl3 to obtain 60-95wt% propylene polymer (random copolymer) having an MFI of 0.02-5g/10min. Then hydrogen concn., polymn. temp., polymn. time and ethylene concn. are adjusted to produce 40-5wt% propylene polymer (random copolymer) having an MFI of 50-1,000g/10min and an ethylene content of 4wt% or lower. As a result, there can be obtd. a PP resin compsn. for extrusion/stretching which has a propylene content of 94wt% or above and an MFI ratio of 10kg load MFI to 2.16kg load MFI of 22-38.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a polypropylene resin composition having a wide molecular weight distribution. More specifically, the present invention relates to a method for producing a polypropylene resin composition that enables the production of a stretched product with excellent extrusion moldability and stretchability.

For example, a polypropylene biaxially stretched film is required to have a balance between transparency and blocking properties, as well as ease of stretching (easy stretchability) and stiffness. Proposed methods to satisfy these properties include mixing modifiers such as olefin wax and petroleum resin, copolymerizing other comonomers, and mixing different types of polymers such as high-density polyethylene. However, all of them had the disadvantage that the rigidity of the film decreased.

As a result of intensive studies aimed at maintaining the rigidity of the film at a high level and further improving the ease of stretching, the present inventors have discovered a propylene-based polymer composition produced by the method specified in the present invention. was found to be particularly suitable for extrusion stretching, and the present invention was completed. That is, the present invention provides a method for homopolymerizing propylene or copolymerizing propylene and ethylene in two or more stages under different polymerization conditions within the same polymerization system, under a load of 230°C.
Melt flow index (hereinafter sometimes referred to as MFI) of 16 to 9 is 0.02 to 5 g 710 minutes, 60 to 95% by weight of a propylene homopolymer or random copolymer with an ethylene content of at most 7% by weight, and melt Flow index is 50-1000 g/l 0 min. It consists of polymerizing 5-40% by weight of a propylene homopolymer or random copolymer with an ethylene content of at most 4% by weight, and a melt flow index of 0.1-20g. /
A polypropylene resin composition for extrusion stretching having a melt flow index ratio (hereinafter sometimes referred to as MLMFI/MFI) of 22 to 38 at a load of 10 Kg and a load of 2,16 K9 for 10 minutes and a propylene content of at least 94% by weight. It's in the way things are manufactured.

The effects of the present invention are most noticeable in stiffness and stretchability. In terms of stiffness, the present composition, which has a mixture of high and low MFI, is greatly improved compared to conventional polypropylene of the same MFI. The higher the MFI of the second component and the greater its proportion, the greater the effect. The effect of improving stretchability is also almost the same.

When this composition is used unstretched, for example, in injection molding, it is not preferred because its impact resistance is lower than that of ordinary MFI products.

When the present composition is used in a polypropylene biaxially stretched film, the rigidity and easy stretchability are improved as described above, and when the composition according to the present invention is used in the production of a PP band, superior strength is obtained at the same stretching ratio. , and the stretch ratio has further improved (improved maximum stretch ratio)
In addition, after orientation in oriented blow molding, a strong molded product can be obtained. In addition, in sheet molding, when compared at the same extrusion rate (production volume) with a propylene polymer for sheets having a conventional molecular weight distribution, the polymer mixture with a widened molecular weight distribution according to the present invention provides a stronger sheet molded product. Demonstrates excellent effects such as

Polymerization is carried out in two or more stages with different concentrations of hydrogen relative to the monomer, and each stage may be divided into several polymerization tanks or carried out in the same polymerization tank. In the first step, MFI (230°C,
In 2.16, a propylene homopolymer with a content of 0.02 to 5 g/10 m or an ethylene propylene random copolymer with an ethylene content of 7% by weight or less (hereinafter sometimes referred to as the first component) is added to a polymer of 60 to 60% of the total polymerization amount. Produce 95% by weight. In the second stage, MFI (230
℃, 2.16 Kf) 50 to 1,000 g/10% propylene homopolymer or ethylene/propylene random copolymer with an ethylene content of 4% by weight or less (hereinafter sometimes referred to as the second component) to the total polymerization amount. It is produced in an amount of 5 to 40% by weight. If the MFI of the first component is lower than 0.02 g/10 min or the MFI of the second component exceeds 1,000, the miscibility with the second component will be poor and the homogeneity of the composition will be poor. It becomes impossible to achieve the desired effects of the invention.

Further, when the MFI of the first component exceeds 5 or the MFI of the second component becomes less than 50, the MLMFI of the composition
/MFI ratio becomes difficult to maintain at 22 or more.

Note that the first stage and the second stage may be manufactured in the reverse order. Usually, if necessary, known deashing treatment and APP removal treatment are performed, and desired additives are added and kneaded to obtain pellets. The polymerization reaction can be carried out by slurry polymerization, solution polymerization, gas phase polymerization, or a combination thereof.
Any known polymerization reactor can be used accordingly. When performing slurry polymerization using a polymerization solvent, any propylene monomer, saturated hydrocarbon, aromatic hydrocarbon, etc. can be used, and the polymerization temperature is 20°C to 120°C.
The trenching is carried out at a temperature of 40°C to 90°C. Solid catalysts for copolymerizing propylene used in the present invention, including titanium trichloride as a main component, such as A type, AA type, HA type, and other titanium trichlorides, and electron-donating compounds and/or Activated with a metal halide compound; Sometimes these are pulverized, or treated with a magnesium compound (e.g. magnesium halide, magnesium hydroxide, etc.) and a titanium compound containing trivalent or tetravalent 7. , a solid catalyst for producing isotactic polypropylene can optionally be used. The organoaluminum component as a promoter component is not particularly limited as long as isotactic polypropylene can be produced in combination with the solid catalyst, but titanium trichloride is the main component. In the case of a solid catalyst, aluminum chloride or a combination thereof with an electron donating compound is used, and when it contains a magnesium compound, it is preferably used mainly with a trialkyl aluminum compound or a combination thereof with an electron donating compound. It will be done. As a result, MFIo, 1 to 20 g/10 min, ethylene content 6% by weight or less MLMF I (:230°tOKg)/
A propylene homopolymer or an ethylene/propylene random copolymer or a polymer mixture of both having an MF'I ratio of 22 to 38 can be obtained and used for extrusion and stretching. The propylene resin composition according to the present invention is suitable for extrusion stretching, such as -axial or biaxial stretching, polypropylene film, inflation biaxial stretching polypropylene film, polypropylene band, oriented flow, sheet, and the like. There are no particular restrictions on these molding methods, and any known method can be used.

Next, the present invention will be explained in more detail by giving Examples and Comparative Examples.

Example-1 Titanium tetrachloride in heptane was reduced with diethylaluminum monochloride at -5 to 0°C, washed with heptane, treated with inamyl ether, and subsequently treated with titanium tetrachloride. 3.3 g of solid catalyst as main components, 20 g of diethylaluminum monochloride, and triphenyl phosphite 3I were charged into a 1501 autoclave purged with nitrogen, and 4 g of propylene was charged.
After introducing 2 kg, polymerization was carried out at 70°C for 1 hour as the first step. At this time, the hydrogen concentration in the liquid was 20% relative to propylene.
It was omolppm. After one hour, a food sample was taken out and measured, and the MFI was 0.26g/10-Gloductivity of the solid catalyst was 4,320El/
It was l/. Subsequently, as a second step, hydrogen was further supplied to bring the hydrogen concentration in the system to 4.00 omOxppm, and polymerization was carried out at 70° C. for an additional 30 minutes. Polymerization was stopped by purging the propylene monomer and deashed by washing twice at 90°C with n-butanol containing 5 volumes of heptane, resulting in a white powder polymer 19.2
I got Kf. The MFI of this one is 1.32 g7'io
m Productivity is 5,92411/g
Based on the product ratio, the ratio of the amount of polymerization in the second stage to the total amount of polymerization was 27.2%. For reference, when only the second stage of polymerization was carried out, the MFI was 340 g/10-.

The MFI of the pellets obtained by pelletizing the above powder using a 50 mm diameter extruder is 1.42 g/1O-is MLMFI/M
The FI was 28, and the polypropylene band was extruded and stretch-molded at a forming speed of 75 m/m while changing the stretching ratio using a 100°C steam-heated two roll stretching device attached to a 55 x φ extruder. did. The cylinder temperature of the extruder is 210°C in the first zone, 210°C in the second zone, 210°C in the first zone, and 220°C in the die.
The extrusion amount was 14 kg/hour when extruded at a motor rotation speed of 60 rpm at ℃. The extruded original fabric was stretched 8 times to a width of 15 m.

A band with a thickness of 0.6 wm was obtained. The strength was measured using a Schopper type tensile tester and was found to be 220 kg.

Also, 222 kg for 8.5 times stretching and 23 kg for 12 times stretching.
It was 0 to 7.

Examples 2 and 3 Polypropylene bands were manufactured in the same manner as in Example 1 by changing the MFI and polymerization ratio of each stage as shown in the table, and polypropylene bands were molded and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 Same as Example 1, but only in the first stage, 1.5 at 70°C
Polymerized for hours. At this time, the H2 concentration relative to propylene was 440 mOII) pm. The MFI of the obtained white pellets was 140. NiLIMFI/MFI used as a guideline for molecular weight distribution was 19.6.

It was extruded using a band forming machine in the same manner as in Example 1, and the time was 14-4 hours at a motor rotation speed of 6 oorpm. The strength of the band obtained by stretching the extruded original fabric 8 times was 190 kg. Furthermore, when the film was stretched 8.5 times or more, it was not stretched and was cut.

Comparative Examples-2, 3, 4 0 Same as Example-1 except that the first stage MFI was 07B.
25% by weight of the total polymerization amount was polymerized under the conditions of 9/10 #III+. As a result of purification and pelletization in the same manner as in Example 1, MF I 1.37 g/10 = + MLM[;”I/M
A white pellet with FI=212 was obtained. (Comparative Example 2) 0 Also, in the same manner as in Example-1, however, the first stage MFIO, 9'
4.9/10 m was polymerized at 96% by weight of the total polymerization amount, and in the second stage, 4% by weight of the total polymerization amount was polymerized under conditions of MFI 120g/10#th. Purification pelletization was carried out in the same manner as in Example-1, MFI 1.46.9/10, MLMFI
/I got a beret with an MFI of 20.7. (Comparative example 3)
0 Next, the same as in Example-1, except that the first stage MFIO, 1
0g/10-49.8% by weight of the total polymerization amount, M in the second stage
The total polymerization amount (D50.2% by weight) of FI 170g/10- was polymerized and pelletized in the same way to obtain MFI 1.31/10-
A pellet of 10 mm MLMF I/MF I = 34.2 was obtained. (Comparative Example 4) Next, PP bands were formed from these in the same manner as in Example 1, and evaluated. The results are shown in Table 1.

Example 4 Same as Example 1 using 3.4 g of the same solid catalyst as in Example 1, except that ethylene was added at 15.4.9 times 12 times every 5 minutes.
Feed L divided into times, H2 concentration is 340 molpp
The first stage was polymerized for 60 minutes at m. At this time, a small sample was taken out and the MFI was 0.62I/10-ethylene content was 1.2% by weight.Productivity was 4.
It was 420 g/y. Subsequently, as a second step, polymerization was carried out at the same temperature for 20 minutes at an H2 concentration of 3.200 moAI) pm. The propylene and ethylene monomers were purged to terminate the polymerization, and the mixture was purified and dried in the same manner as in Example 1 to obtain white powder No. 18.7 and 9. The MFI of the pellets pelletized in the same manner as in Example 1 was 1.74. ! 9/10
Tomi Echi L/7 content 0.95% MLMFI/MFI is 2
5.4-1 Song.

In addition, when polymerization was carried out under the conditions of only this second stage, MFI
is 185. ! It was 9/10-. Further, the ratio of the second stage polymerization amount to the total polymerization amount was 20.5% by weight.

This was supplied to a 40%φ extruder and extruded from a T-die heated to 260°C onto a casting roll at 30°C to obtain an extruded film with a thickness of 70μ and a width of 300m+.

The film was stretched longitudinally at 135°C between two rolls with different circumferential speeds, and then stretched at 160°C with a tenter.
It was stretched in the transverse direction, and the state of longitudinal/horizontal stretching was observed. The results are shown in Table 2.

Example 5 In the same manner as in Example 1, the hydrogen concentrations in the first and second stages were changed to produce a first stage MFI of 0,82, 9/10M and a second stage MFI of 340. ! MFI of i+/10mg two-stage polymerization ratio 267% composition 1.969/101I! =
MLMFI/MFI=268.

Table 2 shows the results of observing the stretched state of the film in the same manner as in Example 4.

Comparative Example-5 Same as Comparative Example-1 except that a small amount of ethylene was fed and the hydrogen concentration was changed to obtain an MFI of 1.80. ! Pellets with an i'/10 ethylene content of 0.90% by weight were produced.

Comparative Example-6 Same as Example 1, except that the hydrogen concentration and polymerization time in each stage of the first stage and second stage were changed, and the first stage MFI was 1.68 g/10.
-Second stage MFI 170.9/10==-, second stage polymerization ratio 4.1% pellet MFI 1.869/10j
thMLMFI/MF I = 20.3.

Table 2 shows the results of observing the stretched state of the film in the same manner as in Example 4.

Biaxial stretching characteristics A: Smooth stretching with no stretching cracks and uneven thickness B; Can be stretched but with uneven thickness C; Stretching was barely possible D: Unstretchable Example-6 Used in Example 1 The melt tension of the pellets at 230'C was 3.4 g, and the pellets were transferred to a stretch blowing machine with an in-line screw injection unit at a nozzle temperature of 2.
A bottomed parison was injection molded at 30° C., and the parison cooled to 60° C. was reheated to 150° C. to perform stretch blow molding into a 200 ml container.

The stretching ratio was 120% in the longitudinal direction and 400% in the transverse direction.

The molded product had no uneven thickness or deformation, and the surface of the molded product was free from roughness.

Comparative Example-7 When the same procedure as in Example 6 was carried out except that the pellets used in Comparative Example 1 (melt tension at 2300 was 2.8 g) were used, the molded product lost its shape and was molded. It was impossible.

Claims (1)

[Claims] In a method of homopolymerizing propylene or copolymerizing propylene and ethylene in two or more stages by changing polymerization conditions within the same polymerization system, the melt flow index is 0.02 to 59710 minutes and the ethylene content is at most 7.
60-95% by weight of a propylene homopolymer or random copolymer, and a propylene homopolymer or random copolymer with a melt flow index of 50-1000 g/10 min and an ethylene content of at most 4% by weight. Consists of 5-40 weight multipolymerization, melt flow index 0.1-20g/10 minutes, load 10K
The ratio of melt flow index of g to load 2.16 Kp is 22 and 38, and the propylene content is at least 94 wt.
A method for producing a polypropylene resin composition for extrusion stretching.