JPH05186600A - Method for mixing polypropylene resin - Google Patents

Abstract

PURPOSE:To enable the mixing of two polypropylene resins having greatly different mol.wts. CONSTITUTION:Two polypropylene resins having greatly different mol.wts. and intrinsic viscosities of which the ratio is at least 2.5 are mixed as follows: first the two resins are melt mixed in such amts. that the amt. of the resin having a higher viscosity is the same as or higher than that of the resin having a lower viscosity and then the resulting mixture is melt mixed with a melt of the lower-viscosity resin in an amt. lower than that of the mixture.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for mixing polypropylene resins. Specifically, it relates to a method for mixing polypropylene resins having different molecular weights.

[0002]

2. Description of the Related Art It is difficult to mix resins having greatly different molecular weights, especially when the proportion of resins having a large molecular weight is small, and it is difficult to sufficiently knead them. Attempts have been made to insert a fine mesh or introduce a sintered metal to give a large share, but this is not sufficient, and in general batch polymerization produces different polymers with different molecular weights, resulting in substantially different molecular weights. Blending of the polymers is done.

[0003]

However, the above-mentioned polymerization method also requires batchwise polymerization and cannot be used for the purpose of mixing the obtained polymers having different molecular weights. The method of introducing a metal requires a large amount of energy but its effect is small.

[0004]

Means for Solving the Problems The inventors of the present invention found that the method of mixing resins having different molecular weights without generation of lumps and solving the above problems is excellent, and that a specific method is excellent. completed.

That is, according to the present invention, in a method of mixing two polypropylene resins having an intrinsic viscosity ratio of 2.5 or more, the proportion of the resin having a high intrinsic viscosity is the same as or higher than that of the resin having a low intrinsic viscosity. A method for mixing polypropylene resins having different molecular weights, characterized in that a melt-kneaded product and a melted resin having a lower intrinsic viscosity in an amount smaller than the melt-kneaded product are further kneaded.

In the present invention, polypropylene resin means
Homopolymer of propylene, propylene and other C2-C2
Any of random or block copolymers with 20 α-olefins can be used, and the steric structure of the propylene unit is applicable to isotactic structure, syndiotactic structure, or atactic structure. ..

What is important in the present invention is to always mix a large proportion of a polymer having a large intrinsic viscosity measured with a tetrahydronaphthalene solution at 135 ° C. during the melt-kneading so that a polymer having a large molecular weight can be obtained. It is to prevent it from becoming particles. Therefore, in the mixture introduced into the kneading machine, the two polymers are mixed so that the polymer having a high intrinsic viscosity is larger than the polymer having a small intrinsic viscosity. Here, the ratio of the polymer having a high intrinsic viscosity and the polymer having a low intrinsic viscosity is 50:50 to 90:10, preferably 60:40 to 80:20.
Is. The ratio of the intrinsic viscosity of the polymer having a high intrinsic viscosity to that of a polymer having a low intrinsic viscosity is 2.5 or more, and when the ratio is less than 2.5, it is possible to perform sufficient mixing by ordinary mixing, and it is not necessary to apply the method of the present invention. There is no particular upper limit, but it is usually 20
It is a degree.

In the present invention, the melt-kneaded product is further mixed with a melt of a polymer having a small intrinsic viscosity. The mixing method can be carried out by introducing both from the side of the extruder and mixing, or by introducing them into a device in which a gear pump and a static mixer are combined.

The amount of the polymer having a lower intrinsic viscosity to be further mixed needs to be smaller than the amount of the polymer melt-kneaded. When the amount is increased, the polymer having a high intrinsic viscosity is formed into particles and mixed uniformly. Not done. By doing so, it is possible to mix a polymer having a large intrinsic viscosity in a ratio of more than 25%, but it is also possible to mix a polymer having a lower intrinsic viscosity, and by doing so, a polymer having a larger intrinsic viscosity can be prepared in a smaller ratio. It becomes possible to mix.

It is preferable that the temperature in the kneading machine is relatively low and the mixing is performed in a state where shearing is applied. Normal
The temperature is 160 to 300 ° C, preferably 180 to 280 ° C.

When an extruder is used as the kneading machine, it is preferable to use one having a relatively large L / D.
It is usually 50 to 500, preferably about 80 to 300.

There is no particular limitation on the method of introducing the additional polymer having a low intrinsic viscosity, but an extruder smaller than the main body or a structure having only a heating zone and a gear pump is generally used.

[0013]

EXAMPLES The present invention will be further described with reference to the following examples.

Example 1 Two kinds of commercially available polypropylene (trade name: Mitsui Noblene, manufactured by Mitsui Toatsu Chemicals, Inc.) were prepared. One has an intrinsic viscosity of 2.8
5 is EP grade and the other is 1.10 J4H grade. Using the 65 mmφ extruder equipped with a 40 mmφ extruder on the side of these 2 grades, the mixture of EP grade and J4H grade at 50:50 is extruded at 40 kg / h, while J4H grade is 40 kg / h from the side. Was introduced, mixed and granulated. Here, the temperature of the kneading part was 220 ° C. A film having a thickness of 30 μm was formed from the obtained pellets, and the film was uniform.

Comparative Example 1 EP grades used in Example 1 and J4H grades were mixed at a ratio of 20:60 and once kneaded at 220 ° C. in an extruder. Many spots were observed and the film was not uniform.

[0016]

By carrying out the method of the present invention, polypropylenes having greatly different molecular weights can be mixed, which is extremely valuable industrially.

Claims (1)

[Claims] 1. A method of mixing two polypropylene resins having an intrinsic viscosity ratio of 2.5 or more, in which a mixture of resins having a high intrinsic viscosity is the same as or higher than a resin having a low intrinsic viscosity and melted. A method for mixing polypropylene resins having different molecular weights, characterized by further kneading a kneaded product and a melted product of a resin having an intrinsic viscosity smaller than that of the melt-kneaded product.