JP2507509B2 - Method for producing opaque polypropylene film - Google Patents

Description

The present invention relates to a method for producing a stretched polypropylene film. More specifically, it relates to a method for producing a stretched film which is substantially composed of a propylene homopolymer and has a high degree of haze.

[Prior Art] Polypropylene is used in various applications because it has excellent rigidity and relatively excellent heat resistance. Among them, an extrusion-molded film, particularly a stretched film, is used in various applications. . On the other hand, due to the recent diversification of uses,
In addition to transparent films that take advantage of the inherent transparency of polypropylene, demand for opaque films is increasing.

This opaque film is used for applications such as giving a high-class feeling by covering the surface of printed matter, has a uniformly roughened surface as a haze film, and has a total haze of 10 to 70%, It is required that the internal haze is 5% or less and that it has appropriate heat resistance.

As a product that meets these requirements, special propylene-
A method is known in which an ethylene block copolymer and a propylene homopolymer are coextruded and stretched in at least one side (for example, JP-A-60-145845), but other physical problems such as poor heat resistance are involved. There was a problem that the manufacturing cost was high.

On the other hand, it is considered that an opaque film is produced from a homopolymer of polypropylene, and a method of adding a special core material such as quinacridone is known (JP-A-57).
-170908).

[Problems to be Solved by the Invention]

However, such a method has special manufacturing conditions,
In addition to problems in productivity, it was difficult to obtain a stretched film having a sufficiently high haze.

[Means for solving problems]

The present inventors diligently studied to solve the above problems,
The inventors have found that an extremely excellent stretched film having a large haze can be obtained by performing a specific treatment using a specific polypropylene, and completed the present invention.

That is, the present invention has a total haze characterized by stretching a sheet obtained by extrusion-molding a composition consisting of polypropylene and a polyalkylvinylsilane or polyalkylallylsilane of 1/1000 to 1/10000000 with respect to polypropylene.
A method for producing an opaque film of polypropylene having 10 to 70%, an internal haze of 5% or less, a thickness of 200 μm or less, and a melting point of 150 ° C. or more measured by a differential scanning calorimeter.

As polypropylene mainly constituting the present invention, in addition to polypropylene which is polymerized by using a generally known stereoregular catalyst, a very small amount of ethylene, for example, 0.01 to 3 wt.
Copolymers of about% can also be used. It is preferably a homopolymer of propylene, and is 90% or more, preferably 94% or more of the ratio II of the extraction residue after extraction with boiling n-heptane for 10 hours, and the limit measured with a tetralin solution at 135 ° C. It is preferable that the viscosity [η] is about 1.5 to 3.0.

Since the film of the present invention is manufactured using the polypropylene as described above, it naturally has a melting point of 150 ° C. or higher, usually 155 ° C. or higher, and is excellent in heat resistance.

The film of the present invention, the above-mentioned polypropylene, the alkyl group is methyl, ethyl group, propyl group, butyl group,
Pentyl group, vinyltrialkylsilane and allyltrialkylsilane such as hexyl group, for example, 0.1-1000 ppm of the polymer obtained by polymerizing using a stereoregular catalyst
After mixing to some extent, form a sheet by extrusion molding,
It is then stretched at a relatively high temperature to produce the desired opacity.

As described above, many catalyst systems are already known as stereoregular catalysts used for producing polypropylene or for polymerizing vinyltrialkylsilane or allyltrialkylsilane, and give polypropylene with high stereoregularity. Any catalyst system may be used, and a catalyst composed of a transition metal catalyst and an organometallic compound is generally used.

Specifically, a titanium compound, a chromium compound, a vanadium compound or the like is used as the transition metal catalyst, and a halogen compound of titanium is particularly preferable. For example, titanium trichloride is co-ground with an electron-donating compound as necessary. thing,
Titanium trichloride obtained by reducing titanium tetrachloride with organic aluminum is optionally treated with an electron donating compound. Further, those obtained by supporting this transition metal compound on a carrier such as magnesium chloride are also used.

Examples of the organometallic compound include organoaluminum, organolithium, organomagnesium, organozinc, and the like. In particular, trialkylaluminum, dialkylaluminum halide, organoaluminum such as alkylaluminum dihalide, and organomagnesium such as dibutylmagnesium and dihexylmagnesium. Is particularly preferable.

These propylene or vinyltrialkylsilanes,
The method for producing a polymer of allyltrialkylsilane is not particularly limited, and known ordinary polymerization methods using known various stereoregular catalysts, for example, solvent polymerization method, bulk polymerization method, gas phase polymerization method, etc. It can be adopted without any trouble, and the polymerization conditions are also normal conditions, that is, the polymerization pressure is atmospheric pressure to 100 k
g / cm ² gauge, normal temperature to 100 ° C is adopted as the polymerization temperature.

Prior to molding the film of the present invention, the above polypropylene is mixed with polytrialkylvinylsilane and polytrialkylallylsilane. At this time, these separately produced polypropylene and polytrialkylvinylsilane may be simply mixed with polytrialkylallylsilane, but firstly, polytrialkylvinylsilane and polytrialkylallylsilane are produced on a catalyst,
Produces a master powder containing polytrialkylvinylsilane or polytrialkylallylsilane by continuously polymerizing propylene with a catalyst which is still active, and mixing with polypropylene containing no other polytrialkylvinylsilane or polytrialkylallylsilane, After first producing a polytrialkylvinylsilane or polytrialkylallylsilane on a catalyst, a propylene may be polymerized subsequently with a catalyst having an active property so that the polytrialkylvinylsilane or polytrialkylallylsilane may be contained in a predetermined amount. As described above, it is preferable to polymerize propylene after the production of polytrialkylvinylsilane or polytrialkylallyl sila to produce a composition because the mixture becomes intimate.

The amount of polytrialkylvinylsilane or polytrialkylallylsilane used is usually 1:10 with respect to polypropylene.
It is about 000000 to 1: 1000, preferably about 1: 1000000 to 1: 10000, and there is no effect if the amount of polytrialkylvinylsilane or polytrialkylallylsilane is less than this range, and it is particularly effective if more than this range. Not necessarily economical.

The film of the present invention may further contain other additives,
It is of course possible to add stabilizers, slip agents, antistatic agents and the like.

In the present invention, the polypropylene containing the polytrialkylvinylsilane or the polytrialkylallylsilane obtained by the above-mentioned method is extruded to form a sheet and then stretched. Stretching may be uniaxial or biaxial, but by stretching at a relatively low temperature, a film having a highly roughened surface and having a uniformly roughened surface is obtained.

Here, the extrusion molding conditions are not particularly limited, and known ordinary conditions can be adopted. For example, the extrusion temperature is usually 180 to 300 ° C.

Further, as the stretching conditions, a relatively high temperature of 145 to 165 ° C. as a stretching temperature, which is higher than that of ordinary conditions, preferably 150.
It is common to carry out at 165 ° C and a draw ratio of 1.5 to 20 times.

〔Example〕

 Hereinafter, the present invention will be further described with reference to examples.

Example 1 A vibration mill equipped with two grinding pots having an inner volume of 0.97 containing 2.2 kg of steel balls having a diameter of 12 mm was prepared, and 20 g of magnesium chloride, 4 ml of tetraethoxysilane and α, α were placed in each pot under a nitrogen atmosphere. , Α-Trichlorotoluene (3 ml) was added, and the mixture was crushed for 40 hours. 10 g of the co-ground product thus obtained
In a 200 ml flask, 50 ml of titanium tetrachloride and 5 ml of toluene.
0 ml was added, and the mixture was stirred at 100 ° C. for 30 minutes. Thereafter, the supernatant was removed, 50 ml of titanium tetrachloride and 50 ml of toluene were similarly added, and the mixture was stirred at 100 ° C for 30 minutes, and the solid content obtained by removing the supernatant was repeatedly washed with n-hexane to obtain a transition metal. A catalyst slurry was obtained. When a part of the sample was sampled and the titanium content was analyzed, it was 1.8 wt%.

Toluene 40m in a nitrogen atmosphere in a flask with an internal volume of 200ml
l, 100 mg of the above transition metal catalyst, 0.24 ml of diethylaluminum chloride, 0.14 ml of methyl p-toluate and 0.2 ml of triethylaluminum were added and mixed, and then the catalyst slurry was thoroughly degassed and the internal volume of n-heptane 1 was added. Put in the autoclave of No. 3 and replace the gas phase with propylene, then put 0.2Nl of hydrogen, then put propylene and add propylene so that the pressure becomes 5kg / cm ² gauge. Polymerization was performed until the charging amount reached 500 g. Then, unreacted propylene was purged, 200 ml of methanol was added, the mixture was stirred at 90 ° C., and the obtained slurry was washed with water for purification. The slurry was filtered to separate powder, and dried at 80 ° C. and 60 mmHg for 12 hours. The obtained powder was analyzed and boiling n-heptane extraction residual rate
II was 97.8% and the intrinsic viscosity [η] measured with a tetralin solution at 135 ° C was 1.66.

On the other hand, a master powder containing a polymer of allyltrimethylsilane was produced using the above transition metal catalyst.
In a flask with an internal volume of 300 ml, 5 g of transition metal catalyst and 5 ml of diethylaluminum chloride were added to 10 ml of allyltrimethylsilane.
l and 10 ml of toluene, and stir at 60 ° C for 2 hours.
Then, this slurry was put into an autoclave having an internal volume of 3, heptane 1, 0.6 ml of methyl p-toluate and 5 ml of trimethylaluminum were added, 0.2 Nl of hydrogen and propylene were charged, and the pressure was adjusted to 5 kg / cm ² gauge. Then the internal temperature 6
Polymerization was carried out at a constant pressure at 0 ° C. until the amount of propylene charged reached 500 g. A master powder containing 12000 ppm of a polymer of allyltrimethylsilane was obtained by the same treatment as above.

Then, a known antioxidant, the above copolymer, and master powder were mixed by an extruder to obtain a composition containing 10 ppm of a polymer of allyltrimethylsila.

This composition was extruded at a temperature of 250 ° C with a 40 mm Ф extruder to a thickness of 5
After being formed into a sheet of 50 μm, it was stretched 5 × 7 times at 155 ° C. with a biaxial stretching machine manufactured by TM Long Co. to obtain a stretched film.

 The physical properties of this film are shown in the table.

The haze in the table is indicated by haze. In addition, the surface condition was evaluated by 5 grades, with 1 being the most uniform and free from visual disturbance.
Others were as follows.

Haze: According to ASTM D1003.

The internal haze was measured by the same method after applying liquid paraffin to the film surface to smooth the surface.

Melting point: Peak temperature of an endothermic peak measured with a display scanning calorimeter at 30 ° C to 10 ° C / min.

Comparative Example 1 A stretched film was obtained in the same manner as in Example 1 except that the polypropylene obtained in Example 1 was used and polytrimethylallylsilane was not used.

 The physical properties of this film are shown in the table.

Example 2 As polypropylene, [η] is 2.30 and II is 98.2.
% Homopolymer, polytrimethylallylsilane content of 20ppm, stretching temperature 158 ℃
A stretched film was obtained in the same manner as in Example 1 except that.

 The physical properties of this film are shown in the table.

Comparative Example 2 A stretched film was obtained in the same manner as in Example 1 except that the stretching temperature was 140 ° C. The obtained film was a transparent film.

 The physical properties of this film are shown in the table.

Example 3 Using polypropylene as a polypropylene having an ethylene content of 2.5 wt% and an [η] of 2.30, polytrimethylvinylsilane was added to a content of 20 ppm to obtain a composition. Extruder for layer extrusion (two extruders with screw diameters of 20 mm and 40 mm share a die for laminating), 20 mm extruder, 40 mm extruder with polypropylene single weight with melt flow index of 1.5 A coalesced product (Mitsui Noblene FO-200 trade name) is supplied and coextruded into a sheet at a thickness ratio of 1: 7 so that the total thickness is 2500 μm, and then stretched at a stretching temperature of 158 ° C. in the same manner as in Example 1. A stretched film was obtained.

 The physical properties of this film are shown in the table.

[Advantages of the Invention] The film of the present invention is excellent in extremely uniform opacity, is used for matting of printed matter, and is industrially extremely valuable.

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Claims (1)

(57) [Claims] 1. Polypropylene and 1 / for polypropylene
A sheet obtained by extruding a composition consisting of 1000 to 1/10000000 polyalkylvinylsilane or polyalkylallylsilane has a total haze of 10 to 70.
%, The internal haze is 5% or less, the thickness is 200 μm or less, and the melting point of the polypropylene opaque film measured by a differential scanning calorimeter is 150 ° C. or more.