JPS5824251B2 - Method for manufacturing thin film made of mineral-filled plastic - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention produces a thin film made of an inorganic-filled high-density polyethylene resin composition, particularly a high-quality ultra-thin film with high tear strength in the longitudinal direction and a thickness of 5 to 30 μm. Regarding the method.

Conventionally, relatively thick films have been made from compositions containing high-density polyethylene resins containing a small amount of amorphous inorganic fillers, using forming methods such as the T-die method or the calendar method, especially for applications such as synthetic paper. However, with the expansion of uses such as packaging materials and agricultural materials, higher quality and thinner films were desired.

Nevertheless, it has been difficult to provide such thin films due to the lack of suitable raw materials and forming methods.

For example, it is difficult to mold a film with a thickness of 200μ or less using the T-die method from a thermoplastic resin composition containing a small amount of inorganic filler, and the obtained film of about 200μ has sufficient strength in the lateral direction. However, it had the disadvantage of being easily torn.

In addition, fairly thin films have been obtained using the inflation method from polyethylene resins that do not contain inorganic fillers, but it is still difficult to obtain films with high tear strength in the longitudinal direction, and furthermore, when incinerated after use, it is difficult to obtain films with high tear strength. It was difficult to put it into practical use because the combustion heat per unit weight was large, which caused damage to the incinerator, and because it had poor crushability, it was difficult to turn it into fine dust.

The present inventors have been conducting research on practical resin films for some time, and as a result of their research, they have created an extremely practical film based on a composition containing a large amount of amorphous inorganic filler in a high-density polyethylene resin. It has high strength before photo-deterioration, but after photo-deterioration, its strength is extremely low and it is easily crushed, and the heat of combustion per unit weight is low, so it can be easily incinerated without damaging it in a normal incinerator. We have invented a film that can do this.

For example, a patent application has already been filed as Japanese Patent Application No. 49-93018 (
However, it is extremely difficult to obtain a high-quality thin film with high tear strength in the transverse direction from such a composition by the same molding method as the conventional method, and further research is needed here. As a result of stacking, the resin composition,
The present inventors have experimentally discovered that an extremely preferable thin film can be obtained when inflation molding is performed using a specific molding machine and molding conditions, and the present invention has been completed.

In the present invention, 100 parts by weight of a high density polyethylene resin having a melt index of 0.2 or less and a flow rate of 15 to 35 and an amorphous inorganic filler of 60 to 3 parts by weight are used.
A composition containing 0.00 parts by weight and a water content of 1100 pp or less is molded at a temperature of 160 to 220°C using a screw with a compression section pitch of 5 or more and a compression ratio of 2.3 to 3.6. , a thin film with a thickness of 5 to 30μ and excellent mechanical strength made of an amorphous inorganic filled plastic characterized by inflation molding with a film ratio of 1:3 to 7 and a frost line length of 200 to 900+u+. This is a manufacturing method.

The practical purpose of the present invention is to have a small combustion heat per unit weight, high strength before photodegradation, but extremely easy to crush after photodegradation, and a thickness of 5 to 30μ. The object of the present invention is to obtain a high-quality film having high tear strength in the longitudinal direction, a smooth surface, and no uneven thickness, bubbles, pinholes, wrinkles, etc., and furthermore to provide a method for efficiently producing such a high-quality thin film. There is a particular thing.

In the present invention, the longitudinal direction of the film refers to the direction in which the resin flows out from the die during film formation and the film is wound up and moves, and the transverse direction refers to the direction perpendicular to this direction.

The tear strength in the longitudinal direction refers to the strength when the film is torn in the longitudinal direction when tension is applied in the transverse direction.

As the measuring method, the method prescribed in JIS Z170'2 is used.

The high-density polyethylene resin contained in the composition used in the method of the present invention includes ethylene polymers, copolymers, and mixtures thereof, such as polyethylene homopolymers, ethylene-propylene copolymers, ethylene-propylene copolymers, and ethylene-propylene copolymers. Butene-1 copolymers and mixtures thereof, etc., whose tart index l2 (A, STMD123
8-65T under a load of 2.16 kg for 10 minutes) is 0.2 or less, and the flow rate is 110/I2 (I
to 10kg according to ASTM D 1238-65T
(measured value under load for 10 minutes) is 15 to 35.

If a composition containing a resin with a tart index of 0.2 and a dog flow rate of 15 to 35 and a resin with a melt index of 0.2 or less and a flow rate outside the range of 15 to 35 is used, It is not possible to operate stably with a high frost line, the moldability is not good, and it is not possible to mold at a high blowing ratio, and as a result, the tear strength in the longitudinal direction is also low, which is a preferable method that satisfies the purpose of the present invention. I can't get the film.

In addition, examples of the amorphous inorganic filler included in the composition used in the method of the present invention include calcium carbonate and basic magnesium carbonate, but the average particle size is usually 1 to 1.
Many have a diameter of about 5μ.

Particularly preferred is calcium carbonate.

Here, the amorphous inorganic filler refers to one in which the ratio of particle diameter to particle thickness (aspect ratio) is smaller than 50:1.

The above-mentioned amorphous inorganic filler must be included in the composition in an amount of 60 to 300 parts by weight per 100 parts by weight of the high-density polyethylene resin, and if it is less than 60 parts by weight, the heat of combustion per unit weight will not be small. Moreover, the crushability after photodeterioration is also insufficient, and if the amount exceeds 300 parts by weight, the strength of the film decreases and it becomes difficult to mold it smoothly.

In particular, 6 parts of amorphous inorganic filler is added to 1-00 parts by weight of resin.
A composition containing 0 to 200 parts by weight is preferred.

Further, it is preferable to use an amorphous inorganic filler from the viewpoint of obtaining a well-balanced longitudinal and lateral mechanical strength of the formed film.

Furthermore, the composition used in the present invention has a moisture content of 1
Must be less than 100pp.

If it exceeds 100 degrees, uneven thickness tends to occur in film formation, and
If the film contains a considerable amount of water, foaming may occur during film formation.
Bubbles, etc. are also generated in the product film, which not only impairs the appearance of the film but also considerably reduces the film strength, making it impossible to obtain a desirable film.

The water content in the composition can be easily adjusted to the above range by drying the composition in a conventional dryer before molding, or by adding a desiccant to the composition at or just before molding. Implemented.

In particular, the water content is preferably 50 ppm or less. Overall, the composition used in the present invention has a melt index of 0.2 or less and a flow rate of 15 as described above.
It is characterized in that it contains 100 parts by weight of a high-density polyethylene resin having a molecular weight of ~35 and 60 to 300 parts by weight of an amorphous inorganic filler, and has a water content of 100 pp[n or less.

In order to obtain the present composition, it is first treated by the method described in JP-A-49-133459, and at that time, as long as the object of the present invention is achieved, other optional agents may be added, such as an ultraviolet deterioration inhibitor. , heat stabilizers, lubricants, colorants, etc. are also used.

In particular, in order to adjust the photodegradation period of the film, it is necessary to adjust the amount of ultraviolet deterioration inhibitor, and to improve the formability during molding, it is necessary to incorporate calcium stearate, etc. In order to prevent deterioration, it is preferable to include a heat stabilizer.

The method of the present invention is a method of inflation molding using an extruder using the above composition, and since the composition is specific as described above, the method is characterized in that a specific molding method is used. There is.

The first is the screw shape of the extruder, and the second is the molding conditions.

That is, the screw of the extruder used in the method of the present invention has a compression section with a pitch number of 5 or more and a compression ratio of 2.
Must be between 3 and 3.6.

A screw with a compression section pitch number of less than 5 and a compression ratio of 2.3 to 3.6, or a compression section with a pitch number of 5 or more and a compression ratio outside the range of 2.3 to 3.6. By using a screw having a pitch number of less than 5 parts and a compression ratio in the range of 2.3 to 3.6, it is impossible to obtain the film targeted by the present invention.

To explain this point in more detail, if molding is performed using a screw with a compression part pitch number of less than 5 and a compression ratio of less than 2.3, gases such as air and moisture will be drawn in during molding, resulting in uneven thickness of the film. Bubbles are likely to occur, and the number of pitches in the compression section is arbitrary, and if a screw with a compression ratio greater than 3.6 is used, the resin will generate heat during molding at a high screw rotation speed, which will cause deterioration. This results in a concomitant reduction in the strength of the resulting film.

A screw in which the number of pitches in the compression section is 5 or more and the compression ratio is less than 2.3 does not have sufficient kneading performance. This is not preferred because it is difficult to obtain a thin film.

Next, in the method of the present invention, the first characteristic of the molding conditions is a molding temperature of 160 to 220°C, the second is a blow ratio of 1:3 to 7, and the third is a frost line length of 200°C. It is located at ~900 Tomo.

In the present invention, the molding temperature refers to the temperature of the resin in the die part of the extruder, and when inflation molding is performed at a temperature lower than the molding temperature of 160°C, a homogeneous inorganic filler and resin are uniformly mixed. It is difficult to obtain a film with good quality, and the film surface often tends to be rough and lack smoothness.

On the other hand, if the molding temperature is higher than 220° C., pinholes are likely to occur in the film, making it difficult to obtain a film with high strength due to thermal deterioration of the resin, which is undesirable.

If the 7'o-ratio is less than 1:3, the obtained film will easily tear in the longitudinal direction, that is, the tear strength in the longitudinal direction will be low, and if it is greater than 7, the bubble stability will not be sufficient and the film will not be efficiently cracked. cannot be manufactured.

Furthermore, when the frost line is less than 200 mm, the obtained film tends to tear in the longitudinal direction, and
If it is thicker than +++m, the frost stability will not be sufficient,
This is undesirable because the resulting film often wrinkles.

Other molding conditions may be the same as those for the normal inflation method.

Film thickness is controlled by winding speed.

According to the method of the present invention, the thickness is 5 to 30 μ, the longitudinal tear strength is 11 kg/CTrL or more, and the impact strength is 3
50kg・crrL/mm or more, a high-quality film with a smooth surface, no uneven thickness, bubbles, pinholes, wrinkles, etc. can be easily obtained, and the film has low combustion heat per unit weight and is light resistant. It has high strength before deterioration, and has the property of being extremely easily crushed after photodegradation, so there is no difficulty in incineration when disposing of it after use, and it is extremely suitable for use as a general packaging film or agricultural film, for example. It is highly practical.

This will be explained below with reference to examples.

Example 1 100 parts by weight of high-density polyethylene with a melt index (abbreviation MI) of 0.1 and a flow rate of 25, 100 parts by weight of amorphous calcium carbonate powder, 1 part by weight of calcium stearate, 0 parts by weight of dilauryl thiodipropionate. After blending .1 part by weight with a mixer, pellets were obtained using a pelletizer.

The pellets were then heated at 120°C in a hopper dryer.
After drying for 4 hours, the moisture content is 3! A composition of Mpm was obtained.

Next, an inflation method film forming apparatus using an extruder with a diameter of 55 + + + m was applied, the number of pitches of the compression section was 11, and the compression ratio was 3.
．． Attach the screw (2) and pull the screw (1).
The dry composition was put into an extruder, the heating was adjusted to a molding temperature of 200'C, and the blow ratio was 6.
When the film was formed into a film with a frost line length of 600 mm, a homogeneous and smooth film with a thickness of 15 μm was obtained.

The film thus obtained was measured for longitudinal and lateral tensile strength and Elmendorf tear strength using the method of JIS Z1702, and for dart impact impact strength using the method of ASTM D1709-67, as shown in Table 1, Example 1. The tensile strength in the longitudinal and lateral directions was moderate, the tensile strength in the lateral direction was large, and the impact strength was high and excellent.

Examples 2 to 4 and Comparative Examples 1 to 11 Films were molded according to the method shown in Example 1 above, with the other items listed in the table, and performance tests were conducted.

The data according to the present application are shown in Table 1, Examples 2 to 4, and the others are shown in Table 2, Comparative Examples.

All of the example films of the present invention were good, but
The film of the comparative example was not sufficient.

Claims (1)

[Claims] 1 100 parts by weight of a high-density polyethylene resin with a melt index of 0.2 or less and a flow rate of 15 to 35 and 60 to 300 parts of an amorphous inorganic filler.
parts by weight and a water content of 1100 pp or less, the compression part has a pitch number of 5 or more and a compression ratio of 2.
．． Molding temperature 16 using a screw that is 3 to 3.6
Excellent mechanical strength with a thickness of 5 to 30μ made of amorphous inorganic filled plastic characterized by inflation molding at 0 to 220℃ with a blow ratio of 1:3 to 7 and a frost line length of 200 to 900iyx. A method of manufacturing a film.