JP3448127B2 - Crystalline polypropylene resin composition - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a crystalline polypropylene resin composition, a sheet made of the polypropylene resin composition, and a stretched film. For more details,
The crystalline polypropylene resin contains a small amount of fluorinated graphite and talc to significantly improve transparency and image clarity, and when forming a uniaxially or biaxially stretched film, the edge roughness of the sheet during the extrusion of the original sheet is prevented. A polypropylene resin composition suitable for a uniaxially or biaxially stretched film which does not occur and has good moldability such as deterioration of thickness accuracy due to uneven stretching of the film in longitudinal stretching, deterioration of thickness accuracy due to uneven stretching of the film in transverse stretching, etc. And a sheet comprising the polypropylene resin composition, and a stretched film.

[0002]

2. Description of the Related Art Stretched polypropylene films, especially biaxially stretched polypropylene films, are widely used as packaging materials because of their excellent mechanical and optical properties. The manufacturing method is generally a sequential biaxial stretching method using a tenter method. However, transparency and image clarity are generally inferior to other highly transparent thermoplastic resins such as polystyrene and polyvinyl chloride due to the high crystallinity of polypropylene.

Several proposals have been made so far in an attempt to improve the transparency and image clarity of a stretched polypropylene film. For example, by extruding a raw sheet during film formation by adding an organic or inorganic nucleating agent such as sorbitol derivative, aromatic carboxylic acid alkali metal salt or aluminum salt, or talc to polypropylene. It is known that when the melted sheet is cooled and solidified at the time of molding, the spherulites inside the solidified raw sheet become smaller and uniform, and the transparency and image clarity of the stretched film are improved. However, these organic nucleating agents have a problem that they are bleeding from polypropylene during extrusion and cause roll fouling, and odor is generated during processing. Further, there is a problem that bleeding occurs when the stretched film is stored for a long time. Furthermore, the aromatic carboxylic acid salt itself or its hydrolyzate reacts with other additives, thereby deteriorating the original performance of the additive and coloring polypropylene.

On the other hand, attempts have been made to improve transparency by using a copolymer of propylene and α-olefin (Japanese Patent Publication No. 32324/1985). However, it cannot be said that the image clarity is sufficient.

It has been found that the transparency and image clarity of a polypropylene stretched film are remarkably improved by incorporating a small amount of graphite fluoride in crystalline polypropylene. Unlike the organic nucleating agent, this fluor graphite does not cause problems such as roll stains during film forming, and is excellent in improving the transparency and image clarity of a stretched film.

However, when the content of the fluorinated graphite increases, the surface of the sheet obtained during extrusion of the raw sheet is roughened during the production of the polypropylene stretched film, and the transparency and the image clarity are deteriorated due to insufficient cooling. Or
In addition, the edge portion of the original sheet becomes wavy, which causes a clip error in tenter stretching, resulting in uneven stretching and tearing of the film in transverse stretching. Further, when the edge portion is roughened in a saw-tooth shape, there is a problem in that the sheet may be stretched and cut in the longitudinal stretching, and there is a problem in the formability of the stretched film.

As described above, conventionally, attempts have been made to improve the transparency and image clarity of the polypropylene stretched film by the above method, but the moldability of the stretched film is still unsatisfactory. That is, the object of the present invention is excellent transparency without the above defects, having image clarity, and, during film formation of the stretched film, does not cause edge roughening of the sheet during extrusion of the original sheet, Polypropylene sheet composed of a crystalline polypropylene resin composition, which has good moldability without stretching break of the sheet in longitudinal stretching, stretching unevenness of the film in lateral stretching, stretching tear, etc., and polypropylene. It is to provide a stretched film.

[0008]

From these viewpoints, the present inventors have made earnest studies on a polypropylene stretched film having improved transparency, image clarity, and stretched film moldability, and as a result, surprisingly, crystalline polypropylene was obtained. In a simple method of containing a small amount of fluorinated graphite and talc in, transparency of the polypropylene stretched film, the image clarity is significantly improved, and the edge roughness of the sheet during the stretched film formation may occur. Therefore, they have found that they are excellent in moldability and have completed the present invention.

That is, according to the present invention, 100 parts by weight of a crystalline polypropylene resin and 0.00001 to 100% by weight of fluorinated graphite are used.
A crystalline polypropylene resin composition containing 0.1 part by weight and 0.005 to 0.4 part by weight of talc having an average particle size of 0.1 to 10 μm, and polypropylene comprising the polypropylene resin composition. Sheet and
It is a polypropylene stretched film stretched at least uniaxially.

The crystalline polypropylene resin used in the present invention is a homopolymer of propylene, propylene and other α.
-A random copolymer with an olefin, or a mixture thereof may be mentioned. Examples of the α-olefin include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-
Nonene, 1-decene, 4-methyl-1-pentene and the like can be mentioned, and the content of these α-olefins is 1
It is preferably 0 mol% or less for maintaining crystallinity.

The crystalline polypropylene resin used in the present invention is not particularly limited to the melt flow rate, but considering the moldability for various stretched films, it is usually in the range of 0.01 to 100 g / 10 min. It is preferably used in the range of 0.1 to 50 g / 10 min.

The crystalline polypropylene resin used in the present invention is crystalline and has an isotactic pentad fraction of 0.85 or more. The isotactic pentad fraction as used in the present invention means A. Zambelli et al., Macromolecules, 6 , 925 (1
923), that is, the fraction in which 5 propylene units are continuously bonded to meso as measured by ¹³ C-NMR.

The molecular weight distribution (ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn)) of the crystalline polypropylene resin used in the present invention is not particularly limited, but the film Considering the case of molding, it is preferably 6 to 20 in order to increase the melt tension and improve the workability. The molecular weight distribution is a value measured by a gel permeation chromatography method (hereinafter, also referred to as GPC) using o-dichlorobenzene as a solvent, and a calibration curve calibrated with standard polystyrene is used.

The fluorinated graphite used in the present invention is a known compound and is a layered compound in which the mesh plane has a layered structure. Generally, it is produced by reacting carbonaceous substances such as graphite, carbon black, activated carbon and coal with fluorine. Depending on the manufacturing method, fluorinated graphite having various fluorine contents is obtained. The fluorinated graphite used in the present invention is not particularly limited in fluorine atom content, but generally (carbon atom) :( fluorine atom) = 1: 0.5.
A compound in the range of ˜1.6, preferably 1: 0.9 to 1.3 can be preferably used because the effect of the present invention is remarkable. The average particle diameter of the fluorinated graphite is preferably 10 μm or less because the dispersibility is good, but from the viewpoint of the effect of the mapping value, the average particle diameter is preferably 0.01 to 5 μm.

The blending amount of the fluorinated graphite used in the present invention in the crystalline polypropylene resin must be in the range of 0.00001 to 0.1 part by weight based on 100 parts by weight of the crystalline polypropylene resin, and 0 0.0005 to 0.05 parts by weight, and more preferably 0.0001 to 0.
More preferably, it is 03 parts by weight. When the amount of fluorinated graphite is less than 0.00001 parts by weight, the effect of exhibiting transparency and image clarity cannot be seen. On the contrary, when the amount exceeds 0.1 parts by weight,
The modulus of elasticity of the molded body increases too much, and when a raw material resin for extrusion molding is used, problems such as an increase in the frequency of breakage of the molded body during molding occur, and further improvements in transparency and image clarity, which are the effects of the present invention. Is not seen and has no meaning from an economic point of view.

The average particle size of talc used in the present invention must be in the range of 0.1 to 10 μm, and 0.5 to 10 μm.
The thickness is preferably 8.0 μm, and more preferably 1.0 to 5.
It is more preferably 0 μm. If the average particle size of talc is less than 0.1 μm, talc causes secondary aggregation,
Since the agglomerated particle size becomes large, the transparency is lowered, and fish eyes are generated to deteriorate the appearance of the film. On the contrary, when the average particle diameter exceeds 10 μm, many voids are generated during stretching of the film, and the transparency of the film decreases.
The method for measuring the average particle size of talc used in the present invention is not particularly limited, but a method using a Coulter counter, an electron microscope or the like is exemplified. Further, as the talc used in the present invention, known ones such as crushed products of natural products or synthetic products are used without limitation. However, considering the nucleating effect on polypropylene, the talc has high crystallinity. It is suitable.

The content of talc in the crystalline polypropylene resin used in the present invention is crystalline polypropylene resin 1
It should be in the range of 0.005 to 0.4 parts by weight with respect to 00 parts by weight, preferably 0.01 to 0.2 parts by weight, and more preferably 0.02 to 0.1 parts by weight. More preferable. If the content of talc is less than 0.005 part by weight, the sufficient nucleating effect of talc cannot be obtained, and edge roughening of the raw sheet occurs. On the contrary, when it exceeds 0.4 parts by weight, the transparency of the film is lowered.

In the crystalline polypropylene resin composition of the present invention, additives for polyolefins which are usually used within the range where the effects of the present invention are not impaired, such as antioxidants, chlorine scavengers, heat stabilizers and antistatic agents. Additives such as anti-fog agents, ultraviolet absorbers, lubricants, antiblocking agents, pigments, other resins and fillers may be added.

The method for mixing fluorinated graphite and talc with the crystalline polypropylene resin is not particularly limited, and a general method can be used. Specifically, there may be mentioned a method in which fluorinated graphite and talc are added to crystalline polypropylene and then mixed using a uniaxial kneading machine, a biaxial kneading machine, a roll, a Brabender plastograph or the like.

As a method for molding the crystalline polypropylene resin composition thus obtained into a sheet or a stretched film, any known method can be adopted without any limitation.
For example, a method for producing a stretched film by a sequential biaxial stretching method by a tenter method is shown. The crystalline polypropylene resin composition is molded into a sheet or film by a T-die method, an inflation method or the like and then supplied to a longitudinal stretching device. Then, the film is longitudinally stretched 4 to 10 times at a heating roll temperature of 120 to 170 ° C., and then a tenter temperature of 130 to 18
This is a method of transversely stretching 4 to 15 times at 0 ° C., and 80 to 80% while allowing 0 to 25% relaxation in the transverse direction, if necessary.
The method of heat-treating at 180 degreeC can be mentioned. Of course, the stretching may be performed again after these stretchings, and in the longitudinal stretching, stretching methods such as multi-stage stretching and rolling can be combined. Also, a stretched film can be obtained by stretching only uniaxially. Further, as a method for producing a polypropylene sheet, a method of melt-extruding a resin by a T-die method and molding the sheet by a cooling roll combined with an air knife or a nip roll can be mentioned.

The thickness of the stretched film and sheet of the present invention is not particularly limited, but is usually 3 to 150 μm for a biaxially stretched film and 10 to 2 for a uniaxially stretched film.
54 μm, and in the case of a sheet, it is in the range of 254 to 3000 μm.

If necessary, one or both surfaces of the stretched film and sheet of the present invention may be subjected to surface treatment such as corona discharge treatment. Further, for the purpose of imparting a function such as heat sealability, a layer made of another polyolefin resin having a melting point lower than that of the crystalline polypropylene resin may be laminated on one side or both sides. The method for laminating other resins is not particularly limited, but a coextrusion method, a laminating method, etc. are preferable.

[0023]

EFFECTS OF THE INVENTION According to the present invention, the transparency and image clarity of a polypropylene stretched film are improved, and in forming a raw sheet when forming a stretched film, surface roughness or edge roughness of the sheet does not occur, A polypropylene stretched film having excellent processability can be obtained without problems such as breakage of stretchability of the sheet, deterioration of thickness accuracy due to uneven stretching of the film, and breakage of stretch.

[0024]

EXAMPLES In order to more specifically describe the present invention, examples and comparative examples will be described below, but the present invention is not limited to these examples. The polypropylene stretched films and polypropylene sheets obtained in the following Examples and Comparative Examples were evaluated by the following methods.

(1) Haze It was measured according to JIS K 6714.

(2) Image Value An optical comb of 0.1 was used using a image clarity measuring device manufactured by Suga Test Instruments Co., Ltd.
Using 25 mm, the comb direction was made parallel to the transverse stretching method of the biaxially stretched film, and the image value was measured.

Table 1 shows the abbreviations of fluorinated graphite used in the present invention.

[0028]

[Table 1]

Example 1 (Granulation) 100 parts by weight of homopolypropylene powder having a melt flow rate of 2.5 g / 10 minutes, a pentad ratio of 0.93 and a molecular weight distribution of 6.8, and 2 parts as an antioxidant , 6-di-t-butylhydroxytoluene was added to 0.
1 part by weight, 0.1 part by weight of calcium stearate as a chlorine scavenger, 100 ppm of fluorinated graphite CF-3 shown in Table 1 and 0.03 part by weight of talc having an average particle size of 4.2 μm were added, and a Henschel mixer was used. After mixing for 5 minutes, use an extrusion granulator with a screw diameter of 65 mmφ for 23
The material was extruded at 0 ° C. and pelletized to obtain raw material pellets.

(Formation of Biaxially Stretched Film) Using the obtained polypropylene composition pellets, a biaxially stretched film was prepared by the following method. The polypropylene composition pellets were extruded at 280 ° C. using a T-die sheet extruder with a screw diameter of 90 mmφ, and a sheet having a thickness of 2 mm was formed with a cooling roll at 30 ° C. Then, this sheet was stretched in the longitudinal direction by using a tenter type sequential biaxial stretching device.
After longitudinal stretching at 50 ° C by 4.6 times, and subsequently by transversely stretching at a mechanical ratio of 10 times in a tenter at 165 ° C, 8%.
After being relaxed and heat-treated, a biaxially oriented polypropylene film having a thickness of 50 μm was formed at a speed of 16 m / min.
The obtained film was measured for haze and image value 48 hours after molding. The results are shown in Table 2.

The state of the edge roughness of the original sheet during film formation was visually evaluated. As an evaluation standard, ◎ when the edge of the sheet is in close contact with the cooling roll and is linear and very good, ∘ when it is slightly separated from the cooling roll but does not cause a problem in film forming, ○, when it is wavy, Δ, saw When the blade was rough, it was marked with x.

The influence of uneven drawing on the thickness accuracy was evaluated by the thickness pattern of the film measured using an infrared thickness measuring machine WEB GAGE manufactured by Yokogawa Electric Co., Ltd., which was installed between the tenter and the winding machine. As the evaluation standard of film thickness accuracy, thickness accuracy less than ± 1 μm is ◎, ± 1 or more and less than 1.5 μm is ○, ± 1.5 or more and less than 2 μm is Δ, ±
2 μm or more was marked with x. Further, continuous operation was carried out for 5 hours, and the number of stretch breaks in the longitudinal stretching of the sheet and the stretch breakage of the film in the tenter was evaluated.

Examples 2 to 9 The same procedure as in Example 1 was carried out except that the type and amount of fluorinated graphite and the average particle size and addition amount of talc were added in the proportions shown in Table 2. The results are shown in Table 2.

[0034]

[Table 2]

Examples 10 to 13 Polypropylene resin 1 having copolymer components shown in Table 3
Example 1 was repeated except that 0.01 part by weight of fluorinated graphite (CF-3) and talc having the average particle size shown in Table 3 were added to 00 parts by weight. The results are shown in Table 3.

[0036]

[Table 3]

Comparative Examples 1 to 7 The same procedure as in Example 1 was carried out except that the types and amounts of fluorinated graphite and the average particle size and amount of talc shown in Table 4 were blended.
The results are shown in Table 4.

[0038]

[Table 4]

Comparative Examples 8 to 10 The procedure of Example 10 was repeated, except that the polypropylene resin having the copolymerization component shown in Table 5 was mixed with the fluorinated graphite and the types and proportions of talc also shown in Table 5. . The results are shown in Table 5.

[0040]

[Table 5]

Continuation of front page (56) Reference JP-A-8-134279 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 23/00-23/36 C08K 3/00-13 / 08 C08J 5/18

Claims (3)

(57) [Claims] 1. (A) 100 parts by weight of crystalline polypropylene resin (B) 0.00001 to 0.1 parts by weight of fluorinated graphite (C) 0.005 to talc having an average particle size of 0.1 to 10 μm.
A crystalline polypropylene resin composition comprising 0.4 parts by weight. 2. A sheet made of the crystalline polypropylene resin composition according to claim 1. 3. A stretched film comprising the crystalline polypropylene resin composition according to claim 1, which is stretched at least uniaxially.