JP4198263B2 - Polypropylene resin composition and shrink-wrapping polypropylene film - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polypropylene resin composition particularly suitable for a shrink wrapping film having high shrinkability and excellent optical characteristics, and a shrink wrapping polypropylene film excellent in optical characteristics having high shrinkage.
[0002]
[Prior art]
So-called shrink wrapping, in which industrial articles, daily necessities, foodstuffs, and the like are tightly packaged with a stretched thermoplastic resin film by utilizing the property of the stretched thermoplastic resin film to shrink, is widely performed.
[0003]
As materials for such shrink wrapping films, thermoplastic resins such as low density polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, and polyester are known. However, none of these thermoplastic resin films have sufficiently satisfactory properties as a shrink wrapping film.
[0004]
For example, a low density polyethylene film is suitable for industrial packaging because it is inexpensive and has high impact strength. However, the low density polyethylene film is not so good in transparency and gloss, and suitable shrinkage temperature is 20-50 ° C. higher than that of a soft vinyl chloride film (hereinafter abbreviated as PVC film). There is no problem.
[0005]
The PVC film is excellent in transparency, so it can enhance the aesthetics of the product being packaged and improve its commercial value, and has a low suitable shrinkage temperature and a wide range of suitable shrinkage temperatures. It has the most favorable performance for packaging. However, PVC films are not always satisfactory for use in industrial packaging in terms of impact strength, particularly low temperature impact strength. Moreover, the substitution to the polyolefin film is examined for the PVC film at the point of blocking resistance.
[0006]
Therefore, the appearance of a polypropylene film for shrink wrapping having good transparency and excellent high shrinkability is desired.
[0007]
[Problems to be solved by the invention]
The present invention seeks to solve the problems associated with the prior art as described above, and is suitable for commercial packaging and also suitable for industrial packaging. More specifically, it has good transparency. And a high shrinkability polypropylene film for shrink wrapping.
[0008]
[Means for Solving the Problems]
The present invention is the following polypropylene resin composition and shrink-wrapping polypropylene film.
[1]: 50 to 95 parts by weight of syndiotactic polypropylene (A) having an MFR of 0.1 to 20 g / 10 min and 5 to 50 parts by weight of propylene / 1-butene random copolymer (B) The propylene / 1-butene random copolymer (B) is (1) a constitutional unit derived from 1-butene in an amount of 50 to 95 mol% of structural units derived from propylene. A polypropylene resin composition comprising units in an amount of 5 to 50 mol%, and (2) an intrinsic viscosity [η] measured in decalin at 135 ° C. of 0.1 to 12 dl / g. .
[2] The polypropylene resin composition according to [1], wherein the syndiotactic pentad fraction of the syndiotactic polypropylene (A) is 0.7 or more.
[3]: 50 to 95 parts by weight of syndiotactic polypropylene (A) having an MFR of 0.1 to 20 g / 10 min, and 5 to 50 parts by weight of propylene / 1-butene random copolymer (B). The propylene / 1-butene random copolymer (B) is derived from (1) propylene. The propylene / 1-butene random copolymer (B) is formed of a polypropylene composition and stretched in at least one direction of the machine direction and the transverse direction. The structural unit is contained in an amount of 50 to 95 mol%, the structural unit derived from 1-butene is contained in an amount of 5 to 50 mol%, and (2) the intrinsic viscosity [η] measured in decalin at 135 ° C. A polypropylene film for shrink wrapping, which is 0.1 to 12 dl / g.
[4]: The shrink-wrapping polypropylene film according to [3], wherein the syndiotactic pentad fraction of the syndiotactic polypropylene (A) is 0.7 or more.
[0009]
As used herein, “film” refers to films and sheets.
[0010]
Hereinafter, the polypropylene resin composition and the shrink-wrapping polypropylene film according to the present invention will be specifically described.
[0011]
The shrink wrapping polypropylene film according to the present invention is formed from a polypropylene composition containing syndiotactic polypropylene (A) and propylene / 1-butene random copolymer (B), and propylene / 1-butene random. The catalyst for producing the copolymer may be a normal Ti catalyst or a metallocene catalyst. Furthermore, it is a uniaxially stretched film or a biaxially stretched film stretched in at least one direction of the machine direction and the transverse direction. Moreover, the multilayer body by which polyethylene, EVA, polypropylene, etc. were laminated | stacked on both surfaces or one side of this film may be sufficient.
[0012]
First, each of these components will be described.
Syndiotactic polypropylene (A)
Examples of the catalyst for producing syndiotactic polypropylene in the present invention include JP-A-2-41303, JP-A-2-41305, JP-A-2-274703, JP-A-2-274704, and JP-A-3. Examples include metallocene catalysts and vanadium catalysts comprising a bridged transition metal compound having asymmetric ligands and a co-catalyst as described in JP-A Nos. 179905 / 3-179006 and JP-A-4-69394. However, even if it is a catalyst of a different structure, it can be used as long as it can produce a polypropylene having a syndiotactic pentad fraction measured by ¹³ C-NMR of 0.5 or more. Any of a slurry polymerization method, a bulk polymerization method, and a gas phase polymerization method can be used.
[0013]
As the syndiotactic polypropylene used in the present invention, a propylene homopolymer or a copolymer of propylene and a small amount of ethylene and / or α-olefin can be used as long as the physical properties of the homopolymer are not impaired. As the α-olefin, those having 4 to 25 carbon atoms can be used. For example, 1-butene, 1-pentene, 1-decene, 1-hexadecene, 1-tetradecene, 1-octadecene and the like are used. Further, it may be a copolymer containing a small amount of olefins such as cyclopentene and norbornene, and dienes such as hexadiene, octadiene, decadiene, dicyclopentadiene and 5-ethylidene-2-norbornene. Such a copolymer can be obtained by copolymerizing propylene and a small amount of a comonomer in the presence of a known catalyst that gives the poly-α-olefin having good syndiotacticity.
[0014]
The syndiotactic polypropylene used in the present invention preferably has a syndiotactic pentad fraction determined by ¹³ C-NMR of 0.7 or more, particularly preferably 0.75 or more.
[0015]
The syndiotactic pentad fraction was measured by the method described in JP-A-3-263411.
[0016]
The syndiotactic polypropylene (A) has an MFR in the range of 0.1 to 20 g / 10 min, preferably 0.2 to 18 g / 10 min, more preferably 0.3 to 15 g / 10 min.
[0017]
MFR was measured according to ASTM D-1238 (230 ° C., 2.16 kg load).
[0018]
In the present invention, the syndiotactic polypropylene (A) is 50 to 95 parts by weight based on 100 parts by weight of the total amount of the syndiotactic polypropylene (A) and the propylene / 1-butene random copolymer (B). Preferably it is used in a proportion of 55 to 90 parts by weight, more preferably 60 to 85 parts by weight.
[0019]
Propylene / 1-butene random copolymer (B)
The propylene / 1-butene random copolymer (B) used in the present invention has a constitutional unit content derived from propylene of 50 to 95 mol%, preferably 55 to 93 mol%, more preferably 60 to 90 mol%. The structural unit content derived from 1-butene is 5 to 50 mol%, preferably 7 to 45 mol%, more preferably 10 to 40 mol%.
[0020]
This propylene / 1-butene random copolymer (B) contains a small amount of structural units derived from an α-olefin other than propylene and 1-butene, for example, in an amount of 10 mol% or less, preferably 5 mol% or less. May be.
[0021]
As α-olefins other than propylene and 1-butene, ethylene and α-olefins having 5 to 20 carbon atoms are used. Specifically, 1-hexene, 4-methyl-1-pentene, 1-octene, 1 -Decene, 1-tetradecene, 1-octadecene and the like are used.
[0022]
The propylene / 1-butene random copolymer (B) has an MFR in the range of 0.1 to 50 g / 10 min, preferably 0.2 to 40 g / 10 min, more preferably 0.3 to 30 g / 10 min. Is in the range of 0.850 to 0.900 g / cm ³ , preferably 0.860 to 0.898 g / cm ³ , more preferably 0.870 to 0.895 g / cm ³ .
[0023]
The propylene / 1-butene random copolymer (B) has an intrinsic viscosity [η] measured in decalin at 135 ° C. of 0.1 to 12 dl / g, preferably 0.3 to 10 dl / g, more preferably 0.5-5 dl / g.
[0024]
The propylene / 1-butene random copolymer used in the present invention may be a partially or completely modified product of unsaturated carboxylic acid or its anhydride. This modified product of propylene / 1-butene random copolymer is excellent in overlap wrapping properties and adhesion to metals.
[0025]
In the present invention, the propylene / 1-butene random copolymer (B) is 5 parts by weight based on 100 parts by weight of the total amount of the syndiotactic polypropylene (A) and the propylene / 1-butene random copolymer (B). -50 parts by weight, preferably 10-45 parts by weight, more preferably 15-40 parts by weight.
[0026]
Polypropylene composition The polypropylene composition used for forming the shrink wrapping polypropylene film according to the present invention is syndiotactic polypropylene (A) and propylene / 1-butene random copolymer (B) as described above. Containing.
[0027]
In such a polypropylene composition, syndiotactic polypropylene (A) and propylene / 1-butene random copolymer (B) are mixed with a tumbler, V-type blender, Henschel mixer, etc., and then an extruder, a Banbury mixer. , Kneading with a kneader, roll or the like. It is desirable to perform the kneading sufficiently.
[0028]
In the polypropylene composition used in the present invention, in addition to syndiotactic polypropylene (A) and propylene / 1-butene random copolymer (B), heat stabilizer, antioxidant, ultraviolet absorber, anti-blocking agent Further, a slip agent, an antistatic agent, a weathering stabilizer, an antifogging agent, a crystal nucleating agent, a base absorbent, a lubricant, a flame retardant, and the like can be added as long as the object of the present invention is not impaired.
[0029]
Shrink wrapping polypropylene film The shrink wrap polypropylene film according to the present invention is formed from the polypropylene composition obtained as described above, and has a longitudinal direction (MD direction) and a transverse direction (TD direction). A uniaxially stretched film or a biaxially stretched film stretched in at least one direction.
[0030]
The polypropylene film for shrink wrapping according to the present invention can be obtained by melting and forming a film after melting the above polypropylene composition. As this film forming method, any known film forming method such as an inflation method, a T-die method, a calendar method and the like can be employed.
[0031]
As the stretching method, any known stretching method such as a uniaxial stretching method using a tenter stretching machine, an inflation-type simultaneous biaxial stretching method, or the like can be employed. As the inflation type simultaneous biaxial stretching method, for example, there is a flat sequential biaxial stretching method or a flat simultaneous biaxial stretching method using a combination of a roll stretching machine and a tenter stretching machine.
[0032]
The draw ratio is 3 to 10 times, preferably 4 to 9 times in the longitudinal direction and the transverse direction, respectively. When stretching is performed so that the stretching ratio is in the above range, a polypropylene film that has sufficient molecular orientation inside the film and can be sufficiently heat-shrinked by heat treatment can be obtained, and film breakage due to stretching will not occur. .
[0033]
In addition, at least one layer of the film is provided with a layer such as an ethylene copolymer or an ethylene / vinyl alcohol copolymer by co-extrusion for the purpose of imparting added value such as poly-resistance and oil resistance, low-temperature heat sealing, transparent It may be laminated by property, gas permeation resistance or post lamination.
[0034]
Further, a multilayer film in which polyethylene, EVA, polypropylene or the like is laminated on both sides or one side of the film may be used.
[0035]
【The invention's effect】
The polypropylene film for shrink wrapping composed of a polypropylene resin composition particularly suitable for the film for shrink wrapping according to the present invention has good transparency and excellent high shrinkability.
[0036]
The polypropylene film for shrink wrapping according to the present invention having the effects as described above can be widely used for commercial packaging such as packaging of foodstuffs and other daily necessities such as miscellaneous goods, and packaging of industrial products ( It can also be widely used for industrial packaging.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.
[0038]
<Melting point (Tm)>
It measured using the Perkin-Elmer DSC-7 type | mold apparatus (differential scanning calorimeter (DSC)).
About 5 mg of sample was packed in an aluminum pan, heated to 200 ° C., held at 200 ° C. for 5 minutes, cooled to −40 ° C. at 10 ° C./minute, held at −40 ° C. for 5 minutes, and then 10 ° C. / It was determined from the endothermic curve when the temperature was raised in minutes.
[0039]
[Measurement of physical properties of stretched film]
<Heat shrinkage>
A 100mm marked line is attached to the center surface of a sample of size 150mm x 20mm in the stretching direction, and left in an air oven set to any temperature (100 ° C, 120 ° C) for 30 minutes, and the distance between the marked lines is measured. Then, the value obtained by dividing the amount of decrease in the distance between the marked lines by the initial distance between the marked lines (100 mm) was displayed as a percentage.
[0040]
<Tensile properties>
A tensile test was performed according to ASTM D-882 to determine the Young's modulus.
[0041]
<Elongation at tensile break>
A tensile test was conducted in accordance with JISK6781 (tensile speed 200 mm / min) to determine the tensile elongation at break.
[0042]
<Internal haze>
A colorless glass shell (4.5 cm × 4.0 cm × 1.4 cm) is filled with cyclohexanol, and a film sample (3 cm × 6 cm) is inserted into the shell, and then haze is measured. Haze was measured according to ASTM D-1330.
[0043]
[Production Example 1]
Production of propylene / 1-butene random copolymer (B) A 2 liter autoclave thoroughly purged with nitrogen was charged with 830 ml of hexane and 100 g of 1-butene, and 1 mmol of triisobutylaluminum was added. After raising the temperature to 0 ° C., propylene was supplied to a total pressure of 7 kg / cm ² G, 1 mmol of triethylaluminum and a titanium catalyst supported on magnesium chloride were added to 0.005 mmol in terms of Ti atoms, and propylene was added. Polymerization was carried out for 30 minutes while supplying continuously and keeping the total pressure at 7 kg / cm ² G. After the polymerization, the mixture was degassed and a propylene / 1-butene random copolymer was recovered in a large amount of methanol and dried under reduced pressure at 110 ° C. for 12 hours.
[0044]
The yield of the obtained propylene / 1-butene random copolymer (B) was 33.7 g. The polymerization activity of (B) was 14 kg · polymer / mmol Ti · hr .
[0045]
In (B), the content of the structural unit derived from 1-butene is 23 mol%, the intrinsic viscosity [η] measured in a decalin solvent at 135 ° C. is 1.91 dl / g, and the melting point is 110 ° C. there were.
[0046]
[Example 1]
90 parts by weight of syndiotactic polypropylene (A) having MFR = 4.1 g / 10 min, Tm = 129 ° C., and syndiotactic fraction = 0.83, and the propylene / 1-butene random copolymer produced in Production Example 1 (B) 10 parts by weight was melted with an extruder (40 mmφ) set at 220 ° C. and pelletized with a pelletizer, and then a film with a width of 300 mm and a thickness of 250 μm was formed with a T-die.
[0047]
Next, this film was cut into a square with a side of 200 mm, and the cut film was stretched 4 times in the machine direction (MD direction) with a pantograph-type simultaneous biaxial stretching machine (stretching temperature: 100 ° C., stretching speed: 9 m / min). The film was held for 30 seconds after completion of stretching, and then immediately cooled to room temperature to obtain a stretched film having a thickness of about 60 μm.
[0048]
Table 1 shows the shrinkage ratio (120 ° C., after 30 minutes) of the stretched film obtained.
[0049]
[Examples 2-3]
Molding and evaluation were performed in the same manner as in Example 1, except that the blend ratio of syndiotactic polypropylene and propylene / 1-butene copolymer was changed as shown in the table.
[0050]
[Comparative Example 1]
In Example 1, a 250 μm film was obtained with a T-die in the same manner as in Example 1 except that syndiotactic polypropylene alone was used. The stretching conditions are also the same as in Example 1.
[0051]
[Comparative Examples 2 to 4]
In Example 1, instead of syndiotactic polypropylene, a stretched film having a thickness of about 60 μm was prepared in the same manner as in Example 1 except that random polypropylene with MFR = 7.0 g / 10 min and Tm = 138 ° C. was used. Obtained.
[0052]
Table 1 shows the shrinkage (120 ° C., 30 minutes later) and Young's modulus results of the obtained stretched film.
[0053]
[Table 1]

Claims (2)

A polypropylene composition containing 50 to 95 parts by weight of syndiotactic polypropylene (A) having an MFR of 0.1 to 20 g / 10 min and 5 to 50 parts by weight of propylene / 1-butene random copolymer (B). The propylene / 1-butene random copolymer (B) is a film formed from a product and stretched in at least one direction of the machine direction and the transverse direction. 0.1 in an amount of to 77 mol%, structural units derived from 1-butene in amounts of 23 to 50 mol%, (2) 135 ° C., an intrinsic viscosity measured in decalin at [eta] A polypropylene film for shrink wrapping, which is 12 dl / g. The polypropylene film for shrink wrapping according to claim 1 , wherein the syndiotactic pentad fraction of the syndiotactic polypropylene (A) is 0.7 or more.