JP2000313753A - Polypropylene-based sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polypropylene-based sheet having a thermoformable wide temperature range and remarkably improved in curl by heat sealing with an aluminum foil. SOLUTION: This sheet is obtained by dispersing a noncrystalline resin, e.g. a noncrystalline polyolefin, a noncrystalline polymethyl methacrylate, a noncrystalline polycarbonate or a noncrystalline polystyrene in the form of a layer in a composition comprising two or more kinds of polypropylenes having 3-40 deg.C difference in melting point measured with a differential scanning calorimeter and a petroleum resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polypropylene sheet which can be formed by a general sheeting method such as extrusion. More specifically, the present invention relates to a polypropylene-based sheet for packaging a drug (solid agent) called PTP, which is required to have moisture-proof properties.

[0002]

2. Description of the Related Art In pharmaceutical packaging, polypropylene-based sheets are being used in order to obtain higher moisture resistance.
However, polypropylene has a serious industrial problem that the thermoformability is extremely poor. That is, polypropylene has a large drawdown due to heat at the time of preheating in thermoforming, and the optimum molding temperature width at which a good molded product can be obtained is about 2 to 3 ° C., which is very narrow. For this reason, in thermoforming polypropylene, very high temperature control is required, and the conventional general-purpose molding machine has a high molding defect rate and is extremely difficult to control the process. Further, polypropylene has a major industrial problem that when heat sealing is performed with an aluminum foil, the curl of the sheet becomes extremely large. In other words, since polypropylene has a large coefficient of linear expansion, the shrinkage after heat-sealing the aluminum foil is large, which causes the product to curl on the opposite side to the aluminum foil, impairing its commercial value, and making it impossible to integrate on an automatic packaging line. There is a problem that such troubles occur.

Various studies have been made on polypropylene having good thermoformability. For example, polypropylene having relatively good moldability, such as polyethylene, ethylene-propylene copolymer, inorganic filler or petroleum resin having a low molecular weight, has been studied. It has been proposed to blend and modify. For example, a method of adding high-viscosity polyethylene (low-density polyethylene) and hydrous magnesium silicate powder to high-viscosity polypropylene during melting (Japanese Patent Publication No.
No. 15744), a method of adding polyethylene (high-density polyethylene) and an ethylene-propylene copolymer to polypropylene (JP-B-63-29704),
A method using polypropylene and polyethylene having a narrow molecular weight distribution to improve moldability and vibration fatigue resistance (Japanese Patent Publication No. 53213/1988), a method of adding a petroleum resin and an ethylene-α-olefin copolymer to polypropylene
(Japanese Patent Publication No. 6-89191).

However, these are effective in improving the formability such as sheet softening tension holding time, melt strength, drawability, drawdown, etc. under specific temperature conditions. There is almost no effect on the expansion of the moldable temperature range, which is a typical index, and a polypropylene-based sheet that is satisfactory with respect to a practical improvement in moldability has not yet been obtained. Also, studies to improve curl have been made in polypropylene multilayer sheets. For example, there is a method of improving curl by adding a petroleum resin (Japanese Patent Publication No. 3-4029). However, although some curl improvement effects were observed, they were not sufficient.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polypropylene sheet having a wide temperature range in which thermoforming can be performed and in which curling due to heat sealing with an aluminum foil is remarkably improved.

[0006]

Means for Solving the Problems The present inventors have conducted research on the above problems, and as a result, have found that a polypropylene-based sheet obtained by dispersing an amorphous resin in a layered manner in a specific combination of polypropylene and petroleum resin has been developed. The present inventors have found that the temperature range in which thermoforming can be performed is wide and the curl due to heat sealing with aluminum foil is remarkably improved, and the present invention has been completed.
That is, the present invention relates to a polypropylene-based composition obtained by dispersing a non-crystalline resin in a layered form in a composition comprising two or more types of polypropylene and a petroleum resin whose difference in melting point measured by a differential scanning calorimeter is 3 to 40 ° C. It is a sheet.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The types of polypropylene used in the present invention include homopolymers obtained by homopolymerizing propylene, block copolymers of propylene and ethylene or α-olefin, and random copolymers.
Two or more kinds of polypropylenes in the present invention have melting points (JIS-K-7121) measured by a differential scanning calorimeter.
Is 3 to 40C, more preferably 5 to 35C. The melting point difference shown here is the difference between the highest melting point and the lowest melting point of the two or more types of polypropylene. If the difference in melting point of the polypropylene is less than 3 ° C., the vacuum and pressure forming properties of the obtained sheet deteriorate, which is not preferable. If the difference in melting point of polypropylene is greater than 40 ° C., the appearance of the sheet will be poor.

In the field where the heat resistance of the sheet is required, the melting point of the highest melting point of the polypropylene to be combined is preferably 150 ° C. or higher,
More preferably, it is 155 ° C. or higher. If the melting point of the polypropylene having the highest melting point is lower than 150 ° C., the heat resistance of the sheet deteriorates. The content of the polypropylene having the highest melting point in the combined polypropylene is 95%.
It is preferably from 50 to 50% by weight, more preferably from 85 to 60% by weight. If the content of the polypropylene having the highest melting point is more than 95% by weight, vacuum and pressure forming properties will be poor, and if it is less than 50% by weight, the heat resistance of the sheet will be poor. The type of polypropylene to be combined is not particularly limited, but when a sheet is required to have a water vapor barrier property, a combination of a homopolymer and a random copolymer or a block copolymer is preferable, and a combination of homopolymers is more preferable.

When the polypropylene sheet of the present invention is prepared by the calendering method, it is preferable that the polypropylene used has a low molecular weight component having a molecular weight of 10,000 or less at 5% by weight or less, more preferably 3% by weight or less. Wt% or less, most preferably 1 wt% or less. If the low molecular weight component having a molecular weight of 10,000 or less is more than 5% by weight, sticking to a hot roll occurs at the time of calendering, resulting in poor smoothness and appearance of the obtained sheet. The ratio of the low molecular weight component can be determined from a differential molecular weight distribution curve measured by gel permeation chromatography.

The petroleum resin used in the present invention is a dicyclopentadiene resin obtained by thermally polymerizing a cyclopentadiene fraction, an aromatic (C9) petroleum resin obtained by cationic polymerization of a C9 aromatic olefin mixture, and a C5 chain. Aliphatic (C5) petroleum resin obtained by cationic polymerization of olefin mixture,
And copolymers or blends of at least two components selected therefrom, furthermore, hydrogenated petroleum resins, and blends of at least two components selected from hydrogenated petroleum resins.
A hydrogenated petroleum resin having excellent odor and stability is preferable, and a dicyclopentadiene-based hydrogenated petroleum resin is preferable for a package requiring higher moisture resistance.

The softening point of petroleum resin is 50 to 16
0 ° C. is preferable, and more preferably 100 to 16 ° C.
It is at 0 ° C. When petroleum resin is added to polypropylene, the elastic modulus near normal temperature is improved, and the curl in the aluminum seal is reduced. If the softening point of the petroleum resin is less than 50 ° C., the effect of curl reduction is reduced because the improvement in the elastic modulus near normal temperature is reduced, and if it exceeds 160 ° C., the thermoformability deteriorates. The molecular weight of the petroleum resin is preferably 3000 or less, more preferably 1000 or less. If the molecular weight of the petroleum resin exceeds 3,000, there is a problem that moldability deteriorates. The addition amount of the petroleum resin is 1 to 30 parts by weight, preferably 3 to 20 parts by weight, and more preferably 5 to 15 parts by weight based on 100 parts by weight of the polypropylene. If the addition amount of the petroleum resin is less than 1 part by weight, the effect of curl reduction is reduced because the improvement in the elastic modulus near normal temperature is reduced, and if it exceeds 30 parts by weight, the impact resistance is deteriorated, which is not preferable.

The non-crystalline resin used in the present invention is, for example, non-crystalline polyolefin, polymethyl methacrylate, polycarbonate, polystyrene and the like.
Among these, an amorphous resin having a glass transition temperature of 80 ° C. or higher is preferable because the shrinkage after heat-sealing the aluminum foil is reduced and the curl is reduced. The expression "dispersing the non-crystalline resin in a layered form" as used herein means that the non-crystalline resin is dispersed in the polypropylene in the form of a plate in the flow direction (MD) of the sheet.

The amorphous resin dispersed in a layered form preferably has an average aspect ratio of 2 to 30 and a length of 0.1 to 30 μm. Furthermore, preferably, the average aspect ratio is 3 to 10,
And the length is 0.5 to 10 μm. If the average aspect ratio of the non-crystalline resin dispersed in a layer is less than 2, the shrinkage improvement at the time of heat sealing with aluminum foil is not sufficient, and the curling reduction effect is insufficient. It is large, and the anisotropy such as mechanical properties becomes remarkable. Further, if the length of the amorphous resin dispersed in a layer is less than 0.1 μm, the shrinkage improvement at the time of heat sealing with the aluminum foil is not sufficient, and the curling reduction effect is insufficient, and if it exceeds 30 μm. Other properties, such as transparency, are significantly reduced. The amount of the non-crystalline resin to be added is preferably from 5 to 45 parts by weight based on 100 parts by weight of the polypropylene. If the amount of the non-crystalline resin is less than 5 parts by weight, the effect of improving shrinkage during heat sealing with the aluminum foil is small, and if it exceeds 45 parts by weight, problems such as whitening of the sheet and reduction in the molding temperature range arise.

Further, the difference in melting point (JIS-K-7121) measured by the differential scanning calorimeter of the present invention is 3 to 40.
The two or more types of polypropylene and amorphous resin at
The viscosity ratio (ρam / ρPP) of the melt viscosity (ρPP) of polypropylene and the melt viscosity (ρam) of the non-crystalline resin measured at 230 ° C. and a shear rate of 121.6 sec ⁻¹ using a capillary rheometer according to JIS K 7199 is 0.01. ~ 1.0
Is more preferable, and more preferably 0.05-1.
0. If the melt viscosity ratio is less than 0.01, the effect of improving shrinkage during heat sealing with the aluminum foil is small, and if it exceeds 1.0, it becomes difficult to disperse the amorphous resin in polypropylene in a layered manner. A method of dispersing an amorphous resin in a layered manner in two or more types of polypropylene having a difference in melting point (JIS-K-7121) of 3 to 40 ° C. measured by a differential scanning calorimeter is to stretch uniaxially after sheet production. Method, or using a twin-screw kneader to shear at a rate of 100 sec.
After kneading at ^-1 or more, it is obtained by a method of forming a sheet. Further, in the case of the polypropylene and the non-crystalline resin having the above-mentioned viscosity ratio, the sheet may be formed by a known molding method using a direct T-die method or the like.

[0015]

The present invention will be described below in detail with reference to examples. Examples and comparative examples were evaluated by the following methods. (Measurement of Melting Point) The melting point was measured with a differential scanning calorimeter according to JIS-K-7121. (Vacuum, compressed air molding) Compressed air molding machine [FBP-M2;
Constant pressure (5kgf / cm ² )
Then, the hot plate temperature was increased in 1 ° C. units between 120 and 160 ° C., and the formability of the obtained sheet was evaluated. The mold was 10 mm in diameter, 4.5 mm in height, and R1.5.
The temperature at which the entire thickness of the obtained molded article was uniform was defined as the moldable temperature, and the temperature range was determined. (Evaluation of curl) Using a pneumatic molding machine [FBP-M2; manufactured by CK Ltd.], molding was performed under conditions showing good moldability, and aluminum foil and heat roll 20 were filled without filling the contents.
After heat sealing at 0 ° C and inserting a slitter at 130 ° C, width: 37 mm, length: 94 mm, corner R: 5 m
The molded product punched to m was placed on a flat surface, and the curl of the molded product 10 minutes after punching was measured. Four corners of each molded product were measured for 10 molded products, and evaluated by an average value. When the size of the curl was less than 4 mm, the result was ○.

The components used in the examples and comparative examples are shown below. (Polypropylene) PP-A (Homo PP); EA7 manufactured by Nippon Polychem Co., Ltd.
A (melting point: 164 ° C) PP-B (homo PP); manufactured by Japan Polyolefin Co., Ltd.
PC410A (melting point: 158 ° C) PP-C (random PP); Japan Polyolefin Co., Ltd.
PB322M (melting point: 149 ° C) (non-crystalline resin) COC (non-crystalline polyolefin); manufactured by Mitsui Chemicals, Inc.
APL6509 PMMA (polymethyl methacrylate); SUMIPEX LG21 (petroleum resin) manufactured by Sumitomo Chemical Co., Ltd. PR; ESCOLETTS 5320 manufactured by Tonex Corporation
(Dicyclopentadiene-based hydrogenated petroleum resin, softening point 125
° C, molecular weight 420)

In Examples and Comparative Examples, sheets were prepared in the following manner. Two or more types of polypropylene having a difference in melting point measured by a differential scanning calorimeter of 3 to 40 ° C.,
230 ° C cylinder temperature with petroleum resin and amorphous resin
After melt-kneading with a 50 mm twin-screw extruder set as described above, a sheet having a thickness of 0.3 mm was produced by a T-die method.

[0018]

[Table 1]

[0019]

According to the present invention, it is possible to provide a polypropylene sheet having a wide thermoformable temperature range and significantly improved curl due to heat sealing with an aluminum foil.

Continued on the front page F term (reference) 4F071 AA14 AA20 AA21 AA22 AA33 AA50 AA84 AF53 AF56 AH19 BB06 BC01 4J002 BA013 BB034 BB121 BB122 BB134 BC044 BG054 CG004 GB01

Claims (1)

[Claims] 1. A polypropylene-based composition obtained by dispersing an amorphous resin in a layered form in a composition comprising two or more types of polypropylene and a petroleum resin having a difference in melting point of 3 to 40 ° C. measured by a differential scanning calorimeter. Sheet.