JP3360532B2 - Thermoforming resin composition and sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a propylene resin composition suitable for general thermoforming materials such as extrusion molding and a sheet thereof. The resin composition of the present invention has a wide temperature range capable of being thermoformed, and is preferable as a material for various packaging containers such as food packaging and pharmaceutical packaging, and in particular, a pharmaceutical product called PTP (solid agent).
Preferred for packaging.

[0002]

2. Description of the Related Art PTP packaging sheets used as packaging materials for solid pharmaceuticals have conventionally used polyvinyl chloride.
(Hereinafter, abbreviated as PVC) is widely used. This PVC sheet has P processing properties such as moldability, transparency, and impact resistance.
It is an excellent sheet that almost satisfies the characteristics required for TP packaging, but has insufficient moisture-proof properties. For this reason, for preparations requiring high moisture resistance, PTP packaging is performed, and then pillow packaging is performed using a laminated film containing aluminum foil, or a PVC sheet coated with polyvinylidene chloride is used. By using a sheet, the moisture-proof property is improved. However, in such a method, the number of steps is increased, and the cost of the packaging material is undesirably increased.

[0003] In recent years, a sheet made of polypropylene has been used in order to prevent environmental pollution due to PVC treatment and to obtain higher moisture proofness. However, polypropylene has a serious industrial problem that the thermoformability is extremely poor. In other words, polypropylene has a large drawdown due to heat during preheating in thermoforming,
The optimal molding temperature range for obtaining good molded products is 2
~ 3 ° C and 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.

[0004] For this reason, various studies have been made on polypropylene having good thermoformability. For example, polyethylene and ethylene-propylene copolymers, inorganic fillers or low molecular weight resins having relatively good moldability have been used for polypropylene. There are proposals for blending and modifying petroleum resins. For example, a method of adding high-viscosity polyethylene (low-density polyethylene) and hydrated magnesium silicate powder to high-viscosity polypropylene at the time of melting (Japanese Patent Publication No. 56-15744), polyethylene (high-density polyethylene) and ethylene A method of adding a propylene copolymer (JP-B-63-29704).
JP-A-63-53213), a method of using polypropylene and polyethylene having a narrow molecular weight distribution to improve moldability and vibration fatigue resistance (JP-B-63-53213), a petroleum resin and an ethylene-α-olefin copolymer (Japanese Patent Publication No. 6-89191) is known. However, although these are effective in improving the formability such as sheet softening tension holding time, melt strength, drawing workability, and drawdown under specific temperature conditions, they are substantial indicators of formability improvement. Has almost no effect on the expansion of the moldable temperature range
No polypropylene has yet been obtained that is satisfactory with respect to realistic moldability improvements. When a low molecular weight compound such as a petroleum resin is blended, bleeding and elution occur, so that it cannot be used for pharmaceutical packaging from a hygienic point of view.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polypropylene resin composition having excellent thermoformability, particularly a polypropylene resin composition for packaging having a wide moldable temperature range during molding and a sheet thereof. It is in. The present inventor has conducted various studies on polypropylene-based resins, and as a result, obtained the knowledge that the above-mentioned problems can be solved by blending a predetermined amount of polypropylene and polyethylene having a specific melt viscosity ratio, and completed the present invention. I came to.

That is, according to the present invention, 80 to 60% by weight of polypropylene and 20 to
A resin composition containing 40% by weight of JIS
250 by capillary rheometer according to K7199
The viscosity ratio (ρPE / ρPP) of the melt viscosity (ρPP) of the polypropylene and the melt viscosity (ρPE) of the polyethylene measured at ⁰ ° C. and a shear rate of 121.6 sec ⁻¹ is 0.05 to 1.
8 is a thermoforming resin composition. In the resin composition of the present invention, the polypropylene has a melt flow rate (hereinafter, referred to as MFR; JIS K7210, condition 14)
It is a homopolymer of 5 g / 10 min, and polyethylene is MFR (JIS K 7210, condition 4) 5 to 20.
It is preferably a high density polyethylene of g / 10 min. The present invention also provides a sheet formed by molding such a resin composition.

[0007]

DETAILED DISCLOSURE OF THE INVENTION

(Polypropylene) Examples of the type of polypropylene used in the resin composition of the present invention include known polypropylenes such as propylene homopolymer, block copolymers of propylene and ethylene or α-olefin, and random copolymers, and mixtures thereof. . In particular, when high moisture resistance, transparency and rigidity are required, a homopolymer of propylene is preferred. These resins are 2
More than one species may be used in combination.

As the polypropylene, those having good extrusion moldability, such as films and sheets, are preferable. Such a resin has an MFR (JIS K 7210, condition 14) of 0.1.
It is preferably from 10 to 10 g / 10 min, more preferably from 1 to 10 g / 10 min, and most preferably from 1 to 5 g / 10 min.
g / 10 min. When the MFR is smaller than the above value,
The surface appearance of the extruded sheet tends to deteriorate, which is not preferable. On the other hand, if the MFR is larger than the above value, the sheet extrusion processability becomes unstable, which is not preferable.

The amount of the polypropylene is from 80 to 60% by weight, preferably from 75 to 60% by weight, more preferably from 70 to 61% by weight, based on the total amount of the composition. If the blending amount of the polypropylene is larger than the above range, the moldability is not sufficiently improved, such as the secondary workability in the case of vacuum / pressure forming the film. On the other hand, if the amount of the polypropylene is less than the above range, heat resistance, which is an excellent property of polypropylene, cannot be obtained.

(Polyethylene) As polyethylene,
For example, any of high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and ultra-low-density polyethylene (VLDPE) can be used. When high moisture resistance is required, it is preferable to use high density polyethylene having excellent moisture resistance as polyethylene.

Also, the viscosity ratio between the melt viscosity of polyethylene (ρPE) and the melt viscosity of the main component polypropylene (ρPP) measured under the above conditions according to JIS K 7199.
(ρPE / ρPP) is 0.05 to 1.8, preferably 0.1 to 1.0, and more preferably 0.2 to 0.7. If the viscosity ratio is smaller than the above range, the resin cannot be mixed sufficiently uniformly, and it becomes difficult to form a film or the like. On the other hand, if it exceeds the above range, the temperature range in which molding can be performed is not sufficiently widened, which is not preferable.

[0012] Polyethylene is MFR (JIS K).
7210, Condition 4) is preferably 2 to 40 g / 10 min, more preferably 4 to 40 g / min, and most preferably 5 to 20 g / min. If the MFR of the polyethylene is smaller than the above range, the surface appearance of the extruded sheet tends to deteriorate, which is not preferable. On the other hand, if it is larger than the above range, the extrudability of the sheet becomes unstable, and the physical properties are further reduced.

The amount of the polyethylene corresponds to the amount of the polypropylene described above, and is 20 to 4 parts by weight based on the total amount of the composition.
0% by weight, preferably 25 to 40% by weight, more preferably 30 to 39% by weight.

In the composition of the present invention, the viscoelastic behavior of the sheet when heated can be precisely controlled over a wide range of temperatures by blending a predetermined amount of polypropylene and polyethylene having a melt viscosity ratio in a specific range. It became. As a result, the moldability at the time of thermoforming, that is, the moldable temperature range was dramatically increased to about 6 ° C. or more.

The composition of the present invention may further contain, if necessary, additives such as dyes and pigments, stabilizers, plasticizers, antistatic agents within a range acceptable for hygiene without impairing basic properties.
UV absorbers, antioxidants, lubricants, nucleating agents, fillers, and the like may be added.

(Production of Resin Composition) In order to produce the resin composition of the present invention, predetermined amounts of the polypropylene and polyethylene are melt-kneaded. An ordinary melt extrusion device or the like may be used for such melt kneading, but for uniform dispersion, a resin temperature of 200 is obtained by a twin-screw kneader capable of obtaining high shear.
It is preferable to carry out the kneading at a temperature of at least C.

For forming the sheet, a known forming method using a T-die method or the like may be employed. The extruded sheet is preferably quenched. In order to obtain a highly transparent sheet, rapid cooling at 60 ° C. or lower is preferable, and rapid cooling at 40 ° C. or lower is more preferable. The obtained sheet may be subjected to a heat treatment in order to improve the formability, the low-temperature rigidity and the moisture-proof property.

[0018]

EXAMPLES Next, the present invention will be described more specifically based on examples. The components used in the examples and comparative examples are shown below. The melt viscosity was measured using Capillograph 1C.
[Toyo Seiki Seisakusho], 250 ° C, shear rate 1
The measurement was performed at 21.6 sec ^-1 using a capillary having a length of 10 mm and a diameter of 1 mm. The MFR was measured under JIS K 7210, condition 14 for polypropylene, and under JIS K 7210, condition 4 for polyethylene.

(Polypropylene) PP (melt viscosity = 553 Pa · s, MFR = 2.3) HT-6004 [manufactured by Chisso Corporation] PP (melt viscosity = 748 Pa · s, MFR = 1.2) S- 131 [manufactured by Sumitomo Chemical Co., Ltd.] (polyethylene) HDPE (melt viscosity = 192 Pa · s, MFR = 2)
0) F6200V [manufactured by Nippon Polyolefin Co., Ltd.] HDPE (melt viscosity = 348 Pa · s, MFR = 8.
0) A6080A [manufactured by Nippon Polyolefin Co., Ltd.] HDPE (melt viscosity = 513 Pa · s, MFR = 5.
0) 5050FD [manufactured by Nippon Polyolefin Co., Ltd.] HDPE (melt viscosity = 1010 Pa · s, MFR =
0.8) S6008G [manufactured by Nippon Polyolefin Co., Ltd.]

[Examples 1 to 8 and Comparative Examples 1 to 4] After sufficiently dry blending the respective components, the components were melt-kneaded at a resin temperature of 250 ° C. using a biaxial kneader to obtain a resin composition for thermoforming. Obtained.

Sample: A T-die extruded sheet having a thickness of 0.3 mm was used.

Tensile test: ASTM-D638 was used.

Formability: Compressed air molding machine [FBP-M
2; manufactured by CK Corporation] under a constant pressure (5 kgf /
cm ² ), the temperature of the hot plate is increased in steps of 1 ° C. at 120 to 160 ° C., and the sample sheet is molded (diameter;
4.5 mm, R; 1.5). 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.

Tables 1 and 2 show the composition and the results of the measured values.

[Table 1] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example of implementation ─────── {1 2 3 4 5 6 7 8} ────────────── [Blending (parts by weight)] PP 79 61 70 61 70 61 PP 70 61 HDPE 21 39 HDPE 30 39 30 39 HDPE 30 39 ──────── ──────────────────────────── ρPE / ρPP 0.35 0.35 0.63 0.63 0.47 0.47 0.93 0.93 ─────────── ───────────────────────── [Thermoformability] Moldable temperature range (° C) 8 12 10 13 8 11 11 14 ───── ─────────────────────────────── [Physical properties] Tensile strength (N / mm ² ) 37 36 38 38 36 36 36 35 Zhang modulus ^{(N / mm 2) 1800 1750} 1800 1860 1210 1450 1810 1740 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━

[0025]

[Table 2] Comparative example 例─────────── 1 2 3 4 ──────────────────────────────── [Formulation ( Parts by weight)] PP 100 70 85 PP 100 HDPE 15 HDPE 30 ρ ρPE / ρPP − − 1.83 0.93 ──────────────────────────────── [Thermoformability] Moldable temperature range (° C) 2 3 3 3 ──────────────────────────────── [Physical property value] Tensile strength (N / mm ² ) 35 35 37 37 Tensile Elastic modulus (N / mm ² ) 1700 820 1800 1920 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

[0026]

The thermoforming composition of the present invention maintains the balance of physical properties, appearance, and moisture proofness of the polypropylene resin and greatly expands the temperature range in which thermoforming is possible. It is excellent in moldability and compressed air moldability, and is preferable as a material for various packaging containers such as pharmaceutical packaging such as food packaging and PTP packaging.

Claims (3)

(57) [Claims] 1. Polypropylene 80 based on the total amount of the composition
A resin composition comprising 60 to 60% by weight of polyethylene and 20 to 40% by weight of polyethylene.
Low rate (JIS K 7210, condition 4) 5 to 20 g /
10min high density polyethylene and JIS
2 by capillary rheometer according to K 7199
For thermoforming, wherein the viscosity ratio (ρPE / ρPP) of the melt viscosity (ρPP) of the polypropylene and the melt viscosity (ρPE) of polyethylene measured at 50 ° C. and a shear rate of 121.6 sec ⁻¹ is 0.05 to 1.8. Resin composition. 2. The polypropylene has a melt flow rate.
(JIS K 7210, condition 14) 1 to 5 g / 10 min
The resin composition for thermoforming according to claim 1, which is a homopolymer of 3. A sheet formed by molding the resin composition according to claim 1.