JPH0952327A - Multilayer sheet and packaging container made of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet in which a lowering of impact resistance due to aged deterioration is small and has improved film forming property and transparency, and which can be easily formed into a packaging container. SOLUTION: This multilayer sheet has an auxiliary layer comprising polyethylene terephthalate having a limiting viscosity of 0.6-1.0dl/g on each side of a main structural layer comprising a propylene resin composition containing propylene having a syndiotactic structure and in which the weight ratio between the main structural layer and auxiliary layer is in the range of 90:10-40:60, and a packaging container is formed from the multilayer sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer structure sheet and a packaging container made of the same. More specifically, the present invention relates to a multi-layered sheet which is transparent and has excellent moldability and whose impact resistance is less likely to deteriorate over time, and a packaging container made of the same.

[0002]

2. Description of the Related Art Polyesters, especially polyethylene terephthalate (hereinafter referred to as PET), are excellent in mechanical properties, heat resistance, chemical resistance, dimensional stability and the like.
Widely used as film and plastic. Recently, a sheet made of PET and a molded product made of PET are easily moldable and have good transparency, gloss, and gas permeability, so that attempts have been made to use them as containers for packaging various products. .

However, the physical properties of these packaging containers deteriorate with time, and it is necessary to improve this point. The impact resistance of the above-mentioned sheet made of PET as a raw material and the packaging container made of the PET is remarkably deteriorated when left for a long time in a high humidity atmosphere. Normal storage conditions (30 ℃, 50
% RH) also has a drawback that the impact resistance is lowered and cracking easily occurs after 3 months or more, and its improvement has been desired.

On the other hand, polypropylene is widely used as a packaging material for hollow molded articles and the like because it is inexpensive and has characteristics such as flexibility, hygienic compatibility, and excellent water vapor permeation resistance. However, there are problems that the sheet made of polypropylene as a raw material and a molded product made of the same have low transparency and poor rigidity, and easily cause drawdown during thermoforming.

As a method for improving the transparency of a sheet made of polypropylene as a raw material, it has been proposed to use a polypropylene resin composition containing polypropylene having a syndiotactic structure (Japanese Patent Laid-Open No. 7-12645).
No. 4, JP-A-7-126458). However, although the transparency is improved, the rigidity, which is another problem of the sheet made of polypropylene, has not been improved.

[0006]

Therefore, the object of the present invention is to eliminate the drawbacks of the sheet made of PET and the sheet made of polypropylene as described above, and the impact resistance is less deteriorated with time. An object of the present invention is to provide a sheet having excellent film formability, transparency, and secondary processability into a packaging container.

[0007]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors for such a purpose, in a multilayer structure sheet comprising a PET layer and a specific polypropylene resin composition layer, P
By defining the weight ratio of the ET layer and the specific polypropylene resin composition layer, a multilayer structure sheet having less deterioration in impact resistance over time and excellent in transparency, film-forming property, secondary processability and appearance can be obtained. The present invention has been found to be obtained and has reached the present invention.

That is, according to the present invention, the intrinsic viscosity is 0.6 to 1.2 on both sides of the main constituent layer made of a propylene resin composition containing polypropylene having a syndiotactic structure.
A multilayer structure sheet having an auxiliary layer of 0 dl / g polyethylene terephthalate resin, wherein the weight ratio of the main constituent layer and the auxiliary layer is in the range of 90:10 to 40:60, and It relates to a packaging container made of it.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The syndiotactic polypropylene used in the present invention is measured by ¹³ C-NMR obtained from a propylene monomer by a known polymerization method such as a thriller polymerization method, a bulk polymerization method and a gas phase polymerization method. A polypropylene having a syndiotactic pentad fraction of 0.7 or more, which is a copolymer containing a small amount of a comonomer other than propylene as long as the transparency and mechanical properties of the multilayer structure sheet of the present invention are not impaired. Is also good.

The propylene resin composition containing the polypropylene having the syndiotactic structure used in the present invention comprises 5 to 95 parts by weight of syndiotactic polypropylene and 95 to 5 of isotactic polypropylene.
A polypropylene resin composition composed of parts by weight is preferable because a sheet having the highest transparency can be obtained. The ratio of syndiotactic polypropylene is 95
If it exceeds the weight part, the fluidity of the resin deteriorates and it becomes difficult to form a sheet. On the other hand, if the proportion of isotactic polypropylene exceeds 95 parts by weight, the transparency of the obtained sheet will be insufficient.

As a method for obtaining a propylene resin composition containing polypropylene having a syndiotactic structure used in the present invention, any method can be adopted, but a syndiotactic polypropylene resin and an isotactic polypropylene resin are used. It is preferable to knead and pelletize under a molten condition in advance using a twin-screw kneader or the like.

The polypropylene resin composition used in the present invention has a melt flow rate of 0.1 at 230 ° C.
-10g / 10min, preferably 0.5-5g / 10mi
n. Melt flow rate at 230 ° C is 10.
When it is higher than 0 g / 10 min, the mechanical properties of the obtained sheet are remarkably deteriorated and the impact resistance is not sufficiently improved. Further, the melt flow rate at 230 ° C. is 0.
If it is lower than 1 g / 10 min, the resin fluidity is deteriorated and it becomes difficult to form a sheet.

The melt flow rate of the polypropylene resin composition described in the present invention means that the polypropylene resin composition is filled in a cylinder having an inner diameter of 9.55 mm and a length of 162 mm, and the resin in the cylinder is melted at 230 ° C. ,
When a plunger with a weight of 2160 g and a diameter of 9.4 mm was placed and the load was evenly applied, the weight velocity (g / 10 min) of the molten polymer extruded from the 2.1 mm diameter orifice provided in the center of the cylinder was measured. Indicates the measured value.

As the PET resin used in the present invention, terephthalic acid or its ester-forming derivative (for example, lower alkyl ester) and ethylene glycol or its ester-forming derivative (for example, monocarboxylic acid ester ethylene oxide) are known. It can be obtained by polycondensation by the above method, and may contain other copolymerization components as long as the original characteristics of the PET resin are not impaired.

Examples of such copolymerizable components include aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1, Examples thereof include diol such as 4-cyclohexanedimethanol, polyethylene glycol, polyalkylene glycol such as poly (tetramethylene oxide) glycol, and the like. The blending amount of these copolymerization components is usually 10 mol% or less, preferably 5 mol% or less.

The PET resin used in the present invention has an intrinsic viscosity of 0.6 to 1.0 dl / g, preferably 0.7 to 0.9 dl.
/ G. When the intrinsic viscosity is lower than 0.6 dl / g, the mechanical properties of the obtained sheet are remarkably deteriorated and the impact resistance is not sufficiently improved. When the intrinsic viscosity is higher than 1.0 dl / g, the resin fluidity becomes poor and it becomes difficult to form a sheet.

The multilayer polyester sheet of the present invention is a substantially unstretched sheet obtained by the conventional film forming means of the PET resin and polypropylene resin composition. Such an unstretched multilayer structure sheet is obtained by melt-mixing the composition of the present invention with an extruder and then discharging it from a general multilayer extrusion die and quenching it with a cooling drum.

The multilayer structure sheet of the present invention is a three-layer sheet having a main constituent layer made of a polypropylene resin composition and auxiliary layers made of PET resin on both sides. The weight ratio of the main constituent layer to the auxiliary layer is 90:10 to 40:60, preferably 80:20 to 70:30. When the weight ratio of the main constituent layer is less than 40% by weight, the impact resistance is not sufficiently improved, and when it is more than 90% by weight, the rigidity of the sheet decreases and the drawdown during thermoforming is reduced. It has the drawback of becoming larger.

As described above, the multilayer structure sheet of the present invention has PE on both sides of the main constituent layer made of the polypropylene resin composition.
Although it is a three-layer sheet having an auxiliary layer made of T resin, if the ratio of the auxiliary layers on both sides is extremely different, the unevenness of the sheet surface becomes remarkable during film formation, which is not preferable, and the weight ratio of the auxiliary layers on both sides is 40: The range of 60 to 60:40 is preferable.

The packaging container of the present invention can be obtained by thermoforming the multilayer structure sheet of the present invention. Thermoforming is carried out by heating and softening the sheet, pressing it against the desired mold, removing the air in the gap between the mold and the material, and adhering it to the mold at atmospheric pressure, or forming the sheet by compressed air above atmospheric pressure. It is possible to apply pressure molding such that it is brought into close contact with the mold, or molding that uses vacuum and pressure together.

[0021]

EFFECT OF THE INVENTION The multi-layered sheet of the present invention and the packaging container comprising the same have excellent transparency, excellent thermoformability and secondary processability, and their impact resistance decreases with time even under high temperature and high humidity. It is few and can be widely used as various packaging containers.

[0022]

The present invention will be described in more detail with reference to the following examples. The main physical property values in the examples were measured by the methods described below. (1) Intrinsic viscosity (IV) 0.5 g of a sample was dissolved in 50 ml of a mixed solution of 60% by weight of phenol and 40% by weight of 1,1,2,2-tetrachloroethane, and measured at 20 ° C. (2) Melt flow rate (MFR) A melt indexer (manufactured by Toyo Seiki Seisaku-sho, Ltd.) was used and measured at a resin melting temperature of 230 ° C. according to JIS-K7210. (3) Transparency (Haze) A 300 μm thick sheet was measured according to JIS-K7105. (4) Impact resistance A sheet having a thickness of 300 µm was punched into a JIS No. 2 type test piece, and the elongation at break (%) obtained by measurement according to JIS-K7113 was evaluated. (5) Rigidity (Elastic Modulus) A sheet having a thickness of 300 μm was punched into a JIS No. 2 type test piece and measured according to JIS-K7113.

Examples 1 to 5 and Comparative Examples 1 to 4 80% by weight of syndiotactic polypropylene having an MFR value of 4.9 g / 10 min and 20% by weight of isotactic polypropylene having an MFR value of 4.0 g / 10 min and a screw diameter of 30 mm. Melt blended using a twin-screw kneader, and MF
A pelletized resin composition having an R value of 6.1 g / 10 min was obtained.

80 cm wide T equipped with three single screw extruders
Using a multilayer sheet extruder having a die, the above resin composition as a raw material is used as a main constituent layer, and the intrinsic viscosity of ethylene glycol and terephthalic acid is 0.58 dl / g, 0.8
A three-layer sheet having a thickness of 0.3 mm was extruded using 3 kinds of PET resin of 5 dl / g and 1.02 dl / g as the auxiliary layer in the ratio shown in Table 1. Cylinder temperature of the main constituent layer extruder is 23
0 ℃, auxiliary layer extruder cylinder temperature 280 ℃, T
The die temperature was 270 ° C., and the cooling roller temperature was 30 ° C. The transparency (haze) and rigidity (elastic modulus) of the sheet were measured.

The obtained sheet was left at room temperature for 3 months under the measurement conditions (40 ° C., 60% RH atmosphere for 7 days).
Then, the change in impact resistance (tensile elongation) was measured.

Using a single-shot vacuum thermoforming machine, this sheet was
A cylindrical container having an inner diameter of 10 cm and a depth of 55 mm was formed at a preheating temperature of 300 ° C., and the formability was evaluated by the preheating time width of the sheet required to obtain a molded product having good shapeability. As the evaluation criteria, the one having a preheating time width of 10 seconds or more was (◯) and the one having a preheating time width of 10 seconds or less was (x).

The molded product thus obtained was allowed to stand in an atmosphere of 40 ° C. and 60% RH for 7 days, then filled with water and dropped from a predetermined height with the bottom portion down, and cracking of the molded product was measured. The evaluation standard was that no one of the five molded products cracked (◯) and one cracked (x). The above evaluation and measurement results are summarized in Table 1.

[0028]

[Table 1]

In Examples 1 to 3, there was one crack each in the 70 cm evaluation of the molded product over time and in the drop impact test, but in the evaluation of 50 cm or less, no cracking occurred at all, and the conventional PET resin was used. A significant performance improvement was observed compared to a single molded product. The sheets and molded articles obtained in Examples 4 and 5 gave satisfactory results in all evaluation and measurement items.
On the other hand, in Comparative Example 1 in which the weight ratio of the main constituent layers was small, the impact resistance (tensile elongation) was not improved and the physical properties were deteriorated over time. On the contrary, in Comparative Example 2 in which the weight ratio of the main constituent layers was large, the rigidity (elastic modulus) of the sheet was low, thermoforming could not be performed, and a molded product worthy of the later evaluation could not be obtained.
Further, when the viscosity of the PET resin of the auxiliary layer was too low as in Comparative Example 3, the impact resistance (tensile elongation) was not improved and the physical properties were deteriorated over time. PE as an auxiliary layer as in Comparative Example 4
If a resin having a high viscosity out of the range was selected as the T resin, a film could not be formed into a sheet, which did not lead to the subsequent tests.

Claims (2)

[Claims] 1. A multilayer having a main constituent layer made of a propylene resin composition containing polypropylene having a syndiotactic structure and an auxiliary layer made of a polyethylene terephthalate resin having an intrinsic viscosity of 0.6 to 1.0 dl / g on both sides. A structural sheet in which the weight ratio of the main constituent layer and the auxiliary layer is 9
A multilayer sheet and a packaging container comprising the same, which are in the range of 0:10 to 40:60. 2. A polypropylene resin composition containing polypropylene having a syndiotactic structure is a polypropylene resin composition comprising 5 to 95 parts by weight of syndiotactic polypropylene and 95 to 5 parts by weight of isotactic polypropylene. Claim 1 characterized by
The multilayer structure sheet described above and a packaging container made of the same.