JP2000272065A - Composite multilayer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To jointly provide a low temperature sealing property, heat resistance, and an easy-opening property by forming a sealing layer with a mixture of the specific ratio of polyethylene resin and polypropylene resin, and setting the ratio of values of the melt flow rate of polyethylene resin and polypropylene resin at a specific value. SOLUTION: The multi-layer sheet of a support layer comprises a seal layer and polyolefin resin, wherein the seal layer is formed of a mixture of polyethylene resin of 30-90 wt.% and polypropylene resin of 10-70 wt.%, and the ratio of values of a melt-flow rate of polyethylene resin and a melt-flow rate of polypropylene resin measured by JISK 6758 is set at 0.5-20. Herein, polypropylene resin is a homopolypropylene, ethylene-propylene random or its block copolymer, etc. Also, polyethylene resin is high density, intermediate density, and low density polyethylene, an ethylene-vinylacetate copolymer, ethylene-vinylalcohol copolymer, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite multilayer sheet for packaging having excellent low-temperature sealability, easy-openability, and heat resistance. More specifically, since it has excellent low-temperature sealing properties with a lid material suitable as a packaging material for foods and beverages, it can be suitably used as a packaging material particularly in the form of a skin pack.

[0002]

2. Description of the Related Art Conventionally, plastic sealed containers having low-temperature sealing properties and easy-opening properties such that a lid can be easily opened have been used as packaging containers for foods and beverages.
The general methods so far include a delamination type in which the sealing strength is controlled by adjusting the strength between the sealing layer of the lid material and the bottom material and the adjacent resin layer, and the resin forming the sealing layer of the lid material. By changing the composition, the sealing strength between the container and the container is controlled, and an interface peeling type in which the interface between the lid material and the container is peeled and opened and a cohesive peeling type in which the seal layer is cohesively broken and opened are generally used. Was.

[0003] However, for example, the amount of heat applied at the time of sealing is small in that the contents are sealed by a method of sealing the bottom material by heating a lid material such as a skin pack package generally used in meat packaging. In the packaging / filling form, adhesion to the contents due to shrinkage of the lid material after sealing is regarded as important, and low-temperature sealing is given priority. For this reason, the melting point of the resin compound of the seal layer is set relatively low,
If only a low-temperature seal is used, a product that can obtain a sufficient seal strength even at a low seal temperature of around 100 ° C. is already on the market. However, in any of the above easy-opening methods, hot water sterilization after filling cannot be performed due to the problem of seal strength,
In particular, there has not yet been developed a packaging material capable of hot water sterilization with a packaging material for a skin pack.

[0004]

SUMMARY OF THE INVENTION The present invention provides a composite multi-layer sheet for packaging which has both low-temperature sealability and heat resistance, which cannot be solved by the prior art, and also has easy-openability. Is what you do.

[0005]

According to the present invention, there is provided an ink jet recording apparatus having a thickness of 1 to 2 mm.
A multilayer sheet comprising at least two layers of a seal layer having a thickness of 00 μm and a support layer made of a polyolefin resin outside the seal layer, wherein the seal layer is composed of 30 to 90% by weight of a polyethylene resin and 10 to 70% of a polypropylene resin.
Made from a mixture of by weight%, melt flow rate of the polyethylene resin (hereinafter referred to as MFR _PE.) And the polypropylene resin has a melt flow rate (hereinafter referred to as MFR _PP.) Was measured by the method prescribed in JISK6758 of A composite multilayer sheet having a numerical value ratio of 0.5 to 20.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a multilayer sheet comprising a seal layer having a peeling function and at least two layers of a support layer outside the seal layer, wherein the MFR of a resin mixture used for the seal layer is _PE / MFR _PP value is 0.5 ~
It is characterized in that it is in the range of 20, but more preferably in the range of 2 to 8. MFR _PE / M
If the FR _PP value is less than 0.5, good low-temperature sealing properties cannot be obtained. Further, when the MFR _PE / MFR _PP value exceeds 20, a good sheet appearance cannot be obtained unless the MFR of the polyolefin resin of the adjacent support layer is increased.
As a result, it becomes difficult to form a sheet due to resin dripping.

[0007] As the polypropylene resin used in the seal layer of the present invention, for example, homopolypropylene, ethylene-propylene random copolymer, ethylene-propylene block copolymer, ethylene-propylene-butene copolymer and the like are used. it can. Although the MFR of the polypropylene resin is not particularly specified, it is 0.5 to 2.0.
g / 10 min is more preferable in consideration of the MFR ratio with the polyethylene resin and the mixing ratio. Further, as the polyethylene resin, for example, high density polyethylene, medium density polyethylene, low density polyethylene,
Linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ionomer and the like can be used. However, for the ethylene-vinyl acetate copolymer, the content of vinyl acetate (VAC), which is a comonomer component, is preferably less than 20 mol% in order to suppress odor. The MFR of the polyethylene resin is not particularly limited, but is preferably 1.0 g / 10 min or more in consideration of the MFR ratio with the polypropylene resin and the mixing ratio.

[0008] The resin mixture used in the seal layer of the present invention contains 30 to 90% by weight of a polyethylene resin.
The blending ratio is 10 to 70% by weight of the polypropylene resin, and more preferably 40 to 60% of the polyethylene resin.
% By weight and 40 to 60% by weight of the polypropylene resin, and in this range, good low-temperature sealing properties can be obtained with respect to both the polyethylene resin and the polypropylene resin. However, when the mixing ratio of the polyethylene resin is less than 30% by weight and the ratio of the polypropylene resin is 70% by weight.
If the content of the polyethylene-based resin exceeds 90% by weight and the proportion of the polypropylene-based resin is less than 10% by weight, the content of the polyethylene-based resin is less than 10% by weight. May cause a problem that good sealing properties cannot be obtained.

The thickness of the sealing layer of the present invention is 1 to 200 μm.
However, it is more preferably 5 to 20 μm. If the thickness of the sealing layer is less than 1 μm, the sealing with the lid material is not stable. On the other hand, if the thickness exceeds 200 μm, fluffing occurs at the time of opening, or the feeling of opening becomes hard, and it cannot withstand actual use.

As the polyolefin resin for the support layer used in the present invention, for example, polyethylene, polypropylene, a copolymer thereof or the like is used, and a polypropylene resin is more preferable. A polypropylene resin having a melt flow rate of 0.5 to 5 g / min is desirable for extrusion molding. In addition, homopolypropylene resin is desirable in order to maintain heat resistance. However, when heat resistance is not required and characteristics are not impaired, other olefin-based or copolymer-based resins such as ethylene may be used alone or as a blend. It does not matter. When the melt flow rate of the polypropylene resin is less than 0.5 g / min, the spread of the resin is poor, and when it exceeds 5 g / min, the resin tends to sag, which hinders sheeting.

The layer adjacent to the sealant is not limited to a single layer of the polyolefin resin. For example, if it is necessary to improve oxygen barrier properties, an ethylene-vinyl alcohol copolymer may be sandwiched between the intermediate layers via an adhesive layer. Necessary resins may be laminated according to required characteristics to form a multilayer structure.

Further, a polyethylene resin may be added to the support layer adjacent to the seal layer, if necessary.

The method for producing the multilayer sheet of the present invention includes coextrusion, dry lamination, and extrusion lamination.
It can be manufactured by a known technique.

The present invention will be described with reference to the following examples and comparative examples, but these are merely examples, and the present invention is not limited to these. Examples 1 to 5, Comparative Example 1
The seal layers Nos. 5 to 5 were made of the resin and the seal layer thickness shown in Tables 1 and 2. The sheet samples shown in Examples and Comparative Examples were prepared by using first to sixth extruders, feed blocks, T dies,
The following resin compositions were extruded from each extruder using a 6-type 6-layer multilayer sheet forming apparatus including a cooling roll, a take-up device, a slitter, and a winder. (First extruder) Seal layer; Mixture of polyethylene-based resin and polypropylene-based resin (details are shown in Tables 1 and 2 below) (Second extruder) Support layer: Polypropylene (MFR = 0.
5g / 10min) Sumitomo Noblen FH1016 (manufactured by Sumitomo Chemical Co., Ltd.) (third extruder) Adhesive layer; maleic anhydride-modified polypropylene Adtex ER313E (Nippon Polyolefin)
(Fourth extruder) Gas barrier layer; ethylene-vinyl alcohol copolymer containing 32 mol% of ethylene;
EVAL F101AZ (manufactured by Kuraray Co., Ltd.) (fifth extruder) Adhesive layer; maleic anhydride-modified polypropylene Adtex ER313E (Nippon Polyolefin)
(Sixth extruder) Support layer; polypropylene (MFR = 0.
5g / 10min) Sumitomo Noblen FH1016 (Sumitomo Chemical Co., Ltd.)

The abbreviations of the raw materials used in Tables 1 and 2 are as follows. PP; homopolypropylene (MFR = 1.0 g / 10
min) PP; ethylene-propylene random copolymer (MF
R = 0.5 g / 10 min) PP; ethylene-propylene block copolymer (MF
R = 1.2 g / 10 min) PP; ethylene-propylene-butene copolymer (MF
R = 3.0 g / 10 min) PP; ethylene-propylene random copolymer (MF
R = 1.6 g / 10 min) PP; ethylene-propylene random copolymer (MF
R = 3.0 g / 10 min) PP; homopolypropylene (MFR = 1.5 g / 10)
min) PP; homopolypropylene (MFR = 2.0 g / 10)
min) PE; high-density polyethylene (MFR = 0.5 g / 10)
min) PE; low density polyethylene (MFR = 4.5 g / 10)
min) PE; linear low-density polyethylene (MFR = 5.8 g)
/ 10 min) PE; ethylene-vinyl acetate copolymer (MFR = 24.
5 g / 10 min, VAC = 5%) PE; ethylene-vinyl alcohol copolymer (MFR
= 34.2 g / 10 min) PE; low-density polyethylene (MFR = 0.5 g / 10 min)
min) PE; ethylene-vinyl acetate copolymer (MFR = 15 g)
/ 10 min, VAC = 20%) PE; high density polyethylene (MFR = 16.5 g / 1)
0 min) PE; ethylene-vinyl acetate copolymer (MFR = 37.
(5 g / 10 min, VAC = 40%)

The low-temperature sealing property is determined under a predetermined condition (each set temperature × 1.5 kg / cm ² × 1.0) using a single-shot sealing machine.
Seconds) with lid material (composition; 0-Ny (stretched nylon) / EVO)
H (ethylene-vinyl alcohol copolymer) / LLDP
E (linear low-density polyethylene) sealant), and a seal temperature at which a seal strength of 100 g or more (15 mm width, 180 ° peeling, 300 mm / min tension) at which cohesive failure of the seal layer of the bottom material was observed was obtained. Was described as the seal lower limit temperature.

The heat resistance is determined by sealing the lid (constituting: 0-Ny / EVOH / LLDPE) under predetermined conditions using a single-shot sealing machine, and further placing the same in hot water at 95 ° C. for 40 minutes, The rate of decrease in seal strength was calculated. Reduction rate of seal strength = (seal strength after hot water treatment / seal strength of untreated product) × 100 (%) The seal strength was evaluated at a width of 15 mm, 180 ° peeling, and a pulling speed of 300 mm / min. Was done.

The peel feeling was determined by subjecting the above-mentioned lid material sealed sample to a width of 30 mm and subjecting the test to peeling the lid material by hand. Δ, those that could not be peeled were rated as ×.

The evaluation of the odor was carried out at a diameter of 70 mm and a height of 45 m.
m, into a cup with a bottom diameter of 30 mm, fill the contents with pure water, seal with a lid material, retort treatment (121 ° C,
After 30 min), the package was opened, and the generated odor was subjected to a sensory evaluation. Those that were not bothersome, those that smelled slightly, and those that clearly felt an odor were evaluated as x.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

According to the present invention, it is possible to obtain a composite multilayer sheet having low-temperature sealing properties, heat resistance, and easy-openability, which could not be achieved conventionally.

Claims (1)

[Claims] 1. A sealing layer having a thickness of 1 to 200 μm,
And a multilayer sheet composed of at least two layers of a support layer composed of a polyolefin resin outside the seal layer,
The seal layer is composed of a mixture of 30 to 90% by weight of a polyethylene-based resin and 10 to 70% by weight of a polypropylene-based resin, and the JIS K675 of the melt flow rate of the polyethylene-based resin and the melt flow rate of the polypropylene-based resin.
The ratio of the numerical values measured by the method specified in 8 is 0.5 to 2
A composite multilayer sheet characterized by being 0.