JPH09150490A - Multilayered sealant film and composite packing material using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered sealant film having both of heat resistance capable of withstanding high temp. filling or boiling sterilization and low temp. sealability and excellent in impact resistance and flexibility. SOLUTION: The base material layer of a sealant film is composed of LLDPE with density of 0.900-0.913g/cm<3> . The seal layer thereof composed of LLDPE having an m.p. of 97-115 deg.C and a wt. average mol.wt./number average mol.wt. value of 1.5-3 and characterized in that a crystal fusion peak is single at crystal fusion temp. measured by a differential scanning calorimeter and a temp. width from the start of the fusion of all crystals of the film to the completion thereof is within 20 deg.C. The thickness of the seal layer is 30% or more of the total thickness of the film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer sealant film used for, for example, liquid food packaging, and more particularly, it has heat resistance capable of withstanding high temperature filling up to 100 ° C. and boiling sterilization, and low temperature sealability. The present invention also relates to a multi-layer sealant film having both excellent impact resistance and flexibility, and further relates to a composite packaging material obtained by using this sealant film.

[0002]

2. Description of the Related Art In recent years, in the food industry, packaging with a plastic film has been frequently carried out for reasons such as hygiene, economy, and ease of handling. In particular, in the field of liquid food packaging, in order to reduce the viscosity of a viscous material and sterilize an object to be packaged, it is heated before packaging or boiled after packaging. The sealant film used for this purpose is made of a polyethylene-based resin having a melting point higher than the heating temperature by 10 ° C. or more so as to prevent deterioration of the sealing portion due to heating and fusion of the sealing surface.

In the conventional sealant film, although the film melting point is sufficiently higher than the heating temperature as described above,
There are drawbacks such that the sealing surfaces are fused and the sealing strength is reduced. This is because components having a melting point lower than the melting point of the film measured by DSC are present in the film due to the raw material resin, and these are heat-sealed or occupy a part of the sealing component. In order to overcome such drawbacks, conventionally, as a polyethylene resin material, a low density polyethylene resin (hereinafter abbreviated as LDPE) or an ethylene-vinyl acetate copolymer having a low melting point (hereinafter abbreviated as EVA) or Linear low-density polyethylene resin (hereinafter LLDP
(Abbreviated as E) was used.

However, when a resin having a high melting point is used, the heat resistance of the film is improved, but the low-temperature sealing property is poor, and the flexibility of the film is insufficient, and the impact resistance is insufficient.

To compensate for the lack of impact resistance of the film, L
LLDPE is preferable to DPE, and in order to further improve impact resistance, LLDPE to be used is L having a lower density.
It is also possible to use a resin material mixed with LDPE (Japanese Patent Laid-Open No. SHO 61-61).
As a low-density flexible polyethylene resin, 4-methyl-1-pentene and 1-
A copolymer of a higher α-olefin such as octene and ethylene was used (see JP-A-61-241340).

However, even if such a resin material is used,
There is a limit to achieving both heat resistance and impact resistance of the film.

On the other hand, there is a demand for speeding up the packaging process due to demands such as reduction in packaging cost and improvement in production efficiency. For this purpose, it is necessary to lower the melting point of the film and lower the sealing temperature. However, if the melting point is lowered, the problems such as film fusion as described above cannot be avoided, so that the film having heat resistance has a sealing temperature higher by about 20 ° C. than the film for low temperature sealing. Therefore, it has been difficult to achieve both high speed packaging process and heat resistance of the film.

[0008]

In view of the above points, the present invention has both heat resistance capable of withstanding high temperature filling up to 100 ° C. and sterilization by boiling, and low temperature sealability, and has impact resistance and flexibility. It is an object of the present invention to provide a multilayer sealant film excellent in heat resistance.

[0009]

The present invention has been devised to solve the above problems and has a melting point of 97 to 115.
Melting point peak by a differential scanning calorimeter (hereinafter abbreviated as DSC) in the range of ° C and a weight average molecular weight / number average molecular weight (hereinafter abbreviated as M _W / M _N ) value of 1.5 to 3. And LLDPE having a temperature range of 20 ° C. or less from the melting peak temperature until all the crystals are melted is used as a raw material resin for the seal layer without mixing with other polyethylene.

That is, the multilayer sealant film according to claim 1 is a multilayer film comprising a base material layer and a seal layer laminated on at least one surface thereof, and the base material layer has a density of 0.900 to 0.90. L that is 0.913 g / cm ³
The sealing layer is made of LDPE and has a melting point of 97 to 115.
In the range of ℃, the value of M _W / M _N is 1.5 to 3,
LL having a single crystal melting peak at a crystal melting temperature measured by DSC and having a temperature range of 20 ° C. or less from the start to the end of melting of all the crystals of the film
It is made of DPE, and the thickness of the seal layer is 30% or more of the thickness of the entire film.

Further, the multilayer sealant film according to claim 2 is a multilayer film comprising a base material layer and a seal layer laminated on at least one surface thereof, and the base material layer comprises
LLD having a density of 0.913 to 0.930 g / cm ^3.
The sealing layer is made of PE and has a melting point of 97 to 115 ° C., a M _W / M _N value of 1.5 to 3, and a DS of
LLDP having a single crystal melting peak at the crystal melting temperature measured by using C and having a temperature range of 20 ° C. or less from the start to the end of melting of all the crystals of the film.
The thickness of the seal layer is 2 of the total thickness of the film.
It is 0% or more.

The invention according to claim 3 is the invention according to claim 1 or 2.
A composite packaging material in which a reinforcing layer is laminated on the non-sealing surface of the described multilayer sealant film.

In the multilayer sealant film according to claims 1 and 2, the melting point is in the range of 97 to 115 ° C,
The value of M _W / M _N is 1.5 to 3, the single crystal melting peak is present at the crystal melting temperature measured by DSC, and the total crystal of the film starts to melt and ends. LLDPE with a temperature range of 20 ° C or less has a single polymerization active point (known as a metallocene catalyst, a single-site catalyst, a Kaminsky catalyst, etc.)
Is obtained by using. However, the above LLDP
The catalyst for producing E is not limited to the structure and combination of single active site catalysts as described above. LLDPE obtained by polymerization with a single active site catalyst is more flexible than conventional LLDPE of the same density.

The melting point of LLDPE forming the seal layer is 9
7 to 115 ° C, but has low-temperature sealability and 10
To maintain heat resistance up to 0 ℃, the melting point of LLDPE is 10
The range of 3 to 110 ° C. is desirable, and the optimum resin is selected according to the heating temperature. The difference between the melting point of LLDPE and the heating temperature is preferably about 4 to 8 ° C. 103 ~ 110 ℃ above
Is about the same as the melting point of the conventional low temperature sealable sealant film, and in this case, the temperature at which the heat seal strength is saturated is about the same as the melting point of the conventional low temperature sealable sealant film. If the melting point of LLDPE is below the above lower limit, heat resistance will not be exhibited, and conversely if it exceeds the above upper limit, low temperature sealability will not be exhibited.

The M _L / M _N of LLDPE of the seal layer is 1.
It is 5 to 3, preferably 1.8 to 2.6. M _W / M _N
When the value is less than the lower limit, it may be very difficult to form a film. On the other hand, when the value is more than the upper limit, the low-molecular-weight fusion component is increased, and fusion during heating is likely to occur.

The LLDPE of the seal layer has one crystal melting peak measured by DSC, and the temperature range from the melting peak temperature to the end of melting of all crystals is 20 ° C.
It is within. If this temperature range exceeds the above value, it is difficult to achieve both heat resistance and low-temperature sealability.

In the multilayer sealant film according to claim 1, the raw material resin of the base material layer has a density of 0.900 to 0.9.
Any LLDPE of 13 g / cm ³ may be used, and LLDPE generally used in the past may be used, or a plurality of types of LLDPE may be mixed and used.

If the density of LLDPE of the base material layer deviates from the above range, the desired heat resistance and impact resistance may not be obtained in some cases. As a raw material resin for the base material layer, LLD is used.
When EVA is used instead of PE, the resulting film has poor heat resistance, and LDPE is not preferable because the film may have insufficient impact resistance.

In the multilayer sealant film according to claim 1, the thickness of the sealing layer is 30% of the thickness of the entire film.
Or more, preferably 33% or more. If the thickness of the seal layer is not sufficient, the temperature range of the rise of the seal strength may be widened and the seal strength of the low-temperature seal may be lowered, and the impact resistance and flexibility of the film of the seal layer may be sufficiently exhibited. It may not be done.

In the multilayer sealant film according to claim 2, the raw material resin for the base material layer has a density of 0.913 to 0.9.
Any LLDPE of 30 g / cm ³ may be used, and LLDPE commonly used in the past may be used, or a plurality of types of LLDPE may be mixed and used.

If the density of the LLDPE of the base material layer deviates from the above range, the desired heat resistance and impact resistance may not be sufficient.

In the multilayer sealant film according to claim 2, the thickness of the sealing layer is 20% of the total thickness of the film.
Or more, preferably 25% or more. If the thickness of the seal layer is not sufficient, the temperature range of the rise of the seal strength may be widened and the seal strength of the low-temperature seal may be lowered, and the impact resistance and flexibility of the film of the seal layer may be sufficiently exhibited. It may not be done.

The method for producing the film is not particularly limited.
For example, the resin composition can be formed into a film by an inflation method, a T-die method, or the like. Further, the method used for lamination is not particularly limited, and a dry laminating method,
Although a coextrusion method or the like can be applied, coextrusion molding is preferable in terms of processability and production efficiency.

Compositions made of polyethylene resins include
Antioxidants, slip agents, anti-blocking materials, etc.,
Additives that are usually added to polyethylene resins can be added within the range of addition amount that does not impair the properties of the film.

As the slip agent, oleic acid amide,
Organic amides such as stearic acid amide and erucic acid amide, ethylenebisoleic acid amide, ethylenebisstearic acid amide, methylbisoleic acid amide, methylenebisstearic acid amide, hexamethylenebisoleic acid amide, hexamethylenebisstearic acid amide An organic amide dimer such as

As the anti-blocking agent, an inorganic filler can be used, and the above polyethylene-based resin may contain, for example, 1000
10000ppm, desirably 3500-7500p
pm.

As the anti-blocking agent, inorganic salts such as calcium carbonate and magnesium carbonate, natural substances such as talc and diatomaceous earth, and synthetic silica such as hollow silica and hydrophobic silica are used.

According to the third aspect of the invention, the reinforcing layer is laminated on the non-sealing surface of the multilayer sealant film according to the first or second aspect, that is, on the surface different from the sealing surface to obtain a composite packaging material. When the multilayer sealant film according to claim 1 or 2 comprises a base material layer and a seal layer laminated on one surface thereof, the reinforcing layer is provided on the opposite surface of the base material layer from the seal layer. When the multilayer sealant film according to claim 1 or 2 comprises a base material layer and seal layers laminated on both surfaces thereof, the reinforcing layer is provided between at least one seal layer and the base material layer. As the reinforcing layer, a plastic film different from the film of the seal layer, for example, a polyamide film, a polyester film, a metal foil, paper or the like is used. Since the multi-layer sealant according to the present invention is configured as described above, the following effects are exhibited.

That is, since LLDPE, which has an extremely low melting point component lower than the film melting point measured by DSC, is used as the raw material resin for the sealing layer, when the high temperature material filling up to 100.degree. Face fusion does not easily occur. Therefore, it becomes possible to bring the melting point of the resin close to the heating temperature, and the sealing layer has a low melting point LLD.
PE can be used.

As described above, the sealing layer has a low melting point of LLDP.
Since it can be constituted by E, it is possible to perform heat sealing at the same sealing temperature as that of the conventional sealant film for low temperature sealing while maintaining heat resistance.

Further, since LLDPE obtained by polymerization using a single active site catalyst is more flexible than conventional LLDPE having the same density, a sealant film which is more flexible than a conventional heat resistant film can be obtained. . This flexibility can be maintained by setting the layer ratio even when laminated with the base material layer.

As described above, according to the present invention, heat resistance that can withstand high temperature filling up to 100 ° C. and sterilization by boiling, and
It is possible to provide a multi-layer sealant film having both low-temperature sealing property and excellent impact resistance and flexibility.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the present invention will be shown below.
The present invention is not limited to these examples.

Comparative Example 1 LLDPE obtained by polymerization using a single active site catalyst
(Density = 0.908 g / cm ³ , melt index (MI) = 1 g / 10 min, melting point by DSC measurement = 10
7 ° C, crystal melting temperature range = 17 ° C, M _W / M _N = 2.5)
From the above, a sealant film having a thickness of 40 μm was obtained by an inflation molding machine. Then, after corona discharge treatment was applied to the surface of the film on the side different from the sealing surface to set the wetting tension to 43 dyn / cm, a biaxially stretched polyamide-based film having a thickness of 15 μm was laminated on the treated surface by dry lamination. .

In this way, a composite packaging film comprising the seal layer and the reinforcing layer was produced.

Example 1 LLDPE obtained by polymerization with a single active site catalyst
(Density = 0.908 g / cm ³ , melt index (MI) = 1 g / 10 min, melting point by DSC measurement = 10
7 ° C, crystal melting temperature range = 17 ° C, M _W / M _N = 2.5)
Is a LLDPE (density = 0.910) obtained by polymerization using a catalyst having a plurality of polymerization active points as a sealing layer resin.
g / cm ³ , MI = 2 g / 10 min, melting point by DSC measurement = 105 ° C. and 121 ° C.) were respectively used as the resin for the base material layer, and a film was formed by a coextrusion method using an inflation molding machine to form a sealing layer. A sealant film composed of the base material layer was obtained. The layer thickness ratio was set to seal layer / base material layer = 1/1.

Then, after corona discharge treatment was applied to the surface of the base material layer of this film to adjust the wetting tension to 43 dyn / cm, a biaxially stretched polyamide film having a thickness of 15 μm was laminated on the treated surface by dry lamination. .

Thus, a composite packaging film consisting of the seal layer, the base material layer and the reinforcing layer was produced.

Example 2 The same LLDPE as in Example 1 was used as the sealing layer resin,
LLDPE (density = 0.918 g / cm ³ , MI = 2.
1 g / 10 minutes, melting point by DSC measurement = 110 ° C. and 123 ° C.) was used as the resin for the base material layer, and a film was formed by a coextrusion method using an inflation molding machine to form a sealant composed of the seal layer and the base material layer. I got a film. The layer thickness ratio was set to seal layer / base material layer = 1/3.

Then, in the same manner as in Example 1, the base layer of this film was subjected to corona discharge treatment, and then the treated surface was subjected to 2
The axially stretched polyamide film was laminated by dry lamination.

Thus, a composite packaging film consisting of the seal layer, the base material layer and the reinforcing layer was produced.

Comparative Example 2 LLDPE (density = 0. 0) obtained by polymerization using a catalyst having a plurality of polymerization active points as a resin for the seal layer.
910 g / cm ³ , MI = 2 g / 10 min, melting point by DSC measurement = 105 ° C. and 121 ° C.), except that a composite packaging film (conventional composite packaging film for low-temperature sealing) was used. Equivalent product) was manufactured.

Comparative Example 3 LLDPE obtained by polymerization using a catalyst having a plurality of polymerization active points as the resin for the seal layer (density = 0.
918 g / cm ³ , MI = 2.1 g / 10 min, melting point by DSC measurement = 110 ° C. and 123 ° C.), except that a composite packaging film (conventional heat-resistant composite packaging) was used. Film equivalent) was produced.

Comparative Example 4 Except that the layer thickness ratio was set to seal layer / base material layer = 1/3,
A composite packaging film including a seal layer, a base material layer, and a reinforcing layer was produced in the same manner as in Example 1.

Performance Evaluation For the sealant film composed of the seal layer and the base material layer, or the composite packaging film composed of the seal base, the base material layer and the reinforcing layer, obtained in Examples and Comparative Examples, the following items were evaluated. Performance evaluation was performed.

(1) Stress (kg / cm) at 2% tension of the flexible sealant film
2) was measured, and the value obtained by dividing this value by 0.02 was taken as the elastic modulus, and the flexibility was evaluated from the results. Table 1 shows the measurement results.

[0047]

[Table 1] From Table 1, the sealant films of Examples are Comparative Examples 2 and 3.
And have better flexibility than those of 4 and Comparative Example 1
It turns out that the film is too soft.

(2) Sealing property The sealing property of the composite packaging film was evaluated by table evaluation using a heat seal bar. Figure 1 shows the measurement results
Shown in

From FIG. 1, the composite packaging film of the embodiment is
It can be seen that it has a low-temperature sealing property (saturation temperature of 120 ° C.) almost equivalent to that of the comparative example 2 which is a conventional equivalent to the low-temperature composite packaging film.

(3) Impact resistance The impact resistance of the composite packaging film was evaluated by the dirt drop test (J
IS-K7124). Table 2 shows the measurement results.

[0051]

[Table 2] From Table 2, it can be seen that the composite packaging films of the examples have better impact resistance than the comparative examples. (4) Thermal fusion test (boil resistance) The thermal fusion test of the composite packaging film was performed by the following method.
That is, by fixing the seal layers of the pouch enclosing water with a zem clip, a more severe condition than actual boil sterilization is set, and the pouch sample is left in hot water of about 80 ° C or 90 ° C for 30 minutes. Then, this was rapidly cooled, the clip was removed, and the presence or absence of fusion of the adhered portion was judged in three stages. The criteria for judgment are as follows. ◯: The seal layers were not fused to each other, Δ: The seal layers were fused but peeled off by hand, ×: the seal layers were strongly fused.

The test results are shown in Table 3.

[0053]

[Table 3] As can be seen from Table 3, there is no fusion between the composite packaging film of Example 2 and the composite packaging films of Comparative Examples 1 and 4 having heat resistance, and fusion is observed in the composite packaging films of Comparative Examples 2 and 3. Was given.

(5) High-temperature object filling test In the automatic filling packaging using the liquid packaging container made of the above-mentioned dressing packaging film, in addition to the purpose of sterilization, in order to reduce the viscosity of the viscous material to be filled, the viscous material is preliminarily used. It may be heated before filling. Therefore, in this test, Mentsuyu was used as the filling, and this was heated to 95 ° C to perform the filling test.
The actual heat resistance was confirmed. The filling speed at this time is 20 m /
The sealing temperature was fixed at 185 ° C. vertically and 145 ° C. horizontally at a constant speed of min. In this test, a sample (size 80 × 65 mm) immediately after filling was pressurized with a pressure of 100 kg and left for 3 minutes (pressure resistance test). The state during this period was observed, and the sealing performance was judged in three stages of ◯: no abnormality, Δ: abnormality of seal portion, and ×: bag breakage. In addition, the presence or absence of fusion was also judged according to the criterion (4) in the heat fusion test.

The test results are shown in Table 4.

[0056]

[Table 4] As can be seen from Table 4, neither fusion nor breakage was observed in the composite packaging films of Examples, and light fusion was observed in the composite packaging films of Comparative Examples 2 and 3. In the composite packaging film of Comparative Example 4, the low temperature sealing property was insufficient, and thus 2
No filling was possible at a speed of 0 m / min.

[0057]

EFFECTS OF THE INVENTION Since the present invention is constituted as described above, it has both heat resistance capable of withstanding high temperature filling up to 100 ° C. and sterilization by boiling, and low temperature sealability, and has impact resistance and flexibility. An excellent multilayer sealant film can be provided.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of a heat seal strength measurement test.

Claims (3)

[Claims] 1. A multilayer sealant film comprising a base material layer and a seal layer laminated on at least one side thereof, wherein the base material layer has a density of 0.900 to 0.913 g / c.
made linear low density polyethylene resin which is m ^3,
The sealing layer has a melting point in the range of 97 to 115 ° C. and a weight average molecular weight / number average molecular weight value of 1.5 to 3.
A linear low density having a single crystal melting peak at a crystal melting temperature measured using a differential scanning calorimeter and having a temperature range of 20 ° C or less from the start to the end of melting of all the crystals of the film. Made of polyethylene resin, the thickness of the sealing layer is 30% or more of the thickness of the entire film,
Multi-layer sealant film. 2. A multilayer sealant film comprising a base material layer and a seal layer laminated on at least one side thereof, wherein the base material layer has a density of 0.913 to 0.930 g / c.
made linear low density polyethylene resin which is m ^3,
The sealing layer has a melting point in the range of 97 to 115 ° C. and a weight average molecular weight / number average molecular weight value of 1.5 to 3.
A linear low density having a single crystal melting peak at a crystal melting temperature measured using a differential scanning calorimeter and having a temperature range of 20 ° C or less from the start to the end of melting of all the crystals of the film. Made of polyethylene resin, the thickness of the sealing layer is 20% or more of the thickness of the entire film,
Multi-layer sealant film. 3. The non-sealing surface of the multilayer sealant film according to claim 1 or 2, when the seal layer is formed on both surfaces of the base material layer, reinforced between at least one of the seal layer and the base material layer. A composite packaging material in which layers are laminated.