KR101269769B1 - Polypropylene composition and Polypropylene Multilayer Film using thereof - Google Patents

Abstract

The present invention relates to a polypropylene resin composition and a polypropylene multilayer film using the same. More specifically, in a polypropylene resin composition comprising an ethylene-propylene random-block copolymer, the ethylene-propylene random-block copolymer is Polypropylene resin composition comprising 75 to 95% by weight of an ethylene-propylene random copolymer having an ethylene content of 0.5 to 5% by weight and 5 to 25% by weight of an elastic ethylene-propylene block copolymer having an ethylene content of 20 to 50% by weight and thus It relates to a polypropylene multilayer film produced.
The present invention provides a polypropylene multilayer film exhibiting excellent low-temperature impact strength during refrigeration and freezing while maintaining transparency, heat resistance, and heat adhesion using a polypropylene resin composition, and the polypropylene multilayer film is effectively applied as a film for food packaging. This is possible.

Description

Polypropylene resin composition and polypropylene multilayer film using same

The present invention relates to a resin composition and a polypropylene multilayer film using the same.

Film packaging materials used in retort food packaging are required to have excellent appearance with little fish eye or transparency, heat resistance, impact resistance at low temperatures, heat adhesiveness or blocking resistance, and the like. In general, in order to obtain such properties, a composite packaging container made by attaching a heat-resistant single layer plastic film, a metal foil or another plastic film in multiple layers to a retort food packaging material is used. In particular, polypropylene resin is mainly used as the plastic film, and the ethylene-propylene block copolymer resin used in the film for high retort which is sterilized at a temperature of 130 ° C. or higher according to the method of sterilizing the retort food; Ethylene-propylene random copolymer resin used for the film for semi retort sterilizing at about 120 degreeC is typical.

Among these, the film for semi-retort which has ethylene-propylene random copolymer resin as a main component is transparency and heat-adhesiveness in addition to heat resistance, a main requirement characteristic. Recently, however, cold resistance is additionally required in consideration of not only long-term storage at room temperature, but also storage and distribution in a low-temperature environment below 0 ° C. or in a refrigerated state. However, polypropylene-based resins having a relatively high melting point have low low-temperature impact strength. In addition, it is generally known that there is a low flexibility, so that cracks or breakages caused by drops, bumps, and bends, which may occur during freezing, refrigeration storage, and distribution, are likely to rot or discharge the package contents.

In particular, the above problems are more serious when the polypropylene film is used alone in the film for semi-retort, wherein the polypropylene film is a non-stretched film formed by co-extrusion of three layers, all of which are ethylene- Propylene random copolymer resins are generally applied. As a result, a large amount of impact reinforcing materials such as thermoplastic elastomers can be added to the ethylene-propylene random copolymer resin, or a polyethylene resin can be used to improve cold resistance, that is, low temperature impact strength, but low melting point and heat resistance. It is difficult to apply due to the problem of inferiority, poor transparency and poor blocking resistance.

An object of the present invention for solving the above problems, while maintaining transparency, heat resistance and heat adhesion, exhibits excellent low-temperature impact strength during refrigeration, freezing and storage of the polypropylene resin composition and polypropylene multilayer film prepared therefrom To provide.

According to an aspect of the present invention,

A polypropylene resin composition comprising an ethylene-propylene random-block copolymer,

Said ethylene-propylene random-block copolymer;

Regarding the polypropylene resin composition comprising 75 to 95% by weight of an ethylene-propylene random copolymer having an ethylene content of 0.5 to 5% by weight and 5 to 25% by weight of an elastic ethylene-propylene block copolymer having an ethylene content of 20 to 50% by weight. will be.

The polypropylene resin composition may further include a thermoplastic elastomer. In addition, the thermoplastic elastomer may be included in 3 to 20% by weight based on the polypropylene resin composition.

According to another aspect of the present invention,

An outer layer made of a first polypropylene resin composition comprising at least one of an ethylene-propylene random-block copolymer and an ethylene-propylene random copolymer having an ethylene content of 0.5 to 5% by weight;

A polypropylene multilayer film comprising an inner layer made of a second polypropylene resin composition comprising an ethylene-propylene random-block copolymer resin.

The ethylene-propylene random-block copolymer is an ethylene-propylene random copolymer having an ethylene content of 0.5 to 5% by weight 75 to 95% by weight and an ethylene content of 20 to 50% by weight of an elastic ethylene-propylene block copolymer 5 to 25 It may consist of weight percent.

The second polypropylene resin composition may further include a thermoplastic elastomer.

The polypropylene multilayer film may be applied to food packaging films. In addition, the food packaging film may be a film for semi-retort.

The polypropylene resin composition according to the present invention can provide a polypropylene multilayer film exhibiting excellent low-temperature impact strength during low temperature storage while maintaining transparency, heat resistance and heat adhesion. In addition, the polypropylene multilayer film can be applied as a film for food packaging, in particular, it can be effectively applied to a semi-retort film that can be distributed and stored in a low-temperature environment or refrigerated conditions of 0 ℃ or less.

1 is a simplified illustration of a polypropylene multilayer film according to the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention provides a polypropylene resin composition comprising an ethylene-propylene random-block copolymer. The polypropylene resin composition may provide a film having excellent low temperature impact strength properties while maintaining transparency, heat resistance and heat adhesion.

The ethylene-propylene random-block copolymer includes an ethylene-propylene random copolymer portion and an elastic ethylene-propylene block copolymer portion.

The ethylene-propylene random copolymer portion may be included in an amount of 75 to 95 wt% based on the ethylene-propylene random-block copolymer. When the content of the ethylene-propylene random copolymer portion is outside the above range, mechanical properties such as impact resistance or strength of the resin composition may be lowered, which is not preferable.

The ethylene content of the ethylene-propylene random copolymer portion may be 0.5 to 5% by weight relative to the random copolymer. If the ethylene content is less than 0.5% by weight, the degree of crystallinity of the copolymer is higher than necessary to reduce the transparency of the resulting resin composition, and if the content exceeds 5% by weight, it may be difficult to apply it as a material for food packaging containers. It is not desirable.

The elastic ethylene-propylene block copolymer portion may be included in 5 to 25% by weight relative to the elastic ethylene-propylene random-block copolymer. When the content of the ethylene-propylene random copolymerization portion is out of the above range, mechanical properties such as impact resistance or strength of the resin composition may be lowered, which is not preferable.

The ethylene content of the elastic ethylene-propylene block copolymer portion may be 20 to 50% by weight relative to the block copolymer. If the ethylene content is less than 20% by weight, the elasticity of the copolymer is reduced and the impact resistance is lowered, if it exceeds 50% by weight, mechanical properties such as strength may be lowered is not preferable.

The absolute viscosity of the ethylene-propylene random-block copolymer may be 0.5 to 2.5 dl / g. When the absolute viscosity is less than 0.5 dl / g, when the resin composition is processed, the dispersibility is good immediately after molding, but as the crystallization of the ethylene-propylene random copolymer portion proceeds, the elastic ethylene-propylene block copolymer component is produced. As the phenomenon of crawling to the surface occurs, the transparency of the molded product may be degraded and the appearance of the product may be greatly deteriorated. If the absolute viscosity exceeds 2.5 dl / g, the elastic ethylene-propylene block air may be formed during molding of the composition including the elastomeric copolymer. Dispersibility of the coalescing component may be lowered, which may reduce transparency, which is undesirable.

The melt index of the ethylene-propylene random-block copolymer may be 1 to 10 g / 10 min at 230 ° C. and 2.16 kg load. When the melt index is less than 1 g / 10 minutes, the extrusion load increases during film forming and the fluidity of the resin decreases, so that it is difficult to obtain desired productivity. When the melt index exceeds 10 g / 10 minutes, the viscosity of the melt index discharged from the die is lowered. It is not preferable because the thickness uniformity may deteriorate and film forming may be difficult.

The ethylene-propylene random-block copolymer is prepared by sequentially polymerizing an ethylene-propylene random copolymer portion and an ethylene-propylene block copolymer portion in one reactor. For example, ethylene and propylene are simultaneously introduced into the polymerization reactor to form an ethylene-propylene random copolymer portion first, and further, the ethylene-propylene block copolymer portion is further formed on the formed ethylene-propylene random copolymer portion to finally form. To prepare an ethylene-propylene random-block copolymer.

The polypropylene resin composition may optionally further include an elastomer. The elastomer may further improve the impact strength of the polypropylene resin composition, it may be included in 3 to 20% by weight relative to the polypropylene resin composition, preferably 5 to 15% by weight. If the content of the elastomer is less than 3% by weight can not be expected to improve the low-temperature impact strength of the resin composition using the elastomer, if it exceeds 20% by weight, it is not preferable because the economical efficiency may be lowered because the elastomer is expensive.

The elastomer may be a thermoplastic elastomer prepared using a metallocene catalyst, preferably a styrene-based elastomer, an olefin-based elastomer, or the like. More specifically, in the group consisting of ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer, styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene block copolymer and the like It may be one or more selected.

The polypropylene resin composition may further include additives commonly used within a range that does not significantly impair the properties, and more specifically, may include an antioxidant, a neutralizer, a nucleating agent, an antistatic agent, a pigment, and the like, but is not limited thereto. .

The present invention provides a polypropylene multilayer film made of the polypropylene resin composition.

The polypropylene multilayer film is prepared using the polypropylene resin composition according to the present invention can be excellent in transparency, heat resistance and heat adhesion as well as provide an improved effect at low temperature impact strength.

Referring to FIG. 1, the polypropylene multilayer film may be a three-layer film including an outer layer 10, 10 ′ and an inner layer 20.

The outer layer 10, 10 ′ and inner layer 20 may comprise the components mentioned in the polypropylene resin composition according to the invention, and more specifically, the outer layer 10, 10 ′ may comprise the ethylene-propylene random. It may consist of a first polypropylene resin composition comprising at least one of a block copolymer and an ethylene-propylene random copolymer. The ethylene content in the ethylene-propylene random copolymer may be 0.5 to 5% by weight, preferably 1.5 to 5% by weight.

The inner layer 20 may be made of a second polypropylene resin composition including the ethylene-propylene random-block copolymer, and the second polypropylene resin composition may further include an elastomer to improve impact strength. . The elastomer is a thermoplastic elastomer prepared using a metallocene catalyst as mentioned above, and may be included in an amount of 3 to 20% by weight based on the second polypropylene resin composition.

The melt index of the first and second polypropylene resin compositions may be 1 to 10 g / 10 min at 230 ° C. and 2.16 kg load. The first and second polypropylene resin compositions may further include conventional additives, and the present invention is not particularly limited.

The polypropylene multilayer film may have a thickness of 30 to 200 μm, and the thickness ratio of each of the outer and inner layers may be 1: 1 to 1:10 (outer layer: inner layer), and preferably 1: 1 to 1: 7, more preferably 1: 2 to 1: 5. When the thickness ratio is included in the above range, it may provide improved low temperature impact strength or mechanical properties and heat resistance.

The polypropylene multilayer film may be prepared according to methods known in the art, and may be preferably co-extruded in a non-stretched film forming method.

The polypropylene multilayer film may be applied as a film for food packaging, preferably as a film for retort, more preferably a film for semi retort.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, these examples are for illustrative purposes only, and the scope of the present invention is not limited to these examples.

Example  1 to 4

Using the polypropylene resin composition shown in Table 1, the non-stretched film, which is coextruded by applying to the outer layer and inner layer of the three-layer structure, by using a non-stretching equipment, has a thickness of 80 μm, and the thickness ratio of the outer layer and the inner layer is 1: The film was formed to be 3, and the impact strength and cloudiness, thermal adhesive strength, heat resistance, and the like of the obtained film were measured. The results are shown in Table 1.

As the non-stretching equipment, a generally used equipment of Batenfield Corporation or Mitsubishi Corporation was used, and there is no difference in film according to the equipment.

Comparative example  1 to 2

Using the polypropylene resin composition shown in Table 1, a film was produced in the same manner as in Example 1 and the properties were evaluated. The results are shown in Table 1.

Each physical property was determined by the following method.

Melt index ( Melt index )

According to ASTM D 1238 conditions were measured at 230 ℃, 2.16kg conditions.

Cloudy road Haze )

Measurement was made according to ASTM D 1003 conditions.

Impact strength ( Impact strength )

The film impact strength at the time of falling at a height of 1 m after storage for a certain time at a constant temperature was measured.

Heat seal  Temperature ( Heat sealing 온도 )

After leaving the film in a constant temperature and humidity chamber at a temperature of 23 ± 1 ° C. and a humidity of 50 ± 5% for 24 hours, the two specimens were bonded to each other by temperature at a pressure of 2 kg / cm 2 and a time of 1 second, and then separated by a tensile tester. When unloading, measure the temperature when the thermal bond between the two specimens does not begin to peel off.

Heat resistance Heat resistance )

Two 100 mm × 15 mm samples were taken and overlapped by about 15 mm, sandwiched between papers, subjected to a load of 1 kg, and left at 120 ° C. hot air oven for 1 hour, and then the peeling strength of the overlapped portions was measured.

 -Good: Good if there is no deformation of the specimen due to peeling of the overlapped part between two specimens

 -Bad: Bad when the overlapped part of two specimens is peeled and the specimen is drawn

Configuration Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Resin composition (outer layer) Random-block PP 100 100 100 Random PP 100 100 100 Resin composition (inner layer) Random-block PP 90 85 85 100 Random PP 100 85 Elastomer 10 15 15 15 Film properties Cloudiness (%) 1.5 1.3 1.5 2.2 1.0 1.1 Impact Strength (23 ℃) 31 38 33 21 11 19 Impact strength (0 ℃) 10.1 14.5 11.9 4.9 2.8 7.3 Heat Bonding Temperature (℃) 145 145 145 145 145 145 Heat resistance Good Good Good Good Good Good

  * Description of the ingredients used in Table 1 above *

1) Random PP: Ethylene-propylene random copolymer resin (RF402, ethylene 3.8% by weight, Samsung Total Co., Ltd.)

2) random-block PP: ethylene-propylene random-block copolymer resin (BI309, melt index: 5g / 10min, absolute viscosity: 2.0dl / g, total ethylene 8% by weight (ethylene content in the ethylene-propylene random copolymerization part 2 Weight%, ethylene content in the ethylene-propylene block copolymerization part 40% by weight), Samsung Total Co., Ltd.)

3) Elastomer: Ethylene copolymer made of metallocene catalyst (Exxon Mobil)

As can be seen from the results of Table 1, Examples 1 and 2 are more effective than conventional films (Comparative Example 1 and Comparative Example 2) when the inner layer including the outer layer made of ethylene-propylene random-block copolymer and the elastomer layer is formed. Transparency, heat adhesion, heat resistance and the like are maintained while expressing improved low temperature impact strength properties. It can be confirmed that Example 3 in which the resin of the outer layer was changed also exhibited excellent low-temperature impact strength characteristics.

In addition, Example 4 is a film made of the ethylene-propylene random-block copolymer alone according to the present invention, it can be seen that the impact strength is improved compared to the film made of the ethylene-propylene random copolymer of Comparative Example 1.

The polypropylene resin composition according to the present invention can provide a polypropylene multilayer film having improved low temperature impact strength while maintaining transparency, heat adhesiveness and heat resistance. In addition, these properties are improved compared to other film products using the same weight ratio of the elastomer, it is possible to lower the content of the expensive elastomer to provide a cost saving effect, in particular, it is possible to provide a film excellent in low-temperature impact strength or mechanical properties. .

10, 10 ': outer layer
20: inner layer

Claims (12)

Ethylene-propylene random-block copolymers; And
Thermoplastic elastomer;
Said ethylene-propylene random-block copolymer;
Polyethylene comprising 75 to 95% by weight of an ethylene-propylene random copolymer having an ethylene content of 0.5 to 5% by weight and 5 to 25% by weight of an elastic ethylene-propylene block copolymer having an ethylene content of 20 to 50% by weight. Propylene Resin Composition.
The method of claim 1,
The absolute viscosity of the ethylene-propylene random-block copolymer is a polypropylene resin composition, characterized in that 0.5 to 2.5 dl / g.
The method of claim 1,
Melt index of the ethylene-propylene random-block copolymer is a polypropylene resin composition, characterized in that 1 to 10g / 10 minutes under 230 ℃, 2.16kg load.
delete The method of claim 1,
The thermoplastic elastomer is 3 to 20% by weight based on the polypropylene resin composition, characterized in that the polypropylene resin composition.
The method of claim 1,
The thermoplastic elastomer is prepared using a metallocene catalyst and is an ethylene-propylene copolymer, an ethylene-butene copolymer, an ethylene-octene copolymer, a styrene-ethylene-butylene-styrene block copolymer and a styrene-ethylene-propylene block. Polypropylene resin composition, characterized in that at least one of the copolymer.
An outer layer made of a first polypropylene resin composition comprising at least one of an ethylene-propylene random-block copolymer and an ethylene-propylene random copolymer having an ethylene content of 0.5 to 5% by weight;
A polypropylene multilayer film comprising an inner layer consisting of a second polypropylene resin composition comprising an ethylene-propylene random-block copolymer.
The method of claim 7, wherein
Ethylene-propylene random-block copolymer in the first and second polypropylene resin composition is 75 to 95% by weight ethylene-propylene random copolymer having an ethylene content of 0.5 to 5% by weight and 20 to 50% by weight of ethylene content Polypropylene multilayer film, characterized in that consisting of 5 to 25% by weight of the elastic ethylene-propylene block copolymer.
The method of claim 7, wherein
The second polypropylene resin composition further comprises a thermoplastic elastomer.
The method of claim 7, wherein
Wherein the thickness ratio of the outer layer to the inner layer is 1: 1 to 1:10.
The method of claim 7, wherein
The polypropylene multilayer film is a polypropylene multilayer film, characterized in that applied to the film for food packaging.
The method of claim 11,
The food packaging film is a polypropylene multilayer film, characterized in that the film for the semi-retort.

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