KR20030001720A - Polypropylene-based resin composition for shrinkable film - Google Patents

Abstract

PURPOSE: Provided is a polypropylene-based resin composition for shrinkable film which shows excellent shrinkage and transparency, by broadening a range of melting point of the resin and reducing a degree of crystallinity of the resin. CONSTITUTION: The polypropylene based resin composition for shrinkable film comprises 100 parts by weight of crystalline ethylene-propylene-1-butene terpolymer having melting point of 125-135 deg.C and melting index(230 deg.C, 2.16 kg) of 5.0-7.0 g/10 min., and 1-50 parts by weight of propylene-1-butene copolymer having density of 0.86-0.90 and melting index(230 deg.C, 2.16 kg) of 1-10 g/10 min. The resin composition further comprises antioxidant, neutralizer, antiblocking agent, slipping agent, and antistatic agent.

Description

Polypropylene-based resin composition for shrinkable film

The present invention relates to a polypropylene resin composition for shrink films, and more particularly, to a poly biaxially-contracted shrink film prepared by adding a low density propylene-1-butene copolymer to an ethylene-propylene-1-butene terpolymer. It relates to a propylene resin composition.

Shrink film can be packaged in a state that maintains the shape of the product, and serves to protect from touch when displaying the product. Types of shrink film are largely divided into packaging and label, biaxial shrink film is used for packaging, uniaxial shrink film is used for labeling.

The main physical properties required for simultaneous biaxially oriented shrink film are excellent shrinkage characteristics such as high shrinkage at low temperature, lateral / longitudinal shrinkage balance, transparency to enhance the appearance of the product, and mechanical strength to maintain film strength. It is physical property. There are various resins used for the simultaneous biaxially stretched shrink film production, such as polypropylene and FVC, but the use of polypropylene has the advantage of obtaining high productivity, excellent transparency and excellent mechanical properties. In particular, it is known to use a propylene-ethylene copolymer or a propylene-ethylene-1-butene terpolymer among polypropylene resins in order to satisfy shrinkage characteristics (see US Patent No. 6,025,079). This is because the resin with high crystallinity has a problem that the shrinkage of the film is lowered due to the low shrinkage tension, and the shrinkage of the film is lowered, and the crystal parts act as morphological disturbances, thereby degrading shrinkage. This is because the -ethylene-1-butene terpolymer is advantageous for shrinkage characteristics. However, if the crystallinity of the resin is too low to lower the softening point of the resin, the film having such a low softening point becomes a cause that makes the operation difficult in the post-processing process of the shrink film.

Meanwhile, Korean Patent No. 96-706400 discloses an example of improving shrinkage and mechanical properties of a shrink film using syndiotactic polypropylene, and Korean Patent No. 99-0045739 discloses a metallocene catalyzed propylene. Shrink films made from homopolymers and propylene-ethylene copolymers are disclosed. However, these special polypropylene resins are not economically expensive due to their high cost compared to general Ziegler-Natta polypropylene.

In contrast, Korean Patent No. 99-008024 discloses an example in which the crystallization of isotactic polypropylene is reduced by adding a modifier to the isotactic polypropylene. It is disclosed that it can be selected from the group consisting of ethylene-propylene copolymers, propylene-butylene copolymers, ethylene-propylene-butylene terpolymers and linear low density polyethylene. However, the resin composition containing such a modifier itself has a disadvantage in that the melting point range is narrow and the shrinkage temperature range is narrow, or the transparency of the film is lowered.

Accordingly, the present invention is to solve the problems of the prior art as described above, by adding a low-density propylene-alpha olefin copolymer to a general Ziegler-Natta polypropylene-based resin to reduce the degree of crystallization while reducing the degree of crystallinity shrinkage characteristics An object of the present invention is to provide a polypropylene resin composition for a shrink film having excellent transparency and excellent transparency.

That is, an object of the present invention is 100 parts by weight of crystalline ethylene-propylene-1-butene terpolymer having a melting temperature of 125 to 135 ° C and a melt index (230 ° C, 2.16 kg) of 5.0 to 7.0 g / 10 min. It is to provide a polypropylene-based resin composition for a shrink film comprising 1 to 50 parts by weight of a propylene-1-butene copolymer having a melt index of 0.86 to 0.90 and a melt index (230 ° C., 2.16 kg) of 1 to 10 g / 10 min.

Hereinafter, the polypropylene resin composition of the present invention will be described in more detail.

The crystalline ethylene-propylene-1-butene terpolymer used as the base resin in the present invention has propylene as a main component. The crystalline ethylene-propylene-1-butene terpolymer may have excellent meltability only when the melting temperature is 125 to 135 ° C. The resin having a melting temperature of less than 125 ℃ has a difficulty in the film production process, the resin having a melting temperature of more than 135 ℃ has a drawback that the stretching temperature is high during the shrink film processing and crystallinity is inferior in shrinkage. In addition, the crystalline ethylene-propylene-1-butene terpolymer has a flowability suitable for a simultaneous biaxially stretched film when the melt index (230 ° C., 2.16 kg) is 5.0 to 7.0 g / 10 min.

The propylene-1-butene copolymer used as the additive resin in the present invention is a copolymer having a low crystallinity with a density of 0.86 to 0.90. If the density is less than 0.86, the low crystalline material increases in the final film, which is not suitable as a shrink film used for packaging. If the density exceeds 0.90, the melting point temperature range of the resin composition is narrowed and the degree of crystallinity is high, thereby reducing the shrinkage of the film. The melt index (230 ° C., 2.16 kg) of the propylene-1-butene copolymer is preferably 1 to 10 g / 10 min. If the melt index is less than 1 or more than 10, the dispersibility with the base resin is lowered and the film is reduced. Of transparency is poor.

The amount of the propylene-1-butene copolymer added is preferably 1 to 50 parts by weight, more preferably 10 to 40 parts by weight based on 100 parts by weight of the crystalline ethylene-propylene-1-butene terpolymer. If the amount of the propylene-1-butene copolymer added is less than 1 part by weight, there is no improvement in shrinkage. If the amount of the propylene-1-butene copolymer is more than 50 parts by weight, the stiffness of the film is low due to the low crystallinity, making the film difficult to use.

In addition to the above components, various additives such as antioxidants, neutralizing agents, anti-blocking agents, antistatic agents, slip agents, and the like may be added to the resin composition of the present invention within a range not departing from the features of the present invention.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples are for illustrative purposes only and should not be construed as limiting the present invention.

Example 1

As shown in Table 1, an appropriate amount of an antioxidant, a neutralizing agent, an antiblocking agent, a slipping agent, and an antistatic agent were blended as additives in 100 parts by weight of the resin 1 , 10 parts by weight of the resin 3 was added and mixed in a mixer, and then, using an extruder. The pellet resin composition was obtained at 210 degreeC. The resin composition was processed with a simultaneous biaxial stretching machine for shrink film processing to obtain a shrink film. In other words, the melted resin composition extruded from the annular extrusion die is quenched to form a fabric tube, and the softening point of the polymer main chain has flexibility while transferring the fabric tube between two sets of nip rolls in the stretching apparatus. At the same time, heating is performed by hot air at the drawing temperature below the melting point, and bubbles are formed by the air injected into the tube at a pressure slightly higher than atmospheric pressure, and then the take-up roll and the amount of air in the bubbles are controlled. The film was then biaxially stretched both horizontally and vertically to form a film. At this time, the extrusion die was 190 deg. The shrinkage and transparency of the shrink film thus prepared are shown in Table 2 below.

Example 2

A shrink film was prepared in the same manner as in Example 1, except that 40 parts by weight of resin 3 was added as shown in Table 1, and the shrinkage and transparency of the film were measured and shown in Table 2 below.

Comparative Example 1

A shrink film was prepared in the same manner as in Example 1, except that Resin 2 was used as the base resin and 20 parts by weight of Resin 3 was added as shown in Table 1, and the shrinkage and transparency of the film were measured. Table 2 shows.

Comparative Example 2

A shrink film was prepared in the same manner as in Example 1, except that only resin 1, which was a base resin, was used as in Table 1, and the shrinkage ratio and transparency of the film were measured and shown in Table 2 below.

Comparative Example 3

A shrink film was prepared in the same manner as in Example 1, except that 20 parts by weight of resin 4 was added instead of resin 3 , as shown in Table 1, and the shrinkage and transparency of the film were measured and shown in Table 2 below. It was.

Comparative Example 4

A shrink film was prepared in the same manner as in Example 1, except that 20 parts by weight of resin 5 was added instead of resin 3 as shown in Table 1, and the shrinkage and transparency of the film were measured and shown in Table 2 below. It was.

division Composition Base resin Additive resin Addition amount (part by weight) Example 1 Resin 1 Resin 3 10 Example 2 Resin 1 Resin 3 40 Comparative Example 1 Resin 2 Resin 3 20 Comparative Example 2 Resin 1 Resin 3 0 Comparative Example 3 Resin 1 Resin 4 20 Comparative Example 4 Resin 1 Resin 5 20

[Remarks]

1) Resin 1 : Terpolymer (propylene-ethylene-1-butene)

Melting Temperature 130 ℃, MI (230 ℃, 2.16kg) = 6.0g / 10min

2) Resin 2 : Random copolymer (propylene-ethylene)

Melt Temperature 150 ℃, MI (230 ℃, 2.16kg) = 6.0g / 10min

3) resin 3 : propylene-1-butene copolymer,

Density 0.88, MI (230 ° C, 2.16 kg) = 6.0 g / 10 min

4) Resin 4 : Propylene-1-butene Copolymer

Density 0.91, MI (190 ° C, 2.16 kg) = 6.0 g / 10 min

5) resin 5 : ethylene-alpha olefin copolymer,

Density 0.86, MI (230 ° C, 2.16 kg) = 6.0 g / 10 min

Film properties Shrinkage (%) Haze (%) Example 1 65 2.0 Example 2 70 2.0 Comparative Example 1 50 2.5 Comparative Example 2 55 2.0 Comparative Example 3 55 2.0 Comparative Example 4 65 4.0

[Measurement of physical properties]

(1) Shrinkage: After shrinking the film 1cm in width, 10cm in length, immersed in glycerin maintained at 120 ℃ for 4 seconds and taken out to measure the reduced length as calculated as follows, the shrinkage is more than 60% is appropriate. :

Shrinkage (%) = (10- (shortened length)) / 10 × 100

(2) Transparency: The blurriness of the shrinkage film was measured by a blurriness meter according to ASTM D1003 standard. As a measure of film transparency, the degree to which light is scattered with respect to incident light is measured, and the larger the value, the lower the transparency.

As shown in Table 2, the film according to the embodiment is excellent in both the shrinkage and transparency, it can be seen that the film according to the comparative example is unfavorable because the characteristics of any one of the shrinkage and transparency are inferior.

As described in detail above, using the resin composition of the present invention can easily provide a shrink film excellent in both shrinkage and transparency.

Claims (1)

100 parts by weight of a crystalline ethylene-propylene-1-butene terpolymer having a melting temperature of 125 to 135 ° C. and a melt index (230 ° C., 2.16 kg) of 5.0 to 7.0 g / 10 min, and a density of 0.86 to 0.90. 230 degreeC, 2.16 kg) The polypropylene resin composition for shrink films containing 1-50 weight part of propylene-1-butene copolymers which are 1-10 g / 10min.