KR20210067265A - Composition of polypropylene resin for higher shrinkage film and shrinkage film prepared using the same - Google Patents

Abstract

The present invention relates to a polypropylene resin composition for a shrinking film, and a shrinking film prepared by using the same. Particularly, the polypropylene resin composition includes, based on the total weight of the polypropylene resin composition: (a) 46-76 wt% of a propylene-ethylene-1-butene random copolymer; (b) 20-50 wt% of an elastomer; and 4-7 wt% of a hydrogenated petroleum resin, wherein the random copolymer (a) includes 1-10 mol% of ethylene and 1-10 mol% of 1-butene, and the elastomer (b) is a propylene-ethylene copolymer including 9-16 mol% of ethylene. It is possible to obtain a heat shrinking label sheet having an improved shrinkage and rigidity by using the polypropylene resin composition according to the present invention.

Description

Polypropylene resin composition for shrink film and shrink film manufactured using the same {COMPOSITION OF POLYPROPYLENE RESIN FOR HIGHER SHRINKAGE FILM AND SHRINKAGE FILM PREPARED USING THE SAME}

The present invention relates to a polypropylene resin composition for a shrink film and a shrink film prepared using the same, and more particularly, to a polypropylene resin composition for a shrink film containing petroleum resin and an elastomer and having improved shrinkage and rigidity, and using the same It relates to the manufactured shrink film.

The shrink film enables packaging while maintaining the shape of the final product, and is generally used for daily necessities such as cup noodles and stationery. Such a method of forming a shrinkable film can be generally obtained by forming a film by biaxial stretching in the transverse and longitudinal directions by a double bubble-type inflation method. There are various resins for the biaxially stretched shrink film, such as polypropylene and PVC, but when polypropylene is used, it has the advantage of obtaining high transparency and excellent mechanical properties.

Most of these polypropylene-based shrink film resins have been using propylene-ethylene-1-butene random copolymer resins in the past, and when this raw material is used alone, the biaxial stretching processability such as bubble stability, bubble bursting, and film thickness deviation is excellent. good, and excellent in transparency and mechanical properties. However, in the case of such a resin, due to the structural problem of the resin, it is limitedly used for the packaging of small products due to the lack of softness, while there is a limit to its application to the shrink packaging of large products, and furthermore, the low-temperature thermal adhesiveness is poor, so there is a limit to high-speed packaging. There is a downside.

In order to solve this problem, a method of adding an elastomer product to the extruder during the production process has been proposed, but the problem of product uniformity is lowered due to the problem of poor dispersion. For example, Korean Patent No. 0783554 discloses a poly for biaxially stretched shrink film prepared by adding an amorphous propylene-1-butene copolymer to a polypropylene random copolymer using a propylene-ethylene-1-butene terpolymer. Although the propylene-based resin composition is disclosed, there are problems such as non-uniformity in shrinkage rate and non-uniformity in surface transparency due to poor dispersion of the elastomer product additionally added to the extruder.

On the other hand, since label paper made of such a shrink film is discarded after use, in terms of environmental protection, it is required to develop a resin composition for a shrink film with a specific gravity of less than 1 that is easy to separate and discharge from products such as PET bottles to which label paper was applied. have.

One aspect of the present invention is to provide a polypropylene resin composition for a shrink film having improved shrinkage and rigidity.

Another aspect of the present invention is to provide a shrink film prepared using the polypropylene resin composition of the present invention.

According to one aspect of the present invention, based on the total weight of the polypropylene resin composition, (a) propylene-ethylene-1-butene random copolymer 46 to 76% by weight; (b) 20 to 50% by weight of an elastomer; and (c) 2 to 7% by weight of a hydrotreated petroleum resin, wherein (a) the random copolymer contains 1 to 10 mol% of ethylene and 1 to 10 mol% of 1-butene in the propylene component, b) the elastomer is a propylene-ethylene copolymer comprising 9 to 16 mole % of ethylene.

According to another aspect of the present invention, there is provided a shrink film prepared using the polypropylene resin composition of the present invention.

In the present invention, a polypropylene resin composition that can produce a shrink film having polypropylene as a main component, but with improved rigidity including petroleum resin, and significantly improved shrinkage by including an elastomer, and having a specific gravity of less than 1 is provided, Heat-shrinkable label paper with improved shrinkage and rigidity can be prepared by using the polypropylene resin composition of the present invention.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiment of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

According to the present invention, there is provided a polypropylene resin composition for a shrink film comprising a petroleum resin and an elastomer and having improved shrinkage and rigidity.

More specifically, the polypropylene resin composition for shrink film of the present invention, based on the total weight of the polypropylene resin composition, (a) propylene-ethylene-1-butene random copolymer 46 to 76% by weight; (b) 20 to 50% by weight of an elastomer; and (c) 4 to 7 wt% of a hydrotreated petroleum resin, wherein (a) the random copolymer comprises 1 to 10 mol% of ethylene and 1 to 10 mol% of 1-butene in the propylene component, and ( b) The elastomer is a propylene-ethylene copolymer comprising 9 to 16 mole % of ethylene.

Hereinafter, each component constituting the present invention will be described in detail.

(a) propylene-ethylene-1- butene random copolymer

(a) propylene-ethylene-1-butene random copolymer of the present invention may be prepared in a polymerization reactor using propylene, ethylene and 1-butene as raw materials.

The propylene-ethylene-1-butene random copolymer may contain 1 to 10 mol% of ethylene and 1-butene, respectively, and the remaining 80 to 98 mol% may be crystalline propylene. In addition, it is preferable that the melting temperature by DSC is 135° C. or less, and the melt index is preferably 3 to 10 g/10 min (230° C., 2.16 kg).

This propylene-ethylene-1-butene random copolymer maintains the transparency of the polypropylene resin composition of the present invention and maintains bubble stability, bubble bursting, film thickness variation, etc. during biaxial stretching processing by inflation, and (b) elastomer to be described later. It gives excellent optical and thermodynamic compatibility with the component.

When the content of ethylene and 1-butene constituting the propylene-ethylene-1-butene random copolymer is less than 1 mol%, respectively, the crystallinity of the copolymer increases more than necessary, so that the heat sealing temperature of the resulting composition can be increased, respectively. When it exceeds 10 mol%, the degree of crystallinity is rapidly lowered and the adhesion due to the low molecular weight is increased, which may cause blocking of the film.

In addition, when the melt index of the propylene-ethylene-1-butene random copolymer is less than 3 g/10 min, the extrusion amount may be lowered, and when it exceeds 10 g/10 min, the bubble may be shaken. In addition, when the melting temperature exceeds 135 ° C., the crystallinity of the copolymer is higher than necessary, thereby increasing the heat-sealing temperature of the resulting composition and increasing softness.

In the present invention, the content of the propylene-ethylene-1-butene random copolymer is 46 to 76% by weight based on the total weight of the polypropylene resin composition in consideration of the content of other components of the resin composition to be described later, for example, 50 to 76% by weight.

In the present invention, propylene, ethylene, and 1-butene raw materials are used to prepare and mix a copolymer by adjusting the content and reaction conditions, etc., thereby maximizing compatibility with the elastomer to provide high shrinkage, transparency and low-temperature heat-sealability. be able to

On the other hand, the random copolymer is preferably prepared using a metallocene-based catalyst, has a narrower molecular weight distribution than that copolymerized by a Ziegler-Natta catalyst, and has less blocking due to the adhesion of the low-molecular-weight polymer, and a low melting temperature. and excellent low-temperature heat-sealability.

(b) elastomer

The elastomer that can be used in the polypropylene resin composition of the present invention is a propylene-ethylene copolymer (PER), and ethylene is preferably contained in an amount of 9 to 16 mol% based on the propylene-ethylene copolymer (PER), The melt index may be 1 to 10 g/10 min, for example, 3 g/10 min (230° C., 2.16 kg load).

When the melt index is less than 1 g/10 min, the extrusion amount may be reduced, and if it exceeds 10 g/10 min, a problem of bubble shaking may occur. In addition, when the melting temperature exceeds 100° C., the degree of crystallinity of the copolymer is higher than necessary, which may cause a problem in that the heat sealing temperature of the resulting composition is increased. In addition, even when the softening point temperature exceeds 80° C., there may be problems in increasing the heat sealing temperature and softness.

In the present invention, the elastomer is included in an amount of 20 to 50% by weight of the resin component of the final composition. When the content of the elastomer is less than 20% by weight, transparency is good, but shrinkage may be reduced, and when it exceeds 50% by weight, more than necessary softness appears, and biaxial stretching workability such as bubble stability, bubble bursting, and film thickness deviation decreases. and the thermal bonding strength may be lowered.

(c) hydrotreated petroleum resin

The (c) hydrotreated petroleum resin that can be used in the present invention is a resin obtained by partially or fully hydrogenating a petroleum-based resin. The petroleum resin may be an aliphatic resin (C5 petroleum resin) or an aromatic resin (C9 petroleum resin), but is preferably an aliphatic resin (C5 petroleum resin).

At this time, the softening point of the petroleum resin is 110 ℃ or more, preferably 125 ℃ or more. For example, 130°C or higher. When the softening point of petroleum-based resin is less than 110 degreeC, stickiness may generate|occur|produce in a film, or it may become cloudy with time. The specific gravity of the petroleum-based resin may be 0.97 to 1.1.

The content of the petroleum resin included in the polypropylene resin composition of the present invention may be 2 to 7 wt%, preferably 2 wt% or more and less than 5 wt%, based on the total weight of the polypropylene resin composition.

When the content of the petroleum-based resin is less than 2% by weight, the film cannot obtain good shrinkage properties, and when the content of the petroleum-based resin exceeds 7% by weight, sufficient shrinkage and rigidity cannot be obtained.

On the other hand, the polypropylene resin composition of the present invention is (d) 0.01 to 0.5 parts by weight of a slip agent, based on 100 parts by weight of the components (a) to (c); (e) 0.01 to 0.5 parts by weight of an anti-blocking agent based on 100 parts by weight of the components (a) to (c); Or it may further include a mixture thereof. Hereinafter, these components will be described in detail.

(d) slip agent

In the present invention, the slip agent is applied to the film surface to reduce the sticky phenomenon and is added to improve the surface slippage, and it is preferable to use an amide-based slip agent. That is, the amide-based slip agent may be preferably used as a compound having a high melting point of an amide series synthesized from fatty acids and having a neutral structure in which a hydroxyl group is substituted with an amino structure.

Although not particularly limited to the amide-based slip agent, for example, erucamide, oleamide, behenamide, stearamide, stearyl stearamide, stearyl erucamide (stearyl erucamide), oleyl palmityl amide, and the like.

In addition, the slip agent has an average particle diameter of 1 to 2 mm, preferably 1.1 to 1.5 mm, for example, 1.3 mm of the beads, and an average particle diameter of the powder is 0.1 to 0.9 mm, preferably 0.2 to 0.6 mm, for example For example, it is preferable to use a 0.4 mm diameter.

The slip agent may be included in an amount of 0.01 to 0.5 parts by weight based on 100 parts by weight of the total of the components (a) to (c) of the resin composition of the present invention. When the amount of the slip agent is less than 0.01 parts by weight, the opening properties of the film may be reduced, and when it exceeds 0.5 parts by weight, the slip property becomes excessive and a problem may occur in storage of the film.

(e) anti-blocking agent

In the present invention, the anti-blocking agent is added to minimize the migration of soluble substances because it serves to hold the low-molecular substances so that the low-molecular substances do not come off the surface of the film, and silica or zeolite may be used, Preferably, silica is used.

The silica is not particularly limited and conventional silica known in the art may be used, but as a porous white amorphous silica, the particle size is 2 to 5.3 μm, the pore volume is 0.4 to 0.8 ml/g, and SiO ₂ It is preferable to use a content of 99 mol% or more. In addition, it is preferable to use particles having a moisture content of less than 2% by weight when dried at 160°C.

In addition, the bulk density of the particles is 0.3 to 0.5 g/ml, the average pore channel size (average pore interconnected channel) is 5 to 15 Å cross-section, preferably 7 to 12 Å cross-section, and the specific surface area is 80 to 200 m ^{It has 3} / g, pH has a value of 8 to 9, and whiteness may be a porous component in the form of a powder having a value of 95 or more.

Such an anti-blocking agent may be included in an amount of 0.01 to 0.5 parts by weight based on 100 parts by weight of the total of the components (a) to (c) of the resin composition of the present invention. If the content of the anti-blocking agent is less than 0.01 parts by weight, the printability and blocking properties of the product using the polypropylene resin composition may be reduced, and if it exceeds 0.5 parts by weight, the transparency of the product may be reduced.

In the preparation of the polypropylene resin composition of the present invention, one or more conventional additives known in the art as other additives other than the above components, such as antioxidants, neutralizers, UV stabilizers, antistatic agents, and the like may be further included. At this time, each additive may be included in the range of 0.01 to 1% by weight based on the total weight of the polypropylene resin composition of the present invention.

The antioxidant is to prevent a phenomenon in which resin molecules are broken by heat, oxygen, etc. when manufacturing a film using the polypropylene resin composition, and the neutralizing agent may be generated by a metal component that is a residue of a catalyst used for polymerization. to neutralize acids that can be used, such as HCl. In addition, the ultraviolet stabilizer is to prevent the molecular chain of the resin from being broken by ultraviolet rays, and the antistatic agent is to reduce the generation of static electricity in a film manufactured using the polypropylene resin composition.

Meanwhile, in the present invention, mixing and extrusion of the components may be performed according to a conventional method known in the art. For example, the propylene-ethylene-1-butene random copolymer, elastomer, hydrotreated petroleum resin and other components prepared in the same polymerization reactor are put into a Henschel mixer, and the Henschel mixer is set at 300 to 700 rpm for 0.5 to 3 minutes, After mixing sufficiently for a total of 2 to 8 minutes by discharging the sample out while mixing at 1,200 to 1,800 rpm conditions for 0.1 to 2 minutes and mixing again at 300 to 700 rpm conditions, the processing temperature is 160 to 230° C., preferably It can be manufactured using a single screw extruder, a multi-screw extruder, a kneader, or a Banbury mixer, etc. having an L/D of 25 or more at 180 to 220°C.

Preferably, the polypropylene resin composition can be prepared using a 40 mm co-directional twin-screw extruder having an L/D of 40 and a side feeder under processing conditions where the molding temperature of the extruder is 160 to 220 ° C and the molding speed of the extruder is 300 to 500 rpm. have.

According to another aspect of the present invention, there is provided a shrink film prepared using the polypropylene resin composition of the present invention.

The polypropylene resin composition of the present invention may be molded into a molded product using a known molding method, and for example, may be manufactured using a molding method such as an inflation method or a flat stretching method. It is preferable to use the flat-type stretching method, especially the uniaxial stretching method using a tenter.

For example, after melt-extruding the resin composition of the present invention, the film may be stretched in uniaxial or more directions at a draw ratio of 2 or more to prepare the film for shrink labels of the present invention. The stretching direction may be uniaxial stretching only in a direction perpendicular to the transport direction of the film or label.

For example, a film may be manufactured from the polypropylene resin composition through a process of stretching the water-cooled film at a high temperature of 100 to 150°C again through a circular die using an extruder having a molding temperature of 150 to 220°C.

The film produced by the present invention is a shrink film that can be used as a label paper, and the thickness of the film of the present invention is not particularly limited, but is 100 μm or less, preferably 30 to 80 μm.

The shrink film of the present invention has excellent heat shrinkage properties, and can be applied, for example, as a material for display labels for PET bottles, a material for display labels for bottle containers, and the like. The shrink film of the present invention has excellent high-speed label packaging, and can be used as a label for packaging glass bottles or PET bottles filled with contents such as low-temperature beverages, especially at low temperatures.

Hereinafter, the present invention will be described in more detail through specific examples. The following examples are merely examples to help the understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

Example One

Based on the total weight of components (a) to (c), (a) a ternary random copolymer of propylene-ethylene-1-butene prepared using propylene, ethylene and 1-butene raw materials through a polymerization reactor (ethylene content) 3.8 mol%, 1-butene content 4.5 mol%, melt index (230°C, load 2.16kg) 5.5g/10 min, density 0.90, softening point 113°C) 76% by weight; (b) 20 wt% of a propylene-ethylene-based (PER) elastomer (ethylene content of 10 mol%, melt index (230°C, load of 2.16 kg) 3 g/10 min, manufactured by ExxonMobil); and (c) hydrotreated hydrocarbon resin as C5 petroleum resin (specific gravity 1.08, weight average molecular weight Mw 550, softening point 132-142°C (Ring&Ball), manufactured by Kolon Industries) 4% by weight was put into the Henschel mixer, the Henschel mixer was mixed at 500 rpm for 1 minute and at 1,500 rpm for 0.5 minutes, and the sample was discharged while mixing again at 500 rpm. The mixture was sufficiently mixed for 3 to 5 minutes. Then, the processing temperature was 180 ~ 220 ℃ using a 40mm single screw extruder L / D 35 to prepare a polypropylene resin composition in pellet form. Thereafter, the prepared pellet-like resin composition was put into a sequential biaxial stretching machine for shrink film processing to obtain a shrink film by stretching MD 2 times and TD 7 times. At this time, the stretching temperature was 115 ℃.

Example 2

Based on the total weight of components (a) to (c), (a) component 46% by weight, (b) component 50% by weight, and (c) component 4% by weight, except that 4% by weight of Example 1 and A shrink film was prepared in the same manner.

comparative example One

Based on the total weight of components (a) to (c), a shrink film was prepared in the same manner as in Example 1, except that only 100% by weight of component (a) was added.

comparative example 2

Based on the total weight of components (a) to (c), a shrink film was prepared in the same manner as in Example 1, except that 96% by weight of component (a) and 4% by weight of component (c) were added.

comparative example 3

Based on the total weight of components (a) to (c), a shrink film was prepared in the same manner as in Example 1, except that 93% by weight of component (a) and 7% by weight of component (c) were added.

The contents of components (a) to (c) added in Examples and Comparative Examples are summarized in Table 1 below.

division (a)% by weight (b) wt% (c) wt% Example 1 76 20 4 Example 2 46 50 4 Comparative Example 1 100 - - Comparative Example 2 96 - 4 Comparative Example 3 93 - 7

Experimental example : Measurement of physical properties of shrink film

The physical properties of the shrink films prepared in Examples and Comparative Examples were measured in the following manner and shown in Table 2.

(1) Loop Stiffness: A value measured using Stiffness Testser (manufactured by Toyoseiki), using a specimen with a width of 25 mm and a length of 200 mm, compressing it at a constant compression rate to automatically form a rope. The indenter in the cell presses the apex of the rope to detect the pressure.

(2) Shrinkage: A 10cm (MD) × 10cm (TD) film was immersed in oil at 100°C, 120°C, and 130°C for 4 seconds, respectively, and then the shrinkage was measured to calculate the shrinkage.

division Loop Stiffness
[mN] Shrinkage (%) 100 ℃ 120 ℃ 130 ℃ Example 1 11 25 40 70 Example 2 10.4 28 44 70 Comparative Example 1 10.4 18 26 50 Comparative Example 2 12.6 20 26.5 53 Comparative Example 3 15.6 20 30 58

As can be seen in Table 2, the shrinkage films of Examples 1 and 2 prepared using the polypropylene resin composition of the present invention significantly improved the shrinkage rate, and it was confirmed that the loop rigidity was also excellent.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations are possible within the scope without departing from the technical spirit of the present invention described in the claims. It will be apparent to those of ordinary skill in the art.

Claims (6)

Based on the total weight of the polypropylene resin composition,
(a) 46 to 76% by weight of a propylene-ethylene-1-butene random copolymer;
(b) 20 to 50% by weight of an elastomer; and
(c) containing 2 to 7% by weight of hydrotreated petroleum resin,
The (a) random copolymer contains 1 to 10 mol% of ethylene and 1 to 10 mol% of 1-butene in the propylene component,
The (b) elastomer is a propylene-ethylene copolymer comprising 9 to 16 mol% of ethylene, a polypropylene resin composition.
According to claim 1, (d) 0.01 to 0.5 parts by weight of a slip agent based on 100 parts by weight of the components (a) to (c); (e) 0.01 to 0.5 parts by weight of an anti-blocking agent based on 100 parts by weight of the components (a) to (c); Or a polypropylene resin composition further comprising a mixture thereof.
According to claim 2, wherein the slip agent erucamide (erucamide), oleamide (Oleamide), behenamide (behenamide) stearamide (stearamide), stearyl stearamide (stearyl stearamide), stearyl erucamide (stearyl) erucamide) and at least one amide-based slip agent selected from the group consisting of oleylpalmityl amide, a polypropylene resin composition.
The polypropylene resin composition according to claim 2, wherein the anti-blocking agent is porous amorphous silica.
The polypropylene resin composition according to claim 1, wherein the (c) hydrotreated petroleum resin is a C5 petroleum resin.
A shrink film prepared using the polypropylene resin composition of any one of claims 1 to 5.