KR100623172B1 - Linear low density polyethylene shrink film and method for producing the same - Google Patents

Abstract

Disclosed are a linear low density polyethylene shrink film of a long side chain type prepared by crosslinking a linear low density polyethylene of a short side chain in an extruder, and a method of manufacturing the same. The method for producing the shrink film is selected from the group consisting of (a) 50 to 95 wt% linear low density polyethylene resin, (b) ethylene vinyl acetate copolymer, low density polyethylene, high density polyethylene, and mixtures thereof, based on the total resin component. Mixing 5 to 50% by weight of the synthetic resin substrate with respect to the total resin component, and (c) 0.02 to 0.3 parts by weight of the crosslinking agent with respect to 100 parts by weight of the total resin component; Melting and kneading the mixture of the linear low density polyethylene resin, the synthetic resin substrate, and the crosslinking agent; And molding the melted and kneaded mixture into a film shape.

Linear Low Density, Shrink Film, Synthetic Resin Base, UV Absorber, Crosslinker, Polyethylene

Description

Linear low density polyethylene shrink film and method for producing the same

The present invention relates to a linear low density polyethylene shrink film and a method for manufacturing the same, and more particularly, to a long side chain type prepared by crosslinking a linear low density polyethylene in a short side chain form in an extruder. It relates to a linear low density polyethylene shrink film and a method of manufacturing the same.

Shrink films are polymer films used for heat shrinkage applications in one or this direction and are widely used as packaging and container materials for large and small scale products (eg, industrial pallets, bottles, magazines, etc.). Low density polyethylene (LDPE) is widely used in the production of shrink films. Since low density polyethylene (LDPE) is long-chained, the shrinkage ratio in the transverse direction and the longitudinal direction is balanced, but the mechanical strength is weak, resulting in a high frequency of hole generation during the shrinking process. On the other hand, Linear Low Density Polyethylene (LLDPE) has excellent mechanical properties, but since it has a single side chain shape, transverse shrinkage does not occur, and only longitudinal shrinkage occurs excessively. Accordingly, it is known that linear low density polyethylene is not suitable for producing shrink films by itself. Republic of Korea Patent Application No. 1988-0017098 and Republic of Korea Patent Publication No. 10-2005-0023418 is a shrinkage film to balance the shrinkage in the transverse direction and longitudinal direction by long-chaining the linear low-density polyethylene (LLDPE) polymerization Disclosed is a manufacturing method of. However, the above methods have disadvantages in that the polymerization process is precisely controlled in order to long side chain the linear low density polyethylene, or the linear low density polyethylene of specific physical properties is selected and used.

Accordingly, it is an object of the present invention to provide a linear low density polyethylene shrink film and a method for producing the same, as well as having excellent balance between shrinkage in the transverse direction and the longitudinal direction.

Another object of the present invention is to provide a method for producing a linear low density polyethylene shrink film in the form of a long side chain (long side chain) without undergoing a separate process for long-chaining the linear low density polyethylene resin in the form of a single side chain.

In order to achieve the above object, the present invention comprises (a) 50 to 95% by weight of linear low density polyethylene resin, (b) ethylene vinyl acetate copolymer, low density polyethylene, high density polyethylene, and mixtures thereof, based on the total resin component Selected from the group, mixing 5 to 50% by weight of the synthetic resin substrate with respect to the total resin component, and (c) 0.02 to 0.3 parts by weight of the crosslinking agent with respect to 100 parts by weight of the total resin component; Melting and kneading the mixture of the linear low density polyethylene resin, the synthetic resin substrate, and the crosslinking agent; And it provides a method for producing a linear low density polyethylene shrinkage film comprising the step of molding the molten, kneaded mixture into a film shape. The present invention also provides a linear low density polyethylene resin of 50 to 95% by weight relative to the total resin component; An ethylene vinyl acetate copolymer, a low density polyethylene, a high density polyethylene, and a mixture thereof, 5 to 50 wt% of a synthetic resin substrate based on the total resin component; And 0.02 to 0.3 parts by weight of a crosslinking agent based on 100 parts by weight of the total resin component.

Hereinafter, the present invention will be described in more detail.

The main component of the resin used in the shrink film and the manufacturing method according to the present invention is a linear low density polyethylene resin. As the linear low density polyethylene resin, a commercially available single side chain form and a linear low density polyethylene resin may be used, and the melt index of the linear low density polyethylene resin is 0.5 to 2.0 g / 10 min, and the density is 0.90 to 0.94 g / cm ^3. Is preferably. The amount of the linear low density polyethylene resin is 50 to 95% by weight, preferably 75 to 95% by weight based on the total resin component, if the content of the linear low density polyethylene resin is less than 50% by weight, the final shrinkage film The mechanical properties such as pinhole resistance may not be sufficiently improved. If the content exceeds 95% by weight, not only the crosslinking agent may be excessively used for the production of the shrink film but also the moldability of the shrink film may be poor. have.

In addition to the linear low density polyethylene resin, the resin component used in the production of the shrink film according to the present invention further includes a synthetic resin substrate selected from the group consisting of ethylene vinyl acetate copolymer, low density polyethylene, high density polyethylene, and mixtures thereof. The synthetic resin substrate is intended to improve the physical properties of the shrink film and to suppress excessive use of the crosslinking agent, and it is more preferable to use low density polyethylene as the synthetic resin substrate, and the amount thereof is 5 to 50% by weight based on the total resin component. If the amount of the synthetic resin substrate exceeds 50% by weight, there is a risk that the mechanical properties such as pinhole resistance of the final shrink film is not sufficiently improved, if less than 5% by weight, excessive crosslinking agent for the production of the shrink film Not only must it be used, there is a fear that the moldability of the shrink film becomes poor.

Of the synthetic resin substrate, low density polyethylene is preferably manufactured by a high pressure tubular (Tubular) process, the melt index (ASTM D1238) of the low density polyethylene is preferably 0.3 to 4.0g / 10min, 0.5 to 0.8g / 10min More preferably, the density (ASTM D1505) is preferably 0.90 to 0.94 g / cm ³ , and more preferably 0.92 to 0.93 g / cm ³ . In addition, the melt index of the ethylene vinyl acetate copolymer is 0.3 to 2.0g / 10min, the density is 0.92 to 0.94g / cm ³ , the content of vinyl acetate is preferably 3 to 15%. The melt index (ASTM D1238) of the high density polyethylene is preferably 1.0 to 10.0 g / 10 min, more preferably 6 to 8 g / 10 min, and a density (ASTM D1505) is preferably 0.96 to 0.99 g / cm ³ , It is more preferable that it is 0.97-0.98 g / cm <^3> . When high density polyethylene is used as the synthetic resin substrate, the content thereof is less than 20% by weight, preferably 3 to 15% by weight based on the total resin component. If the content of the high density polyethylene is too low, the yield point tensile strength is not sufficiently compensated for the weakness of the linear low-density polyethylene, there is a possibility that the handle portion is stretched after shrink film packaging, the content of the high-density polyethylene If it is too high, there exists a problem that a mechanical strength falls rapidly.

The crosslinking agent used in the present invention is a crosslinking of the conventional single-sided linear low-density polyethylene resin in the melting, kneading and / or forming step to convert it into a linear low-density polyethylene resin in the long side chain form, the melting point of 40 to 50 It is preferable to use an alkyl peroxide or aryl peroxide crosslinking agent in the form of a solid at room temperature at room temperature. Specific examples of the crosslinking agent include di-tertbutylperoxide, di-tertamylperoxide, 2,2-bis (tert-butylperoxy) butane (2,2-bis ( tert-butylperoxy) butane), 2,5-dimethylhexane-2,5-di-tertbutylperoxide (2,5-dimethylhexane-2,5-di-tertbutylperoxide), 2,5-dimethyl-3-hexene- 2,5-di-tertbutylperoxide (2,5-dimethyl-3-hexene-2,5-di-tertbutyl peroxide), dicumylperoxide, bis- (2-tertbutylperoxyisopropyl ) Benzene (bis- (2-tertbutylperoxyisopropil) benzene), tert-butylcumylperoxide, a mixture thereof, etc. can be illustrated. The amount of the crosslinking agent used is 0.02 to 0.3 parts by weight, preferably 0.04 to 0.2 parts by weight, more preferably 0.06 to 0.1 parts by weight based on 100 parts by weight of the total resin component. If the amount of the crosslinking agent is less than 0.02 parts by weight, the thermal shrinkage of the shrink film cannot be sufficiently improved. If the amount of the crosslinking agent is greater than 0.3 parts by weight, the appearance of the shrink film is poor due to excessive crosslinking reaction, and sufficient pinhole resistance can be obtained due to the deterioration of mechanical properties. none.

Shrink film according to the present invention, if necessary, may further include additives such as light stabilizers, ultraviolet absorbers, surfactants. As the light stabilizer, a high molecular weight hindered amine light stabilizer may be used, and specifically, poly ((6- (1,1,3,3-tetramethylbutyl) amino) -1,3,5-tri Azine-2,4-diyl) (2,2,6,6-tetramethyl-4-piperidinyl) imino) -1,6-hexanediyl) (2,2,6,6-tetramethyl-4 -Piperidinyl) imino))) (poly ((6- (1,1,3,3-tetramethylbutyl) amino) -1,3,5-triazine-2,4-diyl) (2,2,6 , 6-tetramethyl- 4-piperidinyl) imino) -1,6-hexanediyl) (2,2,6,6-tetramethyl-4-piperidinyl) imino)))], 4-hydroxy-2,2,6, 6-tetramethyl-1-piperidine ethanol [4-hydroxy-2,2,6,6-tetramethyl-1-piperidine ethanol], mixtures thereof and the like can be used. The usage-amount of the said light stabilizer is 0.01-0.5 weight part, Preferably it is 0.05-0.3 weight part, More preferably, it is 0.1-0.2 weight part with respect to 100 weight part of all resin components. If the amount of the light stabilizer is less than 0.01 part by weight, sufficient weather resistance may not be obtained. If the amount of the light stabilizer is more than 0.5 part by weight, excessive whitening may occur on the surface of the film.

The ultraviolet absorber is to improve the weather resistance and ultraviolet shielding properties of the linear low density polyethylene shrink film, it can prevent the discoloration of the package. As the ultraviolet absorber, 2- (5-chloro-2H-benzotriazol-2-yl) -6- (1,1, -dimethylethyl) -4-methyl phenol [2- (5-chloro-2H-benzotriazole -2-yl) -6- (1,1, -dimethylethyl) -4-methyl phenol], 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol [2 , 4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol], 2- (2H-benzotriazol-2-yl) -4,6-dipentpentyl phenol [2- (2H -benzotriazol-2-yl) -4,6-ditertpentylphenol], mixtures thereof, and the like. The ultraviolet absorber is used in an amount of 0.01 to 1 part by weight, preferably 0.1 to 0.8 part by weight, and more preferably 0.5 to 0.7 part by weight based on 100 parts by weight of the total resin component. If the amount of the ultraviolet absorber is less than 0.01 parts by weight, sufficient ultraviolet shielding may not be obtained. If the amount of the ultraviolet absorber is more than 1 part by weight, whitening may occur on the surface of the film.

The surfactant is to improve the anti-condensation of the linear low density polyethylene shrink film, the surfactant is sorbitan ester (sorbitan ester), ethoxylated sorbitan ester (ethoxylated sorbitan ester), glycerol fatty acid ester (glycerol fatty acid esters), glycerol oleate, mixtures thereof, and the like. The usage-amount of the said surfactant is 0.1-5 weight part, Preferably it is 0.5-4 weight part, More preferably, it is 1-3 weight part with respect to 100 weight part of all resin components. If the amount of the surfactant is less than 0.1 parts by weight, sufficient condensation prevention effect may not be obtained. If the amount of the surfactant exceeds 5 parts by weight, the surface of the film may be sticky and whitening may occur.

In order to produce a linear low density polyethylene shrink film according to the present invention, a crosslinking agent, a hindered amine light stabilizer, an ultraviolet light absorber, a surfactant at a suitable time when a resin component comprising a linear low density polyethylene resin and a synthetic resin substrate is processed into a shrink film Put in the back. For example, each of the components forming the shrink film may be mixed, melted and kneaded, and then the melted and kneaded mixture may be molded into a film to produce a shrink film. As the apparatus for kneading, a conventional kneading apparatus such as a kneader, a hansel mixer, a roll-mill, a single screw or a twin screw extrusion molding machine can be used, and the molding method of the shrink film may be a tubular blow method or a plate casting. The usual shaping | molding methods, such as a method, a calendar molding method, and an extrusion molding method, can be used. In addition, the light stabilizer, ultraviolet absorber, surfactant, crosslinking agent and the like, by melting and mixing with a resin component, for example, low-density polyethylene, to prepare a high concentration master batch (master batch), the prepared master batch to form a shrink film It may be mixed with a resin component to form a shrink film. According to the above production method, since the linear low-density polyethylene in the form of short-chain is crosslinked and long-chained, and undergoes a molding process such as extrusion, it is possible to produce a linear low-density polyethylene shrink film having excellent mechanical properties and shrinkage properties even with a simple process. Can be.

The linear low density polyethylene shrink film according to the present invention is composed of the same components as the raw materials, specifically, 50 to 95% by weight of the linear low density polyethylene resin based on the total resin component; An ethylene vinyl acetate copolymer, a low density polyethylene, a high density polyethylene, and a mixture thereof, 5 to 50 wt% of a synthetic resin substrate based on the total resin component; And 0.01 to 0.3 parts by weight of a crosslinking agent with respect to 100 parts by weight of the total resin component, and a light stabilizer, an ultraviolet absorber, and a surfactant as necessary. The thickness of the shrink film according to the present invention may vary depending on the load and the size of the package, but is 30 to 150 μm, preferably 40 to 120 μm. In addition, the transverse shrinkage of the shrink film is 5 to 50%, preferably 10 to 30%, the longitudinal shrinkage is 60 to 90%, preferably 70 to 80%. In addition, the shrink film according to the present invention has a UV transmittance of 0 to 20%, preferably 5 to 10%, and has a light stability of 500 hours or more, preferably 1,000 hours or more.

Hereinafter, the present invention will be described in more detail with reference to specific examples. The following examples are intended to illustrate the present invention more specifically, but the scope of the present invention is not limited by the following examples.

Example 1-16, Comparative Example 1-4 Preparation of Shrink Film

Low density polyethylene (density: 0.920 g / cm ³ , melt index: 3.0 g / 10 min) with 2.0%, 10%, 10%, and 20% by weight of crosslinking agent, hindered amine light stabilizer, ultraviolet absorber and surfactant, respectively It was mixed at a concentration of%, and they were melted and kneaded and extruded to prepare a master batch (concentrate) in pellet form. Master batch prepared, linear low density polyethylene resin (density: 0.920 g / cm ³ , melt index: 1.0 g / 10 min), low density polyethylene (density: 0.920 g / cm ³ , melt index: 3.0 g / 10 min), and high density polyethylene (Density: 0.980 g / cm ³ , Melt Index: 4.5 g / 10 min) were melt kneaded so as to have the component ratios shown in Tables 1 to 5 below, and film molding was extruded to prepare a linear low density polyethylene shrink film having a thickness of 100 μm. In Tables 1 to 5,% indicates weight% unless otherwise indicated.

Shrinkage, UV transmittance, light stability, anti-condensation, etc. of the prepared linear low density polyethylene shrink film were measured by the following method, and are shown in Tables 1 to 5 together.

1) Shrinkage: After immersing the shrinkage film in a glycerin solution at 120 ° C. for 20 seconds, the change in length is measured.

2) UV transmittance: Measured at a wavelength of 300 to 380 nm.

3) Light Stability: Measured by UV-CON at the time when remaining elongation is over 50%.

4) Anti-condensation: After the film is sandwiched between chambers with internal and external temperature differences, it is determined whether the package is visually confirmed by spreading without condensation.

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Comparative Example 4 Low density polyethylene 90% 10% 10% 10% 10% Linear Low Density Polyethylene 10% 90% 90% 90% 90% Crosslinking agent 0 parts by weight 0 parts by weight 0.01 parts by weight 0.1 parts by weight 0.4 parts by weight Product appearance Good Good Good Good Bad Formability Good Bad Good Good Good Shrinkage Good Bad Heterogeneity Good Good Pin Hole Resistance Bad Good Good Good Bad

Table 1 is a composition in which functional additives such as light stabilizers, ultraviolet absorbers, and surfactants are not used. As shown in Table 1, when the crosslinking agent is not prescribed (Comparative Examples 1 and 2), or when the amount of the crosslinking agent is too small (Comparative Example 3), it can be seen that the pinhole resistance, the heat shrinkage rate, the moldability, and the like are lowered. If the amount of is used too much (Comparative Example 4), there is no problem in the heat shrinkage rate, but it can be seen that there is a problem in the appearance of the product and the pinhole resistance.

division Example 2 Example 3 Example 4 Example 5 Linear Low Density Polyethylene 90% 90% 90% 90% Low density polyethylene 10% 10% 10% 10% Crosslinking agent 0.1 parts by weight 0.1 parts by weight 0.1 parts by weight 0.1 parts by weight Light stabilizer 0.01 parts by weight 0.01 parts by weight 0.5 parts by weight 0.3 parts by weight UV absorbers 0.1 parts by weight 1.0 parts by weight 0.5 parts by weight 0.5 parts by weight Light stability (UV-CON) 100> 100> 1,000 < 1,000 < UV shielding rate 80% less than More than 95% More than 95% More than 95% Product appearance Good all sorts of flowers all sorts of flowers Good

As shown in Table 2, when the prescription content of the light stabilizer and the ultraviolet absorbent is low (Example 2), when the prescription content of the light stabilizer or the ultraviolet absorber is large (Examples 3 and 4), the light stability and the ultraviolet shielding are accordingly It can be seen that the yield and product appearance are not preferred.

division Example 6 Example 7 Example 8 Linear Low Density Polyethylene 90% 90% 90% Low density polyethylene 10% 10% 10% Crosslinking agent 0.1 parts by weight 0.1 parts by weight 0.1 parts by weight Surfactants 0.1 parts by weight 5 parts by weight 2 parts by weight Condensation Prevention Bad Good Good Product appearance Good all sorts of flowers Good

As shown in Table 3, it can be seen that if the amount of the surfactant used is too low (Example 6) or too high (Example 7), the condensation prevention property, the product appearance (whitening), and the like are not preferable.

division Example 9 Example 10 Example 11 Linear Low Density Polyethylene 90% 70% 80% Low density polyethylene 10% 10% 10% High density polyethylene 0% 20% 10% Crosslinking agent 0.1 parts by weight 0.1 parts by weight 0.1 parts by weight Yield Point Tensile Strength Inadequate Great Great Handle droop has exist none none Mechanical strength usually Great Great

As shown in Table 4, when the high-density polyethylene content is too small (Example 9), the sagging of the handle portion and the yield point tensile strength after the shrink wrap is also lowered, it can be seen that the mechanical strength is not desirable.

division Example 12 Example 13 Example 14 Example 15 Example 16 Low density polyethylene 10% 10% 10% 10% 30% Linear Low Density Polyethylene 80% 80% 80% 80% 70% High density polyethylene 10% 10% 10% 10% 0% Crosslinking agent 0.1 parts by weight 0.1 parts by weight 0.1 parts by weight 0.1 parts by weight 0.1 parts by weight Film thickness (micron) 30 150 40 60 120 Formability Good Bad Good Good Good Shrinkage Good Good Good Good Good Pin Hole Resistance Bad Good Good Good Good

As shown in Table 5, in the case of the shrink film according to the present invention, if the film thickness is too low (Example 12) or too high (Example 13), it is found that physical properties such as moldability and pinhole resistance are not preferable. Can be.

As described above, the linear low-density polyethylene shrink film according to the present invention not only balances the shrinkage in the transverse direction and the longitudinal direction, but also has excellent mechanical properties. In addition, according to the method for producing a linear low density polyethylene shrink film according to the present invention, the linear low density polyethylene shrink film in the form of a long side chain (long side chain), without going through a separate step of long side chain linear low density polyethylene resin in the form of a single side chain Can be prepared.

Claims (6)

(a) 50 to 95% by weight of linear low density polyethylene resin, (b) ethylene vinyl acetate copolymer, low density polyethylene, high density polyethylene, and mixtures thereof, based on the total resin component, 5 to 50% by weight of a synthetic resin substrate, and (c) mixing 0.02 to 0.3 parts by weight of the crosslinking agent based on 100 parts by weight of the total resin component; Melting and kneading the mixture of the linear low density polyethylene resin, the synthetic resin substrate, and the crosslinking agent; And Method for producing a linear low density polyethylene shrink film comprising the step of molding the molten, kneaded mixture into a film shape. According to claim 1, wherein the melt index of the linear low density polyethylene resin is 0.5 to 2.0g / 10min, the density is 0.90 to 0.94g / cm ^{3 The} method for producing a linear low density polyethylene shrink film. The method of claim 1, wherein the synthetic resin substrate is a low density polyethylene having a melt index of 0.3 to 4.0 g / 10 min and a density of 0.90 to 0.94 g / cm ³ . The method of claim 1, wherein the crosslinking agent is a peroxide crosslinking agent having a melting point of 40 to 50 ℃. 50 to 95% by weight of linear low density polyethylene resin, based on the total resin component; An ethylene vinyl acetate copolymer, a low density polyethylene, a high density polyethylene, and a mixture thereof, 5 to 50 wt% of a synthetic resin substrate based on the total resin component; And A linear low density polyethylene shrink film comprising 0.02 to 0.3 parts by weight of a crosslinking agent based on 100 parts by weight of the total resin component. The method of claim 5, wherein the linear low density polyethylene shrink film comprises 0.01 to 0.5 parts by weight of a light stabilizer, 0.01 to 1 part by weight of an ultraviolet absorber, and 0.1 to 5 parts by weight of surfactant based on 100 parts by weight of the total resin component. Linear low density polyethylene shrink film.