KR101439752B1 - Polyethylene resin composition and Agricultural film of using this - Google Patents

Abstract

The present invention relates to a polyethylene resin composition, and a resin composition for an agricultural film and an agricultural film comprising the same and, more specifically, to a polyethylene resin composition including: an alpha olefin copolymer composed of ethylene and 2-20 carbon atoms; and ethylene-vinyl acetate copolymer including 20-35% of vinyl acetate, and to a resin composition for an agricultural film and an agricultural film comprising the same. The present invention can provide single-layer and multi-layer agricultural film having high transparency and high stiffness by applying a polyethylene resin composition.

Description

TECHNICAL FIELD The present invention relates to a polyethylene resin composition and an agricultural film using the same,

The present invention relates to a polyethylene resin composition, a resin composition for agricultural film containing the same, and an agricultural film.

Ethylene-vinyl acetate copolymer (EVA) is mainly used for agricultural film, and products containing 3% to 12% of VA are commonly used. The higher the VA content in EVA, the higher the transparency and the light transmittance of the film. As a result, the absorption of infrared rays and the warmth can be improved. Because of this functionality, EVA resin is used instead of ordinary polyethylene resin.

However, EVA products are basically polymerized by high-pressure radical method and characterized by a broad molecular weight distribution, and thus have low mechanical strength. In order to solve such problems, film forming by mixing of linear low density polyethylene and ethylene vinyl acetate copolymer and functional film by multi-layer film have been proposed. However, the mechanical strength of the film molding by simple mixing is increased to some extent, but it is lower than the exclusive use of the ethylene vinyl acetate copolymer in the warmth and oiliness.

In the case of the multilayered functional film, the outer layer is mainly composed of a low density polyethylene (LLDPE), the middle layer and the inner layer are composed of an ethylene vinyl acetate copolymer and a low density polyethylene (LDPE) It is mixed and used. By adding appropriate oil stabilizer and UV stabilizer to each layer, it is possible to improve mechanical strength, ensure warmth, and survivability. However, even in this case, transparency deterioration due to multilayered films is problematic, and low polymer due to an excessively broad molecular weight distribution of LDPE and EV used in the middle and inner layers causes transition to transparency over time due to bonding with additives, There is a problem of dropping.

In recent years, efforts have been made to develop resins for agricultural films having properties of low haze and high light transmittance. For example, attempts have been made to improve additives to be mixed in the production of agricultural films (Korean Application 10- 2002-0081235, 1993-0031626, 10-1983-0004209). In this case, the improvement of the transparency is limited but the improvement of the mechanical properties is not suggested. Korean Patent Application No. 10-2010-0009360 discloses a method for producing a film having a yarn-woven intermediate layer in order to improve mechanical strength, but this approach has a problem that the transparency is remarkably deteriorated.

In addition, attempts have been made to improve the transparency by mixing EVA and ethylene alpha olefins with high VA content. For example, in Korea 10-2007-0030187, EVA having a VA content of 3 to 20%, a mixture of ethylene alpha olefins having a flow activation energy of 35 kJ / mol or more and a molecular weight distribution of 6 or more, And a method of producing a film excellent in transparency and durability. In this case, however, the initial haze is not improved clearly, and it can be seen that the tensile strength of the film produced in the examples does not exceed 30 MPa (300 kgf / cm ² ) of the conventional EVA product.

Therefore, in order to improve the transparency and the mechanical strength of the agricultural film, there is a demand for a method of providing a resin which is fundamentally superior in transparency and mechanical strength, rather than merely blending various kinds of resins when improving additives or films.

The object of the present invention is to solve the above-mentioned problems and provide a polyethylene resin composition which is superior in light transmittance to a conventional EVA product in the production of single layer and multi-layer agricultural films, and is capable of producing a film having excellent mechanical strength .

Another object of the present invention is to provide a resin composition for an agricultural film comprising the polyethylene resin composition.

It is still another object of the present invention to provide an agricultural film made of the resin composition for agricultural film.

According to an aspect of the present invention,

In the polyethylene resin composition comprising the component A and the component B,

The component A is:

(1) Density: 0.900 to 0.925 g / cm < ³ >

(2) Melt flow rate (MI): 0.1 to 5 g / min (190 DEG C, 2.16 kg)

(3) Molecular weight distribution (Mw / Mn): 3 to 5 and

(4) Composition Distribution Breadth Index (CDBI) measured by CRYSTAF (Crystallization Analysis Fractionation): 85 to 95%

And an alpha-olefin copolymer having 2 to 20 carbon atoms,

The component B is:

(1) MI: 1 to 15 g / min (190 DEG C, 2.16 kg) and

(2) Molecular weight distribution (Mw / Mn): 3 to 5

And is an ethylene-vinyl acetate copolymer containing 20% to 35% of vinyl acetate,

The component A is contained in an amount of 60 to 90% by weight based on the total weight of the polyethylene resin composition,

The component B comprises 10 to 40% by weight based on the total weight of the polyethylene resin composition,

Wherein the polyethylene resin composition has an MI of 0.7 to 2.0 g / min (190 캜, 2.16 kg) and a molecular weight distribution (Mw / Mn) of 3 to 5.

The component A may be a linear low density polyethylene resin prepared from a metallocene catalyst represented by the following formula (1).

[Chemical Formula 1]

(THI) ₂ RMQp

In Formula 1,

The two THI ligands are the same or different from each other and are tetrahydroindenyl or a derivative thereof substituted or unsubstituted by a substituent,

The substituent may be selected from the group consisting of phenyl (Ph), benzyl (Bz), naphthyl, indenyl, benzindenyl, methyl, ethyl, n- (i-Pr), n-butyl, t-butyl, trimethylsilicon group (Me ₃ Si), alkoxy, cycloalkyl and halogen Or more,

R is a structural bridge that provides steric rigidity between two THI ligands and is an alkylidene, alkylenyl, germanium, silicon, siloxane, alkylphosphine or amine group containing from 1 to 20 carbon atoms ,

M is a transition metal of Group IIIB, Group IVB, Group VB or Group VIB,

Q is a hydrocarbyl group having from 1 to 20 carbon atoms or halogen,

p is 1 to 4;

The ethylene-vinyl acetate copolymer (B) is prepared by reacting an ethylene monomer and a vinyl acetate monomer with a peroxide initiator at a concentration of 50 to 1,000 ppm in a high-pressure reactor at a polymerization temperature of 200 to 260 ° C and a polymerization pressure of 2500 to 3000 kg / .

Another aspect of the present invention relates to a resin composition for an agricultural film comprising the polyethylene resin composition.

Another aspect of the present invention relates to an agricultural film made of a resin composition for agricultural film.

The present invention provides an agricultural film having improved transparency and mechanical properties by using a polyethylene resin composition comprising an ethylene alpha-olefin copolymer and an ethylene-vinyl acetate copolymer having a narrow distribution of copolymerizable monomers and having a uniform copolymer range .

Fig. 1 shows a Crystaf graph of the resin prepared in Synthesis Example 1 of the present invention.
2 shows a Crystaf graph of the resin prepared in Synthesis Example 2 of the present invention.
FIG. 3 is a graph of light transmittance of a three-layer film according to the present invention.
4 is a graph of light transmittance of a three-layer film according to the present invention.
5 is a graph of light transmittance of a single layer film according to the present invention.

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

The present invention provides a polyethylene resin composition. The polyethylene resin composition is excellent in transparency, mechanical strength and moldability, and can be used to provide an agricultural film excellent in mechanical strength and transparency.

Polyethylene resin composition

The polyethylene resin composition may comprise Component A and Component B as shown below.

(1) Component A

The component A is ethylene and an alpha olefin copolymer having 2 to 20 carbon atoms, and is contained in an amount of 60 to 90% by weight based on the total weight of the polyethylene resin composition.

Since the copolymer exhibits a narrow molecular weight distribution range and uniform copolymer range, it can provide high mechanical strength and transparency. More specifically, the copolymer has a density of 0.900 to 0.925 g / cm ³ , a melt flow rate (MI) of 0.1 to 5 g / min (190 ° C, 2.16 kg) and a molecular weight distribution (Mw / Mn) 5. The Composition Distribution Breadth Index (CDBI), measured by Crystallization Analysis Fractionation (CRYSTAF), is the weight percent of the copolymer contained within 50% left and right at 50% of the cumulative fraction of the copolymer distribution curve, 95%. The higher the CDBI value, the more uniform the distribution of the copolymer, and the higher the CDBI value, the higher the mechanical strength and transparency.

The ethylene and the alpha olefin copolymer having 2 to 20 carbon atoms can be produced by gas phase polymerization using a metallocene catalyst represented by the following formula (1).

[Chemical Formula 1]

(THI) ₂ RMQp

In the above Formula 1, two THI ligands are the same or different from each other and are tetrahydroindenyl or derivatives thereof substituted or unsubstituted by a substituent, and the substituents include phenyl (Ph), benzyl (Bz), naphthyl ), Indenyl (Ind), benzindenyl (BzInd), methyl (Me), ethyl, n-propyl, n- ), and t- butyl (t-Bu), trimethyl silicon group (Me ₃ Si), alkoxy, at least one member selected from the group consisting of cycloalkyl and halogen,

R is a structural bridge that imparts steric rigidity between the two THI ligands and is an alkylidene group, alkylenyl group, germanium group, silicon group, siloxane group, alkylphosphine group or amine group containing 1 to 20 carbon atoms ego,

M is a transition metal of Group IIIB, Group IVB, Group VB or Group VIB,

Q is a hydrocarbyl group having from 1 to 20 carbon atoms or halogen,

P is 1 to 4. As the metallocene catalyst _{Et (THI) 2 ZrCl 2,} Me 2 Si (THI) 2 ZrCl 2, Me 2 Si (2-MeTHI) 2 ZrCl 2, Et (2-MeTHI) 2 ZrCl 2, Me 2 Si ( 2-Me, 4-PhTHI) 2 ZrCl 2, Et (2-Me, 4-PhTHI) 2 ZrCl 2, Me 2 Si (2-Me, 4-NaphTHI) 2 ZrCl 2, Et (2-Me, 4- _{NaphTHI) 2 ZrCl 2, Me 2} Si (2-Me, 4,5-BzIndTHI) 2 ZrCl 2, and Et (2-Me, 4,5- BzIndTHI) 2 ZrCl 2 And the like, but the present invention is not limited thereto.

The metallocene catalyst may be used as a supported catalyst supported on a support. The carrier may be a solid or particulate porous or inorganic material, for example, an oxide of silicon or aluminum, and preferably the carrier is an inorganic material of spherical particles, such as spherical particles obtained by spray drying ≪ / RTI > The support of the metallocene catalyst is carried out by reacting the carrier with a mixture of metallocene and methylaluminoxane according to a general method known in the art. The molar ratio of aluminum to transition metal in the metallocene is preferably 100: 1 to 300: 1. The supporting reaction temperature is preferably 80 ° C to 120 ° C. The reaction time is preferably 1 hour to 2 hours.

For example, to suspend silica in a hydrocarbon solution and to produce an activated catalyst, a solution of the corresponding metallocene cation and anionic methyl alumoxane oligomer is prepared by reacting the metallocene catalyst component with a methyl alumoxane solution . The resulting solution is added dropwise to the silica suspension solution, the mixture is heated and heated for a predetermined time to carry out the reaction. Thereafter, the reaction mixture is cooled to room temperature, washed three times with a hydrocarbon solution under nitrogen, and dried to complete the supported catalyst.

As the cocatalyst, an alkyl aluminum compound, aluminoxane, modified aluminoxane, aluminate salt, neutral ionizing activator, ionic ionizing activator, non-coordinating anion, non-coordinating anion, A Group 13 metal of the coordination group, a metaloid anion, a borane compound, and a borate salt. The cocatalyst may be used in a molar ratio of 100 to 1000 with respect to the transition metal of the metallocene catalyst.

In the polymerization process, hydrogen may be used to control the melt index of the polymer, in which case the molar ratio to ethylene is 0.0001 to 0.001 and the mole ratio of ethylene to ethylene is 0.001 to 0.02 for density control. The comonomer may be an alpha-olefin monomer having 2 to 20 carbon atoms.

The polymerization process may be carried out in a lubricant layer reactor, and the gas phase polymerization temperature in the fluidized bed reactor is preferably 70 to 80 占 폚. The operating pressure in the fluidized bed reactor may preferably be 10 to 30 atm.

(2) Component B

Component B is an ethylene-vinyl acetate copolymer and comprises 10 to 40% by weight based on the total weight of the polyethylene resin composition. If the content of the component B is less than 10% by weight, the residual property of the film is lowered. If the content of the component B is more than 40% by weight, the mechanical strength of the film may be lowered.

The MI of the copolymer is 1 to 15 g / min (190 DEG C, 2.16 kg) and the content of vinyl acetate is 20 to 35%. When the content of the vinyl acetate is within the above range, high transparency can be provided and smooth migration performance of the residual agent can be provided.

The component B can be produced by a polymerization process by a high-pressure radical method using a peroxide initiator. For example, the (B) ethylene-vinyl acetate copolymer may be polymerized at a suitable temperature and pressure after the ethylene monomer and the vinyl acetate monomer are added to the tubular reactor and the peroxide initiator is added. The content of the ethylene monomer may be controlled depending on the content of the vinyl acetate of the ethylene-vinyl acetate copolymer (B) mentioned above.

The peroxide initiator may be a mixture of at least one member selected from the group consisting of alkylperoxy ethylhexanoate compounds and dialkyl peroxide compounds in the alkylperoxy pivalate compound. The alkylperoxy pivalate compound may be t-amyl peroxypivalate, t-butyl peroxypivalate or the like. The alkyl peroxyethylhexanoate compound may be t-amylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, and the dialkyl peroxide compound may be di -t-butyl peroxide, di-t-amyl peroxide, and the like.

The mixing weight ratio of the alkyl peroxypivalate compound: alkyl peroxyethyl hexanoate compound and / or dialkyl peroxide compound in the peroxide type initiator mixture may be 15 to 20:85 to 80, If the mixing weight ratio of the oxide initiators is out of the above range, the molecular weight of the resin can not be easily controlled, which is not preferable.

If the addition concentration is less than 50 ppm, the conversion temperature to the EVA is low and the molecular weight is not easily controlled, which is not preferable. When the addition concentration is less than 50 ppm, the peroxide initiator may be added in an amount exceeding 1,000 ppm There is a possibility that the resin is decomposed due to a high reaction temperature during the polymerization and decomposition of the vinyl acetate causes stability of the acetic acid to corrode the reactor.

If the polymerization temperature is lower than 200 ° C, the conversion to EVA is low and the desired molecular weight and molecular weight distribution can not be obtained, which is undesirable. When the temperature exceeds 260 ° C, the decomposition reaction occurs The stability of the reactor is deteriorated due to corrosion of the reactor.

If the polymerization pressure is less than 2500 kg / cm 2, gas or liquid phase separation will occur and the reaction will be insufficient and the stability of the operation will be lowered. If the polymerization pressure exceeds 3000 kg / cm 2 It is undesirable because there is a problem in stability due to the performance limit of the high-pressure pump.

The polymerization time in the polymerization step may be 2 to 20 minutes. If the polymerization time is less than 2 minutes, the conversion to ethylene vinyl acetate copolymer is low and the molecular weight is low, which is undesirable. When the polymerization time exceeds 20 minutes, , A gel may be generated, which is undesirable.

In addition to the above components, (B) conventional additives used in the polymerization process of the ethylene-vinyl acetate copolymer, such as chain transfer agents, may be further used.

The MI of the polyethylene resin composition may be 0.7 to 2.0 g / min (190 캜, 2.16 kg) and the molecular weight distribution (Mw / Mn) may be 3 to 5.

The polyethylene resin composition according to the present invention can be prepared according to the production method of the resin composition known in the art, for example, by charging the components into a stirring-mixing apparatus [for example, a Hensel mixer, a super mixer or a tumbler mixer] And the mixture is stirred and mixed for 1 to 30 minutes, and the two components are melt-mixed and kneaded at a temperature of 180 to 230 ° C using a mill or an extruder to produce granules.

The present invention provides a resin composition for agricultural film containing the polyethylene resin composition.

The content of the polyethylene resin composition may be selected depending on the use of the agricultural film and the structure thereof. More specifically, the polyethylene resin composition may be contained in an amount of 100% by weight or less based on the total weight of the resin composition for agricultural film. According to one embodiment, it may be included in an amount of 20 to 100% by weight, and may be included in an amount of 20 to 90% by weight.

The resin composition for agricultural film may further include an ethylene polymer in consideration of transparency, bubble stability at the time of processing, mechanical strength, etc. For example, the resin composition for agricultural film may include one of linear low density polyethylene (LLDPE) and low density polyethylene And more preferably at least LDPE. The LDPE may have an MI of 1 to 3 g / min (190 캜, 2.16 kg) and a molecular weight distribution of 4 to 7. The ethylene polymer resin may be contained in an amount of 40 to 60% by weight based on the total weight of the resin composition for agricultural film.

The resin composition for an agricultural film may further comprise an additive comprising at least one of an oil agent and a long-life agent. The additive may be added within a range not deviating from the object of the present invention, and preferably from 1.5 to 2.2% by weight based on the total weight of the resin composition for agricultural film. Specific examples of the remedies include: sorbitan fatty acid esters such as sorbitan monostearate, sorbitan monopalmitate, and sorbitan monooleate; And glycerin fatty acid esters such as glycerin monostearate, glycerin distearate, diglycerin monostearate, diglycerin distearate, glycerin monooleate, glycerin diolate, diglycerin monooleate, and diglycerin diolate; And the like.

The weather stabilizer used as the long-lived waterproofing agent may be a light stabilizer and an ultraviolet absorber, and the light stabilizer may be a hindered amine light stabilizer. The hindered amine light stabilizer is a poly [[6 - [(1,1,3,3-tetramethylbutyl) amino] 1,3,5-triazine-2,4- 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] [2,2,6,7-tetramethyl- 4- piperidinyl] (2,2,6,6-tetramethyl-4-piperidyl) sebacate (Bis (2,2,6,6-tetramethyl-4-peperidinyl] imino] , 6,6-tetramethyl-4-piperidyl sebacate, 2-hexyl-4-n-octoxybenzophenone, 2- (2'- (2'-hydroxy-3'-tetra-butyl-5'-methylphenyl) -5-chlorobenzotrizole), 8-acetyl- Silane-7,7,9,9-tetramethyl-1,3,8-triazaspiro [4,5] decene-2,4-dione (8-acetyl-3-dodecyl-7,7,9,9 -tetramethyl-1,3,8-triazaspiro [4,5] decane-2,4-dione) and the like can be used. The ultraviolet absorber may be a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, or a salicylic acid ultraviolet absorber. The oil and longevity counts can be mixed directly or in the form of Master Batch with the raw resin during film forming and are usually used in Master Batch form to improve dispersibility.

The present invention provides an agricultural film made of the resin composition for agricultural film.

The agricultural film can exhibit low haze, high light transmittance and high mechanical strength by applying the resin composition for agricultural film.

The agricultural film may be a single layer or a multilayer film, and the single layer film may be made of the resin composition for agricultural film according to the present invention. According to one embodiment of the present invention, A polyethylene resin composition alone; Or a resin composition for an agricultural film comprising a polyethylene resin composition and LDPE and / or an additive.

According to one embodiment of the present invention, the multi-layer agricultural film may be a two-layer film consisting of an outer layer and an inner layer. The outer layer is referred to as the long-lived layer of the film, and may be prepared by mixing LLDPE for improving mechanical strength and LDPE for reducing the extruder load during film production. The mixing ratio of the LDPE is preferably 30 wt% to 70 wt%, and if it is less than 30 wt%, the transparency deteriorates and the working load of the extruder is increased. If the amount exceeds 70 wt%, the mechanical strength of the entire film is weakened have. The inner layer of the multilayered film is made of the polyethylene resin composition alone according to the present invention; Or a resin composition for an agricultural film comprising a polyethylene resin composition and LDPE and / or an additive.

According to one embodiment of the present invention, the multi-layer agricultural film may be a three-layer film consisting of an outer layer, an intermediate layer and an inner layer. The outer layer is as mentioned above.

The middle layer and the inner layer are mainly made of a polyethylene resin composition according to the present invention for the purpose of exhibiting warmth and legibility; Or a resin composition for an agricultural film comprising a polyethylene resin composition and LDPE and / or an additive. The middle layer and the inner layer may be made of the same or different resin composition for agricultural film.

In the case of the above three-layer film, the thickness of each layer may vary depending on each preferred function and the amount of the functional additive added. Preferably, the thickness ratio of the outer layer: middle layer: inner layer is 1: ~ 3: 1 ~ 2 ratio. When the thickness of the intermediate layer is high, persistence of relativity is improved, and when the ratio of the inner layer is high, initial relativity can be improved.

Hereinafter, the present invention will be described in more detail with reference to the following examples and comparative examples so that those skilled in the art can easily carry out the present invention. The following examples are only illustrative of the present invention and do not limit the scope of protection of the present invention.

Synthetic example  One

Component A: Preparation of linear low density polyethylene resin

(One) Metallocene  Supported catalyst

In a glove box, 100 g of silica and a metallocene catalyst, ethylene-tetrahydroindenyl-zirconium dichloride (Ethylen-Tetra Hydro Indenyl-Zirconium dichloride / silica = 110 μmol / g silica) Slurried with 100 mL of toluene (Toluene) and then injected into the reactor. After the injection, the silica was allowed to stand in the reactor and the supernatant was decanted. On the other hand, a metallocene / MAO mixture was prepared by injecting MAO (MAO (Al) / Metallocene (Zr)) = 109 (mol ratio) into the metallocene and stirred for at least 15 minutes, And the melted state was confirmed. The metallocene / MAO mixture prepared was slowly added to the prepared reactor and thoroughly mixed with the silica in the reactor. Thereafter, the temperature of the reactor was raised to 110 DEG C and the reaction was carried out for 2 hours. After the reaction was completed, the temperature of the reactor was lowered to room temperature, and the supernatant was removed. Then, the reactor was washed with 2000 mL of toluene, and repeatedly allowed to stand and decant. The prepared metallocene supported catalyst was transferred from the reactor to the bottle and then transferred to the glove box. The toluene in the metallocene supported catalyst was removed in the glove box, and the resultant was washed twice with 1000 mL of hexane, and the solution and the decant were repeated to remove the unreacted material. Thereafter, the catalyst was dried in a vacuum state at 80 ° C. for 6 hours to finally prepare a catalyst in the form of Free Flowing Powder.

(2) Polymerization

The linear low density polyethylene as the constituent component A of the present invention was prepared under the polymerization conditions shown in Table 1 below using 1-Hexene as a copolymer in a gas phase polymerization reactor using the metallocene catalyst system prepared above. The basic properties of the prepared copolymer were measured by the following methods, and the results are shown in Table 2. The measured Crystaf results are also shown in FIG.

Item unit Synthesis Example 1 catalyst - Metallocene Polymerization temperature ℃ 80 Polymerization pressure kg / cm ² 19.2 Ethylene (C2) mol% 35 Hydrogen (H2) mol% 0.045 H2 / C2 - 0.0013 1-Hexene mol% 0.35 1-Hexene / C2 0.01 Bed Weight kg 70 Residence time hr 10 output kg / hr 7

Synthetic example  2

Component B: Ethylene Vinyl Acetate Copolymer ( EVA )

The ethylene vinyl acetate copolymer contains monomers of 74% by weight of ethylene monomer and 26% by weight of vinyl acetate monomer based on the total weight of the monomers, t-butyl peroxypivalate, t-butyl peroxy-2-ethylhexanoate (Weight ratio: 15/80/5) as a chain transfer agent and 70 ppm of propionaldehyde as a chain transfer agent as a molecular weight regulator were fed into a tubular reactor using a high-pressure pump , A reaction pressure of 2500 kg / cm 2, a reaction temperature of 240 ° C, and a polymerization time of 10 minutes. After the polymerization reaction, the copolymer was discharged from the reactor in a molten state, and after unreacted monomers were removed, the copolymer was granulated to prepare pellets. The basic properties of the prepared copolymer were measured by the following methods, and the results are shown in Table 2. The measured Crystaf results are also shown in Fig.

Configuration Synthesis Example 1 Synthesis Example 2 A B MI 1.1 g / min
(190 DEG C, 2.16 kg) 8.5 g / min
(190 DEG C, 2.16 kg) density 0.917g / cm ³
0.945g / cm ³ CDBI 93.6 - VA content - 26 Mw / Mn 3.3 3.8

Example  One

(1) Component (C): Preparation of resin composition

83% by weight of component A and 17% by weight of component B in the synthetic example are mixed in an extruder at a constant component ratio according to the following Table 3, melted and kneaded to provide a granulate. The basic properties of the prepared resin mixture were measured by the following methods, and the results are shown in Table 3.

Component (C) Component (A) 83% Component (B) 17% MI 1.3 g / min (190 DEG C, 2.16 kg) density 0.923g / cm ³
VA content 4.3 Mw / Mn 3.4

(2) Blow  Production of film

The inner layer and the outer layer were prepared by using an extruder having an inner diameter of screw extruder of 75 mm and an extruder having an inner diameter of 120 mm. The die diameter is 2 m and the die gap is 3.2 mm. The expansion ratio of the film was 2.0, and the processing temperature for each layer was adjusted from 170 to 190 ° C. The total thickness of the film was 60 μm and the ratio of outer layer: middle layer: inner layer was 1: 2: 1 by controlling the extruder rpm. The outer layer was mixed with 20% of LLDPE and 65% of LDPE, And remnants and longevity Master Batch (manufactured by Samjin Polytec) were added. Master batch was prepared by mixing 1: 1 mixture of sorbitan ethylene glycol fatty acid ester and poly-oxy ethylene, which is glycerine system, with 15 wt% of LDPE [MI 3g / min (190 ℃, 2.16kg), Density 0.922g / cm ³ ] and used. The long batch Master batch is a mixture of poly [[6 - [(1,1,3,3-tetramethylbutyl) amino] 1,3,5-triazine-2,4-dilyl] [2,2,6, LDPE [MI 3g / min (190 ° C, 2.16kg)] was added to 9wt% Density 0.922 g / cm < ³ >].

In the case of the middle layer, 85% of component C, which is the resin mixture proposed in the present invention, was used, and the same residual agent and long-life master batch as the outer layer were added. In the case of the inner layer, the component C was added at 60%, LDPE at 25%, and the residual agent and the long-life agent (UV stabilizer) Master Batch at 10 and 5%, respectively. The initial haze and mechanical properties of the prepared three-layered agricultural film were measured, and the results are shown in Table 4 and FIG.

Example  2

Except that the thickness of the film was changed to 70 탆 and the layer composition was changed to 3: 4: 3, the composition of the outer layer was changed to 50% of LLDPE, 35% of LDPE, and the composition of the inner layer was changed to 85% Was the same as that of Example 1. The same amount of the preservative and long-life agent (UV stabilizer) Master Batch as in Example 1 was prescribed. Initial haze and mechanical properties of the prepared films were measured. The results are shown in Table 4 and FIG.

Example  3

Extruder Screw A single layer film was prepared using an extruder having an inner diameter of 100 mm. The die diameter was 1.5 m and the die gap was 3.2 mm. The expansion ratio of the film was 2.0 and the processing temperature was adjusted from 200 to 210 ° C. The thickness of the produced film was 100 탆. The raw material components were formulated in the same amounts as the component C 42% of the present invention, the LDPE 43% of MI 1 g / min (190 캜, 2.16 kg) and the master batch of the oil remover . Initial haze and mechanical properties of the prepared film were measured, and the results are shown in Table 4 and FIG.

Comparative Example  One

Except that the commercial ZN Catalyst C4 LLDPE product (Grade 4220S, manufactured by Samsung Total, MI 1.2 g / min (190 ° C, 2.16 kg), Density 0.922 g / cm ³ , CDBI 23] was used instead of Component C in Example 1 A film was prepared by the same layer constitution and the same method as in Example 1. Initial haze and mechanical properties of the prepared films were measured. The results are shown in Table 4 and FIG.

Comparative Example  2

The same procedure as in Example 1 was carried out except that the commercial EVA product [MI 0.8 g / min (190 캜, 2.16 kg), VA content 4.2%, Mw / Mn 6.5] A film was prepared. Initial haze and mechanical properties of the prepared films were measured. The results are shown in Table 4 and FIG.

Comparative Example  3

Except that a commercial EVA product [MI 0.8 g / min (190 캜, 2.16 kg), VA content 4.2%, Mw / Mn 6.5] was used in place of component C in Example 2 A film was prepared. Initial haze and mechanical properties of the prepared films were measured. The results are shown in Table 4 and FIG.

Comparative Example  4

A film was prepared in the same manner as in Example 3, except that a commercial EVA product (MI 0.8 g / min (190 캜, 2.16 kg), VA content 4.2% Mw / Mn 6.5) . Initial haze and mechanical properties of the prepared film were measured, and the results are shown in Table 4 and FIG.

Table 4 below shows the physical properties of the films prepared in Examples and Comparative Examples.

Resin property measurement

(1) Melt flow Index

The melt index was measured at 190 占 폚 and 2.16 kg under the conditions of ASTM D1238.

(2) Density

Density was measured in the Density Gradient Column by ASTM D1505 method.

(3) Melt flow rate ratio (MFRR)

The MFRR was calculated as the ratio of the melt index (MI ₂₁ / MI ₂ ) under the load of 21.6 kg (MI ₂₁ ) and 2.16 kg (MI ₂ ) at 190 ° C.

(4) Molecular weight distribution

The molecular weight distribution was calculated as the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured from gel permeation chromatography (GPC).

(5) CDBI measurement

The comonomer distribution index, CDBI, was measured using a CRYSTAF instrument (CRYSTAF-TREF 300, Polymer Char).

Configuration Example 1 Example
2 Example 3 Comparative Example
One Comparative Example 2 Comparative Example 3 Comparative Example
4 Thickness ㎛ 60 70 100 60 60 70 100 Floor composition Outer layer One 3 fault One One 3 fault Middle layer 2 4 2 2 4 Inner layer 3 3 One 3 3 Layer component Outer layer LLDPE 20%
LDPE 65% LLDPE 50%
LDPE
35% Component C 42%
LDPE 43% LLDPE
20%
LDPE 65% LLDPE 50%
LDPE 35% Commercial EVA
42%
LDPE 43% Middle layer Component C
85% LD
85% Commercial LLD
85% Commercial EVA 85% LDPE
85% Inner layer Component C
60%
LDPE 25% Component C 85% Commercial LLD
60%
LD 25% Commercial EVA
60%
LDPE 25% Commercial EVA
85% Haze (%)
ASTM
D 1003 13.0
12.8
13.2
23.0 18.0
16.3
16.5
Seal
(kgf / cm2) MD ASTM
D 882 340 314 303 235 256 237 238 TD 322 311 297 246 260 233 230 Elongation (%) MD ASTM
D 882 127 380 101 120 114 370 82 TD 131 690 115 135 116 682 103 Tear
(kgf / cm) MD ASTM
D 1922 618 114 612 450 508 100 550 TD 685 101 720 380 680 105 700 Puncture
(N) ASTM
D 5748 67 62 85 32 59 56 71 Light transmittance 400 nm 62.2 54.8 43.5 44.9 54.8 48.9 34.7

In the case of Examples 1 and 2 in which a three-layer agricultural film was produced using a mixture of the ethylene copolymer and EVA copolymer of the present invention, Comparative Example 1 using commercial Ziegler Natta LLD or Comparative Example 2 using commercial EVA product It can be confirmed that it shows lower haze value and increased mechanical properties as compared with the case of the present invention. It can be seen that the haze value and the increased mechanical properties are the same in the case of Example 2 in which the component C is applied only to the inner layer of the three-layer film, as compared with Comparative Example 3.

Also in Example 3 in which a single layer film was produced, the same increased transparency and mechanical strength as compared with Comparative Example 4 are exhibited. Thus, it is possible to provide an agricultural film having high transparency and high rigidity, which can not be obtained from conventional EVA, by mixing an ethylene copolymer having high transparency and high rigidity characteristics obtained from a narrow molecular weight distribution and a uniform copolymer distribution and an EVA resin having a high VA content .

Claims (14)

In the polyethylene resin composition comprising the component A and the component B,
The component A is:
(1) Density: 0.900 to 0.925 g / cm < ³ >
(2) Melt flow rate (MI): 0.1 to 5 g / min (190 DEG C, 2.16 kg)
(3) Molecular weight distribution (Mw / Mn): 3 to 5 and
(4) Composition Distribution Breadth Index (CDBI) measured by CRYSTAF (Crystallization Analysis Fractionation): 85 to 95%
And an alpha-olefin copolymer having 2 to 20 carbon atoms,
The component B is:
(1) MI: 5 to 15 g / min (190 DEG C, 2.16 kg) and
(2) Molecular weight distribution (Mw / Mn): 3 to 5
And is an ethylene-vinyl acetate copolymer containing 20% to 35% of vinyl acetate,
The component A is contained in an amount of 60 to 90% by weight based on the total weight of the polyethylene resin composition,
The component B comprises 10 to 40% by weight based on the total weight of the polyethylene resin composition,
Wherein the polyethylene resin composition has an MI of 0.7 to 2.0 g / min (190 캜, 2.16 kg) and a molecular weight distribution (Mw / Mn) of 3 to 5.
The method according to claim 1,
Wherein the component A is a linear low density polyethylene resin prepared from a metallocene catalyst represented by the following formula 1:
[Chemical Formula 1]
(THI) ₂ RMQp
In Formula 1,
The two THI ligands are the same or different from each other and are tetrahydroindenyl or a derivative thereof substituted or unsubstituted by a substituent,
The substituent may be selected from the group consisting of phenyl (Ph), benzyl (Bz), naphthyl, indenyl, benzindenyl, methyl, ethyl, n- (i-Pr), n-butyl, t-butyl, trimethylsilicon group (Me ₃ Si), alkoxy, cycloalkyl and halogen And R is a structural bridge that gives steric rigidity between two THI ligands and is an alkylidene group, an alkylenyl group, a germanium group, a silicon group, a siloxane group, an alkylphosphine group, or an alkylene group containing 1 to 20 carbon atoms An amine group,
M is a transition metal of Group IIIB, Group IVB, Group VB or Group VIB,
Q is a hydrocarbyl group having from 1 to 20 carbon atoms or halogen,
p is 1 to 4;
The method according to claim 1,
The ethylene-vinyl acetate copolymer (B) is prepared by reacting an ethylene monomer and a vinyl acetate monomer with a peroxide initiator at a concentration of 50 to 1,000 ppm in a high-pressure reactor at a polymerization temperature of 200 to 260 ° C and a polymerization pressure of 2500 to 3000 kg / By weight based on the total weight of the polyethylene resin composition.
The method of claim 3,
The peroxide type initiator may be an alkylperoxy pivalate compound; And at least one member selected from the group consisting of alkylperoxyethylhexanoate-based compounds and dialkylperoxide-based compounds.
A resin composition for agricultural film, which comprises the polyethylene resin composition according to any one of claims 1 to 4.
6. The method of claim 5,
Wherein the polyethylene resin composition comprises 20 wt% to 100 wt% of the total weight of the resin composition for agricultural film.
6. The method of claim 5,
Wherein the resin composition for agricultural film further comprises, either alone or in combination with a long-acting agent, a mixture thereof.
6. The method of claim 5,
Wherein the resin composition for agricultural film further comprises a linear low density polyethylene resin and a low density polyethylene resin singly or a mixture thereof.
An agricultural film produced by the resin composition for agricultural film according to claim 5.
An inner layer made of the resin composition for agricultural film of claim 5;
Outer layer; Lt; RTI ID = 0.0 > 2 < / RTI >
11. The method of claim 10,
Wherein the outer layer comprises a linear low density polyethylene resin and a low density polyethylene resin singly or a mixture thereof.
An inner layer made of the resin composition for agricultural film of claim 5;
An intermediate layer made of the resin composition for agricultural film of claim 5; And
Outer layer; A three-layer agricultural film.
13. The method of claim 12,
Wherein the inner layer: middle layer: outer layer has a thickness ratio of 1: 1 to 3: 1 to 2.
13. The method of claim 12,
Wherein the outer layer comprises a linear low density polyethylene resin and a low density polyethylene resin singly or a mixture thereof.

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