KR20160077785A - Method for manufacturing polyethylene resin for protective film - Google Patents

Abstract

The present invention relates to a method for manufacturing low density polyethylene in a tubular reactor via high pressure radical polymerization. When manufactured into a protection film, the polyethylene resin manufactured thereby has little fisheye and high turbidity without generating air marks. The manufacturing method of a polyethylene resin has a polymerization pressure of 2500-3500 kg/cm^2, and comprises a molecular weight adjusting agent represented by a chemical formula, CH_2=CH-R. The amount of molecular weight adjusting agent injected to the reactor constitutes 1-5% of the polymerized polyethylene with respect to a formula, 100 X [molecular weight adjusting agent (kg/hr)]/[production speed of polyethylene (kg/hr)].

Description

TECHNICAL FIELD [0001] The present invention relates to a polyethylene resin for protective film,

More particularly, the present invention relates to a method for producing a polyethylene resin for a protective film, and more particularly to a polyethylene resin produced by a method of producing a low density polyethylene by a high pressure radical polymerization method in a tubular reactor, High degree of air mark does not occur.

The low-density polyethylene resin used for producing the protective film is mainly produced by high-pressure radical polymerization. Methods for producing an EVA resin by a high pressure radical polymerization method are roughly classified into a method of producing the EVA resin in a tubular reactor and a method of producing the EVA resin in an autoclave reactor, and basic manufacturing methods are well known.

The dry film photoresist is composed of three layers such as a base film, a photosensitive layer and a protective film for protecting the photosensitive resin layer. In general, the support film is formed of a poly (ethylene terephthalate) An ester film is used, and its thickness is about 15 탆. Such a support film serves as a support for the photosensitive resin layer during the production of the dry film photoresist, and facilitates handling of the photosensitive resin layer having adhesive force during exposure.

In the case of such a process for producing a dry film photoresist, since the photosensitive film is applied while the support film is being unwound, the solvent is removed by applying heat, the solvent is removed and cooled, and the protective film is laminated and wound in a roll form, One side of which is in contact with the photosensitive resin layer and the other side of which is in contact with the support film.

The protective film prevents damage to the resist during handling and protects the photosensitive resin layer from foreign substances such as dust. The protective film is laminated on the back surface of the photosensitive resin layer on which the support film is not formed, And a film having a thickness of about 20 mu m. Accordingly, when a defect due to fish eyes or the like is present in the protective film itself, defects may occur at the time of pattern formation, and therefore, the zeroing of the protective film is very important.

In recent years, there has been an increase in the use of a high-transparency support film for improving exposure efficiency and the like, and an air mark phenomenon occurs in which air is trapped between the support film and the protective film. And therefore improvement is required.

In the conventional Korean patent document KR20127028161, a method of blending low-density polyethylene with incompatible polypropylene, ionomer resin or the like on the surface layer to improve the surface roughness of the protective film has been proposed. However, such non- It is not preferable.

In order to solve the above problems,

The present invention also provides a method for producing a polyethylene resin which is excellent in providing a protective film for a dry film photoresist which has a small fish eye and a large surface roughness when it is produced as a protective film.

Another object of the present invention is to provide a resin for a protective film for a dry film photoresist which has a small fish eye and a large surface roughness.

Another object of the present invention is to provide a protective film for a dry film photoresist which has a small fish eye and a large surface roughness.

According to an aspect of the present invention,

1. A method of producing polyethylene by radical polymerization in a tubular reactor having two or more reactors, the method comprising the steps of: polymerizing at a polymerization pressure of 2500 to 3500 kg / cm ² ,

Wherein the molecular weight modifier is converted into the following formula (2), and is injected into the reactor at 1 to 5% of the polyethylene to be polymerized.

<Formula 1>

CH ₂ = CH-R

(R is a hydrocarbon compound having 1 to 18 carbon atoms)

<Formula 2>

100x [molecular weight regulator (kg / hr)] / [polyethylene production rate (kg / hr)]

The polyethylene resin produced by the process for producing a polyethylene resin according to the present invention exhibits an excellent effect in providing a protective film for a dry film photoresist which is low in fish eye and high in fog and does not cause an air mark when the film is produced as a protective film.

The polyethylene resin is also applicable as a protective film of a backlight unit optical sheet such as a prism sheet, a micro lens film, a light guide plate and a diffusion plate, or a polarizer protective film.

1 is a conceptual diagram showing an outline of one embodiment of the production facility of the present invention as a tubular reactor having four reactors.

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

1. A method of producing polyethylene by radical polymerization in a tubular reactor having two or more reactors, the method comprising the steps of: polymerizing at a polymerization pressure of 2500 to 3500 kg / cm ² ,

Wherein the molecular weight modifier is converted into the following formula (2), and is injected into the reactor at 1 to 5% of the polyethylene to be polymerized.

<Formula 1>

CH ₂ = CH-R

(R is a hydrocarbon compound having 1 to 18 carbon atoms)

<Formula 2>

100x [molecular weight regulator (kg / hr)] / [polyethylene production rate (kg / hr)]

In the method for producing a polyethylene resin of the present invention, the polymerization pressure is preferably 2500 to 3500 kg / cm ² . If the polymerization pressure is less than 2500 kg / cm ^2, the reaction efficiency of the initiator decreases and a large amount of initiator is consumed, and the byproducts of the initiator act as an impurity of the resin, thereby increasing fish eyes. In addition, at a pressure of less than 2500 kg / cm ² , generation of short-chain branches and long-chain branches becomes excessive, and the density of the film is lowered, and the strength of the film for holding the protective film is lowered. When the polymerization pressure exceeds 3500 kg / cm ² , generation of short-chain branches and long-chain branches is suppressed, and the film becomes too transparent.

In the method for producing a polyethylene resin of the present invention, the polymerization temperature is preferably 120 to 340 ° C in the reaction zone of each reactor. When the lowest temperature is less than 120 ° C, the initial reaction rate is too slow to lower the conversion to polyethylene, and an ultra high molecular weight chain is formed at the initial stage of the reaction to generate a gel. If the polymerization temperature exceeds 340 ° C, decomposition reaction of polyethylene may occur and reaction runaway may occur.

In the method for producing a polyethylene resin of the present invention, the number of the reactors is preferably two or more. The polyethylene produced in one reactor is not preferable because the molecular weight distribution is narrow and processability is poor, and long-chain branches and short-chain branches can not be formed at appropriate levels for increasing the degree of fogging. The maximum temperature of the first reactor and the second reactor is maintained at 340 ° C or lower, the maximum temperature of the first reactor is maintained at 280 ° C or higher, and the highest temperature of the second reactor is maintained at 290 ° C or higher . When the maximum temperature of the first reactor is less than 280 占 폚 or the maximum temperature of the second reactor is less than 290 占 폚, it is difficult to provide a protective film having a high surface roughness when applied to a protective film, .

In the method for producing a polyethylene resin according to the present invention, it is preferable to introduce the above-mentioned molecular weight modifier, and it is more preferable to add a molecular weight modifier selected from compounds having the following structure.

Examples of molecular weight regulators corresponding to the following formula 1 include propylene, 1-butene, isobutene, pentene and pentene isomers, heptene and heptene isomers, octene and octene isomers, Is an olefinic hydrocarbon. These hydrocarbon molecular structures may include linear, branched or cyclic structures. Compounds with more than 18 carbon atoms have a high boiling point and are slow to diffuse, making it difficult to effectively control molecular weight. The molecular structure of the molecular weight modifier may include a benzene structure, another double bond structure, an aldehyde, an ether, an ester, a carboxylic acid, an alcohol, a ketone, an amine and a sulfur.

<Formula 1>

CH ₂ = CH-R

(R is a hydrocarbon compound having 1 to 18 carbon atoms)

In the method for producing a polyethylene resin of the present invention, there is a method of controlling the molecular weight from the first reactor by injecting the above molecular weight adjusting agent into the front end of the compressor, and injecting the side stream of the present invention [Fig. 1] It is also possible to inject all of them into the first reactor and the second reactor.

The molecular weight modifier may be prepared by simultaneously introducing a molecular weight modifier selected from the compounds having the structure of Formula 1 of the present invention and a molecular weight modifier having another structure or by separately charging the same into the reactor.

The molecular weight regulator of the formula 1 proposed in the present invention is characterized in that it inhibits the formation of a polymer chain having a very large molecular weight and that a part of the molecular weight regulator is copolymerized with ethylene to form a short chain branch.

In addition, according to the present invention, the molecular weight regulator of Formula 1 produces polymer chain inhibition and short chain branching unlike conventional molecular weight regulators, thereby improving the degree of fogging, which is an object of the present invention, And it is possible to obtain an effect of reducing fish eyes.

In the past, only a small amount of a molecular weight modifier has been used by adding a molecular weight modifier for the purpose of controlling molecular weight.

In the method for producing a polyethylene resin of the present invention, the molecular weight modifier is converted into the following formula (2) and is injected into the reactor in an amount of 1 to 5% based on polyethylene to be polymerized.

<Formula 2>

100x [molecular weight regulator (kg / hr)] / [polyethylene production rate (kg / hr)]

In the method for producing a polyethylene resin according to the present invention, if the molecular weight modifier is injected at less than 1% of the polyethylene resin to be produced, such effect is not generated, and if it is more than 5%, the molecular weight is greatly reduced. Molding with a protective film results in a decrease in melt strength, which is not preferable.

In the method for producing a polyethylene resin according to the present invention, an organic peroxide initiator can be used. Examples of the organic peroxide initiator include tert-butyl peroxypivalate, di-n-butyl peroxydicarbonate, tert-butyl peroxyneodecanoate, Butyl peroxybenzoate, di-tert-butyl peroxide, tert-butyl cumyl peroxide, 1,3-bis (tert-butyl peroxy Amyl peroxide, isopropyl-benzene, di-tertiary-amyl peroxide, tertiary-amyl peroxide-2-ethyl hexanoate, tertiary amyl peroxypivalate, di-tertiary-hexyl peroxide, tertiary- Peroxy-2-ethylhexanoate and tertiary-hexyl peroxypivalate.

Although the above-mentioned organic peroxide initiator can be used as a single material, since the efficiency as an initiator varies depending on the temperature, two or more kinds of the peroxide initiator can be used for optimum efficiency in the whole temperature range of the reactor.

The above-mentioned organic peroxide initiator is preferably dissolved in a solvent and used. In the present invention, a usual solvent can be used, and the kind thereof is not particularly limited, but is preferably isoparaffin.

In the present invention, additives may be added to the extent that the nature of the invention is not impaired. These additives include hindered phenol antioxidants, phosphite antioxidants, lactone antioxidants, ethanol amine antioxidants, HALS antioxidants, UV stabilizers, UV absorbers, neutralizers, anti-blocking agents, slip agents, nucleating agents, pigments .

The polyethylene resin produced through the process for producing a polyethylene resin according to the present invention preferably has a melt index (ASTM D1238: 190 DEG C, 2.16 kg) of 1 to 5 g / 10 min. When the polyethylene resin is less than 1 g / 10 min, The viscosity of the molten resin discharged from the die during film forming is lowered and the thickness of the film due to the bubble instability of the film is lowered. The uniformity is lowered and the film is not easily formed.

In the present invention, the polyethylene resin preferably has a density of 0.921 to 0.930 g / cm ³ , more preferably 0.922 to 0.925 g / cm ³ .

When the density is less than 0.921 g / cm ³ , the rigidity is lowered and the film is not easily molded. When the density is more than 0.930 g / cm ³ , the flexibility is lowered and the adhesion of the dry film photoresist to the photosensitive resin layer is poor .

In the present invention, it is preferable that the number of fish eyes having a size of 100 mu m or more is 1 / g or less. If the ratio is more than 1 g / g as described above, it is not preferable since the cause of defects can be provided at the time of pattern formation.

The above-mentioned protective film preferably has a high degree of fogging, and is preferably 10% or more. When the degree of cloudiness is less than 10%, air may be trapped between the support film of the dry film photoresist and the protective film, and air marks may be generated.

In the present invention, the main part of the tubular polymerization reaction can be divided into a compressor, a reactor, a separator and an extruder as shown in Fig. The gas phase of the purified ethylene monomers (1) in the first compressor (2) the secondary compressor (5) and with a compression of about 200~300kg / cm ² pressure, the circulation gas (13) from the reactor at 2500 ~ 3500kg / cm ² , and polymerization initiator (14 to 17) is injected into the reactor. In this process, a molecular weight injector to control the molecular weight can be added (3, 4).

The molecular weight regulator is also referred to as a chain transfer agent, and examples thereof include ketones such as acetone and methyl ethyl ketone, aldehydes such as propionaldehyde, olefins such as propylene, isobutene, n-butene, hexene and octene, , Aromatic compounds such as toluene and xylene, alcohols such as ethanol, thioalcohols such as thiol, and hydrocarbons having no functional groups such as butane.

The reaction is controlled by maintaining the predetermined pressure, temperature (100 to 340 캜) and time condition in the reactor, and then the reaction product including polyethylene is separated into polymer and unreacted monomer in the high pressure separator 10 and the low pressure separator 11 The polyethylene separated through the low-pressure separator is cut into a pellet through an extruder and packaged as a product.

The monomer may be injected into the tubular reactor in one or more places, and FIG. 1 shows a method of injecting monomer into two places and polymerizing through a four-stage reactor.

The monomer is injected into the main stream 6, heated to an appropriate reaction temperature through the preheater 8, and then introduced into the first reactor 14 and thereafter to be polymerized. Separately, the compressed monomer is injected through the side stream 7, heated to an appropriate reaction temperature through the preheater 8, mixed with the monomer / polymer of the main stream, and then injected into the second stage reactor 15 Polymerization is carried out. Followed by polymerization in the third reactor (after 16) and the fourth reactor (after 17). Depending on the process, there is also a process in which there is no side stream 7, and it can be understood that the process operates on the same principle as the above process except that the monomer is not further supplied to the reactor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. It is not intended to limit the technical spirit and scope of the present invention.

Hereinafter, a method for producing a polyethylene resin according to the present invention, a polyethylene resin produced by the above-described method, and a protective film made of the above-mentioned polyethylene resin will be described with reference to the following examples.

&Lt; Examples 1 and 2 >

According to the process of the present invention [Figure 1] polyethylene was prepared in a tubular reactor having four reactors as illustrated. The ethylene monomer compressed through the compressor is preheated to the reactor initial temperature and then injected into a tubular reactor of four reaction zones. The monomer was introduced into the main stream entering the first reactor and the side stream directly entering the second reactor, which was introduced at a ratio of 55:45. Propylene was used as the molecular weight regulator, and the injection ratio of the main stream and the side stream was divided by 50:50. The amount of molecular weight regulator injected is as shown in [Table 2]. The types of organic peroxides used as reaction initiators and composition ratios of the respective components are shown in Table 1 below. Polymerization conditions such as pressure, temperature and molecular weight adjuster input amount in each reaction zone are shown in Table 2 below . The ratio of injected molecular weight modifier to injected polyethylene resin was calculated and shown in [Table 2]. The reaction initiator was prepared in the ratio shown in Table 1, and then injected through the tip injection port of each reaction zone to prepare a polyethylene resin. The amount of the reaction initiator introduced into each reactor was controlled in order to adjust the reaction temperature shown in Table 2, and the amount of the initiator added to the final produced polyethylene was 0.5 kg-initiator / ton-polyethylene to 1.5 kg-initiator / ton - It was adjusted within the polyethylene range.

Examples 1 and 2
Comparative Examples 1 and 2 Comparative Examples 3 and 4 Comparative Example 5 The first reactor TBPV 1.0 1.3 1.2 TBPO 3.0 3.8 1.6 TBPIN - - 2.2 DTBP 0.2 0.2 1.5 menstruum 23.4 29.7 45.8 The second reactor TBPV 2.7 3.0 - TBPO 8.3 8.9 0.6 TBPIN - - 1.7 DTBP 0.4 0.5 4.5 menstruum 64.4 69.6 44.8 The third reactor TBPIN - - 1.6 DTBP 0.4 0.5 4.5 menstruum 19.7 27.5 49.3 The fourth reactor TBPIN - - 0.6 DTBP 0.3 0.4 2.6 menstruum 12.8 19.6 45.0

Butylperoxy 2-ethylhexanoate, TBPIN is tert-butylperoxy 3,5,5-trimethylhexanoate, DTBP is a di-tertiary-butyl peroxypivalate, TBPO is tert- -Butyl peroxide, and the solvent is isoparaffin.)

division Example Comparative Example One 2 One 2 3 4 5 1st
Reactor Initial temperature (℃) 141 142 142 141 141 144 161 Maximum temperature (℃) 284 284 285 289 291 292 295 Second
Reactor Initial temperature (℃) 161 159 162 156 155 160 239 Maximum temperature (℃) 298 292 300 300 300 302 298 Third
Reactor Initial temperature (℃) 267 267 268 267 267 273 266 Maximum temperature (℃) 292 288 296 294 288 297 298 Fourth
Reactor Initial temperature (℃) 261 265 261 263 264 267 256 Maximum temperature (℃) 284 286 283 284 284 288 287 Molecular Weight
Modulator Propionaldehyde (kg / hr) 0 0 28 26 0 0 47 Propylene (kg / hr) 280 241 0 0 262 121 153 Reaction pressure (kg / cm ² ) 2550 2600 2650 2600 2250 2400 2620 Ethylene conversion (%) 26.5 26.5 26.2 27.7 26.8 27 27 Polyethylene
Production rate (kg / hr) 17100 16900 16600 17800 16900 17300 30900 Molecular weight regulator
ratio(%) 1.64 1.43 0.17 0.14 1.53 0.7 0.65

※ The ratio of molecular weight regulator was calculated by 100x [molecular weight regulator (kg / hr)] / [polyethylene production rate (kg / hr)].

&Lt; Comparative Examples 1 and 2 >

Was prepared in the same manner as in the methods described in Examples 1 and 2 described above, and propionaldehyde was used as the molecular weight regulator. The propionaldehyde was fed through the main stream to enter the first stage reaction zone and the feed rate is as shown in Table 2.

&Lt; Comparative Example 3 &

The reaction was carried out in the same manner as in Examples 1 and 2, except that the reaction pressure was 2250 kg / cm ² and the pressure was lower than the pressure suggested by the present invention. Propylene was used as the molecular weight regulator, and the ratio of the molecular weight regulator was 1.53%, which satisfied the conditions proposed by the present invention.

&Lt; Comparative Example 4 &

The reaction was carried out in the same manner as in Examples 1 and 2, except that the reaction pressure was 2400 kg / cm ² , and the pressure was lower than the pressure suggested by the present invention. Propylene was used as the molecular weight regulator, and the ratio of the molecular weight regulator was 0.7%, which did not satisfy the conditions proposed by the present invention.

&Lt; Comparative Example 5 &

The same procedure as in Examples 1 and 2 was carried out except that the ethylene monomer was introduced into the first reactor only through the main stream and not into the side stream. Both propionaldehyde and propylene were used as molecular weight regulators, and all were fed through the main stream. The ratio of the molecular weight regulator is 0.65%, which does not satisfy the conditions proposed by the present invention.

Preparation of Blown Protective Films

A protective film having a thickness of 19 μm and a width of 1.6 m was formed at 180 ° C. by using the polyethylene resin prepared in Examples 1 and 2 and Comparative Examples 1 to 5 described above and physical properties of the protective film were measured And the results are shown in Table 3 below.

(However, when molding a protective film, Sumitomo Heavy Industries' modern three-layer coextrusion blown film molding equipment was used and molded under the extrusion amount of 1.8 tons per 2.4 hours.)

In each of the examples, comparative examples and test examples, evaluation items of physical properties and measurement methods thereof are as follows.

(1) Melt Index (MI): Measured under conditions of 190 占 폚 and 2.16 kg according to ASTM D1238 conditions.

(2) Density: According to ASTM D1505, the specimens were boiled in boiling water at 100 ° C for 1 hour, cooled to room temperature, left in a constant temperature and humidity room for 24 hours, and then measured by density gradient method.

(3) Fish eye: After the number of gels was automatically counted using a film surface analyzer FSA-100 manufactured by OCS, the number of gels having a size of 100 탆 or more was counted, Divided by the weight of the film in the area of the area, and expressed in the number per g.

(4) Haze: haze of the produced film was measured using a Toyoseki Gard-II haze meter according to ASTD D1003 conditions.

(5) Air mark: A photosensitive resin was applied using a polyethylene terephthalate (PET) film having a haze of 0.1% as a support, and a protective film was laminated to form a roll. After 30 days at room temperature, Were assessed visually.

division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Melt Index (g / 10 min) 2.0 3.1 2.0 3.2 3.6 1.1 2.0 Density (g / cm ³⁾ 0.923 0.924 0.927 0.928 0.922 0.924 0.925 Fish eye (ea / g) 0.9 0.9 0.9 0.8 3.7 1.5 0.8 Cloudiness (%) 10.5 10.5 8.1 7.7 9.7 19.1 7.5 Air mark Not occurring Not occurring Occur Occur Occur Not occurring Occur

&Lt; Example 1, Comparative Example 1, Example 2 and Comparative Example 2 >

As shown in Table 3, in Examples 1 and 2 using propylene as the molecular weight modifier, the degree of cloudiness was high, no air mark was generated, and fish eyes were good at one or less, but propionaldehyde was used In Comparative Example 1 and Comparative Example 2, the degree of fogging is low and an air mark is generated.

&Lt; Example 2 and Comparative Example 3 >

As shown in Table 3, Comparative Example 3 obtained in Example 2, which was polymerized at a polymerization pressure of 2500 kg / cm ² or more, showed good cloudiness, air mark and fish eye, but polymerized at 2250 kg / cm ² , It was not suitable as a protective film, and an air mark was also generated.

&Lt; Example 1 and Comparative Example 4 >

[Table 3] conduct a polymerization at a polymerization pressure of 2500kg / cm ² or more as described, the chain transfer agent ratio presented more than 1% in Example 1, haze, the air mark, fish eye good one both a polymerization pressure of 2430kg / cm ² , And Comparative Example 4 in which the molecular weight modifier ratio is 0.7% is not suitable for a protective film because of an increase in fish eyes.

&Lt; Example 1 and Comparative Example 5 >

As shown in Table 3, in Example 1 in which the proportion of the molecular weight regulator was more than 1%, Comparative Example 5 in which the degree of cloudiness, the air mark, and the fish eye were both good, while the ratio of the molecular weight regulator was 0.65% Is generated.

Preparation of casting protective film (Examples 3 to 6 and Comparative Example 6)

Layer co-extrusion protective film having a thickness of 20 占 퐉 at a temperature of 170 占 폚 by using the polyethylene resin prepared in Example 1 and Comparative Example 1 described above. The thickness ratio of the outer skin layer, the core layer, and the inner skin layer was maintained at 25:50:25. The physical properties of the polyethylene resin used in each layer and the protective film were measured and shown in Table 4 below. Protective Film Molding Collin 's 3 - layer coextrusion casting film molding equipment was used.

Film structure and properties Example 3 Example 4 Example 5 Example 6 Comparative Example 6 3 layer film layer composition Outer skin layer resin Example 1 Example 1 Comparative Example 1 Comparative Example 1 Comparative Example 1 core layer resin Example 1 Comparative Example 1 Example 1 Comparative Example 1 Comparative Example 1 Inner skin layer resin Example 1 Example 1 Comparative Example 1 Example 1 Comparative Example 1 Cloudiness also% 15 14.4 11.7 11.4 8.3 Air mark Not occurring Not occurring Not occurring Not occurring Occur

&Lt; Examples 3 to 6 and Comparative Example 6 >

As shown in Table 4, when the polyethylene resin produced by the method of the present invention was used in one layer or more of the three-layer co-extruded film, the fogging was excellent and no air mark was generated, It can be seen that it is suitable.

Accordingly, when a protective film for a dry film photoresist is used, which has less fish eyes, has high fogging, and does not generate an air mark, by using the polyethylene resin produced by the method for producing a polyethylene resin according to the present invention, And exhibits excellent effects in providing.

The above-mentioned polyethylene resin can also be applied as a protective film of a backlight unit optical sheet such as a prism sheet, a micro lens film, a light guide plate and a diffusion plate, or a polarizer protective film.

1: ethylene injection
2: Booster Primary compressor
3: Molecular weight control agent injection (main stream direction)
4: Molecular weight control agent injection (side stream direction)
5: Hyper Compressor
6: Primary stream
7: Side stream
8: Shearing heater
9: rear end cooler
10: High pressure separator
11: Low pressure separator
12: Low pressure circulator
13: High-pressure circulator
14: First reactor Reaction initiator inlet
15: Second reactor Reaction initiator inlet
16: Third reactor Reaction initiator inlet
17: Fourth reactor Reaction initiator inlet

Claims (12)

1. A method of producing polyethylene by radical polymerization in a tubular reactor having two or more reactors, the method comprising the steps of: polymerizing at a polymerization pressure of 2500 to 3500 kg / cm ² ,
Wherein the molecular weight modifier is converted into the following formula 2 and injected into the reactor at 1 to 5% of the polyethylene to be polymerized.

<Formula 1>
CH ₂ = CH-R
(R is a hydrocarbon compound having 1 to 18 carbon atoms)

<Formula 2>
100x [molecular weight regulator (kg / hr)] / [polyethylene production rate (kg / hr)]
The method according to claim 1,
Wherein the polymerization temperature in the tubular reactor is 100 to 340 ° C, the maximum temperature of the first reactor is 280 ° C or more, and the maximum temperature of the second reactor is 290 ° C or more.
The method according to claim 1,
Wherein the molecular weight modifier is selected from the group consisting of propylene, 1-butene, isobutene, pentene, pentene isomers, heptene, heptene isomers, octene, octene isomers and olefinic hydrocarbons having a carbon number of 18 or less. By weight or more based on the total weight of the polyethylene resin.
The method according to claim 1,
The method for producing a polyethylene resin for a protective film according to claim 1, further comprising a molecular weight modifier not corresponding to the formula (1).
The method according to claim 1,
The method for producing a polyethylene resin for a protective film according to claim 1, further comprising an organic peroxide initiator as an initiator. 6. The method of claim 5,
The organic peroxide initiator may be selected from the group consisting of tert-butyl peroxypivalate, di-n-butyl peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-butyl peroxy 2-ethylhexanoate, Butyl peroxybenzoate, di-tert-butyl peroxide, tert-butyl cumyl peroxide, 1,3-bis (tert-butylperoxyisopropyl) benzene, ditertiary- Hexylperoxy-2-ethylhexanoate, tertiary-amyl peroxypivalate, di-tertiary-hexyl peroxide, tertiary-hexylperoxy-2-ethylhexanoate, tertiary- Wherein the protective film is at least one selected from the group consisting of polyvinyl alcohol and hydroxypropyl cellulose.
A polyethylene resin for a protective film, which is produced by the method for producing a polyethylene resin for a protective film according to any one of claims 1 to 6.
8. The method of claim 7,
Wherein the polyethylene resin has a melt index of 1 to 5 g / 10 min at 190 占 폚 and 2.16 kg of ASTM D1238.
8. The method of claim 7,
Wherein the polyethylene resin has a density of 0.921 to 0.930 g / cm &lt; ³ &gt;.
A backlight unit such as a prism sheet made of the polyethylene resin of claim 7, a micro lens film, a light guide plate, a diffusion plate, an optical sheet protective film and a polarizer protective film.
A protective film for a dry film photoresist, which is made of the polyethylene resin of claim 7.
12. The method of claim 11,
Wherein the protective film is composed of a multilayer structure and is made of at least one layer of a polyethylene resin of the multilayer structure.

Images