JP2017119816A - Method for producing polyethylene or polyethylene-vinyl acetate copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve processing productivity while maintaining high quality by suppressing the increase in fish eyes due to deterioration during high-temperature extrusion processing.SOLUTION: There is provided a method for producing a low-density polyethylene or a polyethylene-vinyl acetate copolymer by a high pressure radical polymerization method, wherein t-amyl type organic peroxides having a second half-life temperature of 230°C or less are used as radical initiators in a reactor including a reaction temperature region of 230°C or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing polyethylene or polyethylene vinyl acetate copolymer, and more particularly, to a method for producing low density polyethylene or polyethylene vinyl acetate copolymer by high-pressure radical polymerization in a tubular reactor. The produced polyethylene or polyethylene vinyl acetate copolymer resin can suppress the formation of fish eyes when processed at a high temperature, maintain high-grade appearance quality, and increase the processing productivity.

  Polyethylene and polyethylene vinyl acetate copolymer resins produced by the high-pressure radical polymerization method have excellent transparency and good processability, and are widely used in applications such as films, sheets, electric wires, foams, and injection molded products. is there. The high-pressure radical polymerization method is roughly divided into two types, a method for producing with a tubular reactor and a method for producing with an autoclave reactor, and the basic production methods are widely known.

  Polyethylene and polyethylene vinyl acetate copolymer resins produced by high-pressure polymerization methods undergo a cross-linking reaction as a side reaction during the radical polymerization process, which may cause polymer defects called gels or fish eyes to harm the appearance of the product. it can. In particular, it is most important to eliminate fish eyes in applications such as protective films for electronic products that require a high degree of precision, thin film extrusion coating to a thickness of several micrometers, high-voltage electric wires, solar sealing materials, etc. Required characteristics. On the other hand, polyethylene and polyethylene vinyl acetate copolymer resins are used in the process of extruding at high temperature to process into film, sheet, electric wire, etc. in addition to the path where fish eyes are generated during the polymerization production process. ), Radicals are generated, and the fisheye is increased by the crosslinking reaction. In general, the fisheye problem is much more severe when processing at the same temperature condition than when processing at a small scale in the laboratory, but at the same temperature condition, but productivity is low at commercial processing processes. This is because it is a very important factor and it is desired to process with increased productivity. In such a case, the generation of heat and shear becomes much more serious and the generation of fish eyes becomes even more severe. The most common way to prevent the occurrence of fisheye in commercial processing is to reduce the processing temperature and decrease the processing speed to reduce heat and shear, but this increases the productivity of the product. There is a problem of lowering. Resin processing with a lot of fish eyes is problematic even in continuous production. As the continuous processing time increases, the generation of fish eyes due to disassembly and crosslinking inside the extruder becomes more serious, and after processing for a certain period of time, the equipment must be cleaned and the equipment must be cleaned. Product loss occurs.

  Japanese Patent No. 4426221 discloses a technique for reducing fish eyes by washing a heat exchanger and applying a precision filter of 53 microns or less to the extruder. Although this method is useful for temporary fish eye reduction, the fish eye in the polymer form filtered by the filter is retained and continuously decomposed and cross-linked under the influence of heat. Therefore, there is a problem that the equipment must be stopped for regular cleaning, and the productivity cannot be increased due to the extrusion load increased by the filter.

  Japanese Patent Application Laid-Open No. 2003-231759 discloses a technique for reducing fish eyes by introducing a polymerization inhibitor into a reactor to suppress a polymerization-crosslinking reaction. However, this method has a side effect of directly reacting with an organic peroxide added as an initiator to produce a colored side reaction product, and a phenomenon that the molded product is yellowed at the time of extrusion processing, particularly at high temperature processing occurs. There's a problem. In addition, there is a problem that the concentration of the organic peroxide is drastically reduced during the polymerization reaction and the polymerization productivity is lowered.

Japanese Patent No. 4426221 JP 2003-231759 A

  The object of the present invention is to produce polyethylene or polyethylene vinyl acetate copolymer that can increase processing productivity while maintaining high quality by suppressing increase of fish eye due to deterioration during high temperature extrusion processing It is to provide a method.

  To achieve the above object, the present invention provides a method for producing a low density polyethylene or polyethylene vinyl acetate copolymer by a high pressure radical polymerization method, wherein the reactor includes a reaction temperature interval of 230 ° C. or less as a radical initiator. Provided is a method for producing a polyethylene or polyethylene vinyl acetate copolymer, wherein a t-amyl organic peroxide having a half-life temperature of 1 second or less is 230 ° C. or less.

  When the polyethylene or polyethylene vinyl acetate copolymer produced according to the present invention is processed at a high temperature, an increase in fish eye due to deterioration of the resin is suppressed and a small fish eye state can be maintained. Therefore, it is not necessary to process at a low temperature or to reduce the production speed in order to ensure the quality of the fish eye, and it is possible to maintain the quality without performing equipment cleaning for a long time. Therefore, there is an effect that processing productivity is increased as a result. The polyethylene and polyethylene vinyl acetate copolymers are particularly suitable for applications such as protective films for electronic and optical products where fish eye quality is particularly important, thin film extrusion coating, high voltage wires, solar module sealing materials and the like.

It is the figure which showed typically the tubular reactor used in one Example of this invention. For the polyethylene vinyl acetate copolymer produced in Example 2 and Comparative Example 3, when the film was processed at the indicated processing temperature, the change in fish eye according to the processing time was measured using an AFC-100 fish eye automatic counter. It was measured using.

  Hereinafter, the present invention will be described in more detail. However, this is for easy understanding and understanding of the present invention, and does not limit the scope of the present invention.

  A production method according to an embodiment of the present invention is a method for producing a low density polyethylene or polyethylene vinyl acetate copolymer by a high-pressure radical polymerization method, and a reactor including a reaction temperature interval of 230 ° C. or less as a radical initiator. A t-amyl organic peroxide having a one-second half-life temperature of 230 ° C. or lower is used.

According to an embodiment of the present invention, the high-pressure radical polymerization reaction is preferably performed under conditions of a reaction temperature of 130 to 340 ° C. and a reaction pressure of 2200 to 3500 kg / cm ² .

If the lowest point temperature is less than 130 ° C., the initial reaction rate is too slow, the conversion rate to polyethylene is reduced, and an ultra high molecular weight chain is formed at the initial stage of the reaction to generate a gel. When the polymerization temperature exceeds 340 ° C., a decomposition reaction of polyethylene occurs and reaction runaway may occur. Further, it is preferable polymerization pressure is 2200~3500kg / cm ^2, the polymerization pressure is exhausted many initiators reaction efficiency is lowered initiator is less than 2200 kg / cm ^2, by-products of the initiator It acts as an impurity of the resin and causes fish eyes to increase. On the other hand, when the pressure is less than 2200 kg / cm ² , short chain branching and long chain branching are excessively generated to reduce the density of the film, which is undesirable because the film strength is lowered. The higher the polymerization pressure, the better. However, if it exceeds 3500 kg / cm ² , the production of short chain branches and long chain branches is suppressed, the processing load increases during film processing, and the film becomes too transparent. .

  According to a desirable feature of the present invention, it is preferable to use one or more selected from t-amyl organic peroxides as radical initiators.

  In particular, a reactor having a reaction temperature zone in which the reaction temperature is 230 ° C. or lower is preferably selected from t-amyl organic peroxides having a 1-second half-life temperature of 230 ° C. or lower as a radical initiator. It is preferable to use one or more kinds. The half-life temperature data varies depending on the reaction environment such as pressure and solvent, and is usually provided by an organic peroxide manufacturer.

  The reaction temperature section means a temperature section existing inside the reactor. Specifically, if a radical initiator is injected into a reactor with a monomer, the reaction temperature rises due to the heat of polymerization, so there are low and high temperature zones inside the reactor. In such a temperature zone, a reactor having a reaction temperature zone with a reaction temperature of 230 ° C. or lower has a t-amyl organic peroxide as a radical initiator, in particular, a 1 second half-life temperature of 230 ° C. or lower. -It is preferred to use amyl organic peroxides.

  According to one embodiment of the present invention, t-amyl peroxy-2 ethylhexanoate, t-amyl peroxypivalate is used as a t-amyl organic peroxide having a one-second half-life temperature of 230 ° C. or less. , T-amyl peroxyneodecanoate, t-amyl peroxyacetate, t-amyl peroxyisopropyl carbonate, t-amyl peroxy-3,5,5-triethylhexanoate and the like are used.

  According to a desirable feature of the present invention, an organic peroxide initiator used in the production of polyethylene or polyethylene vinyl acetate copolymer without impairing the effects of the present invention and like a t-amyl organic peroxide. Can be used further. Examples thereof include t-butyl peroxypivalate, di-normal-butyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxy Acetate, t-butyl peroxybenzoate, di-t-butyl peroxide, t-butyl cumyl peroxide, 1,3-bis (t-butylperoxyisopropyl) benzene, di-t-amyl peroxide, di- There are t-hexyl peroxide, t-hexyl peroxy-2-ethylhexanoate, t-hexyl peroxypivalate, etc., and one or more selected from either one can be used.

  The t-amyl organic peroxide is preferably contained at least 10% by weight of the total content of the reaction initiator. This is because if it is less than 10% by weight, the crosslinking reaction in the polymerization stage cannot be sufficiently suppressed, and the formation of a polymer gel increases, thereby increasing the production of fish eyes and lowering the appearance quality. is there.

  The above-mentioned organic peroxide can be used by selecting only one kind of substance, but since the efficiency as an initiator varies depending on the temperature, when the reaction temperature range is wide, two kinds are used for optimum efficiency. The above can be mixed and used.

  In addition, the above-described organic peroxide can be diluted with a solvent for efficient operation of the initiator injection pump, and in the present invention, a normal solvent is used, and the type thereof is particularly limited. However, isoparaffin is preferred.

  In the production method of the present invention, a commonly used molecular weight regulator can be added, and the type of compound is not limited. Examples of normal molecular weight regulators are olefinic hydrocarbons such as acetone, propionaldehyde, methyl ethyl ketone, propylene, 1-butene, isobutene, pentene, hexene, heptene, octene. These hydrocarbon molecular structures can include linear, branched or ring structures. The molecular structure of the molecular weight regulator may include a benzene structure, and other double bond structures, such as aldehyde, ether, ester, carboxylic acid, alcohol, ketone, amine, and sulfur.

  Additives can be added to the polyethylene and polyethylene vinyl acetate copolymer of the present invention within a range not impairing the essence of the invention. Such additives include hindered phenolic antioxidants, phosphate antioxidants, lactone antioxidants, ethanolamine antioxidants, HALS antioxidants, UV stabilizers, UV absorbers, neutralization Agents, anti-blocking agents, slip agents, nucleating agents, pigments and the like.

  Hereinafter, a method for producing a polyethylene or polyethylene vinyl acetate copolymer as one embodiment of the present invention will be described in detail with reference to FIG.

  According to one embodiment of the present invention, the main part of the tubular polymerization reaction is divided into a compressor, a reactor, a separator and an extruder as shown in FIG.

The purified ethylene monomer or a mixed gas 1 of ethylene monomer and vinyl acetate monomer 1 is compressed to about 200 to 300 kg / cm ² by the primary compressor 2, and 2 in the secondary compressor 5 together with the circulating gas 13 from the reactor. After compression to 200-3,500 kg / cm < ² >, reaction initiators 14-17 are injected into the reactor and polymerized.

  In this process, a molecular weight injecting agent for adjusting the molecular weight can be further added (3, 4). The molecular weight regulator is also called a chain transfer agent, and its type and performance are described in detail in Mortimer's literature (J. Polymer Science A-1, Vol8, Year 1970, page 1513). For example, ketones such as acetone and methyl ethyl ketone, aldehydes such as propionaldehyde, olefins such as propylene, isobutene, normal butene, hexene and octene, aromatic compounds such as benzene, toluene and xylene, methanol and ethanol Alcohols such as thiol, thioalcohols such as thiol, and hydrocarbons having no functional group such as butane.

After the reaction is controlled by maintaining a predetermined pressure of 2200-3500 kg / cm ² , a temperature of 130-340 ° C. and a residence time in the reactor, the reaction product containing polyethylene is separated in the high pressure separator 10 and the low pressure separator 11. The polyethylene separated from the polymer and unreacted monomer and separated through a low-pressure separator is cut into pellets through an extruder and packaged as a product.

  There may be one or more locations for injecting monomer in the tubular reactor, and FIG. 1 shows a system in which the monomer is injected at two locations and polymerized through a four-stage reactor. After injecting the monomer into the main stream 6 and raising the temperature to an appropriate reaction temperature through the free heater 8, the monomer enters the first reactor (after 14) and polymerizes. However, according to the present invention, any one or more reactors are possible, preferably two or more reactors.

  Separately, the compressed monomer is injected through the side stream 7, heated to an appropriate reaction temperature through the free heater 8, mixed with the main stream monomer / polymer, and then injected into the second reactor (after 15). To polymerize.

  Next, polymerization is performed in the third reactor (after 16) and the fourth reactor (after 17).

  It will be appreciated that some processes may have no sidestream 7 and operate on the same principles as the previous process except that no further monomer is fed into the reactor.

  At this time, if any one of the first to fourth reactors includes a reactor including a reaction temperature zone with a reaction temperature of 230 ° C. or lower, the radical initiator according to the present invention is included in the reactor. That is, the polymerization is carried out by injecting a t-amyl organic peroxide having a half-life temperature of 1 sec. When manufactured by such a method, it is possible to provide a high-quality polyethylene or polyethylene vinyl acetate copolymer with low fish eye despite being manufactured by high-temperature extrusion processing, so that it is suitable for products in which fish eye quality is important. Can be used.

  Hereinafter, preferred embodiments of the present invention and physical properties of each component will be described in detail. This is to explain in detail to the extent that a person having ordinary knowledge in the technical field of the present invention can easily carry out the invention. This does not mean that the technical idea and category of the present invention are limited thereby.

<Example 1>
As shown in FIG. 1, polyethylene resin was produced in a tubular reactor having four reactors. The ethylene monomer and vinyl acetate monomer compressed through the compressor were preheated to the reactor initial temperature and then injected into a tubular reactor consisting of four reaction zones.

  The monomer was charged separately into the main stream entering the first reactor and the side stream directly entering the second reactor, and was charged at a ratio of 55:45. Propionaldehyde or propylene was used as the molecular weight regulator, and the injection ratio of main stream and side stream was divided into 50:50. The injection amount of the molecular weight regulator is as shown in Table 2. The type of organic peroxide used as the reaction initiator and the composition ratio of each component are shown in Table 1 below, and the polymerization conditions such as pressure, temperature, and molecular weight regulator input in the reaction region of each stage are shown in Table 2 below. Indicated.

  The reaction initiator was manufactured at a ratio as shown in Table 1 and then charged through the front inlet of each stage of the reaction region to manufacture a polyethylene resin. The amount of reaction initiator introduced into each reactor is adjusted to match the reaction temperature shown in Table 2, and the amount of total reaction initiator added to the final reaction product is 0.5 kg (initiator). ) / Ton (reactant) to 1.5 kg (initiator) / ton (reactant).

  In the first and second reactors where the reaction temperature is lower than 230 ° C., t-amylperoxy-2-ethylhexanoate (PO-5) having a half-life temperature of 185 ° C. for 1 second is t- A mixture of butyl organic peroxide and a mixture as shown in Table 1 was used.

In Table 1, PO-1 is t-butyl peroxypivalate, PO-2 is t-butylperoxy 2-ethylhexanoate, PO-3 is t-butylperoxy 3,5,5-trimethyl. Hexanoate, PO-4 is di-t-butyl peroxide, PO-5 is t-amylperoxy 2-ethylhexanoate, and PO-6 is di-t-amyl peroxide.

<Example 2>
An ethylene vinyl acetate copolymer was produced by mixing the ethylene and vinyl acetate monomers at the ratios shown in Table 2 in the same manner as in Example 1 described above. In the first and second reactors where the reaction temperature is lower than 230 ° C, t-amyl peroxy-2-ethylhexanoate with a half-life temperature of 185 ° C for 1 second is t-butyl organic peroxidation. The mixture was used together with the product at the ratio shown in Table 1. At the stage of pelletizing the product, 400 mg of SOGNNOX-1076 (octadecyl 3- (3,5-di-t-butyl-4-hydrophenyl) propionate) was formulated as an antioxidant.

<Example 3>
An ethylene vinyl acetate copolymer was produced by mixing the ethylene and vinyl acetate monomers at the ratios shown in Table 2 in the same manner as in Example 1 described above. In the first and second reactors where the reaction temperature is lower than 230 ° C, t-amyl peroxy-2-ethylhexanoate with a half-life temperature of 185 ° C for 1 second is t-butyl organic peroxidation. The mixture was used together with the product at the ratio shown in Table 1. At the stage of pelletizing the product, 1200 ppm of SOGNNOX-1076 (octadecyl 3- (3,5-di-t-butyl-4-hydrophenyl) propionate) was formulated and manufactured as an antioxidant.

<Comparative Example 1>
Production was carried out in the same manner as in Example 1 described above, and as shown in Table 1, polyethylene was produced using only t-butyl organic peroxide without using t-amyl organic peroxide.

<Comparative example 2>
Di-t-amyl peroxide produced in the same manner as in Example 1 and having a half-life temperature of 251 ° C. for 1 second from the first reactor to the fourth reactor in the ratio as shown in Table 1. Polyethylene was produced using a mixture.

<Comparative Example 3>
An ethylene vinyl acetate copolymer was produced by mixing the ethylene and vinyl acetate monomers at the ratios shown in Table 2 in the same manner as in Example 1 described above. As shown in Table 1, the reaction initiator was prepared using only the t-butyl organic peroxide without using the t-amyl organic peroxide. At the stage of pelletizing the product, 400 mg of SOGNNOX-1076 (octadecyl 3- (3,5-di-t-butyl-4-hydrophenyl) propionate) was formulated as an antioxidant.

<Comparative example 4>
An ethylene vinyl acetate copolymer was produced by mixing the ethylene and vinyl acetate monomers at the ratios shown in Table 2 in the same manner as in Example 1 described above. As shown in Table 1, the reaction initiator was prepared using only the t-butyl organic peroxide without using the t-amyl organic peroxide. At the stage of pelletizing the product, 1200 ppm of SOGNNOX-1076 (octadecyl 3- (3,5-di-t-butyl-4-hydrophenyl) propionate) was formulated and manufactured as an antioxidant.

<Experimental example>
The various physical properties of the polyethylene resin and the polyethylene vinyl acetate copolymer prepared through Examples 1 to 3 and Comparative Examples 1 to 4 were measured, and the results are shown in Table 3 below. In each example and comparative example, the evaluation items of various physical properties and the measuring method thereof are as follows.

(1) Melt index (Melt Index, MI)
: Measured under conditions of 190 ° C. and 2.16 kg according to ASTM D1238 conditions.

(2) Density of polyethylene: The specimen was boiled in 100 ° C. boiling water for 1 hour according to ASTM D1505 conditions, then cooled to room temperature and left in a constant temperature and humidity chamber for 24 hours, and then measured by a density gradient tube method.

(3) Vinyl acetate content in ethylene vinyl acetate copolymer: The vinyl acetate content in the copolymer was measured by the FT-IR method.

(4) Fish eye according to processing temperature: Polyethylene or ethylene vinyl acetate copolymer resin was subjected to film forming evaluation at two or more temperatures in order to evaluate the increase in fish eye at high temperature. The film was manufactured with OCS PE30-CR9 casting film molding machine at a thickness of 50 μm, and the size and number of gels were automatically counted using OCS Film surface analyzer FSA-100. The number of gels was counted and divided into the weight of the film of the measured area, and displayed as the number per g. The processing temperature when forming the film was shown based on the extruder cylinder temperature and the die temperature.

<Experimental Results of Example 1, Comparative Example 1, and Comparative Example 2>
As shown in Table 3, the number of fish eyes measured at a low temperature of 180 ° C. was 0.19 / g, 0.22 / g, and 0.25 for Example 1 and Comparative Examples 1 and 2, respectively. The number difference is similar to within 30%, and all are good at 1 piece / g or less.

  The result of processing at 210 ° C. is that t-amylperoxy-2-ethylhexanoate with a 1 second half-life temperature of 185 ° C. in the first and second reactors where the reaction temperature is lower than 230 ° C. In Example 1, which used A, increased 1.8 times to 0.35 / g, but the quality is still good at 1 / g or less.

  On the other hand, in Comparative Example 2 produced only with the t-butyl organic peroxide, it was greatly increased by 7.7 times compared with the case of processing at 180 ° C. to 1.7 pieces / g.

  As a result of processing at 210 ° C. in Comparative Example 2 using di-t-amyl peroxide, in which t-amyl organic peroxide is used, but the half-life of 1 second is out of the range presented in the present invention. The number increased to 5.6 times as 4 / g.

  From the above comparison, when the polyethylene produced by the method of the present invention is processed at a high temperature, it has a fisheye suppressing effect that is 3 to 4 times that of the comparative example.

<Experimental results of Example 2 and Comparative Example 3>
As shown in Table 3, the number of fish eyes measured at a low temperature of 180 ° C. is similar to that of Example 2 and Comparative Example 3 of 0.34 / g and 0.32 / g, respectively. However, as a result of processing at 200 ° C., in Example 2, it increased slightly to 0.76 pieces / g, but in Comparative Example 3, it increased greatly to 1.6 pieces / g.

  As a result of processing at 220 ° C., it was 1.7 pieces / g in Example 2, but was further greatly increased to 15.3 pieces in Comparative Example 3. At a processing temperature of 200 ° C., the fish eye suppression effect according to the present invention was 2.8 times, and at a processing temperature of 220 ° C., a nine times fish eye suppression effect was exhibited by the present invention.

  FIG. 2 is a result of automatically counting the fish eye change according to the film processing time of Example 2 and Comparative Example 3 using OCS Film surface analyzer FSA-100.

  As shown in FIG. 2, in Example 2, the film was processed at a stable level even at a processing temperature of 220 ° C., but in Comparative Example 3, the fish eye continuously increased with time for a long time. It can be seen that the quality cannot be maintained.

<Experimental Results of Example 3 and Comparative Example 4>
As shown in Table 3, the number of fish eyes measured at a low temperature of 180 ° C. is similar to 0.67 / g and 0.68 / g in Example 3 and Comparative Example 4, respectively. However, the result of processing at 210 ° C. was only a small increase to 1.4 pieces in Example 3, but was greatly increased to 2.6 pieces / g in Comparative Example 3. In Example 3 manufactured by the method of the present invention, the fish eye suppression effect is twice that of Comparative Example 4.

  Therefore, the polyethylene and polyethylene vinyl acetate copolymer produced by the production method according to the present invention has an excellent effect in providing a film with less fish eyes by suppressing the formation of fish eyes during extrusion at a high temperature. Since it does not have to be processed at a low temperature to produce a high-quality film with few fish eyes, it has the excellent effect of increasing the processing temperature of high-quality products, reducing the equipment load, and increasing the productivity. is there.

Claims (7)

In the method for producing low density polyethylene or polyethylene vinyl acetate copolymer by high pressure radical polymerization method,
A reactor including a reaction temperature interval of 230 ° C. or less,
A method for producing a polyethylene or polyethylene vinyl acetate copolymer, comprising using a t-amyl organic peroxide having a half-life temperature of 230 ° C. or less as a radical initiator. ^2. The method for producing a polyethylene or polyethylene vinyl acetate copolymer according to claim 1, wherein the high-pressure radical polymerization is performed under conditions of a reaction temperature of 130 to 340 ° C. and a reaction pressure of 2200 to 3500 kg / cm ² .   The t-amyl organic peroxide includes t-amyl peroxy-2 ethylhexanoate, t-amyl peroxypivalate, t-amyl peroxyneodecanoate, t-amyl peroxyacetate, t- 2. The polyethylene or polyethylene vinyl acetate copolymer according to claim 1, wherein at least one selected from the group consisting of amyl peroxyisopropyl carbonate and t-amyl peroxy-3,5,5-triethylhexanoate Manufacturing method of coalescence.   The radical initiator includes t-butyl peroxypivalate, di-normal-butyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxy 2-ethylhexanoate, t-butyl peroxy Oxyacetate, t-butyl peroxybenzoate, di-t-butyl peroxide, t-butylcumyl peroxide, 1,3-bis (t-butylperoxyisopropyl) benzene, di-t-amyl peroxide, di 2. The method according to claim 1, further comprising at least one selected from the group consisting of -t-hexyl peroxide, t-hexyl peroxy-2-ethylhexanoate, and t-hexyl peroxypivalate. A method for producing a polyethylene or polyethylene vinyl acetate copolymer.   The method for producing a polyethylene or polyethylene vinyl acetate copolymer according to claim 1, wherein the radical initiator is used after being diluted with isoparaffin.   The method for producing a polyethylene or polyethylene vinyl acetate copolymer according to claim 1, wherein the reactor is a tubular reactor.   The method for producing a polyethylene or polyethylene vinyl acetate copolymer according to claim 6, wherein the reactor comprises one or more reactors.