CN105802033B - A kind of preparation method and applications of polyethylene film - Google Patents

Abstract

The invention discloses a preparation method of a polyethylene film, which comprises the following steps: 1) using a mixed liquid I as a carrier flow to transport the main catalyst in the catalyst system to the reactor, and the mixed liquid I contains alkanes, olefins and auxiliary Catalyst; Stream III is obtained after adding make-up olefin feed to stream II flowing out of the reactor, stream III is divided into streams IIIa and IIIb, and streams IIIa and IIIb are refluxed to the side and bottom of the reactor, respectively; in the reactor , obtain ethylene polymer through polymerization and discharge from the reactor; wherein, the olefins include α-olefins and ethylene, and the molar ratio concentration ratio of α-olefins and ethylene in the mixed liquid I is at least 1; 2) the The ethylene polymer obtained in step 1) is passed through a blow molding process to obtain a polyethylene film. According to the method provided by the invention, the longitudinal and transverse tensile strength of the obtained film is improved and has uniform longitudinal and transverse tensile strength.

Description

A kind of preparation method and application of polyethylene film

technical field

The present invention relates to a kind of preparation method of polyethylene film, specifically, the present invention relates to a kind of preparation method of polyethylene film and its application.

Background technique

At present, biaxially oriented polypropylene film (BOPP) is the main product in the high-end packaging field because of its light weight, transparency, non-toxicity, moisture resistance and high mechanical strength. The new polyethylene biaxially oriented film (BOPE) shows more excellent performance than BOPP, with lighter weight, better transparency, gloss and printing effect. BOPE mainly has a 3-5 layer membrane structure, the most common is 3 layers, which are the outer base layer, the core base layer and the functional layer. The main component of the core layer is polyethylene (PE), and the addition of PE accounts for about 99% of the weight of the core layer. The tensile strength of the traditional polyethylene film in the longitudinal direction is much greater than that in the transverse direction, which will lead to insufficient transverse elongation of the film during use, thus affecting the performance of the polyethylene film. PE used in traditional polyethylene films mainly include linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE) and metallocene linear low-density polyethylene (mLLDPE).

Chinese patent CN 101608004B discloses a method for synthesizing linear low density polyethylene using ethylene, propylene and 1-butene as raw materials in an autoclave reactor. The catalyst carrier is SiO ₂ , the solvent is n-hexane, and the catalyst is triethyl Aluminum, reaction pressure 0.8MPa, temperature 80°C, the minimum haze of polyethylene obtained is 11%, the molecular weight distribution index is 6-40, the melt flow rate is 0.2-20g/10min, and the density is 0.910-0.940g/cm ³ . The longitudinal tensile strength is about 15MPa, and the transverse tensile strength is about 11MPa. It can be seen that the longitudinal and transverse tensile strengths of the linear low density polyethylene are quite different, which is not conducive to being used as the core material of BOPE.

For this consideration, the purpose of the present invention is to solve the problems exposed by the prior art in the related field, and it is expected to provide a method of utilizing a fluidized bed reactor to prepare high-performance ethylene polymer products with close longitudinal and transverse tensile strengths. method.

Contents of the invention

In view of the above deficiencies in the prior art, one of the purposes of the present invention is to provide a method for preparing ethylene polymers using a fluidized bed reactor, which realizes the use of a single reactor to prepare ethylene polymers with very close longitudinal and transverse tensile strengths. High performance ethylene polymer products.

Another object of the present invention is to provide an application of the polyethylene film prepared according to the method in film products such as packaging materials or commodity labels.

According to one aspect of the present invention, a kind of preparation method of polyethylene film is provided, comprising:

1) Transport the main catalyst in the catalyst system to the reactor by using the mixed liquid I as the carrier stream, the mixed liquid I comprising alkanes, olefins and co-catalysts; adding additional olefin feed to the stream II flowing out from the reactor , to obtain stream III, stream III is divided into stream IIIa and IIIb, and stream IIIa and IIIb are respectively refluxed to the side and the bottom of the reactor; in the reactor, ethylene polymer is obtained through polymerization and discharged from the reactor; wherein, The olefins include α-olefins and ethylene, and the molar ratio of α-olefins to ethylene in the mixed liquid I is at least 1;

2) passing the ethylene polymer prepared in step 1) through a blow molding process to obtain a polyethylene film.

According to the method provided by the invention, a film with uniform longitudinal and transverse tensile strength can be prepared, and the film has low haze, good puncture resistance, high tear strength, tensile strength and tangent modulus. The film prepared by the method of the invention has good comprehensive properties and broad application prospects.

In the method of the present invention, material circulation is carried out in the whole reaction system, thereby recycling raw materials. Among them, the mass flow rate of the stream II flowing out from the reactor is relatively large, and it is a material circulation with a large flow rate. After a small amount of feed is supplemented, the stream III is obtained. In the method of the present invention, the mixed liquid I and streams IIIa and IIIb are added to the reactor, and the alkane contained therein has a high latent heat of vaporization of the alkane, and a large heat transfer of the alkane, so that different temperature reaction zones appear in the reactor; And the mixed liquid I has a high content of α-olefins; therefore, the olefin monomers can obtain highly branched, low-density, high-molecular-weight olefin polymers and low-branched olefins under different temperature conditions in different regions of the fluidized bed reactor. , high-density low molecular weight olefin polymers, so that high and low molecular weight olefin polymers can be continuously mixed and fluidized, and the content of highly branched molecular segments or molecular chains is increased, and because alkanes can be compared The heat removal ability in the fluidized bed reactor is greatly improved, so the method of the present invention can prepare high and low molecular weight and high and low branching degree microscopically mixed olefin polymer products, and the light transmittance of the ethylene copolymer is improved , haze and self-adhesiveness, and the space-time yield of production is significantly improved. Then, use the obtained ethylene polymer through the blow molding process to obtain good properties such as uniform longitudinal and transverse tensile strength, high self-adhesiveness, low haze and high light transmittance, and high puncture resistance, tear strength, Tensile strength and tangent modulus of polyethylene films.

In the method of the present invention, the olefin monomers in the stream III and the mixed liquid I are used as raw materials, and are polymerized separately in multiple reaction zones with different temperatures in the fluidized bed reactor. Different polymerization temperatures and different olefin monomer concentrations can obtain olefin polymers with different structures and properties. According to the present invention, using a mixed solution containing alkanes and olefins as a carrier to transport the catalyst into the reactor can further form multiple low-temperature reaction zones in the reactor and further increase the content of highly branched molecular chains. The longitudinal/transverse tensile strength, haze and self-adhesiveness of the polyethylene produced by this method are improved; furthermore, the comprehensive properties of the obtained film products are improved, such as puncture resistance, tangent modulus, tear strength, self-adhesiveness, etc. Viscosity and light transmission are improved and haze is reduced.

According to the method provided by the present invention, a mixed solution containing alkanes and olefins is used as a carrier to transport the catalyst into the reactor, and the molar content of α-olefins in the mixed liquid is not lower than ethylene, and the α-olefins in the initial stage of catalyst action The high content of polyethylene will increase the branching degree of polyethylene and reduce the density (LDPE low density polyethylene). The polymers obtained according to the present invention have improved longitudinal and transverse tensile strengths at similar molecular weights.

According to a preferred embodiment of the present invention, the mixed liquid I can be used as a carrier flow, capable of transporting the main catalyst powder into the reaction system. Among them, it is preferred to use a rotating device to transport the main catalyst to the pipeline or pipe fitting connected with the polymerization reactor, and then use the mixed liquid I to transport the main catalyst powder into the reaction system. According to a specific embodiment of the present invention, the rotating equipment is selected from pumps, compressors, fans and speed reducers.

According to a preferred embodiment of the present invention, the catalyst system includes a Ziegler-Natta catalyst, a metallocene catalyst, a transition metal catalyst, an inorganic chromium catalyst and an organic chromium catalyst. The catalyst system includes a co-catalyst and a main catalyst. In a specific example, the amount of the main catalyst and the cocatalyst is a conventional amount in the art, such as the molar ratio of the main catalyst and the cocatalyst to the mole of the active metal element in the main catalyst and the active metal element in the cocatalyst The ratio is 1:1-6:1. In a specific embodiment, the cocatalyst contained in the mixed liquid I is triethylaluminum. In another specific example, the amount of the co-catalyst in the mixed liquid is at least 150 ppm (weight content).

According to a preferred embodiment of the present invention, the molar ratio of α-olefin to ethylene in the mixed liquid I is 1-5, such as 1.3-5. In a preferred situation, the molar ratio of α-olefin to ethylene in the mixed liquid I is 1.5-5. At this time, the content of α-olefin is higher, so that the degree of branching of polyethylene increases and the density decreases. The longitudinal and transverse tensile strengths are further improved.

According to another preferred embodiment of the present invention, in the mixed liquid I, the content of alkanes is 5-80wt%. In a preferred situation, the content of alkanes in the mixed liquid I is 10-65wt%. Controlling the alkane content in the mixed liquid is beneficial to controlling the reaction temperature and forming a low-temperature reaction zone.

According to another preferred embodiment of the present invention, the mass flow rate of the mixed liquid I accounts for 0.05%-5% of the mass flow rate of the stream II, preferably 0.1%-3%.

In a specific embodiment, the alkanes in the present invention include at least one of butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane and heptane. The alkanes within the limited range have high latent heat of vaporization and large heat transfer, which is beneficial to forming reaction zones with different reaction temperatures in the reactor.

According to a preferred embodiment of the present invention, the reaction pressure in the reactor is 0.5-10 MPa, and the reaction temperature is 40-150°C. In a specific example, the reaction pressure in the reactor is 1.5-5 MPa. In another specific embodiment, the reaction temperature in the reactor is 60-100°C.

According to the present invention, the alkane, such as the alkane in the mixed liquid I, such as the alkane in the stream IIIa or IIIb, has a high latent heat of vaporization and a large heat transfer, and can be used as a condensing agent. Therefore, the reaction temperature of the polymerization reaction zone having an input of alkane in the reactor will be different from the reaction temperature of other polymerization reaction regions. According to a specific embodiment of the present invention, the reactor is a fluidized bed reactor. The stream is circulated in the entire reaction system including fluidized bed reactors, pipelines, heat exchange equipment, separation equipment, etc.

According to a specific preferred embodiment of the present invention, the reactor contains reaction zones with different temperatures. In the reactor, there is a polymerization reaction zone where the condensing agent (alkane) is input, and the polymerization temperature is relatively low, which is a low-temperature reaction zone. The polymerization reaction zone where there is no condensing agent input, and the polymerization temperature is relatively high, is a high-temperature reaction zone. According to a specific embodiment of the present invention, the reaction temperature in the low-temperature reaction zone is controlled at 60-75°C, preferably 65-75°C; the reaction temperature in the high-temperature reaction zone is controlled at 75-100°C, preferably 80-90°C.

According to a preferred embodiment of the present invention, the superficial fluidization gas velocity of the fluidized bed reactor is 0.1-10 m/s. The purpose of strictly controlling the superficial fluidization gas velocity of the fluidized bed reactor in the method of the present invention is to ensure a good fluidization state of the reactor while avoiding a large amount of powder material being carried out. When the superficial fluidization gas velocity is 0.3-0.8m/s, the method of the present invention can further ensure the stable operation of the fluidized bed reactor, and at the same time ensure the stable existence of the low-temperature reaction zone and the high-temperature reaction zone. The reason may be that the superficial fluidization gas velocity is higher than the initial fluidization velocity of the powder in this system and at the same time lower than the take-out velocity of most powder particles.

According to a preferred embodiment of the present invention, the stream II flowing out from the reactor contains alkanes and may also contain unreacted olefin monomers (possibly involving ethylene and α-olefins). The components of the stream II and the stream III are not much different, and the mass flow rate is also the same. In a specific example, the mass flow rate of stream II accounts for more than 90% of the mass flow rate of stream III, preferably more than 95% to 100%.

As the reaction progresses and polymer is withdrawn, additional olefin feed is required. Said stream III obtained after feeding the make-up olefin feed (involving make-up ethylene feed and make-up α-olefin feed) has an olefin content of 1.0-60.0 mol%, such as preferably 5.0-55.0 mol%. Wherein, in a specific example, in the stream III, the molar concentration of α-olefin accounts for 20%-60% of the molar concentration of ethylene.

According to a preferred embodiment of the present invention, the stream III contains regulators and/or inert components. By using the regulator, the molecular weight and molecular weight distribution of the ethylene polymer obtained by polymerization can be adjusted according to the content of the regulator. Wherein, the regulator is preferably hydrogen. By using inert components, part of the heat generated during the polymerization can be removed and the composition of stream III can be adjusted. Among them, the inert component is preferably nitrogen. In this case, the stream II exiting the reactor may contain regulators and/or inert components. In a specific example, in the stream III, the content of the regulator is controlled to be 0.3-14.5 mol%. In another specific example, in the stream III, the amount of the inert components is controlled to be 25.0-75.0%. In a specific example, in the stream III, the content of alkane is controlled to be 0.5-50.0 mol%, such as 1.0-35.0 mol%. According to the requirements of the process, at least one of supplementary alkane feed, inert component feed and supplementary regulator feed can also be included in stream III, so as to better control the composition of stream III.

According to a preferred embodiment of the present invention, the stream III is divided into streams IIIa and IIIb after compression and gas-liquid separation. Therein, stream IIIa flows into the reactor through the side of the reactor. Instead, stream IIIb flows into the reactor through the bottom of the reactor. According to a specific embodiment of the present invention, the alkanes in stream IIIa account for 60-90 wt% of the total amount of alkanes in stream III. That is, most of the alkanes in stream III flow into the reactor from the side of the reactor through stream IIIa. According to a particular embodiment of the present invention, the olefins in stream IIIa account for 10-50 wt% of the total amount of olefins in stream III.

According to another embodiment of the invention, both in IIIa and IIIb, there are regulators and inert components. Wherein the amount of regulator in IIIb is 50-100%wt of the amount of regulator in III. The amount of inert components in IIIa is 10-100%wt of the amount of inert components in III. Wherein, the α-olefins in stream IIIa account for 10-100 wt% of the total amount of α-olefins in stream III.

In the method of the present invention, the temperature of the polymerization reaction zone refers to the highest temperature in the polymerization reaction zone. According to a specific embodiment of the present invention, the alkane and olefin monomers in stream IIIa are fed into the fluidized bed reactor from the side, and the remaining alkane and olefin monomers in stream III are fed into the fluidized bed reactor from the bottom in the form of stream IIIb. bed reactor. Thus, the heat removal efficiency in the reactor and the space-time yield of the reaction can be further improved.

In the method of the present invention, after the olefin polymer flows out of the fluidized bed reactor, it enters the storage tank and the purge tank to purge and remove the olefin monomer in the olefin polymer with an inert component, and then enters the degassing chamber The olefin monomer inside the olefin polymer is further removed, and finally the ethylene polymer is discharged from the lower part of the degassing chamber for granulation.

According to the present invention, the α-olefin is selected from at least one of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene and 1-decene.

According to a preferred embodiment of the present invention, in the prepared ethylene polymer, the molar content of the α-olefin monomer unit is 1-30%. For example, the molar content of α-olefin monomer units is 1-10%. The content of the α-olefin monomer unit of the polymer is higher than that prepared by other methods, and the degree of branching is high; and wherein, the α-olefin monomer unit is connected head-to-head (referring to two carbon atoms with side groups directly connected to each other) ) The monomer unit content is higher than that prepared by other methods; then, it is beneficial to improve the longitudinal and transverse tensile strength.

According to a preferred embodiment of the present invention, the prepared ethylene polymer has a density of 0.890 g/cm ³ to 0.922 g/cm ³ , preferably 0.895 to 0.917 g/cm ³ . In the ethylene polymer, the melt flow rate under the conditions of 230° C. and 2.16 kg is 0.1-10 g/10 min, preferably 0.5-5.0 g/10 min. The weight average molecular weight of the ethylene polymer is 20000-250000, and the molecular weight distribution index is 2-15.

According to a preferred embodiment of the present invention, the ethylene polymer has a melting point of 110-130°C, preferably 115-125°C, determined by differential scanning calorimetry according to ISO 11357-3 at a heating rate of 20°C/min. The ethylene polymer has a longitudinal tensile strength (MD) and a transverse tensile strength (TD) greater than 15 MPa, and its ratio MD/TD is less than 1.15, preferably less than 1.1.

In the method of the present invention, the space-time yield refers to the yield of olefin polymer per unit bed volume per unit time.

Compared with the prior art, the method of the present invention for preparing olefin polymers by utilizing the fluidized bed reactor condensation process has the following beneficial technical effects: the process is simple; the operation is simple; the cost of facility investment is low; the continuous stability is good ; Diversified ethylene polymer products can be produced; The prepared ethylene polymer products have uniform longitudinal and transverse tensile strength, and the ratio of longitudinal/transverse tensile strength is close to 1.

According to the present invention, in step 2), the ethylene polymer prepared in step 1) is blown to obtain a polyethylene film. The thickness of the film is a conventional thickness in the art. In a specific example, the film is a BOPE film (biaxially oriented polyethylene film).

According to a preferred embodiment of the present invention, in the step 2), the ethylene polymer prepared in the step 1) is used as the core layer to prepare a BOPE film. The skin layer in the BOPE film can adopt the skin layer commonly used in the prior art, such as copolymerized polypropylene and/or linear low-density polyethylene as the skin layer.

According to another aspect of the present invention, application of the polyethylene film prepared by the above method in packaging materials and/or commodity labels is also provided. Wherein, the application includes preparing a film by the above method, and then using it in packaging materials and/or commodity labels. The overall performance of the film is good, with uniform longitudinal and transverse tensile strength, good puncture resistance, high tear strength, tensile strength and tangent modulus, etc., and can be widely used in cooking film, high transparency film, barrier In protective film, heat sealing film or label film.

Compared with the prior art, the present invention utilizes a fluidized bed reactor to prepare ethylene polymers with a liquid condensation process, and utilizes a mixed liquid containing a high α-olefin/ethylene molar ratio to send the main catalyst into the reactor, and the stream IIIa passes through the reaction The side of the reactor flows into the reactor, and the stream IIIb flows into the reactor through the bottom of the reactor; more reaction zones with different temperatures can be further formed in the reactor to obtain high and low molecular weight and high and low degree of branching. Uniform polymers with specific structures further increase the content of highly branched molecular chains, thereby producing high-performance films. According to the method of the present invention, the process is simple; easy to operate; the cost of facility investment is low; the continuous stability is good; diverse polyethylene films can be produced; the comprehensive performance of the obtained film is good, uniform longitudinal and transverse tensile strength, At the same time, the film has good light transmittance and puncture resistance, as well as high tear strength, tensile strength and tangent modulus, etc.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings that need to be used in the description of the embodiments. Obviously, the drawings in the following brief description are only some embodiments of the present invention. Those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort.

Fig. 1 shows a schematic diagram of a reaction apparatus for realizing the method of the present invention.

Fig. 2 shows a schematic diagram of the formation of multiple olefin polymerization reaction zones with different temperatures in a fluidized bed reactor.

In the figures, the same components are designated by the same reference numerals. The figures are not drawn to scale.

The description of the reference signs is as follows:

1 Distribution plate

2 fluidized bed reactor;

3 compression equipment;

4 heat exchange equipment;

5 separation equipment;

6 feed pump;

7 gas circulation pipeline;

8 discharge tank;

9 purge tank;

10 degas chamber;

11. For introducing the main catalyst into the fluid pipeline of the reactor with the mixed solution I as the carrier stream;

12 fluid conduits for introducing stream IIIa into the reactor;

13 Fluid piping for removal of solid ethylene polymer from the reactor;

14 Fluid piping for introducing H ₂ , N ₂ and ethylene into the circulation line;

15 Fluid piping for introducing α-olefin comonomer into the circulation line;

16 Fluid piping for introducing condensate into the circulation line;

17 Fluid pipelines for introducing the stream IIIb separated by the separation device into the reactor;

18 a pump for delivering the mixed liquid I to the pipeline 11;

19. Means for feeding main catalyst powder into pipeline 11.

detailed description

Embodiments of the present invention will be described in detail below in conjunction with examples, but those skilled in the art will understand that the following examples are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all commercially available conventional products.

Characterization Method of Ethylene Polymer Structure and Properties

(1) Characterization of melting temperature and crystallization temperature: differential scanning calorimetry (DSC).

Weigh about 6mg of the sample to be tested, heat it to about 220°C at a rate of 20°C/min, and keep it in nitrogen flow for 2min, then cool it to about 40°C at a rate of 20°C/min, and keep it at this temperature 2 min to crystallize the sample. Then the sample was heated to 220° C. at a heating rate of 20° C./min and melted again. Melting scans are recorded, thermograms are obtained, and melting and crystallization temperatures are read out therefrom.

(2) Characterization of weight average molecular weight (Mw): gel permeation chromatography (GPC).

The sample to be tested was prepared at a concentration of 70mg/50ml of stabilized 1,2,4-trichlorobenzene (250μg/ml BHT (CAS REGISTRYNUMBER 128-37-0); then the sample was heated to 170°C for 2.5 hours to carry out Dissolution; measurement was carried out on Waters GPCV2000 at 145°C at a flow rate of 1.0ml/min. with the same stabilizing solvent; three Polymer Lab columns were used in series (Plgel, 20μm mixed ALS, 300X 7.5 mm).

(3) Determination of molecular weight distribution index (PDI): RMS-800 plate rheometer of Rheometrics Company.

Operate under the condition that the vibration frequency increases from 0.1rad/s to 100rad/s. The crossover modulus (crossover modulus) can be deduced from PI by the following equation: PI=105/Gc, wherein, Gc is the crossover modulus, which is a value (expressed in Pa) determined when G'=G", where G' is Storage modulus, G" is the loss modulus.

(4) Characterization of melt flow index (MFR): Measured according to ISO method 1133 under the condition of 230° C./2.16 kg.

(5) Determination of ethylene content: IR spectroscopy.

(6) Determination of α-olefin content: IR spectroscopy.

(7) Determination of density: determined according to ISO 1183.

(8) Thickness: measured according to GB/T 6672-2001.

(9) Tensile strength and tensile elongation at break: determined according to ISO 527.

(10) Tear strength: Measured simultaneously in the machine direction (MD) and in the transverse direction (TD) according to ASTM D1922.

(11) Puncture resistance: determined according to BB/T 0024-2004.

(12) Tangent modulus: Measured simultaneously in the machine direction (MD) and in the transverse direction (TD) according to ASTM D882.

(13) Transparency: measured according to BB/T 0024-2004;

(14) Haze: measured according to GB/T 2410-2008.

In a specific example, as shown in Figure 1, in the fluidized bed reactor 2 that there is nitrogen fluidization in the inside, at first by device 19 as feeding device, the main catalyst powder in the Ziegler-Natta catalyst is added to In the pipeline 11 connected to the reactor 2, the mixed liquid I containing alkanes and olefins is transported into the pipeline 11 by using the pump equipment 18, and the main catalyst powder is transported into the reactor 2 by using the mixed liquid 11 as a carrier, and the mixed liquid Also contain co-catalyst in I, wherein, the connecting port of pipeline 11 and reactor 2 can have one or more. The pipeline 7 is connected with the top expansion section of the fluidized bed reactor 2, and is used for receiving the stream II from the fluidized bed reactor 2. The material in stream II may contain unreacted olefin monomers as well as alkanes and the like. Stream III is obtained after additional olefin feed (possibly via 14 and line 15). According to the needs of experiments, alkane feed (through line 16) and supplementary regulator (through line 14, such as H ₂ ) and inert component feed (through line 14, such as N ₂ ) can also be added to stream II. , to obtain stream III. Stream III is divided into streams IIIa and IIIb distributed to the bottom and top of the reactor. In a specific example, the stream III from the heat exchanger 4 passes through the gas-liquid separator 5 and is divided into streams IIIa and IIIb. The majority of the total condensing agent content in stream III is located in stream IIIa, which is sprayed into fluidized bed reactor 2 via fluid lines 12 and 19 (possibly via pump 6, increasing the feed rate), and the remainder of the condensing agent is located in stream IIIb , and enter the fluidized bed reactor 2 below the distribution plate 1 along with the fluid pipeline 17, wherein there may be one or more connection ports between the pipeline 19 and the reactor 2. According to the method in the present invention, a high-temperature reaction zone A and a low-temperature reaction zone B are formed in the fluidized bed reactor, as shown in FIG. 2 .

The solid-phase polymer produced in the polymerization reaction is intermittently unloaded from the fluid pipeline 13, and after being devolatilized in the discharge tank 8, the purge tank 9 and the degassing bin 10, it is transported to the downstream section for further processing. Ethylene polymers are obtained.

Example 1

In this embodiment, magnesium chloride _- supported TiCl3 is used as the main catalyst (the feed rate of the main catalyst is 2.18kg/h), and a Ziegler-Natta catalyst with triethylaluminum as the cocatalyst. Wherein, the molar ratio of the main catalyst and the co-catalyst is 3.11 in terms of Ti/Al. The reaction process is shown in Figure 1.

The mass flow rate of mixed liquid I is 1.8 t/h, accounting for 0.42% of the mass flow rate of stream II. In the mixed liquid I, the alkane isopentane content accounts for 50% by weight of the mixed liquid (the molar content is 49%), and the olefin content accounts for 50% by weight of the mixed liquid (the molar content is 51%). The content of 1-hexene accounts for 45.1% by weight of the mixed liquid (the molar content is 38.5%). Mixed liquid I also contained 200 ppm of triethylaluminum cocatalyst.

The superficial fluidization gas velocity in the reactor was 0.75 m/s. The pressure of the reactor was 2.1 MPa, and the temperature was 89°C.

After additional feed in stream II, stream III is obtained. The mass flow rate of stream II accounts for 97.8% of that of stream III. Of the isopentane in stream III, 80% by weight is in stream IIIa and the remainder is in stream IIIb.

The polymerization time is 2 hours, and finally a binary copolymer of ethylene/1-hexene, ie, binary polymer A of ethylene and hexene, is obtained.

The content of each component of stream III in this example is shown in Table 1 below.

Table 1

The performance and structure characterization results of the ethyl-hexane binary polymer A prepared in this example are shown in Table 4 below.

Example 2

In this embodiment, TiCl ₃ supported by magnesium chloride is used as the main catalyst (the loading capacity is 1.75 kg/h), and a Ziegler-Natta catalyst with triethylaluminum as the cocatalyst. Wherein, the molar ratio of the main catalyst and the co-catalyst is 3.11 in terms of Ti/Al. The reaction process is shown in Figure 1.

The mass flow rate of mixed liquid I is 1.3t/h, accounting for 0.30% of the mass flow rate of stream II. In the mixed liquid I, the alkane isopentane content accounts for 45% by weight of the mixed liquid (the molar content is 35%), and the olefin content accounts for 55% by weight of the mixed liquid (the molar content is 65%), wherein the ethylene content accounts for 45% by weight of the mixed liquid (the molar content is 65%). 8.8% by weight (mole content is 17.8%), 1-butene content accounts for 46.2% by weight of the mixed liquid) (molar content is 47.2%), also contains 180ppm triethylaluminum cocatalyst in the mixed liquid.

The superficial fluidization gas velocity in the reactor was 0.70 m/s. The pressure of the fluidized bed reactor is 2.0 MPa, and the temperature is 88°C.

After additional feed in stream II, stream III is obtained. The mass flow of stream II accounts for 96.8% of the mass flow of stream III. Of the isopentane in stream III, 80% by weight is in stream IIIa and the remainder is in stream IIIb.

The polymerization time is 2 hours, and finally a binary copolymer of ethylene/1-butene, ie, ethylene-butylene binary polymer B, is obtained.

The content of each component of stream III in this embodiment is shown in Table 2 below.

Table 2

The performance and structure characterization results of the ethylene-butylene binary polymer B prepared in this example are shown in Table 4 below.

Example 3

In this example, magnesium chloride _- supported TiCl3 is used as the Ziegler-Natta catalyst (feed rate of the main catalyst is 2.03 kg/h), and triethylaluminum is used as the co-catalyst. Wherein, the molar ratio of the main catalyst and the co-catalyst is 3.11 in terms of Ti/Al. The reaction process is shown in Figure 1.

The mass flow rate of mixed liquid I is 1.7t/h, accounting for 0.37% of the mass flow rate of stream II. In the mixed liquid I, the alkane n-hexane content accounts for 25% by weight of the mixed liquid (the molar content is 25%), and the olefin content accounts for 75% by weight of the mixed liquid (the molar content is 75%), wherein the ethylene content accounts for 7.8% by weight of the mixed liquid. % by weight (molar content 23.8%), the content of 1-octene accounts for 67.2% by weight (molar content is 51.2%) of the mixed liquid, and the mixed liquid also contains 180ppm of triethylaluminum cocatalyst.

The superficial fluidization gas velocity in the reactor was 0.68 m/s. The pressure of the fluidized bed reactor is 2.1MPa, and the temperature is 87°C.

After additional feed in stream II, stream III is obtained. The mass flow of stream II accounts for 97.2% of the mass flow of stream III. Of the isopentane in stream III, 80% by weight is in stream IIIa and the rest is in stream IIIb.

The content of each component of stream III in this example is shown in Table 3 below.

table 3

The performance and structure characterization results of the ethyloctine binary polymer C prepared in this example are shown in Table 4 below.

Comparative example 1

In this comparative example, the method disclosed in Example 35 of WO00/02929A1 was used to prepare ethyl-hexane binary polymer D by using ethylene and 1-hexene as raw materials.

Please refer to Table 4 below for the performance and structure characterization results of the ethyl-hexane binary polymer D prepared in this comparative example.

Comparative example 2

Same as Example 1, the difference is that there is no mixed liquid I, the co-catalyst and the main catalyst are directly added to the reactor, and ethylene and 1-hexene are used as raw materials to prepare the ethyl-hexane binary polymer E. That is to say, the method in this comparative example is similar to CN104628904CN. Please refer to Table 4 below for the performance and structure characterization results of the ethyl-hexane binary polymer E prepared in this comparative example.

Comparative example 3

Same as Example 2, the difference is that the liquid I is not mixed, the co-catalyst and the main catalyst are directly added to the reactor, and ethylene and 1-butene are used as raw materials to prepare the ethylene-butylene binary polymer F. That is to say, the method in this comparative example is similar to CN104628904CN. Please refer to Table 4 below for the performance and structure characterization results of the ethyl-hexane binary polymer F prepared in this comparative example.

Table 4

As can be seen from the characterization results of the ethylene polymers prepared in the above examples 1-3 and comparative examples, the ethylhexyl polymer A, the ethylbutylene polymer B, and the ethyloctyl polymer C prepared in the examples 1-3 are compared For the polymers D-F of comparative examples 1-3, the α-olefin monomer unit content, and wherein, the α-olefin monomer unit content of head-to-head connection is high, which shows that the ethylene polymer obtained by the method of the present invention has more Branched chain and higher degree of branching.

In addition, in the case of the same monomer and the weight average molecular weight of the polymers are relatively close, the melt index MFR of the copolymer prepared by the method of the present invention is lower, and the molecular weight distribution coefficient PI, density, and haze are significantly lower than The polymkeric substance of comparative example, longitudinal and transverse tensile strength are all better than the copolymer in comparative example (see embodiment 1 and comparative example 1 and 2, embodiment 2 and comparative example 3), particularly, copolymer A, B The longitudinal and transverse tensile strengths of , C are very close, and their ratios are 1.014, 1.006 and 1.005 respectively, which is obviously better than that of copolymer D-F. This is related to the production method. According to the production method in the present invention, the content of molecular chains with a high degree of branching is large, the degree of chain entanglement is increased, the longitudinal and transverse tensile properties are improved, and the density and haze are reduced.

From the characterization results of the ethylene polymers prepared in the above Examples 1-3 and Comparative Examples 1-3, it can be seen that a mixed solution containing alkanes and olefins is further used as a carrier to transport the main catalyst into the reactor, and control the The molar ratio of α-olefin to ethylene is more conducive to increasing the degree of branching, which is beneficial to improving the tensile properties of the polymer, reducing the density, reducing the haze and narrowing the molecular weight distribution.

The following are examples of BOPE film preparation

Example 4

(1) Preparation of BOPE film

The BOPE film of this embodiment comprises three layers in turn: outer layer 1, core layer and outer layer 2, outer layer 1 and outer layer 2 are respectively connected to both sides of the core layer, and outer layers 1 and 2 are films that are in direct contact with the external environment the outermost layer.

The raw materials used for the outer layer 1 and the outer layer 2 and the proportioning ratio are: 70wt% of Japan's Mitsui Chemicals company's brand is SP1520 linear low density polyethylene (LLDPE), 10wt% of South Korea's LG Chemicals company's brand is H5200 copolymerized polypropylene (MFR =2g/10min), 16wt% of metallocene polyethylene (MPE) of Exceed 1327KD from Exceed 1327KD of ExxonMobil Chemical Company, 4wt% of anti-adhesive masterbatch (ABPP 905DCPP).

The raw materials used for the core layer and the proportioning ratio are: the ethylene/1-hexene copolymer (ethylene-hexane binary polymer A) obtained in the embodiment 1 of 94wt%, the slippery function masterbatch (603PP) of 3wt%, the 3wt% Carbon eight material (ethylene-octene copolymer synthesized by metallocene catalyst, Dow 488-4A).

Mix the outer layer 1, outer layer 2 and core layer materials evenly according to the above ratio, then transport them to the storage tank, and send them to three single-screw extruders through pipelines for extrusion, and then extrude through three-layer co-extrusion dies To form a tube blank, the layered weight ratio of the tube blank is outer layer 1: core layer: outer layer 2 = 20:60:20, the screw diameter of the single-screw extruder for the outer layer is 50mm, and the length-to-diameter ratio is 30:1. The extrusion temperature is 220°C, the screw diameter of the single-screw extruder for the core layer is 100mm, the aspect ratio is 30:1, the extrusion temperature is 220°C, and the extruded materials are merged at the three-layer co-extrusion die to form a tube blank , the temperature of the extrusion die head is 223°C, and the extruded tube blank is drawn into the stretching oven after being cooled. The tube blank is stretched in a stretching oven filled with compressed air. The stretching temperature is 116°C, the transverse stretching ratio is 2.2-2.7, and the longitudinal stretching ratio is 2.2-2.7. A film with a thickness of 25 μm can be obtained, bidirectional The stretched film is forcibly cooled by the air ring, cut in half, wound up, and cut to obtain the final product, namely BOPE film G.

(2) Performance characterization of BOPE membrane

The performance characterization results of the BOPE film G prepared in this example are shown in Table 5 below.

Example 5

(1) Preparation of BOPE film

The BOPE film of this embodiment comprises three layers in turn: outer layer 1, core layer and outer layer 2, outer layer 1 and outer layer 2 are respectively connected to both sides of the core layer, and outer layers 1 and 2 are films that are in direct contact with the external environment the outermost layer.

The raw materials used for the outer layer 1 and the outer layer 2 and the proportioning ratio are: 70wt% of Japan's Mitsui Chemicals company's trademark is SP1520 linear low density polyethylene (LLDPE), 10wt% of South Korea's LG Chemicals company's trademark is H5200 copolymerized polypropylene (MFR =2g/10min), 16wt% of metallocene polyethylene (MPE) Exceed 1327KD from ExxonMobil Chemical Co., 4wt% anti-adhesive masterbatch.

The raw materials used for the core layer and the proportioning ratio are: the ethylene/1-butene copolymer (ethylene-butylene binary polymer B) obtained in the embodiment 2 of 94wt%, the slippery functional masterbatch of 3wt% (same as embodiment 4) , 3wt% carbon eight material (same as embodiment 4).

Mix the outer layer 1, outer layer 2 and core layer materials evenly according to the above ratio, then transport them to the storage tank, and send them to three single-screw extruders through pipelines for extrusion, and then extrude through three-layer co-extrusion dies To form a tube blank, the layered weight ratio of the tube blank is outer layer 1: core layer: outer layer 2 = 20:60:20, the screw diameter of the single-screw extruder for the outer layer is 50mm, and the length-to-diameter ratio is 30:1. The extrusion temperature is 220°C, the screw diameter of the single-screw extruder for the core layer is 100mm, the aspect ratio is 30:1, the extrusion temperature is 220°C, and the extruded materials are merged at the three-layer co-extrusion die to form a tube blank , the temperature of the extrusion die is 223°C, and the extruded tube blank is drawn into the stretching oven after being cooled. The tube blank is stretched in a stretching oven filled with compressed air. The stretching temperature is 116°C, the transverse stretching ratio is 2.2-2.7, and the longitudinal stretching ratio is 2.2-2.7. A film with a thickness of 25 μm can be obtained, bidirectional The stretched film is forcibly cooled by the air ring, cut in half, wound up, and cut to obtain the final product, namely BOPE film H.

(2) Performance characterization of BOPE membrane

The performance characterization results of the BOPE membrane H prepared in this example are shown in Table 5 below.

Example 6

(1) Preparation of BOPE film

The BOPE film of this embodiment comprises three layers in turn: outer layer 1, core layer and outer layer 2, outer layer 1 and outer layer 2 are respectively connected to both sides of the core layer, and outer layers 1 and 2 are films that are in direct contact with the external environment the outermost layer.

The raw materials used for the outer layer 1 and the outer layer 2 and the proportioning ratio are: 70wt% of Japan's Mitsui Chemicals company's trademark is SP1520 linear low density polyethylene (LLDPE), 10wt% of South Korea's LG Chemicals company's trademark is H5200 copolymerized polypropylene (MFR =2g/10min), 16wt% Exxon Mobil Chemical Company brand is the metallocene polyethylene (MPE) of Exceed 1327KD, 4wt% anti-adhesive masterbatch (same as embodiment 4).

The used raw material of core layer and proportioning are: the ethylene/1-octene copolymer (ethyloctene binary polymer C) that obtains in the embodiment 3 of 94wt%, the slippery functional masterbatch of 3wt% (same as embodiment 4) , 3wt% carbon eight material (same as embodiment 4).

Mix the outer layer 1, outer layer 2 and core layer materials evenly according to the above ratio, then transport them to the storage tank, and send them to three single-screw extruders through pipelines for extrusion, and then extrude through three-layer co-extrusion dies To form a tube blank, the layered weight ratio of the tube blank is outer layer 1: core layer: outer layer 2 = 20:60:20, the screw diameter of the single screw extruder for the outer layer is 50mm, and the aspect ratio is 30:1. The extrusion temperature is 220°C, the screw diameter of the single-screw extruder for the core layer is 100mm, the aspect ratio is 30:1, the extrusion temperature is 220°C, and the extruded materials are merged at the three-layer co-extrusion die to form a tube blank , the temperature of the extrusion die head is 223°C, and the extruded tube blank is drawn into the stretching oven after being cooled. The tube blank is stretched in a stretching oven filled with compressed air. The stretching temperature is 116°C, the transverse stretching ratio is 2.2-2.7, and the longitudinal stretching ratio is 2.2-2.7. A film with a thickness of 25 μm can be obtained, bidirectional The stretched film is forcibly cooled by the air ring, cut in half, wound up, and cut to obtain the final product, namely BOPE film I.

(2) Performance characterization of BOPE membrane

The performance characterization results of the BOPE membrane I prepared in this example are shown in Table 5 below.

Comparative example 4

(1) Preparation of BOPE film

The BOPE film of this embodiment comprises three layers in turn: outer layer 1, core layer and outer layer 2, outer layer 1 and outer layer 2 are respectively connected to both sides of the core layer, and outer layers 1 and 2 are films that are in direct contact with the external environment the outermost layer.

The raw materials used for the outer layer 1 and the outer layer 2 and the proportioning ratio are: 70wt% of Japan's Mitsui Chemicals company's trademark is SP1520 linear low density polyethylene (LLDPE), 10wt% of South Korea's LG Chemicals company's trademark is H5200 copolymerized polypropylene (MFR =2g/10min), 16wt% Exxon Mobil Chemical Company brand is the metallocene polyethylene (MPE) of Exceed 1327KD, 4wt% anti-adhesive masterbatch (same as embodiment 4).

The raw materials used for the core layer and the proportioning ratio are: the ethylene/1-hexene copolymer (ethylene-hexane binary polymer D) obtained in the comparative example 1 of 94wt%, the slippery functional masterbatch of 3wt%, the carbon eight material of 3wt% .

Mix the outer layer 1, outer layer 2 and core layer materials evenly according to the above ratio, then transport them to the storage tank, and send them to three single-screw extruders through pipelines for extrusion, and then extrude through three-layer co-extrusion dies To form a tube blank, the layered weight ratio of the tube blank is outer layer 1: core layer: outer layer 2 = 20:60:20, the screw diameter of the single screw extruder for the outer layer is 50mm, and the aspect ratio is 30:1. The extrusion temperature is 220°C, the screw diameter of the single-screw extruder for the core layer is 100mm, the aspect ratio is 30:1, the extrusion temperature is 220°C, and the extruded materials are merged at the three-layer co-extrusion die to form a tube blank , the temperature of the extrusion die head is 223°C, and the extruded tube blank is drawn into the stretching oven after being cooled. The tube blank is stretched in a stretching oven filled with compressed air. The stretching temperature is 116°C, the transverse stretching ratio is 2.2-2.7, and the longitudinal stretching ratio is 2.2-2.7. A film with a thickness of 25 μm can be obtained, bidirectional The stretched film is forcibly cooled by the air ring, cut in half, wound up, and cut to obtain the final product, namely BOPE film J.

(2) Performance characterization of BOPE membrane

The performance characterization results of the BOPE film J prepared in this example are shown in Table 5 below.

Comparative example 5

(1) Preparation of BOPE film

The BOPE film of this embodiment comprises three layers in turn: outer layer 1, core layer and outer layer 2, outer layer 1 and outer layer 2 are respectively connected to both sides of the core layer, and outer layers 1 and 2 are films that are in direct contact with the external environment the outermost layer.

The raw materials used for the outer layer 1 and the outer layer 2 and the proportioning ratio are: 70wt% of Japan's Mitsui Chemicals company's trademark is SP1520 linear low density polyethylene (LLDPE), 10wt% of South Korea's LG Chemicals company's trademark is H5200 copolymerized polypropylene (MFR =2g/10min), 16wt% Exxon Mobil Chemical Company brand is the metallocene polyethylene (MPE) of Exceed 1327KD, 4wt% anti-adhesive masterbatch (same as embodiment 4).

The raw materials used for the core layer and the proportioning are: the ethylene/1-hexene copolymer (ethylene-hexane binary polymer E) that obtains in the comparative example 2 of 94wt%, the slippery functional masterbatch of 3wt% (same as embodiment 4), 3wt% carbon eight material (same as embodiment 4).

Mix the outer layer 1, outer layer 2 and core layer materials evenly according to the above ratio, then transport them to the storage tank, and send them to three single-screw extruders through pipelines for extrusion, and then extrude through three-layer co-extrusion die heads To form a tube blank, the layered weight ratio of the tube blank is outer layer 1: core layer: outer layer 2 = 20:60:20, the screw diameter of the single screw extruder for the outer layer is 50mm, and the aspect ratio is 30:1. The extrusion temperature is 220°C, the screw diameter of the single-screw extruder for the core layer is 100mm, the aspect ratio is 30:1, the extrusion temperature is 220°C, and the extruded materials are merged at the three-layer co-extrusion die to form a tube blank , the temperature of the extrusion die head is 223°C, and the extruded tube blank is drawn into the stretching oven after being cooled. The tube blank is stretched in a stretching oven filled with compressed air. The stretching temperature is 116°C, the transverse stretching ratio is 2.2-2.7, and the longitudinal stretching ratio is 2.2-2.7. A film with a thickness of 25 μm can be obtained, bidirectional The stretched film is forcibly cooled by the air ring, cut in half, wound up, and cut to obtain the final product, namely BOPE film K.

(2) Performance characterization of BOPE membrane

The performance characterization results of the BOPE film K prepared in this example are shown in Table 5 below.

Comparative example 6

(1) Preparation of BOPE film

The BOPE film of this embodiment comprises three layers in turn: outer layer 1, core layer and outer layer 2, outer layer 1 and outer layer 2 are respectively connected to both sides of the core layer, and outer layers 1 and 2 are films that are in direct contact with the external environment the outermost layer.

The raw materials used for the outer layer 1 and the outer layer 2 and the proportioning ratio are: 70wt% of Japan's Mitsui Chemicals company's trademark is SP1520 linear low density polyethylene (LLDPE), 10wt% of South Korea's LG Chemicals company's trademark is H5200 copolymerized polypropylene (MFR =2g/10min), 16wt% Exxon Mobil Chemical Company brand is the metallocene polyethylene (MPE) of Exceed 1327KD, 4wt% anti-adhesive masterbatch (same as embodiment 4).

The raw materials used for the core layer and the proportioning ratio are: the ethylene/1-butene copolymer (ethylene-butylene binary polymer F) obtained in the comparative example 3 of 94wt%, the slippery functional masterbatch of 3wt% (same as embodiment 4) , 3wt% carbon eight material (same as embodiment 4).

Mix the outer layer 1, outer layer 2 and core layer materials evenly according to the above ratio, then transport them to the storage tank, and send them to three single-screw extruders through pipelines for extrusion, and then extrude through three-layer co-extrusion dies To form a tube blank, the layered weight ratio of the tube blank is outer layer 1: core layer: outer layer 2 = 20:60:20, the screw diameter of the single screw extruder for the outer layer is 50mm, and the aspect ratio is 30:1. The extrusion temperature is 220°C, the screw diameter of the single-screw extruder for the core layer is 100mm, the aspect ratio is 30:1, the extrusion temperature is 220°C, and the extruded materials are merged at the three-layer co-extrusion die to form a tube blank , the temperature of the extrusion die is 223°C, and the extruded tube blank is drawn into the stretching oven after being cooled. The tube blank is stretched in a stretching oven filled with compressed air. The stretching temperature is 116°C, the transverse stretching ratio is 2.2-2.7, and the longitudinal stretching ratio is 2.2-2.7. A film with a thickness of 25 μm can be obtained, bidirectional The stretched film is forcibly cooled by the air ring, cut in half, wound up, and cut to obtain the final product, namely BOPE film L.

(2) Performance characterization of BOPE membrane

The performance characterization results of the BOPE film L prepared in this example are shown in Table 5 below.

table 5

Comparing the above Examples 4-6 with Comparative Examples 4-6, it can be seen that the tensile strength, tear strength and puncture resistance of BOPE films G, H and I are significantly better than BOPE films J, K, and L. In particular, the BOPE films G, H, and I formed by the copolymers A, B, and C prepared by the method of the present invention have very close longitudinal and transverse tensile strengths, and their longitudinal and transverse tensile strength ratios are respectively 1.071. . This is because the polyethylene produced by the method of the present invention has a high content of α-olefin monomer units, and among them, a high content of head-to-head connected α-olefin monomer units, and thus a high degree of branching. And among them, the B-octyl copolymer C with octene as the comonomer has the longest branch length, the degree of chain entanglement increases, and the ratio of longitudinal and transverse tensile strength is the lowest.

According to the film provided by the present invention, it has good tensile properties, high light transmittance, high self-adhesiveness, low haze, low density, light weight, improved properties such as tear resistance and puncture resistance, and has a wide range of properties. Application prospects.

Any reference to any numerical value in this invention includes all values in increments of one unit from the lowest value to the highest value if there is a separation of only two units between any lowest value and any highest value. For example, if the amount of one component of life, or the value of process variables such as temperature, pressure, time, etc., is 50-90, in this specification it means that 51-89, 52-88...and 69 Values such as -71 and 70-71. For non-integer values, 0.1, 0.01, 0.001 or 0.0001 may be considered as a unit as appropriate. These are just some specifically indicated examples. In the present application, in a similar manner, all possible combinations of values between the lowest value and the highest value enumerated are considered to have been disclosed.

It should be noted that the above-mentioned embodiments are only used to explain the present invention, and do not constitute any limitation to the present invention. The invention has been described with reference to typical embodiments, but the words which have been used therein are words of description and explanation rather than words of limitation. The present invention can be modified within the scope of the claims of the present invention as prescribed, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the invention described therein refers to specific methods, materials and examples, it is not intended that the invention be limited to the specific examples disclosed therein, but rather, the invention extends to all other methods and applications having the same function.

Claims (10)

1. a kind of preparation method of polyethylene film, comprises the following steps：

1）It is that the major catalyst in catalyst system is transported in reactor by carrier logistics with mixing liquid I, the mixed liquor Body I includes alkane, alkene and co-catalyst；Stream I II is obtained after supplementing raw material into the stream I I flowed out from reactor head, Stream I II is divided into stream I IIa and IIIb, stream I IIa and IIIb are back to sidepiece and the bottom of reactor respectively；Reacting It is aggregated to obtain ethene polymers and discharged from sidewall of reactor in device；Wherein, the alkene includes alpha-olefin and ethene, institute State the mol ratio of alpha-olefin and ethene in mixing liquid I and be at least 1；

2）By step 1）Obtained ethene polymers obtains polyethylene film by blow molding process.

2. according to the method described in claim 1, it is characterised in that the polyethylene film is that Biaxially-oriented polyethylene is thin Film.

3. according to the method for claim 1, it is characterised in that the mol ratio of alpha-olefin and ethene in the mixing liquid I For 1-5；In the mixing liquid, the mass percentage content of alkane is 5 %-80%；The mass flow of the mixing liquid I accounts for The 0.05%-5% of stream I I mass flow.

4. the method according to any one in Claims 2 or 3, it is characterised in that the reaction pressure in the reactor For 0.5-10MPa；Reaction temperature is 40-150 DEG C, and the apparent fluidizing gas velocity in the reactor is 0.1-10m/s, described anti- Answer in device comprising the reaction zone that temperature is different；The reactor is fluidized-bed reactor.

5. according to the method in claim 2 or 3, it is characterised in that in the stream I II, the molar percentage of alkene contains Measure as 1.0%-60.0%；The mole percent level of alkane is 0.5%-50.0%, in the stream I II, alpha-olefin molar concentration The 20%-60% of ethylene molar concentration is accounted for, conditioning agent and/or inert component are included in the stream I II；Wherein, the conditioning agent For hydrogen；The inert component is nitrogen；The mole percent level of the conditioning agent is 0.3%-14.5%；In the stream I I In, the mole percent level of the inert component is 25.0%-75.0%, and the charging of supplement alkane, benefit are included in the stream I II Fill at least one of conditioning agent charging and supplement inert component charging.

6. according to the method described in claim 5, it is characterised in that the alkane that the alkane in stream I IIa is accounted in stream I II The 60-90wt% of total amount；The 10-50wt% for the alkene total amount that alkene in stream I IIa is accounted in stream I II；Stream I I quality stream Amount accounts for more than the 90% of stream I II mass flow.

7. the method according to claim 1 or 3, it is characterised in that the alkane be selected from normal butane, iso-butane, pentane, At least one of isopentane, n-hexane, hexamethylene and heptane；The alpha-olefin be selected from propylene, 1- butylene, 1- amylenes, 1- oneself At least one of alkene, 1- octenes and 1- decene.

8. according to the method for claim 1, it is characterised in that the catalyst system includes metallocene catalyst and transition Metallic catalyst.

9. according to the method described in any one in claim 1-3, it is characterised in that in prepared ethene polymers, α- Molar content shared by olefin monomer unit is 1%-30%；Prepared ethene polymers has following characteristic：Density exists 0.890g/cm³To 0.922 g/cm³；Melt flow rate (MFR) under conditions of 230 DEG C and 2.16kg is 0.1-10g/10min, Weight average molecular weight is 20000-250000, molecular weight distributing index 2-15, longitudinal tensile strength MD and transverse tensile strength TD More than 15MPa, and its ratio MD/TD is less than 1.15, step 2）The longitudinal tensile strength MD and transverse direction of the polyethylene film of preparation Tensile strength TD ratio MD/TD is less than 1.1.

10. the polyethylene film that in claim 1-9 prepared by any one methods described is in packaging material and/or Commercial goods labelses Application.