Propylene / alpha-olefin copolymer as well as preparation method and application thereof

Abstract

The invention relates to a propylene / ethylene or propylene / alpha-olefin copolymer. The copolymer has the following characteristics: (a) the molecular weight Mw is 2.0 * 10 < 4 > g / mol to 40.0 * 10 < 4 > g / mol; (b) a density of from 0.860 to 0.890 g / cm < 3 >; (c) a molecular weight distribution, Mw / Mn, from 2.0 to 4.0; (d) Sigma Delta HT < = 4 J / g, continuously measured from nucleation / annealing (SSA) using a differential scanning calorimeter, where T represents the melting peak temperature of the segmented melting range measured by SSA, 85 DEG C < = T < = 120 DEG C; and sigma delta HT / delta H total is greater than or equal to 90%. The propenyl copolymer serving as an additive is used for a CPP cast film heat sealing layer, and the property of improving the tearing strength and the falling mark impact of a composite film material is shown due to the limited sigma delta HT.

Description

Technical Field

[0001] The present invention relates to a polyolefin elastomer material, and in particular to a propylene / alpha-olefin copolymer, a preparation method and application thereof. Background Art

[0002] Polypropylene is a kind of polyolefin material. It is transparent and light in appearance. It also has excellent chemical resistance, high temperature resistance, electrical insulation and wear resistance. It is widely used in food and drug packaging, automotive parts, clothing and daily necessities, fiber products and other related film fields. From the production process, common polypropylene packaging film materials can be divided into: extrusion cast film, biaxially oriented film and extrusion blown film. Among them, cast polypropylene film, namely CPP cast film, is a large category. It is a non-stretched, non-directional flat extruded film produced by melt casting and quenching. It has the characteristics of good transparency, high gloss, good stiffness, good moisture resistance and excellent heat resistance. The production process includes: feeding, batching and weighing, melt extrusion, thickness measurement, trimming, corona, traction, winding, slitting, packaging and warehousing.

[0003] Traditional CPP cast film can be divided into three or more layers according to its functionality: heat seal layer, core layer and corona layer. The base material of the core layer is mostly homopolymer polypropylene, and various elastomer materials are added to modify and toughen it to reduce brittleness and provide mechanical properties such as stiffness, tear resistance, tensile properties and toughness of the film. Appropriate mechanical properties can ensure the protective effect of the outer packaging material on the packaged items, ensuring that the items will not be scattered or damaged during transportation and transfer.

[0004] From the analysis of the mechanism of blending modification: when adding elastomer materials to homopolypropylene for blending, the microphase structure forms a "sea-island structure", in which homopolypropylene is the continuous phase and the elastomer is the dispersed phase. Among them, the continuous phase provides the mechanical properties related to the modulus of the material; and the introduction of the dispersed phase can reduce the crystallization of the continuous phase, improve the elasticity and impact resistance, etc. Generally speaking, the more uniform the particle size distribution of the dispersed phase and the smaller the particle size, the higher the toughening effect, which is especially obvious under low temperature conditions. On the contrary, if the blending effect is not good, the base material and the modified material will be microphase separated, the toughening effect will be greatly reduced, and the performance of the product will be affected. The modified material with good compatibility will also have greater "elasticity" in the adjustment of the blending formula, that is, adding fewer parts can achieve the same toughening effect and reduce costs.

[0005] In view of this, for polypropylene base materials, how to seek the best tear resistance and drop impact of polypropylene base material modification and the lowest cost through adjusting the composition and structure of the modified material has always been a hot issue in the research field. Summary of the invention

[0006] In order to solve the above problems, the present invention improves the heat sealing performance of the above polyolefin film by regulating the structure and composition of the polyolefin elastomer material, which can simultaneously reduce the sealing temperature and widen the heat sealing temperature range.

[0007] On the one hand: The present invention provides a copolymer of propylene / ethylene or propylene / α-olefin, wherein the copolymer has the following characteristics:

[0008] (a) Molecular weight Mw: 2.0×10 4 g / mol~40.0×10 4 g / mol;

[0009] (b) Density: 0.860 to 0.890 g / cm 3 ;

[0010] (c) molecular weight distribution Mw / Mn: 2.0 to 4.0;

[0011] (d) ∑ΔH measured using differential scanning calorimetry with continuous self-nucleation / annealing (SSA) T ≤4J / g, where T represents the melting peak temperature of the segmented melting range measured by SSA, 85℃≤T≤120℃; and ∑ΔH T / ΔH 总 ≥90%.

[0012] Generally, the molecular weight of a polymer is affected by many factors. For example, the molecular weight of a polymer can be regulated within a wide range by adjusting the temperature of the conditional polymerization reaction. For a given polymerization temperature condition, for a copolymer, adjusting the type and amount of monomer added will also affect the molecular weight of the polymer. To a greater extent, for different catalytic systems, under the same monomer ratio and polymerization temperature and other process conditions, the molecular weight of the polymer product will also vary greatly, and the range of Mw may be from several thousand, tens of thousands or even millions. Furthermore, different molecular weights will affect the processing properties of the polymer and the mechanical properties of the finished product. In the present invention, the weight average molecular weight (Mw) and number average molecular weight (Mn) are polystyrene-converted molecular weights analyzed by gel permeation chromatography (GPC), and the molecular weight distribution can be calculated by the ratio of Mw / Mn.

[0013] Preferably, the weight average molecular weight of the propylene / ethylene or propylene / α-olefin copolymer is in the range of 3×10 4 g / mol~35.0×10 4 g / mol; preferably, the weight average molecular weight range of the propylene / ethylene or propylene / α-olefin copolymer is 3×10 4 g / mol~30.0×10 4 g / mol;

[0014] Preferably, the molecular weight distribution range of the propylene / ethylene or propylene / α-olefin copolymer is 2.5 to 3.5.

[0015] It is also worth mentioning that the copolymer of the present invention is a copolymer of propylene / ethylene or propylene / α-olefin. It should be particularly noted that most of the constituent units in the polymer are derived from propylene.

[0016] Preferably, the propylene / ethylene or propylene / α-olefin copolymer contains 50% to 97% by mole of units derived from propylene and 3% to 50% by mole of units derived from ethylene or α-olefin;

[0017] Preferably, the propylene / ethylene or propylene / α-olefin copolymer contains 60% to 90% by mole of units derived from propylene and 10% to 40% by mole of units derived from ethylene or α-olefin;

[0018] Preferably, the propylene / ethylene or propylene / α-olefin copolymer contains 70% to 90% by mole of units derived from propylene and 10% to 30% by mole of units derived from ethylene or α-olefin;

[0019] Preferably, the propylene / ethylene or propylene / α-olefin copolymer contains 80% to 90% by mole of units derived from propylene and 10% to 20% by mole of units derived from ethylene or α-olefin;

[0020] Preferably, the α-olefin monomer is a C4-20 olefin-based monomer. It is worth noting that for specific examples, one or more of 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-decene may be included, and in specific embodiments, ethylene and α-olefins may be included at the same time.

[0021] Preferably, the comonomer other than propylene in the propylene / ethylene or propylene / α-olefin copolymer is preferably one or more of ethylene, 1-hexene or 1-octene;

[0022] Preferably, the comonomer other than propylene in the propylene / ethylene or propylene / α-olefin copolymer is preferably ethylene.

[0023] In general, the density of olefin-based polymers is affected by the type and amount of monomers used during polymerization, the degree of polymerization, etc., and the copolymer is greatly affected by the amount of comonomer. With the increase of comonomer, propylene / ethylene or propylene / α-olefin copolymers with low density can be prepared, and the type and amount of comonomer that can be introduced into the copolymer depends largely on the copolymerization performance of the catalyst system.

[0024] In the present invention, the polymer density test method is the test method of ASTM D792-2021. Preferably, the density range of the propylene / ethylene or propylene / α-olefin copolymer of the present invention is 0.860 g / cm 3 Up to 0.885g / cm 3 ;

[0025] Preferably, the density range of the propylene / ethylene or propylene / α-olefin copolymer of the present invention is 0.860 g / cm 3 Up to 0.880g / cm 3 .

[0026] In addition, unless otherwise specified, in the present invention, a differential scanning calorimeter (DSC) is used to measure the crystallization temperature and melting temperature of propylene / ethylene or propylene / α-olefin copolymers. The test process is described as follows: first, the copolymer is heated to 200°C, maintained for 5 minutes, the thermal history is eliminated, then cooled to -60°C, and then heated again, and the temperature is raised to 200°C. The rate of increase and the rate of decrease during the entire test process are controlled to be 10°C / min, respectively, and the measurement result during the second temperature increase is calibrated as the melting temperature, and the measurement result during the third temperature reduction is calibrated as the crystallization temperature.

[0027] The propylene / ethylene or propylene / α-olefin copolymer according to an embodiment of the present invention has a crystallization temperature (Tc) of 10° C. to 110° C.;

[0028] Preferably, the crystallization temperature of the propylene / ethylene or propylene / α-olefin copolymer of the present invention is in the range of 10°C to 100°C;

[0029] Preferably, the crystallization temperature of the propylene / ethylene or propylene / α-olefin copolymer of the present invention is in the range of 10°C to 90°C.

[0030] As mentioned above, in the present invention, a large amount of comonomers (ethylene or alpha-olefins) can be introduced using a catalytic system of a transition metal compound. As a result, as mentioned above, the propylene / ethylene or propylene / alpha-olefin copolymer according to an embodiment of the present invention has a suitable molecular weight Mw, density and molecular weight distribution. The olefin copolymer can be prepared using a catalyst composition of a metallocene or non-metallocene transition metal compound. Wherein, the metallocene or non-metallocene transition metal compound can be selected from any one of the following compounds:

[0031]

[0032] It should be noted that the metallocene or non-metallocene transition metal compounds of the present invention are not limited to the above examples.

[0033] Meanwhile, in the preparation of propylene / ethylene or propylene / α-olefin copolymers according to an embodiment of the present invention, the catalytic system may further comprise a co-catalyst for activating the above metallocene or non-metallocene transition metal compound, wherein the co-catalyst is one or more of the substances having the following chemical formula.

[0034] Chemical formula R 17 -[Al(R 18 )-O] n -R 19 , R 17 , R 18 and R 19 Each is independently any one of hydrogen, halogen, a hydrocarbon group having 1 to 20 carbon atoms, and a hydrocarbon group having 1 to 30 carbon atoms substituted by a halogen, and n is an integer greater than 2;

[0035] Chemical formula D(R 20 )3, D is aluminum or boron, R 20 Each is independently any one of a halogen, a hydrocarbon group having 1 to 20 carbon atoms, and a hydrocarbon group having 1 to 20 carbon atoms substituted by a halogen;

[0036] Chemical formula [LH] + [Z(A)4] - or [L] + [Z(A)4] - , L is a neutral or cationic Lewis base, H is a hydrogen atom, Z is a Group 13 element, and A is each independently a hydrocarbon group having 1 to 20 carbon atoms; a hydrocarbonoxy group having 1 to 20 carbon atoms; and a substituent in which at least one hydrogen atom of the above substituent is substituted with at least one substituent of halogen, a hydrocarbonoxy group having 1 to 20 carbon atoms, and a hydrocarbon silyl group having 1 to 20 carbon atoms.

[0037] More particularly, the co-catalyst is of the formula R 17 -[Al(R 18 )-O] n -R 19 A compound of the type described herein is preferably an alkylaluminoxane-based compound such as methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane or tert-butylaluminoxane.

[0038] In addition, the chemical formula D(R 20)3 may include trimethylaluminum, triethylaluminum, triisobutylaluminum, tripropylaluminum, tributylaluminum, dimethylaluminum chloride, triisopropylaluminum, tri-sec-butylaluminum, tricyclopentylaluminum, tripentylaluminum, triisopentylaluminum, trihexylaluminum, trioctylaluminum, ethyldimethylaluminum, methyldiethylaluminum, triphenylaluminum, tri-p-tolylaluminum, dimethylmethoxyaluminum, dimethylethoxyaluminum, trimethylboron, triethylboron, triisobutylboron, tripropylboron or tributylboron, and in particular, may be selected from trimethylaluminum, triethylaluminum or triisobutylaluminum.

[0039] In addition, the chemical formula [LH] + [Z(A)4] - or [L] + [Z(A)4] -The compounds include trisubstituted ammonium salt, dialkylammonium salt or trisubstituted phosphonium salt type borate-based compounds. More specific examples include trisubstituted ammonium salt type borate-based compounds, such as trimethylammonium tetraphenylborate, methyldi(octadecyl)ammonium tetraphenylborate, triethylammonium tetraphenylborate, tripropylammonium tetraphenylborate, tri(n-butyl)ammonium tetraphenylborate, methyltetradecyloctadecylammonium tetraphenylborate, N,N-dimethylanilinium tetraphenylborate, N,N-diethylanilinium tetraphenylborate, N,N-dimethyl(2,4,6-trimethylanilinium)tetraphenylborate, trimethylammonium tetra(pentafluorophenyl)borate, Methyldi(tetradecyl)ammoniumtetra(pentafluorophenyl)borate, methyldi(octadecyl)ammoniumtetra(pentafluorophenyl)borate, triethylammoniumtetra(pentafluorophenyl)borate, tripropylammoniumtetra(pentafluorophenyl)borate, tri(n-butyl)ammoniumtetra(pentafluorophenyl)borate, tri-sec-butylammoniumtetra(pentafluorophenyl)borate, N,N-dimethylaniliniumtetra(pentafluorophenyl)borate, N,N-diethylaniliniumtetra(pentafluorophenyl)borate, N,N-dimethyl(2,4,6-trimethylaniliniumtetra(pentafluorophenyl)borate, trimethylammoniumtetra(2, 3,4,6-tetrafluorophenyl) borate, triethylammonium tetra(2,3,4,6-tetrafluorophenyl) borate, tripropylammonium tetra(2,3,4,6-tetrafluorophenyl) borate, tri(n-butyl)ammonium tetra(2,3,4,6-tetrafluorophenyl) borate, dimethyl(tert-butyl)ammonium tetra(2,3,4,6-tetrafluorophenyl) borate, N,N-dimethylanilinium tetra(2,3,4,6-tetrafluorophenyl) borate, N,N-diethylanilinium tetra(2,3,4,6-tetrafluorophenyl) borate, N,N-dimethyl-(2,4,6 -trimethylanilinium)tetrakis(2,3,4,6-tetrafluorophenyl)borate, etc.; dialkylammonium salt-type borate-based compounds, such as dioctadecylammoniumtetrakis(pentafluorophenyl)borate, ditetradecylammoniumtetrakis(pentafluorophenyl)borate, dicyclohexylammoniumtetrakis(pentafluorophenyl)borate, etc.; or trisubstituted phosphonium salt-type borate-based compounds, such as triphenylphosphoniumtetrakis(pentafluorophenyl)borate, methyldioctadecylphosphoniumtetrakis(pentafluorophenyl)borate, tris(2,6-dimethylphenyl)phosphoniumtetrakis(pentafluorophenyl)borate, etc.

[0040] In addition, during the polymerization reaction, an organic aluminum compound may be optionally injected into the reactor to remove moisture, and the polymerization reaction may be carried out in the presence of the compound. Specific examples of such organic aluminum compounds may include trialkylaluminum, dialkylaluminum halides, alkylaluminum dihalides, dialkylaluminum hydrides or alkylaluminum sesquihalides, and more specific examples may include Al(C2H5)3, Al(C2H5)2H, Al(C3H7)3, Al(C3H7)2H, Al(i-C4H9)2H, Al(C8H 17 )3、Al(C12 H 25 )3、Al(C2H5)(C 12 H 25 )2、Al(i-C4H9)(C 12 H 25 )2, Al(i-C4H9)2H, Al(i-C4H9)3, (C2H5)2AlCl, (i-C3H9)2AlCl or (C2H5)3Al2Cl3. Such an organoaluminum compound may be continuously injected into the reactor, and in order to properly remove impurities such as water and oxygen, the organoaluminum compound may be injected at a ratio of about 0.1 to 10 mol / 1 kg of the reaction medium injected into the reactor.

[0041] In some embodiments, the propylene / ethylene or propylene / α-olefin copolymer is obtained by polymerizing propylene with one or more of ethylene or α-olefin in one or more polymerization reactors;

[0042] In some embodiments, the polymerization reactor is one or more of a non-stirred or stirred cylindrical vessel, a tank vessel, and a circulating loop reactor;

[0043] In some embodiments, when the polymerization reactor type is a stirred cylindrical container or a tank container, by adjusting the aspect ratio or circulation ratio of the reactor, the material entering the reactor will have a temperature distribution and a concentration distribution, thereby further achieving the adjustment of the composition and structure of the polymer generated in different temperature zones in the microscopic region, and ultimately achieving the generation of polymers with specific properties as described in the present invention.

[0044] In some embodiments, when the polymerization reactor type is a circulating loop reactor, by adjusting the ratio of the circulation volume per unit time of the reactor circulation pump to the reactor volume, that is, the circulation ratio, the composition and structure of the polymer generated in different temperature zones in the microscopic region can be further adjusted, and ultimately the generation of polymers with specific properties as described in the claims can be achieved.

[0045] In some embodiments, the reaction temperature of the polymerization reaction is 20°C to 200°C, preferably the polymerization temperature range is 50°C to 200°C, more preferably the polymerization temperature range is 70°C to 180°C, more preferably the polymerization temperature range is 90°C to 180°C, and more preferably the polymerization temperature range is 110°C to 180°C.

[0046] In some embodiments, the polymerization pressure is 10 bar to 100 bar, preferably 10 bar to 80 bar, more preferably 30 bar to 80 bar, and more preferably 30 bar to 60 bar.

[0047] Preferably, the density range of the propylene / ethylene or propylene / α-olefin copolymer of the present invention is 0.860 g / cm 3 Up to 0.880g / cm 3 .

[0048] In some embodiments, when the polymerization reactor is a stirred cylindrical container or a tank container, the length-to-diameter ratio of the reactor is 5:1 to 20:1, preferably 5:1 to 10:1.

[0049] In some embodiments, when the polymerization reactor is a circulating loop reactor, the circulation ratio of the reactor is 100 to 1000, preferably 10:1 to 80:1.

[0050] It should be noted that the feeding order of the polymerization reaction is as follows:

[0051] ① First, introduce the solvent into the reaction system;

[0052] ② The mixed flow of propylene, ethylene and C6 isoparaffin solvent is uniformly mixed in the mixer in advance, and then passed through the cooler and then into the reactor.

[0053] ③ When the concentration in the reactor is uniform and stable, a mixed flow of the main catalyst and the co-catalyst that have been pre-mixed in the mixer is introduced into the reactor to initiate the polymerization reaction.

[0054] The beneficial effect of the present invention is that the propylene-based copolymer of the present invention is used as an additive for the heat-sealing layer of the CPP cast film, and due to the limited ∑ΔH T It shows the property of improving the tear strength and drop impact of the composite film. DETAILED DESCRIPTION

[0055] Example

[0056] Catalyst synthesis example: For the synthesis of similar structures of catalyst I, please refer to patents US20040014950A1, CN116554378A, CN114230702B, CN116212960A and literature J.Am.Chem.Soc.2010,132,5566-5567, etc.; for the synthesis of catalyst II, please refer to patents US6057408A, CN117777183A and literature J.Am.Chem.Soc.1998,120,2308-2321 and Organometallics 1994,13,954-963, etc.

[0057] The following polymerization examples use a main catalyst structure of Zr-4.

[0058] Polymerization example: A small-scale continuous polymerization reaction device was used for polymerization experiments. The polymerization reaction was in the form of solution polymerization. The reaction unit was a polymerization reaction in which multiple reactors were connected in series. The reactor volume was 500 mL, the aspect ratio was 5:1, and the device had a full-load capacity of 1 kg polymer / hour. Before the reaction started, the reactor and the pipeline jacket of the continuous polymerization reaction device were heated to 150°C, and the reactor was started to stir and heat up. After the temperature was raised to the corresponding set temperature, the feed pump was started to start the feeding oil transportation of Isohexanes, and the feed rate was 5.0 L / h. The purpose of the oil transportation is to rinse the residual polymers and other impurities in the polymerization reactor and the material conveying pipeline, and the oil transportation was completed in half an hour. The feed rate of the solvent was adjusted to 2.6L / h, the feed rate of propylene to 1350g / h, the feed rate of ethylene to 60g / h, the feed rate of the main catalyst Zr-4 to 7.0umol / h, the cocatalyst 1 was triisobutylaluminum (TIBA), diluted 120 times, the Al / M ratio was 500, the cocatalyst 2 was N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, diluted 120 times, the B / M ratio was 1.3, and the reaction pressure was 3Mpa. When the temperature was stable, the main catalyst was added to initiate the polymerization. When the polymerization reaction was stable, the polymer that had been quenched and deactivated and flashed was collected and characterized.

[0059] The density of the polymer was measured according to ASTM D-792; the melt index (MI) of the polymer was measured according to ASTM D-1238 (190° C., load 2.16 kg); the melting temperature (Tm) of the polymer was obtained using a differential scanning calorimeter (DSC) 6000 manufactured by PerkinElmer. That is, after the temperature was raised to 200° C., it was maintained at the temperature for 1 minute, then lowered to −100° C., and the temperature was raised again to obtain the top of the DSC curve as the melting point. At this time, the rate of temperature increase and decrease was 10°C / min, and the melting point was obtained during the second temperature increase; weight average molecular weight (Mw, g / mol) and molecular weight distribution (MWD) were measured by gel permeation chromatography (GPC) to measure the number average molecular weight (Mn) and weight average molecular weight (Mw), respectively, and the molecular weight distribution was calculated by dividing the weight average molecular weight by the number average molecular weight, chromatographic column: PL Olexis, solvent: trichlorobenzene (TCB), flow rate: 1.0 ml / min, sample concentration: 1.0 mg / ml, injection volume: 200 μl, column temperature: 160°C, detector: Agilent high temperature RI detector, standard: polystyrene (calibrated using a cubic function).

[0060] [Table 1]

[0061]

[0062]

[0063] * Example 7 Comonomer is propylene / 1-octene copolymer

[0064] [Table 2]

[0065]

[0066] * T represents the melting peak temperature of the segmented melting range measured by SSA, 85°C≤T≤120°C; Example 7 The comonomer is propylene / 1-octene copolymer

[0067] Table 1 shows the process conditions of continuous polymerization reaction, and Table 2 shows the results of characterization of basic properties of corresponding polymerization samples. It can be seen that by adjusting the C3 / C2 monomer ratio and polymerization temperature, the density of the polymer varies from 0.861 g / cm^3 to 0.871 g / cm^3. 3 , the density belongs to the typical range of polyolefin elastomer materials. Overall, the melt index is inversely proportional to Mw; the polymer product always maintains a narrow distribution, PDI <3; the ethylene insertion rate (wt%) is inversely proportional to the C3 / C2 monomer ratio, that is, the more C2 is added to the monomer, the higher the ethylene insertion rate (wt%) of the polymer sample, and vice versa; under all polymerization conditions, γ (%) is greater than 90, which is significantly different from Comparative Examples 1 and 2, with γ (%) of 60 and 7 respectively.

[0068] [Table 3]

[0069]

[0070]

[0071] The propylene-based copolymer of the present invention is used as an additive for the heat-sealing layer of a CPP cast film. T It shows the properties of improving the tear strength and drop impact of the composite film.

[0072] As shown in Table 3, the CPP cast film base material is Yanshan Petrochemical ternary copolymer polypropylene F5606, and 15% of each polymer prepared in Examples 1 to 7 and Comparative Examples 1 and 2 is blended with 85% of the cast film base material F5606 and extruded into a film. The tear strength and dart drop impact performance of each film material are tested. It can be seen that the addition of the elastomeric material in Examples 1 to 7 can effectively improve the tear strength and dart drop impact properties of the composite film material.

[0073] By comparing Example 1, Example 2 and Example 3 in Table 3, it can be concluded that increasing the ethylene composition in the polymerization product can more effectively improve the tear strength and dart drop impact of the substrate, but on the other hand, it is speculated that too high a comonomer composition will make the composite film "soft", affecting the processing performance and rigidity; by comparing Example 1, Example 4, Example 5 and Example 6 in Table 3, it can be concluded that increasing the molecular weight of the polymerization product can also effectively improve the tear strength and dart drop impact of the substrate.

[0074] Comparing Example 1, Comparative Example 1 and Comparative Example 2 in Table 3, the tear strength and drop impact of the composite film material of the comparative example are significantly reduced, even lower than that of the base material. T / ΔH 总 When the content of propylene / ethylene or propylene / α-olefin is less than 90%, the melting range of the copolymer of propylene / ethylene or propylene / α-olefin becomes wider, further affecting the performance of the composite film at room temperature.

Claims

1. A copolymer of propylene / ethylene or propylene / α-olefin, wherein the copolymer has the following characteristics: (a) Molecular weight Mw: 2.0×10 4 g / mol~40.0×10 4 g / mol; (b) Density: 0.860 to 0.890 g / cm 3 ; (c) molecular weight distribution Mw / Mn: 2.0 to 4.0; (d) ∑ΔH measured using differential scanning calorimetry with continuous self-nucleation / annealing (SSA) T ≤4J / g, where T represents the melting peak temperature of the segmented melting range measured by SSA, 85℃≤T≤120℃; and ∑ΔH T / ΔH 总 ≥90%.

2. The copolymer according to claim 1, characterized in that The weight average molecular weight of the propylene / ethylene or propylene / α-olefin copolymer is in the range of 3×10 4 g / mol~35.0×10 4 g / mol; preferably 3×10 4 g / mol~30.0×10 4 g / mol; and / or, the molecular weight distribution range of the propylene / ethylene or propylene / α-olefin copolymer is 2.5 to 3.

5.

3. The copolymer according to claim 1 or 2, characterized in that The propylene / ethylene or propylene / α-olefin copolymer contains 50% to 97% mol% of propylene-derived units and 3% to 50% mol% of ethylene or α-olefin-derived units, preferably 60% to 90% mol% of propylene-derived units and 10% to 40% mol% of ethylene or α-olefin-derived units, more preferably 70% to 90% mol% of propylene-derived units and 10% to 30% mol% of ethylene or α-olefin-derived units, and most preferably 80% to 90% mol% of propylene-derived units and 10% to 20% mol% of ethylene or α-olefin-derived units.

4. The copolymer according to any one of claims 1 to 3, characterized in that The α-olefin monomer is a C4-20 olefin-based monomer, for example, one or more of 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-decene.

5. The copolymer according to any one of claims 1 to 4, characterized in that The crystallization temperature and melting temperature of propylene / ethylene or propylene / α-olefin copolymers were measured using a differential scanning calorimeter (DSC), and the test process was as follows: the copolymer was first heated to 200°C, held for 5 minutes to eliminate the thermal history, then cooled to -60°C, and then heated again to 200°C. The rate of increase and rate of decrease during the entire test were controlled at 10°C / min, respectively, and the measurement result during the second temperature increase was calibrated as the melting temperature, and the measurement result during the third temperature decrease was calibrated as the crystallization temperature.

6. The method for preparing a copolymer of propylene / ethylene or propylene / α-olefin according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: polymerizing propylene and one or more of ethylene or α-olefin in one or more polymerization reactors.

7. The preparation method according to claim 6, characterized in that: The method is carried out in the presence of a catalytic system of a transition metal compound, wherein the transition metal compound is selected from any one of the following compounds:

8. The preparation method according to claim 6 or 7, characterized in that: The method is carried out in the presence of a co-catalyst, which is one or more substances having the following chemical formula: Chemical formula R 17 -[Al(R 18 )-O] n -R 19 , R 17 , R 18 and R 19 Each is independently any one of hydrogen, halogen, a hydrocarbon group having 1 to 20 carbon atoms, and a hydrocarbon group having 1 to 30 carbon atoms substituted by a halogen, and n is an integer greater than 2; Chemical formula D(R 20 )3, D is aluminum or boron, R 20 Each is independently any one of a halogen, a hydrocarbon group having 1 to 20 carbon atoms, and a hydrocarbon group having 1 to 20 carbon atoms substituted by a halogen; Chemical formula [LH] + [Z(A)4] - or [L] + [Z(A)4] - , L is a neutral or cationic Lewis base, H is a hydrogen atom, Z is a Group 13 element, and A is each independently a hydrocarbon group having 1 to 20 carbon atoms; a hydrocarbonoxy group having 1 to 20 carbon atoms; and a substituent in which at least one hydrogen atom of the above substituent is substituted with at least one substituent of halogen, a hydrocarbonoxy group having 1 to 20 carbon atoms, and a hydrocarbon silyl group having 1 to 20 carbon atoms.

9. The preparation method according to any one of claims 6 to 8, characterized in that: The polymerization reactor is one or more of a non-stirred or stirred cylindrical container, a tank container and a circulating loop reactor.

10. The preparation method according to any one of claims 6 to 9, characterized in that: When the polymerization reactor is a stirred cylindrical container or a tank container, the length-to-diameter ratio of the reactor is 5:1 to 20:1, preferably 5:1 to 10:1; and / or when the polymerization reactor is a circulating loop reactor, the circulation ratio of the reactor is 100 to 1000, preferably 10:1 to 80:1.

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