Propylene / alpha-olefin copolymers, process for their preparation and use

Abstract

The application relates to the technical field of polymer synthesis and processing, in particular to a propylene / alpha-olefin copolymer and a preparation method and application thereof, so as to solve the problems that the melting temperature of the propylene / alpha-olefin copolymer is high, the melting range is narrow, and the toughness and strength of the heat-sealing material cannot be effectively balanced in the prior art. The propylene / alpha-olefin copolymer has a melting peak temperature of 40 DEG C to 90 DEG C and a melting range width of 40 DEG C to 80 DEG C, and the melting peak number n(peak) and dH(100) of the propylene / alpha-olefin copolymer satisfy the following conditions: 6 <= n(peak) <= 20, and dH(100)=0.

Description

Technical Field

[0001] This application relates to the field of polymer synthesis and processing technology, and in particular to a propylene / α-olefin copolymer, its preparation method and application. Background Technology

[0002] Polymers obtained by copolymerizing propylene with α-olefins possess excellent properties such as high elasticity, high transparency, and good low-temperature toughness, making them an important direction for the development of high-end polyolefin materials. In particular, propylene / α-olefin copolymers have good compatibility with polypropylene and are used to modify polypropylene products. For example, propylene / α-olefin copolymers are often used in polypropylene heat-sealing materials to enhance their low-temperature toughness.

[0003] However, current propylene / α-olefin copolymers have relatively high melting temperatures. When applied to polypropylene heat-sealing materials, this results in long cooling and sealing times during the heat-sealing process. Furthermore, the narrow melting range of propylene / α-olefin copolymers easily leads to wrinkling and stringing at the seal, resulting in poor heat sealing. In addition, the insertion rate of α-olefins in the propylene / α-olefin copolymer affects the toughness and strength of the heat-sealing material. Balancing these two aspects is a pressing issue that needs to be addressed. Summary of the Invention

[0004] Based on this, some embodiments of this application provide a propylene / α-olefin copolymer, its preparation method, and its application, to solve the problems in the related art, such as the high melting temperature and narrow melting range of propylene / α-olefin copolymers, and the inability to effectively balance the toughness and strength of heat-sealing materials.

[0005] In the first aspect, a propylene / α-olefin copolymer is provided, wherein the melting peak temperature of the propylene / α-olefin copolymer is 40℃~90℃, the melting range is 40℃~80℃, and the melting peak number n(peak) and dH(100) of the propylene / α-olefin copolymer satisfy: 6≤n(peak)≤20, dH(100)=0.

[0006] The melting peak temperature, melting range, number of melting peaks n(peak) and dH(100) of the propylene / α-olefin copolymer can all be measured using a differential scanning calorimeter (DSC).

[0007] n(peak) represents the number of melting peaks. In continuous self-nucleating / annealing SSA measurements using a differential scanning calorimeter, when the heat capacity of each segment is graded relative to the total heat capacity by integrating the temperature-heat capacity curves of different segments of the polymer, n(peak) represents the number of melting peaks in the SSA measurement results, and dH(100) represents the sum of melting enthalpies above 100°C.

[0008] Therefore, n(peak) reflects regions in a polymer that have different crystallization morphologies or varying degrees of crystallization perfection. In the same polymer, differences in polymer chain segment structure can lead to multiple melting peaks. For example, in propylene / α-olefin copolymers, the polypropylene segment and the polyα-olefin segment have different crystallization characteristics, resulting in melting peaks corresponding to the crystallization of these two segments respectively. Similarly, in multiple copolymer segments of propylene and α-olefin, copolymer segments with different α-olefin insertion rates also have different crystallization characteristics, resulting in multiple melting peaks corresponding to different copolymer segments.

[0009] The melting point of each copolymer segment varies depending on the insertion rate of the α-olefin in different copolymer segments. For example, the lower the insertion rate of the α-olefin in a segment, the higher its melting point, and vice versa.

[0010] In the embodiments of this application, the larger n(peak) is, the more segments with different crystallization characteristics there are in the polymer, that is, the more segments with different α-olefin insertion rates there are in the polymer. In other words, the propylene / α-olefin copolymer has multiple segments with different α-olefin insertion rates. Correspondingly, the melting range of the polymer is also larger. dH(100) reflects the sum of the melting enthalpy of the polymer above 100°C. dH(100)=0 indicates that the heat absorbed and released by the changes in intermolecular forces and the transition between crystalline and amorphous states in the polymer at 100°C cancels each other out. There is no transition between crystalline and amorphous states, and the polymer has a lower melting peak temperature.

[0011] In the propylene / α-olefin copolymer provided in the embodiments of this application, the propylene / α-olefin copolymer has a low melting peak temperature, dH(100)=0. Therefore, the propylene / α-olefin copolymer does not have a high crystallinity peak, and thus it is easier to melt. When applied to heat-sealing materials, it can effectively reduce the heat-sealing temperature and improve the heat-sealing efficiency. At the same time, since the propylene / α-olefin copolymer has a large melting range and 6≤n(peak)≤20, it indicates that the propylene / α-olefin copolymer has multiple segments with different α-olefin insertion rates. When applied to heat-sealing materials, it can effectively shorten the cooling and sealing time during the heat-sealing process and reduce phenomena such as sealing wrinkles and stringing, thereby reducing heat-sealing defects.

[0012] Furthermore, when this propylene / α-olefin copolymer is applied to heat-sealing materials, the segments with lower melting points among the multiple segments of the propylene / α-olefin copolymer with different α-olefin insertion rates can have a better toughening effect, while the segments with higher melting points among the multiple segments with different α-olefin insertion rates can increase the compatibility between the propylene / α-olefin copolymer and the base material such as polypropylene, reducing the impact on the strength of the heat-sealing material. Therefore, the toughness and strength of the heat-sealing material can be effectively balanced. In summary, when this propylene / α-olefin copolymer is applied to heat-sealing materials, the overall performance of the heat-sealing material can be effectively improved.

[0013] Optionally, the propylene / α-olefin copolymer satisfies at least one of the following conditions:

[0014] (1) The density of the propylene / α-olefin copolymer is 0.840 g / cm³. 3 ~0.880g / cm 3 ;

[0015] (2) The weight-average molecular weight of the propylene / α-olefin copolymer is 100,000 g / mol ~ 300,000 g / mol;

[0016] (3) The molecular weight distribution width (PDI) of the propylene / α-olefin copolymer is 2.0~3.5;

[0017] (4) The melting enthalpy of the propylene / α-olefin copolymer is 10 J / g ~ 100 J / g;

[0018] (5) The melt index of the propylene / α-olefin copolymer at 230℃ and 2.16kg load is 1.0 g / 10min ~ 50.0 g / 10min;

[0019] (6) The glass transition temperature (Tg) of the propylene / α-olefin copolymer is -35℃ to -15℃;

[0020] (7) The α-olefin in the propylene / α-olefin copolymer is selected from C2~C4. 20 At least one of the olefins;

[0021] (8) The mass fraction of α-olefin in the propylene / α-olefin copolymer is 5%~25%.

[0022] Secondly, a method for preparing a propylene / α-olefin copolymer is provided, comprising:

[0023] A reactor assembly is provided, comprising: a multi-stage reactor connected in series, each stage reactor having a reactant inlet and a reactant outlet disposed opposite to each other along the axial direction of the reactor, the reactant outlet of the preceding stage reactor communicating with the reactant inlet of the following stage reactor, the aspect ratio of each stage reactor being less than or equal to 3, and at least two stages of the multi-stage reactor having different aspect ratios and / or volumes; wherein, the aspect ratio of each stage reactor is equal to the ratio of a first dimension and a second dimension, the first dimension being the dimension between the reactant inlet and the reactant outlet of the reactor, and the second dimension being the radial dimension of the reactor;

[0024] Multiple batches of reactants are controlled to be fed into reactors at different stages, and the different batches of reactants are controlled to polymerize with the reaction products of the previous reactor in each stage of the reactor in a sequential manner to prepare the propylene / α-olefin copolymer; and

[0025] The propylene / α-olefin copolymer prepared in the last stage reactor is quenched and devolatilized to obtain the propylene / α-olefin copolymer.

[0026] Each batch of the reactants includes at least: propylene monomer, α-olefin monomer, solvent and catalyst.

[0027] For reactors with a large aspect ratio, the mixing and mass transfer are efficient, resulting in a relatively uniform distribution of temperature, catalyst, and monomer concentrations within the reactor. The polymerization environment at the active sites is essentially consistent, leading to more homogeneous polymer products. Conversely, for reactors with a small aspect ratio, the mixing, mass transfer, and heat transfer efficiency are relatively poor, and there is an uneven distribution of monomer proportions within the reactor. This allows for the preparation of polymer segments with multiple different α-olefin insertion rates, enabling the construction of polymer segments with varying crystallinity within the polymer molecular chain. This results in polymers with a larger number of melting peaks (n), thus increasing the melting range of the propylene / α-olefin copolymer.

[0028] The residence time of the reactants in the reactor is equal to the reactor volume divided by the reactant flow rate. Therefore, for reactors of different volumes, a larger reactor volume results in a longer residence time of the reactants, leading to a greater number of chain segments and / or molecular chains; conversely, a smaller reactor volume results in a shorter residence time, leading to fewer chain segments and / or molecular chains. Since the aspect ratio of each reactor stage is less than or equal to 3, a non-uniform distribution of monomer proportions can be achieved, thereby preparing polymer segments with multiple different α-olefin insertion rates. This allows for the construction of polymer segments with different crystallinity within the polymer molecular chain, resulting in polymers with a larger number of melting peaks (n), thus increasing the melting range of the propylene / α-olefin copolymer.

[0029] In this process, the propylene monomer, solvent, and co-catalyst contained in each batch of reactants can be pre-mixed evenly before being fed into each stage of the reactor. The remaining raw materials are fed into each stage of the reactor through separate feed pipelines, so that each batch of reactants can be reacted under certain temperature and pressure after entering each stage of the reactor.

[0030] When corresponding batches of reactants are introduced into each stage of the reactor, the reaction product obtained by polymerization of the previous batch of reactants in the previous stage reactor can be the first segment. It can continue to react with the reactants of this batch in the current stage reactor to generate another segment, such as the second segment. When the aspect ratio and / or volume of the previous stage reactor and the subsequent stage reactor are different, the arrangement of the first segment and the second segment and the insertion rate of α-olefin will be different. By controlling the aspect ratio of each stage reactor to be small, the random insertion degree of α-olefin distribution in each stage reactor can be improved, thereby enabling the preparation of propylene / α-olefin copolymers with low melting peak temperature, large n(peak), and wide melting range.

[0031] In the preparation method of propylene / α-olefin copolymer provided in the embodiments of this application, since the aspect ratio of each stage reactor in the reactor group is less than or equal to 3, the monomer ratio in the reactants fed into different reactors can be unevenly distributed, thereby increasing the random insertion degree of α-olefin in the propylene / α-olefin copolymer. At the same time, by controlling the aspect ratio and / or volume of at least two stages of reactors to be different, the insertion rate and / or segment length of α-olefin in different segments of the reactants in each stage reactor can be effectively controlled, thereby further increasing the random insertion degree of α-olefin in the propylene / α-olefin copolymer, increasing the number of melting peaks and the melting range of the propylene / α-olefin copolymer, and thus preparing a propylene / α-olefin copolymer with low melting peak temperature, no high crystallinity peak, and a large melting range. After the propylene / α-olefin copolymer is prepared, the reaction can be terminated in time by quenching and devolatilization treatment of the propylene / α-olefin copolymer, thereby avoiding the introduction of highly crystalline polymer segments into the propylene / α-olefin copolymer and thus controlling the dH(100)=0 of the propylene / α-olefin copolymer.

[0032] In some embodiments, the length-to-diameter ratio of each reactor stage is 0.5 to 3.

[0033] In some embodiments, the preparation method includes controlling the stirring conditions, temperature, and pressure in each stage reactor to be the same.

[0034] Same stirring conditions mean that the specifications and rotation speed of the stirring paddle used for stirring are the same and do not change with the length-to-diameter ratio and volume of the reactor.

[0035] In these embodiments, by controlling the stirring conditions, temperature and pressure in each stage of the reactor to be the same, the difficulty of operation can be reduced, and the reactants entering each stage of the reactor can be controlled in terms of aspect ratio and / or volume to obtain propylene / α-olefin copolymers with low melting peak temperature, no high crystallization peak and wide melting range.

[0036] Optionally, the temperature in each stage of the reactor is 80℃~220℃ and the pressure is 2 MPa~10 MPa.

[0037] Optionally, the preparation method satisfies at least one of the following conditions:

[0038] (1) The mass ratio of propylene monomer and α-olefin monomer in different batches of reactants may be the same or different;

[0039] (2) In each batch of reactants, the mass percentage of α-olefin monomers in propylene monomers and α-olefin monomers is 5% to 25%;

[0040] (3) α-olefin monomers are selected from C2~C 20 At least one of the olefins.

[0041] When the mass ratio of propylene monomer to α-olefin monomer is the same in different batches of reactants, the degree of inhomogeneity and / or degree of polymerization of propylene monomer and α-olefin monomer will also differ in two-stage reactors with different aspect ratios and / or different volumes. Therefore, more segments with different melting capabilities can be formed in the propylene / α-olefin copolymer. When the mass ratio of propylene monomer to α-olefin monomer is different in different batches of reactants, the degree of inhomogeneity and / or degree of polymerization of propylene monomer and α-olefin monomer will also differ in two-stage reactors with the same aspect ratio and / or the same volume. Similarly, more segments with different melting capabilities can be formed in the propylene / α-olefin copolymer.

[0042] Optionally, the preparation method further includes:

[0043] A quenching vessel is connected to the reactant outlet of the last stage reactor in the reactor group, and a devolatilization device is connected to the outlet of the quenching vessel. The quenching vessel and the devolatilization device are used to quench and devolatilize the propylene / α-olefin copolymer prepared in the last stage reactor in sequence to obtain the propylene / α-olefin copolymer.

[0044] In this process, quenching followed by devolatilization can promptly quench the residual catalyst activity in the polymerization reaction solution after polymerization, avoiding the generation of highly crystalline polymer segments during subsequent devolatilization, ensuring that there are no high crystallinity peaks in the propylene / α-olefin copolymer, thereby making the dH(100) of the propylene / α-olefin copolymer = 0.

[0045] Thirdly, the application of the propylene / α-olefin copolymer as described in the first aspect in the preparation of heat-sealing materials is provided.

[0046] Optionally, the propylene / α-olefin copolymer and polypropylene material are mixed at a mass ratio of 1:(4~19), and a cast film is prepared by a casting process to prepare the heat-sealing material.

[0047] Compared with related technologies, this application has at least the following beneficial technical effects:

[0048] This propylene / α-olefin copolymer has a low melting peak temperature, dH(100)=0. Therefore, there is no high crystallinity peak in this propylene / α-olefin copolymer, making it easier to melt. When applied to heat-sealing materials, it can effectively reduce the heat-sealing temperature and improve the heat-sealing efficiency. At the same time, since the propylene / α-olefin copolymer has a large melting range and 6≤n(peak)≤20, it indicates that the propylene / α-olefin copolymer has multiple segments with different α-olefin insertion rates. When applied to heat-sealing materials, it can effectively shorten the cooling and sealing time during the heat-sealing process and reduce phenomena such as sealing wrinkles and stringing, thereby reducing heat-sealing defects.

[0049] Furthermore, when this propylene / α-olefin copolymer is applied to heat-sealing materials, the segments with lower melting points among the multiple segments of the propylene / α-olefin copolymer with different α-olefin insertion rates can have a better toughening effect, while the segments with higher melting points among the multiple segments with different α-olefin insertion rates can increase the compatibility between the propylene / α-olefin copolymer and the base material such as polypropylene, reducing the impact on the strength of the heat-sealing material. Therefore, the toughness and strength of the heat-sealing material can be effectively balanced. In summary, when this propylene / α-olefin copolymer is applied to heat-sealing materials, the overall performance of the heat-sealing material can be effectively improved. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the structure of a reactor assembly provided in an embodiment of this application;

[0051] Figure 2 This is a schematic flowchart illustrating a method for preparing a propylene / α-olefin copolymer, as provided in an embodiment of this application. Detailed Implementation

[0052] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0054] The present application will be further described in detail below with reference to specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0056] In this application, "at least one" means any one, any two, or more of the listed items.

[0057] In this application, the terms "combinations thereof," "any combination thereof," and "any combination thereof" as used include all suitable combinations of any two or more of the listed items.

[0058] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0059] In this application, numerical ranges are involved, and unless otherwise specified, the two endpoints of the numerical range are included.

[0060] In this application, unless otherwise specified, percentage concentrations refer to final concentrations. The final concentration refers to the percentage of the added component in the system after its addition.

[0061] In this application, temperature parameters are involved. Unless otherwise specified, both isothermal processing and processing within a certain temperature range are permitted. The isothermal processing allows temperature fluctuations within the precision range controlled by the instrument.

[0062] To address the problems in related technologies, such as the high melting temperature and narrow melting range of propylene / α-olefin copolymers, and the inability to effectively balance the toughness and strength of heat-sealing materials, the specific embodiments of this application are described as follows:

[0063] In a first aspect, some embodiments of this application provide a propylene / α-olefin copolymer, wherein the melting peak temperature of the propylene / α-olefin copolymer is 40℃~90℃, the melting range is 40℃~80℃, and the melting peak number n(peak) and dH(100) of the propylene / α-olefin copolymer satisfy: 6≤n(peak)≤20, dH(100)=0.

[0064] The melting peak temperature, melting range, number of melting peaks n(peak), and dH(100) of the propylene / α-olefin copolymer can all be measured using differential scanning calorimetry (DSC).

[0065] When measuring the thermal properties of polymers using differential scanning calorimetry (DSC), the melting peak temperature refers to the peak temperature of the endothermic peak on the DS curve when the polymer completely transitions from a crystalline state to a liquid state. This temperature represents the point at which the main crystalline portion of the polymer melts.

[0066] Here, for different propylene / α-olefin copolymers, their melting peak temperature and melting range may be different. All propylene / α-olefin copolymers with melting peak temperatures in the range of 40℃ to 90℃ and melting range widths in the range of 40℃ to 80℃ are within the protection scope of this application.

[0067] The melting range width here refers to the difference between the temperature at which the propylene / α-olefin copolymer is completely melted and the temperature at which it begins to melt. It represents the range covered by the melting range and does not specifically refer to the temperature at which the melting range begins to melt and when it is completely melted.

[0068] For example, the melting peak temperature of the propylene / α-olefin copolymer can be 40°C. In this case, its melting range of 40°C means that the melting range of the propylene / α-olefin copolymer can be 30°C to 70°C, and its melting range is equal to the difference between the complete melting temperature of the propylene / α-olefin copolymer (70°C) and the initial melting temperature (30°C), which is 40°C. Alternatively, the melting peak temperature of the propylene / α-olefin copolymer can be 50°C. In this case, its melting range can be 40°C. In this case, the melting range of the propylene / α-olefin copolymer can be 35°C to 75°C, and its melting range is equal to the difference between the complete melting temperature of the propylene / α-olefin copolymer (75°C) and the initial melting temperature (35°C), which is 40°C. Alternatively, the melting peak temperature of the propylene / α-olefin copolymer can be 70℃, in which case its melting range can be 50℃. In this case, the melting range of the propylene / α-olefin copolymer can be 40℃~90℃, and its melting range is equal to the difference between the complete melting temperature of the propylene / α-olefin copolymer (90℃) and the initial melting temperature (40℃), which is 50℃. Or, the melting peak temperature of the propylene / α-olefin copolymer can be 90℃, in which case its melting range can be 80℃. In this case, the melting range of the propylene / α-olefin copolymer can be 40℃~120℃, and its melting range is equal to the difference between the complete melting temperature of the propylene / α-olefin copolymer (120℃) and the initial melting temperature (40℃), which is 80℃.

[0069] When measuring polymers using a differential scanning calorimeter (DSC), the melting peak represents the thermal transition signal of the polymer as it changes from a solid to a liquid state during heating. n(peak) represents the number of melting peaks. In continuous self-nucleation / annealing (SSA) measurements using a DSC, when the heat capacity of each segment is graded relative to the total heat capacity by integrating the temperature-heat capacity curves of different polymer segments, n(peak) represents the number of melting peaks in the SSA measurement results, and dH(100) represents the sum of melting enthalpies above 100°C.

[0070] Therefore, n(peak) reflects regions in a polymer that have different crystallization morphologies or varying degrees of crystallization perfection. In the same polymer, differences in polymer chain segment structure can lead to multiple melting peaks. For example, in propylene / α-olefin copolymers, the polypropylene segment and the polyα-olefin segment have different crystallization characteristics, resulting in melting peaks corresponding to the crystallization of these two segments respectively. Similarly, in multiple copolymer segments of propylene and α-olefin, copolymer segments with different α-olefin insertion rates also have different crystallization characteristics, resulting in multiple melting peaks corresponding to different copolymer segments.

[0071] The melting point of each copolymer segment varies depending on the insertion rate of the α-olefin in different copolymer segments. For example, the lower the insertion rate of the α-olefin in a segment, the higher its melting point, and vice versa.

[0072] In the embodiments of this application, the larger n(peak) is, the more segments with different crystallization characteristics there are in the polymer, that is, the more segments with different α-olefin insertion rates there are in the polymer. In other words, the propylene / α-olefin copolymer has multiple segments with different α-olefin insertion rates. Correspondingly, the melting range of the polymer is also larger. dH(100) reflects the sum of the melting enthalpy of the polymer above 100°C. dH(100)=0 indicates that the heat absorbed and released by the changes in intermolecular forces and the transition between crystalline and amorphous states in the polymer at 100°C cancels each other out. There is no transition between crystalline and amorphous states, and the polymer has a lower melting peak temperature.

[0073] In the propylene / α-olefin copolymer provided in the embodiments of this application, the propylene / α-olefin copolymer has a low melting peak temperature, dH(100)=0. Therefore, the propylene / α-olefin copolymer does not have a high crystallinity peak, and thus it is easier to melt. When applied to heat-sealing materials, it can effectively reduce the heat-sealing temperature and improve the heat-sealing efficiency. At the same time, since the propylene / α-olefin copolymer has a large melting range and 6≤n(peak)≤20, it indicates that the propylene / α-olefin copolymer has multiple segments with different α-olefin insertion rates. When applied to heat-sealing materials, it can effectively shorten the cooling and sealing time during the heat-sealing process and reduce phenomena such as sealing wrinkles and stringing, thereby reducing heat-sealing defects.

[0074] Furthermore, when this propylene / α-olefin copolymer is applied to heat-sealing materials, the segments with lower melting points among the multiple segments of the propylene / α-olefin copolymer with different α-olefin insertion rates can have a better toughening effect, while the segments with higher melting points among the multiple segments with different α-olefin insertion rates can increase the compatibility between the propylene / α-olefin copolymer and the base material such as polypropylene, reducing the impact on the strength of the heat-sealing material. Therefore, the toughness and strength of the heat-sealing material can be effectively balanced. In summary, when this propylene / α-olefin copolymer is applied to heat-sealing materials, the overall performance of the heat-sealing material can be effectively improved.

[0075] In some embodiments, the density of the propylene / α-olefin copolymer is 0.840 g / cm³. 3 ~0.880g / cm 3 For example, the density of this propylene / α-olefin copolymer can be 0.840 g / cm³. 3 0.845g / cm 3 0.850g / cm3 0.855g / cm 3 0.861 g / cm 3 0.868 g / cm 3 0.870 g / cm 3 0.872 g / cm 3 0.874 g / cm 3 0.876 g / cm 3 0.878 g / cm 3 Or 0.880 g / cm 3 wait.

[0076] In some embodiments, the weight-average molecular weight of the propylene / α-olefin copolymer is 100,000 g / mol to 300,000 g / mol. For example, the weight-average molecular weight of the propylene / α-olefin copolymer can be 100,000 g / mol, 110,000 g / mol, 120,000 g / mol, 130,000 g / mol, 140,000 g / mol, 150,000 g / mol, 160,000 g / mol, 170,000 g / mol, 180,000 g / mol, 190,000 g / mol, 200,000 g / mol, 220,000 g / mol, 235,000 g / mol, 250,000 g / mol, 270,000 g / mol, or 295,000 g / mol, etc.

[0077] In some embodiments, the molecular weight distribution width (PDI) of the propylene / α-olefin copolymer is 2.0 to 3.5. The molecular weight distribution width (PDI) is a parameter used to describe the breadth of the molecular weight distribution of a polymer; a larger PDI indicates a wider molecular weight distribution. For example, the molecular weight distribution width (PDI) of this propylene / α-olefin copolymer can be 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, or 3.5.

[0078] In some embodiments, the enthalpy of fusion of the propylene / α-olefin copolymer is 10 J / g to 100 J / g. Enthalpy of fusion (also called melting enthalpy) refers to the amount of heat absorbed by a unit mass of solid material when it completely transforms into a liquid at the same temperature at its melting point under a given pressure. For example, the enthalpy of fusion of the propylene / α-olefin copolymer can be 10 J / g, 15 J / g, 22 J / g, 30 J / g, 37 J / g, 40 J / g, 50 J / g, 60 J / g, 80 J / g, 90 J / g, or 95 J / g, etc.

[0079] In some embodiments, the melt index (MI) of the propylene / α-olefin copolymer at 230°C and a load of 2.16 kg is 1.0 g / 10 min to 50.0 g / 10 min. For example, the melt index (MI) of the propylene / α-olefin copolymer at 230°C and a load of 2.16 kg can be 1.0 g / 10 min, 1.5 g / 10 min, 2.5 g / 10 min, 3.5 g / 10 min, 5.0 g / 10 min, 9.0 g / 10 min, 13.0 g / 10 min, 17.0 g / 10 min, 22.0 g / 10 min, 28.0 g / 10 min, 33.0 g / 10 min, 38.0 g / 10 min, 42.0 g / 10 min, 47.0 g / 10 min, or 50.0 g / 10 min, etc.

[0080] In some embodiments, the glass transition temperature (Tg) of the propylene / α-olefin copolymer is -35°C to -15°C. The glass transition temperature (Tg) refers to the temperature at which an amorphous polymer (or the amorphous portion of a partially crystalline polymer) transitions from a glassy state to a rubbery state. For example, the glass transition temperature (Tg) of the propylene / α-olefin copolymer can be -35°C, -34°C, -31°C, -29°C, -26°C, -23°C, -20°C, -18°C, or -15°C, etc.

[0081] In some embodiments, the α-olefin in the propylene / α-olefin copolymer is selected from C2~C4. 20 At least one of the olefins. For example, the α-olefin may be selected from one or more of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-eicosene.

[0082] In some embodiments, the mass fraction of α-olefin in the propylene / α-olefin copolymer is 5% to 25%. For example, the mass fraction of α-olefin can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 18%, 20%, 22%, or 25%, etc.

[0083] Optionally, the α-olefin in the propylene / α-olefin copolymer has a mass fraction of 8% to 15%.

[0084] Secondly, some embodiments of this application provide a method for preparing a propylene / α-olefin copolymer, such as... Figure 1 and Figure 2 As shown, the preparation method includes:

[0085] S21. A reactor group is provided, comprising: a multi-stage reactor 11 connected in series, each stage reactor 11 having a reactant inlet 111 and a reactant outlet 112 disposed opposite to each other along the axial direction of the reactor 11, the reactant outlet 112 of the preceding stage reactor 11 communicating with the reactant inlet 111 of the following stage reactor 11, the aspect ratio of each stage reactor 11 being less than or equal to 3, and at least two stages of the multi-stage reactor 11 having different aspect ratios and / or volumes; wherein, the aspect ratio of each stage reactor 11 is equal to the ratio of a first dimension and a second dimension, the first dimension being the dimension between the reactant inlet 111 and the reactant outlet 112 of the reactor 11, and the second dimension being the radial dimension of the reactor 11;

[0086] For reactors with a large aspect ratio, the mixing and mass transfer are efficient, resulting in a relatively uniform distribution of temperature, catalyst, and monomer concentrations within the reactor. The polymerization environment at the active sites is essentially consistent, leading to more homogeneous polymer products. Conversely, for reactors with a small aspect ratio, the mixing, mass transfer, and heat transfer efficiency are relatively poor, and there is an uneven distribution of monomer proportions within the reactor. This allows for the preparation of polymer segments with multiple different α-olefin insertion rates, enabling the construction of polymer segments with varying crystallinity within the polymer molecular chain. This results in polymers with a larger number of melting peaks (n), thus increasing the melting range of the propylene / α-olefin copolymer.

[0087] The residence time of the reactants in the reactor is equal to the reactor volume divided by the reactant flow rate. Therefore, for reactors of different volumes, when the reactor volume is larger, the residence time of the reactants in the reactor is longer, resulting in more chain segments and / or molecular chains. Conversely, the residence time of the reactants in the reactor is shorter, resulting in fewer chain segments and / or molecular chains. Since the aspect ratio of each stage reactor is less than or equal to 3, a non-uniform distribution of monomer proportions can be achieved, thereby preparing polymer segments with multiple different α-olefin insertion rates. This allows for the construction of polymer segments with different crystallinity in the polymer molecular chain, resulting in polymers with a larger number of melting peaks n (peak), thus improving the melting range of the propylene / α-olefin copolymer.

[0088] S22. Controlling multiple batches of reactants to be fed into each stage of reactor 11, and controlling different batches of reactants to polymerize with the reaction product of the previous stage reactor 11 in each stage of reactor 11 sequentially, to prepare the propylene / α-olefin copolymer; and

[0089] S23. Quenching and devolatilization treatment are performed on the propylene / α-olefin copolymer prepared in the last stage reactor to obtain the propylene / α-olefin copolymer.

[0090] Each batch of reactants includes at least: propylene monomer, α-olefin monomer, solvent and catalyst.

[0091] In this process, the propylene monomer, solvent, and co-catalyst contained in each batch of reactants can be pre-mixed evenly before being fed into each stage of the reactor. The remaining raw materials are fed into each stage of the reactor through separate feed pipelines, so that each batch of reactants can be reacted under certain temperature and pressure after entering each stage of the reactor.

[0092] When corresponding batches of reactants are introduced into each stage of the reactor, the reaction product obtained by polymerization of the previous batch of reactants in the previous stage reactor can be the first segment. It can continue to react with the reactants of this batch in the current stage reactor to generate another segment, such as the second segment. When the aspect ratio and / or volume of the previous stage reactor and the subsequent stage reactor are different, the arrangement of the first segment and the second segment and the insertion rate of α-olefin will be different. By controlling the aspect ratio of each stage reactor to be small, the random insertion degree of α-olefin distribution in each stage reactor can be improved, thereby enabling the preparation of propylene / α-olefin copolymers with low melting peak temperature, large n(peak), and wide melting range.

[0093] In the preparation method of propylene / α-olefin copolymer provided in the embodiments of this application, since the aspect ratio of each stage reactor in the reactor group is less than or equal to 3, the monomer ratio in the reactants fed into different reactors can be unevenly distributed, thereby increasing the random insertion degree of α-olefin in the propylene / α-olefin copolymer. At the same time, by controlling the aspect ratio and / or volume of at least two stages of reactors to be different, the insertion rate and / or segment length of α-olefin in different segments of the reactants in each stage reactor can be effectively controlled, thereby further increasing the random insertion degree of α-olefin in the propylene / α-olefin copolymer, increasing the number of melting peaks and the melting range of the propylene / α-olefin copolymer, and thus preparing a propylene / α-olefin copolymer with low melting peak temperature, no high crystallinity peak, and a large melting range. After the propylene / α-olefin copolymer is prepared, the reaction can be terminated in time by quenching and devolatilization treatment of the propylene / α-olefin copolymer, thereby avoiding the introduction of highly crystalline polymer segments into the propylene / α-olefin copolymer and thus controlling the dH(100)=0 of the propylene / α-olefin copolymer.

[0094] In some embodiments, the aspect ratio of each stage reactor 11 is 0.5 to 3.

[0095] In some alternative embodiments, the reactor group may include two or three stages of reactors connected in series. When the reactor group includes two stages of reactors connected in series, the aspect ratios and / or volume ratios of these two stages are different. When the reactor group includes three stages of reactors connected in series, at least two stages of reactors have different aspect ratios and / or volume ratios. This means that the aspect ratios and / or volume ratios of the first and second stages of reactors are different, and the aspect ratios and volume ratios of the first and third stages of reactors are the same; or, the aspect ratios and / or volume ratios of the first and third stages of reactors are different, and the aspect ratios and volume ratios of the first and second stages of reactors are the same.

[0096] In some embodiments, the preparation method includes controlling the stirring conditions, temperature, and pressure in each stage reactor 11 to be the same.

[0097] Same stirring conditions mean that the specifications and rotation speed of the stirring paddle used for stirring are the same and do not change with the length-to-diameter ratio and volume of the reactor.

[0098] In these embodiments, by controlling the stirring conditions, temperature and pressure in each stage of the reactor to be the same, the difficulty of operation can be reduced, and the reactants entering each stage of the reactor can be controlled in terms of aspect ratio and / or volume to obtain propylene / α-olefin copolymers with low melting peak temperature, no high crystallization peak and wide melting range.

[0099] In some embodiments, the mass ratio of propylene monomer and α-olefin monomer in different batches of reactants may be the same or different.

[0100] In these embodiments, when the mass ratio of propylene monomer to α-olefin monomer is the same in different batches of reactants, the degree of inhomogeneity and / or degree of polymerization of propylene monomer and α-olefin monomer will also differ in two-stage reactors with different aspect ratios and / or different volumes. Therefore, more segments with different melting capabilities can be formed in the propylene / α-olefin copolymer. When the mass ratio of propylene monomer to α-olefin monomer is different in different batches of reactants, the degree of inhomogeneity and / or degree of polymerization of propylene monomer and α-olefin monomer will also differ in two-stage reactors with the same aspect ratio and / or the same volume. Similarly, more segments with different melting capabilities can be formed in the propylene / α-olefin copolymer.

[0101] In some embodiments, the above-mentioned α-olefin monomers are selected from C2~C3. 20 At least one of the olefins.

[0102] Optionally, the α-olefin monomer is selected from one or more of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-eicosene.

[0103] In some embodiments, the α-olefin monomer accounts for 5% to 25% of the mass of propylene monomer and α-olefin monomer in each batch of reactants.

[0104] In some embodiments, the catalyst may include a main catalyst and a co-catalyst.

[0105] The main catalyst can be a homogeneous catalyst, such as a metallocene catalyst or a non-metallocene catalyst.

[0106] Optionally, the main catalyst is selected from silyl(N-tert-butylamino)(tetramethylcyclopentadienyl)titanium chloride, dimethyl(N-tert-butylamino)(tetramethylcyclopentadienyl)dimethyltitanium, dimethyl(N-tert-butylamino)(fluorenyl)titanium chloride, (pentamethylcyclopentadienyl)trimethoxytitanium, diphenylmethylene(cyclopentadiene)(9-fluorenyl)zirconium chloride, dimethyldimethsilylbis(2-methyl-4-phenyl-1-indenyl)zirconium chloride, meso dimethylmethsilylbis(1-indenyl)zirconium chloride, bis(methylcyclopentadiene)zirconium chloride, rac-ethylene bis(1-indenyl)zirconium chloride, bis(1,3-dimethylcyclopentadienyl)zirconium chloride, etc. (dienyl)zirconia dichloride, (cyclopentadienyl)(1,2-dimethoxyethane)zirconia trichloride, diphenylsilyl(cyclopentadiene)(9-fluorenyl)zirconia dichloride, racemic dimethylsilylbis(2-methyl-1-indene)zirconia dichloride, diphenylmethylenecyclopentadiene(2,7-di-tert-butyl-fluorenyl)zirconia dichloride, di-p-tolymethylenecyclopentadiene(2,7-di-tert-butyl-fluorenyl)zirconia dichloride, dimethylbis(propylcyclopentadienyl)hafnium, bis(n-butylcyclopentadiene)hafnium dichloride and dimethylsilylbis(2-methyl-4-phenylindene)zirconia dichloride and one or more of the compounds represented by formulas (I) to (III) below.

[0107]

[0108] In some embodiments, the cocatalyst may be selected from one or more of aluminoxanes, alkylaluminum compounds, and alkylaluminum chlorides; or, the cocatalyst may be a combination of one or more of aluminoxanes, alkylaluminum compounds, and alkylaluminum chlorides with one or more organoborides; for example, the cocatalyst may be a combination of aluminoxanes and organoborides, a combination of alkylaluminum compounds and organoborides, or a combination of alkylaluminum chlorides and organoborides.

[0109] In some embodiments, the aluminum oxane is selected from methylaluminoxane (MAO) and / or modified methylaluminoxane (MMAO).

[0110] In some embodiments, the alkylaluminum compound is selected from at least one of triethylaluminum, triisobutylaluminum, and trioctylaluminum.

[0111] In some embodiments, the alkylaluminum chloride is selected from at least one of monochloroethylaluminum, sesquiethylaluminum, and dichloroethylaluminum.

[0112] In some embodiments, the organoborides are selected from at least one of triphenylmethyltetra(pentafluorophenyl)borate, tri(pentafluorophenyl)boron, N,N-dimethylanilinetetra(pentafluorophenyl)borate, dioctadecylmethyltertiaryaminetetra(pentafluorophenyl)borate, and dihydrotallowylmethyltertiaryaminetetra(pentafluorophenyl)borate.

[0113] In some embodiments, the main catalyst and the co-catalyst are mixed in a certain proportion in each batch of reactants.

[0114] For example, in each batch of reactants, when the co-catalyst is selected from one or more of aluminoxanes, alkylaluminum compounds and alkylaluminum chlorides, the molar ratio Al / M of metallic aluminum in the co-catalyst to metallic M in the main catalyst can be 3 to 1000, for example, 3, 5, 10, 20, 50, 80, 100, 120, 140, 160, 180, 200, 300, 400, 500, 600, 700, 800, 900 or 1000, optionally 10 to 200.

[0115] In some embodiments, when the co-catalyst contains an organoboride, the molar ratio B / M of the organoboride (measured in boron) to the metal M element in the main catalyst is 0 to 10, for example, it can be 0, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 9.5 or 10, and optionally 1 to 3.

[0116] In some embodiments, the solvent described above is in a liquid or supercritical state during the polymerization reaction, playing a mass transfer role, and can be a hydrocarbon solvent.

[0117] For example, the hydrocarbon solvent may include: C5~C 12 At least one of aliphatic hydrocarbons, C6-C8 aromatic hydrocarbons, and dichloromethane. For example, the aliphatic hydrocarbon may be one or more of substituted or unsubstituted pentane, methylpentane, hexane, heptane, octane, cyclohexane, C6 mixed alkanes, methylcyclohexane, and hydrogenated naphtha, wherein the substituent may be a C1-C4 alkyl group; the aromatic hydrocarbon may be toluene, xylene, etc.

[0118] Optionally, the solvent is selected from at least one of hexaane, C6 mixed alkanes, methylcyclohexane, and IsoparE (C8-C10 mixed isoalkanes, purchased from Dow Chemical).

[0119] In some embodiments, each batch of reactants may also contain a chain transfer agent, such as hydrogen. This chain transfer agent can adjust the molecular weight, reaction rate, and molecular structure of the propylene / α-olefin copolymer to obtain a propylene / α-olefin copolymer with the required chain length, melting peak temperature, and melting range.

[0120] In some embodiments, the temperature in each stage of the reactor is 80°C to 220°C, and the pressure is 2MPa to 10MPa.

[0121] For example, the temperature in each stage of the reactor can be 80℃, 90℃, 100℃, 110℃, 120℃, 140℃, 150℃, 180℃, 200℃, 210℃ or 220℃, etc., and the pressure can be 2 MPa, 2.2 MPa, 2.5 MPa, 3.0 MPa, 3.5 MPa, 4.0 MPa, 4.5 MPa, 5.0 MPa, 5.5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa or 10 MPa, etc.

[0122] In some embodiments, the preparation method further includes: connecting a quenching vessel 13 to the reactant outlet 112 of the last stage reactor 11 of the reactor group, and connecting a devolatilization device 12 to the outlet of the quenching vessel 13, so as to use the quenching vessel 13 and the devolatilization device 12 to quench and devolatilize the propylene / α-olefin copolymer prepared in the last stage reactor 11 in sequence to obtain the propylene / α-olefin copolymer.

[0123] In these embodiments, propylene / α-olefin copolymers are obtained by sequentially quenching and devolatilizing the polymerization product. In this process, quenching followed by devolatilization effectively eliminates residual catalyst activity in the polymerization reaction solution after polymerization, preventing the formation of highly crystalline polymer segments during subsequent devolatilization. This ensures that the propylene / α-olefin copolymer is free of high crystallinity peaks, resulting in dH(100) = 0 for the propylene / α-olefin copolymer.

[0124] The quenching agent can be a mixture of a carrier gas and a reactant gas. The carrier gas may include nitrogen, and the reactant gas may include at least one of carbon monoxide and water vapor. Nitrogen acts as a dilution and loading agent, while the reactant gas, upon contact with the catalyst, inactivates the catalyst, thereby terminating the reaction.

[0125] In some embodiments, when the quenching agent is a mixture of nitrogen and carbon monoxide, the mass fraction of carbon monoxide is 1 wt% to 3 wt%. When the quenching agent is a mixture of nitrogen and water vapor, the mass fraction of water vapor is 3% to 4%. When the quenching agent is a mixture of nitrogen, carbon monoxide, and water vapor, the mass fraction of carbon monoxide is 0.5% to 1.5%, and the mass fraction of water vapor is 1.5% to 2.5%.

[0126] Thirdly, some embodiments of this application provide the application of the propylene / α-olefin copolymer as described in the first aspect in the preparation of heat-sealing materials.

[0127] In some embodiments, a propylene / α-olefin copolymer is mixed with a polypropylene material at a mass ratio of 1:(4~19), and a cast film is prepared using a casting process to prepare a heat-sealing material.

[0128] In these embodiments, a cast film with good tensile and impact properties can be obtained. When the cast film is used for heat sealing, it has a lower heat sealing temperature and a wider heat sealing temperature range, which can effectively shorten the cooling and sealing time during the heat sealing process and reduce phenomena such as sealing wrinkles and stringing, thereby reducing heat sealing defects.

[0129] Furthermore, since the melting peak number n(peak) of the propylene / α-olefin copolymer satisfies: 6≤n(peak)≤20, the segments with lower melting points among the multiple segments of the propylene / α-olefin copolymer with different α-olefin insertion rates can achieve a better toughening effect, while the segments with higher melting points among the multiple segments of the propylene / α-olefin copolymer with different α-olefin insertion rates can increase the compatibility between the propylene / α-olefin copolymer and the base material such as polypropylene, and reduce the impact on the strength of the heat-sealing material. Therefore, the toughness and strength of the heat-sealing material can be effectively balanced. In summary, the heat-sealing material has good comprehensive performance.

[0130] The specific implementation methods of this application have been described above. In order to objectively illustrate the technical effects produced by this application, the following examples and comparative examples will be used to describe them in detail.

[0131] In the following examples and comparative examples, all raw materials were commercially available, and to maintain the reliability of the experiments, the raw materials used in the following examples and comparative examples had the same physical and chemical parameters or underwent the same treatment.

[0132] The specific information for some of the materials and reagents is as follows:

[0133] 6102, propylene / ethylene copolymer, purchased from ExxonMobil;

[0134] 6202, propylene / ethylene copolymer, purchased from ExxonMobil;

[0135] F5606, ternary copolymer polypropylene, purchased from Yanshan Petrochemical;

[0136] Isopar-E, 100% hydrogenated naphtha, purchased from Mobil;

[0137] Ethylene, polymerization grade, purchased from Air Liquide;

[0138] Propylene, polymerization grade, purchased from Air Liquide;

[0139] 1-Octenene, 98%, purchased from INEOS;

[0140] 1-Hexene, 99%, purchased from Leading Biotech;

[0141] 1-Butene, 99%, purchased from Mingju;

[0142] rac-ethylenebis(1-indenyl)zirconium dichloride, 99%, strem, marked M1;

[0143] Dimethicone (N-tert-butylamino) (tetramethylcyclopentadienyl) dimethyltitanium, 99%, purchased from Xinnoco, marked as M2;

[0144] Diphenylmethylenecyclopentadiene (2,7-di-tert-butyl-fluorenyl)zirconium dichloride, 98%, purchased from Yaodexin Chemical, marked as M3;

[0145] MMAO, a 7% aluminum solution, was purchased from Norinon;

[0146] MAO, a 15% aluminum solution, was purchased from Albemarle;

[0147] Triisobutylaluminum (TIBA) hexane solution, 1 mol / L, purchased from Inokai;

[0148] Triphenylmethyltetrafluorophenylborate, 99%, purchased from Inokai, soluble in toluene, labeled B1.

[0149] Example 1

[0150] Example 1 provides a method for preparing a propylene / α-olefin copolymer, the specific steps of which are as follows:

[0151] (1) Provide a reactor group comprising a two-stage reactor, a quenching vessel and a devolatilization device connected in series. Both stages of the reactor are stirred tank reactors. The first stage reactor has an aspect ratio of 2 and a volume of 1L, and the second stage reactor has an aspect ratio of 2 and a volume of 0.5L.

[0152] (2) The first batch of reactants is introduced into the first reactor. In this first batch of reactants, the α-olefin is ethylene, the mass ratio of propylene to ethylene is 16:1, the main catalyst is M1, the addition amount is 20 μmol / h, the co-catalyst is MMAO, and the Al / M ratio is 500. The second batch of reactants is introduced into the second reactor. In this second batch of reactants, the α-olefin is ethylene, the mass ratio of propylene to α-olefin is 10:1, the main catalyst is M1, the addition amount is 20 μmol / h, the co-catalyst is MMAO, and the Al / M ratio is 500. The temperature in both the first and second reactors is controlled at 124℃, the pressure is 5 MPa, and the stirring speed is 700 r / min. After the reaction is completed, the reactants are quenched, volatile components are removed, and the reactants are dried before extrusion and granulation to obtain propylene / α-olefin copolymer particles. A mixture of nitrogen, carbon monoxide, and water vapor is used as the quenching agent for the reaction. The concentration of carbon monoxide is 1 wt% of the total mass of the mixture, and the concentration of water vapor is 2 wt% of the total mass of the mixture.

[0153] Example 2

[0154] The preparation method of the propylene / α-olefin copolymer provided in Example 2 is basically the same as that of the preparation method of the propylene / α-olefin copolymer provided in Example 1, except that:

[0155] In step (1), in the two-stage reactors connected in series, the first-stage reactor has an aspect ratio of 1.5 and a volume of 2L, and the second-stage reactor has an aspect ratio of 1.5 and a volume of 4L.

[0156] In step (2), the mass ratio of propylene to ethylene in the first batch of reactants is 16:1, the main catalyst is M2 with an addition amount of 375 μmol / h, the co-catalyst is TIBA with an Al / M ratio of 5, and an organoboron compound of type B1 with a B / M ratio of 3 is also added; the mass ratio of propylene to ethylene in the second batch of reactants is 10:1, M2 with an addition amount of 375 μmol / h, the co-catalyst is TIBA with an Al / M ratio of 5, and an organoboron compound of type B1 with a B / M ratio of 3 is also added; the temperature in both the first and second stage reactors is controlled at 138℃, the pressure at 8 MPa, and the stirring speed at 700 r / min.

[0157] Example 3

[0158] The preparation method of the propylene / α-olefin copolymer provided in Example 3 is basically the same as that of the preparation method of the propylene / α-olefin copolymer provided in Example 1, except that:

[0159] In step (1), in the two-stage reactors connected in series, the first-stage reactor has an aspect ratio of 1.5 and a volume of 2L, and the second-stage reactor has an aspect ratio of 1.5 and a volume of 1L.

[0160] In step (2), the first batch of reactants contains 1-butene as the α-olefin, with a mass ratio of propylene to 1-butene of 10:1. The main catalyst is M3, with an addition amount of 600 μmol / h. The co-catalyst is MAO, and the Al / M ratio is 1000. In the second batch of reactants, the mass ratio of propylene to 1-butene is 10:1. The main catalyst is M3, with an addition amount of 600 μmol / h. The co-catalyst is MAO, and the Al / M ratio is 1000. The temperature in both the first and second stage reactors is controlled at 119℃, the pressure at 4 MPa, and the stirring speed at 700 r / min.

[0161] Example 4

[0162] The preparation method of the propylene / α-olefin copolymer provided in Example 4 is basically the same as that of the preparation method of the propylene / α-olefin copolymer provided in Example 1, except that:

[0163] In step (1), in the two-stage reactors connected in series, the first-stage reactor has an aspect ratio of 1 and a volume of 3L, and the second-stage reactor has an aspect ratio of 2 and a volume of 3L.

[0164] In step (2), the first batch of reactants contains 1-butene as the α-olefin, with a mass ratio of propylene to 1-butene of 10:1. The main catalyst is M2, with an addition amount of 300 μmol / h. The co-catalyst is TIBA, with an Al / M ratio of 3. An organoboron compound of type B1 with a B / M ratio of 1 is also added. In the second batch of reactants, the α-olefin is 1-butene, with a mass ratio of propylene to 1-butene of 10:1. The main catalyst for propylene and 1-butene is M2, with an addition amount of 300 μmol / h. The co-catalyst is TIBA, with an Al / M ratio of 3. An organoboron compound of type B1 with a B / M ratio of 1 is also added. The temperature in both the first and second stage reactors is controlled at 120℃, the pressure at 6 MPa, and the stirring speed at 700 r / min.

[0165] Example 5

[0166] The preparation method of the propylene / α-olefin copolymer provided in Example 5 is basically the same as that of the preparation method of the propylene / α-olefin copolymer provided in Example 1, except that:

[0167] In step (1), in the two-stage reactors connected in series, the first-stage reactor has an aspect ratio of 0.5 and a volume of 3L, and the second-stage reactor has an aspect ratio of 1 and a volume of 6L.

[0168] In step (2), in the first batch of reactants, the α-olefin is 1-octene, the mass ratio of propylene to 1-octene is 8:1, the main catalyst is M1, the addition amount is 500 μmol / h, the co-catalyst is MMAO, and the Al / M ratio is 50; in the second batch of reactants, the α-olefin is 1-octene, the mass ratio of propylene to 1-octene is 8:1, the main catalyst is M1, the addition amount is 500 μmol / h, the co-catalyst is MMAO, and the Al / M ratio is 50; the temperature in both the first-stage reactor and the second-stage reactor is controlled at 150℃, the pressure is 10 MPa, and the stirring speed is 700 r / min.

[0169] Comparative Example 1

[0170] The preparation method of the propylene / α-olefin copolymer provided in Comparative Example 1 is basically the same as the preparation method of the propylene / α-olefin copolymer provided in Example 1, except that:

[0171] In step (1), in the two-stage reactors connected in series, the length-to-diameter ratio of the first-stage reactor and the second-stage reactor are both 5, and the volume is 2L.

[0172] In step (2), in the first batch of reactants, the α-olefin is ethylene, the mass ratio of propylene to ethylene is 16:1, the main catalyst is M3, the addition amount is 400 μmol / h, the co-catalyst is MAO, and the Al / M ratio is 1000; in the second batch of reactants, the α-olefin is ethylene, the mass ratio of propylene to ethylene is 10:1, the main catalyst is M3, the addition amount is 400 μmol / h, the co-catalyst is MAO, and the Al / M ratio is 1000; the temperature in both the first and second stage reactors is controlled at 130℃, the pressure is 4 MPa, and the stirring speed is 700 r / min.

[0173] Comparative Example 2

[0174] The preparation method of the propylene / α-olefin copolymer provided in Comparative Example 2 is basically the same as the preparation method of the propylene / α-olefin copolymer provided in Example 1, except that:

[0175] In step (1), in the two-stage reactors connected in series, the length-to-diameter ratio of the first-stage reactor and the second-stage reactor are both 5, the volume is 2L, and they do not include the quenching vessel.

[0176] In step (2), in the first batch of reactants, the α-olefin is ethylene, the mass ratio of propylene to ethylene is 16:1, the main catalyst is M3, the addition amount is 400 μmol / h, the co-catalyst is MAO, and the Al / M ratio is 1000; in the second batch of reactants, the α-olefin is ethylene, the mass ratio of propylene to ethylene is 10:1, the main catalyst is M3, the addition amount is 400 μmol / h, the co-catalyst is MAO, and the Al / M ratio is 1000; the temperature in both the first and second stage reactors is controlled at 130℃, the pressure is 4 MPa, and the stirring speed is 700 r / min, and devolatilization is carried out directly after the reaction is completed.

[0177] Comparative Example 3

[0178] Propylene / ethylene copolymer 6102 was obtained through commercial purchase.

[0179] Comparative Example 4

[0180] Propylene / ethylene copolymer 6202 was obtained through commercial purchase.

[0181] Test case

[0182] The melting peak temperature Tm, melting range, n (peak), dH (100), density, Mw, PDI, MI (230℃, 2.16kg), and glass transition temperature Tg of the propylene / α-olefin copolymers provided in Examples 1-5 and Comparative Examples 1-4 were tested. The test results are shown in Tables 1 and 2 below.

[0183] Table 1

[0184]

[0185] In Table 1, the melting peak temperature T of the polymer is... mBoth the melting enthalpy and melting range were measured using DSC, with data obtained from the second heating cycle at a rate of 10 °C / min. The melting range is the temperature range between the temperature at which the polymer begins to melt and the temperature at which it is completely melted. n(peak) was measured using SSA of DSC, and the specific method is as follows: In the first cycle, the temperature was raised to 150℃, held for 1 minute, and then lowered to -50℃; in the second cycle, the temperature was raised to 120℃, held for 5 minutes, and then lowered to -50℃; in the third cycle, the temperature was raised to 112.5℃, held for 5 minutes, and then lowered to -50℃; the above cycle operation was repeated to raise the temperature, hold for 5 minutes, and then lower it, and then the process was repeated for the fourth cycle (i.e., in the fourth cycle, the temperature was raised to the highest point of 105℃ at 7.5℃ intervals, held for 5 minutes, and then lowered to -50℃), the fifth cycle (i.e., in the fifth cycle, the temperature was raised to the highest point of 97.5℃ at 7.5℃ intervals, held for 5 minutes, and then lowered to -50℃), the sixth cycle, and so on, until the temperature reached -40℃, thereby crystallizing in each temperature range. In the final cycle, the temperature is increased to 150℃ at a rate of 10℃ / min, and the change in heat capacity is measured. n(peak) represents the number of melting peaks in the final cycle, and dH(100) represents the sum of melting enthalpies above 100℃.

[0186] As shown in Table 1, the propylene / α-olefin copolymers provided in Examples 1-5 of this application have a lower melting peak temperature, a larger melting range, and their n(peak) can reach 7-18, and dH(100) is 0. This can effectively increase the insertion rate of α-olefins in the propylene / α-olefin copolymer, reduce the melting temperature of the propylene / α-olefin copolymer, and broaden the melting range of the propylene / α-olefin copolymer.

[0187] Comparing Examples 1-5 and Comparative Examples 1-4, it can be seen that by adjusting the aspect ratio and / or volume of at least two reactors to be different, and controlling the aspect ratio of each reactor to be less than 3, a propylene / α-olefin copolymer with low melting peak temperature, wide melting range, many melting peaks, and dH(100) of 0 can be obtained. Meanwhile, comparing Comparative Examples 1 and 2, it can be seen that timely quenching after the reaction can avoid the generation of highly crystalline polymer segments in the subsequent devolatilization process, so that the dH(100) of the propylene / α-olefin copolymer is 0.

[0188] Table 2

[0189]

[0190] In Table 2, density was measured using a densitometer: The sample was cut from the compression plate and density was measured using a Mettler XS204 densitometer. The impregnation method was used, with anhydrous ethanol (AR) as the impregnation solution. The ambient temperature was 23℃±2℃, and the temperature required internal calibration. The sample mass was >1g, and there were no air bubbles. The mass of the sample in air and in the impregnation solution were weighed separately, and the density of the propylene / α-olefin copolymer was calculated using Archimedes' principle. Molecular weight, molecular weight distribution, and the insertion rate of α-olefins (such as ethylene) were obtained through GPC-IR testing using PolymerChart at 150℃, with a product recovery rate exceeding 95%. The melt index (MI) test method under 230℃ and 2.16kg load conditions is as follows: Approximately 6g of the sample was taken, the temperature was set at 230℃, the load was 2.16kg, and the standard die inner diameter was 2.095mm. After the granules melt in the barrel for 5 minutes, they flow out of the die under pressure. The time taken for the displacement point to change from 46 mm to 20.6 mm is measured and recorded. A sample strip is automatically cut, and its mass is weighed using a balance. The MFR or MVR is then calculated, with units of g / 10min and cm, respectively. 3 / 10min.

[0191] As shown in Table 2, the density, Mw, PDI, MI (230°C, 2.16 kg), and glass transition temperature of the propylene / α-olefin copolymers provided in Examples 1-5 of this application are comparable to those of the propylene / α-olefin copolymers provided in Comparative Examples 1-4, and can meet the same application requirements as existing propylene / α-olefin copolymers.

[0192] Cast film Example 1

[0193] The method for preparing the cast film in Example 1 is as follows:

[0194] The propylene / α-olefin copolymer particles obtained in Example 1 were melt-blended with ternary copolymer polypropylene F5606 at a mass ratio of 1:9 in a casting machine and then cast at a casting temperature of 190°C to control the film thickness to 40 μm.

[0195] Cast film Example 2

[0196] The preparation method of the cast film in Example 2 is basically the same as that of the cast film in Example 1, except that:

[0197] The propylene / α-olefin copolymer particles obtained in Example 2 were melt-blended with ternary copolymer polypropylene F5606 at a mass ratio of 1:9 in a casting machine and then cast.

[0198] Cast film Example 3

[0199] The preparation method of the cast film in Example 3 is basically the same as that of the cast film in Example 1, except that:

[0200] The propylene / α-olefin copolymer particles obtained in Example 3 were melt-blended with ternary copolymer polypropylene F5606 at a mass ratio of 1:9 in a casting machine and then cast.

[0201] Cast film Example 4

[0202] The preparation method of the cast film in Example 4 is basically the same as that of the cast film in Example 1, except that:

[0203] The propylene / α-olefin copolymer particles obtained in Example 4 were melt-blended with ternary copolymer polypropylene F5606 at a mass ratio of 1:9 in a casting machine and then cast.

[0204] Cast film Example 5

[0205] The preparation method of the cast film in Example 5 is basically the same as that of the cast film in Example 1, except that:

[0206] The propylene / α-olefin copolymer particles obtained in Example 5 were melt-blended with ternary copolymer polypropylene F5606 at a mass ratio of 1:9 in a casting machine and then cast.

[0207] Cast film comparative example 1

[0208] The preparation method of the cast film in Comparative Example 1 is basically the same as that of the cast film in Example 1, except that:

[0209] The propylene / α-olefin copolymer particles obtained in Comparative Example 1 were melt-blended with ternary copolymer polypropylene F5606 at a mass ratio of 1:9 in a casting machine and then cast.

[0210] Cast film comparative example 2

[0211] The preparation method of the cast film in Comparative Example 2 is basically the same as that of the cast film in Example 1, except that:

[0212] The propylene / α-olefin copolymer particles obtained in Comparative Example 2 were melt-blended with ternary copolymer polypropylene F5606 at a mass ratio of 1:9 in a casting machine and then cast.

[0213] Cast film comparative example 3

[0214] The preparation method of the cast film in Comparative Example 3 is basically the same as that of the cast film in Example 1, except that:

[0215] The propylene / α-olefin copolymer particles obtained in Comparative Example 3 were melt-blended with ternary copolymer polypropylene F5606 at a mass ratio of 1:9 in a casting machine and then cast.

[0216] Cast film comparative example 4

[0217] The preparation method of the cast film in Comparative Example 4 is basically the same as that of the cast film in Example 1, except that:

[0218] The propylene / α-olefin copolymer particles obtained in Comparative Example 4 were melt-blended with ternary copolymer polypropylene F5606 at a mass ratio of 1:9 in a casting machine and then cast.

[0219] Cast film comparative example 5

[0220] In Comparative Example 5, the cast film was cast only after the ternary copolymer polypropylene F5606 was melt-blended in a casting machine.

[0221] Cast film test case

[0222] The tensile properties, dart impact properties, heat sealing temperature, and heat sealing temperature range of the cast films obtained in Examples 1-5 and Comparative Examples 1-5 were tested. Specifically, the tensile properties were tested according to GB / T 13022-1991, the dart impact strength was tested according to ASTM D 1709, and the heat sealing temperature and heat sealing temperature range were tested according to GB / T-27740-2011. The relevant test results are shown in Table 3.

[0223] Table 3

[0224]

[0225] As shown in Table 3, the cast film of Examples 1-5 of this application has high strength and toughness, as well as low heat sealing temperature and large melting range. When applied to heat sealing film, it can shorten the cooling and sealing time and solve the problems of sealing wrinkling and stringing in related technologies, thereby improving the heat sealing yield.

[0226] Comparative Examples 1-5 and Comparative Examples 1-5 show that by adjusting the aspect ratio and / or volume of at least two reactors to be different, and controlling the aspect ratio of each reactor to be less than 3, a cast film with excellent tensile strength, dart impact strength and tensile elongation at break can be obtained. It can significantly improve the toughness of the cast film while maintaining its high mechanical tensile strength. At the same time, it can also reduce the heat sealing temperature of the cast film and broaden the heat sealing temperature range, thus exhibiting excellent performance.

[0227] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0228] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A propylene / α-olefin copolymer, characterized in that, The melting peak temperature of the propylene / α-olefin copolymer is 40℃~90℃, the melting range is 40℃~80℃, and the melting peak number n(peak) and dH(100) of the propylene / α-olefin copolymer satisfy: 6≤n(peak)≤20, dH(100)=0; the mass fraction of α-olefin in the propylene / α-olefin copolymer is 5%~25%.

2. The propylene / α-olefin copolymer according to claim 1, characterized in that, The propylene / α-olefin copolymer satisfies at least one of the following conditions: (1) The density of the propylene / α-olefin copolymer is 0.840 g / cm³. 3 ~0.880g / cm 3 ; (2) The weight-average molecular weight of the propylene / α-olefin copolymer is 100,000 g / mol ~ 300,000 g / mol; (3) The molecular weight distribution width (PDI) of the propylene / α-olefin copolymer is 2.0~3.5; (4) The melting enthalpy of the propylene / α-olefin copolymer is 10 J / g ~ 100 J / g; (5) The melt index of the propylene / α-olefin copolymer at 230°C and 2.16 kg load is 1.0 g / 10 min ~ 50.0 g / 10 min; (6) The glass transition temperature Tg of the propylene / α-olefin copolymer is -35℃ to -15℃; (7) The α-olefin in the propylene / α-olefin copolymer is selected from C2~C4. 20 At least one of the olefins.

3. A method for preparing the propylene / α-olefin copolymer according to claim 1 or 2, characterized in that, include: A reactor assembly is provided, the reactor assembly comprising: a multi-stage reactor (11) connected in series, each stage of the reactor (11) having a reactant inlet (111) and a reactant outlet (112) disposed opposite to each other along the axial direction of the reactor (11), the reactant outlet (112) of the preceding stage reactor (11) communicating with the reactant inlet (111) of the following stage reactor (11), the aspect ratio of each stage reactor (11) being less than or equal to 3, and at least two stages of the multi-stage reactor (11) having different aspect ratios and / or volumes; wherein, the aspect ratio of each stage reactor (11) is equal to the ratio of a first dimension and a second dimension, the first dimension being the dimension between the reactant inlet (111) and the reactant outlet (112) of the reactor (11), and the second dimension being the radial dimension of the reactor (11); Multiple batches of reactants are controlled to be fed into reactors (11) at different stages, and the different batches of reactants are controlled to polymerize with the reaction products of the previous reactor (11) in each stage of the reactor (11) to prepare the propylene / α-olefin copolymer; and The propylene / α-olefin copolymer prepared in the last stage reactor (11) is quenched and devolatilized to obtain the propylene / α-olefin copolymer; Each batch of the reactants includes at least: propylene monomer, α-olefin monomer, solvent and catalyst.

4. The method for preparing the propylene / α-olefin copolymer according to claim 3, characterized in that, The length-to-diameter ratio of each stage reactor (11) is 0.5~3.

5. The method for preparing the propylene / α-olefin copolymer according to claim 3, characterized in that, The preparation method includes: The stirring conditions, temperature, and pressure in each stage of the reactor are controlled to be the same.

6. The method for preparing the propylene / α-olefin copolymer according to claim 3, characterized in that, The temperature in each stage of the reactor is 80℃~220℃, and the pressure is 2MPa~10MPa.

7. The method for preparing the propylene / α-olefin copolymer according to claim 3, characterized in that, The α-olefin monomer is selected from C2~C3. 20 At least one of the olefins.

8. The method for preparing the propylene / α-olefin copolymer according to claim 3, characterized in that, The preparation method further includes: A quenching vessel (13) is connected to the reactant outlet (112) of the last stage reactor (11) of the reactor group, and a devolatilization device (12) is connected to the outlet of the quenching vessel (13) so that the propylene / α-olefin copolymer prepared in the last stage reactor (11) is quenched and devolatilized in sequence by the quenching vessel (13) and the devolatilization device (12) to obtain the propylene / α-olefin copolymer.

9. The use of a propylene / α-olefin copolymer as described in any one of claims 1 to 2 in the preparation of heat-sealing materials.

10. The application according to claim 9, characterized in that, The propylene / α-olefin copolymer and polypropylene material are mixed at a mass ratio of 1:(4~19), and a cast film is prepared by casting process to prepare the heat-sealing material.

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