Ternary random copolymer, preparation method thereof and multilayer film structure

Abstract

The invention provides a ternary random copolymer, a preparation method thereof and a multilayer film structure, and belongs to the technical field of heat-sealing copolymer resin. The ternary random copolymer has a structure as shown in the following formula (I): # imgabs0 # formula (I), x is more than 0 and less than 1, y is more than 0 and less than 1, and x + y is more than 0 and less than 1; n is more than 150 and less than 2000. The ternary random copolymer disclosed by the invention has a rigid structural unit, so that the ternary random copolymer has relatively good temperature resistance and relatively high melting temperature and is favorably applied as a heat sealing layer subsequently.

Description

Technical Field

[0001] The present invention relates to the technical field of heat-sealing copolymer resins, and mainly to a ternary random copolymer and a preparation method thereof, and a multilayer film structure; more specifically, to a ternary random copolymer containing 1,3-cyclopentylene and a preparation method thereof, and a multilayer film structure. Background Art

[0002] Polyolefin polymers are formed from hydrocarbons such as propylene and α-olefins which are obtained from petrochemicals and are available in large quantities and are useful in a variety of applications and fields.

[0003] In one of the applications, polyolefin polymers are configured and designed for the production of heat-sealing films and packaging. Heat-sealing films for packaging usually contain multiple polymer layers. Among them, at least one surface layer is called a heat-sealing layer. The working principle of the heat-sealing layer can be understood as follows: when heated, the material of the heat-sealing layer melts and flows rapidly, bonding two or more different materials together; after cooling, the heat-sealing layer quickly solidifies to form a tight and firm bond, providing a strong guarantee for the sealing of the packaging.

[0004] One approach in the related art provides a terpolymer of propylene, ethylene and 1-butene, which can reduce the seal initiation temperature of the polymer. Although heat-sealable films have been produced in the related art, there is still room for further improvement. Summary of the invention

[0005] In view of this, in order to at least partially solve the above-mentioned technical problems, the present invention provides a ternary random copolymer and a preparation method thereof, and a multilayer film structure.

[0006] According to an embodiment of one aspect of the present invention, there is provided a ternary random copolymer having a structure as shown in the following formula (I):

[0007] Formula (I), 0<x<1, 0<y<1, and 0<x+y<1; 150<n<2000.

[0008] In some embodiments, in the ternary random copolymer, the molar content percentage of the structural unit derived from the 1-butene monomer is 2-30%, and the molar content percentage of the 1,3-cyclopentylene monomer is 0.1-20%.

[0009] In some embodiments, the weight average molecular weight of the terpolymer is 6×10 4 ~6×10 5 g / mol; molecular weight distribution index is 1.8~3.2.

[0010] In some embodiments, the melting point of the terpolymer is 100-136° C., and the crystallization temperature is 50-105° C.; the isotacticity of the structural units derived from propylene and the structural units derived from 1-butene in the terpolymer is 92-99%, respectively.

[0011] According to an embodiment of another aspect of the present invention, there is provided a method for preparing a ternary random copolymer as described above, comprising: under anhydrous and oxygen-free conditions, copolymerizing propylene monomer, 1-butene monomer and 1,5-hexadiene monomer in an organic solvent in the presence of a hafnium pyridylamine catalyst and a co-catalyst to obtain a ternary random copolymer solution; precipitating and drying the ternary random copolymer solution to obtain a ternary random copolymer; the co-catalyst is aluminoxane or methylaluminoxane, or a combination of an organoaluminum compound and an organoboron compound.

[0012] In some embodiments, the hafnium pyridinamine catalyst has a structure as shown in formula (II):

[0013] Formula (II).

[0014] In some embodiments, the organoaluminum compound includes: at least one of alkylaluminum and alkylaluminum halide; the organoboron compound includes: at least one of triphenylcarbonium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, N,N-dimethylcyclohexylammonium tetrakis(pentafluorophenyl)borate or N,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate.

[0015] In some embodiments, the copolymerization temperature is 25-100° C., and the reaction time is 5-60 min; the drying temperature is 70-100° C., and the drying time is 4-12 h; the organic solvent includes at least one of benzene, toluene, xylene, pentane, hexane, heptane, octane, and nonane.

[0016] According to another embodiment of the present invention, there is provided a multilayer film structure, the multilayer film structure comprising: a base layer comprising a thermoplastic polymer; and a heat-sealing layer comprising the terpolymer as described above.

[0017] In some embodiments, the multi-layer film structure is prepared by multi-layer co-extrusion casting.

[0018] According to an embodiment of the present invention, the present invention introduces a 1,3-cyclopentylene group having a cyclic structure into the structure of the copolymer, and the introduced cyclic structure can increase the rigidity and thermal stability of the ternary random copolymer and improve the mechanical properties of the ternary random copolymer. When the ternary random copolymer is used as a heat seal layer, the introduction of the cyclic structure allows it to have an easy-to-control and wide temperature operating space from crystallization to melting. Due to the introduction of the cyclic structure, the ternary random copolymer has more excellent mechanical strength and thermal properties, and has excellent transparency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The differential scanning calorimetry temperature rise and fall curve of the ternary random copolymer 1 of Example 1 of the present invention is shown;

[0020] Figure 2 The carbon nuclear magnetic resonance spectrum of the ternary random copolymer 2 of Example 2 of the present invention is shown;

[0021] Figure 3 shows the gel permeation chromatogram of the ternary random copolymer prepared in Example 2 and Example 3 of the present invention;

[0022] Figure 4 The stress-strain curves of the ternary random copolymers prepared in Examples 1 to 3 of the present invention are shown;

[0023] Figure 5 The differential scanning calorimetry temperature rise and fall curve of the ternary random copolymer 3 of Example 3 of the present invention is shown;

[0024] Figure 6 A graph showing the variation of the transmittance of the ternary random copolymers prepared in Examples 2, 4 and 6 of the present invention with wavelength;

[0025] Figure 7 The differential scanning calorimetry temperature rise curves of the ternary random copolymers prepared in Examples 3 and 8 of the present invention are shown. DETAILED DESCRIPTION

[0026] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0027] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0028] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0029] In food packaging, the presence of heat-sealing layer effectively blocks the invasion of oxygen, moisture and microorganisms, and effectively extends the shelf life of food. The material of the heat-sealing layer is usually a multi-polymer (such as a copolymer formed by propylene and 1-butene). After heating, the multi-polymer has excellent adhesion to the surface of various materials. For example, the multi-polymer can be tightly combined with plastic film, paper, and metal foil, making the multi-polymer widely used in composite packaging materials. Through its bonding effect, the layered structure of different materials can be firmly combined together, greatly improving the comprehensive performance of the packaging material. For example, when making composite packaging bags, multi-polymers can densely bond multi-layer materials such as polyester film, aluminum foil and polyethylene film, so that the packaging bag has good barrier properties, certain strength and flexibility.

[0030] The related art provides a 1-butene / propylene / ethylene terpolymer that helps to reduce the seal initiation temperature (SIT) of the polymer and can be used as an important component, but the terpolymer is prepared by using a relatively expensive metallocene-based catalyst. The related art also provides a propylene-based random block copolymer or a resin composition containing the copolymer, the purpose of which is to provide a packaging material suitable for sealing food and other packaged items, but the thermal stability is poor and may decompose at high temperatures, reducing the sealing effect.

[0031] In the process of realizing the concept of the present invention, it is found that by introducing 1,3-cyclopentylene into the ternary random copolymer, the rigidity of the ternary random copolymer is improved, thereby improving its thermal stability and mechanical properties.

[0032] Specifically, according to an embodiment of one aspect of the present invention, a ternary random copolymer is provided, wherein the ternary random copolymer has a structure as shown in the following formula (I):

[0033] Formula (I), wherein 0<x<1, 0<y<1, and 0<x+y<1; 150<n<2000.

[0034] According to an embodiment of the present invention, by introducing a 1,3-cyclopentylidene group having a cyclic structure into the main chain of the ternary random copolymer, the cyclic structure helps to improve the rigidity of the ternary random copolymer, restrict the movement of the chain segments, and help to improve the glass transition temperature of the ternary random copolymer, thereby improving its thermal stability. At the same time, the introduction of the cyclic structure helps to provide a certain steric hindrance, improve the chemical corrosion resistance of the ternary random copolymer, and reduce the possibility of oxidative degradation, thereby increasing the service life of the ternary random copolymer as a heat seal layer in the future. In addition, the introduction of propylene can bring about a higher degree of crystallinity; the addition of 1-butene will appropriately increase flexibility and appropriately reduce crystallinity. Based on the synergy of the three groups of propylene, 1-butene and 1,3-cyclopentylidene, it helps to improve the thermal stability of the ternary random copolymer while having good processability.

[0035] It should be noted that the presence of the cyclic structure can hinder the regular arrangement of the molecular chain segments of the ternary random copolymer, and can form a semi-crystalline or amorphous region, which is beneficial to improve the transparency of the ternary random copolymer. When used as a heat-sealing layer in the future, it has good mechanical properties, thermal properties and excellent transparency. In addition, the structural unit derived from the propylene monomer, the structural unit derived from the 1-butene monomer, and the 1,3-cyclopentylene in the ternary random copolymer are not limited to the arrangement shown in formula (I), and the three structural units can be distributed irregularly.

[0036] For example, 0<x<1, x can be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9; 0<y<1, y can be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9; and at the same time, 0<x+y<1 needs to be satisfied. Such a setting helps to adjust the mechanical and thermal properties of the ternary random copolymer based on different application requirements by adjusting the amount of the three monomers, and helps to obtain different heat-sealing film initiation temperatures (SIT) by adjusting the structure of the ternary random copolymer when it is used as a heat-sealing layer in the future.

[0037] It can be understood that the heat-sealing film initiation temperature can be defined as the sealing temperature when the heat-sealing strength of the heat-sealing film first begins to tend upward from zero heat-sealing strength, and the heat-sealing film initiation temperature marks the critical point at which the heat-sealing film begins to transition from a glassy or crystalline state to a viscous flow state. The heat-sealing film initiation temperature is determined as the sealing temperature when a sealing strength of 1.0N / 15mm is achieved.

[0038] Exemplarily, 150<n<2000, n can be, for example, 155, 300, 500, 700, 900, 1100, 1300, 1500, 1700, 1900, 1950, etc. Such a setting helps to ensure that the ternary random copolymer has a higher molecular weight, and the molecular chains are more tightly entangled, which helps to improve its mechanical properties such as tensile strength, Young's modulus and impact resistance. At the same time, a higher molecular weight can ensure that it has better heat resistance. If n≤150, the melting temperature is low and the heat resistance is poor; if n≥2000, the viscosity after melting is too high, the fluidity is poor, and it is difficult to use in the heat sealing layer.

[0039] In some embodiments, in the ternary random copolymer, the molar content percentage of the structural unit from the 1-butene monomer is 2 to 30%, for example, it can be 2%, 5%, 10%, 15%, 20%, 25% or 30%. In this way, the flexibility of the ternary random copolymer can be improved by introducing a suitable content of 1-butene, and it helps to optimize the transparency of the ternary random copolymer. The molar content percentage of 1,3-cyclopentylene is 0.1 to 20%, for example, it can be 0.1%, 2%, 5%, 10%, 15% or 20%. In this way, it helps to widen the heat sealing temperature window when it is subsequently applied to the heat sealing layer, while improving the thermal stability of the ternary random copolymer.

[0040] In some embodiments, the weight average molecular weight of the terpolymer is 6×10 4 ~6×10 5 g / mol, for example, 6×10 4 g / mol, 1×10 5 g / mol, 1.5×10 5 g / mol, 2×10 5 g / mol, 3×10 5 g / mol, 4×10 5 g / mol, 5×10 5 g / mol, 6×10 5g / mol, etc.; such an arrangement enables the ternary random copolymer to have good mechanical properties; the molecular weight distribution index is 1.8~3.2, for example, it can be 1.8, 2, 2.5, 3 or 3.2, etc. Such an arrangement helps to reduce the viscosity of the ternary random copolymer after melting by balancing the low molecular weight part, and improves the processing fluidity; the high molecular weight part helps to maintain the elasticity of the molten part, and in the subsequent application of heat-sealing film, the rupture of the ternary random copolymer during extrusion and other processes is reduced, and the stability of the ternary random copolymer is further improved. When the molecular weight distribution is adjusted to the above width, the low molecular weight component melts at low temperature, and the two high molecular weight components maintain strength at high temperature, which helps to broaden the processing window of the ternary random copolymer and has a more flexible processing temperature control space.

[0041] Preferably, the weight average molecular weight of the ternary random copolymer is 6×10 4 ~3×10 5 g / mol; molecular weight distribution index is 1.8~3.0. Such a setting helps to further improve the mechanical properties and thermal stability of the ternary random copolymer and has a more suitable processing window.

[0042] In some embodiments, the melting point of the ternary random copolymer is 100-136°C, for example, it can be 100°C, 110°C, 120°C, 130°C or 136°C, etc. Since the ternary random copolymer has a large melting point range, the melting point near 100°C is suitable for low-temperature processing of heat-sealing films to reduce thermal degradation; and the melting point near 136°C helps to promote high-temperature molding. This arrangement makes the ternary random copolymer have good thermal stability and high transparency, which helps to broaden the application range of the ternary random copolymer. The crystallization temperature is 50-105°C, for example, it can be 50°C, 60°C, 70°C, 80°C, 90°C, 100°C or 105°C, etc.; this arrangement helps to adjust the crystallinity of the ternary random copolymer by adjusting the cooling conditions and optimize the transparency of the ternary random copolymer. The isotacticity of the structural units from propylene and 1-butene in the ternary random copolymer is 92-99%, for example, 92%, 94%, 96%, 98% or 99%. The isotacticity can be understood as the ternary random copolymer having a stereo configuration and good selectivity. In its repeating units, the side chains of the structural units from propylene and 1-butene point to the same side of the main chain plane, forming a highly ordered structure, providing good rigidity and support. Based on the high isotacticity of the ternary random copolymer, its structure is more orderly, and it has good processing performance in the subsequent processing and molding process, which helps to prepare a more transparent heat-sealing layer.

[0043] In some embodiments, the crystallinity of the ternary random copolymer is 25-35%, for example, it can be 25%, 28%, 30%, 33% or 35%, etc. This configuration makes the ternary random copolymer have a better ordered structure, which helps to prepare a more transparent heat-sealing layer.

[0044] It should be noted that the melting point or melting temperature and crystallization temperature are determined using differential scanning calorimetry (DSC). The melting point is the temperature at which the material changes from solid to liquid, that is, the critical temperature at which the molecular chain segments begin to move freely and the material loses its rigidity. The endothermic peak formed by DSC during the heating process is usually the second peak formed (the first is to eliminate the thermal history). Crystallinity is the proportion (percentage) of the crystalline area in the material as a whole. The molecular chains in the crystalline area are arranged regularly and orderly, while the amorphous area is disordered and entangled. The polymer material has a high degree of crystallinity, and the material rigidity, hardness, melting point and chemical resistance are enhanced, but the toughness and transparency are reduced. If its crystallinity is low, the material is soft, tough and has high transparency.

[0045] One method of determining the crystallinity of a terpolymer is by differential scanning calorimetry (DSC). The terpolymer sample is sealed in a DSC pan, cooled to about -80°C in a DSC cell with a nitrogen purge rate of 25 cm / min, and a standard thermal history of the terpolymer sample is established by heating to 225°C at 10°C / min. It is then cooled to 10°C / min and reheated to 225°C, and the observed heat of enthalpy is recorded. The observed heat of enthalpy is then divided by the heat of enthalpy of polypropylene (isotactic) (164.92 J / g) and multiplied by 100 to obtain the crystallinity of the terpolymer.

[0046] According to another embodiment of the present invention, there is provided a method for preparing the above-mentioned ternary random copolymer, the preparation method comprising the following operations S1 to S2.

[0047] In operation S1, under anhydrous and oxygen-free conditions, propylene monomer, 1-butene monomer and 1,5-hexadiene monomer are copolymerized in an organic solvent in the presence of a hafnium pyridylamine catalyst and a co-catalyst to obtain a ternary random copolymer solution.

[0048] In this embodiment, the pyridinamine hafnium catalyst is used as the main catalyst, wherein the hafnium metal center combines the monomer molecules (propylene monomer, 1-butene monomer, 1,5-hexadiene) through coordination to form an active center, and the pyridinamine ligand regulates the catalytic activity and selectivity through electronic effects and steric hindrance. The addition of a co-catalyst helps to generate a cationic active center by activating the hafnium metal center. The copolymerization reaction is carried out by inserting the three monomers into a metal-carbon bond, performing a chain growth reaction, and then obtaining a ternary random copolymer solution. Among them, 1,5-hexadiene is cyclized under the catalytic action of the pyridinamine hafnium catalyst, which helps to improve the rigidity of the ternary random copolymer and thus improve its thermal stability.

[0049] In operation S2, the ternary random copolymer solution is precipitated and dried to obtain the ternary random copolymer.

[0050] In this embodiment, the precipitation may be performed by, for example, a non-solvent method, by adding a poor solvent to reduce the solubility of the ternary random copolymer, thereby precipitating it. Drying may be performed by, for example, vacuum drying or heating drying, preferably heating and vacuum drying, to remove the residual solvent and unreacted comonomer in the ternary random copolymer, so as to reduce the generation of bubbles or degradation during subsequent processing.

[0051] According to an embodiment of the present invention, the co-catalyst is aluminoxane or methylaluminoxane, or a combination of an organoaluminum compound and an organoboron compound. The addition of aluminoxane or methylaluminoxane helps to activate the hafnium metal active center, and the double bond of 1,5-hexadiene is inserted into the hafnium metal active center through the steric hindrance effect constructed by hafnium pyridineamine, and the 1,5-hexadiene is promoted to form a ring through coordination. In addition, the addition of the above-mentioned co-catalyst helps to promote the molecular chain growth of the ternary random copolymer; the combination of the organoaluminum compound and the organoboron compound can form a complexation, assist in activating the hafnium metal active center, and cooperate with the steric hindrance effect constructed by hafnium pyridineamine to promote the 1,5-hexadiene to form a ring. Similarly, the combination of the two also helps to promote the molecular chain growth of the ternary random copolymer.

[0052] The preparation method of the invention has simple process and readily available raw materials, and the ternary random copolymer with adjustable physical properties is prepared by using known materials.

[0053] It is understood that the organic solvent can be selected from C 5 ~C 20 A hydrocarbon compound, preferably C 5 ~C 12 The hydrocarbon compound specifically includes at least one of monocyclic or polycyclic aromatic hydrocarbons, linear, branched, cyclic aliphatic hydrocarbons or a mixture thereof.

[0054] In some embodiments, after the copolymerization reaction is completed, a poor solvent is preferably used to terminate the copolymerization reaction to obtain a ternary random copolymer solution. Subsequently, the ternary random copolymer solution is slowly added to a polymer poor solvent for precipitation treatment, and the obtained precipitate is vacuum dried to obtain a ternary random copolymer.

[0055] The present invention does not impose any special restrictions on the type and source of the poor solvent. Its main component can be, for example, at least one of anhydrous ethanol, methanol, n-hexane, petroleum ether, etc. Preferably, the poor solvent used in the present invention is a mixed solution of 98% by volume ethanol and 2% by volume hydrochloric acid.

[0056] In some embodiments, the hafnium pyridinamine catalyst has a structure as shown in formula (II):

[0057] Formula (II). As shown in formula (II), by constructing the asymmetric structure of the hafnium pyridinamine catalyst and its steric hindrance effect, the 1,5-hexadiene monomer can be confined to a smaller spatial range for coordination, thereby promoting its cyclization to form 1,3-cyclopentylene, thereby improving the rigidity of the prepared ternary random copolymer and improving its thermal stability. The hafnium pyridinamine catalyst shown in formula (II) has the characteristics of high activity, good polymerization tolerance, high selectivity, etc., and can promote copolymerization and cyclization reactions.

[0058] It is understood that the hafnium pyridylamine catalyst can be prepared by the method described in the literature (the referenced literature is named: Nonconventional catalysts for isotactic propene polymerization in solution developed by using high-throughput-screening technologies. The name and issue of the journal are Angewandte Chemie International Edition, 2006, 45(20): 3278-3283.), and all operations sensitive to water and oxygen are carried out in a glove box filled with high-purity nitrogen. The containers used are all baked to dryness. The preparation process is shown in the following formula (III):

[0059] Formula (III).

[0060] It should be noted that the hafnium pyridinamine catalyst is a non-metallocene catalyst, and its cost is lower than that of the metallocene catalyst, which helps to reduce the production cost of the ternary random copolymer.

[0061] From the perspective of promoting the activation of the active center of hafnium metal, the organoaluminum compound includes: at least one of alkylaluminum and alkylaluminum halide. Preferably, the organoaluminum compound is trialkylaluminum. More preferably, the organoaluminum compound is selected from at least one of trimethylaluminum, triethylaluminum, and triisobutylaluminum, and more preferably triisobutylaluminum. The organoboron compound includes: at least one of triphenylcarbonium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, N,N-dimethylcyclohexylammonium tetrakis(pentafluorophenyl)borate, or N,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate.

[0062] In some embodiments, when the co-catalyst is triphenylcarbonium tetrakis(pentafluorophenyl)borate and triisobutylaluminum, and the main catalyst is the pyridinamine hafnium catalyst shown in formula (II), the molar ratio of the above three catalysts (triisobutylaluminum: triphenylcarbonium tetrakis(pentafluorophenyl)borate: pyridinamine hafnium catalyst shown in formula (II)) is (50~500):(1~10):1, more preferably (100~300):(2~5):1.

[0063] From the perspective of improving the solubility of several reaction raw materials, the organic solvent includes at least one of benzene, toluene, xylene, pentane, hexane, heptane, octane, and nonane. More preferably, the organic solvent is hexane or xylene, and more preferably xylene. The present invention has no special limitation on the amount of solvent used, and the amount of solvent used in the polymerization reaction well known to those skilled in the art can be used.

[0064] In some embodiments, the copolymerization reaction temperature is 25-100°C, for example, it can be 25°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or 100°C, etc., preferably 40-80°C; the reaction time is 5-60min, for example, it can be 5min, 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min or 60min, etc., preferably 15-30min; the drying temperature is 70-100°C, for example, it can be 70°C, 80°C, 90°C or 100°C, etc., preferably 80°C; the drying time is 4-12h, for example, it can be 4h, 6h, 8h, 10h or 12h, etc., preferably 8h.

[0065] In a specific embodiment, the preparation method of the terpolymer can be as follows:

[0066] Preliminary preparation of reaction materials and temperature setting: Before the polymerization reaction, check the fully mixed stirred tank reactor to ensure that its performance indicators are normal, set the reaction temperature between 40~80℃, and then start the heating unit.

[0067] Addition of organic solvent and three monomers: When the temperature in the reactor reaches the set value accurately and stabilizes, add the prepared organic solvent to the fully mixed stirred tank reactor (total polymerization volume is 200mL), control the addition speed and flow rate to prevent large fluctuations in pressure and temperature. After the organic solvent is added and evenly distributed, add propylene, butene, and 1,5-hexadiene in proportion and order, turn on the stirring device at the same time, and stir at an appropriate speed to fully mix the organic solvent and the three monomers.

[0068] Addition of polymerization co-catalyst and catalyst: Before the polymerization reaction begins, polymerization co-catalyst (2-1000 μmol) and hafnium pyridinamine catalyst (5 μmol, 3.6 mg) are added to the reactor to allow the two to be uniformly mixed in the reaction system.

[0069] Termination of polymerization reaction: After the polymerization reaction reaches a predetermined time or degree, add a mixed solution (1 mL) of 98% ethanol and 2% hydrochloric acid to the reactor, which can react quickly with the catalyst to deactivate it. Continue stirring after the addition to allow the quenching reaction to proceed fully to ensure that the reaction is completely stopped. Then, further process and separate the product, and dry it at 80°C for 8 hours under vacuum conditions to obtain a ternary random copolymer.

[0070] According to another embodiment of the present invention, a multilayer film structure is provided, the multilayer film structure comprising: a base layer comprising a thermoplastic polymer; and a heat-sealing layer comprising the terpolymer as described above.

[0071] It should be understood that the substrate layer can be a single layer film or can be made of multiple layers of different thermoplastic polymers. The thermoplastic polymers used to produce one or more substrate layers include polyolefins, such as polypropylene, polyethylene, polybutylene, polystyrene, polyvinyl chloride, ethylene-containing copolymers, propylene-containing copolymers, and their blends. The heat seal layer is formed on the outer surface of the substrate layer. The thickness of the heat seal layer is relatively thin. For example, the thickness of the heat seal layer can be less than 20 μm, preferably less than 5 μm, further less than 3 μm, and greater than 0.1 μm, for example, it can be 0.2 μm, 0.5 μm, 1 μm, 1.5 μm, or 2 μm. The thickness of the substrate layer can be, for example, greater than 10 μm and less than 50 μm, for example, it can be 15 μm, 20 μm, 30 μm, 40 μm, or 45 μm.

[0072] Based on the multi-layer film structure consisting of a base layer and a heat-sealing layer, the heat-sealing starting temperature of the multi-layer film structure is lowered to a certain extent compared with the base layer, thereby reducing the sealing time, reducing the cycle time and increasing the production rate.

[0073] The heat seal initiation temperature (SIT) can be understood as the sealing temperature at which the heat seal strength first starts to tend upward from zero heat seal strength on the heat seal curve using the sealing film. The heat seal initiation temperature (SIT) is determined as the sealing temperature at which a seal strength of 1.0 N / 15 mm is achieved.

[0074] In some embodiments, the multi-layer film structure is prepared by multi-layer co-extrusion casting.

[0075] Furthermore, when the substrate layer is a high isotacticity (isotacticity index is 97) polypropylene film and is co-extruded with the ternary random copolymer of the present invention as a heat-sealing layer, the heat-sealing starting temperature of the multilayer film structure is at least 10°C lower than the heat-sealing starting temperature of the single-layer substrate layer, preferably, at least 20°C lower.

[0076] The present invention further adjusts the ratio of three monomers (propylene monomer, 1-butene monomer, 1,5-hexadiene monomer) to adjust the structure of the terpolymer, thereby obtaining a heat-sealing layer copolymer polypropylene resin of a cast polypropylene film (CPP) with adjustable mechanical properties from strong and hard to soft and tough, wherein the yield strength of the terpolymer is controlled at 3MPa~30MPa, and the elongation at break is 50~1200%.

[0077] The use of the ternary random copolymer of the present invention as a heat seal layer has the advantages of low melting point, good hot melt, wide heat seal temperature, easy sealing, etc., which is conducive to subsequent use as packaging, such as food packaging, drug packaging, commodity packaging, etc., which helps to provide better health and safety protection, bring more development to the packaging industry, and broaden the application field. By compounding the heat seal layer with the polypropylene film to form a multilayer film structure, the application range of polypropylene materials is further broadened. And by introducing a cyclic structural unit, a ternary polymer with crystallization ability is generated, reducing the proportion of soluble structural units from propylene and structural units from 1-butene, thereby helping to be applied in the field of food packaging.

[0078] The present invention is further described below by examples, drawings and related test experiments and results thereof. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, it is obvious that one or more embodiments may also be implemented without these specific details. And, in the absence of conflict, the details in the following embodiments may be combined arbitrarily into other feasible embodiments.

[0079] It should be noted that the following specific examples are only for illustration, and the protection scope of the present invention is not limited thereto. The chemicals and raw materials used in the following examples are commercially available or homemade by recognized processing methods. It should be noted that the pyridinamine hafnium catalyst shown in formula (II) can be prepared by the preparation method of the above-mentioned known literature.

[0080] When performing nuclear magnetic resonance detection, the embodiment of the present invention uses a high-precision, stable Varian Unity-400 nuclear magnetic resonance spectrometer and measures at a constant temperature of 100°C. The constant temperature can reduce the interference of molecular motion and chemical bond vibration on the results, ensuring accuracy and repeatability. Tetramethylsilane (TMS) is used as an internal standard, which has a unique chemical structure and stable properties and can provide an accurate chemical shift reference; deuterated tetrachloroethane is selected as a solvent, which does not interfere with the sample signal, thereby ensuring that the detection results are accurate and reliable.

[0081] The number average molecular weight M of the terpolymer containing 1,3-cyclopentylene structural units n , weight average molecular weight M w and Z average molecular weight M Z and polydispersity (M w / M n ) is determined using the standard determination method of ASTM D6474, and the molecular weight distribution of the ternary random copolymer is clarified by high temperature gel permeation chromatography (GPC). The present invention uses a PL-GPC-220 high temperature gel permeation chromatograph (GPC), which is equipped with a differential index (RI), viscosity, light scattering detector and three PL-Mix-B chromatographic columns. The three-column combination can separate and detect polymers of different molecular weights. The method uses commercially available polystyrene standards to calibrate the GPC.

[0082] The present invention adopts a differential scanning calorimeter (TA Instruments, Q2000) and a Shimadzu UV-3600 ultraviolet-visible-near infrared spectrophotometer to analyze the thermal properties and transparency of the ternary random copolymer containing 1,3-cyclopentylene structural units.

[0083] The thermal properties analysis was conducted to determine the melting temperature (T m ) and crystallization temperature (T c ). During the test, 5-10 mg of the ternary random copolymer was weighed and placed in the sample cell, heated to 200°C at a rate of 10°C / min, and kept for 10 minutes to eliminate the influence of thermal history. Then the temperature was lowered at a rate of 10°C / min, and the crystallization behavior was observed to determine T c The temperature is then raised for the second time at the same rate, with the temperature range of 25~200℃, and the main physical state of the covering material changes. By analyzing the heat flow curve and combining the thermal analysis theory, the temperature parameters are determined.

[0084] Embodiment 1:

[0085] Propylene, 1-butene and 1,5-hexadiene were copolymerized in an anhydrous and oxygen-free environment, using xylene as a solvent, and the total volume of the reaction system in the polymerization kettle was 200 mL. The specific operation was as follows: xylene, triisobutylaluminum (1 mL, 1.0 mol / L) and 1,5-hexadiene (1.5 mL) were first added to the polymerization kettle, followed by a mixture of propylene and 1-butene (1-butene volume fraction was 15%), and then a catalyst system consisting of a pyridinamine hafnium catalyst (5 μmol, 3.6 mg) and triphenylcarbenium tetrakis(pentafluorophenyl)borate (10 μmol) was added in sequence, wherein the molar ratio of the three elements in the pyridinamine hafnium catalyst: triisobutylaluminum: triphenylcarbenium tetrakis(pentafluorophenyl)borate shown in formula (II) was [Hf]:[Al]:[B]=1:200:2. The polymerization temperature was set at 60° C., the polymerization pressure was maintained at 0.6 MPa, and the copolymerization reaction lasted for 15 min, ultimately obtaining a ternary random copolymer solution containing 1,3-cyclopentylene structural units.

[0086] The obtained ternary random copolymer solution was poured into an ethanol solution containing 2% (volume ratio) hydrochloric acid to precipitate the ternary random copolymer, and a filter cake was obtained by suction filtration. Thereafter, the filter cake was placed in a vacuum oven at 80°C and dried for 8 hours to obtain a ternary random copolymer 1 containing 1,3-cyclopentylene structural units, with a mass of 26.8 g.

[0087] Figure 1 The differential scanning calorimetry temperature rise and fall curve of the ternary random copolymer 1 of Example 1 of the present invention is shown as follows: Figure 1 As shown, the melting point of the ternary random copolymer 1 is 124.2°C, the crystallization temperature is 81.5°C, and it has a wide operating temperature space.

[0088] Embodiment 2:

[0089] Propylene, 1-butene and 1,5-hexadiene were copolymerized in an anhydrous and oxygen-free environment, using xylene as solvent, and the total volume of the reaction system in the polymerization kettle was 200 mL. The specific operation was as follows: toluene, triisobutylaluminum (1 mL, 1.0 mol / L) and 1,5-hexadiene (1 mL) were first added to the polymerization kettle, followed by the addition of a mixture of propylene and 1-butene (1-butene volume fraction was 15%), and then the catalyst system consisting of a pyridinamine hafnium catalyst (5 μmol, 3.6 mg) and tetrakis(pentafluorophenyl)borate N,N-dimethylanilinium (10 μmol) was added in sequence, wherein the molar ratio of the three elements in the pyridinamine hafnium catalyst: triisobutylaluminum: tetrakis(pentafluorophenyl)borate N,N-dimethylanilinium was [Hf]:[Al]:[B]=1:200:2. The polymerization temperature was set at 45° C., the polymerization pressure was maintained at 0.6 MPa, and the copolymerization reaction lasted for 15 min, ultimately obtaining a ternary random copolymer solution containing 1,3-cyclopentylene structural units.

[0090] The same precipitation and drying methods as in Example 1 were used to prepare a ternary random copolymer 2 containing 1,3-cyclopentylene structural units, with a mass of 30.1 g.

[0091] Figure 2 The carbon NMR spectrum of the ternary random copolymer 2 of Example 2 of the present invention is shown. Figure 2 As shown, it was confirmed that the prepared ternary random copolymer 2 had a cyclic structural unit.

[0092] Embodiment 3:

[0093] The preparation process of this Example 3 is substantially the same as that of Example 1, except that the polymerization temperature is adjusted to 50° C., and a ternary random copolymer 3 containing 1,3-cyclopentylene structural units is prepared, with a mass of 27.8 g.

[0094] The terpolymers prepared in Examples 2 and 3 were tested. Figure 3 The gel permeation chromatograms of the ternary random copolymers prepared in Examples 2 and 3 of the present invention are shown. Figure 3 As shown, the ordinate is used to represent the polymer weight fraction within the unit logarithmic molecular weight range (ΔlogM), and the abscissa represents the logarithm of the weight average molecular weight. It can be seen that the molecular weight of Example 2 is 33.4×10 4 g / mol, the molecular weight of Example 3 is 29.4×10 4 g / mol. Figure 4 The stress-strain curves of the ternary random copolymers prepared in Examples 1 to 3 of the present invention are shown. Figure 4As shown, the specific stress-strain values ​​are shown in the subsequent Table 3. It should be noted that the stress-strain test was carried out at a tensile rate of 10 mm / min, indicating that Examples 1 to 3 have good tensile strength.

[0095] Figure 5 FIG. 3 shows a temperature rise and fall curve of the differential scanning calorimetry of the ternary random copolymer 3 of Example 3 of the present invention. Figure 5 As shown, the melting point of the ternary random copolymer 3 is 123.2°C, the crystallization temperature is 83.9°C, and it has a wide operating temperature space.

[0096] Embodiment 4:

[0097] Propylene, 1-butene and 1,5-hexadiene were copolymerized in an anhydrous and oxygen-free environment, with xylene as the solvent, and the total volume of the reaction system in the polymerization kettle was 200 mL. The specific operation was as follows: xylene, methylaluminoxane (5 mL, 10 wt%) and 1,5-hexadiene (8 mL) were first added to the polymerization kettle, followed by a mixture of propylene and 1-butene (1-butene volume fraction was 10%), and then the pyridinamine hafnium catalyst (5 μmol) shown in formula (II) was added in sequence, and the molar ratio of the pyridinamine hafnium catalyst shown in formula (II) to the two elements in methylaluminoxane was [Hf]: [Al] = 1: 100. The polymerization temperature was set at 60 ° C, the polymerization pressure was maintained at 0.4 MPa, and the copolymerization reaction lasted for 20 min, and finally a ternary random copolymer solution containing 1,3-cyclopentylene structural units was obtained.

[0098] The same precipitation and drying methods as in Example 1 were used to prepare a ternary random copolymer 4 containing 1,3-cyclopentylene structural units, with a mass of 23.2 g.

[0099] Embodiment 5:

[0100] Propylene, 1-butene and 1,5-hexadiene were copolymerized in an anhydrous and oxygen-free environment, using xylene as a solvent, and the total volume of the reaction system in the polymerization kettle was 200 mL. The specific operation was as follows: xylene, triisobutylaluminum (2 mL, 1.0 mol / L) and 1,5-hexadiene (2 mL) were first added to the polymerization kettle, followed by a mixture of propylene and 1-butene (1-butene volume fraction was 20%), and then a catalyst system consisting of a pyridinamine hafnium catalyst (5 μmol) and tetrakis(pentafluorophenyl)borate N,N-dimethylbenzylammonium (10 μmol) was added in sequence, wherein the molar ratio of the three elements in the pyridinamine hafnium catalyst: triisobutylaluminum: tetrakis(pentafluorophenyl)borate N,N-dimethylbenzylammonium was [Hf]:[Al]:[B]=1:400:2. The polymerization temperature was set at 70° C., the polymerization pressure was maintained at 0.6 MPa, and the copolymerization reaction lasted for 10 min, ultimately obtaining a ternary random copolymer solution containing 1,3-cyclopentylene structural units.

[0101] The same precipitation and drying methods as in Example 1 were used to prepare a ternary random copolymer 5 containing 1,3-cyclopentylene structural units, with a mass of 23.2 g.

[0102] Embodiment 6:

[0103] Propylene, 1-butene and 1,5-hexadiene were copolymerized in an anhydrous and oxygen-free environment, with xylene as the solvent, and the total volume of the reaction system in the polymerization kettle was 200 mL. The specific operation was as follows: xylene, triisobutylaluminum (1 mL) and 1,5-hexadiene (3 mL) were first added to the polymerization kettle, followed by a mixture of propylene and 1-butene (1-butene volume fraction was 10%), and then a catalyst system consisting of a pyridinamine hafnium catalyst (5 μmol) and triphenylcarbonium tetrakis(pentafluorophenyl)borate (10 μmol) was added in sequence, and the molar ratio of the three elements in the pyridinamine hafnium catalyst: triisobutylaluminum: triphenylcarbonium tetrakis(pentafluorophenyl)borate shown in formula (II) was controlled to be [Hf]:[Al]:[B]=1:200:2. The polymerization temperature was set at 50° C., the polymerization pressure was maintained at 0.5 MPa, and the copolymerization reaction lasted for 15 min, ultimately obtaining a ternary random copolymer solution containing 1,3-cyclopentylene structural units.

[0104] The same precipitation and drying methods as in Example 1 were used to prepare a ternary random copolymer 6 containing 1,3-cyclopentylene structural units, with a mass of 25.2 g.

[0105] Figure 6 The graph showing the transmittance of the ternary random copolymers prepared in Example 2, Example 4 and Example 6 of the present invention as a function of wavelength is shown. Figure 6As shown, it can be seen that the transmittance of Example 2, Example 4 and Example 6 is higher, especially the visible light transmittance of Example 4 and Example 6 is higher, which indicates that the prepared ternary random copolymer has good transparency.

[0106] Embodiment 7:

[0107] Propylene, 1-butene and 1,5-hexadiene were copolymerized in an anhydrous and oxygen-free environment, with xylene as the solvent, and the total volume of the reaction system in the polymerization kettle was 200 mL. The specific operation was as follows: xylene, triisobutylaluminum (1 mL, 1.0 mol / L) and 1,5-hexadiene (15 mL) were first added to the polymerization kettle, followed by the addition of a mixture of propylene and 1-butene (1-butene volume fraction of 5%), and then the catalyst system consisting of a pyridylamine hafnium catalyst (5 μmol) and triphenylcarbonium tetrakis(pentafluorophenyl)borate shown in formula (II) was added in sequence, and the ratio of the main catalyst to the co-catalyst was strictly controlled to be [Hf]:[Al]:[B]=1:200:2. The polymerization temperature was set at 60°C, the polymerization pressure was maintained at 0.5 MPa, the copolymerization reaction lasted for 20 min, and finally a ternary random copolymer solution containing 1,3-cyclopentylene structural units was obtained.

[0108] The same precipitation and drying methods as in Example 1 were used to prepare a ternary random copolymer 7 containing 1,3-cyclopentylene structural units, with a mass of 14.2 g.

[0109] Embodiment 8:

[0110] Propylene, 1-butene and 1,5-hexadiene were copolymerized in an anhydrous and oxygen-free environment, with xylene as the solvent, and the total volume of the reaction system in the polymerization kettle was 200 mL. The specific operation was as follows: xylene, triisobutylaluminum (0.75 mL, 1.0 mol / L) and 1,5-hexadiene (0.5 mL) were first added to the polymerization kettle, followed by a mixture of propylene and 1-butene (1-butene volume fraction was 35%), and then a catalyst system consisting of a pyridylamine hafnium catalyst (5 μmol) and triphenylcarbonium tetrakis(pentafluorophenyl)borate was added in sequence, and the ratio of the main catalyst to the co-catalyst was strictly controlled to be [Hf]:[Al]:[B]=1:150:2. The polymerization temperature was set at 50°C, the polymerization pressure was maintained at 0.5 MPa, the copolymerization reaction lasted for 15 min, and finally a ternary random copolymer solution containing 1,3-cyclopentylene structural units was obtained.

[0111] The same precipitation and drying methods as in Example 1 were used to prepare a ternary random copolymer 8 containing 1,3-cyclopentylene structural units, with a mass of 26.2 g.

[0112] Figure 7The temperature rise curves of the ternary random copolymers prepared in Example 3 and Example 8 of the present invention are shown in the differential scanning calorimetry. Figure 7 As shown, it can be seen that the melting point of the ternary random copolymer 3 prepared in Example 3 is 123.2°C, and the melting point of the ternary random copolymer 8 prepared in Example 8 is 103.3°C.

[0113] The performance of the ternary random copolymers containing 1,3-cyclopentylene structural units in Examples 1 to 8 was tested. In Examples 1 to 8, the reaction conditions were adjusted to successfully prepare ternary random copolymers with a cyclic structure, and the arrangement of the three structural units of the ternary random copolymer was random. The molecular structure and performance of the ternary random copolymer are somewhat different from those of the polypropylene copolymer in the related art. The ternary random copolymer of the present invention is used as a heat-sealing layer of cast polypropylene film (CPP), and is expected to be widely used in the field of heat sealing.

[0114] The physical and chemical performance indicators of the ternary random copolymers of Examples 1 to 8 of the present invention are specifically shown in Table 1.

[0115] Table 1 Relevant performance indicators of various embodiments

[0116]

[0117] Where ΔH m represents the thermal enthalpy, expressed by ΔH m The crystallinity of the ternary random copolymer can be determined. Based on the data in Table 1 above, it can be seen that the introduction of 1,3-cyclopentylene with a cyclic structure can improve the thermal stability of the ternary random copolymer and provide an easily controllable and wide temperature operating space from crystallization to melting. In Examples 4 and 7, the high content of 1,3-cyclopentylene and butene units significantly reduced the melting point of the polymer; among them, the polymer of Example 7 was completely suppressed in crystallization ability, and the melting point and crystallization temperature were not detected.

[0118] In order to comprehensively evaluate the performance of the terpolymer containing 1,3-cyclopentylene structural units, especially the mechanical properties, the present invention uses a mechanical properties testing instrument (model INSTRON 5969) for strict testing. The instrument has high loading and displacement control accuracy and can simulate actual mechanical loads. The test is carried out in accordance with GB / T1040-1992 standard to ensure that the results are comparable. The tensile sample is dumbbell-shaped with an effective size of 10×5×1mm 3, so that stress is concentrated on the effective part, and precise size is conducive to accurate results. The test rate is 20mm / min (wherein, the stress-strain test is tested at a tensile rate of 10mm / min), so that the material can fully demonstrate the mechanical response. Each sample is tested at least 5 times to reduce the influence of material unevenness and experimental errors. The data are statistically analyzed, as shown in Table 2 below, to obtain representative and reliable results, providing data support for copolymer performance evaluation and application development.

[0119] Table 2 Mechanical data of ternary random copolymers

[0120]

[0121] As shown in Table 2, the ternary random copolymers of Examples 1 to 8 have good mechanical properties, indicating that the introduction of 1,3-cyclopentylene with a cyclic structure has greatly improved and enhanced the performance of the ternary polymer, which is helpful to further broaden the application space of polypropylene as a heat sealing layer in the future.

[0122] Application examples 1~5:

[0123] Using a single screw extruder (screw length / diameter ratio of 25), 5 g of the ternary random copolymers prepared in Example 1, Example 2, Example 4, Example 6, and Example 8 were extruded at a melt temperature of 210-250°C and a film drawing speed of 7 m / min to prepare copolymer films with a thickness of 50 μm. A propylene homopolymer film with a thickness of 1000 μm, an isotacticity index of 97, and a melt flow rate of 2 g / 10 min was taken, and each of the copolymer films prepared above was superimposed on the propylene homopolymer film. Then, the superimposed films were placed in a press (Carver Company) and kept at 200°C and 9000 kg load for 5 minutes to form a laminated body bonded to each other.

[0124] Each obtained laminate was stretched longitudinally and transversely (i.e., biaxially) at 150°C using a film stretcher, with a stretching ratio of 6 times, to finally obtain a multilayer film structure with a thickness of 20 μm (including a propylene homopolymer film with a thickness of 18 μm and a copolymer film of the embodiment with a thickness of 2 μm), and a sample with a size of 2 cm×5 cm was cut from the multilayer film structure obtained above. The ternary random copolymers of Examples 1, 2, 4, 6, and 8 correspond to Application Examples 1 to 5, respectively.

[0125] The heat seal initiation temperature test was performed on the multilayer film structures of Examples 1 to 5. The test steps are as follows: In each test, two multilayer film structures prepared above are aligned and stacked to ensure that the adjacent layers are copolymer films of the specific example.

[0126] The multilayer film structures corresponding to Examples 1 to 5 were tested respectively, and the relevant performance parameters obtained are shown in Table 3 below. Among them, the transparency test uses a high-precision, wide-wavelength range spectrophotometer. The prepared samples are placed in the sample cell, and the test wavelength range is set to 250nm~400nm (near ultraviolet light region) and 400nm~800nm ​​(visible light region). The transmittance in the near ultraviolet light region reflects the material's ability to block ultraviolet rays, and the transmittance in the visible light region is related to the actual transparency effect. By measuring the transmittance in two wavelength ranges, the transparency of the material and the transmittance characteristics of light of different wavelengths are comprehensively evaluated.

[0127] Using a sealer (model HSG-ETK 745), seal along one of the 2 cm sides of the sample. The sealing pressure was set to 0.1 N / mm² and the sealing time was 0.5 seconds. Starting from about 10 °C below the melting temperature of the terpolymer, the sealing temperature was increased by 4 °C each time the seal was made.

[0128] After sealing, the sample was cooled. After cooling, the unsealed end of the sample was connected to a mechanical testing machine (manufactured by Instron) and tested at a pulling speed of 50 mm / min. Table 3 below shows the relevant performance test results of the multilayer film structure of each application example.

[0129] Table 3 Performance of multilayer film structures in various application examples

[0130]

[0131] Note: The transmittance (%) data in Table 3 corresponds to the embodiment, not the application example. For example, application example 3 corresponds to embodiment 4, whose transmittance is 90%. Temperature range test method: Use a heat seal tester (such as a heat sealer) to accurately control the temperature, pressure and heat seal time. The equipment must comply with relevant standards (such as ASTM F2029, ISO 18738). The test steps are: (1) Take a 10cm×10cm film sample and ensure that the surface is clean and free of impurities. (2) Fix the pressure (usually 0.1-0.3MPa) and time (1-3 seconds), and gradually adjust the temperature (it is recommended to go from low to high, increasing by 5-10℃ each time). (3) Seal the film at different temperatures, and at least 3 parallel samples are required for each test.

[0132] Temperature range determination method: Observe whether the seal is flat, free of bubbles, cracks or excessive melting. Peel strength test: Use a tensile testing machine to measure the peel strength of the seal (unit: N / 15mm), and record the temperature range corresponding to the maximum peel strength. Determine the temperature range: The temperature range where the peel strength reaches more than 80% of the nominal value of the material is the effective temperature range.

[0133] As shown in Table 3, the ternary random copolymers of several embodiments were used as copolymerized polypropylene for experiments. The addition of 1,3-cyclopentylene structural units and butene units can obtain lower heat sealing temperatures and wider temperature ranges, and the heat sealing starting temperature is basically maintained at 30~85°C; the temperature range spans about 40~60°C. The heat sealing starting temperature (SIT) of the multilayer film structure is at least 10°C lower than the heat sealing starting temperature (SIT) of the single-layer cast polypropylene thin (CPP) film. Further, the heat sealing starting temperature (SIT) of the multilayer film structure is at least 20°C lower than the heat sealing starting temperature (SIT) of the single-layer CPP film. The hot adhesive strength is basically maintained at 6~18N / 15mm, and the transmittance is maintained at 68~92%, which has good performance. Among them, the multilayer film structure of Application Example 2, due to its better molecular regularity, is easy to form a thick lamellar structure, which increases the starting heat sealing temperature of the material. The corresponding example 5 is now explained: the heat seal layer is a ternary random copolymer containing 1,3-cyclopentylene structural units prepared in Example 8, and its melting point T m The temperature range of the heat-sealing film is 103.3°C, and it is used as a heat-sealing layer. The initial heat-sealing temperature is 58.6°C, the temperature range is 67.3-114.5°C, the hot tack strength is 12N / 15mm, and the light transmittance of the ternary random copolymer is 84%. For other application examples, please refer to Application Example 5. Among them, the temperature range of the heat-sealing film refers to the temperature range in which it can be effectively heat-sealed, that is, within this temperature range, the film material can be reliably bonded after heating while maintaining the sealing strength and appearance quality. The width of the temperature range directly affects the stability and applicability of the heat-sealing process.

[0134] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A ternary random copolymer, characterized in that: The ternary random copolymer has a structure as shown in the following formula (I): Formula (I), wherein 0<x<1, 0<y<1, and 0<x+y<1; 150<n<2000.

2. The ternary random copolymer according to claim 1, characterized in that In the ternary random copolymer, the molar content percentage of the structural unit derived from the 1-butene monomer is 2-30%, and the molar content percentage of the 1,3-cyclopentylene monomer is 0.1-20%.

3. The ternary random copolymer according to claim 1 or 2, characterized in that: The weight average molecular weight of the ternary random copolymer is 6×10 4 ~6×10 5 g / mol; molecular weight distribution index is 1.8~3.

2.

4. The ternary random copolymer according to claim 1 or 2, characterized in that: The melting point of the ternary random copolymer is 100-136°C, and the crystallization temperature is 50-105°C; The isotacticity of the structural unit derived from propylene and the structural unit derived from 1-butene in the terpolymer is 92-99%, respectively.

5. A method for preparing a ternary random copolymer as claimed in any one of claims 1 to 4, characterized in that: The preparation method comprises: Under anhydrous and oxygen-free conditions, propylene monomer, 1-butene monomer and 1,5-hexadiene monomer are copolymerized in an organic solvent in the presence of a hafnium pyridylamine catalyst and a co-catalyst to obtain a ternary random copolymer solution; The ternary random copolymer solution is precipitated and dried to obtain the ternary random copolymer; The co-catalyst is aluminoxane or methylaluminoxane, or a combination of an organic aluminum compound and an organic boron compound.

6. The preparation method according to claim 5, characterized in that: The hafnium pyridylamine catalyst has a structure as shown in formula (II): Formula (II).

7. The preparation method according to claim 5, characterized in that: The organoaluminum compound comprises: at least one of alkyl aluminum and alkyl aluminum halide; The organic boron compound comprises at least one of triphenylcarbonium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, N,N-dimethylcyclohexylammonium tetrakis(pentafluorophenyl)borate or N,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate.

8. The preparation method according to claim 6, characterized in that: The copolymerization reaction temperature is 25-100°C and the reaction time is 5-60min; The drying temperature is 70-100°C and the drying time is 4-12h; The organic solvent includes at least one of benzene, toluene, xylene, pentane, hexane, heptane, octane and nonane.

9. A multilayer film structure, characterized in that: The multilayer film structure comprises: a substrate layer comprising a thermoplastic polymer; and A heat-sealing layer comprising the ternary random copolymer according to any one of claims 1 to 4.

10. The multilayer film structure according to claim 9, characterized in that: The multi-layer film structure is prepared by multi-layer co-extrusion casting.

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