A low haze polyamide composition, film and method of making and use thereof

Abstract

The present application relates to the field of polyamide film, and discloses a low-haze polyamide composition, a film and a preparation method and application thereof.The low-haze polyamide composition comprises component A and / or component B, and comprises component C and component D;the component A is PA6;the component B is PA612;the component C is MXD6;and the component D is mixed olefin-maleic anhydride copolymer microspheres;when the component A, the component B, the component C and the component D are compounded in a specific content ratio, the obtained crystal regularity is low, and a polyamide biaxial stretching film with high light transmittance and low haze can be obtained at a lower stretching temperature.

Description

Technical Field

[0001] This invention relates to the field of polyamide films, and more specifically, to a low-haze polyamide composition, film, preparation method and application thereof. Background Technology

[0002] Biaxially oriented polyamide films possess excellent mechanical properties, gas barrier properties, food preservation properties, and heat and oil resistance, making them widely used in the packaging film industry. Due to the biaxial stretching and orientation process, polyamide exhibits enhanced molecular chain orientation, increased crystallinity, and significantly improved mechanical properties, transparency, and gas barrier properties, making it a highly promising barrier packaging material.

[0003] The amide groups in polyamide molecules are a key reason for their high crystallinity. Strong hydrogen bonds between polyamide molecules facilitate rapid crystallization into well-structured spherulites. For example, nylon 6 with a number-average molecular weight of around 28,000 can achieve a spherulite growth rate of approximately 3000 nm / s at 140°C. The presence of spherulites can act as stress concentration points, leading to film breakage during biaxial stretching. Furthermore, the strong hydrogen bonds within the spherulites contribute to the high strength and toughness of the cast film, resulting in high stretching temperatures and significant stretching difficulty. While biaxial stretching of polyamide can be achieved at high stretching temperatures, the relaxation process involving orientation and deorientation at these temperatures reduces film strength and increases thermal aging effects. Therefore, appropriately reducing the crystallinity of polyamide to avoid the formation of numerous well-structured spherulites during the casting stage is crucial for biaxially stretched polyamide films. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention proposes a low-haze polyamide composition. Specifically, it relates to a low-haze polyamide composition, a film, a method for preparing the same, and its applications.

[0005] The purpose of this invention is to provide a novel polyamide composition with high light transmittance and low haze, as well as a biaxially oriented film of the above-mentioned polyamide composition and a method for preparing the same.

[0006] The inventors unexpectedly discovered that when components A, B, C, and D of the present invention are compounded in a specific ratio, the resulting crystal regularity is low and the intermolecular forces are weak. At a lower stretching temperature, a polyamide biaxially oriented film with high light transmittance and low haze can be obtained; thus, the present invention was completed.

[0007] One objective of this invention is to provide a low-haze polyamide composition comprising a blended polyamide and mixed olefin-maleic anhydride copolymer microspheres;

[0008] The composition may specifically include component A and / or component B, and also includes components C and D. The blended polyamide may include at least one of component A and component B, and also includes component C. Component A is PA6, component B is PA612, component C is MXD6, and component D is olefin-maleic anhydride copolymer microspheres.

[0009] The weight ratio of component A to component B can be (0-100):(100-0), preferably (60-95):(5-40); more preferably (70-90):(10-30); for example, the specific weight ratio can be 60:40, 65:35, 70:30, 75:25, 80:20, 85:15, 90:10, 95:5 or any value between the above values ​​or a range between any two of the above values.

[0010] The weight ratio of component C to component (A+B) can be (5-50):(50-95), preferably (10-40):(60-90). For example, the specific weight ratio can be 5:95, 10:90, 15:85, 20:80, 30:70, 40:60, 50:50, or any value between the above values ​​or any range between any two of the above values.

[0011] Based on a total weight of 100 parts by weight for components A, B, and C,

[0012] The weight ratio of component D to component (A+B+C) can be (0.01-0.35):100, preferably (0.03-0.2):100, and more preferably (0.03-0.1):100. For example, the specific weight ratio can be 0.01:100, 0.02:100, 0.03:100, 0.04:100, 0.05:100, 0.06:100, 0.07:100, 0.08:100, 0.09:100, 0.10:100, 0.15:100, 0.18:100, 0.20:100, 0.25:100, 0.30:100, or any value between the above values ​​or a range between any two of the above values.

[0013] According to the present invention, the PA6 has a relative viscosity of 1.5-5.0, preferably 2.0-4.0, and the viscosity test standard is ISO 307; and / or,

[0014] According to the present invention, the PA612 has a relative viscosity of 1.5-5.0, preferably 2.0-4.0, and the viscosity test standard is ISO 307; and / or,

[0015] According to the present invention, the MXD6 has a relative viscosity of 1.5-5.0, preferably 2.0-4.0, and the viscosity test standard is ISO307.

[0016] The low-haze polyamide composition according to the present invention may further include at least one of nylon 66, nylon 610, nylon 11, nylon 12, nylon 1012, nylon 46, nylon 69, nylon 6T, nylon 6 / 66, nylon 66 / 6T, and nylon 6T / 6I. In specific implementations, it may be added to the low-haze polyamide composition in appropriate amounts in the form of mixtures, copolymers, or composites, for example, in a composition of components A, C, and D; a composition of components B, C, and D; or a composition of components A, B, C, and D.

[0017] According to the present invention, component D is a mixed olefin-maleic anhydride copolymer microsphere, preferably with a particle size of 100-300 nm.

[0018] In this invention, the composition contains mixed olefin-maleic anhydride copolymer microspheres with the particle size described above. The particle size can be measured using scanning electron microscopy.

[0019] In this invention, preferably, the mixed olefin-maleic anhydride copolymer microspheres are copolymer microspheres of maleic anhydride and C4 olefins prepared by copolymerization reaction of mixed C4 olefins and maleic anhydride in the presence of nitrogen, an initiator, and an organic solvent. The alternating copolymerization reaction can be a one-step reaction using precipitation polymerization.

[0020] Preferably, the copolymerization reaction temperature can be 80-100℃, and the copolymerization reaction pressure can be 0.8-2MPa.

[0021] In specific implementations, the content of maleic anhydride structural units in the mixed olefin-maleic anhydride copolymer microspheres can be 40-70 mol%, preferably 45-60 mol%, more preferably 48-55 mol%. In the mixed olefin-maleic anhydride copolymer microspheres, the maleic anhydride structural units can be located in the main chain, side chain, or end groups. The content of the maleic anhydride structural units can be determined by... 1 H and 13 C NMR determination. The mixed olefin-maleic anhydride copolymer microspheres may also contain olefin structural units formed from at least one of 1-butene, 1,3-butadiene, and isobutene. The content of the olefin structural units in the mixed olefin-maleic anhydride copolymer microspheres can be determined by... 1 H and 13 C NMR determination. For example, the content of olefin structural units in the mixed olefin-maleic anhydride copolymer microspheres can be 45-55 mol%.

[0022] In specific implementations, the mixed olefin-maleic anhydride copolymer microspheres can be copolymer microspheres of maleic anhydride with n-butene and isobutene. The mixed olefin-maleic anhydride copolymer microspheres mainly contain structural units derived from n-butene and isobutene, with a content of 45–55 mol%.

[0023] The mixed olefin-maleic anhydride copolymer microspheres used in this invention can utilize mixed C4 hydrocarbons as raw materials. These mixed C4 hydrocarbons can originate from various petroleum refining processes and can be a mixture of C4 hydrocarbons. Preferably, the mixed C4 hydrocarbons may contain at least one of 1-butene, isobutene, 1,3-butadiene, n-butane, isobutane, cis-2-butene, and trans-2-butene. For example, they can be liquefied fuels produced during petroleum refining, cracked gas from naphtha cracking, or gases produced from methanol-to-olefins processes. The composition of the mixed C4 hydrocarbons can be analyzed by gas chromatography using an Agilent 7890A gas chromatograph (GC).

[0024] Specifically, the composition of the mixed C4 may be 1-99 wt% 1-butene, 1-99 wt% isobutene, 0-99 wt% 1,3-butadiene, 0-50 wt% 1,2-butadiene, 0-99 wt% n-butane, 1-99 wt% isobutane, 5-20 wt% vinylacetylene, 0-99 wt% cis-2-butene, and 1-99 wt% trans-2-butene.

[0025] According to a preferred embodiment of the present invention, the composition of the mixed C4 may be 5-10 wt% 1-butene, 5-15 wt% isobutene, 10-20 wt% 1,3-butadiene, 5-15 wt% 1,2-butadiene, 0.5-5 wt% n-butane, 0.5-2 wt% isobutane, 20-40 wt% cis-2-butene, 2-10 wt% trans-2-butene, and 5-20 wt% vinylacetylene.

[0026] According to another preferred embodiment of the present invention, the composition of the mixed C4 may be 0.1-2 wt% 1-butene, 10-30 wt% isobutene, 0.01-0.1 wt% 1,3-butadiene, 0.5-5 wt% n-butane, 30-40 wt% isobutane, 20-40 wt% cis-2-butene, and 5-20 wt% trans-2-butene.

[0027] According to another preferred embodiment of the present invention, the composition of the mixed C4 may be 5-15% by weight of 1-butene, 0.5-3% by weight of isobutene, 20-30% by weight of n-butane, 15-30% by weight of cis-2-butene, and 35-45% by weight of trans-2-butene.

[0028] In this invention, the 1-butene, isobutene, and 1,3-butadiene in the mixed C4 can be copolymerized with maleic anhydride. Preferably, the weight ratio of the mixed C4 to maleic anhydride is (0.2–3):1; more preferably (0.8–3):1.

[0029] In this invention, the amount of initiator is sufficient to ensure the copolymerization reaction proceeds. Preferably, the amount of initiator is 0.05–20 mol% of maleic anhydride, and the specific amount can be adjusted according to actual conditions. The initiator can be benzoyl peroxide or azobisisobutyronitrile.

[0030] In this invention, the organic solvent is an inert solvent that does not participate in the copolymerization reaction, providing a dispersion medium for the copolymerization reaction. Preferably, the concentration of maleic anhydride in the organic solvent is 5% to 25% by weight; more preferably, it is 10% to 20% by weight. The organic solvent is preferably at least one selected from isoamyl acetate, butyl acetate, isopropyl acetate, and ethyl acetate.

[0031] In this invention, the copolymerization reaction conditions are sufficient to achieve the copolymerization reaction of the C4 olefins and maleic anhydride in the mixed C4. Preferably, the copolymerization reaction temperature is 60–100°C, more preferably 80–100°C, the copolymerization reaction pressure is 0.5–2 MPa, more preferably 0.8–2 MPa, and the copolymerization reaction time is 5–10 h.

[0032] In this invention, a certain amount of mixed C4 atoms can be introduced into a reaction vessel containing a certain amount of maleic anhydride, initiator, and organic solvent. A copolymerization reaction is carried out under a nitrogen atmosphere and the aforementioned copolymerization conditions. The reaction product is then separated by flash evaporation and centrifugation to obtain the mixed olefin-maleic anhydride copolymer microspheres. The amounts of mixed C4 atoms, maleic anhydride, initiator, and organic solvent are as described above. Flash evaporation can be performed in a flash separator at approximately 25°C and 0 MPa. Centrifugation can be performed at approximately 4000 rpm for approximately 20 minutes. The obtained microspheres can be further washed with hexane and filtered through a sintered glass filter to obtain a filter cake. The filter cake is then vacuum dried at approximately 90°C for approximately 8 hours. The resulting product can be analyzed for its composition and used in the polyamide composition.

[0033] In this invention, the polyamide composition may further contain additives, which may be additives that enhance other properties of the polyamide film without adversely affecting the stretching, mechanical properties, and optical properties of the polyamide film. The additives may be, for example, at least one of antioxidants, slip agents, lubricants, plasticizers, acid absorbers, antistatic agents, and anti-sticking agents.

[0034] A second objective of this invention is to provide a method for preparing the aforementioned low-haze polyamide composition, which may include the following steps:

[0035] The low-haze polyamide composition is obtained by blending the components, including components A and / or B, C and D.

[0036] A third objective of this invention is to provide a polyamide molded article made from the aforementioned low-haze polyamide composition, wherein the content of the low-haze polyamide composition can be 80-100% by weight.

[0037] A fourth objective of this invention is to provide a film made from the aforementioned low-haze polyamide composition, preferably a biaxially oriented film. Preferably, the thickness of the biaxially oriented film can range from 5 to 120 micrometers, more preferably from 10 to 100 micrometers.

[0038] A fifth objective of this invention is to provide a method for preparing the thin film. The method may include the following steps:

[0039] The low-haze polyamide composition is melt-extruded and cast into a polyamide sheet; the polyamide sheet is then stretched to form a film; the stretching is preferably biaxial stretching.

[0040] Specifically, this may include the following steps:

[0041] (1) Prepare a mixture containing components A and / or components B, C, and D;

[0042] (2) The mixture is melt-extruded and cast into polyamide sheets to obtain polyamide sheets;

[0043] (3) The polyamide casting is biaxially stretched to form a film. The stretching temperature can be 90-185℃, preferably 95-175℃, and more preferably 100-165℃.

[0044] According to the present invention, step (1) mainly provides a mixture of the components contained in the above composition for subsequent processing to form a polyamide film. Preferably, step (1) includes mixing PA6, PA612, MXD6 and the mixed olefin-maleic anhydride copolymer in a high-speed mixer.

[0045] According to the present invention, before performing step (2), the mixture obtained in step (1) can be extruded and granulated (the temperature of extrusion granulation can be 120-275°C), and the resulting mixture can be used in the operation of step (2).

[0046] According to the present invention, the process of melting and extruding the mixture in step (2) and casting it into a sheet can be carried out in a casting machine. Preferably, the temperature of the melting and extruding is 235-280°C, more preferably 240-270°C; and the temperature of the casting quench roll is 15-70°C, more preferably 20-60°C.

[0047] According to the present invention, the casting die used in the casting can be selected according to the desired film structure. For example, when a film with a single-layer structure is required, a single-layer die can be used; when a film with a multi-layer structure (a film with a three-layer structure of upper surface layer, core layer and lower surface layer) is required, a multi-layer composite die can be used, and at least one layer (core layer) of the multi-layer composite die is connected to the extruder hopper containing the above-mentioned polyamide composition, so that at least one layer (core layer) of the resulting casting is a polyamide layer formed by the above-mentioned polyamide composition. Of course, all the multi-layer composite dies can be connected to the extruder hopper containing the above-mentioned polyamide composition, so that each layer of the resulting casting is a polyamide layer formed by the above-mentioned polyamide composition.

[0048] Therefore, the polyamide casting sheet is a single-layer structure or a multi-layer structure, preferably a three-layer structure consisting of an upper surface layer, a core layer and a lower surface layer, wherein the upper surface layer, the core layer and the lower surface layer are all layers formed of a polyamide composition.

[0049] According to the present invention, in step (3), the biaxial stretching may include simultaneous stretching or step-by-step stretching. Simultaneous stretching refers to simultaneously performing longitudinal (MD) and transverse (TD) stretching of the film, while step-by-step stretching refers to first performing longitudinal stretching of the film and then performing transverse stretching.

[0050] Preferably, the simultaneous stretching method includes preheating the polyamide casting and then simultaneously performing MD and TD stretching. Preferably, the conditions for the simultaneous stretching method include: a stretching temperature of 90-185℃, more preferably 95-175℃, and even more preferably 100-165℃.

[0051] The MD stretch ratio is 2.5 times or more (e.g., 2.5-6 times), the TD stretch ratio is 2.5 times or more (e.g., 2.5-6 times), the MD stretch rate is 100% / s or more (e.g., 100% / s-500% / s), and the TD stretch rate is 100% / s or more (e.g., 100% / s-500% / s).

[0052] Preferably, the step-by-step stretching method includes: first preheating the polyamide casting, then performing MD stretching, followed by preheating and then TD stretching. Preferably, the conditions for the step-by-step stretching method include: the MD stretching temperature can be 90-185℃, preferably 95-175℃, more preferably 100-165℃; the TD stretching temperature can be 90-185℃, preferably 95-175℃, more preferably 100-165℃.

[0053] The MD stretch ratio is 2.5 times or more (e.g., 2.5-6 times), the TD stretch ratio is 2.5 times or more (e.g., 2.5-6 times), the MD stretch rate is 100% / s or more (e.g., 100% / s-200% / s), and the TD stretch rate is 100% / s or more (e.g., 100% / s-200% / s).

[0054] According to the present invention, the method may or may not involve annealing and setting the stretched film. If annealing is performed, the method further includes annealing and setting the resulting film after step (3). The annealing and setting temperature is preferably 180-200°C. The annealing and setting time is preferably 5-60 seconds. This annealing and setting treatment of the stretched film can improve the dimensional stability of the film.

[0055] According to the present invention, the method may further include subjecting the obtained polyamide film to surface corona treatment, edge trimming, and winding, which are conventional operations in the art and are not particularly limited thereto.

[0056] The sixth objective of this invention is to provide applications of the aforementioned low-haze polyamide composition or the aforementioned film.

[0057] This invention can produce biaxially oriented polyamide films with high light transmittance, low haze, and low stretching temperature, which can be used in the field of packaging films. Attached Figure Description

[0058] Figure 1 The image is a polarized isothermal photograph (POM) of the cast film of Example 3, magnified 500 times.

[0059] Figure 2 The image is a polarized isothermal photograph (POM) of the cast film in Comparative Example 1, magnified 500 times. Detailed Implementation

[0060] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0061] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0062] Source of raw materials

[0063] PA6-1 was purchased from Xinhui Meida, with a relative viscosity of 3.4;

[0064] PA6-2 was purchased from Xinhui Meida, with a relative viscosity of 4.0;

[0065] PA612-1 was purchased from Yingji Curing Chemicals; relative viscosity 3.1.

[0066] PA612-2 was purchased from Yingji Curing Chemicals, with a relative viscosity of 2.6.

[0067] MXD6 cured solids M30m, relative viscosity 2.6;

[0068] The composition (weight percentage) of the mixed C4A is as follows: 1,2-butadiene, 7.45%; 1,3-butadiene, 20.04%; 1-butene, 9.19%; trans-2-butene, 6.27%; cis-2-butene, 34.6%; vinylacetylene, 5.03%; isobutane, 0.68%; isobutene, 13.72%; n-butane, 1.5%; and others, 1.52%.

[0069] The composition (weight percentage) of the mixed C4 B is as follows: 1,2-butadiene 0.03%; 1,3-butadiene 0.02%; trans-2-butene 19.26%; isobutane 30.49%; isobutene 10.2%; cis-2-butene 32.41%; 1-butene 1.47%; n-butane 4.87%; others 1.25%.

[0070] The mixed C4 C composition (weight percentage) is as follows: trans-2-butene, 43.11%; cis-2-butene, 17.92%; n-butane, 26.63%; 1-butene, 5.64%; isobutene, 3.2%; others, 3.5%.

[0071] The tensile strength and elongation at break of the biaxially oriented polyamide film were measured according to the methods specified in GB / T 1040.3-2006;

[0072] The haze and transmittance of the biaxially oriented polyamide film were measured according to the methods specified in GB / T 2410-2008;

[0073] The oxygen permeability of the biaxially oriented polyamide membrane was measured according to the method specified in ASTM D-3985;

[0074] The isothermal polarized light images were measured using a Japanese OLYMPUSBX51 polarizing microscope under the following conditions: The temperature was increased from room temperature to 270°C at a rate of 40°C / min, held at that temperature for 3 minutes, and then decreased to 220°C at a rate of 10°C / min. The crystallization process was observed while maintaining the temperature at that time.

[0075] The content of maleic anhydride structural units in mixed olefin-maleic anhydride copolymer microspheres was determined by... 1 H and 13 C NMR measurement;

[0076] The particle size of the mixed olefin-maleic anhydride copolymer microspheres was measured using scanning electron microscopy.

[0077] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0078] Example 1

[0079] This embodiment illustrates the polyamide composition and polyamide film of the present invention and their preparation method.

[0080] (1) Preparation of mixed olefin-maleic anhydride copolymer microspheres

[0081] Under nitrogen protection, 6.3 kg of mixed C4A was passed into a 200 L reactor containing 21 kg of maleic anhydride, 6 kg of azobisisobutyronitrile and 100 L of isoamyl acetate for copolymerization. The copolymerization reaction pressure was 1.3 MPa, the copolymerization reaction temperature was 80 °C, and the copolymerization reaction time was 5 h.

[0082] The copolymerization product was passed through a flash separator for gas-liquid separation at 25°C and 0 MPa. The resulting liquid-solid mixture was further separated by centrifugation at 4000 rpm for 20 min to obtain a solid product. This solid product was then washed with hexane and filtered through a sand core funnel. The resulting filter cake was then vacuum-dried at 90°C for 8 h to obtain copolymer powder, which was the mixed olefin-maleic anhydride copolymer microspheres. The copolymer powder was tested and found to contain 52.3 mol% maleic anhydride structural units; the average particle diameter was 100 nm.

[0083] (2) Weigh 81 parts by weight of PA6-1, 9 parts by weight of PA612-1, and 10 parts by weight of MXD6, and mix them evenly in a high-speed mixer to obtain a blended polyamide; weigh 0.03 parts by weight of mixed olefin-maleic anhydride copolymer microspheres, mix them evenly with the blended polyamide, and add them to the core extruder and the upper and lower surface extruders of the LCR400 multilayer extrusion casting machine of Labtech Company in Sweden for melt extrusion and casting. The temperature of each section of melt extrusion is 240-270℃, and the temperature of the casting quench roll is 25℃, thereby obtaining a polyamide casting composed of an upper surface layer, a core layer and a lower surface layer;

[0084] (3) Place the above polyamide casting into the stretching fixture of the film biaxial stretching equipment, preheat the polyamide casting first, and then perform MD stretching and TD stretching simultaneously; the conditions include: preheating temperature of 105℃, stretching temperature of 105℃, MD stretching ratio of 3 times, MD stretching rate of 100% / s, TD stretching ratio of 3 times, and TD stretching rate of 100% / s.

[0085] The final film has an average thickness of 25 μm and consists of an upper surface layer, a core layer, and a lower surface layer. The raw material for each layer is the polyamide composition of this embodiment. The properties of the resulting biaxially oriented film are shown in Table 1.

[0086] Example 2

[0087] This embodiment illustrates the polyamide composition and polyamide film of the present invention and their preparation method.

[0088] (1) Preparation of mixed olefin-maleic anhydride copolymer microspheres

[0089] Under nitrogen protection, 20 kg of mixed C4B was passed into a 200 L reactor containing 20 kg of maleic anhydride, 3.5 kg of benzoyl peroxide and 100 L of isoamyl acetate for copolymerization. The copolymerization reaction pressure was 1.2 MPa, the copolymerization reaction temperature was 90 °C, and the copolymerization reaction time was 8 h.

[0090] The copolymerization product was passed through a flash separator for gas-liquid separation at 25°C and 0 MPa. The resulting liquid-solid mixture was further centrifuged at 4000 rpm for 20 min to obtain a solid product. This solid product was then washed with hexane and filtered through a sand core funnel. The resulting filter cake was vacuum dried at 90°C for 8 h to obtain copolymer powder. The copolymer powder was tested and found to contain 52.6 mol% maleic anhydride structural units; the average particle diameter was 300 nm.

[0091] (2) Weigh 42 parts by weight of PA6-1, 18 parts by weight of PA612-1, and 40 parts by weight of MXD6, and mix them evenly in a high-speed mixer to obtain a blended polyamide; weigh 0.1 parts by weight of mixed olefin-maleic anhydride copolymer microspheres, mix them evenly with the blended polyamide, and add them to the core extruder and the upper and lower surface extruders of the LCR400 multilayer extrusion casting machine of Labtech Company in Sweden for melt extrusion and casting. The temperature of each section of melt extrusion is 240-270℃, and the temperature of the casting quench roll is 35℃, thereby obtaining a polyamide casting composed of an upper surface layer, a core layer and a lower surface layer;

[0092] (3) The polyamide casting was placed into the stretching fixture of the biaxial stretching equipment. The polyamide casting was preheated first, and then MD stretching and TD stretching were performed simultaneously. The conditions included: preheating temperature of 105°C, stretching temperature of 105°C, MD stretching ratio of 3.5 times, MD stretching rate of 200% / s, TD stretching ratio of 3.5 times, and TD stretching rate of 200% / s. Finally, a film with an average thickness of 20 μm was obtained, which consisted of an upper surface layer, a core layer, and a lower surface layer. The raw materials of each layer were the polyamide composition of this embodiment. The properties of the obtained biaxially stretched film are shown in Table 1.

[0093] Example 3

[0094] This embodiment illustrates the polyamide composition and polyamide film of the present invention and their preparation method.

[0095] (1) Preparation of mixed olefin-maleic anhydride copolymer microspheres

[0096] Under nitrogen protection, 10 kg of mixed C4C was passed into a 200 L reactor containing 20 kg of maleic anhydride, 5.0 kg of benzoyl peroxide and 100 L of isoamyl acetate for copolymerization. The copolymerization reaction pressure was 1.35 MPa, the copolymerization reaction temperature was 85 °C and the copolymerization reaction time was 6 h.

[0097] The copolymerization product was passed through a flash separator for gas-liquid separation at 25°C and 0 MPa. The resulting liquid-solid mixture was further centrifuged at 6000 rpm for 20 min to obtain a solid product. This solid product was then washed with hexane and filtered through a sand core funnel. The resulting filter cake was then vacuum dried at 90°C for 8 h to obtain copolymer powder. The copolymer powder was tested and found to contain 50.2 mol% maleic anhydride structural units; the average particle diameter was 200 nm.

[0098] (2) Weigh 72.25 parts by weight of PA6-1, 12.75 parts by weight of PA612-1, and 15 parts by weight of MXD6, and mix them evenly in a high-speed mixer to obtain a blended polyamide; weigh 0.06 parts by weight of mixed olefin-maleic anhydride copolymer microspheres, mix them evenly with the blended polyamide, and add them to the core extruder and the upper and lower surface extruders of the LCR400 multilayer extrusion casting machine of Labtech Company in Sweden for melt extrusion and casting. The temperature of each section of melt extrusion is 240-270℃, and the temperature of the casting quench roll is 30℃, thereby obtaining a polyamide casting composed of an upper surface layer, a core layer and a lower surface layer;

[0099] (3) Place the above polyamide casting into the stretching fixture of the film biaxial stretching equipment, preheat the polyamide casting first, and then perform MD stretching and TD stretching simultaneously; the conditions include: preheating temperature of 100℃, stretching temperature of 100℃, MD stretching ratio of 3 times, MD stretching rate of 100% / s, TD stretching ratio of 3 times, and TD stretching rate of 100% / s.

[0100] The final film has an average thickness of 25 μm and consists of an upper surface layer, a core layer, and a lower surface layer. The raw material for each layer is the polyamide composition of this embodiment. The properties of the resulting biaxially oriented film are shown in Table 1.

[0101] Example 4

[0102] This embodiment illustrates the polyamide composition and polyamide film of the present invention and their preparation method.

[0103] (1) Preparation of mixed olefin-maleic anhydride copolymer microspheres. The copolymer microspheres with a particle diameter of 100 nm were prepared according to the method in step (1) of Example 1.

[0104] (2) Weigh 80.75 parts by weight of PA6-1, 4.25 parts by weight of PA612-1, and 15 parts by weight of MXD6, and mix them evenly in a high-speed mixer to obtain a blended polyamide; weigh 0.03 parts by weight of mixed olefin-maleic anhydride copolymer microspheres, mix them evenly with the blended polyamide, and add them to the core extruder and the upper and lower surface extruders of the LCR400 multilayer extrusion casting machine of Labtech Company in Sweden for melt extrusion and casting. The temperature of each section of melt extrusion is 240-270℃, and the temperature of the casting quench roll is 40℃, thereby obtaining a polyamide casting composed of an upper surface layer, a core layer and a lower surface layer;

[0105] (3) Place the above polyamide casting into the stretching fixture of the biaxial stretching equipment, preheat the polyamide casting first, and then perform MD stretching and TD stretching simultaneously; the conditions include: preheating temperature of 105℃, stretching temperature of 105℃, MD stretching ratio of 3.5 times, MD stretching rate of 200% / s, TD stretching ratio of 3.5 times, and TD stretching rate of 200% / s.

[0106] The final film has an average thickness of 20 μm and consists of an upper surface layer, a core layer, and a lower surface layer. The raw material for each layer is the polyamide composition of this embodiment. The properties of the resulting biaxially oriented film are shown in Table 1.

[0107] Example 5

[0108] This embodiment illustrates the polyamide composition and polyamide film of the present invention and their preparation method.

[0109] (1) Preparation of mixed olefin-maleic anhydride copolymer microspheres. The copolymer microspheres were prepared according to the method in step (1) of Example 1, with an average particle diameter of 100 nm.

[0110] (2) Weigh 51 parts by weight of PA6-1, 34 parts by weight of PA612-1, and 15 parts by weight of MXD6, and mix them evenly in a high-speed mixer to obtain a blended polyamide; weigh 0.03 parts by weight of mixed olefin-maleic anhydride copolymer microspheres, mix them evenly with the blended polyamide, and add them to the core extruder and the upper and lower surface extruders of the LCR400 multilayer extrusion casting machine of Labtech Company in Sweden for melt extrusion and casting. The temperature of each section of melt extrusion is 240-270℃, and the temperature of the casting quench roll is 25℃, thereby obtaining a polyamide casting composed of an upper surface layer, a core layer and a lower surface layer;

[0111] (3) Place the above polyamide casting into the stretching fixture of the film biaxial stretching equipment, preheat the polyamide casting first, and then perform MD stretching and TD stretching simultaneously; the conditions include: preheating temperature of 105℃, stretching temperature of 105℃, MD stretching ratio of 3 times, MD stretching rate of 300% / s, TD stretching ratio of 3 times, and TD stretching rate of 300% / s.

[0112] The final film has an average thickness of 25 μm and consists of an upper surface layer, a core layer, and a lower surface layer. The raw material for each layer is the polyamide composition of this embodiment. The properties of the resulting biaxially oriented film are shown in Table 1.

[0113] Example 6

[0114] (1) Preparation of mixed olefin-maleic anhydride copolymer microspheres. The copolymer microspheres with a particle diameter of 100 nm were prepared according to the method in step (1) of Example 1.

[0115] (2) Weigh 95 parts by weight of PA6-1 and 5 parts by weight of MXD6 and mix them evenly in a high-speed mixer to obtain a blended polyamide; weigh 0.01 parts by weight of mixed olefin-maleic anhydride copolymer microspheres, mix them evenly with the blended polyamide, and add them to the core extruder and the upper and lower surface extruders of the LCR400 multilayer extrusion casting machine of Labtech Company in Sweden for melt extrusion and casting. The temperature of each section of melt extrusion is 240-270℃, and the temperature of the casting quench roll is 30℃, thereby obtaining a polyamide casting composed of an upper surface layer, a core layer and a lower surface layer;

[0116] (3) Place the above polyamide casting into the stretching fixture of the film biaxial stretching equipment, preheat the polyamide casting first, and then perform MD stretching and TD stretching simultaneously; the conditions include: preheating temperature of 105℃, stretching temperature of 105℃, MD stretching ratio of 4 times, MD stretching rate of 300% / s, TD stretching ratio of 4 times, and TD stretching rate of 300% / s.

[0117] The final film has an average thickness of 15 μm and consists of an upper surface layer, a core layer, and a lower surface layer. The raw material for each layer is the polyamide composition of this embodiment. The properties of the resulting biaxially oriented film are shown in Table 1.

[0118] Example 7

[0119] (1) Preparation of mixed olefin-maleic anhydride copolymer microspheres. The copolymer microspheres with a particle diameter of 100 nm were prepared according to the method in step (1) of Example 1.

[0120] (2) 95 parts by weight of PA612-1 and 5 parts by weight of MXD6 were mixed evenly in a high-speed mixer to obtain a blended polyamide; 0.35 parts by weight of the blended polyamide were weighed and mixed evenly with the blended polyamide, and then added to the core extruder and the upper and lower surface extruders of the LCR400 multilayer extrusion casting machine of Labtech Company of Sweden for melt extrusion and casting. The temperature of each section of melt extrusion was 240-270℃, and the temperature of the casting quench roll was 25℃, thereby obtaining a polyamide casting composed of an upper surface layer, a core layer and a lower surface layer;

[0121] (3) Place the above polyamide casting into the stretching fixture of the film biaxial stretching equipment, preheat the polyamide casting first, and then perform MD stretching and TD stretching simultaneously; the conditions include: preheating temperature of 105℃, stretching temperature of 105℃, MD stretching ratio of 3 times, MD stretching rate of 200% / s, TD stretching ratio of 3 times, and TD stretching rate of 200% / s.

[0122] The final film has an average thickness of 25 μm and consists of an upper surface layer, a core layer, and a lower surface layer. The raw material for each layer is the polyamide composition of this embodiment. The properties of the resulting biaxially oriented film are shown in Table 1.

[0123] Example 8

[0124] (1) Preparation of mixed olefin-maleic anhydride copolymer microspheres. The copolymer microspheres with a particle diameter of 100 nm were prepared according to the method in step (1) of Example 1.

[0125] (2) 25 parts by weight of PA6-1, 25 parts by weight of PA612-1, and 50 parts by weight of MXD6 were mixed evenly in a high-speed mixer to obtain a blended polyamide; 0.01 parts by weight of the blended polyamide were weighed and mixed evenly with the blended polyamide, and then added to the core extruder and the upper and lower surface extruders of the LCR400 multilayer extrusion casting machine of Labtech Company of Sweden for melt extrusion and casting. The temperature of each section of melt extrusion was 240-270℃, and the temperature of the casting quench roll was 25℃, thereby obtaining a polyamide casting composed of an upper surface layer, a core layer and a lower surface layer;

[0126] (3) Place the above polyamide casting into the stretching fixture of the film biaxial stretching equipment, preheat the polyamide casting first, and then perform MD stretching and TD stretching simultaneously; the conditions include: preheating temperature of 105℃, stretching temperature of 105℃, MD stretching ratio of 3 times, MD stretching rate of 200% / s, TD stretching ratio of 3 times, and TD stretching rate of 200% / s.

[0127] The final film has an average thickness of 25 μm and consists of an upper surface layer, a core layer, and a lower surface layer. The raw material for each layer is the polyamide composition of this embodiment. The properties of the resulting biaxially oriented film are shown in Table 1.

[0128] Example 9

[0129] This embodiment illustrates the polyamide composition and polyamide film of the present invention and their preparation method.

[0130] The method described in Example 8 differs in that the specific types of component A and component B used are PA6-2 and PA612-2, respectively.

[0131] The final film has an average thickness of 25 μm and consists of an upper surface layer, a core layer, and a lower surface layer. The raw material for each layer is the polyamide composition of this embodiment. The properties of the resulting biaxially oriented film are shown in Table 1.

[0132] Example 10

[0133] This embodiment illustrates the polyamide composition and polyamide film of the present invention and their preparation method.

[0134] The method described in Example 3 differs from the method described in Example 3 in that:

[0135] Step (3) adopts a step-by-step biaxial stretching method. The specific operation is as follows: the polyamide casting is preheated, then MD stretching is performed first, then TD stretching is performed after preheating; the conditions include: the preheating temperature before MD stretching is 105℃, the MD stretching temperature is 105℃, the MD stretching ratio is 3 times, and the film MD stretching rate is 100% / s; the preheating temperature before TD stretching is 105℃, the TD stretching temperature is 105℃, the TD stretching ratio is 3 times, and the film TD stretching rate is 200% / s.

[0136] The final film has an average thickness of 25 μm and consists of an upper surface layer, a core layer, and a lower surface layer. The raw material for each layer is the polyamide composition of this embodiment. The properties of the resulting biaxially oriented film are shown in Table 1.

[0137] Example 11

[0138] This embodiment illustrates the polyamide composition and polyamide film of the present invention and their preparation method.

[0139] According to the method described in Example 3, the difference is that step (3) adopts a step-by-step biaxial stretching method. The specific operation is as follows: the polyamide casting is preheated, then MD stretching is performed first, then preheated again and then TD stretching is performed. The conditions include: the preheating temperature before MD stretching is 100°C, the MD stretching temperature is 100°C, the MD stretching ratio is 3 times, and the film MD stretching rate is 300% / s; the preheating temperature before TD stretching is 100°C, the TD stretching temperature is 100°C, the TD stretching ratio is 4 times, and the film TD stretching rate is 300% / s.

[0140] The final film has an average thickness of 15 μm and consists of an upper surface layer, a core layer, and a lower surface layer. The raw material for each layer is the polyamide composition of this embodiment. The properties of the resulting biaxially oriented film are shown in Table 1.

[0141] Comparative Example 1

[0142] The method described in Example 1, except that components B, C, and D were not added;

[0143] The resulting cast film ruptured during biaxial stretching.

[0144] Comparative Example 2

[0145] The method described in Example 10, except that components B, C, and D were not added;

[0146] The resulting cast film ruptured during biaxial stretching.

[0147] Comparative Example 3

[0148] According to the method described in Example 1, except that component C was not added, the blended polyamide contained 90 parts by weight of PA6-1 and 10 parts by weight of PA612-1;

[0149] The final film has an average thickness of 25 μm and consists of an upper surface layer, a core layer, and a lower surface layer. The raw material for each layer is the polyamide composition of this embodiment. The properties of the resulting biaxially oriented film are shown in Table 1.

[0150] Comparative Example 4

[0151] The method is the same as described in Example 1, except that component D is not added;

[0152] The final film has an average thickness of 25 μm and consists of an upper surface layer, a core layer, and a lower surface layer. The raw material for each layer is the polyamide composition of this embodiment. The properties of the resulting biaxially oriented film are shown in Table 1.

[0153] Comparative Example 5

[0154] The method described in Example 1 is different except that components A and B are not added, and the blended polyamide contains 100 parts by weight of MXD6.

[0155] The final film has an average thickness of 25 μm and consists of an upper surface layer, a core layer, and a lower surface layer. The raw material for each layer is the polyamide composition of this embodiment. The properties of the resulting biaxially oriented film are shown in Table 1.

[0156] Comparative Example 6

[0157] The method described in Example 1 differs in that the amount of component D added is 0.4 parts by weight, and the resulting cast film ruptures during biaxial stretching.

[0158] Comparative Example 7

[0159] The method described in Example 1 is different except that the amount of component D added is 0.005 parts by weight.

[0160] Finally, each film with an average thickness of 25 μm was obtained, consisting of an upper surface layer, a core layer, and a lower surface layer, with each layer made from the polyamide composition of this embodiment. The properties of the resulting biaxially oriented films are shown in Table 1.

[0161] Comparative Example 8

[0162] The method described in Example 1 is the same, except that the particle size of component D is 500 nm. The preparation process of component D is as follows:

[0163] Under nitrogen protection, 30 kg of mixed C4B was introduced into a 200 L reactor containing 20 kg of maleic anhydride, 3 kg of benzoyl peroxide and 100 L of isoamyl acetate. The copolymerization reaction pressure was 1.2 MPa, the copolymerization temperature was 100 °C and the copolymerization reaction time was 8 h.

[0164] The copolymerization product was passed through a flash separator for gas-liquid separation at 25°C and 0 MPa. The resulting liquid-solid mixture was further centrifuged at 4000 rpm for 20 min to obtain a solid product. This solid product was then washed with hexane and filtered through a sand core funnel. The resulting filter cake was vacuum dried at 90°C for 8 h to obtain copolymer powder. The copolymer powder was tested and found to contain 52.8 mol% maleic anhydride structural units and an average particle diameter of 500 nm. A film with an average thickness of 25 μm was finally obtained, consisting of an upper surface layer, a core layer, and a lower surface layer. The raw materials for each layer were the polyamide composition of this comparative example. The properties of the obtained biaxially oriented film are shown in Table 1.

[0165] Comparative Example 9

[0166] According to the method described in Example 1, the difference is that the amount of component C added is 60 parts by weight, and the blended polyamide contains 36 parts by weight of PA6-1, 4 parts by weight of PA612-1, and 60 parts by weight of MXD6.

[0167] The resulting cast film ruptured during biaxial stretching.

[0168] Table 1

[0169]

[0170] As can be seen from the data in Table 1, the present invention can obtain biaxially oriented polyamide films with high light transmittance, low haze and low stretching temperature.

[0171] From the appendix Figure 1 and 2 It can also be seen that the structures of the cast films obtained in the embodiments and comparative examples of this application are different. The crystals of the cast films in the embodiments exhibit irregular stripes, and the density of structurally complete spherulites is low. In contrast, the crystals of the cast films in the comparative examples are structurally complete spherulites with a high spherulite density. The more complete the crystal structure, the stronger the hydrogen bonds between its molecular chains, requiring a greater tensile force during the stretching process. The cast film of Comparative Example 1 ruptured during the stretching process.

[0172] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A low-haze polyamide composition comprising component A and / or component B, and comprising component C and component D; in, Component A is PA6; Component B is PA612; Component C is MXD6; component D is a mixed olefin-maleic anhydride copolymer microsphere. The weight ratio of component C to component (A+B) is (5~50):(50~95); Based on a total weight of 100 parts by weight for components A, B, and C, the weight ratio of component D to component (A+B+C) is (0.01~0.35):

100. The particle size of the mixed olefin-maleic anhydride copolymer microspheres is 100~300nm; The mixed olefin-maleic anhydride copolymer microspheres are copolymer microspheres of maleic anhydride and C4 olefins prepared by copolymerization reaction of mixed C4 and maleic anhydride in the presence of nitrogen, initiator and organic solvent.

2. The low-haze polyamide composition according to claim 1, characterized in that: The weight ratio of component A to component B is (0~100):(100~0).

3. The low-haze polyamide composition according to claim 2, characterized in that: The weight ratio of component A to component B is (60~95):(5~40).

4. The low-haze polyamide composition according to claim 3, characterized in that: The weight ratio of component A to component B is (70~90):(10~30).

5. The low-haze polyamide composition according to claim 1, characterized in that: The weight ratio of component C to component (A+B) is (10~40):(60~90).

6. The low-haze polyamide composition according to claim 1, characterized in that: The total weight of components A, B, and C is 100 parts by weight; The weight ratio of component D to component (A+B+C) is (0.03~0.2):

100.

7. The low-haze polyamide composition according to claim 6, characterized in that: The total weight of components A, B, and C is 100 parts by weight; The weight ratio of component D to component (A+B+C) is (0.03~0.1):

100.

8. The low-haze polyamide composition according to claim 1, characterized in that: The PA6 has a relative viscosity of 1.5-5.0, and the viscosity test standard is ISO 307; and / or, The PA612 has a relative viscosity of 1.5-5.0, and the viscosity test standard is ISO 307; and / or, The MXD6 has a relative viscosity of 1.5-5.0, and the viscosity test standard is ISO307.

9. The low-haze polyamide composition according to claim 8, characterized in that: The PA6 has a relative viscosity of 2.0-4.0, and the viscosity test standard is ISO 307; and / or, The PA612 has a relative viscosity of 2.0-4.0, and the viscosity test standard is ISO 307; and / or, The MXD6 has a relative viscosity of 2.0-4.0, and the viscosity test standard is ISO307.

10. The low-haze polyamide composition according to claim 1, characterized in that: The content of maleic anhydride structural units in the mixed olefin-maleic anhydride copolymer microspheres is 40-70 mol.

11. The low-haze polyamide composition according to claim 10, characterized in that: The content of maleic anhydride structural units in the mixed olefin-maleic anhydride copolymer microspheres is 45-60 mol.

12. The low-haze polyamide composition according to claim 11, characterized in that: The content of maleic anhydride structural units in the mixed olefin-maleic anhydride copolymer microspheres is 48-55 mol.

13. The low-haze polyamide composition according to claim 1, characterized in that: The copolymerization reaction temperature is 60–100℃, and the copolymerization reaction pressure is 0.5–2.5 MPa.

14. The low-haze polyamide composition according to claim 13, characterized in that: The copolymerization reaction temperature is 80–100°C, and the copolymerization reaction pressure is 0.8–2 MPa.

15. A method for preparing a low-haze polyamide composition according to any one of claims 1 to 14, characterized in that... Includes the following steps: The low-haze polyamide composition is obtained by blending the components, including components A and / or B, C and D.

16. A polyamide molded article made from the low-haze polyamide composition according to any one of claims 1 to 14, wherein the content of the low-haze polyamide composition is 80 to 100 by weight.

17. A film made from the low-haze polyamide composition according to any one of claims 1 to 14.

18. The film prepared from the low-haze polyamide composition according to claim 17, characterized in that... It is a biaxially oriented film.

19. The film prepared from the low-haze polyamide composition according to claim 18, characterized in that: The thickness of the biaxially oriented film ranges from 5 to 120 micrometers.

20. The film prepared from the low-haze polyamide composition according to claim 19, characterized in that: The thickness of the biaxially oriented film ranges from 10 to 100 micrometers.

21. The method for preparing the thin film according to claim 17, comprising the following steps: The low-haze polyamide composition is melt-extruded and cast into a polyamide sheet; the polyamide sheet is then stretched to form a film.

22. The method for preparing the thin film according to claim 21, characterized in that: The stretching is bidirectional; the stretching temperature is 90~185℃.

23. The method for preparing the thin film according to claim 22, characterized in that: The stretching temperature is 95~175℃.

24. The use of the low-haze polyamide composition according to any one of claims 1 to 14 or the film according to any one of claims 17 to 20.

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