Branched nylon 6 composition, preparation method thereof and multi-layer composite film

Abstract

The invention relates to the technical field of nylon 6 composite materials, and discloses a branched nylon 6 composition, a preparation method thereof and a multi-layer composite film. The branched nylon 6 composition contains branched nylon 6, polar polyolefin and an optional antioxidant, and relative to 100 parts by weight of the branched nylon 6, the content of the polar polyolefin is 5-40 parts by weight, and the content of the antioxidant is 0-15 parts by weight. In the branched nylon 6 composition disclosed by the invention, the polar polyolefin component and the branched nylon 6 are relatively good in compatibility, and the toughness and the processing fluidity of the branched nylon 6 can also be improved. The branched nylon 6 composition is used as a middle layer of the film, polyolefin is used as an upper layer and a lower layer respectively, a three-layer co-extrusion composite film is prepared, and the layers of the obtained composite film have good cohesiveness.

Description

Technical Field

[0001] The invention relates to the technical field of nylon 6 composite materials, and in particular to a branched nylon 6 composition and a preparation method thereof and a multilayer composite film. Background Art

[0002] Branched nylon 6 refers to nylon 6 containing branches, which can be obtained by adding multifunctional monomers during the polymerization process, or by adding multifunctional monomers that can react with polyamide molecular chains during the modification process. The branched structure and content of nylon can be regulated by adjusting the type and content of the branching agent. When the content of the branching agent is low, the content of branches in the branched nylon is also low, which not only maintains the advantages of traditional nylon, such as excellent mechanical properties, heat resistance, wear resistance, chemical stability, weather resistance and oxygen barrier properties, good gloss, but also has self-lubricating properties. In addition, the introduction of a small amount of branches can destroy the regularity of the molecular chain, improve the melt strength, and overcome the shortcomings of nylon 6 such as high crystallinity, high viscosity, and insufficient melt fluidity to a certain extent, which is conducive to its processing and molding applications in flow fields dominated by stretching, such as foaming, casting, biaxial stretching, spinning, etc. However, further improvements are needed in terms of toughness and processability. When preparing a multilayer film containing nylon, the adhesion between the nylon layer and the inner and outer layers needs to be improved. Summary of the invention

[0003] The purpose of the present invention is to solve the problem of insufficient toughness and processing fluidity of branched nylon 6 and improve the adhesion between nylon and polyolefin multilayer films, and to provide a branched nylon 6 composition and a preparation method thereof and a multilayer composite film. The branched nylon 6 composition of the present invention has good compatibility, good toughness, good processing fluidity and excellent mechanical properties. The branched nylon 6 composition is used as a film intermediate layer and coextruded with polyolefin to form a multilayer composite film. The obtained multilayer composite film has good adhesion between each layer.

[0004] In order to achieve the above-mentioned object, the first aspect of the present invention provides a branched nylon 6 composition, which contains branched nylon 6, polar polyolefin and optional antioxidant, and relative to 100 parts by weight of the branched nylon 6, the content of the polar polyolefin is 5-40 parts by weight, and the content of the antioxidant is 0-15 parts by weight.

[0005] Preferably, the branch content of the branched nylon 6 is 0.1-1.5%, preferably 0.2-0.6%.

[0006] Preferably, the relative viscosity of the branched nylon 6 is 3.3-3.5.

[0007] Preferably, the weight average molecular weight of the branched nylon 6 is 3×10 4 Up to 5×10 4, molecular weight distribution is 2-3.

[0008] Preferably, the polar polyolefin is a copolymer of ethylene and acrylic acid ester.

[0009] Preferably, the polar polyolefin is at least one of ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer and ethylene-butyl acrylate copolymer.

[0010] Preferably, in the polar polyolefin, the content of the structural unit formed by acrylic acid ester is 15-30% by weight.

[0011] Preferably, the weight average molecular weight of the polar polyolefin is 5×10 4 Up to 12×10 4 .

[0012] Preferably, the antioxidant is at least one of a hindered phenol antioxidant and a phosphite antioxidant.

[0013] The second aspect of the present invention provides a method for preparing the branched nylon 6 composition described above, the method comprising: pre-blending the dried branched nylon 6 with a polar polyolefin and an optional antioxidant, and then adding the mixture into a twin-screw extruder for extrusion and direct pelletizing.

[0014] A third aspect of the present invention provides a multi-layer composite film, comprising polyolefin layers located at the upper layer and the lower layer respectively, and an intermediate layer, wherein the intermediate layer is formed by the branched nylon 6 composition described above.

[0015] According to the technical solution of the present invention, in the branched nylon 6 composition, the polar polyolefin component has good compatibility with the branched nylon 6, and can also improve the toughness and processing fluidity of the branched nylon 6; and, by selecting a branched nylon 6 containing a small amount of branches and introducing a small amount of branches, the branched nylon 6 maintains the advantages of traditional nylon 6 resins, while improving its processing fluidity, melt strength, etc. to a certain extent.

[0016] In addition, the branched nylon 6 composition of the present invention is used as the middle layer of the film, and polyolefin is used as the upper and lower layers respectively to prepare a three-layer co-extruded composite film, and the obtained composite film has good adhesion between the layers. DETAILED DESCRIPTION

[0017] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0018] The branched nylon 6 composition of the present invention contains branched nylon 6, polar polyolefin and optional antioxidant. In the branched nylon 6 composition, the polar polyolefin component has good compatibility with branched nylon 6 and can also improve the toughness and processing fluidity of branched nylon 6.

[0019] In the branched nylon 6 composition of the present invention, the content of the polar polyolefin may be 5-40 parts by weight, preferably 10-35 parts by weight, and more preferably 15-30 parts by weight, relative to 100 parts by weight of the branched nylon 6.

[0020] In the branched nylon 6 composition of the present invention, the content of the antioxidant may be 0-15 parts by weight, preferably 0.1-12 parts by weight, and more preferably 0.5-10 parts by weight, relative to 100 parts by weight of the branched nylon 6.

[0021] In the branched nylon 6 composition of the present invention, in a preferred case, the branch content of the branched nylon 6 is 0.1-1.5%, more preferably 0.2-0.6%. By selecting a branched nylon 6 containing a small amount of branches, the introduction of a small amount of branches allows the branched nylon 6 to maintain the advantages of traditional nylon 6 resins, while improving its processing fluidity, melt strength, etc. to a certain extent. In this article, the percentage of the branch content of the branched nylon 6 is a mass percentage.

[0022] In the branched nylon 6 composition of the present invention, in a preferred case, the relative viscosity of the branched nylon 6 is 3.3-3.5. By selecting a branched nylon 6 with a suitable relative viscosity, the branched nylon 6 composition is used as a film intermediate layer and coextruded with polyolefin to form a multilayer composite film, and the obtained multilayer composite film has significantly better adhesion between the layers.

[0023] In the branched nylon 6 composition of the present invention, in a preferred embodiment, the weight average molecular weight of the branched nylon 6 is 3×10 4 Up to 5×10 4 , the molecular weight distribution is 2-3. By selecting branched nylon 6 with suitable molecular weight and molecular weight distribution, the branched nylon 6 composition is used as the film middle layer, and is coextruded with polyolefin to form a multilayer composite film, and the obtained multilayer composite film has significantly better adhesion between the layers.

[0024] In the present invention, the branched nylon 6 can be prepared according to conventional methods in the art. In some embodiments, the branched nylon 6 is prepared according to the method disclosed in patent application CN108586729A.

[0025] In the branched nylon 6 composition of the present invention, in a preferred case, the polar polyolefin is a copolymer of ethylene and acrylate. Further, in the polar polyolefin, the content of the structural unit formed by acrylate can be 15-30% by weight. These polar polyolefins have good compatibility with branched nylon 6 and can significantly improve the toughness and processing fluidity of branched nylon 6. In some embodiments, the polar polyolefin can be selected from but not limited to at least one of ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA) and ethylene-butyl acrylate copolymer (EBA).

[0026] In the branched nylon 6 composition of the present invention, in a preferred embodiment, the weight average molecular weight of the polar polyolefin is 5×10 4 Up to 12×10 4 .

[0027] In a more preferred embodiment, the weight average molecular weight of the polar polyolefin is 5×10 4 Up to 10×10 4 , and the content of the structural unit formed by acrylic acid ester in the polar polyolefin is 15-30% by weight. According to this preferred embodiment, by selecting a polar polyolefin with a suitable molecular weight and a suitable copolymer composition, the branched nylon 6 composition is used as a film intermediate layer and coextruded with polyolefin to form a multilayer composite film, and the obtained multilayer composite film has significantly better adhesion between the layers.

[0028] In the branched nylon 6 composition of the present invention, the antioxidant can be selected from conventional antioxidants in the art. In some embodiments, the antioxidant is a hindered phenol antioxidant, a phosphite antioxidant, or a combination of a hindered phenol antioxidant and a phosphite antioxidant. The hindered phenol antioxidant can be, for example, the commercially available antioxidant 1010. The phosphite antioxidant can be, for example, the commercially available antioxidant 168.

[0029] According to some embodiments of the present invention, the branched nylon 6 composition contains branched nylon 6 and polar polyolefin, and the content of the polar polyolefin is 5-40 parts by weight relative to 100 parts by weight of the branched nylon 6, the branched content of the branched nylon 6 is 0.1-1.5%, the relative viscosity is 3.3-3.5, and the weight average molecular weight is 3×10 4 Up to 5×10 4 , molecular weight distribution is 2-3.

[0030] According to some other embodiments of the present invention, the branched nylon 6 composition contains branched nylon 6, polar polyolefin and antioxidant. Relative to 100 parts by weight of the branched nylon 6, the content of the polar polyolefin is 5-40 parts by weight, the content of the antioxidant is 0.1-15 parts by weight, the branch content of the branched nylon 6 is 0.1-1.5%, the relative viscosity is 3.3-3.5, and the weight average molecular weight is 3×10 4 Up to 5×10 4 , molecular weight distribution is 2-3.

[0031] According to some other embodiments of the present invention, the branched nylon 6 composition contains branched nylon 6, polar polyolefin and antioxidant, with respect to 100 parts by weight of the branched nylon 6, the content of the polar polyolefin is 15-30 parts by weight, and the content of the antioxidant is 0.5-10 parts by weight; the branched content of the branched nylon 6 is 0.2-0.6%, the relative viscosity is 3.3-3.5, and the weight average molecular weight is 3×10 4 Up to 5×10 4 , molecular weight distribution is 2-3; the polar polyolefin is a copolymer of ethylene and acrylic acid ester.

[0032] According to some other embodiments of the present invention, the branched nylon 6 composition contains branched nylon 6, polar polyolefin and antioxidant, with respect to 100 parts by weight of the branched nylon 6, the content of the polar polyolefin is 15-30 parts by weight, and the content of the antioxidant is 0.5-10 parts by weight; the branched content of the branched nylon 6 is 0.2-0.6%, the relative viscosity is 3.3-3.5, and the weight average molecular weight is 3×10 4 Up to 5×10 4 , molecular weight distribution is 2-3; the polar polyolefin is a copolymer of ethylene and acrylate, and the content of the structural unit formed by acrylate is 15-30% by weight, and the weight average molecular weight is 5×10 4 Up to 12×10 4 .

[0033] According to some other embodiments of the present invention, the branched nylon 6 composition contains branched nylon 6, polar polyolefin and antioxidant, with respect to 100 parts by weight of the branched nylon 6, the content of the polar polyolefin is 15-30 parts by weight, and the content of the antioxidant is 0.5-10 parts by weight; the branched content of the branched nylon 6 is 0.2-0.6%, the relative viscosity is 3.3-3.5, and the weight average molecular weight is 3×10 4 Up to 5×10 4, the molecular weight distribution is 2-3; the polar polyolefin is at least one of ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA) and ethylene-butyl acrylate copolymer (EBA), and the content of the structural unit formed by acrylic acid ester is 15-30% by weight, and the weight average molecular weight is 5×10 4 Up to 12×10 4 The antioxidant is a hindered phenol antioxidant, a phosphite antioxidant, or a combination of a hindered phenol antioxidant and a phosphite antioxidant.

[0034] The present invention also provides a method for preparing the branched nylon 6 composition described above, which comprises: pre-blending the dried branched nylon 6 with a polar polyolefin and an optional antioxidant, and then adding the mixture into a twin-screw extruder for extrusion and direct pelletizing.

[0035] In a specific embodiment, the method for preparing the branched nylon 6 composition comprises:

[0036] The branched nylon 6 was placed in a vacuum drying oven at 90°C for 24 hours, and the polar polyolefin was placed in a vacuum drying oven at 70°C for 24 hours;

[0037] The dried branched nylon 6 and polar polyolefin and an optional antioxidant are physically pre-blended and added into a twin-screw extruder through a feed port. The temperatures from the feed port to the extruder die are 220° C., 245° C., 245° C., 245° C., and 245° C., respectively. The screw speed is 30 r / min, and the products are extruded and directly pelletized to obtain a branched nylon 6 composition.

[0038] The present invention also provides a multilayer composite film, which comprises polyolefin layers located at the upper and lower layers and an intermediate layer, wherein the intermediate layer is formed by the branched nylon 6 composition described above. The multilayer composite film according to the invention has good adhesion between the layers.

[0039] In the multi-layer composite film, the polyolefin layer may be at least one of polyethylene, polypropylene and polyolefin elastomer. In some embodiments, the polyolefin layer is formed of linear low-density polyethylene.

[0040] The branched nylon 6 composition and its preparation method and multilayer composite film of the present invention are further described by examples. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0041] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0042] Example 1

[0043] Branched nylon 6: prepared according to the method of patent application CN108586729A, with a branch content of 0.6%, a relative viscosity of 3.3, and a weight average molecular weight of 3.4×10 4 , the molecular weight distribution is 2.2.

[0044] Ethylene-methyl acrylate copolymer (EMA): weight average molecular weight is 7.1×10 4 , the content of the structural unit formed by methyl acrylate is 18.4% by weight, purchased from Dow Company.

[0045] The branched nylon 6 was placed in a vacuum drying oven at 90° C. and dried for 24 hours, and the ethylene-methyl acrylate copolymer was placed in a vacuum drying oven at 70° C. and dried for 24 hours.

[0046] 90 parts by weight of dried branched nylon 6, 10 parts by weight of ethylene-methyl acrylate copolymer and 1 part by weight of antioxidant 168 / 1010 (compounded in a mass ratio of 1:1) were physically pre-blended and added to a twin-screw extruder through a feeding port. The temperatures from the feeding port to the extruder die were 220° C., 245° C., 245° C., 245° C., and 245° C., respectively. The screw speed was 30 r / min, and the product was extruded and directly pelletized to obtain a branched nylon 6 composition A1.

[0047] Example 2

[0048] Branched nylon 6: prepared according to the method of patent application CN108586729A, with a branch content of 0.2%, a relative viscosity of 3.5, and a weight average molecular weight of 4.2×10 4 , molecular weight distribution is 2.9.

[0049] Ethylene-methyl acrylate copolymer (EMA): weight average molecular weight is 7.1×10 4 , the content of the structural unit formed by methyl acrylate is 18.4% by weight, purchased from Dow Company.

[0050] The branched nylon 6 was placed in a vacuum drying oven at 90° C. and dried for 24 hours, and the ethylene-methyl acrylate copolymer was placed in a vacuum drying oven at 70° C. and dried for 24 hours.

[0051] 80 parts by weight of dried branched nylon 6, 20 parts by weight of ethylene-methyl acrylate copolymer and 1 part by weight of antioxidant 168 / 1010 (compounded in a mass ratio of 1:1) were physically pre-blended and added to a twin-screw extruder through a feeding port. The temperatures from the feeding port to the extruder die were 220° C., 245° C., 245° C., 245° C., and 245° C., respectively. The screw speed was 30 r / min, and the product was extruded and directly pelletized to obtain a branched nylon 6 composition A2.

[0052] Example 3

[0053] Branched nylon 6: prepared according to the method of patent application CN108586729A, with a branch content of 0.4%, a relative viscosity of 3.4, and a weight average molecular weight of 4.9×10 4 , molecular weight distribution is 2.6.

[0054] Ethylene-methyl acrylate copolymer (EMA): weight average molecular weight is 7.1×10 4 , the content of the structural unit formed by methyl acrylate is 18.4% by weight, purchased from Dow Company.

[0055] The branched nylon 6 was placed in a vacuum drying oven at 90° C. and dried for 24 hours, and the ethylene-methyl acrylate copolymer was placed in a vacuum drying oven at 70° C. and dried for 24 hours.

[0056] 70 parts by weight of dried branched nylon 6, 30 parts by weight of ethylene-methyl acrylate copolymer and 1 part by weight of antioxidant 168 / 1010 (compounded in a mass ratio of 1:1) were physically pre-blended and added to a twin-screw extruder through a feeding port. The temperatures from the feeding port to the extruder die were 220° C., 245° C., 245° C., 245° C., and 245° C., respectively. The screw speed was 30 r / min, and the product was extruded and directly pelletized to obtain a branched nylon 6 composition A3.

[0057] Example 4

[0058] Branched nylon 6: prepared according to the method of patent application CN108586729A, with a branch content of 0.6%, a relative viscosity of 3.3, and a weight average molecular weight of 3.4×10 4 , the molecular weight distribution is 2.2.

[0059] Ethylene-ethyl acrylate copolymer (EEA): weight average molecular weight is 10.8×10 4 , the content of the structural unit formed by ethyl acrylate is 26.3% by weight, purchased from Dow Company.

[0060] The branched nylon 6 was placed in a vacuum drying oven at 90°C and dried for 24 hours, and the ethylene-ethyl acrylate copolymer was placed in a vacuum drying oven at 70°C and dried for 24 hours.

[0061] 80 parts by weight of dried branched nylon 6, 20 parts by weight of ethylene-ethyl acrylate copolymer and 1 part by weight of antioxidant 168 / 1010 (compounded in a mass ratio of 1:1) were physically pre-blended and added to a twin-screw extruder through a feeding port. The temperatures from the feeding port to the extruder die were 220° C., 245° C., 245° C., 245° C., and 245° C., respectively. The screw speed was 30 r / min, and the product was extruded and directly pelletized to obtain a branched nylon 6 composition A4.

[0062] Example 5

[0063] Branched nylon 6: prepared according to the method of patent application CN108586729A, with a branch content of 0.6%, a relative viscosity of 3.3, and a weight average molecular weight of 3.4×10 4 , the molecular weight distribution is 2.2.

[0064] Ethylene-butyl acrylate copolymer (EBA): weight average molecular weight is 9.5×10 4 , the content of the structural unit formed by butyl acrylate is 21.4% by weight, purchased from Dow Company.

[0065] The branched nylon 6 was placed in a vacuum drying oven at 90°C and dried for 24 hours, and the ethylene-butyl acrylate copolymer was placed in a vacuum drying oven at 70°C and dried for 24 hours.

[0066] 80 parts by weight of dried branched nylon 6, 20 parts by weight of ethylene-butyl acrylate copolymer and 1 part by weight of antioxidant 168 / 1010 (compounded in a mass ratio of 1:1) were physically pre-blended and added to a twin-screw extruder through a feeding port. The temperatures from the feeding port to the extruder die were 220° C., 245° C., 245° C., 245° C., and 245° C., respectively. The screw speed was 30 r / min, and the product was extruded and directly pelletized to obtain a branched nylon 6 composition A5.

[0067] Example 6

[0068] A branched nylon 6 composition was prepared according to the method of Example 1, except that the branch content of the branched nylon 6 used was 1.5%, thereby obtaining a branched nylon 6 composition A6.

[0069] Example 7

[0070] A branched nylon 6 composition was prepared according to the method of Example 1, except that the branch content of the branched nylon 6 used was 0.1%, thereby obtaining a branched nylon 6 composition A7.

[0071] Comparative Example 1

[0072] A branched nylon 6 composition was prepared according to the method of Example 1, except that ethylene-methyl acrylate copolymer (EMA) was not added, thereby preparing a branched nylon 6 composition D1.

[0073] Comparative Example 2

[0074] The branched nylon 6 composition was prepared according to the method of Example 1, except that the same weight of polyolefin elastomer (POE, weight average molecular weight of 7.1×10 4 , purchased from ExxonMobil) instead of ethylene-methyl acrylate copolymer (EMA) to prepare branched nylon 6 composition D2.

[0075] Test Example 1

[0076] The compatibility and processing fluidity of the branched nylon 6 compositions prepared in the above examples and comparative examples were tested by differential scanning calorimetry (DSC) and rheological methods. The specific criterion for compatibility is the closeness of the melting endothermic peaks of the two components. That is, if the melting endothermic peaks of the two components are obvious melting peaks of the respective components, it means that the compatibility of the two components is poor; if the melting endothermic peaks of the two components are close to each other, or even there is only one melting peak, it means that the compatibility of the two components is good. The processing fluidity can be judged by the viscosity of the rheological test system. The lower the viscosity, the better the processing fluidity.

[0077] The results are shown in Table 1.

[0078] Table 1

[0079] Serial number Compatibility Processing fluidity Example 1 Single melting endothermic peak, good compatibility Viscosity is significantly reduced and fluidity is improved Example 2 Single melting endothermic peak, good compatibility Viscosity is significantly reduced and fluidity is improved Example 3 Single melting endothermic peak, good compatibility Viscosity is significantly reduced and fluidity is improved Example 4 Single melting endothermic peak, good compatibility Viscosity is significantly reduced and fluidity is improved Example 5 Single melting endothermic peak, good compatibility Viscosity is significantly reduced and fluidity is improved Example 6 Single melting endothermic peak, good compatibility Viscosity is significantly reduced and fluidity is improved Example 7 Single melting endothermic peak, good compatibility The viscosity is slightly reduced and the fluidity is slightly improved Comparative Example 1 Melting point 220℃, single component Single component, poor fluidity Comparative Example 2 2 obvious melting peaks, poor compatibility The viscosity is reduced and the processing fluidity is improved

[0080] It can be seen from the data in Table 1 that the branched nylon 6 composition of the present invention has significantly better compatibility and processing fluidity.

[0081] Test Example 2

[0082] The branched nylon 6 composition prepared in the above examples and comparative examples was used as the film middle layer, and a linear low-density polyethylene (weight average molecular weight of 1.27×10 5 , molecular weight distribution of 3.85, purchased from Dow Company) were used as the upper and lower layers to prepare a three-layer co-extruded composite film.

[0083] The adhesion between the layers of these composite films was evaluated by testing the degree of easy peeling between the polyolefin layer and the nylon layer. The results are shown in Table 2 below.

[0084] Table 2

[0085] Serial number Adhesion Example 1 Cannot be peeled off, good adhesion Example 2 Cannot be peeled off, good adhesion Example 3 Cannot be peeled off, good adhesion Example 4 Cannot be peeled off, good adhesion Example 5 Cannot be peeled off, good adhesion Example 6 Cannot be peeled off, good adhesion Example 7 Cannot be peeled off, good adhesion Comparative Example 1 Direct separation, poor adhesion Comparative Example 2 Direct separation, poor adhesion

[0086] It can be seen from the data in Table 2 that the three-layer co-extruded composite film is prepared by using the branched nylon 6 composition of the present invention as the middle layer of the film and polyolefin as the upper and lower layers, and the obtained composite film has significantly better adhesion between the layers.

[0087] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A branched nylon 6 composition, characterized in that: The branched nylon 6 composition contains branched nylon 6, polar polyolefin and optional antioxidant. Relative to 100 parts by weight of the branched nylon 6, the content of the polar polyolefin is 5-40 parts by weight, and the content of the antioxidant is 0-15 parts by weight.

2. The branched nylon 6 composition according to claim 1, characterized in that The branch content of the branched nylon 6 is 0.1-1.5%, preferably 0.2-0.6%.

3. The branched nylon 6 composition according to claim 1 or 2, characterized in that: The relative viscosity of the branched nylon 6 is 3.3-3.

5.

4. The branched nylon 6 composition according to any one of claims 1 to 3, characterized in that The weight average molecular weight of the branched nylon 6 is 3×10 4 Up to 5×10 4 , molecular weight distribution is 2-3.

5. The branched nylon 6 composition according to claim 1, characterized in that The polar polyolefin is a copolymer of ethylene and acrylic acid ester.

6. The branched nylon 6 composition according to claim 5, characterized in that The polar polyolefin is at least one of ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer and ethylene-butyl acrylate copolymer.

7. The branched nylon 6 composition according to claim 1, 5 or 6, characterized in that: In the polar polyolefin, the content of the structural unit formed by acrylic acid ester is 15-30% by weight.

8. The branched nylon 6 composition according to claim 1, 5, 6 or 7, characterized in that: The weight average molecular weight of the polar polyolefin is 5×10 4 Up to 12×10 4 .

9. The branched nylon 6 composition according to claim 1, characterized in that: The antioxidant is at least one of a hindered phenol antioxidant and a phosphite antioxidant.

10. A method for preparing the branched nylon 6 composition according to any one of claims 1 to 9, characterized in that: The method comprises: pre-blending dried branched nylon 6, polar polyolefin and an optional antioxidant, and then adding the dried branched nylon 6 and polar polyolefin and an optional antioxidant into a twin-screw extruder for extrusion and direct pelletizing.

11. A multilayer composite film comprising a polyolefin layer and an intermediate layer respectively located at an upper layer and a lower layer, characterized in that: The middle layer is formed from the branched nylon 6 composition according to any one of claims 1 to 9.