Polyamide composition as well as preparation method and application thereof

Abstract

The invention discloses a polyamide composition as well as a preparation method and application thereof, and belongs to the technical field of modified polyamide compositions. The polyamide composition comprises polyamide, an epoxy polymer, a carbon nanotube, metal chlorate and other auxiliaries, the metal chlorate is one or two of CaCl2 or ZnCl2, and the obtained material does not contain PFAS substances, has good melt strength, is suitable for extrusion blow molding, and can be used for extrusion molding. And the wall thickness uniformity of the blow molding product and the strength of a bottom welding seam are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of modified polyamide compositions, and particularly relates to a polyamide composition, a preparation method thereof, and an application thereof. Background Art

[0002] The molecular structure of polyamide contains repeating amide groups (-CONH-), and these groups form long chains through the polymerization reaction of carboxylic acid and amine. PA6 and PA66 are widely used due to their excellent mechanical properties, heat resistance, and chemical stability. PA6 is polymerized from caprolactam, while PA66 is polymerized from adipic acid and hexamethylenediamine. The high strength, wear resistance, good heat resistance, and chemical stability of these materials make them ideal materials for manufacturing parts with complex shapes. In the extrusion blow molding technology, polyamide materials need to be first extruded into a tubular parison, and then a hollow product is formed through the blow molding process. The parison will sag under the action of gravity during the extrusion process. Therefore, before the mold is closed for blow molding, it is necessary to keep it sagging naturally for a period of time. This process places higher requirements on the melt strength of the material. Materials with low melt strength are extremely unstable during the extrusion of the parison, and problems such as melt fracture, sagging of the extruded parison, and fracture are likely to occur, which will lead to problems such as product appearance defects or uneven wall thickness.

[0003] In order to improve the melt strength of polyamide, the modification of polyamide materials has become an important way to improve their performance. The prior art discloses a polyamide composition with high heat resistance and high melt strength, which can effectively improve the melt strength and avoid the occurrence of sagging phenomenon by adding an appropriate amount of fibrillatable polytetrafluoroethylene-based fluororesin, and improve the blow molding performance. However, due to the control of PFAS substances by environmental protection regulations, the use of fluororesin is restricted, and it is necessary to research and develop fluorine-free polyamide extrusion blow molding materials. In addition, there are few reports on how to improve the weld strength at the bottom of polyamide extrusion blow molding containers.

[0004] Therefore, it is of great research significance and application value to develop a polyamide composition with improved melt strength, weld strength, and uniform wall thickness difference. Summary of the Invention

[0005] To solve the deficiencies in the prior art, the primary object of the present invention is to provide a polyamide composition, which is modified by using carbon nanotubes, Lewis acid metal chlorides, and other additives. The obtained material does not contain PFAS substances, has good melt strength, is suitable for extrusion blow molding, and effectively improves the wall thickness uniformity of blow molded products and the strength of the weld at the bottom.

[0006] Another object of the present invention is to provide a preparation method of the above polyamide composition.

[0007] Another object of the present invention is to provide the application of the above polyamide composition in the field of preparing extrusion blow molding containers.

[0008] To achieve the above object of the invention, the present invention adopts the following technical solutions:

[0009] The present invention protects a polyamide composition, comprising the following components in parts by weight:

[0010] 75 - 90 parts of polyamide, 7 - 15 parts of epoxy polymer, 1 - 3 parts of carbon nanotubes, 2 - 4 parts of metal chloride, and 0 - 2 parts of other additives;

[0011] Wherein, the metal chloride is one or two of CaCl2 or ZnCl2;

[0012] The polyamide is PA6, and the relative viscosity ≥ 3.4.

[0013] The present invention provides a polyamide composition. On the basis of the modification of polyamide by epoxy polymer, carbon nanotubes are used to support the melt to improve the melt strength. The addition of metal ions in the metal chloride generates an interaction force on the molecular chain, improving the strength of the weld seam and the melt strength.

[0014] Carbon nanotubes and metal chlorides act together from both macroscopic and microscopic aspects, effectively improving the melt strength and maintaining the extrusion stability and wall thickness uniformity of the parison.

[0015] The carbon nanotubes used in the present invention are nanofiber - level fibers, which do not melt at high temperatures and are uniformly dispersed in the polyamide matrix. In the extruded melt parison of the obtained polyamide material, the carbon nanotubes play a role in supporting the melt, transferring and bearing the sagging gravity of the melt, and improving the melt strength. Metal ions and the like of the metal chloride used in the present invention can undergo a complexation reaction with the polar amide groups on the polyamide molecule. On the one hand, it destroys the formation of intermolecular hydrogen bonds in the polyamide, can significantly reduce the crystallization temperature and crystallization rate of the polyamide, is beneficial to reducing the surface cooling and solidification rate of the extruded parison, and enables the surface of the parison to maintain a high molecular activity before welding, thereby improving the strength of the weld seam. On the other hand, it makes the intermolecular chains generate stronger intermolecular forces, increases the internal friction between the molecular chains, is also beneficial to the improvement of the melt strength, and weakens the molecular slip of the melt under the action of gravity.

[0016] The epoxy groups of the epoxy polymer react with the carboxyl groups of the PA molecular chain, playing a role in chain extension, viscosity increase and melt strength improvement.

[0017] Preferably, the weight ratio of the carbon nanotubes to the metal chloride is 1:4 - 3:2.

[0018] The relative viscosity of the polyamide is tested with reference to GB / T 12006.1 - 2009.

[0019] Preferably, the relative viscosity of the polyamide is 3.4 to 4.5.

[0020] When the relative viscosity of the polyamide is lower than 3.4, the melt strength of the polyamide is low, and there will be an obvious problem of melt sag; when the relative viscosity is too high, the fluidity of the polyamide material is too low, resulting in difficulties in melt extrusion.

[0021] Preferably, the epoxy polymer is a copolymer containing an epoxy group monomer and at least one olefinic monomer.

[0022] Preferably, the epoxy polymer contains an epoxy group monomer such as glycidyl acrylate and / or glycidyl methacrylate, and the olefinic monomer is one or more of a monounsaturated olefin containing 2 to 8 carbon atoms, an acrylate containing 4 to 12 carbon atoms, a methacrylate, and vinyl acetate.

[0023] Specifically, the olefinic monomers include, for example, ethylene, propylene, 1-butene, 2-butene, 1-pentene, 2-pentene, (meth)methyl acrylate, (meth)ethyl acrylate, (meth)propyl acrylate, (meth) isopropyl acrylate, (meth)butyl acrylate, and vinyl acetate. Preferably, the olefinic monomers constituting the epoxy polymer are selected from α-olefins containing 2 to 8 carbon atoms, preferably ethylene, and / or optionally an acrylate, methacrylate, or vinyl acetate containing 4 to 12 carbon atoms. More preferably, the olefinic monomers constituting the epoxy polymer simultaneously include ethylene and / or optionally an acrylate, methacrylate, or vinyl acetate containing 4 to 12 carbon atoms, and ethylene accounts for 60 to 99% by weight of the epoxy polymer.

[0024] Preferably, the olefinic monomers constituting the epoxy polymer simultaneously include ethylene and / or optionally an acrylate, methacrylate, or vinyl acetate containing 4 to 12 carbon atoms, and ethylene accounts for 85 to 99% by weight of the epoxy polymer.

[0025] The glycidyl acrylate and / or glycidyl methacrylate constituting the epoxy polymer accounts for 1 to 15% by weight of the epoxy polymer. When the content of glycidyl acrylate and / or glycidyl methacrylate is less than 1%, insufficient reaction activity is provided to react with the polyamide resin, and the desired processing performance cannot be obtained. When the content of glycidyl acrylate and / or glycidyl methacrylate is higher than 15%, the appearance of the molded part tends to deteriorate.

[0026] Preferably, the carbon nanotubes are one or both of single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0027] Preferably, the diameter of the carbon nanotubes is 1 to 15 nm.

[0028] Preferably, the length of the carbon nanotubes is 3 to 50 μm.

[0029] Preferably, the other additives are one or more of antioxidants, lubricants or weathering agents.

[0030] Preferably, the amount of the other additives is 0.1 - 2 parts.

[0031] Specifically, it is selected according to the commonly used antioxidants, lubricants or weathering agents in the prior art.

[0032] More preferably, the antioxidant includes one or two of hindered phenol antioxidants or phosphite antioxidants.

[0033] More preferably, the lubricant includes ester lubricants.

[0034] More preferably, the weathering agent includes ultraviolet light absorbers.

[0035] The present invention also provides a method for preparing a polyamide composition, comprising the following steps:

[0036] Mixing polyamide, epoxy polymer, carbon nanotubes, metal chloride and other additives at high speed; extruding the mixed raw materials by melting, and cooling and pelletizing to obtain the polyamide composition.

[0037] Preferably, the conditions for the high-speed mixing are: the rotation speed of the high-speed mixing blender is 100 - 300 r / min, and the mixing time is 5 - 10 min.

[0038] Preferably, the conditions for the melt extrusion are: the melt extrusion temperature is 190 - 230 °C.

[0039] The application of the above polyamide composition in the field of preparing extrusion blow molding containers is also within the protection scope of the present invention.

[0040] The blow molding process is well known to those skilled in the art and generally includes at least the following steps:

[0041] (1) Heating the polyamide composition to melt it into a uniform melt;

[0042] (2) Extruding the melt through a die to form a preform;

[0043] (3) Injecting a pressurized gas into the preform in a closed mold state, and expanding it to fit the mold cavity wall;

[0044] (4) Performing pressure holding until the melt is completely cured;

[0045] (5) Opening the mold to eject the product.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The present invention provides a polyamide composition. On the basis of adding an epoxy polymer, carbon nanotubes, metal chloride salts and other additives are used for modification together. The metal chloride salt is one or two of CaCl2 or ZnCl2. The obtained material does not contain PFAS substances, has good melt strength, is suitable for extrusion blow molding, and effectively improves the wall thickness uniformity of blow molded products and the strength of the bottom melt joint. Detailed implementation manners

[0048] The present invention will be further elaborated below in conjunction with embodiments. These embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. For the experimental methods without specific conditions in the following examples, they are generally carried out according to the conventional conditions in the art or according to the conditions recommended by the manufacturer; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as conventional markets. Any non-substantive changes and substitutions made by those skilled in the art on the basis of the present invention fall within the scope of protection required by the present invention.

[0049] Some of the reagents selected in the embodiments and comparative examples of the present invention are described as follows:

[0050] Polyamide: PA6 BL5400, Sinopec Baling Petrochemical Co., Ltd., relative viscosity 4.0;

[0051] Epoxy polymer 1#: Elvaloy PTW, ethylene-butyl acrylate-glycidyl methacrylate copolymer, a copolymer composed of 67% ethylene, 28% butyl acrylate and 5% glycidyl methacrylate, DuPont;

[0052] Epoxy polymer 2#: AX8840, ethylene-glycidyl methacrylate copolymer (82% / 8%), Arkema;

[0053] Carbon nanotube 1#: GC-22, single-walled carbon nanotube, Shanghai Dazhan Nanomaterials Co., Ltd.;

[0054] Carbon nanotube 2#: CNT103, multi-walled carbon nanotube, tube diameter 8 - 15 nm, length 50 μm, Beijing Deke Daojin Technology Co., Ltd.;

[0055] Short carbon fiber: T700, diameter 7 microns, cut into 6 mm lengths, Toray Industries, Inc., Japan;

[0056] Metal chloride salt 1#: calcium chloride, Weifang Kunxu Chemical Co., Ltd.;

[0057] Metal chloride salt 2#: zinc chloride, Aladdin Chemical Reagent Network;

[0058] Metal chloride 3#: Copper chloride, from Aladdin Chemical Reagent Network;

[0059] Lubricant: Calcium stearate, BS-3818, commercially available;

[0060] Antioxidant: A mixture of a hindered amine antioxidant (N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine) and a phosphite antioxidant (bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite) in a weight ratio of 1:1, commercially available.

[0061] The polyamide compositions of the examples and comparative examples of the present invention were prepared through the following process:

[0062] Weigh the above-mentioned substances in corresponding proportions and mix them evenly in a high-speed mixer. The rotation speed of the mixing blender is 300 - 400 r / min, and mix for 10 min. Then extrude and pelletize the mixture through a twin-screw extruder, and the temperature of the twin-screw extruder is set at 190°C - 230°C.

[0063] The performance test methods and standards for the polyamide compositions of the examples and comparative examples of the present invention are as follows:

[0064] Pre-treat the prepared polyamide composition pellets by drying at 120°C for 4 h before testing.

[0065] (1) Melt strength grade: Use an extrusion device, set the extrusion temperature according to the resin type, the rotation speed is 300 rpm, by setting the melt extrusion rate at 160 cm 3 / min, set the draw line speed at 0.35 m / s, and test the force value required to draw the melt, which is the melt tension, the force value required for the melt to undergo tensile deformation, representing the magnitude of the melt strength. The melt strength is divided into 5 grades:

[0066] Melt tension ≥ 50 cN, the melt strength grade is judged as "++";

[0067] Melt tension ≥ 40 cN and < 50 cN, the melt strength grade is judged as "+";

[0068] Melt tension ≥ 30 cN and < 40 cN, the melt strength grade is judged as "o";

[0069] Melt tension ≥ 20 cN and < 30 cN, the melt strength grade is judged as "-";

[0070] Melt tension < 20 cN, the melt strength grade is judged as "--";

[0071] (2) Wall thickness difference (mm): Extrude a rectangular oil pot with a cross-sectional size of 60×120 mm and a height of 200 mm. The theoretical wall thickness of the tube blank of the extrusion die head is 3.0 mm; Test and calculate the wall thickness difference on the rectangular interfaces at the top and bottom of the oil pot after cooling.

[0072] (3) Weld joint strength (N): Fix the bottom surface of the rectangular oil pot with the weld joint facing up on a universal tensile testing machine, press down with a metal punch with a ball head diameter of 20 mm in the middle of the weld joint, and record the maximum force value at which the weld joint cracks.

[0073] Examples 1-9

[0074] This example provides a series of polyamide compositions, and the weight parts of each component in the formula are shown in Table 1.

[0075] Table 1 Formulas of Examples 1-9 (parts)

[0076]

[0077] Comparative Examples 1-6

[0078] This comparative example provides a series of polyamide compositions, and each component in the formula is shown in Table 2.

[0079] Table 2 Formulas of Comparative Examples 1-6 (parts)

[0080]

[0081]

[0082] The performance test results of the polyamide compositions in each example and comparative example according to the method mentioned above are shown in Table 3.

[0083] Table 3 Performance test results of each example and comparative example

[0084] Performance Melt strength grade Wall thickness difference (mm) Weld line strength (N) Example 1 ++ 0.18 620 Example 2 ++ 0.24 580 Example 3 + 0.31 590 Example 4 + 0.26 600 Example 5 + 0.33 560 Example 6 O 0.39 600 Example 7 ++ 0.22 550 Example 8 ++ 0.28 580 Example 9 ++ 0.30 590 Comparative Example 1 -- 0.72 660 Comparative Example 2 - 0.55 630 Comparative Example 3 - 0.52 600 Comparative Example 4 O 0.32 430 Comparative Example 5 O 0.38 410 Comparative Example 6 - 0.51 610

[0085] As can be seen from Table 3, in Examples 1-9 of the present invention, through the design and mutual compounding of epoxy polymer, carbon nanotubes, and metal chloride salts, the polyamide composition has good melt strength, is suitable for extrusion blow molding, and effectively improves the wall thickness uniformity of blow molded products and the strength of the bottom weld joint; the wall thickness difference of the products obtained by extrusion blow molding <0.4 mm, the weld joint strength ≥550 N, and the comprehensive performance is good, and the performance of Example 1 is the best.

[0086] In Comparative Example 1, without adding epoxy polymer, the melt strength grade is significantly reduced and the wall thickness difference increases, indicating that the epoxy polymer has a significant effect on improving the melt strength and wall thickness difference; in Comparative Example 2, without adding carbon nanotubes, due to the loss of the supporting force of the carbon nanotubes, the melt strength and wall thickness difference decrease significantly; in Comparative Example 3, using ordinary short carbon fibers, the melt strength also decreases and the wall thickness difference increases; in Comparative Example 4, using copper chloride, which cannot complex with amide groups, results in a decrease in strength and a decrease in the strength of the melt joint; in Comparative Example 5, without adding metal chloride, the effect is similarly poor; in Comparative Example 6, the amount of carbon nanotubes is less than the lower limit of the range and the amount of metal chloride is greater than the upper limit of the range, resulting in a large decrease in melt strength and a significant increase in wall thickness difference.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A polyamide composition, characterized in that, Comprising the following components in parts by weight: 75 - 90 parts of polyamide, 7 - 15 parts of epoxy polymer, 1 - 3 parts of carbon nanotubes, 2 - 4 parts of metal chloride, 0 - 2 parts of other additives; wherein, the metal chloride is one or both of CaCl2 or ZnCl2; the polyamide is PA6 with a relative viscosity ≥ 3.

4.

2. The polyamide composition according to claim 1, characterized in that, The epoxy polymer is a copolymer containing an epoxy monomer and at least one olefinic monomer.

3. The polyamide composition according to claim 1, characterized in that, The epoxy polymer contains an epoxy monomer of glycidyl acrylate and / or glycidyl methacrylate, and the olefinic monomer is one or several of mono-unsaturated olefins containing 2 - 8 carbon atoms, acrylate esters, methacrylate esters, and vinyl acetate containing 4 - 12 carbon atoms; wherein the epoxy monomer accounts for 1 - 15% by weight of the epoxy polymer, and the olefinic monomer accounts for 55 - 99% by weight of the epoxy polymer.

4. The polyamide composition according to claim 1, characterized in that, The relative viscosity of the polyamide is 3.4 - 4.

5.

5. The polyamide composition according to claim 1, characterized in that, The carbon nanotubes are one or both of single-walled carbon nanotubes or multi-walled carbon nanotubes.

6. The polyamide composition according to claim 1, characterized in that, The diameter of the carbon nanotubes is 1 - 15 nm.

7. The polyamide composition according to claim 1, characterized in that, The other additives are one or more of antioxidants, lubricants or weathering agents.

8. A method for preparing the polyamide composition according to any one of claims 1 to 7, characterized in that, Comprising the following steps: High-speed mix the polyamide, epoxy polymer, carbon nanotubes, metal chloride and other additives; extrude the mixed raw materials by melting and then cool and pelletize to obtain the polyamide composition.

9. The method for preparing the polyamide composition according to claim 8, characterized in that, The temperature of the melt extrusion is 190 - 230 °C.

10. Use of the polyamide composition according to any one of claims 1 - 7 in the field of preparing extrusion blow molding containers.

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