A precipitation-resistant high-toughness polyamide composition and its preparation method

Abstract

The present invention discloses a precipitation-resistant, high-toughness polyamide composition and a preparation method thereof. The polyamide composition comprises 72-94 wt% semi-crystalline polyamide, 5-15 wt% plasticizer, 0-10 wt% toughening agent, and 1-3 wt% additives. The polyamide composition, prepared through a twin-screw extrusion granulation process, exhibits excellent high- and low-temperature toughness and precipitation resistance.

Description

Technical Field

[0001] The present invention belongs to the field of polymer material synthesis and processing, and specifically relates to a precipitation-resistant high-toughness polyamide composition and a preparation method thereof Background Art

[0002] As an engineering plastic, nylon boasts excellent mechanical strength, fatigue strength, heat resistance, and chemical resistance, and has been widely used in a variety of fields, including automotive and industrial applications. Plasticizers are used in nylon applications, significantly increasing the material's toughness and making it suitable for diverse working conditions. However, most plasticizers are small molecules, which can lead to precipitation and media intolerance during use, impacting the material's long-term performance.

[0003] Because nylon has amide bonds and terminal amino and carboxyl groups, it is necessary to take into account the reactions of nylon's functional groups when improving its performance, such as the breaking of nylon hydrogen bonds, chain extension of terminal amino or terminal carboxyl groups and fillers, etc.

[0004] Patents CN 112480661 A and CN 107325552 A disclose a high-temperature, hydrolysis-resistant modified polyamide piping material and a high-pressure, high-flexibility nylon piping material, respectively. Both utilize small-molecule benzenesulfonamide plasticizers for toughness improvement. However, these materials experience significant precipitation during use, leading to a decrease in material performance and impacting operating conditions. This is particularly true in automotive cooling pipe applications, where precipitation of the small-molecule plasticizer into the coolant significantly reduces coolant efficiency. Patent CN 104610736 A discloses the use of a polar liquid rubber toughening agent to improve the low-temperature toughness of nylon materials. However, liquid rubber itself is a low-molecular-weight toughening agent, and its toughening effect is significantly inferior to that of higher-molecular-weight toughening agents, failing to achieve the desired toughening effect. Patent CN112266609 A discloses a fully renewable toughened nylon, its preparation method and application. It uses a liquid toughening agent such as butyl ricinoleate or epoxidized soybean oil. The -CH2- radicals in the nylon are first excited by an initiator, thereby grafting them with the double bonds of the liquid toughening agent. However, the -CH2- radicals in the nylon main chain are distributed in large quantities and are randomly initiated, which easily causes great uncertainty in the reaction with the double bonds in the toughening agent, affecting the toughening effect. At the same time, due to the random initiation of the excited free radicals, the nylon itself will cause chain scission to generate small molecules, which is more likely to cause precipitation in the system.

[0005] In view of this, with regard to the existing technical solutions, on the one hand, it is necessary to improve the precipitation problem of toughness improvers (plasticizers or toughening agents) in existing materials and improve the long-term performance of the materials. On the other hand, it is necessary to take into account the high toughness of the material itself. Therefore, it is urgent to develop a polyamide material with low precipitation and high toughness to solve the above problems, thereby broadening the application range of the material and improving its long-term service life. Summary of the Invention

[0006] The present invention aims to provide a low-precipitation, high-toughness polyamide composition and its preparation method. The polyamide composition is suitable for applications such as water, oil, and gas pipelines, cables, and structural components. By polymerizing a small molecule plasticizer, optimizing different reactive monomers, using a suitable polymerization method, and regulating the plasticizer's molecular weight, the plasticizer's precipitation resistance is improved, thereby producing a nylon material with low precipitation and high toughness.

[0007] In order to achieve the above object of the invention, the technical solution adopted by the present invention is as follows:

[0008] A precipitation-resistant and high-toughness polyamide composition comprises the following components in percentage by weight:

[0009]

[0010] The semi-crystalline polyamide is an aliphatic polyamide containing a -CO-NH- structure, with a ratio of methylene groups to amide groups of 6.0 or greater, and includes one or more of PA6, PA66, PA610, PA612, PA1012, PA11, PA12, PA1212, PA614, PA616, and PA618. The content of the semi-crystalline polyamide is 72 to 94 wt%, for example, 72%, 73%, 75%, 78%, 80%, 85%, 90%, 92%, 93%, and the like.

[0011] The plasticizer of the present invention can be prepared from component A and component B:

[0012] The general formula of component A is shown below:

[0013]

[0014] The R1 functional group can be H, or an alkyl functional group such as methyl or ethyl.

[0015] The R2 and R3 groups are selected from H or functional groups containing 1-4 carbon atoms, and at least one of them contains an unsaturated functional group. The unsaturated functional group can be selected from one or more of a carbon-carbon double bond, a carbon-carbon triple bond, and an acid anhydride. The preferred component A includes at least one of N,N-diallylbenzenesulfonamide, N,N-diallyl-4-methylbenzenesulfonamide, 4-methyl-N,N-di(prop-2-ynyl)benzenesulfonamide, and N-ethynyl-N,4-dimethylbenzenesulfonamide, more preferably N,N-diallylbenzenesulfonamide.

[0016] Component B is a C2-C4 unsaturated olefin, which can be selected from one or more of ethylene, propylene, n-butene, isobutylene, etc., preferably propylene and / or n-butene;

[0017] The molar ratio of component A / component B is 1:1 to 30:1, preferably 2:1 to 20:1;

[0018] The plasticizer has a molecular weight of 10,000-80,000, preferably 20,000-60,000. Considering the precipitation properties of the copolymer, when the molecular weight is relatively small, for example, a few hundred or even a few thousand, on the one hand, the chain segments are relatively short, which may lead to precipitation. On the other hand, when the environment changes, such as contact with solvents or temperature increases, the molecular motion is intensified, which may also easily lead to precipitation. Therefore, the present invention prefers plasticizers with the above molecular weights.

[0019] The preparation of the plasticizer can be based on a cationic polymerization mechanism or a free radical polymerization mechanism. The specific mechanism is not particularly limited. In some preferred embodiments, the plasticizer is prepared based on a common free radical polymerization mechanism:

[0020] The components for preparing the plasticizer, in addition to component A and component B, further comprise a free radical initiator, preferably selected from at least one of an azo initiator and an organic peroxide initiator, wherein examples of the azo initiator include but are not limited to 2,2-azobis(isobutyronitrile), 2,2-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1-azobis(cyclohexanecarbonitrile), 2,2-azobis[N-(2-propenyl)-2-methylpropionamide], 2,2-azobis[2-(2-imidazolin-2-yl)propane], 2,2-azobis[2-methyl-N-( Examples of organic peroxide initiators include, but are not limited to, tert-butyl hydroperoxide, cumene hydroperoxide, tert-butyl peroxyacetate, tert-butyl peroxybenzoate, tert-butyl peroxyoctanoate, tert-butyl peroxyneodecanoate, tert-butyl peroxyisobutyrate, lauroyl peroxide, tert-amyl peroxypivalate, tert-butyl peroxypivalate, dicumene peroxide, benzoyl peroxide, potassium persulfate, and ammonium persulfate. In some embodiments, 2,2-azobis(isobutyronitrile) is particularly preferred.

[0021] In the example of the preparation of the plasticizer of the present invention, the polymerization reaction time can be set according to the half-life of the initiator, which is 2 to 24 hours, preferably 4 to 16 hours, and the polymerization temperature can be 50 to 90°C, preferably 60 to 80°C. The polymerization atmosphere can be an air atmosphere, an oxygen atmosphere, an inert gas atmosphere such as nitrogen or argon, preferably, an inert gas atmosphere is used. The solvent used for the polymerization reaction includes but is not limited to: alcohols such as methanol, ethanol, isopropanol, ethers such as tetrahydrofuran, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, ethylene glycol diethyl ether, ethylene glycol ethyl methyl ether; alkyl carboxylates, ketones such as acetone, methyl ethyl ketone, cyclohexanone; aromatic hydrocarbons such as benzene, toluene, xylene, etc.; amides such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, etc.;

[0022] The present invention prepares plasticizers with different molecular weights by optimizing the appropriate ratio of component A to component B, utilizing the function of an initiator, and controlling the reaction atmosphere and time.

[0023] The toughening agent of the present invention is an elastomeric copolymer modified with polar functional groups, wherein the polar functional groups are preferably one or more of anhydride, carboxyl, amino, hydroxyl, and derivatives thereof, and the content of the polar functional groups is 0.1 to 5 wt%, for example, 0.1%, 0.5%, 0.8%, 1.0%, 1.5%, 2.0%, 3.0%, or 5.0%. The elastomeric copolymer is preferably one or more of an ethylene-α-olefin copolymer, a terpolymer based on ethylene, a C3 to C12 α-olefin, and a non-conjugated diene, an ethylene / butene copolymer, an ethylene / hexene copolymer, an ethylene / octene copolymer, an ethylene / alkyl (meth)acrylate copolymer, an ethylene / styrene / butadiene copolymer, or a styrene / butadiene copolymer. The content of the toughening agent is 0 to 10 wt%, for example, 0, 1%, 2%, 2.5%, 5%, 8%, or 10%.

[0024] The additive component of the present invention may include one or more of antioxidants, lubricants, fillers, light aging agents, etc.;

[0025] The antioxidant comprises any one or a combination of at least two of aromatic amines, sterically hindered phenols, phosphites, sulfur-containing synergists, hydroxylamine benzofuranone derivatives, or potassium iodide-copper iodide inorganic stabilizers;

[0026] The lubricant is selected from one or more of titanate, stearic acid, erucamide, oleamide and silicone;

[0027] The filler is selected from inorganic fillers or organic fillers, preferably selected from one or more of silicon dioxide, talc, wollastonite and calcium carbonate;

[0028] The photoaging agent includes an ultraviolet absorber and a light stabilizer. The ultraviolet absorber can be selected from one or more of benzoic acid, benzophenone derivatives, benzotriazole, etc., and the light stabilizer can be selected from hindered amine stabilizers, etc.

[0029] The present invention also provides a method for preparing the precipitation-resistant and high-toughness polyamide composition.

[0030] The method for preparing the precipitation-resistant high-toughness polyamide composition of the present invention comprises the following steps: mixing the components in a suitable proportion, granulating the components by a twin-screw extruder, wherein the aspect ratio of the twin-screw extruder is 35 to 44:1, the extrusion processing temperature is 230 to 260°C, the melt temperature is 250 to 275°C, and the precipitation-resistant high-toughness polyamide composition is prepared by pelletizing and screening.

[0031] The present invention prepares plasticizer by the above-mentioned preparation method, and then passes each component through the processing of twin screw by the mode of blending, and the compounding effect of plasticizer and toughening agent, the toughness and precipitation performance of the obtained material have great advantages. The plasticizer in the present invention is a component of benzenesulfonamide and is polymerized with an olefin component, and the plasticizing effect of the material is obvious, not only maintaining the plasticizing efficiency of the original small molecule benzenesulfonamide plasticizer, but also greatly weakening the side effect of the original small molecule plasticizer for low-temperature toughness, on the other hand, the addition of toughening agent and plasticizer achieve synergistic effect, greatly improving the low-temperature toughness of the material. The macromolecular plasticizer used in the present invention is dispersed in the polymer matrix and is not easy to precipitate out. At the same time, under other working conditions, for example, under high temperature conditions, in a medium such as gasoline, diesel, etc., low precipitation can be maintained, and the long-term use performance of the material is maintained.

[0032] In view of the above, compared with the prior art, the present invention has several major advantages:

[0033] 1) The present invention uses polymerization technology to polymerize a small molecule plasticizer with an olefin monomer to obtain a plasticizer. The plasticizing efficiency of nylon products is significantly higher than that of general small molecule plasticizers, such as benzenesulfonamides, and significantly improves the low-temperature toughness of the material.

[0034] 2) When the plasticizer of the present invention is immersed in an organic solvent at high temperature, the precipitation amount of the material is greatly reduced, thereby reducing the pollution of the material itself to the solvent, which will greatly broaden the application field of the material. DETAILED DESCRIPTION

[0035] In order to facilitate researchers in the field to better understand the precipitation-resistant and high-toughness polyamide composition prepared by the present invention and the preparation method thereof, the present invention will be further described below using specific examples, but this is only for further detailed description and does not limit the scope of the present invention.

[0036] See Table 1 for the sources of raw materials:

[0037] Table 1 Source of raw materials

[0038]

[0039]

[0040] Evaluation Method

[0041] 1. Number average molecular weight Mn

[0042] The number average molecular weight of the plasticizer was measured by gel permeation chromatography using Agilent PL-GPC 50, polystyrene as a standard, and tetrahydrofuran as a mobile phase.

[0043] 2. Tensile test:

[0044] The tensile properties of the polyamide compositions were tested according to ISO 527 1A test strips.

[0045] 3. Impact test:

[0046] The tensile properties of the polyamide compositions were tested according to ISO 179 1eA test strips.

[0047] 4. Resistance to precipitation

[0048] Prepare a 100*100*2mm sample plate of the polyamide composition. Weigh the sample plate (m0) (accuracy: 0.1mg) and place it in a 500ml Fuel C environment at 80°C for 96 hours. After 96 hours, let it rest at ambient temperature for 12 hours. After 12 hours, filter the test liquid through a 0.45μm polyethersulfone (PES) filter membrane. Vacuum filter the filtrate into a beaker. The beaker must have been weighed (accuracy: m1) in advance (accuracy: 0.1mg). The filtered liquid is stored in an open beaker and placed in a fume hood for forced evaporation. Once the liquid has completely evaporated (as determined by weight change and odor), weigh the beaker again (accuracy: m2) (accuracy: 0.1mg).

[0049] The precipitation percentage α of the precipitate can be calculated by the following formula:

[0050]

[0051] Plasticizer preparation

[0052] Preparation Example 1

[0053] The monomers, initiator, and solvent used to prepare the plasticizer were weighed in a specific ratio, with a molar ratio of N,N-diallylbenzenesulfonamide to propylene of 2:1. Specifically, 10 g of N,N-diallylbenzenesulfonamide, 0.88 g of propylene, 0.05 g of 2,2-azobis(isobutyronitrile) initiator, and 100 ml of xylene solvent were added to a reactor. A nitrogen atmosphere was introduced into the reactor, and polymerization was initiated in an oil bath at 80°C for 12 hours. After the reaction was terminated, precipitation, separation, and vacuum drying were performed. Finally, the powdered solid plasticizer A was obtained by freeze-grinding at -40°C.

[0054] Preparation Example 2

[0055] 10 g of N, N-diallylbenzenesulfonamide, 0.18 g of propylene, 0.03 g of initiator 2, 2-azobis(isobutyronitrile), and 100 ml of solvent xylene were added to a reactor, and a N2 atmosphere was introduced into the reactor. The polymerization was started in an oil bath at 80°C for 12 h. After the reaction was terminated, the mixture was precipitated, separated, and vacuum-dried. Finally, the solid plasticizer B was obtained by freeze-grinding at -40°C.

[0056] Preparation Example 3

[0057] 10 g of N, N-diallylbenzenesulfonamide, 0.16 g of butene, 0.03 g of initiator 2, 2-azobis(isobutyronitrile), and 100 ml of solvent xylene were added to a reactor, and N2 atmosphere was introduced into the reactor. The polymerization was started in an oil bath at 70°C for 10 h. After the reaction was terminated, the mixture was precipitated, separated, and vacuum-dried. Finally, the solid plasticizer C was obtained by freeze-grinding at -40°C.

[0058] Preparation Example 4

[0059] 10 g of N, N-diallylbenzenesulfonamide, 0.47 g of butene, 0.05 g of initiator 2, 2-azobis(isobutyronitrile), and 100 ml of solvent xylene were added to a reactor, and a N2 atmosphere was introduced into the reactor. The polymerization was started in an oil bath at 70°C for 12 h. After the reaction was terminated, the mixture was precipitated, separated, and vacuum-dried. Finally, the solid plasticizer D was obtained by freeze-grinding at -40°C.

[0060] Preparation Example 5

[0061] 10 g of 4-methyl-N, N-di(prop-2-ynyl)benzenesulfonamide, 0.17 g of propylene, 0.03 g of initiator 2,2-azobis(isobutyronitrile), and 100 ml of solvent xylene were added to a reactor, and N2 atmosphere was introduced into the reactor. The polymerization was started in an oil bath at 80°C for 12 h. After the reaction was terminated, the mixture was precipitated, separated, and vacuum-dried. Finally, the solid plasticizer E was obtained by freeze-grinding at -40°C.

[0062] Preparation Example 6

[0063] 10 g of 4-methyl-N, N-di(prop-2-ynyl)benzenesulfonamide, 0.19 g of butene, 0.04 g of initiator 2,2-azobis(isobutyronitrile), and 100 ml of solvent xylene were added to a reactor, and a N2 atmosphere was introduced into the reactor. The polymerization was started in an oil bath at 80°C for 10 h. After the reaction was terminated, the mixture was precipitated, separated, and vacuum-dried. Finally, the solid plasticizer F was obtained by freeze-grinding at -40°C.

[0064] Preparation Comparative Example 1

[0065] 10 g of N, N-diallylbenzenesulfonamide, 8.85 g of propylene, 0.05 g of initiator 2, 2-azobis(isobutyronitrile), and 100 ml of solvent xylene were added to a reactor, and N2 atmosphere was introduced into the reactor. The polymerization was started in an oil bath at 80°C for 12 h. After the reaction was terminated, the mixture was precipitated, separated, and vacuum-dried. Finally, the powdered solid plasticizer G was obtained by freeze-grinding at -40°C.

[0066] The plasticizer was obtained by the above preparation method, and the number average molecular weight of the plasticizer was tested, as shown in Table 2.

[0067] Table 2 Plasticizer molecular weight

[0068] name Number average molecular weight Plasticizer A 43000 Plasticizer B 19000 Plasticizer C 26000 Plasticizer D 57000 Plasticizer E 21000 Plasticizer F 27000 Plasticizer G 23000

[0069] Preparation of polyamide compositions

[0070] Example

[0071] The components of the polyamide composition were weighed according to a certain mass ratio (see Table 3 for the specific ratios), mixed in a high-speed mixer at a speed of 700 rpm for 2 minutes, and placed in a twin-screw extruder with a length-to-diameter ratio of 40:1. The extrusion temperature was set at 255°C and the screw speed was 600 rpm / min. The mixture was pulled, cooled, cut, and granulated by the twin-screw extruder.

[0072] The comparative example involves the addition of BBSA, which is a liquid and therefore is not added when the components are premixed, but needs to be added on a separate scale.

[0073] Table 3 Polyamide composition component ratio (wt%)

[0074]

[0075] The polyamide composition embodiments and comparative examples were tested and verified using the above test methods. Specific performance is shown in Table 4.

[0076] Table 4 Performance of Examples and Comparative Examples

[0077]

[0078] As can be seen from the results in Table 4, the present invention achieves excellent performance of the polyamide composition by adding the plasticizer, greatly improves the low-temperature impact strength of the material, and exhibits excellent performance in terms of precipitation resistance.

[0079] By comparing Example 1 with Comparative Example 2, and Example 4 with Comparative Example 3, it is found that the plasticizer of the present invention has significantly improved low-temperature impact properties compared to conventional small molecule sulfonamide plasticizers, indicating that the plasticizer of the present invention can achieve higher plasticizing efficiency and a lower precipitation percentage under Fuel C environment, which greatly broadens the application field of the material.

[0080] By comparing Example 5 with Comparative Example 1, the preferred ratio is selected in the plasticizer preparation stage. Compared with other ratios, although the molecular weight of the prepared plasticizer is relatively large, due to the difference in the ratio of component A to component B in the plasticizer, the plasticizing efficiency in Comparative Example 1 is significantly lower than that in Example 5, and its resistance to solvent precipitation is also greatly reduced.

[0081] The above description of the embodiments is intended to facilitate understanding and application of the present invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the embodiments described herein. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A precipitation-resistant and high-toughness polyamide composition comprising the following components in percentage by weight: The plasticizer has a molecular weight of 10,000-80,000 and is obtained by polymerizing component A and component B: The general formula of component A is shown below: Wherein R1 is H, or methyl, ethyl, R2 and R3 are selected from H and functional groups containing 1-4 carbon atoms, and at least one of them contains an unsaturated functional group, and the unsaturated functional group is selected from a carbon-carbon double bond and a carbon-carbon triple bond; Component B is a C2-C4 unsaturated olefin; The molar ratio of component A / component B is 1:1 to 30:

1.

2. The composition according to claim 1, wherein The semi-crystalline polyamide is an aliphatic polyamide containing a -CO-NH- structure, and the ratio of the number of methylene groups to the number of amide groups is greater than 6.

0.

3. The composition according to claim 2, wherein The semi-crystalline polyamide includes one or more of PA6, PA66, PA610, PA612, PA1012, PA11, PA12, PA1212, PA614, PA616, and PA618.

4. The composition according to claim 1, wherein The plasticizer has a molecular weight of 20,000-60,000.

5. The composition according to claim 1, wherein Component A includes at least one of N,N-diallylbenzenesulfonamide, N,N-diallyl-4-methylbenzenesulfonamide, 4-methyl-N,N-di(prop-2-ynyl)benzenesulfonamide, and N-ethynyl-N,4-dimethylbenzenesulfonamide; Component B is selected from one or more of ethylene, propylene, n-butene, and isobutene; The molar ratio of component A / component B is 2:1 to 20:

1.

6. The composition according to claim 5, wherein Component A is N,N-diallylbenzenesulfonamide.

7. The composition according to claim 1, wherein The toughening agent is an elastomeric copolymer modified with polar functional groups; The polar functional group is selected from one or more of anhydride, carboxyl, amino and hydroxyl groups, and the content of the polar functional group is 0.1 to 5 wt%; The elastomeric copolymer is selected from one or more of ethylene-α-olefin copolymers, terpolymers based on ethylene, C3-C12 α-olefins and non-conjugated dienes, ethylene / (meth)acrylate copolymers, ethylene / styrene / butadiene copolymers, and styrene / butadiene copolymers.

8. The composition according to claim 1, wherein The additives include one or more of antioxidants, lubricants, fillers, and light aging agents; The antioxidant comprises at least one of aromatic amines, sterically hindered phenols, phosphites, sulfur-containing synergists, hydroxylamine benzofuranone derivatives, or potassium iodide-copper iodide inorganic stabilizers; The lubricant is selected from one or more of titanate, stearic acid, erucamide, oleamide and silicone; The filler is selected from inorganic fillers or organic fillers; The photoaging agent includes an ultraviolet absorber and a light stabilizer. The ultraviolet absorber is selected from one or more of benzoic acid, benzophenone derivatives, and benzotriazole, and the light stabilizer is selected from hindered amine stabilizers.

9. The composition according to claim 8, wherein The filler is selected from one or more of silicon dioxide, talc, wollastonite and calcium carbonate.

10. A method for preparing the composition according to any one of claims 1 to 9, comprising the steps of: The components are mixed, granulated by a twin-screw extruder, and pelletized and sieved to prepare a precipitation-resistant and high-toughness polyamide composition.

11. The preparation method according to claim 10, wherein The length-to-diameter ratio of the twin-screw extruder is 35-44:1, the extrusion processing temperature is 230-260°C, and the melt temperature is 250-275°C.

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