Polyamide, preparation method thereof, sizing agent and application of sizing agent

Abstract

The invention relates to the technical field of sizing agent preparation, and discloses polyamide and a preparation method thereof as well as a sizing agent and application thereof. The method comprises the following steps: reacting a monomer 1, a monomer 2, an optional monomer 3, triphenyl phosphate, a catalyst and an organic solvent in an inert atmosphere; wherein the monomer 1 is binary acid containing a sulfonate group, the monomer 2 is diamine, the monomer 3 is aliphatic binary acid, and the catalyst contains an organic catalyst and a metal inorganic salt catalyst. The polyamide provided by the invention has relatively high solubility; the polyamide and a polyamide resin matrix have good bonding performance, and the bonding performance of carbon fibers and polyamide resin can be greatly improved by using the polyamide as a sizing agent of the carbon fibers.

Description

Technical Field

[0001] The invention relates to the technical field of sizing agent preparation, specifically to the technical field of carbon fiber sizing agent preparation, and in particular to a polyamide and a preparation method thereof, a sizing agent and an application thereof. Background Art

[0002] Carbon fiber composites have received extensive attention and application due to their excellent performance, but carbon fiber is a brittle material. During the production and processing of carbon fiber composites such as carbon fiber fabrics, mechanical friction can easily cause fuzz and single filament breakage, resulting in reduced fiber strength. Due to the presence of fuzz, the fiber opening of the carbon fiber is affected, so that the carbon fiber cannot be fully impregnated by the matrix resin, resulting in pores in the prepared carbon fiber composite material, affecting the mechanical properties of the composite material. The sizing process is the best surface modification method to improve the interfacial properties of carbon fiber. Sizing is a necessary step in the production of commercial carbon fiber. Its primary purpose is to bundle the carbon fiber tows to facilitate subsequent processing and provide protection for the carbon fiber. In addition, the sizing agent plays an important role in the interfacial bonding between carbon fiber and resin matrix.

[0003] Polyamide (PA) is a polymer material with excellent performance, which has the characteristics of high toughness, high strength, low friction coefficient, excellent impact resistance, etc. At the same time, due to its easy processing and molding, it has been widely used in many fields such as electronics, mechanical parts, chemical industry, aerospace, etc. Carbon fiber is an excellent reinforcing phase, and the prepared polyamide-based carbon fiber composite material can further expand its scope of use, especially in special engineering equipment. And compared with thermosetting resin-based carbon fiber composite materials, carbon fiber / polyamide has the advantage of being recyclable as a thermoplastic composite material. However, the matrix resin of the commonly used carbon fiber sizing agent is generally epoxy resin. The carbon fiber sizing with the existing sizing agent has poor bonding with the epoxy resin matrix, and the prepared composite material has low mechanical properties, which limits its utilization value to a certain extent. Although there are a small number of sizing agents for polyamide resins on the market, these sizing agents have limited effects on improving the bonding between carbon fiber and polyamide resin. Therefore, a carbon fiber sizing agent for compounding with polyamide resin is urgently needed to be developed. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem that the existing sizing agent in the prior art has limited effect on improving the binding property of carbon fiber and polyamide resin, and provide a polyamide and a preparation method thereof, a sizing agent and an application thereof. The polyamide provided by the present invention has a large solubility; the polyamide has good binding property with the polyamide resin matrix, and as a sizing agent for carbon fiber, it can greatly improve the binding property of carbon fiber and polyamide resin; the polyamide also has good binding property with other types of resin matrices, and can be used as a sizing agent for other fibers, and has wide versatility.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a method for preparing polyamide, which comprises: reacting monomer 1, monomer 2, optional monomer 3, triphenyl phosphite, a catalyst and an organic solvent under an inert atmosphere; wherein the monomer 1 is a dibasic acid containing a sulfonate group, the monomer 2 is a diamine, the monomer 3 is an aliphatic dibasic acid, and the catalyst comprises an organic catalyst and a metal inorganic salt catalyst.

[0006] Preferably, the dibasic acid containing a sulfonate group is an aliphatic dibasic acid containing a sulfonate group and / or an aromatic dibasic acid containing a sulfonate group.

[0007] Preferably, the aromatic dibasic acid containing a sulfonate group is sodium 5-sulfoisophthalate.

[0008] Preferably, the diamine is a fatty amine.

[0009] Preferably, the diamine is an aliphatic amine having 2 to 30 carbon atoms.

[0010] Preferably, the diamine is selected from one or more of butanediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, decanediamine or dodecanediamine, meta-xylylenediamine and polyetheramine.

[0011] Preferably, the aliphatic dibasic acid has 2-30 carbon atoms.

[0012] Preferably, the aliphatic dibasic acid is one or more selected from succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid and tridecanedioic acid.

[0013] Preferably, the organic catalyst is pyridine.

[0014] Preferably, the metal inorganic salt catalyst is selected from one or more of potassium persulfate, sodium chloride, potassium chloride, calcium chloride, lithium chloride, magnesium chloride, potassium sulfate, magnesium sulfate and sodium sulfate.

[0015] Preferably, based on the total amount of the monomer 1, the monomer 2, the monomer 3, the triphenyl phosphite and the organic catalyst being 100 parts by weight, the monomer 1 is 10-50 parts by weight, the monomer 2 is 10-50 parts by weight, the monomer 3 is 0-40 parts by weight, the triphenyl phosphite is 10-50 parts by weight, and the organic catalyst is 1-15 parts by weight.

[0016] Preferably, based on the total weight of the monomer 1, the monomer 2, the monomer 3, the triphenyl phosphite and the organic catalyst, the amount of the metal inorganic salt catalyst is 0.1-10% by weight.

[0017] Preferably, the reaction conditions include: temperature of 100° C.-150° C., and time of 10-40 hours.

[0018] The second aspect of the present invention provides a polyamide prepared by the method described above.

[0019] Preferably, the solubility of the polyamide is ≥10 g / L.

[0020] The third aspect of the present invention provides a sizing agent, which contains the polyamide described above.

[0021] Preferably, the sizing agent contains 2-4 wt% polyamide.

[0022] A fourth aspect of the present invention provides a use of the sizing agent described above as a carbon fiber sizing agent.

[0023] Compared with the prior art, the present invention has at least the following advantages:

[0024] (1) The polyamide provided by the present invention has a large solubility and can be used to prepare a pure water-based system sizing agent; the polyamide has good bonding with the polyamide resin matrix and can be used as a sizing agent for carbon fibers to greatly improve the bonding between the carbon fibers and the polyamide resin; the polyamide also has good bonding with other types of resin matrices and can be used as a sizing agent for other fibers, has certain versatility, and has a wider application prospect;

[0025] (2) The method for preparing polyamide described in the present invention combines specific raw materials, namely, a dibasic acid containing a sulfonate group, an optional aliphatic dibasic acid and a diamine as monomers, and triphenyl phosphite as a reaction intermediate, and adopts a simple method to prepare a polyamide with high solubility and good bonding with a polyamide resin matrix; moreover, the raw materials used in the method for preparing polyamide described in the present invention are low in price, and the process is simple, which can be optimized for expanded production and has certain economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the infrared characterization diagram of the product obtained in Example 3. DETAILED DESCRIPTION

[0027] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0028] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0029] The first aspect of the present invention provides a method for preparing polyamide, which comprises: reacting monomer 1, monomer 2, optional monomer 3, triphenyl phosphite, a catalyst and an organic solvent under an inert atmosphere; wherein the monomer 1 is a dibasic acid containing a sulfonate group, the monomer 2 is a diamine, the monomer 3 is an aliphatic dibasic acid, and the catalyst comprises an organic catalyst and a metal inorganic salt catalyst.

[0030] The method described in the present invention uses specific monomer 1, monomer 2, optional monomer 3 and triphenyl phosphite as raw materials, and adopts YAMAZAKI solution polycondensation method to obtain polyamide with good water solubility and can be compounded into a pure water-based sizing agent, which can effectively improve the bonding between carbon fiber and polyamide resin matrix.

[0031] In a specific embodiment, when monomer 3 is not added, the specific reaction process that occurs after mixing monomer 1, monomer 2, triphenyl phosphite, a catalyst and an organic solvent is as follows: triphenyl phosphite and a dibasic acid containing a sulfonate group (monomer 1) react under the action of an organic catalyst to generate phosphate, and then the phosphate and a diamine (monomer 2) react under the action of a metal inorganic salt catalyst to generate polyamide and diphenyl phosphite.

[0032] In another specific embodiment, when monomer 3 is added, the specific reaction process that occurs after monomer 1, monomer 2, monomer 3, triphenyl phosphite, catalyst and organic solvent are mixed is: triphenyl phosphite, dibasic acid containing sulfonate group (monomer 1) and aliphatic dibasic acid (monomer 3) react under the action of organic catalyst to generate respective phosphates, and then the phosphate and diamine (monomer 2) react under the action of metal inorganic salt catalyst to generate polyamide and diphenyl phosphite.

[0033] It is found through experiments that the polyamide prepared by the method of the present invention without adding monomer 3 has a higher solubility than the polyamide prepared by adding monomer 3, and has a stronger bonding property with the polyamide resin matrix.

[0034] In a specific embodiment, based on the total amount of the monomer 1, the monomer 2, the monomer 3, the triphenyl phosphite and the organic catalyst as 100 parts by weight, the monomer 1 is 10-50 parts by weight, the monomer 2 is 10-50 parts by weight, the monomer 3 is 0-40 parts by weight, the triphenyl phosphite is 10-50 parts by weight, and the organic catalyst is 1-15 parts by weight. Limiting the amount of the monomer 1, the monomer 2, the monomer 3, the triphenyl phosphite and the organic catalyst to within this range can not only prepare a polyamide with high solubility and strong bonding with the polyamide resin matrix, but also can adjust the hydrophilicity of the prepared polyamide by adjusting the ratio of the dibasic acid and the diamine.

[0035] In the method of the present invention, the dibasic acid containing a sulfonate group as monomer 1 can be a conventional choice in the art, as long as it contains a sulfonate group and two carboxyl groups. Specifically, the dibasic acid containing a sulfonate group is an aliphatic dibasic acid containing a sulfonate group and / or an aromatic dibasic acid containing a sulfonate group. In a preferred embodiment, the aromatic dibasic acid containing a sulfonate group is sodium 5-sulfoisophthalate.

[0036] In the present invention, the diamine as monomer 2 can be various types of diamines commonly used in the art. In a specific embodiment, the diamine is a fatty amine. In a preferred embodiment, the diamine is a fatty amine having a carbon number of 2-30. In a more preferred embodiment, in order to improve the water solubility of the prepared polyamide and the bonding between the prepared polyamide and the polyamide resin matrix, the diamine is selected from one or more of butanediamine, pentamethylenediamine, 2-methylpentamethylenediamine, hexamethylenediamine, decanediamine or dodecanediamine, meta-xylene diamine and polyetheramine. In a further preferred embodiment, the diamine is a polyetheramine. In the present invention, the polyetheramine can be purchased from Aladdin with a molecular weight of 230-400.

[0037] In the method of the present invention, there is no particular limitation on the aliphatic dibasic acid used as monomer 3. In a specific embodiment, the carbon number of the aliphatic dibasic acid may be 2 to 30. In a preferred embodiment, the aliphatic dibasic acid is selected from one or more of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid and tridecanedioic acid.

[0038] In the present invention, the organic catalyst may be a common catalyst known to those skilled in the art, which can promote the reaction of triphenyl phosphite, monomer 1 and optional monomer 3 to generate phosphate. In a specific embodiment, the organic catalyst is pyridine.

[0039] In the present invention, the metal inorganic salt catalyst can be a common catalyst well known to those skilled in the art, which can promote the dehydration condensation reaction of phosphate and diamine (monomer 2) under the action of the metal inorganic salt catalyst to generate polyamide and diphenyl phosphite. In a specific embodiment, the metal inorganic salt catalyst is selected from one or more of potassium persulfate, sodium chloride, potassium chloride, calcium chloride, lithium chloride, magnesium chloride, potassium sulfate, magnesium sulfate and sodium sulfate.

[0040] In the present invention, the amount of the metal inorganic salt catalyst is not limited, and can be added according to the conventional amount in the art. In a specific embodiment, the amount of the metal inorganic salt catalyst is 0.1-10% by weight based on the total weight of the monomer 1, the monomer 2, the monomer 3, the triphenyl phosphite and the organic catalyst.

[0041] The method of the present invention specifically comprises: reacting monomer 1, monomer 2, optional monomer 3, triphenyl phosphite, a catalyst and an organic solvent under an inert atmosphere, and then post-treating the reaction product to obtain polyamide.

[0042] In a specific embodiment, the reaction temperature can be 100°C-150°C, for example, 100°C, 120°C, 130°C, 140°C or 150°C, and the reaction time can be 10-40 hours, for example, 10 hours, 12 hours, 20 hours, 24 hours, 30 hours, 24 hours, 30 hours, 36 hours or 40 hours.

[0043] The method of the present invention is carried out in a solution polymerization mode. In order to prevent triphenyl phosphite, one of the key reactants, from dissolving in water and hydrolyzing in the presence of water, thereby affecting the reaction, the polymerization reaction needs to be carried out in an anhydrous system. Therefore, the present invention adopts an organic solvent as the reaction solvent of the present invention.

[0044] In the present invention, the organic solvent can be any of various commonly used choices by those skilled in the art. In a specific embodiment, the solvent can be selected from one or more of dimethylacetamide, dimethylformamide, N-methylpyrrolidone and formic acid.

[0045] In a specific embodiment, the amount of the organic solvent is not particularly limited, as long as it can dissolve the reaction raw materials and allow the reaction to occur normally. In a specific embodiment, based on the total amount of monomer 1, monomer 2, optional monomer 3, triphenyl phosphite, catalyst and organic solvent as 100 parts by weight, the amount of the organic solvent is 100-300 parts.

[0046] In the present invention, the step of post-treating the reaction product comprises: cooling the reaction product, placing it in a detergent for precipitation and repeatedly washing it, and drying the washed solid product in an oven to obtain polyamide. The detergent is a solvent that cannot dissolve polyamide, and in a specific embodiment, the detergent can be acetone and / or methanol.

[0047] The second aspect of the present invention provides a polyamide prepared by the method described above.

[0048] The polyamide provided by the present invention has good water solubility and can be used to prepare a pure water-based sizing agent, which does not contain an organic solvent, is green and environmentally friendly, and has a wide range of application prospects. In a specific embodiment, the solubility of the polyamide is ≥10 g / L.

[0049] In the present invention, the solubility test method of the polyamide is as follows: 50 g of the polyamide is placed in 1 kg of 25° C. water and stirred to dissolve, the solution is filtered and dried after 2 hours, and then the mass of the remaining polyamide is weighed using an analytical balance (accurate to 0.01 g), and the solubility of the polyamide at 25° C. is calculated.

[0050] Furthermore, the water solubility of the polyamide of the present invention varies according to its structure and is controllable. In a specific embodiment, the water solubility of the product can be adjusted by adjusting the amount of the monomer containing the hydrophilic group. When the polyamide contains more hydrophilic units, the solubility of the polyamide can reach ≥50g / L.

[0051] The inventors of the present invention have found that the solubility of the polyamide provided by the present invention may be related to the binding property between the polyamide and the polyamide resin matrix. It can be seen from the experimental results that when the solubility of the polyamide is large, the binding property between the polyamide and the polyamide resin matrix is ​​relatively strong; when the solubility of the polyamide is small, the binding property between the polyamide and the polyamide resin matrix is ​​relatively weak.

[0052] Since the water solubility of the polyamide provided by the present invention is controllable, the user can select polyamides with different solubilities according to actual needs. In order to facilitate storage in an environment with high humidity and maintain strong bonding between the polyamide and the polyamide resin matrix, a polyamide with relatively low solubility, i.e., a solubility of 10-45 g / L, can be selected; in an environment with low humidity, in order to further improve the bonding between the polyamide and the polyamide resin matrix, a polyamide with relatively high solubility, i.e., a solubility ≥50 g / L, can be selected.

[0053] The third aspect of the present invention provides a sizing agent, which contains the polyamide described above.

[0054] In a specific embodiment, the preparation method of the sizing agent includes: compounding the polyamide with water to obtain the sizing agent.

[0055] In a preferred embodiment, the sizing agent contains 2-4 wt% polyamide.

[0056] In the present invention, the sizing agent is a pure aqueous sizing agent, that is, the sizing agent of the present invention does not contain an organic solvent; the present invention only uses an organic solvent in the preparation process, and the organic solvent in the obtained product has been completely removed. Therefore, the sizing agent obtained by compounding the polyamide with water is a pure aqueous system.

[0057] In a fourth aspect, the present invention provides a use of the sizing agent described above as a carbon fiber sizing agent.

[0058] The sizing agent of the present invention can be used as a sizing agent for carbon fibers and can also be used as a sizing agent for other fibers, and has certain versatility.

[0059] The sizing agent containing the polyurethane of the present invention is particularly suitable for a sizing agent for carbon fibers; when carbon fibers are combined with a polyamide matrix resin to prepare a composite material, the sizing agent of the present invention is used as a carbon fiber sizing agent, which can greatly improve the bonding between the carbon fibers and the polyamide matrix resin.

[0060] In the present invention, the specific operation process for testing the bonding between the sized fiber and the polyamide matrix resin is as follows: the unsized filament bundle is passed through a roller and immersed in the sizing agent, and the wire feeding speed is controlled at 6.5 m / min; the effective sizing length of the sizing tank is 0.6 m, and the sized filament bundle enters a 180° C. heater for drying, and then is rolled up to obtain the sized fiber; a YG163 type electronic microsphere experimental debonding tester is used to perform a micro-debonding test on the sized carbon fiber, and the interface shear strength between the sized carbon fiber and the polyamide matrix resin is tested.

[0061] The present invention will be described in detail below by way of examples, but the protection scope of the present invention is not limited thereto. In the following examples, unless otherwise specified, the raw materials used are all common commercial products.

[0062] In the following examples, the polyetheramine can be purchased from Aladdin and has a molecular weight of 400.

[0063] Example 1

[0064] (1) Preparation process of polyamide:

[0065] 1) 30 parts by weight of sodium 5-sulfoisophthalate and 15 parts by weight of hexamethylenediamine were put into a dry reaction bottle, and 10 parts by weight of pyridine, 45 parts by weight of triphenyl phosphite, 3 parts by weight of calcium chloride and 2 parts by weight of sodium chloride were added thereto and mixed evenly;

[0066] 2) The system obtained in step 1) was evacuated and then filled with nitrogen, and then 200 parts by weight of N-methylpyrrolidone was added, and the mixture was stirred evenly with a magnetic bar. The system was placed in an oil bath under a nitrogen atmosphere and directly heated to 120° C. The mixture was stirred for reaction for 24 hours, and then the heater was turned off to cool the system to room temperature to obtain a polyamide solution. The polyamide solution was then poured into acetone for precipitation and repeatedly washed with acetone and dried to obtain product A1.

[0067] Through infrared characterization, the product A1 prepared in this example is polyamide.

[0068] (2) Preparation process of sizing agent:

[0069] The product A1 was compounded with water to obtain a sizing agent with a solid content of 2% by weight.

[0070] Example 2

[0071] (1) Preparation process of polyamide:

[0072] 1) 15 parts by weight of sodium 5-sulfoisophthalate, 10 parts by weight of adipic acid and 20 parts by weight of hexamethylenediamine are put into a dry reaction bottle, and 10 parts by weight of pyridine, 45 parts by weight of triphenyl phosphite, 3 parts by weight of calcium chloride and 2 parts by weight of lithium chloride are added thereto, and mixed evenly;

[0073] 2) The system obtained in step 1) was evacuated and then filled with nitrogen, and then 200 parts by weight of N-methylpyrrolidone was added, and the mixture was stirred evenly with a magnetic bar. The system was placed in an oil bath under a nitrogen atmosphere and directly heated to 120° C. The mixture was stirred for reaction for 24 hours, and then the heater was turned off to cool the system to room temperature to obtain a polyamide solution. The polyurethane solution was then poured into acetone for precipitation and repeatedly washed with acetone and dried to obtain product A2.

[0074] Through infrared characterization, the product A2 prepared in this example is polyamide.

[0075] (2) Preparation process of sizing agent:

[0076] The product A2 was compounded with water to obtain a sizing agent with a solid content of 2% by weight.

[0077] Example 3

[0078] (1) Preparation process of polyamide:

[0079] 1) 15 parts by weight of sodium 5-sulfoisophthalate and 25 parts by weight of polyetheramine (D400) were put into a dry reaction bottle, and 15 parts by weight of pyridine, 45 parts by weight of triphenyl phosphite, 3 parts by weight of calcium chloride and 2 parts by weight of sodium chloride were added thereto and mixed evenly;

[0080] 2) The system obtained in step 1) was evacuated and then filled with nitrogen, and then 200 parts by weight of N-methylpyrrolidone was added, and the mixture was stirred evenly with a magnetic bar. The system was placed in an oil bath under a nitrogen atmosphere and directly heated to 120° C. The mixture was stirred for reaction for 24 hours, and then the heater was turned off to cool the system to room temperature to obtain a polyamide solution. The polyamide solution was then poured into acetone for precipitation and repeatedly washed with acetone and dried to obtain product A3.

[0081] The product A3 obtained in Example 3 was characterized by infrared spectroscopy. Figure 1 As shown. Through characterization, it can be seen that the peak is at 3305cm -1 The bands on the left and right are the stretching vibrations of hydrogen-bonded NH bonds, with a peak at 1651 cm -1 It is the stretching vibration peak of amide I with C=O, with a peak at 1545cm -1 It is the deformation vibration of amide II with CN, with a peak at 3078cm -1 It is the frequency doubling peak of the amide II band. Therefore, the product A3 obtained in Example 3 is a polyamide.

[0082] (2) Preparation process of sizing agent:

[0083] The product A3 was compounded with water to obtain a sizing agent with a solid content of 2% by weight.

[0084] Example 4

[0085] (1) Preparation process of polyamide:

[0086] 1) 10 parts by weight of sodium 5-sulfoisophthalate, 10 parts by weight of adipic acid, and 20 parts by weight of polyetheramine (D400) are put into a dry reaction bottle, and 15 parts by weight of pyridine, 45 parts by weight of triphenyl phosphite, 3 parts by weight of calcium chloride, and 2 parts by weight of lithium chloride are added thereto, and mixed evenly;

[0087] 2) The system obtained in step 1) was evacuated and then filled with nitrogen, and then 200 parts by weight of N-methylpyrrolidone was added, and the mixture was stirred evenly with a magnetic bar. The system was placed in an oil bath under a nitrogen atmosphere and directly heated to 120° C. The mixture was stirred for reaction for 24 hours, and then the heater was turned off to cool the system to room temperature to obtain a polyamide solution. The polyamide solution was then poured into acetone for precipitation and repeatedly washed with acetone and dried to obtain product A4.

[0088] Through infrared characterization, the product A4 prepared in this example is polyamide.

[0089] (2) Preparation process of sizing agent:

[0090] The product A4 was compounded with water to obtain a sizing agent with a solid content of 2% by weight.

[0091] Example 5

[0092] (1) Preparation process of polyamide:

[0093] 1) 10 parts by weight of sodium 5-sulfoisophthalate, 10 parts by weight of adipic acid, 10 parts by weight of hexamethylenediamine, and 15 parts by weight of polyetheramine (D400) are put into a dry reaction bottle, and 13 parts by weight of pyridine, 42 parts by weight of triphenyl phosphite, 3 parts by weight of calcium chloride, and 2 parts by weight of sodium chloride are added thereto, and mixed evenly;

[0094] 2) The system obtained in step 1) was evacuated and then filled with nitrogen, and then 200 parts by weight of N-methylpyrrolidone was added, and the mixture was stirred evenly with a magnetic bar. The system was placed in an oil bath under a nitrogen atmosphere and directly heated to 120° C. The mixture was stirred for reaction for 24 hours, and then the heater was turned off to cool the system to room temperature to obtain a polyamide solution. The polyamide solution was then poured into acetone for precipitation and repeatedly washed with acetone and dried to obtain product A5.

[0095] Through infrared characterization, the product A5 prepared in this example is polyamide.

[0096] (2) Preparation process of sizing agent:

[0097] The product A5 was compounded with water to obtain a sizing agent with a solid content of 2% by weight.

[0098] Example 6

[0099] 1) 25 parts by weight of sodium 5-sulfoisophthalate, 10 parts by weight of succinic acid and 10 parts by weight of hexamethylenediamine were put into a dry reaction bottle, and 10 parts by weight of pyridine, 45 parts by weight of triphenyl phosphite, 3 parts by weight of calcium chloride and 2 parts by weight of sodium chloride were added thereto and mixed evenly;

[0100] 2) The system obtained in step 1) was evacuated and then filled with nitrogen, and then 200 parts by weight of N-methylpyrrolidone was added, and the mixture was stirred evenly with a magnetic bar. The system was placed in an oil bath under a nitrogen atmosphere and directly heated to 120° C. The mixture was stirred for reaction for 24 hours, and then the heater was turned off to cool the system to room temperature to obtain a polyamide solution. The polyamide solution was then poured into acetone for precipitation and repeatedly washed with acetone and dried to obtain product A6.

[0101] Through infrared characterization, the product A5 prepared in this example is polyamide.

[0102] (2) Preparation process of sizing agent:

[0103] The product A6 was compounded with water to obtain a sizing agent with a solid content of 2% by weight.

[0104] Comparative Example 1

[0105] Toray T800H×12k carbon fiber (purchased from Toray) was sized, and the interface shear strength between Toray T800H×12k carbon fiber and polyamide matrix resin was directly tested.

[0106] Comparative Example 2

[0107] The mother solution of polyamide sizing agent purchased from McMann on the market was taken and compounded into a sizing agent with a solid content of 2 weight %.

[0108] Comparative Example 3

[0109] The mother solution of epoxy resin sizing agent purchased from Shanghai Petrochemical was taken and compounded into a sizing agent with a solid content of 2 wt %.

[0110] Comparative Example 4

[0111] (1) Preparation process of polyamide:

[0112] 1) 20 parts by weight of adipic acid and 25 parts by weight of hexamethylenediamine were put into a dry reaction bottle, 13 parts by weight of pyridine, 42 parts by weight of triphenyl phosphite, 3 parts by weight of calcium chloride, 2 parts by weight of sodium chloride were added thereto, and then 200 parts by weight of N-methylpyrrolidone were added, and stirred evenly with a magnetic stirrer;

[0113] 2) The system obtained in step 1) was evacuated and then filled with nitrogen, placed in an oil bath under a nitrogen atmosphere and directly heated to 120° C., stirred for reaction for 24 hours, then the heater was turned off and the system was cooled to room temperature to obtain a polyamide solution, and then the polyamide solution was poured into acetone for precipitation and repeatedly washed with acetone and dried to obtain the product DA4.

[0114] (2) Preparation process of sizing agent:

[0115] The product DA4 was compounded with water to obtain a sizing agent with a solid content of 2% by weight.

[0116] Test Case

[0117] (1) 50 g of each of the products A1-A6 prepared in Examples 1-6 and the product DA4 prepared in Comparative Example 4 were placed in 1 kg of 25°C water and stirred to dissolve. After 2 hours, the solution was filtered and dried. Then, the mass of the remaining polyamide was weighed using an analytical balance, and the solubility of the polyamide at 25°C was calculated. The results are shown in Table 1.

[0118] (2) The unsized Toray T800H×12k carbon fiber tow (purchased from Toray, the same as the carbon fiber in Comparative Example 1) was passed through a roller and immersed in the sizing agent prepared in the embodiment and the comparative example, and the wire speed was controlled at 6.5 m / min; the effective sizing length of the sizing tank was 0.6 m, and the sizing tow entered a heater at 180°C for drying, and then was rolled up to obtain the sized fiber; the sizing carbon fiber was subjected to a micro-debonding test using a YG163 electronic microsphere experimental debonding tester, and the interface shear strength between the sizing carbon fiber and the polyamide matrix resin was tested, and the bonding between the sizing carbon fiber and the polyamide matrix resin was tested. The results are shown in Table 1.

[0119] Table 1

[0120]

[0121]

[0122] It can be seen from Table 1 that the polyamide prepared by the method of the present invention has a high solubility and can be used to prepare a pure water-based sizing agent; and after the sizing agent prepared by the embodiment of the present invention is used to sizing the carbon fiber, the bonding between the carbon fiber and the polyamide matrix resin is relatively strong.

[0123] 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 method for preparing polyamide, characterized in that: The method comprises: reacting monomer 1, monomer 2, optional monomer 3, triphenyl phosphite, a catalyst and an organic solvent under an inert atmosphere; The monomer 1 is a dibasic acid containing a sulfonate group, the monomer 2 is a diamine, the monomer 3 is an aliphatic dibasic acid, and the catalyst contains an organic catalyst and a metal inorganic salt catalyst.

2. The method according to claim 2, characterized in that: The dibasic acid containing a sulfonate group is an aliphatic dibasic acid containing a sulfonate group and / or an aromatic dibasic acid containing a sulfonate group; Preferably, the aromatic dibasic acid containing a sulfonate group is sodium 5-sulfoisophthalate.

3. The method according to claim 1 or 2, characterized in that: The diamine is a fatty amine; Preferably, the diamine is an aliphatic amine having 2 to 30 carbon atoms; Preferably, the diamine is selected from one or more of butanediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, decanediamine or dodecanediamine, meta-xylylenediamine and polyetheramine.

4. The method according to any one of claims 1 to 3, characterized in that: The carbon number of the aliphatic dibasic acid is 2-30; Preferably, the aliphatic dibasic acid is one or more selected from succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid and tridecanedioic acid.

5. The method according to any one of claims 1 to 4, characterized in that: The organic catalyst is pyridine; Preferably, the metal inorganic salt catalyst is selected from one or more of potassium persulfate, sodium chloride, potassium chloride, calcium chloride, lithium chloride, magnesium chloride, potassium sulfate, magnesium sulfate and sodium sulfate.

6. The method according to any one of claims 1 to 5, characterized in that: Taking the total amount of the monomer 1, the monomer 2, the monomer 3, the triphenyl phosphite and the organic catalyst as 100 parts by weight, the monomer 1 is 10-50 parts by weight, the monomer 2 is 10-50 parts by weight, the monomer 3 is 0-40 parts by weight, the triphenyl phosphite is 10-50 parts by weight, and the organic catalyst is 1-15 parts by weight.

7. The method according to any one of claims 1 to 6, characterized in that: Based on the total weight of the monomer 1, the monomer 2, the monomer 3, the triphenyl phosphite and the organic catalyst, the amount of the metal inorganic salt catalyst is 0.1-10% by weight.

8. The method according to any one of claims 1 to 7, characterized in that: The reaction conditions include: temperature of 100° C.-150° C., and time of 10-40 hours.

9. A polyamide prepared by the method according to any one of claims 1 to 8.

10. The polyamide according to claim 9, characterized in that The solubility of the polyamide is ≥10 g / L.

11. A sizing agent, characterized in that: The sizing agent contains the polyamide according to claim 9 or 10.

12. The sizing agent according to claim 11, characterized in that The sizing agent contains 2-4% by weight of polyamide.

13. Use of the sizing agent according to claim 11 or 12 as a carbon fiber sizing agent.

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