Water-based bio-based polyurethane sizing agent with heat resistance and preparation method thereof

Abstract

The invention relates to a heat-resistant water-based bio-based polyurethane sizing agent synthesized by a two-step method and a preparation method thereof, and belongs to the technical field of sizing agents. The waterborne polyurethane sizing agent is prepared from the following components in parts by weight: 1 to 5 parts of bio-based polyurethane, 0.5 to 10 parts of a neutralizing agent and 90 to 98.5 parts of deionized water, the structural formula of the polyurethane is as shown in formula 1. The sizing agent not only can effectively improve the interface bonding capacity of the carbon fiber polyamide-based resin composite material, but also has excellent heat resistance. The preparation method of the waterborne polyurethane sizing agent # imgabs0 comprises the following steps: (1) synthesizing a polyurethane prepolymer by using a bio-based raw material; (2) adding a cross-linking agent with heat resistance; (3) preparing a bio-based polyurethane sizing agent; the sizing agent can effectively improve the interface bonding capacity of a carbon fiber nylon 6 matrix resin composite material and improve the heat resistance of the composite material, so that the service life is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of sizing agents, and in particular relates to a water-based bio-based polyurethane sizing agent with heat resistance and a preparation method thereof. Background Art

[0002] Carbon fiber is known as a new type of inorganic material. It has a series of excellent properties such as high specific strength, high specific modulus, high temperature resistance, corrosion resistance, fatigue resistance, radiation resistance, electrical conductivity, heat transfer, shock absorption, noise reduction, etc. It is regarded as a typical high-performance fiber. At present, its application areas are mainly in aerospace vehicles (satellites, launch vehicles, tactical missiles, aircraft, etc.), mainly because it can greatly reduce the weight of structural prefabricated parts and further improve technical performance. At the same time, its application in industrial and civilian products is also expanding. Carbon fiber is also widely used as a reinforcing fiber for advanced resin-based composite materials, and is used in high-end stationery, transportation vehicles, medical equipment, building materials and other industries.

[0003] The surface of carbon fiber is inert and smooth, so the interface bonding performance of the composite material formed is poor, and the mechanical properties of the reinforced composite material are far from the theoretical value. The surface modification method of carbon fiber can improve the interfacial bonding strength between the fiber and the resin matrix, thereby improving the comprehensive mechanical properties of the composite material. The sizing method is not only simple to operate, but also can avoid contamination of the carbon fiber surface, protect the activity of the surface group, improve the fiber bundling, and also can wet the carbon fiber, reduce the surface tension between the carbon fiber and the matrix resin, and enhance the interfacial bonding strength between the carbon fiber and the matrix resin, thereby improving the mechanical properties of the composite material. However, most of the commercial sizing agents today are thermosetting sizing agents, which are not compatible with thermoplastic resins. Nylon 6 is a thermoplastic resin with an amide bond as the repeating unit. It has the advantages of low price and wide application, and it has polar groups itself, so the development of sizing agents suitable for nylon 6 has good application prospects.

[0004] Bio-based polymers have attracted widespread attention due to their pollution-free raw material sources and low cost. However, polyurethane is unstable at high temperatures and easily decomposes, which affects the service life of composite materials. Patent CN105088798 A discloses a water-based polyurethane sizing agent, the main component of which is linear polyurethane, which is prone to yellowing and aging under long-term light conditions, and its application may be limited. Patent CN 109321119 A discloses a water-based polyurethane coating with good stability. The polyurethane is modified by preparing a modifier to obtain a stable emulsion. The operation process is relatively complicated, time-consuming, and has many reaction steps. In summary, the development of a high-temperature resistant and environmentally friendly water-based thermoplastic sizing agent suitable for polyamide resin is of great significance to the development of the carbon fiber industry. At the same time, the carbon fiber treated with the water-based sizing agent has good dispersibility in water and can be used in a variety of fields, such as: the preparation of carbon paper, friction-resistant materials, and sports equipment. Summary of the invention

[0005] The purpose of the present invention is to provide a water-based bio-based polyurethane sizing agent with heat resistance and a preparation method thereof, wherein the sizing agent can not only effectively improve the interface bonding ability of carbon fiber polyamide-based resin composite materials, but also has excellent heat resistance.

[0006] The present invention first provides a water-based bio-based polyurethane sizing agent with heat resistance, which comprises, by weight:

[0007] 1-5 parts of bio-based polyurethane, 0.5-10 parts of neutralizer, 90-98.5 parts of deionized water;

[0008] The structural formula of the heat-resistant bio-based polyurethane is shown in Formula 1:

[0010] In Formula 1, the value range of n is 20 to 80.

[0011] Preferably, the neutralizing agent is triethylamine.

[0012] The present invention also provides a method for preparing a water-based bio-based polyurethane sizing agent with heat resistance, comprising the following steps:

[0013] Step 1: Preparation of bio-based polyurethane prepolymer

[0014] The oligomer polyol, diisocyanate and catalyst are dissolved in a solvent, nitrogen is passed through, and the reaction is carried out at 80° C. to 90° C. for 2 to 4 hours to obtain a bio-based polyurethane prepolymer;

[0015] Step 2: Synthesis of heat-resistant polyurethane

[0016] Dissolve dimethylolpropionic acid in a solvent, add a heat-resistant crosslinking agent to the polyurethane prepolymer, continue to react under nitrogen protection for 2-3 hours, remove the solvent by rotary evaporation, and dry to obtain a bio-based polyurethane;

[0017] Step 3: Preparation of waterborne bio-based polyurethane sizing agent with heat resistance

[0018] The bio-based polyurethane obtained in step 2 is dispersed in water under high-speed stirring, and a neutralizing agent is added dropwise for reaction to obtain a water-based bio-based polyurethane sizing agent with heat-resistant performance.

[0019] Preferably, the oligomer polyol is selected from soybean oil or castor oil.

[0020] Preferably, the diisocyanate is selected from toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate or dicyclohexylmethane diisocyanate.

[0021] Preferably, the catalyst is selected from dibutyltin dilaurate, stannous octoate or tin octoate.

[0022] Preferably, the solvent in step 2 is selected from one of N,N-dimethylformamide, acetone or tetrahydrofuran.

[0023] Preferably, the cross-linking agent is selected from one of guar gum and gallic acid.

[0024] Preferably, the molar ratio of the oligomer polyol, diisocyanate and crosslinking agent is (1-3): (3-10): (3-10).

[0025] Compared with the prior art solutions, the beneficial effects of the present invention are as follows:

[0026] The invention provides a water-based bio-based polyurethane sizing agent with heat resistance and a preparation method thereof. The sizing agent comprises, by weight, 1-5 parts of bio-based polyurethane, 0.5-10 parts of a neutralizer and 90-98.5 parts of deionized water. The bio-based polyurethane in the invention has the characteristics of low viscosity and high functional group density, which is conducive to forming a uniform coating with high functional group density on the surface of carbon fiber, so that the carbon fiber composite material exhibits better mechanical properties. At the same time, due to the heat-resistant crosslinking agent, the bio-based polyurethane can stably exist in a long-term high temperature environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the infrared spectrum of the bio-based polyurethane in the embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention first provides a water-based bio-based polyurethane sizing agent with heat resistance, which comprises, by weight:

[0029] 1-5 parts of bio-based polyurethane, 0.5-10 parts of neutralizer, 90-98.5 parts of deionized water;

[0030] The structural formula of the bio-based polyurethane is shown in Formula 1:

[0031]

[0032] In Formula 1, the value range of n is 20 to 80.

[0033] According to the present invention, the neutralizing agent is preferably triethylamine.

[0034] The present invention also provides a method for preparing a water-based bio-based polyurethane sizing agent with heat resistance, comprising the following steps:

[0035] Step 1: Preparation of bio-based polyurethane prepolymer:

[0036] The oligomer polyol, diisocyanate and catalyst are dissolved in a solvent, nitrogen is passed through, and the reaction is carried out at 80° C. to 90° C. for 2 to 4 hours to obtain a bio-based polyurethane prepolymer;

[0037] The oligomer polyol is preferably selected from soybean oil or castor oil.

[0038] The catalyst is preferably selected from dibutyltin dilaurate, stannous octoate or tin octoate.

[0039] The solvent is preferably selected from one of N,N-dimethylformamide, acetone or tetrahydrofuran.

[0040] The diisocyanate is preferably selected from toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate or dicyclohexylmethane diisocyanate.

[0041] Step 2: Preparation of heat-resistant bio-based polyurethane

[0042] Dissolve dimethylolpropionic acid in a solvent, preferably acetone; add a heat-resistant crosslinking agent to the prepolymer obtained in step 1, continue to react for 2-3 hours under nitrogen protection, remove the solvent by rotary evaporation, and dry to obtain a bio-based polyurethane;

[0043] The molar ratio of the oligomer polyol, diisocyanate, catalyst and crosslinking agent is (1-3): (3-10): (0.3-1.5): (3-10).

[0044] Step 3: Preparation of waterborne bio-based polyurethane sizing agent with heat resistance

[0045] The bio-based polyurethane obtained in step 2 is dispersed in water under high-speed stirring, the stirring speed is preferably 300 rpm, and a neutralizer is slowly added dropwise for reaction, the neutralizer is preferably triethylamine, and the reaction time is preferably 20-30 minutes to obtain a water-based bio-based polyurethane sizing agent with heat resistance.

[0046] The present invention is further described in detail below with reference to specific examples, in which the raw materials involved are all commercially available.

[0047] Comparative Example 1

[0048] The untreated carbon fiber was cut into 5 mm segments, mixed with polyamide 6 at 10% content at 260°C, 60rpm for 15 minutes, and pelletized to obtain a composite material. The interlaminar shear test and bending test specimens were made by injection molding, and the interlaminar shear strength was 45.16MPa and the bending strength was 436.58MPa tested by a universal testing machine. The details are shown in Table 1.

[0049] Example 1

[0050] The preparation method of a bio-based polyurethane water-based sizing agent comprises the following steps:

[0051] (1) Weigh 4.44 g of isophorone diisocyanate and 4 g of modified soybean oil into a three-necked flask equipped with a condenser and a mechanical stirrer, add acetone to mix them thoroughly, then add 2-3 ml of dibutyltin dilaurate to the mixture, and under nitrogen protection, heat to 78° C. and react for 2 h to obtain a bio-based polyurethane prepolymer.

[0052] (2) Add dimethylol propionic acid and a heat-resistant crosslinking agent to the prepolymer obtained in step (1), and continue the reaction at 78°C for 2 hours under nitrogen protection. Finally, use a rotary evaporator to remove acetone from the polyurethane to obtain a heat-resistant bio-based polyurethane. The infrared spectrum of the obtained bio-based polyurethane is as follows: Figure 1 shown.

[0053] (3) Take 10 g of the bio-based polyurethane obtained in step (2), disperse it in water under high-speed stirring at a speed of 300 rpm, slowly add 2 ml of triethylamine, and react for 30 minutes to obtain a water-based bio-based polyurethane sizing agent with heat resistance.

[0054] The carbon fiber cloth was impregnated in the sizing agent prepared in Example 1, and the CF / PA6 composite material was manufactured by hot pressing technology. The CF / PA6 composite material was stacked by eight layers of PA6 film (120mm×100mm×0.3mm) and seven layers of CF fabric (120mm×100mm), and then pressed at 5MPa and 260°C for 30 minutes to obtain a composite material. The interlaminar shear test and bending strength test specimens were obtained by cutting, and the interlaminar shear strength was 59.11MPa and the bending strength was 577.16MPa tested by a universal testing machine, as shown in Table 1. The results show that the mechanical properties are significantly improved compared with the unsized carbon fiber / nylon 6 composite material.

[0055] Example 2

[0056] The preparation method of a bio-based polyurethane water-based sizing agent comprises the following steps:

[0057] (1) Weigh 4.44 g of isophorone diisocyanate and modified soybean oil (7.2 g) into a three-necked flask equipped with a condenser and a mechanical stirrer, add acetone to mix them thoroughly, then add 4-5 ml of dibutyltin dilaurate to the mixture, and under nitrogen protection, heat to 78° C. and react for 2 h to obtain a bio-based polyurethane prepolymer.

[0058] (2) Add dimethylolpropionic acid and a heat-resistant crosslinking agent to the prepolymer obtained in step (1), and continue the reaction at 78° C. for 2 h under nitrogen protection. Finally, remove the acetone in the polyurethane using a rotary evaporator to obtain a high-temperature resistant bio-based polyurethane.

[0059] (3) Take 10 g of the bio-based polyurethane prepared in step (2), disperse it in water under high-speed stirring at 300 rpm, slowly add 15 ml of triethylamine, and react for 30 minutes to obtain a water-based bio-based polyurethane sizing agent with high temperature resistance.

[0060] The carbon fiber cloth was impregnated in the sizing agent prepared in Example 2, and the CF / PA6 composite material was manufactured by hot pressing technology. The CF / PA6 composite material is stacked by eight layers of PA6 film (120mm×100mm×0.3mm) and seven layers of CF fabric (120mm×100mm), and then pressed at 5MPa and 260°C for 30 minutes to obtain a composite material. The interlaminar shear test and bending strength test specimens were obtained by cutting, and the interlaminar shear strength was 58.98MPa and the bending strength was 567.46MPa tested by a universal testing machine, as shown in Table 1. The results show that the mechanical properties are significantly improved compared with the unsized carbon fiber / nylon 6 composite material.

[0061] Example 3

[0062] The preparation method of a bio-based polyurethane water-based sizing agent comprises the following steps:

[0063] (1) Weigh 44.4 g of isophorone diisocyanate and modified soybean oil (20 g) into a three-necked flask equipped with a condenser and a mechanical stirrer, add acetone to mix them thoroughly, then add 5-8 ml of dibutyltin dilaurate to the mixture, and under nitrogen protection, heat to 78° C. and react for 2 h to obtain a bio-based polyurethane prepolymer.

[0064] (2) Add dimethylolpropionic acid and a heat-resistant crosslinking agent to the prepolymer obtained in step (1), and continue the reaction at 78° C. for 2 h under nitrogen protection. Finally, remove the acetone in the polyurethane using a rotary evaporator to obtain a heat-resistant bio-based polyurethane.

[0065] (3) 50 g of the bio-based polyurethane prepared in step (2) was dispersed in water under high-speed stirring at 300 rpm, 20 ml of triethylamine was slowly added dropwise, and the mixture was reacted for 30 minutes to obtain a water-based bio-based polyurethane sizing agent with heat resistance.

[0066] The carbon fiber cloth was impregnated in the sizing agent prepared in Example 3, and the CF / PA6 composite material was manufactured by hot pressing technology. The CF / PA6 composite material is stacked by eight layers of PA6 film (120mm×100mm×0.3mm) and seven layers of CF fabric (120mm×100mm), and then pressed at 5MPa and 260°C for 30 minutes to obtain a composite material. The interlaminar shear test and bending strength test specimens were obtained by cutting, and the interlaminar shear strength was 56.13MPa and the bending strength was 561.44MPa tested by a universal testing machine, as shown in Table 1. The results show that the mechanical properties are significantly improved compared with the unsized carbon fiber / nylon 6 composite material.

[0067] Table 1 shows the results of testing interlaminar shear strength and flexural strength of composite materials prepared after sizing carbon fibers with the aqueous hyperbranched polyurethane sizing agent provided in Comparative Example 1 and Examples 1-3 of the present invention. Table 1 Example 1 Example 2 Example 3 Comparative Example 1 Interlaminar shear strength (MPa) 59.11 58.98 56.13 45.16 Bending strength(MPa) 577.16 567.46 561.44 436.58

Claims

1. A water-based bio-based polyurethane sizing agent with heat resistance, characterized in that: In terms of weight, it comprises: 1-5 parts of bio-based polyurethane, 0.5-10 parts of neutralizer, and 90-98.5 parts of deionized water; the structural formula of the bio-based polyurethane is shown in Formula 1.

2. The water-based bio-based polyurethane sizing agent with heat resistance according to claim 1, characterized in that: The neutralizing agent is triethylamine.

3. The method for preparing a water-based bio-based polyurethane sizing agent with heat resistance according to claim 1, characterized in that: The following steps are involved: Step 1: Preparation of bio-based polyurethane prepolymer The oligomer polyol, diisocyanate and catalyst are dissolved in a solvent, nitrogen is passed through, and the reaction is carried out at 70°C-80°C for 2-4 hours to obtain a polyurethane prepolymer; Step 2: Preparation of heat-resistant bio-based polyurethane Dissolve dimethylolpropionic acid in a solvent, add a crosslinking agent with improved heat resistance to the polyurethane prepolymer, continue to react for 2-3 hours under nitrogen protection, remove the solvent by rotary evaporation, and dry to obtain a bio-based polyurethane; Step 3: Preparation of waterborne bio-based polyurethane sizing agent with heat resistance The bio-based polyurethane obtained in step 2 is dispersed in water under high-speed stirring, and a neutralizing agent is added dropwise for reaction to obtain a water-based bio-based polyurethane sizing agent with heat-resistant performance.

4. The method for preparing a water-based bio-based polyurethane sizing agent with heat resistance according to claim 3, characterized in that: The oligomer polyol is selected from soybean oil or castor oil.

5. The method for preparing a water-based bio-based polyurethane sizing agent with heat resistance according to claim 3, characterized in that: The diisocyanate is selected from toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate or dicyclohexylmethane diisocyanate.

6. The method for preparing a water-based bio-based polyurethane sizing agent with heat resistance according to claim 3, characterized in that: The catalyst is selected from dibutyltin dilaurate, stannous octoate or tin octoate.

7. The method for preparing a water-based bio-based polyurethane sizing agent with heat resistance according to claim 3, characterized in that: The solvent in step 2 is selected from one of N,N-dimethylformamide, acetone or tetrahydrofuran.

8. The method for preparing a water-based bio-based polyurethane sizing agent with heat resistance according to claim 3, characterized in that: The cross-linking agent is selected from guar gum and gallic acid.

9. The method for preparing a heat-resistant water-based hyperbranched polyurethane sizing agent according to claim 3, characterized in that: The molar ratio of the oligomer polyol, diisocyanate and crosslinking agent is (1-3): (3-10): (3-10).

Images