A sizing agent composition, a thermoplastic sizing agent and a method for preparing the same, a composite material

Abstract

The application relates to a sizing agent composition, a thermoplastic sizing agent and a preparation method thereof, and a composite material, and belongs to the technical field of carbon fiber sizing agents. A sizing agent composition comprises, in terms of weight parts of non-volatile components, 4-95 parts of a styrene-maleic anhydride copolymer, 5-96 parts of a phenoxy resin and 1-30 parts of a smoothing agent; the number average molecular weight of the styrene-maleic anhydride copolymer is 2000-18000, and the acid value is 200-500 mgKOH / g. The sizing agent prepared by using the sizing agent composition can significantly enhance the bonding strength between carbon fibers and thermoplastic resins, thereby enhancing the mechanical properties of a thermoplastic resin-based carbon fiber composite material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon fiber sizing agent, and particularly relates to a sizing agent composition, a thermoplastic sizing agent and a preparation method thereof, and a composite material. BACKGROUND

[0002] The thermoplastic resin-based carbon fiber composite material has the advantages of high toughness, large damage tolerance, good dielectric constant, convenient maintenance, similar processing characteristics to metals, low cost, and the like. Moreover, the raw material storage period of the thermoplastic resin-based carbon fiber composite material is not limited, low-temperature storage is not required, the forming and processing cycle is relatively short, and large special equipment such as a heat press tank is not required for forming. In particular, the thermoplastic resin-based carbon fiber composite material has good recyclability, recoverability, reusability and environmental friendliness, and the like, and thus has a very broad application prospect. In the preparation process of the thermoplastic resin-based carbon fiber composite material, the key is to achieve good interfacial bonding strength between the thermoplastic resin and the carbon fiber. At present, many studies have been devoted to developing new thermoplastic sizing agents to improve the performance of the composite material. However, some existing thermoplastic sizing agents have some limitations and challenges.

[0003] In order to improve the interfacial bonding strength between the thermoplastic resin and the carbon fiber, a large number of studies on new sizing agents have been carried out for different thermoplastic resins (such as polyamide (PA6, PA66), polypropylene (PP), polyether sulfone (PES), polyurethane (PU), polyacrylonitrile-butadiene-styrene (ABS), polyether ether ketone (PEEK), polycarbonate (PC), and the like). For example, patent CN114717851A discloses a carbon fiber sizing agent mainly composed of a polyurethane compound. The combination between the sized carbon fiber and the resin is significantly improved. However, the sizing agent belongs to a solvent type sizing agent, and the organic solvent is extremely volatile in the sizing process. Not only will it pollute the production environment and cause safety hazards, but also will harm the health of production personnel. Patent CN109722894A proposes a carbon fiber sizing agent including polyolefin resin powder, sodium polyacrylate, fatty alcohol polyvinyl ether and deionized water. The preparation process of the sizing agent is simple, safe and environmentally friendly, and the comprehensive cost is low. However, the sizing agent needs to add more stabilizing additives, which will weaken the mechanical properties of the composite material. Patent CN110699960A discloses an acid-modified polyolefin resin emulsion sizing agent. The sizing agent has excellent heat resistance. The sized carbon fiber not only has good fiber opening property, but also has good affinity with the thermoplastic resin matrix. However, the acid modification condition is harsh, and the process is complicated. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the embodiments of the present application includes providing a sizing agent composition to improve the interfacial bonding performance of the thermoplastic resin.

[0005] In a first aspect, the embodiments of the present application provide a sizing agent composition, comprising, in terms of weight parts of non-volatile components: 4-95 parts of a styrene-maleic anhydride copolymer, 5-96 parts of a phenoxy resin, and 1-30 parts of a smoothing agent; the styrene-maleic anhydride copolymer has a number average molecular weight of 2000-18000 and an acid value of 200-500 mgKOH / g.

[0006] The present application uses a low molecular weight styrene-maleic anhydride copolymer (with a number average molecular weight of 6000-12000) and a phenoxy resin as the main body of the sizing agent composition. On the one hand, the styrene-maleic anhydride copolymer contains styrene with weak polarity and maleic anhydride with strong polarity, and has amphiphilic properties, thus having good compatibility with thermoplastic resins. Meanwhile, the styrene-maleic anhydride copolymer is a thermoplastic functional polymer material with good thermal stability. The low molecular weight styrene-maleic anhydride copolymer has amphiphilic properties after being saponified with alkali, and is used as an emulsifier in the present application. It has the advantages of strong dispersing ability and good stabilizing effect. Therefore, no additional emulsifier is added in the sizing agent of the present application, and there is no problem of poor heat resistance and adhesion of the sizing agent due to the presence of additional emulsifier. On the other hand, the phenoxy resin not only has excellent heat resistance, but also contains highly polar hydroxyl groups in its molecular structure, and has strong adhesion to carbon fibers, which can improve the bunching of carbon fibers. Therefore, the sizing agent prepared by combining the two has not only excellent heat resistance, but also can improve the compatibility with different thermoplastic resins, and can tightly combine carbon fibers with a thermoplastic resin matrix, thereby enhancing the mechanical properties of the thermoplastic resin-based carbon fiber composite material. The introduction of the smoothing agent makes the carbon fiber tows have good adhesion and good opening properties, which is conducive to the infiltration of the thermoplastic resin into the carbon fibers, thereby improving the interfacial bonding performance of the composite material.

[0007] In the present application, the number average molecular weight of the styrene-maleic anhydride copolymer includes but is not limited to 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, and 18000. The acid value of the styrene-maleic anhydride copolymer includes but is not limited to 200 mgKOH / g, 250 mgKOH / g, 300 mgKOH / g, 350 mgKOH / g, 400 mgKOH / g, 450 mgKOH / g, and 500 mgKOH / g.

[0008] In some embodiments of the present application, the composition comprises, in terms of weight parts of non-volatile components: 15-82 parts of a styrene-maleic anhydride copolymer, 18-85 parts of a phenoxy resin, and 6-15 parts of a smoothing agent.

[0009] In some embodiments of the present application, the number average molecular weight of the styrene-maleic anhydride copolymer is 6000-12000, and the acid value is 300-400 mgKOH / g. The copolymer in the above range of number average molecular weight and acid value has better thermal stability, and the control of the acid value makes the adhesion between the copolymer and the carbon fiber and the thermoplastic resin better.

[0010] In some embodiments of the present application, the weight average molecular weight of the phenoxy resin is 30000-60000. Limiting the weight average molecular weight of the phenoxy resin to the range of 30000-60000 helps the phenoxy resin to have excellent heat resistance, molecular weight stability, adhesion and flowability, which are very important for preparing high-performance thermoplastic resin-based carbon fiber composites. In the present application, the weight average molecular weight of the phenoxy resin includes but is not limited to 30000, 35000, 40000, 45000, 50000, 55000, 60000.

[0011] In some embodiments of the present application, the weight average molecular weight of the phenoxy resin is 30000-40000.

[0012] In some embodiments of the present application, the smoothing agent includes one or more of polyethylene glycol monolaurate, polyethylene glycol monoheptanoate, polyethylene glycol monocaprylate, polyethylene glycol monononanoate, polyethylene glycol dimyristate, polyethylene glycol monotetradecanoate, polyethylene glycol dioctanoate, polyethylene glycol monopalmitate, polyethylene glycol monolinoleate, polyethylene glycol monooleate and polyethylene glycol dioleate.

[0013] In a second aspect, the embodiments of the present application provide a thermoplastic sizing agent using the above composition as a raw material for preparation.

[0014] In a third aspect, the embodiments of the present application provide a preparation method of the above sizing agent, comprising: mixing the styrene-maleic anhydride copolymer and an alkali solution to obtain a styrene-maleic anhydride saponate solution; mixing the phenoxy resin with an organic solvent and a smoothing agent, and under stirring conditions, adding the saponate solution to perform emulsification reaction to obtain an emulsion; evaporating the emulsion to remove the organic solvent to obtain the sizing agent.

[0015] The present application uses the emulsion / solvent evaporation method to prepare the sizing agent, and the preparation process of the sizing agent is simple, does not contain organic solvents, is safe and environmentally friendly, and the emulsion has good stability. Therefore, the sizing agent prepared by the preparation method provided by the present application has the advantages of good heat resistance, strong affinity with carbon fiber and most thermoplastic resins, good fiber opening property, simple preparation, safety and environmental protection, etc.

[0016] In some embodiments of the present application, the alkaline solution is obtained by mixing an alkali and water, wherein the alkali comprises one or more of sodium hydroxide, potassium hydroxide, ammonia, aluminum hydroxide, methylamine, dimethylamine, trimethylamine, and triethylamine.

[0017] In some embodiments of the present application, the mass concentration of the alkali in the alkaline solution is 1-2.5%. Within this mass concentration range, styrene maleic anhydride can be completely dissolved when subjected to alkaline hydrolysis.

[0018] In some embodiments of the present application, the mass ratio of styrene-maleic anhydride copolymer to alkaline solution is 1:(20-40). Alkaline hydrolysis is a key step that converts styrene-maleic anhydride copolymer into a saponified product, laying a foundation for subsequent preparation of sizing agent. Therefore, by controlling the mass ratio of styrene-maleic anhydride copolymer to alkaline solution within the above range, the alkaline hydrolysis reaction of styrene-maleic anhydride copolymer can be more accurately controlled to obtain the desired product.

[0019] In some embodiments of the present application, the organic solvent comprises one or more of toluene, xylene, cyclohexanone, tetrahydrofuran, N,N-dimethylformamide, and methyl ethyl ketone. The role of the organic solvent is to dissolve the phenoxy resin so that it can be emulsified.

[0020] In some embodiments of the present application, the stirring speed is 2000-11000 r / min. Limiting the stirring speed to the range of 2000-11000 r / min helps to achieve controllability of mixing effect, prevent liquid from splashing out, save energy, reduce mechanical wear and tear, and improve control of the reaction.

[0021] In a fourth aspect, the embodiments of the present application provide a composite material comprising the sizing agent described above. DETAILED DESCRIPTION

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. If specific conditions are not specified in the embodiments, conventional conditions or manufacturer-recommended conditions are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0023] The application provides a sizing agent composition, which comprises, by weight of non-volatile components: 4-95 parts of a styrene-maleic anhydride copolymer, 5-96 parts of a phenoxy resin, and 1-30 parts of a smoothing agent; wherein the styrene-maleic anhydride copolymer has a number average molecular weight of 2000-18000 and an acid value of 200-500 mgKOH / g. The application uses a styrene-maleic anhydride copolymer with a number average molecular weight of 6000-12000 and an acid value of 300-400 mgKOH / g as the main body of the sizing agent composition. The copolymer contains acidic functional groups, such as carboxyl groups. These acidic functional groups can interact with the oxygen-containing groups (such as hydroxyl and carboxyl groups) on the surface of the carbon fiber to form chemical bonds such as hydrogen bonds and covalent bonds. This chemical adsorption allows the copolymer to adhere closely to the surface of the carbon fiber, enhancing the bonding strength between the carbon fiber and the thermoplastic resin. Moreover, the molecular structure of the copolymer allows it to have emulsifying properties, which helps to uniformly disperse non-aqueous components such as phenoxy resin and smoothing agent in water to form a stable emulsion. Therefore, no additional emulsifier is needed during the preparation of the sizing agent. The phenoxy resin is also a thermoplastic resin, which not only has excellent heat resistance, but also contains a large number of highly polar hydroxyl groups in its molecular structure. The styrene-maleic anhydride copolymer also contains polar carboxyl groups, so they have good adhesion to both carbon fiber and thermoplastic resin. Furthermore, through the synergistic effect of the styrene-maleic anhydride copolymer and the phenoxy resin, the carbon fiber and the thermoplastic resin can be tightly combined together, thereby enhancing the mechanical properties of the thermoplastic resin-based carbon fiber composite material. At the same time, the introduction of the smoothing agent helps to reduce the friction between the carbon fibers and improves the opening property of the carbon fiber tows. This makes it easier for the carbon fibers to disperse and separate during the sizing process, which helps the resin to better penetrate and coat the carbon fibers, thereby improving the mechanical properties of the composite material.

[0024] In the application, the weight average molecular weight of the phenoxy resin is 30000-60000. Phenoxy resins with a weight average molecular weight in this range generally have good heat resistance. This means that under high temperature conditions, the phenoxy resin can maintain its structural stability and is not easily decomposed or lose its properties. For thermoplastic resin-based carbon fiber composites, high temperature resistance is a key requirement, so choosing a phenoxy resin with good heat resistance helps to improve the temperature range and stability of the material. The weight average molecular weight of the phenoxy resin includes but is not limited to 30000, 35000, 40000, 45000, 50000, 55000, 60000.

[0025] In the embodiments of the present application, the smoothing agent includes, but is not limited to, one or more of polyethylene glycol monolaurate, polyethylene glycol monoheptanoate, polyethylene glycol monocaprylate, polyethylene glycol monononanoate, polyethylene glycol dimyristate, polyethylene glycol monotricosanoate, polyethylene glycol monomyristate, polyethylene glycol dioctanoate, polyethylene glycol monopalmitate, polyethylene glycol monolinoleate, polyethylene glycol monooleate, and polyethylene glycol dioleate.

[0026] The embodiments of the present application also provide a thermoplastic sizing agent, and the preparation of the sizing agent includes the following steps:

[0027] (1) In a reaction container, styrene-maleic anhydride copolymer powder and an alkali solution are sequentially added, and stirring and mixing are performed at 80°C until the solution is transparent to obtain a styrene-maleic anhydride saponate solution. The saponate has amphiphilic properties and is a high-molecular surfactant that can be used as an emulsifier, so no additional emulsifier is added in the preparation of the sizing agent of the present application, and the negative effects of the additional emulsifier are avoided. At the same time, after the alkali hydrolysis of the styrene-maleic anhydride copolymer, the carboxyl groups can interact with the hydroxyl and carboxyl groups on the surface of the carbon fiber to form a firmly bonded surface layer, and the styrene-maleic anhydride copolymer has good compatibility with thermoplastic resins such as polystyrene and its derivatives.

[0028] The styrene-maleic anhydride copolymer and the alkali solution are mixed at a mass ratio of 1:(20-40). Controlling the mass ratio of the styrene-maleic anhydride copolymer and the alkali solution within the above range can more accurately control the alkali hydrolysis reaction of the styrene-maleic anhydride copolymer to obtain the desired product.

[0029] The alkali solution is obtained by mixing an alkali and water, and the mass concentration of the alkali in the alkali solution is 1-2.5%. The alkali includes, but is not limited to, one or more of sodium hydroxide, potassium hydroxide, ammonia, aluminum hydroxide, methylamine, dimethylamine, trimethylamine, and triethylamine.

[0030] (2) The phenoxy resin is dissolved using an organic solvent to obtain a phenoxy resin solution, and the mass concentration of the phenoxy resin in the phenoxy resin solution is 30-40%. Then, the saponate solution prepared in step (1) is added to the phenoxy resin solution for emulsification reaction at 2000-11000 r / min. After the emulsification reaction is completed, the organic solvent is removed by rotary evaporation to obtain the thermoplastic sizing agent. In the present application, the emulsification reaction is performed at room temperature, and the time of the emulsification reaction is not limited in the present application and can be determined according to specific process requirements. In the present application, the mass concentration of the phenoxy resin includes, but is not limited to, 30%, 32%, 34%, 36%, 38%, and 40%.

[0031] The organic solvent includes, but is not limited to, one or more of toluene, xylene, cyclohexanone, tetrahydrofuran, N,N-dimethylformamide, and methyl ethyl ketone.

[0032] The features and performance of the present application are further described in detail below in connection with the examples.

[0033] Example 1

[0034] This example provides a sizing agent, the preparation of which includes the following steps:

[0035] (1) In a reaction vessel equipped with a condenser reflux device and a stirring paddle, 35 g of styrene-maleic anhydride copolymer powder (number average molecular weight of 6000, acid value of 345 mgKOH / g), 1050 g of distilled water, and 21 g of potassium hydroxide were sequentially added. The solution was stirred rapidly at 80°C until it became transparent, obtaining a styrene-maleic anhydride saponified solution.

[0036] (2) 194 g of phenoxy resin solution (phenoxy resin weight average molecular weight of 30000, mass fraction of phenoxy resin of 32%) obtained after dissolution with xylene and 3 g of polyethylene glycol monolaurate were mixed uniformly in the reaction vessel. Under continuous stirring at a speed of 10000 r / min, the styrene-maleic anhydride saponified solution was gradually added for emulsification. After emulsification was completed, the organic solvent was removed by rotary evaporation, obtaining an emulsion, which was the sizing agent.

[0037] Example 2

[0038] This example is basically the same as Example 1, with the difference being that:

[0039] In step (1), 35 g of styrene-maleic anhydride copolymer powder (number average molecular weight of 15000, acid value of 360 mgKOH / g), 1200 g of distilled water, and 24 g of potassium hydroxide were sequentially added in a reaction vessel equipped with a condenser reflux device and a stirring paddle. The solution was stirred rapidly at 80°C until it became transparent, obtaining a styrene-maleic anhydride saponified solution.

[0040] Example 3

[0041] This example is basically the same as Example 1, with the difference being that:

[0042] In step (1), 35 g of styrene-maleic anhydride copolymer powder (number average molecular weight of 6000, acid value of 480 mgKOH / g), 1200 g of distilled water, and 24 g of sodium hydroxide were sequentially added in a reaction vessel equipped with a condenser reflux device and a stirring paddle. The solution was stirred rapidly at 80°C until it became transparent, obtaining a styrene-maleic anhydride saponified solution.

[0043] Example 4

[0044] The present embodiment provides a sizing agent, the preparation of which comprises the following steps:

[0045] (1) 15 g of styrene-maleic anhydride copolymer powder (number average molecular weight of 6000, acid value of 345 mgKOH / g), 450 g of distilled water, and 9 g of potassium hydroxide were sequentially added into a reaction vessel, and stirred rapidly at 80°C until the solution was transparent to obtain a styrene-maleic anhydride saponified product solution.

[0046] (2) 234 g of phenoxy resin solution (phenoxy resin weight average molecular weight of 40000, mass fraction of phenoxy resin of 40%) and 10 g of polyethylene glycol fatty acid ester obtained after dissolution with xylene were mixed uniformly in the reaction vessel, and the styrene-maleic anhydride saponified product solution was gradually added for emulsification under continuous stirring at a rotation speed of 10000 r / min, and after the emulsification was completed, the organic solvent was removed by rotary evaporation to obtain an emulsion, which was the sizing agent.

[0047] Example 5

[0048] The present embodiment provides a sizing agent, the preparation of which comprises the following steps:

[0049] (1) 60 g of styrene-maleic anhydride copolymer powder (number average molecular weight of 6000, acid value of 385 mgKOH / g), 2100 g of distilled water, and 42 g of triethylamine were sequentially added into a reaction vessel, and stirred rapidly at 80°C until the solution was transparent to obtain a styrene-maleic anhydride saponified product solution.

[0050] (2) 63 g of phenoxy resin solution (phenoxy resin weight average molecular weight of 50000, mass fraction of phenoxy resin of 40%) and 20 g of polyethylene glycol monooleate obtained after dissolution with cyclohexanone were mixed uniformly in the reaction vessel, and the styrene-maleic anhydride saponified product solution was gradually added for emulsification under continuous stirring at a rotation speed of 10000 r / min, and after the emulsification was completed, the organic solvent was removed by rotary evaporation to obtain an emulsion, which was the sizing agent.

[0051] The remaining examples and comparative examples are basically the same as Example 1, except for the process parameters, reagents, etc. Please refer to Table 1 for details.

[0052] Table 1

[0053]

[0054] Table 1 (continued)

[0055]

[0056] Table 1 (continued)

[0057]

[0058] Comparative Example 1

[0059] This comparative example is substantially the same as Example 1, except that no smoothing agent is added.

[0060] Comparative Example 2

[0061] This comparative example is substantially the same as Example 1, except that the number average molecular weight of the styrene-maleic anhydride copolymer is 1500.

[0062] Comparative Example 3

[0063] This comparative example is substantially the same as Example 1, except that the number average molecular weight of the styrene-maleic anhydride copolymer is 20000.

[0064] Comparative Example 4

[0065] This comparative example is substantially the same as Example 1, except that the acid value of the styrene-maleic anhydride copolymer is 150.

[0066] Comparative Example 5

[0067] This comparative example is substantially the same as Example 1, except that the acid value of the styrene-maleic anhydride copolymer is 580.

[0068] Comparative Example 6

[0069] This comparative example is substantially the same as Example 1, except that the styrene-maleic anhydride copolymer is replaced by polystyrene, and an emulsifier, polyvinyl alcohol, is additionally added.

[0070] Test Example

[0071] In this test example, the sizing agents prepared in Examples 1-7 and Comparative Examples 1-6 are diluted to 1.0% and attached to T700x12K carbon fiber tows using the infiltration method, and the sizing agent emulsion particle size and stability, thermal stability, sizing carbon fiber tow weight, fiber opening rate, and interlayer shear strength of the sizing carbon fiber / PA66 resin are tested after drying treatment at 130°C.

[0072] (1) The particle size of the sizing agent emulsion is tested by a laser particle size analyzer, Model Microtrac S3500. The emulsion sample is automatically diluted to a suitable concentration for testing; (2) The sizing agent emulsion is respectively left to stand for 3 months, and the emulsion stability is observed. The emulsion is excellent in stability if it has no stratification and no precipitation at the bottom. The emulsion is good in stability if it has no stratification but has precipitation at the bottom. The emulsion is poor in stability if it has stratification and precipitation at the bottom; (3) The prepared sizing agent emulsion is dried in an oven at 120°C, and the thermal stability is tested according to GB / T33047.1—2016. The temperature at which the thermal weight loss is 5% is used as the evaluation standard to evaluate the heat resistance of the sample; (4) The method for testing the hairiness quantity and the opening rate of carbon fibers in Carbon Fibers and Graphite Fibers is used; (5) The interlaminar shear strength is determined according to JC / T 773—2010, and the resin used is PA66 resin. The test data of the particle size and the stability, the thermal stability of the sizing agent emulsion, the hairiness quantity and the opening rate of the sized carbon fibers, and the interlaminar shear strength of the sized carbon fibers / PA66 resin are listed in Table 2.

[0073] Table 2

[0074]

[0075] As can be seen from Table 2, by comparing Examples 6 and 7, it can be seen that when the weight average molecular weight of the phenoxy resin is 30000-60000, the sizing agent has good thermal stability and high interlaminar shear strength. The reason is that the molecular weight of the phenoxy resin is low, the heat resistance is reduced, and the molecular weight is too high, which increases the hardness of the sized carbon fibers and is not conducive to the infiltration of the thermoplastic resin, resulting in a decrease in the interlaminar shear strength. By comparing Comparative Example 1 and Example 1, it can be seen that when no smoothing agent is added, the opening rate of the carbon fibers is low, and the interlaminar shear strength is reduced. The reason is that the carbon fiber tows have strong bunching, and the resin has poor wettability. By comparing Comparative Examples 2, 3 and Example 1, it can be seen that when the number average molecular weight of the styrene-maleic anhydride copolymer is 2000-18000, the emulsion has good temperature resistance and good heat resistance. The reason is that the molecular weight is too low, and the thermal decomposition temperature is reduced. The molecular weight is too high, and the emulsification effect is reduced after saponification. By comparing Comparative Examples 4, 5 and Example 1, it can be seen that when the acid value of the styrene-maleic anhydride copolymer is 200-500 mgKOH / g, the thermal stability is good, and the interlaminar shear strength with the matrix resin is high. The reason is that the anhydride content is increased, and the thermal stability is reduced. The anhydride content is reduced, and the combination with the resin matrix is reduced. By comparing Comparative Example 6 and Example 1, the thermal stability of Comparative Example 6 is reduced, and the interlaminar shear strength is low. The reason is that the emulsifier polyvinyl alcohol has poor thermal stability, and the polystyrene has poor compatibility with the PA66 resin.

[0076] The embodiments described above are only part of the embodiments of the present application, rather than all the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

Claims

1. A sizing agent composition characterized in that, by weight of non-volatile components, comprising: 4-95 parts of styrene-maleic anhydride copolymer, 5-96 parts of phenoxy resin, and 1-30 parts of smoothing agent; the number average molecular weight of the styrene-maleic anhydride copolymer is 2000-18000, and the acid value is 200-500 mgKOH / g.

2. The composition of claim 1, wherein, by weight of non-volatile components, comprising: 15-82 parts of styrene-maleic anhydride copolymer, 18-85 parts of phenoxy resin, and 6-15 parts of smoothing agent.

3. The composition of claim 1, wherein, the number average molecular weight of the styrene-maleic anhydride copolymer is 6000-12000, and the acid value is 300-400 mgKOH / g.

4. The composition of claim 3, wherein, the weight average molecular weight of the phenoxy resin is 30000-60000.

5. The composition of claim 4, wherein, the weight average molecular weight of the phenoxy resin is 30000-40000.

6. The composition according to any one of claims 1-5, characterized in that, the smoothing agent comprises one or more of polyethylene glycol monolaurate, polyethylene glycol monoheptanoate, polyethylene glycol monocaprylate, polyethylene glycol monononanoate, polyethylene glycol dimyristate, polyethylene glycol monopentadecanoate, polyethylene glycol monomyristate, polyethylene glycol dioctanoate, polyethylene glycol monopalmitate, polyethylene glycol monolinoleate, polyethylene glycol monooleate, and polyethylene glycol dioleate.

7. A process for the preparation of a thermoplastic sizing agent, characterized in that, using the composition of any one of claims 1-5 as a raw material for preparation; the preparation method comprising: mixing the styrene-maleic anhydride copolymer and the alkali solution to obtain a styrene-maleic anhydride saponate solution; mixing the phenoxy resin with an organic solvent and the smoothing agent, and adding the saponate solution under stirring to carry out an emulsification reaction, to obtain an emulsion; evaporating the organic solvent from the emulsion to obtain the sizing agent.

8. The preparation method according to claim 7, characterized in that, the alkali solution is obtained by mixing an alkali and water, wherein the alkali comprises one or more of sodium hydroxide, potassium hydroxide, aqueous ammonia, aluminum hydroxide, methylamine, dimethylamine, trimethylamine, and triethylamine.

9. The production method according to claim 8, characterized by, the mass concentration of the alkali in the alkali solution is 1-2.5%.

10. The preparation method according to claim 7, characterized in that, the mass ratio of the styrene-maleic anhydride copolymer to the alkali solution is 1: (20-40).

11. The production method according to any one of claims 7 to 10, characterized by, the organic solvent comprises one or more of toluene, xylene, cyclohexanone, tetrahydrofuran, N,N-dimethylformamide, and methyl ethyl ketone.

12. The production method according to any one of claims 7 to 10, characterized by, the stirring speed is 2000-11000 r / min.

13. A thermoplastic sizing agent characterized in that, obtained by the preparation method of any one of claims 7-10.

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