Preparation method of melt spinning polypropylene-polyvinyl alcohol composite material

Abstract

The invention discloses a preparation method of a melt spinning polypropylene-polyvinyl alcohol composite material. The PVA aerogel microspheres are distributed on the surface of the polypropylene fiber, so that the antistatic capacity of the polypropylene fiber is improved, and the polypropylene fiber is endowed with conductive performance by a conjugated bond generated by heating conjugation of internal polyvinyl alcohol. Meanwhile, the polypropylene is subjected to micro-foaming by utilizing water molecules and carbon dioxide generated by partial degradation of the polyvinyl alcohol aerogel microspheres and carbon dioxide generated by reaction of isocyanate and water, and carbon dioxide gas in foam pores can be used as flame-retardant gas to improve the flame-retardant property of the polypropylene fiber; the problems of limited antistatic capability, poor flame retardant property and the like of the polypropylene fiber are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of polypropylene material modification, and more specifically, relates to a method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material. Background Art

[0002] Polypropylene fiber is a lightweight material, which enables it to reduce the weight of the overall structure in many application scenarios. Polypropylene fiber has almost no water absorption, which means that it is not easily affected by moisture in a humid environment and can maintain good physical properties. Moreover, it has good moisture conductivity and can promote the dissipation of moisture to a certain extent. It is an important hydrophobic fiber and is used to produce functional textiles, such as sports textiles. At the same time, polypropylene fiber is a highly insulating organic polymer material and is prone to generating static electricity during use. This is because its surface resistance is very high and charges are difficult to conduct. During the process of friction or separation, charges are easily accumulated on its surface, thus generating static electricity. For example, in the textile industry, fabrics made of polypropylene fiber will generate static electricity adsorption during wearing or processing. Due to human activities or the friction of machines, the fabrics will stick to the skin or adsorb dust, bringing discomfort to users and also affecting the quality and appearance of the products.

[0003] The antistatic property of polypropylene fibers can be achieved by adding antistatic agents, which can be divided into external coating type and internal addition type. The internal addition type antistatic agent is to mix the antistatic agent with polypropylene resin during the production process of polypropylene fibers, so that the antistatic agent is evenly distributed inside the fibers. When static electricity is generated on the fiber surface, the antistatic agent can migrate to the surface to play an antistatic role. The external coating type antistatic agent is to coat the antistatic agent solution on the surface of polypropylene fibers, which can form a conductive film on the fiber surface to enable the conduction of charges. For example, high-energy particles in the plasma can bombard the surface of polypropylene fibers to generate some polar groups on the surface, such as hydroxyl groups, carboxyl groups, etc. These polar groups can increase the hydrophilicity of the fiber surface, thereby absorbing moisture in the environment to play an antistatic role. It is also possible to introduce antistatic groups on the fiber surface through chemical reactions. For example, through graft copolymerization reaction, monomers containing antistatic groups (quaternary ammonium salts, sulfonic acids, etc.) are grafted onto the surface of polypropylene fibers, which can reduce the surface resistance of the fibers and effectively reduce the generation of static electricity. However, these external coating type antistatic agents are prone to falling off and losing their effects. For example, in CN108276662A, a permanent antistatic polypropylene composite material discloses blending polypropylene with hydrophilic polymers such as polyethylene glycol (PEG). Utilizing the good conductivity and moisture absorption properties of polyethylene glycol, it can absorb moisture in the environment and form a conductive water film on the fiber surface, thereby conducting static electricity out. However, the effect of conducting electricity by absorbing moisture in the environment is not ideal in a dry environment. In addition, polypropylene fibers themselves have poor flame retardancy, and fires need to be strictly prevented during textile and storage processes. Therefore, it is necessary to improve the flame retardancy of polypropylene to improve safety. Summary of the Invention

[0004] The present invention provides a method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material to overcome the problems of limited antistatic ability and poor flame retardancy of existing polypropylene fibers.

[0005] The present invention is achieved by the following technical solutions:

[0006] A method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material, the preparation steps include: mixing polyvinyl alcohol, isocyanate and polypropylene, drying, and then melt-extruding and spinning the mixture at 200-320 °C to obtain a polypropylene-polyvinyl alcohol composite material. The present invention utilizes the distribution of polyvinyl alcohol on the surface of the polypropylene matrix and the generation of conjugated bonds by polyvinyl alcohol when heated to improve the conductivity and antistatic effect of polypropylene. At the same time, the carbon dioxide decomposed by polyvinyl alcohol and the carbon dioxide generated by the reaction of water with isocyanate are used for micro-foaming to endow it with flame retardancy.

[0007] Furthermore, the addition amount of polyvinyl alcohol is 1-60% of polypropylene, and the addition amount of isocyanate is 1-10%.

[0008] Further, the polyvinyl alcohol is a polyvinyl alcohol aerogel microsphere.

[0009] Further, the polyvinyl alcohol aerogel microsphere has a diameter of 10 μm to 100 μm and a pore size of 10 to 200 nm.

[0010] Further, the isocyanate is one or more of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), naphthalene-1,5-diisocyanate (NDI), polymethylene polyphenyl polyisocyanate (PAPI), hydrogenated toluene diisocyanate (HTDI), dicyclohexylmethane diisocyanate (HMDI), tetramethylxylylene diisocyanate (TMXDI), isophorone diisocyanate (IPDI), and JQ glue.

[0011] Further, the temperatures of each section of the melt extrusion spinning are as follows: the first zone of the screw is 200 to 220 °C, the second zone of the screw is 210 to 240 °C, the third zone of the screw is 220 to 240 °C, the fourth zone of the screw is 220 to 250 °C, the fifth zone of the screw is 240 to 320 °C, and the sixth zone of the screw is 210 to 230 °C.

[0012] Further, one or more of a grafting agent and a foam stabilizer are added to the mixture.

[0013] Further, the foam stabilizer is one or more of lecithin, fatty amide, fatty acid acetic acid amide, N-alkyliminodiacetic acid sodium salt, polyacrylic acid, and alkyl betaine sulfonic acid.

[0014] Further, the grafting agent is one or more of maleic anhydride, dibutyl maleate, glycidyl methacrylate, acrylic acid, β-hydroxyethyl methacrylate, and unsaturated silane.

[0015] Further, the polypropylene-polyvinyl alcohol composite fiber is woven into a non-woven fabric, which can be applied to packaging or battery diaphragms.

[0016] Compared with the prior art, the beneficial effects are:

[0017] In the present invention, the added PVA aerogel microspheres will be repelled to the surface of polypropylene fibers due to surface tension, thereby improving the antistatic ability of polypropylene fibers. The conjugated bonds generated by the heat conjugation of internal polyvinyl alcohol further endow the polypropylene fibers with conductive properties. At the same time, by using the degradation of polyvinyl alcohol aerogel microspheres in the molten part of polypropylene to generate water molecules and carbon dioxide, the internally generated micro-foamed structure can make the PVA distribution more uniform, have better compatibility with the matrix, and at the same time increase the probability of PVA contacting each other. The micropores on the surface improve the water adsorption ability of polypropylene fibers and can further improve the antistatic effect. In addition, the amine substance generated by the reaction of isocyanate and water contains a polar terminal amino group and will also be arranged on the surface of polypropylene fibers to improve the antistatic performance. The added isocyanate in the present invention further reacts with water molecules to generate more carbon dioxide, which micro-foams the polypropylene. The carbon dioxide gas in the pores can be used as a flame retardant gas to improve the flame retardant performance of polypropylene fibers. Description of the Drawings

[0018] Figure 1 is the SEM image of polyvinyl alcohol microspheres;

[0019] Figure 2 is the vertical burning diagram of polypropylene-polyvinyl alcohol composites prepared in Examples 1-4 and Comparative Example 1. Detailed Description of the Invention

[0020] The following is further explained and clarified in conjunction with examples, but the specific examples do not limit the present invention in any form. Unless otherwise specified, the methods and equipment used in the examples are conventional methods and equipment in the art, and the raw materials used are all conventional commercially available raw materials.

[0021] The PVA pellets used in this example are polyvinyl alcohol aerogel microspheres, and the preparation steps include:

[0022] Dissolve PVA in water to prepare a PVA aqueous solution. Then add the PVA aqueous solution to dimethyl silicone oil, and then add an emulsifier (such as Tween 80) and a crosslinking agent (such as epichlorohydrin), and mechanically stir at a certain rotation speed to prepare polyvinyl alcohol microsphere hydrogel. Filter, wash, dry, and then perform freeze-drying treatment to prepare polyvinyl alcohol aerogel. As Figure 1 shown, polyvinyl alcohol hydrogel microspheres are prepared in the present invention, and the particle size distribution of the microspheres is uniform. In the above steps, by adjusting the ratio of the emulsifier and the crosslinking agent, as well as the stirring and shear rate, polyvinyl alcohol aerogel microspheres with different particle sizes and pore sizes can be obtained.

[0023] Example 1

[0024] This example provides a method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material, and the steps include:

[0025] S1. Add 0.2 kg of polyvinyl alcohol aerogel microspheres with a particle size of 10 μm and a pore size of 10 nm, 0.1 kg of MDI, and 0.1 kg of maleic anhydride to 1 kg of PP pellets, mix evenly, and dry.

[0026] S2. Then add to a twin-screw extruder for wire drawing. The temperatures of each extrusion section are: screw zone 1 (210 °C), screw zone 2 (230 °C), screw zone 3 (230 °C), screw zone 4 (240 °C), screw zone 5 (240 °C), screw zone 6 (220 °C), to prepare polypropylene-polyvinyl alcohol composite fiber filaments.

[0027] Example 2

[0028] This example provides a method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material, and the steps include:

[0029] S1. Add 0.1 kg of polyvinyl alcohol aerogel microspheres with a particle size of 20 μm and a pore size of 50 nm, 0.2 kg of MDI, and 0.1 kg of maleic anhydride to 1 kg of PP pellets, mix evenly, and dry.

[0030] S2. Then add to a twin-screw extruder for wire drawing. The temperatures of each extrusion section are: screw zone 1 (210 °C), screw zone 2 (230 °C), screw zone 3 (230 °C), screw zone 4 (240 °C), screw zone 5 (240 °C), screw zone 6 (220 °C), to prepare polypropylene-polyvinyl alcohol composite fiber filaments.

[0031] Example 3

[0032] This example provides a method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material, and the steps include:

[0033] S1. Add 0.06 kg of polyvinyl alcohol aerogel microspheres with a particle size of 50 μm and a pore size of 100 nm, 0.1 kg of MDI, and 0.06 kg of maleic anhydride to 1 kg of PP pellets, mix evenly, and dry.

[0034] S2. Then add to a twin-screw extruder for wire drawing. The temperatures of each extrusion section are: screw zone 1 (210 °C), screw zone 2 (230 °C), screw zone 3 (230 °C), screw zone 4 (240 °C), screw zone 5 (240 °C), screw zone 6 (220 °C), to prepare polypropylene-polyvinyl alcohol composite fiber filaments.

[0035] Example 4

[0036] This example provides a method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material, and the steps include:

[0037] S1. Add 0.03 kg of polyvinyl alcohol aerogel microspheres with a particle size of 100 μm and a pore size of 200 nm, 0.1 kg of IPDI, and 0.06 kg of maleic anhydride to 1 kg of PP pellets, mix evenly, and dry.

[0038] S2. Then add it to a twin-screw extruder for wire drawing. The temperatures of each extrusion section are: the first zone of the screw (210 °C), the second zone of the screw (230 °C), the third zone of the screw (230 °C), the fourth zone of the screw (240 °C), the fifth zone of the screw (240 °C), and the sixth zone of the screw (220 °C) to prepare polypropylene-polyvinyl alcohol composite fiber filaments.

[0039] Example 5

[0040] This example provides a method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material, and the steps include:

[0041] S1. Add 0.4 kg of polyvinyl alcohol aerogel microspheres with a particle size of 50 μm and a pore size of 100 nm, 0.1 kg of MDI, and 0.06 kg of maleic anhydride to 1 kg of PP pellets, mix evenly, and dry.

[0042] S2. Then add it to a twin-screw extruder for wire drawing. The temperatures of each extrusion section are: the first zone of the screw (210 °C), the second zone of the screw (230 °C), the third zone of the screw (230 °C), the fourth zone of the screw (240 °C), the fifth zone of the screw (240 °C), and the sixth zone of the screw (220 °C) to prepare polypropylene-polyvinyl alcohol composite fiber filaments.

[0043] Example 6

[0044] This example provides a method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material, and the steps include:

[0045] S1. Add 0.6 kg of polyvinyl alcohol aerogel microspheres with a particle size of 50 μm and a pore size of 100 nm, 0.1 kg of MDI, and 0.08 kg of maleic anhydride to 1 kg of PP pellets, mix evenly, and dry.

[0046] S2. Then add it to a twin-screw extruder for wire drawing. The temperatures of each extrusion section are: the first zone of the screw (210 °C), the second zone of the screw (230 °C), the third zone of the screw (230 °C), the fourth zone of the screw (240 °C), the fifth zone of the screw (240 °C), and the sixth zone of the screw (220 °C) to prepare polypropylene-polyvinyl alcohol composite fiber filaments.

[0047] Example 7

[0048] This example provides a method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material, and the steps include:

[0049] S1. Add 0.5 kg of polyvinyl alcohol aerogel microspheres with a particle size of 100 μm and a pore size of 200 nm, 0.1 kg of IPDI, and 1.0 kg of maleic anhydride to 1 kg of PP pellets, mix evenly, and dry.

[0050] S2. Then add it to a twin-screw extruder for drawing. The temperatures of each extrusion section are: screw zone 1 (220 °C), screw zone 2 (240 °C), screw zone 3 (240 °C), screw zone 4 (250 °C), screw zone 5 (320 °C), screw zone 6 (230 °C), to prepare polypropylene-polyvinyl alcohol composite fiber filaments.

[0051] Example 8

[0052] This example provides a method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material, and the steps include:

[0053] S1. Add 0.1 kg of polyvinyl alcohol aerogel microspheres with a particle size of 50 μm and a pore size of 100 nm, 0.1 kg of MDI, and 0.08 kg of maleic anhydride to 1 kg of PP pellets, mix evenly, and dry.

[0054] S2. Then add it to a twin-screw extruder for drawing. The temperatures of each extrusion section are: screw zone 1 (200 °C), screw zone 2 (210 °C), screw zone 3 (210 °C), screw zone 4 (220 °C), screw zone 5 (240 °C), screw zone 6 (210 °C), to prepare polypropylene-polyvinyl alcohol composite fiber filaments.

[0055] In the above examples, foaming stabilizers such as lecithin, fatty amide, fatty acid acetic acid amide, N-alkyliminodiacetic acid sodium salt, polyacrylic acid, and alkyl betaine sulfonic acid can also be added to stabilize the micro-foamed cell pores.

[0056] Comparative Example 1

[0057] This comparative example provides a method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material, and the steps include:

[0058] S1. Add 0.2 kg of PVA pellets with a particle size of 10 μm and a pore size of 10 nm and 0.06 kg of maleic anhydride to 1 kg of PP pellets, mix evenly, and dry.

[0059] S2. Then add it to a twin-screw extruder for drawing. The temperatures of each extrusion section are: screw zone 1 (210 °C), screw zone 2 (230 °C), screw zone 3 (230 °C), screw zone 4 (240 °C), screw zone 5 (240 °C), screw zone 6 (220 °C), to prepare polypropylene-polyvinyl alcohol composite fiber filaments.

[0060] The polypropylene-polyvinyl alcohol composites prepared in Examples 1 to 4 and Comparative Example 1 were selected for performance testing, and the test results are shown in Table 1 below:

[0061] Table 1

[0062] <![CDATA[Density (g / cm 3 )]]> Flame retardant rating (UL 94) Surface resistivity (Ω·m) Example 1 0.68 VTM-0 <![CDATA[0.6*10 6 > Example 2 0.77 VTM-0 <![CDATA[2.88*10 8 > Example 3 0.89 VTM-1 <![CDATA[7.9*10 10 > Example 4 0.96 NR <![CDATA[2*10 14 <!-- 4 -->]]> Comparative Example 1 0.79 NR <![CDATA[1.4*10 6 >

[0063] According to Examples 1 to 4, the polyvinyl alcohol aerogel microspheres degrade partially in the molten polypropylene to produce water molecules and carbon dioxide, and the micro-foamed structure generated inside can achieve the lightweight of polypropylene. Adding isocyanate reacts further with water molecules to produce more carbon dioxide, which micro-foams the polypropylene. The carbon dioxide gas in the pores can be used as a flame-retardant gas to improve the flame-retardant performance of polypropylene fibers. From Example 1 and Comparative Example 1, it can be seen that the amine substance produced by the reaction of isocyanate with water contains a polar terminal amino group, which will also be arranged on the surface of polypropylene fibers, further improving the antistatic performance.

[0064] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a melt-spinning polypropylene-polyvinyl alcohol composite material, characterized in that: The preparation steps include: mixing polyvinyl alcohol, isocyanate and polypropylene, drying, and then melting, extruding and spinning the mixture at 200-320° C. to obtain a polypropylene-polyvinyl alcohol composite material.

2. The method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material according to claim 1, characterized in that: The added amount of polyvinyl alcohol is 1 to 60% of polypropylene, and the added amount of isocyanate is 1 to 10%.

3. The method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material according to claim 1, characterized in that: The polyvinyl alcohol is polyvinyl alcohol gel microspheres.

4. The method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material according to claim 1, characterized in that: The diameter of the polyvinyl alcohol gel microspheres is 10 μm to 100 μm, and the pore size of the microspheres is 10 to 200 nm.

5. The method for preparing a melt-spun polypropylene-polyvinyl alcohol composite material according to claim 1, characterized in that: The isocyanate is one or more of diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, naphthalene-1,5-diisocyanate, polymethylene polyphenyl polyisocyanate, hydrogenated toluene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylxylene diisocyanate, isophorone diisocyanate, and JQ glue.

6. The method for preparing the melt-spinning polypropylene-polyvinyl alcohol composite material according to claim 1, characterized in that: The temperatures of the melt extrusion spinning sections are: 200-220°C in screw zone 1, 210-240°C in screw zone 2, 220-240°C in screw zone 3, 220-250°C in screw zone 4, 240-320°C in screw zone 5, and 210-230°C in screw zone 6.

7. The method for preparing the melt-spinning polypropylene-polyvinyl alcohol composite material according to claim 1, characterized in that: One or more grafting agents and foam stabilizers are also added to the mixture.

8. The method for preparing the melt-spinning polypropylene-polyvinyl alcohol composite material according to claim 1, characterized in that: The foam stabilizer is lecithin, fatty amide, fatty acid acetic acid amide, N-alkyl iminodiacetic acid sodium salt, polyacrylic acid, and alkyl betaine sulfonic acid.

9. The method for preparing the melt-spinning polypropylene-polyvinyl alcohol composite material according to claim 1, characterized in that: The grafting agent is one or more of maleic anhydride, dibutyl maleate, glycidyl methacrylate, acrylic acid, β-hydroxyethyl methacrylate, and unsaturated silane.

10. The method for preparing the melt-spinning polypropylene-polyvinyl alcohol composite material according to claim 1, characterized in that: Polypropylene-polyvinyl alcohol composites are used in packaging or battery separators.

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