Nylon 6 composite material, chinlon staple fiber and preparation method and application of nylon 6 composite material and chinlon staple fiber

Abstract

The invention discloses a nylon 6 composite material, a chinlon short yarn and a preparation method and application thereof, and belongs to the technical field of high polymer materials, the relative viscosity of the nylon 6 composite material is 2.6-3, the number-average molecular weight is 13000-17000, the molecular weight distribution is 1.6-2, the crystallinity is 20-27%, and the equilibrium moisture absorption rate is 8-10%. By controlling the relative viscosity, the number-average molecular weight, the molecular weight distribution, the crystallinity and the equilibrium moisture absorption rate of the nylon 6 composite material, the subsequent spinning performance can be effectively guaranteed, the number of floating filaments is small in the spinning process, the monofilament strength, the elongation at break and the specific resistance of the chinlon short filaments are effectively improved, and the production cost is reduced. And the double-length fiber content of the chinlon short yarn is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and specifically relates to a nylon 6 composite material, nylon staple fiber, and a preparation method and application thereof. Background Art

[0002] Polyamide, also known as nylon, is one of the four major engineering materials. Due to its excellent mechanical properties, it is widely used in industries such as automobiles, electrical appliances, communications, electronics, and machinery. With the introduction of the national carbon cycle policy, it is necessary to recycle and reuse the nylon materials already produced in the market.

[0003] Fishing nets are generally made of PA6 resin with good fluidity. CN 114836027 A discloses a method for recycling high-viscosity recycled nylon from waste fishing net filaments and its preparation method. By adding a slow-release chain extender composed of a general chain extender and a high-melting-point crystalline polymer to the recycled high-viscosity nylon from fishing net filaments, the general chain extender and the high-melting-point polymer are evenly dispersed together, and the general chain extender is wrapped inside the slow-release chain extender, so that the general chain extender does not directly contact with moisture, playing a better chain extension role, improving the use efficiency of the chain extender and the comprehensive performance of recycled PA6, making the recycled nylon material have higher viscosity and mechanical properties, and reducing the production cost. However, PA6 is prone to aging during the granulation process, and it cannot meet the use conditions for special requirements such as spinning.

[0004] Currently, the main method for recycling fishing nets is preliminary cleaning and simple granulation. During the granulation process, PA6 is prone to aging, the molecular weight decreases and its distribution becomes wider, and it can only be used in ordinary injection molded products and cannot meet the use conditions for special requirements such as spinning. In addition, the existing recycled nylon filaments on the market are mainly prepared from industrial waste filaments, and the recycling of post-consumer fabrics cannot meet the spinning requirements. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a nylon 6 composite material, nylon staple fiber, and a preparation method and application thereof. The nylon staple fiber prepared from the nylon 6 composite material has excellent single filament strength, elongation at break, and specific resistance.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A nylon 6 composite material, the relative viscosity of the nylon 6 composite material is 2.6 - 3, the number average molecular weight is 13000 - 17000, the molecular weight distribution is 1.6 - 2, the crystallinity is 20 - 27%, and the equilibrium moisture regain is 8 - 10%.

[0008] The present invention controls the relative viscosity of the nylon 6 composite material to be 2.6 to 2.8, the number-average molecular weight to be 13,000 to 17,000, the molecular weight distribution to be 1.6 to 2, the crystallinity to be 20 to 27%, and the equilibrium moisture regain to be 8 to 10%. The nylon 6 composite material with these parameters can effectively ensure the subsequent spinning performance, with fewer floating filaments during the spinning process, effectively improving the single-filament strength, elongation at break, and specific resistance of the nylon staple fiber, and reducing the content of long-fiber doubling in the nylon staple fiber.

[0009] Preferably, the relative viscosity of the nylon 6 composite material is 2.6 to 2.9, the number-average molecular weight is 13,000 to 16,500, the molecular weight distribution is 1.6 to 1.9, the crystallinity is 23 to 27%, and the equilibrium moisture regain is 8 to 9%. Especially when each parameter is within this range, the single-filament strength, elongation at break, and specific resistance of the nylon staple fiber are further improved, and the content of long-fiber doubling in the nylon staple fiber is further reduced.

[0010] Preferably, the nylon 6 composite material includes nylon 6 and a chain extender, and the mass ratio of nylon 6 to the chain extender is 100:(0.1 to 0.5).

[0011] Preferably, the mass ratio of nylon 6 to the chain extender is 100:(0.1 to 0.3).

[0012] Preferably, the nylon 6 is recycled nylon 6 obtained by granulating and recycling waste fishing net filaments.

[0013] Among them, fishing nets are generally made of PA6 resin with good fluidity for drawing, and the recycled raw materials are relatively easy to obtain. Therefore, waste fishing net filaments are selected as the recycled material, and using waste fishing nets can turn waste into treasure.

[0014] It should be noted that the source of the recycled nylon 6 is not limited to waste fishing net filaments, as long as the melt index, crystallinity, equilibrium moisture regain, and molecular weight distribution are within the ranges defined in the present invention. For example, it can also be sourced from waste tire cord fabric, waste airbag fabric, waste nylon fabric, and waste nylon packaging materials.

[0015] Exemplarily, the preparation method of the recycled nylon 6 includes the following steps:

[0016] Crush the waste fishing net, wash it with a detergent by grinding, and perform centrifugal separation to obtain recycled nylon 6.

[0017] Among them, the time for grinding and washing is 10 to 30 minutes, the temperature for grinding and washing is 30 to 80 °C, and during grinding and washing, the concentration of the detergent in the grinding and washing solution is 0.5 to 2%.

[0018] Among them, the rotation speed for centrifugal separation is 100 to 300 rpm, the centrifugation time is 20 to 30 minutes, and the number of centrifugation times is 1 to 2 times.

[0019] The melt index of the recycled nylon 6 under the conditions of 250 °C and 2.16 kg is 50-60 g / 10 min, the crystallinity is 22-30%, the equilibrium moisture regain is 4-12%, and the molecular weight distribution ≤ 2.5.

[0020] Preferably, the molecular weight distribution of the recycled nylon 6 is 2-2.5.

[0021] Preferably, the chain extender is an isocyanate chain extender.

[0022] The isocyanate chain extender includes at least one of toluene diisocyanate, methylene diphenyl diisocyanate, bisphenol A diisocyanate, diphenylmethane diisocyanate, and hexamethylene diisocyanate. Using an isocyanate chain extender can make the viscosity, number average molecular weight, and molecular weight distribution of the recycled nylon 6 composite material meet the requirements. At the same time, the isocyanate reacts with the terminal amino group and terminal carboxyl group of nylon respectively to carry out a chain extension reaction. While using other chain extenders, the chain extension effect is poor and cannot meet the requirements.

[0023] The present invention also provides a preparation method of a nylon 6 composite material, including the following steps:

[0024] Adding nylon 6 and a chain extender into a twin-screw extruder, melt-blending under nitrogen protection, vacuum drying, and filtering through a melt filter to obtain a nylon 6 composite material.

[0025] During the preparation process, nitrogen protection is adopted. The addition of nitrogen can reduce the aging of nylon in the extruder.

[0026] Among them, the feeding amount of nitrogen is 100-300 mmL / min.

[0027] After the preparation process, filtering through a melt filter can improve the appearance performance of nylon, reduce the black spots on the surface of nylon. After filtering through a melt filter, there are no black spots above 0.2 mm, and in a 100 g sample, the number of black spots of 0.1 mm is less than 10.

[0028] It should be noted that there are many methods to obtain the nylon 6 composite material of the present invention with a relative viscosity of 2.6-3, a number average molecular weight of 13,000-17,000, a molecular weight distribution of 1.6-2, a crystallinity of 20-27%, and an equilibrium moisture regain of 8-10%. For example, raw materials with appropriate polymerization degree, molecular weight distribution, crystallinity, and equilibrium water absorption can be selected for chain extension treatment, or post-treatment (such as heat treatment, water washing, stretching, etc.) can be selected, or the nylon 6 raw material can be decomposed into monomers and then the monomers can be synthesized.

[0029] The present invention also provides an application of the nylon 6 composite material in the preparation of nylon staple fibers.

[0030] The present invention also provides a method for preparing nylon staple fiber, comprising the following steps:

[0031] Placing the nylon 6 composite material in a spinning machine for spinning to obtain nylon staple fiber;

[0032] The nylon 6 composite material is the nylon 6 composite material as described above.

[0033] Preferably, the spinning speed is 900 - 1500 m / min, and the draw ratio is 1:(1 - 3).

[0034] The beneficial effects of the present invention are as follows: (1) By controlling the relative viscosity of the nylon 6 composite material to be 2.6 - 3, the number-average molecular weight to be 13000 - 17000, the molecular weight distribution to be 1.6 - 2, the crystallinity to be 20 - 27%, and the equilibrium moisture regain to be 8 - 10%, the nylon 6 composite material with these parameters can effectively ensure the subsequent spinning performance, with fewer floating filaments during the spinning process, effectively improving the single-filament strength, elongation at break, and specific resistance of the nylon staple fiber, and reducing the content of long fiber doubling in the nylon staple fiber. Specific embodiments

[0035] In order to better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific examples and comparative examples. The purpose is to understand the content of the present invention in detail, rather than to limit the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention. The experimental reagents and instruments involved in the implementation of the present invention are all common ordinary reagents and instruments unless otherwise specified.

[0036] The raw materials used in the examples and comparative examples are described as follows:

[0037] Recycled nylon 6-1: The waste fishing net is broken, ground and washed with a 1% detergent solution at 80°C for 30 min, centrifuged twice at 200 rpm for 20 min each time to obtain recycled nylon 6-1; the recycled nylon 6-1 has a melt index of 56 g / 10 min at 250°C and 2.16 kg according to the ISO1133-2011 method, a crystallinity of 29%, an equilibrium moisture regain of 6%, and a molecular weight distribution of 2.3.

[0038] Recycled Nylon 6-2: Waste nylon fabric (windbreaker) is crushed, washed with a 1% detergent solution at 80 °C for 30 min, centrifuged twice at 200 rpm for 20 min each time, and recycled nylon 6-2 is obtained; the recycled nylon 6-2 has a melt index of 53 g / 10 min, a crystallinity of 25%, an equilibrium moisture absorption rate of 5%, and a molecular weight distribution of 2.3 according to the ISO1133-2011 method at 250 °C and 2.16 kg.

[0039] Recycled Nylon 6-3: Waste nylon packaging materials are crushed, washed with a 1% detergent solution at 80 °C for 30 min, centrifuged twice at 200 rpm for 20 min each time, and recycled nylon 6-3 is obtained; the recycled nylon 6-3 has a melt index of 20 g / 10 min, a crystallinity of 34%, an equilibrium moisture absorption rate of 5%, and a molecular weight distribution of 2.2 according to the ISO1133-2011 method at 250 °C and 2.16 kg.

[0040] Chain extender - 1: Toluene diisocyanate, commercially available.

[0041] Chain extender - 2: Methylene diphenyl diisocyanate, commercially available.

[0042] Chain extender - 3: Bisphenol A diisocyanate, commercially available.

[0043] Chain extender - 4: Dioxazoline, commercially available.

[0044] Chain extender - 5: Triphenyl phosphite, commercially available.

[0045] Examples 1 - 9, Comparative Examples 1 - 10

[0046] The preparation methods of the nylon 6 composites of Examples 1 - 9 and Comparative Examples 1 - 10 are as follows:

[0047] Recycled nylon 6 and chain extender are added to a twin - screw extruder, melt - blended under nitrogen protection, and vacuum - dried to obtain recycled nylon 6 composites.

[0048] Among them, the nitrogen flow rate, the type and dosage of the chain extender in Examples 1 - 9 and Comparative Examples 1 - 10 are shown in Table 1, and the chain extender content refers to the proportion of the chain extender in recycled nylon 6.

[0049] Among them, the recycled nylon 6 in Examples 1 - 8 and Comparative Examples 1 - 9 is recycled nylon 6-1.

[0050] Among them, the recycled nylon 6 in Example 9 is recycled nylon 6-2.

[0051] Among them, the recycled nylon 6 in Comparative Example 10 is recycled nylon 6-3. Among them, the relative viscosity of the examples and comparative examples was tested in accordance with GB / T 38138-2019.

[0052] The test method for number average molecular weight and distribution is as follows: The molecular weight is tested by GPC. First, the material is dissolved, and then the molecular weight and molecular weight distribution are tested through the elution volume.

[0053] The test method for crystallinity is as follows: Crystallinity is determined by DSC (Differential Scanning Calorimeter). Specifically: In a nitrogen gas stream with a flow rate of 40 ml / min, at a heating rate of 10 °C / min, the heat of fusion of crystallization is obtained based on the area of the endothermic peak in the temperature range of 120-230 °C, and the heat of fusion of the sample is obtained. The crystallinity (Xc) is calculated by the following formula: Xc = ΔH1 / ΔH2 × 100%, where ΔH1 is the heat of fusion of the sample, and ΔH2 is the heat of fusion of polyamide 6. The heat of fusion of polyamide 6 is calculated as 45 cal / g.

[0054] The test method for equilibrium moisture regain is as follows: In an environment of 23 °C and 50% humidity, the material absorbs moisture from the environment until it reaches an equilibrium state. The weights before and after moisture absorption are m1 and m2 respectively. The equilibrium moisture regain (w) is calculated by the following formula: w = [(m2 - m1) / m1] × 100%.

[0055] Table 1

[0056]

[0057]

[0058] Example 10

[0059] A method for preparing polyamide staple fiber includes the following steps:

[0060] Place the recycled nylon 6 composite material in a spinning machine and spin it at a speed of 900 m / min with a draw ratio of 1:3 to obtain polyamide staple fiber.

[0061] Performance test

[0062] Prepare the polyamide staple fibers of Examples 1-9 and Comparative Examples 1-10 according to the method of Example 10 and conduct performance tests.

[0063] The single filament strength was tested in accordance with the provisions of GB / T14344-2008.

[0064] The elongation at break was tested in accordance with the provisions of GB / T14344-2008.

[0065] The content of double-length fibers was tested in accordance with the provisions of GB / T14336-2008.

[0066] The specific resistance is tested in accordance with GB / T 14342-2015.

[0067] Abnormal situations are observed by observing whether there are drawing breaks during the spinning process. Among them, the determination of the breakage situation in spinning abnormalities is based on the number of floating filaments during the spinning process. When the floating filament situation = 0, there is no abnormal situation; when the number of floating filaments = 1, there is a small amount of breakage; when the number of floating filaments is 2-3, there is partial breakage; when the number of floating filaments is 4-9, there is serious breakage; when the number of floating filaments ≥ 10, spinning cannot be carried out.

[0068] Table 2

[0069]

[0070]

[0071] As can be seen from Table 2, the nylon staple fibers spun from the recycled nylon 6 composite material described in the present invention have high mechanical properties, low content of long-fiber doubles, high specific resistance, and few floating filaments during the spinning process.

[0072] Among them, by using an isocyanate chain extender and controlling the relative viscosity of the recycled nylon 6 composite material to be 2.6-3, the number-average molecular weight to be 13000-17000, the molecular weight distribution to be 1.6-2, the crystallinity to be 20-27%, and the equilibrium moisture regain to be 8-10%, nylon staple fibers with a single-filament strength ≥ 3.6 cN / dtex, an elongation at break ≥ 39%, a specific resistance ≥ 1.6×10 10 Ω*cm, and a content of long-fiber doubles ≤ 10 mg / 100 g can be prepared.

[0073] Comparing Example 1 with Comparative Examples 1-10, it can be seen that some parameters of the relative viscosity, number-average molecular weight, molecular weight distribution, crystallinity, and equilibrium moisture regain in the comparative examples exceed the scope of this application, either resulting in inability to spin or significantly worse performance than the examples.

[0074] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and not to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A nylon 6 composite material, characterized in that, The relative viscosity of the nylon 6 composite material is 2.6 to 3, the number-average molecular weight is 13,000 to 17,000, the molecular weight distribution is 1.6 to 2, the crystallinity is 20 to 27%, and the equilibrium moisture regain is 8 to 10%.

2. The nylon 6 composite material according to claim 1, wherein The relative viscosity of the nylon 6 composite material is 2.6 to 2.9, the number-average molecular weight is 13,000 to 16,500, the molecular weight distribution is 1.6 to 1.9, the crystallinity is 23 to 27%, and the equilibrium moisture regain is 8 to 9%.

3. The nylon 6 composite material according to claim 1, wherein The nylon 6 composite material comprises nylon 6 and a chain extender, and the mass ratio of the recycled nylon 6 to the chain extender is 100:(0.1 to 0.5).

4. The nylon 6 composite material according to claim 3, characterized in that, The mass ratio of the nylon 6 to the chain extender is 100:(0.1 to 0.3).

5. The nylon 6 composite material according to claim 3, characterized in that, The melt index of the nylon 6 under the conditions of 250 °C and 2.16 kg is 50 to 60 g / 10 min, the crystallinity is 22 to 30%, the equilibrium moisture regain is 4 to 12%, and the molecular weight distribution ≤ 2.

5.

6. The nylon 6 composite material according to claim 3, wherein The chain extender is an isocyanate-based chain extender.

7. The preparation method of the nylon 6 composite material according to any one of claims 1 to 6, characterized in that, It includes the following steps: Add nylon 6 and the chain extender into a twin-screw extruder, melt and blend under nitrogen protection, vacuum dry, and filter through a melt filter to obtain the nylon 6 composite material.

8. Use of the nylon 6 composite material according to any one of claims 1 to 7 in the preparation of nylon staple fibers.

9. A method for preparing nylon staple fiber, characterized in that, It includes the following steps: Place the nylon 6 composite material in a spinning machine for spinning to obtain nylon staple fibers; The nylon 6 composite material is the nylon 6 composite material according to any one of claims 1 to 7.

10. The preparation method of the polyamide staple fiber according to claim 9, characterized in that, The spinning speed is 900 to 1500 m / min, and the draw ratio is 1:(1 to 3).

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