Preparation method of high-content aramid pulp master batch

Abstract

This invention discloses a method for preparing high-aramid-content pulp masterbatch. First, nylon resin is made into meltblown microfibers, which are then pulped into fiber pulp. Next, this fiber pulp is dissolved in water with aramid pulp and short aramid fibers to form a uniformly mixed pulp. This pulp is then processed through papermaking, drying, and hot pressing to form composite paper sheets. Finally, the paper sheets are cut into strips and continuously fed into a twin-screw granulator for granulation. This invention solves the problem of uneven mixing caused by the difference in morphological density between nylon resin and aramid pulp by fiberizing and pulping the nylon resin. By using a "papermaking" process to produce a homogeneous and dense paper strip, it solves the industry problem of continuously and stably feeding high-bulk materials into the screw, achieving continuous, stable, and uniform production of masterbatch with an aramid pulp content as high as 50-85%.

Description

Technical Field

[0001] This invention belongs to the field of polymer material modification and masterbatch preparation technology, and particularly relates to a method for preparing a high-content aramid pulp masterbatch. Background Technology

[0002] Aramid pulp is a special material with high specific surface area and a fluffy structure obtained by fibrillation of aramid fibers. Adding it to nylon resin can significantly improve the wear resistance, dimensional stability, heat resistance and mechanical strength of the composite material. It is widely used in friction sealing, electronics and electrical, high-performance engineering plastics and other fields.

[0003] However, significant technical bottlenecks exist in the preparation of masterbatches containing high-content aramid pulp (mass fraction typically >50%): 1) Aramid pulp has extremely low bulk density, is loose, and is easily scattered, making it difficult to mix evenly with nylon resin particles; 2) The density difference between aramid pulp and common nylon resin particles (such as nylon 6, nylon 66, MXD6, and high-temperature nylon) is huge. During physical blending and subsequent feeding, severe stratification easily occurs due to gravity, vibration, etc., with resin particles sinking and aramid pulp floating, resulting in the mixture failing to achieve a stable and continuous "piston flow" in the hopper, frequently causing bridging and material interruption; 3) Due to uneven mixing and unstable feeding, when directly using a twin-screw extruder for melt granulation, the process fluctuates greatly, and the aramid pulp content in the product is extremely unevenly distributed, making it impossible to achieve high-quality, continuous, and stable production.

[0004] Therefore, there is an urgent need to develop a preparation method that can achieve efficient and uniform pre-dispersion of aramid pulp and nylon resin, and ensure subsequent stable and continuous feeding and granulation. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing high-content aramid pulp masterbatch. This method fundamentally solves the problems of uneven mixing and feeding caused by the differences in morphology and density between aramid pulp and nylon resin particles by changing the physical morphology of nylon resin, thus enabling continuous and stable production of high-content, highly uniform aramid pulp masterbatch.

[0006] To achieve the above objectives, this application adopts the following technical solution: This invention provides a method for preparing high-aramid content pulp masterbatch, comprising the following steps: S1, Nylon resin is prepared into meltblown microfiber by meltblowing method; S2, the meltblown microfiber is pulped and decomposed to prepare nylon fiber pulp; S3, the nylon fiber pulp, aramid pulp and aramid short fibers are dissolved and mixed in water to prepare a mixed pulp; S4, the mixed pulp is formed by papermaking, dried and hot-pressed at high temperature to make composite paper sheets; S5, cut the composite paper sheet into paper strips of a specific width; S6, the paper tape is fed into a twin-screw granulator, and after melt mixing, extrusion and pelletizing, the aramid pulp masterbatch is obtained.

[0007] In the above technical solution, in step S3, the dry weight mass fraction ratio of the aramid pulp, aramid short fiber and nylon fiber pulp is (50-85):(5-10):(10-45).

[0008] In the above technical solution, in step S1, the average diameter of the meltblown ultrafine fiber is 1-20 μm.

[0009] In the above technical solution, in step S1, the nylon resin includes one or more of nylon 6, nylon 66, MXD6, and high-temperature nylon.

[0010] In the above technical solutions, the high-temperature nylon includes one or more of PA46, PA6T, PA9T, and PA10T.

[0011] In the above technical solution, in step S3, the aramid pulp is para-aramid pulp or meta-aramid pulp.

[0012] In the above technical solution, in step S3, the length of the aramid short fiber is 1-10mm.

[0013] In the above technical solution, in step S4, the temperature of the high-temperature hot pressing is 10-50°C above the melting point of the nylon resin, the pressure is 1-10MPa, and the time is 10-300S.

[0014] In the above technical solution, in step S5, the cutting width of the paper tape is 5-100mm.

[0015] In the above technical solution, in step S6, the screw diameter of the twin-screw granulator is 20-95mm.

[0016] The beneficial effects of this invention are as follows: (1) Solve the problem of uneven mixing: Nylon resin is transformed into "fiber pulp" form, making it similar to the form of aramid pulp (fluffy, high specific surface area), and the density difference is greatly reduced. The two can achieve true micro-uniform dispersion by pulping and dispersing in the liquid phase (water), forming a homogeneous slurry, which completely solves the macro-segregation caused by density and particle size differences in dry mixing.

[0017] (2) Solving the problem of continuous feeding: Through papermaking and hot pressing processes, the uniformly dispersed mixture is made into a "composite paper sheet" with a dense structure, uniform density, and moderate strength, and then cut into regular paper strips. The paper strips have a constant width, thickness, and density, which can achieve stable, controllable, and continuous feeding to the twin screws like plastic strips, completely avoiding the "bridging" and "disruption" phenomena of loose materials in the hopper, and ensuring the continuity of production.

[0018] (3) Achieving high content and high uniformity: Since the pulp is uniformly dispersed at the micro-nano level in the resin melt and the subsequent process is not destructive, the aramid pulp content in the final masterbatch can stably reach more than 50%, and the distribution is extremely uniform, with excellent batch stability.

[0019] (4) Good process compatibility: This method is applicable to a variety of common nylon resins, and the width of the cut paper tape and the specifications of the twin screws used can be flexibly adjusted according to the output, making it easy to achieve industrial production. Attached Figure Description

[0020] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the accompanying drawings are merely schematic illustrations, used to help illustrate the technical solutions and preferred embodiments of the present invention, and do not constitute a limitation on the scope of protection of the technical solutions of the present invention. Within the scope defined by the claims of the present invention, any equivalent transformations or modifications based on the principles of the present invention should be considered to fall within the protection scope of the present invention.

[0021] Figure 1 This is a flowchart of the preparation process of aramid pulp masterbatch according to the present invention; Figure 2 This is a schematic diagram of paper tape feeding and aramid pulp and resin layered feeding, in which... Figure 2 A is a schematic diagram of paper tape feeding. Figure 2 B is a schematic diagram of the aramid pulp and resin being fed in layers. Detailed Implementation

[0022] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below in conjunction with specific embodiments. This invention can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concept to those skilled in the art. This invention will be defined only by the claims.

[0023] Unless otherwise specified, the test methods or experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are obtained from conventional commercial sources or prepared by conventional methods.

[0024] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0025] like Figure 1 The diagram shows a flow chart of the preparation method of high-content aramid pulp masterbatch of the present invention, which specifically includes the following steps: S1, Nylon resin is prepared into meltblown microfiber by meltblowing method; The nylon resin includes one or more of nylon 6, nylon 66, MXD6, and high-temperature nylons (PA46, PA6T, PA9T, PA10T, etc.). The average diameter of the meltblown microfiber is 1-20 μm.

[0026] S2, meltblown microfiber and a certain proportion of water are added to a pulping machine for disintegration and fiberization to prepare nylon fiber pulp suspension.

[0027] S3, add aramid pulp and aramid short fiber to the nylon fiber pulp suspension, and continue to fully dissolve and mix in the pulper to make the aramid pulp, aramid short fiber and nylon fiber pulp evenly dispersed to form a stable mixed pulp; The aramid pulp is either para-aramid (PPTA) pulp or meta-aramid (PMIA) pulp. The aramid short fibers are 1-10mm in length. Adding aramid short fibers increases the strength of the aramid paper during papermaking, thereby mitigating the risk of material breakage and improving process reliability. The dry weight ratio of aramid pulp, aramid short fibers, and nylon fiber pulp is (50-85):(5-10):(10-45). S4, the mixed pulp is conveyed to the paper forming machine, where it is formed and dewatered to create a wet sheet material.

[0028] S5, the wet sheet material is dried to remove moisture and obtain a dry paper sheet.

[0029] S6 involves hot-pressing the dry paper sheet at a temperature higher than the melting point of the nylon resin, causing the nylon fiber pulp to partially melt and act as an adhesive, thereby obtaining a composite paper sheet with a dense structure and a certain strength. The hot-pressing process involves setting the temperature 10-50°C above the melting point of the nylon resin, the pressure 1-10 MPa, and the time 10-300 seconds. The purpose of hot pressing is to act as a bond, increasing the strength of the paper sheet, maintaining stability during feeding, and ensuring a more uniform distribution of the nylon. Without hot pressing, the paper fibers are prone to breakage during feeding.

[0030] S7, cut the composite paper sheet into continuous or fixed-length paper strips; The cutting width of the paper tape is 5-100mm.

[0031] S8, the paper tape is fed into the co-rotating twin-screw granulator in a stable and continuous manner through a forced feeder or directly, and then melt-mixed, extruded, cooled and pelletized to obtain high-content aramid pulp masterbatch; The screw diameter of the twin-screw granulator is 20-95mm.

[0032] like Figure 2 The diagram illustrates paper tape feeding and stratified feeding of aramid pulp and resin. The advantages of paper tape feeding are: the paper tape has a constant width, thickness, and density, allowing for stable, controllable, and continuous feeding to the twin-screw extruder like plastic strips, completely avoiding bridging and material breakage in the hopper, thus ensuring production continuity. The disadvantages of stratified feeding are: aramid pulp is relatively light and fluffy, tending to remain on the upper layer during feeding, while resin chips remain on the lower layer, leading to uneven feeding and problems such as bridging and material breakage.

[0033] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto.

[0034] Example 1

[0035] The preparation method of aramid pulp masterbatch in this embodiment specifically includes the following steps: Step 1: Nylon 6 (PA6) resin is processed into ultrafine fibers with an average diameter of about 5 μm using a melt-blowing device.

[0036] Step 2: Take the above-mentioned nylon 6 meltblown fiber (dry weight 20kg) and water and add it to a pulping machine. Dissolve for 30 minutes to make PA6 fiber pulp suspension.

[0037] Step 3: Add para-aramid (PPTA) pulp (70 kg dry weight) and PPTA short fibers (10 kg dry weight) with a length of 3 mm to the pulper, and continue to loosen and stir for 60 minutes to form a uniformly mixed pulp.

[0038] Step 4: Pump the mixed pulp into the cylinder paper forming machine, form, press and dewater to obtain a wet paper web.

[0039] Step 5: Dry the wet paper web in a 120°C hot air drying oven until the moisture content is <1%.

[0040] Step 6: Place the dried paper sheet in a hot press and press it at 235℃ (above the melting point of PA6) and 5MPa for 60 seconds to obtain a dense composite paper sheet with a thickness of 0.8mm.

[0041] Step 7: Use a slitting machine to cut the composite paper sheet into continuous paper strips with a width of 40mm.

[0042] Step 8: The paper tape is stably fed into a co-rotating twin-screw extruder with a screw diameter of 35mm via a forced feeder. The barrel temperature is set to 250℃. After melt extrusion and pelletizing, nylon-based high-content aramid pulp masterbatch with a aramid pulp content of 70% is obtained. The entire process is smooth with no material interruption, and production is continuous and stable.

[0043] Example 2

[0044] The preparation method of aramid pulp masterbatch in this embodiment specifically includes the following steps: Step 1: Nylon 66 (PA66) is processed into ultrafine fibers with an average diameter of about 8 μm using a meltblown equipment.

[0045] Step 2: Take the above PA66 meltblown fiber (dry weight 30kg) and make fiber pulp suspension.

[0046] Step 3: Add meta-aramid (PMIA) pulp (60 kg dry weight) and PMIA short fibers (10 kg dry weight) with a length of 6 mm, and loosen them into a mixed pulp.

[0047] Step 4, the subsequent papermaking and drying steps are the same as in Example 1.

[0048] Step 5: Hot press at 265℃ and 8MPa for 90 seconds to obtain composite paper.

[0049] Step 6: Cut the paper into strips with a width of 50mm.

[0050] Step 7: Feed the material into a twin-screw granulator with a screw diameter of 65mm and a barrel temperature of 280℃ to obtain PA66-based masterbatch with an aramid pulp content of 60%. The feeding process is stable and continuous.

[0051] Example 3

[0052] The preparation method of aramid pulp masterbatch in this embodiment specifically includes the following steps: Step 1: Take the above-mentioned nylon MXD6 meltblown fiber (dry weight 15kg) and water and add them to a pulping machine to break it down into an MXD6 fiber pulp suspension.

[0053] Step 2: Add para-aramid (PPTA) pulp (75 kg dry weight) and PPTA short fibers (10 kg dry weight) with a length of 2 mm to the pulper, and loosen and mix for 60 minutes to form a uniform mixed pulp.

[0054] Step 3: Form the mixed pulp into a wet paper web and dry it at 150°C.

[0055] Step 4: Place the dried paper sheet in a hot press and press it at 270℃ and 8MPa pressure for 120 seconds to obtain a composite paper sheet with a thickness of 0.7mm.

[0056] Step 5: Cut the composite paper sheet into continuous paper strips with a width of 100mm.

[0057] Step 6: The paper strip is fed into a twin-screw extruder with a screw diameter of 85mm. The barrel temperature is set to 280℃. After melt granulation, MXD6-based high-temperature resistant and high-wear-resistant masterbatch with an aramid pulp content of 75% is obtained. The feeding is stable throughout the production process.

[0058] Example 4

[0059] The preparation method of aramid pulp masterbatch in this embodiment specifically includes the following steps: Step 1: High-temperature nylon (PA10T) is processed into fine fibers with an average diameter of about 15μm using a melt-blowing device.

[0060] Step 2: Take the above PA10T meltblown fiber (dry weight 45kg) and make fiber pulp suspension.

[0061] Step 3: Add meta-aramid (PMIA) pulp (50 kg dry weight) and PMIA short fibers (5 kg dry weight) with a length of 8 mm, and loosen them into a mixed pulp.

[0062] Step 4, the subsequent papermaking and drying steps are the same as before.

[0063] Step 5: Hot press at 320℃ and 3MPa for 40 seconds to obtain composite paper.

[0064] Step 6: Cut the paper into strips with a width of 60mm.

[0065] Step 7: Feed the material into a twin-screw granulator with a screw diameter of 75mm and a barrel temperature of 315℃ to obtain PA10T-based lightweight, high-strength masterbatch with an aramid pulp content of 50%. Suitable for lightweight automotive parts.

[0066] Example 5

[0067] The preparation method of aramid pulp masterbatch in this embodiment specifically includes the following steps: Step 1: Meltblown nylon PA6 and PA6T separately at a dry weight ratio of 1:1 (12.5kg each), and then mix the two meltblown microfibers.

[0068] Step 2: Mix the meltblown fibers to make a fiber pulp suspension.

[0069] Step 3: Add para-aramid (PPTA) pulp (70 kg dry weight) and PPTA short fibers (5 kg dry weight) with a length of 7 mm, and loosen them into a mixed pulp.

[0070] Step 4, the subsequent papermaking and drying steps are the same as before.

[0071] Step 5: Use zoned hot pressing. First, hot press at 200-310℃, pressure 5MPa, time 100 seconds, control the material to stay in the high temperature range for a short time, and obtain composite paper sheets.

[0072] Step 6: Cut the paper into strips 30mm wide.

[0073] Step 7: Feed the material into a twin-screw granulator with a screw diameter of 45mm. Set the barrel temperature to 310℃. Allow the material to remain in the high-temperature zone for a short time. Granulate the material to obtain PA6 / PA6T alloy-based masterbatch with an aramid pulp content of 70%, which combines toughness and low cost.

[0074] Comparative Example 1 The same mass of nylon 6 (PA6) resin as in Example 1 was mixed with para-aramid (PPTA) pulp using the following method: Figure 2 When extruding using the traditional mixing method shown in B, the direct blending of aramid pulp and nylon resin can lead to severe fiber entanglement and agglomeration, causing blockage at the feed inlet, unstable feeding and uneven dispersion, which prevents the extrusion blending process from proceeding normally.

[0075] Comparative Example 2 The preparation method of this comparative example is largely the same as that of Example 1, except that in step 2, 5 kg of the above-mentioned nylon 6 meltblown fiber (dry weight) is used. In step 3, "70 kg of para-aramid (PPTA) pulp (dry weight) + 10 kg of PPTA short fiber (dry weight)" is replaced with "90 kg of para-aramid (PPTA) pulp + 5 kg of PPTA short fiber (dry weight)". Due to the insufficient content of nylon 6 (PA6) resin, the final masterbatch is loose and cannot be successfully molded.

[0076] Comparative Example 3 The preparation method of this comparative example is largely the same as that of Example 1, except that the hot pressing temperature in step 6 is 150°C (lower than the melting point of PA6), which prevents the resin in the paper from bonding effectively, resulting in insufficient paper tape strength after hot pressing and frequent material breakage and jamming during feeding.

[0077] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing high-aramid content pulp masterbatch, characterized in that: Includes the following steps: S1, Nylon resin is prepared into meltblown microfiber by meltblowing method; S2, the meltblown microfiber is pulped and decomposed to prepare nylon fiber pulp; S3, the nylon fiber pulp, aramid pulp and aramid short fibers are dissolved and mixed in water to prepare a mixed pulp; S4, the mixed pulp is formed by papermaking, dried and hot-pressed at high temperature to make composite paper sheets; S5, cut the composite paper sheet into paper strips of a specific width; S6, the paper tape is fed into a twin-screw granulator, and after melt mixing, extrusion and pelletizing, the aramid pulp masterbatch is obtained.

2. The method for preparing aramid pulp masterbatch according to claim 1, characterized in that: In step S3, the dry weight mass fraction ratio of the aramid pulp, aramid staple fiber and nylon fiber pulp is (50-85):(5-10):(10-45).

3. The method for preparing aramid pulp masterbatch according to claim 1, characterized in that: In step S1, the average diameter of the meltblown microfiber is 1-20 μm.

4. The method for preparing aramid pulp masterbatch according to claim 1, characterized in that: In step S1, the nylon resin includes one or more of nylon 6, nylon 66, MXD6, and high-temperature nylon.

5. The method for preparing aramid pulp masterbatch according to claim 4, characterized in that: The high-temperature nylon includes one or more of PA46, PA6T, PA9T, and PA10T.

6. The method for preparing aramid pulp masterbatch according to claim 1, characterized in that: In step S3, the aramid pulp is para-aramid pulp or meta-aramid pulp.

7. The method for preparing aramid pulp masterbatch according to claim 1, characterized in that: In step S3, the length of the aramid short fiber is 1-10 mm.

8. The method for preparing aramid pulp masterbatch according to claim 1, characterized in that: In step S4, the temperature of the high-temperature hot pressing is 10-50°C above the melting point of the nylon resin, the pressure is 1-10 MPa, and the time is 10-300 seconds.

9. The method for preparing aramid pulp masterbatch according to claim 1, characterized in that: In step S5, the cutting width of the paper tape is 5-100mm.

10. The method for preparing aramid pulp masterbatch according to claim 1, characterized in that: In step S6, the screw diameter of the twin-screw granulator is 20-95mm.

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