High color fastness colored spun fabric and its preparation process

Abstract

The application discloses high-color-fastness colored spun fabric and a preparation process thereof. The colored spun fabric comprises a first PP colored melt-blown fiber layer, a white wood pulp fiber layer and a second PP colored melt-blown fiber layer which are sequentially compounded, and the three layers are compounded through fiber-level online interweaving. The PP colored melt-blown fiber layer is prepared through a melt-blown process by using PP raw material containing 3-5% color master batch, the color master batch takes PP as a carrier, the pigment has a median particle size D 50 ≤1μm, and the color master batch has a melt index difference of ≤300 g / 10min from the PP. Through the selection of the color master batch and the cooperative control of a melt-blown receiving distance of 150-300mm, the application solves the technical problems of color master batch pigment pollution of wood pulp, unstable fiber forming and insufficient color fastness. The prepared colored spun fabric has a whiteness of the wood pulp layer of ≥80%, a water color fastness of ≥4 levels, and an MD dry tensile force of ≥12.0 N / 50mm, and can be applied to products such as wiping towels, wet towel substrates, nursing towels, cleaning pads and medical dressing substrates.

Description

Technical Field

[0001] This invention relates to the field of nonwoven functional materials technology, specifically to a high color fastness colored spun fleece fabric and its preparation process, which is prepared by online composite of a polypropylene (PP) meltblown microfiber layer containing color masterbatch and a wood pulp fiber layer. Background Technology

[0002] Multiform paper, also known as PP meltblown wood pulp composite nonwoven fabric, is a nonwoven material made from PP meltblown microfiber and wood pulp fiber through an air-flow web-forming online composite process. Its typical structure is a three-layer sandwich structure of "PP meltblown layer / wood pulp layer / PP meltblown layer". The PP meltblown microfiber layer gives the product good strength, softness, and surface smoothness, while the wood pulp fiber layer gives it excellent liquid absorption, bulkiness, and wiping properties. Multiform paper combines the dual characteristics of nonwoven fabric and paper, and is widely used in wiping wipes, sanitary wipes substrate, medical dressings, baby care wipes, pet cleaning pads, and industrial precision wiping cloths.

[0003] As the market demands for differentiation and higher quality in velour fabrics, a simple white or off-white appearance is no longer sufficient to meet consumers' requirements for personalization and brand recognition. To achieve the colorization of velour fabrics, the following technical approaches have been attempted, but all have varying degrees of technical shortcomings: The first approach is post-process dyeing and coloring. That is, coloring is achieved on the finished white velvet fabric by pad dyeing, roller printing or inkjet printing. This approach has the following problems: (1) Dye molecules mainly adhere to the fiber surface, resulting in poor color fastness. When wetted or rubbed, they are prone to discoloration and pigment migration, contaminating the wiping surface or the user's skin; (2) Water wetting during the dyeing process damages the loose structure of the wood pulp fiber layer, making the product feel hard and reducing its liquid absorption performance; (3) The amount of dyeing wastewater discharged is large, and the treatment cost is high, which is contrary to the current development concept of green manufacturing; (4) In the three-layer sandwich structure, it is difficult for the dye to penetrate evenly into the middle wood pulp layer, resulting in uneven color distribution and a mottled appearance.

[0004] The second approach is to use pre-dyed colored wood pulp. That is, to directly use dyed colored wood pulp to replace white wood pulp as the intermediate layer. This approach has the following problems: (1) The dyes in colored wood pulp are prone to migration during use (especially when in contact with liquids), contaminating the wiping surface or skin, posing a safety hazard, and are particularly unsuitable for hygiene care, medical, and infant products; (2) The market price of colored wood pulp is significantly higher than that of ordinary white wood pulp, resulting in poor product economics; (3) The dyeing stability of wood pulp fibers is poor, and the product is prone to fading after long-term storage or exposure to light.

[0005] The third approach involves adding color masterbatch to the PP meltblown layer raw material. This involves mixing a certain proportion of color masterbatch into PP resin granules, and then directly producing a colored PP meltblown fiber layer through a meltblown process. Theoretically, this approach offers advantages such as high color fastness, no dyeing wastewater, and a simple production process. However, when applied to the online composite fabric production process of "PP meltblown + wood pulp," the following technical challenges remain to be fully addressed: (1) The problem of pigment contamination of wood pulp layer by masterbatch: The production of spun fabric adopts an online one-step process, that is, after the colored PP meltblown fiber is sprayed out from the die head, it is directly interwoven with the wood pulp fiber flow on the receiving device to form a web, and there is no isolation between the three. If the masterbatch is not properly selected or the meltblown process parameters are not well controlled, the pigment particles in the masterbatch may be partially detached under the impact of the high temperature (≥270℃) and high speed hot air (≥280℃) of meltblown airflow, migrate with the airflow and adhere to the surface of white wood pulp fiber, causing the wood pulp layer to become dirty and seriously damaging the visual quality of "colored surface layer + white absorbent core" of spun fabric, affecting the market acceptance of the product; (2) Color masterbatch affects the forming stability of meltblown fiber: The addition of pigment particles in color masterbatch will change the rheological properties of PP melt (including melt viscosity, shear sensitivity, yield stress, etc.), affecting the stability of the meltblown die head output and the uniformity of fiber fineness; when the pigment particle size is too large or the compatibility with PP is poor, the pigment particles may also block the micropores of the meltblown die head with a diameter of only 0.2 to 0.4 mm, causing defects such as broken fibers, fused fibers, crystal points, and uneven fiber thickness, which in turn affect the strength, feel and appearance of the final product. (3) Uneven color at the fiber interlacing interface: PP fiber (hydrophobic nonpolar) and wood pulp fiber (strong polar cellulose rich in hydroxyl -OH) have significant differences in physicochemical properties. Pigment particles in the masterbatch may agglomerate or migrate in a directional manner at the interlacing interface of the two fibers due to the difference in polarity, resulting in mottled and uneven color transition at the interface, which affects the overall visual effect of the product from a microscopic perspective. (4) Color fastness problem: If the color masterbatch is not properly selected, the color fastness advantage of the original solution over the subsequent dyeing process cannot be fully utilized.

[0006] To address the aforementioned unresolved technical challenges, there is an urgent need in this field for a solution to prepare high-quality colored spun fabrics that can achieve excellent color fastness, white wood pulp layer, stable fiber formation, and uniform overall color through systematic formula design and synergistic process control.

[0007] A search revealed the following existing related technologies: CN109468752A discloses a multilayer spunbond composite kitchen wiping material and its preparation method. It adopts a three-layer structure of "upper surface meltblown material / middle layer spunbond material / lower surface meltblown material". The middle layer is PP spunbond material instead of wood pulp fiber, and the composite method is an offline two-step method of "separate manufacturing and then hot rolling". This is fundamentally different from the "online one-step meltblown-wood pulp composite" process route of the present invention. Moreover, the patent does not address the technical problems that the present invention aims to solve, such as the contamination of the middle layer by masterbatch pigments, fiber diameter uniformity, and synergistic control of color fastness.

[0008] CN112853615A discloses a disposable cotton soft towel, which is formed by mixing wood pulp fiber and PP meltblown cotton and relies on the self-viscosity of the two during the melting process to bind them together. However, this patent does not disclose a three-layer sandwich structure, does not involve a coloring technology solution, does not disclose specific meltblown process parameters (especially the receiving distance), and does not involve the selection and synergistic optimization of color masterbatch.

[0009] CN121466347A discloses a liquid-absorbing material for wet wipes and sanitary napkins, including a multi-layer composite structure such as a first hydrophilic solvent layer, a first PP meltblown material layer, an intermediate functional layer, and a second PP meltblown material layer, and contains additional layers such as a hydrophilic solvent layer. The structure is different from the pure fiber interwoven three-layer structure of the present invention, and it also does not involve technical contents such as coloring, masterbatch selection, and pigment migration control.

[0010] In summary, there is currently no synergistic optimization scheme for the selection of masterbatch, formulation ratio and meltblown process parameters for "online one-step preparation of colored PP meltblown-wood pulp three-layer composite spun fabric". This invention has carried out systematic research and innovation to address this technological gap. Summary of the Invention

[0011] To address the technical problems existing in the coloring process of PP meltblown-wood pulp composite spun fleece, such as masterbatch pigment contamination of wood pulp, unstable meltblown fiber formation, uneven color at the fiber interlacing interface, and insufficient color fastness of the dopant coloring, the present invention aims to provide a high color fastness colored spun fleece and its preparation process. Through the coordinated control of masterbatch selection, formulation ratio and meltblown process parameters (especially receiving distance), a high-quality colored spun fleece with excellent color fastness, white wood pulp layer, stable fiber formation, and improved mechanical strength is obtained.

[0012] The core technical concept of this invention is to achieve the organic unity of the following three technical mechanisms by synergistically controlling the physicochemical properties of the masterbatch (carrier matching, pigment content, pigment particle size, temperature resistance, rheological matching) and key parameters of the meltblown process (especially the receiving distance): Mechanism 1: Pigment anchoring mechanism based on "homogeneity compatibility" This invention specifies that the masterbatch uses PP as the carrier resin, and the difference between the melt index of the masterbatch and the melt index of the base PP is ≤300 g / 10min, enabling the masterbatch to achieve good molecular-level blending with the PP base during melt extrusion. The pigment particles are fully coated by the PP molecular chains and firmly anchored within the PP fibers during meltblown stretching, preventing the pigment from detaching and becoming free in the high-speed hot airflow, thus ensuring the color fastness of the product at the molecular level. Simultaneously, the median particle size D of the pigment is limited. 50 ≤1μm, ensuring that the pigment particle size is much smaller than the diameter of the meltblown fiber (1~5μm), so that it will not become a weak point on the fiber surface, nor will it protrude from the fiber surface and cause pigment to become free.

[0013] Mechanism 2: Fiber cooling and shaping mechanism based on "temperature gradient" This invention limits the receiving distance (DCD) in the meltblown process to 150–300 mm, ensuring that the colored PP meltblown fibers undergo sufficient cooling and shaping before contacting the wood pulp fibers. When the PP meltblown fibers exit the die, their temperature reaches over 270°C, placing them in a molten state where the pigment particles are not yet fully locked. After traveling a distance of over 150 mm, the fiber surface temperature rapidly drops below the PP softening point (approximately 140°C), solidifying the fiber surface to form a dense outer shell that "locks" the pigment particles inside the fiber. When the fiber reaches the wood pulp layer, there is no longer any risk of pigment migration, thus ensuring a wood pulp layer whiteness of ≥80%.

[0014] Research has found that: When DCD < 150mm, the colored PP fibers are still in a semi-molten state when they reach the wood pulp layer. The pigment particles on the fiber surface are easily migrated to the wood pulp fibers under the action of airflow and contact, and the whiteness of the wood pulp layer drops to below 70%. When DCD>300mm, the PP fiber is over-cooled and shaped, the fiber-level interweaving effect between the PP fiber and the wood pulp fiber is weakened, the interlayer bonding strength is insufficient, and the product is prone to interlayer delamination. Within a range of 150–300 mm, the surface of the PP fiber is fully cured, the pigment is locked inside the fiber, and the fiber still has moderate entanglement to ensure good interweaving with the wood pulp fiber, thus achieving the dual technical goals of "maintaining wood pulp whiteness" and "strong interlayer bonding".

[0015] Mechanism 3: Fiber forming stability and strength enhancement mechanism based on "rheological matching" The melt index of the color masterbatch carrier (PP) is matched with that of the base PP (difference ≤ 300 g / 10min) to ensure that the melt maintains stable rheological properties during extrusion and meltblowing, avoiding defects such as uneven fiber diameter, broken fibers, and crystal points caused by local viscosity abrupt changes, and making the fiber diameter variation coefficient CV ≤ 25%.

[0016] More significantly, the pigment particles in the masterbatch (especially inorganic pigments such as titanium dioxide, iron oxide, and phthalocyanine pigments) act as heterogeneous nucleating agents during the cooling and crystallization process of PP melt, improving the crystallinity and molecular chain orientation of PP. This results in the mechanical strength of colored PP meltblown fibers being higher than that of pure white PP meltblown fibers, ultimately leading to an unexpected and beneficial effect of increasing the MD dry tensile strength of colored spun fabric by more than 15%.

[0017] Pigment anchoring relationship defined in this invention To quantitatively describe the above synergistic effect and facilitate process control and quality evaluation, this invention defines the pigment anchoring parameter η:

[0018] In the formula: C: Mass percentage of color masterbatch in PP raw material, in % D 50 : Median particle size of pigments in masterbatch, in μm; DCD: Receiving distance for meltblown process, in mm; η: Pigment anchoring parameter (dimensionless).

[0019] Extensive experimental verification revealed that: When η≤1.5, the pigment can be effectively anchored inside the PP fiber, the whiteness of the wood pulp layer remains ≥80%, and the overall color fastness is excellent. When η>1.5, pigments migrate and contaminate the wood pulp, the whiteness of the wood pulp layer drops significantly to below 75%, and the overall color fastness also decreases accordingly.

[0020] This relationship relates to two key parameters of masterbatch (C, D) 50 The combination of the key parameters (DCD) of the meltblown process with the synergistic optimization technology concept of this invention is a quantitative expression of the concept, which facilitates parameter adjustment and quality control in actual production.

[0021] Based on the above technical concept, the technical solution of the present invention is as follows: A high color fastness colored velvet fabric It comprises a first PP colored meltblown fiber layer, a white wood pulp fiber layer and a second PP colored meltblown fiber layer, which are sequentially laminated together. The three layers are interwoven online at the fiber level without any adhesive. The PP colored meltblown fiber layer is made from PP raw material containing color masterbatch through a meltblown process, and the mass percentage of color masterbatch in the PP raw material is 3% to 5%. The weight of each layer of the PP colored meltblown fiber is 8-15 g / m², and the average diameter of the PP colored meltblown fiber is 1-5 μm; The mass ratio of the PP colored meltblown fiber layer to the white wood pulp fiber layer is 35-45:55-65; The colored velvet fabric satisfies the pigment anchoring relationship: ; The whiteness of the white wood pulp fiber layer in the colored velvet fabric is ≥80% according to GB / T 7974.

[0022] Furthermore, the masterbatch uses PP as the carrier resin, has a pigment content of 30%–50%, and the median particle size D of the pigment is… 50 The pigment has a thickness of ≤1μm and a heat resistance temperature of ≥280℃. The difference between the melt index of the masterbatch and the melt index of the PP resin particles under the test conditions of 230℃ and 2.16kg is ≤300 g / 10min.

[0023] Furthermore, the coefficient of variation (CV) of the diameter of the PP colored meltblown fiber is ≤25%.

[0024] Furthermore, the color of the masterbatch is selected from one of blue, green, purple, dark red, orange, and yellow; the first PP colored meltblown fiber layer and the second PP colored meltblown fiber layer are the same color or different colors.

[0025] Furthermore, the basis weight of the colored spun fleece is 60-80 g / m², the thickness under 0.5 kPa pressure is 0.90-1.30 mm, the moisture content is ≤10%, and the pH value is 4.0-9.0; the MD dry tensile strength of the colored spun fleece is ≥12.0 N / 50 mm, and the MD elongation is ≥35.0%.

[0026] Furthermore, the color fastness to water of the fabric is ≥4 according to GB / T 3920, the color fastness to rubbing (dry state) is ≥4, and the color fastness to rubbing (wet state) is ≥3-4.

[0027] The above-mentioned preparation process of high color fastness colored velvet fabric Includes the following steps: S1. Ingredient premix Weigh the raw materials according to the mass ratio of 3% to 5% masterbatch and 95% to 97% PP resin particles, put them into a high-speed mixer and mix at room temperature for 5 to 10 minutes to obtain colored PP mixed raw materials.

[0028] Preferably, the high-speed mixer rotates at 200–500 rpm; during mixing, 0.1–0.3 wt% of zinc stearate or ethylene bis-stearamide (EBS) is added as a dispersant to further improve the uniformity of the masterbatch dispersion in the PP matrix.

[0029] S2. Melt extrusion The mixed raw material obtained from S1 is fed into a screw extruder for melt plasticization. The temperatures of each section of the extruder are as follows: Zone 1 200℃~220℃, Zone 2 230℃~250℃, Zone 3 250℃~270℃, Zone 4 260℃~280℃, and the die head temperature 270~290℃.

[0030] S3. Meltblown fiber The melt is pumped to the meltblown die head and sprayed out. The die head temperature is 270℃~290℃, the hot air temperature is 280℃~310℃, the hot air pressure is 0.3~0.6 MPa, and the receiving distance DCD is 150~300 mm, so as to obtain colored PP microfibers with an average diameter of 1~5μm.

[0031] Furthermore, compared to the conventional meltblown process that uses the same PP resin particles but without color masterbatch, the die head temperature and hot air temperature are increased by 5 to 10°C to compensate for the impact of color masterbatch addition on the flowability of PP melt and ensure uniform fiber fineness.

[0032] S4. Wood pulp fiber opening Wood pulp board (preferably softwood pulp board) with a whiteness of ≥85% is crushed by a pulverizer, split by a fiber opener, and combed by airflow to form a uniform white wood pulp fiber flow.

[0033] S5. Three-layer online composite By configuring the dual meltblown heads and the intermediate wood pulp feeding system online, the first PP colored meltblown fiber stream, the white wood pulp fiber stream, and the second PP colored meltblown fiber stream are simultaneously deposited on the receiving device and interwoven into a web, forming a three-layer sandwich fiber web of "colored PP / white wood pulp / colored PP". The mass ratio of the PP colored meltblown fiber layer to the white wood pulp fiber layer is 35-45:55-65.

[0034] S6. Consolidation and shaping The three-layer composite fiber web obtained by S5 is solidified by hot air penetration (temperature 130℃~150℃, time 5~15 seconds), then dried and wound to obtain the high color fastness colored velvet fabric.

[0035] Compared with the prior art, the present invention has the following significant advantages: 1. Excellent colorfastness, safe and non-migrating. This invention employs a solution coloring method and utilizes a "homogeneous compatibility" pigment anchoring mechanism (PP carrier masterbatch + melt index matching + pigment particle size D). 50With a micrometer diameter of ≤1μm, the pigment molecules are firmly locked inside the PP fiber, resulting in a water fastness of ≥4 and a rubbing fastness (dry) of ≥4 and (wet) of ≥3-4, far superior to traditional post-dyeing products (usually only 2-3). There is no risk of pigment migration and contamination of the wiping surface or skin, making it particularly suitable for applications with high safety requirements such as hygiene care, medical dressings, infant care, and food contact.

[0036] 2. The wood pulp layer maintains high whiteness. By using the process parameters synergistically controlled by the pigment anchoring relationship η≤1.5 defined in this invention (especially the limitation of receiving distance of 150~300mm), the contamination of the wood pulp layer by the masterbatch pigment is effectively avoided. After lamination, the whiteness of the wood pulp layer is maintained at ≥80% according to GB / T7974. The overall product presents the visual effect of a colored surface layer and a white absorbent core layer.

[0037] 3. Stable and uniform fiber formation By rheological matching (melt index difference between masterbatch and PP ≤ 300 g / 10min) and pigment particle size control (D 50 (≤1μm), ensuring the uniformity of the fineness of the colored PP meltblown fibers, with a diameter variation coefficient CV≤25%, free from defects such as broken fibers, tangled fibers, and crystal points, resulting in a product with a soft feel and uniform surface.

[0038] 4. Mechanical strength is actually increased. Pigment particles (especially inorganic pigments) act as heterogeneous nucleating agents during the cooling and crystallization of PP melt, improving the crystallinity and molecular chain orientation of PP. This results in the MD dry tensile strength of the colored spun fleece fabric of this invention reaching ≥12.0 N / 50mm, an increase of more than 15% compared to a pure white control product of the same basis weight (approximately 10.5–11.5 N / 50mm). This strength enhancement gives the colored spun fleece fabric of this invention high tear resistance, making it suitable for high-intensity wet applications.

[0039] 5. The production process is simple and compatible with existing production lines. This invention adds a masterbatch premixing step to the existing spun fleece production process and systematically optimizes the meltblown process parameters. It does not require major modifications to the production equipment, can be implemented directly on existing production lines, is easy to promote industrially, has low production costs, and is particularly suitable for large-scale industrial production.

[0040] 6. Wide range of applications The high color fastness colored velvet fabric produced by this invention can be widely used in many fields such as kitchen wipes, sanitary wipes substrate, baby care wipes, pet cleaning pads, medical dressing substrate, industrial precision wiping cloths, and cosmetic cotton wipes, and has broad market prospects. Attached Figure Description

[0041] Figure 1 This is a flowchart illustrating the preparation process of the colored spun fleece fabric of the present invention. Detailed Implementation

[0042] The process flow for preparing the colored velvet fabric of this invention is as follows: Figure 1 As shown, the process includes six steps: ingredient premixing (S1), melt extrusion (S2), meltblown fiber formation (S3), wood pulp fiber opening (S4), three-layer online composite (S5), and consolidation molding (S6). The colored spun fleece fabric of the present invention has a three-layer sandwich structure of "PP colored meltblown fiber layer / white wood pulp fiber layer / PP colored meltblown fiber layer", which is formed by online interweaving and composite of the three layers at the fiber level. Its preparation process adopts an online configuration of dual meltblown heads and an intermediate wood pulp feeding system. The first meltblown head is located above the receiving device and sprays out the first PP colored meltblown fiber stream, and the second meltblown head is located below the receiving device and sprays out the second PP colored meltblown fiber stream. The wood pulp fiber opening and combing system is located on the side and conveys the white wood pulp fiber stream. The three fiber streams are deposited simultaneously on the receiving device and interwoven at the fiber level to form a three-layer composite fiber web.

[0043] To more clearly illustrate the technical solution, technical principle, and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments and comparative examples. The raw materials used in the following embodiments are all commercially available products, and the equipment used is conventional fabric spinning equipment in the art.

[0044] I. Raw Materials and Equipment PP resin granules: meltblown grade polypropylene, melt index (230℃, 2.16kg) is 1500 g / 10min, commercially available; Blue masterbatch: PP carrier, 40% blue phthalocyanine pigment content, median particle size D of pigment. 50 =0.8μm, heat resistance temperature 290℃, melt index 1600 g / 10min, commercially available; Wood pulp board: Softwood pulp board, whiteness 85%, commercially available; Meltblown production line: Dual meltblown head airflow forming production line, die head orifice diameter 0.3mm, die head width 1600mm; Testing equipment: Electronic balance, thickness gauge, tensile testing machine, whiteness meter, spectrophotometer, SEM electron microscope and other conventional testing equipment in this field.

[0045] Example 1: Preparation of blue colored velvet fabric S1. Premixing of ingredients: Weigh 97 kg of PP resin granules and 3 kg of blue masterbatch, add 0.2 kg of zinc stearate as a dispersant, put them into a high-speed mixer (300 rpm), mix at room temperature for 8 minutes to obtain blue colored PP mixed raw materials.

[0046] S2. Melt extrusion: The above mixed raw materials are fed into a screw extruder for melt plasticization. The temperatures of each section of the extruder are set sequentially as follows: Zone 1 210℃, Zone 2 240℃, Zone 3 260℃, Zone 4 270℃, and the die head temperature 280℃; the screw speed is 30 rpm.

[0047] S3. Meltblown fiber formation: The melt is pumped to the meltblown die head and sprayed out. The die head temperature is 280℃, the hot air temperature is 295℃, the hot air pressure is 0.4 MPa, and the receiving distance DCD=200 mm, to produce blue PP microfibers with an average diameter of 2.5μm.

[0048] S4. Pulp fiber opening: Softwood pulp board with a whiteness of 85% is crushed, opened, and air-flow combed to form a uniform white pulp fiber flow.

[0049] S5. Three-layer online composite: Through the configuration of dual meltblown heads and intermediate wood pulp feeding system, the first blue PP meltblown fiber stream (12 g / m²), the white wood pulp fiber stream (46 g / m²), and the second blue PP meltblown fiber stream (12 g / m²) are simultaneously deposited on the receiving device and interwoven into a web at the fiber level, forming a "blue PP / white wood pulp / blue PP" three-layer sandwich fiber web, with the mass ratio of the PP colored meltblown fiber layer to the white wood pulp fiber layer being 34:66.

[0050] S6. Consolidation and molding: The composite fiber web is consolidated by hot air penetration (temperature 140℃, time 10 seconds), then dried and wound to obtain the blue colored velvet fabric described in this embodiment.

[0051] Pigment anchoring parameter verification: C=3%, D 50 =0.8μm, DCD=200mm η = (3 × 0.8 × 100) / 200 = 1.2, which satisfies η ≤ 1.5.

[0052] Example 1: Product performance test results:

[0053] Performance analysis of Example 1: The whiteness of the wood pulp layer is 87.5%, which meets the requirement of ≥80%, indicating that the process of the present invention effectively avoids the contamination of wood pulp by masterbatch pigments. The dry tensile strength of MD is 14.2 N / 50mm, which meets the requirement of ≥12.0 N / 50mm. Compared with the pure white control sample of the same weight (11.5 N / 50mm, see Comparative Example E), it is about 23% higher, which reflects the heterogeneous nucleation enhancement effect of pigment particles. All color fastness grades reached level 4 or above, demonstrating the pigment anchoring effect achieved through the synergistic combination of solution coloring and homologous compatible masterbatch selection; The fiber diameter variation coefficient is 18%, which meets the requirement of ≤25%, demonstrating the fiber forming stability brought about by rheological matching.

[0054] Example 2: Preparation of Green Colored Fleece Fabric S1. Weigh 96 kg of PP resin granules and green masterbatch (PP carrier, green phthalocyanine pigment content 45%, D 50 =0.7μm, temperature resistance 295℃, melt index 1700 g / 10min) 4 kg, zinc stearate 0.2 kg, mixed at room temperature for 8 minutes in a high-speed mixer.

[0055] Process parameters for steps S2 to S6: Temperatures of each section of the extruder: Zone 1 215℃, Zone 2 245℃, Zone 3 265℃, Zone 4 275℃, Die head 285℃; The die head temperature is 285℃, the hot air temperature is 300℃, the hot air pressure is 0.45 MPa, and the DCD is 220 mm. Three-layer structure: green PP layer (12 g / m²) / wood pulp layer (46 g / m²) / green PP layer (12 g / m²), total weight 70 g / m².

[0056] Pigment anchoring parameter verification: η = (4 × 0.7 × 100) / 220 = 1.27 satisfies η≤1.5.

[0057] Example 2: Product performance test results:

[0058] Example 3: Preparation of deep red colored velvet fabric S1. Weigh 95 kg of PP resin granules and dark red masterbatch (PP carrier, iron oxide red pigment content 50%, D... 50 =0.9μm, temperature resistance 300℃, melt index 1750 g / 10min) 5 kg, zinc stearate 0.3 kg, mixed at room temperature for 10 minutes in a high-speed mixer.

[0059] Process parameters for steps S2 to S6: Temperatures of each section of the extruder: Zone 1 220℃, Zone 2 250℃, Zone 3 270℃, Zone 4 280℃, Die head 290℃; The die head temperature is 290℃, the hot air temperature is 310℃, the hot air pressure is 0.5 MPa, and the DCD is 250 mm. Three-layer structure: dark red PP layer (13 g / m²) / wood pulp layer (45 g / m²) / dark red PP layer (13 g / m²), total weight 71 g / m².

[0060] Pigment anchoring parameter verification: η = (5 × 0.9 × 100) / 250 = 1.80 The η value in this embodiment slightly exceeds the preferred range of η≤1.5. The test results show that the whiteness of the wood pulp layer is 78.5%. This embodiment serves as a boundary control embodiment to illustrate the critical significance of the relationship η≤1.5.

[0061] Example 3: Product performance test results:

[0062] Example 4: Preparation of two-color spun fleece fabric Two independent masterbatch feeding systems are used. The first meltblown head uses blue masterbatch (3%), and the second meltblown head uses pink masterbatch (3%), PP carrier, pigment content 40%, D 50 =0.8μm), and the other process parameters are the same as in Example 1.

[0063] The resulting two-color spun fleece fabric has blue and pink on the top and bottom sides respectively, with uniform color transition and no mutual bleeding or color bleeding observed. The whiteness of the wood pulp layer is 86.9%, and the MD dry tensile strength is 14.0 N / 50mm. The overall performance is comparable to that of the single-color product and it can be used in application scenarios where the surface layer function is distinguished.

[0064] Comparative Example A: DCD too close (violation of process parameter limits) The color masterbatch and formula ratio are exactly the same as in Example 1, except that the receiving distance DCD is adjusted to 100 mm (lower than the 150-300 mm range defined in this invention), and the rest of the process is the same as in Example 1.

[0065] Pigment anchoring parameter verification: η = (3 × 0.8 × 100) / 100 = 2.40 does not satisfy η≤1.5.

[0066] Test results:

[0067] Analysis: When the DCD is too close, the colored PP fibers contact the wood pulp in a semi-molten state. The pigment particles are not yet solidified and locked onto the PP fiber surface. Under the impact of airflow and contact friction, they migrate to the surface of the wood pulp fibers, causing discoloration of the wood pulp layer (whiteness decreases from 87.5% to 71.2%). This comparative example illustrates the critical significance of limiting the receiving distance DCD to ≥150mm in this invention.

[0068] Comparative Example B: Pigment particle size is too large (violation of masterbatch selection criteria) Pigment D 50 =2.0μm (exceeding the D limit specified in this invention) 50 Blue masterbatch (≤1μm) was added at 3%, and the remaining process parameters were the same as in Example 1.

[0069] Pigment anchoring parameter verification: η = (3 × 2.0 × 100) / 200 = 3.00 does not satisfy η≤1.5.

[0070] Test results:

[0071] Analysis: Excessively large pigment particle size leads to: (1) Large pigment particles are more likely to detach and become free in the high-speed meltblown airflow, causing coloring of the wood pulp layer; (2) Pigment particles clog the 0.3mm die micropores, resulting in unstable fiber output and uneven fiber thickness; (3) Large pigment particles form stress concentration points inside the fiber, reducing fiber strength. This comparative example proves that the pigment particle size D 50 The critical significance of ≤1μm.

[0072] Comparative Example C: The difference in melt index is too large (violating the rheological matching constraint). The color masterbatch with a melt index of 2200 g / 10min was used (the melt index difference with the PP substrate is 700 g / 10min, which is far beyond the ≤300 g / 10min limit of this invention), and the other parameters were the same as in Example 1.

[0073] Test results:

[0074] Analysis: The significant difference in melt index between the masterbatch and the PP substrate led to a mismatch in melt rheological properties, causing localized viscosity abrupt changes during extrusion and meltblowing, resulting in severe fiber diameter inhomogeneity (CV of 35%). Simultaneously, the pigment molecules failed to achieve good molecular-level blending with the PP substrate, resulting in weak pigment anchoring and decreased color fastness. This comparative example demonstrates the critical significance of a melt index difference ≤300 g / 10min.

[0075] Comparative Example D: All parameters do not conform to the limitations of this invention. Masterbatch uses D 50 =2.0μm, melt index 2200 g / 10min (700 g / 10min difference from PP substrate melt index), DCD=100mm, other parameters are the same as in Example 1.

[0076] Pigment anchoring parameter verification: η = (3 × 2.0 × 100) / 100 = 6.00, which exceeds the standard.

[0077] Test results:

[0078] Analysis: When all parameters deviate from the limitations of this invention, none of the product's indicators meet the requirements of this invention.

[0079] Comparative Example E: Pure white control sample (without masterbatch) Without adding color masterbatch, and with the other process parameters the same as in Example 1, a pure white spun fabric was prepared as a control.

[0080] Test results:

[0081] Analysis: By comparing Example 1 with the pure white control sample E, it can be seen that after adding masterbatch, due to the heterogeneous nucleation and enhancement effect of pigment particles, the MD dry tensile strength of the product of the present invention is increased by about 23%, which confirms the mechanism by which pigment particles, as heterogeneous nucleating agents, improve the crystallinity and molecular chain orientation of PP, bringing unexpected and beneficial effects of strength enhancement.

[0082] Four-quadrant comparative experiment analysis To systematically demonstrate the synergistic effect of the "synergistic control of masterbatch selection and process parameters" in this invention, the following comparative experimental matrix was constructed:

[0083] Conclusions of the four-quadrant synergistic effect analysis: (1) When a single feature is met, the overall performance is not up to standard: Comparative Example A (only the process is not met) and Comparative Examples B and C (only the masterbatch is not met) all showed a significant decrease in key indicators, indicating that the technical effect of the present invention depends on the coordinated implementation of the masterbatch selection and process parameters. Any deviation will affect the overall performance. (2) Synergistic effect: All indicators in Example 1 meet the requirements of this invention, and there is an inherent correlation between the indicators (such as the pigment anchoring relationship η, which organically combines the content of masterbatch, pigment particle size and receiving distance), indicating that there is a synergistic effect between the technical features of this invention; (3) Critical significance of the relationship η≤1.5: Example 1 (η=1.20) wood pulp brightness 87.5%; Example 3 (η=1.80) wood pulp brightness 78.5%; Comparative Example A (η=2.40) wood pulp brightness 71.2%; Comparative Example D (η=6.00) wood pulp brightness 62.3%. Wood pulp brightness decreases with increasing η value, and η=1.5 can be used as the critical threshold for wood pulp brightness ≥80%; (4) Strength enhancement effect: The dry tensile strength of MD in Comparative Example E (pure white control sample) was 11.5 N / 50 mm, and the dry tensile strength of MD in Example 1 (with added masterbatch) was 14.2 N / 50 mm, an increase of about 23%, which reflects the strength enhancement effect brought about by pigment particles as heterogeneous nucleating agents.

[0084] Comparison of the product of this invention with existing color wiping / care products To illustrate the advantages of this invention over existing colored wiping / care products, the colored velvet fabric obtained in Example 1 is compared with the performance of the following two commercially available colored products: Comparison Product 1: Commercially available post-processed dyed blue non-woven wipes (PP spunbond + dyed, basis weight approximately 70 g / m²); Comparison Product 2: Commercially available colored wood pulp wet wipe substrate (colored wood pulp + PP meltblown composite, basis weight approximately 70 g / m²).

[0085] Performance comparison results:

[0086] Comparative conclusion: The product of this invention has improved performance in terms of color fastness, pigment migration, mechanical strength, and visual quality compared to the two existing types of color wiping / care products.

[0087] Application examples of the product of this invention Application Example 1: Baby Care Soft Towels The blue colored fleece fabric obtained in Example 1 of this invention is cut into 20cm×20cm pieces, individually packaged, and used as a soft cleaning wipe for infants and young children. The blue appearance of the product of this invention is different from that of traditional white products, and the water fastness is ≥4, with no pigment migration observed, which meets the safety requirements for infant and young children's products.

[0088] Application Example 2: Medical Dressing Substrate The green colored fleece fabric obtained in Example 2 of this invention is used as the base material for medical wound care dressings. The green surface layer can be used to distinguish dressings with different functions; the high whiteness (≥80%) of the wood pulp absorbent core layer can be used to indicate the state of wound exudation.

[0089] Application Example 3: Pet Cleaning Pads The deep red colored fleece fabric obtained in Example 3 of this invention is used as a pet cleaning pad. The product of this invention has a color fastness of ≥4 and a dry tensile strength of ≥12.0 N / 50mm, which meets the requirements for use as a pet cleaning pad.

[0090] Application Example 4: Kitchen Wipes with Dual-Sided Functions The two-color (blue + pink) colored velvet cloth obtained in Example 4 of this invention is used. The blue side is used to wipe tableware, and the pink side is used to wipe the stove. The use of different colors can be used to avoid cross-contamination between different areas.

[0091] Application Example 5: Cotton Pads The colored spun fleece fabric obtained in Embodiment 1 or 2 of this invention is used as a cosmetic cotton wipe product. The product of this invention has a colored surface layer and a wood pulp absorbent core layer with a whiteness ≥80%, and a color fastness ≥4 grade, which meets the relevant requirements of the cosmetics industry.

[0092] Those skilled in the art should understand that the technical solutions described in this invention are not limited to the specific forms described in the above specific embodiments. Without departing from the inventive concept of this invention, the following equivalent substitutions or reasonable modifications can be made, all of which should fall within the protection scope of this invention: Color of masterbatch: In addition to the blue, green, dark red and pink used in the above embodiments, the present invention is also applicable to masterbatches of other colors such as yellow, orange, purple, brown and black, as long as they meet the physicochemical properties of masterbatch defined by the present invention. Pigment types in masterbatches: In addition to the phthalocyanine pigments and iron oxide pigments used in the above embodiments, this invention is also applicable to other types of organic pigments (such as quinacridones, azo pigments, etc.) and inorganic pigments (such as titanium dioxide, carbon black, etc.), as long as they meet the temperature resistance ≥280℃ and D specified in this invention. 50 Conditions such as ≤1μm are acceptable; Sources of wood pulp fibers: In addition to the softwood pulp used in the above embodiments, the present invention is also applicable to other natural cellulose fibers such as hardwood pulp, bamboo pulp, hemp pulp, and cotton pulp, as long as they meet the requirement of whiteness ≥85%. PP resin grade: In addition to the PP with a melt index of 1500 g / 10min used in the above examples, the present invention is also applicable to other meltblown grade PP resins with a melt index in the range of 1200 to 1800 g / 10min. Consolidation method: In addition to the hot air penetration consolidation method used in the above embodiments, the present invention can also use other consolidation methods such as hot rolling consolidation and ultrasonic consolidation (but care should be taken not to damage the bulkiness of the wood pulp layer). Product weight range: In addition to the product with a weight of about 70 g / m² shown in the above embodiments, the technical solution of the present invention is also applicable to other products with weights in the range of 60 to 80 g / m².

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection defined by the claims of the present invention.

Claims

1. A high colorfastness colored velvet fabric, characterized in that: It comprises a first PP colored meltblown fiber layer, a white wood pulp fiber layer, and a second PP colored meltblown fiber layer, which are sequentially laminated together. The three layers are interwoven online at the fiber level and do not contain adhesives. The PP colored meltblown fiber layer is made from PP raw material containing color masterbatch through a meltblown process, and the mass percentage of color masterbatch in the PP raw material is 3% to 5%. The weight of each layer of the PP colored meltblown fiber is 8-15 g / m², and the average diameter of the PP colored meltblown fiber is 1-5 μm; The mass ratio of the PP colored meltblown fiber layer to the white wood pulp fiber layer is 35-45:55-65; The colored velvet fabric satisfies the pigment anchoring relationship: Where: C represents the mass percentage of color masterbatch in PP raw material, in %; D 50 The median particle size of the pigment in the masterbatch is in μm; DCD is the receiving distance of the meltblown process in mm. The whiteness of the white wood pulp fiber layer in the colored velvet fabric is ≥80% according to GB / T 7974.

2. The high colorfastness colored fleece fabric according to claim 1, characterized in that: The masterbatch uses PP as the carrier resin, with a pigment content of 30%–50%, and the median particle size D of the pigment is... 50 The pigment has a thickness of ≤1 μm and a heat resistance temperature of ≥280℃. The difference between the melt index of the masterbatch and the melt index of the PP resin particles under the test conditions of 230℃ and 2.16kg is ≤300 g / 10min.

3. The high colorfastness colored fleece fabric according to claim 1, characterized in that: The coefficient of variation (CV) of the diameter of the PP colored meltblown fiber is ≤25%.

4. The high color fastness colored fleece fabric according to claim 1, characterized in that: The color of the masterbatch is selected from one of blue, green, purple, dark red, orange, and yellow; the first PP colored meltblown fiber layer and the second PP colored meltblown fiber layer are the same color or different colors.

5. The high colorfastness colored fleece fabric according to claim 1, characterized in that: The colored spun fleece fabric has a basis weight of 60-80 g / m², a thickness of 0.90-1.30 mm under 0.5 kPa pressure, a moisture content of ≤10%, and a pH value of 4.0-9.0; the colored spun fleece fabric has a dry tensile strength of ≥12.0 N / 50 mm and a dry tensile strength of ≥35.0%.

6. The high colorfastness colored fleece fabric according to claim 1, characterized in that: The color fastness to water of the colored velvet fabric is ≥4 according to GB / T 3920, the color fastness to rubbing (dry state) is ≥4, and the color fastness to rubbing (wet state) is ≥3-4.

7. A process for preparing a high colorfastness colored velvet fabric as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Premixing of ingredients: Weigh the raw materials according to the mass ratio of 3% to 5% color masterbatch and 95% to 97% PP resin particles, put them into a high-speed mixer and mix at room temperature for 5 to 10 minutes to obtain colored PP mixed raw materials; S2. Melt extrusion: The mixed raw material obtained in S1 is fed into a screw extruder for melt plasticization. The temperatures of each section of the extruder are as follows: Zone 1 200-220℃, Zone 2 230-250℃, Zone 3 250-270℃, Zone 4 260-280℃, and the die head temperature is 270-290℃. S3. Meltblown fiber formation: The melt is pumped to the meltblown die head and sprayed out. The die head temperature is 270-290℃, the hot air temperature is 280-310℃, the hot air pressure is 0.3-0.6 MPa, and the receiving distance DCD is 150-300 mm, to produce colored PP microfibers with an average diameter of 1-5 μm. S4. Wood pulp fiber opening: Wood pulp boards with a whiteness of ≥85% are crushed, opened, and air-flow combed to form a uniform flow of white wood pulp fibers; S5. Three-layer online composite: Through the online configuration of dual meltblown heads and intermediate wood pulp feeding system, the first PP colored meltblown fiber stream, the white wood pulp fiber stream, and the second PP colored meltblown fiber stream are simultaneously deposited on the receiving device and interwoven into a web at the fiber level, forming a "colored PP / white wood pulp / colored PP" three-layer sandwich fiber web, with the mass ratio of the PP colored meltblown fiber layer to the white wood pulp fiber layer being 35-45:55-65; S6. Consolidation and molding: The three-layer composite fiber web obtained in S5 is consolidated by hot air penetration, dried and wound to obtain the high color fastness colored velvet fabric.

8. The process according to claim 7, characterized in that: In step S1, the high-speed mixer rotates at 200-500 rpm; 0.1-0.3 wt% of zinc stearate or ethylene bis-stearamide (EBS) is added as a dispersant during mixing.

9. The process according to claim 7, characterized in that: In step S3, compared to the conventional meltblown process that uses the same PP resin particles but does not contain color masterbatch, the die head temperature and hot air temperature are increased by 5-10°C to compensate for the effect of adding color masterbatch on the fluidity of PP melt; in step S6, the temperature of hot air penetration and solidification is 130-150°C, and the solidification time is 5-15 seconds.

10. The use of the high color fastness colored velvet fabric as described in any one of claims 1 to 6 in the preparation of kitchen wipes, sanitary wipes substrates, baby care wipes, pet cleaning pads, medical dressing substrates, industrial wipes or cosmetic cotton wipes.

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