Food grade packaging nonwoven fabric and method for manufacturing the same

Abstract

The application relates to the technical field of non-woven fabrics, in particular to a food-grade non-woven fabric for packaging and a preparation method thereof. The application provides a non-woven fabric, wherein all raw materials are food-grade; the non-woven fabric comprises 20-50 wt% of one or more than two plant-based fibers, 30-50 wt% of one or more than two low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers with a melting point lower than 180 DEG C, and 10-30 wt% of one or more than two water-based binders. The non-woven fabric uses low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers, has low heat sealing temperature and can guarantee heat sealing strength, the low content of the binders solves the sticking problem during the processing of the non-woven fabric and reduces production energy consumption; through the matching of the components, the key performances can be balanced, on the basis of guaranteeing excellent heat sealing performance, the non-woven fabric also has good processing performance, mechanical performance, hydrophilic performance and the like, the fabric surface is not stuck, and the non-woven fabric has excellent technical effects in terms of dry and wet stiffness, moisture absorption and roughness.

Description

Technical Field

[0001] This application relates to the field of nonwoven fabric technology, specifically to a food-grade packaging nonwoven fabric and its preparation method. Background Technology

[0002] Nonwoven fabrics are commonly used to manufacture bags for containing single-serving products. The market for this type of oral bagged product has expanded to include so-called “modern oral” products, which can be used to package a wide variety of materials such as non-tobacco nicotine, flavorings, tea, coffee, herbal medicines, and / or other food-grade products.

[0003] Nonwoven fabrics for food packaging should possess the following performance characteristics: good food contact (food grade), heat-sealing performance (heat-sealing temperature and heat-sealing strength), mechanical properties (transverse and longitudinal mechanical properties), support for rapid processing (stiffness and elasticity), hydrophilicity (moisture absorption and softness), porosity, and air permeability (release rate); the core requirement is to achieve a very good balance among the above key properties.

[0004] Currently, the mainstream international manufacturers of nonwoven fabrics for packaging are Nonwoven (UK) and KANISHK (India), which are commonly referred to as British fabric and Indian fabric.

[0005] Currently, British nonwoven fabric is a top-tier product in the industry, the first choice for high-end product packaging, but it is expensive and has a long delivery time. However, it has several drawbacks in key performance aspects: ① It uses 100% viscose fiber or 100% lyocell fiber and binder as the main raw materials. Since neither viscose nor lyocell fiber has good heat-sealing properties, a high binder content (30%-50%) is required to achieve good heat-sealing performance. The fiber web formation process also involves impregnating the fibers in binder to achieve bonding between fibers, resulting in the need for a large amount of binder in nonwoven fabric production. ② The large amount of binder causes the finished product to stick together during use, making it difficult to pull, and the binder sticks to the cutter, forming black, sticky stains over time, which is a current pain point in use. ③ Because heat sealing mainly relies on binder, its heat-sealing performance is unstable. ④ The higher the amount of binder used, the higher the unit energy consumption required for drying during processing, which is not low-carbon and environmentally friendly.

[0006] The product disclosed in patent application CN20228001078.9 is quite similar to the mainstream British fabric currently circulating in the market, with a target weight of 25-40 gsm. Its core formula consists of short fibers and a binder. The short fibers are 100% lyocell, with a preferred fiber fineness of 0.9-2.2 dtex. The binder content accounts for 30%-50% of the dry weight, and the binders are mainly PLA, acrylics, PBS, vinyl acetate copolymers, vinyl acrylate copolymers, etc. The binder is mainly added to the fiber network through impregnation and spraying, followed by drying and reinforcement. The product described in this patent application suffers from a relatively limited selection of fibers and a high binder content, leading to fabric adhesion that hinders rapid packaging. Nearly 100 meters of the roll core are unusable due to adhesion, resulting in over 10% waste. The excessively high binder content also leads to low yield and high energy consumption. Furthermore, the binder is mainly composed of thermoplastic polymers, whose food-grade environmentally friendly aqueous solutions are difficult to produce, posing a quality and safety risk. Moreover, the core heat-sealing performance is provided by the binder in the nonwoven material, which leads to problems such as insufficient heat-sealing strength and unstable heat-sealing performance.

[0007] Indian cloth is currently mainly used in low-end products. Its main disadvantages include: ① poor mechanical properties, with transverse and longitudinal strength and feel similar to paper; ② uneven cloth surface and poor fiber distribution control; ③ poor fiber strength and poor heat-sealing performance; ④ poor appearance, with yellowing cloth surface and poor quality control; ⑤ poor compatibility, not resistant to oil and acidic substances such as menthol, and cannot be used in wet-process tobacco products; ⑥ long delivery time.

[0008] To address the above-mentioned problems in the prior art, this application provides a food-grade nonwoven fabric for packaging that balances heat-sealing and processing performance, and a method for preparing the same. Summary of the Invention

[0009] The purpose of this invention is to overcome the problems existing in the prior art and provide a food-grade nonwoven fabric for packaging that balances heat-sealing performance and processing performance, as well as its preparation method. The nonwoven fabric described in this application uses low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers, has a low heat-sealing temperature while ensuring heat-sealing strength, and a low adhesive content, which solves the adhesion problem during nonwoven fabric processing and reduces energy consumption.

[0010] In a first aspect, this application provides a nonwoven fabric comprising:

[0011] 20-50% by weight of one or more plant-based fibers,

[0012] 30-50% by weight of one or more low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers with melting points below 180°C.

[0013] And 10-30% by weight of one or more water-based adhesives.

[0014] The raw materials used in the nonwoven fabric described in this application are preferably food-grade raw materials. Plant-based fibers mainly serve a hydrophilic and wetting function, which is beneficial for the stiffness of processing, easy to chew, and has a good taste; low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers provide heat-sealing performance and a uniform fabric surface; the binder mainly serves a web-forming and reinforcing function, is easy to foam, hydrophilic and easy to dry, and a small part serves a heat-sealing function.

[0015] In one set of embodiments, the nonwoven fabric includes

[0016] 25-45% by weight of one or more plant-based fibers,

[0017] 35-45% by weight of one or more low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers with melting points below 180°C.

[0018] And 15-25% by weight of one or more water-based adhesives.

[0019] In one embodiment, the content of plant-based fibers is preferably 30-40% by weight, more preferably 32-35% by weight. The content of low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers is preferably 38-42% by weight, more preferably 40% by weight. The content of water-based binder is preferably 18-25% by weight, more preferably 20-25% by weight.

[0020] In one set of embodiments, the nonwoven fabric also includes other thermoplastic fibers.

[0021] In one embodiment, the nonwoven fabric is composed of one or more plant-based fibers, one or more low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers with melting points below 180°C, other thermoplastic fibers, and one or more water-based binders, with the sum of the contents of each component being 100% by weight.

[0022] In one embodiment, the nonwoven fabric is composed of one or more plant-based fibers, one or more low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers with a melting point below 180°C, and one or more water-based binders, with the sum of the contents of each component being 100% by weight. Preferably, the nonwoven fabric is composed of 35% by weight of one or more plant-based fibers, 40% by weight of one or more low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers with a melting point below 180°C, and 25% by weight of one or more water-based binders.

[0023] In one set of embodiments, the melting point of the low-melting-point thermoplastic fiber or thermoplastic bicomponent fiber is below 165°C, preferably below 150°C.

[0024] In one embodiment, the low-melting-point thermoplastic fiber or thermoplastic bicomponent fiber may be selected from PE, PP, PLA, LPET, PE / PET, LPET / PET, PE / PP, PE / PLA, etc., preferably selected from PE / PET and LPET / PET. The fiber fineness range is 0.8-7 dtex, and the fiber length is 6-51 mm.

[0025] In one embodiment, the plant-based fiber is selected from natural plant-based fibers or regenerated plant-based fibers; preferably, the plant-based fiber is selected from viscose fiber, lyocell fiber, bamboo fiber, hemp fiber, wood fiber, cotton fiber, etc.; more preferably, the plant-based fiber is selected from viscose fiber, bamboo fiber, and hemp fiber. The fineness of the plant-based fiber ranges from 1 to 6 dtex, preferably 1.2 to 3 dtex, and the fiber length is 12 to 51 mm.

[0026] In one set of embodiments, the water-based adhesive is selected from: vinyl acetate-ethylene copolymers, acrylates, polyurethanes, polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxyalkanoates (PHA), vinyl acetate copolymers, vinyl acrylate copolymers, and styrene-butadiene copolymers, etc. Preferably, the water-based adhesive is selected from: vinyl acetate-ethylene copolymers and acrylates.

[0027] In one embodiment, other thermoplastic fibers are selected from polyester fibers, TPU fibers, PHA fibers, PA fibers, PBT fibers, etc. The fiber fineness ranges from 0.8 to 7 dtex, and the fiber length ranges from 6 to 51 mm.

[0028] In one set of embodiments, the nonwoven fabric contains plant-based fibers selected from one or more of viscose fiber, bamboo fiber, and hemp fiber; low-melting-point thermoplastic fiber or thermoplastic bicomponent fiber selected from one or two of PE / PET and LPET / PET; and water-based binder selected from one or two of vinyl acetate-ethylene copolymers and acrylates.

[0029] In a second aspect, this application provides a bagged product, comprising a bag formed from the aforementioned nonwoven fabric and a product inside the bag. Preferably, the product inside the bag is food or traditional Chinese medicine, etc.

[0030] In a third aspect, this application provides a method for preparing the aforementioned nonwoven fabric, comprising the following steps in accordance with the aforementioned composition requirements of the nonwoven fabric: fiber unpacking, opening, mixing and metering feeding, pre-carding, transverse web laying, main carding, longitudinal web laying, web trimming, foaming, foam gluing, and drying; optionally including the final winding and slitting steps. Preferably, a defect inspection step is included between drying and winding.

[0031] In one set of embodiments, drying is selected from steam drying, electric heating drying, etc.

[0032] The nonwoven fabric preparation method described in this application includes the following stages: In the unpacking and opening stages, multiple fibers are simultaneously mixed according to the formula requirements; in the carding stage, pre-carding and main carding ensure more uniform fiber distribution and more stable transverse and longitudinal properties of the nonwoven fabric; in the adhesive application stage, adhesive foaming technology is used, allowing a small amount of adhesive to bond the fibers into a web, while the foam points are evenly dispersed throughout the fiber web, resulting in uniform pore size, more even air permeability, and more uniform material release in the finished nonwoven fabric; in the drying stage, due to the low adhesive content, rapid drying is possible, resulting in low energy consumption and high production efficiency. Online defect inspection utilizes online visual inspection to ensure full product inspection, increasing quality, safety, and reliability.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) The nonwoven fabric described in this application uses low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers and low-content water-based binders. The low binder content solves the adhesion problem during nonwoven fabric processing. At the same time, the drying temperature is about 100°C, which reduces energy consumption. The heat sealing temperature is low and the heat sealing strength can be guaranteed. The heat sealing temperature is less than 200°C. Preferably, the heat sealing strength can reach more than 14.5N.

[0035] (2) The nonwoven fabric described in this application can balance various key properties through the optimal ratio between the components. In addition to ensuring excellent heat sealing performance, it also has good processing performance, mechanical properties, hydrophilic properties, etc. The fabric surface is non-sticky, and the dry and wet stiffness, moisture absorption and roughness have excellent technical effects.

[0036] (3) The low binder content and drying temperature of around 100℃ solve the problems of low yield and high energy consumption, and it is clean and easy to operate. The two-stage carding process ensures the uniformity of the nonwoven fabric in both the transverse and longitudinal directions and the stability of its performance. The foam method is used to spray the binder onto the fiber web, which requires less binder to achieve better performance. The foam breaks into bonding points scattered on the fibers, resulting in a larger specific surface area, faster production speed, higher yield, and lower energy consumption.

[0037] (4) The product range and applications are wider. It can produce food-grade nonwoven fabrics with a basis weight of 20-120gsm, which can be promoted to more application scenarios and is more conducive to fast and stable packaging production and processing. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0039] The abbreviations used in this application have the following meanings:

[0040] PE: Polyethylene fiber

[0041] PP: Polypropylene fiber

[0042] PLA: Polylactic acid fiber

[0043] LPET: Low melting point polyester fiber

[0044] PET: Polyester fiber

[0045] PA: Polyamide fiber

[0046] PBT: Polybutylene terephthalate fiber

[0047] PE / PET: Bicomponent low-melting-point fiber with polyethylene / polyester core.

[0048] PE / PP: ES fiber

[0049] PE / PLA: Bicomponent low-melting-point fiber consisting of polyethylene / polylactic acid sheath and core.

[0050] LPET / PET: Low melting point polyester bicomponent fiber

[0051] TPU: Thermoplastic Polyurethane

[0052] PHA: Polyhydroxyalkanoate

[0053] This application provides a nonwoven fabric comprising:

[0054] 20-50% by weight of one or more plant-based fibers,

[0055] 30-50% by weight of one or more low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers with melting points below 180°C.

[0056] And 10-30% by weight of one or more water-based adhesives.

[0057] I. Preparation methods of nonwoven fabrics

[0058] According to the composition requirements of nonwoven fabric, the following steps are performed in sequence: fiber unpacking, loosening, mixing and metering cotton feeding, pre-carding, transverse web laying, main carding, longitudinal web laying, web cotton edge trimming, foaming, foam gluing, drying, online defect inspection, and winding and slitting.

[0059] In the unpacking and opening stages, multiple fibers are simultaneously mixed according to the composition requirements of nonwoven fabrics. In the carding stage, pre-carding and main carding ensure more uniform fiber distribution and more stable transverse and longitudinal properties of the nonwoven fabric. In the gluing stage, adhesive foaming technology is used, allowing a small amount of adhesive to bond the fibers into a web. Simultaneously, the foam dots are evenly distributed throughout the fiber web, resulting in uniform pore size, improved air permeability, and more even material release in the finished nonwoven fabric. In the drying stage, due to the low adhesive content, drying is rapid, resulting in low energy consumption and high production efficiency. Online defect inspection utilizes online visual inspection to ensure full product inspection, increasing quality, safety, and reliability. Steam drying is preferred. II. Specific Implementation Methods

[0061] The key indicators of nonwoven fabrics are determined according to the internationally recognized standard ISO 9073.

[0062] 1. Comparison of the effects of using different thermoplastic fibers

[0063] Nonwoven fabrics were prepared according to the composition requirements shown in Table 1, and their key indicators were tested (using the internationally recognized standard ISO 9073).

[0064] Table 1 Comparison of the effects of using different thermoplastic fibers

[0065]

[0066]

[0067] As shown in Table 1, Examples 1-7 used low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers and low-content binders. The resulting nonwoven fabrics achieved a heat-sealing temperature below 200°C while maintaining heat-sealing strength, thus solving the problem of fabric adhesion during processing and resulting in low energy consumption. Among Examples 1-7, Example 1-2 exhibited the best heat-sealing strength, exceeding 14.5 N. In terms of stiffness and fabric surface roughness, Example 1-2 was superior to Examples 6-7, and even more superior to Examples 3-5.

[0068] 2. Comparison of the effects of using different plant-based fibers

[0069] Nonwoven fabrics were prepared according to the composition requirements shown in Table 2, and their key indicators were tested.

[0070] Table 2 Comparison of the effects of using different plant-based fibers

[0071]

[0072]

[0073] As shown in Table 2, Examples 1 and 8-12, using different plant-based fibers, produced nonwoven fabrics with heat-sealing temperatures below 200°C while maintaining heat-sealing strength. This solved the problem of fabric adhesion during processing and resulted in low energy consumption. The use of viscose fiber and bamboo fiber resulted in higher heat-sealing strength (greater than 14.5 N) and better performance in terms of stiffness, moisture absorption, and roughness. Conversely, excessively low content of low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers led to excessively high heat-sealing temperatures and low heat-sealing strength.

[0074] 3. Comparison of the effects of using different plant-based fibers

[0075] Nonwoven fabrics were prepared according to the composition requirements shown in Table 3, and their key indicators were tested.

[0076] Table 3 Comparison of the effects of using different plant-based fibers and low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers.

[0077]

[0078]

[0079] As shown in Table 3, Examples 1 and 13-20, using different plant-based fibers and combinations of different low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers, produced nonwoven fabrics with heat-sealing strength maintained at temperatures below 200°C, solving the problem of fabric adhesion during processing and resulting in low energy consumption. The PE / PET and LPET / PET combinations exhibited higher heat-sealing strength (greater than 14.5 N) and better performance in terms of stiffness, moisture absorption, and roughness.

[0080] 4. Comparison of the effects of using different adhesives

[0081] Nonwoven fabrics were prepared according to the composition requirements shown in Table 4, and their key indicators were tested.

[0082] Table 4 Comparison of the effects of using different adhesives

[0083]

[0084]

[0085] As shown in Table 4, Examples 1 and 21-24, using different amounts of adhesive, all solved the problem of fabric adhesion during processing. The resulting nonwoven fabrics achieved heat sealing strength at temperatures below 200°C with low energy consumption; the heat sealing strength was greater than 14.5N, and the fabrics also exhibited excellent performance in terms of stiffness, moisture absorption, and roughness.

[0086] As can be seen from the embodiments of this application, this application uses plant-based fibers, low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers and water-based binders. The nonwoven fabric, while ensuring heat-sealing strength, has a heat-sealing temperature below 200°C, resulting in low energy consumption and a low binder content, thus solving the problem of fabric adhesion during processing. In a preferred embodiment of this application, by using specific low-melting-point thermoplastic fibers or thermoplastic bicomponent fibers, the heat-sealing strength can reach above 14.5N, and further improve processing performance, including dry and wet stiffness, moisture absorption, and roughness.

[0087] Therefore, this application achieves a balance between heat-sealing performance such as heat-sealing temperature and heat-sealing strength, as well as mechanical properties such as non-adhesion of the fabric surface, dry and wet stiffness, moisture absorption, roughness, hydrophilicity, and processing performance by controlling the components and content of each component in the nonwoven fabric.

[0088] In the description of this specification, the terms "a specific embodiment," "a set of embodiments," "example," "specific example," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0089] The scope of protection of this application is not limited to the embodiments described above. Obviously, those skilled in the art can make various modifications and variations to this application without departing from the scope and spirit of the invention. If such modifications and variations fall within the scope of the claims of this application and their equivalents, then the intent of this application also includes such modifications and variations.

Claims

1. A nonwoven fabric, characterized in that, It is composed of the following components, the sum of which is 100% by weight: 30-35% by weight of one or two plant-based fibers, 35-40% by weight of one or two thermoplastic bicomponent fibers selected from PE / PET and LPET / PET. And 25-30% by weight of water-based adhesives such as vinyl acetate-ethylene copolymers; The plant-based fibers are selected from viscose fiber and bamboo fiber.

2. The nonwoven fabric according to claim 1, characterized in that, The nonwoven fabric consists of 35% by weight of one or two plant-based fibers, 40% by weight of one or two thermoplastic bicomponent fibers selected from PE / PET and LPET / PET, and 25% by weight of a water-based binder of vinyl acetate-ethylene copolymer.

3. A bagged product comprising a bag formed from the nonwoven fabric of any one of claims 1-2 and a product inside the bag.

4. The bagged product according to claim 3, characterized in that, The product inside the bag is food or traditional Chinese medicine.

5. A method for preparing a nonwoven fabric, characterized in that, According to the composition requirements of the nonwoven fabric as described in any one of claims 1-2, the following steps are performed in sequence: fiber unpacking---opening---mixing and metering feeding---pre-carding---transverse web laying---main carding---longitudinal web laying---web cotton edge trimming---foaming---foam adhesive application---drying; including the final winding step; and a defect inspection step is also included between drying and winding.

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