Production process for improving the strength of a cup using nanofiber reinforcement technology

Abstract

The present application relates to paper cup production technical field, especially utilize nanometer fiber reinforced technology to promote the production process of cup body strength, including the following steps: nanometer fiber material is added in dispersion medium, and the pre-dispersion, high shear dispersion and high pressure homogenization treatment are carried out in turn, and nanometer fiber dispersion liquid is obtained; The nanometer fiber dispersion liquid is added to the paper pulp system, so that the nanometer fiber accounts for 1-3 wt% of the total mass of slurry, and the slurry is obtained; The slurry is spread on the forming wire through the headbox, and the wet paper page is formed by vacuum dewatering; The wet paper page is pressed and dried, and the paper base is obtained; The coating liquid is applied to the surface of the paper base and dried, wherein the nanometer fiber content in the coating liquid is 2-4 wt%, and the coating amount is 2-6 g / m2; The thermoplastic material is compounded on the surface of the coating layer by extrusion film coating method, the extrusion temperature is 260-320 DEG C, and the composite material is formed; The composite material is die cut, rolled and thermoformed, and the paper cup is obtained.

Description

Technical Field

[0001] This invention relates to the field of paper cup manufacturing technology, and in particular to a manufacturing process that utilizes nanofiber reinforcement technology to improve the strength of the cup body. Background Technology

[0002] Disposable paper cups are widely used in the catering and beverage industry, and are typically composed of a paper base material and an inner barrier layer. Current paper cup manufacturing processes mainly include pulp preparation, paper forming, surface coating or lamination, and die-cutting. Cup strength is primarily achieved by increasing the paper's basis weight and optimizing the fiber ratio.

[0003] In recent years, attempts have been made to improve the mechanical properties of paper-based materials by adding nanofibers to pulp or by applying coatings to the paper surface to enhance strength and barrier properties. However, most of these improvements are limited to a single process stage and lack synergistic design between different process steps.

[0004] In practical applications, the above technical solutions still have the following shortcomings: there is a lack of effective connection between the internal fiber bonding of the paper base and the surface layer structure. When subjected to force or heated liquid, the load is difficult to be effectively transferred between different structural layers, which can easily lead to local stress concentration, insufficient interface bonding or structural instability.

[0005] Therefore, although existing technologies can improve the performance of paper cups to some extent, the overall strengthening effect is limited, and it is difficult to balance strength and structural stability without significantly increasing the amount of material used. Summary of the Invention

[0006] In view of the problem that nanofibers are usually introduced alone only in the pulp preparation stage or surface treatment stage in the above or existing technologies, resulting in them exhibiting a localized reinforcement state inside or on the surface of the paper matrix and failing to form a continuous reinforcement system between the internal structure and the interface structure of the material, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to provide a manufacturing process that utilizes nanofiber reinforcement technology to improve the strength of the cup body.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a manufacturing process for improving the strength of a cup body using nanofiber reinforcement technology, comprising the following steps: S1: Add nanofiber materials to a dispersion medium and perform pre-dispersion, high-shear dispersion and high-pressure homogenization treatment in sequence. The high-pressure homogenization pressure is 600–1200 bar and the number of treatments is 3–8 times to obtain nanofiber dispersion. S2: Add the nanofiber dispersion to the pulp system, so that the nanofiber accounts for 1-3 wt% of the total mass of the pulp, and stir at 500-1500 rpm for 10-30 min to obtain the pulp; S3: The pulp is spread onto the forming wire through a headbox and dewatered under vacuum to form a wet paper sheet, wherein the vacuum dewatering degree is -0.04 to -0.08 MPa; S4: The wet paper sheet is subjected to pressing and drying treatment, wherein the pressing pressure is 3–6 MPa and the drying temperature is 90–120℃ to obtain paper base; S5: Apply a coating liquid to the paper base surface and perform a drying treatment, wherein the nanofiber content in the coating liquid is 2–4 wt% and the coating amount is 2–6 g / m². S6: A thermoplastic material is laminated onto the surface of the coating layer by an extrusion coating process, wherein the extrusion temperature is 260–320°C, to form a composite material; S7: The composite material is die-cut, rolled and thermoformed to obtain a paper cup.

[0009] As a preferred embodiment of the production process of the present invention that utilizes nanofiber reinforcement technology to improve the strength of the cup body, in step S1 the high shear dispersion speed is 3000–8000 rpm and the time is 5–20 min.

[0010] As a preferred embodiment of the production process of the present invention that utilizes nanofiber reinforcement technology to improve the strength of the cup body, wherein the average particle size of the nanofiber dispersion obtained in step S1 is less than 200 nm.

[0011] As a preferred embodiment of the production process of the present invention that utilizes nanofiber reinforcement technology to improve the strength of the cup body, wherein the nanofiber content in step S2 is 2–3 wt%.

[0012] As a preferred embodiment of the production process of the present invention that utilizes nanofiber reinforcement technology to improve the strength of the cup body, wherein: in step S2, the stirring speed is 800–1200 rpm and the time is 15–25 min.

[0013] As a preferred embodiment of the production process of the present invention that utilizes nanofiber reinforcement technology to improve the strength of the cup body, the coating liquid in step S5 further includes 3–6 wt% polyvinyl alcohol and 0.5–1 wt% layered inorganic materials.

[0014] As a preferred embodiment of the production process of the present invention that utilizes nanofiber reinforcement technology to improve the strength of the cup body, wherein the coating method in step S5 is blade coating or roller coating.

[0015] As a preferred embodiment of the production process of the present invention that utilizes nanofiber reinforcement technology to improve the strength of the cup body, wherein: the thermoplastic material mentioned in step S6 is polyethylene with a thickness of 10–30 μm.

[0016] As a preferred embodiment of the production process of the present invention that utilizes nanofiber reinforcement technology to improve the strength of the cup body, wherein: the nanofiber content in step S2 is 3 wt%, and the coating amount in step S5 is 4–6 g / m².

[0017] As a preferred embodiment of the production process of the present invention that utilizes nanofiber reinforcement technology to improve the strength of the cup body, wherein: the basis weight of the paper base in step S3 is 180–200 g / m², and the nanofiber content in step S2 is 2 wt%.

[0018] The beneficial effects of the manufacturing process of this invention, which utilizes nanofiber reinforcement technology to improve the strength of the cup body, are as follows: This invention improves the structural stability and mechanical strength of paper cups by introducing nanofibers in stages during the pulping and surface coating stages, and controlling their distribution and dosage in different process stages. By introducing nanofibers into the pulp and distributing them among the pulp fibers, a multi-point connection structure is formed during papermaking and drying, thereby improving the degree of bonding between fibers and making the internal structure of the paper base more stable. By constructing a nanofiber-containing coating on the paper substrate surface, the pores on the paper substrate surface are filled and a continuous layer structure is formed, thereby improving the structural integrity of the paper substrate surface; By introducing the above two-stage method, a continuous transition relationship is formed between the internal structure and the surface structure of the paper base. In the subsequent composite and molding process, it is beneficial to the bonding between different structural layers. When the composite barrier layer is applied, the interface contact is more sufficient, thereby improving the stability of the composite structure. Through the production process of this invention, good structural stability can still be obtained under relatively low paper basis weight conditions, thereby reducing the amount of material used to a certain extent. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the overall manufacturing process for improving the strength of a cup body using nanofiber reinforcement technology. Detailed Implementation

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0023] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0024] Example 1, referring to Figure 1 This is the first embodiment of the present invention. This embodiment provides a production process that uses nanofiber reinforcement technology to improve the strength of the cup. By introducing nanofiber materials in stages during the pulp preparation stage and the surface treatment stage, a multi-scale structure with synergistic bulk and interfacial reinforcement is constructed, thereby improving the structural stability and mechanical strength of the paper cup.

[0025] The nanofiber material uses cellulose nanofibers with an average diameter of 10–30 nm and a length of 1–5 μm. Initially, it is a slurry, which is first dispersed.

[0026] The nanofiber slurry was diluted to 3 wt% in deionized water and pre-dispersed under mechanical stirring at room temperature at a speed of 2000 rpm for 8 min to achieve macroscopic uniform distribution. The system was then further processed using a high-shear dispersion device with the shear speed increased to 6000 rpm for 12 min to effectively dissociate the original nanofiber aggregates. To further improve the dispersion uniformity, the dispersion system was processed using a high-pressure homogenizer with a homogenization pressure controlled at 800 bar and the process was repeated 5 times to transform the nanofibers from the initial bundle structure to a relatively independent dispersed state.

[0027] If the high-pressure homogenization step is omitted, localized areas of nanofiber enrichment may easily appear in the subsequent paper sheets. These areas are prone to stress concentration when subjected to pressure, which leads to a decrease in the compressive strength of the paper cup.

[0028] The well-dispersed nanofiber system was added to the pulp system in proportion. The pulp raw material was a mixture of softwood pulp and hardwood pulp, with softwood pulp accounting for 65% by mass and hardwood pulp accounting for 35% by mass. The pulp freeness was controlled at 35°SR. A certain fine fibrous structure had been formed on the fiber surface, which was conducive to hydrogen bonding between fibers, but still retained a certain pore space, providing conditions for the embedding of nanofibers.

[0029] Nanofibers account for approximately 2 wt% of the total pulp mass. During the addition process, stirring is maintained at a speed of around 1000 rpm for about 20 minutes to ensure that the nanofibers are evenly distributed among the pulp fibers. At the same time, a wet strength agent with a mass fraction of 0.5 wt% is added to improve the wet bonding strength.

[0030] Nanofibers can be adsorbed onto the surface of pulp fibers and form bridging structures between fiber intersections, thereby establishing a continuous load transfer path at the microscale.

[0031] When the nanofiber content is less than 1 wt%, discrete connection structures are formed only in local areas, which has limited effect on improving the overall strength. However, when the content is higher than 3 wt%, the viscosity of the system increases significantly, the fluidity of the pulp decreases, the papermaking process becomes unstable, and new agglomeration phenomena are prone to occur.

[0032] Therefore, controlling the nanofiber content within the range of 1–3 wt%, especially around 2 wt%, can achieve the best balance between reinforcement effect and process feasibility.

[0033] The reinforced pulp, after being uniformly mixed, is spread through the headbox onto the forming wire for papermaking. The basis weight of the finished product is controlled to be approximately 220 g / m², and the vacuum dewatering degree is approximately -0.06 MPa. Moisture is rapidly removed, and pulp fibers and nanofibers are deposited together to form a wet paper sheet.

[0034] Because nanofibers fill the pore areas between fibers, the paper structure becomes denser, and the reduced porosity makes the stress distribution more uniform when the material is under pressure, thus helping to improve its compressive strength.

[0035] The wet paper sheets are then pressed and dried. The pressing pressure is controlled at 4 MPa to further remove moisture and improve the tightness of fiber contact. The drying stage adopts a multi-stage drying cylinder method, and the drying temperature is controlled at about 105℃. The final paper sheet moisture content is controlled below 6%.

[0036] Nanofibers and pulp fibers form a stable bond through numerous hydrogen bonds, and once the structure is fixed, a stable bulk reinforcement system is formed, providing a foundation for the overall strength of the paper cup.

[0037] After the paper base is formed, its surface is coated with nanofiber reinforcement. The coating solution consists of nanofibers: 3 wt%, polyvinyl alcohol: 5 wt%, and montmorillonite: 0.8 wt%. The nanofibers are used to construct a dense network structure, PVA provides continuous film formation capability, and montmorillonite is used to improve barrier properties. The coating solution is uniformly applied to the paper base surface using a doctor blade coating method, and the coating amount is controlled to be about 4 g / m². Then, it is dried at about 100°C for about 40 s to form a continuous and dense film layer.

[0038] The film layer not only fills the micropores on the surface of the paper base, but also forms a transition interface between the paper base and the subsequent barrier layer. When under stress, it can act as a stress buffer to reduce local stress concentration.

[0039] Based on this, a polyethylene barrier layer is composited on the coating surface through an extrusion coating process. The coating temperature is controlled at 300℃ and the thickness is 20 μm. Due to the presence of the aforementioned nanofiber reinforcement layer, the surface roughness and polarity of the paper base are improved, thereby enhancing the adhesion performance of the polyethylene layer.

[0040] The enhanced interface can effectively prevent interlayer delamination under the action of hot liquids.

[0041] Finally, the composite material is die-cut and rolled into paper cups using thermoforming equipment. The forming temperature is controlled at 140℃, the forming pressure is about 0.5 MPa, and the cups are then rolled and shaped.

[0042] This embodiment constructs a bulk nano-reinforced network in the slurry stage and forms a dense interfacial reinforcement layer on the surface, enabling both the material's interior and interface to have good load transfer capabilities, thereby achieving a synergistic improvement in mechanical and barrier properties. The segmented introduction method can exert a reinforcing effect at different scales simultaneously, and its performance improvement is not a simple additive effect, but rather stems from the structural synergistic effect.

[0043] Example 2, refer to Figure 1 This is the second embodiment of the present invention. Based on embodiment 1, this embodiment provides an optimization of the production process for improving the strength of the cup body by utilizing nanofiber reinforcement technology.

[0044] In the nanofiber dispersion stage, in order to improve the degree of dispersion and further reduce potential agglomeration, the nanofiber slurry was diluted to 3 wt%. After pre-dispersion and high-shear dispersion, it entered high-pressure homogenization treatment. The homogenization pressure was increased to 1000 bar and the number of cycles was increased to 7. The nanofiber bundles were more fully dissociated, and compared with Example 1, it had higher uniformity, which provided the necessary conditions for the subsequent formation of a continuous reinforcing network.

[0045] During the pulp preparation stage, the above dispersion is added to the pulp system to increase the nanofiber content to 3 wt%, which is the upper limit of the 1–3 wt% range. At this concentration, the nanofibers not only form bridging structures between pulp fibers, but also gradually tend to form a continuous nanonetwork.

[0046] Compared to the 2 wt% content in Example 1, the nanofibers are more densely connected between fibers, and a mesh-like coating structure is formed in some areas. That is, the nanofibers form a continuous coating layer around the pulp fibers, thereby significantly improving the bonding strength between fibers.

[0047] When the nanofiber content is increased from 2 wt% to 3 wt%, the tensile strength of the paper increases; however, when it is further increased to 4 wt%, the secondary agglomeration between nanofibers in the system leads to uneven structure and a decrease in tensile strength.

[0048] During the paper forming stage, the pulp is evenly spread on the forming wire through the headbox, and the basis weight is controlled at about 230 g / m² to match the high strength requirements. Due to the high content of nanofibers, their filling effect is more significant during the dewatering process, which further reduces the porosity inside the paper sheet. The reduced porosity means that the internal voids of the material have less space to collapse when under pressure, thereby improving the overall compressive stability.

[0049] The material is then subjected to pressing and drying processes. The pressing pressure is controlled at 5 MPa to further improve the density of the structure, and the drying temperature is controlled between 105 and 110°C. During this process, a denser hydrogen bond network is formed between the nanofibers and the pulp fibers, further enhancing the overall rigidity of the material.

[0050] In the surface treatment stage, the strength of the interface reinforcement layer is further improved. The content of nanofibers in the coating liquid is increased to about 4 wt%, the content of PVA is maintained at 5 wt%, and the content of montmorillonite is 0.8 wt%.

[0051] Using a doctor blade coating method, the coating amount is controlled at approximately 6 g / m². As the coating thickness increases, the nanofibers form a denser network structure on the surface, and the coating exhibits a continuous, dense film structure without obvious pores. When the coating amount exceeds 6 g / m², internal stress concentration is easily generated during the drying process, which can lead to microcracks. Therefore, in this embodiment, it is controlled to be within 6 g / m².

[0052] The interface reinforcement layer not only further reduces the air permeability and water permeability of the material, but also acts as a stress dispersion layer during the stress process, significantly improving the density of the interface.

[0053] In the barrier layer composite stage, the same polyethylene coating process is used, with the coating temperature controlled at about 300℃ and the thickness at 20 μm. Due to the denser interface reinforcement layer and higher surface polarity, the bond between the polyethylene layer and the substrate is stronger.

[0054] Nanofiber reinforcement layers not only play a physical filling role in interfacial bonding, but also enhance interlayer bonding by increasing the contact area and interfacial energy.

[0055] Finally, the composite material is die-cut and thermoformed at a temperature of 140–150°C and a pressure of approximately 0.5–0.6 MPa. It is then rolled and shaped to produce the target paper cup.

[0056] This embodiment increases the content of nanofibers in the slurry to the critical upper limit and simultaneously increases the density of the interface reinforcement layer, so that a continuous multi-scale reinforcement network is formed inside and on the surface of the material, thereby significantly improving the overall mechanical properties.

[0057] Example 3, referring to Figure 1 This is the third embodiment of the present invention. Based on embodiment 1, this embodiment provides an optimization of the production process for improving the strength of the cup body by utilizing nanofiber reinforcement technology.

[0058] In the nanofiber dispersion stage, the same dispersion process as in Example 1 was used.

[0059] The dispersed nanofibers were then added to the pulp system, with their content controlled at approximately 2 wt%, and stirred at 1000 rpm for 20 min to ensure that the nanofibers were evenly distributed among the pulp fibers.

[0060] The papermaking basis weight was reduced to about 190 g / m², which is about 13%–15% lower than that in Example 1. During the papermaking process, the pulp is spread to the forming wire through the headbox, and the vacuum dewatering degree is controlled at about -0.06 MPa.

[0061] Due to the presence of nanofibers, they preferentially deposit and fill the spaces between fibers during the dehydration process, allowing the paper to maintain good structural integrity even at low basis weights.

[0062] The material is then pressed and dried, with the pressing pressure controlled at 3.5–4 MPa and the drying temperature controlled at approximately 100–105°C. The nanofibers and pulp fibers form a stable bond through hydrogen bonds.

[0063] Because of their larger specific surface area, nanofibers provide far more bonding sites per unit mass than traditional fibers, so the overall bonding strength can still be maintained even when the total amount of material is reduced.

[0064] In the surface treatment stage, the coating thickness is reduced to balance material cost and processing efficiency. The content of nanofibers in the coating liquid is controlled at about 3 wt%, PVA at 5 wt%, and montmorillonite at 0.8 wt%. A doctor blade coating method is used, and the coating amount is controlled at about 3 g / m² to form a continuous interface reinforcement layer.

[0065] The coating can effectively cover the pores on the paper base surface and form a continuous film structure. It has a dual role in lightweight structures: on the one hand, it fills the surface pores and improves the overall density; on the other hand, it disperses local stress during the stress process and avoids local instability caused by the reduction of material thickness.

[0066] In the barrier layer composite stage, the same polyethylene coating process is used, with a coating temperature of about 300℃ and a thickness of about 20 μm. Due to the presence of a nanofiber reinforcement layer, the interfacial bonding performance is still improved.

[0067] Paper cups are finally produced by die-cutting and thermoforming. The forming temperature is controlled at about 135–140℃ and the forming pressure is about 0.4–0.5 MPa. The pressure is appropriately reduced to avoid local crushing.

[0068] In this embodiment, the loss of structural strength caused by the reduction in material usage is compensated by the synergistic reinforcement effect of nanofibers in the bulk phase and interface, while reducing the amount of material used by about 15%.

[0069] Nanofibers form a high-density interconnected network between fibers, improving the effective load-bearing capacity per unit mass of material; at the same time, the interface reinforcement layer improves stress distribution, making the overall structure more uniform under stress.

[0070] Compared with existing technologies that simply increase strength by increasing material usage, this embodiment maintains high performance while reducing resource consumption, representing a significant technological advancement.

[0071] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A manufacturing process that utilizes nanofiber reinforcement technology to enhance the strength of a cup body, characterized in that, Includes the following steps: S1: Add nanofiber materials to a dispersion medium and perform pre-dispersion, high-shear dispersion and high-pressure homogenization treatment in sequence. The high-pressure homogenization pressure is 600–1200 bar and the number of treatments is 3–8 times to obtain nanofiber dispersion. S2: Add the nanofiber dispersion to the pulp system, so that the nanofiber accounts for 1–3 wt% of the total mass of the pulp, and stir at 500–1500 rpm for 10–30 min to obtain the pulp; S3: The pulp is spread onto the forming wire through a headbox and dewatered under vacuum to form a wet paper sheet, wherein the vacuum dewatering degree is -0.04 to -0.08 MPa; S4: The wet paper sheet is subjected to pressing and drying treatment, wherein the pressing pressure is 3–6 MPa and the drying temperature is 90–120℃ to obtain paper base; S5: Apply a coating liquid to the paper base surface and perform a drying treatment, wherein the nanofiber content in the coating liquid is 2–4 wt% and the coating amount is 2–6 g / m². S6: A thermoplastic material is laminated onto the surface of the coating layer by an extrusion coating process, wherein the extrusion temperature is 260–320°C, to form a composite material; S7: The composite material is die-cut, rolled and thermoformed to obtain a paper cup.

2. The manufacturing process for improving the strength of the cup body using nanofiber reinforcement technology according to claim 1, characterized in that: In step S1, the high-shear dispersion speed is 3000–8000 rpm, and the time is 5–20 min.

3. The manufacturing process for improving the strength of the cup body using nanofiber reinforcement technology according to claim 2, characterized in that: The average particle size of the nanofiber dispersion obtained in step S1 is less than 200 nm.

4. The manufacturing process for improving the strength of the cup body using nanofiber reinforcement technology according to claim 3, characterized in that: The nanofiber content in step S2 is 2–3 wt%.

5. The manufacturing process for improving the strength of the cup body using nanofiber reinforcement technology according to claim 4, characterized in that: In step S2, the stirring speed is 800–1200 rpm and the time is 15–25 min.

6. The manufacturing process for improving the strength of the cup body using nanofiber reinforcement technology according to claim 5, characterized in that: The coating liquid in step S5 further includes 3–6 wt% polyvinyl alcohol and 0.5–1 wt% layered inorganic material.

7. The manufacturing process for improving the strength of the cup body using nanofiber reinforcement technology according to claim 6, characterized in that: In step S5, the coating method is either blade coating or roller coating.

8. The manufacturing process for improving the strength of a cup body using nanofiber reinforcement technology according to claim 7, characterized in that: The thermoplastic material mentioned in step S6 is polyethylene with a thickness of 10–30 μm.

9. The manufacturing process for improving the strength of a cup body using nanofiber reinforcement technology according to claim 8, characterized in that: The nanofiber content in step S2 is 3 wt%, and the coating amount in step S5 is 4–6 g / m².

10. The manufacturing process for improving the strength of a cup body using nanofiber reinforcement technology according to claim 9, characterized in that: In step S3, the paper base basis weight is 180–200 g / m², and in step S2, the nanofiber content is 2 wt%.

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