A strain responsive electrostatically dissipative wood fiber foam and method of making the same

Abstract

This invention discloses a strain-responsive electrostatic dissipative wood fiber foam and its preparation method. The preparation method includes the following steps: (1) mixing wood fiber and CNF thoroughly in an aqueous solution to obtain a mixed slurry. (2) mixing the mixed slurry from step (1) with ammonium polyphosphate (APP), sodium dodecyl sulfate (SDS), and carbon fiber (CF) at 3000 rpm for 10 min. (3) pouring the mixture from step (2) into a polytetrafluoroethylene circular hollow mold to filter out unstable moisture. (4) drying the wet foam obtained in step (3) in an oven to obtain a dry wood fiber foam. The wood fiber foam prepared in this application has excellent strain-responsive electrostatic dissipative properties and has broad application prospects in the fields of electronic product packaging and transportation.

Description

Technical Field

[0001] This invention belongs to the field of foaming materials technology, specifically relating to a wood fiber foam with strain response and electrostatic dissipation and its preparation method. Background Technology

[0002] Petroleum-based plastic foam is the most widely used cushioning material in the packaging and transportation of electronic products. However, its non-degradability and difficulty in recycling lead to large-scale accumulation and incineration after use, placing a heavy burden on the environment. Pulp fiber foam, with its natural, degradable, and recyclable properties, holds promise as a replacement for petroleum-based foam. However, the high insulation properties of wood fiber foam limit its application in electronic products. Therefore, it is necessary to develop a static dissipative wood fiber foam to replace commercially available petroleum-based plastic foam, which is crucial for social development and environmental health.

[0003] According to ANSI / ESDA standards, the volume resistivity of antistatic dissipative materials is 10. 4 -10 11 Ω-cm or surface resistivity of 10 5 -10 12 Ω / sq. Therefore, the packaging and transportation of high-precision products in the electronics industry (computers, televisions, communication and medical equipment, etc.) require higher antistatic properties of foam materials (<10). 9 (Ω-cm). Improving the conductivity of foam is mainly achieved by adding conductive materials (metal particles, carbon, graphene, and conductive polymers, etc.) to adjust the resistivity and meet various application scenarios. Carbon fiber (CF) has a fibrous and soft appearance, is easy to process, and possesses high temperature resistance and excellent conductivity, making it an excellent conductive additive. Furthermore, due to the chemical inertness of carbon fiber, physical blending during recycling facilitates the separation of lignocellulose and carbon fiber, making it more natural and environmentally friendly compared to plastic foam.

[0004] Existing commercially available antistatic foams have significant limitations, including: First, their durability is poor; prolonged use or aging under high temperatures greatly affects their antistatic performance. This aging can also generate microparticles, affecting the cleanliness of packaged items and significantly impacting the application of sensitive equipment. Second, due to the complex manufacturing process, their cost is high; and their protective performance during the transportation of large equipment is not as good as other materials such as rigid plastics. Additionally, some antistatic foam materials may have hygroscopic properties, which can affect their antistatic effect in humid environments and may cause short circuits or other malfunctions in electronic components such as circuit boards due to moisture. A major problem with widely used antistatic foams is their difficulty in recycling and degradation, increasing environmental pressure and burden. Different types of antistatic foams exhibit significant differences in static dissipation rates, and some products may not meet stringent industry standards or specific application requirements, potentially failing to effectively protect equipment at critical moments. In conclusion, although antistatic foams play an important role in many fields, their limitations and potential problems deserve attention. When selecting materials, it is essential to comprehensively consider various factors to ensure effective protection and an economical solution. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a wood fiber foam with strain response and electrostatic dissipation and its preparation method.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing electrostatic dissipation with strain response, comprising the following steps:

[0008] Mechanically treated wood fibers and nanocellulose (CNF) are thoroughly mixed. Ammonium polyphosphate (APP), carbon fiber (CF), and ammonium dodecyl sulfate (SDS) are then added and stirred at high speed in deionized water. The concentration of wood fiber is 2%, the amount of CNF is 6% of the oven-dry pulp mass, the amount of APP is 15% of the oven-dry pulp mass, the amount of SDS is [not specified], and the amount of CF is 0%-80% of the oven-dry pulp mass. The high-speed stirring speed is 3000 rpm, and the stirring time is 10 minutes.

[0009] A specific method for preparing a strain-responsive electrostatic dissipative wood fiber foam includes the following steps:

[0010] (1) The wood fiber and CNF are thoroughly mixed in an aqueous solution to obtain a mixed slurry;

[0011] (2) The mixed slurry from step (1) is stirred at high speed with ammonium polyphosphate (APP), sodium dodecyl sulfate (SDS) and carbon fiber (CF);

[0012] (3) Pour the mixture after stirring in step (2) into a polytetrafluoroethylene circular hollow mold to filter out unstable water;

[0013] (4) The wet foam obtained in step (3) is dried in an oven to obtain dry wood fiber foam, and the electrostatic dissipative wood fiber foam has excellent electrostatic dissipative strain response effect.

[0014] More preferably, in step (1), the wood fiber needs to be pretreated in advance by pulping the wood fiber with a PFI pulper for 6000-12000r.

[0015] More preferably, in step (1), the oven-dry weight of the wood fiber is 10-20g, and the oven-dry weight of CNF is 0.6-1.2g.

[0016] More preferably, in step (1), the CNF is Tempo-oxidized nanocellulose.

[0017] More preferably, in step (2), the length of the carbon fiber is 4-8 mm.

[0018] More preferably, in step (2), the high-speed stirring speed is 20,000-30,000 rpm; the time is 10-20 min.

[0019] More preferably, in step (2), the amount of APP is 15-25%, the amount of SDS is 0.4-0.8%, and the amount of CF is 3-8%, wherein the amount of each additive is relative to the oven-dry weight of the wood fiber.

[0020] More preferably, in step (4), the drying time is 8-12 hours and the drying temperature is 60-80°C.

[0021] The applicant discovered through experiments that the extremely low impedance of CF can effectively improve the electrical conductivity of wood fiber foam. Furthermore, the electrical conductivity of wood fiber foam changes due to deformation caused by external pressure, exhibiting a specific strain response. Therefore, the electrical conductivity can be adjusted based on the change caused by the amount of CF used to meet different environmental requirements.

[0022] In some embodiments, the mechanical treatment method is as follows: after the unbleached softwood pulp board is defrosted, the pulp is mechanically beaten using a PFI refiner. The beating speed is 9000 revolutions per minute, and the beating concentration is 10%.

[0023] In some embodiments, the CNF is Tempo-oxidized cellulose nanoparticles.

[0024] In some embodiments, the solvent is water.

[0025] In some embodiments, the length of the CF is 6 mm.

[0026] Secondly, the present invention provides a wood fiber foam material with strain response and electrostatic dissipation, prepared by the aforementioned preparation method.

[0027] Thirdly, the present invention provides a wood fiber foam material with strain response and electrostatic dissipation prepared by a one-pot wet process followed by drying.

[0028] In some embodiments, the mixed solution after stirring is poured into a polytetrafluoroethylene mold with a filter screen, and after the wet foam stabilizes, it is placed in an oven at 60°C for 12 hours to dry to obtain dried wood fiber foam.

[0029] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:

[0030] CF can effectively improve the electrostatic dissipation capacity of wood fiber foam. Furthermore, wood fiber foam exhibits excellent electrostatic dissipation, therefore, CF-modified wood fiber foam has broad application prospects in fields such as electronic product packaging and transportation. Attached Figure Description

[0031] Figure 1 This is a graph showing the change in volumetric resistance of foam during compression. Detailed Implementation

[0032] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0033] A method for preparing a strain-responsive electrostatic dissipative wood fiber foam includes the following steps:

[0034] (1) The wood fiber and CNF are thoroughly mixed in an aqueous solution to obtain a mixed slurry;

[0035] (2) The mixed slurry from step (1) is stirred at high speed with ammonium polyphosphate (APP), sodium dodecyl sulfate (SDS) and carbon fiber (CF);

[0036] (3) Pour the mixture after stirring in step (2) into a polytetrafluoroethylene circular hollow mold to filter out unstable water;

[0037] (4) The wet foam obtained in step (3) is dried in an oven to obtain dry wood fiber foam.

[0038] In the above method, in step (1), the wood fiber needs to be pretreated in advance by pulping the wood fiber with a PFI pulper for 6000-12000r, preferably 9000r.

[0039] In the above method, in step (1), the oven-dry weight of the wood fiber is 10-20g, preferably 10g, and the oven-dry weight of CNF is 0.6-1.2g, preferably 0.6g.

[0040] In the above method, in step (1), the CNF is Tempo-oxidized nanocellulose.

[0041] In the above method, in step (2), the length of the carbon fiber is 4-8 mm.

[0042] In the above method, in step (2), the high-speed stirring speed is 20000-30000 rpm; the time is 10-20 min.

[0043] In the above method, in step (2), the amount of APP is 15-25%, the amount of SDS is 0.4-0.8%, and the amount of CF is 3-8%, wherein the amount of each additive is relative to the dry weight of the wood fiber.

[0044] In the above method, in step (4), the drying time is 8-12 hours and the drying temperature is 60-80℃.

[0045] The electrostatic dissipative wood fiber foam of the present invention has excellent electrostatic dissipative strain response.

[0046] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0047] Example 1

[0048] (1) Weigh 10g of oven-dry pulp (after pulping) and mix it thoroughly with 6% CNF in an aqueous solution.

[0049] (2) The mixed solution from step (1) was stirred at high speed for 10 minutes at 3000 rpm with 15% APP, 4% SDS and 0% CF.

[0050] (3) Pour the mixture after stirring in step (2) into a polytetrafluoroethylene circular hollow mold to filter out unstable water.

[0051] (4) The wet foam obtained in step (3) is dried in an oven at 60°C for 12 hours to obtain dry wood fiber foam.

[0052] Example 2

[0053] (1) Weigh 10g of oven-dry pulp (after pulping) and mix it thoroughly with 6% CNF in an aqueous solution.

[0054] (2) The mixed solution from step (1) was stirred at high speed for 10 minutes at 3000 rpm with 15% APP, 4% SDS and 30% CF.

[0055] (3) Pour the mixture after stirring in step (2) into a polytetrafluoroethylene circular hollow mold to filter out unstable water.

[0056] (4) The wet foam obtained in step (3) is dried in an oven at 60°C for 12 hours to obtain dried wood fiber foam.

[0057] Example 3

[0058] (1) Weigh 10g of oven-dry pulp (after pulping) and mix it thoroughly with 6% CNF in an aqueous solution.

[0059] (2) The mixed solution from step (1) was stirred at high speed for 10 minutes at 3000 rpm with 15% APP, 4% SDS and 40% CF.

[0060] (3) Pour the mixture after stirring in step (2) into a polytetrafluoroethylene circular hollow mold to filter out unstable water.

[0061] (4) The wet foam obtained in step (3) is dried in an oven at 60°C for 12 hours to obtain dry wood fiber foam.

[0062] Example 4

[0063] (1) Weigh 10g of oven-dry pulp (after pulping) and mix it thoroughly with 6% CNF in an aqueous solution.

[0064] (2) The mixed solution from step (1) was stirred at high speed for 10 minutes at 3000 rpm with 15% APP, 4% SDS and 50% CF.

[0065] (3) Pour the mixture after stirring in step (2) into a polytetrafluoroethylene circular hollow mold to filter out unstable water.

[0066] (4) The wet foam obtained in step (3) is dried in an oven at 60°C for 12 hours to obtain dry wood fiber foam.

[0067] Example 5

[0068] (1) Weigh 10g of oven-dry pulp (after pulping) and mix it thoroughly with 6% CNF in an aqueous solution.

[0069] (2) The mixed solution from step (1) was stirred at high speed for 10 minutes at 3000 rpm with 15% APP, 4% SDS and 60% CF.

[0070] (3) Pour the mixture after stirring in step (2) into a polytetrafluoroethylene circular hollow mold to filter out unstable water.

[0071] (4) The wet foam obtained in step (3) is dried in an oven at 60°C for 12 hours to obtain dry wood fiber foam.

[0072] Example 6

[0073] (1) Weigh 10g of oven-dry pulp (after pulping) and mix it thoroughly with 6% CNF in an aqueous solution.

[0074] (2) The mixed solution from step (1) was stirred at high speed for 10 minutes at 3000 rpm with 15% APP, 4% SDS and 70% CF.

[0075] (3) Pour the mixture after stirring in step (2) into a polytetrafluoroethylene circular hollow mold to filter out unstable water.

[0076] (4) The wet foam obtained in step (3) is dried in an oven at 60°C for 12 hours to obtain dry wood fiber foam.

[0077] Example 7

[0078] (1) Weigh 10g of oven-dry pulp (after pulping) and mix it thoroughly with 6% CNF in an aqueous solution.

[0079] (2) The mixed solution from step (1) was stirred at high speed for 10 minutes at 3000 rpm with 15% APP, 4% SDS and 80% CF.

[0080] (3) Pour the mixture after stirring in step (2) into a polytetrafluoroethylene circular hollow mold to filter out unstable water.

[0081] (4) The wet foam obtained in step (3) is dried in an oven at 60°C for 12 hours to obtain dry wood fiber foam.

[0082] Example 8

[0083] Conductivity tests were performed on the foam materials prepared in Examples 1-7. Figure 1 It can be seen that the wood fiber foams prepared in Examples 1-7 of this application have an uncompressed volume resistivity of 7.75*10. 9Ω~4.42*10 8 Ω. The volumetric resistance of pulp foam varies greatly with increasing carbon fiber content; adding only 8% carbon fiber increases its volumetric resistance from 10. 9 Ω drops to 10 4 Ω. Example 6: The volume of the foam undergoes two processes during compression. First, the resistance value decreases from 3.99 * 10⁻⁶. 6 Ω (strain at 0.00%) changes rapidly to 5.64*10 5 Ω (strain of 9.21%), strain of approximately 10%, shows the inflection point between antistatic and conductivity levels (10). 6 Ω). In the second stage, the volume resistivity of the wood fiber foam changes slowly, with values ​​around 10 Ω. 4 -10 5 Between Ω. Wood fiber foam is at an antistatic level under no-pressure conditions, thus reducing the influence of external static charges. However, 10% deformation of pulp foam can be easily achieved by the pressure generated during product transportation. When the deformation of pulp foam exceeds 10%, the change in conductivity is small, indicating that the wood fiber foam prepared by this method has excellent electrostatic dissipation strain response.

[0084] In summary, the wood fiber foam prepared in this application has excellent electrostatic dissipation properties due to strain effect, and has broad application prospects in fields such as electronic product packaging and transportation.

[0085] It should be understood that the above detailed description of the technical solutions of the present invention with reference to optimized embodiments is illustrative and not restrictive. It should not be considered that the specific implementation of the present invention is limited to this. For those skilled in the art, any modifications to the technical solutions described in the embodiments or equivalent substitutions of some technical features without departing from the concept of the present invention should be considered as falling within the scope of patent protection defined by the claims submitted by the present invention.

[0086] The above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a strain-responsive electrostatic dissipative wood fiber foam, characterized in that, Includes the following steps: (1) The wood fiber and CNF are thoroughly mixed in an aqueous solution to obtain a mixed pulp; the wood fiber needs to be pretreated in advance by beating the wood fiber with a PFI refiner for 6000-12000r; the oven-dry weight of the wood fiber is 10-20g and the oven-dry weight of CNF is 0.6-1.2g; the CNF is Tempo oxidized nanocellulose; (2) The mixed slurry from step (1) is stirred at high speed with ammonium polyphosphate (APP), sodium dodecyl sulfate (SDS), and carbon fiber (CF); the high-speed stirring speed is 20,000-30,000 rpm; the stirring time is 10-20 min; the amount of APP is 15-25%, the amount of SDS is 0.4-0.8%, and the amount of CF is 3-8%, wherein the amount of each additive is relative to the oven-dry weight of the wood fiber; the length of the carbon fiber is 4-8 mm; (3) Pour the mixture after stirring in step (2) into a polytetrafluoroethylene circular hollow mold to filter out unstable water; (4) The wet foam obtained in step (3) is dried in an oven to obtain dry wood fiber foam.

2. The method for preparing a strain-responsive electrostatic dissipative wood fiber foam according to claim 1, characterized in that, In step (4), the drying time is 8-12 hours and the drying temperature is 60-80℃.

3. The strain-responsive electrostatic dissipative wood fiber foam prepared by the preparation method according to any one of claims 1 to 2.

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