Method for preparing plant fiber-based foaming material

Abstract

The invention discloses a preparation method of a plant fiber-based foaming material through high-concentration baking foaming, which comprises the following steps: firstly, carrying out high-concentration sufficient dispersion on paper pulp fibers in a solid content range of 10-30% under the action of a dispersing agent and high-speed shearing; and then adding related auxiliaries into the fiber dispersion material, uniformly mixing, and performing high-speed shearing to obtain a fiber pre-foaming paste material, injecting the prepared fiber pre-foaming paste material into a mold, and directly and continuously performing foaming molding and drying under a hot-pressing condition to obtain the fiber foaming material. According to the method, the high-concentration paper pulp fiber can be directly baked and foamed in the mold without adding a water filtering process, the drying efficiency of the fiber foaming material is effectively improved, and the forming and drying choices for preparing the fiber foaming material from the fiber dispersion suspension are expanded.

Description

Technical Field

[0001] The invention relates to the field of preparation of plant fiber foaming materials, and in particular to a method for preparing foaming materials by high-concentration baking and foaming of plant fibers. Background Art

[0002] Cellulose-based foam materials are green and environmentally friendly materials made from plant fibers, usually called pulp fibers, with adhesives, foaming agents, cross-linking agents and other additives added through dehydration, foaming, molding, drying and other steps. Because the surface of pulp fibers contains abundant hydroxyl groups, they have a strong tendency to internally bind after re-drying. At higher concentrations, it is difficult to obtain full dispersion even with sufficient external force. Only when the concentration is below 2% can it be well dispersed through a deflaker or a pulper. For this reason, when using pulp fibers as raw materials to prepare foaming materials, a low-concentration fiber deflaking process is generally included. The fully dispersed pulp fibers are then fully mixed with adhesives such as starch and polyvinyl alcohol and foaming agents at a certain solid content to form a foamed or to-be-foamed mixture to obtain foamed products.

[0003] In the method for forming a fiber product provided in CN105829414A, the preparation process of the fiber foam includes molding, dehydration and drying steps. The method adopts a foaming method in which a surfactant is added to an aqueous suspension, mechanical foaming is performed, and then dehydration and drying are performed to obtain a fiber foam material. In its embodiment, it is clearly proposed to include a step of extracting water from the fiber foam.

[0004] In order to obtain a foam with controllable pore size and distribution, the fiber must be fully dispersed when preparing the foam material using plant fiber as raw material, which greatly limits the options for molding and drying when the fiber foam raw material liquid concentration is low. It is difficult for fiber foams with high water content to adapt to the method of direct molding, foaming and drying in the mold to prepare fiber foam products. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing high-concentration baking and foaming of plant fibers. The technical feature of the method is that a fiber dispersant is added under the action of high-speed shearing to achieve high-concentration and full dispersion of the plant fibers, an appropriate amount of auxiliary agent is added to the obtained fiber dispersion, and the mixture is mixed evenly and then subjected to high-speed shearing to obtain a pre-foamed paste, and the pre-foamed paste is injected into a mold and continued to be hot-pressed, foamed, dried and demolded to obtain a fiber foam material.

[0006] The fiber dispersant is not the polyethylene oxide dispersant and partially hydrolyzed polyacrylamide dispersant commonly used in the papermaking process, but a colloidal dispersant that can give the fiber surface a uniform negative charge. This colloidal dispersant has sufficient high shear resistance, which can give the fiber surface sufficient negative charge when the pulp fiber is subjected to high shear treatment at high concentration, thereby giving the fiber surface sufficient lubrication, thereby avoiding the re-flocculation and agglomeration of the fiber and achieving full dispersion of the fiber at high concentration. The pulp fiber dispersion concentration is 5-40%, and the preferred concentration is 10-25%. The linear speed of the high-speed shear stirring is 2-10 m / s, and the preferred linear speed is 3-7 m / s. The dispersant is a colloidal dispersant, and the preferred colloidal dispersant is guar gum, sodium alginate and sodium carboxymethyl cellulose. The amount of the dispersant is 1-5% to the absolute dry pulp fiber, and the preferred amount is 2-3.5%. The high-speed shear dispersion time is 10-30 minutes, and the preferred dispersion time is 15-25 minutes. The plant fibers include coniferous wood pulp, broadleaf wood pulp, non-wood plant fibers, mixtures thereof or mixtures thereof with regenerated cellulose fibers.

[0007] The preparation process of fiber pre-foaming paste includes: (1) adding adhesive, surfactant, foaming agent, nucleating agent and release agent to fiber dispersion material and fully mixing to form fiber paste; (2) preparing pre-foaming paste with a foaming rate of 100-200% under the action of high-speed shearing of the fully mixed paste. The adhesive includes a mixture of starch, polyvinyl alcohol and latex. The surfactant is sodium octadecyl sulfonate. The foaming agent is an inorganic foaming agent, and the inorganic foaming agent includes sodium bicarbonate, ammonium carbonate and ammonium bicarbonate. The nucleating agent includes inorganic fillers such as kaolin, calcium carbonate and talcum powder. The release agent includes stearic acid and magnesium stearate.

[0008] The pre-foamed paste is injected into a mold and foamed and dried under the condition of a hot pressing temperature of 180 to 250° C. and a time of 180 to 360 seconds.

[0009] The present invention has at least the following beneficial effects: it realizes the preparation of fiber foam material by baking and foaming high-concentration pulp fibers in a mold, and obtains a foam material with uniform pore distribution and controllable size by combining pre-foaming and foaming in a mold. It effectively improves the drying efficiency of the fiber foam material and expands the molding and drying options for preparing the fiber foam material from the fiber dispersion suspension. DETAILED DESCRIPTION

[0010] The present invention is further described below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0011] Example 1

[0012] Put the 30% coniferous pulp fiber raw material in a high-speed disperser, control the shear line speed of the disperser to 4.5m / s, add 3% guar gum to the coniferous pulp fiber raw material during the high-speed shear dispersion process, and continue to disperse at high speed for 25 minutes under this condition after the addition is completed to obtain a uniformly dispersed high-concentration fiber dispersion. Add 34% cassava starch, 15% polyvinyl alcohol, 1% sodium octadecyl sulfonate, 1% stearic acid, 1% kaolin and 1% sodium bicarbonate to the fiber dispersion in sequence, mix evenly, and then obtain a pre-foamed paste with a foaming rate of 150% through high-speed shearing. Inject the foamed paste into a mold, heat press it in a hot press at 180°C for 3 minutes, then cool it for 2 minutes and demould it to obtain a fiber foam product.

[0013] Example 2

[0014] Place a 25% coniferous pulp fiber raw material in a high-speed disperser, control the shear line speed of the disperser to 4.5m / s, add 3% guar gum to the coniferous pulp fiber raw material during the high-speed shear dispersion process, and continue to disperse at high speed for 20 minutes under this condition to obtain a uniformly dispersed high-concentration fiber dispersion. Add 40% cassava starch, 10% polyvinyl alcohol, 1% sodium octadecyl sulfonate, 1% stearic acid, 1% kaolin and 2% sodium bicarbonate to the fiber dispersion in sequence, mix evenly, and then obtain a pre-foamed paste with a foaming rate of 120% through high-speed shearing. Inject the foamed paste into a mold, heat press it in a hot press at 210°C for 2 minutes, then cool it for 2 minutes and demould it to obtain a fiber foam product.

[0015] Example 3

[0016] Place a 20% coniferous pulp fiber raw material in a high-speed disperser, control the shear line speed of the disperser to 4.0 m / s, add 2% guar gum to the coniferous pulp fiber raw material during the high-speed shear dispersion process, and continue to disperse at high speed for 20 minutes under this condition after the addition is completed to obtain a uniformly dispersed high-concentration fiber dispersion. Add 25% cassava starch, 5% polyvinyl alcohol, 2% sodium octadecyl sulfonate, 1% stearic acid, 1% kaolin and 1% sodium bicarbonate to the fiber dispersion in sequence, mix evenly, and then obtain a pre-foamed paste with a foaming rate of 180% through high-speed shearing. Inject the foamed paste into a mold, heat press it in a hot press at 210°C for 2 minutes, then cool it for 2 minutes and demould it to obtain a fiber foam product.

[0017] Table 1

[0018]

Claims

1. A method for preparing a plant fiber-based foam material, characterized in that A fiber dispersant is added under high-speed shearing to fully disperse the plant fiber at high concentration, and a proper amount of auxiliary agent is added to the obtained fiber dispersion and mixed evenly, and then subjected to high-speed shearing to obtain a pre-foamed paste. Finally, the pre-foamed paste is injected into a mold and continued to be hot-pressed, foamed, dried and demolded to obtain a fiber foam material.

2. The method for preparing a plant fiber-based foam material according to claim 1, characterized in that The preparation process of fiber pre-foamed paste includes: (1) adding adhesive, surfactant, foaming agent, nucleating agent and release agent to fiber dispersion material and fully mixing to form fiber paste; (2) preparing pre-foamed paste with a foaming rate of 100-200% under the action of high-speed shearing of the fully mixed paste.

3. The method for preparing a plant fiber-based foam material according to claim 2, characterized in that The adhesive includes a mixture of starch, polyvinyl alcohol and latex, the surfactant is sodium octadecyl sulfonate, the foaming agent is an inorganic foaming agent, and the inorganic foaming agent includes sodium bicarbonate, ammonium carbonate and ammonium bicarbonate, the nucleating agent includes inorganic fillers such as porcelain clay, calcium carbonate and talcum powder, and the release agent includes stearic acid and magnesium stearate.

4. The method for preparing a plant fiber-based foam material according to claim 1, characterized in that The pre-foamed paste is directly injected into a mold for hot pressing foaming molding, and the hot pressing temperature is 180-250° C. and the time is 180-360 seconds.

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