A low-formaldehyde high-density fiberboard and its preparation method

Abstract

This invention relates to the field of fiberboard technology, and proposes a low-formaldehyde high-density fiberboard and its preparation method. The low-formaldehyde high-density fiberboard comprises a modifier-modified fiber and an adhesive; the modifier includes polyvinyl alcohol; the preparation method of the low-formaldehyde high-density fiberboard includes the following steps: spraying the adhesive onto the modifier-modified fiber, laying it up, pre-pressing, and hot-pressing to obtain the low-formaldehyde high-density fiberboard. This technical solution solves the problems of high formaldehyde content or low strength in existing high-density fiberboard.

Description

Technical Field

[0001] This invention relates to the field of fiberboard technology, specifically to a low-formaldehyde high-density fiberboard and its preparation method. Background Technology

[0002] High-density fiberboard (HDF) is a type of board made from wood or other plant materials, which are processed into fibers, bonded with adhesives, and then pressed under heat and pressure. The adhesives used are 90% urea-formaldehyde resin and its modified products, which release formaldehyde and are often a major source of formaldehyde pollution in indoor air.

[0003] The main sources of formaldehyde in high-density fiberboard are: unreacted free formaldehyde during the resin production process; and unstable groups such as ether bonds and hemiacetals that may be formed during the synthesis of formaldehyde and urea, which will release formaldehyde during the hot pressing process.

[0004] Currently, the main methods to reduce the formaldehyde content of fiberboard are: ① using low molar ratio modified urea-formaldehyde resin adhesive; ② adding formaldehyde scavengers, but both of these methods result in low product strength. Summary of the Invention

[0005] This invention proposes a low-formaldehyde high-density fiberboard and its preparation method, which solves the problems of high formaldehyde content or low strength in related technologies.

[0006] The technical solution of the present invention is as follows:

[0007] A low-formaldehyde high-density fiberboard, comprising a modifier, modified fibers, and an adhesive;

[0008] The modifier includes polyvinyl alcohol.

[0009] As a further technical solution, the mass ratio of the modified fiber and the adhesive is 10:1~2.

[0010] As a further technical solution, the preparation method of the modifier-modified fiber includes the following steps: mixing the fiber with a polyvinyl alcohol aqueous solution evenly and drying it to obtain the modifier-modified fiber.

[0011] As a further technical solution, the mass concentration of the polyvinyl alcohol aqueous solution is 2-5%.

[0012] As a further technical solution, the mass ratio of the fiber to the polyvinyl alcohol aqueous solution is 1:20~40.

[0013] As a further technical solution, the modifier also includes styrene oxide.

[0014] This invention uses polyvinyl alcohol and styrene oxide to modify fibers. Adding styrene oxide can not only prevent polyvinyl alcohol from falling off the fiber surface in polyvinyl alcohol modified fibers, but also improve the strength of the fiberboard.

[0015] As a further technical solution, the method for preparing the modified fiber includes the following steps:

[0016] S1. Mix polyvinyl alcohol aqueous solution, methanol and styrene oxide evenly to obtain a mixture;

[0017] S2. Mix the fiber with the mixture evenly and dry to obtain modifier-modified fiber.

[0018] As a further technical solution, the mass concentration of the polyvinyl alcohol aqueous solution is 2-5%;

[0019] The mass ratio of the polyvinyl alcohol aqueous solution, methanol, and styrene oxide is 30:10:1~5.

[0020] As a further technical solution, the adhesive is composed of urea-formaldehyde resin and ammonium chloride in a mass ratio of 100:0.5~1.5.

[0021] This invention also proposes a method for preparing low-formaldehyde high-density fiberboard, comprising the following steps: spraying adhesive onto modified fibers with modifier, laying, pre-pressing, and hot-pressing to obtain low-formaldehyde high-density fiberboard.

[0022] The working principle and beneficial effects of this invention are as follows:

[0023] This invention utilizes polyvinyl alcohol-modified fibers to reduce the formaldehyde content of fiberboard, providing a low-formaldehyde high-density fiberboard. This is primarily because, during the hot-pressing process of the fiberboard, the polyvinyl alcohol adhering to the fiber surface can react with free formaldehyde, effectively absorbing it. Simultaneously, the resulting solids can fill the interior of the fiberboard, thereby reducing its formaldehyde content and increasing its strength. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] In the following examples and comparative examples, the fiber was wood fiber with a moisture content of 5% and a length of 20 mm, purchased from Shijiazhuang Tengbang Mineral Products Co., Ltd.; the polyvinyl alcohol was polyvinyl alcohol 2488; and the urea-formaldehyde resin was urea-formaldehyde resin 563#, with a solid content of 60-65%, a pH value of 7-8, and a viscosity of 60-100 mPa·s, purchased from Jining Hongming Chemical Reagent Co., Ltd.

[0026] Example 1

[0027] S1. Preparation of polyvinyl alcohol modified fiber: Mix 1 kg of fiber with 30 kg of 3 wt% polyvinyl alcohol aqueous solution evenly, separate the fiber, and dry to obtain polyvinyl alcohol modified fiber;

[0028] S2. Preparation of adhesive: Mix urea-formaldehyde resin and ammonium chloride at a mass ratio of 100:1 and stir evenly to obtain the adhesive;

[0029] S3. Preparation of fiberboard: 150g of adhesive is evenly sprayed onto 1kg of polyvinyl alcohol modified fiber, and the fiberboard is laid out using a laying machine to form a blank. After the blank is pre-pressed at room temperature, it is hot-pressed at 150℃ and 5MPa for 15min to obtain low formaldehyde high-density fiberboard.

[0030] Example 2

[0031] S1. Preparation of polyvinyl alcohol modified fiber: Mix 1 kg of fiber with 40 kg of 2 wt% polyvinyl alcohol aqueous solution evenly, separate the fiber, and dry to obtain polyvinyl alcohol modified fiber;

[0032] S2. Preparation of adhesive: Mix urea-formaldehyde resin and ammonium chloride at a mass ratio of 100:0.5 and stir evenly to obtain the adhesive;

[0033] S3. Preparation of fiberboard: 100g of adhesive is evenly sprayed onto 1kg of polyvinyl alcohol modified fiber, and the fiberboard is laid out using a laying machine to form a blank. After the blank is pre-pressed at room temperature, it is hot-pressed at 150℃ and 5MPa for 15 minutes to obtain a low-formaldehyde high-density fiberboard.

[0034] Example 3

[0035] S1. Preparation of polyvinyl alcohol modified fiber: Mix 1 kg of fiber with 20 kg of 5 wt% polyvinyl alcohol aqueous solution evenly, separate the fiber, and dry to obtain polyvinyl alcohol modified fiber;

[0036] S2. Preparation of adhesive: Mix urea-formaldehyde resin and ammonium chloride at a mass ratio of 100:1.5 and stir evenly to obtain the adhesive;

[0037] S3. Preparation of fiberboard: 200g of adhesive is evenly sprayed onto 1kg of polyvinyl alcohol modified fiber, and the fiberboard is laid out using a laying machine to form a blank. After the blank is pre-pressed at room temperature, it is hot-pressed at 150℃ and 5MPa for 15min to obtain low formaldehyde high-density fiberboard.

[0038] Example 4

[0039] S1. Preparation of polyvinyl alcohol modified fiber: Mix 1 kg of fiber with 40 kg of 1 wt% polyvinyl alcohol aqueous solution evenly, separate the fiber, and dry to obtain polyvinyl alcohol modified fiber;

[0040] S2. Preparation of adhesive: Mix urea-formaldehyde resin and ammonium chloride at a mass ratio of 100:0.5 and stir evenly to obtain the adhesive;

[0041] S3. Preparation of fiberboard: 100g of adhesive is evenly sprayed onto 1kg of polyvinyl alcohol modified fiber, and the fiberboard is laid out using a laying machine to form a blank. After the blank is pre-pressed at room temperature, it is hot-pressed at 150℃ and 5MPa for 15 minutes to obtain a low-formaldehyde high-density fiberboard.

[0042] Example 5

[0043] S1. Preparation of polyvinyl alcohol modified fiber: Mix 1 kg of fiber with 40 kg of 7 wt% polyvinyl alcohol aqueous solution evenly, separate the fiber, and dry to obtain polyvinyl alcohol modified fiber;

[0044] S2. Preparation of adhesive: Mix urea-formaldehyde resin and ammonium chloride at a mass ratio of 100:0.5 and stir evenly to obtain the adhesive;

[0045] S3. Preparation of fiberboard: 100g of adhesive is evenly sprayed onto 1kg of polyvinyl alcohol modified fiber, and the fiberboard is laid out using a laying machine to form a blank. After the blank is pre-pressed at room temperature, it is hot-pressed at 150℃ and 5MPa for 15 minutes to obtain a low-formaldehyde high-density fiberboard.

[0046] Example 6

[0047] S1. Preparation of modified fiber: Mix 30 kg of 3 wt% polyvinyl alcohol aqueous solution with 10 kg of methanol and 3 kg of styrene oxide evenly, add 1 kg of fiber and continue mixing, separate the fiber, dry, and obtain modified fiber.

[0048] S2. Preparation of adhesive: Mix urea-formaldehyde resin and ammonium chloride at a mass ratio of 100:1 and stir evenly to obtain the adhesive;

[0049] S3. Preparation of fiberboard: Spray 150g of adhesive evenly onto 1kg of modified fiber with modifier, lay it up with a laying machine to form a board blank, pre-press the board blank at room temperature, and then hot-press it at 150℃ and 5MPa for 15min to obtain low formaldehyde high-density fiberboard.

[0050] Example 7

[0051] S1. Preparation of modified fiber: Mix 30 kg of 3 wt% polyvinyl alcohol aqueous solution with 10 kg of methanol and 1 kg of styrene oxide evenly, then add 1 kg of fiber and continue mixing. Separate the fiber and dry it to obtain modified fiber.

[0052] S2. Preparation of adhesive: Mix urea-formaldehyde resin and ammonium chloride at a mass ratio of 100:1 and stir evenly to obtain the adhesive;

[0053] S3. Preparation of fiberboard: Spray 150g of adhesive evenly onto 1kg of modified fiber with modifier, lay it up with a laying machine to form a board blank, pre-press the board blank at room temperature, and then hot-press it at 150℃ and 5MPa for 15min to obtain low formaldehyde high-density fiberboard.

[0054] Example 8

[0055] S1. Preparation of modified fiber: Mix 30 kg of 3 wt% polyvinyl alcohol aqueous solution with 10 kg of methanol and 5 kg of styrene oxide evenly, add 1 kg of fiber and continue mixing, separate the fiber, dry, and obtain modified fiber.

[0056] S2. Preparation of adhesive: Mix urea-formaldehyde resin and ammonium chloride at a mass ratio of 100:1 and stir evenly to obtain the adhesive;

[0057] S3. Preparation of fiberboard: Spray 150g of adhesive evenly onto 1kg of modified fiber with modifier, lay it up with a laying machine to form a board blank, pre-press the board blank at room temperature, and then hot-press it at 150℃ and 5MPa for 15min to obtain low formaldehyde high-density fiberboard.

[0058] Comparative Example 1

[0059] S1. Preparation of adhesive: Mix urea-formaldehyde resin and ammonium chloride at a mass ratio of 100:1, stir evenly to obtain the adhesive;

[0060] S2. Preparation of fiberboard: Spray 150g of adhesive evenly onto 1kg of fiber, lay it up with a laying machine to form a board blank, pre-press the board blank at room temperature, and then hot-press it at 150℃ and 5MPa for 15min to obtain low formaldehyde high-density fiberboard.

[0061] The low-formaldehyde high-density fiberboard obtained in Examples 1-8 and Comparative Example 1 were tested for formaldehyde content, static bending strength (three-point bending method) and internal bonding strength according to the methods in GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels". The test results are recorded in Table 1.

[0062] Table 1 Formaldehyde content, static bending strength and internal bonding strength of fiberboard

[0063]

[0064] As can be seen from Table 1, the formaldehyde content of the low-formaldehyde high-density fiberboard provided by the present invention is below 6.7 mg / 100g, the static bending strength is above 36.3 MPa, and the internal bonding strength is above 1.02 MPa. It has both low formaldehyde content and high strength.

[0065] Compared with Comparative Example 1, Example 1 used polyvinyl alcohol modified fibers, while Comparative Example 1 used unmodified fibers. The formaldehyde content of the fiberboard obtained in Example 1 was lower than that in Comparative Example 1, while the static bending strength and internal bonding strength were higher than those in Comparative Example 1. This indicates that using polyvinyl alcohol modified fibers can significantly reduce the formaldehyde content of fiberboard and improve its static bending strength and internal bonding strength.

[0066] Compared with Examples 6-8, the formaldehyde content of the fiberboard obtained in Example 1 was higher than that in Examples 6-8, while the formaldehyde content of the fiberboard obtained in Example 1 was lower than that in Examples 6-8, and the static bending strength and internal bonding strength were lower than those in Examples 6-8. This indicates that using the co-modified fiberboard of polyvinyl alcohol and styrene oxide can further reduce the formaldehyde content of the fiberboard and significantly improve the static bending strength and internal bonding strength of the fiberboard.

[0067] The low-formaldehyde high-density fiberboard obtained in Examples 1 and 6-8 was tested for density according to the method in GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels". The test results are recorded in Table 2.

[0068] Table 2 Density of Fiberboard

[0069]

[0070] As can be seen from Table 2, the density of the fiberboard provided in Examples 1 and 6-8 of the present invention is 0.86 g / cm³. 3 The above belong to high-density fiberboard.

[0071] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-formaldehyde high-density fiberboard, characterized in that, Including modifiers for modified fibers and adhesives; The modifiers include polyvinyl alcohol and styrene oxide; The method for preparing the modified fiber by the modifier includes the following steps: S1. Mix polyvinyl alcohol aqueous solution, methanol and styrene oxide evenly to obtain a mixture; S2. Mix the fiber with the mixture evenly and dry to obtain modified fiber; The mass concentration of the polyvinyl alcohol aqueous solution is 2-5%; The mass ratio of the polyvinyl alcohol aqueous solution, methanol, and styrene oxide is 30:10:1~5; The fiber is wood fiber; the mass ratio of the fiber to the polyvinyl alcohol aqueous solution is 1:20~40; the adhesive is composed of urea-formaldehyde resin and ammonium chloride in a mass ratio of 100:0.5~1.

5.

2. The method for preparing a low-formaldehyde high-density fiberboard according to claim 1, characterized in that, Includes the following steps: Adhesive is sprayed onto modified fibers, then laid, pre-pressed, and hot-pressed to obtain low-formaldehyde high-density fiberboard.

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