Ammonium sulfite complex long-acting aldehyde reducing agent for artificial board and preparation method and application thereof

Abstract

The application discloses a kind of ammonium sulfite composite long-acting artificial board aldehyde-reducing agent and its preparation method and application, belong to artificial board auxiliary technical field.Product is ammonium sulfite as main aldehyde-removing component, compound ammonium bisulfite, modified urea, ethylene glycol and sodium citrate-potassium dihydrogen phosphate buffer system.The application solves the problem that single ammonium sulfite aldehyde-reducing agent is easy to oxidize and stratify, high-temperature failure, board late aldehyde return, damage glue strength, finished product pH is stable, storage period can reach more than 6 months, aldehyde-reducing efficiency is excellent, after adding, can stabilize the formaldehyde of artificial board to E0 grade, raw material cost is low, suitable for particle board, density board industrialization mass use.

Description

Technical Field

[0001] This invention belongs to the field of chemical additives for wood-based panels, specifically relating to a composite formaldehyde-reducing agent with ammonium sulfite as the main agent. It is suitable for capturing free formaldehyde and inhibiting formaldehyde in the later stage of urea-formaldehyde resin glued wood-based panels, and can be widely used in the manufacturing processes of particleboard, fiberboard, and plywood. Background Technology

[0002] Urea-formaldehyde resin adhesive is the most widely used adhesive in the engineered wood products industry due to its low cost and excellent bonding performance. However, urea-formaldehyde resin suffers from hydrolytic instability, resulting in the continuous release of free formaldehyde during the production and use of engineered wood products. Existing formaldehyde-reducing agents mainly have the following drawbacks: pure ammonium sulfite aqueous solution has the lowest cost, but it is prone to oxidation during storage, has unstable pH, fails quickly under high-temperature hot pressing, and causes severe formaldehyde reversion in the later stages; urea-based formaldehyde-reducing agents have weak initial formaldehyde reduction and cause long-term slow release of formaldehyde within the board; hydrazide-based formaldehyde-reducing agents have good effects but are extremely expensive, preventing widespread industrial application; conventional compound formaldehyde-reducing agents generally have problems such as affecting the internal bond strength of the board, causing bubbling during application, and delamination during storage. Currently, the industry lacks a low-cost, highly stable, heat-press-resistant, non-damaging, and long-lasting ammonium sulfite-based formaldehyde-reducing agent that inhibits formaldehyde formation. Summary of the Invention

[0003] Technical problems to be solved To address the shortcomings of traditional ammonium sulfite formaldehyde degrading agents, such as unstable storage, high-temperature failure, short formaldehyde degrading cycle, formaldehyde reversion in boards, and impact on bonding strength, we provide a low-cost, long-lasting, and stable composite formaldehyde degrading agent suitable for large-scale engineered wood production lines. Technical solution

[0004] A long-lasting formaldehyde-reducing agent for engineered wood products, made from the following raw materials in parts by weight: 45 parts ammonium sulfite, 7 parts ammonium bisulfite, 13 parts modified urea, 5 parts ethylene glycol, 2 parts sodium citrate, 1 part potassium dihydrogen phosphate, and 27 parts deionized water. The functions of each raw material are as follows: Ammonium sulfite acts as the main scavenger, capturing free formaldehyde at room temperature; ammonium bisulfite enhances the reactivity of high-temperature hot-pressing, overcoming high-temperature failure defects; modified urea seals the micropores of the adhesive layer, inhibiting the later hydrolysis and formaldehyde reversion of the board; ethylene glycol stabilizes the solution, prevents crystallization, protects the adhesive layer, and avoids bubbling and reduced strength of the board; sodium citrate and potassium dihydrogen phosphate form a buffer system, stabilizing the system pH and preventing oxidation and stratification of the raw materials.

[0005] The preparation method of this formaldehyde degrading agent is as follows: 1) At room temperature (20-30℃), add sodium citrate and potassium dihydrogen phosphate to deionized water, stir for 10 minutes until completely dissolved, and prepare a buffer solution; 2) Add ammonium sulfite and ammonium bisulfite in batches, and stir continuously for 30 minutes until completely dissolved; 3) Add modified urea and ethylene glycol, and stir at a constant temperature of 25-32℃ for 50 minutes; 4) Let stand at room temperature for 2 hours to mature, filter to remove trace impurities, and obtain a light yellow transparent liquid product.

[0006] Application method: When the urea-formaldehyde resin is cooled to 50-55℃ at the end of the glue-making process, add this formaldehyde reducing agent at 3.0% of the total mass of the urea-formaldehyde glue, stir for 15 minutes to mix evenly, and then apply the glue normally to produce artificial boards. Beneficial effects

[0007] 1. The product's pH remains stable between 7.5 and 8.0. It does not separate, oxidize, or lose efficacy after 6 months of sealed storage at room temperature. 2. It captures formaldehyde in two stages: room temperature and hot pressing, providing both immediate formaldehyde removal and long-term formaldehyde inhibition, preventing formaldehyde reversion in finished boards. 3. It does not damage the adhesive layer structure after addition, and there is no decrease in the internal bond strength or static bending strength of the board, nor any bubbling or mold growth. 4. The raw materials are readily available, and the production cost is low, far lower than that of hydrazide-based formaldehyde-reducing products. 5. It is highly versatile and compatible with various urea-formaldehyde glue production lines for particleboard, MDF, and plywood. Specific Implementation

[0008] Example 1: 45 parts ammonium sulfite, 7 parts ammonium bisulfite, 13 parts modified urea, 5 parts ethylene glycol, 2 parts sodium citrate, 1 part potassium dihydrogen phosphate, and 27 parts deionized water. The finished product has a pH of 7.7. Added at 3.0% of the glue weight, the formaldehyde release from the particleboard reaches E0 level, with an overall formaldehyde reduction rate ≥75%. The system remains stable and transparent after 6 months of storage. Example 2: 40 parts ammonium sulfite, 6 parts ammonium bisulfite, 15 parts modified urea, 4 parts ethylene glycol, 2 parts sodium citrate, 1 part potassium dihydrogen phosphate, and 32 parts deionized water; formaldehyde reduction rate 71.8%, and storage stability is satisfactory. Example 3: 50 parts ammonium sulfite, 9 parts ammonium bisulfite, 10 parts modified urea, 6 parts ethylene glycol, 2 parts sodium citrate, 0.5 parts potassium dihydrogen phosphate, and 22.5 parts deionized water; formaldehyde reduction rate 74.2%, and excellent high-temperature resistance. Comparative example: 45 parts ammonium sulfite, 55 parts pure water, no compound additives; with the same amount of additives, the formaldehyde rate decreased by only 41%, and after 15 days the liquid became turbid due to oxidation, resulting in severe formaldehyde reversion and deterioration of mechanical properties in the later stages of board production.

Claims

1. An ammonium sulfite complex long-acting aldehyde reducing agent for artificial boards, characterized in that, It is composed of the following raw materials in parts by weight: 45 parts ammonium sulfite, 7 parts ammonium bisulfite, 13 parts modified urea, 5 parts ethylene glycol, 2 parts sodium citrate, 1 part potassium dihydrogen phosphate, and 27 parts deionized water.

2. The ammonium sulfite composite long-acting formaldehyde-reducing agent for engineered wood products according to claim 1, characterized in that: The pH value of the finished product is controlled between 7.5 and 8.

0.

3. A method for preparing the ammonium sulfite composite long-lasting formaldehyde-reducing agent for engineered wood products according to claim 1, characterized in that, The process includes the following steps: (1) Dissolve sodium citrate and potassium dihydrogen phosphate in deionized water at 20-30℃ by stirring for 10 minutes; (2) Add ammonium sulfite and ammonium bisulfite in sequence and stir for 30 minutes until completely dissolved; (3) Add modified urea and ethylene glycol and keep warm at 25-32℃ for 50 minutes; (4) After aging at room temperature for 2 hours, filter to obtain the finished formaldehyde depressant.

4. The application of the formaldehyde-reducing agent according to claim 1 in urea-formaldehyde resin for engineered wood products, characterized in that: When the final temperature of urea-formaldehyde resin preparation is 50-55℃, add the formaldehyde-reducing agent at 3.0% of the total mass of urea-formaldehyde resin, stir for 15 minutes, and then apply it to the wood-based panels.