Aldehyde reducing technics for artificial boards

Abstract

An artificial plate aldehyde reducing process firstly carries out the vacuum disposal by arranging the artificial plate into a sealing container, releases the ammonia gas into the sealing container and infiltrated into the interior of the artificial plate, and finally completely reclaims the residual ammonia gas. The vacuum ranges from minus 0.0085 MPa to minus 0.0095 MPa and is kept for 20 min through 40 min when the artificial plate is disposed in the vacuum. The pressure ranges from 0.05 MPa to 0.1 MPa and is kept form 5 min through 20 min when the ammonia gas is released into the sealing container. The ammonia gas is adsorbed into the artificial plate and is reacted with the dissociated aldehyde residual in the plate material to generate the compound hexamethylene tetramine (CH2)6N4 with stable performance. The invention has the beneficial effects of reaching the aldehyde reducing object by pumping out the dissociated aldehyde in the artificial plate by the vacuum method in the normal temperature and causing the ammonia gas adsorbed by the plate, suitable for the artificial plate with all types and thickness, good aldehyde reducing effect, small manufacture difficulty, low cost, and easy operation, large disposal quantity, low ammonia consumption and low cost of aldehyde reduction when the aldehyde reduction disposal for the artificial plate is carried out.

Description

technical field [0001] The invention relates to a free formaldehyde reduction process for wood-based panels such as medium-density fiberboard, high-density fiberboard, particleboard, plywood and blockboard, etc., which use urea-formaldehyde resin adhesives, especially for the reduction of formaldehyde in wood-based panels whose formaldehyde emission exceeds the standard. Aldehyde process. Background technique [0002] There are generally four ways to reduce formaldehyde emission from wood-based panels: [0003] 1. Use urea-formaldehyde resin with high urea-formaldehyde molar ratio. When synthesizing urea-formaldehyde resin, appropriately increasing the molar ratio of urea: formaldehyde in the raw material can reduce the free aldehyde content of the resin-based wood-based panel to a certain extent. [0004] 2. Use formaldehyde scavenger. Under certain conditions, these capture agents can chemically react with formaldehyde to generate another stable new substance, or absorb...

AI Technical Summary

Problems solved by technology

[0007] There are many insurmountable shortcomings in the first to third methods above, such as the decline of physical and mechanical properties, the increase of adhesive cost, the shortening of storage period, the increase of hot pressing time, and the reduction of production capacity, etc.

[0008] The fourth method, such as using a large-volume sealed chamber to treat ammonia under normal pressure, the effect of reducing aldehydes is not ideal, and the treatment time is long, resulting in an increase in the turnover period of production funds; the patent publication No. CN1526528A proposes to form a With a pressure difference of about 0.1MPa, the ammonia gas medium penetrates the plate vertically, and the free formaldehyde is discharged or reacts with the ammonia gas, so as to achieve the purpose of reducing aldehydes

This method has a good effect on reducing aldehydes, but only 10-15% of the ammonia reacts with formaldehyde, and 85-90% of the ammonia is wasted, and the ammonia consumption for wood-based panels reaches 3.86-11.348kg / cm 3

Moreover, a pressure difference of 0.1 MPa is formed on both sides of the board, and a 1.22×2.44m specification board has to withstand a pressure of up to 3,000 tons, which is not suitable for wood-based panels with small thickness.

Therefore, the manufacturing of the equipment is relatively difficult and the cost is relatively high, such as the sealing of the upper and lower sides of the plate, and the fixing of the plate are relatively strict.

In addition, the aldehyde reduction treatment temperature should be carried out at a relatively high temperature of 40-70°C, which consumes a lot of energy and increases the complexity of the equipment; recently, some domestic manufacturers have introduced the AF aldehyde reduction production line from the United States. CN1526528A patent is basically the same, and the effect of reducing aldehyde is also better, but the price is as high as more than 5 million yuan, so it is difficult to popularize and use