SK1332022U1 - Formula to reduce formaldehyde emissions from wood industry products - Google Patents

Abstract

Described is a preparation for reducing formaldehyde emissions in wood industry products in a total amount of 100% by weight. contains from 5.0% to 40% wt. of ammonium nitrate, from 5% to 30% wt. urea, from 0.5% to 20% wt. of at least one sulfur compound from the group including dithionates and thiosulfates of alkali metals and ammonium thiosulfate and from 30% to 50% wt. of water, with an addition of 0.1% to 5.0% wt. ammonia, while sodium dithionite can be replaced by sodium thiosulfanone, or they can be used simultaneously in a total amount from 0.5% to 20% wt.

Description

The field of technology

The technical solution concerns a preparation for reducing formaldehyde emissions in wood industry products, especially wood composites with joints glued with formaldehyde-based polycondensation glues.

Current state of the art

Polycondensation urea-formaldehyde (UF) resins are currently the most widely used wood glues in the woodworking industry. Currently, it accounts for approximately 95% of the total amount of wood adhesives used for the production of formaldehyde-based wood composites, followed by melamine-formaldehyde and phenol-formaldehyde adhesives. The industrial dominance of UF resins, with an estimated annual consumption of approximately 11 million tons worldwide, is due to their high reactivity, excellent adhesive properties, water solubility, low curing temperatures, short molding times, easy handling, relatively low cost, and resistance to microorganisms. The annual production of UF adhesives in Europe is around 4.8 million tons, of which 60% is consumed in the production of chipboard (DTD), 30% in the production of semi-hard fiberboard (MDF) and 10% in gluing furniture, interior doors and plywood production . The disadvantage of this type of adhesives is their low resistance to moisture and water and the subsequent release of formaldehyde from the finished products, which causes a burden on the environment with formaldehyde emissions. Many previous works describe the emission of formaldehyde mainly from three sources: residual formaldehyde present in the resin, formaldehyde formed by the polycondensation reaction between hydroxymethyl groups and formaldehyde released by hydrolytic degradation of the cured resin, especially under conditions of increased humidity and increased temperature. Formaldehyde is categorized as a dangerous substance, causing serious health problems, and therefore testing the content and emission of formaldehyde has become an integral part of testing the parameters of glued materials.

Formaldehyde emissions and the harmful effects of formaldehyde become a problem especially with products used indoors. Formaldehyde is a poisonous gas, it has strong antiseptic properties, it is a compound with undesirable biological effects on living organisms, it can destroy most microorganisms, including spores. In general, people spend up to 90% of their time indoors, where there are various mixtures of pollutants, including formaldehyde. Exposure to formaldehyde can cause respiratory irritation, asthma, tumors, multiple neuro-psychological abnormalities, or even death. The International Agency for Research on Cancer (IARC) classifies formaldehyde as a type 1B carcinogen - believed to have carcinogenic potential for humans.

Manufacturers of adhesives therefore focus on research and the use of available raw materials, which will allow not only to reduce the costs of the production of adhesives, but also to ensure the environmental safety of the manufactured product. Modern research and development in the field of woodworking polycondensation adhesives is directed towards the search for new technologies or targeted modification of existing technologies.

Chemical curing of polycondensation adhesives requires the presence of hardeners that provide a chemical environment for the formation of chemically stronger and more stable methylene chemical bonds and the transformation of less stable dimethyl ether bonds into stable methylene bonds. The ratio of stable methylene bonds and unstable dimethyl ether bonds is a determining indicator of the curing quality of polycondensation UF adhesives. Formaldehyde emissions from wood-based boards depend on many external (exogenous) and internal (endogenous) factors.

Currently, there are many ways to reduce Fd from wood composites. The main ones are:

a) reduction of the formaldehyde-urea molar ratio,

b) addition of formaldehyde scavengers such as tannins, lignin, starch, wheat flour and rice husk flour to urea-formaldehyde resin or substances for the surface treatment of wooden furniture or other materials (starch derivatives, charcoal, zeolite, urea) that trap formaldehyde,

c) changing the pressing parameters, such as pressing time or increasing the pressing temperature,

d) additional treatment of wood-based products or surface treatment,

e) mixing UF resin with other resins or using alternative adhesive systems based on carbon materials, biopolymers containing modified amide, carboxymethyl cellulose and soy flour.

SK 133-2022 U1

Formaldehyde traps can be divided into the following three types:

- synthetic interceptors,

- biological traps (natural traps),

- nano-catchers.

The essence of the technical solution

The stated shortcomings are largely eliminated by the preparation for reducing formaldehyde emissions in wood industry products, especially wood composites with joints glued with formaldehyde-based polycondensation glues, according to the technical solution, the essence of which is that the preparation contributes to the substantial reduction of formaldehyde emissions in wood industry products according to the presented technical solution, the essence of which is that in the total amount of 100% wt. preparation contains from 5.0% to 40% wt. ammonium nitrate, from 5% to 30% wt. urea, from 0.5% to 20% wt. of at least one sulfur compound from the group including dithionates and thiosulfates of alkali metals and ammonium thiosulfate and from 30% to 50% wt. water with an addition of 0.1% to 5.0% wt. ammonia. The mentioned substances together form a homogeneous stable solution.

The modification of polycondensation adhesives with the preparation according to the presented technical solution significantly reduces the toxicity caused by the hydrolysis of the adhesive and thus the release of formaldehyde emissions from the finished products. It thus solves problems related to the environment and human health caused by formaldehyde emissions from finished wood-based boards and ensures compliance with strict legislative regulations aimed at reducing emissions of formaldehyde and other volatile organic compounds (VOCs) from wood products issued by many countries.

Preparations according to this technical solution were applied to urea-formaldehyde glue during the preparation of adhesive mixtures. The emission of formaldehyde and the quality of the bonded joint were compared with reference UF adhesive mixtures prepared by applying a standard hardener (DAM 390). The test method according to STN EN ISO 12460-5 was used to determine formaldehyde emissions. The measured emissions of the tested solutions confirmed the decrease in formaldehyde emissions at all concentrations of the additive prepared according to the technical solution. The most significant decrease in formaldehyde emissions from wood industry products by up to 44.0% was achieved with the application of 5.0% by weight. preparation according to the technical solution when compared with the reference sample with the application of the standard hardener RODA M 210.

Implementation examples

Example 1

The preparation for reducing formaldehyde emissions from wood composites glued with urea-formaldehyde glues was prepared by dissolving the following components:

ammonium nitrate urea sodium dithionitrate water 35% wt. 10% wt. 15% wt. 40% wt.

and adding: ammonia

5.0% wt.

Example 2

The preparation for reducing formaldehyde emissions from wood composites glued with urea-formaldehyde glues was prepared by dissolving the following components:

ammonium nitrate urea sodium dithionitrate sodium thiosulfate water 25% wt. 10% wt. 1% wt. 14% wt. 50% by weight

and adding: ammonia

1.0% wt.

SK 133-2022 U1

Example 3

The preparation for reducing formaldehyde emissions from wood composites glued with urea-formaldehyde glues was prepared by dissolving the following components:

ammonium nitrate urea sodium dithionitrate sodium thiosulfate water 5% wt. 30% wt. 14.5% wt. 0.5% wt. 50% by weight

and adding: ammonia

1.0 wt. parts

Example 4

The preparation for reducing formaldehyde emissions from wood composites glued with urea-formaldehyde glues was prepared by dissolving the following components:

ammonium nitrate urea sodium thiosulfate water 40% wt. 5% wt. 20% wt. 35% wt.

and adding: ammonia

0.5% wt.

Example 5

The preparation for reducing formaldehyde emissions from wood composites glued with urea-formaldehyde glues was prepared by dissolving the following components:

ammonium nitrate urea ammonium thiosulfate water 10% wt. 30% wt. 20% wt. 40% wt.

and adding: ammonia

0.1% wt.

Industrial applicability

The preparation for reducing formaldehyde emissions according to the presented technical solution is used primarily in the woodworking industry for gluing and joining wood composites with thermo-reactive urea-formaldehyde glues.

SK 133-2022 U1

Claims (1)

1. The preparation for reducing formaldehyde emissions in wood industry products, especially wood composites with joints glued with formaldehyde-based polycondensation glues, is characterized by - 5 c i with the fact that in the total amount of 100% wt. contains from 5.0% to 40% wt. of ammonium nitrate, from 5% to 30% wt. urea, from 0.5% to 20% wt. of at least one sulfur compound from the group including dithionates and thiosulfates of alkali metals and ammonium thiosulfate and from 30% to 50% wt. of water, with an addition of 0.1% to 5.0% wt. ammonia.