CS240470B1 - A method for determining residual monomers and diluents in solid lignocellulosic materials - Google Patents

Abstract

The purpose of the invention is to determine residual monomers and diluents in solid lignocellulosic materials. The solution is that a sample of solid lignocellulosic material is destroyed, e.g. by grinding, scraping or grinding under the surface of a solvent, which dissolves the released residual monomers and diluents. In the resulting solution, the concentration of the determined substance is determined by gas chromatography, spectrophotometry or titration.

Description

240470

The present invention provides a method for determining residual monomers and diluents in solid ligand cellulosic materials. The current state of determination of volatile substances, so-called. residual monomers and diluents, such as styrene, methyl methacrylate, acetone, ethanol, etc., of wood-plastic materials are based on an indirect method of tracking some physico-mechanical properties, e.g., hardness, depending on the amount of residual monomer in the wood-plastic material . By increasing the amount of residual monomer, the hardness of the wood-plastic material decreases. A disadvantage of the method of determining the hardness of a material is that it gives only a rough image of the amount of unreacted monomer in the wood material. The amount of solvents in the wood-plastic material is determined by determining the weight loss of the wood-plastic material during the long-term constant weight evaporation. In wood-based materials such as wood-chip, fibreboard, plywood, cork, etc., where a formaldehyde-based adhesive is used, it is necessary to accurately determine the amount of unreacted formaldehyde in the wood material. -if. The release formaldehyde, similar residual monomers and solvents described above have an adverse effect on environmental hygiene. The current method for the determination of formaldehyde used in timber plants, especially in the NSR, Austria, Finland, Italy is the method of Fypsum. The method described is based on the extraction of bodies of 25 x 25 x 18 mmtoluene at the boiling point of toluene for hours.

The amount of formaldehyde is determined tritially from the aqueous solution. Mohl H.R., Holzais Roh- und Werkstoff, 36, 1978. Standards, formaldehyde is determined by evaporating formaldehyde from the disintegrated material at 60 ° C for four hours above water level. Subsequently, the amount of absorbed form aldehyde is determined by trituration in a solution of water which has been cooled in a refrigerator for one hour. Other methods known in the art are known which determine formaldehyde in ambient air of a sample by chemical reaction of formaldehyde with a chemical reagent, as well as titration determination, as well as spectral evaluation. The disadvantage of the described methods is the long determination time, which makes it impossible to control formaldehyde in the technological process and to modify the technological parameters. In order to accelerate these methods, an increased assay temperature is used in most cases. In some cases, the increase in temperature has an adverse effect on the accuracy of formaldehyde determination. E.g. by determining the free formaldehyde in the particleboard method by the method of the method, extraction of the sample with toluene at 110.6 ° C shifts the equilibrium reaction between formaldehyde and polymeric paraformaldehyde to the monomeric formaldehyde side, Walker JF, Formaldehyde, Second Edition, New York, 1953, resulting in higher levels of formaldehyde in the sample.

The above drawbacks of the current state of the art are remedied by the method of determination of residual monomers and diluents in solid lignocellulosic materials according to the invention, which is characterized in that the sample of the solid lignosulphurous material is destroyed below the solvent level and the residual monomer and diluent released below the solvent surface and Subsequently, the concentration of residual monomers and diluents, preferably by gas chromatography, is determined spectrophotometrically or by titration. The advantages of the invention lie in the possibility of a direct determination of the exact residual monomer content, respectively. solvents in the plastic material. Currently, there is no known method for directly and accurately determining residual monomers, respectively. solvents in the wood material. According to the invention, it is possible to advantageously utilize a time-consuming determination of formaldehyde in the wood material to monitor it during the technological preparation. According to the invention, the preparation of the sample for the analytical determination of formaldehyde is reduced by 2 to 4 hours. Přikladl

A sample of wood-plastic material is sized 10 x 10 x 200 mm. Exactly 100 ml of methanol are poured into the grinding apparatus, the enclosure is closed and the sample is immersed in methyl alcohol. Subsequently, the sample is truncated under the level of methanol by grinding the end of the sample with a screw knife. The sawdust obtained has a dimension of 93% in the range of 0.2 to 0.7 mm, the remaining 7% being less than 0.2 mm.

After 15 minutes, the suspension is stirred and filtered. The amount of residual methyl methacrylate and styrene monomers is determined in the filtrate by a three-meter gas chromium column chromatography packed with Chromosorb W AW-DMCS with a particle size of 0.14 to 0.15 mm with an anchored phase of 15% di-dodecyl phthalate. Example 1

The sample of wood-plastic material is treated as in Example 1 by determining the acetone in the filtrate by gas chromatography under the same conditions as in Example 1. The acetone is used as the diluent of the impregnating system used.

Claims (1)

SUBJECT Method for the determination of residual monomers and diluents in solid lignocellulosic materials by absorption of monomers in solvents, characterized in that a sample of solid lignocellulosic material is destroyed below the solvent level and the residual monomers and diluents released are dissolved below the solvent level and the residual monomer concentration determined. and diluents, preferably by gas chromatography, spectrophotometric or titration.