GB2108978A - A method of producing a fire- retardant or non-inflammable chipboard, particularly for coating purposes - Google Patents

Abstract

By a method of producing a fire- retardant or non-inflammable chipboard, particularly for coating purposes, the wooden chips are impregnated with ammonium sulphate prior to glueing, and after glueing the chips are mixed with unglued vermiculite and then the mixture is compressed to form a board. The proportion of impregnated wooden chips is preferably selected so as to mount to more than 50% of the mixture.

Description

SPECIFICATION A method of producing a fire-resistant or noninflammable chipboard, particularly for coating purposes This invention relates to a method of producing a fire-retardant or non-inflammable chipboard, particularly for coating purposes.

It has already been proposed to produce such boards by mixing wooden chips after glueing with unglued, expanded vermiculite and then compress the mixture to form a board.

In this way it has been possible to produce chipboards retaining the ordinary good properties of boards produced of wooden chips only, as they are easy to work and possess a good tensile strength and bending strength but at the same time are highly fire-retardant. The mechanical strength of the composite board is inter alia due to the fact that the unglued vermiculite is dispersed most evenly in the board thus providing direct reinforcement. Even if the proportion of vermiculite amounts to up to 70-75% the composite board does not lose its good advantages of strength, working and appearance, and such a board is practically non-inflammable.

Composite boards of the said type have advantageously been used for producing fireretardant doors, a board containing 40 parts of wooden chips and 60 parts of vermiculite being fireretardant for about 60 minutes. If the proportion of vermiculiate is increased, the fire resistance will be increased without the board losing its other advantages, but as vermiculite is more expensive than wooden chips, the price of the composite board will also rise. High-class boards having great fire resistance may therefore often be too expensive, e.g. if they are to be used as coating boards.

It is the object of the present invention to provide composite boards of the type disclosed above at a relatively low price even though they are highly non-flammable, and without reducing the said advantages of working and strength.

This object is obtainable according to the invention by impregnating the wooden chips with ammonium sulphate before glueing and by mixing the chips with unglued vermiculite after glueing as known per se, whereafter the mixture is compressed to form a board.

It is known per se to use ammonium sulphate as proofing to increase the fire resistance of wood. It is surprising, however, that it has proved that by impregnating the wooden chips with ammonium sulphate prior to glueing mixing with unglued vermiculite and then compressing, such increase of the fire resistance is obtainable that the proportion of vermiculite in the consolidssted board may be substantially less than hitherto presumed, and that the consolidated board therefore may be cheaper even by class A requirements to inflammability. It has proved that these high-class requirements may be met already with a proportion of vermiculite of abt.

40% of the total mixture, i.e. such a board may contain abt. 60% of relatively cheap wooden chips.

As it is the wooden chips that are to be glued, this ratio of mixture further means that the board will contain more glue relative to board in which the amount of vermiculite is equal to or even higher than the amount of chips, the strength of the board being thereby made paricularly high without losing any of the said advantages. On the contrary, the further advantage is obtained that the toxicity of the flue gas developed when the sheet is exposed to fire is reduced when using ammonium sulphate as proofing for the chips because this will bind formaldehyde escaping from the glue.

Altogether, it is thus possible by means of the invention in a simple way to provide a chipboard which is easy to work and has high fire resistance and mechanical strength simultaneously with being economic in production.

Claims

1. A method of producing a fire-retardant or non-inflammable chipboard, particularly for a coating purposes, characterised in that before glueing the wooden chips are impregnated with ammonium sulphate and that after glueing the chips as known per se are mixed with unglued vermiculite whereafter the mixture is compressed to form a board.

2. A method according to claim 1 for producing a non-inflammable chipboard, characterised in that the proportion of impregnated wooden chips is selected so as to amount to more than 50% of the mixture.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A method of producing a fire-resistant or noninflammable chipboard, particularly for coating purposes This invention relates to a method of producing a fire-retardant or non-inflammable chipboard, particularly for coating purposes. It has already been proposed to produce such boards by mixing wooden chips after glueing with unglued, expanded vermiculite and then compress the mixture to form a board. In this way it has been possible to produce chipboards retaining the ordinary good properties of boards produced of wooden chips only, as they are easy to work and possess a good tensile strength and bending strength but at the same time are highly fire-retardant. The mechanical strength of the composite board is inter alia due to the fact that the unglued vermiculite is dispersed most evenly in the board thus providing direct reinforcement. Even if the proportion of vermiculite amounts to up to 70-75% the composite board does not lose its good advantages of strength, working and appearance, and such a board is practically non-inflammable. Composite boards of the said type have advantageously been used for producing fireretardant doors, a board containing 40 parts of wooden chips and 60 parts of vermiculite being fireretardant for about 60 minutes. If the proportion of vermiculiate is increased, the fire resistance will be increased without the board losing its other advantages, but as vermiculite is more expensive than wooden chips, the price of the composite board will also rise. High-class boards having great fire resistance may therefore often be too expensive, e.g. if they are to be used as coating boards. It is the object of the present invention to provide composite boards of the type disclosed above at a relatively low price even though they are highly non-flammable, and without reducing the said advantages of working and strength. This object is obtainable according to the invention by impregnating the wooden chips with ammonium sulphate before glueing and by mixing the chips with unglued vermiculite after glueing as known per se, whereafter the mixture is compressed to form a board. It is known per se to use ammonium sulphate as proofing to increase the fire resistance of wood. It is surprising, however, that it has proved that by impregnating the wooden chips with ammonium sulphate prior to glueing mixing with unglued vermiculite and then compressing, such increase of the fire resistance is obtainable that the proportion of vermiculite in the consolidssted board may be substantially less than hitherto presumed, and that the consolidated board therefore may be cheaper even by class A requirements to inflammability. It has proved that these high-class requirements may be met already with a proportion of vermiculite of abt. 40% of the total mixture, i.e. such a board may contain abt. 60% of relatively cheap wooden chips. As it is the wooden chips that are to be glued, this ratio of mixture further means that the board will contain more glue relative to board in which the amount of vermiculite is equal to or even higher than the amount of chips, the strength of the board being thereby made paricularly high without losing any of the said advantages. On the contrary, the further advantage is obtained that the toxicity of the flue gas developed when the sheet is exposed to fire is reduced when using ammonium sulphate as proofing for the chips because this will bind formaldehyde escaping from the glue. Altogether, it is thus possible by means of the invention in a simple way to provide a chipboard which is easy to work and has high fire resistance and mechanical strength simultaneously with being economic in production. Claims

1. A method of producing a fire-retardant or non-inflammable chipboard, particularly for a coating purposes, characterised in that before glueing the wooden chips are impregnated with ammonium sulphate and that after glueing the chips as known per se are mixed with unglued vermiculite whereafter the mixture is compressed to form a board.

2. A method according to claim 1 for producing a non-inflammable chipboard, characterised in that the proportion of impregnated wooden chips is selected so as to amount to more than 50% of the mixture.