BG51244A3 - Method for the preparation of decorative plates of low inflammability and reduced fumes formation - Google Patents

Abstract

The method produces decorative plates with low flammability and smoke formation and low water absorption, applicable in railway systems and in shipbuilding. The plates are made by impregnating modified wood-core paper or decorative paper with a solution of phenol-melamine-formaldehyde resin, then packaging at elevated temperature and pressure. Wood pulp paper containing 5 to 10% by weight Ammonium polyphosphate is impregnated with an aqueous solution of resole phenolic resin, which is condensed in the presence of divalent metal oxides, in particular in the presence of magnesium oxide, and contains polyphosphoric acid. The latter is a mixture of compounds with at least three phosphorus atoms and solutions of aliphatic primary, secondary or tertiary amines or -hydroxyamines in ammonia water or in methanol in such an amount that the pH of the solution is from 7 to 8. 4 claims

Description

The invention relates to the production of decorative plates with low flammability and smoke generation, which can find application in the railway system and shipbuilding.

Various methods are known for producing materials with low flammability. In the production of layered materials, which use paper and polycondensation resins with reduced flammability, antimony trioxide is used for the paper and a halogen derivative flame retardant for the resin.

The production of decorative plates is based on conventional methods. During the pressing process, the halogen derivative undergoes decomposition, which leads to undesirable effects such as bubbles or delamination (split) of the plates.

A method is known for producing decorative panels with low flammability by means of cellulose paper modified with a synergistic mixture of additive flame retardants, such as antimony trioxide and copolymers, such as vinyl chloride and vinylidene chloride /1/. Phosphoric acid esters are also used to increase the fire resistance of paper panels (layers). This method produces panels that are slow-spreading materials. However, when burning, they produce large amounts of suffocating gases, which make them unsuitable for use in confined spaces, particularly in railway systems or in the shipbuilding industry.

A method is known in which ammonium phosphate, diammonium phosphate and phosphoric acid are used to make fireproof paper. However, these agents are short-lived and their effect consists in the decomposition of ammonia and phosphoric acid at temperatures below 100°C, while the release of phosphoric acids and water occurs at higher temperatures /2/. Since the decomposition occurs at temperatures below 100°C, the paper made in this way cannot be used for the production of plates, because the drying of the impregnating agents and the pressing into blocks (plates) are carried out at temperatures above

100°C. Moreover, the structure of such paper does not allow its saturation with resin.

It is known to use ammonium polyphosphate for the preparation of fire-resistant coatings. It is also known to use polyphosphoric compounds for anhydrous polymers in single-stage production processes, for example for the production of cast articles with fire-resistant filler, etc. It is not at all possible or at least very difficult to add phosphorus compounds to alkaline aqueous solutions of resole resins, especially when they are used for multi-stage processing, for example for the production of plates (layers) connected by paper impregnation, drying before impregnation or pressing into plates. The aqueous medium almost leads to hydrolysis of acids and phosphate salts, which leads to gelation of the resins and, accordingly, their premature binding.

The use of organophosphorus polymers containing 15% phosphorus and 27% chlorine is known to retard (prevent) fire from polyurethane foams, polymethylmethacryl, and phenolic, epoxy, and polyester resins.

However, organophosphorus polymers are not water-soluble, so they cannot be used for aqueous resin solutions. Furthermore, the combustion process results in the release of large amounts of smoke due to the high percentage of organic particles and chlorine. This again makes their use impossible for any materials for enclosed spaces.

The task of the invention is to create a method for producing plates with low flammability and low smoke generation, which meet the conditions for low-flammability materials in enclosed spaces.

The addition of an amine solution to ammonia water and then of polyphosphoric acid to an aqueous solution of a resole phenolic resin or a solution of a melamine-formaldehyde resin ensures the stabilization of the aqueous solution of the resin and leads to the correct course of the process of paper impregnation, drying of the impregnant and pressing into plates. As a result, plates are obtained that meet the requirements of the shipbuilding industry.

The essence of the method according to the invention consists in impregnating wood core paper containing from 5 to 10% by weight ammonium polyphosphate with an aqueous solution of a resole phenolic resin condensed in the presence of divalent metal oxides, in particular magnesium oxide, containing 15% by weight polyphosphoric acid - a mixture of compounds of at least three phosphorus atoms and a solution of aliphatic primary, secondary or tertiary amines or β - hydroxyamine in ammonia water or in methanol in such an amount that the pH of the resin solution is from 7 to 8. It is best to use β - hydroxyamine dissolved in methanol, as well as an amine solution.

According to a variant of the method of the invention, wood core paper is impregnated with an aqueous solution of a resole phenolic resin condensed in the presence of magnesium oxide containing 10-15% by weight of polyphosphoric acid as a mixture of compounds with at least three phosphorus atoms and a solution of β-hydroxyamine in methanol in such an amount that the pH of the resin solution is from 7 to 8. In this case, the decorative paper is impregnated with a solution of melamine-formaldehyde resin containing 5-10% by weight of metatetraphosphoric acid and a methanol solution of β-hydroxyamine in such an amount as to provide a pH of the resin solution of 8 to 9.

It is best to impregnate wood-core paper with a mixture of 10 to 30% by weight of ammonia, calcium or magnesium phosphates or with an aqueous solution of a resole phenolic resin condensed in the presence of magnesium oxide.

The combustion process of the plates described above, used for fire prevention of polyphosphoric compounds, proceeds differently from that of the known slow-burning plates. Polyphosphoric compounds are mainly a mixture of tripolyphosphoric compounds and cyclic acids or their salts. The introduction of phosphorus in a condensed form of the resin has a great influence on the mechanism of the combustion process. There is a tendency for the phosphoric acid to decompose in an immediate initial stage, producing non-volatile particles of much larger molecular size, which, undergoing further destruction, yield large quantities of primary organic carbon in the form of charred residues (radicals) and small quantities of non-flammable gases due to the polyphosphoric compounds used. The reaction of the phosphoric acid or its anhydride at the decomposition stage limits the oxidation of the carbon. Moreover, the bound phosphorus produces a mirror-smooth coating on the surface of the burning material. This protective coating limits the access of oxygen and constitutes (becomes) a barrier to flammable carbon monoxide or other flammable volatile substances.

An advantage of the method is that when carbon is oxidized, phosphorus is reduced. This is an endothermic reaction that leads to further absorption of heat from the combustion process. Metal oxides used to condense the resin additionally form complexes with the phosphorus groups, which contribute to reducing the possibility of combustion by producing a mechanical agent that interrupts the oxygen flow. The low water solubility of polyphosphoric compounds due to the low percentage of hydroxyl groups is an additional advantage that ensures low water absorption of the plates. This parameter is very important for products used in the shipbuilding industry. This also creates the possibility of using these plates in different climatic conditions.

The following examples illustrate the invention.

Example 1. A lacquer coating tank of an impregnation machine is filled with an aqueous solution of a resole phenolic resin condensed in the presence of magnesium oxide containing 10% by weight polyphosphoric acid and a solution of triethanolamine in methanol. The solution has a pH

7-8, and its viscosity is 8-100, measured by the Ford test cup method. A roll (ribbon) of cellulose paper containing 10% by weight ammonium polyphosphate is passed through this mixture until the carrier absorbs 32-39% of the resin. The paper is then passed through the drying tube of the impregnating machine until 6-8% by weight volatile particles are absorbed. This carrier paper is then cut into strips of the required size and stored in bundles together with strips of unmodified decorative embossed cellulose paper, saturated with a melamine-formaldehyde resin solution and heat-treated in the same way as the paper core.

1*

The packages are then pressed for 5 minutes in accordance with known methods at a temperature of 140 to 145°C and a pressure of 7.85 - 8.83 MPa, until the package is 1 millimeter thick.

The plates made in this way have a fire spread index on their surface below 20, which is in accordance with the instructions of 1МСО РР Х11/В. The smoke generation index meets the requirements of А5ТМЕ-05.02.

Example 2. A roll of cellulose paper passes through the varnish coating tank of an impregnating machine, which is filled with an aqueous solution of a resole phenolic resin condensed in the presence of magnesium oxide with a pH of 8 and a viscosity of 80-120 s, measured by the Ford test cup method, containing 20% by weight polyphosphoric acid and a solution of β hydroxyamine in ammonia water. At the moment when the percentage of resin in the carrier reaches 32-39% by weight, the package passes into the drying tube in the heated zone of the impregnating machine until the volatile substance solution becomes 6-8% by weight. This carrier paper is cut into strips of the required size and cooled in packages together with strips of decorative cellulose paper, the latter being saturated with a solution of melamine-formaldehyde resin with a pH of 8 containing 5% by weight. polyphosphoric acid solution and β-hydroxyamine solution in ammonia water. It is thermally processed, just like core paper.

Then the package is pressed for 5 minutes to 1 millimeter in accordance with the known method at a temperature of 140 - 145 ° C at a pressure of 7.85 - 8.83 MPa. The plate obtained in this way meets the requirements for quality and smoke formation of class 1 according to the Scandinavian Method ΝΤ Rie 004.

Example 3. A roll of cellulose paper containing 15% by weight of ammonium, calcium and magnesium polyphosphate in a mixture is passed through the varnish coating tank of an impregnating machine, which is filled with an aqueous solution of a resole phenolic resin condensed in the presence of magnesium, with a pH of 7-8 and a viscosity of 8-120 seconds according to the Ford test cup method, until the percentage of resin in the carrier becomes 32-39% by weight. The roll is then passed through the drying tube of the impregnating machine until 6-8% by weight of the volatile matter remains.

This carrier paper is cut into strips of the required size and stored in packages together with the strips of decorative paper, which is pre-saturated with an aqueous solution of melamine-formaldehyde resin and heat-treated in the same way as the core paper. The package is pressed for 5 minutes to 1 millimeter according to the known method at a temperature of 145-150°C and a pressure of 7.83 MPa. The plate thus obtained has a surface fire spread index of about 10, i.e. it meets the requirements of 1МСОРПХ113, appendix 1, and the smoke generation complies with Standard A8ТМЕ - 05.02.

Claims (4)

Patent claims 1. Method for obtaining decorative 20 plates by impregnating modified wood core paper with an aqueous solution of resole phenolic resin containing a fire retardant, and decorative paper saturated with a solution of melamine-formal25 aldehyde resin, and subsequent pre-drying of the impregnated paper layers at a temperature of 120 to 140°C, forming packages containing core layers and decorative layers at a temperature of 130 to 30 150°C at a pressure of 7.85 to 8.85 MPa, characterized in that the wood core paper containing 5 - 10% by weight of ammonium polyphosphate is impregnated with an aqueous solution of a resole phenolic resin condensed in the presence of divalent metal oxides, in particular magnesium oxide, containing 5-15% by weight of polyphosphoric acid as an agent, said acid being a mixture of compounds of at least three phosphorus atoms and a solution of aliphatic primary, secondary and/or tertiary amines or β-hydroxyamine in ammonia water or in methanol in such an amount that the pH of the resin solution is from 7 to 8. 2. Method for obtaining decorative 45 plates according to claim 1, characterized in that the β-hydroxyamine is dissolved in methanol and used as the amine solution. 3. Method for obtaining decorative 50 plates according to claim 1, characterized in that the wood core paper is impregnated with an aqueous solution of resole phenolic resin, condensed in the presence of magnesium oxide, containing 10-15% by weight polyphosphoric acid, which is a mixture of compounds of three phosphorus atoms and a solution of β-hydroxyamine in methanol in such an amount that the pH of the solution is from 7 to 8, and the decorative paper is impregnated with a solution of melamine-formaldehyde resin, containing 5-10% by weight metatetraphosphoric acid and a methanol solution of β-hydroxyamine in such an amount that the pH of the solution is from 8 to 9. 4. A method for producing decorative plates according to claim 1 from modified wood core paper by impregnation with an aqueous solution of a resole phenolic resin, and also of decorative paper with a solution of melamine-formaldehyde resin, followed by pre-drying of the impregnated paper layers and by forming packages at elevated temperature and elevated pressure, characterized in that the wood core paper, containing 10-30% by weight of ammonium, calcium or magnesium phosphate or a mixture thereof, is impregnated with an aqueous solution of a resole phenolic resin, condensed in the presence of magnesium oxide.