FI67874C - ELASTISKT SKUMMATERIAL BASERAT PAO EN MELAMIN / FORMALDEHYD-KONDENSATIONSPRODUKT OCH FOERFARANDE FOER FRAMSTAELLNING AV DETTA - Google Patents

Abstract

1. A process for the preparation of a resilient foam based on a melamine/formaldehyde condensate by foaming an aqueous solution or dispersion, which contains a melamine/formaldehyde precondensate, an emulsifier, a volatile blowing agent and a curing agent, with or without conventional additives, and then curing the foam, wherein a) the concentration of the precondensate in the mixture of precondensate and water (without additives) is selected to be above the salient point of the 1st derivative of the curve which is obtained when, keeping all other conditions constant, the amount of water in the mixture of precondensate and water is varied and the viscosity of the mixture (measured at the boiling point of the blowing agent under the conditions prevailing at the start of foaming) is plotted against the concentration of the precondensate, which concentration must however not be higher than the value which in the curve described corresponds to a viscosity of 5,000 dPas, b) during the foaming process, up to the time at which the foam has reached 80% of the maximum attainable rise height, the viscosity of the aqueous solution or dispersion must not fall below the value which, in the curve described under a, corresponds to the minimum concentration defined there, but must not exceed 6,000 dPas, and c) after reaching the time defined under b, the viscosity exceeds a value of 10,000 dPas, due to curing of the precondensate, within 8 min, the viscosities referred to in b and c being measured, in each case, on a parallel system which is free from blowing agent.

Description

I · - * § ***! ΓΒ1 M1 NOTICE OF PUBLICATION 5707 /

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"(45)} J, '' 3 '3 ^ v (51) Kv.lk.4 / lnt.CI.4 C 08 J 9 / 1A // C 03 L 61/28 FINLAND —FINLAND (21) Patent application - Patentansökning 800888 (22) Date of application - Ansökningsdag 21 .03.80 (En) (23) Date of commencement - Giltighetsdag 21.03.80 (41) Has become public - Blivit offentlig 1 8.10.80

National Board of Patents and Registration Date of publication and publication. -

Patent- och registerstyrelsen 'Ansökan utiagd och utl.skriften pubiicerad 28.02.85 (32) (33) (31) Pyydetty etuoikeus — Begärd priority 1 7. OA. 79

Federal Republic of Germany Förbundsrepubliken Tyskland (DE) P 2915 * »67.4 (71) BASF Aktiengesel1schaft, Ludwigshafen, Federal Republic of Germany Förbundsrepubl iken Tyskland (DE) (72) Harald Mahnke, Ludwigshafen, W Peter Peter Woerner

Heinz Weber, Gruenstadt, Federal Republic of Germany Förbundsrepubliken Tyskland (DE) (7 * 0 Oy Koi s te r Ab (5 **) Mel ami ini / forma 1 dehyde condensate Elastic foam material based on the product and method for its production - Elastiskt skum- material based on melamine / formaldehyde condensation products and for products from fram1111

The invention relates to a process for preparing a resilient foam material based on a melamine / formaldehyde condensation product by foaming a highly concentrated aqueous solution or dispersion containing a melamine / formaldehyde precondensate, an optional curing agent, an emulsifier, a volatile blowing agent and a volatile blowing agent. The invention also relates to a product obtained by the process.

It is known that foam materials based on melamine resins can be prepared by foaming an aqueous solution of the precondensate. According to DE 870 027 and DE 1 157 385, air is mixed with an aqueous solution of melamine resin containing an emulsifier and a hardener. According to DE 2 348 476, a mixture of water and a blowing agent (anionic detergent) is formed, which is foamed by mixing or blowing 67874 - ii.

gas into it. Melamine resin is added to the foam and curing is performed using an acid catalyst. However, the foam materials formed are hard and brittle and break easily during machining. DE 1 297 331 discloses a process for the production of foam materials from phenolic, urea or melamine resins, in which an aqueous solution of the resin containing a blowing agent and a hardener catalyst is foamed. If the examples are followed, only brittle foam materials are obtained - even if overhead - even if the phenolic or urea resin in the compositions is replaced by melamine resin. U.S. Patent 3,093,600 discloses melamine resin foams to which triols have been added, for example trimethylolpropane, to improve resilience and tear strength. However, it has been shown that the resilience and, above all, the recovery after compression are not sufficient. In addition, the addition of larger amounts of triol impairs the fire behavior of the foam materials. U.S. Patent 3,063,953 discloses a method for improving aminoplastic resin foams based on urea resins in particular, mechanical strength, resilience and softness. With this method, the said properties of the melamine resin foams produced according to the prior art can be slightly improved, but not significantly.

DE 2 402 441 discloses a process for the preparation of aminoplastic foams, in which a strong acid is added as a hardener to an alkaline-regulated aminoplastic precondensate containing a blowing agent. The heat released during neutralization causes the blowing agent to boil and thus appears to be foaming. Since curing and foam formation take place simultaneously with this procedure, a relatively brittle foam material is obtained.

The object of the invention was to develop a method for obtaining soft and resilient, flammable foam materials based on melamine / formaldehyde condensation products. According to the invention, this object is achieved by foaming a solution or dispersion of a relatively high concentration of melamine / formaldehyde precondensate under such conditions that only a slight increase in viscosity occurs first and hardening increases as the viscosity only occurs after the main foaming event.

The invention thus relates to a process for preparing a resilient foam material based on a melamine / formaldehyde condensation product by foaming an aqueous solution or dispersion containing a melamine / formaldehyde precondensate, an emulsifier, a hardener, a volatile blowing agent and a hardener, and optionally conventional blowing agents. The method is characterized in that a) the concentration of the precondensate in the mixture containing precondensate and water (without additives) is chosen to be above the refractive point of the first derivative of the curve obtained if all other conditions in the mixture of precondensate and water are varied and then plotted a curve of the viscosity of the mixture (measured at the boiling point of the blowing agent under the conditions prevailing at the beginning of the flotation event) as a function of the pre-condensate concentration, but not more than 5000 dPas has reached 80% of its maximum achievable head, the viscosity of the aqueous solution or dispersion, on the other hand, must not fall below a value which, on the curve defined in (a), corresponds to the low and on the other hand must not exceed 6000 dPas and that, after reaching the time specified in (c), the viscosity due to precondensation hardening exceeds 10 000 dPas within 8 minutes, in which case the viscosity in (b) and (c) is always measured from a blowing agent-free parallel system.

Surprisingly, this method provides resilient, soft foam materials which, when used as dampers, meet the requirements imposed on these materials in the construction industry, in particular as regards their thermal and sound insulation, their mechanical properties and their fire behavior. The foaming of highly concentrated solutions and dispersions is new and surprising, since the use of melanic resins has so far always avoided the use of such high concentrations, in which the dispersions in particular are not storage stable.

Examination of the foam materials prepared according to the invention under a microscope shows that the foam structure contains numerous, interconnected, three-dimensional, branched bridges (see Figure 3). Melamine resin foams are only sufficiently resilient when the bridges meet the following conditions: 1. The average length / thickness ratio must be greater than 10: 1, preferably greater than 12: 1 and especially greater than 15: 1. 2. The density of the bridge must be greater than 1.10, preferably greater than 1.20, especially greater than 1.30 g / cm.

Bridges that are too short (too low a l: d ratio) are obtained if curing begins too early, before the foaming process substantially ends. Too low a density in the bridge means that there are small cavities inside the bridge, bubbles caused by secondary foaming. Such secondary foaming occurs if the water content of the melamine resin precondensate is too high. In both cases, brittle foam materials are obtained.

The average l: d ratio is determined microscopically, with the length of the bridge and its thickness being determined by statistical calculation methods. The length of the bridge is the distance between the centers of two adjacent nodes, and the thickness of the bridge is measured at the narrowest point of the bridge, in each case determined from a microscopic image. To determine the density of the foam bridge, the foam material is placed in a suitable liquid, for example isopropanol, which is allowed to penetrate its open pores. The density of the bridge is then determined using the Archimedean principle.

The process according to the invention uses melamine / formaldehyde precondensate as starting material. The molar ratio of melamine to formaldehyde can then vary within wide limits, between 1: 1.5-1: 4, preferably between 1: 2.0-1.3: 5. The degree of condensation of the precondensate must be so small that curing during further condensation is possible. The average molecular weight - as measured osmometrically - may be in the range of 200-1000, preferably in the range of 250-800.

The aqueous solution or dispersion of melamine resin contains an emulsifier, preferably in an amount of 0.5 to 5% by weight and especially 1.0 to 3.0% by weight based on the weight of the resin. The function of the emulsifier is to ensure that the organic blowing agent in the aqueous solution or dispersion is evenly distributed; it also ensures the stability of the system and prevents the mixture from separating during the foaming operation, which would result in inhomogeneous foam. The higher the foaming temperature, the more effective the emulsifier must be and the higher concentrations it must be used. The emulsifier also acts as a nucleating agent in the foaming process. Suitable anionic compounds are, for example, metal salts of alkylsulfonates and alkylarylsulfonates having 8 to 20 carbon atoms in the alkyl residue, preferably sodium salts; also suitable are sulfonic succinic acid esters, sulfitized castor oils, alkylnaphthalenesulfonic acids, phenol sulfonic acids, sulfuric acid esters such as, for example, hydrogen sulfate sulfates and hydrogen sulfate hydrogen sulfates; further cationic compounds such as petroleum acid triethanolamine esters or laurylpyridine chloride; as well as non-ionogenic compounds such as ethoxylated castor oil, ethoxylated tallow fatty alcohols, ethoxylated stearic acid or oleic acid, and ethoxylated nonylphenol.

The aqueous solution or dispersion further contains a volatile blowing agent having a boiling point of between -20 ° C and + 100 ° C, in particular between + 20 ° C and + 80 ° C. Examples are hydrocarbons, halogenated hydrocarbons, alcohols, ketones, ethers and esters. Preferred blowing agents are pentane, hexane, trichlorofluoromethane and trichlorotrifluoroethane. The amount of blowing agent is determined by the desired density of the foam material, it may be between 1 and 50% by weight, preferably between 5 and 40% by weight based on the weight of the resin.

As hardeners, compounds are used which, under the reaction conditions, give off protons or form them, which then catalyze the melamine resin as the condensation continues. The amount is ____ _____ L .. ..... ..

6 67874 between 0.01 and 20, preferably between 0.05 and 5% by weight based on the weight of the resin. Suitable inorganic and organic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, oxalic acid, lactic acid, amino acids; latent hardeners such as halogenated carbonic acid salts, chloroacetic acid pyramide, hydrogen phosphates, acid anhydrides and ammonium salts. Formaldehyde itself can also decompose at high temperatures to form formic acid and thus act as a hardener.

The aqueous solution or dispersion is preferably free of additives. However, for many purposes it may be advantageous to add up to 20% by weight, preferably less than 10% by weight, of conventional additives based on the resin, such as fibrous or powdered inorganic reinforcing agents or fillers, pigments, dyes, flame retardants, plasticizers, flame retardants or to promote. Because the foam materials are open-porous and can absorb water, it may be necessary for a number of purposes to add water repellents in amounts of 0.2 to 5% by weight. Suitable are, for example, alkylphenols, silicones and paraffins having 5 to 15 carbon atoms in the alkyl residue.

The additives are mixed uniformly with the aqueous solution or dispersion of melararin resin, whereby the blowing agent can also be added under pressure, if necessary. A solid, for example spray-dried, melamine resin can also be used as a starting material and then mixed with an aqueous solution of the blowing agent and emulsifier and a hardener. When adding ingredients, the order of addition is determined by the selected mixing procedure. The mixture is brought to the boiling point of the blowing agent corresponding to the pressure prevailing in each solution or dispersion. This can be done by heating, for example with hot air, steam or high-frequency radiation, or also by utilizing the heat of reaction. In this case, the blowing agent changes to a gaseous state and may appear to be foamable. During the isothermal foaming operation, the aqueous solution or dispersion assumes the temperature of the blowing agent at the respective pressure. Preferably, normal pressure and a pulp temperature of 20-80 ° C are used, whereby the ambient temperature can be considerably higher.

7 67874

A critical feature a) of the present invention is the concentration of precondensate in the mixture of precondensate and water (without additives). The optimum concentration is different for each foaming temperature, thus being determined by the quality of the blowing agent. For the minimum content, the following condition applies according to the invention: it must be above the inflection point of the 1st derivative of the curve obtained by changing the water content in the precondensate and water mixture under constant conditions and then plotting the mixture viscosity (measured at the boiling point of the blowing agent under conditions prevail at the beginning of the foaming event) as a function of precondensate concentration. In practice, the procedure for determining the minimum content is to prepare mixtures of precondensate and water with varying concentrations of water and then heat these mixtures to the temperature at which the blowing agent begins to boil at the pressure prevailing at the beginning of the foaming operation. The corresponding viscosity is then measured for each concentration of melamine resin under these conditions. A plot of the measured viscosities is then plotted against the selected concentration. The curve thus obtained is first a straight line rising in shape, then rising more and more strongly and finally taking on a parabolic shape. From this curve, the 1st derivative is formed graphically. This is initially in the shape of a straight line, then has a curvature-changing fold area and finally becomes a sharply rising line. The refractive range generally extends up to about 1 percent of the precondensate concentration. This range represents the minimum concentration of melamine resin. If it is desired to determine the inflection point even more precisely, in the curve showing the 1st derivative, the lines are extended and their point of intersection is determined. The upper limit of the melamine resin content is determined by the following condition: it must not be greater than the value corresponding to a viscosity value of 5000 dPas, preferably 2000 dPas and especially 1000 dPas, on the curve shown.

For the preferred blowing agents, the following preferred resin concentrations can be used within the given ranges: n-pentane: 70-80, preferably 72-79 and especially 73-78.5% by weight; n-hexane: 73-85, preferably 74-84 and very __ .. ι: 8 67874 and 78-83% by weight; trichlorofluoromethane; 68-78, preferably 69-77 and especially 70-76% by weight; trichlorotrifluoroethane: 72-82, preferably 74-80% by weight.

The concentration levels indicated again refer to a mixture of pre-condensate and water without additives.

Another critical feature b) of the invention is based on the fact that during the foaming operation until the time when the foam has reached 80% of the maximum achievable head, the viscosity of the aqueous solution or dispersion must not fall below the minimum concentration determined by the curve in a) and shall not exceed 6000 dPas.

A third critical feature c) is that after reaching the time defined in b), the value of the viscosity precondensate must have exceeded 10,000 dPas in 8 minutes, preferably 6 and especially 4 minutes, i.e. the resin must have cured within this time. Both conditions (b) and (c) ensure that foaming and curing take place in proportion to each other; this can be accomplished using a specified blowing agent and at the same time a specified flotation temperature by properly selecting the quality and amount of hardener. In practice, two aqueous solutions or dispersions are prepared, one containing the melamine resin in the concentration indicated in (a), the emulsifier and hardener and the blowing agent and possibly additives, and the other containing the same ingredients but no blowing agent. Both mixtures are then brought to the foaming temperature. A co-mixture of a blowing agent-free solution or dispersion must be prepared because the blowing agent-containing mixture foams under these conditions and thus its viscosity cannot be measured. From the first mixture, the rise height of the foam is plotted as a function of time and thus the time at which the foam has reached 80% of the maximum rise height achievable. The viscosity of the second mixture is measured over time. It shall then be examined whether the requirements set out in (a) and (b) have been met. If this is not the case, the conditions for the curing event must be changed, which is best done by changing the quality and quantity of the hardener and, if necessary, also by selecting a second blowing agent and thus a different foaming temperature. In this case, the optimum concentration of melamine resin must be determined again in accordance with (a).

Sparkling, low-density stable foam can only be obtained when foaming and curing are carried out under the conditions described in a), b) and c). If the initial content of the melamine resin is chosen to be too low, or if the viscosity falls below the specified initial viscosity when the foam rises to 80% of its maximum value, a brittle foam material is obtained, as is the case with the prior art methods. If too viscous solutions or dispersions are prepared in advance, or if the viscosity before the foam reaches 80% of its maximum rise height rises above the specified permissible limit, the blowing pressure will no longer be sufficient to form a perfect foam and foams with too high a density and insufficient elasticity will be obtained. If, after the foam has reached 80% of its maximum rise height, the viscosity does not increase fast enough, i.e. if the foam does not harden quickly enough, it will break and a brittle, uneven foam material with too high a density will be obtained.

It is advantageous to keep the pressure in the flotation device and thus also the temperature of the pulp constant during the flotation operation. However, in certain embodiments of the method, these conditions may also be changed during the flotation event. Foaming generally takes from 20 seconds to 20 minutes, preferably from 30 seconds to 10 minutes, depending on the nature and intensity of the heating. It is finished when the foam resin is completely foamed and hardened to such an extent that it retains its shape.

In a preferred embodiment of the invention, the finished foam material is further subjected to a heat treatment. It is then heated for a period of 1 to 180 minutes, preferably 5 to 60 minutes, to a temperature between 120 and 300 ° C, preferably between 150 and 250 ° C, whereby the water, the blowing agent and the formaldehyde are substantially removed and the post-curing of the foam resin takes place. This heat treatment 10 67874 can be carried out immediately after the foam has been made in the same device or in a device installed thereafter; however, it can also be performed at a later time, regardless of the flotation event. The heat-treated foam material has a significantly lower tendency to shrink and absorb water than the untreated product. Formaldehyde removal is also greatly reduced.

In another preferred embodiment of the invention, the foam material is compressed to a size of 40-90% of its original height one or more times before or after the possible heat treatment and then allowed to expand again. As a result of this compression treatment, residues of hard areas in the cellular structure are presumably destroyed. This improves the resilience of the foam and provides less shrinkage during thermal storage.

The properties of the foam material according to the invention are as follows: a) its raw density according to DIN 53 420 is between 4 and 80, preferably between 8 and 40 μg; b) the thermal conductivity according to DIN 52 577 is less than 0.06, preferably less than 0.04 / Wm ** ° KJ · c) the tensile hardness according to DIN 53 577 at 60% compression divided by the raw density is less than 0.3, preferred -sometrically less than 0.2 / S.cm / gl J, in which case the measurement of the hardness at 60% compression must be at least 70%, preferably at least 90%, of the original material; d) the modulus of elasticity according to DIN 53 423 divided by the raw density r ~ 2 -i- is less than 0.25, preferably less than 0.5 (N.mm / g.l _); e) the deflection deflection according to DIN 53 423 is greater than 6, preferably greater than 12 / mm /; f) the tensile strength according to DIN 53 571 is preferably at least Q, Q7, in particular at least 0.1. g) they are at least normally non-flammable, preferably non-flammable, in accordance with DIN 4102.

The process according to the invention can be carried out as a discontinuous continuous operation. In a preferred continuous operation, the aqueous solution or dispersion is conveniently applied to a continuously moving, preferably heated, metal strip, spread evenly and foamed in the heating channel, and cured. In order to prevent the formation of a brittle shell on the surface of the foam, foaming can be carried out between two plastic films which move together with the metal strip. This may then be immediately followed by heat and / or compression treatment.

Foam materials can be made into sheets or strips with a thickness of 50 cm or more or into foam sheets a few millimeters thick. When using a discontinuous production method, shaped bodies can also be obtained. The foam materials can be provided on one or both sides with cover layers or coated with, for example, paper, cardboard, glass wool gauze, wood, gypsum boards, metal sheets or films, plastic films, which can also be foamed if desired.

The main field of application of the foam materials produced according to the invention is the thermal and sound insulation of buildings and building components, in particular partitions but also roofs, facades, doors and floors; further thermal and acoustic insulation of vehicles and aircraft as well as insulation at low temperatures such as refrigeration plants, oil tanks and liquefied petroleum gas tanks. Other uses include as an insulating wall cladding material and as an insulating and shock absorbing packaging material.

The parts, percentages and ratios mentioned in the examples are by weight.

Example 1

In an open vessel, spray-dried melamine / formaldehyde precondensate (1: 3 molar ratio, molecular weight about 400) was added to an aqueous solution containing 3% formic acid and 1.5% sodium salt of a mixture of alkylsulfonates containing 12-18 C atoms in the alkyl residue (emulsifier K AG), where the percentages are calculated for melamine resin. The resin content calculated from the resin-water mixture was 74.0 percent. The mixture was stirred vigorously and then 20% pentane was added. Stirring was continued until (about 3 minutes) until a homogeneous dispersion was obtained. It was applied to a substrate of sheronized Teflon glass fiber fabric and foamed and cured in an oven at 150 ° C, whereupon the temperature of the pulp in the foam reached a boiling point of pentane of 37.0 ° C under these conditions.

After 4 1/2 minutes, the foam reached 8Q percent of its maximum elevation. The foam was allowed to stand for another 10 minutes at 150 ° C in an oven. It was then heat treated at 180 ° C for 30 minutes. The properties are shown in Table 1.

To determine the optimal melamine resin content, the viscosity dependence of the dispersion viscosity on the melamine resin density was measured before foaming as follows: Mixtures of melamine resin precondensate and water in different mixing ratios were prepared.

The mixtures were heated to 37.0 ° C and the viscosities of the mixtures were measured using a rotary viscometer. In the drawing (see Figure 1), the viscosity'P0 dPas values are plotted as a function of concentration c as a percentage by weight of solid. A derivative was formed

Δ Ti ~ K ~ C

and was drawn in the figure as two straight lines intersecting at the fold K. The inflection point corresponds to a concentration of 71.7% in this case.

The curve approaches asymptotically a concentration value of about 80%, so that the recommended maximum viscosity of 1000 dPas corresponds to a concentration of about 79%. For the flotation event of the example, a concentration of approximately the middle of these values, namely 74.0%, was chosen. The corresponding viscosity was 88 dPas.

The proportions of the ingredients in the foamable mixture were now chosen so that the ratio of melamine resin to water (including the water supplied with the hardener and emulsifier) was 74:26. Prior to the actual foaming, the maximum rise height and viscosity versus time of the two samples were determined. In this case, the above mixture was heated once to a flotation temperature using the blowing agent mixture and a second time without it. Figure 2 shows graphically the dependence of the pitch height h and the viscosity 71 on the time t. The maximum pitch height was 10.25 cm; 80 percent of the 67874 maximum climb height had been reached after 4 1/2 minutes. Currently, the viscosity was 170 dPas. After three minutes of this, the viscosity had reached 10,000 dPas.

Example 2

The procedure was as in Example 1 except that only 13% of pentane was used instead of 20%.

Example 3

The procedure was as in Example 1 except that 3% sulfuric acid was used as the acid, 1.5% sodium dodecylbenzenesulfonate as emulsifier and 28% trichlorotrifluoroethane as blowing agent. The resin content was 76 percent. The temperature of the pulp in the flotation was 47 ° C. The foam was not heat treated.

Example 4

The procedure was as described in Example 1 using 6% phosphoric acid, 1.5% sodium lauryl sulfonate and 12% pentane. A melamine resin was used in which the molar ratio of melamine to formaldehyde was 1: 3.5. The resin content was 74 percent. The foam was not heat treated.

Example 5

To the open vessel was added a solution containing, in addition to the melamine resin, 2.8% formic acid and 1.4% of the alkyl sulfonate of Example 1 based on the resin. The resin content, calculated from the mixture of resin and water, was 75.5 percent. With vigorous stirring, 20% pentane was added. Flotation, curing and heat treatment were performed as in Example 1.

Example 6

The procedure was as in Example 5, using a resin with a molar molar ratio of melamine to formaldehyde of 1: 2.5. The resin content was 76 percent. 0.20% formic acid was used as the hardener, 3% of the alkyl sulfonate of Example 1 as emulsifier, 0.3% of the weakly saturated fatty acid and 23% of n-hexane as the blowing agent. The temperature of the pulp in the flotation was 69.0 ° C. The foam was heat treated as in Example 1.

Example 7

A homogeneous mixture according to Example 67874 1 was applied to the continuously moving metal strip. The tape transfer rate was 0.4 .mu.m. It was heated to 130 ° C. The mixture was evenly distributed on the strip by means of Rachel in a layer about 2 mm thick. The mixture was foamed with hot air to 150 ° C in a heated flotation channel to give a pulp temperature of 37.0 ° C. After about 4 1/2 minutes, 80 percent of the final rise height of the foam had been reached, and after about 6 minutes, the final thickness of the foam, 15 cm, had been reached. The foam was then passed through the flotation channel for about 7 minutes, at which point the temperature of the pulp rose to about 98 ° C. The foam material was heat treated for an additional 15 minutes at a pulp temperature of 17 ° C and the edges were cut.

Example 8

The procedure was as in Example 6, with the addition of a resin having a melamine molar ratio of formaldehyde of 1: 2.0. The resin content was 80 percent. 2.5% formic acid was used as the hardener, a mixture containing 0.6% of sodium diisobutylnaphthalenesulfonic acid and 1.6% of a weakly ethoxylated saturated fatty acid and 16% of pentane as a blowing agent was used as the emulsifier.

Example 9

The procedure was as in Example 1, with 1.8% formic acid being added as an acid and 2.2% sodium dodecylbenzenesulfonate as an emulsifier. The heat treatment was performed at 190 ° C.

__ 67874 15

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17 67874

Continuation of the table from the previous pages

Bridge length Bridge_ ^ density

Eg. f /, cm

Bridge thickness 1> 15 s- 1, 3 2 m 10 "-1,3 3 '-10 -1,3 H>) 0> 1,3 3 - 12> 1,3 6> 12> 1,3 7> 15 '> 1,3 8> io> 1,3 9> 25 3 l, 3 18 67874

A process for preparing elastic foam materials based on a melamine / formaldehyde condensation product by foaming an aqueous solution or dispersion / containing a melamine / formaldehyde precondensate, a known emulsifier, an emulsifier, a volatile blowing agent and a hardener, that (a) the concentration of the precondensate in the mixture containing precondensate and water (without additives) is chosen to be above the refractive point of the first derivative of the curve obtained if all other conditions in the mixture of precondensate and water are varied and then plotted against the viscosity of the mixture ( measured at the boiling point of the blowing agent under the conditions prevailing at the beginning of the flotation process) as a function of the pre-condensate concentration, however, the pre-condensate concentration must not exceed the value given in the brochure. (b) during the flotation event up to the time when the foam has reached 80% of its maximum achievable head, the viscosity of the aqueous solution or dispersion, on the other hand, must not fall below the value corresponding to the lowest concentration specified in (a); and, on the other hand, shall not exceed 6000 dPas and that, after reaching the time specified in (c), the viscosity due to precondensation hardening exceeds 10 000 dPas within 8 minutes, in which points (b) and (c) are always measured from a blowing agent-free parallel system.

Process according to Claim 1, characterized in that the foam material is heated for 1 to 180 minutes at a temperature of 120 to 300 ° C, the water, blowing agent and formaldehyde being substantially removed and further curing takes place.

A method according to claim 1, characterized in that the foam material, if desired before or after the heat treatment according to claim 2 of claim 6, is compressed one or more times to 40-90% of the original height, after which its allowed to re-expand.

Method according to Claim 1, characterized in that the foam material is provided with one or two cover layers.

5. A resilient foam material based on a melamine / formaldehyde condensation product containing at least 50% by weight of condensed melamine and formaldehyde units and which may contain up to 50% by weight of condensed and other amino-, amide-, hydroxyl- or carboxyl-containing thermosetting plastics on the one hand and aldehydes on the other hand, characterized in that it has the following properties: a) a raw density according to DIN 53 420 of 4-80 £ gl ^ 7 »b) a thermal conductivity according to DIN 52 612 of less than 0 , 06 / Wm-1 ° K_J17; c) the tensile hardness according to DIN 53 577 with a tensile strength of 60% _ _2 -i_ divided by the raw density is less than 0.30 /N.cm /g.l_/, in which case the recovery of the foam material must be at least 70 percent of original size; d) the modulus of elasticity according to DIN 53 423 divided by the raw density - -2 -1 is less than 0.25 /_N.mm ~ / g.l _J; 3) the deflection at break according to DIN 53 423 is greater than 6 / mm7; f) the tensile strength according to DIN 53 571 is preferably at least 0.07 / N.mm ^ 7; g) According to DIN 4102, at least normally non-flammable.

Claims (2)

67874 20 A process for preparing elastic foam materials based on a melamine / formaldehyde condensation product by foaming an aqueous solution or dispersion containing a melamine / formaldehyde condensate, an emulsifier, a volatile blowing agent and a hardener, and, if desired, conventional additives, whereafter the foam is cured, characterized in that a) the concentration of the precondensate in the mixture containing precondensate and water (without additives) is chosen so that it is above the breaking point of the first derivative of the curve obtained when maintaining all other conditions in the mixture of the pre-condensate and water constant, the amount of water varies and then plots a curve of the viscosity of the mixture (measured at the boiling temperature of the blowing agent under conditions which start at the start of the foaming process) as a function of the pre-condensate concentration, however, the concentration of the precondensate must not be higher than the value. in the described the curve corresponds to a viscosity of 5000 dPas, that b) during the foaming process until the time the foam reaches approximately 80% of the maximum achievable rise height, the viscosity of the aqueous solution or dispersion on the one hand must not fall below the value described in the curve under a) corresponds to the lowest concentration defined therein and, on the other hand, does not exceed 6000 dPas, and that c) upon reaching the time defined in b) the viscosity through the curing of the precondensate exceeds 10,000 dPas within 8 minutes, whereby ib) and c) viscosities are always measured in a blowing agent-free parallel system. 2. A process according to claim 1, characterized in that the foam material is heated 1-180 minutes at a temperature of 120-300 ° C, whereby water, blowing agent and formaldehyde are substantially removed and further curing takes place.