CA1151350A - Preparation of resilient foams based on a melamine/formaldehyde condensate - Google Patents
Preparation of resilient foams based on a melamine/formaldehyde condensateInfo
- Publication number
- CA1151350A CA1151350A CA000347095A CA347095A CA1151350A CA 1151350 A CA1151350 A CA 1151350A CA 000347095 A CA000347095 A CA 000347095A CA 347095 A CA347095 A CA 347095A CA 1151350 A CA1151350 A CA 1151350A
- Authority
- CA
- Canada
- Prior art keywords
- foam
- precondensate
- melamine
- foaming
- din
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
- C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
- C08J9/14—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent organic
- C08J9/141—Hydrocarbons
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2361/00—Characterised by the use of condensation polymers of aldehydes or ketones; Derivatives of such polymers
- C08J2361/20—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
- C08J2361/26—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with heterocyclic compounds
- C08J2361/28—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with heterocyclic compounds with melamine
Abstract
O.Z. 0050/033,801 Abstract of the Disclosure: A process for the prepara-tion of a resilient foam based on a melamine-formaldehyde condensate, wherein a very concentrated aqueous solution or dispersion which contains a melamine/formaldehyde pre-condensate, an emulsifier, a volatile blowing agent and a curing agent is foamed under conditions such that init-ially there is only a slight increase in viscosity and the curing process, accompanied by a large increase in viscosity, only commences when foaming has substantially ended.
Description
1~5135 o.Z. 0050/033801 Preparation of resilient foams based on a melamine/formaldehyde condensate The present invention relates to a process for the preparation of a resilient foam based on a melamine/
formaldehyde condensate, wherein a very concentrated aqueous solution or dispersion, which contains a melamine/
formaldehyde precondensate, an emulsifier, a volatile blowing agent and a curing agent, with or without conven-tional additives, is foamed and the foam is then cured.
The preparation of foams based on melamine resins by foaming an aqueous solution of a precondensate is known.
lo According to German Patent 870,027, air is stirred into an aqueous melamine resin solution which contains an emulsi-fier and a curing agent. However, the resulting foams are hard and brittle, and easily break during use.
British Patent 1,161,338 discloses a process for the pre-paration of foams based on phenolic, urea or melamine resins, wherein an aqueous resin solution which contains a blowing agent and a curing catalyst is foamed. On repeating the E~amples, it is found that the foams obtained - if any - are brittle, even if the phenolic or urea resins in the formulations are replaced by melamine resins. U.S. Patent 3,093,600 describes melamine resin foams which allegedly have improved resilience and resist-ance to cracking as a result of the incorporation of triols, eg. trimethylolpropane However, it is found that the resilience, and especially the recovery after compression, of such foams is inadequate for many applica-tions. Furthermore, on incorporating substantial lls~3so
formaldehyde condensate, wherein a very concentrated aqueous solution or dispersion, which contains a melamine/
formaldehyde precondensate, an emulsifier, a volatile blowing agent and a curing agent, with or without conven-tional additives, is foamed and the foam is then cured.
The preparation of foams based on melamine resins by foaming an aqueous solution of a precondensate is known.
lo According to German Patent 870,027, air is stirred into an aqueous melamine resin solution which contains an emulsi-fier and a curing agent. However, the resulting foams are hard and brittle, and easily break during use.
British Patent 1,161,338 discloses a process for the pre-paration of foams based on phenolic, urea or melamine resins, wherein an aqueous resin solution which contains a blowing agent and a curing catalyst is foamed. On repeating the E~amples, it is found that the foams obtained - if any - are brittle, even if the phenolic or urea resins in the formulations are replaced by melamine resins. U.S. Patent 3,093,600 describes melamine resin foams which allegedly have improved resilience and resist-ance to cracking as a result of the incorporation of triols, eg. trimethylolpropane However, it is found that the resilience, and especially the recovery after compression, of such foams is inadequate for many applica-tions. Furthermore, on incorporating substantial lls~3so
- 2 - O~Z. 0050/033801 amounts of triols into the foams, the combustibility of the latter is increased substantially. U.S. Patent
3,06~,953 discloses 2 process for improving the mechani-cal strength, resilience and softness of aminoplast resin foams, preferably foams based on urea resins.
Using this process, the above properties of melamine resin foams produced by prior art methods can be improved somewhat, but not substantially.
German Laid-Open Application DOS 2,402,441 lo (equivalent to South African Patent Application 403/74) describes a process for the preparation of aminoplast foams, wherein a strong acid is added as a curing agent to an alk~line aminoplast pre-condensate containing a blowing agent. The heat liberated by the neutralization causes the blowing agent to boil and hence to foam. Since, in this process, curing and foaming take place simultaneously, relatively - brittle foams result.
It is an object of the present invention to pro-vide a process by means of which soft and resilient foamswhich are based on melamine/foamaldehyde condensates and have very low flammability are obtained. We have found that this object is achieved, according to the invention, by a process wherein a relatively concentrated solution or dispersion of a melamine/formaldehyde precondensate is foamed under conditions such that first there is only a slight increasein viscosity,and the curing process, accom-panied by a 13rge increase in viscosity, only commences when foaming has substantially ended.
_ 3 _ o.z. ooSo/033801 Accordingly, the present invention relates to 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/form-aldehyde 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 mix-ture of precondensate and water (without additives) is selected to be above the salient point of the 1st deriva-tive 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 vis-cosity 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, preferably 2,000 dPas and especially 1,000 dPas, b) during the foaming process, up to the time at which the foam has reached 80% ~ 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,ooo dPas, preferably 2,500 dPas and especi~lly 1,200 dPas, and c) after reaching the time defined under b), the vis-cosity exceeds a value of 10,000 dPas, due to curing of ~151350 the precondensate, within 8 minutes, preferably within 6 minutes and especially within 4 minutes, the viscosities referred to in b) and c) being measured, in each case, on a parallel system which is free from blowing agent.
This process surprisingly gives resilient, soft foams which when used as insulating materials meet the standards placed by the building trade on such materials, especially in respect of their heat-insulating and sound-insulating properties, their mechanical properties and their behavior on exposure to fire. The foaming of very concen-trated solutions or dispersions must be regarded as a bold step into technologically new territory, since the art has always avoided using melamine resin concentrations which are so high that, in particular, the dispersions are not stable on storage.
On microscopic examination of the foams produced according to the invention it is found that the foam structure t comprises a plurality of mutually connected three-dimensionally branched webs.
In order to better understand the invention without limiting the same, reference is made to the accompanying drawings wherein:
Figure 1 shows a graph in which the viscosity ~ of a melamine resin dispersion and its first derivative ~n/~c are plotted against the concentration c.
Figure 2 shows a graph in which the rise height h and the viscosity ~ of a foaming m~lamine resin dispersion are plotted against the time t, and Figure 3 shows a schematic view of the three-dimensional structure of the melamine resin foam.
Melamine resin foams are sufficiently resilient only if ~15~350
Using this process, the above properties of melamine resin foams produced by prior art methods can be improved somewhat, but not substantially.
German Laid-Open Application DOS 2,402,441 lo (equivalent to South African Patent Application 403/74) describes a process for the preparation of aminoplast foams, wherein a strong acid is added as a curing agent to an alk~line aminoplast pre-condensate containing a blowing agent. The heat liberated by the neutralization causes the blowing agent to boil and hence to foam. Since, in this process, curing and foaming take place simultaneously, relatively - brittle foams result.
It is an object of the present invention to pro-vide a process by means of which soft and resilient foamswhich are based on melamine/foamaldehyde condensates and have very low flammability are obtained. We have found that this object is achieved, according to the invention, by a process wherein a relatively concentrated solution or dispersion of a melamine/formaldehyde precondensate is foamed under conditions such that first there is only a slight increasein viscosity,and the curing process, accom-panied by a 13rge increase in viscosity, only commences when foaming has substantially ended.
_ 3 _ o.z. ooSo/033801 Accordingly, the present invention relates to 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/form-aldehyde 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 mix-ture of precondensate and water (without additives) is selected to be above the salient point of the 1st deriva-tive 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 vis-cosity 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, preferably 2,000 dPas and especially 1,000 dPas, b) during the foaming process, up to the time at which the foam has reached 80% ~ 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,ooo dPas, preferably 2,500 dPas and especi~lly 1,200 dPas, and c) after reaching the time defined under b), the vis-cosity exceeds a value of 10,000 dPas, due to curing of ~151350 the precondensate, within 8 minutes, preferably within 6 minutes and especially within 4 minutes, the viscosities referred to in b) and c) being measured, in each case, on a parallel system which is free from blowing agent.
This process surprisingly gives resilient, soft foams which when used as insulating materials meet the standards placed by the building trade on such materials, especially in respect of their heat-insulating and sound-insulating properties, their mechanical properties and their behavior on exposure to fire. The foaming of very concen-trated solutions or dispersions must be regarded as a bold step into technologically new territory, since the art has always avoided using melamine resin concentrations which are so high that, in particular, the dispersions are not stable on storage.
On microscopic examination of the foams produced according to the invention it is found that the foam structure t comprises a plurality of mutually connected three-dimensionally branched webs.
In order to better understand the invention without limiting the same, reference is made to the accompanying drawings wherein:
Figure 1 shows a graph in which the viscosity ~ of a melamine resin dispersion and its first derivative ~n/~c are plotted against the concentration c.
Figure 2 shows a graph in which the rise height h and the viscosity ~ of a foaming m~lamine resin dispersion are plotted against the time t, and Figure 3 shows a schematic view of the three-dimensional structure of the melamine resin foam.
Melamine resin foams are sufficiently resilient only if ~15~350
- 4 a -the webs conform to the following conditions: L
1. The mean length : width ratio must be greater than 10 : 1, preferably greater than 12 : l and in particular greater than 15 : 1.
2. The density of the webs must be greater than 1.10, preferably greater than 1.20, and in particular greater than 1.30 g/cm3.
Webs which are too short (i.e. in which the 1 : d /
/
llS13S(l
1. The mean length : width ratio must be greater than 10 : 1, preferably greater than 12 : l and in particular greater than 15 : 1.
2. The density of the webs must be greater than 1.10, preferably greater than 1.20, and in particular greater than 1.30 g/cm3.
Webs which are too short (i.e. in which the 1 : d /
/
llS13S(l
5 - o. z~ 0050~03380 ratio is too low) are obtained if the curing process commences too early, before foaming has substantially ended Too low a web density indicates that there are minor cavities, bubbles and the like in the interior of the webs, resulting from secondary foaming. Such secondary foaming occurs if the water content of the melamine resin precondensate was too high. In both cases, brittle foams are obtained.
The mean ~ : d ratio is determined microscopi-cally, the length and width of the webs being determined by a statistical counting method The web length is defined as the distance between the centers of two nodes, and the web width is defined as the narrowest part of a web, in each case measured on a photomicrograph. To determine the density of the foam webs, the foam is placed in a suitable liquid, for example isopropanol, with which it becomes fully impregnated by virtue of its open-cell character, The density of the webs is then determined by the principle of Archimedes The starting material for the process according to the invention is a melamine/formaldehyde precondensate.
The molar ratio of melamine to formaldehyde in the precon-densate can vary within wide limits, namely from l : 1.5 to 1 : 4, but is preferably from l : 2.0 to l : 3.5.
The degree of condensation of the precondensate should be sufficiently low to allow curing accompanied by further condensation. The mean molecular weight, measured osmometrically, can be from 200 to l,000, preferably from 250 to 800, llS~350
The mean ~ : d ratio is determined microscopi-cally, the length and width of the webs being determined by a statistical counting method The web length is defined as the distance between the centers of two nodes, and the web width is defined as the narrowest part of a web, in each case measured on a photomicrograph. To determine the density of the foam webs, the foam is placed in a suitable liquid, for example isopropanol, with which it becomes fully impregnated by virtue of its open-cell character, The density of the webs is then determined by the principle of Archimedes The starting material for the process according to the invention is a melamine/formaldehyde precondensate.
The molar ratio of melamine to formaldehyde in the precon-densate can vary within wide limits, namely from l : 1.5 to 1 : 4, but is preferably from l : 2.0 to l : 3.5.
The degree of condensation of the precondensate should be sufficiently low to allow curing accompanied by further condensation. The mean molecular weight, measured osmometrically, can be from 200 to l,000, preferably from 250 to 800, llS~350
- 6 - O.Z. 0050/033801 The aqueous solution or dispersion of the melamine resin contains an emulsifier, preferably in an amount of from 0 5 to 5% by weight, and especially from 1 O to 3.0%
by weight, based on resin. The purpose of the emul-sifier is to disperse the organic blowing agent homogene-ously in the aqueous solution or dispersion; accordingly, the emulsifier ensures the stability of the system and prevents phase separation during foaming; such phase separation would result in an inhomogeneous foam. The o higher the foaming temperature, the more effective the emulsifier must be, and the higher should be the concen-tration used. The emulsifier furthermore acts as a nucleating agent for the foaming process Suitable materials are anionic co~pounds, especially metal alkyl-sulfonates and alkylarylsulfonates, where alkyl is of 8 to 20 carbon atoms, the metal preferably being sodium;
metal salts of sulfosuccinic acid esters, sulfonated castor oils, alkylnaphthalenesulfonic acids, phenol-sulfonic acids and sulfuric acid esters, for example C12-C18-alkyl hydrogen sulfates and C16-C18-fatty alcohol - hydrogen sulfates, are also suitable, as are cationic compounds, eg. oleic acid triethanolamine ester and lauryl-pyridinium chloride, and non-ionic compounds, eg. oxy-ethylated castor oil, oxyethylated tallow alcohols, oxy-ethylated stearic acid or oleic acid, and oxyethylated nonylphenol.
The aqueous solution or dispersion additionally contains a ~olatile blowing agent, preferably boiling at from -20 to 100C, especially from +20 to +80C.
by weight, based on resin. The purpose of the emul-sifier is to disperse the organic blowing agent homogene-ously in the aqueous solution or dispersion; accordingly, the emulsifier ensures the stability of the system and prevents phase separation during foaming; such phase separation would result in an inhomogeneous foam. The o higher the foaming temperature, the more effective the emulsifier must be, and the higher should be the concen-tration used. The emulsifier furthermore acts as a nucleating agent for the foaming process Suitable materials are anionic co~pounds, especially metal alkyl-sulfonates and alkylarylsulfonates, where alkyl is of 8 to 20 carbon atoms, the metal preferably being sodium;
metal salts of sulfosuccinic acid esters, sulfonated castor oils, alkylnaphthalenesulfonic acids, phenol-sulfonic acids and sulfuric acid esters, for example C12-C18-alkyl hydrogen sulfates and C16-C18-fatty alcohol - hydrogen sulfates, are also suitable, as are cationic compounds, eg. oleic acid triethanolamine ester and lauryl-pyridinium chloride, and non-ionic compounds, eg. oxy-ethylated castor oil, oxyethylated tallow alcohols, oxy-ethylated stearic acid or oleic acid, and oxyethylated nonylphenol.
The aqueous solution or dispersion additionally contains a ~olatile blowing agent, preferably boiling at from -20 to 100C, especially from +20 to +80C.
- 7 _ o.Z. 0050/033801 Examples are hydrocarbons, halohydrocarbons, alcohols, ketones, ethers and esters. Preferred blowing agents are pentane, hexane, trichlorofluoromethane and trichloro-trifluoroethane The amount of blowing agents depends on the desired density of the foam and can be from 1 to 50% by weight, preferably from 5 to 40% by weight, based on resin, The curing agents employed are compounds which under the reaction conditions split off, or form, protons, lo which then catalyze the further condensation of the mel-amine resin. The amount used is from 0.01 to 20, preferably from 0.05 to 5, % by weight, based on the resin~
Examples of suitable compounds are inorganic and organic acids, eg. hydrochloric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, oxalic acid, lactic acid and aminoacids, and latent curing agents, eg s~lts of halocarboxylic acids, chloroacetamide, hydrogen phosphates, acid anhydrides and ammonium salts. Formaldehyde it-self can also undergo disproportionation at elevated tem-peratures, to form formic acid, and can thus act as a curing agent, The aqueous solution or dispersion is preferably free from additives, For some purposes it can however be advantageous to add up to 20% by weight, but preferably less than 10% by weight, based on resin, of conventional additives, such as fibrous or pulverulent inorganic rein-forcing agents or fillers, pigments, dyes, flameproofing agents, plasticizers, agents for reducing the toxicity of the gas evolved on combustion or agents to promote
Examples of suitable compounds are inorganic and organic acids, eg. hydrochloric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, oxalic acid, lactic acid and aminoacids, and latent curing agents, eg s~lts of halocarboxylic acids, chloroacetamide, hydrogen phosphates, acid anhydrides and ammonium salts. Formaldehyde it-self can also undergo disproportionation at elevated tem-peratures, to form formic acid, and can thus act as a curing agent, The aqueous solution or dispersion is preferably free from additives, For some purposes it can however be advantageous to add up to 20% by weight, but preferably less than 10% by weight, based on resin, of conventional additives, such as fibrous or pulverulent inorganic rein-forcing agents or fillers, pigments, dyes, flameproofing agents, plasticizers, agents for reducing the toxicity of the gas evolved on combustion or agents to promote
- 8 - o.Z. 0050/033801 carbonization. Since the foams have an open-cell structure and can absorb water, it may be necessary, for some purposes, to add from 0.2 to 5% by weight of a water-repellent agent. Examples are alkylphenols, where alkyl is of 5 to 15 carbon atoms, silicones and paraffins, The additives are mixed homogeneously with the aqueous solution or dispersion of the melamine resin, during which mixing the blowing agent can be forced in, where appropriate under pressure, However, it is lo also possible to start from a solid, for example spray-dried, melamine resin and to mix this with the blowing agent and with an aqueous solution of the emulsifier and of the curing agent, The sequence of addition of the components depends on the particular mixing process.
The mixture is brought to the boiling point of the blow-ing agent in the solution or dispersion at the prevailing pressure. This may be done by heating, for example with hot air, steam or high frequency radiation, or by utilizing the heat of reaction On being brought to this temperature, the blowing agent is transformed to a gas and is thus able to cause the mixture to foam.
During the isothermal foaming, the aqueous solution or dispersion assumes the boiling point of the blowing agent at the prevailing pressure. Preferably, the process is carried out under atmospheric pressure, with the mater-ial at from 20 to 8~C, though the temperature of the surroundings may be substantially higher.
A critical feature a) of the present invention is the concentration of the precondensate in its mixture with llS1350
The mixture is brought to the boiling point of the blow-ing agent in the solution or dispersion at the prevailing pressure. This may be done by heating, for example with hot air, steam or high frequency radiation, or by utilizing the heat of reaction On being brought to this temperature, the blowing agent is transformed to a gas and is thus able to cause the mixture to foam.
During the isothermal foaming, the aqueous solution or dispersion assumes the boiling point of the blowing agent at the prevailing pressure. Preferably, the process is carried out under atmospheric pressure, with the mater-ial at from 20 to 8~C, though the temperature of the surroundings may be substantially higher.
A critical feature a) of the present invention is the concentration of the precondensate in its mixture with llS1350
- 9 - O. Z. 0050/033801 water (without additives). The optimum concentration is different for every foaming temperature, ie. it depends on the nature of the blowing agent, According to the invention, the minimum concentration must conform to the condition that it should lie above the salient point of the 1st derivative of the curve which is o~ned 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 lo the boiling point of the blowing agent under the condi-tions prevailing at the start of foaming) is plotted against the concentration of the precondensate,; In practice, the minimum concentration is determined by pre-paring mixtures of precondensate and water, containing various amounts of the latter, and then heating these mixtures to a temperature at which the blowing agent would boil under the pressure envisaged for the start of foam-ing, The corresponding viscosity for each concentra-tion of the melamine resin is then measured under these conditions, Thereafter, the measured viscosity is plotted against the particular concentration, The initial part of the resulting curve has the shape of` a straight line of only slight slope, but then rises pro-gressively more rapidly and ultimately assumes a parabo-loid course, The 1st derivative of this curve is obtainedby graphicalmethods, It isinitially inthe formof a horizontal straight line, followed by a curved salient region, and ultimately becomes a steep straight line, The salient region in general extends over a range of at
- 10 - o.Z. 0050/033801 most about 1% difference in concentration of the precon-densate This region represents the minimum concen-tration of the melamine resin. If it is desired to locate the salient point even more precisely, the straight line portions of the curve representing the 1st derivative are extrapolated and their point of inter-section is determined. The upper limit of the melamine resin concentration must conform to the following condi-tion: it must not exceed the value which, in the curve lo described, corresponds to a viscosity of 5,000 dPas, preferably 2,000 dPas and especially 1,000 dPas.
For the preferred blowing agents, the preferred resin concentrations, which lie within the range defined above, are as follows:
n-pentane: from 70 to 80, preferably from 72 to 79, especially from 73 to 78.5, % by weightS
n-hexane: from 73 to 85, preferably from 74 to 84, and especially from 78 to 83, % by weight;
trichlorofluoromethane: from 68 to 78, preferably from 69 to 77, especially from 70 to 76, % by weight;
trichlorotrifluoroethane: from 72 to 82, preferably from 74 to 80, % by weight.
The above concentrations are again based on the mixture of precondensate and water, without additives The second critical feature b) of the i~vention is that during foaming, up to the time at which the-foam has reached 80% of the maximum attainable rise height,the viscosity ofthe aqueous solution or dispersion must not fall below the value which corresponds, on the curve described . .
1151~
~ o.z. 0050/033801 under a), to the minimum concentration defined under a), but must not exceed 6,000 dPas.
The third critical characteristic c) means that after reaching the time defined under b) the-viscosity must, due to curing of the precondensate, exceed a value of 10,000 dPas within 8 minutes, preferably within 6 minutes, especially within 4 minutes, ie the resin must have cured within this time The two conditions b) and c~ ensure that foaming and curing are correctly balanced; for a given blowing agent and hence a given foaming temperature, the two conditions can be met if the nature and amount of the curing agent are correctlychosen.
In practice, two aqueous solutions or dispersions are prepared, of which one contains the melamine resin in the concentration determined according to a), the emulsifier, the curing agent, the blowing agent and the additives, if any, whilst the other contains the same constituents, but without blowing agent, Both systems are then brought to the foaming temperature. The parallel batch com-prising the solution or dispersion which is free fromblowing agent must be prepared since the system containing blowing agent foams under these conditions and hence its viscosity cannot be measured. For the first system, the rise height of the foam is plotted against time in order to determine the time at which the foam has reached 80% of the maximum attainable rise height. Usingthe second system, the viscosity is measured as a function of time The results are then checked as to whether the re~uire-ments stated under b) and c) are met. Should this not 1~51350 - 12 - O.Z. 0050/033801 be the case, the curing conditions must be varied, and this can best be achieved by varying the nature and amount of the curing agent and, where necessary, also by selecting a different blowing agent and hence a different foaming temperature, In the latter case, however, the optimum concentration of the melamine resin would have to be determined afresh, in accordance with a).
A resilient, stable foam of low density is only obtained if during foaming and curing the conditions specified under a), b) and c) are observed. If the initial concentration of melamine resin is too low, or if the viscosity drops below the defined initial viscosity before the foam has reached 80% of its maximum rise height, brittle foams are obtained, as with the prior art pro-cesses. If solutions or dispersions which are initially too viscous are employed, or ifthe viscosity increases above the defined permissible limit before 80% of the maximum foam rise height has been reached, the foaming pressure no longer suffices for satisfactory foaming, and the foams obtained are too dense and insufficiently resilient.
If, after reaching 80% of the maximum rise height of-the foam, the viscosity increases insufficiently rapidly, ie.
if the foam does not cure sufficiently rapidly, it collapses and a brittle, inhomogeneous foam having too high a density is produced, Preferably, the pressure in the foaming apparatus, and hence the material temperature during foaming, are kept constant. However, in special embodiments of the process these conditions can be varied in the course of ~1513SO
- 13 - o.Z. oOS0/033801 the foaming process, The foaming process in general requires from 20 seconds to 20 minutes, preferably from 30 seconds to 10 minutes, depending on the nature and intensity of heating employed. It is considered to have finished when the resin has finished foaming and has cured to the point that it retains its shape, In a preferred embodiment of the invention, the finished foam is subjected to a subsequent heat treatment, In this, it is heated for from 1 minute to 180 minutes, lo preferably for from 5 to 60 minutes, at from 120 to 300C, preferably from 150 to 250C, during which time water, blowing agent and for~aldehyde are substantially removed and post-curing of the foamed resin occurs, ~his heat treatment can be carried out immediately following the production of the foam, in the same apparatus or in a downstream apparatus, It can however also be carried out at a later point in time, independently of the foam-ing process. Heat-treated foams show substantially less tendency to shrink and to absorb water than do pro-ducts which have not been heat-treated. The emission of formaldehyde is also greatly reduced, In a further preferred embodiment of the inven-tion, the foam is compressed once or several times, before or after any heat treatment, by from 40 to 90% of its original height, and is then allowed to re-expand, It is presumed that this milling process destroys residual hard zones in the cell structure, This results in an increase in the resilience of the foam, and in less shrinkage on storage at elevated temperatures, - 14 - o.Z. 0050~033801 The foams prepared according to the invention exhibit the following properties-a) the bulk density, measured according to DIN 53,420, is from 4 to 80, preferably from 8 to 40, [g l 1];
b) the heat conductivity, measured according to DIN
52,612, is less than 0.06, preferably less than 0,04, [ l o 1]
c) the compressive strength, measured according to DIN
53,577 at 60% compression, divided by the bulk density, lo is less than 0.3, preferably lessthan O 2, [N.cm 2/g.l 11 and in determining the compressive strength at 60% compres-sion, the foam must recover to at least 70%, preferably at least 90%,of its original height;
d) the modulus of elasticity, measured by methods simi-lar to DIN 5~,423, divided by the bulk density is less than 0.25, preferably less than 0.15, [N.mm 2/g l 1];
e) the deflection on break, measured according to DIN
53,423, is greater than 6, preferably greater than 12, [mm];
f) the tensile strength, measured according to DIN 53,571, is preferably not less than 0.07, in particular not less than 0.1, [N.mm 2 3; and g) the foams are of not more than normal flammability, and preferably of low fl~m~ability, whenassessed according to DIN 4,102.
The process according to the invention can be carried out batchwise or continuously. In continuous operation, which is preferred, the aqueous solution or dispersion is advantageously applied to a continuously moving, preferably heated, metal belt, on which it is ~151350 - 15 - o.Z. OOSo/033801 spread uniformly and then foamed and cured in a heated tunnel. To prevent the formation of a brittle skin on the surface of the foam, the foaming process can advan-tageously be carried out between two plastic films travelling synchronously with the metal belt. This foaming can be followed directly by the heat treatment and/or milling treatmen~
The foams can be produced in the form of slabs or webs having a thickness of 50 cm or more, or in the form lo of sheets only a few mm thick, In batchwise operation, molded articles can also be produced. On one or both sides, the foams can be provided with covering layers or be laminated with, for example, paper, cardboard, glass mat, wood, gypsum boards, metal sheets or foils, or plastic films, which may also be foamed, The main field of use of the foams produced according to the invention is heat insulation and sound insulation in buildings and building components, especi-ally partitions, but also roofs, facades, doors and floors, as well as heat insulation and sound insulation in vehicles and aircraft, and low temperature insul-ation, for example of cold stores, oil tanks and liquefied gas con-tainers. Other fields of use are as an insulating wall cladding and as an insulating and shock-absorbing packaging material.
In the Examples, parts, percentages and ratios are by weight.
A spray-dried melamine/~ormaldehyde precondensate (molar ratio L:3, molecular weight about 400) was added, in an open vessel, to an aqueous so:Lution containing 3%
of formic acid and 1.5% of a mixture of sodium alkyl-sulfonates, where alkyl is of 12 to 18 carbon atoms, the percentages being based on me.lamine resin. The concentration of the resin, based on its mixture with water, was 74.0%.
The mixture was stirred vigorously and 20% of pentane were then added. Stirring was then continued until, after about 3 minutes, a homogeneous dispersion had formed. This dispersion was knife-coated onto a PTFE-coated glass fabric D
as the base material and foamed and cured in an oven at an air temperature of 150C.
Under these conditions, the foam assumed a temperature equal to the boiling point of pentane, which under these conditions was 37.0C. After 4 l/2 minutes, the foam had reached 80% of its maximum rise height, the latter being ultimately reached after 7 - 8 minutes. The foam was left for a further 10 minutes in the oven at 150C. It was then heated for 30 minutes at 180C. The properties of the foam are shown in Table l.
To determine the optimum melamine resin concentration, the dependence of the viscosity of the dispersion on the melamine resin concentration had been measured as follows, before the foaming process: Mixtures of the melamine resin precondensate and water in various ratios ~ --_~J~
11513~0 - 17 - o.z. 0050/033801 were prepared, The mixtures were then heated at 37,0C
and their viscosity was determined in a rotary viscometer, The viscosity ~ in dPas was plotted as a graph (see Figure l) against the concentration c in % by weight of solids.
The 1st derivative ~ ~ of the resulting curve was obtained ~ c graphically and plotted on the graph in the form of two straight lines intersecting at the salient point K, In the present case, this point is at a concentration of 71.7%. The curve asymptotically approaches a concen-tration of about 80%, so that the preferred m OEimum vis-cosity of 1,000 dPas corresponds to a concentration of about 79%. For the foaming procedure described in thé
Example, the concentration chosen was about halfway bet-ween these values, namely 74.0%. The corresponding viscosity was 88 dPas, The ratio of the components in the mixture to be foamed was then selected to give a ratio of melamine resin to water (including the water introduced with the curing agent and the emulsifier) of 74 : 26, Before the actual foaming process, the maximum rise height and the dependence of the viscosity on time were determined in two trial batches. To do this, the mixture described above, in one case with and in one case without added - blowing agent, was heated to the foaming temperature.
Figure 2 shows a graph in which the rise height h and the viscosity ~ have been plotted against time t. The maximum rise height was 10,25 cm; 80% of the maximum rise height was reached after 4~ minutes, At that time, the viscosity was 170 dPas, After a further 3 minutes, - ~1513SO
- 18 - O.Z. 0050/033801 the ViSCOsity had exceeded a value of 10,000 dPas.
The procedure followed was as in Example 1, except that instead of 20% only 13% of pentane was employed, The procedure followed was as in Example 1, but using 3% of sulfuric acid as the acid, 1.5% of sodium dodecylbenzenesulfonate as the emulsifier and 28% of tri-chlorotrifluoroethane as the blowing agent, The resin concentration was 76%. The material temperature, during foaming, was 47C, The foam was not heat-lo treated, The procedure followed was as in Example 1, butusing 6% of phosphoric acid, 1,5% of sodium laurylsulfon-ate and 12% of pentane. A melamine resin with a molar ratio of melamine to formaldehyde equai to 1 : 3,5 was employed, The resin concentration was 74y. The foam was not heat-treated, 2,8% of formic acid and 1.4yo of the alkylsulfon-ate from Example 1 were added to a solution of a melamine resin in an open vessel; the percentages are based on resin, The concentration of resin, based on its mix-ture with water, was 75,5%, 20yo of pentane was added with ~igorous stirring. Foamlng, curing and heating were carried out as in Example 1, The procedure followed was as in Example 5, using ~1513S() - 19 - o.z. 0050/033801 a melamine resin with a molar ratio of melamine to form-aldehyde equal to 1 : 2,5, The resin concentration was 76%. 0.20% of formic acid was used as the curing agent, 3% of the alkylsulfonate from Example 1 plus 0,3%
of an oxyethylated saturated fatty alcohol (with a low degree of oxyethylation) were used as the emulsifier, and 23% of n-hexane was used as the blowing agent. The material temperature during foaming was 69,0C. The foam w~s heat-treated as in Example 1, The homogeneous mixture described in Example 1 was applied to a metal belt travelling continuously at a speed of 0.4 [m,min 1], the belt being heated to about 130C~ The mixture was uniformly spread on the belt, as a layer about 2 mm thick, by means of a knife coater.
It was then foamed in a foaming tunnel heated by air at 150C, with the material temperature assuming a value of 37.0C, After about 41 minutes, 80% of the ultimate rise height of the foam was reached, and after about 6 minutes the final height of 15 cm was attained, The foam was then passed through the foaming tunnel for a further 7 minutes, during which the material temperature rose to about 98C. Thereafter the foam was heated for 15 minutes at a material temperature of about 170C, and the block was then trimmed, The procedure followed was as in Example 6, using a melamine resin with a molar ratio of melamine to form-aldehyde equal to 1 : 2,0, The resin concentration - 20 - 0. Z. 00~;0/033801 was 80%. 2.5% of formic acid was used as the curing agent, a mixture of 0,6% of sodium diisobutyinaphthalene-sulfonate and 1.6% of an oxyethylated saturated fatty alcohol (with a low degree of oxyethylation) was used as the emulsifier and 16% of pentane was used as the blowing agent.
The procedure followed was as in Example 1, using 1,8% of formic acid as the acid and 2, 2% of sodium do-decylbenzenesulfonate as the emulsifier. The heat lo treatment was carried out at 190C.
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115~3SO
- 23 o.z. 0050/033801 TABLE (continuation) Example Web length Web density Web thickness g. cm ~1.'3 2 ~10 ~1.3 3 >10 > 1,'3 4 ,~10 >1.3 >12 >1.3 6 >12 >1.'3 7 ~15 >1.'3' 8 ~10 ~1.'3 g >z5 ~ ,
For the preferred blowing agents, the preferred resin concentrations, which lie within the range defined above, are as follows:
n-pentane: from 70 to 80, preferably from 72 to 79, especially from 73 to 78.5, % by weightS
n-hexane: from 73 to 85, preferably from 74 to 84, and especially from 78 to 83, % by weight;
trichlorofluoromethane: from 68 to 78, preferably from 69 to 77, especially from 70 to 76, % by weight;
trichlorotrifluoroethane: from 72 to 82, preferably from 74 to 80, % by weight.
The above concentrations are again based on the mixture of precondensate and water, without additives The second critical feature b) of the i~vention is that during foaming, up to the time at which the-foam has reached 80% of the maximum attainable rise height,the viscosity ofthe aqueous solution or dispersion must not fall below the value which corresponds, on the curve described . .
1151~
~ o.z. 0050/033801 under a), to the minimum concentration defined under a), but must not exceed 6,000 dPas.
The third critical characteristic c) means that after reaching the time defined under b) the-viscosity must, due to curing of the precondensate, exceed a value of 10,000 dPas within 8 minutes, preferably within 6 minutes, especially within 4 minutes, ie the resin must have cured within this time The two conditions b) and c~ ensure that foaming and curing are correctly balanced; for a given blowing agent and hence a given foaming temperature, the two conditions can be met if the nature and amount of the curing agent are correctlychosen.
In practice, two aqueous solutions or dispersions are prepared, of which one contains the melamine resin in the concentration determined according to a), the emulsifier, the curing agent, the blowing agent and the additives, if any, whilst the other contains the same constituents, but without blowing agent, Both systems are then brought to the foaming temperature. The parallel batch com-prising the solution or dispersion which is free fromblowing agent must be prepared since the system containing blowing agent foams under these conditions and hence its viscosity cannot be measured. For the first system, the rise height of the foam is plotted against time in order to determine the time at which the foam has reached 80% of the maximum attainable rise height. Usingthe second system, the viscosity is measured as a function of time The results are then checked as to whether the re~uire-ments stated under b) and c) are met. Should this not 1~51350 - 12 - O.Z. 0050/033801 be the case, the curing conditions must be varied, and this can best be achieved by varying the nature and amount of the curing agent and, where necessary, also by selecting a different blowing agent and hence a different foaming temperature, In the latter case, however, the optimum concentration of the melamine resin would have to be determined afresh, in accordance with a).
A resilient, stable foam of low density is only obtained if during foaming and curing the conditions specified under a), b) and c) are observed. If the initial concentration of melamine resin is too low, or if the viscosity drops below the defined initial viscosity before the foam has reached 80% of its maximum rise height, brittle foams are obtained, as with the prior art pro-cesses. If solutions or dispersions which are initially too viscous are employed, or ifthe viscosity increases above the defined permissible limit before 80% of the maximum foam rise height has been reached, the foaming pressure no longer suffices for satisfactory foaming, and the foams obtained are too dense and insufficiently resilient.
If, after reaching 80% of the maximum rise height of-the foam, the viscosity increases insufficiently rapidly, ie.
if the foam does not cure sufficiently rapidly, it collapses and a brittle, inhomogeneous foam having too high a density is produced, Preferably, the pressure in the foaming apparatus, and hence the material temperature during foaming, are kept constant. However, in special embodiments of the process these conditions can be varied in the course of ~1513SO
- 13 - o.Z. oOS0/033801 the foaming process, The foaming process in general requires from 20 seconds to 20 minutes, preferably from 30 seconds to 10 minutes, depending on the nature and intensity of heating employed. It is considered to have finished when the resin has finished foaming and has cured to the point that it retains its shape, In a preferred embodiment of the invention, the finished foam is subjected to a subsequent heat treatment, In this, it is heated for from 1 minute to 180 minutes, lo preferably for from 5 to 60 minutes, at from 120 to 300C, preferably from 150 to 250C, during which time water, blowing agent and for~aldehyde are substantially removed and post-curing of the foamed resin occurs, ~his heat treatment can be carried out immediately following the production of the foam, in the same apparatus or in a downstream apparatus, It can however also be carried out at a later point in time, independently of the foam-ing process. Heat-treated foams show substantially less tendency to shrink and to absorb water than do pro-ducts which have not been heat-treated. The emission of formaldehyde is also greatly reduced, In a further preferred embodiment of the inven-tion, the foam is compressed once or several times, before or after any heat treatment, by from 40 to 90% of its original height, and is then allowed to re-expand, It is presumed that this milling process destroys residual hard zones in the cell structure, This results in an increase in the resilience of the foam, and in less shrinkage on storage at elevated temperatures, - 14 - o.Z. 0050~033801 The foams prepared according to the invention exhibit the following properties-a) the bulk density, measured according to DIN 53,420, is from 4 to 80, preferably from 8 to 40, [g l 1];
b) the heat conductivity, measured according to DIN
52,612, is less than 0.06, preferably less than 0,04, [ l o 1]
c) the compressive strength, measured according to DIN
53,577 at 60% compression, divided by the bulk density, lo is less than 0.3, preferably lessthan O 2, [N.cm 2/g.l 11 and in determining the compressive strength at 60% compres-sion, the foam must recover to at least 70%, preferably at least 90%,of its original height;
d) the modulus of elasticity, measured by methods simi-lar to DIN 5~,423, divided by the bulk density is less than 0.25, preferably less than 0.15, [N.mm 2/g l 1];
e) the deflection on break, measured according to DIN
53,423, is greater than 6, preferably greater than 12, [mm];
f) the tensile strength, measured according to DIN 53,571, is preferably not less than 0.07, in particular not less than 0.1, [N.mm 2 3; and g) the foams are of not more than normal flammability, and preferably of low fl~m~ability, whenassessed according to DIN 4,102.
The process according to the invention can be carried out batchwise or continuously. In continuous operation, which is preferred, the aqueous solution or dispersion is advantageously applied to a continuously moving, preferably heated, metal belt, on which it is ~151350 - 15 - o.Z. OOSo/033801 spread uniformly and then foamed and cured in a heated tunnel. To prevent the formation of a brittle skin on the surface of the foam, the foaming process can advan-tageously be carried out between two plastic films travelling synchronously with the metal belt. This foaming can be followed directly by the heat treatment and/or milling treatmen~
The foams can be produced in the form of slabs or webs having a thickness of 50 cm or more, or in the form lo of sheets only a few mm thick, In batchwise operation, molded articles can also be produced. On one or both sides, the foams can be provided with covering layers or be laminated with, for example, paper, cardboard, glass mat, wood, gypsum boards, metal sheets or foils, or plastic films, which may also be foamed, The main field of use of the foams produced according to the invention is heat insulation and sound insulation in buildings and building components, especi-ally partitions, but also roofs, facades, doors and floors, as well as heat insulation and sound insulation in vehicles and aircraft, and low temperature insul-ation, for example of cold stores, oil tanks and liquefied gas con-tainers. Other fields of use are as an insulating wall cladding and as an insulating and shock-absorbing packaging material.
In the Examples, parts, percentages and ratios are by weight.
A spray-dried melamine/~ormaldehyde precondensate (molar ratio L:3, molecular weight about 400) was added, in an open vessel, to an aqueous so:Lution containing 3%
of formic acid and 1.5% of a mixture of sodium alkyl-sulfonates, where alkyl is of 12 to 18 carbon atoms, the percentages being based on me.lamine resin. The concentration of the resin, based on its mixture with water, was 74.0%.
The mixture was stirred vigorously and 20% of pentane were then added. Stirring was then continued until, after about 3 minutes, a homogeneous dispersion had formed. This dispersion was knife-coated onto a PTFE-coated glass fabric D
as the base material and foamed and cured in an oven at an air temperature of 150C.
Under these conditions, the foam assumed a temperature equal to the boiling point of pentane, which under these conditions was 37.0C. After 4 l/2 minutes, the foam had reached 80% of its maximum rise height, the latter being ultimately reached after 7 - 8 minutes. The foam was left for a further 10 minutes in the oven at 150C. It was then heated for 30 minutes at 180C. The properties of the foam are shown in Table l.
To determine the optimum melamine resin concentration, the dependence of the viscosity of the dispersion on the melamine resin concentration had been measured as follows, before the foaming process: Mixtures of the melamine resin precondensate and water in various ratios ~ --_~J~
11513~0 - 17 - o.z. 0050/033801 were prepared, The mixtures were then heated at 37,0C
and their viscosity was determined in a rotary viscometer, The viscosity ~ in dPas was plotted as a graph (see Figure l) against the concentration c in % by weight of solids.
The 1st derivative ~ ~ of the resulting curve was obtained ~ c graphically and plotted on the graph in the form of two straight lines intersecting at the salient point K, In the present case, this point is at a concentration of 71.7%. The curve asymptotically approaches a concen-tration of about 80%, so that the preferred m OEimum vis-cosity of 1,000 dPas corresponds to a concentration of about 79%. For the foaming procedure described in thé
Example, the concentration chosen was about halfway bet-ween these values, namely 74.0%. The corresponding viscosity was 88 dPas, The ratio of the components in the mixture to be foamed was then selected to give a ratio of melamine resin to water (including the water introduced with the curing agent and the emulsifier) of 74 : 26, Before the actual foaming process, the maximum rise height and the dependence of the viscosity on time were determined in two trial batches. To do this, the mixture described above, in one case with and in one case without added - blowing agent, was heated to the foaming temperature.
Figure 2 shows a graph in which the rise height h and the viscosity ~ have been plotted against time t. The maximum rise height was 10,25 cm; 80% of the maximum rise height was reached after 4~ minutes, At that time, the viscosity was 170 dPas, After a further 3 minutes, - ~1513SO
- 18 - O.Z. 0050/033801 the ViSCOsity had exceeded a value of 10,000 dPas.
The procedure followed was as in Example 1, except that instead of 20% only 13% of pentane was employed, The procedure followed was as in Example 1, but using 3% of sulfuric acid as the acid, 1.5% of sodium dodecylbenzenesulfonate as the emulsifier and 28% of tri-chlorotrifluoroethane as the blowing agent, The resin concentration was 76%. The material temperature, during foaming, was 47C, The foam was not heat-lo treated, The procedure followed was as in Example 1, butusing 6% of phosphoric acid, 1,5% of sodium laurylsulfon-ate and 12% of pentane. A melamine resin with a molar ratio of melamine to formaldehyde equai to 1 : 3,5 was employed, The resin concentration was 74y. The foam was not heat-treated, 2,8% of formic acid and 1.4yo of the alkylsulfon-ate from Example 1 were added to a solution of a melamine resin in an open vessel; the percentages are based on resin, The concentration of resin, based on its mix-ture with water, was 75,5%, 20yo of pentane was added with ~igorous stirring. Foamlng, curing and heating were carried out as in Example 1, The procedure followed was as in Example 5, using ~1513S() - 19 - o.z. 0050/033801 a melamine resin with a molar ratio of melamine to form-aldehyde equal to 1 : 2,5, The resin concentration was 76%. 0.20% of formic acid was used as the curing agent, 3% of the alkylsulfonate from Example 1 plus 0,3%
of an oxyethylated saturated fatty alcohol (with a low degree of oxyethylation) were used as the emulsifier, and 23% of n-hexane was used as the blowing agent. The material temperature during foaming was 69,0C. The foam w~s heat-treated as in Example 1, The homogeneous mixture described in Example 1 was applied to a metal belt travelling continuously at a speed of 0.4 [m,min 1], the belt being heated to about 130C~ The mixture was uniformly spread on the belt, as a layer about 2 mm thick, by means of a knife coater.
It was then foamed in a foaming tunnel heated by air at 150C, with the material temperature assuming a value of 37.0C, After about 41 minutes, 80% of the ultimate rise height of the foam was reached, and after about 6 minutes the final height of 15 cm was attained, The foam was then passed through the foaming tunnel for a further 7 minutes, during which the material temperature rose to about 98C. Thereafter the foam was heated for 15 minutes at a material temperature of about 170C, and the block was then trimmed, The procedure followed was as in Example 6, using a melamine resin with a molar ratio of melamine to form-aldehyde equal to 1 : 2,0, The resin concentration - 20 - 0. Z. 00~;0/033801 was 80%. 2.5% of formic acid was used as the curing agent, a mixture of 0,6% of sodium diisobutyinaphthalene-sulfonate and 1.6% of an oxyethylated saturated fatty alcohol (with a low degree of oxyethylation) was used as the emulsifier and 16% of pentane was used as the blowing agent.
The procedure followed was as in Example 1, using 1,8% of formic acid as the acid and 2, 2% of sodium do-decylbenzenesulfonate as the emulsifier. The heat lo treatment was carried out at 190C.
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115~3SO
- 23 o.z. 0050/033801 TABLE (continuation) Example Web length Web density Web thickness g. cm ~1.'3 2 ~10 ~1.3 3 >10 > 1,'3 4 ,~10 >1.3 >12 >1.3 6 >12 >1.'3 7 ~15 >1.'3' 8 ~10 ~1.'3 g >z5 ~ ,
Claims (5)
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 minutes, the viscosities referred to in b) and c) being measured, in each case, on a parallel system which is free from blowing agent.
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 minutes, the viscosities referred to in b) and c) being measured, in each case, on a parallel system which is free from blowing agent.
2. A process as claimed in claim 1, wherein the foam is heated at from 120 to 300°C for from 1 to 180 minutes, during which water, blowing agent and formaldehyde are substantially removed and further curing takes place.
3. A process as claimed in claim 1, wherein the foam is compressed, before or after the heat treatment of claim 2, once or several times by from 40 to 90% of its original height, and is then allowed to re-expand.
4. A process as claimed in claim 1, wherein the foam is provided with 1 or 2 covering layers.
5. A resilient foam based on a melamine-formaldehyde condensate which exhibits the following properties:
a) the bulk density, measured according to DIN 53,420, is from 4 to 80 [g.1-1];
b) the heat acnductivity, measured according to DIN
52,612, is less than 0.06 [W.m-1.° K-1];
c) the compressive strength, measured according to DIN 53,577 at 60% compression, divided by the bulk density, is less than 0.30 [N.cm-2/g.1-1], and in determining the compressive strength at 60% compression, the foam must recover to at least 70%, of its original height;
d) the modulus of elasticity, measured by methods similar to DIN 53,423, divided by the bulk density is less than 0.25 [N.mm-2/g.1-1];
e) the deflection on break, measured according to DIN 53,423, is greater than 6 [mm];
f) the tensile strength, measured according to DIN 53,571, is preferably not less than 0.07 [N.mm-2];
and g) the foam is of not more than normal flammability when assessed according to DIN 4,102.
a) the bulk density, measured according to DIN 53,420, is from 4 to 80 [g.1-1];
b) the heat acnductivity, measured according to DIN
52,612, is less than 0.06 [W.m-1.° K-1];
c) the compressive strength, measured according to DIN 53,577 at 60% compression, divided by the bulk density, is less than 0.30 [N.cm-2/g.1-1], and in determining the compressive strength at 60% compression, the foam must recover to at least 70%, of its original height;
d) the modulus of elasticity, measured by methods similar to DIN 53,423, divided by the bulk density is less than 0.25 [N.mm-2/g.1-1];
e) the deflection on break, measured according to DIN 53,423, is greater than 6 [mm];
f) the tensile strength, measured according to DIN 53,571, is preferably not less than 0.07 [N.mm-2];
and g) the foam is of not more than normal flammability when assessed according to DIN 4,102.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19792915467 DE2915467A1 (en) | 1979-04-17 | 1979-04-17 | METHOD FOR PRODUCING ELASTIC FOAMS BASED ON A MELAMINE / FORMALDEHYDE CONDENSATION PRODUCT |
| DEP2915467.4 | 1979-04-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1151350A true CA1151350A (en) | 1983-08-02 |
Family
ID=6068510
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000347095A Expired CA1151350A (en) | 1979-04-17 | 1980-03-06 | Preparation of resilient foams based on a melamine/formaldehyde condensate |
Country Status (11)
| Country | Link |
|---|---|
| EP (1) | EP0017671B1 (en) |
| JP (1) | JPS55142628A (en) |
| AT (1) | ATE2224T1 (en) |
| AU (1) | AU531639B2 (en) |
| BR (1) | BR8002360A (en) |
| CA (1) | CA1151350A (en) |
| DE (2) | DE2915467A1 (en) |
| DK (1) | DK158045C (en) |
| ES (1) | ES490632A0 (en) |
| FI (1) | FI67874C (en) |
| NO (1) | NO151291C (en) |
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|---|---|---|---|---|
| US6284077B1 (en) | 1997-08-29 | 2001-09-04 | Dap Products Inc. | Stable, foamed caulk and sealant compounds and methods of use thereof |
| US6291536B1 (en) | 1998-02-07 | 2001-09-18 | Dap Products Inc. | Foamed caulk and sealant compounds |
| US6333365B1 (en) | 1996-09-19 | 2001-12-25 | Dap Products Inc. | Stable, foamed caulk and sealant compounds and methods of use thereof |
| US8937106B2 (en) | 2010-12-07 | 2015-01-20 | Basf Se | Melamine resin foams with nanoporous fillers |
| US9056961B2 (en) | 2009-11-20 | 2015-06-16 | Basf Se | Melamine-resin foams comprising hollow microbeads |
| US9353232B2 (en) | 2011-05-16 | 2016-05-31 | Basf Se | Melamine-formaldehyde foams comprising hollow microspheres |
| US9663625B2 (en) | 2012-09-04 | 2017-05-30 | Basf Se | Method for producing melamine/formaldehyde foams |
| US11254795B2 (en) | 2016-11-23 | 2022-02-22 | Basf Se | Production of melamine-formaldehyde foams |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2950289A1 (en) * | 1979-12-14 | 1981-06-19 | Basf Ag, 6700 Ludwigshafen | ELASTIC FOAM BASED ON A UREA / FORMALDEHYDE CONDENSATION PRODUCT |
| DE3037683A1 (en) * | 1980-10-04 | 1982-05-19 | Basf Ag, 6700 Ludwigshafen | ELASTIC DUROPLAST FOAMS |
| EP0068673A1 (en) * | 1981-06-13 | 1983-01-05 | BP Chemicals Limited | Phenolic foam of increased resilience and process for making it |
| DE3534738A1 (en) * | 1985-09-28 | 1987-04-09 | Basf Ag | METHOD FOR PRODUCING ELASTIC MELAMINE FOAMS |
| DE3534739C2 (en) * | 1985-09-28 | 1994-02-03 | Basf Ag | Process for the production of foams based on melamine resins |
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| US5317339A (en) * | 1989-10-03 | 1994-05-31 | Siemens Aktiengesellschaft | Printing module for an ink-printing system having an ink storage container with an integrated ink-printing head |
| US5650222A (en) * | 1995-01-10 | 1997-07-22 | The Procter & Gamble Company | Absorbent foam materials for aqueous fluids made from high internal phase emulsions having very high water-to-oil ratios |
| US5563179A (en) * | 1995-01-10 | 1996-10-08 | The Proctor & Gamble Company | Absorbent foams made from high internal phase emulsions useful for acquiring and distributing aqueous fluids |
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| US5633291A (en) * | 1995-06-07 | 1997-05-27 | The Procter & Gamble Company | Use of foam materials derived from high internal phase emulsions for insulation |
| US5550167A (en) * | 1995-08-30 | 1996-08-27 | The Procter & Gamble Company | Absorbent foams made from high internal phase emulsions useful for acquiring aqueous fluids |
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| JPH1187978A (en) * | 1997-09-09 | 1999-03-30 | Nitto Boseki Co Ltd | Incombustible radio wave absorber |
| US6160028A (en) * | 1998-07-17 | 2000-12-12 | The Procter & Gamble Company | Flame retardant microporous polymeric foams |
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| DE10047717A1 (en) * | 2000-09-27 | 2002-04-18 | Basf Ag | Hydrophilic, open-cell, elastic foams based on melamine / formaldehyde resins, their manufacture and their use in hygiene articles |
| DE10047719A1 (en) * | 2000-09-27 | 2002-04-11 | Basf Ag | Hydrophilic, open-cell, elastic foams based on melamine / formaldehyde resins, their manufacture and their use in hygiene articles |
| AT410211B (en) | 2000-12-15 | 2003-03-25 | Agrolinz Melamin Gmbh | HALVES AND MOLDINGS FROM AMINO LASTS |
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| JP3783039B2 (en) | 2002-04-24 | 2006-06-07 | 国立大学法人広島大学 | Natural tooth brush |
| DE10335957A1 (en) | 2003-08-04 | 2005-02-24 | Basf Ag | Moldings of melamine / formaldehyde foams with low formaldehyde emission |
| US7331087B2 (en) | 2003-12-22 | 2008-02-19 | Kimberly-Clark Worldwide, Inc. | Activatable fastening system and web having elevated regions and functional material members |
| CN100434471C (en) * | 2005-07-27 | 2008-11-19 | 北京绿寰宇化工有限公司 | Production method of nanometer material modified toughened melamine foamed plastic |
| DE102006001862A1 (en) | 2006-01-13 | 2007-07-19 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Propellant-free amino resin foam, process for its preparation and its use |
| WO2008110475A1 (en) * | 2007-03-12 | 2008-09-18 | Basf Se | Antimicrobially modified melamine/formaldehyde foam |
| CA2701976C (en) | 2007-10-12 | 2016-04-12 | Borealis Agrolinz Melamine Gmbh | Thermoplastically processible aminoplastic resin, thermoset microfibre non-wovens, and process and plant for their production |
| DE102011009397A1 (en) | 2011-01-25 | 2012-07-26 | Basf Se | Composite foam, useful for soundproofing, comprises first foam layer comprising polysulfone foam and second foam layer comprising melamine-formaldehyde foam |
| WO2012147422A1 (en) | 2011-04-27 | 2012-11-01 | 株式会社イノアックコーポレーション | Mat and manufacturing method therefor |
| EP2709507B1 (en) | 2011-05-16 | 2016-08-10 | The Procter and Gamble Company | Cleaning implement based on melamine-formaldehyde foam comprising hollow microspheres |
| JP5968429B2 (en) | 2011-05-16 | 2016-08-10 | ビーエーエスエフ ソシエタス・ヨーロピアＢａｓｆ Ｓｅ | Melamine / formaldehyde foam material containing micro hollow spheres |
| WO2013178537A1 (en) | 2012-05-31 | 2013-12-05 | Basf Se | Binding agent |
| DE102016212418B4 (en) | 2016-07-07 | 2019-06-06 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Process for the preparation of a biopolymer particle-containing amino resin foam, amino resin foam and its use |
| US11259680B2 (en) | 2016-11-23 | 2022-03-01 | The Procter & Gamble Company | Cleaning implement comprising a modified open-cell foam |
| US11224328B2 (en) | 2016-11-23 | 2022-01-18 | The Procter & Gamble Company | Cleaning implement comprising a modified open-cell foam |
| CN106674890A (en) * | 2016-12-05 | 2017-05-17 | 钦州市钦南区生产力促进中心 | Polymer foam material and preparation method thereof |
| US11759983B2 (en) | 2017-09-13 | 2023-09-19 | Basf Se | Auxetic polyurethane and melamine foams by triaxial compression |
| CA3074273C (en) | 2017-09-22 | 2022-10-18 | The Procter & Gamble Company | Cleaning article comprising multiple sheets and methods thereof |
| US20200015651A1 (en) | 2018-07-13 | 2020-01-16 | The Procter & Gamble Company | Cleaning article comprising multiple sheets and methods thereof |
| EP3962990B1 (en) | 2019-05-02 | 2023-03-22 | Basf Se | Melamine formaldehyde foam with reduced formaldehyde emission |
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Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE870027C (en) * | 1944-07-28 | 1953-03-09 | Ciba Geigy | Process for the production of foam insulation compounds |
| US3063953A (en) * | 1960-08-22 | 1962-11-13 | Scott Paper Co | Process of improving the physical characteristics of an amine-formaldehyde foam by compression and product produced thereform |
| DE2348476A1 (en) * | 1973-10-22 | 1975-04-03 | Coordenacao Dos Programas De P | RIGID FOAM MADE FROM RESIN SYSTEMS AND VARIOUS FILLING AGENTS AND PROCESSES FOR THEIR PRODUCTION |
-
1979
- 1979-04-17 DE DE19792915467 patent/DE2915467A1/en not_active Withdrawn
- 1979-12-17 EP EP79105216A patent/EP0017671B1/en not_active Expired
- 1979-12-17 DE DE7979105216T patent/DE2964510D1/en not_active Expired
- 1979-12-17 AT AT79105216T patent/ATE2224T1/en not_active IP Right Cessation
-
1980
- 1980-03-06 CA CA000347095A patent/CA1151350A/en not_active Expired
- 1980-03-21 FI FI800888A patent/FI67874C/en not_active IP Right Cessation
- 1980-04-14 JP JP4815980A patent/JPS55142628A/en active Granted
- 1980-04-16 DK DK160780A patent/DK158045C/en not_active IP Right Cessation
- 1980-04-16 ES ES490632A patent/ES490632A0/en active Granted
- 1980-04-16 AU AU57512/80A patent/AU531639B2/en not_active Ceased
- 1980-04-16 NO NO801102A patent/NO151291C/en unknown
- 1980-04-16 BR BR8002360A patent/BR8002360A/en not_active IP Right Cessation
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6333365B1 (en) | 1996-09-19 | 2001-12-25 | Dap Products Inc. | Stable, foamed caulk and sealant compounds and methods of use thereof |
| US6395794B2 (en) | 1996-09-19 | 2002-05-28 | Dap Products Inc. | Stable, foamed caulk and sealant compounds and methods of use thereof |
| US6284077B1 (en) | 1997-08-29 | 2001-09-04 | Dap Products Inc. | Stable, foamed caulk and sealant compounds and methods of use thereof |
| US6291536B1 (en) | 1998-02-07 | 2001-09-18 | Dap Products Inc. | Foamed caulk and sealant compounds |
| US6414044B2 (en) | 1998-02-07 | 2002-07-02 | Dap Products Inc. | Foamed caulk and sealant compounds |
| US9056961B2 (en) | 2009-11-20 | 2015-06-16 | Basf Se | Melamine-resin foams comprising hollow microbeads |
| US8937106B2 (en) | 2010-12-07 | 2015-01-20 | Basf Se | Melamine resin foams with nanoporous fillers |
| US9353232B2 (en) | 2011-05-16 | 2016-05-31 | Basf Se | Melamine-formaldehyde foams comprising hollow microspheres |
| US9663625B2 (en) | 2012-09-04 | 2017-05-30 | Basf Se | Method for producing melamine/formaldehyde foams |
| US11254795B2 (en) | 2016-11-23 | 2022-02-22 | Basf Se | Production of melamine-formaldehyde foams |
Also Published As
| Publication number | Publication date |
|---|---|
| FI67874C (en) | 1985-06-10 |
| AU5751280A (en) | 1980-10-23 |
| DK158045B (en) | 1990-03-19 |
| ES8101098A1 (en) | 1980-12-01 |
| NO801102L (en) | 1980-10-20 |
| NO151291B (en) | 1984-12-03 |
| AU531639B2 (en) | 1983-09-01 |
| EP0017671B1 (en) | 1983-01-12 |
| EP0017671A1 (en) | 1980-10-29 |
| FI800888A (en) | 1980-10-18 |
| JPS638976B2 (en) | 1988-02-25 |
| DK158045C (en) | 1990-08-13 |
| JPS55142628A (en) | 1980-11-07 |
| DK160780A (en) | 1980-10-18 |
| ES490632A0 (en) | 1980-12-01 |
| NO151291C (en) | 1985-03-13 |
| DE2964510D1 (en) | 1983-02-17 |
| FI67874B (en) | 1985-02-28 |
| ATE2224T1 (en) | 1983-01-15 |
| BR8002360A (en) | 1980-12-02 |
| DE2915467A1 (en) | 1980-10-30 |
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