DE102007009127A1 - Open-cell aminoplastics foam for thermal and acoustic insulation in building, vehicle or aircraft, low temperature insulation, insulating shock-absorbing packaging material, cleaning sponge or hygiene product contains fibrous filler - Google Patents

Abstract

Open-cell foam based on aminoplastics contains 0.5-50 wt.% fibrous filler. An independent claim is included for the production of this foam.

Description

The The invention relates to an open-celled foam based on a Aminoplast containing 0.5 to 50 wt .-% of a fibrous filler, and a method for its production.

open cell elastic foams based on melamine / formaldehyde resins and processes for their preparation by heating with hot air, water vapor or microwave irradiation with foaming and crosslinking of a propellant-containing solution or dispersion of a melamine / formaldehyde precondensate are known and described for example in EP-A 17672 and EP-A 37470.

she are suitable for different heat and soundproofing Applications in buildings and vehicles, as well as insulating and shock-absorbing packaging material.

The EP-A 0 221 330 describes foams and fibers of melamine resins with elevated Strength at which 1 to 80 wt .-% of the melamine by hydroxyalkylmelamine, preferably hydroxyalkylmelamine are replaced.

task The aim of the present invention was to determine the mechanical properties in particular the compressive strength of open-cell foams to increase.

Accordingly, became the above-described open-cell foam based on a Aminoplasts found.

Prefers contains the foam 5 to 20 wt .-% of a fibrous filler.

Fibrous filler:
Short or long fibers made of glass, carbon or melamine resin are particularly suitable as a fibrous filler. The fibers preferably have an average length in the range of 2 to 2000 mm and an average thickness in the range of 5 to 25 μm. The ratio of length: diameter of the fibers is preferably in the range of 5: 1 to 500: 1.

Prefers Melamine fibers are used in which due to the similar chemical composition such as the material of the cell webs of the foam on additional Adhesion promoters or layers can be dispensed with. The production The preferred melamine fibers may be used, for example in EP-A 93 965, DE-A 23 64 091, EP-A 221 330, EP-A 408 947, DE-A 10029334 or DE-A 10133787 described.

Especially preferred melamine fibers contain as monomer unit (A) 90 to 100 mol% of a mixture consisting essentially of 30 to 100, preferably 50 to 99, particularly preferably 85 to 95, in particular 88 to 93 mol% melamine and 0 to 70, preferably 1 to 50, especially preferably 5 to 15, in particular 7 to 12 mol .-%, of a substituted Melamine or mixtures thereof. Suitable substituted melamines are 2- (2-hydroxyethylamino) -4,6-diamino-1,3,5-triazine, 2,4-di- (2-hydroxyethylamino) -6-amino-1,3,5-triazine, 2,4,6-tris- (2-hydroxyethylamino) -1,3,5-triazine, with the 2-hydroxyisopropylamino group substituted melamines, such as 2- (2-hydroxyisopropylamino) -4,6-diamino-1,3,5-triazine, 2,4-di (2-hydroxyisopropylamino) -6-amino-1,3,5-triazine 2,4,6-tris (2-hydroxyisopropylamino) -1,3,5-triazine, 2- (5-hydroxy-3-oxapentylamino) -4,6-diamino-1,3,5-triazine, 2,4,6-Tris- (5-hydroxy-3-oxapentylamino) -1,3,5-triazine, 2,4-di (5-hydroxy-3-oxapentylamino) -6-amino, 1,3,5 triazine, 2- (6-aminohexylamino) -4,6-diamino-1,3,5-triazine, 2,4-di- (6-aminohexylamino) -6-amino-1,3,5-triazine, 2,4,6-tris- (6-aminohexylamino) -1,3,5-triazine or mixtures of these compounds, for example a mixture of 10 mol% of 2- (5-hydroxy-3-oxapentylamino) -4,6-diamino-1,3,5-triazine, 50 mole percent 2,4-di- (5-hydroxy-3-oxapentylamino) -6-amino-1,3,5-triazine and 40 mole percent 2,4,6-tris- (5-hydroxy-3-oxapentyamino) -1,3,5-triazine.

When further monomer (B) contain the preferred melamine fibers 0 to 10, preferably from 0.1 to 9.5, in particular from 1 to 5, mol%, based on the total number of moles of monomer units (A) and (B), a phenol or a mixture of phenols.

Suitable phenols (B) are one or two hydroxyl-containing phenols which are optionally substituted by radicals selected from the group consisting of C ₁ -C ₉ -alkyl and hydroxy and by C ₂ -C ₄ -alkanes which are substituted by two or three phenol groups, Di (hydroxyphenyl) sulfones or mixtures of these phenols.

When preferred phenols are: phenol, 4-methylphenol, 4-tert-butylphenol, 4-n-octylphenol, 4-n-nonylphenol, catechol, resorcinol, hydroquinone, 2,2-bis (4-hydroxyphenyl) propane, Bis (4-hydroxyphenyl) sulfone, more preferably phenol, resorcinol and 2,2-bis (4-hydroxyphenyl) propane.

The preferred melamine fibers are conventional by reacting the components (A) and (B) with formaldehyde or Formaldehyde-supplying compounds and subsequent spinning available, where the molar ratio of melamines to formaldehyde in the range of 1: 1.15 to 1: 4.5, preferred from 1: 1.8 to 1: 3.0.

formaldehyde One sets usually as watery solution at a concentration of, for example, 40 to 50% by weight or in Form of compounds used in the reaction with (A) and (B) formaldehyde provide, for example as oligomeric or polymeric formaldehyde in solid form, such as paraformaldehyde, 1,3,5-trioxane or 1,3,5,7-tetroxane.

to Preparation of the preferred melamine fibers is usually polycondensed Melamine, optionally substituted melamine and optionally Phenol together with formaldehyde or formaldehyde-supplying compounds. You can submit all components right at the beginning or you can can bring them in portions and successively to the reaction and the Preformed condensates formed subsequently further melamine, substituted Add melamine or phenol.

The Polycondensation leads in a manner known per se (see EP-A 355 760, Houben-Weyl, Bd. 14/2, p. 357 ff). The reaction temperature is chosen in general in a range from 20 to 150, preferably from 40 to 140 ° C. The reaction pressure is usually not critical. You generally work in one Range of 100 to 500 kPa, preferably below atmospheric pressure. Further leads the polycondensation generally in a pH range above from 7 out. Preferably, the pH range is from 7.5 to 10.0, especially preferably from 8 to 9.

you can carry out the reaction with or without solvent. In As a rule, no use is made of aqueous formaldehyde solution solvent to. When using formaldehyde bound in solid form, one chooses as a solvent usually Water, the amount used usually in the range of 5 to 40, preferably from 15 to 20 wt .-%, based on the total amount used monomers.

Of further you can the reaction mixture small amounts usual Additions, such as alkali metal sulfites, e.g. Sodium disulfite and sodium sulfite, Alkali metal formates, e.g. Sodium formate, alkali metal citrate, e.g. Sodium citrate, phosphates, polyphosphates, urea, dicyandiamide or add cyanamide. They can be used as pure individual compounds or as mixtures with each other, each in bulk or as an aqueous solution, while or after the condensation reaction.

Other Modifiers are amines and amino alcohols, such as diethylamine, Ethanolamine, diethanolamine or 2-diethylaminoethanol.

When other additives are fillers or emulsifiers. As fillers you can, for example fibrous or powdery inorganic reinforcing agents or fillers, such as glass fibers, metal powders, metal salts or silicates, e.g. Kaolin, Talc, barite, quartz or chalk, pigments and dyes deploy. As emulsifiers are usually used the usual nonionic, anionic or cationic organic compounds with long-chain alkyl radicals.

The Polycondensation can be carried out batchwise or continuously, for example in an extruder (see EP-A 355 760), according to itself perform known methods.

to Production of fibers is usually spun the melamine resin according to the invention in a conventional manner, for example after addition of a curing agent, usually acids, such as formic acid, sulfuric acid or Ammonium chloride, at room temperature in a rotary spinning machine and hardens subsequently the raw fibers in a heated atmosphere, or you spun in a heated atmosphere, at the same time evaporates the serving as a solvent water and hardens the condensate off. Such a method is described in DE-A-23 64 091 described in detail.

However, it is also possible to use other customary methods for producing the melamine fibers, for example stringing, extruding and fibrillating processes. The fibers obtained are generally my pre-dried, optionally stretched and then cured at 120 to 250 ° C.

Commercially available melamine fibers are common 5 to 25 μm thick and 2 to 2000 mm long.

Open cell foam:
The apparent density of the open-cell foam is generally in the range from 5 to 100 g / l, preferably in the range from 8 to 20 g / l. The cell count is usually in the range of 50 to 300 cells / 25 mm. The tensile strength is preferably in the range of 100 to 150 kPa and the elongation at break in the range of 8 to 20%.

to Production of an open-celled foam based on the Aminoplast's preferred melamine / formaldehyde (MF) resin can after EP-A 071 672 or EP-A 037 470 a highly concentrated, propellant-containing solution or dispersion of a melamine-formaldehyde precondensate with hot air, water vapor or foamed and cured by microwave irradiation.

According to the invention Mix before heating 0.5 to 50 wt .-%, preferably 5 to 20 wt .-%, based on the solid the mixture, a fibrous one filler is added.

at the method according to the invention one starts from a melamine / formaldehyde precondensate. Melamine / formaldehyde condensation products can in addition to melamine up to 50, preferably up to 20 wt .-% of other thermoset builders and besides formaldehyde up to 50, preferably up to 20,% by weight Contain other aldehydes condensed. Particularly preferred an unmodified melamine / formaldehyde condensation product. As Duroplastbildner For example, alkyl- and arylalkyl-substituted melamine, urea, Urethanes, carboxylic acid amides, Dicyandiamide, guanidine, sulphurylamide, sulphonic acid amides, aliphatic amines, Glycols, phenol and its derivatives in question. As aldehydes, e.g. Acetaldehyde, trimethylolacetaldehyde, acrolein, benzaldehyde, furfurol, Glyoxal, glutaraldehyde, phthalaldehyde and terephthalaldehyde used become. More details about Melamine / formaldehyde condensation products can be found in Houben-Weyl, Methods of Organic Chemistry, Volume 14/2, 1963, pages 319 to 402nd

The molar ratio Melamine to formaldehyde is usually less than 1: 1.0, it lies preferably between 1: 1.2 and 1: 4.0, in particular between 1: 1.3 and 1: 1.8. According to EP-B 37470, the melamine resins contain advantageous Condensed sulfite groups, which, for example, by addition of 1 to 20 wt .-% sodium hydrogen sulfite in the condensation of the resin can happen. It has been shown that a relatively high sulfite group content At constant melamine to formaldehyde ratio higher formaldehyde emission of the foam. The pre-condensate used should Therefore, they contain virtually no sulfite groups, that is, the sulfite group content should be below 1%, preferably below 0.1% and especially 0% be.

to Emulsification of the blowing agent and stabilization of the foam the addition of an emulsifier or an emulsifier mixture is required. As an emulsifier can anionic, cationic and nonionic surfactants and mixtures thereof be used.

suitable anionic surfactants are diphenylene oxide sulfonates, alkane and alkyl benzene sulfonates, Alkylnaphthalenesulfonates, olefin sulfonates, alkyl ether sulfonates, Fatty alcohol sulfates, ether sulfates, alpha-sulfofatty acid esters, Acylaminoalkanesulfonates, acylisethionates, alkylethercarboxylates, N-acyl sarcosinates, alkyl and alkyl ether phosphates. As nonionic Surfactants can Alkylphenol polyglycol ethers, fatty alcohol polyglycol ethers, fatty acid polyglycol ethers, fatty acid, EO / PO block copolymers, Amine oxides, glycerol fatty acid esters, Sorbitan esters and alkyl polyglucosides are used. As cationic Emulsifiers come Alkyltriammoniumsalze, Alkylbenzyldimethylammoniumsalze and alkylpyridinium salts. The emulsifiers are preferably in amounts of 0.2 to 5 wt .-%, based on the resin added.

To form a foam from the melamine resin solution, it must contain a propellant, the amount depending on the desired density of the foam. In principle, both physical and chemical blowing agents can be used in the process according to the invention. Suitable physical blowing agents are, for example: hydrocarbons, halogenated, in particular fluorinated hydrocarbons, alcohols, ethers, ketones and esters in liquid form or air and CO ₂ as gases. Suitable chemical blowing agents are, for example, isocyanates mixed with water, in which CO _{2 is} released as the effective blowing agent, furthermore carbonates and bicarbonates mixed with acids which likewise produce CO ₂ , and azo compounds, such as azodicarbonamide. In a preferred embodiment of the invention, the aqueous solution or dispersion is added between 1 and 40% by weight, based on the resin, of a physical blowing agent having a boiling point between 0 and 80 ° C .; for pentane, it is preferably 5 to 15 Wt .-%.

When Harder are used acidic compounds, the further condensation catalyze the melamine resin. The amounts are between 0.01 and 20, preferably between 0.05 and 5 wt .-%, based on the Resin. In question are inorganic and organic acids, e.g. Hydrochloric acid, Sulfuric acid, Phosphoric acid, Nitric acid, formic acid, Acetic acid, oxalic acid, toluenesulfonic, amidosulfonic and acid anhydrides.

The aqueous solution or dispersion is preferably free in addition to the fibrous fillers of other additives. For however, it can be beneficial for some purposes be, up to 20 wt .-%, preferably less than 10 wt .-%, based on the resin, more usual Additives, such as dyes, flame retardants, UV stabilizers, Means for the reduction of the fire gas toxicity or for the promotion to add to the charring.

There the foams can absorb water due to the open-celledness it for Some applications may be necessary in water repellents Amounts of 0.2 to 5 wt .-% add. In question, for example, Silicones, paraffins, silicone and fluorosurfactants, hydrophobic hydrocarbon surfactants, Silicone and fluorocarbon emulsions.

The Concentration of the melamine / formaldehyde precondensate in the mixture from precondensate and solvent can be within wide limits between 55 and 85, preferably between 63 and 80, wt .-% vary. The preferred viscosity of the mixture from precondensate and solvent is between 1 and 300 ° dPas, preferably between 5 and 2000 dPas.

The fibrous fillers and additives are mixed with the aqueous solution or dispersion of the melamine resin mixed homogeneously, the propellant if necessary, even pressed under pressure can be. However, it is also possible to use a solid, e.g. spray-dried Melamine resin go out and this then with an aqueous solution of the emulsifier, the hardener and mix the propellant. The mixing of the components can e.g. be made in an extruder. After mixing is the solution or dispersion through a nozzle discharged and immediately afterwards heated and foamed.

The Heating the propellant-containing solution or dispersion can basically - as in EP-B 17671 described - by name is Gases or radiofrequency radiation are made. Prefers but is the required heating by ultra-high frequency radiation carried out according to EP-B 37470. In this dielectric radiation can basically with microwaves in the frequency domain from 0.2 GHz to 100 GHz. Stand for industrial practice Frequencies of 0.915, 2.45 and 5.8 GHz are available, with 2.45 GHz especially are preferred. Radiation source for dielectric radiation is the magnetron, although with multiple magnetrons simultaneously can be irradiated. It is important to note that during the irradiation the field distribution as possible is homogeneous.

Conveniently, the irradiation is carried out in such a way that the power consumption of the solution or Dispersion between 5 and 200, preferably between 9 and 120 KW, based on 1 kg of water in the solution or dispersion is. If the recorded power is lower, then does not foam more and the mixture hardens only off. If you work within the preferred range, so foamed the faster the mixture, the faster the power consumption. Above about 200 KW per kg of water, the foaming speed increases not much more.

The Irradiation of the to be foamed Mixture takes place immediately after leaving the frothing nozzle is. This is due to temperature increase and evaporation of the blowing agent foaming Mix on rotating bands applied, which form a rectangular channel for forming the foam.

to Production of foams based on a melamine / formaldehyde condensation product with low formaldeyde emission can be described as in WO 01/94436 a MF precondensate with a molar ratio of melamine to formaldehyde from bigger than 1: 2 used. To achieve very low formaldehyde emissions, the foam can after heating for 30 minutes at 220 ° C annealed become. After tempering, however, the foams are cured and no longer thermoformable.

After its preparation, the foams according to the invention are subjected to a temperature treatment. They are usually heated for 1 to 180 minutes, preferably for 5 to 60 minutes at temperatures between 100 and 300 ° C, in particular between 150 and 250 ° C, wherein water, propellant and form aldehyde is largely removed.

The elastic foams produced according to the invention, which preferably contain virtually no sulfite groups, have a density of from 5 to 50 g ^-1 .

Around To improve the performance characteristics, the Foams afterwards, for example, as described in EP-B 37470, tempered and pressed become,. The foams can to the desired Shape and thickness tailored and one or both sides with cover layers be laminated. For example, a polymer or metal foil be applied as a topcoat.

The Foams can be produced as plates or sheets with a height up to 2 m or as foam sheets with a thickness of a few mm. The preferred foam height (in the foaming direction) is present when using 2.45 GHz frequency microwaves 50 cm and 150 cm. From such foam sheets can all desired Plate or film thicknesses be cut out. The foams can with one or both sides with Cover layers or laminated, e.g. with paper, cardboard, glass fleece, Wood, gypsum boards, metal sheets or foils, plastic films, which may also be foamed can.

The Main field of application of the foams produced according to the invention is the heat and sound insulation of buildings and building parts, in particular of partitions, but also from roofs, Facades, doors and floors; Farther the heat- and sound insulation the engine and interior spaces of vehicles and aircraft as well as the low-temperature insulation, z. B. of cold storage, oil tanks and containers of LPG. Further fields of application are the use as insulating wall cladding as well as insulating and shock-absorbing Packing material. Due to the high hardness of crosslinked melamine resins can the foams also for slightly abrasive cleaning, grinding and polishing sponges used become.

The open-cell structure of the foams additionally allows the Picking up and storing suitable cleaning, grinding and polishing agents inside the foams. Also, the sponges for special Cleaning tasks hydrophobic and oleophobic be equipped.

going one of formaldehyde-poor precondensates, the foams of the invention can be also in the hygiene sector e.g. in the form of thin fleeces as a wound dressing or as part of baby diapers and incontinence products.

by virtue of the elasticity the open-cell foam this can in a simple way to insulation in already prefabricated container parts added become. Even at low temperatures, for example, below -80 ° C remains the foam elastic. Damage caused by embrittlement occurs not up. It is therefore particularly suitable for flexible Isolation of moving pipes, for example for filling hoses of liquid Nitrogen.

Examples

Examples 1 to 3

To produce the melamine resin foams served in the EP 17 671 specified procedure. In the examples according to the invention, the parts by weight of melamine resin fibers indicated in the table were added to the blowing agent-containing resin mash prior to foaming. The melamine fibers were produced by the process of DE-A-23 64 091.

The results summarized in Table 1 show that by adding of melamine resin fibers, the compressive strength of the melamine resin foam is significantly improved at comparable density.

• The densities were determined according to EN ISO 845.
• The compressive stresses were measured according to DIN 5342 at 10% Upsetting.

Claims (8)

An open-cell foam based on an aminoplast, characterized in that it contains 0.5 to 50% by weight of a fibrous filler. Open cell foam according to claim 1, characterized characterized in that it has a bulk density in the range of 5 to 100 g / l. Open-cell foam according to claim 1 or 2, characterized in that the fibrous filler has a ratio of Length: Diameter ranging from 5: 1 to 500: 1. Open-cell foam according to one of claims 1 to 3, characterized in that the fibrous filler has an average length in the range from 2 to 2000 mm. Open-cell foam according to one of claims 1 to 4, characterized in that the fibrous filler has an average thickness in the range of 5 to 25 μm having. Open-cell foam according to one of claims 1 to 5, characterized in that the fibrous filler of glass, carbon or melamine resin. Process for producing an open-celled foam according to claim 1 by heating under foaming and crosslinking a mixture containing a melamine / formaldehyde (MF) precondensate, a hardener and a propellant, characterized in that the mixture before heating 1 to 50 wt .-%, based on solids of the mixture, of a fibrous filler is added. Method according to claim 7, characterized in that that the molar ratio Melamine / formaldehyde of the precondensate in the range of 1: 1.3 to 1: 4 is.