Patent Application
20170298184
The present invention relates to a needling additive for the manufacture of needle felts of mineral wool wherein formaldehyde- and fluorine-free needling additive for the manufacture of needle felts of mineral wool is characterized by containing an aqueous solution or an aqueous dispersion of at least one halogen-free cationic polymer on the basis of azacyclopropane (ethyleneimine), a needle felt obtained by needling mineral wool using a formaldehyde- and fluorine-free needling additive characterized by containing an aqueous solution or an aqueous dispersion of at least one halogen-free cationic polymer on the basis of azacyclopropane (ethyleneimine), and use of an aqueous solution or an aqueous dispersion of at least one halogen-free cationic polymer on the basis of azacyclopropane (ethyleneimine) as a needling additive for the manufacture of formaldehyde- and fluorine-free needle felts made of mineral wool.
Needle felts made of mineral wool are suited particularly well for heat insulation in household appliances, e.g. in ovens and stoves as well as in industrial muffle kilns.
The manufacture of such needle felts has been known to a person skilled in the art for a long time and is described, for example, in EP 363 707 A2.
In needling mineral wool felts, needling additives, so-called avivages, is to be applied to the fibers of the mineral wool felt to be needled. In the past, such avivages were mostly produced, according to EP 363 707 A2, on the basis of mineral oils, natural oils or fatty acid derivatives. In particular, avivages of high viscosity were used.
Avivages are used in order to render the fibers more supple and reduce inter-fiber friction during needling so as to prevent, if possible, tearing or breaking of the fibers during needling. Furthermore, an avivage also must be capable of binding dusts arising during the production process in order to enable processing and application of the needle felt without additional measures for dust protection.
Typically, such avivages are sprayed onto the fibers in the chute of a fiberization unit for molten glass or directly onto the felt. In doing so, a viscosity compromise has to be accepted in that, on the one hand, it is to be safeguarded that the fibers are sufficiently sprayed and, on the other hand, that during the evaporation of the carrier medium material of sufficient viscosity remains in order to ensure the aforementioned advantages during needling.
Additionally, DE 699 16 112 T2/EP 1 141 462 B1 discloses fibre lubricants as component of binder/sizing compositions for glass fibre needle mats used in the reinforcement of thermoplastic materials. Useful glass fiber lubricants according to this prior art include cationic, non-ionic or anionic lubricants and mixtures thereof. Generally, the amount of fiber lubricant can be about 1 to about 25 weight percent of the sizing composition on a total solids basis. Some examples of the many known fiber lubricants include amine salts of fatty acids (which can, for example, include a fatty acid moiety having 12 to 22 carbon atoms and/or tertiary amines having alkyl groups of 1 to 22 atoms attached to the nitrogen atom), alkyl imidazoline derivatives (such as can be formed by the reaction of fatty acids with polyalkylene polyamines), acid solubilized fatty acid amides (for example, saturated or unsaturated fatty acid amides having acid groups of 4 to 24 carbon atoms such as stearic amide), condensates of a fatty acid and polyethylene imine and amide substituted polyethylene imines, such as EMERY® 6717, a partially amidated polyethylene imine commercially available from Henkel Corporation.
Therefore, in the past particularly lubricating oils and lubricants on the basis of mineral oils were suited as avivages. However, the disadvantage in the use of such substances as needling additive was to be seen in that for the preparation of an aqueous dispersion or emulsion, considerable amounts of one or several emulsifier(s) had to be added, so that phase separation into a mineral oil phase and an aqueous phase did not already occur in the reservoir of the dispensing device of the avivage. In the past, particularly alkoxylates of alcohol and/or nonylphenols were used as emulsifiers, which, however, entail the disadvantage that in needle felts that are used for heat insulation in household appliances, e.g. ovens and stoves as well as industrial muffle kilns, they can decompose during heating, thereby splitting off formaldehyde.
However, in the past it likewise turned out that even if needle felts were treated thermally after needling for removing the needling additive, in addition to increased energy input and hence increased costs, residues of the avivage and particularly of the emulsifiers contained therein nevertheless may lead to unpleasant smell or even to a release of undesired volatile organic compounds (VOC), in particular formaldehyde, even in a final consumer.
To circumvent those difficulties various approaches were tested in the prior art. Thus, it was tried, for example, to disperse mineral oil products in water via a high-pressure dispersion mixing device such that no emulsifier had to be added. This, however, on the one hand, resulted in a great deal of technical effort and, on the other hand, did not provide the intended results.
A further approach for circumventing the problem was to be seen in that in accordance with DE 42 01 868 a thixotroping additive was added to a standard avivage on the basis of fatty acid polyglycol ester. Such a thixotroping additive has the advantage of having high static viscosity and thus maintain the fiber slings in their anchoring position obtained by the needling process while good needling properties and a good lubricating effect arise if a low moving viscosity is provided. As a result of the low viscosity as part of the effect of the needles on the felt to be needled it is possible that merely low amounts of a needling additive have to be added, the VOC emission in case of temperature effects being reduced correspondingly.
However, a disadvantage of the avivage or the needle felts of the prior art is that unpleasant smells and thermal decomposition products still occur, which is not desired particularly in the field of household appliances.
A further approach for the development of to a large extent VOC emission-free needle felts suited for households was the needling additive in accordance with DE 196 28 477 C1 and its parallel European patent EP 819 788 B1.
The documents describe a needling additive that contain an aqueous dispersion of at least one partially halogenated polymer.
According to DE 196 28 477 C1, such partially halogenated polymers may be selected from the group consisting of:
In practice, perfluorinated polyethers have turned out to be particularly well suited needling additive in accordance with DE 196 28 477 C1, on the one hand, as those ethers may bring about extremely favorable sliding properties between the fiber slings during needling and, on the other hand, that due to the fact that virtually all hydrogen atoms within the polyether system are replaced by fluorine atoms, such perfluorinated polyethers are chemically inert and also thermally resistant.
It merely was of disadvantage that the perfluorinated needling additive had to be stabilized using an inflammable solubilizing agent, particularly t-butyl alcohol, in order to keep the fluorinated polyethers in solution or dispersion.
During the investigations conducted in 1996 it turned out that, using the detection methods known at that time, formaldehyde or fluorinated anorganic or organic compounds could be detected neither in the chute nor in the later needle felt that was subjected to a temperature of up to 500° C. for more than 1 hour, if a perfluorinated needling additive in accordance with DE 196 28 477 C1 was used for needling of the felt.
This likewise held for investigations during the operation of stoves insulated with needle felts that contained a perfluorinated needling additive in accordance with DE 196 28 477 C1. Typically, during the heat-up phase in the first weeks of operation of the stoves virtually no unpleasant smells occurred.
However, in meanwhile 20 years of practice it has turned out that the detection limits for formaldehyde and fluorine have decreased considerably, on the one hand, on account of far more sensitive test methods and particularly detection systems thereof available today in high-pressure liquid chromatography (HPLC) methods used in routine applications, as well as in methods of gas chromatography-mass spectrometry (GC-MS).
On the other hand, the exposition temperature of the needle felts introduced in ovens has doubled from a maximum operating temperature of approximately 250° C. to today's cleaning temperature of approximately 500° C. since the time of introduction of perfluorinated needling additives.
This is explained by the fact that modern stoves frequently have a so-called pyrolytic cleaning function in which through activation of pyrolysis after baking, roasting or grilling, baking, roasting or grilling residues are decomposed to ash at temperatures of up to 500° C. After cooling down the oven, the ash may be wiped away with a cloth.
Such pyrolysis constitutes extreme thermal stress to the needle felt insulation and particularly to the organic-chemical components contained therein.
In more recent investigations using high-sensitive analyzing methods it has turned out that the perfluorinated needling additive well-established in practice may lead to the release of undesired inorganic and organic components when subjected to higher thermal stress.
It was reported in some cases that during the first pyrolytic cleaning phase of the oven, pets, in particular birds, died if they were present in the kitchen during such pyrolytic cleaning phase.
On account of such findings the emission behavior of stoves insulated with needle felts that contained perfluorinated needling additives was newly examined.
In so doing, it turned out that fluorinated VOC could be proved particularly under the given high thermal stress of pyrolytic cleaning. Those low-molecular organic fluorine compounds, with the silicon of the mineral wool, may convert to volatile inorganic compounds such as SiF4, which may then hydrolyze with the water in the ambient air to form SiO2 and HF. The investigation of the emission behavior of such needle felts and the measurement of the fluorine content or PFC content resulted in fluorine concentrations of >180 ppm under unfavorable conditions. Both the volatile organic fluorine compounds and in particular HF are problematic for humans and animals in terms of health and moreover are corrosive.
In light of the foregoing, there is a need in needling additives for the manufacture of needle felts of mineral wool that essentially do not emit unhealthy compounds even in modern household appliances under the conditions of an increased heat exposition of the needle felts used for heat insulation.
Based on the prior art of DE 196 28 477 C1, it is therefore an object of the present invention to provide a needling additive for the production of needle felts of mineral wool that are suited for heat insulation of ovens, stoves and muffle kilns and that release virtually no decomposition products, in particular neither formaldehyde nor fluorinated compounds, that might be harmful to the health, even at temperatures of about 500° C., as may occur during the pyrolytic cleaning of ovens.
With regard to the needling additive, the object is solved by the characterizing features of a formaldehyde- and fluorine-free needling additive for the manufacture of needle felts of mineral wool characterized by containing an aqueous solution or an aqueous dispersion of at least one halogen-free cationic polymer on the basis of azacyclopropane (ethyleneimine), a needle felt obtained by needling mineral wool using a formaldehyde- and fluorine-free needling additive characterized by containing an aqueous solution or an aqueous dispersion of at least one halogen-free cationic polymer on the basis of azacyclopropane (ethyleneimine), and using an aqueous solution or an aqueous dispersion of at least one halogen-free cationic polymer on the basis of azacyclopropane (ethyleneimine) as a needling additive for the manufacture of formaldehyde- and fluorine-free needle felts made of mineral wool.
The present invention relates in particular to a formaldehyde-free and fluorine-free needling additive for the manufacture of needle felts of mineral wool, which contains an aqueous solution or an aqueous dispersion of at least one halogen-free cationic polymer on the basis of azacyclopropane (ethyleneimine).
Such needling additives, on the one hand, are excellently suited for needling felts of mineral wool and fulfill all requirements posed to the manufacturing process with regard to the sliding properties of the needles of a needle beam through the fiber slings in the felt as well as a sufficiently high reduction of restoring forces of the fiber slings pushed into the interior of the felt by the needles. This results in mechanically perfect needle felts.
On the other hand, the halogen-free cationic polymers used as needling additive in accordance with the present invention exclusively consist of the atoms C, H and N, so that even at increased temperatures of up to 500° C. during the pyrolytic cleaning phase of modern ovens, no halogen compounds, particularly fluorine compounds, and also no hydrogen fluoride can be formed.
Moreover, the invention relates to a needle felt obtained by needling a mineral wool path thereby using the needling additive in accordance with the present invention.
In analyzing the gaseous products that arise from the organic applied to the fibers in heating the needle felts in accordance with the invention to 500° C., the fluorine content of the gathered emission samples was below a detection limit measured by way of GC-MS, whereas the fluorine content in the needle felts in accordance with the prior art of DE 196 28 477 C1 was above 180 ppm.
The concentration of formaldehyde in emission samples of the stoves insulated with the needle felts in accordance with the invention was below 10 ppm, so that the products fulfill the current requirements (<10 ppm) to the emission of formaldehyde in first pyrolytic cleaning, i.e. are formaldehyde-free from a practical perspective.
In heating up to approximately 500° C., the needle felts in accordance with the invention thus substantially neither release aldehydes, particularly formaldehyde and/or acetaldehyde, nor halogens or hydrogen halide, particularly HF.
In addition to the advantage of virtually emitting no formaldehyde and fluorine and/or fluorine compounds, the needling additive in accordance with the present invention has the particular advantage of not requiring any additional emulsifiers that again might have an adverse effect on the gas emission tendency of the needle felts treated with the needling additive, on account of the water solubility of the halogen-free cationic polymers used, in particular polyethyleneimines. No separation of the needling additive solutions is to be feared and the prepared solutions are stable over a period of several months.
Furthermore, no inflammable solubilizing agents such as t-butyl alcohol or the like are required so as to keep the polymers in solution.
In pilot studies on the production line, polyethyleneimine has turned out to be the halogen-free cationic polymer that is particularly suited. Especially well suited is a homopolymer of azacyclopropane (CAS No. 9002-98-6) or a copolymer of ethane-1,2-diamine and azacyclopropane (CAS-No.: 25987-06-8); as well as mixtures thereof.
Moreover, those halogen-free cationic polymers that have a weight average molecular weight (Mw) of between 500 and 3 000 Da, in particular approximately 500 Da, preferably 1 500 Da, have turned out to be particularly suited needling additives. Especially preferred are those polyethyleneimines that are copolymers of ethane-1,2-diamines and azacyclopropane and have an Mw of 800 or 1 300 Da.
Such polyethyleneimines are well known to a person skilled in the art and are commercially available.
It is a preferred embodiment of the present invention to apply the needling additive onto the fibers of the mineral wool in an aqueous solution in concentrations of 0.05 to 0.5 percent by weight, in particular 0.1 to 0.3 percent by weight, with regard to the fiber mass of halogen-free cationic polymer.
Preferably, the needling additive is sprayed onto the fibers already in the chute, following the fiberization unit. Alternatively, it may also be applied to the felt already put on a conveyor belt prior to being fed into the needling area.
The needle felts in accordance with the present invention thus are excellently suited for heat insulation in household appliances, particularly in ovens and stoves, as they, upon the initial operation in a final consumer, neither generate unpleasant smells nor decomposition products that may constitute a health risk.
Within the scope of the present invention it should be noted that the needling additive in accordance with the present invention for needling mineral wool also is suited particularly for glass wool.
Further advantages and features of the present invention are to be seen from the description of embodiments and on the basis of a comparative example.
Devices and Chemicals:
Determination of formaldehyde by way of a reaction with 2,4-Dinitrophenylhydrazine
Emission analytics GC-MS
Production of needle felt:
Determination of the emission of formaldehyde by baking out in air at 350° C. and 500° C. in accordance with the provisions of Stiftung Warentest (German consumer organization)
10 g each of the corresponding material are positioned in a quartz glass tube and the tube is heated in a tubular furnace to 350° or 500° C. In so doing, dry, synthetic air flows through the sample for 60 min with 1 l/min and the waste gas is led through washing bottles filled with water.
The emission samples thus obtained are transferred to a 250 ml volumetric flask and filled with water up to a mark. Subsequently, 10 ml of the solution are transferred to a 25 ml flask and filled up with a DNPH reaction solution up to the mark. After 1 hour the sample is analyzed and evaluated.
HPLC column:
Determination of volatile organic substances by way of thermodesorption GC-MS
Test arrangement GC-MS:
For determining the emissions of fluorine compounds and VOC 100-200 mg or the respective material sample were used. In table 2, results of a one-time run of the temperature program and a repeated run, five-time herein, of the temperature program are contrasted with each other, the emission for the five runs being added up. It turned out that with the fifth run the emission decreased to the range of the detection limit, so that repeated heating was terminated.
The determined fluorine compounds are indicated as perfluorooctane.
Thus, the needle felts of the present invention are excellently suited for use as heat insulating material in modern household appliances such as ovens or stoves with pyrolytic cleaning at increased temperature.
For the preparation of the formulation of needling additive an aqueous micro-emulsion of a perfluoroether is used, which is commercially available under the name “Fomblin FE 20C”. The emulsion has a polymer proportion of approximately 20 percent by weight and is stabilized with approximately 18 percent by weight of t-butyl alcohol.
For preparation of a solution or dispersion ready to use the commercially available solution is diluted with water to a polymer proportion of approximately 12 percent by weight.
By further adding water an end concentration of approximately 0.1 and 0.2 percent by weight of perfluoropolyether is set and then sprayed onto a glass wool felt, which is then guided under a needle bank and subjected to needling, using the parameters in accordance with examples 1 and 2.
A needle felt of glass wool produced in such a manner has a gross density of approximately 50 kg/m3 and a thickness of approximately 20 mm.
By analogy of the examples 1 and 2, the needle felts thus produced were examined for the emission of formaldehyde and volatile fluorine compounds.
A formaldehyde content of 2 to 8 ppm was measured (cf. table 1). The value is below the stipulated threshold values, so that a formaldehyde-free product likewise may be assumed.
However, in measuring the needle felts of the comparative example of volatile fluorine compounds by way of GC-MS values of up to approximately 190 ppm were found (cf. table 2). It thus is to be assumed that the needle felts of the prior art, which were produced using the perfluorinated needling additive, release fluorine compounds to the environment of an oven.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2016 202 401.9 | Feb 2016 | DE | national |
This application is a United States Non-provisional Application claiming priority under 35 U.S.C. §119 from German Patent Application No. DE 10 2016 202 401.9, filed Feb. 17, 2016, the entire contents of which are herein incorporated by reference.
