Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-06-19
2002-05-28
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S494000, C524S594000
Reexamination Certificate
active
06395819
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to thermal or acoustic insulation products based on mineral wool, especially glass wool or rock wool, and on an organic binder based on formaldehyde-derived condensates used in these insulation products. Specifically, the present invention relates to an insulation product and a binder or sizing composition used therein which emits a reduced amount of volatile organic compounds, and to a manufacturing process for producing the insulation product.
2. Discussion of the Background
Products based on mineral wool are made by a multi-step process in which the wool itself is made by, for example, the technique known as centrifugal drawing, in which a molten mineral material is converted into filaments, and then the filaments are drawn and entrained by a high-temperature high-speed gas stream, thereby forming a sheet of the filaments in a receiving member. In order to ensure the cohesion of the sheet, a sizing composition containing a thermosetting sizing resin is sprayed onto the mineral wool (i.e., the filaments of the mineral material) as it travels towards the receiving member. The sheet thus treated is then subjected to a heat treatment in an oven in order to polycondense the sizing resin and thereby obtain a product having the desired properties, such as dimensional stability, tensile strength, thickness recovery after compression, and homogeneous color.
The sizing compositions which are sprayed onto the mineral wool, are generally aqueous compositions containing a phenol-formaldehyde resin and additives such as a catalyst for curing the resin, a silane adhesion promoter, antidusting mineral oils, etc. The ability of these compositions to be applied by sprayed is determined by the “dilutability” of the resin—that is, how well the resin can be diluted in water. The dilutability of the sizing resin is defined as the maximum degree of dilution of the sizing resin with room temperature water (room temperature is about 15 to 25° C., generally around 20° C.), for which no permanent turbidity of the diluted solution is observed. Preferably, a resin intended to be used in a sizing composition may be diluted on the order of at least 1000% at 20° C. (i.e., 10 ml of resin diluted with 100 ml of water or more, without the mixture becoming turbid). Consequently, it is common practice to limit the degree of condensation of the formaldehyde and phenol, in order to avoid the formation of long polymer chains which are not very hydrophilic and which would reduce the dilutability of the sizing resin. Sizing resins produced in this manner contain unreacted monomers, in particular formaldehyde. Because of its volatility, unreacted formaldehyde or other volatile monomers may produce undesirable emissions of organic compounds into the atmosphere.
Because of this problem, phenol-formaldehyde resins used in sizing compositions are generally treated with urea, which reacts with the free formaldehyde to form non-volatile condensation products. Furthermore, the presence of urea in the resin is economically advantageous because urea is inexpensive and may be introduced in relatively large quantities without appreciably affecting the service properties of the resin, especially the mechanical properties of the final product. This can significantly reduce the total cost of the resin. See, for example, EP-A-148,050.
However, this solution to the problem of volatile formaldehyde emission from sizing resins is not entirely satisfactory with regard to atmospheric pollution since the urea-formaldehyde condensation products are not very heat stable. When such resins are used in the sizing of mineral wool, the resin is exposed to temperatures of greater than 100° C. At such temperatures, the urea-formaldehyde condensation product generates urea, formaldehyde and ammonia gas, which are then released into the atmosphere of the factory.
Because of this problem, attempts have been made either to modify the urea-formaldehyde condensates chemically, in order to make them thermally more stable, or to reduce the proportion of urea-formaldehyde condensates in the resin. See, for example, EP-A-480,778. However, in each case, considerable amounts of the urea were nevertheless used in the resin in order to reduce the cost of the resin.
Although such modified sizing resins reduce the emission of undesirable organic compounds into a factory's atmosphere during manufacture of the insulation product, environmental standards are becoming increasingly more stringent. It is therefore always desirable to lower the level of emissions even further, particularly for insulation products exposed to high temperatures, and especially in the case of insulation products used in mass-produced thermal appliances, such as stoves and ovens.
The mineral wool based insulation products of the present invention are intended to minimize the of emission of pollutants, both during manufacturing and during use of the product by the end user. In the course of achieving this objective, the present inventors found that the presence of certain nitrogen compounds in the sizing resin may lead, at high temperature, to the emission of isocyanates, a type of pollutant that has hitherto not been recognized. The present inventors have identified urea as the foremost of these nitrogen compounds which can cause the emission of isocyanate pollutants. For example, when an insulation product containing a phenol-formaldehyde resin containing urea is heated to a high temperature, i.e., about 350° C., the emissions of at least one isocyanate, particularly methyl isocyanate, are approximately proportional to the amount of urea present in the sizing composition, and therefore in the insulation product.
SUMMARY OF THE INVENTION
The present invention is an insulation product based on mineral wool, especially glass wool or rock wool, containing a sizing resin based on a phenol-formaldehyde resin which is substantially free of urea or of a urea derivative, and in addition, the corresponding sizing composition.
DETAILED DESCRIPTION OF THE INVENTION
The term “urea derivative” means any product liable to be formed by the reaction of urea with at least one of the compounds in the resin. In particular, a sizing resin used in the manufacture of an insulation product according to the present invention contains no, or substantially no urea, nor a urea-formaldehyde condensation product.
To a lesser degree, ammonia, defined herewith as either ammonia or ammonium salts, may also be a source of isocyanate under certain conditions. In a preferred embodiment, the insulation product according to the present invention is substantially free of ammonia.
The expression “substantially free” means that only a minor amount of the specified compound, is present. An insulation which is substantially free of ammonia contains only minor amounts of ammonia, so that only insignificant amounts of the corresponding isocyanate emission can be measured. Alternatively, the amount of ammonia remains below an environmentally acceptable level, which level may vary depending on the use to which the product is put.
It is usually difficult to estimate the content of certain organic constituents of the insulation product as it leaves the manufacturing line in the finished state. Even though the amount of material used in each of the manufacturing steps may be precisely known, material may be lost into the atmosphere by evaporation or condensation, etc. during manufacturing, or subject to other sources of variability so that the final amount of a particular constituent may vary from one product to another during the same manufacturing run. By way of illustration, it may be estimated that an insulation product according to the present invention contains, on average, preferably at most 0.004%, more preferably 0.002%, by weight of urea or of a urea derivative, and in a most preferred embodiment the product contains no urea or urea derivative. Preferably, an insulation product according to the invention contains at most 0.2% by weight of
Espiard Philippe
Mahieuxe Bruno
Mallier Jean-Louis
Tetart Serge
Saint-Gobain Isover
Sanders Kriellion A.
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