Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2001-12-17
2003-11-11
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S137000, C528S140000, C528S145000, C528S162000, C528S164000, C528S230000, C528S239000, C528S256000, C528S257000, C528S489000, C528S492000, C528S503000, C524S841000
Reexamination Certificate
active
06646094
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the manufacture of mineral fiber insulation materials, and more particularly to the preparation of phenolic resin for glass fibers.
2. Brief Description of the Prior Art
Aqueous dispersions of phenol-formaldehyde resole resins are frequently used in the manufacture of mineral fiber insulation materials, such as insulative glass fiber batts for walls, in roofs and ceilings, insulative coverings for pipes, and the like. Typically, after glass fiber has been formed, the still hot fiber is sprayed with aqueous binder dispersion in a forming chamber or hood, with the fibers being collected on a conveyer belt in the form of a wool-like mass associated with the binder. In some cases, a glass fiber web is sprayed with the aqueous dispersion. Both resole and urea-modified resole resins have been employed for this purpose, the urea contributing to the “punking” resistance of the binder (i.e., resistance to exothermic decomposition at elevated temperatures), and reducing volables liberated when the resin is cured at elevated temperature. A problem sometimes encountered in this process is “precure” of the binder. Ideally, the water associated with the binder first volatilizes leaving behind the resinous binder, then the binder cures. If the binder cures too quickly, subsequent drying of the product may become difficult, requiring additional energy, and reducing the quality of the product.
An excess of formaldehyde over phenol is typically used so as to minimize the free phenol in the reaction product Subsequently, other components (for example, urea and/or ammonia) may be included to scavenge free formaldehyde.
Frequently, in the manufacture of mineral fiber insulation materials, the aqueous resole resin is prepared in advance of the preparation of the binder, or is supplied by a resin manufacturer and stored until shortly before use. The resole is typically prepared by reaction of phenol and formaldehyde under basic conditions, the resulting reaction mixture being neutralized to a slightly basic pH by addition of a strong acid, to provide a water-dilutable resole. Although the aqueous resole resin can be stored at a reduced temperature, the resin contains chemically reactive species that continue to react during storage of the resin, increasing the average molecular weight of the resin and diminishing the water dilutability of the resin. If the resin is stored for too long a period, it may become unusable by virtue of increased molecular weight and diminished water dilutability. On the other hand, unless the resin is actually made at or near the site where it is going to be used, some storage and transportation are inevitable. Minimizing monomer emissions from resins that must be stored for extensive periods presents significant problems. If the resin is permitted to “cook” until monomer levels are minimized, storage stability can be severely compromised. On the other hand, terminating the condensation reaction early may provide good storage stability, but residual monomer concentrations are likely to remain high. Good storage stability and low monomer emissions appear to be mutually contradictory goals.
The binder is prepared by adding to the resole resin an acid catalyst for curing the resin, water to dilute the dispersion, and optionally other components, such as a silane glass-adhesion promoter, an oil emulsion lubricant, and urea to reduce volatile materials liberated during curing. Alternatively, a “premix” for the binder can be prepared by mixing the resin with a formaldehyde-scavenging agent, such as urea and/or ammonia, prior to the addition of the remaining components of the binder.
U.S. Pat. No. 5,296,584 discloses resole melamine dispersions for use as high temperature adhesives, in which melamine is solubilized in low formaldehyde-containing resole resin melt having a high base or alkali ratio. The resulting uncured resinous compositions show improved water solubility.
Reduction of residual free formaldehyde can be achieved by “over-condensing” the resin, such as disclosed in International Patent Application WO9903906.
Given the large volume of resinous binder compositions required in the production of fiberglass insulation and for other uses, and the need to minimize offensive emissions of formaldehyde and other compounds during manufacture, there is a continuing need for phenol-formaldehyde resin compositions which exhibit low emissions during cure, and yet which show good storage stability.
SUMMARY OF THE INVENTION
The present invention provides an improved method or process for preparing a phenolic resin for use as a binder for mineral fibers and giving lower emissions during cure than prior art processes, as well as an improved resin and an improved binder, and mineral fiber products made using the improved binder. Advantageously, the present process provides a reduction in both the level of the residual formaldehyde and the residual phenol, while maintaining the water solubility and the storage stability of the resultant phenolic resin at high levels, at neutral pH. The present invention provides a product having a good balance of shelf life, reduced monomer emissions, good processing characteristics and ease of use, and binder efficiency, while minimizing overall product costs. In comparison with prior art processes, both the residual free phenol and the residual free formaldehyde are advantageously reduced by the process of the present invention. While the prior art provides various strategies for reducing free formaldehyde, the reduction of free phenol has proven more problematic since phenol is the limiting reagent. The present invention provides a reduction in free phenol overcoming a significant deficiency of such prior art processes. Simultaneously, the present invention provides a resin with an extended stability or shelf life, a significant and unexpected result when viewed in connection with the residual free monomer reduction.
The process comprises preparing a water-soluble resin, preferably a water-soluble phenol-formaldehyde resole resin, from three components: (1) at least one hydroxy-functional aromatic compound, preferably phenol, (2) at least one reactive aldehyde, preferably formaldehyde, and (3) at least one basic polymerization catalyst, preferably an alkali metal base or alkaline earth metal base. An initial aqueous mixture is first prepared. The initial aqueous mixture includes the at least one hydroxy-functional aromatic compound and a second component selected from the at least one reactive aldehyde and the at least one basic polymerization catalyst The third component, that is the at least one reactive aldehyde when the basic polymerization catalyst is mixed with the at least one hydroxy-functional aromatic compound to form the initial aqueous mixture, or the basic polymerization catalyst when the at least one reactive aldehyde is mixed with the at least one hydroxy-functional aromatic compound to form the initial aqueous polymerization mixture, is then added to the initial aqueous polymerization mixture.
In the process of the present invention, a high level of catalyst is employed to reduce residual monomers and simultaneously minimize the proportion of high molecular weight species in the product. High molecular weight species undesirably reduce the water solubility of the resin product and reduce its storage stability. Further, since free formaldehyde tends to solubilize some such high molecular weight species, processing difficulties can be encountered when a free formaldehyde scavenger such as urea is added to the resole resin to form a premix for preparing a binder for mineral fibers, as this may cause the high molecular weight species to precipitate.
On the other hand, the extent of reaction is preferably carefully monitored during the process of the present invention so that overcondensation, resulting in reduced water solubility and reduced storage stability, is avoided.
Preferably, the amount of catalyst employed in the present process is at least
Espiard Philippe
Herault Pierre C.
Malhieuxe Bruno
Malhotra Vinay
Tessari Domenic
Certain-Teed Corporation
Paul & Paul
Truong Duc
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