Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1999-05-24
2001-07-10
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S099000, C521S155000, C523S215000, C524S080000
Reexamination Certificate
active
06258864
ABSTRACT:
INTRODUCTION
The present invention is directed to improvements in the field of polymer foams, especially closed-cell polymer foams useful for thermal insulation applications and the like, containing surface-modified carbonaceous fillers. This invention also relates to novel compositions useful in the manufacture of such polymer foams.
BACKGROUND
Polymer foams containing filler materials, such as particulate filler materials, are widely known and used. Closed cell rigid polymer foams, especially polyurethane and polyisocyanurate foams containing particulate filler, such as carbon black or other particulate filler, are widely used for thermal insulation purposes. Foams of this type and their use for thermal insulation purposes are disclosed, for example, in U.S. Pat. No. 5,604,265 to DeVos et al. Also, in U.S. Pat. No. 5,373,026 to Bartz et al, polymer foam structures incorporating carbon black filler are taught for thermal insulation purposes.
In polymer foams such as, for example, polyurethane and polyisocyanurate foams, cost reduction and/or thermal insulation improvement can be achieved by improving dispersion of filler material in the foam, by controlling foam cell size, and/or by increasing infrared absorption. The windows of the cell structure are believed to be significantly transparent to infrared radiation. The thermal conductivity of these foams should be improved by increasing the infrared absorption of the cell windows. One way to do this is to add infrared absorbing materials, such as carbon black, to the foam. However, the distribution of carbon black in these foams typically is poor, such that the majority of carbon black resides in the struts of the foam. The windows of the foam may contain little or no carbon black. In fact, it is doubtful that prior work has achieved carbon black concentrations in the windows equivalent to the carbon black concentration found in the struts.
There is a recognized need in the polymer foam industry for foams having improved performance characteristics and/or reduction in the cost and complexity of manufacturing such foams. In certain applications, such as foam insulation and in refrigeration units or other appliances or for architectural insulation, this need has been increased due to the loss of insulation performance caused by the reduction or elimination of halogenated blowing agents. Some substitute blowing agents are found to produce foams having higher thermal conductivity. Hence, there is an increased need for lowering the thermal conductivity of polymer foams suitable for use in various insulation applications, particularly appliance and architectural thermal insulation uses.
It is an object of the present invention to provide improved polymer foams. It is a particular object of the invention to provide polymer foams having lower thermal conductivity, or, the alternative, lower thermal conductivity per unit cost of the foam. In accordance with certain preferred embodiments of the invention, it is an object to provide rigid, closed cell polymer foams incorporating chemically modified carbonaceous filler materials not previously used for such applications, and being suitable for various insulation purposes. These and additional objects and advantages of the present invention will be apparent to those skilled in the art from the following disclosure of the invention and detailed description of certain embodiments.
SUMMARY
In accordance with a first aspect, novel polymer foams are provided which comprise certain chemically modified carbonaceous (“CMC”) fillers, that is, chemically modified carbonaceous material dispersed in the polymer foam. The chemically modified carbonaceous filler employed in the present invention comprises carbonaceous particulate material carrying polymer units, optionally being chemically functionalized polymer units, attached to the surface of the particles. As disclosed and described further below, the chemically modified carbonaceous filler comprises carbonaceous material having polymer moiety attachments. In accordance with preferred embodiments, the chemically modified carbonaceous filler is carbonaceous particulate filler, such as carbon black, graphite, activated carbon and the like, which has been surface-modified to attach multiple polymer moieties per filler particle. It is a significant feature that the polymer moieties of a chemically modified carbonaceous filler are directly attached to the surface of the carbonaceous particle by ionic, covalent or equivalent chemical bond. Thus, these filler materials incorporated into the novel polymer foams of the present invention are not mere polymeric coatings on carbonaceous particles which adhere due to van der Waals forces or like attractive forces. Mere coatings of that type have been known in the art, but have not been sufficiently processible and have not provided the needed improvement in thermal insulation performance or cost reduction in commercially manufactured polymer foams. Mere polymeric coatings on carbonaceous filler particulates, such as were obtained by mixing surfactants or other polymers with filler materials, especially if the polymers were of a type and polymer chain length effective to provide substantially improved thermal insulation value in the finished polymer foam, are understood to be stripped in substantial quantity from the carbonaceous particles by the shear forces encountered in commercial polymer foam manufacturing methods. The shear forces encountered in commercial reaction injection molding (RIM) methods, for example, have been found to strip substantial quantities of polymeric coatings from carbonaceous particles, such as carbon black or the like. In contrast, the chemically modified carbonaceous fillers disclosed here for use as fillers in polymer foams, particularly the preferred embodiments, are not stripped in substantial quantity from the carbonaceous particles even under shear forces encountered in commercial polymer foam manufacture. In accordance with preferred embodiments, the chemically modified carbonaceous fillers comprise surface-modified carbonaceous particulate material having chemically bonded polymer moieties, which remain chemically bonded to the carbonaceous particles even under shear forces encountered in RIM processes for manufacturing polyurethane foam insulation and the like. While not wishing to be bound by theory, at least certain preferred embodiments of the chemically modified carbonaceous fillers disclosed here have valence-orbital interactions with the surface of the carbonaceous particle or with a functional group which is itself likewise chemically bonded to the carbonaceous particle. The nature of the surface of the carbonaceous particle covalently or ironically bonded to the polymer moieties is different from the surface of the same particle merely coated with analogous polymer through van der Waals forces or the like.
As disclosed and described further below, the chemically modified carbonaceous filler can be prepared by attaching polymeric moieties to the surface of carbonaceous particulate material. As used here, the polymeric moieties may be a oligomeric. Suitable carbonaceous particulate materials include carbon black, activated carbon, graphite, carbon fibers, fibrils and the like, chemically modified in accordance with any of the chemical modifications further described below. Also, suitable carbonaceous particulate materials include carbon-silica multi-phase material, such as carbon-silica dual-phase particulate filler material available from Cabot Corporation, Boston Mass. under the trademark Ecoblack™, silica-coated carbon black, and/or metal-treated carbon black forming a multi-phase particulate material, all of which may be chemically modified in accordance with the disclosure below. Mixtures of any of the filler materials disclosed here may be used in the filled polymer foams of the invention. Preferably the chemically modified carbonaceous filler is used in an amount of from 0.1 to 18.0 weight percent filler in the final foam composition, more preferably about 1.0 to
Dalton Dennis M.
Kinsman David A.
Krajkowski Lynn M.
MacKay Adam L.
Cabot Corporation
Foelak Morton
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