Pitch pocket and sealant

Details Pitch pocket and sealant Pitch pocket and sealant

2000-12-12

2003-06-17

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...

C524S377000, C524S588000

Reexamination Certificate

active

06579924

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a one-part moisture curable pourable sealer composition, and more particularly to a one-part moisture curable, pourable sealer composition that achieves fast, deep curing.
BACKGROUND OF THE INVENTION
A particular application for a one-part moisture curable, pourable sealer composition that achieves fast, deep curing is in the field of sealing mechanical penetrations in a waterproof membrane covering a roof substrate. In a typical low slope membrane roof, provision must be made for sealing penetrations of the roof by vent pipes, support straps, conduits, guy anchors and similar elements. Generally, a pitch pocket or pan which surrounds the penetrating element is used. Although the invention is useful with generally any type of pitch pocket, examples of preferred pitch pockets are described in commonly owned U.S. Pat. Nos. 5,493,827, and 5,768,838. A sealant is poured into the pitch pocket or pan around the penetrating element. Generally a two-part urethane pourable sealant composition is used. An advantage with two-part pourable urethane sealant compositions is that they set in approximately two hours to form a solid composite seal with the perimeter or inner surface of the walls or curbs of the pitch pocket. However, a disadvantage with the two-part pourable urethane sealant compositions is that they must be shipped to the site at which they are used in two separate parts that are mixed just prior to being poured into a pitch pocket. Thus, the use of a two-part pourable urethane sealer composition, as opposed to a one-part sealer composition, involves an additional undesirable step. Additionally, care must be taken during the mixing step to insure that the two components are thoroughly mixed, and mixed in the proper proportions, as improper mixing can adversely affect performance of the roof penetration seal. Thus, a one-part sealant composition that eliminates the need for mixing would be highly desirable.
One-part sealants have been used for sealing mechanical penetrations in a waterproof membrane covering a roof substrate. However, the one-part sealants that have been used heretofore have disadvantages. For example, molten asphalt or coal tar have been used as one-part sealants for sealing roof penetrations. These materials shrink upon curing, and exhibit poor weatherability. Also, because of their thermoplastic nature, they often melt and run into a building. This can lead to disastrous results in a fire situation. Solvent-based asphalt and rubber-modified asphalt have also been used as one-part sealants for sealing roof penetrations in a waterproof membrane covering a roof substrate. However, these products have generally all of the same disadvantageous associated with bituminous materials (e.g., molten asphalt or coal tar), and exhibit even greater shrinkage caused by evaporation of the solvent. One-part moisture curable urethanes have also been used. Although one-part moisture curable urethanes are thermosetting, known one-part urethane sealants are capable of only shallow cures, usually less than ⅜ inch deep. Deeper cures of at least 2 inches are desired. Inadequate depth of cure can result in splitting and cracking of the seal. Cure times for these one-part moisture curable urethanes have been extremely lengthy. Also, they contain small amounts of solvent that can cause volume shrinkage when poured into a pitchpan.
Accordingly, there remains a need for a one-part pourable sealant that is thermosetting, non-shrinking, and capable of quickly curing in a closed cavity to a depth of at least two inches.
SUMMARY OF THE INVENTION
The invention overcomes problems associated with known one-part thermosetting sealant compositions by achieving rapid, deep curing without significant shrinkage. The advantages of this invention are achieved by employing a one-part moisture curable, pourable sealer composition containing a silyl-terminated polymer.
In one aspect of the invention there is provided a one-part moisture curable, pourable sealer composition containing a silyl-terminated polymer and a hygroscopic plasticizer.
In accordance with another aspect of the invention, there is provided a method of forming a seal around a roof penetration, that includes a step of dispensing a one-part moisture curable, pourable sealer composition containing a silyl-terminated polymer into a pitchpan or pitch pocket formed around a roof penetration.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification and claims.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The one-part, moisture curable, pourable sealer compositions in accordance with a preferred embodiment of this invention comprise a silyl-terminated polymer, a hygroscopic plasticizer, and a catalyst for promoting curing of the silyl-terminated polymer. Other ingredients that may be included in the composition include one or more fillers, antioxidants, ultraviolet absorbers, adhesion promoters, dehydrating agents, and colorants.
Examples of silyl-terminated polymers that may be used include silylated polyurethane, silylated polyethers, and silylated polyesters. The silylated polymers or silyl-terminated polymers of this invention include two or more reactive silyl groups, with alpha, omega-telechelic silane-terminated polymers being preferred.
An example of a suitable silyl-terminated polymer that may be used is an oxyalkylene polymer having at least one reactive silyl group at each end of the polymer molecule. The backbone of the silyl-terminated oxyalkylene polymer has repeating units represented by the formula: —R—O— wherein R represents a divalent organic group, preferably a straight or branched alkylene group containing 1 to 14 carbon atoms, and more preferably straight or branched alkylene groups containing 2 to 4 carbon atoms. Especially preferred are polypropylene oxide backbones, polyethylene oxide backbones, and copolyethylene oxide/polypropylene oxide backbones. Other repeating units may include, but are not limited to —CH
2
O—, —CH
2
CH(CH
3
)O—, —CH
2
CH( C
2
H
5
)O—, —CH
2
C(CH
3
)
2
O—, , —CH
2
CH
2
CH
2
CH
2
O— to and the like.
The reactive silyl group contained in the silyl-terminated polymers may be represented by the formula:
—[Si(R
2
)
2−a
(X)
a
O]
p
—Si(R
3
)
3−b
(X)
b
wherein R
2
and R
3
are the same or different and each represents an alkyl group containing 1 to 20 carbon atoms, an aryl groups containing 6 to 20 carbon atoms, an aralkyl group containing 7 to 20 carbon atoms or a triorganosiloxy group of the formula (R
4
)
3
SiO— (wherein R
4
independently represents a hydrocarbon group containing 1 to 20 carbon atoms) and, when two or more R
2
and/or R
3
groups are present, they may be the same or different; X represents a hydrolyzable group or a hydroxyl group and, when two or more X groups are present, they may be the same or different; a represents an integer of 0 to 2; b represents an integer of 0 to 3; and p represents an integer of 0 to 19 and, when p is 2 or more, the —[Si(R
2
)
2−a
(X)
a
O]groups may be the same or different. In the reactive silyl group represented by the above general formula, there is at least one hydrolyzable group or hydroxyl group represented by X.
The above-mentioned alkyl group containing 1 to 20 carbon atoms includes, but is not limited to methyl, ethyl, isopropyl, butyl, t-butyl, cyclohexyl and the like.
The above-mentioned aryl group containing 6 to 20 carbon atoms includes, but is not limited to, phenyl, naphthyl and the like.
The above-mentioned aralkyl group containing 7 to 20 carbon atoms includes, but is not limited to, benzyl and the like.
The above-mentioned monovalent hydrocarbon group containing 1 to 20 carbon atoms includes, but is not limited to, methyl, ethyl, isopropyl, butyl, t-butyl, pentyl, ethynyl, 1-propenyl, vinyl, allyl, 1-methylbutyl, 2-ethylbutyl, phenyl and the like.
The above-mentioned hydrolyzable group represented by X is not l

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