Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-05-08
2002-05-07
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C106S271000, C106S273100, C106S277000, C106S278000, C524S059000, C524S060000, C524S061000, C524S068000, C524S069000
Reexamination Certificate
active
06384112
ABSTRACT:
The present invention relates to a bitumen emulsion composition useful, for example, in the binding of bituminous waterproofing layers to substrates such as roof bases.
Conventionally, before applying a bituminous waterproofing layer to a substrate such as a roof base comprising, for example, iron, steel, or concrete, the substrate must first be coated with a tackifying substance, or tack coat, which acts to bond the bituminous waterproofing layer to the substrate. The waterproofing layer is then applied, and the tack coat and waterproofing layer heated together to achieve bonding to the substrate. The tack coat typically comprises a polymer-modified bitumen composition containing a substantial proportion, e.g. 40-60 wt %, of light flux(es) the flux being required to reduce the viscosity of the bitumen to enable it to be applied to the substrate. After applying the tack coat to the substrate a delay is incurred before the waterproofing layer can be applied as the flux must first be allowed to evaporate. Even so, there is a likelihood that some of this highly inflammable flux may still be present, causing potential health and safety hazards to roofing operators when the tack coat is heated. There is therefore a need for a tack coat composition which reduces the delay caused by the evaporating flux and minimises the dangers when heating the tack coat.
One solution might be to use a bitumen emulsion for the tack coat. An emulsion has the advantage that it is already in a form suitable for cold (ie. ambient temperature) application onto a substrate, and therefore no flux is required. Therefore there is little or no delay in applying the waterproofing layer after the application of the tack coat, i.e. no need to wait for the flux to evaporate, and the danger of using inflammable flux is removed.
However, because of the high temperatures that waterproofing composites may be subjected to during their lifetime it is important that the bitumen binder used for the tack coat has a high softening point, for example, for roofing applications the softening point should typically be at least 80° C., preferably at least 90° C., and more preferably 100° C. or higher. However, bitumens with a high softening point also tend to have high viscosities at elevated temperatures making them difficult to emulsify. An alternative route is the use of polymers to modify the bitumen, but they also tend to increase the viscosity of the bitumen making it difficult to emulsify.
Accordingly there is a need for a bituminous binder which has a viscosity low enough for it to be emulsified, but a softening point high enough to withstand the temperatures occurring in uses such as tack coats in binding a waterproofing bituminous layer to a substrate.
The present invention provides an oil-in-water emulsion comprising:
(a) from 30 to 70 wt % of a bituminous binder having a penetration of from 40 to 150 mm/10 (ASTM D5), a softening point from 60 to 120° C. (ASTM D36) and a kinematic viscosity at 160° C. of less than 250 mm
2
/s, preferably from 150 to 250 mm
2
/s (ASTM D2170), the binder comprising from 88 to 99.5 wt % bitumen having a penetration of from 70 to 300 mml/10 and a softening point from 30 to 50° C., and from 0.5 to 12 wt % of an oxidised wax;
(b) from 0.01 to 5 wt % emulsifier; and
(c) from 25 to 69.9 wt % water.
The oxidised wax is preferably derived from a high density polyethylene wax, for example by air oxidation of a high density polyethylene wax. Preferably the oxidised wax has a melting point of from 100 to 150° C. (ASTM D3418) more preferably from 120 to 140° C., a dynamic viscosity at 150° C. from 200 to 10000 mPa.s measured using a Brookfield viscometer, and an acid number of from 10 to 50 mg KOH/g (ASTM D1386).
Commercially available examples of such oxidised wax are LUWAX OA3 available from BASF, and A-C 316 and A-C 330 waxes available from Allied Signal. LUWAX, A-C 316 and A-C 330 are trade names.
The bituminous binder used in the emulsion according to the invention has the advantage that it is of low enough viscosity to enable it to be emulsified whilst having a high enough softening point to withstand the high temperatures likely to occur in applications such as roofing applications. These properties are achieved by the incorporation of the oxidised wax into the bituminous binder. A polyethylene wax, more especially an oxidised high density polyethylene wax, is characterised by a high melting point and low melt viscosity; the wax thus modifies the properties of the bituminous binder in which it is incorporated and enables the binder to have a high softening point without a correspondingly high viscosity at high temperature. In addition it is believed that the polar functionality of the wax due to its oxidised state improves the compatibility of the wax with the bituminous binder and further facilitates the emulsification of the binder.
It is preferred to incorporate one or more polymers into the bituminous binder according to the invention to improve the mechanical performance of the bituminous binder over a wide temperature range, for example tensile resistance, cohesion, low temperature flexibility. Preferably the total amount of polymer material contained in the binder, other than the oxidised wax, is from 0.5 to 10 wt % based on the total weight of the binder.
The polymers may be elastomers or plastomers and are selected from styrene-alkadiene copolymers, &agr;-olefin copolymers, alkylene-vinyl acetate copolymers, alkylene-acrylate copolymers and alkylene-alkylacrylate copolymers, or a mixture of two or more thereof. Beneficially the emulsion contains from 0.1 to 6 wt %, preferably from 1 to 4 wt % of an elastomer selected from styrene-alkadiene-styrene copolymers, and from 0.1 to 10 wt %, preferably from 1 to 6 wt % of a plastomer selected from alkylene-vinyl acetate copolymers, alkylene-acrylate copolymers and alkylene-alkylacrylate copolymers, wherein the alkylene monomer preferably contains from 1 to 5 carbon atoms, the weight percents being based on the total weight of the bituminous binder.
Examples of suitable styrene-alkadiene copolymers for the elastomer include styrene-butadiene block copolymer (“SBS”) and styrene-isoprene block copolymer, with SBS being a preferred copolymer. The molar proportion of styrene:butadiene is typically in the range from 20:80 to 45:55, and the molecular weight of the SBS typically is in the range from 50,000 to 150,000.
Examples of suitable copolymers for the plastomer include ethylene-vinyl acetate copolymer (“EVA”), ethylene-methacrylate copolymer (“EMA”) and ethylene-methylmethacrylate (“EMMA”), with EVA being a preferred copolymer. Preferably the vinyl acetate content of the EVA is from 10 to 30 mole percent, and the EVA preferably has a melt index of from 100 to 4,000. The molecular weight of the plastomer is preferably from 5,000 to 50,000, more preferably from 10,000 to 30,000.
The bitumen employed in the emulsion may be obtained from a variety of sources including straight-run vacuum residue; mixtures of vacuum residue with diluents such as vacuum tower wash oil, paraffin distillate, aromatic and naphthenic oils and mixtures thereof; oxidised vacuum residues or oxidised mixtures of vacuum residues and diluent oils and the like. Typically, the bitumen will have an atmospheric boiling point of at least 380° C., a penetration (mm/10) from 70 to 300, preferably 150 to 250, at 25° C. (Standard Test ASTM D5), a softening point (Ring and Ball) from 30 to 50° C., preferably 35 to 50° C. (ASTM D36 ), and a kinematic viscosity from 100 to 500 mm
2
/s at 135° C. (ASTM D2170). A mixture of two or more different bitumens may be used.
The amount of emulsifier employed may range from 0.1 to 5 weight percent, but usually an amount from 0.1 to 2 wt %, more preferably 0.1 to 1 wt % is employed, depending upon the type of emulsifier, as would be readily determined by the skilled person. The emulsifier may be cationic, anionic or non-ionic, or a mixture of cationic and non-ionic, or anionic and non-ionic emulsifiers, depending upon the desired electrochemical
Allocca Joseph J.
ExxonMobil Research and Engineering Company
Szekely Peter
LandOfFree
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