Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
1998-07-24
2001-09-18
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S075000, C528S084000, C554S156000
Reexamination Certificate
active
06291625
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a polyol composition intended to react with a polyisocyanate to form a polyurethane resin.
BACKGROUND OF THE INVENTION
Polyurethanes have a very wide range of applications in surface coatings, protective flooring products, adhesives, sealants and the like to provide protective surfaces with high resistance to aggressive chemicals, physical damage and abrasion. They exhibit very good adhesion to most substrates and can provide long term protection against corrosion and erosion in the most severe of environments. They are generally made by reacting together the components of a two-component composition, one of which includes a polyisocyanate while the other includes a component having two or more hydroxyl groups to react with the polyisocyanate.
It is to be understood that by “a two-component composition” we mean a composition comprising two essential components. Such a composition may additionally comprise one or more other optional components.
Although it is possible to manufacture single component coating systems containing available isocyanate groups, which cure by reaction with atmospheric moisture, such products have limited application because they are invariably solvent-containing, difficult to pigment and unsuitable for situations where a high-build of coating, e.g. 100 microns or more, is required.
For the above reasons, compositions based upon two components, usually polyhydroxy materials and polyisocyanates are preferred. Coatings designed on this basis may contain particulate mineral fillers, pigments and other additives or materials, can be applied as thick films in one application and usually offer improved performance compared with the single component moisture curing products. Because of the vast range of available polyhydroxy compounds (polyols), it is possible to produce a wide range of physical properties in the cured products. Coatings may be designed to be very hard, soft and elastomeric, or any physical character between these.
A problem which arises in making polyurethanes is that the polyisocyanates used react easily with water, for example that contained within the raw materials used, in surfaces to which the polyurethane is to be applied or as atmospheric moisture. As well as reducing the number of isocyanate groups available to react with the polyol, the reaction with water generates carbon dioxide, leading to foaming and incomplete cross-linking. This is particularly damaging in the case of protective films. Steps therefore have to be taken to exclude water from the components, and if the polyurethane is to be applied to a wet surface such as an underground pipe, or damp concrete floor, or in external conditions where surfaces are damp or may encounter rain, unwanted isocyanate reaction will inevitably result.
The inevitability of the reaction between isocyanates and water means that all raw materials for inclusion in conventional compositions must be water-free, or must be dried before or during inclusion and that such compositions are totally unsuitable for use where water is present.
EP-A-0 145 269 discloses two-component compositions which are capable of curing in the presence of water to form polyurethane resins. The compositions comprise highly reactive polyols and solvent-based propolymers with less reactivity than monomeric diisocyanates such as methylene di-p-phenylene isocyanate (MDI) to and toluene isocyanate (TDI). A large excess of water and calcium hydroxide is employed by the compositions to act as a scavenger for carbon dioxide produced. The polyurethane resins formed have limited strength and there are disadvantages, such as flammability and environmental and disposal problems of volatile organic solvents, inherent in the use of solvent-containing materials.
SUMMARY AND OBJECTS OF THE INVENTION
The present invention aims to provide a polyol composition for use as a component of a two-component polyurethane composition which exhibits complete water tolerance, and will even cure under water without any unwanted effects resulting from isocyanate/water reactions.
In the first aspect the present invention provides a polyol composition for reacting with a polyisocyanate isocyanate to form a polyurethane, comprising:
(a) a triglyceride of a saturated or unsaturated C
12
to C
25
, hydroxy-substituted fatty acid or a C
12
to C
25
hydroxy-substituted fatty acid (or Group IIA metal salt thereof) and glycerol, which can react together to produce a triglyceride, and
(b) at least 0.1 mole (and preferably up to 2.0 mole), per mole of triglyceride (a) or triglyceride capable of being formed from the fatty acid and the glycerol, of an oxide, hydroxide or carbonate of a metal from Group IIA of the periodic table.
On heating the composition in the presence of water, which may be added or contained as an impurity, the triglyceride is hydrolyzed by the oxide, hydroxide or carbonate thereby breaking the ester bonds to produce free fatty acid and glycerine (glycerol). The fatty acid is then saponified by the oxide, hydroxide or carbonate to produce fatty acid salts of the metal and the oxide, hydroxide or carbonate also reacts with the glycerine to produce metal glycerates.
Accordingly in a second aspect the present invention provides a composition for reacting with a polyisocyanate to form a polyurethane, comprising the reaction products of:
(a) a triglyceride of a saturated or unsaturated C
12
to C
25
hydroxy-substituted fatty acid or a C
12
to C
25
hydroxy-substituted fatty acid (or Group HA metal salt thereof) and glycerol, which can react together to produce a triglyceride; and
(b) at least 0.1 mole (and preferably up to 2.0 mole), per mole of triglyceride (a) triglyceride capable of being formed from the fatty acid and the glycerol, of an oxide, hydroxide or carbonate of a metal from Group IIA of the periodic table,
i.e. fatty acid salts of the metal and glycerates of the metal (and optionally free fatty acid and glycerol), or a like mixture of fatty acid salts of the metal and glycerates of the metal (and optionally free fatty acid and glycerol produced other than by reaction of reactants (a) and (b)).
The fatty acid is preferably an unsaturated fatty acid with one or more hydroxy groups present in the aliphatic chain.
According to a third aspect of the invention there is provided a composition for forming a polyurethane resin and comprising a composition according to the first or second aspect of the invention and a polyisocyanate.
It has been found that such compositions, according to the third aspect of the invention, will cure in the presence of water, even when submerged, to a high strength and will exhibit a firm bond when applied to wet surfaces such as steel, cast-iron or concrete, with no deleterious effect from the presence of water.
Thus by means of the present invention, there can be provided two-part polyurethane compositions which are water tolerant, cure to a high strength and do not require the use of water or organic solvents within their formulations.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The triglyceride is preferably provided by castor oil, i.e.: the composition according to the first aspect of the invention preferably comprises castor oil.
Castor oil has as its main component (about 80%) the triglyceride of ricinoleic acid. Each ricinoleic side chain has a hydroxy group on the ninth carbon atom and for this reason castor oil has frequently been used as a low cost polyol in polyurethane compositions, although it tends to introduce flexibility, which may not be desired. We have found that castor oil, when hydrolyzed by an oxide, hydroxide or carbonate of a metal from group IIA of the Periodic Table, produces a mixture of long-chain hydroxy-containing salts of the metal and the glycerate of the metal.
The castor oil may be “first pressing” material, pharmaceutical grade commercial or second grade. The oil should preferably conform to BS650 1967 but this is not essential.
The metal oxide, hydroxide or carbonate is preferably a hydroxide of an alkaline earth metal su
Gorr Rachel
Thames Water Services Limited
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