Aqueous resin dispersions

Details Aqueous resin dispersions Aqueous resin dispersions

2001-05-29

2003-04-15

Cain, Edward J. (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...

C524S589000

Reexamination Certificate

active

06548588

ABSTRACT:

The present invention relates to certain water-dispersible, air-drying uralkyd resins, aqueous dispersions and compositions thereof optionally containing vinyl polymer(s).
Uralkyd resins are polyurethane polymers formed from reactants comprising a polyisocyanate(s) (normally a diisocyanate(s)) and an unsaturated fatty acid residue-containing ester polyol(s) (normally a diol(s)). The resulting unsaturation in the polyurethane imparts latent crosslinkability so that when a coating composition thereof is dried in the air (often in conjunction with a drier salt) the film coating material undergoes crosslinking, thereby improving its properties, e.g. its chemical resistance, hardness and durability.
The use of such air-drying uralkyds for providing protective surface coatings especially for wooden substrates (e.g. flooring or other wooden surfaces subject to wear) is known.
With regard to the ester polyol component used for making the uralkyd it is known to employ an N,N-dialkanolamine such as diethanolamine in the synthesis thereof, thereby forming an amide ester polyol in order to achieve still further improved properties (such as hydrolytic stability and reduced dispersion viscosity). For example a diolamine may be reacted with a triglyceride oil, as in U.S. Pat. No. 4,094,834, or with a fatty acid or fatty acid ester or chloride, as in U.S. Pat. No. 5,104,737, to form the fatty acid residue-modified amide ester diol. The fatty acid residue-modified amide ester diol is then further reacted with polyisocyanate and usually other components to form the uralkyd (although in the process of U.S. Pat. No. 4,094,834, the amide ester diol is first subjected to reaction with phthalic anhydride to form a half ester before reaction with isocyanate).
The property of water-dispersibility in uralkyds, by which is generally understood that the uralkyd can self disperse in an aqueous system without the requirement for external surfactants (although these can also be used if desired), has been achieved by building chain-pendant anionic dispersing groups into the resin. Examples of such groups include carboxylic acid groups which, if necessary, are neutralised with bases (usually ammonia or amines) to form anionic salt groups.
In the absence of other factors, it is necessary to employ such uralkyds which are of high acid value in order to achieve effective self dispersion in water, because the fatty acid-modified alkyd moieties of the uralkyds are very water-insoluble. Typically, acid values of 35 mg KOH/g or more are necessary, with acid values of 50 mg KOH/g or more being used in practice.
For example, U.S. Pat. No. 5,104,737 discloses the reaction of a fatty amide ester diol, a diisocyanate and an acid functional compound which also has two active hydrogen atoms, other than acid groups, which are reactive with isocyanate (typically dimethylol propionic acid DMPA) to form a water-dispersible air-drying uralkyd which is preferably prepared so as to have an acid value of at least 25 mg KOH/g, more preferably at least 40 mg KOH/g (preferred ranges being 25-150, more preferably 40-150 mg KOH/g) and the acid groups of which on neutralisation with base provide water-dispersibility. In the worked examples of U.S. Pat. No. 5,104,737 uralkyds with acid values of 55, 63 and 49 mg KOH/g are used.
However, such high acid values in the uralkyds have disadvantages. High acid value uralkyds tend to give species which are outright dissolved in water or result in very small sized particles, both of which result in increased viscosity in the dispersion. Also the relatively high level of acid groups in the uralkyd tends to render a coating made therefrom less stable hydrolytically and so less durable.
It would therefore be advantageous to employ lower acid values in the uralkyd, although of course not at the expense of vitiating the effectiveness of water-dispersibility.
We have now discovered a certain uralkyd of the type discussed above, i.e. prepared from reactants which include an amide ester diol product obtained from the reaction of a triglyceride oil and an N,N-dialkanolamine and a polyisocyanate, but also incorporating chain pendant and/or terminal polyethyleneoxide (PEO) groups as well as anionic dispersing groups resulting in a dual stabilised urealkyd. This dual stabilisation allows the use of lower acid values thus resulting in a dispersion with a lower viscosity, along with improved water resistance of a dried uralkyd resin coating made with the dispersion while retaining effective water-dispersibility of the uralkyd.
According to the present invention there is provided a water-dispersible, air-drying uralkyd resin comprising the reaction product of:
i) 5-75 wt %, more preferably 20 to 60 wt % of an amide ester diol product obtainable from the reaction between a triglyceride oil and an N,N-dialkanolamine;
ii) 15-50 wt %, more preferably 20 to 40 wt % of an organic polyisocyanate(s);
iii) a carboxylic acid-bearing polyol(s) for providing chain-pendant carboxylate ion dispersing groups in the resultant uralkyd resin;
iv) 1-10 wt % more preferably 2 to 7 wt % of an isocyanate-reactive polyethyleneoxide chain containing compound(s), for providing chain pendant and/or terminal polyethyleneoxide chains in the resultant uralkyd resin;
v) 0-50 wt %, more preferably 2 to 20 wt % of organic polyol(s) other than those provided by i), iii) and iv), provided that the amount of any such other polyol(s) which is not a diol(s) must not exceed 10 wt %;
and wherein further the acid value of the uralkyd resin is within the range of from 5 to 30 mg KOH/g of resin, more preferably of from 12 to 25 mg KOH/g of resin.
According to a second embodiment of the present invention there is provided an aqueous dispersion comprising a water-dispersible, air-drying uralkyd resin wherein said uralkyd resin is as defined above.
According to a third embodiment of the present invention there is provided a process for making a water-dispersible, air-drying uralkyd resin, wherein said process comprises:
I: reacting a triglyceride oil with an N,N-dialkanolamine to form an amide ester diol product i);
II: reacting 5-75 wt %, more preferably 20 to 60 wt %, of the amide ester diol product
i) with
ii) 15-50 wt %, more preferably 20 to 40 wt %, of an organic polyisocyanate(s);
iii) a carboxylic acid-bearing polyol(s) for providing chain-pendant carboxylate ion dispersing groups in the resultant uralkyd resin;
iv) 1-10 wt %, more preferably 2 to 7 wt %, of an isocyanate-reactive polyethyleneoxide chain containing compound(s) for providing chain pendant and/or terminal polyethyleneoxide chains in the resultant uralkyd resin;
v) 0-50 wt %, more preferably 2 to 20 wt % of organic polyol(s) other than those provided by i), iii) and iv), provided that the amount of any such other polyol(s) which is not a diol(s) must not exceed 10 wt %;
and wherein further the acid value of the uralkyd resin is within the range of from 5 to 30 mg KOH/g of resin, more preferably of from 12 to 25 mg KOH/g of resin.
According to a fourth embodiment of the present invention there is provided a process for making an aqueous dispersion of a water dispersible uralkyd resin wherein said process comprises:
A: forming a water-dispersible, air-drying uralkyd resin using a process as defined above, and
B: forming an aqueous dispersion of said uralkyd resin.
In addition to all of the foregoing, it is known to modify the properties of conventional polyurethane coatings derived from aqueous dispersions thereof by incorporating vinyl polymers, and in particular acrylic polymers, into the dispersions. For example, the use of acrylic polymers may allow upgrading of the properties of the coatings by increasing their hardness, and as a result of this, improving hardness-related properties such as block resistance and imprint resistance. While such dispersions may include the polyurethane and vinyl polymers as a simple blend of the preformed polymers, it is also known to be more advantageous to form the vinyl polymer in-situ by polymerising one or more vinyl monomers in the presence of

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