Alkyd resin emulsion

Details Alkyd resin emulsion Alkyd resin emulsion

2002-11-26

2004-08-24

Niland, Patrick D. (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...

C524S077000, C524S366000, C524S599000

Reexamination Certificate

active

06780910

ABSTRACT:

This invention relates to emulsions and in particular to aqueous emulsions of polyesters and more particularly to oil-modified polyester resins also known as alkyd resins and to their production.
Polyester resins are well known materials with wide uses in surface coatings e.g. paints. Generally, they are film forming substances which are the products of esterification of polybasic acids and polyhydric alcohols. They can be either saturated or unsaturated. Typical applications of polyesters include industrial wood coatings, can and coil coatings, industrial enamels, domestic appliances coatings and stoving enamels.
Alkyd resins are the largest group of synthetic resins used in the coating industry, are polyester resins which include residues of polybasic, usually di-basic, acid(s) and polyhydroxy, usually tri- or higher hydroxy alcohols and further including monobasic fatty acid residues. The monobasic residues may be derived (directly or indirectly) from oils (fatty acid triglycerides) and alkyd resins are also referred to as oil modified polyester resins. Alkyds used in surface coatings are generally curable usually either from residual carboxyl and hydroxyl functionality or by unsaturation (often multiple unsaturation) in the monobasic fatty acid residues. Some alkyds are used as plasticisers e.g. for other alkyd resins, and these materials are not usually curable. Alkyd resins may include other residues and/or additives to provide specific functionality for the intended end use e.g. sources of additional carboxyl groups may be included to improve water compatibility. Alkyds have found widespread use in paints, particularly solvent based paints. In developing low VOC's formulations, much effort has been directed to making aqueous emulsions of alkyd resins, (including those using mixed solvent/water vehicles). The alkyds are usually formed into an emulsion before incorporation into the paint and emulsification typically involves formation of an alkyd in water emulsion in which the alkyd is dispersed in the water phase as uniformly and generally as finely as possible. To do this emulsifiers, either as single components or in combination, are commonly used.
The present invention is based on our finding that combinations of certain classes of alcohol alkoxylates, particularly ethoxylates, based on branched primary alcohols can give alkyd resin emulsions in water that have a low average particle size and narrow particle size distribution.
Accordingly, the present invention provides an aqueous emulsion of an alkyd resin which comprises as an emulsifier at least one branched primary alcohol alkoxylate of the formula (I):
 [CH
3
.(CH
2
)
n
][CH
3
.(CH
2
)
m
].CH.[(CH
2
)
p
.O.(AO)
q
.H]  (I)
where
n and m are each independently from 1 to 13; and p is 1 or 2; such that n+m+p is from 5 to 15;
AO is an alkylene oxide residue having from 2 to 4 carbon atoms; and
q is from 5 to 50.
Within the invention, we have found that particularly good results may be obtained using combinations of non-ionic surfactants, including compounds of the formula (I), and anionic surfactants to emulsify alkyd resins. Accordingly, the invention further provides an aqueous emulsion of an alkyd resin which comprises as an emulsifier at least one branched primary alcohol alkoxylate of the formula (I) above in combination with at least one anionic surfactant
In compounds of the formula (I), n and m are desirably each independently at least 2 and not more than 12, p is desirably 1 and the total number of carbon atoms in the branched alkyl residue is desirably from 8 to 18, particularly 10 to 15 and especially is about 12 (corresponding to n+m+p from 5 to 15, particularly 7 to 12 and especially about 9). Mixtures of compounds having such branched residues can be used.
The alkylene oxide groups are desirably ethylene oxide and/or propylene oxide residues. Desirably, all the residues are ethylene oxide residues although mixtures of ethylene oxide and propylene oxide residues, desirably with a molar ratio of ethylene oxide to propylene oxide residues from 1:5 to 10:1, can be used. When mixed alkylene oxide residues are used, the polyoxyalkylene chain can be a random or block copolymeric chain. Within the range 5 to 50, q is desirably 10 to 30. The number of units in the polyoxyalkylene chain, ‘q’, is an average value and may be non-integral.
The alkoxylates of the formula (I) can be used alone or and desirably, in combination with similar alkoxylates of linear primary alcohols, containing similar numbers of carbon atoms. The proportion of branched alkoxylate, of the formula (I), is desirably at least 30% and more usually at least 40%.
The alkoxylates used in this invention can be made by alkoxylation of the corresponding primary alcohols under conventional alkoxylation conditions, typically under alkali catalysis, particularly alkoxide catalysis e.g. using NaOH or KOH to form alkoxide in situ. Where the alkoxylate is wholly of the formula (I), the alcohol used is substantially wholly branched primary alcohol as can be made by the guerbet process. Where the alkoxylate is a combination of alkoxylates of the formula (I) with similar alkoxylates of linear primary alcohols, the alcohol used can be a mixture of the branched primary alcohols with linear primary alcohols, containing similar numbers of carbon atoms. Such mixed alcohols can be made by the oxo process using feedstocks including internal olefins (internal olefins isomerise under typical oxo reaction conditions).
The term non-ionic surfactant is sometimes herein used to refer to branched or mixtures of branched and linear alcohol alkoxylates used in this invention.
The alkyd resins used in this invention are typically resins which are the reaction products of:
one or more polybasic (di- or higher basic) organic acid/anhydride: e.g. phthalic anhydride,
one or more polyhydric (usually a tri- or higher) alcohol: e.g. glycerol; and
one or more monobasic fatty acid, usually an unsaturated fatty acid, or one or more ester, particularly triglyceride of such fatty acids: e.g. soya oil, tall oil fatty acids.
The molar proportions of these component monomers are chosen to give the desired physical properties and molecular weight distribution of the resulting polyester. The monobasic fatty acid or triglyceride, often includes unsaturation e.g. vegetable oils or fatty acids, and the presence of unsaturation leads to the air-curing properties of these materials. Most alkyds are film-forming polymers with a relatively low glass transition temperature, typically below 0° C., that are readily pigmented and usually accept additives to form coatings with a wide range of appearance, performance, and application characteristics. The alkyd resins used in this invention are typically air-curing types as used in surface coating end use applications. Typically alkyd resins used in this invention will have an oil length of from 25 to 100%, typically from 50 to 80%. Siliconized alkyds can also be used. Suitable alkyds are widely available and are used extensively in surface coating applications.
Although effective emulsification can be achieved using surfactants of the formula (I) on their own, they can also be used in combination with anionic surfactants particularly phosphate esters, ether carboxylates, alkyl ether sulphate, alkyl aryl sulphonates or mixtures of these types of anionic surfactants.
Ether carboxylates which can be used in the invention are typically of the formula (II):
R
1
O—(EO)
n
—CH
2
CO
2
M  (II)
where
R
1
is a C
10
to C
18
hydrocarbyl, particularly a C
12
to C
16
alkyl, group;
EO is an ethyleneoxy group;
n is from 3 to 10, particularly 4 to 8, especially about 6; and
M is hydrogen, alkali metal, especially Na or K or ammonium (including amine onium).
In formula (II) R
1
can represent mixed groups e.g. mixed alkyl groups such as mixed C
13
to C
15
alkyl groups, as are commonly used in making surfactants and n (like q in formula (I)) is an average value and may be non-integral. Ethe

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