Anionic alkoxylate surfactant

Details Anionic alkoxylate surfactant Anionic alkoxylate surfactant

2001-08-09

2003-07-08

Yoon, Tae H. (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...

C524S710000, C524S713000, C524S745000, C524S760000, C526S209000

Reexamination Certificate

active

06590030

ABSTRACT:

This invention relates to anionic alkoxylate surfactants and to their use in preparing aqueous polymeric dispersions.
Nonionic alkoxylate surfactants have been known for many years and they have been used in many industrial applications including the preparation of aqueous polymeric dispersions. These non-ionic alkoxylate surfactants typically consist of a hydrophobic portion or chain which is covalently bonded to a poly(oxyalkylene) chain, especially poly(oxyethylene), which provides the hydrophilic portion of the surfactant.
WO91/13849, the entire contents of which is incorporated by reference, discloses fatty alcohol alkoxylate surfactants in which the fatty alcohol chains contain a pair of conjugated double bonds having opposite geometric isomerism which are reactive in dispersion polymerisation. These surfactants are described as being useful as stabilisers in the preparation of aqueous dispersions of film forming addition polymers.
In certain aqueous dispersions of polymerisation preparations the solely nonionic characteristics of these stabilisers means that relatively high levels of stabilisers are required to be used to prepare the desired fine particle size aqueous dispersions. This may add to the raw material costs of such dispersions and/or cause a degradation in resulting film properties, especially properties associated with high levels of water soluble species such as early water resistance. The solely nonionic character may also result in limitations in processing conditions. For example, with this class of surfactants lower temperature polymerisation is often required to provide dispersions with low levels of coagulum. These lower temperatures may result in extended processing time and hence increased manufacturing costs.
The use of small amounts of anionic surfactants in combination with these prior-art non-ionic stabilisers is capable of producing the desired small particle size dispersions while maintaining the desired low levels of non-ionic stabiliser. However, these polymer dispersions suffer from problems commonly associated with the use of conventional anionic surfactants. These include residual water sensitivity in films formed from such aqueous dispersions, intolerance to polyvalent species and foaming.
The alkylphenol hydrophobe has exceptional adsorption onto hydrophobic surfaces and therefore generally has superior performance to aliphatic analogues. Alkylphenol ethoxylate non-ionic surfactants have been previously converted to anionic sulfates or phosphates and this class of surfactant has been known for several years. However, this class of anionic alkoxylates can also lead to residual water sensitivity in films formed from aqueous film forming dispersions prepared with this class of surfactants as stabilisers. Additionally, alkylphenol ethoxylates are thought to be environmentally unfavourble due to their poor biodegradability and subsequent aquatic toxicity.
Anionic alkoxylate surfactants are claimed in U.S. Pat. No. 4,939,283 by Yokota et al. These surfactants are typically prepared by reacting a hydrophobe such as nonylphenol (1 mole) with allyl glycidyl ether (1 mole) and condensing ethylene oxide (10-50 moles). The terminal hydroxyl is then converted to the sulphate ester, phosphate ester, sulfosuccinate half ester or sulfosuccinate diester. Salts of these species are included and these are the alkali metal, ammonium and low alkanolamine salts. These surfactants offer some improvement in colloidal stability. However, in certain applications they appear to be less useful and it is speculated that this may attribute to the relatively low reactivity of the meth(allyl) unsaturated group in certain copolymerisation reactions.
It is an object of the present invention to overcome or at least alleviated one or more of the problems associated with the stabilisers described in the prior art.
Accordingly the present invention provides an anionic alkoxylate surfactant of the formula I
where R is a di- or tri-unsaturated C
4-22
straight or branched hydrocarbon chain, at least two double bonds of said unsaturated chain being conjugated and exhibiting opposite geometric isomerism;
m is 0 or 1;
Y is O or NR′;
each R′ is independently selected from hydrogen, C
1-6
alkyl and phenyl; n is 1 to 50; and OX is a anionic group selected from the group consisting of acids or salts of sulphate, phosphate, sulphosuccinate, succinate, carboxymethyl, maleate, carboxyethyl, alkenylsuccinate, phthalate, sulphoethyl, 3-sulpho-2-hydroxypropyl, sulphopropyl, oxalate and citrate.
Preferably the surfactant has an R group of the following structure:
CH
3
—(CH
2
)
13-K
—CH=CH—CH=CH—(CH
2
)
K
—
where K is 8 or 9.
Preferably R is a surfactant accordingly to claim
1
wherein R is derived from linoleyl or linolenyl alcohol or acid by alkoxylation of said alcohol or acid.
The
units may be the same or different.
Preferably at least one R′ on the or each —(CHR′—CHR′—O)— unit is hydrogen. More preferably both R′ on the or each —(CHR′—CHR′—O)— unit are hydrogen.
Preferably OX is sulphate, phosphate, sulphosuccinate, carboxymethyl or a salt thereof.
Preferably the salt is an amine, ammonium or alkali metal salt.
The surfactant of formula I is preferably derived from a fatty alcohol such that m is 0. The surfactant may also be derived from fatty acid esters, fatty amines, and fatty acid amides. Where Y is NR′, R′ is preferably H or CH
3
.
The invention provides in an alternative form an aqueous dispersion of polymeric particles wherein the dispersion is formed in the presence of a stabilising amount of anionic alkoxylate surfactants as described above.
Preferably the polymer dispersion is prepared by addition polymerisation of addition polymerisable monomer. Preferably the addition polymerisable monomer is an ethylenically unsaturated monomer.
Preferably the polymer dispersion is film forming at or near ambient temperature with the optional use of external plasticisers.
The aqueous dispersion may also be prepared by dispersion of a condensation polymer.
The invention also provides the use of an anionic surfactant as described above as a stabiliser in the preparation of an aqueous dispersion of polymeric particles, or as a substitute for alkylphenol based surfactants in the preparation of aqueous dispersion of polymeric particles and coating compositions.
DETAILED DESCRIPTION OF THE INVENTION
The anionic alkoxylate surfactants of the present invention can be prepared by first forming alkoxylate product on a suitable hydrocarbon chain and then converting the hydroxyl group to an appropriate anionic species. Preferred hydrocarbon chains are the fatty chains of unsaturated fatty alcohols. The preferred alkylene oxides are ethylene oxide.
As well, as for example, condensing fatty alcohol with ethylene oxide, other alkylene oxides can be used either alone or as a mixture. For example, a random co-polymer of ethylene and propylene oxide can be used. Alternatively a block alkoxylate copolymer could be prepared by first reacting a fatty alcohol with, for example, propylene or butylene oxide and then condensing this adduct with ethylene oxide. Similar alkoxylation products can be obtained from the corresponding esters, amines and amides.
The fatty alcohols that are preferred are the C18 fatty alcohols, linoleyl and linolenyl alcohols. Other fatty alcohols and or the corresponding fatty acids can be used. In certain embodiments fatty amines and fatty amides may be used as the hydrophobe of the surfactants. Fatty alcohols of other chain lengths may be used, the most preferred having 10-22 carbon atoms. The corresponding carboxylic acids, etc. are also suitable.
The poly(oxyalkylene) chain length of the surfactant corresponds to that from 1-50 alkylene oxide units. The nature of the individual units is very much determined by the end use to which the compound will be put. For example, if the compound is to be a reactive surfactant in an aqueous emulsion polymerisation system, the poly(oxyalkylene) chain will consist mainl

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