GB2463927A

GB2463927A - p-Alkyl phenol alkoxylate co-oligomers and process for preparing o- or p- alkyl or alkenyl phenol alkoxylate oligomers or co-oligomers useful as demulsifiers

Info

Publication number: GB2463927A
Application number: GB0817118A
Authority: GB
Inventors: Terence Cox
Original assignee: LINCHEM Ltd
Current assignee: LINCHEM Ltd
Priority date: 2008-09-18
Filing date: 2008-09-18
Publication date: 2010-04-07
Also published as: GB0817118D0

Abstract

A process for preparing an o- or p-alkyl or alkenyl phenol alkoxylate oligomer or co-oligomer comprises adding a methylene donor to one or more o- or p-alkyl or alkenyl phenol alkoxylates. Suitable methylene donors include aldehydes or derivatives thereof, hexamethlene tetramine, an N-(substituted hydroxyalkyl) melamine compound or various derivatives thereof, an alkyloxyalkylpyridinium compound, oxazolidine or N-methyl-1,3,5-dioxazene. In particular, paraformaldehyde is added to p-nonylphenol 4 mole ethoxylate. The oligomers or co-oligomers may be useful as demulsifiers or emulsion breakers in the petroleum industry. A non-statistical non-random p-alkyl phenol alkoxylate co-oligomer wherein there are at least two different C3-12-alkyl residues as the p-alkyl residues is also claimed.

Description

PROCESS

The present invention relates to a process for preparing an o-or p-alkyl or alkenyl phenol alkoxylate oligomer or co-oligomer and to ap-alkyl phenol alkoxylate co-oligornerper se.

Alkyl phenol formaldehyde resin alkoxylates are used widely as demulsifiers or emulsion breakers in the petroleum industry to separate emulsions of aqueous media (such as water or saline) and petroleum. The elimination of water and saline is essential to prevent corrosion in the refinery. Approximately one third of demulsifiers used worldwide are alkyl phenol formaldehyde resin alkoxylates.

A conventional two-step process for preparing an alkyl phenol formaldehyde resin alkoxylate involves preparing firstly an alkyl phenolic resin from alkyl phenol and an aldehyde or aldehyde and amine in a solvent such as heavy aromatic naphtha (I-IAN).

The solvent provide a solution which is sufficiently non-viscous for reaction with an alkylene oxide in the second step. Ethylene oxide and propylene oxide are the alkylene oxides of principle commercial interest and they must be used with great care in costly specialist reactors. Two alkylene oxides may be used in the second step of the reaction to produce a random or statistical copolymer. Alkylene oxides may also be added sequentially to produce a block copolymer.

The present invention is based on the recognition that o-or p-alkyl or alkenyl phenol alkoxylates may be linked by a methylene donor to prepare o-orp-alkyl or alkenyl phenol alkoxylate oligomers or co-oligomers in a single step.

* * Thus viewed from a first aspect the present invention provides a process for preparing an o-orp-alkyl or alkenyl phenol alkoxylate oligomer or co-oligorner comprising: (a) adding a methylene donor to one or more o-or p-alkyl or alkenyl phenol *:::: alkoxylates. *

The process may be straightforwardly carried out in a single generally available : reaction vessel or kettle. The process may permit better quality control by exploiting the precise compositional tolerances exhibited by commodity starting reagents.

Preferably step (a) is carried out in the absence of a solvent. The absence of a solvent allows the oligomer or co-oligomer to be prepared nominally as 100% active and reduces the effective shipment costs of the product. The absence of a solvent contributes to improved reactor throughput and resin quality.

Typically the oligomer or co-oligomer is non-uniform. The co-oligomer may be a random co-oligomer, a statistical co-oligomer, a block co-oligomer or an alternating co-oligomer.

The oligomer or co-oligomer may have up to 25 phenolic units (eg a dimer, a trimer, a tetramer, a pentamer or a hexamer). Preferred is an oligomer or co-oligomer having 5 to 20 phenolic units.

The o-orp-alkyl or alkenyl group may be linear or branched. The o-orp-alkyl or alkenyl group may be cyclic or acyclic. The a-orp-alkyl or alkenyl group may be interrupted by one or more heteroatoms (eg N). The o-or p-alkyl or alkenyl group may be substituted by one or more substituents.

Preferably the (or each) a-orp-alkyl or alkenyl group is a linear or branched a-orp-C124-alkyl or C124-alkenyl group.

In a preferred embodiment, the a-orp-alkyl or alkenyl phenol alkoxylate oligomer or co-oligomer is ap-alkyl phenol alkoxylate oligomer or co-oligomer and the (or each) o-orp-alkyl or alkenyl phenol alkoxylate is ap-alkyl phenol alkoxylate.

* ** Preferably the (or each) p-alkyl phenol alkoxylate is a linear or branched p-C1 24-alkyl phenol alkoxylate. Particularly preferably the (or each) p-alkyl phenol alkoxylate is a linear or branched p-C3. 12-alkyl phenol alkoxylate. More preferred is a p-alkyl phenol : alkoxylate selected from the group consisting ofp-tertbutyl phenol alkoxylate, p- *:. isoamyl phenol alkoxylate, p-isooctyl phenol alkoxylate, p-nonyl phenol alkoxylate and p-C12-phenol alkoxylate. Most preferred are p-tertbutyl phenol alkoxylate and p-nonyl phenol alkoxylate. Preferably thep-nonyl phenol alkoxylate is branched.

Preferably the methylene donor is an aldehyde (eg formaldehyde, benzaldehyde or furfural) or a derivative thereof, hexamethylene tetramine, an N-(substituted hydroxyalkyl) melamine compound (eg a N-(substituted hydroxymethyl) melamine compound) which is optionally N-alkylated or an ether derivative thereof, an alkyloxyalkylpyridinium compound (eg an alkyloxymethylpyridinium compound), oxazolidine or N-methyl-1,3,5-dioxazene.

The rnethylene donor may be selected from the group consisting of hexamethylene tetramine, N-methylol-rnelamine, N,N'-dimethylol-melamine, N,N',N" -trimethylol- melamine, tetra-N-methylol-melamjne, penta-N-methylol-melamine, hexa-N-methylol-melamine, trioxan hexamethylol-melamine, N,N',N"-triinethyl-N,N,N trimethylolmelamine, N,N',N'tributyl-N,N,N"-trimethy[olmelamine N,N',N"tris(methoxymethyl) melamine, hexakis(methoxymethyl)melamine, lauryloxymethyl pyridinium chloride, ethyloxymethyl pyridinium chloride, oxazolidine, N-methyl-i,3,5-dioxazene and formaldehyde or a derivative thereof (eg paraformaldehyde or trioxane).

Preferably the methylene donor is selected from the group consisting of hexamethylene tetramine and paraformaldehyde.

A particularly preferred methylene donor is paraformaldehyde. Typically paraformaldehyde is used in step (a) in the presence of an acid catalyst.

A particularly preferred methylene donor is hexamethylene tetraamine.

Hexamethylene tetraamine advantageously oligomerises directly an alkyl phenol alkoxylate by acting as a base catalyst and methylene donor without the need for an exogenous acid or base catalyst. S...

Typically the (or each) p-alkyl phenol alkoxylate used in step (a) is present in *::: * admixture with up to 5wt% of the equivalent o-alkyl phenol alkoxylate, up to Swt% of *: 2,4-dialkyl phenol alkoxylate and trace amounts of phenol and water. It is desirable to reduce the amount of phenol and dialkyl to prevent side reactions. Typically the dialkyl content is reduced to <2wt%.

Step (a) may be carried out in the presence of a catalyst. The catalyst may be an acid (eg a Lewis acid) or base catalyst.

A preferred acid catalyst is an alkyl or aryl monosuiphonic or polysuiphonic acid or a Lewis acid. Particularly preferred is an acid catalyst selected from the group consisting of a Lewis acid, methanesuiphonic acid, p-toluenesulphonic acid, dodecylbenzenesulphonic acid and methane polysulphonic acid, more preferably the group consisting of methane disulphonic acid, methane trisulphonic acid and a mixture thereof The base catalyst may be an inorganic base or an amine. Preferably the base catalyst is an alkali metal or alkaline earth metal compound. An example is KOH.

In an embodiment of the invention (for example when using a base catalyst), the o-or p-alkyl or alkenyl phenol alkoxylate oligomer or co-oligomer may in part form a calixarene.

Preferably step (a) is carried out in the presence of an antifoaming agent. An example of a suitable antifoaming agent is a siloxane such as polydimethylsiloxane. Preferred is polydimethysiloxane in admixture with fumed silica.

In a preferred embodiment, step (a) is carried out in the presence of an extending agent to promote the formation of high molecular weight oligomers or co-oligomers.

An example of a suitable extending agent is a dimethylolated phenol (eg 2,6-dimethylol p-cresol) which gives two methylene bridges separated by a p-cresol moiety. * .*

The process of the invention may further comprise: (bl) removing water. **** * * S. *

:. Step (bi) may be carried out by evacuation (eg vacuum pumping). Step (bi) may be :::: carried out at an elevated temperature (eg a temperature in excess of 80°C).

The process of the invention may be a condensation reaction. Typically the condensation reaction is carried out in the present of an acid or base catalyst. In this embodiment, the process may further comprise step (b 1).

The process may further comprise: (b2) sparging during step (a).

Sparging may be carried out with an inert gas such as nitrogen, argon or helium.

The process of the invention may be other than a condensation reaction. In this embodiment, the process may further comprise step (b2).

The amount of methylene donor and one or more a-orp-alkyl or alkenyl phenol alkoxylates in step (a) is typically sufficient to provide a molar weight ratio of methylene to o-or p-alkyl or alkenyl phenol alkoxylate in the range 0.5:1 to 1.5:1, preferably 0.9:1 to 1.1:1, particularly preferably about 1:1.

At least one of the one or more o-orp-alkyl or alkenyl phenol alkoxylates may be a a-orp-alkyl or alkenyl phenol polyalkoxylate. The (or each) o-orp-alkyl or alkenyl phenol polyalkoxylate may have up to 100 alkylene oxide units which may be the same or different (eg ethylene oxide and/or propylene oxide). The (or each) a-orp- alkyl or alkenyl phenol polyalkoxylate may be a linear or branched polymer or co-polymer. The (or each) o-orp-alkyl or alkenyl phenol polyalkoxylate may be a block or random copolymer (eg an ethylene/propylene block or random copolymer).

In a preferred embodiment, the one or more a-or p. alkyl or alkenyl phenol alkoxylates is a single o-orp-alkyl or alkenyl phenol alkoxylate. e..

* In a preferred embodiment, the one or more a-or p-alkyl or alkenyl phenol *:::: alkoxylates is a plurality of o-or p-alkyl or alkenyl phenol alkoxylates. Particularly preferably the plurality of a-or p-alkyl or alkenyl phenol alkoxylates includes (or consists of) ap-alkyl phenol ethoxylate and ap-alkyl phenol propoxylate. *. * * S S * IS

*:*. Preferably the (or each) p-alkyl phenol alkoxylate is of formula I: -0 I 0 H (wherein: R is a linear or branched C124-alkyl each R' is independently hydrogen or methyl m is an integer of 1 or more and n is an integer of I or more).

Preferably each R' is hydrogen.

Preferably n is in the range 1-50, particularly preferably 4-40, more preferably 5-20, most preferably 8-15.

Preferably m is 2, 3 or 4, particularly preferably 2 or 3, more preferably 2.

Preferably R is a linear or branched C3.12-alkyl. R may be selected from the group consisting of nonyl, tertbutyl, isoamyl, isooctyl and C12. Preferably R is selected from the group consisting of nonyl and tertbutyl. Preferably the nonyl is branched.

The nonyl group may be obtainable by alkylation with a propylene trimer. The C12 group may be obtainable by alkylation with a propylene tetramer. * **

In a preferred embodiment, the p-alkyl phenol alkoxylate oligomer or co-oligomer is composed of oligomeric molecules each characterised independently by (eg * :: : consisting essentially of) a unit of formula (II)

S S..

S SS * * SS * ** S. * * * (II)

(wherein: R, R', m and n are as hereinbefore defined and s is an integer of 2 or more).

Typically s is in the range 2 to 20, preferably 2 to 10. Particularly preferably s is 2 or 3.

Preferably the oligomeric molecules are characterised predominantly by (eg consist essentially of) a unit of formula II in which s in the range 2 to 20, preferably 2 to 10.

Particularly preferably s is 2 or 3.

In a preferred embodiment, the p-alkyl phenol alkoxylate co-oligomer is composed of oligomeric molecules each of at least a proportion (eg substantially the whole) of which is independently characterised by (eg consists essentially of) a first unit of formula (II) as hereinbefore defined and a second unit of formula (II) as hereinbefore defined, wherein the first unit of formula (II) and the second unit of formula (II) are different.

Particularly preferably the at least a proportion (eg substantially the whole) of the oligomeric molecules are characterised predominantly by (eg consist essentially of) a first unit of formula (II) as hereinbefore defined and a second unit of formula (II) as * * hereinbefore defined, wherein the first unit of formula (II) and the second unit of formula (II) are different. *.* S * * ****

This embodiment may exploit the flexibility of the process of the invention to make it possible to ensure that non-random and non-statistical co-oligomers may be prepared :::: reproducibly. For example, the co-oligomer may be a block co-oligomer.

The first unit of formula (II) and the second unit of formula (II) may differ in one or more of R, R', n or m. Preferably the first unit of formula (II) and the second unit of formula (II) differ in at least the integer m.

The first unit of formula (II) and the second unit of formula (II) may be the same with the sole exception of the integer n which may be different.

The first unit of formula (II) and the second unit of formula (II) may be the same with the sole exception of R which may be different.

The first unit of formula (II) and the second unit of formula (II) may be the same with the sole exception of R1 which may be different.

Preferably the first unit of formula (II) and the second unit of formula (II) are the same with the sole exception of the integer m which is different. Preferably in the first unit of formula (II), the integer m is 2 and in the second unit of formula (II), the integer m is 3.

The process of the invention enables the synthesis of hitherto inaccessible co-oligomers in which the distribution of alkoxy groups is neither random nor statistical but instead is reproducibly predictable.

Viewed from a further aspect the present invention provides a non-statistical non-random p-alkyl phenol alkoxylate co-oligomer composed of oligomeric molecules each of at least a proportion (eg substantially the whole) of which is independently characterised by (eg consists essentially of) a first unit of formula (II) as hereinbefore defined and a second unit of formula (II) as hereinbefore defined, wherein the first unit of formula (II) and the second unit of formula (II) are different.

*:: : *. Preferably the non-statistical non-random p-alkyl phenol alkoxylate co-oligomer is a block co-oligomer. ** *

Preferably the non-statistical non-random p-alkyl phenol alkoxylate co-oligomer is * obtainable by a process as hereinbefore defined.

The present invention will now be described in a non-limitative sense with reference to Examples and the accompanying Figures in which: Figure 1: Structure of Nonyl Phenol, Ethoxylated; Figure 2: Viscosity comparison of products and NP4 reagent; Figure 3: IR spectrum of Cafion NP4 and oligomer produced by method la; Figure 4: IR spectrum of paraformaldehyde; Figure 5: Spectrum of oligomer produced by method 2; Figure 6: MALDI-MS Spectrum for oligomer produced by method Ia; Figure 7: Carbon NMR of product from reaction of method La; and Figure 8: Hydrogen NMR of products from reaction of method la, The purpose of the work was to test the feasibility of a route to an alkoxylated phenolic resin from a nonyl phenol.ethoxylate paraformaldehyde reaction. The structure of nonyl phenol, ethoxylated is shown in Figure 1. This represents one of around 20 or so isomer structures present in commercial branched nonyl phenol (see Moeder et al: Journal of Chromatography A; Volume 1102, Issues 1-2, 13 January 2006, Pages 245-255).

Reagents p-Nonylphenol 4 mole ethoxylate (NP4) was provided by Univar.

Paraformaldehyde (PF), dodecylbenzenesulfonic acid (DDBSA) and potassium hydroxide (KOFI) were obtained from Sigma Aldrich.

Ethanol was obtained from Fisher Scientific. * *. * . * * S.

Polydimethylsiloxane (PDMS) antifoam with dispersed fumed silica was obtained from S...

Basildon Chemicals. S... * S * S. *

S 55.

Syntheses * Two syntheses of an alkoxylated alkylphenol-formaldehyde resin were performed.

S * . . * **

Method la: Reaction of NP4 and PF with acid catalyst NP4 (99.14g, 0.25 mol) was placed in a 250 ml round bottom flask and charged with acid catalyst DDBSA (1.42g) by cold mixing using a magnetic stirrer. PF (11 85g, 0.375 mol) and PDMS antifoam (0.1 g) were added to the catalysed NP4 solution. The round bottom flask was attached to a distillation column, condenser and a cold finger for collection of water and volatile components. The reaction mixture was continuously stirred and the temperature was increased and held at 80 °C for 4 hrs. The reaction temperature was further raised to 120 °C and held for 4 hrs.

The distilled water was collected in a cold finger over dry ice. Maximum vacuum was pulled using a two stage Edwards pump while the reaction temperature was further raised to 160 °C and held for 4 hrs.

A yellowish brown viscous product was obtained and the amount of water and isopropanol distillate was 6.2 ml. The isopropanol arises from the DDBSA solution.

The reaction was repeated using approximately similar amounts of reactants but the mixture was first purged with nitrogen before raising the temperature to 160 °C. A dark yellow product was obtained. The amount of water and isopropanol distilled overhead was 6.1 ml.

Method ib:. Economical reactant level of NP4 and PF with acid catalyst NP4 (99.2g, 0.25 mol) was placed in a 250 ml round bottom flask and charged with the acid catalyst DDBSA (0.72g) by cold mixing using a magnetic stirrer. PF (8.7g, 0.275 mol) and PDMS antifoam (0.1 g) were added to the catalysed NP4 solution. The round bottom *. *. flask was attached to a distillation column, condenser and a cold finger for collection water S.,.

and volatile components. *5S*

The reaction mixture was continuously stirred and the temperature was increased and held at 80 °C for 4 hrs. The reaction temperature was further raised to 120 °C and held for 4 hrs. * * S * *. * * . * *.

The distilled water was collected in a cold finger over dry ice. Maximum vacuum was pulled using a two stage Edwards pump while the reaction temperature was further raised to 160 °C and held for 4 hrs. A yellowish brown viscous product was obtained and the amount of water and isopropanol distillate was 5.6 ml.

Method 2. Reaction of NP4 and PF with base catalyst NP4 (99. 14g, 0.25 mol) was placed in a 250 ml round bottom flask and charged with the base catalyst alcoholic KOH (1.99g of 50 % active KOH) by cold mixing using a magnetic stirrer. PF (1 1.85g, 0.375 mol) and PDMS antifoam (0.1 g) were added to the catalysed NP4 solution. The round bottom flask was attached to a distillation column, condenser and a cold finger for collection water and volatile components.

The reaction mixture was continuously stirred and the temperature was increased and held at 80 °C for 4 hrs. The reaction temperature was further raised to 120 °C and held for 4 hrs.

The distilled water was collected in a cold finger over dry ice. Maximum vacuum was pulled using a two stage Edwards pump while the reaction temperature was further raised to 160°C and held for 4 hrs.

A black viscous product was obtained and the amount of water and ethanol distillate was 5.1 ml.

The reaction was repeated using approximately similar amounts of reactants but the mixture was first purged with nitrogen before raising the temperature to 160 °C. A black viscous product was obtained and the amount of water and ethanol distillate was 5.2 ml.

*: Characterisation of oligomers Viscosity Measurements IS.I * . . S Viscosity measurements were carried out on the products using a Bohlin S..

Rheometer. Figure 2 illustrates a viscosity comparison of products and NP4 reactant. The viscosity measurements show that NP4 has the lowest viscosity of

S * SS * *.

0.273 Pas and that the product from experiment la has the highest viscosity of 1.215 Pas.

Part of the product from acid catalysed reaction (la) was placed in a rotary evaporator for 4 hr at a temperature of 140 °C. The product had a slightly lower viscosity compared with the original product.

JR Spectroscopy The JR spectrum of the different products showed that there is a considerable decrease in the ethoxylated group in the product compared with NP4. This suggests that oligomerisation has taken place.

Figure 3 shows the percentage transmittance versus wavelength of Caflon NP4 with an air reference compared with oligomer produced from method Ia. After oligomerisation a significant decrease in the 3449.48 cm peak was observed.

Figure 4 shows the plot of % transmittance versus wavelength of paraformaldehyde.

Figure 5 shows the percentage transmittance versus wavelength of the oligomer produced from method 2. It was observed that after oligomerisation, the 3449.48 cm1 peak does not decease significanly compared with that of NP4. This indicates a lower level of oligomerisation.

The mass spectra from the soft ionisation technique (MALDI-MS) shows four different average mass distributions (Figure 6). The highest distribution was centred at 887.6 m/z. The next mass distributions were at 1251.9 nilz, 1660.2 rn/z and 2069.5 mlz. The highest intensity only indicates the extent to which the samples are ionised and does not give a true idea about the average mass of the oligomer * S. * . *** From the carbon and hydrogen NMR (figures 7 and 8) it can be inferred that *: polymerisation has occurred. Carbon NMR suggests that the product is a nonyl ** phenol formaldehyde resin. * S S * ** S. S * * **

Claims

CLAIMS1. A process for preparing an o-or p-alkyl or alkenyl phenol alkoxylate oligomer or co-oligomer comprising: (a) adding a methylene donor to one or more o-orp-alkyl or alkenyl phenol alkoxylates.
2. A process as claimed in claim I wherein the oligomer or co-oligomer has 5-20 phenolic units.
3. A process as claimed in claim 1 or 2 wherein the o-or p-alkyl or alkenyl phenol alkoxylate oligomer or co-oligomer is ap-alkyl phenol alkoxylate oligomer or co-oligomer and the (or each) o-or p-alkyl or alkenyl phenol alkoxylate is a p-alkyl phenol alkoxylate.
4. A process as claimed in any preceding claim wherein the (or each) p-alkyl phenol alkoxylate is a linear or branched p-C312-alkyl phenol alkoxylate.
5. A process as claimed in any preceding claim wherein the (or each) p-alkyl phenol alkoxylate is selected from the group consisting ofp-tertbutyl phenol alkoxylate, p-isoamyl phenol alkoxylate, p-isooctyl phenol alkoxylate, p-nonyl phenol alkoxylate andp-C12 phenol alkoxylate.
6. A process as claimed in any preceding claim wherein the (or each) p-alkyl phenol alkoxylate is selected from the group consisting ofp-tertbutyl phenol alkoxylate and p-nonyl phenol alkoxylate. * **
7. A process as claimed in any preceding claim wherein the methylene donor is * an aldehyde or a derivative thereof, hexamethylene tetramine, an N-(substituted * :: hydroxyalkyl) melamine compound which is optionally N-alkylated or an ether *:. derivative thereof, an alkyloxyalkylpyridinium compound, oxazolidine or N-methyl-::::
8. A process as claimed in any preceding claim wherein the methylene donor is selected from the group consisting of hexamethylene tetramine and paraformal dehyde.
9. A process as claimed in any preceding claim wherein the methylene donor is paraformaldehyde in the presence of an acid catalyst.
10. A process as claimed in any of claims I to 8 wherein the methylene donor is hexamethylene tetramine.
11. A process as claimed in any preceding claim wherein the methylene donor is in the presence of an acid catalyst selected from the group consisting of a Lewis acid, methane disulphonic acid, methane trisuiphonic acid and a mixture thereof.
12. A process as claimed in any of claims 1 to 10 wherein the methylene donor is in the presence of a base catalyst
13. A process as claimed in any preceding claim wherein step (a) is carried out in the presence of an antifoaming agent.
14. A process as claimed in any preceding claim wherein the one or more p-alkyl phenol alkoxylates includes or consists of a p-alkyl phenol ethoxylate and a p-alkyl phenol propoxylate.
15. A process as claimed in any preceding claim wherein the (or each) p-alkyl phenol alkoxylate is of formula I: * ** * * S * ** 5*S r I) (c * * (wherein: R is a linear or branched C124-alkyl each R' is independently hydrogen or methyl m is an integer of I or more and n is an integer of I or more).
16. A process as claimed in claim 15 wherein each R' is hydrogen.
17. A process as claimed in claim 15 or 16 wherein n is in the range 5-20.
18. A process as claimed in claim 15, 16 or 17 wherein m is 2 or 3.
19. A process as claimed in any of claim 15 to 18 wherein R is a linear or branched C312-alkyl.
20. A process as claimed in any of claim 15 to 19 wherein R is nonyl or tertbutyl.
21. A process as claimed in any preceding claim wherein the p-alkyl phenol alkoxylate oligomer or co-oligomer is composed of oligomeric molecules each characterised independently by a unit of formula (II) (wherein: R, R', m and n are as defined in any of claims 15 to 20 and s is an integer of 2 or more).
22. A process as claimed in claim 21 wherein s is 2 or 3.
23. A process as claimed in either of claims 21 and 22 wherein the p-alkyl phenol alkoxylate co-oligomer is composed of oligomeric molecules each of at least a proportion of which is independently characterised by a first unit of formula (II) as defined in any of claims 19 and 20 and a second unit of formula (II) as defined in any of claims 19 and 20, wherein the first unit of formula (II) and the second unit of formula (II) are different.
24. A process as claimed in claim 23 wherein the first unit of formula (II) and the second unit of formula (II) differ in at least the integer m.
25. A process as claimed in claim 23 or 24 wherein the first unit of formula (II) and the second unit of formula (II) are the same with the sole exception of the integer m which is different.
26. A process as claimed in any preceding claini carried out in step (a) or subsequently in the presence of an extending agent.
27. A non-statistical non-random p-alkyl phenol alkoxylate co-oligomer composed of oligomeric molecules each of at least a proportion of which is independently characterised by a first unit of formula (II) as defined in any of claims 19 to 25 and a second unit of formula (II) as defined in any of claims 19 to 25, wherein the first unit of formula (II) and the second unit of formula (II) are different. * . * . S * S. * S *a41 S.., * SSSS S..S S. S * * * * S.SS S * SS * S