Polyester association thickeners

Details Polyester association thickeners Polyester association thickeners

2002-04-26

2004-06-01

Acquah, Samuel A. (Department: 1711)

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...

C528S275000, C528S300000, C528S307000, C524S081000, C524S608000, C106S031130

Reexamination Certificate

active

06743855

ABSTRACT:

The present invention relates to novel polyesters derived from polyethyleneglycol (hereinafter PEG) and alk(en)ylsuccinic anhydrides (hereinafter ASA) and their use as “Association Thickeners” in aqueous based coatings such as paints and printing inks. Many of these polyesters are believed to function according to the “Micellar Bridging” theory.
The terms “Association Thickener” and “Micellar Bridging” are explained in U.S. Pat. No. 4,426,485 and refer to the manner by which the hydrophobic parts (hereinafter hydrophobe) of a water-soluble thickener are absorbed by a solute particle such as a latex particle to provide a network of low molecular weight thickener molecules giving good flow and levelling characteristics to water borne coatings and latex systems under high shear conditions.
Association Thickeners, including thickeners which function by Micellar Bridging theory, generally contain hydrophobes which are spaced either randomly or in clusters along a hydrophilic, especially water soluble, polymer backbone. It has now been found that polyesters which exhibit Association Thickening can be conveniently prepared by polymerising a hydroxy polyethylene alk(en)yl succinate carboxylic acid (herein after HPASCA) where the alk(en)yl hydrophobe may be distributed randomly or in clusters along the polyester backbone chain.
According to the invention there is provided a polyester of general formula 1
RO&Brketopenst;(A)(B)&Brketclosest;
n
COX  1
wherein
R is hydrogen or a polymerisation terminating group;
A is the residue of poly-C
2-6
-alkyleneglycol containing not less than 80% by weight polyethyleneglycol;
B is the residue of C
4-50
-alk(en)ylsuccinic acid;
the repeat unit represented by —(A)(B)— may be the same or different;
X is hydroxy, a group ROA—, a group —OR
1
, —NHR
1
or —O
−
M
+
;
R
1
is C
1-18
-alk(en)yl;
M
+
is a metal cation; and
n is from 2 to 100.
The Polyester Association Thickeners of formula 1 are hereinafter referred to as PAT's.
For clarity, the residues A and B are linked via an ester group —O—CO— formed between a terminal hydroxy group of the poly(C
2-6
-alkyleneglycol) and a carboxylic acid group of alk(en)ylsuccinic acid or its anhydride.
It is to be understood that the repeat units —(A)(B)— of the polyester chain may contain the same or different residues A and/or the same or different residues B.
However, it is much preferred that the polyester contains different residues represented by A and/or different residues represented by B. These different residues represented by A and B may be randomly or sequentially distributed along the polyester backbone chain. It is much preferred that the residue represented by B is sequenced in the polyester backbone chain since this results in clusters of the hydrophobes which aids Micellar Bridging. This sequencing of B is readily achieved by varying the residue A.
When R is a polymerisation terminating group it is preferably C
1-20
-alkyl, more preferably C
1-10
-alkyl, even more preferably C
1-6
-alkyl and especially C
1-4
-alkyl, for example, methyl.
Preferably, R is hydrogen.
When A is the residue of a poly-C
2-6
-alkylene glycol containing not less than 80% by weight polyethylene glycol it is preferably a polyalkylene glycol containing ethylene oxy (EO) and propylene oxy (PO) groups. It is particularly preferred that A contains not less An than 90% and especially not less than 95% by weight polyethylene glycol.
When A contains both EO and PO groups, it is preferred that the PO groups occupy a central position in the polyether moiety i.e. EO PO EO.
When A is polyethylene glycol it may consist of two polyethylene glycol chains linked together by a linking compound via urethane or ester groups. Examples of suitable linking compounds are dicarboxylic acids or anhydrides such as succinic anhydride, maleic anhydride and phthalic anhydride or di-isocyanates such as 1,6hexane di-isocyanate and tolyl di-isocyanate.
It is much preferred, however, that A is the residue of polyethylene glycol and that the number average molecular weight of the polyethylene glycol is preferably from 200 to 35,000.
Examples of suitable polyethylene glycols are PEG 200, PEG 1500, PEG 2000, PEG 3000, PEG 4000, PEG 6000, PEG 8000, PEG 10,000 and PEG 35,000 wherein the numbers signify approximate number average molecular weight.
Preferably, the alk(en)yl group in residue B contains not greater than 30 and especially not greater than 20 carbon atoms. It is also preferred that the alk(en)yl group contains not less than 8 and especially not less than 12 carbon atoms since this aids Micellar Bridging. The alk(en)yl group may be linear or branched. Examples of alk(en)yl groups are 2-octenyl, octadecanyl, n-decyl, n-decenyl, n-tetradecyl, n-hexadecyl, n-octadecyl, dodecenyl and polyisobutylene.
Preferably, X is hydroxy or a group O
−
M
+
. It is to be understood that M
+
can be a monovalent, divalent or trivalent cation. When M
+
represents a di-or tri-valent cation it forms a salt with two or three anions derived from the polyester of formula 1. Examples of suitable cations are ammonium, quatemary ammonium, benzalkonium, pyddinium, cetyl pyridinium, amine (primary, secondary and tertiary), alkali metal (especially sodium, potassium or lithium) and alkaline earth (especially barium, calcium and magnesium) including mixtures thereof.
Preferably, X is hydroxy.
It is preferred that n is not greater than 70, more preferably not greater than 50 and especially not greater than 30.
The number average molecular weight of the polyester of formula 1 can vary over a large range depending on the size of the hydrophobes and the length of the poly-C
2-6
-alkylene glycol chain residue. Nonetheless, it is preferred that the number average molecular weight does not exceed 100,000.
The acid value of the polyester of formula 1 wherein X is hydroxy is preferably less than 25, more preferably less than 15, even more preferably less than 10 and especially not greater than 5 mg KOH/g. Particularly useful thickeners have been obtained which exhibit an acid value between 0.5 and 3 mg KOH/g.
The polyesters of formula 1 may be conveniently prepared by polymerising one or more HPASCA's of formula 2
HO(A)(B)COOH  2
wherein A and B are defined hereinbefore.
The HPASCA of formula 2 itself is obtainable by reacting a poly C
2-6
-alkylene glycol with an alk(en)ylsuccinic acid or preferably its anhydride (hereinafter ASA) of formula 3 in the presence of a base as catalyst and preferably in an inert atmosphere.
wherein
R
2
is C
4-50
-alk(en)yl which may be linear or branched.
Examples of ASA's are 2-octen-1-ylsuccinic anhydride, octadecenylsuccinic anhydride, n-decylsuccinic anhydride, n-decenylsuccinic anhydride, n-tetradecylsuccinic anhydride, n-hexadecylsuccinic anhydride, n-octadecylsuccinic anhydride, dodecenylsuccinic anhydride and poly isobutylenesuccinic an hydrides (hereinafter PIBSA).
The ASA's and PIBSA's of formula 3 are well known and can be made by any processes known to the art. Some of these processes are summarised in U.S. Pat. No. 4,749,500.
The reaction between the poly C
2-6
-alkylene glycol and the ASA is preferably carried out at a temperature between 150 and 250° C. and especially between 170 and 190° C.
The base is preferably soluble in the reactants and can be a tertiary aliphatic amine, aromatic amine or pyridine derivative. Bases which are non-volatile under the reaction conditions are preferred since the equipment required does not need to be adapted to contain the base. The preferred base is 4-(N,N-dimethylamino) pyridine.
The inert atmosphere may be provided by any of the inert gases of the Periodic Table according to Mendeleev and is especially nitrogen.
The PAT's are prepared by heating one or more HPASCA's of formula 2 at between 180 and 200° C. in an inert atmosphere and preferably in the presence of an esterification catalyst such as tetra-alkyl titanate, for example tetrabutyl titanate, zinc salt of an organic acid, for example zinc acetate, zirconium salt

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