Polyether phosphates

Details Polyether phosphates Polyether phosphates

1998-06-09

2001-02-20

Cooney, Jr., John M. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From carboxylic acid or derivative thereof

C252S391000, C252S391000, C528S361000, C558S108000, C558S110000, C558S114000, C558S153000, C558S156000, C558S160000

Reexamination Certificate

active

06191253

ABSTRACT:

The present invention relates to a compound for dispersing particulate solids in an aqueous medium, its method of preparation and compositions containing said compound and a particulate solid, including paints.
Mill-bases for water-borne paints are conventionally prepared by subjecting an aqueous medium containing a water-insoluble particulate solid such as a pigment to a grinding operation in the presence of a dispersing agent in order to uniformly distribute the finely divided solid throughout the medium. However, when such mill-bases are added to a paint, the dispersing agent can adversely effect the film-forming characteristics of the paint and/or its durability as a paint film. Some dispersing agents also adversely affect the gloss of the resulting paint film. Consequently, improved dispersing agents are required which are capable of dispersing greater amounts of particulate solid in the medium, and exhibiting increased stability of the dispersion and superior properties in the resulting paint film, especially higher gloss finish.
EP 555,950 discloses aqueous mill bases containing a pigment and dispersant which is a polycyclic compound having a poly (C
2-4
-alkyleneoxy) chain containing from 3 to 50 alkyleneoxy groups. Although the dispersant of the present invention also contains a polyalkylene chain it does not contain a terminal polycyclic group such as a naphthalene ring and the present dispersants have been found to provide a paint film with a much superior gloss.
According to the present invention there is provided a dispersant obtainable by reacting a polyethylene glycol (hereinafter “PEG”) with a molar excess of a hydroxycarboxylic acid containing from 4 to 17 carbon atoms or lactone thereof (hereinafter “HCA”) and/or with a C
3-4
-alkylene oxide (hereinafter “AO”) to form a polymeric diol and phosphating the diol by reaction with a phosphating agent to give a phosphate ester. The dispersant may be in the free acid form or it may form a salt with an alkali metal, ammonia, an amine, alkanolamine or quaternary ammonium cation. The phosphate ester group may also be further partially esterified by reaction with an alcohol or may form a salt with an alkanolamine. Thus, in one aspect of the invention the dispersant is derived from a polymeric diol obtainable by reacting a PEG with a molar excess of a HCA.
It is to be understood that the PEG includes block copolymers of ethylene oxide (EO) and propylene oxide (PO) wherein the latter constitutes a middle portion attached at each end to EO units and wherein the amount of PO is less than 50%, preferably less than 30% and more preferably less than 10% by weight relative to the total weight of PEG. It is especially preferred that the PEG consists essentially of EO units.
In another aspect of the invention the dispersant is derived from a polymeric diol obtainable by reacting a PEG with a molar excess of a AO.
In a still further aspect of the invention the dispersant is derived from a polymeric diol obtainable by reacting a PEG with a molar excess of a HCA and a AO wherein the reaction of the PEG with the HCA and the AO is carried out either simultaneously or sequentially.
In all three aspects, the polymeric diol is a block co-polymer having terminal hydroxyl groups.
In a preferred aspect of the invention the dispersant is obtainable from a polymeric diol of general formula (1):
H—A—O—[CH
2
CH
2
—O]
n
—A—H  (1)
wherein:
A is the group
 or the group —[O—D—]
m
;
B is C
4-17
-alkylene;
D is C
3-4
-alkylene;
m is from 2 to 50; and
n is from 4 to 500.
Preferably, the repeat unit
is derivable from 6-hydroxyhexanoic acid, ricinoleic acid, 12-hydroxystearic acid, 12-hydroxydodecanoic acid, 5-hydroxydodecanoic acid, 5-hydroxydecanoic acid, 4-hydroxydecanoic acid and &egr;-caprolactone including mixtures thereof. It is especially preferred that B is —(CH
2
)
5
— and that the repeat unit is derived from &egr;-caprolactone.
Preferably, m is at least 3, more preferably at least 4 and especially at least 6. It is preferred that m is less than 40, more preferably less than 30 and especially less than 20.
Preferably, n is at least 6, more preferably at least 8 and especially at least 10. It is also preferred that n is less than 400, preferably less than 300, more preferably less than 200 and especially less than 100.
The ratio of the molecular weight of —A— and molecular weight of the group [—CH
2
—CH
2
—O]
n
— is preferably between 2.5:1 and 1:5 and especially between 1.5:1 and 1:3.
The polymeric diol is preferably converted to the phosphate ester by reacting the diol with polyphosphoric acid, P
2
O
5
or POCl
3
. Preferably, the ratio of the hydroxy groups of the diol to the phosphorus atom of the phosphating agent is from 3:1 to 1:1 and especially from 2:1 to 1:1.
The reaction between the phosphating agent and the polymeric diol may optionally be carried out in the presence of an alcohol or alkanolamine or the phosphate ester of the polymer diol may be subsequently reacted with an alcohol or an alkanolamine. When the reaction involves an alcohol the phosphate end group(s) are partially further esterified. When the reaction involves an alkanolamine additional ester and/or amide groups and/or amine salts with the phosphated polymeric diol are formed. It is believed that the reaction product is mainly an amine salt.
The alcohol or alkanolamine preferably has a molecular weight below 250 and especially below 100. Examples of suitable alkanolamines are ethanolamine, diethanolamine, 2-dimethylaminoethanol and 2-amino-2-methyl-1-propanol.
The preferred dispersants are those derived from PEG having a molecular weight from 500 to 6000. It is also preferred that the HCA is derived from &egr;-caprolactone. Preferably, the PEG is end-capped at each end with poly(5-hydroxy hexanoic acid) (PHHA) such that the ratio of the MW's of PHHA to PEG is from 1 to 10, more preferably from 1 to 5 and especially from 1 to 1.
The polymeric diol can be made by reacting the PEG with the HCA at elevated temperatures optionally in the presence of an inert solvent. Preferably the two components are reacted together in the absence of a solvent, especially in the presence of a catalyst and more especially in an inert atmosphere such as nitrogen. Preferably the two components are reacted together at a temperature above 100° C., more preferably above 140° C. and especially above 160° C. Preferably the temperature is below 250° C., more preferably below 200° C. and especially below 180° C.
Preferred catalysts are alkyl titanates, especially tetraalkyl titanates such as tetrabutyltitanate.
When the PEG is reacted with a AO to form the polymeric diol similar reaction conditions may be used except that the catalyst is normally an alkali metal hydroxide such as potassium hydroxide and the reaction vessel is preferably pressurised to prevent loss of the volatile AO. Consequently, the reaction between the PEG and AO is preferably carried out a temperature below 100° C. and in an inert atmosphere such as nitrogen.
As noted hereinbefore the dispersants according to the present invention are suitable for uniformly distributing a particulate solid in a liquid medium, especially an aqueous medium.
Thus, according to a further aspect of the invention there is provided a composition comprising a dispersant as hereinbefore defined and a particulate solid.
Preferably, the composition further comprises a liquid, especially one in which the dispersant is at least partially soluble and more especially is either water or an organic liquid which is miscible with water including mixtures thereof. Examples of suitable liquids include alcohols such as C
1-10
-aliphatic alcohols; glycols such as C
2-6
-alkylene glycols; alcohol ethers such as methoxy-, ethoxy-, propoxy- and butoxyethanol and methoxy-, ethoxy- and propoxypropanol; and glycol ethers such as diethylene glycol and propylene glycol. Generally, the liquid is selected to meet the requirements of the end-use to which the composition is put, especially compatibility with any medium with wh

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