Dispersants

Details Dispersants Dispersants

1999-04-30

2001-03-06

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...

C524S539000, C528S354000

Reexamination Certificate

active

06197877

ABSTRACT:

This invention relates to a new class of dispersants, to dispersions containing such dispersants together with a particulate solid and an organic medium, to millbases and the use of such dispersions and millbases in paints and printing inks.
Dispersants containing a poly(oxypentamethylene carbonyl) chain are well known and are generally prepared by polymerisation involving &egr;-caprolactone. They are said to be particularly useful for dispersing particulate solids in an organic liquid media and contain either acid or basic terminating groups. Dispersants containing terminal basic groups are described in EP 208041 and WO94/21368 and include the reaction products of poly(ethyleneimine) with &egr;-caprolactone in the presence of aliphatic or hydroxyaliphatic carboxyl acids as chain terminators during the polymerisation of the &egr;-caprolactone. Dispersants containing terminal acid groups are described in EP 164817 and include phosphate esters of &egr;-caprolactone polymerised in the presence of a fatty alcohol as chain terminator.
It has now been found that superior dispersants can be made by replacing the &egr;-caprolactone used in the preparation of such dispersants by alkyl substituted &egr;-caprolactone either wholly or in part and by using a mixture of &dgr;-valerolactone with optionally alkyl substituted &egr;-caprolactone. Dispersants derived from block or random copolymerisation of &egr;-caprolactone and alkyl substituted &egr;-caprolactone or from &egr;-caprolactone and &dgr;-valerolactone have been found particularly advantageous.
According to the invention there is provided a dispersant of general Formula 1.
T—(A)
n
(B)
p
—Z   (1)
wherein:
T is hydrogen or a polymerisation terminating group;
Z is an acidic or basic group or a moiety containing either an acidic or basic group;
A and B are each, independently, oxyalkylenecarbonyl groups derivable from &dgr;-valerolactone, &egr;-caprolactone or alkyl substituted &egr;-caprolactone provided that both are not &egr;-caprolactone or &dgr;-valerolactone;
n and p are integers; and
n+p is from 2 to 100;
including salts thereof.
Preferably n+p is not greater than 70, more preferably not greater than 50 and especially not greater than 20.
When (A)
n
is derivable from &egr;-caprolactone and (B)
p
is derivable from either &dgr;-valerolactone or alkyl substituted &egr;-caprolactone, the ratio of n:p is preferably between 12:1 and 1:6, more preferably between 8:1 and 1:2, even more preferably between 8:1 and 1:1 and especially between 4:1 and 1:1. Particularly useful effects have been achieved when the ratio of n:p is about 2:1.
Where Z is polyfunctional there may be more than one group T—(A)
n
(B)
p
— atttached to each Z.
Preferably A is derivable from &egr;-caprolactone and B is derivable from alkyl substituted &egr;-caprolactone or &dgr;-valerolactone.
The alkyl group(s) in &egr;-caprolactone may be linear or branched and is preferably C
1-8
-alkyl, more preferably C
1-6
-alkyl and especially C
1-4
-alkyl. Examples of such groups are methyl and t-butyl.
The alkyl substituted &egr;-caprolactones are obtainable by oxidation of alkyl substituted cyclohexanone and consequently many are mixtures of alkyl substituted &egr;-caprolactone. Thus, the oxidation of 2-methyl cyclohexanone often results in a mixture of 7-methyl (95%) and 3-methyl &egr;-caprolactone (5%). However, the oxidation of 4-alkyl cyclohexanone results in only the 5-alkyl &egr;-caprolactone. Other examples of alkyl substituted &egr;-caprolactone are 6-methyl; 4methyl; 5-methyl; 5-tert butyl; 4,6,6-trimethyl and 4,4,6-trimethyl derivatives. 7-methyl &egr;-caprolactone is preferred.
(Co) polymerisation of the lactone precursors of the oxyalkylene carbonyl groups A and B in Formula 1 results in a poly(oxyalkylenecarbonyl) chain (hereinafter “POAC” chain) having a terminal hydroxy and terminal carboxylic acid group. The groups T and Z may, therefore, be attached to the (co) polymer either via oxygen or the group —COOO—. When Z is a basic group or a moiety containing a basic group such as a polyamine or polyimine the group T is preferably hydrogen or a polymerisation terminating group attached via the oxygen atom of the POAC. When Z is an acidic group or a moiety containing an acidic group such as carboxylate, sulphate, sulphonate, phosphonate or phosphate, the group T is preferably a polymerisation terminating group attached via the —COO— group of the POAC.
Preferred dispersants are derivable from either a POAC acid (i.e. a POAC chain having a terminal carboxylic acid group) which is end-capped by a polymerisation terminal group (hereinafter TPOAC acid) or from a POAC alcohol (i.e. a POAC chain having a terminal hydroxy group) which is end-capped by a polymerisation terminal group (hereinafter TPOAC alcohol).
According to a first aspect of the invention, the dispersant comprises a polyallylamine or especially a poly(C
2-4
-alkyleneimine) (hereinafter “PAI”) carrying at least two POAC chains of Formula 2.
T—(O—V—CO)
{overscore (n+p)}
  (2)
wherein:
V is a POAC chain moiety —(A)
n
(B)
p
−
; and
T, n and p are as defined hereinbefore.
For clarity, the oxygen and carbonyl groups in the POAC chain of Formula 2 have been included to indicate the manner of attachment of the group T and do not represent additional oxygen or carbonyl groups over and above those present in the oxyalkylene carbonyl group —(A)
n
(B)
p
−
.
Each POAC chain is preferably linked to the polyallylamine or PAI through either a covalent amide link —CO—N< formed between a terminal carbonyl group of the POAC chain and the nitrogen atom of a primary or secondary amino group in the polyallylamine or PAI, or through an ionic salt link —COO
−
HN
+
≡formed between a terminal carboxylate group of the POAC chain and a positively charged nitrogen atom of a substituted ammonium group in the polyallylamine or PAI. Because the dispersant contains at least two POAC chains it may contain a mixture of amide and salt links depending on the severity of the reaction conditions used in its preparation.
The dispersant of the first aspect of the invention may be conveniently represented by the general Formula 3.
wherein:
X—*—*—X represents polyallylamine or PAI;
Y represents a POAC chain linked to polyallylamine or PAI via an amide or salt linkage;
q is from 2 to 2000; and
PAI and POAC are as defined hereinbefore.
Preferably q is not less than 4 and especially not less than 10. It is also preferred that q is not greater than 1000 and preferably not greater than 500.
It is also preferred that the weight ratio of the POAC chain represented by Y to the polyallylamine or PAI represented by X—*—*—X is between 30:1 and 1:1, more preferably between 20:1 and 4:1 and especially between 15:1 and 8:1.
The PAI is preferably a poly(ethyleneimine) which may be linear or branched (hereinafter PEI).
The PAI preferably has a weight-average molecular weight from 500 to 600,000, more preferably from 1,000 to 200,000, even more preferably from 1,000 to 100,000 and especially from 10,000 to 100,000.
The dispersant of the first aspect of the invention is obtainable by reacting polyallylamine or a PAI with a TPOAC acid of Formula 4 or by reacting polyallylamine or a PAI with a lactone(s) in the presence of a polymerisation terminating compound.
wherein:
T, V, n and p are as defined hereinbefore.
The length of the POAC chain may be controlled by the presence of a chain stopper or terminating compound, such as a carboxylic acid, in the preparative process. Where the dispersant contains POAC chains formed by the polymerisation of a lactone(s) in the presence of polyallylamine or a PAI there is less need for a chain stopper because the POAC chains grow on the polyallylamine or the PAI and cannot react together. In such cases the pendant POAC chains are terminated by hydroxy groups i.e. T is H in the TPOAC acid of Formula 4.
The dispersant may be derived from polyallylamine or a PAI having at least two primary, secondary or tertiary amino groups and a TPOAC acid or lactone(s) precursor

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