Continuous process for preparing polymer based pigment...

Details Continuous process for preparing polymer based pigment... Continuous process for preparing polymer based pigment...

2002-08-09

2004-04-13

Zalukaeva, Tatyana (Department: 1713)

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...

C524S522000, C524S523000, C524S700000, C526S064000, C526S088000, C526S227000, C526S319000, C526S329700

Reexamination Certificate

active

06720382

ABSTRACT:

The present invention relates to an improved process for preparing pigment preparations by mixing a with a monomer and simultaneously polymerizing the monomers in an extruder at elevated temperatures.
In view of the strong tendency towards improved industrial hygiene, customers are more and more switching from powder pigments towards the use of pigment preparations. Pigment preparations however, do consist of pigment on the one hand and a carrier material on the other. Consequently, by using pigment preparations, carrier material together with the pigment are introduced into the applications system. In order to minimise possible effects of the carrier material in the end application, its concentration should be as low as possible, or, in other words, the pigment concentration should be as high as possible, while maintaining optimal dispersion properties.
In general the manufacturing processes for pigment preparations use ready-made polymers and ready-made pigments as raw materials and then disperse the pigment into the polymer material. The production process essentially consists of two steps, the separate manufacturing of the polymer material followed by pigment dispersion. EP-A 456 610 and EP-A 542 669 describe a process for the manufacture of pigment preparations comprising up to 10% by weight of a coloured composition but all in polycondensation resins, such as thermoset crosslinked resins (bulk condensation of a sulphonamide with an aldehyde) and polyamide, polyester, polycarbonate or polyurethane resins respectively, whereby the reactants (monomers) for the formation of said polycondensation resin are introduced continuously together with the coloured composition into an extruder and polymerised therein at elevated temperatures. A major drawback of these processes is the fact that only up to 10% of a colored composition can be incorporated into the polycondensation resins. A further drawback is, that the polydispersity M
w
/M
n
is too high, because for a lot of applications a narrow distribution is preferred. For some applications, too, polymers with low molecular weights are desired.
Hence, the object of this invention was to provide a process yielding pigment preparations which contain more than 10% of pigment and exhibit an improved polydispersity. In addition, pigment preparations should be provided wherein the polymers do have a low molecular weight.
Accordingly, an improved process for preparing pigment preparations by mixing a dyestuff with a monomer and simultaneously polymerizing the monomers in an extruder at elevated temperatures has been found, wherein the process essentially consists of the following steps:
(A) introducing continuously into an extruder
(a) from 40 to 90% by weight of a pigment,
(b) from 60 to 10% by weight of a monomer or a monomer mixture, and
(c) from 0.01 to 10% by weight, related to the amount of monomer component (b), of an initiator or a mixture of initiators, and
(d) from 0 to 10% by weight, related to the amount of monomer component (b), of a chain transfer agent,
whereby the amounts of the pigment and the monomer or monomer mixture sum up to 100%, and whereby the monomer component (b) is admixed with either the initiator or mixture of initiators (c), or the chain transfer agent (d), or the initiator or initiator mixture (c) and the chain transfer agent (d), before it is introduced into the extruder,
(B) simultaneously mixing the components (a) to (c), as well as (d) if present, and polymerizing the monomer or copolymerizing monomer mixture within the extruder, and
(C) withdrawing continuously the obtained reaction mixture from the extruder.
In addition, new pigment preparations, a high molecular weight organic material pigmented with the inventive pigment preparation and its use were found, too.
According to the inventive process, the monomer component (b) is admixed with either
the initiator or mixture of initiators (c),
or the chain transfer agent (d),
or the initiator or initiator mixture (c) and the chain transfer agent (d),
before it is introduced into the extruder. Preferably the monomer is admixed with the initiator or mixture of initiators (c), or the initiator or initiator mixture (c) and the chain transfer agent (d), most preferred the monomer component (b) is admixed with the initiator or initiator mixture (c) and the chain transfer agent (d).
The admixture can be carried out by known methods e.g. by mixing the components in usual vessels and agitators, static mixers etc.
If the initiator or mixture of initiators (c) is admixed with the monomer component (b) with or without the chain transfer agent (d), it is preferred to cool the admixture after it is admixed, especially if it is desired to store it, usually at a temperature in the range of from −30 to 5° C., preferably from −20 to −5° C.
Pigments which can be used according to the instant invention are any of the solid colorants normally used in the industry for the colouring of high molecular organic material. These include organic pigments and inorganic pigments as well as carbon black. Typical organic pigments are those of the quinacridone, diketopyrrolopyrrole, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, dioxazine, phthalocyanine or azo series, or a mixture thereof.
Examples of suitable inorganic pigments are metal oxide pigments, such as iron oxide, titanium oxide and chromium oxide, cadmium pigments, such as cadmium sulfide, bismuth pigments, such as bismuth vanadate, chromate pigments, such as lead chromate, molybdate pigments, such as lead molybdate, and the like, or a mixture thereof. Mixtures of all kinds of pigments can also be used.
The amount of pigment to be introduced into the extruder is chosen in the range of from 40 to 90, preferably from 40 to 80, more preferably from 45 to 80, most preferably from 45 to 75% by weight, based on the total amount of introduced pigment and monomer(s).
Accordingly, the amount of pigment in the inventive pigment preparation usually—depending inter alia on the degree of polymerization—is within the range of from 40 to 90, preferably from 50 to 75, and in some cases it can be as high as from 60 to 75% by weight, based on the total composition.
According to the inventive process the monomer or monomer mixture is selected from the group consisting of
an acrylate or methacrylate of the formula I
CH
2
═CR
1
—COOR
2
(1)
 wherein R
1
is hydrogen or methyl, and R
2
is hydrogen, C
1
-C
12
alkyl, CH
2
—CH
2
—N(R
3
)(R
4
), CH
2
—CH═CH
2
, CH
2
CF
3
, CH
2
—CH
2
OR
3
, or CH
2
—CHOH—R
3
, R
3
and R
4
independently of each other are hydrogen or C
1
—C
4
alkyl, and
acrylonitril, acrylamide, styrene, vinylacetate, and vinyl alcohol,
whereby the term “monomer” in the context of this application encompasses also prepolymers, e.g. oligomers, i.e. polymerizable compounds with a molecular weight of usually not higher than 1,000 g/mol.
In a preferred embodiment of this invention, acrylate and/or methacrylate monomers of the formula I
CH
2
═CR
1
—COOR
2
(1)
wherein R
1
is hydrogen or methyl
R
2
is hydrogen, C
1
-C
12
alkyl, CH
2
—CH
2
—N(R
3
)(R
4
), CH
2
—CH═CH
2
, CH
2
CF
3
, CH
2
—CH
2
OR
3
or CH
2
—CHOH—R
3
,
R
3
and R
4
independently of each other are hydrogen or C
1
-C
4
alkyl,
as well as acrylonitril, acrylamide, styrene, vinylacetate, vinyl alcohol, or mixtures thereof, are preferred.
Suitable C
1
-C
12
alkyl groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec.-butyl, i-butyl, tert.-butyl, amyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl or dodecyl, preferably C
1
-C
4
alkyl such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec.-butyl, i-butyl or tert.-butyl, more preferably methyl, ethyl and n-butyl.
If desired, prepolymers obtained from the above-mentioned monomers can be used, too.
Preferred acrylate monomers are those of formula I, wherein R
1
is hydrogen or methyl and R
2
is C
1
-C
4
alkyl, or a mixture thereof.
A preferred embodiment of this invention uses mixtures of methylmethacrylate (“MMA”) and n-butylacrylate (

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