Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-03-31
2002-04-09
Sanders, Kriellion (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S353000
Reexamination Certificate
active
06369131
ABSTRACT:
FIELD OF APPLICATION
In its broadest aspect, the present invention relates to the treatment of ingredients choosen in the group of pigments, anti-flame agents, UV and temperature stabilizers, vulcanizing agents, reticulating agents, initiators, viscosity modifiers, anti-flocculating agents and the like and mixtures of the same pigments or agents in order to promote their incorporation in final application carriers.
In particular, the present invention relates to dry master batches with high content of pigments, specifically suited for the preparation of inks and paints or for the pigmentation of plastic materials.
The present invention relates also to a process for the preparation of said master batches.
The term “pigments” is meant to include also the so called optical bleaching agents, that is to say those organic or inorganic materials able to bleach, i.e. to turn the substrate whiter, with which they come in contact, and flame retardants.
It is known that inks and paints may be prepared by mixing while stirring the pigments with suitable, in general resin-based, dispersion carriers, able to disperse effectively the pigments particles so to obtain the end product with the desired dye and gloss properties.
It is also known that, in order to obtain paints or inks with good dye and gloss properties, the size of the pigment particles must be sufficiently reduced, generally below 1 &mgr;m. In case of organic pigments, particles of such granulometry may be obtained from synthesis processes in aqueous phase. Such particles are separated from the reaction mixture by means of filtration under pressure, thus obtaining cakes which are then dried.
During the drying, the pigment particles undergo a fast agglomeration that increases the granulometry to values greater than 1 &mgr;m, so that it is necessary to grind those particles in order to restore the desired granulometry, during the incorporation in the final dispersion carrier in dedicated equipment, such as sand mills, ball mills and alike.
In order to avoid the milling process, according to a method proposed in the prior art, the still wet filter pressed cakes are mixed, in a vacuum kneading machine and at a predetermined temperature, with resin solutions, such as solutions of glycerophthalic resins, in suitable organic solvents.
As pigments generally have a greater affinity for such solvents, the pigment particles dissolve before the agglomeration takes place and at the same time the particles are freed from the water of the cakes, which is removed from the mixture by the combined effect of vacuum and heating.
By exposing such mixture while stirring to vacuum and heating for a long period of time, the organic solvents are slowly removed and the pigment particles are dispersed in the resins devoided of such solvents.
At the end of the process, dried master batches are obtained, wherein the granulometry of th e dispersed particles of the pigments is substantially unchanged with respect to that initially provided on the filter pressed cake, so that such mixtures can be added to a final dispersion carrier without any milling being required.
The aforesaid process has the drawback that master batches with the aforesaid characteristics may be obtained, only if the pigments weight percentage in the final mixtures does not exceed 30%.
The high resin content of such mixtures strongly limits their compatibility with the final dispersion carriers up to a point where, in order to have an effective dispersion of the pigments therein, it is often necessary to employ in the dispersion carriers, the same resins used in the master batches.
As result, the master batches prepared with the aforesaid process find applicability in a rather limited field.
The technical problem at the basis of the present invention is that of providing dry master batches comprising pigments and dispersion carriers wherein the main component of the mixture consists of particles of such pigments of a proper granulometry, wherein said mixtures can be in turn dispersed without the need of milling them in various final carriers with different chemical-physical properties, carriers which range from the dispersion carriers employed for the preparation of inks and paints to plastic materials.
Such problem is solved by a dry master batch comprising at least one pigment and a dispersion carrier, characterized by comprising at least 80% in weight calculated on the weight of the mixture of particles of said at least one pigment having a granulometry lower than 1 &mgr;m dispersed in said carrier.
Preferably, the master batches of this invention comprise at least 90% of pigment particles dispersed in the dispersion carrier.
The pigments of the master batches of this invention can be obtained through synthesis processes in aqueous or organic phase.
The dispersion carrier is chosen according to the final application of the mixtures of the invention. The mixtures may be advantageously employed both for the preparation of inks and paints and for the pigmentation of plastic materials.
When the master batches are employed for the preparation of inks and paints, the dispersion carrier for the mixtures may consist of one or more resins chosen in the group comprising glycerophthalic resins and derivatives thereof, polyamide resins, polyvinyl alcohols, colophonies and mixtures thereof, which have a good compatibility with various resins of the end dispersion carriers such as maleic resins, ketonic resins, phenol-formaldehyde resins cerophthalic resins, esterified arabics, colophonies or hydrogenated colophonies.
On the contrary, when the master batches are used for the pigmentation of plastic materials, the dispersion carrier can consist of one or more polyolefins and the mixtures may be used for the pigmentation of plastic materials consisting of styrene, vinyl, polyolefin, polyurethane polymers and block copolymers.
The dry master batches according to the present invention are produced with a process comprising the steps of:
providing a turbo-mixer comprising a cylindrical tubular body, provided in some case with a heating jacket on the inner wall thereof, with at least one inlet opening for at least one pigment in form of filter pressed, tape pressed or centrifuged wet cake (that is to say, impregnated with water or organic solvents according to the synthesis process for the pigments), with at least one inlet opening for a solution of a dispersion carrier, at least one discharge opening and one rotor provided with blades rotatably supported in the cylindrical body and having the blades arranged helicoidally;
feeding continuously and concurrently a flow of said at least one pigment and a flow of solution of said dispersion carrier in the turbo-mixer;
centrifuging said flows by means of said rotor provided with blades against the inner wall of said turbo-mixer, with the formation of a dye paste arranged in a thin tubular, turbulent and dynamic layer that is advanced by the blades of said rotor towards said at least one discharge opening of said turbo-mixer, said blades subjecting to a severe mechanical machining the dye paste of said thin tubular, turbulent and dynamic layer;
discharging in continuously a flow of said dye paste from said at least one discharge opening of said turbo-mixer; and
drying said dye paste obtaining said dry master batch.
In the process according to the invention, the rotor provided with blades of said turbo-mixer is made to rotate at a speed of 200-1000 rpm and said heating jacket is maintained at a temperature comprised between 20° C. and 60° C.
In the turbo-mixer, the aforesaid at least one inlet opening for the solution of dispersion carrier can consist of a feed opening for said solution or of distributing nozzles for said solution or of both.
It has surprisingly been found that, processing dye pastes in the form of a thin tubular, turbulent and dynamic layer according to the process of the present invention, dry master batches may be obtained, which have a high pigment content in excess of 80% by weight calculated on the weight of the final master batch, wherein
Geoline S.r.l.
Sanders Kriellion
Sughrue Mion Zinn Macpeak & Seas, PLLC
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