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...
Reexamination Certificate
1999-12-21
2002-07-02
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...
C427S391000, C427S411000, C524S425000, C524S445000, C524S446000, C524S447000, C524S449000, C524S451000
Reexamination Certificate
active
06414074
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to new aqueous suspensions of mineral fillers intended, for example, for the paper industry and the use thereof in the manufacture of paper and in the manufacture of coating color for paper.
2. Discussion of the Background
In practice, aqueous suspensions of mineral fillers, the rheology of which is such that it facilitates their use, are used as part of the process of manufacturing sheet paper and cardboard by mixing them with aqueous suspensions of cellulose fibers in order to improve the opacity, whiteness or printability of the paper produced.
They are also used in all applications during which the paper is coated, and are so in the form of aqueous compounds referred to as coating colors, essentially made up of water, binders and pigments or mineral fillers.
These pigments or mineral fillers, which may of various origins, have a different affinity to water depending on their nature. A first category consists of mineral substances with a charged hydrophilic surface such as natural or synthetic calcium carbonates, in particular chalks, calcites or marbles, the dolomites or alternatively kaolins as well as calcium sulphate or titanium oxides, satin white, aluminium hydroxides or others, for example. A second category covers mineral fillers with a hydrophobic surface such as talc, mica or others, for example.
Although these two types of mineral substances do not exhibit the same rheological behavior when placed in suspension in water, particularly when prepared in high concentrations, they must nevertheless exhibit the same quality criteria for the user. The aqueous suspensions of mineral substances must therefore possess a sufficiently yield stress to avoid all risk of sedimentation as well as a high enough but not too high Brookfield viscosity to prevent any hardening of particles of the mineral substances, so that they will be easy for the user to handle even after storage in tanks for several days without agitation. Furthermore, these suspensions must have as high a content of mineral substance as possible in order to reduce all the costs inherent in transportation due to the quantity of water present.
Previously, suspensions of mineral substances with a charged hydrophilic surface have conventionally contained dispersing agents or crushing aids consisting of polyacrylates. with a low molecular weight (EP 100 947, EP 542 643, EP 542 644). However, these agents have a disadvantage in that they are not very efficient when placing in suspension and/or crushing hydrophobic substances, such as talc or mica, which are commonly used alone or in mixtures. One skilled in the art currently uses suspensions of minerals with a hydrophobic surface containing other dispersing agents and/or crushing aids, these being copolymers in which one of the monomers has a surface-active structure (EP 0 003 235, EP 215 565). These copolymers, however, have a disadvantage in that they are not efficient when it comes to placing in suspension and/or crushing mineral substances with a hydrophilic surface such as the calcium carbonates or kaolins, calcium sulphate, titanium oxides, satin white, aluminium hydroxides or others.
Consequently, until now, in order to disperse and/or crush a mineral substance with a hydrophobic surface, it has been extremely difficult for the skilled person to use a dispersing and/or crushing agent known for its efficiency in dispersing and/or as an aid for crushing mineral substances with a hydrophilic surface and vice versa.
Faced with this problem of using dispersing agents and/or a crushing aid specific to a type of mineral substance, the applicant has conducted extensive research and has developed new suspensions of mineral pigment fillers which, irrespective of the nature of the mineral substance, have the same Theological properties and contain the same dispersing agent and/or crushing aid.
SUMMARY OF THE INVENTION
One of the objects of the present invention, therefore, is to obtain aqueous suspensions of mineral substances that are easy for the user to handle and can be used in the paper industry, regardless of whether these mineral substances have charged hydrophilic surfaces or hydrophobic surfaces.
Another object of the invention is the use of these aqueous suspensions of mineral fillers as proposed by the invention in the manufacture of paper and coating colors for paper.
The objects of the present invention, and others, may be accomplished by using as a dispersing agent and/or crushing aid a copolymer which contains the following monomers in polymerized form:
(a) at least one ethylenically unsaturated monomer having at least one carboxyl function,
(b) optionally, at least one ethylenically unsaturated monomer having at least one sulphonic and/or phosphoric function,
(c) optionally, at least one ethylenically unsaturated monomer which has no carboxyl function, and
(d) at least one surface-active, oxyalkylated, ethylenically unsaturated monomer ending with a hydrophobic chain, the radical of which is selected with a view to using the copolymer as a dispersing agent and/or crushing aid regardless of the type of mineral substances to be dispersed and/or crushed.
Monomer (d) is represented by the formula:
where
m is at most 100,
p is at most 100,
n is at most 100,
q is a number at least equal to 1 and such that 0≦q (n+m+p)≦100,
R
1
is hydrogen or a methyl or ethyl radical,
R
2
is hydrogen or a methyl or ethyl radical.
R is a polymerizable unsaturated radical derived from an acrylic, methacrylic, maleic, itaconic, crotonic, or vinylphthalic ester or an unsaturated urethane, and
R′ is a hydrophobic radical.
Accordingly, the present invention provides for an aqueous suspension comprising water, at least one mineral substance, in addition to the copolymer described above.
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description.
DETAILED DESCRIPTION OF THE INVENTION
In one embodiment, the aqueous suspensions of mineral substances of the invention, which meet the above-mentioned quality criterion, are characterized in that the copolymer, dispersing agent and/or crushing aid contains:
(a) at least one ethylenically unsaturated monomer having a carboxyl function, selected from among the mono-acids such as acrylic, methacrylic, crotonic, isocrotonic or cinnamic acid, the diacids such as itaconic, fumaric, maleic or citraconic acid, the anhydrides of carboxylic acids such as maleic anhydride and the hemi-esters of diacids such as the monoesters at C
1
-C
4
of maleic or itaconic acids, or mixtures thereof,
(b) optionally, at least one ethylenically unsaturated monomer having a sulphonic function, selected from among acrylamido-methyl propane-sulphonic acid, sodium methallylsulphonate, the vinyl sulphonic acids and styrene sulphonic acids, or having a phosphoric function selected from among ethylene glycol methacrylate phosphate, propylene glycol methacrylate phosphate, ethylene glycol acrylate phosphate, propylene glycol acrylate phosphate and their ethoxylates, or mixtures thereof,
(c) optionally, at least one ethylenically unsaturated monomer having no carboxyl function, selected from the group comprising the esters of acrylic or methacrylic acids such as the methyl, ethyl, butyl, 2-ethyl-hexyl acrylates or methacrylates or acrylonitrile, methacrylonitrile, vinyl acetate, styrene, methylstyrene, diisobutylene, vinylpyrrolidone, vinylcaprolactam, or alternatively the unsaturated amides such as acrylamide, methacrylamide or their substituted derivatives such as, for example, dimethylaminopropyl acrylamide or methacrylamide, the acrylic or methacrylic esters of glycol, methacrylamidopropyl-trimethyl-ammonium chloride or sulphate, methacrylate of trimethylammonium-ethyl chloride or sulphate as well as their acrylate and quaternized acrylamide counterparts and/or dimethyldiallylammonium chloride, and
(d) at least one ethylenic
Niland Patrick D.
Pluess-Staufer AG
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