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
1999-12-22
2002-07-09
Cain, Edward J. (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...
C524S460000, C516S087000
Reexamination Certificate
active
06417264
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a cationic polymer-modified silica dispersion and a production process for the same. More specifically, the present invention provides a novel cationic polymer-modified silica dispersion which is useful as a raw material for a coating liquid for an ink jet recording sheet, and a production process for the same.
DESCRIPTION OF THE PRIOR ART
A silica dispersion has so far been used for a raw material for a coating liquid for an ink-jet recording sheet, and a silica dispersion in which a cationic reagent is compounded has so far been used in order to enhance an optical density and a water resistance of an ink-jet recording sheet.
Cation-modified colloidal silica covered with a compound of polyvalent metal ion such as an aluminum ion is proposed in Japanese Patent Publication 19037/1992 as a silica dispersion used as the preceding coating liquid for an ink-jet recording sheet, and proposed in Japanese Patent Publication 57114/1993 is a composition prepared by blending synthetic silica having an average coagulated particle diameter of 0.5 to 30 &mgr;m with a cationic polymer containing a quaternary ammonium group.
However, an ink-jet recording sheet coated with a coating liquid using silica which is described in Japanese Patent Publication 19037/1992 has the defect that the performances such as a water resistance and a color developing property are not satisfactory. Further, an ink-jet recording sheet coated with the coating liquid using a composition described in Japanese Patent Publication 57114/1993 is improved in a water resistance and a color developing property but has the defect that the surface flatness and the glossiness are low due to large silica particles.
Accordingly, in order to solve the problems described above, a cation-modified silica dispersion comprising silica particles having an average particle diameter of less than 200 nm and a cationic polymer is investigated. In the present invention, an average particle diameter means a volume-based intermediate diameter D
50
determined by means of a light scattering diffraction type particle size distribution meter.
PROBLEMS TO BE SOLVED BY THE INVENTION
In general, however, there has been the problem that if a cationic polymer is mixed with a silica dispersion in which silica fine particles having an average particle diameter of less than 200 nm are dispersed, the silica particles are coagulated and not turned back to an original dispersion state even by redispersing them by means of a conventional disperser such as a turbine stator type high-speed rotary stirring disperser (for example, a homogenizer and the like), a colloid mill and a supersonic emulsifier.
An increase in the average particle diameter of silica due to coagulation of the silica particles described above brings about the problem that not only a flatness on the surface of the coated layer is not obtained but also light is prevented from transmitting, so that the coated layer is turned opaque and the glossiness comes short.
Accordingly, an object of the present invention is to provide a cationic polymer-modified silica dispersion which does not cause such coagulation of silica particles as described above and which comprises silica fine particles having an average particle diameter of less than 200 nm and a cationic polymer, and a process for producing the same.
MEANS TO SOLVE THE PROBLEMS
Intensive researches continued by the present inventors regarding the problems described above have resulted in finding that a mixed solution obtained by mixing silica fine particles having an average particle diameter of less than 200 nm with a cationic polymer in a polar solvent is oppositely-collided at a treating pressure of 300 kgf/cm
2
or more or passed through an orifice under a condition that a pressure difference between the inlet side and the outlet side of the orifice is 300 kgf/cm
2
or more, whereby the silica dispersion which is redispersed to an original dispersion state can be obtained again.
Thus, according to the present invention, provided is a cationic polymer-modified silica dispersion in which silica and a cationic polymer are dispersed in a polar solvent, wherein the silica particles contained in the above dispersion have an average particle diameter of less than 200 nm, and the above dispersion which is diluted to a solid concentration of 1.5% by weight has a light scattering index (n value) of 2.0 or more.
EMBODIMENTS OF THE INVENTION
The silica used in the present invention shall not specifically be restricted. Accordingly, publicly known silicas such as wet processed silica, dry processed silica, sol-gel processed silica and the like can be used as a raw material in the present invention.
Precipitation processed silica formed by neutralizing sodium silicate with a mineral acid to deposit silica in a solution is representative of wet processed silica described above, and it is called “white carbon” as well. Also, gel process silica prepared by neutralizing sodium silicate with an acid in the same manner can be used as well. Further, a dewatered silica cake which is only filtered and washed after a neutralization reaction and is not subjected to a drying step can be used as well.
In general, dry processed silica described above is obtained by burning silicon tetrachloride in oxygen-hydrogen flame at a high temperature and called fumed silica.
The sol-gel processed silica described above can be obtained usually by hydrolyzing an alkoxide of silicon such as tetraethoxysilane and tetraethoxysilane in an acidic or alkaline water-containing organic solvent.
In the present invention, wet processed silica and dry processed silica out of the silicas described above are suited,
In the present invention, any polymers can be used as the cationic polymer without specific restrictions as long as they are dissociated when they are dissolved in water to present a cationic property. Among them, the polymers having a primary to tertiary amine or a quaternary ammonium salt can suitably used, and the polymers having a quaternary ammonium salt are more suitable.
The polar solvent used in the present invention shall not specifically be restricted as long as it is a polar solvent in which silica and a cationic polymer are easily dispersed. Examples which can be give as such polar solvent include water; alcohols such as methanol, ethanol and isopropyl alcohol; ethers; and ketones. Among the polar solvents described above, water is suited. Further, mixed solvents of water and the polar solvents described above can be used as well.
In order to elevate the stability and the dispersibility of the silica particles, a small amount of a surfactant and the like may be added to the cationic polymer-modified silica dispersion of the present invention as long as the effects of the present invention are not damaged.
In the present invention, the amounts of silica and the cationic polymer contained in the cationic polymer-modified silica dispersion shall not specifically be restricted. The amount of silica contained in the silica dispersion is preferably 8 to 50% by weight, more preferably 8 to 25% by weight, and the amount of the cationic polymer is preferably 3 to 50 parts by weight per 100 parts by weight of the silica.
If the amount of silica contained in the silica dispersion is more than 50% by weight, a fluidity of the slurry is extremely deteriorated, so that it is difficult to mix it with the cationic polymer. On the other hand, if the amount is smaller than 8% by weight, a large apparatus for drying the dispersion is required, so that the energy cost grows high.
If the amount of the cationic polymer contained in the silica dispersion is smaller than 3 parts by weight per 100 parts by weight of the silica, a balance of the surface charge of the silica particles becomes uneven, and the silica particles are liable to cause firm coagulation. On the other hand, if the amount of the cationic polymer is more than 50 parts by weight per 100 parts by weight of the silica, the viscosity grows high, so that dispersion treat
Fukunaga Kenji
Ishizu Kenichi
Kono Hiroyuki
Tagashira Yoshinori
Cain Edward J.
Lee Katarzyna W.
Tokuyama Corporation
LandOfFree
Cationic polymer-modified silica dispersion and production... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cationic polymer-modified silica dispersion and production..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cationic polymer-modified silica dispersion and production... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2873727