JP2002500257A - Preparation and use of mixed opacifiers based on titanium oxide and silica oxide - Google Patents

Abstract

This invention relates to a method for preparing a TiO ₂ based composition which serves as an opacifier. The opacifier is aqueous TiO ₂ under conditions such that the two mineral species combine in the mixed mineral floc, where the TiO ₂ particles are separated from each other by spacer particles and / or aggregates as a whole. It is present in a mixture with the dispersion (at least an aqueous dispersion of inorganic spacers). The present invention also provides, TiO ₂ and SiO ₂ particles, relates to compositions based on TiO ₂ and SiO _2, characterized in that it is combined in the form of mixed inorganic flocs which are based on TiO ₂ and SiO _2. Here, the TiO ₂ particles are separated from one another as a whole by agglomerates of silica and are used as opacifiers, especially in the paper industry.

Description

DETAILED DESCRIPTION OF THE INVENTION

The object of the present invention is to provide an opacifying agent, especially in laminated paper.
compounds having a TiO ₂ base for use as gents), and preparation processes which make it possible to obtain compositions.

Laminated paper, commonly referred to as decorative paper, is a surface element that has both opaque and decorative functions, which is used in the manufacture of laminated panels designed for use in the upholstery industry. Is done.

[0003] Decorative papers have a very high percentage of TiO ₂ (possible up to 40% of the weight of the dried sheet).

[0004] In comparison, printing paper and writing paper may contain 10% in absolute maximum.

In practice, the level of opacity required for decorative paper is a high TiO ₂ content. The paper undergoes a resin binding process that makes it transparent. This process is incompatible with opacifying and decorative purposes and must be improved by the addition of opacifying agents.

[0006] Titanium dioxide is traditionally used in this application because it is the only white pigment (due to the high refractive index) that can provide the desired level of opacity.

[0007] However, in the application WO 89/08739, the TiO ₂ is replaced by 5 to 40% by weight of precipitated amorphous silica, and since they are more economical, the corresponding mixture as charge in the papermaking industry is Suggest to use.

[0008] Sheets of paper have traditionally been composed of cellulose fibers and most of the T dispersed in water.
It is prepared from a mixture of inorganic charges containing iO ₂ . The mixture is contained in a "breastbox" which provides the canvas from which the sheet is formed by draining and filtering. During filtration, the cellulose fibers and portions of the inorganic charge are retained on the canvas, with or without interaction with the tangled fibers. Thus, after drying, a "fiber mat" is obtained, which produces a paper sheet.

[0009] In fact, only a fraction of the initial amount of TiO ₂ is retained in the fiber mat and, furthermore, in this fractionation, the TiO ₂ is generally very agglomerated, thus exhibiting maximum opacity. You can see that you can not.

During the formation of the fiber mat, TiO_TwoIn order to reduce the loss of cellulose, the paper industry generally incorporates a retention agent into the cellulose mixture. These reagents are usually
TiO2 on the fiber through uniform and non-uniform aggregation phenomena _Two Enables immobilization of particles.

However, when retaining opacifying charges such as titanium dioxide, the use of electrically charged polymers reduces the effect of opacification due to excessively broad and excessively dense agglomeration.

As a result, it becomes clear that simply retaining TiO ₂ in the fiber mat is not sufficient on its own in terms of opacity. It is also necessary to keep the TiO ₂ in the fiber mat in a well-dispersed form, which also makes it possible to retain its pigmentary properties and express excellent opacifying capabilities. Advantageously, it is possible to obtain the same opacity with less adhesion to TiO ₂ . The opacity of TiO ₂ is thereby increased sufficiently.

For this purpose, International Patent Application WO 97/18268 proposes a process for treating the surface of TiO ₂ particles. The treatment consists of covering the TiO ₂ particles with a single layer of inorganic particles such as silica, which is smaller than the TiO ₂ particles. This single particle layer coating allows the TiO ₂ particles separated from each other to be arranged at regular intervals.

It is an object of the present invention, inter alia, to propose a novel compound having a TiO ₂ base that meets all of the above requirements.

More particularly, it allows both to improve the retention of TiO ₂ during the formation of the fiber mat and to keep the TiO ₂ in an agglomerated structure that can be opaque with minimal harm. A new opacifier system is proposed.

The present inventors have also proposed a solution to the problem of aggregation of inorganic charges, by adding particles of a reagent called an inorganic spacer, irrespective of the form of aggregation between the TiO ₂ particles, to form a mixed inorganic aggregate. Prove to make body.

The mixed mineral aggregate obtained according to the invention is advantageous for several reasons: This aggregate allows the TiO ₂ particles to be well dispersed during the various steps in the formation of a sheet of paper. It is possible to keep it as it is, so that its maximum value can develop pigment properties and contribute to the opacity of the dry sheet.

This assemblage has an open structure, which is advantageous for better retention.
).

This assemblage has also been demonstrated to be sufficiently resistant to resist capillary bleeding, which occurs during the ejection and drying of the fiber mat, and possible shearing during the manufacture of the sheet. did.

[0020] Indeed, internal cohesive mixed inorganic aggregate is derived from the coupling of at least one inorganic spacing agent having a TiO ₂ (spacing agent), this is, established between the TiO ₂ and the spacing agent Depends on the strength of the ionic bond. This agglomeration results directly from the process used to prepare the mixed mineral aggregate.

More precisely, these aggregates are obtained under operating conditions such that the TiO ₂ and the inorganic spacing agent in question have, on the contrary, sufficiently different surface charges. In particular, the TiO ₂ and mineral spacing agent in question must have sufficiently different isoelectric points, so that these two types of minerals
It must be in the pH range with the opposite charge. Under these conditions, the two types of minerals attract each other electrostatically. The resulting attraction must be sufficient to obtain, on the one hand, the structural arrangement of the two compounds and, on the other hand, to stabilize in this form.

Accordingly, a first object of the present invention is to provide an opaqueizing agent.
containing TiO ₂ base that can be used as gent), a process for the preparation of compounds, processes according to the following: in the dispersion in an aqueous solution of -TiO _2, at least one inorganic spacing agent (spacing agent) is TiO ₂ the step (this step is mixed into the aqueous dispersion of, a stirring and is carried out at a pH between respective isoelectric points of the TiO ₂ and the spacing agent, and TiO ₂ and spacing agent, mixing inorganic collection coalescence (congregate) (which is, TiO ₂ particles, particle operators and / or aggregates of the spacing agent by (aggregate), overall are isolated from one another) their placement under the influence of electrostatic forces to Two dispersions, which are opposite and are selected to have sufficiently different surface charges Mixing accompanied by); - when necessary, the step of adjusting the value established and the pH in step 1, - the aqueous dispersion of the resulting mixture inorganic aggregate particles of TiO ₂ particles and Supeshi ing agent and / or The hardness of the bond achieved between the aggregates (solidi
curing at a temperature sufficient to enhance ty), recovering the compound of the invention in the form of an aqueous dispersion of the mixed inorganic aggregate (rec)
over) and a step which can enable the compounds of the invention to be formulated in dry form.

FIG. 1 schematically shows the structure of a mixed inorganic aggregate obtained according to the present invention. This is shown in FIG. 2 as a negative print from a transmission electron micrograph.
active print).

In the terms of the present invention, the term “aggregate” means an agglomerate of a mixture of two minerals of the TiO ₂ type and a mineral spacing agent (eg SiO ₂ ). These populations are derived from the association between the agglomerates of the spacing agent and TiO ₂ particles.

The spacing agent is formed from particles or a population of particles that insert themselves between the TiO ₂ particles.

The isoelectric point is a pH at which the surface charge of the inorganic type particles is net 0.
The net charge is negative for pH above this value and positive for lower pH.

The TiO ₂ used according to the invention is preferably rutile TiO ₂ .

More preferably, it is a pigment size rutile TiO ₂ .

If warranted, it can be coated with a mineral surface treatment.

The surface treating agent is preferably alumina, silica, zirconia, phosphate,
It contains at least one compound selected from cerium oxide, zinc oxide, titanium oxide, and mixtures thereof.

The content of oxide (s) is 1 to 20% by weight or less, or preferably 3 to 10% by weight or less, based on the total pigment weight.

As examples of these titanium dioxides, two kinds of rutile pigments, Rhodit
RL18 and RL62 from Rhone-Poulenc may be particularly cited. These two types of pigments are distinguished by the composition of the surface treating agent and the obtained zeta potential.

RL18 is a silica / alumina surface treating agent having a negative zeta potential at pH 6 (
SiO ₂ / Al ₂ O ₃ ) and is referred to as “anionic TiO ₂ ”.

RL62 has a phosphate / alumina surface treatment (P ₂ O ₅ / Al ₂ O ₃ ) that has a positive zeta potential at pH 6, and is referred to as “cationic TiO ₂ ”. The choice of pH 6 approaches the pH for industrial use.

In the present invention, the choice of anionic or cationic TiO ₂ is, of course, determined by the choice of the inorganic spacing agent bound to it.

In each case, an inorganic spacing agent having an isoelectric point sufficiently different from that of the TiO ₂ in question causes an electrostatic attraction between the two compounds (which is due to their arrangement). ) Is selected so that) can occur.

The aqueous dispersion of TiO ₂ used according to the invention contains about 5 to 80% by weight of TiO ₂ , preferably about 5 to 40% by weight. In this regard, the limiting factor is the viscosity of the suspension, which must be maintained at a reasonable value for easy handling.

According to a preferred embodiment of the present invention, the TiO ₂ employed is the cationic pigment rutile TiO ₂ , specifically Rhoditan RL62.

When considering mineral spacing agents in accordance with the present invention, they must not interact with other agents traditionally used in the paper industry.

Preferably, they do not significantly absorb any visible light.

Generally, these particle sizes are smaller than TiO ₂ particles. However, these particles are preferably used in the form of agglomerates and are therefore larger than the size of the TiO ₂ particles. The agglomerates are preferably about 0.5-2 μm in size.

As examples of inorganic spacing agents which can be used according to the invention, the following may be mentioned in particular: oxides of silicon, titanium, zirconium, zinc, magnesium, aluminum, yttrium, antimony, cerium and tin; barium Sulfates of calcium and calcium; zinc sulfide; carbonates of zinc, calcium, magnesium, lead and mixed metals; aluminum, calcium,
Magnesium, zinc, cerium and alloy phosphates; magnesium, calcium, aluminum and alloy titanates; magnesium and calcium fluorides; zinc, zirconium, calcium, barium, magnesium, mixed alkaline earth metals, and silicides Inorganic (silicated mineral)
Alkali and alkaline earth aluminosilicates; calcium, zinc, magnesium, aluminum and alloy oxalates; zinc, calcium, magnesium and alkaline earth aluminates; aluminum hydroxide, and Mixture.

The spacing agent is, of course, selected to have an isoelectric point sufficiently different from the type of TiO ₂ employed.

As inorganic spacing agents particularly suitable for the present invention, the following inorganic oxides are cited, which can be preferentially selected from oxides of silicon, zirconium, aluminum, antimony, cerium and tin and mixtures thereof: .

In certain cases where the cationic pigment rutile-type TiO ₂ is employed, preferred inorganic spacing agents are silica, alumina, silico-aluminates, or mixtures thereof.

The ratio between TiO ₂ and spacing agent is, of course, variable due to the type of spacing agent employed.

[0047] The lower limit of this percentage is a positive effect (posi) at the level of opacification.
It is generally formed by the minimum amount of mineral spacing agent needed to observe the active effect. And the upper limit is formed by the maximum amount of spacing agent that exceeds the level at which the undesired effect appears for paper incorporating the compound obtained according to the claimed process.
These undesired effects can particularly turn into paper weakening, depending on whether the resistance is dry or wet.

The spacing agent is generally present in a proportion of about 1 to 40% by weight, preferably about 5 to 15% by weight and even more preferably about 10% by weight, based on the weight of TiO ₂ . Can be used in proportions.

As explained above, the two compounds are, in the form of corresponding aqueous dispersions, heterocoagulation of TiO ₂ with particles and / or aggregates of particles from the mineral spacing agent, That is, mixing is performed while manipulating the conditions expressed by the mixed inorganic aggregate. Spacing agents can also
Can be precipitated in situ. In this case, the pH favorable for heterogeneous aggregation can be adjusted after the step of precipitating the spacing agent.

These operating conditions which favor the appearance of heterogeneous agglomeration between the mineral spacing agent and TiO ₂ are, in particular, the choice of pH within the range determined by their respective isoelectric points. In order for the two compounds to have diametrically opposite and sufficiently different surface charges, p
Choosing H is a good idea.

For operational reasons, it is desirable that the isoelectric points of the spacing agent and TiO ₂ be separated by at least 1 pH unit.

A mixed inorganic aggregate containing the expected compound is thus formed under stirring of the dispersion, generally at ambient temperature and at a pH as defined above. if needed,
The pH must be adjusted during the reaction to maintain a value that favors the formation of aggregates.

It is preferable to keep stirring for about 15 minutes in order to stabilize the system before the curing stage, but immediately attract.

According to a preferred variant of the invention, TiO ₂ is used in the cationic pigment rutile form, preferably RL62®, and the associated spacer is silica.

Even more preferably, the silica used is a silica having a large specific surface area between 20 m ² / g and 300 m ² / g. Aggregate morphologies that are between about 0.5 μm and 10 μm in size can be envisioned.

The use of silica as a spacing agent according to the present invention is advantageous for several reasons.

First, it has an isoelectric point near 2, which is a value sufficiently different from that of the cationic form of TiO ₂ (6.5-7).

In addition, silica has the advantage that it does not significantly absorb visible light, which is favorable for sheet whitening.

The pH for exposing the two corresponding dispersions to each other depends on the spacing agent and the T
It is between the isoelectric points of iO ₂ . The isoelectric point of the TiO ₂ in question is usually at the upper limit, and the isoelectric point of the spacing agent used is at the lower limit. In the case of the present invention, this pH will be between 2 and 6.5. However, in the particular case of RL62, it is necessary to avoid dissolution of the surface treatment agent. To achieve this, the pH range is limited to between 4.5 and 6.5. Even more preferably, the process according to the invention is performed at a pH of about 5.5.

To prepare a compound comprising the cationic pigment rutile form of TiO ₂ , which is bound to aggregates of silica particles, in certain cases the silica is at least 1% by weight, based on the weight of TiO ₂ Used in proportions.

It is only with this amount of silica that a significant increase in opacity retention begins to occur. The amount of silica can be increased to about 20 wt% of TiO _2. In the above case, you will encounter the paper weakening problem described above.

Accordingly, silica is preferably used in a proportion of about 5 to 15% by weight of TiO ₂ , and more preferably at 10% by weight.

The silica can either be introduced in the form of a slurry-type aqueous dispersion of silica particles or can be produced in situ by acidification of a silicate solution.

In the particular case where the silica is precipitated in situ in a dispersion of TiO ₂ , following this precipitation step, the reaction environment is characterized by the appearance of an electrostatic force between TiO ₂ and the silica thus produced. It is adjusted to a value convenient for These forces are necessary for their heterogeneous aggregation.

The second step required according to the claimed process is the actual operation for treating the mixed inorganic aggregate formed in the previous step.

As mentioned above, the mixed mineral aggregate obtained according to the claimed process is specifically designed to be used as an opacifier in the paper industry. This involves a generally continuous handling of this assemblage.

Thus, when a situation arises, these aggregates may be responsible for the aggregation effect of the polymer derivative (eg, PAE (polyamino-amide-epichlorohydrin)) and the elimination of water during formation and drying of the sheet. Need to be stiff enough to resist shearing.

The TiO ₂ particles present in the compound obtained according to the invention are then sufficiently dispersed to improve their opacity and are better retained during sheet formation. is important.

As a result, curing operations performed according to the claimed process may be particularly advantageous for enhancing the chemical (even steric) action established within the mixed mineral aggregate. I understand. In addition, some ionic bonds may be converted to covalent bonds as a result of the curing step.

In the particular case of the preparation of the compound of the mixed inorganic aggregate having a TiO ₂ and SiO ₂ base, this curing step is carried out at a temperature above 40 ° C. Preferably, this temperature is between about 60C and 100C.

The heating time lasts at least 30 minutes and can be extended if necessary up to 3 hours. As a result of the heating step, the resulting compound can be cooled to ambient temperature and recovered.

The compounds can be used directly, in the form as opacifying agents.

However, it is also conceivable that it is formulated in dry form. For this purpose, it has been found that conventional drying techniques can be applied to the dispersion obtained according to the invention.

In particular, this can be achieved by spray-drying or thin-film drying.
). However, simple drying can properly redisperse
Does not result in a product that has been modified. As the aggregates agglomerate during drying, it is preferred to mill the product using an air-blast grinding step (micronization).

According to another variant of the claimed process, the first of this process
Alternatively, the mixed inorganic aggregate obtained as a result of the second step may be subjected to an inorganic surface treatment. This is at least one hydrated ox as defined above.
ide). These latter can be precipitated in the reaction environment after the TiO ₂ and spacing agent dispersion have been exposed to each other.

The inorganic surface treating agent represents about 16% by weight or less, or preferably about 10% by weight or less, of the total weight of the mixed inorganic substance aggregate thus treated.

The present invention includes TiO ₂ -based compounds that can be obtained according to the claimed process.

Another object of the present invention is a compound having a TiO ₂ and SiO ₂ base,
This is because the TiO ₂ and SiO ₂ particles are in the form of a mixed inorganic aggregate (here, Ti
O ₂ particles are generally spaced from one another by agglomerates of silica) and are located there.

The aggregate of these mixed TiO ₂ and SiO ₂ is stabilized by the electrostatic force established between the TiO ₂ particles and the SiO ₂ aggregate. In addition, the stability of the mineral aggregates is increased by the fact that they undergo the previously described curing. This curing operation particularly contributes to the formation of covalent bonds between TiO ₂ and SiO ₂ in the assemblage.

In the case of the mixed inorganic aggregate according to the present invention, the aggregates of the inorganic spacing agent around the TiO ₂ particles are not uniformly distributed. This distribution is discontinuous. Figures 1 and 2 provide a representation of the structure of this assembly.

Preferred TiO ₂ is pigment size rutile TiO ₂ .

If necessary, this can be coated using a mineral surface treatment. This surface treatment includes phosphate, alumina, silica, zirconia, cerium oxide, zinc oxide,
It can be selected from among titanium oxide and mixtures thereof.

The amount of oxide (s) is from about 1 to 20% by weight, based on the total weight of the pigment.
Or less, or preferably less than about 3-10% by weight.

Preferred TiO ₂ is the cationic pigment rutile type TiO ₂ .

A preferred TiO ₂ is RL62.

The silica used is more preferably silica having a large specific surface, in particular between about 20 m ² / g and 300 m ² / g. Silica is present in the form of aggregates, whose size is between about 0.5 μm and 10 μm. Preferred silicas are precipitated silicas. It can also be a silica produced in situ by the acidification of a silicic acid solution.

Preferably, the silica is present in a proportion of about 1 to 20% by weight of the TiO ₂ , and preferably in a proportion of about 5 to 15% by weight, even more preferably in a proportion of 10%.

If necessary, these TiO ₂ and SiO ₂ based mineral aggregates can be coated using at least one mineral surface treatment as defined above.

The amount of inorganic surface treatment can be up to about 16% by weight, preferably about 10% by weight, based on the total weight of the mixed inorganic aggregate.

The compounds as defined above or obtained according to the invention are intended for the preparation of papers, including laminated papers, in particular for the retention of TiO ₂ at the cellulose fiber level and the opacity of TiO ₂ used. It is advantageous from the viewpoint of.

In general, conventional processes for the preparation of laminated or decorative paper use, in addition to anionic cellulosic fibers and opacifiers, polymeric agents and retention agents that are essentially cationic as reinforcing agents. I do.

When compounds based on TiO ₂ / SiO ₂ inorganic aggregates are used as opacifiers, the retention of chemicals by electrostatic attraction is advantageously enhanced compared to the individual cationic forms of TiO _2. Is observed.

This amplification of retention can be explained in the following manner; in the absence of a cationic polymer, cationic TiO ₂ is attracted by anionic cellulose fibers, which are preferred for TiO ₂ retention. Conversely, if there is a polymer, fiber -TiO ₂ interaction is changed, and TiO ₂ retention decreases. By covering the TiO ₂ with the cationic polymer, the phenomenon shifts to the cationization of the cellulose fibers.

Conversely, in compounds based on TiO ₂ / SiO ₂ inorganic aggregates, the cationic T
There is a mixture of iO ₂ and anionic SiO ₂ charges, the net zeta potential of which is negative. Thus, this mixed inorganic aggregate acts like an anionic charge. Under such conditions, it can be assumed that the mixed aggregates can enter into attractive interactions with the positively charged cellulose fibers by the cationic polymer via the negatively charged silica aggregates containing them. . This results in increased retention.

The compounds based on mixed mineral aggregates claimed and obtained according to the invention are of particular interest as opacifiers, especially in the paper manufacturing industry.

The accumulation of the following two phenomena visibly results in an increase in opacity, measured on sheets prepared using the mixed mineral aggregate base compound according to the invention: on paper sheets The increased amount of retained TiO ₂ results in better retention when the fiber mat is formed; and, by better dispersing the titanium particles contained in the aggregate, The opaque capacity is improved.

It should further be noted that these compounds increase the whiteness of the paper into which they are incorporated.

In addition to applications in the paper manufacturing industry, the compounds claimed and obtained in accordance with the present invention are also advantageous when used as opacifiers in the paint and plastics industries.

The following examples and figures are provided by way of illustration and do not limit the invention.

Materials and Methods The product utilized is a commercial product: The titanium dioxide used in this example was obtained from a Rhone-Poulenc co.
mpany is a rutile titanium dioxide sold under the name Rhoditan RL62. This pigment is aluminum phosphate (P ₂ O ₅ / Al ₂ O ₃ )
Formed of rutile type TiO ₂ coated by the surface treatment. It has a negative zeta potential at pH 6. This isoelectric point is between about 6.5 and 7.

Cellulose fibers: Dry sheet with a 70/30 mixture of short / long fibers pre-purified at 35 ° SR (supplied from Arjo Wiggins company).

[0102] Silica is a precipitated silica, which has a large specific surface area between 20 m ² g ^-1 and 300 meters ² g ^-1, with a size chunks of between 0.5μm and 10 [mu] m. This isoelectric point is about 2.

PAE resin (polyaminoamide epichlorohydrin (epchlorohydrod)
rin)) (R4947® from CECA company).

A. “Test Sheet Retention” Test Apparatus: Dispermat® and Pendraulik® High Speed Disperser Mixing Tank “Test Sheet Retention” Machine, Techpap company.

Procedure: Preparation of the Fiber / TiO ₂ Dispersion The TiO ₂ slurry or suspension of the product according to the invention, required to derive 15 g of dry TiO _2, was added to a 3,000 rpm Dispermat. Inside, add to 15 g of fiber redispersed in 500 ml of deionized water for 10 minutes.
This, it is considered a TiO ₂ slurry extracts or suspensions according to the present invention. This addition takes place in a mixing tank. Subsequently, it is diluted to 4 liters with deionized water.

(Preparation of test sample) Transfer a 500 ml test sample of the well homogenized mixture to a test tube. Here, using a micropipette, add the desired amount of PAE resin (10-fold diluted commercial solution). The tube is rotated twice to mix well. Then
The test sample is introduced into a test sheet holding machine to obtain a sheet.

(Measurement of Retention) Agitation for 30 seconds at a speed of 1300 rpm, followed by a rest time of 1 second,
Sheet formation occurs. The resulting sheet is collected on a canvas in "lump" form, dried in a drier and then calcined at 800C. The resulting ash weighs about 10 ^-4 g.

The retention is given as P2 / P1. P1 = weight of charge (TiO ₂ + SiO ₂ ) when the first 500 ml were removed. P2 = ash weight after calcining the prepared sheet.

B. Opacity Test To understand the spatial distribution of titanium dioxide in the dried sheet, an opacity test was performed using the test sheets made.

Test sheets were made according to the operating procedures described in the following paragraphs.

The optical properties of the impregnated and compressed test sheets were also measured according to the methods described below.

1. Preparation of Test Sheet i) Formation of Paper Pulp Cellulose: 15 g (this corresponds to 100 parts) Opacifying compound: 100 parts (expressed in TiO ₂ ) or 15 g PAE: cell 0.8% drying on the sauce ii) Pulp preparation: defibring After wetting with water, the cellulose is torn by hand into small squares. Dis
While stirring at 1000 rpm in a permat bowl, the small square cellulose is slowly added to 500 ml of water. After addition of the cellulose, the speed is increased to 3000 rpm and stirring is continued for 10 minutes.

Iii) Opacifier / fiber compound mixture Dilute defibrated cellulose to 1 liter. It is then stirred into a mixer with paddles. The opacifying compound is added in powder or suspension form, and the mixture is then stirred for 5 minutes. Finally, the entire mixture is diluted to 4 liters to make a sheet of 80 g / m ² material.

Iv) Preparation of the test sheet 500 ml of the well homogenized suspension are placed in a test tube. Add PAE (commercial solution diluted 10-fold to obtain sufficient sample dose) (ie, 1 ml). The tube is rotated several times for good mixing.

Pour the contents of the test tube into a bowl filled with 6 liters of distilled water,
Pour out the test sheet. Mix by bubbling for 10 seconds, followed by 1
The sheet is made by stopping for 0 seconds and then extruding under vacuum.

Next, the sheet is collected on a felt substrate, and then dried in vacuum for 7 minutes.

Next, the weight of this sheet is accurately measured, the volume to be removed is adjusted, and the desired g
ms substance (three rules) is obtained.

If one sheet has the desired gms and no defects are created, this sheet is selected for the remaining operations (ie, chemical and optical assays).

(2. Measurement of amount of ash) The amount of TiO ₂ present in the 80 g / m ² sheet was reduced by 1/3 of the test sheet to 1
Measured by calcining at 800 ° C. for a time.

The percentage of TiO ₂ present in the sheet is calculated below.

[0121]

(Equation 1) The amount of ash measures the amount of inorganic charge present in the sheet. This measurement was performed using the NF 03-047 method (French Paper, Carton, and
Pulp Standards: test methods, Volume A, 4th edition,
1985).

3. Measurement of the opacity of the impregnated and compressed sheet i) Preparation of melamine formol resin (Inilam resin 3240 from CECA) Heat 400 g of water to 60 ° C. When this temperature is reached, 245 g of pre-weighed resin is slowly poured into the continuous stream. Once everything is solubilized, continue stirring at 60 ° C. for 30 minutes. After cooling, filtration is performed through a 50 μm canvas.

Ii) Impregnation-compression A piece of paper is cut into 7 cm × 10 cm. The strip is then impregnated by capillary action by placing the strip on the resin for 1 minute. This is squeezed between two glass rods and dried with a dryer at 120 ° C. for 2 minutes.

This small piece is impregnated twice by immersing it in a resin for one minute. These are squeezed between one steel rod and one glass rod. This is dried with a dryer at 120 ° C. for 3 minutes.

The sheets are glued to a substrate formed from bottom to top by two white walls and three kraft walls, and the test sheet is brought into direct contact with the kraft walls.

The laminate obtained is compressed for 8 minutes at 150 ° C. at a pressure of 100 bar.

Iii) Measurement of Optical Properties The opacity of the laminate was measured by comparing the contrast ratio of each paper tested between the area on the kraft substrate and the area on the white substrate with Datacolor Elreph.
o Measured by evaluating using the 2000 spectral colorimetric method.

Example 1 Preparation of Compounds of Mixed Inorganic Assemblies According to the Invention in Aqueous Suspension Form RL62 is used in aqueous suspension form, which titrates 40 g / l.

Inorganic aggregates are produced by heterocoaggregation of TiO ₂ particles with silica aggregates.

The heterocoaggregation process consists of adding a silica slurry at a controlled pH at the bottom of a stirred tank containing the TiO ₂ suspension. The pH of this heterocoaggregation is 4
. It can be between 5 and 6.5, but it is preferred to work at pH = 5.5. The pH is adjusted by simultaneously adding an HCl solution to the slurry. This operation is performed at ambient temperature. The final suspension contains 10% by weight of silica as compared to the content of TiO ₂ pigment, and the total dry extract (TiO ₂ + SiO ₂ ) is about 11%.

After 15 minutes of contact at the adjusted pH of 5.5, the suspension is brought to a temperature of up to 60 ° C., still stirring, and boiled for 1 to 3 hours, then cooled to room temperature I do.

All samples prepared according to this protocol were tested by preparing test sheets (round sheets). For all tests, the volume of the “fiber + charge + PAE” mixture removed from the mixing tank was adjusted to obtain a sheet with the same grams (80 g / m ² ) of material.

-One section of the test sheet is calcined to determine the amount of oxide present in the dry sheet (SiO ₂ + TiO ₂ ). Knowing the amount of silica added with respect to TiO _2, and calculates the percentage of TiO ₂ present in the dry sheet. The protocol for forming the test sheets and the rules for calculating the amount of TiO ₂ are described in the previous section, Materials and Methods (Materials and Meth).
ods) ".

Quantification of TiO ₂ and SiO ₂ on the resulting sheet using X-ray fluorescence demonstrated that there was no favorable retention of some or other types of minerals. The SiO ₂ / TiO ₂ ratio was maintained throughout the sheet forming process.

-Infiltrate the other sections of the test sheet with the resin and then compress to obtain a laminated paper for measuring opacity and whitening. Protocols for infiltration and for measuring opacity are also described above.

Some samples are also tested in a test sheet retention test to evaluate the assembly's resistance to shear. The test consists of subjecting the "fiber + charge + PAE" mixture to rapid agitation and shearing for a specified amount of time just before forming the test sheet.

The contribution of each of the two phenomena (retention and spacing effect) to the total increase in opacity measured for each test is detailed in Tables 1 and 2.

Table 2 (lower) also shows the results obtained with Control Compound 1 (T1). This was prepared by simply mixing the silica and TiO _2.

[0139]

[Table 1]

[0140]

[Table 2] Δash = increase in the amount of ash resulting from the best retention of TiO ₂ during sheet formation Δopa = Δret + Δspac = increase in total opacity Δret = Δash ^* Slope = increase in amount of TiO ₂ retained in the sheet Increased opacity (good retention) Δspac = Δopa−Δret = increased opacity resulting from good dispersion of TiO ₂ retained in the sheet due to the spacing effect of the silica agglomerates.

The results of Tests 1-5 show that the use of mixed inorganic aggregates not only allows for improved retention in the first pass (higher amounts of ash), but also reduces the retention of TiO ₂ . It clearly shows that transparency can be improved. This is because, in all cases, the increase in opacity (Δopa) in the amount of ash (Δret) is usually greater than the expected increase in opacity.

In contrast, a comparison of the results from Control Test 1 (T1) with the results of Tests 6 and 7 is a simple mixture (ie, this does not involve any particular attention to pH levels and curing conditions). Clearly indicates that no opacity improvement occurs.

A significant increase in resin uptake is indicative of a porous and heterogeneous structure.

With respect to the effect of the amount of silica, note that tests performed with 5% and 10% silica are clearly more productive than tests performed with 1% silica.

Consequently, the above results show that, compared to the conventional formulation (TiO ₂ without silica), the use of mixed minerals containing 5% and 10% silica resulted in an equivalent proportion of ash, 0%
. Allows for an opacity increase of 6-0.9 points. This increase corresponds to the opacity score measured for the highest performing test.

Since the mixed minerals improve the amount of ash and the percentage of opacity, these compounds according to the invention can be used with less TiO ₂ , and at the same time with a conventional silica-free formulation. It is also conceivable to maintain the same level of opacity. Potential benefit in TiO ₂ can be estimated by evaluating the equal correct increase in the amount of ash corresponding to an increase in opacity to the output of the opacity. The value reported for the amount of ash in the silica-free test corresponds to the percentage of TiO ₂ that can be preserved while remaining at the same level of opacity as the control test. Hold Nfuri formulation and opacity of the same level - in these conditions, by using a mixed inorganic substance containing 10% silica, to allow retention of at least 7 to 10% TiO _2, Note conventional silico I do.

Example 2 The "test sheet retention" test was used to compare the retention capacity of this product obtained according to the invention with that of "traditional" titanium oxide. Product A: prepared according to the invention, SiO ₂ = 10% Product B: prepared according to the invention, SiO ₂ = 15% Product C: TiO ₂ , RhoditanRO18 Product D: TiO ₂ , Rhoditan RL62.

Table 3 shows the results of the “test sheet retention” test.

At a PAE ratio of 0.8% (standard ratio in this application), the product according to the invention gives a retention ratio better than RL62 and a retention ratio equal to RL18. This is due to its anionic properties as well as the specific structure achieved by the synthetic process which is the object of the present invention.

At 0% PAE, the self-retaining properties of the product become apparent. While more anionic than RL18, the products of the present invention exhibit even more pronounced self-retaining properties. This is clear evidence of a particular geometry formed from less dense loose cohesion, and in this case this retention is simply an electrostatic interaction between the fiber (essentially ionic) and the charge Demonstrates that it is far from being the result of

[0151]

[Table 3] Example 3 (Determination of the Influence of the Cured Phase) a) Effect on Retention: The shear resistance of the specific inorganic aggregate compound identified in Example 1 was tested using the “Retention Sheet Test”.

FIG. 3 shows the change in charge retention for different compounds as a function of the agitation speed imposed on the “cellulose / PAE / charge” mixture before the formation of the fiber mat.

It is clear that the retention of the mixed inorganic aggregate decreases as the stirring speed increases. Nevertheless, it remains significantly higher than that obtained with the silica-free charge. Therefore, we can conclude that the mixed mineral aggregate is sufficiently resistant to shear to preserve good retention in the first pass.

The results obtained also demonstrate the following: The reduction in cure time from 3 hours to 1 hour has little effect on the resistance of the assemblage.

• A system containing 10% silica provides better retention than a system containing 5% silica regardless of the agitation speed. The results confirm that the use of 10% silica is preferred.

B) Effect on opacity In fact, it has proven that it is not possible to obtain a good quality single sheet of paper with a RL62 SiO ₂ mixture having 10% SiO ₂ which does not undergo a curing step.

As soon as the cellulose and PAE are added to the mixing tank, flocculation and “balling” occurs.

[0158] Therefore, the curing step is an essential step for forming an effective mixed inorganic aggregate.

Example 4 (Effect of Laminated Sheet of Mixed-Type Inorganic Aggregate According to the Present Invention on Whitening of Paper) The whiteness (measured on a white background area) of the laminated sheet was measured for each test. The results are summarized in Table 4 below.

The whiteness was measured by using Datacolor Elrepho 2000 (registered trademark).
Performed according to CIEI ^* a ^* b ^* scale using a spectrocolorimeter.

[0161]

[Table 4] In general, it can be observed that the use of the compounds according to the invention improves the whiteness of the laminated sheet, even with increasing amounts of silica. Using 5 and 10% silica, a gain of about 0.2 points was measured at L ^* and 0.4 at b ^* .
A reduction of ０．６0.6 point is measured. This reduction in b ^* gives a clear blue tone to the laminated sheet that enhances the whiteness impression.

In addition to improved retention and opacity from retained TiO ₂ , they also result in improved whiteness of the laminated sheet.

Example 5 Preparation of Mixed-Type Inorganic Aggregate Compound in Powder Form In this example, heterocoaggregation is observed according to the procedure described in Example 1. After the curing step (1 hour at 90 ° C.), the product is dried in a thin layer (150
15 hours with a dryer at ℃. The product obtained is divided into two parts. One is used as it is, and the other is pulverized by air blasting (refining).

An opacity test is performed on both of these products. These are used on cellulose fibers after being in a slurry with a 40% dry residue. These were then placed in a control product: Rhoditan RL62 in a 40% slurry.
Compared with titanium oxide. The formulation used in this example is: Cellulose fiber: 100 parts (15 g) Opacifying pigment: 100 parts (15 g) PAE resin: 0.8% dry / fiber.

For the control product, 15 g of RL62 TiO ₂ were introduced. For the product according to the invention, 15 g of TiO ₂ + SiO ₂ combination were introduced.

The rest of the procedure is identical to that described in the “Opacity Rate” test.

Table 5 shows the results.

These results clearly demonstrate that the product made according to the invention subjected to simple drying (Test 2) is no better than the standard product (Test 1). On the other hand, after the miniaturization step (test 3), all possibilities of improvement in opacity for this same product are performed. In fact, this results in a sheet of paper, which
After lamination, opacity, i.e., to deliver 2.4 points higher opacity than laminated paper which has been developed from the reference product RhoditanRL62, and has an amount of TiO ₂ to fully comparable in sheets.

[0169]

[Table 5]

[Brief description of the drawings]

FIG. 1 is a schematic diagram of TiO ₂ pigments spaced by SiO ₂ aggregates.

FIG. 2 is a transmission electron micrograph of a mixed inorganic aggregate having TiO ₂ and SiO ₂ bases.

FIG. 3 shows the change in charge retention of different mixed minerals as a function of agitation speed on the “cellulose / PAE / charge” mixture before formation of the fiber mat.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C09D 201/00 C09D 201/00 D21H 17/67 D21H 17/67 19/64 19/64 (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SZ, UG, ZW), EA (AM, AZ) , BY, KG, KZ, MD, RU, TJ, TM), AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE , DK, EE, ES, FI, GB, GE, GH, GM, HR, HU, ID, IL, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA UG, US, UZ, VN, YU, ZW (71) Applicant 95, rue de General de Gaulle, 68800 Tanne, France (72) Inventor Fajardi, Frank France F-91140 Villebon-sur-Yvette, Residence Les Villebons 1 (72) Inventor Freon, Michelle France F-77360 Veil-sur-Marne, Abgne du General Leclerc 50 F-term (see ) 4J002 AA001 AB011 DE136 FB076 4J037 AA08 AA09 AA10 AA11 AA13 AA18 AA22 AA24 AA25 CA09 CA12 CA19 CA22 CA24 DD05 DD07 EE03 EE28 EE43 EE46 EE48 FF02 4J038 AA011 HA116 HA196 HA16 HA08 HA196 HA416 HA08 PB03 PB05 PC10 4L055 AG17 AG18 AG19 AG20 AG23 AG87 AG98 AH01 AH18 AH37 FA10 FA12

Claims (32)

[Claims] 1. A process for the preparation of a TiO ₂ -based compound for use as an opacifier, comprising the steps of: An aqueous dispersion of at least one mineral spacer is added to an aqueous dispersion of TiO _2. are mixed, the mixture of the two dispersions, under stirring, and the is carried out at a pH between the isoelectric points of the TiO ₂ and the spacers, and the TiO ₂ and the front Symbol Supesa is opposite and Under the influence of electrostatic forces, the TiO ₂ particles are selected to have sufficiently different surface charges, and the TiO ₂ particles are arranged by the spacer particles and / or agglomerates into a mixed inorganic mass that is totally separated from each other. If necessary, the pH is adjusted to the value set in step 1; wherein the process is also characterized in that it comprises the following steps: The resulting aqueous dispersion of mixed inorganic aggregates is used to enhance the strength of the bond established between the TiO ₂ particles and the spacer particles and / or aggregates. Curing at a sufficient temperature; recovering the compound in the form of an aqueous dispersion of mixed inorganic aggregates, wherein the compound can be capable of being formulated in a dry form. 2. The process according to claim 1, wherein the titanium dioxide used is rutile TiO ₂ . 3. The titanium dioxide used is a pigment-sized rutile-type Ti.
The process according to claim 1, wherein the process is O ₂ . 4. The process according to claim 1, wherein the TiO ₂ is coated with an inorganic surface treating agent. 5. The process according to claim 4, wherein the surface treating agent is alumina, silica, zirconia, phosphate, cerium oxide, zinc oxide, titanium oxide,
And at least one compound selected from mixtures thereof. 6. The aqueous dispersion of the TiO ₂ is characterized in that it comprises from about 5 to 80 wt% of TiO _2, the process according to any one of claims 1 to 5. 7. The aqueous dispersion of the TiO ₂ is characterized in that it comprises from about 5 to 40 wt% of TiO _2, The process of claim 6. 8. The process according to claim 1, wherein the inorganic spacer comprises: silicon oxide, titanium oxide, zirconium oxide, zinc oxide, magnesium oxide, aluminum oxide, yttrium oxide, Antimony oxide, cerium oxide, and tin oxide; barium sulfate and calcium sulfate; zinc sulfide; a mixture of zinc carbonate, calcium carbonate, magnesium carbonate, lead carbonate, and metal carbonate; aluminum phosphate, calcium phosphate, magnesium phosphate, phosphoric acid A mixture of zinc, cerium phosphate, and a metal phosphate; a mixture of magnesium titanate, calcium titanate, aluminum titanate, and a metal titanate; magnesium fluoride and calcium fluoride; zinc silicate, zirconium silicate; Calcium silicate, Barium silicate, magnesium silicate, mixed alkaline earth metal silicate, and silica combined inorganic silicate; alkali metal aluminosilicate and alkaline earth metal aluminosilicate; calcium oxalate, oxalate A mixture of zinc oxide, magnesium oxalate, aluminum oxalate, and a metal oxalate; selected from zinc aluminate, calcium aluminate, magnesium aluminate, an aluminate of an alkaline earth metal; aluminum hydroxide and mixtures thereof A process characterized by that: 9. The method according to claim 1, wherein the inorganic spacer is selected from silicon oxide, zirconium oxide, aluminum oxide, antimony oxide, cerium oxide and tin oxide, and a mixture thereof. The process of claim 1. 10., wherein the inorganic material spacers are used in a ratio of about 1 to 40 wt% based on the weight of the TiO _2, any of the preceding claims 1
The process described in section. 11., wherein the inorganic material spacers are used in a ratio of about 5 to 15 wt% relative to the weight of the TiO _2, the process according to any one of claims 1 to 10. 12. The process according to claim 1, wherein the TiO ₂ is a cationic pigment rutile type TiO ₂ . 13. The process according to claim 12, wherein the inorganic spacer is silica, alumina, silico-aluminate or a mixture thereof. 14. The method according to claim 14, wherein the inorganic spacer is silica, and
_{2. The} method according to claim 1, wherein the O ₂ is a cationic pigment rutile type TiO _2.
A process according to any one of the preceding claims. 15. The process according to claim 14, wherein said silica has a specific surface area of between about 20 and 300 m ² / g. 16. The process according to claim 14, wherein the silica occurs in the form of aggregates of a size between about 0.5 and 10 μm. 17. The process according to claim 14, wherein the silica is formed in situ by acidification of a solution of a silicate. 18. The process according to claim 17, wherein the pH is adjusted to generate an electrostatic force between the TiO ₂ and the silica thus formed after in-situ precipitation of the silica. Process, characterized in that it is adjusted to a certain value. 19. The process according to claim 14, wherein the two aqueous dispersions are brought together at a pH of the order of 5.5. 20. The method of claim 19, wherein silica is the characterized in that it is used in a proportion of about 5 to 15 by weight% based on the weight of TiO _2, the process according to any one of claims 14 to 19 . 21. The method according to claim 19, wherein the curing step is performed at 60 ° C. to 100 ° C. for at least 30 minutes.
21. The process according to any one of claims 14 to 20, characterized in that it is carried out at a temperature between. 22. The process according to claim 1, wherein the mixed inorganic aggregate is obtained from the first or second step of receiving an inorganic surface treating agent. 23. The process of claim 22, wherein the inorganic surface treatment agent indicates less than about 16% by weight, based on the total weight of the mixed inorganic aggregate being treated. . 24. A TiO ₂ -based compound, which can be obtained by a process as defined in any one of claims 1 to 23. 25. A TiO ₂ -based and SiO ₂ -based compound, wherein the TiO ₂ and the SiO ₂ particles are arranged in the form of a mixed inorganic aggregate having a TiO ₂ base and a SiO ₂ base. the TiO ₂ particles, characterized in that it entirely away from one another by aggregates of the silica mosquitoes, compound. 26., wherein the silica occurs in about 5 to 15 wt% of the percentage with respect to the TiO _2, A compound according to claim 25. 27. The compound according to claim 25, wherein the TiO ₂ is a cationic pigment rutile type TiO ₂ . 28. The method according to claim 18, wherein the silica has a specific surface area of between about 20 and 300 m ² / g and / or occurs in the form of aggregates of a size between about 0.5 and 10 μm. A compound according to any one of claims 25 to 27. 29. The compound according to claim 25, wherein the TiO ₂ -based and SiO ₂ -based mixed inorganic aggregate is coated with an inorganic surface treating agent. 30. The compound of claim 29, wherein the inorganic surface treatment agent exhibits less than about 16% by weight based on the total weight of the mixed inorganic aggregate. 31. A compound obtained according to any one of claims 1 to 23,
Or the use of a compound as defined in any one of claims 24 to 30 as an opacifier. 32. The use according to claim 31, in the paper, plastics and paints industry.