JPH0413613A - Dentifrice composition silica miscible particularly organic amino compound - Google Patents

Abstract

PURPOSE: To obtain silica that is produced by reaction of a silicate with an acid, and aging at three steps, has compatibility with a fluorine-containing amine, betaine, etc., and becomes aqueous suspension varying in a specific pH range, and a toothpaste composition containing such silica. CONSTITUTION: This silica, which becomes aqueous suspension varying in a pH range defined by two inequalities, expression I [(C) is weight concentration of aqueous silica suspension which is expressed by SiO2 %] and expression II, and also in a range defined by expression III [(D) is electric conductivity of the aqueous silica suspension expressed by microsiemens.cm<-1> ], is obtained by making a silicate react with an acid at 60-95 deg.C, aging the resultant at first, second and third aging steps in condition of pH6-8.5, pH6.0 or less, and pH5.0 or less, respectively, then washing with water and drying the formed silica. Thus obtained silica is compatible with a fluorine-containing amine betaine, metal cation, chlorhexidine, etc., and can be used for preparation of toothpaste composition.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to silica particularly useful in dentifrice compositions, a method for producing the same, and dentifrice compositions incorporating the silica.

It is known that silica is widely used in the manufacture of dentifrice compositions and can serve several functions in such compositions.

It first acts as an abrasive. Its mechanical action aids in the removal of tartar. It can also serve as a thickening agent to impart certain rheological properties to the toothpaste and as a fluorescent agent to impart the desired coloration.

In addition, toothpastes are commonly used as anti-cavity agents, usually sodium fluoride or monofluorophosphate; binders such as algae colloids such as carrageenan, guar gum or xanthan gum; humectants such as polyalcohols such as glycerin, sorbitol, xylit and propylene. It is known to contain glycols (which can be glycols). Optional ingredients such as surfactants,
Tartar or tartar reducing agents, taste correctors, colorants, pigments, etc. are also present.

Among the different ingredients in toothpaste formulations are organic amino compounds. The term "organic amino compound" is understood to mean an active molecule used in toothpaste formulations containing at least one nitrogen atom. More particularly, the following compounds may be mentioned: Fluorine-containing amines used as anti-caries agents, especially long-chain amino acids or amino adducts with hydrogen fluoride, such as cetylamine hydrofluoride, bis-(hydroxyethyl)
Aminopropyl-N-hydroxyethyloctadecylamine dihydrofluoride, octadecylamine fluoride and NN',N'-1-ly(polyoxyethylene)-N-hexadecylpropylenediamine dihydrofluoride; Amino oxides used as nonionic surfactants obtained by oxidation of trialiphatic amines, especially those of the formula R(CH,), N -0 (R is a straight or branched chain of about 10 to 24 carbon atoms) alkyl amine oxide, which is an alkyl group.

Also, amine oxides of the formula R(CH, (:RtOH) or a compound of formula RN(
dimethylalkylamine and cetyltrimethylammonium bromide of CHs)*; alkylbetaine (N
-N-alkyl derivatives of dimethylglycine) and alkylamidoalkylbetaines (hereinafter referred to as alkylbetaines) may also be mentioned.

An example of this type of amphoteric surfactant is the formula: %formula% Alkyl betaine and formula: CH.

R-CO-NHi-(CHs)s-N''-
CHi -COO-CHi (R is a straight chain to branched chain alkyl group having 10 to 24 carbon atoms) alkylamidopropyl dimethyl betaine.

The presence of organic amino compounds raises the problem of compatibility with silica. Thus, especially as a result of its absorption capacity, it may have a tendency to react with the compound, so that the silica can no longer perform its function.

It is thus an object of the present invention to provide novel silicas, more particularly said organic amino compounds, which can be used in toothpaste formulations in a manner compatible with such fluorine-containing amines and betaines. The purpose is to provide silica.

Another object of the present invention is to provide a silica that has good compatibility with the various cations present in dentifrice formulations, such as zinc, strontium, tin, etc.

Another object of the present invention is to provide silica with guanidine type compounds that are as compatible as possible with bis-biguanides, the most representative of which is chlorhexidine.

Yet another object of the invention is a method for producing such compatible silica.

Applicants have found that the compatibility sought essentially depends on the surface chemistry of the silica used. established the following conditions.

The characteristics of the silica according to the present invention are that the pH is a function of the silica concentration according to the following two inequalities:
indicates the weight concentration of an aqueous silica suspension expressed in 5iO-%] and the pH varies as a function of the conductivity of the silica by the following two inequalities: ) and (IIb), (D)
represents the electrical conductivity of an aqueous silica suspension in microSiemens cm-'.

Another feature of the silica according to the invention is that it has an acidity function HO of at least 4.0.

Another feature of the silica according to the invention is that it has a number of OH sites per Hm'' of 12 or less.

Another feature of the silica according to the invention is that it has a zero charge point (ZCP) of at least 4.

One feature of the silica according to the invention is that it has at least 30% compatibility with organic amino compounds, more particularly from the group consisting of fluorine-containing amines, amine oxides, alkyl amines and alkyl betaines. It should have a compatibility of at least 50%, preferably at least 80%, with the selected organic amino compound.

Another feature of the silica according to the invention is that it has a compatibility with metal cations of at least 50%, more particularly at least 70%.

Another feature of the silica according to the invention is that it has a compatibility with guanidine type compounds of at least 30%, especially at least 60%, with chlorhexidine.

The present invention also provides, for this purpose, that when producing the silica according to the present invention, a silicate and an acid are reacted to form a suspension or a silica gel, and the first aging is carried out at a pH of 6 to 85. , a second aging at a pH below 6 followed by a third aging at a pH below 5 to separate the silica, which has a pH as measured on a 20% 5iO suspension. The following formula % formula % () (In the formula, e is a constant value of 0.6 or more and 1.0 or less, d is a constant value of 70 or more and 8.5 or less, and (D) is MicroSiemens co+-' conductivity of the aqueous suspension expressed by )) and drying the resulting suspension.

Furthermore, the present invention relates to a tooth brushing composition characterized by containing silica as described above and produced according to the above method.

Other characteristics and advantages of the invention are apparent from the following description and non-limiting examples.

The silica according to the invention is characterized in that the pH of its aqueous suspension varies as a function of its concentration and its electrical modulus according to the equation given above. A method for measuring the pH as a function of the concentration of an aqueous silica suspension and its conductivity is shown below.

As already mentioned, the essential feature of silica according to the present invention is its surface chemistry.More specifically, one aspect of this surface chemistry that should be taken into account is acidity. One feature of the silica according to the invention is the power of its acid surface sites.

Here, the term acidity is understood in the Lewis sense. That is, acidity describes the tendency of a base to accept electron pairs according to the following formula: The acidity function JHo was developed by F1amll1ett to investigate the tendency of
is used. The function HO is thus defined by the following standard relation: To measure the power of the acid sites of silica according to the invention using the Hammett method, Walli
The indicator first reported by ng is used (J
, Aa+, CheIl, Sac,, 1950.7
2, p1164). The strength of the acid site is measured by a color indicator, and the passage pKa between the acid form and the base form is known under the conditions of use.

Thus, the lower the pKa of the indicator that causes the color change, the more acidic the acid site. Non-limiting examples of HamIIlett indicators useful for covering Ho values by determining in which form two consecutive indicators are adsorbed are illustrated in the table below: Indicator Base Form Acid Form pKa Neutral Red Yellow Red +68 methyl red
Yellow Red +4.87 Enylazonaphthylamine Yellow Red +
40p-dimethylaminoazobenzene Yellow Red + 332-amino-5-1zotoluene Yellow Red + 2
0 Benzeneazodiphenylamine Yellow Solid + 154-Tmethylamino 1C 1-Naphthalene Yellow Solid + 12
crystal violet blue
Yellow + 08 Ginnafluacetone Yellow Shindo -30 Benzalaldehyde Colorless
Yellow -56 Anthraquinone Colorless Yellow -82 The color of the indicator adsorbed on silica is a measure of the strength of the acid site. If the collar is that of the acid form of the indicator, the HO function value of the surface is less than or equal to the pKa of the indicator. Low Ho values correspond to high acid sites. Thus, for example, silica which exhibits a red color with p-dimethylaminoazobenzene and a yellow color with 2-amino-5-azotoluene has an acidity function in the range 3.3 to 2.

In an experiment, 0.2 g of silica is placed in a test tube and assayed in the presence of a 100 mg/l indicator solution in cyclohexane.

The silica was dried in advance at 190°C for 2 hours in a desiccator.
Keep dry. As a result of stirring, adsorption occurs in a few minutes, if at all, and a macroscopic color change is observed. In some cases, the characteristic absorption spectrum of the adsorbed color indicator is examined in the form of an acid or base image.

The first characteristic of the silica according to the invention is that it has an acidity function of at least 4.0, as investigated above.

The surface condition of the silica according to the invention is such that the condition regarding the number of acid surface sites is fulfilled. The number can be determined by the number of OH- or silanol per nm''.

This number is measured as follows. The number of surface sites is
Compared to the amount of water released by silica between 190 and 900°. The silica sample is pre-dried at 105° C. for 2 hours. Silica with a mass of P0 is placed in a thermobalance and heated at 190° for 2 hours, and the resulting mass is P +a.

shall be. The silica is then heated at 900'C for 2 hours and the newly obtained mass is defined as P9°0.

The number of OH sites is calculated by the following formula Pl.

In the formula, N0H- is the number of OH sites per nm of the surface, and A is,
It is the specific surface area of a solid, measured by BET and expressed in m2/g.

In this case, the silica according to the invention advantageously contains less than or equal to 12 and more particularly at most 1O or from 6 to 100)(-/n
m”.

The nature of the OH moieties of silica according to the invention may also constitute a characterization of its surface chemistry, and also the pH of the silica suspension, where the charge on the solid surface is zero, whatever the ionic power of the medium. It is also possible to evaluate using the zero charge point defined by the number. This ZCP measures the true pH of a surface unless it contains all ionic impurities.

Charge is measured by a potentiometer. The principle of the method is based on the synthesis of adsorbed and desorbed protons on the silica surface at a given pH.

Referring to the equation describing the overall balance of operation, it is easy to prove that the surface charge associated with the counter equation, which corresponds to zero surface charge, is given by: where A is the solid's surface charge. represents the specific surface area, m''/g, M is the amount of solid in the suspension, g, F is faraday, (H4) or (OH-3 are respectively
Or it represents the change per surface unit of OH- ions.

The experimental method for measuring ZCP is as follows.

Using the method reported by Berube and Bruyn (J, Coloid Interface
Sc, 1968.27, p 305), the silica is prewashed with high resistivity deionized water (10 megaohm cm), dried and predegassed. Actually, KOH
Or by adding HNO, 1O-5 to 1
Neutral electrolyte (K
A series of solutions containing pHo=8.5 are prepared containing NO, ).

A predetermined amount of silica is added to these solutions to stabilize the pH of the resulting suspension, which is completed by stirring at 25° C. under nitrogen for 24 hours. That is, pH'o becomes that value.

For the standard solution, a portion of the same suspension was heated at 1100 Orp for 30
It is made up of the supernatant obtained by centrifugation for minutes. That is, pH'o is the pH of the supernatant.

Then, p of a given volume of the suspension and the corresponding standard solution
The H is brought to pH by adding the required amount of KOH and the suspension and standard solution are stabilized for 4 hours. ■. □
-NoH- is the number of base equivalents added to drive a known volume (V) of suspension or standard solution from pH'o to pHo.

Potentiometric assays of suspensions and standard solutions were performed at pHf =
It is carried out on a pHo basis by adding nitric acid to 2.0. Preferably, the procedure includes adding an acid increment corresponding to a pH change of 0.2 pH units. After each addition, allow the pH to stabilize for 1 minute. That is, V
u+·NH+ represents the number of acid equivalents to reach pHf.

Starting from pHo, (VM+·NH+−Vo
Plot the value of H-・No+<-).

For each pH value (0.2 unit steps), a difference occurs between the Ho to OH- consumption of the suspension and the corresponding standard solution. By repeating this operation for all ionic forces, (H”)−
The value of (OH-) is obtained. Calculate the surface charge using the equation shown above. The surface charge curves are then plotted as a function of pH for all ionic forces considered. The ZCP is defined by the intersection of the curves.

The silica concentration is adjusted as a function of its specific surface area. For example, a 2% suspension is mixed with three ionic forces (0, 1, 0, 0
1 and 0.001 mol/ε). The assay is carried out using 0.1 M calcium hydroxide on 100 ml of suspension.

In practice it is preferred that the zcp value is at least 4, especially in the range 4-6. For better compatibility with metal cations it is at most 6.5. For good compatibility with fluorine, the ZCP is preferably at most 7.

Additionally, to improve compatibility, especially with fluorine,
The content of cations with a valence of 2 or more in the silica is at most 1
1000 pp is advantageous. It is preferred that the aluminum content of the silica according to the invention is at most 500 ppm. The ionic content of the silica according to the invention is advantageously at most 200 ppm. In a preferred embodiment, the calcium content is at most 500 ppm,
More preferably at most 300 ppm. Also, the silica according to the invention preferably contains at most 50 p p
m more particularly has a carbon content of at most 10 ppm.

The silica according to the invention is compatible with organic amino compounds, but also with various metal cations used in dentifrice compositions. The composition thus comprises, among other things:
Contains a metal cation with a valency greater than 1 provided by the active molecule.

For example, reference is made to metal cations with a valence of 2 or more selected from Groups 2A, 3A, 4A and 8 of the Periodic Table. More particularly, the Group 2A cations calcium, strontium and barium, the Group 3A cations aluminum and indium, the Group 4A cations germanium, tin and lead;
cations of the group namely manganese, iron, nickel, zinc,
Mention is made of titanium, zirconium, palladium, etc.

The cations may be in the form of inorganic salts such as chlorides, fluorides, nitrates, phosphates or sulfates, or in the form of organic salts such as acetates, citrates and the like. Specific examples thereof are zinc citrate, zinc sulfate, strontium chloride, in the single salt form (SnF) or in the double salt form (SnF z KF).
) of tin fluoride, tin-chlorofluoride 5nC12F and zinc fluoride (Zn, Fg).

The silica according to the invention can be a variety of metal cations.

said Shitsuru, a customer. The compatibility of silica with cations, as defined according to the tests described below, is at least about 50%, preferably at least 70%, more preferably at least 80%.

As a result, the silica according to the present invention can be used in toothpaste compositions containing cations with a valence of 2 or more, mixed with at least one of the following components: zinc citrate, zinc sulfate, strontium chloride, and tin fluoride. It can be used advantageously for things.

According to a particular embodiment of the invention, the silica of the invention is also compatible with guanidine, particularly chlorhexidine. Compatibility, as determined by the test described below, is at least about 3
It is 0%. It can be improved by at least 60%, preferably at least 90%.

In this case, silica is S04''-, C1-1NO1-1P
The anion content of the 04- or C0-1 type is at least 5·10-" mol/100 g silica. The lower the content, the higher this compatibility; according to a preferred alternative, it is at most 1-10-” moles more specifically O
12.1 O-3 mol/100 g silica.

For silica prepared from sulfuric acid, the anion content is S0
4", in which case the content is at most 0.1%. According to a preferred alternative of the invention, it is more specific at most 0.05%. and at most 0.01%.

The silica according to the invention is particularly well suited for use in dentifrice compositions containing guanidine and bisguanides. U.S. Patent No. 3.934. OO2 and OO4,
110.083 may be mentioned.

The pH of the silica according to the invention, measured according to twin NFT 45-007, is generally at most 8 and more particularly 6.
It is 0 to 7.5.

The above properties make it possible to have silica compatible with the organic amine compounds listed above, metal cations and optionally fluorides and guanidine, especially chlorhexidine.

Apart from the surface chemical properties and compatibility conditions mentioned above, the silica according to the invention also has physical properties that make it suitable for use in toothpastes. This structural characteristic will be described below.

Generally, the BET surface area according to the invention is between 40 and 600 m
2/g, more specifically 40 to 350 m2/g. Its CTAB surface area is usually 40-400 m”/g
More specifically, it varies in the range of 40 to 200 m2/g.

BET surface area is Journal of the Am
erican Chemical Society,
vol, 60, p309. February 1938 and Standard N
BRUNAUER described in FXO-622+3.31
- Measured according to the EMMET LER method.

The CTAB surface area is the external area measured according to the standard ASTM D 3765, while the adsorption of hexadecyltrimethylammonium bromide (CTAB) is carried out at pH 9 and 35A2 is taken as the projected area of the CTAB molecule.

The silica according to the invention clearly corresponds to the three types commonly identified in the field of tooth brushing. Thus, the silica according to the invention can first of all be of the abrasive type.

Thus, it has a BET surface area ranging from 40 to 300 m2/g. In this case, the CTAB surface area is 40~loo
m”/g.

The silica according to the invention can also be of the thickening type. Thus, it has a BET surface area in the range 120-450 m''/g, more specifically 120-200 m2/g, and its CTAB surface area in the range 120-400 m''/g.
The g range is more specifically 120-200 m''/g.

According to another type, the silica according to the invention can be bifunctional and have a B of 80 to 200 m''/g.
It has an ET surface area and a CTAB surface area of 80 to 200
m2/g.

The silica according to the invention also has an oil absorption in the range of 80 to 500 cff13/100 g when measured according to standard NET30-022 (March 53) using dibutyl phthalate. More specifically, the oil absorption ranges from 100 to 140 cm''/100 g for abrasive types of silica, from 200 to 400 for thickening types, and from 100 to 300 for bifunctional types.

Furthermore, for use in tooth brushing, silica is preferably 1
It has a particle size of ~10 μm. This average particle size (d so)
is measured with a Coulter counter.

Apparent density generally varies between 0.01 and 0.3. According to a particular embodiment of the invention, the silica is precipitated silica. Finally, the silica according to the invention has approximately 1.440
It has a refractive index of ~1.465.

Here, the method for producing silica according to the present invention will be described in detail.

As previously mentioned, the method is of the type that involves reacting a silicate with an acid resulting in the formation of a suspension or silica gel.

Of note, any known operating procedure can be used to reach the suspension or gel (addition of acid to silicate precipitate, simultaneous total or partial addition of acid and silicate to water precipitation or silicate solution). (additions, etc.) can be used, and the choice essentially depends on the physical properties of the silica desired to be obtained.

One preferred embodiment of the invention comprises water, a colloidal silica dispersion with a silica content of 0 to 150 g/l expressed as S L Ox, the silicate being an inorganic or organic salt, preferably an alkali metal salt (eg sodium sulphate or acetic acid). It consists of preparing a suspension or silica gel by simultaneously adding a silicate and an acid to a precipitating agent, which can be sodium. The two reagents are added simultaneously so that the pH is kept constant in the range 4-10, preferably 8.5-95. The temperature is advantageously between 60 and 95°C.

The procedure for preparing colloidal silica preferably having a concentration in the range from 20 to 150 g/l is to heat an aqueous silicate solution, e.g. adding acid to the aqueous solution until a pH of . The concentration of the aqueous silicate solution, expressed as 5in2, preferably ranges from 20 to +50 g/j2. Dilute acids to concentrated acids can be used, the normality of which varies from 05 to 36N, preferably from 1 to 2N.

Above, the term silicate advantageously refers to alkali metal silicates, preferably SiO2/N az 0 weight ratio 2
-4 and more preferably 3.5 was taken to mean sodium silicate. The acid may be a gas, such as carbonic acid, or a liquid, preferably sulfuric acid.

In another step of the invention, the suspension or gel is subjected to an aging operation.

The initial aging is carried out at a pH of at most 8.5, e.g.
8.5 Preferably carried out at 8. Aging preferably occurs at a temperature of 10 minutes to 2 hours at a temperature of, for example, 60 to 100°C, more preferably 95°C.

Another variant of the invention is to add an acid to the silicate-containing precipitating agent.
By gradually adding W! until the desired aging pH is obtained. P, consisting of preparing pickles or silica gel. This operation is preferably carried out at a temperature in the range of 60-95°C. Aging of the suspension or silica gel takes place under the conditions described above.

A second aging is then carried out at a pH below 6, preferably between 5 and 6, more particularly at a pH of 55. Temperature and time conditions are the same as for the first aging. For this,
Adjust the pH to the desired aging pH by adding acid.
Make it. For example, inorganic acids such as nitric acid, hydrochloric acid, sulfuric acid or phosphoric acid or carbonic acid formed by carbon dioxide gas bubbling are used.

The third aging is carried out at a pH below 5, preferably between 3 and 5, more preferably at a pH of about 4.

Temperature and time conditions are the same as the two other aging operations. The desired aging pH is obtained by addition of acid. The silica is then separated from the reaction medium using any known means, such as a vacuum filter or a filter press. Thus, the silica cake is collected.

The method according to the invention can then be carried out according to two main variants.

A first variant involves the production of silicas that are compatible with organic amino compounds and metal cations with a valence of 2 or higher. In this case, in this method, the pH of the suspension or medium before drying is determined by the following formula: % formula % ([[) (where e is a constant value of 0.6 or more and 10 or less, and d is 7. It is a constant value of 0 or more and 8.5 or less, and (D) includes washing the cake under conditions that comply with MicroSiemens C "Aqueous silica represented by 1!!! Indicating the conductivity of pickles". Ru.

For this reason, cleaning with water is generally performed using deionized water and (
or) washing with an acid solution of pH 2-7 can be observed.

The acid solution can be, for example, a solution of an inorganic acid such as nitric acid.

However, according to certain embodiments of the invention, the acid solution can be a solution of an organic acid, especially an organic complexing acid.

The acid can be selected from carboxylic acids, dicarboxylic acids, hydroxycarboxylic acids and aminocarboxylic acids. An example of such an acid is acetic acid, and examples of complexing acids are tartaric acid, maleic acid, glyceric acid, gluconic acid and citric acid.

Particularly when using solutions of inorganic acids, it may be advantageous to carry out a final wash with deionized water.

A second process variant concerns the production of vine silicas which are also compatible with guanidine, especially chlorhexidine.

In similar cases, more obvious cleaning is performed.

It is possible to obtain a clean washing liquid and its conductivity is high (
But 200 microSiemens cm-'preferably 1
This must be continued until it is below 00 microSiemens.01'. As mentioned above, it is important that the anion concentration is at most 5.101 mol/100 g of silica.

Depending on the case, the washing operation can be carried out more than once, generally twice with an aqueous solution of water, preferably deionized water and/or an organic acid, especially the acids mentioned above. .

From a practical point of view, the washing operation may occur by passing a washing solution over the cake or introducing the cake into the resulting suspension, followed by ? The collapse of the block of doors is carried out. Thus,
Prior to drying, the mass is subjected to a disintegration operation using any known means, such as a high-speed rotating stirrer.

As a result, the silica cake is disintegrated before or after washing and dried using any known means. Drying can take place, for example, by atomization in a tunnel or matzuru furnace or with a stream of hot air.

The inlet temperature may be in the range of about 200-500°C and the outlet temperature in the range of about 80-100°C. Residence time is lO
It is from seconds to S minutes. If necessary, the dry material can be ground to obtain the desired particle size. The operation is carried out in conventional equipment such as impeller mills or air jet mills.

The invention also relates to dentifrice compositions containing silica of the type described or obtained by the method in question. The amount of silica according to the invention used in dentifrice compositions can vary within a wide range and is usually between 5 and 35%.

The powder according to the invention can be used particularly preferably in dentifrice compositions containing at least one element selected from the group comprising fluorides, phosphates, guanidine and especially chlorhexidine. Therefore, they can have at least 90% compatibility with each of these elements according to the tests described below.

They are also suitable for dentifrice compositions containing at least one element selected from the group consisting of an organic amino component and a component supplying divalent or higher valence metal cations. In this case, they can have up to 80% compatibility for each element according to the tests described below.

The silica according to the invention comprises at least one element selected from the group of single inorganic fluorides and organic fluorides, at least one element selected from the group of alkylbenbenes, and the group of guanidine and especially chlorhexidine. It is particularly suitable for dentifrice compositions which simultaneously contain at least one element selected from:

More particularly, sodium fluoride and/or tin fluoride and/or fluorine-containing amines, more particularly cetylamine hydrofluoride, and bis-(hydroxyethyl)-aminopropyl-N-hydroxyethyl- Mention may be made of compositions containing octadecylamine dihydrofluoride, an alkyl betaine and chlorhexidine.

The silica according to the invention is compatible with maleic acid-vinylethyl ether copolymers and can therefore be incorporated into dentifrice compositions comprising these copolymers.

Regarding the fluorine-containing compound, the amount is preferably from 0.01 to
1% by weight, more particularly in the range 0.1 to 0.5% by weight, relative to the fluorine concentration in the composition. Fluorine-containing compounds are especially monofluorophosphates, more particularly sodium,
Monofluorophosphates and difluorophosphates of potassium, lithium, calcium, aluminum, ammonium,
and various fluorine-containing fluorides in the bound ionic form, especially alkali metal fluorides, such as sodium, lithium, potassium, ammonium fluorides, stannous fluoride, manganese fluoride, zirconium fluoride, aluminum fluoride, (addition products of these fluorides with each other or with other fluorides such as potassium, sodium or manganese fluoride).

Other fluorides can also be used in the present invention, such as zinc fluoride, germanium fluoride, palladium fluoride, titanium fluoride, as well as alkali metal fluorozirconates, such as sodium or potassium fluoride, and stannous fluoride. Zirconates and sodium or potassium fluosulfates or fluoborates can also be used.

The organofluorine compounds mentioned at the beginning of this specification can also be used, preferably fluorinated thylamine and bis-(hydroxyethyl)-aminoallopyl-N-hydroxyethyl-octadecylamine dihydrofluoride. .

Regarding components supplying divalent or higher valence metal cations, among those mentioned in the specification, zinc citrate, zinc sulfate, strontium chloride, and tin fluoride are particularly frequently used.

For elements that can be used as anti-plaque agents of the poly*a salt, polyphosphonate, guanidine and subiguanide type, see US Pat.
083, the teachings of which are hereby cited for reference.

The dentifrice composition can also contain a binder.

The main binders used are selected in particular from the following: Cellulose derivatives: methylcellulose, hydroxyethylcellulose and sodium carboxymethylcellulose: Viscous substances: carraginate, alginate, agar-agar and gelose: Gums v4: gum arabic and gum tragacanth, gum xanthan and gum karaya. : Carphoki divinyl and acrylic polymer: polyoxyethylene Ia4 resin.

In addition to the silica according to the invention, the dentifrice compositions also contain coarsely precipitated calcium carbonate, magnesium carbonate, di- and tricalcium phosphates, insoluble sodium metaphosphate, beer
One or more abrasives selected from fIJa calcium, titanium dioxide (whitening agent), silicates, alumina, aluminosilicate, curved lead oxide and tin, talc and kaolin can also be included.

(Dentifrice compositions can also contain surfactants, humectants, fragrances, sweeteners, colorants, and preservatives.

The most widely used surfactants are sodium lauryl phosphate, sodium lauryl sulfoacetate and sodium lauryl ether sulfate, sodium dioctyl sulfosuccinate, sodium lauryl sarcosinate, sodium lysyl phosphate and sulfated monoglycerides.

The most widely used humectants are selected from polyalcohols such as glycerin, turditol (particularly as a 10% solution in water) and propylene glycol.

The main aromatic agents (fragrances) are selected from anise oil, perilla oil, mustard oil, company pine oil, cinnamon oil, clove oil and rose oil.

The principal sweeteners are especially selected from orthosulfobenzoimides and cyclamates.

The primary colorant is selected depending on the desired color.

Namely: Red and pink: alamance, acylbin, catechu, newcoccin (PONeEAU 4R>, D-thinyl and erythrosin; green: chlorophyll and chlorophyllin: yellow Nisan yellow (orange S) and quinoline yellow.

The most widely used preservatives are parahydroxybenzoate, formol and the substances that generate it, hexitidine, quaternary ammonium, hexachlorophene, 70mofene and hexamazine.

Finally, dentifrice compositions also contain therapeutic agents, the most important of which are preservatives, antibiotics, enzymes, oligoelements and the aforementioned fluorine-containing compounds.

Hereinafter, the present invention will be briefly described by way of examples, although the present invention is not limited thereto.

However, before that, a method of measurement for DH as a function of 1llfi rate and concentration will be described, as well as tests to determine the compatibility of silica with different elements.

To measure DH as a function of silica concentration and conductivity, silica suspensions of increasing concentrations varying from 0 to 25% by weight were pre-dried over 2 hours IJk to 12[)''C mass. The suspension was prepared by dispersing 1100 m of silica in 1100 m of deionized and degassed water (Millipore quality).The suspension was stirred at 25°C for 24 hours.

A portion of the suspension was added at aooor', o, va, 40
pH of suspensions and solutions obtained after centrifugation for minutes and filtration through a 0.22 iJs Millipore filter
was measured at 25° C. under a nitrogen atmosphere using a Meto0-Muro12 titroprocessor measuring device.

Similarly, the conductivity measurements of the suspensions and solutions obtained at 25 °C were carried out using a radiometer conductivity meter (C0M83) equipped with a COC304 cell with a cell constant equal to 1 ca+-1. there was. Electrical conductivity is expressed as μSiemens/'Cm.

The pH difference between the pH of the 20% silica suspension and the pH of the supernatant solution separated by centrifugation causes
).

(1) Add 33% fluorine-containing amine of 5(+) to 95 g of propanediol in double-distilled water to 1.65%
An aqueous solution (1) containing a fluorine-containing amine was prepared.

(2>4(+) silica was dispersed in 16(l) of the solution obtained in (1) above. The suspension thus obtained was stirred at 37° C. for 4 weeks.

(3) The suspension was then heated at 8000 r, p, m for 3
Centrifuge for 0 minutes, and use the supernatant obtained in (3) for 0.0 minutes.
It was filtered through a 22-leg Millipore filter.

(4) i The concentration of fluorine-containing amine was determined by nitrogen trace analysis in the solution obtained in (1) above and the supernatant liquid obtained in (3) above.

(5) Compatibility was determined by the following relationship: % fluorine-containing amine compatibility is hereinafter referred to as AF.

Determination of compatibility with cetylamine hydrofluoride (1)
1.72 (+913.2
An aqueous solution (1) containing 172 g% of fluorine-containing amine was prepared by dissolving in 8CI of double-distilled water.

(2) 4(l) of silica was dispersed in the solution obtained in 16() above (). The suspension thus obtained was stirred at 37° C. for 4 weeks.

(3) The suspension was then heated at 8000 r, p, m for 30
Centrifuge for 1 minute, and add 0.2 min of supernatant obtained in (3).
It was filtered with a 2-Yanagi Millipore filter.

(4) The free fluorine-containing amine concentration was determined by nitrogen trace analysis of the solution obtained in (1) above and the supernatant obtained in (3) above.

(5) Compatibility was determined by the following relationship: % fluorine-containing amine compatibility is hereinafter referred to as AF.

Determination of compatibility with alkylbetaines - The alkylbetaines used are the products marketed by the company AKSO as Almotelik LB®.

(i> 6.67 g of 30% alkyl betaine at 93
．． 33 g of double-distilled water (dissolved) to create an aqueous solution (1) containing 2% alkyl betaine.

(2>4 g of silica was dispersed in the solution obtained in (1) above in 169. The suspension thus obtained was
The mixture was stirred at 7°C for 4 weeks.

(3) The suspension was then heated at 8000 r, p, +n, for 3
Centrifuge for 0 minutes, and use the supernatant obtained in (3) for 0.0 minutes.
It was filtered through a 22-mm Millipore filter.

(4) The concentration of free alkyl betaine was determined by microanalysis of organic carbon in the solution obtained in (1) above and the supernatant obtained in (3) above.

(5) Compatibility was determined by the following relational expression: ■ Below, % alkylbetaine compatibility is referred to as a3eta.

Compatibility with alkylamidoalkylbetaine 0 ■ Feet (1) 6.67 (+ 30% alkylamidoalkylbetaine is dissolved in 93.33Q double distilled water,
An aqueous solution (1) containing 2.0% alkylamidoalkyl betaine was prepared.

(2> The wrinkle strength of Ag is 16Q obtained in (1) above.
It was dispersed in a solution of The suspension thus obtained was stirred at 37° C. for 4 weeks.

(3) The suspension was then heated at 800 Or, p, m for 30
Centrifuge for 1 minute, and add 0.2 min of supernatant obtained in (3).
It was filtered with a 2-Yanagi Millipore filter.

(4) The concentration of free alkylamide furkyl betaine is
The organic carbon content of the solution obtained in (1) above and the supernatant liquid obtained in (3) above was determined by trace analysis of organic carbon.

(5) Compatibility was determined by the following relationship: Hereinafter, % alkylamidoalkylbetaine compatibility will be referred to as beta.

Determination of compatibility with chlorhexidine - 4Q silica was prepared with 1% concentration of chlorhexidine digluconate.
It was dispersed in 6 g of chlorhexidine aqueous solution. This suspension was stirred at 37°C for 24 hours. Then the suspension was
The mixture was centrifuged for 30 minutes at 00 Or, p, ra, and the resulting supernatant was filtered through a 0.2 mm Millipore filter. The 0.5 d solution thus filtered was sampled and diluted with 100 d of water in a graduated flask. This solution constitutes the test solution.

A comparison solution was made using the same procedure but without silica. 1% chlorhexidine digluconate aqueous solution
The mixture was stirred at 7° C. for 24 hours, centrifuged at 2000 Or, p, m, and the supernatant was filtered through a 0.2 m Millipore filter. 0.5 d of the solution thus obtained was diluted with 100 ml of water in a graduated flask.

The absorbance of these two solutions was then measured using a spectrophotometer (Uvikon 810/820) at 254rv+.

The amount of free chlorhexidine, referred to as % compatibility, was determined by the following relationship: 4 g of silica was dispersed in 16 (0.3% sodium fluoride solution, NaF). This suspension was heated at 37°C for 24 hours.
Stir for hours. After centrifuging the suspension at 2000 Or, p, m for 30 min, the supernatant was filtered through a 0.2μ Millipore filter. The solution thus obtained constitutes the test solution. A comparison solution was made using the same procedure but without silica.

Fluoride compatibility was determined by percent free fluoride as measured by a selective fluoride electrode (Orion). This is determined by the following relation: 4g(D)force 100d 0.06%ZnSO4
・Dispersed in 20 solutions for 7 days. A suspension is obtained, whose D
H to 7 to 15 by addition of NaOH or H2SO4
Allowed to stabilize for minutes. This suspension was then incubated at 37°C for 2
Stir for 4 hours and at 2000 Or, p, m, 3
Centrifuged for 0 minutes. The supernatant liquid is filtered through a 0.2-mm Millipore filter and constitutes the test solution.

A comparison solution was made using the same procedure but without silica. The free zinc concentration of the two solutions is determined by the atomic absorbance (21
4 nm).

Compatibility is determined by the following relationship: or dispersed in a potassium suspension. The suspension was stirred at 37°C for 24 hours and then heated to 2000 Or, p, m.

The mixture was centrifuged for 30 minutes. The supernatant was filtered through a 0.2 gm Millipore filter. A solution of 0.2 () was diluted with 100 () of water in a graduated flask, which constituted the test solution. A comparative solution was made using the same procedure but without silica.

Free pyrophosphate ion (P207-
) was determined by ion chromatography (DIONEX 2000i system) equipped with an integrating needle. Compatibility was determined by the ratio of the peak areas obtained in the chromatograms and corresponding to the pyrophosphate retention times for both test and comparison.

4 g of silica was added to 16 jJ of 1.5% sodium pyrophosphate with a temperature and DH controll device and a propeller stirring device (Hix
8,321 sodium silicate and 1 μs/'Cl with a silica concentration of 1309/i2 and a S i 02 /N820 molar ratio of 3.5.
8,331 soft water with a conductivity of 11 was introduced. After starting the stirring operation (350 r, p, Sono, ), the formed precipitate was heated to 90 °C. After reaching the desired temperature, add sulfuric acid with a concentration of 80a/j to 0.4012/Il.
A pH of 9.5 was achieved by adding at a constant flow rate of +n.

Then at the same time a silica concentration of 130Q/l and a Si 02 /N820 molar ratio of 3.5 and 0.7541/m
45.251 of sodium silicate and 29.641 of 80 g #sulfuric acid with a flow rate of in. The rate of sulfuric acid was adjusted to maintain the pH of the reaction medium at a constant value of 9.5.

After 60 minutes of addition, the sodium silicate addition was stopped and the sulfuric acid addition was continued at a rate of 0.494 Il/ii until the pH of the reaction mixture stabilized at 8. During this period, the temperature of the medium rose to 95°C. This was followed by aging at 95° C. for 30 minutes.

During ripening, the pH was maintained at 8 by addition of acid.

After completion of aging, the pH was brought to 5.5 by addition of sulfuric acid at a flow rate of 0.4941/l1 lin, followed by aging at said pH and 95° C. for 30 minutes. After the end of maturation, the pH was brought to 3.5 by addition of @acid and maintained at this level for 30 minutes.

After stopping the heating, the mixture was filtered and the resulting cake was washed with deionized water until a filtrate with a conductivity of 2000 tt S/cm was obtained. The cake obtained after washing was dispersed in the presence of deionized water for 1
A suspension was formed with a silica concentration of 0%. The pH of this suspension was adjusted to 6 by addition of acetic acid.

This was followed by a second filtration, followed by a water wash and a
The conductivity was adjusted to 0 μS/c+a and the pH was adjusted to 5.5 by washing with water whose pH was adjusted to 5 with acetic acid. Tests were then carried out to ensure that the following relationship was satisfied: pH 8,20 - 0,9110 (D) The cake was then crushed and the silica was spray dried. The obtained silica was ground in a mill and measured with a Courta-Calator to obtain a powder having an average particle size of 8 legs.

The physicochemical properties of the silica thus obtained are shown in the table below: SET surface area m2/g CTAB surface area m2/Q DOP oil absorption d/100 g Silica pore volume Hg Cm3/'0 pI-1 (5% water) Refractive index translucency % 1.90 6.2 1.450 O Na+l:1m SOa=ppm AI3+ppm Fe3+ppm Ca2+ppm Cj-ppm ppm Table 1 shows the surface chemical properties of the silica according to the present invention and its resistance to organic amine compounds. Compatibility results are also shown. Table 1 shows compatibility results for conventional ingredients of dentifrice compositions: chlorhexidine, fluoride, zinc and pyrophosphate.

■-2 Temperature and pH control device and propeller stirring device (Hixe
A sodium silicate solution of 5301 with a silica concentration of 135 (1/ff and a molar ratio of S i 02 /'Na20 of 3.5) and 1 μS/
One tank of soft water with a conductivity of 'cm was introduced. After starting the stirring device (35 Or, p, m, ), the formed precipitate was heated to 90°C. After reaching this temperature,
80 (1/l IIi[@ acid with 0.38 (
! /min 17) Constant flow rate addition to pH 9.5
I made it.

Then, simultaneously with a silica concentration of 135 (It/l) and 3,
S+02/Na2O molar ratio of 5 and 0.754N/wi
44.701 of sodium silicate and 25.301 of 130 g/'l sulfuric acid were added with a flow rate of n.

[The rate of i was adjusted to maintain the pH of the reaction medium at a constant value of 9.5.

After 60 minutes of addition, the sodium silicate addition was stopped and the sulfuric acid addition was continued at a rate of 0.3501/IQin until the reaction mixture 17) pH stabilized at 84:1. During this period, the temperature of the medium rose to 95°C. This was followed by aging at this pH and 95° C. for 30 minutes. During ripening, the pH was maintained at 8 by addition of acid. After aging, the pH was adjusted to 0.400j/si.
5 by addition of sulfuric acid at a flow rate of n, and then aged at this pH and 95° C. for 30 minutes. After completion of aging, pI-1 was adjusted to 3.5 by adding sulfuric acid, and this pH
was maintained at 3.5 for 30 minutes.

After stopping the heating, the mixture was filtered and the resulting cake was washed with deionized water until a filtrate with a conductivity of 2000 μS/cm was obtained. The cake was then crushed in the presence of water to form a 20% silica suspension and the pH
was adjusted to 5.1 to obtain the following relationship:.

pH≦8.20-0.91 log ([)) The silica was dried by spraying and ground in a blade mill to obtain a powder with an average particle size of 8#.

The physicochemical properties of the silica thus obtained are shown in the table below: SET surface area m2/'q CTAB surface area m2/g DOP oil absorption Wd! /100CI Sisi pore volume Hg cma/'g pH (5% water) Refractive index translucency % Power 200 3°35 6.5 1.455 SOa"% Na 10% AI!3+ppm F e3"p pm Ca2"ppm C1-Dpm ppm 0, 5 0.25 Table 1 shows the surface chemical properties of the silica according to the invention, as well as the compatibility results with organic amino compounds. Compatibility results are shown for the conventional components of chlorhexidine, fluoride, zinc and pyrophosphate.

Example 3 Temperature and pH control device and propeller stirring device (Hix
5,601 sodium silicate having a concentration of 135 (1/e 1.17) and a SiO2/N8 molar ratio of 3.5 was introduced into a reactor equipped with a SiO2/N820 molar ratio of 3.5. After starting the stirrer (350 r, p, t), the resulting precipitate was heated to 85 °C. After reaching this temperature, 8
Sulfuric acid having a concentration of 5 tJy'l and preheated to 70°C was added at a constant flow rate of O,SOε/'1n to produce 9.7
The pH was set to .

This was followed by a simultaneous silica concentration of 135all and 3.
S i 02 /Na2O molar ratio of 5 and 0.74511
52.671 of sodium silicate and 30ε of 85(]/j sulfuric acid were added with a flow rate of 1/11 in. The rate of sulfuric acid was adjusted to maintain the pH of the reaction medium at a constant value of 9.7. Additions were carried out at 89°C with reagents preheated to 70°C.

After 45 minutes of addition, the sodium silicate addition was stopped and the sulfuric acid addition was continued until the pH of the reaction mixture stabilized at 8!0.4504! The process continued at a speed of 1/1 liter. During this period, the temperature of the medium rose to 95°C. Following this, it was aged in 1) H at 95° C. for 10 minutes. During ripening, the DH is reduced to 8 by addition of acid.
maintained. After aging, l) H was 0,750 (1/m
5 by addition of sulfuric acid at a flow rate of in, followed by aging at pI-1 and 95° C. for 15 minutes. At the end of aging, the pH was brought to 3.1 by addition of sulfuric acid and this pH level was maintained for 60 minutes.

After stopping the heating, the mixture was filtered and the resulting cake was diluted with deionized water until the filtrate was reduced to 2000 μS/'Cl1l.
was washed until a conductivity of . The cake was then crushed in the presence of water to form a 20% silica suspension;
and the pH was adjusted to 5.5 so that the following relationship holds: pl-1<7.5-0.701Q(] (D) The silica was spray dried and ground in a blade mill. Average particle size is 8
A powder of # was obtained.

Physicochemical properties of the silica thus obtained SET surface area m2/g CTAB surface area m2/'cJ DOP oil absorption d/100C] Silica pore volume HQ Cm3/g pH (5% water) Refractive index Translucency % 2.65 7.0 1.460 SO4=% Na+% Aj2"ppm Fe"'ppm ca2"ppm Ce DOm ppm The following table describes the surface chemical properties of silica according to the invention as described in Examples 1-3. In general, it also shows the compatibility results of silica and organic amono compounds according to the invention.

Table 1 shows the compatibility results for conventional ingredients used in dentifrice compositions, namely phosphorhexidine, fluoride, zinc and pyrofIA salts.

For comparison purposes, Tables 1 and 2 also show the properties and different compatibility of commercially available silicas, with the table below showing representative ranges: S81 Nijilobran 81 (Brace) 2113: Zeodent 113 (Zuber) Sid12 Niji Punto 12
(Degutsa) Syl 15: Sirotux 15 (Brace) T73: Thixocyl 73 (Lon Boulin)
The symbols used in the table above have the following meanings: [)H/
I OCI (C) is the formula 1) H=ba, l0cI
(C) where a and b are two constants and C is the weight percent of silica in the suspension: pH/
I OCI (D) is 2pl-1=b'-a'Og(
D>, where b' and a' are two constants,
and D is the conductivity of the silica suspension in μSiemens/'cm; SE indicates the suspension effect measured by the relationship 5E = DH suspension - pH supernatant; H○ is the Hammett constant Meri: ZCP indicates the pH at which the surface charge of silica becomes ○: AF
, AFc, [3eta, a13eta, and CI-IX represent the percent compatibility of the fluorine-containing amine, alkylbetaine, and chlorhexidine, respectively, the amounts of which are defined herein.

Fluorine-containing amine AFc and alkyl betaine aBeta
The % compatibility obtained for is similar to that obtained for AF and [3eta, respectively.

Compatibility of silica with active molecules Compatibility % ln+'+F eta 71]3 S+d12 y115 Example 1 Example 2 A3 The results in this table show that the silica according to the invention is compatible, especially with organic amino compounds. The following relationship shows that the silica with a high pH value is significantly different from the standard silica: pH≦8.5-0.40 to (1(D) and pH≧7
．． 0-0.6010(](D)p)-1<7.5-0
．． 70 foct (C) and pH≧5.0-0.5
010g(C) Procedural amendment January 31, 1991

Claims (1)

[Claims] 1. pH is a function of silica concentration according to the following two inequalities: pH≦7.5-0.7log(C) (Ia) and pH≧5.0-0.5log(C)( I b) [In the inequalities (I a) and (I b), (C) is SiO
indicates the weight concentration of the aqueous silica suspension expressed in _2%] and the pH varies as a function of the conductivity of the silica by the following two inequalities: pH≦8.5-0
．． 4log(D)(IIa) and pH≧7.0-0.6log(D)(IIb) [inequality (
In IIa) and (IIb), (D) denotes the electrical conductivity of the aqueous silica suspension in microSiemens cm^-^1, resulting in an aqueous suspension varying in the region defined by Silica characterized by. 2. Silica according to claim 1, characterized in that it has a surface chemistry such that the acidity function Ho is at least 4. 3. The silica according to claim 1 or 2, characterized in that it has a surface chemistry such that the number of OH^- per nm^2 is not more than 12, preferably from 6 to 10. . 4. Silica according to any one of claims 1 to 3, characterized in that the zero charge point (ZCP) is at least 4, preferably between 4 and 6. 5. Silica characterized by a compatibility with organic amino compounds of at least 30%. 6. Compatibility with organic amino compounds is at least 50%;
Silica according to claim 5, more particularly characterized in that it is at least 80%. 7. The silica according to claim 5 or 6, which is compatible with an organic amino compound selected from the group consisting of fluorine-containing amines, amine oxides, alkyl amines, and alkyl betaines. 8. The organic amino compound is cetylamine hydrofluoride, bis-(hydroxyethyl)aminopropyl-N-hydroxyethyl-octadecylamine dihydrofluoride, amine oxide of formula R(CH_3)_2N→0, formula R-N^+ Alkylbetaine of (CH_3)_2-CH_2-COO^- or formula R-CO-NH_2-(CH_
2)_2-N^+(CH_3)_2-CH_2-COO
8. The silica according to claim 7, which is a ^-alkylamidoalkylbetaine (R represents a straight-chain or branched-chain alkyl group having 10 to 24 carbon atoms). 9. A patent characterized in that the compatibility with a metal cation with a valence of 2 or more selected from Groups 2A, 3A, 4A and 8 of the Periodic Table is at least 50%, more particularly at least 70%. Silica according to claim 1. 10. Claim 9, characterized in that the metal cation is calcium, strontium, barium, aluminum, indium, germanium, tin, lead, manganese, iron, nickel, zinc, titanium, zirconium, or palladium. of silica. 11. Claim 9, characterized in that the metal cation is in the form of an inorganic salt, ie, a chloride, fluoride, nitrate, phosphate or sulfate, or in the form of an organic acid salt, ie, an acetate or a citrate. The silica according to item 1 or item 10. 12. Silica according to claim 11, characterized in that the metal cation is in the form of zinc citrate, zinc sulfate, strontium chloride or tin fluoride. 13. Claim 1 characterized in that the compatibility of the guanidine type product with chlorhexidine is at least 30%, more particularly at least 60%.
Silica as described in Section. 14, SO_4^2^-, Cl^-, NO_3^-, P
Claims 1 to 13, characterized in that the anion content of O_3^- or CO_3^2^- type is at most 5.10^-^3 mol/100 g silica.
Silica according to any one of paragraphs. 15. Silica according to claim 14, characterized in that the anion content is at most 1.10^-^3 mol, more particularly 0.2.10^-^3 mol/100 g silica. . 16. Any of the claims characterized in that the sulphate content, expressed as SO_4^m, is at most 0.1%, preferably at most 0.05%, more particularly at most 0.01%. The silica described in paragraph 1. 17. The content of metal cations with a valence of 2 or more is at most 10
Silica according to any one of claims 1 to 16, characterized in that it has a content of 0.00 ppm. 18. Aluminum content at most 55 ppm, iron content at most 200 ppm, calcium content at most 5
18. Silica according to claim 17, characterized in that it contains 00 ppm and more particularly at most 300 ppm. 19. Silica according to any one of claims 1 to 18, characterized in that the carbon content is at most 50 ppm, more particularly at most 10 ppm. 20, pH is at most 8, more specifically 6.0-7.5
Claims 1 to 19 are characterized in that:
Silica according to any one of paragraphs. 21. The silica according to any one of claims 1 to 20, which has a BET surface area of 40 to 600 m^2/g. 22. The silica according to any one of claims 1 to 21, which has a CTAB surface area of 40 to 400 m^2/g. 23. Claims 1 to 1 of the polishing type, characterized in that the BET surface area is 40 to 300 m^2/g.
The silica according to any one of Item 22. 24. The silica according to claim 23, which has a CTAB surface area of 40 to 100 m^2/g. 25. Any one of claims 1 to 22 of the thickening type, characterized in that the BET surface area is 120 to 450 m^2/g, more specifically 120 to 200 m^2/g. Silica listed. 26. The silica according to claim 25, which has a CTAB surface area of 120 to 400 m^2/g. 27. Bifunctional type silica according to any one of claims 1 to 22, characterized in that the BET surface area is 80 to 200 m^2/g. 28. The silica according to claim 27, which has a CTAB surface area of 80 to 200 m^2/g. 29. The silica according to any one of claims 1 to 28, which has an oil absorption of 80 to 500 cm^3/100 g. 30. The silica according to any one of claims 1 to 29, characterized in that the average particle size is 1 to 10 μm. 31. The silica according to any one of claims 1 to 30, which has an apparent density of 0.01 to 0.3. 32. The silica according to any one of claims 1 to 31, which is a precipitated silica. 33. When producing the silica according to any one of claims 1 to 32, a silicate and an acid are reacted to form a suspension or silica gel, and 6 or more 8.
a first aging at a pH of 5 or below, a second aging at a pH of 6.0 or below, and a third aging at a pH of 5.0 or below to separate the silica;
The pH of the silica measured for a 20% SiO_2 suspension is expressed by the following formula: pH=d-elog(D)(III) (where e is a constant value of 0.6 or more and 1.0 or less, d is 7.0
8.5 or less, and (D) indicates the conductivity of the aqueous suspension expressed in microSiemens cm^-^1). A method characterized in that it comprises drying the suspension obtained. 34, water, silica content expressed as SiO_2 0~
150 g/l of colloidal silica dispersion, preparing a suspension or silica gel by simultaneous addition of silicate and acid to a precipitating agent which can be a silicate or an inorganic or organic salt, preferably an alkali metal salt. 34. A method according to claim 33, characterized in that: 35. Process according to claim 34, characterized in that the addition of the two reagents takes place simultaneously so that the pH is kept constant in the range from 4 to 10, preferably from 8.5 to 9.5. 36. The method according to claim 34 or 35, characterized in that the temperature is 60 to 95°C. 37. A colloidal silica dispersion with a silica content of 20-150 g/l is prepared by heating an aqueous silicate solution at 60-95°C;
The aqueous solution is charged with an acid in the range of 8 to 10, preferably 9.5 p.
35. Process according to claim 34, characterized in that it is prepared by adding H until obtained. 38. The method of claim 38, characterized in that it consists in preparing a suspension or silica gel by gradually adding acid to a precipitating agent containing a silicate at 60-95°C until the desired aging pH is obtained. The method according to scope item 33. 39. Claims 33 to 36, characterized in that the initial aging of the suspension or silica gel takes place at a pH of 6 to 8.5, preferably 8, and a temperature of 60 to 100°C, preferably 95°C. The method described in any one of paragraphs. 40, characterized in that the second aging of the suspension or silica gel takes place at a pH of 5-6, preferably 5.5, and a temperature of 60-100°C, preferably 95°C. The method according to any one of paragraph 39. 41. Claims 33 to 40, characterized in that the third aging of the suspension or silica gel takes place at a pH of 3 to 5, preferably 4, and a temperature of 60 to 100°C, preferably 95°C. The method described in any one of . 42. Process according to claim 33, characterized in that the washing takes place with water or an acid solution. 43. The method according to claim 33, characterized in that the washing is carried out until the conductivity of the washing liquid filtrate is at most 200 microSiemens cm^-^1. 44. Process according to claim 43, characterized in that the washing takes place with water or an acid solution. 45. Process according to claim 42 or 44, characterized in that the acid solution is a solution of an organic acid, in particular a complexing acid. 46. The method according to claim 45, characterized in that the organic acid is selected from the group consisting of carboxylic acids, dicarboxylic acids, aminocarboxylic acids and hydroxycarboxylic acids. 47. Claim 45 or 46, characterized in that the organic acid is selected from the group comprising acetic acid, gluconic acid, tartaric acid, citric acid, maleic acid and glyceric acid.
The method described in section. 48, characterized in that it contains the silica according to any one of claims 1 to 32 or the silica prepared by the method according to any one of claims 33 to 47. A toothpaste composition. 49. The dentifrice composition according to claim 48, which comprises at least one element selected from the group consisting of fluorine, fluorine, phosphate, and guanidine. 50. The tooth brushing composition according to claim 48, characterized in that it contains at least one element selected from the group comprising: 50, an organic amino compound, and a cation having a valence of 2 or more. 51. The tooth brushing composition according to claim 48, which comprises at least one organic amino compound selected from the group consisting of 51, fluorine-containing amines, amine oxides, alkyl amines, and alkyl betaines. 52, the organic amino compound is cetylamine hydrofluoride, bis-(hydroxyethyl)aminopropyl-N-
Hydroxyethyl-octadecylamine dihydrofluoride, amine oxide of formula R(CH_3)_2N→0,
Formula R-N^+(CH_3)_2-CH_2-COO^-
alkyl betaine or an alkyl betaine of formula R-CO-NH_2-(CH
_2)_3-N^+(CH_3)_2-CH_2-CO
52. The toothpaste composition according to claim 51, which is O^-alkylamidoalkylbetaine (R represents a straight or branched alkyl group having 10 to 24 carbon atoms). thing. 53. The tooth brushing composition according to claim 48, comprising at least one metal cation having a valence of 2 or more selected from Groups 2A, 3A, 4A and 8 of the Periodic Table. 54. Claim 53, characterized in that the metal cation is calcium, strontium, barium, aluminum, indium, germanium, tin, lead, manganese, iron, nickel, zinc, titanium, zirconium, or palladium. toothpaste composition. 55. Claim 53, characterized in that the metal cation is in the form of an inorganic salt, i.e., a chloride, fluoride, nitrate, phosphate or sulfate, or in the form of an organic acid salt, i.e., an acetate or a citrate. The tooth brushing composition according to item 54. 56. The tooth brushing composition according to claims 53 to 55, characterized in that the metal cation is in the form of zinc citrate, zinc sulfate, strontium chloride or tin fluoride. 57. The tooth brushing composition according to claim 48, which comprises chlorhexidine.