KR20040098585A - Surface-modified precipitated silicas - Google Patents

Abstract

PURPOSE: Provided are a surface-modified precipitated silica which does not affect the transparency of a coating agent when added and is useful as a matting agent for a transparent coating material, and its preparation method. CONSTITUTION: The surface-modified precipitated silica is a precipitated silica whose surface is modified with a polymer, wherein the transmittance of a transparent coating material with a refractive index (nD20) of 1.4492 containing 5 wt% of the surface-modified precipitated silica is increased by 20 % or more compared with an identical transparent coating material containing 5 wt% of a precipitated silica treated with a polyethylene wax. Preferably the polymer is a polyorganosiloxane or a modified polyorganosiloxane. Preferably the polymer is represented by the formula 1 or 2. In the formula 1, Y is OH, OR, H5C2-O-(C2H4O)m-, H7C3-O-(C3H6O)m- or R2C=C-(CH2-CH(COOR3))k- (wherein R2 and R3 are independently an alkyl group; and m and k are independently 0-100); R is an alkyl group; and a, b, c and d are independently 0-100. In the formula 2, R1 is a methyl group, (CH3)2CHC(=O)OCH2C(CH3)2CH(CH(CH3)2)-O- and/or (CH3)2CHC(=O)OCH(CH(CH3)2)C(CH3)2CH2O-; the total sum of a is 0-100; the total sum of b is 0-15; b is 1 or more if a is 0; and a is 5 or more if b is 0.

Description

Surface-modified precipitated silicas

FIELD OF THE INVENTION The present invention relates to surface modified precipitated silica, and methods of making the surface, wherein the surface is modified by polymer treatment to be particularly suitable for use as a matte agent.

Surface modification of precipitated silica has long been known and is used to make functional enhancers for silicone rubber (as matt), ink-jet coatings or coating materials.

Thus, EP 0 922 671 describes a process for the preparation of hydrophobic precipitated silica, comprising adding a polyethylene wax emulsion to conventional dried precipitated silica and then milling it in a split mill or in an opposite jet fluid bed mill.

DE 25 13 608 describes a method for hydrophobizing finely divided silica by treating anhydrous silica with an organosilane in a fluid state at 200 to 300 ° C.

To simplify the hydrophobization process, EP 0 341 383 proposes to introduce a silicone oil emulsion into a suspension of precipitated silica.

A similar process is described in DE 24 35 860 where the precipitated silica suspension is reacted with an optionally preconcentrated organohalosilane. After the solid is separated by filtration, it is heated at a temperature of 300 to 400 ° C. and then milled.

Precipitated silica is often used to matte coated surfaces. This matte coating should exhibit minimal gloss at various viewing angles. Hydrophilic precipitated silicas tend to be precipitated seriously in the coating and are difficult, but not impossible, to restirr, so wax coated precipitated silicas are usually used as matt. Wax coating of the silica surface substantially improves the precipitation behavior. In the case where all of the matte precipitates, this precipitation is negligible so that restirring can occur without excessive energy consumption.

When a transparent coating material is used, it is preferable that the transparency of the coating material is not affected by the incorporation of the matte agent.

It is therefore an object of the present invention to provide surface modified silica which improves the properties of the coating when used as a matte in a transparent coating. The present invention also provides a method of making surface modified silica.

Surprisingly, it has been found that the silica of the present invention improves the transparency of the coating and the precipitation properties are at least as good as the silica coated with polyethylene wax (PE wax). Therefore, they are advantageous over wax coated matting agents, which often cause turbidity of the transparent coating.

Precipitated silica has been found to be modified by coating with a specific polymer so that the coating material having a refractive index in the range of 1.4000 to 1.5000 can be modified by coating with the specific polymer so that the coating material incorporating the precipitated silica of the present invention exhibits excellent transparency. Compared to coatings comprising conventional PE wax coated silica matte and having a refractive index in the range of 1.4000 to 1.5000, the corresponding coating comprising silica of the invention as a matte exhibits greatly improved transparency even in the liquid phase, and also the precipitation characteristics Excellent While the transparent coating material matted with conventional matting agents is usually cloudy in the liquid phase, the transparent coating material matted with the precipitated silica of the present invention is clear and transparent even in the liquid phase.

1 compares the turbidity of an acid cured (AC) varnish comprising an ACEMATT OK 412 to an AC varnish comprising a matting agent according to Example 2. FIG.

FIG. 2 compares the turbidity of an acid cured (AC) varnish with acemat OK 412 to an AC varnish with a matting agent according to Example 3. FIG.

Accordingly, the present invention relates to a precipitated silica whose surface is modified with a polymer, wherein when the modified precipitated silica contains 5% by weight of a transparent coated material having a refractive index [n _D 20] of 1.4492, the transmittance of the transparent coated material is treated with polyethylene wax. Provided is a surface modified polymer-precipitated silica, characterized in that it is at least 20% higher than the same transparent coating containing 5% by weight of molten precipitated silica.

The present invention further provides

(A) precipitating an alkali metal silicate solution with an acidifying agent under mildly to alkaline conditions,

additionally adding an acidifying agent so that the pH is 7-2, to provide a silica suspension (b),

(C) separating the precipitated solid by filtration,

Preparing a precipitated silica by drying the solid such that the residual moisture content of the product is less than 10% by slow drying (e.g., rotary tubular dryer or plate dryer) or rapid drying (e.g. spray dryer, spin flash dryer) (d ) And

(E) modifying the precipitated silica into a polymer, wherein in selecting the amount and properties of the polymer, 5 wt% of the modified precipitated silica is contained in the transparent coating material having a refractive index [n _D 20] of 1.4492. The transmittance of is selected to be 20% or more higher than the same transparent coating material containing 5% by weight of reference precipitated silica treated with polyethylene wax, to provide a method for producing surface-modified precipitated silica.

The surface-modified silica of the present invention is coated with a polymer, and as a result, when 5 wt% of the modified precipitated silica is contained in a transparent coating having a refractive index [n _D 20] of 1.4492, the transmittance of the transparent coating is treated with polyethylene wax. A precipitated silica that is at least 20% higher than the same transparent coating containing 5% by weight of reference precipitated silica.

This light transmittance is preferably improved by at least 25%, in particular at least 30%. Reference silica treated with polyethylene wax is preferably a product commercially available from Degussa and has an acemat specification with specifications according to the product information sheet of December 2002, which is hereby incorporated by reference in its entirety. OK 412. As reference precipitated silica, precipitated silica having the same properties of untreated silica and coated with polyethylene wax may be used.

According to the December 2002 product information sheet, the ACEMATT ^R OK 412 has physicochemical data as shown in Table 1:

Features and test methods unit Ace Mat ^R OK 412 Loss on drying for 2 hours at 105 ° C in accordance with DIN EN ISO 787-2 % 6 Loss on ignition for 2 hours at 1000 ° C in accordance with DIN EN ISO 3262-1 ¹⁾ % 13 PH of 5% in water according to DIN EN ISO 787-0 -- 6 Sulfate content as SO ₄ , according to the degussa method of the IR spectrometer % One Particle Size Average Dimension (TEM) d ₅₀ Value (Laser Diffraction) Μm 36.0 Surface treatment abandonment Unsealed tapping density according to DIN EN ISO 787-11 g / l 130 Density according to DIN EN ISO 787-10 g / cm ³ 1.9 Oil according to DIN EN ISO 787-5 g / 100g 220 SiO ₂ content according to DIN EN ISO 3262-19 ²⁾ % 98 1) Based on dried material 2) Based on flammable material.

The silica of the present invention is further characterized by the following physical and chemical data:

Particle distribution d ₅₀ : 1 to 50 μm, preferably 1 to 40 μm, 1 to 30 μm, 2 to 20 μm, and 3 to 15 μm.

Oil absorption DBP: 100-600 g / 100 g, preferably 150-500 g / 100 g, 200-450 g / 100 g, 250-400 g / 100 g.

C content: 1 to 20%, preferably 1 to 10%, 2 to 8%.

Shear Number V ₂ : less than 25 ml / 5 g.

As surface modified polymers, polyorganosiloxanes or modified polyorganosiloxanes can be used. Modified polyorganosiloxanes are in particular polyether modified and acrylate and / or polyacrylate modified polyorganosiloxanes. Polyalkoxysiloxanes may also be used.

One preferred embodiment of the present invention uses the polyorganosiloxane of formula (I).

In Formula 1 above,

Y is -OH, -OR, H ₅ C ₂ -O- (C ₂ H ₄ O) _m- , H ₇ C ₃ -O- (C ₃ H ₆ O) _m -or (Wherein R ₂ and R ₃ are each independently alkyl, m and k are each independently 0 to 100),

R is alkyl, in particular methyl or ethyl,

a, b, c and d are each independently 0-100.

Another preferred embodiment of the present invention uses the polyorganosiloxane of formula (2).

In Formula 2 above,

R ₁ is a methyl radical, And / or Wherein the ratio of methyl radical to alkoxy radical in radical R ₁ is less than 50: 1,

The sum of the units a is from 0 to 100,

The sum of units b is from 0 to 15,

If a is 0, b is 1 or more,

When b is 0, a is 5 or more.

More details, especially with regard to the preparation of these polysiloxanes, can be found in DE 36 27 782 A1. The contents of this patent are incorporated herein by reference in their entirety.

The alkyl radical is a straight or branched chain alkyl radical having 1 to 100 carbon atoms, preferably 1 to 25 carbon atoms, more preferably 1 to 10 carbon atoms, and a cycloalkyl radical having 1 to 10 carbon atoms. Alkyl radicals may contain one or more double or triple bonds, each atom may be replaced by a heteroatom such as O, N or S.

In steps (a) and (b) of the process of the invention, the aqueous alkali metal silicate solution used is sodium silicate with a density of about 1.343 kg / l and has a weight fraction of SiO ₂ 27.3% and Na ₂ O 7.9%. . The acidifier used is any inorganic acid, in particular concentrated sulfuric acid (96% H ₂ SO ₄ ) or CO ₂ .

In step (a), the components as described, for example, in DE 31 44 299 are mixed with each other with stirring. The content of DE 31 44 299 is hereby incorporated by reference in its entirety. Optionally, the acidifying agent may be added simultaneously with the water glass to the initial charge of water or sodium silicate. Precipitation should be performed while maintaining a slightly acidic to alkaline pH. The pH is especially 6-12. Any precipitation can be carried out at a constant pH or at a constant alkali value.

In step (b), an acidifying agent is added, especially if an acidifying agent has already been used for precipitation, to maintain a pH in the acidic or neutral range (pH 7-2).

In step (c), optionally, after a waiting time of 0 to 90 minutes, preferably 15 to 60 minutes, the silica present in the suspension is separated by filtration and washed until neutral with deionized water.

In step (d), the solids are dried such that the residual moisture content of the product is less than 10% by rapid drying (eg spray dryer, spin flash dryer) or slow drying (eg rotary tubular dryer or plate dryer).

Surface modification (step (e)) can be carried out at different time points.

In embodiment 1) of the process of the invention, in step (e), 0.5-30% by weight of the surface modified polymer is introduced into the silica suspension adjusted to pH 7-2 in step (b). Such addition is preferably carried out for 1 to 30 minutes, in particular for 5 to 15 minutes, at the reaction temperature at the time of precipitation in step (a), ie especially at 50 to 90 ° C., preferably at 50 to 65 ° C. It is desirable to be. Subsequently, the surface modified silica as described in steps (c) and (d) is separated and dried by filtration.

In embodiment 2) of the process of the invention, the silica precipitated according to steps (a) and (b) is separated by filtration as described in step (c), optionally washed with deionized water and then with water or sulfuric acid or It is resuspended with a mixture of water and sulfuric acid, and then in step (e) 0.5 to 30% by weight of the surface modified polymer is introduced into the resuspension and the resulting suspension is sprayed with a spray dryer so that surface modification is carried out during the drying process. In addition, the silica suspension and the siloxane may be designed to be introduced simultaneously through the nozzle. Spray drying may be performed at 200-500 ° C. such that the residual moisture content of the product is less than 10%. The solids content of the silica suspension to be sprayed can be up to 25% by weight.

In embodiment 3) of the process of the invention, silica is prepared and dried as described in steps (a) to (d). Subsequently, in step (e), the dried precipitated silica is combined with 0.5-30% by weight of the surface modified polymer and mixed homogeneously. The polymer is added over 0 to 120 minutes, preferably 0 to 60 minutes, more preferably 0 to 30 minutes. The mixture is further mixed at 20-150 ° C. for 0-2 hours. Mixing is preferably carried out at 20 to 100 ° C, more preferably at 20 to 80 ° C. The mixing process is preferably carried out for 0 to 1 hour, more preferably 0 to 30 minutes.

In the process of the invention, the polymer is added so that the ratio of polymer to silica is 0.5g: 100g to 30g: 100g, in particular 2g: 100g to 20g: 100g, especially 3g: 100g to 13g: 100g while the polymer and silica are reacting. It is preferable.

As the surface modified polymer, the method of the present invention may use polyorganosiloxane or modified polyorganosiloxane. Modified polyorganosiloxanes are in particular polyether modified and acrylate and / or polyacrylate modified polyorganosiloxanes. Polyalkoxysiloxanes may also be used.

One preferred embodiment of the present invention uses the polyorganosiloxane of formula (I).

Formula 1

In Formula 1 above,

Y is -OH, -OR, H ₅ C ₂ -O- (C ₂ H ₄ O) _m- , H ₇ C ₃ -O- (C ₃ H ₆ O) _m -or (Wherein R ₂ and R ₃ are each independently alkyl, m and k are each independently 0 to 100),

R is alkyl, in particular methyl or ethyl,

a, b, c and d are each independently 0-100.

Another preferred embodiment of the present invention uses the polyorganosiloxane of formula (2).

Formula 2

In Formula 2 above,

R ₁ is a methyl radical, And / or Wherein the ratio of methyl radical to alkoxy radical in radical R ₁ is less than 50: 1,

The sum of the units a is from 0 to 100,

The sum of units b is from 0 to 15,

If a is 0, b is 1 or more,

When b is 0, a is 5 or more.

More details, especially with regard to the preparation of these polysiloxanes, can be found in DE 36 27 782 A1. The content of DE 36 27 782 A1 is hereby incorporated by reference in its entirety.

Optionally, for embodiments 1) and 2), for example, an emulsifying aid such as LA-S 687 (TEGO GmbH) can be added. This is particularly suitable for organosilicon compounds that are not water soluble.

In order to achieve the desired particle distribution, the surface modified silica needs to be dried and then milled and simultaneously sorted in step (f). Such milling can be carried out on conventional cross-flow mills commercially available (such as those sold by Alpine or Netzsch-Condux).

To avoid being too large or small, particles having a diameter of more than 50 μm, preferably more than 30 μm, in particular more than 20 μm, after the surface modified precipitated silica is dried or after they are milled or milled in step (f) It is advantageous to separate and remove them. Depending on the fineness of the matte agent, this can be done, for example, by means of corresponding sieve or classifier means which can be incorporated into the mill.

Physicochemical data of the precipitated silica of the present invention is determined by the following method:

Transmittance Measurement of Coating Material

Transmittance measurements are performed using an ultraviolet / visible spectrometer Specord 200 (Analytik Jena GmbH) in 1 cm quartz cells at room temperature with respect to air as reference. Slot width and stair length are 2 nm.

For this purpose, an acid-curing (AC) varnish having a refractive index n _D 20 = 1.4492 and having the following composition is introduced as an initial charge and 2.5 g of each matte (surface modified silica) is incorporated. :

Xylene 30.2 wt%;

15.1 wt.% Ethoxypropanol;

Ethanol 15.1 wt%; And

39.5% of 60% concentration of Plastopal BT (urea-formaldehyde containing urethane groups and etherified with short chain alcohols, sold by BASF AG, Ludwigshafen, Germany).

The matte was dispersed in 50 g of AC varnish using a paddle stirrer at 2000 rpm for 10 minutes at room temperature. Dispersion is carried out in a 180 ml PE mixed beaker at room temperature. The paddle diameter of the stirrer is 43 mm. Subsequently, the newly prepared dispersion is placed in a 1 cm quartz cell and the ultraviolet / visible spectrum is recorded at a transmittance of 190 to 1100 nm.

Measurement of Modified Shear Value of Silica

By titrating the silica with a potassium hydroxide solution of pH 6-9, the modified shear value (hereinafter, referred to as V ₂ ) as a measure of the number of free hydroxyl groups can be measured.

The measuring method is based on the following Scheme 1.

In Scheme 1 above,

"Si" -OH is a simplified description of silanol groups.

step

10.00 g of silica in powder, bead or granular form with a water content of 5 ± 1% is milled for 60 seconds on an IKA Universal Mill M20 (550 W; 20,000 rpm). It may be necessary to control the moisture content by drying at 105 ° C. or homogenizing wetting in a drying cabinet. 2.50 g of the silica thus treated was metered into a 250 ml titration vessel at room temperature, and methanol p.a. 60.0 ml is added. Once the sample is fully wetted, 40.0 ml of deionized water is added and the mixture is dispersed using Ultra Turrax T 25 (stirrer shaft KV-18G, 18 mm diameter) for 30 seconds at a rotational speed of 18,000 rpm. Sample particles stuck to the vessel and stirrer edges are rinsed into the suspension with 100 ml of deionized water and the suspension is conditioned to 25 ° C. in a temperature controlled water bath.

pH meter (Knick, model: 766pH meter kalimatic with temperature sensor) and pH electrode (composite electrode manufactured by Schott, type N7680) were calibrated at room temperature using buffers (pH 7.00 and 9.00). Charges. First measure the initial pH of the suspension at 25 ° C. using a pH meter, and then adjust the pH to 6.0 using potassium hydroxide solution (0.1 mol / l) or hydrochloric acid solution (0.1 mol / l), depending on the measurement results. . The amount (ml) that KOH or HCl solution is consumed until the pH reaches 6.00 is called V ₁ '.

Next, 20.0 ml of sodium chloride solution (250.00 g of NaCl pa is added to 1 L of deionized water) is metered in. Subsequently titrate to 0.100 with KOH 0.1 mol / l. The amount (ml) of KOH solution consumed until the pH reaches 9.00 is called V ₂ '.

Subsequently, the volume V ₁ 'and V _2' is first normalized to the theoretical sample weight of 1g by five times the expansion provides the V ₁ and V ₂ of jeondanga ml units per 5g. In each case, measure twice.

DBP absorbance

DBP absorbance (DBP), a measure of the absorbance of precipitated silica, is measured according to standard DIN 53601.

step

12.50 g of powder or bead form silica having a moisture content of 0 to 10% (their moisture content is properly adjusted by drying at 105 ° C. in a drying cabinet) is added to the kneader chamber of the Brabender Absorber "E" (product number 279 061). For granules, a sieve fraction of 3.15 to 1 mm (stainless steel sieve from Retsch) is used (using a plastic spatula to gently press the granules through the sieve having a pore size of 3.15 mm). use). While continuously mixing (end speed of the blade of the kneader: 125 rpm), dibutyl phthalate is added dropwise to the mixture at a rate of 4 ml / min at room temperature by a Brabender T 90/50 drop meter. This incorporation by mixing requires only a small amount of force and is monitored by digital display. As detection of the mixture ends, the mixture gradually pastes, as indicated by the rapid increase in the required force. On display reading of 600 digits (torque of 0.6 Nm), electrical contact stops both the kneader and the DBP supply. A motor running at the same speed for the DBP supply can be coupled with a digital counter to read the DBP consumption (ml).

evaluation

DBP absorbance is calculated using the following equation 1 from the measured DBP consumption. The DBP density at 20 ° C. is usually 1.047 g / ml.

DBP Absorbance (g / 100g) = DBP Consumption (ml) * DBP Density (g / ml) * 100 / 12.5g

DBP absorbance is defined for anhydrous dried silica. If wet precipitated silica is used, the figures should be corrected by the following calibration table.

A correction value corresponding to the moisture content is added to the experimental DBP value. For example, a water content of 5.8% implies the addition of 33 g / 100 g of DBP absorbance.

Determination of Moisture Content in Silica

The volatile fraction of silica (abbreviated below as "water content"), acting along the line of ISO 787-2 according to the method, is measured after drying at 105 ° C. for 2 hours. Loss on drying usually consists mainly of moisture.

step

10 g of silica in powder, bead or granule form is metered into an anhydrous glass metering boat equipped with milled glass leads (8 cm in diameter and 3 cm in height) with an accuracy of 0.1 mg (sample weight E). The lid is opened and the sample is dried at 105 ± 2 ° C. for 2 hours in a drying cabinet. The metering boat is then sealed and cooled to room temperature in a drying cabinet using silica gel as desiccant. Final weight A is measured by hydrometer.

Moisture content (%) is measured as [E (g) -A (g)] * 100% / E (g).

The measurement is performed twice.

Measurement of flammable loss

2 hours at 1000 ° C. after drying, DIN 55 921 / 3.4, ISO 3262.

measurement of d50

Aggregate Size Distribution by Laser Diffractometer (Coulter)

Device:

Laser Diffraction System LS 230 [Manufacturer: Coulter]

Bandelin Ultrasonic Rod, Type HD 2200, with DH 13 G Horn

Cooling Tank 80ml

Eppendorf Pipette 5ml

Centrifugal Glass, Height 7cm, Φ3cm

Petri dish, height 4 cm, Φ 7 cm

Dewar Container, Height 21cm, Φ4cm

Digital Thermometer, Accuracy ± 0.1 K

reagent:

Ethanol, p.a. from Merck

Triton x-100 manufactured by Merck

Sodium Hexamethaphosphate from Baker

Sample manufacture:

Place the granules in a mortar and grind the coarse granules, but do not bond them with mortar.

1 g of unaged silica (prepared within 10 days) is weighed and metered into a 30 ml glass vessel with roll edges, and 20 ml of dispersion (20 g of sodium hexametaphosphate added to 1000 ml of deionized water) is added. Subsequently, the sample is placed in a cooling bath to prevent the suspension from overheating and sonicated for 1 minute (20 W power, 80% pulse).

Three dispersion samples are prepared continuously for each silica.

The suspension is placed in a Petri dish equipped with a magnetic stirrer to prevent precipitation until the sample is introduced into the liquid module.

process:

Before starting the measurement, the device and the liquid module are warmed up for at least 30 minutes and the module is automatically cleaned for 10 minutes (menu bar "adjust / clean").

In the control bar of the Coulter software, the file window "Optimum model calculation" is selected via the menu item "Measure" and the refractive index is defined (actual liquid refractive index = 1.332; actual material refractive index = 1.46, hypothetical = 0.1).

In the file window "measurement cycle", the pump speed level is set to 26% and the ultrasonic power is 3%. The ultrasonic items to be activated are "while samples are added", "before each measurement", and "during measurement".

In addition, the file window of the following items is selected:

Offset measurement (once daily)

control

Background measurement

Setting measurement concentration

Inflow Sample Information

2 measurement starts

Self-cleaning

PID data use

Once the calibration is complete, add the sample. Dispersed silica is added until the absorbance reaches 45% and the device is reported to be operating normally. This measurement is carried out by the Fraunhofer model using standard software of the laser diffractometer LS 230 (Coulter).

Three double measurements of 60 seconds are performed for each sample added.

From the raw data plots, the software calculates the particle size distribution based on the volume distribution.

Determination of Carbon Content

Device:

C-Matt 500 [Strohlein Instruments]

Analytical Balance

Porcelain boat with lead

tongs

Measuring spoon

reagent:

Euro analysis control sample 077-2 (Stripline Instruments)

Oxygen

step

Measurement of Control Sample

First, a control sample is measured.

For this purpose, 0.14 to 0.18 g of sample is metered onto a fully baked and cooled porcelain boat with an analytical balance. When the initiating key is actuated, the balance is coupled with the C-mat so it carries weight. The boat should be pressurized into the middle of the combustion tube within 30 seconds. When combustion is complete, the measured values are converted into pulses and evaluated by computer. Make at least two measurements. In some cases, you may need to set a new device parameter. The factor is calculated according to the following equation:

Measurement of Silica Samples

After the factor is measured, the silica sample is measured. For this purpose, 0.04 to 0.05 g of each silica is metered into the porcelain boat and the boat is covered with porcelain lead. Subsequently, the silica sample is measured in the same manner as in the control sample. If the horseshoe is higher than 0.005%, the third measurement and, if necessary, further measurements are taken and averaged.

evaluation

Carbon content is calculated according to the following equation (3):

In Equation 3 above,

P is a pulse,

F is a factor,

E is the initial weight in grams.

Record of results

The results are expressed in% of carbon up to two decimal places.

Remark

The C-Mat 500 can be processed according to the operating instructions from Stripline Instruments.

The examples described below are provided to illustrate the present invention and are not intended to limit the scope of protection herein as shown in the claims.

Examples 1 to 3

Silica is prepared by the method of DE 1767332:

80 liters of water was charged into a 120 liters settler vessel equipped with a stirrer and the alkalinity was determined using 5.5 liters of water glass (density = 1.346 g / l, SiO ₂ content = 27.3%, Na ₂ O content = 7.9%). Adjust to 20. This initial charge is heated to 85 ° C. At this temperature the entire precipitation process is carried out. In parallel, water metering with a metering feed rate of 207 ml / min and sulfuric acid (50%) with a metering feed rate of 45 ml / min are metered in, but there is no change in alkali value. After 30 minutes, the shear imparting device is connected and the precipitation suspension is sheared to an intensity such that a particle distribution d ₅₀ = 7 μm is obtained at the end of precipitation during the subsequent precipitation. After 45 minutes, the metered supply of water glass and sulfuric acid is stopped for 30 minutes. The water glass and the acid are then reused and metered at the same rate as described above. After an additional 45 minutes, the metered supply of water glass is stopped and sulfuric acid is metered in until the pH reaches 3.5. Subsequently, precipitation occurs at the end.

Subsequently, the desired amount of polyorganosiloxane emulsion (TEGO Foamex 1435, manufactured by TEGO GmbH) listed in the table below is added all at once to the silica suspension and stirring is continued for 30 minutes at elevated temperature. The silica thus coated is then separated by filtration, washed, dried and milled and then classified by the method of DE 17 67 332.

Table 3 compares the three surface modified silicas prepared by the above method using untreated silica acemat HK 400 (a commercially available commercially available from Degussa). Examples 1-3 are silicas treated with different amounts of polyorganosiloxane.

unit Comparative Example 1 Example 1 Example 2 Example 3 Silica Ace Mat HK 400 Ace Mat HK 400 Ace Mat HK 400 Ace Mat HK 400 Manufacturer and Supplier Degusa Age Degusa Age Degusa Age Degusa Age Amount of silica ℓ - 60 60 60 Suspension solids g / ℓ - 80 80 80 Siloxane - Aqueous emulsion containing 20% ethoxypolysiloxane Aqueous emulsion containing 20% ethoxypolysiloxane Aqueous emulsion containing 20% ethoxypolysiloxane Amount of siloxane emulsion added kg 1.25 2.50 5.00 Stirring temperature ℃ - 60 60 60 Stirring time minute - 30 30 30 d ₅₀ Μm 7.55 6.63 7.45 8.55 DBP g / 100g 273 288 278 254 C content % 0 2.1 6.3 11.1 Shear ml / 5g Not measured 21.1 14 10.6 Drying loss % 4.5 4.1 3.5 2.8 Print loss % 4.9 5.5 10.2 17.7

Example 4

The matte agent of the present invention is compared to the matte agent of the prior art by measuring the light transmittance on the coating material. For this purpose, three coating mixtures are prepared and 2.5 g of each matte are incorporated into 50 g of an acid hardening (AC) varnish [refractive index n _D 20 = 1.4492] having the following composition:

Xylene 30.2 wt%;

15.1 wt.% Ethoxypropanol;

Ethanol 15.1 wt%; And

60% concentration of Plastopal BT (a urea-formaldehyde resin containing urethane groups and etherified with short-chain alcohols sold by BASF AG, Ludwigshafen, Germany).

Sample manufacture:

For the measurement, 2.5 g of matte are dispersed in 50 g of AC varnish for 10 minutes at room temperature using a 2000 rpm paddle stirrer. Dispersion is carried out in a 180 ml PE mixed beaker at room temperature. The paddle diameter of the stirrer is 43 mm.

Measure:

The ultraviolet / visible spectrum of the newly prepared dispersion is recorded with a transmittance of 190 to 1100 nm. This measurement is carried out using an ultraviolet / visible spectrometer Specord 200 (Analytik Jena GmbH) in 1 cm quartz cells at room temperature with respect to air as reference. Slot width and stair length are 2 nm.

According to the instructions, the light transmittance value of the coating material comprising the matte or PE wax coated matte ace mat OK 412 according to Examples 2 or 3 is measured. Acemat OK 412 is a publicly available product that is commercially available from Degussa and has specifications according to the December 2002 product information sheet. In addition, the light transmittance values of ordinary varnishes without a matte agent are measured.

The obtained light transmittance values are shown in Table 4 below.

Sample assignment Transmittance% at 600 nm Transmittance% at 700 nm Carbon content (%) Matte AC Varnish 92.9 93.0 Not measured Comparative Example 2, Ace Mat OK 412 35.1 39.5 5.2 Example 2 76.8 77.5 6.3 Example 3 85.8 86.5 11.1

As is evident from Table 4 above, the light transmittance values of the coating material comprising the matting agent of the present invention obtained from Examples 2 or 3 are very close to those of the conventional varnish unmatted. Thus, this cladding material is very clear and transparent.

Coatings comprising the commonly used matte acemat OK 412 show poor transmittance of at least 35%, which clearly shows that the coating is severely turbid.

1 and 2 compare the acid set (AC) varnish comprising the matting agent according to Examples 2 or 3 in each case with the corresponding AC varnish comprising ACEMET OK 412. It is apparent that the coating comprising the matting agent of the present invention is substantially more transparent.

Claims (30)

Precipitated silica whose surface is polymer-modified, and 5 wt% of the modified precipitated silica is contained in the transparent coating material having a refractive index [n _D 20] of 1.4492, and the reference precipitated silica whose transmittance of the transparent coating material is treated with polyethylene wax is 5 weight%. Precipitated silica modified with a surface, characterized in that it is at least 20% higher than the same transparent coating containing%. 2. The precipitated silica of claim 1, wherein the physicochemical data is d ₅₀ of _1-50 μm, DBP of 100-600 g / 100 g, and carbon content of 1-20%. 3. Precipitated silica according to claim 1 or 2, characterized in that the shear is V ₂ less than 25 ml / 5 g. 4. The precipitated silica according to claim 2, wherein the particle distribution d ₅₀ is 1 to 40 μm. The precipitated silica according to any one of claims 2 to 4, wherein the oil absorption DBP is 200 to 500 g / 100 g. Precipitated silica according to any one of claims 2 to 5, characterized in that the carbon content is 1 to 10%. 7. The reference precipitated silica according to any one of claims 1 to 6, wherein the transparent coating material has a light transmittance of polyethylene wax treated by containing 5% by weight of modified precipitated silica in the transparent coating material having a refractive index [n _D 20] of 1.4492. Precipitated silica modified with a surface, characterized in that at least 25% higher than the same transparent coating material containing 5% by weight. 7. The reference precipitated silica according to any one of claims 1 to 6, wherein the transparent coating material has a light transmittance of polyethylene wax treated by containing 5% by weight of modified precipitated silica in the transparent coating material having a refractive index [n _D 20] of 1.4492. Precipitated silica modified with a surface, characterized in that at least 30% higher than the same transparent coating containing 5% by weight. The surface-modified precipitated silica according to claim 1, wherein the transmittance is improved compared to the ACEMATT ^R OK 412 used as reference precipitated silica. The surface-modified precipitated silica according to claim 1, wherein the transmittance is improved compared to the reference precipitated silica comprising the same untreated precipitated silica but coated with polyethylene wax. The surface-modified precipitated silica according to claim 1, wherein the polymer is polyorganosiloxane or modified polyorganosiloxane. The precipitated silica of claim 11, wherein the polymer is a polyorganosiloxane of formula (I). Formula 1 In Formula 1 above, Y is -OH, -OR, H ₅ C ₂ -O- (C ₂ H ₄ O) _m- , H ₇ C ₃ -O- (C ₃ H ₆ O) _m -or (Wherein R ₂ and R ₃ are each independently alkyl, m and k are each independently 0 to 100), R is alkyl, in particular methyl or ethyl, a, b, c and d are each independently 0-100. The precipitated silica of claim 11, wherein the polymer is a polyorganosiloxane of formula (2). Formula 2 In Formula 2 above, R ₁ is a methyl radical, And / or Wherein the ratio of methyl radical to alkoxy radical in radical R ₁ is less than 50: 1, The sum of the units a is from 0 to 100, The sum of units b is from 0 to 15, If a is 0, b is 1 or more, When b is 0, a is 5 or more. (A) precipitating an alkali metal silicate solution with an acidifying agent under mildly to alkaline conditions, additionally adding an acidifying agent so that the pH is 7-2, to provide a silica suspension (b), (C) separating the precipitated solid by filtration, Preparing a precipitated silica by drying the solid such that the residual moisture content of the product is less than 10% by slow drying (e.g., rotary tubular dryer or plate dryer) or rapid drying (e.g. spray dryer, spin flash dryer) (d ) And (E) modifying the precipitated silica into a polymer, and in selecting the amount and properties of the polymer, the transparent coating material is contained in the transparent coating material having a refractive index [n _D 20] of 1.4492 by 5% by weight of the modified precipitated silica. A method of producing surface-modified precipitated silica, characterized in that the light transmittance of is selected to be 20% or more higher than the same transparent coating material containing 5% by weight of reference precipitated silica treated with polyethylene wax. The silica suspension according to claim 14, wherein in step (e) 0.5 to 30% by weight of the surface modified polymer as shown in any of claims 11 to 13 is adjusted to pH 7 to 2 in step (b). A method for producing surface modified precipitated silica, characterized in that it is introduced into. 16. The process of claim 14 or 15, wherein the addition in step (e) is carried out with stirring for 1 to 30 minutes. 17. The method of any of claims 14-16, wherein the silica suspension temperature in step (e) is characterized by 20-100 ° C. 15. The process of claim 14, wherein the silica is separated by filtration as described in step (c), optionally washed with deionized water and then resuspended with water or sulfuric acid or with a mixture of water and sulfuric acid and then in step (e). 15. A surface modified precipitated silica, characterized in that 0.5-30% by weight of the surface modified polymer according to any one of claims 11 to 13 is added to the resuspension and the resulting suspension is dried, preferably spray dried. Manufacturing method. 19. The method of claim 18, wherein the drying after step (e) is carried out such that the residual moisture content of the product is less than 10%. 20. The process according to claim 18 or 19, wherein the temperature of the silica suspension in step (e) is between 20 and 100 ° C. The method according to claim 14, characterized in that, following step (d), the surface modifying polymer according to any one of claims 11 to 13 is added to the silica in step (e) and the two components are mixed homogeneously. A method for producing surface-modified precipitated silica. The method of claim 21, wherein the addition in step (e) is carried out with stirring for 0 to 120 minutes. 23. The method of claim 22, wherein the silica and polymer are mixed for at least 0-2 hours. 24. The method of any of claims 21 to 23, wherein the temperature of the mixture in step (e) is between 20 and 150 ° C. 25. The method of claim 14, wherein the polymer is polyorganosiloxane or modified polyorganosiloxane. 25. 27. The method of claim 25, wherein the polymer is a polyorganosiloxane of formula (I). Formula 1 In Formula 1 above, Y is -OH, -OR, H ₅ C ₂ -O- (C ₂ H ₄ O) _m- , H ₇ C ₃ -O- (C ₃ H ₆ O) _m -or (Wherein R ₂ and R ₃ are each independently alkyl, m and k are each independently 0 to 100), R is alkyl, in particular methyl or ethyl, a, b, c and d are each independently 0-100. 26. The method of claim 25, wherein the polymer is a polyorganosiloxane of formula (2). Formula 2 In Formula 2 above, R ₁ is a methyl radical, And / or Wherein the ratio of methyl radical to alkoxy radical in radical R ₁ is less than 50: 1, The sum of the units a is from 0 to 100, The sum of units b is from 0 to 15, If a is 0, b is 1 or more, When b is 0, a is 5 or more. 25. The method of any of claims 14 to 24, wherein the milling process is carried out in step (f) after the surface modified precipitated silica is dried. The diameter of any one of claims 14 to 24 and 28, wherein the surface modified precipitated silica is dried or after the milling process is carried out in step (f) or while the milling process is carried out. A process for producing surface-modified precipitated silica, characterized by separating and removing particles larger than m. Use of the surface modified silica according to any one of claims 1 to 13 in matting agents.