Polysiloxane modified titanium dioxide

[0001] The present invention relates to a particle obtained by the action of polysiloxane on titanium dioxide. Mixtures of these particles with organic polymers are disclosed.

BACKGROUND OF THE INVENTION [0002] Titanium dioxide has found wide application. It is usually used in another matrix to give it specific properties. For example, it is widely used as a white pigment for paints and polymers. Other applications use small titanium dioxide particles that have different optical properties. For these and other applications, having a good dispersion of titanium dioxide is crucial. Dispersants are often added to titanium dioxide. The choice of dispersant is often a compromise between performance, cost, compatibility with other matrix additives, and matrix performance. For this reason, much work has been done to improve the dispersion of titanium dioxide in various matrices.

[0003] Various interactions have been studied. In US Patent No. 6,646,037 the interaction of titanium dioxide with alkyl salts of sulfonic acids was investigated and in US Patent No. 6765041 with alkyl esters of phosphate acid. Organosilicon compounds were used. For example, US Patent No. 4061503 discloses the interaction of titanium dioxide particles with a silicon-substituted polyether compound to improve the dispersibility of titanium dioxide in pigmented and / or paint-filled plastics, and composite reinforced plastic compositions.

[0004] US Patent No. 4810305 discloses organic polysiloxane with better dispersibility. The polysiloxane is a hydrosiloxane such as polymethylhydrosiloxane. US Patent Nos. 5607994, 5631310, 5889090 and 5959004 disclose the use of a mixture of a hydrolysable silane, such as for example butyltrimethoxysilane and a polysiloxane such as polydimethylsiloxane. US Patent No. 5932757 describes a mixture of alkylalkoxysilane oligomers.

[0005] US Patent No. 6,620,234 discloses the mixing of reactive chlorosilane e.g. hexyl trichlorosilane with titanium dioxide in an aqueous medium to produce coated titanium dioxide. The by-product in the form of hydrochloric acid is neutralized and removed as a salt.

[0006] DE 197 24 638 A1 discloses a flame retardant in the form of a polycarbonate composition comprising titanium dioxide and optionally an organic polysiloxane.

[0007] EP 1 690 902 A2 discloses nanoparticles of materials such as titanium dioxide, which are modified with polysiloxane of the general formula (R¹xR²3-xSiR³)_sR⁵where R¹, R², R³, R⁵, X and Y are defined.

[0008] Although there has been a lot of research on coating titanium dioxide with silanes and siloxanes, further improvements are needed. To date, machining techniques are often a compromise between processability and end properties. Many silicon-containing compounds are not sufficiently reactive with titanium dioxide to achieve a coating effect. Other silicon-containing compounds are either volatile or produce volatile by-products. In order to improve reactivity, functional groups such as alkoxy groups have been used, but the alcohol produced as a by-product can create environmental problems during the production of the pigment. The use of halosilanes in the aquatic environment may solve this problem, but it is a more complicated process and increases costs. Despite significant research in this area, there is a need for further improvement.

SUMMARY OF THE INVENTION [0009] The invention is a blend of particles with an organic polymer as defined in claim 1. The particles are obtained by treatment of polysiloxane on titanium dioxide. One or more silicon polysiloxane atoms are substituted with an alkylene group which is terminated with a silyl group containing three substituents selected from the group consisting of hydroxyl, halogen, alkoxy, acetoxy, and mixtures thereof.

DETAILED DESCRIPTION OF THE INVENTION [0010] The invention is a blend of particles with an organic polymer. These particles are obtained by the action of polysiloxane with titanium dioxide. Any form of titanium dioxide is suitable for forming the particle. Preferably, the titanium dioxide is in the form of rutile or anatase. Titanium dioxide can be produced by any known method, such as a sulfate or chloride process.

[0011] Titanium dioxide useful for the invention has a typical particle size in the range of 0.001 to 20 pm. For use in typical pigment applications, titanium dioxide preferably has a particle size in the range of 0.1 to 0.5 μη, more preferably 0.2 to 0.35 μη. For photocatalytic applications, titanium dioxide preferably has a particle size in the range of 0.001 to 0.1 pm.

[0012] Titanium dioxide may be unprocessed titanium dioxide obtained directly by a sulphate or chloride process. Alternatively, titanium dioxide can be treated with at least one coating material before or after the reaction with the polysiloxane. Suitable coating materials include inorganic oxides such as alumina, silicon phosphate dioxide, zirconia, inorganic, acid soluble titanium dioxide and the like. Suitable organic coating materials include polyalcohols such as trimethylolpropane and alkanolamines such as triethanolamine. Preferably, the titanium dioxide is coated with alumina. The amount of alumina is preferably 0.01-0.8% by weight with respect to Al₂ABOUT₃ against TiO₂. Processes for depositing metal oxides on titanium dioxide are well known to those skilled in the art. Preferably, metal oxides are added through wet treatment or vapor deposition. Suitable wet working techniques are described in US Patent Nos. 3767455, 4052223 and 6695906. [0013] Suitable vapor deposition techniques are presented in US Patent Nos. 5562764 and 6852306.

[0014] Titanium dioxide is subjected to polysiloxane. One or more polysiloxane is substituted with an alkylene group that is terminated with a silyl group containing three substituents selected from the group consisting of hydroxyl, halogen, alkoxy, acetoxy, and mixtures thereof.

are from

in the action of silicon atoms [0015] Polysiloxane has the general formula:

<img file="PL2094484T3_D0001.tif" />

wherein R1 and R2 are each independently selected from the group consisting of C1 to C14 hydrocarbyl; each R3 substituent is selected from the group consisting of hydroxyl, halogen, alkoxy and acetoxy, R4 is selected from the group consisting of Ci to C22 hydrocarbyl, x is an integer from 1 to 22, m is an integer from 0 to 500, and n is an integer from 1 to 5 00. Preferably R3 is selected from the group consisting of hydroxy and alkoxy. Preferably R4 is C6 to C10 hydrocarbyl. Preferably, R1 is methyl. Preferably, the sum of m + n is greater than 12, more preferably greater than 20. Preferably, m is greater than n, more preferably greater than 3n.

[0016] Polysiloxane can be produced by any method. One convenient method is to combine the cyclic precursor in an acid or base catalyzed reaction. E.g:

<img file="PL2094484T3_D0002.tif" />

[0017] The silane-containing cyclic monomer can be produced by any method. One convenient method is to form it from hydrosiloxane and silane, as shown below:

<img file="PL2094484T3_D0003.tif" />

[0019] Titanium dioxide is treated with polysiloxane. Polysiloxane can be added in pure form, as a solution, or as an emulsion. Preferably, the polysiloxane is added in pure form or as an aqueous emulsion.

The methods for adding polysiloxane may be similar to the methods for adding other surface-active agents that are flexible and that can easily be incorporated into titanium dioxide production processes. Thus, in the titanium dioxide production process there are many places where polysiloxane can be added and the addition sites described herein should not be understood as exhaustive. The optimal point at which polysiloxane can be added depends in part on the way it is to be introduced.

[0020] In the simplest methods, polysiloxane can be added by spraying or pouring into a system in which titanium dioxide is already present. To increase the homogeneity of the polysiloxane dispersion, it is preferable to use a mixing device for mixing and to mix the polysiloxane and titanium dioxide. Appliances such as V-shell mixers equipped with comminution rods for use with liquids and powder or other suitable mixers known today or those which may be known to those skilled in the art may be used.

[0021] One preferred mixing device is a micronizer. The polysiloxane can be dosed into a micronizer or jet atomizer together with the titanium dioxide powder for grinding. Air or steam micronization techniques can be used in the temperature range from room temperature to 250 ° C or higher.

[0022] In a classic production process, based on another example, polysiloxane can be added to the spray dryer feedstock or re-reconstituted cake, in a high flow milling apparatus or micronizer feedstock, before or simultaneously with micronization. In other titanium dioxide processes, it may be desirable to add polysiloxane to the fluidized washed cake while stirring to ensure homogeneous mixing of the polysiloxane with the titanium dioxide particles. In addition, in some embodiments, it is desirable to add polysiloxane after any filtration and rinsing step, but before each drying step.

[0023] If polysiloxane is added to dry titanium dioxide, such as, for example, a spray dryer product or micronizer raw material, special care must be taken when mixing the polysiloxane with the titanium dioxide powder to ensure homogeneity. This can be done, for example, with a Vshell mixer equipped with a comminution bar or with other suitable mixing devices. After mixing the polysiloxane with titanium dioxide, the titanium dioxide thus formed can be comminuted using fluid energy using steam or air to produce processed, finished titanium dioxide.

[0024] Preferably, the weight ratio of polysiloxane to titanium dioxide is in the range of 0.001: 1 1 to 0.5: 1 1 and more preferably in the range of 0.001: 1 to 0.02: 1.

[0025] For use in pigmentation, preferably the titanium dioxide treated with polysiloxane has an average particle diameter in the range of 0.2 to 0.35 microns. For certain other applications, preferably the particles have an average diameter less than 0.2 microns.

[0026] Titanium dioxide particles treated with polysiloxane are mixed with the organic polymer. Preferably, the treated titanium dioxide is dry mixed with the organic polymer and then melted. This can be achieved, for example, using a Banbury mixer or twin screw extruder. The amount of processed titanium dioxide used will vary depending on the end use. One convenient way is to first prepare the treated titanium dioxide concentrate with the organic polymer, and then mix the concentrate with more organic polymer to achieve the desired weight ratio.

[0027] The organic polymer is polyethylene. Depending on the application, the processed titanium dioxide and organic polymer composition may contain other additives, fillers and pigments. Preferred pigments for use in the composition are zinc sulfide, barium sulfate, calcium carbonate, and combinations thereof [0028] The following examples merely illustrate the invention. Those skilled in the art recognize many variants that fall within the scope of the claims.

EXAMPLE 1

Siloxane modified titanium dioxide 1

<img file="PL2094484T3_D0004.tif" />

Sodium aluminate (30.8 ml 343 g of Al₂ABOUT₃/ l aqueous solution) is added to the aqueous suspension 5,000 g of fine titanium dioxide particles obtained from the rutile chloride process (350 g TiO₂/ l) and stirred at 70 ° C.

The suspension is adjusted to pH 7 using concentrated hydrochloric acid (aqueous solution) and allowed to age for 30 minutes with continuous stirring. The aged suspension is filtered and washed twice with 5000 ml deionized water at 80 ° C, and then dried in an oven at 110 ° C overnight. Dried filter cake (0.2% Al₂ABOUT₃ on TiO₂) is passed through an 8 mesh screen to prepare for treatment with organic compounds.

[0031] Dry part, 8 mesh, TiO₂ coated with aluminum oxide (1000 g), shatters to a thickness of 1 cm on a polyethylene film and Siloxan 1 (12.2 g, molecular weight 5400 g / mol, molar ratio m / n = 19: 1) is added dropwise in a circular motion to obtain 1.2% load level. The pigment is mixed using a large spatula and transferred to a Nalgene bottle with a wide neck with a capacity of one gallon. The bottle containing the pigment is rotated on rollers for 10 minutes in a roller mill. This pigment is subjected to steam micronization to produce the finished pigment. [0032] The ready pigment (125 g) is dry mixed with low density polyethylene (LDPE 125 g 722 available from Dow Chemical Company) and fed into a Haake Rheomix 3000 preheated chamber at a mixer with rotors operating at 50 rpm minute. A minute after adding the mixture, the temperature in the chamber is raised to 105 ° C. The heat of friction generated in the mixing process allows the regulation of the TiO introduction rate₂ to LDPE until the mixture reaches equilibrium. The concentrate is removed from the mixing chamber and placed in a Cumberland crusher to produce finely granulated samples of 50% concentrate. Granulated concentrates are stored for 48 hours at 23 ° C and 50% relative humidity. The concentrate is then suspended in LDPE to achieve a 20% TiO load₂ on the final foil.

[0033] The extrusion test is carried out on a 25 mm extruder equipped with a slot die for film casting. The following temperature profile was used: 330 ° C nozzle, 270 ° C pressure ring, 215 ° C Zone 3, 175 ° C Zone 2, 150 ° C Zone 1. The screw rotation speed is set to 90 rpm. The 25.4 cm chromed chill roll set up in conjunction with the extruder is used to maintain film thickness of 75 microns, and to cool and transport the film. The distance between the cooling roll and the nozzle mouthpiece is approximately 22 mm and the temperature is approximately ° C.

[0034] After placing the TiO mixture₂/ LDPE in a hopper, the material is blown until the first appearance of white coloration of the film. To ensure that TiO concentration₂ on the film stabilized, a period of two minutes is allowed before observing the extrusion and obtaining a sample of the film. The performance achieved is determined by calculating the relative size and number of holes formed on the sample of the film spread over a dark surface. A rating system of 1.0 - 3.0 was used. A rating of 1 is given to the non-embossed film, 2 is awarded to the film showing the start of extrusion and 3 is awarded to the film with extreme extrusion. Increases of 0.1 are considered as an indicator of relative performance between samples. A 1.0 gauge film indicates low volatility and excellent temperature stability.

[0035] Using a small-scale laboratory extrusion device, measuring the dispersion of inorganic solid particles in an organic polymer is obtained by measuring the relative amount of solids entrapped on the extruder screens. Tests are performed using a 75% TiO concentrate₂ in low density polyethylene prepared with a Haake Rheomix 3000 mixer. The mixer is controlled and monitored with a Haake 9000 Rheocord

Torque Rheorneter.

[0036] A 75% concentrate is obtained by dry mixing the final pigment (337.7 g) and LDPE (112.6 grams NA209 Available from Equistar Chemicals) and adding the mix to a 75 ° C mixing chamber with rotors operating at 50 rpm / min. The mixer temperature is programmed to rise to 120 ° C, one minute after the dry mix is ​​introduced into the mixing chamber. After reaching equilibrium of the mixture, the compound is stirred for an additional 3 minutes. The compound is removed from the chamber and granulated using a Cumberland crusher.

[0037] Dispersion tests are carried out using a Killion single screw extruder model KL-100 with a length to diameter ratio of 20: 1. The extruder is preheated at 165, 175, 200, 195 ° C from zone 1 to the die head, respectively, at a working speed of 70 rpm. The system is cleaned with 1000 LDPE passes through the system, and a new set of sieves is installed.

The sieve set consists of sieves 40/500/200/100 mesh from the nozzle of the head towards the throat of the extruder. After stabilizing the temperature, granulated 75% concentrate (133.3

g) fed to the extruder. This is followed by emptying of the hopper with 1500 g of LDPE laxative. After extrusion of the LDPE purge, the sieves are removed, separated and tested using a relative counting technique from measurements from an fluorescent X-ray spectrometer. The number of TiO counts₂ per second is obtained for a set of 100, 200 and 500 mesh sieves and added together to obtain a dispersion result. A lower number of TiO counts is desired₂ for a second. A count result of less than 5000 is considered to be perfect dispersion. The concentrate had 670 counts per second, which indicates excellent dispersion.

EXAMPLES 2-4

Siloxane Modified Titanium Dioxide [0038] In a similar manner to Example 1, blends of siloxane 1-modified titanium dioxide with different min ratios, different siloxane molecular weights, and different siloxane loading levels were prepared and analyzed. The conditions and results obtained are shown in Table 1. They all show excellent dispersion, low volatility and excellent temperature stability.

EXAMPLES 5-7

Siloxane-modified titanium dioxide [0039]

<img file="PL2094484T3_D0005.tif" />

[0040] In a similar manner to Example 1, blends were prepared and analyzed from siloxane-modified titanium dioxide, which was added to titanium dioxide as an aqueous emulsion (50% solids). The conditions and results obtained are shown in Table 1. They all show excellent dispersion, low volatility and excellent temperature stability.

EXAMPLES 8-13

Siloxane Modified Titanium Dioxide Sulphate Process [0041] In a similar manner to Example 1, blends of siloxane modified titanium dioxide were prepared and analyzed. Mixtures are prepared using titanium dioxide from the rutile sulphate process with 0.4% Al2O3 on T1O2. The conditions and results obtained are shown in Table 1. They all show excellent dispersion, low volatility and excellent temperature stability, showing the general advantages of siloxanes and their suitability for modification of titanium dioxide produced in the sulphate process.

COMPARATIVE EXAMPLE 14

Triethanolamine Modified Titanium Dioxide [0042] In a similar manner to Example 1, the blend is prepared and analyzed from titanium dioxide from the rutile chloride, triethanolamine-modified rutile method, a known modifier instead of siloxane. The conditions and results obtained are shown in Table 1. The dispersion is much worse than that obtained for siloxane modifiers

TABLE 1

<td rowspan="2">Example</td><td rowspan="2">modifier</td><td colspan="3">Zone reaction conditions</td><td colspan="2">AND</td>

<td colspan="2">MW load</td><td>m / n</td><td>Dispersion</td><td>extrusion</td>

<td> 1</td><td>Siloxane 1</td><td> 1,2</td><td> 5400</td><td> 19</td><td> 670</td><td> 1,0</td>

<td> 2</td><td>Siloxane 1</td><td> 0,9</td><td> 5600</td><td> 9</td><td> 490</td><td> 1,0</td>

<td> 3</td><td>Siloxane 1</td><td> 0,9</td><td> 5800</td><td> 4</td><td> 430</td><td> 1,0</td>

<td> 4</td><td>Siloxane 1</td><td> 0,9</td><td> 26000</td><td> 19</td><td> 2660</td><td> -</td>

<td> 5</td><td>Siloxane 2</td><td> 0,75</td><td> -</td><td> 30</td><td> 650</td><td> 1,3</td>

<td> 6</td><td>Siloxane 2</td><td> 0,9</td><td> -</td><td> 30</td><td> 460</td><td> 1,3</td>

<td> 7</td><td>Siloxane 2</td><td> 0,9</td><td> -</td><td> 9</td><td> 480</td><td> 1,4</td>

<td> 8</td><td>Siloxane 1</td><td> 0,9</td><td> 5400</td><td> 19</td><td> 690</td><td> 1,1</td>

<td> 9</td><td>Siloxane 1</td><td> 1,2</td><td> 5600</td><td> 9</td><td> 1360</td><td> 1,1</td>

<td> 10</td><td>Siloxane 1</td><td> 0,9</td><td> 5800</td><td> 4</td><td> 1230</td><td> -</td>

<td> 11</td><td>Siloxane 2</td><td> 1,1</td><td> -</td><td> 30</td><td> 900</td><td> 1,2</td>

<td> 12</td><td>Siloxane 2</td><td> 1,5</td><td> -</td><td> 30</td><td> 420</td><td> 1,4</td>

<td> 13</td><td>Siloxane 2</td><td> 1,1</td><td> -</td><td> 9</td><td> 490</td><td> 1,2</td>

<td>C14</td><td>triethanolamine</td><td> 0,6</td><td> -</td><td> -</td><td> 13700</td><td> 1,4</td>

<td></td><td>amine</td><td></td><td></td><td></td><td></td><td></td>

[0043] The examples given are for illustrative purposes only. The invention is defined by the claims as understood below

24160 / PE / 14 EP 2094484