WO2010100330A1

WO2010100330A1 - Method for forming a silicon compound

Info

Publication number: WO2010100330A1
Application number: PCT/FI2010/050148
Authority: WO
Inventors: Jonas Roininen; Petri Uusi-Kyyny; Ali Harlin; Karita Kinnunen; Thaddeus Maloney
Original assignee: Oy Keskuslaboratorio - Centrallaboratorium Ab
Priority date: 2009-03-06
Filing date: 2010-02-26
Publication date: 2010-09-10
Also published as: FI20095226A; FI20095226A0

Abstract

The invention relates to a method for forming a silicon-oxygen compound. According to the invention, the silicon-oxygen compound consisting mainly of nanoscale particles is manufactured from silicon-based starting material substantially in connection with the manufacture of a carrier material, and the formed silicon-oxygen compound is provided in connection with the carrier material to modify the surface properties of the carrier material.

Description

METHOD FOR FORMING A SILICON COMPOUND

FIELD OF THE INVENTION

The invention relates to a method for forming a silicon-oxygen compound as defined in the preamble of claim 1.

BACKGROUND OF THE INVENTION

Known from the prior art are different sili- con-based and silicate-based compounds and methods for manufacturing them, e.g. in the field of papermaking. Especially known in the field of papermaking is the use of water glass, kaolin and talc as fillers in paper and in the coating of paper. Those materials are added to the paper pulp or spread as a coating on the surface of paper by applicable methods.

Known is the manufacture of silicate-based products by the ion exchange technique. In connection with the manufacture of silicate-based products, salt that has been formed is removed. Alternatively, silicate-based products may be manufactured by a more complicated and expensive process in which salt is not formed in connection with the manufacture of the product. Salt in connection with silicate particles is problematic because it accelerates agglomeration of the particles during transportation and in storage. Agglomeration of silicate products during storage can be reduced by additives, which increases the costs. Removal of salt complicates the process and increases the process costs.

OBJECTIVE OF THE INVENTION

The objective of the invention is to eliminate the drawbacks referred to above. A further objective of the invention is to disclose a new nanoscale silicon-oxygen compound and a method for manufacturing it substantially in connection with the manufacture of a carrier material.

SUMMZVRY OF THE INVENTION

The method for manufacturing a silicon-oxygen compound according to the invention is characterized by what has been presented in the claims. The invention is based on a method for forming a silicon-oxygen compound. According to the invention, the silicon-oxygen compound which mainly consists of nanoscale particles is manufactured from silicon-based starting material, e.g. siliceous start- ing material, such as siliceous solution, substantially in connection with the manufacture of a carrier material, and is provided in connection with the carrier material. Preferably, the produced silicon-oxygen compound is provided on the surface of the carrier ma- terial, e.g. the carrier material is coated with the silicon-oxygen compound, or as a filler or additive in the carrier material. Surface properties of the carrier material can preferably be modified by the silicon-oxygen compound that is being formed and by its composition.

The invention is specifically based on forming a silicon-oxygen compound substantially in a carrier material in connection with its manufacture. In addition, the invention is based on a silicon-oxygen compound which is substantially reactive. In this case, the formed silicon-oxygen compound is ready for use immediately. Preferably, the formed silicon-oxygen compound is used substantially immediately because of its high reactivity. In one embodiment of the invention, the carrier material is selected from the group of a web, fi- brous carrier material, platy base, rubber, paint and their combinations .

In this connection, by a web is meant any fiber-based paper, board or fibrous web or an equivalent web or a sheet cut from a web or the like. The web may be formed from chemical pulp, mechanical pulp, chemi- mechanical pulp, recycled pulp or other pulp. Any suitable fibers, e.g. softwood fibers, hardwood fibers, cotton fibers or equivalent fibers may be used as fibers in the manufacture of the web.

In one embodiment of the invention, the silicon-based starting material is selected from the group of silicates, silanes, oxysilanes, silicones, silox- anes, silicate minerals such as wollastonite and other suitable silicon compounds and their derivatives and their mixtures. The starting material may contain additives such as surface-active agents.

In one embodiment, the silicon-based starting material may be in the form of a solution, suspension or dispersion which may be formed in water or a suitable solvent. In one embodiment, the formed silicon- oxygen compound is in the solid, solution, suspension or dispersion form.

In one embodiment of the invention, the sili- con-oxygen compound is selected from the group of silicon oxides, silicates, siloxanes, silicic acids and equivalent silicon-oxygen compounds and their derivatives and their mixtures.

In one embodiment of the invention, the sili- con-oxygen compound is silicon oxide or its derivative. In one preferred embodiment, the silicon-oxygen compound is silicon dioxide, SiO₂, or its derivative. The silicon oxide compound is formed from a compound or compounds containing silicon and oxygen. In one embodi- ment, the silicon oxide compound is formed by precipitation. In one preferred embodiment, the SiO₂ produced in the reaction forms, as it precipitates, nanoparti- cles, the surface properties of which being changeable.

The silicon-oxygen compound may contain dif- ferent additives and fillers.

In one embodiment, the silicon-oxygen compound is formed substantially close to the surface of the carrier material, preferably as close to the surface of the carrier material as possible, in which case the re- action takes place substantially close to the carrier material .

In one embodiment of the invention, the silicon-oxygen compound is formed on the surface of the carrier material, the surface acting at the same time as a reaction and supply environment.

In one embodiment, the silicon-oxygen compound is formed substantially on site in connection with the carrier material, either in connection with a finished carrier material or in connection with the manufacture of the carrier material.

Preferably, the silicon-oxygen compound is formed substantially in connection with the manufacture of the carrier material, e.g. a paper web. The silicon- oxygen compound may be manufactured and provided as coating material or filler in the carrier material. In one embodiment, the silicon-oxygen compound is provided substantially on the surface of the carrier material.

In one embodiment, the silicon-oxygen compound is provided on the surface of the carrier material by a technique selected from the group of spray coating, foam coating, roll coating or other method known per se. In one embodiment, the reaction to form the silicon-oxygen compound takes place at the same time as the compound is provided on the surface of the carrier ma- terial, e.g. during spraying, or in connection with the carrier material, e.g. as a filler. In one embodiment of the invention, the silicon-oxygen compound is prepared by precipitation e.g. from a siliceous solution. In one embodiment, the silicon-oxygen compound nanoparticles are manufactured by precipitation with an acid compound. The acid compound is selected from the group of: different acids such as sulfuric acid, and acid gases such as carbon dioxide, or their derivatives. In one embodiment, the silicon- oxygen compound particles are manufactured by precipi- tation from sodium silicate solution. Any silicon- and/or silicate-based compound applicable to the purpose of use may be used as the starting material.

In one embodiment, the following chemical reactions take place in the precipitation in using car- bon dioxide.

CO₂ + H₂O → H₂CO₃

H₂CO₃ + Na₂O- 3, 3SiO₂ -→ Na₂CO₃ + 3,3 SiO₂I + H₂O

In one embodiment, the following chemical reaction takes place in the precipitation in using sul- furic acid.

H₂SO₄ + Na₂O- 3, 3SiO₂ → Na₂SO₄ + 3,3 SiO₂; + H₂O

Preferably, the acid is selected so that any produced salt need not be removed in the application.

In one embodiment of the invention, properties of the silicon-oxygen compound are adjusted by the reaction conditions. In one embodiment, surface properties of the silicon-oxygen compound particles may be modified. In one embodiment, surface of the silicon- oxygen compound particles is treated e.g. by absorbing suitable ions on the surface of the particles to modify the properties.

In one embodiment, reaction temperature of 70 to 120 °C is used to provide the reactive product according to the invention. In one embodiment, pH value of 8 to 13 is used in the reaction. In one embodiment of the invention, acid is added gradually in connection with the formation of the silicon-oxygen compound. In one embodiment, substantially slow acid feed is used. In one embodiment, high mixing intensity is used in connection with the formation of the silicon- oxygen compound.

In one embodiment, short dwell time in used in the reaction of forming the silicon-oxygen com- pound.

In one preferred embodiment, the carrier material is provided in optimum process conditions in which the reactive silicon-oxygen compound may be formed.

In one embodiment, by-products which prefera- bly do not cause problems because of their lower reactivity and/or thanks to quick providing of the silicon-oxygen compound in the carrier material may be formed in connection with the manufacture of the silicon-oxygen compound. Preferably, the formed silicon-oxygen compound is used, i.e. provided in connection with the carrier material, substantially within short time from the formation of the silicon-oxygen compound and thus before agglomeration takes place to a harmful extent, preferably during less than 24 hours, more preferably less than 4 hours and most preferably less than 1 hour. In this case, any possibly formed salt need not be separated from the product before use of the product . In one embodiment of the invention, a mixture containing silicon and oxygen is stirred with high intensity to control agglomeration in connection with the manufacture of the silicon-oxygen compound.

In one embodiment, the silicon-oxygen com- pound product is formed in more than one reactor. Alternatively, the silicon-oxygen compound product is formed in one reactor. In one embodiment, the product is formed in sequential reactors connected in series. In one embodiment, the product is formed in a multicompartment reactor in which individual sequential stages are integrated inside one case. Any reactor suitable for the purpose of use, e.g. a batch stirred reactor, precipitation reactor or the like, may be used as the reactor. In one embodiment, a combined stirred and spray reactor in which the starting mate- rials are mixed and the formed product is sprayed into the carrier material is used as the reactor.

In one embodiment, dispersing means are included in the reactor or substantially in connection with it to disintegrate, i.e. disperse, aggregates which are possibly formed. Different grinding devices, mills, e.g. a bead mill, or the like may be used as the dispersing means. In one embodiment, means to prevent or reduce agglomeration are included in the reactor or substantially in connection with it. In one embodiment, the produced nanoparticles may be kept in the reactor in which the particle size distribution is kept predetermined by high shear forces, ultrasound or the like until the product is used. Important advantages are achieved by the invention compared with the prior art .

The invention provides a new method for adjusting the surface properties of a carrier material, such as paper, by nanoscale silicon compound parti- cles. The method according to the invention is suited for use directly in the manufacture of the carrier material, such as paper.

In the method according to the invention, properties of the silicon compound particles may be controlled by the reaction conditions and by the reac^¬ tion equipment, and surface properties of the parti- cles may be modified according to surface properties selected for the carrier material, e.g. paper or board.

The silicon-oxygen compound particles accord- ing to the invention need not be stabilized, in which case reactivity of the particles may be raised. Stabilizers or additives for storage durability need not be added to the product.

In addition, unit operations related to de- salination are not needed in connection with the method according to the invention. Furthermore, thanks to the method according to the invention, the costs related to treatment of spent solutions and spent ion- exchange resin may be reduced. E.g. colloidal silicate products which are manufactured by the complicated ion exchange process may be replaced in papermaking with the product manufactured by the method according to the invention. These products may be used in papermaking at the wet end e.g. as retention and drainage aids, and in the finishing of paper as spraying applications to add friction to paper and ameliorate printing properties of paper.

An industrially applicable easy method of good quality to form a silicon-based compound e.g. in connection with papermaking is achieved by the invention. Tailored silicon compound nanoparticles may be produced by the method according to the invention on site and/or on line in the manufacture of a carrier material, e.g. at the papermill, from inexpensive starting materials. Because the silicon compound product is manufactured substantially in connection with the manufacture of the carrier material, it has an effect on the logistics costs and environmental CO₂ emissions. In addition, the product or the intermediate product need not be stabilized. The method enables flexible finishing of paper and control of the surface properties of paper. Finishing of paper by the silicon compound nanoparti- cles enables total or partial replacement of internal sizes (AKD, ASA) used at the wet end, which has an effect on the runnability and production efficiency of the paper machine .

In addition, the tailored silicon compound nanoparticles enable development of new paper and fi- ber products.

The method according to the invention is suited for use in connection with the manufacture of paper and fibrous webs and the manufacture of e.g. rubber, varnishes and paints.

DETAILED DESCRIPTION OP THE INVENTION

In the following, the invention will be described according to detailed examples of its embodi- ments.

Example 1

Different methods to manufacture the silicon- oxygen compound according to the invention were examined in this test series.

First, acid neutralization, precipitation and coagulation methods to manufacture the silicon-oxygen compound were tested. All methods were based on neu- tralization of water glass, i.e. sodium silicate, by an acid. Only small particles of approximately IOnm in diameter were provided by the acid neutralization method, and the product was instable. Primary particles of approximately 10 to 50nm were provided by the precipitation method. It was possible to provide particles of even lOOnm by the coagulation method, but the large amount of coagulant required In the process was problematic.

In the tests it was observed that the precipitation method would be an advantageous application to be used to manufacture the silicon-oxygen compound.

Next, nanoscale particles of silicon dioxide were manufactured from wollastonite. The particles were formed by precipitation with sulfuric acid or carbon dioxide according to reaction equations (1) and (2) presented below. The formed particles were provided on the surface of paper.

H₂SO₄ + CaSiO₃ → SiO₂ + CaSO₄ + H₂O (1)

CO₂ + CaSiO₃ → SiO₂ + CaCO₃ ( 2 )

The first tests to form the silicon compound were carried out by an apparatus comprising a cascade reactor known per se with many sequential reactor tanks, in this case four, connected in series. The acid is added gradually and mixed in the sequential reactor tanks. The second tests to form the silicon compound were carried out by an apparatus comprising a multicompartment reactor in which individual sequential stages are integrated inside one case. The volumes of individual compartments were provided small and the mixing intensities high. It was discovered that agglomeration of the particles can be controlled preferably by high mixing intensity, short dwell time and slow and stagewise acid feed. The intensive mixing aids in keeping the pH constant. Agglomeration may be reduced by breaking the agglomerates e.g. by using high shearing stress. In addition, agglomeration can be avoided by reducing interaction of the particles by repulsion, e.g. by adsorbing potentially defined ions on the surface of the particle to achieve highly loaded surfaces. The produced electrostatic repulsion forces reduce the amount of collisions of the particles with each other.

The third tests to form the silicon compound and to spray it on the surface of the carrier material were carried out by an apparatus in which the acid and the silicon-containing starting material are fed into an agitation box from which the produced silicon- oxygen compound is conducted via a spraying nozzle to the surface of the carrier material. The acid and the starting material are mixed with high mixing intensity. Formation of large agglomerates of the particles is prevented by atomizing the silicon-oxygen compound to be conducted out in very small drops. The reaction may still continue in connection with the spraying- out. In this case, the feed of acid and the silicon- based starting material must be adjusted very carefully and the mixing intensity must be kept high to prevent gelation and agglomeration of the particles.

The fourth tests to form the silicon compound were carried out in a modified Taylor-Couette reactor comprising two coaxial cylinders, the inner one of which was rotating. The space between the cylinders forms a mixing area. The silicon-based starting material is fed from the end of the cylinder and the acid is fed from many feeders to the mixing area. The cylinders may be equipped with projections to add shear forces.

In summary, it could be noted that the silicon dioxide according to the invention can be easily formed in different devices and it can be easily provided on the surface of the carrier material. Nano- scale silicon dioxide particles were provided in the tests. In addition, surface properties of the carrier material could be modified by the formed silicon diox- ide provided on the surface. Example 2

In this test, silicon dioxide was formed from water glass and carbon dioxide in a combined stirred and spraying reactor. First, water and water glass were loaded to a first cylinder tank in the ratios of: a) 300 water: 50 water glass; and b) 200 water: 120 water glass. The tank was pressurized by pressurized air to 20 bars. Carbon dioxide was loaded to a second cyl- inder tank. The outlet pressure of the carbon dioxide tank was 5 bars. Temperature of the heating device was set to 100°C, and the nozzle area was heated to maintain the reaction temperature. PH of the reaction was between 10.17 and 11.12. Carbon dioxide and water glass were conducted to the nozzle, mixed in the nozzle and immediately sprayed into a sample container or water containers in which the temperature of the water was 23°C or 80°C. The spraying rate was approximately lOOg/min. The flow rate of carbon dioxide was approxi- mately lOOOml/min (NPT) . The samples were analyzed by a Malvern Zetasizer device. Swagelok 1/16" (1.6mm) was used as the nozzle.

Based on the test it was observed that by a larger amount of water glass in relation to water, i.e. 120 water glass: 200 water, a higher carbon dioxide yield of approximately 10.50 w-% and an average particle size of less than IOnm were provided. Instead, by a smaller amount of water glass in relation to water, i.e. 50 water glass: 300 water, a smaller silicon dioxide yield was obtained.

The method according to the invention to form a silicon-oxygen compound substantially in connection with a carrier material is suited in different appli- cations to be used for the manufacture of most different products. The invention is not limited merely to the examples referred to above; instead, many variations are possible within the scope of the inventive idea defined by the claims.

Claims

1. A method for forming a silicon- oxygen compound, c h a r a c t e r i z e d in that the silicon-oxygen compound consisting mainly of nanoscale particles is manufactured from silicon-based starting material substantially in connection with the manufacture of a carrier material, and the formed silicon- oxygen compound is provided in connection with the carrier material to modify the surface properties of the carrier material.

2. The method according to claim 1, c h a r a c t e r i z e d in that the carrier material is selected from the group of a web, fibrous carrier material, platy base, rubber, paint and their combinations.

3. The method according to claim 1 or

2, c h a r a c t e r i z e d in that the silicon-based starting material is selected from the group of silicates, silanes, oxysilanes, silicones, siloxanes, silicate minerals, their derivatives and their mixtures.

4. The method according to any one of claims 1 to 3, c h a r a c t e r i z e d in that the silicon-oxygen compound is selected from the group of silicon oxides, silicates, siloxanes, silicic acids, their derivatives and their mixtures.

5. The method according to claim 4, c h a r a c t e r i z e d in that the silicon-oxygen compound is silicon dioxide or its derivative.

6. The method according to any one of claims 1 to 5, c h a r a c t e r i z e d in that the si- licon-oxygen compound is formed substantially on site in connection with the carrier material.

7. The method according to any one of claims 1 to β, c h a r a c t e r i z e d in that the silicon-oxygen compound is formed substantially on the sur- face of the carrier material.

8. The method according to any one of claims 1 to 7, c h a r a c t e r i z e d in that the silicon-oxygen compound is manufactured by precipitation.

9. The method according to any one of claims 1 to 8, c h a r a c t e r i z e d in that the silicon-oxygen compound is manufactured by precipitation of nanoparticles with an acid compound.

10. The method according to claim 9, c h a r a c t e r i z e d in that the acid compound is selected from the group of different acids, acid gases and their derivatives.

11. The method according to any one of claims 1 to 10, c h a r a c t e r i z e d in that the silicon-oxygen compound particles are precipitated from sodium silicate solution.

12. The method according to any one of claims 1 to 11, c h a r a c t e r i z e d in that properties of the silicon-oxygen compound are adjusted by the reaction conditions.

13. The method according to any one of claims 1 to 12, c h a r a c t e r i z e d in that surface of the silicon-oxygen compound particles is treated to modify the properties.

14. The method according to any one of claims 1 to 13, c h a r a c t e r i z e d in that gradual acid feed is used to form the silicon-oxygen compound.

15. The method according to any one of claims 1 to 14, c h a r a c t e r i z e d in that a mix- ture containing silicon and oxygen is stirred with high intensity to control agglomeration in connection with the manufacture of the silicon-oxygen compound.