HK1190421B - Method of concentrating an aqueous dispersion comprising organic polymer particles and silicon dioxide particles - Google Patents

Description

Method for concentrating an aqueous dispersion comprising organic polymer particles and silica particles

The present invention relates to a process for concentrating an aqueous dispersion comprising organic polymer particles and silica particles. The invention also relates to concentrated aqueous silicon dioxide dispersions obtained by the process of the invention and to the use of such dispersions as adhesives.

The combination of silica dispersions with organic polymer dispersions, such as adhesive dispersions, is believed to have a number of beneficial effects. This combination can be achieved by polymerizing the monomers in the presence of the inorganic particle dispersion or by mixing preformed inorganic particles and organic polymer dispersion.

An example of the first case is given in US 2004/0077761 a1, which discloses organic polymer dispersions containing fillers. The organic polymer of the dispersion is polymerized in the presence of particles of at least one filler. The ratio of the particle size of the filler particles to the polymer particles is in the range of 1.1:1 to 20: 1.

An example of the latter case is given in US 2006/0115642 a1, in which a process for finishing fibrous products with an article based on an aqueous dispersion of polychloroprene and a process for preparing fabric-reinforced and fiber-reinforced concrete and other cement-based products (including those finished products) are provided. In a method of reinforcing one of concrete and cement, the improvement disclosed therein comprising soaking a fibrous product in an article comprising: (a) from about 20 to about 99 weight percent of an aqueous polychloroprene-based dispersion; and (b) from about 1 to about 80 weight percent of an aqueous suspension based on an inorganic solid selected from the group consisting of oxides, carbonyls and silicates; (c) optionally, a polymer dispersion selected from the group consisting of polyacrylates, polyacetates, polyurethanes, polyureas, rubbers and epoxides, and (d) optionally, additives and adjuvants selected from the group consisting of resins, stabilizers, antioxidants, crosslinking agents, crosslinking promoters, fillers, thickeners and fungicides, wherein the weight percentages of (a) and (b) add up to 100% by weight and are based on the weight of the non-volatile fraction.

When mixing commercially available binder dispersions with commercially available silica dispersions, undesirable dilution of the resulting mixture, especially with respect to the silica content, may occur. This necessitates a subsequent concentration step.

Several methods are known in the art to increase the solids content of polymer latexes such as SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), polychloroprene, polybutadiene, polyisoprene, natural rubber, polyvinyl chloride or dispersions of (meth) acrylate dispersions or copolymers thereof.

A non-exhaustive compilation of such methods is given in Houben-Weyl, Vol.XIV/1 "Makromolekulare Stoffe", Vol.1, 4 th edition, p.515 (1961), in Polymer Colloids, Elsevier Applied Science Publishers, p.272 (1985) or Industrial and Engineering Chemistry, Vol.43, February 1951, p.406. 412, Ernst Schmidt and R.H. Kelsey "creating Latex with Ammonium Alginate".

For example, US 2009/0234064 a1 discloses aqueous dispersions of elastomers comprising a dispersed phase and an aqueous phase. The dispersed phase comprises an elastomer comprising a curable aliphatic conjugated diene elastomer, such as polyisoprene, and a minor amount of at least one additive. The aqueous phase includes water and other optional components in a soluble or dispersed state. Aqueous dispersions of elastomers can be prepared by dissolving an elastomer, such as a rubber, and additives in a solvent mixture and then converting the resulting solution into an aqueous emulsion. The aqueous emulsion is concentrated and the solvent is stripped therefrom to produce a dilute latex. The resulting thin latex was reconcentrated. Articles made from the elastomeric aqueous dispersion include medical gloves, condoms, probe covers, dental dams, finger cots, catheters, and the like.

There is no description of the concentration of the combination of dispersions of inorganic and organic substances.

The disclosed method of concentrating dispersions of organic substances has the following disadvantages: agglomeration of the particles of the dispersion may occur (upon addition of electrolyte, freezing, water evaporation), the filter pores may be blocked (ultrafiltration) or foaming may prevent effective separation (centrifugation). In the use of creamers, the particle size of the latex being treated is considered to be of decisive importance. Although natural rubber latex with a particle size of 400 nm can be creamed rapidly without any problem, creaming with ammonium alginate, for example SBR latex with a particle size of 78 nm, has not been successful (ind. eng. chem. 43, 407 (1951)).

It would therefore be desirable to be able to concentrate a dispersion of polymer particles and silica particles without the above-mentioned disadvantages. It is an object of the present invention to provide such a method.

According to the invention, this object is achieved by a process for concentrating an aqueous dispersion comprising organic polymer particles and silica particles comprising the steps of:

a) providing an aqueous dispersion comprising organic polymer particles and silica particles, said dispersion having an initial content of organic polymer and an initial content of silica;

b) contacting the dispersion of step a) with a creaming agent to produce an aqueous clear phase and an aqueous concentrated phase,

said clear liquid phase having a lower content of organic polymer than the initial content of organic polymer in the dispersion of step a) and/or having a lower content of silica than the initial content of silica in the dispersion of step a), and

said concentrated phase having a higher content of organic polymer than the initial content of organic polymer in the dispersion of step a) and/or having a higher content of silica than the initial content of silica in the dispersion of step a), and

c) separating the clear phase from the concentrated phase.

Another embodiment of the presently claimed invention is a method of concentrating an aqueous dispersion comprising organic polymer particles and silica particles comprising the steps of:

a) providing an aqueous dispersion comprising organic polymer particles and silica particles, said dispersion having an initial content of organic polymer and an initial content of silica;

b) contacting the dispersion of step a) with a creaming agent to produce an aqueous clear phase and an aqueous concentrated phase,

said clear liquid phase having an organic polymer content which is lower than the initial content of organic polymer in the dispersion of step a) and having a silica content which is lower than the initial content of silica in the dispersion of step a), and

said concentrated phase having a content of organic polymer higher than the initial content of organic polymer in the dispersion of step a) and having a content of silica higher than the initial content of silica in the dispersion of step a), and

c) separating the clear phase from the concentrated phase.

It has surprisingly been found that the process of the present invention enables concentration of polymer particle/silica dispersions without agglomeration of the particles during the concentration step. The particle size distribution of the dispersion, in particular with respect to the silica particles, is hardly changed.

It is also surprising that the composition of the creaming mixture can be influenced in terms of organic and inorganic components by the choice of the creaming agent.

The addition of a dispersion of polymer particles, in particular a polymer latex, to an inorganic dispersion prior to creaming increases the achievable concentration and achieves a homogeneous distribution of organic and inorganic particles. The particle concentration of the creamed mixture is significantly higher than that achieved by concentrating the components separately and then mixing.

Step a) of the process involves providing an aqueous dispersion comprising organic polymer particles and a silica dispersion having the respective initial (meaning prior to the upconcentration step) contents of the particles described above. It is not strictly necessary but organic cosolvents or other dissolved organic substances, such as ethylene oxide-based emulsifiers, may also be present in such dispersions, for example in amounts of up to 20% by weight, based on the dispersion.

Step b) of the process requires that such dispersion is contacted with a creaming agent. The creaming agent can be provided, for example, in aqueous solution, hydrocolloid or solid form. If desired, co-solvents may also be present.

Different methods of creaming are reported in the literature:

Stevens AH (1934): Improvements Relating to the Treatment of RubberLatex B. P. 415, 133；appl. 23.2.33；publ. 23.8.34

Rhodes E, Sekaran KC (1937): Concentration of latex. B.P.474, 651；appl. 24.8.36；publ. 4.11.37.

Dafader NC, Haque ME, Akhtar F, Ahmad MU, Utama MJ (1996),Macromol.Sci., A 33, 1 (2): 73.

Peethambaran NR, Kuriakose B, Rajan M, Kuriakose APJ (2003):Rheological behaviour of nature rubber latex in the presence of surface-active agents；Appl. Polym. Sci., 41(5-6): 975。

suitable creaming agents for the process according to the invention are all creaming agents known from the prior art, but preference is given to using alginates, cellulose derivatives, methylcellulose, agar, salts of poly (meth) acrylic acid, copolymers of alkyl (meth) acrylates and/or styrene with unsaturated sulfonic acid derivatives or ethylenically unsaturated mono-or polycarboxylic acids or salts thereof and salts of divalent ions, for example calcium acetate. The size of the creaming agent is below the polymer particle size as given herein, i.e. below 10 nm.

The creaming agent has the effect of separating the dispersion into a solids-rich aqueous phase and a solids-poor aqueous phase (clear liquid phase). Thus, the (dispersed) solids content in the clear phase is lower than in the initially provided dispersion, while the (dispersed) solids content in the concentrated phase is higher than in the initially provided dispersion. Due to the high density of the inorganic solids, the concentrated phase constitutes in particular the lower phase and the clear liquid the upper phase. For example, the clear liquid phase may have, in absolute terms, a solids content of ≦ 25 wt.%, and preferably ≦ 20 wt.%. The phase boundaries can be determined, for example, visually or by other optical means.

The separation in step c) may be carried out in a settler as described in DE 10145097 a 1.

The creaming can be a discontinuous or continuous process at temperatures below, at, or above room temperature. The process is preferably carried out at about room temperature, i.e. 10 to 35 ℃. It is also possible to wait a predetermined time before the separation step c). The predetermined time may be 24 hours.

The present invention is described in more detail in connection with preferred embodiments. They may be freely combined unless the context clearly indicates otherwise.

In one embodiment of the process according to the invention, the organic polymer particles are selected from styrene butadiene rubber particles, acrylonitrile butadiene rubber particles, polychloroprene particles, chloroprene-dichlorobutadiene copolymer particles, polybutadiene particles, polyisoprene particles, chlorinated polyisoprene particles, polyurethane particles, natural rubber particles, polyvinyl chloride or (meth) acrylate particles and/or copolymer particles thereof.

The organic polymer particles are preferably polyurethane particles and/or polychloroprene particles, such as poly-2-chloroprene or poly (2-chloroprene-2, 3-dichlorobutadiene 1, 3) copolymers. Polychloroprene dispersions can be obtained by emulsion polymerization of chloroprene and optionally copolymerizable ethylenically unsaturated monomers in an alkaline medium. Examples are given in WO 2002/24825a1, DE 3002734 a1 or US 5,773,544. Particularly preferred are polychloroprene dispersions prepared by continuous polymerization, as in WO 2002/24825a1 example 2 and DE 3002734 a1 example 6, wherein the regulator content can be varied between 0.01% and 0.3%.

The polyurethane dispersion may be obtained by emulsion polymerization. In US 20050085584A 1, Table 1 Dispersion B (Dispercoll from Bayer Material Science AG, Germany)^®U) or in the examples in US 20050131109 a1, table 1.

In another embodiment of the process according to the invention, the organic polymer particles are present in the form of a polymer latex. In the context of the present invention, a polymer latex is understood to be a dispersion of solid polymer particles dispersed in a liquid phase, and wherein this phase forms an emulsion in water. The preferred polymer latex is one having a density of 1.01 g/cm or more³And more preferably 1.06 g/cm or more³Those of (a).

In a further embodiment of the process according to the invention, the initial content of organic polymer in the dispersion of step a) is ≥ 20% by weight and ≤ 99% by weight. The initial content is preferably ≥ 30% by weight to ≤ 90% by weight.

In another embodiment of the process according to the invention, the organic polymer particles have an average particle size of ≥ 20 nm to ≤ 400 nm. The average particle size may also be referred to as the primary average particle size and may be determined by ultracentrifugation according to H.G. Muller, Progr. Colloid Polymer. Sci. 107, 180-. It is expressed as mass average. Those polymer particles having a primary average particle diameter of 40 nm or more and 200 nm or less are preferably used.

In a further embodiment of the process according to the invention, the silica particles are present in the form of a silica sol, a silica gel, a dispersion of pyrogenic silica, a dispersion of precipitated silica or a mixture of these.

Silica sols are colloidal solutions of amorphous silica in water, which are also referred to as silica sols, but are often referred to simply as silica sols. Wherein the silica is in the form of surface hydroxylated spherical particles. The colloidal particles typically have a diameter of 1 to 200 nm, the BET specific surface area (by g.n. Sears, Analytical) associated with this particle sizeChemistry volume 28, N.12, 1981-1983, month 12 1956) is 15 to 2000 square meters per gram. The SiO₂The surfaces of the particles have charges compensated by corresponding counter-ions to stabilize the colloidal solution. The alkali-stable silica sols generally have a pH of from 7 to 11.5 and comprise an alkalizing agent, for example a small amount of Na₂O、K₂O、Li₂O, ammonia, organic nitrogen bases, tetraalkylammonium hydroxides or alkali metal or ammonium aluminates. The silica sol may also be in a weakly acidic form, being a semi-stable colloidal solution. Furthermore, by using Al₂(OH)₅The Cl coats the surface and a cationic formulated silica sol can be prepared. The silica sol typically has a solids concentration of 5 to 60 wt.% SiO₂。

The procedure for the preparation of the silica sol essentially comprises the following production steps: dealkalization, setting and stabilization of water glass by ion exchange of the specific SiO required₂Particle size (distribution), setting of the desired specific SiO₂Concentration, and if appropriate, modification of SiO₂The surface of the particles, e.g. with Al₂(OH)₅Cl, or with silanes, as set forth in, for example, WO 2004/035474. In these steps SiO₂None of the particles remained colloidally dissolved. This explains the presence of discrete primary particles which are very effective as binders, for example.

Silica gel refers to silica having a pore structure varying from relatively loose to dense, elastic to solid consistency, with or without the formation of a colloid. The silica is a highly concentrated polysilicic acid. Siloxane and/or silanol groups are present on the surface. Silica gel is prepared from water glass by reaction with a mineral acid. The primary particle size is generally from 3 to 20 nm and the specific surface area is generally from 250 to 1000 m/g (in accordance with DIN 66131).

Further distinction is made between pyrogenic silica and precipitated silica. In the precipitation method, water is introduced and then water glass and an acid, such as H, are added simultaneously₂SO₄. This produces colloidal primary particles which, as the reaction proceeds, agglomerate and grow together to form agglomerates. The specific surface area is generally from 30 to 800 square meters per gram (DIN 66131) andthe particle size of the grades is typically 5 to 100 nm. The primary particles of these solid silicas are strongly crosslinked, forming secondary agglomerates.

Fumed (fumed) silica can be prepared by flame hydrolysis or by means of an optical arc process. The main synthesis of fumed silica is flame hydrolysis, in which a tetrafluorosilane is decomposed in an oxyhydrogen flame. The silica formed in this process is X-ray amorphous. Fumed silicas have significantly fewer OH groups on their nearly nonporous surfaces than precipitated silicas. Fumed silicas prepared by flame hydrolysis generally have a specific surface area of from 50 to 600 square meters per gram (DIN 66131) and a primary particle size of generally from 5 to 50 nm; the silicas produced by the light-arc process generally have a specific surface area of from 25 to 300 square meters per gram (DIN 66131) and a primary particle size of from 5 to 500 nm.

Further details regarding the synthesis and properties of silica in solid form can be found, for example, in K.H. Buchel, H.H. Moretto, P.Woditsch "Industrial ville Anorganische Chemie", Wiley VCHVerlag 1999, section 5.8.

If SiO is present in isolated solid form₂Starting materials, such as pyrogenic or precipitated silicas, are used in the polymer dispersions of the invention, which are converted by dispersion into SiO₂An aqueous dispersion.

For the preparation of the silica dispersion, use may be made of known dispersers, preferably those suitable for generating high shear rates, such as Ultraturrax or disk-type dissolvers.

The preferred silica dispersion is colloidal silica. The SiO₂The particles also preferably have hydroxyl groups on the surface of the particles.

In a further embodiment of the process according to the invention, the initial content of silica in the aqueous silica dispersion of step a) is from ≥ 1% by weight to ≤ 80% by weight. The initial content is preferably 10% by weight or more and 70% by weight or less.

In another embodiment of the method according to the inventionIn the aqueous silica dispersion of step a), the silica particles have an average particle size of from ≥ 1 nm to ≤ 400 nm, which average particle size can also be referred to as primary average particle size and can be determined by ultracentrifugation, preferably as set forth in H.G. M ü ller, progr. Colloid Polymer. Sci.107, 180-₂Those aqueous silica dispersions whose particles have a primary average particle diameter of from 3 nm or more to 100 nm or less, and particularly preferably from 5 nm or more to 70 nm or less. When precipitated silicas are used, they are ground to reduce the particle size.

In a further embodiment of the process according to the invention, in the dispersion of step a), the silica particles have a bimodal or multimodal particle size distribution. For example, in the case of a bimodal particle size distribution, one maximum may be in the range from ≧ 5 nm to ≦ 15 nm, and the other maximum may be in the range from ≧ 45 nm to ≦ 65 nm. The process of the present invention enables the preparation of concentrated bimodal or multimodal dispersions which are not otherwise obtainable.

In another embodiment of the process according to the invention, the creaming agent is selected from the group consisting of alginates, cellulose derivatives, methylcellulose, agar-agar, poly (meth) acrylates, and/or copolymers of alkyl (meth) acrylates and/or styrene with unsaturated sulfonic acid derivatives or ethylenically unsaturated mono-or polycarboxylic acids or salts thereof.

The creaming agent is preferably sodium alginate, potassium alginate and/or ammonium alginate.

In a further embodiment of the process according to the invention, the creaming agent is provided in the form of an aqueous solution and the content of creaming agent in the aqueous solution is between 0.5% by weight and 10% by weight. The concentration is preferably from ≥ 1% to ≤ 5% by weight, and more preferably from ≥ 1.5% to ≤ 4% by weight.

In a further embodiment of the process according to the invention, the creaming agent is present in an amount ≥ 0.2% by weight and ≤ 10% by weight, based on the solid content of the dispersion of step a). The preferred amount is 0.3 wt.% or more and 8 wt.% or less, and more preferably 0.4 wt.% or more and 7 wt.% or less.

In another embodiment of the process according to the invention, the separation in step c) is at least partly performed by centrifugation. This greatly accelerates the separation of the clear liquid.

The invention also relates to a concentrated aqueous dispersion comprising organic polymer particles and silica particles obtained by the process according to the invention. With regard to the preferred embodiment of such a dispersion, reference is made to the description of the process according to the invention in order to avoid repetitions.

The invention also relates to a concentrated aqueous dispersion, wherein the aqueous dispersion comprises a residual amount of creaming agent of 0.01 wt. -% or more to 1 wt. -% or less and an amount of silicon dioxide of 10 wt. -% or more to 60 wt. -% or less and an amount of organic polymer particles of 40 wt. -% or more (all components add up to 100 wt. -%).

"polymeric particles" in this application refers to water insoluble particles. The term "polymer dispersion" or "latex" preferably refers to a stable colloidal dispersion of polymer particles in an aqueous phase. The diameter of the organic polymer particles as described herein is preferably from 10 nm to 100 microns, more preferably from 10 nm to 1 micron. Preferably, the stability of the dispersion is achieved by surface-active ingredients, such as surfactants or protective colloids, or by incorporating ionic groups (internal emulsifiers) in the polymer backbone.

The polymer dispersions can be synthesized from the monomers by different polymerization methods, such as emulsion polymerization or suspension polymerization, directly or by dispersing the polymer. Natural rubber from the rubber tree (Hevea Brasiliensis) is an example of a naturally occurring polymer dispersion. The dispersion produced according to the process preferably comprises polychloroprene and/or polyurethane as organic polymer particles.

The dispersions according to the invention may optionally contain further additives and auxiliaries known from binder and dispersion technology, such as resins, stabilizers, antioxidants, crosslinking agents and crosslinking promoters. For example, fillers such as quartz flour, quartz sand, barite, calcium carbonate, chalk, dolomite or talc may be added, optionally together with crosslinking agents, for example polyphosphates such as sodium hexametaphosphate, naphthalenesulfonic acid, ammonium or sodium polyacrylate, wherein the fillers are preferably added in an amount of from 10 to 60% by weight, more preferably from 20 to 50% by weight, and the crosslinking agents are preferably added in an amount of from 0.2 to 0.6% by weight, all percentages by weight being based on the non-volatile fraction.

Preferably, further suitable adjuvants, such as organic thickeners, can be added in amounts of from 0.01 to 1% by weight (based on the nonvolatile fraction), or inorganic thickeners, such as bentonites, can be added to the dispersions (a) or (b) or to the entire preparation, preferably in amounts of from 0.05 to 5% by weight (based on the nonvolatile fraction), the thickening effect in the preparation preferably not exceeding 1000 mPas.

Fungicides may also be added to the compositions of the present invention for preservation. These are preferably used in amounts of from 0.02 to 1% by weight, based on the nonvolatile fraction. Suitable fungicides are, for example, phenol and cresol derivatives or tin inorganic compounds or azole derivatives, such as TEBUCONAZOL or KETOCONAZOL.

Tackifying resins, for example unmodified or modified natural resins, such as rosin esters, hydrocarbon resins or synthetic resins, such as phthalate resins, may also optionally be added to the components used to prepare these in the compositions or dispersed form of the invention (see, for example, "Klebharze" R. Jordan, R. Hinterwaldner, pages 75-115, Hinterwaldner Verlag, Munich, 1994). Alkylphenol resin and terpene phenol resin dispersions having softening points preferably above 70 c, more preferably above 110 c are preferred.

Another aspect of the invention is the use of the dispersion of the invention as an adhesive. These adhesive compositions exhibit high storage stability, can adjust their viscosity to a desired level, have high initial adhesive strength (regardless of their water content), open time before bonding parts, and high thermal stability.

Another aspect of the invention is an adhesive layer and also a substrate obtained by using the dispersion according to the invention as an adhesive. Such substrates include, for example, shoes, foam blocks, wooden structures such as furniture and toys, articles of clothing, and articles used in the automotive industry, such as dash trim foil, and the like.

The invention is further described with reference to the following examples and the accompanying drawings, without wishing to be limited thereto.

Examples

Glossary:

Manutex sodium alginate (creaming agent), Monsanto, UK

SiO used₂Dispersion:

raw material:

Polychloroprene dispersions polymerization is carried out in a continuous process according to EP 0032977A 1.

Dispersion a:

the aqueous phase (W) and the monomer phase (M) were introduced in a constant ratio by means of a measuring and control system into the first reactor of a polymerization cascade having 7 identical reactors each having a volume of 70 liters. An activator phase (A) is also introduced. The average time in each reactor was 25 minutes. The reactors correspond to those described in DE 2650714A 1 (amounts given are parts by weight per 100 parts by weight of monomers used).

Monomer phase (M) chloroprene 100.0 parts by weight

0.11 part by weight of n-dodecyl mercaptan

0.005 part by weight of phenothiazine

Water in the water direction (W) 115.0 parts by weight of deionized water

2.6 parts by weight of sodium salt of abietic acid

1.0 part by weight of potassium hydroxide

Activator phase (A) 0.05 parts by weight of an aqueous solution (1%) of formamidinesulfinic acid (formamidinesulfine)

0.05 part by weight of sodium persulfate

Anthraquinone-2-sulfonic acid sodium salt 0.005 weight portion.

The reaction starts easily at an internal temperature of 10 ℃. The heat of polymerization was dissipated by external cooling and the polymerization temperature was maintained at 10 ℃. After 70% conversion of the monomers, the reaction was stopped by addition of diethylhydroxylamine. Residual monomers were removed from the polymer by steam distillation. A strongly crystalline product is obtained. The product had a solids content of 33% by weight, a gel content of 0% by weight and a pH of 13.

Dispersion B:

the process is the same as for dispersion a, but the amount of modifier is increased to 0.03 wt%, the monomer conversion is increased to 80%, and the polymerization temperature is increased to 45 ℃ to obtain a polymer with high gel content. A less strongly crystalline product is obtained. The product had a solids content of 38% by weight, a gel content of 60% by weight and a pH of 12.9.

Method of producing a composite material:

1. Creaming an aqueous dispersion of an organic polymer dispersion and a silica dispersion to determine the optimum amount of creaming agent:

a creaming test was conducted to determine the amount of creaming agent needed to achieve the maximum solids concentration in the dispersion. The equipment used were a Brookfield LV DV III viscometer, a Knick KR301 pH meter and a Sartorius 1364 laboratory balance. In addition, the creaming agent Manutex was provided as a 2% solution [ w/w ] in deionized water (freshly prepared the day before).

The pH of the mixture was recorded and 8 parts of a 100 gram sample of the silica dispersion was bottled. To the samples were added 10, 20, 30, 40 and 50 grams of 2% creaming agent solutions, respectively, and gently mixed. Visual inspection of the samples was performed after 24 hours storage at room temperature.

The clear solution formed above the dispersion was measured with a ruler and the results were also recorded. Finally the sample was homogenized by shaking at maximum speed and the pH was recorded again.

2. Particle size distribution:

the average particle size of the silica particles was determined by ultracentrifugation according to H.G. Muller, Progr. Colloid Polymer. Sci.107, 180-188 (1997) and expressed as a mass average.

3. Solid content:

the solids content was determined by drying the dispersion at 100 ℃ for 16 to 18 hours. After heating the sample at 850-1000 ℃ for 30 minutes, SiO was measured₂As ash content.

Results:

Examples 1-5 determination of the optimum amount of creaming agent:

examples	1	2	3	4	5
						Polychloroprene Dispersion B [ g)]	50	50	50	50	50
Levasil 50 [g]	50	50	50	50	50
						2% Manutex solution [ g]	10	20	30	40	50
Height of clear liquid [ cm ]]	4.7	5.9	6.0	5.2	4.9
						Appearance of clear liquid	Is not transparent	Is transparent	Is transparent	Is not transparent	Is not transparent

According to these experiments, the optimum amount of creaming agent was found to be 30 grams of said 2% solution per 100 grams of silica/polychloroprene dispersion.

Other creaming examples 6-8:

examples	6	7	8
				Levasil 50 [g]	50	50	-
Levasil 300 [g]	-	-	50
				Polychloroprene Dispersion A [ g]	-	50	50
Polychloroprene Dispersion B [ g)]	50	-	-
				Solids content of the mixture [% ]]	44	41.5	31.5
Optimal amount of 2% Manutex solution [ g]	30	60	80
				The solid content of the concentrated phase [% ]]	60.15	63.4	77
The solids content of the clear solution after drying at 100 [% ]](Polymer, alginate, SiO)2)	5.1	2.4	18.3
				The solid content of the clear liquid after pyrolysis [% ]](SiO Only2)	4.48	1.84	16.8
The content of organic matter in the clear liquid [% ]]	0.62	0.56	1.5

50 grams of Levasil and 50 grams of the polychloroprene dispersion were mixed and a 2% Manutex solution was added. After 24 hours, two samples were taken from the lower concentrated phase. The viscosity of the samples was measured (Brookfield, spindle nr. 3, 60/min) and the solids content was measured after drying at 100 ℃. The supernatant phase contained solids (dried at 100 ℃). After pyrolysis, a solid remains, containing silica.

Example 9 composition of the post-creamed dispersion, depending on the concentration of creaming agent:

50 g of Levasil 200A (32%) and 50 g of polychloroprene dispersion B (38%) were mixed and a 2% solution of Manutex was added in the amounts specified. After storing the resulting mixture, the concentrations of the components in the two phases were determined (absolute data). The results are summarized below and depicted in fig. 1.

Figure 1 shows the solids content (y-axis) of the dispersion mixture at various concentrations (x-axis) of Manutex alginate given in%. The solid line connects the data points for organic content in the upper phase and the dashed line connects the SiO in the upper phase₂And (4) content. The squares represent the organic content in the upper phase and the triangles represent the SiO in the lower phase₂And (4) content. As can be seen from the figure, SiO is considered₂The higher the concentration of Manutex (alginate), the better the result. The organic content increased slightly in the upper phase (supernatant) and remained constant in the lower phase (high solids zone). But we see that in the lower phase, e.g. SiO in the high solids region₂The content is obviously improved. The chemical composition of the organic and inorganic portions in the high solids region changed from 68% organic and 32% inorganic to 57% organic and 43% inorganic.

Examples 10 and 11 the creaming process was accelerated by centrifugation with direct addition of the solid creaming agent:

the results show that centrifugation for about 10 minutes is sufficient to achieve the desired results, as follows inorganic SiO in the "high solids" phase₂And high amounts of organic polymer dispersions.

Claims (14)

1. A process for concentrating an aqueous dispersion comprising organic polymer particles and silica particles, comprising the steps of:

a) providing an aqueous dispersion comprising organic polymer particles and silica particles, said dispersion having an initial content of organic polymer and an initial content of silica;

b) contacting the dispersion of step a) with a creaming agent to produce an aqueous clear phase and an aqueous concentrated phase,

said clear liquid phase having a lower content of organic polymer than the initial content of organic polymer in the dispersion of step a) and/or having a lower content of silica than the initial content of silica in the dispersion of step a), and

said concentrated phase having a higher content of organic polymer than the initial content of organic polymer in the dispersion of step a) and/or having a higher content of silica than the initial content of silica in the dispersion of step a), and

c) separating the clear phase from the concentrated phase.

2. The process according to claim 1, wherein the organic polymer particles are selected from styrene butadiene rubber particles, acrylonitrile butadiene rubber particles, polychloroprene particles, chloroprene-dichlorobutadiene copolymer particles, polybutadiene particles, polyisoprene particles, chlorinated polyisoprene particles, polyurethane particles, natural rubber particles, polyvinyl chloride or (meth) acrylate particles and/or copolymer particles thereof.

3. The method according to claim 1, wherein the organic polymer particles are present in the form of a polymer latex.

4. The process according to claim 1, wherein the initial content of organic polymer in the dispersion of step a) is from ≥ 20% to ≤ 99% by weight.

5. The process according to claim 1, wherein the average particle size of the organic polymer particles, determined by ultracentrifugation according to H.G. Muller, Progr. Colloid Polymer.Sci.107, 180-.

6. The process according to claim 1, wherein the silica particles are present in the form of a silica sol, a silica gel, a dispersion of pyrogenic silica, a dispersion of precipitated silica or a mixture of these.

7. The process according to claim 1, wherein the initial content of silica in the aqueous silica dispersion of step a) is from ≥ 1% by weight to ≤ 80% by weight.

8. The process according to claim 1, wherein in the aqueous silica dispersion of step a), the silica particles have an average particle size, determined by ultracentrifugation according to H.G. Muller, Progr. Colloid Polymer. Sci.107, 180-.

9. The process according to claim 1, wherein in the dispersion of step a) the silica particles have a bimodal or multimodal particle size distribution.

10. A process according to claim 1 wherein the creaming agent is selected from the group consisting of alginates, cellulose derivatives, agar, poly (meth) acrylates, and/or copolymers of alkyl (meth) acrylates and/or styrene with unsaturated sulfonic acid derivatives or ethylenically unsaturated mono-or polycarboxylic acids or salts thereof.

11. A process according to claim 10 wherein the creaming agent is methylcellulose.

12. The process according to claim 1, wherein the creaming agent is provided in the form of an aqueous solution and the creaming agent content in the aqueous solution is between 0.5% by weight and 10% by weight.

13. The process according to claim 1, wherein the creaming agent is present in an amount of ≥ 0.2% by weight to ≤ 10% by weight, based on the solid content of the dispersion of step a).

14. The method according to claim 1, wherein said separation in step c) is at least partially performed by centrifugation.