EP1577372A1 - Stable aqueous dispersion of particles , its use and its process of production - Google Patents

Abstract

Stable aqueous dispersion of particles (I) comprises a polymer stabilizer that stabilizes (I), where the stabilizer is a polycarboxylate. An independent claim is also included for the preparation of (I).

Description

Technical area

The invention relates to stable aqueous dispersions of particles.

The invention also relates to the use and Production process of such stable aqueous dispersions of particles.

State of the art

Aqueous dispersions of particles are in different Applications used. For example, graphite dispersions are called Lubricating and separating agent, for example in the hot forming of Metals used. It is required that such graphite dispersions stick to cold and hot metal surfaces and a lubricating and Make protective film. This should not only make the metal easier to deform, but also reduce tool wear during deformation. Or the Graphite dispersions are used as coatings, for example in the Internal coating of battery cups or rubber vulcanizates, for example for windscreen wipers, but also as conductive coatings on plastics, glass, Ceramic and other uses.

Of the aqueous dispersions in addition to physiological Safety and storage stability especially a universal processability required. For example, depending on the application, such dispersions mainly sprayed on. The viscosity of the aqueous dispersion plays thereby an important role and low viscosity dispersions are needed.

Graphite dispersions without additives are extremely high viscosity and partially thixotropic. This is due to the platelet-shaped structure of Graphite particles, which in liquids a so-called house structure build up. This house of cards structure is also of other platelike Substances, such as clay minerals or kaolins known. Here can however, through the use of peptizers this house of cards structure collapsed and the stability by using electrostatic effective substances are increased. Such mechanisms of action with Peptizers do not work with graphite.

According to the known state of the art are used for the stabilization of Graphite dispersions additionally used macromolecular substances. Such macromolecular substances from the linking groups of Mono- and polysaccharides act as protective colloids under increasing the viscosity. Also polyelectrolytes such as sodium carboxymethyl cellulose, Alginates or salts of lignosulfonic acids are known Spectrum. When using protective colloids according to the state There is a problem in the art of breaking down molecular chains, provided that they are added before grinding.

For the preparation of aqueous dispersions of particles, numerous Methods and formulations proposed.

In US 5800739 is a conductive graphite dispersion proposed, which is stabilized with a dispersant, which Having alkylene oxide groups and a hydrophilic lipophilic balance of 12 has. This balance is commonly referred to as HLB value Hydrophilic Lipophilic Balance). This materials are used as for example, polyoxyethylene-polyoxypropylene copolymers, sodium salts organic sulphonic acids, but also water-soluble polymers such as Polyvinylpyrrolidone, which is already known from US 2978428. A disadvantage of these dispersions is the rapid sedimentation. True will be wetted by the surface-active substances of the graphite and dispersed, but not sufficiently stabilized against sedimentation. Due to the platy structure of graphite, the sediments are very dense and difficult to redispersible.

US 5476580 proposes a process for the preparation of Coating materials on graphite and / or carbon black basis. The teaching looks a combination of water-soluble dispersing and wetting agents. When Dispersants are anionic substances, such as called Alkalipolyacrylate. As wetting agents are also anionic, but also cationic products used. The binders comprise virtually the entire group of poly- and Monosaccharides and resins and polymer dispersions. Some of the Although proposed substances are known as good dispersants, they have the disadvantage that the viscosity of the dispersions is greatly increased. As a result, in particular, the rheological behavior of the dispersion affected.

In US 4401579 an aqueous dispersion is proposed, which are essentially the prior art aids contains. As new is the use of fumaric acid and / or their Salts considered. Fumaric acid salts may have a lubricant effect However, they are without to improve the dispersion stability Effect.

All the known methods are liable as a disadvantage that the concentrations were not the use concentrations correspond. The dispersions must be at the desired level Application concentrations are diluted down. The resulting obtained low concentration lowers the effectiveness of the additives so much that Dilutions only a few hours sedimentation stable.

Presentation of the invention

Object of the present invention is to provide a stable aqueous To provide dispersion of particles having a high dispersion stability shows and as far as possible can be processed with almost all application methods.

According to the invention, this is achieved by the features of the first claim reached.

The advantages of the invention can be seen inter alia in that by the use of polycarboxylate as stabilizer and dispersant a high storage stability of the aqueous dispersion is achieved. The Polycarboxylate wraps around the particles and prevents them from becoming steric Stabilize the mutual approach of the particles and thus the Agglomerates. This is particularly advantageous because in disperse systems the size of the exchange surface, as well as the thickness of the boundary layers is authoritative. The specific phase boundary depends on hyperbolic Particle diameter. Very finely divided dispersions <1.0 microns therefore tend reinforced agglomerate, so that the theoretical stability advantage, such it results from the Stockschen law, by the education of large Agglomerate parts is lifted. Agglomerates sediment with comparable speed, as equal-sized primary particles. By the Use of polycarboxylates ensures agglomeration prevented.

By the binding of the polycarboxylates as Stabilisierungsbeziehungsweise Dispersant on the particle surface is the Stabilization by this mechanism. So the dispersion stays with you a dilution stable, since the stabilization is no longer above the viscosity he follows.

Further advantageous embodiments of the invention will become apparent the dependent claims.

Ways to carry out the invention

The present invention relates to a stabilizer or a Dispersants from the group of polycarboxylates for the production of stable aqueous dispersions of particles.

Polycarboxylates are comb polymers which consist of a Main chain, to the carboxylic acid groups as free acids or in the form of their Salts are bound, and side chains made of polyalkylene oxide. Such Polycarboxylates are known per se, e.g. from EP 1 136 508 A1, EP 1 138 696 A1 and EP 1 138 697 A1 of the Applicant. The revelation of this Polycarboxylates is included below.

The polyalkylene oxide or polyalkylene glycol side chains can over Ester bond, amide bond or ether bond attached to the main chain be. In addition to the carboxylic acid groups and the polyalkylene oxide side chains may contain other functional or non-functional groups to which Be tied to the main chain.

Such comb polymers can be obtained, for example, by copolymerization of unsaturated mono- or di-carboxylic acids with unsaturated Carboxylic acid esters, unsaturated carboxylic acid amides, allyl ethers or Vinyl ethers are produced. The carboxylic acids in the finished comb polymer may be in the form of their free acid or in whole or in part in the form of their salts available.

The comb polymers can also be prepared by polymer-analogous reactions getting produced. In this case, a polymer which is latent or free Carboxyl groups containing one or more compounds, the amine or Hydroxyl functions contained under conditions that are too partial Amidation or esterification of the carboxyl groups lead.

The polyalkylene glycol of the side chain is based on polymerized epoxy-containing compounds, such as ethylene oxide, propylene oxide, 1-butene oxide, phenylethylene oxide, etc. Preferably, the Polyether side chain thus made of polyethylene oxide or polypropylene oxide or a mixed copolymer of ethylene oxide and propylene oxide and has on the free End of a hydroxyl group, a primary amino group or an alkyl group having 1 to 20 carbon atoms which is linear, branched or cyclic is preferred a linear alkyl group having 1 to 4 carbon atoms.

These polycarboxylates have a molecular weight of 5,000 to 200,000, preferably 8,000 to 100,000, more preferably one Molecular weight of 10,000 to 80,000. The Cabonsäuresalze can Alkali metal or alkaline earth metal salts or salts of other di- or trivalent Metal ions, ammonium ions, organic ammonium groups or Be mixtures.

M =

Wasserstoff, Alkalimetallion, Erdalkalimetallion, zwei- oder dreiwertiges Metallion, Ammoniumion, organische Ammonium Gruppe oder eine Mischungen davon,

R =

jedes R unabhängig von den anderen Wasserstoff oder Methyl-,

R¹ und R² =

C₁ bis C₂₀ Alkyl, Cycloalkyl, oder Alkylaryl, -[AO]_n-R4,
wobei A = C₂ bis C₄ Alkylen, R4 = C₁ bis C₂₀ Alkyl, Cyclohexyl, oder Alkylaryl, und n = 2 - 250, bevorzugt n = 8 - 200, besonders bevorzugt n = 11 - 150,
insbesondere n = 11-100 ist,

R³ =

-NH₂, -NR⁵R ⁶, -OR⁷NR⁸R⁹,
wobei R⁵ und R⁶ unabhängig voneinander eine C₁ bis C₂₀ Alkyl-, Cycloalky-I oder Alkylaryl- oder Arylgruppe ist oder eine Hydroxyalkylgruppe, wie beispielsweise Hydroxyethly-, Hydroxypropyl-, Hydroxybutylgruppe ist, oder eine Acetoxyethyl- (CH₃-CO-O-CH₂-CH₂-), Hydroxy-isopropyl- (HO-CH(CH₃)-CH₂-), Acetoxyisopropylgruppe (CH₃-CO-O-CH(CH₃)-CH₂-), oder R⁵ und R⁶ zusammen einen Ring bilden, von dem der Stickstoff ein Teil ist, um einen Morpholin- oder Imidazolinring aufbauen,
wobei R⁷ eine C2-C4 Alkylengruppe und R⁸ und R⁹ unabhängig voneinander eine C₁ bis C₂₀ Alkyl-,
Cycloalky-,
Alkylaryl- oder Arylgruppe oder eine Hydroxyalkylgruppe wie beispielsweise Hydroxyethyl-, Hydroxypropyl- oder Hydroxybutylgruppe ist

a/b/c/d =

(0.1 - 0.9) / (0.1 - 0.9) / (0 - 0.8) / (0 - 0.3),

bevorzugt

(0.1 - 0.9) / (0.1 - 0.9) / (0 - 0.5) / (0 - 0.1),

mehr bevorzugt

(0.1 - 0.9) / (0.1 - 0.9) / (0 - 0.3) / (0 - 0.06),

noch mehr bevorzugt

(0.2 - 0.8) / (0.199 - 0.799) / (0.001 - 0.09) / (0 - 0.06),

insbesondere bevorzugt

(0.2 - 0.8) / (0.19 - 0.79) / (0 - 0.1) / (0.01 - 0.3), und a + b + c + d = ist.

Die Abfolge der bausteine a, b, c, d kann blockweise, alternierend oder zufällig sein.In one embodiment, the polycarboxylate according to the invention consists of four structural units (a, b, c and d) and has the structural formula A.

M =

Hydrogen, alkali metal ion, alkaline earth metal ion, divalent or trivalent metal ion, ammonium ion, organic ammonium group or mixtures thereof,

R =

each R is independent of the other hydrogen or methyl,

R ¹ and R ² =

C ₁ to C ₂₀ alkyl, cycloalkyl, or alkylaryl, - [AO] _n -R 4,
where A = C ₂ to C ₄ alkylene, R ₄ = C ₁ to C ₂₀ alkyl, cyclohexyl, or alkylaryl, and n = 2 to 250, preferably n = 8 to 200, particularly preferably n = 11 to 150,
in particular n = 11-100,

R ³ =

-NH ₂ , -NR ⁵ R ⁶ , -OR ⁷ NR ⁸ R ⁹ ,
wherein R ⁵ and R ^{6 are} independently a C ₁ to C ₂₀ alkyl, cycloalkyl-I or alkylaryl or aryl group, or a hydroxyalkyl group such as hydroxyethyl, hydroxypropyl, hydroxybutyl, or an acetoxyethyl- (CH ₃ -CO -O-CH ₂ -CH ₂ -), hydroxy-isopropyl- (HO-CH (CH ₃ ) -CH ₂ -), acetoxyisopropyl group (CH ₃ -CO-O-CH (CH ₃ ) -CH ₂ -), or R ⁵ and R ⁶ together form a ring, of which the nitrogen is a part, to form a morpholine or imidazoline ring,
where R ^{7 is} a C ₂ -C 4 -alkylene group and R ⁸ and R ⁹ are each independently a C ₁ to C ₂₀ -alkyl group,
Cycloalky-,
Alkylaryl or aryl group or a hydroxyalkyl group such as hydroxyethyl, hydroxypropyl or hydroxybutyl group

a / b / c / d =

(0.1 - 0.9) / (0.1 - 0.9) / (0 - 0.8) / (0 - 0.3),

prefers

(0.1 - 0.9) / (0.1 - 0.9) / (0 - 0.5) / (0 - 0.1),

more preferred

(0.1 - 0.9) / (0.1 - 0.9) / (0 - 0.3) / (0 - 0.06),

even more preferred

(0.2 - 0.8) / (0.199 - 0.799) / (0.001 - 0.09) / (0 - 0.06),

especially preferred

(0.2 - 0.8) / (0.19 - 0.79) / (0 - 0.1) / (0.01 - 0.3), and a + b + c + d =.

The sequence of building blocks a, b, c, d can be block-wise, alternating or random.

Polycarboxylates according to the formula A can be built up imagine, from a main chain of polymerized units of acrylic acid and methacrylic acid or a mixed copolymer thereof. The polyalkylanoxide side chains are linked via ester or amide groups to this main chain.

At the main chain of the polycarboxylates, besides the Carboxylic acid groups or the carboxylic acid salts and the polyalkylene glycol side chains still further groups bound via ester or amide bond be such as alkyl groups, cycloalkyl groups, aromatics, substituted aromatics, hydroxyalkyl groups, dialkylaminoalkyl groups, or heterocyclic rings in which the N of the amide group is an ingredient, such as For example, morpholine or imidazole.

Examples of groups R ³ which are bonded via their N as amides to the main chain are amine radicals which have one or two independent aliphatic, cycloaliphatic or aromatic radicals of 1 to 20 carbon atoms, such as, for example, methyl, ethyl, propyl, isobutyl. Propyl, butyl, iso-butyl or cyclohexyl radicals. Examples of such amine radicals are dibutylamine or dicyclohexylamine. Further examples are amine radicals with hydroxyalkyl groups such as ethanolamine or diethanolamine.

Examples of groups R ³ attached via their O as esters to the main chain are aliphatic, cycloaliphatic or aromatic radicals of 1 to 20 carbon atoms, such as methyl, ethyl, propyl, iso-propyl, butyl, iso Butyl or cyclohexyl radicals. Further examples are aminoalcohol radicals such as methyldiethanolamine, triisopropanolamine, triethanolamine, dibutylaminoethanol, diisopropanolamine, diethylaminoethanol, dimethylaminoethanol.

Any particles may be used as particles to be suspended containing graphite, but also metals and alloys, Metal compounds such as metal sulfides, metal oxides but also organic Compounds such as polyaniline and combinations of the aforementioned substances. This list is not exhaustive and is intended to be broadly applicable clarify.

Especially minerals such as graphite, molybdenum disulfide, Boron nitride, mica, microtalc, hydrotalcite or montmorillonite may be used become. These minerals may have a platelet-shaped structure, which consists of individual layer planes and in different directions each having different properties. For example, graphite is perpendicular to Layer plane electrically a bad conductor, parallel but a good conductor.

The structure of the polycarboxylates causes an interaction with the Particles / substrate, forming a polymer film and thereby achieve a steric shielding. This not only the agglomeration of the Particles prevented, but in addition the particles held in suspension.

Experiments have shown that the inventive polycarboxylates the particles in water well dispersed and that the obtained aqueous Dispersions have a low viscosity of 200 to 900 mPas, in particular of 300 to 600 mPas. This allows the use of such Dispersions in spray applications. This can be done in the classic compressed air spraying process (Air Spraying) as well as airless (airless) done. The dispersions according to the invention can also be used as lubricants, Release agent, coating, coating are used, the dispersion in addition to the spray application also by dipping method, by brush, Rollers, etc. can be applied

The dispersions of the invention, in addition to the suitability for All application systems also have a flawless surface on top coating surface. That it becomes a smooth streak-free surface, no crater formation (orange peel effect), no tears, impeccable Course and good adhesion (adhesion) achieved.

The novel polycarboxylates give aqueous Dispersions which are storable for at least more than 4 weeks.

The particle size of the particles which can be used in these dispersions is preferably in a size range of 0.05 to 40 microns, in particular 0.3 to 5.0 μm.

The stabilizer in the dispersion has a content / concentration of 0.1-5% by weight, preferably 0.5-2% by weight. The proportion / concentration the particle in the dispersion is preferably 1-40% by weight, in particular 10 to 30% by weight.

The following are some examples that illustrate the invention should further illustrate the scope of the invention but in no Restrict the way.

Examples polymers

• PEG1000
  = Polyethylenglykol mit einem mittleren Molekulargewicht von etwa 1000,
• PPG600
  = Polypropylenglykol mit einem mittleren Molekulargewicht von etwa 600,
• EO/PO(60/40)2000
  = Block-Copolymer aus Ethylenoxid und Propylenoxid im Verhältnis 60:40 mit einem mittleren Molekulargewicht von 2000,
• Mw = mittleres Molekulargewicht

The following polymers are some examples of polycarboxylates as can be used in slurries, especially mineral slurries. The details relate to the structural formula A.
Explanation of terms:

• PEG1000
  = Polyethylene glycol having an average molecular weight of about 1000,
• PPG600
  = Polypropylene glycol with an average molecular weight of about 600,
• EO / PO (60/40) 2000
  = Block copolymer of ethylene oxide and propylene oxide in the ratio 60:40 with an average molecular weight of 2000,
• Mw = average molecular weight

Polymer A1:

M=

H- und/oder Na

R =

H-

R¹ =

CH₃-PEG1000-

R² =

CH₃-EO/PO(60/40)1000-

a/b/c/d =

0.60/0.35/0.05/0.00

Mw =

13000

Polymer according to structural formula A with

M =

H and / or Na

R =

H-

R ¹ =

CH ₃ -PEG1000-

R ² =

CH ₃ -EO / PO (60/40) 1000-

a / b / c / d =

0.60 / 0.35 / 0.05 / 0.00

Mw =

13000

Polymer A2:

M=

H- und/oder Na

R =

H-

R¹ =

Gemisch von CH₃-PEG1000- und CH₃-PEG3000- im Mol-Verhältnis 60:40

R² =

CH₃-EO/PO(50/50)2000-

a/b/c/d =

0.660/0.339/0.001/0.000

Mw =

28000

Polymer according to structural formula A with

M =

H and / or Na

R =

H-

R ¹ =

Mixture of CH ₃ -PEG1000 and CH ₃ -PEG3000- in the molar ratio 60:40

R ² =

CH ₃ -EO / PO (50/50) 2000-

a / b / c / d =

0,660 / 0,339 / 0,001 / 0,000

Mw =

28000

Polymer A3:

M=

H- und/oder Na

R =

H-

R¹ =

CH₃-PEG1000-

R² =

CH₃-PEO500-

a/b/c/d =

0.65/0.33/0.02/0.00

Mw =

22000

Polymer according to structural formula A with

M =

H and / or Na

R =

H-

R ¹ =

CH ₃ -PEG1000-

R ² =

CH ₃ -PEO 500

a / b / c / d =

0.65 / 0.33 / 0.02 / 0.00

Mw =

22000

Polymer A4:

M=

H- und/oder Na

R =

H-

R¹ =

Gemisch von CH₃-PEG1000- und CH₃-PEG3000- im Mol-Verhältnis 50:50

R³ =

HO-CH2CH2-NH-

a/b/c/d =

0.75/0.20/0.00/0.05

Mw =

26000

Polymer according to structural formula A with

M =

H and / or Na

R =

H-

R ¹ =

Mixture of CH ₃ -PEG1000 and CH ₃ -PEG3000- in a molar ratio of 50:50

R ³ =

HO-CH2CH2-NH-

a / b / c / d =

0.75 / 0.20 / 0.00 / 0.05

Mw =

26000

Polymer A5:

M=

H- und/oder Na

R =

CH₃-

R¹ =

CH₃-PEG1000-

R³ =

Dicyclohexyl-NH-

a/b/c/d =

0.75/0.20/0.00/0.05

Mw =

26000

Polymer according to structural formula A with

M =

H and / or Na

R =

CH ₃ -

R ¹ =

CH ₃ -PEG1000-

R ³ =

Dicyclohexyl-NH-

a / b / c / d =

0.75 / 0.20 / 0.00 / 0.05

Mw =

26000

Polymer A6:

M=

H- und/oder Na

R =

H- für Struktur a und CH₃- für Struktur b und c

R¹ =

CH₃-PEG2000-

R² =

CH₃-EO/PO(70/30)2000-

a/b/c/d =

0.70/0.29/0.01/0.00

Mw =

36000

Polymer according to structural formula A with

M =

H and / or Na

R =

H- for structure a and CH ₃ - for structure b and c

R ¹ =

CH ₃ -PEG2000-

R ² =

CH ₃ -EO / PO (70/30) 2000-

a / b / c / d =

0.70 / 0.29 / 0.01 / 0.00

Mw =

36000

Polymer A7:

M=

H- und/oder Na

R =

H-

R¹ =

CH₃-PEG1100-

R² =

n-Butyl-PPO600-

R³ =

(n-Butyl)₂-N-CH₂CH₂-O-

a/b/c/d =

0.40/0.50/0.09/0.01

Mw =

18000

Polymer according to structural formula A with

M =

H and / or Na

R =

H-

R ¹ =

CH ₃ -PEG1100-

R ² =

n-Butyl-PPO600-

R ³ =

(n-butyl) ₂ -N-CH ₂ CH ₂ -O-

a / b / c / d =

0.40 / 0.50 / 0.09 / 0.01

Mw =

18000

Polymer A8:

M=

H- und/oder Na

R =

CH₃-

R¹ =

CH₃-PEG1100-

a/b/c/d =

0.50/0.50/0.00/0.00

Mw =

18000

Polymer according to structural formula A with

M =

H and / or Na

R =

CH ₃ -

R ¹ =

CH ₃ -PEG1100-

a / b / c / d =

0.50 / 0.50 / 0.00 / 0.00

Mw =

18000

Polymer A9:

M=

H- und/oder Na

R =

CH₃-

R¹ =

CH₃-PEG1100-

a/b/c/d =

0.75/0.25/0.00/0.00

Mw =

23000

Polymer according to structural formula A with

M =

H and / or Na

R =

CH ₃ -

R ¹ =

CH ₃ -PEG1100-

a / b / c / d =

0.75 / 0.25 / 0.00 / 0.00

Mw =

23000

Polymer A10:

M=

H- und/oder Na

R =

CH₃-

R¹ =

Mischung auf CH3-PEG500- und CH3-PEG3000- im Mol-Verhältnis 3:2

R² =

n-Butyl-PPO800-

R³ =

(CH₃)₂-N-CH₂CH₂O-

a/b/c/d =

0.74/0.23/0.02/0.01

Mw =

45000

Polymer according to structural formula A with

M =

H and / or Na

R =

CH ₃ -

R ¹ =

Mixture to CH3-PEG500- and CH3-PEG3000- in molar ratio 3: 2

R ² =

n-Butyl-PPO800-

R ³ =

(CH ₃ ) ₂ -N-CH ₂ CH ₂ O-

a / b / c / d =

0.74 / 0.23 / 0.02 / 0.01

Mw =

45000

Polymer A11:

M=

H- und/oder Na

R =

H-

R¹ =

Gemisch von CH₃-PEG1000- und CH₃-PEG3000- im Mol-Verhältnis 50:50

R³ =

(HOCH₂CH₂)₂-N-

a/b/c/d =

0.598/0.400/0.002/0.000

Mw =

52000

Polymer according to structural formula A with

M =

H and / or Na

R =

H-

R ¹ =

Mixture of CH ₃ -PEG1000 and CH ₃ -PEG3000- in a molar ratio of 50:50

R ³ =

(HIGH ₂ CH ₂ ) ₂ -N-

a / b / c / d =

0,598 / 0,400 / 0,002 / 0,000

Mw =

52000

Comparative Examples

In the comparative examples are aqueous dispersion of particles, especially platelet-shaped minerals, without the use of inventive polycarboxylates described.

Comparative Example 1: Graphite dispersion for the forging industry

In a container with stirrer 75 kg of deionized water are submitted and dissolved therein 5 kg of sodium silicate. Subsequently, 20 kg of graphite having an average particle size d ₅₀ = 1.5 microns is added with stirring. This is followed by passage through an agitator ball mill equipped with zirconia balls. The finished dispersion has a high viscosity of 2200 mPas. After 6 days, a sedimentation of graphite began.

Comparative Example 2: Graphite dispersion for the forging industry

On the basis of Comparative Example 1, a polyoxyethylene-polyoxypropylene Copolymer having a molecular weight of 12600 and a HLB value of 20 supplied. The amount of polyoxyethylene-polyoxypropylene Copolymer is used by the amount of that used in Comparative Example 1 Withdrawn water of 75 kg.

In a container with stirrer 73 kg of deionized water are submitted and dissolved therein 5 kg of sodium silicate. Thereafter, 2 kg of polyoxyethylene-polyoxypropylene copolymer and subsequently 20 kg of graphite having an average particle size d ₅₀ = 1.5 microns are added with stirring. This is followed by passage through an agitator ball mill equipped with zirconia balls. The finished dispersion has a high viscosity of 1020 mPas. After 6 days, a sedimentation of graphite began.

Comparative Example 3 Boron Nitride Dispersion

Based on Comparative Example 2 20 kg boron nitride with an average particle size d ₅₀ = 1.8 microns is now added instead of the graphite. The finished dispersion has a high viscosity of 1310 mPas. After 6 days, a sedimentation of the boron nitride began.

Examples according to the invention Example 1: Graphite dispersion for the forging industry

In this inventive example, which is based on the Comparative Example 1 is carried out, now the polymer A9 as an aqueous Solution supplied with a content of 35% of the polymer A9. The amount of used water according to Comparative Example 1 is characterized by the Amount of supplied 35% aqueous polymer A9 reduced.

In a container with stirrer 73 kg of deionized water are submitted and dissolved therein 5 kg of sodium silicate. Thereafter, 2 kg of polymer A9 are added as a 35% aqueous solution and subsequently with stirring 20 kg of graphite having an average particle size d ₅₀ = 1.5 microns. This is followed by passage through an agitator ball mill equipped with zirconia balls. The finished dispersion has a viscosity of 550 mPas and is storage-stable for more than 4 weeks.

Compared to Comparative Example 1, the viscosity of the Example 1 according to the invention about 4 times lower and is well suited for a spray application. Also the dispersion stability becomes with the employment of the Polymers A9 significantly improved.

Example 2: Molybdenum disulfide dispersion

As stated in Example 1 with the polymer A9, instead of the graphite 20 kg Molydändisulfid having an average particle size d ₅₀ = 1.4 microns are added. The finished dispersion has a low viscosity of 330 mPas and is storage-stable for more than 4 weeks.

Example 3: Boron nitride dispersion

As stated in Example 1 with the polymer A9, 20 kg of boron nitride having an average particle size d ₅₀ = 1.8 microns are added instead of the graphite. The finished dispersion has a low viscosity of 460 mPas and is storage-stable for more than 4 weeks.

Example 4: Graphite Dispersion for Screen Coating

In this example, the polymer A2 is used.

In a stirred tank according to Example 1 62 kg of water and 1.5 kg of polymer A2 is presented as a 40% aqueous solution. With continuous stirring, 13 kg of sodium silicate are dissolved and then added 15 kg of iron oxide having an average particle size d ₅₀ = 0.1 microns and 8.5 kg of graphite having an average particle size d ₅₀ = 1.5 microns. Thereafter, according to Example 1, a passage through an agitator ball mill. The dispersion obtained has a low viscosity of 380 mPas and is storage-stable for more than 4 weeks.

Example 5: Graphite dispersion for rubber coating

50 kg of a heat-reactive acrylic-latex-polymer emulsion having a solids content of 49% are placed in a stirred vessel. This emulsion is then diluted with 30 kg of deionized water with constant stirring. Then 2 kg of polymer A2 are added as a 40% aqueous solution and 18 kg of graphite having an average particle size d ₅₀ = 1.8 microns stirred. The dispersion is usable without further treatment and has a low viscosity of 650 mPas. This dispersion also shows a storage stability of more than 4 weeks.

Of course, the invention is not limited to those shown and limited embodiments described.

Claims (12)

Stable aqueous dispersion of particles, wherein the particles are stabilized in the aqueous medium by a polymeric stabilizer,
characterized in that the stabilizer is a polycarboxylate. Stable aqueous dispersion according to claim 1,
characterized in that the polycarboxylate has side chains corresponding to a comb structure. Stable aqueous dispersion according to claim 1 or 2, characterized in that the polycarboxylate has a structural formula A

having,

M =

Hydrogen, alkali metal ion, alkaline earth metal ion, divalent or trivalent metal ion, ammonium ion, organic ammonium group or mixtures thereof,

R =

each R is independent of the other hydrogen or methyl,

R ¹ and R ² =

C ₁ to C ₂₀ alkyl, cycloalkyl, or alkylaryl, - [AO] _n -R 4,
where A = C ₂ to C ₄ alkylene, R ₄ = C ₁ to C ₂₀ alkyl, cyclohexyl, or alkylaryl, and n = 2 to 250, preferably n = 8 to 200, more preferably n = 11 to 150,

R ³ =

-NH ₂ , -NR ⁵ R ⁶ , -OR ⁷ NR ⁸ R ⁹ ,
wherein R ⁵ and R ⁶ independently of one another are a C ₁ to C ₂₀ alkyl, cycloalkyl-I or alkylaryl or aryl group or a hydroxyalkyl group, or an acetoxyethyl- (CH ₃ -CO-O-CH ₂ -CH ₂ -) Hydroxy-isopropyl- (HO-CH (CH ₃ ) -CH ₂ -), acetoxyisopropyl group (CH ₃ -CO-O-CH (CH ₃ ) -CH ₂ -), or R ⁵ and R ⁶ together form a ring, of which the nitrogen is a part, to build up a morpholine or imidazoline ring,
wherein R ^{7 is} a C ₂ -C 4 -alkylene group and R ⁸ and R ^{9 are} independently a C ₁ to C ₂₀ alkyl, cycloalky, alkylaryl or aryl group or a hydroxyalkyl group,

that

a / b / c / d =

(0.1 - 0.9) / (0.1 - 0.9) / (0 - 0.8) / (0 - 0.3),

and a + b + c + d = 1. Stable aqueous dispersion according to claim 3,
characterized in that the hydroxyalkyl group is a hydroxyethyl, hydroxypropyl, hydroxybutyl group. Stable aqueous dispersion according to claim 3 or 4,
characterized in that

a / b / c / d =

(0.1 - 0.9) / (0.1 - 0.9) / (0 - 0.5) / (0 - 0.1), preferably

a / b / c / d =

(0.1 - 0.9) / (0.1 - 0.9) / (0 - 0.3) / (0 - 0.06).

Stable aqueous dispersion according to one of the preceding claims,
characterized in that the particles of graphite, metal, metal alloys, metal compound such as metal sulfide, metal nitride, metal oxides, and / or an organic compound and combinations of the aforementioned substances. Stable aqueous dispersion according to one of the preceding claims,
characterized in that the particles are mineral, in particular platelet-shaped minerals such as graphite, clay minerals, kaolins, molybdenum disulfide, mica, boron nitride, microtalc, hydrotalcite, montmorillonite or mixtures thereof. Stable aqueous dispersion according to one of the preceding claims,
characterized in that the particles are electrically conductive. Stable aqueous dispersion according to one of the preceding claims,
characterized in that the dispersion has a viscosity of 200 to 900 mPas, in particular from 300 to 600 mPas. Use of the stable aqueous dispersion according to one of preceding claims as a lubricant, release agent, coating and / or in a spray application. Process for the preparation of a stable aqueous dispersion according to claims 1 to 9,
characterized in that water is introduced, that an aqueous solution of the polycarboxylate is added, and that the particles to be suspended are added. Process for the preparation of a stable aqueous dispersion according to claim 11,
characterized in that after the addition of the particles, the solution thus obtained is further processed in a stirred ball mill.