Fine-particle, stable suspensions of functionalized, completely or partially hydrogenated nitrile rubbers
View Patent ↗Novel stable aqueous suspensions of a functionalized, completely or partially hydrogenated nitrite rubber are provided with very low emulsifier content and small particle diameter, furtheron a process for production thereof and the use thereof for producing composite materials via coating of substrate materials with the suspension.
1. A process for producing an aqueous suspension of a carboxylated, completely or partially hydrogenated nitrile rubber, characterized in that
1) a carboxylated, completely or partially hydrogenated nitrile rubber is first dissolved in an organic solvent to form an organic phase,
2) the organic phase is then brought into contact with an aqueous phase, the pH of which is greater than or equal to 6, where the water dissolves completely or partially in the organic solvent, the carboxylated, completely or partially hydrogenated nitrile rubber precipitates, and a suspension therefore forms, and
3) the organic solvent is completely or partially removed, wherein the organic solvent is selected from the group consisting of acetone, methyl ethyl ketone, formic acid, acetic acid, tetrahydrofuran, dioxane, or a mixture thereof.
2. The process according to claim 1 , wherein the pH of the aqueous phase which is used and with which the organic phase is brought into contact in step 2) is at least 3 under the proviso that within the organic phase from step 1) there is an amount of base present such that when the organic and aqueous phase are brought into contact in step 2) the resultant pH is at least 6.
3. The process according to claim 1 , wherein, in step 2), at least 10% by weight of water, based on the total amount of solvent used, dissolve in the solvent under the precipitation conditions.
4. The process according to claim 1 , wherein use is made of one or more organic solvents which undergo complete mixing in any ratio with water under the selected precipitation conditions.
5. The process according to claim 1 , wherein the concentration of the carboxylated, completely or partially hydrogenated nitrile rubber in the organic phase (i.e. entirety of solvent and nitrile rubber) is in the range from 0.1% by weight to 30% by weight.
6. The process according to claim 1 , wherein the dissolution of the carboxylated, completely or partially hydrogenated nitrile rubber takes place at a temperature in the range from 0° C. to 200° C.
7. The process according to claim 1 , wherein the dissolution of the carboxylated, completely or partially hydrogenated nitrile rubber takes place at a temperature in the range from 10° C. to the boiling point of the solvent used at atmospheric pressure.
8. The process according to claim 1 , wherein the temperature of the organic phase prior to addition of the aqueous phase in step 2) is above 0° C. and below the boiling point of the organic solvent, at the pressure at which the precipitation process is carried out.
9. The process according to claim 1 , wherein the pH of the aqueous phase is set via addition of one or more basic substances selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate, sodium phosphate, potassium phosphate, lithium phosphate, ammonia, primary, secondary or tertiary aliphatic or aromatic amines and derivatives of these.
10. The process according to claim 1 , wherein the pH of the aqueous phase is set via addition of one or more basic substances selected from the group consisting of methylamine, ethylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, methylethylamine, methylpropylamine, ethylpropylamine, diisopropylamine, tripropyl-amine, triethylamine, trimethylamine, dimethylethylamine and methylethylpropylamine.
11. The process according to claim 1 , wherein the ratio by mass of the organic phase which comprises the carboxylated, completely or partially hydrogenated nitrile rubber to the aqueous phase is from 50:1 to 1:1.