CS270990B1 - Method of polyurethans' solutions production - Google Patents

Abstract

The method of production of polyurethane solutions during which the heat generation in the first reaction phase is controlled by adding a diisocyanate component to a diol component in at least two stages so that the temperature does not exceed 120 degrees Celsius, and further course of the polymeric reaction of diisocyanate with diols is controlled by adding at least one low-molecular diol to the reaction mix of the polyol and diisocyanate component in at least two stages so that in a reactive mix there constantly is an excess of isocyanate groups. The polymeric reaction advantageously proceeds in at least one solvent, e.g. in dimethyl-formamide the reaction rate being controlled by adding the solvent to the reactive mix at least in two stages. The growth reaction of the polyurethane polymeric chain gets completed by aliphatic alcohol with 1 up to 6 carbon atoms in the chain.

Description

The invention relates to a process for preparing polyurethane solutions with easy control of the course of the reaction.

Currently, polyurethane solutions are produced in three basic ways. One is the production of polyurethane solutions by dissolving the granulate prepared by reacting the polymerization components in an extruder in various solvents. A disadvantage of this process is the need for additional dissolution of the polyurethane.

Another possibility is to prepare polyurethane solutions by reacting the polymerization components directly in the solvent solution in either a two-step or a one-step process. In the two-step process, a prepolymer is first prepared by reacting a polymeric diol in a diisocyanate, and this is further extended in the solvent solution by reaction with β low molecular weight diol. The disadvantage of this method is the low reaction rate of the elongation reaction and hence the high time required.

In a one-step process for the production of polyurethane solutions, all the components of the reaction are mixed together and the reaction is then carried out in a solvent solution. The disadvantage of this method of production is the high heat generation in the first phase of the reaction, especially when using a larger number of reaction components which form hard segments, i.e. diisocyanate and low molecular weight diol. Also, control of the course of the reaction and the structure of the polyurethanes is very difficult and requires the use of catalysts that impair the stability of the end product and the determination of end groups during the reaction.

These disadvantages are overcome by the process for the production of polyurethane solutions according to the invention, in which the diisocyanate is added to the reaction mixture in at least two stages in the initial phase of the reaction, thereby avoiding excessive heat generation in large reactors or reactors with low heat dissipation. reactions, such as chain branching to form allophanates, which would lead to deterioration of the polyurethane pitch. The progress of the polymerization reaction of the diisocyanate with the diols is controlled by the gradual addition of a low molecular weight diol, which also results in improved control of the polyurethane structure and a higher reproducibility of the physico-mechanical properties. It has further been found that by successively adding a low-fat diol to the reaction mixture of a polymer diol and a diisocyanate, a polyurethane structure is obtained which improves its structural strength, which is an important property especially for surface treatment polymers, thereby achieving higher abrasion resistance.

The polyurethane solutions of the present invention are prepared by feeding a portion of the solvent, a polymer diol, a portion of a low molecular weight diol, and a portion of a diisocyanate into a stirred stirred reactor. An additional portion of the diisocyanate is added so as not to overheat the reaction mixture, thereby avoiding undesired side reactions. The reaction mixture is stirred and maintained at the desired temperature, which is generally 20 ° C to 140 ° C, preferably 60 to 140 ° C. Gradual addition of other parts of the low molecular weight diol or a mixture of low molecular weight diols regulates the course of the reaction. During the reaction time, the viscosity of the resulting polyurethane increases, which is maintained at the desired level depending on the type of polymerization apparatus used by dilution with a solvent or a diluent which, when an aromatic diisocyanate is used, is dimethylformamide or its mixture with another solvent that dissolves the polyurethane being prepared. functional groups capable of reacting with 8 isocyanate groups,

CS 270 990 B1 or their reaction rate is of an order of magnitude different from that of the hydroxyl groups. This method of diluting the reaction mixture solution has the great advantage of keeping the reactants at a higher concentration (limited by the type of polymerization apparatus), thereby allowing a higher rate of polymerization than the conventional method in which the solvent is fed at the same time Catalysts are then often treated to deteriorate the properties of the product, particularly aging resistance.

When the desired molecular weight of the polyurethane is reached, the polyaddition reaction is terminated with an amount of a terminating agent, in particular a primary alcohol, sufficient to react with the free isocyanate groups contained in the polyurethane.

The polymer diol used to prepare the polyurethanes of this invention may be of the polyether type, for example polypropylene glycol, polyethylene glycol, polytetramethylene glycol, or of the polyester type, for example, polyethylene adipate, polybutylene adipate, polyhexamethylene adipate. For the surface-treatment polymers, polycaprolactones are preferably used. If some special properties of polyurethanes are required, polymer diols can be combined or copolymers used. The number average molecular weight of the polymer diol may range from 500 to 5,000, preferably 1,500 to 2,500.

The low molecular weight diols suitable for preparing the polyurethanes of the present invention are diols containing from 2 to 12 carbon atoms in their chain, for example ethylene glycol, butanediol, neopentyl glycol. However, it is also possible to use low molecular weight diols containing a benzene nucleus in their molecule, for example hydroquinone dihydroxyethyl ether.

As with polymer diols, a mixture of low molecular weight diols can be used.

There is also a wide variety of diisocyanates which can be used to synthesize said polyurethanes. These are primarily aromatic diisocyanates (4,4'-diphenylmethane diisocyanate, 2,4- or 2,6-toluenediisocyanate, etc.) but also aliphatic, for example hexamethylenediisocyanate or isophorone diisocyanate. In some cases, it is possible to use a mixture of several diisocyanates.

The process for preparing the polyurethane solutions of the present invention is best illustrated by the following examples, which, however, do not limit the scope of use.

Example 1

350 parts by weight of dimethylformamide, 200 parts by weight, parts of molten polycaprolactone of 2000, 8 parts by weight, parts by weight of neopentyl glycol and 19 parts by weight, parts by weight of 1,4-butanediol are charged into a reactor equipped with a stirrer and tempering. After homogenizing the reaction mixture, 80 parts by weight of 4,4% diphenylmethane diisocyanate are added. The temperature of the reaction mixture rises to 100 ° C.

Upon completion of the temperature rise, an additional 22.3 parts by weight of 4,4% diphenylmethane diisocyanate was added and the reaction mixture was maintained at 60-2 ° C with stirring while stirring. When a viscosity of 17.3 Pa · e is reached, 0.25 parts by weight of 1,4-butanediol dissolved in

92.5 parts by weight of dimethylformamide. The process of adding 1,4-butanediol ee was repeated until all 20 parts by weight of 1,4-butanediol were fed into the reactor. The addition of dimethylformamide was also repeated each time a viscosity of 17-3 Pa.s was reached. Once after all 20 masses, parts of 1,4-butanediol and 770 wt. dimethylformamide reaches a viscosity of 17 and 3 Pa.8. a further polyaddition reaction of 40 parts by weight of butanol is stopped. The finished polyurethane solution is then diluted to 25% with DMF.

CS 270 990 B1

Example 2

350 parts by weight of dimethylformamide, 200 parts by weight of molten polycaprolactone of 2000 and 20 parts by weight of 1 * 4-butanediol, respectively, are metered into the reactor of Example 1.

After homogenizing the reaction mixture, 90 parts by weight of 4 * 4 * diphenylmethane diisocyanate are added. After completion of the temperature rise due to the heat of reaction, an additional 12 * 3 parts by weight of 4 * 4 * diphenylmethane diisocyanate was added and the reaction mixture was kept at 60 ° C with stirring. Upon reaching a viscosity of 17-3 Pa.s. The reaction mixture was diluted with 92 * 5 parts by weight of dimethylformamide. The process of adding dimethylformamide was repeated each time the indicated viscosity was reached until all 770 parts by weight of dimethylformamide had been consumed. With a decrease in the reaction rate * indicated by the viscosity increase over time *, 2 parts by weight of 1 * 4-butanediol are added to the reaction mixture until all 27 parts by weight of 1 * 4-butanediol are consumed. When the viscosity reached after addition of all parts of dimethylformamide and 1,4-butanediol of 17-3 Pa.s · polyaddition reaction, 40 parts by weight of butanol were terminated. The finished polyurethane solution is diluted to 25% with dimethylformamide.

Example 3

The preparation of the polyurethane solution proceeds in the same manner and on the same apparatus as in Example 2 *, only 200 parts by weight of polycaprolactone is used, 200 parts by weight of polybutylene adipate of an average 2000 MW molecular weight are used.

Example 4

300 parts by weight of dimethylformamide * 200 parts by weight, parts by weight of polybutylene adipate of 2000 and 3 parts by weight, and parts by weight of 1 * 4-butanediol, are metered into the reactor of Example 1.

After homogenizing the reaction mixture, 20 parts by weight of toluene diisocyanate are added. After completion of the temperature increase due to the heat of reaction, an additional 4 parts by weight of toluene diisocyanate were added and the reaction mixture was kept at 60 ° C with stirring. When a viscosity of 15 - 3 Pa.s. The reaction mixture is diluted with 100 parts by weight of dimethylformamide. The process of adding dimethylformamide was repeated each time the indicated viscosity was reached until all 770 parts by weight of dimethylformamide had been consumed. As the reaction rate *, which is indicated by the viscosity increase over time *, is reduced to 0 * 4 parts by weight of 1 * 4-butanediol. When the viscosity reached after addition of all parts of dimethylformamide and 1,4 * -butanediol 15-3 Pa · s, the polyaddition reaction was terminated with 40 parts by weight of butanol. The finished polyurethane solution is diluted to 20% with methyl ethyl ketone.

Example 5

The preparation of the polyurethane solution proceeds in the same manner and on the same apparatus as in Example 2 only the polyaddition reaction is terminated instead of 40 masses, parts of butanol 20 masses, parts of ethanol.

Example 6

The preparation of the polyurethane solution proceeds in the same manner and on the same apparatus as in Example 2 * only the finished polyurethane solution is diluted to a concentration of 12% with methyl ethyl ketone.

Claims (4)

Process for the production of polyurethane solutions, characterized in that the heat generation in the first phase of the reaction is controlled by adding the diisocyanate component to the diol component in at least two stages so that the temperature does not exceed 120 ° C and the polymerization reaction of the diisocyanate with diols is controlled. % of one low molecular weight diol to the reaction mixture of the polyol and diisocyanate component in at least two stages such that there is a constant excess of isocyanate groups in the reaction mixture. 2. A process according to claim 1 wherein the polymerization reaction is carried out in at least one solvent, for example dimethylformamide. 3. A process according to claim 1, wherein the reaction rate is controlled by adding the solvent to the reaction mixture in at least two stages. 4. A process according to any one of claims 1 to 3, wherein the growth reaction of the polymeric polyurethane chain is terminated with an aliphatic alcohol with 4 to 1 to 6 carbon atoms in the chain.