Ballast and process for the production of ballast

1. A process for the production of ballast for railway track laying and road construction and dike systems, said ballast comprising a polyurethane foam and ballast stones, said process comprising:

1) spreading out ballast stones,

and

2) applying a polyurethane foam forming reaction mixture between the spread out ballast stones, wherein the polyurethane foam forming reaction mixture consists of:

a) one or more isocyanate compounds selected from the group consisting of (I) polyisocyanates having an NCO group content of 28 to 50 wt. % and (II) NCO prepolymers having an NCO group content of 10 to 48 wt. %, in which the NCO prepolymers comprise the reaction product of one or more polyisocyanates having an NCO group content of 28 to 50 wt. %, with a hydroxyl group containing compound selected from the group consisting of one or more polyetherpolyols having a hydroxyl number of 6 to 112, one or more polyoxyalkylenediols having a hydroxyl number of 113 to 1100, one or more alkylenediols having a hydroxyl number of 645 to 1850 and mixtures thereof;

b) at least one or more polyetherpolyols having a hydroxyl number of 21 to 56 and a functionality of 1.8 to 8; in the presence of

c) up to 26% by weight, based on 100% by weight of the sum of reaction components b) through g), of one or more chain extenders selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, triethanolamine, glycerol, trimethylolpropane, and short-chain alkoxylation products having a hydroxyl number in the range of from 245 to 1850;

d) 0.05 to 5% by weight, based on 100% by weight of the sum of reaction components b) through g), of one or more blowing agents;

e) 0 to 5% by weight, based on 100% by weight of the sum of reaction components b) through g), of one or more catalysts;

f) 0 to 50% by weight, based on 100% by weight of the sum of reaction components b) through g), of one or more fillers; and

g) 0 to 25% by weight, based on 100% by weight of the sum of reaction components b) through g), of one or more auxiliary substances and/or additives, wherein said one or more auxiliary substances and/or additives is selected from the group consisting of stabilizers, coloring agents, flameproofing agents, and plasticizers;

wherein said polyurethane is formed by the reaction of a) with b) in the presence of c) and d) and optionally in the presence of e), f), and g),

wherein the isocyanate index of the polyurethane foam forming reaction mixture ranges from 70 to 130, and

wherein said polyurethane foam has a compression set of less than or equal to 0.01%, according to DIN EN ISO 1856; 40%, 5 min., 25° C.

2. The process as claimed in claim 1 , wherein component g) is selected from the group consisting of coloring agents, flame proofing agents, and plasticizers.

3. The process as claimed in claim 1 , wherein component g) is a coloring agent.

4. The process as claimed in claim 1 , wherein component g) is a flame proofing agent.

5. The process as claimed in claim 1 , wherein component g) is a plasticizer.

6. The process as claimed in claim 1 , wherein the one or more blowing agents are present in the amount of 0.3 to 3.5% by weight, based on 100% by weight of the sum of reaction components b) through g).

7. The process as claimed in claim 6 , wherein component f) is present.

8. The process as claimed in claim 6 , wherein component g) is present.

9. The process as claimed in claim 1 , wherein component b) is at least one or more polyetherpolyols having a functionality of 1.8 to 6.

10. The process as claimed in claim 1 , wherein component e) is present.