Asphalt is apt to stick to conveyors, containers, working equipment and other implements that come into contact with it. To release the asphalt from these objects, release agents are needed. In prior art, the use of various oils, such as naphtha and fuel oil, for releasing asphalt is known.

A problem with these prior-art oils is that they are harmful to both people and environment. When such oils are sprayed, they evaporate and the workers are exposed to these noxious vapours. Moreover, naphtha and fuel oil pollute the environment.

Specification SU 801961 describes the use of a tall oil based oil, which may also contain acetone, as a releasing dressing composition in moulds.

Specification US 5194584 presents a vegetable oil based concrete release oil with tall oil dispersed in it. Specifications JP 63315207, CN 1113256, JP 47044968 and JP 72044968 describe concrete mould releasing compositions that, in addition to tall oil, also contain other components than acetone and water.

Specification FI 873349 presents a biodegradable, vegetable oil based, sticking composition that may contain tall resin oil distilled from tall oil, and its use as lubricant or mould release agent.

All the above-mentioned specifications describe mould releasing compositions, especially releasing compositions for concrete moulds. However, casting concrete into moulds and releasing the castings from the moulds is technically different from releasing asphalt from surfaces that come into contact with it, because concrete and asphalt mixtures differ from each other in their chemical nature. Concrete is

a hardenable mixture of cement, rock and water, whereas asphalt is an oil based solidifiable mixture.

None of the above-mentioned specifications state or suggest that tall oil based oil could be used as release oil for releasing oil based mixtures, such as asphalt.

Specification CH 542278 presents a liquid cleaning agent for releasing rubber, oil, coke, tar, resin and similar impurities from concrete. The cleaning agent contains aromatic hydrocarbons as its main component (50-55 parts) and saponified tall oil as an additional component.

A problem with the cleaning agent of the above specification, which also releases oil based mixtures, is that the main component is harmful to people and environment. Aromatic hydrocarbons are noxious to people and pollute the environment.

The object of the present invention is to eliminate the drawbacks described above.

A specific object of the invention is to disclose an environmentally friendly release oil that is safe for the user.

As for the features characteristic of the invention, reference is made to the claims.

The release oil used according to the invention is a water soluble, biodegradable tall oil based oil.

The release oil used according to the invention has the advantage that it is environment and user friendly. The tall oil based release oil does not pollute the environment and is not noxious to people.

A further advantage of the invention is that the release oil can be washed away with water, so the washing does not require the use of solvents.

Moreover, the invention has the advantage that the tall oil based release oil can be used

directly as asphalt release oil without harmful hydrocarbons or other detrimental additives.

The release oil used according to the invention is readily applicable for use at an asphalt factory to release asphalt from conveyors, containers, transport means, working equipment, such as e.g.

spreaders, tools and other surfaces that come into contact with asphalt.

It is possible to add acetone to the release oil used according to the invention to improve its sprayability/fluidity. In an embodiment of the invention, acetone is added so that the release oil to be used contains 0 + 20 w-% acetone, preferably 5 + 15 w-% acetone, while the rest is tall oil based oil.

The release oil used according to the invention may also be a mixture of tall oil based oil and water, in which case the release oil contains 50 i 40 w-%, preferably 50 w-% tall oil based oil and about 50 + 40 w-%, preferably 50 w-% water.

Furthermore, the release oil used according to the invention may contain various additives, such as antioxygen agent and/or anti-foaming agent.

Additives may have been added to prevent oxidation of the object to which the release oil is applied and/or of the tall oil based oil itself and to prevent foaming of the tall oil based oil. The amount of additives in the release oil used according to the invention is preferably very low to ensure that the release oil will meet the standards relating to environmentally friendly products.

In an embodiment, the release oil used according to the invention contains 0 - 5 w-%, preferably 0.5 - 2 w-% antioxygen agent and/or 0 - 5 w-%, preferably 0.2 - 1 w-% anti-foaming agent.

In the invention, asphalt' refers to natural asphalt or bitumen.

In the following, the invention will be described by the aid of a few examples.

EXAMPLE 1 The table below gives some properties of the release oil used according to the invention.

Table 1 Property Oil Viscosity mm2/s 32 40 OC Viscosity mm2/s 8 100 OC Viscosity index 220 Flashing point 200 Solidification -24 point Density g/cm2 20 OC 0.96 Due to its polar properties, the tall oil based oil sticks to the surfaces to be protected and lubricates them well. Having a low solidification point, the oil works well in cold conditions, too. In addition, the oil has a good heat resistance.

EXAMPLE 2 The release oil used according to the invention was tested by using it to release asphalt from the platform of a freight vehicle. The release oil used contained about 50 w-% tall oil based oil with about 10 w-% acetone and about 40 w-% water added to it. Tall oil based oil quickly forms a water emulsion and retains well its emulsified condition.

The release oil was sprayed onto the empty platform of a freight vehicle before loading it with asphalt.

The release oil used in a second test contained about 20 w-% acetone while the rest of it was tall oil based oil.

In a third test, release oil as used in the first test was sprayed onto the shovel box and elevator of a spreader and onto the tools before loading the spreader with asphalt.

It was established that the release oil used according to the invention is well applicable for use as asphalt release oil. It was also established that the release oil forms a good protection of the surfaces oiled with it.

The invention has been described above by presenting examples to illustrate the invention without limiting it in any way.