Description of the Prior Art WO-A-80/02846 discloses a method of manufacturing a sorbent of the kind referred to above. This material advantageously can be used in sorbing friction-reducing liquids, e. g. in connection with cleaning-up the site of a road accident where spilled oil and possibly other liquids may constitute a danger to other road users because the road surface has become slippery due to the oil spilled on the surface. The same situation can of course arise at other places as in buildings where oil or another fat liquid has been spilled on a floor surface which thus can be dangerous for people to walk on due to the risk of slipping.

In order to eliminate these risks it is proposed according to WO-A-80/02846 to increase the friction coefficient of the oil contaminated surface by mixing splinters of clay, i. e. a friction increasing substance, into the sorbent material. It is recommended to do this by admixing the substance to the urea formaldehyde material

during foaming thereof; no other way of adding the friction increasing substance to the sorbent is proposed.

Probl em invol ved When practicing the invention according to WO-A- 80/02846 it has been found that the friction increasing material, such as sand, entrained into the urea formaldehyde foam due to the brittleness of the foam separates from the foam and collects at the bottom of the container in which the sorbent is stored and delivered, and is not spread together with the liquid-absorbing material on the surface from which a contaminating liquid shall be absorbed by means of the liquid-absorbing material.

Summary of the Invention In order to overcome the problem accounted for the invention provides a liquid absorbing material comprising a hardened urea formaldehyde foam comminuted into porous pieces, and a friction increasing particulate substance, which is characterized in that the surface of the pieces of hardened urea formaldehyde foam and/or the particles of the friction increasing particulate substance is sticky to maintain the friction increasing particulate substance adhered to the surface of said pieces.

The invention also provides a method in manufacturing the liquid absorbing material, which is characterized in that pieces of hardened urea formaldehyde foam and/or the particles of the friction increasing particulate substance are sprayed with a heated oil to make the surface of the pieces and/or the particles, respectively, sticky after the oil having cooled, and that the pieces of hardened urea formaldehyde foam and the friction increasing particulate substance are tumbled together to make the substance adhere to the surface of the pieces.

Further features of the invention are defined in the dependent claims.

Detailed Description of the Invention A sorbent of the invention comprises pieces of hardened urea formaldehyde foam which are produced in the manner disclosed in WO-A-80/02846 and are coated with a surfactant such as soap water in order to increase the absorption rate of the sorbent. The pieces are then tumbled and a heated oil is sprayed onto the pieces during tumbling. Any kind of oil can be used but preferably the oil is a biologically degradable oil such as a vegetable oil. Linseed oil should be avoided, however, in view of the risk of self-ignition. According to the invention it is preferred to use rape oil. When the oil cools on the surface of the pieces a sticky surface will be left on the pieces.

Then, the sticky pieces of formaldehyde foam are tumbled together with a particulate friction increasing substance such as sand, ash, dry clay, or a similar particulate substance which adheres to the sticky surface of the pieces. The sorbent thus prepared is then packed into containers under hermetic seal.

Alternatively, the oil can be sprayed onto the particles of the particulate friction increasing substance during tumbling of the substance before it is tumbled together with the pieces of hardened urea formaldehyde foam. As another alternative the oil can be sprayed onto the pieces and the particles when they are tumbled together.

When a surface has been contaminated by crude oil, diesel oil, or any other fat liquid which makes the surface slippery the sorbent is spread over the contaminated surface and absorbs immediately the liquid and at the same time increases the friction of the surface due to the presence of the sand or a similar particulate substance in order to avoid the risk of persons slipping when walking on the surface or the risk of vehicles skidding on a contaminated road surface.