CA2263990A1

CA2263990A1 - Use of cashew nut husk oil in rubber and duroplastics recycling

Info

Publication number: CA2263990A1
Application number: CA 2263990
Authority: CA
Inventors: Martin Ernst Stielau
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-08-20
Filing date: 1997-08-19
Publication date: 1998-02-26
Also published as: EP0922068A1; AU3788897A; WO1998007777A1; JP2001504523A; BR9711222A

Abstract

The invention concerns the use of cashew nut husk oil in rubber and duroplastics recycling. It describes how this natural substance can eat into or even dissolve the vulcanised rubber car tyres and be involved in their revulcanisation.

Description

?1020CA 02263990 l999-02- 19USE OF CASHEW NUT HUSK OIL IN RUBBERAND DUROPLASTICS RECYCLINGFields of useThe present invention covers the recycling of rubber andthermosetting plastics.BackgroundCashew nutshell oil (hereinafter referred to as CNSO) is a by-product of the food industry and it is obtained in the preparation of cashew nuts.This liquid, which is found underneath the nutshell and is releasedwhen the shell is opened, is a 9:1 mixture of a fatty acid (anacardic acid, whichcontains a phenolic group at its benzene ring) and a diphenol (Cardol), both ofwhich have chains with 15 carbon atoms and 27 hydrogen atoms and one to threedouble bonds.The current uses of this product are mainly in the ?eld ofphenoplasts, where, by neglecting the chains with their double bonds, thefollowing occurs:0 after decarboxylating the fatty acid using a small amount of sulphuric acid,0 the phenolic groups are reacted with aldehydes. This results in products that?CA 02263990 l999-02- 19are mainly characterised by their high level of resistance to heat and abrasion.In the ?eld of rubber, an American researcher, Mortimer T. Harvey,had discovered and patented numerous ways of combining CNSO with thismaterial (US patent nÂ°s 1,819, 416 of 8ââ August 1931 and 1,771,785 of 28"âNovember 1925). It is obvious that these discoveries referred to "natural rubber",since synthetic rubber did not become important until after the second world war.Nowadays, crude oil derivatives account for more than 60% of rubber productionin general. Thus, the Harvey inventions were not able to acquire the economicimportance that they deserved. The present invention, however, refers to therecycling of rubber obtained from car tyres, which, depending on the level of thetechnique used, contain more than 50% synthetic rubber. In the ?eld of recycling,the preparation or incorporation of particles of old rubber before or duringagglomeration or revulcanization is always problematic. This invention - both thepreparation of the surfaces and their agglomeration - provides simple andeconomic solutions.An earlier patent of the same author (Portuguese patent applicationnÂ° 101.761 of 215â August 1995) explains how polyisocyanates can reticulateCNSO owing to the phenolic groups of the benzene rings.The present invention pays more attention to the side chains of thecomponents with their double bonds, as well as the obvious capacity of CNSO todepolymerize recycled rubber (i.e. in particular the mixture of natural andsynthetic rubber) and other thermosetting materials.Contents of the inventionIt has been discovered that at fairly high temperature, CNSO can?CA 02263990 l999-02- 19"melt" vulcanized recycled rubbers and other therrnosetting materials. Accordingto the composition and granulometry of the sample, the mixture is heated whilebeing stirred at a temperature of between 200 and 300Â°C, and newly reticulatableand/or vulcanizable rubbers are obtained. A preparation - even under coldconditions - of the old rubber with CNSO improves "recasting" in the newrubber, owing to the causticity of the product. As explained in theabovementioned Portuguese patent application nÂ° 101.761, this reticulation canbe effected using a diâ and/or polyisocyanate or sulphur, or both of them. It hasalso been discovered that in order to agglomerate the powder or rubber ?bresfrom car tyres, the mechanical results greatly improve if sulphur is used that hasbeen treated with CNSO. The acceleration and modi?cation systems seem toreact in the same way.Description of the inventionWhen rubber powder taken from car tyres is heated with CNSO, itcan be seen that as the temperature rises to above 180Â°C the recycled rubberdissolves in the liquid. In the case of a reticulated polyester or epoxy resin, asimilar phenomenon occurs at a higher temperature. After being left to cooldown, the mixtures obtained can be repolymerized. A way of using CNSO as abinder has also been discovered: the recycled rubber can be mixed when coldwith CNSO, sulphur and possibility accelerators and additives, and heated to atemperature of around 150Â°C for 15 minutes, in order to obtain appreciable bondsbetween particles of the old rubber and/or the new rubber. These results can beimproved by means of the preliminary preparation, followed by the vulcanizer:CNSO and sulphur are mixed together, for example in a ratio of 1:2, and are leftto react for at least 24 hours before use.Example 1?CA 02263990 l999-02- 19100 g of CNSO are heated at 180Â°C with 20 g of rubber powdertaken from a car tyre until the powder has completely "di1uted". The mixture isleft to cool down and 33 g of an MDI are added (Bayer type 44V20). A rubberwith a high level of elasticity and mechanical resistance is obtained.Example 210 g of CNSO are mixed with 20 g of powdered sulphur and themixture is stirred until a homogenous paste is obtained. After being left to maturefor 24 hours, plasti?ers and other additives can be added in order to make abinder for the recycled rubber.

Claims

1. Use of cashew nutshell oil (CNSO) in order to bind together particles of agglomerate of particles of recycled rubber.

2. Use according to claim 1 in order to bind the particles of recycled car tyres.

3. Use according to claims 1 or 2 in order to bind particles of recycled rubber containing more than 50% synthetic rubber.

4. Use according to claims 1 to 3 in order to form a pre-preparation of cashew nutshell oil with sulphur and in order for this pre-preparation to be used to bind the particles together by means of vulcanization.

5. Use of cashew nutshell oil in order to prepare rubber with a high level of elasticity and mechanical resistance so that the thermoset product, such as rubber from recycled car tyres, in particular recycled rubber containing synthetic rubber, polyester or epoxy resins, undergoes a depolymerization process and the depolymerized intermediate product thereby obtained is reticulated by adding a di- and/or polyisocyanate.

6. Product obtained according to any one of claims 1 to 5.