Technical Field

The aim of the present invention is to provide com- positions by using thermoplastic polymers (polyethylene, polypropylene, ethylene - vinyl acetate copolymer, poly(vinyl chloride) and its copolymers, polyurethane, polyamide, polyester, polystyrene and styrene copolymers, cellulose derivatives, as well as other thermoplastics), which compositions are characterized in that they contain - in addition to other modifying components - scrap leather and/or waste rubber as ingredient in a relatively high quantity (10-70 % by mass) as compared to the polymer matrix and these compositions may be processed by standard methods applicable for thermoplastics. Background Art

The Austrian patent specification No. 368 446 dis¬ closes a process for producing carpets made from poly- urethane-bonded rubber granulates, wherein 10-20 parts of polyurethane to be crosslinked and 100 parts of rubber are combined mechanically (by pressing).

The Austrian patent specification No. 355 291 dis¬ closes a process for producing floor coverings and carpets by using shredded tyres _ after cleaning the shredded wastes are linked together under pressure with curing materials.

The Austrian patent specification No. 339 797 des¬ cribes a floor covering for sport establishments, accord¬ ing to that solution 6-20 % of ground rubber of 1-10 mm grain size are applied together with crushed sand or breakstones, by using bituminous or latex binder.

The Austrian patent specification No. 370 168 dis¬ closes a process for producing building elements from used tyres and building bodies from the elements. The said des- cription relates to the assembling of elements and sections

obtained from a specific dimensional cutting of tyres, as well as to the shape of the building elements.

A permeable floor covering for sporting grounds, walk¬ ing surfaces and others may be known from the Austrian patent specification No. 287 047- According to the concrete aim, rubber granulates of 0,1-4 πim grain size are used, combined with adhesives, e.g. with caoutchouc dispersion. The properties of the floor covering may be changed with asbestos flour, sand and cement additives and the product may be dyed.

The patent specification No. DE 3 409 015 discloses a process for producing sheetlike or blocklike moulded bo¬ dies. The process comprises mixing ground rubber the grain size of which is inferior to 6 mm with prefoamed poly- ethylene and crosslinking the mixture in mould, under pres¬ sure.

Prom the Swiss patent specification No. 601 67 a sporting ground covering has become known, the surface abrasive layer and lower damping layer of which contain used tyre sections and polyurethane binder.

The patent specification No. DD 121 744 discloses a process for the utilization of used rubber granulates, especially for the purposes of road construction. The work¬ ing in of the rubber granulates of about 25 mm grain size obtained by grinding used tyres is carried out in concrete mixer, with cement, sand and water, thus a heat-insulating or elastic layer is formed, particularly for road construc¬ tion. As binder, bitumen can also be used.

The patent specification No. DD 252 945 describes a process for producing heat- and sound-insulating moulded bodies, wherein ground used tyres and phenol-formaldehyde resin binder are utilized for developing the insulating moulded bodies.

Thus the literature does not contain any data concern ing the combination of leather with polymer, and no really

up-to-date method is known for the processing and combina¬ tion of waste rubber, by means of which the ingredient could be embedded in the polymer matrix.

The aim of the invention is to process on a large scale waste rubber, leather and plastics by developed tech¬ nology and modern techniques into polymer mixtures or fi¬ nished products satisfying wide-spread demands.

It is well-known that ingredients are mixed with dif¬ ferent polymers in order to improve various properties or to reduce the price of the product, in many cases even at the cost of the deterioration of other, similarly important characteristics. Generally, ingredients of different type are used to improve the mechanical properties, electric features, sound- and heat-insulating capacity, resistance to heat and chemicals, etc.

Disclosure of the Invention

The compositions of the invention contain waste rubber and/or scrap leather as ingredient.

In the polymer systems combined in melt state the rub- ber and leather grains duly adhere to the polymer matrix, at the same time they bring about - as elastic fillers - a surprisingly peculiar behaviour of the polymer system.

Due to their macromolecular structure, the rubber and leather ingredients are very near to the polymers from physical and chemical point of view as well.

The specific surface of leather and rubber is high arising from the grinding process and owing to their fine structure, and as a result of their macromolecular nature they are in closer physical interaction with the polymer matrix molecule than the traditional, small molecular in¬ gredients of non-polymer type would be. In addition, the elastic rubber and leather ingredients of polymer type are attracted to the molecules of polymer matrix with secondary chemical forces, too. As a consequence, they may be filled in the basic

material in larger quantities than the usual ingredients, without hindering the forming operations of thermoplastic polymers, besides, the characteristics of the processed product change favourably. The properties of the compositions may be altered suitably in a wide range, primarily according as fundamen¬ tally different, fine-structure leather or rubber is used as ingredient in a wide range of concentration and with various distributions of grain size or the joint applica- tion thereof is intended to reach special combinations of properties. As secondary modifying possibilities, known odifyers may be used, such as fire retardants, blowing agents, moisture-binding agents, traditional fillers, co¬ lourin agents and pigments, lubricants and stabilizers, crosslinking agents, etc.

Examinations have been made with regard to the capa¬ city of a polymer to take rubber or leather. It has proved to be capable of taking 10-70 o by mass, the physical and chemical properties of the combined polymer can be modified by changing the quantity of rubber/leather and polymer, as well as by the specific surface of the filler.

After that, examinations have been carried out in such a manner that various polymers have been mixed in dif¬ ferent degrees, whereby their properties have been added up, then the above mentioned quantity of leather and/or rubber ingredient was fed. It has turned out that the phy¬ sical and chemical properties of the new polymer mixtures can be changed favourably as compared to the previous ones. During these experiments it has been noted that the application of a polymer containing vinyl acetate (EVA), e.g. ESC0RINE UL 0-0220 CH 1, has changed the properties of the polymer mixture in an extremely favourable manner. It is well-known that a lot of polymers contain ad¬ ditives of tenside type which have lubricating effect or facilitate the mixing with other polymers, as well as

contribute to the better formation of secondary bonds of the elastic filler (rubber/leather).

After the above conclusions, research has been carried out to the effect of how the various tensides would in- fluence the linkage of polymer mixtures to an elastic fil¬ ler. With this end in view, tensides of various types and in various quantities (0,02-5 % by mass) have been added to various quantities of polymer mixtures and to this has been added the rubber and/or leather ingredient. By means of the obtained filled polymer mixture there have been brought about materials wit extremely good physical and chemical properties, changeable in a wide range and suitable for multiple utilization.

The structure of the filled polymer mixtures has been examined with electron microscope and it has been found that in case of the tenside containing filled polymer mix¬ tures the polymers receive the filler favourably, their ad¬ hesion is very strong, the objects produced thereof tolerate deformation better, without interruption of contact. The fillers used for polymers up to now were mainly inorganic materials, the continuity of which was broken in the polymer mixtures, therefore they resulted in unfavour¬ able properties.

On the basis of our experiments it can be stated that the polar parts of the leather/rubber filler establish con¬ tact with the polar groups of the tenside, thus the tenside- -coated filler shows outwards a nonpolar character owing to the nonpolar ends of the tenside. The filler which has be¬ come nonpolar in this way is well miscible with nonpolar polymers (e.g. polyethylene, polypropylene). As a result of the tenside, the surface is increased in which favourable contact is established between the filler and polymer mix¬ ture.

In addition to an advantageous development of the technical parameters (tensile strength, modulus of elasticity,

sound- and heat-insulating capacity, resistance to che¬ micals, lame-proofness, density, etc.), the practical applicability of these compositions has a great economic and environment protecting advantage. The destruction, safe also from the point of view of environment protection, or profitable reutilization of waste rubber and leather accumulating in large quantities causes great concern all over the world. For example, scrap leather may be destroyed only in closed stoves which in- volves considerable costs. The chromium containing ash arising in the stove may be stored only in poison ceme¬ teries.

In Hungary about 13-15-000 tons of chrome-tanned scrap leather and about 40.000 tons of waste tyres arise a year. For the compositions of the invention vegetable- and chrome-tanned scrap leathers arising in tanneries, scrap leathers of shoemaking and clothing industries, wastes of the rubber industry (first of all used tyres) may be utilized in crushed, ground state, but waste polymers are also suitable (first of all poly(vinyl chloride) and poly- urethane)•

From the wastes fine ground material may be produced in two ways:

1. Traditional process: Hide-fibres or ground rubbers are produced in knife mills.

By this process materials of the following grain size are obtained: under 0,50 mm 15

0,50 - 1,00 mm 35 % above 1,00 mm 50 %

2. Cold grinding:

It is a known but not wide-spread process. The waste rubber are cooled to -80 °c by standard methods, then passed through a special crushi g machine with an inner temperatur of -75 °C, As a result, fractions of the following fineness

are obtained: under 0,50 mm 60 % 0,50 - 1,00 mm 305δ above 1,00 mm 10 % After the preparatory processes the obtained hide fibres and/or ground rubbers are mixed step-by-step or con¬ tinuously with the polymers and additives corresponding to the individual formulae, at a temperature above the melt¬ ing point of the polymer components, preferably in a mixer ensuring the highest homogeneity.

The good characteristics of these compositions may be best utilized by processing on single-purpose machines, but the majority of the existing machines used for the pro¬ cessing of various polymers are also suitable for manu- facturing these compositions economically and in good quality.

From the mixtures granulates may be produced by extru¬ sion, from which plates, foils and other profiles may be extruded or numerous forms of products may be manufactured by injection moulding and pressing.

The appropriately chosen compositions are suitable for the extrusion of 0,5-5 mm thick plates which may be further formed by vacuum forming, deep drawing, pneumatic forming. Owing to their thermoplastic nature, the products produced from these compositions can be stuf -coloured and welded with their own material. For aesthetic and functional reasons, the surface of solid or foamed products can be changed, according to the demands, with known materials (e.g. foil and sheet made of traditional polymer, fleece, textile, leather, artificial leather, etc).

In certain cases the value of the product may be in¬ creased as a result of the peculiarity of the compositions of the invention that they retain their original leather and rubber smell, thereby they further the replaceability of the original leather and rubber products.

The compositions of the invention enable, on the one hand, the waste leather and rubber to be processed in as large a proportion as possible and, on the other hand, the wastes arising on process and on utilization may be pro- cessed again. Thus the quantity of material intended for final destruction may be reduced to minimum, but due to their high polymer content these compositions require con¬ siderably less heating energy and they pollute the environ¬ ment less than the starting scrap leather and waste rubber. The above mentioned advantageous properties of the compositions of the invention may be utilized above all in the following fields of application:

A. Walking surfaces (mainly with fire retardant additives)

- formation of the surfaces of undergrounds, railway trains, airports and other vehicles.

B. Vv'ater insulations

- groundwater insulations

- lining of basins, flood-preventing foils

- roof boarding - insulations for building industry.

In case of the applications under point B) there arises the advantage that the compositions may be welded on the spot with their own material.

C. Outsoles - finished products of the shoemaking industry

- repair network of the shoemaking industry.

D. Mechanical rubber goods

- automobile carpets

- cloth-reinforced conveyors - cloth-insertion belts

- washers, packings

- horticultural protecting foils for repeated utiliza¬ tion, the foils may be repaired.

The products may be reprocessed at any time, the manufactur- ing wastes may be returned in certain phases of the producti

Best Mode of Carrying out the Invention The following Examples illustrate the possibi¬ lities of carrying out in practice the solution of the invention. Example 1

In a laboratory inner mixer produced by Werner- Pfleiderer 30 % by mass of hide fibres, 30 % by mass of ethylene-vinyl acetate copolymer of ESCORENE UL (ESS0) 4028 type and 40 % by mass of linear poly- ethylene of TIPELIN PS 380-09 type are stirred for 20 minutes at 170 C, then the melt is cooled while pressed on a bowl into 2 mm thick plates. The cooled material is shredded with plate shears and ground in rotary grinder. From the ground material plates are extruded at 180 °C on Viscosystera laboratory extruder in plate production mode. The produced plate is vacuum formable.

Example 2

Under the conditions of Example 1 ground material is prepared from a mixture containing 50 by mass of hide fibres, 25 % by mass of ethylene-vinyl acetate copolymer of ESCORENE UL 4028 type and 25 - by mass of polyethylene of TIPELIN FS 340-02 TVK type. The ground material is then processed on a BATTENFELD BSKM 30/50 injection moulding machine. Oblong test specimen is obtained the size of which is 6 x 50 mm and the thickness is 1 and 3 mm. Example 3

Ground material is prepared under the conditions of Example 1, with the following composition: 15 by mass of hide fibres, 20 % by mass of ethylene-vinyl acetate copolymer of

ESCORENE UL 4028 (ESSO) type, 25 o by mass of polyethylene of TIPOLEN FA 2210 TVK type,

40 % by mass of aluminium hydroxide.

The melt is rolled on a bowl into 2 mm thick plates. The obtained material is favourable from the point of view of flame proof ess: after having been lit and the source of flame removed, it becomes self-extinguishable. Example 4

Under the conditions of Example 1, but applying an inner temperature of 150 °C, ground material is prepared with the following composition: 30 % by mass of hide fibres,

30 % by mass of ethylene-vinyl acetate copolymer of

ESCORENE UL 4028 (ESS0) type, 30 % by mass of polyethylene of TIPELIN PS 380-09 (TVK) type, 10 % by mass of azodicarbonamide of EVIPOR type (product of Egyesult Vegyimuvek). By rolling this melt into plates, a material is obtained which is foamed if put for 10 minutes in a drying oven heated to 180 °C and keeps its foam structure after cooling, it has excellent heat- and sound-insulating properties. Example 5

Under the conditions of Example 3 and with identical composition, 2 mm thick plates are rolled on a bowl in such a manner that simultaneously with charging the melt between the rolls, polyethylene fleece is introduced between the melt and the roll, on one or both sides of the melt. Thus a plate is obtained to which the polyethylene fleece sticks evenly due to its partial melting. Example 6 25 % by mass of polyethylene (TIPELIN PS 380-09, TVK),

25 % by mass of ethylene-vinyl acetate copolymer (ESCORENE

UL 4028, ESSO) and 50 o by mass of ground rubber of 0,40 mm grain size are equalized. From the mixture plates are produced on an extruder with slot die, at a temperature of 160-200 °C.

The obtained plate is pliable and solid. Example 7

To the composition of Example 6 0,2-4 % of azodicarbon¬ amide blowing agent is mixed and plates are prepared under the conditions of Example 6. The obtained product is pliable as rubber and has a foamed structure. Example 8

The foamed melt produced according to Example 7 is laminated, on calender coming after the extruder, with a 0,5 - 1,50 mm thick, solid polyethylene layer of TIPELIN PS 380-09 (TVK) type. One surface of the produced plate is of foamed structure, the other is solid and smooth. Example 9

On the extruder described in the previous examples, fire-retardant plate is extruded at 180 °C which was pre¬ viously converted into homogeneous mixture at 170 °C be¬ stirring with an inner mixer, the melt mixture was rolled between the calender rolls into 1 mm thick plates, shredded with plate shears, ground, then from the ground material plates were extruded.

Composition of the prepared fire-retardant plate: 40 io by mass of aluminium hydroxide,

20 _% by mass of polyethylene (TIPELIN FE 600-04, TVK), 20 % by mass of ethylene-vinyl acetate copolymer (ESCORENE UL 4028, ESSO),

20 % by mass of ground rubber (grain size: 1,4 mm). Example 10

Under the conditions of Example 6, plates are produced with the following composition: 50 % by mass of ethylene-vinyl acetate copolymer (ESCORENE UL 4028, ESSO), 40 io by mass of ground rubber,

10 _o by mass of scrap leather made fibrous in a known way.

Owing to the combined effect of the leather and rubber in- gredients, the properties of the obtained product are more

favourable than those of the plate with a composition ac¬ cording to Example 6. Example 11

Under the conditions of Example 10 plates are manufac- tured, with the exception that polyethylene of TIPELIN PS 380-09 (TVK) type and ethylene-vinyl acetate copolymer of ESCORENE UL 4028 (ESSO) type are used in 1:3 ratio as poly¬ mer component. Example 12 25 % by mass of polyethylene (TIPELIN PS 380-09),

25 % by mass of ethylene-vinyl acetate copolymer (ESCORENE

UL 0-0220 CH 1) and 507« by mass of ground rubber of 1 mm grain size are equalized. From the mixture plates are produced on an extruder with slot die, at a temperature of 170-200 °C. The obtained plate is solid and vacuum-formable.

Example 13 50 % by mass of ground rubber of 1 mm grain size, 28 % by mass of polyethylene of TIPELIN PS 330-09 type, 2 ^c o by mass of glycerine monostearate, 20 by mass of polypropylene are converted into melt on a bowl, then rolled into rubber plates.

Example 14 45 >5 by mass of leather,

3 % by mass of zinc stearate, 22 % by mass of ESCORENE UL 0-0220 CH 1, 30 by mass of TIPELIN FE 600-04 are mixed in a Werner-Pfeiderer inner mixer, then plates are extruded therefrom at 180 °C. The obtained plate is vacuum- -formable and dyeable.

Electron microscope tests were carried out to compare the structure of the products of the invention and of known products. The test results are given in Figures 1-4, wherein Figure 1 shows the structure of a product containing rubber

ingredient, without tenside, Figure 2 shows the structure of a product with identical composition, but containing tenside, Figure 3 shows the structure of a product containing leather ingredient, without tenside,

Figure 4 shows the structure of a product with identical composition, containing tenside. It appears from the drawings that in case of polymer compositions containing tenside, the ingredient - i.e. rub- ber or leather - is well embedded in the polymer matrix, in a homogeneous manner, while in case of compositions not containing tenside, agglomerated structure and considerably smaller adjoining surfaces between the ingredient and poly¬ mer matrix may be observed. The surface of the products prepared from the composi¬ tions of the invention may be combined, depending on the processing technology, with natural or artificial fleece or woven textiles, with stiff materials.