DE29515721U1 - Rubber grist - modified thermoplastics - Google Patents

Description

Description

Ground rubber modified thermoplastics as a replacement or blend of thermoplastic elastomers (TPE) or impact modified thermoplastics.

In recent years, thermoplastic elastomers (TPE) have become economically viable. They combine good mechanical properties with the advantages of thermoplastic processing. The development potential is determined by the range of classic, cross-linked elastomers that exist today. These start with soft silicone rubbers and extend to extremely stable perfluoroelastomers.

In polymer research, the development of polymer blends has reached a high level. Polymer blends are plastics that are produced by compounding various organic polymers via the melt. This makes it possible to achieve properties that were previously not achieved with known homopolymers and multipolymers. The reason for this development is the requirement for higher utility values and more productive processing technologies.

Most polymers are thermodynamically immiscible with one another. In many cases, chemical incompatibility also prevents the polymers from being finely dispersed into one another. However, it is precisely the finely dispersed distribution that has a significant influence on the interaction in the phase boundaries and thus also on the properties of the polymer blend. Polymer blends made of thermoplastic polymers and elastomers are of particular interest here. Thermoplastics with an elastomer content of over 50% are referred to as thermoplastic elastomers (TPE). If the elastomer content is less than 30%, they are referred to as impact-modified thermoplastics.

* «GebgauchsmtKteranmeMiufg * Page 4

In order to achieve high strength values in these polymer blends, the dispersed elastomer component is vulcanized in the thermoplastic matrix. The mixing process of the two polymers must be carried out in such a way that the cross-linking reaction only occurs when the elastomer is finely dispersed in the thermoplastic matrix. For the TPEs, polypropylene (PP) is used in particular as a matrix polymer. An ethylene-propylene-diene copolymer (EPDM) is used as the elastomer component, which is usually incorporated into the PP matrix during the polymerization phase. In the other case, uncross-linked EPDM virgin material is distributed into the thermoplastic matrix in a compounding process, e.g. on a twin-screw extruder.

In addition to the chemical bonds that lead to the formation of macromolecular chains from monomers, physical bonds hold the macromolecules together to form compact polymer materials. These physical bonds can also be viewed as interactions between the neighboring atoms of these macromolecules. A distinction is made between:

• Hydrogen bonds,

• Dipole interactions,

• induced dipole interactions and

• Dispersion interactions.

The chemical bond energy is many times greater than the physical bond energy. However, it must be taken into account that the number of interactions between two macromolecule chains can correspond to the number of monomer units in the chain. This may result in the total energy contribution of the interactions being significantly higher than that of the chemical bonds. The prerequisite here is the immediate proximity of the neighboring macromolecules. In different polymer chains, an interaction between the macromolecules can only occur if the polymers are thermodynamically miscible. Most polymers are thermodynamically immiscible or

'»Cjebrauchsrrmstefanmeiaung· Page 5

Mixing range Miscibility gaps depending on temperature, concentration and molar mass.

The thermodynamic incompatibility of different polymers is, however, one reason why new properties can be achieved in a polymer alloy. These new properties result from the combination of the properties of the different polymers, some of which are retained in the polymer alloy.

When mixing or compounding, interfaces are created between the different polymer phases. Low compatibility means few interactions in the interfaces of the polymer phases, which leads to a low strength of the compound. With higher compatibility, the dispersity or the degree of distribution of one polymer phase in the other also increases. For the subsequent processing, it is necessary to stabilize the phase distribution achieved. The aim is therefore to create compounds with a finely dispersed distribution of one polymer in another with good adhesion or interaction in the phase interfaces despite low thermodynamic miscibility. Within the scope of the invention, radical formers (e.g. peroxide) or acids (e.g. maleic anhydride) or functionalized copolymers containing double bonds are used for chemical bonding. The matrix is protected by antioxidants (e.g. phenols) against degradation due to environmental influences (e.g. light, heat, etc.).

The invention specified in claims 1-4 is based on the problem that, in contrast to thermoplastics, vulcanized rubber residues can no longer be melted and thus, as production waste and after the end of their product life, can no longer be used directly for the manufacture of the original products. The residues can only be reused after a chemical, complex process which dissolves the cross-linking (so-called regeneration) or after mechanical shredding. The large-scale chemical process has been discontinued by most operators of such plants in the past due to environmental regulations and lack of economic viability. Shredded rubber is

' .^rebrauchsimtstefanmefduiTg*

currently used as rubber granulate (1-6 mm) or as rubber powder (<1 mm) mainly in secondary products. In these applications, rubber or various PUR systems are also used as binding agents. Another, very small proportion due to the predominantly high requirements, is used in primary rubber processing (e.g. agricultural tires). Rubber powder is also used in the bitumen industry (e.g. roofing membranes).

The aim is to create a material that combines the positive properties of vulcanizates with the simple processing options for thermoplastics.

The problem is solved with the features listed in claims 1-4. Instead of the uncrosslinked rubber, a crosslinked rubber is used, which is mechanically crushed to a grain size of <600 pm (preferably 80 - 300 pm).

The invention makes it possible, in accordance with the Recycling Management Act, to recycle rubber waste into high-quality primary applications. Added to this are the economic advantages of the simple and therefore inexpensive processing options for the new material.

A further advantage of the invention is given in claim 3. By adding adhesion promoters and antioxidants, a large number of mechanical requirements can be taken into account.

" .C?ebreuchsMasteranmdäufl&*

An embodiment of the invention is explained using Table 1. It shows various mixtures of various recycled rubbers with PP and their characteristics from the tensile test according to DIN 53283.

Table 1: Composition and parameters from the tensile test according to DIN 53283 iiiiii iiiiiiiii lllllll IiIiIII 111 ipSSS Uli Iiiiiii [IIIIII iiiiiiiii HUH !is
iiiiiiiii Illllllllil &iacgr;&idiagr;&idiagr;&idigr;&igr;&igr;&igr;&igr;
Illllllllil 37.6 Lsmm
llllll: iiiiii mi IIIII llllljl liliiiiil SiSSiSSSS:
SiSSiSi-SS:
iiiiiiiii - 34.1 31.1 20.2 7 7 36 1781 100% PP 20% CR 31.1 26.6 28.4 9 9 33 1470 80% PP 30% CR 26.6 22.3 24.9 12 12 42 1255 70% PP 40% EPDM 22.4 20.3 20.4 18 18 43 887 60% PP 40% SBR 20.3 12.1 19.3 17 17 60 1013 60% PP 60% SBR 15.1 15.4 14.9 52 52 72 629 40% PP 60% EPDM 15.4 14.5 15.3 178 178 184 375 40% PP 60% EPDM
Foam rubber 14.5 14.4 175 175 184 321 40% PP

· oebpauchsiAGstttanmdfluntr*

Table 2: Abbreviations Abbreviation Description

CR EPDM NR PP PUR SBR SBS SEBS TPE

Chloroprene rubber Ethylene-propylene-diene rubber Natural rubber Polypropylene Polyurethane Styrene-butadiene rubber Styrene-butadiene-styrene Styrene-ethylene-butylene-styrene Thermoplastic elastomers Tensile strength Yield strength Tear strength Tensile elongation Yield elongation Elongation at break Elastic modulus

Claims (5)

* Taxpayer registration* * Page Protection claims IGrubber ground material-modified thermoplastics, preferably PP ₁ SBS, SEBS as a replacement or blend of thermoplastic elastomers (TPE) or impact-modified thermoplastics, characterized, that finely ground rubber with a grain size of <600μηη is physically incorporated into the matrix of the thermoplastic with 10-80% by weight. 2. Rubber ground material-modified thermoplastics according to claim 1 characterized, that finely ground rubber with a grain size of <600μιδι is partly chemically incorporated into the matrix of the thermoplastic with 10-80% by weight in addition to physical integration. Typical type: through peroxidic cross-linking or acid functionalization. 3. Rubber-modified thermoplastics according to claim 1 characterized in that that finely ground rubber with a grain size of <600pm together with adhesion promoters and antioxidants is chemically and physically incorporated into the matrix of the thermoplastic with 5-90% by weight in different proportions. 4. Rubber-modified thermoplastics according to claims 1-3, characterized in that that ground rubber residues with a grain size <600 μm (post-consumer goods or production residues) are used as finely ground rubber. 5. Rubber-modified thermoplastics according to claims 1-4, characterized in that that SBR, SBR/NR and EPDM with a grain size <600pm are preferably used as finely ground rubber or ground rubber residues.