DE2131544C3 - Vulcanizable ter- or copolymer mixtures and their use - Google Patents

Description

The invention relates to vulcanizable ter- or copolymer mixtures based on ethylene-propylene terpolymers with the usual additives such as fillers, processing aids, plasticizers and the like as well as optionally blowing agents and their use for the production of especially foam rubber profile strips.

Ethylene-propylene copolymers stand out characterized by high aging resistance. They can be crosslinked with radical formers, especially peroxides. Ethylene-propylene terpolymers (EPDM) are well-known polymers that have unsaturation points from ethylene, propylene and a third, unsaturated component, for example dicyclopentadiene, hexadiene, Borneol derivatives, ethylidene norbornene and other compounds with at least two double bonds in the molecule. The vulcanizates produced from these polymers are characterized by a high resistance to aging and fatigue. Their processing properties vary greatly particularly with foot-filled mixtures, depending on the ethylene content of the copolymer. In particular Copolymers with ethylene contents above 60 percent by weight tend even at low injection speeds very strong to tear on the profile edges. It is also known that these types of copolymers the vulcanizate has a comparatively poor permanent tensile deformation, an unfavorable one Give impact resilience and an unfavorable elongation residue. The Shore hardness is significantly higher than that of the blends based on copolymers with a low ethylene content, the latter in turn show in the production of foam rubber profile strands, i.e. in the production of essentially cellular ones Vulcanizates, an only weakly developed vulcanization skin. This tendency This is particularly noticeable in the case of profiles, the comparatively deep, groove-like undercuts exhibit. Here in the bottom of the groove there is only an incomplete formation of a vulcanization skin, and the pores appear to be much stronger than in the edge area of the profile at the inside. The vulcanizate also sticks strongly to the heating mold and is difficult to remove from the mold. This one Disadvantages can be countered by the fact that the profile strand with a less distended Enclosure is provided, but such a measure leads to a cumbersome manufacturing process.

The object of the invention is to simplify and improve the production of foam rubber profile strips as well as the improvement of the properties of vulcanizable ter- or. Copolymer blends based on EPDM.

The object is achieved in that a mixture of ethylene-propylene copolymers and / or terpolymers is used, of which at least one

JO contains more than 60 percent by weight of ethylene.

Particular advantages are achieved when an EPDM terpolymer with an ethylene content of more than 60 percent by weight in one proportion

) 5 between 25 and 60 percent by weight, preferably 40 to 50 percent by weight of that contained in the mixture various EPDM copolymers and / or terpolymers is used. Such a mixture leads to vulcanizates with well-balanced properties with regard to skin formation, elasticity and softness of the cellular objects obtained. EPDM copolymers with an ethylene content appear particularly pronounced in this property of more than 60 percent by weight and ethylidene norbornene as the unsaturated component, with particular Advantages in the use of sequential polymers of this type can be achieved.

This diene component is probably also in the case of peroxide crosslinking for improved To blame hot tear resistance, especially in the case of peroxidically crosslinked cellular Products cannot be observed otherwise. But the pronounced one must be particularly surprising Softness and pliability of the fabric obtained

tig vulcanizates, especially since EPDM with a high ethylene content leads to vulcanizates of higher hardness which is due to the higher ethylene content of this polymer. But especially noteworthy is the very pronounced skin formation, which is also

bo continues in the groove bottom of the profiles and even there it appears a little more pronounced, so that see an extremely good resistance to deformations and stresses in them Areas shows.

The following exemplary embodiment shows an explanation of the invention.

A peroxide crosslinkable rubber mixture of the following structure is produced:

EPDM with an ethylene content

of about 50 percent by weight

EPDM with an ethylene content

of 65 percent by weight

Quick fuel furnace soot

Plasticizers

Basement filler and ZnO

peroxide

Blowing agent

Processing aid

100.00

From this rubber mixture, a blank is injected into a suitably designed Vulkan'isierform z. B. is vulcanized to the profile shown in the drawing with expansion.

For comparison, a similar rubber mixture was produced in which the EPDM copolymer with the higher proportion of ethylene by the same Amount of the first-mentioned copolymer was replaced.

The mixture according to the invention was distinguished from the conventional one by an improved one Injectability, the blanks made from the mixture according to the invention had an improved raw state

Parts by weight strength and greater handling safety

(Raw strength) against deformation were also

18.00 can be stored for longer as it has a lower tendency

had to relocate than the conventional

18.00 5 construction.

6.90 Both the injection molding and the one received

30.00 finished articles in the structure according to the invention showed

19.00 a smoother surface compared to using

3.60 of mixtures of the uniform EPDM with low

4.00 in rem ethylene content.

0.50 Particularly noteworthy is the much stronger formation of a closed surface skin of the profile made from the mixture according to the invention / its higher hot / tear resistance and its more even, finer pore pattern. It should also be emphasized that the closed Skin 2 in the expanded area of the profile strip is also particularly pronounced in the bottom of the groove 2 ', This is the case with an article of the same shape made from a conventional EPDM mixture Bending apart the professionals in this area Make flaws in the skin noticeable. The foam rubber part from the inventive EPDM mixture, which contains a ter- or copolymer with a higher ethylene content, appears against all expectation softer than the same part from a mixture that does not contain this ter- or copolymer.

1 sheet of drawings

Claims (4)

Claims; 1. Vulcanizable, optionally expandable mixture of two differentiated from one another binary and / or ternary copolymers of ethylene and propylene, which are the usual Additives such as fillers, processing aids and plasticizers as well as crosslinking agents and, where appropriate, I mean that the polymer mixture consists of: A: 40 to 75 percent by weight of a binary and / or ternary copolymer of the Ethylene with an ethylene content of less than 60 percent by weight and B: 25 to 60 percent by weight of a binary and / or ternary copolymer of the Ethylene with an ethylene content of more than 60 percent by weight. 2. Mixture according to claim 1, characterized in that ds9 is the diene component, at least im high-ethylene terpolymer, consists of norbornene and the terpolymer is a sequential polymer is. 3. Mixture according to claims 1 and 2, characterized in that it contains peroxide crosslinking agents contains. 4. Use of vulcanizable mixtures according to claims 1 to 4 for the production of foam rubber moldings, preferably profile strips with a solid outer skin and good weather resistance.