DE2232254A1 - Hardened thermoplastics rubber - by mixing SB copolymer and polystyrene with added silica preventing segregation - Google Patents

Abstract

A method of making granulate of a homogeneous mixt. of thermoplastics butadiene-styrene-copolymers with polystyrene, utilising conventional plastics processing machines, is as follows; these two components, together with other additives are combined in a rapid mixer at up to 170 degrees C to form a plastic mass; then silica or related products are added to bring it to a fluid state. In a preferred variant, 100 parts buadiene-styrene copolymer, 30 parts polystyrene granulate, 15 parts naphthenic oil, 0.2 parts anti-oxidising agent, 0.2 parts heat stabiliser and 5 parts synthetic silica are mixed for 10 minutes to 120 degrees C in a mixer; to this hot mixt. 2-8 parts of silica are added. followed by furtehr mixing for 5-30 seconds. This results in a crumbled material of variable grain size.

Description

Horst Müller, Lichtenfels / Ofr. and Pranz Laux, 6651 Kleinottweiler / Uo Homburg (Saar) Process for the production of granulates based on Budatien styrene copolymers and polystyrene The invention relates to a process for the production of Budatien styrene copolymers and polystyrene on conventional plastics processing machines.

So-called "thermoplastic rubbers" based on Budatienstyrene copolymers have been known for a long time. It is also already known through training suitable thermoplastics, preferably polystyrene, the hardness of the Bertigungsmischwung to change, as it is well known that the hardness of the Bertig mix due to increasing polystyrene proportion zuiftmmt0 This means that polyblends with a Shore A hardness of 40 - 950 can be produced will. This mixture comes in the form of granules and can be added to conventional machines suitable for thermoplastics for the finished product, such as sealing profiles, Shoe sole and the like are further processed0 For homogeneous distribution of the two main components of the mixture, crumbly rubber and polystyrene in granulate form, it is necessary to intimately incorporate the individual components of the mixture knead each other in the warmth. As a rule, heated ones are used here Internal mixers - or kneaders - heavy construction. The individual components of the mixture are heated all at once or in a certain order Kneader given up to a temperature of 140 - 1700 c. mixed and after done Homogenization and, as a rule, ejected after cooling the kneader with cooling water. The mix then goes to a rolling mill. The rolled head strips peeled off from it are cooled and crushed by a granulator. The ejected hot mixture can also be fed to an extruder or a continuously operating kneader, whereby the mass is pressed through a perforated disc and either directly on the perforated disc or after cooling the individual strands into so-called lens or cylinder granules is cut. The disadvantage of this method via kneader and rolling mill is in addition to high machine investments in the high operating costs.

It would now be a significant cost saving if one were thermoplastic Could produce rubber granules on granulation systems, as they have been for a long time for the production of thermoplastic granules, especially PVC granules are used. In the production of PVC granules, the PVC powder is put together with the additives, such as plasticizers, stabilizers, paraffins and the like. in an "open" high-speed mixer by primary friction so far heated until a free-flowing powder has formed. This powder goes straight in a granulating machine, such as fin-fold or twin-screw extruders, planetary roller extruders Or the like., Is plasticized there and then crushed into granules.

The production of thermoplastic rubber granulate using the PVO process however, this is not possible without further ado. So occurs in the case of cold mixing, so of short-term mixing, again after the material to be mixed has left the mixer an extensive mixture of the two components rubber / polystyrene, as a result their different grain size and shape (Fig. 1) in the feed hopper of the granulating machine a, so that different finished granules in their composition the result are.

In addition, due to the different melting range of Budstienstyroloopolymerisaten and polystyrene a homogenization of the two components with normal granulating machines, insofar as this is not the case, granules are produced in the finished product Polystyrene particles that have not yet been melted are present. In the sense of a 'perfect Digestion of the polystyrene could one the granules several times the Graruliermaschine let go through, but this is not a rational one in terms of output Procedure would represent.

In the case of hot mixing above 750 ° C. however, the mix packs as a result So stickiness together, so that the mix once very difficult in the hallway Granulating machine can be transferred, on the other hand there as a coherent No longer lump or will. So the only way here would be via a rolling mill left over, However, this also does not significantly simplify the process compared to the conventional one Rubber preparation would be given.

The object of the invention is a method for economical and simple Manufacture of thermoplastic rubber granules using the PVC process which the disadvantages outlined above are no longer given.

According to the method according to the invention, this is possible in that Budatien styrene copolymers and polystyrene together with other additives in a high-speed mixer at a temperature of up to 1700 O. to a plastic one Mass combined and then by adding silica or related products be brought into a free-flowing state.

Small amounts of powdery substances are expediently added to the mix added with a large inner surface, so that on the one hand a crushing of the resulting hot dough-like mass is achieved into free-flowing crumbs and On the other hand, a kind of powder effect arises, which means that the prevents hot crumbs. The free-flowing material created in this way can now be similar to a PV0 mixture on an existing granulating machine can be further processed into granules.

Depending on the design and plasticizing capacity of the existing granulating machines two particularly preferred mixing processes are preferably possible.

1.) Mixing process for mixing Budatienstyrene copolymers and Polystyrene (Fig. 1), with -dem up to a temperature of max.

1400 C. is mixed. This is where the silicic acid compounds are added Crumbs that are partly firmly adhering, partly firmly enclosed, contain the little deformed polystyrene (Fig. 2 a). This mixing process is advantageously used in granulating machines which plasticize well, with a Granules with sufficient homogenization of the rubber / polystyrene components is obtained. The primary goal here is the non-segregation of the two components rubber / polystyrene accounted for in the hopper of the granulating machine, the in The thermal energy contained in the crumbs has a positive effect on the optimal distribution of the polystyrene in rubber. In this mixing process, the first thing to do is to "debak" the material to be mixed Additions of silicic acid compounds of only 1 - 2% necessary.

2.) Mixing process in which temperatures of 140 - 1700 C.

is being worked on. Here lies after the addition of silica compounds the polystyrene finely distributed in the rubber before (Fig. 2 b).

This mixing method is preferably used in granulating machines with moderate plasticizing performance, which is due to the already well-distributed polystyrene nevertheless a homogeneous granulate is obtained. Primary is this mixing process the weight on a good digestion of the polystyrene during the Mixing process. As a result of the stronger caking of the mix compared to the Method 1.) higher additions of about 4 - 8 fo are necessary for "de-baking".

Care should be taken with the latter method that the hot, crumbly Mixture during further processing in the sense of not sticking together again is treated as gently as possible.

In other words, the hopper of the granulating machine should, if possible be equipped with no or only a slow-running agitator. Doing so should the agitator arms must be designed so that the material is between the agitator arm and the hopper wall is not subjected to friction. If a cooling mixer is available, the mix can must be cooled to approx. 300 C., which prevents subsequent caking will.

It should be noted that the effect of improving flowability of powder smells due to the addition of synthetic silica is already known. The ability of synthetic silicas to produce large quantities is also known Soak up liquid without changing its flowability. In contrast however, it is not known to pour hot melts and melt-like products into free-flowing, not to transfer again 'packed goods.

An embodiment of the method is given below, the apparatus for performing this method in Pig. 3 is shown.

Description of the process Mixture formulation: 100.0 parts of Budatiene styrene copolymer 30.0 parts of granular polystyrene, 15.0 parts of naphthenic oil, 0.2 part of antioxidant 0.2 parts of heat stabilizer, 5.0 parts of static silica.

The above Mix components are in a 500 1 high speed mixer 1 for approx. 10 minutes up to a temperature of 1200 C.

mixed. At this temperature the mixture is honey-like Baked mass, with the polystyrene granulate depending on the mixing temperature more or less melted and stored in the rubber-like plasticized rubber and is bound. After 2 to 8 parts of silica have been added to this hot mass is mixed again about 5 to 30 lowers, whereby the previously coherent The dumpling disintegrates into crumbs with a grain size of approx. 5 - 30 mm. As a result of excess Silicic acid is practically powdered into the individual crumbs, which causes them to stick together again 0 By attaching a filter bag 2 to the mixer lid, a Prevents dust pollution of the work areas. The crumbly mix is now placed in the funnel of the granulating machine 3 and after homogenization in the Granulating machine 4 cut into granules at the granulating head 5.

Claims (7)

EXPECTATIONS 1.) Process for the production of granules of a homogeneous mixture from thermoplastic and styrene copolymers with polystyrene to conventional ones Plastics processing machines, characterized in that Budatiene styrene copolymers and polystyrene along with other aggregates in a high-speed mixer a temperature up to 1700 a. combined into a plastic mass and then by adding silica or related products to a free-flowing state to be brought. 2.) Method according to claim 1, characterized in that 100.0 parts Budatienstyroloopolymerisat, 30.0 parts of polystyrene granules, 15.0 parts of naphthenic Oil, 0.2 part antioxidant, 0.2 part heat stabilizer and 5.0 parts synthetic Silica in a blender for about 10 minutes to a temperature of 1200 a. mixed, 2 - 8 parts of silica are added to this hot mass, whereupon the whole thing again for about 5 - 30 seconds. is mixed until it disintegrates into crumbs of different grain sizes. 3.) The method according to claim 1, characterized in that the mix is heated up to a temperature at which the polystyrene granulate is not yet or is only partially melted. 40) Method according to claim 3, characterized in that the mix is heated to a temperature of max. 1400 C. 5.) The method according to claim 1, characterized in that the mix is heated to a final temperature at which the polystyrene is already homogeneously distributed is present in rubber. 6.) The method according to claim 5, characterized in that the mix to a final temperature of 140 - 1700 C. is heated. 7.) Method according to claim 1 and some of the preceding claims, characterized in that the crumbly Miachgut in a cooling unit, preferably in a cooling mixer, is cooled. L e r s e i t e