Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1997-02-27
1997-12-16
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
210767, 210773, 521 47, 521 59, 521 60, 521 94, 521146, 521129, C08G 920, B01D 3518
Patent
active
056986033
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to expandable styrene polymers containing recycled material which can be converted into foams having an improved foam structure.
Plastics based on styrene and styrene-containing copolymers are produced in large amounts and are used in many areas of industry. Considerable importance is also attached to foamed products.
The production and use of these products have been known for some time and have been described in a variety of publications.
A problem which has become particularly important in recent times is the recycling of used plastics.
In the case of polystyrene foams, various recycling methods are known.
One possibility comprises using polystyrene foam or unfoamed polystyrene waste for the extrusion of polystyrene foams.
This recycled material can be used either alone or as a mixture with fresh polystyrene.
The production of foams from the recycled materials can be carried out directly here, as usual, by steam-treatment of the polymer in the extruder with subsequent foaming to give boards or by extrusion to give minigranules, which can be impregnated with blowing agent and foamed.
It is also possible to dissolve the used polystyrene in monomeric styrene and to re-polymerize this solution by known methods, for example as described in U.S. Pat. No. 5,269,948 and JP-A-5,660,096.
A particular disadvantage in the polymerization of solutions of recycled polystyrene in monomeric styrene is that the foam structure of the foams produced using these styrene polymers is unsatisfactory. In particular when recycled polystyrene grades containing flameproofing agents are used, the resultant polystyrene foams have small cells, which is undesired.
It is an object of the present invention to provide polystyrene containing recycled material which has a uniform foam structure without the undesired fine-cell content and has good mechanical properties and is simple to prepare.
We have found that, surprisingly, this object is achieved by adding alkyldi(2-hydroxyethyl)amines to the solution of recycled polystyrene in vinylaromatic monomers, in particular styrene, during the polymerization.
The present invention accordingly provides expandable styrene polymers containing recycled polystyrene to which alkyldi(2-hydroxyethyl)amines have been added during the polymerization.
The content of recycled polystyrene in the novel products is from 10 to 50% by weight, based on the total weight of the polystyrene.
The alkyldi(2-hydroxyethyl)amines are added to the polystyrene containing recycled material in an amount of from 50 to 1000 ppm, preferably from 50 to 500 ppm, based on the total mixture of recycled material and monomer.
The alkyldi(2-hydroxyethyl)amines are preferably not added until after stabilization of the bead size, i.e. after addition of the suspension stabilizer.
The fact that it was possible to achieve the object of the invention by adding alkyldi(2-hydroxyethyl)amines was unforeseeable to the person skilled in the art.
Although the use of amines in the production of polystyrene foams has been disclosed, for example in DE-A-25 20 635, these products are usually used in the production of flameproofed polystyrene particle foams or as coating agents for improving the antistatic properties.
The prior art did not reveal that the use of such compounds in polystyrene foams containing recycled material would result in a uniform foam structure.
The alkyldi(2-hydroxyethyl)amine used is, in particular, a C.sub.12 -C.sub.14 -alkyldi(2-hydroxyethyl)amine. This product is commercially available, for example, as Armostat.RTM. 400 from Akzo.
In a particularly advantageous embodiment, the alkyldi(2-hydroxyethyl)amines are used together with a polyethylene wax. The latter is preferably employed in an amount of from 500 to 1000 ppm.
The polyethylene waxes used here generally have a mean molecular weight (number average) of from 2000 to 6000, preferably from 2000 to 4000, particularly preferably from 2500 to 3500. A particularly suitable polyethylene wax is BASF Luwax.RTM. having a mean molecular weight (numb
REFERENCES:
patent: 3755209 (1973-08-01), Nintz et al.
patent: 5269948 (1993-12-01), Krutchen
Hahn Klaus
Lorenz Maria
Scherzer Dietrich
Witt Michael
BASF - Aktiengesellschaft
Foelak Morton
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