Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
21~41;~
Production of flameproofed polystyrene bead foams contA;nlng
recycled polystyrene foam
The present invention relate~ to a process for the production of
flameproofed polystyrene bead foams con~;n~ng recycled
polystyrene foam, and to products produced by this process.
Plastics based on styrene and sLy~e},e-cont~in1ng copolymers are
10 produced in large volumes and are used in many areas of industry.
Foamed products also have con~iderable importance here.
The production and use of these products have been known for some
time and have~been described in a number of publications.
An aspect which has increased in importance recently is the
recycling of used plastics.
In the case of polystyrene foams, various recycling methods have
20 been disclosed.
For example, it is possible to dissolve the used polystyrene in
monomeric styrene and to re-polymerize this solution by known
methods, for example as described in US-A-5,269,948 and
JP-A-56-60096.
Another possibility comprises using foamed or unfoamed
polystyrene waste for the production of polystyrene foams by the
extrusion method.
The recycled material here can be used either alone or as a
mixture with fresh polystyrene.
It is furthermore known to convert ground polystyrene foam waste
mixed to high proportion (up to 70 ~ by weight) with freshly
produced, prefoamed polystyrene beads into moldings.
It has hitherto not been possible to use this process for the
production of flameproofed polystyrene foam parts, as must be
40 used in the construction industry, for example for thermal
insulation of buildings or for struc~uLe borne soundproofing,
from recycled material comprising non-flameproofed polystyrene
foams, in particular packaging waste.
DE-A 42 40 109 discloses solving this problem by fusing
polystyrene bead foam waste together with a finely divided
styrene polymer cont~;n~ng a flameproofing agent both in
- 21 71 ~ 3
homogeneous distribution and as a surface coating to give
moldings which have the re~uisite flame resistance for use in the
construction industry.
However, this process re~uires the provision of specially treated
expandable styrene polymers, which is very inconvenient and
requires additional storage.
It is an object of the present invention to provide flameproofed
10 polystyrene bead foams containing recycled material which are
simple and inexpensive to produce.
We have found that, surprisingly, this object is achieved by
providing the ground polystyrene foam beads with a coating of at
least one flameproofing agent and then converting the coated
beads together with freshly produced, prefoamed polystyrene beads
into moldings.
The present invention accordingly provides flameproofed
20 polystyrene bead foams cont~;n;n~ recycled material which are
produced by coating comminuted polystyrene foams with
flameproofing agents, and converting them, together with freshly
produced, prefoamed polystyrene beads, into moldings.
The content of recycled polystyrene foam in the novel products is
up to 70 % by weight, preferably up to 50 ~ by weight, based on
the total weight of the molding. If larger amounts of recycled
material are used, the properties of the moldings may be
impaired.
In order to produce the novel polystyrene foams, the recycled
polystyrene foam, usually packaging waste comprising polystyrene
bead foam, is first commin~ted, usually by gr;n~;ng. A mean
particle size of 3 mm is preferred for the purposes of the
invention. The foam beads are then coated with the flameproofing
agents. The coating is preferably carried out in drum or paddle
mixers, as usually employed for coating expandable styrene
polymers. The amount of coating composition is preferably from
0,3 to 4.0 % by weight. If smaller amounts are used, the flame-
40 proofing action is inadeguate, and if larger amounts are used,fusing of the foam beads to give moldings may be impaired. Flame-
proofing agents which can be employed are conventional and known
compounds, for example flameproofing agents based on organo-
bromine or organochlorine compounds, sueh as trisdibromopropyl
phosphate, hexabromocyclododecane, chlorinated paraffin, and
synergists for flameproofing agents, such as dicumyl, dicumyl
peroxide and highly unstable organic peroxides. Preference is
` 21714~3
given to halogen-contA~ g co...~ounds, ln particular bromine-
contA;n~nq compounds. A frequently used bromine-contA~n~ng flame-
proofing aqent is hexabrL -,~yclododecane (H~CD). When halogen-
contA~ n~ ~g flameproofing agents are used, it is usual to add a
synergist, preferably dicumyl or dicumyl peroxide.
The freshly produced, prefoamed pol~y~ene beads are
conventional prefoamed beads comprising expandable styrene
polymers, but preferably thosQ comprising flameproofed expandable
10 polystyrene.
The ex~An~hle styrene polymers are prepared by polymerization of
monomer~ contAIn1ng vinyl 41~ups, in particular styrene. Ilowa~er,
it is also pQssible to employ mixtures of styrene with other
monomer8 contA~ ni ng vinyl yL~u~s.
These mixtures advantageously have a styrene content of at least
50 ~ by weight. The other monomers cont~ n~ ng vinyl yLOU~8 can
be, for example, acrylonitrile, methylstyrene, ring-halogenated
20 or ring-alkylated styrenes, esters of acrylic acid or methacrylic
acid with alcohols having up to 8 carbon atoms, N-vinyl
c~ ou~,ds, such as vinylcarbazole, or alternatively small amounts
of c~u.~ound~ cont~;ning two polymerizable double bonds, such as
butadiene, divinylbenzene or butadiene diacrylate.
The styrene polymers can also contain conventional additions of
other substances which provide the expandable products with
certain properties, for example antistatics, stabili2ers, dyes,
lubricants, fillers and substances which have a non-stick action
30 during foaming, such as zinc stearate, melamin-formaldehyde
condensates and silicic acid, and agents for shortening the
demolding time during final expansion, such as glycerol esters or
hydroxycarboxylic acid esters. Depending on the intended action,
the additives can be homogeneously distributed in the particles
or in the form of a surface coating.
The polymerization is usually carried out by the suspension
polymerization process. To this end, the monomers are converted
into an agueous suspension and polymerized therein. The blowing
40 agent can be added during the polymerization or in a subsequent
step.
After the polymerization, the polymer beads are worked up in a
conventional manner by drying, sieving and coating.
- 2171413
In order to produce the moldings, the beads impregnated with the
blowing agent are first prefoamed in a prefoamer and in this form
converted, together with the recycled material, into moldings.
The novel moldings are produced by conventional fusing of the
expanded polystyrene beads and the recycled polystyrene foam
beads in non-gas-tight molds by heating, usually using steam as
heat-transfer medium.
10 A detailed description of the polymerization, the work-up and the
foaming is given, for example, in Runststoffhandbuch, Valume 5,
Polys~yLene, edited by R. Vieweg and G. Daumiller,
Carl-Hanser-Verlag, Munich, 1969.
Surprisingly, it was possible, during coating of the recycled
polystyrene foam with the flameproofing agent, to apply
sufficient coating ~v...~osition to achieve a flameproofing action.
The person skilled in the art would have had to expect here that,
owing to the small external surface area of these beads, coating
20 to the reguisite extent would not have been possible. Neither was
there any impairment of the fusion of the resultant beads with
the expanded polystyrene beads nor any di~advantages in the
mechanical properties of the resultant moldings.
The moldings produced by the novel ~Locess are preferably used in
the construction industry, for example for thermal insulation or
structure-borne sound insulation. Their properties are not
inferior to those of moldings produced exclusively from fresh
product.
The novel products pas~ the B2 fire test of DIN 4102.
The invention is described in greater detail with reference to
the example~ below:
Examples 1 to 3
300 g of polystyrene foam from used packaging matQrials which had~
been comminuted to a mean particle si2e of from 2 to 4 mm by
40 grinding were provided with the amounts shown in the table of a
coating mixture comprising 5 parts by weight of hexabromocyclo-
dodecane and 1 part by weight of dicumyl in a Lodige paddle
mixer. The residence time in the mixer was 15 minutes.
- 2 1 7 1 4 1 3
The foam beads were then foamed together with 300 g of a
flameproofed, bead-form, prefoamed polystyrene of the S~lupor~
F 14 type from BASF AG having a mean bead size of 3 mm in an ELAB
automatic molding machine using steam to give a molding.
The B2 fire test of DIN 4102 waq carried out on this molding.
Example 4 (comparison)
10 The procedure wa~ similar to that of Example~ 1 to 3, but the
comminuted polystyrene foam from used packaging materials was not
coated.
The precise~mixing ratio~ and the results of the B2 fire test of
DIN 4102 are ~hown in the table.
Table
Example Amount of
recycled Amount of Amount of coating
material S~y~upor~Fl4 composition Foam density ~2 test
[g] [g] [g] tg/l] tsec]
1 300 300 1.2 20.0 4
2 300 300 2.4 20.5 3
3 300 300 3.6 19.8 2
4 300 300 - 20.1 burns
completely
