DE1200535B - Process for making foamable polystyrene beads - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

C08f

German class: 39 b-22/06

Number: 1200 535

File number: S 66283IV c / 39 b

Filing date: December 15, 1959

Opening day: September 9, 1965

Polystyrene foams are great for having thermal and electrical insulation however, the disadvantage that they are very easily combustible. In order to limit the area of use To reduce the flammability of the polystyrene foams, it is already known to mix the foams of antimony oxide and a non-volatile halogenated hydrocarbon. This mixture will however, generally not added to the foamable polymer beads, but rather to the pre-expanded one Polystyrene. It is known that in the production of polystyrene foams it is customary to start with the foamable ones Polystyrene beads, e.g. B. contain a volatile hydrocarbon as a blowing agent, to pre-expand. This prefoaming is normally carried out in such a way that the polymer beads in the form of a thin, loose layer heated for a short time with steam or hot water. Through this heat treatment pre-expanded polystyrene beads are obtained, the diameter of which is considerably larger than that of the foamable polystyrene beads used as starting materials. After the pre-expanded Polystyrene beads have been stored for some time, they are placed in a closed mold and z. B. heated by steam. Through this post-foaming, the pre-foamed beads are cemented together, whereby a solid molded body is obtained.

However, since the specific weight of the pre-expanded polystyrene beads is considerably lower than that of the mixture of antimony oxide and a halogenated hydrocarbon, it settles; it therefore this mixture cannot be mixed homogeneously with the pre-expanded polystyrene beads. Such an uneven distribution of this mixture of antimony oxide and a halogenated hydrocarbon is very undesirable as this tends to prevent the porous end product is equally flame retardant in all places.

This disadvantage can be remedied by adding the mixture of antimony oxide and the adding non-volatile halogenated hydrocarbons to the not yet prefoamed polystyrene beads, as it segregation occurs again after prefoaming, which in turn leads to uneven distribution the fire retardant properties in the end product made of polystyrene foam.

According to a known method, however, blowing agent-containing polystyrene beads can be mixed with a mixture treat from antimony oxide and a hydrogen halide, in order to achieve a certain adhesion, the pearls are covered with an adhesive coating beforehand. Water-insoluble ones serve as adhesives Process for making foamable polystyrene beads

Applicant:

Shell Internationale Research Maatschappij N.V., The Hague

Representative:

Dr.-Ing. F. Wuesthoff, Dipl.-Ing. G. Pulse and Dipl.-Chem. Dr. rer. nat. E. Frhr. v. Pechmann, patent attorneys, Munich 9, Schweigerstr. 2

Named as inventor:

Pieter Johannes Adrianus Beersma, Delft (Netherlands)

Claimed priority:

Netherlands of December 17, 1958 (234 306) - -

polymeric substances such as polyvinyl acetate, polystyrene and the like. In practice, this means an additional operation. However, satisfactory adhesion of the fire-retardant substances is not guaranteed despite the adhesive coating. Already during prefoaming at about 100 ⁰ C, the poorly adherent to the beads mixture settles in sticky mold so that the foam partially sticks in the mold and also a nonuniform distribution of the flame-retardant additives having (s. Comparative experiments, Example 4).

The subject of the invention is a method for producing foamable polystyrene beads, wherein the pearls with an adhesive and a mixture of antimony oxide and a halogenated hydrocarbon coated, which is characterized in that 0.1 to 20% as the adhesive. based on the weight of the mixture of antimony oxide and halogenated hydrocarbon, methyl cellulose or ethyl hydroxyethyl cellulose is used.

The disadvantages of the known method are avoided because the adhesive as a result of it Insolubility in heat neither during prefoaming with warm water or steam nor migrates from the bead surface during post-foaming. In addition, the impregnation with the adhesive and the flame-retardant mixture take place simultaneously, so that one operation under The use of an additional organic solvent is saved and the additives are distributed completely evenly. The inventively

509 650/536

Traded pearls can also be used after pre-foaming, in which they do not stick together, are stored for any length of time and are not damaged during transport.

The non-volatile halogenated hydrocarbons used to prepare the flame retardant mixture are preferably halogen paraffins, but other common compounds such as polyvinyl chloride, can be used with good success. Solid halogen paraffins, especially chlorinated paraffins with a chlorine content of about 60 to 80 percent by weight, especially 70 percent by weight, proved proved to be very suitable. These solid chlorinated paraffins not only give the foamed polymer a great deal good fire retardant properties, but also absorb very little water, so only one very small amount of water is required to apply the water-soluble adhesive. Another The advantage here arises from the fact that the solid chlorinated paraffin used during the pre-expansion partially melts, as a result of which the adhesion to the resulting pre-expanded polymer beads is improved will. These benefits can be further enhanced by using the solid chlorinated paraffin a small amount of a liquid chlorinated paraffin with a chlorine content of about 35 to 55 percent by weight, in particular 40 to 50 percent by weight, mixed.

The mixture of antimony oxide and the halogenated hydrocarbon is generally used in an amount from 1 to 40%. in particular 5 to 30%> based on the Weight of foamable polymer beads is used. The water-soluble adhesive is used in an amount from 0.1 to 20%, in particular 5 to 15%, based on the weight of the mixture of antimony oxide and the Halocarbon, used. The aforementioned mixture of antimony oxide and the halogenated hydrocarbon consists of 10 to 90% halogenated hydrocarbons, based on the weight of the mixture.

example 1

100 g of foamable polystyrene containing a volatile hydrocarbon blowing agent were added 20 g of a chlorinated paraffin (chlorine content 70 percent by weight), 10 g of antimony oxide, and 2 g of methyl cellulose each of different viscosity (15 cP in one experiment, 100 cP in a second) mixed and each 10 g of water were added.

The adhesive swelled causing the powder to adhere to the polymer beads. The foamable compositions were then pre-expanded in a rotary drum by means of air at a temperature of about 30 ⁰ C and then dried by heating for 7 minutes with steam of 98 ⁰ C. The pre-expanded material was placed in molds which were ^{treated with steam under 1.5 to 2 kg / cm 2} pressure.

Because of the adhesive additive, the flame retardant additives both adhered before foaming very good on the polystyrene beads and then on the foam, its flammability was uniformly largely reduced through the entire porous mass.

Example 2

According to Example 1, preparations were made, the 10 g of antimony oxide, 20 g of various Contained halogenated hydrocarbons and various amounts of adhesive.

Table I.

Halogenated hydrocarbons

Adhesive

Amount of

added

Water

(G)

Adhesion of the flame retardant mixture

of foamable
Polystyrene

on pre-expanded
Polystyrene

Burn time
in seconds

after ignition

of the porous

Product

20 grams of polyvinyl chloride
20 grams of polyvinyl chloride

20 g chlorinated paraffin
(70% chlorine)

2 grams of methyl cellulose
(Viscosity 15 cP)
10 grams of methyl cellulose
(Viscosity 15 cP)
2 grams of methyl cellulose
(Viscosity 15 cP)

20th
20th
10

Well

excellent
Well

very moderate

pretty good

Well

44

Example 3

Contained propellant, and 10 g of antimony oxide mixtures prepared, to which different sizes According to Example 1, 100 g of foamable amounts of solid and liquid chlorinated paraffins were made from polystyrene, that a volatile hydrocarbon as such as methyl cellulose were added.

Table II

Solid chlorine
paraffin with
a salary
at 70 weight
percent chlorine
(G) Liquid
Chlorinated paraffin lot
the added
Methyl cellulose
(G) Be liable Bulk density
(g / l) Incineration
in seconds 15th
14th
13th
12th
14th
10
14th Ig (chlorine content 42%)
2 g (chlorine content 42%) ^J.
3 g (chlorine content 42%)
4 g (chlorine content 42%)
2 g (chlorine content 42%)
2 g (chlorine content 50%)
2 g (chlorine content 42%) 1
1
2 small amount
moderate
moderate
moderate
excellent
excellent
excellent 28
27
28
30th
28
26th
26th 1
0
2
2
1
1
0

Example 4
(Comparison test)

There were 100 parts by weight of foamable polystyrene beads with 30 parts by weight of a mixture of Chlorinated paraffin (chlorine content 70 percent by weight) and antimony oxide (weight ratio 2: 1) with simultaneous Admixture of one of the following adhesives:

IO

1. About 20% aqueous polyvinyl chloride emulsion;

2. 10% aqueous polyvinyl acetate dispersion;

3. 46% aqueous vinyl acetate-vinyl chloride copolymer dispersion;

4. methyl cellulose "M 15";

5. methyl cellulose "C M 20";

6. Ethyl hydroxyethyl cellulose "M 20".

The amount of adhesive (calculated as solids) was in each case 2 percent by weight, based on foamable polystyrene. In the case of adhesives 4, 5 and 6 - which are soluble in cold water but practically insoluble in warm water (90 to 100 ° C.) - a small amount (about 10 percent by weight) of water was added. The so obtained foamable polystyrene beads were pre-expanded first with air at about 30 C and then dried by passing steam for 5 minutes at 100 ⁰ C in a vessel equipped with a perforated base open container.

In the tests with the water-insoluble adhesives 1, 2 and 3, it was found that they were unsatisfactory as a result Adhesion of the flame-retardant mixture a significant migration of the same took place, so that the flame-retardant Material settled in sticky form on the sieve bottom, which made the passage of steam difficult.

The pre-expanded material was placed in a closed mold and in it Processed into foam bodies for 20 to 30 seconds with steam under an overpressure of 0.7 to 1 atm. The moldings obtained using the known adhesives 1, 2 and 3 were the flame-retardant properties significantly reduced; another occurred during the shaping Migration of the flame-retardant components on, and when the foam body is lifted out of the The mold was damaged by parts of it sticking to the wall.

In the tests with the adhesives 4, 5 and 6 according to the invention, none of these disadvantages occurred on, there have been obtained products with excellent flame retardant properties, respectively, and the Foam bodies remained undamaged.

Claims (1)

Claim: A method for making foamable polystyrene beads, wherein the beads with a Coated with adhesive and a mixture of antimony oxide and a halogenated hydrocarbon, characterized in that the adhesive used is 0.1 to 20%, based on the weight the mixture of antimony oxide and halogenated hydrocarbons, methyl cellulose or ethyl hydroxyethyl cellulose used. Considered publications:
Belgian patent specification No. 535 774. 509 660/536 8.65 © Bundesdruckerei Berlin