EP2438110A1

EP2438110A1 - Particulate, expandable polystyrene as well as a method for preparing the same

Info

Publication number: EP2438110A1
Application number: EP10727156A
Authority: EP
Inventors: Jan Noordegraaf; Franciscus Petrus Antonius Kuijstermans; Leendert Edelman; Henricus Johanna De Swart
Original assignee: Synbra Technology BV
Current assignee: Synbra Technology BV
Priority date: 2009-06-02
Filing date: 2010-06-01
Publication date: 2012-04-11
Also published as: WO2010140882A1; CN102459435A; NL1037008C2; KR20120034638A

Abstract

The present invention relates to a particulate, expandable polystyrene (EPS) which can be processed into a foam having a fine cell structure and a low density and which, in order to improve the fire resistance thereof, contains a fire retarding material. The present invention further relates to a method for preparing a particulate, expandable polystyrene (EPS), wherein styrene monomer is subjected to a polymerization reaction in the presence of one or more additives under elevated temperature conditions.

Description

PARTICULATE , EXPANDABLE POLYSTYRENE AS WELL AS A METHOD FOR PREPARING THE SAME

The polystyrene referred to in the introduction is known from European patent publication EP 1 514 895 in the name of the present inventor, in which graphite, in particular graphite of the expandable type, is used as a fire retarding material in an amount of 40 - 80 wt.%. U.S. Pat. No. 3,063,954 relates to a process for producing flame-retardant expandable polystyrene particles, wherein an aqueous suspension of a solution of styrene monomer and bromiπated polystyrene is formed, which solution is polymerized by heating said suspension and subsequently adding a volatile hydrocarbon, in particular a mixture of isopentane and n-pentane so as to cause said hydrocarbon to be incorporated in the aforesaid particles, thereby rendering said particles expandable.

U.S. patent application US 2007/0238794 relates to a process for producing flame-resistant, expandable styrene polymers, wherein an organic bromine compound is used as flame retardant and a peroxide is used as a synergist. The flame retardant is previously mixed into the styrene polymer melt and added to a styrene polymer melt containing a blowing agent, followed by extrusion in an extruder.

U.S. Pat. US 5,112,898 relates to a flame-retarding, high impact polystyrene compound containing a combination of high impact polystyrene, an antimonium-based synergist and brominated polystyrene having a low molecular weight, viz. oligomers having a degree of polymerization of 3 - 20. The effective amount of brominated polystyrene oligomer ranges between 3 and 20 wt.%, based on the total weight of oligomer and polystyrene compound.

In addition to being used as a packaging material, particulate, expandable polystyrene (EPS) is generally used for construction purposes, for example as panels in house construction. Special requirements are made of such panels as regards thermal insulation, sound insulation and fire retardation, among other things. The present invention in particular relates to the development of a particulate, expandable polystyrene (EPS) in which the fire retardancy of materials incorporating EPS is optimized, which means that such applications must comply with the current strict fire requirements, in particular those of the DIN 4101-B2 fire rating test.

Another aspect of the use of fire retardants in EPS-based materials is the burden on the environment. At the end of the technical or the economic life of the materials that contain EPS, such materials will be regarded as waste, and it is desirable that the burden on the environment this constitutes be minimized. This means that the amount and the type of fire retarding materials must be selected so that the burden on the environment is minimal. The object of the present invention is thus to provide a particulate, expandable polystyrene (EPS) in which a fire retarding material is incorporated, wherein the polystyrene thus obtained meets the strict requirements of fire retardancy.

Another object of the present invention is to provide a particulate, expandable polystyrene (EPS) in which the amount of fire retarding material is minimised and in which the burden on the environment by the end product is low.

The present invention as described in the introduction is characterised in that brominated polystyrene is present in the polystyrene particles as the fire retarding material in an amount of 0.5 - 5 wt.%, based on the amount of styrene polymer.

One or more of the above objects are accomplished by using the aforesaid brominated polystyrene. It is in particular preferable if the amount of brominated polystyrene as the fire retarding material is 1 - 3 wt.%, based on the amount of styrene polymer, in which connection the present inventors have found that the molecular weight of brominated polystyrene preferably ranges from 10,000 - 400,000, in particular 120,000 - 280,000.

A very good fire retardation is obtained if the bromine content in brominated polystyrene is at most 75 wt.%, preferably at most 50 wt.%, in particular if the bromine content in brominated polystyrene ranges from 20 - 40 wt.%. It is furthermore preferable if the bromine content, in particular in the master batch, viz. the mixture of components from which the granules are obtained, is between 0.4 wt.% and higher, preferably 0.8 and higher, in particular 1.2 wt. % and higher. In preferred embodiments an amount of 4 wt.%, in particular 3 wt.%, preferably 2.5 wt.% can be applied as an upper limit. The aforesaid values apply both to the polymerization process and to the extrusion process, as described herein.

The fire retardation of the present brominated polystyrene in EPS is in particular observed if one or more synergists are added to the fire retarding material, wherein the synergist is selected from the group of peroxides and brominated bisphenol compounds. A suitable synergist is dicumyl peroxide, in particular in an amount of 0.1 - 3 wt.%, in particular 0.5 - 2 wt.%, based on the amount of styrene polymer. Suitable synergists of the brominated bisphenol compound type include: tetrabromine bisphenol A allylether, tetrabromine bisphenol A, tetrabromine bisphenol A; phenoxy-terminated carbonate oligomer and tetrabromine bisphenol A bis(2,3-dibromine propylether).

The present inventors have found that the use of the combination of one or more of the aforesaid synergists and brominated polystyrene makes it possible to considerably reduce the amount of brominated polystyrene required in comparison with EPS in which only brominated polystyrene not containing one or more of the aforesaid synergists is used, in order to comply with the currently applicable DIN 4101-B2 rating. Accordingly it has been found to be desirable to use a combination of synergists, in particular dicumyl peroxide and tetrabromine bisphenol A allyl ether, in addition to the presence of brominated polystyrene. It is in particular preferable to use only brominated polystyrene as a fire retarding material, but also other applications are possible in which the presence of graphite, besides other additives, such as graphene, metal oxides, metal pigments, silicates, glass fibres, blowing agents, for example, is desirable.

The present invention further relates to a method for preparing a particulate, expandable polystyrene (EPS) as referred to in the introduction, wherein brominated polystyrene is added to the styrene monomer in an amount of 0.5 - 5 wt.%, based on the amount of polystyrene, before the polymerization reaction takes place, after which the polymerization reaction is carried out in the presence of one or more additives. A particularly suitable additive is a peroxide-type synergist, in particular dicumyi peroxide, in an amount of 0.1 - 3 wt.%, in particular 0.5 - 2 wt.%, based on the amount of styrene polymer.

After the polymerization and subsequent cooling of the reactor contents, it is desirable that the EPS particles thus formed be provided with a coating, a suitable coating being the coating disclosed in European patent application EP 1 907 461 in the name of the present applicant, which European application can be considered to be fully incorporated herein as regards the special coating. After the thus polymerized EPS particles have been provided with the aforesaid coating, in particular prefoaming to a desired density of 10 - 30 kg/m³ takes place, with the thus prefoamed particles being further processed in a press to form a desired moulded part, for example an insulation panel.

In addition to the aforesaid polymerization method it is also possible to prepare expandable polystyrene (EPS) via an extrusion process, as known from International application WO 00/43442, wherein styrene polymer is added to an extruder in the presence of one or more additives, among which brominated polystyrene as a fire-retarding material, in which extruder blending takes place, with the extruded material being cooled and further reduced into particles. It is also possible, however, to process styrene polymer together with the brominated polystyrene as a fire retarding material in an extruder, after which the intermediate material thus obtained is subjected to an impregnation treatment with a blowing agent so as to obtain a starting material, which starting material is further cooled and processed into particles.

The present invention will now be explained in more detail by means of an example, in which connection it is noted, however, that the present invention is by no means limited to such a special example.

Example 1

In a metering vessel, brominated polystyrene (bromine content: 41 wt.%) was added in an amount of 1.1 wt.%, based on the amount of styrene polymer to be obtained, to an amount of styrene monomer. The amount of bromine in the MB (master batch) was 0.4 wt.%. After dissolving, the solution thus obtained was fed to a polymerization reactor, whilst also dicumyi peroxide was added as a synergist in a weight ratio of 0.3 wt.% in the presence of the usual additives for polymerization, such as initiators. The contents of the polymerization reactor were heated to a temperature of 92 ⁰C, with the subsequent addition of pentane as a blowing agent. The reactor contents were subsequently further heated to 120 ⁰C, whereupon the polymerization reaction took place. After cooling of the reactor contents, the whole was dried and the granules thus formed were screened out. The granules thus obtained were provided with a coating as disclosed in European 5 application EP 1 907 461 and pre-foamed to a density of 20 kg/m³. After maturing for at least 4 hours, the thus pre-foamed granules were further processed to form a plate.

The plate thus obtained is subjected to a fire test in accordance with DIN 4101-B2, the tested materials all met the requirements of the B2 test. iO Example 2

Example 1 was repeated, with this difference that in addition to dicumyl peroxide as the synergist also tetrabromine bisphenol A allyl ether was added in an amount of 0.1 wt.%, based on the amount of styrene polymer to be obtained. The obtained granules were further processed to form a plate, which plate I5 was subsequently subjected to a fire test in accordance with DIN 4101 -B2, the requirements of which B2 test were met.

Example 3

Example 2 was repeated, using half the amount of brominated polystyrene. The result of the presence of the combination of the two synergists was !0 that the plates formed from the granules met the requirements of a fire test in accordance with DIN 4101-B2.

Example 4

Example 1 was repeated, with this difference that the amount of brominated polystyrene was increased to an amount of 5 wt.%, based on the amount >5 of styrene polymer to be obtained. The same results as in Example 1 were obtained, but a significant improvement in the results of the fire test was not observed.

Comparative Example 1

Example 1 was repeated, with this difference that the amount of brominated polystyrene was increased to an amount of 8 wt.%, based on the amount

50 of styrene polymer to be obtained. Upon examination it was found that the distribution of brominated polystyrene in the final product was non-homogeneous, and accordingly the fire test was not carried out.

Comparative Example 2

Example 1 was repeated, with this difference that the amount of brominated polystyrene was decreased to an amount of 2 wt.%, based on the amount of styrene polymer to be obtained. The same results as in Example 1 were obtained.

Comparative Example 3 Example 1 was repeated, with this difference that the amount of brominated polystyrene was decreased to an amount of 0.35 wt.%, based on the amount of styrene polymer to be obtained. The granules thus obtained were further processed to form a plate, which plate did not meet the requirements of the fire test. Example 5 In an extruder, non-flame retarding EPS granules containing 5.5% pentane, type Styrex 1016R (particle size 1.0 - 1.6 mm), were melted with the simultaneous addition of 6% polymer BPS 40, viz. a brominated polystyrene having a bromine content of 40%. The amount of added bromine is effectively 2.4%, therefore. In addition to that, 5% graphite having a particle size of 2 - 4 μm is added. After pre-foaming to a density of 20 gr/l and being formed into a plate, the material met the DIN 4101-B2 test. Example 6

In an extruder, non-flame retarding EPS granules containing 5.5% pentane, type Styrex 1016R (particle size 1.0 - 1.6 mm), were melted with the simultaneous addition of 6% polymer BPS 40, viz. a brominated polystyrene having a bromine content of 40%. The amount of added bromine is effectively 2.4%, therefore. In addition to that, dicumyl peroxide was added via a master batch with an effective metered amount of 0.35%. Furthermore, 5% graphite having a particle size of 2 - 4 μm was added. After pre-foaming to a density of 20 gr/l and being formed into a plate, the material met the DlN 4101-B2 test.

Claims

1. Particulate, expandable polystyrene (EPS) which can be processed into a foam having a fine cell structure and a low density and which, in order to

5 improve the fire resistance thereof, contains a fire retarding material, characterised in that brominated polystyrene is present in the polystyrene particles as the fire retarding material in an amount of 0.5 - 5 wt.%, based on the amount of styrene polymer.

2. Particulate, expandable polystyrene (EPS) according to claim 1 , 0 characterised in that the amount of brominated polystyrene as the fire retarding material is 1 - 3 wt.%, based on the amount of styrene polymer.

3. Particulate, expandable polystyrene (EPS) according to one or both of the preceding claims, characterised in that the molecular weight of brominated polystyrene ranges from 10,000 - 400,000, in particular 120,000 - 280,000.

5 4. Particulate, expandable polystyrene (EPS) according to one or more of the preceding claims, characterised in that the bromine content in brominated polystyrene is at most 75 wt.%, preferably at most 50 wt.%.

5. Particulate, expandable polystyrene (EPS) according to one or more of the preceding claims, characterised in that the bromine content in brominated

IO polystyrene is in the 20 - 40 wt.% range.

6. Particulate, expandable polystyrene (EPS) according to one or more of the preceding claims, characterised in that the fire retarding material is used in the presence of one or more synergists, said synergist being selected from the group of peroxides and brominated bisphenol compounds.

!5 7. Particulate, expandable polystyrene (EPS) according to one or more of the preceding claims, characterised in that dicumyl peroxide is used as a synergist in an amount of 0.1 - 3 wt.%, in particular 0.5 - 2 wt.%, based on the amount of styrene polymer.

8. Particulate, expandable polystyrene (EPS) according to one or more IO of the preceding claims, characterised in that tetrabromine bisphenol A ally! ether is used as a synergist in an amount of 0.1 - 3 wt.%, in particular 0.5 - 2 wt.%, based on the amount of styrene polymer.

9. A method for preparing particulate, expandable polystyrene (EPS), in which styrene monomer is subjected to a polymerisation reaction in the presence of one or more additives under elevated temperature conditions, characterised in that brominated polystyrene is added to the styrene monomer in an amount of 0.5 - 5 wt.%, based on the amount of polystyrene, before the polymerisation reaction takes place, after which the polymerisation reaction is carried out in the presence of one or more additives.

10. A method according to claim 9, characterised in that after polymerisation and subsequent cooling, the EPS particles thus formed are provided with a coating and prefoamed to a density of 10 - 30 kg/m³.

11. A method according to one or both of claims 9-10, characterised in that the prefoamed particles are further processed in a press to form a moulded part.

12. A method according to one or more of claims 9-11 , characterised in that the amount of bromine in the composition to be subjected to the polymerization reaction is at least 0.4 wt.%, preferably at least 0.8 wt.%, based on the weight of the aforesaid composition.

13. A method for preparing particulate, expandable polystyrene (EPS), in which EPS is extruded in the presence of one or more additives, characterised in that EPS granules are mixed with brominated polystyrene as a fire retarding material in the extruder in the presence of one or more additives, whereupon the material thus obtained is subjected to a prefoaming and moulding treatment, with brominated polystyrene being added in an amount of 0.5 - 5 wt.%, based on the amount of styrene polymer.

14. A method according to claim 13, characterised in that the amount of bromine in the composition to be subjected to the extrusion process is at least 0.4 wt.%, preferably at least 0.8 wt.%, based on the weight of the aforesaid composition.

15. A method according to one or more of the preceding claims 9-14, characterised in that the fire retarding material is used in the presence of one or more synergists, wherein the synergist is selected from the group of peroxides and brominated bisphenol compounds.

16. A method according to claim 15, characterised in that dicumyi peroxide and tetrabromine bisphenol A allyl ether are added, each in an amount of 0.1 - 3 wt.%, in particular 0.5 - 2 wt.%, based on the amount of styrene polymer.