WO2001005884A1

WO2001005884A1 - Process for balling and flame-proofing of polystyrene

Info

Publication number: WO2001005884A1
Application number: PCT/HU2000/000082
Authority: WO
Inventors: Béla BOLDOGHY; József KUMMERT; Lajos Lieberman
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-07-16
Filing date: 2000-07-14
Publication date: 2001-01-25
Anticipated expiration: 2002-01-16
Also published as: HUP9902391A2; HU9902391D0; HUP9902391A3; AU6308500A

Abstract

The subject of the invention is a process for balling and flame-proofing of polystyrene foam preferably recycled polystyrene, during the process an additive is added to the polystyrene by which a polystyrene foam of increased tensile strength is produced and the spreading power of flame of the material produced is inhibited. During the process a raw material of beaded and/or flaked polystyrene is filled into a shaping space where balling with heat-treatment and intromission of hot steam takes place. The process is characterized by that, during balling of polystyrene foam an additive of boric content, a hexabromo-cyclododecane (HBCD) is added to the - partly or wholly recycled - raw material to be balled, and the balling of the raw material provided with the additive this way is executed with intromission of high temperature, preferably of low vapor content steam.

Description

Process for balling and flame-proofing of polystyrene

The subject of the invention is a process for balling and flame-proofing of polystyrene foam preferably recycled polystyrene, during the process an additive is added to the polystyrene by which a polystyrene foam of increased tensile strength is produced and the spreading power of flame of the material produced is inhibited.

According to the prior art Hungarian patent application P 97 01523 published 28 April 1998 makes known a process for making expanded polystyrene flameproof. According to this process the foamed polystyrene particles are mixed with water solution of sodium-silicate and dried in a cast mold. The foamed polystyrene sheets produced this way include particles completely coated with a thin layer of silicate protecting them from fire. The adjoining particles are mechanically joined ensuring tensile strength of the sheet.

The disadvantage of the solution is that the silicate applied as binder makes polystyrene heavier decreasing field of application as lightweight building material. In applications where light-weight framework is an important requirement, polystyrene element of this type can have limited application only. An additional disadvantage is that ordinary production technologies of polystyrene balling can not be used, so the process described in the application referred to can not be directly brought in Ijne with the existing technologies, equipment and facilities necessary for this process should be set up on a different site. The combustibility of the silicate-polystyrene complex made this way is not considerably reduced. The disadvantage of the solution is that it can be applied only in certain fields to a limited extent, because under heat effect polystyrene burns respectively shrinks in the silicate while load-bearing capacity of silicate structure weakens and the static strength of the building structure deteriorates. An additional disadvantage of applying sodium-silicate as binder is that it is not waterproof enough, under water effect it solves, which also limits its application, because it worsens static, mechanic load-bearing capacity. When elaborating the solution according to the invention we aimed to create a process using preferably partly or completely recycled raw material suitable for producing a light-weight, flameproof block- polystyrene of improved mechanical properties, which can be properly adjusted to the production technologies already in use.

When we worked out the solution according to the invention, we realized that in the case an additive of boric content a hexabromo- cyclododecane (HBCD) is added to the raw material used for balling which is partly or completely recycled and the balling is made with intromission of high temperature, preferably low vapor content steam then the set aim can be achieved.

The invention is a process for balling and flame-proofing of polystyrene foam preferably recycled polystyrene, during which a raw material of beaded and/or flaked polystyrene is filled into a shaping space where balling with heat-treatment and intromission of hot steam takes place. The process is characterized by that, during balling of polystyrene foam an additive of boric content, a hexabromo- cyclododecane (HBCD) is added to the - partly or wholly recycled - raw material to be balled, and the balling of the raw material provided with the additive this way is executed with intromission of high temperature, preferably of low vapor content steam.

In a preferable application of the process according to the invention the additive is injected to the raw material in the shaping space.

In another preferable application of the process according to the invention the additive is mixed to the raw material before filling it into the shaping space.

In a further preferable application of the process according to the invention in case of raw material of 4...8 mm particle size the rate of quantity of the additive is 10...900 grams/m3, in given case preferably 60 grams/m3, and the balling is executed with the intromission of steam of preferably minimum 105 C° temperature and minimum 0,2 bar pressure. The process according to the invention is going to be described further by some preferable definite examples as follows:

In case of one of the definite applications of the process according to the invention we use virgin beaded polystyrene. A rate of 40...80 grams/m3, in given case 60 grams/m3 HBCD is added to the beaded polystyrene raw material filled to the shaping space, then the balling is executed with the intromission of minimum 105 C° temperature minimum 0,2 bar pressure steam. With the HBCD added to the raw material this way we achieve improved mechanical strength, more favourable flame-proofhess than in case of balling of virgin beaded polystyrene by the conventional technology.

In a second preferable definite application of the process according to the invention the raw material used for balling is partly virgin beaded polystyrene, partly flaked polystyrene and/or dissociated recycled particles. The rate of their mixture is the same in given case as the mixing rate of other technologies for balling, for example the content of recycled material is 20..30..40 % and the HBCD additive is put into this raw material in a rate of 40...80 grams/m3, in given case in rate of 60 grams/m3. Balling is executed preferably with the intromission of a minimum 105 C° temperature minimum 0,2 bar pressure steam into the shaping space. In case of the block polystyrene with HBCD added this way the mechanical strength is improved and the flame-proofhess is more favourable, than in case of balling with conventional technology and similar mixing rate.

In a third preferable definite application of the process according to the invention the raw material used is partly virgin beaded polystyrene, partly flaked and or dissociated recycled polystyrene, but the rate of recycled material is considerably bigger, 40...60...80 % than in case of conventional balling technologies. The raw material of this mixture is added with 40...80 grams/m3, in given case with 60 grams/m3 HBCD additive. Balling is executed preferably with the intromission of a minimum 105 C° temperature minimum 0,2 bar pressure steam into the shaping space. In case of conventional technologies this rate of mixture and the use of ordinary additives do not ensure proper mechanical strength. HBCD additive helps strengthen bonding between the particles of the raw material and this way the mechanical strength of the block polystyrene is improved as well, not to mention the improvement of flameproof parameters. This is the aim of the invention. So the additive applied at the process according to the invention promotes better bonding making possible the use of considerably bigger quantity of recycled raw material.

In a fourth preferable definite application of the process according to the invention the raw material used is entirely 100% recycled polystyrene. This raw material is added with 40...80 grams/m3, in given case with 60 grams/m3 HBCD. Balling is executed preferably with the intromission of a minimum 105 C° temperature minimum 0,2 bar pressure steam into the shaping space. In case of a raw material of wholly recycled material balling can not be executed with the generally used additives with conventional technologies, because proper mechanical strength can not be achieved. The HBCD additive is capable of ensuring flame-proofhess and besides proper bonding between the particles of the recycled raw material and provide mechanical strength equal to or even better than that of the original raw material.

In a further preferable definite application of the process according to the invention the production of block polystyrene foam from mainly recycled polystyrene foam. The first step of the process is the cutting, disintegrating of the scrap polystyrene. During this the pre-sorting of polystyrene pieces of various size, from broken fragments to box-size pieces happens, including removing contamination, then rough cutting of polystyrene. It is followed by grinding when scrap polystyrene is dissociated to particles and/or flakes. The grinding of polystyrene is of importance, as compared with other cutting methods it is possible to achieve 4...8 mm particle size by grinding, which is favourable during balling from the point of view of homogeneity and joining of particles.

The delivery of the ground polystyrene to the storing silo takes place by an air-flow. The supply of the smashed polystyrene to processing takes place in a measured form by charges just like with other polystyrene production methods. 80% volume-rate of flaked, recycled polystyrene, 20 % virgin beaded polystyrene is used for balling, the smooth mixing of the raw materials takes place during filling it to the molding tool.

Balling of the ground polystyrene takes place in the molding tool of required shape. Together with the filling of the smashed polystyrene into the mold the intromission of hexabromo-cyclododecane (HBCD) ensuring fire-proofing and bonding takes place as well. Establishment of bonding takes place in the sample case with injecting so called dry steam of known parameters, of high temperature, of relatively low vapor content, the parameters of which are preferably minimum 105 C° temperature minimum 0,2 bar pressure. Solid polystyrene block is produced this way.

The steam used for balling ensures the temperature at which the polystyrene particles respectively flakes stick together, further under the effect of this temperature gas is released spontaneously from the inside of the polystyrene particles. These processes take place both in case of conventional balling and in the process according to the invention.

Fireproofing of hexabromo-cyclododecane (HBCD) applied as additive takes place so, that it infiltrates between the particles respectively of the flakes of the polystyrene through a surface bonding and establishes bonding exactly at the joining of polystyrene particles respectively flakes. This way together with promoting joining of particles and flakes it also improves flame-proofing effect. From this point of view the technique of the pre-treatment of the polystyrene raw material, is essential, because the rate of additive is determined by the size of the recycled polystyrene. The quantity of the additive is in connection with the particle size, accordingly the necessary quantity of additive between 10...900 grams/m3 given values depends on the size of particles respectively flakes. The volume rate relating to the portioning rate of the additive the preferable 40...80 grams/m3 in given case 60 grams/m3 was determined experimentally. Significantly less additive does not produce the required effect, much more additive causes no change in flameproof and tensile strength parameters. Under effect of heat respectively flame the polystyrene foam block produced by the process according to the invention shrinks, but does not ignite. It is possible to adjust a determined minimum fireproofing with the size of the particles respectively flakes and the quantity of additive independently from the fireproofing value of the polystyrene pieces ground into the recycler.

In case of the process according to the invention during the balling an adjustable tool is used and the applied pressure is not so big as in case of conventional technologies. Preferably a blend principle producing mold is applied, by which billets with specified length but with a wide range of side-sizes can be produced. The mold is preferably pre-heated ensuring the steady temperature of the raw material and preventing loss of heat during balling.

The advantage of the solution according to the invention is, that the applied additive induces improved cohesion and fastening of the polystyrene particles respectively flakes compared with other bonding methods. This way the process can be applied with recycled polystyrene as well, a better quality recycled material of improved flame-proofing can be received. In case of using recycled raw material the process according to the invention makes possible to produce a block material of homogeneous flame-proofhess from different recycled material, which can not be ensured by other balling processes.

Due to the fact, that during the current recycling processes the material is not ground, but only cut, maximum 30% can be used for recycling. The process according to the invention makes possible a considerably larger, 40...60...80 % rate or even 100% of recycling.

The advantage of the process according to the invention is, that requirement of resting is short, the ready polystyrene block can leave the plant after a few days compared with the traditionally long, in given case several months of rest, so period of storing is short. It can be delivered from the place of production at once, no resting , drying time is required, no space is blocked for storing. Consequently the process according to the invention ensures improved flame-proofhess with the use of a new material, hexabromo- cyclododecane (HBCD) and with improved structural strength it ensures more widescale use of recycled polystyrene, and a further advantage is that a material of homogeneous structure is produced during balling.

Claims

CLAIMS:

1. A process for balling and flame-proofing of polystyrene foam preferably recycled polystyrene, during which a raw material of beaded and/or flaked polystyrene is filled into a shaping space where balling with heat-treatment and intromission of hot steam takes place,

characterized by that,

during balling of polystyrene foam an additive of boric content, a hexabromo-cyclododecane (HBCD) is added to the - partly or wholly recycled - raw material to be balled, and the balling of the raw material provided with the additive this way is executed with intromission of high temperature, preferably of low vapor content steam.

2. Process as in claim 1 characterized by that, the additive is injected to the raw material in the shaping space.

3. Process as in claim 1 characterized by that, the additive is mixed to the raw material before filling it into the shaping space.

4. Process as in any of the claims 1 to 3 characterized by that, in case of raw material of 4...8 mm particle size the rate of quantity of the additive is 10...900 grams/m3, in given case preferably 60 grams/m3, and the balling is executed with the intromission of steam of preferably minimum 105 C° temperature and minimum 0,2 bar pressure.