EP2561013A1

EP2561013A1 - Insulating foamed moulded part

Info

Publication number: EP2561013A1
Application number: EP11722582A
Authority: EP
Inventors: Petrus Frederikus Maria Rensen; Jan Noordegraaf; Christianus Marcus Gijsbertus Maria Buijk; Walter Van Casteren; Matthijs Gebraad
Original assignee: Synbra Technology BV
Current assignee: Synbra Technology BV
Priority date: 2010-04-21
Filing date: 2011-04-21
Publication date: 2013-02-27
Also published as: JP2013525538A; NL2004587C2; WO2011133035A1

Abstract

The present invention relates to an insulating foamed moulded part based on particulate expandable polystyrene (EPS). Said moulded part according to the invention comprises recycled polystyrene particles in addition to EPS. The object of the present invention is thus to provide an insulation material in which useful use is made of starting materials, and also to provide an insulation material having good insulation values.

Description

Insulating foamed moulded part

The present invention relates to an insulating foamed moulded part based on particulate expandable polystyrene (EPS).

Such a material is known per se from European patent EP 1 486

530 in the name of the present applicant. Said European patent discloses a foam having a fine cell structure and a low density, in which, in order to improve the thermal insulation value thereof, active coal is present in the polystyrene particles as a thermal insulation value-increasing material.

The moulded part mentioned in the first paragraph is also known from U.S. Pat. No. 6,465,533, in which the expandable polystyrene particles contain aluminium particles.

Furthermore, European patent application EP 1 587 860 discloses an insulating foamed material formed from expandable styrene polymer particles, which material consists of 10-90 wt.% pigmented styrene polymer particles and 90-

10 wt.% pigment-free styrene polymer particles. Examples of pigments mentioned therein include carbon black, metal oxides, metal powders, colorant pigments and graphite.

Canadian application CA 2 171 413 discloses a method for fire resistant polystyrene foam materials in which recycled polystyrene foam is provided with a coating of a flame retardant material, and said foam material thus treated are mixed with pre foamed polystyrene beads to obtain moulded parts.

British application GB 2 449 353 relates to an expandable particulate composite material that fulfills the requirements of the B2 test according to DIN 4102 after moulding. The composite material contains an amount of graphite in the 2.0 - 15.0 wt% range.

International application WO 2009/155066 discloses a method for manufacturing a foamed polymer, in which a foaming facilitating material is added to the polymer material. As examples one dimensional nano micro materials have been mentioned, chosen from the group of smectite clays, organo clays and nano graphites.

From EP 0 235 831 a EPS material is known, on which surface a coating layer has been applied.

From JP 2 222 435 a flame retardant styren is known, in which HBCD and styrene resin have been mixed in a specific ratio.

US 2010/099782 discloses a suspension polymerization proces for manufacturing a foamed polymer.

The present inventors have found that there is a need in the packaging industry, both for food products and for non-food products, and in the construction industry for insulation materials that exhibit a sound ratio between the thickness of the insulation material used and the height of the insulation value. In the house-construction industry, for example, panels are used for insulating houses, so that heat will not be lost unnecessarily to the outside upon heating such houses. In the packaging industry it is desirable, for example, that deep-frozen products be able to retain their low temperature.

It is known to design the insulation panels as such to have a great thickness so as to obtain a high insulation value. A drawback of such a solution is the fact that the insulation material will take up more volume in the house, resulting in a decreased net volume of the house.

Another possibility is to add to the insulation material specific thermal insulation value-increasing materials, in which regard reference is made in particular to European patent No. 1 486 530 in the name of the present applicant.

The present inventors have furthermore found that there is an increasing desire to reduce the formation of waste flows and, in those cases in which such waste flows do occur, to reuse the materials obtained. Thus there is a desire to reuse "discarded" materials in the production process, which has a positive effect on the total consumption of raw materials. A decreased use of raw materials will in turn lead to a reduced emission of C0₂, which gas is regarded as one of the causes of the greenhouse effect.

in daily practice the present inventors have experienced that fitters installing insulation panels made of virgin EPS complain of "snow blindness". Said panels are coloured white and reflect a large amount of incident sunlight, installing the panels is thus found to be a strenuous job and in some cases fitters even need to wear dark sunglasses.

The object of the present invention is thus to provide an insulation material which provides a solution to one or more of the aforesaid problems.

The insulating foamed moulded part as mentioned in the introductory paragraph is characterised in that the moulded part, in addition to EPS, comprises recycled polystyrene particles.

Using recycled polystyrene particles in the present insulating foamed moulded part, it has been found to be possible to reduce the amount of virgin expandable polystyrene (EPS) to be used, which consequently has a positive effect on the consumption of so-called "virgin" starting materials.

The term "recycled polystyrene particles" is to be understood to mean polystyrene particles from already foamed moulded parts, as for example obtained from waste materials from building sites and from packaging materials, which already foamed moulded parts are crushed into small fragments before they can be processed in accordance with the present invention. The amount of blowing agent in such a recycled polystyrene particles is less than 1 wt.%, viz. less than the percentage of blowing agent present in "virgin" pre-foamed EPS, in which material the amount of blowing agent after pre-foaming is about 2-3 wt.%.

In a special embodiment it is furthermore desirable if the moulded part, in addition to the aforesaid EPS-based starting materials, also comprises particulate expandable polystyrene provided with one or more additives, which additives are preferably selected from one or more of active carbon, exfoliated graphite and pulverized carbon.

It should be explicitly noted that according to the present invention the terms active carbon, exfoliated graphite and pulverised carbon are not to be understood to include carbon black or the usual or common graphite having a particle size of more than 1 micrometer. Graphene is a carbon-like compound, which can be regarded as an atomic layer of sp2-bonded carbon atoms, whereas graphite is composed of a number of stacked-together layers of graphene. The present inventors assume that because of the specific spatial structure of graphene and exfoliated graphite, the amount of graphene and/or exfoliated graphite to be added in order to achieve the objective set is significantly less than, for example, the usual amount of graphite or carbon black.

The use of active carbon, exfoliated graphite and pulverized carbon has a positive effect on the fusion of the EPS particles in the moulding step. The present inventors have found that because of the presence of active carbon, exfoliated graphite and/or pulverised carbon in the EPS particles yet to be pre- foamed, less blowing agent escapes during the actual pre-foaming step. The amount of blowing agent of such already pre-foamed EPS provided with one or more of such additives is about 3-4 wt.%.

The particle size of the aforesaid additive is preferably≤ 12 micron, in particular <; 8 micron, in particular preferably≤ 5 micron.

From additional experiments the present inventors found that the graphene material as mentioned in the description is to be understood as exfoliated graphite having a particle size of 0,1 - 0,8 micrometer. Consequently, the term graphene in the description is to be understood as exfoliated graphite having a particle size of 0,1 - 0,8 micrometer. A lowering of the amount of thermal insulation value increasing material as added has a positive effect on the colour of the EPS obtained, which material has originally a white colour. The additives as mentioned contribute to a certain grey colour of the originally white coloured EPS.

The exfoliated graphite referred to in the present application can be obtained by subjecting a carbon source to mechanical shearing forces, in particular by subjecting graphite to such a treatment. An example of such a treatment is the extrusion process in which graphite is in an extruder subjected to major shearing forces, causing the graphite to be converted into flat carbon platelets, in particular exfoliated graphite. In certain embodiments the carbon source can be added as a masterbatch, or directly as a powdered material, which powdered material has been pretreated to obtain the desired particle size as specified in the claims.

In a special embodiment it is in particular desirable for exfoliated graphite having an aspect ratio of ≥ 10: 1 , in particular≥ 100:1 , to be used. Such a layered structure will have a particularly good influence on raising the thermal insulation value.

It is particularly desirable for the amount of carbon to amount to 1-15 wt.%, based on the polymer, preferably for the amount of carbon to amount to 2-8 wt.%, based on the polymer.

In yet another special embodiment it is furthermore preferable if the present insulating foamed moulded part comprises yet another type of EPS, viz. EPS provided with a so-called colour coating, also called coloured EPS. Such coloured EPS can be regarded as particulate expandable polystyrene particles provided with a coating, which coating contains pigments. Such a coating is present on the outer side of the polystyrene particles and should not be confused with the pigmented styrene polymer particles used in EP 1 587 860, in which the pigments are distributed in the styrene particles, viz. randomly spread over the entire volume, in particular do not exhibit any accumulation or concentration at a particular position in the particle. Using such coloured EPS, a foamed moulded part is obtained whose external configuration is such that any snow blindness problems are minimised.

The insulating foamed moulded part according to the present invention is preferably composed so that the amount of particulate expandable polystyrene (EPS) is 10-70 wt.%, the amount of recycled polystyrene particles is 10- 70 wt.%, the amount of EPS provided with one or more additives is 0-70 wt.%, and the amount of EPS provided with a colour coating is 0-40 wt.%, based on the total weight of the moulded part.

in a special embodiment it is desirable that the amount of particulate expandable polystyrene (EPS) is 10-30 wt.%, the amount of recycled polystyrene particles is 10-40 wt.%, the amount of EPS provided with one or more additives is 30-50 wt.%, and the amount of EPS provided with a colour coating is 5- 15 wt.%, based on the total weight of the moulded part.

In certain embodiments it is desirable if the present insulating foamed moulded part comprises one or more thermal insulation value-increasing materials selected from the group of graphite, aluminium powder, AI(OH)₃, Mg(OH)₂, Al₂0₃, iron, zinc, copper and alloys thereof, in an amount of at most 10 wt.%, based on the final foamed moulded part.

In order for the present moulded part to meet specific fire resistance requirements, the presence of one or more fire retardants selected from the group of hexabromine cyclododecane (HBCD), dicumyl peroxide, brominated polymer compounds and 2.3-dimethyl-2.3-diphenyi butane, or combinations thereof, in the moulded part is desirable. Another suitable fire retardant is the group of compounds derived from brominated polystyrene compounds, in particular brominated polystyrene having a molecular weight preferably ranging from 10,000 - 400,000, in particular 120,000 - 280,000, with the amount of fire retardant of the brominated polystyrene type preferably not exceeding 50 wt.%. In a special embodiment, brominated polystyrene and dicumyl peroxide are used as synergists in an amount of 0.1-3 wt.%, in particular 0.5-2 wt.%, based on the amount of styrene polymer.

The present invention in particular relates to the provision of an insulating foamed moulded part whilst realising a useful reuse of recycled polystyrene particles. Such recycled polystyrene particles contain a small amount of pentane, so that the expansion force during the final moulding in a mould, which process generally involves the use of steam, will be small. The present inventors have found that in particular by composing the present insulating foamed moulded part preferably of a number of different starting materials, the A value, which expresses the insulation value, and the mechanical properties can be selected so that the aimed-at thermal insulation properties and mechanical properties that are required in practice be met. Thus it has been found to be possible to compose an insulating foamed moulded part whose λ value ranges from 0.031 - 0.036 VWmK, preferably 0.032 - 0.035 W/mK, in combination with good mechanical properties.

It is also possible to use expandable particulate polystyrene (EPS) of varying density in the present moulded part, said densities varying from 15-30 kg/m³, with the λ value of the materials varying from about 0.040 to 0.030 W/mK, respectively. It is also possible to use varying densities ranging from 10-30 kg/m³ for EPS provided with one or more additives, with the A value varying from about 0.035 to 0.030 W/mK, respectively.

The present inventors have furthermore found that the inclusion in the present foamed moulded part of EPS provided with a colour coating, which material is used in a smaller particle size and a higher density than those of the other EPS-based starting materials present in the moulded part, will result in the thus coloured EPS migrating to the outer side of the moulded part to be formed, so that there will be an increased accumulation of the aforesaid coloured EPS on the outer side of the moulded parts, which increased accumulation will have a dominant effect on the external appearance of the obtained moulded part because of its special position on the outer side. Thus, the predominantly bright white colour, which is generally found to be objectionable, is adapted in order to prevent problems of snowbiindness. Although mention is made herein of EPS provided with a colour coating which migrates to the outer side of the moulded part, the aforesaid other EPS-based starting materials used in the present process may also be selected so that the presence thereof in the moulded part is concentrated at a specific location.

If the recycled polystyrene particles used in the present insulating foamed moulded part contain a very small amount of pentane, it is desirable if the starting materials contain active carbon, in connection with which material the present inventors have found that the blowing agent used during the pre-foaming step, in particular pentane, will remain present in the thus pre-foamed material, which blowing agent can expand more during the final moulding step, resulting in a stronger expansion and a proper fusion of the starting materials, in particular the polystyrene particles.

The manufacture of the present moulded part takes place by using a method in which the starting materials, which may have been pre-expanded, are confined in so-called steam chambers, in which further expansion of the polystyrene particles takes place. During the pre-foaming step, if used, virgin EPS, for example, is pre-treated, using steam, during which process the EPS granules can freely expand. After such a treatment, the thus pre-foamed EPS may be subjected to a next treatment, viz. maturing, in particular by storing the granules thus treated for a particular period of time, for example 4-48 hours. Final moulding takes place by further treating the various starting materials with steam in a mould. The particles will bond together during said process and form a compact structure. Before the aforesaid steam chambers or moulds are filled with a combination of starting materials, a mixture of the desired EPS materials must first be composed, the required formulation of which is defined in the subclaims. Following the composing of the required mixture, with the starting materials in particular being obtained from hoppers, the mould cavities are filled, after which steam is passed through. Because of the high temperature of the steam, the blowing agent that is present will attempt to expand, and the EPS particles will fuse into an insulating foamed moulded part as a result of being heated by steam to a temperature above their glass transition temperature and because of the limited space in the mould. The mould to be used in that process is provided with small openings through which blowing agent and steam can exit. In a special embodiment it is also possible to use hot air instead of steam. The dimension of the thus foamed moulded part is in principle not bound by limitations, making it possible to produce blocks for use in the construction industry as well as packaging materials for food products and non-food products.

For the determination of the particle size of exfoliated graphite the next analysis method was used. An amount of 10 g of grey foamed EPS was dissolved in 28 ml of toluene. The slurry was analysed. The residue was dispersed ultrasonically with the addition of toluene and analysed with an ALV instrument. A Malvern Zetasizer was used to measure the particle size. Further dilution with toluene followed if necessary. Zetasizer GMA is a so-called Dynamic Light Scattering instrument having the following specifications: Correlator: ALV5000/60X0, External Goniometer Correlator: ALV-125, Detector: ALV / SO SIPD Single Photon Detector with Static and Dynamic Enhancer ALV Laser Fiber optics: Cobolt Samba 300 DPSS Laser, Wavelength: 532 nm, 300 mW Power Temperature Control: Static Thermal Bath: Haake F8-C35. No special standards were used; the instrument measures the Brownian motion of the particles and the Einstein-Stokes equation was used to convert the measured values into particle sizes, it is assumed that the solvent is water and that the particles are by approximation spherical. The radius was measured.

Claims

1. An insulating foamed moulded part based on particulate expandable polystyrene (EPS), characterised in that the moulded part comprises recycled polystyrene particles in addition to EPS.

2. A moulded part according to claim 1 , characterised in that the moulded part further comprises EPS provided with one or more additives.

3. A moulded part according to claim 2, characterised in that said one or more additives are selected from the group of active carbon, exfoliated graphite and pulverized carbon.

4. A moulded part according to claim 3, characterised in that the particle size of the additive is≤ 12 micron, in particular≤ 8 micron.

5. A moulded part according to claim 3, characterised in that as additive exfoliated graphite is used, the particle size thereof is in the range of 0, 1 - 0,8 micrometer.

6. A moulded part according to one or more of the preceding claims, characterised in that the moulded part further comprises EPS provided with a colour coating.

7. A moulded part according to one or more of the preceding claims, characterised in that the amount of particulate expandable polystyrene (EPS) is 10-

70 wt.%, the amount of recycled polystyrene particles is 10-70 wt.%, the amount of EPS provided with one or more additives is 0-70 wt.%, and the amount of EPS provided with a colour coating is 0-40 wt.%, based on the total weight of the moulded part.

8. A moulded part according to one or more of the preceding claims, characterised in that the amount of particulate expandable polystyrene (EPS) is 10- 30 wt.%, the amount of recycled polystyrene particles is 10-40 wt.%, the amount of EPS provided with one or more additives is 30-50 wt.%, and the amount of EPS provided with a colour coating is 5-15 wt.%, based on the total weight of the moulded part.

9. A moulded part according to one or more of the preceding claims, characterised in that additionally one or more thermal insulation value-increasing materials selected from the group of graphite, aluminium powder, AI(OH)₃, Mg(OH)₂, Al₂0₃, iron, zinc, copper and alloys thereof are present in the moulded part.

10. A moulded part according to one or more of the preceding claims, characterised in that one or more fire retardants selected from the group of hexabromine cyclododecane (HBCD), dicumyl peroxide, brominated polymer compounds and 2.3-dimethyl-2.3-diphenyl butane, or combinations thereof, are present in the moulded part.

11. A moulded part according to claim 10, characterised in that compounds derived from brominated polystyrene are used as brominated polymer compounds.

12. A moulded part according to either one or both of claims 10-11 , characterised in that dicumyl peroxide in combination with brominated polystyrene is used as a fire retardant.