GB1601013A

GB1601013A - Composite product comprising foamed particles

Info

Publication number: GB1601013A
Application number: GB10752/78A
Authority: GB
Original assignee: CHARBONNAGES SICCA
Current assignee: CHARBONNAGES SICCA
Priority date: 1977-03-18
Filing date: 1978-03-17
Publication date: 1981-10-21
Also published as: DE2811347A1; PT67766A; OA05912A; BR7801659A; ES467991A1; ZA781584B; NL7802855A; BE865001A; IT1111452B; LU79248A1; GR63108B; DK121378A; EG13152A; IT7867605A0; FR2401191A1; FR2401191B1; NO780972L; CA1109598A; SE7803037L; JPS53115775A

Description

(54) COMPOSITE PRODUCT COMPRISING FOAMED PARTICLES (71) We, SOCIETE INDUSTRIELLE ET COMMERCIALE DES CHARBON NAGES - SICCA, a French body corporate of 6 rue de Teheran, 75008 Paris, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention is concerned with a novel composite foam body and a process of preparing such a foam body.

A process for obtaining plates or other shaped articles is known in which expansible granules or beads are moulded in a thermoplastic resin; during moulding, the granules, which may be pre-heated, are heated so as to cause them to expand and adhere to one another, so as to form a single article.

Many years ago, a process for preparing moulded bodies was also described, in which particles of expanded or expansible polystyrene are connected together by means of a suitable adhesive or binder, examples of such adhesives or binders being urea-melaminephenol-formaldehyde resins or cresol-resorcinol-formaldehyde resins.

However, the products obtained by these processes do not have adequate mechanical and insulating properties.

We have now devised a novel composite foam body having a remarkable combination of properties, and a process of preparing such a foam body.

According to a first aspect of the present invention, there is provided a composite foam body, which comprises polystyrene foam particles in an amount of 75 to 95% by volume relative to the volume of the body, and, filling the gaps between the particles, foamed phenol-formaldehyde resin of density 50 to 500 grams per litre.

According to a second aspect of the invention, there is provided a process of preparing a composite foam body, which comprises filling a mould cavity with polystyrene foam particles and phenol-formalehyde resin containing a foaming agent and an acid catalyst, and heating to cause foaming and cross-linking of the resin until the latter attains a density of 50 to 500 grams per litre, the polystyrene foam particles and the phenol-formaldehyde resin being used in such amounts that the polystyrene foam particles constitute 75 to 95% by volume of the resulting composite foam body.

The polystyrene particles are preferably in the form of balls, such balls being substantially spherical and preferably having a diameter of 0.6 to 10 mm (more preferably 0.8 to 10 mm).

It is advantageous, in order to control the properties of the composite foam body, to use mixtures of balls of different average diameter (that is at least two groups of balls, the first group having substantially a first diameter and a second group having substantially a second diameter). This enables one to minimise the natural gaps (before use of the resin) between the balls. This is analogous to a method used in the concrete industry which allows a suitable selection of the dimensions of the granulates to minimise the quantity of hydraulic binder to be used, so as to obtain a closed concrete with the aid of these granulates.

It is particularly preferred that the balls comprise a first group having an average diameter of substantially 0.8 mm and a second group having an average diameter of 6 mm.

A particularly preferred combination is a mixture of 1 part by volume of expanded polystyrene balls of average diameter 6 mm with 0.4 part by volume of expanded polystyrene balls of average diameter close to 0.8 mm.

The foamed phenol-formaldehyde resin has, as mentioned above, a density of 50 to 500 grams per litre. It is generally obtained by limited expansion of a slightly viscous resol containing a foaming agent such as Freon, for example (Freon is a Trade Mark); this resol also advantageously contains a surface-active agent making it possible to obtain closed cells in the resulting foamed resin. Of course, the resol also contains an acid catalyst for the polycondensation reaction.

The resulting foamed resin fills the gaps between the polystyrene foam particles.

In the composite foam bodies according to the invention, the polystyrene foam particles are preferably contiguous or close to one another; in practice, the volume of the composite body is 5 to 25% greater than the apparent expanded volume of the foam particles.

Thus, for example, if the foam body has a volume of 1 litre, substantially 1 litre (by apparent expanded volume) of expanded polystyrene balls of average diameter 6 mm may be used and, to fill the gaps between these balls, 0.2 to 0.4 litre of expanded polystyrene balls of average diameter 0.8 mm. Sufficient phenol-formaldehyde resin is used to fill all the gaps remaining between the polystyrene balls, after expansion of the resin, with foamed resin having a density of between 50 and 500 g/l.

It is possible to obtain products of different apparent densities; for this purpose, one may; - either vary the density of the foamed resin, without changing either the quantity or size of the balls; - or, by maintaining the density of the foamed resin constant, vary the size of the balls and the quantity of balls used (for example, modifying the quantity of small balls with respect to the large ones).

The composite foam bodies according to the invention have remarkable properties of fire resistance, mechanical resistance compared to their density and heat insulation (the latter often being lower than 0.035 kcal/m/h C.). They may be in the form of blocks in which there are no intercommunicating gaps, thus avoiding any absorption of water by these products and allowing charged or non-charged resins to be moulded thereto without penetration into the foam body.

In the process according to the invention, the phenol-formaldehyde resin is preferably used in the form of an emulsion (containing the catalyst and foaming agent and also a surface-active agent). The emulsion is preferably injected into a bed of foam particles, previously charged into a mould cavity, the temperature of the mould being raised so as to effect the expansion and polycondensation of the phenol-formaldehyde resol until the mould is filled while ensuring that the temperature does not each one at which softening of the foam particles takes place.

It will be noted that in this process the foam particles are never subjected to a pressure during manufacture of the products, except, possibly, when the particles are placed in the mould, this (low) pressure then being used to prevent expansion of said particles.

The foam particles used may be uncoated or, advantageously, they may be pre-coated by a resin emulsion as indicated above.

The heating of the phenol-formaldehyde resin to effect expansion and cross-linking of the phenol-formaldehyde resin may be effected by any known means. However, it will be noted that, since initially the (coated or uncoated) foam particles fill the whole of the mould, it is advantageous to effect heating by means of a high-frequency current.

On carrying out the process according to the invention, it has been noted that the composite foam bodies obtained have, even when thick, very high homogeneity; this means not only that the polystyrene foam particles are regularly distributed throughout the body, but also that the cells of the foamed phenol-formaldehyde resin are substantially completely regular.

The present invention enables foam bodies of very varied shapes to be produced; if in particular glass fabrics or mats are disposed inside or on the surface of the mould in which the foam body is made, the phenol-formaldehyde resin (preferably used in slightly larger quantities than those previously described) will impregnate such fabrics or mats and a composite material having advantageous properties will be directly obtained. Bodies may also be produced which comprise reinforcing elements or inserts, located inside or preferably on the surface of the bodies prepared according to the invention. Decorative elements may also be disposed on the surface of the foam bodies according to the invention.

Finally, rigid or supple, porous panels, themselves made of foam particles (for example, panels made by agglomeration of expanded polystyrene beads) may be incorporated by using a slight excess of phenolformaldehyde resin; this latter, during its expansion, penetrates into the gaps in the porous panels, forming a complex composite material having interesting properties.

In order that the present invention may be more fully understood, the following Examples are given by way of illustration only.

Example I A mould was used having an internal volume of 1000 litres (the dimensions being 2.50 metres x 4 metres x 0.10 m); this mould was filled, with the aid of "venturis", with a mixture of 1000 litres of expanded polystyrene balls (density 12 kg per m3), of average diameter 6 mm, and of 400 litres of expanded polystyrene balls (density 20kg per m3), of average diameter 0.6 mm; about 40 kg of emulsified phenol-formaldehyde resin constituted by 30 kg of resol, 3 kg of hardener (acid), 7 kg of foaming agent (Freon - Freon is a Trade Mark) and 30 g of surface active agent, were injected into this mould. The whole was heated to about 45"C for about 1 hour. The panel obtained, when removed from the mould, was left to mature in an oven for about 2 hours at around 70"C.

Examples 2 to 6 The technique used in these examples was the so-called pre-coating technique in which, in a preliminary operation, expanded polystyrene balls (density 12 kg/m3) were coated with a certain quantity of phenol-formaldehyde resin in the form of an emulsion and containing a foaming agent (for example 20 to 30% by weight of Freon with respect to the resin - Freon is a Trade Mark), a surface-active agent (used for example at a rate of 1 to 3% by weight with respect to the resin) and an acid catalyst (used for example at a rate of 2 to 10% by weight with respect to the resin); then in a second operation, these pre-coated balls were introduced into a mould, the mould was closed and the material therein heated with the aid of high frequency (27kHz emitted by plates); the duration of heating was about one minute which is considerably shorter than is conventional.

In this way, by varying the quantities of balls and resin, panels having the following properties were obtained: Polystyrene balls Phenol- Resistance Insulation formal- to compress- Coefficient dehyde ion (kg/ (kcal/mlm2/ resin cm2) h/ C) 1 m3 of diameter 6 mm 0.4 m3 of diameter 0.8 to 2mm 20 kg 1.66 0.0296 1 m3 of diameter 6 mm 0.4 m3 of diameter 0.8 to 2 mm 30 kg 2.41 0.0292 1 m3 of diameter 6 mm 0.4 m3 of diameter 0.8 to 2 mm 80 kg 2.61 0.032 1 m3 of diameter 6 mm 40 kg 2.49 0.0282 1 m3 of diameter 0.8 to 2 mm 40 kg 3.70 0.0360 Example 7 A composite panel was made comprising, on its two faces, a glass mat and at the centre a foam body according to the invention. A first glass mat (mat of 300 g/m2 and a thickness of about 0.7 mm) was firstly deposited on the bottom of the mould, then the normal quantity, according to the invention, of foamed polystyrene balls precoated with an emulsion of phenol-formaldehyde resin (as described in Example 2) was deposited on this mat and a supplementary quantity of emulsion of phenol-formaldehyde resin about (1.2 kg of resin per square metre of panel to be produced), was added. A second glass mat, identical to the first, was deposited on the upper surface of the balls, the mould was closed and the whole heated (for example up to 40-50"C) so as to cause the phenol-formaldehyde resin to foam and cross-link.

WHAT WE CLAIM IS: 1. A composite foam body, which comprises polystyrene foam particles in an amount of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. interesting properties. In order that the present invention may be more fully understood, the following Examples are given by way of illustration only. Example I A mould was used having an internal volume of 1000 litres (the dimensions being 2.50 metres x 4 metres x 0.10 m); this mould was filled, with the aid of "venturis", with a mixture of 1000 litres of expanded polystyrene balls (density 12 kg per m3), of average diameter 6 mm, and of 400 litres of expanded polystyrene balls (density 20kg per m3), of average diameter 0.6 mm; about 40 kg of emulsified phenol-formaldehyde resin constituted by 30 kg of resol, 3 kg of hardener (acid), 7 kg of foaming agent (Freon - Freon is a Trade Mark) and 30 g of surface active agent, were injected into this mould. The whole was heated to about 45"C for about 1 hour. The panel obtained, when removed from the mould, was left to mature in an oven for about 2 hours at around 70"C. Examples 2 to 6 The technique used in these examples was the so-called pre-coating technique in which, in a preliminary operation, expanded polystyrene balls (density 12 kg/m3) were coated with a certain quantity of phenol-formaldehyde resin in the form of an emulsion and containing a foaming agent (for example 20 to 30% by weight of Freon with respect to the resin - Freon is a Trade Mark), a surface-active agent (used for example at a rate of 1 to 3% by weight with respect to the resin) and an acid catalyst (used for example at a rate of 2 to 10% by weight with respect to the resin); then in a second operation, these pre-coated balls were introduced into a mould, the mould was closed and the material therein heated with the aid of high frequency (27kHz emitted by plates); the duration of heating was about one minute which is considerably shorter than is conventional. In this way, by varying the quantities of balls and resin, panels having the following properties were obtained: Polystyrene balls Phenol- Resistance Insulation formal- to compress- Coefficient dehyde ion (kg/ (kcal/mlm2/ resin cm2) h/ C) 1 m3 of diameter 6 mm 0.4 m3 of diameter 0.8 to 2mm 20 kg 1.66 0.0296 1 m3 of diameter 6 mm 0.4 m3 of diameter 0.8 to 2 mm 30 kg 2.41 0.0292 1 m3 of diameter 6 mm 0.4 m3 of diameter 0.8 to 2 mm 80 kg 2.61 0.032 1 m3 of diameter 6 mm 40 kg 2.49 0.0282

1 m3 of diameter 0.8 to 2 mm 40 kg 3.70 0.0360 Example 7 A composite panel was made comprising, on its two faces, a glass mat and at the centre a foam body according to the invention. A first glass mat (mat of 300 g/m2 and a thickness of about 0.7 mm) was firstly deposited on the bottom of the mould, then the normal quantity, according to the invention, of foamed polystyrene balls precoated with an emulsion of phenol-formaldehyde resin (as described in Example 2) was deposited on this mat and a supplementary quantity of emulsion of phenol-formaldehyde resin about (1.2 kg of resin per square metre of panel to be produced), was added. A second glass mat, identical to the first, was deposited on the upper surface of the balls, the mould was closed and the whole heated (for example up to 40-50"C) so as to cause the phenol-formaldehyde resin to foam and cross-link.

75 to 95% by volume relative to the volume of the body, and, filling the gaps between the particles, foamed phenol-formaldehyde resin of density 50 to 500 grams per litre.

2. A foam body according to claim 1, in which the particles are in the form of balls.

3. A foam body according to claim 2, in which the balls comprise a first group having an average diameter of substantially 0.8 mm and a second group having an average diameter of 6 mm.

4. A foam body according to any of claims 1 to 3, which further comprises reinforcement bonded by the phenol-formaldehyde resin.

5. A foam body according to any of claims 1 to 3, which comprises further foamed material bonded to the body by the phenol-formaldehyde resin.

6. A process of preparing a composite foam body, which comprises filling a mould cavity with polystyrene foam particles and phenol-formaldehyde resin containing a foaming agent and an acid catalyst, and heating to cause foaming and cross-linking of the resin until the latter attains a density of 50 to 500 grams per litre, the polystyrene foam particles and the phenol-formaldehyde resin being used in such amounts that the polystyrene foam particles constitute 75 to 95% by volume of the resulting composite foam body.

7. A process according to claim 6, in which the particles are in the form of balls.

8. A process according to claim 7, in which the balls comprise a first group having an average diameter of substantially 0.8 mm and a second group having an average diameter of 6 mm.

9. A process according to any of claims 6 to 8, in which the phenol-formaldehyde resin is used in the form of an emulsion.

10. A process according to claim 9, in which the phenol-formaldehyde is introduced into the mould in the form of a coating on the particles.

11. A process according to any of claims 6 to 10, in which said heating is effected by means of a high frequency current.

12. A process according to claim 6, substantially as herein described in any of Examples 1 to 7.

13. A composite foam body when prepared by a process according to any of claims 6 to 12.