IE42474B1 - Improvements in or relating to a silicate-containing flame-resistant adhesive composition - Google Patents

Description

This invention relates to a flame-resistant adhesive composition having a long pot life, useful for adhering together a variety of articles and. objects and. also for coating substrates made of various materials.

The composition of this invention is characterized in that it comprises (l) an inorganic component which, with respect to the total weight of the composition, consists of (a) from 20% to • 90% by weight of a concentrated aqueous solution of alkali metal silicate, (b) from 5% to 25% by weight of a clay and (e) from 2% to 7% hy weight of deflocculated asbestos fibres; and (2) an organic component,present as a 30-70% aqueous solution, selected from a carboxymethylcellulose, a starch ester, a dextrin- and mixtures theroof, said component being present in an amount comprising about 0.2% to about 2% (dry weight) by weight of the total composition.

According to an embodiment of this invention, the composition is applicable to the bonding of articles and the inorganic compo. nent comprises 50-90% of said silicate solution, 5-25% of sail clay and 2-6^5 of said asbestos.

According to another, embodiment, the composition is applicable to the production of coatings and the inorganic component comprises 20-50% of said silicate solution, 7-20% of said clay and 2-7% of said asbestos, the solution containing additionally 30-60% inorganic filler by weight of the total composition.

According to still another embodiment, the composition is applicable to the production of coatings which swell under the effect of heat and comprises, additionally, 1-20% swelling agent ( . hy weight of the total composition.

This invention-relates also to a process for the preparation of tiie abow+deaoribed conpoaiion, comprising (a) charging said silicate solution in a container and rotating it in a given direction; (b) intimately dispersing the aqueous organic component solution in the stirred silicate while rotating said organic component solution in the direction opposite to that in which the silicate was rotated; (c) on completion of the dispersion, adding the clay with continued stirring and (d) thereafter dispersing the deflocculated asbestos in the stirred mixture.

According to another feature of this invention, the inor10 ganic filler, when used, is added after step (b) and prior to addition of the clay.

Other features and advantages of this invention will be apparent from the following detailed description.

The flame-resistant adhesive composition of this invention comprises essentially (1) an inorganic component and (2) an organic component. » The inorganic component comprises a combination of three constituents, viz.; (a) 20-90wt$, by weight of the total composition, of a concentrated aqueous solution of an alkali metal silicate; it is preferred to use a 38-40° Be sodium silicate solution of a 42° Be potassium silicate solution; (b) 5-25wt$, by weight of the total composition, of a clay, preferably powdered kaolin; and (c) 2-7wt$, by weight of the total composition, of deflocculated short asbestos fibres, i.e., submitted prior to use to a mechanical deflocculating treatment to loosen and separate the fibres from one another.

The organic component consists of a 30-70$ (preferably about . 50$) aqueous solution of a carb.oxymethylcellulose, of a starch ester or of a dextrin or a mixture thereof, The organic component - 3 4S474 comprises 0.2-2 wt/ (dry weight) by weight of the total composition.

One of the applications of the composition of this invention is tho bonding of various articles,for example the bonding of (a) pieces or sheets made of aluminum, of black sheet iron, of galvanized sheet metal or of zinc-plated sheet metal, of glass, of cement, etc., on (b) wood, plywood,' particle or fibre boards, polystyrene foam, phenol resins, polyurethanes, and the like. The following bondings may also be achieved: wood-wood, wood-polysty10 rene, carpet-floor, cement-wood, and the like, A highly adhesive bonding is obtained thereby. The composition is flame-resistant and flameproof) it withstands elevated temperatures and does not release any toxic gas. Therefore, the adhesive layer obtained after setting constitutes a barrier . against fire due to its fire-retarding action, preventing flame propagation and the evolution of smoke, etc..

Officially controlled standard tests have shown the composition to he classified as flame-resistant according to the usual standard specifications.

For the latter application, the inorganic component comprises advantageously 50-90/ of said silicate solution, 5-25/ of said clay and 2-6/ of said asbestos. It is preferred to add to the composition 1-3wt/, by weight of the total composition, of a liquid silicone to impart water-repellent properties to the adhesive composition. Setting accelerators (in an amount of 1-3wt/ for example) such as zinc chloride, cadmium chloride, fluosilicates, etc., may also he added to the composition.

Whenever 4esi*ed, the adhesive composition may be colored by means of suitable· inorganic pigments. - 4 42474 The bonding composition may be applied with a brush} with a roller, with a gun, with a sizing machine or by any suitable conventional means. Setting occurs normally within 12--24 hours at room temperature and may be accelerated by heating.

Another highly important application of the composition of this invention is the production of flame-resistant and flameproofing coatings on a variety of substrates such as wood, plywood, particle or fibre boards, expanded polystyrene, phenol foams, polyurethanes, cardboard-reinforced plaster, and the like.

For this latter1 application, the inorganic component comprises advantageously 20-50% of said silicate solution, 7-20% of said clay and 2-7% of said asbestos and the composition contains additionally 30-60wt%, by weight of the total composition, Of an inorganic filler which may be, for examples (a) a powdered lava such as oriolite (Perlite) having a particle size from about 1 micron to about 1mm; (b) a powdered silica having a particle size from about 1 micron to about 1 mm;, (c) unexpanded powdered mica having a particle size from about 1 mm to about 2 mm.

In said application also, the presence of.a liquid silicone, in an amount of 1-3wt%, by weight of the total composition, is advantageous.

To ensure the swelling of the coating at elevated tempera25 tures, a swelling agent, typically dinitrosopontamcthylenetetramine (PllP'f), or a phenol-formaldehyde , urea-formaldehyde, or melamine resin, etc., should be added to the composition in an amount of about 1v.t% to about 20wt%, by weight of.the total composition. - 5 _ 43474 Thus in the case of a high temperature increase (such as will occur during a fire, for example), the coating itself is found to swell (from 1 mm up to 2-4 mm) with resulting formation of closed cells and swelling of the coating with respc-ct to the substrate, with 2-3 cm spacings therebetween, thereby forming insulating pockets. No cracking of the coating is found to occur and no toxic gases are evolved. The coating may withstand temperatures in excess of 12OO°C.

The coating composition may also, if desired, contain T(0 setting accelerators and pigments, as previously mentioned.

The coating composition may be applied oh the substrates by any suitable conventional means .

The process according to the invention for the preparation of the composition is carried out in the following manner.

Tho silicate solution is charged in a suitable container and is then rotated inva given direction by means of a suitable stirring device, at a speed preferably comprised between 500 rpm and 2000 rpm (advantageously at about 1000 rpm).

The aqueous organic component solution is prepared separa20 tely and is then intimately dispersed in the stirred silicate solution. To effect said dispersion, the organic solution is added portionwise, preferahly near the bottom of the container, while rotating it in a direction opposite to that used to rotate the silicate solution; this may be achieved, for example, by means of a perforated dispensing head rotating at a speed of 250-1000 r.p.m. (preferahly at a speed of about 500 r.p.m.).

On completion of the dispersion, the clay is added, with continued stirring, and the deflocculated asbestos fibres are then added and thoroughly dispersed in the liquid mixture. - 6 43474 When a mineral filler is io he added, this is added io ihe dispersion prior io addition of ihe clay; the liquid, silicone, when used, is added after ihe asbestos and ihe optional swelling agents are added Iasi.

All ihe process steps are conducted at ordinary temperature (preferably 5°C).

The resulting composition may be stored in conventional pots, drums or closed containers without setting to a mass during a period of time of at least six months. Thus, it has a remarkably long shelf life for a composition of this typo, which makes its use particularly advantageous and practical.

The following non limiting examples are giveh to illustrate the invention.

EXAMPLE I The two following adhesive compositions are prepared according to the above-described method: Composition 1 Composition 2 (weight $) (weight $) Sodium silicate (38/40° B6) 85 76 Kaolin 7 16 Deflocculated asbestos fibres 4 4 Solvitose CL* (50$ aqueous solution) 2 2 Methyl siliconate (liquid silicone) 2 2 100 100 * Starch ester sold by Doitteau, France.

Both compositions exhibit outstanding tack and, after setting, are classified flame-resistant and fireproof according to the usual standard specifications.

The tensile strength is found' to be 11-15 kg/cm2 at normal - 7 temperature when black sheet iron is bonded to concrete; after 7 days at 40°C and. 95% relative humidity, the tensile strength is 11-18 kg/cm2.· Agglomerated wood-fibre boards were bonded to concrete 5 with the above compositions; the agglomerate breaks at 8-9 kg/cm2 at normal temperature but the bonding plane remains intact.

Plywood was bonded, with the composition: the plywood was found to break between 12 and 14 kg/cm2, but the bonding plane remained intact.

Compositions exhibiting analogous properties were obtained by substituting the starch ester with carboxymetliyl cellulose or dextrin, - EXAMPLE 2 Using the above-described process, the following coating composition was prepared: Weight % Potassium silicate (42°. Be) . 41 Kaolin 13 Deflocculated asbestos fibres 4 Crude Perlite 40 Solvitose CL (50% aqueous solution) 1 Methyl siliconate J_ 100 A flame-resistant and fireproofing coating is obtained after setting.

EXAMPLE 3 Using the previously described process, the following coating composition is prepared: • - 8 43474 Vcighl, ji Sodium silicate (38/40° Be) 41 Kaolin 8 Defloe ciliated asbestos fibres 4 Crude Perlite , 40 Solvitose CL (50# aqueous solution) 1 Methyl siliconate 1 DNPT (swelling agent) J> 100 This compositions produced flame-resistant and fireproofing coatings which swell under the action of heat, as previously described.

For example, a sheet of Okoume-wood , 300 mm x 400 mm x 5 mm, coated on both sides with 1 nun of the above coating, was classified flame-resistant according to the standard radiator .test.

Vben the composition is to exhibit excellent resistance to humidity, and even to immersion, salts or oxides of metals such as Al, kin, Cr, Pb, Ti, Ca, Pe, etc., may be added thereto, in an amount of about 0.5wt# to about 35wt#, by weight of the silicate.

Anialkali metal (typically sodium) fluosilicate may also be incorporated at the time of use, in an amount of 5-1 Out#, by weight of the total composition.

To dry the composition, silicides may bo added in the case of air-drying, but the mixture may also he heated at a temperarature of up to 200°C.

Claims (18)

1. WHAT I CLAIM IS :

1. Silicate-containing flame-resistant adhesive composition, comprising (l) an inorganic component consisting, with respect to the total weight of the composition, of (a) 20-90wt% of a 5 concentrated aqueous alkali metal silicate solution, (b) 5-2?wt% of a clay and (c) 2-7wt% of deflocculated asbestos fibres; and (2) an organic component present as a 30-70% aqueous solution and selected from a carboxymethylcellulose, a starch ester, a dextrin and mixtures thereof, said component, calculated as 10 dry weight, being present in an amount of about 0.2wt% to about 2. Vt% by weight of the total composition.

2. Composition as claimed in claim 1 for the bonding of articles , wherein the inorganic component comprises 50-90% of said silicate solution,' 5-25% of said clay and 2-6% of said 15 asbestos.

3. Composition as claimed in claim 1 for the formation of coatings, wherein the inorganic component comprises 20-50% of said silicate solution, 7-20% of said clay and 2-7% of said asbestos, said composition containing additionally 30-60wt% of an 2q .inorganic filler, by weight of the total composition,

4. Composition as claimed in claim 3, wherein is additionally present a swelling agent, in an amount of 1wt% to 20wt% by weight of the total composition.

5. Composition as claimed in claim 3 or 4, whereim the 25 inorganic filler is a powdered lava, a powdered silica or powdered mica. · . ' ·

6., Composition as claimed in any one of the preceding - 10 42474 claims, wherein a liquid silicone is present in an amount of 1wt/ to 3wt/, hy weight of the total composition,

7. Composition as claimed in any one of the preceding claims, whoroin the concentrated silicate solution is 38/iO 1 ' Be 5 sodium silicate or 42° Bo potassium silicate.

8. Composition as claimed in any one of the preceding claims, wherein said clay is kaolin.

9. Composition as claimed in any one of the preceding claims, wherein is also present a metal salt or oxide, in an 10 amount of 0.5wt/ to 35wt/, by weight of the silicate. •

10. Composition as claimed in any one of claims 1-8, wherein is also present an alkali metal fluosilicate, in an amount of 0.5wt/ to 10wt%, by weight of the total composition,

11. Process for the preparation of a composition as claimed 15 in claim 1, comprising (a) charging the silicate solution in a container and rotating 'same in a given direction; (b) intimately dispersing the aqueous organic component solution in the stirred silicate while rotating said organic solution in a direction opposite to that in which the silicate was rotated; (c) adding 20 said clay on completion of the dispersion, with continued stirring and (d) then dispersing said deflocculated asbestos in the stirred mixture.

12. Process as claimed in claim 11, wherein an inorganic filler is added after step (h) and prior to the addition of 25 said clay. 48474

13. An adhesive composition as claimed in claim 1 substantially as herein described. IA. An adhesive composition as claimed in claim ) substantially as herein described In any of Examples 1 to 3.

14. 15. A process for the preparation of an adhesive composition as claimed in claim 1 substantially as herein described.

15. 16. A process for the preparation of an adhesive composition as claimed in claim 1 substantially as herein described in any of Examples 1 to 3.

16. 17·. An adhesive composition as claimed in claim 1 whenever prepared by a process as claimed in any of claims 11, 12, 15 and 16.

17.

18. Articles bonded or coated with an adhesive composition as claimed in claim 1.