GB1604072A

GB1604072A - Intumescent fire retardant composites

Info

Publication number: GB1604072A
Application number: GB1871678A
Authority: GB
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1977-05-11
Filing date: 1978-05-10
Publication date: 1981-12-02
Also published as: FR2390399B1; FR2390399A1; JPS53139400A; DE2820873A1; JPH0228632B2; DE2820873C2

Description

(54) INTUMESCENT FIRE RETARDANT COMPOSITES (71) We, MINNESOTA MINING AND MANUFACTURING COMPANY, a corporation organised and existing under the laws of the State of Delaware, United States of America, of 3M Center, Saint Paul, Minnesota 55101, United States of America, 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: This invention relates to an intumescent fire retardant material, and particularly a material which has the ability to remain in the flexible unexpanded form, until heat, such as that produced by a fire, is applied, at which time it will expand to become a substantially rigid refractory thermal insulator.

Industry has long sought better materials to effectively fill voids left by burning or melting cable insulation as in the case of a fire in modern office buildings. Better thermal insulating covering for walls, doors, ceilings, etc., are also needed. The materials heretofore employed provided protection for only limited periods because of poor stability at elevated temperatures or damage by high-pressure water sprays due to low mechanical strength.

They have had the further disadvantage that they were not waterproof and had low volume expansions and pressure generation, particularly at low temperatures, with a resultant loss in their capacity to fill void areas or provide thermal insulation, thus allowing the spread of smoke or fire.

U.S. Patent 3,786,604 is illustrative of the prior art and discloses the concept of filling the gap between a concrete floor slab and an upright curtain wall with a urea formaldehyde resin foam which is supported in a trough made of thin resilient sheet steel. The steel trough support is required because the mechanical strength of the foam is relatively low and that of the charred foam is even lower.

U.S. Patent 3,429,836 discloses a process for producing thermal insulating coverings from organic (polystyrene and copolymers of styrene) foam materials in combination with alkali metal silicates. The composition is made into rigid boards for use as thermal insulating covers on surfaces such as walls, ceilings, and doors. The foamed board-like material must be coated with a protective layer of lacquers or plastic films to render it moisture resistant.

U.S. Patent 3,983,082 relates to a silicone resin base fire retardant system having a temperature capability to at least about 230"C., and combines intumescent characteristics with a crusting and charring capability. These materials are intended primarily for use in aircraft gas turbine engines and they are most effective at relatively high temperatures on the order of 1000"C., or higher.

The present invention relates to dense flexible heat expandable, fire retardant composite materials which have the capability of expanding up to ten times their original volume when exposed to heat. According to the invention, a dense, flexible, heat expandable, fire retardant composite material is provided which is capable of subsisting substantially indefinitely in sheet or putty form, includes an organic char-forming component, and which comprises an intumescent component in granular form, the individual granules of said intumescent component each being capable of enlarging solely upon the application of heat; and a fully polymerized or vulcanized organic binder component.

In use, composite materials of the invention are normally applied in sheet or putty form, and can remain in their flexible unexpanded state until such time as they are subjected to heat, for example of the order of 100"C., as in a burning building. When thus heated, the composite materials readily intumesce to seal voids caused by burning or melting material and provide seals against smoke, vapours, water, steam pressure and due to its refractoriness, protects against spread of fire from one area to another or from floor to floor. An added advantage provided by the unexpanded flexible fire retardant composites of the present invention, particularly in paste or putty form, resides in the provision of an elastomeric seal against vapours, smoke and even water.

Preferred embodiments of composite material according to the invention, capable of expanding to at least twice their onginal size upon heating, each comprise 15 to 80 percent by weight of an alkali metal silicate in granular form, the individual alkali metal silicate granules each being capable of enlarging solely upon the application of heat, 15 to 40 percent by weight of a fully polymerized or vulcanized binder component, up to 40 percent by weight of an organic char-forming resin and up to 50 percent by weight filler comprising up to 20 percent by weight active (as herein defined) filler and up to 40 percent by weight inactive as herein defined) filler. Suitable fillers include granular inorganic materials, organic or inorganic fibres, vulcanization aids, and plasticizers. The consistency of the material can range from a soft putty-like consistency up to a hard rubber.This range of "hardness" is achieved by selectively varying the individual components of the composite material. For example, a Shore "A" durometer hardness in the range 35 to 95 can be achieved using a chloroprene rubber as the binder component.

The fillers referred to above are classified as "active" and "inactive". The active fillers are either chemically and/or physically reactive components and contribute to the "green" state characteristics of the intumescent composite materials of the present invention and include those fillers such as plasticizers, vulcanization aids, blowing agents and solvents.

The inactive fillers are inert materials, and include "active" fillers which may be present in excess, which are chemically unreactive and function during or after a fire as a refractory or endothermic material. The active fillers can comprise up to 20% by weight of the composite material and the inactive fillers can be present up to 40% by weight, provided, however, that the total filler content of the composite materials does not exceed 50% by weight.

It has been found that an especially preferred material for the alkali metal silicate is granular sodium silicate with particle sizes of from 0.2 mm. to 2.0 mm.; i.e., with 95% of the particles being greater than 0.2 mm., a moisture content of 5 to 30% and an SiO2 and Na2O ratio of 2 to 3.75:1. In this connection, we have found that as the proportion of silica to alkali in the alkali metal silicate decreases, the rate of solution of the alkali metal silicate increases. For example, if all other factors remain the same, a sodium silicate having an SiO2:Na2O ratio of 2.0 will dissolve more rapidly than a sodium silicate having a 3.75 ratio.

This rapid attack by water is detrimental from a long-term environmental stability and performance standpoint. Accordingly, materials having SiO2:Na2O ratios less than 2.0 have been found to be less than satisfactory. Additionally, as the SiO2:Na2O ratio decreases, the refractoriness of the composite material also descreases and thus results in a material lacking stability when subjected to water and water sprays during a fire. Other hydrated alkali metal silicates such as potassium silicate can also be utilized to form fire retardant composites of the present invention provided that the silica to alkali ratio is within the contemplated range.

It has been found that when about 80% of the particle sizes of the alkali metal silicate; e.g., sodium silicate, utilized in the composite material, was less than 0.15 mm., the composite material when subjected to heat intumesced only slightly. In a comparative test, a composite material produced with sodium silicate having about 95% of the particle sizes greater than 0.2 mm., expanded to twice its original volume and the composite material produced with sodium silicate particle sizes less than 0.15 mm., had a volume expansion of only 0.5.

In a particularly preferred embodiment of the invention, a composite material capable of expanding to ten times its original volume upon heating, comprises 52 percent by weight of granular sodium silicate intumescent component; 95 percent by weight of the particles being greater than 0.2 mm., the particles each enlarging solely upon the application of heat, and the sodium silicate having a moisture content of 19 percent; 23 percent by weight of a chloroprene rubber binder component, 6 percent by weight of powdered phenolic char-forming resin, and 19 percent by weight of a filler comprising 11 percent by weight of active filler as herein defined) and 8 percent by weight of inactive filler (as herein defined).

Among the useful organic char-forming resins are phenolic resins, polycarbodiimide, urea-formaldehyde and melamine formaldehyde which, when charred in combination with the other components, contribute to formation of a highly refractory composition.

Those matenals which may be used as fillers in the composite materials of the present invention include quartz sand (silica), anti-oxidants, vulcanization aids, clay, fly ash, blowing agents, plasticizers, perlite, vermiculite, inorganic fibres such as glass fibres and mineral wool and organic fibres.

Exemplary binder materials include char-forming elastomers such as chloroprene and acrylonitrile rubbers and non-char-forming polymers such as chlorosulfonated polyethylene, polybutene and polysulfide polymers.

The invention will now be illustrated by way of the following examples, in which flexible sheet materials as well as paste or putty-like materials were produced by standard forming procedures. These materials begin to intumesce at temperatures as low as 110 C., and when heated to 600DC., have volume expansions of at least 2, flexural strengths of at least 20 kg.

per cm.2 and withstand temperatures greater than 1000"C. In addition, these materials generate expansion pressures greater than 14 kg./cm.2 when tested in the Instron "Pressure Test".

Example I Batching The following materials were prebatched by dry blending: Ingredients Wt.% Neoprene W 25 Sodium Silicate - (Britesil H24) 56 Phenolic Resin - (Varcum 5485) 11 Silica (Min-U-Sil) 8 Compounding The above materials were charged to a Banbury mixer for compounding using the following conditions: Step Comments 1 Charge all materials to a water cooled Banbury 2 Lower Ram - 3 kg./cm.2 3 Raise Ram and sweep 4 Lower Ram 5 When temperature reaches 90"C., raise Ram until temperature drops to 650C.

6 Lower Ram 7 Repeat steps 5-6 three times. On third time, dump material and transfer to rubber mill.

Milling Mill material until material bands on mill. Set mill gap to desired thickness and sheet out material. The resulting sheet will be a flexible rubber-like material which can be die cut to form the desired configurations.

Testing The following tests were conducted on the above material: 1. Expansion (X) at 600"C. under weight where X = Final Vol. - Int. Vol.

Int. . Int. Vol.

Test method: A 50 mm. diameter disk is die cut from the material and the volume and weight of the disk is determined. The disk is set on a ceramic plate and a metal disk weighting 760 gm. is set on top of the material. The sample is then placed in a preheated kiln for 30 minutes at 600"C. The sample is removed and weight and volume are determined.

In addition to expansion, LOI, green bulk density, and fired bulk density are determined.

2. Low Temperature Expansion A sample is placed in an oven set at 120 C. to determine if expansion takes place at low temperatures. This is a pass/fail test.

3. Strength MOR (a) Test samples are prepared as follows: The green material is cut into 50 mm. long x 13 mm. wide x 6 mm. thick bars.

These bars are expanded under confinement at a kiln temperature of 600"C.

with a soak time of 30 minutes.

(b) The modulus of rupture is determined on an Instron strength testing machine.

The method used is the MOR for a three-point load, and is calculated by: MOR = 3PT, where 2bd P = load required to break bar L = span distance between outer supports b = width of bar d = depth of bar 4. Refractory Test Samples of the above material, 25 mm. x 50 mm. x 6 mm. are placed in a kiln at 1090"C. The samples are monitored for three hours. Failure is determined by melting of the material within three hours.

5. Pressure Generation The pressure generated kg./cm.2 during expansion is determined by use of a free-piston device. The piston is rested on a test sample which is heated. The device was loaded at room temperature and placed in an Istron tester. The sample was heated to 230"C. slowly, allowing the sample to generate pressure. Piston clearance is maintained to allow expansion gases to escape. Sample size was chosen to allow direct readout of kg./cm.2 on the Instron tester.

6. In addition to the above tests, the following standard tests were also performed: NEL-PIA/MAERP Standard Method of Fire Test ASTM D-395 Compression Set-Method B 22 Hours at Room Temperature Test Results Actual Test TEST Range ALL Compositions Results Expansion - X 2 - 10 2.46 LOI - to 20 - 60 30.9 Green Density - gm./cc. 1.0 - 1.65 1.48 Fired Density - gm./cc. .05 - .5 .34 MOR - kg./cm.2 28 - 84 40 Refractory Pass/Fail Pass Pressure Generation kg./cm.2 > 14 18 Low Temperature Expansion Pass/Fail Pass ASTM E-119-73 Pass/Fail Pass NEL-PIA/MAERP Pass/Fail Pass ASTM D-395 - % compression 10 - 80 70 Shore "A" Durometer 35 - 95 83 A simulated firedoor test was conducted with the intumescent material of the example.A 17 guage steel frame measuring about 180 mm. x 215 mm. x 25 mm. was loaded with test material and set into a refractory brick assembly, then subjected to 8150C. produced by a propane burner. The first test (A) used two 20 mm. styrofoam test panels. The second test (B) used two 20 mm. styrofoam panels sandwiched between two 1.6 mm. flexible firestop sheets. Temperatures were recorded on the hot and cold side fusing Chromel-Alumel thermocouples attached to the center of the frame and are shown below.

Time Minutes Hot Temperature ("C.) Cold Temperature ("C.) A B A B 0 22 22 22 22 4 650 730 50 40 8 690 760 100 65 12 760 760 160 85 16 760 790 210 100 20 790 815 240 110 30 815 - 420 32 - 815 - 140 Examination after 30 minutes revealed that the styrofoam panels had been completely consumed whereas the intumescent fire retardant sheets had expanded and hardened into a rigid insulating material.

Example 2 The following materials were batched and compounded according to the procedures of Example 1: Ingredients Wt.% Neoprene W 24.2 Sodium Silicate (Britesil H-24) 54.2 Phenolic Resin (Varcum 5485) 10.6 *Silica (Min-U-Sil) 7.7 **Zinc Oxide 1.3 **Magnesia 1.0 **Sulfur - .24 **Tetramethylthiuram Monosulfide (Thionex) .32 **N-Phenyl-Alpha-Naphthylamine (Neozone A) .44 *Inactive Filler **Active Filler NEOZONE IS A Registered Trade Mark.

After normal processing, the above material was heat treated at 850C., in a forced air oven for 24 hours. The material, when tested as in Example 1, exhibited the following test results.

Test Test Result Expansion - X 7.6 LOI- % 36.5 Green Density - g./cc. 1.48 Fired Density - g./cc. 0.11 MOR - kg./cm.2 42 Refractory Pass Pressure Generation - kg./cm.2 20 ASTM-E-119-73 Pass ASTM D-395 Method B - % compression 23 Low Temp. Expansion Pass Shore "A" Durometer 94 Example 3 An intumescent putty-like composition was formulated from the following materials: Material Wt.% Polybutene (Oronite &num;32) (ORONITE is a registered Trade Mark) 28.6 Phenolic resin (Reichold Varcum Type 5416) 21.4 Sodium Silicate (Britesil H-24) 38.6 Fiberglass (Owens-Corning 799AB 1/4" chopped) 6.0 Silica - (Min-U-Sil-) 5.4 The fiber, sodium silicate, and phenolic resin were mogul mixed into the polybutene. The composite had the consistency of a caulking putty.When fired at 6000C. for ten minutes, the material expanded 2.1X.

Examples 4 - 20 In these examples, intumescent fire retardant composite materials with the indicated components (weight percent) were formulated according to the compounding procedure of Example 1, (4-160 and Example 3 (17-20) and were also tested in the manner set forth in Example 1.

EXAMPLES Components 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Neoprene W 25 20.3 30 20.8 15 40 15 40 40 40 Nitrile Rubber 25 Neoprene WRT 25 Neoprene GRT 25 Polybutene 40 15 25 40 Britesil H-24 56 56 56 56 45.4 64.5 46.7 80 15 45 40 40 30 15 80 56 40 Phenolic Resin 11 11 11 11 8.9 9.2 5 40 40 20 30 40 5 11 15 Filler - Inactive 8 8 8 8 14.6 5.5 12.5 5 20 5 - 8 5 Active 10.8 10.8 TEST RESULTS Expansion (X) 2.5 7.6 2.3 4.2 6 5.3 6 5.3 10 2.5 3.4 5 6.8 2 4.4 4.6 5.2 LOI% 28 37 39 29 24.5 29 28.3 24 60 29 40 39 48 59 36 40 46 Green Density g/cc 1.49 1.48 1.49 1.59 1.2 1.60 1.34 1.67 1.46 1.14 1.56 1.29 1.21 1.29 1.05 1.34 1.66 Fired Density g/cc .36 .11 .28 .22 0.13 .18 0.14 .23 .065 .23 .21 .19 .17 .18 .13 .14 .14 MOR kg./cm.2 40 42 27 62 28 74 32 50 27 38 28 28 18 Hard Hard Hard Hard Refractory pass/fail Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Low Temp. Expansion Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass NEL-PIA/MAERP Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Putty putty putty putty Shore "A" Durometer 83 94 83 90 35 90 51 85 83 88 68 76 80 Putty Putty Putty Putty Examples 21 - 25 In these examples, intumescent fire retardant composite materials with the indicated components (weight percent) were formulated according to the compounding procedure of Example 1 and were also tested in the manner set forth in Example 1.

EXAMPLES Components 21 22 23 24 25 Neoprene W 20.3 22.0 20.0 20 23.4 Britesil - H-24 45.4 40.0 35.0 25 52.4 Phenolic Resin 8.0 8.0 5 5 5.5 (a) Agerite Stalite S 0.37 0.4 0.39 0.39 0.46 (a) Dioctyl Phthalate 8.3 8.35 10 10 8.26 (a) Unads 1.04 1.1 1.03 1.03 1.21 (a) Sulfur 0.05 0.05 0.05 0.05 0.06 (a) Red Lead Oxide 1.04 1.1 1.03 1.03 1.21 (b) Silica 14.6 19.0 27.5 37.5 7.5 (a) Active filler 10.8 11 12.5 12.5 11.2 (b) Inactive filler 14.6 19 27.5 37.5 7.5 Expansion (x) 6.4 5.2 5.5 5.7 8.7 LOl % 33.4 37 47.4 47.5 26.5 Green Density (gms/cc) 1.4 1.37 1.37 1.39 1.4 Fired Density (gms/cc) .14 .17 .13 .13 0.118 MOR kg./cm.2 Not measured Refractory pass/fail Pass Pass Pass Pass Pass Low Temperature Ex Expansion Pass Pass Pass Pass Pass Shore "A" Durometer 50 50 45 45 55 As used throughout the specification, the following components are available under the trade names shown from the manufacturer or supplier indicated. The components were obtained in the form indicated.

Component - Trade Name Composition Type Form Company (Supplier) Neoprene Polychloroprene W Rubber chunks Dupont Neoprene Polychloroprene WRT Rubber chips Dupont Chemigum (registered Nitrile Elastomer Ng Solid Block Goodyear Tire & Rubber Trade Mark) Britesil Sodium silicate, hydrous H-24 Granules Philadelphia Quartz (10-65 mesh 95%) Oronite Polybutene 32 Vis. liquid Chevron Chem. Co.

Varcum Phenolic Resin Phenolic Resin 5485 One step phenolic RCI Chemicals, Inc.

thermoset powder Varcum Phenolic Resin Phenolic Resin 5416 One step phenolic RCI Chemicals, Inc.

thermoset powder Maglite (registered Magnesium Oxide D Powder (fine) Merck Trade Mark) Zinc Oxide Zinc Oxide - Powder Merck Sulfur Sulfur Tire Brand Powder Stauffer Chemicals Thionex Tetramethylthiuram E Powder DuPont Monosulfide Min-U-Sil Silica 50 Powder Philadelphia Glass & Sand Neozene N-phenyl-Aplha- A Pellets DuPont (registered Naphthylamine Trade Mark) DOP Dioctylphthalate - Liquid Merck Component - Trade Name Composition Type Form Company (Supplier) Chlorowax Chlorinated Paraffin 500-C Liquid Diamond Shamrock Unads Tetramethylthiuram - Powder R. T. Vanderbilt Co.

monosulfide Agerite Stalite Mixtures of alkylated S Powder R. T. Vanderbilt Co.

diphenylamines Red Lead Oxide Pb3O4 95% Powder Hammond Lead Products

Claims

WHAT WE CLAIM IS:

1. A dense, flexible, heat expandable, fire retardant composite material capable of subsisting substantially indefinitely in sheet or putty form, the material including an organic char-forming component, and comprising an intumescent component in granular form, the individual granules of said intumescent component each being capable of enlarging solely upon the application of heat; and a fully polymerized or vulcanized organic binder component.

2. A dense, flexible, heat expandable, fire retardant composite material capable of subsisting substantially indefinitely in sheet or putty form, and capable of expanding at least up to twice its original volume upon heating, which material comprises 15 to 80 percent by weight of an alkali metal silicate in granular form, the individual alkali metal silicate granules each being capable of enlarging solely upon the application of heat, 15 to 40 percent by weight of a fully polymerized or vulcanized binder component, up to 40 percent by weight of an organic char-forming resin and up to 50 percent by weight filler comprising up to 20 percent by weight active (as herein defined) filler and up to 40 percent by weight inactive (as herein defined) filler.

3. A composite material according to claim 2 wherein the alkali metal silicate is granular sodium silicate having particle sizes of from 0.2 to 2.0 mm., a moisture content of 5 to 30 percent and a SiO2 to Na2O ratio of 2 to 3.75:1.

4. A composite material according to any preceding claim wherein the binder component is a chloroprene rubber, the composite material having a Shore "A" durometer hardness in the range 35 to 95.

5. A composite material according to any of claims 1 to 3 wherein the binder component is a chloroprene rubber the composite material having a putty-like consistency.

6. A composite material according to any of claims 1 to 3 wherein the binder component is a polybutene polymer, the composite material having a putty-like consistency.

7. A composite material according to any preceding claim wherein the organic char-forming component is a phenolic resin.

8. A composite material according to claim 1 wherein the binder component constitutes the char-forming component.

9. Dense, flexible, heat expandable, fire retardant composite material capable of subsisting substantially indefinitely in sheet or putty form, and capable of expanding to ten times its original volume upon heating, which material comprises 52 percent by weight of granular sodium silicate intumescent component; 95 percent by weight of the particles being greater than 0.2 mm, the particles each enlarging solely upon the application of heat, and the sodium silicate having a moisture content of 19 percent; 23 percent by weight of a chloroprene rubber binder component, 6 percent by weight of powdered phenolic char-forming resin, and 19 percent by weight of a filler comprising 11 percent by weight of active filler as herein defined) and 8 percent by weight of inactive filler (as herein defined).

10. Fire retardant composite material substantially as described in any of the Examples herein.