GB2084624A - Insulation board - Google Patents

Abstract

A board-like thermal insulation product having a composition of about 50 to 80% expanded perlite, about 3 to 30% clay, about 5 to 30% newsprint fiber, about 1 to 6% B2O3, up to 25% non-combustible fibrous material, a binder and a waterproofing material. The board is manufactured in a continuous process by removing a liquid vehicle from a slurry of solid material. The liquid in the slurry contains boron compounds in a concentration sufficient to impart from about 1 to 6% B2O3 to the board upon drying.

Description

SPECIFICATION Fire-retardant perlite composition board and method of manufacture This invention relates to a fire-retardant insulating board. In particular, it is an insulating board composed essentially of expanded perlite, fibers, binders and fire-rntardants.

Inert materials such as perlite orvermiculite have been used for some years as insulating materials.

Such materials have been put to various uses, including loose insulation and as an ingredient along with binders and fillers to produce boards with insulating characteristics. Perlite is a generic term for certain volcanic glasses available in ground form which upon heating to a controlled temperature suddenly expand to form light weight particles having excellent thermal and sound insulating properties.

Insulating boards using a large proportion of perlite with a relatively small proportion of otherfillers and binders have been used primarily as thermal insulating boards which have a dimensional stability. However, such boards have low strength properties and may be, depending upon the binders used, quite brittle.

Products of th is type may be formed by a "wet" process. Such a process includes the steps of making a water slurry of the board ingredients and uniformly suspending the solids throughout the slurry by agitation, de-watering the slurry over a screen to produce a wet board and then lightly compressing the wet board to give a uniform thickness an finally drying the board.

Insulating boards of this type have many uses, however, for uses such as roof deck insulation some types of such boards lack some qualities which are useful in a good product.

It is desirable for a roof deck insulation to be largely water-repellent, to have poor thermal conductance, to possess a good strength factor and be strong enough so that it can stand uptoa certain amount of handling and traffic. In addition, in order to meet the building code requirements of several countries it is important that the material befireretardant and when subjected to combustion conditions that it not give off a large amount of toxic gases.

The prior art insulating boards lack one or more of the characteristics necessary for a superior roof composition board. Certain boards which possess the strength and brittleness qualifications achieve these qualities by the use of fibers or fire retardants which are expensive or which contribute to the level of toxic gases given off when subject to combustion conditions. Other boards designed to have low toxic gases eliminate the fibrous materials and certain types of binders which produce such gases upon combustion and thus sacrifice flexibility.

It is an object of this invention to provide afire- retardant insulating board which can be manufactured relatively inexpensively and which has sufficient insulating capacity, strength and flexibility for use as a roof insulating board and in addition which can pass certain standard tests for toxicity. Such a board may be produced by a wet process on, for example, a Fourdrinier machine.

I have found that a fire-retardant thermal insu lat- ing board consisting essentially of from 50-80% expanded perlite, 3-30% clay, 5-15% newsprint fiber, 1-6% B203, up to 25% of a non-combustible fibrous material, a binder and waterproofing material, can be manufactured in a continuous process by the removal of a liquid vehicle from a slurry of solid materials where the liquid in the slurry contains boron compounds in a concentration sufficient to impart from 1-6% B203 to the board upon drying.

Such a board has both insulating and fire-retarding properties as well as sufficient strength and flexibil ityto be used as roof insulating boards. This material, when subject to combustion conditions, gives off relatively low amounts of toxic gases. Gases such as carbon monoxide are given off in concentrations low enough so that the material passes building code testing procedures, such as, for example, the German DIN 4102 A2 tests. A thermal insulating board which passes less stringent tests, such as the German DIN 4102 B1 tests can be produced by the same process and using from 50-80% expanded perlite, 3-30% clay, 5-30% newsprint fiber, 1-6% B203, up to 25% of a non-combustible fibrous material, a binder and waterproofing material.

Insulation boards made according to this invention have properties which are arrived at by balancing many conflicting specification requirements, for example, toxicity, strength, brittleness and water absorption. In order to achieve optimal ranges for each of these characteristics, the properties of the various materials making up the composition board and their interplay must be considered. For example, starch is used to provide strength but too large a concentration of starch reduces fire-retardancy of the board.

Materials such as boron compounds may be used to make insulating boards fire-retardant; however, these compounds contribute to brittleness if used in too large a concentration.

Clay is used in boards to bind perlite particles together. It also contributes to fire-retardancy. However, in high concentrations it may reduce the drainage rate of liquid from the slurry. It may also contribute to brittleness in a board.

Asphalt may be used to provide water repellency in an insulating board. However, it contributes to any toxic gases given off during combustion and in too great a concentration produces boards which can not pass standard toxicity tests.

Newsprint fiber is used as a binding component and prevents the board from being too brittle. In large concentrations it contributes organic matter which releases toxic gases upon combustion, which has a detrimental effect on toxicity tests.

The combination of these materials by a wet process within the ranges of this invention, however, provides an insulating board which is inexpensive, fire-retardant, of low toxicity, has good thermal insulating qualities, and is of sufficient strength and flexibility for use as a roof insulation board.

The insulation board of the present invention, as embodied and described herein, has improved fireretardant properties. According to a preferred embodiment this board is composed of expanded perlite, newsprint fiber, clay, starch, polybor and a silicone compound. The board may also include low amounts of asphalt although inclusion of asphalt has some detrimental effect on the ability of the board to pass toxicity tests.

Perlite is a non-combustible mineral which, in its expanded form, serves as an insulating material. As such it is the major constituent of the insulating board. Being non-combustible it contributes to the fire-retardant properties of the board. If incorporated in the insulating board in amounts lower than about 50% by weight of the finished board, the board has a reduced insulating value and in amounts lower than about 30% the resulting board lacks sufficient insulating value to serve its intended purposes. In amounts greater than above 80% by weight perlite becomes so large a constituent of the insulating board that other properties of the board suffer. For example, the strength and flexibility of the board are reduced because sufficient amounts of newsprint fiber and clay cannot be incorporated.For use as a roof insulation board it is preferred that perlite be incorporated in a range of 40 to 75 percent by weight.

Newsprint fiber in amounts ranging from 5 to 30% by weight are incorporated in the insulating board for purposes of providing strength. Tests of boards made by the method of this invention indicate that the Modulus of Rupture (MOR) flexural strength decreases to unacceptably low levels if the percentage of newsprint fibers or similar material, such as kraft fiber is below about 5% by weight. Tests to determine MOR were carried out according to ASTM procedure C203; however, samples of 2"x6" on a 4" span were used rather than 3"x12" samples on a 10" span as called for by the ASTM procedure. Newsprint fiber or other organic fiber in amounts in excess of about 30% provides too great a percentage of combustible material in the board for it to be considered fire-retardant. Also, newsprint contributes to the quantity of toxic gases produced during combustion of the boards.It has been found that the insulating board can pass the German A2 toxicity test if the amount of newsprint fiber is less than 15% by weight and the insulating board can pass the German B1 tests, with up to 30% by weight of newsprint fiber.

For control of toxic gases and to provide sufficient strength, a range of from about 5 to 10 weight % of newsprint fibers is preferred.

Components must be added to the insulating board to improve its MOR strength. Both clay, such as bentonite clay, and starch are useful as binders and contribute strength to the insulating board.

These components improve MOR measurements when present in certain ranges. However clay, in amounts over about 30 weight %, makes the insulation board so brittle that it is not usable for applications where there is any traffic over it such as in roof insulation. In addition such high concentrations makes the board difficult to manufacture and handle without breaking. On the other hand, sufficient clay which I have determined is at least about 3% must be added to the composition to contribute to the strength of the board. Being an inorganic substance, clay is non-combustible and adds to the fire-retardant quality of the board. Clay, when dispersed, physically covers and protects newsprint fibers from combustion.In orderforitto contribute significantly to fire-retardancy and to bind other components together, the clay should be well dispersed throughout the slurry mixture and the dry board.

Starch contributes to the strength of the board and is also a binder. Corn starch has been found to be useful in the various board compositions. Starch is most effective as a binding agent and also exhibits a high MOR strength factor. For example, raw corn starch has been used successfully, it being gelatin- s ized in the drying process during forming. Starch is combustible and in high concentrations contributes to the amount of toxic gases given off under combustion conditions, thus, it reduces the fire-retardant property of the board. In order for an insulation board to maintain its shape when subjected to combustion conditions, a noncombustible binder, such as clay, is also present in the board.If the perlite and other ingredients were bound together only by a combustible binder such as starch, the board would completely disintegrate once this binder was substantially combusted. The range of starch in the board composition should be sufficiently great to act as a binder but not so high as to contribute significantly to the combustibility of the board. I have found that it can be used in concentrations up to about 4 weight % with good effect.

In order to further increase the fire-retardance of the insulation board, the addition of boron compounds is preferred. This may be added to the slurry from which the board is made so that it mixes with the combustible components. It can be added in forms such as polybor, a commercially available boron containing compound or by in-situ addition of acid to borax.

Amounts of less than about one weight percent B2O3 do not provide a significant measure of fireretardance. Since it has been found that in this com position, boron, in the form of polybor, for example, contributes significantly to the brittleness of the board, amounts of more than about 6 weight percent B203 should not be used. In concentrations higher than 6 weight percent B2O2 the insulation board is brittle and difficult to install for use as roof insulation. Such a concentration also makes the board dif-4 ficultto manufacture or handle without excessive breakage.

Other means of achieving fire-retardance are, as mentioned above, use of perlite and clay to reduce the amount of combustible material present in the board.

For use as roof insulation or any other exterior application, it is useful for the insulating boards to be water-repellent. This may be accomplished by adding a waterproofing agent to the slurry. Both silicone and asphalt compounds are of use in making the board water-repellent. Silicone may be used in much smaller weight concentrations than asphalt to achieve the desired results. For example, 0.1 to 0.3 wt. % of silicone compounds, such as RE-28 or Y-9106 made by Union Carbide, provide acceptable water repellency. Use of this range of a silicone compound provides an insulating board which absorbs 2% by volume of water during a two-hour immersion in water and 5.6% in a twenty-four hour period. To obtain similar results 3 wt. % or more of asphalt compounds must be used.Silicone is preferred because of its ability to impart water repellancy in low concentrations and also because asphalt compounds contribute excessively, even when present in small amounts, to the toxic gases given off during combustion conditions.

Additional materials may be added to the insulation board to provide some improvement in flexibility. For example, rockwool or short lengths of fiberglass fibers incorporated into the board add non-combustible materials to the board and contribute to flexural strength or lack of brittleness. However, they add to the cost of the board to some degree.

In addition to making an insulation board which is fire-retardant, compositions of the materia Is within the ranges set out above also can produce a board which is non-toxic. Toxicity is measured by a standard test such as the DIN 4102-A2 test used in West Germany to determine the amount oftoxic gases produced during combustion of products. In order to pass the A2 toxicity test, a product sample 60 cm long is fed into a furnace heated to 4006C. at 1 cm per minute. The combusted samples must produce no fatalities among rats exposed to the gases produced and the CO level of the rats blood must be below 35%.

Insulation boards which do not meet the A2 toxicity tests may meet the less stringent DIN 41 02-B1 test. The B1 test is performed to test fire retardancy by subjecting four 190 mmx 1000 mm samples to a 750"C. oven for ten minutes. The samples must have an average value of at least 150 mm undisintegrated, with none of the samples being completely disintegrated. In addition, the gas temperature in the center of the flue of the testing apparatus must not exceed 250"C.

Manufacture of fire-retardant insulation boards of the present invention may be carried out in a continuous process by removing a liquid vehicle from a slurry of the solid materials and the boron compounds and drying the resulting felt. The board ingredients of starch, clay, newsprint fiber and a boron compound are combined with water in a mixing apparatus such as a pulper. When the components are sufficently mixed, a waterproofing material is added and the expanded perlite added. The entire slurry is then fed into any conventional fiiter- .

ing apparatus such as a Fourdrinier machine to be de-watered. This apparatus leaves a mat or felt of uniform thickness which is pressed to the desired thickness and the mat is then fed into a drying oven to produce a dry board.

If a non-combustible fiberous material such as rockwool'is added, care must be taken to not break up the fibers in the mixing operation. When stronger fibers such as fiberglass are used such precautions are less necessary.

In order to illustrate several embodiments of the present invention, the following examples are pro vided: Example I: A fire-retardant insulation board was made using: 525 kg of newsprint, 360 kg of bentonite clay, 210 kg of pre-cooked starch, 1500 kg of Polybor, 780 kg of rockwool and 10,000 liters of water.

These materials were combined in the following manner: 5,000 liters of water were introduced into a pulper and the newsprint, bentonite, starch and polybor were added. The pulper was run until the newsprint was pulped and the rockwool was added.

Rockwool was mixed for only about 3 minutes which allowed about 2 minutes for the rockwool to be broken up and wet and about 1 minute for mixing.

During this period the remaining 5,000 liters of water were added. The pulper load was then dumped into a mixing chest where 100 kg of asphalt emulsion was added along with another 10,000 liters of water.

This mixture was then transferred to a machine chest and then a blender where the perlite was added continuously. The whole slurry was then fed by means of a headbox to a Fourdrinier and after de-watering, fed to a drying oven and finishing process.

The perlite used in this example had a density of 3 to 61b/ft3, the bentonite clay was a calcium bentonite from Chemacid, Brussels, Belgium called bentonite A. The starch was a pregelatinized cornstarch made by Marigel in France, coded AC. Rockwool used was Basalt wool made by Isola, Hasslinghausen, Germany and the polybor was a mixture of boric acid and borax having the approximate composition Na2B8013.4 H2O obtained from U.S. Borax. The asphalt emulsion used was Shell 205 from Ghent, Belgium.

Since polybor is water soluble, the polybor is present only in the mat water and not as part of the mat solids. It becomes solid only after the water is removed. Since extra water is added with the perlite and at different stages of the process, the amount of polyboradded to the slurry must take into account this dilution. In order to calculate the amount of polybor to be added during the forming process, the following calculation may be used:

% Polybor wanted in Wt. polybor = water + water x Theoretical x dry board added solids solids Bd. Weight 100 slurry mat In this calculation the weight added is the amount of polyborwhich should be added to the slurry mixture. The amount of water is the amount of water used in the initial slurry mixture and the amount of solids is the solids present in the original slurry mixture. This is divided by the water and amount of sol ids present in the board after pressing. The theoretical board weight is determined based on the weight of the solids in the slurry mixture. The precent additive wanted in the dry board is determined by preselecting the desired amount of polybor.

The amount of solids and water in the slurry mixture is known when the formula is selected. The water to solids ratio in the wet pressed board is not known until after the board is prepared so an approximation is made in order to calculate polybor weight.

In a continuous process, the white water becomes saturated with polybor and the amount added to the pulper can be decreased.

The weight percentages of materials in the dry board produced in this example were: Parts By Weight Ingredients 58.0 Perlite 9.2 Newsprint 1.8 Asphalt 7.4 Bentonite 3.7 Starch 15.2 Rockwool 4.7 Polybor The board had the following properties: Density=12 pcf; Water Absorption (2 hours): 4% by volume; Modulus of Rupture (MOR)=64 psi; German DIN 4102=passed rated, A2.

Example II: Afire-retardant insulation board was made by the same procedure as in Example land the weight percent of materials in dry board were: Parts By Weight Ingredients 65 Perlite 15 Newsprint 10 Rockwool 2 Pregelatinized Starch (Marigel AC) 5 Asphalt Emulsion (Shell 205) 4 Bentonite Clay 2 Polybor This board had the following properties: Density=11 pcf; MOR=76 psi; While such board was not actually tested, it could be expected to pass the German DIN 4102 test and receive a B rating.

Example Ill: To manufacture a fire-retardant insulation board, the following ingredients were placed in a five-gallon container: 113 grams perlite (expanded from No Agua, New Mexico ore to a 3.6 density); 60 grams pulped newsprints (25% soiids); 1.5 grams uncooked cornstarch; 10 grams CTS-1 clay (Kentucky Tennessee Clay Company); 1.1 grams RE-28 silicone emulsion (Union Carbide); 27 grams polybor; 1.7 liters water.

These ingredients were mixed using a clover leaf impeller, and after being sufficiently mixed, the perlite was added and mixing continued until the perlite was dispersed. The slurry was then placed in a Tappi board former where most of the water was removed, forming a mat which was pressed with a hydraulic press. The board was then dried for 16 hours at 250"F. in an air circulating oven. The board contained: Parts By Weight Ingredients 75 Perlite 10 Newsprint 1 Starch 6.8 Clay 4.8 Polybor 0.3 Silicone The board had the following properties: Density=1 1 pcf; MOR 60 psi; Water Absorption (2 hours) =2% by volume.

The conditions under which a board is dried have an effect on the MOR strength of the resultant board.

If a high temperature cycle is used, as would normally be the case in a production process, higher MOR strengths may be achieved than by using a constant 250"F. drying cycle. For example the cycle of 420"F. for one hour reduced to 320"F. for two hours, then to 230cm. for one hour and a final reduction to room temperature produces boards with significantly higher MOR strength than the 250"F. drying.

Example IV: Fire-retardant insulation board was again made as in Example III except glass fibers were added with the newsprint during pulping. The additional ingredients used were 111 grams perlite of 3.2 pcf density; 48.5 grams pulp containing 14.5 grams newsprint and 1.5 grams 114 inch glass fibers from chopped roving; 5 grams Flintkote 205 asphalt emulsion (60% solids); 10.2 grams bentonite clay; 6 grams uncooked cornstarch; 0.4 grams RE-28 silicone emulsion (Union Carbide), 30 grams polybor and 1.7 liters of water.

The dry board consisted of: Parts By Weight Ingredients 74 Perlite 9.5 Newsprint 1 1/4 inch glass fibers 2 Asphalt (solids) 7 Clay 4 Starch 0.1 Silicone 4.7 Polybor The board has the following properties: Density=11 pcf; MOR=90 psi; Water Absorption (2 hours)=2.3% by volume.

Additional procedures may be used in combining the ingredients, for example, the perlite may be pretreated with a spray of diluted asphalt emulsion and then dried to impart a waterproof coating on the perlite particles rather than introducing the asphalt into the slurry. This may have some advantageous effects in improving the water repellency of the resulting board. In addition, a mixture of acid and borax may be used rather than polyborto leave boron in the insulation board. This has an advantage of leaving a higher proportion of the boron compound in the insulation board rather than in the white water.

It was also found that to effectively disperse fine clay particles, starch granules, and emulsified asphalt particles and to aid in dewatering without a loss of solid materials from the board an organic polymer polyelectrolite such as Lufax 295 may be incorporated. -Boards made with about 0.5% Lufax were found to have less stratification of particles and more homogeneous distribution throughout the board.

It is intended that modifications and variations of the above embodiments can be made within the scope of the invention as defined by the appended claims and their equivalents.

Claims (8)

1. A fire-retardant thermal insulation board consisting essentially of from 50 to 80% expanded perlite, 3 to 30% clay, 5 to 30% newsprint fiber, 1 to 6% B2O2, up to 25% of a non-combustible fibrous material, a binder and a waterproofing material, said board being manufactured in a continuous process by the removal of a liquid vehicle from a slurry of solid materials, said liquid in said slurry containing boron compounds in a concentration sufficient to impart from 1 to 6% B2O2 to said board upon drying.

2. The insulation board of claim 1 wherein said non-combustible fibrous material is selected from the group consisting of rockwool and fiberglass.

3. The insulation board of claim 1 wherein said board includes up to 8% starch, up to 6% asphalt, and up to 2% silicone.

4. The insulation board of claim 1 wherein said boron compounds comprise a mixture of boric acid and a sodium borate.

5. The insulation board of claim 1 wherein the board is formed by removing said liquid in said slurry in a Fourdrinier process and subsequently drying said board by the application of heat.

6. The insulation board of claim 1 which is substantially non-toxic.

7. The insulation board of claim 6 having from 5.

to 15% newsprint fiber.

8. A fire-retardant thermal insulation board substantially as hereinbefore described.