EP0033391B1 - Process for preparing flame retardant or non-combustible products based on fibrous materials - Google Patents

Description

The ever increasing demands on the fire protection of materials of all kinds make it necessary to protect everyone, including organic fiber materials, from fire or to equip them in such a way that they do not contribute to the development or continuation and support of a fire. However, the production of materials from organic fiber materials is only possible economically using the wet process, i.e. in very thin aqueous suspensions. However, this wet manufacturing process prevents the introduction of fire protection agents that are soluble in water or that can be washed away with the wastewater.

The object of the invention is therefore to introduce such water-soluble fire retardants, in particular boric acid, into the products to be formed from fibrous materials, without the proven and economically feasible wet process in the manufacture of the fiber materials having to be abandoned. Another consideration is that it should be possible; to produce fiber-reinforced gypsum boards based on the known wet process for the production of paper, cardboard, cardboard and fiberboard, which have good strength properties with a low swelling rate and low water absorption capacity. Such gypsum boards are particularly needed for dry interior finishing and plastering of walls, since they not only have good properties that improve the indoor climate and can be nailed by the fiber reinforcement and have sufficient strengths that determine their utility value, but also easy to assemble and, when using the inventive method Process, should also be economically producible. Fire protection would of course also be very important here, since this protection must be required for the interior lining of rooms.

A known method is described in US-A-3,983,040. Here, a calcium / sodium-containing boron mineral is mixed with sulfuric acid and stirred for a certain time. The resulting product is then dried and pulverized so that a powder containing about 34% boric acid and about 60% calcium / sodium sulfate is present, which can be added as a fire retardant to corresponding products. Since the fibrous materials necessary for the structure of sheet-like or plate-like products are missing, such products cannot be produced by this method.

It is also known to make a fibreboard flame-retardant by adding borax to the aqueous pulp. In order to enable the dewatering of this slurry, a small amount of sulfuric acid is also added according to the process described in GB-A-1 025188.

It is therefore known, on the one hand, to produce a fire protection powder based on calcium-containing boron minerals and sulfuric acid, which can be admixed with organic, fibrous materials and, on the other hand, borax in an aqueous state to the starting raw materials for fiber materials, together with a small amount of sulfuric acid, to adjust the pH To add value. On the other hand, a solution to the above problem, namely water-soluble fire retardants, is not known in the products to be formed from fibrous materials in the wet process or even to produce the fiber-reinforced gypsum boards mentioned further.

According to the invention, it is possible to produce flame-retardant or non-flammable products, in particular sheet-like or plate-like products, on the basis of fibrous organic materials which contain boric acid and calcium sulfate as additives, in an economical manner in that the fibrous materials become aqueous Porridge is prepared, that calcium-containing boron minerals and sulfuric acid are intimately mixed into this porridge and that after a ripening period for the conversion of the calcium-containing boron mineral into boric acid and calcium sulfate, the mixture thus formed is fed to nonwoven and fiber dewatering machines, dewatered and then dried.

Without abandoning the proven wet process, minerals are added to the fibrous starting materials, which in themselves have a fire-retardant effect, but also boric acid, which is known to have very good fire protection properties. These fire protection materials do not disrupt the proven manufacturing process, which can therefore be carried out on the existing machine lines without further investment. However, an extraordinary step forward is that the end materials are not only fire-protected, but also that, when using inexpensive calcium-containing boron minerals, calcium sulfate (gypsum), a very high strength of the materials is achieved. This can be explained by the fact that the calcium sulfate supports the binding of the individual fibers to one another or that the fiber tangle structure is extremely solidified. In this way, not only fire-protected products can be produced, but also reinforced gypsum boards, whereby if the calcium sulfate that forms is not sufficient for the characteristics of the fiber material that forms as a gypsum board, gypsum plastered can also be added to the fiber pulp . The result is a completely new fiber material, which is extremely important, particularly for the interior finishing of rooms, since it has fire protection and also significantly improved strength properties compared to the known gypsum boards.

These products produced by the process according to the invention also have a very special property which has an extremely positive influence on their utility value, namely that the boric acid particles, like the gypsum particles, are firmly bonded to the fibrous organic materials. This is due to the fact that when carrying out the process according to the invention, both the boric acid and the calcium sulfate are formed only by the reaction of the calcium-containing boron minerals with the sulfuric acid and this in the presence of the fibrous organic materials. This results in flawless fire protection that applies to the entire material.

With regard to the properties of such a product, it should also be noted that it can be changed by adding various minerals, which of course must not be flammable. Expanded minerals such as expanded clay, expanded slate, pearl stone or vermiculite have proven particularly useful. These expanded minerals are non-flammable, but make a significant contribution to the thermal insulation and nailing ability of the products made with them.

Organic fibers, which are inexpensive and partly available as waste products, are used as fibrous materials.

In order to obtain a neutral, non-aggressive product, the mineral acid is expediently added in a stoichiometric ratio. It can be added in such an amount that the mixture immediately after adding the mineral acid reaches a pH between 1.5 and 3.0, preferably 2.0. A tendency towards neutralization can be achieved when the process is carried out by extending the ripening time after adding the sulfuric acid.

If a weighting of the starting material is necessary or desired, it is also possible to add further coarse to fine-grained minerals to the pulp before further processing, expediently those that glaze or ceramicize in the event of a fire. It has proven very useful that the production water is recirculated, as this means that the chemicals dissolved in this production water, in particular the proportion of fire retardants dissolved in the water, are added back to the production process. This production water can also be sprayed back onto the nonwoven fabric on the wire section, whereby water-soluble fire protection agents can also be sprayed on. It is also possible to produce two- or multi-layer boards, fiber pulp with a relatively higher boric acid / calcium sulfate content being able to be poured onto a preceding or forming fleece by means of a two-material or multi-material headbox. It has proven to be extremely expedient that the temperature of the pulp is kept at room temperature, approximately up to 20 ° C., during production. This avoids implementation, especially of the fire protection materials and their possible loss through the waste water.

All in all, this results in a product made from fibrous materials, on the fibers of which boric acid particles are deposited and the spaces between the individual fibers are at least partially filled with gypsum, i.e. fibrous materials which, depending on the mineral content, are more fibrous or gypsum-shaped.

The process according to the invention will be explained in more detail using six examples:

Example 1 :

To produce approx. 1000 kg of a flame-retardant wood fiber board, 643 kg of defibrator material or wood pulp or a mixture of the two materials is introduced into a Dutch machine with 15 m ³ . This mixture is brought to the desired degree of grinding by subsequent grinding and then 240 kg of boron mineral colemanite (approx. 45% boron content) are mixed in homogeneously and then sulfuric acid is slowly mixed in until the pH of the mixture is 2.0 to 2.5. The mixture is then to be ripened in a chest and then sent for further processing. The pH after ripening has risen to about 4.5 to 4.8. The fiber suspension, which is diluted as necessary in the machine chest, is dewatered on a Fourdrinier machine to form a fiber fleece, which is then fed to the drying tunnel. Here drying takes place to approx. 5% residual moisture. The inlet temperature in the drying tunnel is kept below 100 ° C so that the fleece is initially evenly heated and the water can still escape from the inside during final drying.

Example 2:

To produce a fiber-reinforced gypsum board, 225 kg of wood pulp or defibrator material or a mixture of both are introduced into a Dutchman and brought into a fiber suspension with 5% solids content with production water. Then 480 kg of colemanite (approx. 45% boron content) are added and mixed until a homogeneous mixture is obtained. Then 235 kg of sulfuric acid are slowly mixed in, the pH of the acidified mixture should not be below 2.0, but also not above 2.8. This mixture matures in the subsequent storage chest, the pH increasing to 4.5 to 4.8. The fiber mixture is then further processed like a fiber insulation board, but the end product is to be addressed as a reinforced gypsum board. It is interesting here that the boric acid content of the gypsum board with circulated production water is about 26% by weight in the end product, so the product is therefore non-flammable in the sense of DIN 4102, class A2. In order to further preserve the character of a gypsum board when this process is carried out, it is possible to additionally add gypsum to the ripened pulp expediently with production water. The drainage then takes place on one suitable, known drainage machine. The end result is definitely a reinforced plasterboard, which is not only fire-resistant or non-flammable, but also has remarkable strength properties.

Example 3:

The same batch of material as in Example 1 is used to produce a fire-protected hardboard. Before the finished fiber-colemanite-sulfuric acid mixture from the Dutch or a mixing chest expires, 0.5 to 2% of an acid-curing synthetic resin is added. After leaving the dewatering machine, the nonwovens are dewatered in a press and pressed to a hardboard, which receives the usual strength through the connection of the fiber under pressure and heat and is also fire-protected.

Example 4:

For the production of flame-retardant fiber insulation boards that are to be subsequently processed into shaped bodies, a fiber suspension according to Example 1 must first be produced in a Dutch or a mixing chest. After the mixture ripened, the pH rose to about 5.0. Now at least 20 parts by weight of a precipitable thermoplastic in powder or dispersion form are added to the fiber pulp and fixed on the fibers by the usual precipitation process. It is advisable to choose a plastic containing plasticizer. The fiber pulp is then further processed into fiber insulation panels as described in Example 1. The finished fiber insulation board can now be pressed under pressure and heat in a mold made of a matrix and a male mold to form a molded body.

Example 5:

• 321 kg atro Altpapier (Zeitungspapier),
• 321 kg atro gekollerte Natronzellulose und, nach genügendem Faseraufschluss,
• 240 kg Colemanit mit 44% Borgehalt, feingemahlen.

To produce a flame-retardant paper for packaging, the following are entered in a Dutchman for approx. 1000 kg of end product:

• 321 kg of dry waste paper (newsprint),
• 321 kg dry rolled sodium cellulose and, after sufficient fiber digestion,
• 240 kg colemanite with 44% boron content, finely ground.

The fibrous material should have a solids content of approximately 5% by weight.

Fresh water and later the wastewater from the rotary or Fourdrinier machine from the production of such paper is used for the pulp.

The fiber / colemanite mixture is then acidified to a pH of 2.0 to 2.5 by slowly adding 117 kg of sulfuric acid. The mixture should then ripen for at least one hour and is then processed as usual. Up to this processing, the pH has increased to approx. 4.5. The end product is a solid, non-flammable paper.

Example 6:

• 300 kg atro gekollertes Natronkraftpapier
• 200 kg atro Altpapier (gekollerte Akten)
• 100 kg la Natronkraft

To produce a flame-retardant box, for example for the interior lining of automobiles, the following are entered in a Dutchman for 1000 kg of end product:

• 300 kg dry rolled sodium kraft paper
• 200 kg of dry waste paper (rolled files)
• 100 kg of sodium bicarbonate

Fresh water and, after the start of production, the return water from the suction section of the Fourdrinier machine are used to produce the pulp. The solids content should be 5%. 240 kg of colemanite (approx. 45% boron content) are mixed homogeneously into the pulp. As soon as the fiber / colemanite mixture has reached the desired uniform distribution, 117 kg of concentrated or the corresponding amount of dilute sulfuric acid are slowly added to the circulating fiber pulp and mixed until the mixture is homogeneous and has a pH of 2.0 to 2. 5 has reached. The fabric can mature in the storage chest; the pH then rose to about 4.5 to 4.8. The mixture is brought to the required level of preparatory work in the machine chest. The fiber pulp is processed as usual. The result is a solid box that is no longer flammable.

Claims (10)

1. Process for the manufacture of products of lowflammability or non-combustible products, in particular sheet-like or board-like products, based on fibrous organic materials which contain boric acid and calcium sulphate as additives, characterised in that an aqueous paste is prepared from the fibrous materials, that calcium-containing boron minerals and sulphuric acid are intimately admixed to the paste and that the mixture thus formed, after a ripening period for converting the calcium-containing boron mineral into boric acid and calcium sulphate, is passed to mat-forming and fibre-draining machines, drained and then dreied.

2. Process according to Claim 1, characterised in that gypsum is added to the ripened fibre paste.

3. Process according to Claim 1, characterised in that a mineral acid is added in such a quantity that, before ripening, the mixture reaches a pH value between 1.5 and 3.0, preferably 2.0.

4. Process according to one or more of the preceding claims, characterised in that further minerals, ground to a coarse to fine grain size, are added to the fibre paste before further processing.

5. Process according to one or more of the preceding claims, characterised in that expanded granular minerals, in particular vermiculites, expanded clay, expanded slate or perlite, are added to the fibre paste before further processing.

6. Process according to one or more of the preceding claims, characterised in that the production water is circulated.

7. Process according to Claim 6, characterised in that production water is jetted onto the fibre mat on the wet end.

8. Process according to Claim 6 or 7, characterised in that water-soluble fire-proofing agents have been added to the production water.

9. Process according to one or more of the preceding claims, characterised in that fibre paste having a relatively higher content of boric acid/ calcium sulphate is poured, by two-stuff or multi- stuff feeding, onto a mat which has been previously formed or is forming.

10. Process according to one or more of the preceding claims, characterised in that the fibre paste is maintained at a temperature of up to 20° C during processing.