DE1642203A1 - Process for protecting lignocellulosic material - Google Patents

Description

Dr. F. Zumsfein - Dr. E. Assmann

Dr. R. Kosiiic-bsrger
Dip !. Phys. R. H ^ ir'iauer

Munich 2, Bräuiiaussiraije 4 / III I D 4 Z 2 O

State of Israel, Min istry of Trade a n d Industry,

Jerusalem (Israel)

Process for protecting lignocellulose

containing material

The present invention relates to a method for rendering lignocellulosic materials non-flammable and incombustible Materials and pulps. In the present description, the term "lignocellulosic pulp" means lignocellulosic pulp Cellulose pulp understood how it is used for the production of paper, cardboard, insulation board, hard cardboard and the like. suitable. "Lignocellulosic material or objects" are lignocellulosic structures such as wooden beams, veneers or rods, sheets of paper,

GW, -OB.

5/25/66. - 1 -

Case Lewin 23 + 24

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Newsprint, articles made of compressed wood, yarn, woven or knitted textile materials, or ropes Lignocellulose fibers, e.g., jute, kenaf, sisal, hemp or the like, understood.

Wood is composed of three main components, namely cellulose, hemicellulose and lignin. The first two components are long-chain carbohydrates, while lignin is a compound containing ondensed phenylpropane units. Most plant materials contain these three main components, but in varying amounts. In some cases, for example with cotton, a cellulosic material made from this plant is essentially free of lignin; however, in most of the other products made from plants, some lignin is retained. This is particularly true of sawdust, which is the main ingredient in the manufacture of zesting paper. Such wood meal can contain up to about 27 % lignin, depending on the type of wood from which it was made and also depending on the bleaching process used. Semi-chemical pulps, which are used to make paperboard and corrugated board, contain varying amounts of lignin. Jute and sisal fibers contain substantial amounts, as do other bast and leaf fibers.

BATH ORIGINAL

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Lignin and hemicellulose form the so-called middle lamella, which is located between the fibrous cells in the Wood and numerous other plant tissues; Lignin also occurs in lignocellulosic fibers such as fibers from Jute, hemp and sisal. The middle lamellae surround the fiber cells, which in turn are mainly made of cellulose and cement the fibers together, thereby forming the structure of the fiber bundle.

From Israeli Patent No. 15481 and corresponding patents in other countries, e.g., U.S. In U.S. Patent 3,150,919, it is known to make lignocellulosic pulp or articles thereof flame-resistant by halogenation close. Dj.e halogenation treatment intervenes in the lignin component of the lignocellulosic material, and it is this halogenated lignin that then has improved flame resistance and that of the entire pulp or the Imparts a high degree of incombustibility to the article which is resistant to prolonged leaching in water. To Various concentrations of halogenating agent can be used in the cited method, depending on the degree and the intensity of the flame resistance to be achieved.

According to Israeli patent 15481, a lignocellulosic material or pulp in a

Level halogenated.

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INSPECTED

For example, the material with elemental bromine or an aqueous solution of elemental bromine or a aqueous solution capable of forming elemental bromine in situ, for example a bromide-bromate solution which is gradually acidified, or a bromide solution into which elemental chlorine is gradually introduced is brominated.

It has now been found that when the halogenation is carried out in one step, the distribution of the of bound halogen is unequal across the cross-section of the treated pulp or article, the degree the lignin halogenation decreases from the surface inwards. A concentration gradient thus occurs. This Gradient can occasionally be very steep and the formation of a relatively thin layer with a relatively high content of halogenated lignin and a core with low content of halogenated lignin or even with non-halogenated Show lignin. This observation can be explained by the fact that a relatively large amount of the lignin in the vicinity of the The surface of the object reacts and consumes most of the available halogen, while only a small amount of halogen penetrates into the inner part of the body.

This creates a difficult problem in making lignocellulosic material flame resistant

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Halogenation, which consists in obtaining a substantially uniform distribution of the halogenated lignin in a larger batch of lignocellulose-containing product, which as pulp or in solid form, e.g. from Cardboard, lumber, veneer or the like is present. Because of the formation of a concentration gradient two possibilities, namely either to halogenate only a thin outer layer and the core with a low halogen content to leave, or to carry out the halogenation so intensively that the core halogenates to the desired degree is, in which case the outer parts are halogenated too strongly.

The present invention is an improved process for the halogenation of lignocellulosic Articles and pulps, for the purpose of imparting increased flame resistance, by which process a better and more even distribution of the halogenated lignin over the cross-section of the material treated in this way is obtained.

In the method according to the invention, by which The lignocellulose substrate becomes the lignocellulose substrate if the products treated in this way are given increased resistance to inflammation and continued burning initially with a reaction mixture that

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is capable of participating in a lignin halogenation reaction, impregnated (impregnation stage), and. that so impregnated The substrate is then developed under conditions which cause the halogenation of the lignin (development stage ).

By performing the halogenation of the lignocellulosic material a better and more even distribution of the halogenated lignin is ensured in two stages. During the impregnation step, the reaction solution penetrates into the internal spaces of the material to be treated and thus becomes available throughout the material. Accordingly, halogenation takes place in the development stage of the lignin essentially throughout the product.

In addition to fire resistance, the method according to the invention gives the treated material a considerable degree of resistance Resistance to biodegradation by fungi.

Preference is given to hydrohalic acids and / or other acids that remain in the substrate after development, neutralized before the halogenated lignocellulosic material is further used.

According to one embodiment of the invention contains the reagent used in the impregnation min-

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at least one halide bath, elemental halogen, and the development takes place by bringing the impregnated substrate into contact with an oxidizing agent. For example, can impregnate with a bromide and use elemental chlorine as an oxidizing agent during development. In this In this case, the bromide is oxidized to elemental bromine during the development stage and the lignin is thus brominated.

Better distribution of the liquid halogenating medium is also obtained when using elemental halogen or an aqueous solution of elemental halogen in the impregnation stage. In this case, the halogenation already takes place partially during the impregnation, with the simultaneous formation of hydrogen halide, which penetrates further into the material and remains in the wood or pulp until development with an oxidizing agent takes place. If, for example, a solution of elemental bromine is used, the bromine consumption in the impregnation stage is on the order of magnitude of 25 to 35 $. If the development stage then begins by adding a bromine-oxidizing agent, the hydrogen bromide formed as a by-product is oxidized to elemental bromine, which is available for further bromination. In this way the utilization of the bromine is increased to 80 to 95 ⁰ J ₀ .

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According to a further embodiment of the invention, the contains applied in the impregnation stage Reaction mixture an oxidizing agent and an acid, and during the development stage the impregnated substrate becomes brought into contact with elemental halogen or an aqueous halide solution.

According to a further embodiment, the reaction mixture used in the impregnation stage contains both Halide as well as oxidizing agent, the composition of the mixture being such that no noticeable conversion from halide to halogen, and an acid is used for development. For example, you can impregnate with an aqueous bromide / bromate solution and with sulfuric acid, hydrochloric acid, perchloric acid or another develop suitable acid that releases free bromine from the bromide / bromate mixture. The halogenation also takes place here of lignin only in the development stage.

According to a further embodiment, a reaction mixture, the components, is used in the impregnation stage contains, xvelche releasing elemental Halogen can react with one another, the composition of the reaction mixture and the impregnation conditions be chosen so that no significant amounts of

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elemental halogen released during impregnation are, and wherein the conditions in the development stage are changed so that the reaction between the said Components occurs.

In these cases you can, for example, increase the temperature in the development stage, change the degree of humidity, Apply pressure or the like. f

In the latter case, the reaction mixture with which it is impregnated can be a halide, e.g. an alkali metal or ammonium halide, an oxidizing agent, e.g. a metal or ammonium halide, and a compound which, when the physical conditions change, releases an acid and thereby the pH of the reaction mixture belittles. If you work with bromination, the reaction mixture used for impregnation contains a bromide, ™ e.g. an alkali metal or ammonium bromide, a bromate such as an alkali metal bromate, ammonium bromate, calcium bromate, Magnesium bromate or zinc bromate. A Lewis acid such as ammonium chloride or zinc chloride can be used as the acid-releasing compound use. Will dab lignocellulosic material impregnated with such a mixture at room temperature, 80 no perceptible change occurs during the impregnation.

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mix reaction and ds * mixture penetrates unchanged into the material. If the material is then heated, for example by treatment with steam, the pH value falls to about 2-3, whereupon the reaction of. Bromide and bromate are used together, and the lignin is brominated. At the end of the bromination, the pH is usually 3.5 to 6.0, which is usually satisfactory and sufficient for solid wooden objects.

According to the last-mentioned embodiment, it is also possible to use a proton-donating acid in the Add the reaction mixture used for impregnation. In this case it has the applied during the impregnation Reaction mixture already has the pH value required for development, with the composition of the reaction mixture however, under the physical conditions of the impregnation step, lignin halogenation is slow is compared to the rate of penetration of the reaction mixture into the substrate. With this procedure it is occasionally possible to use the reaction mixture without change the physical conditions extend to halogenation to let develop. In other cases, however, it may be advisable to change the conditions somewhat, e.g. by

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Heating and / or the application of pressure in order to accelerate the halogenation reaction in this way.

If desired, the treated material can be neutralized after halogenation. This can in particular be recommended in the case of pulp.

If necessary, one can use the even distribution the reactants used in the impregnation can be improved by adding the impregnation carried out under reduced pressure, the development at any rate Normal or positive pressure.

Furthermore, if a second reactant or a reaction mixture which impregnated under reduced pressure is used during the development step Discharge lignocellulosic material from the negative pressure atmosphere by exposing the second reactant or introduces the reaction mixture.

Furthermore, the lignocellulose-containing substrate can be heated and hot before the halogenation according to the invention are impregnated.

In addition, the flame retardant finish according to the invention can be used have a surface treatment followed, e.g. with conventional flame retardants such as the borates. Under the term "surface treatment" is used

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in this description a treatment understood that in In contrast to the treatment according to the invention, only the surface of the substrate is changed.

In the practice of the present invention, bromination has proven particularly suitable.

The amount of halogen used to halogenate the lignocellulosic material depends on several factors such as the halogen used, the type of material being treated and the degree of flame resistance desired. For a given degree of halogenation, the time required for halogenation is generally shorter if finely divided lignocellulose is to be treated. Such material is, for example, wood flour or wood pulp before, furthermore in the case of substrates with a large specific surface, for example yarns and ropes, in contrast to Pressed wood bodies or veneers and larger structures made of wood.

Oxidizing agents suitable for carrying out the process according to the invention are acidic aqueous solutions of Alkali halogenates such as bromates or chlorates, elemental Chlorine or aqueous solutions thereof, hydrogen peroxide, Potassium permanganate, acidic sodium or potassium dichromate solutions, Chromic acid and the like. The named Oxyda-

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agents are only examples of a large group of suitable substances.

As already mentioned, the halogenation of lignocellulose by means of aqueous solutions is in situ Form elemental halogen, e.g. with acidic bromide / bromate solutions, known from the Israeli patent 15481. The fundamental difference between the known and the inventive method is that there the halogenation is carried out in one stage, which leads to leads to the disadvantages already mentioned, while in the inventive If the halogenation takes place in two stages, resulting in a better distribution of the bound Halogen over the cross section of the treated material or only a small concentration gradient from the surface to the core is achieved.

Example 1:

2 pieces of wood 6.45 cm, 15 cm long

placed in a pressure vessel evacuated to 0.1 to 500 mm of mercury, and the pressure becomes at least one Maintained for one minute. To remove the moisture content To improve in the wood, the vacuum can be applied and removed again several times. Closing

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lent one lifts the vacuum by introducing the appropriate Solutions of the treatment agents shown in Table I, Column 1. Due to the diminished The treatment liquid is sucked into the inner spaces of the wood under pressure. About the impregnation To intensify, pressure is applied after the end of the first stage, in one beneficial for the pressure vessel

Mass. Pressures between 0.2 - 20 kg / cm have proven to be useful proven.

After the end of the impregnation, the pressure is released, excess liquid is drawn off and, if necessary, the wood is dried, e.g. by repeated evacuation and return to normal pressure.

In the second process stage, the pre-treated Samples placed under vacuum as in the first stage, whereupon one of the agents according to column 2 of table I is introduced into the evacuated vessel. Then there is pressure

abandoned to the second liquid in the inner spaces to press the wood. After impregnation is complete, the pressure is released and the samples are dried and are ready for testing. If an acidic by-product is formed during the oxidation, it is advisable to add it again

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ORIGtNAt INSPECTED

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evacuate and relax by adding an alkali. Then with borax, boric acid or mixtures thereof, sodium or Ammonium phosphate, sodium carbonate, calcium hydroxide or the like are post-treated.

When the treated samples were placed in a flame, improved flame resistance was found.

The following reagents were used according to the above example:

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Table_I H ₂ SO ₄ Level I. Stage II NaBr ₊ H ₂ SO ₄ NaBr - HBr ₊ HBrO ₀ NaBr KBrO ₃₊ H ₂ SO ₄ NaBr ₊ NaBrO ₃ NaCl - HBr NaBr + NaBrO H ₂ SO ₄ NaBrO_
ο KBrO ₃₊ H ₂ SO ₄ MgBr ₂ HBr ₊ HCl H ₂ SO ₄ MgBrO, H ₂ SO ₄ NaBr + NaC10 ₃ NaBrO ₀
O Bromine water KMnO ₄₊ H ₂ SO ₄ NH ₁ BrO ₀ K ₂ Cr ₂ O ₇₊ H ₂ SO ₄ KBrO ₃ + Br ₂ H ₂ O ₂₊ H ₂ SO ₄ V / a s s he Na ₂ O ₂₊ H ₂ SO ₄ H ₂ S0 ₄ + NaBr Cl water NaBr Chloramines NaBr Chlorotriazines NaBr NaBrO ₃₊ H ₂ SO ₄ NaBr - 16 -
109828/0390 NaBr NaBr NaBr NaCl + NaBr

Flame resistance after leaching with water

only slight improvement significant improvement no improvement significant improvement

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ORIGINAL INSPECTED

The same treatment was applied to lignocellulose pulp performed. Use of vacuum and pressure is not necessary with pulp. The final pulp is washed and neutralized with a lime slurry or the like and then into sheets or boxes under pressure deformed. Samples produced in this way also showed improved flaram resistance when held in one Flame.

For example, pulp from sawdust results in 7 to 18% by weight after the treatment according to the invention. has bound bromine, a paper that does not burn when lit with a match.

Control samples were prepared by removing the initially applied vacuum by adding a solution containing the was suitable for single-stage halogenation and contained the appropriate amount of brominating agent, relaxed. These samples also showed improved flame resistance. However, there will be layers of 1 mm each from the surface of the samples to the inside, it turns out that the amount of halogen on the surface is much higher and few Millimeters below the surface already very low.

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Example 2: · ·

3 mm thick ponderosa pine veneers, each weighing 140 g, were heated to 105-110 ° C. until completely dry. They were then impregnated at 20 ° C. for 30 seconds with an aqueous solution which impregnated 141.4 g / l NaBrO, 96 g / l NaBr and 5 g / l Ultravon JU (trade name of a wetting agent from Ciba Ltd.). The veneers absorbed 60 wt.% Solution, based on the dry weight of the wood.

The impregnation was followed by drying at 105 ° C. for 30 minutes and then in 2N sulfuric acid for one minute immersed. Then they were immersed in a 5 $ aqueous sodium borate solution submerged. It was then dried and tested for fire resistance. The British Standard test 476-53 gave the value 1 for the flame spread.

10 mm thick plywood panels were produced, the veneers described above being used as the outer layer while the inner layer consisted of 4 mm thick untreated material. The plywood was made in conventional Way made by gluing with an adhesive and hot pressing. The resulting boards showed the same quality value as the individual veneers.

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ORIGINAL INSPECTED

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Example 3:

3 kg of Okume shavings were sprayed with 2.4 kg of an aqueous solution containing 114 g of ammonium bromide, 168 g of sodium bromate, Contained 70 g of anhydrous aluminum sulfate and 30 g of sodium chloride. The pH of the solution was 3.6 After sufficient soaking, the chips were treated with water vapor in a closed vessel at 100 ° C. for 30 minutes and then dried to a moisture content of 2-3% at the same temperature. The pH of the aqueous extract of the chips was 4.4. The invention Equipment was over.

For the production of cardboard, the chips were then washed with 480 ml of a commercially available urea-formaldehyde solution containing 50 wt.% Solids sprayed. Then a mat was molded for 8 minutes at 130 ° C. and 19 kg / cm of pressure. The cardboard had a specific weight of 0.65 g / cm. The bond strength was 135 kg / cm and corresponded to the strength of cardboard which had been produced in the same way from chips that had not been made flame-resistant.

In the incombustibility test according to British Standard 476-53, the samples received a value of 1 for flame spread .

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Example 4:

680 g of oven-dry pulp (cardboard quality) were suspended in 30 l of water. In the impregnation step, 79 g of sodium bromide dissolved in 1 liter of water were added to the suspension, followed by stirring for 15 minutes. In the next stage of development, 15 liters of What is? containing 7.34 g of chlorine per liter, added all at once with vigorous stirring. The bromination was complete after 50 seconds, whereupon 90 g of dry calcium hydroxide were added to the suspension. Then it was processed on cardboard and pressed down to a moisture content of 120%. 200 ml of a solution containing 8.2 g of anhydrous borax and 9.8 g of boric acid were sprayed onto the damp mat, which weighed 1100 g. Then in a hot press for 1 minute at a plate temperature of 10 ° C and a pressure of 42 kg / cm, then 4 minutes at a pressure of 3.5 kg / cm and 6.5 minutes at a pressure of 10 kg / cm cm and 180 ° C pressed. The hard cardboard obtained in this way was then heated to 150 ° C. for 4 hours. The paperboard was tested for non-flammability according to British Standard 476-53 and the value was obtained.

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Example 5:

3 kg pine sticks with a specific weight of 0.4 g / cm and the dimensions 15x30x 3 cm were placed in an autoclave with a capacity of 10.5 liters. The autoclave was evacuated to 0.1 atmospheres and then filled with a solution containing 240 g NaBr, 340 g Na3rO and 150 g sulfuric acid; it was set a pressure of 5 atmospheres. After 10 minutes, excess liquid was drained off quickly. In order to the impregnation step, during which part of the reaction took place, was completed. The stage of development existed in the introduction of steam at 115 C for 30 minutes. Then the steam was released and the autoclave filled with a 5% borax solution that remained for 15 minutes. The excess borax solution was drawn off and the wooden panels were removed and dried.

Samples were tested for non-flammability according to British Standard 476-53; the figure of merit 1 was obtained

Further samples were tested for resistance to fungal attack in accordance with ASTM standard D-1413-56T and D-2017-62T, using a subculture of Poria monticola Murr tested. While not brominated

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Comparative samples were completely covered by the fungus after one week, the brominated samples were still completely undisturbed after 6 months.
Example 6:

3 kg of pine chips similar to those used in Example 5 were obtained in the same manner as in FIG Example 5 treated, but in the present case in the second stage no water vapor in the autoclave was introduced. Instead of the supply of water vapor, the platelets were together with the for 7 hours Leave the liquid in the Aiartoclave and then treat it further as described in Example 5. Similar ones were obtained Test results as in example 5.

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Claims (19)

IZ claims 1. Process for the halogenation of lignocellulosic articles or pulp, in order to improve the Flame resistance and resistance to, biodegradation, characterized in that the lignocellulosic Substrate first with a reactant or reaction mixture that is capable of participating in a lignin halogenation is capable of being impregnated (impregnation stage) and the impregnated substrate is then developed under conditions which cause halogenation of the lignin (Stage of development). · 2. The method according to claim 1, characterized in that the halogenated lignocellulose-containing material remaining acid is neutralized after the development stage. 3. The method according to claim 1 or 2, characterized in that the used in the impregnation stage Reagent containing at least one halide or elemental halogen, and developing by contacting the impregnated substrate is carried out with an oxidizing agent. - 23 " _{ft n Λ} ORIQVNAL INSPECTED 109828/0390 4. The method according to claim 3, characterized in that there is a bromide as the halide and as Oxidizing agent elemental chlorine or an aqueous solution of elemental chlorine is used. 5. The method according to claim 1 or 2, characterized in that the impregnation stage during & er applied reactant contains an oxidizing agent and an acid, and the impregnated substrate with elemental halogen or an aqueous halide solution is brought into contact. 6. The method according to claim 1 or 2, characterized in that the used in the impregnation Reaction mixture contains a halide and an oxidizing agent, the composition of the mixture such is that there is no noticeable conversion of halide to halogen and an acid is used for development. 7. The method according to claim 1 or 2, characterized in that the reaction mixture used for impregnation Contains components which are capable of reacting with one another, releasing elemental halogen are, the composition of the reaction mixture and the impregnation conditions are chosen so that none - 24 109828/0390 OWGlNAL INSPECTED significant amount of elemental halogen is released during the impregnation, and the conditions in the Development stage can be changed in such a way that the components react with one another, releasing elementary elements Halogen. 8. The method according to claim 7, characterized in that the reaction mixture is at least one halide, contains at least one halogenate and at least one compound which generates an acid upon heating. 9. The method according to claim 7, characterized in that the used in the impregnation step Reaction mixture has the pH value required for development, the composition of the mixture such is that under the physical conditions prevailing during the impregnation, the lignin halogenation is slow compared to the rate of penetration of the reaction mixture into the lignocellulosic substrate. 10. The method according to claim 9, characterized in that during the development stage the physical Conditions are changed so that the halogenation reaction is accelerated. 10 9 8 2 8 / "of 90 Ü; ., 2203 11. The method according to any one of claims 7 to 10, characterized in that in the development stage impregnated material is treated with steam. 12. The method according to any one of the preceding claims, characterized in that in the impregnation stage the lignocellulosic material is first placed under reduced pressure and then with the impregnating agent is brought into contact. 13. The method according to any one of the preceding claims, characterized in that in the development stage increased pressure is applied. 14. The method according to any one of the preceding claims, characterized in that the lignocellulose-containing Brominated material. 15. The method according to any one of the preceding claims, characterized in that the lignocellus-containing Material treated with a bromide and a bromate. 16. The method according to any one of the preceding claims, characterized in that after the development treatment the halogenated lignocellulosic substrate is subjected to a surface treatment. 109828 / $ r90 1ο., 2203 17. The method according to claim 16, characterized in that the surface treatment in an impregnation rait consists of a conventional refractory agent. 18. The method according to any one of the preceding claims, characterized in that the lignocellulose-containing substrate is hot impregnated. 19. Halogenated lignocellulose-containing materials produced by the process according to claim 1. 109828 / 2353-90