DD297461A5 - REINFORCING AND / OR PROCESS FIBERS BASED ON PLANT FIBERS, METHOD FOR THEIR PRODUCTION AND THEIR USE - Google Patents

Abstract

The invention relates to reinforcing and processing fibers based on vegetable fibers, which are obtained by removing vegetable fibers freed from wood components with a aqueous solution of at least one metal compound selected from metal oxides, hydroxides, carbonates, sulfates, thiosulfates, sulfites, treated silicates or phosphates, followed by treatment with an inorganic or organic binder or neutralized the non-washed fibers with a mineral acid, or treated with liberated vegetable fibers from wood components with an oxidizing agent or vorzelte vegetable fibers at 250 to 350C treated under controlled air supply, so that a charring of the fibers takes place {reinforcing fibers; Prozeszfasern; Plant fibers; manufacture; pretreatment; post-treatment; Oxidant; pyrolysis; Moldings; insulation materials; friction linings; Filler}

Description

Field of application of the invention

The invention relates to reinforcing and / or processing fibers based on vegetable fibers, processes for their preparation and their use.

Characteristic of the known state of the art

It is known that moldings are often admixed with asbestos fibers. Recently, however, it has emerged that asbestos is by no means harmless from a health point of view. Despite this disadvantage, these fibers continue to be widely used, because they have great advantages in many fields of application and genuine alternatives are currently not available in the market.

The same applies to glass fibers. Also, synthetic fibers are not safe, since at higher temperatures decomposition reactions can take place to form toxic vapors.

Also on the basis of plant fibers has already been trying to find a substitute material for asbestos. For example, DE-OS 3008204 describes a process for producing a reinforcing fiber, in which plant fibers are first opened with respect to the capillaries and the plant fibers treated in this way are then impregnated with a slurry of lime and water and, after intermediate drying, with a waterglass solution containing formaldehyde. These treatment steps can also be carried out in reverse order. However, this method has not led to the desired success.

Object of the invention

The invention is therefore based on the object to provide reinforcing and processing fibers which possess the advantageous properties of the asbestos fiber, without having their harmful disadvantages.

Explanation of the essence of the invention This object is achieved by reinforcing and processing fibers based on vegetable fibers, which are characterized by the following Procedures are available. The process for producing the reinforcing and processing fibers according to the invention is characterized in that

a) free the fibrous parts of fiber plants from wood components and other undesirable components of the plant,

b) if desired, treating the liberated from wood components plant fibers with an aqueous solution of at least one metal compound selected from metal oxides, metal hydroxides, metal carbonates, metal sulfates, metal thiosulfates, metal sulfites, metal silicates or metal phosphates, then washed and treated with an inorganic or organic binder or the non-washed Neutralized fibers with a mineral acid, or

if desired, treating the plant fibers freed from wood components with an oxidizing agent, or

d) treating the raw non-pretreated plant fibers at 250 to 35O ⁰ C under controlled air supply, so that a charring of the fibers takes place.

For the production of the reinforcing and processing fibers according to the invention, fibers of all fiber plants are suitable. Preference is given to using bast fibers, such as the stem fibers of flax, hemp, jute, nettle plants, the leaf fibers of agaves, the seed hair, for example, the cotton and the fibers of the fruit peel of coconut. Also useful are fibers that are available from grasses, especially elephant grass, which has a fiber content of about 50%.

The plant fibers in cut or uncut form must first be freed from wood components and other undesirable plant components. This is done by known and customary methods, for example by roasting and renneting of green flax.

According to a preferred embodiment, the removal of the wood components by digestion of the vegetable fibers is carried out with an ultrasound treatment in an aqueous medium. The ultrasonic wavelength is not critical. Depending on the apparatus, it is preferably chosen so that optimum sound intensity is achieved and ultrasonic cavitation occurs. The aqueous medium used is preferably a mixture of water with at least one polar organic solvent. The organic solvent used is preferably a C 1 to C ₄ mono or dialcohol, a C 1 to C 14 ketone, a water-miscible ether or a mixture thereof. Particularly preferred are methanol, ethanol and acetone. The volume ratio of water to organic solvent is preferably in the range of 5: 1 to 1: 5, in particular 3: 1 to 1: 3.

The ultrasound method is a particularly rapid, simple and gentle method for removing the wood components and other unwanted components of the raw plant fibers. The plant fibers obtained in this way are not mechanically damaged and they have the tensile strength of the original fiber. Since the other unwanted plant constituents, in particular the binder, are largely removed by the ultrasonic treatment, the fibers are well compatible with other materials, so that they can be easily absorbed into a matrix. The plant fibers obtained after ultrasound treatment are therefore also suitable for the further application areas mentioned below without further aftertreatment.

If desired, the fibers freed of wood particles may then be treated with the aqueous solution of a metal compound. This solution contains in particular 1 to 30 wt .-%, particularly preferably 10 to 30 wt .-% of the metal compound, based on the total weight of the solution. Preferably, the treatment is carried out at 50 to 100 ° C. If necessary, the fibers are then washed with water and optionally dried and treated with the binder or they are neutralized with a mineral acid, in particular hydrochloric acid, phosphate acid or sulfuric acid, optionally dried and treated with the binder.

Preferred metal compounds are alkali or alkaline earth oxides, hydroxides, carbonates, thiosulfates or sulfates and basic iron, titanium, antimony or aluminum salts. Particularly preferred are alkali metal or alkaline earth metal hydroxides, alkali metal silicates and Alkalithiosulfate ,? For example, sodium or potassium hydroxide, sodium metasilicate and sodium thiosulfate. The binders used are in particular cement, gypsum, silicates, alkali or alkaline earth salts of mineral acids, bitumen, asphalt, natural and synthetic elastomers, polyurethanes, phenolic resins, resoles, melamine resins, epoxy resins or mixtures thereof.

The application of these binders can be carried out in an aqueous or organic medium (solvent). The amount of binder is preferably 5 to 20 wt .-%, based on the fiber content.

The fibers are impregnated with an aqueous or organic solution or suspension of the binder by, for example, dipping or spraying it in the solution or suspension. The impregnation is preferably carried out at room temperature, followed by drying.

Instead of the fibers obtained in the manner described above, it is also possible to treat the fiber components obtained in the flax processing directly with the binder.

Depending on the intended use of the fibers according to the invention, additional treatment stages may be provided. For example, if a light fiber is desired, one can bleach after pretreating the fibers. For this purpose, the fibers are usually treated at room temperature or at elevated temperature with a peroxide or hypochlorite solution or with chlorine water and then rinsed with water. If a tribological effect is desired, they can be added to a solid lubricant. Suitable solid lubricants are, for example, molybdenum disulfide, graphite, zinc sulfite, tricalcium phosphate, titanium oxide and the like.

If additional flame retardant finish is desired, one may add a flame retardant compound such as antimony oxide, iron sulfate, alum, bismuth oxide, urea phosphate or chlorinated paraffin.

As a preservative, a bactericide such as a heavy metal salt or a chlorophenol compound may also be added thereto.

The fibers according to the invention, in particular the fibers obtained after ultrasonic treatment, can also be hydrophobized, for example with a fluorocopolymer, paraffin, polysiloxane, reactive hydrophobing agent (silanes, isocyanates) or zirconium or zinc salt.

As already mentioned above, in a further variant of the method according to the invention, plant fibers which still contain the organic constituents (wood constituents, sugar substances, pectins) can be pyrolyzed. They are subjected to a treatment at a temperature of 250 to 350 ° C under controlled air supply. The plants do not burn, but they char. For example, the fibers are heated with vigorous mixing in an externally heated tube furnace. The gases formed are sucked off and the admission of air regulated so that no combustion and a pressure reduction of about 0.1 to 0.5 bar. Alternatively, inert gases such as carbon dioxide, nitrogen, nitrogen / hydrogen, etc. may be added to lower the oxygen content. It is also possible to work under a substantially pure inert gas atmosphere.

The heating time is chosen so that the degree of carbonization is about 20 to 80%, in particular 20 to 60%. Surprisingly, in this way, without pretreatment, a fiber is obtained which can replace environmentally harmful fibers in certain fields of application.

The fiber obtained by pyrolysis is relatively brittle and can be very easily comminuted, so that the fiber is present as a microfiber. This can be shown by the specific surface area (according to Blaine-Dyckerhoff) and the density:

Specif. upper density area (cmVg) g / cm ³ According to the invention pyrolytic 6100 1.58 fiber (made of flax receive) asbestos 9900 2.5 Flax fiber (untreated, 2000 1.47 cut)

If desired, the fibers obtained by pyrolysis may be further impregnated by pouring them into a solution

a resin, synthetic or natural rubber or elastomer dipped or sprayed with this solution. These

Impregnation serves to facilitate the wetting and processing of the fiber. According to a further embodiment of the method according to the invention, the plant fibers of a chemical Subjected to oxidation. For this purpose one treats Pflanzenfasert-, which frees from wood components and

are suitably cut to about 3 to 10mm in length, with an aqueous solution of an oxidizing agent. When

Oxidizing agents are in particular alkali metal periodates.Alkalimetallpersulfate, preferably alkali metal permanganates and

especially suitable potassium permanganate.

The fibers are wetted with the oxidizing solution, for example by spraying, impregnating and the like. The Treatment takes place at a temperature of about 6O ⁰ C to the boiling point of the solution, preferably at about 80 to 95 ° C and

especially at 85 to 95 ° C.

After the oxidation, which is generally completed after a few minutes, the fibers are washed and dried. The Drying takes place at a maximum temperature of 140 ^° C. The oxidized fibers are difficult to ignite and have favorable tribological properties. Yarns can be oxidized. In this case, the oxidation process must be controlled so that the yarn is not destroyed. This

takes place via the concentration of the oxidation solution and the contact time with the oxidation solution and by a subsequent reduction of the treated fibers with a conventional reducing agent, for. For example, sodium sulfite.

In the following, application areas for the fibers according to the invention are explained: In the cement fiber industry, the "mineralized" fibers of the present invention are useful in the preparation of, for example Cement boards and cement moldings useful. For this purpose, the fibers are treated as described above, on a Length of for example 4 to 8mm cut and treated with a metal compound as described above. The Incorporation of the fibers in the cement is carried out in a conventional manner, for example by admixing the cement or to the

made concrete mixture.

In the same way gypsum boards and plaster moldings can be made. The application of mineralized plant fibers is

not mandatory here, because the mineralization can occur when using the plant fibers in gypsum slurry. The length of the

Fibers depend on the desired mechanical strength of the gypsum pieces. In addition, for the production of gypsum for medical purposes, the fibers are bleached as described above

simultaneously causes a sterilization.

For the production of plaster and fillers based on gypsum and glue or water-soluble resins you set the

pretreated fibers together with a common preservative. Also in this case is the desired

Strength decisive for the length of the fibers used. The fibers of the invention are also for the production of sound insulation materials, such as machine linings and masses

suitable for underbody protection of vehicles and for use in sealants, roofing membranes and road surfaces. For this purpose, for example, they are mixed with bitumen gum, asphalt and epoxy resins. The length of the fibers is determined by the application method. In the case of coatings to be sprayed on, the length of the fibers should not exceed 10 mm, whereas the length of the fibers in the case of trowelled coatings may be 20 to 50 mm.

The fibers according to the invention are particularly suitable as an additive to phenoplasts or thermoplastics,

especially in the production of plastic moldings.

The pyrolyzed and the oxidized fibers are particularly advantageous for insulating materials and friction linings, which consist of a Agglomerate of several component, ι consist and are pressed using pressure and temperature. The

Fibers according to the invention serve to ensure optimum distribution and homogeneous mixing of the numerous

Individual components that can have a very different density to ensure. The pyrolyzed and oxidized Fibers can also be used to improve the flowability of cement, plastics, etc. Because of your

tribological properties, they can also be used for the production of technical papers.

The fibers of the invention (including the oxidized fibers) may also be in the form of yarns or fabrics in Phenoplasts or thermoplastics are used, which to sliding and wearing parts and pressed Machine parts, such as brake bands, clutches and friction linings are processed. They give the moldings

excellent mechanical properties, such as tensile, tear and bending strength.

Bleached or unbleached fibers of the invention are used in the paper and paperboard industry. For this They were preferably used with a resin solution (sizing) consisting of resin, soaps, water glass and casein,

impregnated. In the same way, the fibers according to the invention can also be used in the production of felt.

The fibers of the invention can also be used for the preparation of polishing agents. For this purpose will be Fibers of about 2 to 4mm in length impregnated with wax or a gum solution and then through an extruder to Molded globules. Beeswax, synthetic hard waxes, plant waxes, such as Carnauba wax, candelilla wax and the like. Depending on the type of wax, the ratio of wax to fiber is Range of 3 to 5g of wax per 1g of fiber. By a suitable choice of the wax can also be the hardness and the thermal Influence the stability of the beads. As a gum solution are natural or synthetic gum, dissolved in a solvent, such as methylene chloride and Hydrocarbons such as xylene, toluene and latex useful. Latex can also be used in an aqueous medium.

The fiber balls impregnated with wax or rubber are used in particular as a drum material for cleaning and polishing various materials (leather, wood, metal). They can also be used as blasting material for blast cleaning (eg sand blasting). The rubber beads impregnated with rubber can be incorporated advantageously also in molding compounds. They do not dust and have better anchoring in the matrix in the presence of resins or in the reinforcement of elastomers.

embodiments

example 1

Greenflax fibers were liberated by roasting and dehulling wood components. 1OOkg the freed from wood constituents fibers were in a 5% aqueous sodium hydroxide 30 minutes bsi 60 ⁰ C stirred. The fibers are isolated and neutralized by spraying with 10% phosphoric acid. Subsequently, the fibers are dried in a stream of hot air, for example in a fluidized bed.

Example 2

The procedure described in Example 1 is repeated, but after treating the fibers with sodium hydroxide solution, the fibers are isolated, washed with water and then sprayed with cement slurry.

Example 3

100 kg cut green flax fibers are heated at 280 to 300 ⁰ C in an oven with vigorous mixing. The gases formed are sucked off and replaced by fresh air so that no combustion takes place. The heating is carried out until the desired degree of carbonation, z. B. 80%.

Example 4

800g freed from wood constituents flax fibers are impregnated with a solution of 300g of potassium permanganate in water 3.51 with a temperature 90-93 ⁰ C. After 3 to 4 minutes, foaming occurs and the oxidation process is completed. Then remove the oxidizing agent and wash the flax fibers several times with water. After washing, the fibers are dried at about 110 to 120 ^° C.

The oxidized fibers have a density of 3.5 g / cm ³ and a Blain Dyckerhoff specific surface area of 8600 cmVg.

Length distribution of the oxidized fibers:

80% between 10 and 500mm

5% between 1 and 2 mm 12.5% between 2 and 3 mm

2.5%> 3 mm

Thickness distribution of the oxidized fibers:

20% between 5 and 8pm 25% between 10 and 16μηι 17,5% between 30 and 32 μηι 25%> 40μηι (between 50 and 500pm).

Example 5

Sliced rawhide stems, which were only depleted on the surface, are cut to 10 cm in length and immersed in a mixture of 50% water and 50% ethanol (v / v) and sonicated at room temperature. The ultrasonic generator was set at 700 kHz at a power of 50 watts / cm ² via a piezoelectric array. The digestion was stopped after 10 minutes and the bath temperature rose to 3O ⁰ C. The fibers were then isolated and dried in a hot air stream.

Claims (22)

1. reinforcing and / or process fibers based on vegetable fibers, obtainable by liberated from wood components plant fibers with an aqueous solution of at least one metal compound selected from metal oxides, hydroxides, carbonates, sulfates, thiosulfates, sulfites, silicates or phosphates, then washed and treated with an inorganic or organic binder or the non-washed fibers are neutralized with a mineral acid, or treated wood fibers freed with an oxidizing agent or untreated vegetable fibers at 250 to 35O ⁰ C. treated under controlled air supply, so that a charring of the fibers takes place. 2. Fibers according to claim 1, obtainable by using flax, jute, nettle, hemp, cotton or sisal fibers. 3. Fibers according to claim 1 or 2, obtainable by using as metal compound alkali or alkaline earth oxides, hydroxides, carbonates, thiosulfates or sulfates and basic iron, titanium, antimony or aluminum salts. 4. Fibers according to claim 3, obtainable by using sodium or potassium hydroxide, sodium metasilicate or sodium thiosulfate as the metal compound. 5. Fibers according to one of the preceding claims, obtainable by treating the vegetable fibers with a 1 to 3 wt .-%, preferably 10 to 30 wt .-%, aqueous solution of the metal compound. 6. Fibers according to one of the preceding claims, obtainable by treating the vegetable fibers with the aqueous solution of the metal compound at 50 to 100 ⁰ C. 7. Fibers according to one of the preceding claims, obtainable by using as binder cement, gypsum, silicates, bitumen, asphalt, natural or synthetic elastomers, polyurethanes, phenolic resins, resoles, melamine resins, epoxy resins or mixtures thereof. 8. Fibers according to one of the preceding claims, obtainable by using 5 to 20 wt .-% of binder, based on the Faserartteil used. 9. Fibers according to one of the preceding claims, obtainable by bleaching the liberated from wood components plant fibers before treatment with the aqueous solution of the metal compound by treatment with peroxides, hypochlorite or chlorine water. 10. Fibers according to claim 1 or 2, obtainable by using as the oxidizing agent an alkali metal periodate, an alkali metal persulfate or alkali metal permanganate. 11. Fibers according to claim 10, obtainable by using potassium permanganate as the oxidizing agent. 12. Fibers according to claim 10 or 11, obtainable by carrying out the oxidation at a temperature of 75 to 95 ° C. 13. Fibers according to one of the preceding claims, characterized in that they are additionally equipped with a means for flameproofing equipment, a solid lubricant and / or a preservative. 14. Fibers according to claim 1 or 2, characterized in that impregnating the fibers obtained by pyrolysis with a resin, natural or synthetic rubber or an elastomer. 15. A process for the preparation of reinforcing and / or process fibers based on vegetable fibers, characterized in that a) free the fibrous parts of fiber plants from wood components and other undesirable components of the plant, b) if desired, treating the liberated from wood components plant fibers with an aqueous solution of at least one metal compound selected from metal oxides, metal hydroxides, metal carbonates, metal sulfates, metal thiosulfates, metal sulfites, metal silicates or metal phosphates, then washed and treated with an inorganic or organic binder or the non-washed Neutralized fibers with a mineral acid, or if desired, treating the plant fibers freed from wood components with an oxidizing agent, or d) treating the raw, non-pretreated plant fibers at 250 to 350 ⁰ C under controlled air supply, so that a charring of the fibers takes place. 16. The method according to claim 15, characterized in that one carries out the method according to item a) by subjecting the fiber-containing Pt'anzenteile an ultrasonic treatment in an aqueous medium. 17. The method according to claim 16, characterized in that the ultrasound treatment is carried out in a mixture of water and a polar organic solvent. 18. The method according to claim 17, characterized in that one uses as an organic solvent, a C ₁ to C ₄ mono- or dialcohol, a C ₁ to C ₄ -ketone or a water-miscible ether. 19. The method according to claim 18, characterized in that one uses as an organic solvent, methanol, ethanol or acetone. 20. Reinforcing and / or process fibers based on vegetable fibers, obtainable by a process according to one of claims 15 to 19. 21. Use of the fibers according to one of claims 1 to 14 and 20 for the production of moldings. 22. Use of the fibers according to one of claims 1 to 14 and 20 for the production of cement, plastic and plaster moldings, sound insulation materials, friction linings, as well as in sealants, roofing membranes, road surfaces, polishes and as a filler.