Process for improving the properties of fibre-made articles and apparatus for the application of the process.

p0001The invention relates to a process for equity sheep⁺ sverbesserung, in particular the water resistance and mechanical strength of produced from cellulosic pulp slurry by press moldings, wherein the mold parts subjected to a vacuum, then wetted with a suitable flowable resin, subjected to a pressure increase and subsequently cured. `

p0002According to today's state of the art such moldings described, for example, in German Patents 803 019 and 803 085 prepared in substantially volumes, partially rounded desirable in their properties image by surface impregnation with synthetic resins, and used wherever technically where the achievable end properties with the requirements are to be brought into line specifically. Large applications will find such moldings currently etc. as support of interior parts in motor vehicle and as a material for speaker cones.

p0003The aim is to improve the properties of pulp-molded parts to using this to achieve the level of properties of plastic moldings and simultaneously take advantage of the known high proportion of available and renewable raw materials.

p0004From DE-PS 864 917 is a process for finishing molded compositions made from fiber materials, such as wood or cellulose fibers, known by which these materials are impregnated with diisocyanates under pressure, wherein the impregnating agent is then cured, with or without pressure. By this known method, the surface hardness is increased and greatly reduces the water swellability of the wood. In order to enable the penetration of the resin into the fibrous molding under pressure, the resin with a solvent such as butyl acetate, is added. This known method has various disadvantages. Firstly, the use of a solvent increases the economic burden for carrying out the method. Further measures must be taken in order to evaporate the solvent, where environmental impacts are to be avoided. Finally, the curing process requires the application of pressure in order to avoid leakage of the resin from the pulp structure. The entire treatment course lasts several hours here.

p0005In the impregnation of wood with vinyl monomers have been exposed to even a vacuum and wet in vacuum with resin according to DE-Z "wood as a raw material", 1968, page 110, Unit 7.2.4 the parts. Subsequently, the pressure was raised to atmospheric pressure and the excess resin is removed after four hours, after which the pressure to 21 bar was increased, and the parts were exposed to this pressure for 18 hours. This was followed by a slow pressure reduction during 1.5 hours.

p0006Besides also hours of impregnation duration of this known method especially disadvantageous that when a reactive resin with the fiber material, the total amount of resin used would anreagiert and could no longer available for further use therefore. The economic yield of this known method is therefore unsatisfactory for two reasons. In addition, is also here obviously hardening only under higher pressure (20 atmospheres) possible to get in drips and runner-free surfaces.

p0007The invention is based on the object of specifying an operation preceded by better utilization and shorter-term resin impregnation treatment more economical method for impregnating fiber moldings, with no drop and sag to occur on the surfaces of the impregnated moldings.

p0008To achieve this object, the method characterized in claim 1 is proposed according to the invention.

p0009By applying the method according to the invention the problem is solved, because the impregnation time can be shortened to just minutes-long duration. Moreover, which is still in the vacuum of the wetted moldings separated and therefore not anreagierte resin for subsequent further impregnations available, so contributing to economic efficiency is greatly increased.

p0010It is known that liquid containing isocyanate monomers, oligomers and / or polymers with ingredients from wood and / or cellulose material components react chemically to solids and process together with these a cure, such as in - "Polyurethane in the fifth decade" - v G.. Oertel KUNSTSTOFFE 1/81 - above, are subjected, without requiring a further component, such as a polyol. In addition, the presence of relatively high gas and / or fluid uptake and permeability with said fibrous moldings is typical.

p0011Furthermore, the sensitivity of liquid technical isocyanates with respect to the reactive components with them by contact materials in terms of undesirable change in the delivery forms or their storage stability is known.

p0012The treatment of pulp-molded parts is accordingly performed with isocyanate, liquid resins under conditions that exploit the fluid intake of the moldings and everywhere safely exclude the same time the contact of reacting with isocyanate molding ingredients with the resin, which outside of the part, the storage stability of the liquid phase must be preserved.

p0013The nature and content of the invention is thus in an economical process that ensures the penetration of fibrous moldings with an appropriate isocyanate, while the contact of ingredients of the moldings with not penetrated into these resin shares excludes certain. The curing of the penetrated resin portion is carried out by chemical reaction with components of the parts. The reaction products are deposited on the fiber structure to, fix and seal it largely.

p0014In a preferred embodiment enters a non-toxic isocyanate resin, which is matched in viscosity, reactivity, NCO content and chemical structure to the fluid intake and the content of the reaction partners of the pulp molded article, and the desired final properties through such on the application, the resin preferably having already degassed mold parts is brought to the wetting and penetrating in contact by increasing the pressure in the mold parts.

p0015The moldings can be located on an isocyanate-fluid level in the same container. After reaching the desired vacuum in the vessel, 30-- about 100 torr, the resin is flooded parts. The pulp-molded parts are separated even in the vacuum of excess fluid after expires at these superficial discrete adipose resin. In the pressure increase, preferably in the range from atmospheric pressure to about 20 bar, then penetrates only the quantity of still adhering to the parts resin film and liquid droplet and rotor developments are excluded.

p0016Subsequently, the curing may take place in a separate container at elevated temperature.

p0017In a further preferred embodiment, these operations take in a rotatable and / or tiltable bottom and / or pressure vessel instead, whereby by rotating the vessel about 180 ° of the dipping process of the molding material molded parts in a Isocyanatharzbad and by reversing or further rotation of the re-separation of the two components takes place.

p0018After the aforementioned embodiments, the patients treated with the single-component isocyanate resin fibrous moldings are available, if necessary, curing forcierenden Bedin conditions suspended while the unutilized portion of the resin for repetition of the procedure remains available and is filled as needed with fresh produce.

p0019The pulp can be enriched with high mechanical firmer fibers to intra structurally incorporate their specific properties in the final properties des.nachträglich reinforced molding.

p0020The new opportunities that arise through the process of the invention, leading to inexpensive reinforced fiber moldings, which consist primarily of renewable, long-term availability of raw materials and thereby these parts previously unknown properties such as, inter alia, water and weather resistance, temperature resistance, high mechanical strength, lend Recoatable with solventborne systems and the ability to universal application of force and thus in the promising competition with commercial molding materials which have similar characteristics, occur or can open up completely new application areas for fiber moldings.

Example:

p0021Five commercial Fibrit^R-Carrier (Car door trim) are fixed one above the other in a grid cage by a distance of about 10 mm and mounted in a lid-tank containing 300 liters of a commercially available MDI resin, above the liquid level at suitable internals.

p0022After closing the lid, the entire tank is evacuated bar at a temperature of 35 ° C up to a pressure of 0.07 and tilted 5 min. At 180 °. Using the framework Fibrit^R-Carrier in the resin liquid, remain there for 30 seconds or by tilting by a further 180 ° back to the starting position. - After venting of the tank and the lid is opened, the parts are free of major adhering liquid residues and a few hours at 95 ° C cured.

p0023The increase in weight of the parts is 24.5 to 26.0 wt .-%. The reinforced moldings are boiling-resistant and show a relation to the baseline at the 3, five-fold increase in modulus of elasticity in the bending test. Weathering shows after 18 months except yellowing no negative findings. The excess resin portion does not change measurably by this procedure in viscosity and NCO content.