SE470101B - Procedure for making board - Google Patents

Abstract

In a process for making board according to the wet method, a stock is prepared from fibres produced from a fibrous raw material, and a binder is added prior to dewatering and pressing. The process is distinguished by adding the binder to the fibres before the preparation of the stock. The binder may be a water-soluble binder which is precipitated and fixed to the fibres by acidification. Acidification may take place in connection with the preparation of the stock or prior thereto as well as prior to the addition of the binder. The binder can be added to the fibres in the blow line from the defibrator for producing the fibres from the fibrous raw material, or it may be added to the fibres before the defibrator.

Description

15 20 25 30 35 4-70 '307 2 materials for recipients). This has resulted in the content of zero fiber and dissolved With the present invention, these disadvantages substances in the backwater can be further increased. largely avoided.

Accordingly, it was an object of the present invention to make better use of the adhesive on the fiber matrix itself in board production. It was also an object of the invention to be able to dose the desired amount of resin onto the fibers without affecting the subsequent dewatering. The object of the present invention was thus achieved, as is apparent from the claims, by a process for producing board according to the wet method in which fibers, made from fiber raw material, such as e.g. chips and shavings, are prepared into a stock and binder is added followed by added to the fibers before stock preparation. It turned out surprisingly to the fibers early in the process, before the supply of the water for stock preparation, the binder could be used much more efficiently with dewatering and pressing, whereby the binder that by adding the binder improved sheet properties as a result. It also became possible to add very large amounts of binder without detriment to the further process.

In the method according to the invention, conventional equipment for producing board according to the wet method is used. the wood raw material via Thus, preheating, with steam, is passed to a defibrillator for decomposition. The resulting fibrous mass is transported through a blow line to tanks for stock preparation. Fresh water and / or back water is added to the tank so that a stock with a content of about 5 - 15% is obtained. This stock is taken to a refiner for final adjustment of the stock to a so-called machines where the final dilution with water / backwater grinding degree. From the refiner led takes place. The stock then has a content of about 2 - 3%. This stock is fed to a pick-up machine for dewatering, pressing and drying / press drying (hot pressing).

According to the present method, the binder can be placed at any time before that for stock preparation. A suitable place for the fibers when a place where a substantial amount of water is added to the binder is the blow line from the defibrillator. There the fibers have a dry content This is a preferred embodiment for the fibers of about 40 - 60% by weight. of the invention. The binder can also be placed before the defibrillator. in the process, those within the curing organic The binders used in the technique are predominant. These are constituents or inorganic binders such as phenolic resins, amino resins, silicates or mixtures thereof. Commonly used When water-soluble resins are used the fibers. This water-soluble binder. these must be precipitated and fixed on alum or acid. connection to â is achieved by acidification with e.g.

The acidification can be done, preferably, in the stock preparation or before this and thereby also before the addition of binder. When the precipitating reagent is added in connection with the stock preparation, it can be added to the first dilution vessel where the stock concentration is approx. 1 - 15 weight. If the acidification is allowed to take place late in the process, e.g. so that a part of the water-soluble binder applied to the fiber matrix dissolves and and instead precipitates%, usually 5 - 15% by weight. in the machine tank, there is a risk of other material in the stock with deteriorating performance as a result. With the present invention, it has also become the penetration of the resin into the fiber. The properties of this board can be affected in different directions, and flexural strength versus swelling and water absorption. If a solution is difficult to dissolve or is used when dosing the resin, the penetration is reduced and the resin is concentrated on the fiber surfaces. This increases the possibility of more active adhesive joints between the fibers with increased strength as a result. In the inverse ratio, that dilute and low-viscosity resins are used, the penetration is increased, whereby lower swelling and mainly lower water absorption are obtained. An additional way to reduce alum / acid before defibrillator or Thus achieved to surface and possible to cause, for example, cross-section II concentrated resin penetration is to dose before the addition site of binder. the binder precipitates directly on the penetration of the fiber Sura 10 15 20 25 30 35 479 191 4. The present invention thus enables several ways to control the properties of the end product in a certain direction.

The process also added to the dewatering on the pick-up machine is made more difficult. according to the invention enables very large amounts of binders without the method according to the prior art limiting the dosing of binders up to about 6-8% and then with the aid of certain flocculants above this level more difficult chemicals. When dosing, the drainage from the wire so that there is a risk of crushing the sheet in the press section. With the process according to the invention 40% by weight (based on dry resin on dry fiber matrix), suitably up to about 15% - the binder is used in an amount of about 0.5 - 10% by weight, the content can be levels of from about 0.5 up to about 20% by weight, dosed without problems. Usually preferably 1 to 5% by weight.

Preparation of board * according to the wet process with the process according to the invention does not affect other process conditions. Dosing of binders can be done via a simple one. The amount of binder is regulated with a dosing pump. The binder can be precipitated in a first stock concentration with alum. connecting pipe on the blow line after defibrillator - e.g. dilution tank at approx. 10% Thereafter, the glued stock may continue in the usual way in the process via refiner, dilution tank, machine and pick-up machine in a conventional manner. relatively easily incorporated into existing processes.

The process can thus be described with parts now by the following examples where and percent refers to parts by weight and% by weight unless otherwise stated.

Example 1 Porous board production: Phenolic resin with a concentration of 40% by weight was applied k blow line dosing directly after the defibrillator via a Phenolic resin app- with s insert tube centered in the blow line. thus concentrated on about 150 ° C hot concentrated fiber (about 50% by weight dry matter). The resin was dosed with a suitable dosing pump. The resin was precipitated and fixed on the fiber at a high stock concentration, 8-10%, immediately after cyclone in the first dilution vessel.

Precipitation took place with alum solution dosed in the dilution water.

The glued fiber (stock) then continued in the usual way in the process via refiners, machines and a pick-up machine.

Disc thickness 13 mm.

Dosing Phenolic resin MOTH IB Swelling Water ab procedure dosing% MPa MPa 2h% 2h% According to the invention 5 6.5 0.26 1.9 12.4 Dosed in machines 5 3.0- 0.08- 2.3- 18 -30 type values * 3.5 0.12 3.5 Standard- 0, lI 7.0 173 board 0 2.7 *) Addition of wax is included in this quality.

Example 2.

Porous board 16 mm: The procedure of Example 1 was repeated with the difference that in this experiment concentrated phenolic resin was dosed 43% (by weight), thus having a higher viscosity than the resin of Example 1. Dosage Phenolic resin MOTHER IB Swelling Water ab procedure dosing% MPa MPa 2h% 2h% According to invention 5 4.0 0.16 3.2 Dosed in machines * 2 2.2 0.07 3.5 22 *) Addition of wax (2%) included in this quality Here it is shown how the properties can be controlled towards increased strength, but less effect on swelling or water absorption by allowing resin to penetrate less.

Claims (11)

10 15 20 25 30 35 470 101 7 Patent claims A process for producing board according to the wet method in which fibers, made from fiber raw material, are prepared into a stock and binder is added followed by dewatering and pressing, characterized in that the binder consists of hardening organic or inorganic binders and is added to the fibers. before stock preparation. 2. A method according to claim 1, characterized in that the binder consists of a water-soluble binder which is precipitated and fixed on the fibers by acidification. 3. A method according to claim 2, characterized in that the acidification takes place in connection with the stock preparation. 4. A method according to claim 2, characterized in that the acidification takes place before the stock preparation. 5. A method according to claim 2, characterized in that the acidification takes place before the addition of binder. Process according to one of Claims 2 to 5, characterized in that acidification takes place with alum or acid. 7. A method according to claim 1, characterized in that the binder is added to the fibers in the blow line from the defibrillator to produce the fibers from the fiber raw material. 8. A method according to claim 1, characterized in that the binder is added to the fibers before the defibrots to produce fibers from the fiber raw material. 9. A method according to claim 1, characterized in that the binder consists of a sparingly soluble or concentrated resin. 10. A method according to claim 1, characterized in that the binder consists of a diluted low-viscosity resin. 11. A method according to claim 1, characterized in that the binder can be added in an amount of from about 0.5 up to about 40% by weight (based on dry resin on dry fiber matrix).