FI96976B - Process for making a disc - 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

96976

The present invention relates to a method for manufacturing a sheet according to a method commonly referred to as a wet method. More specifically, the invention relates to an improved method of making a sheet by adding a binder at an early stage in the method. This method can be used to produce, for example, insulation boards, building boards and hard boards.

10 In the production of boards according to the wet process, a stock is made from a fibrous raw material, such as fibers produced from chips and sawdust, by mixing the fibers in water in several steps. The binder is added to bind the fibers in the board, after which the stock is dewatered and the pulp is pressed. The binder is added to the stock and, if it is water-soluble, it is precipitated and attached to the fibers by an acid-free 1S club stock, e.g. with alum or acid. The binder can be added at a point where the consistency of the stock is about 5-15%, e.g. in a flat box, whereby precipitation and fixing by acidification takes place at a point where the consistency of the stock is about 2-3%, e.g. in a machine box. Alternatively, both the addition of the binder and its precipitation on the fibers can take place in the machine tank.

20 This method has the disadvantage that when the binder precipitates, it precipitates not only on the fibers but also on other substances in the stock. In addition to the useful fibers, the stock contains fibrous fragments, commonly referred to as fines, as well as dissolved carbohydrate, and to a certain extent, lignin substances in dissolved and colloidal form. Since the process water is at least partially recycled by using recycled water from the dewatering step in the pulp manufacturing step, the concentration of these by-products is relatively high. When part of the binder precipitates on these components, this part is not useful for the fiber matrix. Thus, it has become necessary to increase the amount of binder added, which, however, has not led to the desired result in certain cases. The dosage of the resin is also limited by the fact that the dewatering of the stock becomes more difficult if the amount of resin exceeds a certain level (about 6-8%). In addition, many European record producers have adapted their methods for environmental reasons. more or less closed (reduced recipient emissions of COD consuming substances 2 96976). As a result, concentrations of fines and solutes in circulating water have increased even more. However, the present invention largely eliminates these drawbacks.

It is therefore an object of the invention to make more efficient use of the binder 5 in the fiber matrix in the manufacture of the board. Another object of the invention is to enable the desired amount of resin to be dispensed into the fibers without subsequently affecting the subsequent dewatering.

As will be apparent from the appended claims, the objects of the invention are achieved by a process for producing a board by a wet process in which a pulp is made from fibrous raw material such as chips and sawdust and the binder is added before dewatering and compression. It has surprisingly been found that the binder can be utilized much more efficiently if it is added to the fibers at an early stage in the process, before water is added to make the stock, which results in better sheet properties. It has also become possible to add large amounts of binder without adversely affecting the subsequent process.

The method according to the invention uses conventional equipment for manufacturing the sheet according to the wet method. Thus, the wood material is passed, preheating with steam, to a defiberer to decompose it. The resulting fibrous pulp is passed through a blow line to the cone where the pulp is made. Fresh water and / or circulating water is added to the vat to give a stock density of about 5-15%. This mass is passed to a grinder to finally adjust the degree of grinding. From the refiner, the pulp is passed to a machine-type silicon, where its final dilution with water / circulating water takes place. At this point, the consistency of the pulp is about 2-3%. This mass is fed to a wet machine for dewatering, pressing and drying / pressing-drying (hot press).

In the process of the invention, the binder may be added to the fibers at any point 30 prior to the point where a substantial amount of water is added to make the stock. The binder is suitably added to the blow line from the fiberizer. Here, the dry solids content of the 96976 3 fibers is about 40-60% by weight. This is a preferred embodiment of the invention. The binder can also be added to the fibers before the fiberizer.

The process of the invention uses binders commonly used in the art. These are curable organic or inorganic binders such as phenolic resins, amino resins, silicates or mixtures thereof. Water-soluble binders are commonly used. When water-soluble binders are used, they must be precipitated and attached to the fibers, which is achieved by acidification, e.g. using alum or acid. Preferably, the oxidation is carried out during or before the production of the stock, and in that case also before the addition of the binder. When added to the stock during this preparation, the precipitant may be added to the first diluent box where the consistency of the stock is about 1-15% by weight, generally 5-15% by weight. If the oxidation is allowed to take place at a late stage in the process, e.g. in a machine bath, there is a risk that some of the water-soluble binder added to the fiber matrix will dissolve and precipitate on other substances in the stock, leading to a degraded result.

With this invention, it is also possible to "control" the penetration of the resin into the fiber. As a result, the properties of the sheet can be affected in different directions, e.g., internal bond strength (IB) and modulus of rupture (MOR) 20 with respect to swelling and water absorption. If a sparingly soluble or concentrated resin is used, the penetration is reduced and the resin is concentrated on the surface of the fibers. This. · Increases the possibility of obtaining active adhesive bonds between spawns, leading to higher silicon strengths. In the opposite situation, i.e. when dilute and low-viscosity resins are used, the penetration increases, leading to less swelling and, above all, low water absorption. Penetration can also be reduced by adding alum / acid before the fiberizer or before the point where the binder is added. In this way, the binder precipitates directly on the surface of the acidic fibers, and the penetration is reduced to a minimum. Thus, the invention provides several means for adjusting the properties of the final product in a particular direction.

30

The method according to the invention also makes it possible to add very large amounts of binder without making dewatering in a wet machine more difficult. In prior art 4,96976 methods, the binder dose is limited to about 6-8%, in addition to requiring the use of certain flocculating chemicals. If the dose exceeds this amount, water removal from the wire becomes more difficult to the extent that there is a risk that the sheet will break in compression. The process of the invention has no dosage problems when using concentrations ranging from about 0.5% by weight to about 40% by weight (calculated as dry resin from the dry fiber matrix), suitably up to about 15-20% by weight. The binder is generally used in an amount of about 0.5 to 10% by weight, preferably 1 to 5% by weight.

The production of sheets by the wet method using the method according to the invention does not affect other process conditions. The binder can be added through a simple connecting pipe in the blow line after the fiberizer. The amount of binder is adjusted by means of a dosing pump. The binder can be precipitated, e.g. in the first dilution box, at a pulp consistency of about 10% alum. The adhesive stock is then allowed to pass through the grinder, dilution box, machine hopper and wet machine in the process in the conventional manner. The method according to the invention can thus be relatively simply incorporated into already existing processes.

The invention is described in more detail below in the following examples, in which parts and percentages are by weight unless otherwise indicated.

Example 1 Manufacture of insulation board

A phenolic resin having a concentration of 40% by weight was added by so-called blow line dosing immediately after the fiberizer through a tube centrally mounted in the blow line. Thus, the phenolic resin was added to concentrated hot fibers having a temperature of about 150 ° C (dry solids content about 50% by weight). The resin was dispensed with a suitable dosing pump, and precipitated and fixed to the fibers using a high mass concentration (8-10%) immediately after the cyclone in the first dilution plate.

Precipitation was achieved by adding alum solution to dilute water.

il mi uin m i m 96976 5

The adhesive-containing fiber (pulp) was then passed in the process through fiberizers, machine types and a wet machine in the manner of a conventional weapon.

5 The thickness of the plate was 13 mm.

Dosage- Phenolic Resin- MOR IB Swelling Vesiabs. method dose% MPa MPa 2 h% 2 h% 10 According to the invention 5 6.5 0.26 1.9 12.4

Added machine type, typical value *) 5 3.0-3.5 0.08-0.12 2.3-3.5 18-30

Standard plate 0 2.7 0.11 7.0 173 20 *) Wax added to this grade • Example 2

Insulation plate 16 mm The procedure of Example 1 was repeated, the only difference being that concentrated phenolic resin, 43% by weight, was used, thus having a higher viscosity than that used in Example 1.

30 6 9 6 9 7 6

Dosage- Phenolic Resin MOR IB Swelling Wateriabs.

method dose% MPa MPa 2 h% 2 h%

According to invention 5, 5 4.0 0.16 3.2 15

Added to machine type 2 2.2 0.07 3.5 22 10 *) Wax included in this quality (2%)

It is obvious how conditions can be adjusted in the direction of better strength by reducing resin penetration, although the effect on swelling and water absorption is less.

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Claims (10)

9697 6 A process for producing a board by a wet process, in which a pulp is made from fibers obtained from a fibrous raw material and a water-soluble curable organic or inorganic binder is added before dewatering and compression, characterized in that the binder is added to the fibers before the pulp is made and precipitated and fixed. 2. A patent according to claim 1, which is incorporated herein by reference, is incorporated into the invention. Process according to Claim 1, characterized in that the acidification takes place in connection with the production of the stock. 3. A patent according to claim 1, which is incorporated herein by reference in its entirety. Process according to Claim 1, characterized in that the acidification takes place before the pulp is prepared. 4. A patent according to claim 1, which is intended to be surgically incorporated into a binder. 25 5. The form of the invention is set forth in claims 1-4, which are incorporated herein by reference in their entirety. Process according to Claim 1, characterized in that the acidification takes place before the addition of the binder. Process according to one of Claims 1 to 4, characterized in that the acidification takes place with alum or acid 6. The first claim of claim 1, which is incorporated herein by reference, provides an account for the use of a fibrillation for the manufacture of a fiber-to-30 fuse. A method according to claim 1, characterized in that the binder is added to the fibers in a blow line from a fiberizer in which fibers are produced from the fibrous raw material. 7. For the purposes of claim 1, kännetecknät därav, att bindemedlet provision has been made for the use of defibrators for the manufacture of fibers. Of (f 9, 8. For example, a patent 1 is used, the binder is a compound 5 or a solid or concentrated resin. A method according to claim 1, characterized in that the binder is added to the fibers before the fiberizer in which the fibrous raw material is made. fibers. Process according to Claim 1, characterized in that the binder is a sparingly soluble or concentrated resin. 96976 Process according to Claim 1, characterized in that the binder is a dilute, low-viscosity resin. Process according to Claim 1, characterized in that the binder 5 is added in an amount of from about 0.5% by weight to about 40% by weight (calculated as a dry resin from a dry fiber matrix). Article 10 och fixeras pä fibrerna genom Surgöring. 15 9. A method according to claim 1, comprising a binding agent, said binder having a final resin. 10 10. Förfarande enligt patentkravet 1, kännetecknät därav, att bindemedlet account— provided that the game is about 0.5 up to a maximum of 40% (baser of torrt resin on a fiber matrix).