AU665817B2 - Process 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

pr r i OPI DATE 05/10/93 AOJP DATE 09/12/93 APPLN. ID 37715/93 PCT NUMBER PCT/SE93/00205 III11IIIAU9337715 llll AU9337715

(PCT)

(51) International Patent Classification 5 (11) International Publication Number: WO 93/18227 D21H 23/14, D21J 1/00 Al (43) International Publication Date: 16 September 1993 (16.09.93) (21) International Application Number: PCT/SE93/00205 (81) Designated States: AU, CA, CZ, FI, HU, JP, KP, KR, NO, NZ, PL, RO, RU, SK, UA, US, European patent (AT, (22) International Filing Date: 9 March 1993 (09.03.93) BE, CH, DE, DK, ES, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE).

Priority data: 9200784-8 13 March 1992 (13.03.92) SE Published With international search report.

(71)Applicant (for all designated States except US): CASCO NOBEL AB [SE/SE]; Box 11538, S-100 61 Stockholm

(SE).

(72) Inventors; and Inventors/Applicants (for US only) FLODMAN, Leif [SE/ SE]; CastorvAigen 5, S-852 59 Sundsvall NOR- DQVIST, Jan-Erik [SE/SE]; Renstiernas gata 29, 5 tr., S- 116 31 Stockholm (SE).

(74) Agent: SCHOLD, Zaid; Nobel Industries AB, Patent Department, Box 115 54, S-100 61 Stockholm (SE).

(54)Title: PROCESS FOR MAKING BOARD (57) 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 bloiv line from the defibrator for producing the fibres from the fibrous raw material, or it may be added to the fibres before the defibrator.

WO 93/18227 PCT/SE93/00205 PROCESS FOR MAKING BOARD The present invention relates to a process for making board according to what is commonly referred to as the wet method. More specifically, the invention concerns an improved process for making board, by adding the binder at an early stage of the process. Insulation board, building board and hardboard, for instance, can be produced by this process.

When making board according to the wet method, a stock is prepared from fibres produced from a fibrous raw material, such as chips and sawdust, by mixing the fibres with water in several steps. A binder is added to bind the fibres in the board, whereupon the stock is dewatered and the fibre pulp is pressed. The binder is added to the stock and, if water-soluble, is precipitated and fixed to the fibres by acidification of the stock, e.g. by alum or acid. The binder may be added at a site where the stock concentration is about 5-15%, e.g. in the level box, whereupon precipitation and fixation by acidification take place where the stock concentration is about e.g. in the machine chest. Alternatively, both the addition of the i binder and the precipitation thereof on to the fibres may take place in the machine chest.

This process has the disadvantage that the binder, when precipitated, deposits not only on the fibres, but also on the remaining material in the stock. Apart from ,iseful fibres, the stock contains fibre fragments, i.e.

what is commonly referred to as fines., as well as dissolved I carbohydrate material and, to a certain extent, ligneous substance in dissolved and colloidal form. Since the water in the process is at least partly recycled by using, in the preparation of the stock, the white water from the dewatering step, the contents of these by-products will be comparatively high. As a portion of the binder deposits on these components, this portion will be of no avail to the fibre matrix. It has thus become necessary to increase the amount of binder added, which nevertheless has not given the desired result in certain cases. The dosage of resin is WO 93/18227 PCT/SE93/00205 2 also restricted by the fact that dewatering of the stock.is rendered more difficult if the amount of resin exceeds a certain level (about In addition, many board manufacturers in Europe have made their processes more or less closed for environmental reasons (reduced discharge of COD-consuming materials to recipients). As a result, the contents of fines and dissolved substances in the white water have increased even further. However, the present invention largely obviates these disadvantages.

One object of the invention is, therefore, to utilize the adhesive on the fibre matrix more effectively in the making of board. Another object of the invention is to enable dosage of the desired amount of resin on the fibres without affecting the subsequent dewatering.

As appears from the appended claims, the objects of the invention are achieved by a process for making board according to the wet method, in which a stock is prepared from fibres produced from a fibr.ous raw material, such as chips and sawdust, and a binder is added prior to dewatering and pressing, the binder being added to the fibres before the preparation of the stock. It has surprisingly been found that the binder can be utilized far more effectively if added to the fibres early in the process, before the supply of water for preparing the stock, resulting in improved properties of the board. Also, it has become possible to add very large amounts of binder without adversely affecting the subsequent process.

In the process according to the invention, conventional equipment is used for making board according to the wet method. Thus, the wood raw material is conducted, by preheating with steam, to a defibrator for disintegration.

The resulting fibre pulp is conveyed through a blow line to chests where the stock is prepared. Fresh water and/or white water is added to the chests, resulting in a stock having a content of about 5-15%. This stock is conducted to: a refiner for final adjustment of the beating degree. From the refiner, the stock is conveyed to a machine chest, where the final dilution with water/white water is per-

I

L WO 93/18227 PCT/SE93/00205 3 formed. At this stage, the stock has a content of about 2- This stock is conducted to a wet machine to be dewatered, pressed and dried/press-dried (hot press).

In the process according to the invention, the binder may be added to the fibres at any time before the site where a substantial amount of water is added for preparing the stock. The binder is suitably added in the blow line from the defibrator. Here, the fibres have a dry solids content of about 40-60% by weight. This constitutes a preferred embodiment of the invention. The binder may also be added to the fibres before the defibrator.

In the inventive process, use is made of such binders as are predominant in the art. These are curing organic or inorganic binders, such as phenolic resins, amino resins, silicates or mixtures thereof. Water-soluble binders are generally used. When water-soluble resins are employed, they have to be precipitated and fixed to the fibres, which is brought about by acidification, e.g. by means of alum or acid. Preferably, acidification is performed in connection with the preparation of the stock or prior thereto, and in that case also prior to the addition ofI the binder. When added in connection with the preparation of the stock, the precipitating reagent may be added to the first dilution chest, where the stock concentration is about 1-15% by weight, usually 5-15% by weight. If acidi- ~I fication is allowed to take place at a late stage of the process, e.g. in the machine chest, there is a risk that some of the water-soluble binder applied to the fibre 30 material in the stock, resulting in impaired performance.

j rj30 atrx i disolvd areisuting peipared prormane.he With the present invention, it is also possible to "control" the penetration of resin into the fibre. As a result, the properties of the board can be influenced in different directions, e.g. internal bond strength and modulus of rupture versus swelling and water absorption. If a sparingly soluble or concentrated resin is used, penetration is reduced and the resin is concentrated on the fibre surfaces. This enhances the possibility of obtaining i_ r. WO 93/18227 PCr/SE93/00205 active glue joints between the fibres, resulting in higher strength. In the opposite case, i.e. when diluted and lowviscosity resins are used, penetration increases, resulting in lower swelling and, above all, lower water absorption.

Pe .tration may also be reduced by adding alum/acid before the defibrator or before the site where the binder is added. Thus, the binder will be precipitated directly on K the surface of the acid fibre, and penetration is reduced' to a minimum. Consequently, the present invention enables several ways of controlling in a given direction the properties of thae end product.

Also, the process according to the invention enables H the addition of very large amounts of binder without ren- U dering dewatering on the wet machine more difficult. The prior-art process restricts the dosage of the binder to about requiring at that the aid of certain flocculating chemicals. if the dosage exceeds this level, devwatering from the wire is impeded to such an extent that there is a risk of crushing the sheet in the press section.

In the process according to the invention, there are no dosing problems with contents of from about 0.5% by weight to about 40% by weight (based on dry resin on a dry fibre matrix), suitably up to about, 15-20% by weight. Generally, the binder is used in an amount of about 0.5-10% by weight, preferably 1-5% by weight.

making board according to the wet method by the process according to the invention does not influence the other process conditions. The binder can be added through a simple connecting tube on the blow line after t.he defibrtor.The amount of binder is adjusted by a dosing pump.

The binder can be precipitated in e.g. a first dilution chest at a stock concentration of about 10% by means of 4 alum. T~hen, the sized stock is allowed to continue in the process via a refiner, a dilution chest, a machine chest and a wet machine in conventional manner. Thus, the process according to the invention is fairly easy to incorporate mi existing processes.

The invention will now be described in more detail WO 93/18227 PCT/SE93/00205 with the aid of the following Examples, in which the part and percentage figures concern parts by weight and per cent by weight, unless otherwise stated.

Example 1 The making of insulation board.

Phenolic resin having a concentration of 40% by weight was applied by so-called blow-line dosage immediately after the defibrator through an insert pipe centered in the blow line. Thus, the phenolic resin was applied to concentrated hot fibre having a temperature of about 150°C (a dry solids content of about 50% by weight). The resin was dosed by a suitable dosing pump, and was precipitated and fixed to the fibre at a high stock concentration immediately after the cyclone in the first dilution chest.

Precipitation was brought about by the addition of an alum solution to the diluting water.

j The sized fibre (the stock) was then conducted further in the process via refiners, machine chests and a wet machine in conventional manner.

The board thickness was 13 mm.

Dosing Phenolic resin MOR IB Swelling -Water abs.

process dosage MPa MPa 2 h 2 h According to the invention 5 6.5 0.26 1.9 12.4 j 30 Added in machine chest typical va- 5 3.0- 0.08- 2.3- 18-30 lues* 3.5 0.12 Standard board 0 2.7 0.11 7.0 173 An addition of wax forms part of this grade.

i. r :-11 WO 93/18227 PCr/SE93/00205 Example 2 Insulation board 16 mm.

The process according to difference being that use phenolic resin of 43% by cosity than the resin used Example 1 was repeated, the only was here made of concentrated weight, i.e. having higher visin Example 1.

Dosing process Phenolic resin dosaae MOR IB MPa MPa Swelling Water abs.

2 h 2 h According to the invention Added in machine chest 4.0 0.16 3.2 2.2 0.07 An addition of wax forms part of this grade.

It is apparent how the properties can be controlled towards increased strength by reducing resin penetration, although with lesser effect on swelling and water absorption.

j

Claims (12)

1. A process for the manufacture of board according to the wet method comprising the steps of adding a binder to fibres, said binder selected from water soluble curing organic and inorganic binders, preparing a stock of fibres, precipitating and fixing said binder to the fibres by acidification, dewatering said stock and pressing the fibres into a board, wherein the binder is added to the fibres before preparing said stock and the step of preparing and fixing said binder occu,'s prior to dewatering.

2. A process as claimed in claim 1, wherein acidification takes place in connection with the step of preparing the stock.

3. A process as claimed in 'aim 1 wherein acidification takes place before the step of preparing the stock.

4. A process as claimed in any one of claims 1 to 3 wherein acidification takes place before the step of adding the binder.

A process as claimed in any,one of claims 1 to 4 wherein alum or acid are used for acidification in the acidification step.

6. A process as claimed in claim 1, 2, 3 or wherein the binder is added to the fibres in a blow line from a defibrator for producing the fibres from fibrous raw material.

7. A process as claimed in claim 6, wherein the binder is added to the fibres before the fibrous raw material is passed through the defibrator.

8. A process as claimed in any one of claims 1 to 7 wherein the binder is a sparingly soluble or concentrated resin.

9. A process as claimed in any one of claims 1 to 8, wherein the binder is a diluted, low-viscosity resin.

A process as claimed in any one of claims 1 to 9, stat/af/koep/specV37715.93-1 18,10 r :1 r~ i 8 wherein the binder is added in an amount of from 0.5% by weight to 40% by weight, based on dry resin on a dry fibre matrix.

11. A board produced by the process as claimed in any one of claims 1 to 11.

12. A process for the manufacture of board a% hereinbefore described with reference to the accompanying drawings. DATED THIS 18TH DAY OF OCTOBER 1995. CASCO NOBEL AB By its Patent Attorneys: GRIFFITH HACK CO Fellows Institute of Patent Attorneys of Australia I Sstaffl/ae/eep/spec37715.93_1 18.10 U 7' V -7 INTERNATIONAL SEARCH REPORT international application No. PCT/SE 93/00205 A. CLASSIFICATION OF SUBJECT MATTER IPCS: D21H 23/14 D21J 1/00 According to International patent Classification (IPC) or to both national classification and IPC B. FIELDS SEARCHED Minimum documentation searched (classificaaion system followed by classificat~ion symbols) D21H, D21J Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched SE,DK,FI,NO classes as above Electronic data base consulted during the international search (name of data base and, where practicable, search terms used) PAPERCHEM, U.S. PATENTS, CLAIMS, JAPIO, WPI C. DOCUMENTS CONSIDERED TO BE RELEVANT Category* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No. XWO, Al, 8802417 (SIMONSON, RUNE ET AL), 11 7 April 1988 (07.04.88), see the claims; page 4-6; rX page 9, lines 24-34; abstract A US, A, 4486501 WKELD HOLBEK), 4 December 1984 11 (04.12.84), abstract D Further documents are listed in the continuation of Box C. [jSee patent family annex. Special categories of cited documens IT' later document published after the international filing date or priority W document defining the general same of the art which is not considered dato and not in conflict with the application but cited to undlersd to be of particular relevance the principle or thecy underlying the invention edier document but publishied on or after the utteroatinnal filing data X' document of particular relevanice the claimed invention cannot be L doumet wich ay hso doha o pnntyclam~s)or hic ~,considered novel or cannot be considered to involve an inventive cited to establish the publication date of sntfe ctation 6r ottp IL-itdcmntetkn ln special reason (as specified) document of particular releviacc, the claimned invention cannot be '0O document refering to an oral disdoeure. ue, exhibition or other considered to involve an inventive step when the document is QeAnS combined with one or more other such documents, such combioation 'P document published prior to the international filing date but later du being obvti= to a person skilled in the art the priority date cleimed document member of the same patent fazidly Date of the actual completion of the inttrnational search Daeof mailing of the international search report 23 -06- 1993 Name and mailing address of the ISA/ Authorizete officer Swedish Patent Office Box 5055, S-102 42 STOCKHOLM Barbro Nil sson Facsimile No. 46 9 666 02 86 1Telephone No. 46 8 782 25 00 Form PCT/lISA/210 (second sheet) (July 1"92) V I- INTERNATIONAL SEARCH REPORT Itrainlapiaio o Information on patent family membersInrainaaplctoN. 28/05/93 1 PCT/SE 93/00205 Patent document Pbcion Patent famiily Puolication cited in search report daemember(s) date ~1WO-Al- 8802417 07/04/88 AU-B- 606893 21/02/91 AU-A- 8036387 21/04/88 EP-A,B- 0328533 23/08/89 US-A- 4486501 04/12/84 EP-A- 0032928 05/08/81 Form PCT/ISA/210 (patent family Mannx) (Juy 1992)