SE410003B - BINDERS CONTAINING LIGNOSULPHONATES AND PHENOLFORMAL HYDE RESINS FOR THE MANUFACTURE OF PLYWOOD, SPANISH, FIBER DISCS AND THE LIKE - Google Patents

Description

7312584-1 2 It has been suggested that heating in two steps can be avoided by using pre-treated, chlorinated lye. The same purpose is stated in an article entitled "Ueber die Herstellung von Holz- chipplatten auf Basis von Sulfitablauge II. Ueber ein neues und snnels Verfahren zur Herstellung Sulfitablauge gebundener Spanplatten", Holzforschung 25 (1971), 149 - 55. According to this article, heating in two steps is avoided by mixing phenol formaldehyde resin with the sulphite liquor. Studies have shown that the optimum pH value of the binder is 4-5, since when using alkaline solution strong swelling of the discs in the thickness direction is obtained.

According to U.S. Pat. No. 2,786,008, acidic ammonium-based sulfite liquor mixed with phenol formaldehyde resin has been used as a binder for fibreboard and plywood.

Lignosulfonates separated from a solution of sulphite liquor have also been used in admixture with phenol formaldehyde resin as binders for particle board and fibreboard, for example according to Canadian Patent Specification 735,389, and as plywood binders for indoor use, as set forth in the article "Thermosetting adhesives from electrophonylated lignos". , Tap 50 (1967), 92-4A. For the latter purpose, the lignosulfonates have been mixed with phenol-formal ahy resin. in the present invention is based on an investigation of the possibility of using lignosulfonates in sulphite liquor for the production of a water-resistant binder. Efforts have been made to develop a binder which is suitable for industrial use for the production of plywood, chipboard, fibreboard and similar products in a technically advantageous manner. Studies have shown that certain very precisely definable properties of lignosulfonates are required to ensure satisfactory bonding. It has surprisingly been found that the molecular weight distribution of lignosulfonates has a decisive effect on the sizing result. Thus, it has been found that the majority of the lignosulfonates must have a molecular weight above 5,000. If lignosulfonates in the manner of the present invention are added to a solution of phenol formaldehyde resin, a binder is obtained which is advantageously useful for the production of plywood, particle board, fibreboard and similar products. when using binders according to the invention, the same compression conditions and temperature can be used as when using commercial phenol formaldehyde resin in the production of plywood. Since plywood produced in this way meets the requirements for outdoor use and because the lignosulfonates used in the binder are significantly cheaper, the use of this binder is economically advantageous. The moderate alkalinity of the binder does not cause corrosion or defects in the veneer as is the case when using acidic binders.

Weather-resistant chipboard can be made using adhesives according to the invention. This is a significant advantage because boards glued with phenol formaldehyde are not weatherproof, as stated in the publication "Fenoliliimatun lastulevyn ominaisuuksista Ja niiden tutkimisesta" (properties of phenolic glued chipboard and examination thereof) in the publication "Sarja I - Puu 42" (series I - - wood 42) from the Finnish State Institute of Technical Research. The advantages of the production method compared with other processes in which sulphite liquor or lignosulfonates are used are e.g. hardening of the discs in one step and the short compression time required.

The corrosive and corrosive action of an acidic binder is also avoided. The above-mentioned advantages obtained according to the invention have an extremely favorable effect on the economic aspects of the manufacturing method when applied on an industrial scale.

Lignosulfonates which are suitable for use as raw materials for adhesives due to the molecular weight distribution according to the invention can be separated, for example, from sulphite liquor in a manner known per se.

The suitability of lignosulfonates as raw materials for adhesives can be determined on the basis of the molecular weight distribution. Thus, at least 55% by weight of the lignosulfonates should have a molecular weight exceeding 5000.

The suitability of lignosulfonates for the preparation of binders according to the invention can also be determined by means of the viscosity. The viscosity of an aqueous solution containing 50% by weight of these lignosulfonates, prepared after potential neutralization, exceeds 10,000 cP measured at 2300 with a Brookfield RVT viscometer at 50 rpm.

The lignosulfonates are used in the form of alkali or alkaline earth salts, optionally containing excess alkali or alkaline earth metal so that the pH of a solution containing 10 g of lignosulfonate / 100 ml is 6 .mu.l.

Binders according to the invention are obtained by preparing an aqueous solution containing these lignosulfonates and phenol formaldehyde resin. The weight ratio of lignosulfonates: phenol formaldehyde resin is 1s12se4-1 4 for gluing plywood 70:30 - 20:80 and for chipboard and corresponding products 90: 10 - 20:80. The water content of the binder can be 40 - - 70%. The viscosity can be changed by regulating the water content or by heating the binder. A suitable viscosity range is often 100 - 2000 cP.

Aldehyde, for example formaldehyde, paraformaldehyde or furfuraldehyde, can be added to the binder to act as a hardener.

Conventional excipients, such as chalk, wood flour and wheat flour, can be used in binders for plywood and chipboard.

In the production of chipboards using adhesives according to the invention, for example, paraffin can be added to the binder or chips separately to improve the swelling properties of the boards. In Example 1. (Comparative Example). The following examples illustrate the suitability of two lignosulfonate products and sulphite liquor for the preparation of the binder. The pH value, distribution and viscosity values of these three agents are given in Table I.

Table I lignosulfonate-lignosulfonate-sulphite product 1 product 2 lye PH 716 6: 8 ° 5: 0 proportion of macromolecular lignosulfonates (M> 5000) of the total amount of lignosulfonates' 42 5 45 ß 44 5 viscosity of aqueous solution with dry matter content 50% by weight Brookfield RVT, 23 C 720 cP 170 cP 100 cP The binders were prepared as follows: 160 g of lignosulfonate product 1 or 2 were dissolved in 240 g of water and the solution was mixed with 600 g of commercial phenol formaldehyde resin having a solids content of 40 ß. 55% technical sulphite liquor was diluted to 40% and 400 g of this solution were mixed with 600 g of commercial phenol formaldehyde resin having a solids content of 40%, 10 g of paraformaldehyde were added.

The binders were mixed for a period of 60 minutes and then spread on 1.5 mm thick birch veneer with a moisture content of 4%.

The amount spread was 150 g / m 2 and is spread on one side of the veneer. Three-layer plywood boards were produced. The pre-compression pressure was 5 kp / bm2 and the time was 5 minutes. The hot pressing temperature was 5 ° C and the pressure was 16 kp / bmg and the time was 10 minutes.

Using the same pressing conditions and amount of glue, three-ply plywood boards were produced with commercial phenol-formaldehyde resin as binder, paraformaldehyde (binder 1) as hardener and powder of quebracho, chalk, wood and wheat flour (binder 2) as extenders, for comparison.

The properties of the produced boards, measured according to the Finnish plywood standard O.IV.l, are given in table ll (average values for five boards).

Table II dry wet shear fracture in 7 shear fractures in tension wood tension wood ngnosulfenate 1 21.9 kp / cmg 57 y; 152 kp / cn? 7; lißnosulfonate? 23.6 "40 1 10,?" Lt 3 (commercial) - sulfite 16.9 "111 7; 22.9" - commercial phenol ~ 32.6 "90 fl 23.4" 85 formaldehyde resin (binder 1) commercial phenol 514.4 "93 9.". 18.1 "91 few formic acid resins in (binder 2) Plywood boards made using lignosulfonate product 1 or 2 or sulfite liquor mixed with phenol formaldehyde resin as the binder did not meet the requirements set forth in this standard, according to which dry shear stress of 20.9 kp / omg is required, or fracture of the wood 50% wet shear stress of 14.1 kp / bme, or fracture of the wood 50 ß.

Example 2.

Production of plywood boards using adhesives according to the invention.

Na-lignosulfonates in which the percentage by weight of macromolecular lignosulfonates (MW> 5000) of the whole amount of lignosulfonates amounted to 67 ß, were used in the manufacture of the binder. An aqueous solution containing 50% by weight of these lignosulfonates had a viscosity> 80,000 cP (Brookfield RVT ~ viscometer, 50 rpm, 23 ° C). The pH of an aqueous solution containing 10% by weight was 8.2. 160 g of these lignosulfonates were dissolved in 300 g of water. The solution was mixed with 600 g of phenol formaldehyde resin having a solids content of 40%. 10 g of paraformaldehyde were added and the binder was mixed for 60 minutes. The viscosity of the binder was 216 cP.

The method of production of the plywood boards was identical to that given in Example 1. Five boards were manufactured, five test pieces were taken from each board to determine the dry strength and, in the same way, five to determine the wet strength. The results of the determinations are given in Table III (mean values for 25 test pieces as well as reliability limits for 95 Å probability, 'Table III - dry wet cloud / voltage g 35.1 in 1.7 kp / emz - 22.2 ¿1, 2 kp / emz Fault 1 wood * 914 f; 91 The boards fully met the requirements of the Finnish standard for plywood intended for outdoor use and had properties corresponding to those obtained using commercial phenol formaldehyde resin.

Example §.

Na-lignosulfonates with a weight percentage of macromolecular lignosulfonates (MW> 5,000) of the total amount of lignosulfonates amounting to 83% were used in the preparation of the binder. An aqueous solution containing 50% by weight of these lignosulfonates had a viscosity of 80,000 cP (Brookfield RVT viscometer, 50 rpm, 2300). The pH of an aqueous solution containing 10% by weight was 7.4. The binder was prepared in the manner set forth in Example 2.

The viscosity of the binder was 640 cP.

Three-layer plywood boards were prepared in the manner set forth in Example 1. Five specimens were taken from each of the five manufactured disks to determine the wet strength. The properties of the discs are given in Table IV (mean values for 25 test pieces and confidence limits for 95% probability). 0 Table IV dry wet shear stress 36.2 in 1.2 kp / emg 20.0 in 1.5 kp / ema Error 1 wood 93 74 90 f; 7 7312584 ~ 1_ Exemgel H.

Na-lignosulfonates, in which the weight percentage of macromolecular lignosulfonates (MW> 5,000) of the total proportion of lignosulfonates was 61%, were used in the preparation of the binder. An aqueous solution containing 50% by weight of these lignosulfonates had a viscosity> 80,000 cP (Brookfield HVT viscometer, 50 rpm, 2500). The pH of an aqueous solution containing 10% by weight was 7.6. 160 g of these lignosulfonates were dissolved in 500 g of water. The solution was mixed with 600 g of phenol formaldehyde resin having a solids content of # 0%. 5 g of paraformaldehyde, 10 g of wheat flour, 10 g of chalk and 20 g of wood flour were added to this solution. The binder was mixed for 60 minutes. After mixing, the viscosity was 660 cP and after 48 hours 712 cP.

The procedure for the production of the plywood boards was identical to that given in Example 1. Five specimens were taken from each of the five prepared disks to determine the dry strength and similarly five for the wet strength determination. The properties of the disks are given in Table V (average values for 25 test pieces and reliability limits for 95 ß probabilities).

Table V dry wet ... > P - Shear stress 55.6 in 5.6 kp / bmi 20.2 in l, Ä kp / bm Error 1 wood 93% 90% - Exemgel 5.

Production of chipboard.

Na-lignosulfonates were used in the preparation of the binder.

The content of macromolecular lignosulfonates (MW> 5,000) was 57 5.

An aqueous solution containing 50% by weight of these lignosulfonates had a viscosity> 80,000 cP (Brookfield RVT viscometer, 50 rpm, 25 ° c). The pn value nes a water solution containing io weight percent was 7.8. 1000 g of these lignosulfonates were dissolved in 1,970 g of water. 100 g of sodium hydroxide was added to the aqueous solution. 2500 g of commercial phenol formaldehyde resin with a solids content of H0 5 were mixed with the solution. M5 g of paraformaldehyde was added and the solution was mixed for a period of 60 minutes.

The binder prepared in this way was sprayed on chips from the surface of a birch log with a moisture content of 2.1 S and chips from the inner part of a birch log with a moisture content of 5.0 S. The dry matter content of the sprayed binder was to 12% of the dry surface chips and 10 fl of the dry inner chips. 1% paraffin calculated on the dry weight of the chips was added to the binder before spraying.

Three-layer boards were made consisting of 40 ß surface chips and 60% inner chip with a volume weight of about 750 kg / m3 and a nominal thickness of 15 mm. The compression pressure was 27 kp / bmg and the time to 60 sec./mm thickness and the temperature to 215 ° c.

The strength properties of the chipboards were determined in accordance with Finnish standard 0.IV.2, and the swelling properties and tensile strength after water leaching for 2 hours at 100 ° C (V 100) in accordance with German standard DIN 68761. The properties of the produced boards was as follows: Bending strength 227 xp / amg Tensile strength 6.0 "Thickness swelling 2h 1.7 ß -" - than 10.3 ß V 100 test 4.0 kp / bme g The requirements according to these standards are: Bending strength at least 180 kp / bma , tensile strength not less than 3.5 kp / rev, thickness swelling 2 h not more than 6%, 24 hours not more than 15%, and after V 100 treatment a tensile strength of not less than 1.5 kp / bmg. As the example shows, these requirements are well exceeded. 'Example voice.

Na-lignosulfonates were used in the preparation of the binder.

The percentage of macromolecular lignosulfonates (MW> 5,000) was 62%. An aqueous solution containing 50% by weight of these lignosulfonates had a viscosity of> 80,000 cP (Brookfield RVT viscometer, 50 rpm, 2300). The pH of an aqueous solution containing 10% by weight was 7.5. 1000 g of these lignosulfonates were dissolved in 111 g of water. 100 g of sodium hydroxide was added to the aqueous solution. 1670 g of a commercial phenol formaldehyde resin were mixed with the solution. The solids content of the resin was 40 ß. 57 Daraformaldehyde was added and the solution was mixed for 60 minutes.

Particleboard with three layers was produced. The manufacturing conditions, the bulk density and the nominal thickness were identical to those given in Example 5. The properties of the manufactured discs were as follows: Bending strength 255 kp if Tensile strength 7.0 "Thickness swelling 2 h 2.0 5 _ _" _ en n 11, 9 ß QV l00fprovning 9.2 kp / cm.

Claims (3)

1. Eatentkrav. 1. Adhesives for the manufacture of plywood, particle board, fibreboard and similar products, containing lignosulfonates and phenol-formaldehyde resin in a weight ratio of 90:10 - 20:80, characterized in that the majority of lignosulfonates have a molecular weight exceeding 5,000. Binder according to Claim 1, characterized in that at least 55% by weight of the lignosulfonates have a molecular weight exceeding 5,000. Binder according to Claim 1, characterized in that the lignosulfonates are in the form of alkali or alternatively alkaline earth salts containing an excess of alkali or alkaline earth to such an extent that a solution containing 10 g of lignosulfonate / 100 ml has a pH of 6 - l3. Binder according to Claim 1, characterized in that the lignosulfonates in the form of a 50% aqueous solution have a viscosity exceeding 10,000 cP at a temperature of 23 ° C. PUBLICATIONS MADE: Sweden patent application 9 610/73 (C09j 3/16) US 3,395,033 (106 ~ 123), 3,677,884 (161-262) '7312584-1