Rune Simonson

A simplified procedure for the acetylation of hardwood and softwood flakes for flakeboard production.

Abstract Southern pine and aspen flakes were acetylated with acetic anhydride alone without cosolvent or catalyst by a simple dip procedure. The new procedure greatly shortens reaction time and simplifies chemical recovery. Acetylation weight gains of 15% to 20% can be achieved in 1 to 3 hours with southern pine flakes and in 2 to 4 hours with aspen flakes. Flakeboards made from acetylated southern pine or aspen flakes absorbed much less water, both in water-soaking tests and when subjected to humid air, and swelled at a lower rate and to a lower extent than did control boards. Hygroscopicity of the resulting flakeboards decreased with increased level of wood acetylation. The equilibrium moisture content (EMC) for flakeboards made from acetylated flakes was lower at each relative humidity tested than that of control boards.

Resistance of acetylated wood to biological degradation

3).Exposure of acetylated mini stakes to three different unsterile soils in the laboratory showed that decay was significantly reduced at acetyl contents of 15.1%. An acetyl content of 18.5% prevented most attack by brown, white and soft rot fungi. Acetyl levels above 20.9% were required to eliminate attack by tunneling bacteria.Acetylated wood samples were also tested in seawater on the Swedish West Coast for their resistance to marine borers (EN 275). Results show that the acetylation of wood gives only minor protection against marine borers, although the degree of attack is lowered with increased acetyl content.3. Labortests an Kleinproben in unsteriler Erde ergaben, daß der Abbau schon bei einem Acetylgehalt von 15,1% deutlich verringert ist. Ein Gehalt von 18,5% verhindert weitgehend den Angriff von Braun, Weiß- und Rotfäulepilzen. Ein Acetylgehalt von 20,9% ist erforderlich, um das Eindringen von Tunnel-Bakterien auszuschließen. Acetyliertes Holz wurde auch in Meerwasser an der schwedischen Westküste gegen den Angriff von Bohrmuscheln nach EN 275 geprüft. Der Angriff ist zwar mit steigendem Acetylgehalt verringert; dennoch verleiht die Acetylierung nur einen geringen Schutz gegen Bohrmuscheln.

Kraft lignin in phenol formaldehyde resin. Part 1. Partial replacement of phenol by kraft lignin in phenol formaldehyde adhesives for plywood

The objective of this study was to investigate the potential for partially replacing phenol with kraft lignin in the phenol formaldehyde (PF) resin designed for application as an adhesive in the production of plywood. The kraft lignin, considered to be an environmentally friendly alternative to phenol, was precipitated from black liquor recovered from kraft pulping of softwood. Kraft lignin phenol formaldehyde (KLPF) resin was prepared in a one-step preparation with different additions of lignin. Replacing 50 wt% of the phenol with kraft lignin (50KLPF) was, under the conditions used, considered to be optimal with respect to resin viscosity, storage stability, and bonding ability. The resin consists of an integrated kraft lignin-phenol network. The hot-pressing time in the plywood manufacturing had to be increased by approximately 30% at 150°C for the 50KLPF resin compared with that normally used for PF resin, in order to comply with plywood standard demands. The mechanical properties of test samples made...

A study of strength, hardness and deformation of acetylated Scandinavian softwoods

In this work, properties such as bending strength (expressed as modulus of rupture and modulus of elasticity), hardness, and deformation under cyclic relative humidity have been studied for acetylated Scandinavian pine and spruce. The acetylation was performed with a limited amount of liquid acetic anhydride without addition of catalyst or organic cosolvent. The weight gain due to acetylation was 19.1% for the pine samples. Two kinds of spruce samples were acetylated to 18.2% (narrow annual rings) and 23.3% (broad annual rings), respectively. The results indicated that only small changes in strength were obtained. For pine, modulus of rupture decreased with about 6%, and increased with about 7% for spruce. The modulus of elasticity also decreased for pine but increased for spruce. For practical applications, these properties can be considered unaltered. Acetylated pine wood showed increased Brinell hardness. Acetylated spruce wood did not tend to deform as much as unmodified wood when exposed to moisture cycled between 40 and 90% relative humidityZusammenfassungAn acetylierten Proben von skandinavischem Kiefern-und Fichtenholz wurden mechanische Eigenschaften (MOE, MOR), Härte und Verformung unter zyklischen Feuchtebedingungen gemessen. Die Acetylierung erfolgte mit reduziertem Anteil an flüssigem Acetanhydrid und ohne Zugabe eines Katalysators oder anderer organischer Lösemittel. Der Gewichtszuwachs betrug bei Kiefernholz 19,1%, bei Fichtenproben 18,2% (enge Jahrringe) bzw. 23,3% (weite Jahrringe). Nur geringfügige Veränderungen der Festigkeitswerte wurden beobachtet. Die MOR-Werte fielen bei Kiefernholz um 6% ab; bei Fichtenholz stiegen sie um 7%. Die MOE-Werte verhielten sich ähnlich. Für praktische Zwecke kann man die mechanischen Eigenschaften als unverändert ansehen. Die Brinellhärte des Kiefernholzes stieg nach der Acetylierung an. Die Verformungstendenzen unter zyklischem Wechselklima (40/90) wurden durch die Behandlung verringert.

Fungal Resistance of Pine Particle Boards Made from Various Types of Acetylated Chips

Four different non-catalyzed methods were used to acetylate pine wood chips to various levels of acetyl weight gains; vapor phase acetylation using acetic anhydride, vapor phase acetylation with ketene gas, liquid phase acetylation using refluxing xylene/acetic anhydride, and liquid phase acetylation using a limited amount of acetic anhydride. Particle boards made from the different types of chips were evaluated with respect to their resistance to fungal attack when placed in unsterile soil in a fungus cellar. White, brown and soft rot fungi, and tunneling bacteria were present in the soil. Boards made from chips acetylated in a liquid phase procedure, using either a limited amount of acetic anhydride or a refluxing mixture of xylene and acetic anhydride, were the most resistant to attack. At acetyl weight gains of about 15% of the chips, both types of boards were not attacked after 12 months. When chips were acetylated using vaporous acetic anhydride or ketene gas, the resulting boards were less resistant.

Acetylation of solid wood using microwave heating Part 1: Studies of dielectric properties

ɛ′) and relative loss factor (ɛ′′) give information on how the microwaves can penetrate into the wood object and of possible thermal gradient effects on the wood during modification. This investigation shows that microwave energy effectively heats the acetic anhydride used for modification by acetylation and that the power penetration depth (dp) of the microwaves is about 10 cm in acetic anhydride impregnated wood. The relative permittivity and the relative loss factor were found to decrease with increasing temperature, which indicates that the energy absorption will preferably be directed to less heated parts of the wood object. This will promote a more uniform heat distribution, and, accordingly, a more uniform acetylation of the wood.dp) für das getränkte Holz etwa 10 cm beträgt. Dielektrizitätskonstante und Verlustfaktor nehmen mit steigender Temperatur ab; d.h. die Energieaufnahme wird vorzugsweise zu den weniger erhitzten Teilen des Holzes gelenkt. Das wiederum fördert eine gleichförmige Acetylierung des Holzes.

Acetylation of solid wood using microwave heating Part 2. Experiments in laboratory scale

r × t × l) of the same origin were acetylated separately, but under the same conditions in the microwave reactor. The variation in acetyl content both within and between the samples was less than 2% units. In general, a somewhat higher acetyl content was obtained in the middle of the acetylated wood than in the outer part of it. Microwave energy was also shown to be efficient in the removal of excess acetic anhydride and by-product acetic acid by evaporation under vacuum. During the vacuum step, about 70% of the chemicals could be removed within the first 30 minutes. Pine and spruce wood samples acetylated for 2 hours at 130 °C followed by a vacuum step for two hours at 120 °C, obtained an acetyl content of about 17% and the content of residual chemicals was about 3% calculated on a basis of dry acetylated wood. The temperature in the wood samples could be maintained at about 130 °C even at very low contents of residual excess chemicals without any formation of hot spots.r × t × l) vom gleichen Ursprung nacheinander und unter gleichen Bedingungen acetyliert wurden. Die Variation des Acetylgehaltes lag sowohl innerhalb der einzelnen Proben, als auch zwischen den Proben unterhalb 2%. Allgemein war der acetylgehalt im Probeninneren etwas höher, als in den äußeren Bereichen. Die Mikrowellenbestrahlung erlaubte zudem eine effektive Entfernung des überschüssigen Acetanhydrids und anderer Nebenprodukte durch Vakuumverdampfung. Unter Vakuum konnten ca. 70% der Chemikalien innerhalb von 30 min. entfernt werden. Keifern- und Fichtenholz enthielt nach 2-stündiger Acetylierung bei 130 °C und 2-stündiger Vakuumbehandlung bei 120 °C einen Acetylgehalt von 17%. Der Gehalt an restlichen Chemikalien betrug 3%, bezogen auf trockenes, acetyliertes Holz. Die Temperatur in den Holzproben konnte bei 130 °C gehalten werden, ohne Ausbildung von heißen Zonen, auch wenn nur geringe Überschüsse von Reaktionsmitteln verwendet wurden.

Removal of Lignin-rich Surface Material from Unbleached Kraft Fibres

The composition and structure of the surface material of kraft fibres can affect properties of the pulp such as the reactivity in, for example, bleaching processes. In order to study the nature of the surface material, conditions for a gentle removal of fibre surface material from unbleached kraft fibres have been evaluated. An unbleached softwood kraft pulp with a lignin content of 6.2% (kappa number 32) was treated mechanically using three different types of laboratory equipment : a PFI-mill, a high intensity mixer, and a disintegrator. The number of revolutions and the pulp concentration were varied and the removal of surface material was followed by chemical and microscopical analyses. These analyses revealed that there is lignin-rich material present on the fibre surface which can be removed by a mild mechanical treatment. The lignin content of the surface material abstracted was between 2.5 and 4.5 times higher than that of the fibres. The primary fines (obtained by fractionation of unbeaten pulp, 20μm), also originating from the fibre surface, had a lignin content almost 5 times higher than that recorded in the fibres. For analytical studies of the surface material, a mechanical treatment of the kraft fibres in a disintegrator at a pulp concentration of 4.5% and at 20.000-200.000 revolutions is an efficient and suitable treatment for gradual removal of material from the fibre surface.

Vapor Phase Acetylation of Southern Pine Douglas-Fir and Aspen Wood Flakes

Abstract Southern pine, Douglas-fir, and aspen wood flakes were acetylated with acetic anhydride vapor and compared with flakes acetylated with liquid acetic anhydride diluted with xylene. The rate of acetylation was much lower for the vapor than for the liquid phase reaction. Acetylation weight percent gains above 20 were achieved by both methods. Flakeboards made from both types of flakes absorbed much less water, both in water soaking tests and when subjected to humid air, and swelled at a lower rate and to a lower extent than did control boards. At low weight gains of vapor phase acetylation, the rate and extent of swelling were higher than those found for the controls. Hygroscopicity of the resulting flakeboards decreased with increased level of wood acetylation. The equilibrium moisture content for flakeboards made from liquid phase acetylated flakes was the lowest at each relative humidity tested as compared to control boards, and boards made from vapor acetylated flakes at the same weight gain.