DD205382A1 - METHOD FOR ACTIVATING WOODEN PARTICLES FOR WOOD PRODUCTION OF MATERIALS - Google Patents

Abstract

The invention relates to a method for activating wood particles to improve the fiber - fiber bond for wood material production with or without the addition of binders, wherein the binding ability of the wood particles to be made accessible by chemical activation for this bond. This is achieved by adding nucleophilic agents and / or modifying products of the wood treated with nucleophilic agents before, during and / or after the fiberization process but before the solidification process.

Description

Title of the invention

Method for activating wood particles for woodworking production

Application of the invention

The invention relates to a method for activating wood particles to improve fiber-fiber bonding with or without the addition of binders.

Characteristic of the known technical solutions

The production of wood-based materials takes place predominantly

using binders anchored at $ 20- $ 30 in the cost of the final product. In wood, however, the prerequisites for natural bonds by micromorphological structures and by chemical and physical binding forces are present. All conventional methods for the production of wood-based materials (chipboard, fiberboard) use these natural bonds insufficiently. The achieved strength values are achieved by adding binders and / or using additional energy. However, the major chemical constituents of the wood have many reactive functional groups, but due to the structural relationships of the woody cell walls are limited available for bonds.

The cellulose contains primarily primary and secondary hydroxyl groups as well as aldehyde groups. Most of the hydrosyl groups, however, are blocked. The amorphous hemicelluloses also have such groups, but are blocked by hydrogen bonding and true chemical bonds in the wood dressing. The lignin shows the

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complicated chemical structure of the wood components on -j whose functional groups are crosslinked to form a copolymer. The reactivity of lignin is essentially determined by phenolic hydroxyl, benzyl alcohol groups and double bonds. In the native state, a variety of alcoholic and phenolic hydroxyl groups are blocked by ether linkages to enhance the bonding strength of wood particles.

A klebstofflo.se fiber bonding in wood particle materials requires exposing or activating the functional groups and reactive sites.

For activation, the hydroxyl groups are mainly responsible. If there is sufficient approximation of these activated groups, the formation of chemical main valence bonds is to be expected in addition to hydrogen bonding.

Options for activation result from targeted influencing of the wood components by thermo-mechanical, thermal, hydrothermal, chemical and biological means. Mechanical or thermo-mechanical crushing is required for the production of wood-based materials. At the same time hydration is necessary. The digestion process causes a considerable enlargement of the surface and thus conditions for the release of the radioactive groups.

However, the grinding process is associated with disadvantages, since on the one hand the energy expenditure for this digestion multiplies, on the other hand, however, resulting from high fines the following disadvantages for wood material formation:

- Reduction of drainage speed

- reduced hygroscopic properties

- high material densities

- strong flow during pressing

The effect of elevated temperatures on the wood induces a number of chemical and structural changes which, as a result, affect the physical properties of the wood-based material.

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The most commonly used soling method, the defibrator method, is generally operated with such teohnological parameters that allow a reactivation of the binding forces of the wood only to a limited extent. In addition, the thermal fiberization process is difficult to control so that excessive plasticization of the lignin is avoided while preserving and exposing the binding forces. The chemical influence of the reactivity is given by the action of the binding mechanisms in the wood. Although information about the proportion of wood constituents in the binding mechanism is known, it does not allow any conclusions for the activation of the wood particles. The best known activation treatment of fibrillated wood pulp by the addition of acid-binding solutions does not serve to expose functional groups, but only to influence swelling processes.

Object of the invention

The aim of the invention is to reinforce the binding forces of the reactive groups released by the technological fiberization process.

Explanation of the essence of the invention

The invention has for its object to make the binding ability of the wood particles by chemical activation for the fiber-fiber bond increasingly accessible. This is achieved by adding according to the invention before, during and / or after the chemical fiberization process, however, before the solidification process, nucleophling agents and / or modification products of the wood treated with nuoleophilic agents. This cleaves ether bonds and increases the double bond fraction. The increase in the proportion of alcoholic and phenolic hydroxyl groups and double bonds in the fiber material leads to the enhancement of the binding capacity.

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The method is explained in more detail on an exemplary embodiment.

The starting material (logs, rinds or industrial waste made of wood) are broken down to suitable chips or other comminution units for wood chips or chips. If the particle activation takes place before defibration (defibrator, mill, refiner, etc.), the chips or chips are impregnated in the activating solution by several hours of storage and activated. Then the defibration takes place. When activating during the defibering process, the activating agent is usually introduced in the solid state to the wood particles in the fiberizing aggregate. The third option is to activate the pulp after pulping by adding the activator to the pulp suspension. The further processing of the nucleophil-activated pulp is carried out by the usual methods of fiber plate technology with or without further binder additives. Curing to the wood material is ensured duroh the thermohydromechanical pressing at elevated temperatures.

An overview of application examples with formulation information, including results achieved, illustrating the advantages of nucleophilic activation is given.

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Overview of Application Examples 236179

Λ » Example

Fiberboard made of pine pulp without additional mortar

Type of nucleophilic activation

bonding strength

absolute values in

IiIPa percent strength compared to baseline

1. without activation

2. Activation by 24-hour impregnation before the defibrillation process

(Pine chop in solution of 14% NaOH + 5.3%

18.5

28.7

100

155

3. activation during the

Defibration process 26.6 144 (watered pine chips + 14% NaOH + 5.3% Na _? S without additional water)

Note: By Naohmahlen the pulp after the

Defibrating by 2 SR, a further increase in strength of 20% was achieved.

2nd example

Fibrous plates made of cellulose model fibers with nucleohhilic Ligninzusätzen

stock addition

flexural strength

absolute ^Response in MPa

percent strength versus baseline%

1. Model fiber

2. Addition of non- nucleophilic dimethylsulfoxide ligand

3. Addition of nucleophilic active sulfate waste lignin

5.3

6.5 20.8

100

123

393

Claims (3)

 '"236 179 8 invention claim 1. A method for activating wood particles to improve the fiber-fiber bond for the Holzwerk- »fabric production with or without the addition of binders, characterized in that before, during and / or after the fiberization process, but before the solidification process, nucleophilic agents and / or modification products of the wood treated with nuoleophilic agents. 2. The method according to item 1, characterized in that as nucleophilic agents alcoholates, mercaptans, thiosulfates, sulfites, hydrogen sulfites, rhodanides, sulfides, hydrogen sulfides, amines and / or hydroxides are added individually or in mixture. 3. Method according to item 1, characterized in that nucleophilically activated technical lignins, e.g. Sulfatabi-eye lignin and / or activated native lignin, e.g. Wood particles are added.