RU2608531C2 - Sawdust chipboard - Google Patents

Abstract

FIELD: wood working industry.

SUBSTANCE: invention relates to production of board materials like wood-fiber boards from a wood raw material using no binding substances and can be used for making articles in construction and furniture industries. Sawdust chipboard contains softwood sawdust subjected to cavitation treatment to form active reaction centers, needle softwood chips, 25–30 % solution of sodium hydroxide and water.

EFFECT: invention provides producing a board material from softwood sawdust having high physical-mechanical and adhesion properties and being environmentally safe.

1 cl, 1 tbl, 3 ex

Description

The invention relates to the production of plate materials such as wood fiber boards from wood raw materials without the use of binders and can be used for the manufacture of products in the construction and furniture industries.

Known plate material made without the use of a binder [1]. The composition of the wood board includes: sawdust or particles of cereal straw with a moisture content of 3-8%, a fraction of up to 1.25 mm and 2 cm, respectively, subjected to cavitation treatment, water (hydromodule equal to 10), sulfuric acid can vary up to 1% to the mass of plant materials. The press mass in the form of plant materials (sawdust, cereal straw, etc.) is subjected to cavitation for various periods of time (15-120 min). The process is accompanied by spontaneous heating of the mixture to 95 ° C. After processing, the mixture is hot pressed. When pressing the press material, a composite material is obtained with physicomechanical parameters that meet the requirements of the standards.

The disadvantages of this material are high density and low water resistance. When the density of the plates is more than 1.5 times higher in comparison with materials manufactured with the addition of synthetic binders, their mechanical properties are of equal value. With prolonged exposure to water on the material obtained without the addition of adhesives, its complete destruction occurs.

Closest to the claimed invention are plate materials containing, dispersed in a hydrodynamic disperser with radially directed channels, wood particles to sizes: length not less than 1.5 mm, thickness from 0.01 to 0.05 mm and width from 0.03 to 0.06 mm with active reaction centers [2]. The raw mix consists of 15% of sawdust treated 40-60 times, and 85% of water without additives. Plate material is prepared as follows. Wood particles (sawdust) of coniferous or deciduous species with a moisture content of 8 to 100% are mixed with water with a mass ratio, m.h .: from 10 to 20 and from 80 to 90, respectively. After that, the mass is subjected to cavitation treatment in a hydrodynamic dispersant with the formation of active reaction centers. The treated particles are mechanically squeezed to a moisture content of 180%. Next is the formation of the carpet. The resulting carpet on a mesh pallet is pressed in a hot flat press at a temperature of 190 ° to 220 ° C and a specific pressure of 1.0 to 1.6 MPa.

The disadvantages of this material are the low physical and mechanical properties of the plate material and the duration of the pressing process due to the high humidity of the raw material mixture.

The invention solves the problem of developing the optimal composition of plate materials using reinforcing elements that will improve their physical and mechanical properties.

The technical result consists in the development of environmentally friendly plate material with high physical and mechanical properties from sawdust of conifers processed in a hydrodynamic dispersant, with the addition of reinforcing elements (needle shavings of coniferous species) and an increase in the adhesive properties of the mixture by adding a solution of sodium hydroxide (NaOH) concentration 25-30%.

The specified technical result is achieved by the fact that a sawdust-particle board containing sawdust of coniferous trees, subjected to cavitation treatment with the formation of active reaction centers, and water, additionally contains needle-like coniferous shavings and a 25-30 percent solution of sodium hydroxide in the following ratio of components, wt .%:

Sawdust 9.50-18.00 Shavings 3.00-12.00 Sodium Hydroxide (NaOH) 0.15-0.40 Water 70.00-87.00

As the initial raw material for the manufacture of boards, wood particles (sawdust of coniferous species) with sizes from 0.5 to 10 mm with a moisture content of more than 30% were used, which were subjected to hydrodynamic processing. After activation, reinforcing elements (needle-shaped coniferous wood shavings) were introduced into the resulting pulp, the concentration of which in the mass (in the absolutely dry state) of the wood boards varied from 3 to 12 wt.%. The prepared wood composition was hot pressed according to the established operating parameters: pressing temperature - 195 ° C, pressing pressure 2.5 MPa, specific pressing time 2.5 min / mm. The resulting plate has a density of 900 kg / m ³ .

Preliminary processing of sawdust with passage through the dispersant at least 40 times allows for a high content of active centers on the surface of wood particles. The addition of alkali to wood pulp leads to its qualitative changes, namely, to a greater degree of destruction of wood substance and, in this case, not only the formation of free hydroxyl, but also carboxyl groups. In this case, wood pulp can act as a binder for large particles, like chips.

According to the indicated technological parameters, slabs were produced with the content of reinforcing elements (needle wood chips) in an amount of 20 to 40% (wood pulp / chips). Sodium hydroxide was used as a modifying agent in an amount of from 0.15 to 0.4% of the total weight of the material in an absolutely dry state.

The plate material prepared on the basis of the proposed composition has the following properties: tensile strength with static bending 13.59-19.87 MPa, tensile strength perpendicular to the formation 0.25-0.4 MPa, volumetric swelling in 24 hours 9.8 -25%.

To substantiate the essence of the invention, examples of the production of plate material are given.

Example 1. Purified from extraneous mechanical impurities sawdust of softwood in the amount of 311.06 g (9.57 wt.%) Is mixed with 2799.57 g (86.16 wt.%) Of water (hydraulic unit is 10), then subjected to processing in a hydrodynamic dispersant with radially directed channels for 20 min, a ratio of 40. After processing, the resulting wood pulp is filled with needle-shaped coniferous wood shavings in an amount of 133.31 g (4.10 wt.%), the mixture is mixed. Removing excess moisture is carried out by pressing in a cold press to a moisture content of 190%. 5.62 g (0.17 wt.%) Of a modifying agent, a 25% sodium hydroxide solution, are added to the resulting mass and mixed. From the finished mass in the form of 250 × 250 × 100 mm with a mesh tray form a package by cold pressing. Then the package is removed from the mold and sent to a hot press. Pressing takes place on metal pallets with the following values: pressing temperature - 195 ° C; pressing pressure 2.5 MPa, specific pressing duration 2.5 min / mm. After a pressing cycle, the plate is removed from the press and cooled. The plate has dimensions 250 × 250 × 8 mm.

Example 2. The operations were carried out analogously to example 1, while 355.63 g (14.42 wt.%) Of coniferous wood sawdust cleaned from extraneous mechanical impurities were mixed with 2015.21 g (81.75 wt.%) Water, (hydromodule equal to 15), then subjected to processing in a hydrodynamic dispersant for 20 minutes After processing, the resulting wood pulp is added with needle-like coniferous wood shavings in the amount of 88.97 g (3.61 wt.%), Mixed. Removing excess moisture is carried out by pressing in a cold press to a moisture content of 190%. 5.47 g (0.22 wt.%) Of a modifying agent, a 27% sodium hydroxide solution, are added to the resulting mass and mixed. Next, the process is conducted as in example 1.

Example 3. The operations were carried out analogously to example 1, while 266.76 g (17.58 wt.%) Of coniferous wood sawdust cleaned from extraneous mechanical impurities were mixed with 1067.04 g (70.34 wt.%) Of water (hydraulic unit is 20), then subjected to processing in a hydrodynamic dispersant for 20 minutes After processing, the resulting wood pulp was introduced with a needle-like coniferous wood shavings in an amount of 177.84 g (11.72 wt.%), Mixed. Removing excess moisture is carried out by pressing in a cold press to a moisture content of 190%. 5.40 g (0.36 wt.%) Of a modifying agent, a 30% sodium hydroxide solution, are added to the resulting mass and mixed. Next, the process is conducted as in example 1.

Physico-mechanical properties of the plates obtained in examples 1-3 are presented in table 1.

The production of the resulting plate material is more environmentally friendly, does not require large production capacities and can be implemented in small-scale production.

Information sources

1. RU 2541323 C1, IPC C08L 97/02, B27K 9/00, B27N 3/04, publ. 02/10/2014, bull. Number 4.

2. RU 2541323 C1, IPC C08L 97/02, B27N 3/04, publ. 02/10/2015, bull. Number 4.

Claims (2)

A sawdust chipboard containing sawdust of conifers, subjected to cavitation treatment with the formation of active reaction centers, and water, characterized in that it additionally contains needle shavings of coniferous species and a 25-30% sodium hydroxide solution in the following ratio of components, wt.% : Sawdust 9.50-18.00 Shavings 3.00-12.00 Sodium Hydroxide (NaOH) 0.15-0.40 Water 70.00-87.00