CS211883B1 - Method of processing the wood by steaming - Google Patents

Description

The essence of the wood steaming method according to the invention is that the wood raw material is impregnated with aqueous solutions of substances of an acidic nature such as acetic acid, aluminum chloride, before steaming the wood with steam, at a temperature of 80 to 160 ° C and a pressure of 0.98 to 1.15 MPa. , formic acid, p-toluenesulfonic acid or a base such as ammonium hydroxide, sodium hydroxide triethanolamine at a concentration of 0.5% to 5% by weight. Advantageously, the wood raw material can be impregnated with solutions of acidic and alkaline substances, of a neutral nature such as 2-furanaldehyde with an aqueous prehydrolysate from pulp production and a condensate from a steaming or defibrating apparatus. Volatile substances of an acidic and alkaline nature, such as acetic acid, formic acid and ammonia, are advantageously added directly to the steaming device shortly before or during steaming, in which case impregnation may be omitted.

The present invention provides a method of steam treatment of wood which achieves better properties, in particular, the coloring of the treated wood to better suit the furniture needs or for use as a decorative cladding material.

Wood steaming is generally and widely used in the woodworking industry, which observes the softening of the door, i.e. the transition from the vitreous to the viscoelastic state, thereby favorably affecting the subsequent course of the pressing or bending of the wood. Steamed wood dries quickly and there are no undesirable tensions in its structure. Impregnation is used to protect materials and achieve color changes, ie wood raw material is pickled with protective impregnation solutions or color solutions to achieve color changes in solids or veneer materials. Steaming and achieving color changes in the wood raw material is time consuming. Several authors have observed color changes that occur due to steaming of different woody species and suggest that such changes be used as wood treatment to achieve more favorable coloring. So far, however, there are no works to explain in more detail the course of color changes in wood during steaming or to propose to intensify such changes.

The aforementioned drawbacks are remedied by the method of wood steaming according to the invention, which consists in impregnating wood raw material with aqueous solutions of substances of an acidic nature prior to steaming the wood with water steam at a temperature of 80 to 180 ° C, a pressure of 0.98 to 1.15 MPa. acetic acid, aluminum chloride, formic acid, p-toluenesulfonic acid or of a basic nature such as ammonium hydroxide, sodium hydroxide, triethanolamine at a concentration of 0.5% to 5% by weight. The wood raw material may preferably be impregnated with solutions of acidic or alkaline substances, of a neutral nature such as 2-furanaldehyde with an aqueous prehydrolysate from pulp production and condensation from steaming or. defibračného zařízení. Volatile substances of acidic and basic nature, such as acetic acid, formic acid and ammonia, are advantageously added directly to the steaming device shortly before or during steaming, in which case impregnation may be omitted.

Impregnation of wood raw material before steaming with substances of acid, alkaline and neutral nature, resp. the addition of these substances results in a more intensive color change of the wood, so that the steaming time can be reduced to 1/5 without compromising the mechanical properties of the treated products.

The coloring of the wood raw material according to the invention is achieved by impregnating the wood raw material with an acidic nature such as acetic acid, aluminum chloride, formic acid, p-toluenesulfonic acid or a basic nature such as ammonium hydroxide, sodium triethanolamine which steaming during the steaming. they accelerate or the wood is impregnated with substances which are themselves colored, respectively. they become discolored during steaming and cause color changes in the steamed wood interaction. During the steaming of the wood some organic acids have been formed which catalyze the formation of furanaidehyde, 2-furanaldehyde may, during further reactions, provide dark colored products which cause darkening of the steamed wood to a reddish, brown or brownish-black shade. The addition of the abovementioned acids, substances of basic nature and 2-furanaldehyde, respectively. the addition of other substances such as tannins or water-extractable substances results in a more intense color change of the wood.

The wood steaming method according to the invention makes it possible to use low-value woody species (such as, for example, acacia, birch, poplar, alder) as a substitute for exotic furniture raw materials (teak, mahogany, villain, etc.).

Example 1

The alder idireva blanks (3 x 8 x 100 cm, x x x x x x d) were impregnated by soaking in an aqueous solution containing 0.5% p-toluenesulfonic acid, 4.2% 2-furanaldehyde and 2.5% furfuryl alcohol for 8 hours. After this time, they were drained of excess solution and placed in a pressure steaming apparatus where they were exposed to water vapor at a pressure of 1.1 MPa and 108 ° C for 5 hours. They were then air dried for 8 hours and in an electrically heated oven at 105 ° C for 12 hours. After mechanical treatment, the blanks darkened to a brown shade.

Example 2

Acacia blanks of dimensions as in Example 1 were soaked in an aqueous prehydrolysate from beech pulp production at a hydromodule of 1: 5 for a soak time of 8 hours. After removal of the excess solution, parenl billets were subjected to a temperature of 90-105 ° C for 8 hours. Permanent bile brown color shade has become dry after the blanks have dried.

Example 3

Acacia blanks of the dimensions as in Example 1 were filled into a 80 L steaming machine to which 0.5 L of a 3: 1 solution of acetic acid and formic acid was added. Steaming was carried out for 40 hours at a temperature of 105-110 ° C, and after drying, blanks of brown color were obtained.

Claims (2)

Method of steam treatment of wood at a temperature of 80 ° C to 160 ° C and a pressure of 0.98 to 1.15 MPa, characterized in that the woody raw material is treated with aqueous solutions of acidic substances such as acetic acid before or during steaming, aluminum chloride, formic acid, p-toluenesulfonic acid or a base such as ammonium hydroxide, sodium hydroxide, triethanolamine at a concentration of 0.5% to 5% by weight, but of a neutral nature such as 2-furanaldehyde or derivatives thereof. 2. A steam-treatment process according to claim 1, wherein the wood raw material is impregnated with an aqueous extract, an aqueous prehydrolysate from a hunting plant, or a condensate from a steaming or defibrating process containing organic acids and 2-furanaldehyde and wood-extractable substances.