DE1289982B - Process for the finishing of wood and wood-based materials - Google Patents

Description

The invention relates to a method for finishing wood and wood-based materials by impregnation with aqueous synthetic resin solutions and subsequent curing of the resin introduced.

It is known that the properties of wood, such as strength, Hardness and dimensional stability, through soaking with synthetic resin solutions and curing the introduced resin to improve.

It is known to use solutions of phenol-formaldehyde resins as impregnating agents to be used in water or organic solvents, in the latter case while watering. Extensive safety measures must be taken for drying and curing are. To convert phenolic resins into the state of residency. are temperatures of at least 140'C required. In the case of thicker workpieces, these high temperatures must exceed long periods of time, usually several hours, are adhered to, reducing the properties of the wood is impaired, in particular its strength values are reduced.

It is also known to use solutions of ureas in formaldehyde or Urea-formaldehyde precondensates in aqueous solutions for the impregnation of To use wood, avoiding the disadvantages outlined above. These However, solutions are poorly and unevenly distributed in the material to be soaked, since the substances they contain age relatively quickly, d. H. in higher molecular weight Skip connections. To ensure a transition of the resin introduced into the wood into To achieve the state of resit, the solutions must hardeners, such as Ammonium salts, which deal with the labile methylol groups of the precondensate, are added react to form hexamethylenetetramine, with an equivalent amount of acid becomes free, which causes a pFl value shift in the range 3.0 to 3.5. the Aging of the urea-formaldehyde solution is accelerated and the As a result, the impregnation is even more uneven.

It has therefore also become known that hardening, i.e. H. the overpass of the resin in the resitz state, in a special operation after the impregnation to carry out with the precondensate in the way. that another impregnation with a Hardener solution is made. However, this method has the disadvantage with it that the resins lying in the outer layers of wood harden and one prevent further penetration of the hardening agent solution into the interior of the wood, so that there the resin remains in the uncured state.

It is also known to use Ilölzer with condensation products from diurethanes and formaldehyde soak. Products of this kind can only be made with strong acid active hardeners at elevated temperatures in the resitz state. More advantageous it is, however, to use stable but more reactive condensates.

In order to eliminate this disadvantage, a method has become known, in which the hardening of urea-formaldehyde solutions or condensates impregnated Wood is carried out after drying by exposure to sulfur dioxide. However, this procedure is very complex and because of the high level of aggressiveness of the sulfur dioxyds make high demands on the material of the equipment.

The purpose of the invention is to impregnate wood or wood-based materials to refine with an impregnation agent, wherein the impregnation agent is the material penetrates evenly and completely, cannot be washed out in the wood once it has hardened remains fixed and thus the pressure, bending and abrasion resistance as well as the hardness of the wood are increased, the swelling and shrinking of the wood with changing influence largely suppressed by moisture and dryness and the wood against fungal attack is protected.

The task was therefore to create a method in which these conditions can be met while eliminating the disadvantages outlined above. This object is achieved in that the impregnation of the wood or the wood-based material is made with an aqueous synthetic resin solution, the one with alkanols. Alkyl or alkanolamines or alkyl or alkanolketo-hexahydro-1 3,5-triazines modified Urea-formaldehyde precondensate with a maximum molecular weight of 1000 and usual Amounts of food that won't do in the cold. but very effective in the heat contains, the molar ratio of urea to formaldehyde 1> 1.5, preferably 1: 1.8 to 5, and the modifying agents in amounts of 2 to 10 percent by weight, preferably 4 to 6 percent by weight, based on the solids content of modified Urea-formaldehyde precondensate, and that this is in the wood or Pre-condensate introduced into the wood-based material hardens at temperatures that are expedient are above 50 C.

A hardening agent have become salts of amines, especially of pyridine and its homologues. proved to be particularly suitable. You bring the other one This has the advantage that the impregnation solutions obtained are also in the pH range of 4 Do not age up to 5 at temperatures below 40 C for a longer period of time, but maintain their full effectiveness. This makes it possible for the Impregnation Impregnation solution not absorbed by the wood after adding freshly prepared Re-use synthetic resin solution for further impregnations.

The drink solutions used according to the invention already make the wood so fungicidal that biological tests carried out in the usual way showed the weight losses are below the permissible limit. As the soaking solutions are extremely stable, they can be highly effective in reinforcing the fungicidal properties Middle. such as sodium fluoride, potassium dichromate and potassium arsenate are added, without affecting the impregnation effect. The addition of these substances to the impregnation solution takes place in the amounts known for this and is added before the impregnation made of woods.

The solids content of the drinking solutions can be within a proportionate range further limits can be varied and will depend on the type of impregnation Wood material, on the other hand, determined by the desired effect in terms of application.

The impregnation of the woods can be done in a known manner, for. B. in the vacuum pressure process, be performed.

The hardening of the condensate introduced into the wood can in a known manner in suitable chambers or by means of high-frequency heating be carried out in a continuous process.

The percentages given in the examples below are it is percent by weight, the parts listed are parts by weight.

Example 1 8 m3 planks made of pine wood with dimensions of 8 20 600 cm and with a wood moisture content of 20% were mixed with 6 m3 of an aqueous synthetic resin solution soaked using the vacuum / pressure method.

In the process, 2 m3 of impregnation solution was absorbed from wood. The soaked ones Pine planks were then placed in a drying chamber over the course of 40 hours dried at temperatures rising up to 108 C.

The pine wood refined in this way was Water absorption, hardness, wear, flexural strength and compressive strength in comparison tested with untreated pine and tropical woods. The determined Values are shown in diagrams 1 to 6.

The synthetic resin solution used for the impregnation was prepared as follows: In 570 parts of 37% aqueous formaldehyde solution and 288 parts of a 40% aqueous solution of l-methyl-4-ketohexahydro-1,3,5-triazine was 180 parts of urea dissolved with stirring. this solution is heated to 70 ° C., after 60 minutes by means of 30% strength Hydrochloric acid set a pl-l value of 3.5 and afterwards to a temperature of 50 C cooled and a viscosity of 60 cP was reached, neutralized with sodium hydroxide solution.

750 parts of the resin solution thus obtained were mixed with 20 parts of a 50% aqueous solution of 2,6-lutidine hydrochloride and 230 parts of water are added and muddled.

Example 2 X m: 3 pine planks according to Example 1 were in the there described manner soaked with a synthetic resin solution. The one used for impregnation Synthetic resin solution was prepared as follows: In 1200 parts of a 30% aqueous Solution of formaldehyde were dissolved at a pH of 8.0 300 parts of urea. The solution was then heated to a temperature of 70 ° C. and at this temperature held with stirring for 60 minutes.

The addition of 30% hydrochloric acid then gave a pH of 4.0 set, and condensation was continued until the solution had a viscosity of Had reached 12 to 15 cP. After the solution is neutralized using sodium hydroxide solution it was concentrated to a solids content of 58%.

900 parts of this concentrated solution were mixed with 450 parts of methanol and 20 parts of 30% salt. iule added and at a temperature of 40 C 30 Minutes stirred. It was then neutralized by adding sodium hydroxide solution and that excess methanol removed by means of reduced pressure. 500 parts of this way The resulting resin solution was mixed with 480 parts of water and 20 parts of a 50% aqueous Solution of the hydrochloride of a pyridine base mixture with a boiling point of 130 to 160 ° C offset and mixed.

The pine planks finished with this soaking solution showed at the exam also the Values as given in diagrams 1 to 6.

Example 3 With 750 cm3 of the impregnation solution described in Example 2 were 10 pinewood blocks with dimensions of 5 # 2.5 # 1.5 cm and with a wood moisture content impregnated by 20% using the vacuum pressure method. By adding freshly prepared The solution not absorbed by the wood during the impregnation was applied to the impregnation solution original volume of 750 cm3 refilled. That way each The solution that was replenished was used for further impregnations of 10 pinewood blocks each time used. This experiment was continued over a period of 20 days. To the Control of the stability of the impregnation solution was continuously carried out in the following Values listed in the table.

From the table it can be seen that the utility value of the impregnation solution does not decrease even during a longer period of time.

Table 1 Viscosity and pH values of an impregnation solution and the increase in weight of the pinewood blocks after impregnation over a period of 20 days Weight gain of a soaked one Viscosity of the pine block after the Day in cP pH value curing and conditioning Day n JP 'pH in grams (Mean value from 5 test specimens each) 1 5.2 5.2 1.87 7 5.7 4.5 2.16 4 6.4 4.5 2.51 5 6.3 4.5 2.48 6 7.2 4.5 1.90 9 6.5 4.5 2.25 11 4.7 4.5 2.24 12 5.5 4.5 2.18 13 6.8 4.5 1.89 15 6.6 4.5 1.93 16 6.8 4.5 2.27 17 6.4 4.5 2.11 18 6.6 4.5 19 6.4 4.5 2.40 20 6.0 4.5 # 2.18 Example 4 In each case 500 cma of the impregnation solution prepared according to Example 2 were mixed with fungicidally highly effective compounds; then the stability of the impregnation solutions was tested over a period of 5 days.

The values given in the table below were determined.

From the table it can be seen that the utility value of the impregnation solutions also not impaired by the addition of fungicides, highly effective compounds will.

Table 2 Viscosity and pH values of impregnating solutions to which fungicidally active compounds are added over a period of 5 days Impregnation solution Day + 1% K3AsO4 + 1% NaF + 1 ° / 0 K2Cr207 cP pH value cP pH value cP pH value 0 6.3 4.8 8.5 6.1 6.7 3.7 1 7.2 4.3 7.6 6.5 7.0 3.0 2 6.9 4.5 6.8 6.2 6.4 3.0 3 6.9 4.5 6.6 6.0 6.4 3.0 4 6.6 4.3 6.4 5.8 6.4 2.8 5 7.0 4.1 6.3 5.4 6.5 2.8 Example 5 10 blocks of beech wood with dimensions of 45-6 by 6 cm and with a wood moisture content of 20% were soaked in the vacuum / pressure process. The solution used for this was prepared as follows: 1,800 parts of urea were added to 7000 parts of a 300% strength aqueous formaldehyde solution and 4800 parts of a 33% strength aqueous solution of 1-ethoxy-4-keto-hexahydro-1,3,5-triazine Stirring dissolved.

The solution was heated to a temperature of 70 C and 60 minutes held at this temperature. Then was with concentrated hydrochloric acid adjusted to a pH of 3.5 and cooled to a temperature of 50'C. As soon a viscosity of 25 cP was reached, was neutralized with sodium hydroxide solution. This Resin solution were now 275 parts of an aqueous solution of pyridine hydrochloride admitted.

With this resin solution in the manner described in Example 1 Soaked beechwood blocks were examined with regard to the soaking effect.

In the edge zone, to a depth of 1 cm, there was a solid resin content from 3511/1), based on the total weight of the refined wood, determined while in the middle the solid resin content was still 280/11.

Claims (4)

Claims: 1. Process for the finishing of wood and wood-based materials by soaking in aqueous synthetic resin solutions and then curing the injected resin, dadruch g e k e n n -z e i n e t that the impregnation with a solution is made, the one with alkanols, alkyl or. Alkanolamines or Alkyl- or alkanolketo-hexahydro-1,3,5-triazine-modified urea-formaldehyde precondensate with a maximum molecular weight of 1000 and usual amounts of a curing agent that not in the cold, but very effective in the heat. where is the molar ratio from urea to formaldehyde 1:> 1.5 and the modifiers in Quantities of 2 to 10 percent by weight, based on the solids content of modified Urea-formaldehyde precondensate, and that this is in the wood or the pre-condensate introduced into the wood-based material hardens at temperatures that are expedient are above 50 C. 2. The method according to claim 1, characterized in that the molar ratio from urea to formaldehyde is 1: 1.8 to 1: 2.5 and the modifying agents in amounts of 4 to 6 percent by weight, based on the solids content of modified Urea-formaldehyde precondensate. 3. The method according to claim 1 to 2, characterized in that as Hardening agents salts of amines, in particular of pyridine and its homologues, be used. 4. The method according to claim 1 to 3, characterized in that the Soaking solution known fungicidally active substances, such as sodium fluoride, potassium dichromate or potassium arsenate, can be added in the usual amounts.