DE2345620A1 - METHOD OF TREATMENT OF WOOD - Google Patents

Description

2030 Abbott Road ^Οφ! · ⁸ "' _{Münchw 2} 7, MShlstr. 22

Midland, Michigan, U.S. 16,215-F

Method of treating wood.

The present invention relates to a method at which wood is treated with modifying additives, e.g. preservatives, fire retardants, dyes, etc. will. Specifically, it is a continuous process using methylene chloride or a Similar halogenated solvents as carriers and heat transfer agents for impregnating wood with pentachlorophenol or other preservatives, dyes, fire retardants, etc.

A number of methods are known in which Halogenated hydrocarbon solvents, e.g. perchlorethylene, Trichlorethylene and methylene chloride, used as the main vehicle for wood treatment agents. As examples of such Methods include methods described in the following patents: U.S. Patent 2,650,885 (Hudson), Can. Patent 519,730 (Tanner), U.S. Patent 2,860,070 (McDonald), Can Patent 863,885 (Dunn). All of these procedures are because of the nature of theirs Reaction steps and the time required to complete a single process cycle (i.e. treatment of a batch of wood) either unsuitable for large-scale use or only suitable for the technical treatment of a few Types of wood. Hudson and McDonald use relatively high-boiling perchlorethylene and trichlorethylene, which are made from the Inside the treated wood cannot be easily removed when vacuum treatment is used. Tanner describes a solvent impregnation of wood, apparently carried out at room temperature, with removal the solvent is carried out by various methods, but without specifying the recovery of the solvent; it is about "... iwdoutig a slow process

409816/0752 BATH ORIGINAL ¹

which is more wasteful with the solvent. Slim describes a technically feasible method using of methylene chloride as the treatment medium, although there appears to be an inadequate use of steam and cooling water devices required are.

The method of the invention is a modification of the latter method, being quick and practical continuous wood treatment with highly effective use of energy and treatment materials is achieved. The process can be used for more permeable types of wood, e.g. the southern yellow spruce and ponderosa spruce, as well as for denser hardwoods are used.

The method according to the invention is characterized in that that wood at about 50-125 ° C with the steam of a chlorinated aliphatic hydrocarbon solvent under superatmospheric pressure brought in contact so long that the wood is heated approximately to the temperature of the solvent vapor is, the heated wood in a boiling solution of at least one wood treatment agent in this chlorinated solvent immersed in the same temperature range and under superatmospheric pressure until the wood was largely removed from the solution is impregnated, the excess solution is removed from contact with the impregnated wood and the pressure on the impregnated Wood is reduced to at least about atmospheric pressure, causing instantaneous evaporation of at least a substantial portion of the solvent contained in the wood will.

The advantages of this method are best expressed when practically using it continuously several pressure treatment vessels are carried out which are appropriately linked and coordinated with one another; one then works in alternating cycles using a common source of boiling, pressurized one Treatment solution, where · in the wood impregnation part of the treatment cycle pressurized solvent vapor from einsni Boiler is used, with which new wood in another

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Boiler. Is heated. Furthermore, common devices are for Condensation of solvent vapor and for recirculation of the condensate in the process, as well as a conventional tank for refilling of the solution present.

With this procedure, the energy requirement per treatment tank is minimal and a practically continuous one is obtained Process in which manual labor is reduced to such an extent that it practically only consists of loading the treatment boiler with new wood and unloading the treated wood consists.

The accompanying drawing is a diagram showing a preferred apparatus for treating wood according to the invention Procedure is shown. The device consists of three treatment chambers in the form of horizontally arranged cylindrical pressure vessels, each of which has a closed and an open end, which is provided with an opening for loading and unloading the wood is provided; it must be possible to close and seal the opening in such a way that it is central Withstands over-atmosphere pressures. The three cylinders have a common source of hot treatment solution ("reboiler"), a common tank for topping up the solution, a common condensing device for solvent vapor at about Atmospheric pressure and another such device for the condensation of solvent vapor at superatmospheric pressure, furthermore suitable circulation pumps for the treatment solution, all of these devices with suitable connecting lines and valves, temperature and pressure regulators, outlet openings and drains are provided, insofar as this is required.

In the following, the device suitable for carrying out the method according to the invention will be explained in more detail with reference to the drawing. Three pressure cylinders 10, 11 and 12 _C have 1eweils (not shown) through which optionally ds.s wood to be treated in the cylinder, or from a entrio öffnv.r ". .Ir. On may be, said opening ä? n cylinder, so dic-it closes ^J ;, since '"no liquid or D:." V5i- under

409816/0752 BADORIQiNAL

_ Zj. _

Excessive atmospheric pressure can escape from the cylinder. Each cylinder 10, 11 and 12 is provided with a pump drum 13, 14 and 15, respectively. A high pressure condenser 16 cooled with water is connected to each pump drum 13, 14 and 15 by the line 2M-. A temperature sensitive control valve 16A maintains the pressure in the condenser 16 across the temperature sensitive element 15B. The condensate from the condenser 16 is conveyed by the pump ISD via the line 150 to the heater 17. The heater 17 is connected by line 21 to the three cylinders lö, 11 and 12. Each cylinder 10, 11 and 12 is connected to a low pressure condenser 18 which includes a temperature sensitive control 18A connected to a temperature sensitive element 18B. The condensate from the low pressure condenser 18 is fed to the storage tank 19 for fresh solvent and pentachlorophenol mixture. Additional amounts of pentachlorophenol and fresh solvent are introduced into tank 19 through lines 19A and 19B, respectively. If desired, solvent is drawn off from the tank 19 by the pump 20 and passed into the heater 17. Various other lines are used for the connection, which transfer the liquids from one cylinder to the other. There are also valves to control the flow of liquid. These valves and lines as well as the process cycles are described in more detail below.

The present invention is explained here using the example of the treatment of timber made of yellow spruce. With others The treatment cycles are different for wood types. However, it can be stated quite generally that the average Treatment cylinder e.g. about 30 minutes for loading and takes an equal amount of time to discharge; a normal cylinder takes about 75 minutes to remove. air and for heating the wood to the treatment temperature. The device (pumps, lines, etc.) limits the filling speed the cylinder with liquid and the build-up of pressure so that filling takes about 4-5 minutes. It is known that bundles of yellow spruce need about 105 minutes for impregnation. The draining, the solvent recovery as well as the relaxation of the pressure on.

409816/075 2

Printing takes about the same time as filling and impregnation and cleaning. The following is an equation with the help of which the Oyclen on a multi-cylinder process can be set:

2L + P + 2FD + S + B / rio. cyl. = Time here mean L = time of loading or unloading

P - time of cleaning and steam heating FD = time of filling or draining S = impregnation side

'R = time for solvent recovery.

If the times given in minutes are inserted into this equation, then one obtains in for a single cycle a cylinder the following time:

2 (30) + 75 + 2 (4-5) + 105 + 120 = 4-50 minutes (or 7 1/2 hours).

If you decide to use three cylinders, you can divide each cycle into three equal periods of Split 150 minutes (2 1/2 hours); you then know that the second cylinder 2 1/2 hours after the first cylinder was opened for loading, for loading and starting the cycle must be ready, likewise the third cylinder 5 hours after the zero time of the first cylinder. That way you can the cylinders for vapor exchange, for liquid treatment etc. are used, whereby energy is saved and yet-a adequate treatment is ensured.

The sequence of a parallel cycle is described in Tables I and II for the three-cylinder apparatus shown in the drawing. Certain numbers of time units are assigned to the individual stages of the process, so that the approximate relative duration of these stages is displayed. However, this changes depending on the dimensions of the pieces of wood and in particular depending on the Holaa ^ u. As an example of a wood treatment process, each time unit of 15 minutes can be used. ^:

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Table I. Level 1, time units 1-2

Cylinder 1

Cylinder is with
Load wood and
Door closed.

C ylinder 2

Wood is made from cylinder with boiling, pressurized solution impregnated.

Level 2, time units 3-7

Air becomes from the
Cylinder with hot
Solvent vapor
removed from cylinder 2.

Wood is further impregnated.

Cylinder 3

Solution is made from the impregnated EoIz withdrawn into the cylinder 3, then pressure is created by the low-pressure condensate. reduced to atmospheric pressure, so that solvents in the wood are removed in a flash will.

Solvent is stripped off as above.

Level 3, time units 8-10

Cylinder is with
boiling, under
More pressure
Solution from 2 filled.

Solution is withdrawn after 1.

Air is admitted, the door is opened and removed the wood.

Level 4, time units 11-17

Wood is impregnated.

Reducing the pressure to atmospheric pressure, The solvent is quickly drawn off through the low-pressure condenser Loading with new wood, removing air and heating the dei Wood with hot solvent vapor from 1.

Level 5, time units 18-20

Peeling off the
Solution after 3

Entry of air, opening for removal of the wood.

Entry of the solution of 1, impregnation of the wood.

Level 6, time unit 21

The solvent is removed from the wood in a flash
through the low pressure condenser
and reduction of the
Pressure on atmospheres pressure.

Balaüen with wood.

409816/0752 Impregnation of the mole.

Level 7, time inheiteη 22-26

Cylinder 1

Remove the solvent as in time unit 21.

Cylinder 2

Removal of air and heating of the wood with heiSera, under pressure

Solvent vapor from 3.

Level 6, initiate time 27-2f

Reduction of the
Pressure to atmospheric pressure, access of air.

Heating the wood with steam from 3, access from hot solution

3.

Level 9, time units 29-30 Unloading the wood. Holζ impregnation.

Cylinder 3

Impregnating the solvent.

Impregnate the wood, then peel off the solution after 2.

Solution is drawn to 2

Table II summarizes the valve sequence during the treatment process according to Table I. With every valve "O" under a specific unit of time means that the valve is open. A valve not marked in this way is closed,

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409 816/0752

In a treatment process according to Tables 1 and II using a boiling methylene chloride solution of pentachlorophenol as the treatment solution, the wood impregnation stage is operated, for example, at a temperature of the solvent vapor of about 78 ° 0 and a pressure of about 4.5 atmospheres. The following table III shows the typical ■ process pressures in cylinder 1, in the heater and in the high-pressure condenser in the various stages.

• Table III High pressure condenser Level no. Cylinder 1 Pressure (atü)
Heater 4.5 1 O 4.5 2.1 2 initially O,
then 2.1 4.3 4.5 3 2.1-4.5 4.4 4.5-2.1 4th 4.5 4.5-4.3 ■ 4.5 5 4.5-3.5 4.4 4.5 6th 3.5-0 4.5 4.5-2.1 7th 0 4.5-4.3 2.1-4.5 - 8th 0 4.3-4.4- 4.5 9 0 4.4-

The first heating carried out, whereby the wood with the hot pressurized solvent vapor in. Contacting is preferably carried out at about 50-100 ° C and a pressure of about 1.1-5 atmospheres. This stage takes about 0.5-4 hours, depending on the the temperature used, the type of wood, the dimensions of the pieces and the amount of moisture in the wood.

The same preferred temperature range is also used for the impregnation step in which the hot wood is immersed in the superheated treatment solution. For • this level "one prefers slightly higher pressures, e.g. up to about 15 atmospheres. The impregnation time changes depending on the degree of penetration desired, the dimensions of the treated pieces, as well as depending on the moisture content and the density of the wood. Impregnation times can be up to

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Use up to 10 hours, about 0.5-3 hours are preferred.

Chlorinated ones suitable for the process according to the invention Solvents are those with a boiling point between about 35 and 125 ° C, e.g. polychloromethanes such as methylene chloride, Chloroform and carbon tetrachloride; Polychlorethanes, such as Ethylene dichloride, methyl chloroform and 1,1,2-irichloroethane; Polychlorethylene, such as 1,2-dichloroethylene, trichlorethylene and perchlorethylene. Other useful chlorinated aliphatic ones Solvents may be mentioned propylene dichloride, as well as the compounds described above, some of which Chlorine atoms have been replaced by fluorine, e.g. 1,2-dichloro-1,2,2-tetrafluoroethane, Dichlorofluoromethane and trifluoromethane. As an essential characteristic of the new process, the use of solvent vapor and treatment solution at temperatures well above normal boiling point of the solvent, solvents with a relatively low boiling point are preferred, e.g., in the range of about 35-80 ° C. Methylene chloride is particularly preferred.

The wood preservative used in the invention Process preferably pentachlorophenol or a mixture of pentachlorophenol and a small amount Tetrachlorophenol. The treatment solution advantageously contains about 2-10 wt .- ^ pentachlorophenol. Other wood preservation chemicals can also be used in the treatment solution, either alone or in combination with pentachlorophenol. In addition, the treatment solution can contain other components, e.g. fire retardant chemicals, dyes or other additives to modify the properties of the treated Wood «

The method is preferably used for impregnating dried wood with preservatives, fire retardants Chemicals, dyes, and other wood-treating compositions or mixtures thereof are used »However, you can can also be used on green or partially dry wood, whereby " it is then a combination of drying and impregnation processes. In this case something can longer heating and impregnation stages may be required.

409816 / Q752

BATH ORIGINAL

example

The following example describes the procedure and the Results obtained with a single process cycle suitable for a multi-chamber process, wherein the individual cycles alternate and are coordinated in such a way that the filling time of the treatment solution in one chamber with the removal time of the solution from another chamber matches.

A horizontally mounted one is used as the treatment chamber Steel cylinder (approx. 4 m long and 60 cm in diameter), one end of which is permanently closed, while the other End has a sealable opening. The device contains a steam coil, a trolley, along the floor Bring pieces of wood in and out of the cylinder; it is with suitable line connections for access and removal of liquid and steam as well as connections to a water-cooled condenser and a storage tank for the liquid provided. The whole system is set up so that you work under moderate ÜberatmoSpäreη pressure can.

Ten dried, 2.40 m long, thin pieces of wood made of yellow spruce ("two-by-fours") attached to the cylinder on the trolley; then close the cylinder door and introduce sufficient 5 # pentachlorophenol solution in methylene chloride to cover the steam coil. Steam is now fed into the coil to heat the solution to a boil; the air in the cylinder is replaced by the methylene chloride vapor and withdrawn from the cylinder. As soon as the air has been displaced from the system, heating is continued so that the treatment ^{cylinder is kept at about 78 °} C. and 2.1 atmospheric pressure. After three and a half hours under these conditions, the pieces of wood are completely heated, whereupon further treatment solution is pumped into the cylinder so that. the wood is covered. The vapor pressure in the coil is then increased until a final temperature of 91 ⁰ C and a pressure of 4.5 atü

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inside the cylinder. The wood will take 4-5 minutes exposed to these conditions of the action of the solution. Then the steam is turned off and the solution from the cylinder in a storage tank withdrawn. The cylinder is then vented through a water-cooled condenser, using most of the solvent evaporated in the hot pieces of wood, condensed in the condenser and is collected.

The cooled pieces of wood are later removed from the cylinder; they have gained about 2.26 kg of which 1.36 kg is pentachlorophenol and the remainder is methylene chloride. Air drying for 7 days removes the remaining solvent. The dried pieces of wood contain about 4-53 g of pentachlorophenol per 30 cm and show good penetration. The treatment also reduced the water content of the pieces of wood from 15.2 % to 13.4 %. The treated wood shows no cracks or crevices, it has little or no discoloration.

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Claims (5)

Patent a η s ρ r ü c h e ί1. / Process for treating wood, characterized in ^^ that one (a) Wood at around 50-125 ° C under over-atmospheric pressure for as long with a vaporized chlorinated aliphatic solvent in contact that the wood etv / a to the temperature of the evaporated solvent is heated, (b) the heated wood for about 0.1-10 hours at about the same Temperature and superatmospheric pressure in a solution of at least one wood treatment agent in this chlorinated Immersed in solvent, (c) the excess solution from. Contact with the impregnated with it Wood removed and (d) the pressure above the impregnated wood to at least Atmospheric pressure reduced, whereby at least a substantial part of the solvent contained in the wood evaporates will. 2. The method according to claim 1, characterized in that the solvent evaporated from the treated wood condenses and is recycled back into the process " 3. The method according to claim 2, characterized in that the solvent used is methylene chloride. 4-,. Method according to claim 3, characterized in that that pentachlorophenol is used as a wood treatment agent. 5. The method according to claim 1, characterized in, that the heated wood is immersed under superatmospheric pressure in a boiling wood treatment solution and the hot Solvent vapors of the boiling solution can be used at least partially under superatmospheric pressure to with a * To contact the second batch of wood in the treatment process and to heat it, before the one heated in this way second batch of wood under superatmospheric pressure in the . boiling solution is immersed, which of the first treated Wood batch removed, so that a practically continuous natural wood treatment process. 409816 / Q762 Blank page