BE624149A - - Google Patents

Description

       

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  Improvements made to wood treatment processes.



   The invention relates to the treatment of wood; and, more particularly, it relates to a process for acetylating wood in order to improve its property with regard to dimensional stability and resistance to decomposition while maintaining the other qualities inherent in wood.



   Wood is a widely used material because it has high mechanical strength for its weight, is easy to form and assemble, has low thermal and metric conductivity,

       has high impact resistance and is decorative. Wood has certain drawbacks, however, because of the water-lief power of its cell-forming hydroxyl groups, the drink is hygienic and undergoes variations in size when exposed to severe conditions.

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 humidity variables.

   In addition, the wood is destroyed by certain fungi and insects which are able to feed themselves using certain components of the wood.



   It is possible to cause chemical modification of wood by esterifying cellulosic hydroxyl groups with organic acids or with the corresponding anhydrides of
 EMI2.1
 so as to correct the faults listed above. If we esteriti. a sufficient proportion of the hydroxyl groups, the cellulolytic compounds of the attacking organisms are in the presence of an incompatible substrate which prevents destruction of the wood.
 EMI2.2
 Testing also has the effect of expanding the wood, and thus prevents strong dimensional changes due to variations in humidity.



  A suitable esterification reaction for wood is acetylation. Sawdust was acetylated by rucha (Ber. 1, 948), Suida (Ber. 1, 1599) and Hom (Ber. L 2542) in 1928. Fuchs and Horn used acetic anhydride containing 0.25 % sulfuric acid. Suida used mixtures of acetic anhydride and pyridine or acetic anhydride alone, and the operation consisted of a 15 hour treatment.

   In 1930,
 EMI2.3
 11'188- '(Ber..21, 1902) acetylated powdered bowls at room temperature using a mixture of acetic acid and acetic anhydride which was catalyzed by sulfuric acid.
 EMI2.4
 The 3.U.à. not. 2,417,995 filed on November 3, 1944 describes the treatment of veneer lumber approximately three millimeters thick with an acetylating medium free of moisture containing acetic anhydride (free of acetic acid), ie alone. or mixed with other components such as a tertiary amine and acetone. The treatments are preferably carried out in phase
 EMI2.5
 steam with a mixture of acetic anhydride and pyridine, a medium which can be used as a faith. blowing agent and 4 "" 'p tS'.d.d. for, p.tt! 1It: t ,.

   A 11 reaction said to continue * This acetylation has not been adopted industrially because of

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   some disadvantages; in fact, pyridine tomes complexes which make recovery difficult; pyridine and acetone swell the wood and cause it to split on drying just like water, and
 EMI3.1
 also require the operation to be carried out at a temperature low enough that the reaction time is relatively long;

   and,
 EMI3.2
 the various operations also require extensive handling of toxic or flammable chemicals. Use of acetic anhydride alone will require the preparation of excess anhydride in order to achieve sufficient acetylation of the bot; this excess will cause the wood to shrink when it is removed during drying.
 EMI3.3
 



  The object of the invention is a process for improving the diipensional stability of wood by aCth11atil / n by impregnating the wood with acetic anhydride under pressure at a temperature.
 EMI3.4
 M high then drying of the drink until constant weight; which proceeds is characteristic in that the acetic anhydrida is mixed with an aromatic, aromatic or inert chloro-hydrocarbon solvent, non-swelling in the wood, practically non-target with water * tsisâibie * v a.'Mb (dl3.li & '40-Cttque and having a point 4'4bul11ti <m 4', u minus 80 *, acetic anhydride being present in sufficient proportion * on the basis of the density of the wood, to cause by impregnation a gain in weight of the wood of at least 18% based on the density of the wood before impregnation.



   A suitable mining technique practicing the invention consists essentially of loading partially dried or green wood into a treatment cylinder and drying the wood by vapor phase treatment. For this, we introduce vapors
 EMI3.5
 of an organic, aronatic, hydroaromatic or chlorohydrocarbon non-wood-swelling solvent, practically immiscible with water, miscible with acetic anhydride and having a
 EMI3.6
 boiling point of at least about 80 ° in the cylinder of "ua1-

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 mentally; under these conditions, a fraction of the solvent vapors condenses on the surface of the wood and drives off moisture in the form of vapor.

   The condensed solvent is removed from the cylinder. The steam, water liberated and the organic vapors in excess are taken out of the treatment cylinder. condensed and separated by decan. tation. The treatment is continued until complete desiccation for a time which depends on the initial water content of the wood.



  Or then establishes in the treatment cylinder, after the drying period, a vacuum which aims to remove residual traces of moisture and vapors.



  The elementary operation of acetylation comprises the introduction. tion of acetic anhydride with an aromatic, hydroaromatic or chlorohydrocarbon solvent which is non-swelling for wood, practically immiscible with water, miscible with acetic anhydride and having a boiling point of at least about 80 inside the cylinder to about 125. The pressure in the cylinder is increased to about 10 to 11 kg cm2, and this pressure and a temperature of 125 is maintained for an acetylation time of about twelve hours.

   The treatment solution contained in the cylinder is then emptied. The residual acetic acid and acetic anhydride in the wood are removed by vapor drying with the solvent for about twelve hours at 125, under a pressure of 200 mm Hg. The treatment solution can be reused several times as well. removed before it needs to be purified by distillation. Distillation of the condensate which contains acetic acid, acetic anhydride and solvent will recover acetic anhydride and solvent for recycling, and additionally provides comal acetic acid. product.

   After applying a final vacuum, the acetylated wood is taken out of the cylinder. If there is still residual solvent, it can be removed by heating in an oven or allowed to evaporate.



   The acetylation procedure described above is

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   advantageous because it is not necessary to carry out wood handling & impregnation between two basic operations.
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  Green wood can be placed in a processing cylinder, acetylated again, dried and taken out ready for shipment without any intermediate handling. The execution of all the operations representing the processing cycle
 EMI5.2
 being thus carried out inside the same cylinder makes it possible to eliminate very anntaceu. # mt almost completely the provo irrigation. which * by acetic anhydride.



     . The impregnation solution is prepared by mixing acetic anhydride (or suitable anhydrides other than propionic anhydride or butyric anhydride) with a
 EMI5.3
 an aromatic, hydroaromatic or chloro-hydrocarbon solvent, non-swelling for wood, practically immiscible with water, miscible with acetic anhydride and having a boiling point of at least about 9011 This particular class of high PE solvents is preferably used because the PE of the acitylom medium and therefore the reaction temperature is then sufficiently high. for the atylation to proceed at a reasonable meat rate in the absence of a catalyst.



  The removal of a catalyst is extremely desirable because the use of a catalyst of the mineral acid or acid salt type causes hydrolysis of the cellulose chains, which results in making the wood brittle. When an alkaline catalyst such as pyridine is used, the wood is not made fragile 881 .. it is very difficult to separate the pyridine from the excess acetic anhydride and the acid. acetic acid formed as we produce, and such a separation operation is expensive and time consuming.
 EMI5.4
 



  -a hair '"". ,,' ti'1tA plus 4014 ftoUItt undergoes leflu4o uëen du 'l ("II., 104u.1. 4mi adnitliui liatide â9 <tiqu <and 8 # 114 ât' u) J'd, I'1 3rui a # * obi pmdmt K odebate M phase u-

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 fear. The use of solvents which do not swell the wood, this is necessary so that the wood warps and splits as little as possible during drying. The wood will tighten if it has been swollen, and then undergoes shrinkage when a blowing agent leaves.

   For the solvents belonging to the group indicated above, preferably mono- and di-chlorobenzenes, toluene, xylene, benzene, alkylbenzenes, trichlorethylene, tetrachlorethylene, carbon tetrachloride, cumene, and mixtures of these solvents will be used *
In order to acetylate thick pieces of wood in a reasonable time, it is necessary that the reagent be brought into contact with all of the wood as quickly as possible. Cool is produced under the best conditions by implementing a full-cell insulated pressure impregnation technique consisting of a vacuum operation followed by a pressurization operation.

   The proportion of reagent injected can be adjusted by acting at its concentration in the impregnating solution.



  Complete retention of the impregnant depends on the degree of porosity or void volume of the wood, which can be determined from the density of the wood. It is important to inject only the proportion of reagent necessary to achieve this. acetylation in order to keep to their minimum value the mechanical stresses imposed on the wood during the removal of the excess reagent and the by-product. For this, it suffices to carefully measure the correct proportion of anhydride required to achieve the desired weight gain from the wood, so that there is no excess reagent left in the wood which will have to be driven from the wood during drying, which would likely cause severe shrinkage.

   Since the solvent used as the vehicle for the reagent is particularly characterized by being inert and non-swelling with respect to the wood, no additional shrinkage of the wood will occur during the removal of the salt. Experimental unification, carried out in the manner described hereinafter in the examples, has shown that a fila of weight (regul-

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 EMI7.1
 so much acetylation of at least 18 percent, and preferably 20 percent, is desirable to produce wood having desirable properties.

   It is therefore possible to calculate the ratio of acetic anhydride to solution in the solvent
 EMI7.2
 that will inject a sufficient amount of antfdri4. acetic so that a 20 percent increase in weight results on wood of varying density.



   Table 1 gives some results of such calculations,
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 JMBNMSJt.



  Approximate amount of diluent required for IR, japrépratton fixed at 1a. .



  ..e.,. t..P "5."., ll, ...:
 EMI7.4
 Density of P anhydride parts, zt1e. of diluent bols actit1que in 1Qlume by volume (c1,). , -
 EMI7.5
 
<tb> 0.1 <SEP> 1 <SEP> 20
<tb>
<tb> 0.29
<tb>
<tb> 0.3 <SEP> 1 <SEP> 5
<tb>
<tb> 0.4 <SEP> 1 <SEP> 3.2
<tb>
<tb> 0.5 <SEP> 1
<tb>
<tb> 0.6 <SEP> 1 <SEP> 1.3
<tb>
 
 EMI7.6
 0.7 1 '0.7
 EMI7.7
 
<tb> 0.8 <SEP> 1 <SEP> 0.33
<tb>
   The values obtained in the preceding table are based on the following calculations, By way of example, it will be assumed that a sample of wood with a density of
 EMI7.8
 0.5 C / al.

   To determine the void volume of the sample, the following formula 8 Vacuum Tolume is applied. weight of 1 ml of wood (g) Total volume (al) - # '# "i"> #' ##### # <- total volume mi) density of the reacting material (lignocellulose
 EMI7.9
 10 5 & / mi) In a sample of wood having, when dry, a density of 0.5 r./ml, one ml of wood will weigh 0. 'g * The density of the

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 EMI8.1
 lignoeellulose contained in the same sample is 1 # 5 & 181.



  By introducing these numerical values in the expression above, we find that the total volume of the voids of this specimen
 EMI8.2
 of bol 's is equal to 0.667 ml. To obtain an increase in weight of z on a volume of wood of 1 ml which weighs 0.5, a weight gain of, 0 a must be achieved. The weight gain of the wood will result from the substitution by acetyl groups that will occur in the wood. The amount of acetic anhydride (compound which yields acetyl groups.) Required to provide the 20% weight gain can be calculated by applying the following formula
 EMI8.3
 Molecular Weight of Acet Anhydride1 x Gain in Neo. '1 Molecular Weight of Acetyl Group
 EMI8.4
 In the example chosen, this gives 43. X 0.10. 0.238 of acetic anhydride.



  It is known that the anhydride & 0 't1QU. or a density1 of 1.08 clml; the volume of the voids to be filled far 0.238 t; of acetic anhydride to impart to the wood a weight gain of 20% will therefore be equal to 0.220 ml. With the test piece of wood in question which has a void volume of 0.667 ml, to ensure full injection to fill the entire void volume during impregnation, the 0.447 ml of void volume remaining will need to be filled with the non-swelling solvent. The mixture of anhydride and solvent to be used for this particular impregnation should therefore contain two parts of solvent to one part of acetic anhydride.



   The elementary impregnation operation is not limited to any particular temperature and pressure interval. In most cases, a vacuum will be applied first, then pressure; the aim of the impregnation is to bring the acetylating solution into contact with the wood, and this can be easily achieved by using well known techniques of impregnation under pressure. For some kinds of bowls, an empty

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 monitoring of atmospheric pressure will suffice. For others, it
 EMI9.1
 is necessary to apply pressures up to z., 4 kg / = 2.



  Impregnation conditions will vary with the species of wood and with the size of the cross section of the part to be impregnated.
 EMI9.2
 pregaer. Since the pressure is maintained on the cylinder during the reaction time of 8 to 16 hours., The time required to carry out the impregnation is not individually distinct from the reaction time * The acetylating solutions used
 EMI9.3
 conformed to the invention are much less viscous than conventional impregnating solutions such as creosote and, consequently,

     the impregnation of ordinarily difficult permeable woods proceeds easily.



   After the impregnation and the reaction, the excess acetic anhydride and the acetic acid formed as a by-product distill out of the wood in the vapor phase drying operation. The condensate obtained during this drying operation can subsequently be distilled to collect the acid.
 EMI9.4
 acetic acid, and the higher boiling solvent and excess acetic anhydride which can be recycled to reconstitute an acetylating solution after addition of the necessary makeup of fresh acetic anhydride to repeat the reaction.



   Large pieces of wood that have been acetylated in the manner described above exhibit decreased sound.
 EMI9.5
 at least 75 percent of their impact resistance is impaired, and they are further characterized by a rectar. good resistance to attack by cryptogams and wood-destroying termites, moreover, they split rmavquablomtat May
Hereinafter are given a few examples, of course not limiting, of ease of implementation of the invention.

   These are not laboratory tests involving large pieces of drink.
 EMI9.6
 Aoitylies using acetic anhydride diluted with an inert hydrocarbon solvent, the improvements in the properties of the wood thus acetylated will be described.

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 EMI10.1
 B! ËEÎ <EJ.



  Several pieces of ponderosa pine measuring, in
 EMI10.2
 cross section, about 51 ost 102 mu are dried in a 1050 weighing oven, placed in shallow maxst3.tes, and covered with a treatment solution containing 50% acetic anhydride dissolved in xylene on the base volume by volume. The processing pots are placed in a
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 Double-walled processing cylinder, for application of vacuum and pressure, and a vacuum of about 68 centiate "very mercury is applied for one hour, followed by air pressure of 10 * 5 to 12 kg / co2 for 16 hours at 1054 * The pieces of wood are then transferred to a resin pot where a rack has been placed, above $ 00 ml of xylene, to support the test pieces.

   The xylene-acetic anhydride-acetic acid mixture is distilled aztSotrop1qulitme.nt at p *? Ti? from the 13th-1400 kettle while adding fresh xylene dropwise to the air. of a stopcock to constantly maintain a volume of 500 ml of xylene in the resin pot. This distillation is continued until there is no longer any acetic anhydride (reagent in excess) or acetic acid (by-product) in the distillate; it takes 10 hours. In use
 EMI10.4
 With this drying technique, it can be seen that the treated 4prOUY8t- tes do not split *
The procedure of Example 1 is carried out to impregnate several different species of wood.

   The results of these impregnations are shown in Table 11.

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 EMI11.1
 lu = .u4.
 EMI11.2
 
<tb> Example) <SEP> - <SEP> Species <SEP> of <SEP> wood <SEP> Solvent <SEP> forma-
<tb>
 
 EMI11.3
 tion, slits XX 8apia * 'cigu <' from the West isonzene Nil III Maple Er chloride, o Nil IV Drowned? blane from A) a <ri <;

  ne toluene Nil song roua 0 Chlorobensfene iant VI Cherry tree Nil tetrachloride carbon yarn Xylene Xêènt VIII Catit C = en Nil lx Mahogany Dieblorobansene Nil X Doublas fir t3ty.?,ar,ëx Nil XI Southern yellow pine Trichloroetoetbylene Xenous N64nt
 EMI11.4
 The procedure of the example is carried out.

   except that identical wood samples *
 EMI11.5
 The waters used in Examples 1 to XII are used with undiluted acetic anhydride. After drying in vapor phase, all, * our samples are very clearly stretched, PEOPLE XIV
 EMI11.6
 Woods prepared by * lie by carrying out the procedure of Examples * 1 to XII are measured to assess their dimensional stability.
 EMI11.7
 



  It is known that, when 1 $ * aup in either vapor phase or liquid phase, enters a cellulose fiber, hydrogen bonds 8 'establish between water and cellulosic hydroxyl groups in the amorphous regions. water is forced into the cellulose chain, and

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 the fiber swells. The wood swells especially in the tangen direction. tial, that is to say tangentially to the annual circles, half as much in the radial direction, and very little, if at all, in the longitudinal direction.

   When these hydroxyl groups are converted into acetate the hydrogen bond with water is decreased in proportion to the fraction of accessible hydroxyl groups converted. In addition, the relatively large size of the acetyl groups distends the cellulose chains and maintains the wood in a permanently swollen state: when the wood is dried. Such wood is said to be dimensionally stable.

   Swelling and shrinkage of wood cannot be completely prevented by treatment with a reagent whose molecules are larger than those of water, but swelling and shrinkage can be greatly reduced.

   This change in swelling is called "percent reduction in swelling" and is equal to: tangential swelling of the treated specimen (%) 1 - 100 tangential swelling of the control (%)
Table III shows the values of tangential swelling by exposure to a humid atmosphere and by exposure in liquid water for 12 species of wood before and after acetylation at 125 with acetic anhydride in a hydrocarbon solvent which does not swell the wood. wood.

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 EMI13.1
 



  TAPMSA9 1: 11- 22ntlimm entil. dg divereea k2ro de P9 ', cetrJé 5.4
 EMI13.2
 Gont1.en: .ent in% of the tangential dimension ¯¯¯¯¯¯¯ of the pea '9çh6 0 to 26.7 * in an atmos- in water at z of relative liquid humidity. ### ##### 'undermined * non-acetylated no. acetylated treated treated treated.



  Pondorota pine 2.6 0.5 5.6 1.3, Sap1n-ciu1 de lfouooz 5.5 0.9 12.3 2.7 Maple 4.5 1.0 UP4 2.7
 EMI13.3
 
<tb> Walnut <SEP> white <SEP> of America <SEP> 3.8 <SEP> 0.7 <SEP> 12.0 <SEP> 2.3
<tb>
<tb> Oak <SEP> red <SEP> 3.8 <SEP> 0.8 <SEP> 8.8 <SEP> 2.2
<tb>
<tb> Cherry tree <SEP> 3.0 <SEP> 0.9 <SEP> 8.2 <SEP> 2.2
<tb> Walnut <SEP> 3.0 <SEP> 0.8 <SEP> 8.8 <SEP> 2.1
<tb>
 
 EMI13.4
 Catiw 2.8 0.5 7.0 1.5
 EMI13.5
 
<tb> Mahogany <SEP> 2.7 <SEP> 0.8 <SEP> 6.4 <SEP> 1.9
<tb>
<tb> Fir <SEP> of <SEP> Douglas <SEP> 2.4 <SEP> 0.6 <SEP> 5.1 <SEP> 1.5
<tb>
<tb> Yellow <SEP> pin <SEP> of the <SEP> South <SEP> 2.3 <SEP> 0.5 <SEP> 5.7 <SEP> 1.7
<tb>
<tb> Sequoia. <SEP> 2.2 <SEP> 0.4 <SEP> 4.6 <SEP> 1.2
<tb>
 EXAMPLE XV.



     - We submit the species of wood that have been acetylated.
 EMI13.6
 in the * preceding examples ... tests to determine their resistance to attack by destructive cryptogams of drinks. Small blocks of around 19 mm edge cut from the specimens of these woods are potted for one month in a laboratory apparatus simulating the action of bad weather, then exposed for three months to the action of destructive organisms at try by implementing the operating mode (called due 'block of
 EMI13.7
 sol *) by Duncan and Richard., described in Pro *. the.

   Wood Preserver * Association 46 j 131-151 (1950), Cryptogams (fungi) cuti- i1 ", both M l1617) and ix.vM (Madison e97) * The results obtained are shown in Table IV.

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  TABLE IV.
 EMI14.1
 B2mool.ttien-gn seI'1 topèceq d2 x ctv141 A l'.u.UOJ !. 4, cwi2umea, {çhsmn1R11ons) <tt-structa) 1st wood sie
 EMI14.2
 
<tb> Species <SEP> Treatment <SEP> Net gain <SEP> <SEP> Loss <SEP> of <SEP> Loss <SEP> of
<tb> of <SEP> weight <SEP> weight <SEP>% <SEP> weight <SEP>% <SEP>
<tb> due <SEP> to <SEP> by <SEP> action <SEP> by <SEP> action
<tb> treat- <SEP> of <SEP> Madison <SEP> of <SEP> Madison
<tb> ment <SEP> 617 <SEP> 697
<tb>
<tb>
<tb> Acetylated fir-hemlock <SEP> <SEP> 27.6 <SEP> 0.9 <SEP> 1.1
<tb>
<tb> Fir-hemlock <SEP> witness <SEP> 38.6 <SEP> 27.3
<tb>
<tb> Acetylated <SEP> yellow <SEP> pin <SEP> south <SEP> <SEP> - <SEP> 19.6 <SEP> 1.6 <SEP> 1.4
<tb>
<tb> Yellow <SEP> pin <SEP> of the <SEP> south <SEP> indicator light <SEP> 24.8 <SEP> 29.0
<tb>
<tb> Oak <SEP> acetylated <SEP> 19.3 <SEP> 1.2 <SEP> 0.9
<tb>
<tb> Oak <SEP> witness <SEP> 19,

  8 <SEP> 53.9
<tb>
 
 EMI14.3
 Douglas fir ae4tjlé "25.1 1.6 0.9
 EMI14.4
 
<tb> <SEP> Douglas fir <SEP> <SEP> witness <SEP> 14.6 <SEP> 6.0
<tb>
<tb> Sequoia <SEP> acetylated <SEP> - <SEP> 25.2 <SEP> 1.6 <SEP> 2.3
<tb>
<tb> Sequoia <SEP> indicator <SEP> 1.2 <SEP> 1.5
<tb>
<tb> Pin <SEP> ponderosa <SEP> acetylated <SEP> 25.7 <SEP> 1.5 <SEP> 1.3
<tb>
<tb> Pin <SEP> ponderosa <SEP> witness <SEP> 28.2 <SEP> 31.4
<tb>
<tb> Maple <SEP> acetyl4 <SEP> 19.0 <SEP> 0.5 <SEP> 4.6
<tb>
<tb> Maple <SEP> indicator <SEP> 70.7 <SEP> 36.3
<tb>
 
 EMI14.5
 'm 3rd ..

   Samples of southern yellow pine wood measuring approximately 19 x 19 x 51 millimeters are acetylated by carrying out the procedure of Example 1 until weight gains ranging from 8 to 28 percent are obtained, placed during 30 days in the laboratory apparatus simulating bad weather, then polished with sandpaper on all sides. Each block is then buried in wet sand contained in a pot containing 25 termites.

   After 20 days, we dig up the blocks, we calculate the volume gates of the bots and we draw the curve according to
 EMI14.6
 weight gain of each block during lo & tylat1on "This curve is characterized by the appearance of a threshold located in the
 EMI14.7
 neighborhood of a weight gain value during 1- * acetylation

 <Desc / Clms Page number 15>

 is 18 percent. It therefore appears that ternites can
 EMI15.1
 attack acetylated wood at low degrees of acetylation, but cannot remain on acetylated wood at higher degrees of acetylation * 9 .....

   Samples of southern alder pine (pas), ponderosa pine (PP) and Douglas fir (SD) are cut into
 EMI15.2
 blocks of approximately 51 x 254 millimeters and are cleaned by carrying out the procedure of Example 1, then exposed to various weather conditions. The dimensional stabilities of these specimens are determined after 3, 6 and 12 months. We submit to
 EMI15.3
 same tests several test-specimens. maae wood in its natural state. The results shown in Table V show a small, practically negligible decrease in the dimensional stability of the treated samples as the weathering time increases.
 EMI15.4
 



  3'AB.U.K.



  Resistance ..du P9U 'fëYl; .4 ,. , .. 1l '\ tepbJ.u
 EMI15.5
 xgpboo rrsitly t ps: 1lti "'124 Jt! .h.u.m1c1i.tLnl.ú .. of exhibition in Prizes" Bougie- riri: acetyl sition of huui. ment tan- of the sta- i (month) $ 5 # called% lnt1Gl bilisation ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ .... ,,. ¯¯, JU ,, ...... ¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯ ..rt Pis control 0 4, fez 12.0 3.1 # PJS control 5.3 i3.2 3.4 pia control 5, 3 13.2 3.4 ..



  PIS control 6 4.7 10.8 2.6 #!
 EMI15.6
 
<tb> PJS <SEP> indicator <SEP> 12 <SEP> 4.6 <SEP> 11.9 <SEP> 2.6
<tb>
<tb>
<tb>
<tb> PJS <SEP> acetylated <SEP> 0 <SEP> 21 <SEP>, 5 <SEP> 4.6 <SEP> 0.7 <SEP> 78
<tb>
<tb>
<tb>
<tb> PJS <SEP> acetylated <SEP> 3 <SEP> 23.2 <SEP> 5.5 <SEP> 1.0 <SEP> 69
<tb>
<tb>
<tb>
<tb> PJS <SEP> acecylated <SEP> 6 <SEP> 20.8 <SEP> 4.4 <SEP> 0.9 <SEP> 66
<tb>
 
 EMI15.7
 PIS acetyl 12 21.1 5.0 0.9 64
 EMI15.8
 
<tb> PP <SEP> indicator <SEP> 0 <SEP> 4.7 <SEP> 11.0 <SEP> 2.5
<tb>
<tb> PP <SEP> indicator <SEP> 3 <SEP> 4.6 <SEP> 12.4 <SEP> 2.9
<tb>
<tb> PP <SEP> indicator <SEP> 6 <SEP> 3.7 <SEP> 10.1 <SEP> 2.6
<tb>
<tb> PP <SEP> indicator <SEP> 12 <SEP> 4.6 <SEP> 11.6 <SEP> 2.6
<tb>
<tb> PP <SEP> acetylated <SEP> 0 <SEP> 22.9 <SEP> 3.9 <SEP> 0.6 <SEP> 76
<tb>
<tb> PP <SEP> acetylated <SEP> 3 <SEP> 23.4 <SEP> 4.8 <SEP> 0,

  8 <SEP> 71
<tb>
<tb> PP <SEP> acetylated <SEP> 6 <SEP> 21.5 <SEP> 3.9 <SEP> 0.8 <SEP> 67
<tb>
<tb> PP <SEP> acetylated <SEP> 12 <SEP> 22.4 <SEP> 4.3 <SEP> 0.9 <SEP> 66
<tb>
<tb>
<tb>
<tb> SD <SEP> indicator <SEP> 0 <SEP> 4.4 <SEP> 10.6 <SEP> 2.7 <SEP> -
<tb>
<tb> SD <SEP> indicator <SEP> 6 <SEP> 5.4 <SEP> 9.5 <SEP> 2.2
<tb>
<tb> SD <SEP> indicator <SEP> 12 <SEP> 5.3 <SEP> 10.5 <SEP> 2.3 <SEP> -
<tb>
<tb> SD <SEP> acetylated <SEP> 0 <SEP> 24.0 <SEP> 3.5 <SEP> 0.7 <SEP> 75
<tb>
<tb> SD <SEP> acetylated <SEP> 6 <SEP> 22.9 <SEP> 3.2 <SEP> 0.6 <SEP> 73
<tb>
<tb> SD <SEP> acetylated <SEP> 12 <SEP> 24.4 <SEP> 3.7 <SEP> 0.8- <SEP> 65
<tb>
 
 EMI15.9
 hmhl.i, ..m 111 1. "., 1 .im it-ur '<1' i - '## 1 i mille" il 1 "" ..1.H11 .jij,' 1 ", 1.1. 1111 '.m nmir *
 EMI15.10
 
<tb>
<tb>
 

 <Desc / Clms Page number 16>

 
 EMI16.1
 PJS m southern yellow pine PP a ponderosa pine;

   SD = fir
Douglas * The acetyl content given is total apparent acetyl, that is to say not corrected for the content of untreated wood.
 EMI16.2
 Eyemple MOELI, - Samples of southern yellow pine and ponderosa pine measuring approximately $ 1 x 152 x 381 millimeters are acetylated, by carrying out the procedure of Example I until weight gains of 18 to 20% , then are cut into
 EMI16.3
 12.7 x 12.7 x 127 aca test tubes for shock res1! twwtt assay at the same time as spotted witnesses. on the * extracted. These specimens are put in condition and are broken on a Tinius Olsen apparatus for the impact resistance test of plastics with a Charpy sheep on a spacing of 101.6 mm.



  The results are given in Table VI.



   TAPLEAU VI
 EMI16.4
 Impact resistance of boJJLJI.y-P.iU-tt ± y! 8
 EMI16.5
 
<tb> Species <SEP> Treatment <SEP> Number <SEP> Resistance <SEP> to <SEP> shock <SEP> Deviation
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> test <SEP> in <SEP> kilogram- <SEP> meters <SEP> Normal
<tb>
 
 EMI16.6
 ¯ .... ,, yett.es .., ,,, ..,.,,, # ¯. v ,, .....- ..,! ,,,., Pis acetYI4 76 0.43 13.3 Pis Control 53 0.495 - 13.4 pp aedtylated 78 0.23 480
 EMI16.7
 
<tb> PP <SEP> indicator <SEP> 79 <SEP> 0.20 <SEP> # <SEP> 3.7
<tb>
 It appears that any variation in the impact strength of these pine species associated with unoacetylation remains within the limits of error of the methods used to determine this characteristic.

   It can therefore be legitimately concluded that the acetylation carried out in accordance with the invention does not reduce the impact resistance of the treated wood.



   From the above it. emerges that it is now possible, thanks to the implementation of the process for the acetylation of wood which is the object of the invention, to lead to the production of a product having better dimensional stability. and better resistance to decomposition, a product that can be used for making models and templates, musical instruments,

 <Desc / Clms Page number 17>

   items * of port, furniture $ of bowling alleys, parquet $, parts of mills and crushers, barrels of guns,

     printing blocks and ship frames. Wood prepared by mine using the process in question retains all the desirable properties of the bowls including impact resistance, low thermal and electrical conductivity, high mechanical resistance given its weight, aesthetic value, shaping and assembly. easy
Strong cracking of acetylated wood would result in a reduction in mechanical resistance and a poor appearance of the treated wood.

   The use, in accordance with the invention, of non-swelling solvents to form mixtures with acetic anhydride has made it possible to overcome these drawbacks. The swelling and shrinkage of wood treated in accordance with the invention will be only 20 to 30 percent of that of the original wood. Measurements prove that there is no deterioration in toughness or impact strength, and that other dry strength properties are retained.

   There is no unfavorable change in the decorative appearance, and in fact, some types of wood acquire an attractive lighter color. The invention relates more particularly to certain modes of application, as well as certain embodiments of the aforementioned improvements; and it relates more particularly still, and this as new industrial products, to treated wood of the type in question comprising application of the aforementioned characteristics or obtained by means of said processes, the devices suitable for ease of use. of the processes specified above. *, the assemblies or installations comprising these devices, as well as the materials, articles or articles made with the aid of these treated wood,


    

Claims (1)

ABSTRACT. The object of the invention is to make improvements * to the processes for improving the dimensional stability of wood by scetylation by impregnating the drink with acetic anhydride under pressure at a high temperature, then drying the wood to constant weight, which improvements have the following characteristics used alone or in any technically possible combination; 1) the process consists essentially in mixing acetic anhydride with an aromatic, hydroaromatic or inert chloro-hydrocarbon solvent, non-swelling for the bowls, practically immiscible with water, miscible with acetic anhydride and not - having a boiling point of at least 80, acetic anhydride being present in sufficient proportion, based on the density of the wood, to cause by impregnation a gain in water weight minus 18% on the basis of the density of the wood before impregnation; 2) in a process according to 1, the wood is subjected to the vapor of said solvent so that a portion of the solvent vapor condenses on a portion of the wood in order to drive off the moisture in the form of vapor, the bowl is separated from the condensed solvent, the bowls are subjected to a vacuum so that the remaining portion of solvent and moisture is removed from the wood, then the wood is subjected to the action of a mixture of acetic anhydride and solvent under a higher pressure at atmospheric pressure and at an elevated temperature until, until the wood is impregnated until a weight gain of at least 18%, the acetic anhydride is removed from the wood, again subjecting the wood to the action of solvent values which condense on the wood, the wood is repaired the condensed vapors, and then the wood is dried; 3) in a process according to-1 or 2, the wood is dried in an oven at a temperature of 100; 4) in a process according to 1, 2 or 3, the higher pressure <Desc / Clms Page number 19> re at atmospheric pressure is about 10.5 kg cm2 and the high temperature is 100 to 130.