A PROCESS FOR IMPREGNATING CELLULOSIC MATERIALS AND PRODUCTS HEREBY OBTAINED

Abstract: Process for impregnating a cellulosic material, especially wood, to improve its resistance to moisture and to increase its dimensional stability, wherein the material is brought into contact with an agent comprising a silane of the formula: (FORMULA) wherein R<u1>u, R<u2>u and R<u3>u are same or different and are selected from the group comprising: alkoxy with 1 to 6 carbon atoms, and R<u4>u is equal to any of R<u1>u, R<u2>u and R<u3>u or selected from the group comprising: alkyl and cycloalkyl with 1 to 6 carbon atoms, aryl, aralkyl and organo-functional radicals, or with a hydrolysate or hydrolysate-condensate of such silane. The invention also extends to products prepared by such process.

Description: TITLE OF INVENTION: A PROCESS FOR IMPREGNATING CELLULOSIC MATERIALS AND PRODUCTS HEREBY OBTAINED: TECHNICAL FIELD: The present invention relates to a process for the impregnation of eellulosic materials, especially wood, to improve their resistance to moisture and to increase their dimensional stability. BACKGROUND ART : Among eellulosic materials wood is a very useful material which for its manufacture does not require large quantities of energy since it is formed in nature and since its processing is relatively simple. Wood possesses many advantages from the point of view of its use as a raw material and is thus easily machined,has a relatively high strength and good heat insulating properties, it is resistant to chemical attack etc. Wood is mostly used as a construction material for the manufacture of furniture, for domestic interior decoration and, of course,it is a highly Important raw material for the building industry. It is known that wood can decompose due to atmospheric conditions, uptake of water etc. and it is of importance to protect wood products by impregnating and/or surface treatment. Impregnation is a process whereby the pore system of the wood permanently or temporarily are filled with active substances in gas or liquid form. The surface treatment consists in the provision of different types of surface coatings, such as paint, lacquer or the like. A principal problem in using wood as a construction material resides in the fact that the wood by variations in moisture content is subjected to dimensional changes with disadvantageous results. Thus, fissures or cracks can form enabling transportation of moisture and spores resulting in for example attack by microorganisms. The dimensional instability can further result in damages to paint, interior decoration etc. Several attempts have bee made to reduce the dimensional variations of wood due to variations in moisture content but so far with little or no success. Most of the known methods for treating wood and wood products have for a main purpose to eliminate t growth of microorganisms by the introduction of fungicide Thus, the prior art methods have not for a main purpose t reduce or. eliminate dimensional changes. SUMMARY OF THE INVENTION: The present invention has for its purpose to provi a process for impregnation of eellulosic materials, par- ticularly wood or wood products, to reduce or eliminate dimensional changes due to varying environmental condi¬ tions. The present invention also relates to elimination or reduction of water uptake, thus improving the resistan to moisture attacks thereby impairing the conditions for microorganisms, such as fungi and the like. Another object is to provide for an impregnating process whereby the treated material will be improved wit regard to better adhesion to paint, resins etc. As a result of research and experimentation it has now been found that eellulosic materials, especially wood and wood products, can be modified to obtain a significan ly improved moisture resistance and dimensional stability by bringing the material into contact with an impregnatin agent or composition comprising silane of the formula: .2 — Si - 1 - R R 3 wherein R, , 2 and are same or differ ■ ent and are con- R 3 ^υιϋ O stituted by alkoxy with 1 to β carbon atoms, inclusive, and R is equal to any of R, , R p and R^ or constituted by alkyl or cycloalkyl having 1 to 6 carbon atoms, inclusive, aryl, aralkyl or an organofunctional radical. The process of the invention is operable also by using an impregnating agent comprising a hydrolysate or hydrolysate-condensate of such silane or mixture of silanes. It is preferred to use as an impregnating agent or composition a solution, a suspension or an emulsion of the silane or of the product derived therefrom. As a continuous phase or transport medium there may be used gases, such as air or water vapour, liquids, such as water, alcohols, such as lower alkanols with 1 to 4 carbon atoms, mixtures of water and such alcohols, light petrol, naphtha or other petroleum products, ligroin, esters, benzene, toluene, xylene, hydrocarbons and chlorinated hydrocarbons, tars, creosot oils etc. A preferred impregnating composition is a solution of- the silane or hydrolysate or hydrolysate-condensate thereof, but it is also conceivable in accordance with this invention to use a suspension or emulsion of the active ingredient. Particularly useful for impregnating solutions are lower alkanols, such as methyl or ethyl alcohol, iso- propyl alcohol, light petrol or naphtha, tars and creosot oils. Preferred silanes or products derived therefrom, as indicated above, are tetraalkoxy silanes, such as the ethyl ester of orthosilicic acid,i.e. tetraethoxysilane, wherein the above substituents R-,, R ? , R-, and R j , are all equal to C ≥ H 5 0. A particularly preferred hydrolysate-condensate for use in the impregnating composition are esters of different polysilicic acids, such as compounds of the following formula: OMPI (oligomer) wherein R indicates lower alkyl, i.e. alkyl having 1 to carbon atoms, particularly 2 or 3 carbon atoms, and n is an integer from 2 to 8, inclusive. These types of com¬ pounds are mostly colourless liquids insoluble but hydro lysable in water but soluble in many organic solvents, such as aromatic solvents, chlorinated hydrocarbons, alkanols and hydrocarbons, tars and creosot oils. Another preferred group of compounds for use as active ingredients in the impregnating composition are alkyl trialkoxysilanes, i.e. compounds where substituent R- j , R p and R^ above stand for alkoxy groups, particularl methoxy or ethoxy groups, and R^ stands for lower alkyl, such as methyl, propyl, ethyl etc. Hydrolysates and hydrolysate-condensates thereof are also, of course, useful and preferred. In addition to improving the properties of eellu¬ losic materials with regard to dimensional stability and other characteristics the process of this invention also enables treatment of for example wood and wood products improve their affinity to paints, glues, resins, dyes et This is accomplished by using as an active ingredient in the impregnating composition a silane or hydrolysate or hydrolysate-condensate thereof wherein R in the above formula is an organofunctional radical. This technique o improving adhesion of inorganic materials towards organic polymers is known but to the best of my knowledge have hever been applied to eellulosic materials, such as wood. Examples of such silanes containing an organofunctional group are the following: -^l_E Chemical name - Structure Vinyltrimethoxysilane CΗ 2 =CH-Si(0CH,), Vinyltriethoxysilane CH 2 =CH-Si(0C 2 H 5 ) 3 Vinyl-tris(β-methoxy- ethoxy)silane CH 2 =CH-Si(0CH 2 -CH 2 -0-CH ) 7-methaeryloxypropyltri- methoxysilane (CH 2 ) 3 -Si(0CH ) 7-glycidyloxypropyltri- methoxysilane This new technique constitutes an important aspect of this invention significantly broadening the area of application of the invention. It is to be noted that the process of the invention can be combined with known preservation and hydrophobation processes, such as treatment with silicons, fatty acid derivatives, oils, paraffines, waxes, tars, fungicides, insecticides, flame retardents etc. The treatment according to the invention can be per¬ formed at " normal temperature and pressure but it is con- ceivable and also frequently preferred to perform the pro¬ cess at increased temperatures, such as up to 1 0 C, for example at the normal drying temperature for wood products between about 0 and about 6θ°C. The impregnation can, of course, be operated at an increased or decreased pressure as is conventional in the known impregnation procedures. This is all per se conventional in the art and need no further detailed explanation. It has been found that the impregnating process of this invention can be frequently optimized by using poly- merization catalysts, i.e. agents improving polymerization and condensation of different preparations, as in the preparations of silicons. OMPI Among such useful catalysts are the following typ A first group of catalysts are thosedisclosed in for example Swedish patent No. 381, 53 constituted by either organo-functional silanes with basic organo group and/or alcoholates of silicon and/or metals from the firs or the second principal group and the fourth of the fift side group of the periodic system. A suitable example of such catalyst is 7-aminopropyltriethoxysilane, H 2 N-CH 2 -CH 2 -CH 2 -Si(OC H,-) A second group of catalysts of a conventional nature for operating and accelerating silane and silanol condensation and possible polymerisation are disclosed i U.S. patent No. 3,328,481, i.e. organic amines with a pre ferred dissociation constant of at least 10 " , preferabl primary, secondary and tertiary amines. A third group of catalysts for use in the process of this invention are also disclosed in said U.S. patent specification and can be described as condensation produc of aliphatic aldehydes and aliphatic primary amines. A fourth group of catalysts to be used in this invention are metal salts of carboxylic and polycarboxyli acids and hydroxy carboxylic acids. Metals used are inter alia lead, tin, nickel, cobolt, iron, cadmium, chromium, zinc, copper, manganese, aluminium, magnesium, barium, strontium, calcium, eecium, potassium, sodium, lithium, titanium, zirconium and vanadium. Examples of such cata¬ lysts are disclosed in Swiss patent specification 594576 where they-, however, are used in a totally different con¬ text, namely in the preparation of a particular binder. A fifth group of polymerization catalysts useful i this invention are metal oxides and organic peroxides. A sixth group of agents useful in connection with this invention are so-called chelate complexes. A particu type of chelate complexes used in the manufacture of O silicons are obtained by reaction of metal alcoholates and chelates such as betadiketones, betahydroxy or beta- aminoketones or betaketo esters, a process which is described in principal in Belgian patent specification B 564 179- All these catalysts are flexibly useful and are easily introduced into the solvent system used and certain catalysts may also be evaporized and transferred to the site in gas form. Moreover, most of the technically used fungicides are also polymerisation catalysts and thus useful in this invention. Although the invention is noϋ to be bound by any particular theory it is quite conceivable that the active ingredients used in the impregnating composition when operating the process of the invention will react with hydroxy groups of the eellulosic or lignine material to provide for some internal cross-linking in the material treated. Thus, it may well be that ester linkages may be formed between the silicon compounds from which alkoxy groups have been removed by hydrolyses and the hydroxy groups of the eellulosic material. This is a conceivable theory in view of the fact that the impregnation process of this invention results in products with significantly improved dimensional stability under varying humidity conditions and varying moisture contents. EXAMPLES: The invention will now be further described by non-limiting examples. Example 1. In this example the test bodies used are wood pieces of Scotch fir, 70 x 70 _ 10 mm. The wood is dried in the open air and contains on average 5 to 10 per cent by weight of moisture. The pieces are squares with the smallest dimension, 10 mm, in the direction of the fibres. The treating composition is prepared by dissolving the active ingredient, i.e. the silicon compound, in the solvent, which in this Example is absolute ethanol, napht or a mixture thereof. The treatment is performed by letting the test bodies float on the solution prepared for a period of tim of about 2 hours and at room temperature. The test bodies are then removed from the solution and examined with rega to absorbed quantity of liquid after treatment, remaining a quantity of liquid after drying in air at room tempera¬ ture for 48 hours and 1 year, and per cent circumferentia expansion after treatment, I.e. expansion along the annual rings of the wood. silan called m called Dynasil A and an oligomeric ester Dynasir 40, a West Germany. (probably propy trimethoxy silane). The structures of Dynasil A and Dynasil 40 are stated to be the following: and respectively. The test results from this Example are summarized in Table I as enclosed. In the Table, the control tests consist of treatment with water or ethanol only, whereas the other experiments exemplify treatments in accordance OMP with this invention. In the Table, all percentages refer to volume except for, of course, the data on expansion. As can be seen from the results of the Table certain compositions are solutions provided for almost no circum- ferential expansion at all. It seems that naphtha is an advantageous solvent, including a mixed solvent where naphtha is a major constituent. Example 2. The same type of test bodies as in Example 1 are used. The treating solution again contains Dynasylan BSM or Dynasil 40 and the treatment of the wood pieces is per¬ formed in the same manner as per Example 1 above but with a period of treatment of only 1 hour. After 2 weeks storage in open air at room temperature the impregnated test bodies are investigated and further tested with regard to water-uptake and circumferential expansion. The water-uptake experiment is performed by immersing the test bodies into water at a depth of 100 mms. The experimental results are summarized in Table II as enclosed. It is seen from the results that the water-uptake and the circumferential expansion are significantly reduced with regard to the test bodies treated in accord¬ ance with this invention. Example 3. The same types of test bodies as per Example 1 are again used. In this example the impregnating composition contains hydrolyzed Dynasil 40. The composition is prepared by stirring Dynasil 40 into aqueous ethanol (60 % C p H j -OH) containing sulphuric acid to a pH of about [3. After some time a clear solution is obtained containing the oligo¬ meric ester in a hydrolyzed form. The impregnation of the test bodies is performed in the same manner as in Example 2, and after treatment and ^U E4- OMPI there is -used in Example 1 above. The impregnating compo¬ sition contains Dynasylan BSM and Dynasil 40 ("Silane" and "olig. ester") . Water-uptake and circumferential expansion are measured after storage in an atmosphere of 100 % relative humidity and at a temperature of about 8θ C after 1 hour and after 24 hours. The results are summarized in Table V as enclosed and the improvement by using this invention are obvious therefrom. Example 6. This example, using the same type of test bodies as.. Example 1, has for its purpose to illustrate the improve¬ ment in water-resistance of wood impregnated in accordance with the invention. The test bodies are impregnated with different compositions using Dynasylan BSM (silane), Dynasil A (monom. ester) and Dynasil 40 (olig. ester) and a hydrolysate of the last substance. The impregnation is performed in the same manner as per Example 1 above, and after about 2 weeks drying in open air and at room temperature the test bodies are subjected to experimenta¬ tion. The experiment performed on the impregnated pieces of wood consists in applying one drop of water to one of the major surfaces of the piece of wood, i.e. to the surface containing the cut ends of the fibres, and the time interval for disappearance of the drop into the wood by absorption in seconds is measured and recorded. The results are summarized in Table VT as enclosed and it can be clearly seen from the results of the table that using the treatment of the invention results in a significant improvement of the water-resistance of the treated test bodies. _OMPI Table I • Treating agent Absorbed Remaining quantity Ex no quantity (gs) after dryin : expansion solvent silane ester ( % ) monomer oligomer of liquid (gs) 48 hrs 1 year after treatment 1:1 (control) - - 13 2 0 9-3 1:2 a " 100 7 1 0 5-7 l:3 a 60 40 8 2 1 5.0 l:4 a 60 20 20 8 6 3 .3 l:5 a " 70 30 8 4 3 0.7 l:6 a 60 40 8 7 5 0 l:7 a 60 35 5 8 3 2 5-7 l:8 b " 100 7 3 0 0 l:9 b " 100 6 3 2 0.7 ' 1:10 " ' 60 40 6 3 1 0 1:11° " 80 20 6 4 2 0 a: solvent use 3d absolute C p Hp-OH -~ ~ _J b: naphtha c: 50 nai Dhtha + 3 0% absoliite C H ^ OH Table II a: solvent used naphtha, catalyst: 0.1 zirconium naphtenate (by weight) b: " " absolute CgH^OH (no catalyst) x: RH = relative humidity. Table-III Treating agent nsion after: Ex. Water up-take % Expa solvent active in¬ (gs) after 1 hour Water Storage at 20 W C no (*) . gredient (contact with up-take and 100 % RH water surface) 60 mins 24 hrs 100 hrs 3:1 (control) 8 7.1 7.8 8.5 3:2 H 2 0/C 2 H 5 0H hydrolysate 4 3-5 4.2 5.7 20$ (1:4) _ll _ 3 3* _"_ 3 2.8 3-5 5.0 x: with 0,1 cobalt octoate as a catalyst Table IV x: with 0.1 $ zinc naphtenate as a catalyst Table V μ 4 a: solvent used absolute ethanol b: " ■ " naphtha c: II It a + b, 1:1 by volume Table VI x: hydrolysate according to Ex. a: solvent used naphta b: " " " + ethanol (1:1 by vol.) c: " " acetone + ethanol -"- d: " " ethanol

Claims: -CLAIMS : 1. A process for impregnating a eellulosic mate rial, especially wood, to improve its resistance to mois ure and to increase its dimensional stability, charact¬ erized by bringing the material into contact with an age comprising a silane of the formula: . R, - Si - R j , 1 I ^ R 3 wherein R-, , R p and R-, are same or different and are selected from the group comprising: alkoxy with 1 to 6 carbon atoms, and R j , is equal to any of R-, , R 2 and R-. or selected from the group comprising: alkyl and cycloalkyl with 1 to 6 carbon atoms, aryl, aralkyl and organo-func- tional radicals, or with a hydrolysate or hydrolysate-co densate thereof. 2. A process according to claim 1, characterized by bringing the material into contact with an-impregnating agent consisting of a solution, suspension or emulsion of the silane or the product derived therefrom. 3« A process according to claim 2, characterized by using a treating agent containing as a continuous phas water, a lower alkanol, light petrol, naphtha, tars, creosot oils or mixtures thereof. 4. A process according to any of claims 1 to 3, characterized by performing the impregnation in the presence of a polymerisation catalyst. 5. A process according to any of claims 1 to 4, characterized by performing the impregnation with an agen comprising a tetra alkoxy silane or hydrolysate or oligo¬ meric hydrolysate-condensate thereof. 6. A process according to claim 5 wherein the tetraalkoxy silane is an ethoxy silane. 7- A process according to any of claims 1-4, characterized by performing the impregnation with an agent comprising a trialkoxyalkyl silane. 8. A process according to claim 7-. wherein the alkoxy units of the silane have 1 or 2 carbon atoms. 9. A process according to any of claims 1 to 8, characterized by using a solution of the agent for the impregnation. 10. Products prepared by the process of any of claims 1-9. / ^ - ^ _r ~ ~- OMPI

Inventors: PUEHRINGER J
Applicants: PUEHRINGER J
Application year: 1980
Main classification: B27K3
IPC codes: B27K3