SURFACE MODIFYING AGENT FORMULATION

Abstract

The present invention describes the production of wood panel boards, or the like, in which a surface modifying agent is mixed with a polyol to prepare a stable surface modifying agent polyol composition. The resultant composition is reacted with an isocyanate, and in particular, a polymeric di-isocyanate resin, in the presence of wood chips, fibers or the like, for the production of lignocellulosic based panels, such as oriented strand board (OSB), MDF, HDF and particle board panel products. In use, the surface modifying agent polyol composition is mixed with the polymeric di-isocyanate resin and the resultant mixture is applied to a lignocellulosic material, such as wood chips or fibers, immediately prior to hot pressing of the mixture to produce the panels. Sticking of the panels to the metal press belts or press plates typically used during production, is reduced or eliminated.

Claims

1. A method for the production of a cured lignocellulosic panel comprising: preparing an isocyanate-containing mixture; spraying said resin mixture onto a lignocellulosic material to produce a sprayed mat of lignocellulosic material; compressing said sprayed mat of lignocellulosic material in a press, at pressures of between 1 to 8 MPa specific pressure in a press heated to a temperature of between 150° C. to 220° C. to form the cured lignocellulosic panel; and removing said cured lignocellulosic panel from said press, wherein the resin mixture comprises an isocyanate resin in admixture with a surface modifying agent polyol comprising a mixture of a polyol and a surface modifying agent, wherein said surface modifying agent is a carboxylate having the formula (I): ##STR00002## wherein M is a metal selected from the group consisting of Group 1A, 2A, 4B, 4A, 1B, 2B and 8 of the Periodic Table of Elements; and R is a saturated or unsaturated hydrocarbon, and R is, or includes, a primary, secondary or tertiary alcohol, and has a hydroxyl functionality of between 1 and 5.

2. The method according to claim 1, wherein said lignocellulosic material is selected from the group consisting of wood strands, wood chips, wood fibres, wood shavings, wood veneers, wood wool, cork, bark, sawdust, waste products of the wood working industry, paper, bagasse, straw, flax, sisal, hemp, rushes, reeds, rice hulls, husks, grass, and nutshells, and wherein said panel has a weight ratio of isocyanate resin to lignocellulosic material in the range of 1.0:100 to 10:100.

3. The method according to claim 1, wherein said panel is an MDF panel, an HDF panel, a particleboard panel, plywood, or an OSB panel.

4. The method according to claim 1, wherein R is a straight chain or branched chain, saturated or unsaturated aliphatic hydrocarbon, or wherein R is a cycloalkyl radical.

5. The method according to claim 1, wherein R has between 10 to 25 carbon atoms.

6. The method according to claim 1, wherein said carboxylate is the reaction product of a metal-containing material together with an organic acid.

7. The method according to claim 6, wherein said carboxylate is a metal carboxylate, and wherein said organic acid is Stearic acid, Lauric acid, Myristic acid, Palmitic acid, Stearic acid, Oleic acid, Ricinoleic Acid, Linoleic acid, Linolenic acid, Hydroxypentanoic acid, Dihydroxybutanoic acid, Dihyroxybenzoic acid, Glycolic acid, Lactic acid, Tartaric acid, Citric acid, or Malic acid, and wherein M in formula 1 is sodium, potassium, magnesium, lithium, calcium, titanium, tin, lead, copper, silver, zinc, cadmium, iron, cobalt, nickel, or platinum.

8. The method according to claim 7, wherein said metal carboxylate is zinc stearate, magnesium stearate, lithium stearate, calcium stearate or cobalt stearate.

9. The method according to claim 1, wherein said composition comprises between 25 and 75%, by weight of said surface modifying agent.

10. The method according to claim 1, wherein said surface modifying agent is a metal carboxylate, and said composition comprises a mixture of equal parts, by weight, of said metal carboxylate and an aliphatic or aromatic polyol.

11. The method according to claim 1, wherein said polyol is a polyester, polyether, or caprolactone-based polyols, is liquid at room temperature, and has a molecular weight of between 400 and 4500.

12. The method according to claim 11, wherein said polyol has an isocyanate reaction functionality of between 2 and 4.

13. The method according to claim 1, wherein said polyol is glycerol, 3-(2-hydroxyethoxy)-1,2-propanediol, 3-(2-hydroxypropoxy)-1,2-propanediol, 2,4-dimethyl-2-(2-hydroxyethoxy)-methylpentanediol-1,5,1,2,6-hexanetriol, or 1,1,1,-trimethylolpropane, or wherein said polyol is prepared by reacting ethylene oxide (EO), propylene oxide (PO) or butylene oxide (BO) with 1,1,1-tris[(2-hydroxyethoxy)methyl]ethane, 1,1,1,-tris-[(2-hydroxypropoxy)methyl]propane, triethanolamine, triisopropanolamine, pyrogallol or phloroglucinol, in order to form a chain-extended polyol.

14. The method according to claim 1, wherein said polyol is, or comprises castor oil, a soy-based polyol, or wherein said polyol is a polybutadiene resin.

15. The method according to claim 1, wherein said isocyanate binder resin is diphenylmethane diisocyanate or is a mixture of methylene bridged polyphenyl polyisocyanates containing diisocyanates, triisocyanates and polyisocyanates, or is a polymeric mixture of methylene bridged polyphenyl polyisocyanates (PMDI) containing diisocyanate, triisocyanate and higher functionality polyisocyanates.

16. The method according to claim 1, wherein said PMDI has an isocyanate content of between 20%-35%, and has an functionality range of between 2.5 and 2.9.

17. The method according to claim 1, comprising between 80 to 65% isocyanate resin, and between 20 to 35% of said surface modifying agent polyol composition, by weight.

18. The method according to 17, wherein the ratio of isocyanate resin to the surface modifying agent polyol composition ranges from an isocyanate resin to surface modifying polyol composition ratio of from about 3:1 to about 4:1, by weight.

19. A lignocellulosic panel formed from the method of claim 1.

20. The panel according to claim 19, wherein said lignocellulosic material is selected from the group consisting of wood strands, wood chips, wood fibers, wood shavings, wood veneers, wood wool, cork, bark, sawdust, waste products of the wood working industry, paper, bagasse, straw, flax, sisal, hemp, rushes, reeds, rice hulls, husks, grass, and nutshells, and wherein said panel has a weight ratio of isocyanate resin to lignocellulosic material in the range of 1.0:100 to 10:100.

21. The panel according to claim 20, wherein said panel is an MDF panel, an HDF panel, a particleboard panel, plywood, or an OSB panel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Embodiments of this invention will now be described by way of example only in association with the accompanying drawings in which:

[0068] FIG. 1 is a partial cut-away, side view of a collection of wood chips ready being coated with the final resin system, in a mixer;

[0069] FIG. 2 is a side view of the components of a pressing assembly of the type used in the examples; and

[0070] FIG. 3 is a side view of an OSB panel, after pressing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0071] The novel features which are believed to be characteristic of the present invention, as to its structure, organization, use and method of operation, together with further objectives and advantages thereof, will be better understood from the following examples. Where appropriate, reference is made to the drawings in which a presently preferred embodiment of the invention will also be illustrated by way of example only. In the drawings, like reference numerals depict like elements.

[0072] It is expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. Also, unless otherwise specifically noted, all of the features described herein may be combined with any of the above aspects, in any combination.

EXAMPLES

[0073] The features of the present invention are now illustrated by the following, non-limiting examples.

Example 1

Preparation of the Metal Carboxylate:

[0074] By way of example only, sample metal carboxylate materials of use in the practice of the present invention, were prepared according to the following techniques:

[0075] (a) 1 mol of zinc sulphate was dissolved in 12.5 L of water at 30° C., and this was reacted with 2 mols of sodium stearate, dissolved in 12.5 L of water, at 70° C. The reaction temperature was held at 70° C. for 4 hours. The reaction precipitate was collected and was filtered under vacuum. The precipitate was washed twice with 12 L of deionized water. The wet cake was then dried in a vacuum oven at 100° C. for 4 hours to produce a dry product.

[0076] (b) 1 mol of zinc sulphate is dissolved in water is reacted with 2 mols of sodium ricinoleate, under constant agitation, to produce zinc ricinoleate as the metal carboxylate. The zinc ricinoleate precipitate is filtered and then washed with distilled water and allowed to dry in a desiccant dryer.

[0077] (c) 1 mol of zinc sulphate is dissolved in water is reacted with 2 mols of sodium hydroxypentanoate, under constant agitation, to produce zinc hydroxypentanoate as the metal carboxylate. The zinc hydroxypentanoate precipitate is filtered and then washed with distilled water and allowed to dry in a desiccant dryer.

[0078] (d) 1 mol of zinc sulphate is dissolved in water is reacted with 2 mols of sodium 2,3-dihydroxybutanoate, under constant agitation, to produce zinc dihydroxybutanoate as the metal carboxylate. The zinc dihydroxybutanoate precipitate is filtered and then washed with distilled water and allowed to dry in a desiccant dryer.

[0079] (e) 1 mol of zinc sulphate is dissolved in water is reacted with 2 mols of sodium 2,3-dihydroxybenzoate, under constant agitation, to produce zinc dihydroxybenzoate as the metal carboxylate. The zinc dihydroxybenzoate precipitate is filtered and then washed with distilled water and allowed to dry in a desiccant dryer.

[0080] (f) 1 mol of zinc sulphate is dissolved in water is reacted with 2 mols of sodium 3-hydroxypentanoate under constant agitation to produce zinc hydroxypentanoate as the metal carboxylate. The zinc hydroxypentanoate precipitate is filtered and then washed with distilled water and allowed to dry in a desiccant dryer.

[0081] Other metal carboxylates were prepared, using similar reaction techniques, starting with calcium sulphate, magnesium sulphate and sodium sulphate. The resulting metallic carboxylates were the calcium, magnesium and sodium analogues to the zinc carboxylates listed in examples 1(a) to 1(f).

Blending with Polyol:

[0082] The resultant metallic carboxylates from examples 1(a) to 1(f), were blended with various polyols, including polyether, polyester, polycaprolactone, polybutadiene, castor or soybean oils, or with some of the polyols previously mentioned, in order to produce various metallic carboxylate and polyol blends. Where needed, the metallic carboxylate and polyol blends were shear mixed. The resulting blends produced free flowing liquid materials with no visible particles in the metal carboxylate and polyol composition.

[0083] First, the metal carboxylate, as the surface modifying agent, in the total surface modifying polyol composition was used at an amount of either 25 or 75% by weight, of the total weight. A storage stable composition was obtained. Blends were also made at a weight ratio of 2 parts polyol to 1 part metal carboxylate (66% polyol), and again, a storage stable composition was obtained. Finally, mixtures of 1 part polyol to 1 part metal carboxylate were also prepared (50% polyol), and these blends were also storage stable.

[0084] By storage stable is meant that the composition remained as a liquefied material for more than 24 hours, with minimal thickening or settling of the metal carboxylate.

Reaction with Isocyanate:

[0085] Various metal carboxylate and polyol blend compositions described hereinabove, were blended with various isocyanate materials, and in particular, the preferred PMDI resins, previously described.

[0086] Generally, the resins were pre-mixed in a ratio of 1 part (by weight) of the metal carboxylate and polyol blend composition, with 6 parts (by weight) PMDI resin. The isocyanate-containing blended composition was added to aspen wood chips at a ratio of 7 parts by weight of the blended resin composition (e.g. 6 parts PMDI and 1 part of the surface modifying agent polyol composition), to 100 parts by weight wood chips, in the manner as shown in FIG. 1.

[0087] In FIG. 1, a loose collection of aspen wood chips 10 are shown in the mixing drum 20 (partially cutaway) of a Lodige™ plough mixer 28. In FIG. 1, wood chips 10 are being coated with an isocyanate-containing blended resin composition, stored in tank 12 which is being sprayed onto the wood chips, by spray nozzle 14. The resin composition is a mixture of a isocyanate resin and the surface modifying agent polyol which are mixed together immediately prior to use. For this “batch” operation, the isocyanate and surface modifying agent can be pre-mixed, and transferred to tank 12, and then sprayed onto wood chips 12 using spray nozzle 14. For continuous operation, the isocyanate and polyol mixture would be blended immediately prior to spraying.

[0088] The collection of resin-coated aspen wood chips 10 is mixed by movement of mixing blade 16, inside of drum 20. Mixing blade 16 is moved using motor 22.

[0089] Wood chips 10 are added to drum 20 using top opening 24, and after mixing, are removed from drum 20 using bottom opening 26, where they are collected in bucket 30. Before the resin system can cure completely, the wood chips in bucket 30 are transferred to the pressing operation, as described hereinbelow.

[0090] It should be noted that the PMDI resin to wood chip ratio, equal to 6 parts of PMDI to 100 parts of wood chips was used to illustrate a high polyurethane concentration and its effect on sticking. As such, the amount of isocyanate in the mixture of the surface modifying agent polyol composition was approximately 86% by weight. The amount of wood chips in the final mixture is approximately 93%, by weight.

[0091] It should also be noted that in the prior art, normal concentrations of PMDI polyurethane resins to wood chips would be in the range of 2 to 4 parts of PMDI, to 100 parts by weight of wood chips. This ratio results in much lower levels of the isocyanate being used in the pressing operation, and as such, it would be expected that there would be a reduction in the degree of sticking observed. As such, the examples described hereinbelow are generally being conducted under more severe conditions.

[0092] After spraying the wood chips, each mixture was blended in the Lodige plough blender for three minutes to thoroughly coat the wood chips, prior to pressing.

Example 2

Pressed Panels

[0093] 3 kg of air dry Aspen chips with a moisture content of approximately 6.5% were blended with a mixture of 180 g of HUNTSMAN Rubinate M PMDI and 30 g of a pre-mixed blend of 15 grams zinc stearate and 15 grams of Pluracol 492, by air atomized spray application in a 60 litre Lodige plough blender, as described hereinabove with reference to FIG. 1.

[0094] As seen in FIG. 2, over a lower press platen 32, pre-heated to 200° C., a carbon steel press frame 34 (having interior dimensions of 325 mm×325 mm×50 mm) was placed to hold the treated wood chips.

[0095] Separately, a 1 mm thick, clean, solvent-wiped lower caul press plate 36 made from carbon steel was placed in press frame 34, so that it would rest on the heated lower press platen 32.

[0096] An uncompressed lignocellulosic material mat 38 was formed, generally with the dimensions of 325 mm×325 mm×50 mm by placing 1000 g of the treated wood chips 20 inside the press frame 34, and onto the lower caul press plate 36.

[0097] A hydraulic press 40 which was modified in such a way that an upper caul platen 42 with the dimensions of 300×300 mm×40 mm was fixed to a heated upper press platen 44, and this was also heated to a temperature of 200° C.

[0098] Prior to pressing, a second carbon steel caul plate 46 was placed on the lignocellulosic mat 38.

[0099] Within 20 seconds of placing the lignocellulosic mat 38 into the press frame 34, the hydraulic press 40 was activated so as to move the lower press platen 32 upwards in the direction of the arrow shown, and thus result in forcing upper caul platen 42 to be inserted into steel press frame 34, and thereby press second carbon steel caul plate 46 down under pressure, onto lignocellulosic mat 38. The lignocellulosic mat 38 was thereby consolidated to a thickness of 9 mm, and held at that thickness for 120 seconds at a temperature of 200° C., and at a specific pressure of 2.45 MPa, between the upper (46) and lower (36) mild carbon steel caul plates.

[0100] Later, after 10 seconds of decompression, the press was opened to provide a resultant pressed board, with both the upper and lower carbon steel caul plates, remaining on the lower platen, on each side of compressed lignocellulosic mat 38. As a result of the pressing operation, the lignocellulosic mat 38 of FIG. 2 was compressed, and the resin system was cured, in order to form an OSB panel 50 having a thickness of 9 mm, as shown in FIG. 3. The upper and lower caul plates were easily removed from panel 50 without applying any force, and there was no damage to the resultant pressed board panel 50 caused by sticking.

[0101] This pressing process was then repeated several times with additional mats of the same lignocellulosic material and resins, without any sticking to the upper and lower carbon steel caul plates.

Comparative Example 1

[0102] As comparison the experiment of example 2 was repeated using no surface modifier material blended with the polyol prior to reaction with the polymeric di-isocyanate resin. Consequently, 1 part of Pluracol 492, which was the polyol used in Example 2, was used and mixed with 6 parts of PMDI. Again, a PMDI to wood chip ratio of 6 parts to 100 parts was used to illustrate a high PMDI concentration and its effect on sticking.

[0103] Following the pressing instructions given above, the resulting board did not release from the upper and lower caul plates. In fact, the board could not be removed from the upper caul platen without significant damage or destruction of the board.

Example 3

Additional Pressed Panels

[0104] 3 kg of air dry Aspen chips with a moisture content of approximately 6.5% were blended with a mixture of 180 g of Covestro Mondur MR Light PMDI and 30 g of a pre-mixed blend of 15 g zinc ricinoleate and 15 g of Dow XD-1421, by air atomized spray application in a 60 litre Lodige plough blender.

[0105] As in Example 2, over the pre-heated lower press platen, a carbon steel frame with a interior dimensions measuring 325 mm×325 mm×50 mm was placed to hold the treated wood chips. In this example though, a 1 mm thick, clean, solvent wiped caul press plate made from stainless steel was placed in the press frame onto the heated lower press platen.

[0106] A mat was formed with the dimensions of 300 mm×300 mm by using 1000 g of the treated wood chips inside the press frame.

[0107] Prior to pressing, a second stainless steel caul plate was placed on the mat.

[0108] Within 20 seconds the press was closed and the mat was consolidated to a thickness of 9 mm for 120 seconds at a temperature of 200° C. and a specific pressure of 2.45 MPa, between the upper and lower stainless steel caul plates.

[0109] After 10 seconds decompression the press opened and the board remained on the lower platen. The upper and lower stainless steel caul plates were both easily removed without applying of force. This process was repeated several times without any sticking to the upper and lower stainless steel caul plates.

Comparative Example 2

[0110] For comparison, the experiment of example 3 was repeated using no surface modifying agent blended with the polyol prior to reaction with the same polymeric di-isocyanate resin. In this example, 1 part of the same polyol, Dow XD-1421, was again used to 6 parts of PMDI. Again, a PMDI to wood chip ratio of 6 parts to 100 parts was used to illustrate a high PMDI concentration and its effect on sticking.

[0111] Following the pressing instructions given above, the resulting board did not release from the upper and lower stainless steel caul plates. In fact, the board could not be removed from the upper caul platen without significant damage or destruction of the board.

Example 4

Further Pressed Panels

[0112] 3 kg of air dry Aspen chips with a moisture content of approximately 6.5% were blended with a mixture of 90 g of BASF Lupranate M PMDI and 30 g of a pre-mixed blend of 10 g of calcium stearate and 20 g of castor oil, by air atomized spray application in a 60 litre Lodige plough blender. In this example, a PMDI to wood chip ratio of 100 to 3, by weight, was used to show a lower PMDI to wood chip ratio. The amount of surface modifying agent in the surface modifying agent polyol composition was also reduced to a level of 33% by weight, and thus provide a polyol to calcium stearate ratio of 2:1, by weight.

[0113] As in Example 2, over the pre-heated lower press platen, a carbon steel frame with a interior dimensions measuring 325 mm×325 mm×50 mm was placed to hold the treated wood chips.

[0114] In this example, a 1 mm thick, clean, solvent wiped caul press plate made from aluminum was placed in the press frame onto the heated lower press platen.

[0115] Again, a mat was formed with the dimensions of 300 mm×300 mm by using 1000 g of the treated wood chips inside the press frame.

[0116] Prior to pressing, a second aluminum caul plate was placed on the mat.

[0117] Within 20 seconds the press was closed and the mat was consolidated to a thickness of 9 mm for 120 seconds at a temperature of 200° C. and a specific pressure of 2.45 MPa, between the upper and lower aluminum caul plates.

[0118] After 10 seconds decompression the press opened and the board remained on the lower platen. The upper and lower caul plates were easily removed from the aluminum caul plates, without applying of force. This process was repeated several times without any sticking to the upper and lower aluminum caul plates.

Comparative Example 3

[0119] As comparison the experiment of example 4 was repeated using no surface modifying agent blended with the polyol prior to reaction with the same polymeric di-isocyanate resin. In this example, 1 part of the same polyol, castor oil, was mixed with 3 parts of PMDI. As such, for this example, a PMDI to wood chip ratio of 3 parts to 100 parts was used. Following the pressing instructions given above, the resulting board did not release from the upper and lower aluminum caul plates. In fact, the board could not be removed from the upper caul platen without significant damage or destruction of the board.

[0120] Thus, it is apparent that there has been provided, in accordance with the present invention, a surface modifying agent for use in the production of lignocellulosic panels, which fully satisfies the goals, objects, and advantages set forth hereinbefore. Therefore, having described specific embodiments of the present invention, it will be understood that alternatives, modifications and variations thereof may be suggested to those skilled in the art, and that it is intended that the present specification embrace all such alternatives, modifications and variations as fall within the scope of the appended claims.

[0121] Additionally, for clarity and unless otherwise stated, the word “comprise” and variations of the word such as “comprising” and “comprises”, when used in the description and claims of the present specification, is not intended to exclude other additives, components, integers or steps. Further, the invention illustratively disclosed herein suitably may be practiced in the absence of any element which is not specifically disclosed herein.

[0122] Moreover, words such as “substantially” or “essentially”, when used with an adjective or adverb is intended to enhance the scope of the particular characteristic; e.g., substantially planar is intended to mean planar, nearly planar and/or exhibiting characteristics associated with a planar element.

[0123] Further, use of the terms “he”, “him”, or “his”, is not intended to be specifically directed to persons of the masculine gender, and could easily be read as “she”, “her”, or “hers”, respectively.

[0124] Also, while this discussion has addressed prior art known to the inventor, it is not an admission that all art discussed is citable against the present application.