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Title:
POLYISOCYANATE COMPOSITIONS FOR FAST CURE
Document Type and Number:
WIPO Patent Application WO/2001/009216
Kind Code:
A1
Abstract:
An organometallic composition, for use in accelarating the binding of lignocellulosic material, comprising a complex of at least one metal selected from iron and aluminum and at least one $g(b)-dicarbonyl compound wherein the molar ratio of metal to $g(b)-dicarbonyl compound is in the range 1:3.5 to 1:10.

Inventors:
SKINNER CHRISTOPHER JOHN (BE)
Application Number:
PCT/EP2000/006058
Publication Date:
February 08, 2001
Filing Date:
June 29, 2000
Export Citation:
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Assignee:
HUNTSMAN ICI CHEM LLC (US)
SKINNER CHRISTOPHER JOHN (BE)
International Classes:
C07F15/02; C07F15/06; C08G18/22; C08L97/02; B01J31/22; (IPC1-7): C08G18/22; B01J31/20; C08L97/02
Domestic Patent References:
WO1995013323A11995-05-18
WO1997017388A11997-05-15
Foreign References:
US5733945A1998-03-31
US4871854A1989-10-03
US2933462A1960-04-19
Other References:
DATABASE WPI Week 9723, Derwent World Patents Index; AN 267089, XP002149197, "Resin composition useful for paint"
Attorney, Agent or Firm:
Moens, Marnix Karel Christiane (Huntsman ICI BVBA Huntsman Polyurethanes Intellectual Property Dept. Everslaan 45 Everberg, BE)
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Claims:
CLAIMS
1. An organometallic composition, for use inaccelarating the binding of lignocellulosic material, comprising a complex of at least one metal selected from iron and aluminum and at least one Pdicarbonyl compound wherein the molar ratio of metal todicarbonyl compound is in the range 1: 3.5 to 1: 10.
2. An organometallic composition according to claim 1 characterised in that the molar ratio of metal to pdicarbonyl compound is in the range 1: 4 to 1: 8.
3. An organometallic composition according to claim 1 or 2 characterised in that the (3dicarbonyl compound is acetylacetone, benzoyl acetone, dibenzoylmethane, 2,2,6,6tetramethylheptanedione, 1, 1, 1trifluoro2,4pentanedione, ethylacetoacetate, methylacetoacetate, isopropylacetoacetate or tertiarybutylacetoacetate.
4. An organometallic composition according to any one of the preceding claims characterised in that the complex is derived from a condensed alkoxide of aluminum.
5. A polyisocyanate composition comprising an organometallic composition according to any one of the preceeding claims.
6. A polyisocyanate composition according to claim 5 characterised in that the amount of organometallic composition present is in the range 0.01 to 10 per cent by weight.
7. A polyisocyanate composition according to claim 5 or 6 characterised in that the polyisocyanate is diphenylmethane diisocyanate or a mixture of methylene bridged polyphenyl polyisocyanates.
8. A polyisocyanate composition according to any one of the preceding claims in which the complex is prepared from an alkoxide or condensed alkoxide and displaced alcohol is removed.
9. A polyisocyanate composition according to any one of the preceding claims in which the complex is present in an amount in the range 0.03 to 1 % by weight based on the polyisocyanate.
10. A polyisocyanate composition according to claim 9 in which the amount of complex is in the range 0.05 to 0.5 % by weight based on the polyisocyanate.
11. A polyisocyanate composition according to any one of the preceding claims in which the polyisocyanate is diphenylmethane diisocyanate or a mixture of methylene bridged polyphenyl polyisocyanates.
12. A polyisocyanate composition according to any one of the preceeding claims additionally comprising a diluent.
13. A polyisocyanate composition according to claim 12 in which the diluent is a phthalate, an aliphatic carboxylate, a fatty acid ester, linseed oil or soybean oil.
14. A polyisocyanate composition according to claim 13 in which the diluent is present in an amount in the range 1 to 40 parts by weight per 100 parts by weight of polyisocyanate.
15. A polyisocyanate composition according to any one of the preceeding claims additionally comprising a formaldehyde condensate adhesive resin.
16. A polyisocyanate composition according to claim 15 in which the formaldehyde condensate adhesive resin is present in an amount in the range 1 to 40 parts by weight per 100 parts by weight of polyisocyanate.
17. A polyisocyanate composition according to claim 16 in which the formaldehyde condensate adhesive resin is present in an amount in the range 1 to 20 parts by weight per 100 parts by weight of polyisocyanate.
18. A process for binding lignocellulosic material comprising the steps of a) bringing lignocellulosic material into contact with a polyisocyanate composition according to any one of the preceding claims and b) subsequently allowing said material to bind.
19. A process according to claim 18 in which the polyisocyanate composition is brought into contact with the lignocellulosic material and the combination thereby formed is hotpressed between metal plates at a temperature in the range 140° C to 270° C and a specific pressure in the range 2 to 6 MPa.
20. A process according to claim 18 or 19 in which the polyisocyanate composition is applied in such an amount as to give a weight ratio of polyisocyanate to lignocellulosic material in the range 0.1: 99.9 to 20: 8.
Description:
POLYISOCYANATE COMPOSITIONS FOR FAST CURE This invention relates to novel organometallic compositions and polyisocyanate compositions containing them and, in particular, to organometallic compositions based on iron or aluminum and which are useful in polyisocyanate compositions for binding lignocellulosic material.

The use of organic polyisocyanates as binders for lignocellulosic material in the manufacture of sheets or moulded bodies such as waferboard, chipboard, fibreboard and plywood is well known. In a typical process the organic polyisocyanate, optionally in the form of a solution, dispersion or aqueous emulsion, is applied to the lignocellulosic material which is then subjected to heat and pressure.

It has now been surprisingly found that P-dicarbonyl compounds can be used to prepare polyisocyanate compositions which are very stable on prolonged and provide significant acceleration to the binding of lignocellulosic material when used in the core layers of waferboard (known extensively as oriented strand board), medium density fiberboard and particleboard.

According to one aspect of the invention an organometallic composition, suitable for use in curing polyisocyanate compositions, comprises a complex of at least one metal selected from iron and aluminum and at least one P-dicarbonyl compound wherein the molar ratio of metal to p-dicarbonyl compound is in the range 1: 3.5 to 1: 10.

Also according to the invention, a polyisocyanate composition comprises an organometallic composition, said organometallic composition being a complex of at least one metal selected from the group consisting of iron and aluminum and a p-dicarbonyl compound in which the molar ratio of metal to P-dicarbonyl compound is in the range 1 : 3.5 to 1: 10.

The iron or aluminum composition used in the polyisocyanate composition of the invention is described herein as a"complex". It is believed that some of the ß-dicarbonyl compound will be chemically bound to the metal (Fe or Al) but some can be described as

"free"ester. The exact proportions which are bound and free will depend partly upon the exact molar ratios present in the complex and which metal is used, but it has been shown that the"free"ester does influence the properties, particularly the stability on storage, of the polyisocyanate composition as a binder for lignocellulosic materials. The use of the word"complex"does not imply that said complex is necessarily separately prepared before addition to a polyisocyanate to form the polyisocyanate compositions of the invention. The complex can be formed in the course of preparing the inventive polyisocyanate composition using alternative methods as described hereinafter.

The p-dicarbonyl compound used to prepare the complexes of the invention can be any suitable p-dicarbonyl compound. Preferred p-dicarbonyl compounds include acetylacetone (2,4-pentanedione), benzoyl acetone, dibenzoylmethane, 2,2,6,6- tetramethylheptanedione and 1,1,1-trifluoro-2,4-pentanedione and esters of acetoacetic acid such as ethylacetoacetate, methylacetoacetate, isopropylacetoacetate and tertiarybutylacetoacetate. A complex may be based on one p-dicarbonyl compound but particularly useful complexes have been prepared from a mixture of P-dicarbonyl compounds, such as a mixture of acetylacetone and ethylacetoacetate.

The molar ratio of metal to p-dicarbonyl compound in the complex is in the range 1 : 3.5 to 1: 10. Preferably, the molar ratio is preferably in the range 1: 4 to 1: 8 and more preferably in the range 1: 5 to 1: 8. In agreement with conventional theories about the co-ordination chemistry of iron or aluminum, it is believed that three molecules of the b-dicarbonyl compound will be chemically bound to a metal atom and the remainder will be"free".

Typically, the complexes of iron or aluminum are prepared from aluminum or iron alkoxides having the general formula M (OR) 3 in which M is Al or Fe and R is a substituted or unsubstituted, cyclic or linear, alkyl, alkenyl, aryl or alkyl-aryl group or mixtures thereof. Preferably, R contains up to 8 carbon atoms and, more preferably, up to 6 carbon atoms. Generally, all three OR groups will be identical but alkoxides derived from a mixture of alcohols can be used and mixtures of alkoxides can be employed when more than one metal is present in the complex. Suitable alkoxides include trimethoxyaluminum, trimethoxyiron, triethoxyaluminum, triethoxyiron, tri- isopropoxyaluminum, tri-isopropoxyiron, tri-n-propoxyaluminum, tri-n-propoxyiron,

tritertiarybutoxy-aluminum, tritertiarybutoxyiron, tri-sec-butoxyaluminum and tri-sec- butoxyiron.

Alternatively, the complex can be prepared from compounds known as condensed alkoxides of aluminum. A condensed alkoxide is typically prepared by the controlled addition of water to an alkoxide, followed by removal of alcohol which is displaced. The condensed alkoxides which are produced consist of a mixture of polymeric compounds containing Al-O-Al linkages and AIOR groups in which R has the meaning given above. Complexes of condensed aluminum alkoxides can also be prepared by forming a complex of a p-dicarbonyl compound with an alkoxide, adding water to the complex and removing any by-product alcohol.

Other aluminum or iron compounds, such as aluminum or iron trichloride or alkoxides which have been substituted with other moieties can be used as raw materials for the formation of the complex used in the invention.

The complex can be readily prepared by mixing, for example, an alkoxide or condensed alkoxide with an appropriate amount of P-dicarbonyl compound. Alcohol from the alkoxide will be displaced by the p-dicarbonyl compound and, preferably, the displaced alcohol is removed by, for example, distillation. In a preferred method, 3 moles of P-dicarbonyl compound (e. g. acetylacetone) per atom of A1 or Fe are added to an alkoxide or condensed alkoxide and the displaced alcohol is removed by distillation. Any additional acetoacetate ester required is then added to the stripped product. This method is advantageous because it provides a consistent product of known stoichiometry.

In one method of preparing the polyisocyanate compositions of the invention, a product containing 2 or 3 moles of ß-dicarbonyl compound per Fe or A1 atom can be mixed with additional P-dicarbonyl compound to produce the complex of the invention and this complex can be added to a polyisocyanate composition. For aluminum complexes, a product containing 1 mole of p-dicarbonyl compound per A1 atom is a suitable starting material for this method. Alternatively, the product containing 2 or 3 moles of p-dicarbonyl compound per Fe or Al atom can be prepared and any additional (3-dicarbonyl compound required to produce the polyisocyanate composition of the invention can be added to the polyisocyanate before or after the iron or aluminum compound has been added. Other methods of preparing the composition of the invention will be apparent to a person skilled in this art.

The amount of iron or aluminum complex present in the polyisocyanate composition of the invention is usually in the range 0.01 to 10 % by weight, based on the polyisocyanate and, preferably, the amount is in the range 0.1 to 4%. More preferably, the amount of complex present is in the range 0.2 to 1% by weight with respect to polyisocyanate.

Polyisocyanates for use in the composition of the present invention may be any organic polyisocyanate compound or mixture of organic polyisocyanate compounds, provided said compounds have at least 2 isocyanate groups. Organic polyisocyanates include diisocyanates, particularly aromatic diisocyanates, and isocyanates of higher functionality.

Examples of organic polyisocyanates which may be used in the composition of the present invention include aliphatic isocyanates such as hexamethylene diisocyanate; and aromatic isocyanates such as m-and p-phenylene diisocyanate, tolylene-2,4- and tolylene- 2,6-diisocyanate, diphenyl-methane-4,4'-diisocyanate, chlorophenylene-2,4-diisocyanate, naphthylene-1,5-diisocyanate, diphenylene-4,4'-diisocyanate, 4,4'-diisocyanate- 3,3'- dimethyl-diphenyl, 3-methyldiphenylmethane-4,4'-diisocyanate and diphenyl ether diisocyanate; and cycloaliphatic diisocyanates such as cyclohexane-2,4- and-2,3- diisocyanate, 1-methylcyclohexyl-2,4- and-2,6-diisocyanate and mixtures thereof and bis- (isocyanatocyclohexyl) methane and triisocyanates such as 2,4,6-triisocyanatotoluene and 2,4,4-triisocyanatodiphenylether.

Modified polyisocyanates containing isocyanurate, carbodiimide or uretonimine groups may be employed as well. Further blocked polyisocyanates, like the reaction product of a phenol or an oxime and a polyisocyanate, may be used, having a deblocking temperature below the temperature applied when using the polyisocyanate composition.

The organic polyisocyanate may also be an isocyanate-ended prepolymer made by reacting an excess of a diisocyanate or higher functionality polyisocyanate with a polyol.

Water-emulsifiable organic polyisocyanates like those described in UK patent no. 1 444 933, in European patent publication no. 516 361 and in PCT patent publication no.

91/03082 can also be used.

Mixtures of isocyanates may be used, for example a mixture of tolylene diisocyanate isomers such as the commercially available mixtures of 2,4- and 2,6-isomers and also the mixture of di-and higher polyisocyanates produced by phosgenation of aniline/formaldehyde condensates.

Such mixtures are well-known in the art and include the crude phosgenation products containing methylene bridged polyphenyl polyisocyanates, including diisocyanate, triisocyanate and higher polyisocyanates together with any phosgenation by- products.

Preferred isocyanates to be used in the present invention are those wherein the isocyanate is an aromatic diisocyanate or polyisocyanate of higher functionality such as a pure diphenylmethane diisocyanate or a mixture of methylene bridged polyphenyl polyisocyanates containing diisocyanates, triisocyanates and higher functionality polyisocyanates.

Methylene bridged polyphenyl polyisocyanates are well known in the art. They are prepared by phosgenation of corresponding mixtures of polyamines obtained by condensation of aniline and formaldehyde. For convenience, polymeric mixtures of methylene bridged polyphenyl polyisocyanates containing diisocyanate, triisocyanate and higher functionality polyisocyanates are referred to hereinafter as polymeric MDI. Suitable TM TM TM polyisocyanates include SUPRASEC DNR, SUPRASEC 2185, RUBINATE and RUBINATETM 1840, all available from Huntsman Polyurethanes.

Preferably the polyisocyanate is liquid at room temperature.

In order to further improve the storage stability of the polyisocyanate composition of the present invention a diluent may be added to the composition. Suitable diluents include plasticizers of the type mentioned in"Taschenbuch der Kunststoff-Additive", Ed. by R. Gachter and H. Muller, Carl Hanser Verlag Munchen, third edition, 1989. Preferred diluents are phthalates, aliphatic carboxylates, fatty acid esters, linseed oil and soybean oil.

These diluents are added in amounts of from 1 to 40 parts by weight per 100 parts by weight of polyisocyanate and preferably in amounts of from 1 to 15 parts by weight per 100 parts by weight of polyisocyanate.

The composition further may also comprise conventional additives like flame retardants, lignocellulosic preserving agents, fungicides, waxes, sizing agents, fillers, surfactants, thixotropic agents and other binders like formaldehyde condensate adhesive resins and lignin (optionally in combination with a lignin solvent such as described in PCT Patent Application No. EP96/00924).

The polyisocyanate composition of the present invention can be made by simply mixing the ingredients at room temperature.

The present invention is also concerned with a process for preparing lignocellulosic bodies by bringing lignocellulosic parts into contact with the present polyisocyanate composition and by pressing this combination.

Therefore the present invention also provides a process for binding lignocellulosic material comprising the steps of a) bringing said lignocellulosic material in contact with the present polyisocyanate composition and b) subsequently allowing said material to bind.

The lignocellulosic bodies are prepared by bringing the lignocellulosic parts into contact with the polyisocyanate composition by means such as mixing, spraying and/or

spreading the composition with/onto the lignocellulosic parts and by pressino the combination of the polyisocyanate composition and the lignocellulosic parts, preferably by hot-pressing, normally at 140° C to 270°C and 2 to 6 MPa specific pressure.

Such binding processes are commonly known in the art.

In waferboard manufacture the lignocellulosic material and the polyisocyanate composition may be conveniently mixed by spraying the present polyisocyanate composition on the lignocellulosic material while it is being agitated.

The lignocellulosic material after treatment with the polyisocyanate composition is placed on caul plates made of aluminium or steel which serve to carry the furnish into the press where it is compressed to the desired extent usually at a temperature between 140° C and 2700 C.

While the process is particularly suitable for the manufacture of waferboard known extensively as oriented strand board and will be largely used for such manufacture, the process may not be regarded as limited in this respect and can also be used in the manufacture of medium density fiberboard, particle board (also known as chipboard) and plywood.

Thus the lignocellulosic material used can include wood strands, woodchips, wood fibres, shavings, veneers, wood wool, cork, bark, sawdust and like waste products of the wood working industry as well as other materials having a lignocellulosic basis such as paper, bagasse, straw, flax, sisal, hemp, rushes, reeds, rice hulls, husks, grass, nutshells and the like. Additionally, there may be mixed with the lignocellulosic materials other particulate or fibrous materials such as ground foam waste (for example, ground polyurethane foam waste), mineral fillers, glass fibre, mica, rubber, textile waste such as plastic fibres and fabrics.

When the polyisocyanate composition is applied to the lignocellulosic material, the weight ratio of polyisocyanate/lignocellulosic material will vary depending on the bulk density of the lignocellulosic material employed. Therefore, the polyisocyanate compositions may be applied in such amounts to give a weight ratio of polyisocyanate/lignocellulosic material in the range of 0.1: 99.9 to 20: 80 and preferably in the range of 0.5: 99.5 to 10: 90.

If desired, other conventional binding agents, such as formaldehyde condensate adhesive resins, may be used in conjunction with the polyisocyanate composition.

More detailed descriptions of methods of manufacturing waferboard and similar products based on lignocellulosic material are available in the prior art. The techniques and equipment conventionally used can be adapted for use with the polyisocyanate compositions of the present invention.

The sheets and moulded bodies produced from the polyisocyanate compositions of the present invention have excellent mechanical properties and they may be used in any of the situations where such articles are customarily used.

The invention is illustrated but not limited by the following examples.

EXAMPLE I Iron (III) acetylacetonate (0.4g) was mixed with ethylacetoacetate (0.4g) in a molar ratio (1 mole PRODUCT A to 2.5M ethylacetoacetae) to yield PRODUCT A.

A polyisocyanate composition was then prepared comprising 0.8 parts weight of PRODUCT A described above and 500 parts by weight of standard polyisocyanate (SUPRASEC DNR, available from Huntsman Polyurethanes) to yield a material PRODUCT B.

To evaluate the utility of PRODUCT B in accelerating the curing of the core layers of an OSB panel against a standard polyisocyanate composition used industrially within the core of an OSB panel PRODUCT B was used to bind the softwood strands used in the core layers in the following manner: Panels containing Product B 3 Layer boards were prepared of 25 mm x 400 mm x 400 mm at a density 650 kg/m3. Standard isocyanate resin (Suprasec DNR, available from Huntsman Polyurethanes) was used to bind the face layers (11% resin loading based on dry wood).

PRODUCT B was used to bind the core layer (4% resin loading based on dry wood). Both layers also contained a sizing wax emulsion (SPG 60 available from Condea Chemie) at 1 % loading (solid wax) based on dry wood. The pre-pressing target moisture content was 11 % in the face layers and 6% in the core layer. The measured moisture content was 9.5% in the face layers and 5.3% in the core layer.

Standard Isocyanate (comparative) 3 Layer boards were prepared of 25 mm x 400 mm x 400 mm at a density 650 kg/m3. Standard isocyanate resin (SUPRASEC DNR, available from Huntsman Polyurethanes) as used to bind the face layers (11% resin loading based on dry wood) and standard polyisocyanate (SUPRASEC DNR, available from Huntsman Polyurethanes) used to bind the core layer (4% resin loading based on dry wood). Both layers also contained a sizing wax emulsion (SPG 60 available from Condea Chemie) at 1 % loading (solid wax) based on dry wood. The pre-pressing target moisture content was again 11 % in the face layers and 6% in the core layer. The measured moisture content was 9.8% in the face layers and 5.6% in the core layer.

To determine the minimum cycle time a press temperature of 190° C was used. The minimum possible cycle time was obtained by reducing the overall cycle time until a failure in panel performance was evident (either through a loss of control over panel thickness or through adhesive failure). The following results were obtained for panels prepared as described earlier: Standard Polyisocyanate PRODUCT B Minimum cook time (seconds of pressing per mm 1 2s/mm I I s/mm of panel thickness)