Polyisocyanate composition

Details Polyisocyanate composition Polyisocyanate composition

1996-10-30

2001-09-11

Gorr, Rachel (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From reactant having at least one -n=c=x group as well as...

C527S401000, C252S182200

Reexamination Certificate

active

06288200

ABSTRACT:

This invention relates to polyisocyanate compositions and in particular to polyisocyanate compositions for use in 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.
The high quality of the resulting materials is due, to a very large extent, to the excellent adhesive properties of organic polyisocyanates. At the same time, however, the excellent adhesive properties offered by a polyisocyanate creates an offsetting disadvantage in that it causes severe sticking of the lignocellulosic material to the hot metal surfaces with which it comes into contact during the hot-pressing operation. Most often the product is damaged in removing it from the press and much time is required to remove adhering cellulosic material from the surfaces of the press parts.
Several attempts have been made to overcome this adhesion problem. One of these approaches involves applying a release agent internally with the polyisocyanate.
As such internal mold release agents are described compounds which catalyse the formation of isocyanurate from isocyanates (see U.S. Pat. No. 3,870,665) such as certain metal salts of carboxylic acids. Particularly efficient internal mold release agents are zinc stearate and dialkyl tin bismaleates or zinc bismaleates as described in PCT Patent Publication No. 95/02619. In order to solubilise these metal carboxylates, and in particular those based on zinc, in the polyisocyanate composition compatibilising agents as described in PCT Patent Publication No. 95/13323 can be added.
However release performance and/or board properties of lignocellulosic bodies bound with polyisocyanate compositions containing the above described internal release agents are still not satisfactory.
Therefore it is an object of the present invention to provide a polyisocyanate composition that yields satisfactory release of the lignocellulosic bodies bound with said composition from the metal press surfaces without detrimentally affecting the other board properties.
The present invention provides a polyisocyanate composition comprising an organic compound derived from a metal of Group IVB of the Periodic Table of Elements, said organic compound being a metal carboxylate or metal alkoxide or a chelate complex with the metal as central atom and at least one polydentate ligand.
Polyisocyanate compositions containing such organic compounds derived from Group IVB metals show improved release from the press platens and enhanced cure of the lignocellulosic bodies bound with said polyisocyanate compositions.
Preferably the Group IVB metal is titanium or zirconium, most preferably titanium. In case of zirconium based compounds the stability of the composition is improved.
Suitable titanium based organic compounds for use in the present invention include those described in Japanese patent publication no. 63/207622, especially isopropyltriisostearoyltitanate.
Suitable carboxylates or alkoxides include those derived from saturated or unsaturated, aliphatic or cycloaliphatic or aromatic carboxylic acids or alcohols, preferably having from 1 to 30, more preferably from 8 to 20 and most preferably from 10 to 18 carbon atoms. Particularly suitable carboxylic acids include, for example, oleic acid, lauric acid, palmitic acid, stearic acid, mixtures thereof and the like. Particularly suitable alcohols include isopropanol.
The organic compound for use in the present invention can be derived from the same or different carboxylic acids and/or alcohols. Mixed carboxylates/alkoxides can also be used such as diisopropoxy titanium dioleate.
The organic compound for use in the present invention can also contain besides the carboxylate and/or alkoxide groups an alkyl group substituent on the central metal atom.
The chelate complex preferably contains as a polydentate ligand a &bgr;-dicarbonyl compound such as acetylacetonate or an acetoacetate. But also polydentates based on bonds between the Group IVB metal and S or N are included within the scope of this invention.
According to a preferred embodiment of the present invention the polyisocyanate composition contains a chelate complex corresponding to the following formula (I)
wherein X
1
, X
2
, X
3
, X
4
, X
5
and X
6
(same or different) represent O or S or N, z and z′ (same or different) are 0 or 1, y and y′ (same or different) are 0 or 1, R
1
and R
4
(same or different) represent an aliphatic hydrocarbon radical having 1 to 30 carbon atoms, R
2
and R
3
(same or different) represent an aliphatic hydrocarbon radical having 1 to 30 carbon atoms, R
5
and R
6
(same or different) represent an aliphatic hydrocarbon radical having 1 to 30 carbon atoms and M represents Ti or Zr or Hf.
Preferably M is Ti or Zr, most preferably Ti.
Preferably X
1
, X
2
, X
3
, X
4,
X5 and X
6
all represent O
Preferably R
5
and R
6
contain from 1 to 20 carbon atoms, most preferably 2 to 3 carbon atoms. Preferably z and z′ are both 0.
Preferably R
1
, R
2
, R
3
and R
4
contain from 1 to 20 carbon atoms.
According to one preferred embodiment of the present invention y and y′ are both 0 and R
1
, R
2
, R
3
and R
4
contain from 1 to 3 carbon atoms. According to another preferred embodiment of the present invention y and y′ are both 0, R
2
and R
3
contain from 1 to 3 carbon atoms and R
1
and R
4
contain from 10 to 18 carbon atoms.
Preferred compounds for use according to the present invention are those corresponding to formula (Ia)
(R
7
O)
a
M(R
8
C(O)CHC(O)R
9
)
b
  (Ia)
wherein M represents Ti or Zr, R
7
represents an alkoxy or carboxy group, R
8
represents an alkyl or aryl group, R
9
represents an alkoxy, aryloxy, alkyl or aryl group, a is 4-b and b is 1 or 2 in case of M being Ti and b is 1, 2, 3 or 4 in case of M being Zr.
The present organic compound derived from a Group IVB metal can be obtained by simple exchange reactions of Group IVB metal alkoxides (e.g. isopropyl based) or chlorides (e.g. TiCl
4
) with alkanol amines, carboxylic acids, hydroxyacids, diketones, keto-esters, glycols and the like; this followed either by destillation of the corresponding alcohol (e.g. isopropanol) or removal of HCl when using e.g. TiCl
4
.
The present organic compound derived from a Group IVB metal is used in amounts varying between 0.01 and 20%, preferably between 0.1 and 10%, more preferably between 0.2 and 7% and most preferably between 0.5 and 4% by weight based on the polyisocyanate.
In order to improve the stability of the present polyisocyanate composition a compatibilising agent as described in PCT Patent Publication No. 95/13323, incorporated herein by reference, can be added.
Thus the present invention also provides a polyisocyanate composition containing the present organic compound derived from a metal of Group IVB of the Periodic Table of Elements and a compatibilising agent being a compound corresponding to general formula (II) or the reaction product of an organic mono- or polyfunctional isocyanate therewith
wherein Y
1
and Y
2
(same or different) represent O or S; n and n′ (same or different) represent an integer of from 0 to 1, R and R′ (same or different) represent an aliphatic hydrocarbon radical containing from 1 to 30 carbon atoms and wherein the sum of the total number of carbon atoms of R and R′ is between 7 and 40.
The term “aliphatic hydrocarbon radical” as used herein is meant to include straight and branched chain alkyl and cycloalkyl radicals that may include unsaturated groups and/or F, Cl, Br, N, P, S, Si or O containing groups in their chain.
Preferred compounds of formula (II) are those wherein the sum of the total number of carbon atoms of R and R′ is between 9 and 20.
Preferably R and/or R′ represent aliphatic hy

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