Self-releasing binder based on isocyanate and the use thereof in a process for the production of molded articles

The present invention relates to a substantially anhydrous binder having a self-releasing effect for the production of pressed articles comprising: PA1 (A) a polyisocyanate; and PA1 (B) a sulfonic acid corresponding to the general formula: EQU R--SO.sub.3 H).sub.n PA1 wherein PA2 n represents an integer of 1 or 2; PA2 R represents an aromatic hydrocarbon radical having from 6 to 14 carbon atoms, an aliphatic hydrocarbon radical having from 10 to 18 carbon atoms, a cycloaliphatic hydrocarbon radical having from 6 to 15 carbon atoms, an araliphatic hydrocarbon radical having from 7 to 15 carbon atoms or an alkaromatic hydrocarbon radical having from 7 to 24 carbon atoms; and PA2 the equivalent ratio of the components (A) and (B) is 100:0.5 to 100:20. The invention is also directed to the use of such binders in the production of shaped articles by the hot pressing of a wide variety of organic and/or inorganic materials.

BACKGROUND OF THE INVENTION 
The present invention relates to substantially anhydrous binders based on 
polyisocyanates which are modified by the addition of an organic sulfonic 
acid such that they have a self-releasing effect. The invention is also 
directed to the use of such binders in the production of shaped articles 
such as panels by the hot pressing of a wide variety of organic and/or 
inorganic materials such as substances containing lignocellulose. 
Pressed materials such as chip boards, composite panels and other shaped 
articles are usually produced by hot pressing the inorganic or organic raw 
material such as a composition of wood shavings, wood fibers or another 
material containing lignocellulose, with binders such as aqueous 
dispersions or solutions of urea/formaldehyde or phenol/formaldehyde 
resins. It is also known to use isocyanates or isocyanate solutions as 
binders for pressed panels instead of formaldehyde resins (German 
Auslegeschrift No. 1,271,984; German Offenlegungsschriften Nos. 1,492,507; 
1,653,177 and 2,109,686). The use of polyisocyanates as binders improves 
the stability and the moisture-resistance of the products and improves 
their mechanical properties. In addition, polyisocyanates have a wide 
range of processing advantages as binders as disclosed in German 
Offenlegungsschrift No. 2,109,686. 
The large scale production of materials which are bonded with 
polyisocyanates, in particular materials containing lignocellulose such as 
chip boards, fiber boards or plywood is, however, impaired by the marked 
tackiness of the polyisocyanates. This tackiness, after the hot pressing 
treatment, causes the molded articles to adhere strongly to metal 
articles, in particular the steel or aluminum surfaces of the press. Such 
adherence thus makes it more difficult to remove the molded articles from 
the mold. 
Previously proposed methods of solving this mold release problem suffer 
from significant disadvantages. Release agents which have been developed 
especially for isocyanates frequently have a good release action but, in 
industrial applications, they are neither reliable nor economical enough 
and, additionally, may cause faulty bonding or difficulties in coating 
during the subsequent processing of the plates. 
It has been proposed in German Offenlegungsschrift No. 1,653,178 that, 
during the production of panels or shaped articles by the hot pressing of 
mixtures of materials containing lignocellulose and polyisocyanates, the 
surfaces of the press or pressing molds be treated with polyhydroxyl 
compounds such as glycerin, ethylene glycol or polyester and polyether 
polyols before the pressing operation. A disadvantage of this process is 
that a separate operation is required to apply this release agent and, in 
addition, a proportion of the polyisocyanate is consumed by the reaction 
with the release agent. According to German Offenlegungsschrift No. 
2,325,926, another possible way of improving the release behavior of the 
shaped articles involves using as release agents those compounds which act 
as catalyst with isocyanates to form isocyanate. However, a disadvantage 
of this approach is that the catalysts have a destabilizing effect on the 
isocyanate and thus prevent the formation of a suitable isocyanate binder. 
An object of the present invention is to overcome the above-mentioned 
disadvantages in the production of shaped articles using polyisocyanates 
by providing binders based on isocyanates which may be stored and which 
ensure that the pressed articles may be removed from the mold without 
difficulty. It has surprisingly been found that this object may be 
achieved if the isocyanate is used in combination with an organic sulfonic 
acid. 
DESCRIPTION OF THE INVENTION 
The present invention relates to a substantially anhydrous binder for the 
production of pressed articles, optionally containing organic solvents, 
which has a self-releasing effect and is based on a polyisocyanate 
comprising: 
(A) a polyisocyanate; and 
(B) a sulfonic acid corresponding to the general formula: 
EQU R--SO.sub.3 H).sub.n 
wherein 
n represents the integer 1 or 2, preferably 1; and 
R represents an aromatic hydrocarbon radical having from 6 to 14 carbon 
atoms, an aliphatic hydrocarbon radical having from 10 to 18 carbon atoms, 
a cycloaliphatic hydrocarbon radical having from 6 to 15 carbon atoms, an 
araliphatic hydrocarbon radical having from 7 to 15 carbon atoms or an 
alkaromatic hydrocarbon radical having from 7 to 24 carbon atoms; 
the equivalent ratio of components (A):(B) being from 100:0.5 to 100:20, 
preferably from 100:1 to 100:5. 
Those sulfonic acids corresponding to the general formula wherein R 
represents an araliphatic hydrocarbon radical having from 7 to 15 carbon 
atoms or an alkaromatic hydrocarbon radical having from 7 to 24 carbon 
atoms are preferred. 
Particularly preferred for the modification of the isocyanate component are 
those sulfonic acids corresponding to the above general formula wherein R 
represents an alkyl-substituted phenyl radical having a total of from 9 to 
20 carbon atoms. It is, however, also possible to use as release agents 
those sulfonic acids corresponding to the above general formula wherein R 
also contains inert substituents such as halogen or nitro substituents. 
Specific representatives of suitable sulfonic acids include, for example, 
decane sulfonic acid, octadecane sulfonic acid, benzene sulfonic acid, 
toluene sulfonic acid, naphthalene sulfonic acid, cyclohexane sulfonic 
acid and, in particular, aromatic monosulfonic acids of the type which may 
be obtained in known manner by the sulfonation of alkyl benzenes such as 
hexyl-benzene, dodecyl-benzene, octadecyl-benzene or mixtures thereof. 
The present invention also relates to a process for the production of 
shaped articles by the hot pressing of an organic and/or inorganic 
material which is mixed and/or impregnated with a compound containing 
isocyanate groups as binder, using an agent to release the molded article 
from the surfaces of the pressing mold, the process being characterized in 
that the binder combinations of the present invention are used. 
A process for the production of modified polyisocyanates has been disclosed 
in German Offenlegungsschrift No. 2,441,843 in which organic 
polyisocyanates are reacted in a molar ratio of from 100:0.1 to 100:50 
with from 0.1 to 5% by weight water-containing organic sulfonic acid until 
from 50 to 100% of the carbon dioxide theoretically expected to be evolved 
as a result of the reaction of all the water with the isocyanate groups 
has been evolved. The polyisocyanates which have been modified in this way 
are used as isocyanate components in the production of hydrophilic 
polyurethane foams. There is not, however, any reference to the use of 
these modified polyisocyanates as binders in the production of molded 
articles. Moreover, according to German Offenlegungsschrift No. 2,441,843, 
while they are being modified, the polyisocyanates are reacted with 
sulfonic acids containing a considerable quantity of water which would be 
disadvantageous for the present invention as it would reduce the 
isocyanate content of the binder unnecessarily. Although adducts are 
formed between the isocyanate groups and the sulfonic acid groups which 
are not fully understood in the substantially anhydrous binder 
combinations according to the present invention, this process should be an 
essentially physical association in which the content of NCO groups 
(although possibly partly in masked form) remains unchanged. Elimination 
of carbon dioxide is not observed. 
Suitable isocyanate components for the binder combinations according to the 
present invention include virtually any polyisocyanates, but preferably 
aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic 
polyisocyanates which are liquid at room temperature, of the type 
described, for example, by W. Siefken in Justus Liebigs Annalen der 
Chemie, 562, pages 75 to 136. Examples of suitable isocyanate components 
include, for example, those polyisocyanates of the general formula: 
EQU Q(NCO).sub.n 
wherein 
n represents an integer of from 2 to 4, preferably 2; and 
Q represents an aliphatic hydrocarbon radical having from 2 to 18, 
preferably from 6 to 10 carbon atoms, a cycloaliphatic hydrocarbon radical 
having from 4 to 15, preferably from 5 to 10 carbon atoms, an aromatic 
hydrocarbon radical having from 6 to 15, preferably from 6 to 13 carbon 
atoms, or an araliphatic hydrocarbon radical having from 8 to 15, 
preferably from 8 to 13 carbon atoms. 
Examples of such polyisocyanates include: ethylene diisocyanate; 
1,4-tetramethylene diisocyanate; 1,6-hexamethylene diisocyanate; 
1,12-dodecane diisocyanate; cyclobutane-1,3-diisocyanate; cyclohexane-1,3- 
and -1,4-diisocyanate as well as mixtures of these isomers; 
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (German 
Auslegeschrift No. 1,202,785, U.S. Pat. No. 3,401,190); 2,4- and 
2,6-hexahydrotolylene diisocyanate as well as mixtures of these isomers; 
hexahydro-1,3- and/or -1,4-phenylene diisocyanate; perhydro-2,4'- and/or 
4,4'-diphenylmethane-diisocyanate; 1,3- and 1,4-phenylene diisocyanate; 
2,4- and 2,6-tolylene diisocyanate as well as mixtures of these isomers; 
diphenylmethane-2,4'- and/or -4,4'-diisocyanate and 
naphthylene-1,5-diisocyanate. 
Examples of other suitable polyisocyanates include: 
triphenylmethane-4,4',4"-triisocyanate; polyphenyl polymethylene 
polyisocyanates of the type obtained by aniline/formaldehyde condensation 
followed by phosgenation and described, for example, in British Pat. Nos. 
874,430 and 848,671; m- and p-isocyanato-phenyl sulfonyl-isocyanates 
according to U.S. Pat. No. 3,454,606; perchlorinated aryl polyisocyanates 
of the type described, for example, in German Auslegeschrift No. 1,157,601 
(U.S. Pat. No. 3,277,138); polyisocyanates containing carbodiimide groups 
of the type described in German Pat. No. 1,092,007 (U.S. Pat. No. 
3,152,162) as well as in German Offenlegungsschriften No. 2,504,400; 
2,537,685 and 2,552,350 and norbornane diisocyanates according to U.S. 
Pat. No. 3,492,330. Additional suitable polyisocyanates include those 
containing allophanate groups of the type described, for example, in 
British Pat. No. 994,890, Belgian Patent No. 761,626 and Netherlands 
Patent Application No. 7,102,524; polyisocyanates containing isocyanurate 
groups of the type described, for example, in U.S. Pat. No. 3,001,973, in 
German Patent Nos. 1,022,789; 1,222,067 and 1,027,394 as well as in German 
Offenlegungsschriften 1,929,034 and 2,004,048; polyisocyanates containing 
urethane groups of the type described, for example, in Belgian Patent No. 
752,261 or in U.S. Pat. Nos. 3,394,164 and 3,644,457; polyisocyanates 
containing acylated urea groups according to German Patent No. 1,230,778; 
polyisocyanates containing biuret groups of the type described for 
example, in U.S. Pat. Nos. 3,124,605 and 3,201,372 as well as in British 
Pat. No. 889,050; polyisocyanates produced by telomerization reactions of 
the type described, for example, in U.S. Pat. No. 3,654,106; 
polyisocyanates containing ester groups of the type described, for 
example, in British Pat. Nos. 965,474 and 1,072,956, in U.S. Pat. No. 
3,567,763 and in German Patent No. 1,231,688; reaction products of the 
above-mentioned diisocyanates with acetals according to German Patent No. 
1,072,385 and polyisocyanates containing polymeric fatty acid esters 
according to U.S. Pat. No. 3,455,883. 
It is also possible to use the distillation residues which contain 
isocyanate groups produced during the generally known production of 
isocyanates, optionally dissolved in one or more of the above-mentioned 
polyisocyanates. Moreover, it is possible to use mixtures of the 
above-mentioned polyisocyanates. 
Examples of particularly preferred polyisocyanates include: 2,4- and 
2,6-tolylene diisocyanate as well as mixtures of these isomers ("TDI"); 
polyphenyl polymethylene polyisocyanates of the type produced by 
aniline/formaldehyde condensation with subsequent phosgenation ("crude 
MDI"); and polyisocyanates containing carbodiimide groups, urethane 
groups, allophanate groups, isocyanurate groups, urea groups or biuret 
groups ("modified polyisocyanates"), particularly those modified 
polyisocyanates which are derived from 2,4- and/or 2,6-tolylene 
diisocyanate and from 4,4'- and/or 2,4'-diphenylmethane diisocyanate. 
Suitable isocyanate components also include prepolymers containing terminal 
NCO groups having an average molecular weight of from about 300 to 2000 of 
the type obtained in known manner by the reaction of higher molecular 
weight and/or lower molecular weight polyols with an excess of 
polyisocyanate. Suitable higher molecular weight polyols include, in 
particular, compounds containing from 2 to 8 hydroxyl groups, particularly 
those having a molecular weight of from 400 to 10,000, preferably from 800 
to 5,000 such as polyesters, polyethers, polythioethers, polyacetals, 
polycarbonates and polyester amides containing at least two, generally 
from 2 to 8, preferably from 2 to 4, hydroxyl groups of the type which are 
known for the production of noncellular and of cellular polyurethanes. 
Suitable polyesters containing hydroxyl groups include, for example, 
reaction products of polyhydric, preferably dihydric, and optionally also 
trihydric alcohols with polybasic, preferably dibasic, carboxylic acids. 
The corresponding polycarboxylic acid anhydrides or corresponding 
polycarboxylic acid esters of lower alcohols or mixtures thereof may be 
used for the production of the polyesters instead of the free 
polycarboxylic acids. The polycarboxylic acids may be aliphatic, 
cycloaliphatic, aromatic and/or heterocyclic and may optionally be 
substituted, for example by halogen atoms, and/or may be unsaturated. 
Examples of suitable carboxylic acids and derivatives thereof for the 
preparation of the polyesters include: succinic acid; adipic acid, suberic 
acid; azelaic acid; sebacic acid; phthalic acid; isophthalic acid; 
trimellitic acid; phthalic acid anhydride; tetrahydrophthalic acid 
anhydride; hexahydrophthalic acid anhydride; tetrachlorophthalic acid 
anhydride; endomethylene tetrahydrophthalic acid anhydride; glutaric acid 
anhydride; maleic acid; maleic acid anhydride; fumaric acid; dibasic and 
tribasic unsaturated fatty acids optionally mixed with monobasic 
unsaturated fatty acids, such as oleic acid; terephthalic acid dimethyl 
ester and terephthalic acid-bis-glycol ester. Examples of suitable 
polyhydric alcohols include: ethylene glycol; propylene glycol-(1,2) and 
-(1,3); butylene glycol-(1,4) and -(2,3); hexane diol-(1,6); octane 
diol-(1,8); neopentyl glycol; 1,4-bis-hydroxymethyl cyclohexane; 
2-methyl-1,3-propane diol; glycerin; trimethylol propane; hexane 
triol-(1,2,6); butane triol-(1,2,4); trimethylol ethane; pentaerythritol; 
quinitol; mannitol; sorbitol, formitol; methyl glycoside; diethylene 
glycol; triethylene glycol; tetraethylene glycol and higher polyethylene 
glycols; dipropylene glycol and higher polypropylene glycols as well as 
dibutylene glycol and higher polybutylene glycols. The polyesters may 
contain a proportion of terminal carboxyl groups. Polyesters of lactones, 
for example .epsilon.-caprolactone, or of hydroxycarboxylic acids, for 
example .omega.-hydroxycaproic acid, may also be used. 
Polyethers containing at least two, generally from 2 to 8, preferably 2 or 
3 hydroxyl groups which may be used according to the invention include 
those known compounds which may be prepared, for example, by 
self-polymerization of epoxides such as ethylene oxide, propylene oxide, 
butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin, for 
example in the presence of Lewis catalysts such as BF.sub.3 ; or by 
addition of these epoxides, preferably ethylene oxide and propylene oxide, 
optionally in mixture or in succession, to starting components containing 
reactive hydrogen atoms such as water, ammonia, alcohols or amines. 
Examples of such starting components include: ethylene glycol; propylene 
glycol-(1,3) or -(1,2); trimethylol propane; glycerin; sorbitol; 
4,4'-dihydroxydiphenylpropane; aniline; ethanolamine or ethylene diamine. 
Sucrose polyethers of the type described, for example, in German 
Auslegeschriften Nos. 1,176,358 and 1,064,938 as well as polyethers which 
are started on formitol or formose (German Offenlegungsschriften Nos. 
2,639,083 or 2,737,951) may also be used according to the invention. In 
many cases, it is preferable to use those polyethers which contain 
predominantly (i.e. up to 90% by weight, based on all OH groups present in 
the polyether) primary OH groups. Polybutadienes containing OH groups may 
also be used. 
The polythioethers include, in particular, the self-condensation products 
of thiodiglycol and/or the condensation products of thiodiglycol with 
other glycols, dicarboxylic acids, formaldehyde, amino carboxylic acids or 
amino alcohols. Depending on the co-components, the products are, for 
example, polythio mixed ethers, polythio ether esters or polythio ether 
ester amides. 
Suitable polyacetals include, for example, the compounds which may be 
produced from the reaction of glycols such as diethylene glycol, 
triethylene glycol, 4,4'-diethoxy diphenyldimethyl methane and hexane diol 
with formaldehyde. Polyacetals suitable for the present invention may also 
be produced by polymerization of cyclic acetals such as trioxane (German 
Offenlegungsschrift No. 1,694,128). 
Suitable polycarbonates containing hydroxyl groups include those known 
compounds which may be prepared, for example, by reaction of diols such as 
propane diol-(1,3); butane diol-(1,4) and/or hexane diol-(1,6); diethylene 
glycol; triethylene glycol; tetraethylene glycol or thiodiglycol, with 
diaryl carbonates such as diphenyl carbonate, or with phosgene (German 
Auslegeschriften Nos. 1,694,080; 1,915,908 and 2,221,751 and German 
Offenlegungsschrift No. 2,605,024). 
The polyester amides or polyamides include, for example, the predominantly 
linear condensates obtained from polybasic saturated or unsaturated 
carboxylic acids and anhydrides thereof and polyfunctional saturated or 
unsaturated amino alcohols, diamines, higher polyamines and mixtures 
thereof. 
Polyhydroxyl compounds already containing urethane or urea groups as well 
as optionally modified natural polyols such as castor oil, or 
carbohydrates such as starch may also be used. Addition products of 
alkylene oxides with phenol/formaldehyde resins or with urea/formaldehyde 
resins may also be used. 
Suitable lower molecular weight polyols (i.e. having a molecular weight of 
from 62 to 400) include, for example, the compounds listed above as 
starting components for the production of higher molecular polyols. 
As mentioned above, polyphenyl polymethylene polyisocyanates are preferably 
used as the isocyanate component of the binder. It is particularly 
advantageous (see German Offenlegungsschrift No. 2,711,598) to use as the 
isocyanate component, the phosgenation product of the undistilled bottom 
fraction of the type produced during the removal of from 25 to 90% by 
weight, preferably from 30 to 85% by weight, of 2,2'-, 2,4'- and/or 
4,4'-diamino diphenylmethane from an aniline/formaldehyde condensate, or 
to use an undistilled bottom fraction of the type obtained during the 
removal of from 25 to 90% by weight, preferably from 30 to 85% by weight, 
of 2,2'-, 2,4'- and/or 4,4'-diisocyanato-diphenylmethane from the crude 
phosgenation product of an aniline/formaldehyde condensate. These 
preferred polyisocyanates contain from 35 to 70% by weight, preferably 
from 45 to 60% by weight, of diisocyanato-diphenylmethanes, the content of 
2,4'-diisocyanato-diphenyl methane amounting to from 1 to 8% by weight, 
preferably from 2 to 5% by weight, and the content of 
2,2'-diisocyanato-diphenylmethane amounting to from 0 to 2% by weight. 
These preferred polyisocyanates have viscosities at 25.degree. C. of from 
50 to 600 mPas, preferably from 200 to 500 mPas, and an NCO content of 
from 28 to 32% by weight. 
Suitable bottom fractions can be obtained, for example, during the removal 
of from 45 to 90% by weight, preferably from 55 to 85% by weight, of 
4,4'-diisocyanato-diphenylmethane from a crude diphenylmethane 
diisocyanate containing more than 85% by weight, preferably more than 90% 
by weight, of 4,4'-diisocyanato-diphenylmethane. A crude diphenylmethane 
diisocyanate of this type may be obtained, for example, by the process in 
German Offenlegungsschrift No. 2,356,828. 
Another method involves distilling from 25 to 80% by weight, preferably 
from 30 to 60% by weight, of 2,4'-diisocyanato-diphenylmethane and 
optionally 4,4'- or 2,2'-diisocyanato-diphenylmethane from a crude 
phosgenation product containing from 60 to 90% by weight, preferably from 
65 to 75% by weight, of diisocyanato-diphenylmethane isomers which contain 
from 20 to 60% by weight, preferably from 30 to 40% by weight, of 
2,4'-isomers. In each case, distillation may be carried out in such a way 
that the residue has the desired composition. 
However, it is also possible (and in many cases, also simpler in practice) 
to obtain the desired isomer or oligomer composition of the polyphenyl 
polymethylene polyisocyanate by blending various bottom fractions. 
Examples of suitable raw materials containing lignocellulose which may be 
bound with the binders according to the invention include: wood, bark, 
cork, bagasse, straw, flax, bamboo, alfalfa, rice husks, sisal fibers and 
coconut fibers. However, pressed articles may also be produced according 
to the invention from other organic (for example, plastic scraps of 
various types) and/or inorganic raw materials (for example, expanded mica 
or silicate beads). In this case, the material may be present in the form 
of granules, shavings, fibers, beads or dust and may have a moisture 
content of, for example, from 0 to 35% by weight. 
It is possible, but less preferable, to apply the two components in the 
binder combination (polyisocyanate and sulfonic acid) separately to the 
material to be bonded, the components optionally being dissolved in an 
inert organic solvent. It is preferable to modify the polyisocyanate with 
the sulfonic acid in a separate operation. In this case, the sulfonic acid 
is used in a virtually anhydrous form (preferably having a water content 
of less than 0.1% by weight). From 0.5 to 20 equivalents, preferably from 
1 to 5 equivalents, of sulfonic acid groups are used per 100 equivalents 
of isocyanate groups. The components may be combined, for example, at from 
10.degree. to 90.degree. C., preferably from 20.degree. to 60.degree. C., 
optionally in the presence of an inert organic solvent such as hydrocarbon 
fractions. The resulting binder combinations, which has a self-releasing 
effect, are stable in storage and may be used when required in the process 
of the invention. 
The organic and/or inorganic material to be bonded is reacted with the 
binder in a quantity of from about 0.5 to 20% by weight, preferably from 2 
to 12% by weight, based on the total mass of the molded article, and is 
pressed into panels or three-dimensional, shaped articles, generally under 
the influence of heat and pressure (for example, from 70.degree. to 
250.degree. C. and from 1 to 150 bar). 
Similarly, multilayered panels or shaped articles may be produced from 
veneers, paper or fabrics by treating the layers with the binder in the 
manner described above and then pressing them generally at elevated 
temperatures and elevated pressure. Preferably temperatures of from 
100.degree. to 250.degree. C., more preferably from 130.degree. to 
200.degree. C., are maintained. The initial pressure is preferably from 5 
to 150 bar and the pressure generally falls towards 0 in the course of the 
pressing operation. 
According to the present invention, the polyisocyanates which have been 
modified with sulfonic acids may also be used as binders in combination 
with the polyhydroxyl compounds described above in an NCO:OH ratio of from 
1.2:1 to 10:1, preferably from 1.5:1 to 1:1. In this case, it is possible 
to use the two components separately or as a reactive mixture. These 
combinations of polyisocyanate and polyhydroxyl compounds are of practical 
importance as binders, for example in the bonding of granulated cork. It 
is also possible to add known blowing agents in a quantity of from about 
0.5 to 30% by weight, based on binder or impregnation material. 
Additionally, other additives which influence the formation of foam during 
the chemical reaction between polyisocyanates, material containing 
lignocellulose and optionally polyhydroxyl compounds such as stabilizers, 
catalysts and other known additives may be used in a quantity of from 0.05 
to 10% by weight, based on binder or impregnation agent. 
The binders of the invention may also be combined with the aqueous 
solutions of condensation products of formaldehyde with urea and/or 
melamine and/or phenol which have been used predominantly up until now in 
the timber industry. It is also possible to use the binders of the 
invention with other less common binders and impregnation agents such as 
those based on polyvinyl acetate or other plastic latices, sulfite waste 
liquor or tannin. A mixing ratio of the binders according to the present 
invention with these additional binders is generally maintained at from 
1:20 to 20:1, preferably from 1:5 to 5:1. The polyisocyanate mixtures and 
the additional binders may be used either separately or in admixture. 
These combinations are particularly advantageous in the production of 
multilayered panels having specialized properties. For example, the outer 
layers may be reacted with polyisocyanate mixtures in accordance with the 
present invention (alone or together with conventional adhesives) and one 
or more internal layers with conventional adhesives (alone or together 
with the polyisocyanate mixtures) and then pressed together. 
The panels or shaped articles based on raw materials containing 
lignocellulose produced using the process of the invention are 
particularly suitable for use in the construction industry due to their 
excellent mechanical properties as well as their desirable behavior during 
changes in humidity. In order to impart to the panels or shaped articles 
resistance to attack by fungus or insects or to the effects of fire, it is 
possible to add to the binders conventional organic or inorganic 
protectants in pure form or in solution form in a quantity of from about 
0.05 to 30% by weight, preferably from 0.5 to 20% by weight, based on raw 
materials containing lignocellulose. Suitable solvents include water or 
organic solvents such as residual oils from petroleum refining, 
chlorinated hydrocarbons etc. Bonding quality is not generally impaired by 
the solvents. In contrast to panels which have been bonded with 
phenol/formaldehyde resin, neither efflorescence of salt nor "bleeding" 
occur with the materials produced according to the invention. 
The mixtures used according to the invention provide substantial advantages 
over conventional binders based on phenol/formaldehyde or 
urea/formaldehyde resins during the production of chip boards both with 
respect to mechanical properties and to processing. Thus, in the case of 
wood chip boards, it is possible either to achieve a flexural strength 
which is increased by up to 50% with the same quantity of binder, in the 
case of phenol/formaldehyde or urea/formaldehyde resins (in addition to an 
improvement in other mechanical properties) or to achieve the same 
mechanical property spectrum with a binder concentration which is reduced 
by from 25 to 70%. These optimum material properties are achieved, in 
particular, if a polyphenyl polymethylene polyisocyanate having the 
viscosity and isomer distribution described above are used as binders. 
It does not matter whether the polyisocyanate mixture has been produced by 
distilling off 2,2'- and/or 4,4'-diisocyanato-diphenylmethane from crude 
diphenylmethane diisocyanate or similarly by separating pure 
diamino-diphenylmethane from crude diamino-diphenylmethane and then 
phosgenating the undistilled bottom fraction of polyarylamines thus 
obtained. 
If the polyisocyanate contains more than 75% by weight of 
diisocyanato-diphenylmethanes, the physical properties of the chip board 
are impaired considerably. On the other hand, if the content of 
diisocyanato-diphenylmethane falls to below 35% by weight, the binder 
generally becomes to viscous at room temperature and may no longer be 
mixed uniformly with the raw material containing lignocellulose on 
conventional bonding machines. 
The following Examples illustrate the present invention. Numerical 
quantities are to be interpreted as parts by weight or percentages by 
weight unless otherwise indicated. 
The following polyisocyanate components have been used in the Examples: 
A 1: Sufficient diisocyanato-diphenylmethane is distilled from the crude 
phosgenation product of an aniline/formaldehyde condensate for the 
distillation residue to have a viscosity of 100 cP at 25.degree. C. 
(2-nuclear content: 59.7%; 3-nuclear content: 21.3%; content of higher 
nuclear polyisocyanates: 19.0%). 
A 2: Polyisocyanates were produced similarly to A 1 but having a viscosity 
of 200 cP at 25.degree. C. (2-nuclear content: 44.3%; 3-nuclear content: 
23.5%; content of higher nuclear polyisocyanates: 32.2%). 
A 3: Polyisocyanates were produced similarly to A 1 but having a viscosity 
of 400 cP at 25.degree. C. (2-nuclear content: 45.1%; 3-nuclear content: 
22.3%; content of higher nuclear polyisocyanates: 32.6%). 
A 4: Polyisocyanates were produced similarly to A 1 but having a viscosity 
of 300 cP at 25.degree. C. (2-nuclear content: 56.8%; 3-nuclear content: 
27.6%; content of higher nuclear polyisocyanates: 15.6%). 
The commercial alkyl benzene sulfonic acid, MARLON.RTM.AS.sub.3 (commercial 
product made by the firm Chemische Werke Huls AG) was used as sulfonic 
acid in the Examples. 
Component distribution of the sulfonic acid: 
C.sub.10 about 5% by weight 
C.sub.11 about 45-50% by weight 
C.sub.12 about 35-40% by weight 
C.sub.13 about 10-15% by weight 
C.sub.14 about 1% by weight.

EXAMPLES 
EXAMPLE 1 
900 g of polyisocyanate A 2 are placed in a reaction vessel. The sulfonic 
acid is added dropwise over a period of 30 minutes at from 20.degree. to 
30.degree. C. with stirring. The mixture is stirred for a further hour at 
50.degree. C. and a product having an NCO content of 28.1% and a viscosity 
of 600 cP/25.degree. C. is obtained. The products shown in Table I below 
were similarly obtained: 
TABLE I 
______________________________________ 
Ex- Iso- Sub- NCO 
am- cyanate Sulfonic Temp. sequent 
% by Viscosity 
ple (g) acid (g) (.degree.C.) 
stirring 
weight 
(cp/25.degree. C.) 
______________________________________ 
1 900 A 2 100 20-30 1 hour 
28.1 600 
50.degree. C. 
2 950 A 4 50 20-30 1 hour 
28.5 800 
50.degree. C. 
3 970 A 2 30 20-30 1 hour 
29.1 300 
25.degree. C. 
4 900 A 2 100 80 1 hour 
28.0 700 
80.degree. C. 
5 900 A 1 100 20-30 1 hour 
28.2 400 
50.degree. C. 
6 950 A 2 50 50 1 hour 
28.6 600 
50.degree. C. 
7 900 A 4 100 20-30 1 hour 
27.0 1500 
50.degree. C. 
______________________________________ 
EXAMPLE 8 
3000 parts of an industrially produced mixture of coniferous/deciduous 
timber chips having a moisture content of 10% are mixed with 164 parts of 
the product according to Example 1. A molding is formed from the material 
on a steel sheet which is pressed for two minutes at a hot plate 
temperature of 170.degree. C. and a starting pressure of 25 bar. 
The chip board obtained releases itself from the sheet and the heating 
plate spontaneously and is completely equivalent in its mechanical 
properties to a chip board which has been produced using the same quantity 
of the unmodified isocyanate A 2. 
EXAMPLE 8A: COMISON 
An alternative experiment was carried out to produce a chip board using the 
unmodified isocyanate A 2 by the process described in Example 8. In 
contrast, the sheets adhered so strongly to the chip board that the sheets 
could not be removed without damaging the chip board. 
EXAMPLE 9 
12,000 parts of wood chips having a 9% moisture content are wetted with 440 
parts of the product from Example 2. A transporting pallet is produced 
from the material under pressure and heat in a refined steel mold and may 
be removed easily once the press has been opened. The product is far 
superior in mechanical properties to a pallet which is bonded using a 
conventional urea/formaldehyde resin. 
EXAMPLE 10 
3000 parts of comminuted wheat straw are reacted with a mixture of 60 parts 
of the product from Example 3, 480 parts of a 65% aqueous 
urea/formaldehyde resin (1:1.4) and 20 parts of a 1% solution in white 
spirit of the insecticide 
hexachloroepoxyoctahydroendo-exodimethanonaphtalene. A molding is formed 
from the material on an aluminum sheet by air separation and is cured at 
200.degree. C. hot plate temperature under pressure. 
A chip board is obtained which is generally equal to a conventional 
commercial wooden chip board but is superior in its flexural and edge 
strength. The panel releases itself from the sheet and heating plate 
spontaneously after the pressing operation and is protected from damage by 
insects. 
EXAMPLE 11 
1000 parts of surface layer chips made of coniferous wood having a moisture 
content of 20% are wetted with 58 parts of the product from Example 4. In 
addition, 2000 parts of middle layer chips which have been treated with 
160 parts of water and 17 parts of potassium hydrogen fluoride are wetted 
with 110 parts of the unmodified polyisocyanate A 3. A three-layered 
molding is formed from the materials on a steel screen and is then cured 
at 130.degree. C. under pressure. The panel obtained releases itself 
readily from the steel sheet and the heating plate and exhibits durable 
resistance to the attack of wood-destroying fungi in addition to excellent 
strength. 
EXAMPLE 12 
Five beech veneers of 1 mm thickness having a moisture content of 7% are 
immersed in a mixture of 95 parts of the product according to Example 7 
and five parts of N-methyl-pyrrolidone. After a short draining time, the 
veneers are positioned on top of each other in criss-cross fashion between 
steel sheets not previously treated with release agent and cured at 
140.degree. C. under pressure. A weather-resistant, improved plywood board 
of high quality is obtained which releases itself from the sheets without 
difficulties after the pressing operation. 
EXAMPLE 13 
3000 parts of expanded mica having a moisture content of 8% are wetted with 
167 parts of the product according to Example 5. A molding is formed from 
it on an aluminum sheet and is pressed for 8 minutes at 150.degree. C. A 
fireproof panel which readily releases itself from the sheet and heating 
plate after the pressing operation is obtained.