Gel compounds, their production and use

Improved gel compounds based on reaction products of polyols and polyisocyanates are characterized in that the polyol component consists of a mixture of a) one or more polyols having hydroxyl values below 112 and b) one or more polyols having hydroxyl values of 112 to 600 and in that the isocyanate index of the reaction mixture is in the range from 15 to 70. They may be used as pressure-distributing elements.

This invention relates to improved gel compounds based on polyols and 
polyisocyanates, to a process for the production of these gel compounds 
and to their use in pressure-distributing elements. 
Known gel compounds for use in pressure-distributing elements, for example 
in cushions for wheelchairs, are based above all on polyvinyl chloride, 
polyorganosiloxanes and polyurethanes, i.e. reaction products of polyols 
and polyisocyanates. Gel compounds based on polyurethanes of the type 
described in EP-A 0 057 838 have proved to be particularly advantageous 
for specific adaptation of their properties to the particular application 
envisaged. 
Polyurethane gels of this type, which may be obtained from polyols of 
relatively high molecular weight and polyisocyanates, have the 
disadvantange that the two reaction components have to be mixed with one 
another in very different quantities. Accordingly, where the gels are 
produced by machine, the polyisocyanate component which is used in 
relatively small quantities has to be metered very accurately and with 
only minimal variations, otherwise gel compounds of variable consistency 
are obtained. In addition, it is virtually impossible for the components 
to be homogeneously mixed in such mixing ratios. This applies in 
particular where the machines used are so-called high-pressure machines 
where the mixing times are only fractions of a second. Finally, the very 
different viscosities of the two reaction components also make it 
difficult to obtain a homogeneous reaction mixture. Inhomogeneous reaction 
mixtures naturally lead to non-uniform gel compounds. 
Another disadvantage of the known polyurethane gel compounds is their 
limited structural strength under particular stressing, for example in the 
form of the flexural and shear stressing applied to pressure-distributing 
gel overlays on hospital beds. 
Improved gel compounds based on reaction products of polyols and 
polyisocyanates have now been found and are characterized in that the 
polyol component consists of a mixture of 
a) one or more polyols having hydroxyl values below 112 and 
b) one or more polyols having hydroxyl values in the range from 112 to 600 
and in that the isocyanate index of the reaction mixture is in the range 
from 15 to 70. 
The gel compounds according to the invention are generally water-free. 
The isocyanate index is the equivalent ratio (NCO/OH) .times.100. For 
example, an isocyanate index of 15 means that, for one reactive OH group 
in the polyols, there are 0.15 reactive NCO groups in the polyisocyanate 
or, for one reactive NCO group in the polyisocyanate, there are 6.67 
reactive OH groups in the polyols. Accordingly, an isocyanate index of 70 
means that, for one reactive OH group in the polyols, there are 0.7 
reactive NCO groups in the polyisocyanate or, for one reactive NCO group 
in the polyisocyanate, there are 1.43 reactive NCO groups in the polyols. 
Polyols having a hydroxyl value below 112 may also be referred to as 
relatively high molecular weight polyols while polyols having a hydroxyl 
value of 112 to 600 may also be referred to as low molecular weight 
polyols. 
The ratio by weight of relatively high molecular weight polyols to low 
molecular weight polyols may be, for example, between 90:10 and 10:90 and 
is preferably between 85:15 and 50:50. 
In addition, gel compounds according to the invention may optionally 
contain fillers and/or additives known per se from polyurethane chemistry, 
for example in total quantities of up to 50% by weight, based on the total 
weight of the gel compound. 
The present invention also relates to a process for the production of gel 
compounds which is characterized in that a mixture of 
a) one or more polyisocyanates and 
b) a polyol component consisting of 
one or more polyols having hydroxyl values below 112 and 
one or more polyols having hydroxyl values in the range from 112 to 600 and 
c) optionally a catalyst for the reaction between isocyanate and hydroxyl 
groups and 
d) optionally fillers and/or additives known per se from polyurethane 
chemistry, 
the isocyanate index of the mixture being between 15 and 70, is allowed to 
gel. 
The polyols used may contain primary and/or secondary hydroxyl groups. 
Where mixtures of polyols containing primary and secondary hydroxyl groups 
are used, it has been found that the primary hydroxyl groups react 
preferentially with the isocyanate component. In this case, only the 
primary hydroxyl groups of the polyol component could be taken into 
consideration for the expression "functionality of the polyol component". 
However, all the hydroxyl groups of the polyol component have to be used 
for calculating the isocyanate index in the context of the present 
invention. 
In the production of gel compounds according to the invention, the product 
of the isocyanate functionality and the functionality of the polyol 
component should be at least 5.2 and is preferably at least 6.5 and, more 
preferably, at least 7.5. 
In addition to its function as a synthesis component for the polyurethane 
matrix, the polyol component also acts as a dispersant. The polyols to be 
used in accordance with the invention are preferably the 
polyhydroxypolyesters, polyethers, polythioethers, polyacetals, 
polycarbonates, polyester amides, polyamides or polybutadienes known per 
se in polyurethane chemistry which are liquid at 10.degree. to 60.degree. 
C. and which have hyroxyl values in the ranges mentioned above. 
The polyhydroxypolyesters may be, for example, reaction products of 
polyhydric, preferably dihydric and, optionally, trihydric alcohols with 
polybasic, preferably dibasic, carboxylic acids. Instead of the free 
polycarboxylic acids, the corresponding polycarboxylic anhydrides or 
corresponding polycarboxylic acid esters of lower alcohols or mixtures 
thereof may have been used for the production of the polyester. The 
polycarboxylic acids may be aliphatic, cycloaliphatic, aromatic and/or 
heterocyclic and may optionally be substituted, for example by halogen 
atoms, and/or unsaturated. 
The following are examples of such carboxylic acids, anhydrides and esters: 
succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, 
phthalic acid, isophthalic acid, trimellitic acid, phthalic anhydride, 
tetrahydrophthalic anhydride, hexahydrophthalic anhydride, 
tetrachlorophthalic anhydride, endomethylene tetrahydrophthalic anhydride, 
glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimerized 
and trimerized unsaturated fatty acids (optionally in admixture with 
monomeric unsaturated fatty acids, for example oleic acid), terephthalic 
acid dimethyl ester and terephthalic acid bis-glycol ester. Suitable 
polyhydric alcohols are, for example, ethylene glycol, 1,2- and 
1,3-propylene glycol, 1,4-, 1,3- and 2,3-butylene glycol, hexane-1,6-diol, 
octane-1,8-diol, neopentyl glycol, 1,4-bis-hydroxymethyl cyclohexane, 
2-methylpropane-1,3-diol, glycerol, trimethylol propane, 
hexane-1,2,6-triol, butane-1,2,4-triol, trimethylol ethane, 
pentaerythritol, quinitol, mannitol, sorbitol, formitol, methyl glycoside, 
diethylene glycol, triethylene glycol, higher polyethylene glycols, 
dipropylene glycol, higher polypropylene glycols, dibutylene glycol and 
higher polybutylene glycols. The polyesters may contain terminal carboxyl 
groups. Polyesters of lactones, for example .epsilon.-caprolactone, or of 
hydroxycarboxylic acids, for example .omega.-hydroxycaproic acid, may also 
be used. 
The polyhydroxypolyethers may be, for example, polyethers containing at 
least two, generally two to eight and preferably three to six hydroxyl 
groups. Polyhydroxypolyethers such as these are known per se and may be 
produced, for example, by polymerization of epoxides, such as ethylene 
oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide 
and/or epichlorohydrin on their own, for example in the presence of Lewis 
catalysts, such as BF.sub.3, or by addition of these epoxides, preferably 
ethylene oxide and/or propylene oxide, in admixture or successively (where 
two or more epoxides are used), onto starter components containing 
reactive hydrogen atoms, such as water, alcohols, ammonia or amines, for 
example ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 
trimethylol propane, glycerol, sorbitol, 4,4'-dihydroxydiphenyl propane, 
aniline, ethanolamine or ethylenediamine. Sucrose polyethers, for example 
of the type described in DE-AS 1 176 385 and in DE-AS 1 064 938, and 
formitol- or formose- started polyethers (see DE-OS 2 639 083 and DE-OS 2 
737 951) may also be used. 
Other suitable polyols are OH-functional polybutadienes. 
Among the polyhydroxypolythioethers, the condensation products of 
thiodiglycol on its own and/or with other glycols, dicarboxylic acids, 
formaldehyde, aminocarboxylic acids and/or aminoalcohols are of particular 
interest. Depending on the co-components, the products are, for example, 
polythio mixed ethers, polythioether esters or polythioether ester amides. 
Suitable polyhydroxypolyacetals are, for example, the compounds obtainable 
from glycols, such as diethylene glycol, triethylene glycol, 
4,4'-dioxyethoxydiphenyl dimethyl methane and hexanediol with 
formaldehyde. Polyacetals suitable for the purposes of the invention may 
also be obtained by polymerization of cyclic acetals, for example trioxane 
(see DE-OS 1 694 128). 
Suitable polyhydroxypolycarbonates are, for example, types known per se 
which may be obtained, for example, by reaction of diols, such as 
propane-1,3-diol, butane-1,4-diol, hexane-1,6-diol, diethylene glycol, 
triethylene glycol, tetraethylene glycol and/or thiodiglycol, with diaryl 
carbonates, for example diphenyl carbonate, or phosgene (see DE-AS 1 694 
080, DE-AS 1 915 908, DE-AS 2 221 751 and DE-OS 2 605 024). 
The polyhydroxypolyester amides and polyamides may be, for example, the 
predominantly linear condensates obtained from polybasic saturated or 
unsaturated carboxylic acids or anhydrides thereof and polyfunctional 
saturated or unsaturated aminoalcohols, diamines, polyamines and mixtures 
thereof. 
Polyhydroxyl compounds already containing urethane or urea groups and 
optionally modified natural polyols, such as castor oil, may also be used 
as polyol component in the process according to the invention. 
In addition, polyhydroxyl compounds containing high molecular weight 
polyadducts, polycondensates or polymers in finely disperse or dissolved 
form may optionally be used as the polyol component. Polyhydroxyl 
compounds such as these may be obtained, for example, by carrying out 
polyaddition reactions (for example reactions between polyisocyanates and 
aminofunctional compounds) or polycondensation reactions (for example 
between formaldehyde and phenols and/or amines) in situ in the. 
hydroxyfunctional compounds mentioned above. Processes such as these are 
described, for example, in DE-AS 1 168 075, DE-AS 1 260 142 and in DE-OSS 
2 324 134, 2 423 984, 2 512 385, 2 513 815, 2 550 796, 2 550 797, 2 550 
833, 2 550 862, 2 633 293 and 2 639 254. It is also possible to use high 
molecular weight polyhydroxyl compounds containing polyadducts, 
condensates or polymers which are obtained by mixing an aqueous polymer 
dispersion with a polyhydroxyl compound and subsequently removing the 
water from the mixture (see U.S. Pat. No. 3,869,413 and DE-OS 2 550 860). 
Polyhydroxyl compounds modified by vinyl polymers, of the type obtainable 
for example by polymerization of styrene and acrylonitrile in the presence 
of polyethers (see U.S. Pat. Nos. 3,383,351, 3,304,273, 3,523,093 and 
3,110,695 and DE-AS 1 152 536) or polycarbonate polyols (see DE-PS 1 769 
795 and U.S. Pat. No. 3,637,909), are also suitable as polyol component 
for the process according to the invention. Where polyether polyols 
modified by graft polymerization with vinyl phosphonic acid esters and, 
optionally, (meth)acrylonitrile, (meth)acrylamide or OH-functional 
(meth)acrylates in accordance with DE-OSS 2 442 101, 2 644 922 and 2 646 
141 are used, gel compounds having particularly pronounced flame 
resistance are obtained. 
Polyol components suitable for use in accordance with the invention are 
described, for example, in High Polymers, Vol. XVI, "Polyurethanes, 
Chemistry and Technology", edited by Saunders-Frisch, Interscience 
Publishers, New York/London, Vol. I, (1962), pages 32-42 and pages 44-54 
and Vol. II (1964), pages 5-6 and 198-199 and in Kunststoff-Handbuch, Vol. 
VII, Vieweg-Hochtlen, Carl-Hanser-Verlag, Mnchen (1966), for example on 
pages 45-71. Mixtures of the above-mentioned compounds, for example 
mixtures of polyethers and polyesters, may of course also be used. 
According to the invention, the above-mentioned polyhydroxypolyethers known 
per se in polyurethane chemistry containing 2 to 8 and preferably 3 to 6 
hydroxyl groups per molecule are preferably used as the polyol component. 
Particularly preferred polyhydroxypolyethers--optionally in admixture with 
other polyethers--are those which at least terminally contain ethylene 
oxide units and hence primary hydroxyl groups. The percentage content of 
ethylene oxide sequences in polyethers to be used in accordance with the 
invention is preferably at least 15% by weight and, more preferably, at 
least 20% by weight. 
The polyisocyanates used for the production of gel compounds in accordance 
with the invention are, for example, aliphatic, cycloaliphatic, 
araliphatic, aromatic and/or heterocyclic polyisocyanates of the type 
described, for example, by W. Siefken in Justus Liebigs Annalen der 
Chemie, 562, pages 75 to 136, for example those corresponding to the 
following formula 
EQU Q(NCO).sub.n 
in which 
n=2 to 4, preferably 2, and 
Q is an aliphatic hydrocarbon radical containing 2 to 18 and preferably 6 
to 10 carbon atoms, a cycloaliphatic hydrocarbon radical containing 4 to 
15 and preferably 5 to 10 carbon atoms, an aromatic hydrocarbon radical 
containing 6 to 15 and preferably 6 to 13 carbon atoms or an araliphatic 
hydrocarbon radical containing 8 to 15 and preferably 8 to 13 carbon 
atoms. 
Individual compounds of this type are ethylene diisocyanate, 
1,4-tetramethylene diisocyanate, 1,6-hexamethylene 1,12-dodecane 
diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and 
-1,4-diisocyanate and mixtures of these isomers, 
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl cyclohexane (DE-AS 1 202 
785 and U.S. Pat. No. 3,401,190), 2,4- and 2,6-hexahydrotolylene 
diisocyanate and mixtures of these isomers, hexahydro-1,3- and/or 
-1,4-phenylene diisocyanate, perhydro-2,4'- and/or -4,4'-diphenyl methane 
diisocyanate, 1,3- and 1,4-phenylene diisocyanate, 2,4- and 2,6-tolylene 
diisocyanate and mixtures of these isomers, diphenylmethane-2,4'- and/or 
-4,4'-diisocyanate and naphthylene-1,5-diisocyanate. 
Other suitable polyisocyanates are, for example, 
triphenylmethane-4,4',4"-triisocyanate, polyphenyl polymethylene 
polyisocyanates of the type obtained by phosgenation of 
aniline-formaldehyde condensates and described, for example, in GB-PS 
874,430 and in GB-PS 848,671, m- and p-isocyanatophenyl sulfonyl 
isocyanates (see U.S. Pat. No. 3,277,138), polyisocyanates containing 
carbodiimide groups (see DE-PS 1 092 007, U.S. Pat. No. 3,152,162 and 
DE-OSS 2 504 400, 2 537 685 and 2 552 350), norbornane diisocyanates 
(according to U.S. Pat. No. 3,492,330), polyisocyanates containing 
allophanate groups (see GB-PS 994,890, BE-PS 761 626 and NL patent 
application 71 02 524), polyisocyanates containing isocyanurate groups 
(see U.S. Pat. No. 3,001,973, DE-PSS 1 022 789, 1 222 067 and 1 027 394, 
DE-OSS 1 929 034 and 2 004 048), polyisocyanates containing urethane 
groups (see BE-PS 752 261, U.S. Pat. No. 3,394,164 and U.S. Pat. No. 
3,644,457), polyisocyanates containing acylated urea groups (see DE-PS 1 
230 778), polyisocyanates containing biuret groups (see U.S. Pat. Nos. 
3,124,605 and 3,201,372 and GB-PS 889,050), polyisocyanates produced by 
telomerization reactions (see DE-PS 3 654 106), polyisocyanates containing 
ester groups (see GB-PSS 965,474 and 1,072,956, U.S. Pat. No. 3,567,763 
and DE-PS 1 231 688), reaction products of the above-mentioned isocyanates 
with acetals (see DE-PS 1 072 385) and polyisocyanates containing 
polymeric fatty acid esters (see U.S. Pat. No. 3,455,883). 
It is also possible to use the distillation residues containing isocyanates 
groups obtained in the industrial production of isocyanates, optionally 
dissolved in one or more of the above-mentioned polyisocyanateso. Mixtures 
of the above-mentioned polyisocyanates may also be used. 
Preferred isocyanates are, for example, 2,4- and 2,6-tolylene diisocyanate 
and mixtures of the isomers, polyphenyl polymethylene polyisocyanates of 
the type obtainable by phosgenation of aniline-formaldehyde condensates 
and polyisocyanates containing carbodiimide groups, urethane groups, 
allophanate groups, isocyanurate groups, urea groups or biuret groups. 
Particularly preferred polyisocyanates are biuretized or trimerized 
1,6-hexamethylene diisocynate, 
tripropylene-glycol-modifieddiphenylmethane-4,4'-diisocyanate, mixtures of 
polyphenyl polymethylene polyisocyanates and diphenylmethane-2,4'- and 
-4,4'-diisocyanates in which the binuclear component preferably makes up 
more than 70% by weight and the 2,4'-isomer content is more than 30%. 
The content of polyisocyanates in the mixtures to be produced in accordance 
with the invention for gel compounds is, for example, from 5 to 50% by 
weight and preferably from 10 to 35% by weight, based on the total weight 
of the polyol component and the polyisocyanates. 
The basically slow gel-forming reaction may optionally be accelerated by 
addition of catalysts. Suitable catalysts are catalysts known per se which 
accelerate the reaction between hydroxyl and isocyanate groups, for 
example tertiary amines, such as triethylamine, tributylamine, N-methyl 
morpholine, N-ethyl morpholine, N,N,N',N'-tetramethyl ethylenediamine, 
1,4-diazabicyclo-(2,2,2)-octane, N-methyl-N'-dimethylaminoethyl 
piperazine, N,N-dimethyl benzylamine, bis-(N,N-diethylaminoethyl)-adipate, 
N,N-dimethyl benzylamine, pentamethyl diethylenetriamine, N,N-dimethyl 
cyclohexylamine, N,N,N',N'-tetramethyl-1,3-butane diamine, 
N,N-dimethyl-.beta.-phenyl ethylamine, 1,2-dimethyl imidazole and 2-methyl 
imidazole. Other suitable catalysts are Mannich bases known per se of 
secondary amines, such as dimethylamine, and aldehydes, preferably 
formaldehyde, or ketones, such as acetone, methyl ethyl ketone or 
cyclohexanone, and phenols, such as phenol, nonylphenol or bisphenols. 
Other suitable catalysts are silaamines containing carbon-silicon bonds 
(see, for example DE-PS 1 229 290 and U.S. Pat. No. 3,620,984), for 
example 2,2,4-trimethyl-2-silamorpholine and 1,3-diethylaminomethyl 
tetramethyl disiloxane. 
Other suitable catalysts are nitrogen-containing bases, such as tetraalkyl 
ammonium hydroxides, alkali metal hydroxides, such as sodium hydroxide, 
alkali metal phenolates, such as sodium phenolate, or alkali metal 
alcoholates, such as sodium methylate. Hexahydrotriazines may also be used 
as catalysts. 
Organometallic compounds, more particularly organotin compounds, are also 
suitable catalysts. Preferred organotin compounds are tin(II) salts of 
carboxylic acids, such as tin(II) acetate, octoate, ethylhexoate, and 
tin(IV) compounds, for example dibutyl tin(IV) oxide, chloride, acetate, 
dilaurate, maleate or dioctyl tin acetate. 
Other catalysts and information on the way in which they work can be found 
in Kunststoff-Handbuch, Vol. VII, edited by Vieweg and Hochtlen, 
Carl-Hanser-Verlag Munchen 1966, for example on pages 96 to 102. 
Mixtures of different catalysts may also be used. 
The catalysts may be used, for example, in a quantity of 0.1 to 10% by 
weight, based on the total weight of the mixture used to produce the gel 
compounds. 
The fillers and/or additives known per se from polyurethane chemistry 
optionally present in the gel compounds according to the invention may be, 
for example, inorganic and/or organic fillers, coloring agents, 
water-binding agents, surface-active agents, plant protection agents, 
extending agents and/or plasticizers. 
Inorganic fillers may be, for example, heavy spar, chalk, gypsum, 
kieserite, soda, titanium dioxide, quartz sand, kaolin, carbon black, 
glass microbeads and hollow glass microbeads. Organic fillers may be, for 
example, powders based on polystyrene, polyvinyl chloride, 
urea-formaldehyde compounds and/or polyhydrazodicarbonamides (obtained, 
for example, from hydrazine and tolylene diisocyanate). For example, 
urea-formaldehyde resins or polyhydrazodicarbonamides may have been 
directly produced in one of the polyols to be used for the production of 
the gel compounds in accordance with the invention. Hollow microbeads of 
organic origin may also be added. 
Inorganic and/or organic fillers may also be used in the form of chopped 
strands. Suitable chopped strands are, for example, glass fibers and/or 
fibers of organic origin, for example polyester or polyamide fibers. The 
chopped strands may be, for example, from 0.01 to 1 cm long. Inorganic 
fillers may also be metal powders, for example iron or copper powder. 
The gel compounds according to the invention may contain organic and/or 
inorganic dyes and/or pigments known per se, for example iron oxide and/or 
chromium oxide pigments and phthalocyanine- and/or monoazo-based pigments, 
as coloring agents, for example for pigmenting polyurethanes. 
Preferred water-binding agents are zeolites. Suitable synthetic zeolites 
are commercially available, for example under the name Baylith.RTM.. 
Suitable surface-active agents are, for example, cellulose powder, active 
carbon and silica preparations. 
The flameproofing agents used may be, for example, sodium 
polymetaphosphates or amine phosphates, for example melamine phosphates. 
Suitable extending agents are, in particular, liquid, substantially inert 
substances which have a boiling point above 150.degree. C. (under normal 
pressure), for example alkyl-, alkoxy- and/or halogen-substituted aromatic 
compounds, such as dodecylbenzene, m-dipropoxybenzene and/or 
o-dichlorobenzene, halogenatd aliphatic compounds, such as chlorinated 
paraffins, organic carbonates, such as propylene carbonate, carboxylic 
acid esters, such as dioctyl phthalate, and also dodecyl sulfonic acid 
esters and organophosphorus compounds, such as tricresyl phosphate. 
Esters of polybasic, preferably dibasic, carboxylic acids with monohydric 
alcohols are mentioned as examples of plasticizers. The acid component of 
these esters may be derived, for example, from succinic acid, isophthalic 
acid, trimellitic acid, phthalic anhydride, tetra- and/or 
hexahydrophthalic anhydride, endomethylene tetrahydrophthalic anhydride, 
glutaric anhydride, maleic anhyride, fumaric acid and/or dimeric and/or 
trimeric fatty acids, such as oleic acid, optionally in admixture with 
monomeric fatty acids. The alcohol component of the esters may be derived, 
for example, from branched and/or unbranched aliphatic alcohols containing 
1 to 20 carbon atoms, such as methanol, ethanol, propanol, isopropanol, 
n-butanol, sec. butanol, tert. butanol, the various isomers of pentyl 
alcohol, hexyl alcohol, octyl alcohol (for example 2-ethyl hexanol), nonyl 
alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, 
stearyl alcohol, and/or from naturally occurring fatty and wax alcohols or 
from fatty and wax alcohols obtainable by hydrogenation of naturally 
occurring carboxylic acids. Other suitable alcohol components are 
cycloaliphatic and/or aromatic hydroxy compounds, for example cyclohexanol 
and homologs thereof, phenol, cresyl, thymol, carvacrol, benzyl alcohol 
and/or phenyl ethanol. 
Other suitable plasticizers are esters of the above-mentioned alcohols with 
phosphoric acid. Phosphoric acid esters of halogenated alcohols, such as 
trichloroethyl phosphate for example, may also be used. In their case, a 
flameproofing effect may be obtained simultaneously with the plasticizer 
effect. Mixed esters of the above-mentioned alcohols and carboxylic acids 
may of course also be used. 
The plasticizers may also be so-called polymeric plasticizers, for example 
polyesters of adipic, sebacic and/or phthalic acid. 
Alkyl sulfonic acid esters of phenol, for example paraffin sulfonic acid 
phenyl ester, may also be used as plasticizers. 
The content of fillers and/or additives in the gel compounds according to 
the invention and during their production may amount, for example, to a 
total of up to 50% by weight, based on the total weight of the gel 
compound. 
In one particular embodiment of the production of gel compounds in 
accordance with the invention, air or another gas may be introduced under 
pressure or stirred into the reaction mixture, for example in a quantity 
of up to 20% by weight, based on the gel compound. The gel compounds 
obtained in this way are lighter in weight. 
The gel compounds according to the invention may be used, for example, as 
pressure-distributing elements. To this end, the gel compounds generally 
have to be provided with a partial, one-sided or all-round coating, 
covering or envelope. 
In applications where the specifically variable adhesiveness of the gel 
compounds is to be utilized, for example in padding for human or animal 
body surfaces, the gel compounds need only be coated or covered partially 
or on one side. This is particularly the case where the gel compounds are 
used for disposable articles. 
In many applications, all-round, i.e. complete, envelopment of the gel 
compound is necessary for hygienic reasons. To enable the gel compounds 
fully to develop their pressure-distributing effect, it is of advantage to 
use elastic, extensible envelope materials for this purpose. Particularly 
suitable materials of this type are elastic films, for example polymer 
films which combine good tough and resilient behavior (as measured, for 
example, in the biaxial penetration test according to DIN 55 373) with 
high elongation at break and ultimate tensile strength (as measured for 
example, in accordance with DIN 53 455). 
Such films may be, for example the polyurethane films marketed under the 
names Walopur.RTM. by Wolff-Walsrode and Platilon.RTM. by Plate. Other 
suitable films may have been produced from thermoplastic polyester 
elastomers (for example Hytrel.RTM., a product of DuPont) or from styrene- 
and butadiene-based block copolymers, optionally in admixture with 
polyolefins. Suitable styrene-based block copolymers are, for example, the 
products marketed by Shell under the name Cariflex.RTM.. 
Styrene/ethylene/butylene/stryene block copolymers are also suitable. 
Block copolymers such as these are marketed, for example, by Shell under 
the name Kraton.RTM.. Other suitable films are films of ethylene/vinyl 
acetate polymers, optionally in conjunction with other polymer films, and 
also thin films or natural or synthetic rubber materials. Films of 
plasticized polyvinyl chloride may also be used. 
These films may be thermoformed, welded or bonded. Accordingly, it is 
particularly simple to make these films into suitable envelopes for 
pressure-distributing elements containing gel compounds according to the 
invention. 
In one particular embodiment, envelopes for gel compounds according to the 
invention may also be obtained by welding or bonding a surface film to 
thermoformed articles of the above-mentioned films or by bonding or 
welding to thermoformed half-shells of these films to one another. 
Other suitable envelopes are coated, elastic flat textiles, such as woven 
fabrics, knitted fabrics or nonwovens of natural or synthetic, organic or 
inorganic fibers of elastic character which show high elongation at break 
and ultimate tensile strength (according to DIN 53 455). Suitable coatings 
for these elastic textile materials are, for example, elastic polyurethane 
coatins of the type marketed, for example, by Bayer AG under the name 
Impranil.RTM.. Coatings based on plasticized polyvinyl chloride are also 
possible. 
The coated textile materials may be stitched, bonded or welded. 
Accordingly, it is particularly simple to make suitable envelopes for the 
gel compounds according to the invention from coated flat textile 
materials. 
The gel compounds according to the invention may also be enveloped by 
application to the surface of the gel compound of a liquid or dissolved 
material which solidifies to an elastic material on the surface and can be 
subjected there to another film-forming process. Particularly suitable 
coating materials for this purpose are polyurethane-based materials of the 
type marketed, for example by Bayer AG under the name Impranil.RTM. which 
may be applied in solution or dispersion to a gel compound according to 
the invention and, after removal of the solvent or dispersant, form a 
suitable elastic envelope. 
Suitable flexible envelopes may also be obtained by coating the gel 
compound with a polyurethane-forming two-component lacquer. 
The production of gel compounds in accordance with the invention may be 
carried out in various ways. 
For example, they may be produced by the one-shot process or by the 
prepolymer process. In the one-shot process, all the components, for 
example polyols, polyisocyanates, catalyst, if any, and optionally fillers 
and/or additives, may be combined all at once and intensively mixed. 
If the prepolymer process is used, it may be carried out in two ways. 
Either an isocyanate prepolymer is initially prepared by reaction of part 
of the polyol with the total quantity of polyisocyanate required to form 
the gel and the rest of the polyol and, optionally, catalyst, fillers 
and/or additives are then added to and intensively mixed with the 
prepolymer obtained. It is also possible initially to react the total 
quantity of polyol required to form the gel with part of the 
polyisocyanate to form a hydroxyl prepolymer and subsequently to add the 
rest of the isocyanate and the optional components. 
A variant of the one-shot process in combination with the hydroxyl 
prepolymer process is particularly advantageous. In this variant, the 
polyol mixture, the catalyst and/or fillers and/or additives, if any, and 
two different polyisocyanates are combined all at once and intensively 
mixed. One of the polyisocyanates is aromatic, the other aliphatic. On 
account of the considerable difference in the reactivity of these two 
polyisocyanates, a hydroxyl prepolymer is initially formed from the polyol 
as a whole and the more reactive polyisocyanate and subsequently reacts 
with the less reactive polyisocyanate, generally within a few minutes, to 
form the gel. Particularly tough gel compounds are obtained in this way. 
In all these processes, individual components or mixtures of components may 
be transported, metered and mixed by the units known per se in 
polyurethane chemistry. 
Pressure-distributing elements containing the gel compounds according to 
the invention may be produced in various ways. For example, the gel 
compounds may initially be produced in a mold and the gel compound, which 
is pressure-resistant after fully reacting, may be covered with a flexible 
film or flexible material or lacquered or coated. In a particularly 
preferred and very simple procedure, the components required to produce 
the gel compound may be mixed in a mechanical mixer and the resulting 
mixture may be directly poured into an envelope of an elastic, flexible 
film or an elastic, coated flat textile material. 
After addition of the mixture, the envelope may be tightly closed and the 
gel-forming reaction left to take place therein. The envelope may be 
placed between two planoparallel plates or introduced into another mold 
during formation of the gel. In this case, the pressure-distributing 
element formed has substantially parallel upper and lower surfaces or a 
shape corresponding to the inside of the mold used. Depending on the type 
of reaction components used, the catalysts added and the temperature 
profile, the time taken to complete gel formation may be, for example, 
between 1 minute and 12 hours. The temperature of the components used is 
preferably in the range from 10.degree. to 60.degree. C. 
This particularly preferred procedure enables pressure-distributing 
elements of any shape and size to be produced simply by forming the 
envelopes in the corresponding mold by generally known methods and filling 
them with the compound formed. Particularly shapes and sizes are square 
and rectangular cushions having an edge ledge length of, for example, 20 
to 60 cm. 
The thickness of the pressure-distributing elements may also be varied 
within wide limits. Where the pressure-distributing elements are used as 
seat cushions, generally square in shape with an edge length of 35 to 45 
cm, the best results are obtained with thicknesses of more than 2 cm. 
Where the pressure-distributing elements are used as mattresses, mattress 
inlays or mattress overlays, smaller thicknesses may be of advantage. 
In applications where a self-adhesive gel compound according to the 
invention is placed directly on the body surface of human beings or 
animals, thicknesses of the gel layers of 1 mm to 2 cm are generally of 
advantage. 
The gel compounds according to the invention have the property of deforming 
under pressure and, in doing so, distributing the pressure, i.e. 
flattening pressure peaks, and returning to their original state after 
removal of the deforming force. The effect of this property is that 
pressure-distributing elements containing gel compounds according to the 
invention are capable of deforming under the pressure of a person lying or 
sitting on them to such an extent that any pressure sores are avoided or 
existing sores heal more quickly. 
Pressure-distributing elements containing gel compounds according to the 
invention may be used in various ways, for example as gel cushions in 
orthopedic shoes and sports shoes, on motorcycle saddles, under riding 
saddles, on wheelchairs and hospital beds, on seat cushions, back cusions, 
headrests and armrests of chairs, car seats and other seats, on operating 
tables or medical examination tables or in incubators. 
In addition, pressure-distributing elements which consist of a gel compound 
according to the invention covered or coated on one side and which show 
high adhesive strength may be used, in particular, on body surfaces of 
human beings and animals, for example as pads on elbows, shin bones or 
feet for avoiding and reducing the effects of injuries, particularly in 
sport; as pads for cosmetic masks, for example face masks, as 
self-adhesive coverings for eye or ear bandages for fastening purposes; as 
padding for supporting sagging breast tissue; as padding under riding 
saddles, on prostheses or on sanitary napkins for preventing pressure 
points. 
The present invention provides gel compounds which can be made by machine 
more easily than before and which show higher structural strength than 
hitherto known gel compounds. 
The invention is illustrated by the following Examples.

EXAMPLES 
General 
The following polyisocyanates, polyols and catalysts were used in the 
Examples: 
Polyisocyanate 1 
4,4'-Diisocyanatodiphenyl methane liquefied by prepolymerization with 
tripropylene glycol: average NCO functionality 2.05, NCO content 23% by 
weight. 
Polyisocyanate 2 
Commercially available biuretized 1,6-hexamethylene diisocyanate: average 
NCO functionality 3.6, NCO content 21% by weight, average molecular weight 
(number average) 700. 
Polyisocyanate 3 
Technical polyisocyanate isomer mixture obtained by phosgenation of 
aniline/formaldehyde condensates (binuclear content 90% by weight, content 
of 2,4-isomers 45% by weight) and modified with a mixture of lower 
propylene glycols: NCO content 24.5% by weight. 
Polyols 1 to 4 
These polyols are polyether polyols obtained by addition of ethylene oxide 
and propylene oxide onto a starter molecule. The are listed in the 
following Table. TMP stands for trimethylol propane. 
______________________________________ 
Propylene Ethylene 
Polyol 
oxide % oxide % Starter 
OH OH func- 
No. by weight by weight molecule 
value tionality 
______________________________________ 
1 3 97 TMP 250 3 
2 18 82 Sorbitol 
100 6 
3 45 55 TMP 56 3 
4 83 17 TMP 35 3 
______________________________________ 
Polyol 5 
Polyester of adipic acid, butane-1,3-diol and butane-1,4-diol: hydroxyl 
value 54. 
Catalyst 1 
1,4-diazabicyclo-(2,2,2)-octane in the form of a 33% by weight dispersion 
in dipropylene glycol. 
Catalyst 2 
Di-n-butyl tin(IV) dilaurate. 
In the following, parts are parts by weight. 
EXAMPLE 1 
420 Parts polyisocyanate 3 were added to and homogeneously mixed with a 
mixture of 600 parts polyol 1, 1,050 parts polyol 3 and 1,350 parts polyol 
4. 10 Parts of catalyst 1 were added to the resulting mixture and 
thoroughly dispersed therein by intensive stirring for 30 seconds. The 
reaction mixture obtained was immediately poured into a 40.times.40 cm 
envelope of 0.2 mm thick polyurethane film. The film envelope was 
hermetically sealed and immediately placed on a support. Solidification of 
the reaction mixture to the gel began 4 minutes after addition of the 
catalyst and was largely over after another 15 minutes. The gel cushion 
obtained was 2 cm thick. As a pressure-distributing overlay on foam seats, 
it prevents pressure sores in injured people who have to sit for long 
periods. 
EXAMPLE 2 
A mixture of 60 parts polyol 1, 105 parts polyol 3 and 135 parts polyol 4 
was homogeneously mixed with 46.8 parts polyisocyanate 3. 3 Parts catalyst 
1 were homogeneously dispersed in the resulting mixture over a period of 
30 seconds. The reaction mixture obtained was immediately poured into a 
thermoformed shell which consisted of 0.15 mm thick polyurethane film and 
which was arranged in a supporting mold. 
Solidification of the mixture to the gel began 1 minute after addition of 
the catalyst and was largely over after another minute. A polyurethane 
film was placed on the surface of the gel and was welded all round to the 
edge of the thermoformed film shell. A gel pad measuring 
1.5.times.10.times.20 cm was obtained. A gel pad such as this is suitable 
for cushioning elbows and ankles of bedridden patients. 
EXAMPLE 3 
A mixture of 200 parts polyol 1, 50 parts polyol 2 and 50 parts polyol 3 
was homogeneously mixed with 87.5 parts polyisocyanate 3. 2.5 Parts 
catalyst 1 were dispersed in this mixture over a period of 30 seconds. The 
reaction mixture obtained was immediately poured into an open mold (base 
area 10.times.10 cm, height 4 cm). Solidification of the mixture to the 
gel began 60 seconds after addition of the catalyst and was largely over 
after another 30 seconds. The gel obtained is suitable in the form of 
small gel pads for cushioning sports shoes. 
EXAMPLE 4 
A mixture of 200 parts polyol 1, 50 parts polyol 2 and 50 parts polyol 5 
was homogeneously mixed with 105 parts polyisocyanate 3. 2.5 parts 
catalyst 1 were dispersed in this mixture over a period of 30 seconds. The 
reaction mixture obtained was poured immediately into a thermoformed shell 
which consisted of 0.15 mm thick polyurethane film and which was arranged 
in a supporting mold. Solidification of the mixture to the gel began 60 
seconds after addition of the catalyst and was largely over after another 
30 seconds. The gel obtained is suitable for filling an envelope of 
polyurethane film (for example 200 .mu.m thick) to form a gel overlay 
measuring 60.times.60.times.1.5 cm which may be used as an overlay on 
hospital beds and operating tables for avoiding pressure sores. 
EXAMPLE 5 
A mixture of 60 parts polyol 1, 105 parts polyol 3 and 135 parts polyol 4 
was homogeneously mixed with 48 parts polyisocyanate 1. 1 Part catalyst 2 
was dispersed in this mixture over a period of 30 seconds. The reaction 
mixture obtained was immediately poured into a thermoformed shell which 
consisted of 0.15 mm thick polyurethane film and which was arranged in a 
supporting mold. Solidification of the mixture to the gel began 40 seconds 
after addition of the catalyst and was largely over after another 30 
seconds. A gel obtained in this way can be used in the same way as the gel 
of Example 4. 
EXAMPLE 6 
A mixture of 20 parts polyol 1 and 80 parts polyol 3 was homogeneously 
mixed with 10.5 parts polyisocyanate 2. The cloudy emulsion obtained was 
left standing for 5 days. It proved to be stable in storage. Thereafter, 2 
parts catalyst 2 were homogeneously dispersed in the emulsion over a 
period of 1 minute. An open mold measuring 15.times.15 cm for a height of 
2 mm was filled to the brim with the reaction mixture obtained. The mold 
was lined with a 1 mm thick film of polytetrafluoroethylene and had been 
preheated to 80.degree. C. in a drying cabinet. After 5 minutes (counting 
from the addition of catalyst), an 18.times.18 cm piece of an elastic 
woven fabric of polyamide and polyurethane fibers (80:20) was placed 
centrally on the reaction mixture. Solidification of the gel occurred 
after another 2 minutes. After a curing time of 15 minutes at 80.degree. 
C. and cooling to room temperature, a self-adhesive pad was obtained and 
may be used to protect shins and elbows against sports injuries. 
EXAMPLE 7 
a) 160 Parts polyol 1, 40 parts polyol 3 and 64 parts polyisocyanate 3 were 
homogeneously mixed. 1 Part catalyst 1 was then added and dispersed over a 
period of 20 seconds. Solidification of the mixture to the gel began 1 
minute after addition of the catalyst and was largely over after another 3 
minutes. A soft elastic gel compound was obtained. It consistency was 
determined by the method described below. A penetrometer value of 77 was 
determined. 
Similar reaction mixtures were prepared and allowed to solidify, the 
difference being that polyisocyanate 3 was used in a smaller quantity. 
b) Where 63.1 parts polyisocyanate 3 were used, a soft and elastic gel 
having a penetrometer value of 98 was obtained. 
This means that, in a batch according to the invention of 265 parts 
reaction mixture, a deficiency of -0.9 part polyisocyanate does not result 
in any particularly pronounced change in the consistency of the product 
obtained. 
c) Where 60.8 parts polyisocyanate 3 were used, a highly viscous mass with 
a penetrometer value of 210 was obtained. This means that, in a batch 
according to the invention of 265 parts reaction mixture, only a 
deficiency of -3.2 parts polyisocyanate produces a very pronounced change 
in the consistency of the product obtained. 
Determination of Gel Consistency 
The consistency of the gel compounds was determined with a DIN and ASTM 
penetrometer. It was tested under the following conditions: 
______________________________________ 
penetration element: 
25 mm diameter hemisphere 
penetration weight: 
100 g 
penetration time: 
10 seconds 
temperture of the 
25.degree. C. 
gel compounds: 
______________________________________ 
The particular depth of penetration was read off in 1/10 mm units from an 
indicator and represents the particular penetrometer value. 
EXAMPLE 8 (Comparison Example) 
a) A comparison gel compound (produced without a polyol having a hydroxyl 
value greater than 112), which had a similar penetration value to the gel 
of Example 7a), was obtained as follows: 
200 Parts polyol 3 and 18 parts polyisocyanate 3 were homogeneously mixed. 
4 Parts catalyst 1 were then added and dispersed over a period of 30 
seconds. Solidification of the mixture to the gel began 1 minute after 
addition of the catalyst and was largely over after 12 seconds. The soft 
and elastic gel compound obtained had a penetrometer value of 79, as 
determined by the method described in Example 7. 
b) The corresponding preparation and gelation of a reaction mixture 
containing only 17.1 parts as opposed to 18 parts of polyisocyanate 3 
produced a highly viscous mass which had a penetrometer value of 225. 
This means that, in a comparison batch of 222 parts reaction mixture, a 
deficiency of -0.9 parts polyisocyanate leads to a very pronounced change 
in the consistency of the product obtained.