Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-05-24
2002-01-08
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S137000, C521S159000, C521S914000
Reexamination Certificate
active
06337356
ABSTRACT:
The present invention relates to a process for producing sound-absorbing PUR foams having an adhesive surface by reacting organic and/or modified organic polyisocyanates (a) with a polyetherol mixture (b) and, if desired, further compounds (c) bearing hydrogen atoms which are reactive toward isocyanates, in the presence of water and/or other blowing agents (d), catalysts (e) and, if desired, further auxiliaries and additives (f), wherein a specific polyetherol mixture is used.
The production of polyurethanes (PURs) by reacting organic polyisocyanates with compounds having at least two reactive hydrogen atoms, for example polyoxyalkylenepolyamines and/or preferably organic polyhydroxyl compounds, in particular polyetherols having molecular weights of, for example, from 300 to 6000, and, if desired, chain extenders and/or crosslinkers having molecular weights of up to about 400 in the presence of catalysts, blowing agents, flame retardants, auxiliaries and/or additives is known and has been described many times. A summary overview of the production of PUR is given in, for example, Kunststoffhandbuch, Volume VII, Polyurethane, Carl-Hanser-Verlag, Munich, 1st edition 1966, edited by Dr. R. Vieweg and Dr. A. Höchtlen, and 2nd edition 1983 and 3rd edition 1993, edited by Dr. G. Oertel.
The main area of application for cold-cure flexible foams is upholstery elements for the furniture industry and seat elements for the automobile industry. In addition, numerous flexible PUR foams are used for sound-damping purposes, e.g. automobile carpets.
The open-pore foam framework offers favorable prerequisites for airborne sound absorption. The damping behavior of flexible foams, which can be described, for example, by the loss factor &eegr;, is regarded in numerous publications as a parameter for optimizing sound damping. The loss factor &eegr;
&eegr;=W
l
/2&pgr;W
r
indicates the proportion of sound which is irreversibly converted into heat during an oscillation period. High loss factors accordingly effect higher sound damping.
A number of publications describe sound-absorbing, flexible PUR foams, but these do not have an adhesive carpet surface.
Thus, DE-A-2751774 describes a sound-damping composite system based on a combination of rigid foam polyols and flexible foam polyols having a high proportion of fillers, which has an adverse effect on the weight per unit area of the workpiece.
EP-A-433878 discloses carpet foams having viscoelastic properties. These comprise a special combination of hydrophilic and hydrophobic polyols. These systems have good sound absorption performance, but demix after a short time during storage if they are not permanently stirred. DE-A-3942330 likewise describes specific polyol mixtures for producing such viscoelastic foams.
EP-A-331941 claims acoustic foams having a loss factor of >0.5. These foams are produced by means of a combination of specific hydrophilic and hydrophobic polyetherols. According to DE-A-4001044, sound-absorbing properties can be achieved by means of a combination of polyester alcohols and polyether alcohols. These systems have a very strong tendency to demix.
In a few cases, attempts have been made to achieve an adhesive surface character of the foams by means of special processing, in particular substantial under-crosslinking. Here, foaming is generally carried out at an index of from about 60 to 80. (The index indicates the equivalence ratio of the isocyanate component to the polyol component.) Thus, DE-A-3710731 describes such a flexible foam having sound-insulating properties. These carpet elements which are manufactured at relatively high foam densities are produced with an adhesive surface. The adhesive surface properties, which are achieved as a particular advantage, require foaming in an index region <80, preferably about 70.
DE-A-3510932 describes a relatively complicated method of subsequently providing a foam with an adhesive coating. DE-A-4129666 uses incompatible polyols which slowly demix. The high proportions of polyols rich in ethylene oxide and adherence to indexes of <80 enable an adhesive carpet surface to be achieved.
The inventions disclosed in the prior art all allow the production of flexible foams having sound-absorbing properties and an adhesive surface, but there is still considerable room for improvement in terms of the properties and processability of this class of materials. In particular, it should be noted that at the indexes of <80, frequently <70, required according to the prior art, the mechanical properties of the carpets are frequently unsatisfactory.
It is an object of the present invention to produce sound-absorbing, easy-to-process, flexible PUR foams having a loss factor of >0.3 and an adhesive surface.
We have found that this object is achieved by using a polyetherol mixture (b) comprising
b1) at least one bifunctional to eight-functional polyetherol based on ethylene oxide and propylene oxide and having an OH number of from 20 to 80 mg KOH/g and a proportion of primary OH groups of >50%,
b2) at least one polyetherol based on ethylene oxide and propylene oxide and/or butylene oxide and a bifunctional to eight-functional initiator and having an OH number of from 20 to 80 mg KOH/g, where the proportion of ethylene oxide in the polyetherol is >30% by weight, in amounts of from 10 to 50 parts by weight, and
b3) at least one polyetherol based on propylene oxide and/or butylene oxide and, if desired, ethylene oxide and a bifunctional to eight-functional initiator and having an OH number of from 30 to 400 mg KOH/g, where the proportion of ethylene oxide in the polyetherol is <30% by weight,
for producing the sound-absorbing PUR foams.
The present invention accordingly provides a process for producing sound-absorbing polyurethane foams having an adhesive surface by reacting organic and/or modified organic polyisocyanates (a) with a polyetherol mixture (b) and, if desired, further compounds (c) bearing hydrogen atoms which are reactive toward isocyanates, in the presence of water and/or other blowing agents (d), catalysts (e) and, if desired, further auxiliaries and additives (f), wherein the polyetherol mixture (b) comprises
b1) at least one bifunctional to eight-functional polyetherol based on ethylene oxide and propylene oxide and having an OH number of from 20 to 80 mg KOH/g and a proportion of primary OH groups of >50%,
b2) at least one polyetherol based on ethylene oxide and propylene oxide and/or butylene oxide and a bifunctional to eight-functional initiator and having an OH number of from 20 to 80 mg KOH/g, where the proportion of ethylene oxide in the polyetherol is >30% by weight, in amounts of from 10 to 50 parts by weight, and
b3) at least one polyetherol based on propylene oxide and/or butylene oxide and, if desired, ethylene oxide and a bifunctional to eight-functional initiator and having an OH number of from 30 to 400 mg KOH/g, where the proportion of ethylene oxide in the polyetherol is <30% by weight,
The invention further provides the sound-absorbing PUR foams produced by this process and provides for their use as damping material.
In our investigations we surprisingly found that the use of the specific polyetherol mixture employed according to the present invention makes it possible to produce flexible PUR foams which have good sound-absorbing properties, are easy to process and have a high loss factor of >0.3 and an adhesive surface.
The following may be said about the components used according to the present invention in the polyol mixture:
Constituent (b1) comprises at least one bifunctional to 8-functional polyetherol based on ethylene oxide and propylene oxide and having an OH number of from 20 to 80 mg KOH/g and a proportion of primary OH groups of >50%, preferably >70%.
Examples are: polyetherols based on glycerol, trimethylolpropane and sorbitol as initiator substances and having a propylene oxide block and an ethylene oxide end cap, by means of which the content of primary OH groups can be reliably brought to proportions of >50%
Falke Peter
Schmaler Kirsten
Zaschke Bernd
BASF - Aktiengesellschaft
Borrego Fernando A.
Cameron Mary K.
Cooney Jr. John M.
LandOfFree
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