Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-06-09
2002-04-30
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S106000, C521S107000, C521S165000
Reexamination Certificate
active
06380273
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a process for the production of flame-resistant flexible polyurethane foams having a low susceptibility to core discoloration, and to the use of halogen-free hydroxyalkyl phosphonates for the production of flame-resistant flexible polyurethane foams having a low susceptibility to core discoloration. Finally, the invention also relates to a flame-resistant flexible polyurethane foam having a low susceptibility to core discoloration.
Polyurethane foams are employed as plastics in many areas, such as furniture, mattresses, transport, construction and industrial insulation. In order to achieve high flame resistance requirements, as required for materials, inter alia, for the automobile, rail and aircraft interior fittings sector and building insulation, polyurethane foams must generally be provided with flame retardants. A multiplicity of different flame retardants are known and commercially available for this purpose. However, considerable technical problems and/or toxicological reservations frequently stand in the way of their use.
Thus, metering problems occur on use of solid flame retardants, such as, for example, melamine, ammonium polyphosphate and ammonium sulfate, frequently requiring modifications of the foaming plants, i.e. complex modification and adaptation. A majority of the liquid flame retardants employed, such as, for example, tris(2-chloroethyl) phosphate, tris(2-chloroisopropyl) phosphate and tetrakis(2-chloroethyl) ethylene-diphosphate, are characterized by a clear migration tendency, which substantially restricts the potential use in open-cell flexible polyurethane foams stems for automobile internal fittings, owing to the requirements of condensable emissions (fogging). Fogging is taken to mean the condensation of evaporated volatile constituents from the motor vehicle interior fittings on glass surfaces, in particular on the windscreen. This phenomenon can be assessed quantitatively in accordance with DIN 75201.
Furthermore, halogen-free flame retardant systems are preferred from ecotoxicological points of view and owing to improved secondary phenomena associated with fire with respect to smoke density and smoke toxicity. For technical reasons too, halogen-free flame retardants may be of particular interest. Thus, strong corrosion phenomena are observed on the plant parts used for flame lamination of polyurethane foams in the case, for example, of the use of halogenated flame retardants. This is attributable to the hydrohalic acid emissions which occur during flame lamination of halogen-containing polyurethane foams.
Flame lamination is the term used for a process for bonding textiles and foams in which one side of a foam sheet is partially melted with the aid of a flame and immediately thereafter pressed with a textile web.
Against the background of the trend toward taking into account gaseous emissions (volatile organic compounds=VOCs), there are in addition increasing demands on the migration stability of flame retardants, which make even use of additive high-molecular-weight flame retardants questionable, so that alternative solutions must be sought.
The liquid halogen-free flame retardant systems known hitherto, such as, for example, dimethyl methane-phosphonate or various alkyl and aryl phosphates, only satisfy the abovemetioned demands of the migration stability to an inadequate extent.
Solutions in the sense of high migration stability are offered here by aromatic bisphosphates, as described in JP 06306277, and hydroxyl-carrying oligomeric phosphoric acid esters (DE-A 43 42 972). These exhibit only very low fogging values, but have a significant core discoloration problem in the production of polyurethane foams which can be only partly reduced with the aid of core discoloration inhibitors, for example those based on hydroquinone (U.S. Pat. No. 4,045,378).
Core discoloration is taken to mean the brown coloration of polyurethane foams which occurs during industrial trial production owing to thermal oxidation. In the case of ether slabstock foams, this brown coloration occurs in the slab interior, inter alia if oxidation reactions occur with residual isocyanate groups or ether groups due to gas exchange of carbon dioxide by the advancing air. The resulting core discoloration (also known as scorching) may increase on use of certain additives. The temperature in the slab interior can increase so much that self-ignition can occur in the case of flexible ether foams.
In the case of a low degree of core discoloration, only a slight yellow coloration of the foam occurs, without significant effects on the mechanical properties. With increasing yellow-brown coloration, by contrast, the commencement of decomposition of the polyurethane foam is observed, with impairment of the mechanical properties.
The previous processes for the production of polyurethane foams have the disadvantage that, on use of liquid halogen-free flame retardants, the above-described core discoloration frequently occurs during the production process, which means that the production of polyurethane foams of low density is excluded owing to the increased risk of fire, white foam grades cannot be produced, and large amounts of flame retardant cannot be processed.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a process for the production of polyurethane foams containing halogen-free flame retardants and having high oxidative thermal resistance during foaming. The process should be usable for flexible ester and ether foams and for rigid foams and should facilitate the production of polyurethane foams having low fogging values. At the same time, the process should give polyurethane foams having high aging resistance of the flame resistance, i.e. the polyurethane foam still has effective flame resistance after a corresponding storage duration, even at elevated temperature.
The present object is achieved by a process for the production of flame-resistant flexible polyurethane foams having a low susceptibility to core discoloration, which comprises employing hydroxyalkyl phosphonates as halogen-free flame retardants and as core discoloration inhibitors.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The hydroxyalkyl phosphonates preferably conform to the general formula I
in which
u denotes a chain length of from 0 to 10
R
1
and R
5
are identical or different and are a hydroxyl-containing radical of the general formula II
R
2
and R
4
are identical or different and are an alkyl, aryl or alkylaryl group having 1 to 12 carbon atoms
R
3
is a radical of the general formula III
{overscore (a)} denotes an average chain length of from 0 to 4
{overscore (i)} denotes an average chain length of from 0 to 4
R
6
, R
7
, R
8
and R
9
are identical or different and are, independently of one another, H or an alkyl group having 1 to 6 carbon atoms.
Particularly preferably,
u denotes a chain length of 0 or 1
{overscore (a)} denotes an average chain length of from 1 to 2
{overscore (i)} denotes an average chain length of from 1 to 2
R
2
and R
4
are identical or different and are, independently one another, an alkyl group having 1 to 5 carbon atoms
R
6
, R
7
, R
8
and R
9
are identical or different and are, independently of one another, H or an alkyl group having 1 or 2 carbon atoms.
In the formulae of the abovemetioned hydroxyalkyl phosphonates employed in accordance with the invention, numbers such as u (for the formula I) indicate how often a certain group is present in the molecule. Mixtures of different hydroxyalkyl phosphonates are also possible, i.e. the values for u may be different and ultimately a mean value {overscore (u)} is obtained.
The hydroxyalkyl phosphonates are preferably hydroxyethyl methanephosphonate, hydroxyethyl ethanephosphonate, hydroxypropyl methanephosphonate, hydroxypropyl ethanephosphonate, hydroxyethyl propanephosphonate, hydroxypropyl propanephosphonate, diethylene glycol bis(hydroxyalkoxy) methanephosphonate and/or ethylene glycol bis(hydroxyalkoxy) ethanephosphonate.
The process according to
Eilbracht Christian
Sicken Martin
Bagwell-Bissett Melanie
Bisulca Anthony A.
Clariant GmbH
Seidleck James J.
LandOfFree
Process for producing flame-retardant flexible polyurethane... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing flame-retardant flexible polyurethane..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing flame-retardant flexible polyurethane... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2817077