Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1997-09-22
2001-02-06
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C252S401000, C252S405000, C252S182290, C521S095000, C521S128000, C521S129000, C521S155000, C521S159000, C521S170000, C524S087000, C524S091000, C524S589000, C524S590000, C568S582000
Reexamination Certificate
active
06184262
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns stabilization of polyether polyols and polyester polyols and the use of the stabilized polyols in the preparation of polyurethane foam. In particular the invention relates to stabilization of polyols with benzotriazole stabilizer compositions and the color or scorch inhibition of flexible, semiflexible and rigid polyurethane foams made from the stabilized polyols.
In the production of polyurethane foam from polyether polyols and polyester polyols, discoloration or scorch occurs during processing and production of the foam in the form of slabs, buns or other shapes. The foam becomes scorched under certain reaction conditions and severely degrades the physical properties of the product. The scorch manifests as discoloration at the center of the bun and can range from slight yellow to dark brown, rendering the foam unsuitable for commercial use. Furthermore, some bun foams become discolored or scorched when removed hot from the production line and stored in stacks due to heat dissipation from the center of the stack.
To prevent discoloration during processing and storage, scorch inhibitors are added to the polyol. Scorch inhibitors prevent degradation of the foam during the exotherm curing step when most of the degradation takes place, as well as during storage of the foam.
Prior art discloses the use of aromatic amine type scorch inhibitors, as for example in U.S. Pat. No. 3,637,865. Some commercial aromatic amines contain free amine which is liberated during processing of the polyol and, even in low quantities, is undesirable in the workplace atmosphere because of worker health and environmental considerations.
Aromatic amine scorch inhibitors are employed in conjunction with other stabilizers such as triesters of 1,3,5-tris(2-hydroxyethyl)-s-triazinetrione disclosed in U.S. Pat. No. 4,228,247.
Surprisingly, it has been discovered that certain benzotriazole compounds enhance the oxidative stability of polyether polyols and polyester polyols and furthermore, provide good scorch inhibiting properties to polyurethane foam. Moreover, benzotriazole and its alkyl derivatives can be combined with aromatic amines in relatively low ratios to form synergistic scorch inhibitors.
SUMMARY OF THE INVENTION
According to the invention, there are provided polyoxyalkylene polyether polyol and polyester polyol compositions stabilized against oxidative degradation with a stabilizing amount of benzotriazole compounds of formula I
wherein R is hydrogen or lower alkyl, R
1
is alkyl or phenylalkyl, R
2
is R
1
or hydrogen, and R
3
is alkyl having up to 11 carbon atoms or hydrogen.
According to another aspect of the invention, there are provided polyether polyol and polyester polyol compositions stabilized against oxidative degradation with a stabilizing amount of a synergistic mixture of (1) benzotriazole compound of formula II
wherein R
4
is hydrogen or lower alkyl and
(2) aromatic amine of formula III
wherein R
6
is alkyl or phenylalkyl and R
5
is R
6
or hydrogen, and the weight ratio of the benzotriazole to the amine is from about 50:50 to about 90:10.
An object of the invention is to provide a method for the stabilization of a polyether polyol and polyester polyol against oxidative degradation comprising adding to the polyol about 0.01 to 5.0 percent by weight of a benzotriazole compound of formula I described hereinabove.
Another object of the invention relates to a method for stabilizing a polyether polyol and polyester polyol comprising adding a synergistic composition consisting of (1) a benzotriazole compound of formula II described hereinabove and
(2) an aromatic amine of formula III described hereinabove wherein the weight ratio of the benzotriazole to the amine is from about 50:50 to about 90:10 and the synergistic composition is added in the amount of about 0.01 to 5.0 percent by weight based on the weight of the polyol.
This invention further relates to polyols stabilized by the method of this invention and to stabilized polyurethane foams prepared from such stabilized polyols together with polyisocyanates.
DETAILED DESCRIPTION OF THE INVENTION
The benzotriazole compounds of formula I
are prepared in a known manner from a benzotriazole, aldehyde and a secondary amine by means of the condensation reaction. The aldehyde may be formaldehyde, butyraldehyde, 2-ethylhexyl aldehyde or the like. Preferred are aldehydes having up to 12 carbon atoms. The benzotriazole may be substituted by a lower alkyl group to form tolutriazole compounds and the like.
The secondary amine reactant is selected from aromatic amines. Diphenyl amines may be substituted by alkyl groups or arylalkyl groups on the benzene rings. Particularly preferred are alkyl group substitutents having 1 to 24 carbon atoms. Exemplary amines from which the compounds are derived include, among others, octylated diphenylamine, nonylated diphenylamine, octylated aryl alkylated diphenylamine (VANOX® 830 available from R. T. Vanderbilt Company, Inc.), styrenated diphenylamine, 2,2′-diethyl-4,4′-(dimethylbenzyl) diphenylamine, 4,4′-dibenzyldiphenylamine, 4,4′-di(phenylethyl)diphenylamine. The secondary amine may be a mixed isomeric reaction product prepared by reacting diphenylamine, styrene and 2,4,4-trimethylpentene by known alkylating reaction methods to form essentially octylated diphenylamine. A similar mixed octylated diphenylamine is prepared by alkylating diphenylamine with 2,4,4-trimethylpentene. Nonylated isomeric reaction products are prepared by alkylation of diphenylamine with 1-propene trimer. Another alkylated diphenylyamine reaction mixture may be produced from 2-ethyl-N-(2-ethylphenyl)benzenamine and 1-propene trimer. The reaction mixtures contain some isomers, small amounts of monoalkylated and trialkylated diphenylamines. Preferred are alkylated diphenylamines containing no or only trace amounts of unreacted diphenylamine for an environmentally safer product.
The benzotriazole compounds of formula I are good scorch inhibitors when incorporated in the polyol precursors in an amount effective to produce the desired stability.
The benzotriazole compounds of formula II, which are used as precursors for the preparation of the compounds of the invention, possess no scorch inhibiting function. The benzotriazoles, however, show synergism when combined with secondary amines of formula III in a critical ratio. The synergistic scorch inhibiting function is effective for compositions containing a benzotriazole of formula II and a secondary amine of formula III in the weight ratio of the benzotriazole to the amine from about 50:50 to about 90:10. The preferred ratio of the benzotriazole to the amine is about 70:30 to 65:35. The benzotriazole synergists are compounds of formula II where R
4
is hydrogen or lower alkyl group. Preferred are benzotriazole and tolutriazole.
The aromatic amine synergists of formula III may be substituted by alkyl or arylalkyl groups on the benzene rings. The alkyl groups may have from 1 to 24 carbon atoms. The alkylated diphenylamines may be prepared by known methods. The alkylated diphenylamines may be in the form of isomeric reaction products prepared by alkylation methods described hereinabove.
The present synergistic compositions contain a relatively low proportion of the amine. It is, however, preferred that the alkylated diphenylamines contain no or trace amounts of free residual diphenylamine, to enhance the environmental safety of the product.
The compositions of the invention may be incorporated in the polyol precursors in an amount effective to produce the desired stability. Typically, an amount from about 0.01 to 5.0 percent will be sufficient. A preferred range is from about 0.3 to 1.0 percent by weight of the total polyol composition.
The stabilizer compositions may be diluted with mineral oil, paraffinic oil, petroleum oil, or vegetable oil for easier processing. The stabilizer composition may be incorporated into the polyol by simply stirring at ambient temperatures.
The polyol components which may b
Karol Thomas J.
Suhoza Richard A.
Talbot James J.
Baker & Botts L.L.P.
Niland Patrick D.
R. T. Vanderbilt Company, Inc.
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