CA1322815C

CA1322815C - Use of phosphines and/or diphosphanes in the production of isocyanate-based plastics

Info

Publication number: CA1322815C
Application number: CA000585336A
Authority: CA
Inventors: Peter Haas; Hans Hettel
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1987-12-18
Filing date: 1988-12-08
Publication date: 1993-10-05
Anticipated expiration: 2010-10-05
Also published as: DK703788D0; DE3855842D1; EP0320761B1; DK703788A; ATE150780T1; ES2101673T3; JPH01197558A; EP0320761A2; DK173996B1; EP0320761A3

Abstract

Mo-3116 LeA 25,714 THE USE OF PHOSPHINES AND/OR DIPHOSPHANES
IN THE PRODUCTION OF ISOCYANATE-BASED PLASTICS
ABSTRACT OF THE DISCLOSURE
This invention relates to a method for inhibiting core discoloration in the production of isocyanate-based foams, preferably polyurethanes based on polyesters containing at least two hydroxyl groups and having a molecular weight of from about 400 to about 10,000 or polyisocyanurates, comprising using one or more phosphines or diphosphanes in the production of such foams.

Mo-3116

Description

1322815 Mo-3116 LeA 25,714 THE USE OF PHOSPHINES AND/OR DIPHOSPHANES
IN THE PRODUCTION OF ISOCYANATE-BASED PLASTICS
BACKGROUND OF THE INVENTION
Polyurethane foams of low growth density show a tendency towards core discoloration on account of the highly exothermic nature of the blowing reaction in the presence o~ large quan~ities of water. Several stabiliæers for counteracting this temperature-reduced discoloration reaction are known ~rom the literature.
A first ma~or group of stabilizers comprises sterically hindered phenols, although aromatic amines, piperidines, various esters of phosphorous acids, and phenothiazines and phenothiazine derivatives may also be used.
Each of these classes of compounds has certain disadvantages. For example, sterically hindered phenols show a yellowing reaction promoted by various factors, but mainly by reactions at the para positlon of the aromatic component to form nitro and nitroso compounds 0 and derivatives thereof. (See l{.C. Smeltz, Textile , 15, No. 4; E. Schmidt, Textilveredlun~, 17, (1982), No. 6; and H.-W. Hemmpel, Textil Praxis Xnternational, 1983, March/April Edition.
Although phenothiaæines and their derivatives are 5 extremely effective, they have an undesirable color.
Another major group of stabilizers comprises phosphorous acid esters (i.e., phosphites). Although basically effective in preventing core discoloration, phosphorous acid esters are sensitive to hydrolysis~
Accordingly, there has been no shortage of attemp~s to reduce the hydrolytic degradation of ~hese esters.
However, this has not been possible, even for aromatic esters which are highly substi~uted. As a consequence, the polyurethane foæm, as well as the production site, Mo-3116 ,~

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smells strongly of the phenolic hydrolysis products.
The particular disadvan~age of polyurethane ester foams lies in the formation of phosphorous acid, which initiates autocatalytic decomposition in the ester segments, resulting in rapid degradation of the polymer structure under moist aging conditions.
The use of phosphorous acid esters, generally with a combinatlon o~ other antioxidants as synergists, i9 described, for example, i.n DOS 2,848,922, U.S. Patent 4,135,042, DOS 2,905,808, DDR-PS 135,208, JA 52,128,996, JA 52,093,463, DDR-PS 146,9$9, DDR PS 146,961, DOS

2,945,855, U.S. Patent 3,459~837, and U.S. Patent 3,354,241. These publications however, always disclose combination antidiscoloration finishes that are attended hy the disadvantages mentioned above, namely, formation of additive-speciic chromophores~ the color of the phenothiazines, and hydrolysis of the phosphorous acid esters.
Particularly stringent requirements are imposed in the production of polyurethane polyester foams with applications in the textile field, because the yellowing reactions mentioned can result both in diffusion of the chromophores into the textiles and in polymer damage caused by degradation products~
Although, in addition to phosphites, phosphines (also known according to recent nomenclature as phosphanes) and sulfides in combination with sterically hindered phenols are mentioned in DE-OS 2,231,069 9 there is again no reference to the above-mentioned disadvantages.
It has now surprisingly been found that phosphines and diphosphanes of the invention are excellent hydrolysis-stable core-discoloration inhibitors, even when used alone.

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SUMMARY OF THE INVENTION
The present invention relates to the use of phosphines and/or diphosphanes corresponding to the following formula Rl ~
\

~2 wherein Rl and R2 are independently C2-C~4 alkyl, C4-C14 cycloalkyl, or C6-C10 aryl, and 15 X has the same meaning as Rl or R2 or is ~R
_p \ R2 wherein Rl and R2 are defined as above, as hydrolysls-stable core-discoloration inhibi~ors in the production of isocyanate-based foams.
DETAILED DESCRIPTION OF THE INVENTION
The preparation of compounds usP.ful in the : present invention is known pcr se.
According to the invention, the phosphines and/or diphosphanes are preerably used in a quantity of about 0.01 to about 5% by weight and, more prefexably, in a quantity of about 0.05 to about 1% by weight, basèd on the isocyallate-based foam.
The following are mentioned as examples of compounds suitable for use in accordance with the invention:

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~ - P (preferred) C2H9 \
P C4Hg C4Hg /

C4~9 /
P--~ .
C4Hg C3H7 \ / C3H7 C3H.~ / C3H7 ~ ~ P-P ~ (preferred) Mo-3116 :

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~`(~ ~ C2H5 : p p ~ 2 5 C~13 CH3 ~ p The stabilization brought about by the core-discoloration-inhibiting effec~ according to the invention affords manufacturers of polyester polyurethanes enormous advantages in terms of industrlal hygiene, because the foams produced (and hence the production site) no lon~er smell of phenols or cresols.
On the contrary, the foams with aryl phosphines are substantially odorless and no longer show any deterioration in their aging behavior under moist conditions brought about by the stabilizers.
The production of isocyanate-based foams is known and is described, for example, in DE-OSS
1,6949142, 1,694,215, and 1,720,768; and in Kunststoff~
Handbuch, Vol. VII, Polyurethane, edited by Vieweg and Hffchtlen, Carl Hanser Verlag, M~nchen 1966, and in the new edition of this book edited by G. Oertel 9 Carl Hanæer Verlag, M~nchen, Wein 1983. Such foams are predominantly foams containing urethane, isocyanurate, Mo-3116 .

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allophanate, uretdione, urea, ~arbodiimide groups, or a combi.nation thereof. The preferred use according ~o the invention is the productlon of polyure~hane and polyisocyanurate foams.
The following materials are used for the production of the isocyana~e-based ~oams:
1. Suitable starting components include aliphatic, cycloaliphatic, araliphatic, aromatic, and heterocyclic polyisocyana~es of the type described, for example, by W. Siefken in Justus Liebi~s ~ em~e, 562, pages 75 to 136, such as those corresponding to the following formula Q(NCO)n, wherein n is a number from 2 to 4 (preferably 2 or 3), and Q is an aliphatic hydrocarbon radical containing 2 to 18 (preferably 6 to 10) carbon atoms, a cycloaliphatic hydrocarbon radical containing 6 to 15 (preferably 6 to 13) carbon atoms, or an araliphatic hydrocarbon radical containing 8 to 15 (preferably 8 to 13) carbon atoms, such as, for example, the polyisocyanates described on pages 10 and 11 of DE-OS
2,832,253. In general, it is particularly preferred to use the co~mercially readily obtainable polyisocyanates such as 2,4- and 2,6-tolylene diisocyanate, and mixtures of these isomers ("TDI"); polyphenyl polymethylene polyisocyanates of the type obtained by phosgenation of aniline-formaldehyde condensates ("crude MDII'); and polyisocyanates containing carbodiimide groups, urethane ~
groups, allophanate groups, isocyanurate groups, urea groups or biuret groups ("modified polyisoeyanates"), more especially the modified polyisocyanates derived from 2,4- and/or 2,6-tolylene diisocyanate and from 4,4'- and/or 2,4'-diphenylmethane diisocyanate.

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2. Other suitable starting components include compounds containing at least two isocyanate-reac~ive hydrogen atoms and having a molecular weight of from about 400 to abou~ 10,000. In addition to compounds containing amino groups, thio groups, or carboxyl groups, such compounds include, prefera`bly, compounds containing hydroxyl groups, more especially compounds containing 2 to 8 hydroxyl groups and h~ving molecular weights in the range ~rom 1000 to 6000 (pre~erably in the range from 2000 to 6000). Such preferred hydroxyl-containing compounds include, for example, polyethers and polyesters containing at least 2, generally 2 to 8, and preferably 2 to 6 hydroxyl groups, as well as polycarbonates and polyester amides of the type known Rer se for the production of homogeneous and cellular polyurethanes and described, for example, on pages 11 to 18 of DE-OS 2,832,253, Polyesters containing at least 2 hydroxyl groups are preferred~
3. Other optional starting components include compounds containing at least 2 isocyanate-reactive hydrogen atoms and having a molecular weight of 32 to 399. Such compounds include compounds contain hydroæyl groups, amino groups, thiol groups, carboxyl groups (preferably hydroxyl groups and/or amino groups) and serve as chain-extending or crosslinking agents. Such compounds generally containing 2 to 8 (preferably 2 to 4) isocyanate-reactive hydrogen atoms. Examples of theqe compounds can be ound on pages 19 and 20 of DE-OS
2,832,2S3.
- 30 4. Water and/or readily volatile organic compounds are used as blowing agents.

5. Optional starting component~ include auxiliaries and additives, such as a) catalysts known per se, Mo-3116 ~l322~
b) surface-active additives, such as emulsifiers and foam stabilizers, c) reaction retarders, for example, acid-reacting compounds such as hydrochloric acid or organic acid halides; cell regulators known per se, such ~9 paraffills or atty alcohols or dimethyl polysiloxanes$ p~gments or dyes; flameproofing agents known per se, for example, tricL^esyl pho~pha~e; stabilizers agalnst the e~f~cts o aging ancl weather; plasticizers; fungistatic and bacteriostatic agents; and fillers, such aq barium sulfate, kieselguhr, carbon black or whiting.
These optional auxiliaries and additives are 15 described, for example, on pages 21 to 2bl of DE-OS
: 2,732,292. Further examples of surface-active additives ; and foam ~tabilizers, cell regulators, reaction retarders, stabilizers, flameproofing agents, plasticizers, dyes, ~illers, ungistatic and 20 bacteriostat:Lc agents, which may optionally be used in accordance with the invention, and information on the use of these additives and the way in which they work can be found in Kunststoff-Handbuch, Vol. VII, edited by Vieweg and H~chtlen, Carl Hanser Verlag, ~nchen 1966 for example, on pages 103 to 113.
The process for the production of polyurethane foams may be carried out using any of the following methods: .
The reaction components are reacted by the one-shot process, by the prepolymer process, or by the semi-prepolymer process. Machines such as tho~e described in U.S. Patent 2,764,56S are frequently useful for such reactions. Information on processing machines which may be used in accordance with the invention can be found in Kunststoff-Handbuch~ Vol. VII, edited by Mo-3116 : -8-:

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Vieweg and H~chtlen, Carl Hanser Verlag, M~nchen 1966, for example on pages 121 to 205.
According to the invention, it is also possible to produce cold-hardening foams. See &B-PS 1,162,517, DE-OS 2,153,086.
Foams may, of course, also be produced by block foaming or by the laminator process known per 8e.
Polyisocyanura~e foams may also be produced by known processes.
The products obtainable in accordance with the invention are usecl, for example, in furniture upllolstery, textile linings, ma~tresses, car seats, arm rests, sponges and structural components, and in the padding of chairs and instrument panels.
The effect of the alkyl or aryl phosphines or diphosphanes is surprising insofar as, contrary to previous opinion, they are active when used alone as core discoloration inhibi~ors.
The present invention, which is set forth in the foregoing dlsclosure, is not to be construed or limited either in spirit or in scope by these examples. Those skilled in the art will readily understand that known variations of the conditions and processes of the following preparative procedures can be used~ In the following examples, all percentages are percentages by weight and all temperatures are degrees Celsius unless otherwise noted.
DESCRIPTTON OF THE PRRFERRED EMBODIMENTS

In a standard UBT foaming machine, a reaction mixture consisting of the following components is foamed to a block measuring 50 cm (height) by 200 cm (leng~h) by 120 cm (width3:
75 parts by weight of a partially branched polyester 3~ (OH number 60) based on adipic Mo-3116 _g _ :~223~ ~
acid t diethylene glycol, and trimethylolpropane;
25 parts by weight of a partially branched polyester (OH number 210) based on adipic acid, phthalic acid, trimethylolpropane, and propylene gly~ol;
5.5 parts by weight water;
1.0 part by weight of a stabilizer (alkoxylated nonylphenol, OH value 70);
1.5 parts by weight o a tertiary amine activator (Desmorapi.d~ DB, a product of Bayer AG);
1.0 part by weight SE 232, silicone-based stabilizer made by BP; and 70.8 parts by weight of a mixture consisting of 50% by weight of a mixture o 80Z by weight 2,4- and 20~ by weight :
2,6-tolylene diisocyanate and 50Z
by weight of a mixture of 65% by : wei.ght 2,4- and 35~ by weight 2,6-tolylene diisocyanate.
The resulting polyurethane oam has a gross density of 20 kg/m3. Table 1 presents tes~ data for foams according to Example 2 prepared with triphenyl phosphite (comparison) and triphenylphosphine (of the invention).

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S ~ O ~ 3 0 C~ N
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S C ~ ~ E O ~ S C 2 Sn 2 ~U C C U ~ ~ O A
O ~ C C ~_ O ~ C ~ C

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Aging under moist conditions was also investigated for a polyurethane oam having a gross density of 62 kg/m3 and obtained in accordance with the ~5 following formulation:
,~ ~100 parts by weight of the polyester (OH value 60) of Example l;
1.65 parts by weight water;
; :0.85 parts by weight silicone-based foam stabilizer 10B 5055 (Goldschmidt AG);
0.20 parts by weight activator RC A117 (Rhein-Chemie, Mannheim); and 0.50 parts by weight dimethylethanolamine are foamed as in Example 1 with 27 parts by welght of the polyisocyanate mixture of Example 1 to form a foam block.
Table 2 presents test data as in Table 1 for ~: ~ foams according to Example 2.

: 20TABLE 2 : Test 2 CH after CS after No. Stabiliza~ion CH ) CS3) Ford Test4) Ford Test5) 25 1 none 7.5 2.6 5.2 4.5 ~ :
2 0.25 part by 7.5 2.7 destroyed weight tri-phenyl phos-phite .~ 3 0.25 part by 7.6 2.8 5.0 5.0 weight tri-~ phen~l phos-- phine To evaluate thermal aging behavior, test specimens measuring 5 x 5 x 8 cm were heated for 5 hours Mo-3116 .

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at 175C in a recirculating-air drying cabinet before the Ford tes~.
Results of the heat treatment of test specimens of Example 2 are presented in Table 3.

Test Color after Color after No. Initial Color thermal aging Ford test 1 white yellow yellow-brown 10 2 white yellow dark brown 3 white white yellow The Examples show that the compounds according to the invention are highly effective core discoloration inhibi~ors with no adverse effect on aging behavior under moist conditions. In addition, they have a positive effect on thermal aging behavior.
Whereas a 0.25% solution o triphenyl phosphite in polyester polyols has undergone approximately 50% hydrolysis after only 6 months, the corresponding triphenylphosphine solution shows no reduction in its effect. This is even more noticeable under elevated temperature conditions: Only 50% of the initial quantity of triphenyl phosphite is present after storage for 2 months at 80C.

.
The inhibitors according to the invention are also effective in polyurethane polyether foams.
Advantageously, when t`ne compounds of the invention are used, sterically hindered phenols (a group of compounds which tend to undergo yellowing reactions) are not required as an inhibitor component.
To a polyether polyol based on trimethylol-'~ propane containing 15Z by weight ethylene oxide and 85%

Mo-3116 :

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by weight propylene oxide as structural componen~s (OH-number of 45) was added 0.2X by weight triphenyl-phosphine as the inhibitor. In order to reach a high temperature, a tenfold charge of the following formulation was foamed in a box with side lengths in each case of 45 cm:
100 parts by weight of a polyol ~tabilized with 0.2%
triphenylphosphine (OH-number 45);
parts by weight water;
0.18 parts by weight tin octoates 1.4 pflrts by weight silicone-based foam stabilîzer OS 22 (Bayer AG);
0.2 parts by weight amine activator PS 207 (Bayer AG); and 5 60 parts by weight of a mixture of 80% by weight 2,4- and 20% by weight 2,6~tolylene diisocyanate.
The foam was then after-heated for 20 minutes at 100C.
Upon cutting the foam, no discoloration was found in the center. The air resistance tmeasure of open-cellularity) is equivalent to a 90-mm water-column pressure.

An inhibitor combination containing a sterically hindered amine under machine~processing conditions is used according to the following formulation:
100 parts by weight of the polyol according to Example 3 stabilized with 0.2Z by weight of Vulkanox~ OCD octyla~ed diphenylamine (Bayer AG);
parts by weight water;
1.4 parts by weight silicone-based foam stabilizer OS 22 (Bayer AG);
0.18 parts by weight tin octoate; and Mo-3116 .' ' ` ' "
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part~ by weight of a mixture of 80% by weight 294- and 20% by weight of 2,6-tolylene diisocyanate.
The 55-cm high foam displayed vir~ually no core discoloration in the center of the block.

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Claims

1. A method for inhibiting core discoloration in the production of isocyanate-based foams comprising adding a core discoloration inhibitor during the production of said foams, wherein said core discoloration inhibitor comprises one or more compounds of the formula wherein R1 and R2 are independently C2-C14 alkyl, C4-C14 cycloalkyl, or C6-C14 aryl, and X has the same meaning as R1 or R2 or is wherein R1 and R2 are defined as above.

2. A method according to Claim 1 wherein the core discoloration inhibitor is triphenyl phosphane, having the formula Mo-3116CA

3. A method according to Claim 1 wherein the core discoloration inhibitor is tetraphenyl diphosphane, having the formula

4. A method according to Claim 1 wherein the core discoloration inhibitor is used in a quantity of about 0.01% by weight to about 5% by weight, based on the isocyanate-based foam.

5. A method according to Claim 1 wherein the core discoloration inhibitor is used in a quantity of about 0.05% by weight to about 1% by weight, based on the isocyanate-based foam.

6. A method according to Claim 1 for inhibiting core discoloration in the production of isocyanate-based foams comprising adding a core discoloration inhibitor during the production of said foams, wherein said core discoloration inhibitor comprises triphenyl phosphane, tetraphenyl diphosphane, or a mixture thereof in a quantity of about 0.05%
by weight to about 1% by weight, based on the isocyanate-based foam.

7. A method according to Claim 1 wherein the isocyanate-based foam is a polyurethane foam.

8. A method according to Claim 7 wherein the polyurethane foam is based on a polyester containing at least two hydroxyl groups and having a molecular weight of from about 400 to about 10,000.

9. A method according to Claim 1 for inhibiting core discoloration in the production of polyurethane foam comprising adding a core discoloration inhibitor during the production of Mo-3116CA

said polyurethane foam, wherein said polyurethane foam is based on a polyester containing at least two hydroxyl groups and having a molecular weight of from about 400 to about 10,000 and wherein said core discoloration inhibitor comprises triphenyl phosphane, tetraphenyl diphosphane, or a mixture thereof in a quantity of about 0.05% by weight to about 1% by weight, based on the polyurethane foam.

10. A method according to Claim 1 wherein the isocyanate-based Foam is a polyisocyanurate foam.

11. A method according to Claim 1 for inhibiting core discoloration in the production of a polyisocyanurate foam comprising adding a core discoloration inhibitor during the production of said polyisocyanurate foam, wherein said core discoloration inhibitor comprises triphenyl phosphane, tetraphenyl diphosphane, or a mixture thereof in a quantity of about 0.05% by weight to about 1% by weight, based on the polyisocyanurate foam.

12. Use of a compound of the formula wherein R1 and R2 are independently C2-C14 alkyl, C4-C14 cycloalkyl, or C6-C14 aryl, and X has the same meaning as R1 or R2 or is Mo-3116CA

wherein R1 and R2 are defined as above, for inhibiting core discoloration in the production of isocyanate-based foams.

13. Use of triphenyl phosphane, having the formula for inhibiting core discoloration in the production of isocyanate-based foams.

14. Use of tetraphenyl diphosphane, having the formula for inhibiting core discoloration in the production of isocyanate-based foams.

15. Use of a compound according to Claim 12 for inhibiting core discoloration in the production of a polyurethane foam.

16. Use of a compound according to Claim 12 for inhibiting core discoloration in the production of a polyisocyanurate foam.

Mo-3116CA