CA1050698A - Flameproof polyurethanes - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Production of flameproof polyurethanes or polyure-thane foams containing an ammonium polyphosphate of the general formula:

H(n-m)+2(NH4)mPnO3n+1 in which n stands for a whole number averaging a value of more than 400 up to about 1000, and the ratio of m:n is approximately 1:1, as a flameproofing agent, if desired in combination with a further flameproofing sub-stance.

Description

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The present invention relates to ~lameproof poly-urethanes or polyurethane foams, wherein the flameproof-ing agent producing its valuable properties as early as in the polyurethane batch, is an ammonium polyphosphate having a certain chain length which may be used, if desired, in ad~ixture with further flameproofing sub-stances.
It is known that polyurethanes can be rendered flameproof by means of phosphorus compounds containing nitrogen, e.g. diammonium orthophosphate, which are added to the polyurethane batch. Diammonium orthophos-phate as a water-soluble compound is, however, likely -to be washed out from the plastics, under the influence of moisture, whereby the plastic is deprived of its - initial flamepxoofness, which is disadvantageous. -It has therefore been proposed (cf German Patent Specification "Auslegeschrift" l 283 532) to render poly-urethanes flameproof by means of substantially water~
insoluble ammonium polyphosphates of the general for-mula~

(n-m)+2( 4)m n 3n+1 ~ ;
,, in which n stands for a whole number having an average value greater than lO, m stands for a whole number of up to n + 2, and m/n stands for a number between about 0.7 and 1.1. It is customary for these known ammonium poly-phosphates to be used in proportions between 5 and 15weight %, based on the batch. Commercially available are only those polycondensation products of the above ~' ' ~ ~ 2 - ~
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formula, wherein n averages a value between about 20 and 400, which is deterl~ned tcf van Wazer, Griffiter and ~ Mc.Cullough Anal. Chem. 26 (1~54), pa~e 1755) by ter-- minal group titration once the ammonium polyphosphates - have been transformed to the acid stage with the aid of ion exchanger resins. ~;
Ammonium polyphosphates having a degree of conden-sation n between 100 and 400 are, however, difficult to meter into a polyurethane batch. To permit mechanical , processing of the liquid feed components into polyurethanes, it is necessary for them to be intimately blended together within seconds. Prior to blending, it is more particularly : .
customary for the solid ammonium polyphosphates to be pasted up with one of the feed components, preferably ~; with the polyol, or with a preliminary blend prepared - from the polyol, catalysts and/or stabilizers and expanding agents. As a result, the phosphate salt is ;
completely wetted and easy to blend with the other com-ponents making the batch. Owing to the difference j 20 between the density of the ammonium polyphosphate and ;~
-i that of the polyol component or that of the polyol pre-- liminary blend, the phosphate salt begins, once it has been made into a paste, to settle gradually in the mix-ing vessel and to form a sediment therein. ~eedless to `~ say irregularly concentrated pastes are initially obtain~
ed and reacted later with the isocyanate compound natural-~ ly with the resultant formation of differently flame- ~
I proof polyurethanes. ~;
We have now found that it is possible for the above undesirable phenomenon of sedimentation to be avoided by , -- : .
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substituting a highly condensed ammoni~ polyphosphate for those amtnonium polyphosphates which are commonly used. As compared with the above com-mercially available products, the highly condensed ammonium polyphosphate of the present invention ~ends to form a gel in aqueous suspension, although ` it is less water-soluble.
The present invention relates more particularly ~o flameproof polyurethanes or polyurethane foams containing, as the flameproofing agent, between about Q.5 and 20 weight % of an ammonium polyphosphate, if desired in combination with a further flameproofing substance, the ammonium poly-phosphate having the general formula: ;
H~n m)+2(NH~)mPnO3n~
in which n stands for a whole number averaging a value of more than 600 upto about 1000 and the ratio of m:n is approximately 1.
In accordance with the present invention, use should conveni-ently be made of an ammonium polyphosphate having a degree of condensation _ be~ween about 600 and 800. The polyphosphate should preferably be used in a proportion between about 1 and 10 weight %, based on the total weight.
- It is possible for the ammonium polyphosphate of the present invention to be used alone or in combination with further flameproofing substances, e.g. tris-~2-chloroethyl)-phosphate, which may be used in a proportion between about 2 and 30 weight %, based on the total weight of the polyurethane.
The preparation of the polyurethanes or polyure-`.', ' ';
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50 6g~ A
thane foams does not directly form part of the present invention.
The plastics can be made in known manner by reacting one or more polyhydroxyl compounds of h:igh molecular weight with one or more polyisocy-anates in the presence of a catalyst, e~panding agents, surfactants and further processing aids. The preparation of the ammonium poly-phosphate, which is used in the present invention has been described in German Patent Specification P 22 30 ~74.8, wherein approximately equimolecular quantities of ammonium orthophosphate and phosphorus pentoxide are heated to temper-atures bètween 170 and 350 C in the presence of gaseous ammonia~ while continuously and simultaneously mixing, kneading and comminuting the mat-erial to undergo reaction.
The polyhydroxyl compounds which may conveniently be used for making polyurethanes include diols~ polyols~ polyethers3 polyesters or polyester amides, which commonly have a molecular weight within the range about 60 and 5000~ contain at least two O~-groups per molecule, and have a hydroxyl number within the range about 40 and 700 mg of KOH/gram.
The polyisocyanate which is a further necessary feed component may be an aromatic or aliphatic isocyanate containing at least two NCO- ;
groups per molecule. More particularly~ -Imonomeric or polymeric polyisocy-anates or so-called prepolymers, the latter being obtained by partial reaction of polyisocyanates with polyols, can be used.
It is customary for the reaction to be accelerated by means of minor proportions of a catalyst or catalys~ mixture. The preferred ca~alysts comprise tertiary amines or organometal compounds such as bivalent tin or lead compounds.
The poly~rethane batch is normally prepared so as to have a minor stoichiometric excess of NCO-groups therein~ based on the hydroxyl groups of the polyol compound~ It is also possible, however, for the batch to contain a deficiency of NC0-grollps. With respect to the hydroxyl groups~ the NC0-groups are used within the limits between about 90 and 130 %~ preferably 102 and 110 %, based on the stoichiometric quantity.
Depending on the degree of flame-resistance desire~ to be pro-duced7 the polyurethane batch is admixed with between about 0O5 and 20 weight %, preferably between 1 and lO weight %~ of ammonium polyphosphate~ based on the total weight of the batch. The ammonium polyphosphate should preferably be incorporated into the polyol prior to blending the latter with the isocy-anate compound. It is also possible for the ammonium polyphosphate to be blended with further liquid flame-proofing agents and for the blend to be added to the polyurethane batch.
In accordance with the present invention, it is possible to pro-duce compact or foamed polyurethanes~ The polyurethane foams are produced with the aid of customary expanding agents, such as low-boiling chlorinated or fluorinated alkanes and/or water. The quantity of expanding agent is selected in accordance with the unit weight desired for the polyurethane foam.
Further processing aids used in making the polyurethanes are foam j stabilizers regulating the cell structure~ the preferred foam stabilizers being surface-active silicons or polysiloxanes.
Depending on the polyol which is used in each particular case and on the quantitative ratio selected for the individual feed components, it is possible to make rigid or elastic foams. For the production of rigid foams, ~-~ such as those needed as insulatory material in constructional engineering, it is necessary to use highly cross-linked polyols containing a ]arge number of hydroxyl groups.
As compared with the ammonium polyphosphates, which are customarily used for the flameproofing of polyurethane moulding compositions~ those of ~.
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the present invention are less water-soluble and accord-ingly not like-ly to be washed out under the influence of moisture. ln other words, the plastics remain flameproof over a prolonged period of time. As a result of the gel~forming properties of the ammonium polyphosphates used in accor-dance with the present invention, it is possible for them to be uniformly dis~ributed in the polyurethane batchg especially in the polyol preliminary blend~ substantially without any significant sedimentation of phosphate.
In other words, it is possible for preliminary polyol blends containing phosphate, which are made with the polyphosphates of the present invention, to be stored in view of the fact that the phosphate component is not likely to settle over a prolonged period of time. The following Examples illustrate -` the invention.
EXA~LE 1:
An ammonium polyphosphate as used in the present invention~ which had a degree of condensation n of approximately 700, a m/n-ratio of 1 and a P205-content of 72 weight %, was tested as to its solubility in water and the result obtained was compared with the solubility values determined for the following commercially available ammonium polyphosphates, which had a degree of condensation n within the range 20 and 400. The following com-mercially available products were tested:
1. VP Kn 504 ~: Manufacturer Hoechst Aktienge-sellschaft~ Werk KNAPSACK~
Knapsack bei ~oln 20 Phos-Check P/30 ~: Manufacturer Monsanto Company, United States America 3. Go-Cut ~ - 100: Manufacturer Asahi Chemical Ltd., Japan VP Kn 504 ~ is a product containing 71-72 %-of phosphorus (P205) 9~
and 14-15 ~ of nitrogen. It has a specific weight of 108 g/cc and decom-poses at 330C. A suspension of 1 g of the product in 100 g of water has a pH-value between 4.5 and 6.
Phos Check P/30(~)is a product having the following physical pro-perties:
Phosphorus content: 32 %
Specific weight: 1.79 Decomposition temperature: 375-400 C
pH-value of dispersion 6.5 10 g/100 g H20 Refractive index 1.48-1.49 Go-Cut(~)- 100 is a product containing 30-32 % of phosphorus and l3-15 ~ of nitrogen. The product has the following further properkies:
Specific weight: 0.4-0.8 - Decomposition temperature: 330-450 C
Refractive index: 1.486 The solubility in water was determined as follows: 5 g sf ammonium polyphosphate was introduced in~o 100 cc of water and the whole was stirred for 1 hour at 40 CO The resulting solution was rapidly cooled down to room temperature and insoluble fractions were removed by centrifugation over a period OI 75 minutes at the temperature. The supernatant clear solution was decanted and boilecl for a short while to effect cleavage of dissolved ammon-ium polyphosphate, if any. The conductivity~ density and dissolved phos-phate fractions were determined on aliquote portions of the individual sol-utions. The results ~btained are indicated in the fo11Owing Tsble 1:

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~ T~BLE 1 : .
Product I II III
.
VP Kn 504 1665 1.003 20.9 Phos-Check P/30 1644 1.003 19.5 Go-Cut - 100 2018 1.004 31.8 Product of invention 605 1~001 9.3 With reference to the Table:
Column I: Electric conductivi~y of solution (~ = micro5 iemens) Column II: Density of solution at 20 C (g/cc) Column III: Dissolved phosphate fraction at 40C (wgt~
Table 1 shows that the product of the present invention is con-siderably less wa~er-soluble than the comparative produc~s.
-~ EXAMPLE 2 ,, ,~
Two polyurethane foams having the composition described below ~ were prepared with the use of two different batches identified as batch I
-~ and batch II~ respectively. Batch I contained as the flameproofing agent :, :
an ammonium polyphosphate having a degree of condensation n of approx~
imately 700, ~nd batch II was free from flameproofing agent. The following substances were intimately blended at room temperature:

- 20 Batch ~ Polyetherpolyol (propoxylated100 g 100 g ;1 glycerol/sucrose-mixture having an OH-number of 520 mg KOH~/g~ a 1 molecular weight of about 350 and a viscosity of 6000 centipoises 1 Water 1 g 1"g j Trichlorofluorome~hane 24 g 24 g Triethylamine 3 g 3 g 1, ~
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Table 1 cont~cL

Silicon stabilizer (dimethyl- 1 g 1 g polysiloxc~e-polyoxyalkylene ester copolymer) Ammoniwm polyphosphate 10 g -150 g of methylene diphenyl-4~ 41-diisocyanate was introduced with vigorous agitation into each of the blends prepared from the above sub-- stances and the resulting reaction mixtures were poured into two 5 litre card board con~ainers. After 30 secO oP creaming time c~nd 120 seconds of rise~ two rigid polyurethane foam blocks were found to have been formed which were hard within 10 minutes. The foam blocks had the properties indicated in Table 2 hereinafter.
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TABLE II

Prope~ies Foam . ~

Unit weight g/1 36 35 Compressive strength Kg/cm DIN ~German Industrial 2.71 2.63 ~
Standard) S3 421 ~-;

Flexural strength Kg/cm 2~202.27 Shear strength Kg/~m 1.501.54 mN 53 4~2 Dimensional stability % -6.3 -3.7 ; (change of volume at 70 C c~nd 95% of relative atmospheric moisture~
after 2 weeks) - Burn-up tests (ASTM-D 1692) were made on foams I cmd II. Foam I ~;
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was found to be ~'self-extinguishing" after a burn~up length of 26 mm. Foam II was found to burn off ~complete]-y~

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The same components, except for trichlorofluoro-methane, as those :. : ''.
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used in Example ~ for making batch II were used to prepare ~ltogether 8 specimens of a homogenized blend. Each o~ specimens 1 to 4 were further blended with 10 g of an ammonium polyphosphate having a degree of conden-sation n of approximately 800, and each of specimens 5 to 8 were further blended with 10 g of Phos-Check P/30 ~ having a degree of condensation of appro~imately 300. The individual specimens were stored in beakers for 4 weeks~ Samples were taken from each of specimens 1 to.l4 and 5 to 8 at in-tervals of 1 week and the sedimentation volume of the ammonium polyphos-phate expressed in % of the total volume, was determined. Following this, the sample was homogenized once again by stirring it with a blade agitator at 150 rpm and the time, which was necessary until the homogenization be-came visible was identified. The sample was then admixed with 24 g of trichlorofluoromethane and 150 g of methylene-diphenyl-4~4~-diisocyanate and made into a polyurethane foam.
; The sedimentation volumes and homo~enization periods identified during the test series are indicated in the following Table III.
TABLE III
Sam~le 1 2 3 ~ ~ 6 7 8 ` Number of weeks 1 2 3 4 1 2 3 4 ~ . , ; 20 Homogenization 10 10 15 20 25 40 60 > 180 period (seconds~
., _ . ., ,_ . _, . . ... .
- Sedimentation 0 0 1 6 6 14 12 10 volume %
- ,,_, After having been allowed to stand over a period of 4 weeks, sample 8 was no longer homogenizable. More particularly, a very hard deposit of ` sedimented ammoni~n polyphosphate was found to have been formed. Speaking generally~ samples 1 to 4 needed shorter homogenization periods than compar-ative samples 5 to 8. In clear contrast with the latter~ samples 1 to 4 were completely homogeneous after 2 weeks.

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~3506~8 _ The following componen~s were intimately blended at room temper-ature:
100 g of a polyesterpolyol (adipic acid-die~hylene-glycolpolyester) having an OH-number of 60 mg KOH/g, a molecular weight of approx imately 2000~ and a viscosity of approximately 20 000 centipoises~
~;~ 4-7 g of water, - 1.0 g of a silicon stabilizer (polyoxyalkylene-polydimethylsiloxane-copolymer), 1.0 g of dichlorotetrafluoroeth`y~lene, 0.4 g of dimethylbenzyl amine~
.
` 0.15 g of tin-II-octoate~ and ~- 7 g of an ammonium polyphosphate ha~ing a degree of condensation n of 700.
51 g of a mixture of the 2,4_ and 2,6-isomers of toluylenediiso-- cyanate, which were used in a mixing ratio of 80:209 was rapidly stirred into the blend so made. After 33 seconds of creaming time and 116 seconds of rise~ a flameproof elastic polyurethane foam was obtained in a ca~d board container. ; ;
A comparative foam ~ree from flameproofing agent was prepared under analogous conditionsO The foams so made had the properties indicated in Table IV~
TABIE IV
,''1 . , , of foam A B
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-~ Unit weight ~g/l) 24 23 Permanent set after (%~ 6.3 5.2 compression (EINo53 572 after 22 h at 70 C and ; 50 % compression c Tensile strength(Kg/cm ) -95 1 05 (DIN 53 571) ~ ' ..... . . .. ... . .

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Table IV cont'd Dimensional stability (%) -2-4 ~0.4 (Change of volume at 70 C
and 95 % of relativ,e moisture, after 2 weeks) A = Flameproofing agent added B = Free from flameproofing a~gent.
Burn-up tes~s (ASTM D 1692) were made on foa~s A and B. Foam A
was self-extinguishing after a burn-up :Length of 22 mm. Foam B burned off completely.
The above experiment showed that the foam properties were sub-stantially not affected by the addition of the flameproofing agent.

10 specimens were prepared from a blend homogenized at roomtemperature and made from the following components:
100 g of a polyesterpolyol (adipic acid-diethylene-glycolpolyes~er) having an OH-number of 60 mg KOH/g, a molecular weight of ~ ,~
approximately 2000 and a viscosity of approximately 20000 , centipoises, 4.7 g of water ~'j 1.0 g of a silicon stabilizer (polyoxyalkylene-polydimethylsiloxane~
co-polymer), 0.4 g of dimethy1ben~yl aminea and 0.15 g of tin-II-octoate.
Each of specimens 1 to 5 were admixed with 7 g of Go~Cut ~ hav-., ; ,, .
ing a degree of condensation of approximately 200 and each of specimens 6 ~- to 10 were admixed ~nth 7 g of an ammonium polyphosphate having a degree of condensation n of about 600. The individual specimens were stored in beak-ers over a period of 5 weeks. At one week intervals~ samples were taken from each of specimens 1 to 5 and 6 to 10 and the volume of a clear liquids ~ ;
layer which formed above suspension due to sedimentation of the ammonium poly_ ~
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~ 13-phosphate, was determined and expressed in ~, based on the total volume of the specimen. Following this, ~he sample was homogenized once again with the aid of a blade agitator at 150 rpm and the time, which was necessary until the homogeni~ation bec~ne visible, was identified. The results ob-tained are indicated in the following Table V:
TABLE V
~; Specimen 1 2 3 4 5 6 7 8 9 10 .. ~ .
Number of weeks 1 2 3 4 5 1 2 3 4 5 -;

Homogeni7ation30 5590 150 21010 35 45 60 75 period in sec.

Volume of clear 9 14 21 25 30 0 1 4 1~ 12 liquids layer in %

Table V shows that the necessary homogenization periods were ~- shorter for specimens 6 to 10 (invention) than for comparative specimens 1 to 5. In addition to this~ specimens 6 to 10 had a less pronounced tendency to sediment. This effect becomes even more obvious on further admixing ~-specimens~1 to 10 with 1 g of water ~cfo Table VI):
TABLE VI
.. . ...
Specimen 1 2 3 4 5 6 7 8 910 Number of 1 2 3 4 5 1 2 3 4 5 weeks Homogenization 20 50 80 140 195 0 20 3050 65 period in sec. ~ ;

~ . .. _ __ _~
Volume of clear 11 18 27 32 36 0 1 2 4 7 ;~ liquids layer -, in %
i ' Each of specimens 1 and 6 of Table V were blended with 1 g of dichlorotetrafluoroethylene and each of the resulting blen~s were reacted with 51 g of a mixture of the 2~4_ and 2~6-isomers of toluylene diisocya-lOSO~;~B
nate (which were used in ~ mixing rat,io of 80:20~. The re.sulting foc~ms had properties which could not 'be found to d.iffer significantly from those of the ~lameproof fo~m made as described :in Example 4.

6 specimens were made from a blend homogenized at room temperature and prepared from:
:~ 100 g of a polyether (propoxylated trimethylolpropane having an OH-number of 375 mg KOH/g~ a molecular weight of about 400 and a viscosity of ~ 650 centipoises)~
g of trichlorofluoromethane, 1. 5 g of a silicon stabilizer (dimethylpolysiloxane-polyoxyalkylene :, ether-copolymer)~
0.5 g of triethylene diamine, and 200 g of triethyl amine.
i Specimens 2 to 6 were blended with varying proportions of an ammon,- ~ , ~, ium polyphosphate having a degree of condensation n of about 700 and each of the specimens were reacted with 100 g of polymethylene-polyphenylene-poly-isocyanate containing approximately 32% of reactive NCO-groups and having a ,.
viscosity of 250 centipoises at 20 C. The specimens were placed in card board containers and gave qualitatively reliable rigid foamed blocks of :
polyurethane. The individual polyurethane specimens were subjected to burn~
up tests (ASTM D~ 1692). The results indicated in Table VII were obtained.
ThBLE VII
. _ ; Specimen l_ ~
: .
' Quantity of0 2 6 15 25 40 ~:
; flameproofing -.
,i a~ent (g) Cate~ory _ b _b s s s s :~

Burn-off 236 104 ~ ~ ~ ~ '~
velocity ~.
(mm/sec~ ' ::. --1~

Burn-up length - - 55 19 11 10 (mm) , . . . . . . . .
b = combustible s = self-extinguishing .E~A~LE ?:
A paste was made from 40 weight % of an ammonium polyphosphate having a degree of condensation n of about 100 and 60 weight % of tris-(2-chloroethyl)-phosphate.
~ 10 g of the paste so made was blended wi~h:
;~ 100 g of a polyetherpolyol (propoxylated ethylene diamine having an OH-number of 480 mg EOH/g, a molecular weight of about 400 and a viscosity of about 3000 centipoises at 25C), -`
`'. ,

2 g of hexamethyl-triethylene tetramine~ ;-2~ g of trichlorofluoromethane, 2 g of water, 1 g of a silicon stabilizer (dimethylpolysiloxane-polyoxyalkylene ;;
ether-copolymer~) and 150 g of methylenediphenyl-4,4'-diisocyanate.
The blend so made was poured into a card board container, in which a rigid foam of reliable quality was obtained~ after 30 seconds of creaming time and 112 seconds rise. The unit weight was 32 g/l. In the burn-up test (ASTM D 1692), the foam was found to be self-extinguishing, after a burn up length of 21 mm.

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Claims (7)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Flameproof polyurethanes or polyurethane foams containing as a flameproofing agent, between about 0.5 and 20 weight % of an ammonium polyphosphate, the ammonium polyphosphate having the general formula:

H(n-m)+2(NH4)mPnO3n+1, in which n stands for a whole number averaging a value of more than 600 up to about 1000, and the ratio of m:n is approximately 1:1.

2, The polyurethanes as claimed in claim 1, wherein n stands for a whole number between about 600 and 800,

3. The polyurethanes as claimed in claim 1, containing between about 1 and 10 weight %, of the ammonium polyphosphate, based on the total weight of the polyurethanes.

4. The polyurethanes as claimed in claim 1, being obtained by reacting a polyhydroxyl compound of high molecular weight with polyisocya-nates in the presence of a catalyst, expanding agents, surfactants and fur-ther processing aids.

5. The polyurethanes as claimed in claim 1, containing tris-(2-chloroethyl)-phosphate as the further flameproofing substance.

6. The polyurethanes as claimed in claim 5, containing tris-(2-chloroethyl)-phosphate in a proportion between about 2 and 30 weight %, based on the total weight.

7. The polyurethanes as claimed in claim 1, containing an ammonium polyphosphate being obtained by heating substantially equimolecular propor-tions of ammonium orthophosphate and phosphorus pentoxide to temperatures between 170 and 350°C in the presence of gaseous ammonia while continually and simultaneously mixing, kneading and comminuting the material to undergo reaction.