CA1123167A - Process for the production of elastomeric moldings - Google Patents

Abstract

Mo-1845 PROCESS FOR THE PRODUCTION OF ELASTOMERIC MOLDINGS

ABSTRACT OF THE DISCLOSURE
The instant invention is directed to a process for the production of elastomeric moldings comprising:

(A) introducing a reaction mixture into a closed mold, said reaction mixture comprising:

(i) an organic polyisocyanate, (ii) a hydroxyl group containing compound having a molecular weight of from 1800 to 12,000, (iii) a catalyst for the reaction between hy-droxyl groups and isocyanate groups, (iv) an active aromatic diamine having at least one alkyl substituent in the ortho-position to a first amino group and two alkyl substituents in ortho-position to a second group, and (v) air and/or nitrogen dissolved under pres-sure in any one or more of Components (i), (ii), (iii) or (iv), (B) allowing said reaction mixture to react in said mold and (C) removing the resultant product from said mold, the improvement wherein in any of Components (i), (ii), (iii) or (iv) which does contain said air and/or nitrogen dissolved therein there is included an inorganic, finely divided, nitro-gen adsorbing agent in an amount sufficient to accelerate the transition of the air and/or nitrogen from the dissolved state to the dispersed state upon release of the pressure (i.e., as Mo-1845 the liquid reacting mixture flows into the mold). It is this dispersed state which allows for adequate blowing during the process.

Mo-1845

Description

~1O-1845 ~123~6~

OC~:SS l;`OR ~ r~ ODU~`'l'L~)N Ol'l.LAST()~ lOrll~lNGS

B~CKGRO~ND Ol` Tlll~ INVEN'l'I~N
~ . . . _ In recent years, there has been mucll interest in producing a variety of different moldecl ~arts by the so-called "reaction injection moldinc3" (l~lM) process. Thisprocess involves a technique of filling a closed mold with highly reactive, liquid starting.componellts withill a very short time, generally by using hig}l out~ut, higll pressure dosing apparatus after the components llave been mixed in so-called "positively controlled" mixheads.

The RIM process is wiclely known and a detailed description of tlle techllology tllereof may be Eound, for - example, in the following references:

- Piechota/Rohr: "Intec~ralscl-aumstoffe", Carl llallser-VerlacJ, Munich/Viellna, 1975;

Pr.-pelka/Wharton: "~eaction Injection Molding in tl~e ~utomotive Industry", Journa1 of Cell. I'lastics, Vol. II, Nc~.2, 1975 Knip~: "Plastics for ~utomobile SaEety Bumpers", Journal of Cell.
Plastics, Nov. 2, 1~73.

Ludwico/Taylor: "l'he BayElex*llO Systellls - Tl~e New Generatioll oE Rl~i Materials", ~resented at S~L~ Passellc~er Car MTG, l~etroit, September 1977.

* Registered Trademark Mo-18~5 .. _ , . . . _ , .

31~7 The reaction injection molding -technique may be used for producing large moldings weighing from 3 to 10 kg or more, such as the flexible car body parts also known in the motor industry as "soft face elements",i.e. reversibly - 5 shaped front and rear parts of motor vehicles.

The following technical advance is generally achieved by the RIM procedure: large quantities of liquid, highly reactive starting materials are delivered mechani-cally within a very short time (from about 2 to 4 seconds), are mixed, and are introduced into a closed mold in which the mixture is cured to yield the finished product within a time (from 30 to 120 seconds) which is also very short for polyurethane materials.

Realization of this technology required a solu-tion to the following three problems:

1. In view of t~le high reactivity of the startingcomponents (polyisocyanates and compounds which are reactive with polyisocyanates) the reaction mixture must be intro-duced into the mold within the shortest possible time which should not exceed the cream time (i.e., the time between mixing of the reactants and the first visible signs of a chemical reaction). This nècessitated the development of highly efficient axial and radial piston pumps which when installed in high pressure machines were capable of deliver-ing at a rate of from 2.5 to 6.5 kg/second. Machines ofthis type are now known and have been described, for example, in German Offenlegungsschriften 1,778,060 and 2,146,054.

Mo-1845 -2-~ , .

~L~23~i7

2. Production o~ a ~aultless molding required not only exact dosing of the components to keep them at a partic-ular ratio prescribed by the given formulation over the whole period o~ lnjection, but also required intimate mixing of the components from the first to last drop.
Perfect mixing is made enormously difficult by the fact that due to their high flow velocitles, the components have only a very short residence time in the mixing chamber of the mixing head. This problem could be solved by using so-called positively controlled "mixheads" which operate on the principle of counterflow injection (see e.g., U. S.
Patents 3,709,640 and 3,857,550, and German Offenlegungs-schriften 2,007,935 and 2,364,501).

3. When the reaction mixture enters the closed mold, it almost instantly displaces the air contained in the mold. To ensure that this does not lead -to inclusions of air in the reaction mixture and hence faults in the end product, the liquid streaming into the mold must, in effect, "push" the air forward in front of it in the form of a "flow front" and expel it through predetermined slots.
To ensure complete absence of turbulence during filling of the mold, the material must enter the mold over a wide front along the wall of the mold in a laminar stream.
This has been achieved by developing a certain technique of injectlon through so-called "film gates" described in German Offenlegungscchriften 2,348,658 and 2,348,608.

In spite of -the many advantages of the RIM pro-cess, there is a continual searching for faster reactive systems, particularly for use in mass production industries, such as the automotive industry.

Mo-1845 ~3~

, 9.lZ316~7 A very promising reactive system has rc celltly been developed whicll is based on the use of an active aro-matie diamine having at least one alkyl subsl ituent in the ortho-position to a first amino yroup and two alkyl 5 substituents in ortho-position to a second amino c~roup.
These active aromatic diamines are ~enerally used in com-bination with organie polyisocyanates hydroxyl group-eontaining materials and catalysts for the reaction between hydro~yl groups and isoeyanate groups. These systems 10 are the sub jeet of the Ludwic:~o/rPaylor papers hereinbe Eore referred to.

;

These active systems gel so quiekly upon mi~iny 15 of the components that the final products prc~cluced therefrom have relatively hig}l densities (i.e., 70 lbs. per eubie ft . ) since conventional organic blowin~ agents do not volatilize quickly enough to have any blowing ef ~ect .
Consequently the molcls used are cJenerally overpaeked in orcler 2() tQ en~lll~e adecluate filling of the mold. This overpàcking necessarily results in (a) an increasc in thc pressure in the molcd requiring inereased clamping pressures to keep the mold elosed and (b) visual surfaee defeets. While the surface defeets are not physical (i.e., they do not aEEeet 25 the surface physieally and do not appear to affeet the physieal pro~?erties), their visual appearanee renders thern unaeeeptable Eor usc in a variety oE cliEferellt a[Jplieations, partieularly Eor e~cE~osecl autonlc)tive parts.

.

Mo- 1 8 4 5 - 4 ~
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. . . .. . . .. . ... .. . . . .

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~L23~L6~7 It woulcl be desirablc to reduce tlle dellsity of the products o[ the above-noted reactive syst~ms (e.g., to abou-t 60 lbs. pc?r cubic foot), whilc-~ at thc~ same time reduciny the internal mold press~re ancl eliminatincJ the surface defects.

SillCe COIlVell tional orc3allic blowincJ acJellts are ineffective, one suc3yestion, whicll has met with some success, has been to include in one or more o~ the com-ponents air and/or nitrogen uncler pressure. The use of air and/or nitrogen in polyurethane systems is, of course, ~nown, as are the many and varied techniq~les for providing such dissolved air and/or nitrocJen. For exalllple, air and/or nitrogen has been introduced directly into -the mixincJ
chamber and mixed simultaneously with tlle reactive mixture.
Additionally, the air and/or nitroc3en has bcen whipped into one or more of the components. The creamy mixture formed is then metered by-means of a pump to a final mixing chamber where it is mixed w~th the other reactive cornponents. When the meterinc3 pump clischarc3es at a sufficierltly hic3h pressure, the quantity o~ c3as whicll is initially clissolved and/or dispersed in the starting material, which is Eecl to the meterincJ pump, dissolves at the higller pressure in a very short period of time. The lic~uid fcd to the mixhcad then con-tains gas in the dissolved state. Upon being fed to the mixhead, dissolution takes plaee in a very short time. In general, it is prefcrred that the c~as be dis-solvc(l in one or mc)J^e of the compol-lc~llts. Othc!r tcchlli(lues for dissolving c3ases are also known and are clcscribed in e ~J U.S. Patents 4,050,896 and U.S. 4,089,206.

Mo-1895 -5-.. .
.

11;Z3~7 Although the use of such dissolved air and/or nitrogen has met with some success with the highly active systems noted above, it has been found that the resultant molded part, while of reduced density (e.g., from 62 to 68 lbs. per cubic ft.), will have varied densities throughout the molded part.

As noted above, air and/or nitrogen is effectively dissolved under pressure in one or more of the components.
It has been observed that when this pressure is relieved (e.g., upon passage of the components through the mixhead and into the mold), the air and/or nitrogen does not immediately pass from the dissolved sta*e to the dispersed state. It is believed that a state of super saturation exists in liquid reacting system containing the dissolved gas for some finite period of time. For these highly reactive systems, this delay in passage from the dissolved to the dispersed state is sufficiently long so that gelation occurs in the mold before proper blowing.

All of the above-noted problems have now been substantially removed by the instant invention.

DESCRIPTION OF THE INVENTION

The instant invention is directed to a process for the production of elastomeric moldings comprising:

(A~ introducing a reaction mixture into a closed mold, said reaction mixture comprising:

(i) an organic polyisocyanate, (ii) a hydroxyl group containing compound having a molecular weight of from 1800 to 12,000, Mo-1845 -6-:~L123:~7 (iii) a catalyst for the reaction between hydroxyl groups and isocyanate groups, (iv) an active aromatic diamine having at least one alkyl substituent in the ortho-position to a first amino group and two alkyl substituents in ortho-position to a second group, and (v) air and/or nitrogen dissolved under pressure in any one or more of Components (i), (ii), (iii) or (iv), (B) allowing said reaction mixture to react in said mold and (C) removing the resultant product from said mold, the improvement wherein in any of Components (i), (ii), (iii) or (iv) which does contain said air and/or nitrogen dissolved therein there is included an inorganic, finely divided, nitrogen adsorbing agent in an amount sufficient to accelerate the transition of the air and/or nitrogen from the dissolved state to the dispersed state upon release of the pressure.

It has been found that the use of the above-noted inorganic, finely divided, nitrogen adsorbing agents (i) significantly enhance the blowing action of the air and/or nitrogen,(ii) provide for uniform density of the molded part, (iii) allow for the reduction of internal 2~ mold pressures, and (iv) substantially eliminate surface defects. These effects are obtained due to the ability of the nitrogen adsorbing agents to accelerate the transition of the air and/or nitrogen from the dissolved state to the dispersed state when the pressure is relieved.

Mo-1845 -7-,. ... _ _ ~231~i7 The nitrogen adsorbing agents useful in the instant invention are known, and are described in Kirk-Othmer, "Encyclopedia of Chemical Technology", Second Edition, completely revised, Volume 1, page 460, and Perry, "Chemical Engineers' Handbook", Fifth Edition, pages 16~5 and 16-6.
Speeifie useful nitroc3en aclsorbinc3 agents inelude aluminas sueh as aetivatecl alumina, ancl aetivated bau~ite; silieeous adsor~ents sueh as zeolite, alumino-1~ silieates, aeid-treated elays, mac~nesia-siliea c~el, and Fuller's earth, siliea cJel; earbons sueh as aetivated earbon ancl earbon blaek; iron o~ides; and the like.
Presently ~referred are aetivated earbons ancl iron oxides.
In general, the only requirement for useful adsorbiny I r~ a-lents are that they have a relatively larc3e surfaee area, c1enerally in e~eess o~ 10 m jcl, and that they-clo not adversely affeet tlle pllysieal pro~erties of tile final yroduet. In cJeneral also, less abrasive materials are more desirable i31 orcler to avoicl unclue wear on some hi~l 2~l pressure meterinc~ pumps.

In general, the amount of nitrocJell a~sorbincl ac;ent used must be suffieient to substantially enllallee the blowiny e~fieieney of the system when the air alld/or nitrogell is dissolved in-one or more of the eomponents uncler pressure.
~5 Thus, the minimal amount neeessary ean be eharaeterized in two ways: (a) as an amount suffieient to reduee the amount of c3as whieh must be dissolved in the system to aeilieve a part havillc~ a c~ivell speeiEie cJravity, or (b) as an amoun-t WiliCil at the same cJas loaclinc~ (i.e., dicsolved clas) will a]low ~or tlle produetion oE a final produet having a lowel- speeiEie c~ravit~ than whell no adsorbincJ ac3ent is used. In cJe~l~eral, the amoullt addecl Mo-1845 -8--~L23~L~7 will range from 0.01 to 1 ~ by weight based on the amoun-t of hydroxyl group containing material. It is preferred, however, that the amount used be from 0.1 to 0.7 % by weight, and will most preferably be about 0.5 ~ by weight.
In use, the adsorbing agent is merely added to the component or components in which it is desired to dissolve the air and/or nitrogen. The air and/or nitrogen is then dissolved using art recognized techniques.

The polyisocyanates used as starting components according to the present invention may be aliphatic, cyclo-aliphatic, araliphatic, aromatic or heterocyclic polyiso-cyanates (for purposes of the instant invention, the term "polyisocyanate" is intended to include any isocyanate having two or more isocyanate groups) such as those described, for example, by W. Siefken in Justus Liebigs Annalen der Chemie, 562, pages 75 to 136. Specific examples include ethylene diisocyanate; tetramethylene-1,4-diisocyanate;
hexamethylene-1,6-diisocyanate; dodecane-1,12-diisocyanate;
cyclobutane-1,3-diisocyanate; cyclohexane-1,3- and -1,4-20 diisocyanate and mixtures of these isomers; l-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (German Auslegeschrift 1,202,785-and U. S. Patent 3,401,190);
hexahydrotolylene-2,4-diisocyanate and -2,6-diisocyanate and mixtures of these isomers; hexahydrophenylene-1,3-25 diisocyanate and/or 1,4-diisocyanate; perhydrodiphenyl-methane-2,4'-diisocyanate and/or -4,4'-diisocyanate;
phenylene-1,3-diisocyanate and 1,4-diisocyanate; tolylene-2,4-diisocyanate and -2,6-diisocyanate and mixtures of these isomers; diphenylmethane-2,4'-diisocyanate and/or 30 -4,4'-diisocyanate; naphthylene-1,5-diisocyanate, triphenyl-methane-4,4',4"--triisocyanate; polyphenyl-polymethylene polyisocyanates which may be obtained by aniline-formaldehyde Mo-1845 -9-~3~67 condensation followed by phosgenation and which have been described, for example, in British Patents 874,430 and 848,671; _- and p- isocyanatophenyl-sulphonyl isocyanates as described in U S. Patent 3,454,606; perchlorin~ted aryl polyisocyanates, such as those described in U. S. Patent 3,277,138; polyisocyanates having carbodiimide groups as described in U. S. Patent 3,152,162; diisocyanates of the type described in U. S. Patent No. 3,492,330; poly-isocyanates containing allophanate groups as described, e.g. in British Patent 994,890, in Belgian Patent 761,626 .
and in published Dutch Patent Application 7,102,524;
polyisocyanates containing isocyanurate groups as described in U. S. Patent No. 3,001,973, in German Patents 1,022,789;
1,222,067 and 1,027,394 and in German Offenlegungsschriften 1,929,034 and 2,004,048; polyisocyanates containing urethane groups as described in Belgian Pate~t No. 752,261 and U. S. Patent 3,394,164; polyisocy~nates containing acylated urea groups as described in German Patent 1,230,778;
- polyisocyanates containing biuret groups as described in U. S. Patents 3,124,605 and 3,201,372 and in Brit;sh Patent 889,050; polyisocyanates prepared by telomerization reactions as described, for example, in U. S. Patent 3,654,106;
polyisocyanates having ester groups, such as those mentioned, for example, in British Patents 965,474 and 1,072,956, U. S. Patent 3,567,763 and in German Patent 1,231,688;
reaction products of the above-mentioned isocyanates with acetals as described in German Patent 1,072,385; and poly-isocyanates containing polymeric fatty acid groups as de-scribed in U. S. Patent 3,455,883.

Particularly suitable for the process according to the present invention are diisocyanates or polyisocyanates based on 4,4'-diisocyanatodiphenylmethane. Pure 4,4'-Mo-1845 -10-~1231~7 diisocyanatodiphenylmethane (m. p. approx. 40C) may also be used according to the present invention.

The presently preferred starting components (a) are liquid polyisocyanates having urethane groups, which may be obtained (e.g. as described in German Offenlegungsschrift 1,618,380) by reacting 1 mol of 4,4'-diisocyanatodiphenyl-methane with from 0.05 to 0.3 mols of low molecular weight diols or triols, preferably with polypropylene glycols having a molecular weight below 700, or diisocyanates having carbodiimide and/or uretoneimine groups based on diphenyl-methane diisocyanate, which are obtainable according to U. S. Patent 3,152,162. Mixtures of the last-mentioned preferred polyisocyanates are also highly useful. Aliphatic and cycloaliphatic isocyanates are generally less suitable for the purpose of the present invention.

The compounds used as Component (ii) in the process according to the present invention are preferably polyhydroxy materials having molecular weights of from 1800 to 12,000, and most preferably from 3000 to 7000. Polyethers are suitable for the process of the present invention. Pre-ferred are those having at least 2, and preferably 2 or 3 hydroxyl groups are known and may be prepared, e.g. by polymerization of epoxides, such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuranl styrene oxide or epichlorohydrin, either on their own, e.g. in the presence of BF3, or by a process of chemical addition of these epoxides, optionally as mixtures or successively, to starting components having reactive hydrogen atoms, such as water, ammonia, alcohols, or amines. Examples of suitable starting components include ethylene glycol, propylene glycol-(1,3) or -(1,2), trimethylolpropane, 4,4'-dihydroxy-diphenylpropane, aniline, ethanolamine or ethylene Mo-1845 -11-~2~ 7 diamine. Sucrose polyethers which have been described in German Auslegeschriften 1,176,358 and 1,064,938 may also be used according to the present invention. It is in many cases preferred to use polyethers which contain predominant amounts of primary OH groups (up to 90%, by weight,, based on all the OH groùps present in the polyether). Polyethers modi-' fied with vinyl polymers are also suitable. These may be obtained, for example, by the polymerization of styrene and~acrylonitrile in the presence of polyethers (U. S.
Patents 3,383,351; 3,304,273; 3,523,093 and 3,110,695;
and German Patent No. 1,152,536). Polybutadienes having OH groups may also be used.

According to the present invention, however, there may also be used polyhydroxyl compounds which contain high molecular weight polyadducts or polycondensates in a finely dispersed form or in solution. Such modified polyhydroxyl compounds are obtained when polyaddition reactions (e.g.
reactiQns between polyisocyanates and amino functional com-pounds) or polycondensation reactions (e.g. between formalde-hyde and phenols and/or amines) are directly carried out in situ in the above-mentioned hydroxyl compounds. Processes .
for the production of this,type of material have been de-scribed in German Auslegeschriften 1,168,075 and 1,260,142 and in German Offenlegungsschriften 2,324,1,34; 2,423,984;
2,512,385; 2,513,815; 2,550,796; 2,550,797; 2,550,833 and 2,550,862. Such polyhydroxyl compounds may also be obtained according to U. S. Patent 3,869,413 or German Offenlegungs-schrift 2,550,860 by mixing an aqueous polymer dispersion with a polyhydroxyl compound and then removing water from 30~ the mixture.

Mo-1845 -12-~123~

According to the present invention, hydroxyl-containing polyesters, polythioethers, polyacetals, poly-carbonates or polyester amides of the type known for the production of both homogeneous ancl cellular polyurethanes may also be used instead of or together with polyether polyols.

Suitable polyesters containing hydroxyl groups in-clude, reaction products of polyhydric, (preferably dihydric alcohols,) optionally with the addition of trihydric, alcohols, and polybasic (preferably dibasic) carboxylic acids. In-stead of free polycarboxylic acids, the corresponding poly-carboxylic acid anhydrides or corresponding polycarboxylic acid esters of lower alcohols or mixtures thereof may be used for preparing the polyesters. The polycarboxylic acids may be aliphatic, cycloaliphatic, aroma~ic and/or heterocyclic and they may be substituted, e.g. by ~alogen atoms, and/or may be unsaturated. The ~ollowing are mentioned as examples: succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, trimellitic acid, phthalic acid anhydride, tetra-hydrophthalic acid anhydride, hexahydrophthalic acid anhydride, tetrachlorophthalic acid anhydride, endomethylene tetrahydrophthalic acid anhydride, glutaric acid anhydride, maleic acid, maleic acid anhydride, fumaric acid, dimeric and trimeric fatty acids, such as oleic acid, optionally mixed with monomeric fatty acids, dimethyl terephthalate and terephthalic acid-bis-glycol esters. The following are examples o~ suitable polyhydric alcohols: ethylene glycol, propylene glycol-(1,2) and -(1,3), butylene glycol-(1,4) and -(2,3), hexanediol-(1,6), octanediol-(1,8), neopentylglycol, cyclohexanedimethanol (1,4-bis-hydroxy-methylcyclohexane), 2-methyl-1,3-propane-diol, glycerol, Mo-1845 -13-.

3 ~Z3~ ~;7 trimethylolpropane, hexanetriol-(1,2,6), butanetriol-(1,2,4), trimethylolethane, pentaerythritol, quinitol, mànnitol and sorbitol, methyl glycoside, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycols, dipro-pylene glycol, polyprcpylene glycols, dibutylene glycoland polybutylene glycols. The polyesters may also contain a proportion of carboxyl end groups Polyesters of lac-tones, such as E-caprolactone, or hydroxycarboxylic acids, such as w-hydroxycaproic acid, may also be used.

Particularly to be mentioned among the polythio-ethers are the condensation products obtained by reacting thiodiglycol on its own and/or with other glycols, dicar-boxylic acids, formaldehyde, aminocarboxylic acids or - amino alcohols. The products obtained are polythio-mixed ethers, polythio-ether esters or polythio-ethçr ester amides, depending on the co-components.

Suitable polyacetals include, for example, the compounds which may be prepared from glycols, such as di-ethylene glycol, triethylene glycol, 4,4'-dioxethoxy-diphenyl dimethylmethane and hexanediol, and formaldehyde.Suitable polyacetals for the purpose of the present invention may also be prepared by the polymerization of cyclic acetals.

The polycarbonates containing hydroxyl groups used may be~of the type known. Highly useful are those which may be prepared by the reaction of diols, such as propane-diol-(1,3), butanediol-(1,4) and/or hexanediol-(1,6), diethylene glycol, triethylene glycol or tetrae-thylene glycol, with diarylcarbonates, e.g. diphenylcarbonate, or phosgene.

Mo-1845 -14-l~Z3~7 Suitable polyester amides and polyamides include, for example, the predominantly linear condensates prepared from polybasic saturated and unsaturated carboxylic acids or the anhydrides thereof and polyvalent saturated or un-saturated amino alcohols, diamines, polyamines and mixturesthereof.

Representatives of the hydroxyl functional compounds which may be used according to the present invention are generally known and have been described, for example, in High Polymers, Vol. XVI, "Polyurethanes, Chemistry and Technology"
by Saunders-Frisch, Interscience Publishers, New York, London, Volume I, 1962, pages 32 - 42 and pages 44 - 54 - and Volume II, 1964, pages 5 - 6 and 198 - 199 and in Kunststoff-Handbuch, Volume VII, Vieweg-Hochtlen, Carl-15 Hanser-Verlag, Munich, 1966, on pages 45 to 71.

In the process according to the present invention, Component (ii) preferably consists solely of the classical polyether polyols of polyurethane chemistry having molecular weights of from 1800 to 12,000, preferably from 3000 to 7000, and containing two or most preferably three hydroxyl groups.
Mixtures of polyethers having two or three hydroxyl groups are preferred.

The active aromatic diamines, are preferably liquid or dissolved in or blended with the polyol component. By "active" diamines are meant those whose reactivity towards isocyanates has not been reduced by electron at-tracting substituents, such as halogen, ester, ether or disulphide groups, as is the case, for example, with methylene-bis-chloraniline (Moca). Also excluded from the term "active"
are amines which contain other functional groups reactive with isocyanate-s. The active diamine is generally used in Mo-1845 -15-l~Z3167 the process according to the present invention in quanti-ties of from 5 to 75~ by weight, preferably from 5 to 35~ by weight, and most preferably from 8 to 35% by weight, based on Component (ii).

Liquid or dissolved aromatic amines which have proved to be particularly suitable for the process according to the present invention are those which con-tain at least one alkyl substituent in the ortho-position to a first amino group and two alkyl substituents in the ortho-position to a second amino group. Examples include: 1,3-diethyl-2j4-diamino-benzene, 2,4-diaminomesitylene, 1-methyl-3,5-diethyl-2,4-diaminobenzene, 1-methyl-3,5-diethyl-2,6-diamino-benzene, 1,3,5-triethyl-2,6-diaminobenzene, 3,5,3',5'-tetraethyl-4,4'-diaminodiphenylmethane and the like. The above-mentioned active aromatic amines may, of course, be used as mixtures with each other or in combination with other active aromatic amines.

It is generally preferred to use aroma-tic diamines which have an alkyl subs-tituent (preferably of from 1 to 4 carbon atoms) in both ortho-positions to each amino group.
For processing by the RIM process, it is generally preferred that the diamine be liquid at room temperature and miscible with the polyhydroxyl compounds in any proportion, particularly with polyhydroxypolyethers. Particularly preferred in this connection is the compound 1-methyl-3,5-diethyl-2,4-diamino-benzene or a mi~cture of this compound with l-methyl-3,5-diethyl-2,6-diarninobenzene.

Catalysts (iii), which are also essential to the present invention and without which it is not possible to obtain a molding which sets rapidly in the mold and has technologically interesting mechanical properties, are Mo-1845 -16-. .

;2316~7 preferably selected from the group of organic me-tal compounds known for use in polyurethane chemistry. According to the pre-sent invention, it is preferred to use organic tin compounds such as tin (II) salts of carboxylic acids, (such as tin (II) 5 acetate, tin (II) octoate, tin (II) ethyl hexoate or tin (II) laurate), and the dialkyl tin salts of carboxylic acids, (such as dibutyl tin diacetate, dibutyl tin dilaurate, dibutyl tin maleate or dioctyl tin diacetate,) either alone or most preferably as a complex with amidines, such as 2,3-10 dimethyl-3,4,5,6-tetrahydropyrimidine or 2-methyl-3-cyclo-hexyl-3,4,5,6-tetrahydropyrimidine, aminopyridines, amino-pyrimidines, hydrazino pyridines or hydrazino pyrimidines.
Synergistically acting catalyst combinations of this type are known and have been described, for example, in German 15 Offenlegungsschriften 2,434,185; 2,601,082 and 2,603,834.

Other catalystswhich may be used include: known tertiary amines, such as triethylamine, tributylamine, N-methylmorpholine, N-ethylmorpholine, N-cocomorpholine, N,N,N',N'-tetramethyl-ethylenediamine, 1,4-diaza-bicyclo-20 (2,2,2)-octane, N-methyl-N'-dimethylaminoethyl-piperazine, N,N-dimethylbenzylamine, bis-(N,N-diethylamino-ethyl)-adipate, N,N-diethylbenzylamine, pentamethyl-diethylene-triamine, N,N-dimethylcyclohexylamine, N,N,N',N'-tetra-methyl-1,3-butanediamine, N,N-dimethyl ~-phenylethylamine, 25 1,2-dimethylimidazole and 2-methylimidazole. A preferred catalyst of this type is 1,4-diaza-bicyclo-(2,2,2)-octane.

Tertiary amines having isocyanate-reactive hydrogen atoms include, e.g. triethanolamine, triisopropanol-amine, N-methyl-diethanolamine, N-ethyl-diethanolamine and 30 N,N-dimethyl-ethanolamine may also be used. Reaction products of these compounds with Mo-1845 -17-3~L~7 al]iylene oxides, sucn as ;-~ropylene oxidt-? all(l/or ethylene oxide are also suitable.

Silaamines llaving carbon-silicon boncis as described, e.g. in Germall Pate~nt 1,229,2~0 nlay also be used as catalysts.
Exam;?les include 2,2,4-trimethyl-2-silamorpllol:ine or 1,3-diethylaminomethyl-tetrarnethyl-disiloxane.

Basic nitrogen compounds, such as tetralkylan~lonium hydroxides, alkali metal hydroxides such as sodium llydroxide, alkali metal pllenolates, such as svdium pherlolate, and alkali metal alcoholates, such as sodium methylate, may also be used as catalysts. Ile~allydrotriazines are also suitable catalyst.

The above-mt-~lltioned catalysts may be used alone, (e.g. most preferably 1,4-diaza-bicyclo-(2,2,2)-octane,) or in combination with organic metal compounds, and in particular the organic tin compounds noted above.

Other re~preselltatives of catalysts which may be uscd accordiny to the present invention and details COIl-cerning-tlle action of the catalysts may be fourl~, e.g., in Kunststoff-ilandbuch, Volume VII, published by Viewt?g and 20 llochtlen, Carl-ilanser-Verlag, Munich 1966, pacJes 96 to 102.

The catalysts are gene~rally used in a quantity of from about 0.01 to 10~ by weight, and preferably from 0.05 to 1~ by weight, based on the quantity of Compounds (ii).

~ir and~or nitroqt-~ll is also ncct?ssary and is introcluccd into onc or more of tht-~ compollellts UsillcJ t~chniques known in the art. It is ~reselltly ~)reEerrt?d to use commt?r-cial tecllniques such as ~ifuser Stone-KI~lEX mixers and venturi type mixers o tilC type ciescribeclin U.S. Patent

4,132,83~.

Mo-1845 -18-.~

gl~L23~67 ~ nOUCJIl gas is CUStOm.lri Iy ~ut into tlle system in an amount in excess oE the amount nccessary to saturate the particular componellt at a feed tank pressure of ~rom 30 to 50 psi. As is known in thc art, material Elows from the feed tan-k throucJIl a transfer pump (whicll increascs the pressure of the particular cornponerlt) throuclil a metering pump to the mixhead. Discharge pressures of the -transfer pump are generally in the range o~ 50 to 100 psi, wllile discharge pressures of the metering pump are generally in the range of 2000 to 3000 psi. Thc amount of the c~as in the system is generally monitored using commerci.ll measuring equipment which responds to changes in specific gravity of the liquid components. One such device is the Dynatrol*
(Mfg. by ~utomation Products). This device permits the effeetive control of the gas eontent by monitoring any changes in the specific gravity of the liquid.component.

Surface-active additives (emulsifiers and foarn stabilizers) may also be used accord~ng to the present invention. Suitable emulsifiers include the soclium salts of ricinoleic sulphonates or oE fatty acids, or salts of fatty acids with amines, such as oleic aci.d diethylamine or stearic acid diethanolamine. ~lkali metal or an~lonium salts of sulphonic acids, such as dodecylbenzene sulphorlic acid or dinaphthylmethane disulphonic aeid, or of fatty aeids, such as ricinoleie acid, or of polymeric fatty acids may also be usecl as surface active additives.

rl`he most useful Eoam stclbilizcrs are l)rimarily watcr-soluble po:Lyethc!r siloxaner,. These compo~lllds generally llave a polydimethylsilox.llle group attached to a copolymer of ethylene oxide ancl propylelle oxide. ~oalll sta~ilizers of this type are knowll all(J llave becn clescribed, for cxample, in * Registered Trademark Mo-1845 -1')-.~

, . _ ~123167 U. S. Patent 2,764,565.

Known cell regulators, such as paraffins or fatty alcohols or dimethylpolysiloxanes, pigments, dyes, flame retarding agents, such as bis-chloroethylphosphate or ammonium phosphate and polyphosphate, stabilizers against ageing and weathering, plasticizers, fungistatic and may also be used according to the present invention.

Other examples of surface active additives, foam stabilizers, cell regulators, stabilizers, flame retarding substances, plasticizers, dyes, fillers and fungistatic and bacteriostatic substances which may be used according to the present invention and details concerning the use and action of these additives are known and may be found in Kunststoff-Handbuch, Volume VI, published by Vieweg and Hochtlen, Carl Hanser-Verlag, Munich, 1966, pages 103 to 113:

The quantity of polyisocyanate (Component (i)) used in~ the process according to the present invention is preferably calculated so that the foamable mixture has an isocyanate index of from 70 to 130, in particular from 90 to 110. By "isocyanate index" is meant the quotient of the number of isocyanate groups and number of groups which are reactive with isocyanates multiplied by 100.

The known reaction injection molding technique (RIM process) is used for carrying out the process according to the present invention. In general, Components (i), (ii), - and (iii) may be mixed simultaneously, or the non-reactive components may be pre-mixed and the-n mixed with the reactive components.

Mo-1845 -20-. . . .. .

Z3~L67 A starting temperature of from 10 to 50C, prefer-ably from 20 to 30C, is chosen for the mixture introduced into the mold. The temperature of the mold itself is generally from 40 to 100C, and preferably Erom 50 to 70C.

S Although the very rapid reaction between the components may render -the use of mold release agents unneces-sary, e.g. for removal of the molded product from polished metal molds, the known mold release agents based on wax or silicone may be used if desired. Furthermore, when carrying out the process according to the present invention, the internal mold release agents known in the art, such as those described, for example, in German Offenlegungsschriften 1,953,637 and 2,121,670, may also be used.

The moldings obtainable by the process according to the present invention are particularly suitable for the manufacture of flexible car bumpers and car body elements.
However, with suitable variation of the starting components and particularly if a relatively low proportion of the active diamine is used, it is also possible to produce materials which have good abrasion resistance and high mechanical strength e.g. flexible polyurethane shoe soles.

The invention is further illustrated, but is not intended to be limited by the following examples in which all parts and percentages are by weight unless otherwise specified.

Mo-1845 -21-~L23~

XAMP LES

100 parts by weight of a polyether prepared from glycerin, propylene oxide and ethylene oxide, having an OH
number of 28.
21.5 parts by weight of a mixture of 65 parts by wei~ht of l-methyl-3,5-diethylphenylene-2,4-diamine and 35 parts by weight of 1-methyl-3,5-diethylphenylene-2,6-diamine, less than 0.1 part by weight of water, and 0.1 part by weight of a complex of 1 mol of dibutyl tin dilaurate and 1 mol of 2,3-dimethyl-3,4,5,6-tetra-hydropyridine were combined to form a polyol blend. The isocyanate used in this example was a reaction product of tripropylene glycol and 4,4'-diphenylmethane diisocyanate (23~ by weight N~O).

The mold used was a Monza 2+2 front fascia, pro-duction caliber, nickel-plated steel mold. Its dimensions were about 8' x 4' x 4'. The polyol blend and isocyanate were metered using a commercial HK 1000 RIM metering unit and were mixed in a commercial direct impingement KRAUSS-MAFFEI mixhead in a weight ratio of isocyanate to blend of about 50 parts isocyanate per 100 parts of blend.

~ .
The isocyanate was maintained at a temperature of 90F and the blend was maintained at 85F. The temperature of the mold was kept at 135F and the mold residence time was 30 seconds. As hereafter set forth, the polyol Mo-1845 -22-~L~Z31~7 dellsity was nlol)itc)rt-~d and eontr~lled at eacll lo-aclin(-J Level oE nitrogen. Tlle density was measurecl usincJ a commercial pieee of e~uipmel-t known as a DYNATROL* whose outL~ut resL)onds to chanc3es in the s~eciEic cJravity oE a licluid streanl.

In a first experiment the c3as loadincJ in the blend was adjusted until a I~YNArlll~OL*readin~ oE 1 volt was obtained (eorrespondiny to a minimum density of the blend of 0.65 ~/ee at atmospherie pressure). When the blend and isoeyanate were metcred and mixed as noted above at a shot time oE 2.38 SeCOlldS a l)art was o~tained havinc-l nun~erous surEaee deEeets (havincJ a minimum speeiEie ~ravity of 1.04).

In a seeond experiment using the same throucJIlput, (about 3 lbs./see.) SllOt time temperatures and DYN~TROL*
readinc3 but with 0.3 ~arts oE a cGmmercial ~5 millimieron partiele size carbon black (available Erom Mdnoc31em Corpor-ation) added to the ~lend for every 100 par-ts by weight of blend, a part was ob-tained having a speciEic cJravity oE
about 1.01. No surEace defeets were detectable. From this e~periment it was concluded that tl~e addition of carbon blaek allowed for fillinc3 of the mold with the resultant produet having a lower speeifie cJravity and without surfaee defeets.

E~Ai~lPLE 2 rhe seeond experiment oE Lxal~ le 1 was repeated but usin(3 a DYNArr~OL readirlg oE 0.2 volts ~i e. a larcJer quantity of c3as was used). Ac3ain the resultant part had - no observable surEaee dcEeets.

In order to Eairly assess the use oE the carbon blaek in a eonunereial productiol- this experiment usincJ the 0.2 volt DYNATROL*readillcJ was repeated 10 times continuously.

* Registered Trademark ~10-1845 -23-~ ~ .
_ . _ , . .. _ ... . .

L6~
~ft~r c~acl~ ot, tl~ rt Eor~ l.s r(~ v~ (l t ll ~ o l c]
sur~ace was coate(l witll a commercially availabLe release agent (Cl~EMTREND XMI~-252, a stearate in an isoprop~nol/
water mixture). There was no bu~fincJ of th~ )l.d between each loading. Even after tlle l0th part was made, no surface defects were observed. l~ithout carbon black, this was not possible under the same molding conc-~itions since the intensity of surface defects increased after a few successive shot/spray operations.

E,~MPLE 3 - In this examE)le, the polyol, activc amine anc' isocyanate used were identical to tllose used in Example l but they were used in amounts corresponding to 82 parts, 18 parts and ~7 parts, respectively. 'l'he catalysts used were 0.33 parts of triethylene diamine and 0~0l part of dibutyl tin dilaurate. The mold used was in the shape of a PINTO front ileac1lamp part and was a nickel plated steel having the approximate dimensions: 4' x 3" x 2'.

A DYN~TROL,*reading of the blend correslondinc3 to a specific gravity of 0.977 at 50 psi was selected. 'I'he same metering and mixing equipment was used as in Example l.
After a shot time of l.15 seconds at a -throughput of 3 l~s/sec.
a part was produced, having non-uniform densities, par-ticularly in the areas farthest from the point where the mixture entered the mo:ld. lncomplete fillillcf was observed at the points fartllest from thc? poirlt ~twlliclltllc? mixture entered the mold.

* Registered Trademark Mo-l845 -2~-- - . -~ , .

~123~6~
Usinc~ tll~ sa~le eonditio1lx~ ~ut with tlle acldition of 0.1 ~art of a e(>mlllereial earbon ~laek (Sl'l.~l~L BLACK 4 -DEGUSS~) at the same DYN~TROL readin(J, it was possible -to ob-tain a full part witll uniEorm dells:ity aEter a sllot time

5 of only 1.10 seeonds at the identieal throucJIlput of 3 lbs./see., whieh would amount to material savings in exeess of 5 ~.

MPL~S 4 TIIRO~II 19 In order to test the ability of a variet~ of different inorc3anie nitrogen adsor~incJ agen-ts, the foll.owinc~
10 tests were eondueted. In eaeh instanee, 180 parts of the blend of Example 1 was plaeed in a elosed vessel and kept at a temperature of 25C. Nitroc3en was introdueed into the system and the vessel was maintained at a pressure of 75 psi.
~s soon as the preSSurc? was applied, the vessel eontaininc;
15 the blend was acJitated for a period of l~.minutes. The pressure was then released and vessel was opened. Its eontents were immediately poured into a seeond vessel provided witll a hydrometer to measure the speeifie gravity of tlle licluid. ~ readinc~ of tlle ~speeifie yrav~ty was taken 20 every 30 seconds for 8 minutes. In eael~ instanee, the amount of additive used was 0.5 parts per 100 parts of blend.

In eaeh ease, the hydrometer readincJ deereasecl as a funetion oE time, eorresponding to the ehange of the gas 25 from the dissolved state to the dispersed state i.n tile ~olyol licluid. The .initi.al c1ell.sity of th(? syxtenl in wllicllc?sselltially all c~as was in tlle ciixsolved state in eaell ease was 1.()21 cl/ee whiel~ is i.clelltie.l.l to tlle polyol lic~uid density at 25~C
without any cJas. 'I'hat is, the effeet oE clissolve(i cJas on 30 polyol speeifie (Iravi.ty i.x necJlicl;.ble. Dispc?rsed gas will, of eourse, reduee xpeei.fi( gr~vity of the lic3uicl.

* Registered Trademark ~10-1845 -2~-~.

~L~231t~7 The hydrometer reading vs. time for the base polyol was compared with the same resp~onse for each of the additives,by computing the change in specific gravity with time from an assumed initial value of 1.021 g/cc, -to the value at 3 minute as follows:

rate = 1.021 - SG 3 min. = ~SG
~ min. ~t ' where ~3 min = the specific gravity after 3 minutes.
It should be noted that for all of the experiments, the specific gravity change over the first -three minutes repre-sented most of the total change. This rate for the polyol with additive was then compared with the base polyol to arrive at a % increase in rate of specific gravity change as follows:

- % increase in rate = rate - rate standard ra-te standard where rate standard = rate without additive The higher the % increase in rate of change of specific gravity, the more effective the additive was in increasing blowing agent efficiency. The results are as set forth in Table 1.

Mo-1845 -26-In Table l, thc 10 llowincJ addi t:LVeS wc re usecl Cll;~l~CO~ a vailal)le from PiL t s bu ry h ,~etiv~-ted Carbol):
I'article si.7.e G5-75-~ Illin~ls 325 m~
'i`otal surfaee area: :lOOO-llOO 111 /~J
(N~ B~T r~lethocl).
Cl~i'CO~I, BT'L: ~vailabl(~ from Pittsbur(~l ~c~tivatec~ Carl~oll 2 Total surfaee area: ]050-1150 311 /~
i~pparent density (bulk dellsity, delise packin(l) Cl/cc = 0.48 Real density (lle displaeement) g/ee = 2.1.
C15~RCO~ 'CB: ~vaila~le from Pittsburc~l i\ct~vated Car~on Total surfaee area: l:L50-1250 m2/q ,~pparellt densit~ = 0.44 g/ee Real density = 2.2 y/cc.
Cll~RCO~L RB: ~vailable from Pittsbur~h ~etivated Carbon 'rotal surfaee area: 1150-1350 n~2/g ~pparent dens:it~ c~/cc = O.dsl Real dellsity c3/ee = 2.35 Partiele size: 65-75% microns 325 mesll.
25 B,'~YF`~RI~O,Y*130 Rl:L): ~ re~c.l i.ron oxide available from Mobay Chelllical Corporatioll, bavincJ
a predominallt partie.le siZC? of ().17 microns ancl a residu~? on a 325 I~STM mesh screcn of 0.05 %, with an ~e203 eontent of 95-97%~
Bf~ ERRO~ *130 ~ lD: Same as l30 red L)ut havincl a residue on a 325 ASTM mesll screer or less than 0.001 'c-~, with an l'e203 COIl-tent of 95-97~.
Bf~ L`~ O`~*l80_r~ ~'L): /~ red iron oxi.cle avclil--ablc from rlobay Cllelll.ieal Corporation, h.lVillC
a predominant partiel.e si~:e of () .70 microns and a residue on a 325 ~STrl mes}l scrf~ell o[
less thall 0.001C, with an E~e2O3 contellt of 96.97~ .
P.~YI`ERRO~*llO ~I REI): ~ red iron o~ide avail-able from Mobay Chemi.eal Corporatic)n, l~avirlq a predorllillant partiele si.ze o'~ ().0') mierons ~nd a residue on a 325 l~SrrM mesh screc?n of less than 0.001 ~, Witll an E`e20 eontent of 9~-96%. 3 B~S'~ O,Y 31~ L~ CIC~ lc-lk irorl o~i.de available fronl Mcjl~a~ Ch~?miecll CorL)oration, l~avincl a predolnil-~allt partiele SiZC? of 0.2 mic~l-olls, a re?siclu~ on a 325 AS'L'I'I mt-~c;ll screell of 0.13, allcl al~ l;'e O content of 93-95c~, 2 3 * Registered Trademark Mo-1845 -27-,~

. q_ . _ . . _ _ _- :

~112316~

BAYFERROX*420 YELLOW: A yellow iron oxide available from Mobay, having a predominant particle size of 0.1 x 0.7 microns, a residue on a 325 ASTM mesh screen of 0.05 %, and an Fe2O3 content of 86-87%.
BAYFERROX*910 YELLOW: A yellow iron oxide avail-able from Mobay, havins a predominant particle size of 0.1 ~ 0.6 microns, a residue on a 325 ASTM mesh of 0.039 and an Fe O content of 85-87~. 2 3 DEGUSSA: A carbon black available from DeGussa having a 325 ASTM mesh residue of 0.05%, an average particle size of 25 millimicrons, and a surface area (BET method) of 180 m2/g.
SYLOID*244: A silica available from Davison Chem-icals Division of Grace Indust~ial Chemicals having a surface area of 310 m /g, an average particle size of 4 microns and a density of 7 lbs./ft.3.
SYLOSIL*120: A crystalline sodium alumino-silicate zeollte powder auailable from Davison Chem. having -an average particle size of 2-3 microns and a bulk density of 30 lbs./ft.3.
MISTRON*VAPOR: A talc powder`available from Cyprus Industrial Minerals Co., having an average par-ticle size of 1-1/2 microns.

*Registered Trademark Mo-1845 3~l67 - Tl\13 ~ L

increase in ra te speci fic ~I ravi ty i\ SG f change o E
_t 3 mil~ ~tsl~eci:Eic c~ravity Standard . Y33.0293 --Charcoal PW~ .775.0820 179.9 Charcoal BPL .797.0747 154.9 Charcoal PCB . 835.0620 111.6 Charcoal RB . 828.0643 119.6 Iron O~;ide 130 Red .818.067G 130.9 i' 130 m Red .844 .059() 101.4 180 m Rc:d .9ln . 0370 26.3 110 m Recl .~)05 .03U732.1 " 910 Yellow . 870 . U503 71.8 " 420 Yel]ow .917 .034718.4 " 318 Black .924 .032310.3 DeGussa . 903 .039334.1 Syloid*244 .870. U503 71.8 Sylosil 1;~0 .868 ~051074.1 ~li stron *Vapor .909 .037327.3 * Registered Trademark ~o - 184 5 - 29 -s . ~ . ~. .-.

Claims (13)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the production of elastomeric moldings comprising:

(A) introducing a reaction mixture into a closed mold, said reaction mixture comprising:

(i) an organic polyisocyanate, (ii) a hydroxyl group containing compound having a molecular weight of from 1800 to 12,000, (iii) a catalyst for the reaction between hydroxyl groups and isocyanate groups, (iv) an active aromatic diamine having at least one alkyl substituent in the ortho-position to a first amino group and two alkyl substituents in ortho-position to a second group, and (v) air and/or nitrogen dissolved under pressure in any one or more of Components (i), (ii), (iii) or (iv), (B) allowing said reaction mixture to react in said mold and (C) removing the resultant product from said mold, the improvement wherein in any of Components (i), (li), (iii) or (iv) which does contain said air and/or nitrogen dissolved therein there is included an inorganie, finely divided, nitrogen adsorbing agent in an amount sufficient to accelerate the transition of the air and/or nitrogen from the dissolved state to the dispersed state upon release of the pressure.
Mo-1845 -30-

2. The process of Claim 1 wherein said adsorbing agent is selected from the group consisting of aluminas, silicas, carbons, and iron oxides.

3. The process of Claim 1 wherein said adsorbing agent has a surface area of more than 10 m2/g.

4. The process of Claim 1 wherein said adsorbing agent is used in an amount of from 0.01 to 1% by weight based on the amount of Component (ii).

5. The process of Claim 4 wherein said adsorbing agent is used in an amount of from 0.1 to 0.7% by weight based on the amount of Component (ii).

6. The process of Claim 5, wherein said adsorbing agent is used in an amount of 0.5%.

7. The process of Claim 4 wherein said Component (iv) is used in an amount of from 5 to 75% by weight based on the amount of Component (ii).

8. The process of Claim 7 wherein said Component (iv) is used in an amount of from 5 to 35% by weight based on the amount of Component (ii).

9. The process of Claim 8 wherein said Component (iv) is used in an amount of from 8 to 35% by weight based on the amount of Component (ii).

10. The process of Claim 7, wherein the amounts of reactants are chosen so that the mixture has an iso-cyanate index of from 70 to 130.

Mo-1845 -31-

11. The process of Claim 10, wherein the amounts of reactants are chosen such that the mixture has an isocyanate index of from 90 to 110.

12. An elastomeric molded article of uniform density having substantially no surface defects made by the process of Claim 1.

13. An elastomeric molded article of uniform density having substantially no surface defects made by the process of Claim 10.

Mo-1845 -32-