CA1099057A - Coagulating and coating bath for uncured elastomer objects - Google Patents
Coagulating and coating bath for uncured elastomer objectsInfo
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- CA1099057A CA1099057A CA350,820A CA350820A CA1099057A CA 1099057 A CA1099057 A CA 1099057A CA 350820 A CA350820 A CA 350820A CA 1099057 A CA1099057 A CA 1099057A
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Abstract
ABSTRACT
Hontacky, elastomeric shaped objects (e.g., pellets or filaments) comprising a normally tacky, uncured elastomer having an integral, porous coating of silicic or aluminic acid polymer can be prepared by bringing shaped bodies of a normally tacky, uncured elastomer later into contact with an aqueous bath containing a soluble coagulating salt for the latex, and a silicic or aluminic acid polymer, and washing and drying the resulting coated shaped objects. The shaped objects are highly porous before washing and drying, and some porosity remains even after washing and drying.
Hontacky, elastomeric shaped objects (e.g., pellets or filaments) comprising a normally tacky, uncured elastomer having an integral, porous coating of silicic or aluminic acid polymer can be prepared by bringing shaped bodies of a normally tacky, uncured elastomer later into contact with an aqueous bath containing a soluble coagulating salt for the latex, and a silicic or aluminic acid polymer, and washing and drying the resulting coated shaped objects. The shaped objects are highly porous before washing and drying, and some porosity remains even after washing and drying.
Description
'~ }
5~ CR 7 6 0 7 -1 BACKGROUND OF THE INVENTION
(1) Field Or the Inventlon Thls lnventlon ls concerned wlth nontacky shaped ob~ects o~ norm~lly tacky elastomers~ and ~ process for pre-parlng them.
5~ CR 7 6 0 7 -1 BACKGROUND OF THE INVENTION
(1) Field Or the Inventlon Thls lnventlon ls concerned wlth nontacky shaped ob~ects o~ norm~lly tacky elastomers~ and ~ process for pre-parlng them.
(2) Descri~tion of the ~rior Art It is a well known process to emulsify polymeriz-able monomers in water and then convert them to polymers in dispersed form. The resulting dispersions are called latices.
Natural rubber also occurs as a latex. Some latices are highly useful as formed, for example, basic formulations for latex paints. For other uses, it is necessary to coagulate the polymer and separate it from the latex. The most important commercial form for these polymers is as washed and dried, nontacky shaped objects. These shaped objects should be washed until they contain less than about 3% by weight of water soluble material, and dried until they con-tain less than about 1~ by weight of volatile material.
If the coagulated polymer is inherently nontacky, the polymer is readily isolated from the aqueous phase, washed and dried to form a free-flowing powder which is readily handled in further processinq. If, however, the polymer is inherently tacky, coagulating of the latex yields the polymer in an agglomerated mass which is difficult to wash free of impurities and also difficult to dissolve, to blend with other materials, and to feed in compounding, curing and molding operations.
In the field of natural and synthetic r~bber, much attention has been given to the problem of agglomcration of
Natural rubber also occurs as a latex. Some latices are highly useful as formed, for example, basic formulations for latex paints. For other uses, it is necessary to coagulate the polymer and separate it from the latex. The most important commercial form for these polymers is as washed and dried, nontacky shaped objects. These shaped objects should be washed until they contain less than about 3% by weight of water soluble material, and dried until they con-tain less than about 1~ by weight of volatile material.
If the coagulated polymer is inherently nontacky, the polymer is readily isolated from the aqueous phase, washed and dried to form a free-flowing powder which is readily handled in further processinq. If, however, the polymer is inherently tacky, coagulating of the latex yields the polymer in an agglomerated mass which is difficult to wash free of impurities and also difficult to dissolve, to blend with other materials, and to feed in compounding, curing and molding operations.
In the field of natural and synthetic r~bber, much attention has been given to the problem of agglomcration of
3~ normally tacky polymers before curing. Some opcrable solutions ~L
q~
have keen found.
In U.S. 2,879,173, Yacoe shows a process for coagulating a polychloroprene latex by suspending drops in a volatile, water-immiscible, orqanic liquid in which the poly-chloroprene latex is insoluble while maintaining the liquid below about -20C until the drops are completely frozen and coagulated. The resulting frozen pellets are separated and coated, while still frozen, with from 5% to 20% by weight of an inert powder, such as talc, so that they will not stick together when thawed and dried. However, the use of this process has been limited by the cost of organic liquid recovery, the energy cost of the refrigeration, and the un-desirable high loading of inert material. The need for a more practical and economical method of preparing nontacky, washed and dried shaped objects of normally tacky elastomers remains.
In U.S. 3,053,824, Heinz shows coagulation of a phosphate or borate buffered elastomer latex by running it into an aqueous aluminum or titanium salt solution contain-ing also an alkali metal or alkaline earth metal salt. The patent states that the resulting coagulated particles do not stick together before being washed to remove the coagulating salts. There is no statement as to the tack of the par-ticles after washing.
In U.S. 3,846,365, Berg et al. show a powdery, filled polymer prepared by emulsifying together a dilute solution of an elastomer in a volatile organic solvent and a solid, finely-divided filler for the elastomer, passing the emulsion into an aqueous alkali silicate solution at a pH preferably of 7 to 12, and evaporating the organic ,,~,.
..~
solvent. A finely-divided, tack-free coprecipitate of the latex and silicic acid residue is formed. It is stated that condensation of the silicate anions should be avoided.
SUM~P~Y OF THE INVENTION
This invention is based on the discovery that nontacky, uncured, washed ~nd dried,elastomeric snape~ ob-~ects can be produced from a normally tacky elastomer latex - by a simple and inexpensive process. This invention provides nontacky, elastomeric shaped objects which comprise a normally tacky, uncured elastomer containing, based on the total weight of the shaped object, less than about 3% by weight of water soluble material, and less than about 1% by weight of volatile material, and having about 0.05 to about 3% by weight of an integral, porous coating of a water insoluble, hydrous inorganic oxide selected from the group consisting of ~ilicic and aluminic ~cid polymers, siliclc acid-aluminic acid copolymers, and mixtures thereof, said shaped objects having a minimum dimension of about O.Ol to about lO milli-meters. By "integral" is meant a coating which has unity, rather than being composed of discrete particles such as in the case of a powder coating. By "minimum dimension" is meant the diameter of the smallest round hole through which the shaped object will pass lengthwise.
A unique feature of this invention is that,prior to removing the water soluble and volatile materials, the nontacky shaped objects are highly porous. This porosity is evidenced by the objects being opaque in appearance whcn dispersed in water, and by their cross section having a vesicular structure in micrographs. Because of this ~orosity, water soluble and volatile materials are easily removed by washing and drying techniques. Some of the porosity is retained even after washing and drying.
The nontacky,elastomeric shaped ~bjects of this invention are prepared by a process which comprises bringing shaped bodies of a normally tacky, uncured elastomer latex having a solids content of 20% to 65% by weight into contact with an aqueous bath contalning, based on the total weight of the bath, a) about 0.5% to ab~ut 25% by weight o~ a soluble coa~ulating salt for the latex, and b) about 0.01% t~ about 5~ by wei~ht Or a soluble or colloidally dispersed, hydrous inorganic oxide selected from the group conslsting of silicic and aluminic acid polymers, silicic acid-alum nic acid copolymers, a~d mixtures thereof, aid bath having a p~ of about 2 to about 7 such that, when a drop of l.ON NaOH is added to the bath, the drop is immediately surrounded by a cloudy coating of gelled, hydrous inorganic oxlde, thereby coa6ulating the latex and forming highly porous ~haped obJects of the coagulated elastomer coated wlth water lnsoluble, hydrous, inorganic oxide. These shsped ob~ects can then be washed with water until the water soluble material content is less than about 3~ by weight, and drled until the ~olatile material content ls less than about 1% by weight, thereby providin~ free-flowinG, nontac~
elastomerlc ~haped ob~ects. This lnvention ls partlcularly cuitable for producing nontacky pellets of uncured neoprene.
The term "shaped body'l is used herein to designate - --~ ;
~a~s~s7 the lQtex before it contacts the aqueous bath. The term "shaped obJect n i8 used herein to designate the l~tex ~nd subsequent elastomer after the ~haped body enters the bath.
BRl~ DESC~IPTION OF THE DRA~INGS
Flgure 1 illustrate~ a ~le~ ln central vertical section and partlally in slde ele~atlon of a preferred apparatus for carrying out one embodiment Or the process o~
thls invention. Thi6 apparatus and the method of using lt is claimed ln U.S. Patent 4,110,491 of R. M. Secor, whlch ~ssued 1978 August 2g.
~ igure 2 illustrates a top vlew o~ the same apparatus as Figure 1 taken through cut 2-2.
Flgure 3 i~ a photomicrograph of a cross sect~on Or a porous shaped ob~ect ln accordance wlth this in~entlon.
DESCRIPTION OF TRE PREFERR}D EMBODIMENTS
In accordance ~ith this invention, an inorganic oxide polymer coatlng is chemically deposited on a shaped obJect Or normally tacky elastomer from solutlon or disper-sion in an aqueous bath. The coatlng, as formed, is there-rOre a porous, nonpartlculate, unltary pelllcle entirelysurroundlng each shaped ob~ect. Because of the integral nature Or the coating, nontacky ob~ects can be obtained with very small loadings Or coating material. Thi8 18 particularly lmportant for elastomers that are ~ubsequently dlssolved berore curlng, and i8 ln sharp contra6t to the requisite heary loadlngs of partlculate materlals, such as talc, ~hich have previ~usly been used to render uncured ela~tomeric ob~ects nontacky.
m e products Or this in~ention are nontacky 6haped ob~ects Or normally tacky, uncured elastomers. The term "ela~tomer" i~ well known to those ~kllled ln the art ~nd has be~n derined ~n publications such as "ASTM Gloss~ry of Terms Relatin~ to Rubber and Rub~er l.lk~ Materials", page 38. By "normally tacky elastomer" ls meant an elastomer, two ~ieces of h;h~ch, w~en uncured and ~n the most decrystallized condition, will stick together at room te~perature.
Suitable elastomers for use in accordance with this invention include homopolymers and copolymers of conjugated dienes such as neoprene and natural rubber;
copolymers of conjugated dienes with other polymerizable, organic monomers, for example butadiene-acrylonitrile and butadiene-styrene copolymers; elastomeric fluoropolymers (fluorine-containing polymers), preferably copolymers of vinylidene 1uroide and at least one other fluorine-containing monomer, for example copolymers of vinylidene fluoride and hexafluoropropene (U.S. 3,051,677), and ter-polymers of tetrafluoroethylene, vinylidene fluoride and hexafluoropropene (U.S. 2,96~,649); adhesive-type elastomers such as polyvinyl acetate and ethylene-vinyl actate co-polymers; acrylate rubbers such as the lower alkyl acrylate ester polymers; hydrocarbon elastomers such as polyiso-butylene, the terpolymers of ethylene, propylene and non-conjugated dienes; and similar materials.
The preferred elastomer is neoprene. By "neoprene"
is meant an elastomer comprisins at least about 50g chloro-prene (2-chloro-1,3-butadiene). Representative comonomers . that can be used with chloroprene include vinyl aromat~c compounds, such as styrene, the vinyl toluenes, and vinyl-naphthalenes; aliphatic conjugated diolefin compounds such a5 1,3-butadlene, isoprene, 2,3-dimethyl-1,3-butadiene J and 1:~9~57 2,3-dichloro-1,3-butadiene; vinyl ethers, esters, and ketones, such as methyl vinyl ether, vinyl acetate, and methyl vinyl ketone; esters, amines, and nitriles of acrylic and meth-acrylic acids, such as ethy] acrylate, methyl methacrylate, methacrylamide, and acrylonitrile; and the like.
~ eoprene latices for use in this invention may be prepared by the known aqueous emulsion polymerization of chloroprene, using a sodium rosinate dispersant and a free-radical type polymerization catalyst such as potassiul~
persulfate. The sodium rosinate dispersant may be prepared n situ from rosin acids and sodium hydroxide.
Additives such as fillers, antioxidants and the like may be present during the polymerization. The polymerization is allowed to proceed to a predetermined degree of completion, after which a catalyst shortstop can be added, and residual chloroprene monomer is stripped off. Minor variations in the procedure yield latices of polymers varying in molecular weight, viscosity, crystallinity, and other properties. In order to form pellets in the process of this invention,the latex should have a solids content of at least about 20~
by weight. Suitable latices can have solids contents up to about 65~. Latices generally coagulate when the solids content goes above about 65go. Preferably the latex has a solids content from about 35~ to about 50~.
This invention involves the process Or acld !'~
drops, a controlled stream~ or so~e other di5pensed form of a latex of the normal]y tacky elastomer to an aquec)us coagulating and coating bath thereby forming a coated shaped object. The latex emulsion should be stable enough to survive through the addition step until the shaped ~99~57 object ~ 5 fully penetrated by the coagulating salt and any neutralizing agent present. Neoprene latices arc normally stabilized against premature c~alescence by sodium rosinatc;
natural rubber by ammonia.
The aqueous coagulating and coating bath contains a coagulating salt for the latex, that is, a salt which will coagulate the elastomer latex. Suitable coagulating salts are well known to those skilled in the art; for example, see ~Neoprene Latexr, by J. C. Carl, pages 19-21, published by E. I. du Pont de Nemours and Company (Inc.), Wilmington, Delaware. Operable salts which may be employed include the water soluble sulfates, chlorides, bromides, nitrates, citrates, acetates, formates and phosphates of ammonium, sodium, potassium, calcium, magnesium, strontium, barium, lithium, beryllium, aluminum, manganese, zinc, yttrium, iron and cadmium. Mixtures of such salts may also be used.
Desirable, but nonlimiting, characteristics of the coagulating salt include low cost, colorless solutions, catlons and anions which are no~ readlly oxidizable or re-ducible, noncopreclpitating wlth the alkali metal salt accumulating in the bath, nontoxic, and nonpolluting. Pre-ferably, the salt should be chemically inert to the elasto-mer and insoluble therein. The preferred salts are soluble chlorides, sulfates, acetates, nitrates and phosphates of 80dium, 2otassium, ammonium, calcium, magnesium and aluminum. The most preferred salts are the soluble chlorides and sulfates of the above cations. The coagulating salt may constitute from about 0.5~ to about 25~ by weight of the bath. The operable amount of coagulating salt within this range in any given case will depend upon thc particular 1099~S7 latex, the pH of the bath,and the particular inor~anic oxide present. Generally, the optimum and preferred amol~nt of salt is in the range of about 1% to about 10%.
The bath al80 contains a solu~le or colloldally dispersed, hydrous lnoreanic oxide ~elected from the group consistlng of sillclc and aluminlc acid polymers, sillcic acid-aluminic acid copolymers, and mixtures thereof. These oxides are those commonly considered as existing in poly-meric form, the structure of which may be linear chains~
ribbonsJ or when highly cros6-linked, even globules, in which atoms of the inorganic element alternate wlth oxygen atom6. In such polymers, some Or the peripheral groups are -OH groups.
The inorganic oxide may be used in water soluble form, as in the case of polysilicic acid and polyaluminic acid, or in more highly polymerized, particulate form as in the case of colloidally dispersible silica sols as described in ~.S. 2,574,902 and alumina sols as described in U.S. 2,590,833. In practice, most aqueous systems containing such compounds have at least part of the polymeric oxide in the form of disperséd particles. The terms, "silicic acid polymers" and "aluminic acid polymers"
are intended to include these polymers in both the soluble and the colloidally dispersible form. The inorganic oxides may be in crystalllne or amorphous form, and a mixture Or two or more such oxides may be used. The most preferred inorgan~c oxides are polysilicic acid, polyaluminic acid and siliclc acld-aluminic acid copolymers.
If the coagulating salt employed is an alumlnum salt and the inorganic oxide is polysillclc acld, some of the alumlnlc hydroxylQ generated at the alkallne surface of the latex may copolymerize by condensation with sllanol groups to form an aluminic acid-sillcic ~cid copolymer. If the coagul~tin~ salt employed ls not ~n aluminum salt, partlcularly if the bath i~ utillzing polyslliclc acid as the coatlng materlal, it i8 desirable, though not essential, to add to the bath about 0.002~ to about 2~ by welght of an lonlzable alumlnum salt. Although copolymerizatlon of the aluminum has not been established, it is believed that thls accounts for the inorganic oxide being rendered more e~fective as a coatlng, posslbly by reduclng any subsequent ~olubility of the coating ln the wash water. ~or this pur-pose, it has been found that yttrlum salts are equlvalent to aluminum salts and may be substituted in whole or in part therefor. Accordingly, the term "silicic acid-alumlnlc acid copolymer" should be construed in the claims to cover thls substltution of equlvalents.
It is generally recognized that, in freshly prepared silicic acid solutions, the silicic acid is not monomeric, but has a molecular weight of the order of about lO00. As the silicic acid solution ages, the molecular weight continues to rise until finally the solution gels (see Bechtold, J. Phys. Chem., 59, 532-541 (1955)). The silicic acid solution used in accordance with this invention should not have aged for more than about 90Qo of its gel time prior to being added to the bath. Preferably, the silicic acid solution has aged for about 5~ to about 70% of its gel time prior to being added to the bath. When operating in a continuous manner, silicic acid is continuously added to and removed from the bath, whereby the average age of the 1~99~57 polysilicic acid reaches a const~nt value which i8 less than its gel time.
The hydrous inorganic oxide may constitute from about 0.01~ to about 5~ by weight of the coagulating bath.
~he presence of more than about 5% inorganic oxide does not lead to any further improvement in the nontacky properties of the product. Preferably the inorganic oxide is present in the amount of about,0.03% to about 2~. The oxide may be polymerized or crystallized during the coating operation. One criterion for determining when a bath is no longer suitable for the present process is coagulation of the bath due to changed conditions such as pH or to exhaustion of essential ingredients.
Optionally, the bath may also contain a minor amount of surfactant to reduce the air-liquid interfacial tension and assist penetration of the shaped latex body into the bath. Suita~le surfactants are characterized by being effective at low concentrations and being compatible, that i~ not causing polymerization or cross-linking of the hydrous oxide component, and being inert to the coag~lating salt. A wide variety of nonionic, anionic, cationic and amphoteric surfactants may be used. Examples of suitable surfactants include lower alkyl alcohols such as ethanol, the trimethylnonanol ether of ethylene oxide, sodium heptadecyl sulfate, sodium lauryl sulfate, the condensation product5 of tertiary amines wlth ethylene oxlde, fluori-. nated ~mphoteric 8urractants, and the like. The ~urractantpreferably is added in an amount sufficient to reduce the air-liquid interfacial tension to less than about 50 dynes/cm and particularly less than about 35 dynes/cm.
The bath is operable in a pH range of about 2 to about 7. If the pH is below about 2, the inorganic oxide is difficult to gel on the surface of the shaped object.
If the pH is above about 7, the inorganic oxide may be converted to a soluble salt. The operable pH within this range for any given system will depend on the particular latex, coagulating salt and inorganic oxide present.
Within this range, pH values from about 2.5 to about 5.5 are particularly preferred for optimum balance of bath stability with coating effectiveness. If the pH of the bath is maintained in the desired range by proportional addition of a neutralizing agent as the alkaline latex bodies enter the bath, the life of the bath can be substantially prolonged. Organic and inorganic acids such as acetic acid and aquenous hydrochloric acid, and hydro-lyzable acidic salts such as AlC13 are particularly suitable neutralizing agents.
Operability of the bath to provide a coating on the shaped object is a function of the amount and type of hydrous inorganic oxide present and the pH of the bath. It has been found that not all combinations of the above variables lead to operable baths. Although the requirements for a functional bath are not fully understood, a simple test has been found for determining whether the bath is functional.
In this test, a drop of l.ON sodium hydroxide is added to the bath. If the drop is immediately surrounded by a cloudy coating of gelled hydrous oxide, the bath is functional.
Although the pH of various latices vary over wide limits, it is preferable that the pH of-the latex be equal 3~ to or greater than the pH of the bath. When the latex is neoprene containing sodium rosinate as the stabilizer, the pH of the latex will be greater than about 7 unless it has been acidified.
When the latex is added as drops, the precipitated shaped objects obtained may be lumps, beads, pellets (with or without a "tail"), discs or rings depending on the sur-face tension and density of the precipitating bath and the speed and direction of the latex as it enters the bath.
When the latex is added as a controlled stream, the stream may be filamentous, yielding a precipitated fiber or bead-ing, or the stream may be spread out in flat or curved form yielding a precipitated ribbon, sheet or tube. Drops and controlled streams may be added either above or below the surface of the bath. Preferably the latex is added as drops above the surface of the bath.
Entry of the latex into the bath and movement of the precipitated, coated object through the bath impart to the bath a degree of agitation. Additional agitation in the form of stirring or shaking may be supplied, if desired, to assist in maintaining the uniformity of the bath. Agi-tation is particularly desirable when the pH of the bath is being maintained by addition of acid as noted above.
The present process may be operated at temperatures in the range from about 0C to about 100Cr Temperatures in the range from about 5C to about 70C are preferred, with the range from about 10C to about 40C being par-ticularly preferred because of the improved stability of the bath in this range.
Pressure is not a critical Yariable in the present process and pressures both above and below atmospheric 1~99~57 pre~8ure are oper~ble. ~tmospheric pressure i~ preferred ~or convenlence.
The time from entry of a particular elastomeric latex body into the bath until removal of the nontacky elastomeric shaped object therefrom may be varied widely, depending somewhat on the minimum dimension of the object being coated. The time may vary from about 0.5 second up to about 6 hours or more. On contact with the bath, the latex starts to coagulate and a nontacky coating is formed immediately on the surface of the coagulated shaped object, e.g., within about 0.5 to about 5 seconds. Longer retention of the coated object in the bath is employed when it is desired to complete coagulation and neutralization of the latex in the center of the coated object before it is removed from the bath. In preferred baths, this requires less than about 6 minutes. Complete coagulation in the bath is not essential since coagulant which has penetrated the shaped object can continue to migrate toward the center of the object after removal of the object from the bath. It is preferable, however, to leave the ob~ect in the bath until $
sufficient coagulant has penetrated the object to complete the coagulation.
Referring now to the drawings, Figure 1 shows a preferred embodiment of suitable apparatus for carrying out the process of this invention. This apparatus comprises a cylindrical tank 11 (27.94 cm i.d.) and a cylindrical draft tube 12 ~12.7 cm i.d.) which is concentric with tank 11.
The tube and tank may be c~nstructed of any ri~,id materlal such as ~lass, metal, or plastic. Drart tube 12 ~s extende~
on lts upper end by a wlre mesh screenl~ havin~ a mesh size 1~99~57 smaller than the size of the shaped objects being produced.
Bathl4 containlng the lnorganic oxide po~ymer and the coagu-lating salt is maintained at a liquid level such that the bath surface 15 is slightly below the upper edge of screen 13.
Drops or discrete masses of polymer latex are introduced into the bath within the zone circumscribed by screen 13. In this embodiment, stainless steel capillary tubes 16 (1.9 cm long, O.86 mm i.d. and 1.3 mm o.d.) are used for forming the latex drops. These tubes are mounted through polytetrafluoroethyl-ene plugs in a stainless steel plate bolted to the lower endof pipe 17 (10.1 cm i.d.). The center-to-center distance between the tubes mounted in the plate is 1.11 cm. Sixty-one tubes are arranged in a hexagonal array with five tubes on a side. The frequency of drop addition to the bath is adjusted by varying the level of latex in pipe 17.
An agitator 18 is provided in the bottom of tank 11 to promote circulation of the bath in such a manner that flow of the bath solution is generally down through the draft tube, up through the space between the draft tube and the tank wall, and through the screen to the confined bath surface. For this purpose, a 3-lobed (15.24 cm diameter) marine propeller is used.
The screen at the top of the draft tube provides a means of passing a solution which is free of shaped objects to the top of the draft tube. It also keeps out foam produced by the agitation and helps keep the surface free of disturbances which might affect the uniformity of the sha~eA ob~ects drop?ed throuah the surface. T~
increase agltation and thereby aid ~uspension of the coated latex particles ln the annular EpaCC outslde the draft tube, baffles 19 (3.81 cm wide) are placed vertically along the walls of tank 11 at 90 intervals. These baffles are not always necessary depending on the type of agitation used.
Through the action of the draft tube, screen, agitator and baffles, the shaped bodies contact a fresh solution, free of coated particles and foam. The shaped objects remain discrete as they pass down through the draft tube. By the time they emerge from the draft tube they are coated so that the tendency to agglomerate with previously coated shaped objects is eliminated. The coated shaped objects are then held in suspension outside of the draft tube until they are removed from the bath.
A typical batch run can be made using this apparatus as follows: First, bath 14 comprising an aqueous solution of an inorganic salt, a small amount of surfactant, and the coating material is prepared. The salt serves to coagulate the latex during coating and after it is coated. The surfactant facilitates passage of latex drops through the surface of the bath.
Latex is added to standpipe 17 to produce a given head pressure and then continuously added to maintain this head pressure on the capillary tubes. Since no solution is withdrawn from the bath during the run, the bath level rises due to the addition of latex. Both standpipe 17 and draft tube 12 are mounted so that they can be moved vertically.
They are moved during the course of each run to maintain the capillary exits about 2.54 cm above bath surface`15, and the upper edge of screen 13 about 0.835 cm above bath surface 15.
Although the apparatus illustrated in the drawings allows only batch removal of coated shaped objects at the ~q9~s~
conclusion of each run, the process can be operated contin-uously by providing an overflow tube in tank 11 for continuous removal of coagulated, coated shaped objects from the bath, fil-tering the suspension of shaped objects passing through the overflow tube, recycling the filtrate to the bath, and re-placement of the bath components as they become exhausted.
A major advantage of the invention is that, when large numbers of uncured shaped objects are stored in contact with each other under ordinary conditions, they do not agglomerate, but remain readily separable and free flowing.
The shaped objects have a minimum dimension of about 0.01 to about lO millimeters. The minimum dimension should be at least about O.Ol mm to avoid dusting. Shaped objects with a minimum dimension above about 10 mm require excessive power to mix with other ingredients in use applications.
Preferably the shaped objects have minimum dimensions of about 0.1 mm to about 5 mm.
Since the shaped bodies added to the bath are com-posed of latex, the water soluble coagulating salt quickly penetrates into the aqueous phase of the shaped objects, thereby coagulating the latex with a minimum of internal coalescence. As a result, the coagulated elastomer within the nontacky coating remains sufficiently porous for a sufficient period of time to permit the washing out of water soluble components, including the coagulating salt. In the case of relatively crystalline elastomers, this porosity is retained indefinitely. In the case of relatively noncrystalline elastomers such as neoprene, the porosity decreases on long standing, but it does not completely disappear.
After the precipitated shaped objects have been 10~9057 coagulate~ and coated they can be sel?arated frorn the bath by any ~uitable means. It is deslrable to remove watel soluble and volatile materials ~rom the shaped obJects aIter they have been separated from the bath. Thls may be accomplished by washing with water or a polar organic solvent, followed by squeezing, centrifuging or drying, using con-ventional techniques. The shaped objects should be washed until they contain less than about 3~ by weight of water soluble material, and preferably less than about 1%.
After the water soluble material has been removed to the desired extent, the shaped objects are dried to remove volatile material. Drying may be carried out at air temper-atures of about 25C to about 250C. Preferably the drying is carried out at air temperatures of about 100C to about 135C. During this drying operation the temperature of the shaped objects is kept below the known thermal decomposition temperature of the polymer. Drying is continued until the shaped objects contain less than about 1% by weight of volatile material, and preferably less than about 0.5~.
Vuring these finishing steps, polymers that are relatively stiff (because of crystallinity, for example) remain opaque and porous, while normally tacky polymers coalesce further to translucence. Nevertheless, even these retain vestiges of their formerly highly porous structure, and the nontacky nature of the hydrous oxide coating deposited on their exterior surrace is retained.
This nontacliy coating may be supplemente~ by minor additions of talc, for example, in the latter st~es of high tempera-ture drying, if deslred.
~he nontacky coating on the normally tacky lOq90S7 elastomer is initially also porous so that moisture, solvents, soluble reaction ingredients and by-products can be readily removed from within the coated object. The coating may represent from about 0.05 to about 3% by weight of the coated shaped object. Less than about 0.05% generally does not provide adequate nontacky properties, while more than about 3% usually gives no added advantage to offset increased cost. Preferably the coating is about 0.5 to about 2% by weight of the coated object. Washing operations, such as noted above, point up the necessity for both the nontacky coating and the coagulated elastomer being porous for a period of time after formation of the shaped objects.
Figure 3 is a photomicrograph of a cross section of a typical,porous shaped object in accordance with this invention. In this photograph, the porosity of the shaped object is apparent; voids appear as dark areas as observed at 20. The nontacky coating appears as light areas as is readily observed at 21.
The noniac~;y coated objects of this invention can also contain fillers, pi~ents, color~nts, softeners, extenders, antioxidants, st2bilizers, curing agents, and the like. Such m~terials ma~ be incorporated by ~dding them to the starting polymer latex or to the coa~ulatin~
and coatin~ bath.
The followin~ examples illustrate the prep2ration Or nontacky,elastomeric shaped objects of this invention.
. Each ~f the ~ashed and dried,nontacky,elastGmeric-shaped objects prepared in these examples had a water soluble material content of less than about 3~ by weight and a volatile material content of less than about 1~. In each case the inorganic oxide pol~mer coating was about 0.05 to about 3~ by weight of the shaped objects and the minimum dimension of the shaped objects was about 0.01 to about 10 millimeters. All parts and percentages are by weight throughout the examples.
The neoprene latices used in these examples were prepared as follows:
Neoprene Latex #l This latex was prepared from an aqueous, alkaline 10 emulsion containing 100 parts of chloroprene and 0.23 part of dodecyl mercaptan as modifier and stabilized by 2.9 parts of the sodium salt of disproportionated wood rosin. Chloro-prene was polymerized by adjusting the emulsion tempera-ture to 40C and adding continuously, at a rate allowing control of the temperature at 40C by external cooling, an aqueous solution containing 0.3% K2S2O8 and 0.015~ Na salt of anthraquinone-~- sulfonic acid. The polymerization was - terminated at about 67% conversion of the chloroprene mono-mer by the addition of an aqueous emulsion of a toluene 20 solution containing 0.015 part of phenothiazine and 0.015 part of 4~tert.-butylcatechol.
After removal of residual monomer by distillation, the latex contained about 37~ solids. The polymer had an inherent viscosity of 1.20 ~0.1 g/100 ml benzene at 30C).
The pH of the latex was about 12.
Neoprene Latex #2 An a~ueous, alkaline emulsion was prepared con-taining 100 parts of chloroprene, 0.15 part of dodecyl mer-captan and 3.5 parts of the sodium salt of disproportionated wood rosin. Chloroprene was polymerized by adjusting the ~0~ ;7 emulsion temperature to 10C and adding continuously an aqueous dispersion containing 1.0% X2S2O8, 0.05% sodium salt of anthraquinone-~-sulfonic acid, and 0.14% cumene hydroperoxide at a rate allowing control of the temperature between 10 and 20C. The polymerization was terminated at about 85% conversion of the chloroprene monomer by addition in the form of an aqueous emulsion of a toluene solution of 0.03 part of phenothiazine and 0.03 part of
q~
have keen found.
In U.S. 2,879,173, Yacoe shows a process for coagulating a polychloroprene latex by suspending drops in a volatile, water-immiscible, orqanic liquid in which the poly-chloroprene latex is insoluble while maintaining the liquid below about -20C until the drops are completely frozen and coagulated. The resulting frozen pellets are separated and coated, while still frozen, with from 5% to 20% by weight of an inert powder, such as talc, so that they will not stick together when thawed and dried. However, the use of this process has been limited by the cost of organic liquid recovery, the energy cost of the refrigeration, and the un-desirable high loading of inert material. The need for a more practical and economical method of preparing nontacky, washed and dried shaped objects of normally tacky elastomers remains.
In U.S. 3,053,824, Heinz shows coagulation of a phosphate or borate buffered elastomer latex by running it into an aqueous aluminum or titanium salt solution contain-ing also an alkali metal or alkaline earth metal salt. The patent states that the resulting coagulated particles do not stick together before being washed to remove the coagulating salts. There is no statement as to the tack of the par-ticles after washing.
In U.S. 3,846,365, Berg et al. show a powdery, filled polymer prepared by emulsifying together a dilute solution of an elastomer in a volatile organic solvent and a solid, finely-divided filler for the elastomer, passing the emulsion into an aqueous alkali silicate solution at a pH preferably of 7 to 12, and evaporating the organic ,,~,.
..~
solvent. A finely-divided, tack-free coprecipitate of the latex and silicic acid residue is formed. It is stated that condensation of the silicate anions should be avoided.
SUM~P~Y OF THE INVENTION
This invention is based on the discovery that nontacky, uncured, washed ~nd dried,elastomeric snape~ ob-~ects can be produced from a normally tacky elastomer latex - by a simple and inexpensive process. This invention provides nontacky, elastomeric shaped objects which comprise a normally tacky, uncured elastomer containing, based on the total weight of the shaped object, less than about 3% by weight of water soluble material, and less than about 1% by weight of volatile material, and having about 0.05 to about 3% by weight of an integral, porous coating of a water insoluble, hydrous inorganic oxide selected from the group consisting of ~ilicic and aluminic ~cid polymers, siliclc acid-aluminic acid copolymers, and mixtures thereof, said shaped objects having a minimum dimension of about O.Ol to about lO milli-meters. By "integral" is meant a coating which has unity, rather than being composed of discrete particles such as in the case of a powder coating. By "minimum dimension" is meant the diameter of the smallest round hole through which the shaped object will pass lengthwise.
A unique feature of this invention is that,prior to removing the water soluble and volatile materials, the nontacky shaped objects are highly porous. This porosity is evidenced by the objects being opaque in appearance whcn dispersed in water, and by their cross section having a vesicular structure in micrographs. Because of this ~orosity, water soluble and volatile materials are easily removed by washing and drying techniques. Some of the porosity is retained even after washing and drying.
The nontacky,elastomeric shaped ~bjects of this invention are prepared by a process which comprises bringing shaped bodies of a normally tacky, uncured elastomer latex having a solids content of 20% to 65% by weight into contact with an aqueous bath contalning, based on the total weight of the bath, a) about 0.5% to ab~ut 25% by weight o~ a soluble coa~ulating salt for the latex, and b) about 0.01% t~ about 5~ by wei~ht Or a soluble or colloidally dispersed, hydrous inorganic oxide selected from the group conslsting of silicic and aluminic acid polymers, silicic acid-alum nic acid copolymers, a~d mixtures thereof, aid bath having a p~ of about 2 to about 7 such that, when a drop of l.ON NaOH is added to the bath, the drop is immediately surrounded by a cloudy coating of gelled, hydrous inorganic oxlde, thereby coa6ulating the latex and forming highly porous ~haped obJects of the coagulated elastomer coated wlth water lnsoluble, hydrous, inorganic oxide. These shsped ob~ects can then be washed with water until the water soluble material content is less than about 3~ by weight, and drled until the ~olatile material content ls less than about 1% by weight, thereby providin~ free-flowinG, nontac~
elastomerlc ~haped ob~ects. This lnvention ls partlcularly cuitable for producing nontacky pellets of uncured neoprene.
The term "shaped body'l is used herein to designate - --~ ;
~a~s~s7 the lQtex before it contacts the aqueous bath. The term "shaped obJect n i8 used herein to designate the l~tex ~nd subsequent elastomer after the ~haped body enters the bath.
BRl~ DESC~IPTION OF THE DRA~INGS
Flgure 1 illustrate~ a ~le~ ln central vertical section and partlally in slde ele~atlon of a preferred apparatus for carrying out one embodiment Or the process o~
thls invention. Thi6 apparatus and the method of using lt is claimed ln U.S. Patent 4,110,491 of R. M. Secor, whlch ~ssued 1978 August 2g.
~ igure 2 illustrates a top vlew o~ the same apparatus as Figure 1 taken through cut 2-2.
Flgure 3 i~ a photomicrograph of a cross sect~on Or a porous shaped ob~ect ln accordance wlth this in~entlon.
DESCRIPTION OF TRE PREFERR}D EMBODIMENTS
In accordance ~ith this invention, an inorganic oxide polymer coatlng is chemically deposited on a shaped obJect Or normally tacky elastomer from solutlon or disper-sion in an aqueous bath. The coatlng, as formed, is there-rOre a porous, nonpartlculate, unltary pelllcle entirelysurroundlng each shaped ob~ect. Because of the integral nature Or the coating, nontacky ob~ects can be obtained with very small loadings Or coating material. Thi8 18 particularly lmportant for elastomers that are ~ubsequently dlssolved berore curlng, and i8 ln sharp contra6t to the requisite heary loadlngs of partlculate materlals, such as talc, ~hich have previ~usly been used to render uncured ela~tomeric ob~ects nontacky.
m e products Or this in~ention are nontacky 6haped ob~ects Or normally tacky, uncured elastomers. The term "ela~tomer" i~ well known to those ~kllled ln the art ~nd has be~n derined ~n publications such as "ASTM Gloss~ry of Terms Relatin~ to Rubber and Rub~er l.lk~ Materials", page 38. By "normally tacky elastomer" ls meant an elastomer, two ~ieces of h;h~ch, w~en uncured and ~n the most decrystallized condition, will stick together at room te~perature.
Suitable elastomers for use in accordance with this invention include homopolymers and copolymers of conjugated dienes such as neoprene and natural rubber;
copolymers of conjugated dienes with other polymerizable, organic monomers, for example butadiene-acrylonitrile and butadiene-styrene copolymers; elastomeric fluoropolymers (fluorine-containing polymers), preferably copolymers of vinylidene 1uroide and at least one other fluorine-containing monomer, for example copolymers of vinylidene fluoride and hexafluoropropene (U.S. 3,051,677), and ter-polymers of tetrafluoroethylene, vinylidene fluoride and hexafluoropropene (U.S. 2,96~,649); adhesive-type elastomers such as polyvinyl acetate and ethylene-vinyl actate co-polymers; acrylate rubbers such as the lower alkyl acrylate ester polymers; hydrocarbon elastomers such as polyiso-butylene, the terpolymers of ethylene, propylene and non-conjugated dienes; and similar materials.
The preferred elastomer is neoprene. By "neoprene"
is meant an elastomer comprisins at least about 50g chloro-prene (2-chloro-1,3-butadiene). Representative comonomers . that can be used with chloroprene include vinyl aromat~c compounds, such as styrene, the vinyl toluenes, and vinyl-naphthalenes; aliphatic conjugated diolefin compounds such a5 1,3-butadlene, isoprene, 2,3-dimethyl-1,3-butadiene J and 1:~9~57 2,3-dichloro-1,3-butadiene; vinyl ethers, esters, and ketones, such as methyl vinyl ether, vinyl acetate, and methyl vinyl ketone; esters, amines, and nitriles of acrylic and meth-acrylic acids, such as ethy] acrylate, methyl methacrylate, methacrylamide, and acrylonitrile; and the like.
~ eoprene latices for use in this invention may be prepared by the known aqueous emulsion polymerization of chloroprene, using a sodium rosinate dispersant and a free-radical type polymerization catalyst such as potassiul~
persulfate. The sodium rosinate dispersant may be prepared n situ from rosin acids and sodium hydroxide.
Additives such as fillers, antioxidants and the like may be present during the polymerization. The polymerization is allowed to proceed to a predetermined degree of completion, after which a catalyst shortstop can be added, and residual chloroprene monomer is stripped off. Minor variations in the procedure yield latices of polymers varying in molecular weight, viscosity, crystallinity, and other properties. In order to form pellets in the process of this invention,the latex should have a solids content of at least about 20~
by weight. Suitable latices can have solids contents up to about 65~. Latices generally coagulate when the solids content goes above about 65go. Preferably the latex has a solids content from about 35~ to about 50~.
This invention involves the process Or acld !'~
drops, a controlled stream~ or so~e other di5pensed form of a latex of the normal]y tacky elastomer to an aquec)us coagulating and coating bath thereby forming a coated shaped object. The latex emulsion should be stable enough to survive through the addition step until the shaped ~99~57 object ~ 5 fully penetrated by the coagulating salt and any neutralizing agent present. Neoprene latices arc normally stabilized against premature c~alescence by sodium rosinatc;
natural rubber by ammonia.
The aqueous coagulating and coating bath contains a coagulating salt for the latex, that is, a salt which will coagulate the elastomer latex. Suitable coagulating salts are well known to those skilled in the art; for example, see ~Neoprene Latexr, by J. C. Carl, pages 19-21, published by E. I. du Pont de Nemours and Company (Inc.), Wilmington, Delaware. Operable salts which may be employed include the water soluble sulfates, chlorides, bromides, nitrates, citrates, acetates, formates and phosphates of ammonium, sodium, potassium, calcium, magnesium, strontium, barium, lithium, beryllium, aluminum, manganese, zinc, yttrium, iron and cadmium. Mixtures of such salts may also be used.
Desirable, but nonlimiting, characteristics of the coagulating salt include low cost, colorless solutions, catlons and anions which are no~ readlly oxidizable or re-ducible, noncopreclpitating wlth the alkali metal salt accumulating in the bath, nontoxic, and nonpolluting. Pre-ferably, the salt should be chemically inert to the elasto-mer and insoluble therein. The preferred salts are soluble chlorides, sulfates, acetates, nitrates and phosphates of 80dium, 2otassium, ammonium, calcium, magnesium and aluminum. The most preferred salts are the soluble chlorides and sulfates of the above cations. The coagulating salt may constitute from about 0.5~ to about 25~ by weight of the bath. The operable amount of coagulating salt within this range in any given case will depend upon thc particular 1099~S7 latex, the pH of the bath,and the particular inor~anic oxide present. Generally, the optimum and preferred amol~nt of salt is in the range of about 1% to about 10%.
The bath al80 contains a solu~le or colloldally dispersed, hydrous lnoreanic oxide ~elected from the group consistlng of sillclc and aluminlc acid polymers, sillcic acid-aluminic acid copolymers, and mixtures thereof. These oxides are those commonly considered as existing in poly-meric form, the structure of which may be linear chains~
ribbonsJ or when highly cros6-linked, even globules, in which atoms of the inorganic element alternate wlth oxygen atom6. In such polymers, some Or the peripheral groups are -OH groups.
The inorganic oxide may be used in water soluble form, as in the case of polysilicic acid and polyaluminic acid, or in more highly polymerized, particulate form as in the case of colloidally dispersible silica sols as described in ~.S. 2,574,902 and alumina sols as described in U.S. 2,590,833. In practice, most aqueous systems containing such compounds have at least part of the polymeric oxide in the form of disperséd particles. The terms, "silicic acid polymers" and "aluminic acid polymers"
are intended to include these polymers in both the soluble and the colloidally dispersible form. The inorganic oxides may be in crystalllne or amorphous form, and a mixture Or two or more such oxides may be used. The most preferred inorgan~c oxides are polysilicic acid, polyaluminic acid and siliclc acld-aluminic acid copolymers.
If the coagulating salt employed is an alumlnum salt and the inorganic oxide is polysillclc acld, some of the alumlnlc hydroxylQ generated at the alkallne surface of the latex may copolymerize by condensation with sllanol groups to form an aluminic acid-sillcic ~cid copolymer. If the coagul~tin~ salt employed ls not ~n aluminum salt, partlcularly if the bath i~ utillzing polyslliclc acid as the coatlng materlal, it i8 desirable, though not essential, to add to the bath about 0.002~ to about 2~ by welght of an lonlzable alumlnum salt. Although copolymerizatlon of the aluminum has not been established, it is believed that thls accounts for the inorganic oxide being rendered more e~fective as a coatlng, posslbly by reduclng any subsequent ~olubility of the coating ln the wash water. ~or this pur-pose, it has been found that yttrlum salts are equlvalent to aluminum salts and may be substituted in whole or in part therefor. Accordingly, the term "silicic acid-alumlnlc acid copolymer" should be construed in the claims to cover thls substltution of equlvalents.
It is generally recognized that, in freshly prepared silicic acid solutions, the silicic acid is not monomeric, but has a molecular weight of the order of about lO00. As the silicic acid solution ages, the molecular weight continues to rise until finally the solution gels (see Bechtold, J. Phys. Chem., 59, 532-541 (1955)). The silicic acid solution used in accordance with this invention should not have aged for more than about 90Qo of its gel time prior to being added to the bath. Preferably, the silicic acid solution has aged for about 5~ to about 70% of its gel time prior to being added to the bath. When operating in a continuous manner, silicic acid is continuously added to and removed from the bath, whereby the average age of the 1~99~57 polysilicic acid reaches a const~nt value which i8 less than its gel time.
The hydrous inorganic oxide may constitute from about 0.01~ to about 5~ by weight of the coagulating bath.
~he presence of more than about 5% inorganic oxide does not lead to any further improvement in the nontacky properties of the product. Preferably the inorganic oxide is present in the amount of about,0.03% to about 2~. The oxide may be polymerized or crystallized during the coating operation. One criterion for determining when a bath is no longer suitable for the present process is coagulation of the bath due to changed conditions such as pH or to exhaustion of essential ingredients.
Optionally, the bath may also contain a minor amount of surfactant to reduce the air-liquid interfacial tension and assist penetration of the shaped latex body into the bath. Suita~le surfactants are characterized by being effective at low concentrations and being compatible, that i~ not causing polymerization or cross-linking of the hydrous oxide component, and being inert to the coag~lating salt. A wide variety of nonionic, anionic, cationic and amphoteric surfactants may be used. Examples of suitable surfactants include lower alkyl alcohols such as ethanol, the trimethylnonanol ether of ethylene oxide, sodium heptadecyl sulfate, sodium lauryl sulfate, the condensation product5 of tertiary amines wlth ethylene oxlde, fluori-. nated ~mphoteric 8urractants, and the like. The ~urractantpreferably is added in an amount sufficient to reduce the air-liquid interfacial tension to less than about 50 dynes/cm and particularly less than about 35 dynes/cm.
The bath is operable in a pH range of about 2 to about 7. If the pH is below about 2, the inorganic oxide is difficult to gel on the surface of the shaped object.
If the pH is above about 7, the inorganic oxide may be converted to a soluble salt. The operable pH within this range for any given system will depend on the particular latex, coagulating salt and inorganic oxide present.
Within this range, pH values from about 2.5 to about 5.5 are particularly preferred for optimum balance of bath stability with coating effectiveness. If the pH of the bath is maintained in the desired range by proportional addition of a neutralizing agent as the alkaline latex bodies enter the bath, the life of the bath can be substantially prolonged. Organic and inorganic acids such as acetic acid and aquenous hydrochloric acid, and hydro-lyzable acidic salts such as AlC13 are particularly suitable neutralizing agents.
Operability of the bath to provide a coating on the shaped object is a function of the amount and type of hydrous inorganic oxide present and the pH of the bath. It has been found that not all combinations of the above variables lead to operable baths. Although the requirements for a functional bath are not fully understood, a simple test has been found for determining whether the bath is functional.
In this test, a drop of l.ON sodium hydroxide is added to the bath. If the drop is immediately surrounded by a cloudy coating of gelled hydrous oxide, the bath is functional.
Although the pH of various latices vary over wide limits, it is preferable that the pH of-the latex be equal 3~ to or greater than the pH of the bath. When the latex is neoprene containing sodium rosinate as the stabilizer, the pH of the latex will be greater than about 7 unless it has been acidified.
When the latex is added as drops, the precipitated shaped objects obtained may be lumps, beads, pellets (with or without a "tail"), discs or rings depending on the sur-face tension and density of the precipitating bath and the speed and direction of the latex as it enters the bath.
When the latex is added as a controlled stream, the stream may be filamentous, yielding a precipitated fiber or bead-ing, or the stream may be spread out in flat or curved form yielding a precipitated ribbon, sheet or tube. Drops and controlled streams may be added either above or below the surface of the bath. Preferably the latex is added as drops above the surface of the bath.
Entry of the latex into the bath and movement of the precipitated, coated object through the bath impart to the bath a degree of agitation. Additional agitation in the form of stirring or shaking may be supplied, if desired, to assist in maintaining the uniformity of the bath. Agi-tation is particularly desirable when the pH of the bath is being maintained by addition of acid as noted above.
The present process may be operated at temperatures in the range from about 0C to about 100Cr Temperatures in the range from about 5C to about 70C are preferred, with the range from about 10C to about 40C being par-ticularly preferred because of the improved stability of the bath in this range.
Pressure is not a critical Yariable in the present process and pressures both above and below atmospheric 1~99~57 pre~8ure are oper~ble. ~tmospheric pressure i~ preferred ~or convenlence.
The time from entry of a particular elastomeric latex body into the bath until removal of the nontacky elastomeric shaped object therefrom may be varied widely, depending somewhat on the minimum dimension of the object being coated. The time may vary from about 0.5 second up to about 6 hours or more. On contact with the bath, the latex starts to coagulate and a nontacky coating is formed immediately on the surface of the coagulated shaped object, e.g., within about 0.5 to about 5 seconds. Longer retention of the coated object in the bath is employed when it is desired to complete coagulation and neutralization of the latex in the center of the coated object before it is removed from the bath. In preferred baths, this requires less than about 6 minutes. Complete coagulation in the bath is not essential since coagulant which has penetrated the shaped object can continue to migrate toward the center of the object after removal of the object from the bath. It is preferable, however, to leave the ob~ect in the bath until $
sufficient coagulant has penetrated the object to complete the coagulation.
Referring now to the drawings, Figure 1 shows a preferred embodiment of suitable apparatus for carrying out the process of this invention. This apparatus comprises a cylindrical tank 11 (27.94 cm i.d.) and a cylindrical draft tube 12 ~12.7 cm i.d.) which is concentric with tank 11.
The tube and tank may be c~nstructed of any ri~,id materlal such as ~lass, metal, or plastic. Drart tube 12 ~s extende~
on lts upper end by a wlre mesh screenl~ havin~ a mesh size 1~99~57 smaller than the size of the shaped objects being produced.
Bathl4 containlng the lnorganic oxide po~ymer and the coagu-lating salt is maintained at a liquid level such that the bath surface 15 is slightly below the upper edge of screen 13.
Drops or discrete masses of polymer latex are introduced into the bath within the zone circumscribed by screen 13. In this embodiment, stainless steel capillary tubes 16 (1.9 cm long, O.86 mm i.d. and 1.3 mm o.d.) are used for forming the latex drops. These tubes are mounted through polytetrafluoroethyl-ene plugs in a stainless steel plate bolted to the lower endof pipe 17 (10.1 cm i.d.). The center-to-center distance between the tubes mounted in the plate is 1.11 cm. Sixty-one tubes are arranged in a hexagonal array with five tubes on a side. The frequency of drop addition to the bath is adjusted by varying the level of latex in pipe 17.
An agitator 18 is provided in the bottom of tank 11 to promote circulation of the bath in such a manner that flow of the bath solution is generally down through the draft tube, up through the space between the draft tube and the tank wall, and through the screen to the confined bath surface. For this purpose, a 3-lobed (15.24 cm diameter) marine propeller is used.
The screen at the top of the draft tube provides a means of passing a solution which is free of shaped objects to the top of the draft tube. It also keeps out foam produced by the agitation and helps keep the surface free of disturbances which might affect the uniformity of the sha~eA ob~ects drop?ed throuah the surface. T~
increase agltation and thereby aid ~uspension of the coated latex particles ln the annular EpaCC outslde the draft tube, baffles 19 (3.81 cm wide) are placed vertically along the walls of tank 11 at 90 intervals. These baffles are not always necessary depending on the type of agitation used.
Through the action of the draft tube, screen, agitator and baffles, the shaped bodies contact a fresh solution, free of coated particles and foam. The shaped objects remain discrete as they pass down through the draft tube. By the time they emerge from the draft tube they are coated so that the tendency to agglomerate with previously coated shaped objects is eliminated. The coated shaped objects are then held in suspension outside of the draft tube until they are removed from the bath.
A typical batch run can be made using this apparatus as follows: First, bath 14 comprising an aqueous solution of an inorganic salt, a small amount of surfactant, and the coating material is prepared. The salt serves to coagulate the latex during coating and after it is coated. The surfactant facilitates passage of latex drops through the surface of the bath.
Latex is added to standpipe 17 to produce a given head pressure and then continuously added to maintain this head pressure on the capillary tubes. Since no solution is withdrawn from the bath during the run, the bath level rises due to the addition of latex. Both standpipe 17 and draft tube 12 are mounted so that they can be moved vertically.
They are moved during the course of each run to maintain the capillary exits about 2.54 cm above bath surface`15, and the upper edge of screen 13 about 0.835 cm above bath surface 15.
Although the apparatus illustrated in the drawings allows only batch removal of coated shaped objects at the ~q9~s~
conclusion of each run, the process can be operated contin-uously by providing an overflow tube in tank 11 for continuous removal of coagulated, coated shaped objects from the bath, fil-tering the suspension of shaped objects passing through the overflow tube, recycling the filtrate to the bath, and re-placement of the bath components as they become exhausted.
A major advantage of the invention is that, when large numbers of uncured shaped objects are stored in contact with each other under ordinary conditions, they do not agglomerate, but remain readily separable and free flowing.
The shaped objects have a minimum dimension of about 0.01 to about lO millimeters. The minimum dimension should be at least about O.Ol mm to avoid dusting. Shaped objects with a minimum dimension above about 10 mm require excessive power to mix with other ingredients in use applications.
Preferably the shaped objects have minimum dimensions of about 0.1 mm to about 5 mm.
Since the shaped bodies added to the bath are com-posed of latex, the water soluble coagulating salt quickly penetrates into the aqueous phase of the shaped objects, thereby coagulating the latex with a minimum of internal coalescence. As a result, the coagulated elastomer within the nontacky coating remains sufficiently porous for a sufficient period of time to permit the washing out of water soluble components, including the coagulating salt. In the case of relatively crystalline elastomers, this porosity is retained indefinitely. In the case of relatively noncrystalline elastomers such as neoprene, the porosity decreases on long standing, but it does not completely disappear.
After the precipitated shaped objects have been 10~9057 coagulate~ and coated they can be sel?arated frorn the bath by any ~uitable means. It is deslrable to remove watel soluble and volatile materials ~rom the shaped obJects aIter they have been separated from the bath. Thls may be accomplished by washing with water or a polar organic solvent, followed by squeezing, centrifuging or drying, using con-ventional techniques. The shaped objects should be washed until they contain less than about 3~ by weight of water soluble material, and preferably less than about 1%.
After the water soluble material has been removed to the desired extent, the shaped objects are dried to remove volatile material. Drying may be carried out at air temper-atures of about 25C to about 250C. Preferably the drying is carried out at air temperatures of about 100C to about 135C. During this drying operation the temperature of the shaped objects is kept below the known thermal decomposition temperature of the polymer. Drying is continued until the shaped objects contain less than about 1% by weight of volatile material, and preferably less than about 0.5~.
Vuring these finishing steps, polymers that are relatively stiff (because of crystallinity, for example) remain opaque and porous, while normally tacky polymers coalesce further to translucence. Nevertheless, even these retain vestiges of their formerly highly porous structure, and the nontacky nature of the hydrous oxide coating deposited on their exterior surrace is retained.
This nontacliy coating may be supplemente~ by minor additions of talc, for example, in the latter st~es of high tempera-ture drying, if deslred.
~he nontacky coating on the normally tacky lOq90S7 elastomer is initially also porous so that moisture, solvents, soluble reaction ingredients and by-products can be readily removed from within the coated object. The coating may represent from about 0.05 to about 3% by weight of the coated shaped object. Less than about 0.05% generally does not provide adequate nontacky properties, while more than about 3% usually gives no added advantage to offset increased cost. Preferably the coating is about 0.5 to about 2% by weight of the coated object. Washing operations, such as noted above, point up the necessity for both the nontacky coating and the coagulated elastomer being porous for a period of time after formation of the shaped objects.
Figure 3 is a photomicrograph of a cross section of a typical,porous shaped object in accordance with this invention. In this photograph, the porosity of the shaped object is apparent; voids appear as dark areas as observed at 20. The nontacky coating appears as light areas as is readily observed at 21.
The noniac~;y coated objects of this invention can also contain fillers, pi~ents, color~nts, softeners, extenders, antioxidants, st2bilizers, curing agents, and the like. Such m~terials ma~ be incorporated by ~dding them to the starting polymer latex or to the coa~ulatin~
and coatin~ bath.
The followin~ examples illustrate the prep2ration Or nontacky,elastomeric shaped objects of this invention.
. Each ~f the ~ashed and dried,nontacky,elastGmeric-shaped objects prepared in these examples had a water soluble material content of less than about 3~ by weight and a volatile material content of less than about 1~. In each case the inorganic oxide pol~mer coating was about 0.05 to about 3~ by weight of the shaped objects and the minimum dimension of the shaped objects was about 0.01 to about 10 millimeters. All parts and percentages are by weight throughout the examples.
The neoprene latices used in these examples were prepared as follows:
Neoprene Latex #l This latex was prepared from an aqueous, alkaline 10 emulsion containing 100 parts of chloroprene and 0.23 part of dodecyl mercaptan as modifier and stabilized by 2.9 parts of the sodium salt of disproportionated wood rosin. Chloro-prene was polymerized by adjusting the emulsion tempera-ture to 40C and adding continuously, at a rate allowing control of the temperature at 40C by external cooling, an aqueous solution containing 0.3% K2S2O8 and 0.015~ Na salt of anthraquinone-~- sulfonic acid. The polymerization was - terminated at about 67% conversion of the chloroprene mono-mer by the addition of an aqueous emulsion of a toluene 20 solution containing 0.015 part of phenothiazine and 0.015 part of 4~tert.-butylcatechol.
After removal of residual monomer by distillation, the latex contained about 37~ solids. The polymer had an inherent viscosity of 1.20 ~0.1 g/100 ml benzene at 30C).
The pH of the latex was about 12.
Neoprene Latex #2 An a~ueous, alkaline emulsion was prepared con-taining 100 parts of chloroprene, 0.15 part of dodecyl mer-captan and 3.5 parts of the sodium salt of disproportionated wood rosin. Chloroprene was polymerized by adjusting the ~0~ ;7 emulsion temperature to 10C and adding continuously an aqueous dispersion containing 1.0% X2S2O8, 0.05% sodium salt of anthraquinone-~-sulfonic acid, and 0.14% cumene hydroperoxide at a rate allowing control of the temperature between 10 and 20C. The polymerization was terminated at about 85% conversion of the chloroprene monomer by addition in the form of an aqueous emulsion of a toluene solution of 0.03 part of phenothiazine and 0.03 part of
4-tert.-butylcatechol.
After removal of residual monomer the emulsion contained 37% solids and had a pH of 12.5.
Neoprene Latex #3 The preparation of neoprene latex #l was repeated except that the 100 parts of chloroprene was replaced by a mixture of 92 parts of chloroprene and 8 parts of 2,3-dichloro-1,3-butadiene. The polymerization was stopped at 65~ conversion, and the latex, after stripping, contained about 33% solids and had a pH of 12.
Neoprene Latex #4 The procedure described for neoprene latex #2 was repeated except that the amount of dodecyl mercaptan in the monomer emulsion was 0.12 part instead of 0.15 part.
The resulting latex had a solids content of 37~ and a pH of 12.5.
Example 1 A bath containing approximately 0.7% SiO2 and 3.9%
Ca(NO3)2 was made by combining 90 ml of 0.25M aqueous silicic acid (produced by the ion exchange of H+ for Na+ in 0.25M
sodium metasilicate solution), 10 ml of a 50% aqueous Ca(NO3)2 solution, and 100 ml of absolute ethanol. About 20 ml of neoprene latex ~l (37~ so:Lids, pH 12) was added dropwise to this bath from an oriflce about 2 cm above it.
The surface of the drops coagulated on contact to yield globules which withln a few minutes were coagulated through-out and covered with a nontacky coating. The resulting opaque pellets were lifted from the bath and dried in a 60C
oven. At room temperature they remained dry to the touch and free-flowing.
For comparison the following experiment, not within the scope of the invention, was carried out. The above example was repeated using 90 ml of water in place of the silicic acid solution. The drops of emulsion coagulated rapidly, but remained very tacky and were difficult to separate after drying at 60C.
Exam~le 2 A bath containing approximately 3.6% SiO2 and -2.6% CaC12 was made by mixing lO00 ml of lM silicic acid, 60 ml of 50% CaCl2 solution, 700 ml of absolute ethanolr and 240 ml of distilled water. About 200 ml of neoprene latex #l (37% solids, pH 12) was introduced into the bath dropwise. The resulting pellets were allowed to remain in the bath for 30 minutes. They were removed, washed with 70% ethanol and dried for 48 hours in a vacuum drying pistol heated by re-fluxing acetone. The resulting pellets had the following analysis: Ca, 0.25;Na, 0.38; Si, Q~51r% ash, 2.8. Pellets prepared in this way retained a small amount of alkali.
Such amounts of residual alkali stabilize neoprene against HCl degradation. A 5% suspension of these pellets in wa~er had a pH of 9Ø The pellets were more than 90% soluble in toluene, indicating little or no crosslinking of the neoprene -~ - 22 -1~99~57 had occurred.
Example 3 An alcohol-free bath containing approximately 1.5~ SiO2 and 2.1% CaC12 was made, utilizing a dilute aqueous nonionic surfactant solution to reduce interfacial tension at the air-liquid interface. A mixture of 10 ml of freshly prepared 0.5~5 silicic acid, 9.4 ml of 0.2~ aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TM~-6, Union Carbide), and 0.6 ml of 50~ CaC12 completed the bath.
About 2 ml of neoprene latex ~1 (37% solids, pH 12) introduced dropwise into the bath formed opaque nonsticking pellets.
These were isolated, washed with water, and air dried to pro-duce free-flowing, nonsticking pellets 3-4 mm in diameter. The moisture content of the pellets was 0.38%; the ash residue was 3.05%; other analyses were: Ca, 0.44%;
Na, 0.26%; Si, 1.11%.
Exam~le 4 A bath containing approximately 1.5% SiO2 and 2.1~
CaC12 was prepared from 1000 ml of 0.5M silicic acid (pH 3.3), 940 ml of 0.2~ aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TMN-6), and 60 ml of-50% aqueous CaC12 solution. The initial pH of the bath was 4.45. One hundred milliliters of neoprene latex #l (37% solids, p~l 12) was added dropwise over a period of 10 minutes during which the bath was stirred and the pH was maintained at 4.0 by continuous addition of 1.0N hydrochloric acid. The bath showed no evidence of gelation. The neoprene pellets which formed were filtered from the bath on a 100 mesh stainless steel screen, washed with cold water and dried. They were non-tacky and free-flowing.
Example 5 A silicic acid solution was prepared from a sodium silicate solution having an SiO2/Na20 ratio of 1.95. The sodium silicate solution utilized was Grade 6 (Du Pont Co.) which had a viscosity of 60,000 centipoises (68C), a specific gravity of 1.708, % ~a20 = 18.4, and % SiO2 = 36Ø This solution (166.5 ml) was diulted to 2 liters with distilled water. The resulting solution was passed through a cation exchange column in acid form containing 1300 gms of cation exchange resin (Rexyn lOlj H ). The first 500 ml of effluent, e~uivalent to the retention volume of the column, was dis-carded and the remainder collected.
A 1000 ml portion of this 0.85M silicic acid solution was employed in the procedure of Example 4 to give a bath containing approximately 2.5% SiO2. At the start of the addition of neoprene latex the bath was at pH 3.1 and at the conclusion the pH was 4~1. The resulting pellets were washed with distilled water and dried. They showed little tendency to aggregate.
Example 6 A bath containing approximately 1.4% SiO2 and 7.6%
NaCl was prepared from 15 ml of 10% aqueous NaCl and 5 ml of l.OM aqueous silicic acid. About 2 ml of a 55% solids latex of a copolymer derived about 18% from vinyl acetate and about 82% from ethylene was added dropwise to the bath. The drops coagulated into pellets which were filtered from the bath, dried under vacuum at 80C, washed with water to remove all traces of NaCl and again dried. They were nontacky and free-flowing.
For comparison, the following experiments, not within ~ - 24 -~, ~ . ., ~9~57 the scope of the invention, were carried out. The above example was repeated twice, first with replacement of the NaCl solution by water, and second by replacement of the silicic acid solution by water. In both instances, the treated drops were too fragile to be removed whole from the bath.
Example 7 A solution containiny approximately 1.4% SiO2 and 6.1% NaCl was prepared by adding 262 ml of lN HCl, 14.7 gm of NaCl, and 38 ml of H2O to 100 ml of rapidly stirred 1~
Na2SiO3 9H2O. To this solution at about 0C were added 20 drops of the vinyl acetate/ethylene copolymer latex described in Example 6. After 10 minutes, the resulting pellets were removed from the bath and dried in a vacuum oven at 80C
for 2 hours. The pellets were coated with a nontacky coating and were free-flowing.
About 200 ml of a 62% solids natural rubber latex (LATEX TSC*, General Latex Co.) was added dropwise to a bath containing approximately 0.9% SiO2 and 2.5~ CaC12 which was prepared from 250 ml of lM silicic acid, 1750 ml of absolute EtOH, and 60 ml of 50% aqueous CaC12. The latex rapidly coagulated and a nontacky coating formed on the surface of the particles. When isolated and dried, the pellets were nontacky and free-flowing.
Example 9 Into neoprene latex #1 (37% solids, pH 12~ was mixed enough carbon black ISTERLING R*, Cabot) to yield a uniform emulsion containing 4% of carbon black based on the neoprene. About 20 ml of this modified latex was added *denotes trade mark -l~g~
dropwise to a bath containing 1.5~ SiO2 and 2.1% CaC12 prepared from 100 ml of 0.5M aqueous silicic acid, 94 ml of 0.2% aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TMN-6), and 6 ml of 50% aqueous CaC12. The drops were delivered from a Pasteur pipette near the surface of the bath and the bath was stirred by a magnetic bar. After 30 minutes in the bath the pellets which formed were removed by decantation, washed three times with 500 ml portions of water and air dried. The carbon-containing pellets were nontacky and free-flowing.
Example 10 The procedure of Example 9 was repeated with the exception that the 4~ of carbon black in the latex was re-placed by 10% of atomized aluminum powder. Nontacky, free-flowing aluminum-containing pellets were obtained.
Example ll ~he procedure of Example 9 was repeated with the exception that the 4% of carbon black in the latex was re-placed by 10% of alumina trihydrate (powder, baked at 135-195C). Nontacky, free-flowing alumina-containing pellets were obtained.
Exampl-e 12 The procedure of Example 9 was repeated with the exception that the 4& of carbon black in the latex was re-placed by 10% of magnetic iron oxide (Fe304 r M0-423~*, Pfi~er Minerals). Nontacky, free-flowing iron oxide-containing pellets were obtained which were readily manipulated with magnets.
EXample 13 About 100 ml of a 65% solids latex of fluoro-*denotes-trade mark lOq9~5~
elastomer terpolymer derived from 45% vinylidene fluoride, 30% hexafluoropropylene and 25% tetrafluoroethylene was added dropwise to a bath prepared from S~0 ml of 0.5M aqueous silicic acid saturated with BaC12, 500 ml of water saturated with BaC12, and 2 ml of 2~ aqueous trimethyl-nonanol ether of ethylene oxide (Tergitol~ TM~-6). The drops flattened on contact with the bath, but coagulated throughout and were coated with a nontacky coating. The particles were decanted from the bath, washed repeatedly with water and air dried to give white, free-flowing flakes about 5 mm in diameter.
Example 14 A mixture was prepared from equal volumes of neo-prene latex ~1 (37% solids, pH 12) and the aqueous fluoro-elastomer latex described in Example 13. This mixture (20 ml)was introduced dropwise into a bath containing approximately 1.5% SiO2 and 2.1% CaC12 prepared from 100 ml of 0.5M aqueous silicic acid, 94 ml of 0.2% aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TMN-6), and 6 ml of 50~ aqueous CaC12. ~he pellets which formed were washed with water and then dried, first in air and then over,P2O5 under vacuum at room temperature. The resulting mixed elastomer pellets were nontacky and free-flowing.
Example 15 A portion (422 ml) of sodium silicate solution (Grade F, Du Pont Co., SiO2/Na2O ratio = 3.25, Na2O = 8.7~, SiO2 ~ 28.4%, viscosity (68C) = 160 cp, specific gravity e 1.386) was diluted to 4 liters with distilled water. This solution was put through the cation exchange column in acid form described in Example 5. A bath containing approximately ~"9QS7 0.5~ SiO2 and 7.6~ NH4Cl was prepared using 250 ml of the resulting approximately 0.69M silicic acid solution, 1000 ml of 15~ NH4Cl, 250 ml of distilled water, and 500 ml of 0.05% aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ T~-6). Two hundred ml of neoprene latex ~2 - (37~ solids, pH 12.5) was added dropwise to the bath. The pellets which formed were allowed to remain in the bath for 30 minutes. The bath was decanted and the pellets were washed three times with 2-liter portions of water. The pellets were air dried at room temperature and atmospheric pressure. The resulting pellets were nontacky and free-flowing.
~xample 16 A bath was prepared with a buffer to resist the pH elevation associa~ed wi~h the addition o~ alkaline neoprene latex. The buffer was prepared by diluting a mix-ture of 1.75 ml of 2M HCl, 0.1 g of trimethylnonanol ether of ethylene oxide (Tergitol~ T~IN-6), and 12.60 ml of 2~S
glycine solution to 50 ml with distilled ~ater. The buffer was then addcd to 100 ml of 0.69~l silicic acid (prepared according to Example 15), and 50 ml of 30~ aqueous ~114Cl.
Twenty ml of neoprene latex #2 (37~ solids, pH 12.5) was added to the bath dropwise. The pH of the bath changed from 3.35 to 3.55 as compared to a p~ change to approximately 6.0 for a similar unbuffered bath. Approximately 80 ml of the latex could be added to the buffered bath before the pH rose above 6.0, at which pH gelation of the bath occurred rapidly.
Example 17 A bath containing approximately 2.0% SiO2 and 7.9%
~H4Cl was prepared from 1000 ml of 0.69M silicic acid, (prepared according to Example 15) 500 ml of 30% NH4Cl~ and ~o99~s~
500 ml of 0.2S aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TMN-6). A 200-ml sample of neoprene latex #3 (33~ solids, pH 12) was adjusted from pH 12.0 to pH 12.5 by addition ~r lN ~aOH. This latex was added dropwise to the bath. The pellets which formed were washed wit~ water and then rreeze-dried at about -178~C under high vacuum.
At room temperature the dried pellets were nontacky and free-flowing.
Ex~m~le 18 h bath was prepared usin~ an ~lumina-modiried silica sol (Ludox~ 130M, Du Pont Co.), This product is a 30% solids, acidic, aqueous dispersion of positively-char~eQ
colloidal particles consistin~ o~ a dense silica core coated with positively-char~ed polymeric alumina, The approximate chemical composition is SiO2 = 26%, A1203 = 4.0~, Cl = 1.4~o~
MgO = 0.2%, viscosity (25C) = 5-15 cp, pH (25C) = 4.3-4.5, approximate particle diameter = 16 m~, and speci~ic gravity (25~C) = 1.23.
The bath containing approximately 0.7% SiO2/A1203 snd 6.1% NH4Cl was composed of 116 ml of 0.2~ aqueous sodium heptadecyl sulfate anionic surfactant (Tergitol~ Anionic 7, ~.
Union Carbide), 80 ml of 15% aqueous NH4Cl, and 4 ml of the slumina-modlrled sillca sol descrlbed abo~e. To this bath wa~ added dropwlse 20 ml o~ neoprene latex #2 (~7% solids, pH 12.5). The drop~ coagulated and the re6ultlng coated pellets were wa~hed and dried. Nontacky, free-flowing pellets were obt~lned.
Example 19 A bath containing approximately 1.0% SiO2 and 8.0~ AlC13 was prepared ~rom 5 ml of 0.69M aqueous silicic ~0~9Q~;~
acid (prepared according to Example 15), 9 ml of 30% aqueous AlC13-6H20, 5 ml of 0.2% aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TMN-6), and 1 ml of distilled water.
To this bath was added dropwise 2 ml of neoprene latex ~2 (37% solids, pH 12.5). The drops coagulated and were removed from the bath, washed and dried. Nontacky, fre~-flowing pellets were obtained.
Exam~les 20-23 Four baths were prepared, each from 2.5 ml o~
0.6~M aqueous silicic acid (prepared according to Exam~le 15), 5 ml of 0.5% aqueous trimethylnonanol ether Or ethylene oxide (Tergitol~ TMN-6~,and 12.5 ml of a 30% aqueous solution of the indicated salts~
Example 20 NH4Br Example 21 tNH4)2Hc6H5o7(citrate) Example 22 INH4)2Cr2O7 Example 23 NH4SCN
To each bath was then added dropwise 2 ml of neoprene latex #2 (37% solids, pH 12.5). The elastomer pellets which formed were separately washcd with water and dried. All yielded nontacky, free-flowing pellets.
Example 24 Ten ml of naphthenic extender oil (Sundex~ 790, Sun Oil Co.) was added to 90 ml of neoprene latex ~2 (37~
solids, pH 12.5) and the mixture vigorously shaken to give ~n emulsion. A bath containing approximately 1.0~ SiO2 and 7.6% NH4Cl was prepared from 50 ml of 0.69M aqueous silicic acid ~prep:-red according to Example 15), 100 ml of 15% aqueous NH4Cl, and 50 ml of 0.05~ aqueous trlmethylnonanol ether Or ethylene oxlde tTergltol~ TMN-6). The oil extended 1099~'7 polymer latex was added dropwise tc the bath. The pellets which formed were separated from the bath, washed with water and dried to yield nontacky, free-flowin6 pellets of oil-extended elastomer.
Example 25 A bath containing approximately 0.9% SiO2 and 10.0~ NaCl was prepared by dissolving 100 g of NaCl in 900 g of 0.35~1 aqueous silicic acid, dissolving 100 9 of NaCl in 900 g of 0.05~ aqueous trimethylnonanol ether of eth~lene oxide (Tergitol@ T~-6), and combining the two solutions. The bath was maintained at pH 4-4.5 by additions of lN HCl during the dropwise addition of 200 ml of neoprene latex ~2 (37~O solids, pH 12.5). The pellets which formed were allowed to stand in the bath for 16 hours, then washed with water and dried to yield nontacky, free-flowing pellets of uncured elastomer.
~xample ?6 A bath containing approximately 1.3~ SiO2, 3.9~
NH4Cl and 11.1% NaCl was made ~y combinin~ 25 ml of 0.69~1 silicic acid (prepared in accordance with ~xample 15), 10 ml of 30~ NH4Cl in 0.2% aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TMN-6), 40 ml of 20% NaCl in 0.2%
aqueous trimethynonanol ether of ethylene oxide (Tergitol~
TMN-6), and 125 ml of distilled water. The bath was adjusted to pH 5.0 with lN NaOH. Twenty milliliters of neoprene latex #2 (37% solids, pH 12.5) was added to the bath dropwise while the pH was maintained at 5.0 by dropwise addition of lN HCl. The resultln~ pellets were re~o~ed rrom the bath after one hour, washed three times with 500-ml portions of distilled water, and air dried to ~()g9~57 yield nontacky, free-flowing pellets.
Example 27 A bath containing approximately 0.5% chlorhydrol (aluminum chlorohydroxide polymeric complex containing 47.0%
A12O3 and 16.3% chloride, Reheis Chemical Co.) and 2.3% CaC12 was prepared by combining 10 ml of 10% aqueous chlorhydrol, 175 ml of 0.05% aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TMN-6), and 15 ml of 25% aqueous CaC12. The solution was brought to pH 5.0 with lM NaOH. As 20 ml of neoprene latex #2 (37% solids, pH 12.5) was added dropwise, the bath was gently stirred and maintained at pH 5.0 by dropwise addition of IN HCl. The pellets were allowed to remain in the bath for 1 hour, after which they were washed with three 250~ml charges of distilled water. The pellets were then air dried to form free-flowing nontacky elastomer particles.
Example 28 A surfactant-free bath containing 1.0% SiO2 and 7.6%
NH4Cl was prepared from 100 ml of 0.69M aqueous silicic acid (prepared according to Example 15), 200 ml of 15% aqueous NH4Cl, and 100 ml of distilled water. A 100 ml graduated cylinder was filled with this bath. From a 10 ml syringe fitted with a 20 gauge needle r neoprene latex #2 (37% solids, pH 12.5) was extruded as a continuous stream onto the surface of the bath at one side of the graduated cylinder, forming a small puddle. By grasping the edge of the puddle with tweezers at the other side of the graduated cylinder a continuous fiber of coagulated, hydrous silica-coated polychloroprene was drawn off. After being washed and air dried, the fiber was nontacky, Example 29 lO~9~S~
The procedure of Example 28 was repeated except that more ~orce was used on the syringe, thus causing the stream o~ latex to ~o through the sur~ace Or the bath. ~he weight Or the coagulating stream pulled it to the bottom Or the bath ~here a nontacky continuous riber Or the elasto~
about 1-2 mm ~n diameter collécted.
Example 30 The procedure Or Example 29 was repeated excep~
that, a~ter the interface at the surface of the bath had been penetrated by the latex stream, the force on the syr~nge was reduced and adjusted so that free drops fell from the needle into the bath. The pellets which formed were non-tacky and free-flowing when washed and dried, Example 31 Part A
To 200 ml of a 30% solids aqueous colloidal sol of alumina-modi~ied silica Or pH 8~6-~3 (Ludox~ AM, Du Pont Co.) under agitation in a blender was added 2.0 ml Or con-centrated ~Cl (38%). The resulting colloidal solution con-taining approximately 29~ solids had a pH of 3ØPart B
A modified neoprene latex was prepared by adding 10 ~1 of a 1~ aqueous solution of hydroxyethyl cellulose (Cello-size~ QP 30,000, Union Carbide Corp.) to 90 ml of neoprene latex #2 ~37% solids, pH 12.5). The emulsion was kept agitated to avoid creaming.
Part C
A bath containing approximately 4.3% SiO2/A12O3 and 7.5~ NH4Cl was prepared by mixing 2.5 ml of the col-loidal silica aolution prepared in Part A above, 10.0 ml of 9()57 15~ aqueous N~4Cl, 1 ml Or a 0.2~ aqueous solution Or an amphoteric fluorinated surfactant (Zonyl~ ~SB, Du Pont Co.), and 6.5 ml of wa~er. To this bath was addcd dropwise about
After removal of residual monomer the emulsion contained 37% solids and had a pH of 12.5.
Neoprene Latex #3 The preparation of neoprene latex #l was repeated except that the 100 parts of chloroprene was replaced by a mixture of 92 parts of chloroprene and 8 parts of 2,3-dichloro-1,3-butadiene. The polymerization was stopped at 65~ conversion, and the latex, after stripping, contained about 33% solids and had a pH of 12.
Neoprene Latex #4 The procedure described for neoprene latex #2 was repeated except that the amount of dodecyl mercaptan in the monomer emulsion was 0.12 part instead of 0.15 part.
The resulting latex had a solids content of 37~ and a pH of 12.5.
Example 1 A bath containing approximately 0.7% SiO2 and 3.9%
Ca(NO3)2 was made by combining 90 ml of 0.25M aqueous silicic acid (produced by the ion exchange of H+ for Na+ in 0.25M
sodium metasilicate solution), 10 ml of a 50% aqueous Ca(NO3)2 solution, and 100 ml of absolute ethanol. About 20 ml of neoprene latex ~l (37~ so:Lids, pH 12) was added dropwise to this bath from an oriflce about 2 cm above it.
The surface of the drops coagulated on contact to yield globules which withln a few minutes were coagulated through-out and covered with a nontacky coating. The resulting opaque pellets were lifted from the bath and dried in a 60C
oven. At room temperature they remained dry to the touch and free-flowing.
For comparison the following experiment, not within the scope of the invention, was carried out. The above example was repeated using 90 ml of water in place of the silicic acid solution. The drops of emulsion coagulated rapidly, but remained very tacky and were difficult to separate after drying at 60C.
Exam~le 2 A bath containing approximately 3.6% SiO2 and -2.6% CaC12 was made by mixing lO00 ml of lM silicic acid, 60 ml of 50% CaCl2 solution, 700 ml of absolute ethanolr and 240 ml of distilled water. About 200 ml of neoprene latex #l (37% solids, pH 12) was introduced into the bath dropwise. The resulting pellets were allowed to remain in the bath for 30 minutes. They were removed, washed with 70% ethanol and dried for 48 hours in a vacuum drying pistol heated by re-fluxing acetone. The resulting pellets had the following analysis: Ca, 0.25;Na, 0.38; Si, Q~51r% ash, 2.8. Pellets prepared in this way retained a small amount of alkali.
Such amounts of residual alkali stabilize neoprene against HCl degradation. A 5% suspension of these pellets in wa~er had a pH of 9Ø The pellets were more than 90% soluble in toluene, indicating little or no crosslinking of the neoprene -~ - 22 -1~99~57 had occurred.
Example 3 An alcohol-free bath containing approximately 1.5~ SiO2 and 2.1% CaC12 was made, utilizing a dilute aqueous nonionic surfactant solution to reduce interfacial tension at the air-liquid interface. A mixture of 10 ml of freshly prepared 0.5~5 silicic acid, 9.4 ml of 0.2~ aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TM~-6, Union Carbide), and 0.6 ml of 50~ CaC12 completed the bath.
About 2 ml of neoprene latex ~1 (37% solids, pH 12) introduced dropwise into the bath formed opaque nonsticking pellets.
These were isolated, washed with water, and air dried to pro-duce free-flowing, nonsticking pellets 3-4 mm in diameter. The moisture content of the pellets was 0.38%; the ash residue was 3.05%; other analyses were: Ca, 0.44%;
Na, 0.26%; Si, 1.11%.
Exam~le 4 A bath containing approximately 1.5% SiO2 and 2.1~
CaC12 was prepared from 1000 ml of 0.5M silicic acid (pH 3.3), 940 ml of 0.2~ aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TMN-6), and 60 ml of-50% aqueous CaC12 solution. The initial pH of the bath was 4.45. One hundred milliliters of neoprene latex #l (37% solids, p~l 12) was added dropwise over a period of 10 minutes during which the bath was stirred and the pH was maintained at 4.0 by continuous addition of 1.0N hydrochloric acid. The bath showed no evidence of gelation. The neoprene pellets which formed were filtered from the bath on a 100 mesh stainless steel screen, washed with cold water and dried. They were non-tacky and free-flowing.
Example 5 A silicic acid solution was prepared from a sodium silicate solution having an SiO2/Na20 ratio of 1.95. The sodium silicate solution utilized was Grade 6 (Du Pont Co.) which had a viscosity of 60,000 centipoises (68C), a specific gravity of 1.708, % ~a20 = 18.4, and % SiO2 = 36Ø This solution (166.5 ml) was diulted to 2 liters with distilled water. The resulting solution was passed through a cation exchange column in acid form containing 1300 gms of cation exchange resin (Rexyn lOlj H ). The first 500 ml of effluent, e~uivalent to the retention volume of the column, was dis-carded and the remainder collected.
A 1000 ml portion of this 0.85M silicic acid solution was employed in the procedure of Example 4 to give a bath containing approximately 2.5% SiO2. At the start of the addition of neoprene latex the bath was at pH 3.1 and at the conclusion the pH was 4~1. The resulting pellets were washed with distilled water and dried. They showed little tendency to aggregate.
Example 6 A bath containing approximately 1.4% SiO2 and 7.6%
NaCl was prepared from 15 ml of 10% aqueous NaCl and 5 ml of l.OM aqueous silicic acid. About 2 ml of a 55% solids latex of a copolymer derived about 18% from vinyl acetate and about 82% from ethylene was added dropwise to the bath. The drops coagulated into pellets which were filtered from the bath, dried under vacuum at 80C, washed with water to remove all traces of NaCl and again dried. They were nontacky and free-flowing.
For comparison, the following experiments, not within ~ - 24 -~, ~ . ., ~9~57 the scope of the invention, were carried out. The above example was repeated twice, first with replacement of the NaCl solution by water, and second by replacement of the silicic acid solution by water. In both instances, the treated drops were too fragile to be removed whole from the bath.
Example 7 A solution containiny approximately 1.4% SiO2 and 6.1% NaCl was prepared by adding 262 ml of lN HCl, 14.7 gm of NaCl, and 38 ml of H2O to 100 ml of rapidly stirred 1~
Na2SiO3 9H2O. To this solution at about 0C were added 20 drops of the vinyl acetate/ethylene copolymer latex described in Example 6. After 10 minutes, the resulting pellets were removed from the bath and dried in a vacuum oven at 80C
for 2 hours. The pellets were coated with a nontacky coating and were free-flowing.
About 200 ml of a 62% solids natural rubber latex (LATEX TSC*, General Latex Co.) was added dropwise to a bath containing approximately 0.9% SiO2 and 2.5~ CaC12 which was prepared from 250 ml of lM silicic acid, 1750 ml of absolute EtOH, and 60 ml of 50% aqueous CaC12. The latex rapidly coagulated and a nontacky coating formed on the surface of the particles. When isolated and dried, the pellets were nontacky and free-flowing.
Example 9 Into neoprene latex #1 (37% solids, pH 12~ was mixed enough carbon black ISTERLING R*, Cabot) to yield a uniform emulsion containing 4% of carbon black based on the neoprene. About 20 ml of this modified latex was added *denotes trade mark -l~g~
dropwise to a bath containing 1.5~ SiO2 and 2.1% CaC12 prepared from 100 ml of 0.5M aqueous silicic acid, 94 ml of 0.2% aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TMN-6), and 6 ml of 50% aqueous CaC12. The drops were delivered from a Pasteur pipette near the surface of the bath and the bath was stirred by a magnetic bar. After 30 minutes in the bath the pellets which formed were removed by decantation, washed three times with 500 ml portions of water and air dried. The carbon-containing pellets were nontacky and free-flowing.
Example 10 The procedure of Example 9 was repeated with the exception that the 4~ of carbon black in the latex was re-placed by 10% of atomized aluminum powder. Nontacky, free-flowing aluminum-containing pellets were obtained.
Example ll ~he procedure of Example 9 was repeated with the exception that the 4% of carbon black in the latex was re-placed by 10% of alumina trihydrate (powder, baked at 135-195C). Nontacky, free-flowing alumina-containing pellets were obtained.
Exampl-e 12 The procedure of Example 9 was repeated with the exception that the 4& of carbon black in the latex was re-placed by 10% of magnetic iron oxide (Fe304 r M0-423~*, Pfi~er Minerals). Nontacky, free-flowing iron oxide-containing pellets were obtained which were readily manipulated with magnets.
EXample 13 About 100 ml of a 65% solids latex of fluoro-*denotes-trade mark lOq9~5~
elastomer terpolymer derived from 45% vinylidene fluoride, 30% hexafluoropropylene and 25% tetrafluoroethylene was added dropwise to a bath prepared from S~0 ml of 0.5M aqueous silicic acid saturated with BaC12, 500 ml of water saturated with BaC12, and 2 ml of 2~ aqueous trimethyl-nonanol ether of ethylene oxide (Tergitol~ TM~-6). The drops flattened on contact with the bath, but coagulated throughout and were coated with a nontacky coating. The particles were decanted from the bath, washed repeatedly with water and air dried to give white, free-flowing flakes about 5 mm in diameter.
Example 14 A mixture was prepared from equal volumes of neo-prene latex ~1 (37% solids, pH 12) and the aqueous fluoro-elastomer latex described in Example 13. This mixture (20 ml)was introduced dropwise into a bath containing approximately 1.5% SiO2 and 2.1% CaC12 prepared from 100 ml of 0.5M aqueous silicic acid, 94 ml of 0.2% aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TMN-6), and 6 ml of 50~ aqueous CaC12. ~he pellets which formed were washed with water and then dried, first in air and then over,P2O5 under vacuum at room temperature. The resulting mixed elastomer pellets were nontacky and free-flowing.
Example 15 A portion (422 ml) of sodium silicate solution (Grade F, Du Pont Co., SiO2/Na2O ratio = 3.25, Na2O = 8.7~, SiO2 ~ 28.4%, viscosity (68C) = 160 cp, specific gravity e 1.386) was diluted to 4 liters with distilled water. This solution was put through the cation exchange column in acid form described in Example 5. A bath containing approximately ~"9QS7 0.5~ SiO2 and 7.6~ NH4Cl was prepared using 250 ml of the resulting approximately 0.69M silicic acid solution, 1000 ml of 15~ NH4Cl, 250 ml of distilled water, and 500 ml of 0.05% aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ T~-6). Two hundred ml of neoprene latex ~2 - (37~ solids, pH 12.5) was added dropwise to the bath. The pellets which formed were allowed to remain in the bath for 30 minutes. The bath was decanted and the pellets were washed three times with 2-liter portions of water. The pellets were air dried at room temperature and atmospheric pressure. The resulting pellets were nontacky and free-flowing.
~xample 16 A bath was prepared with a buffer to resist the pH elevation associa~ed wi~h the addition o~ alkaline neoprene latex. The buffer was prepared by diluting a mix-ture of 1.75 ml of 2M HCl, 0.1 g of trimethylnonanol ether of ethylene oxide (Tergitol~ T~IN-6), and 12.60 ml of 2~S
glycine solution to 50 ml with distilled ~ater. The buffer was then addcd to 100 ml of 0.69~l silicic acid (prepared according to Example 15), and 50 ml of 30~ aqueous ~114Cl.
Twenty ml of neoprene latex #2 (37~ solids, pH 12.5) was added to the bath dropwise. The pH of the bath changed from 3.35 to 3.55 as compared to a p~ change to approximately 6.0 for a similar unbuffered bath. Approximately 80 ml of the latex could be added to the buffered bath before the pH rose above 6.0, at which pH gelation of the bath occurred rapidly.
Example 17 A bath containing approximately 2.0% SiO2 and 7.9%
~H4Cl was prepared from 1000 ml of 0.69M silicic acid, (prepared according to Example 15) 500 ml of 30% NH4Cl~ and ~o99~s~
500 ml of 0.2S aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TMN-6). A 200-ml sample of neoprene latex #3 (33~ solids, pH 12) was adjusted from pH 12.0 to pH 12.5 by addition ~r lN ~aOH. This latex was added dropwise to the bath. The pellets which formed were washed wit~ water and then rreeze-dried at about -178~C under high vacuum.
At room temperature the dried pellets were nontacky and free-flowing.
Ex~m~le 18 h bath was prepared usin~ an ~lumina-modiried silica sol (Ludox~ 130M, Du Pont Co.), This product is a 30% solids, acidic, aqueous dispersion of positively-char~eQ
colloidal particles consistin~ o~ a dense silica core coated with positively-char~ed polymeric alumina, The approximate chemical composition is SiO2 = 26%, A1203 = 4.0~, Cl = 1.4~o~
MgO = 0.2%, viscosity (25C) = 5-15 cp, pH (25C) = 4.3-4.5, approximate particle diameter = 16 m~, and speci~ic gravity (25~C) = 1.23.
The bath containing approximately 0.7% SiO2/A1203 snd 6.1% NH4Cl was composed of 116 ml of 0.2~ aqueous sodium heptadecyl sulfate anionic surfactant (Tergitol~ Anionic 7, ~.
Union Carbide), 80 ml of 15% aqueous NH4Cl, and 4 ml of the slumina-modlrled sillca sol descrlbed abo~e. To this bath wa~ added dropwlse 20 ml o~ neoprene latex #2 (~7% solids, pH 12.5). The drop~ coagulated and the re6ultlng coated pellets were wa~hed and dried. Nontacky, free-flowing pellets were obt~lned.
Example 19 A bath containing approximately 1.0% SiO2 and 8.0~ AlC13 was prepared ~rom 5 ml of 0.69M aqueous silicic ~0~9Q~;~
acid (prepared according to Example 15), 9 ml of 30% aqueous AlC13-6H20, 5 ml of 0.2% aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TMN-6), and 1 ml of distilled water.
To this bath was added dropwise 2 ml of neoprene latex ~2 (37% solids, pH 12.5). The drops coagulated and were removed from the bath, washed and dried. Nontacky, fre~-flowing pellets were obtained.
Exam~les 20-23 Four baths were prepared, each from 2.5 ml o~
0.6~M aqueous silicic acid (prepared according to Exam~le 15), 5 ml of 0.5% aqueous trimethylnonanol ether Or ethylene oxide (Tergitol~ TMN-6~,and 12.5 ml of a 30% aqueous solution of the indicated salts~
Example 20 NH4Br Example 21 tNH4)2Hc6H5o7(citrate) Example 22 INH4)2Cr2O7 Example 23 NH4SCN
To each bath was then added dropwise 2 ml of neoprene latex #2 (37% solids, pH 12.5). The elastomer pellets which formed were separately washcd with water and dried. All yielded nontacky, free-flowing pellets.
Example 24 Ten ml of naphthenic extender oil (Sundex~ 790, Sun Oil Co.) was added to 90 ml of neoprene latex ~2 (37~
solids, pH 12.5) and the mixture vigorously shaken to give ~n emulsion. A bath containing approximately 1.0~ SiO2 and 7.6% NH4Cl was prepared from 50 ml of 0.69M aqueous silicic acid ~prep:-red according to Example 15), 100 ml of 15% aqueous NH4Cl, and 50 ml of 0.05~ aqueous trlmethylnonanol ether Or ethylene oxlde tTergltol~ TMN-6). The oil extended 1099~'7 polymer latex was added dropwise tc the bath. The pellets which formed were separated from the bath, washed with water and dried to yield nontacky, free-flowin6 pellets of oil-extended elastomer.
Example 25 A bath containing approximately 0.9% SiO2 and 10.0~ NaCl was prepared by dissolving 100 g of NaCl in 900 g of 0.35~1 aqueous silicic acid, dissolving 100 9 of NaCl in 900 g of 0.05~ aqueous trimethylnonanol ether of eth~lene oxide (Tergitol@ T~-6), and combining the two solutions. The bath was maintained at pH 4-4.5 by additions of lN HCl during the dropwise addition of 200 ml of neoprene latex ~2 (37~O solids, pH 12.5). The pellets which formed were allowed to stand in the bath for 16 hours, then washed with water and dried to yield nontacky, free-flowing pellets of uncured elastomer.
~xample ?6 A bath containing approximately 1.3~ SiO2, 3.9~
NH4Cl and 11.1% NaCl was made ~y combinin~ 25 ml of 0.69~1 silicic acid (prepared in accordance with ~xample 15), 10 ml of 30~ NH4Cl in 0.2% aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TMN-6), 40 ml of 20% NaCl in 0.2%
aqueous trimethynonanol ether of ethylene oxide (Tergitol~
TMN-6), and 125 ml of distilled water. The bath was adjusted to pH 5.0 with lN NaOH. Twenty milliliters of neoprene latex #2 (37% solids, pH 12.5) was added to the bath dropwise while the pH was maintained at 5.0 by dropwise addition of lN HCl. The resultln~ pellets were re~o~ed rrom the bath after one hour, washed three times with 500-ml portions of distilled water, and air dried to ~()g9~57 yield nontacky, free-flowing pellets.
Example 27 A bath containing approximately 0.5% chlorhydrol (aluminum chlorohydroxide polymeric complex containing 47.0%
A12O3 and 16.3% chloride, Reheis Chemical Co.) and 2.3% CaC12 was prepared by combining 10 ml of 10% aqueous chlorhydrol, 175 ml of 0.05% aqueous trimethylnonanol ether of ethylene oxide (Tergitol~ TMN-6), and 15 ml of 25% aqueous CaC12. The solution was brought to pH 5.0 with lM NaOH. As 20 ml of neoprene latex #2 (37% solids, pH 12.5) was added dropwise, the bath was gently stirred and maintained at pH 5.0 by dropwise addition of IN HCl. The pellets were allowed to remain in the bath for 1 hour, after which they were washed with three 250~ml charges of distilled water. The pellets were then air dried to form free-flowing nontacky elastomer particles.
Example 28 A surfactant-free bath containing 1.0% SiO2 and 7.6%
NH4Cl was prepared from 100 ml of 0.69M aqueous silicic acid (prepared according to Example 15), 200 ml of 15% aqueous NH4Cl, and 100 ml of distilled water. A 100 ml graduated cylinder was filled with this bath. From a 10 ml syringe fitted with a 20 gauge needle r neoprene latex #2 (37% solids, pH 12.5) was extruded as a continuous stream onto the surface of the bath at one side of the graduated cylinder, forming a small puddle. By grasping the edge of the puddle with tweezers at the other side of the graduated cylinder a continuous fiber of coagulated, hydrous silica-coated polychloroprene was drawn off. After being washed and air dried, the fiber was nontacky, Example 29 lO~9~S~
The procedure of Example 28 was repeated except that more ~orce was used on the syringe, thus causing the stream o~ latex to ~o through the sur~ace Or the bath. ~he weight Or the coagulating stream pulled it to the bottom Or the bath ~here a nontacky continuous riber Or the elasto~
about 1-2 mm ~n diameter collécted.
Example 30 The procedure Or Example 29 was repeated excep~
that, a~ter the interface at the surface of the bath had been penetrated by the latex stream, the force on the syr~nge was reduced and adjusted so that free drops fell from the needle into the bath. The pellets which formed were non-tacky and free-flowing when washed and dried, Example 31 Part A
To 200 ml of a 30% solids aqueous colloidal sol of alumina-modi~ied silica Or pH 8~6-~3 (Ludox~ AM, Du Pont Co.) under agitation in a blender was added 2.0 ml Or con-centrated ~Cl (38%). The resulting colloidal solution con-taining approximately 29~ solids had a pH of 3ØPart B
A modified neoprene latex was prepared by adding 10 ~1 of a 1~ aqueous solution of hydroxyethyl cellulose (Cello-size~ QP 30,000, Union Carbide Corp.) to 90 ml of neoprene latex #2 ~37% solids, pH 12.5). The emulsion was kept agitated to avoid creaming.
Part C
A bath containing approximately 4.3% SiO2/A12O3 and 7.5~ NH4Cl was prepared by mixing 2.5 ml of the col-loidal silica aolution prepared in Part A above, 10.0 ml of 9()57 15~ aqueous N~4Cl, 1 ml Or a 0.2~ aqueous solution Or an amphoteric fluorinated surfactant (Zonyl~ ~SB, Du Pont Co.), and 6.5 ml of wa~er. To this bath was addcd dropwise about
5 ml of the modified neoprene latex prepared in Part ~ above.
The pellets which formed were separated from the bath, washed with water, and dried to obtain nontacky, free-flowing, substantially spherical pellets o~` modified neoprene.
Example 32 A bath containing approximately 0.5% SiO2, 7.6%
NH4Cl and 0.01~ AlC13 was prepared by mixing 250 ml of 0.69 aqueous silicic acid (prepared according to Example 15 and aged for two days), 1000 ml of 15% aqueous NH4Cl, 200 ml of water, 500 ml of 0.05% aqueous trimethylnonanol ether of eth~l-ene oxide (Tergitol3 TMN-6), and 50 ml of 1% aqueous AlC13-6H20 which had been adjusted to pH 5.0 by addition of lN NaOH.
This bath was kept at pH 4.5-5.0 by addition of lN HCl ~during the dropwise addition o~ 200 ml o~ neoprene latex ~2 (37~ solids, pH 12.5) which took eight minutes, and for one hour thereafter. The drops, which coagulated, were separated from the bath, washed three times with wa-ter, soaked for three hours in water, and then air dried. The resulting pellets were nontacky and free-flowing.
xample 33 A silica sol containing approximately 4.6~ solids with a pH of 5.0 was prepared by adding 265 ml of a 15%
solids aqueous silica sol (Nyacol~ 215, Nyacol, Inc., pH 10.5) dropwise with vigorous stirring to a solution cf 70 ml of lN HCl in 595 ml of water. A bath containing approximately 0.6% SiO2, 7.6~ N~34Cl and 0.013~ AlC13 was prepared by mixing 250 ml of the above sol, 1000 ml of 15 ~"9~57 a~ueous NH4Cl, 700 ml of a 0.03~ aqueous solution of an amphoteric fluorinated surfactant (Zonyl~ FSB, Du Pont Co.), and 50 ml of 1~ aqueous AlC13 6H2~ which had been adjusted to pH 5.0 with lN NaOH. The resulting bath had a pH of 4.3.
This bath was stirred and kept at pH 4~5-5.0 by addition of HCl during the dropwise addition of 200 ml of neoprene latex #2 (37% solids/ pH 12.5). The pellets which formed were stirred in the bath for one hour, separated, washed three times with water and soaked in 2 liters of water. After dry-ing the pellets were nontacky and showed little tendency toagglomerate.
Example 34 In the manner of Example 33, 42 ml of a 49~ solids aqueous colloidal silica sol (Ludox~ TM, Du Pont Co~, pH
8.9, particles 220-250A in diameter) was blended with 3.9 ml of lN HCl and 454 ml of water to give an aqueous sol con-taining 5.6% SiO2. A bath containing approximately 0.7~ -SiO2, 7.6~ NH4Cl and 0.013~ AlC13 was prepared by substituting 250 ml of the above sol for the sol employed in Example 33 and maintained at a pH of 5.0 by addition of lN HCl. The remaining procedure of Example 33 was then repeated to yield nontacky, free-flowing elastomer pellets.
EXample 35 In the manner of Example 33, 125 ml of a 30%
solids aqueous colloidal silica sol (Ludox~ SM, pH 9.9, Du Pont Co.) in 125 ml of distilled water, was blended with 28 ml-of lN HCl and 637 ml of water. A bath was prepared by substituting 250 ml of the above sol for the sol employed in Example 33 and the remaining procedure of Example 33 was repeated. Nontacky, free-flowing pellets were obtained.
~, - 35 -l~9~S7 Example 36 To 400 ml of a 30% solids aqueous colloidal sol of alumina-modified silica of pH about 8.9 (Ludox~ AM, Du Pont Co.) was added 4.0 ml of concentrated (38%) hydro-chloric acid with vigorous agitation. The resulting sol had a pH of 3.0 and a solids content of about 29.7%. A bath con-taining approximately 4.3% SiO2 and 7.5% NH4Cl was prepared from 250 ml of this sol, 1000 ml of 15% aqueous NH4Cl, 650 ml of water, and 100 ml of a 0.2% aqueous amphoteric fluorosur-factant solution (Zonyl~ FSB, nu Pont Co.). The bath had apH of 3.7 and was kept below pH 4.5 by adding O.lN HCl during the dropwise addition of 200 ml of neoprene latex #2 (39%
solids, pH 12.5). The drops coagulated and were stirred in the bath for 30 minutes, separated, washed three times with water and dried at 60 C to obtain nontacky pellets.
Example 37 A bath containing approximately 1.5% SiO2 and 7.6%
NH4Cl was prepared by mixing 100 ml of 0.69M aqueous silicic acid (prepared according to Example 15), 94 ml of 0.2%
trimethylnonanol ether of ethylene oxide tTergitol~
TMN-6) in ethanolj and 6 ml of a 50% aqueous solution of CaC12 2H2O. To this bath was added dropwise about 20 ml of a 40% solids butadiene/acrylonitrile copolymer latex ~Chemigum Nitrile Latex 550, Goodyear) having a pH of 8Ø
The coagulated drops were stirred in the bath for one hour, separated, and dried under vacuum at 60C to obtain per-fectly spherical pellets which were nontacky and free-flowing.
Example 38 A mixed latex was prepared from 100 ml of neoprene latex #2 t37% solids, pH 12.5) and 60 ml of natural rubber X
lQ99~
latex TSC (62~ solids, General Latex Co.). The resulting mix-ture was brought to pH 12.2 by adding 1~ NaOH. A bath w~s plC-pared like the one in E~ample 37, e~cept on a 10-fold larger scale. During dropwise addition of the mix~d ]atex to the bath, the bath was maintained at pH 5.0 by the addition of lN HCl. The coagulated drops remained in the bath for one hour. They were then separated, washed three times with water, and dried, first for five hours in air and then for three days under vacuum over P205 at room temperature. The coated pellets of neoprene/rubber were nontacky and free-flowing.
Example 39 A bath containing approximately 0.7% SiO2/A12O3 and 7.6~ NH4Cl was prepared by mixing 40 ml of a positive alumina-modified silica sol (Ludox~ 130 M, Example 1~), 1000 ml of 15~ aqueous NH4Cl, and 960 ml of 0.05% aqueous sodium lauryl sulfate (Duponol@ WAQE, Du Pont Co.). The bath had a pH of 4.9 and was maintained at pH 5.0 by addi-tion of lN HCl during dropwise addition of 200 ml of neoprene latex ~ (37~ solids,pH 12.5). The coagulated drops were stirred in the bath for one hour, washed with water, and air dried to yield nontacky, free-flowing pellets.
Example 40 A bath containing approximately 0.1~ chlorhydrol and 7.6~ N1~4Cl was prepared by mixing 1000 ml of 15~
aqueous NH Cl, 980 ml of 0.1~ aqueous sodium lauryl sulfate (Duponol~ WAQE), and 20 ml of 10 aqueous chlorh~drol (A1203 47.0~, chloride 16.3~, Reheis Chemical Co.). To the bath was added dropwise 200 ml of neoprene latex ~4 while maintaining the bath at p~3 ~.5 by adding lN ~3Cl.
10~9~57 After the addition,the pellets were stirred in the bath for one hour, washed with water, and air dried. The un-cured elastomer pellets were nontacky and free-flowing.
Example 41 Using the apparatus illustrated in Figures 1 and 2,the following aqueous solutions were mixed in tank 1.
10,000 ml of 15~ aqueous ammonium chloride 9,500 ml of 0.03/r aqueous sodium lauryl sulfate surfactant (Duponol~ WAQE) 500 ml of 30% solids colloidal alumina-modified silica sol (Ludox~ 130M, Example 18) The bath thus prepared had a pH of 5.4 and contained appro~i-mately 0.9~ SiO2 and 7.6~o NH4Cl. While providing agitation, 3~80 g of a 40% solids neoprene latex prepared in the manner of neoprene latex #2 was added through the capillary tubes over a period of 13 minutes. Simultaneously, the pH of the bath was maintained at 5.4 by gradual addition of 51 ml of lN hydrochloric acid. Immediately following the 13-minute latex addition period, agitation was continued for 17 minutes with no further addition of acid, during which time the pH of the bath rose to 6.6. The particles were kept in suspension by agitation during the 17-minute holding period. The agitator was then turned off, the particles were allowed to settle, and the supernatant liquid was separated from the pcrticles by decantation.
The particles were washcd by addition of 8000 ml of distilled water followed by a 5-minute agitation per~od.
The agitator was then turned off and the supernatant liquid was separated from the particles by decantation.
This washing procedure was repeate~ twice. The particles 1~"9057 were allowed to dry in the zir to a constant weight of 1315 g. They were free-flowing ancl nontacky.
ExamPle 42 ~ Blng the apparPtus lllustrated ln Flgures 1 and 2, a bath wa6 prepared by mlxing the rollowlng aqueous solution-~ ln tank 1.
10,000 ml of 1~% aqueou~ ammonlum chloride 9,950 ml of 0.03% aqueous sodium lauryl sulfate surfactant (Duponol~ WAQE) 50 ml of a polyaluminlc acid-modified aqueous col-loldal slllca ~ol The modified silica sol was prepared ~y slowly adding 500 g of 35~ aqueous boric acid-stabllized basic aluminum ~cetste solution (N~aproof~, Union Carbide Corp.) to 400 g of agueous colloidal silica sol [Ludox~ SM, Du Pont Co., 30% SiO2, averaqe particle size 7 m~, weight ratio SiO2/Na20 50, pH -~
(25C) 9.9, freezing point 0C] in a blender and filtering the mixture through coarse filter paper tp remove the small amount of gel. The bath thus prepared had a pH of 5.3 and contained approximately 0.1% colloidal silica sol coated with polyaluminic acid and 7.6~ NH4Cl.
While providing agitation,3590 g of 40~ solids neo-prene latex prepared like neoprene latex #l was added to the bath through the capillary tubes over a period of 9 minutes, during which time the pH of the bath rose to 6.7. Agitation was continued, keeping the particles in suspension for an additional 51 minutes, with no appreciable change in pH of the bath. The agitator was turned off, the particles were allowed to settle and the supernatant liquid was separated from the partlcles by decantation.
10~
The particles were washed by addition of 8000 ml of distilled water followed by a 10-minute agitation period. The agitator was then turned off and the super-natant liguid was separated from the particles by decanta-tion. This washing pr3cedure was repeated three times.
The particles were allowed to dry in the air to a constant weight of 1446 g. They were free-flowing and nontacky.
Example 43 Ucing the apparatus illustrated in Figures 1 and 2, the following aqueous solutions were mixed in tank 1.
10,000 ml of 15~ aqueous ammonium chloride 9,950 ml of 0.03% aqueous sodium lauryl sulfate surfactant (Duponol~ WAQE) 5O ml of the polyaluminic ac~d-modlfled aqueous colloldal sllica sol described in ~xalple 42 The bath thus prepared had a pH of 5.2. While providing agitation, 4578 g of 40~ solids neoprene latex prepared like neoprene latex ~2 was added through the capillary tubes over a period of 18 minutes, during which time the pH rose to
The pellets which formed were separated from the bath, washed with water, and dried to obtain nontacky, free-flowing, substantially spherical pellets o~` modified neoprene.
Example 32 A bath containing approximately 0.5% SiO2, 7.6%
NH4Cl and 0.01~ AlC13 was prepared by mixing 250 ml of 0.69 aqueous silicic acid (prepared according to Example 15 and aged for two days), 1000 ml of 15% aqueous NH4Cl, 200 ml of water, 500 ml of 0.05% aqueous trimethylnonanol ether of eth~l-ene oxide (Tergitol3 TMN-6), and 50 ml of 1% aqueous AlC13-6H20 which had been adjusted to pH 5.0 by addition of lN NaOH.
This bath was kept at pH 4.5-5.0 by addition of lN HCl ~during the dropwise addition o~ 200 ml o~ neoprene latex ~2 (37~ solids, pH 12.5) which took eight minutes, and for one hour thereafter. The drops, which coagulated, were separated from the bath, washed three times with wa-ter, soaked for three hours in water, and then air dried. The resulting pellets were nontacky and free-flowing.
xample 33 A silica sol containing approximately 4.6~ solids with a pH of 5.0 was prepared by adding 265 ml of a 15%
solids aqueous silica sol (Nyacol~ 215, Nyacol, Inc., pH 10.5) dropwise with vigorous stirring to a solution cf 70 ml of lN HCl in 595 ml of water. A bath containing approximately 0.6% SiO2, 7.6~ N~34Cl and 0.013~ AlC13 was prepared by mixing 250 ml of the above sol, 1000 ml of 15 ~"9~57 a~ueous NH4Cl, 700 ml of a 0.03~ aqueous solution of an amphoteric fluorinated surfactant (Zonyl~ FSB, Du Pont Co.), and 50 ml of 1~ aqueous AlC13 6H2~ which had been adjusted to pH 5.0 with lN NaOH. The resulting bath had a pH of 4.3.
This bath was stirred and kept at pH 4~5-5.0 by addition of HCl during the dropwise addition of 200 ml of neoprene latex #2 (37% solids/ pH 12.5). The pellets which formed were stirred in the bath for one hour, separated, washed three times with water and soaked in 2 liters of water. After dry-ing the pellets were nontacky and showed little tendency toagglomerate.
Example 34 In the manner of Example 33, 42 ml of a 49~ solids aqueous colloidal silica sol (Ludox~ TM, Du Pont Co~, pH
8.9, particles 220-250A in diameter) was blended with 3.9 ml of lN HCl and 454 ml of water to give an aqueous sol con-taining 5.6% SiO2. A bath containing approximately 0.7~ -SiO2, 7.6~ NH4Cl and 0.013~ AlC13 was prepared by substituting 250 ml of the above sol for the sol employed in Example 33 and maintained at a pH of 5.0 by addition of lN HCl. The remaining procedure of Example 33 was then repeated to yield nontacky, free-flowing elastomer pellets.
EXample 35 In the manner of Example 33, 125 ml of a 30%
solids aqueous colloidal silica sol (Ludox~ SM, pH 9.9, Du Pont Co.) in 125 ml of distilled water, was blended with 28 ml-of lN HCl and 637 ml of water. A bath was prepared by substituting 250 ml of the above sol for the sol employed in Example 33 and the remaining procedure of Example 33 was repeated. Nontacky, free-flowing pellets were obtained.
~, - 35 -l~9~S7 Example 36 To 400 ml of a 30% solids aqueous colloidal sol of alumina-modified silica of pH about 8.9 (Ludox~ AM, Du Pont Co.) was added 4.0 ml of concentrated (38%) hydro-chloric acid with vigorous agitation. The resulting sol had a pH of 3.0 and a solids content of about 29.7%. A bath con-taining approximately 4.3% SiO2 and 7.5% NH4Cl was prepared from 250 ml of this sol, 1000 ml of 15% aqueous NH4Cl, 650 ml of water, and 100 ml of a 0.2% aqueous amphoteric fluorosur-factant solution (Zonyl~ FSB, nu Pont Co.). The bath had apH of 3.7 and was kept below pH 4.5 by adding O.lN HCl during the dropwise addition of 200 ml of neoprene latex #2 (39%
solids, pH 12.5). The drops coagulated and were stirred in the bath for 30 minutes, separated, washed three times with water and dried at 60 C to obtain nontacky pellets.
Example 37 A bath containing approximately 1.5% SiO2 and 7.6%
NH4Cl was prepared by mixing 100 ml of 0.69M aqueous silicic acid (prepared according to Example 15), 94 ml of 0.2%
trimethylnonanol ether of ethylene oxide tTergitol~
TMN-6) in ethanolj and 6 ml of a 50% aqueous solution of CaC12 2H2O. To this bath was added dropwise about 20 ml of a 40% solids butadiene/acrylonitrile copolymer latex ~Chemigum Nitrile Latex 550, Goodyear) having a pH of 8Ø
The coagulated drops were stirred in the bath for one hour, separated, and dried under vacuum at 60C to obtain per-fectly spherical pellets which were nontacky and free-flowing.
Example 38 A mixed latex was prepared from 100 ml of neoprene latex #2 t37% solids, pH 12.5) and 60 ml of natural rubber X
lQ99~
latex TSC (62~ solids, General Latex Co.). The resulting mix-ture was brought to pH 12.2 by adding 1~ NaOH. A bath w~s plC-pared like the one in E~ample 37, e~cept on a 10-fold larger scale. During dropwise addition of the mix~d ]atex to the bath, the bath was maintained at pH 5.0 by the addition of lN HCl. The coagulated drops remained in the bath for one hour. They were then separated, washed three times with water, and dried, first for five hours in air and then for three days under vacuum over P205 at room temperature. The coated pellets of neoprene/rubber were nontacky and free-flowing.
Example 39 A bath containing approximately 0.7% SiO2/A12O3 and 7.6~ NH4Cl was prepared by mixing 40 ml of a positive alumina-modified silica sol (Ludox~ 130 M, Example 1~), 1000 ml of 15~ aqueous NH4Cl, and 960 ml of 0.05% aqueous sodium lauryl sulfate (Duponol@ WAQE, Du Pont Co.). The bath had a pH of 4.9 and was maintained at pH 5.0 by addi-tion of lN HCl during dropwise addition of 200 ml of neoprene latex ~ (37~ solids,pH 12.5). The coagulated drops were stirred in the bath for one hour, washed with water, and air dried to yield nontacky, free-flowing pellets.
Example 40 A bath containing approximately 0.1~ chlorhydrol and 7.6~ N1~4Cl was prepared by mixing 1000 ml of 15~
aqueous NH Cl, 980 ml of 0.1~ aqueous sodium lauryl sulfate (Duponol~ WAQE), and 20 ml of 10 aqueous chlorh~drol (A1203 47.0~, chloride 16.3~, Reheis Chemical Co.). To the bath was added dropwise 200 ml of neoprene latex ~4 while maintaining the bath at p~3 ~.5 by adding lN ~3Cl.
10~9~57 After the addition,the pellets were stirred in the bath for one hour, washed with water, and air dried. The un-cured elastomer pellets were nontacky and free-flowing.
Example 41 Using the apparatus illustrated in Figures 1 and 2,the following aqueous solutions were mixed in tank 1.
10,000 ml of 15~ aqueous ammonium chloride 9,500 ml of 0.03/r aqueous sodium lauryl sulfate surfactant (Duponol~ WAQE) 500 ml of 30% solids colloidal alumina-modified silica sol (Ludox~ 130M, Example 18) The bath thus prepared had a pH of 5.4 and contained appro~i-mately 0.9~ SiO2 and 7.6~o NH4Cl. While providing agitation, 3~80 g of a 40% solids neoprene latex prepared in the manner of neoprene latex #2 was added through the capillary tubes over a period of 13 minutes. Simultaneously, the pH of the bath was maintained at 5.4 by gradual addition of 51 ml of lN hydrochloric acid. Immediately following the 13-minute latex addition period, agitation was continued for 17 minutes with no further addition of acid, during which time the pH of the bath rose to 6.6. The particles were kept in suspension by agitation during the 17-minute holding period. The agitator was then turned off, the particles were allowed to settle, and the supernatant liquid was separated from the pcrticles by decantation.
The particles were washcd by addition of 8000 ml of distilled water followed by a 5-minute agitation per~od.
The agitator was then turned off and the supernatant liquid was separated from the particles by decantation.
This washing procedure was repeate~ twice. The particles 1~"9057 were allowed to dry in the zir to a constant weight of 1315 g. They were free-flowing ancl nontacky.
ExamPle 42 ~ Blng the apparPtus lllustrated ln Flgures 1 and 2, a bath wa6 prepared by mlxing the rollowlng aqueous solution-~ ln tank 1.
10,000 ml of 1~% aqueou~ ammonlum chloride 9,950 ml of 0.03% aqueous sodium lauryl sulfate surfactant (Duponol~ WAQE) 50 ml of a polyaluminlc acid-modified aqueous col-loldal slllca ~ol The modified silica sol was prepared ~y slowly adding 500 g of 35~ aqueous boric acid-stabllized basic aluminum ~cetste solution (N~aproof~, Union Carbide Corp.) to 400 g of agueous colloidal silica sol [Ludox~ SM, Du Pont Co., 30% SiO2, averaqe particle size 7 m~, weight ratio SiO2/Na20 50, pH -~
(25C) 9.9, freezing point 0C] in a blender and filtering the mixture through coarse filter paper tp remove the small amount of gel. The bath thus prepared had a pH of 5.3 and contained approximately 0.1% colloidal silica sol coated with polyaluminic acid and 7.6~ NH4Cl.
While providing agitation,3590 g of 40~ solids neo-prene latex prepared like neoprene latex #l was added to the bath through the capillary tubes over a period of 9 minutes, during which time the pH of the bath rose to 6.7. Agitation was continued, keeping the particles in suspension for an additional 51 minutes, with no appreciable change in pH of the bath. The agitator was turned off, the particles were allowed to settle and the supernatant liquid was separated from the partlcles by decantation.
10~
The particles were washed by addition of 8000 ml of distilled water followed by a 10-minute agitation period. The agitator was then turned off and the super-natant liguid was separated from the particles by decanta-tion. This washing pr3cedure was repeated three times.
The particles were allowed to dry in the air to a constant weight of 1446 g. They were free-flowing and nontacky.
Example 43 Ucing the apparatus illustrated in Figures 1 and 2, the following aqueous solutions were mixed in tank 1.
10,000 ml of 15~ aqueous ammonium chloride 9,950 ml of 0.03% aqueous sodium lauryl sulfate surfactant (Duponol~ WAQE) 5O ml of the polyaluminic ac~d-modlfled aqueous colloldal sllica sol described in ~xalple 42 The bath thus prepared had a pH of 5.2. While providing agitation, 4578 g of 40~ solids neoprene latex prepared like neoprene latex ~2 was added through the capillary tubes over a period of 18 minutes, during which time the pH rose to
6.7. Agitation was continued, keeping the particles in suspension for an additional 42 minutes, with no appreciable change in pH of the bath. The agitator was turned off, the particles were allowed to settle and the supernatant liquid was separated from the particles by decantation.
The particles were washed by addition of 20,000 ml of distilled water followed by a 10-minute agitation period.
The agitator was then turned off and thc supernatant liquid was separated from the particles by decantation. This washing procedure was repeated once. The particles were allowed to dry in air to a constant wcight of 1767 g. They lO9S~
were free-flowing and nontacky.
Example 44 A bath containing approximately 0.6~ SiO2, 0.9~
CaC12, 0.3~ AlC13 and 0.6~ NaCl was prepared by mixing 1694 g of H2O, 10.0 g of AlC13 6H2O, 24.2 g of CaC12 2H2O, 12.0 g of ~aCl, 1.2 g of an amphoteric fluorinated surfactant (Zonyl~
~SB, Du Pont Co.), and 250 ml of a colloidal silica sol havina a pH of 2.0 and containing 4.8~ SiO2. This colloidal sol was prepared by adding a mixture of 125 ml of a 30~ solids aqueous silica sol (Ludox~ SM, Du Pont Co.) and 125 ml of H20 to a running blender containing 637 ml of H20 and - 40 ml of lN HCl.
To this bath was added dropwise 198 ml of 40~ solids neoprene latex prepared like neoprene latex ~1. After 30 minutes, the bath was decanted from the pellets which had formed. The pellets were soaked in 2 liters of H2O for 30 minutes and then filtered from the wash water and spun for 2 minutes in a basket centrifuge. The pellets were then shaken with 1.5% of their weight of talcum powder and spread in a tray to air dry overnight. They were further dried over P2O5 under vacuum at room temperature. The resulting non-tacky free-flowing pellets contained 1.56 milliequivalents of residual alkalinity per 100 g of isolated polymer, as shown by nonaqueous titration to a bromophenol end point.
Example 45 A bath containing approximately 0.5~ SiO2, 0.9~
CaC12 and 0.3% AlC13 was prepared by mixing 1714.6 ml of H2O, 10.0 9 of AlC13 6H2O, 24.4 9 of CaC12-2H2O, 1.2 9 of the tri-methylnonanol ~ther of ethylene oxidc (Tergitol~' TM~-fi) and 250 ml of 0.69M silicic acid which had aged for five days.
lO~91QS7 To this bath was added dropwise 200 ml of 40~ solids neoprene latex prepared likc neoprene latex #1. The pellcts which formed were isolated, washed and dried as in the procedure of Example 44. The resulting free-flowing, nontacky pellets had a residual alkalinity of 2.43 meq/100 g.
Example 46 A latex mixture was prepared from 2 ml of the sodium silicate solution described in Example 15, 15 ml of lN NaOH, and 198 ml of 40~O solids neoprene latex prepared like neoprene latex $2. This mixture was added dropwise to a bath containing approximately 1.8~ CaC12, 1.7% NaCl, 0.6%
AlC13 and 0.6% modified sol prepared from 898.6 ml of H2O, 1000 ml of 2% AlC13 6H20 (adjusted to pH 3.5 with lN NaOH), 36.4 g of anhydrous CaC12, 34 g of NaCl, 1.0 g of 30 sodium lauryl sulfate (Duponol~ WAQE), and 30 ml of the modified aqueous colloidal silica sol described in Example 42. The pellets which formed were removed from the bath after 15 minutes, washed with water, centrifuged, treated with talc and dried as described in Example 44.
The resulting pellets were nontacky and free-flowing.
The applicatlon 18 a division Or copending Appllcation Serlal No. 281 448, filed 1977 June 27.
The particles were washed by addition of 20,000 ml of distilled water followed by a 10-minute agitation period.
The agitator was then turned off and thc supernatant liquid was separated from the particles by decantation. This washing procedure was repeated once. The particles were allowed to dry in air to a constant wcight of 1767 g. They lO9S~
were free-flowing and nontacky.
Example 44 A bath containing approximately 0.6~ SiO2, 0.9~
CaC12, 0.3~ AlC13 and 0.6~ NaCl was prepared by mixing 1694 g of H2O, 10.0 g of AlC13 6H2O, 24.2 g of CaC12 2H2O, 12.0 g of ~aCl, 1.2 g of an amphoteric fluorinated surfactant (Zonyl~
~SB, Du Pont Co.), and 250 ml of a colloidal silica sol havina a pH of 2.0 and containing 4.8~ SiO2. This colloidal sol was prepared by adding a mixture of 125 ml of a 30~ solids aqueous silica sol (Ludox~ SM, Du Pont Co.) and 125 ml of H20 to a running blender containing 637 ml of H20 and - 40 ml of lN HCl.
To this bath was added dropwise 198 ml of 40~ solids neoprene latex prepared like neoprene latex ~1. After 30 minutes, the bath was decanted from the pellets which had formed. The pellets were soaked in 2 liters of H2O for 30 minutes and then filtered from the wash water and spun for 2 minutes in a basket centrifuge. The pellets were then shaken with 1.5% of their weight of talcum powder and spread in a tray to air dry overnight. They were further dried over P2O5 under vacuum at room temperature. The resulting non-tacky free-flowing pellets contained 1.56 milliequivalents of residual alkalinity per 100 g of isolated polymer, as shown by nonaqueous titration to a bromophenol end point.
Example 45 A bath containing approximately 0.5~ SiO2, 0.9~
CaC12 and 0.3% AlC13 was prepared by mixing 1714.6 ml of H2O, 10.0 9 of AlC13 6H2O, 24.4 9 of CaC12-2H2O, 1.2 9 of the tri-methylnonanol ~ther of ethylene oxidc (Tergitol~' TM~-fi) and 250 ml of 0.69M silicic acid which had aged for five days.
lO~91QS7 To this bath was added dropwise 200 ml of 40~ solids neoprene latex prepared likc neoprene latex #1. The pellcts which formed were isolated, washed and dried as in the procedure of Example 44. The resulting free-flowing, nontacky pellets had a residual alkalinity of 2.43 meq/100 g.
Example 46 A latex mixture was prepared from 2 ml of the sodium silicate solution described in Example 15, 15 ml of lN NaOH, and 198 ml of 40~O solids neoprene latex prepared like neoprene latex $2. This mixture was added dropwise to a bath containing approximately 1.8~ CaC12, 1.7% NaCl, 0.6%
AlC13 and 0.6% modified sol prepared from 898.6 ml of H2O, 1000 ml of 2% AlC13 6H20 (adjusted to pH 3.5 with lN NaOH), 36.4 g of anhydrous CaC12, 34 g of NaCl, 1.0 g of 30 sodium lauryl sulfate (Duponol~ WAQE), and 30 ml of the modified aqueous colloidal silica sol described in Example 42. The pellets which formed were removed from the bath after 15 minutes, washed with water, centrifuged, treated with talc and dried as described in Example 44.
The resulting pellets were nontacky and free-flowing.
The applicatlon 18 a division Or copending Appllcation Serlal No. 281 448, filed 1977 June 27.
Claims (7)
1. A coagulating and coating bath which comprises, (a) 0.5 to 25% by weight of a soluble coagulating salt for a normally tacky, uncured elastomer latex, and (b) 0.01 to 5% by weight of a soluble or colloidally dis-persed, hydrous, inorganic oxide selected from the group consisting of silicic acid-aluminic acid copoly-mers, and mixtures thereof, said bath having a pH of 2 to 7 such that, when a drop of 1.ON
NaOH is added to the bath, the drop is immediately surrounded by a cloudy coating of gelled, hydrous inorganic oxide.
NaOH is added to the bath, the drop is immediately surrounded by a cloudy coating of gelled, hydrous inorganic oxide.
2. The bath of Claim 1 which contains 1 to 10% by weight of coagulating salt including, (a) 0.002 to 2% by weight of an ionizable salt of a metal selected from the group consisting of aluminum and yttruim, and (b) 0.03 to 2% by weight of inorganic oxide, and the pH of the bath is 2.5 to 5.5.
3. The bath of Claim 2 in which the inorganic oxide is soluble.
4. The bath of Claim 3 in which the inorganic oxide is polysilicic acid.
5. The bath of Claim 2 in which the inorganic oxide is a colloidally dispersible sol.
6. The bath of Claim 5 in which the colloidally dis-persible sol is silica sol.
7. The bath of Claim 4 which also contains sufficient compatible surfactant to reduce the air-liquid interfacial tension to less than 50 dynes/cm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA350,820A CA1099057A (en) | 1976-06-29 | 1980-04-29 | Coagulating and coating bath for uncured elastomer objects |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US70096576A | 1976-06-29 | 1976-06-29 | |
| US700,965 | 1976-06-29 | ||
| CA281,448A CA1091864A (en) | 1976-06-29 | 1977-06-27 | Nontacky shaped objects from polymer latices |
| CA350,820A CA1099057A (en) | 1976-06-29 | 1980-04-29 | Coagulating and coating bath for uncured elastomer objects |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1099057A true CA1099057A (en) | 1981-04-14 |
Family
ID=27165157
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA350,820A Expired CA1099057A (en) | 1976-06-29 | 1980-04-29 | Coagulating and coating bath for uncured elastomer objects |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1099057A (en) |
-
1980
- 1980-04-29 CA CA350,820A patent/CA1099057A/en not_active Expired
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