US3123579A - Latex recycling process - Google Patents

Latex recycling process Download PDF

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US3123579A
US3123579A US3123579DA US3123579A US 3123579 A US3123579 A US 3123579A US 3123579D A US3123579D A US 3123579DA US 3123579 A US3123579 A US 3123579A
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latex
bath
dispersion
container
latexes
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2021/00—Use of unspecified rubbers as moulding material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/0058—Liquid or visquous
    • B29K2105/0064—Latex, emulsion or dispersion
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

Definitions

  • aqueous polymer latexes use a bath of latex which is exposed to the atmosphere. For example, some articles are made by dipping a form into the bath of latex. Other procedures involve coating a substratum by passage of the substratum in close proximity to the surface of the bath of latex and picking up the desired coating from the meniscus formed between bath and substratum. In this latter instance it is apparent that the level of the bath must be kept constant within the limits of the ultimate meniscus height.
  • Such latex baths present problems. For example, it is known that a skin may form on some latexes when exposed to the air for prolonged periods. Also, a substratum, either as a belt or roll, when passed over a latex bath, will usually not be as wide as the latex bath so that a fresh surface over the entire bath surface will not necessarily be continuously renewed by the removal of latex from the bath surface onto the substratum. An additional problem with an exposed bath surface is the chance for contamination of the bath from the atmosphere.
  • the prior known conventional means for maintaining liquid bath levels substantially constant usually involve mechanical regulating and metering devices, such as float controlled valves, nozzles and the like. With polymer latexes these frequently become coated or clogged with coagulum or coalesced latex particles. This coating or clogging impairs the mechanical performance of the regulating device to the point where its usefulness for its intended purpose is questionable. It is to be desired to keep such moving parts in contact with a polymer latex to a minimum.
  • the above object is accomplished by means of the process wherein fresh latex is metered into a bath of the same latex at such a rate to provide a continuously renewed surface without creating turbulence in said surface, the excess of that metered into said bath which is not used up through fabrication caused to overflow and be recycled into the fresh latex being introduced into said bath.
  • the process may be employed with any latex of any polymeric material.
  • the only latex properties of material concern are mechanical stability and fluidity or viscosity. It should be apparent that the latex must be capable of being pumped or at least flowed through pipes and conduits. Because of this permissive latitude of latex type, it is possible to employ a wide variety of polymer types.
  • aqueous latexes of synthetic polymers exemplary of which are the homopolymers, copolymers, and interpolymers of vinyl and vinylidene halides, such as vinyl chloride and vinylidene chloride; of monoalkenyl aromatic monomers, such as styrene, vinyl toluene, alpha-methyl styrene, and the chicrinated styrenes; of the alkyl, cycloalkyl, and aryl acrylates, such as methyl, ethyL'butyl, Z-ethylhexyl, dodecyl, cyclohexyl, and phenyl acrylates; of the alkyl, cycloalkyl, and aryl alkacrylates, such as methyl methacrylate, ethyl ethacrylate, cyclohexyl methacrylate, and phenyl methacrylate; of the vinyl
  • latexes are commercially available products.
  • styrene/ butadiene, polyvinyl acetate, vinyl chloride/vinylidene chloride, vinylidene chloride/acrylonitrile, butadiene/acrylonitrile, and acrylate-containing latexes are well known and readily available through commercial sources.
  • the process is equally operable with the aqueous latexes of natural polymeric materials, such as Hevea latex.
  • Latexes are stable latex-like dispersions which result from the suspension of finely divided solids of polymeric materials, such as the polyolefins, including polyethylene, polypropylene, copolymers of ethylene and propylene and polyisobutylene; the condensation polymers, such as the polyamides, including polyhexamethylenediadiparnide, and polyesters, including polyethylene-terephthalate.
  • polymeric materials such as the polyolefins, including polyethylene, polypropylene, copolymers of ethylene and propylene and polyisobutylene
  • condensation polymers such as the polyamides, including polyhexamethylenediadiparnide
  • polyesters including polyethylene-terephthalate
  • the latexes may be of any polymer solids content and of any particle size distribution as long as the requisite minimum stability and fluidity are present. With those latexes which do not exhibit the needed mechanical stability, it is frequently observed that the required stability may be achieved by incorporating in the latex small amounts of additional wetting agent as a post stabilizer.
  • Latexes that contain the conventional additives which are commonly included in latex formulations can also be employed in the process. Typical of these are heat and light stabilizers, antioxidants, fungicides and other similar agents, dyes, pigments, and fillers. It should be apparent that these additives should not adversely affect the required minimum stability to storage and mechanical stress nor the fluidity of the latex formulation.
  • FIGURE 1 represents in schematic outline a procedural sequence for carrying out the process
  • FIGURE 2 represents a particular design of la.ex bath vessel.
  • a reservoir 10 for holding a relatively large supply of latex and for intermixing recycled latex with fresh latex.
  • agitation means included in the design of the reservoir 10.
  • a supply tank 11 connected to the reservoir 10 by a conduit 12. It is frequently desired to maintain the quantity of latex in the reservoir 10 essentially constant to assure that the ratio of fresh latex to recycled latex is as constant as possible. This may be achieved by a number of known ways, such as the imposition on the supply tank 11 of a pressure head using an inert gas, such as nitrogen, by the use of metering pumps, or by similar means.
  • the intermixed fresh/recycle latex is pumped from the reservoir 10 using a centrifugal pump or other suittion rates.
  • FIGURE 2 A preferred design for the latex bath vessel is illustrated in FIGURE 2.
  • the vessel consists of a container 20, inlet 2-1 and discharge 22 ports, and a pattern of weirs and battles that cause desirable fiow characteristics.
  • the container 20 preferably has cylindrical or divergent side walls that permit maximum exposed surface for a given volume of latex, that allow for uniform flow patterns without latex being entrapped in corners, and that permit easy cleaning when it is desired to change latexes.
  • a port 21 to which is aflixed a conduit 23 (corresponding to 16 in FIGURE 1) leading from the reservoir 15) through the metering l3 and filtering 15 means.
  • a port 21 Through this port 21 latex is introduced into the container 20.
  • a second port 22 Near the opposite end of the container 20 and also in the bottom there is located a second port 22 to which there is atiixed a conduit 24 (corresponding to 18 in FIGURE 1) leading back to the reservoir 16.
  • a first weir, 25 Extending upwardly from the bottom of the container 20 is a first weir, 25 preferably, occupying the full cross section of the container 20 up to within a small distance of sides of the container 20.
  • the height of the first weir 25 should be approximately the level of latex which will be employed in the bath.
  • This first weir 25 is so located as to place the inlet port 21 between it and the nearest end of the container 20. This position of weir 25 isolates a portion of the container 2t) into a surge chamber A and settling pot for the infiuent latex.
  • baffle 26 Projecting downwardly from the top of the sides of the container 25 is a baffle 26.
  • This bafile 26 must project below the top surface of the first weir 25 to assure that the infiuent latex will enter the operating portion of the vessel without short circuiting directly across the surface of the bath to the outlet.
  • the baffie 26 should come as close to the bottom of the container 2% as will permit the desired flow rates to be used without creating turbulence.
  • a second weir 27 similar in construction and of equal height to the first weir 25. This second weir 27 isolates the turbulence (e.g. in the vortex) created by the overflow from the main body of the container 20 and in conjunction with the first weir 25 provides a bath of constant level.
  • the present process and apparatus provide the desired benefits independent of the size of apparatus or produc-
  • the dimensions and capacity of equipment to be used depend upon the fabricating technique employed, the production rates desired, preferences of the individual, and upon similar reasons. For practical reasons it is preferred that an excess of bath surface be provided over that amount of surface which 18 used in the fabricating technique used.
  • the influent latex enters the bath, travels over the first weir, under the baffle, rises steadily toward the surface, and excess flows in essentially planar flow over the second weir to the outlet port.
  • essentially planar flow is meant that a layer of the latex of substantially constant depth flows over the top of the second weir.
  • the second weir may be made out of the end plate of the container with the effluent latex spilling into a catch basin.
  • the invention is not limited to the precise disposition of the various elements making up the vessel but only to their relative positions. It is necessary that the operating surface of the latex bath fall between an overflow weir and a bafile plate that causes the introduction of the influent latex to enter the operating portion of the bath in essentially laminar non-turbulent flow at a point near the bottom of the container.
  • the effluent latex may be discarded or disposed of in any desired manner. However, for reasons of economy it is preferred to recycle the efiiuent latex through the process repetitively.
  • a conduit is afiixed to the outlet port and leads back to the reservoir. When equilibrium is reached, there will be a constant ratio of fresh latex to that which has passed through the bath. This is of vital importance to any fabrication technique that depends upon the film formability or other similar property of the latex.
  • any of the elements in the process may be provided with heating or cooling means to maintain the latex at a temperature at which it is most stable, at which its properties are most favorable for the fabrication technique employed, or for other reason.
  • the film formaoility of the latex requires inter alia that the polymer particles be of predominantly amorphous state. Crystallinity is dependent in a large part with a particular polymer on a time/ temperature relationship. In such a case it would be desirable to cool the reservoir to extend the useful life of the polymer.
  • the elements used in the apparatus described supra may be of any suitable material.
  • the usual styrene/butadiene latexes permit the use of almost any structural material, including wood, plastics, and steel, sheet metal and other metals.
  • the vinyl and vinylidene halides require the use of stainless steels, nickel, and glass or plastic coated metals. These considerations will be knOWn to the skilled worker.
  • the process was employed in a continuous coagulation technique with an aqueous latex of a copolymer prepared from about 97 percent by weight vinylidene chloride and 3 percent by weight of acrylonitrile.
  • a deposition roll is wetted with an aqueous electrolyte solution and is then rotated so that the wetted surface approaches in close proximity to the surface of the latex bath.
  • a coating of latex is deposited on the roll through the meniscus formed between the roll and the latex bath.
  • the stainless steel latex bath vessel was slightly narrower than the diameter of the deposition roll and slightly longer than the length of that roll.
  • the vessel was a half cylinder.
  • the arrangement of ports, weirs, and baffle was as shown in FIGURE 2 of the annexed drawing.
  • the overflow rate of latex could be varied between 0.4
  • the overflowed latex was returned to a reservoir where it was intermixed with a large volume of fresh latex and the so-formed blend pumped through a filter to the latex bath.
  • a process for providing a liquid bath of an aqueous latex-like dispersion of an organic, polymeric material so that the surface of said bath is continuously renewed comprising the continuous metering of said aqueous latex-like dispersion from an inventory of said dispersion through a surge and settling chamber then in continuous non-turbulent planar flow into the bottommost portion of a bath of said dispersion at a rate in excess of that at which said dispersion is removed from said bath by the fabricating technique employed, causing the unused excess of said dispersion to be removed from the surface of said bath in essentially planar flow, the
  • said latexlike dispersion is the emulsion polymerizate of at least one olefinically unsaturated monomer.
  • said emulsion polymerizate is of an interpolymer composed of vinylidene chloride with any remainder of at least one monoethylenically unsaturated comonomer.

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  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
  • Processes Of Treating Macromolecular Substances (AREA)
  • Treatment Of Fiber Materials (AREA)
US3123579D 1960-05-05 Latex recycling process Expired - Lifetime US3123579A (en)

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3432339A (en) * 1965-03-03 1969-03-11 Nat Distillers Chem Corp Process for coating substrates with polymers
US3520279A (en) * 1967-11-16 1970-07-14 Maurice W Hoover Continuous vacuum impregnator
US3851662A (en) * 1973-07-18 1974-12-03 Eastman Kodak Co Photographic processing solution filling and circulating apparatus
US3858229A (en) * 1972-04-19 1974-12-31 Agfa Gevaert Ag Apparatus for wet treatment of photosensitive material
US3956540A (en) * 1973-09-10 1976-05-11 Omnitech Inc. Method of coating articles
US4565638A (en) * 1983-09-22 1986-01-21 Jerry Zucker Method for purifying ink
US5188670A (en) * 1990-04-05 1993-02-23 Norian Corporation Apparatus for hydroxyapatite coatings of substrates
US5538644A (en) * 1993-01-26 1996-07-23 Henkel Corporation Apparatus and method for maintaining a stable bath for an autodeposition composition by periodically separating particular metal ions from the composition

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1958118A (en) * 1927-07-18 1934-05-08 American Anode Inc Method and apparatus for homogenizing aqueous dispersions
US2058044A (en) * 1933-03-22 1936-10-20 Ralph A Spencer Separator for removing oil from water, sand, and gravel
US2712161A (en) * 1951-08-10 1955-07-05 Rena Bell Hardman Method of forming dipped articles

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1958118A (en) * 1927-07-18 1934-05-08 American Anode Inc Method and apparatus for homogenizing aqueous dispersions
US2058044A (en) * 1933-03-22 1936-10-20 Ralph A Spencer Separator for removing oil from water, sand, and gravel
US2712161A (en) * 1951-08-10 1955-07-05 Rena Bell Hardman Method of forming dipped articles

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3432339A (en) * 1965-03-03 1969-03-11 Nat Distillers Chem Corp Process for coating substrates with polymers
US3520279A (en) * 1967-11-16 1970-07-14 Maurice W Hoover Continuous vacuum impregnator
US3858229A (en) * 1972-04-19 1974-12-31 Agfa Gevaert Ag Apparatus for wet treatment of photosensitive material
US3851662A (en) * 1973-07-18 1974-12-03 Eastman Kodak Co Photographic processing solution filling and circulating apparatus
US3956540A (en) * 1973-09-10 1976-05-11 Omnitech Inc. Method of coating articles
US4565638A (en) * 1983-09-22 1986-01-21 Jerry Zucker Method for purifying ink
US5188670A (en) * 1990-04-05 1993-02-23 Norian Corporation Apparatus for hydroxyapatite coatings of substrates
US5538644A (en) * 1993-01-26 1996-07-23 Henkel Corporation Apparatus and method for maintaining a stable bath for an autodeposition composition by periodically separating particular metal ions from the composition

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NL302344A (en)) 1900-01-01
BE642016A (en)) 1964-06-30

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