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International Latex Conference 1998 - Paper Abstracts
ACRYLICS-VERSATILE EMULSION CHEMISTRY
Theodore Del Donno, Ph.D., PolymerLatex Inc.
Acrylic polymers and copolymers are used in almost every latex application in the market. They offer versatility to the polymer chemist to allow design of systems from very soft pressure sensitive adhesives to very hard highly crosslinked films.
This paper will discuss basic aspects of acrylic chemistry from polymer design to end use. Topics will include a discussion of the basic polymer building blocks, basic polymerization techniques, formation of polymer films and various types of crosslinking chemistry available. These topics will provide an overview of the versatility of this chemistry.
The discussion will then focus on newly developed technology within acrylic chemistry that provides enhanced performance. A short discussion of various end uses for these polymers will conclude the discussion.
POLYURETHANE DISPERSIONS: A REVIEW OF THE MATERIALS AND THEIR APPLICATIONS
Francine Shuster, The BFGoodrich Company
Polyurethanes ae used in a wide variety of applications from kitchen cabinet coatings, wood and vinyl flooring, and leather coatings to release coats, gloves, and medical devices. This paper reviews the different types of polyurethanes, which encompasses a wide class of materials including polyethers, polyesters, and polyureas. A discussion of how the synthesis variables control the physical and mechanical performance through hard and soft segmentation and polymer chain branching are presented. The possiblilities for this technology offer exciting potential in the Personal Protection market.
ENZYME-TREATED NATURAL RUBBER LATEX: A PRACTICAL APPROACH
Frank Perrella, Ph.D., Tillotson Healthcare Corporation
Natural rubber latex (NRL) products are found almost everywhere in the world. During the manufacturing of medical gloves, naturally occurring NRL proteins can migrate to the surface. The traditional water leaching process removes many of these proteins, but measurable amounts can still remain. Since proteins can be a source of allergens, manufacturers are continuing to modify the glove maufacturing processes in ways that reduce protein levels. One such approach aimed at reducing the allergenicity of proteins, is that of treating NRL with proteolytic enzymes to digest the proteins into smaller and potentially less allergenic pieces. This method is not meant to be a cure all to latex allergy but a practical approach to reducing latex allergens. There may be a risk, however, of developing allergy to the smaller peptides and the enzymes.
Gloves made from enzyme-treated latex were tested for risidual extractable protein and allergen levels using the ASTM D5712 Lowry assay for total protein, the LEAP/ELISA immunologic assay for antigenic protein, and the RAST Inhibition assay for latex allergens. The results of the Lowry assay showed no significant differences in the amount of residual proteins between the enzyme-treated and control untreated gloves. This was attributed to the fact that the Lowry assay can detect both intact and digested proteins. To evaluate further the effectiveness of the protease digestion of NRL proteins, a LEAP/ELISA immunologic assay for antigenic latex proteins was performed. The results of the LEAP assay showed a significant reduction in the level of antigenic proteins from gloves made of enzyme-treated NRL. To determine if the ELISA data for antigenic protein correlated with human latex allergens, RAST Inhibition studies were performed on gloves made of enzyme-treated latex. The results showed a significant reduction in the measurement of human latex allergens. Further studies using sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) of latex proteins also revealed a significant reduction in stained protein over a wide molecular weight range (200 to 10 kDa). This preliminary study demonstrates that proteolytic enzymes can be used effectively to digest natural rubber latex allergens
SYNTHETIC RUBBER DISPERSIONS FOR SPECIAL APPLICATIONS
Hans-Gunter Vogt, Ph.D., PolymerLatex
Paper coating and carpet backing are the largest fields of application for synthetic rubber dispersions. Usually, therefore, a high production capacity of styrene-butadiene latices is the backbone of every latex producer.
However, in order to meet the diversified needs of the global market place, the development and production of special rubber dispersions is indispensable. These dispersions, based on polymers of styrene-butadiene, acrylonitrile-butadiene, and chloroprene are especially important from the technical point of view.
This paper reports about special products developed for the following important fields of application: reinforced non wovens, footwear materials, and dipped goods
The technical background of application and the chemistry and colloidal properties of the applied polymer dispersions will be discussed.
A SEMI-BATCH EMULSION POLYMERIZATION PROCESS WITH CONTINUOUSLY VARIABLE FEED RATES: A SYNTHESIS OF STYRENE-BUTADIENE PRESSURE-SENSITIVE LATEX
Jan J. Spitzer, BASF Corporation
Many emulsion polymers are commercially produced by semi-batch (semi-continuous) polymerization processes employing more than one monomer. Often, a seed latex is used for the control of particle size, and hence the reaction rate. Such processes offer a great deal of latitude in the design of molecular weight distributions and glass transition temperature distributions (T) within an emulsion copolymer particle. Nearly 20 years ago acrylic "gradient" copolymers were synthesized for the coatings industry using variable feed rates, defined as "power feeds". Indeed, the control of composition and structure of latex particles by means of suitably designed feed profiles has remained the subject of current research in both acrylic and other monomer systems, the emphasis usually being to control the compositional drift caused by different co-polymerization ratios and by different water solubilities of monomers used. In related research efforts it was shown that molecular weight (MW) distributions can be broadened by forced oscillations of the chain transfer agent (CTA) feed in continuous stirred reactor co-polymerization of styrene and butadiene.
The above concepts were applied to the emulsion copolymerization of styrene and butadiene in a seeded, semi-continuous process, with a view of obtaining an emulsion copolymer with useful pressure-sensitive properties. The structure-property relationships for styrene-butadiene pressure-sensitive copolymer may be estimated from known compounding techniques, e.g. from approaches used for hot melt pressure sensitive adhesives. Such compounding strategies can be generalized to suggest that pressure-sensitive adhesives may be compounded in gereral from a low T polymeric component (either partly gelled or capable of physical X-linking as in tri-block styrene-butadiene copolymers), from a plasticizing oil (or low MW, low T polymeric fraction), and from a tackifying resin fraction (low MW, high T). Such generalized approach in defining polymer requirements for pressure-sensitive adhesives has proved successful in a two-stage ("core-shell") polymerization of styrene and butadiene. The synthetic approach employing variable feed rates of styrene, butadiene and the CTA (gradient feed) however offers much greater flexibility in the design, as well as offering the prospect of greater compatibility of the different fractions synthesized within the emulsion particle. It is generally recognized that such compatibility of different fractions is necessary for obtaining a good balance of pressure-sensitive properties.
POLYCHLOROPRENE LATEX FOR ADHESIVES
Lance Christell, Ph.D., DuPont Dow Elastomers L.L.C.
No abstract available
GUAYULE LATEX: PRODUCTION, CHARACTERIZATION, AND TESTING
W.W. Schloman, Jr., The University of Akron
Stable, low-allergen polyisoprene latices were produced by direct isolation from ground guayule(parthenium argentatum) (native GR latex) or by emulsification-desolventization of solvent-extracted GR(semisynthetic GR latex). The suitability of these latices for the production of cured dipped films was evaluated.
GR latex, and dipped films produced from compounded GR latex, contain none of the Hevea allergens known to elicit Type I systemic allergic reactions. The polymer phase of GR latex has a lower bulk viscosity and a higher resin content than that of NR. Lipase-catalyzed hydrolysis is an effective means of reducing the resin content. In part due to its low protein content, GR latex lacks the activating components present in NR latex. As a result, GR latex cures more slowly and reaches a lower state of cure. The aged stress-strain properties of cured GR films are nonetheless similar to those of NR films.
Semisynthetic latices may be prepared using solvent-swollen GR extracted from ground shrub. The swollen GR has an especially low protein content. Emulsification with anionic surfactants followed by vacuum desolventization yields stable, low-resin products. Cured dipped films produced from semisynthetic GR latices have protein yields significantly lower than that from native GR latex film.
SYNTHETIC EMULSIONS: HOW TO SELECT THE RIGHT MATERIALS FOR YOUR APPLICATION
Martin A. Cohen, Ph.D., The BFGoodrich Company
A wide variety of synthetic emulsion polymers are commercially available on an international scale.
With all these materials accessible, how does the Product Developer select an appropriate polymer system? And how does the Product Developer know how to build a formulation based on the selected emulsion?
First, the Product Developer must understand the requirements established by the actual product use conditions.
During this presentation, the reasons for selecting a specific emulsion polymer will be discussed, along with general characteristics of emulsions. Emulsion stabilization systems and final product durability will be presented. The major families of emulsion polymers will be reviewed. For each family, the general chemical properties of the emulsions will be discussed as well as some of the major end use applications.
A STUDY OF HANDLING AND PROCESSING OF GRANULAR VS POWDER PRODUCT FORMS OF RUBBER CHEMICALS FOR LATEX DISPERSIONS
Alies T. Gonlag, Flexsys
Traditionally, rubber chemicals for the preparation of dispersions used in latex product manufacture have been supplied as powders in bags. During unloading, handling and emptying of the bags, a fine dust can form that often compromises the work environment. In experiments, a significant reduction in dust formation, together with improvements in general handling and processing are observed when granular form rubber chemicals are used as starter materials. The granular product contains special blend of stabilizers which yield the following advantages compared to normal powders: it is non-caking, low dusting and there is no need to add stabilizers in the dispersion formulation. The granules are dispersed by using the standard equipment used in the latex industry. Various dispersion formulations are tested, and their performance indicators, including dispersion, viscosity and stability are discussed. Particle size distributions of aqueous dispersions made from both the traditional powder form and granular ZDEC are also presented.
USING ACCELERATORS TO ADJUST PHYSICAL PROPERTIES OF SYNTHETIC LATEXES
Robert T. Dzikowicz, R.T. Vanderbilt Company, Inc.
Latex chemists generally agree that there are two phases to compounding. The "getting into the ballpark" phase and the "fine tuning" phase. The former deals with selecting the polymer and suitable colloidal surfactants, determining the filler level and type, choosing a general purpose antioxidant and specialty chemicals like pigments, fire retardants, waxes, resins, etc. Finally, a general purpose curing system is penciled-in: a nominal amount of crosslinker, activator and - well! Let's go with this one- acclerator.
This paper deals with the second phase of compounding, fine-tuning or optimizing physical properties.
Two synthetic latex compounds are examined: a polychloroprene and an acrylonitrile. The focus is on the accelerator. Zinc oxide and sulfur levels remain constant so that the effect of the accelerator on physical properties: tensile strength, modulus and elongation: is isolated. Dwell times and temperatures of selected compounds are varied. For the polychloroprene latex two dithiocarbamates, a thiuram, two guanidines and a thiourea are selected. For the acrylonitrile latex: two dithiocarbamates, two thiurams and two thiazoles.
A REVIEW OF CARBOXYLATED SBR LATEX STABILIZATION
Jennifer T. Braden, The Goodyear Tire & Rubber Co.
Carboxylated SBR latex is used extensively in carpet backing and upholstery applications. Long service life is a common requirement for these applications. An effective antioxidant system for carboxylated SBR latex is controlled primarily by its ability to prevent degradation, generally manifested in the form of embrittlement, and to prevent discoloration in the final product. Other criteria that should be considered in the selection of a stablizer system are the ability to be easily dispersed, persistence, non-staining/non-discoloring color properties, volatility and cost. This presentation will provide a review of commercial stabilizers currently used in these applications, a review of the critical criteria for stabilizer selection, and a comparison of data detailing stabilzer performance.
NON-STAINING ANTIOXIDANTS FOR LATEX RUBBER APPLICATIONS
Bonnie Stuck, Sovereign Chemical Co.
The objective of this laboratory study was to evaluate several new antioxidants versus two control antioxidants in a natural rubber latex compound. The control antioxidants were 1) Control 1, abutylated reaction product of p-cresol and dicyclopentadiene and 2) Control 2, tetra-bis-methylene 3-(3,5'-di-t-butyl-4'-hydroxyl phenyl) propionate methane which are commonly used in latex compounds. The results of this study showed several new antioxidants were developed with improved heat resistance, color properties and economics compared to the traditional control antioxidants.
AN OVERVIEW OF EMULSION AND DISPERSION TECHNOLOGY IN LATEX COMPOUNDING
James G. Ferguson, Harwick Chemical Manufacturing Corporation
An important aspect in latex compounding is the proper preparation of additives. These additives can range from curatives and antioxidants to plasticizers and fillers. This paper will examine the role additives play in a latex compound as well as define the different ways these materials can be prepared. Surfactant chemistry, particle size implications, testing and storage/handling issues will also be reviewed.
ENGINEERING LATICES TO ENHANCE THE PRINTING PROPERTIES OF COATED PAPERS
Michael Forbes, Ph.D, GenCorp, Inc.
Synthetic latices are used as the predominant coating binder in papers manufactured for offset and rotogravure printing. Controlling the polymerization variables to provide the proper particle size distribution, polymer composition and degree of crosslinking is critical to imparting the proper printing characteristics to the coated surface. In sheetfed offset printing, the surface must be open enough to give good ink transfer and setting, but must also be closed enough to provide good ink holdout and printed gloss. In web offset grades the coating must be porous enough that steam generated in the paper during printing can escape without blistering the printed product. The latex binder must also provide enough strength to insure that portions of the coating are not "picked" from the surface by the high-tack inks used in the process. In rotogravure printing, the strength of the coating is of less importance, but the surface must be smooth, compressible and uniform so it contacts all of the gravure cells and provides a print with a minimum number of "missing dots."
POLYMER AGGREGATE TREATMENT SYSTEM FOR ASPHALT PAVING APPLICATIONS
Laurand Lewandowski, Ph.D., The Goodyear Tire & Rubber Company
One of the primary distresses observed in asphalt pavements is increased damage due to water. This damage is caused by the lack of adhesion of the asphalt to the aggregate in the presence of water. This moisture damage mechanism is referred to as stripping. The end results of stripping are raveling, which is the loss of aggregate on the pavement surface and the formation of potholes. There are several approaches used in the industry to reduce the moisture sensitivity of mixtures containing asphalt, fine and coarse aggregates. Historically lime and amines have been used to address stripping, but several problems are associated with these systems. Each of these methods provides a different approach to reducing stripping. The amines are added to the asphalt and act as surfactant to help wet the aggregate surface. Lime is added to the aggregate, and generally provides resistance to stripping by forming water-resistant calcium salts of the acids from the asphalt, which have migrated to the aggregate surface. Another approach is the use of SBR latex. Goodyear has developed and recently introduced in collaboration with Ultrapave a special latex system, along with application equipment, for coating aggregate to impart superior performance properties. The latex is applied directly to the aggregate and forms a rubber coating on the surface of the aggregate. The advantages and disadvantages of the various systems will be discussed as well as data presented to compare the moisture sensitivity of the asphalt mixtures containing each treatment.
EXTRUDER ISOLATION OF POLYMERS AND ELASTOMERS FROM LATEX EMULSIONS
Carl G. Hagbert, NFM/Welding Engineers, Inc.
A twin screw extrusion process has been developed and commercialized by NFM/Welding Engineers to isolate the solids from latex emulsions. It applies to both rubber and polymer latex.
The extruder accepts a latex feed of from 10% to 50% solids and performs the steps of coagulation, dewatering, washing, devolatilization and extruding shapes all in the same extruder. Fines losses from the extruder are low and no volatile emissions escape to the atmosphere. Final extruded product is pelletized or cut into shapes for sale.
Many different rubbers and polymers have been run successfully. Commercial process applications include SBR,NBR, Neoprene, ABS and several others.
EVALUATING THE CHEMICAL RESISTANCE OF GLOVES
C. Nelson Schlatter, Ansell Edmont Industrial Incorporated
You may notice that the title of this paper uses the word "gloves" and not "latex gloves."
If you are responsible for worker safety, the manufacturing process for the gloves that protect your workers is irrelevant to you, even if you are managing a plant that makes latices or latex-based products. Most chemical protective gloves are made using latices, using either of two processes, but there are at least three other ways to do the job. The methods of evaluation that I will be discussing can apply to gloves made using any of these processes.
THE EFFECT OF THE PROPERTIES OF LATEX MODIFIER ON SHINGLE MAT
R. M. Kell, Franklin International
This paper describes the contribution of latex toward improving the properties of fiber glass mat used in shingles. The mat is commonly stiffened with a binder and then used to reinforce asphalt shingles. The binder consists mainly of a urea formaldehyde resin plus a latex. This paper presents results showing how variations in the physical properties and functionality of the latex affect strength of the mat.
ALLERGIES TO NATURAL RUBBER LATEX
Dennis R. Ownby, M.D., Section of Allergy-Immunology, Medical College of Georgia
Types of allergic reactions
Immune basis of allergic reactions
Clincal manifestations of latex allergy
Current clinical quandaries
THE NATURAL LATEX MARKET: PAST, PRESENT AND FUTURE
David St. Cyr, The Ore & Chemical Corporation
No abstract is available.
MINIEMULSION RESEARCH IN THE EMULSION POLYMERS INSTITUE AT LEHIGH UNIVERSITY
Eric Daniels, Ph.D., Lehigh University
No abstract is available.
SMALL BUSINESS GUIDE TO LATEX ALLERGY RESPONSE
Lillie Thomas, M.S., Custom Services International, Inc.
The purpose of this paper is to discuss business strategies for small latex manufacturers and resellers to use to deal with consumers who may experience latex reactions. Consumers with latex allergies, particularly health care workers, are increasingly active regarding the promotion of legislation to ban latex and/or control the content of latex containing products. Potential laws are pending in several states and are discussed. These demands require manufacturers to develop strategies to address latex allergy to minimize liability and to continue to successfully market latex products. The symptoms and types of latex reactions are identified and discussed. A strategy for understanding and dealing with latex reactions is essential for manufacturers and marketers of latex products to remain competitive. The discussion of these strategies include (1) testing; (2) labeling, and (3) development and implementation of latex education programs for support. The paper identifies latex allergy support groups, their function, and how small businesses can provide educational programs with minimal expense. Additionally, the paper discusses the symptoms of latex allergy, so that it can be properly recognized by customer service personnel receiving incoming calls concerning adverse reactions. The issues surrounding latex allergy must be addressed by business to comply with federal requirements.
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