Polychloroprene latices

About one dozen polychloroprene latices have been developed for adhesive... 

There is only one non-ionic latex Neoprene latex 115) all other polychloroprene latices are anionic and are emulsified with rosin soaps. 

Neoprene latex 115 contains a copolymer of chloroprene and methacrylic acid, stabilized with polyvinyl alcohol [15], With respect to other polychloroprene latices, this latex has two major advantages (1) excellent colloidal stability, which gives high resistance to shear and a broad tolerance to several materials ... 

Among the anionic polychloroprene latices, the following grades are the most common. 

Solvent-borne CR adhesives and polychloroprene latices will be considered separately. 

It has to be kept in mind that the polymer properties desired in polychloroprene latex formulations may be totally different from those needed in dry grades. Polychloroprene latices generally exhibit lower contactability than dry polychloro-prenes because of the presence of residual soaps and salts, appreciable gel content and segregation of tackifier [79]. For this reason, the polychloroprene latices have usually medium to low crystallinity. 

Polychloroprene latices are mainly used for high-pressure lamination, for foam bonding and for vinyl adhesion [82]. Also they are used for foil lamination, carpet installation, and PVC floor tile bonding. 

Water-borne contact adhesives are growing in importance because of environmental regulations, occupation health and the flammability of solvents. The solids content in the water-borne polychloroprene adhesives varies between 40 and 60 wt%, and viscosities between 15 and 500 mPa can be obtained. Although polychloroprene Unices are water based, they are generally inflammable as the resin is dissolved in organic solvents before emulsifying. All polychloroprene latices are susceptible to coagulation by mechanical, thermal and chemical means. 

Polychloroprene latices are mainly used for high-pressure lamination, for foam bonding and for vinyl substrates (such as PVC) adhesion. Also, they are used for foil lamination, carpet installation, and PVC floor tile bonding. Bonding and shaping of foams is done with highly crystalhzable water-borne polychloroprene adhesives. The adhesive is sprayed on the foam and immediately the foam pieces are placed in contact. The assembly is wet-bonded because no drying is necessary as the water will dissipate into the foam. 

The development of two new polychloroprene latices, designated Dispercoll C LS-2324 and Dispercoll C LS-2373, which are suitable for the manufacture of waterborne contact adhesives, is reported. Examples are presented of formulations in which blends of these polychloroprene latices are used to optimise initial green strength, contact bond life and heat resistance. 

Polychloroprene latices relatively new in the field provide a wide range of effective base polymers and modifiers from which to formulate useful environmentally friendly and cost effective coatings for a wide range of substrates [94, 95]. 

Nitrile and polychloroprene latices are made by the industrial process of emulsion polymerization, in which the polymerization reaction and the formation of an aqueous emulsion occur simultaneously. In this process, reaction temperature and control of the polymer molecular weight are important in order to obtain the desired final glove properties. In the case of the nitrile latex, the ratio of the three monomers can also be used by the polymer chemist as an important tool in tailoring the final product properties. 

Inevitably, refinements and modifications have to be added to the basic principles to yield a viable, commercial dipping process. This section describes some of the methodology used in achieving practical systems. Since at present the only significant use of synthetic emulsion polymers is with nitrile and polychloroprene latices for glove manufacture, the following notes are necessarily directed towards this area. 

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