Binders & Additives I

Polymeric materials have been used for many years to re-enforce the fiber entanglements of durable nonwoven constructions.  Typically, the re-enforcing binder has been and continues to be composed of a base emulsion polymer and a melamine and/or urea formaldehyde crosslinker.  Due to the continuing pursuit of more environmentally friendly, cost effective binder systems for the durable nonwovens industry, the primary objective of this paper will be to evaluate the relative performance of binder systems that contain and produce very low levels of formaldehyde.  A dynamic mechanical rheometer is employed to measure the relative degree of re-enforcement that the binder can provide through the measurement of the complex viscosity of the polymer mixture. 

Thermally cross-linkable formaldehyde free acrylic binders are used in numerous nonwoven and composite applications where formaldehyde resins (urea formaldehyde, melamine formaldehyde, and phenolics) have historically been used.  These formaldehyde free binder systems provide nonwovens with durability and high tensile strengths, while imparting resistance to heat and water. It is advantageous to have the ability to vary binder properties of these thermosetting resins by blending them with emulsion polymers. Properties such as fabric flexibility and hydrophobicity can be adapted for specific application requirements.  These thermosetting acrylic resin blends were investigated in terms of the impact of emulsion polymer addition on the nonwoven and binder properties and binder stability effects. Both fabric testing and analytical methods were used to characterize these blends and their performance. 

Acrylic thermosets are a new thermosetting technology.  These novel resins are provided as a non-hazardous aqueous formulation.  When applied to a fibrous or particulate substrate and cured, acrylic thermosets impart shape and rigidity to previously non communicative materials.  These cured substrates find utility in many building and construction products such as, fiberglass batts, ceiling tiles, laminated countertops, flooring, air filters, and durable particle and strand board.  Often the marketplace requires that thermosetting resins impart specific properties that can distinguish products offered by several suppliers.  Since acrylic thermosets are not prepared with formaldehyde or formaldehyde generating ingredients, labels touting this virtue are present in the marketplace.  Other performance distinctions such as, water resistance, feel, appearance – brightness can also be formulated into an acrylic thermoset. In fact, the modular nature of acrylic thermoset technology easily allows for formulation alterations permitting end users to distinguish their products from seemingly similar products.  The modular attribute of acrylic thermoset chemistry will be presented.  Several examples of formulation flexibility to impart commercially valuable properties will also be discussed.

Finishing treatments with dimethyloldihydroxyethyleneurea (DMDHEU) have historically been used for woven or knitted fabrics in order to cross-link cellulose for durable press applications and to improve other performance enhancing properties.  More recently, DMDHEU finishes were applied to spunlace cotton nonwoven fabrics to improve the smooth-drying properties after laundering. The results were quite surprising; in addition to improved smooth-drying properties, the fabric samples had significantly less fuzzing and better integrity after multiple launderings.  It may be possible to use DMDHEU treatments to enhance the end use of certain spunlace nonwovens from “disposable” to “semi-reusable”.