Fulatex PD0128X

Fulatex PD0128X is an anionic carboxylated styrene-butadiene copolymer dispersion supplied as a white, low-odour aqueous emulsion for paper and paperboard wet-end and coating systems. The product model PD0128X identifies a partially crosslinked, carboxylated, low-VOC grade within the PD series. The dispersion is manufactured for high pigment-binding efficiency in blade-coated offset papers, lightweight coated rotogravure base stocks, folding boxboard precoats, and specialty nonwoven binding. Typical solids content is 49.0–51.0 wt% with a pH of 6.5–7.5 at 25 °C. The product is stabilised by an anionic emulsifier system and is compatible with alkaline coating colours containing calcium carbonate and kaolin. In wet-end applications it contributes wet strength and runnability when added as a saturation binder, provided the white water pH remains above 6.0.

Product Chemistry and Colloidal Structure

The synthesis route for Fulatex PD0128X is emulsion polymerisation of styrene and 1,3-butadiene with a carboxylic acid comonomer, typically itaconic or acrylic acid, under an anionic surfactant package. Residual monomer content is reduced by steam stripping; the manufacturer’s certificate of analysis reports styrene below 0.05 wt% and 1,3-butadiene below 0.01 wt% by gas chromatography per ISO 13741-1. The carboxylic acid groups are concentrated at the particle surface, creating electrosteric stabilisation and pH-responsive viscosity. Particle size measured by dynamic light scattering per ISO 22412:2017 is 140–180 nm with a unimodal distribution. Differential scanning calorimetry per ISO 11357-2:2020 gives a glass transition temperature of −12 ± 2 °C, and minimum film formation temperature is below 0 °C per ISO 2115:1996. The polymer contains a controlled gel fraction that increases cohesive film strength and solvent resistance after drying. The surface tension is 38–45 mN/m per ASTM D1331-14, which controls wetting of ground calcium carbonate and coating colour deaeration.

Film formation of Fulatex PD0128X proceeds by particle coalescence after water removal. Below the glass transition temperature the film remains brittle; above the minimum film formation temperature capillary pressure and polymer creep close voids. In coated paper drying, web surface temperatures are held below 100 °C to avoid binder migration and blistering. The product tolerates short excursions to 120 °C for 2–3 seconds in air flotation dryers, but prolonged exposure at 140 °C can cause yellowing and embrittlement. The carboxylated surface reacts slowly with added zinc oxide or ammonium zirconium carbonate, allowing wet strength development without wholesale coagulation. Cast films prepared per ISO 2115:1996 typically exhibit elongation greater than 300% at 23 °C and tensile strength of 1.5–3.0 MPa depending on drying conditions; however, these values are not product guarantees and should be confirmed on current production lots.

In high-speed blade coating, the coating colour is subjected to shear rates exceeding 1 × 10⁶ s⁻¹ in the metering nip, followed by rapid viscosity recovery before application. Latex binders with inadequate high-shear stability produce visible blade streaks and coating scratches on a 3.6 m wide coater running at 1,100 m/min. Fulatex PD0128X is formulated to maintain viscosity recovery after exposure to production-scale blade coater nip shear; pH adjustment to 8.0–8.5 with ammonia reduces shear-thickening and improves coat weight uniformity in field experience with similar carboxylated SBR grades. The product is typically added at 8–14 parts per 100 parts pigment in sheet-fed offset coating colour and at 5–9 parts per 100 parts pigment in lightweight coated rotogravure precoats. Coating colour solids is usually 58–65 wt%; pH is held at 8.5–9.0 with sodium hydroxide or ammonia. High-speed dispersion should be performed with a saw-tooth Cowles blade at tip speeds of 18–22 m/s; prolonged dispersion above 30 m/s may generate foam and increase surface defects. Filtration of the coating colour through 150–200 µm backwash screens before the coater reduces blade scratches from coagulum or skinning.

What Limiting Rheological Parameters Govern Binder Selection in Blade Coating?

Brookfield viscosity at 25 °C is 80–200 mPa·s per ISO 2555:2018, spindle 2 at 60 rpm. This low-shear value is not sufficient to predict blade runnability; high-shear viscosity and water retention are more relevant to coat weight stability and blade bleed. The anionic character of Fulatex PD0128X favours viscosity control with alkali swelling; raising pH from 7.0 to 8.5 increases low-shear viscosity by 50–100%, an effect that is reversible with pH reduction. Water retention measured by TAPPI T 701 is in the range typical of carboxylated SBR binders; formulators combine the latex with carboxymethyl cellulose or starch to meet coat holdout requirements under ISO 535:2014 Cobb testing. The product is incompatible with cationic fixatives, aluminium salts, and polyvalent metal ions unless a protective colloid is present. These limits define the operating envelope in circulation systems on coaters.

For wet-end saturation of paper and nonwovens, the product can be used at 10–25 parts per 100 parts fibre. The anionic charge requires retention aid optimisation, and white water pH must be maintained above 6.0. In continuous saturation lines, the dispersion is metered directly into the beater chest; feed lines should be stainless steel or lined carbon steel because the product slowly corrodes unlined steel. Excess heat above 40 °C during processing increases skinning and should be avoided.

Specification Ranges and Test Standardisation

The following tabulated values are drawn from the manufacturer’s certificate of analysis and are measured according to the indicated standard methods.

Replacement of non-carboxylated SBR latex with Fulatex PD0128X at the same binder content typically raises wet pick strength without increasing bulk stiffness. The carboxylic acid functionality improves adhesion to oxidised starch and mineral pigment surfaces; coating colour water retention measured by TAPPI T 701 is maintained because the high surface area of the carboxylated polymer immobilises water within the filter cake. Compared with styrene-acrylic latex, Fulatex PD0128X has a lower glass transition temperature and lower intrinsic hydrophobicity, which reduces crack propagation on folded board but requires external insolubilisation or a harder topcoat where wet rub resistance is critical. Published data for this specific configuration is limited; however, general carboxylated SBR performance in paper coating is documented in pigment-binder interaction studies. The product differs from non-crosslinked PD grades by a tighter particle size distribution and lower residual monomer, which contributes to lower odour and more consistent coating colour viscosity.

When Fulatex PD0128X Replaces Styrene-Acrylic in Folding Boxboard Barrier Precoats

Barrier performance in folding boxboard precoats relies on mineral packing and binder film continuity rather than a single polymer barrier layer. The product is not intended as a stand-alone barrier polymer; its oxygen permeability is higher than ethylene-vinyl alcohol or polyvinylidene chloride, but as a binder in mineral-filled precoats it can reduce penetration of subsequent topcoat starch into the substrate. Trials on folding boxboard lines have used 10–12 pph Fulatex PD0128X in a precoat with 70 parts coarse ground calcium carbonate and 30 parts fine kaolin. The precoat solids were 64 wt%; drying was performed with air cap temperatures of 180–220 °C and web surface temperatures below 100 °C. The carboxylated binder retards the binder migration that causes surface gloss mottle in subsequent blade topcoats. Formulators should evaluate water absorption by Cobb ISO 535:2014 and dry pick strength by IGT ISO 3783:2013; a minimum of 12 minutes conditioning at 23 °C and 50% RH per ISO 187:1990 is required before testing. If wet rub resistance must exceed 50 cycles on a 1 kg weighted crockmeter, a harder topcoat or crosslinking cobinder should be evaluated.

In nonwoven high-loft applications, Fulatex PD0128X is applied by spray or foam at 10–20% solids, dried at 130–150 °C, and tested for wet tensile strength per ISO 9073-3:1989. The carboxylated SBR chemistry imparts a softer hand than acrylic binders of similar tensile strength, but the product is not suitable for outdoor nonwovens without UV stabilisation.

Storage stability is dependent on temperature and pH. The product should be stored between 5 °C and 35 °C. Freeze-thaw cycling destroys the colloidal dispersion; product that has been frozen must not be re-dispersed mechanically. Before use, the latex should be mixed with a low-shear propeller agitator at 30–60 rpm for 10–15 minutes. Filtration through 150–200 µm backwash filters before the coating station reduces blade scratches from coagulum or skinning. The manufacturer’s shelf-life specification is 6 months from the date of manufacture when stored in sealed containers under recommended conditions. Outflow from storage tanks must not be returned to the main supply unless it has passed screen filtration and pH adjustment. In areas where relative humidity exceeds 60%, pre-drying of starch-based co-pigments is required to prevent moisture swings in the coating colour. Avoid combination with amine-based additives at pH above 9.5 because ammonia release and viscosity drift can occur; amine bases such as monoethanolamine are not recommended for pH control.

Compliance Matrix and Industrial Hygiene

From a regulatory standpoint, Fulatex PD0128X is classified as a non-dangerous mixture under CLP Regulation (EC) No 1272/2008, but residual styrene below 0.05 wt% requires local exhaust ventilation in coating kitchens. The product is manufactured in accordance with REACH Regulation (EC) No 1907/2006; a safety data sheet should be consulted for full exposure scenarios. Food-contact suitability is not self-certified; compliance with FDA 21 CFR 176.170 and 176.180 must be verified by migration testing under intended end-use conditions. The product is suitable for formulation in coatings subject to Directive 2011/65/EU RoHS Annex II limits: lead 0.1 wt%, mercury 0.1 wt%, cadmium 0.01 wt%, hexavalent chromium 0.1 wt%. Toy safety under EN 71-3 also requires end-use testing because the paper substrate may influence extractable metals.