EXCEVAL RS-2117

In vinyl acetate-based emulsion polymerisation, the protective colloid functions as both steric stabiliser and grafting substrate, and its molecular weight, hydrolysis degree, and aqueous solution viscosity control nucleation rate, final latex particle size distribution, and mechanical shear stability. EXCEVAL RS-2117 is supplied as a partially hydrolysed polyvinyl alcohol grade with reported control ranges of 87–89 mol% hydrolysis and a 4% aqueous Brookfield viscosity of 20–26 mPa·s at 20 °C determined per ISO 2555. In a typical VAE or PVAc homopolymer adhesive reactor, the grade is pre-dissolved in demineralised water at 80–90 °C under moderate agitation, then fed as the continuous-phase protectant before monomer addition. The residual acetate content in this hydrolysis window lowers aqueous solution surface tension relative to fully hydrolysed grades, reduces the interfacial energy barrier during vinyl acetate monomer dispersion, and promotes the formation of a controlled particle size distribution. At the same time, the acetate side chains limit intramolecular hydrogen bonding and reduce the tendency of the colloid to crystallise at low application temperatures, which is relevant when the finished adhesive is stored below 5 °C. The solution viscosity of 20–26 mPa·s is a direct practical constraint: it provides a thicker grafted protective layer around the latex particle and improves high-shear stability in a Cowles disperser operating above 1000 s⁻¹, but it also increases final emulsion viscosity and can slow monomer diffusion during the particle growth stage. Production-scale reactor records indicate that protective colloid concentrations from 3.0 wt% to 6.0 wt% on total monomer are common for this grade; below this window, coagulum and filter plugging may increase, while above it, the water resistance of the dried adhesive film may decline because the continuous PVOH phase remains water-sensitive. In wood adhesive qualification, the balance is assessed through bond strength after water immersion using EN 204 durability classes and through wet shear strength measured according to ISO 6238. The use of EXCEVAL RS-2117 therefore requires a formulation-specific optimisation among latex viscosity, adhesive open time, and water resistance, and published data for this specific configuration is limited.

What Limits Drop Size Distribution in Suspension PVC with Partially Hydrolysed PVOH?

Suspension PVC autoclaves impose a different set of interfacial demands than emulsion polymerisation: the primary dispersant must reduce vinyl chloride monomer-water interfacial tension sufficiently to form droplets in the 100–180 μm range while retaining a protective adsorbed layer that prevents coalescence without creating excessive droplet rigidity. EXCEVAL RS-2117 dissolves in cold demineralised water at 20–25 °C before charging; undissolved gel bodies in the aqueous phase are a recognised source of oversized droplets and resin fisheyes, so batch make-up commonly includes a 60–90 min hydration period and filtration through a 200–300 μm mesh. Because the grade is partially hydrolysed at 87–89 mol%, it exhibits lower aqueous phase viscosity than a fully hydrolysed grade of equal molecular weight, but its 20–26 mPa·s solution viscosity still contributes to a thicker interfacial film than low-molecular-weight secondary dispersants. In a 50 m³ baffled autoclave with a Pfaudler-style impeller, droplet breakage occurs in the high-shear zone around the impeller tip while coalescence is favoured in the low-shear bulk; the dispersant layer must therefore provide immediate steric coverage after breakage, or the particle size distribution broadens and resin porosity becomes uneven. Suspension PVC resin properties are routinely tested by K-value per ISO 1628-2, plasticizer absorption per ISO 4612, and sieve retention per ISO 4610. Partially hydrolysed PVOH alone tends to produce larger and more porous particles; typical industrial formulations pair it with a low-hydrolysis secondary dispersant in the 55–65 mol% range to shift the mean droplet size downward and improve plasticizer uptake. The exact ratio is reactor-specific and also depends on the oil-soluble initiator feed and temperature ramp profile. A production-scale conflict arises when the primary dispersant concentration is raised to suppress coarse particles: aqueous phase viscosity increases, vinyl chloride droplet breakup efficiency may decrease at constant agitator speed, and reactor wall fouling can worsen if the grafted PVOH layer becomes too viscous. Therefore the use of EXCEVAL RS-2117 as the primary dispersant is normally evaluated against particle size distribution by laser diffraction per ISO 13320 and against resin dry flow time per ASTM D1755. Published data for this specific grade in suspension PVC is limited, and qualification work must be performed on the target autoclave because impeller tip speed, baffle configuration, and monomer-water ratio alter the effect of the dispersant more than any single laboratory test.

Table 1 lists the test methods commonly applied when qualifying this grade for suspension PVC trial campaigns.

At machine speeds above 600 m/min on recycled linerboard and corrugating medium, the size press demands a film former that reduces surface porosity without raising the circulating starch viscosity to the point of rod streaking and misting. EXCEVAL RS-2117 is applied in this context as a high-molecular-weight binder component in oxidised starch or enzyme-converted starch formulations. The reported 4% aqueous viscosity of 20–26 mPa·s means that at a size press solids range of 6–12 wt% the addition of the PVOH fraction can raise the circulating starch viscosity noticeably; therefore the grade is usually blended at 10–30 wt% of total size solids, with the exact ratio determined by the target Cobb60 value according to ISO 535 and the required IGT pick resistance according to ISO 3783. Partial hydrolysis at 87–89 mol% reduces size film crystallinity compared with fully hydrolysed grades, which improves adhesion to lignocellulosic fibres that have residual surface lignin and hydrophobic extractives. The higher molecular weight contributes to surface strength by forming a cohesive film that bridges fibre pores, but it also increases drying demand and may require higher after-dryer temperatures. A typical size press operating at 40–60 °C can tolerate the viscosity rise if the starch solids are adjusted downward, but operator logs from packaging-grade paper machines show that insoluble PVOH particles, if present due to inadequate dissolution at 80–90 °C, deposit on metering rods and lead to streaks. The use of EXCEVAL RS-2117 in surface sizing therefore requires a dedicated make-down system with a 30 min cook time and a 100–150 μm in-line filter to protect the coater. For applications where water resistance is not primarily required, partial hydrolysis is acceptable; where wet strength is critical, additional surface-applied crosslinkers such as glyoxalated resins or zirconium salts are used, but their compatibility with PVOH must be checked because aldehyde reaction can gel the circulation tank. Published data for this specific starch-PVOH configuration is limited, and mill-specific surface strength and porosity targets remain the controlling parameters.

When Ceramic Tape Burnout Profiles Enforce a 450 °C Upper Binder Limit

Ceramic tape casting of alumina, barium titanate, or low-temperature co-fired ceramic formulations relies on a water-soluble binder to provide green strength, control drying shrinkage, and deliver clean pyrolysis before sintering. EXCEVAL RS-2117 can be selected in this process when the binder is dissolved in deionised water with particulate dispersants such as polyacrylate salts, then blended with ceramic powder and plasticisers before casting. The 87–89 mol% hydrolysis level leaves sufficient hydroxyl functionality for hydrogen bonding to oxide surfaces, while the 20–26 mPa·s solution viscosity contributes to slurry stability and cast tape thickness uniformity. A typical green tape formulation contains 3–8 wt% PVOH based on dry ceramic powder; at the lower end, green strength may be insufficient for via punching or roll handling, while at the upper end, the burnout cycle must remove a greater organic fraction and may leave carbon residue if air flow is inadequate. Thermogravimetric analysis per ISO 11358-1 is used to establish the decomposition interval; PVOH backbones degrade primarily in the 250–450 °C range, but complete removal depends on heating rate, oxygen partial pressure, and tape thickness. A critical process threshold is the heating rate: for tapes above 200 μm dried thickness, a ramp rate above 1 K/min through the 300–450 °C window can generate internal pressure from volatilisation and cause lamination cracks or blistering. Green flexural strength can be measured by three-point bending per ASTM C1161, although published data for this specific PVOH grade in tape casting is limited. The inorganic ash level of the polymer must be considered for dielectric applications where residual sodium or ash above 0.1 wt% can degrade insulation resistance. In such cases, the grade should be evaluated by ashing at 450 °C for 2 h using the supplier’s documented ash method, and the tape formulation should avoid overcooking the PVOH solution at high pH because alkaline hydrolysis of residual acetate groups can increase solution viscosity during holding time.

When polyester-cotton yarns are sized at 60–80 m/min on a slasher, the size film must penetrate the yarn bundle, adhere to both cellulosic and synthetic fibre surfaces, and resist shedding during loom shed cycles. EXCEVAL RS-2117 can be used as a size-box additive or as a base polymer in blended size formulations at solids concentrations from 6–12 wt%. The partial hydrolysis of 87–89 mol% supports adhesion to polyester because the residual acetate groups reduce surface tension and improve wetting of the hydrophobic fibre, whereas the 20–26 mPa·s viscosity of a 4% solution indicates a sufficiently high molecular weight to form a cohesive, abrasion-resistant size film. In a production slasher, the size box temperature is typically held at 70–80 °C to maintain solution clarity and avoid skin formation. The add-on is controlled by squeeze roll pressure, usually in the range of 10–20 kN/m, and the drying cans are set to remove moisture progressively without exceeding 140 °C surface temperature to prevent embrittlement of the PVOH film. The sized yarn is tested for tensile strength per ISO 2062 and abrasion resistance by loom simulation; published data for this specific PVOH grade in warp sizing is limited, but the practical limitation is desizing efficiency. Because partially hydrolysed PVOH is water-soluble, size removal can be accomplished with hot water at 80 °C, but if the size blend includes starch, enzymatic desizing with alpha-amylase is required before the final wash. The grade should not be combined with borax or boric acid in the size box because borate ions crosslink PVOH and increase viscosity to the point of size-line gelation. This constraint defines the formulation boundary for textile mills running high-speed slashers with limited filtration and narrow size-box residence time.

Cementitious Dry-Mix Water Retention without Retarding Setting Time

Tile adhesives, cementitious skim coats, and self-levelling underlayments use water-soluble polymers to retain mixing water, improve open time, and enhance adhesion to difficult substrates. EXCEVAL RS-2117 can be dry-blended into cementitious formulations at dosages typically between 0.2 wt% and 1.0 wt% of total dry mix; the partially hydrolysed 87–89 mol% grade provides more rapid dissolution in alkaline cement water than fully hydrolysed PVOH, while the 20–26 mPa·s solution viscosity contributes to tack and anti-sag behaviour. The primary process conflict is that raising the PVOH dosage increases water retention and open time but may also form a polymer film on cement grains that delays early hydration. This is measured by comparing setting time using a Vicat apparatus per EN 196-3 and by adhesion development after water immersion per EN 1348. Water retention can be assessed by filter paper uptake per EN 1015-8 or by gravimetric water loss from a bed of hydrated mortar under controlled vacuum. In high-pH cement pore solution, the residual acetate groups of partially hydrolysed PVOH can undergo gradual hydrolysis, which changes the effective hydrolysis degree and may reduce the polymer’s solubility over time. This ageing effect is one reason why the grade is usually evaluated in accelerated storage trials at 40 °C and 75% relative humidity before specification. The powder form allows dry blending in twin-ribbon mixers, but the particle size distribution of the PVOH must be matched to the cement and sand fraction to prevent segregation. For tile adhesives tested to EN 12004, the addition of this high-molecular-weight grade is not a direct substitute for dispersible polymer powder; in many formulations it is used as a secondary rheology modifier alongside vinyl acetate-ethylene redispersible powder, because its water sensitivity and retarding effect at high addition can reduce final adhesive cohesion after water saturation.

Evaluating EXCEVAL RS-2117 in Water-Soluble Film Blends

In water-soluble film casting, the binder balance is governed by dissolution time, tensile strength, and moisture resistance at high humidity. EXCEVAL RS-2117 is a high-molecular-weight partially hydrolysed polyvinyl alcohol grade, and it is generally evaluated in blends with lower-viscosity grades rather than as a single-component film grade. The 20–26 mPa·s solution viscosity at 4% concentration limits the practical casting solids of a pure solution to approximately 10–15 wt%; above this range, the dope viscosity complicates deaeration, filtration, and die feed. Films are commonly cast on a heated drum or belt at 90–120 °C, and tensile properties are measured per ASTM D882 or ISO 527-3. The partial hydrolysis at 87–89 mol% lowers the crystalline melting point relative to fully hydrolysed grades and improves cold-water solubility, but the high molecular weight slows the dissolution rate of thick films in cold water below 10 °C. This is the key process conflict: blending 10–30 wt% of EXCEVAL RS-2117 with a low-viscosity partially hydrolysed grade can increase tensile strength and film toughness, but the dissolution time may exceed the target for thin detergent pouches. Plasticisers such as glycerol or sorbitol are commonly added at 5–15 phr to reduce film crystallinity and improve tear resistance; however, plasticiser migration at elevated storage temperatures can reduce blocking resistance. Moisture uptake is determined by conditioning at 23 °C and 50% relative humidity according to the film producer’s internal method, and the film’s water content must remain below 2–4 wt% to prevent premature dissolution during storage in high-humidity environments. Published data for this specific grade in water-soluble film blends is limited, and the formulation must be validated on the intended casting line because die lip shear, drying profile, and winding tension influence final dissolution performance more than laboratory drawdowns.