ELVANOL 52-22

Where a rod-metering size press operates on recycled linerboard at 350–800 m/min, the substitution of oxidized corn starch with an ELVANOL 52-22/starch blend changes film split behaviour and sheet holdout in a measurable way. ELVANOL 52-22 is slurried at 8–12 wt% in cold water and then cooked at 90–95 °C for 45–60 min in a steam-jacketed tank, producing a stock solution with a solution viscosity of 22.0–26.0 mPa·s at 4% solids and 20 °C. The cooked PVOH is let down into a starch carrier that has been jet-cooked separately at 105–110 °C. Final size press solids are held at 5–9% and the PVOH portion is limited to 2–5 parts per 100 parts of starch. Higher replacement levels reduce sheet porosity and can slow drainage on the wire section. The film-forming contribution improves surface strength measured by IGT pick and reduces Cobb 60 water absorption by 15–30% compared with the same size press solids using starch alone, depending on furnish, calender pressure, and recycled fibre content. Finished board used for corrugated medium and folding carton stock must comply with ISO 535 for water absorption and ISO 2759 for bursting strength. Where the board is intended for aqueous and fatty food packaging, the finished article must meet the extraction limits of 21 CFR 176.170 rather than the raw PVOH specification alone. In starch/PVOH size systems, the addition of more than 0.5% borax based on total size solids generates a viscosity climb that cannot be controlled by the rod-metering supply loop. The size press temperature is held between 60 °C and 70 °C; below that range ELVANOL 52-22 begins to gel under high shear, and above that range the starch component thins excessively.

Does ELVANOL 52-22 Function as a Grafting Site Donor in VAc–Ethylene Polymerization?

In vinyl acetate–ethylene (VAE) emulsion polymerization, partially hydrolysed PVOH acts both as a high molecular weight protective colloid and as a grafting substrate for vinyl acetate radicals. ELVANOL 52-22 carries 87–89 mol% hydrolysis and a 4% solution viscosity of 22.0–26.0 mPa·s at 20 °C, placing it in a range where grafting frequency and aqueous-phase viscosity build are balanced for medium-viscosity emulsion architectures. A typical reactor charge contains 3–6 parts by weight of ELVANOL 52-22 per 100 parts of total monomer, pre-dissolved as a 10 wt% aqueous solution and buffered with sodium acetate to pH 4.0–5.0. The reaction is run at 55–65 °C with a redox initiator and a monomer delay of 4–6 h. The final emulsion at 54–56% solids typically falls within 1,500–3,500 mPa·s at 25 °C when measured under ISO 2555.

The grafted PVOH layer stabilises latex particles in the 0.5–2.0 μm range and prevents shear coagulation during unload pumping and later formulation with fillers. In paper coating and carpet-backing compounds, high-shear stability is checked by passing the emulsion through a Cowles disperser at 2,000–3,000 rpm for 10 min and recording grit retention on a 45 μm sieve. Film formation temperature and wet-tack development are controlled less by the PVOH alone and more by ethylene content and plasticiser selection. Where the VAE emulsion is formulated into wood adhesives, bond strength is tested according to EN 204 D3 or the equivalent national standard. Overdosing ELVANOL 52-22 above 6 phm raises aqueous phase viscosity before radical generation, reduces heat transfer through the cooling coil, and increases coagulum adhesion to baffle plates. Use with cationic surfactants is not recommended because charge neutralisation and serum viscosity rise can occur before monomer addition is complete.

Envelope Machine Speeds Exceed the Open Time of Dextrin-Only Remoistenable Gum

Remoistenable envelope and label gums based solely on dextrin and sucrose suffer wet-tack failure when machine speeds exceed 20,000 envelopes/hour. A formulation using ELVANOL 52-22 at 18–26 parts by weight per 100 parts of wet adhesive supplies the film toughness and rewetting uniformity required for rubber roller and stencil application systems. The batch is prepared in a steam-jacketed kettle by dispersing ELVANOL 52-22 in cold water, adding dextrin at 10–15 parts and sucrose at 5–10 parts, then heating to 85–90 °C for 30–45 min. After cooling to 50–55 °C, glycerin is added at 2–5 parts to control film brittleness. Final Brookfield viscosity is typically 1,000–3,000 mPa·s at 25 °C.

The applied glue film weight is controlled at 25–50 g/m² wet depending on substrate porosity. Dried glue lines must survive block testing at 40 °C and 60% RH without sticking but rehydrate within 2–5 s when exposed to a lick roller. T-peel adhesion on paper is assessed using ASTM D1876; the paper seal failure should occur before the glue film separates from the paper. For food-contact packaging adhesives, the compounded adhesive must comply with 21 CFR 175.105. Below 35% RH, dried PVOH films can curl the envelope flap, so stock is wrapped and conditioned at 50–60% RH before gluing. Terminal products include pressureless envelope seal strips, paper labels, and roll wrap. This is not a pressure-sensitive adhesive and develops no tack at room temperature before remoistening.

When slasher operators replace 30–50 parts of modified starch in a warp-size formula with ELVANOL 52-22, the size add-on on cotton–polyester blended yarn can be reduced without losing weaving efficiency. A mixed yarn of 65% polyester and 35% cotton, spun to Ne 20–40, is typically sized on a multi-cylinder slasher with a size box temperature of 80–85 °C. ELVANOL 52-22 is cooked first as a 10% solution and blended with gelatinised starch to give a final solids range of 10–14%. Size pick-up is held at 8–12% on warp weight. Below that range, hairiness defects appear on air-jet looms running above 650 picks/min, though published comparative data for this exact air-jet loom abrasion threshold is limited and mill-specific slasher trials are used to set the final replacement ratio. Yarn tensile strength and elongation before and after sizing are tested according to ISO 2062 and ASTM D2256. Desizing is accomplished with a 70–80 °C water wash or with an amylase desizing step where starch is the majority component. The partially hydrolysed PVOH does not require oxidative desizing, but sulphate caustic desizing can accelerate residual film removal on dense constructions. Sized warp storage should remain below 70% RH to prevent blocking on section beams. Terminal products include workwear fabrics, bedsheet greige, and cotton–polyester apparel fabric.

Ceramic Spray-Dried Granule Binder Requirements and Burnout Profile

In porcelain stoneware slip preparation, ELVANOL 52-22 functions as a temporary green binder that increases the mechanical strength of spray-dried granules before pressing. It is introduced as a 6–10 wt% aqueous solution into the ceramic slip at a dosage of 0.8–2.0% by weight of dry body. The slip is spray-dried at an inlet temperature of 180–220 °C and an outlet temperature of 90–110 °C. The resulting granules are controlled to 5–7% moisture and a median size of 250–400 μm. Pressing at 35–45 MPa forms tiles with improved edge retention and reduced lamination cracks caused by granule rebound.

During bisque firing, the PVOH decomposes by thermo-oxidative degradation between 300 °C and 450 °C. Because the ash content of ELVANOL 52-22 is specified as ≤0.5%, the residual alkali contribution in whiteware bodies remains low enough to avoid glaze pinholing from volatile burnout channels. Fired tile water absorption and modulus of rupture are tested under ISO 10545-3 and ISO 10545-4. The operational limit appears above 2.0% dry binder addition: granule hardness increases, but the compacted body develops closed pores at the kiln stage when the binder burns out too rapidly below 400 °C. Humidity above 70% RH in granule storage causes caking and partial dissolution at the silo wall. Terminal products include porcelain stoneware floor tiles, technical alumina substrates, and pressed ceramic cores.

When Cementitious Skim Coats Demand Extended Open Time Without Retarder

Cement-based tile adhesives and gypsum skim coats can be formulated with ELVANOL 52-22 as a dry-blended water-retention and anti-skinning additive at 0.5–2.0 kg per 100 kg of dry mix. The polymer dissolves during mixing and increases the viscosity of the interstitial water phase, which slows evaporation from the surface and extends the open time of a thin-bed C1 tile adhesive from a typical 15–20 min window to the longer intervals required by EN 12004 when tested at 23 °C and 50% RH. The addition rate is kept below 2% because higher PVOH levels can entrain air and lower compressive strength, particularly in gypsum-based materials tested under EN 13279-1.

The dry mix is prepared in a horizontal ribbon blender. ELVANOL 52-22 is added before cellulose ether to limit electrostatic dust losses and to achieve uniform polymer distribution. The mixed powder is combined with water at the ratio specified by the adhesive manufacturer. After mixing, the mortar is slaked for 3–5 min and remixed for 15–30 s. The ELVANOL fraction delays surface skin formation more strongly than starch-ether or clay-based water-retention additives because the film-forming PVOH migrates to the surface and forms a thin membrane. At addition rates above 2.5 kg per 100 kg, the surface membrane can interfere with tile wetting and reduce adhesion after 28-day water immersion. The final tile adhesive is tested under EN 12004 for initial adhesion, after water immersion, after heat ageing, and after freeze–thaw cycling. Terminal products include C1 and C2 cementitious tile adhesives, gypsum skim coats, and repair mortars.