ELVANOL 75-15

ELVANOL 75-15 is a low-viscosity fully hydrolysed polyvinyl alcohol grade produced by Kuraray Co., Ltd. The product is supplied as a white to off-white granular solid and is specified for aqueous solution processes requiring controlled solution viscosity, low cold-water sensitivity after drying, and film strength in downstream sizing or coating. The numerical segment of the product designation corresponds to a nominal 4% aqueous solution viscosity range of 13.0–16.0 mPa·s at 20 °C. The degree of hydrolysis is typically 99.0–99.8 mol%, which differentiates ELVANOL 75-15 from partially hydrolysed grades with higher residual acetate content and lower crystallinity. In textile warp sizing, paper surface sizing, adhesive compounding, and emulsion polymerization protective colloid systems, ELVANOL 75-15 is selected where lower molecular weight permits higher solids at a given machine viscosity. Compared with higher-viscosity ELVANOL grades in the fully hydrolysed series, the product delivers reduced solution viscosity and lower film cohesive strength at equivalent solids. These differences are controlled primarily by molecular weight, not by hydrolysis level.

What are the specification boundaries for ELVANOL 75-15?

Specification data should be read against the supplier technical data sheet, because lot-to-lot variability and test preparation influence PVOH measurements. The values in Table 1 are representative of the commercial product. Viscosity is measured on a 4% aqueous solution at 20 °C using rotational viscometry aligned with ISO 2555. The degree of hydrolysis is determined by saponification titration and is reported as mole percent of vinyl alcohol units. pH is determined on the same 4% solution. Volatile matter and ash are controlled to limit the effect of moisture and inorganic residues on film clarity and adhesive performance.

The pH range of 5.0–7.0 is typical for fully hydrolysed PVOH and is stable in non-buffered aqueous solutions. The viscosity specification is narrow relative to generic PVOH, which allows closer control of size-press pickup and adhesive coat weight in continuous processes. Published data for this specific grade in on-line viscometer validation is limited; calibration of in-line viscometers should be performed against laboratory rotational measurements at the same temperature.

Dissolution of fully hydrolysed PVOH differs from partially hydrolysed grades because the high degree of hydrolysis reduces swelling and solubility at ambient temperature. ELVANOL 75-15 is typically slurried in water at 20–30 °C and then heated to 90–95 °C under low-shear agitation. Production vessels using side-sweep turbines or low-speed anchor impellers provide effective dispersion without excessive air entrainment. A hold time of 30–45 min at temperature is common in vessels with a liquid depth-to-diameter ratio of 1.0–1.5. High-speed dispersers and cavitating pumps should not be used because shear-induced chain scission can lower viscosity. In plants where ambient humidity exceeds 60 %, the granular product should be stored in sealed hoppers or pre-dried because moisture uptake changes the effective solids content. Dissolved solutions are sensitive to borate ions, certain multivalent salts, and strongly acidic conditions, which can produce gelation or viscosity instability. Strong oxidisers may initiate chain scission. Sustained melt processing above 200 °C may liberate acetic acid and discolour the polymer; therefore, direct steam injection should be controlled to avoid localised hot spots. These handling boundaries are consistent with fully hydrolysed PVOH of comparable molecular weight.

Solution rheology and film formation under controlled shear

At 4% solids and 20 °C, ELVANOL 75-15 displays a solution viscosity of 13.0–16.0 mPa·s, placing it at the low-viscosity end of the fully hydrolysed product line. The lower molecular weight reduces chain entanglement and permits higher solution solids before a given pump, transfer line, or roll-nip pressure limit is reached. In size presses and blade coaters, the reduction in water load per kilogram of applied film can decrease after-drying energy consumption. Film formation from the fully hydrolysed grade is controlled by the 99.0–99.8 mol% hydrolysis level. The low residual acetate content allows strong hydrogen bonding and high crystallinity after water removal, producing a clear film that resists cold-water dissolution but re-dissolves when heated above 90 °C. The trade-off for low solution viscosity is lower film tensile strength compared with higher-viscosity products. Because PVOH solutions are pseudoplastic under high shear, laboratory Brookfield viscosity values at 20 °C should not be extrapolated directly to high-speed coating. A cone-and-plate or capillary viscometer is required to characterise viscosity at shear rates above 1000 s⁻¹. Published data for this specific grade in high-shear rheology is limited.

In emulsion polymerization, ELVANOL 75-15 is used as a protective colloid for vinyl acetate and acrylic systems. The low solution viscosity permits the preparation of high-solids stabilising solutions without excessive reactor charge viscosity. Fully hydrolysed PVOH provides high grafting efficiency with vinyl acetate and contributes to the final emulsion viscosity and particle size distribution. The 99.0–99.8 mol% hydrolysis level reduces water sensitivity of the dried film compared with partially hydrolysed protective colloids, but reduces cold-water solubility of residual PVOH. The lower chain length may require more protective colloid by weight to achieve equivalent emulsion shelf stability compared with medium-viscosity grades. Process control during reactor charging should account for the high solution temperature required to dissolve the product; if added as a cold slurry, undissolved granules may persist. Published data for this specific grade in pressure-rated emulsion reactors is limited.

When ELVANOL 75-15 replaces higher-viscosity fully hydrolysed grades in slasher sizing and adhesive compounding

Formulators replace a medium-viscosity grade such as ELVANOL 71-30 with ELVANOL 75-15 when the process objective is to raise solids at constant machine viscosity or to improve penetration into dense substrates. The trade-off is a reduction in film cohesive strength because the lower molecular weight yields shorter polymer chains. In adhesive compounding, this reduction may require an increase in total PVOH content or the addition of a compatible tackifier. In slasher sizing on high-speed rapier and air-jet looms, the lower viscosity allows size solution to penetrate more deeply into spun cotton yarns and reduces viscosity drift in the size box during continuous running. A comparison of the fully hydrolysed product line is shown in Table 2. The values are from supplier technical bulletins and represent typical ranges, not release specifications.

The selection among these grades is driven by the minimum film strength required in the end use. In paper applications, the high hydrolysis level of ELVANOL 75-15 maintains water resistance after drying, while the low viscosity helps avoid film piling behind doctor blades on high-speed coaters. However, the same property reduces the ability to build thick surface films. If surface film thickness and cohesive strength are the primary requirements, a higher-viscosity fully hydrolysed grade should be specified. In textile sizing, add-on levels are often adjusted to compensate for lower film strength when ELVANOL 75-15 replaces a medium-viscosity product. Published data for this specific grade in commercial air-jet loom trials is limited; mills should conduct controlled size box evaluations because yarn count, size press configuration, and loom speed affect the result.

Partially hydrolysed grades with 87–89 mol% hydrolysis dissolve at lower temperatures and retain less water resistance after drying. Compared with those grades, ELVANOL 75-15 requires dissolution above 90 °C but yields films with higher cold-water resistance and higher tensile strength under humid conditions. The choice is therefore not governed by viscosity alone; hydrolysis level determines solubility and water resistance, while viscosity determines application thickness and penetration.

For indirect food-contact applications, the supplier regulatory datasheet lists clearances under 21 CFR 175.105 for adhesives, 21 CFR 176.170 for components of paper and paperboard in contact with aqueous and fatty foods, and 21 CFR 176.180 for components in contact with dry food. These clearances are end-use specific and require confirmation against the final formulation and food-contact conditions. Under REACH, polyvinyl alcohol as a polymer is not subject to registration as a monomer-reacted polymer, but downstream users are responsible for evaluating monomer impurities and national occupational exposure limits. The product should be handled with local dust extraction to keep respirable dust below the applicable workplace exposure limit. Bulk handling equipment should be grounded to avoid static charge accumulation. Published data for this specific grade in European food-contact compliance is limited beyond the supplier regulatory datasheet.