GOHSENOL EG-40P

GOHSENOL EG-40P is a partially hydrolysed polyvinyl alcohol supplied as a white to pale yellow granular powder. The product is a vinyl alcohol–vinyl acetate copolymer with a degree of hydrolysis specified within 86.5–89.0 mol% and a Brookfield viscosity of 40.0–46.0 mPa·s for a 4% aqueous solution at 20°C, determined in accordance with JIS K6726. The corresponding residual acetate content is 11.0–13.5 mol%. This places EG-40P in the medium-to-high viscosity segment of partially hydrolysed polyvinyl alcohol grades, where formulation requirements include cold-water dispersibility, film cohesive strength, and controlled thickening behaviour without the hot-water dissolution constraints of fully hydrolysed polyvinyl alcohol.

Analytically, the product has a pH specification of 5.0–7.0 for a 4% aqueous solution. Volatile matter is controlled at a maximum of 5.0% by mass, and ash, expressed as sodium oxide, is controlled at a maximum of 0.5%. The material has CAS Registry Number 9002-89-5. The partial hydrolysis level and viscosity grade distinguish EG-40P from fully hydrolysed polyvinyl alcohol grades, which typically require heating to 80–95°C for dissolution and exhibit greater film water resistance but lower rewettability.

What Limits Protective-Colloid Efficiency in High-Shear Emulsion Polymerization?

In vinyl acetate and vinyl acetate–ethylene emulsion polymerization, EG-40P is predissolved in demineralized water and charged as a protective colloid before monomer addition. The 11.0–13.5 mol% residual acetate groups lower interfacial tension at the vinyl acetate–water interface, while the 40.0–46.0 mPa·s aqueous viscosity provides a higher molecular weight than low-viscosity partially hydrolysed grades. This combination increases the hydrated steric barrier on developing latex particles. In stirred stainless-steel reactors equipped with turbine impellers, protective-colloid loadings are commonly 2–10 parts per hundred parts vinyl acetate monomer, with the exact loading set by target particle size, latex viscosity, and shear stability requirements.

The grade is also used in acrylic and styrene–acrylic emulsion systems where reduced pre-emulsion preparation time is required. Because residual acetate groups suppress crystallinity, the polymer does not require high-temperature cook-out. Agitation during dissolution should avoid vortexing and air entrainment; air-entrained foam stabilised by surface-active polyvinyl alcohol can persist for several hours and interfere with particle size analysis by dynamic light scattering. High-shear post-processing in rotor-stator dispersers or high-pressure homogenizers can strip weakly adsorbed colloid and increase coagulum if the aqueous-phase polymer concentration falls below the critical coverage concentration. Published data for this specific equipment configuration is limited; therefore, reactor shear profile and colloid demand should be confirmed by pilot-scale trials.

Specification control is performed on each production lot. The degree of hydrolysis is measured by saponification back-titration according to JIS K6726:1994, and viscosity is measured on a fully deaerated 4% aqueous solution at 20°C with a Brookfield viscometer. The ash limit of 0.5% and volatile matter limit of 5.0% are relevant to emulsion polymerization and adhesive compounding because ionic residues can destabilise latex or affect electrical properties. The specified pH window of 5.0–7.0 reduces neutralisation demand in neutral latex systems, but buffering remains necessary when vinyl acetate hydrolysis releases acetic acid during storage or polymerisation.

Specification Boundary Conditions and Analytical Test Designations

Batch-to-batch viscosity variation is controlled within a 6.0 mPa·s span at the 4% concentration, which supports continuous emulsion polymerisation lines where feed viscosity must remain in a narrow operating window. Powder particle size distribution influences dissolution time; coarser granules dissolve more slowly than fine powder but reduce dust generation during direct addition. Closed handling with dried conveying air is recommended when the product is stored at relative humidity above 60%, because moisture uptake can reduce flowability and weighing accuracy.

Low-viscosity partially hydrolysed grades in the same series are specified where lower solution viscosity at equal concentration is required for high-solids coating or spray drying. EG-40P is selected when higher thickening efficiency, higher film tensile strength, or greater protective-colloid molecular weight is required. Fully hydrolysed polyvinyl alcohol grades with degrees of hydrolysis ≥98 mol% provide improved water resistance and lower dissolution rate; they are preferred for barrier coatings and for film applications requiring low equilibrium moisture uptake. Substitution between EG-40P and a lower-viscosity grade should be based on equal-solution-viscosity comparison using a Brookfield viscometer at the application temperature, not on equal mass replacement.

When Fully Hydrolysed PVOH Is Replaced by EG-40P in Remoistenable Adhesive Films

Remoistenable adhesives for envelopes, labels, and paper tape require a dry film that develops tack after application of a thin water layer. EG-40P provides this response because its 86.5–89.0 mol% hydrolysis level leaves sufficient acetate groups to disrupt crystalline domains after drying. Fully hydrolysed grades develop stronger interchain hydrogen bonding and therefore require more water and longer dwell time to regenerate tack. The 40.0–46.0 mPa·s solution viscosity produces films with greater cohesive strength and block resistance than low-viscosity partially hydrolysed grades, reducing fibre pick during high-speed converting. Adhesion to porous paper substrates can be quantified by peel resistance testing under ASTM D903 or by fibre tear testing under TAPPI T 459; published data for this specific formulation is limited.

In remoistenable adhesive compounding, EG-40P is dissolved in water at 10–20% solids and applied by roller or gravure coating. Drying at elevated paper surface temperatures can increase crystallinity in the dried film and reduce re-wetting speed, while residual moisture from insufficient drying can increase blocking. The product should not be compounded with amine-based additives that raise pH above 7.0 and accelerate ester hydrolysis of residual acetate groups. Such hydrolysis shifts the grade toward fully hydrolysed behaviour and reduces cold-water tack responsiveness.

In paper coating and surface sizing, EG-40P is used as a water-soluble binder in formulations containing precipitated calcium carbonate or kaolin. The polymer is typically applied at 5–15% by mass of dry polymer on pigment, depending on coating speed and IGT pick strength requirements. The 40.0–46.0 mPa·s viscosity at 4% solids translates to higher aqueous-phase viscosity at coating solids than low-viscosity polyvinyl alcohol grades. This can improve water retention and film splitting but may increase blade pressure on high-speed blade coaters. Coating formulations containing polyvinyl alcohol should be evaluated for high-shear rheology using a capillary viscometer or slit die viscometer; Brookfield data alone do not predict blade coater behaviour.

Textile sizing formulations incorporate EG-40P when warp yarns require high film cohesion and easy desizing. A size bath prepared at 6–12% solids is applied to cotton or polyester/cotton yarns on slasher sizing machines. Film tensile properties can be measured on cast films according to ASTM D882-18. Because EG-40P is partially hydrolysed, it can be removed by cold-water desizing, reducing energy demand compared with fully hydrolysed grades that require hot-water desizing. Size film resistance to high-humidity weaving environments is lower than that of fully hydrolysed polyvinyl alcohol; relative humidity above 60% can soften the size film and reduce abrasion resistance. Pre-drying of sized yarn before the shed may be required under these conditions.

Rheological Response Depends Strongly on Aqueous Concentration

The aqueous solution behaviour of EG-40P is non-linear with respect to concentration. At 4% solids and 20°C, the viscosity is 40.0–46.0 mPa·s. As concentration increases, apparent viscosity rises more steeply than predicted by dilute solution theory, consistent with polymer coil overlap. Solutions at 10–20% solids typically exhibit pseudoplastic behaviour under shear; a Brookfield RV spindle at low rotational speed provides an apparent viscosity reading that is strongly affected by thixotropy and air entrainment. A cone-and-plate viscometer with controlled shear rate is advisable when specifying the product for continuous metering pumps.

The polymer should be added to the vortex of mechanically agitated water at 20–30°C. After initial dispersion, the batch may be heated to 80°C for 30–60 min to ensure complete dissolution. The absence of gel particles can be checked by filtration through a 100 μm screen using a pressure filter; retained gel bodies indicate that dissolution time or agitation intensity should be increased. Temperature control during emulsion polymerisation is a critical boundary. The protective-colloid solution should not be held for prolonged periods at temperatures above 80°C because thermal hydrolysis can reduce residual acetate content and increase viscosity drift. In continuous processes, jacketed feed tanks maintain the aqueous polyvinyl alcohol phase at 20–30°C to limit viscosity loss and microbial growth; biocides may be required if hold time exceeds 24 h. The product is compatible with nonionic and anionic surfactants, but incompatible with high-valent metal salts that can complex with hydroxyl groups and precipitate the polymer. These operational boundaries are based on standard polyvinyl alcohol solution preparation practice; published data for this specific configuration is limited.

Compliance Verification Requires Article-Specific Migration Data

These references are a compliance screening list and do not replace article-specific migration testing or end-use certification for the formulated product.