China vs Japan PVA Grade Cross-Reference (1799→Poval)

Polyvinyl alcohol (PVA) grade equivalence between Chinese domestic specifications and Japanese Poval designations is a recurring technical query in import substitution, dual-source qualification, and coating formulation transfers. The shorthand “1799→Poval” appears in procurement documents for fully hydrolysed, medium-polymerisation PVA. In Chinese resin nomenclature, grade 1799 is read as a nominal degree of polymerisation of 1,700 and a nominal degree of alcoholysis of 99 mol%. The nearest Kuraray Poval product in the same class is Poval 117. This equivalence is a formulation starting point, not a specification identity.

How Does the 1799→Poval 117 Cross-Reference Hold Under GB/T 12010 and JIS K6726 Classification Logic?

Under GB/T 12010.1-2008, the Chinese grade number is generated from two separate property classes: the first two digits are an approximate degree of polymerisation decoded as hundreds, while the last two digits are the nominal alcoholysis degree in mol%. The Japanese Poval designation for 117 encodes the fully hydrolysed series by the leading unit digit and the solution viscosity class by the subsequent digits; the product is described in technical literature as a medium-viscosity, fully hydrolysed grade. The cross-reference therefore maps 1799 to Poval 117 on the basis of overlapping hydrosol viscosity ranges, not on identical molecular weight distribution. The practical consequence is that a direct substitution may be acceptable in textile sizing where viscosity tolerance is wide, but not in narrow-window applications such as suspension polymerisation dispersant dosing.

Hydrolysis Degree, Solution Viscosity, and Ash Content Differences That Alter Downstream Processing

Supplier data for 1799 typically state a 4% aqueous solution viscosity of 25.0–31.0 mPa·s at 20°C when measured by GB/T 12010.3-2010; Poval 117 is listed at 27.0–33.0 mPa·s under JIS K6726:2005. The overlap is substantial but not complete, and the upper Poval values can produce a 6–8% increase in formulated aqueous dope viscosity relative to a low-lot 1799. In slot-die film casting, a dope viscosity shift of this magnitude changes pump discharge pressure at constant line speed; positive displacement gear pumps running at 1,250 rpm have been observed to require 0.4–0.6 MPa additional discharge head when the Poval lot sits at the upper viscosity boundary. For adhesive compounding, the same shift may require reformulation of wetting agent dosage to maintain a coating viscosity of 1,800–2,200 mPa·s on a Brookfield RV viscometer with a No. 4 spindle at 20 rpm. Ash content is the most common source of film fisheyes. Chinese 1799 lots may be supplied with ash ≤0.5% under GB/T 12010.5-2010, whereas Poval 117 technical literature commonly specifies ≤0.3% for selected grades. In optical-grade cast film, ash above 0.3% can generate insoluble gel nuclei that register as surface defects greater than 50 µm under transmitted light inspection. A 100-megapixel line-scan inspection system may reject at 0.8–1.2 defects per m² when ash is at the upper limit.

In cotton and polyester/cotton warp sizing, 1799 is typically cooked at 8–10% solids in a jacketed atmospheric sizing kettle at 90–95°C for 30 min, then transferred to a size box maintained at 85°C. Single-end sizing machines with a 1,600 mm working width and a squeeze roller pressure of 12–14 kN are used in many high-speed sizing lines. When Poval 117 is substituted, the size pick-up on a 14.5 tex cotton yarn may rise by 0.5–1.0 percentage points unless size-box viscosity is trimmed with water or the solid concentration is reduced by 0.3–0.5 wt%. The desizing efficiency after enzymatic treatment with α-amylase at 60°C for 20 min is generally insensitive to the substitution, but the higher ash content in some 1799 lots can deposit scale on squeeze rolls and reduce roll life. Textile mills operating at ambient relative humidity above 60% must pre-dry the resin and maintain hopper feed to the cooking kettle below 45°C to prevent agglomeration. Published data for this specific configuration is limited, but production records indicate that viscosity drift is the primary control variable rather than adhesion.

When a 1799 Replacement Is Evaluated in PVC Suspension Polymerisation Stabiliser Feeds

In vinyl chloride suspension polymerisation, 1799 functions as a primary dispersant because the fully hydrolysed chain adsorbs onto vinyl chloride monomer droplets and provides steric stabilisation. A commercial reactor of 30 m³ capacity typically charges a primary dispersant solution at 0.02–0.08 parts per hundred monomer, with a secondary partially hydrolysed grade such as 1788 at 0.01–0.04 parts per hundred monomer. The ratio is trimmed to control PVC resin particle size distribution between 120–180 µm and plasticizer absorption in the range 20–28 g DOP per 100 g resin. Poval 117 has a comparable alcoholysis degree, but its viscosity distribution can narrow the droplet coalescence window when the polymerisation temperature is maintained at 57–63°C. If the primary dispersant solution is prepared at 2 wt% and dosed through a mass flow meter with an accuracy of ±0.5%, a batch-to-batch viscosity increase of 2 mPa·s can shift the Sauter mean diameter by 5–10 µm and reduce the K-value reproducibility measured by ISO 1628-2:1998. Reactor operators should requalify the Poval lot by running a bench-scale suspension test in a 5 L jacketed glass reactor before changing supplier. Incompatibility with cationic additives should be checked when the dispersant is blended with quaternary ammonium compounds, as neutralised PVA can precipitate at high ionic strength; published data for this specific configuration is limited.

Film Casting, Barrier Properties, and Plasticizer Compatibility Limits

For water-soluble film and polarising film intermediate layers, 1799 is dissolved at 10–14 wt% in deionised water, cast through a slot die with a lip gap of 0.6–0.8 mm, and dried on a chrome-plated drum at 85–95°C with air humidity controlled at 30–50% RH. Under ASTM D882-18, a fully hydrolysed 1799 film with 10 phr glycerol as plasticiser typically exhibits tensile strength of 40–55 MPa and elongation at break of 150–220%, depending on drying rate and heat treatment. Poval 117 films cast under identical conditions may show slightly higher tensile strength because the tighter molecular weight distribution and lower ash reduce film flaws; comparative data published in supplier bulletins place the difference at 3–5 MPa. The water vapour transmission rate measured by ASTM E96/E96M-22 is more sensitive to film thickness than to the 1799/Poval substitution when the film is above 30 µm, but below 20 µm, defects from ash can increase the measured WVTR by 10–15%. Plasticizer compatibility differs only when the alcoholysis degree drifts below 98.5 mol%; at that point the cold-water solubility increases and the film becomes more sensitive to glycerol migration. The operational boundary is therefore alcoholysis degree and ash, not viscosity. Film producers should reject lots with volatile matter above 5% because residual water in the feed can shift dope rheology and create die-lip deposit. Use of amine-based corrosion inhibitors in the casting line humidification water is not recommended because volatile amines can migrate into the dope and alter pH during long runs; published data for this specific configuration is limited.

Adhesive compounding operations that employ 1799 as a colloid stabiliser and rheology modifier typically run a high-shear mixer at 1,500 rpm with a saw-tooth impeller. The final polyvinyl acetate or acrylic hybrid formulation may require a Brookfield viscosity of 3,000–5,000 mPa·s at 25°C. Substitution with Poval 117 generally preserves the shear-thinning profile, but an upper-viscosity lot can increase the final adhesive viscosity by 300–500 mPa·s and reduce wetting on polyethylene terephthalate film. The specification window should be set at ±5% of the qualified control lot viscosity. Because 1799 is fully hydrolysed, the adhesive film has higher hot-water resistance than 1788-based formulations; the cross-reference to Poval 117 maintains that property. Additives containing borate ions must be avoided unless a controlled gelation response is desired, as borate can crosslink PVA diol units and raise viscosity beyond the mixer torque limit. Storage above 35°C combined with relative humidity above 60% can cause caking in unopened bags and should be addressed by pre-drying at 60°C for 2–4 h before use.

Where indirect food contact is regulated under FDA 21 CFR 175.105 and 176.170, a cross-reference table is insufficient for audit unless the supplier lot-specific certificate of analysis confirms the same compliance. For food-contact film and packaging, migration testing under EU 10/2011 may be required, and the migration limit for vinyl alcohol-derived substances should be checked against the specific framework conditions. REACH registration status and residual methanol or methyl acetate emissions during drying should be documented in the technical file. Without those documents, the cross-reference remains a sourcing filter rather than a qualified equivalence.