Shuangxin 17-86 PVA (PVA 086-20)

Shuangxin 17-86 PVA, also listed as PVA 086-20 in export documentation, is a partially hydrolyzed polyvinyl alcohol resin produced by controlled alcoholysis of polyvinyl acetate. The grade designation combines a nominal polymerization degree of 1700 with a nominal alcoholysis degree of 86 mol%. The material is supplied as white to off-white free-flowing granules or powder. A 4% aqueous solution at 20 °C exhibits a Brookfield viscosity of 20.0–26.0 mPa·s when tested in accordance with GB/T 12010.3-2010. Volatile matter is limited to ≤5.0 wt% and ash to ≤0.5 wt%; pH of a 4% aqueous solution is controlled in the range 5.0–7.0. The residual acetyl content reduces crystallite formation, which lowers the dissolution energy compared with fully hydrolyzed polyvinyl alcohol grades of equivalent polymerization degree.

A Partially Hydrolyzed Resin with a Controlled Residual Acetate Window

The 86.0–89.0 mol% alcoholysis band places 17-86 in the intermediate hydrophilicity class. Residual acetate groups disrupt interchain hydrogen bonding and limit the extent of crystalline domains after drying. The practical consequence is a broader aqueous processing window: a clear solution can be prepared at 85–90 °C under low-shear agitation in 30–45 min, and the solution remains fluid on cooling to 40 °C. In comparison with a fully hydrolyzed grade with ≥99.0 mol% hydrolysis, the 17-86 grade shows lower gelation tendency and lower minimum film formation temperature. The trade-off is reduced dry-film water resistance, which makes 17-86 more suitable for applications requiring repulpability or controlled solubility rather than permanent wet strength.

The PVA 086-20 code identifies the same viscosity band in export purchasing. Within the producer’s product family, 17-86 is distinguished from lower-DP partially hydrolyzed grades such as 05-88 by higher solution viscosity and higher film tensile strength. It is distinguished from fully hydrolyzed 17-99 by lower dissolution temperature and lower crystallinity after film formation. Film tensile specimens cast from 4% solutions and conditioned at 23 °C and 50% RH can be tested according to ISO 527-3 to confirm the strength difference against lower-DP grades.

In starch-based paper surface sizing, 17-86 is typically blended with oxidized or cationic starch at size-press solids of 6–10 wt%. A starting addition level of 20–40 wt% product on dry starch is conventional for fine paper and linerboard grades. The 17-86 solution is cooked separately at 90 °C for 30 min and then combined with cooked starch before the machine chest. The high molecular weight increases size-film tensile strength and reduces surface dusting on printing grades. Because the alcoholysis band is partial, the film remains redispersible in water, which supports repulping of broke and reduces the risk of blocking in rewound rolls under ambient humidity. Bench testing with a laboratory RK-coater or pilot size press is recommended at 0.5–1.5 g/m² dry film weight to establish the optimum ratio for a specific base sheet. Viscosity drift in size-press circulation loops is a processing bottleneck. 17-86 solutions show stable Brookfield viscosity over 6 h at 60 °C, provided that shear rates remain below 1,000 s⁻¹. In high-speed film-transfer coaters, shear-thinning behaviour may reduce apparent viscosity; the formulation should be evaluated with a cone-and-plate viscometer at 25 °C and 10–1,000 s⁻¹ before machine trials.

Warp sizing of spun cotton and polyester/cotton yarns uses 17-86 at size-box solids of 6.0–9.0 wt%. The product is mixed with oxidized starch, acrylic binder, and lubricant; 17-86 contributes the main film-forming fraction. On high-speed air-jet looms, size film undergoes cyclic extension in the shedding zone, and the 1700 nominal DP provides higher abrasion resistance than lower-DP grades at equivalent solids. A commonly used split is 30–60 wt% 17-86 on total size solids, with the balance starch and wax dispersion. Size-box temperature is held at 85–90 °C; viscosity should be checked every 30 min because evaporative water loss concentrates the bath and shifts wet pickup. Desizing after weaving uses hot water at 70–80 °C or an amylase desizing bath; the residual acetyl groups in 17-86 do not inhibit enzyme action on starch. Weaving performance is affected by relative humidity: below 45% RH, film brittleness increases, and a hygroscopic plasticizer or lubricant is required.

What Changes When 17-86 Replaces a Fully Hydrolyzed 17-99 Grade in Aqueous Compounding?

Substitution of 17-86 for a fully hydrolyzed 17-99 grade changes cooling and film behaviour of aqueous formulations. At equal solids and temperature, the partially hydrolyzed resin has a lower gelation threshold and remains pumpable at lower circulation temperatures, reducing steam input on size-press and coating lines. The dried film is softer and more flexible, but its water resistance is lower. In adhesive compounding for paper and packaging, this is often acceptable because the bond line requires water-borne tack and repulpability. In applications where wet strength or moisture barrier is the primary requirement, a 17-99 grade or a crosslinking additive is preferred. The crosslinking response of 17-86 with glyoxal or zinc nitrate dihydrate is available but requires pH adjustment and pot-life monitoring; residual acetate groups can consume crosslinker differently than fully hydrolyzed material, so initial jar tests are required to avoid premature viscosity rise. In remoistening adhesive formulations for envelopes and labels, 17-86 is applied at 10–20 wt% solids with plasticizers and fillers. The dried adhesive remains non-blocking at 25 °C and 50% RH but remoistens rapidly on water contact at 60–70 °C. Fully hydrolyzed PVA would require higher remoistening temperatures. The addition of dextrin or glycerin modifies tack time; the ratio must be adjusted with viscosimetric checks because 17-86 increases high-shear viscosity more than dextrin at equal solids.

Vinyl acetate and vinyl acetate-ethylene emulsion polymerisation uses 17-86 as a protective colloid at 4–8 wt% on total monomer. The high molecular weight fraction raises latex viscosity and shear stability; the 86.0–89.0 mol% hydrolysis range provides surface activity without the foam generation associated with low-DP fully hydrolyzed grades. The standard procedure is to pre-dissolve the product at 5–8% solids in demineralized water and charge it to a jacketed stainless-steel reactor equipped with a slow anchor impeller at 60–100 rpm. During polymerisation, a portion of the polyvinyl alcohol grafts to the growing polyvinyl acetate chains, influencing particle size distribution and final viscosity. Protective colloid concentration influences reactor particle nucleation. Excessively high viscosity can impede monomer droplet breakup and increase reactor wall fouling. In continuous stirred tank reactors, impeller tip speed should be monitored; tip speeds above 2.5 m/s may increase foaming. Because the agitation profile and initiator feed rate interact strongly with the graft fraction, published data for this specific configuration is limited; pilot batches are recommended to define the coagulum threshold at a given tip speed. Formulators requiring lower latex viscosity may replace a portion of 17-86 with lower-DP 05-88 while monitoring mechanical stability.

When Dissolution Temperature and High-Shear Stability Define the Processing Envelope

The dissolution process for 17-86 is a two-stage sequence. Dry granules swell in cold water at 30–40 °C without dissolving; chain disentanglement proceeds only after the batch reaches 85 °C. In a jacketed mixing vessel with a bottom-entering disperser, the recommended order of addition is to charge water at 30–40 °C, add 17-86 slowly under agitation at 600–900 rpm, then heat at 1.0–1.5 °C/min to 90–95 °C. The temperature is held for 30–45 min until the solution clears. High-shear mixing above 1,500 rpm is not required and can mechanically degrade the high-DP fraction, producing a measurable drop in solution viscosity. The solution pH should remain between 5.0 and 7.0; exposure to strong alkali above pH 9.0 accelerates hydrolysis of residual acetate groups and shifts the material toward fully hydrolyzed behaviour, increasing the risk of skin formation on cooling. Borate ions and zirconium crosslinkers should be excluded from the dissolution vessel because they form three-dimensional gel networks that are difficult to remove from spray nozzles and size-press rolls.

Dry resin storage should be maintained below 30 °C and 60% RH. If bags have been exposed to humid air, the product should be pre-dried at 60 °C for 4 h before use. Prepared solutions without preservative should be consumed within 8 h; preserved solutions may be stored for 24–48 h in closed tanks under slow agitation. The product is not intended for use with amine-based additives that create an alkaline environment and may accelerate viscosity drift. For food-contact or pharmaceutical applications, the user must verify compliance against FDA 21 CFR 175.105, EU 10/2011, or applicable national positive lists for polyvinyl alcohol.