GOHSENOL KP-08R

What Limits Secondary Dispersant Loading in Vinyl Chloride Suspension Polymerisation?

GOHSENOL KP-08R is specified as a partially hydrolysed polyvinyl alcohol with a 4 % aqueous viscosity in the 6.0–9.0 mPa·s range at 20 °C and a degree of hydrolysis in the 71–75 mol% band under JIS K6726. In batch suspension PVC production, vinyl chloride is dispersed at a water-to-monomer mass ratio of 1.10:1 to 1.30:1 in a full-jacketed stainless autoclave, typically 60 m³ or larger, fitted with a reflux condenser and top-entering agitator. Initiation is performed with dialkyl peroxydicarbonates at 0.03–0.08 parts per 100 parts monomer. The dispersant package is split between a high-hydrolysis primary grade and KP-08R as the secondary grade. The secondary fraction is held to 20–35 % of total dispersant solids because the lower-hydrolysis PVA depresses interfacial tension more aggressively than the primary grade. Excess secondary dispersant shifts the droplet size distribution below 150 µm, increases fine-particle formation, reduces bulk density below 0.500 g/cm³ after drying, and narrows the cold plasticiser absorption window. Reactor temperature is maintained at 56–62 °C; polymerisation pressure decays from approximately 0.9 MPa to 0.6 MPa before recovery and degassing.

The process conflict occurs during the first 5 % conversion: reducing the KP-08R charge to raise bulk density can destabilise the vinyl chloride droplet phase and produce reactor fouling on the baffles and condenser. Gravimetric dosing of the secondary dispersant is therefore controlled to ±0.002 parts per 100 parts monomer to avoid batch-to-batch shifts in particle size. Resin evaluation follows ISO 1628-2 for K-value, ISO 60 for apparent density, and ASTM D3367 for cold plasticiser absorption. Typical targets for suspension PVC made with this dispersant class are K-value 65–68 and cold plasticiser absorption 25–35 parts per 100 parts resin. Terminal PVC grades are used in rigid pipe fittings, window profile compounds, and cable sheathing where consistent grain morphology is non-negotiable.

In high-solids vinyl acetate–ethylene emulsion polymerisation, KP-08R functions as a primary protective colloid rather than as a secondary suspending agent. The grade is dissolved in demineralised water at 8–10 % solids in a jacketed make-down vessel heated to 80–85 °C under low-shear agitation; the solution is then cooled to 40 °C before charging to the reactor. The reactor charge commonly contains 1.0–3.5 parts dry PVA per 100 parts total monomer, with the exact loading set by the desired final emulsion viscosity and particle size. In an ethylene-vinyl acetate campaign, ethylene is pressurised to 20–35 bar after the initial vinyl acetate seed stage, while reactor temperature is held at 65–75 °C. The low-viscosity character of KP-08R permits final solids of 55–60 % without exceeding 10 000 mPa·s Brookfield viscosity at 20 rpm, spindle 4, 25 °C. Residual vinyl acetate monomer is reduced below 0.5 % by post-polymerisation addition of tert-butyl hydroperoxide and sodium metabisulphite. Dispersion quality is measured by ISO 13320 laser diffraction, with a target volume-median particle diameter of 0.8–1.5 µm.

Water resistance of the dry film is evaluated under EN 204/D3 immersion conditions. Borate salts must not be added to the finished dispersion because partially hydrolysed PVA reacts with borate ions to form a gel or a sharp viscosity climb, which can crack the storage tank agitator coupling. REACH registration for polyvinyl alcohol, CAS 9002-89-5, must be confirmed by the formulator for the specific grade. The resulting emulsions are used in wood-assembly adhesives, nonwoven binders, and low-odour interior coatings where VOC limits restrict solvent use.

If Cold-Water Reconstitution Governs High-Speed Envelope Gum Converting

Remoistenable adhesive compounds for envelopes and labels are formulated with KP-08R as the film-forming resin. The dry gum is prepared at 25–35 % solids in water; glycerol is added at 5–10 parts per 100 parts dry PVA as plasticiser, and a dextrin or starch component may be blended to adjust open time and fibre-tear activation. The compound is applied by interrupted roll or gravure coating at line speeds of 50–120 m/min. A low-viscosity PVA grade is required to maintain coating viscosity below 1 500 mPa·s at 30 °C so that the applicator roll does not sling at high speed. Drying is performed in an impingement oven at 60–90 °C for 3–8 seconds. Rewet activation is measured by applying 10 µL water per 25 mm × 25 mm bond area and evaluating fibre tear after 10–15 seconds open time. Blocking resistance is assessed at 40 °C and 60 % relative humidity. The grade complies with the paper-components provisions of US FDA 21 CFR 176.170 and the adhesives provision 21 CFR 175.105 when used at levels necessary to achieve the intended effect. The operational boundary is humid storage: above 70 % relative humidity, the gum surface absorbs moisture and blocking occurs unless a barrier overwrap is used. End products include envelope flaps, stamp gumming, and label adhesives.

Oxidised starch is the main size-press binder in many uncoated woodfree papers; KP-08R is introduced at 5–15 % of total binder solids to suppress dusting and lift IGT pick resistance. The size-press liquor is maintained at 4–8 % solids and 45–55 °C. The low degree of hydrolysis allows the PVA to dissolve without high-temperature cooking and to blend with oxidised starch without phase separation. Addition of 0.05–0.2 parts of a nonionic defoamer per 100 parts liquor is common; high-shear circulation must be avoided because excessive mechanical energy can generate foam and destabilise the film. The impregnation is performed on a two-roll size press at nip pressure of 20–45 kN/m. Sheet testing follows ISO 535 for Cobb water absorption, ISO 2470 for brightness, and ISO 3783 for IGT pick resistance. A surface-sizing process conflict occurs when the size-press roll temperature exceeds 70 °C: starch retrogradation and PVA skinning on the rolls can cause web breaks. The KP-08R content is therefore capped at the lower end for lightweight base papers. The resulting base papers are converted into inkjet and laser office stock, envelope stock, and preprint forms.

Slashing of High-Density Polyester Warp Yarns and Desizing Effluent COD

Hydrophobic polyester filament warps require a size film that adheres under high reed beat-up; partially hydrolysed PVA such as KP-08R is combined with acrylic size and wax at a PVA solids level of 6–10 %. The size-box viscosity is held between 10 and 15 s on a Zahn cup 3 at 75 °C. The grade dissolves at 70–80 °C in a jet cooker and is transferred to the slasher sump. Slashing speed is set at 15–40 m/min depending on yarn linear density; cylinder drying temperatures are staged from 110 °C to 130 °C. Sized warp tensile strength and elongation are measured by ISO 13934-1. Weaving efficiency is monitored directly on high-speed air-jet looms operating at 700–1 000 rpm. After weaving, the size is removed by hot-water scouring at 80–90 °C without enzymatic or oxidative chemicals, because the grade is readily re-dissolved. Effluent chemical oxygen demand is controlled by ultrafiltration and size recovery; industrial recovery systems commonly achieve 80–90 % size recovery, but published data for KP-08R in a specific desizing configuration is limited. The main limitation is the absence of water resistance: finished greige must not be stored in humid conditions before desizing, or biological growth can stain the warp. End products include polyester shirting, automotive upholstery, and high-density voile.

Technical ceramic tape casting for alumina and barium titanate substrates uses KP-08R as a low-ash binder in aqueous slurries. The binder is prepared as a 6–10 % solution and added at 3–6 parts dry PVA per 100 parts ceramic powder. A polycarboxylate dispersant at 0.5–1.5 parts per 100 parts powder is added before the binder to control the ion layer on the particle surface. Slurry rheology is targeted to 2 000–4 000 mPa·s at 10 s⁻¹ shear rate on a cone-and-plate rheometer. The tape is cast at doctor-blade gaps of 200–400 µm onto a polyester carrier film at 0.5–2.0 m/min. Drying is carried out in a three-zone air-float dryer at 60–90 °C. Green tape tensile strength is measured by a modified ISO 527-3 procedure, and density is checked by Archimedes immersion. During burnout, the binder decomposes below 500 °C; the low ash content of KP-08R is critical to prevent residual sodium or potassium that depress dielectric breakdown strength. A processing limitation appears when slurry pH drifts above 9: hydrolysis of residual acetate groups can alter binder solubility and green strength. The finished electronic component must meet RoHS Directive 2011/65/EU restrictions; the PVA binder does not introduce lead, cadmium, mercury, or hexavalent chromium. Published data for KP-08R specifically in multilayer ceramic capacitor tape casting is limited; the operating window is derived from the low-viscosity, low-ash PVA binder class. Terminal components include multilayer ceramic capacitors, LTCC modules, and sensor substrates.