GOHSENOL C-500

GOHSENOL C-500 is a fully hydrolyzed polyvinyl alcohol resin with a degree of hydrolysis between 98.0 and 99.0 mol% and a 4 % aqueous solution viscosity of 4.8–5.8 mPa·s at 20 °C. The grade is supplied as a white granular powder with ash content no greater than 0.5 % and volatile content no greater than 5.0 %. These parameters place C-500 in the medium-viscosity, fully hydrolyzed segment of the GOHSENOL range, where high film tensile strength, oil resistance, low-foam dissolution, and shear stability are required. The following application routes are limited to established industrial conversions in which C-500 functions as a protective colloid, binder, surface size, or temporary barrier film former.

Protective Colloid Performance in High-Pressure Ethylene Vinyl Acetate Emulsion Reactors

In continuous and semi-continuous vinyl acetate-ethylene emulsion polymerization, GOHSENOL C-500 is introduced as a pre-dissolved 8–10 % aqueous solution into the pre-emulsion feed line. Dosage is calculated against total vinyl acetate monomer mass. At 2.0–6.0 wt%, the fully hydrolyzed PVOH forms a grafted protective layer around the vinyl acetate-ethylene copolymer particles during nucleation and growth. Production-scale observations on a 20 m³ stirred tank reactor equipped with a radial flow impeller, internal cooling coil, and external plate heat exchanger indicate that C-500 concentration governs median particle size, final dispersion viscosity, and coagulum formation. When the dosage falls below 2.0 wt%, wet-screen coagulum typically exceeds 0.15 % because surface coverage at the particle-water interface becomes insufficient. At dosages above 6.0 wt%, the final dispersion viscosity may rise beyond 15 000 mPa·s at 25 °C, limiting heat removal through the external loop and extending the post-polymerization hold period. The preferred production window for a 50–55 % solids VAE dispersion is 3.5–4.5 wt% C-500 based on vinyl acetate monomer.

The dissolution protocol for reactor feed requires C-500 to be hydrated at 85–90 °C for 45–60 min under low-shear agitation. Air entrainment during dissolution is controlled by maintaining the agitator below 120 rpm in a baffled tank. The solution is cooled to 40–50 °C before being metered into the pre-emulsion vessel. The reaction mass is held at 80–90 °C under an ethylene partial pressure of 20–45 bar, with ethylene distributed through a sparge ring into the liquid monomer phase. A separate redox initiator feed, normally persulfate/bisulfite, is used because direct premixing with the PVOH solution can generate radical transfer sites and premature color development.

Compliance documentation for emulsions stabilized with C-500 references EU REACH EC 1907/2006, GB 18583-2008 for volatile organic compound limits in Chinese adhesive markets, and US FDA 21 CFR 175.105 when the resulting dispersion is used in food-contact laminating adhesives. Finished emulsions are screened through a 250 µm stainless steel filter basket before drumming. The final pH is typically buffered to 4.0–5.5 with sodium acetate. The table below summarizes representative production-scale ranges for a VAE dispersion stabilized with C-500.

The terminal emulsions are converted into water-based wood assembly adhesives, single-component construction adhesives, paper and board laminating adhesives, and nonwoven binder systems. A formulation boundary exists at low plasticizer content: the fully hydrolyzed PVOH shell raises minimum film formation temperature relative to partially hydrolyzed alternatives, which can reduce cold-temperature film coalescence in exterior wood adhesives.

Surface sizing of uncoated woodfree paper with GOHSENOL C-500 is specified when the mill requires oil holdout, surface strength, and lint resistance beyond the performance of oxidized starch alone. The size press preparation follows a two-kitchen sequence. C-500 is first dissolved in a jacketed dissolver at 8–12 % solids and 85–90 °C for 45 min. The solution is transferred to the starch holding tank and combined with enzymatically or thermally degraded cationic starch at a dry ratio of 0.5–2.0 parts PVOH per 100 parts starch. The final size press bath is held at 50–65 °C and 30–120 mPa·s, with 0.05–0.20 % of a polydimethylsiloxane defoamer where air entrainment is detected downstream of the screen. On a metering size press running at 800–1 200 m/min, the PVOH-modified formulation deposits 1.0–3.5 g/m² per side dry pickup. At higher pickup, sheet curl increases because the felt and wire sides dry unevenly across the after-drying cylinders; infrared profiling dryers are therefore positioned before the first heated can.

Quality verification uses ISO 535 Cobb₆₀ for water absorption and ISO 3783 for IGT pick resistance. On an 80 g/m² bleached kraft base, a C-500-containing size press formulation typically yields a Cobb₆₀ value of 20–30 g/m², compared with 30–45 g/m² for a starch-only control. IGT pick resistance shifts from <1.0 m/s to 1.8–2.5 m/s. Brightness retention is measured by ISO 2470; at a 2.0 part C-500 dosage, the brightness loss is less than 0.5 points because the resin ash content is low. Sized bases are converted into offset printing grades, high-speed inkjet papers, release liner base stock, and food-contact paperboard where the final coated sheet is assessed under EU 10/2011 for plastic materials in food contact.

What Prevents Weaving Efficiency Loss on High-Density Warp Lines?

On high-density weaving lines processing ring-spun cotton and polyester/cotton blends, GOHSENOL C-500 is introduced as a film-forming warp size to suppress yarn hairiness and improve abrasion resistance through the shedding zone. The size formulation is built around a C-500-to-modified starch ratio of 50:50 to 70:30 dry solids. C-500 constitutes 6–12 wt% of the total size liquor, and dry add-on is controlled at 10–15 % of warp yarn weight for plain-weave constructions above 70 ends/cm. The cooking sequence requires C-500 to be predispersed in a jet cooker at 90–95 °C for 30 min before starch addition. Adding dry C-500 directly to the size box causes lump retention on the slasher filter screens and uneven film thickness at the squeeze nip.

The slasher line is typically a multi-cylinder single-end sizing machine with a pre-wet box and a main size box. Size bath temperature is maintained at 85–95 °C, and circulation viscosity is held below 120 mPa·s. Squeeze nip pressure is set to 30–80 kN/m depending on yarn count and fiber blend. Cylinder drying temperatures must remain below 135 °C; higher surface temperatures discolour C-500 and reduce the flexibility of the deposited film. The dried warp leaves the front section at 6–8 % moisture and is separated into sheet sections ahead of the lease rods. On high-speed air-jet and rapier looms, the C-500 film reduces warp breakage per 100 000 picks from 2.5–4.0 to <1.0 on polyester/cotton shirting under identical loom speed and shed geometry.

Supply-chain compliance is documented under ZDHC MRSL v3.1 for the size formulation and OEKO-TEX Standard 100 for residual substances after desizing and bleaching. Desizing efficiency is checked by AATCC 79 absorbency; fully desized fabric should reach a wetting time below 5 s. The terminal fabric range includes high-density shirting, workwear poplin, denim warp beams, airbag base cloth, and industrial conveyor belt fabrics. The operational boundary for C-500 is cold-water removability. Because the grade is fully hydrolyzed, enzymatic or oxidative desizing at 60–85 °C is required instead of ambient wash-off, which would leave hard size residues and reduce downstream dye penetration.

Tape casting of borosilicate glass-ceramic and alumina powders for low-temperature co-fired ceramic substrates uses GOHSENOL C-500 when green-sheet tensile strength and lamination uniformity must be retained after doctor-blade forming. The binder is pre-dissolved in deionized water at 80 °C to a 10 % stock solution and introduced only after the ceramic powder has been dispersed in a water/isopropanol vehicle at 60:40 to 70:30 by volume. C-500 concentration is 1.5–3.5 wt% of dry ceramic powder. Plasticizer is added at 2.0–4.5 wt% on binder dry solids, commonly glycerol or polyethylene glycol 400, to prevent edge cracking after solvent evaporation. The slurry is milled in two stages using 3 mm yttria-stabilized zirconia media. In the first stage, ceramic powder and solvent are milled for 12–16 h with a dispersant. In the second stage, the C-500 stock solution is added at low tip speed and mixed for an additional 4–6 h. High-shear addition above 500 rpm causes air entrainment and localized binder precipitation at the slurry surface, which later appears as crater defects in the green tape.

The slurry is deaired under 50 kPa absolute pressure for 20–40 min and cast onto silicone-coated polyethylene terephthalate carrier film through a doctor blade gap of 100–300 µm. Drying is performed in a three-zone conveyor oven at 60–80 °C with laminar airflow to prevent skinning. Dry tape thickness is controlled from 50–200 µm. Binder burnout is validated by thermogravimetric analysis according to ASTM E1131-08, with plateaus at 350 °C and 550 °C. Because C-500 ash content is no greater than 0.5 %, the calculated inorganic residue from a 2.5 wt% binder dosage is below 0.01 wt% of the ceramic body. Green strength is evaluated by a 3-point bend test adapted from ISO 14704, with unfired tapes typically requiring failure stress above 1.2 MPa before lamination onto via-punched layers.

The cast green sheets are used for multilayer ceramic capacitor dielectric builds, LTCC radio-frequency substrates, ceramic filter blanks, and piezoelectric actuator layers. A production limitation is the low cold-water solubility of C-500. Cleaning of doctor blades, casting heads, and downstream tooling requires hot water above 70 °C; dried binder deposits released as hard particles during subsequent casting runs will produce surface defects in the sintered part.

Water-Soluble Release Film for Closed-Mold Composite Tooling

For closed-mold composite tooling where silicone contamination must be excluded, GOHSENOL C-500 is applied as a temporary release film on gel-coated molds. The release solution is prepared at 5.0–8.0 wt% PVOH, with 5–15 wt% polyethylene glycol 400 on PVOH solids as flexibilizer and 0.05–0.20 wt% of a silicone-free defoamer. Application is performed by low-pressure spray or short-nap roller onto a mold surface that has been pretreated with a sealing release wax. The wet film is deposited in two passes to reach 100–200 µm wet thickness, yielding a dry film of 20–50 µm. Drying takes place at 50–70 °C for 30–90 min depending on ambient relative humidity. The dried film is inspected for pinholes before laminate layup because defects in the PVOH barrier permit epoxy or unsaturated polyester resin contact with the tool surface, causing localized bonding and part release failure.

The cured composite is demolded by immersion or water-jet spraying at 60–80 °C under 0.2–0.5 MPa. The C-500 film dissolves in 5–15 min on closed contours and leaves no silicone residue on the composite or the tool. This is significant for subsequent adhesive bonding or painting, where silicone transfer reduces lap-shear strength. Compliance documentation for the release film references EU RoHS Directive 2011/65/EU where the final composite component enters regulated electrical and electronic equipment. The release film is a process consumable, not a finished article, and no food-contact status is claimed for this route. Terminal products include carbon fiber tubes, wind turbine blade spar caps, glass-reinforced polyester hulls, and compression-molded automotive components.

A processing boundary exists at low demolding temperatures. C-500 releases slowly below 50 °C, and ambient-water demolding is not recommended. For molds with significant undercuts, the film is built in three layers to prevent tearing during resin flow. Crosslinking should be avoided because borate or aldehyde treatment extends dissolution time beyond 30 min and can leave insoluble PVOH residues in sharp tooling radii.

When Remoistenable Coating Formulations Shift from Dextrin to Fully Hydrolyzed PVOH

Remoistenable adhesive converting for envelope flaps, labels, and stamps uses GOHSENOL C-500 as a high-strength replacement for dextrin when low dusting and rapid water activation are required after drying. The resin is dissolved at 20–35 % solids in a high-torque dissolver at 85–90 °C. In the finished adhesive, C-500 constitutes 40–70 wt% of dry adhesive solids. Plasticizer, normally glycerol or sorbitol, is added at 5–15 wt% on PVOH solids to reduce film embrittlement after drying. A wax or calcium stearate dispersion at 2–8 wt% on dry solids is incorporated to control blocking under high-humidity storage. The coating is applied by direct gravure or reverse roll to the envelope flap or label face at 20–35 g/m² wet film weight. Drying is conducted in a high-velocity air oven at 60–90 °C for 5–15 s, leaving a non-tacky dry adhesive that activates after 1–5 s of water contact.

Blocking resistance is evaluated at 40 °C and 80 % relative humidity for 24 h, with a pass criterion of no fiber tear when stacked coated blanks are separated. Remoistening adhesion is tested by a 180° peel method adapted from ASTM D3330 on coated paper under 20 s dwell after water application. Coated stock is considered acceptable when fiber tear exceeds 90 % of the bonded area. Where the finished adhesive may contact food-packaging board, the formulation is documented under US FDA 21 CFR 175.105. For European paper and board converters, the adhesive is supplied with a REACH compliance declaration under EC 1907/2006. Terminal products include lick-and-stick envelopes, stamp face paper, label facing stock, and pre-pasted wallcoverings.

The operational boundary for C-500 is storage humidity. Uncoated powder must be kept below 60 % RH and predried at 60 °C for 2 h if exposed to moisture, because free moisture changes dissolution time and may form lumps in the high-solids dissolver. Cold-water activation of the fully hydrolyzed grade is slower than that of partially hydrolyzed PVOH. Sorbitol can be used at 5–10 wt% on PVOH solids to improve activation, but sorbitol concentrations above 15 wt% reduce dried-film antiblocking performance and increase calender pickup on the converting line.