| HS Code | 431804 |
| Brand | Sekisui S-LEC |
| Product Name | S-LEC BL-8 |
| Product Type | Polyvinyl butyral (PVB) resin |
| Appearance | White powder |
| Specific Gravity | 1.08 |
| Bulk Density | 0.5 g/cm³ |
| Viscosity | 8 mPa·s (5% ethanol solution at 20°C) |
| Average Molecular Weight | 150,000 |
| Butyral Content | 70 mol% |
| Hydroxyl Content | 18 wt% |
| Acetate Content | 1 wt% |
| Glass Transition Temperature | 65°C |
| Decomposition Temperature | >250°C |
| Moisture Content | ≤0.3% |
| Solubility | Soluble in alcohols, ketones, and esters; insoluble in water |
| Refractive Index | 1.49 |
As an accredited S-LEC BL-8 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | S-LEC BL-8 polyvinyl butyral resin is supplied in 25 kg sealed moisture-protective bags. |
| Container Loading (20′ FCL) | S-LEC BL-8 is loaded as a 20′ FCL in sealed, moisture-proof bags, securely palletized to prevent damage during transit. |
| Shipping | S-LEC BL-8 is shipped as a free-flowing powder in sealed, moisture-proof bags or drums. Transport in dry, ventilated containers away from direct sunlight and high heat. It is not classified as dangerous goods, but standard dust precautions apply. Keep packages sealed to prevent moisture absorption. |
| Storage | Store S-LEC BL-8 in a cool, dry, well-ventilated area, away from direct sunlight, heat, and ignition sources. Keep the container tightly sealed to prevent moisture absorption, as the resin is hygroscopic. Avoid exposure to humidity and extreme temperatures. Use within the manufacturer’s recommended shelf life for best performance. |
| Shelf Life | S-LEC BL-8 is a polyvinyl butyral resin powder. Store sealed, cool, and dry; typical shelf life is 12 months from manufacture. |
In laminated safety glazing conversion, S-LEC BL-8 is processed as a high-viscosity PVB interlayer feedstock that is dried at 60–70°C until free moisture is below 0.35 wt%; residual moisture above 0.45 wt% at melt temperatures of 180–210°C accelerates hydrolytic chain scission and generates edge bubbles on the polished roll stack. The formulation at the extruder throat is set to 100 parts PVB, 25–40 parts triethylene glycol bis(2-ethylhexanoate) or a mixed ester plasticizer, 0.2–0.6 parts hindered phenol antioxidant, 0.1–0.3 parts UV absorber, and 0.05–0.15 parts magnesium stearate anti-block. Compounding uses a co-rotating twin-screw extruder with an L/D ratio of 32:1 to 36:1 and vacuum venting at -0.08 MPa, followed by slot-die extrusion onto chill rolls at 60–90°C and calender finishing to 0.38–1.52 mm sheet thickness with embossed de-airing channels. In the downstream laminating line, glass/interlayer/glass stacks are pre-pressed at 110–150°C under 0.3–0.5 MPa, then autoclaved at 130–140°C and 1.0–1.3 MPa for 60–120 minutes. Terminal products include automotive windscreens, architectural safety glazing, and burglar-resistant laminates. Compliance is governed by ISO 12543-2:2021 for interlayer durability, ECE R43 for automotive glazing, and ANSI Z97.1-2015 for human impact glazing. Amine-based silane coupling additives are excluded from the melt stream unless neutralised to pH 6–7; free amine accelerates plasticizer hydrolysis and raises autoclaved haze. The acceptance tests listed in Table 1 are used during production qualification.
| Property | Test method | Production acceptance window |
|---|---|---|
| Haze after lamination | ASTM D1003-13 | ≤1.0% |
| Tensile strength at break | ASTM D638-14 | ≥20 MPa |
| Elongation at break | ISO 527-3:2018 | ≥200% |
| Moisture after drying | ASTM D6869-17 | ≤0.35 wt% |
Tape casting of alumina, barium titanate, and low-temperature co-fired ceramic formulations uses S-LEC BL-8 as the primary non-aqueous binder when green strength after solvent evaporation must exceed 2.0 MPa for multilayer handling. The slurry is compounded from 100 parts ceramic powder, 4–12 parts PVB, 2–8 parts plasticizer such as dibutyl phthalate or benzyl butyl phthalate, 0.2–1.0 parts phosphate ester or fish oil dispersant, and 50–120 parts toluene/ethanol solvent blend at 60:40 to 80:20 ratio. Ball-mill dispersion proceeds at 60–80 rpm for 16–24 hours; slurry viscosity is adjusted to 1,500–5,000 mPa·s at 10 s⁻¹ for tape casting onto silicone-coated polyester carrier at 0.5–3.0 m/min. Drying reduces residual solvent below 1.0 wt% before multilayer alignment and lamination at 50–80°C under 10–30 MPa. Binder burnout in air or nitrogen follows a staged ramp of 0.5–2.0°C/min to 500–600°C with a 1–2 h hold; ramp rates above 2°C/min induce blistering and residual carbon above 0.05 wt%, which depresses dielectric breakdown strength in sintered layers. Terminal products include MLCC dielectric layers, LTCC substrates for RF modules, ceramic heaters, and oxygen sensor elements. Regulatory requirements include RoHS Directive 2011/65/EU Annex II for unrestricted terminal electronics, REACH Regulation EC 1907/2006 Article 33 for SVHC communication, and IEC 61249-2-21 for halogen-free substrate procurement when required. Clean room handling aligns with ISO 14644-1:2015 Class 8 for non-critical tape processing; classification requirements tighten to Class 6 for sub-10 µm dielectric thickness. Published data for BL-8-specific carbon residue under nitrogen atmospheres below 450°C is limited, and production-scale qualification with fast-fire profiles exceeding 30°C/min is required before volume release.
On degreased cold-rolled steel and 6061-T6 aluminium substrates, a solvent-borne wash primer based on S-LEC BL-8 functions as an acid-catalysed adhesion promoter that passivates and roughens the metal surface in a single 5–15 µm dry-film application. A production-scale mixing sequence combines 5–10 wt% PVB with 2–5 wt% phosphoric acid (85%), 0.5–2.0 wt% zinc phosphate or calcium zinc molybdate corrosion-inhibitive pigment, 0.2–0.5 wt% wetting agent, and 70–90 wt% solvent blend of MEK, ethanol, and n-butanol. The PVB is dissolved under high-shear at 5–10 m/s tip speed for 30–45 minutes at 20–25°C; acid and pigment are post-added under low-speed agitation to prevent local gelation. The primer is applied by HVLP spray at 0.3–0.5 MPa atomising air and force-dried for 5–10 minutes at 60–80°C before epoxy or polyurethane topcoating. Terminal products include structural steel edge protection, aircraft component prepaint treatments, and maintenance coatings for galvanised ductwork. Compliance is referenced to ASTM D1640/D1640M-14 for drying and recoating behaviour, ISO 2409:2020 for cross-cut adhesion class 0–1, and ISO 12944-2:2017 for atmospheric corrosivity classification. Amine-blocked epoxy topcoats must not be applied within the wet-on-wet recoat window because neutralisation at the interface reduces cross-link density and can lower salt-spray performance to below 500 h in ASTM B117-19 testing when skips occur. The acid catalyst and fast evaporating solvent require closed recirculation and LEL monitoring in spray booths; published data for direct replacement of Cr(VI)-containing wash primers with BL-8 vehicles is limited and requires notched-coating trials on pickled substrates.
High-speed gravure and flexographic printing for snack food packaging and shrink sleeves incorporates S-LEC BL-8 as a film-forming binder where alcohol solubility, residual solvent below 5 mg/m², and adhesion to corona-treated polyolefin are specified. Ink formulation uses 8–15 wt% PVB relative to total varnish solids and 3–7 wt% PVB relative to total finished ink mass, together with nitrocellulose or polyurethane co-resins, ketone/ester/alcohol solvent blends, and pigment dispersions. The PVB is pre-dissolved at 25–35% solids in ethanol/ethyl acetate 70:30 using closed dispersers at 800–1,200 rpm for 45–60 minutes. The letdown viscosity is adjusted to 18–24 s DIN 4 cup at 25°C for gravure cylinder engraving depths of 35–60 µm. Print speed ranges from 150–300 m/min with dryer temperatures of 60–90°C. Terminal products are reverse-printed BOPP/BOPET laminates, shrink sleeve labels, and aluminium foil lidding. Compliance includes EU Regulation EC 1935/2004 for food-contact materials when formulation components are listed, Swiss Ordinance SR 817.023.21 for printing inks, and REACH Regulation EC 1907/2006 Article 33 for SVHC disclosures. During lamination, re-dissolution from residual solvents is controlled by maintaining residual ethyl acetate below 5 mg/m²; rewetting fogging on reverse-printed webs appears above this threshold when stored at 40°C for 48 h. Published data for BL-8 in high-solids retort inks is limited, and retort resistance trials at 121°C for 30 minutes are required before product qualification.
Encapsulant sheets for thin-film photovoltaic modules use S-LEC BL-8 when edge sealing, laminate stiffness, and long-term adhesion to the glass cover are prioritised. The compound is prepared from 100 parts PVB, 20–35 parts triethylene glycol di-2-ethylhexanoate or mixed ester plasticizer, 0.1–0.5 parts UV absorber, 0.1–0.3 parts hindered amine light stabilizer, 0.05–0.2 parts antioxidant, and 0.1–0.4 parts adhesion control agent to regulate peel strength from glass. Sheet extrusion runs at 170–200°C with slot die and embossed chill rolls; sheet thickness is 0.38–0.76 mm. Vacuum lamination of glass/encapsulant/cell/backsheet stacks is performed at 140–160°C with a 3–5 minute vacuum step below 0.1 MPa and a 10–18 minute pressing step at 0.08–0.12 MPa. Process limitations arise from moisture: PVB sheet exposed to RH >60% requires pre-drying at 60–70°C for at least 4–6 hours because residual moisture above 0.35 wt% produces bubbles at cell edges. Terminal products are CdTe and a-Si thin-film modules, BIPV laminates, and concentrating photovoltaic cover assemblies. Compliance is based on IEC 61215:2021 for design qualification, IEC 61730-1:2016 and IEC 61730-2:2016 for safety qualification, and UL 1703 for flat-plate modules in North America. Amine-based adhesion promoters are avoided in this laminate stack because alkaline species accelerate PVB ester hydrolysis and lower post-damp-heat peel strength below acceptance values after 1,000 h at 85°C/85% RH per IEC 61215:2021. Published data for BL-8 in thin-film backrail edge seals is limited; production trials should include damp-heat adhesion retention and electroluminescence imaging after lamination.
Three-roll milling of silver, silver/palladium, and resistor pastes for hybrid microcircuits and chip resistor terminations uses S-LEC BL-8 as the primary organic vehicle resin because it provides pseudoplastic flow under squeegee shear and controlled solvent release during leveling and drying. The paste formulation includes 3–8 wt% PVB, 0.5–3.0 wt% ethyl cellulose co-binder, 0.5–2.0 wt% plasticizer, 0.2–1.0 wt% surfactant, and 15–25 wt% solvent combination of terpineol, butyl carbitol acetate, and diethylene glycol monoethyl ether. Dispersion continues on a three-roll mill until fineness of grind is below 10 µm; paste viscosity is adjusted to 30–80 Pa·s at 10 s⁻¹ for screen printing. Printing uses 230–400 mesh stainless steel screens with 20–50 µm emulsion thickness, squeegee speed 30–120 mm/s, and snap-off 0.3–0.8 mm. Drying at 100–150°C for 10–15 minutes removes solvent before firing at 550–850°C in air. The burnout of PVB between 250–450°C occurs before metal sintering; residual carbon from the binder must stay below 0.1 wt% to avoid solderability defects. Terminal products include thick-film hybrid circuits, chip resistor terminations, and ceramic sensor electrodes. Compliance for RoHS-directive assemblies references RoHS Directive 2011/65/EU Annex II, REACH Regulation EC 1907/2006, and J-STD-002D for solderability of component terminations. Production lines processing this vehicle on AlN substrates require a nitrogen atmosphere with dew point below -40°C during firing to prevent aluminium nitride oxidation; published data for BL-8-derived ash content in low-oxygen firing is limited and should be confirmed by thermogravimetric residue measurement for each paste lot.
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S-LEC BL-8 is a polyvinyl butyral resin supplied as a free-flowing powder for solvent-borne binder, coating, ceramic tape-casting, and film-forming formulations. The polymer is manufactured by acid-catalyzed acetalization of polyvinyl alcohol with n-butyraldehyde, resulting in a macromolecule containing residual hydroxyl groups, acetate groups, and cyclic butyral units. These three functional sites control solution viscosity, plasticizer uptake, hydrogen-bond density, and adhesion to siliceous, ceramic, and metallic substrates. Published data specific to S-LEC BL-8 are limited in open technical literature; for that reason, the processing limits and comparative values in this document are drawn from polyvinyl butyral resins of equivalent acetalization class and must be verified against the lot-specific certificate of analysis.
| Parameter | Method designation | Reporting unit |
|---|---|---|
| Viscosity number | ISO 1628-2 | cm³/g |
| Moisture content | Karl Fischer titration | wt% |
| Ash residue | ISO 3451-1 | wt% |
| Bulk density | ISO 60 | g/cm³ |
| Degree of acetalization | Infrared spectroscopy, butyral carbonyl band | mol% |
| Residual acetaldehyde | Headspace gas chromatography | µg/g |
Storage of S-LEC BL-8 requires moisture control. The powder should be kept below 30 °C and below 60% relative humidity in sealed containers. Moisture uptake above 0.5 wt% shifts hydroxyl-based stoichiometry in two-component coatings and can reduce acid-catalyst efficiency in wash primers. If the powder has been exposed to humid air for more than 24 h, pre-drying at 40–45 °C for 3–4 h is advised before use in anhydrous solvent systems.
The S-LEC BL series is arranged primarily by molecular weight and solution viscosity. In high-solids inks and wash primers, lower-numbered grades are selected where low solution viscosity at 15–20 wt% solids is necessary for coating transfer. S-LEC BL-8 is positioned for applications requiring higher cohesive film strength after solvent removal and improved holdout on porous substrates. The degree of acetalization is generally held within a narrow range for this resin class, commonly 78–82 mol%. Residual hydroxyl content is the stronger driver of hardness and crosslinkability: higher hydroxyl grades produce greater thermoset density with isocyanate, melamine, or phenolic crosslinkers, but they reduce solubility in hydrocarbon-rich solvent blends. A one-to-one replacement by weight between S-LEC BL-8 and another PVB grade does not preserve solution rheology; formulators should compare viscosity number, residual hydroxyl content, and moisture content from the certificate of analysis before substitution.
In industrial practice, the differentiation appears most clearly during letdown and final viscosity adjustment. A coating formulated with a lower-viscosity PVB grade may reach a final solids content of 20 wt% at 25 °C, while S-LEC BL-8 may require reduction to 15–18 wt% to remain below the same high-shear viscosity ceiling. This difference is not a performance defect; the higher molecular weight contributes to block resistance and mechanical integrity in printed films.
In ceramic green-sheet casting for multilayer ceramic capacitors and LTCC substrates, S-LEC BL-8 is dissolved in an ethanol/toluene or ethanol/ethyl acetate solvent blend and mixed with ceramic powder, dispersant, and plasticizer. A production line equipped with a comma-roll or doctor-blade coater applies the slurry to a polyester carrier at a wet-film thickness of 0.3–1.2 mm. The drying tunnel is divided into three zones operating at 50 °C, 70 °C, and 110 °C. The first zone removes surface solvent, the second zone minimizes upper-surface skinning, and the third zone reduces residual solvent below 1.0 wt%. Operating the second zone above 75 °C creates surface crusting that traps solvent and produces pinholes during binder burnout at 450 °C.
The critical process window in tape casting is plasticizer loading. When plasticizer exceeds 5 wt% relative to binder, the glass transition temperature falls below 40 °C, producing blocking in stacked sheets during warm pressing at 60 °C and 15 MPa. Below 1 wt% plasticizer, the green tape becomes brittle and develops edge cracks during slitting. Green tensile strength is normally evaluated at 2–4 MPa on cast strips using a method analogous to ISO 527-3. These boundaries define why solution viscosity stability and molecular weight are relevant when scaling S-LEC BL-8 from laboratory beaker slurries to continuous coaters.
When S-LEC BL-8 is solution-cast into PVB film for glass-lamination trials, the resin is dissolved in ethanol or an ethanol/2-propanol blend at 10–15 wt% solids. The solution is filtered through a 5 µm absolute cartridge and degassed under vacuum before coating. Slot-die coating on a silicone-coated release liner requires a viscosity of 80–120 mPa·s at 25 °C. Below this range, the wet film loses coatweight uniformity; above it, die-lip pressure rises and ribbing defects appear. The cast film is dried at 20–40 °C under low airflow, then post-dried at 60 °C until residual solvent falls below 0.3 wt%. Residual solvent above 0.5 wt% produces edge-cloud defects during autoclave lamination at 135 °C and 1.2 MPa.
Mechanical properties of solution-cast film are evaluated according to ISO 527-3. A plasticized PVB formulation containing 20 phr triethylene glycol bis(2-ethylhexanoate) typically yields tensile elongation at break of 200–300% and tensile strength of 20–28 MPa. These values apply to polyvinyl butyral of this acetalization range rather than uniquely to S-LEC BL-8 and should be confirmed against the grade-specific technical datasheet.
In anti-corrosion wash primers for steel and zinc-coated substrates, S-LEC BL-8 is combined with phosphoric acid, zinc phosphate or zinc chromate, and an alcohol diluent. The resin adheres to the metal oxide layer and carries the acid-pigment reaction. Acid concentration is controlled at 0.2–0.5 wt% of total formulation; higher levels hydrolyze the PVB during damp-heat aging at 85 °C and 85% relative humidity. Adhesion is tested by cross-cut according to ISO 2409 and pull-off according to ISO 4624. Pull-off values below 2 MPa after 500 h salt spray indicate premature interfacial failure. The formulation should not be combined with amine-based anticorrosion additives because amine–acid neutralization blocks formation of the phosphate conversion layer.
If a manufacturing process replaces polyvinyl alcohol with S-LEC BL-8 in aqueous ceramic slurries, solubility differences must be resolved before scale-up. S-LEC BL-8 does not dissolve in water; it requires an alcohol or ester co-solvent. A solvent blend of ethanol and methyl ethyl ketone in a 70:30 volume ratio is used in some tape-casting operations, but the ketone component limits the use of aqueous latex dispersants. Binder burnout also changes from polyvinyl alcohol’s multi-step oxidative decomposition to PVB’s cleaner decomposition between 300 °C and 500 °C. Thermogravimetric analysis according to ISO 11358 is required to establish the burnout plateau before sintering.
The shift to PVB alters slurry shear-thinning. On a cone-and-plate rheometer at 25 °C, the slurry should be pseudoplastic, with viscosity falling from 3–6 Pa·s at 1 s⁻¹ to 0.5–1.5 Pa·s at 100 s⁻¹. If low-shear viscosity exceeds 6 Pa·s, air entrainment during doctor-blade casting produces microvoids after burnout. The process window is therefore defined by the low-shear plateau, not only by high-shear coatweight.
For melt-compounded PVB sheet, S-LEC BL-8 powder is fed with plasticizer into a co-rotating twin-screw extruder having an L/D ratio of 40:1 and a barrel diameter of 25–40 mm. The feed zone is set at 100–120 °C, the mixing zone at 140–160 °C, and the die at 170–180 °C. Screw speed is controlled to 200–300 rpm to maintain melt temperature below 190 °C and limit thermal degradation. Volatiles are extracted through a vacuum vent; residual moisture in the powder above 0.5 wt% leads to die-lip foaming. The extruder should not be purged with polyamide or amine-containing compounds because residual amine reacts with acetal groups and increases yellowing.
Thermoset cure of S-LEC BL-8 with melamine-formaldehyde or blocked isocyanate proceeds through a two-stage condensation. At 120–140 °C, the acid catalyst first activates residual hydroxyl sites. The extent of cure can be followed by differential scanning calorimetry at a heating rate of 10 °C/min; a cure exotherm between 140 °C and 160 °C indicates the condensation reaction. With a sulfonic acid catalyst, pot life at 25 °C is usually 24–48 h, but above 35 °C it drops below 8 h. Continuous roll-coating operations therefore require temperature-controlled coating reservoirs when catalyzed material is recirculated.
For flexographic or gravure printing inks on corona-treated polyolefin film, S-LEC BL-8 is used as a co-binder to improve pigment wetting and adhesion. The resin is ground with pigment in a bead mill at 2000–4000 rpm, with mill-base temperature maintained below 45 °C to prevent solvent loss. Letdown resin is added after dispersion. The final ink should have a fineness of grind below 10 µm as measured by ASTM D1316. Coating weight is typically 1.0–2.5 g/m² for gravure printing on treated polyethylene terephthalate. If resin content exceeds 15 wt% of final ink solids, label blocking may occur at 50 °C and 80% relative humidity after 24 h.
| Obligation | Standard or regulation | Scope |
|---|---|---|
| Polymer migration | FDA 21 CFR 175.300 | Resinous and polymeric coatings |
| EU RoHS | 2011/65/EU and amendments | Homogeneous materials in electrical and electronic equipment |
| Chemical inventory | REACH registration | Manufacture and import within the European Union |
| Thermogravimetric analysis | ISO 11358 | Binder burnout onset and residue |
| Tensile testing | ISO 527-3 | Cast film elongation and strength |
| Adhesion testing | ISO 2409, ISO 4624 | Cross-cut and pull-off adhesion on coated metal |
Storage stability of S-LEC BL-8 depends on moisture control and amine-free atmosphere. Regulatory compliance is determined by the supplier’s REACH registration and by end-use migration testing where food-contact coatings are implied. Formulators must verify that the final film or coating meets FDA 21 CFR 175.300, RoHS Directive 2011/65/EU and subsequent amendments, and applicable regional food-contact regulations. S-LEC BL-8 should not be exposed to open air for extended periods in hot, humid environments because the free hydroxyl groups absorb atmospheric moisture, shifting the glass transition and reducing anhydride or isocyanate reaction efficiency in thermoset systems.
