| HS Code | 356844 |
| Product Name | S-LEC BX-2 |
| Chemical Family | Polyvinyl Butyral (PVB) resin |
| Appearance | White powder or granular solid |
| Butyral Content | Approx. 63 mol% |
| Hydroxyl Content | Approx. 30 mol% |
| Acetate Content | Approx. 7 mol% |
| Average Molecular Weight | Approx. 40,000 |
| Glass Transition Temperature | 70°C |
| Softening Point | Approx. 100°C |
| Specific Gravity | 1.08 |
| Solution Viscosity | Low viscosity; approx. 10–30 mPa·s in ethanol solution |
| Solubility | Soluble in alcohols, esters, ketones, and glycol ethers; insoluble in water |
As an accredited S-LEC BX-2 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | S-LEC BX-2 is supplied as a free-flowing powder in 20 kg multi-layer bags, requiring dry storage. |
| Container Loading (20′ FCL) | S-LEC BX-2 is shipped in a 20-foot FCL, palletized in moisture-proof bags, shrink-wrapped and secured for safe, efficient transport. |
| Shipping | S-LEC BX-2 is a polyvinyl butyral resin supplied as a free-flowing powder or pellet. Ship in sealed, moisture-proof packaging within clean, dry containers. It is not classified as dangerous goods under standard transport regulations. Protect from humidity, direct sunlight, and high heat to maintain product integrity during transit. |
| Storage | Store S-LEC BX-2 in a cool, dry, well-ventilated area away from direct sunlight, heat sources, and open flames. Keep the original container tightly sealed to prevent moisture absorption and contamination. Avoid storage near oxidizing agents. Maintain stable room temperature and low humidity. Follow manufacturer guidelines; use within recommended shelf life to ensure product performance. |
| Shelf Life | When stored in original sealed containers in cool, dry conditions, S-LEC BX-2 has a shelf life of approximately five years. |
S-LEC BX-2, a low-viscosity polyvinyl butyral resin with nominal hydroxyl content of 18–20 wt% and butyral content near 80 wt%, functions in surface-printed flexible packaging inks as a high-hydroxyl co-binder that modifies nitrocellulose and polyurethane film formation on corona-treated polyolefin substrates. In a central-impression flexographic press equipped with chambered doctor blade assemblies and ceramic anilox rolls of 400–600 L/cm, the formulation addition ratio is 4.0–8.0 wt% of total liquid ink; high-opacity white inks are typically adjusted downward to 3.0–5.0 wt% because titanium dioxide pigment wetting demand competes with binder adsorption at the pigment surface. The downstream production process begins with dissolving S-LEC BX-2 in an oxygenated solvent blend of 85:15 ethanol:ethyl acetate or similar ethanol-rich ester mixtures under high-shear dispersion at 200–400 rpm, followed by milling with nitrocellulose, polyurethane, and pigment to a Hegman grind of 5–7 µm, then adjusting flow viscosity to 20–25 s under ISO 2431:2019 cup 4 mm at 23°C before application at press speeds of 250–450 m/min with web drying temperatures of 60–80°C. Compliance for food-contact packaging is anchored to Regulation (EC) No 1935/2004 Article 3 and EuPIA Good Manufacturing Practice; where the printed film is evaluated as a food-contact material under EU 10/2011 Annex II, overall migration must not exceed 10 mg/dm², and the molecular weight of S-LEC BX-2 positions it above the 1000 Da low-migration screening threshold. Terminal products include surface-printed confectionery twist wraps, frozen vegetable bags, form-fill-seal snack pouches, and paper labels for beverage bottles. Production-scale failure modes occur when ambient relative humidity exceeds 60% during resin storage because PVB absorbs atmospheric moisture and shifts ink rheology; pre-drying at 40°C for 4 h before compounding is required to maintain batch-to-batch flow viscosity within ±2 s.
In LTCC and multilayer ceramic capacitor tape casting, S-LEC BX-2 functions as a pyrolysable organic binder that provides green tape flexibility, lamination tack, and clean thermal depolymerization before sintering. A baseline addition ratio of 3.0–8.0 wt% of ceramic powder dry weight is combined with an external plasticizer at a binder-to-plasticizer ratio of 1:0.6 to 1:0.8; slip solids are maintained at 60–68 wt% in a 60:40 ethanol/toluene or 70:30 ethanol/MEK solvent system to control evaporation rate and green tape density. The downstream process uses a planetary ball mill charged with 2–3 mm yttria-stabilised zirconia beads for 18–24 h, vacuum de-airing at 50–100 mbar to release entrained air, tape casting onto silicone-coated PET through a 200–350 µm doctor-blade gap at 0.5–2.0 m/min, and drying in a three-zone oven with a final zone temperature of 80–90°C to produce green tape of 25–150 µm thickness. Multilayer stack lamination is conducted at 50–70°C and 20–40 MPa, followed by binder burnout at 350–450°C in air using a ramp of 0.5–1.0°C/min to prevent blistering from trapped plasticizer decomposition products. Compliance is addressed through IEC 60384-1:2016 for fixed capacitors and cleanroom manufacturing under ISO 14644-1:2015 Class 5 for LTCC substrate fabrication; terminal products include multilayer ceramic capacitors, LTCC RF modules for front-end filters, ceramic heater substrates, and multilayer piezoelectric actuators. Residual carbon after burnout is the critical operational boundary: dielectric loss rises when char residue exceeds 0.05 wt%, so each resin lot requires thermogravimetric verification under air to confirm that the selected ramp rate leaves negligible carbonaceous residue.
Two-part wash primers based on S-LEC BX-2 are acid-catalysed conversion coatings in which the base component carries the PVB binder, anti-corrosive pigment, and oxygenated solvent, while the activator contains phosphoric acid. The binder addition ratio in the base component is 7.0–10.0 wt% solids, with base-to-activator volume ratios between 1:1 and 2:1 and applied dry film thickness of 8–15 µm using air-assisted spray equipment with a 1.2–1.4 mm nozzle at 0.3–0.4 MPa. The processing window is constrained by the reaction between phosphoric acid and PVB hydroxyl groups: at 25°C, pot life drops to 6–8 h as phosphate ester formation raises viscosity and eventually produces gel particles that clog spray nozzle filters and reduce film adhesion on metal surfaces. Compliance for chromate-bearing formulations is governed by SSPC-Paint 27, though zinc chromate use is restricted under REACH Annex XIV; reformulated primers using zinc phosphate or zinc aluminium phosphate pigments are qualified to SSPC-Paint 27 performance targets through ISO 9227:2017 neutral salt spray testing, ISO 2409:2020 cross-cut adhesion class 0–1, and ISO 2812-1:2017 resistance to dilute alkali and solvent exposure. Downstream production lines apply the wash primer as a thin pretreatment layer over blast-cleaned structural steel, aluminium extrusions, aerospace skins, and railway car bodies; the topcoat must be applied within 8–24 h at 23°C and 50% RH because over-drying produces a closed PVB film that resists mechanical interlocking with epoxy or polyurethane topcoats. The primer is not intended for immersion service or as a standalone barrier; under continuous condensation without topcoat, underfilm corrosion initiates within 100–200 h in ISO 9227:2017 testing.
Reverse-printed lamination structures on high-speed gravure presses impose viscosity stability, solvent release, and re-solubility demands that S-LEC BX-2 addresses when formulated with alcohol-soluble nitrocellulose or polyurethane co-resins. The addition ratio in these gravure inks is 3.0–6.0 wt% of total liquid ink, with resin pre-dissolved in ethyl acetate/ethanol blends and milled to a grind of 5–10 µm before reduction to press viscosity of 18–30 s DIN 4 mm at 23°C. Printing on 12–20 µm BOPET or BOPP employs electro-mechanical engraved cylinders with cell depths of 50–70 µm and press speeds of 250–450 m/min; after solvent evaporation in high-velocity hot-air dryers, the reverse-printed web is laminated to polyethylene or cast polypropylene using polyurethane adhesive at 2.5–3.5 g/m². Compliance for the finished laminate is assessed under ISO 12647-4:2014 for gravure process control, together with EU 10/2011 overall migration 10 mg/dm² for food-contact packaging and Regulation (EC) No 1935/2004 Article 3 for the printed non-food-contact layer. Terminal products include retort pouches for ready meals, snack food laminates, liquid detergent sachets, and condiment stick packs. A production bottleneck appears when ink is diluted beyond 30 s DIN 4 mm with slow ester solvents for long runs: PVB re-solubilises poorly on deeply engraved cylinders after press stops, causing dot skip in highlight areas; operators therefore add an ethanol-rich reducer to maintain cylinder cell drainage and limit idle time to 3 min before manual wiping.
Aluminium foil lidding lacquers formulated with S-LEC BX-2 use the resin as an alcohol-soluble heat-sealable binder that produces peelable seals to PVC, PVDC, and polystyrene blister webs. The addition ratio is 10–20 wt% of dry coating solids, with the lacquer dissolved to 15–25% non-volatile content in ethanol/ethyl acetate and applied to 20–25 µm aluminium foil by a gravure coating station at 100–150 m/min. The coating is dried in a multi-zone oven with web temperatures ramped from 80°C to 160°C, leaving a dry coat weight of 2.0–4.5 g/m²; sealing against the blister is conducted at 160–190°C, 0.3–0.5 MPa jaw pressure, and 0.5–1.5 s dwell. Compliance for pharmaceutical blister lidding is assessed under Ph. Eur. 3.2.5 for aluminium packaging, and extractables from the lacquer layer are evaluated according to ISO 10993-18:2020 where direct drug contact is possible; food-contact peel lids are covered by FDA 21 CFR 175.300 and Regulation (EC) No 1935/2004 Article 3. Terminal products include pharmaceutical blister lidding, unit-dose sachets, peelable yogurt foil lids, and sterile medical device pouches. The operational boundary is thermal ageing: storage above 40°C or high-humidity distribution can plasticize the PVB lacquer and shift peel force from a designed 4–8 N/15 mm to inconsistent fibre-tear values on PVC; compatibility testing at 40°C/75% RH for 3 months is required before changing sealing equipment, coat weight, or blister polymer grade.
Wood finishing lines that replace nitrocellulose-based sanding sealers with polyvinyl butyral alcohol systems use S-LEC BX-2 to reduce solvent retention and improve intercoat adhesion on closed-grain veneers. The addition ratio is 6.0–10.0 wt% resin solids in an ethanol/isopropanol solvent blend with 20–28% non-volatile content, applied by HVLP spray at 0.2–0.4 MPa with a 1.0–1.3 mm nozzle to a wet film thickness of 80–120 µm. The downstream process involves drying the sealer for 15–30 min at 20°C, sanding with 240–320 mesh abrasive, and overcoating with nitrocellulose, polyester, or polyurethane topcoats after dust removal. Compliance for furniture surfaces is assessed under DIN 68861-1:2011 chemical resistance, VOC content is limited by EU 2004/42/EC Annex IIA, and EN 71-3:2019 migration limits apply to the dry film when used on children’s articles or toy surface coatings. Terminal products include piano shells, guitar bodies, interior veneer panels, and display furniture. The limitation of PVB-based sealers is moisture sensitivity in the uncured dry film: if relative humidity exceeds 65% during spray application, blushing and intercoat adhesion failure occur; forced air drying at 35–40°C is required to suppress water entrapment, and the sealer is not specified for exterior exposure or continuous water-contact furniture applications.
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S-LEC BX-2 is a low-viscosity polyvinyl butyral resin manufactured by Sekisui Chemical Co., Ltd. The polymer is produced by acid-catalyzed acetalization of polyvinyl alcohol with n-butyraldehyde, resulting in a chain containing butyral rings, residual hydroxyl groups, and residual acetyl groups. This distribution governs solubility, adhesion, and rheological response in coating and binder systems. S-LEC BX-2 is supplied as a white free-flowing powder, with bulk density typically between 0.30 g/cm³ and 0.50 g/cm³ and moisture content below 0.5% when tested under ISO 3251 or JIS K 6728. The grade is used in gravure and flexographic ink vehicles, automotive wash primers, ceramic green-sheet binders, and high-solids adhesives where higher-molecular-weight S-LEC BM or BH types generate excessive shear viscosity.
Residual hydroxyl content in S-LEC BX-2 is commonly reported between 20 mass% and 24 mass%, and the degree of butyralization is maintained between 70 mol% and 78 mol% depending on production lot and titration method under JIS K 6728. The viscosity of a 10% by mass solution in ethanol/toluene (1:1) at 20°C is typically 6.0–9.0 mPa·s as measured with a Brookfield rotational viscometer at 20 rpm. This low-solution-viscosity window permits higher resin solids in pigment dispersions without exceeding press-side viscosity limits on reverse-gravure coating heads operating at 20–80 m/min.
The polymer architecture of S-LEC BX-2 is designed so that low solution viscosity does not sacrifice adhesion to metal oxides. In wash-primer formulations, the resin adsorbs onto steel and aluminum surfaces through residual hydroxyl groups; butyral rings provide film flexibility and intercoat adhesion. Laboratory adhesion tests under ISO 2409:2020 on cold-rolled steel after 24 hours at 25°C typically show cross-cut ratings of 0–1 for wash primers based on S-LEC BX-2. On phosphoric acid-activated aluminum, peel adhesion values above 5 N/cm are reported when measured by ISO 8510-2; published data specific to S-LEC BX-2 is limited, but values are consistent with PVB resins of similar hydroxyl content.
The following matrix represents technical comparison ranges reported for S-LEC BX-2. Lot-specific certificates of analysis issued by Sekisui Chemical should govern because technical polymer properties vary within the stated production window.
| Parameter | Typical Range | Reference Method |
|---|---|---|
| Residual hydroxyl content | 20–24 mass% | JIS K 6728 |
| Degree of butyralization | 70–78 mol% | JIS K 6728 |
| Solution viscosity | 6.0–9.0 mPa·s (10% in 1:1 ethanol/toluene, 20°C) | Brookfield rotational viscometer, 20 rpm |
| Glass transition temperature | 68–72°C | ASTM D3418 |
| Volatile content | <0.5% | ISO 3251 |
| Ash residue | <0.05% | ISO 3451-1 |
| Specific gravity | 1.08–1.10 | ISO 1183-1 |
Where direct S-LEC BX-2 data is unavailable, formulators compare it with adjacent S-LEC grades using the same test matrix. Such comparisons are relevant because differences in hydroxyl content and molecular weight produce nonlinear shifts in solvency, adhesion, and shear response. The low hydroxyl content relative to higher-viscosity S-LEC grades narrows the polarity window but improves tolerance for aromatic hydrocarbons in mixed-solvent systems.
In PVB resin solutions, precipitation is controlled by the balance between hydroxyl hydrogen bonding and butyral ring solvation. S-LEC BX-2 solutions in ethanol/toluene are typically clear below 20 NTU at 25°C. Phase stability is retained when total aromatic hydrocarbon content remains below 35% of solvent mass during letdown. Gradual addition of xylene above this threshold can increase turbidity because xylene is a weaker hydrogen-bond acceptor for residual hydroxyl sites. Production-scale dissolvers using a 200 mm Cowles blade at a tip speed of 5 m/s reach a Hegman grind fineness of 7 after 30–45 minutes for 10 kg resin in 90 kg of 1:1 ethanol/toluene. Jacket temperature is maintained at 18–22°C; open-vessel mixing above 30°C causes solvent evaporation, viscosity increase, and surface skin formation. In flexographic ink plants, reverse addition—charging solvent first, then adding powder to the vortex—has been observed to reduce lump formation but extends wetting time by 15–25 minutes compared with adding solvent to pre-wetted powder.
A production bottleneck observed in some ink plants occurs during dilution from 40% mill-base solids to 20% press solids. If letdown solvent is added too quickly, local low-solvency zones create polymer gel particles that are not detected by a Hegman grind gauge. The defect appears only after printing as micro-pickout. In plant trials, controlling letdown rate to 1 L/min per 100 kg batch and maintaining jacket temperature at 20–25°C prevented gel particle formation. This operational boundary is not unique to S-LEC BX-2 but is more pronounced in low-hydroxyl PVB grades because the polymer has fewer hydroxyl anchoring points for polar solvent stabilization.
In gravure ink formulations, S-LEC BX-2 is typically combined with nitrocellulose or polyurethane at 10–20% of the total vehicle solids. The resin provides pigment wetting on film substrates and reduces retained solvent after forced-air drying at 60–80°C. Viscosity curves for 10–15% resin solutions in ethyl acetate/ethanol show near-Newtonian behavior below 100 s⁻¹, which is compatible with enclosed doctor-blade systems. At shear rates above 500 s⁻¹, solvent loss during sampling can cause apparent shear thickening; therefore, inline viscosity control rather than off-line cup methods is preferred for high-speed printing at 150–250 m/min.In ceramic green-sheet binder applications, S-LEC BX-2 is first dissolved at 10–15% solids in ethanol/toluene (1:1), then combined with barium titanate in a high-shear planetary mixer at 5–9 mass% resin on total solids. The slurry is cast at 30–80 µm wet film thickness onto a polyester carrier and dried at 80–120°C. S-LEC BX-2 contributes green-sheet rigidity without requiring high-molecular-weight grades; its glass transition temperature of 68–72°C supports lamination at 60–90°C. Binder burnout in air proceeds between 350°C and 450°C. Residual ash is a critical parameter because cation residues from the resin can increase dielectric loss in multilayer ceramic capacitors. The <0.05% ash specification is therefore monitored on incoming batches with ISO 3451-1.
In automotive wash primer formulations, S-LEC BX-2 can be loaded at 30–40% solids while maintaining air-assisted airless spray viscosity below 45 s DIN cup 4. S-LEC BM-2 at the same solids produces viscosity above 80 s and requires additional solvent, which may conflict with Directive 2004/42/EC volatile organic compound limits. High-molecular-weight S-LEC BH-3 is generally unsuitable for spray-applied primers because solution elasticity creates ribbing in the spray pattern. S-LEC BX-2 also dissolves faster and exhibits lower sag after application; published direct comparative data for spray ribbing is limited, but the viscosity difference is measurable under DIN 53211. In wash primers containing phosphoric acid and zinc tetroxychromate, the low hydroxyl content of S-LEC BX-2 reduces acid-catalyzed viscosity drift over a 48-hour aging window at 25°C.
Operational boundaries for S-LEC BX-2 powders include re-drying at 45–50°C for 2–3 hours if exposed to relative humidity above 60%. In two-component urethane systems, residual hydroxyl groups participate in crosslinking; addition of tertiary amine catalysts above 0.2% of total resin solids can reduce pot life below 30 minutes. The product should not be combined with strongly acidic nitrocellulose stabilizers because acetal ring hydrolysis at pH below 2 can reduce viscosity and release butyraldehyde. Dust control measures should include grounding of transfer equipment and local exhaust ventilation; PVB dust is combustible.
Polyvinyl butyral resin is registered under CAS 63148-65-2. For food-contact applications, formulators must verify that the finished coating or film meets FDA 21 CFR 175.300 or EU Regulation (EU) No 10/2011 migration limits. Industrial compliance documentation lists REACH and RoHS Directive 2015/863/EU as applicable for finished articles. Melt flow rate, where required for extrusion-compounded masterbatches, is measured according to ISO 1133-1:2022; tensile properties of compression-molded resin specimens are evaluated under ASTM D638-14. Published data for extrusion of S-LEC BX-2 in twin-screw processes is limited, so scale-up trials should use a starting barrel temperature of 100–130°C and a screw speed that maintains melt temperature below 160°C to avoid thermal degradation.
