| HS Code | 628296 |
| Manufacturer | Sekisui Chemical Co., Ltd. |
| Product Name | S-LEC BL-2 |
| Product Type | Polyvinyl butyral (PVB) interlayer film for laminated glass |
| Thickness | 0.76 mm (typical) |
| Width | Up to 2600 mm |
| Length | 100 m per roll (typical) |
| Tensile Strength | ≥ 20 MPa |
| Elongation At Break | ≥ 200% |
| Haze | ≤ 1.0% |
| Luminous Transmittance | ≥ 88% |
| Uv Cutoff Wavelength | ≤ 380 nm |
| Density | 1.07 g/cm³ |
| Refractive Index | 1.48 |
As an accredited S-LEC BL-2 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | S-LEC BL-2 is supplied in 25 kg net polyethylene-lined paper bags, ensuring dry, protected storage for handling. |
| Container Loading (20′ FCL) | S-LEC BL-2 loaded as 20′ FCL, palletized bags secured, container stuffed to maximize capacity while ensuring safe transport. |
| Shipping | S-LEC BL-2 is supplied as free-flowing granules in sealed, moisture-resistant packaging. Ship in dry containers, protected from rain, humidity, and direct sunlight. Avoid excessive heat and ignition sources. Not regulated as dangerous goods under standard transport conditions, but minimize dust during handling. Keep packaging intact to prevent contamination and ensure safe delivery. |
| Storage | Store S-LEC BL-2 in its original sealed container in a cool, dry, well-ventilated area, away from direct sunlight, heat sources, and open flames. Protect from moisture and humidity, as it may affect performance. Keep containers tightly closed when not in use and follow safe handling practices to prevent contamination. |
| Shelf Life | S-LEC BL-2 has a shelf life of 24 months when stored sealed, cool, and dry in original container. |
Dispersion of S-LEC BL-2 in an azeotropic methyl ethyl ketone/ethanol solvent at 15–20 wt% resin solids is the starting point for tape-casting binders used in alumina and barium titanate multilayer ceramic capacitors. Incoming resin moisture is controlled by Karl Fischer titration according to ISO 15512; values above 0.5 wt% increase solution haze and reduce slurry viscosity by more than 15%. The resin is dissolved under low-shear mixing until a clear solution of <100 mPa·s at 25 °C is obtained, then ceramic powder is added incrementally with a high-shear disperser equipped with a dissolver disc at 15 m/s peripheral speed. Slurry solids are held at 68–75 wt% for nonconductive layers; rheological flow curves measured by cone-and-plate viscometry under ISO 3219 confirm pseudoplastic behaviour with a Casson yield stress below 20 Pa, while doctor-blade gap settings of 150–250 μm on a polyethylene terephthalate carrier film produce dried green tape in the 40–80 μm thickness band after transit through a three-zone dryer with zone temperatures of 40 °C, 60 °C and 80 °C. A typical burnout schedule raises the laminate at 0.5 °C/min to 450 °C and holds for 2 h under flowing air; residual carbon content after burnout must remain below 0.1 wt% by thermogravimetric analysis according to ASTM E1131. Green density after lamination at 70–85 °C and 20–35 MPa for 10 min is measured by mercury porosimetry; laminated tape should reach 55–60% of theoretical density before cosintering. Published manufacturer data for this specific S-LEC BL-2 grade in cofired copper electrode systems indicates reduced residual carbon relative to higher-molecular-weight PVB, but furnace atmosphere and gas flow must be validated on each production line because redox control at 450 °C directly governs copper oxidation and end-termination adhesion.
In two-component wash primers, S-LEC BL-2 is supplied as a 10–15 wt% base component in a mixed solvent of methyl isobutyl ketone and n-butanol. The base component is filtered through a 60 μm bag filter before acid mixing, and spray application viscosity is adjusted to 18–22 s in a DIN 4 cup at 25 °C. The acid component, typically a 10% phosphoric acid solution in isopropanol and water, is mixed 30–60 min before spray application. The hydroxyl groups remaining on the PVB chain participate in room-temperature phosphate ester formation with the substrate; adhesion to blasted carbon steel and hot-dip galvanized surfaces is evaluated by ISO 2409 cross-cut, requiring classification 0 or 1 before topcoating. Salt spray resistance of a 10 μm dry film under a 40 μm epoxy primer is tested according to ISO 9227; scribe creep should not exceed 2.5 mm after 500 h. Zinc-rich or zinc chromate alternatives depend on the PVB binder to suspend pigment and control sagging; anti-settling index measured by ASTM D869 after 7 days at 50 °C should remain below 2. The main processing boundary is the acid/base pot life, which shortens below 4 h at room temperature when the phosphoric acid content exceeds 12% of total nonvolatile volume; gelling occurs through acetal ring opening and crosslinking via metal-organic phosphate bridges. Spray equipment using pressure pots with continuous agitation and stainless-steel nozzles rated for pH < 2 is specified.
S-LEC BL-2 serves as the primary film-forming binder in solvent-based flexographic and gravure inks for corona-treated low-density polyethylene and oriented polypropylene. Ink viscosity at press is adjusted to 22–28 s with a Zahn cup 2 at 25 °C. Typical letdown formulations contain 8–12 wt% resin, 15–20 wt% pigment, 5–8 wt% nitrocellulose and 50–60 wt% ethyl acetate/n-propanol; the PVB resin contributes pigment wetting and re-solubility on press. Corona-treated LDPE surface energy should be at least 38 mN/m measured by DIN 53364. Printability trials on an 8-colour central-impression flexographic press at 120 m/min show that blocking resistance measured by ASTM D4946 at 50 °C and 35 kPa reaches a rating of 4 or higher after 24 h. Bond strength of extrusion lamination adhesive to the printed surface is assessed by ASTM F904; values above 1.5 N/15 mm are required for snack packaging. The main limitation is high retention of n-propanol in thick ink films, which shifts the coefficient of friction; gas chromatography headspace by ISO 11890-3 should confirm total residual solvent below 5 mg/m² after drying at 60 °C in the final oven zone. Published data for this specific configuration is limited for water-based inks, where PVB solubility decreases and pH must be maintained above 8.0 with ammonia.
Aluminium foil coatings based on S-LEC BL-2 are applied with gravure cylinders at 2–4 g/m² dry coat weight and dried at 120–140 °C for 5–8 s. The resin is blended with plasticizers such as dibutyl sebacate or polymeric adipate at 5–15 phr to adjust hot-tack and seal initiation temperature. Hot-tack force is measured by ASTM F1921; a minimum of 3 N/25 mm after 0.2 s cooling at a 130 °C seal bar is considered production-ready for high-speed vertical form-fill-seal lines. Retort resistance at 121 °C for 30 min in a counter-pressure autoclave is evaluated by visual whitening, peel strength and migration. For direct food contact, the dry coating must comply with European Plastics Regulation (EU) No 10/2011, Annex I, with an overall migration limit of 10 mg/dm² using 3% acetic acid and 10% ethanol simulants according to EN 1186-1. The resin’s hydroxyl functionality also provides adhesion to aluminium without a separate primer; dry bond strength measured by ASTM D903 T-peel should exceed 2.0 N/15 mm before and after retort. Coefficient of friction of the coated side should remain below 0.35 according to ASTM D1894 to maintain bag feed reliability. A limitation arises when coating weight exceeds 6 g/m²: retained solvent in the sealed seam produces odour defects above sensory threshold, so a post-printing conditioning tunnel maintaining 40 °C and 40% RH for 48 h is used.
PVB-phenolic structural adhesive films are formulated with S-LEC BL-2 as the thermoplastic toughening component in a thermosetting resole matrix at 15–35 wt% of total resin solids. The blend is coated from methyl ethyl ketone onto release paper and B-staged at 90–100 °C until residual volatiles are below 1.5%. Lamination of aluminium skins to aramid honeycomb core uses cure cycles of 0.6 MPa at 150 °C for 60 min in an autoclave. Lap shear strength of bonded 2024-T3 aluminium adherends after phosphoric acid anodising is tested by ASTM D1002; typical values range from 20 to 28 MPa at room temperature. The PVB component contributes peel toughness; floating roller peel strength by ASTM D1781 improves from 35 N/25 mm to 60 N/25 mm when the PVB content is increased from 15 to 30 phr, but the upper limit is set by a co-cure viscosity drop below 60 Pa·s at 120 °C measured by a cone-and-plate rheometer, causing honeycomb core strike-in. The ratio is therefore capped at 35 phr unless a flow-control silica addition of 2–4 wt% is used.
Powder injection molding feedstock based on 17-4PH stainless steel or zirconia with 6–8 vol% S-LEC BL-2 as a backbone binder component is compounded on a co-rotating twin-screw extruder with L/D 40 at 130–150 °C. Feedstock viscosity at 150 °C and 1000 s⁻¹ through a capillary rheometer should be 80–150 Pa·s for consistent mould filling. The PVB backbone is first removed in a solvent debinding step using acetone at 40 °C; 85–90% of the backbone is removed before thermal debinding. Thermogravimetric analysis by ISO 11358 under nitrogen at 10 °C/min establishes a decomposition onset near 230 °C and complete volatilisation by 500 °C; the furnace schedule holds at 350 °C for 2 h to avoid internal pressure defects in sections above 10 mm. Carbon residue after debinding before sintering must be below 0.2 wt% by LECO carbon analysis; this is the principal acceptance criterion for aerospace-grade metal parts. A problem observed on production lines is that insufficient solvent debinding — less than 70% removal — leads to blistering during thermal debinding when heating rate exceeds 2 °C/min. Feedstocks with S-LEC BL-2 are therefore processed with two-stage debinding and an upper heating rate limit of 1.5 °C/min between 200 °C and 450 °C.
Glass frit seal paste for low-temperature cofired ceramics is prepared by dissolving S-LEC BL-2 at 8 wt% in terpineol and adjusting the paste to 25 Pa·s on a three-roll mill; published data for this specific configuration is limited beyond the preceding tape-casting context.
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S-LEC BL-2 is a polyvinyl butyral (PVB) resin supplied under the S-LEC B series by Sekisui Chemical. It is manufactured by acetalization of polyvinyl alcohol with n-butyraldehyde and is supplied as a white free-flowing powder. The grade is used as a temporary organic binder in ceramic green-sheet processing, solvent-borne flexographic and gravure inks, and adhesion-promoting primer systems where lower solution viscosity is required. Representative technical data place the hydroxyl group content in the 20–24 mol% range, the acetyl group content below 3 mol%, and the butyral group content in the 72–76 mol% range when determined by the supplier’s PVB-specific titration method referenced to JIS K 6729:1995. In a 10 wt% solution of 1:1 ethanol/toluene at 20 °C, the dynamic viscosity is reported in the 20–40 mPa·s band using a rotational viscometer under ISO 2555. The resin is supplied without external plasticizer; film formation after solvent evaporation is controlled by the residual hydroxyl population and the resulting hydrogen-bonding density. These values are representative technical data and are not a substitute for a lot-specific certificate of analysis, because the hydroxyl interval directly shifts solution viscosity and final adhesion at the process endpoints.
On production equipment, the low solution viscosity permits high-solids ceramic slurries without exceeding the tape-casting window. A 200 L high-shear dissolver fitted with a 350 mm diameter disperser blade operating at 8–12 m/s tip speed can incorporate the resin into methyl ethyl ketone/ethanol blends within 45–60 min at 25 °C when the powder is added slowly under low agitation. Moisture pickup above 0.5 wt% causes lump formation and local viscosity spikes; therefore, the powder is pre-dried at 40 °C for 4 h in a desiccant dryer before use in environments above 60% RH.
Incoming inspection for S-LEC BL-2 should focus on hydroxyl content, acetyl content, solution viscosity, moisture, and ash. Hydroxyl content is the primary lot-selection parameter because it governs solubility in alcohol/aromatic diluent blends and controls hydrogen-bonding density. A hydroxyl deviation of ±1 mol% can shift the time to reach a transparent solution by 20–40 min on a 200 L dissolver and can alter flexographic ink transfer by changing the resin’s interaction with cellulosic and ceramic substrates. Acetyl content acts as a second control point because it reduces crystallinity and moisture affinity; a higher acetyl value within the allowed range improves solubility in weaker hydrogen-bonding solvents, while a lower value tends to improve thermal burnout residue in ceramic applications. The following table summarizes the representative specification profile published in technical data sheets.
| Property | Representative range or limit | Test basis |
|---|---|---|
| Volatile content | ≤2.0 wt% | JIS K 6729:1995, loss on drying at 105 °C for 3 h |
| Hydroxyl group | 20–24 mol% | JIS K 6729:1995 |
| Acetyl group | ≤3 mol% | JIS K 6729:1995 |
| Butyral group | 72–76 mol% | JIS K 6729:1995 |
| Solution viscosity | 20–40 mPa·s at 10 wt% in 1:1 ethanol/toluene | ISO 2555 |
| Glass transition temperature | 55–65 °C | ISO 11357-2:2020, DSC at 10 K/min |
| Ash content | ≤0.05 wt% | ISO 3451-1:2019 |
| Density | 1.10–1.12 g/cm³ | ISO 1183-1:2019 |
| Bulk density | 0.25–0.45 g/cm³ | ISO 60 |
Moisture content is not only an incoming property but also a process variable. In a gravure ink plant, powder stored in open totes at 70% RH and 25 °C can reach 0.5 wt% moisture within 24 h. A moisture level above the specification limit depresses dissolution rate and can produce microgels that remain visible as fisheye defects in drawdown films. Pre-drying is therefore integrated into the feed sequence rather than treated as an optional step. Glass transition data are used for primer formulations because a Tg near 60 °C limits blocking at ambient temperatures while allowing heat-assisted lamination.
In multilayer ceramic capacitor tape casting, S-LEC BL-2 is used as a sacrificial organic binder. The grade is selected over higher-molecular-weight BM and BX products when slurry solids must remain above 50 wt% without exceeding the viscosity limits of a slot-die or doctor-blade coater. A typical production slurry contains 45–55 wt% BaTiO₃, 3–5 wt% S-LEC BL-2, 0.5–1.5 wt% dioctyl phthalate or benzyl butyl phthalate, and 0.1–0.3 wt% phosphate ester dispersant, with the balance as methyl ethyl ketone/ethanol. The slurry is dispersed in a bead mill with 0.4–0.6 mm yttria-stabilized zirconia media for 6–12 h, de-aerated at −80 kPa, and cast at 0.3–1.0 m/min with a doctor blade gap of 100–400 µm. The target slurry viscosity is typically 1.2–2.0 Pa·s at 50 s⁻¹; higher viscosity reduces leveling and creates thickness variation across the web.
Thermogravimetric analysis in air at 10 K/min under ISO 11358-1:2022 shows the main decomposition event between 250 °C and 450 °C, with residual ash at 550 °C typically below 0.05 wt%. The furnace profile used for binder burnout is staged at 0.5–1.0 K/min from 250 °C to 450 °C to prevent carbonaceous residue from the acetyl and butyral side groups from forming conductive pathways in sintered BaTiO₃. Ramp rates above 2 K/min can generate localized overpressure at the tape centre and produce delamination blisters or edge curl before densification. Published thermogravimetric data for the exact grade in all solvent blends is limited; the burnout profile should be confirmed by DSC/TGA on each lot and adjusted for the solvent system and ceramic loading.
Compared with ethylcellulose binders used in some ceramic formulations, S-LEC BL-2 generally leaves lower ash because the PVB backbone is not derived from a mineral-containing raw stock. However, ethylcellulose can offer longer open time in high-humidity cleanrooms, so substitution must be evaluated against drying kinetics and green-tape flexibility rather than ash alone. The S-LEC BL-2 grade is also used in printed silver paste and dielectric paste applications where the resin must dissolve in terpineol or mixed ester/alcohol solvents and then burn out cleanly during sintering.
S-LEC BL-2 occupies the low-viscosity end of the S-LEC B resin ladder. The BX series carries higher molecular mass and is used where film toughness and glass adhesion dominate; the BM series is intermediate. In identical 10 wt% solutions, a BL-2 lot at the mid-specification viscosity of 30 mPa·s can be an order of magnitude lower than a BM-2 lot and two orders lower than a BX-2 lot; this ratio changes with shear rate because high-molecular-weight PVB is shear-thinning. The viscosity gap permits BL-2 to be formulated at 10–15 wt% in flexographic ink without exceeding press viscosity limits of 25–50 mPa·s at 20 °C, while BX-2 at equivalent solids can exceed 200 mPa·s. Exact comparative ratios vary with solvent, hydroxyl content, and shear history; published data for this specific configuration is limited.
The trade-off is adhesion and film strength. Lower molecular weight and controlled hydroxyl content reduce ultimate peel strength on glass relative to BX grades. For laminated glass interlayers requiring ISO 12543 adhesion performance, plasticized S-LEC Film grades are used rather than the unplasticized BL resin. BL-2 is not specified for laminated glass interlayer applications. Where a plasticizer-free coating requires higher glass adhesion, BM or BX grades are selected, often in combination with silane coupling agents applied as a separate primer.
S-LEC BL-2 differs from S-LEC Film products in physical form and function. S-LEC Film grades are extruded plasticized polyvinyl butyral sheet with adhesion-control salts and defined edge geometry for architectural and automotive safety glass. BL-2 is a powder resin for solution processing, ceramic binder systems, and ink vehicles. The difference is not simply molecular weight; the film grades contain plasticizer systems that intentionally lower glass transition and modify impact energy absorption, while BL-2 is supplied as a relatively rigid, high-Tg resin whose final flexibility is controlled by downstream formulation.
Storage, moisture, and incompatibility boundaries are production-critical. The powder should be stored sealed at 10–30 °C and used within 12 months when maintained below 50% RH. Avoid contact with strong acids and bases; under acidic conditions, acetal hydrolysis regenerates hydroxyl species and changes solution rheology. Avoid prolonged dry heating above 120 °C because the powder may sinter and form gel bodies that are difficult to dissolve. Regulatorily, lot-specific conformity for 2011/65/EU annex II restricted substances and EC 1907/2006 REACH obligations must be confirmed through supplier documentation; the resin contains no intentionally added lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyls, or polybrominated diphenyl ethers, but contamination control at the 1000 ppm threshold for restricted substances requires compliant raw-material handling.
