| HS Code | 821677 |
| Product Name | Butvar B-76 |
| Chemical Family | Polyvinyl butyral (PVB) |
| Cas Number | 63148-65-2 |
| Physical Form | White granular powder |
| Molecular Weight Mw | 90,000 |
| Specific Gravity | 1.083 |
| Refractive Index | 1.488 |
| Glass Transition Temperature | 72 °C |
| Hydroxyl Content | 11.0 - 13.0 wt% |
| Acetate Content | 1.0 - 3.0 wt% |
| Tensile Strength | 7,000 psi |
| Elongation At Break | 30% |
As an accredited Butvar B-76 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Butvar B-76 polyvinyl butyral resin is supplied as a free-flowing white powder in 25 kg multi-wall paper bags. |
| Container Loading (20′ FCL) | 20′ FCL: Bagged Butvar B-76 resin loaded on pallets, secured and protected from moisture for safe transit. |
| Shipping | Butvar B-76 is shipped as a non-hazardous solid resin in sealed, moisture-proof containers to prevent clumping. Keep dry, avoid heat and ignition sources. No special transport classification required, but use standard industrial packaging with proper labeling and documentation. |
| Storage | Store Butvar B-76 in a cool, dry, well-ventilated area away from heat, sparks, open flames, and strong oxidizers. Keep the container tightly closed when not in use to prevent moisture absorption and contamination. Store in original packaging, protected from direct sunlight and humidity. Follow manufacturer guidelines for shelf life and handling. |
| Shelf Life | Shelf life is typically two years when stored in a cool, dry place in original sealed container. |
Wash primers formulated with B-76 are required where a thin acid-reactive tie layer must be applied directly to prepared aluminium or galvanised steel before a high-solids epoxy or polyurethane topcoat. The resin is first dissolved to a 10 wt% resin solids content in a 3:1 ethanol:n-butanol solvent blend, after which 85% phosphoric acid is added slowly to a final concentration of 2.5–4.0 wt% of the mixed primer. In chromated aerospace versions, zinc tetroxychromate or strontium chromate at 5.0–8.0 wt% remains the active inhibitive pigment where REACH Annex XIV authorisation applies; non-chrome alternatives substitute zinc phosphate at 6.0–10.0 wt% but require a shift in acid level to avoid viscosity rise. The formulation is sprayed with a 1.2 mm HVLP nozzle at 0.25–0.30 MPa; a DIN 4 mm cup viscosity of 18–22 s at 23°C is targeted. Wet-film thickness is controlled to 7–12 µm using an ASTM D4414 comb gauge. The acid-resin reaction raises pot temperature and produces a slow viscosity increase; pot life is normally judged when the same cup viscosity exceeds 30 s, typically after 36–72 h at 20°C. A butanol-rich diluent at 5–10 wt% of total solvent extends the working window but increases drying time and can destabilise pigment suspension.
| Substrate condition | B-76 resin | Phosphoric acid 85% | Inhibitive pigment | Solvent blend |
|---|---|---|---|---|
| Aluminium, chromated | 8.0 wt% | 3.0 wt% | strontium chromate 6.0 wt% | 3:1 ethanol:butanol to 100 wt% |
| Aluminium, non-chrome | 8.0 wt% | 2.5 wt% | zinc phosphate 8.0 wt% | 3:1 ethanol:butanol to 100 wt% |
| Galvanised steel, chromated | 7.5 wt% | 3.2 wt% | strontium chromate 5.0 wt% | 3.5:1 ethanol:butanol to 100 wt% |
Performance validation is carried out after application to aluminium 2024-T3 clad panels abraded to Sa 2½ per ISO 8501-1. After 30 min at 23°C and 50% RH, the primed panels are overcoated. Cross-cut adhesion to ISO 2409 should show class 0 or 1 before salt spray exposure. Under ASTM B117, scribe creep is commonly specified at 2.5 mm or less after 1,000 h for marine systems; validation on the actual topcoat stack is mandatory because the acidic primer can react with amine-catalysed high-solids coatings to produce osmotic blistering. Dry-film primer above 12 µm increases the risk of cohesive failure in the primer itself; below 5 µm, the passivating effect is insufficient on blast-cleaned steel. Application defects observed on production lines include mottling from excessive humidity above 70% RH, which causes premature phosphoric acid absorption and gives rise to loose powder on the surface; dehumidification to 40–60% RH is required. This segment is not a generic barrier coat but a chemically active tie layer; every acid and pigment change requires revalidation of topcoat interlayer adhesion.
In high-speed solvent-based flexographic and gravure printing on corona-treated biaxially oriented polypropylene, PVDC-coated polyester, and chemically primed polyester films, B-76 is compounded into the vehicle as a co-binder at 2.0–6.0 wt% of total ink to increase adhesion without causing blocking on the rewind at film surface temperatures of 45–55°C. Its dissolution is carried out in n-propyl acetate/ethanol/ethyl acetate blends at 15–20 wt% resin solids, then let down with a nitrocellulose-polyurethane pigment base. On a Cerutti gravure line running 150–300 m/min, a 30–38 µm electromechanically engraved cylinder applies a wet film of 10–12 µm; drying tunnel air temperature is set at 70–85°C with air velocity of 20–25 m/s to bring residual solvent below 5 mg/m². A ISO 3 mm flow cup viscosity of 15–20 s at 25°C is common; higher B-76 dosage above 7 wt% raises viscosity beyond 28 s and reduces ink transfer from the cells, producing gravure streaks. Below 2 wt%, adhesion loss occurs on critical substrates and coefficient of friction rises because the nitrocellulose-polyurethane matrix lacks sufficient PVB to control free volume. For indirect food contact packaging, resin compliance must be confirmed against the intended use conditions of FDA 21 CFR 175.105 or the relevant country-specific positive list; migration testing under Commission Regulation (EU) No 10/2011 is mandatory for EU food-contact inks. B-76 has broad solubility but is not suitable as the sole film former in water-based inks because its water tolerance is low; solvent-borne laminations and surface-print lines are the applicable domain. Terminal products include confectionery twist wraps, laminated snack food overwrap, and pharmaceutical cold-form lidding.
In dry lamination for printed OPP or polyester film to aluminium foil, a B-76 solution is prepared at 12–18 wt% solids in ethyl acetate or methyl ethyl ketone and combined with an aliphatic polyisocyanate hardener at an NCO:OH ratio of 1.4:1 to 2.2:1. The hydroxyl equivalent weight of B-76 is determined from the 11–13 wt% polyvinyl alcohol content reported for the grade; failure to correct for solvent moisture above 500 ppm shifts the effective NCO:OH ratio downward because water consumes free isocyanate and leaves the polyvinyl butyral network undercured. The mixed adhesive is gravure-coated at 1.8–2.6 g/m² dry weight, dried at 70–80°C, and nipped to the foil at 80–95°C and 0.4–0.6 MPa. Seal activation on the finished laminate is evaluated by ASTM F88 with a dwell time of 1 s and jaw pressure of 0.25 MPa; a B-76-modified system often requires 105–125°C sealing temperature, while plasticiser-free films lose low-temperature seal performance below 95°C. Addition of 5–10 phr of a polyester plasticiser reduces the minimum seal temperature but increases blocking in high-humidity storage above 60% RH. Organotin catalysts at 0.02–0.05 wt% give a pot life of 8–12 h; tertiary amines cause rapid viscosity rise and must be avoided. Do not combine the adhesive with amine-based primers or ink additives that migrate to the sealant interface, because premature crosslinking and channeling in the applied film have been observed. Peel strength below 1.5 N/15 mm in ASTM D1876 indicates insufficient anchorage; a value above 3.0 N/15 mm may indicate over-cure and brittle failure at the foil surface. Terminal structures are dry mix pouches, lidding film for cups, and metallised barrier overwrap.
A non-aqueous tape-casting slurry for X7R multilayer ceramic capacitors is prepared by dispersing 55–65 vol% barium titanate powder in a 50:50 MEK:ethanol mixture with 0.5–1.0 wt% of a phosphate ester dispersant. B-76 is then added as a 15 wt% solution at 4.5–7.0 wt% based on ceramic powder weight, together with 0.8–1.5 wt% of a non-volatile plasticiser. The slurry is de-aired under vacuum at 0.08 MPa for 20 min and cast onto siliconised PET with a doctor blade gap of 300–500 µm at a line speed of 0.5–1.5 m/min. Drying is conducted in three zones at 50°C, 65°C, and 75°C with solvent dewpoint below -20°C to prevent skinning and pinhole formation. Green tape tensile strength is evaluated in a universal testing machine at a crosshead speed of 2 mm/min; industrial handling and via punching require at least 1.5 MPa, and edge cracking occurs when B-76 falls below 4.5 wt%, while binder content above 7.0 wt% slows burnout and increases fired shrinkage variation.
Binder removal is the critical threshold in this application. Thermogravimetric analysis of PVB with similar hydroxyl content under flowing air at 5°C/min shows an onset of mass loss near 260°C, a maximum rate at 370–410°C, and complete removal by 500°C. Published data for B-76 in this specific tape-casting configuration is limited; therefore, furnace profiling must be generated on the actual green multilayer stack. Industrial burnout cycles typically ramp at 0.5–1.0°C/min from 200°C to 450°C and hold for 4–6 h with forced air, because a rapid ramp above 2°C/min causes blistering and delamination in stacks above 50 layers. Residual carbon above 0.1 wt% shifts X7R capacitance and aging characteristics; binder removal atmosphere should be oxidising until 500°C. Lamination of printed sheets is performed at 70°C and 7–15 MPa for 60 s; moisture in the green tape above 1.5 wt% reduces interlayer adhesion and must be controlled by dry storage at 20% RH or lower. This application remains a deep-dive zone because the processing window between adequate green strength and complete binder oxidation is narrow; changes in particle size distribution or plasticiser ratio shift the burnout profile and require re-tuning of the hold segment.
For temporary protection of polished stainless steel sheet and large-format architectural glass during handling and installation, B-76 is formulated at 18–25 wt% solids in a solvent blend of ethanol, toluene, and methyl ethyl ketone with 10–20 phr of a non-phthalate plasticiser such as triethylene glycol bis(2-ethylhexanoate). A hydrophobic fumed silica at 0.5–1.5 wt% is dispersed to impart anti-slip stackability to the dried film. The coating is applied by airless spray at 6–12 MPa or by curtain coating at a curtain head height of 80–120 mm; dry film thickness is set at 60–100 µm using an ASTM D4414 wet-film gauge. Drying at 25°C reaches a peelable, non-tacky state in 20 min under forced air, but full mechanical properties require 24 h at 40–60% RH. Peel adhesion at 180° is measured by ASTM D903 and is controlled between 0.2 and 0.7 N/mm. Below 0.2 N/mm, edge lifting and particulate ingress occur during transport; above 1.0 N/mm, removal becomes discontinuous and may delaminate fragile surface coatings. On stainless steel, the absence of residue is checked by water-break and solvent wipe tests; any unreacted plasticiser migration can be detected after 30 days at 50°C by infrared reflectance. UV absorber at 0.5–1.0 phr is added for outdoor storage because prolonged UV exposure above 6 months oxidises the PVB and raises peel force to over 2.0 N/mm, causing film shattering during stripping. Terminal products include architectural glass, anodised aluminium profiles, stainless steel cladding, and coil-coated aluminium panels.
Competitive Butvar B-76 prices that fit your budget—flexible terms and customized quotes for every order.
For samples, pricing, or more information, please contact us at +8615380400285 or mail to sales2@liwei-chem.com.
We will respond to you as soon as possible.
Tel: +8615380400285
Email: sales2@liwei-chem.com
Flexible payment, competitive price, premium service - Inquire now!
The polyvinyl butyral resin designated Butvar B-76 is supplied by Eastman Chemical Company as a free-flowing white powder produced by condensation of polyvinyl alcohol with butyraldehyde. Residual acetate and hydroxyl functionality after acetalization governs solubility, adhesion, and crosslinking response. In the B-76 grade, the manufacturer controls hydroxyl content within 11.0–13.0 wt% and acetate content within 0.5–2.5 wt%. The polymer has a specific gravity of 1.100 when measured according to ASTM D792 and a glass transition temperature of 62–72 °C by differential scanning calorimetry. The grade is used in corrosion-inhibiting wash primers, laminating adhesives, gravure and flexographic ink binders, ceramic green-tape binders, and structural film adhesives. Selection of Butvar B-76 over lower-molecular-weight Butvar grades is typically driven by higher solution viscosity, greater film toughness, and stronger adhesion to glass, metal oxides, and polar plastics.
| Property | Typical range | Test basis |
|---|---|---|
| Hydroxyl content | 11.0–13.0 wt% as polyvinyl alcohol | Manufacturer specification |
| Acetate content | 0.5–2.5 wt% | Manufacturer specification |
| Specific gravity | 1.100 | ASTM D792 |
| Glass transition | 62–72 °C | ASTM D3418 |
| Weight-average molecular weight | 90,000–120,000 g/mol | GPC, manufacturer |
Within the Butvar series, grade selection is based on molecular weight, hydroxyl content, and the resulting viscosity-solids relationship. B-76 is positioned as a high-molecular-weight, moderate-hydroxyl member of the traditional coatings and adhesives range; Butvar B-72 and B-74 supply lower solution viscosity at equivalent resin solids, allowing higher application solids in spray-applied systems. The higher molecular weight of B-76 increases dilute-solution viscosity and produces a more entanglement-dense dried film. That characteristic raises tensile strength and mar resistance in supported films but reduces maximum resin solids in gravure inks and high-speed coil coating formulations. In production equipment, the practical difference appears as a limitation in rotor-stator mixers: a B-76 solution at 10 wt% in 60:40 toluene:ethanol may require a lower final solids target than a B-74 solution to remain pumpable through a 20 µm cartridge filter. The hydroxyl content in 11.0–13.0 wt% also provides reactive sites for crosslinkers such as phenolic, melamine-formaldehyde, and isocyanate systems; this reactivity is lower than high-hydroxyl PVB grades, which reduces premature gelation in acid-catalyzed wash primers.
Solvent swelling and dissolution behavior in production mixing vessels is controlled by solvent polarity, resin particle size, and agitator shear. A standard dissolution sequence adds the B-76 powder slowly to a pre-blended solvent mixture under high-speed disperser agitation at 500–1,000 rpm in a jacketed vessel. Alcohol-rich blends solvate the hydroxyl groups rapidly; aromatic hydrocarbons delay viscosity build and reduce shear heating. In a 200 L stainless steel dissolver, a 10 wt% resin charge in 60:40 toluene:ethanol reaches a clear, particle-free solution within 30–60 min when the solvent temperature is maintained at 25–30 °C. If the resin is added too rapidly, particle agglomeration produces fisheye defects that persist for the remainder of the batch and require filtration through a 10–25 µm bag filter. Batch-to-batch variation in hydroxyl content within the specification range can shift solution clarity in ketone-lean blends; a resin batch near the upper hydroxyl limit generally disperses faster in alcohol-rich solvent and may require higher aromatic content to avoid seeding.
Laminating adhesive formulations based on B-76 use a two-part solvent balance: an active oxygenated solvent to keep the resin in solution and a diluent to reduce cost and adjust drying rate. The preferred oxygenated solvents are methyl ethyl ketone, ethyl acetate, and isopropanol; aromatic hydrocarbons such as toluene or xylene are added to 20–40 vol% of the blend depending on flash-point requirements. Viscosity is measured on a Brookfield RVT rotational viscometer at 25 °C; production batches are typically adjusted to 800–2,000 mPa·s at 20 rpm for gravure coating and 2,000–4,000 mPa·s for reverse-roll adhesive application. Because B-76 produces higher dilute-solution viscosity than B-74, formulators reduce resin solids by 2–4 wt% to match the same application viscosity. Drying behavior depends on the solvent blend; in a 3-zone forced-air tunnel at 90–110 °C, residual solvent in a 12 µm dry adhesive layer drops below 10 mg/m² within 20 s. Such drying profiles are line-specific and must be validated by gas chromatography on production laminate.
When B-76 replaces a lower-molecular-weight PVB in a two-pack acid-activated wash primer for cold-rolled steel, the principal processing variable is the viscosity after acid addition. The phosphoric acid component protonates residual hydroxyl groups and promotes adsorption onto iron oxides; the high molecular weight of B-76 accelerates the increase in low-shear viscosity and can shorten the working window after mixing. In a typical production line using a pressure-pot spray system with a 1.2 mm nozzle at 400–600 kPa, the mixed primer is reduced to 18–22 s on a DIN 4 mm cup before application. Dry film thickness is controlled at 5–8 µm, and adhesion is assessed by cross-cut and pull-off testing according to ISO 2409 and ISO 4624. The higher molecular weight of B-76 improves salt-spray resistance relative to B-72 when formulated with the same pigment volume concentration, but the resin solids must typically be reduced by 1–2 wt% to maintain spray viscosity. In chrome-free zinc phosphate formulations, the acid concentration and mixed-pot-life specification are set by the coating manufacturer; published data for direct substitution in all military specification wash primers is limited.
Thermosetting crosslinker response of B-76 is dictated by the residual hydroxyl functionality and the acid value of the co-resin. Phenolic resins with methylol groups condense with the PVB hydroxyls in bake schedules above 150 °C; melamine-formaldehyde systems cure through acid catalysis at 120–140 °C. In coil coating trials, a B-76/phenolic blend applied to chromate-pretreated aluminum and baked for 60 s at 230 °C metal peak temperature exhibits solvent resistance exceeding 100 methyl ethyl ketone double rubs when tested according to ASTM D5402. The same formulation without added adhesion promoters retains mandrel flexibility at 2T bend. Isocyanate crosslinking at ambient temperature is possible but the resin must be dissolved in urethane-grade solvents with water content below 0.05 wt% to avoid carbon dioxide gassing. In high-humidity production environments above 60% RH, pre-drying of the resin and activated molecular sieve in the solvent line are required.
Although B-76 is primarily processed from solvent, the resin can be melt-compounded with plasticizers in twin-screw extruders fitted with vacuum devolatilization. The selection of plasticizer is constrained by compatibility; low-polarity esters such as dioctyl phthalate are less effective than dibutyl phthalate or triethylene glycol bis(2-ethylhexanoate). At plasticizer loadings above 20 phr, the glass transition of B-76 can be depressed below 30 °C, but tensile strength decreases and blocking of extruded sheet increases. On a co-rotating twin-screw extruder with a 40:1 L/D ratio and 150–170 °C barrel profile, the resin should be pre-blended with plasticizer and stabilizer before the feed throat to prevent agglomeration. Torque and melt pressure are monitored continuously; melt temperatures above 200 °C lead to acetal ring opening, release of butyraldehyde, and yellowing. The processing window is narrow, with a recommended melt-temperature range of 160–190 °C. Published data for injection molding of unplasticized B-76 is limited because the polymer does not flow sufficiently without plasticizer at conventional melt temperatures.
Polyvinyl formal and polyvinyl butyral differ in acetal substituent length and solubility profile. B-76 is selected for adhesion to copper and aluminum conductors in some low-solids enamel primer formulations, but it does not replicate the thermal dimensional stability of polyvinyl formal at service temperatures above 130 °C. In comparative wire-coating trials, B-76-based primers show equivalent adhesion to annealed copper wire at 10 µm dry film thickness but lower cut-through temperature when tested according to IEC 60317 methods. The substitution is therefore limited to low thermal class enamels below 130 °C or as a component in a blend with higher-heat-resistant resins. When B-76 replaces polyvinyl formal, the formulator should increase the phenolic crosslinker content by 5–10 wt% on resin solids to restore thermomechanical resistance, but this also reduces flexibility and may require a change in cresylic acid solvent ratio.
In multilayer ceramic capacitor tape casting, B-76 is dissolved with methyl ethyl ketone and ethanol and combined with a phthalate or citrate plasticizer to produce a homogeneous slip. The high molecular weight of the grade improves green tape tensile strength relative to B-72, allowing cast thickness below 20 µm without excessive tearing during slitting. Slip rheology is measured on a cone-and-plate viscometer at 25 °C; a typical starting formulation contains 4–8 wt% B-76 on ceramic powder. Binder burnout in air is conducted with a stepped profile to 450–500 °C, with the final soak dependent on binder loading and tape thickness. Insufficient oxygen flow in the burnout kiln produces carbonaceous residue that can reduce dielectric performance; published data for this specific configuration is limited and must be validated against the ceramic dielectric specification.
