| HS Code | 442446 |
| Product | Sinopec-SVW SS-7 Low-Temperature Water Soluble PVA Fiber |
| Grade Code | SS-7 |
| Material Family | Water-soluble modified polyvinyl alcohol |
| Fiber Form | Staple fiber |
| Appearance | White, even, clean staple fibers with smooth surfaces and uniform cut ends |
| Water Solution Temperature | About 70 degrees Celsius nominal for low-temperature water soluble grade |
| Solubility Characteristic | Fully soluble in water at the rated temperature without leaving insoluble residue |
| Linear Density Range | 1.5 to 3.0 dtex |
| Staple Length Range | 38 to 76 mm |
| Dry Tenacity | Approximately 5 cN/dtex or higher |
| Breaking Elongation | 15 to 20 percent |
| Initial Modulus | 2.0 to 3.5 GPa |
| Density | 1.23 to 1.30 g/cm3 |
| Thermal Decomposition Temperature | Above 200 degrees Celsius |
As an accredited Sinopec-SVW SS-7-Low-Temperature Water Soluble PVA Fiber factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in 25 kg woven bags with polyethylene lining, ensuring moisture protection and safe handling during transport and storage. |
| Container Loading (20′ FCL) | 20' FCL shipment of Sinopec-SVW SS-7 water-soluble PVA fiber, securely packed in woven bags on pallets for safe transport. |
| Shipping | Ship via sealed, moisture-proof packaging to prevent premature dissolution or clumping. Store in cool, dry, ventilated area away from water, humidity, and direct sunlight. Handle gently to avoid fiber damage. No special hazardous cargo restrictions, but protect from rain during transport. |
| Storage | Store in a cool, dry, well-ventilated area away from direct sunlight, heat sources, and ignition. Keep packaging tightly sealed to prevent moisture absorption, which can cause premature dissolution. Avoid prolonged exposure to high humidity. Maintain room temperature and separate from strong oxidizers. Handle gently to prevent fiber damage. Keep container dry. |
| Shelf Life | Shelf life: 12 months when stored in original sealed packaging in cool, dry, well-ventilated conditions away from sunlight and moisture. |
On Schiffli and multi-head embroidery lines, Sinopec-SVW SS-7 low-temperature water-soluble PVA fibre is converted into a carded, lightly needle-punched or calender-bonded nonwoven scrim that functions as a temporary stabilizer for tulle and open-lace constructions. The fibre’s low-temperature solubility permits cold-water extraction after the embroidery frame is removed. Typical scrim basis weight in this downstream route falls between 25 g/m² and 40 g/m², with lighter webs used for dense repeat patterns and heavier webs used for coarse openwork where needling damage must be reduced. The scrim is positioned under the base fabric and clamped at the frame perimeter; hydrophobic embroidery threads do not require adhesive fixation. During stitching, the PVA web absorbs needle penetration energy and suppresses puckering at high stitch counts. After embroidery, the assembled piece is immersed in water at 20–30°C for 5–15 min. Mechanical agitation controls dissolution more than temperature because the low-temperature PVA grade first forms a swollen gel before complete solvation. Bath solids are maintained below 1.0 wt% using continuous overflow and 50 µm filtration to reduce re-deposition on mesh openings. Finished lace intended for skin-contact apparel is tested against OEKO-TEX Standard 100 Annex 4. Storage above 60% RH produces surface tack and tensile loss; preconditioning at 20°C and 40–50% RH for 24 h restores dimensional stability before frame loading. Trim waste can be dissolved in warm water and reintroduced into low-value adhesive sizing, but published data on SS-7-specific solution viscosity is limited and conversion trials should establish the maximum acceptable bath solids for a given line.
Health-care tunnel washers impose a cold pre-rinse stage that typically operates at 15–20°C for 2–4 min, followed by thermal disinfection at 60–65°C for 10 min or 71°C for 3 min under EN 14065:2016-compatible laundry protocols. For containment bags made from SS-7 fibre, the first cold pre-rinse initiates dissolution and allows bag structure to disperse before the main wash. The dominant processing risk is seam failure. Heat-sealed PVA nonwoven seams require a sealing window between 120°C and 160°C; below 120°C, seal strength is insufficient for rated fill weight, while above 160°C oxidative degradation may create locally insoluble brittle domains that fail under flexural stress. Seam tensile pull is measured on a 25 mm strip using ISO 9073-3:2023. Leakage risk rises when bags are handled with wet hands or stacked against damp stainless steel trolleys, so converters commonly specify an embossed outer face to reduce contact area. Because SS-7 is a low-temperature grade, a conventional PVA requiring 60°C would not disperse until the main wash and could obstruct drain screens in tunnel washers. Hospital laundry managers frequently set a site-specific residual fibre limit below 10 fibres/L in drained rinse water, verified by particle counter or optical microscopy. Tear resistance after exposure to 80% RH for 24 h is assessed according to ISO 9073-4:2023. The bag itself is not generally a medical device under Regulation (EU) 2017/745, but the laundry operation must document biocontamination control under EN 14065:2016. Published data for SS-7-specific seam strength after humid ageing is limited; hospital converters typically compare dry, 50% RH, and 80% RH conditioned specimens before release.
Angling bait presentation in cold-water fisheries uses PVA fibre in knitted net or nonwoven mesh to contain boilies, pellets, and groundbait. Early-season carp and barbel waters operate between 2°C and 15°C, where conventional water-soluble PVA mesh may disperse too slowly and retain bait at the lakebed. A low-temperature grade such as SS-7 is selected for dissolution onset in cold water, but release rate is also controlled by water flow, yarn tex, knit density, and packing pressure. PVA angling mesh is typically warp-knitted on crochet machinery with yarn counts from 18 tex to 25 tex, then cut and heat-sealed or tied with PVA tape. Dissolution time for a filled 50 mm bag in moving water is often measured in seconds to a few minutes, but published data for SS-7-specific mesh is scarce because lakebed current and temperature dominate the result. Bait suppliers therefore run internal bucket tests at 5°C and 15°C using site water. The finished article is a filled mesh bag of 30–60 mm diameter and 50–120 mm length, tied or folded closed. The bag must withstand brief contact with damp hands during filling and casting but dissolve without leaving fibrous residue on the bait. PVA polymers of this class undergo aerobic degradation in freshwater sediments, but ready biodegradability under OECD 301B may be incomplete within the 28-day test window; long-term mineralization data are more relevant. Storage must be in resealable airtight containers because moisture from rain or wet fingers causes localized gelation. There is no standard method for PVA mesh dissolution, so suppliers typically describe a weighted mesh bag under defined water velocity and temperature as an internal release test. The low-temperature feature of SS-7 permits presentation of loose feed in cold weather without a hot-water activation step that would otherwise alter bait attraction.
In wet-laid nonwoven furnish preparation, SS-7 staple is dispersed as a temporary binder that contributes dry web cohesion before drying and then dissolves to leave an open sheet structure. The main process conflict is premature dissolution ahead of sheet formation. Stock temperature is held below 20°C during blending, and retention time between dispergation and forming is shortened to limit polymer solvation in white water. Addition levels for specialty paper and wet-laid nonwovens range from 2 wt% to 8 wt% of bone-dry furnish; above 8 wt%, dissolved PVA raises headbox viscosity and retards dewatering. White-water viscosity is monitored with a Brookfield viscometer at 25°C according to ISO 2555; an increase above 5 mPa·s over baseline is a practical alert for excessive dissolution. Machine trials on inclined-wire and rotary-screen formers indicate that PVA staple should be added after refining and before the fan pump, using low-shear mixing to limit fibre breakage. Drying section temperatures are kept between 80°C and 120°C; higher temperatures can anneal the PVA and raise its dissolution temperature, which is undesirable when the binder must be removed later. For food-contact paper, the converter must verify compliance under FDA 21 CFR 176.170; polyvinyl alcohol film is recognized under 21 CFR 177.1670, but fibre-form use in food-contact paper may require migration testing under intended conditions of use. For European markets, Regulation (EC) No 1935/2004 and Commission Regulation (EU) No 10/2011 apply where plastic or PVA layers are present in multilayer articles. Finished products include seed germination paper, porous release base paper, and wet-laid cleaning wipes where the PVA binder provides dry handling strength and then dissolves upon wetting. Published data for SS-7-specific wet-laid retention and dewatering resistance is limited; each furnish formulation requires a drainage test on a Schopper-Riegler freeness apparatus according to ISO 5267-1 to quantify the influence of dissolved polymer on drainage time.
Ring-spinning trials with SS-7 blended into cotton show that the fibre acts as a sacrificial support phase for producing low-twist, high-drape woven fabrics. The PVA staple is blended at 5–20 wt% with cotton or wool and processed through carding and drawing. The low dissolution temperature of the grade allows extraction in cold water after weaving and scouring. The primary process conflict is static electricity generation at carding; the PVA staple develops static below 55% RH, causing cylinder loading and uneven sliver formation. Spinning room humidity is maintained at 55–65% RH and 22–25°C. Roving twist and traveller speed are adjusted for the lower fibre-to-fibre friction of PVA; spindle speeds are typically reduced by 5–10% compared with all-cotton production to reduce end breaks. Yarn tensile properties are measured under ISO 2062:2009, and linear density under ISO 2060:1995. After weaving, the fabric is processed through an open-width desizing range with a cold-water bath at 20–25°C, followed by washing to remove the PVA solution. Extraction progress is verified by iodine-boric acid staining; residual PVA forms a blue-green colour, but published data for SS-7-specific residual levels is limited. Woven structures produced by this route include lace curtain fabrics, hollow tubular tapes, and lightweight medical gauze where yarn spacing opens after PVA removal. Final fabric tensile strength is tested under ASTM D5034-21, and dimensional change under ISO 5077:2007 after the first cold-water wash. The cold-water extraction stage must not exceed 30°C; above this threshold, the fibre can soften and become tacky before full dissolution, depositing on guide rollers and producing surface patches. Dissolved PVA in wash water is diluted below 0.5 wt% to prevent roller build-up. Strongly alkaline scouring above pH 10 can change dissolution rate and should be neutralized or avoided. The method eliminates high-temperature desizing and permits cold-water extraction of sacrificial PVA support yarn, though recovery economics depend on lot size.
Under municipal agitation, hydroentangled dispersible wipes containing SS-7 lose structural integrity when the low-temperature PVA component dissolves during sewer transport, but this early dissolution is also what enables flushability. The fibre is blended at 5–15 wt% with wood pulp, regenerated cellulose, and a wet strength control agent, then carded and hydroentangled at water pressures from 60 bar to 150 bar. Drying after hydroentanglement must remain below 95°C to avoid polymer annealing that would raise the dissolution temperature. The finished wipe must maintain dry tensile strength for packaging and use but disintegrate under household drainline shear. The applicable assessment is INDA/EDANA GD4, which evaluates seven flushability attributes: toilet and drainline clearance, household pump, settling, aerobic biodisintegration, anaerobic biodisintegration, sieve fraction, and municipal pump compatibility. SS-7 accelerates the transition from a wet-strength structure to dispersed fibres, but excessive PVA content can create a gel-like mass that blocks household pumps; the addition level must be tuned with the wet strength additive. Dry and wet tensile strength is measured under ISO 9073-3:2023, with the wet test conducted after immersion in water at 20°C for 60 s. Storage stability is a boundary condition: once a tub is opened, wipes exposed to 80% RH for 24 h lose measurable dry tensile strength. Wastewater operators often target 95% of fibres passing through a 1 mm sieve after 30 min agitation. Published data for SS-7-specific disintegration time in GD4 test apparatus is limited; brand owners should request lot-specific flushability reports before changing fibre source. The finished products are dispersible adult wipes, pet wipes, or surface wipes labelled as unsuitable for septic systems with high solids retention time.
| Evaluation stage | Standard / method designation | Relevance to SS-7 wipe matrices |
|---|---|---|
| Dry and wet tensile strength | ISO 9073-3:2023 | Determines handling strength before flush |
| Flushability assessment | INDA/EDANA GD4 | Seven-test municipal disposal compatibility |
| Aerobic biodegradability | ISO 14855-1:2012 | Ultimate aerobic degradation of PVA/cellulose matrix |
| Anaerobic biodegradability | ISO 15985:2014 | High-solids anaerobic digestion biogas method |
| Basis-mass uniformity | ISO 9073-1:2023 | Nonwoven sheet uniformity after hydroentanglement |
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Sinopec-SVW SS-7-Low-Temperature Water Soluble PVA Fiber is a polyvinyl alcohol staple fiber designed for ambient-water dissolution in temporary binder, fugitive yarn, and sacrificial-spacer applications. The product is supplied in cut lengths of 4 mm, 6 mm, and 12 mm with a nominal linear density of 1.7 dtex ± 0.2 dtex measured under ISO 1973:2021. Its low-temperature designation derives from a dissolution onset near 20 °C, in contrast to conventional hot-water PVA grades that require 60 °C to 80 °C. The fiber is intended for dry-lay nonwovens, wet-lay papermaking, stitch-bonded fabrics, and composite preforms where temporary support must be removed without exposing the core substrate to thermal stress exceeding 40 °C.
The polymer matrix is a partially hydrolyzed polyvinyl alcohol with an alcoholysis degree in the 88–92 mol% range. This compositional window reduces crystallite size and increases the amorphous fraction available for water ingress relative to fully hydrolyzed ≥99 mol% grades. The fiber is wet-spun and drawn under controlled conditions that preserve dissolution latency while maintaining sufficient tensile integrity for carding and needle-punching. Dry tenacity is intentionally set at 3.8–4.6 cN/dtex; this is below the 5.5–7.0 cN/dtex typical of high-crystallinity PVA staple and must be considered when temporary fabrics carry mechanical load during forming.
Under laboratory conditions using 1% w/w fiber in deionized water at 20 °C and 200 rpm agitation, SS-7 disintegrates within 30 min and yields a clear solution in 90–120 min. Dissolution rate increases as pH shifts from neutral to mildly alkaline; at pH 8–9, complete dissolution time falls to 45–60 min. Acidic baths below pH 4 slow swelling and may produce a gel residue unless shear is maintained. The dissolved polymer contributes to chemical oxygen demand in process water; closed-loop systems should monitor COD load because PVA is biodegradable under specific acclimated activated sludge conditions but is not removed in short conventional flocculation without biological adaptation.
Dissolution kinetics follow a two-stage mechanism: initial water diffusion into amorphous domains and subsequent disentanglement of polymer chains at the fiber surface. The apparent activation energy for dissolution in the 10–40 °C interval is dominated by polymer chain mobility rather than chemical degradation. In a pilot-scale continuous dissolution tank with a 1.5 m³ working volume and a pitched-blade turbine at 120 rpm, a 1% w/w SS-7 slurry is reported to reach greater than 95% single-fiber disappearance in 25 min at 25 °C; the same tank requires 45–60 min when the agitator is reduced to 60 rpm, indicating that shear-assisted removal of the hydrated surface layer is rate-limiting once the fiber has swollen.
The values in the following table are manufacturer-published typical data for SS-7 staple, not batch release guarantees. They are intended for process design; actual results may vary with cut length, finish level, and conditioning history.
| Property | Test method | Typical value/range |
|---|---|---|
| Linear density | ISO 1973:2021 | 1.7 dtex ± 0.2 dtex |
| Cut length tolerance | supplier QC sieve method | ± 0.5 mm at 6 mm nominal |
| Dry tenacity | ISO 5079:2020 | 3.8–4.6 cN/dtex |
| Elongation at break | ISO 5079:2020 | 15–22% |
| Dissolution temperature onset | in-house turbidity method | ≤ 20 °C |
| Complete dissolution at 20 °C | 1% w/w, 200 rpm | 90–120 min |
| Moisture regain at 65% RH | gravimetric equilibrium at 20 °C, 65% RH | 8–12% |
| Ash content | ISO 3451-1:2019 | ≤ 0.5% |
| Thermal decomposition onset in N₂ | ISO 11358-1:2022 | 220–240 °C |
Production-scale dry-lay processing is sensitive to moisture content and crimp stability. On a roller-top card with cylinder speed 80–120 m/min, conditioning SS-7 at 20 °C and 55% RH for 24 h is recommended to reduce fly and static clumping. If ambient RH drops below 35%, non-ionic antistatic agents should be evaluated for compatibility with PVA dissolution residue. Cationic antistats can precipitate anionic sizing or contaminant fractions in recycled water and are not recommended without filtration trials. Crimp loss above 30% of incoming crimp frequency during prolonged recirculation can reduce web uniformity, particularly at cut lengths of 4 mm.
In wet-laid nonwovens, addition of 2–10 wt% SS-7 provides temporary green strength. A subsequent cold-water extraction at 15–25 °C removes the PVA component without the curling or shrinkage typical of hot-water extraction above 60 °C. The dissolved fiber can increase viscosity of the white water; for sheet forming on a 300 mm laboratory sheet former, a 5 wt% addition is reported to increase wet-web tensile index by 15–20% relative to the all-cellulose control. After full dissolution, tensile index returns to control levels; published data for this specific configuration is limited to laboratory forming and the effect is dependent on basis weight and refining level.
SS-7 is deployed when heat-activated PVA or hot-water-soluble fibers would impose unacceptable thermal load on heat-sensitive substrates. In embroidery backing and water-soluble nonwoven interlinings, the fiber is processed into a support web and then removed in a cold-water rinse at 20 °C after stitching. For stitch-bonded fabrics, the fiber may be used as a fugitive insertion yarn; the final composite is scoured in a rotary drum washer at a bath temperature of 20 °C to 25 °C with a residence time of 20–40 min, depending on fabric weight and liquor ratio. A liquor ratio of 1:20 is typical; lower ratios require circulation rather than static soaking because the dissolved PVA creates a viscous boundary layer at the fiber surface. High-shear dispersion of SS-7 in aqueous slurry should be conducted at ≤ 15 °C if immediate dissolution is not intended; above 20 °C, the fiber surface hydrates rapidly and prolonged mixing can foul impellers with stringy gel phase.
Because the fiber dissolves at 20 °C, it can be combined with heat-sensitive fibers such as polylactic acid, polyhydroxyalkanoate, or protein-based fibers that would hydrolyze or denature in hot-water extraction. The spin finish applied to SS-7 is a non-ionic surfactant system selected to be water-soluble and to leave minimal residue after dissolution. Finish-on-fiber is typically 0.2–0.5% by weight. In high-purity wet-lay applications, a pre-wash at 10 °C for 5 min removes surface finish before the final dissolution step, reducing foam and COD load in the extraction bath.
The principal difference from conventional hot-water PVA fiber is the trade-off between dissolution temperature and dry tenacity. SS-7 exhibits dry tenacity of 3.8–4.6 cN/dtex, while fully hydrolyzed PVA staple typically reaches 5.5–7.0 cN/dtex. In a comparative immersion test under ISO 5079:2020 wet-conditioning, SS-7 retains less than 20% of its dry tenacity after 60 s in water at 30 °C, whereas conventional hot-water PVA retains over 80%. Against plasticizer-modified cold-water PVA copolymer fibers, SS-7 avoids fugitive plasticizer additives and maintains plasticizer content below 0.1% w/w, which reduces migration and surface tack during storage.
| Parameter | SS-7 | Conventional hot-water PVA staple | Plasticized low-temperature PVA fiber |
|---|---|---|---|
| Dissolution onset | 20 °C | 60–80 °C | ≤ 10 °C |
| Dry tenacity | 3.8–4.6 cN/dtex | 5.5–7.0 cN/dtex | 2.5–3.5 cN/dtex |
| Alcoholysis degree | 88–92 mol% | ≥99 mol% | 80–88 mol% |
| Plasticizer content | < 0.1% w/w | < 0.1% w/w | may exceed 5% w/w |
| Primary processing limitation | lower wet tenacity; avoid borates | requires high extraction energy | surface tack and plasticizer migration |
SS-7 is not an ethylene-vinyl alcohol copolymer fiber; EVOH is not water-soluble and is used as an oxygen barrier. SS-7 is also distinct from polyvinyl acetate fiber, which is hydrophobic and requires solvent or saponification. These distinctions are relevant when specifying sacrificial fibers for water-removable composites because only PVOH with controlled hydrolysis and crystallinity displays the required cold-water fugitive behavior.
SS-7 should be stored in sealed polyethylene-lined containers at or below 30 °C and 60% relative humidity. Moisture regain at 65% RH is 8–12%; absorbed water plasticizes the fiber and can cause premature surface tackiness, which degrades carding and opening. If bags are exposed to high humidity for more than 24 h, pre-drying in a forced-air oven at 50 °C for 4 h is advised. Pre-drying temperatures should not exceed 70 °C because the fiber surface may soften and fuse at cut ends.
Borate-containing additives, including borax and borated flame retardants, are contraindicated because borate crosslinks the PVA diol groups and shifts the dissolution temperature upward. Strong oxidizing agents such as sodium hypochlorite above 0.5% active chlorine degrade the polymer backbone and reduce fiber tenacity before dissolution. The fiber is not recommended for continuous use in acidic baths below pH 4 unless high-shear dissolution is designed, because gel residues may form. It is also not suitable for load-bearing wet applications after immersion; wet tenacity falls rapidly and the fiber loses structural function once swelling begins.
The supplier provides an SDS indicating no classification under EU CLP and no SVHC above 0.1% w/w under REACH. For food-contact uses, the final article must be evaluated by the converter against the relevant authorization in 21 CFR 177.1670, because fiber residues and dissolution by-products are article-specific. Airborne fiber dust should be controlled under local dust explosion guidance; combustible dust testing according to ASTM E1226 provides explosion severity data when the fiber is dry and finely divided. The dissolved polymer exhibits a Brookfield viscosity of 20–28 mPa·s for a 4% aqueous solution at 20 °C, determined with a spindle LVT viscometer at 60 rpm. This viscosity is low enough for subsequent filtration through 10 µm absolute filters but high enough to alter white water rheology at concentrations above 1%; process engineers should account for viscosity when specifying extraction pumps and heat exchangers.
