Fibra PVA solúvel em água de Fujian Fuwei (Vinylon)

In wetlaid nonwoven production, Fujian Fuwei water-soluble PVA fibre is introduced into the furnish at the pulper before the machine chest. The fibre is cut to a staple length of 3 mm to 6 mm and blended with wood pulp or viscose staple. The headbox consistency is maintained between 0.05% and 0.5% solids. This fibre acts as a temporary binder until the web reaches the hydroentanglement manifold. Water jets at pressures from 40 bar to 120 bar entangle the base fibres. If the water temperature is below the dissolution temperature of the PVA grade, the PVA fibre remains largely intact and contributes to wet-web tensile strength. If the water temperature exceeds the dissolution threshold, the PVA fibre partially or fully dissolves and the web loses temporary reinforcement. Wet-web tensile strength is measured according to ISO 9073-3 strip method on samples taken before the dryer. Published field data for specific Fujian Fuwei grades at varying hydroentanglement temperatures is limited. Mill trials on inclined-wire wetlaid machines with vacuum dewatering boxes have shown that a dissolution temperature margin of at least 10 °C above the maximum water temperature at the first hydroentanglement jet reduces premature loss of wet-web strength. The dissolved PVA contributes to chemical oxygen demand in the process water. The nonwoven fabric after drying is used as a dispersible wipe substrate or a temporary interlining. A furnish addition range of 1.0 wt% to 5.0 wt% is commonly evaluated. Below 1.0 wt%, the reel handling strength is generally insufficient. Above 5.0 wt%, white-water clarification becomes more difficult. The final fabric basis weight is typically 40 g/m² to 70 g/m².

What Controls Dissolution Temperature Selection in Papermaking Furnish Addition?

The selection of dissolution temperature in papermaking furnish addition depends on the wet-end water temperature, dryer profile, and intended void structure of the finished sheet. PVA fibre is added to the pulp slurry at the mixing chest. The cut length is normally 4 mm to 6 mm. Addition levels are determined by wet-web tensile response on a Rapid-Köthen sheet former according to ISO 5269-2. A typical furnish addition range is 1.0 wt% to 3.0 wt% of oven-dry fibre mass. At addition below 1.0 wt%, the wet-web tensile increase is generally insufficient to prevent open draws in high-speed paper machines. At addition above 3.0 wt%, the fibre can contribute to excess dissolved solids in the white-water system. The dissolved PVA increases chemical oxygen demand load in the mill effluent. The wet-web tensile is determined according to ISO 1924-2 at 23 °C and 50% RH. If the paper machine wet-end temperature reaches 45 °C, a PVA fibre grade with a dissolution temperature of 60 °C is chosen. If the wet-end temperature remains below 20 °C, a cold-water grade with dissolution at 20 °C or below can be used. The final sheet porosity after drying is measured by ISO 5636-3. When the PVA fibre dissolves during pressing and drying, it leaves a pore network. Published data for specific Fujian Fuwei fibre grades in papermaking furnish is limited. Mill experience on fourdrinier and twin-wire machines indicates that the dissolution must be completed before the size press to avoid film formation on dryer fabrics. The residual PVA in finished paper can be quantified by iodine colorimetric detection according to JIS K6726. The final sheet is suitable for high-porosity filter paper, tea bag base, or security paper structures.

On embroidery backing lines, cold-water-soluble PVA nonwoven fabric is used as a temporary stabilizer. The fabric is produced from water-soluble PVA fibre by carding and through-air bonding or spunlace. Stitch density ranges from 1.5 mm to 4.0 mm needle pitch. The stabilizer is removed by immersion in water at the dissolution temperature specified for the fabric grade. Cold-water grades dissolve in water at 10 °C to 20 °C within 60 seconds under agitation. Warm-water grades require 40 °C to 60 °C. Residual PVA after dissolution is measured gravimetrically. The test method is JIS K6726 iodine colorimetric detection. The embroidery frame tension is set between 20 N and 50 N hoop tension. Excessive tension above 50 N can cause the PVA stabilizer to tear at the needle penetration line. The liberated PVA polymer in the wash bath must be considered in wastewater handling. The dissolved PVA is not removed by standard activated sludge processes in all municipal treatment plants. In high stitch-density embroidery, the residual PVA content after rinse must be below 0.1 wt% to avoid stiffness in the finished garment. Specific dissolution residue data for Fujian Fuwei embroidery backing grades should be confirmed against the supplier certificate of analysis. The terminal product is a residue-free embroidered garment panel or lace.

Dispersible Wet Wipe Converting and Sealing Limits

Converting of dispersible wipes containing water-soluble PVA fibre requires control of lotion chemistry, folding tension, and seal temperature. The base nonwoven is produced with a basis weight of 40 g/m² to 70 g/m². The fabric is folded on commercial multi-lane folders at speeds of 400 to 800 wipes per minute. The folding tension is set between 5 N and 15 N per lane. Higher tension causes permanent deformation and localised fibre breakage. The lotion load is typically 2.5 to 4.0 times the dry fabric weight. The lotion pH is maintained between 4.0 and 8.0. Outside this range, the PVA fibre can undergo hydrolysis or crosslinking that alters dissolution behaviour. Lotions containing borate ions or boric acid are incompatible. Borate crosslinks the PVA hydroxyl groups and forms a gel network that retards dissolution. The dissolution residue after a 10-minute immersion at 20 °C increases when borated lotions are present. Seal integrity of the wipes is evaluated by a peel test on a tensile tester at 300 mm/min. The relevant standard for nonwoven tensile is ISO 9073-3. For dispersibility testing, no single ISO standard applies universally. Industry-accepted slosh-box or tube-dispersibility methods are used. Published data for specific Fujian Fuwei grades with different lotion formulations is limited. Converting plants should pre-trial each lotion chemistry at the target production speed before full-scale implementation. The finished wipe package is a folded stack or canister of dispersible wet wipes.

For woven support structures, water-soluble PVA fibre is converted into spun yarn or filament yarn. The yarn is used as a temporary warp or weft insertion in fabrics that require a hollow or open construction. The PVA yarn count is typically 15 denier to 40 denier. The yarn breaking force is measured according to ISO 2062 with a 500 mm gauge length and a constant rate of extension. The elongation at break is generally 10% to 15%. During weaving, the warp tension is limited to 10 cN/tex to 15 cN/tex. Higher tension produces filament breakage at the reed. The PVA yarn is removed after weaving by scouring in hot water. The scouring bath is maintained at 80 °C for 15 minutes. The residual PVA is checked by iodine colorimetric analysis. A residual level below 0.05 wt% is considered fully dissolved. This temporary support yarn process is used in tubular fabrics, spacer fabrics, and open-work knits. Published data for specific Fujian Fuwei yarns on jacquard looms is limited. Weaving mills should determine the maximum shed opening and weft insertion speed that the PVA yarn can withstand. The dissolution rate is faster in soft water than in hard water. Calcium ions in hard water can form insoluble complexes with carboxylate-modified PVA grades. For standard fully hydrolysed grades, hardness up to 150 mg/L as CaCO₃ has a minor effect on dissolution time. No universal standard governs PVA yarn removal efficiency. The resulting fabric is a hollow, open-work, or spacer textile after aqueous scour.

When Dissolution Temperature Is Below 40°C in Water-Soluble Laundry Bag Nonwovens

When the dissolution temperature of the PVA fibre is below 40 °C, the nonwoven laundry bag must be stored and handled in a controlled environment. The bag is used for contaminated linen in hospitals and cleanrooms. The nonwoven fabric is converted into bags with a basis weight of 30 g/m² to 45 g/m². The fabric tensile strength is measured according to ISO 9073-3 strip method. The machine-direction tensile strength should be sufficient to hold a load of 5 kg without rupture at 20 °C and 65% RH. The bag is sealed with heat-sealing equipment at 120 °C to 150 °C. The seal strength is measured by a peel test at 300 mm/min. During use, the bag is placed in a washer extractor with a wash cycle at 80 °C for 10 minutes. The bag dissolves and releases the linen. The dissolution time depends on the water temperature, agitation, and load size. Differential scanning calorimetry according to ISO 11357-1 confirms the crystallinity of the PVA fibre. Higher crystallinity raises the dissolution temperature. The crystallinity of water-soluble PVA fibre is typically below 30% for low-temperature grades. If the storage area has relative humidity above 60%, the fibre can absorb moisture and block. Pre-drying is required at 40 °C for 2 hours before heat sealing. Published data for specific Fujian Fuwei laundry bag grades in hospital washing cycles is limited. Testing in the target washer extractor is necessary to confirm the dissolution endpoint.