Enhanced Absorbency of Embossed SAM Sheets

Example 1

A 1 g compressed SAM sheet was formed without embossing. To ensure that Comparative Example 1 had the same compactness as Example 1, meaning that both samples experienced the same compressing pressure, the SAM sheets were each placed between two flat metal plates and compressed twice with a 1000 lb load for 10 minutes using the Carver hydraulic compressor (CE, Model 4350). In this way, the void volumes between and within SAM particles are quite close, if not the same, for Comparative Example 1 and Example 1. The sample was dried in a convection oven at 80° C. for 12 hours before testing.

A 1 g compressed SAM sheet was formed without embossing. The prepared SAM sheet was placed on a flat metal plate, covered with a 1″×1″ metal patterned plate with protruding balls of 250 μm diameter, the balls side facing downward towards the SAM sheet (FIG. 1). The Carver hydraulic compressor (CE, Model 4350) was used to create the embossing pattern by applying a 1000 lb load to a plasticized SAM sheet for 5 minutes. After that, the SAM sheet was flipped over and compressed one more time with the metal balls under same pressure and same dwell time. The resultant SAM sheet has a clear pattern on the surface (FIG. 2). The scale bar shows the diameter of dent of 243 μm. The size of the dent is consistent with the size of metal balls of the embossing plate.

The final 1 g compressed SAM sheet had two-sided embossing. The sample was dried in a convection oven at 80° C. for 12 hours before testing.

The protrusions of this example were ball-shaped, but the protrusion of the pins could be any shape. Shapes without sharper corners, such as spheres, could be less damaging to the SAM particles. The depth of the indentations from the shapes could be in the range of from about 10 μm to 200

Absorbency Evaluation.

Equal masses of embossed and non-embossed SAM sheet samples were each individually dropped in a 100 mL beaker containing 30 mL NaCl solution, which contained blue dye to improve visualization during testing. The time and process of the SAM sheet completely absorbing the saline solution was monitored and compared.

The testing process for both samples to compare their absorbency properties is shown in FIGS. 3a-3e. FIG. 3a shows the testing beakers with 30 mL NaCl solution and blue dye. FIG. 3b shows at the start of the testing (0 min) by adding SAM sheets into the respective NaCl solutions. FIG. 3c shows the completion of absorption of liquid for Example 1 at 27 minutes. After completion, the swollen SAM particles were cast off onto white paper to verify the complete absorption of the fluid (FIG. 3d). At 40 min, Comparative Example 1 completed absorbing all fluid and was cast off onto white paper to verify completion (FIG. 3e). By the time Comparative Example 1 was cast off onto white paper, Example 1 had already turned white because it had finished the absorbing process 13 minutes earlier and the absorbed fluid already diffused into the center of each SAM particle. Absorbency times are summarized in Table 1.

Compressing SAM particles into sheets generally leads to lower intake rates and higher intake times compared with SAM particles that are not compressed into sheets due to the loss of free volume within SAM molecular structure and surface area. However, the results demonstrated herein prove that SAM with surface embossing could lead to increase of surface area, thereby increasing the absorbency intake rate compared to the compressed SAM without embossing.

Flexible Absorbent Binder Film.

FAB is a proprietary crosslinked acrylic acid copolymer that develops absorbency properties after it is applied to a substrate and dried, FAB itself can also be casted into film and dried, yet the resultant 100% FAB film is quite rigid and stiff. The chemistry of FAB is similar to standard SAPs except that the latent crosslinking component allows it to be applied onto the substrate of choice as an aqueous solution and then converted into a superabsorbent coating upon drying. When the water is removed, the crosslinker molecules in the polymeric chain come into contact with each other and covalently bond to form a crosslinked absorbent.

In the examples of this disclosure, FAB was coated on a nonwoven substrate to provide a single layer with both intake and retention functions, as well as flexibility. FAB solution with 32% (wt/wt) solids was coated on a nonwoven substrate through a slot die with two rolls. After coating, the coated film was cured by drying in a convection oven at 55° C. for 20-30 minutes, or until the film was dry, to remove the water.

Compression embossing was applied on FAB films. Two-sided embossing was applied on a FAB film. The absorbent properties were characterized and compared through saline absorption testing. The FAB film with an embossed pattern showed 91.67% faster intake rate compared with the FAB film without an embossed pattern.