Apparatus and method for embossing web material

In an apparatus for embossing a thermoplastic web material and including a first embossing member having a resilient embossing surface providing a primary embossing pattern defined by lands and recesses, said recesses extending about 3 to 50 mils below the surface of said lands;

• a second embossing member having a resilient embossing surface providing a secondary embossing pattern having a depth less than that of said recesses of said primary embossing pattern;
• means mounting said first and second embossing members for relative movement to define a roll nip therebetween;
• means to pass a heated thermoplastic web material through said nip to form an embossed pattern thereon;
• the improvement wherein both said resilient surfaces have a thickness of at least about 0.16 centimeters, said resilient surface of said first embossing member having a hardness of about 50 to 85 durometer on the Shore A scale and being at least about 5 durometer on the Shore A scale harder than said resilient surface of said second embossing member, the resilient surface of said second member having a hardness of about 45 to 80 durometer on the Shore A scale and said roll nip exerting sufficient pressure to temporarily deform both said resilient surfaces therein, the associated web material being pressed in said nip between said resilient surfaces into surface-conforming contact with said first embossing member and remaining in contact with said primary embossing pattern thereof upon passage from said nip;
• and means for stripping the associated web material from said primary embossing pattern of said first embossing member at a point spaced from said nip in the direction of rotation of said first embossing member.

In a method for embossing a thermoplastic web material, the steps comprising:

• a. heating a thermoplastic web material to an elevated temperature to its softening range;
• b. passing the heated web material into a roll nip formed between first and second embossing members having respective resilient embossing surfaces, said resilient embossing surface of said first embossing member providing a primary embossing pattern and having a hardness of about 50 to 85 durometer on the Shore A scale and at least about 5 durometer on the Shore A scale harder than said resilient embossing surface of said second embossing member, the resilient embossing surface of said second embossing member providing a secondary embossing pattern of lesser depth than the depth of the primary embossing pattern, said embossing surface of said second embossing member having a hardness of about 45 to 80 durometer Shore A scale;
• c. exerting sufficient pressure in said nip to temporarily deform both said resilient surfaces therein and to press said web material between said resilient surfaces into surface conforming contact with said first embossing member and into surface conforming contact with said secondary embossing pattern;
• d. withdrawing said web material from said nip while maintaining it in contact with said primary embossing pattern while said first embossing member rotates away from said nip;
• e. allowing said web material to cool while in contact with said primary embossing pattern sufficiently to set the embossed pattern therein;
• and
• f. removing the embossed web material from said primary embossing pattern of said first embossing member at a point spaced from said nip.