Method and apparatus for manufacturing a dryformed fibrous web
The present invention relates to webs made of cellulose fibers admixed with thermobonding fibers, wherein the web surfaces are sealed to a greater or lesser extent by adding thereto a binder in modest amounts. The binder is applied without any attempt to provide deep penetration of said binder into the web material. By applying the binder in the form of a foam, a minimum of binder is required to provide bonded webs exhibiting minimal linting.
1. A process for manufacturing an absorbent dryformed paper web having a plurality of layers, with an optional center layer containing a superabsorbent material comprising:
a. laying a web of cellulose fibers, admixed with thermobonding fibers, onto a forming wire, wherein the thermobonding fibers comprise about 3–25 wt % of the total fiber content, wherein the thermobonding fibers are distributed such that there is a gradual increase in thermobonding fiber concentration nearer the surface of the web;
b. applying a binder to form binder layers on the top surface and bottom surface of the web of cellulose fibers, wherein the amount of dry matter in the binder is from about 0.5–15 wt % and the amount of dry matter applied to the surface of the web is from about 0.5–20 g. of dry matter per square meter of web surface; and
c. heating the web to a temperature sufficient to melt the thermobonding fibers and increase the tensile strength of the finished product.
2. The process according to claim 1 wherein the amount of dry matter in the binder is from about 0.5–15 wt %.
3. The process according to claim 1 wherein the binder is applied in an amount of about 0.5–10 grams dry matter per square meter of web surface.
4. The process according to claim 1 wherein the binder is an aqueous binder.
5. The process according to claim 1 wherein the binder contains pigments admixed therewith.
6. The process according to claim 2 wherein said web comprises about 10–25 wt % thermobonding fibers and the amount of binder applied to the surface of the web is about 0.5–10 grams per square meter of web surface.
7. The process according to claim 2 wherein said web comprises about 3–7 wt % of thermobonding fibers and the amount of binder applied to the surface of the web is about 5–20 grams per square meter of web surface.
8. A process for manufacturing an absorbent dryformed paper web having a plurality of layers, comprising:
a. laying a web of cellulose fiber, admixed with thermobonding fibers, onto a forming wire, wherein the thermobonding fibers comprise about 3–25 wt % of the total fiber content, wherein the thermobonding fibers are distributed such that there is a gradual increase in the thermobonding fiber concentration nearer the surface of the the web;
b. applying a binder to the top surface and to the bottom surface of the web of cellulose fibers to form a binder layer on the top surface and on the bottom surface of the web of cellulose fibers, wherein the amount of dry matter in the binder is from about 0.5–15 wt % and the amount of dry matter applied to the surface of the web is from about 0.5–20 g of dry matter per square meter of web surface; and
c. heating the web to a temperature sufficient to melt the thermobonding fibers to provide sealing of dusting fibers under the surface of the binder and increase the tensile strength of the fiber product.
9. The process according to claim 8 wherein the web of cellulose fibers contains a super-absorbent material.
10. The process according to claim 8 wherein the binder is applied as a foam.