Fibrillated rayon-containing, water-decomposable fibrous sheet

Abstract

Conventional water-decomposable fibrous sheets for cleaning sheets capable of being disposed of in toilets and others do not have well-balanced decomposability in water and strength. The water-decomposable fibrous sheet containing from 5 to 100% by mass of fibrillated rayon having a fiber length of at most 10 mm and having a degree of beating of at most 700 cc, optionally along with other fibers having a length of at most 10 mm, has good decomposability in water and high wet strength. When subjected to water-jetting treatment, it becomes more bulky to have a soft feel.

What is claimed is:  
     
         1 . A water-decomposable fibrous sheet, comprising from 3% by mass to 100% by mass of fibrillated rayon comprising primary fibers and microfibers extending therefrom, and from 0% by mass to 97% by mass of other fibers having a length of at most 10 mm, wherein: 
 the fibrillated rayon has a degree of beating of at most 700 cc; the primary fibers have a length in a range of from 1.8 mm to 10 mm at a peak of mass distribution thereof; and at least the microfibers extending from the primary fibers of the fibrillated rayon are entangled with at least one of other primary fibers, other microfibers extending from the other primary fibers and the other fibers.    
     
     
         2 . The water-decomposable fibrous sheet as claimed in  claim 1 , wherein the primary fibers have a length of from 2 5 mm to less than 4.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of smaller than 400 cc.  
     
     
         3 . The water-decomposable fibrous sheet as claimed in  claim 2 , wherein the microfibers having a length of at most 1 mm account for from 0.5 to 15% by mass of the self-weight of the fibrillated rayon.  
     
     
         4 . The water-decomposable fibrous sheet as claimed in  claim 1 , wherein the primary fibers have a length of from 2.5 mm to less than 4.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of from 400 cc to 700 cc  
     
     
         5 . The water-decomposable fibrous sheet as claimed in  claim 4 , wherein the microfibers having a length of at most 1 mm account for from 0.1 to 5% by mass of the self-weight of the fibrillated rayon.  
     
     
         6 . The water-decomposable fibrous sheet as claimed in  claim 1 , wherein the primary fibers have a length of from 4 5 mm to 7 5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of smaller than 400 cc.  
     
     
         7 . The water-decomposable fibrous sheet as claimed in  claim 6 , wherein the microfibers having a length of at most 1 mm account for from 8 to 65% by mass of the self-weight of the fibrillated rayon.  
     
     
         8 . The water-decomposable fibrous sheet as claimed in  claim 1 , wherein the primary fibers have a length of from 4.5 mm to 7.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of from 400 cc to 700 cc.  
     
     
         9 . The water-decomposable fibrous sheet as claimed in  claim 8 , wherein the microfibers having a length of at most 1 mm account for from 0.3 to 50% by mass of the self-weight of the fibrillated rayon.  
     
     
         10 . The water-decomposable fibrous sheet as claimed in  claim 1 , wherein the fibers having a length of at most 10 mm are biodegradable fibers.  
     
     
         11 . The water-decomposable fibrous sheet as claimed in  claim 10 , wherein the biodegradable fibers are those of at least one selected from the group consisting of regenerated cellulose, pulp, aliphatic polyesters, polyvinyl alcohol and collagen  
     
     
         12 . The water-decomposable fibrous sheet as claimed in  claim 1 , of which the basis weight falls between 20 and 100 g/m 2 .  
     
     
         13 . The water-decomposable fibrous sheet as claimed in  claim 1 , which has a degree of decomposition in water of at most 200 seconds, as measured according to JIS P-4501.  
     
     
         14 . The water-decomposable fibrous sheet as claimed in  claim 1 , which has a wet strength of at least 110 g/25 mm.  
     
     
         15 . The water-decomposable fibrous sheet as claimed in  claim 1 , which has a dry strength of at least 350 g/25 mm.  
     
     
         16 . The water-decomposable fibrous sheet as claimed in  claim 1 , which is a non-woven fabric having been subjected to water-jetting treatment.  
     
     
         17 . The water-decomposable fibrous sheet as claimed in  claim 1 , wherein the fineness of the fibrillated rayon is from 1.2 to 1.9 dtex.  
     
     
         18 . The water-decomposable fibrous sheet as claimed in  claim 1 , wherein the primary fibers have a length of 3±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 0.1 to 10% by mass of the self-weight of the fibrillated rayon.  
     
     
         19 . The water-decomposable fibrous sheet as claimed in  claim 1 , wherein the primary fibers have a length of 4±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 1 to 14% by mass of the self-weight of the fibrillated rayon.  
     
     
         20 . The water-decomposable fibrous sheet as claimed in  claim 1 , wherein the primary fibers have a length of 5±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 0.3 to 45% by mass of the self-weight of the fibrillated rayon.  
     
     
         21 . The water-decomposable fibrous sheet as claimed in  claim 1 , wherein the primary fibers have a length of 6±0.5 mm at a peak of mass distribution thereof and the microfibers having a length of at most 1 mm account for from 5 to 50% by mass of the self-weight of the fibrillated rayon.  
     
     
         22 . The water-decomposable fibrous sheet as claimed in  claim 1 , wherein the primary fibers have a length of 7±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 10 to 65% by mass of the self-weight of the fibrillated rayon.  
     
     
         23  A water-decomposable fibrous sheet, comprising from 3% by mass to 100% by mass of fibrillated rayon comprising primary fibers and microfibers extending therefrom, and from 0% by mass to 97% by mass of other fibers having a length of at most 10 mm, wherein. 
 the primary fibers have a length in a range of from 1.8 mm to 10 mm at a peak of mass distribution thereof; the microfibers having a length of at most 1 mm account for from 0 1 to 65% by mass of the self-weight of the fibrillated rayon; and at least the microfibers extending from the primary fibers of the fibrillated rayon are entangled with at least one of other primary fibers, other microfibers extending from the other primary fibers and the other fibers.  
 
     
     
         24 . The water-decomposable fibrous sheet as claimed in  claim 23 , wherein the primary fibers have a length of from 2.5 mm to less than 4.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of smaller than 400 cc.  
     
     
         25 . The water-decomposable fibrous sheet as claimed in  claim 24 , wherein the microfibers having a length of at most 1 mm account for from 0.5 to 15% by mass of the self-weight of the fibrillated rayon.  
     
     
         26 . The water-decomposable fibrous sheet as claimed in  claim 23 , wherein the primary fibers have a length of from 2.5 mm to less than 4.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of from 400 cc to 700 cc.  
     
     
         27 . The water-decomposable fibrous sheet as claimed in  claim 26 , wherein the microfibers having a length of at most 1 mm account for from 0 1 to 5% by mass of the self-weight of the fibrillated rayon.  
     
     
         28 . The water-decomposable fibrous sheet as claimed in  claim 23 , wherein the primary fibers have a length of from 4 5 mm to 7.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of smaller than 400 cc.  
     
     
         29 . The water-decomposable fibrous sheet as claimed in  claim 28 , wherein the microfibers having a length of at most 1 mm account for from 8 to 65% by mass of the self-weight of the fibrillated rayon.  
     
     
         30 . The water-decomposable fibrous sheet as claimed in  claim 23 , wherein the primary fibers have a length of from 4.5 mm to 7.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of from 400 cc to 700 cc.  
     
     
         31 . The water-decomposable fibrous sheet as claimed in  claim 30 , wherein the microfibers having a length of at most 1 mm account for from 0.3 to 50% by mass of the self-weight of the fibrillated rayon.  
     
     
         32 . The water-decomposable fibrous sheet as claimed in  claim 23 , wherein the fibers having a length of at most 10 mm are biodegradable fibers.  
     
     
         33  The water-decomposable fibrous sheet as claimed in  claim 32 , wherein the biodegradable fibers are those of at least one selected from the group consisting of regenerated cellulose, pulp, aliphatic polyesters, polyvinyl alcohol and collagen.  
     
     
         34  The water-decomposable fibrous sheet as claimed in  claim 23 , of which the basis weight falls between 20 and 100 g/m 2 .  
     
     
         35  The water-decomposable fibrous sheet as claimed in  claim 23 , which has a degree of decomposition in water of at most 200 seconds, as measured according to JIS P-4501.  
     
     
         36 . The water-decomposable fibrous sheet as claimed in  claim 23 , which has a wet strength of at least 110 g/25 mm.  
     
     
         37 . The water-decomposable fibrous sheet as claimed in  claim 23 , which has a dry strength of at least 350 g/25 mm.  
     
     
         38 . The water-decomposable fibrous sheet as claimed in  claim 23 , which is a non-woven fabric having been subjected to water-jetting treatment.  
     
     
         39 . The water-decomposable fibrous sheet as claimed in  claim 23 , wherein the fineness of the fibrillated rayon is from 1.2 to 1.9 dtex.  
     
     
         40 . The water-decomposable fibrous sheet as claimed in  claim 23 , wherein the primary fibers have a length of 3±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 0.1 to 10% by mass of the self-weight of the fibrillated rayon  
     
     
         41  The water-decomposable fibrous sheet as claimed in  claim 23 , wherein the primary fibers have a length of 4±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 1 to 14% by mass of the self-weight of the fibrillated rayon  
     
     
         42 . The water-decomposable fibrous sheet as claimed in  claim 23 , wherein the primary fibers have a length of 5±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 0.3 to 45% by mass of the self-weight of the-fibrillated rayon.  
     
     
         43 . The water-decomposable fibrous sheet as claimed in  claim 23 , wherein the primary fibers have a length of 6±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 5 to 50% by mass of the self-weight of the fibrillated rayon.  
     
     
         44 . The water-decomposable fibrous sheet as claimed in  claim 23 , wherein the primary fibers have a length of 7±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 10 to 65% by mass of the self-weight of the fibrillated rayon  
     
     
         45 . A water-decomposable fibrous sheet, comprising from 3% by mass to 100% by mass of fibrillated rayon comprising primary fibers and microfibers extending therefrom, and from 0% by mass to 97% by mass of other fibers having a length of at most 10 mm, wherein 
 the fibrillated rayon has a degree of beating of at most 700 cc, the primary fibers have a length in a range of from 1.8 mm to 10 mm at a peak of mass distribution thereof; and at least the microfibers extending from the primary fibers of the fibrillated rayon are hydrogen bonded with at least one of other primary fibers, other microfibers extending from the other primary fibers and the other fibers.    
     
     
         46 . The water-decomposable fibrous sheet as claimed in  claim 45 , wherein the primary fibers have a length of from 2.5 mm to less than 4.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of smaller than 400 cc.  
     
     
         47 . The water-decomposable fibrous sheet as claimed in  claim 46 , wherein the microfibers having a length of at most 1 mm account for from 0.5 to 15% by mass of the self-weight of the fibrillated rayon.  
     
     
         48 . The water-decomposable fibrous sheet as claimed in  claim 45 , wherein the primary fibers have a length of from 2.5 mm to less than 4.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of from 400 cc to 700 cc  
     
     
         49 . The water-decomposable fibrous sheet as claimed in  claim 48 , wherein the microfibers having a length of at most 1 mm account for from 0 1 to 5% by mass of the self-weight of the fibrillated rayon.  
     
     
         50 . The water-decomposable fibrous sheet as claimed in  claim 45 , wherein the primary fibers have a length of from 4 5 mm to 7.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of smaller than 400 cc.  
     
     
         51 . The water-decomposable fibrous sheet as claimed in  claim 50 , wherein the microfibers having a length of at most 1 mm account for from 8 to 65% by mass of the self-weight of the fibrillated rayon.  
     
     
         52 . The water-decomposable fibrous sheet as claimed in  claim 45 , wherein the primary fibers have a length of from 4.5 mm to 7.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of from 400 cc to 700 cc.  
     
     
         53 . The water-decomposable fibrous sheet as claimed in  claim 52 , wherein the microfibers having a length of at most 1 mm account for from 0.3 to 50% by mass of the self-weight of the fibrillated rayon.  
     
     
         54 . The water-decomposable fibrous sheet as claimed in  claim 45 , wherein the fibers having a length of at most 10 mm are biodegradable fibers  
     
     
         55 . The water-decomposable fibrous sheet as claimed in  claim 54 , wherein the biodegradable fibers are those of at least one selected from the group consisting of regenerated cellulose, pulp, aliphatic polyesters, polyvinyl alcohol and collagen.  
     
     
         56 . The water-decomposable fibrous sheet as claimed in  claim 45 , of which the basis weight falls between 20 and 100 g/m 2 .  
     
     
         57 . The water-decomposable fibrous sheet as claimed in  claim 45 , which has a degree of decomposition in water of at most 200 seconds, as measured according to JIS P-4501.  
     
     
         58 . The water-decomposable fibrous sheet as claimed in  claim 45 , which has a wet strength of at least 110 g/25 mm.  
     
     
         59 . The water-decomposable fibrous sheet as claimed in  claim 45 , which has a dry strength of at least 350 g/25 mm.  
     
     
         60 . The water-decomposable fibrous sheet as claimed in  claim 45 , which is produced in a paper-making process.  
     
     
         61 . The water-decomposable fibrous sheet as claimed in  claim 45 , wherein the fineness of the fibrillated rayon is from 1.2 to 1.9 dtex.  
     
     
         62 . The water-decomposable fibrous sheet as claimed in  claim 45 , wherein the primary fibers have a length of 3±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 0.1 to 10% by mass of the self-weight of the fibrillated rayon.  
     
     
         63  The water-decomposable fibrous sheet as claimed in  claim 45 , wherein the primary fibers have a length of 4±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 1 to 14% by mass of the self-weight of the fibrillated rayon  
     
     
         64  The water-decomposable fibrous sheet as claimed in  claim 45 , wherein the primary fibers have a length of 5±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 0.3 to 45% by mass of the self-weight of the fibrillated rayon.  
     
     
         65 . The water-decomposable fibrous sheet as claimed in  claim 45 , wherein the primary fibers have a length of 6±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 5 to 50% by mass of the self-weight of the fibrillated rayon.  
     
     
         66 . The water-decomposable fibrous sheet as claimed in  claim 45 , wherein the primary fibers have a length of 7±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 10 to 65% by mass of the self-weight of the fibrillated rayon  
     
     
         67  A water-decomposable fibrous sheet, comprising from 3% by mass to 100% by mass of fibrillated rayon comprising primary fibers and microfibers extending therefrom, and from 0% by mass to 97% by mass of other fibers having a length of at most 10 mm, wherein: 
 the primary fibers have a length in a range of from 1.8 mm to 10 mm at a peak of mass distribution thereof; the microfibers having a length of at most 1 mm account for from 0.1 to 65% by mass of the self-weight of the fibrillated rayon; and at least the microfibers extending from the primary fibers of the fibrillated rayon are hydrogen bonded with at least one of other primary fibers, other microfibers extending from the other primary fibers and the other fibers  
 
     
     
         68 . The water-decomposable fibrous sheet as claimed in  claim 67 , wherein the primary fibers have a length of from 2.5 mm to less than 4.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of smaller than 400 cc.  
     
     
         69 . The water-decomposable fibrous sheet as claimed in- claim 68 , wherein the microfibers having a length of at most 1 mm account for from 0.5 to 15% by mass of the self-weight of the fibrillated rayon.  
     
     
         70 . The water-decomposable fibrous sheet as claimed in  claim 67 , wherein the primary fibers have a length of from 2.5 mm to less than 4.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of from 400 cc to 700 cc.  
     
     
         71 . The water-decomposable fibrous sheet as claimed in  claim 70 , wherein the microfibers having a length of at most 1 mm account for from 0.1 to 5% by mass of the self-weight of the fibrillated rayon  
     
     
         72 . The water-decomposable fibrous sheet as claimed in  claim 67 , wherein the primary fibers have a length of from 4.5 mm to 7.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of smaller than 400 cc.  
     
     
         73 . The water-decomposable fibrous sheet as claimed in  claim 72 , wherein the microfibers having a length of at most 1 mm account for from 8 to 65% by mass of the self-weight of the fibrillated rayon.  
     
     
         74 . The water-decomposable fibrous sheet as claimed in  claim 67 , wherein the primary fibers have a length of from 4.5 mm to 7.5 mm at a peak of mass distribution thereof and the fibrillated rayon has a degree of beating of from 400 cc to 700 cc.  
     
     
         75 . The water-decomposable fibrous sheet as claimed in  claim 74 , wherein the microfibers having a length of at most 1 mm account for from 0.3 to 50% by mass of the self-weight of the fibrillated rayon.  
     
     
         76 . The water-decomposable fibrous sheet as claimed in  claim 67 , wherein the fibers having a length of at most 10 mm are biodegradable fibers.  
     
     
         77 . The water-decomposable fibrous sheet as claimed in  claim 76 , wherein the biodegradable fibers are those of at least one selected from the group consisting of regenerated cellulose, pulp, aliphatic polyesters, polyvinyl alcohol and collagen  
     
     
         78 . The water-decomposable fibrous sheet as claimed in  claim 67 , of which the basis weight falls between 20 and 100 g/m 2 .  
     
     
         79 . The water-decomposable fibrous sheet as claimed in  claim 67 , which has a degree of decomposition in water of at most 200 seconds, as measured according to JIS P-4501.  
     
     
         80 . The water-decomposable fibrous sheet as claimed in  claim 67 , which has a wet strength of at least 110 g/25 mm  
     
     
         81 . The water-decomposable fibrous sheet as claimed in  claim 67 , which has a dry strength of at least 350 g/25 mm.  
     
     
         82 . The water-decomposable fibrous sheet as claimed in  claim 67 , which is produced in a paper-making process.  
     
     
         83 . The water-decomposable fibrous sheet as claimed in  claim 67 , wherein the fineness of the fibrillated rayon is from 1.2 to 1.9 dtex.  
     
     
         84  The water-decomposable fibrous sheet as claimed in  claim 67 , wherein the primary fibers have a length of 3±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 0.1 to 10% by mass of the self-weight of the fibrillated rayon.  
     
     
         85 . The water-decomposable fibrous sheet as claimed in  claim 67 , wherein the primary fibers have a length of 4±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 1 to 14% by mass of the self-weight of the fibrillated rayon.  
     
     
         86  The water-decomposable fibrous sheet as claimed in  claim 67 , wherein the primary fibers have a length of 5±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 0.3 to 45% by mass of the self-weight of the fibrillated rayon.  
     
     
         87 . The water-decomposable fibrous sheet as claimed in  claim 67 , wherein the primary fibers have a length of 6±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 5 to 50% by mass of the self-weight of the fibrillated rayon.  
     
     
         88 . The water-decomposable fibrous sheet as claimed in  claim 67 , wherein the primary fibers have a length of 7±0.5 mm at a peak of mass distribution thereof, and the microfibers having a length of at most 1 mm account for from 10 to 65% by mass of the self-weight of the fibrillated rayon.  
     
     
         89 . A water-decomposable fibrous sheet, comprising from 3 to 100% by mass of fibrillated rayon of such that primary fibers constituting it have a length of from 1.8 to 10 mm, and from 0 to 97% by mass of other fibers having a length of at most 10 mm, and having; 
 a basis weight of from 20 to 100 g/m 2 , a thickness of at least 0.2 mm, a degree of decomposition in water in a previously wetted condition as measured according to JIS P-4501 of at most 200 seconds, and a wet strength of at least 110 g/25 mm.