A CELLULOSE PAPER COMPOSITE AND PROCESS FOR PREPARATION THEREOF

Abstract

The present invention relates to a cellulose paper composite having enhanced ear propagation strength, ratio of tensile strength for cut and uncut paper, tensile strength and tensile modulus. The present invention further relates to a process for the preparation of cellulose paper composite having enhanced tensile strength and tensile modulus.

Claims

1. A cellulose paper composite comprising 80-85% of micro-cellulose and 15-20% of nanocellulose, wherein the tear propagation resistance of the composite is increased by 50-70%.

2. The cellulose paper composite as claimed in claim 1, wherein the the ratio (R) of tensile strength of sample with an existing cut or tear to the tensile strength of the sample without a cut is 75-95%.

3. The cellulose paper composite as claimed in claim 1, wherein the increase in tensile modulus is 15-40%, and tensile strength by 30-50%, when compared to micro cellulose paper composite.

4. A process for the preparation of cellulose paper composite as claimed in claim 1, wherein said process comprising the steps of: a) cutting the nanocellulose source material into small pieces; b) subjecting the pieces of step (a) to alkali treatment by washing with base for 4 to 5 hours under mechanical stirring to form fibres; c) subjecting the fibres of step (b) for bleaching treatment by using bleaching solution at temperature ranging from 70 C. to 80 C. for the time period ranging from 3 to 4 h; repeating process for 2 to 3 times to afford pulp; d) filtering and rinsing the pulp of step (c) followed by grinding the pulp in ultra-fine micro grinder; and e) combining the nanocellulose pulp prepared as per above steps (a-d) with microcellulose pulp in different compositions to make a composite paper.

5. The process as claimed in claim 4, wherein said nanocellulose source material of step (a) is selected from cotton rag, sugarcane bagasse and sisal fibers.

6. The process as claimed in claim 4, wherein said alkali treatment of step (b) is carried out by washing small pieces of nanocellulose source material with 1-10% base solution at 50 to 80 C.

7. The process as claimed in claim 4, wherein said alkali treatment of step (b) is carried out by washing small pieces of nanocellulose source material with 1-10% sodium hydroxide solution at 50 to 80 C.

8. The process as claimed in claim 4, wherein said bleaching solution of step (c) comprises 1:1 ratio of aqueous sodium hypochlorite (NaOCl in water) and an acetate buffer (NaOH and glacial acetic acid, diluted to 1 L using distilled water).

9. The process as claimed in claim 4, wherein the fiber to liquor ratio is maintained 1:30 for both alkali and bleaching treatment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1: Paper making process

[0034] FIG. 2: With cut and without cut samples

DETAILED DESCRIPTION OF THE INVENTION

[0035] The invention will now be described in detail in connection with certain preferred and optional embodiments, so that various aspects thereof may be more fully understood and appreciated.

[0036] In view of the above, the present invention provides a reinforced cellulose paper composite comprising 50 to 90% of micro-cellulose and 10 to 50% of nanocellulose having enhanced tensile strength and tensile modulus. The higher surface area of nanocellulose fibrils, leads to more number of hydrogen bonds and more bonding area between the microcellulose and nanocellulose which linked with good mechanical interlocking provide necessary strength and stiffness to the composite paper.

[0037] In an embodiment, the present invention provides a reinforced cellulose paper composite comprising 50 to 90% of micro-cellulose and 10 to 50% of nanocellulose having enhanced tensile strength and tensile modulus.

[0038] In a preferred embodiment, the present invention provides a cellulose paper composite comprising 80 to 85% of micro-cellulose and 15 to 20% of nanocellulose having enhanced tensile strength and tensile modulus.

[0039] The tensile strength of reinforced cellulose paper composite is in the range of 20-50 MPa. In preferred embodiment, the tensile strength of with cut and without cut sample of cotton rag nanocellulose is in the range of 20-35 MPa and 25-40 MPa respectively.

[0040] The tensile modulus of reinforced cellulose paper composite is in the range of 3150 to 5050 MPa.

[0041] In another embodiment, the present invention provides a process for the preparation of said Reinforced Cellulose Paper composite comprising the steps of: [0042] a) cutting the nanocellulose source material into small pieces; [0043] b) subjecting the pieces of step (a) to alkali treatment by washing with base for 4 to 5 hours under mechanical stirring to form fibres; [0044] c) subjecting the fibres of step (b) for bleaching treatment by using bleaching solution at temperature ranging from 70 C. to 80 C. for the time period ranging from 3 to 4 h; repeating process for 2 to 3 times to afford pulp; [0045] d) filtering and rinsing the pulp of step (c) followed by grinding the pulp in ultra-fine micro grinder and [0046] e) combining the nanocellulose pulp prepared as per above steps (a-d) with microcellulose pulp in different compositions to make a composite paper.

[0047] In a preferred embodiment, the nanocellulose source material of step (a) is selected from cotton rag, sugarcane bagasse or sisal fibers.

[0048] The alkali treatment of step (b) is carried out by washing small pieces of nanocellulose source material with 1-10% base solution at 50 to 80 C. Preferably, the alkali treatment of step (b) is carried out by washing small pieces of nanocellulose source material with 1-10% sodium hydroxide solution at 50 to 80 C.

[0049] The bleaching solution of step (c) comprises 1:1 ratio of aqueous sodium hypochlorite (NaOCl in water) and an acetate buffer (NaOH and glacial acetic acid, diluted to 1 L using distilled water).

[0050] The fiber to liquor ratio are maintained 1:30 for both alkali and bleaching treatment. The nanocellulose pulp of step (d) is combined with microcellulose pulp to afford composite paper.

[0051] In yet another embodiment, the present invention provides a paper making process comprising the steps of: [0052] a) preparing A4 printing paper pulp with the consistency of 1.2 to 1.57 wt %; [0053] b) beating the pulp in valley beater to get required Schopper-Riegler (SR) value, e.g. 40, 50, or 60 as per requirement and [0054] c) adding said A4 recycled pulp of step (b) to sheet former machine to form paper.

[0055] In a preferred embodiment, different source of nanocellulose/A4 recycled composites paper are made by varying nanocellulose content from 10 to 50%. In another preferred embodiment, the process is carried out at ambient temperature.

[0056] The present invention provides effect of with cut and without cut sample of nanocellulose source material on tensile strength and tensile modulus of A4 recycled paper.

[0057] Table 1 represent the effect of cotton rag (CR) nano cellulose on the mechanical properties of the composite paper. Values in bracket represent the standard deviation.

TABLE-US-00001 TABLE 1 Sample Tensile Strength (MPa) Tensile Modulus (MPa) Name Without Cut With Cut Without Cut With Cut A4 28.0 (0.7) 21.2 (0.8) 3156 (88) 3202 (107) 10CR 36.5 (1.7) 26.7 (1.5) 3689 (310) 3288 (177) 15CR 37.3 (1.2) 33.4 (0.9) 3896 (62.4) 3812 (337) 20CR 39.0 (0.5) 34.4 (2.9) 4328 (110) 4323 (207)

[0058] The tensile strength of with cut and without cut sample of cotton rag nanocellulose is in the range of 25-35 MPa and 35-40 MPa respectively.

[0059] The tensile modulus of with cut and without cut sample of cotton rag nanocellulose is in the range of 3250-4330 MPa and 3600-4400 MPa respectively.

[0060] Table 2 represent the effect of sugarcane (SC) nanocellulose on the mechanical properties of the composite paper. Values in bracket represent the standard deviation.

TABLE-US-00002 TABLE 2 Sample Tensile Strength (MPa) Tensile Modulus (MPa) Name Without Cut With Cut Without Cut With Cut A4 28.0 (0.7) 21.2 (0.8) 3156 (88) 3202 (107) 10 SC 35 (0.55) 27.6 (1.47) 3505 (205) 3950 (339) 20 SC 41 (0.45) 35 (0.6) 4090 (144) 5045 (217) 50 SC 48.41 (1.13) 26.9 (1.06) 3432 (381) 3519 (131)

[0061] The tensile strength of with cut and without cut sample of sugarcane nanocellulose is in the range of 25-40 MPa and 30-50 MPa respectively.

[0062] The tensile modulus of with cut and without cut sample of sugarcane nanocellulose is in the range of 3500-5100 MPa and 3400-4200 MPa.

[0063] Table 3 represent the effect of sugarcane nano cellulose from sisal on the mechanical properties of the composite paper. Bracket value represents the standard deviation.

TABLE-US-00003 TABLE 3 Sample Tensile Strength (MPa) Tensile Modulus (MPa) Name Without Cut With Cut Without Cut With Cut A4 28.0 (0.7) 21.2 (0.8) 3156 (88) 3202 (107) 10 Sisal 36.0 (0.55) 27.1 (1.44) 4009 (90) 4664 (94) 15 Sisal 38.0 (0.95) 32.6 (1.6) 4246 (225) 4646 (151) 20 Sisal 39.3 (0.46) 33.0 (0.6) 3946 (179) 3614 (147)

[0064] The tensile strength of with cut and without cut sample of sisal nanocellulose is in the range of 25-35 MPa and 30-40 MPa.

[0065] The tensile modulus of with cut sample of sisal nanocellulose is in the range of 3500-4800 MPa and 3700-4300 MPa respectively.

[0066] The ratio of tensile strength and tensile modulus for Cotton rag, sugarcane and sisal nano cellulose paper composites is listed in Table 4

TABLE-US-00004 Tensile Strength (MPa) Tensile Modulus (MPa) Sample Without With Without With Name Cut Cut R* Cut Cut A4 1.00 1.00 76% 1.00 1.00 10CR 1.30 1.26 73% 1.17 1.03 15CR 1.33 1.58 90% 1.23 1.19 20CR 1.39 1.62 88% 1.37 1.35 Tensile Strength (MPa) Tensile Modulus (MPa) Sample Without With Without With Name Cut Cut R Cut Cut A4 1.00 1.00 76% 1.00 1.00 10 SC 1.25 1.30 79% 1.11 1.23 20 SC 1.46 1.65 85% 1.30 1.58 50 SC 1.73 1.27 56% 1.09 1.10 A4 1.00 1.00 76% 1.00 1.00 10 Sisal 1.29 1.28 75% 1.27 1.46 15 Sisal 1.36 1.54 86% 1.35 1.45 20 Sisal 1.40 1.56 84% 1.25 1.13 *R = ratio of tensile strength with cut to tensile strength without cut, R is a measure of tear propagation resistance to total tear resistance, Total tear resistance consists of tear initiation and tear propagation resistance

[0067] The tensile strength and tensile modulus in table 4 is expressed as a ratio of tensile strength or modulus of paper measured for each concentration of nano cellulose (with or without cut) to tensile strength or modulus of A4 paper(with or without cut respectively).

[0068] In an embodiment, referring to tables 1-4, an increase in tensile modulus by 15-40%, preferably 20-40%, is achieved by the addition of 15-20% nano cellulose for uncut paper.

[0069] In an embodiment, referring to tables 1-4, an increase in tensile strength by 30-50% is achieved by the addition of 15-20% nano cellulose for uncut paper.

[0070] In one more embodiment of the invention, the ratio (R) of tensile strength of sample with a existing cut or tear (which is a measure of only tear propagation resistance) to the tensile strength of the sample without a cut (a measure of both tear initiation and propagation resistance) is measured. Referring to table 4, a 75-95% enhancement is seen for an addition of 15-20 nano cellulose.

[0071] In a preferred embodiment, the ratio R is enhanced by 80-90% for an addition of 15-20 nano cellulose.

[0072] In yet another embodiment of the invention, tear propagation resistance is studied. Tear propagation resistance is the ratio of ratio of tensile strength of paper with cut measured for each concentration of nano cellulose to tensile strength or modulus of A4 paper with cut. The tear propagation resistance of cut paper is increased by 50-70% for an addition of 15-20% nano cellulose to micro cellulose. The tear propagation resistance is preferably enhanced by 50-65% by the addition of 15-20% nano cellulose to micro cellulose.

[0073] There is no suggestion in any prior art to add nano cellulose in the range of 15-20% to micro cellulose to accomplish enhancement of total tear resistance which consists of tear initiation and tear propagation resistance. It is surprisingly that the concentration range of 15-20% causes enhancement, while increasing the concentration greater than 20% or less than 15% does not cause an enhancement. The prior arts neither suggest nor teach that the specific range of nano cellulose causes enhancement of key parameters of measure of strength of paper.

[0074] The FIG. 1 is pictorial representation of nanocellulose preparation form the raw source material. A1, B1, C1 represent the raw material sugarcane bagasse, cotton rag and sisal respectively. A2, B2, C2 represent the bleached pulp of sugarcane bagasse, cotton rag and sisal respectively. A3, B3, C3 represent the final nanocellulose product of sugarcane bagasse, cotton rag and sisal respectively.

[0075] The FIG. 2 shows with cut and without cut samples. Without cut samples data gives information about tensile strength and modulus for the specimen which is not having any deformation in it. It is similar to Edge-tearing strength (TAPPI standard T-470) and is a measure of the force needed to initiate a tear. With cut samples data gives information about tensile strength and modulus of a specimen where a tear is already initiated. This is similar to commonly used tearing test (TAPPI T-414), also often called the Elmendorf tear test, which measures the internal tearing resistance of paper rather than the edge-tear strength of paper.

[0076] The paper composite prepared by the composition of the invention comprising 80-85% micro cellulose and 15-20% nano cellulose is useful in preparing security documents. The paper composition of the invention has enhanced folding resistance and is smooth and is versatile to be used for preparing paper for security applications. Security documents are documents made of paper that need to identified or authenticated as genuine using security features and are selected from, but not limited to currency notes, passports, bonds, certificates, agreements, stamp or stamp paper, share certificates and such like.

[0077] Examples Following examples are given by way of illustration therefore should not be construed to limit the scope of the invention.

EXAMPLE

Preparation of Reinforced Cellulose Paper Composite

[0078] The nanocellulose source material was cut into small pieces. Alkali treatment was carried out by washing the pieces with base for 4 to 5 hours under mechanical stirring to form fibres. Bleaching treatment was carried out on fibres by bleaching solution at the temperature ranging from 70 C-80 C. for the time period ranging from 3 to 4 h; repeating process for 2 to 3 times to afford pulp. Then it was filtered and rinsed followed by grinding said pulp in ultra-fine micro grinder. Then the nano cellulose pulp was combined with micro cellulose pulp to form composite paper in ratios listed in the tables. After drying the paper are tested by tensile testing machine (INSTRON UTM) at rate lmm/min. The 13 mm40 mm rectangular shape specimen are used. At least 6 specimens were tested for each composition listed below in the tables 1-3. Two types of mode were tested with cut and without cut.

[0079] A. Effect of Cotton Rag Nanocellulose on Tensile Strength and Tensile Modulus of A4 Recycled Paper. Figures in Bracket Indicates Std Deviation

TABLE-US-00005 TABLE 1 Sample Tensile Strength (MPa) Tensile Modulus (MPa) Name Without Cut With Cut Without Cut With Cut A4 28.0 (0.7) 21.2 (0.8) 3156 (88) 3202 (107) 10CR 36.5 (1.7) 26.7 (1.5) 3689 (310) 3288 (177) 15CR 37.3 (1.2) 33.4 (0.9) 3896 (62.4) 3812 (337) 20CR 39.0 (0.5) 34.4 (2.9) 4328 (110) 4323 (207)

[0080] B: Effect of Sugarcane Nanocellulose on Tensile Strength and Tensile Modulus of A4 Recycled Paper.

TABLE-US-00006 TABLE 2 Sample Tensile Strength (MPa) Tensile Modulus (MPa) Name Without Cut With Cut Without Cut With Cut A4 28.0 (0.7) 21.2 (0.8) 3156 (179) 3202 (147) 10 SC 35 (0.55) 27.6 (1.47) 3505 (205) 3950 (339) 15 SC 39 (0.95) 29.5 (1.6) 3802 (175) 3762 (181) 20 SC 41 (0.45) 35 (0.6) 4090 (144) 5045 (217) 50 SC 48.41 (1.13) 26.9 (1.06) 3432 (381) 3519 (131)

[0081] C: Effect of Sisal Nanocellulose on Tensile Strength of and Tensile Modulus A4 Recycled Paper.

TABLE-US-00007 TABLE 3 Sample Tensile Strength (MPa) Tensile Modulus (MPa) Name Without Cut With Cut Without Cut With Cut A4 28.0 (0.7) 21.2 (0.8) 3156 (179) 3202 (147) 10 Sisal 36.0 (0.55) 27.1 (1.44) 4009 (90) 4664 (94) 15 Sisal 38.0 (0.95) 32.6 (1.6) 4246 (225) 4646 (151) 20 Sisal 39.3 (0.46) 33.0 (0.6) 3946 (179) 3614 (147)

Advantages of the Invention:

[0082] 1) A Reinforced Cellulose Paper composite showing better tensile strength and tensile modulus is provided. [0083] 2) Reinforced Cellulose Paper composite shows smoothness and folding endurance.