Paper-Making Aid Composition and Process for Increasing Tensile Strength of Paper

Abstract

A paper-making aid composition, as well as processes for increasing tensile strength in paper and paper-making processes are provided. The paper-making composition comprises an anionic dialdehyde-modified polyacrylamide and a polyamide polyamine-epichlorohydrin (PAE) resin present in the paper-making aid composition at a weight ratio of PAE resin to anionic dialdehyde-modified polyacrylamide of from about 5:1 to about 1:1.6. The processes utilize an anionic dialdehyde-modified polyacrylamide and PAE resin at certain ratios. The anionic dialdehyde-modified polyacrylamide and PAE resin may be added to the pulp slurry as a composition or separately.

Claims

1. A paper-making aid composition comprising an anionic dialdehyde-modified polyacrylamide and a polyamide polyamine-epichlorohydrin (PAE) resin present in the paper-making aid composition at a weight ratio of PAE resin to anionic dialdehyde-modified polyacrylamide of from about 5:1 to about 1:1.6.

2. The paper-making aid composition of claim 1, wherein the PAE resin and the anionic dialdehyde-modified polyacrylamide are present at a weight ratio of PAE resin to anionic dialdehyde-modified polyacrylamide of from about 3.5:1 to about 1:1.6.

3. The paper-making aid composition of claim 1, wherein the paper-making aid composition has active content of dialdehyde-modified polyacrylamide and the PAE resin of from about 10 wt % to about 50 wt %.

4. The paper-making aid composition of claim 1, wherein, except for the anionic dialdehyde-modified polyacrylamide and the polyamide polyamine-epichlorohydrin resin, the amount of other chemical aids for paper-making in the paper-making aid composition is from about 0 wt % to about 50 wt %.

5. The paper-making aid composition of claim 1, wherein the paper-making aid composition is free of cationic and amphoteric dialdehyde-modified polyacrylamide.

6. The paper-making aid composition of claim 1, consisting of the PAE resin, the anionic dialdehyde-modified polyacrylamide, and water.

7. The paper-making aid composition of claim 1, wherein the anionic dialdehyde-modified polyacrylamide is glyoxalated polyacrylamide.

8. The paper-making aid composition of claim 1, wherein the paper-making aid composition is free of cationic polyacrylamide polymer.

9. A process for increasing tensile strength of paper comprising adding an anionic dialdehyde-modified polyacrylamide and a polyamide polyamine-epichlorohydrin (PAE) resin at a weight ratio of PAE resin to anionic dialdehyde-modified polyacrylamide of from about 5:1 to about 1:1.6 to a slurry comprising pulp in a pulping process and/or a paper-making process.

10. The process of claim 9, wherein the anionic dialdehyde modified polyacrylamide and the PAE resin are added separately to the paper-making process.

11. The process of claim 9, wherein the pulp comprises softwood bleached kraft pulp and hardwood bleached kraft pulp.

12. A paper-making process comprising: (a) adding an anionic dialdehyde-modified polyacrylamide and a polyamide polyamine-epichlorohydrin (PAE) resin at a weight ratio of PAE resin to anionic dialdehyde-modified polyacrylamide of from about 5:1 to about 1:1.6 into pulp slurry to obtain a treated stock; (b) forming the treated stock obtained in step (a) to obtain a wet paper web; (c) pressing and draining the wet paper web obtained in step (b) to obtain a wet paper sheet; and (d) drying the wet paper sheet obtained in step (c) to obtain a paper sheet.

13. The paper-making aid composition of claim 1, wherein, except for the anionic dialdehyde-modified polyacrylamide and the polyamide polyamine-epichlorohydrin resin, the amount of other chemical aids for paper-making in the paper-making aid composition is from about 0 wt % to about 20 wt %.

14. The paper-making aid composition of claim 1, wherein, except for the anionic dialdehyde-modified polyacrylamide and the polyamide polyamine-epichlorohydrin resin, the amount of other chemical aids for paper-making in the paper-making aid composition is from about 0 wt % to about 5 wt %.

15. The paper-making aid composition of claim 1, wherein the paper-making aid composition is free of amphoteric dialdehyde-modified polyacrylamide.

16. The paper-making aid composition of claim 1, further comprising a retention aid.

17. The process of claim 9, wherein the slurry is thick stock.

18. The process of claim 9, wherein the slurry is carton board furnish.

19. The paper-making process of claim 12, wherein the pulp slurry is thick stock.

20. The paper-making process of claim 12, wherein the pulp slurry is carton board furnish.

Description

EXAMPLES

[0079] The invention is described in more detail by referring to the following Examples and Comparative Examples, but is not limited to these Examples.

1. Paper-Making Process and Characterization of Paper

(a) Method for Making Hand Sheet

[0080] The pulp slurry (thick stock) is obtained from a paper mill. The thick stock comprises a mixed slurry of softwood bleached kraft pulp and hardwood bleached kraft pulp, or other pulp, as main component. Sheet-making is performed after the thick stock is diluted with tap water or white water from paper-making plant to a concentration of about 0.7%.

[0081] Semi-automatic Tappi standard sheet-making machine, provided by FRANK-PTI Co., is used as the sheet-making machine. The specific test method is described in T205 Introduction sp-02. To the diluted pulp, a fixing agent, test additives and retention aids are added successively at a rotation speed of about 800 rpm.

[0082] The pulp added with the agents is poured into a forming cylinder of paper-making machine and undergoes filtering and forming. Afterwards, the forming cylinder is opened, and a bibulous paper is taken to cover the wet paper sheet which is then covered with a flat clamp to remove part of water. Then the paper sample is transferred to a new bibulous paper which is then covered with stainless steel clamp, onto which a bibulous paper is covered again, the wet paper sample is thus accumulated. When accumulating 5 to 10 paper samples, they are provided into a special press machine to perform a two-section pressing, further removing water from paper.

[0083] The pressed paper is transferred to a constant temperature and humidity lab (about 50% humidity at 23 C.), and every single paper sample is placed into a special metal ring. Piling up the metal rings and placing a heavy object onto the metal ring where the paper sample lies on. After air drying for about 24 hours, the paper sample can be peeled successively from stainless steel clamp for corresponding test.

(b) Test Method for Internal Bonding Strength

[0084] The principle of the internal bond impact tester is to measure the energy required to separate the paper sheet by a mechanical equipment so as to reflect the magnitude of the internal bonding strength. The measurement of the internal bonding strength is to express the resistant force that is required to overcome for separating the single or multiple fiber layer(s), which is frequently used to discuss the delamination problem of the paper sheet or paperboard. The test method adopted in the experiment comprises the determination of the force applied by a pendulum to splitting the paper along Z-direction. When the fibers of a hand sheet align in X-Y plane, the exhausted energy is mainly used for the bonding of the fiber, and the length of the fiber and the strength of the fiber itself have no influence on the Scott bonding.

[0085] The equipment used in the experiment was purchased from PTI company. The test method refers to Tappi T569.

[0086] For a test, a paper with a size of around 25.4 mm200 mm is cut out previously, and then tape and paper sample are attached to a base following a sequence of tape-paper sample-tap, and the double-sided adhesive tape and the paper sample are attached to each other closely by applying a force. Afterwards, a pendulum is released to knock and separate the paper sample when the equipment automatically records the force that is required to separate the bonding of the fiber layers for each time, expressed in kg.Math.cm/in.sup.2, J/m.sup.2.

(c) Determination of Viscosity

[0087] Brookfield Programmable LVDV-II+viscometer, manufactured by Brookfield Engineering Laboratories, Inc, Middleboro, Mass., is utilized in this experiment.

0-100 cps, measured by Spindle 1 at 60 rpm
100-1000 cps, measured by Spindle 2 at 30 rpm
1000-10000 cps, measured by Spindle 3 at 12 rpm

2. Preparation Example

[0088] (a) Preparation of PAE resin

[0089] PAE resin used in the examples and comparative examples was polyamide polyamine epichlorohydrin, manufactured and sold by Nalco. Co., which was prepared according to the following process:

[0090] About 82 kg of diethylenetriamine, about 15 kg of distilled water and about 1 kg of p-toluenesulfonic acid were put into a reaction vessel. Then, about 110 kg of adipic acid was added portion-wise with stirring, and the mixed solution was allowed to automatically warm up to about 125 C. After fractionation of water, the system was further heated to about 150160 C., and kept the temperature for about 3 h. When the total amount of distillated water and amine was approximately 35 kg, the reaction tended to complete. Then, the system was cooled to below 100 C., and about 160 kg of water was added and stirred until a uniform bright red, transparent viscous liquid was obtained, having a solids content of about 50% and a viscosity (25 C.) of about 6001000 mPa.Math.s. About 400 kg of water was added to the above-obtained polyamide, and about 80 kg of epichlorohydrin was added with stirring. After reacting at 70 C. for about 12 h until the required viscosity was achieved, acetic acid was added to adjust pH to about 35, giving the PAE resin.

[0091] The basic properties of the PAE resin:

Active substance: polyamide polyamine epichlorohydrin
Solids content: 25%
Viscosity: 6001000 mPa.Math.s
pH value: 35

(b) Preparation of Glyoxalated Polyacrylamide (GPAM Copolymer) Solution

[0092] GPAM copolymer used in the examples and comparative examples was prepared according to the following process:

(1) Synthesis of Polyacrylamide Base Polymer 1 (Intermediate 1)

[0093] To a 2 L three-neck flask with a heating and a cooling tube, about 90 g deionized water, about 0.1 g ethylenediamine tetraacetic acid (EDTA) and about 160 g diallyldimethylammonium chloride (DADMAC) were added. An initiator comprising about 4 g ammonium persulfate and about 16 g deionized water was added once the obtained solution was heated to about 100 C. and the addition took about 137 minutes to complete. The addition of monomer phase containing about 625 g acrylamide (concentration 50%) was started after adding the initiator for about 2 minutes. The addition of monomer phase took about 120 minutes to complete. After completing the addition of the initiator, the solution was incubated at about 100 C. The reaction ended in about 1 hour, affording an intermediate 1 with a solids content of about 41 wt % and a viscosity of about 2000 cps, wherein the concentration of cationic monomeric units was about 12 mol %.

(2) Synthesis of Polyacrylamide Base Polymer 2 (Intermediate 2)

[0094] To a 2 L three-neck flask with a heating and a cooling tube, about 113.486 g deionized water, about 16.25 g 48% sodium hydroxide aqueous solution, about 26.27 g 75% phosphoric acid solution, about 7.6 g sodium formate, and about 0.1 g ethylenediamine tetraacetic acid were added. An initiator comprising about 4.4 g ammonium persulfate and about 13.2 g deionized water was added dropwise once the obtained solution was heated to about 100 C. and the addition took about 130 minutes to complete. The addition of a mixed solution containing about 768.401 g 50% acrylamide and about 20.6 g 100% acrylic acid was started after adding the initiator for about 2 minutes. The addition took about 120 minutes to complete. After completing the addition of the initiator, the solution was incubated at about 100 C. The reaction ended in about 2 hours, affording an intermediate 2 with a solids content of about 41 wt %, a viscosity of about about 1380 cps, and a molecular weight of about 15,00025,000, wherein the concentration of anionic monomeric units was about 5 mol %.

(3) Synthesis of Polyacrylamide Base Polymer 3 (Intermediate 3)

[0095] To a 2 L three-neck flask with a heating and a cooling tube, about 200.78 g deionized water, about 16.25 g 48% sodium hydroxide aqueous solution, about 26.27 g 75% phosphoric acid solution, about 7.6 g sodium formate, about 0.1 g ethylenediamine tetraacetic acid and about 109.4 g diallyldimethylammonium chloride (concentration 62%) were added. An initiator comprising about 4.4 g ammonium persulfate and about 13.2 g deionized water was added dropwise once the obtained solution was heated to about 100 C. and the addition took about 130 minutes to complete. The addition of a mixed solution containing about 609.5 g 50% acrylamide and about 12.5 g 100% acrylic acid was started after adding the initiator for about 2 minutes. The addition took about 120 minutes to complete. After completing the addition of the initiator, the solution was incubated at about 100 C. The reaction ended in about 2 hours, affording an intermediate 3 with a solids content of about 39 wt %, a viscosity of about about 530 cps, and a molecular weight of about 15,00020,000, wherein the concentrations of cationic and anionic monomeric units were respectively about 8.5 and 3.5 mol %.

(4) Synthesis of Glyoxalated Cationic Polyacrylamide Copolymer 1 (GPAM 1)

[0096] To a 2 L glass container, about 727 g deionized water, about 195 g the above intermediate 1 and about 49 g 40% glyoxal solution were separately added and mixed at about 25 C. in a mechanical stirrer for about 15 minutes. The pH value of the obtained solution was adjusted to about 8.4 with a 48% sodium hydroxide solution. During the reaction, samples were taken for the determination of the viscosity until a product with a viscosity of about 18 cps was obtained. The obtained product was adjusted with a 50% sulfuric acid until pH value is about 3, affording a modified polymer having a solids content of about 10 wt % and a molecular weight of about 1,200,000 Dalton. The final product was marked with GPAM 1.

(5) Synthesis of Glyoxalated Anionic Polyacrylamide Copolymer 2 (GPAM 2)

[0097] To a 2 L glass container, about 783.5 g deionized water and about 155.5 g the above intermediate 2 were added, and the obtained solution was adjusted to have a pH value of about 9 with about 3 g 48% sodium hydroxide solution. Then, about 47.2 g 40% glyoxol solution was added, and the pH value was adjusted to about 8.5 with about 6.8 g 5% sodium hydroxide solution. The reaction was carried out at a normal temperature, and a viscometer was used to monitor the viscosity of the reaction solution. At the beginning, the viscosity of the reactant was about 45 cps. When the reactant reached a viscosity of about 14 cps, 50% sulfuric acid was added to adjust the pH value of the product to be about 3, so as to obtain a polymer having a solids content of about 8 wt % and a molecular weight of about 1,200,000 Dalton. The final product was marked with GPAM 2.

(6) Synthesis of Glyoxalated Amphoteric Polyacrylamide Copolymer 3 (GPAM 3)

[0098] To a 2 L glass container, about 732.63 g deionized water and about 205.5 g of the above intermediate 3 were added, and the obtained solution was adjusted to have a pH value of about 9 with about 4.07 g 48% sodium hydroxide solution. Then, about 50.3 g 40% glyoxol solution was added, and the pH value was adjusted to about 8.5 with about 7.5 g 5% sodium hydroxide solution. The reaction was carried out at a normal temperature, and a viscometer was used to monitor the viscosity of the reaction solution. When the reactant reached a viscosity of about 18 cps, 50% sulfuric acid was added to adjust the pH value of the product to be about 3, so as to obtain a polymer having a solids content of about 10 wt % and a molecular weight of about 1,000,000 Dalton. The final product was marked with GPAM 3.

(c) Preparation of Cationic Polyacrylamide Copolymer

[0099] The cationic polyacrylamide copolymer used in the examples was prepared according to the following process:

[0100] To a 2 L three-neck flask equipped with a heating and a cooling tube, about 21.1 g deionized water, about 546 g acrylamide (concentration 50%), about 10 g oxalic acid, about 15 g urea, about 105 g acryloyloxyethyl trimethylammonium chloride (DMAEAMCQ), about 20 g crude oil and about 15 g of sorbitan monooleate were added. The solution was heated to about 45 C. and rapidly stirred until fully dissolved. Subsequently, nitrogen gas was charged, and about 0.3 g azobisisobutyronitrile was added. The reaction was carried out at about 45 C. for about 3 hours until complete, to obtain a cationic polyacrylamide copolymer having a solids content of about 35 wt % and a viscosity of about 1500 cps.

3. Examples

Example 1

[0101] The PAE resin solution and GPAM 2 were respectively diluted 15 times by adding the ionized water. The diluted PAE resin solution and GPAM2 solution were added into the furnish in sequence in an active concentration mass ratio of about 1.25:1. The interval of adding the components was about 60 s. The hand sheet samples of the invention were prepared according to the hand sheet preparation method as described above with two different dosages (about 3 kg/ton or about 6 kg/ton). The thick stock used in this Example was a mixed slurry of softwood bleached kraft pulp and hardwood bleached kraft pulp.

[0102] It should be noted that the dosage of the tested additive herein refers to the amount of the active ingredient in the solution (agent) relative to the dry fiber in the pulp slurry. The meaning of dosage also applies to the following examples. The composition and amount ratios of different paper-making aids used in the example and the measured properties were listed in Table 1.

TABLE-US-00001 TABLE 1 Composition and ratios of different paper-making aids and measured properties Dosage of Dry Dry Wet Wet Composition and paper- tensile tensile tensile tensile ratio (mass ratio) of making strength strength strength strength Cohesion Cohesion paper-making aid aids, kg/t N .Math. m/g increase % N .Math. m/g increase % J/m.sup.2 increase % Blank 21.1 1.44 74.48 100% PAE 3 23.77 12.7 4.94 243.1 89.68 20.4 100% PAE 6 26.11 23.7 6.15 327.1 97.28 30.6 100% GPAM2 3 20.02 5.1 1.66 15.3 71.44 4.1 100% GPAM2 6 20.6 2.4 1.69 17.4 69.92 6.1 PAE:GPAM2_1.25:1 3 26.34 24.8 5.25 264.6 103.36 38.8 PAE:GPAM2_1.25:1 6 32.17 52.5 7.49 420.1 133.76 79.6

[0103] As seen from Table 1, the use of a combination of PAE resin and anionic GPAM2 in a mass ratio of about 1.25:1 according to the present invention as strength agent will result in better dry tensile strength and wet tensile strength and higher tensile strength increase as compared with the use of the PAE resin or GPAM2 alone at the same dosage. Meanwhile, in the case of comparable dry tensile strength and wet tensile strength and tensile strength increase, the amount of the strength aids, especially the amount of polluting PAE resin, can be significantly reduced by using the paper-making aid according to the present invention as strength agent.

Example 2

[0104] The PAE solution and GPAM 2 were respectively diluted 15 times by adding the ionized water, and added into the furnish in sequence in different active concentration mass ratios (see Table 2 below). The interval of adding the components was about 60 s. The hand sheet samples of the invention were prepared according to the hand sheet preparation method as described above with two different dosages (about 2 kg/ton or about 4 kg/ton). The thick stock used in the Example was a mixed slurry of softwood bleached kraft pulp and hardwood bleached kraft pulp.

TABLE-US-00002 TABLE 2 Optimization of the combination of PAE resin and GPAM2 Wet Dry Paper-making Dosage Wet tensile Dry tensile aid of the tensile strength tensile strength composition aid strength, increase, strength, increase, (PAE:GPAM2) kg/t N .Math. m/g % N .Math. m/g % Blank 0 1.79 33.17 1:0 2 4.75 165.4 34.9 5.2 1:0 4 6.34 254.2 36.94 11.4 0:1 2 1.94 8.4 33.08 0.3 0:1 4 2.23 24.6 34.35 3.6 3.5:1 2 4.89 173.2 36.04 8.7 3.5:1 4 6.87 283.8 39.78 19.9 2:1 2 4.61 157.5 35.57 7.2 2:1 4 7.2 302.2 40.2 21.2 1:1 2 4.78 167.0 36.3 9.4 1:1 4 7.27 306.1 42.98 29.6 1:2 2 3.74 108.9 35.43 6.8 1:2 4 4.8 168.2 36.74 10.8 1:3 2 2.93 63.7 35.29 6.4 1:3 4 3.8 112.3 36.14 9.0

[0105] As seen from Table 2, when the mass ratio of PAE resin and anionic GPAM2 is in the range as claimed in the present invention, the use of a combination of these two components as strength agent will result in better tensile strength as compared with the use of the PAE resin or GPAM2 alone. However, when the mass ratio is below or equal to about 1:2 (for example, 1:2 or 1:3), as the mass of GPAM2 increases, the wet tensile strength increase will significantly decrease, even inferior to the use of the PAE resin.

Example 3

[0106] This example was carried out on the basis of Example 2 making a further comparison in the vicinity of the active mass ratio of PAE resin:GPAM2=1:1 so as to obtain the optimum mass ratio. In this example, the operation of Example 2 was repeated except for using further specified mass ratios as shown in Table 3 below. The data of tensile strength as measured were listed in this table.

TABLE-US-00003 TABLE 3 Further optimization of active mass ratio of PAE resin to GPAM2 Wet Dry Paper-making Dosage Wet tensile Dry tensile aid of the tensile strength tensile strength composition aid strength, increase, strength, increase, (PAE:GPAM2) kg/t N .Math. m/g % N .Math. m/g % Blank 0 1.97 33.2 9.7:1 4 7.05 257.9 37.86 14.0 5:1 2 5.02 154.8 35.57 7.1 5:1 4 7.48 279.7 39.22 18.1 1.08:1 2 4.98 152.8 37.13 11.8 1.08:1 4 7.92 302.0 41.8 25.9 1:1.23 2 4.46 126.4 36.11 8.8 1:1.23 4 7.23 267.0 41.12 23.9

[0107] As summarized from Table 1, Table 2 and Table 3, it can be seen that, when the active mass ratio of the PAE resing to GPAM2 is controlled between about 1.2:1 and 1:1, the optimum dry and wet tensile strength can be achieved.

Example 4

[0108] This example was carried out to compare the addition manners of the PAE resing and GPAM2. In this example, the PAE resin and GPAM2 as prepared above were added to a pulp in a active mass ratio of about 1:1 in two different manners, i.e. separate addition (separately) or pre-mixing addition (pre-mixing). When the PAE resin and GPAM2 were added separately, PAE resing was added first and then, after about 60 s, GPAM2 was added.

TABLE-US-00004 TABLE 4 Comparison of addition manners of PAE resin and GPAM2 Wet Dry Paper-making Dosage tensile Wet tensile tensile Dry tensile aid composition Addition of aid strength, strength strength, strength (mass ratio) manners kg/t N .Math. m/g increase, % N .Math. m/g increase, % Blank Blank 0 1.67 30.59 Only PAE \ 2 4.1 145.5 33.9 10.0 4 6.1 265.3 34.6 12.1 PAE:GPAM2 1:1 separately 2 4.91 194.0 36.4 17.5 separately 4 7.95 376.0 40.52 29.9 pre-mixing 2 3.71 122.2 34.5 11.8 pre-mixing 4 4.48 168.3 36.1 16.6

[0109] As seen from Table 4, separately adding the PAE resin and GPAM2 performed obviously better than the pre-mixing manner.

Example 5

[0110] Comparison was made between different charged GPAM when combining with 64897 as strength solutions.

[0111] PAE resing, GPAM 1, GPAM 2 and GPAM 3 were diluted 15 times respectively using ionized water first, the PAE resin combined with GPAM1, GPAM2 and GPAM3 were used as test additives with about 1.2:1 mass ratio in two dosages (about 3 kg/t and about 6 kg/t) in the preparation of the handsheet samples of the invention according to the handsheet preparation method described above. The other steps of the experiment are the same as Example 1.

[0112] As seen from Table 5, the combination of PAE resin with anionic GPAM 2 performed better than the combination of PAE resin with cationic or amphoteric GPAM copolymer.

TABLE-US-00005 TABLE 5 Dosage Wet Dry Dry Paper-making of the tensile Wet tensile tensile tensile aids composition aid strength, strength strength, strength Cohesion Cohesion (mass ratio) kg/t N .Math. m/g increase, % N .Math. m/g increase, % J/m.sup.2 increase % Blank 0 1.51 21.43 71.44 PAE:GPAM1 3 4.85 221.2 24.15 12.7 89.68 25.5 (1.2:1) PAE:GPAM1 6 6.22 311.9 30.38 41.8 114 59.6 (1.2:1) PAE:GPAM2 3 5.06 235.1 26.5 23.7 97.28 36.2 (1.2:1) PAE:GPAM2 6 7.34 386.1 31.55 47.2 121.5 70.1 (1.2:1) PAE:GPAM3 3 4.86 221.9 25.6 19.5 95.76 34.0 (1.2:1) PAE:GPAM3 6 6.42 325.2 29.46 37.5 115.5 61.7 (1.2:1)

Example 6

[0113] This example was focused on a comparison between a dual component strength solution composed of the PAE resin and GPAM 2 and a ternary component strength program composed of PAE resin, GPAM 2 and cationic polyacrylamide copolymer.

[0114] The PAE resin and GPAM2 was added with about 1:1 mass ratio, followed by the cationic polyacrylamide copolymer. The addition of chemistries was done in about 60 second intervals. The dual and ternary component strength solutions were used as test additives in the preparation of the handsheet samples of the invention according to the handsheet preparation method described above. Specific dosage of the additives was presented in Table 6. The thick stock used in the Example was a mixed slurry of softwood bleached kraft pulp and hardwood bleached kraft pulp.

[0115] As seen from Table 6, the ternary component strength program composed of the PAE resin, GPAM2 and the cationic polyacrylamide copolymer was less effective than the dual component strength program composed of the PAE resin and GPAM2. Moreover, the higher dose of the cationic polyacrylamide copolymer was the worst with respect to strength performance.

TABLE-US-00006 TABLE 6 Dosage Dosage of Wet Dry Paper-making of the cationic tensile Wet tensile tensile Dry tensile aid composition aid polyacrylamide strength, strength strength, strength (mass ratio) kg/t copolymer, kg/t N .Math. m/g increase, % N .Math. m/g increase, % PAE:GPAM2 0 0 1.97 33.2 (1:1) 2 0 8.17 314.7 43.94 32.3 2 0.05 8.02 307.1 42.95 29.4 2 0.1 7.56 283.8 41.8 25.9 2 0.2 7.33 272.1 41.89 26.2

Example 7

[0116] Application of the invented strength solution in carton board furnish was studied in this experiment, wherein the active mass ratio of PAE resing to GPAM 2 was about 1:1, the addition of chemistries was done in about 60 second intervals. The new strength solutions were used as test additives in two dosages (about 3 kg/t and about 6 kg/t) in the preparation of the handsheet samples of the invention according to the handsheet preparation method described. The thick stock used in the Example was a mixed slurry of bleached chemi-mechanical pulp, de-inked pulp, hardwood bleached kraft pulp and waste paper pulp.

[0117] As seen from Table 7, the new strength solution composed of the PAE resin and GPAM 2 showed comparable wet strength but higher dry strength than using the PAE resin alone.

TABLE-US-00007 TABLE 7 Wet Dry Paper-making Wet tensile Dry tensile aid Dosage tensile strength tensile strength composition of the aid strength, increase, strength, increase (mass ratio) kg/t N .Math. m/g % N .Math. m/g % Blank 0 0.66 16.91 PAE:GPAM2 3 4 506 21.84 29 (1:1) PAE:GPAM2 6 5.87 789 25.52 51 (1:1) PAE 3 4.28 548 21.19 25 P 6 5.98 806 23.12 36