A method for detecting the effect of a wet strength agent for household paper

Abstract

The application relates to the technical field of analysis and detection, and provides a household paper wet strength agent effect detection method, which solves the defects that the existing detection method can only detect the content of the wet strength agent and cannot directly detect the effect, and comprises the following detection steps: (1) slurry preparation; (2) preparation of a slurry sample to be detected; (3) preparation of a standard detection sheet; (4) temperature and humidity balance treatment; (5) physical property detection; and (6) data processing.

Description

Technical Field

[0001] This invention relates to the field of analytical testing technology, and in particular to a method for testing the effect of wet strength agents on household paper. Background Technology

[0002] Household paper products (such as toilet paper, facial tissues, and hand towels) are fast-moving consumer goods that frequently come into contact with water or sweat during use. To prevent the paper from cracking and losing its wiping function when wet, wet-strength agents are usually added during the production process. Currently, the most widely used wet-strength agent in the industry is polyamide epichlorohydrin resin (PAE resin). Its mechanism is to form a three-dimensional network cross-linked structure inside the paper fibers, sealing the hydroxyl groups on the fiber surface, thereby preventing water molecules from entering the interfiber gaps and breaking the hydrogen bonds, significantly improving the wet strength of the paper.

[0003] Currently, the testing of wet strength agents for papermaking is mainly conducted according to the national standard GB / T 2793 "Determination of Non-volatile Matter Content in Adhesives". The main test is to determine the amount of PAE contained in the wet strength agent. Although this method can directly determine the content of substances with wet strength effect in the wet strength agent product, it cannot directly reflect the strength of its effect on the paper (the molecular weight of PAE affects its effect). Especially for pulp used in tissue paper, which has low beating degree and low overall strength, it is necessary to test different brands of wet strength agents according to the characteristics of this pulp to obtain the wet strength agent effect that conforms to the actual production.

[0004] Due to the lack of direct quantification of "effects", companies find it difficult to scientifically evaluate the cost-effectiveness of wet strength agents from different brands or batches, and are unable to accurately determine the optimal addition amount, which can easily lead to waste of additives or fluctuations in product quality.

[0005] Chinese Patent No. 202411354673.7 discloses a method for detecting the content of active ingredient in polyamide epichlorohydrin wet strength agent. The detection method includes the following steps: (1) preparing PAE test solution; (2) obtaining reaction solution one through acid hydrolysis reaction; (3) obtaining reaction solution two through esterification reaction; (4) testing the response value of diethyl adipate in the test sample using gas chromatography-mass spectrometry; (5) calculating the concentration of diethyl adipate in the test sample by plotting a standard curve; (6) excluding the concentrations of diethyl adipate and adipic acid in the test sample; (7) calculating the content of active ingredient in the polyamide epichlorohydrin wet strength agent sample using a formula. This method is used to detect the content of active ingredient in polyamide epichlorohydrin wet strength agent, which can accurately calculate the content of PAE active ingredient in wet strength agent, significantly improve the accuracy and reliability of the determination, reduce the detection cost and operation difficulty, and has wide applicability. However, it can only detect the active ingredients in PAE, and cannot directly detect the effect of wet strength agent. Summary of the Invention

[0006] Therefore, in view of the above problems, the present invention provides a method for testing the effect of wet strength agent in household paper, which solves the defect of existing testing methods that can only measure the content of wet strength agent but cannot directly measure the effect.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for testing the effect of wet strength agent in tissue paper, comprising the following testing steps: (1) Pulp preparation: Take long-fiber wood pulp and short-fiber wood pulp respectively, dilute them with water to a concentration of 1.5±0.05wt%, tear the pulp board into fragments and soak them for 4-5 hours to swell; use a standard fiber dissociator to dissociate at a concentration of 1.5% for 30,000 revolutions; after concentrating to a concentration of 10±0.5% through a 200-mesh filter, use a PFI refiner to refine according to GB / T 29287-2012, set the blade distance to 9.6mm, refine short fibers at 1500 revolutions and long fibers at 2100 revolutions; take the refined long fibers and short fibers and mix them at a mass ratio of 20%:80%, dilute to 1.5±0.05%, and dissociate for 10,000 revolutions to obtain a mixed pulp; (2) Preparation of slurry samples to be tested: dilute the mixed slurry to a concentration of 1±0.05%, control the temperature at 21℃-25℃, add wet strength agent in a stepwise gradient according to the dry slurry weight, stir for 15 minutes, and then dilute to a concentration of 0.2%-0.3% to obtain the slurry samples to be tested; (3) Preparation of standard test strips: In accordance with GB / T 24326-2009, prepare 3-5 standard test strips with a quantitative amount of 25 g / m² and 60 g / m² for each additive gradient, and at the same time prepare control samples without wet strength agent; (4) Temperature and humidity equilibration treatment: Place the test strip in an environment with a temperature of 20℃-25℃ and a humidity of 40%-60% for 24 hours for equilibration treatment; (5) Physical performance testing: The dry tensile strength of the test piece shall be determined according to GB / T 24323-2009, and the wet tensile strength of the test piece shall be determined according to GB / T24328.4-2020; (6) Data processing: The wet strength retention rate is calculated based on the dry and wet tensile strengths. The formula is: Wet strength retention rate = (a1 / a + b1 / b) / 2 × 100%; where a1 is the wet strength index of the 25g / m² test piece, and a is the wet strength index of the 25g / m² test piece. 2 The dry strength index of the test piece is b1, which is 60 g / m². The wet strength index of the test piece is b, which is 60 g / m². 2 The dryness index of the test piece.

[0008] Furthermore: the long-fiber wood pulp mentioned in step 1) is softwood pulp, and the short-fiber wood pulp is eucalyptus pulp.

[0009] Furthermore: the stepwise gradient mentioned in step 2) includes the addition amounts of 1 kg / t, 2 kg / t, 5 kg / t, and 10 kg / t oven-dry pulp.

[0010] Furthermore: In step 2), before adding the wet strength agent, the solid content and pH value of the wet strength agent must be measured in advance to ensure that the performance is within the qualified range.

[0011] Furthermore: In step 3), the forming plate and cylinder wall must be cleaned before each sheet forming to prevent the accumulation and residue of wet strength agent.

[0012] Furthermore, it also includes plotting an "addition amount-retention rate" curve based on the wetting strength retention rate data, and determining the effective concentration, unit addition efficiency, and maximum wet strength retention rate plateau accordingly. The "effective concentration" is the minimum amount of wet strength agent added that makes the wetting strength retention rate significantly higher than that of the control sample. The "unit addition efficiency" is the slope of the curve during the rapid increase of the wetting strength retention rate with the addition amount. The larger the slope, the higher the conversion efficiency of the wet strength agent. The "maximum wet strength retention rate plateau" is the critical addition amount and stable plateau value corresponding to when the wetting strength retention rate no longer increases significantly with the addition amount.

[0013] By adopting the aforementioned technical solution, the beneficial effects of the present invention are as follows: 1. This invention abandons the indirect method of the traditional GB / T 2793 standard, which only tests the solid content, and directly measures the physical strength of the paper sheet by simulating the actual papermaking process. This method eliminates the interference of PAE molecular weight, degree of polymerization, and impurities on activity, and can truly reflect the retention rate and cross-linking effect of wet strength agents on tissue paper pulp, providing direct data support for production formulation.

[0014] 2. This invention defines specific beating degrees (1500r for short fibers and 2100r for long fibers) and a long-to-short fiber ratio (2:8), accurately reflecting the pulp characteristics of "low beating degree and weak fiber bonding" in tissue paper. Compared with general testing methods, this invention can more sensitively capture the reinforcing differences of different wet strength agents in low-strength pulp, avoiding the problem of high beating degree pulp masking the performance differences of wet strength agents.

[0015] 3. By simultaneously targeting 25g / m 2 and 60g / / m 2 The dry and wet strength tests were conducted on two types of test pieces with different weights, and the weighted retention rate was calculated. This effectively eliminated the test deviation caused by differences in paper bulk and uniformity, making the performance comparison of wet strength agents from different brands and batches more objective and fair.

[0016] 4. By plotting the "addition amount - retention rate" curve, we can not only know the effect of wet strength agent, but also accurately define the effective concentration (minimum effective addition point), unit addition efficiency (cost-effectiveness slope), and maximum wet strength retention rate plateau (saturation point). This helps companies identify the "inefficient zone" and the "excess zone", accurately add materials while ensuring product quality, and reduce production costs. Attached Figure Description

[0017] Figure 1 This is a graph showing the relationship between the amount of wet strength agent A and wet strength agent B added and the wetting strength retention rate in the embodiments of the present invention. Detailed Implementation Example

[0018] A method for testing the effect of wet strength agents on household paper, the specific steps of which are as follows: (1) Slurry preparation Each time, take 30g of oven-dry long-fiber pulp and short-fiber pulp (the batch of pulp must be the same for each test; long-fiber pulp is softwood pulp, and short-fiber pulp is eucalyptus pulp), add 2L of water, tear the pulp board into fingernail-sized pieces, and let it stand and soak for 4 hours at 21℃-25℃ to allow the fibers to fully swell; use a standard fiber dissociator to dissolve the pulp at a concentration of 1.5% at a dissociation speed of 30000r; then use a 200-mesh filter to concentrate the pulp to a concentration of 10%; The pulp was refined using a PFI refiner according to GB / T 29287-2012 "Laboratory Pulp Refining (PFI) Method". The blade spacing was set to 9.6 mm. The refining speed was 1500 rpm for short fiber (eucalyptus pulp) and 2100 rpm for long fiber (softwood pulp). Testing showed that the freeness of short fiber was 18°SR and the freeness of long fiber was 21.5°SR. After refining, the long and short fibers were mixed at a mass ratio of 20%:80%, diluted to a concentration of 1.5%, and then re-refined for 10,000 rpm to obtain a mixed pulp for later use. (2) Preparation of wet strength agent Two commercially available wet strength agents, A and B, were selected as samples for testing. Their physicochemical properties were pre-tested, and the results are as follows: Wet strength agent A: pH value 3.15, solid content 15%; Wet strength agent B: pH value 3.74, solid content 15%; both are within the acceptable range for use. (3) Preparation of slurry samples to be tested The above-mentioned mixed pulp was diluted to a concentration of 1%, and the temperature was controlled at 21℃-25℃. A stepwise addition gradient was set according to the oven-dry pulp quality. In this embodiment, the amount of wet strength agent stock solution added was 0, 10, 20, 30, 40, and 50 kg / t of paper (corresponding to the actual addition amount per 30g of pulp of 0g, 0.3g, 0.6g, 0.9g, 1.2g, and 1.5g, respectively). Add the wet strength agent to the slurry, stir thoroughly for 15 minutes, and then dilute to a concentration of 0.2%-0.3% to prepare the slurry sample to be tested; (4) Preparation of standard test strips According to GB / T 24326-2009 "Preparation of Laboratory Paper for Physical Experiments - Rapid Kaiser Method", each of the above-mentioned gradients was copied. For each addition amount, five standard test pieces were prepared in parallel at concentrations of 25 g / m² and 60 g / m². A blank control sample without added wet strength agent was also prepared. Before each test piece preparation, the forming plate and cylinder wall must be cleaned to prevent residual wet strength agent from the previous batch of slurry from affecting subsequent experimental results. (5) Temperature and humidity balance treatment All the prepared test strips were transferred to a standard constant temperature and humidity laboratory, with the environment controlled at a temperature of 23±1℃ and a relative humidity of 50±2%. The test strips were subjected to temperature and humidity equilibration treatment for 24 hours under this environment. (6) Physical performance testing Remove the balanced test piece and immediately perform physical performance testing: Dry tensile strength: According to GB / T 24323-2009 "Determination of physical properties of pulp and paper in laboratory", the dry strength index of the 60 g / m² test sheet was 34.40 Nm / g, and the dry strength index of the 25 g / m² test sheet was 23.31 Nm / g. Wet tensile strength: Tested according to GB / T 24328.4-2020 "Toilet paper and its products - Part 4: Determination of wet tensile strength", the specific test data are shown in Table 1 below: Table 1. Wet strength index (Nm / g) of different wet strength agents at different addition amounts A wet strength agent 60gsm wet strength index (Nm / g) 0.10 4.11 5.34 6.84 7.50 8.48 8.66 B wet strength agent 60gsm wet strength index Nm / g 0.10 3.96 4.68 6.10 7.23 8.23 8.55 A wet strength agent 25gsm wet strength index Nm / g 0.08 2.63 3.92 5.52 6.61 7.20 8.01 B wet strength agent 25gsm wet strength index Nm / g 0.08 2.49 3.82 5.40 6.53 7.01 7.99 (7) Data processing and analysis Based on the dry and wet tensile strengths obtained from the tests, the wetting strength retention rate is calculated using the following formula: Wetting strength retention rate = (a1 / a + b1 / b) / 2 × 100%; where a1 is 25 g / m 2 The wet strength index of the test piece, a, is 25 g / m. 2 The dry strength index of the test piece, b1, is 60 g / m. 2 The wet strength index of the test piece, b, is 60 g / m. 2 The dryness index of the test piece.

[0019] The calculation results are shown in Table 2: Table 2 Calculation results of wetting strength retention rate Wet strength retention rate of wet strength agent A / % 0.320% 11.600% 16.200% 21.800% 25.100% 27.800% 29.765% Wet strength retention rate of wet strength agent A / % 0.320% 11.100% 15.000% 20.400% 24.500% 27.000% 29.566% (8) Evaluation index determination A curve was plotted with the wet strength agent addition amount on the x-axis and the wetting strength retention rate on the y-axis. See the attached curve for details. Figure 1 .

[0020] Effective concentration: As the data shows, when the addition amount increases from 0 to 10 kg / t, the retention rate jumps from 0.32% to about 11%. Therefore, 10 kg / t is the effective concentration.

[0021] Unit addition efficiency: In the range of 10-30 kg / t, the slope of wet strength agent A is approximately (21.8-11.6) / (30-10)=0.51, and the slope of wet strength agent B is approximately (20.4-11.1) / (30-10)=0.47, indicating that wet strength agent A has a higher conversion efficiency in this stage.

[0022] Maximum wet strength retention plateau: When the addition amount exceeds 50 kg / t, the retention rate growth tends to level off (close to 30%), indicating that 50 kg / t is the critical point, and further increasing the addition amount has extremely low cost-effectiveness.

[0023] As can be seen from the above embodiments, the present invention can accurately distinguish the performance differences of different wet strength agents under the same conditions, and can guide enterprises to determine the optimal addition range, thus avoiding waste of additives.

[0024] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A method for testing the effect of wet strength agent on household paper, characterized in that: The following testing steps are included: (1) Pulp preparation: Take long-fiber wood pulp and short-fiber wood pulp respectively, dilute them with water to a concentration of 1.5±0.05wt%, tear the pulp board into fragments and soak them for 4-5 hours to swell; use a standard fiber dissociator to dissociate at a concentration of 1.5% for 30,000 revolutions; after concentrating to a concentration of 10±0.5% through a 200-mesh filter, use a PFI refiner to refine according to GB / T 29287-2012, set the blade distance to 9.6mm, refine short fibers at 1500 revolutions and long fibers at 2100 revolutions; take the refined long fibers and short fibers and mix them at a mass ratio of 20%:80%, dilute to 1.5±0.05%, and dissociate for 10,000 revolutions to obtain a mixed pulp; (2) Preparation of slurry samples to be tested: dilute the mixed slurry to a concentration of 1±0.05%, control the temperature at 21℃-25℃, add wet strength agent in a stepwise gradient according to the dry slurry weight, stir for 15 minutes, and then dilute to a concentration of 0.2%-0.3% to obtain the slurry samples to be tested; (3) Preparation of standard test strips: In accordance with GB / T 24326-2009, prepare 3-5 standard test strips with a quantitative amount of 25 g / m² and 60 g / m² for each additive gradient, and at the same time prepare control samples without wet strength agent; (4) Temperature and humidity equilibration treatment: Place the test strip in an environment with a temperature of 20℃-25℃ and a humidity of 40%-60% for 24 hours for equilibration treatment; (5) Physical performance testing: The dry tensile strength of the test piece shall be determined according to GB / T 24323-2009, and the wet tensile strength of the test piece shall be determined according to GB / T 24328.4-2020; (6) Data processing: The wet strength retention rate is calculated based on the dry and wet tensile strengths. The formula is: Wet strength retention rate = (a1 / a + b1 / b) / 2 × 100%; where a1 is the wet strength index of the 25 g / m² test piece, and a is the wet strength index of the 25 g / m² test piece. 2 The dry strength index of the test piece is b1, which is 60 g / m². The wet strength index of the test piece is b, which is 60 g / m². 2 The dryness index of the test piece.

2. The method for testing the effect of wet strength agent on household paper according to claim 1, characterized in that: The long-fiber wood pulp mentioned in step (1) is softwood pulp, and the short-fiber wood pulp is eucalyptus pulp.

3. The method for testing the effect of wet strength agent on household paper according to claim 1, characterized in that: The step gradient mentioned in step (2) includes the addition amounts of 1 kg / t, 2 kg / t, 5 kg / t, and 10 kg / t oven-dried pulp.

4. The method for testing the effect of wet strength agent on household paper according to claim 1, characterized in that: In step (2), before adding the wet strength agent, the solid content and pH value of the wet strength agent must be measured in advance to ensure that the performance is within the qualified range.

5. The method for testing the effect of wet strength agent on household paper according to claim 1, characterized in that: In step (3), the forming plate and cylinder wall need to be cleaned before each sheet forming to prevent the wet strength agent from accumulating and remaining.

6. The method for testing the effect of wet strength agent on household paper according to claim 1, characterized in that: It also includes plotting an addition amount-retention rate curve based on the wetting strength retention rate data, and determining the effective concentration, unit addition efficiency, and maximum wet strength retention rate plateau accordingly. The effective concentration is the minimum amount of wet strength agent added that makes the wetting strength retention rate significantly higher than that of the control sample. The unit addition efficiency is the slope of the curve during the rapid increase of the wetting strength retention rate with the addition amount. The larger the slope, the higher the conversion efficiency of the wet strength agent. The maximum wet strength retention rate plateau is the critical addition amount and stable plateau value corresponding to when the wetting strength retention rate no longer increases significantly with the addition amount.

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