Halogen-free polyamide polyamine papermaking cylinder adhesive and preparation method thereof

Abstract

The preparation method comprises the following steps that under the condition of antioxidant protection, polyenoic acid containing at least one allyl hydrogen and maleic anhydride are mixed and subjected to an Alder-Ene reaction for 5-12 h at the temperature of 160-240 DEG C, modified polyenoic acid is prepared, and the molar ratio of olefin functional groups in the polyenoic acid to maleic anhydride is 1.5: 1.0-2.0: 1.0; the modified polybasic carboxylic acid and polyethylene polyamine are subjected to a dehydration polycondensation reaction at the temperature of 160-190 DEG C, the molar ratio of terminal amino of the polyethylene polyamine to carboxyl of the modified polybasic carboxylic acid is 1.05: 1.0-1.40: 1.0, and modified polyamide is prepared; the modified polyamide is dissolved in water at the temperature of 50-100 DEG C to be diluted, the PH value is adjusted to be 5.0-9.0, and the halogen-free polyamide polyamine papermaking cylinder adhesive is prepared. Epoxy chloropropane is not used, the poison problem of chloropropanol and organic halogen is avoided, modified polycarboxylic acid serves as a cross-linking agent, and the adhesive has good binding power and has flexibility and film forming water resistance.

Description

Technical Field

[0001] The present invention relates to the field of papermaking aid production, in particular to a halogen-free polyamide polyamine papermaking cylinder sticking agent and a preparation method thereof. Background Art

[0002] In the production process of crepe paper, the drying of the dryer cylinder and the impact of the doctor blade are the key processes for forming paper wrinkles. This process endows the paper with excellent softness, water absorption, and fluffiness through controllable mechanical actions, while improving the tactile quality of the finished product. To achieve an ideal wrinkling effect, an appropriate bonding strength needs to be maintained between the paper sheet and the dryer cylinder surface. Especially in high-speed papermaking equipment, the bonding force of the fibers themselves is difficult to meet the process requirements, and it must be dynamically adjusted through a dryer cylinder coating aid system (including a cylinder sticking agent, a peeling agent, and a modifier), which is crucial for ensuring the stability and controllability of the wrinkling process.

[0003] The performance of the coating aids directly affects the product quality and the operation stability of the equipment. If selected improperly, it will not only cause defects such as paper pinholes, dead wrinkles, and holes, but may also lead to equipment damage accidents such as doctor blade jumping and vibration. In the aid system, the cylinder sticking agent, as the core material for coating construction, its performance balance is particularly important. The main technical bottleneck faced by the current industry is that traditional cylinder sticking agents are difficult to simultaneously meet the multi-dimensional performance requirements such as bonding strength, film-forming flexibility, bulging degree requirements, coating uniformity, and service life.

[0004] Polyamide polyamine-epichlorohydrin (PAE) -type cylinder sticking agents have become one of the mainstream choices for industrial applications due to their comprehensive performance advantages. The PAE resin has a polyamide polyamine as the main chain backbone, and uses the cross-linking effect of epichlorohydrin to construct a three-dimensional network structure. Its advantages include: (1) excellent film-forming performance; (2) the low-viscosity characteristic in the aqueous phase system ensures coating uniformity; (3) the controllable cross-linking degree brings high bonding strength; (4) the density of end functional groups improves the interface bonding efficiency.

[0005] However, PAE adhesives still have significant technical drawbacks, primarily high-temperature aging caused by irreversible crosslinking reactions and residual chloropropanols. High-temperature aging refers to the exponential growth of polymer molecular weight during continuous production due to the ongoing crosslinking reaction, which can lead to hardening of the coating. This can cause abnormal blade vibration, cracking and shedding of the coating, resulting in holes and even paper breaks, and downtime due to periodic coating re-coating. Chloropropanol residues are a concern because epichlorohydrin is used in the PAE resin synthesis process. Its hydrolysis products, chloropropanols (including various isomers such as DCP and MCPD), are highly biotoxic and can be absorbed through skin contact or migration, causing cumulative damage to the nervous system and internal organs. The World Health Organization's Joint Expert Committee on Food Additives (WHO / JECFA), the World Health Organization's International Agency for Research on Cancer, and the European Food Safety Authority (EFSA) have all described their hazards. my country's national food safety standard GB4806.8-2022 also clearly establishes limits for food contact paper and paperboard materials and products.

[0006] Many researchers have used PAE resin as a base for molecular structure modification or blending in an attempt to overcome PAE's shortcomings of aging and residual chloropropane. Patent CN106574445A reduces the residual chloropropane in PAE by increasing molecular weight with alkali treatment, but this results in decreased product stability and a significant reduction in effective content, which in turn increases the cost of PAE. Patent CN107012731A utilizes polyvinyl alcohol to enhance PAE's flexibility, employs dialdehydes as crosslinking agents, and uses an etherifying agent as a cationizing agent, avoiding the use of epichlorohydrin. However, this design, as the raw materials for the etherifying agent contain epichlorohydrin, which may contain some residual epichlorohydrin, also introduces aldehyde groups from the dialdehyde, resulting in decreased product storage stability and reduced water resistance. Patent JP2020033672A introduces urea as a crosslinker to reduce the amount of epichlorohydrin, resulting in a (polyurea) polyamide-epichlorohydrin resin. This resin produces a soft film with low residual chloropropanol. However, due to the reduced crosslinker dosage, the overall film water resistance is poor, making it difficult to adjust and use on some paper machines with large moisture fluctuations. Patent CN111440324A discloses a method for preparing a polyamide polyamine-polyetheramine adhesive. This uses polyetheramine as a crosslinker instead of epichlorohydrin. However, the crosslinking ability of amino and carboxyl groups in the aqueous phase is insufficient. While this improves softness, it also results in certain water resistance drawbacks.

[0007] In the prior art, chloropropanol or organic halogen used as a cross-linking agent has significant biological toxicity. Summary of the Invention

[0008] The object of the present invention is to overcome the disadvantages of the prior art through repeated intensive research, and provide a halogen-free polyamide polyamine papermaking sizing agent and a preparation method thereof. Without using epichlorohydrin, the problems of the toxicity of chloropropanol and organic halogens are avoided. Using a modified polycarboxylic acid as a cross-linking agent, it has good adhesion, and combines softness and film-forming water resistance.

[0009] To this end, the present invention adopts the following technical solutions: A preparation method of a halogen-free polyamide polyamine papermaking sizing agent, comprising the following steps: A. Under antioxidant protection conditions, mix a polyenoic acid containing at least one allyl hydrogen with maleic anhydride, and carry out an Alder-Ene reaction at 160~240 °C for 5-12 hours to obtain a modified polyenoic acid. The molar ratio of the olefin functional group in the polyenoic acid to maleic anhydride is 1.5:1.0~2.0:1.0; B. Carry out a dehydration polycondensation reaction between the modified polycarboxylic acid and polyethylenepolyamine at 160~190 °C. The molar ratio of the terminal amino group of the polyethylenepolyamine to the carboxyl group of the modified polyenoic acid is 1.05:1.0~1.40:1.0 to obtain a modified polyamide; C. Dissolve the modified polyamide in water at 50~100 °C for dilution, and adjust the pH value to 5.0~9.0 to obtain a halogen-free polyamide polyamine papermaking sizing agent. It should be noted that 1 part of acid anhydride is regarded as 2 parts of carboxyl groups.

[0010] In one embodiment of the present invention, the polyenoic acid is selected from one or more of linoleic acid, conjugated linoleic acid (CLA), α-linolenic acid, γ-linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid.

[0011] In one embodiment of the present invention, step A includes first heating linoleic acid to 40-70 °C, dropping in pre-melted maleic anhydride while stirring, and after the dropping is completed, raising the temperature to 160-220 °C to start heat preservation, raising the temperature by 10 °C every 1-3 h, and keeping warm at 180~240 °C for a total of 8 h.

[0012] In one embodiment of the present invention, step B includes adding polyethylenepolyamine after cooling the modified polyenoic acid to below 130 °C, and then raising the temperature to 160~190 °C and keeping warm for 3-10 hours for dehydration polycondensation reaction.

[0013] In one embodiment of the present invention, the polyethylenepolyamine is selected from one or more of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine. The acid used to adjust the pH in step C is one or more of hydrochloric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, tartaric acid, and citric acid.

[0014] In one embodiment of the present invention, the solid content of the sizing agent after dilution in hot water is 10~30%.

[0015] In one embodiment of the present invention, under antioxidant protection conditions, nitrogen, carbon dioxide or an inert gas is used to isolate oxygen.

[0016] In one embodiment of the present invention, under antioxidant protection conditions, it further includes adding an antioxidant with a mass ratio of 0.1‰ - 1.5‰ to the sum of polyunsaturated fatty acids and maleic anhydride.

[0017] In one embodiment of the present invention, the antioxidant is selected from one or more of antioxidant 264, antioxidant 330, antioxidant 1010, and antioxidant 1076.

[0018] The present invention also provides a halogen - free polyamide polyamine papermaking cylinder - sticking agent, which is prepared by the preparation method of the halogen - free polyamide polyamine papermaking cylinder - sticking agent described in any one of the above.

[0019] The advantages of the present invention are as follows: The polyamide polyamine resin containing polyunsaturated fatty acids has a high initial molecular weight, and its viscosity is not easily changed over time. When used as a cylinder - sticking agent, it has appropriate bonding strength; without using epichlorohydrin as a cross - linker, the drying cylinder coating maintains a controllable cross - linking speed, is not easily aged or hardened, and extends the operation cycle of the paper machine; the long - carbon - chain components on the polyunsaturated fatty acid chain segment endow the drying cylinder coating with certain peelability and slipperiness, protect the doctor blade, extend the service life of the doctor blade, improve the bulging degree of crepe paper, and thus reduce the production cost of crepe paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the reaction principle diagram of step A of the present invention.

[0021] Figure 2 is the reaction principle diagram of step B of the present invention.

[0022] Figure 3 is the component table of the embodiment of the present invention.

[0023] Figure 4 is the physical and chemical test result table of solid content and viscosity of the present invention.

[0024] Figure 5 is the test result table of bonding strength, hardness, and water resistance of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative work fall within the protection scope of the present invention. Embodiment

[0026] In a 500 mL four-necked glass flask equipped with an oil bath heater, nitrogen protection, a stirrer, a dropping device, and a thermometer, add 74.8 g (0.27 mol) of linoleic acid and 0.05 g of antioxidant 1010 solid. Replace the air with nitrogen, start stirring, keep the temperature at 50 °C, and dropwise add 32.7 g (0.33 mol) of pre-melted maleic anhydride. Raise the temperature to 180 °C and start timing for heat preservation. Increase the temperature by 10 °C every 2 h, and keep the temperature at 180 - 210 °C for a total of 8 h to carry out a typical Alder-Ene reaction to obtain a modified polycarboxylic acid. After the heat preservation is completed, cool the temperature to 130 °C or lower, add 51.6 g (0.55 mol) of diethylenetriamine, re-raise the temperature to 160 °C for polycondensation reaction, keep the temperature at 160 °C for 2 h, and keep the temperature at 170 °C for 2 h. After the heat preservation is completed, transfer the material to 700 g of hot water at 70 °C with stirring while it is still hot. Keep stirring, cool to room temperature in a cold water bath, and add 10.0 g of phosphoric acid to adjust the pH to 8.05 to obtain a polyamide polyamine sizing agent PA-1 with a solid content of 18.3% and a viscosity of 102.3 cPs.

[0027] Examples 2 - 12 Except as Figure 3 shown by changing the raw material composition, the rest are the same as in Example 1, thus obtaining sizing agents PA-2 - 12 of polyamide polyamine using modified polyenoic acid. The acid type and dosage, solid content, viscosity, and pH value are as Figure 4 shown.

[0028] Comparative Example 1 A commercially available sizing agent PAE-1 in a certain city, with a solid content of 15.37%, pH 4.50, and viscosity 15.4 cPs Comparative Example 2 A commercially available sizing agent PAE-2 in a certain city, with a solid content of 12.55%, pH 5.32, and viscosity 23.7 cPs Comparative Example 3 A sizing agent PAE-3 synthesized according to Example 1 of Patent JP2020033672A, with a solid content of 12.55%, pH 5.32, and viscosity 23.7 cPs Comparative Example 4 A sizing agent PAE-4 synthesized according to Example 1 of Patent CN111440324A, with a solid content of 10.04%, pH 6.50, and viscosity 16.7 cPs Comparative Example 5 A commercially available sizing agent PEI-1 in a certain city, with a solid content of 10.87%, pH 8.70, and viscosity 30.3 cPs Comparative Example 6 In a 500 mL four-necked glass flask equipped with oil bath heating, nitrogen protection, stirring, dropping device, thermometer, etc., add 150 g (0.52 mol) of high-purity oleic acid and 0.05 g of antioxidant 1010 solid. Replace the air with nitrogen, start stirring, keep the temperature at 50 °C, and dropwise add 32.5 g (0.33 mol) of pre-melted maleic anhydride. Raise the temperature to 180 °C and start timing for heat preservation. Raise the temperature by 10 °C every 2 h, and keep the temperature at 180 - 210 °C for a total of 8 h to carry out a typical Diels-ene reaction to obtain a modified polycarboxylic acid. After the heat preservation is completed, cool down to 130 °C or below, add 51.7 g (0.55 mol) of diethylenetriamine, and re-raise the temperature to 160 °C for polycondensation reaction. Keep the temperature at 160 °C for 2 h and at 170 °C for 2 h. After the heat preservation is completed, transfer the material to 700 g of hot water at 70 °C with stirring while it is still hot. Keep stirring, cool down to room temperature in a cold water bath, add 10.0 g of phosphoric acid to adjust the pH to 8.75 to obtain a non-uniform liquid containing oily floating matter and flocculates. After filtering through a 300-mesh screen, a turbid polyamide polyamine sizing agent PA-13 with a solid content of 25.3% and a viscosity of 87.9 cPs is obtained.

[0029] Test methods and results 1. Test for the content of chloropropanol Using the GC-MS method, adsorb, test and calculate the results for the sample, which are listed in Figure 5 , the technical solution of this application does not contain 1,3-DCP and 3-MCPD, and is friendly to humans and the environment.

[0030] 2. Test for bonding strength Dilute the sample to 10%, take 10 g and place it in a stainless steel trough plate with a groove of size 50 mm × 100 mm. After pre-drying at 105 °C for 10 min, place a cloth strip cut into 15 mm wide and 150 mm long on the groove trough plate. The trough plate is pre-scored to fix the cloth strip at the same position. After drying at 105 °C for 60 min, take it out and dry and cool to room temperature. Use a tensile tester to test the strength (gf) when the cloth strip is peeled off, which is listed in Figure 5 . When the bonding strength is too large (>175 gf), the coating on the paper machine dryer cylinder is too hard, affecting the service life of the doctor blade; when the bonding strength is too small (<75 gf), the bonding strength of the coating on the paper machine dryer cylinder is insufficient, and it is difficult to establish a stable coating. The bonding strength of this application is very appropriate, and it can establish a stable coating without affecting the service life of the doctor blade.

[0031] 3. Test for softness and hardness Dilute the sample to 10%, take 10 g and place it in a stainless steel trough plate with a groove of size 50 mm × 100 mm. After drying to form a film at 105 °C for 60 min, take it out and place it on a hot plate at 90 °C. After standing for 5 min, use a Shore hardness tester type A to test the hardness at multiple points and calculate the average value, which is listed inFigure 5 When the hardness is too high (>10.0), the coating strength is too high, and the doctor blade wears severely, resulting in increased production costs and a decline in paper grade. Often, a plasticizer needs to be additionally added for adjustment. When the hardness is too low (<5), the coating strength is insufficient, and it is easily carried away by the doctor blade, making it difficult to protect the dryer. Seriously, it may even cause the doctor blade to directly impact the dryer, resulting in irreversible damage. Often, a crosslinking aid needs to be additionally added for adjustment. The hardness of this application is moderate and can be directly used without additional compounding adjustment, with a wide product application range.

[0032] 4. Water resistance test Dilute the sample to 10%. Take 10 g and place it in a stainless-steel trough plate with a groove of 50 mm × 100 mm. After drying and forming a film at 105 °C for 60 min, take it out and dry it to room temperature, and measure the weight M1. Add 30 mL of deionized water to a watch glass. Immerse the film for 0.5 h and then take it out. After drying at 105 °C for 60 min, take it out and dry it to room temperature, and measure the weight M2. Calculate the water resistance parameter (%): Water resistance parameter = M2 / M1 × 100% The water resistance test results are listed in Figure 5 , and the larger the parameter value, the better the water resistance effect of the coating. The technical solution of this application has good water resistance test results.

[0033] When the viscosity is large, the initial molecular weight of the cylinder adhesive is large, the crosslinking degree is high, and the coating establishment speed is fast, thus improving the product applicability. However, it will make the product production process difficult to control. When the viscosity is small, although the production process is easy to control, the product molecular weight is insufficient, the crosslinking degree is not enough, and the coating establishment speed is slow, resulting in an increase in the dosage of the cylinder adhesive and an increase in the production and operation costs of the paper machine. The viscosity of this application is controlled within the maximum stable range, with high cost performance.

Claims

1. A preparation method of a halogen-free polyamide polyamine papermaking cylinder sticking agent, characterized in that, It includes the following steps: Under antioxidant protection conditions, a polyenoic acid containing at least one allylic hydrogen is mixed with maleic anhydride, and an Alder-Ene reaction is carried out at 160-240 °C for 5-12 hours to obtain a modified polyenoic acid. The molar ratio of the olefin functional group in the polyenoic acid to maleic anhydride is 1.5:1.0-2.0:1.0; The modified polycarboxylic acid and polyethylenepolyamine are subjected to a dehydration polycondensation reaction at 160-190 °C. The molar ratio of the terminal amino group of the polyethylenepolyamine to the carboxyl group of the modified polyenoic acid is 1.05:1.0-1.40:1.0 to obtain a modified polyamide; The modified polyamide is dissolved in water at 50-100 °C and diluted, and the pH value is adjusted to 5.0-9.0 to obtain a halogen-free polyamide polyamine papermaking cylinder sticking agent.

2. The preparation method of the halogen-free polyamide polyamine papermaking sizing agent according to claim 1, characterized in that, The polyenoic acid is selected from one or more of linoleic acid, conjugated linoleic acid (CLA), α-linolenic acid, γ-linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid.

3. The preparation method of the halogen-free polyamide polyamine papermaking cylinder sticking agent according to claim 2, characterized in that, Step A includes first heating linoleic acid to 40-70 °C, dropwise adding pre-melted maleic anhydride while stirring, and after the addition is complete, raising the temperature to 160-220 °C to start timing for heat preservation, raising the temperature by 10 °C every 1-3 h, and keeping warm at 180-240 °C for a total of 8 h.

4. The preparation method of the halogen-free polyamide polyamine papermaking cylinder sticking agent according to claim 3, characterized in that, Step B includes cooling the modified polyenoic acid to below 130 °C, adding polyethylenepolyamine, and then raising the temperature to 160-190 °C and keeping warm for 3-10 hours for a dehydration polycondensation reaction.

5. The preparation method of the halogen-free polyamide polyamine papermaking cylinder adhesive according to claim 4, characterized in that, The polyethylenepolyamine is selected from one or more of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine. The acid used to adjust the pH in step C is one or more of hydrochloric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, tartaric acid, and citric acid.

6. The preparation method of the halogen-free polyamide polyamine papermaking cylinder sticking agent according to claim 5, characterized in that, The solid content of the cylinder sticking agent after dilution in hot water is 10-30%.

7. The preparation method of the halogen-free polyamide polyamine papermaking cylinder sticking agent according to claim 6, characterized in that, The antioxidant protection conditions mean using nitrogen, carbon dioxide or inert gas to isolate oxygen.

8. The preparation method of the halogen-free polyamide polyamine papermaking cylinder sticking agent according to claim 7, wherein, The antioxidant protection conditions also include adding an antioxidant of 0.1‰-1.5‰ of the total mass of the polyenoic acid and maleic anhydride.

9. The preparation method of the halogen-free polyamide polyamine papermaking cylinder sticking agent according to claim 8, characterized in that, The antioxidant is selected from one or more of antioxidant 264, antioxidant 330, antioxidant 1010, and antioxidant 1076.

10. A halogen-free polyamide polyamine papermaking sizing agent for paper sticking, characterized in that, It is prepared by the preparation method of the halogen-free polyamide polyamine papermaking cylinder sticking agent described in any one of claims 1-9.

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