Wet-strength Resins Research Articles

Understanding polyamidoamine epichlorohydrin (PAAE) retention in paper

Polyamidoamine epichlorohydrin (PAAE) is a permanent wet strength resin used in papermaking. When applied to paperboard, some amount of resin is retained in the sheet, and some is lost to the white water. The papermaker usually knows the amount of PAAE charged to the pulp but has no idea how much chemical is retained in the sheet. In addition, the influence of PAAE dosage, freeness, zeta potential, and pulp kappa number variability on PAAE retention is not well understood. Factorial design experiments using unbleached and bleached softwood (loblolly pine) kraft pulps were conducted to understand the factors that affect PAAE retention. The results revealed that PAAE retention, wet tear index, and tensile index not only depended on the PAAE charged of the pulp but also depended significantly on the pulp freeness. In lieu of freeness, zeta potential data can be used to predict PAAE retention. In addition, at similar freeness, bleached pulp has the highest retention of PAAE compared to low and high kappa unbleached kraft pulps. The results also suggest that lignin may have potential as a wet strength agent.

Striving for Sustainable Solutions: Optimizing Utility Properties of Recycled Paper with the Addition of Wet Strength Resin

Paper producers are increasingly challenged to meet customer demands for high-quality sanitary papers amidst rising price pressures and diminishing quality of recycled fibers. One promising avenue for enhancing paper quality involves augmenting wet strength. For this purpose, synthetic wet strength resins are used, among other things. This study explores the efficacy of utilizing a polyamide-epichlorohydrin resin-based agent for the internal sizing of white wastepaper. Such chemicals, when added to cellulosic fibers in proper amounts before the paper is made, can not only improve water resistance and air permeability of the finished product but also significantly affect both the dry and wet strength paper, which is a crucial aspect for sanitary papers. This study shows that the appropriate addition of resin allows the wetted recycled paper to retain even more than 30% of its dry strength, while in the dry state, the breaking strength of the paper is improved by approximately 46%. As the demand for more sustainable and resistant paper products continues to grow, the use of wet strength agents is expected to increase in the coming years, as well as the need for research in this field. This research therefore undoubtedly contributes to advancing sustainable practices within the paper industry, aligning with the principles of circular economy by optimizing the utility of recycled fibers while maintaining product quality.

Improved bleached eucalyptus kraft pulp-based tissue papers incorporating wet-strength resins

Abstract Common tissue paper manufacturing trends aim at partial or total replacement of softwood pulp with hardwood pulp for its production, such as bleached eucalyptus kraft pulp (BEKP), in order to optimize the process and the final product properties such as softness. However, the use of a single type of hardwood fiber results in lower strengths of both wet and dry webs. To maintain necessary strength and desired properties, the incorporation of several additives is often required. In this context, low molecular weight polyethylene glycol (PEG) and different wet strength resins, such as polyamideamine-epichlorohydrin (PAE) and glyoxalated polyacrylamide (GPAM) resins, were combined to achieve an innovated product with improved properties. In particular, wet and dry tensile strength was significantly improved when combining PEG and wet strength resins, especially observed in tissue papers prepared with PAE resin, high-charge cationic agent and bulk applied aqueous PEG solution. Noteworthy that water absorption capacity and softness of tissue paper were not critically affected by PEG incorporation, regardless of application method used (in bulk or by spray).

An analytical method to quantitatively determine the amount of polyamide epichlorohydrin (PAE) in paperboard and white water

Polyamide epichlorohydrin (PAE) is a permanent wet strength resin. When applied to paperboard, some amount of resin is retained in the sheet, and some is lost to the white water. An analytical method for quantifying the amount of PAE retained in the sheet and lost into the white water has been developed. This method hydrolyzes the PAE to adipic acid, which in turn is derivatized to diethyl adipate and quantified by pyrolysis gas chromatography–mass spectrometry (pyGCMS). In addition, the hydrolysis conditions of the PAE were studied by the Taguchi approach, and PAE material balances around the dry sheet and white water for 3 and 6 lb/ton PAE applications have been performed. The PAE resin recovery was 95.4% with 65.0% in the sheet for the 3 lb/ton PAE-charged paper-board, and the recovery was 96.7% with 36.1% in the sheet for the 6 lb/ton PAE-charged paperboard.

Application of additives to manufacture quality towel grade tissue paper with accelerated productivity

Nowadays in paper business sector there is only tissue paper business where growth rate is in double digits since five years consecutivelywhich motivates and encourage entrepreneurs to take up the business with more vigor. Tissue paper is generally categorized in four grades -Napkin grade paper, Toilet grade paper, Facial grade paper and Towel grade paper. Due to higher consumption of towel grade tissue paper at several outlets like offices, educational institutions, aesthetic purposes, common toiletries andhospitalities.This towel grade is being used for wiping wet hands, to meet out these requirements we need to develop high strength in towel grade tissue paper.This study is being conducted to high strength in towel grade tissue paper with application of DSR and WSR. Chemical additives play essential role in production performance of towel grades tissue paper. A significant amount of their tensile strength are retained by wet and dry strength resins .Mixed bleached pulp was collected from pulp mill of a well-known industry. It was refined to different degrees of freeness (°SR) i.e. 25, 30 and 35. Handsheets of pulp refined to different extent, were prepared and physical properties investigated. Based on the specific energy consumption of refiner and the pulp strength properties obtained, pulp freeness with 35°SR were selected for further study. DSR was added in three different doses i.e.2.0, 3.0&4.0 kg/ton and WSR in dosages of 15, 25 & 35 kg/t of pulp. Breaking length and wet strength were enhanced by 32 % and 42 % respectively. On account of this, significant reduction in paper breaks observed on paper machine, which further improved machine runability, reducing downtime. Productivity of machine was enhanced along with supreme quality of towel (interfold) grade tissue paper.

Chloropropanols (3-MCPD, 1,3-DCP) from food contact materials: GC-MS method improvement, market survey and investigations on the effect of hot water extraction

ABSTRACT The chloropropanols, monochloropropane-1,2-diol (3-MCPD) and 1,3-dichloro-2-propanol (1,3-DCP) are potential contaminants that may be found in food contact materials (FCM) from paper and paperboard that have been treated with certain wet-strength resins. They can migrate from the paper matrix to aqueous food and beverages and, due to their potentially carcinogenic properties, are of increasing interest in quality assurance or official controls of paper-based FCM. We hereby describe an improved method for the analysis of 3-MCPD and 1,3-DCP in water extracts of FCM making use of 1-chloro-3-methoxy-2-propanol (CMP) as a novel internal standard. The LOD and LOQ were determined to be 0.4 µg/L and 1.2 µg/L for both analytes, making the method appropriate for the quantification of 3-MCPD and 1,3-DCP below the current legal limits. The method was applied to an extensive market survey of food contact articles made from paper and paperboard including 674 samples. The survey revealed that a high percentage of the products available on the market (e.g., up to 55% of the analysed drinking straws) exceed the BfR limits with values of up to 327 µg/L 3-MCPD and 20 µg/L 1,3-DCP detected in the cold water extract. Remarkable differences were observed concerning the release of 3-MCPD and 1,3-DCP from different kinds of paper-based FCM products, with drinking straws, cupcake cases, bagasse bowls and kitchen rolls showing particularly high rates (>10%) of non-conformity with the legal limits. A number of samples with especially high concentrations were additionally analysed by hot water extraction, which surprisingly yielded considerably lower results for the release of 3-MCPD and 1,3-DCP than cold water extraction. The results indicate that cold water extraction is the most sensitive method to detect the migration and control the risk of exposure to 3-MCPD and 1,3-DCP.

Challenges to Achieving Strong but Fully Degradable Adhesive Joints between Wet Cellulose Surfaces.

The dramatic loss of strength upon exposure to water is one of the challenges preventing the widespread substitution of plastic packaging with paper and paperboard. Although treatment with conventional wet strength resins and other adhesive polymers can strengthen wet paper, it is at the expense of green credentials, including easy recycling or rapid composting. The goal of this work was to demonstrate the adhesive requirements for strong, wet cellulose-cellulose joints that can be recycled easily because the joint strength can be destroyed by the presence of a weak reducing agent. Cellulose membrane surfaces were first treated with a bound layer of carboxymethyl cellulose, modified to have covalently tethered hydrazide groups. Joints were fabricated by laminating two hydrazide-modified membranes with a polymeric adhesive bearing aldehyde functionality. Aldehydes spontaneously condense with hydrazide to give hydrazone bonds. When the adhesive was oxidized dextran, the wet laminates had an intermediate strength. Upon exposure to a reducing agent, the joint strength was reduced to nearly zero because every hydrazone moiety connecting two cellulose surfaces included a cleavable disulfide linkage. By contrast, glyoxalated cationic polyacrylamide gave very strong wet joints. However, the wet adhesion was dominated by polyelectrolyte complexation, and the presence of hydrazone linkages had little influence on the wet adhesion. We conclude that robust joint degradability will require cleavable linkages in the adhesive backbone while minimizing polyelectrolyte complexation.

Cellulose fibre- perlite depth filters with cellulose nanofibre top coating for improved filtration performance

Depth type composite filters are used to remove contaminants from liquids by combining mechanical entrapment and adsorption. Commonly, depth filters can adsorb either anionic or cationic charged contaminants, but not both, as well as filter micron-sized particles. Therefore, there is still a need to improve the existing depth filter performance. In this study, we developed a two-layer filters with enhanced functionality by spray coating an anionically charged cellulose nanofibre (CNF) layer onto a cationically charged depth filter layer. The depth filter layer was prepared via papermaking technique of vacuum filtration from wood pulp fibres, perlite adsorbent and cationic polyamide-amine epichlorohydrin (PAE) wet strength resin. The CNF coat weight ranged from 4 to 30 g per square metre (gsm). The two layer filters were proven to have triple functionality, capable of adsorbing anionic molecules in the cationic depth filter layer, while the anionic CNF layer could adsorb cationic molecules and was also a microfiltration membrane. A gradual increase in CNF coat weight improved filtration performance but decreased the filter flux. The optimum performance was found at an 8 gsm CNF coat weight, where the membrane layer rejected 80% of 5000 kDa molecular weight polyethylene glycol, at a flux of 133 Litres per square meter per hour (LMH) under 1.5 bar pressure, while still achieving a good breakthrough curve when absorbing cationic methylene blue dye.

Switching off PAE wet strength

Abstract The wet strength of cellulose-cellulose joints, reinforced with PAE-loaded microgels, was decreased by nearly a factor of two when the labile disulfide crosslinks on the supporting microgels were exposed to a reducing agent. The supporting microgels were temperature and pH sensitive poly(N-isopropylmethacrylamide-co-acrylic acid) microgels, prepared with a disulfide crosslinker. The level of PAE loading increased with the microgel carboxyl content. This work illustrates a new approach to increasing the recyclability and compostability of wet-strength papers made with PAE wet-strength resin.

Regulatory and sustainability initiatives lead to improved polyaminopolyamide epichlorohydrin (PAE) wet-strength resins and paper products

Polyaminopolyamide-epichlorohydrin (PAE) resins are the predominant commercial products used to manufacture wet-strengthened paper products for grades requiring wet-strength permanence. Since their development in the late 1950s, the first generation (G1) resins have proven to be one of the most cost-effective technologies available to provide wet strength to paper. Throughout the past three decades, regulatory directives and sustainability initiatives from various organizations have driven the development of cleaner and safer PAE resins and paper products. Early efforts in this area focused on improving worker safety and reducing the impact of PAE resins on the environment. These efforts led to the development of resins containing significantly reduced levels of 1,3-dichloro-2-propanol (1,3-DCP) and 3-monochloropropane-1,2-diol (3-MCPD), potentially carcinogenic byproducts formed during the manufacturing process of PAE resins. As the levels of these byproducts decreased, the environmental, health, and safety (EH&S) profile of PAE resins and paper products improved. Recent initiatives from major retailers are focusing on product ingredient transparency and quality, thus encouraging the development of safer product formulations while maintaining performance. PAE resin research over the past 20 years has been directed toward regulatory requirements to improve consumer safety and minimize exposure to potentially carcinogenic materials found in various paper products. One of the best known regulatory requirements is the recommendations of the German Federal Institute for Risk Assessment (BfR), which defines the levels of 1,3-DCP and 3-MCPD that can be extracted by water from various food contact grades of paper. These criteria led to the development of third generation (G3) products that contain very low levels of 1,3-DCP (typically <10 parts per million in the as-received/delivered resin). This paper outlines the PAE resin chemical contributors to adsorbable organic halogens and 3-MCPD in paper and provides recommendations for the use of each PAE resin product generation (G1, G1.5, G2, G2.5, and G3).

The wet strength of water- and foam-laid cellulose sheets prepared with polyamideamine-epichlorohydrin (PAE) resin

Abstract Some paper and paperboard grades require strength also when rewetted. The purpose of this study was to investigate the impact of web forming method, different foaming agents, polyamideamine-epichlorohydrin (PAE) wet strength resin, and retention aids on the strength development of hand sheets. Only a slight, if any, improvement in dry tensile strength due to PAE resin was observed. PAE improved the wet strength of the water-laid sheets, and the retention systems had a minor but positive impact. Although wet strength was lower at given PAE addition levels, the trend was similar with the sheets foam-laid with an anionic foaming agent, except at high PAE levels. With the non-ionic surfactant the maximum level of wet strength was reached already at a low PAE addition level and use of retention aids decreased wet strength. Such differences between the water- and foam-laid sheets are most likely due to the chemical interactions between PAE, foaming agents, and other additives.

Wet-peel: a tool for comparing wet-strength resins

Abstract We propose that a testing procedure we call wet-peel significantly augments conventional wet paper testing when comparing wet-strength resin efficacy or the influence wood pulp fiber surface treatments on wet paper strength. A thin layer of wet-strength resin is sandwiched between a pair of thin, wet regenerated cellulose membranes to form a laminate, which is a physical model for fiber-fiber joints in paper. In the wet-peel method, the ninety-degree wet-delamination force gives a direct measure of adhesion in the wet cellulose-cellulose joint. Wet-peel measurements offer: 1) comparisons of wet-strength polymers at the same content of polymer in the laminate joint without the influences of varying fines contents, formation or paper density; 2) measurements of both the wet-strength of cured, dried joints, and the strength of never-dried joints (i. e. analogous to wet-web strength); 3) demonstrations of the influence of fiber surface chemistry modifications including oxidation and the presence of firmly bound polymers; and, 4) the evaluation of more exotic joint structures including layer-by-layer assemblies, microgels and colloidal polyelectrolyte complexes.

Propolis and chitosan as antimicrobial and polyphenols retainer for the development of paper based active packaging materials

Abstract The research investigates the potential combination of propolis and chitosan to develop a completely bio-based active food packaging material. Propolis glycolic extract was used as antioxidant and antimicrobial, due to its polyphenols content. Two commercial chitosans with different molecular weights were comparatively used as antimicrobial, wet strength additive substitute and polyphenols retainer. The effects of the addition of carboxymethyl- (CMC) or microfibrillated cellulose (MFC) and two pH values in paper production were investigated for polyphenols retention and paper strength. Chitosan, in replacement of the most commonly used wet strength resin (PAAE), increased polyphenols retention more than 10 times. Paper sheets produced with the highest molecular weight chitosan, at pH 7 and with MFC addition showed the best wet strength (7.4 ± 0.5 Nm/g) and wet resistance (13.3 ± 1.2%). Paper antimicrobial activity was confirmed on thinly sliced raw veal meat, where a decrease of intentionally inoculated L. innocua of around 1 log cycle was achieved in 48 h at 4 °C.

Hydrazide-Derivatized Microgels Bond to Wet, Oxidized Cellulose Giving Adhesion Without Drying or Curing.

Hydrazide-derivatized poly(N-isopropylacrylamide-co-acrylic acid) microgels gave strong adhesion to wet, TEMPO oxidized, regenerated cellulose membranes without a drying or heating step. Adhesion was attributed to hydrazone covalent bond formation with aldehyde groups present on the cellulose surfaces. This is one of only three chemistries we have found that gives significant never-dried adhesion between wet cellulose surfaces. By contrast, for cellulose joints that have been dried and heated before wet testing, the hydrazide-hydrazone chemistry offers no advantages over standard paper industry wet strength resins. The design rules for the hydrazide-microgel adhesives include: cationic microgels are superior to anionic gels; the lower the microgel cross-link density, the higher the adhesion; longer PEG-based hydrazide tethers offer no advantage over shorter attachments; and, adhesion is independent of microgel diameter. Many of these rules were in agreement with predictions of a simple adhesion model where the microgels were assumed to be ideal springs. We propose that the unexpected, high cohesion between neighboring microgels in multilayer films was a result of bond formation between hydrazide groups and residual NHS-carboxyl esters from the preparation of the hydrazide microgels.

Multilayer assembly onto pulp fibres using oppositely charged microfibrillated celluloses, starches, and wetstrength resins − Effect on mechanical properties of CTMP-sheets

The effects of multilayering of microfibrillar cellulose (MFC) onto a chemi-thermomechanical pulp (CTMP), from which the fines material had been removed, were investigated with regard to the mechan ...

3-MONOKLORO-1,2-PROPANDIOL PADA KEMASAN KERTAS DUPLEKS SERTA MIGRASINYA KE DALAM SIMULAN PANGAN

3-Monochloro-1,2-propandiol (3-MCPD) is a carcinogenic food contaminant. 3-MCPD is formed during food processing, and can also be derived from food contact packaging materials, including paper. Wet-strength resin is often added into paper food packaging to provide moisture resistance and thus enhancing food shelf-life and consumer usage. The wet-strength resins which are manufactured from epichlorohydrin-based starting materials, are known to initiate the formation of 3-MCPD. Thus, the objectives of this study were: 1) to validate an analytical method for the analysis 3-MCPD in duplex paper packaging, 2) to analyze3-MCPD content in duplex paper, and 3) to analyze 3-MCPD migration from duplex paper packaging into food simulants. 3-MCPD content in duplex paper was analyzed by a validated GC-MS method with linearity value (R2) of 0.993, limit of detection (LOD) of 6.65 ppb, limit of quantification (LOQ) of 22.15 ppb, and recovery range of 83.00–114.13%. The 3-MCPD content of five sample duplex papers obtained from different packaging paper manufacturers were ranging from 753.43 to 825.36 ppb, and there was no significant differences between the samples. Direct contact between food simulants and duplex paper for 24 hours at 40°C generated migration of 3-MCPD at levels of 40.55 to 57.61%.

Development and validation of an improved method for the determination of chloropropanols in paperboard food packaging by GC-MS

The objective of this study was to develop an improved analytical method for the determination of 3-chloro-1,2-propanediol (3-MCPD) and 1,3-dichloropropanol (1,3-DCP) in paper-type food packaging. The established method includes aqueous extraction, matrix spiking of a deuterated surrogate internal standard (3-MCPD-d5), clean-up using ExtrelutTM solid-phase extraction, derivatisation using a silylation reagent, and GC-MS analysis of the chloropropanols as their corresponding trimethyl silyl ethers. The new method is applicable to food-grade packaging samples using European Commission standard aqueous extraction and aqueous food stimulant migration tests. In this improved method, the derivatisation procedure was optimised; the cost and time of the analysis were reduced by using 10 times less sample, solvents and reagents than in previously described methods. Overall the validation data demonstrate that the method is precise and reliable. The limit of detection (LOD) of the aqueous extract was 0.010 mg kg−1 (w/w) for both 3-MCPD and 1,3-DCP. Analytical precision had a relative standard deviation (RSD) of 3.36% for 3-MCPD and an RSD of 7.65% for 1,3-DCP. The new method was satisfactorily applied to the analysis of over 100 commercial paperboard packaging samples. The data are being used to guide the product development of a next generation of wet-strength resins with reduced chloropropanol content, and also for risk assessments to calculate the virtual safe dose (VSD).

Application of Ultrafiltration in a Paper Mill: Process Water Reuse and Membrane Fouling Analysis

High water consumption is a major environmental problem that the pulp and paper industry is facing. Ultrafiltration (UF) can be used to remove the dissolved and colloidal substances (DCS) concentrated during the recycling of white water (the process water) to facilitate the reuse of white water and reduce fresh water consumption. However, membrane fouling limits the application of UF in this industry. In this study, super-clear filtrate obtained from a fine paper mill was purified with a polyethersulfone (PES) ultrafiltration membrane to evaluate the reuse performance of the ultrafiltrate. The membrane foulants were characterized by scanning electron microscopy, energy-dispersive spectrophotometry, attenuated total reflection-fourier transform infrared spectroscopy, and gas chromatography-mass spectrometry. The results indicate that the retention rate of stock and the strength properties of paper increased when the ultrafiltrate was reused in the papermaking process compared to when super-clear filtrate was used. The reversible membrane foulants during ultrafiltration accounted for 85.52% of the total foulants and primarily originated from retention aids, drainage aids, and wet strength resins, while the irreversible adsorptive foulants accounted for 14.48% and mostly came from sizing agents, coating chemicals, and others. Moreover, the presence of dissolved multivalent metal ions, especially Ca2+, accelerated membrane fouling.

Effects of Resins and Adhesives on the Preservation of Converted Handmade Papers

This study focused on the effects of resins and adhesives on the preservation of a series of dyed handmade papers, called ”multi-colored, gold-embossed papers”. The substrates included filter paper, lab-prepared handmade papers, and commercial water-patterned handmade papers. The resins or adhesives were impregnated into the papers and then 105℃ dry heat was applied for accelerated aging treatment. Changes in the paper strengths and colors were determined afterward. The results indicated that the paper substrates exerted significant influences. Although the commercial paper upon impregnating with various gelatins could markedly increase its folding endurance, after 12 d of 105℃ dry-heat, however, the folding endurance was almost reduced to 0; tearing strength retention was merely 20%. Thus it was not durable and would not be suitable for use as a medium for artistic creations. Individual resins and adhesives exhibited differing effects; they affected the original strengths of the substrate papers, but also the aging responses and changes in coloration. For tearing strength retention, the 2 wet-strength resins, sodium alginate, alum-added gelatin, and starch showed poorer strengths after the 105℃ dry-heat treatment. Resins or adhesives added with an insolubilizer, AZC, were superior to alum, and the effects were more distinctive in filter paper than in handmade papers, mainly because there was no calcium carbonate in the filter paper to neutralize the acidity of the alum.

Application of Confocal Laser Scanning Microscopy (CLSM) for Observing Adhesives in Paper

Many kinds of adhesives are used to produce paper and prints. However, it is difficult to observe the distribution of these adhesives in situ because most are transparent and of low content. We have developed a fluorescence staining technique, which observes adhesives in paper with a confocal laser scanning microscope (CLSM) after staining with specific fluorescent dyes. In this review, we present our observations using this technique on a wet strength resin in paper, the vehicle of offset printing ink on uncoated paper, and the coating binder in coated paper. The polyamide epichlorohydrin (PAE) resin, a wet strength resin, was selectively stained with Sulforhodamine 101 acid chloride, while the pulp fibers were stained with Acridine Orange. The distribution of PAE could be observed in a CLSM fluorescence image at the excitation wavelength of 543 nm, and the pulp fibers could be observed in a fluorescence image at the excitation wavelength of 473 nm. From this it was found that PAE tends to concentrate at fiber crossings. In order to quantify the penetration of the ink vehicle into the base paper sheet, cyan offset inks stained with Rhodamine B were printed on various paper samples. The location of the vehicle was determined with CLSM. The penetration of the ink vehicle was observed in three-dimensional images. Coated papers were soaked in a solution of Rhodamine B in ethanol, and then they were rinsed with pure ethanol. The styrene–butadiene latex of the coating binder was selectively stained with Rhodamine B. The distribution and position of latex in the coating layer was characterized with CLSM.