The present paper aims to study a new high-performance coating formulation while avoiding the use of cross-linkers.
By using acrylic polymers with carbonyl functional groups, the negative environmental effects of the finishing process can be minimized. These new polymers can give very good physical properties without losing the inherent properties
of flexibility and elasticity needed in upholstery leatherPostprint (published version

Bacardit Dalmases, Anna

Font Vallès, Joaquim

Labastida, Luis

Ollé Otero, Lluís

Urteaga, Eva

UPCommons. Portal del coneixement obert de la UPC

AfinidAd LXViii, 551, Enero - Febrero 2011 15Resumen El presente trabajo tiene como objetivo estudiar una nue-va formulación de altas prestaciones evitando el uso de reticulantes. Mediante el uso de polímeros acrílicos con grupos funcionales carbonilo, se pueden minimizar los efectos ambientales negativos del proceso de acabado. Estos nuevos polímeros pueden dar muy buenas propie-dades físicas sin perder las propiedades inherentes de fle-xibilidad y elasticidad necesarias en la tapicería de cuero.Palabras clave: polímeros acuosos carbonilo funcionales; libre de reticulante; acabado del cuerosummaRyThe present paper aims to study a new high-performance coating formulation while avoiding the use of cross-linkers. By using acrylic polymers with carbonyl functional groups, the negative environmental effects of the finishing process can be minimized. These new polymers can give very good physical properties without losing the inherent properties of flexibility and elasticity needed in upholstery leather. Key words: Water-based carbonyl functional polymers; Cross-linker-free; leather finishResumEl present treball té com a objectiu estudiar una nova formulació d’altes prestacions evitant l’ús de reticulants. Mitjançant l’ús de polímers acrílics amb grups funcionals carbonil, es poden minimitzar els efectes ambientals ne-gatius del procés d’acabat. Aquests nous polímers poden donar molt bones propietats físiques sense perdre les pro-pietats inherents de flexibilitat i elasticitat necessàries en la tapisseria de cuir.Paraules clau: polímers aquosos carbonil funcionals; lliu-re de reticulant; acabat del cuirUse of water-based carbonyl-functional polymers on a cross-linker-free high-performance leather finish Luis Ollé, eva urteaga, Joaquim Font, Luis Labastida, anna Bacardit*Igualada engineering school (eeI). universitat Politècnica de Catalunya (uPC) Plaça del Rei, 15. 08700-Igualada (spain)Uso de polímeros acuosos carbonilo-funcional para el acabado del cuero de altas prestaciones sin el uso de reticulantes Ús de polímers aquosos carbonil-funcional per l’acabat de la pell d’altes prestacions sense utilitzar reticulantsRecibido: 6 de diciembre de 2010; revisado: 10 de marzo de 2011; aceptado: *Corresponding author: annab@euetii.upc.eduAfinidAd LXViii, 551, Enero - Febrero 2011161. IntROduCtIOnThe technical specifications that are required from an up-holstery leather are very strict. However, aqueous finishes do not conform to the physical requirements by them-selves. That is why, on most occasions, the use of cross-linkers is necessary. Traditionally, the most commonly used cross-linkers are polyaziridines and polyisocyanates. Ep-oxy compounds, polycarbodiimides and polysilanes have been used of late, but the most appropriate cross-linker to apply to finish solutions is yet to be found. It is true that, in general, the physical resistances improve with specific concentrations. However, other characteristics such as reaction time and temperature of application usually pres-ent problems, as do the development of these physical resistances (some cross-linkers improve resistances one month after their application, which is too long a wait for a tanner) (1-8).The aim of the present study is to use acrylic polymers with carbonyl-functional groups in order to obtain a high-perfomance finish on upholstery leather for baby and child booster car seats without the use of cross-linkers. The carbonyl group can react readily with the multi-functional diamines or polyamines, hydrazides or semicarbazides contained in the finishing product itself. A crosslinking mechanism is established during film formation owing to the fact that water is produced in the condensation reac-tion. This crosslinking system is fast at room temperature without the disadvantage of toxicity typical of cross-linkers such as polyaziridine. These polymers can give very good physical properties without losing the inherent properties of flexibility and elasticity needed in upholstery leather(9-11).2. exPeRImentaL2.1. materialThe tests were carried out on Spanish chrome tanned cattle hides shaved at 1.1-1.2 mm. The hides were first retanned using synthetics, tannins and resins; next, they were fatliquored using ester phosphate, lecithin and beef tallow. Finally, the hides were dried (vacuum-aired) and fin-ished according to the formulation detailed in Table I. 2.2. methodologyIn order to study the effect that each of the products used has on the final properties of the finished leather, as well as their interrelations, both a multilevel centralized factorial experimental design and an analysis of variance (ANOVA) have been employed as statistical tools. An experimen-tal design with 2 variables and 2 levels (22) was chosen in order to carry out the experimentation. The variables to study were: basecoat resin and topcoat resin. Table II shows the thirteen experiments required to carry out this experimental design. The levels of experimental design were carefully chosen and are detailed in Table III.On a second stage of the study, the results obtained with the optimized formulation were compared to those ob-tained using cross-linkers (epoxy compound, polycarbodi-imide and polyisocyanate). The finishing formulation using cross-linkers is shown in Table IV.TABLE iCoating formulation (on crust ):Pre-bottom                                    50     Penetrator            450     Water                             500     Polyurethane                     Spray 2 wet g/ft2Basecoat                                   20      Pigment                                                    50     Protein binder                                       400     Water                                  75     Wax                                  60    Silica                                                     X     Basecoat resin*                                   Spray 10 wet g/ft2   topcoat         X        Topcoat resin*                                   X        Water                                         Spray 4 wet g/ft2                                                  Plate 80ºC / 80 bar / 1”                                                  Test after 7 days’ storage*Amount according to Table II and IIITABLE iiExperimental designtest Basecoat resin topcoat resin1 -1 -12 -1 13 1 -14 1 15 0 -1.4146 0 1.4147 -1.414 08 1.414 09 0 010 0 011 0 012 0 013 0 0AfinidAd LXViii, 551, Enero - Febrero 2011 172.3. evaluationIn order to study the effect of the basecoat resin and top-coat resin on the finish properties, the following tests were carried out:IUP 15. Measurement of water vapour permeability. IUP 20. Measurement of flex resistance by flexometer method (dry and wet). IUP 46. Measurement of fogging characteristics. IUF 402.  Colour fastness of leather to light: Xenon Lamp. IUF 412. Leather fastness test: Change of colour with ac-celerated ageing.IUF 450. Color fastness of leather to dry, wet and perspira-tion rubbing (1000, 500 and 100 rubs). IUF 470. Leather-Test for adhesion of finish (dry and wet).TABLE iVCoating formulation using cross-linkers (on crust ):Basecoat                                        50        Penetrator                                                   450      Water                                            500      Polyurethane                                 Spray 2 wet g/ft2Basecoat                                        20        Pigment                                 50         Protein binder                                      400       Water                                 75        Wax                                 60        Silica                                         100       Acrylic resin                                                   100       Polyurethane 1                                      100       Polyurethane 2                                                  x          Cross-linker*                               Spray 10 wet g/ft2     Topcoat                                     75        Top polyurethane 1                                  25       Top polyurethane 2                                                  100      Water                                                   x        Cross-linker*                                     Spray 4 wet g/ft2                                                  Plate 80ºC / 80 bar / 1”                                                  Test after 7 days’ storage* The cross-linkers used were: 10 g/L epoxy compound, 4 g/L polyisocyanate and 10g/L polycarbodiimide3. ResuLts and dIsCussIOnTable V presents the results obtained in each of the prop-erties analyzed. By means of the Statgraphics Plus Pro-gram, the statistical analysis of the results obtained were performed. Since no differences were found in dry and wet flex re-sistance, accelerated ageing and dry rub fastness when changing the amounts to use of basecoat resin and top-coat resin, these tests were not considered in the statisti-cal analysis. Additionally, no factor was found significant in water vapour permeability.The statistical analysis indicates that the amount of basecoat resin was found significant in the fogging, light fastness, wet and perspiration, rub fastness, and dry and wet adherence tests. Topcoat resin has an effect on wet rub fastness and light fastness.To continue with the statistical analysis, no significant fac-tors were excluded. Then, the statistically valid regression coefficients of the polynomial models fitted to the experi-mental data are the following:a) Fogging Test = 9.81 + 0.54*Basecoat resin + 0.43*Basecoat resin2 b) Light fastness = 3.50 - 0.37*Basecoat resin2 - 0.25*Top-coat resin2 c) Wet rubbing = 4.50 - 1.40*Basecoat resin2 - 1.15*Top-coat resin2d) Perspiration rubbing = 4.69 + 0.52*Basecoat resin e) Dry adherence = 2.8 + 0.4*Basecoat resin f) Wet adherence = 1.52 + 0.39*Basecoat resin As can be seen in the polynomial models, the amount of basecoat resin was found significant in the fogging, light fastness, wet and perspiration, rub fastness, and dry and wet adherence tests. Topcoat resin has an effect on wet rub fastness and light fastness. However, as shown in Fig-ure 1, there appears to be an inflection point in the results obtained in the fogging, light fastness and wet rub fastness tests with regard to the optimal surface area for each of these tests. In this case, and by means of the experimental design, we can learn from the combination of factor levels which optimizes each of the properties analyzed. Table VI shows the optimization response for each analysis.Although the lowest amount of basecoat resin and topcoat resin has to be used in order to maximize the water vapour permeability values and minimize the fogging test values, it can be concluded that, from the optimization values for each property, the optimum amount of topcoat resin to use is 350 parts. This is the optimum amount to maximize those values obtained in light fastness, wet and perspira-tion rub fastness, dry and wet adherence. In addition, the amount of basecoat resin that allows to obtain a stable TABLE iiiLevels of experimental designLevels -1.414 -1 0 1 1.414Basecoat resin 300 373 550 727 800Topcoat resin 200 244 350 456 500AfinidAd LXViii, 551, Enero - Febrero 201118Estimated Response Surface-1 -0,6 -0,2 0,2 0,6 1Basecoat resin-1 -0,6-0,20,20,61Topcoat resin2,833,23,43,6Light fastnessEstimated Response Surface-1 -0,6 -0,2 0,2 0,6 1Basecoat resin-1 -0,6-0,20,20,61Topcoat resin9,69,81010,210,410,610,8Fogging testEstimated Response Surface-1 -0,6 -0,2 0,2 0,6 1Basecoat resin-1 -0,6-0,20,20,61Topcoat resin1,92,42,93,43,94,44,9Wet rub fastnessEstimated Response Surface-1 -0,6 -0,2 0,2 0,6 1Basecoat resin-1 -0,6-0,20,20,61Topcoat resin4,14,34,54,74,95,15,3Perspiration rub fastnessEstimated Response Surface-1 -0,6 -0,2 0,2 0,6 1Basecoat resin-1 -0,6-0,20,20,61Topcoat resin2,32,52,72,93,13,3Dry adherenceEstimated Response Surface-1 -0,6 -0,2 0,2 0,6 1Basecoat resin-1 -0,6-0,20,20,61Topcoat resin1,11,31,51,71,92,1Wet adherence fig. 1. Estimated response surface for each property analyzedTable VPhysical and fastness tests analysedtest IuP 15 (mg/cm2h)IuP 20 dry IuP 20 wetIuP 46 (mg)IuF 402IuF 412IuF 450 dryIuF 450 wetIuF 450 persp.IuF 470 dry (n)IuF 470 wet (n)1 1.9 100000 50000 10.1 2-3 5 5 1 3-4 1.8 0.62 2.1 100000 50000 9.0 2-3 5 5 1 3 1.9 0.63 1.8 100000 50000 10.9 2-3 5 5 3-4 5 3.0 2.04 2.0 100000 50000 11.7 3 5 5 1 5 3.5 2.25 2.0 100000 50000 11.2 3 5 5 1 5 3.0 1.36 1.5 100000 50000 9.4 3-4 5 5 4 5 3.0 1.27 1.7 100000 50000 10.2 3-4 5 5 1 4-5 2.5 1.38 1.6 100000 50000 10.8 3 5 5 3 5 2.8 1.49 1.8 100000 50000 9.6 3-4 5 5 4-5 5 3.5 1.810 1.7 100000 50000 9.5 3-4 5 5 4-5 5 2.8 1.811 1.7 100000 50000 9.5 3-4 5 5 4-5 5 2.9 1.912 1.8 100000 50000 9.6 3-4 5 5 4-5 5 2.8 1.913 1.8 100000 50000 9.5 3-4 5 5 4-5 5 2.9 1.8AfinidAd LXViii, 551, Enero - Febrero 2011 19balance in all the properties analyzed is 550 parts. There-fore, a test to be conducted at an industrial plant scale was established. The chosen formulation allowed us to obtain a good balance between all the properties analysed (test #9, which corresponds to central points) using 550 parts of basecoat resin and 350 parts of topcoat resin. The results obtained were compared to those obtained using cross-linkers. The results are shown in Table VII.Although slightly higher values are obtained in the fogging test, and lower values in dry and wet adherence and light fastness tests as compared to those obtained using cross-linkers, the values obtained in water vapour permeability, dry, wet and perspiration rub fastness are better. There-fore, the use of water-based acrylic polymers containing carbonyl-functional groups allow to obtain a high-perfor-mance upholstery leather without the use of cross-linkers.4. COnCLusIOnsA high-performance finish on upholstery leather for baby and child booster car seats can be obtained using water-based acrylic polymers containing carbonyl-functional groups. The amount of basecoat resin was found signifi-cant in the fogging, light fastness, wet and perspiration rub fastness and dry and wet adherence tests. Topcoat resin has an effect on the wet rub fastness and light fastness tests. These polymers can give very good physical proper-ties without losing the inherent properties of flexibility and elasticity needed in upholstery leather. At the same time, the use of cross-linkers, which are harmful to the health and the environment, is avoided.5. BIBLIOGRaPHy1. Ollé, Ll., Bacardit, A., Morera, J.M., Bartolí, E., Argel-ich, J.; Binders cross-linked with polyaziridine. Study of cross-linked polymers for aqueous finishing. Part I: behaviour of polyurethane, JSLTC 92, 3, 96-102.2. Bacardit, A., Ollé, Ll., Morera, J.M, Bartolí, E., Fernán-dez, D.; Binders cross-linked with polyaziridine. Study of cross-linked polymers for aqueous finishing. Part II: behaviour of acrylic binders, JSLTC, 92, 4, 157-161.3. Ollé, Ll., Bacardit, A., Borràs, M.D., Morera, J.M., Co-bos, M., Borràs, E.; Binders cross-linked with poly-aziridine. Study of cross-linked polymers for aqueous finishing. Part III: influence of a cationic pre-bottom, JSLTC 93, 3, 91-96.4. Bacardit, A., Cobos, M., Borràs, E., Ollé, Ll.,; Binders cross-linked with epoxy resin for aqueous finishing. JSLTC 94, 1, 1-8.5. Ollé, Ll., Cobos, M, Solé, O., Bacardit, A.; Aqueous finishing with polyisocycianate cross-linked binders. JSLTC 93, 6, 222-228.6. Bacardit, A., Ollé, Ll., M.D. Borràs, Cobos, M., Jericó, A., Solé, O.; Binders cross-linked with polycarbodi-imide for aqueous finishing.  JSLTC, 94, 3, 117-123. 7. Ollé, Ll., Cobos, M., Combalia, F., Jorge, J., Bacardit, A.; Binders cross-linked with polysilane for aqueous finishing.  JSLTC, 94, 3, 111-116.8. Bacardit, A., Shendrick, A., Combalia, F., Jorge, J., Ollé, Ll.; Study of cross-linking reactions on butadi-ene binders in aqueous finishing. JSLTC accepted and pending of publication.9. Riasol, J. Pont, J.M., El acabado del cuero con polímeros carbonil funcionales, AQEIC, 3, 100, 2006.10. Nakayama, Y.; Development of novel aqueous coat-ing meet the requirements of ecology-conscious soci-ety: novel cross-linking system based on the carbon-yl-hydrazide reaction and its applications, Progress in Organic Coatings, 51, 280, 2004.11. Ollé, Ll., Bacardit, A., Morera, J.M., Bartolí, E., Shen-drick, A.; Study of a nubuck finishing with water-based carbonyl-functional polymers, JSLTC, 92, 5, 187-191.Table ViOptimization responseanalysis  Basecoat resin topcoat resinIUP 15 300 200IUP 46 440 250IUF 402 550 350IUF 450 (Wet) 550 350IUF 450 (Perspiration) 800 350IUF 470 (Dry) 800 350IUF 470 (Wet) 800 350Table ViiPhysical and fastness tests analysedtest IuP 15 (mg/cm2h)IuP 20 dry IuP 20 wetIuP 46 (mg)IuF 402IuF 412IuF 450 dryIuF 450 wetIuF 450 persp.IuF 470 dry (n)IuF 470 wet (n)9 1.8 100000 50000 9.6 3-4 5 5 4-5 5 3.5 1.8Isocy. 1.1 100000 50000 7.9 6 5 4-5 1-2 3 8.0 4.5Carbod. 1.6 100000 50000 8.8 6 5 2-3 1 1-2 5.0 3.2Epoxy 1.5 100000 50000 8.8 5-6 5 4-5 2-3 4 8.5 7.2

English

Use of water-based carbonyl-functional polymers on a cross-linker-free highperformance leather finish

Use of water-based carbonyl-functional polymers on a cross-linker-free high performance leather finishing

The present paper aims to study a new high-performance coating formulation while avoiding the use of cross-linkers.

By using acrylic polymers with carbonyl functional groups, the negative environmental effects of the finishing process can be minimized. These new polymers can give very good physical properties without losing the inherent properties

of flexibility and elasticity needed in upholstery leathe

Use of water-based carbonyl-functional polymers on a cross-linker-free high performance leather finishing

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