Avantha Centre for Industrial Research & Development, Yamuna Nagar – IMPROVEMENT IN OPTICAL AND PRINT PROPERTIES OF COATED RECYCLED BOARD USED FOR PACKAGING DECEMBER 11, 2015 Amit K. Singhal, S. Bhardwaj, Sunil Kumar, N. K. Bhardwaj & R. Varadhan IPPTA WORKSHOP 2015

Introduction Purpose of the study Materials and methods Results and discussion Conclusions OUTLINE OF THE PRESENTATION 2

INTRODUCTION ABOUT COATING 3

Base paper Precoat (First coating layer) Topcoat (Second coating layer) 4 INTRODUCTION ABOUT COATING

5 Printability  Smoothness  Uniformity  Ink receptivity Visual Properties  Brightness & Whiteness  Opacity  Gloss Uncoated paper Coated paper PURPOSE OF COATING APPLICATION

Coating improves the paper quality in terms of gloss, smoothness, brightness, whiteness, shade and printability. For good quality coated papers, the different layers of coating color are applied on base paper – Precoat: Coarse grade ground calcium carbonate (GCC) – Topcoat: Fine grade GCC along with clay The amount of pigments and their properties in topcoat formulation are planned depending upon the final paper quality. The important ingredients of the coating color are pigments, which in a dry coating layer make up wt% of the total coat weight. 6 INTRODUCTION ABOUT COATING

Pigment being the major constituent, its properties play a key role in determining the rheology of coating color and the optical properties i.e. brightness and whiteness of coated paper. These optical properties are the most important and determine the final cost of coated paper. Like other technological development, coating formulation too has undergone a sea change; new ingredients and processes have been introduced. The other method to reduce the cost is through use of recycled fibres in papermaking and its use as base for coating application. The demand for recycled raw material is increasing as available wood resources in natural forests are declining. Depending upon the requirement and end use, such coated recycled board can be used for packaging applications. 7 PURPOSE OF COATING APPLICATION

 As the trend of using recycled fibres is increasing in coating application, it is of vital importance to establish the most effective coating formulation for maintaining the desired coated recycled board properties.  To investigate the effect of various pigment systems in precoat and topcoat coating formulation on rheological properties of coating color.  To understand the effect of different coating formulations on final coated recycled board properties. Approach: Optimization of pigments in precoat and topcoat formulation 8 PURPOSE OF THE STUDY 8

MATERIALS AND METHODS Precoat coating color was prepared using coarse grade GCC & clay. Fine grade GCC & clay were used in topcoat coating formulation. The conventional method was used for the preparation of coating formulation in laboratory. The coating formulations prepared using GCC and clay in ratio 100:0 and 50:50 were selected as control for precoat and topcoat formulations, respectively. The parts of clay were increased in precoat formulation while same was reduced in topcoat formulations. The attempts were made to adjust the viscosity of coating color for all the trials by increasing the solids level or parts of rheology modifier in coating formulation. The other coating ingredients were kept constant for all the trials. 9

MATERIALS AND METHODS The low shear viscosity of coating color was measured using BF viscometer. Water retention value was measured on AAGWR water retention meter. The coating color was applied on the recycled board sheets of 285 g/m 2 (bulk: 1.30; brightness: 61 %ISO and whiteness: 78) using an automatic laboratory bar coater (RK print coater). The coating amount was adjusted using bars of different numbers and coat weight was maintained to and g/m 2, respectively for precoat and topcoat application. The coated board sheets were immediately placed for drying for 60 s in an oven maintained at C. The coated recycled board sheets were supercalendered through soft nip on plant scale supercalender to achieve the desired properties. Standard methods were followed for all testing parameters. 10

MATERIALS AND METHODS IngredientsPrecoat Trials ABCDEF GCC (Coarse) Clay (Coarse)Nil Topcoat Trials GHIJKL GCC (Fine) Clay (Fine) Nil 11

12 RESULTS AND DISCUSSION A:PRECOAT (100:0); G-L:TOPCOAT (50, 55, 65, 75, 85 & 100 GCC PARTS) 12

13 RESULTS AND DISCUSSION 13 B:PRECOAT (85:15); G-L:TOPCOAT (50, 55, 65, 75, 85 & 100 GCC PARTS)

14 RESULTS AND DISCUSSION 14 C:PRECOAT (75:25); G-L:TOPCOAT (50, 55, 65, 75, 85 & 100 GCC PARTS)

15 RESULTS AND DISCUSSION 15 D:PRECOAT (65:35); G-L:TOPCOAT (50, 55, 65, 75, 85 & 100 GCC PARTS)

16 RESULTS AND DISCUSSION 16 E:PRECOAT (55:45); G-L:TOPCOAT (50, 55, 65, 75, 85 & 100 GCC PARTS)

17 RESULTS AND DISCUSSION 17 F:PRECOAT (50:50); G-L:TOPCOAT (50, 55, 65, 75, 85 & 100 GCC PARTS)

18 RESULTS AND DISCUSSION A-F:PRECOAT (100, 85, 75, 65, 55 & 50 GCC PARTS); G:TOPCOAT (50:50) 18

19 RESULTS AND DISCUSSION 19 A-F:PRECOAT (100, 85, 75, 65, 55 & 50 GCC PARTS); H:TOPCOAT (55:45)

20 RESULTS AND DISCUSSION 20 A-F:PRECOAT (100, 85, 75, 65, 55 & 50 GCC PARTS); I:TOPCOAT (65:35)

21 RESULTS AND DISCUSSION 21 A-F:PRECOAT (100, 85, 75, 65, 55 & 50 GCC PARTS); J:TOPCOAT (75:25)

22 RESULTS AND DISCUSSION 22 A-F:PRECOAT (100, 85, 75, 65, 55 & 50 GCC PARTS); K:TOPCOAT (85:15)

23 RESULTS AND DISCUSSION 23 A-F:PRECOAT (100, 85, 75, 65, 55 & 50 GCC PARTS); L:TOPCOAT (100:0)

24 RESULTS AND DISCUSSION 24 Clay in both precoat & Topcoat No clay in both precoat & Topcoat

25 RESULTS AND DISCUSSION 25 Coarse clay Fine clay Fine GCCCoarse GCC

26 Selection of different pigments and their dosages in coating color are of prime importance. The parts of different pigments in topcoat coating formulation have great impact on optical and print properties of coated recycled board. Increased GCC parts in topcoat formulation have positive impact on surface strength of board indicating possibility of reducing polymer emulsion and thus the overall cost. The pigment ratio i.e. GCC:clay can be changed depending upon the customer requirements/ final coated recycled board quality. The attempts should be made to increase the solids level of the coating formulation for better properties of coated board and cost reduction. Depending upon the requirement and end use, such coated recycled board can be used for packaging applications. CONCLUSIONS 26

27 27 Thank You 27