Jo urn al o f Scientific & Industria l Resea rch
Vo L 62, March 2003, pp 179- 183
Development of Specialty Paper is an Art: Bleached Absorbent Kraft from
Indigenous Raw Materials - Part-In
Dharm Dutt' , 1 S Upadhyaya, R S Malik, A K lindal and C H Tyagi
Department of Paper Techno logy, Ind ian Institute of Techno logy Roorkee, Saharanpur Campus, Saharanpur - 247 001
Received: 20 June 2002; accepted : 08 October 2002
Bleached absorbent Kraft base paper is hi g hl y specialized paper used for manufacturing of expensive decorat ive
laminates and paper phenoic copper clad (PPCC) whi ch is co mmerciall y kno wn as pictorial circuit board. 0 fill er loading
and pu lp bcating is req uired in thi s paper. A furnish ratio of mill pulp havi ng pine, bamboo and eucalyptus in the rdlio of
I :2 .3: I I and so ft wood hein g I: I is fou nd to he su itable for manufac turin g of bleached absorbent kran base paper and fulfil
all th e requirements lik e water klen:n, COP, tear strength , o pac ity, and bri ghtness. One per cent MF resin dose at pH 6. 17 is
o ptimum to get speci lied va lu e for cross- li nkin g. The paper should be calendered to get a thi ckness between 280-3 10 pm and
porosit y 2300-2700 mUmin. No BIS speci li ca tion is avai lah le; hen ce specifications from leadin g decorative laminates and
PPCC we re col lec ted. The linai results of laho rato ry made hand sheets arc co mpared with specificati o ns prescribed by
leading manufacturers o f PPCC and bleached Kraft and mi ll made bleached absorbent paper. TIle results are promising.
whic h tempted th e Indian paper makers to develop it indi ge nou sly.
Introduction
Bl eac hed absorbent Kraft is a hi ghl y spec iali zed
paper, whi ch is excl us ive ly used for manufacturing of
ex pens ive deco rati ve laminates and PPCC (Paper
Pheno li c Copper Clad). A decorative laminate
consists of multipl e layers, each hav in g its own
di stinct fun cti on (Figure I). It is impregnated by
me lamin e fo rmaldehyde, which is cured to form an
inert, hard co mpos ite sheet with the fibre structure o f
the paper. T he hi ghl y vis ibl e use o f the lam inates are
as workin g tabl es, cup board front s, floo r sets , very
hi gh demands on the appearance of th e lam in ate,
whi ch mu st be c lea n, have the correct li ght-res istant
shade and surface stru cture, and are res istant to wear
and scratc hin g. Th e laminate is normall y built on a
body of absorbent Kraft which may be fo ll owed by
li ght und erl ay paper and then a decora ti ve pape r,
givin g th e appea rance of the lamin ate, and fina ll y an
overl ay paper givin g wea r res istan ce.
For making lam in ates the plies o f absorbent
Kraft are impregnated with MF res in after w hi ch they
are cut int o sheets and pressed togethe r in a hi gh• Au th o r fo r corresponde nce
Ema il : dharm_dutt C@ yahoo.com
Pho ll e: () 132-7 1 1740
density press, with separating plates between the
lam in ate boards. The pressure is hi gh e nough for
press ing out any gases in the laminate , which thu s
becomes a so lid, pore less structure .
Pictorial c ircu it board (PCB) or PPCC is built
on a body of barrier pape r of basis we ight 80-90 glm2 .
These are impregnated w ith 32 pe r cent urea
formaldehyde res in of the weight of paper. ow five
to six layers of bleached absorbe nt kraft paper of
2
basis we ights 80-145 glm impregnated with urea
formald ehyde one by one. Further, a layer of barrier
2
paper of basis we ight 80-90 glm is laid on it and
impregnated with urea formaldehyde in a similar
manne r. Fina ll y, a copper film of thickness 35 ~m is
c laded. Now c ircuit outline is drawn on paper
phenolic copper clad. After application of chemicals
on PPCB , the exposed surface other than ci rcuit
diagram gets dissolved .
The bleached absorbent Kraft is basically a
normal Kraft with hi gh degree of porosity. Bleac hed
absorbent Kraft is an 80- 145 g/m 2 paper and for
laminate 2-5 plies are used . The followin g are the
important propert ies for bleached absorbent Kraft :
• It should have a reasonably good formati on and
good profile for the uniformity of the laminate.
J SC I INO RES VOL 62 MARCI-1 2003
180
Copper him (35 ,cJ1l1)
Harrier paper XO-l)O g/m2
Bleached absorbent kran 80-] 45 ginl
Barrier paper XO-90 g/111 2
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Fi gure 1-
Hi gh densi ty laminated built on adsorbent kraft for paper phenol ic co pper clad (PPCC)
• Th e paper he re acts as a hydrophili c, porous
medium with hi g h wate r absorpti o n po te nti a l,
he nce water absorbency, maximal unbound fibre
surface, and bulk a nd po rosity are the mos t
impo rtant pro pe rti es_ No rosin s iz in g is required.
• In order to increase wet web stre ngth , c ross
inte rs
link ing,
resins
like
me lamine
formaldehyde or urea formaldehyde is used in
stock pre parat io n.
• Mechani ca l stre ngth , like tea r, te ns il e, and
bursting stre ng th s are less importa nt but the
pape r have suffi c ient strength , so that it should
not brea k durin g ordinary use. Othe r pro pe rti es,
li ke w ire mark a nd stiffn ess are less impo rtant.
• Bri g htness and opacity are the most important
prope rti es . The ash conte nt s hould be less th an
0 .5 pe r cent hence, the use of fill e rs s hould be
avo ided.
• Two s idedn ess, s had e variat io n and bri g htness
reve rsio n shou ld be avo ided .
In th e present co nte xt, atte mpts have been made
to prepare b leached absorbe nt kraft from indi geno us
ra w material s, like pine, bamboo, a nd e uca lyptus in
the rat io o f I :2.3 : II . A s thi s ex pe nsive pape r is
impo rted, he nce the deve lo pme nt of bl eac hed
absorbent Kraft will he lp to save fo re ig n exc hange.
However th e HIS spec ifi cati o n is not ava il ab le for
compariso n of labo rato ry made ha nd sh ee ts .
Th e refore, s pecificati o ns from leading ma nufacturers
of pape r ph eno lic copper c lad and decorative
la minates were co ll ected . The resul ts of decorative
laminates are promising and te mpted the Ind ian paper
manufac ture rs to deve lop bl eached absorbe nt Kraft
from indi genou s raw mate ria ls.
Experimenta l Methodology
Raw Material Prepara tion- Mill pulp hav in g
furnish co mp os iti o n pin e, bamb oo and uc a l yp tu ~
in th e ra t io of I :2.3: II that was bl eac he d by usin g
Cep HH b le aching seq ue nce to get brightness 86 per
cent C G E) was co ll ec te d fro m integrate d paper
mill . Th e bl eac hed mi ll pulp was bl e nd e d w ith
so ftwood pulp of Ca nadian o ri g in mak e bri g htn ess
92 pe r ce nt C GE). Both the pulps were beaten in
WEVERK vall ey beater to 35 °SR and e va luated
fo r various ph ys ica l pro pe rti es as pe r BIS : 1060
pa rt I, IT a nd m ( 1960 a nd 1966). Th e res ul ts are
re ported in Tabl e I .
Collectio/l of Bleached absorhent KrL{ft Base
Paper - The b leac hed absorbe nt kraft base paper
was co ll ected from market a nd analyzed for various
prope rties, as s pec ifi ed by leading manu facturers of
decorative lamin ates and PPCc. The results are
co mpared with lahoratory made hand-s heets and
repo rted in T ab le 2 .
DUTI el ClI.: DEVELOPMENT OF SPECIALTY PAPER
Table I Properties of laboratory made hand-s heets of
bleached mill pulp coll ected from integrated paper mill in th e
vicinit y of Saharanpur having furnish composition, pine,
I I and
bamboo, and eucalyptus in the ratio of I 2.3
Canadian soft wood pulp
Bleache
d mill
pulp
Bl eached
so ftwo od
pulp
Initi al freeness, "SR
20
13
2
Final freeness, "SR
35
35
3
Ash, per cent
107
0.32
59
60
33
88
4878
10300
SI
Particul ars
o.
2
4
Basi s weight, g/m
5
Burst fac tor
6
Breakin g length , III
7
Tear factor
60
106
Ii
Bri ghtness, per cent (ISO)
82
90
9
Opaci ty, per cent
86.86
86
Beating, Blending and Slack PreparationBoth th e pulps were defibered in WEVERK make
va lley beater (without load) and freeness level were
determined .
Set I havin g 100 per cent mill was loaded with
one per cent melamine formaldehyd e res in and a pH
level 7.0-7.5 is maintained with th e help of alum with
continuos stirring. In the simil ar mann er, one per cent
melamine formaldehyde was added in set 2 hav ing
100 per cent softwood pulp and a pH leve l about 6.57.5 was maintained with the help of alum. In set 3,
mill pulp and softwood pulp was blended in the rati o
of I: I. Accordin gly, one per cent melamine
formaldehyd e was added and a pH level between 6.57.5 was maintained wit h alum.
Sh eet Making, Pressing and Evaluafiol1Laboratory hand-sheets of 155±3 g/ml were prepared
on British sheet forming machine. The sheets were
pressed in ord er to get stipulated porosity and sheet
thickness. The sheets were air-dried, conditi oned, and
test ed as per BIS-I 060: Part 1, II and III ( 1960) for
vari ous properti es required for bleached absorbent
kraft. The res ults are reported in Table 3.
Results and Discussion
Table I prese nts th e properti es of laboratory
made hand -s heets of mill pulp and softwood pulp of
Canadian ori gin . Based on the water kl emn, spirit
absorbency, caster oi I penet rati on value, tear strengt h,
181
brightness and opacity, a blend of mill pulp and
softwood pulp in the ratio of I: I was taken for the
development of bleached absorbent base paper for
decorative laminates and pictorial c ircuit Board .
Table 3 presents the test results of laboratory
made hand sheets having mill pulp and softwood pulp
in the ratios of 1:0, 0: I and I: I. In order to get
specified sheet thickn ess · of 280-310 ,..U11 and
Bendsten porosity 2300-2700 mLimin ; it is
imperative to press the sheet during sheet making. Tn
paper machine, these specified properties cou ld be
achieved by paper calendaring only. Tn set I, havin g
mill pulp and softwood pulp in th e rat io of 1:0,
brightness and tear strength is on lower side, wh ereas
in set 2 having mill pulp and softwood in th e ratio of
0: I, brightness and tearin g strength are on hi gher
side. When both the pulps were blended in th e rat io of
I: I, not only brightness and tearing strength
improved but all other properties that are essenti all y
required for bleached absorbent Kraft closely
resembl e with mill made paper also.
Table 2 shows a compari son of properti es
between
laboratory
made
hand-sheets
and
specifications collected by PPCC and decorative
laminate manufacturers and mill made absorbent
paper. The thickness of laboratory mad e hand-sheet is
320 pm, compared to 280-310 pm that is slightly on
hi gher side and can be reduced durin g' al endaring.
The sp irit absorbency and water kl emen values are 36
and 66 mm/4 min , respect ively, whi ch closely
resembl e with specifications. However the water
klemn of mill made paper is very hi gh, i.e., 82.5 mm/4
min , but water kl em n of laboratory made hand-s heet
resembl es with specifications. All other properti es, like
porosity, brightness, opacity, pH , and co ndu ctivity of I
per cent water extract are in close proximity with the
specification. Wet strength of laboratory ma~ e handsheet is 306 g/cm, which is hi gher than that of mill
made paper and specified va lue.
Conclusions
(i)
Based on absorbent properti es, like water
kl emn, spirit abso rbency, COP tear strength and
brightness th e ratio of mill pulp and softwood
pulp is I: I which is found to be suitable for
manufacturin g of bl eached absorbent Kraft
paper. The compos iti on of mill pulp hav ing
pine, bamboo and euca lyptus is in th e ratio of
I :2.3: II .
182
J SCi IND RES VOL 62 MARCH 2003
Table 2 -
SINo
Co mp a r i~on
or propert ies of labo ratory rmd e hand-sheets wit h Specili cat ions fo r paper r henolic copper clad (PPCC ) and
decorative laminates &nd mill made bleached absorb'~ nt paper
Spec ifi cati ons prescribed by
leadi ng ma nufacturers of PPCC
and ble:1ched kraft
Part ieLl lars
Basis weight , g/ m~
153±3
Bleached ahsorhent
kr~lft
Mill-A
LM HS
160
159
2
Thi ckness, pm
280-310
325
320
3
Moisture, per cent (max )
7
6.78
6.50
4
Impregnativll time. s T5
12
WS
g
Avg.
10
5
6
y
Spirit absorbency, s M D
40
38
CD
30
34
Avg.
35
36
Water klemn , s MD
65
90
CD
58
70
Avg.
65 .5
82.5
36
66
12
<)
WS
8
<)
Avg .
10
9
8
Burst factor
10
7
<)
Tear factor M D
11 5
7
COP at 35± I (lC, s TS
13X
CD
126.5
Avg.
10
II
Double fold,
!10
MD
6
Avg.
24
13endsten porosit y, ml/m1 n TS
3200
WS
2700
Avg .
2500
Bri ghtness, per cent (liCE)
13
Opacit y. per cent
86
42
CD
12
2900
2600
90
89
97 .7
98.6
6.5-7 .5
7.58
7.70
< 0.5
0.5
0.37
14
pH of 10 per cent hot ex trac t
15
Ash, per cent
16
Wet strength, g/cm MD
385
CD
20
> 200
Avg.
17
Conciuctivi tyo f I per cent water extnoct.
18
Finer analyses
~~
mhos/cm
202.5
306
21
< 22
SW:HW
53:47
SW: Mill
pulp
50:50
LMH5 ~ Lahorato ry made hand-sheet. SW
1:2.3: I I
= Softwooci , HW = Hardwood,
Mi ll pulp
~_
= Pine:
Eucalyp tu s: Bamboo in the nl tio of
o
Table 3 SINo
183
TT e l (Ii.: DEVELOPM ENT OF SPECIALTY PAPER
Test results of laboratory made hand-sheets
Laboratory made hand-sheets
Parti cul ars
100 per cent bleached
mill pul p*
100 per cent bleached
so ftwood pulp ""
Softwood and mill
pu lp in the rat io of I: I
Fi nal !'reeness, IlSR
20
13
15
2
Basis weight , g/m2
156
148
159
3
T hie~ n ess, f1 m
340
320
:135
4
Bul k, cmJ/g
2. 18
2. 16
2. 11
5
Ash , per cent
0.5
0.3
0. 37
6
Burst factor
6
10
7
7
Tear fac tor
70
165
86
8
Water klemn, mm/4min
50
80
66
9
COP al 35± I Ilc. s TS
WS
Avg
9
8
8.5
10
9
9.5
9
9
9
10
Bendsten porosity, ml/min
2650
2600
2600
II
Brightness. per cent (IlGEl
86
92
89
12
Opacity. per cent
98.S>
98.2
98.6
13
pH of 10 per cent hot waler extract
7.65
7.7
7.7
14
Wet strength. g/cm
280
33 0
306
* = Mill pulp collected from integrated paper mill s in the vici ni ty of Saharanpur having pine, bamboo and eucalypt us in the rati o of
I :2.3: I I
** = Sol"twood pu lp of make Canadian origin
(ii )
Minimum re finin g is required in this paper;
he nce it is imperative to pass the pulp through
refin er, preferably without load , be fore bein g
taken to machine.
(iii ) O ne per cent me lamin e formaldeh yde added to
furnish , havin g pH 7.7, is sufficient to deve lop
wet strength during we ttin g.
(iv) In order to get sheet thi c kness between 28 0-310
I-lm and po rosity 2300-2700 mLimin ; it is
necessa ry to li se calendaring durin g paper
manufac turin g.
(v)
In laboratory m ade hand-sheet as h leve l of 0 .37
pe r cent is found which is less than spec ifi ed
value of 0.5 per cent.
(v i) All the results of laborato ry made hand-sheets
resemble with the results of spec ificati ons
prescribed by leadin g manufacture rs of PPCC
and bl eac hed absorbent kraft and results of mill
made bl eac hed abso rbe nt pape r. He nce, based
on labo ratory mad e bl eac hed abso rbe nt kraft
hand-sheets' results, it can be co nc lud ed th at
labo rato ry made bl eac hed absorbe nt Kraft handsheets can successfull y be used for PPCC and
deco rati ve laminates.