Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: A METHOD O~ T[;RING A ~ICROWA~ ~; F~TWAE~E
ARTICL13 ~D~ OF ~ ~TIC M~ T aT, TNE ~RT~C~ ~DU~u
THER~:~ay ~ND AN INK-IMPRINTED FIIM CC~PONENT ~OR USE IN
MAKING THE FLATMA~ TICLE.
FIELD OF THE IN~EUTION
The present inventlon relzltes to a process ~or manufact;urin~
articles made of synLhetic materlals s~lch a~ polycarbonat~, that
are decurated with a deslgn elemen~ embedded un~er the ~urf~ce of
the article. The in~ention i~ pzrticularly w~]1 suite~ ~or
manufacturing flatware such as dishes or cups ~hat can be safely
u~ed in a ~icrow~ve oven ~ince the de~ign el~ment is encapsulated
in the surrounding material and thUS lt 1~ unl~kely to releas~
armful fumes wheJI subjected to i~tense ~lectromaqnetic r~dlation.
~he invention ~l~o e~t~nds to ~uch novel miGrowaveable article wit~
an embedded design element and to a fil~ compo~ent bear1ng a de~i~n
eleme~t for u3e in manufacturing the ~icrowavea~le ~rticle.
r~C~ OF T~E INVENTION
Chil~ren in p~rti.cular enjoy eat.inq from ~1atwa~e ~rticle~
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th~t are imprinted with colou~ful decorations .such as cartcn
ca~a~ters~ It is known to ~a~u~act~re such fla~ware articles
from melamine resin ~y e~beddi~g i~ the base m~lamine resin
material a paper film be~ring the colourfu.l ~oration.
Mel~ine resin howcve~, ~ele~ses ~armful vapours when
sub~ec~ to intense electromagnetic r~di~lon and it i5 therefore
not suitable for ~anufacturin~ flatware that c~n be used to heat
f~nd in ~ micro~ave oven. Mor~ov~r, the em~edded paper ~ilm may
react with the electrvmagne~ic çnergy in the ~icrow~e o~en,
releasing ~umes that ~ay contaminate the contents being heated.
~u~t~ermore the paper ~i3.m which surfacerJ the article, pr~vides
a poor surfa~e finlsh that is prone to scratche~
deterioration.
M~ny ~latw~re artic~.~s, as reali~ed i~ the prior ~rt a~e
made fro~ poLycar~ona~e, a m~terlal wh~e molecules do ~ot react
with t~e acti~ity of ~ microwave o~en. Accordi~gly those
a~ticles ~an s~fcly be use~ in a micro~a~e vven witho~lt risk of
~0 food conta~ination by toxic fumes. To decorate such poly~arbonate
articles, a decorative indici~ i.s pri.nted on thei.r surf~c~, such
indicia ~lowever is pro~l~ to scratches and when su~jected to
intense electromagnçtic ~nergy in a microwav~ ove~, m~ bubbl~,
or cau~e the ink-imprinted decor~tion ~o fa~e and rele~e toxic
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fu~es. Thus the article can not be safe~y used in A microwave
oven even tho~gh the ~ody mat~rial is inherently suitable for a
~icro~ave envir~n.~ent.
Although attempts have been made to improve the alrea~y
existent microwa~eable ~la~ware a~ticles wi t~l a decor~ti~e
in~iGi.a, none ~f them are s~tlsfactory. Thus there is a nee~ to
prnvide a fl~twa.re article with a surfac~ ~ecor~ted with an
aesthetic design element that is resi~l-ant t~ scr~c~es and when
used in a microw~ve oven will nor fade, bu~bl~ no~ emit harm~ul
toxic fumes.
] S OE~ECTIVES AND S$ATEMENT OF THE INV~NTION
It i~ an obj ect of the pr~sent irlvention to pr~v ide
procesS for manufacturing a fla~w~re arti~,~e with a surface
pro~ided with an ~esthe~ic design elem~n~ that when used in a
~0 mic~owave oven will r.o~ f~de, ~ubble ~lor emit har~ful toxic
f~mes.
It is another obj~c~ ~f ~}1~ inver~ion to pr~vi.de a process
fo~ manufac~llring a. flatware ~rt~ic~ e w:i.th a surfa~e provi~ed
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with a~ thetic desigrl ele~ent which has a ql(~ssy ~urfac:~
finish that is highly resistant to scratches.
It ls a further object o~ the inven~if)n to pro~7ide
Elatware ar~icle with a surfa~e pro~rided w1th ~n aesthetic design
ement that when u~e~ in a microwa~re will not f~de, ~ubble nor
emit harxnful toxic ~ume.~.
. Yet it is another object ~f Lhe invention to pr~ride all ink-
imprinted film componer~t for prt~vl ding the aesthetic dcsigrl
elemer~t on the surface of the fl~tware arti~le that when used in
a mi~rowa~re will rlOt fade, bu~ble ~or emit harmful toxic fumes
As em~odied ~nd broadly descri~ed herein, th~. i nv~nt~ on
pr~vides a microwavea~le arti~le for holding food products, said
microwatJeable article comprising:
- a main body includin~ a first synthe~ic material;
- a decorative i~dicia placed on a surfa~e c~f ~aicl Irain
body;
- a film inc~luding a .~e~ond syntheti_ Tnat~erial overlaying
saicl decorative indiciai
~aid film ~laving ~ thiclcness and tran~;parency selected
tc alLow said dee~¢)r~tive lndicia to be vl~i~le to ~he hum~r eye
through the f i lm;
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sai~ fil~ be~ng bonde~ to sai~ body alon~ an area of
juncture whe~eb~ ~aid decoxati~e indicia is encapsulated ~etween
said main bo~y and s?~id film;
- said first ?~d second mate~i.als b~ing co~petible with one
another ~here~y sald area of juncture is resistant to
delaminati~n when said article is used ln a Iuicrowave o~en; and
- said first and second ~a~erials bein~ select~d to
sub~tan~ially prevent degradatiun and relea~e or toxic vapo~rs
wh~n used in ~ micro~rave oven.
1.0
~ s embodied and bro~dly described herein, the invention also
provides a proce~ fvr manuf~cturing a ~icrowavea~le article ~or
hol.ding food prodllcts, said proce~s co~prising the step~ of:
- placing in a mould a film carrying on an inn~r .surface
1~ thereof a d~rative indi~ia, said film ~eing sukst~ntidl1y
transp?~rent ~n~ made of a first ~ynt~eti~ m~eri.dl, said lnner
surf~ce f~cing a ca~ity of sai~ mould to cont~ct. ~aterial
in~e~ed therein
- in~ecting in said mould a ~e~nd synthetic ma~erial, said
second syn~heti~ material heing in a molte~ state ~o ~t least
partially fill said ~ould and bond ~it~l t3ald film alon~ a line of
~un~ture t~a~ at le~st ~?lrtially surroun~s sai~ decor~tive
indici~, whe~eby said d~or~tiv~ indicia is enc~s~lated betw~
said film ~nd s~i~ se~on~ synthetic ~.~teriai when the seco~
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syntheti~ ~aterial solidi~ies,
- said fir~ an~ ~eco~ ter~ls ~eing compatible with or,e
another wheYeby said ~rea of juncture when tne secon~ synthetic
material solidifie~ is resista~t to delamination wh~n ~aid
~rticle is used in a ~icrowave oven: an~
- said fi LSt an~ ~e~on~ ~aterials being ~ele~L~d to
subs~ntiall~ preve~t degradati~r. and release r~f tox~c vapour~
when ~sed in a microwave oven.
In a preferred embo~imentr ~h~ microwaveab~e article is
~anu~actured by in~ection ~ulding. A fil~ with a printed indl~la
on one 3ide is placed in~ide the mould wi~h the printed indicia
facing the ~ould e~vity. Polyc~rhon~te that forms the main ~ody
of the ~rticle is then inj~cted in~o the mould to bond wit~ the
film and Lhus encapsulate ~he d~corative indicia. Polyc~rbonate
is the mate~ial of choose for ~anuf~çt.uri~g t~e m~in bGdy of the
article because it has a hlgh impact strengt~, is dimensiona1l.y
~ta~le, and can be used in a microwave oven wi~h ro rlsks of
distorting, ~o~teni~g or releasing toxic futnes. Polycarbonate is
al~o characterised as h~i n~ goo~ r~sis~ance to chemica~ 5 and
ultraviolet light and it is crack resist~nt.
In a most preferre~ çmbodiment, the fil~ is a c~s~ ~ype
clear polycar~ te fil~, more particular, a polycarb~nate
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Acrylonitrile-~utadiene-Styren~ ~hereinafter ~eferred ~o a~ ~BS)
co~tcd materi~l with low shrinka~e and glossy surface fi~ish.
The ABS coating a~lo~s ~o pro~ a surf~e with ~ h ~mp~ct
resiS~ance, excellent surface finish, hi~h di.m~nsional sta~ility
at high temperatures, good chemical resis~ance and good stress
crackin~ resistance.
The film has a low flow index and a ~lolecl;llar weigh~ between
~7 000 ~nd 30 000 y/~ol. The fi~.m has a thickness in th~ range
]O ~m about 0. 02~ to abou~ 0.~8mm ~nd the surfaçe of the film is
tre~te~ tG obtain a surface textu~e in the range from about 2~ tn
55 Dyn~ on Whl~ he dec~orative indi cia i.s printecl. The surfacP
roug~n~ss allows the i.nk of the decora~i~e indicia to a~here
4etter to the sllrface.
After the inj ection process i s compleLed, the fornled piece
is subjected to a hea~ treatrment proces!; to relie~e stresses that
may have developed at the in~erface bet~een the film an~ the main
body. M~st prefer~bly, t.he ~leat treatment process is an
2a annealing prc~ess ~hat ~nsists of heating th~ piece to a
constant elevated tempe~atur4 for ~ periad of ti~e ~nd then
allol,rin~ it to c~ a slow ra~e.
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DES~:RIPTION OF T}IE 1: RAWIN~
Figuro 1 i~ ~ persp~;ive ~iew of a flatware article well sllited
for use in a microw~ve oven, that is constr~cted in ~;c~rd~nce to
the invention;
Figure 7 i.s a persp~ctivc ~iew of a ~le~r ~olycarbon~e film
coate~ on th~ unc~erside wi~h arl ink ~mpre~ion providing ~
de~o~ati~e indicia for use in ~anufacturing the flatware article
in figure 1;
Figure 3 ls a cro~s sectional view taken alon~ lines 3-3 in
figure 2;
Figure 4~ is a cross sectional ~iew of ~n injecL:ion mou.ld, for
man~facturing the flatware article shown in figure 1;
Figure 4~ is an enlar~ed cr~s sectional ~ie~ of the mould ca~it~
shown ~t figure 4a, the mould being closed and ~he i.njection
process initiatedi an~
~igure 5 is a further enl~rged view of the mould cav;ty showing
the distri~tlon of the injecte~ polymer an~ the ciear
polycarbnnate film t~erein.
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PESCRIPTION OF THE PREFERRED EMBODIM~NT
Referring ~o~ to the drawings, figure l ill~].stra~es a novel
flat~are ~rticle in the form of the dish 10 th~ is char~cterized
ky an aesth~t.ic design ~dici~ on the rece~sed ~ood contacting
surface of the dish. ~he dlsh l0 is const.ruct~A ~-~ch that it can
be ~fely used in a microwave ove~. In o~her wor~s, th~ materi~
of the dish '0 wi~l ~ot release L~xic f~mes ~at c~n con~aminate
the foad under ~he e~fect nf electro~agnetic radiat.iorl ~nd heat.
~ore specific~lly, the dish l0 inclu~e~ a cup-shaped ~ain
~ody l2 includlng a ~ownwardly sloping ~ide ~ll and ~ flat
bottom w~l 16. ~he decorative indicia is applie~ lo the ~l~t
bottom wall 16. Contr~r~ to conven~ional p.rocesses where the
indicia is si~ply printed on ~he surface of th~ dish, in the
present ~ase the indici~ is embed~ed in t-he material of the di~h
so it is ~hie1ded from contact with the food.
As best shc~n in f~Lgure~ ~ a~d ~ the decorative i21~iCi~
whiCh is an ink-i~pression 17 is shielde~ by a ~].ear
polycarbonat~ film 13 that .is bonded with the ~ase mater.ial of
the dish l0. The film 1R includes a ~hin cle~r c~st type l~ye~ of
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pol~c~rbonate ~comme~ial desig~ation Merlon ~,ex~n) 20~ one
surface thereo~ being printed with the ind.i.cia an~ the other
surface ~oated with c~ ABS layer 22 that 1~ very t~in by
comparison ~o the polycar~onate layer ~n. The ABS layer provides
S a st~ng long l~sting surface ~oatingr resistant to stains,
scrat~hes, stress cracking and ~hemical~. The film ~0 possess a
low ~low index with ~ molecula~ weight bet.ween 27 000 an~ 30 000
g/mol. The thickn~ss ~f t~e film~excluding the thickness o~ the
ink i~pres~i~n) is in the rany~ Lrom ~bout O.O~m~ to about 0.0
mm. Most prefe~ably ~he rh~kness of the film is of O.O~mm.
The surf~c~ of ~he flll~ Qn ~hich the i~k- lmpression 17 is
made is tre~te~ in a manner well known to those skilled in the
art to obtain a su~face texture ~etween 25 to 55 Dyn~s. Most
prefer~bly, ~le surfac~ o~ the film has ~ texture of 42 Dynes.
The surf~ce ro~ghness allows to ~etain well the ink-impressi~n
w~ich has a ~ypi~al thickness in the r~ e from about 0.C02 m~
and abou~ O.OlOmm. If the ink impression is ~ubstantially less
than 0.002 mm it ~i]l ~ virtllally transparent, while if it is
~oo thick ie., substan~lc~lly greate~ than O.OlOmm, it will ~pre~d
and bot~h the design on the film upon injection of the synth~ttc
material forminy Lhe main body.
The ~anufa~ture of the dish 10 is ~cGomplished in two
i
11
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stages, the first is the in~ction mouldin~ process, ~epi~ted at
figures 4, a and 5B and the final ~tage is an anneaLing step to
release intern~l stresses tha~ may develop at the i~lterfa~e of
th~ f.ilm 18 and the base material of the dish lO.
Wh~n the oLd is opened ~ in figure 4a, th~ film ~.~ which
has previously ~een printed ~ith t~e decorati~e in~ici.a and die-
cut to size is electrostat1~ally charged (in a manner well known
to those skllled in the art~ is pl~ed in trhe injectl~n old. The
film is pla~ed such that the A~S ~.~ated sldQ, la is ~ttracted due
to its charge agairlst ~he cld plunger 24 ~nd the or inked side
faces the oid ~vity, At Lhis point, t~e old plunge~ is displaced
in to close the moul~ ~avi~y.
15The injecti~n process begins by heati~g(a~oYe ~30 C~
polycarbon~.e mate~ial and melting it into a polycar~late
resin. ~n in-line ~eed screw injects the molt~n polycarbona~e
materi~l thro~gh a passage 28 into the enclose~ c~vity as shown
in figurc 6B.
Poly~arbon~te i~ an amorphous po~ymer w~ich when h~at~d to a
temperaturo above its glass t~nsition point 150 de~rees C and
then subjecte~ to shearin~ str~ss, the ~ol~cules will tend to
align themsel~es in the gener~l direction o~ th~ stress. If the
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mass is then cooled ~elow its transition temperat.ure whil~ the
~olecules are stil~ under stres~, the molecules remain in an
oriented stat~. Such an orientatlon c~ have ~i~nifiGa~t effects
on the properties of the p~l~mer mass. Thus in inj ection
moulding, th~ shear stress ~cting durin~ the flow of th~
poly~arbonat.e causes molec~lar ~rien~ation up~ ooli.ng. In
order to ~void the ~ndesirable bullt-in stre~s due to such
orienLat.ion of molec~les before the plastic mass sets, the mould
cav'ties are kept wa~m ie between 100 and ~2-~ degrees C and the
in~ection rates are fast.
~ ft~r the injection of t~le pol~carbonate has been comple~ed
the material gradu~lly cools down ~nd solidi~ies. ~uring such
cool~ng proces~ the polycarbonate shrlnks~ The fil~l 18 ~.hat h~s
1~ been heated by Lhe molten polycarbonate also coo1s down and
shrinks. ~ince the film 1~ and the polycarbonate formi~g the
remaining p~.rt of the dish 10 are unlikely t.o ~e of the same
d~lsity, ~oth co~ponents sh~ink at differen~ rates whi~ induces
stresses ~t the zone of }unct~re film l~main ~ody 14. 'rO ~edu~e
s~ch lnt~rn~l stresses, annealih~ is ~arried ~ut to re~ie~e
stresses that developed during the ph~se tran~for~ticn of the
two slmilar polycarhon~te ~terials of difEere~lt densiti~s.
Distortion and c~acking may result if ~hese stresse3 ~re not
redu~ed, causing a poor weak bound betwe~n the film and the main
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~dy. The ter~. annealing refers to a heat tre~tment in which a
material is exposed ~o an elev~ted te~perature for an extended
lengt;~ of t.ime an~ thereafter slowly cooled. ~enerally speaking,
temperatures ~ould range between 80C to 150 C a~d the trea~me~t
time betwe~n 0.5 hour tv 4 hours. Most preferably the di~h 1 n is
treated a~ for ~ hours ~d then allo~d to slowly cool.
T~le above description~ of a preferred embodiment should not
be interprete~ in any li~iting mallrler since varia~ions and
refinements are Possible which are within the spirit and scope ~r
the present inve~.tio~. The scope of ~e invention i.s defined in
the apper.ded clai~s arld their eq~ivalents.
14
