CA2193773A1

CA2193773A1 - Injection molding of long fiber reinforced thermoplastics

Info

Publication number: CA2193773A1
Application number: CA002193773A
Authority: CA
Inventors: Paul C. Isenberg; Christopher J. Beard; Nick R. Schott
Original assignee: HH Brown Shoe Co Inc
Current assignee: HH Brown Shoe Co Inc
Priority date: 1995-12-22
Filing date: 1996-12-23
Publication date: 1997-06-23
Also published as: US6159589A

Abstract

An injection molded fiber-impregnated thermoplastic composite material comprising a plastic polymer matrix wherein the fibers are sufficiently interwoven and entangled in said polymer matrix to provide improved resistance to mechanical loading, and wherein said composite material is particularly suited for the preparation of an injection molded toe cap for a protective shoe.

Description

~EC-20-19gh 16:51 FROM H~'~E~3. SOLOWR'~, ET.~L. TO GCll~iLlNG STRRTHY P.0~

219377~

INJE~TIO~ ~OLDING OF ~O~G FIB~ REINFO~CED T~ERMOP~ASTICS

Backgr~und of the Invention ~ h~ present invention ~elates t~ the in~eet~o~ moldin~ of fiber ~einforced thermoplastics, containing a substan~ially interwoven fibor orientatio~ in an in~ection molde~ thermopla~ti¢
matrix, w~erein the fibers di~play no pr~~erential orien~atlon and a high deg~ee o~ en~anglement bene~ic~al to ~he preparati~n of molded arti cles which experience ccmplex loa~ ng in actual use. ~ .
Prior Art Th~ use of lolly fi~er reinforc~d ~hermoplastics for injection ~olding ha~ grown in recent years, along with it~ a~socia~ed and ide~ified ~oblems, the mos~ c~itical and most of~e~ addressed being the p~o~lem of fiber degradation.
Fo~ in5ta~ce, duri~ injeetio~ ~olding~ poly~e~ materi~l is plasticated, melted and metered, howeYer, ~he ~mpregnated ~ibex i5 known to experierce degradation during ~his pr~eSs. ~he ~ajori~y of ~iber de~r~dation ~ypi~ally oCcurs at the ~irst part o~ the transitio~ zone ih the nje~tion molding s~rew. The injection p~ase has also been shown to be ~ large contr~butor to ~ib~r breakag~ during the ov~rall ~ycle. Fiber breakage auring in~e~ion molding is also se~n to o~Ur at the nozzle ~ the DEC-20-19Y6 16:51 FRO~1 h~r'ES, SOLOWR'f, ET.RL. TO GOWLli,~G ST~f:THY P.08 21 9~773 1' ..

inje~t~on molding ma~:hine~y, ~nd to a grea~e~ extent, a~ the gate.
Furthermore, wi th regards ~o details o~ er deg~adatic>n, i'c .l has more or le ~ been c2tegori~ed in~o thr~e bas~c mechanisms:
fiberJ~iber, fiber~equipment, and ~iber m~rix irl~e~actions~

~hat is, each of these ha~re ~:~een ~;hown ~co comb~ ne ~nd con~bute to the overall ~iber dcgradation rne~hanism duri ng ~he in}ection molding c~cle. See, e.g. "Fiber l)e~ada~ion ~uring the Pcecip~o~:ating Screw Pl~lsticiza~ion, " Doctoral Thesis, Unlversity of Massa~husetts, ~owell l 1992 ) .
~ot surprisingly, therefore, va~ious solu'cions ha~re been ~dvancc~ with regard~ to controlling and minimizing fiber degradatic7n. For example, ~ is generall~ known that the use of a cons~nt taper or io~ ~ompregsion screw ac~ually i.ncrea$es the a~nount of riber degrada~ion. In additiorl, mold design modifi~:ations ~o minin~ize tegrad~.t~on inc:lude; increa~ed venting, short polished spr~le, fu11 r~und ru~ners, large gates, and hardened sur~aces. In add~icn, the~ g~.~e should be made as large as reasonable for a gi~en p~rt ~ased cn mater~al ~ost and ae the~s as well as cycle time and economics.

Additionally, in some cases, simple proc~ssing ~ariations can be made in order to reduce ~ er d~g~r~.dation, ob~ ting any need to mo~i~y the in~ec~ion ~nol~ing machine, or the mold itsc~f. For example, in~re~sed ~cr~w speed su4jects ma~e~ial ~o in~reased D~C-20-lg96 16:52 FROM HR~tE', S~LOWflY, ET.flL. TO GOWLING STR~TH~ P.0g 219~77~

, l sh~ar and thu~ increases ~iber degradati~n In ~njection mo~ded par~s. A~cord~ngly, ~we~ scre~ speeds are desi~able~
Simil~rl~, high in~e~tion speeds lead ~o incre~sed she~r, and deg~ada~ion. ~he~e~ore, lowe~ inje~tion speeds may contribu~e ~o a reduc~ion in f~ber des~ ction.
What eme~ge~, ~herefore~ from the abo~e review of the prior a~t is that the indus~ry has correc~ly an~ prope~ly focused on ~he preparation ~f fibex-impregn~ted ~hermoplastic parts w~erein ~ umber ~f variables hav~ been explo~ed to min~mize deg~ad~ n ~f th4 fi~ers ~hemselves. Cert~inly, ~ the extent th~t ~ny success i5 wi~h.n reach ~ith regards to the preparation of fiber~
impre~nated injection molded thermoplastics, degr~a~-ion ~ust be minimized.
In ad~ition to the abo~e, it i~ also worth notin~ that studies h~ve be~ done which focus o~ the ~stribu~io~ of fi~ers in the in~e~tion molaed samples themselves~ This is s~ since fiber o~ienta~ion ~n and will af~ec~ ~he s~ren~h ~f the compo~i~e material. For example, ~iber len~h for certain long flber thermoplasti~s wer~ seen to indica~e, under identifie~
pro~edurec, a ~-modal distribution. Tha~ is, ~he fiber length ne~r the w~ll was found ~ be shor~er than the f~ber le~gth in ~he Core regio~. See~ e.g. "Co~po~ite M~eri~ls Te~hnology Process and Proper~ies,ll Hanser Pu~lishers, ~ew York, 19~.
In ~dditlon, ~t should be noted ~hat in the co~text o~ the DEC-20-l~gh 16:52 FROM Hfl~ES, SOLOWR'f, ET.RL TU GnWLlNG STRRTHY P.10 .

prasent invention w~ich finds e~han~ed utility in a shoe application, ~ por~ion O~e the prior art has inde~d focused on the prepar~ion of ftber-impregn~ted plas~i~ materials, specificalLY
for ~he purpose of preparing a toe eap irlse~t for what is knvwn as pro~ective shoe. Attention is th~refore direc:ted ~o ~he followin~ ~nited States and ~oreign patents an~lor ~ppli~ations ~rhl~h colLectivel~ de~cribe the de~elopment of composite ~cype plastic mate~ials speci~ically for protective shoe manufac~ure:
U.S. Patent Nos. ~,331,751; 5,210,963; 4 "35,003; 4 1~3,438;
3,950,855; 3,045,367; 2,740,209; Eu~opean Pa~ent Appli~tion 83~0404~.2; ~ur~pean P~ten~ No. 009$~61; and U.~ Pa~ent App1i~atio~ Nos. 2,071,98~ and 2,138,272.
~ ccordingly~ ~e above review demonstr~es t~at there i5 a continuing need in the pl~stic:s industry ~or ~ fiber-impregnated in jec~ion molded ~chermoplastic part wherein f ib~r degradation is mini~ized, ~r ~or that matter ~limina~ed entirel~. In addi~ion, given the import~nce of fiber orientation, th~re is ~l~o c~itica1 need fo~ a pro~edure wherQb~ fiber orie~tation is simultaneously man~ged to optimize mechan~cal p~operties for a given applic~ion.
Therefore, i~ is ~n ob j~ct of this inventi~n ~o ov~rcome the disadvantages of th~ prior ~r~ and prepare a long ~iber reill~orc:ed injectic~ rnolde~d plas~;ic p~ , wherein fiber degr*da~ion is su~s~antially avoided, and tvherein a ~ubstantially _4_ I~Er~-20-lg9h 15:53 FRC~l HRYE~, SOLOWCS, ET.hL. TU GClWLlNG STF~iTHY F.ll 219~773 in~erwoven fiber orienta~io~ is developed in the thermopla~ti~
matxix ~here~y improving an~ op~i~i7ing resis~an~e ~o co~plex mech~ical loading.
It ~ also an obiec~ of the present invention to prepare a long fi~er reinfor~ed injeetion molded thermoplasti~ pa~t, wherei~ the fi~ers display ~o preferential orientat~on, alo~g wi~h a high degree of fiber entanglement, ~nd i~ conjun~tiv~ wi~h the de~ lop~nt of such produ~t, to identi~y ~ proc~ss for manufac~ure thereof.
~inally, and more ~pecifi¢ally, it is also an obje~t of this inventi.on to prepare a long fiber rein~orced injection molded thermoplastic p~r~ par~icularLy adapted as an insert ~oe cap for a protec~ive shoe, although o~her utilities are fully contemplate~ and fall within ~he ~roa~ scope of the molded plasti~Jinterwoven ~nd impregn~ted composi~e fiber invention sclosed here~n su~mary of ~he Invention An injection molded fiber-impregnate~ plastic ~mp~si~e m~erial comprising a thermoplastic polymer ma~-rix wherein th~
fibers ~re suffi~ently interwo~en and ent2ngl~d in $aid pol~mer matri~ to provide improved resistance ~o mechanical ~oading. In p~rticular, th~ present inventivn descri~s an in jec~ion molded toe ~p for a protective ~h~ o~ the type ha~ing a rearwardly openin~ shoe toe-~haped body inclllding a roo~ which blends DEC-'0-1996 1~:53 F~O~ HRYE5, SOLOWRY, ET.~L. TO GOWLING 5TRRTH~ P.l~
219377~
. . .

smoothly into opposite l~ter~l generally verti ::~1 si~e walls ~e.g., by the use of a ~ounded edge) and a g~rlerally v~rtical front walL~ and an open re~r edge end defined by a rear edge including the rear edg~?s of the roof and said walls, said toe cap compri~ing a fibe~-impr~gnated p~ astic resin l~ody t~aving a maJor portion o~ ~che f~~er~ in the resin pcrtion ~ormi~g an in~erwoven and e:~tangled or~ en~ation throughout . Furthermore, in process ~orm, the prese~t invention des~:ribes ~he preparation of an i~jec~ion motde~-fiber ~mpre~nated plagtic composi~e materiai cont~ining a suhstantially intexwoven ~iber orientation ~ompri~ing ~upp~ying of a f iber- i~npregn~ed thermoplastic resi~2 pe~ le~, and in jection molding said pellet, wherein ~he leve~ o~
f~ber impre~nat1on, fi~er length, f~ber diameter, viscosit~ of the ther~noplastic re~in ~ moldin~ te~nperature, in je~ on time, and ~all thi~knes~ e~f the c:ompo~ ite ;~aterial subsec~ent to tlle molding pr~ed~re are ~justed ~-o provide a substantially inter~oven f~ber orienta~ion.
~etailed De~cr~ption o~ PreferLed E~bodiment~ .
As noted, the presen~ invention ~ompri~es an lnje~tion molded fiber-impregnated pl~st~s composi~e material compr~ing a Shermoplastic poly:ner mdtrix wherein ~he ~ ers a~e sufficiently in~erwoven ~d ent~gled in sai~ poly~er matrix to provide resis~anee to mechanic~l lo~ding. In this regard, i~ will ~e app~eciated ~y those skilled in the art tha~ by the interwo~en ~EC-2E3-13gh 16:5~ FRGM H~ES, 50LnW~, ET.FiL. TO GOWLING 5TRRTHY P.13 ...

a2~d entan~led cor~f iguration of the composite f ibers ~ ~b~ rd ' s nes'c" orien~a~ion of the fibers i~ present, ~nd such orientation pro~ide~ in the part an enhan¢e~d resistance ~o complex me~hanical loading . That is, regardle~s of what ~pecif ic type of mech~r~ical load~ng i~ applied t~ the composite, t~e flbers are without preferential orientation, and the~efore, a p~rtion of the fibers can always serve ~o in~rease ~he me¢hanical s~reng~h of ehe part, in 'che direct ion o~ the ra21do~ly ~pplied load . More p~rticularly, the interwoven and enLangled ~ibers increase t~e flexural modulu~; of the comp~site i~nd s21d c~posite distribu~es and ~ar~ies ~n applied load in multi-direc~ionS.
Furthe~more, it has been found tha~ sui~a~le plastic mate~ials for preparing th~ composite materi~l described herein are preferentially ~ho~e p~as~ic m~terials which lend themselves to in~ectiO~ moldins. Prefera~ly, the pl~stic ma'ceri~ls ~omprise nylon-6, nylon-~,~, or a thermopl~tic polyure~hane resin.
However, o~her t~pes of thermoplastic mate~rials ~ould ~e su~.table prov~ ded they interac~ with the ~; bers in such a way ~o pro~ide the appropriate flow behavior iin the injection molding cycle to cause th~ irdls nest" inter~oVQn ~rienta~icn of the fi~ers upon cooling.
With regard~ ~o ~he f~ers found sui~a41e f~r the composite i~aterial ~scri~e~ therein, glass type fibers, gen~rally known a~
"S Glass" and ~E ~las~" have been foun~ 3uitable, and ~re present i 1, DEC-Z0-1996 l6:54 FROM H~ S- SOLOW~Y, ET.f~L. Tr~ GOI~L~ G 8T~4THY P.14 in ~he compos~e at level~ of about 40_50~ by weig~t-Prefe~ably, ~he f~bQrs are pre~e~t in th~ neighborhood o~ 50-6 by weight, and ~he pre~ise level o~ fiber ~an be a~ju~ted to m3~i i ze ~echanical perfor~ e. I~ addi~ion, the ~ibe~s ~r~
generalli~ About 0.5~ inches in length, and such l~ngth vf ~iber is conveniently and best provid~d in pellets of the sa~e dimension. Sueh pellets ~ontaining a ~ber leng~h that is simil~r to pellet length is preferaoLy achieved by the process of pultrusion, and in ~ preferred embodiment sUch pelle~s of the thermoplastic polyurethane v~riety are av2ilable from DSM, Inc.
In particula~, the most p~eferred ther~oplastic potyurethane i~
sold under th~ d~signation DSM G-1~8, which contains 50~ fiber content (~-gla~) and ~ ~.5 - l.Q i~ch pelle~ length.
In regards to the processing e~uipment found .uita~le for the preparatiOn of the compo8ite material des~ribed herein, it has been found preferable ~o ou~it the i~jection moldlnq machlne ~ith an easy flow tip and no~le Along wi~h a large s~rew which are all commer~ially av~ilable from In~e~tion Moldin~ Supply, ~nc. ~n accord~nce with the p~e~ent invention, it i~ prefer~ble to develop ea~y flow and low pressur~ drops in the mold, f~r the purposes of providing 'che le~st Ciber damago. ~ist~!d below in Table 1 ~re the ~aterial specifi~atio~ for the ~refe~e~ resins, ~oilowed by Table 2, whl~h details the preferred ~oldin~
profiles:

I

~ r~ r~ v~i3~

DEC-20-19~ 16:55 FR0~1 Hfl'~ES, SOLOW~'f, ET.~L. T[i GOWLING STRf~Tl~Y P.15 Tahle i T~ ic Material Da~a ~l~t.JProp.RTP V~F ~SM S~% LP~P Verton~ Cellstran~DC~llstr~n~) ~7SM G
8~2l1 ~ylon-~,6~- R~-700-10 PPCi50 PUG6001 S 108PUR
1~50 ~a~s resin~ylon-6,61~1~1on-6,6 Nylon 6,6 Polypropylene PUR PUR
F;b~t Cont~rlt ~0 50 ~0 S0 ~0 50 ~o~o~
Sp. ciravit~ 1.7 1.57 i.57 1.33 1.76 1.~3 Moldul~ 2~-3 2~-~ 3.5E-3 ~ E~.~
Shrinkage (In/in) ~ t/~in.
W3ter ~ 4~ ~A
~1~50rption ~/s (~ hrs. ~ ~3 C~
~otohed 120d 8 5.7 ~i 14 Impact Stre~tb (ft Ib/int Tensile 40,000 3'7,0~ 37,000 34 000 33 000 5~eng~ (psi~
T~nsile 3 2 4 2.
E~
~ensile 3.~6 2.5E6 ~.~E~~odulus (psi) ~Icx~ l 5g.1~00 S5.000 )g,0(X~ 47~00(~
S~ength (~si~ I
Fk%ural 2.8~6 Z.21~6 2.3E6 2.4E6 1 8E6l~odulus (psi) HDT~F~264 psi) 500 505 470 210 ~20 Note I Vc~ton~ is a r~gi~c,ed tradon~rk of I.~P CO., ~nd S-2 glassqP is a registeled ~d~n ~ k of Owens-Corning Fi~er~lass ~o., a~d Cellstra~ i~ a re~istered t~der~xk ~ Hoechst Celanesc.
~ote 2: ~o material p~operties ~vailable for Speciaity co~.pounds f~om Owens-Co;ning ~ibe~gla~s.

TOTFIL P . 15 DEC-2~-199~ 17:01 FRor1 HRYES, SOLOW~Y. ET.RL. TO GOWLING STR~THY P.13 Table 2 ocessillg Con~itio~s RTP V~ 8Q21 I VS~ e~ b~P Venon~ ~P Y~on~ C~ r~n~ DSivt G-108PUi~ Ow~n~
Nylon-6,6G-1~50 R~-7~10 RF7OO-12 P~G~0.01-4 C~in~
Spcci~lty C~mv~lnd ~l~h 500~ .
S-~ ~lu;~
fii~r SaeW Spee~
(RPM) ~5 25 ~5 ~S ~5 Z5 25 Injc~ti~n Pr~ssu~e 65 6S 65 65 60 ~0 6S
~o~o~
tnjecli~ Spoed l'f~) ~C 40 ~ 40 SO 50 40 M~14 T~mp C (F) 104(220) lO~(22~) 104~220) 104(220) 88(19~) 8B~1~0) 104~22 tnieet;~nTiTnet5~ 2 5 ~.S 2 5 l.S 3 3 2.5 H~dTime(s) 10 10 10 10 1~ 10 1 Hol~ine ~essure 40 40 40 40 2~ 20 40 Cxiing T~ s~ Z~ 20 20 20 ~0 30 ZO
~on~p. (~1 0.3 0.3 0.3 0.3 0.3 0.3 0.3 'rcnp.C~F) 2~1(5~) 271i~!0) ~7I(~20) 27l(52~) 22~440~ 227(440) ~1(520 ~n~ 1 28~1550) 288~55~ 288(550) 288~5$0~ 23~ 450) 232(45~ 288(550 zo~e2 293~56C) ~9~(560) 2~3(560) 293~60) ~38~46~ 238~46~ 2q3~5601 kl~eE~ 288-293 ~8g-~93 2g8-293 288-293 23~ 238 232-23~ 2~g Z9;
~S50-56(~) ~550-56C~ (5~0-S60) (550-560) ~4$0-460~ (4S~460) (550 560 :
Note 1: ~fert~n~ is a re~istered trademark o~ P Cc>.~ and S-2 glass~ is a rc~isu,~,d t~atemark of Owens-C~rning Fi~oer~iass Co., a~d Cellstran~ is a ,~i3te~d t-~den~ f Hoechst Cell~nese.
~lote 2: ~laximum :njection pressure is 2t()0~ pSi cyiinder pressure! and ma~imum ir~jection speed ;s 4.~ inf~
~l~tc 3: All l~ateriats were dried at 82 C ~180 F~ for 4 hours prior t~ molding.
The ~wrail cycl~ time for ~he5e material~ can be de~ermined by utilizing $he ploce~ g ps~eters. For the llytons the cycle times ~ere all ~he same a~nd for the pclyurethane thcy were all the same~ From the data above the cycle ti~es ~e~e 32 8 ~ec and 43 3 sec for the nylon~fi,6 a~d polyuretha~e resp~ti-~ely. This does 210t include the time for mold ctose ard open. Illerefore thc total cycle times were about 40 sec ~or the rlylon-6,6 and 48 sec for the poly~rethane.
~he shear rate in thc mold was also Gf great impol~tance. The highest sheat r~tes wo~lld be fo-;nd ir~ ~;
the thinnest cros~ sec~i~n of the molding. ~heref~r~, the shear rate ill the mold c~vity was c~lculated. ~

-DEC-20-1Yg~ 02 FR3M HhYES. SULOWRY, ET.~L. TO GOWLING STRRTHY P.14 :
i She~rR~t~ ~ .wher~V =Ye~o~ity dnlt h-Cavity~hickness with~n~linje~tioll~p~e~oF4~ (4in/~e~we~e~ in/~e~n~h~ -t).~5/2i~
~here~or~=l4.2sec~l .

~ith ~egar~s to mold design, as ~n the ~se of the design and ! s~lec~ion of in3ection mo~ding equipment, ~he mold should be design~d to pro~ide easy ~1OW wi~h ~inimum ~i~er damage. In this regard, thic~ runners a~e preferably u~ed to minimize pre~sure drop~ in the mold~ which resul~ in minimum fiber breaka~e and heat loss. Th~ dia~te~ o~ ~he runner i~ generally about 0.2~-~.50 inches, and preferably, 0~37~ inches.
with regards to ~he g~in~ of the mold, the gate is pre~eren~ially stre~mlined, meaning that no sharp ~orners or restri~tions shou~d be p~esent to therefore prov~d~ a smo~th t~ansition ~one duri~g filling. Prefera~ly, the thicknes~ of the gate i~ ~pproxi~tely equal to the part thickness and ~uch ga~ing ~llows sufficient packing and ~voids p~emature freeze off of ~he inje~tion molded composite. Listed below in T~le 3 are the preferentiai ~achine pe~ificatio~s.

DEC-2E~-1'3g6 17:02 FRU11 HhYES, SOLOW~Y. ET.RL. TO GOWLING STI~RTllY P. 15 l~qa~hine Specifications Cin~ innati Screw ~ia. (In . } 1.6 Flighted Length ( In . ~ 3 2 . 5 Ll~ 20~ 1 Compression Ratio 2. 6:l Scre~ Type S~uare Pitch Metering S¢rew E'light Width ~ in . ~ O . 2 ~light Clearance ~in. ) 0 . 0 Turrl rh~nnel ~e~?th ~ in . ) Feed S~ction 0-lO 0 . 26 'r~an~ition Section ll . O O . 23~
12 ~ 0 ~ . 213 13.~ 0.175 14.0 ~.143 15.0 0.112 Me~erirlg 5ection 16-~ 0.103 * ~ * * *
Tes~ing ~ n investiga~ion o~ a new safety shs:~e application ~s done by following ANSI Z-41 ~L991). Molded safetAv shGe toe cap3 were te&te~ based on ~hi s protocol . The protocol cal l~ for impact ~nd cortlpression testing o~ molded s~fQty shoe toe caps in~orporated into shoes. ~ pro~otype in~eçtion :nold was produced in o~der to ~old samples ~o ~e tested. The mold was a single c~vity cast bron~e/alu;ninum al~o~. The ae~ign w~nt through thr~e i~eratic1ns e~ch with ~ diffe~ent gate size. The mold design wa~ done in TOT~L P . 15 ~EC-20-1~U6 17 18 F~OM H~'r'ES, ~OLUWH~, ET.~L. -ro GCWLING STR~TH~ P.02 21~3773 -orde~ to minimize the de~radation of the fibe~s during injection as discus~ed previous~y. Therefore, the part ~as sprue gated and c~nly o~ righ~ angle turn into _he cavity w~s used. The ~r~SI z- -41 standards ~o~ safe~y shoe toe protection are as follow~ fr~m ~SI Z-4~ ~1991~

Table 4 ~SI ~-41 Standa~ds I;r~pac~
I~7$ = 1~1.7J ~75 ~t. ~f) I/~O = 67.8J (SO ft. ~b~) I/30 ~ 40.7J (30 ~t. lbf~
Compressic>n C/75 - 11,121 N ~2500 lb) C/5Q = 7r784 N (1750 lb) C13~ = 4, 448 N tlO0~ lb) Clear~l~e is: MQn - 12.7 mm (15J32 in) Wc~ n ~ 15 . 32 in ~ fo~ all tes~s .

T~st~ng was done~ in ac~orda~lce with P,NSI-41 ~ l9gl~ ~tandards for safety shoe foo~wear, and he resul~s are lis~e~ b~low in T~ble 5: ¦

T~T~L P 02 DEf-Z13-1996 16:''.8 F~?OM Hh~ES, SCILI~WRY, ET.RL. TO GOWLIN5 STP~THY P.04 ', 2 19~77~
Table 5 ANZI Z41 Testing R~sults Mate~ial Impact C~earanceCo~ ,s~ion Load Cycle Time (min sec~
(1175) (Ib) ~! 0.~ ~nch cl~lce l~ewcott Cr~cked N~ 20.0 Specialty pre~ d cut ~lay p~eg ~ 2 Ic~,5 in) O~ens-Comin~ cta~ked and NAL 1~.0 SD~ l~0 deformed {c0 5 in.) Owens-~orning Cracked a~d NA 10.0 DB 170 de~o~ne~ ~c~.S iu.) Dl~S G-10~ .64 2,~00 ~ 48 P~lyurethallc 1, PCI PUG60-0l .70 ~,g40 0.48 4 Polyu~el~ane Cellstr~g PPG-5~ c~ 5 1,75~ Q 48 Polypropylene RTP 8~211 ~ot rested ill shoe - ~.36 50~~ long glass Cracked out of shQe : l.
fibcr ~yl~n4~6 3SM G-l/5~ Not ~e~ted in sho~ - 0.36 ~0% lo~g gl~ss Cracked out of shoe ~Iber ~Iylon-6 Owens-~or~in~ .87~ 3~300 0.36 S-~ C;lass'~D ~ylon-6,6 LNP verton~ Not tested i~ shoe 0.36 ~F-7~0~ 10 Nylon-6,~ Cracked out of shoc Note- ~erton~D is a ~ d (lad~ of L~P Co., and S-~ gl~ss6 i; a registe~ed trademark o~
Owens-Co~ing Fi~erglass Co., ~nd Cel~ is a registered trademdrk of Hoechst Cell~tese.

I~EC-20-1396 16:58 FROM HRYES, S'~LOW~'f ET.flL. TO GOWLING ST~RTHY P.~5 _, - 219377~

. .
.
It should ~e note~ that the toe cap of the present invention :
may be mol~ed to sn~ conven~onal style a~d Yhape ~f toe ca~, and which include a rearward~y opening shoe, toe-6haped bvdy having ro~f which blends smoothly in cur~ed ~ransition ~egion~ in~o opposite lateral genera~ly verticai ~ide walls ~e.g., by a ~¦
rounded edge~ and a generally vertic~l front wall ~o define a conv~ntional ~oe cap body. ~h~ body ~s mad~ of th~ molded fiber-imp~egnated ~hermoplas~ic compo~it~ m~terial described herein wherein the fi~ers ar~ ~nterwoven and entangled to provide ~esis~ance ~o m~chani~al loading. In addit~on, the t n~ectior.
molded toe cap for a protected shoe of the prese~t inven~ion has an addi~i~nal feature: a tapering of the ro~f (i.e. a feathering to a thinner e~ge) a~ the op~n rear ed~e relative to the ~hi~kne~s of the r~of appxoximate to the vertical ~xo~t wall of the toe cap. It has been found that ~hLs ~apering is a particul~rly pr~ferred design since computerized stru~tural analysis of a toe cap h~s indf c~ted ~hat the rear edge is r~ot as load-bear~ng as th~ rema~nder of the bod~ of ~he ~oe çap. In fact, by ~apering, the r~ar edge is made re~atively more fLe~ible ;.
during ~omp~ex loading which uni~uely serves to dissipate energy e efficient~y witho~t failure. In addition, there has been found tc~ be a t:osmetic: ~enefit to a tapered rear edge, namely ~he toe cap does no~ give birth to a shoe line which can ~e ~en ~hrough ~he leather or other material t~t is commonly used in a ''.

~EC-2E3-lYg~ 16:5~ FROM H~YES, SOLOWR~, ET.RL. TO GOWLING S-R~:IT~IY P.0h safety shc>e manu~a~tur~.
I~ process form, the present invention comprises a me~.hod for ~he preparation of ~n injection mol~:led fibex~-irnpregnated ~her~noplastic composite ~aterial contairling a ~ubst.antiall~
lnter~oven fiber orien~ation comprising sllpplying of a fiber-imp~egna~ed ~hertnoplastic resin pellet an~ injec~ n molding ~aid pellet, wh~rein the le~rel of fibe~ impregna'ci~, fiber ~ength, fiber diameter, viscosi~y of t}Le therlnoplastie resin, mold~ng t:emp~rature, in jec~ion ti~ne, and wall thlckness of ~he ~omposite ma~erial to be molded ar~ ~dju!ited to develop a su~stanti~lly interwo~ren f~er orie~tation in the ~hermoplasti~ composite~ .
material sub6e~uen~ ~o molding. Preferably, t~e impregna'ced ~hermoplastic composi~e ma~er~ onta~ ns a le~el of f iber ~mpre~nation of about 4~-60~ o.dditi~, the fiber impregn~ted thermoplastic composite ~nateriai ~ontai~s a ~iber length of about ~ . 5-1. 0 in~hes . Prefer~bly, ~he pel~e~ diameter is about 0 . lZ5 lnch. Mold~ng temper~ture~ ~e preferably about 4~0~t~ for polyurethene and 5~0~C for n~lon/polyami~es. Further~or~, the wall thicknes~ of the part produced is preferabiy 0.150 inche~s.
Acco~dirlgly, by ~rarying the above-ment ~ oned parameters, and p~efera~ly, var~ing ~aid parameters ~ chin ~e l~arlgQs so ;~
indica~ed ~ see, ~ g ., Table 2 ~, a ~u~stantiall~ interwoven fiber orientation in an inje~ion molded ~hermopl~stic ~aterial c~n ~e produce~ .

DEC-20-199~ 16:59 FROM HRYE', SOLDWRY, ET.RL. TC GOWLING STRRTHY P.07 f -.

In sum, ~rious modes o~ carrying out the present invention are c~ontemplated as ~eing wi~hin the 5GOpe of t~he ~ol lowing t ~laims particul~rly poin~in~ out and distincti~ claim~ng the sub~e~ ma~ter d~s¢ribed he~ein.

Claims

1. An injection molded fiber-impregnated thermoplastic composite material comprising a thermoplastic polymer matrix wherein the fibers are interwoven and entangled in said polymer matrix to provide resistance to mechanical loading.

2. The injection molded fiber-impregnated thermoplastic composite material of claim 1, wherein the fiber length prior to molding is about 0.5-1.0 inch.

3. The injection molded fiber-impregnated thermoplastic composite material of claim 1, wherein the thermoplastic resin is nylon-6 or nylon-6,6.

4. The injection molded fiber-impregnated thermoplastic composite material of claim 1, wherein the thermoplastic resin is a thermoplastic polyurethane material.

5. The injection molded fiber-impregnated thermoplastic composite material of claim 1, wherein the wall thickness of the material is at least 0.075 inch.

6. The injection molded fiber-impregnated thermoplastic composite material of claim 1, wherein the wall thickness of the material is about 0.20 inch.

7. The injection molded fiber-impregnated thermoplastic composite material of claim 1, wherein the fiber is present at a level of about 40-60% wt.

8. The injection molded fiber-impregnated thermoplastic composite material of claim 1, wherein the fiber is present at a level of about 50-60% wt.

9. The injection molded fiber-impregnated thermoplastic composite material of claim 1, wherein the fiber is S-glass or E-glass.

10. A process for the preparation of an injection molded-fiber impregnated thermoplastic composite material containing a substantially interwoven fiber orientation comprising supplying a fiber-impregnated thermoplastic resin pellet and injection molding said pellet, wherein the level of fiber impregnation, fiber length, fiber diameter, viscosity of the thermoplastic resin, molding temperature, injection time, and wall thickness of the composite material to be molded are adjusted to develop a substantially interwoven fiber orientation in the thermoplastic composite material subsequent to molding.

11. A process for the preparation of an injection molded-fiber impregnated thermoplastic composite material of claim 10, wherein the level of fiber impregnation is about 40-60%.

12. A process for the preparation of an injection molded fiber-impregnated thermoplastic composite material of claim 10, wherein the fiber length prior to molding is about 0.5-1.0 inch.

13. A process for the preparation of an injection molded fiber-impregnated thermoplastic composite material of claim 10, wherein the pellet diameter is about 0.125 inch.

14. A process for the preparation of an injection molded-fiber impregnated thermoplastic composite material of claim 10, wherein the molding temperature is about 480°F for a polyurethane and about 560°F for a nylon.

15. A process for the preparation of an injection molded fiber impregnated thermoplastic composite material of claim 10, wherein the wall thickness is at least 0.075 inch.

16. A process for the preparation of an injection molded fiber-impregnated thermoplastic composite material of claim 10, wherein the thermoplastic material is nylon-6 or nylon-6,6.

17. A process for the preparation of an injection molded fiber-impregnated thermoplastic composite material of claim 10, wherein the thermoplastic material is a thermoplastic polyurethane.

18. A process for the preparation of an injection molded-fiber impregnated thermoplastic composite material containing a substantially interwoven fiber orientation comprising supplying a fiber-impregnated thermoplastic resin pellet and injection molding said pellet, wherein said pellet contains a fiber level of about 40-60% wt, a fiber length of about 0.5-1.0 inch, a pellet diameter of about 0.125 inch, and the wall thickness of the composite material is at least 0.125 inch.

19. An injection molded toe cap for a protective shoe of the type having a rearwardly opening shoe toe-shaped body including a roof which blends smoothly into opposite lateral generally vertical side walls and a generally vertical front wall,and an open rear edge end defined by a rear edge including the rear edges of the roof and said walls, said toe cap comprising a fiber-impregnated plastic resin body having a major portion of the fibers in the resin portion forming a substantially interwoven and entangled orientation throughout.

20. The injection molded toe cap for a protective shoe of claim 19, wherein the fiber is S-glass or E-glass.

21. The injection molded toe cap for a protective shoe of claim 20, wherein the open rear-edge of the roof is tapered relative to the thickness of said roof proximate to said vertical front wall.