CA2083151A1

CA2083151A1 - Low friction, abrasion resistant polymer coating

Info

Publication number: CA2083151A1
Application number: CA002083151A
Authority: CA
Inventors: Virginia R. Cross; Cindy B. Shulman
Original assignee: Individual
Current assignee: ExxonMobil Chemical Patents Inc
Priority date: 1990-05-18
Filing date: 1991-05-16
Publication date: 1991-11-19
Also published as: EP0527929A1; DE69112399D1; EP0527929B1; WO1991017900A3; WO1991017900A2; DE69112399T2; US5110685A; JPH05506882A

Abstract

The invention relates to certain low friction abrasion resistant polymer coatings. The polymer coatings consist of thermoplastic materials based on blends of elastomers with high density polyethylene comprising a high molecular weight component. The appropriate balance of crystallinity, durability and flexibility can be achieved by selecting the proper amount of low, medium and high molecular weight high density polyethylene. The coating is particularly useful for weather-stripping material for automobile window channels.

Description

~VOsl/17900 PCT/US91/03450 2 ~

W FRICTION, ABRASION RESISTANT POLYMER COATING

SPECIFI~A~IO~

FIE~ OF THE I~VENTION
This invention relates to certaln low friction S a~rasion resistant polymer coatings. The poly~er coatings consist of thermoplastic materials based on high density polyethylene ~HDPE) blends exhib~ting appropriate balance of crys~allinity, durability an~
flexibil~ty.
ACXGROU~ OF TME 12~E~TION
As is well known to those skilled in the art, window c~annel weatherstripping ~aterials ha~e traditionally been made ~rom ethylene-propylen2-diene terpolymers (EPDM) or thermoplastic elastomer~ (TPE)~
A thermoplastic elastomer is defined as a mechanical blend of fully or part~ally cross-l~nked rubber and t~ermoplastic material. One o~ the problems ~it~ these material~3, however, i8 that they present too l~UG3~
friction relative to glass and as a result ~tic~ to glass. ~hi~ sticklness to gla~s intereres w~t~
~ovement of the glass with respect to th~

W091/17900 PCT/US91/03~5 weatherstr~pp~ng and also contribute~ to a b~eakdown and degradatlon of the weatherstripping ~aterlal. That problem has traditionally been overcome by flocXing the surfaces of t~e weatherstripping ~aterial which reduces S the friction and thereby ell~inate~ ~ticking.
The flocking process adds several steps to the manufacturing process i~cluding ~) abrading ~he weatherstripping surface; (2) applylng ad~esive, g3]
applying ~locking; and (~) baking.
~ecently, a variety of approaches hav~ been taXen to obv~ate the need ~or flocking. For example, European Patent No. 0 325 830 A2 teaches a coextruded ~lend o~
EPDM and a wear resistant ther~oplastic suc~ ~
polypropylene; French Patent No. 2,580,285 teache~ a coatlng of low riction or ~el~-lubricating mater$al such as high molecular weight polyethylenè; Japanese Patent No. 58/042,6~ teaches a lubricant l~yer co~prising crosslinked elastomer binder and a lubricating powder; ~est German Patent No. 3,405,973 teac~es sealing strips composed of a rubber or ~las~omer and plastic or woven textile ~trip ~h~ch are coextruded; and Japanese Paten~ No. 6lJla4~8~2 teaches a rubbery elastomer co~prlsing a rubb~ry elastomex substrate, a ~ylon res~n fil~, ~nd a pri~er layer set between the~. The pri~er layer is co~posed of c~lorinated polypropylene, acid anhydr~de, epoxy resin, and an a~ine curing agent.
~ low friction, abra~on resistant polymer coat~ng would present several advantaqes,o~er ~locking. A more intimat~ contact between th~ weatherstrlpp~ng and the glas~ would ~e achieYed. Further~ore, such ~ coating could be coextruded wit~ the ~eather~tripping ~aterial.
~dditionally, a coatl~ belng all poly~eric ~ould be .. . ~

WO 91J17900 PCl /U~;91/034~0 2~31~ I

more environmentally saf~ because such ~ coat~ng would obvlate the need ~or ~olvent-based adhesives now used with flocking.
A need ~till exlsts or a low friction, abrasion s resistant coating with good adhesion to the weathers~ripping ~aterial and good elast~c~ty to prevent breaking upon flexiny. Additionally, the coating should ex~ibit ultraviolet stability and a broad service temperature range.
SUMMARY OF TH~ I~VENTION
This invention relates to low ~riction, abras~on reslstant coatinqs with good adhes~on to th~
weatherstrippinq ~aterial~ and good elas~ic~ty to prevent breaking upon flexinq. Additionally, the coating should exhib~t ultraviolet stability and broad service temperature ran~eO
The coatings comprise an abrasion resistant HDPE
polymer, an elastomer; and optionally an ultraviolet l~ght resistant component blended to produce ~n appropriate balance o~ crystallinlty, dura~llity and flexibility. Additionally, by selecti~g the proper ultraviolet ligh~ reslstant component, the color of the resulting coat may controlled.

IPTION OF THE Pl~EFERRED EMBODIMENT
This invention relates to car~ain low frictlon, abrasi~n resistant coatlngs with good adhesion lto wea~h~rstripping material~, good ~lasticity to prevent breaking upon flexing, good ultraviolet stabillty and broad service temperature.
The coatings o~ Sba invention ara ther~oplas ic HDPE blen~ havlng an approprlatQ balance o~

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WO91/1~900 PCT/US91/0~50 ~$3 ~.5;~

crystallinity, dura~ility, flexi~llity. ~ddlt~onally, by selecting the proper ultravlolet l~ght res~stant component, the color of the result~ng c~at ~ay controlled.
These HDPE blends comprise polymers selected to contribute specific properties, as outlined above, to the coatlng.
Since abrasion resistance increases w~th increased density or increased ~olecular weight, h~y~ density polyethylenes (HDPE), with ~ m~ni~u~ dens~ty of 0.9~5, are used ln the coating of the invent~on. Preferably the density ranqes between 0.950 and 0.970 with a dens~ty of about 0.952 most preferred.
High density polyethylene polymers useful ~n the preparation of the coatings of the ~nYention range in molecular weight from about 1,000 to about 4,000,000, preferably from ~bout-100,000 to about 800,000.
In a preferred embodiment of the ~nvention, tbe abrasion res~stance is achie~ed ~ith a blend o~ hig~
density polyethylenes. Blends use~ul in t~e practice of the invention include b~odal ~olec~lar welghk distribution (MWD~ high dens~ty ~olyethylene Suc~
bimodal MWD HDPEs have a bigh ~olecular we~ght component and a low molecular ~eight co~ponent~ The 2S hiqh molecular weight co~ponent ranges in molecular weigbt fro~ about ~00,000 to about ~,OOO,ooO, preferably from about 100,000 to about 800,000. The low molecular weight component ranges ~n molecular weight fro~ about 1000 to about 50,000, pre~erably fro~
about 10,000 to about 50,000. Th~ high ~olecular weight component ~parts both abraslon reslstance a~ well a~
toughnes~. ~he low ~olecular we~ght component contr~bute~ to processabllity.

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In a pre~erred embcd~ent of t~e ~nvent~on th~
above described bimodal poly~er ~ 8 co~bined with ~
~ediu~ ~olecular weight HDP~ having ~ ~olecular ~e~ght ranging from about 50,000 ~o about lO0,000, pr~ferably from about 80,000 to about lO0,000. This mediu~ MW
~DP~ is added to enhance melt low rates during processinq.
The amount of high molecular weight component in the blend of HDPE can range ~rom lO to 80 per cent by weight, preferably lO to 60 per cent most preferably about 15 to 25 per cent. The amount of medium molecular weight component, if present, in the blend of HDPE ranges from about 0 to about 80 per cent, more preferably about 20 to 70 per cent and most,preferably about 55 to about 65 per cent. The balance o~ the HDPE
blend is made up o~ low molecular weight compo~ent.
To i~part coating flex~bil~ty and elastlcity th~
above recited abrasion resistant polymers are blended with elastomers. Elastomers u5eful in the practice o the ~nvention are ethylene/propylene rubbers (~PR) ~such as Vistalon 503 brand EPR) and blends o~
ethylene/propylene rub~er wit~ HDPE. ~lends us~ful the practice of the invention are blends oY 2P~ and HDPE, where~n the amount of EPR ranges fro~ about 99 2S to a~out 50 per cent EPR.
The ratio of HDPE or HDPE blends to elastomer ranges ~ro~ about 3:1 to a~out l9:l, preferably about 9:l by we~ght.
To achieve proper ultra~olet l~ght protect~on an ultra~iolet light resistant ~aterial ~ay be blended wit~ the above reci~ed formul~tions. Pre~erred ultraviolet l~ght resistant ~ater~als are carbon black formulations such a~ blend~ oP carbon black wlt~ loY

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wo 91/17900 PCI/lJS~1/03450 dens~ty polyethylene (~DP~). Preferred blends range fro~ about 1.O to a~out lO.0 weight per cent carbon black preferably 2.0 to about 3Ø Alternatively, hindered am~nes ~ay ~e used a~ the ultraviolet light S res~stant materials. Use o~ hlndered am~nes allow6 or the requlat~on of color to t~e coatinq. Preferred hindered am~nes are coDlpounds o~ the formula bis(2 t 2,6,6-tetramethyl-4-plperidyl)~ebacates. The ~ost preferred bi~(2,2,6,6-tetra~ethyl-4-piperidyl)sebacate is commercially available under the na~e T~nuv~n T-770.
The amount of ~inuvln T-770 ranges fro~ about O.l to about l.0 weight per cent.
In a preferred embodi~ent of the ~nvention, stabll~zinq agents are blended ~ith the above referenced for~ulations. Preferred ~tab~lizing a~ent~
are compounds such as tetrakis [~ethylene(3,5-di-tert-butyl-4-hydroxy~ydroc~nna~ate)~ethane or bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite. The ~ost preferred tetrakis tmet~ylene(3~5-di-tert-but 4-hydroxyhydrocinnamate)~ methane co~pound ~8 commercially available under the na~e Irqanox lOlOo The most preferred bi~(2,4-dl-tert-butylp~enyl) pentaerythritol diphosphite is com3erc~ally ava1lable under the name Ultranox 626.
The amount of Irganox lOlO to bæ added ranges fro~
a~out 200 to about lS00, and l~ preferably about 900 pp~. The amoun~ of Ultranox 626 added ran~e~ fro~
a~out 200 to about lO00, preferably abo~t 600 pp~.
Prepara~ion o~ Coatin~_~or~ula~on~
The coating co~ponents a~ rec~ted abo~e were ~u~bla blended to for~ a ho~ogenou~ ph~cal ~ixtur~.

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WO 91~17900 PCl/US91/03450 2~3~l The homogenous mlxture ~as extruded at melt temper~tures ranglng froo 193-C to 215~C ln order to homogenke, blend and pelletl2e the ~ater1als. The temperature range o~er ~hlch the homogenous mlxture cou1d be extruded ts 180-C to 240~C. ~he materials ~ere extruded uslng a 24:1 Relfenhauser Extruder slngle scre~ extruder, although any extruder capable of processlng the mlxture could be used. The extruder used had ~ barr1er screY ~lth a Maddox mlxer sectlon and ~ 5 hole dle.
Extruslons ~ay be conducted under an lnert gas atmosph~re;
the extruslons mentloned here ~ere conducted under nltrogen.

Pregar~lQn of ~Q~ted We~th~rs~rlp~lng The coat~ngs of the lnYention ~ere coextruded ~lth rubbery polymers, for example, EPOW. The extruslon ~as done at l90'C on a 24:) slngle screw extruder; ho~ever, the type of extruder ls not crlt~cal and the temperatur~ used need only be suffklent to aelt the polymer yet less than the temperature at ~hlch slgn1flcant ther~al degradation of the poly~er occurs. The HDPE blends ~ere extruded ~t 215-C on 24:1 slngle stre~ extruder. After coextruslon the coated ~eatherstrlpplng mater1al ~as vulcanl2ed for 2 ~ln. at 205~C
and then ~ater cooled. A llne speed of approxlmately 7 ftlmln ~as ~alntalned throughout the extrusion process.
Table 1 dep1cts varlous formulat~ons, for polyethylene based polymers, ~hlch ~ere tested.

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WO 91/17900 PCrlUS91/034~0 2 ~3 ~

o Polyethylen~ Ba3ed Coatlng Compo~ltlon CO~PO~N~ ~DDISIVB~
T~lc I S~lc I~
Sam~le aE~ B~HDP~ BLASTOMER~ I Ç~
l 90 -- 10 I 5 - __ 3 5~ 36 lO I S
~ S~ 36 lO I S ~ 6 .. _ . __ -- -- . -- -- . . :
l~ ~11 oample~ contalned 900 ppm Irganox lOlO and 600 pp~ Ultrano~ 626 a- stab1ll~1n~ agenta.
HDP~ elt Index t l90 C) ~ ~dq/~lnt 0.952 Den~iey B~HDPt -- blmcdal HDP~ ~ n 0.07dg/~ln 0.952 DenDlty l:t blend of hlgh ~olecular ~el8ht to l~w molecular ~e~8ht tlaato~r - 67/33~ blend of Vl-talon S03 brand ~t~yl~n-/propyl~n~
rubbsr (more ~ully dea~rlbed ln ~.S. P-tent No. ~,895,a97) ~nd HDPt Component~ ~r- ba~ed on welght ~ of plymerlc ln~redl~nt~.
Add1t1Ye~ ~re ~elg~t ~ ba~ed on total polyceslc 1ngr~d1ent-.
20 CB -- 1:1 blend of carbon black and LDPE.
'ralc I -- ~flzer M 12-50.
'ralc II -- Pflzer Microtuf lOO0.

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wosl/17900 PCT/US91/0~50 2~

Table 2 depicts test results ~or abras~on resistance as well as coefficient o~ fr~ct~on measurements. The test formulations were coextruded onto a thermoplastic elas omer, in tbe form of s automobile window channels and then were tes~ed as indicated. The Honda and Toyota abrasion tests are very similar and involve cycling a piece of weighted glass back and forth at 1 cycle/second in the window channel. In the ~onda test, the glass i8 we~g~ted with a 1.5 Xg weight wh~le a 3 kg weiqht ~ used in th~
Toyota test. Satisfactory performance is achleved ~n each test if the coating withstands 10,000 cy~l2~
w~thout crac~ing or wearing through to the underly~ng weatherstripping substrate ~aterial. Ihe coating should have coefficient o~ fr~ction (COF) close to t~at of floc~ing that is to say close to 0.26.
As can be seen all sa~ples passed t~e ~onda test.
Under the ~ore rigorous Toyota test only sa~ple 3, a blend of 36 weight per cent ~imodal HWD polyethylene polymer with 54 weight per cent ~ediu~ ~olecular veight HDPE, passed the test. Thls sample ex~ib~ted only ~0 per cent wear after 10,000 Toyota cycle~, ~nd ~t~ll did not exhibit failure after 20,000 Toyota cyclesO All samples exhibited COF values in the desired xange.

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WO 91/17900 2 ~ 8 ~ .L PCr/US91/03450 Polyethylane Based ~oatlng Compo~lt~on~ ~er~orman~
Hond~Soyot~
Sam~l~ c~cie~l~clo~ to Gla~
1 lo,ooo soo 0.18~0.25 2 10,0001,500 0.18-0.2~
3 10,00020,0~0 0.2~-0.23 ~o,oool,aoo 0.19-0.26 ~1 . S Xg we ighe 0 ~3.0 l~g wQlght COJ to Gla~- mea~uram~nt- ~ad- ln ~ccordanco ~ltb ~S~ D 1894.

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Wo 91/17900 PCI/US91/03450 2 ~

Table 3 depicts Shore D hardnes~, flexural ~odulus and ~elt index values for the polyethylene based for~ulations. Since all samples are HDPE based, the flexural moduli fall in a relatively narrow range. ~o correlatlon is apparent between abrasion resistance results and ths flexural ~alue~.
T~e talc filled sample exhibitad a ~igher degree of stiffness and higher ~oduli than the corresponding talc-free sampl~.

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As can be seen from the results 1n ~A8LE 2, Sample 3 sho~ed dramatlc lmprovement in the Toyota test. The polymer1c ~ngredlents of Sample 3 conslsted of about 54 ~t.~ of med~u~
molecular ~e~ght HDPE, 18 ~t.~ of h~gh molecular ~elght HDPE, 18 S ~t.X of low molecular ~lght HDP~, and 10 ~t.X elastomer. When cons~der~ng only the HDPE component the percentages are a~out 60 ~t.X med~um molecular ~e~ght component, about 20 ~t.~ hlgh molecular ~elght component and about 20 ~t.~ lo~ molecular ~elght component.

These coat~ng compos~tlons can be adhered as a layer onto a layer of rubbery polymers by kno~n methods such as co-extruslon or lam~nat~on to form excellent ~eatherstrlpplng ~aterials.

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Claims

AMENDED CLAIMS
[received by the International Bureau on 23 December 1991 (23.12.91);
original claims 1-35 replaced by amended claims 1-33 (7 pages)]

1. A low friction, abrasion resistant polymer coating composition comprising;
(a) a high density polyethylene component comprising a blend of (i) high molecular weight, high density polyethylene;
(ii) low molecular weight, high density polyethylene; and (iii) medium molecular weight, high density polyethylene; and (b) an elastomer component comprising a blend of ethylene/propylene rubber and high density polyethylene.

2. The polymer coating composition defined in claim 1 wherein said high molecular weight, high density polyethylene has a molecular weight of between 100,000 and 9,000,000.

3. The polymer coating composition defined in claim 1 wherein said low molecular weight, high density polyethylene has a molecular weight of between 1,000 to 50,000.

4. The polymer coating composition defined in claim 1 wherein said medium molecular weight, high density polyethylene has a molecular weight of between 50,000 and 100,000.

5. The polymer coating composition defined in claim 1 wherein the ratio of said high molecular weight high density polyethylene to low molecular weight high density polyethylene is 1:1.

6. The polymer coating composition defined in claim 1 wherein said high molecular weight, high density polyethylene comprises from about 10 to 80 percent by weight of said high density polyethylene; 20 to 70 percent by weight medium molecular weight, high density polyethylene and the balance low molecular weight, high density polyethylene.

7. The polymer coating composition defined in claim 1 or 5 wherein said elastomer comprises from about 50 to 99 weight percent ethylene/propylene rubber and 50 to 1 percent by weight high density polyethylene.

8. The polymer coating composition defined in claim 1 wherein the ratio of said high density polyethylene component to said elastomer component ranges from about 3:1 to about 19:1.

9. The polymer coating composition defined in claim 1 further comprising an ultraviolet resistant material.

10. The polymer coating composition defined in claim 9 wherein said ultraviolet resistant material is selected from the group comprising hindered amines and blends of carbon black with low density polyethylene.

11. The polymer coating composition defined in claim 1 further comprising a stabilizing agent.

12. The polymer coating composition defined in claim 11 wherein said stabilizer is selected from the group comprising tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane and bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, and mixtures thereof.

13. A low friction, abrasion resistant polymer coating composition comprising:

(a) a high density polyethylene blend comprising:
(i) a 10 to 80 percent by weight of high molecular weight high density polyethylene;
(ii) 0 to 80 percent by weight of medium molecular weight high density polyethylene;
(iii) 10 to 80 percent by weight of low molecular weight high density polyethylene and:
(b) an elastomer component comprising a blend of 99 to 50 weight percent ethylene/propylene rubber and 1 to 50 weight percent high density polyethylene:
wherein the ratio of said high density polyethylene component to said elastomer component ranges from 3:1 to 19:1.

14. The polymer coating composition defined in claim 13 wherein the molecular weight of said high molecular weight polyethylene ranges from about 100,000 to 4,000,000.

15. The polymer coating composition defined in claim 13 wherein the molecular weight of said medium molecular weight high density polyethylene ranges from about 50,000 to about 100,000.

16. The polymer coating composition defined in claim 13 wherein the molecular weight of said low molecular weight high density polyethylene ranges from about 1,000 to about 50,000.

17. The polymer coating composition defined in claim 13 wherein the ratio of said high molecular weight high density polyethylene to said low molecular weight high density polyethylene is about 1:1.

18. The polymer coating composition defined in claim 13 further comprising ultraviolet resistant material.

19. The polymer coating composition defined in claim 17 wherein said ultraviolet resistant material is present in an amount ranging from about 1.0 to 10.0 weight percent.

20. The polymer coating composition defined in claim 17 or 19 wherein said ultraviolet resistant material is selected from the group comprising hindered amines and blends of carbon black and low density polyethylene.

21. The polymer coating composition defined in claim 13 further comprising a stabilizing agent.

22. The polymer coating composition defined in claim 21 wherein said stabilizing agent is present in an amount ranging from 200 to 1000 ppm.

23. The polymer coating composition defined in claim 21 wherein said stabilizing agent is selected from the group comprising tetrakis [methylene (3,5-di-tert)-butyl-4-hydroxyhydro-cinnamate)] methane and bis(2,4-di-tert.butyl phenyl) pentaerythritol diphosphite.

24. The polymer coating composition defined in claim 13 wherein said EPR comprises 67 weight percent of said elastomer component.

25. The polymer coating composition defined in claim 13 wherein the ratio of said high density polyethylene component to said elastomer component is 3:1.

26. A coated weather stripping material comprising:
(a) a first layer comprising a rubbery polymer and (b) a second layer comprising a polymer coating composition, said polymer coating composition comprising:
i) a high density polyethylene component comprising A) 20 to 80 weight percent high molecular weight high density polyethylene;
B) 0 to 80 weight percent medium molecular weight high density polyethylene;
C) 20 to 80 weight percent low molecular weight high density polyethylene; and ii) an elastomer component comprising a blend of 99 to 50 weight percent ethylene/propylene rubber and 1 to weight percent high density polyethylene; the ratio of said high density polyethylene component to said elastomer component ranging from 3:1 to 19:1.

27. The coated weatherstripping defined in claim 61 wherein said elastomer component comprises 67 weight percent ethylene/propylene rubber and 33 weight percent high density polyethylene.

28. The coated weather stripping material defined in claim 61 wherein the ratio of said high molecular weight high density polyethylene to said low molecular weight high density polyethylene is 1:1.

29. The coated weatherstripping defined in claim 26 wherein said polymer coating composition further comprises 1.0 to 10.0 weight percent of an ultraviolet resistant material.

30. The coated weatherstripping defined in claim 29 wherein said ultraviolet resistant material is selected from the group comprising hindered amines and blends of carbon black and low density polyethylene.

31. The coated weatherstripping defined in claim 26 wherein said polymer coating composition further comprises 200 to 1000 ppm of a stabilizing agent.

32. The coated weatherstripping defined in claim 31 wherein said stabilizing agent is selected from the group comprising tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane and bis(2,4-di-tert-butyl phenyl) pentaerythritol diphosphite.

33. The coated weatherstripping of claim 61 wherein said high density polyethylene component comprising 20 weight percent high molecular weight high density polyethylene having a molecular weight of between 100,000 and 4,000,000; 60 weight percent medium molecular weight high density polyethylene having a molecular weight of between 50,000 and 100,000 and 20 weight percent low molecular weight high density polyethylene having a molecular weight of between 1,000 and 50,000 and said elastomer component comprising 67 weight percent ethylene/propylene rubber and 33 weight percent high density polyethylene, the ratio of said high density polyethylene component to said elastomer component being 9:1 and further comprising 5 weight percent of a 1:1 blend of carbon black and low density polyethylene.