Note: Descriptions are shown in the official language in which they were submitted.
~!O 95/04608 216 ~ 7 3 ~ PCT/US94/08696
~esc, i~Lio, I
COMPOSITION AND PROCESS FOR PREPAINTING TREATMENT OF PLASTICS
, ~ Technical Field
The invention relates to a water-based liquid cor"~lositio,) for t,t:ali"g plas-tics, particularly plastic moldings, more particularly those made of polypropylene,
polyu, etl ,ane, and the like, that are used, e.g., as body panels, bumpers, or the
5 like in aulo" ,obiles. The invention is especially suited to pre,uai, llil ,9 ll eal",e, ll
of such pl - ~lics. The invention is ac~, di"gly des~ ibed below pri",a, ily with ref-
erence to prepainting l,ea~",e, ll for plastic moldings, but more ye"eralized appli-
cation to plastic surfaces is within the scope of the invention.
Background Art
The plastic moldings used for aulor"ûlive bumpers, etc., usually are cur-
rently manufactured by injection molding. In the case of resins that are prone to
stick to the mold, such as polyu, ~ll ,dne, the mold surface is usually coated prior
to actual molding with a wax-based exte" ,al, ~,lease agent, and a metal soap (for
exa~ e, zinc sleardte)~ which fu"c~ions as an i"le" ,al r~lease agent, is also fre-
5 quently added to such resins in advance of molding. Various additives other than
i, llel "al release agent often are also blended into resins for the purpose of im-
proving the sl,~, Iyll " improving paint a.ll ,e,~"ce, improving the resisla"ce to ag-
ing, and the like. As a result, during the molding prucess the sl~unyly hydl u,.~hob-
ic i, llel "al additives and of course any inle" ,al release agent bleed onto the sur-
20 face to some degree. The presence on the surface of s~ ~nsl~ ,ces such as ex-temal, _lease agent and bled-out i"le" ,al additives i",pai, :j the post-painting ad-
h er~:nce by the paint film and also r::n ~-ses paint uawling and thereby co" "~ro" ,is-
es the ap~,earance of the paint film. The preparalo,y l, edl",enl that precedes
painti"g must therefor~ not only remove conla" ,i, Idl llS adl ,eri"g after molding,
25 such as dust and oil, but must also remove subsldl ,ces such as e,~ler"al release
agent and internal additives that have bled onto the surface.
The llt:d~lllel ll of plastic moldings prior to pa;, Iti~ ~y has herelorore consisl-
ed mainly of the use of solvent cleaners such as 1,1,1-trichloroethane, freons,
and the like. This type of t, eall "enl can dissolve and remove r ~lease agents and
wogs/~608 ~ ,6Q~o PC~/~JSg4/~\86~
also has an P~cellent oper;3li"g efficiency due to its ease of drying. However as
is well known envi,o"",e"lal consider~lio,ls have made the dcvelop",ent of sub-
stitute prel,e~l",e, ll methods a matter of urgency.
Cleaning with acidic and alkaline water-based cl~aners and cleaning with
emulsified solvent clea"er~ have been investigated as substitute F~r~ dl")e"l
IllelhOd~. These ",ell lods differfrom solvent cleaning in that they require a rinse
step and lhert:ru,e require a drying step (see Japanese Laid Open Patent Appli-
cation Numbers Hei 4-27472 [27 472/1992] and Hei 5-39499 ~39 499/1993]).
However even after release agent on the surface has been removed by
clea";. ,~ drying must be cond~ ~cte~ at low te",5~erdlures since inler"al release
agent and sl,ùnyly h~huphobic i"le" ,al additives bleed onto the surface during
the drying step. This len~tl ,ens the drying time and thus necessildles the use of
large-scale equipment. In ad~ilion since inle" ,al ,elease agents and sl,onyly hy-
drophobic i"~" ,al additives graduaily bleed onto the surface even at room tem-
perature the pai"lal~ility also beco",es i""~aired when a lengthy period of timeis allowed to elapse between cleaning and painting. This requires that the
cleaned molding be p, ump~ly painted.
As .les~ ibed above ,t7searc;h has l ,eretorure focused on the removal of
internal additives once they have bled onto the surface of the plastic molding
from within the molding; however up to now in the knowledge of the applicants
there have been no invesli-g~lio"s into the inhibition of bleed-out by intemal addi-
tives onto the surface.
Disclosure of the Invention
Problems to Be Solved by the Invention
The p, ese, ll invention is direc~ed to an inhibition of the surface bleed by
i"le" ,al plastic additives that occurs with e~apse(l time and during the drying step
in the interval after the water-based l~edLme~ ll of plastic moldings prepdl dlUI y to
their pa;. ,ling. More sue~irically the ~ se, lt invention takes as its objects an in-
crease in the drying ler"~.erdlure in order thereby to support equi~.,nenl downsiz-
ing an improvement in the painlability (e.g. paint crawling paint adl ,er~"ce)
andlor in particular a 51~ ion of the pai"lability through an inhibition of time-
wise changes in the paint-receiving surface.
~vo 95/04608 21 6 8 7 3 6 PCT/US94/08696
Summarv of the Invention
The inventors discovered that tlea~ g the surface of a plastic Illold"~9 with
an ~ eolls solution cOI ,laini"g specific organic acids results in an inhibition of
the surface bleed by i, llel "al plastic additives and thus in an inhibition of timewise
5 Chdl ~yes in the paint-receiving surface and a stabilization of the paintability. In
specilic terms one er,ll,odi",ent of the present invention is a water-based liquid
composition for l,ealing plastic ",oldings prior to the painling tl ~eleor wherein
said CGIll,uùSiliol, is an ~ueo~s solution that in addiliun to water co",prises
prererably co, Isisls esse"lially of or still more prere, al~ly consi~ls of at least 0.û5
~o weight % of at least one selection from ca, L,oxylic acids that do not conlain any
te""i"al alkyl group in their molecular structure and hydroxyca~l oxylic acids that
do not cou~;, ~ any terminal alkyl group in their mol~cr ll_r structure; oplionally the
colllposiliu"s according to the invention may also co"lair, su,ra~;tallls other
builders and/or other acids. A prucess according to the invention incll Irles at a
15 minimum a step of conla.;tiny a plastic surface with a col"posiliol, acco,di"53 to
the invention as .les-;, iL,ed herein.
Des~ lion of r,ere"~d E"ILodi",e"ls
The most i" ,po, lal ll Chdl ~,tel ialic of the water-based co" ~posi~ir," or agent
in accor~ance with the pr~sent invention for llt:d~ 5a plastic moldings priorto their
20 painting (I,erei"~rler abbreviated as the prepainl l,ealn,~l,l agent) is that said
agent is an a~ ~eo! ~s sol~ltion that conl&i"s as its essel ,lial cor, IpGnenl at least
one s~lQ~ tion from ca,l,oxylic acids that do not co"lain any terminal alkyl group
in their molecular structure and hydroxyca, boxylic acids that do not conl~i" any
ter",inal alkyl group in their molec~ r structure.
2s For the p~.".. oses of the preselll invention the aL,se"ce of any tell"i"al
alkyl group from the " - u ~ structure means that no group having the formula
-CnH2n~, is ,u, esenl in the molecule.
Terminal alkyl-free carboxylic acids are specifically exemplified by oxalic
acid r"alo"icacid succinicacid glutaricacid andadipicacid.
Terminal alkyl-free hydroxyca, Lw(ylic acids are specirically exemplified by
glycolic acid malic acid tartaric acid and citric acid.
The ~ueo! ~-s solution p, e~ bly contains at least 0.û5 weight % and more
WO 95/04608 ; - 2 ~ ~7 3 ~ PCT/US94/086~
~,erer~bly at least 0.1 weight % of the one or more selections from te"";. ,al alkyl-
free calboxylic acids and terminal alkyl-free hydroxycal boxylic acids. The sur-face bleed of i"Le" ,al additives from within the plastic molding usually is not ade-
quately inhibited at below 0.0~ weight %. Independently for reasons of econ-
s omy the a~ueo~ ~-s solution accor~ing to the invention prererably COI ,lai"s not
more than 5 or more ~,rererably not more than 2.2 weight % of these acids.
The ~q~ ~eous solution in accorda"ce with the presenl invention as de-
s~ iL ecJ above (= ~ eous solution that co"lains at least one selection from ter-
minal alkyl-free carboxylic acids and ~e" "i"al alkyl-free hydroxycarl.oxylic acids)
o fu"~io,)s to inhibit bleed-out by i"le" ,al additives present in the plastic molding.
However a su, rdcta, ll normally must also be used to remove other co"lar"ir,-
ants for example dust and oil that al~l ,era after molding. Said surfactant may
be used in the prepaint Iradl" ,e, ll agent of the invention in combination with or-
ganic acid as specirie.~ above for the invention. Alternatively co"la",inants such
5 as dust and oil may first be removed using a solution that conL~;"s su~ rd~ldl ll and
lledl",el,l may then be carried out using a su,rd~;~a"l-free prepai"l treatment
agent in accorda"ce with the invention.
No particular ra:,l, i~tiu, ,s apply to the s~,racla"l and its type and quantityof use should be ælQ~ted as a function of the particular condiliol ,s such as the
20 nature of the resin the status of ~hesiGI ~ of the dust and oil etc.
In addilio" to Sl" rd~La, ll the ~ pa;. ll tle~llllt:l IL agent of the invention may
contain other builders.
Plastic moldings can be treated with the pre,~,~i, ll treatment agent of the
invention by spraying or immersion. The bath ter"peral-lre is not critical to the
25 effect of the invention i.e. the il ll ,iLiLion of bleed-out by internal additives. How-
ever when SlJ~ rd~La, IL is pr~senL in the ,..repainl treatment agent of the invention
and this agent is relied on for ge, ,ercl cleaning as well as for the inhibition of
bleed-out the le",pe~L~re should be selected as a function of such considera-
tions generally known in the art, as the adhesion status of any oil dust or the
30 like in order to acco" Iplish their removal by the s~" raclal)l.
Treatment with the water-based ,ulelledllllenl agent of the invention is
1~ e' 3~lred to i"u ~ase the surFace free energy of plastic surfaces. This effect is not
~IO 95/04608 ~ 1 ~ 8 7 3 ~ PCTIUS94/08696
destroyed even by water washing after tredl"~er,L and is not degraded by drying
or by the p~-ssage of time after drying. It is thought that the inhibition of surface
bleed by i"le" ,al additives is ~use~ by this i"crease in the surface free energy
of the plastic surface. The organic acids specified for the present invention donot contain any te""inal alkyl group in the molecule. In fact however ter",i"al
t alkyl~ontaining o~ 9dl liC acids do appear to produce an increase in the surface
free energy i" " "e~ 'ely after l, edll l lel Il but with these compounds the surface
free energy is redtlced by drying and by the elapse of time. It is for this reasol)
that the use of alkyl-co"tai"i"g orga"ic acids does not yield an ade~ te im-
provement in the pdinlabilily.
Moreover the modificdliGI I of surface properties as a result of execution
of the prepainl lledllllenl of the invention results in an improved wettability by
aqueous solutions and thus in improved drying cl)ardcterislics.
The invention and its be, lerils may be further a,upre~ i ~'ed by c~"~ lerali~n
of the following Examples (acco, L ,y to the invention) and Com~ arali~/e Examp-les (not accordir,y to the invention).
F~mples and CG"~parali~/e Examples
Test ",alerials
- amine-cured polyuretl ,ane (bumper "~aLerial)
exlernal release agent: oxi~ Prlwaxtype
internal release agent: zinc stearate
- hard polypropylene (bumper material)
2. CG~ osiliol~ of the prel,~dL"~e"l agents
Pretreatment agent 1
(CorreSpG~ IdS to a prepaint lreal",er~l agent of the invention)
sulfuric acid: 3 wt %
polyoxyethylene nonylphenyl ether 0.5 wt %
organic acid see Table 1
water re"~ai"ller
wo 95/04608 ` -2 16 8 ~ PCT/US94/0869~
Pretreatment agent 2
(not a p,-e5~ai, ll treatment agent of the invention)
sulfuric acid 3 wt %
polyoxyethylene nonylphenyl ether 0.5 wt%
(HLB: 12)
water remainder
Pretreatment agent 3
(cor, espor)ds to a p, e~ai, ll treatment agent of the invention)
orya"ic acid see Table 1
water rer"ai"der
r, ~l, edl" ,e, ll agent 4
(co"~s~.o"ds to a ~,rt:pai"l t,eal",enl agent of the invention)
polyoxyethylene nonylphenyl ether 0.~ wt %
(HLB: 12)
organicacid seeTable 1
water remainder
3. Treal",e,ll rllt~ Ods
Method A:
llnelllwithprelrt:dl",entagent1 (180sec, 80C)
water wash (30 sec, ambient temperature)
wash with pure water (30 sec, a" Ibiel IL temperature)
2s drain and dry (10 min, 80 C or 120 C)
Method B:
treatment with pretreatment agent 2 (180 sec, 80 C)
water wash (30 sec, ambient len~perdlure)
lr~l",e, ll with pr~, e&l"~e, ll agent 3 (10 sec, ambient te",~ erdlure)
~I~o 95/04608 `~!-1 B~ 73 ~ PCTlUSg4/08696
wash with pure water(30 sec ambient temperature)
drain and dry (10 min 80 C or 120 C)
M~tl lOJ C
l, eal" ,e"l with prel, eal"~ent agent 4 (180 sec 80 C)
v
drain and dry (10 min, 80 C or 120 C)
(Spraying was used for l, t:d~ lel Il with the ~rel, ~dl",enl agent and for the
water washes.)
,o 4 Painting
After ~rel,edl",enL the sample was held as specified below and then
painted.
I loldi"y condilio"s 1: pai"led within 12 hours after ,urelreal,,,enl.
Holding conditions 2: painled on the fifth day after prelreal",enl.
r, i" ,~r~:
In the case of the amine-cured poly~ rell ,~ne: Soflex~) 1000 from Kansai Paint
Kabushiki Kaisha bakingfor 15 minutes at 110 C film thichness = 15 to 20 mi-
c, ù" ,~t~
In the case of the hard polypropylene: Sofle~ 2500 from Kansai Paint Kabushi-
ki Kaisha baking for 10 minutes at 100 C film thickness = 15 to 20 ,nic,u,,,ele,
Top coat:
The following was used as the top coat for both sa",,l~lc ",dlerials: Sof-
le~ 1200 from K~nsai Paint Kabushiki Kaisha baking for 20 minutes at 120 C
film ll ,i. hr,ess = 35 to 40 n,ic,ul,,ele,~.
5. Test " ,eU ,ods used for evallJ~tion
(Contact angle)
After the ~ec~tion of the prelredlll~enl and drain and dry or for other
sa"~ les after completion of the holding period in ~ itio" a drop of distilled wat-
er was placed on the surface of the sample and the cc, ItdCl. angle was measuredwith a goniometer-type conld~t angle instrument. (The value measured i",r"edi-
ately after drain and dry only is desiy"aled "initial" below.) Lower contact angles
WO 95/04608 216 8~ 3 ~ PCT/US94/086JI
are indicative of lower i"le,racial energies between water and the treated solidsurface and hence of better paintabilities.
(A~l ,esion after Water Soak)
After a holding period of 24 hours after painting a cheche,~oc~rd pattern
s of 100 squares each 2 mm on a side was cut in the paint surface using a sharp
cutter. After an ensuing i""~,er~,on for 240 hours in de-ionized water at 40 C
cellopl ,a"e tape was applied to the cl~eche,~oar J and then sharply peeled off and
the number of residual paint film squares was counted. A larger number of re-
sidual squares is indicative of a better adhesion.
10 (Paint crawling test)
The appear~nce of the primer was visually ev~ ted after its application
and was scored on the following throo Icvcl scale.
+ + : no primer crawling was observed
+ : orange-peel crawlingwasobserved
5 X : crawling is observed to such a degree that the substrate
has become visible
The results of the pe,ru""a"ce evaluations are l~po,led in Table 1 and
these results support the following conclusions:
1. The conla~ angle whether measured initially or after the holding period
20 was smaller and its va,idliGn was less in Examples 1 to 6 of the invention than in
Colll,udldli~e Examples 1 to 7. This was tnue even when high temperature paint-
baking co,)~lilions were employed. The adi,esiol1 after water soak was exce" nt
in ExamplEs 1 to 6 and no paint crawling was observed in Examples 1 to 6.
These excellent pr~ e,ly values cor,ri",led the inhibition of i"le",al additive bleed
25 from the plastic moldings.
2. In Examples 1 to 6 of the invention the dirre~"ces among ll~dllllel ll meth-
ods A B and C did not cause dirr~rt:nces among the initial Col ~lacl angle values
the timewise va, idlion in the conldct angle values the ad hesiG" after water soak
or paint crawling. This indicates that there is no drrrer~nce between use of the30 sulrd~talll in the prepaint l,~al",e,)l agent of the invention and preliminary treat-
ment with a solution that contains only s~" ra.ilanl followed by tleatlllel)l with sur-
factant-free prepaint lr~al",enl agent in acco,dance with the pr~senl invention.
~O 9~/04608 2i 6~Q 73~ PCT/US94/08696
Table 1: TEST VARIABLES AND RESULTS OF THE PERFORMANCE
EVALUATIONS
6 Pr~ Orgsnic AcidInitial Contact ~rain/ Elold-
treat- Anglein Degrees Dry ing
ment On: Temp.,Condi-
Code Type % PU PP C Code
Conc.
E~ 1 A S.lcr.inic 0.5 66 97 120
Es. 2 B Malic 0.1 67 99 80 2
Es. 3 C Tartaric + 0.3 64 83 120
Citric
Es. 4 C M~lonic 1.0 65 85 80 2
Es. S A Oxalic 0.0S 68 100 120
Es. 6 B Citric 2.0 65 99 120
C. Es. A none - 82 98 120
C. Es. A none - 83 101 80 2
C. Es. B Malic0.03 80 99 120
C. Es. B Tartaric 0.01 79 98 80 2
C Es. A Methyl 1.0 67 100 120
Succinic
C. Es. B Lactic 2.0 68 98 120
C. Es. C Acetic 0.5 65 102 80 2
Notes for Table 1
"PU" = Polyul~;Ll~ e; "PP" = Polyl.lupylene; "Ex." = [Working] F.x;....l,lc; "C. Ex."
= COl~ aLi~ F y ;1~ c
(Table 1 is co~tin~led on the next page)
w095/b4608 216~rl36 PCT/US94/086
Table 1 confin~led
For Polyurethane: For Polypropylene
Contact Adhe- Paint Contact Adh~ Paint
Angle, sion Crawl- Angle, sion Crawl-
After ing After ing
Water Water
Soak Soak
E~ 1 66 100 ++ 98 100 ++
6 Es. 2 68 100 ++ 100 100 ++
E~ 3 64 100 ++ 82 100 ++
E~ 4 64 100 ++ 86 100 ++
Es. 5 69 100 ++ 101 100 ++
Es. 6 65 100 ++ 96 100 ++
10 C.Es.l 106 29 x 112 94 +
C. E~ 2 92 82 + 108 96 +
C. E~ 3 98 67 x 110 95 +
C.E~.4 86 94 + 110 97 +
CE~5 102 32 x 109 94 +
16C. E~. 6 98 56 x 110 93 +
C. E~. 7 85 96 + 109 97 +
Notes for Table 1 c~J"~ ..ed
Values for contact angle in colllmn~ in which the words "Contact Angle" in the
column he~rlinp are not ;~ e~ ly preceded by the word "Initial" were measured
on the treated s-lrf~ces a~er pl~ .. .I followed by drain and dry and then
followed by the holding period, but before p~;..l;.~ the surface.
~VO 95/04608 216 87 3 6 PCT/US94/086
3. The values for the ~,, ope, ly set (initial co, ILacl angle value timewise vari-
ation in the co,)~ angle value adhesion after water soak and paint crawling)
in Cor"par~live Examples 1 and 2 (with no ~- Id;liol l of organic acid) were inferior
to those of Examples 1 to 6.
4. Comparative Examples 3 and 4 did employ ter"~inal alkyl-free organic
acids, but at CGI Icel Ill dliorls of 0.01 to 0.03 weight % or lower than the 0.05 to
2.0 weight % used in E)~a",~les 1 to 6. The values for the property set (initialCCII Itd ,t angle value, timewise V11 idLiol I in the conta~ angle value adhesion after
water soak and paint crawling) were again inferior. This indicates that 0.05
lo weight % is a critical organic acid c~"ce"lr~lion value with regard to the develop-
- ment of the effects of the invention.
5. Co",,~ar~ /e Examples 5 to 7 which used terminal alkyl-containing organ-
ic acids gave app,o,(i",a~aly the same initlal contact angle values as Examples
1 to 6, but had inferior values for the timewise va, idliGn in the co, lldcl angle ad-
5 hesion after water soak and paint crawling. This was true clespite use of the ter-
minal alkyl-cc, llail ,i"g organic acids at co"cenlralio,1s of 0.5 to 2.0 weight %.
Benefits of the Invention
The surface bleed of inte, nal additives pr~sent in plastic moldings is inhib-
ited by l~lll)enl with the water-based prepai, It t,edll,~ent agent in accor-la"ce
20 with the p,esent invention. This results in the following highiy desirable erre~s:
high-te",~e,dlure drying beco",es possible which supports a sho, leni"y of the
drying time and equipment do~ i"y and ~h~l ,ges in the surface with elarsed
time are inhibited; this 5labili~es the ~Jdil ,tability and improves the workability.
-
