Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
9~
POLYVINYL CHLORIDE MOLDING
POWDER
The present invention relates to a polyvinyl chloride
powder molding composition, e.g. for making covering material
for automobile inner parts such as crash pads, armlrests, head
xests, console boxes, metex covers and door trims. In recent
years there has been increasing demand for latter such items of
complicated shape which are ligh-~ in weight, have embossed or
stitched patterns, and are soft and high-quality to the touch.
Hitherto, there have been two kinds of covering
material, one being vacuum-ormed from plasticized sheet composed
mainly of polyvinyl chloride resin and ABS resin, and the othe
being rotationally molded- or slush-molded from paste sols
composed mainly of polyvinyl chloride paste resin and plasticizer.
l`he vacuum-o~ned product meets the requirement for
light weLght, but is hard to the touch. Besides, it is
extremely diffioult to obtain vacuum-formed products of
complicated shape havirlg embossed or stitched patterns of high-
guality feel. ~1e vacuum-formed product also has the defect
that, because of its large residual strain, cracks are easily
formed during long-term use.
On the other hand, the sol molded product has a soft
feel, but the sol, because of its low gelation temperature,
rapidly melts in the mold so that phenomena such as flow mark,
lip, stringiness of the sol, etc. appear. The sol molded product,
therefore, has the defects that its inside surface lacks smooth-
~ '~
~0~9~:3
-- 2 --
ness, that it may be too thick, and sol removal from the
mold takes too long~
The 501 also has the problems that a great deal of
labor is required in cleaning tanks, pipes, etc. for color change,
and that its viscosity changes with lapse of time so that it can
not stand long-term storage. I
In recent years, powder molding methods have a~tracted
public attention as a means to solve these defects and problems.
The powder molding methods include fluidized bed
coating, electrostatic coating, powder flame spray coating, powder
ro~atlonal molding, powder slush molding and the like.
A powder composition used in these techniques should he free-
flowlng and of good moldabllity.
It is well known to produce powder compositions by
dry-blending polyvinyl chloride resinsl plasticizers,
~tabillzers, pigments, fillers and auxilliaries etc. on blenders
or high speed rotating mixers equi.pped with a heating jacket.
It is al50 well known ~o add smal1 amounts of polyvinyl
chloride resin fine powders or inorganic fillers such as calcium
carbonate fine powders, etc. in order to improve the flowabili~y
~Rubber Digest, Vo1~14, No.8, 32 - 40; Polyvinyl Chloride ~ Its
Chemist~y and Industry - II, pp.367 - 370, 1968; and Japanese Patent
Publication No.157511962).
In powder molding, a polyvinyl chlorlde powder composi-
tion is molded in a mold kept at high temperatuxes, so that the
surface of the mold i5 gradually stained as the number of molding
shots increases. Conse~uently, molding works must stop operation
.
" ~3~g9~
temporarily fox mold cleanins, as a result of which productivity
is markedly reduced and extra labor is required for cleaning.
When the mold is heaviIy stained, the molded covering material
becomes difficult to detach from the mold, stains on the mold
S are transferred to the sur~ace of the coverin~ material, and in
some cases, the thickness of the molded material becomes too great.
It is therefore very important industrially and econom-
ically to develop polyvinyl chloride powder compositions which
produce less stain on molds, in other words, are superior in
resistance to mold staining.
To this end, after extensive study, we found it
desirab1e to use in such powder compositions a stabilizer
comprising the metal soap of a fatty acid having a C5-C8 alkyl
group.
In its most preerred aspect, the invention pxovides
a polyv.tnyl chloride powder molding compdsition ~usually a dry
blend with one or more of plastiaizers, stabil.izers, pigments
and others such as fil.lers and au~iliaries added as need arises],
contai.ning barium and æinc fatty acid soap stabilizers selected
from -~ose of the formula:
( RC00)2Me
wherein R represents a C5-C8 alkyl group and Me represents barium
and zinc. This stabilizer is preferably present in an amount of
0.1 to 10 w/w ~. based:on the polyvinyl chloride resin. It
preferably contains the barium and zinc fa-tty acid soaps in bariunl:
25 zinc meta]. wei.ght ratios of 1:2 to 5:1.
In po~der molding, since polyvinyl chloride powder
comp~sitions are molded in a mold kept at high temperatures, too
''"'
~3~99C~
,,
great an importance has been put on the thermal resistance of the
composition. ~s a result, it has been normal to use the same
metal soap stabilizers as for common extrusion and calendering,
i.e. the metal soaps of fatty acids having alkyl groups of not
less than 9 carbon atoms, for example stearates
~C17H35COO-~, pa1mitates (C15H31Coo-~, laurates ~CllH23COO-~, caprates
~Cg~1gCOO~), etc. We have appreciated, however, that powder
molding is different from common extrusion and calendering in
that the powder is brought in~o contact with the mold at high
temperatures for only a short time, and that little shear is
applied to the powder. The popularly used stabilizers,
comprising the metal soaps of fatty acids having alkyl groups of
not less than 9 carbon atoms, are of a powdery form in many cases.
In powder molding, however, we have found that such stabilizers
are poor in dispersibility and, because of their high melting
points,: do not melt sufficiently but remain in part as powder.
We also found that, even when the above known
stabilizers are well kneaded with liquids such as solvents,
plasticizers, etc., compatibility with the PVC is poor and also
the plate-out phenomenon occurs; when the mold has fine embossed
or stitched surface patterns, occurrence of this plate-out
phenomenon makes it very troublesome to remove stains from the
mold.
On the other hand, the metal soaps df fatty acids
having alkyl groups of not more than 8 carbon atoms, for example
nonanoates [C8H17COO-~, octanoates ~C7~15COO ~,
heptanoates ~C6H13COO-~, bexanvate5 [C5HllCOO-~, etc.,
~3~
.
have less thermal resista1lce and ll~ricating action and are
difficu1t to produce, and so are not generally used in common
extrusion and calendering - at 1east, no-t in the substantial
absence of metal soap of fatty acid having an alky]. group of not
less than 9 carbon atoms.
The present invention thus provides a polyvinyl chloride
powder molding composition resistant to mold staining, including
metal soap of a fatty acid having a C5-C~ al]yl group; the metal
moiety of such soap is preferably barium and zinc. Suitable
`) 10 barium-containing soaps include barium nonanoate, barium
octaboate, barium heptanoate and barium hexanoate. Suitable
zinc-containing soaps include zinc nonanoate, zinc octanoate,
zinc heptanoate and æinc hexanoate.
In the present invention, the barium-cont~ining and
zinc-containing stabilizers are best used in combination, preferably
at a metal wei~ht ratio of barium to zinc of 1:2 to 5:1.
When æinc is in excess relative to barium, e.g. thLs
barium:~inc weight ratio is smaller than 1:2, there is danger
;.~ of inadequate thermal resistance, formation of black specks
and focuning of the molded covering material. Such weight ratio
is not therefore preferred.
Contrary to this, when barium is in excess relative to
zinc, e.g.this barium:zinc weight ratio is larger than 5:1,
initial coloration on moulding tends to ~ecome strong, particularly
a tendency to be colored red. As a result, since the color of
the molded covering material deviates from that desired, color
matching becomes difficult.
~L30~
-- 6 --
The amount of the barium/zinc-containing stabilizer
used is preferably ~rom 0.1 to 10 parts by weight based on
100 parts by weight of polyvinyl chloride resin; when it is less
than 0.1 part by weight, the thermal resistance may be inadequate;
when it is more than 10 parts by weight, there is a danger of
the stabilizer bleeding to the surface of the moldad covering
material, and the cost may increase to become uneconomic.
In order to provide as a final product a covering
material for automobile im1er parts, polyurethane can be formed
in place on the inside surface of the molded covering material.
In thls in situ polyurethane foaming, it is well known
to use a first component composed mainly of polyol, water,
foaming agent, catalyst and other auxiliaries, and a second
component composed mainly of polyisocyanate.
In this polyurethane foaming, amine compounds
are used as cat.alyst, e.g. ethylenediamine,
triethylenediamine, triethylenetetramine, triethanolamine, etc~
these may he used alone or in combination, and as addition
products with alkylene oxides such as ethylene oxide, propylene
oxide, butylene oxide, epichlorhydrin~ styrene oxide.
These amine compounds, on contact with the polyvinyl chlorida
covering material, markedly promote discoloration and deterior-
ation o~ the material.
Consequently, there has been a need for polyvinyl
chloride powder molding compositions resistant to discoloration
and deterioration by amine compounds ~hereinafter referred to as
amine resistance). We have found that our PVC powder molding
-- 7 --
composition is improvad in amine resistance by inclusion of
magnes~um compound, preferably in an amount of from 0.1 to 5
parts by weight per 100 parts by weight of polyvinyl chloride
resin.
In the development of our polyvinyl chloride powder
compositlon superior in amine resistance, we examined the
thermal resistance ~gear oven 110C) and light fastness (sun-
shine weather-0-meter or fade-0-meter; black panel temperature,
83C) of a two-layer sheet comprising the polyvinyl chloride
covering material and polyu~ethane foamed in situ, and found
that the zinc compound has an ability to prevent discoloration
by amine compounds. We believe the reason for this to be as
follows : in systems whereln a polyvinyl chloride resin and an
amine compound coexist, dehydrochlorination is promoted or a
complex co~npound is formed by reaction between the resin and
the amine compound to develop a characteristic color; but when
a zinc stabilizer i9 present in the system, another complex
compound is formed from the stabilizer and the amine compound,
and in this case, a complementary relationship applies between
the colors of the complex compounds to produce a harmless
color. The invention, however, is not bound by theory.
In the foregoing thermal resistance and light fastness
tests on the polyvinyl chloride/polyurethane two-layer sheet
described above, we sought 3 method to maintain the discoloration
resistance for longer, and after extensive study found that
amine resistance can be improved by including a magnasium
compound. We also found that the use of magnesium compound is
~ ~`r ~cJe ~ ~nC~ S
~3~)~99~3
-- 8 --
accompanied by improved maintenance of adhesion strength
between the polyvinyl chloride covering materlal and polyurethane
layer even after prolonged thermal resistance and light fastness
tests.
Suitable magnesium compounds for use in the present
invention include for example magnesium oxide, magnesium
hydroxide, magnesium phosphate, magnesium perchlorate, basic
magnesium carbonate, magnesium/aluminum compounds ~e.g. hydro-
talcite) and the like. These compounds may be used alone or in
combination.
The amount of the magnes1um compound used is preferably
in the range of O.l to 5 parts by weight based on 100 parts by weight
.. . . .
of polyvinyl chloride resin. -
When said amount is less than 0.1 part by weiyht, the
improvement in amine resistance and the adheslon strength of the
polyvinyl chloride/polyurethane two-layer sheet after the aging
tests may be insu~ficient.
When said amount is more than 5 parts by weight, the
ilm strength o~ the polyvinyl chloride covering material may be
insufficient, and the initial coloratlon of the material on
molding tends to be strongly reddish, so that such amount is
not preferred.
The stabilizers used in the present invention may be
added when dry-blending the composition. In this case, they
may be added alone, or with one or more components selected from
solvents, plasticiæers, epoxy compounds, antioxidants, photo-
stabilizers, ultraviolet absorbers, phosphorus chelaters,
9g~
alcohols and pigments.
The stabilizers used in the present invention may be
used with small amounts of other stabilizer or inorganic
compound described below. Such other stabilizers are metal
soaps other than those of Eatty acids having an alkyl group of
not less than 9 carbon atoms, and include for example calcium,
magnesium, barium, zinc and aluminum metal soaps of monohydric
carboxylic acids (e.g. benzoic acid, toluic acid, acetyoxy-
benzoic acid)and dihydric carboxylic acids te.g. oxalic acid,
malonic acid, succinic acid, glutaric acid, adipic acid, sebacic
acid, phthalic acid). The inorganic compounds include for
example caxbonates, phosphates, phosphites, silicates, calcium
carbonate fine powder, aluminum hydroxide, alumina~silica sol,
perchlorates and the like.
The polyvinyl chloride resins usable in ~ e present
invention include vinyl chloride homopolymers, copolymers of
vinyl chloride wlth ethylene, propylene or vinyl acetate and
graft copolymers of vinyl chloride with ethylene/vinyl acetate
aopolymer ~EVA). These polymers and copolymers can be produced
by suspension polymerization, bulk polymerization or e~ulsion
polymerization, and they may be used alone or in combina~ion.
The polyvinyl chloride resins for the present invention are
not limited to these polymers and copolymers.
As plasticizers for use in the pxesent invention, there
are given for example phthalic acid esters such as dibutyl
phthalate, dioctyl phthalate, diisodecyl phthalate, diisoundecyl
phthalate, etc.; trimeLlitic acid esters such as trioctyl tri-
, .
o
-- 10 --
mellitate, tri-2-ethylhexyl trimellitate, tridecyl trimellitate,
etc.; adipic acid esters such as dioctyl adipate, diisodecyl
adipate, etcO; phosphoric acid esters such as tricresyl
phosphate, trioctyl phosphate, etc., epoxy plasticizers and
liquid polyesters. The plasticizers suitable are not limited
to these compounds. I
As the polyol, catalyst, foaming agent, polyisocyanate,
etc. for the in situ polyurethane foaming, the well known ones
commonly used in the production of polyurethane foams are
adequate, there being no special limitation.
The present invention is illustrated specifically by
the following Examples, which are not however to be interpret2d
as limitlng the invention.
To a 20-lliter super-mixer WAS added 2 kg of a straight
polyvinyl chloride resin having an average polymerization degree
of 700 produced by conventional suspension polymerization
~Sumilit ~ SX-7GL; produced by Sumitomo Chemical Co.). Separately
from this, 25 g of barium octanoate and 25 g of zinc octanoate,
70 g of epoxidized soybean oil and llO g of a g~ay pigment
contalning 3 g of a thioether antioxidant ~Antigen ~ OS; produced by
Sumitomo Chemical Co.) and 2 g of a ul~raviolet absorber (Viosorb ~
580; produced by Kyodo Yakuhin Co.) were thoraughly dispersed in 400 g
of trioctyl trimellitate. This dispersian liquid and then l kg
of trioctyl trimellitate were added to the super-mixer while stirring
at a controlled revolution speed, and the mixture was dried by
heating.
9~
11 --
After cooling, the dried product was uniformly mixed with
200 g of a polyv1nyl chloride pas~e resin fine powder produced by the
micro-suspension method ~Sumillt ~ PXQL; produced by 5umitomo Chemical
Co~) to produce a powder-composition ofgood flowability.
lU0 Grams of this powder composition was sprinkled for 10
seconds on a nickel mirror plate ~100 mm X100 mm X3 mm thick ~ kept
at 220 C on an electric hot plate. The mirror plate was
then taken off the hot plate, and after removing the unmolten powder,
th~ mirror plate havinq the molten resin' attached thereto was again
placed ~n the hot plate and heated for 30 seconds to complete fusion.
After cooling and removing the formed sheet, the mirror plate was
again placed on the hot plate and the above procedure was'repeated
five times. After the test,'the degree o~ aloudiness of the mirror
platc was examined ko find that the plate had little cloudiness,
snowing a"good appearance.
xample 2
A powder composition was prepared in the same manner-~s in
~xample 1 but using 120 g of a liquid comprising 60~ of dodecylbenzene
and as a stabilizer, 40% of barium/zinc octanoate previously adjusted
to a barium:zinc metal we,ight ratio of 2:1. The Example 1 test was
repeated five times on the same hot plate, and the degree of
cloudiness of ~he nickel mirror plate examined; it was found
that the plate had little cloudiness, precisely as in Example 1,
showing a good appearance.
Example 3
A powder composition was prepared in ~he same manner as in
Example 1 but using as a stabilizer 120 g of the barium/zinc
octanoate used 1n Example 2 and 4 g of magnesi~m.oxide. The Exam~le 1
test was repeated five times.on the same hot plate, and the
degree of cloudiness of the nickel mirror plate examined;
it was found that the plate had little cloudlness, precisely as
in Example 1.
Ex~ le 4
A powder composition was prepared in the same manner as in
Example 1 but using as a s~abilizer 120'g of the barium/zinc
octanoate used in Example 2.znd 4 g of magnesium hydroxide.
The Ex.1 test.was re~eated ~.ive times on the-same hot plate, and
the degree of ~loudiness of the nickel mirror plate e~camined;
it was found that the plate had little cloudiness, precisely
as in Example l.
' _xam~ Q S
A powder composition'was prepared in the same manner'as in
Example 1 but using as a stabilizer 120 y of the barium/zinc
octanoate used in Example 2',`4'g of magnesium hydroxide and'4'g of'
hydrotalcite IDHT-4, produced by Xyowa Kagaku Co.). The Ex.1 test
':~' 20 was.repeated f1ve times on the same hot plate, ~nd the.degree
of cloudiness oF the nickel mirror plate examined; it was
~~ou'n'd~that the 'plate' had'littlë cloudiness , precisely
as in Example 1. ''
.Comparative example 1
~he procedure was carried out in precisely the_same manner
as'in Example i but using 40 g of barium stearate and 40 g.of...zinc
e-~Q~k
99~1
- 13 -
stearate as a stabilizer. The result of the test was unsatis-
factory, and white thin film-like stalns were obser~ed 'on the surface
of the mirror plate.
Comparative example 2
.
The procedure was carried out in precisely the same manner
as in Example l but using 40 g of barium stearateland 35 g of zinc
laurate as a stabilizer. The result of the ~est was unsatis-
~actory, and white thin film-like stains were observed on the surface
of the-mirror plate as in Comparative example 1.
'~ Com~arative~example'3-
The procedure was carried out in precisely the same manneras in Example l but using 35 g of barium laurate and lO g of zinc
octanoate as a stabilizer. The result of the test ~as less
sati'sfactory than 'the results'of Examples~l' to--~4-,'--and
slightly white thin film-like' stains were observed on the surface of
'the mirror plate.
Comparative example 4
The procedure was carried out in precisely the same manner
--as in Example 1 but using 24 g o barium stearate, 12 g of bar'ium
palmitate, 4 g of barium laurate and 40 g of zinc stearate as a
stabiiizer and 4 g of magnesium hydroxide. - The result of-ehe
test was unsatisfactory, ~a in Comparative example 1.
~omparative example 5
, . .. __
The procedure was carried out in precisely the same manner
as in Example -l but using ~4-g-of ba~ium s~earate,-12 g of barium
palmitate, 4 g of ~arium laurate and 40 g of zinc stearate as a
L9~
- 14 -
stabilizer, 4 g of magnesium hydroxide and 16 g of hydrotalcitç
DHT-4 (produced by.Kyowa Kagaku Co.). The result of the test was
also unsatisfactory, as in Comparati~e example 1.
The po~der compositions obtained in Examples l to 5 and
Comparative examples l to 5 were formed into shee~ as described below,
and the amine resistance was tested. I
500 Grams of. powder composition was sprinkled on -an
electroformed nickel plate with embo6sed patter~ ~300 mm X 300 mm)
' kept at 220C~in a furnace wherein the atmospheric temperature
lo was 300C; and after
10 seconds the plate was taken from the furnace and the un~olten
powder was..removed. ~he plate having the m'olten'po~der attached
thereto was' agaih~placed'in the furnace and heated for-one-minute--at-
-an atmospheric tempera`ture of 300C td complete fusion.
After cooling, the formqd sheet was removed.. . . ~he thickness of~the
sheet was 1 mm on average.
__ __. Ther~a~ter,.the formed.sheet.was placed, with its embossed --
surface downwards, on an aluminum support ~rame ~300 mm X300 mm X
lO mm th'ick ~ plac~d on an aluminum foaming plate. Separately
from this, water, triethanolamine and triethylenediamine were added
to polyol composed mainly of glycerin/propylene oxide and glycerin/
ethylene oxide adducts to prepare a mixture. I'nto the~above
sUpport frame were..injected this mixtu~e and polymeric MDI-having an
NCO content of 30.5% so that the total amount was 153 g and the
' weight ratio of former to latter was 100 par~s to 50 parts by weight,
whereby a polyurethane foam firmly adhered to
9o
- 15 -
the back surface of the sheet was obtained. This polyurethane
foam had a thickness of 10 mm and a foam density of 0.16 gtcm3.
This polyvinyl chloride/polyurethane two-layer sheet was
cut into a desired si~e of 70 mm X150 mm to prepare a test sheet.
~our pieces of the test sheet were placed in a gear oven
wherein the atmosphere was kept at 110C; one test
piece was taken out every 100 hours, and a 400-hour thermal
discoloration test was carried out. Similarly, four pieces of the
test piece were placed in a Sunshine weather-O-metèr, wherein the
temeerature of the black panel was adjusted to 83C ; one test
piece was taken out every lOO hours, and a 400-hour photo-
discoloration test.was carried.out. ~he resistance
to thermal discoloratIon and photo~discoloration was expressed by
grade using the gray scale.
; l'able 1
~esistance to mold staining and amine resistance
. . __
__ Resistance to ~mine resistance '
mold staining ~esistance to Resistance to
. thermal dis- photo-discolor-
. colorationation
~grade) ~grade~
_ . _ ~_
Exampl~ 1 . O . 3 4 -3
a - 2 3 4--3
~- 3 . O ~ . ~ 5~4
. Q 41 5~4
~ 5 C~ . 4 5~4
Comparative . .
example~l ~ 3 4 - 3
2 X 3 4 - 3
3 ~ 3 ~ -3
4 X 4 S -4
. _ _ _ _ 4 5 -4
~L3~1~9~
Note 1
Assessment of reslstance to mold staining : according to the
degree of cloudiness of nickel mirror plate.
0 Little cloudiness is observed.
~ Cloudiness is observed to some degree.
X Marked cloudiness is observed.
Note 2
Assessment of amine resistance :
~hermal resistance : Gear oven, 110C x 400 hours.
Li~ht fastness : Sunshine weather-0-meter,
83C x 400 hours.
Assessment of discoloratio~ : according to the grades on the
gray scale.
.
