Note: Descriptions are shown in the official language in which they were submitted.
- 1- 131~619
RESINOUS COMPOSITION FOR POWDER COATING
The present invention relates to a resinous
composition for powder coating, more particularly a resinous
composition which is excellent in adhesion with a metal and
is able to form a coating layer which is superior in heat
resistance and extensibility, compounding a given amount
each of (A) modified polypropylene, tB~ ethylene polymer,
(C) metal oxide or hydroxide and (D) polymers of vinyl
cycloalkane having at least six carbon atoms.
Powder coating on the basis of such olefin
polymer as ethylene polymer and propylene polymer has been
widely used to provide corrosion resistance, chemical
resistance! durability, staining resistance and so on to
metal articles. Difficulty encountered in this sort of
coating is that the coating is inferior in adhesion with
metals since olefin polymer is non-polar. Modification
of olefin pol~mer, e.g., grafting or copolymerizing
monomers having polar groups on or with the olefin polymer
is proposed in order to solve the difficulty above
(Japanese patent Kokai Nos. 48-103645, 54-155242, 55-118975
59-36841 and others). However, these improvements in
adhesion with metals are not satisfactory yet even after
such modification is made.
Furthermore, ethylene polymer hardly provides
enough heat resistance when coating is made on pipes for
supplying hot water environmental parts of engines of
automobiles and so on which are subjected to high temperature.
Propylene polymer is not tolerable with respect to rust
prevention or protection, since elongation of coated
layer is so small that the layer is ready to be cracked
. . .
- 2 - 1 31 6 61 ~
when deformation working of a metal base is made or impact is
applied to, although the polymer is superior in heat
resistance.
According to the present invention, a resinous
composition suitable for powder coating is provided which
comprises (~1 80 - 95 parts by weight of polypropylene modified
by grafting unsaturated carboxylic acid anhydride thereof
on at least a part of crystalline random copolymer of (a)
90 - 99 ~ ~y weight of propylene and (b) 10 - 1 % by
weight of ~-olefin having 2 - 10 carbon atoms excluding
propylene, (B)20 - 5 parts by weight of ethylene polymer,
(C~ 0.1 - 10 parts by weight of metal oxide or hydroxide,
and (D~ a sufficient amount of vinyl cycloalkane polymer
to ha~e 0.001 - 1.0 % by weight of vinyl cycloalkane unit
contained in the composition, said cycloalkane having at
least six carbon atoms.
The present composition is so ready to be
pul~erized mechanically that a period of time to this
effect is short and energy required is small. Coated layer
produced by fluidized dipping or electrostatic coating has
the following features:
1. good at adhesion with a metal,
2. superior in heat resistance,
3. high elongation and excellent in bending,
4. high surface hardness and hardiy scratched and
5. good at melt flowability, so that surface is smooth.
Examples of shaped articles to which the present
coating is applied are
1, kitchen appliances such as hot water supplying pipes
and a drainboard,
2. parts for automobiles such as an electro magnetic
shield,
~ 3 ~ 131~619
3. household appIiances` such as a dishwasher and a basket
in a washing machine and
4. others such as gardening tools, building materials
and daily goods.
(A) Modified polypropylene
Basic resin is crystalline random copolymer
comprising a) 90 - 99 % by weight of propylene and b) 10 -
1 % by weight of a-olefin having 2 - 10 carbon atoms
excluding propylene. Preference is that ~-olefin is
ethylene and is used in an amount of 2 - 8 ~ by weight.
When ~-olefin (b) used is less than 1 % by weight,
smooth coating surface is scarcely produced, since melting
point and melt viscosity of the resin are too high.
Although smooth surface of coated layer is able to be
obtained when a base metal is pre-heated to 300 C or higher
at fluidized dipping coating, such layer is not excellent in
respect to strength and elongation, since the layer has
been subjected to heat degration. When an amount of
a-olefin (b) exceeds 10 ~ by weight, coated layer is
inferior in heat resistance and surface hardness, since
melting point of the resin is too low. Preferable melt
index (JIS K-6758, referred to hereinafter as "MI") is
1 - 20.
Modified polypropylene is prepared by any of
conventional processes such as tho$e disclosed in
~apanese patent Kokoku Nos. 43-27421 (melt kneading process),
44-15422 tsolution modification process) and
43-18144 (slurry modification process),
.
1316619
Unsa~Urated carboxylic acid for graftil~s is
acrylic acid, methacrylic acid, maleic acid, fumaric acid,
itaconic acid, crotonic acid, citraconic acid, sorbic
acid, mesaconic acid and the like Unsaturated dicarboxy
anhydride is maleic anhydride, itaconic anhydride,
citraconic anhydride, himic anhydride, and the like.
Preference are acrylic acid and maleic anhydride.
10Peroxide used in grafting is 2,5-dimethyl-2 r S-di
(t-butylperoxy)hexane, 2,S-dimethyl-2,5-di(t-butylperoxy)-
hexyne-3-dicumylperoxide, t-butylperoxylaurate,
t-butylperoxyisobutyrate, diisopropylbenzene hydroperoxide
and the like. Proper variety of peroxide is selected
lS depending on basic resin to be modified and conditions for
modification. Grafting is effected usually at 100 - 250~C.
Grafted polypropyLene thus obtained may be used
alone and in the form o a mixture with unmodified
polypropylene.
Unsaturated carboxylic acid or anhydride thereof
contained in gxafted polypropylene is preferably 0.01 - S
parts by weight per 100 parts by weight of the crystalline
random copolymer. When the amount is smaller than 0.01
part by weight, lack in adhesion is brought about and when
the amount is larger than S parts by weight, discoloration
is caused.
30MI of modified polypropylene is preferably 10 -
60.
(~ Ethylene polymer
Suitable ethylene polymer is low density poly-
ethylene or linear low density polyethylene. Copolymer of
etllylene witll 10~ by weight or less o~ ester of unsa~-
urated carboxylic acid or viny]ester o~ ~a~ty acid may
- 5 - 131661~
be used, said esters ~eing such as vinyl acetate, vinyl
propionate, methyl acrylate, ethyl acrylate and methyl
methacrylate.
(C) Metal oxide or hydroxide
Proper oxide or hydroxide is that of metals of IIa,
IIIa and IVb of the Mandeleev's Periodic Table.
Example is magnesium oxide, calcium oxide,
aluminum oxide and titanium dioxide, Preference is
magnesium oxide, most preferably powdery one having at
least 20 mg I/g MgO in terms of iodine absorption, such as
"Kyowa Mag" ~ 30 manufactured by Kyowa Kagaku Co., Ltd.,
Japan.
Example of hydroxide is magnesium hydroxide,
calcium hydroxide, o-titanic acid, strontium hydroxide and
the like, preferably calcium hydroxide.
Median diameter of the metal oxide or hydroxide
is usually smaller than 25 ~m, preferably smaller than
10 ~m, from view points of uniform dispersibility in a
resin phase and an improvement in adhesion.
(D) Polymer of vinyl cycloalkane
The polymer includes homopolymer of vinyl
cycloalkane, random copolymer of a vinyl cycloalkane with
a small amount of the other vinyl cycloalkane or a-olefin
or block copolymer of vinyl cycloalkane with a-olefin.
The block copolymer mentioned above is copolymer
obtained by multi-step copolymerization between vinyl
cycloalkane and a-olefin. It includes (1) copolymer obtained
by polymerization of propylene alone after polymerization
of vinyl cycloalkane is effected, (2) copolymer obtained
- 6 - 131~6~
by random co-polymerization of propylene and the other
~-olefin after polymerization of vinyl cycloalkane is
effected, (3) copolymer obtained by random copolymerization
with propylene alone or other ~-olefin after vinyl
cycloalkane firstly is polymerized and secondly propylene
alone is polymerized. Preferable copolymer is the block
copolymer above, and most preferably block copolymer with
propylene as exemplified in (l) - (3) above.
Vinyl cycloalkane has six or more carbon atoms
and includes vinyl cyclobutane, vinyl cyclopentane, vinyl-
3-methylcyclopentane, vinyl cyclohexane, vinyl-2-
methylcyclohexane, vinyl-3-methylcyclohexane, vinyl norbornane
and the like.
(E) Compounding ratio
The present composition contains (A?, (B), (C)
and (D) in amounts of 80 - 95 parts by weight, 20 - 5
parts by wei~ht, preferably 15 - 7 parts by weight, 0.1 -
lO parts by weight, preferably 0.5 - 5 parts by weight,
and up to 20 parts by weight, respectively. As to (D), it
should be controlled so that 0.0~1 - l.0 ~ by weight in
terms of vinyl cycloalkane unit is present in the composition.
When amount of (B) is smaller than 5 parts by
weight, no smooth surface of coated layer is obtained, but
when the amount is larger than 20 parts by weight, remarkable
degradation is brought about in heat resistance as well as
in hardness of coating.
When amount of (C) is shorter than 0.1 part by
weight, adhesion with a metal is decreased, while when the
amount exceeds lO parts by weight, elongatiOn is
lowered and smooth and glossy coated layer is rarely produced.
Furthermore, the use of such a large amount is not
economical, since it is beyond saturation.
13~6619
(F) Production of the composition
Any of conventional melt-kneading processes for
an olefin polymer composition is available, e.g,, those
using mixing rolls kneaders, Banbury mixers or extruders.
Before the melt-kneading, it is preferable to dry-blend
the components by Henschel mixers, ribbon blenders or
tumblers until a uniform composition is prepared. After
being melt-kneaded, a composition is pelletized,
mechanically pulverized under room temperature or freezing
to obtain a powder coa~ing composition.
Other additives may be added, if desirea, such as
commercially available phenol, sulfur or phosphor
antioxidants such as "Irganox" ~ 1010, "Cyanox" ~ 1790,
"Sumilizer" ~ BHT, "Goodright" ~ 3114, "Sumilizer" ~ TPS,
and "Mark" ~ PEP-8; commercially available benzotriazole,
benzophenoné and hindered amine light resistant agents such
as "Tinuvin" ~ 328, "Sumisorb" ~ 510, "Sanol" CR) 770,
"Tinuvin" ~ 622; halogen, phosphorus and inorganic fire
retardants such as tetrabromobisphenol A, tris (~-
chloroethyl~phosphate, antimony trioxide and magnesium
hydroxide; pigments such as copper phthalocyanine blue,
submarine blue, carbon black, titanium dioxide and
cadmium yellow; fillers such as calcium carbonate,
magnesium carbonate, calcium sulfate, magnesium sulfate, silicon
dioxide, alumina, talc, mica, glass fiber, kaoline and wooden
powder, and the like.
Materials to be coated are metals such as iron,
aluminum, zinc, tin and their alloys and metals or glass
on which the metals above are plated. They may be in any
shape such as pipes, bars, wires, plates, boxes and the
like.
The present composition may be applied to by
fluidized dippin~, rotary shaping, sintering shaping or
electrostatic coating.
8- 1316619
Examples
The present invention is explained in more detail
by the following non-limitative examples.
a) Fluidized dipping coating
Into a fluidized dipping vessel having a porous
plate at a bottom is charged a powdery composition (80
mesh or less) prepared by a mechanical pulverizer.
Air is charged from the bottom of the vessel to
form a stable fluidizing bed of the powder. A grid
blasted steel plate (roughness. No. 100, produced by Taiyu
Kizai K.K., defatted by xylene, 150 mm x 70 m~ x 3.2 mm) which
has been heated in an oven at 230 C, is dipped in a
fluidizing; bed for 15 seconds. After being taken out,
the plate is subjected to baking in an oven (20G ~C) for 5
minutes and left to stand at room temperature until a coated
plate is o~tained.
(b) ~elt Index
JIS K-6758 for propylene polymer (230 C,
2.16 Kg load~
JIS K-6760 for ethylene polymer (19G ~C~
2.16 Kg load)
~c~ Adhesion
Coatea layer obtained in (a) above is slit
into a strip (1 mm wide) and subjected to a tear tester
(50 mm/minute) to observe a value when peeling reaches
180
(d~ Elongation
Silicon greese is coated as a parting agent on a
steel plate before being subjected to fluidizea dipping.
Coated layer is ready to be peeled off. Coated layer
parted is slit to a strip (1 mm wide) and subjected to a
tensile tester (50 mm/minute~.
(e~ Surface smoothness
Marked eye observation.
1316619
(f) Heat resistance
Vicat softening point ( 1 Kg load) according to
JIS K-7206 using coated layer obtained in the same manner as
in (d). Test specimens are piled up at least 1 mm high.
(g) Surface hardness
Shore hardness according to JIS K-7215 using
coated layer obtained in the same manner as in (d).
(h) Limiting viscosity [ n ]
Ubbelohde viscometer is used (135 C, in
tetralin or 20 C in carbon tetrachloride).
Example 1
Crystalline propylene/ethylene random copolymer
(ethylene 2.3 % by weight; ~I: 7.6 g/10 min.,
hereinafter referred to as PP (1~, 100 parts by weight),
t-butyl peroxylaurate (0.2 part by weight), maleic anhydride
(0.5 part by weight) and "Irganoxl' ~ 1010 (produced
by Ciba Geigy~ 0.2 part by weight, antioxidant) were dry-
blended for 3 minutes in a HensChel mixer.
The blend was extruded at 200 C through a
uni-axial extruder (30 mm in diameter) to obtain modified
PP(1).
The PP(1) (90 parts by weight), low density
polyethylene (hereinafter referred to LDPE) and
magnesium oxide ("Kyowa Mag" ~ 30j 20 parts by weight),
propylene/vinyl cyclohexane copolymer (hereinafter
referred to as PVCH (1), 1.0 part by weight), "Irganox"
1010 (0.2 part by weight, an antioxidant) and
calcium stearate (O.03 part by weight, a neutralizer)
were dry-blended in a Henschel mixer for 3 minutes.
-
1316619
-- 10 --
The blend was melt-kneaded at 200 C in a uni-axial
extruder (30 mm in diameter) to product pellets
(MI: 39 g/10 min.) which were subjected to a pulvelizer
to obtain powder (80 mesh or less).
Powder coating was effected by fluidized dipping.
Evaluation of coated layer is shown in Table 1.
Examples 2 - 14 and Comparative Examples 1 - 6
F1uidized dippings were carried out according
to Example 1 under the temperatures of steel plates
heated before the dipping, using varieties and amounts of
A, B, C and D components given in Table 1.
Results are shown in Table 1.
The table substantiates that components C and D
are critical factors to adhesion to metals and elongation
o~ coated layer.
,.
ll- ~31661~
. .... . _
~ o o, ~ o o o o
J O --~~ ~ ~ D `~ ~ N ~ ~
. â :~ ~ æ
~ .
~ O O O O O O O O O O
~4 ~ N ~ t~i ~
~ .
~ _ oo
_ .~ ~ ~
_ ~ ~ ~ ,
. ~ ~ 0~ 0 0 ~ ,0~
~ - U~ I`
_l ~ ~ ~
P m ~
_ ;~ O O O O O O O O O O
~? a ~ .
~ .~
_ ~ ~
~: - ~
~ o
- - ~
- 12 - 1~1661~
~ .~ o, o o
~ ~l ~ O
U ~
_
~ ~ o o, o o o o o o
~ o^ ~^
_ ~ ~
_ ~ ~
.. ..
_ ~ ~ Q~ ~? O ~ o ~ ~ o ~ o ~ ~o ~o
,~5 ~ .. ___ I
~ ~ ~ .,
~ m 1~
E~ ~ ~ o o o o o o o o ~ o o
~ ~ ~ - ~ -
_
_ ~ . _ .. ~.
- 13- 131~61
u~ ~ u~ u~ u~
a
c~ ~ o ,~ O
~--t o ~1 (~ t~l ~1 ~1 ~ 1~ 1~1 t~ (~) t~
- O ~ _ ~
.~ _ ,
O O O O O O O O O O O
o
1~ .
~
_.
'd
3 ~ o ~ 40
v ~ ~ ~1 ~ ~1 0 ~ ) ~1 ~ ~ O ~1 0 ~ O -I O ~1 0 -I O
~- ~ ~ ~. ~ . ~
.
_ ~ D O u~
~
u~: ...
o-l-- OOOOOOOOOOO
o o o o o o o o o o o
O ~ u~ ~ ~r ~ ~ ~ ~ r~
~
~ ' O ~ ~V ~
o _~
.
- 14 - 131661~
_ ~ ~ ~o ~9 ~ ~ ~ U~ ~ ~
. .~ -I
.l _ ~ O 0~ N a~ O
O ~ _ ~ 7 N ~ N ~Y) N ~I t~ t~
.
~ ^ ~ ~ ~ ,0~ 0 0 0 0 0
~ ~ ~0~ 0~ 0~ 0~ 0~
.~ ~ ;~ ~ o ~
O ~ _ -S ~ -S ~, S ~ -S ~, -S ~, S ~
Q ~ ~ ~ cn
E~ ~ ~ ~ ~ ~ ~7
. ,~, _ o o o o o o o o o o
.. .
3 ~ s ~ ~
h ~ ~-- o o o o o o o o o o
q~ ~~r ~r ~r
E~ q NN N ~I N ~ 1 N N N
O~
.
'
131661~
- 15 -
Notes
l: Modified PP (1): maleic anhydride-modified product
(maleic anhydride content; 0.1 % by weight and MI;
48 g/10 min.) of crystalline propylenefethylene
random copolymer (ethylene content; 2.3 % by weight
and MI; 7.6 g/10 min.)
2: Modified PP (2~: blended product (MI; 22 g/10 min.)
of 40 parts by weight of modified PP (l) and 60
parts by weight of crystalline propylene/ethylene
random copolymer (ethylene content; 2.3 % by weight
and MI; 17.6 g/10 min.)
3: Modified PP (3): maleic anhydride-modified product
(maleic anhydride content; 0.11 ~ by weight and
MI; 51 g/10 min.) of crystalline propylene/butene-1
copolymer (butene-1 content; 6.7 % by weight and
MI; 3.8 g/10 min.)
4: LDPE: low density polyethylene (density; 0.927
g/cm3 and MI; 7.1 g/10 min.)
5: LLDPE: linear low density polyethylene (density;
0.925 g/cm3 and MI; 6.8 g/10 min.)
6: EVA: ethylene/vinyl acetate random copolymer
(vinyl acetate content; 6.3 % by weight and MI;
6.7 g/10 min.)
7: EMMA: ethylene/methyl methacrylate random copolymer
(methyl methacrylate content; 9.7 ~ by weight and
MI; 7.0 g/10 min.)
8: MgO (l): "Kyowa Mag" ~ 30; a product of Kyowa
Kagaku Co. (median diameter; 2.7 ~m, iodine
absorption; 35 mg I/g MgO)
9: MgO (2): "Kyowa Mag" ~ 100; a product of Kyowa
Kagaku Co. (median diameter; 2.5 ~m, iodine
absorption; 110 mg I/g MgO)
10: Ca(OH)2: reagent, first class, a product of
Wako Junyaku Co. (median diameter; 2.4 ~m)5 11: Mg(OH)2: reagent, a product of Wako Junyaku Co.
(median diameter; 3.1 ~m)
- 16 - 1316~1~
12: PVCH (1): propylene/vinyl cyclohexane copolymer
(limiting viscosity in tetralin; 1.9 dl/g and
vinyl cyclohexane content; 0.98 % by weight),
prepared according to the procedure disclosed in
Japanese Patent Kokai Nos. 60-139710 and 60-139731.
13: PVCH (2): propylene/ethylene/vinyl cyclohexane
copolymer (limiting viscosity in tetralin; 2.2
dl/g, ethylene content; 3.4 % by weight and vinyl
cyclohexane content; 0.21 % by weight), prepared
according to the similar procedure to PVCH (1).
14: PVCH (3): vinyl cyclohexane homopolymer (limiting
viscosity in carbon tetrachloride; 0.6 dl/g),
prepared by similar procedure to PVCH (1).
15: PP (2): crystalline propylene/ethylene random
copolymer (limiting viscosity in tetralin; 2.3
dl/g and ethylene content; 3.8 ~ by weight)
16: PP (3): propylene homopolymer (limiting viscosity
in tetralin; 1.8 dl/g)
