Note: Descriptions are shown in the official language in which they were submitted.
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PRIMER COMPOSITION
BACKGROUND OF THE INVENTION
1. Field of the Invention
The presE~nt invention relates to a primer
composition c:apablE~ of providing a satisfactory adhesion
property to a nonadhesible or hard-to-bond material such
as polyolefin and high solid paint (i.e., highly
corrosion-resistant: paint ) .
2. De~~criptpon of the Related Art
Recently,, parts such as automobile parts
heretobefore manufactured from steel materials are being
substituted with rE:sin products for the purpose of
reducing the weight: and cost thereof. Moreover, there
has been increasing the proportion of a highly corrosion-
resistant paint, namely, a so-called high solid paint, as
paints for automobiles, etc.
Those materials having excellent corrosion-
resistant properties, such as resins (e. g., polyolefin)
and high solid paints, generally have poor adhesion
properties, and it is difficult to obtain the good
adhesibility (or adhesion properties) when conventional
primers are used.
For this reason, attempts have been made to
obtain good adhesibility when these hard-to-bond
materials are bonded, by adding various additives to the
primers. For example, Japanese Unexamined Patent
Publication (Kokai) No. 61-152755 proposes a primer
composition contain.i.ng, for example, chlorinated
polyolefin.
However, these proposed primer compositions are
still not sufficient to provide the desired good adhesive
properties to the hard-to-bond materials, and therefore,
there is a need for such a primer composition that can
bond hard-to-:bond materials with good adhesivity.
SUMMARY OF THE INVENTION
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Accordingly, the objects of the present invention
are to solve the above-mentioned problems in the prior
art and to provide a primer composition capable of
providing a sufficient adhesivity even to hard-to-bond
materials such as polyolefins and high solid paints.
Other objects and advantages of the present
invention wiJ_1 be apparent from the following
description.
In accordance with the present invention, there is
provided a primer composition comprising a polyisocyanate
component and a phosphate {or phosphoric acid salt).
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The primer cornposition of the present invention will
now be illustrated in detail below.
The fundamental constitution of the primer
composition according to the invention is the
polyisocyanat.e component and the phosphate.
There are no particular limitations to the
polyisocyanate component usable in the present invention.
Examples of such a polyisocyanate component include
4,4'-diphenylmethane diisocyanate (MDI), tolylene
diisocyanates (TDI), xylene diisocyanates (XDI),
hexamethylene diisocyanate (HMDI), hydrogenated MDI,
hydrogenated TDI, hydrogenated XDI, isophorone
diisocyanate (IPDI), aromatic aliphatic polyisocyanate
(e. g., arylalkyl polyisocyanates), aromatic
polyisocyanates (e. g., aryl polyisocyanates),
triphenylmethane triisocyanates, tris(p-isocyanatophenyl)
thiophosphate, and mixtures thereof obtained by suitably
mixing any above-mentioned compounds.
A combination of MDI, tris(p-isocyanatophenyl)
thiophosphate and aromatic aliphatic isocyanate is
preferably used.
The phosphate (or phosphoric acid salt) usable in
the present invention is not specifically limited, and
various phosphates can be used in the present invention.
Typical examples of the phosphates suitably used in the
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present invention are aluminum phosphate, zinc phosphate
and aluminum dihydrogentripolyphosphate. Aluminum
dihydrogentr_ipolyphosphate is particularly preferably
used in the present invention.
The above-mentioned phosphates may be subjected to
various treai~ments .
Especia_Lly, phosphates surface treated with Si
and/or Zn, particu.larly, aluminum dihydrogentripoly-
phosphate surface 'treated with Si and/or Zn can provide
extremely excellent adhesive properties, and more
preferable results can be obtained therefrom.
Furthermore, phosphates subjected to a dehydrating
treatment arE: preferred in the present invention.
In the primer composition of the present invention,
there is no particular limitation as to the amount ratio
of the phosphate to the polyisocyanate component. The
ratio may be suitably determined according to the types
of the polyi~~ocyanate component and the phosphate. The
phosphate is usual:Ly used in an amount of about 5 to
100 parts by weight., more preferably 30 to 60 parts by
weight, based. on 100 parts by weight of the
polyisocyanat.e component.
When the phosphate is used in the amount as defined
above, based on the polyisocyanate component, the effect
of adding the phosphate can be sufficiently obtained, and
the phosphate can be appropriately dispersed in the
primer composition to provide the good adhesive
properties.
Furthermore, more preferable results for, for
example, the percent: cohesive failure of adhesive can be
obtained by using the phosphate in an amount of 30 to
60 parts by weight, based on 100 parts by weight of the
polyisocyanate companent.
The primer composition of the present invention may
include, if necessary, various solvents, especially
organic solvents.
Any conventional solvents inactive to an isocyanate
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group are usable in the present invention. Typical
examples of t:he solvent usable in the present invention
include ethyl. acetate, methyl ethyl ketone (MEK), acetone
and toluene.
The amount of the solvent added is appropriately
determined according to, for example, the type of the
polyisocyanat:e compound, and is not specifically
restricted. Preferably, the amount is 500 to 1000 parts
by weight, more preferably 600 to 800 parts by weight,
based on 100 parts by weight of the polyisocyanate
component.
Furtherrr~ore, according to the present invention,
various catalysts may be used in combination with the
primer composition..
Examples of the catalyst usable in the present
invention include amine catalysts such as
triethylenediamine, pentamethylenediethylenetriamine,
morpholine type amine and triethylamine, and tin
catalysts such as di-n-octyltin dilaurate, dibutyltin
dilaurate and stannous octoate.
The amount of the catalyst added in the present
invention is preferably determined according to, for
example, the type of. the polyisocyanate compound, and is
not specifically limited. The amount is preferably about
0.1 to 1 part by weight, more preferably 0.2 to 0.5 parts
by weight, based on 100 parts by weight of the
polyisocyanate component.
In the primer composition of the present invention,
there may be used, i.n combination, urethane resin such as
polyester polyurethane resin and polyether polyurethane
resin, polyester resin, and the like to obtain good
working or processing properties. The amount of these
resins added are not specifically restricted, but it is
preferably 10 to 30 parts by weight, based on 100 parts
by weight of the polyisocyanate component.
Furthermore, a dehydrating agent inactive to
isocyanate groups, such as synthetic zeolite may be used
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in combination for securing the stability of the primer
composition.
The primer composition of the present invention can
be prepared by any various known methods for sufficiently
mixing each of the components, for example, by mixing the
components b:~ a ball mill.
The primer composition according to the present
invention may be used in the same manner as conventional
isocyanate based primer compositions. The area or region
to be bonded may b~e coated therewith by spraying, dried
by allowing i:he area to stand for a suitable period of
time, and bonded t:he area by a conventional method.
Examples of adhesives applicable to the primer
composition of the present invention include urethane
adhesives and epoxy adhesives.
Since the primer composition of the present
invention as described above exhibits extremely good
improvement in adhesive properties compared with
conventional primer compositions, it can be extremely
effectively utilized as a primer coating for effectively
bonding between adhesive-resistant materials such as
polyolefins (e.g., polyethylene and polypropylene), and
high solid paints.
EXAMPLE.~~
The present invention will now be further
illustrated fey, but: is by no means limited to, the
following Examples.
Examples 1 - 5 and Comparative Example 1
Various materials listed below were provided to
prepare primer compositions.
PolyisocyanatEa component:
a. MDI
b. tris(p-isocyanatophenyl) thiophosphate
(Desmodur HL, manufactured by Bayer Ltd.)
c. aromatic aliphatic isocyanate (Desmodur
RFE, manufactured by Bayer Ltd.)
The mixture of the above-mentioned isocyanate
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compounds with a molecular ratio of a:b:c being equal to
2:2:6
Solvent: ethyl acetate
Desiccant: synthetic zeolite '
Catalyst: di-n-octyl dilaurate
Urethane resin: Pandex T 5205 (manufactured
by Dainippon Ink K.K.)
Phosphate a: aluminum
dihydrogentr.ipolyphosphate (K-WHITE #845, treated with Si
and Zn, manu:Eactured by Teika Corporation)
Phosphate b: aluminum
dihydrogentr:ipolyphosphate (A1HZP301o ~ 2H20 )
The above-mentioned materials were mixed in ratios
(ratios by weight) listed in Table 1 below to give
various primE~r compositions. The mixing was effected at
room temperai~ure for 48 hours by a ball mill.
Polypropylene containing 40g by weight of glass
fibers and a high ;solid paint for automobiles (with which
a steel sheet, was ~~oated) were bonded together, as
samples to be bonded, by using a primer prepared
mentioned above and a one-pack type urethane adhesive
(WS-100, manufactured by Yokohama Rubber Co., Ltd.).
The bonding was conducted as follows. Namely, both
samples to be bondE~d each having a width of 25 mm and a
thickness of 5 mm were coated with the above-mentioned
primer compoaition,, and after drying, were coated with
the adhesive, followed by bonding together, by
overlapping them air a width of 10 mm, and allowed to
stand at a tE~mperai~ure of 20°C and a relative humidity
(RH) of 55~ for 7 days.
The shear strE:ngth (kgf/cm2) and percent cohesive
failure of adhesive of the bonded samples were measured
by pulling bath samples in the directions reverse to each
other at a rate of 50 mm/min.
The kinds of :samples to be bonded and phosphates
used, and the measured results as to the shear strength
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and percent cohesive failure of adhesive are listed in
Table 1. In addition, the polypropylene and high solid
paint for aut.omobi)_es used as the samples are designated
by "PP" and "Paint", respectively, in Table 1.
Table 1
Example Comparati
ve
No. Example
1 2 3 4 5 1
Polyisocyanate100 100 100 100 100 100
Component
750 750 750 750 750 750
Solvent
100 100 100 100 100 100
Carbon Black
15 15 15 15 15 15
Desiccant
0.3 0.3 0.3 0.3 0.3 0.3
catalyst
15 15 15 15 15 15
Polyurethane
Resin
5 30 60 30 0 0
Phosphate
a
0 0 0 0 30 0
Phosphate
b
Sample PP PP PP Paint PP pp
Shear Strength15 38 30 68 15 11
Ikgf/cm2~
z Cohesive
Failure of 5 50 20 100 10 0
Adhesive
As is clear from the results shown in Table 1, the
hard-to-bond materials such as polypropylene and high
~40 solid paint for automobiles which have heretofore been
incapable of being ;satisfactorily bonded with
conventional primer, can be effectively~bonded together
to exhibit good adhE=sion by the use of the primer
composition according to the present invention.
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The effect of the present invention is clear from
the aforementioned results.
As illustrated in detail above, hard-to-bond
materials such as polyolefins and high solid paint can be
bonded to exhibit adequate adhesion by the use of the
primer composition according to the present invention.
The primer composition of the present invention can
therefore be suitably applied to, for example, the
automobile industry, building industry, electronic and
electric industry.
