Note: Descriptions are shown in the official language in which they were submitted.
1068845
1 BACKGR~UND OF THE INV~NTION
1. Field of the Invention
This invention relates to an adhesive composition
comprising polyolefins containing carbonyl groups and calcium
chloride and/or magnesium chloride which provides improved
waterproof and chemical-resistant adhesion between a metal and
a polyolefin.
2. Descri~ _ on of the Prior Art
It has been a wide practice, as one method of preventing
the corrosion of metals, to coat the surface of the metals with
resins. Polyolefin resins such as polyethylene or polypropylene
~` and polyvinyl chloride, for example, have been used for this
purpose. From the standpoint of resistance to brittleness at
low temperatures and food sanitation, a coating of polyethylene
has especially been desired in many types of industries.
. However, since polyethylene is non-polar, it is difficul'c
to adhere polyethylene directly to a metal. Therefore, the
adhesion of polyethylene to a metal has been increased by
subjecting the polyethylene to a corona discharge treatment or
by using an adhesive. As adhesives for adhering polyolefins to
metals, ethylene copolymers containing polar groups (e.g., ethylene/
vinyl acetate copolymers and polyethylene containing chloro-
sulfonic acid groups) are widely used.
These adhesives are superior in adhering polyolefins to
metals, but almost all of them have defects in waterproof
adhesiveness. When a metal is completely coated with a resin,
the waterproofness of the adhesive scarcely poses a problem
because the adhesive does not come into contact with water unless
the resin coating breaks. However, in actual use of the coated
metal, frequently the coated resin breaks and the base metal is
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1068845
1 e~posed because of pinholes formed during the production of the
resin, due to cutting, welding and thread-cutting operations
conducted during the processing of the coated metals, or as a
result of impact after processing. When the waterproof adhesive-
ness of the adhesive is poor, the coated resin peels off within
short periods of time, and the corrosion protection of the metal
is destroyed.
Chlorosulfonated polyethylene is now in use as a
feasible waterproof adhesive for adhering polyolefins to metals.
However, this adhesive has the defect that because of its poor
heat stability, the temperature range at which it can be utilized
is very narrow, and the handling of the adhesive is difficult.
Further, since the synthesis of this adhesive requires complicated
procedures, it is higher in cost than other adhesives of a similar
nature Some polyolefins containing polar groups exhibit equal
or superior salt water-resistant adhesiveness to chlorosulfonated
polyethylene, but a polyolefin containing polar groups which
excels chlorosulfonated polyethylene both in salt water-
resistant adhesiveness and salt crock-resistant adhesiveness has
20 never been obtained.
In an attempt to improve the salt crock-resistant and
` salt water-resistant adhesive properties of ethylene copolymers
`~ containing a polar group, organic and inorganic additives have
been extensively studied, and consequently it has now been found
that only calcium chloride and magnesium chloride unexpectedly
provide striking effects. Accordingly, this invention provides
an adhesive composition comprising (1) a polyolefin having therein
at least one repeating unit containing a carbonyl group and
(2) at least one of calcium chloride, magnesium chloride or a
30 mixture thereof.
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~068845
1 DETAILED DESCRIPTION OF THE INVENTION
Various organic and inorganic compounds have in fact
been used heretofore in the art to improve the waterproof
adhesiveness of adhesives, but calcium chloride and magnesium
chloride, partly because of their deliquescent nature, have never
been used as additives for improving the waterproof adhesiveness
of adhesive compositions. Calcium and magnesium compounds other
t~an the chlorldes do not exhibit any effect in improving the
salt water-resistant and salt crock~resistant adhesive properties
of polyolefins containing carbonyl groups.
It wàs quite unexpected that the chemical (e.g., hydro-
chlor;c acid, sodium hydroxide~-resistant adhesiveness of poly-
olefins containing carbonyl groups can be improved by adding
calcium chloride and/or magnesium chloride to a polyolefin con-
taining carbonyl groups.
Polyolefins containing carbonyl groups which can be
used in this invention can be any of those which are adhesive
to metals or glass, and specific examples include (1) polyolefins
- (e.g., high density-, medium density-, low density-polyethylene,
polypropylene, or a block or rubbery copolymer of ethylene and ~ -
propylene) modified with an acid anhydride ~e.g., maleic anhydride)
and ~2) bi- or multi-component copolymers of ethylene and ethyleni-
cally unsaturated monomers containing a carbonyl group, and the
saponified products thereof.
Examples of suitable ethylenically unsaturated monomers
include vinyl esters containing 2 to 6 carbon atoms in the
saturated carboxylic acid component~ (e.g., vinyl acetate, and
vinyl propionate): vinyl benzoate; acrylate or methacrylates
containing 1 to 18 carbon atoms in the saturated alcohol component
~e.g., methyl-, ethyl-, propyl-, butyl-, 2-ethylhexyl-, cyolohexyl-,
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1068845
1 dodecyl- and octadecyl-acrylate or methacrylate); maleic anhydridei
mono- and di-maleatcs containing 1 to 18 carbon atoms in the
saturated alcohol components (e.g., mono- or di-methyl, ethyl,
butyl, cyclohexyl, 2-ethylhexyl, dodecyl, and octadecyl maleate);
N-vinyl lactams ~e.g., N-vinyl pyrrolidone and N-vinyl caprolactam);
acrylamide compounds; secondary vinyl carboxylic acid amides;
N-vinyl-N-alkylcarboxylic acid amides; and unsaturated glycidyl
monomers ~e.g., ~lycidyl methacrylate~.
The polyolefin containing carbonyl groups can be used
10 either individually or as a mixture thereof. Other synthetic
resins or rubbery materials can be added to the polyolefins so
long as the additional components do not impair the adhesive
effects of the polyolefins. Also, other additives such as a heat
~ stabilizer, a fire retarding agent, a filler, a colouring agent
; ~pigment), a dispersing agent, an antistatic agent, a rustproofing `
agent, a lubricating agent, or a processing adjuvant can also be
incorporated into the polyolefin contàining carbonyl groups in
amounts which do not impair the effect of the present invention.
The adhesive composition of this invention can be
20 applied to various kinds of metals, such as steel, stainless
steel, zinc-coated iron, tin-plated iron, pig iron, cOpper, brass,
` aluminum, electrolytically oxidized aluminum, and other
conventional metal materials in suitable forms, such as sheets
or tubes.
Polyolefins as coating materials to which the adhesive
`' composition of this invention is to be applied include high
density, mediu~ density and low density polyethylene, poly-
propylene, a block or rubbery copolymer of ethylene and propylene,
a copolymer of ethylene and butene-l, a ternary ethylene-propylene-
30 diene rubbery copolymer, and copolymers composed of ethylene or -
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1068845
1 propylene units as main units and units derived from a vinyl
compound such as vinyl acetate, an acrylic acid ester and vinyl
chloride. These polyolefins can be used either individually or
as a mixture thereof. Mixtures of polyolefins with other
synthetic resins or rubbery materials can also be used in this
invention
Additives such as a heat stabilizer, a fire retarding
agent, a filler, a colouring material (pigment), a dispersing
agent, an antistatic agent, a rustproofing agent, a lubricating
10 agent or a processing adjuvant can also be incorporated into the
polyolefin in amounts which do not adversely affect the advantages
of this invention.
Calcium chloride and/or magnesium chloride can be added
to the polyolefin containing carbonyl groups employing known
kneading methods using, for example, a two-roll machine, Bambury
mixer or an extruder. The composition can also be liquefied using
a solvent which dissolves or disperses the polyolefin containing
polar groups. The calcium chloride and/or magnesium chloride
does not necessarily have to be soluble in the solvent, but can
- 20 be suspended in a solution or dispersion of the polyolefin in such
a solvent. The resulting adhesive has been found to also exhibit
the effects achieved on adding the calcium chloride and/or
magnesium chloride.
The calcium chloride and magnesium chloride to be added
to the polyolefin containing carbonyl groups can be used in an
s anhydrous or hydrated form. Specific examples of calcium chlorides
and magnesium chlorides include anhydrous calcium (magnesium)
` chloride, calcium ~magnesium) chloride monohydrate, calcium
(magnesium) chloride dihydrate, calcium (magnesium) chloride
30 hexahydrate and calcium ~magnesium) chloride tetrahydrate. Of
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1 these, anhydxous calcium chloride is most effective. The particle
size of the cal~ium chloride and/or magnesium chloride to be
added is not more than about 1 mm from the standpoint of ease of
kneading and coating operations, but depending upon the thickness
of the adhesive layer, the particle size can be greater than about
1 mm. ~ preferred particle size is not more than 0.5 mm, and a
particularly preferred particle size is 0.0001 to 0.2 mm.
A suitable amount of the calcium chloride and/or
magnesium chloride to be added to the polyolefin containing car-
bonyl groups is about 0.01 to 70~ by weight on the basis of the
`~ total weight of the composition. If the amount is less than
about 0.01% by ~eight, the effect of addition is small, and if
the amount exceeds about 70% by weight, uniform dispersion of the
additive is difficult. Depending on the conditions of use,
amounts outside this range are also feasible. The especially
effective amount of these compounds is 0.1 to 20% by weight, and
most preferably, 0.1 to 10% by weight, based on the total weight
of the composition.
When the adhesive composition of this invention is solid,
~` 20 the composition can be applied to a base metal by pressing or
extrusion coating. ~hen the adhesive composition is in the form
n of a powder, the composition can be applied by electrostatic
coating or by dipping in a fluidized bed. When the adhesi.ve
- composition is liquid, the composition can be applied by spraying,
dipping or brush coating. These coating methods are well known
in the art.
The polyolefin coating can be coated by various known
methods such as pressing, extrusion coating, electrostatic coating,
or dipping in a fluidized bed simultaneously with or after the
30 coating of the adhesive composition of this invention.
Various methods of testing the waterproof adhesiveness
of resin-coated metals are known, but the following salt water-
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~068845
1 resistance testing and the salt crock-resistance testing shown below
were used in th~ present invention. In Example 1 and Comparative
Example 1, a test for chemical resistance was also performed.
The salt water-resistance testing was carried out by
immersing a test piece of a resin-coated metal, in which a slit lead-
ing to the surface of the metal had been made, in a 3% by weight
salt water solution at 60C for 10 days,and evaluating the resistance
in terms of the area of the coated resin which was peeled off.
The salt crock-resistance testing was carried out by
using the same test piece as a cathode and graphite as an anode,
and passing a direct current of 3 V for 10 days through a 3% by
weight salt water solution at room temperature (about 20-30C), and
evaluating the resistance in terms of the area of the coated resin
which was peeled off~
The test for chemical resistance was carried out by
immersing a resin coated steel plate, slit in the same way as for
the test piece used in the salt water-resistance testing, in a
chemical at room temperature for 10 days, and evaluating the
resistance in terms of the area of the coated resin which was -
peeled off,
`i The following Examples and Comparative Examples are given
to illustrate the present invention in greater detail. It should be
understood that the invention is not in any way to be construed as
being limited to these examples. All percents, parts, ratios and -
the like in these examples are by weight unless otherwise indicated.
EXAMPLE 1,
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5 g of anhydrous calcium chloride was mixed with 95 g of -
' a vinyl acetate/ethylene copolymer ~vinyl acetate content: 30 wt%;
melt index (ASTM-1238-57T): 20 g/10 min.), and the mixture was
kneaded using a two-roll machine with the rolls being held
at 50C to form a sheet-like thermofusible adhesive having a -
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10688~5
1 thic~ness of 1 mm. The resulting adhesive was interposed between
a degreased iron sheet and a sheet of low density polyethylene
(density (JIS-K6760-1966): 0.920 g/cm ; melt index (ASTM-1238-57T):
` 7 g/10 min.), and the assembly was heated for 5 minutes at 200C
under a pressure of 50 kg/cm2,
The results of evaluations are shown in Tables 1 and 2.
It is clear from these results that calcium chloride was very
effective for improving the waterproof adhesiveness of the
adhesive.
COMPAR~TIVE EXAMPLE 1
Using a 1 mm-thick sheet-like adhesive of a vinyl
acetate/ethylene copolymer ~vinyl acetate content: 30 wt~; melt
index ~ASTM-1238-57T): 20 g/10 min.) not containing anhydrous
calcium chloride, polyethylene was bonded to an iron sheet in the
same way as in Example 1.
The results of the evaluations made are also shown in
Tables 1 and 2.
EXAMPLE 2
Polyethylene was bonded to an iron sheet in the same
manner as in Example 1 except that a glycidyl methacrylate-
ethylene copolymer ~glycidyl methacrylate content: 12 wt~; melt
index ~ASTM-1238-57T): 2 g/10 min.~ was used instead of the vinyl
acetate/ethylene copolymer used in Example 1.
The results of evaluations made are shown in ~able 1.
It is clear from the results that calcium chloride was very -
effèctive in improving the waterproof adhesiveness of the adhesive.
; COMPARATIVE_EXAMPLE 2
Polyethylene was bonded to an iron sheet in the same
way as in Example 2 using an adhesive of the same composition
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10~884S
1 except that calcium chloride was not added to the adhesive. The
results of the evaluations made are also shown in Table 1.
COMPAR~TIVE EXAMPLE 3
. . _ .
Polyethylene was bonded to an iron sheet in the same
way as in Example 1 using an adhesive of the same composition
except that the same amount of sodium chloride was used instead of
the calcium chloride used in Example 1. The results of the
evaluations made are also shown in Table 1.
COMPARATIVE EX~MPLE 4
Polyethylene was bonded to an iron sheet in the same
way as in Example 1 using an adhesive of the same composition
except that the same amount of calcium hydroxide was used instead
of the calcium chloride used in Example 1. The results of the
evaluations made are also shown in Table 1.
EXAMPLE 3
Polyethylene was bonded to an iron sheet in the same
~a~ as in Example 1 using an adhesive of the same composition
i except that the same amount of magnesium chloride was used instead
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`~ of the calcium chloride used in Example 1. The results of the
evaluations made are also shown in Table 1. It is clear from the
results that magnesium chloride was very effective in improving -
the waterproof adhesiveness of the adhesive.
EXAMPLE 4
The adhesive composition of Example 1 was added to tri~
chloroethylene in an amount of 20% and dissolved therein at 70C.
over the course of 1 hour. The calcium chloride was not dissolved,
but was suspended in the trichloroethylene. The resulting sus-
pension was coated on a degreased iron sheet and dried, and then a
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~68845
1 polyethylene sheet (density (JIS-K6760-1966): 0.920 g/cm ; melt
index (ASTM-1238-57T): 7 g/10 min.) was superimposed thereon. The
assembly was heated for 5 minutes at 200C under a pressure of
50 kg/cm .
The results of the evaluations made are shown in Table 1.
It is clear from the results that calcium chloride was very
effective for improving the waterproof adhesiveness of the
adhesive.
EXAMPI.E 5
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3 g of anhydrous calcium chloride having a particle
diameter of less than 0.2 mm was mixed with 97 g of the same vinyl
acetate/ethylene copolymer as described in Example 1. The mixture
was kneaded and granulated in an extxuder heated at 90 to 110C
to form a thermofusible adhesive in the form of milk-white pellets.
A 0.5 mm-thick sheet was prepared from the pellets, and using the
sheet, polyeth~lene was bonded to an iron sheet in the same way
as in Example 1.
The results of the evaluations made are shown in Table 1.
It is clear that calcium chloride was very effective for improving
the waterproof adhesiveness of the adhesive.
EXAMPLE 6
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3 g of anhydrous calcium chloride having a particle ~ -~
diameter of less than 0.2 mm was mixed with 97 g of an ethylene-
ethyl acrylate copolymer (ethyl acrylate content: 18 wt%; melt
index ~ASTM-1238-57T): 20 g/10 min.). The mixture was kneaded and
granulated using an extruder heated at lS0 to 160C to form a
thermofusible adhesive in the form of milk-white pellets. A 0.5
mm-thick sheet was prepared from the pellets, and polyethylene was
30 bonded to an iron sheet with the adhesive in the same way as in -
Example 1.
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1~68845
1 The results of the evaluations made are shown in Table
1. It is clear that calcium chloride was very effective for
improving the waterproof adhesiveness of the adhesive.
COMPARAT IVE EXAMPLE 5
Polyethylene was bonded to an iron plate in the same way
as in Example 6 using an adhesive of the same composition except
that calcium chloride was not added to the adhesive. The results
; of the evaluations made are also shown in Table 1.
TAELE 1
Waterproof Adhesiveness
Run No. AdditiveSalt Water Test Salt Crock Test
... ~ . . _ _ .. ..
~cm ) ~cm~)
Example 1 CaCQ2 0 0
Comparative
Example 1 ~- 4 36
Example 2 CaC~2 0 0
Comparative
Example 2 -- 49 32
Comparative .
Example 3 NaCQ 64 64
Comparative
Example 4 Ca(OH)2 32 64
Example 3 MgCQ2
Example 4 CaCQ2 0.5
Example 5 CaCQ2 0 0
Example 6 CaCQ2 1 0
Comparative
~ Example 5 -- 50 36
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68845
1 TABLE 2
Chemical Resistance Adhesiveness
. .
Run No. 0.lN HCQ 0.1N NaOH 0.lN NaCQO .
_ __ _ _ _ _ _ 3
(cm2) ~cm ~ ~cm2)
Example 1 0.5 0.5 0-5
Comparative
Example 1 60 8 7
While the invention has been described in detail and
with reference to specific embodiments thereof, it will be
apparent to one skilled in the art that various changes and
modifications can be made therein without departing from the
spirit and scope thereof.
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