Note: Descriptions are shown in the official language in which they were submitted.
~ CA 02240670 1998-06-16
Herberts Gesellschaft mit beschrankter Haftung
A coating medium and a process for the coating of plastics substrates in
particular
This invention relates to coating media which are particularly suitable for the lacquer
coating of plastics substrates, such as polyethylene and polypropylene substrates.
They are particularly suitable for the lacquer coating of motor vehicle parts made of
plastics.
Plastics parts are being used increasingly more widely in industry. In order to produce
a good, visually uniform surface, particularly when they are used with parts made of
another material, they are frequently coated with a lacquer. Moreover, the surface is
protected by the coating from environmental effects, which results in a longer service
life of the parts. It is also possible deliberately to influence certain properties by the
coating, e.g. the sliding properties or electrical conductivity of plastics parts.
In order to ensure such properties, firm adhesion of the coating to the substrate is
necessary. Moreover, it has to be ensured that the mechanical properties of the plastics
part are still satisfactory after lacquer coating. However, lacquer coatings on plastics
substrates usually have a negative effect on the mechanical stability of the plastics
part ("Farbe + Lack", No. S, 1988, page 337; "Defazet", No. 2, 1979, page 59).
In order to achieve good adhesion, known primer and wash coats have high solvent
contents. The solids content of these coating media is between 2 and 30 %, for
example.
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JP 57-198763 describes coating media for polyolefine substrates. The binder vehicle
mixture of these coating media consists of 10 to 90 % by weight of a copolymer of
methacrylic acid amides and of unsaturated monomers which can be copolymerised
therewith, and of 90 to 10 % by weight of chlorinated polyolefines. A crosslinking
S agent is not used in this coating composition; the coating dries physically.
JP 56-050971 describes coating media for plastics substrates which consist of a
mixture of an acrylate polymer, a chlorinated polyolefine, and a resin cont~ining more
than two epoxide groups per molecule. The acrylic polymer consists of acrylic
10 monomers which contain basic nitrogen, and of (meth)acrylic ester monomers, as well
as other copolymerisable monomers. Polyethers which contain epoxide groups are
described as the component which contains epoxide groups.
FR-A-2 432 542 describes a two-component coating medium which contains an
15 acrylate resin containing basic nitrogen, and which crosslinks via epoxy resin. These
coating media are employed for the coating of automobile bodies during lacquer
coating for repair purposes.
EP-A-0 513 659 describes a priming process for plastics substrates, in which a coating
20 medium is used which is based on hydroxy-functional polyacrylates (obtained by the
reaction of polyacrylates of (meth)acrylamides, hydroxyalkyl (meth)acrylates andolefinically unsaturated compounds with polyisocyanates), optionally further binder
vehicles (polyesters, polyurethane resins), organic solvents, pigments and/or
extenders, lacquer technology additives, and a crosslinking agent which comprises
25 epoxy resins or polyisocyanates. The (meth)acrylamide monomers may contain tert.-
amino groups. This coating medium can be used as a single-component (lC) or two-component (2C) material. These coatings exhibit good adhesion as well as good cold
impact strength. However, these properties cannot be achieved on what are termedmodified polypropylene-polyethylene plastics substrates. These modified plastics are
30 essentially characterised by a reduction of the elastomeric component which is based
CA 02240670 1998-06-16
on butadiene units, and by a partial reinforcement of the mineral constituent in order
to achieve greater stiffness, a higher free-flowing capacity and a lower thermalexpansion coefficient. Lacquer coating these new plastics materials with the
conventional lacquer systems described above does not achieve the quality of theS lacquer coating of previous plastics. In particular, the cold elasticity is not
satisfactory.
The object of the present invention is to make possible the coating of plastics,particularly polypropylene-polyethylene, and particularly of modified polypropylene-
10 polyethylene plastics parts, whilst avoiding the disadvantages described above. For
these plastics parts in particular, it should be possible to achieve good adhesion with a
high level of flexibility at the same time, without a negative effect on the hardness and
scratch-resistance of the coating, or on the mechanical stability of the plastics parts.
15 This object is achieved by a coating medium based on
A) 5 to 40 % by weight of a binder vehicle which contains OH groups, which
comprises tert.-amino groups and/or amino groups substituted by a tert.-alkyl
group, and which is obtainable by the reaction of one or more copolymers of
one or more (meth)acrylic esters and/or (meth)acrylamides which comprise a
tert.-amino group or an amino group substituted by a tert.-alkyl group, one or
more hydroxyalkyl (meth)acrylates and one or more copolymerisable
olefinically unsaturated compounds which are different therefrom, wherein the
copolymers have a number average molecular weight (Mn) of 1500 to 10,000
and a glass transition temperature of -20 to +75~C, with polyisocyanates,
B) 1 to 20 % by weight of the reaction products of aromatic diglycidyl ethers with
dimerised fatty acids as crosslinking agents,
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C) 0 to 30 % by weight of one or more further binder vehicles which are different
from A),
D) 30 to 70 % by weight of one or more organic solvents,
s
E) 15 to 45 % by weight of pigments and/or extenders and
F) 0 to 15 % by weight of customary lacquer technology additives.
10 The expression " (meth)acrylic" which is used here denotes methacrylic andlor acrylic
in each case.
The coating medium exists as a two-component (2C) system, wherein one component
contains (meth)acrylic copolymers A) and optionally other binder vehicles, and the
1 j other component contains reaction products B) of diglycidyl ethers with fatty acids,
and also optionally contains other binder vehicles. Both components may contain the
additives, solvents and/or pigments/extenders, completely or in part.
The invention also relates to a process for the coating of substrates, in which the
20 coating medium according to the invention is used. In the process according to the
invention, the coating medium is applied to the substrate and is then dried and
crosslinked at room temperature or at elevated temperature. For the crosslinkingprocess, which, without being bound to any theory, proceeds via an anionic reaction
mech~ni~m, hardener component B) is incorporated in the binder vehicle matrix. This
25 surprisingly results in a coating, the elasticity of which is considerably improved.
Other coating layers, e.g. primer surfacers, or base- and/or covering lacquers, may
also optionally be applied to the primer coat which is obtained in this manner.
Application may also be effected wet-into-wet, after which the coats are then
hardened jointly.
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The copolymers used for the production of component A) are preferably synthesised
from the following monomers:
a) S to 40 % by weight of one or more (meth)acrylic esters and/or
S (meth)acrylamides which comprise a tert.-amino group or an amino group
which is substituted by a tert.-alkyl group,
b) S to 30 % by weight of one or more hydroxyalkyl (meth)acrylates, and
10 c) 20 to 80 % by weight one or more copolymerisable olefinically unsaturated
compounds.
Polymerisation is preferably conducted as a solution polymerisation process, forexample at temperatures between 60 and 180~C, preferably at 80~ to 140~C. The
15 polymerisation reaction can be initiated by using known polymerisation initiators.
Examples of suitable initiators include per- or azo compounds. Chain transfer agents
can also be used. Examples of suitable solvents include those which can also be used
later in the finished coating medium, and which are described below.
20 The polymerisation conditions (temperature, solvent concentration, metered addition
of monomers) are selected so that the number average molecular weight (Mn) is
between 1500 and 10,000. The copolymers have a glass transition temperature of
-20~C to +75~C.
25 80 to 98 % by weight of the copolymers obtained as above are preferably modified
with 2 to 20 % by weight of polyisocyanates which comprise one or more uncapped
isocyanate groups, or which optionally also comprise capped isocyanate groups, and
which react with part of the OH groups of the copolymer. The procedure is such that
the binder vehicle obtained has an OH number of 20 to 120, preferably 30 to 80. The
30 acrylate resins obtained can also subsequently be modified via the OH groups. It is
CA 02240670 1998-06-16
also possible optionally to react the OH groups of the monomer, for modification,
before polymerisation takes place.
Particular examples of (meth)acrylic esters and (meth)acrylamides of component a)
S include alkyl (meth)acrylates and alkyl (meth)acrylamides comprising, for example, 1
to 18, e.g. 2 to 6 C atoms in their alkyl radical, wherein the alkyl radical bears
(preferably in a terminal position) an N,N-disubstituted amino group, e.g. an N,N-
dialkylamino group with 1, 2, 3 or 4 C atoms, for example, in the alkyl groups, which
may be the same or different, or a tert.-alkylamino group, wherein the tert.-alkyl
10 radical comprises 4 to 6 C atoms, for example, and in particular is a t-butyl radical.
These monomers may be present on their own or in admixture. For example, those
comprising N,N-dialkylamino groups can be used in admixture with those comprising
a tert.-alkylamino group.
15 Particular examples of the aforementioned monomers include (meth)acrylamide
monomers and (meth)acrylate monomers which comprise tert.-amino groups and
which are based on (meth)acrylic acid and omega-tert.-aminoalkylamines or omega-tert.-amino alcohols, for example N-(N,N-diethylaminopropyl)-(meth)acrylamide and
N-(N,N-dimethylaminoneopentyl)-(meth)acrylamide, N,N-dimethylaminoethyl
20 (meth)acrylate or N,N-dimethylaminopropyl (meth)acrylate, particularly the
corresponding methacrylamides or methacrylates. 2-tert.-butylaminoethyl
(meth)acrylate, particularly the methacrylate, is an example of a monomer which
contains a tert.-alkylamino group.
25 Comonomers of component b) which can be used for the copolymers of component
A) are copolymerisable monomers which are different from the monomers of
component a) and from the hydroxyalkyl (meth)acrylates of component b), e.g.
aromatic vinyl compounds such as styrene, (meth)acrylic esters such as methyl, ethyl,
n-butyl-, isobutyl- or tert.-butyl acrylates or methacrylates, vinyl esters such as vinyl
30 acetate, or alkyl esters of unsaturated polycarboxylic acids.
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The hydroxyalkyl (meth)acrylates of component b) which are preferably used are
those which comprise an alkyl radical cont~ining 2 to 6 C atoms. Examples include
hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl
(meth)acrylate or 6-hydroxyhexyl (meth)acrylate. These monomers may optionally be
reacted at their OH group before polymerisation. For example, compounds which
contain reactive epoxide groups or reactive isocyanate groups can be reacted with
these OH-functional monomers.
10 E~amples of polyisocyanates which are used for the synthesis of component A)
include those which, at least in part, contain uncapped isocyanate groups which react
with the OH groups of the copolymer. In addition, they may also contain capped
isocyanate groups. The customary acidic CH, NH or OH compounds which are
known from the literature can be used as capping agents. The reaction with the
15 polyisocyanate is advantageously conducted so that the equivalent ratio of reactive
hydroxyl groups of the copolymer to the partially capped and uncapped isocyanategroups of the polyisocyanate varies from 99: 1 to 70: 3, preferably from 95: 5 to 85
: 15. Polyisocyanates which only contain one free isocyanate group per molecule are
preferably used. The reaction products of copolymers and polyisocyanates, as
20 described in EP-A-0- 260 456 for example, can also be used.
According to the invention, the reaction products which are formed by the reaction of
aromatic glycidyl ethers with dimerised fatty acids are used as hardener component
B). The numerical ratio of the glycidyl groups of the diglycidyl ethers used to the
25 carboxyl groups of the dimerised fatty acids ranges from 1: 0.8 to 1: 0.2, preferably
from 1: 0.5 to 1: 0.3.
E~amples of aromatic diglycidyl ethers which can be used include bisphenol A-
epichlorohydrin reaction products (Epikote types) or the reaction products of novolacs
30 ~ith epichlorohydrin which are commercially available. Particular examples include:
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Epikote 828: an aromatic diglycidyl ether with an epoxide equivalent weight of 182 to
198 g/mole (epoxide value 0.52 to 0.55) and a viscosity of 12 to 14 Pa.s at 25~C;
Epikote 1001: an aromatic diglycidyl ether with an epoxide equivalent weight of 470
to 500 g/mole (epoxide value 0.2 to 0.22), a melting point of 50 to 62~C and a
viscosity (40 % in butyl diglycol) of 130 to 160 mPa.s at 25~C.
Further examples include mixtures of aromatic diglycidyl ethers with an average
epoxide equivalent weight of 180 to 2000 g/mole.
10 Other examples of aromatic diglycidyl ethers which can be used include those which
are known from the literature, e.g. those which are described in Houben-Weyl,
"Methoden der organischen Chemie", 4th Edition, page 462 et seq.. Bisphenol A
diglycidyl ethers can preferably be used.
lS Examples of dimeric fatty acids include the dimerisation products, which are known
from the literature, of unsaturated, preferably linear fatty acids, for example those
comprising 16 to 18 C atoms. These can be prepared, for example, by the
polymerisation (Diels-Alder reaction) of isolene fatty acids, which are linear. Pure
dimeric fatty acids with a content of trimer less than S % are preferred. Examples of
dimerised fatty acids which can be used are described in the literature, e.g. by E.
Gulinsky, "Pfl~n~liche and tierische Fette and Ole", page 82 et seq. The preferred
examples of dimeric fatty acids which can be used are the commercial products ofUNICHEMA Int., which comprise dimeric faKy acids with a dimer content of at least
90 %. One particular example is PRIPOL 1009: this is a dimeric fatt~v acid containing
about 98 % dimeric, about 1 % trimeric and about 0.1 % monomeric fatty acid, andwhich has an acid number of 191 - 198 mg KOH/g and a saponification number of
196 - 200 mg KOH/g.
The reaction products of diglycidyl ethers and dimeric fatty acids which can be used
according to the invention can be produced by customary methods. Reaction of the
CA 02240670 1998-06-16
oxirane groups with the carboxyl groups is preferably effected at temperatures of 80~
to 180~C, most preferably at 130~ to 160~C.
The reaction products can be incorporated in the coating media according to the
invention, after thinning with an organic solvent to a solids content of 60 to 80 %,
preferably 70 to 75 %, for example.
Together with the binder vehicles described above (component A) and the reactionproducts (component B), up to 30 % by weight of further binder vehicles (component
10 C) may be added. These may be based on film-forrning resins which are different
from component A); for example, they may be based on customary film-forming
polyester resins, polyurethane resins, polyurea resins, phenolic resins or polyether -
binder vehicles. By using these additional binder vehicles, it is possible deliberately to
influence the properties of the film, for example to control the chemical stability,
15 viscosity and flow properties. Exarnples of known binder vehicles are described in
DE-A-34 21 122 and EP-A-0 393 609. The arnount of these binder vehicles may be
up to 30 % by weight with respect to the solids content of the binder vehicle
according to the invention and of the crosslinking agents.
20 Linear or branched hydroxy- or carboxy-functional saturated polyesters or
polyurethanes are other exarnples of binder vehicles of component C). These may
optionally also be OH-functional.
The molecular weight (Mn) may be 500 to 5000, the acid number may be 5 to 30 and25 the OH number may be 40 to 160, for example. The polyesters are produced by the
reaction of di- or tricarboxylic acids with di- or polyols. The binder vehicles may be
reacted, via reactive groups, with di- or polyisocyanates. This results in polymers
which contain urethane groups, and which have somewhat lower functionalities andhigher molecular weights. Polyurethane resins are produced, for example, by the
30 reaction of polyethers with di- or polyisocyanates (e.g. DE-A-34 21 122, EP-A-0 393
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609). Other known binder vehicles, for example OH-functional polyesters or
polyurethanes, can also be added. Moreover, known crosslinking agents can be used
in addition, such as melamine resins, urea resins or benzogl-~n~mine resins, e.g. those
which are described in EP-A-0 245 786. These serve for the crosslinking of the
5 additional binder vehicle components.
The degree of branching, the functionality or the viscosity of the coating mediaaccording to the invention can be influenced by the choice of additional binder vehicle
components, for example.
Customary lacquer solvents are suitable as solvents. The viscosity can be influenced
via their dissolving power for the binder vehicle. The physical drying of the lacquer
surface can be influenced by the boiling point of the solvent. High-boiling solvents
keep the lacquer film liquid for a long time and thus enable good flow to be achieved.
15 The solvent content should be as low as possible, for reasons of environmental
protection. Examples of solvents include ketones, alcohols, glycols, ethers, linear,
branched, cyclic, aliphatic or aromatic hydrocarbons, and also mixtures thereof.
The pigments or extenders which can be used are pigments and extenders such as
20 those which are customary in the lacquer industry. Examples include colouréd or
achromatic organic- or inorganic-based pigments, e.g. titanium dioxide, carbon black
or iron oxides, organic- or inorganic-based extenders, e.g. french chalk, aluminium,
silicates, organic crosslinked microparticles, anti-corrosion pigments, transparent or
microdispersed pigments e.g. pyrogenic hydrated silica, conductivity pigments or25 solid catalysts. The pigments are preferably dispersed and then comminuted so that
their particle size is very small and a smooth surface on the coating film is made
possible.
E~camples of additives which can be used include customary lacquer additives such as
30 flow enhancers, anti-foaming agents, anti-crater agents, catalysts, wetting agents and
CA 02240670 1998-06-16
bonding agents; these are preferably used in amounts of 0.1 to 15 % by weight. These
additives are known and can be selected depending on the properties to be influenced.
The bonding agents which can also be used serve to ensure that the coating film
adheres to the substrate. The bonding agents can be specially matched to the substrate
5 so that the adhesion is significantly improved. Examples of bonding agents include
chlorinated polyolefine (CPOs). The amount thereof which is used can be 0.1 to 15 %
by weight, preferably 0.5 to 7.5 % by weight. CPOs are commercially available and
mostly exist dissolved in organic solvents. Examples of CPOs include polyethylene or
polypropylene polymers with a degree of chlorination of 10 to 40 % by weight
1 0 chlorine.
The solids content of the coating medium according to the invention is generally 20 to
70 % by weight. It depends on the type of application and on the viscosity which is
thereby required. In stored form, the solids content may be higher, and is first adjusted
15 with solvent before the application of the coating medium.
The coating media can be produced from the binder vehicles, pigments and additives
by known methods. The binder vehicles, including parts of the additives, solvents and
pigments/extenders for e~ample, forrn one component, and the hardener, which also
20 includes parts of the additives, solvents and pigments/extenders for example, forms
the second component. Shortly before application, the two components are mixed in
the desired mixture ratio and the ready-to-apply lacquer is produced. Drying and the
crosslinking reaction can take place either at room temperature or at elevated
temperature.
The coating media according to the invention can be used as primers, as primer
surfacers and as coating media in the interior space of automobiles, for example.
The usual plastics substrates are suitable as substrates, for exarnple those based on
30 resins such as phenol-formaldehyde-resins, polyurethane resins or polyurea resins,
CA 02240670 1998-06-16
polyolefines, polyesters, PVC, polyamides, polycarbonates and the like. Substrates
based on polyamide or polyolefine are preferred; substrates based on polypropylene or
polyethylene, particularly what is termed modified polypropylene-polyethylene with a
small proportion of elastomeric components, are particularly preferred. Apart from the
usual plastics substrates, however, other surfaces can also be coated, e.g. metal
surfaces.
The substrates may be flexible, i.e. they may be deformable, either elastically or with
subsequent flow, within certain limits when subjected to damage by impact.
The substrates are prepared for lacquer coating by customary methods. These include
the removal of burrs and defects by rubbing down, washing with solvents, and
o~idative pretreatment, for example.
15 Application of the coating media according to the invention is effected in the usual
manner (e.g. by spraying, roller application, dipping), and is jointly determined by the
geometry of the substrate. Newer methods of application can also be used, such as the
Unicarb process (supercritical CO2), the HVLP process (high-volume-low-pressure
process), the airless spraying process, and the ESTA process (electrostatic). The
20 viscosity of the coating medium is adjusted depending on the requirements. After
application and crosslinking, further coats of coating films can be applied.
The dry film thickness is generally 5 to 50 llm (depending on the purpose of use). 10
to 25 ~lm are preferred. The drying and crosslinking conditions vary within wide25 limits between 15 to 120~C. Temperatures of 20~ to 80~C are particularly suitab-le.
If different plastics substrates have different resistances to heat, the coating medium
can be selected depending on the drying or crosslinking temperatures to be used.
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A homogeneous surface is obtained on substrates of different types when employing
the procedure according to the invention. The invention is therefore particularly well
suited to the production of further lacquer films thereon. Good adhesion and good
elasticity are achieved, particularly in the cold also, especially for modified
S polypropylene/polyethylene plastics substrates which are deemed to be difficult to
coat, and the requisite hardness and scratch-resistance are achieved. Plastics parts
which are coated in this manner exhibit good resistance to heat. The coating media
can be used in the automobile industry and for other purposes also. Since the coating
media can be dried or crosslinked at different temperatures it is possible to match this
10 temperature to the respective substrate. The dimensional accuracy and structure of the
plastics substrates are thus ensured.
The following examples serve to explain the invention. Parts (pts.) and percentages
(%) are each given by weight.
E~ample 1
Preparation of component A:
20 200 g xylene were placed in a 2 litre flask fitted with a stirrer, thermometer, condenser
and two dropping funnels and were heated to 100~C with stirring. A mixture of
monomers comprising isobutyl acrylate (70 pts.), 2-ethylhexyl acrylate (101.5 pts.),
methyl methacrylate (143.4 pts.), 2-hydroxypropyl methacrylate (45.9 pts.) and
dimethylaminopropylmethacrylamide (79.7 pts.) was added drop-wise over 5 hours,
25 simultaneously with an initiator solution comprising xylene (35 pts.) and 2,2'-
azobis(2-methylbutyronitrile) (2.8 pts.); the temperature was accurately maintained at
100~C. After this drop-wise addition, an initiator solution comprising xylene (27 pts.)
and 2,2'-azobis(2-methylbutyronitrile) (1.2 pts.) was added over 70 minutes at 100~C.
After this addition was complete, the dropping funnels were rinsed with xylene (93
30 pts.); thereafter the batch was polymerised for 3 hours. The conversion was then about
CA 02240670 1998-06-16
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98 %. The (meth)acrylic copolymer was then diluted with xylene (146.7 pts.) and
cooled to 60~C. 33.8 pts. of a partially capped polyisocyanate were added; this was
prepared by the reaction of 564 parts of the trimer of hexamethylene diisocyanate with
196 pts. caprolactam in a mixture comprising 150 pts. xylene and 90 pts.
5 methoxypropyl acetate. The reaction of the partially capped polyisocyanate with the
(meth)acrylic copolymer which contained OH groups was conducted at 60~C. After areaction time of 2 hours, the binder vehicle obtained was practically free from NCO.
It was subsequently diluted with xylene (20 pts.) to a solids content of 45 %.
10 Preparation of component B:
Example 2
128 pts. xylene, 800 pts. Epikote~ 828 (bisphenol A-epichlorohydrin reaction product;
a commercial product supplied by Shell), 360 pts. Pripol 1009 (a dimeric fatty acid; a
commercial product supplied by Unichema) and 0.65 pts. triphenyl phosphite were
weighed into a 2 litre, three-necked flask with a standard taper-ground joint, which
was fitted with stirrer, contact thermometer, bulb condenser and separator, and were
heated to 150~C. The batch was m~int~ined at this temperature until an acid number
20 of 11.3 mg KOH/g was obtained. This corresponded to an epoxy equivalent weight of
about 430 g. The batch was subsequently cooled to 130~C and was diluted with
257.25 pts. xylene. The resin solution had a solids content of 75.7 % and a viscosity
of 2600 mPa.s/25~C.
25 Example 3
128 pts. xylene, 720 pts. Epikote 828 and 80 pts. Epikote 1001 (a cornmercial product
supplied by Shell), 360 pts. Pripol 1009 (a commercial product supplied by
Unichema) and 0.65 pts. triphenyl phosphite were weighed into a 2 litre, three-necked
30 flask with a standard taper-ground joint, which was fitted with stirrer, contact
CA 02240670 1998-06-16
- 15-
thermometer, bulb condenser and separator, and were heated to 150~C. The batch was
maintained at this temperature until an acid number of 11.4 mg KOH/g was obtained.
This corresponded to an epoxy equivalent weight of about 470 g. The batch was
subsequently cooled to 130~C and was diluted with 257.25 pts. xylene. The resin
solution had a solids content of 70.3 % and a viscosity of 5060 mPa.s/25~C.
E~ample 4
134 pts. xylene, 800 pts. Epikote 828 (a commercial product supplied by Shell), 410
10 pts. Pripol 1009 (a commercial product supplied by Unichema) and 0.68 pts. triphenyl
phosphite were weighed into a 2 litre, three-necked flask with a standard taper-ground
joint, which was fitted with a stirrer, contact thermometer, bulb condenser and
separator, and were heated to 150~C. The batch was maintained at this temperature
until an acid number of 12.2 mg KOH/g was obtained. This corresponded to an epoxy
15 equivalent weight of about 480 g. The batch was subsequently cooled to 130~C and
was diluted with 268.32 pts. xylene. The resin solution had a solids content of 70.0 %
and a viscosity of 5080 mPa.sl25~C.
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Production of the primer
Example 5
50 pts. of the copolymer (component A) from example 1 were mixed and
homogeneously comminuted with 27 pts. titanium dioxide, 0.7 pts. finely dispersed
hydrated silica, 0.05 pts. carbon black, l l pts. aluminium magnesium silicate and 4.5
pts. xylene. 21 pts. of a commercially available CPO solution (about 20 % chlorinated
polyolefine) were then added and the batch was adjusted to a solids content of 45 %
10 with a further 33.4 pts. xylene. 4 pts. of the epoxy ester (component B) from example
2 were added thereto and homogenised well. This primer was adjusted to its
processing consistency with xylene/n-butyl acetate, was sprayed on to the substrate
(modified polypropylene) and was crosslinked at elevated temperature.
15 Example 6
40 pts. of the copolymer (component A) from example 1 were mixed and
homogeneously comminuted with 15 pts. titanium dioxide, 0.3 pts. finely dispersed
hydrated silica, 0.8 pts. carbon black, 10 pts. aluminium magnesium silicate and 3.3
20 pts. xylene. The batch was adjusted to a solids content of 40 % with a further 49 6 pts.
xylene. 10 pts. of the epoxy ester (component B) from example 2 were added thereto
and homogenised well. After adjusting to its processing consistency with xylene/n-
butyl acetate, the primer was sprayed on to modified polypropylene which had a
sufficiently high free surface energy (e.g. as obtained by flame- or plasma treatment)
25 and was crosslinked at elevated temperature.
CA 02240670 1998-06-16
Comparative test 1
25 pts. of the acrylic resin (copolymer) (45 % in butyl acetate) were homogeneously
mixed with 13 pts. titanium dioxide, 0.3 pts. finely dispersed hydrated silica, 0.02 pts.
carbon black and 6 pts. aluminium magnesium silicate, adjusted to a suitable viscosity
with xylene and comminuted. 15 pts. of a commercially available CPO solution were
then added and the batch was adjusted to a solids content of about 45 % with further
xylene. 7 pts. of a commercially available polyepoxide resin (Mn about 400) werethen added thereto as a 50 % solution in butyl acetate, and the batch was homogenised
10 well. After adjusting to the processing viscosity, the primer was sprayed on to
modified polypropylene and was crosslinked at elevated temperature.
Comparative test 2
15 25 pts. of the acrylic resin (copolymer) (45 % in butyl acetate) were homogeneously
mixed with 13 pts. titanium dioxide, 0.3 pts. finely dispersed hydrated silica, 0.02 pts.
carbon black and 6 pts. aluminium magnesium silicate, adjusted to a suitable viscosity
with xylene, comminuted, and adjusted to a solids content of about 42 % with further
xylene. 7 pts. of a commercially available polyepoxide resin (Mn about 400) were20 then added thereto as a S0 % solution in butyl acetate, and the batch was homogenised
well. After adjusting to the processing viscosity, the primer was sprayed on to
modified polypropylene and was crosslinked at elevated temperature.
The lacquers of examples 5 and 6 and of comparative tests 1 and 2 above were applied
25 to 10 x 15 cm modified polypropylene panels with a thickness of 4 mm. The panels had
previously been washed with a solution comprising deionised water and S0 %
isopropanol and had been dried for 10 minutes at 25~C. The polypropylene panels for
lacquer example 6 and for comparative test 2 had subsequently been flame-treated. The
primer according to the invention was applied by spraying, and after a ventilation period
CA 02240670 1998-06-16
-18-
of S minutes was dried for 20 minutes at 80~C. The coat thicknesses obtained were 20
llm to 2 j ~Lm.
The specimens were subsequently over-sprayed with a commercially available 2C
5 polyurethane covering lacquer, and were thereafter ventilated for 5 minutes and dried
again for 45 minutes at 80~C. The covering lacquer coat thickness was 35 ~m.
The panels obtained were subjected to a puncture impact test according to DIN 53 443
at -25~C, wherein the total energy absorbed (Etot) was evaluated as a criterion. The
10 results obtained are listed in the following Table, which shows the outstanding cold
impact strength of the substrates which were coated according to the invention.
Primer coat thickness Total energy absorbed
(Etot)
Example 5 20 llm 80 - 100 %
Example 6 25 !lm 80 - 100 %
Comparative test 1 20 ~m 40 - 60 %
Comparativetest2 20 ~m 40 - 60 %
Unlacquered substrate 100 %
