U.S. patent application number 09/997089 was filed with the patent office on 2002-08-01 for powder paint binder composition.
This patent application is currently assigned to DSM N.V.. Invention is credited to Belder, Eimbert G., Gehrels, Coenraad M., Koldijk, Fokeltje A., Misev, Tosko A..
Application Number | 20020103329 09/997089 |
Document ID | / |
Family ID | 19764787 |
Filed Date | 2002-08-01 |
United States Patent
Application |
20020103329 |
Kind Code |
A1 |
Koldijk, Fokeltje A. ; et
al. |
August 1, 2002 |
Powder paint binder composition
Abstract
The invention relates to a powder paint binder-composition
comprising a polymer that contains endomethylene tetrahydrophthalic
acid units and a crosslinker. The polymer has been obtained by
preparing an unsaturated polymer in a first step, which then reacts
with cyclopentadiene at a temperature between 160.degree. C. and
220.degree. C. in a second step. The polymer preferably contains
more than 10 wt. % endomethylene tetrahydrophthalic acid units and
is preferably an unsaturated polyester.
Inventors: |
Koldijk, Fokeltje A.;
(Zwolle, NL) ; Belder, Eimbert G.; (Zwolle,
NL) ; Gehrels, Coenraad M.; (Zwolle, NL) ;
Misev, Tosko A.; (Zwolle, NL) |
Correspondence
Address: |
Pillsbury Winthrop LLP
Intellectual Property Group
1600 Tysons Boulevard
McLean
VA
22102
US
|
Assignee: |
DSM N.V.
|
Family ID: |
19764787 |
Appl. No.: |
09/997089 |
Filed: |
November 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09997089 |
Nov 30, 2001 |
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09417844 |
Oct 14, 1999 |
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09417844 |
Oct 14, 1999 |
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PCT/NL98/00202 |
Apr 9, 1998 |
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Current U.S.
Class: |
528/302 ;
428/402; 524/401; 524/81; 525/438; 525/440.04; 525/445; 528/303;
528/306; 528/308.6 |
Current CPC
Class: |
Y10T 428/31794 20150401;
C08L 63/00 20130101; C09D 167/06 20130101; Y10T 428/2982 20150115;
C08L 2666/28 20130101; Y10T 428/31786 20150401; C08G 63/553
20130101; C09D 167/06 20130101; C09D 167/06 20130101 |
Class at
Publication: |
528/302 ;
528/303; 528/306; 528/308.6; 525/438; 525/440; 525/445; 524/81;
524/401; 428/402 |
International
Class: |
B32B 015/02; C08F
020/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 14, 1997 |
NL |
1005809 |
Claims
1. A curable powder paint binder composition comprising a polymer
comprising endomethylene tetrathydrophthalic acid units and a
crosslinker.
2. A composition according to claim 1, characterized in that the
polymer has been obtained by first preparing an unsaturated polymer
which is subsequently reacted with cyclopentadiene at a temperature
between 160.degree. C. and 220.degree. C.
3. A composition according to any one of claims 1-2, characterized
in that the polymer contains at least 10 wt. % endomethylene
tetrathydrophthalic acid units.
4. A composition according to any one of claims 1-3, characterized
in that the polymer is an unsaturated polyester.
5. A composition according to claim 4, characterized in that the
unsaturated polyester is built up of fumaric acid units, maleic
acid units and/or terephthalic acid units and of ethylene glycol
units; polypropylene glycol units and/or neopentyl glycol
units.
6. A composition according to any one of claims 1-5, characterized
in that the crosslinker is triglycidyl isocyanurate or bisphenol-A
epoxy resin.
7. A compositions according to any one of claims 1-6, characterized
in that the endomethylene, tetrahydrophtalic acid units containing
polymer contains virtually no lineair alkyl chains with more than 5
carbon atoms.
8. A powder paint composition comprising a binder composition
according to any one of claims 1-7 and optionally pigment,
catalyst, fillers and additives.
9. A powder coating obtained after curing of a powder paint
composition according to claim 8.
10. Wholly or partly coated substrate, characterized in that as
coating a powder coating according to claim 9 has been used.
Description
[0001] The invention relates to a powder paint binder composition
comprising a polymer that contains endomethylene tetrahydrophthalic
acid (HIMIC) units.
[0002] A powder paint binder composition based on such a polymer is
described in U.S. Pat. No. 3,956,228. This patent discloses the
esterification of a mixture, consisting of 10-50 mol %
endomethylene tetrahydrophthalic acid (HIMIC) and dibasic acids
with a glycol after which curing to yield a coating takes place by
means of air drying. The coatings based on these compositions
exhibit poor mechanical properties such as impact resistance.
[0003] Furthermore these compositions do not result in colorless or
light-colored powder coatings.
[0004] It is an object of the present invention to provide a powder
paint binder composition comprising HIMIC-units which composition
results in powder coatings having a good impact resistance.
[0005] The powder paint binder composition according to the
invention comprises a polymer that contains endomethylene
tetrahydrophthalic acid units and a crosslinker.
[0006] This binder composition has a good storage stability and a
good reactivity and after curing results in a powder coating with a
combination of desirable properties such as, for example, good
flow, hardness, scratch resistance, chemical resistance and
mechanical properties.
[0007] Furthermore, in spite of the presence of HIMIC double bonds
in the curable polymer a light coloured powder coating can be
obtained.
[0008] According to a preferred embodiment of the invention the
acid or hydroxyl functional polymer containing HIMIC units is
obtained by first preparing an unsaturated polymer which is
subsequently reacted with cyclopentadiene (CPD) at a temperature
between about 160.degree. C. to about 220.degree. C.
[0009] Generally, prior art two-step methods for the preparation of
polyesters are difficult to control due to several exothermic
reactions resulting from HIMIC being prepared in the first step
followed by the combination with other monomers in a second step
and subsequent esterification of the polymer. Said exothermic
reactions can lead to high pressures and to high temperatures.
[0010] The two step procedure according to the present invention
provides a safe process.
[0011] According to another preferred embodiment of the invention
the polymer contains at least 10 wt. % HIMIC but less than 100 wt.
% (relative to the monomers), and preferably between about 35 and
about 80 wt. %, as a result of which the good impact resistance is
obtained.
[0012] The HIMIC-units in the polymer can (in contrast to the
HIMIC-units in the polymer according to U.S. Pat. No. 3,956,228)
act as functional acid end groups which can react with the
crosslinkers.
[0013] It is a further advantage that the less reactive, compared
with for example fumaric acid, HIMIC need not be incorporated and
is not obtained until the reaction over the acid groups has taken
place, so that the overall reaction time can be shortened and a
well defined product can be obtained.
[0014] Preferably the unsaturated polymer is an unsaturated
polyester.
[0015] The unsaturated polester prepared in the first step is
generally formulated from one or more aliphatic and/or
cycloaliphatic mono-, di- and/or polyvalent alcohols and one or
more aliphatic, cycloaliphatic and/or aromatic di- or polyvalent
carboxylic acids and/or esters derived therefrom. If desired also
monocarboxylic acids can be applied.
[0016] Examples of suitable alcohols include benzyl alcohol,
ethylene glycol, propylene glycol, neopentyl glycol, butane diol,
hexane diol, dimethylol cyclohexane, diethylene glycol, glycerol,
trimethylolpropane, pentaerythritol, dipentaerythritol, hydrated
bisphenol-A, 2,2-bis-(2-hydroxyethoxy)phenylpropane and/or
2,2-bis-2-hydroxypropoxy phenylpropane. Instead of or in addition
to the alcohol compound(s) one or more epoxy compounds, such as for
example ethylene oxide, propylene oxide and/or allylglycidyl ether
or dicyclopentadiene can be used.
[0017] Examples of suitable di- or polyvalent carboxylic acids
include maleic acid, fumaric acid, itaconic acid, citraconic acid,
malonic acid, succinic acid, glutaric acid, adipic acid, sebacic
acid, 1,4cyclohexane dicarboxylic acid, hexahydrophthalic acid,
hexachloroendomethylene tetrahydrophthalic acid, dichlorophthalic
acid, isophthalic acid, terephthalic acid and/or trimellitic acid
or esters thereof. The carboxylic acid can also be used in the form
of an anhydride, for example tetrahydrophthalic anhydride,
endomethylene tetrahydrophthalic anhydride, hexahydrophthalic
anhydride, maleic anhydride or phthalic anhydride.
[0018] For the acid component fumaric acid in combination with
isophthalic acid and/or terephthalic acid can be used. Optionally,
saturated or unsaturated monocarboxylic acids, such as synthetic
and/or natural fatty acids with 2 to 36 carbon atoms or esters
prepared from these carboxylic acids and polyvalent alcohols such
as glycerol can also be used. Examples of suitable monocarboxylic
acids are lauric acid, stearic acid, oleic acid, linolic acid,
benzoic acid, acrylic acid and/or methacrylic acid.
[0019] According to a preferred embodiment of the invention the
unsaturated polymer is an unsaturated polyester containing fumaric
acid, maleic acid (anhydride) and/or terephthalic acid as acid
units.
[0020] The alcohol component of the unsaturated polyester is
preferably ethylene glycol, propylene glycol and/or neopentyl
glycol.
[0021] The unsaturated polyester may be both crystalline and
amorphous.
[0022] The amount of double bonds in the unsaturated polyester is
usually between about 120 and about 2000 grams per unsaturated
group and preferably between about 125 and about 1500.
[0023] The molecular weight M.sub.n (number average molecular
weigth) of the unsaturated polyester is usually between about 500
and about 6000, preferably between about 1000 and about 4500.
[0024] Acid functional polyesters usually have an acid number
between about 25 mg KOH/grams resin and about 145 mg KOH/grams
resin, preferably an acid number between about 30 mg KOH/grams
resin and about 120 mg KOH/grams resin.
[0025] Hydroxyl-functional polyesters usually have a hydroxyl
number between about 25 mg KOH/grams resin and about 145 mg
KOH/grams resin, preferably a hydroxyl number between about 30 mg
KOH/grams resin and about 120 mg KOH/grams resin.
[0026] The functionality is generally between about 1.5 and about 4
and is preferably between 1.9 and 3.5.
[0027] The polymerization reaction in the preparation of the
unsaturated polyester generally takes place in the presence of
catalysts and inhibitors.
[0028] Suitable catalysts include for example tetrabutyl titanate
and dibutyl tin oxide.
[0029] Suitable inhibitors include for example butyl alcohol and
hydroquinone.
[0030] In the formation of the unsaturated polyester catalysts and
inhibitors are generally used in amounts between about 0.005 and
about 1 wt. % relative to the monomers.
[0031] The preparation of the unsaturated polyester can take place
via a one-step process or via a multistep process.
[0032] If the unsaturated polyester preparation takes place via a
one-step process, glycols, acids, catalysts and optionally
inhibitors can be esterified to the desired acid number or hydroxyl
number at a temperature lower than 220.degree. C. To remove
low-molecular material or to obtain the desired acid number or
hydroxyl number, optionally a vacuum can be applied at reduced
temperature.
[0033] If the unsaturated polyester preparation takes place in two
steps, in the first step saturated acids, glycols, catalysts and
inhibitors can be esterified at temperatures between, for example,
about 210.degree. C. to about 260.degree. C. during for a period of
about 2-10 hours, and in the second step the unsaturated compounds,
acids and glycols can be esterified at temperatures between, for
example, about 180.degree. C. to about 220.degree. C. for a period
of about 5-16 hours. The monomers and the reaction conditions can
be varied depending on the desired properties.
[0034] After the unsaturated polyester has been obtained
dicyclopentadiene (DCPD) is added to the unsaturated polyester at
temperatures between about 160.degree. C. and about 220.degree. C.
resulting in a retro Diels-Alder reaction forming CPD.
[0035] Next the cyclopentadiene (CPD) and the fumaric acid or
maleic acid groups in the unsaturated polyester react by forming
HIMIC units. The amount of DCPD added is generally between 2 and 40
wt. % relative to the total weight of the monomers.
[0036] The functional acid or hydroxyl groups do not react during
this reaction and can at a later stage, in the presence of a
suitable crosslinker, cure to yield a powder coating.
[0037] Preferably the polymer that contains HIMIC units contains
virtually no linear alkyl chains with more than 5 carbon atoms.
This results in a higher glass transition temperature, while the
flow is very good.
[0038] The preparation of thermosetting powder coatings in general
and the chemical curing reactions of powder paints to form cured
coatings are described by Misev in Powder Coatings, Chemistry and
Technology (1991, John Wiley) on pp. 42-54, p. 148 and 224-226 the
complete disclosure of which is incorporated herein by reference. A
thermosetting binder composition is generally defined as the
resinous part of the powder paint comprising a polymer and
crosslinker.
[0039] Depending on the functionality and nature of the polymer,
crosslinkers such as, for example, triglycidyl isocyanurate (TGIC),
blocked isocyanates, amino resins, bisphenol-A epoxy resins,
compounds containing .beta.-hydroxyalkyl amide groups, and
crosslinkers that contain epoxy groups and that have an aliphatic
chain with 5-26 carbon atoms such as epoxidized oils, can be
selected.
[0040] Preferably TGIC and bisphenol-A epoxy resin are used as
crosslinker in the present invention.
[0041] The polymer:crosslinker weight ratio can be adjusted as
necessary depending on the final use of the is powder paint binder
composition. It is also possible to use a mixture of resins. The
ratio between functional polymer groups:functional crosslinker
groups can range, for example, between about 1:0.5 and 1:1.5.
[0042] The powder paint binder composition and the powder paint
system according to the invention can, if desired, include
customary additives such as, for example, pigments, fillers,
degassing agents, flow agents and stabilizers.
[0043] Suitable pigments include without limitation inorganic
pigments, such as for example titanium dioxide, zinc sulphide, iron
oxide and chromium oxide, as well as organic pigments, such as for
example azo compounds. Suitable fillers include, for example, metal
oxides, silicates, carbonates and sulphates.
[0044] Suitable stabilizers, include, for example, of primary
and/or secondary antioxidants, UV stabilizers such as, for example,
quinones, (sterically hindered) phenolic compounds, phosphonites,
phosphites, thioethers and HALS compounds (hindered amine light
stabilizers).
[0045] Suitable degassing agents include for example benzoin and
cyclohexane dimethanol bisbenzoate.
[0046] Suitable flow agents include for example, polyalkyl
acrylates, fluorohydrocarbons and silicon oils. Other suitable
additives include, for example, additives for improvement of the
tribo-electric charging properties, such as sterically hindered
tertiary amines, which are described in EP-B-371528.
[0047] Powder paints according to the invention-can be applied in
the customary manner, for example by electrostatic spraying of the
powder onto an earthed substrate and curing of the coating
by-exposure to heat at a suitable temperature during a sufficiently
long period depending on for example the susbtrate. The powder
applied can, for example, be heated in a gas oven, an electric
furnace or by means of infrared radiation.
[0048] Thermosetting coatings from powder paint (coating)
compositions for use in industrial applications are further
described in a general sense in Powder Coatings, Chemistry and
Technology, Misev, pp. 141-173 (1191), the complete disclosure of
which incoporated herein by reference.
[0049] Compositions according to the present invention can be used
in powder coatings intended for use on metal, wood, paper and
plastic substrates. The preferred susbtrate is metal. Examples are
general-purpose top coats for use in industry, equipment coatings
and for example for cans, domestic and other small equipment. The
coatings are also highly suitable in the automotive industry for
coating of external and/or internal parts.
[0050] The invention will be further demonstrated with reference to
the following, non-limiting examples.
[0051] Experiment I
[0052] Preparation of a HIMIC-containing Polyester
[0053] A 2-liter reactor vessel with thermometer, stirrer and
distillation set-up was filled with 361 g neopentyl glycol, 493 g
terephthalic acid, 0.05 wt. % dibutyltin oxide and 0.10 wt. %
triphenyl phosphite. After this, with a nitrogen stream being
supplied for 8 hours, the temperature was raised to 225.degree. C.
while water was distilled off. After the temperature of the
distilled-off water had dropped to 80.degree. C., the mixture was
cooled to 160.degree. C., after which 88 g fumaric acid and 0.5 g
is t-butyl hydroquinone were added. The temperature was then raised
to 205.degree. C. in 9 hours. At an acid value of 49 mg KOH/g
resin, cooling to 185.degree. C. took place and a vacuum was
applied for 30 minutes.
[0054] Subsequently, the temperature was raised to 200.degree. C.
and 58 g dicyclopentadiene was metered in an hour. The temperature
was then kept at 180.degree. C. for half an hour, after which a
vacuum was applied for half an hour.
[0055] The polyester with 20 wt. % HIMIC was characterized by:
1 acid number: 42 mg KOH/g resin hydroxyl number: 7 mg KOH/g resin
viscosity: 190 dPas (Emila, 165.degree. C.) glass transition
temperature: 60.degree. C. (Mettler, TA3000, 5.degree. C./min.)
[0056] In the following examples the characteristics are determined
as follows:
2 gel time: DIN 5599 Part B 200.degree. C. flow: visually reversed
impact: ASTM-D2794/69 colour: Dr. Lange Cielab DIN 6174 gloss: ASTM
D523/70
EXAMPLE I
[0057] Powder Paint Preparation
[0058] A physical mixture consisting of 140 g polyester according
to Experiment I, 60 g bisphenol A epoxy (Aradite GT7004.TM.), 100 g
titanium dioxide (Kronos 2310.TM.), 3 g Resiflow-PV5.TM.
(polyacrylate flow agent from Worle), 0.4 g triphenyl methyl
phosphoniumbromide and 1.5 g benzoin was first mixed in a premixer
(Prism Premixer Lab 6) and then mixed in an extruder (Prism, TSE 16
PC). The extrudate was cooled, ground and screened, yielding a
powder paint having a particle size of 90.mu.. The powder paint was
then electrostatically applied, in a layer thickness of about
50.mu., on a metal substrate and cured for 10 minutes at
200.degree. C. in an air circulation furnace.
[0059] The properties of the resulting powder paint and powder
coating were as follows:
3 gel time 110 sec flow good reversed impact 160 inchpound colour
L* 96.0, a* -0.3 b* 1.3 gloss 20.degree. 90 gloss 60.degree. 98
[0060] The powder paint binder composition based on the polyester
with 20% HIMIC resulted in a powder coating with good flow
properties and in a light-coloured coating having an excellent
reversed impact resistance, colour and flow.
EXAMPLE II
[0061] Powder Paint Preparation
[0062] A physical mixture consisting of 328 g polyester according
to Experiment I, 21.3 trisglycidylisocyanurate (Aradite PT
810.TM.), 175 g titanium dioxide (Kronos 2310.TM.), 5.25 g
Resiflow-PV5.TM. (polyacrylate flow agent from Worle), 0.1 g
triphenyl methyl phosphoniumbromide and 2.63 g benzoin was first is
mixed in a premixer (Prism Premixer Lab 6) and then mixed in an
extruder (Prism, TSE 16 PC). The extrudate was cooled, ground and
screened, yielding a powder paint having a particle size of 90.mu..
The powder paint was then electrostatically applied, in a layer
thickness of about 50.mu., on a metal substrate and cured for 10
minutes at 200.degree. C. in an air circulation furnace.
[0063] The properties of the resulting powder paint and powder
coating were as follows:
4 gel time 157 sec flow good reversed impact 160 inchpound colour
L* 96.0, a* -0.3 b* 1.4 gloss 20.degree. 86 gloss 60.degree. 94
[0064] The powder paint binder composition comprising TGIC as
crosslinker (instead of the epoxy crosslinker in Example I) also
resulted in a powder coating with good flow properties and in a
light-coloured coating having an excellent reversed impact
resistance, colour and flow.
COMPARATIVE EXAMPLE A
[0065] Example I has been repeated without a crosslinker with
curing by heating in the air (10 minutes, 200.degree. C).
[0066] The properties of the resulting powder paint and
powdercoating were as follows:
5 gel time >480 sec reversed impact <20 flow moderate gloss
20.degree. 89 gloss 60.degree. 97
[0067] In case the curing takes place in the absence of a
crosslinker the impact resistance is unacceptable. The value of the
gel time made clear that there is nearly no crosslinking.
[0068] Experiment II
[0069] Preparation of a HIMIC-containing Polyester
[0070] A 3-liter reactor vessel with thermometer, stirrer and
distillation set-up was filled with 604.1 g propylene glycol, 820.6
g terephthalic acid, 160.8 g trimethylol propane, 0.05 wt. %
dibutyltinoxide and 0.10 wt. % triphenyl phosphite. After this,
with a nitrogen stream being supplied for 8 hours, the temperature
was raised to 225.degree. C. while water was distilled off. After
the temperature of the distilled-off water had dropped to
80.degree. C., the mixture was cooled to 160.degree. C., after
which 764.9 g fumaric acid and 1.1 g t-butyl hydroquinone were
added. The temperature was then raised to 205.degree. C. in 9
hours. At an acid value of 138 mg KOH/g resin, cooling to
185.degree. C. took place and a vacuum was applied for 30
minutes.
[0071] Subsequently, the temperature was raised to 200.degree. C.
and 435.2 g dicyclopentadiene was metered in an hour. The
temperature was then kept at 180.degree. C. for half an hour, after
which a vacuum was applied for half an hour.
[0072] The polyester with 45 wt. % HIMIC was characterized by:
6 acid number 81 mg KOH/g resin hydroxyl number 8 mg KOH/g resin
viscosity 140 dPas (Emila, 165.degree. C.) glass transition
temperature 61.degree. C. (Mettler, TA3000, 5.degree. C./min.)
EXAMPLE III
[0073] Powder Paint Preparation
[0074] A physical mixture consisting of 100 g polyester according
to Experiment II, 100 g bisphenol A epoxy (Aradite GT7004.TM.), 100
g titanium dioxide (Kronos 2310.TM.), 3 g Resiflow-pVS.TM.
(polyacrylate flow agent from Worle), 0.4 g triphenyl methyl
phosphoniumbromide and 1.5 g benzoin was first mixed in a premixer
(Prism Premixer Lab 6) and then mixed in an extruder (Prism, TSE 16
PC). The extrudate was cooled, ground and screened, yielding a
powder paint having a particle size of 90.mu.. The powder paint was
then electrostatically applied, in a layer thickness of about
50.mu., on a metal substrate and cured for 10 minutes at
200.degree. C. in an air circulation furnace.
[0075] The properties of the resulting powder paint and powder
coating were as follows:
7 flow good reversed impact 160 inchpound colour L* 95.0 a* -0.7 b*
1.1
[0076] The powder paint binder composition comprising a polyester
with 45% by weight HIMIC resulted in a powder coating with good
flow properties and in a light-coloured coating having an excellent
reversed impact resistance.
[0077] Experiment III
[0078] Preparation of a HIMIC-containing Polyester
[0079] A 2-liter reactor vessel with thermometer, stirrer and
distillation set-up was filled with 215 g ethylene glycol, 281 g
terephthalic acid, 0.05 wt. % dibutyltinoxide and 0.10 wt. %
triphenyl phosphite. After this, with a nitrogen stream being
supplied for 5 hours, the temperature was raised to 225.degree. C.
while water was distilled off. After the temperature of the
distilled-off water had dropped to 80.degree. C., the mixture was
cooled to 160.degree. C., after which 276 g fumaric acid and 1.1 g
t-butyl hydroquinone were added. The temperature was then raised to
205.degree. C. in 2 hours. At an acid value of 118 mg KOH/g resin,
cooling to 185.degree. C. took place and a vacuum was applied for
30 minutes.
[0080] Subsequently, the temperature was raised to 200.degree. C.
and 228 g dicyclopentadiene was metered in an hour. The temperature
was then kept at 180.degree. C. for half an hour, after which a
vacuum was applied for half an hour.
[0081] The polyester with 50 wt. % HIMIC was characterized by:
8 acid number 81 mg KOH/g resin hydroxyl number 13 mg KOH/g resin
viscosity 150 dPas (Emila, 165.degree. C.) glass transition
temperature 39.degree. C. (Mettler, TA3000, 5.degree. C./min.)
EXAMPLE IV
[0082] Powder Paint Preparation
[0083] A physical mixture consisting of 100 g polyester according
to Example III, 100 g bisphenol A epoxy (Aradite GT7004.TM.), 100 g
titanium dioxide (Kronos 2310.TM.), 3 g Resiflow-PV5.TM.
(polyacrylate flow agent from Worle), 0.4 g triphenyl methyl
phosphoniumbromide and 1.5 g benzoin was first mixed in a premixer
(Prism Premixer Lab 6) and then mixed in an extruder (Prism, TSE 16
PC). The extrudate was cooled, ground and screened, yielding a
powder paint having a particle size of 90.mu.. The powder paint was
then electrostatically applied, in a layer thickness of about
50.mu., on a metal substrate and cured for 10 minutes at
200.degree. C. in an air circulation furnace.
[0084] The properties of the resulting powder paint and coating
were as follows:
9 geltime 158 sec. flow good reversed impact 160 inchpound colour
L* 95.0, a* -0.3 b* 1.7 gloss 20.degree. 80 gloss 60.degree. 98
[0085] Also a powder paint binder composition based on the ethylene
glycol based polyester with 50 wt. % HIMIC resulted in a powder
coating with good flow properties and in a light-coloured coating
having an excellent reversed impact resistance.
[0086] Experiment IV
[0087] One-step-preparation of a HIMIC-containing Polyester
[0088] A 2-liter reactor vessel with thermometer, stirrer and
distillation set-up was filled with 141 g propylene glycol, 441 g
fumaric acid, 142 g neopentylglycol, 0.05 wt. % dibutyltinoxide and
0.10 wt. % triphenyl phosphite. After this, with a nitrogen stream
being supplied for 6 hours, the temperature was raised to
205.degree. C. while water was distilled off. At an acid value of
140 mg KOH/g resin, cooling to 185.degree. C. took place and a
vacuum was applied for 30 minutes.
[0089] Subsequently, the temperature was raised to 190.degree. C.
and 275 g dicyclopentadiene was metered in an hour. The temperature
was then kept at 180.degree. C. for half an hour, after which a
vacuum was applied for half an hour.
[0090] The polyester with 72 wt. % HIMIC was characterized by:
10 acid number 54 mg KOH/g resin hydroxyl number 5 mg KOH/g resin
viscosity 40 dPas (Emila, 165.degree. C.) glass transition
temperature 34.degree. C. (Mettler, TA3000, 5.degree. C./min.)
EXAMPLE V
[0091] Powder Paint Preparation
[0092] A physical mixture consisting of 118 g polyester according
to Experiment IV, 82 g bisphenol A epoxy (Aradite GT7004.TM.), 100
g titanium dioxide (Kronos 2310.TM.), 3 g Resiflow-PV5.TM.
(polyacrylate flow agent from Worle), 0.4 g triphenyl methyl
phosphoniumbromide and 1.5 g benzoin was first mixed in a premixer
(Prism Premixer Lab 6) and then mixed in an extruder (Prism, TSE 16
PC). The extrudate was cooled, ground and screened, yielding a
powder paint having a particle size of 90.mu.. The powder paint was
then electrostatically applied, in a layer thickness of about
50.mu., on a metal substrate and cured for 10 minutes at
200.degree. C. in an air circulation furnace.
[0093] The properties of the resulting powder paint and coating
were as follows:
11 geltime 128 sec. flow moderate/good reversed impact 160
inchpound colour L* 93.0, a* 0.4 b* 3.4 gloss 20.degree.: 82 gloss
60.degree.: 97
[0094] Very surprisingly even the powder paint binder composition
based on a polyester with said relatively very high amount HIMIC
resulted in a powder coating with good flow properties and in a
light-coloured coating having an excellent reversed impact
resistance.
[0095] Experiment V
[0096] Preparation of a HIMIC-containing End-capped Polyester
[0097] A 2-liter reactor vessel with thermometer, stirrer and
distillation set-up was filled with 319 g neopentylglycol, 204 g
terephtalic acid, 0.05-wt. % dibutyltinoxide and 0.10 wt. %
triphenyltinphosphite. After this, with a nitrogen stream being
supplied for 5 hours, the temperature was raised to 205.degree. C.
while water was distilled off. After the temperature of the
distilled-off water had dropped to 80.degree. C., the mixture was
cooled to 160.degree. C., after which 213 g fumaric acid and 0.3 g
t-butyl hydroquinone were added. The temperature was then raised to
205.degree. C. in 2 hours. At an acid value of 140 mg KOH/g resin,
cooling to 124.degree. C. took place and a vacuum was applied for
30 minutes.
[0098] Subsequently, the temperature was raised to 190.degree. C.
and 143 g dicylopentadiene was metered in an hour. The temperature
was then kept at 180.degree. C. for half an hour, after which a
vacuum was applied for half an hour. 120 g trimellitic anhydride
was added and the temperature was kept constant at 180.degree. C.
for one hour
[0099] The polyester with 36 wt. % HIMIC was characterized by:
12 acid number 76 mg KOH/g resin hydroxyl number 10 mg KOH/g resin
viscosity 710 dPas (Emila, 165.degree. C.) glass transition
temperature 57.degree. C. (Mettler, TA3000, 5.degree. C./min.)
EXAMPLE VI
[0100] Powder Paint Preparation
[0101] A physical mixture consisting of 120 g polyester according
to Experiment V, 80 g bisphenol A epoxy (Aradite GT7004.TM.), 100 g
titanium dioxide (Kronos 2310.TM.), 3 g Resiflow-PV5.TM.
(polyacrylate flow agent from Worle), 0.4 g triphenyl methyl
phosphoniumbromide and 1.5 g benzoin was first mixed in a premixer
(Prism Premixer Lab 6) and then mixed in an extruder (Prism, TSE 16
PC). The extrudate was cooled, ground and screened, yielding a
powder paint having a particle size of 90.mu.. The powder paint was
then electrostatically applied, in a layer thickness of about
50.mu., on a metal substrate and cured for 10 minutes at
200.degree. C. in an air circulation furnace.
[0102] The properties of the resulting powder paint and coating
were as follows:
13 geltime 81 sec. flow good reversed impact 160 inchpound colour
L* 96.0, a* -0.8 b* 1.1 gloss 20.degree. 89 gloss 60.degree. 98
* * * * *