U.S. patent application number 16/004441 was filed with the patent office on 2018-10-11 for epoxy resin-based gel coat for surface finishing of components made of fibre-reinforced plastics.
This patent application is currently assigned to MANKIEWICZ GEBR. & CO. GMBH & CO. KG. The applicant listed for this patent is MANKIEWICZ GEBR. & CO. GMBH & CO. KG. Invention is credited to JENS BUENING, JOCHEN WEHNER.
Application Number | 20180291231 16/004441 |
Document ID | / |
Family ID | 49510864 |
Filed Date | 2018-10-11 |
United States Patent
Application |
20180291231 |
Kind Code |
A1 |
BUENING; JENS ; et
al. |
October 11, 2018 |
EPOXY RESIN-BASED GEL COAT FOR SURFACE FINISHING OF COMPONENTS MADE
OF FIBRE-REINFORCED PLASTICS
Abstract
A composition for the manufacture of a gelcoat includes a main
component and a curing component. The main component includes at
least one epoxide resin selected from glycidyl ethers of bisphenol
A, glycidyl ethers of bisphenol F, trimethylolpropane triglycidyl
ethers, and mixtures thereof, and up to 5 wt.-% of at least one of
a filler and a pigment based on a total weight of the main
component. The curing component includes at least one
cycloaliphatic amine. The main component or the curing component
further includes at least one polytetrahydrofuran polyol. The
gelcoat is transparent.
Inventors: |
BUENING; JENS; (REPPENSTEDT,
DE) ; WEHNER; JOCHEN; (HAMBURG, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MANKIEWICZ GEBR. & CO. GMBH & CO. KG |
HAMBURG |
|
DE |
|
|
Assignee: |
MANKIEWICZ GEBR. & CO. GMBH
& CO. KG
HAMBURG
DE
|
Family ID: |
49510864 |
Appl. No.: |
16/004441 |
Filed: |
June 11, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14402314 |
Nov 20, 2014 |
10023762 |
|
|
PCT/DE2013/000272 |
May 21, 2013 |
|
|
|
16004441 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08J 2363/00 20130101;
C08J 2475/04 20130101; Y02E 10/72 20130101; C08L 63/00 20130101;
Y10T 428/31511 20150401; B32B 37/15 20130101; C09D 163/00 20130101;
C08J 7/0427 20200101; F03D 1/0675 20130101; Y02E 10/721
20130101 |
International
Class: |
C09D 163/00 20060101
C09D163/00; F03D 1/06 20060101 F03D001/06; B32B 37/15 20060101
B32B037/15; C08L 63/00 20060101 C08L063/00; C08J 7/04 20060101
C08J007/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 21, 2012 |
DE |
10 2012 010 583.5 |
Claims
1. A composition for the manufacture of a gelcoat, the composition
comprising: a main component comprising, at least one epoxide resin
selected from the group consisting of glycidyl ethers of bisphenol
A, glycidyl ethers of bisphenol F, trimethylolpropane triglycidyl
ethers, and mixtures thereof, and up to 5 wt.-% of at least one of
a filler and a pigment based on a total weight of the main
component; and a curing component comprising at least one
cycloaliphatic amine, wherein, the main component or the curing
component further comprises at least one polytetrahydrofuran
polyol, and the gelcoat is transparent.
2. The composition as recited in claim 1, wherein the main
component comprises up to 2 wt.-% of the at least one of a fillers
and a pigment based on the total weight of the main component.
3. The composition as recited in claim 1, wherein the at least one
epoxide resin of the main component is present in an amount of from
40 to 90 wt.-% based on the total weight of the main component.
4. The composition as recited in claim 1, wherein the main
component comprises the at least one polytetrahydrofuran polyol in
an amount of from 2 to 40 wt.-% based on the total weight of the
main component.
5. The composition as recited in claim 4, wherein the at least one
polytetrahydrofuran polyol has an average molecular mass of from
1000 to 3000 g/mol based on a number average molecular weight.
6. The composition as recited in claim 1, wherein the at least one
cycloaliphatic amine of the curing component is present in an
amount of from 60 to 100 wt. % based on a total weight of the
curing component.
7. The composition as recited in claim 1, wherein the at least one
cycloaliphatic amine is isophorone diamine.
8. The composition as recited in claim 1, wherein the at least one
epoxide resin comprises epoxide groups and the at least one
cycloaliphatic amine comprises N--H groups, the epoxide groups and
the N--H groups being present in a molar ratio of from 1 to 0.7 to
1 to 1.4.
9. The composition as recited in claim 1, wherein the composition
further comprises at least one plasticizer selected from the group
consisting of polyurethane prepolymers having blocked isocyanate
groups.
10. The composition as recited in claim 1, wherein the main
component further comprises at least one plasticizer consisting of
isocyanate prepolymers blocked with at least one of substituted
phenols and pyrazoles.
11. The composition as recited in claim 1, wherein the curing
component further comprises at least one plasticizer consisting of
isocyanate prepolymers blocked with secondary monoamines.
12. A method of using a gelcoat for a surface treatment of a fiber
reinforced compound plastics material, the method comprising:
providing a fiber reinforced compound plastics material; providing
the composition as recited in claim 1; manufacturing the gelcoat
from the composition; and surface treating the fiber reinforced
compound plastics material with the gelcoat.
13. A method for manufacturing a surface-treated fiber-reinforced
compound plastics material as a construction element, the process
comprising: providing the composition as recited in claim 1; mixing
the main component and the curing component of the composition so
as to obtain a mixture; placing the mixture in a component mold;
allowing the mixture to gel so as to form a gelcoat film; applying
a woven fabric, a non-woven fabric, or a laid fabric together with
a laminating resin to the gelcoat film so as to obtain a laminate;
and curing the laminate so as to form the construction element.
14. The method as recited in claim 13, further comprising:
providing the woven fabric, the non-woven fabric, or the laid
fabric together with the laminating resin as at least one prepreg;
and applying the at least one prepreg on the gelcoat film so as to
obtain the laminate.
15. The method as recited in claim 13, wherein the mixture is
placed in the component mold and the mixture allowed to gel so as
to form a gelcoat film in a non-covering thickness.
16. A structural element of a fiber-reinforced compound plastics
material, wherein a surface of the structural element is coated
with the gelcoat layer produced from the composition as recited in
claim 1.
17. The structural element as recited in claim 16, wherein the
structural element is a rotor blade for a wind turbine.
Description
[0001] CROSS REFERENCE TO PRIOR APPLICATIONS
[0002] This application is a continuation of U.S. application Ser.
No. 14/402,314, filed on Nov. 20, 2014, which is a U.S. National
Phase application under 35 U.S.C. .sctn. 371 of International
Application No. PCT/DE2013/000272, filed on May 21, 2013 and which
claims benefit to German Patent Application No. 10 2012 010 583.5,
filed on May 21, 2012. The International Application was published
in German on Nov. 28, 2013 as WO 2013/174362 A1 under PCT Article
21(2).
FIELD
[0003] The present invention relates to compositions based on epoxy
resins for the production of gelcoats and the use of said gelcoats
for the surface treatment of fiber reinforced plastics. The present
invention also relates to processes for the production of the
gelcoats, as well as to processes for the manufacture of surface
treated components made of fiber reinforced plastics, in particular
to manufacturing processes that employ prepegs.
BACKGROUND
[0004] Surfaces of laminates or components composed of fibers such
as glass fibers, carbon fibers, or plastic fibers in a matrix of
curable resins such as epoxy resins, unsaturated polyester resins,
or vinyl ester resins generally feature less acceptable surfaces,
which, moreover, are not resistant to light and weathering. These
must first be treated with protective coatings if these components
are to be employed in applications for which decorative or
weather-resistant surfaces are required.
[0005] Components' surfaces are as a rule painted with suitable
coating materials, predominantly weather-resistant and
anticorrosive paints, for example, those based on aliphatic
polyurethanes. To ensure sufficient adhesion of the coating to the
component, the surfaces to be painted must, however, first undergo
complex pretreatment. Surfaces ready for painting are usually
obtained following a number of process steps. The surface of the
demolded component is first sanded to effect a complete removal of
any mold releasing agents. The surface is then coated or smoothed
with a filling compound to level out any surface defects such as
pores or individual protruding fibers exposed by the sanding
treatment. Once the filling compound has hardened, the surface is
again sanded to obtain a smooth surface ready for painting.
[0006] One alternative to this time-consuming and laborious
pretreatment process is the application of a gelcoat. A gelcoat is
a composition based on a resin system and is applied to the
surfaces of components using an in-mold composite construction
process. The use of gelcoats yields smooth surfaces during the
manufacturing process of the component, which surfaces are ideal
for sanding. The surfaces may then be painted immediately following
sanding. The gelcoat is generally placed in a component mold as the
first layer, which is then pre-cured or incipiently gellated to an
extent at which the dryness grade 6 in accordance with DIN 53 150
has been reached, at which it complies with the mechanical
requirements for subsequent processing. Fibers, for example, in the
form of woven fabrics, non-woven fabrics, or laid webs, and the
laminating resin containing the thermosetting resin employed as a
matrix are then placed on the partially gellated gelcoat film. The
entire composition is then hardened to completion. The gelcoat film
must be sufficiently stable that the fibers can be applied, and
where necessary removed again, without damaging the film. In the
case of extremely large molds, such as rotor blades for wind
turbines, woven fabrics or non-woven fabrics are usually applied by
hand. It must consequently also be possible to walk on the gelcoat
film without the film sustaining damage.
[0007] Use has until now been made of filled gelcoats. The filler
distributed in the resin system forms a framework which provides
the required mechanical stability with only minimal precuring or
only after minimal progression of the curing reaction of the
gelcoat. The use of transparent gelcoats is more advantageous since
laminating flaws, such as gas bubbles or dry areas in the laminate
which have not been coated by resin, can be readily detected and
repaired following removal of the component from the mold.
Transparent gelcoats not containing filler require a much more
intense curing process to0 achieve the required stability of the
film. More intense progression of the curing reaction, however,
results in considerably shorter laminating times. The laminating
time is taken to be the amount of time occurring between the point
in time at which the gelcoat placed in the mold becomes tack-free
and the point in time at which the gelcoat film must be
sufficiently laminated to provide adhesion between the gelcoat and
the laminate.
[0008] For these reasons, transparent gelcoats are as yet only
employed for the production of laminates using liquid laminating
resins. In prepreg procedures, the mechanical stability of the
gelcoat film must be considerably higher since the tackiness of the
prepreg impedes handling and, in particular, application thereof on
the gelcoat film. It is not generally possible to adjust
positioning since the film will tear upon removal of the prepreg
from the gelcoat film, or the entire composition might even be
wrenched out of the mold. If the gelcoat film is subjected to more
intense curing to attain greater stability, however, the laminating
time will be insufficient for the formation of laminate layers,
particularly in relatively large molds.
SUMMARY
[0009] An aspect of the present invention is to provide improved
materials and procedures to allow for the use of transparent
gelcoats, in particular in prepreg procedures, whilst retaining the
known advantages thereof.
[0010] In an embodiment, the present invention provides a
composition for the manufacture of a gelcoat which includes a main
component and a curing component. The main component comprises at
least one epoxide resin selected from the group consisting of
glycidyl ethers of bisphenol A, glycidyl ethers of bisphenol F,
trimethylolpropane triglycidyl ethers, and mixtures thereof, and up
to 5 wt.-% of at least one of a filler and a pigment based on a
total weight of the main component. The curing component comprises
at least one cycloaliphatic amine. The main component or the curing
component further comprises at least one polytetrahydrofuran
polyol. The gelcoat is transparent.
DETAILED DESCRIPTION
[0011] The compositions of the present invention for the production
of a gelcoat contain a main component which contains at least one
or more epoxy resins, and a curing component which contains one or
more amines. Unlike the conventional gelcoat resin systems based on
radically curing resins, such as unsaturated polyesters (UP), vinyl
esters, or acrylate-terminated oligomers, the epoxy resin-based
gelcoats according to the present invention do not indicate any
monomeric emissions. They also show only minimal shrinkage during
curing, or no shrinkage at all, and thus avoid stresses in the
composite material or gelcoat boundary surface so as to provide a
stable boundary surface. Epoxy resin-based composite materials (EP)
moreover demonstrate excellent adhesion to the gelcoats of the
present invention.
[0012] Epoxy resins suitable for use in the present invention are
aromatic glycidyl compounds such as glycidyl ethers of bisphenol A,
glycidyl ethers of bisphenol F, phenol novolak glycidyl ethers,
cresol novolak glycidyl ethers, glyoxal tetraphenol tetraglycidyl
ethers, p-tert. butylphenol glycidyl ethers, cresyl glycidyl
ethers, N,N-diglycidyl aniline, p-aminophenol triglycid,
tetraglycid-4,4'-methylene dianiline, cycloaliphatic glycidyl
compounds such as methyl tetra hydro phthalic diglycidyl ether,
hexahydrophthalic diglycidyl ether, cyclohexane dimethanol
diglycidyl ether, glycidyl ethers of hydrated bisphenol A and
glycidyl ethers of hydrated bisphenol F, epoxidated cycloolefins,
aliphatic glycidyl ethers such as trimethylolpropane triglycidyl
ether, the diglycidyl ethers of 1,6-hexane diol and 1,4-butane
diol, n-dodecyl glycidyl ether, n-tetradecyl glycidyl ether, as
well as glycidyl ethers of polyoxyethylene polyols. Low-viscosity
and medium-viscosity fluid epoxy resin types, semi-solid and solid
epoxy resin types as well as combinations thereof may also be used.
In accordance with the present invention, the use of glycidyl
ethers of bisphenol A, glycidyl ethers of bisphenol F, trimethylol
propane triglycidyl ethers and combinations thereof can, for
example, be used. Epoxy resins are used in quantities of from 40 to
90%, for example, between 60 and 80%, and, for example, between 65
and 75% by weight, based on the main component.
[0013] The composition furthermore contains one or more polyols.
The polyols may be present in the main component as well as in the
curing component. In accordance with the present invention, the
polyols can, for example, be used in the main component. Suitable
polyols include polyacrylate polyols, polyester polyols, polyether
polyols, polycarbonate polyols, polycaprolactones, and polyurethane
polyols. The average molecular weights based on the number average
of polyols can, for example, be 1000 to 3000 g/mol, for example,
between 1500 and 2500 g/mol, and, for example, between 1800 and
2000 g/mol. The polyols are applied in amounts of from 2 to 40%,
for example, between 5 and 30%, and, for example, between 10 and
20%, by weight of polyols, based on the main component including
the polyols. Polytetrahydrofuran polyols can, for example, be
used.
[0014] In order to facilitate application of the transparent
gelcoat, fillers and/or pigments may be added in small amounts. The
fillers are considered below to be particulate substances virtually
insoluble in the application medium and are used in order to
influence the optical characteristics. They may moreover also be
conducive to increasing volume in order to achieve or improve
technical properties. The term pigments relates below to substances
that are virtually insoluble in the application medium and that are
applied as chromophoric substances or dyes. The compositions of the
present invention are very slightly dulled with fillers and/or
pigments to facilitate management thereof to the effect that
material which has already been applied is more readily discernible
during the application process. In this regard, the content of
fillers and/or pigments in the main component of the compositions
of the present invention can, for example, be not more than 5%, for
example, not more than 2%, for example, not more than 1%, and, for
example, not more than 0.5%, by weight of the main component. The
composition will become non-transparent if greater quantities are
added. Suitable fillers and pigments include mineral materials such
as kaolin or talcum, synthetic materials such as barium sulphate or
calcium carbonate, and also inorganic or organic pigments as used
conventionally in paint production, and combinations thereof.
Titanium dioxide or soot can, for example, be used in accordance
with the present invention.
[0015] In an embodiment of the present invention, the curing
component can, for example, contain one or more amines. Suitable
amines include polyamines selected from the group consisting of
polyethylene polyamines such as ethylene diamine, diethylene
triamine, triethylene tetramine, tetraethylene pentamine,
pentaethylene hexamine, pentane-1,3-diamine, 2-methyl
pentamethylene diamine, propylene amines such as propylene diamine,
dipropylene triamine, dimethylaminopropylamine, trimethyl
hexamethylene diamine, polyether polyamines such as
polyoxypropylene diamines or polyoxypropylene triamines,
polyoxypropylene polyamines, polyoxyethylene polyamines,
polytetrahydrofuran polyamines, or butanediolether diamines or
N-aminopropyl cyclohexyl amine, alkylene diamines such as
hexamethylene diamine, trimethylhexamethylene diamine, or methyl
pentamethylene diamine, cycloaliphatic amines such as
tricyclododecane diamine, N-aminoethyl piperazine, isophorone
diamine, or diaminocyclohexane, aromatic amines such as
diaminodiphenylmethane or diaminodiphenylsulfone, araliphatic
amines such as m-xylylene diamine and modifications thereof, for
example, polyaminoamides, Mannich bases and epoxy adducts, as well
as combinations thereof. Cycloaliphatic amines, and in particular
isophorone diamine, can, for example, be used. The amines are added
in quantities of from 60 to 100%, for example, between 80 and 95%,
and, for example, between 85 and 95% by weight of the curing
component.
[0016] The curing components of the present invention may
additionally include accelerants. Suitable accelerants are tertiary
amines such as N,N-dimethyl aniline or dimethyl benzylamine,
alkoxides, imidazoles, Mannich bases such as (dimethyl
aminomethyl)phenol or tris(dimethyl aminomethyl)phenol, boron
trifluoride complexes, Broensted acids, alkyl phenols, polyphenols,
onium salts, triarylsulfonium salts, iron arene complexes or salts
of alkali metals or of alkaline earth metals such as lithium
bromide or calcium nitrate. Accelerants can, for example, include
phenols, polyphenols, alkali metal salts or alkaline earth metal
salts. Calcium nitrate tetrahydrate can, for example, be added. The
accelerator is added in quantities of from 0.2 to 40%, for example,
from 0.5 to 20%, and, for example, from 1 to 10% by weight of the
curing component.
[0017] The composition contains plasticisers. Suitable plasticisers
are polyurethane prepolymers having blocked isocyanate groups. The
plasticisers can be present in the main component as well as in the
curing component. Isocyanate prepolymers blocked with substituted
phenols and/or pyrazoles can, for example, be added in the main
component as described in EP 0688803 A1, the disclosure of which is
incorporated by reference herein.
[0018] Linear polymers having terminal isocyanate groups blocked
with alkylphenol groups can, for example, be used. If the
plasticisers are added to the curing component, isocyanate
prepolymers in which the isocyanate groups are blocked with
secondary monoamines, as described in EP 0457089 A2, can, for
example, be used. The disclosure of EP 0457089 A2 is incorporated
by reference herein.
[0019] The compositions according to the present invention may
further contain conventional additives as commonly used by the
person skilled in the art. Rheology modifiers such as fumed silica,
flow control agents or defoamers, for example, may thus be used in
the usual quantities.
[0020] In accordance with the present invention, the use of epoxy
resins and amines can, for example, be used in the molar ratio of
epoxy groups to N--H-groups reactive to epoxy groups (EP:N--H) of
from 1 to 0.7 to 1 to 1.4, for example, from 1 to 0.8 to 1 to 1.3,
and, for example, from 1 to 0.9 to 1 to 1.2.
[0021] The gelcoats which can be produced from the compositions
according to the present invention are transparent, that is to say,
they exhibit a poor hiding power. The hiding power of the gelcoat
according to the present invention is defined in DIN EN ISO 2814 on
a checkered card. The hiding power measured thereby can only be
ascertained at a film thickness of more than 1 mm. The film
thickness of an applied gelcoat is considerably less and usually
measures approx. 500 .mu.m.
[0022] The gelcoats according to the present invention show
relatively short gellation times. Due to these short gellation
times, the hold time for the mold is reduced considerably, allowing
for shorter mold hold cycles. The materials are tenacious and not
brittle in the form of a gelcoat film in an insidiously gellated
state. A comparison with regular transparent gelcoats shows
considerably superior elongation at break and tear propagation
strength in the case of the gelcoat according to the present
invention. Repositioning of applied prepregs according to the
present invention without causing damage thereto is also possible
when using the gelcoat films.
[0023] Despite their transparency, the gelcoats according to the
present invention exhibit the mechanical stability required for
subsequent processing stages. They in particular also fulfill the
requirements for the manufacture of laminates or fiber plastic
composite components in the prepreg process. As with the
conventional, filled gelcoats, they also exhibit excellent adhesion
to the laminate, are easily sanded in a cured state, and are
suitable for the application of paint thereon.
[0024] The present invention also provides the use of the gelcoat
according to the present invention for the surface treatment of
fiber plastic composite components or laminates. The gelcoat can,
for example, be applied to surfaces of the component using the
in-mold method. The gelcoat film is placed in the component mold as
a first layer to this end. The composition according to the present
invention is first added to a mold following mixing of its reaction
components, the main component and the curing component, within the
pot life. The pot life is the period during which the mix remains
workable. It begins at the point in time at which the two reaction
components are mixed and ends at the point in time at which the
viscosity of the reaction mixture has risen to such an extent that
it is possible to apply a layer that is even in thickness. The
layer obtained following gellation is sufficiently mechanically
stable that it does not sustain damage upon application of the
laminating resin and the fibers, but is sufficiently reactive to
create a stable bond when the laminating resin cures. Examples of
the laminating resins used are epoxy resins, unsaturated polyester
resins, and vinyl ester resins. Examples of the fibers used are
woven fabrics, laid webs, and non-woven fabrics of glass, carbon,
or plastic fibers. To provide sufficient adhesion between
laminating resin and gelcoat, the gelcoat layer must be brought
into contact with the laminating resin within the laminating period
of the gelcoat. The laminating resin and gelcoat will then harden
to completion.
[0025] The gelcoats according to the present invention can, for
example, be used for the surface treatment of epoxy resin composite
materials because they exhibit better adhesion to these materials
than gelcoat based on other resinous systems. They also do not
contain any volatile monomers and are therefore less encumbering
with regard to industrial hygiene.
[0026] The present invention also provides a method for
manufacturing surface-treated fiber plastic composite components or
laminates. Firstly, the required two components, the main component
and the curing component, are mixed with the composition of the
present invention. The mixture is transferred to the component mold
as a first layer using the application method conventionally
applied by the expert, for example, by painting, rolling, spraying,
or pouring. The applied mixture is then gellated or pre-cured to
form a gelcoat film. Fibers in the form of woven fabrics, laid
webs, or non-woven fabrics, as well as the laminating resin are
then applied to the gelcoat film. In the next stage, the entire
composite mixture is hardened to form the desired component. The
component is then removed from the mold and its surface is
subsequently sanded and then painted.
[0027] Fibers and laminating resins can be applied to the gelcoat
film by various methods. Usual laminating methods, such as the
vacuum bag method, the injection method, the infusion method, and
the wet laminating method are known to the person skilled in the
art. One way of producing the fiber composite material involves the
use of prepregs. Prepregs are impregnated resin/fiber mats which
are placed in the component mold. The resin is partially pre-cured
and exhibits relatively strong adhesion properties at room
temperature. One problem incurred by the use of prepregs is that of
repositioning on the gelcoat film. Component molds are generally
pretreated with a mold release agent to ensure that the gelcoat
film itself will not stick to the mold. When adhesive prepreg is
applied to the gelcoat and then removed therefrom, the gelcoat
should not tear or break. Since there is no adhesiveness relatively
to the mold, the gelcoat film must accordingly be mechanically
stable. The gelcoats according to the present invention form films
which exhibit the required mechanical properties, and can therefore
be used in prepreg methods. The compositions of the present
invention also require only short gellation times. Since the curing
process is considerably quicker in the prepreg method than in other
methods, they are particularly suitable for use in these methods
also for this reason.
[0028] Examples of gelcoat compositions according to the present
invention are examined below to compare the properties of the
gelcoats according to the present invention with those of
commercially-used transparent gelcoats.
TABLE-US-00001 TABLE 1a Composition of Main Component Content in
parts by weight Substance S1 S2 S3 Bisphenol A diglycidyl ether 25
25 25 Bisphenol F diglycidyl ether 10 10 10 Trimethylol propane
triglycidyl ether 40 47 40 Polytetramethylene oxide polyol 12 -- --
Polypropylene oxide polyol -- 15 12 Plasticiser 10 -- 10 Fumed
silica 2.99 3 2.99 Titanium oxide 0.01 -- 0.01
TABLE-US-00002 TABLE 1b Composition of Curing Component Content in
parts by weight Substance HA HB Isophorone diamine 65 92 Phenolic
accelerator 35 -- Calcium nitrate tetrahydrate -- 4 Propandiol --
4
TABLE-US-00003 TABLE 1c Composition of Gelcoat Main Curing Molar
proportion Example No. component component MP 1.1 S1 HB 1.09 1.2 S1
HA 1.13 1.3 S2 HB 0.87 1.4 S3 HA 1.07 2.1 Commercially available
transparent gelcoat 2.2 Commercially available transparent
gelcoat
[0029] The following tests for elongation at break properties, tear
propagation resistance, and prepreg re-position ability were
performed on gelcoat films gellated under various curing
conditions.
[0030] The elongation at break was determined via a mandrel bending
test in accordance with the test specification set forth in DIN EN
ISO 1519. Metal plates, to which the coating under test were
applied, were bent around a mandrel. The smaller the radius of the
mandrel around which the plate could be bent without damaging or
fracturing the coating, the greater the elongation at break of the
coating.
[0031] The tear propagation resistance was determined via tear
propagation tests in accordance with test specification set forth
in DIN EN ISO 13937-2. The force necessary to enlarge a crack in
the coating undergoing examination was measured. The greater the
applied force, the more tear-resistant the coating.
[0032] The prepreg repositioning was determined via the following
test set-up which simulates a laminate structure in a component
mold. A mold release agent was applied to a sufficiently large
metal plate. A gelcoat composition was then coated over an area of
1 m.sup.2 on the prepared plate. The composition was gellated on
the gelcoat film at the prescribed temperature and for the
prescribed duration. A prepreg of dimensions DIN A4 was laid
centrally on the gelcoat film and pressed down firmly with a
defined force for 1 minute. The prepreg was then removed swiftly at
an angle of 90 .degree.. Visible damage to the gelcoat film was
rated as follows:
TABLE-US-00004 ++ No changes + Detachment of the gelcoat film from
the metal plate at up to three positions without damaging the
gelcoat film itself 0 Detachment at up to 10 positions with damage
at a maximum of three positions - Increased damage of the gelcoat
film -- Total detachment of the gelcoat film from the metal
plate
[0033] Tables 2a and 2b show the results of the tests on gelcoat
films gellated under various conditions. The gelcoats according to
the present invention show considerably improved values in relation
to elongation at break and tear growth resistance. In contrast to
commercially available gelcoats, the removal of a prepreg applied
under pressure did not cause any damage to the gelcoat according to
the present invention. It may thus be applied in processes
involving prepregs without incurring the usual disadvantages.
TABLE-US-00005 TABLE 2a Properties of the gelcoat film gellated at
60.degree. C. (Temperature was maintained until a dryness grade of
6 according to DIN 53 150 was reached.) Gelcoat no. 1.1 1.2 1.3 1.4
2.1 2.2 Elongation at break Mandrel diameter in [mm] 40 25 8 12 1)
1) without fracture Mandrel diameter in [mm] 25 20 6 8 220 220 with
fracture Tear growth resistance Force in [N/mm] 3.7 1.1 0.5 2.8 2)
2) Prepreg repositioning ability Damage assessment ++ ++ + ++ -- --
1) Value was not determined 2) Value not measurable due to
splintering of the coating
TABLE-US-00006 TABLE 2b Properties of the Gelcoat Film Gellated at
23.degree. C. (Temperature was maintained for 18 hours.) Gelcoat
no. 1.1 1.2. 1.3 1.4 2.1 2.2 Elongation at break Mandrel diameter
in [mm] 40 55 40 25 1) 1) without fracture Mandrel diameter in [mm]
32 40 32 32 220 220 with fracture Tear growth resistance Force in
[N/mm] 4.3 4.5 0.3 2.1 2) 2) Prepreg repositioning ability Damage
assessment ++ ++ + ++ -- -- 1) Value was not determined 2) Value
not measurable due to splintering of the coating
[0034] The following tests for adhesion of the laminate to the
gelcoat, for sandability, and for paintability were performed on
the cured laminates. The gelcoat compositions were placed in a mold
and gellated, the prepreg was then applied to the gelcoat film. The
mold was sealed and a vacuum bag attached and evacuated. The entire
composition was then cured, the curing conditions being prescribed
by the respective prepreg used. The following tests were performed
on the cured laminates.
[0035] The elongation at break was determined using the
aforementioned mandrel bending test. Metal strips were coated in
gelcoat as described above, the gelcoat being gellated and cured
under the same temperature conditions as those applied for curing
of the prepreg laminates. The smaller the mandrel diameter, the
greater the elongation at break. The adhesive strength of the
gelcoat on the laminate was determined by means of pull-off tests
in accordance with test specification set forth in DIN EN ISO 4624.
The greater the force required to pull off the seal, the stronger
the adhesion.
[0036] In order to assess the laminate surfaces treated with
gelcoat, their sandability, i.e., their abrasion resistance, and
their paintability, i.e., the adhesion of paint coats on their
surfaces, were determined. The resistance to abrasion was
determined gravimetrically in accordance with test specification
set forth in ASTM D 4060 using a S33 wheel rotating at 500 rpm
under a load of 1000 g. The greater the difference in weight, the
higher the abrasion resistance and, consequently, the better the
sandability.
[0037] For the purpose of assessing the paintability, the laminate
surfaces were first sanded with grade 180 sandpaper. The sanding
dust was then removed from the surface, which was then painted with
a suitable commercially available paint. On completion of curing of
the paint film, the adhesion thereof, i.e., its adhesive strength,
was determined by means of stripping tests in accordance with test
specification set forth in DIN EN ISO 4624. The greater the tension
required to pull off the film, the stronger the adhesion.
[0038] Table 3 shows the results on the surface-treated laminate
according to the present invention compared with regular
surface-treated laminates. The laminates according to the present
invention also fulfill, as in the case of the regular laminates,
all requirements with regard to adhesion, sandability, and
paintability.
TABLE-US-00007 TABLE 3 Properties of the Cured Laminates Gelcoat
no. 1.1 1.2. 1.3 1.4 2.1 2.2 Elongation at break Mandrel diameter
in [mm] 70 70 85 70 70 85 with no fracture Mandrel diameter in [mm]
55 55 70 55 55 70 with fracture Adhesion of gelcoat to laminate
Stripping tension in [N/mm.sup.2] 9.1 9.8 8.7 9.2 8.9 8.8 Taber
abrasion Difference in [mg] 986 864 793 891 762 1) Adhesion paint
on gelcoat Stripping tension in [N/mm.sup.2] 6.3 5.3 6.1 5.9 6.6
4.4 1) Not determined
[0039] The present invention is not limited to embodiments
described herein; reference should be had to the appended
claims.
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