Note: Descriptions are shown in the official language in which they were submitted.
8~
-- 1
Case 3-13918/~
A process for curing acid-curable abrasive compositions
The present invention relates to a process for curing
acid-curable abrasive compositions based on an acid-
curable resin containing a masked curing catalyst.
By a grinding tool is meant in general the combination
of a hard granular abrasive, optionally also of a carrier
element or reinforcement, with a binder to form a closed
composite material.
Grinding tools can be classified, according to typical
structural features, under two main groups, namely,
grinding wheels or disks, such as abrasive wheels, rings
or points, and flexible abrasives on flat or sheetlike
carrier materials.
In the case of flexible abrasives on flat carrier
materials, there are used as binders the most varied
synthetic resins, including however to the greater extent
the pheno- and aminoplasts, and also the alkyd-melamine
resins.
To produce these abrasives, the carrier material
is coated with a thin film of a liquid base binder and the
abrasive grain; the binder is then dried, and subsequently
cured by heat treatment to such a degree that the abrasive
grain is sufficiently anchored so as not to become
r/,
~2~16
-- 2
displaced or turned over during further treatment. A
final covering binder layer, which is usuall~ filled with
calcium carbonate, is afterwards applied, and is likewise
cured by ~eing subjected to a a heat ~reatment, the two
operations taking several hours to perform. '['he reason
for this considerable amount of drying and curlng time
being required is in particular the fact that the binders
used are in most cases in the form of aqueous dispersions,
so that firstly the dispersion water has to be removed in
the drying operation, and that, especially with the use
of phenol-formaldehyde reslns as binders, a further amount
of water is released on curing, and consequently this also
has to be removed. Furthermore, high temperatures are
necessary for curing.
The use of acid curing catalysts to accelerate the
curing of acid-curable resins is indeed known, including
for example organic acids such as p-toluenesulfonic acid
(cp. in this connection Houben-Weyl, ~ethoden der
organischen Chemie (Methods in organic Chemistry), Vol.
20 14/2, 4th Edition (1963), p. 238, or German Patent Specifi-
cation No. 2,406,992). For the production of abrasive
compositions based on acid-curable binders, the use of
such acids as catalysts to accelerate the curing stage is
however not possible, since acids of this type effect already
25 during the drying phase premature curing of the resin.
This leads to undesirable bubble formation which is caused
by the water or condensation product entrapped by the resin.
To accelerate the drying and curing process, there
has also been suggested, in the German Offenlegungsschrift
30 No. 2,444,525, a process for producing abrasive compo-
sitions, in which phenol-resol binders in polar organlc
solvents are used in place of the customary aqueous binders.
This process does not however satisfy in all respPcts the
3 1~8~6
demands made.
It has now been found that with speci~ic, so-called
masked catalysts, which as a result oE exposure to liyht
rays during the curing stage are rapidly degraded with
the formation of free sulonic acids, the curiny p~ocess
can be considerably accelerated and shortened. Curing
can moreover be carried out at a lower temperature.
The essential advantage of curi~g catalysts of the
said type is that, as inactive compounds during the drying
stage, they effect no undesirable premature curing of the
binder. By virtue of this factor, the use of acid
catalysis for the curing of abrasive compositions is
for the first time rendered possible.
Subject matter of the present invention is accordingly
a process ~or curing abrasive compositions containing an
acid-curable binder and, as curing catalyst, an organic
sulfonic acid releasable by the action of light, in which
process the abrasive compositions after drying are
exposed to the action of light rays and thus cured.
Of particular interest as masked curing catalysts
are organic compounds of the formulae I and II
o R20 1 ~ R ,R6~8
L 3 ~D L 7
(I) (II)
wherein
n is 1 or 2,
Rl is phenyl or naphthyl which is unsubstituted or sub-
stituted by 1, 2 or 3 radicals : -Cl, - Br, -CN,
-N02, Cl-C12-alkyl, Cl-C4-alkoxy, phenyloxy, tolyloxy,
phenylthio, tolylthio, Cl-C8-alkylthio,
-SCH2CH20H, Cl-c4-alkylsulfonyl~ phenylsulfonyl,
~r
~Z~L68~ 6i
-- 4
C2-C4-alkoxycarbonyl, Cl-C4-alkylamino, C2-C~-
dialkylamino, phenyl-CONH- or Cl-C~-alkyl-CONH-,
or by benzoyl, or
Rl is anthryl., phenanthryl, thienyl, pyridy.~, ~uryl,
indolyl o~ tetrahydronaphthyl, and
R2 and R3 independently o~ one another are each hydrogen,
or Cl-C8-alkyl which is unsubstituted or substituted
by -OH. -Cl, Cl-C4~alkoxy, -CN, C2-C5-alkoxycarbonyl,
phenyl, chlorophenyl, C7-C10-alkylphenyl or C7-C10-
alkoxyphenyl, or they are benzoyl, in addition
R3 is phenyl which is unsubstituted or substituted by
-Cl, Cl-C4-alkyl, Cl-C4-alkoxy or Cl-C4-alkylthio,
or it is C2-C8-alkoxycarbonyl, -CN, Cl-C4-alkyl-NH-
CO-, phenyl-NH-CO- or -CONH2, or
R2 and R3 together with the carbon atom to which they
are bound form a C4-C6-cycloalkyl ring,
R4 is, when n = 1, Cl-C18-alkyl, phenyl which is unsub-
stituted or substituted by halogen, Cl-C12-alkyl,
Cl-C4-alkoxy, Cl-C4-alkyl-CONH-, phenyl-CONH-, -N02
or benzoyl, or it is naphthyl which is unsubstituted
or substituted by halogen, Cl-C12-alkyl or Cl-C4-
alkoxy, or it is C5-C6-cycloalkyl, C7-Cg-aralkyl,
campheryl, -CF3, -CC13, -F or -NH2, and
R4 is, when n = 2, a -(CH2) group, wherein m is 2 to 8,
or phenylene or naphthylene each unsubstituted or
substituted by Cl-C12-alkyl, is phenyl or naphthyl
which are each unsubstituted or substituted by 1,
2 or 3 radicals: -Cl, -Br, Cl-C12-alkyl, ~henyl,
Cl-C4-alkoxy, phenyloxy, benzyloxy, Cl-C8-alkylthio,
phenylthio, -SCH2CH20H, Cl-C4-alkyl-CONH-, benzoyl-
amino or demethylamino,
,.... ...
~Zl~
-- 5
or by benzoyl, or R5 is ~nthryl or phenanthryl,
R6 is hydrogen, ~OH, Cl-C~-alkoxy,-OSi(CH3)3~ -OCOCH3,
or Cl-C8-alkyl which is unsubstituted or substi-
tuted by phenyl,
R7 is hydrogen, or Cl-C8-alkyl which is unsubsti~uted
or substituted by phenyl, or R7 is -CN, henzoyl,
Cl-C4-alkylcarbonyl, C2-C5-alkoxycarbonyl or phenyl,
R8 is hydrogen, Cl-C8-alkyl which is unsubstituted or
substituted by -0~1, -Cl or phenyl, or it is phenyl
which is unsubstituted or substituted by -OH, -Cl,
Cl-C4-alkyl or Cl-C4-alkoxy, or R8 is c2-C6-alkenyl,
C8-Cg-phenylalkenyl, furyl, thienyl or -CC13, or
saturated or unsaturated C5-C6-cycloalkyl, and moreover
Rs with ~7, R7 with R8 or R6 with R7, together with the
carbon structure to which they are bound, ~orm a
5- or 6-membered ring which contains 1 to 5: -CH2-,
-CH(CH3)-, -C(CH3)2-, -O-, -S-, -SO-, -S02-, -CO-,
-N(CO-Cl-C4-alkyl)- or -N(COC6H5)- groups.
When phenyl and naphthyl, as Rl and R5, are substituted
by Cl-C12-alkyl, they are straight-chain or branched-chain
substituents, for example methyl, ethyl, n-propyl, iso-
propyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl,
heptyl, octyl, nonyl, decyl or dodecyl, especially however
methyl~ If phenyl and naphthyl, as Rl and R5, are sub-
stituted by Cl-C4-alkoxy, they are for example methoxy,
ethoxy, propoxy or tert-butoxy.
When phenyl and naphthyl, as Rl and R5, are substiti-
tuted by Cl-C8-alkylthio, they are straight chain or
branched-chain substituents, for example methyl, ethyl,
n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,
pentyl, hexyl, heptyl or octyl 3 particularly methylthio.
If Rl is a phenyl or naphthyl substituted by Cl-C4-
alkylamino or C2-C~-dialkylamino, it is for example
- 6- lZ~8~6
a methy~, ethy~, propyl- or n butylamino group, or a
dimethyl- or diethylamino substitution group.
When phenyl or naphthyl as Rl is substituted by
Cl-C~-alkylsulfonyl, it is for example methyl-, ethyl-,
5 propyl-, butyl~ or tert-butylsulonyl.
When phenyl or n~phthyl denoted by Rl is substituted
by Cl-C4-alkyl-CONH-, the substituents are for example
methyl-, ethyl-, propyl- or n-butyl-CONH-. If phenyl
as R4 contains Cl-C4-alkyl-CONH-, the substituents are
for example methyl-, ethyl-, propyl- or n-butyl-CONH-.
Where Rl is thienyl, pyridyl, furyl, indolyl or
tetrahydronaphthyl, all position isomers come into
consideration. Preferred position isomers are however:
2-thienyl, 3-pyridyl, 2-furyl, 3-indolyl or 1,2,3,4-
tetrahydro-6-naphthyl.
1 8 yl~ R2, R3, R6 and R8 are straight-chain
or branched-chain alkyl groups, preferably however straight-
chain Cl-C4-alkyl groups, for example methyl, ethyl,
n-propyl or n-butyl.
When Cl-C8-alkyl in the case of R2 and R3, and phenyl
or naphthyl in the case of R4, are substituted by Cl-C4-
alkoxy, and if R6 is Cl-C4-alkoxy, they are for example
methoxy, ethoxy, propoxy or tert-butoxy substituents.
When Gl-C8-alkyl, as R2 and R3, is substituted by
C7-C10-alkylphenyl or C7-C10-alkoxyphenyl, the substituents
are for example methyl-, methoxy-, ethyl-, ethoxy ,
tert-butyl- or tert-butoxyphenyl.
If alkyl as R3 is substituted by Cl-C4-alkylthio,
the substituents are for example methyl-, ethyl-, propyl-
and tert-butylthio.
When R2 and R3 together with the C atom to which they
_ 7 _ ~2~16
are bound form a C4-C6-cycloalkyl ring, it is ~or exa~ple
a cyclopentane, cyclohexane or cycloheptane ring, in
particular however a cyclohexane ring.
When R4, i~ n = 1, is Cl-C18-alkyl, it is a straight-
5 chain or branched-chain group, such as: methyl, ethyl,
propyl, isopropyl, butyl, tert-butyl, pentyl, hexyl,
heptyl, octyl, nonyl, decyl, 2-ethylhexyl, undecyl,
dodecyl, tert-dodecyl, tridecyl, tetradecyl, hexadecyl
or octadecyl.
When phenyl or naphthyl as R4 is substituted by
Cl-C12-alkyl, it is a straight-chain or branched-chain
alkyl group.
Where R4 is C5-C6-cycloalkyl, it is cyclopentyl and
cyclohexyl.
If R4 is C7-C9-aralkyl, it is for example l-phenylethyl,
2-phenylethyl or benzyl.
Where R4 is campheryl, it is 10-campheryl.
When R4, if n = 2, is a -(CH2)m- group, it is for
example ethylene, propylene, butylene, pentylene or
20 hexamethylene.
When phenylene and naphthalene are substituted by
Cl-C12-alkyl, they are straight-chain or branched-chain
alkyl groups.
I~ the various phenyl groups in the radicals Rl, R3-R4,
25 R5 and R8 are substituted by radicals other than hydrogen
atomsg this substitution occurs in the ortho-, meta- or
para-position, especially in the para-position.
When R6, R7 and R8 are Cl-C8-alkyl substituted by
phenyl, they are for example benzyl or phenylethyl groups.
If R7 is Cl-C4-alkylcarbonyl, the substituents are
~ZlÇ~6
-- 8 --
for example methyl-, ethyl-, propyl- or tert-butyl-
carbonyl.
I~ R7 is C2-C5-alkoxycarbonyl, substituents are e.g
methoxy-, ethoxy-, isopropoxy-, butoxy- or tert-butoxy-
carbonyl.
When phenyl as R8 is substituted by Cl-C4-alkyl or
Cl-C4-alkoxy, the substituents are methyl, ethyl,
n-propyl, isopropyl, n-butyl or tert-butyl, or methoxy,
ethoxy, n-propoxy, isopropoxy, n-butoxy or tert-butoxy.
When R8 is C2-C6-alkenyl, it is for example vinyl,
l-propenyl, 2-propenyl, isopropenyl, 2-butenyl, isobutenyl,
2-pentenyl, 2-hexenyl or 5-hexenyl, particularly however
vinyl, isobutenyl or l-propenyl.
When R8 is C8-Cg-phPnylalkenyl, substituents are
styryl or 3-phenylpropenyl, especially however styryl.
If R8 is furyl or thienyl, all position isomers come
into consideration. Preferred position isomers are
however 2-furyl and 2-thienyl.
If R8 is unsaturated C5-C6-cycloalkyl, it is for
example 2-cyclopenten-1-yl, l-cyclohexen-l-yl or 3~cyclo-
hexen-l-yl.
Particularly preferred curing catalysts of the formulae
I and II are those wherein n = 1, and Rl is phenyl which
is unsubstituted or substituted for example by: chlorine,
methyl, methoxy, methylthio, phenylthio, -SCH2CH20H or
benzoyl, R2 is hydrogen or Cl-C4-alkyl, R3 is hydrogen
or Cl-C4-alkyl, or R2 and R3 together with the carbon atom
to which they are bound form a cyclohexane ring, -R4
is Cl-C18-alkyl, phenyl or ~aphthyl each unsubstituted or
substituted by Cl-C12-alkyl, or it is campheryl, R5 is
phenyl which is ~msubstituted or substituted by: -Cl,
- 9 -
Cl-C4-alkyl, Cl-C4-alkoxy, -SC~3 or phenyl, R6 is -OH
or Cl-C4-alkyl, R7 is Cl-C~-alkyl or phenyl, and R8 is
-H, cl-c4-alkyl, furyl or -CC13, or R7 with R8 together
wi~h ~he carbon atom to which they are bound form a
cyclohexane ring.
More especially preferred are cwring catalysts of
the formulae I and II wherein n = 1, Rl and R5 are each
phenyl, p-tolyl or p-methylthiophenyl, R2 is hydrogen,
R3 is methyl, isopropyl, n-decyl or benzyl, R~ is phenyl,
p-tolyl or p-n~dodecylphenyl, R6 is -OH, R7 is -CH3 or
phenyl, and R8 is -~.
The compounds of the formula I are known and can be
produced by known processes, for example by reaction of
the corresponding hydro~yl compounds of the formula tA)
O R2
Rl c - c - OH (A)
R3
I
with one or half an equivalent of the corresponding mono-
or di-sulfonic acid chlorides of the formula (B)
R4-(S02Cl)n (B),
in the presence of a base (cp. in this connection: Journal
of the Chemical Society Perkin I, 1981, p. 263), or by
reaction of the corresponding bromine derivatives of the
formula (C)
o
Rl - C - C/R2 ~C)
Br
with one or half an equivalent of the silver salts of the
corresponding mono- or disulfonic acid derivatives of
the formula (D)
- lo- 1~16~
( g 3 ~ 4 (D) 7
as for example according to the process given in the
Journal of Organic Chemistry of the UdSSR, Vol. 8,
p. 2166 (1972). In the formulae (A), (B3, (C) and (D)~
the symbols Rl to R4 and n have the meanings defined
in the foregoing.
The intermediates of the formulae (A), (B), (C) and
(D) are known compounds which can be produced by known
processes, for example by those which are described in
10 Houben-Weyl, Methoden der Organischen Chemie: Vol. V/4,
pp. 171-189, for the compounds of the formula (C);
Vol. IX, p. 411 or 563, for the compounds of the formula
(B); and for the compounds of the formula (A): the
references A. 526, 143, 164 (1936)~ Am.Soc. 76, 4402
(1954) or Z. obsc. Chim. 34, 3165 (1964).
The compounds of the formula (II) are known and can
be produced by known processes, for example by reaction
of the corresponding epoxy compound of the formula (E)
11 1 7 ~R
R5-C-C~C 8 (E)
20 with one equivalent of the corresponding monosulfonic acid
derivative of the formula (F), or with half an equivalent
of the disulfonic acid derivative of the formula (G)
R4 - S03H (F) 3 4 S03M (G),
for example by the processes described in Ber. Deutsch.
25 Chem. Ges. 69, 2753 (1936), and in J. Chem. Soc. 1949, 315;
or by reaction of a corresponding hydroxyl compound of
the formula 1~ 0 R6 R8
R - C C - CH
. 5 I t
R7 OH
z~
with a mono- or disulfonic acid chloride of the formulae
R4 - S02Cl and C102S-R4-So2cl, respectively, according to the
process given in the German Of~enlegwngssehrift 1,919,678.
In the formulae (E), (F) and (G), the symbols R5, R6,
R7, R8 and R4 have the mea~in.gs defined in the ~oregoing.
The required epoxy compounds of the formula (E) can
be produced by known processes, for example by chlorination
of the corresponding compound of the formula (H)
.
' R - C - CH - R (H)
to the corresponding chlorine derivative of the formula (K)
o
Il
R - C - CH - R (K)
Cl
which is reacted by subsequent condensation with the
corresponding aldehyde of the formula (L)
I' o
11
R8 ~ c -El (L)
to the corresponding epoxy compound of the formula (E)
[cp. in this respect: Chem. Soc. 75, 2042 (1953)];
or by an aldol condensation of the corresponding compound
of the formula (H) with the corresponding aldehyde of the
formula (L) to give the corresponding compound of the
formula (M)
O R
Il _ 17 ~R8
C (M),
~1
which is subsequently reacted for example by means of
hydrogen peroxide to the corresponding epoxy compound
- 12 - ~Z~8~6
of the for~ula (E) [cp. in this connection: J Ch~m. Soc.,
79, 928 (1901)] and Org. Syntheses 60, 88 (1981) 7 or the
aldol condensation, and J. Org. Chem~ 28, 250 (1963) or
Org. Syntheses 55, (1967), ~or the ormation of the
epoxy derivatives].
In the ~ormulae (H), (K), (L) and (M), the symbols
R5, R7 and R8 are as defined in the foregoing.
The compounds of the formulae (F) and (G) can be
produced by known processes, for example by those which
lo are described in Houben-Weyl, Methoden der Organischen
Chemie, Vol. IX, p.p. 347 and 435.
Further masked curing catalysts can be used in
the present process. Examples of these are a-methylol-
benzoinsulfonic acid esters, which are described in the
German Offenlegungsschrift No. 1,919,678; 4-benzoyl-4-
phenyl-2-oxo-1,3,2-dioxathiolane (according to German
Offenlegungsschrift No. 2,842,002); and N-sulfonyloxy-
imides, which are described for example in the European
Patent Application ~o. 58638.
The curing catalysts which are usable according to the
invention are added to the resins in an amount sufficient
for curing. The required amount depends not only on the
type of resin, but also on the intended curing temperature
and curing time. The amount used in general is 0.1 to
10 % by weight, preferably 0.5 to 5 % by weight, of
curing catalyst, relative to the solvent-free resin. Also
mixtures of such curing catalysts can be used.
Suitable as acid-curable binders for abrasives are
the resins of which the curing can be accelerated by
acid catalysts. They are in particular pheno-and
aminoplasts, for example the condensation products of
formaldehyde with phenol, resorcin, cresol, xylenol, and
- 13 ~ ~ ~ ~ 6 ~ ~ ~
mixtures thereof, urea, anilines or melamine. Other
aldehydes, such as acetaldehyde, ~urfurol and acrole~
can be wsed in place of formaldehyde.
The acid-curable phenol resins and aminoplasts are
described in detail in "Methoden der Organischen Chemie",
Houben-Weyl, Vol. 14/2~ 4th Edition (1963), p.p. 193-302
and 319-400.
Further acid-curable resins can be modified melamine
resins, including etherified, esterified and otherwise
modified melamine resins, for example alkydmelamine resins,
as well as acrylic esters or polyesters, or alkyd resins.
The binders can moreover consist of several identical
or different acid-curable resins. Mixtures of various
phenol resins, which are described for example in the
European Patent Applicat;on No. 12409, can also be used.
The phenol-formaldehyde resins are particularly
preferred, especially the aqueous-liquid, weakly alkaline
to neutral phenol-formaldehyde condensation products of
the resol type, which have greatly gained in importance.
It is advantageous with the use of aqueous-liquid alkaline
resins to neutralise resins of this type before the
addition of the curing catalyst.
More especially of interest are aqueous phenol-
formaldehyde resins (the so-called resol types) which have
been made neutral to weakly acid (pH 4-6).
The binders can be solutions or dispersions of the
resin in an organic solvent, preferably in aliphatic
alcohols, or in water. They can contain, in addition to
the abrasive and the curing catalyst, also fillers and
additives, such as those customarily used in the abrasives
industry, for example: agents improving the viscosity index~
thickeners, dispersing agents~ additives for improving the
- 14 - lLZ~G~8~6
mechanical and thermal properties of the abrasives,
and also adhesion promoters.
As abrasives or abrasive grain, there are used
substances having a very great hardness and diferent
particle sizes, the actual chipping or cutting work
being done by these substances. Corundum and silicon
carbide are mainly used. Further known abrasive grains
are zirconium oxide, boron carbide, boron nitride,
quartz, granate, or glass, and various metal powders,
such as Si, Cu, Ag or Ni, as well as metal alloys.
Examples of fillers and additives are: graphite,
molybdenum disulfide, iron pyrite, potassium sulfate,
barium sulfate, cryolite, iron sulfide, sodium chloride3
magnesia, calcium oxide, calcium fluoride, calcium
lS carbonate, kaolin, glass fibres and also various plastics,
for example vinyl chloride/vinylidene chloride copolymers,
polyvinylidene chloride and PVC, or various halides,
sulfates or sulfites, or mixtures thereof, or other fillers
known in the abrasives industry.
The binders can also contain smallish amounts of
special additives, for example co-initiators, as well as
spectroscopic sensitisers. Examples of these are benzoln
and derivatives thereof, benzil and derivatives thereof,
and a-di- and trisubstituted acetophenones, derivatives
of anthracene or thioxanthone, and also organic dyes.
The mentioned resins and binders, abrasives, fillers
and additives constitute no limitation of scope: they are
given merely by way of example of an embodiment of the
invention.
Preferred abrasive compositions ar~ as follows:-
for the covering binder:
A) 30 - 70 % by weight of a filler,
- 15 - ~ 2 ~ 6
70 - 30 % by weight of resol (80 % by weight in water),
1 - 5 % by weight of water, and
0.2 - 2% by weight of a curing catalys~;
and for the base binder:
~) 2 20 % by weight of filler(.s),
80 - 98 % by weight of resol (80 % by weight in water),
1 - 5 % by weight of water, and
1 - 4 % by weight of catalyst:
with the proviso that the sum of the four components
of the composition amounts always to 100 % by weight.
As already mentioned, the process for producing
flexible abrasives passes through two phases, namely,
the drying phase for the abrasive composition and the
subsequent curing phase.
In the drying phase, the employed solvent or water
is partially to completely evaporated off.
In the subsequent curing phase, the binder is cross-
linked to the extent that the abrasive grain is adequately
anchored during further treatment and can thus be no longer
moved. This anchoring is of decisive importance for the
quality of the finished product. The preliminary curing
is usually performed at relatively high temperature, for
example at 130C and above, and for one to several hours.
With the use of the masked catalysts which are
applicable according to the present invention, the
curing process can however be performed at relatively low
temperatures and with short~ned curing times~ thus for
example at temperatures of below 100C, preferably at
between 60 and 90C, and within 1 to Z00 min~ttes.
These relatively low curing temperatures and shortened
curing times in the process according to the invention
- 16 - ~ Z ~ 6 ~ ~ ~
are of considerable technical importarlce; ~hus for e~ample
in the case where water-containing substrates are used
a subsequent tempering in a humiclity chamber in order
to recover flexibility is renclered unnecessary by virtue
of these advantages. ~ further factor is the resulting
saving in energy costs.
A further advantage of the process according to the
invention is that the storage stability of the abrasive
compositions is not impaired, even though they contain
a curing catalyst. Furthermore, the curing catalyst becomes
active not in the drying phase but subsequently in the
irradiation phase, effecting not until then the curing
of the binder with formation of free sulfonic acid.
The exposure of the resin to light rays is performed
pre~erably with W light, for which purpose there is
available today a variety of suitable commercial devices.
These incorporate medium pressure, high pressure or low
pressure mercury vapour lamps, as well as fluorescent
tubes, the emission maxima of which are at 250 to 400 nm.
The exposure times necessary depend on the layer thickness
of the resin, on the ~illing of the abrasive composition,
on the light intensity of the lamps and on the distance
between the lamps and the material being exposed. An
abrasive composition at the customary layer thickness
requires in the usual W radiation aparatus an exposure
time of several seconds to minutes. In this time, the
latent catalyst has become photochemically transformed
with the formation of free sulfonic acid.
When photosensitisers are added to the resin, the
irradiation can be carried o~t also with daylight lamps.
Examples of known photosensitisers are condensed aromatic
compounds, for example perylene, aromatic amines (such as
are described for example in the U.S. Patent Specification
1 Z~L~81~
- 17 -
No, ~,069,054)9 or cationic and basic dyes ~s~lch as are
rlescribed for example in the U.S. Patent Speciication No.
4,026,705),
The curing catalysts which are applicable
according to the invention can be used also in the sub-
sequent treatment, in which a covering binder layer,
usually filled with fillers such as calcium carbonate, is
applied, and then cured by exposure to light and heat
treatment, in consequence of which the curing of the
covering binder is accelerated and the curing time
shortened.
A tempering treatment in a humidity chamber can if
required be performed following the curing operation.
The further processing steps in the production of the
abrasives are carried out in the manner customary in
practice.
The process according to the invention is suitable in
particular for producing flexible abrasives on flat
(sheetlike) carrier material, for example on fibres, such
as vulcanised fibres, abrasive fabrics or abrasive paper,
as well as on combinations of paper and textile fabrics.
The process is suitable moreover for the production of
abrasive disks, such as abrasive elements, rings, points~
segments, cylinders or heads.
The following ~xamples further illustrate the process
of the invention on the basis of specific compositions
acccrding to the invention. The term 'parts' denotes
parts by weight, and percentages are per cent by weight.
~Z~L~i8~6
- 18 -
Example 1: Testing of -the anchoring of the abrasive grain,
and also of the curing of the base binder in the presence
of cwring catalysts applicable accor-:ling to the invention
....
30 % by weight (relative to the solid content o the
5 phenol-formaldehyde resin) of a 10 % (by weight) catalyst
solution (in methylpentyl ketone) is mixed up in an
aqueous phenol-formaldehyde resin MS 7215(*). The phenol-
formaldehyde resin solution thus obtained is applied with
a 200 ~u coating knife to an aluminium sheet (dry-film
10 thickness about 40-50 ~), and subsequen~ly coated with
corundum. For this purpose, the corundum is placed into
a longish V-shaped funnel, the slit-shaped opening of which
is covered with a metal sieve~ and the funnel is secured
to a vibrator. For applying the corundum coating, the
; 15 vibrator is switched on, whereupon the aluminium sheet
coated with resin is passed at a uniform rate under the
funnel (amount applied per m2: 400-600 g of corundum).
For removal of the water, the aluminium sheet thus coated
- is afterwards transferred for 35 minutes to a circulating-
20 air chamber at 90C, and is then exposed at a distance
of l$ cm to light rays from fluorescent tubes (Philips
TLK ~ 40/09) for 5, lQ and 15 minutes, in the course of
which there is liberated from the catalyst applicable
according to the invention an organic acid which catalyses
25 the curing of the binder. The specimens are tested after
; subsequent curing for 20 minutes at 90C.
The anchoring of the abrasive grain (corundum) in the
preliminarily cured phenol-formaldehyde resin is quali-
tatively tested by the surface of the specimens being
30 touched, and assessed according to the following system
of classification:
A = can be moved with the finger
B = is firmly anchored, and can no longer be moved with
the finger.
- 19 - ~21~ii8~6
The degree of curing of the binder is measured on
a binder film without corundum according to the Knoop-
measuring method (ASTM D 1474). The results are shcwn
in Table 1.
(*) phenol-formaldehyde resin MS 7215 (Ciba-Geigy):
77 % by weight of solid substance; aqueous solution;
pH = 4.5; viscosity = 2.5 - 3 Pas at 25C; molar ratio
phenol:formaldehyde = 1:1.2.
- 20 ~ 12~68~i
_ _ _ _ . _
4~s~
C ¢ F4 F4 F4 ¢ F4 F4 F4 ¢ F4 F4 F4 ¢ F4 F4 F4
3~
~t__ . , ._ . __ _
* ~ ~X ~ `J ~ -X ~
~3' ~ ~ ~ 1
¢ . . ____ ___
E
5~ ~ O n o u~ O u) O u~ o ~ o ~n o U~ o ~
o 3~ ~ ~ ~ ~ ~ ,/ ~
F~l ~
_ ._. . __ . .
Y . Il i il
C~ ,//-\. ~/ '~,/
o W ~/- o~ ~-o~
o~ //o o~ ,//Y\. .//Y\.
i i l l I ~1 l ll
.~ ."~fi~. "~ . \~, ~,
~ ~.,"~., ~., ~o/ ~ ~
~1 z . . . . . ~
F-l X F4 _ F~
- 21 - ~L2~
~,~ . ..... .....
C ~ ¢ a~ 4 ¢ ~ ~q ~q ¢ ¢ ¢ ¢
~ _
,.
~' ~X ~t Ll~ ~ # ~ ~ ~ X -X -X ~X
--¢ _ _._
.~
~.~ o U~o U~ o U) ~ U~
X"~
[~ . ~ .
,o '~d o .//\ 1,~, ~ ,~
~d t) 5: 1 ~ ~ t
o~ o- ~ ~) .~ a)
.~ .~ O=C~ O=t~ ~ r
~ ~ /i ~ ~,
ZO; _ _ ~
E-l ~ ~ _ ~ . J,~
.
~LZ~ti816
- 22 -
The results show that the catalysts applicable according
to the invention effect no prelirninar~ curing during the
drying phase (the unexposed coatings are still sot an~
sticky, the corundum is not firml~ anchored), Not until
exposure to light rays does the catalyst becorne de~raded
with the ~ormation of active sulfonic acids, which render
possible a rapid preliminary curing of the binder at low
temperatures, in consequence of which the curing process
is simultaneously shortened. An adequate preliminary
curing of the binder has occurred after 20 minutes at
90C, whereas the corresponding specimen without catalyst
is still soft and sticky after the same curing time. The
abrasive is already well anchored after an exposure time
of 5 minutes, in comparison to which the unexposed specimens
are freely movable.
Example 2: Testin~ of the curin~ of the coverin~ binder
The phenol-formaldehyde resin MS 7215 described in
Example 1 is mixed with 30 % by weight (relative to the
solid content of the phenol resin) of a 10 % (by weight)
20 catalyst solution (in methylpentyl ketone), and then filled
with chalk [ratio of resin (100% solid substance? to
chalk is 2 to 11. The mixture obtained is applied, by the
~rocess given in Example 1, to an aluminium sheet. For
removal of the water, the coa~ed aluminium sheet is placed
for 35 minutes into the oven at 90C; it is then exposed
for 5, 10 and 15 minutes, at a distance of 15 cm, to the
light from fluorescent tubes (Philips TLK ~ 40/09). After
subsequent curing of these test specimens for 20 minutes
at 90C, the degree of curing of these specimens is
determined according to the Knoop measuring method
(ASTM D 1474).
The results are summarised in Table 2.
- 23 -
Table 2
. Catalyst of the formula IExposure time -j ~s,~
in minutes 1 1~74
C-C-C~l2OSO2~ --n-C H ~ 5 1 14
CH ~.=./ 12 25 1 17 ¦
* measurement not possible; specimen sticky and soft.
The results show that the exposed specimens have a
sufficient hardness already after 5 minutes' exposure time
and a curing time of 20 minutes at 90C, whereas the
unexposed specimen is still soft and sticky after a curing
time of 20 minutes.
Example 3- 30 % by weight (relative to the solid content
of the phenol-formaldehyde resin) of a 10 % (by weight)
catalyst solution (in methylpentyl ketone) is mixed up in
an aqueous phenol-formaldehyde resin MS 7216 (*). The
solution thus obtained is applied onto an aluminium sheet
by the method described in Example 1, and thereupon coated
with corundum; it is afterwards placed into an air-circu-
lating oven at 90C for 35 minutes, and then exposed for
5, 10 and 15 minutes under fluorescent tubes. After
subsequent curing for 20 minutes at 90C, the specimens
are tested as in Example 1. The results are summarised
in Table III.
.
~ 24 - ~ 2
Table III
Exposure Hardness ,Anchoring o
Catalyst of the formulal tlme in AS'~M D Ithe abraslve
,' minutes ;147~ ' grain
~ C-C-~ ~. 5 3L ¦ ~
,\.=./ ¦ \.=./ ~---~ 10 i 35 B
CH2-OSO2--\ / C 3l 15 ' 29 ¦ B
...... -- ~
* measurement not possible; specimen sticky and soft;
A. B: see classification in Example 1.
(*) phenol-formaldehyde resin MS 7216 (Ciba-Geigy):
79 % by weight of solid substance; aqueous solution;
pH = 4.5; viscosity: 2.5 - 3.0 Pas at 25C; molar ratio
phenol:formaldehyde = 1 : 1.8.
Note
In the preceding disclosure reference is made to
various patent publications. Fuller details for these are
as follows:
Page 2: West German Patent Specification 2,406,992;
published April, 1982 assigned to Dynamit Nobel.
West German OLS 2,444,525; published April,
1976 assigned to Feldmuhle Dusseldorf.
Page 11: West German OLS 1,919,673; published November~
1970 assigned to Bayer; see also U.S. Patent 3,732,273.
- 2~a -
Page 12: West German OLS 1,919,678; published November,
1970 asslgned to Bayer; see also U.S. Patent 3,732,273.
West German OLS 2,842,002; published April,
1980 assigned to Bayer.
European Application 58,638; published Augus-t,
1982 assigned to Ciba Geigy.
Page 13: European Application 12,409; published June,
1980 assigned to Hoechst.
