NO831755L - PROCEDURE FOR THE CURE OF ACID-HARDWARE Abrasive Compositions. - Google Patents

Description

The invention relates to a method for curing acid-curable abrasive compositions based on an acid-curable resin containing a masked curing catalyst.

By a grinding tool one usually understands the union of one

hard-grained abrasive material, optionally also a support element or a reinforcement with a binder for a closed composition.

Grinding tools can be divided according to typical structural features

in two main groups, namely the grinding wheels as grinding bodies,

-rings or pins and the flexible abrasives on flat-shaped carrier materials.

In the case of the flexible abrasives on flat-shaped carrier materials, various synthetic resins are used as binders, including, however, predominantly phenolic or amino plastics and alkyd-melamine resins.

For their manufacture, the carrier material is coated with a thin

film of a liquid base binder and the abrasive grains. Then; the binder is dried and then hardened by heat treatment to the extent that the abrasive grains are sufficiently anchored during the further treatment and can no longer be displaced or rearranged. Then another layer of covering binder, mostly filled with calcium carbonate, is applied which, for curing, also

is then subjected to a heat treatment. Both processes last several hours. These considerable drying and curing times are particularly justified by the fact that the binders used are mostly available as aqueous dispersions so that primarily the dispersion water is removed during the drying process and especially when using phenol formaldehyde resins as a binder, a further amount of water is released during curing and consequently also has to be removed . In addition, high temperatures are required for curing.

It for accelerating the curing of acid curable resins

it is admittedly known to use acidic curing catalysts including, for example, organic acids such as p-toluenesulfon-

acid (see Houben-Weyl, Methoden der organischen Chemie, volume 14/2, 4th edition (1963), page 238 or DE-PS 2,406,992). However, in the production of abrasives based on acid-curable binders, the use of such acids as the catalyst for accelerating the hardening step is not possible,

as such acids already during the drying phase cause a premature hardening of the resin. This leads to unwanted bubble formations which are caused by the water enclosed by the resin or condensation products.

To accelerate the drying and curing process, it was

further in DE-OS 2.4 44.5 25 proposed a method for the production of abrasives in which instead of aqueous ordinary binders a phenol resol binder is used in polar organic solvents. However, this method does not satisfy the requirements in every respect.

It has now been found that with certain so-called masked catalysts which, when irradiated with light during the curing step, quickly break down to form free sulphonic acids, the curing process can be significantly accelerated and shortened. Furthermore, the curing can thereby be carried out at a lower temperature. The essential advantage of such curing catalysts is that they, as inactive compounds in the drying trirane, do not cause premature undesired curing of the binder. This first enables the use of acid catalysis when hardening abrasive compositions.

The object of the invention is therefore a method for curing abrasive compositions containing an acid-curable binder and, as curing catalyst, an organic sulphonic acid that can be released under the influence of light, the method being characterized by irradiating and curing the abrasive composition after drying with light.

Of particular interest as masked curing catalysts are organic compounds of formulas I and II

in which

n means the numbers 1 or 2, and

R^ denotes an unsubstituted or, for example, with 1, 2 or 3

residues - Cl, -Br, -CN, -N02, C1~C12-alkyl, C-^-C^-Alkoxy, phenyloxy, tolyloxy, phenylthio, tolylthio, C^-Cg-alkylthio,

-SCH2CH2OH, C1-C4-alkylsulfonyl, phenylsulfonyl, C2-C4~ alkoxycarbonyl, C^-C4-alkylamino, C2-C4-dialkylamino, phenyl-CONH-, C-^-^-alkylø-CONH- or phenyl substituted with benzoyl or naphthyl, or R further means anthryl, penanthryl, thienyl, pyridyl, furyl, indolyl or tetrahydronaphthyl, and

R 2 and R 3 independently of each other mean hydrogen, unsubstituted or, for example, with -OH, -Cl, C-C-C-Alkoxy, -CN, C2-C-C-Alkoxycarbonyl, phenyl, chlorophenyl, C-C-C-C-Alkyl- phenyl or C 7 -C 10 -Alkoxyphenyl substituted C -C 8 -alkyl,

further benzoyl, moreover

Rg means unsubstituted or for example with -Cl, C-^-C^alkyl,

C₁-C₄-Alkoxy or C₁-C₄-Alkylthio substituted phenyl, C₂-<C>g-Alkoxycarbonyl, -CN,<C>1-C₄-Alkyl-NH-CO-, phenyl-NH-C0- or -CONH2 , or R2 and R^ mean, together with the carbon atom to which they are attached, a C4-C8 cycloalkyl ring,

R 4 means when n = 1, C 1 -C 1 -alkyl, unsubstituted or for example with halogen C 1 -C 4 -alkyl, C 1 -C 4 -alkyl, C 1 -C 4 -alkyl-CONH-, phenyl-CONH, -NO 2 or benzoyl-substituted phenyl, unsubstituted or, for example, with halogen, C^-C-^-alkyl or C^-<C>4-alkoxy-substituted naphthyl, C^-Cg-cyclo-

alkyl, C 7 -C 8 aralkyl, campheryl, -CF 3 , -CCL 3 , -F or

NH2, and

R 4 means when n = 2 a -(CH 2 )m~ group, where m means the numbers

2 to 8 or unsubstituted or for example with C^~C]_2~

alkyl substituted phenylene or naphthylene,

Rc- means an unsubstituted or with 1, 2 or 3 residues -Cl,

Br, C-j_-C -alkyl, phenyl, C-^-C^alkyloxy, phenyloxy, benzyloxy, <C>1-Cg-alkylthio, phenylthio, -SCH2CH2OH, C1-C4~alkyl-CONH-, benzoylamino , dimethylamino or with benzoyl substituted phenyl or naphthyl, or R^ further means anthryl or

fenantryk,

Rg means hydrogen, -OH, C₁-C₁ alkoxy, OSi(CH3)3, -OCOCHg or

unsubstituted or phenyl-substituted C 1 -C 8 -alkyl,

R^ means hydrogen, unsubstituted or phenyl-substituted C-^-C8-alkyl, -CN, benzoyl, C-^-^-alkylcarbonyl, C2-C5~

alkoxycarbonyl or phenyl,

Rg means hydrogen m unsubstituted or with -OH, -Cl or phenyl substituted C-^-Cg-alkyl, unsubstituted or with -OH, -Cl, C-^-C^-alkyl or C1-C4~ alkoxy substituted phenyl, C2~ C 8 -alkenyl, C 8 -C 8 -phenylalkenyl, furyl, thienyl, -CCl 3 or saturated or unsaturated C 8 -C 8 -cycloalkyl or further forms Rj. with R^, R^ with Rg or Rg with R^ together with the carbon structure to which they are attached a 5- or 6-ring containing 1 to 5 -CHW~, -CH(CH3)-f-C(CH3)2- , -O-, -S-, -SO-, -SO2-, -CO-, -N(CO-C1-C4-alkyl)- or -N(C0CgH5) groups.

If phenyl or naphthyk as R-^ and R^ are substituted with C 1-C]-2-alkyl, then these are straight-line or branched substituents such as, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec.-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl or dodecyl, especially, however, methyl. If phenyl or naphthyl as R^ and R^ are substituted with C--C-C4-alkyloxy, then it is, for example, methoxy, ethoxy, propoxy or tert-butoxy.

If phenyl or naphthyl, such as R^ and R,, are substituted with C]_~Cg- alkylthio, then these are straight-line or branched substituents such as, for example, methyl-, ethyl-, n-propyl-, isopropyl-, n-butyl-, sec.-butyl-, tert.-butyl-, pentyl-, hexyl-, heptyl- or octyl-, especially if methylthio.

If R means a phenyl or naphthyl substituted with C-^-C^-alkylamino or C2-C4-dialkylamino respectively, it is for example a methyl-, ethyl-, propyl- or n-butylamino or a dimethyl- or diethylamino substitution group .

If phenyl, naphthyl as R 1 is substituted with C 1 -C 4 -alkylsulfonyl, then it is, for example, methyl-, ethyl-, propyl-. butyl or tert.butylsulfonyl.

If phenyl or naphthyl as R^ is substituted with C-^-C^-alkyl-CONH-, then the substituents are, for example, methyl-, ethyl-, propyl- or n-butyl-CONH-. Contains phenyl such as R^C-^-C^-alkyl-CONH-, then it is, for example, methyl, ethyl, propyl or n-butyl CONH substituents.

If R means thienyl, pyridyl, furyl, indolyl or tetrahydronaphthyl, then all positional isomers are taken into account. However, preferred positional isomers are 2-thienyl, 3-pyridyl, 2-furyl, 3-indolyl or 1,2,3,4-tetrahydro-6-naphthyl.

As C1-C8-alkyl, R2, R3, Rg and Rg are linear or branched alkyl groups, preferably, however, linear C-3-C4-alkyl groups such as methyl, ethyl, n-propyl, n-butyl.

Is C--C8-alkyl at R2 and R3, respectively phenyl or naphthyl at R4 substituted with C--C-----------------------------------------------------------------------------------

then it concerns, for example, methoxy, ethoxy, propoxy or tert.-butoxy substituents.

If C 1 -C 8 -alkyl as R 2 and R 3 is substituted with C 7 -C 10 -alkylphenyl or C 7 -C 10 -Alkoxyphenyl, then it is, for example, methyl, methoxy, ethyl, ethoxy, tert-butyl or tert. r butoxy enyl substituents..

b

If phenyl as R 3 is substituted with C 1 -C 3 -alkylthio, then it is, for example, methyl, ethyl, propyl or tert-butyl thio substituents.

If R 2 and R 2 together with C atoms to which they are attached form C 4 -C 8 cycloalkyl, then it is, for example, a cyclopentane, cyclohexane or cycloheptane ring, but in particular a cyclohexane ring.

When n = 1:

means R^C-^-C^g-alkyl, then it concerns straight-line or branched groups, such as methyl, ethyl, propyl, isopropyl, butyl, tert.-butyl, pentyl, hexyl, heptyl, octyl, nonyl, deceyl , 2-ethylhexyl, undecyl, dodecyl, tert.-dodecyl, tridecyl, tetradecyl, hexadecyl or octadecyl.

Is phenyl or naphthyl as R^ substituted by C-^-C^-alkyl

then it concerns linear or branched alkyl groups.

If R4C3-C8-cycloalkyl means cyclopentyl and cyclohexyl.

If R 4 C 1 -C 8 -aralkyl means, for example, 1-phenylethyl, 2-phenylethyl or benzyl.

If R4 means camphoryl, then it is about 10-camphoryl.

When n = 2:

R4 means a -(CH2)m group, then it is, for example, ethylene, propylene, butylene, pentylene or hexamethylene.

If the phenylene or naphthylene is substituted with Cl-C12~alkyl, then these are linear or branched alkyl groups.

Are the different phenyl groups in the residues R-^. R 8 -R 4 , R 4 and

Rg substituted with radicals other than hydrogen atoms" then this substitution takes place in the ortho-, meta- or para-position, especially however in the para-position.

If Rg, R7 and Rg are phenyl-substituted C--C8-alkyl, then they are, for example, benzyl or phenylethyl groups.

If R-, C1-C3-alkylcarbonyl means, for example, methyl, ethyl, propyl or tert-butylcarbonyl substituents are involved.

If R_ is C2-C5~ alkoxycarbonyl, then it concerns, for example

whether methoxy-, ethoxy-, isopropoxy-, butoxy- or tert.- . butoxycarbonyl substituents.

If phenyl as Rg is substituted with C₁-C₂-alkyl or C₁-C₂- alkoxy, then it is methyl, ethyl, n-propyl, isopropyl, n-butyl or tert.-butyl, respectively methoxy, ethoxy, .n-propoxy, isopropoxy, n-butoxy or tert.-butoxy substituents.

If R0 means C_-C,-alkenyl, then it is, for example, vinyl,

o 2. b

1-propenyl, 2-propenyl, isopropenyl, 2-butenyl, isobutenyl, 2-pentenyl, 2-hexenyl or 5-hexenyl substituents, especially however vinyl, isobutenyl or 1-propenyl.

If Rg means Cg-Cg-phenylalkenyl, then it is about styryl or 3-phenylpropenyl substituents, especially styryl.

If Rg means furyl or thienyl, then all positional isomers are taken into account. However, preferred positional isomers are 2-furyl and 2-thienyl.

If Rg means unsaturated C 1 -C 8 -cycloalkyl, then it is, for example, 2-cyclopenten-1-yl, 1-cyclohexen-1-yl or 3-cyclohexen-1-yl substituents.

Of particular note are curing catalysts. with the formulas

I and II, wherein n = 1 and R-^ means an unsubstituted or for example vis with chlorine, methyl, methoxy, methylthio, phenylthio, -SCr^OH or benzoyl substituted phenyl, R2 means hydrogen, C]_""C4~

alkyl, R 3 means hydrogen or C 1 -C 4 alkyl, or R 2 and R 4

together with the carbon atom to which they are attached form a cyclohexane ring, R4 means C-^-C^g-alkyl unsubstituted or with

C1-C12-alkyl substituted phenyl or naphthyl or campheryl, R,, means an unsubstituted or with -Cl, C^-C4~alkyl, C^~C4~alkoxy, -SCHj ., or phenyl substituted phenyl, RD, means - 0H or C1-C4~alkyl, R-, means C1-C4~alkyl or phenyl and Rg means -H, C1-C4~alkyl, furyl or ~CCl3 or further R_, •form with Rg together with the carbon atom to which they are attached a cyclohexane ring.

Particularly preferred are curing catalysts of the formulas I and II in which n = 1 and R-^ and R,, means phenyl, p-tolyl or p-methylthiophenyl, R2 means hydrogen, R^ means

methyl, isopropyl, n-decyl or benzyl, R4 is phenyl,

p-tolyl or p-n-dodecyl enyl, R^ b means -OH, R-/, means

-CH 3 or phenyl and R 8 means -H.

The compounds of formula I are known and can be prepared

according to known methods, for example by reacting the corresponding hydroxy compounds with formula (A)

with a respective half equivalent of the corresponding mono-respective di-sulfonic acid chloride of formula (B) in the presence of a base (see here Journal of the Chemical Society Perkin I, 1981, page 263) or also by reacting the corresponding bromine derivatives with formula (C) with a respective half equivalent of the silver salts of corresponding mono- and respectively disulfonic acid derivatives of formula (D)

as, for example, according to the method indicated in the Journal of Organic Chemistry of the UdSSR, volume 8, page 2166 (1972).

In the formula (A), (B), (C) and (D) the residues of R 4 and n have the above meaning.

Intermediates of formula (A), (B), (C) and (D) are known

■compounds which can be prepared according to known methods such as those described in Houben-Weyl, Methoden der Organischen Chemie, volume V/4, pages 171-189 for compounds of formula (C), volume IX, page 411 and 563 respectively for compounds of formula (B) and for the compounds of formula (A) the literature citations A. 52_6, 143 , 164 (1936), Am.Soc. 76_, 4402 (1954)

or Z. obsc. Chim. 3_4, 3165 (1964).

The compounds of formula II are known and can be prepared

according to known methods, for example by reacting the corresponding epoxy compound with formula (E)

with one equivalent of the corresponding monosulfonic acid derivative of formula (F) or with half an equivalent of the disulfonic acid derivative of formula (G) as, for example, according to the method described in Ber.Deutsch.Chem.Ges. 69>, 2753 (1936) or in J.Chem. Soc. 1949, 315 or by reacting a corresponding hydroxy compound with formula

with a mono- or respectively disulfonic acid chloride of the formula R4—SO2C1 respectively C102S—R4—SO2C1 according to that in DE-OS

1 919 678 specified method. In formula (E), (F) and (G)

the residues R5, <R>g, <R>^, Rg and R4 have the above meanings.

The necessary epoxy compounds with formula (E) can be prepared according to methods known per se, thus for example

• by chlorination of the corresponding compound with formula (H)

to the corresponding chlorine derivative of formula (K) as by subsequent condensation with the corresponding aldehyde of formula (L)

is converted to the corresponding epoxy compound with formula

(E) (see in this connection Chem. Soc. 75, 2042 (1953)).

or also by an aldol condensation of the corresponding compound of formula (H) with the corresponding aldehyde of formula

(L) to the corresponding compound of formula (M)

which is then, for example, converted with the help of hydrogen peroxide to the corresponding epoxy compound with formula (E) (see J.Chem. Soc. 79, 928 (1901) and Org. Syntheses 60_, 88 (1981) for aldol condensation and J.Org. Chem. 2_8, 250 (1963) or Org. Syntheses 55, (1967) for the formation of the epoxy derivative).

In formula (H), (K), (L) and (M) the residues , R7 and Rg have the above meaning.

The compounds of formula (F) and (G) can be prepared according to known methods such as, for example, those described in Houben-Weyl, Methoden der Organischen Chemie, volume IX, page 34 7 and 435 respectively.

Additional masked curing catalysts can also be used

1 according to the present method. Examples of this are α-methylolbenzoin sulfonic acid esters which are mentioned in DE-OS 1 919 678, 4-benzoyl-4-phenyl-2-oxo-1,3,2-dioxathiolanes (according to DE-OS 2 842 002) as well as N-sulfonyloxyimides which for example is mentioned in EP application 58638.

The curing catalysts relevant according to the invention are added to the resins in a sufficient quantity for curing. The amount required depends not only on the type of resin, but also on the intended curing temperature and curing time. Usually 0.1 to 10% by weight is used, preferably 0.5

to 5% by weight of the curing catalyst, referred to the solvent-free resin. Mixtures of such curing catalysts can also be used.

As acid-curable binders for abrasives, it comes on

resins whose curing is accelerated by acid catalysts.

These are above all pheno and amino plastics such as the condensation products of formaldehyde with phenol, resorcin, cresol, xylenol and their mixtures, urea, alinins or melamine. Instead of formaldehyde, other aldehydes such as acetaldehyde, furfurol or acrolein can also be used.

The acid-curable phenolic resins and aminoplasts are discussed in detail in "Methoden der Organischen Chemie", Houben-Weyl,

volume 14/2, 4th edition (1963), pages 193-302 and 319-400.

Further acid-curable resins can be modified melamine resins including etherified, esterified or otherwise modified melamine resins such as alkyd-melamine resins as well as acrylic, polyester or alkyd resins. The binder can also consist of several identical or different acid-curable resins. Mixtures of different phenolic resins, for example described in EP-OS 12 40 9, can also be used.

Particularly preferred are the phenol formaldehyde resins, in particular

the aqueous, liquid weakly alkaline to neutral phenol-formaldehyde condensation products of the resol type which have greatly increased in importance. When using aqueous, liquid alkaline resins, it is advantageous to neutralize such resins before adding a curing catalyst.

Of particular interest are aqueous phenol-formaldehyde resins (the so-called resol types) which are set neutral to weak

acidic (pH 4-6).

The binders can be solutions or dispersions of the resins in an organic solvent, preferably in aliphatic alcohols or in water. In addition to the abrasive and the hardening catalyst, they can also contain fillers and additives as is common in the abrasive industry, for example viscosity index improvers, thickeners, dispersants, additives to improve the mechanical and thermal properties of abrasives as well as adhesives mediators.

As abrasives or grains, substances with a high

great hardness and with different grain sizes that perform the actual chip removal work. Corundum or silicon carbide is mainly used. Other known grains are zirconium oxide, boron carbide, boron nitride, quartz, garnet, glass, various metal powders such as Si, Cu, Ag or Ni as well as metal alloys.

Examples of fillers and additives are graphite, molybdenum sulphide, iron pyrite, calcium sulphate, barium sulphate, cryolite, iron sulphide, sodium chloride, magnesia, calcium oxide, calcium fluoride, calcium carbonate, kaolin, glass fibers and various synthetic materials such as vinyl chloride-vinylidene chloride copolymers, polyvinylidene chloride, PVC or various halides, sulphates, sulphites or mixtures thereof or other fillers known in the abrasives industry.

The binders can also contain smaller amounts of special additives, for example coinitiators and spectral sensitisers. Examples of this are benzoin and its derivatives, benzyl and its derivatives and α-di- and tri-substituted acetophenones, derivatives of anthracene or thioxanthone and organic dyes.

The mentioned resins, respectively binders, abrasives, fillers and additives are not a limitation, but should only indicate an exemplary embodiment according to the invention.

Preference is therefore given to abrasive compositions of:

before tire binder

A) 30 - 70% by weight filler

70 - 30 wt% resol (80 wt% in water)

1 - 5% by weight water

0.2 - 2% by weight curing catalyst

and for basic binder

B).2 - 20% by weight filler(s)

80 - 98 wt% resol (80 wt% in water)

1 - 5% by weight water

1 - 4 wt% catalyst

with the precaution that the sum of the four components of the composition in total amounts to 100% by weight. •As already mentioned, the process for producing the flexible abrasives takes place over two phases, namely the drying phase and the abrasive composition of the subsequent hardening phase.

During drying, the used solvent or water evaporates partially completely.

During the subsequent curing phase, the binder is cross-linked to the extent that the abrasive grain is sufficiently anchored during the further treatment and can no longer be moved. This anchoring is of decisive importance for the quality of the finished product. This is usually cured at a relatively high temperature, for example 130°C and higher, and over the course of one to several hours.

When using the masked curing catalysts according to the invention, on the other hand, the curing process can take place at relatively low temperatures and reduced curing times, for example at temperatures below 100°C, preferably between 60 and 90°C and within 1 to 200 minutes.

The relatively low curing temperatures and shortened curing times in the method according to the invention are of considerable technical importance, thus for example when using water-containing substrates whereby a subsequent tempering in a humid climate to recover the flexibility is omitted. Furthermore, energy can thereby be saved.

A further advantage of the method according to the invention

is that the storage stability of the abrasive compositions is not affected, although they contain a hardening catalyst.

Furthermore, the curing catalyst does not react during the drying phase, but causes curing of the binder only upon irradiation during the formation of free sulphonic acid.

The irradiation of the resin with light takes place preferably with UV light, for which there are currently a number of suitable technical devices. These contain mercury medium-pressure, high-pressure or low-pressure lamps as well as fluorescent tubes whose emission maximum lies at 250 to 400 nm. The necessary irradiation times depend on the layer thickness of the resin, the filling of the abrasive composition, the light pressure of the lamps and the distance from the lamp. An abrasive composition in normal layer thickness requires an illumination time of a few seconds to minutes in normal UV irradiation devices. During this time, the latent catalyst has converted itself photochemically, forming free sulphonic acid.

If you add photosensitizers to the resin, you can

also carry out irradiation with daylight lamps. Examples of known photosensitizers are condensed aromatics, e.g. perylene, aromatic amines (such as those described in US patent 4,069,054) or cationic and basic dyes

(as they are, for example, discussed in US patent 4,026,705).

Furthermore, the curing catalysts in question according to the invention can also be used in subsequent treatment, where another layer of covering binder filled mostly with fillers such as calcium carbonate is applied and cured by lighting and heat treatment. This also accelerates the curing of the tire binder and shortens the curing time.

In connection with the hardening, if necessary, tempering can also take place in a humid climate. The further processing steps in the production of abrasives are carried out as usual practice.

The method according to the invention is particularly suitable for the production of flexible abrasives with flat support material such as, for example, also abrasive fibers such as volcanic fibers, abrasive fabrics, abrasive paper and on combinations of paper and textile fabrics. The method is also suitable for the production of grinding discs such as grinding bodies, rings, struts,

cements, cylinders or containers.

The invention shall be explained in more detail with the help of some examples in which parts mean parts by weight and percentages mean percentages by weight.

Example 1:

Examination of the anchoring of the abrasive grain as well as the hardening of the base binders in the presence of curing catalysts relevant according to the invention 1 an aqueous phenol formaldehyde resin "MS 2715" (77% by weight solids aqueous solution, pH 4.5, viscosity 2.5-3 Pas at

2 5°C, molar ratio phenol : formaldehyde =1 : 1.2) are mixed

30% by weight (referred to the solids content of the phenol formaldehyde resin) of a 10% by weight catalyst solution (in methylpentyl ketone). The phenol-formaldehyde resin solution thus formed is applied with a 200 y Rakel to an aluminum tin (dry film thickness approx. 40 - 50 y) and then coated with corundum. The corundum is then filled in an elongated V-shaped funnel where the slot-shaped opening is covered with a metal sieve. The funnel is attached to a vibrator. For coating with corundum, the vibrator is switched on, as the resin-coated aluminum sheet passes under the funnel at a regular speed (application quantity/m : 400-600 g corundum). To remove water, the thus coated aluminum tin is then filled for 35 minutes at 90°C in a circulation drying cabinet and then illuminated for 5, 10 and 15 minutes under a Philips "TLK" 40/09 fluorescent tube at a distance of 15 cm, since according to catalyst in question in the invention, an organic acid is released which catalyzes the hardening of the binder. After subsequent curing for 20 minutes at 90°C, the samples are examined.

Anchoring of the abrasive grains (corundum) in the hardened phenol formaldehyde resin is examined qualitatively by touching the surface of the samples and is assessed according to the following scale:

A = can be moved with the finger

B = firmly anchored and can no longer be moved with the finger.

The degree of hardening of the binder is measured on a binder film without corundum according to the Knoop measurement method (ASTM D 1474). The results are listed in table 1. The results show that, according to the invention, the catalysts in question during the drying phase do not cause any hardening of the binder (unexposed coatings are still soft and sticky, the corundum is not firmly anchored). Led by lighting, the catalysts are broken down to form active sulphonic acids which enable rapid curing of the binder at low temperatures. Thereby, the curing process is simultaneously reduced. After 20 minutes at 90°C, sufficient curing of the binder has taken place, while the corresponding sample without catalyst after the same curing time is still soft and sticky. The abrasive is already firmly anchored at an illumination time of 5 minutes, but still freely movable with the unilluminated sample.

Example 2:

Examination of the curing of the tire binder.

The phenol formaldehyde resin "MS 7215" mentioned in example 1 is mixed with 30% by weight (referred to the phase body content of the phenolic resin) of a 10% by weight catalyst solution (in methyl phentyl ketone) and then filled with chalk (ratio resin (100% solids ) to chalk is 2 to 1). The thus formed mixture is applied according to the method indicated in example 1 on

an aluminum can. To remove water, the coated aluminum tin is placed in the oven for 35 minutes at 90°C, then illuminated for 5, 10 and 15 minutes under Philips "TLK" 40/09 fluorescent tubes at a distance of 15 cm. After subsequent hardening of these test samples for 20 minutes at 90°C, the degree of hardening of these samples is determined according to the Knoop measurement method (ASTM D 1474).

The results are listed in table 2.

- measurement not possible, sample sticky cg soft.

The results show that the illuminated samples already after 5 min. lighting time and 20 min. curing time at 90°C has a sufficient hardness. In contrast, the unilluminated sample is still soft and sticky after 20 min. curing time.

Example 3:

In an aqueous phenol formaldehyde resin MS 7216 (phenol formaldehyde resin (Ciba-Geigy) : 79% by weight solids, aqueous solution, pH 4.5, viscosity 2.5-3 Pas at 25°C, molar ratio phenol : formaldehyde is 1 : 1.8 ), 30% by weight (referred to the solids content of the phenol formaldehyde resin) is mixed with a 10% by weight catalyst solution (in methylpentyl ketone). The solution thus formed is applied according to the method mentioned in example 1 to an aluminum tin, stirred with corundum, placed for 35 minutes at 90°C in a circulation drying cabinet and then illuminated for 5, 10 and 15 minutes under fluorescent tubes. After the subsequent curing for 20 minutes at 90°C, the samples are tested as in example 1. The results are listed in Table III.

"♦measurement not possible, sample sticky and soft. A, B: explanation in example 1.

Claims (13)

1. Process for curing abrasive compositions containing an acid-curable binder and as curing catalyst an organic sulfonic acid that can be released by exposure to light, characterized by irradiating the abrasive composition after drying with light and curing. 2. Method according to claim 1, characterized in that the curing takes place at temperatures between 60°C and 100°C. 3. Method according to claim 1, characterized in that the illumination takes place with UV light. 4. Method according to claim 1, characterized in that organic ■compounds of formula I and II are used as curing catalyst in which n means the numbers 1 or 2 and R, means an unsubstituted or, for example, with 1, 2 or 3 residues -Cl, -Br, -CN, -NO2 , C -C -C -alkyl, C -C -Alkoxy, phenyloxy, tolyloxy, phenylthio, tolylthio, C -C -C alkylthio, -SC H2 CH2 OH, <C>1 -C4 -alkylsulfonyl, phenylsulfonyl, C2~ C4 -alkoxycarbonyl, C-^ -^ -alkylamino, C2 -C4 -aialkylamino, phenyl-CONH-, C-^ -C^ alkyl- CONH- or benzoyl-substituted phenyl or naphthyl, or R^ further means anthryl, phenanthryl, thienyl, pyridyl, furyl, indolyl or tetrahydronaphthyl, and R 2 and R^ independently of each other mean hydrogen, unsubstituted or for example with -OH, -CL, C^-^-Alkoxy, -CN, C2-C^-Alkoxycarbonyl, phenyl, chlorophenyl, C7-C1Q-alkylphenyl or C7-C1Q-Alkoxyphenyl substituted C1-C8-alkyl, further benzoyl, Furthermore, Rg means unsubstituted or, for example, with -Cl, C -C -C alkyl. C₁ -C₄ -aloxy or C₁ -C₄ alkylthio substituted phenyl, C₂ -C₆ -alkoxycarbonyl, -CN, C₁ -C₄ -alkyl-NH-CO-, phenyl-NH-CO- or -CONH2 or R2 and Rg together form a carbon atom where- until they are attached a C4 -C8 cycloalkyl ring, R 4 means when n = 1, C 1 -C 1 g -alkyl, unsubstituted or example show with halogen, C-^ -C-^ -alkyl, C-i _-C4 - alkoxy, C-j^ -C^ alkyl-CONH-, phenyl-CONH, ~ N02 or benzoyl substituted phenyl, unsubstituted or for example with halogen, C^ -C-j^ -alkyl or C-^C^- alkoxy substituted naphthyl, C5 -Cg-cycloalkyl, C7 -Cg-aralkyl, campheryl, -CFg, -CClg, -F or~ NH2 , and R4 means when n = 2, a -(CH2 )m~ group, where m means the numbers 2 to 8, or unsubstituted or, for example, with C] _~ C] _2~ alkyl substituted phenylene or naphthylene, R5 means an unsubstituted or with 1, 2 or 3 residues -Cl, Br, C-L-C12 -alkyl, phenyl, C-^ -^-Alkoxy, phenyloxy, benzyl-oxy, CjL-Cg-alkylthio, phenylthio, -SCH2 CH2 OH, C-j^ -C^^ -alkyl-CONH-, benzoylamino , dimethylamino or with benzoyl substituted phenyl or naphthyl or R,, is further anthryl or phenanthryl, Rg means hydrogen, -OH, C₁₋₄-Alkoxy, OSi(CHg)g, -OCOCHg or unsubstituted or phenyl substituted C 1 -C 8 -alkyl, Ry means hydrogen, unsubstituted or phenyl substituted C 1 -C 8 -alkyl, -CN, benzoyl, C 1 -C 4 ~ alkylcarbonyl or C 2 -C 4 -alkylcarbonyl or phenyl, Rg means hydrogen, unsubstituted or with -OH, -Cl or phenyl substituted Cj -Cg-alkyl, unsubstituted or with -OH, -Cl, C-^-C^j-alkyl or C-j^ -C^j - alkoxy substituted phenyl, C 2-C 8 -alkenyl, C 5 -C 8 -phenylalkenyl, furyl, thienyl, -CC 1 or saturated or unsaturated C 5 -C 8 -cycloalkyl or furthermore, R5 with Rg, R7 with Rg or Rg with R-,- together with the carbon structure to which they are attached form a 5- or 6-ring containing 1 to 5 -CH2~ , -CH(CHg)-, -C (CHg).2 -, -0-, -S-, -SO-, -SO2 -, -CO-, -N(CO-C1 -C4 -alkyl)- or -N(COCgH5 ) groups. 5. Method according to claim 4, wherein in formulas I and II n means the number 1, R 1 means an unsubstituted or with chlorine, methyl, methoxy, methyl thio, phenylthio, -SCH^ CI^ OH or benzoyl substituted phenyl, R2 means hydrogen, C-^ -C^ -alkyl and Rg means hydrogen or C-^-C4 -alkyl or R2 and Rg form together with the carbon atom to which a cyclohexane ring is attached, R 4 means C 1 -C 8 -alkyl, unsubstituted or with C 1 -C 2 -alkyl substituted phenyl or naphthyl or campheryl, R^ means an unsubstituted or with -Cl, Cl-C4~ alkyl, C^-- C^- alkoxy, -SCHg or phenyl substituted phenyl, R6 means -OH or C1 -C4~ alkyl, R? means C 1 -3 -alkyl or phenyl and Rg means -H, C-1-4-alkyl, furyl or -CCl, or further R^ with Rg together with the carbon atom to which they are attached form a cyclohexane ring. 6. Method according to claim 4, characterized in that in the formulas I and II n means the number 1, R] _ and R,- means phenyl, p-tolyl or p-methylthiophenyl, R2 means hydrogen, Rg means methyl, isopropyl, n- decyl or benzyl. R4 means phenyl, p-tolyl or p-n-dodecylphenyl, Rg means -OH, R4 means -CHg or phenyl and Rg means -H. 7. Method according to claim 1, characterized in that the acid-curable binder is a pheno or amino plastic and mixtures thereof. 8. Method according to claim 7, characterized in that the acid-curable binder is a phenol formaldehyde resin. 9. Method according to claim 7, characterized in that the acid-curable binder is a resol. 10. Method according to claim 1, characterized in that the acid-curable binder contains 0.1 to 10% by weight, referred to the solvent-free binder, of the curing catalyst. 11. Method according to claim 1, characterized in that the binder is a basic binder. 12. Method according to claim 1, characterized in that the binder is a cover binder. 13. Method according to claim 1 for the production of flexible abrasives on flat support materials.