WO2025131235A1 - Abrasive article - Google Patents

Abstract

The invention relates to an abrasive article comprising, in at least one abrasive layer, at least one binder. The binder contains at least one resin N, the resin N being preparable by a polymer-forming reaction, more particularly polycondensation, of a starting monomer composition, the starting monomer composition comprising at least one B monomer or at least one B monomer and at least one A monomer, the at least one A monomer being selected from the group consisting of phenol, catechol, catechol-like compounds, resorcinol, resorcinol-like compounds, such as 1,3,5-trihydroxybenzene and phloroglucide, 2,6-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 1,5-dihydroxynaphthalene and flavones, and the at least one B monomer being selected from the group consisting of aromatic aldehydes.

Description

Grinding articles

DESCRIPTION

The invention relates to an abrasive article comprising at least one binder in at least one abrasive layer.

Abrasive articles are known for numerous applications in different designs and shapes and are disclosed, for example, in the documents WO 2020147922 A1, WO 2018036616 A1, WO 2020078563 A1, WO 2017032396 A1, WO 2011080328 A2, WO2011109188A2.

Abrasive articles, especially those comprising abrasive grains, usually contain a binder. The abrasive grains (e.g., shaped or optionally crushed) can, for example, be attached to a substrate via the binder or be embedded in the binder matrix.

The binders usually contain a resin as a matrix-forming component, which must have sufficient stability and strength to meet the requirements during grinding and to keep the abrasive grains stable, but at the same time release the abrasive grains to a sufficient extent depending on the type of abrasive article.

In the prior art, it is particularly known to use phenolic resins for this purpose, which are known to be produced by polycondensation of phenol and formaldehyde and are therefore phenol-formaldehyde resins. However, due to the harmful effects of formaldehyde on the environment and health, there is a need to develop environmentally friendly and non-toxic alternative materials that do not suffer any loss of properties with regard to the respective application.

The present invention was therefore based on the object of providing an abrasive article of the type mentioned above, in the production of which environmentally and health-damaging substances, such as formaldehyde in particular, can be omitted, or their amounts can at least be significantly reduced, at least in the binder. At the same time, the abrasive article is to be optimized with regard to the sustainability of the substances used in the binder.

In comparison to abrasive articles containing only phenol-formaldehyde resins in the binder, the abrasive article should continue to exhibit good grinding behavior and thus show no or no significant losses in the properties relevant for the application.

The object is achieved by the abrasive article according to claim 1.

Further advantageous and preferred embodiments of the invention can be found in the claims dependent on claim 1 and in the present description.

The invention encompasses all combinations of features. In particular, the invention also encompasses combinations of features with different levels of preference, including the embodiments. Thus, for example, the invention also encompasses the combination of a feature identified as preferred with another feature identified as particularly preferred. The abrasive article according to the invention comprises at least one binder in at least one abrasive layer.

In the context of the present invention, an “abrasive layer” is understood to mean any type of layer which comprises abrasive elements, such as abrasive grains, and can thus be used to remove material from other objects.

In the context of the present invention, a “binder” is understood to mean the material which binds and thus holds the abrasive elements, such as abrasive grains, to the abrasive article.

The abrasive grains can be embedded in the binder as described above or attached to a substrate via the binder.

Abrasive grains bonded to a backing are also referred to as "coated abrasives." Various materials are known for the backing, such as paper and cotton, as disclosed, for example, in WO 2022090821 A1. For example, these can be sandpapers, which are either used directly or serve as semi-finished products for the production of other abrasive articles, such as abrasive sleeves, sanding belts, flap discs, and fan wheels, as disclosed, for example, in WO 2018036616 A1.

In the context of the present invention, the abrasive layer thus comprises abrasive elements, such as abrasive grains, and at least one binder for holding the abrasive elements. The abrasive article according to the invention thus comprises, in particular in at least one abrasive layer, at least one binder for binding abrasive elements, such as abrasive grains.

The abrasive article according to the invention is, in particular and for example, an article in which the abrasive grains are arranged on a backing via the binder or in which the abrasive grains are fixed in a binder (bonded wheels). The binder may contain fibers, such as organic fibers or glass fibers, for reinforcement. For example, it may be nonwoven textiles.

“non-woven”, such as fleece), or woven textiles, or knitted fabric or glass fabric.

In particular, the abrasive article according to the invention is sandpaper, a grinding wheel, for example in the form of a straight or offset cut-off wheel, a cup wheel, a grinding block, a rough grinding wheel, a grinding pin, a grinding pad, or a flap wheel. The different designs are harmonized, among others, by DIN ISO 525 / EN 12413 and ANSI B.7 / B74.2.

The abrasive elements are, in particular, abrasive grains, whereby the term "abrasive grain" in the context of the present invention is to be understood both in the singular and in the plural and also includes mixtures of abrasive grains of different sizes and/or different types. These can be, without restriction, all abrasive grains known to the person skilled in the art, such as, for example and in particular, abrasive grains made of molten or sintered mono- or polycrystalline grain, i.e., Al2O3, zirconium grain, sintered, microcrystalline sol-gel a-aluminum oxide, cubic boron nitride, Diamond, silicon carbide, silicon nitride, boron carbide, tungsten carbide, titanium carbide, garnet, iron oxide, chromium, cerium, titanium, silicates, tin oxide, silica.

The abrasive grains may also have a surface coating, as is known to those skilled in the art.

According to the invention, the binder contains at least one resin N, wherein the resin N can be prepared by a polymer formation reaction, in particular polycondensation, of a starting monomer composition, wherein the starting monomer composition comprises at least one B monomer or at least one B monomer and at least one A monomer, wherein the at least one A monomer is selected from the group consisting of phenol, catechol, catechol-like compounds, resorcinol, resorcinol-like compounds such as 1,3,5-trihydroxybenzene and phloroglucid (CAS: 491-45-2), 2,6-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 1,5-dihydroxynaphthalene and flavones, and wherein the at least one B monomer is selected from the group consisting of aromatic aldehydes.

The term “B monomer” is freely chosen in the context of the present invention and is defined as a monomer selected from the group consisting of aromatic aldehydes.

The B monomers are specifically chosen to be electron-poor, electrophilic reaction partners. The phrase "electron-poor, electrophilic reaction partners" refers primarily to the carbonyl functionality and is always relative to the electron density of the nucleophilic reaction partner. In the context of the present invention, the terms “B monomer” and “monomer B” are used synonymously.

The term “A-monomer” is freely chosen in the context of the present invention and is defined as being an aromatic hydroxy-containing compound selected from the above-mentioned group.

The A monomers are specifically chosen to be electron-rich, nucleophilic reaction partners. The phrase "electron-rich, nucleophilic reaction partners" is always relative to the electron density of the electrophilic reaction partner.

In the context of the present invention, the terms “A monomer” and “monomer A” are used synonymously.

The term “resin N” is freely chosen within the scope of the present invention and is defined by the fact that it can be prepared by a polymer formation reaction, in particular polycondensation, from the monomers B mentioned alone or from the monomers B and A, each optionally in combination with further monomers.

Surprisingly, it has been found that abrasive articles could be produced which have at least one resin N in the binder in at least one abrasive layer without any significant loss in the properties of the abrasive article.

Due to the above-mentioned selection of B monomers in the starting monomer composition, the resin N can be produced formaldehyde-free, thus eliminating the use of substances that are harmful to the environment and health. At the same time, the aforementioned monomers A and B can be obtained from renewable raw materials such as lignin.

The abrasive article according to the invention can thus be produced in a more sustainable and environmentally friendly manner while maintaining comparable grinding performance.

The proportion of monomers from renewable raw materials in the resin N can be detected in particular via the ¹⁴ C content of the carbon.

The binder contains resin N as a component of its matrix.

In other words, the resin N, optionally in combination with other resins, provides the binder matrix to or in which the abrasive elements are bound.

The at least one B monomer is selected from the group consisting of aromatic aldehydes.

Preferably, the aromatic aldehyde of the B monomers has a benzene ring as the aromatic group.

Preferably, the aromatic aldehyde is selected from the group consisting of

Terephthalaldehyde (benzene-1,4-dicarbaldehyde),

Isophthalaldehyde (benzene-1,3-dicarbaldehyde),

Vanillin (4-Hydroxy-3-methoxybenzaldehyde),

isovanillin (3-hydroxy-4-methoxybenzaldehyde),

anisaldehyde (4-methoxybenzaldehyde),

Syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde), benzaldehyde,

Salicylaldehyde (2-Hydroxybenzaldehyde), 3-Hydroxybenzaldehyde, 4-Hydroxybenzaldehyde, 2-Tolulaldehyde, 3-Tolulaldehyde, p-Tolulaldehyde (4-Tolulaldehyde), veratrumaldehyde (3,4-dimethoxybenzaldehyde), o-veratrumaldehyde (2,3-dimethoxybenzaldehyde), 2,3-dihydroxybenzaldehyde,

Protocatechualdehyde (3,4-dihydroxybenzaldehyde),

3, 5-dihydroxybenzaldehyde, 2, 6-dihydroxybenzaldehyde,

Piperonal (3,4-(methylenedioxy)benzaldehyde),

2.3.4-Trihydroxybenzaldehyde, 2,4,5-Trihydroxybenzaldehyde,

3.4.5-Trihydroxybenzaldehyde, 2,4,6-Trihydroxybenzaldehyde,

2.3.4.6-Tetrahydroxybenzaldehyde, 2,4,5,6-Tetrahydroxybenzaldehyde.

According to preferred embodiments, the aromatic aldehyde is selected from the group consisting of terephthalaldehyde, isophthalaldehyde, vanillin, isovanillin, anisaldehyde, syringaldehyde, benzaldehyde, 4-hydroxybenzaldehyde, p-tolulaldehyde, veratrumaldehyde, o-veratrumaldehyde, salicylaldehyde, protocatechualdehyde, piperonal, 2,3,4-trihydroxybenzaldehyde, 2,4,5-trihydroxybenzaldehyde, 3,4,5-trihydroxybenzaldehyde,

2,4,6-Trihydroxybenzaldehyde.

According to particularly preferred embodiments, the aromatic aldehyde is selected from the group consisting of terephthalaldehyde (benzene-1,4-dicarbaldehyde), isophthalaldehyde (benzene-1,3-dicarbaldehyde), vanillin (4-hydroxy-3-methoxybenzaldehyde), isovanillin (3-hydroxy-4-methoxybenzaldehyde), anisaldehyde (4-methoxybenzaldehyde), syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde), benzaldehyde, salicylaldehyde (2-hydroxybenzaldehyde), 3-hydroxybenzaldehyde, 4-hydroxybenzaldehyde, 2-tolulaldehyde, 3-tolulaldehyde, p-tolulaldehyde (4-tolulaldehyde), veratrumaldehyde (3,4-dimethoxybenzaldehyde), o-veratrumaldehyde (2,3-dimethoxybenzaldehyde), protocatechualdehyde (3,4-dihydroxybenzaldehyde), piperonal (3,4-(methylenedioxy)-benzaldehyde), 2,3,4-trihydroxybenzaldehyde, 2,4,5-trihydroxybenzaldehyde, 3,4,5-trihydroxybenzaldehyde, 2,4,6-trihydroxybenzaldehyde.

These monomers can be obtained particularly well from renewable raw materials, allowing the abrasive article according to the invention to be manufactured more sustainably. Surprisingly, this is achieved without any significant loss in the performance of the abrasive article.

In the event that only monomers B are present and thus no phenolic monomer A is present, the aromatic aldehyde is preferably selected from the group consisting of vanillin, isovanillin, 2-hydroxybenzaldehyde, 3-hydroxybenzaldehyde, 4-hydroxybenzaldehyde, 2,3-dihydroxybenzaldehyde, 3,4-dihydroxybenzaldehyde, 3,5-dihydroxybenzaldehyde, 2,6-dihydroxybenzaldehyde, 2,3,4-trihydroxybenzaldehyde, 2,4,5-trixydroxybenzaldehyde, 3,4,5-trixydroxybenzaldehyde, 2,4,6-trihydroxybenzaldehyde, 2,3,4,6-tetrahydroxybenzaldehyde, 2,4,5,6-tetrahydroxybenzaldehyde.

This eliminates the need for a phenolic component, i.e., monomer A, in the starting monomer composition. This has a beneficial effect on the complexity and cost-effectiveness of producing the abrasive articles according to the invention.

Particularly preferred within the scope of the present invention are terephthalaldehyde and/or vanillin and/or isophthalaldehyde. These aromatic aldehydes in the starting monomer composition of the resin N of the binder result in particularly good abrasive articles with regard to grinding behavior. At the same time, these monomers, especially vanillin, can be obtained on an industrial scale from renewable raw materials.

Since not all monomers usually react in a polycondensation reaction and thus traces of the starting monomers remain, the aromatic aldehydes, in particular terephthalaldehyde and/or vanillin, can be detected in the abrasive article via their characteristic odor, which can also be considered an advantage.

The at least one A monomer is selected from the group consisting of phenol, catechol, catechol-like compounds, resorcinol, resorcinol-like compounds such as 1,3,5-trihydroxybenzene and phloroglucide, 2,6-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, and flavones.

In the context of the present invention, the term “catechol-like compound” is understood to mean a chemical compound which, like catechol, has at least two hydroxy groups in the ortho position to one another on the aromatic ring system and which in particular cannot be regarded as a B monomer and is therefore in particular not an aromatic aldehyde which can react as a B monomer.

Preferably, the catechol-like compound is defined by being selected from the group consisting of dopamine, 4-fluorocatechol, 4-chlorocatechol, 4-bromocatechol, 4-methylcatechol, 1,2-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 1,2,4-trihydroxybenzene, 3-methoxycatechol, 4/e/7-butylpyrocatechol, 3,4-dihydroxybenzophenone, hydroxychavicol, 4,4'-(2,3-dimethylbutane-1,4-diyl)dibenzene-1,2-diol, caffeic acid, caffeic acid ester, 4-allylpyrocatechol, 2-(3,4-dihydroxyphenyl)ethyl alcohol, 1,2,3-trihydroxybenzene, tannic acid, 2, 3, 6, 7, 10, 11-hexahydrotriphenylene, and 2,3,4,4-tetrahydroxydiphenylmethane.

In the context of the present invention, the term "resorcinol-like compound" refers to a chemical compound which, like resorcinol, has at least two hydroxyl groups in the meta position to one another on the aromatic ring system and preferably does not have two hydroxyl groups in the ortho position to one another. In particular, it cannot be regarded as a B monomer and is therefore not an aromatic aldehyde that can react as a B monomer. The resorcinol-like compound is preferably selected from 1,3,5-trihydroxybenzene and phloroglucid.

Resin N can be produced by polycondensation from the aforementioned monomers. This means that resin N can formally be traced back to a corresponding starting monomer composition.

It is known to the person skilled in the art that, instead of the monomers mentioned, derivatives of the monomers can also be used as direct starting substances, which in particular and for example represent formal intermediates of the reaction of an aldehyde in such a polycondensation reaction or have a similar reactivity and provide the same monomer building blocks in the polycondensate.

Instead of the aldehydes mentioned, the corresponding alcohols, such as methyl alcohols, or aromatic carboxylic acid esters, such as methyl or ethyl esters, can also be used.

As a carboxylic acid ester of terephthalaldehyde (benzene-1,4-dicarbaldehyde), a 1,4-benzenedicarboxylic acid alkyl ester, such as 1,4-benzenedicarboxylic acid methyl ester, can also be used as the starting monomer.

The corresponding alcohol is 1,4-benzenedimethanol (CAS: 589-29-7). As a carboxylic acid ester of vanillin, the methyl ester methyl 4-hydroxy-3-methoxybenzoate can be used, for example.

The invention thus also encompasses an abrasive article which has a resin N in the binder which is produced by polycondensation of a starting monomer composition containing the corresponding alcohols, such as methyl alcohols, or aromatic carboxylic acid esters, such as methyl or ethyl esters, of the above-mentioned aromatic aldehydes.

According to particularly preferred embodiments of the invention, the starting monomer composition contains at least one A monomer in addition to at least one B monomer.

Catechol and/or phenol are particularly preferred as the A monomer. These monomers have been found to react particularly well with an aromatic aldehyde, especially vanillin and/or terephthalaldehyde and/or isophthalaldehyde, to form a corresponding polycondensate, making them particularly suitable for industrial-scale production.

At the same time, the abrasive articles produced with it have good grinding properties.

In addition, catechol and phenol can be obtained from renewable raw materials such as lignin.

The mass fraction of catechol and/or phenol is preferably at least 50%, particularly preferably at least 70%, in particular 100%, in each case based on the total mass of the A monomers. It is therefore conceivable that other A monomers mentioned above may also be present. However, the highest possible proportion of catechol and/or phenol is particularly preferred.

According to preferred embodiments of the invention, the starting monomer composition contains as B monomer at least terephthalaldehyde, isophthalaldehyde and/or vanillin.

It has been found that these monomers react particularly well to form a corresponding polycondensate, making them particularly suitable for large-scale production.

The corresponding resins N produced from them also have sufficient temperature stability so that they can withstand the conditions during curing of the abrasive articles.

At the same time, the abrasive articles produced with it have good grinding properties.

In addition, terephthalaldehyde, isophthalaldehyde and vanillin can be obtained from renewable raw materials such as lignin.

The mass fraction of terephthalaldehyde, isophthalaldehyde and/or vanillin is preferably at least 50%, particularly preferably at least 70%, in particular 100%, in each case based on the total mass of the B monomers.

It is therefore conceivable that other B monomers mentioned may also be present. However, the highest possible proportion of terephthalaldehyde and/or vanillin and/or isophthalaldehyde is particularly preferred.

As stated above, the B monomers in particular are selected so that the use of free formaldehyde as a monomer in the starting monomer composition of resin N is avoided. which makes the production of the resin and thus that of the binder and the abrasive article according to the invention more environmentally friendly and non-toxic.

According to particularly preferred embodiments of the invention, the starting monomer composition is therefore free of formaldehyde. The term "free of formaldehyde" means, in particular, a mass fraction of 0 to 0.1%, ideally 0%, based on the total mass of the monomer composition.

However, it is also conceivable that small amounts of formaldehyde are added, provided that this seems appropriate for the respective reaction procedure, for example.

The advantage achieved by the invention is nevertheless realized, although not to the maximum extent.

According to preferred embodiments of the invention, the combined mass fraction of the above-mentioned A monomers and B monomers in the monomer composition is therefore at least 50%, preferably at least 60%, particularly preferably at least 70%, very particularly preferably at least 80%, again preferably at least 90%, in particular 100%, in each case based on the total mass of the monomer composition.

In all embodiments and explanations in which reference is made to the mass fraction of certain monomers relative to the total mass of the monomer composition, only monomers are considered.

Catalysts contained in the initial reaction mixture are not taken into account in these data and are added additionally. In the embodiments in which the combined mass fraction of the A monomers and B monomers in the monomer composition is less than 100%, further monomers which do not fall under the list of A or B monomers are included.

For example, formaldehyde may be included as an additional monomer, but preferably in the smallest possible amounts, in particular up to 2%.

Furthermore, further monomers may be included in the monomer composition which can polycondense with the B monomers or the B and A monomers to form a resin.

However, the combined mass fraction of the A monomers and B monomers in the monomer composition is particularly preferably 100% based on the total mass of the monomer composition.

As a result, all monomers are non-toxic, available from renewable raw materials and, due to their reactivity, suitable for reacting in a polycondensation to form a resin N.

According to preferred embodiments, the resin N contained in the binder can be produced by polycondensation of B monomers alone, i.e. without A monomers.

The mass fraction of the above-mentioned B monomers in the starting monomer composition is thus preferably 80 to 100%, preferably 90 to 100%, in particular 100%, in each case based on the total mass of the monomer composition. Vanillin is preferably present as B monomer in a mass fraction of 90 to 100%, preferably 100%, based on the total mass of the B monomers, in the starting monomer composition.

According to these embodiments, resin N is thus a vanillin resin without a corresponding phenolic component. What's special about this is that the aldehyde function of the vanillin undergoes self-condensation with the aromatic backbone of the vanillin. Thus, it is formally an "AB2 monomer."

A special feature of this monomer type is that condensation results in so-called hyperbranched polymers (HBPs). Due to their globular structure, such polymers exhibit lower viscosity, higher solubility, and a higher degree of functionality than their more linear analogues. The following literature describes the possible structures that AB2-type HBPs can adopt, as well as the thermal, mechanical, and rheological properties of polymers of this type: Higashihara, T., Segawa, Y., Sinananwanich, W. et al. Synthesis of hyperbranched polymers with controlled degree of branching. Polymer Journal 44, 14-29 (2012).

To achieve a high degree of polymerization or a high crosslinking density in a 3D network, the stoichiometric ratio of A to B functional groups must be balanced. This is not the case with an AB2-type monomer. As a result, type A monomers or polymers are required for effective crosslinking (see also the Carothers equation according to Wallace Hume Carothers).

In the manufacture of the abrasive article, such a vanillin resin is therefore preferably mixed, for example in powder form, with a liquid and/or A powdered component of the A-monomer group, such as phenol, or a liquid and/or powdered additional resin N comprising the above-mentioned A-monomers, is mixed. Subsequently, the abrasive articles are then cured during heating to form a thermoset in order to achieve sufficient hardness and strength.

According to particularly preferred embodiments, the resin N contained in the binder can be prepared by polycondensation of at least one B monomer with at least one A monomer.

According to particularly preferred embodiments, the resin N is a catechol-vanillin resin or a catechol-terephthalaldehyde resin or a phenol-terephthalaldehyde resin or a catechol-isophthalaldehyde resin.

The production of the resin N contained in the binder of the abrasive article according to the invention is carried out in particular analogously to the production of conventional phenol-formaldehyde resins.

The production and curing of phenol-formaldehyde resins are known to the person skilled in the art and are described, among other things, in “Phenolic Resins, Chemistry, Application, Standardization, safety and Ecology”,

A. Gardziella, L.A. Pilato, A. Knop Springer Verlag, ISBN: 3-540-65517-4.

The person skilled in the art is also aware of a number of catalysts and corresponding amounts of catalysts used for the condensation reaction between aromatics and carbonyl functions. Phenol-formaldehyde resins are divided into novolaks and resoles depending on the molar ratio of formaldehyde to phenol and the pH value during production or the catalyst used - acidic or basic.

Resoles are typically produced using base catalysis, and an excess of formaldehyde relative to phenol is used. As a result, the resulting resins contain methylol residues as end groups. These resins have lower storage stability and are thermally self-curing.

Novolaks are typically produced using acid catalysis and an excess of phenol. The resulting prepolymer is a thermoplastic that requires a hardener to form a three-dimensional network. Hexamethylenetetramine is typically used as the hardener.

It has been found that the conditions mentioned can be transferred analogously to the production of the resin N contained in the invention.

The basic or acidic catalysts and catalyst concentrations commonly used for the production of resoles or novolaks can be transferred to the resins N. For novolaks, see: Controlled Synthesis of High-Ortho-Substitution Phenol-Formaldehyde Resin, 2004, DOI: 10.1002/app.21808.

The basic catalysts known for the production of resoles can be transferred. However, when using aromatic aldehydes, in contrast to phenol-formaldehyde resoles, no primary methylol groups are formed, but rather secondary alcohols at the methyleneol Bridge between two aromatics. Furthermore, Grenado et al. were able to demonstrate that, especially during prepolymer characterization when using aromatic dialdehydes, especially terephthalaldehyde, the second aldehyde function remains largely unreactive, as demonstrated by NMR and IR spectroscopy: "Toward Sustainable Phenolic Thermosets with High Thermal Performances," 2019, DOI: 10.1021/acssuschemeng.8b06286.

This means that if the resins can be classified as resoles based on the phenol-formaldehyde nomenclature in the case of an excess of the aldehyde function and basic catalysis, their behavior may differ from the classic phenol-formaldehyde resoles.

According to preferred embodiments, the amount of catalyst used is, for example, between 3 and 5 mol% based on the phenolic component, i.e., based on the amount of monomers A. However, it is also conceivable to use smaller or larger amounts. Furthermore, it is known that catalysts that can be present as solids, such as sodium hydroxide (NaOH), can be used dissolved in water or water/ethanol, with the solvent and, if applicable, the condensation products then being distilled off again during the reaction.

It is also known to the person skilled in the art that in the production of phenol-formaldehyde resins, the monomers phenol and formaldehyde or, where appropriate, reactive intermediates thereof can be used in different molar ratios to one another in order to influence the properties of the resin. However, within the scope of the present invention, the inventor was able to identify particularly suitable molar ratios of B monomers to A monomers and correspondingly catalyzed reaction conditions.

All ratios mentioned in the context of the present invention are exemplary and have been identified as preferred within the scope of the invention.

According to preferred embodiments of the invention, the molar ratio of B monomers to A monomers in the starting monomer composition is from 1:0.5 to 1:4 (1 to 0.5 to 1 to 4), particularly preferably from 1:1.2 to 1:4, most preferably from 1:1.5 to 1:3.2.

The reaction preferably takes place under acidic conditions. In principle, all acids known for the production of novolaks are suitable in amounts known to those skilled in the art.

Suitable acids include, for example, oxalic acid and phosphoric acid.

The resins N obtained then correspond to novolak resins.

Because A monomers with a number of more than one functionality, such as catechol, and B monomers that may also have functionalities of A monomers, such as the AB2 monomer vanillin, can be included in the monomer composition, molar ratios of B monomers to A monomers that are 1 to less than 1 (such as 1:0.5) also lead to novolak-like resins. According to further preferred embodiments of the invention, the molar ratio of B monomers to A monomers in the starting monomer composition is from 1:0.25 to 2 (1 to 0.25 to 2), preferably from 1:0.25 to 1.1, particularly preferably from 1:0.3 to 1:1, again preferably from 1:0.3 to 1:0.85.

The reaction preferably takes place under basic conditions. All bases known for the production of resoles are suitable.

Sodium hydroxide solution is a suitable and preferred base.

The resins N obtained then correspond to resol resins.

Here too, depending on the type of monomers and the reaction procedure, a deficiency of B monomers is conceivable and a resole resin can still be achieved.

Even a resin N that can be produced by polycondensation of B monomers alone, such as the vanillin resin described above, can be produced as a hyperbranched polymer under basic conditions. The resulting resins N then correspond to hyperbranched polymers (HBPs), or HBP resins.

After polycondensation has taken place, the “A-state” or “B-state” of the resin, known to those skilled in the art, is initially obtained as a prepolymer in which the resin is still deformable.

The resin N can be present as a powder resin (P-resin) or as a liquid resin (F-resin). Preferably, the resin N has a weight average molecular weight distribution M _w of 400 to 4000 g/mol, particularly preferably of 500 to 2500 g/mol.

The determination of the weight average molecular weight distribution M _w is carried out in the present invention according to GPC (gel permeation chromatography, conventional calibration with polystyrene (PS) standards, eluent: THF/0.1vol% TFA, pre-column: PSS SDV, 3pm, Guard, ID 8.00mm x 50.00mm, 3 columns: PSS SDV, 3pm, 1000Å, ID 8.00mm x 300.00mm, flow rate: 1.0 mL/min, injection system: PSS-SECcurity 1260 autosampler; injection volume: 20 pL; sample concentration: 5.0 g/L; 23 °C; detectors: SECcurity ² differential refractometer detector (RI); evaluation: PSS - WinGPC UniChrom version 8.4).

In particular, the resin N has a melting range, measured using the Kotier heating bench system, of 80 to 180 °C, preferably 90 to 170 °C.

The Kotier heating bench system can be used for a wide range of tasks and enables the rapid identification of organic substances in the temperature range from 50 °C to 260 °C. Manufacturer: Wagner & Münz.

Calibration substances: Azobenzene (68 °C), Benzil (95.0 °C), Acetanilide (114.5 °C), Phenacitin (134.5 °C), Benzanilide (163 °C), Salophen (191 °C), Dicyandiamide (210 °C), Saccharin (228 °C).

Basis of the test method: Ground powder resin is placed on the Kofler heating bench and the melting range is determined. Powder applied below the melting range remains unchanged; in the melting range, Resin that is too dense sticks to the heating bench. In the first zone above the melting point, the resin is liquid, and in the uppermost zone, it has already fully cured.

The manufacturer states that the accuracy of the measurement depends on the calibrated range on the heating bench. For example, if the heating bench is calibrated for the medium range, the measurement accuracy is within this range of ± 1°C. The further the sample is from the calibrated range, the less accurate the measurement results become. For this reason, a calibration substance should always be used whose melting point is close to the melting point of the substance being tested.

To produce the binder, resin N is mixed with other components if necessary.

Depending on the type of abrasive article, at least one liquid resin or at least one liquid resin and at least one powder resin in combination with one another are used in the binder during production.

In the case of an abrasive article in which the abrasive grains are bonded to a backing, at least one liquid resin is added to the binder, with only an optional further resin in powder form being added.

In the case of an abrasive article in which the abrasive grains are incorporated into the binder matrix, at least one powder resin and preferably at least one liquid for wetting the abrasive grains and for binding the powder resin to the abrasive grains are added to the binder. The liquid can be water, an organic solvent, or a liquid resin, with liquid resins being used within the scope of are preferred in the present invention. Furthermore, abrasive grains and optional fillers, such as, in particular, abrasive-active fillers, are added to the binder.

In addition, such binders can contain reinforcing fabrics (“non-woven”, “woven” or “knitted”), e.g. glass fabric or organic fibers, see above.

After the binder has been produced, it is arranged as a component of the abrasive article, as is known to those skilled in the art, and is shaped and compacted into the appropriate form, for example in the form of a straight or offset cutting-off wheel or a grinding pin or a grinding cup or grinding block.

The abrasive article is then baked, which cures the resin N and thus, in particular, converts it into the so-called "C-stage." The curing of abrasive articles is known to those skilled in the art and is described, among other things, in "Phenolic Resins, Chemistry, Application, Standardization, Safety and Ecology," by A. Gardziella, L.A. Pilato, A. Knop, Springer Verlag, ISBN: 3-540-65517-4.

The resin N is then present in the binder of the at least one abrasive layer of the abrasive article according to the invention in particular as a thermoset.

According to preferred embodiments, the binder contains the at least one resin N in a combined mass fraction of 90 to 100%, in particular 100%, based on the total amount of resins contained in the binder. As a result, the abrasive article according to the invention is particularly optimized with regard to the object underlying the invention.

According to preferred embodiments of the invention, the B monomers and/or A monomers of the starting monomer composition were obtained from renewable raw materials, such as lignin, in a combined mass fraction of 50 to 100%, preferably 80 to 100%, in particular 100%, based in each case on the total mass of the monomer composition. The proportion of renewable raw materials can be determined, as is known to those skilled in the art, by determining ^{the 14} C content of the carbon.

According to further preferred embodiments, the binder additionally contains at least one phenol-formaldehyde resin.

For example, in the case of a combination of powder resin with a liquid resin, the resin N can be added as powder resin and the phenol-formaldehyde resin as liquid resin to the uncured binder, or vice versa.

Furthermore, it is conceivable that at least one resin N and at least one phenol-formaldehyde resin are added as powder resins.

It is also conceivable that at least one resin N and at least one phenol-formaldehyde resin are added as liquid resin.

Particularly advantageous results with regard to grinding behavior are achieved with embodiments in which the mass ratio of resin(s) N to phenol-formaldehyde resin(s) in the binder is 4: 1 to 1:4, in particular 1.32: 1 to 1:3.33. According to particularly preferred embodiments of the invention, the mass ratio of resin(s) N to phenol-formaldehyde resin(s) in the binder is 1:1.36 to 1:2.53.

In addition to the resins described, the binder may contain other components such as adhesion promoters and/or fillers, in particular abrasive fillers such as potassium aluminum fluoride, and/or pigments such as graphite.

Another aspect of the present invention is a resin N for use in binders of abrasive layers of abrasive articles.

All of the above statements apply to the resin N according to the invention.

A further aspect of the present invention is a process for producing the resin N according to the invention, which is characterized by appropriate selection of the above-mentioned monomers including all preferred features and embodiments.

A further aspect of the present invention is a process for producing the abrasive article according to the invention, which is characterized by appropriate selection of the above-mentioned monomers and process steps including all preferred features and embodiments.

The invention will now be further illustrated by means of exemplary embodiments.

Tables 1 and 2 list resins N which are used according to the invention in binders of abrasive articles. The resins were each prepared as prepolymers using the indicated monomers in the respective molar ratio (V) and the indicated catalyst (Cat.) in a manner otherwise known to those skilled in the art. Table 1 lists powder resins and also provides the values for M _w and the melting range of the resins.

Table 2 lists liquid resins and their viscosities.

Tabelle 2

Table 1

Table 2

So-called resin-bonded abrasive articles were manufactured in which the resins N according to the invention according to Table 1 or 2 were used in the abrasive layer and were tested according to Test 1 (P 1) and Test 2 (P 2) with regard to their cut number “S”.

The results are summarized in Table 3. The examples according to the invention are marked with "E." The respective reference is marked with "V" as a comparative example.

Before testing, the abrasive articles are dried for 24 hours (h) at 130 °C and then subjected to accelerated aging in a climate chamber. Accelerated aging corresponds to storage for 7 to 8 weeks in a temperate northern European climate. Examination 1 (P 1)

This is a self-developed automated test bench in which all relevant grinding parameters (contact pressure, feed rate, speed, etc.) are kept constant. The test is performed on round steel (material number 1.4301). The results are evaluated relative to the standard.

Examination 2 (P 2)

This is a self-developed automated test bench in which all relevant grinding parameters (contact pressure, feed rate, speed, etc.) are kept constant. The test is performed on 10 mm flat steel (material number 1.0038).

The results of test 1 and test 2 are each evaluated relative to the respective comparison reference, whereby the cut number of the respective reference was set to 100%.

Positive values for the examples according to the invention mean an improvement in the number of cuts compared to the reference, i.e. “+8” for example means a performance of 108%.

Negative values mean correspondingly lower values compared to the reference, so “-H” for example means a performance of 89%.

The abrasive article is a cut-off wheel with the specified thickness and resin-bonded abrasive grains. The mass of the respective abrasive article is also specified in Table 3.

The abrasive articles were manufactured in a manner known to those skilled in the art by arranging and shaping the components and then Finally, the resins were cured in the binder by heating, as disclosed in particular in “Phenolic Resins, Chemistry, Application, Standardization, safety and Ecology”, A. Gardziella, LA Pilato, A. Knop Springer Verlag, ISBN: 3-540-65517-4 (short “Phenolic resins”).

For each test, an abrasive article with the same parameters and the same raw material batches (e.g., grain and fillers) was used, but the binder contained only phenol-formaldehyde resin (liquid and powder resin). Curing and conditioning were performed at the same time in the same oven/climate chamber.

As liquid phenol-formaldehyde resin, a resole resin with a M _w between 300 and 1500 g/mol was used, according to the recommendation in “Phenolic Resins”, especially pages 323 and 324.

A novolak with a M _w of 6000 g/mol was used as the powdered phenol-formaldehyde resin. The melting range and the corresponding flow distance (ISO 8019) as well as the required hardener content (hexamethylene tereate) (ISO 8988) are based on the recommendation of "Phenolic Resins," page 326, Table 6.82 No. 4, for dry grinding with high thermal stability.

In the examples according to the invention, phenol-formaldehyde resin was partially or completely replaced in the powder resin (P-resin) or in the liquid resin (F-resin), whereby all other parameters were kept constant and, in particular, the same raw material batch of the phenol-formaldehyde resins was used in each case compared to the respective reference.

Table 3 shows the resulting proportion of the respective resin N in the binder. In addition to the resin, the respective binder contains an abrasive filler (potassium aluminum fluoride) and a pigment (graphite). The abrasive grains are crushed, coated single-crystal corundum with a primary grain size of F46 according to FEPA. To increase mechanical stability, the abrasive article contains two external glass fiber support fabrics, as is common in the industry.

As can be seen from Table 3, the abrasive articles according to the invention comprising at least one resin N in the abrasive layer of abrasive articles achieve comparable cut numbers compared to abrasive articles containing only conventional phenol-formaldehyde resin, and any performance losses are limited to such an extent that the abrasive articles continue to be high-performance. The abrasive articles according to the invention have the advantage of being improved in terms of sustainability and toxicity.

Table 3

According to further examples, grinding tools were manufactured according to the disclosure WO 2018149483 in a manner known to those skilled in the art, in particular according to the disclosure in “Phenolic resins”. The tool Each had shape 29 according to the ISO standard. Precision-shaped, polycrystalline aluminum oxide was used as the abrasive grain.

The reference is an abrasive article with the same parameters and the same raw material batches (e.g. grain and fillers), but which only contains phenol-formaldehyde resin in the binder.

In the examples according to the invention, this phenol-formaldehyde resin was partially replaced in the liquid resin (F resin). The above specifications apply to the phenol-formaldehyde resins used, whereby all other parameters were kept constant and, in particular, the same raw material batch of phenol-formaldehyde resins was used in each case compared to the respective reference.

Table 4 shows the resulting proportion of the respective resin N in the binder.

In addition to the resin, the respective binder contains at least one abrasive filler (potassium aluminum fluoride) and a pigment (graphite).

The samples were tested for total removal and aggressiveness according to Test 3.

Exam 3

This is a self-developed automated test bench in which all relevant grinding parameters (contact pressure, feed rate, speed, etc.) are kept constant. The test is performed on 10 mm flat steel (material number 1.0038). The results are evaluated relative to the standard. The aggressiveness is defined here as the total removal divided by the grinding time and is given in g/min.

In Table 4, the comparison reference has again been normalized to 100% and the values for the examples according to the invention show either an upward (positive numbers) or downward (negative numbers) performance deviation.

Assessing aggressiveness plays a key role in the handling of abrasive products, as higher aggressiveness results in increased productivity, which compensates for any increased tool wear. Therefore, an increase in aggressiveness compensates for any loss in overall removal rate.

This also applies to the examples according to the invention, as shown in Table 4.

Examples E9 and E10 in Table 4 therefore show comparable properties compared to reference V7.

Table 4

Claims

Patent claims 1. An abrasive article comprising at least one binder in at least one abrasive layer, characterized in that the binder contains at least one resin N, wherein the resin N can be produced by a polymer formation reaction, in particular polycondensation, of a starting monomer composition, wherein the starting monomer composition comprises at least one B monomer or at least one B monomer and at least one A monomer, wherein the at least one A monomer is selected from the group consisting of phenol, catechol, catechol-like compounds, resorcinol, resorcinol-like compounds such as 1,3,5-trihydroxybenzene and phloroglucide, 2,6-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 1,5-dihydroxynaphthalene and flavones, and wherein the at least one B monomer is selected from the group consisting of aromatic aldehydes. 2. Abrasive article according to claim 1, characterized in that the aromatic aldehyde has a benzene ring as an aromatic group and is preferably selected from the group consisting of terephthalaldehyde, isophthalaldehyde, vanillin, isovanillin, anisaldehyde, syringaldehyde, benzaldehyde, 4-hydroxybenzaldehyde, p-tolulaldehyde, veratrumaldehyde, o-veratrumaldehyde, salicylaldehyde, protocatechualdehyde, piperonal, 2,3,4-trihydroxybenzaldehyde, 2,4,5-trihydroxybenzaldehyde, 3,4,5-trihydroxybenzaldehyde, 2,4,6-trihydroxybenzaldehyde, with terephthalaldehyde, isophthalaldehyde and/or vanillin being particularly preferred. 3. Abrasive article according to claim 1 or 2, characterized in that the catechol-like compound is selected from the group consisting of dopamine, 4-fluorocatechol, 4-chlorocatechol, 4-bromocatechol, 4-methylcatechol, 1,2-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 1,2,4-trihydroxybenzene, 3-methoxycatechol, 4-butylpyrocatechol, 3,4-dihydroxybenzophenone, hydroxychavicol, 4,4'-(2,3-dimethylbutane-1,4-diyl)dibenzene-1,2-diol, caffeic acid, caffeic acid ester, 4-allylpyrocatechol, 2-(3,4-dihydroxyphenyl)ethyl alcohol, 1,2,3-trihydroxybenzene, tannic acid, 2,3, 6, 7, 10, 11 -hexahydrotriphenylene, and 2,3,4,4 -tetrahydroxydiphenylmethane. 4. Abrasive article according to one of the preceding claims, characterized in that the starting monomer composition contains at least catechol and/or phenol as A monomer, wherein the mass fraction of catechol and/or phenol is preferably at least 50%, particularly preferably at least 70%, in particular 100%, in each case based on the total mass of the A monomers. 5. Abrasive article according to one of the preceding claims, characterized in that the starting monomer composition contains as B monomer at least terephthalaldehyde, isophthalaldehyde and/or vanillin, wherein the mass fraction of terephthalaldehyde, isophthalaldehyde and/or vanillin is preferably at least 50%, particularly preferably at least 70%, in particular 100%, in each case based on the total mass of the B monomers. 6. Abrasive article according to one of the preceding claims, characterized in that the starting monomer composition is free of formaldehyde. 7. Abrasive article according to one of the preceding claims, characterized in that the combined mass fraction of the A monomers and B monomers in the monomer composition is at least 50%, preferably at least 60%, particularly preferably at least 70%, very particularly preferably at least 80%, again preferably at least 90%, in particular 100%, in each case based on the total mass of the monomer composition. 8. Abrasive article according to one of the preceding claims, characterized in that the mass fraction of B monomers in the starting monomer composition is 80 to 100%, preferably 90 to 100%, in particular 100%, in each case based on the total mass of the monomer composition, wherein vanillin is preferably present as B monomer in a mass fraction of 90 to 100%, preferably 100%, based on the total mass of the B monomers, in the starting monomer composition. 9. Abrasive article according to one of the preceding claims, characterized in that the resin N is a catechol-vanillin resin or a catechol-terephthalaldehyde resin or a phenol-terephthalaldehyde resin or a catechol-isophthalaldehyde resin or a vanillin resin. 10. Abrasive article according to one of the preceding claims, characterized in that the molar ratio of B monomers to A monomers in the starting monomer composition is from 1:0.5 to 1:4, particularly preferably from 1:1.2 to 1:4, most preferably from 1:1.5 to 1:3.2. 11. Abrasive article according to one of claims 1 to 9, characterized in that the molar ratio of B monomers to A monomers in the starting monomer composition is from 1:0.25 to 2, preferably from 1:0.25 to 1.1, particularly preferably from 1:0.3 to 1:1, again preferably from 1:0.3 to 1:0.85. 12. Abrasive article according to one of the preceding claims, characterized in that the B monomers and/or A monomers of the starting monomer composition were obtained from renewable raw materials, such as lignin, in a combined mass fraction of 50 to 100%, preferably 80 to 100%, in particular 100%, based in each case on the total mass of the monomer composition. 13. Abrasive article according to one of the preceding claims, characterized in that the binder contains the at least one resin N in a combined mass fraction of 90 to 100%, in particular 100%, based on the total amount of resins contained in the binder. 14. Abrasive article according to one of the preceding claims, characterized in that the binder additionally contains at least one phenol-formaldehyde resin. 15. Abrasive article according to claim 14, characterized in that the mass ratio of resin(s) N to phenol-formaldehyde resin(s) is 4:1 to 1:4, in particular 1.32:1 to 1:3.33 and particularly preferably 1:1.36 to 1:2.53.