US20170050294A1

US20170050294A1 - Impregnated abrasive support and abrasive article produced therefrom

Info

Publication number: US20170050294A1
Application number: US15/308,425
Authority: US
Inventors: Christine Doege; Werner Hörl; Peter Karl
Original assignee: Neenah Gessner GmbH
Current assignee: Neenah Gessner GmbH
Priority date: 2014-05-08
Filing date: 2015-05-07
Publication date: 2017-02-23
Also published as: DE102014006822A1; DE102014006822B4; EP3140079A1; WO2015169446A1

Abstract

The invention relates to an abrasive support comprising a support material composed of at least one wet- or dry-laid nonwoven based on natural and/or synthetic fibers. The support material is impregnated with a thermally curable polymer solution on one side and with an aqueous polymer dispersion on the opposite side. The thermally curable polymer solution penetrates at least 50% and at most 80% of the thickness of the support material, while the aqueous polymer dispersion penetrates at least 25% and at most 50% of the thickness of the support material.

Description

FIELD OF THE INVENTION

The invention relates to an abrasive-material carrier and to abrasive articles that comprise an abrasive-material carrier of this type.

PRIOR ART

In order to meet the many technical requirements nowadays, abrasive-material carriers are required which are tough and strong so that they do not tear during sanding and so that the sanding force can be effectively transferred to a workpiece. Furthermore, it is however also desirable for the abrasive-material carrier to have high elasticity so that it can adapt to the contours of a workpiece without permanently deforming in the process.
For many years, non-woven materials made of natural or synthetic fibres have been used as a carrier material for the production of curved, strip-shaped and discoid abrasive articles. In order to give the abrasive-material carriers sufficient strength for the intended use, they are usually impregnated with a binder. Either polymer dispersions, such as styrene-butadiene lattices, acrylonitrile butadiene lattices, natural latex or acrylate dispersions, or polymer solutions, such as phenol resin in methanol, epoxy resin in methanol, urea formaldehyde resin in water or melamine formaldehyde resin in water, are often used as a binder. The polymer solutions are preferably thermally crosslinking or crosslinkable.
One example of an abrasive paper that is impregnated with a polymer dispersion is described in WO 2000/015389 A2. A non-woven material impregnated with a polymer solution is disclosed in EP 442218 A2, for example.
Impregnations consisting of polymer dispersions are generally flexible and tough, but do not give the abrasive-material carrier the high strength that it often needs. In these abrasive-material carriers, particularly the plybond strength is often insufficient. The plybond strength is a measure of the fibre/fibre bond perpendicular to the surface of the abrasive-material carrier. High plybond strength is required so that the abrasive particles applied later do not become detached from the abrasive-material carrier when it is being provided with an abrasive coating due to fibre/fibre bonds that are too weak.
By contrast, impregnations consisting of polymer dispersions have the great advantage that they close the pores of the carrier due to the long chain length of the polymers and therefore seal said carrier against being penetrated by base coat that is applied later when an abrasive coating is applied. The base coats used for the application of an abrasive coating are generally very hard. If they penetrate too deeply into the abrasive-material carrier, said carrier is rendered brittle, and it becomes hard and fragile.
When using polymer solutions, in particular polymer solutions that can be thermally crosslinked, abrasive-material carriers having excellent strength are obtained. However, these impregnation agents have the significant drawback that they barely seal the abrasive-material carrier, and render it permeable to the base coat applied when it is provided with an abrasive coating. As already mentioned, this then leads to hard and fragile abrasive articles.
The use of abrasive-material carriers that are treated on either side with different impregnation agents is also known in principle. Therefore, in U.S. Pat. No. 4,084,941, a woven carrier material is impregnated on one side with a phenol formaldehyde resin and on the other side with an aqueous polymer dispersion. In this case, the phenol formaldehyde resin is adjusted by means of a filler and viscosity-increasing additives such that it does not penetrate the woven material and thus does not contribute to increasing the plybond strength.
The aqueous polymer dispersion with which the woven carrier material according to U.S. Pat. No. 4,084,941 is impregnated from the other side is intended to completely penetrate the carrier material and is mainly responsible for the strength and dimensional stability. An abrasive-material carrier produced in this way is equivalent to an abrasive-material carrier which for example has been dip-impregnated with an aqueous polymer dispersion and has then been given a coating of a phenol formaldehyde resin. Furthermore, it is a very complicated process to select the suitable aqueous polymer dispersion, since a balanced ratio of glass transition temperature Tg, viscosity and impregnation weight needs to be taken into account.

SUMMARY OF THE INVENTION

One problem addressed by the present invention is therefore to provide an improved abrasive-material carrier that particularly overcomes the drawbacks of conventional abrasive-material carriers. A carrier of this type for abrasive materials should preferably have high strength, in particular plybond strength, dimensional stability and elasticity, and should at the same time be sealed against the penetration of the base coat when said carrier is being provided with an abrasive coating. In addition, it should be cost-effective to produce. Another problem addressed by the invention is to provide an abrasive article that comprises an abrasive-material carrier of this type.
This problem is solved according to the invention by an abrasive-material carrier having the features of claim 1 and by an abrasive article having the features of claim 11. Advantageous embodiments are found in the rest of the claims.

DETAILED DESCRIPTION OF THE INVENTION AND EMBODIMENTS

The abrasive-material carrier according to the invention comprises a carrier material made of at least one wet-laid or dry-laid non-woven material based on natural and/or synthetic fibres, wherein the carrier material is impregnated on one side with a thermally curable polymer solution and on the other side with a polymer dispersion. The thermally curable polymer solution penetrates the thickness of the carrier material by at least 50% and at most 80%, while the aqueous polymer dispersion penetrates the thickness of the carrier material by at least 25% and at most 50%.
The present invention differs from U.S. Pat. No. 4,084,941 in the selection of the carrier material and in that the thermally curable polymer solution, which for example may also consist of a phenol formaldehyde resin, penetrates the thickness of the carrier material by at least 50% to at most 80%. The other side of the carrier material is impregnated with an aqueous polymer dispersion such that the dispersion penetrates the thickness of the carrier material by at least 25% to at most 50%. As a result, the abrasive-material carrier according to the invention can preferably be completely saturated with impregnation agent, but the thermally curable polymer solution and the aqueous polymer dispersion are distributed in different quantities over the thickness of the carrier material. The distribution of the two different impregnation agents means that the abrasive-material carrier according to the invention has very high strength, in particular plybond strength, and dimensional stability, with a high level of impermeability at the same time. An additional barrier layer to protect against the penetration of a base coat, as provided in U.S. Pat. No. 4,084,941, is no longer absolutely necessary.
Non-woven materials are understood to be any materials that are made up of finite or continuous fibres. They differ from woven materials in their random, disorganised fibre orientation.
Dry-laid staple fibre non-woven materials consist of fibres having a finite length. Both natural and synthetic fibres can be used to produce dry-laid staple fibre non-woven materials. Examples of natural fibres are cellulose, wool, cotton and flax. Synthetic fibres are for example polyolefin fibres, polyester fibres, polyamide fibres, polytetrafluoroethylene fibres, polyphenylene sulfide fibres and carbon fibres. The fibres used may be either straight or crimped. For the purpose of bonding, the air-laid staple fibre non-woven material may contain single-component or multi-component fusible binder fibres that melt completely or partially at a temperature below the melting point of the other fibres and bond the non-woven material. Air-laid staple fibre non-woven materials are produced in accordance with the known prior art as described in the book “Vliesstoffe [non-woven materials], W. Albrecht, H. Fuchs, Wiley-VCH, 2012”. The dry-laid staple fibre non-woven materials can be bonded by the single-component or multi-component fusible binder fibres already mentioned. Other bonding options are for example needling, water jet needling, or saturating or spraying the non-woven material with liquid binders followed by drying.
Melt-blown non-woven materials consist of continuous polymer fibres. To produce the melt-blown non-woven materials for the filter material according to the invention, the melt-blowing process known among experts is used, as described for example in Van A. Wente, “Superfine Thermoplastic Fibres”, Industrial Engineering Chemistry, vol. 48, pages 1342-1346. Suitable polymers are for example polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyamide, polyphenylene sulfide and polyolefin. The typical fibre diameter ranges between 0.5 and 10 μm, preferably between 0.5 and 3 μm. Depending on requirements, additives such as hydrophilising agents, hydrophobising agents, crystallisation accelerators, dyes or anti-static agents can be admixed to the polymers. Depending on requirements, the properties of the surface of the melt-blown non-woven materials can be altered by surface-treatment processes, such as corona treatment or plasma treatment. In addition, the melt-blown non-woven materials can be compressed by means of a calender if necessary.
Spunbonded materials also consist of continuous polymer fibres of which the fibre diameter is, however, usually considerably greater than that of melt-blown fibres. Spunbonded materials are produced in accordance with spunbonding processes known among experts, as described for example in U.S. Pat. No. 4,340,563 A, U.S. Pat. No. 3,802,817 A, U.S. Pat. No. 3,855,046 A and U.S. Pat. No. 3,692,618 A. Polymers that are suitable for the spunbonding process are e.g. polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyamide, polyphenylene sulfide and polyolefin.
Wet-laid non-woven materials or papers within the meaning of this invention are all non-woven materials that can be produced using the wet-laying processes known among experts for producing abrasive papers. The papers for the abrasive-material carrier according to the invention consist of natural, synthetic or inorganic fibres, or a mixture thereof. Examples of natural fibres are cellulose, cotton, wool or hemp, it being possible for the cellulose material used to be wood-free and/or wood-containing celluloses of conifers and/or deciduous trees, regenerated celluloses and fibrillated celluloses. Inorganic fibres are for example glass fibres, basalt fibres, quartz fibres, carbon fibres and metal fibres. Polyester fibres, polypropylene fibres, multi-component fibres having different melting points of the separate components, polyamide fibres and polyacrylonitrile fibres are suitable as synthetic fibres, for example. The titre of the synthetic fibres is typically 0.1 dtex to 8.0 dtex, preferably 0.5 dtex to 5 dtex, and the cut length is typically 3 mm to 20 mm, preferably 4 mm to 12 mm. The papers for the filter material according to the invention may consist 100% of natural, synthetic or inorganic fibres, but any mixture of these types of fibres is also possible.
Non-woven materials for producing the abrasive-material carrier according to the invention have a grammage of from 20 g/m²to 800 g/m², preferably of from 30 g/m²to 750 g/m², a thickness of from 0.010 mm to 2,000 mm, preferably of from 0.020 mm to 1,800 mm, a longitudinal breaking resistance when dry of from 10 to 800 N/15 mm, preferably of from 20 to 750 N/15 mm, a transverse breaking resistance when dry of from 5 to 600 N/15 mm, preferably of from 10 to 500 N/15 mm, a Mullen bursting pressure of from 50 kPa to 1500 kPa, preferably of from 100 kPa to 1400 kPa, a transverse plybond strength of at least 0.20 N/25 mm, preferably of at least 0.5 N/25 mm, a Fenchel wet expansion of from 0.01% to 3.50%, preferably of from 0.05% to 3.0%, and a transverse Elmendorf tear strength of at least 100 mN, preferably of at least 200 mN.
The abrasive-material carrier according to the invention may consist of one or more non-woven layers. If the abrasive-material carrier consists of at least two layers, they can either be identical or different in terms of their texture and properties. Therefore, it is for example quite possible for two identical papers or two different papers or for a paper and a spunbonded material to be combined with one another. It is clear that the combinations given are merely examples, and do not limit the scope of the present invention.
The at least two non-woven materials for the abrasive-material carrier according to the invention can be connected by means of bonding or via welded connections, or a combination thereof, before or after impregnation.
Advantageous adhesives have a softening point of over 200° C. For the intended use, the abrasive-material carrier according to the invention is exposed to temperatures of up to 150° C. and high mechanical loads. Under these conditions, the adhesive bond cannot be broken. Suitable adhesives for this application are polyurethane adhesives, polyamide adhesives or polyester adhesives. Here, polyurethane adhesives that crosslink in atmospheric humidity are particularly preferred. The adhesives may be applied either in the form of a powder or melted on by means of anilox rollers or spray nozzles. The application weight of the adhesive is typically between 5 and 20 g/m², preferably between 5 and 10 g/m².
The welded connection can be formed both by an ultrasound system and by a thermocalender. In this process, the polymers of the layers to be welded are either melted on over the entire surface or in certain regions and are welded together. The welded connections that are in certain regions can have any geometric shape, such as dots, straight lines, curved lines, diamonds, triangles, etc. The surface area of the welded connections that are in certain regions is preferably at most 10% of the total surface of the abrasive-material carrier according to the invention.
Particularly preferably, the individual non-woven layers are connected by bonding.
In order to obtain the abrasive-material carrier according to the invention, the at least one non-woven material is impregnated with a polymer binder in order to obtain the required properties such as tear strength, plybond strength, elasticity, water resistance, dimensional stability and impermeability. For a person skilled in the art, it is always particularly difficult to set a balanced ratio between high plybond strength and a high level of impermeability. In order to achieve a high level of plybond strength, a strong fibre-fibre bond is required, which is only achieved by polymer solutions. Abrasive-material carriers impregnated with polymer solutions are, however, not sufficiently impermeable to the penetration of a base coat when said carriers are being provided with an abrasive coating. By contrast, polymer dispersions do seal the abrasive-material carrier very well against the base coat, but they do not provide sufficient plybond strength. Following many tests, the inventors have now succeeded in producing an abrasive-material carrier having high plybond strength that nevertheless has a high level of impermeability to the penetration of a base coat when said carrier is being provided with an abrasive coating. These properties are achieved by the above-described non-woven materials being impregnated from one side with a thermally curable polymer solution and from the other side with a soft polymer dispersion, or by at least two non-woven layers being combined with one another, of which at least one layer is impregnated with a thermally curable polymer solution and at least one layer with an aqueous polymer dispersion.
Various methods can be used to impregnate the non-woven materials for the abrasive-material carrier according to the invention. If the non-woven material consists of just one layer or at least two layers have already been interconnected before impregnation, then one side can be impregnated with a thermally curable polymer solution and the other side with an aqueous polymer dispersion. A person skilled in the art knows which side of the non-woven material to select to be treated with which impregnation agent in accordance with the requirements placed on the abrasive-material carrier according to the invention. The impregnation takes place such that the thermally curable polymer solution penetrates the thickness of the abrasive-material carrier according to the invention by at least 50% to at most 80%, while the aqueous polymer dispersion penetrates the thickness of the abrasive-material carrier by at least 25% to at most 50%. Suitable impregnation methods are for example roller application, a doctor roller or doctor blade, or spraying.
In another working step, the impregnation is dried. Here, it is possible to dry each of the two impregnations straight after they are applied, or to dry them together after the second impregnation has been applied. The thermal polymer solution can either be cured immediately after drying or later, for example when the abrasive-material carrier is being provided with an abrasive coating.
It is thus also possible to combine two or more non-woven materials produced in this way with one another. In a preferred embodiment, the side of one non-woven material impregnated with the aqueous polymer dispersion is connected to the side of second non-woven material impregnated with the thermally crosslinkable polymer solution. Suitable connection techniques are bonding and welding, as already described above. Bonding is preferred here, using a polyurethane adhesive that cures under atmospheric humidity.
If the abrasive-material carrier according to the invention consists of at least two non-woven layers, it is also quite possible to impregnate each non-woven layer separately and to only join them after impregnation. In this case, at least one non-woven layer is completely impregnated with a thermally curable polymer solution and at least one non-woven layer is completely impregnated with an aqueous polymer solution. Preferably, at least two non-woven materials are combined such that the thickness of the non-woven material(s) impregnated with thermally curable polymer solution makes up at least 50% and at most 80% of the thickness of the entire abrasive-material carrier according to the invention, while the thickness of the non-woven material(s) impregnated with the aqueous polymer dispersion is at least 25% and at most 50% of the total thickness of the abrasive-material carrier.
In one embodiment, the at least two non-woven layers can be joined together after impregnation and before drying, the non-woven layers being bonded to one another by the impregnation agent. After drying, the thermally curable polymer solution can be cured either straightaway or later, for example when the carrier is provided with an abrasive coating.
In a preferred embodiment, the at least two non-woven materials are impregnated and dried separately from one another and are then interconnected. The thermally curable polymer solution can either be cured immediately after drying or later, for example when the carrier is provided with an abrasive coating. Suitable connection techniques are bonding and welding, as described above. This is preferably bonding using a polyurethane adhesive that cures under atmospheric humidity.
Suitable impregnation methods are for example dip-impregnation, size-press impregnation, double-sided roller application and double-sided spraying.
The possible combinations of non-woven material for producing the abrasive-material carrier according to the invention will now be illustrated by way of example with reference to a number of drawings. The drawings all show a cross section through an abrasive-material carrier. The drawings only serve to illustrate the invention, and do not represent a selection having a limiting effect. Particularly for the multi-layered abrasive-material carriers, a larger number of combinations of non-woven material are possible that may differ in terms of type, properties and number and cannot all be dealt with in detail for reasons of space.
FIG. 1 shows a single-layer abrasive-material carrier. The thermally curable polymer solution penetrates its thickness from one side by at least 50% to at most 80%, while the aqueous polymer dispersion penetrates its thickness from the other side by at least 25% to at most 50%. Both impregnations may mix together in a transition region.
FIG. 2 shows a two-layer abrasive-material carrier. The two non-woven layers were interconnected before the impregnation using one of the connection techniques described above. Two identical or two different non-woven layers can be used. The thickness ratio of the two non-woven layers does not play a role here. It is only important that the thermally curable polymer solution penetrates the total thickness of the abrasive-material carrier from one side by at least 50% to at most 80%, while the aqueous polymer dispersion penetrates its total thickness from the other side by at least 25% to at most 50%. In this case, one of the two impregnations may go beyond the connection point of the two non-woven layers. It is also possible for the two types of impregnation to mix in a transition region in this case.
FIG. 3 shows a three-layer structure. The three non-woven layers were interconnected before the impregnation using one of the connection techniques described above. Either identical or different non-woven layers can be used. The thickness ratio of the non-woven layers does not play a role here. It is only important that the thermally curable polymer solution penetrates the total thickness of the abrasive-material carrier from one side by at least 50% to at most 80%, while the aqueous polymer dispersion penetrates its total thickness from the other side by at least 25% to at most 50%. In this case, one of the two impregnations may go beyond one or both connection points of the three non-woven layers. It is also possible for the two types of impregnation to mix in a transition region in this case.
FIG. 4 shows an abrasive-material carrier that is made up of two non-woven layers. The non-woven layers were separately impregnated before being connected. Non-woven layer A was saturated with a thermally curable polymer solution and non-woven layer B with an aqueous polymer solution. The thickness of the non-woven layer A makes up at least 50% to at most 80% of the total thickness of the abrasive-material carrier, while the non-woven layer B contributes at least 25% to at most 50% to the total thickness. In this variant too, two identical or two different non-woven layers may be used.
The abrasive-material carrier shown in FIG. 5 is made up of three non-woven layers, which were also separately impregnated before being connected. Two non-woven layers are impregnated with the thermally crosslinkable polymer solution and one non-woven layer is impregnated with the aqueous polymer dispersion. Here, the three non-woven layers may be identical or different. The thickness of the two non-woven layers impregnated with the thermally crosslinkable polymer solution together makes up at least 50% to at most 80% of the total thickness of the abrasive-material carrier, while the thickness of the non-woven layer that is impregnated with the aqueous polymer solution contributes at least 25% to at most 50% to the total thickness.
FIG. 6 essentially corresponds to FIG. 5, only that here one non-woven layer is impregnated with the thermally crosslinkable polymer solution and two non-woven layers are impregnated with the aqueous polymer dispersion. In this case too, the thickness of the non-woven layer impregnated with the thermally crosslinkable polymer solution contributes at least 50% to at most 80% of the total thickness of the abrasive-material carrier. The thickness of the two non-woven layers that are impregnated with the aqueous polymer dispersion together makes up at least 25% to at most 50% of the total thickness.
FIG. 7 shows a combination of two layers of the abrasive-material carrier shown in FIG. 1. The two layers were impregnated separately from one another and were then interconnected such that the side of layer A impregnated with the aqueous polymer dispersion comes to rest on the side of layer B impregnated with the thermally crosslinkable polymer solution. Here too, the two non-woven layers may be identical or different.
FIG. 8 essentially corresponds to FIG. 7, only that here three layers of the abrasive-material carrier shown in FIG. 1 are combined with one another. The three layers were impregnated separately from one another and were then interconnected such that the side of layer A impregnated with the aqueous polymer dispersion comes to rest on the side of layer B impregnated with the thermally crosslinkable polymer solution. The side of non-woven material C impregnated with the thermally curable polymer solution is connected to the side of non-woven material B that is impregnated with the aqueous polymer dispersion. The three non-woven layers may be identical or different.
FIG. 9 essentially corresponds to FIG. 8, only that here three layers of the abrasive-material carrier shown in FIG. 1 are combined with one another. The three layers were impregnated separately from one another and were then interconnected such that the side of layer A impregnated with the thermally crosslinkable polymer solution comes to rest on the side of layer B impregnated with the thermally crosslinkable polymer solution. The side of non-woven material C impregnated with the thermally curable polymer solution is connected to the side of non-woven material B that is impregnated with the aqueous polymer dispersion. The three non-woven layers may be identical or different.
FIG. 10 shows a combination of two layers of the abrasive-material carrier shown in FIG. 2. The two layers were impregnated separately from one another and were then interconnected such that the side of non-woven material A impregnated with the aqueous polymer dispersion comes to rest on the side of non-woven material B impregnated with the thermally crosslinkable polymer solution. All the non-woven layers may be identical or different.
FIG. 11 essentially corresponds to FIG. 10, only that here three layers of the abrasive-material carrier shown in FIG. 2 are combined with one another. The three layers were impregnated separately from one another and were then interconnected such that the side of non-woven material A impregnated with the aqueous polymer dispersion comes to rest on the side of non-woven material B impregnated with the thermally crosslinkable polymer solution. The side of non-woven material C impregnated with the thermally curable polymer solution is connected to the side of non-woven material B that is impregnated with the aqueous polymer dispersion. All the non-woven layers may be identical or different.
FIG. 12 essentially corresponds to FIG. 10, only that here three layers of the abrasive-material carrier shown in FIG. 2 are combined with one another. The three layers were impregnated separately from one another and were then interconnected such that the side of non-woven material A impregnated with the thermally crosslinkable polymer solution comes to rest on the side of non-woven material B impregnated with the thermally crosslinkable polymer solution. The side of non-woven material C impregnated with the thermally curable polymer solution is connected to the side of non-woven material B that is impregnated with the aqueous polymer dispersion. All the non-woven layers may be identical or different.
Phenol resins, epoxy resins, melamine formaldehyde resins, urea formaldehyde resins, polyvinyl alcohols, polyurethane resins or mixtures thereof are suitable as thermally curable polymer solutions, for example. Depending on the type of resin used, suitable solvents are either water or organic solvent, such as methanol.
The polymers are either thermally self-crosslinking in themselves, or they can be rendered crosslinking by the addition of suitable crosslinkers, such as polyamines, polycarboxylic acid, hexamethylenetetramine, formaldehyde or metal compounds.
If required, other additional substances such as dyes, fillers, surface-active substances, flame-retardant agents or antistatic agents can be added to the thermally curable polymer solutions.
The thermally crosslinkable polymer solutions have a solids content of from 10% to 100% and a viscosity of from 2 mPas to 15,000 mPas.
Suitable aqueous polymer dispersions for impregnating the carrier material are for example aqueous dispersions of acrylic acid esters, polyvinyl acetate, acrylonitrile butadiene rubber, acrylic acid ester/styrene copolymers, ethylene vinyl acetate copolymers, styrene butadiene rubber, phenol resin, epoxy resin, natural rubber or mixtures thereof.
If required, other additional substances such as dyes, fillers, surface-active substances, flame-retardant agents or antistatic agents can be added to the aqueous polymer dispersions.
Suitable aqueous polymer dispersions have a glass transition temperature of from −20° C. to 70° C. Before said dispersions are used as impregnation agents, they are adjusted by adding water and, if necessary, a suitable viscosity regulator, for example polyacrylic acid, to a viscosity of 5 mPas to 1000 mPas, preferably of 10 mPas to 500 mPas, and a solids content of from 5% to 50%, preferably of from 10% to 45%.
The carrier material is impregnated with 5 wt. % to 50 wt. % of the dried polymer solution, based on the weight of the impregnated carrier material. The impregnation agent content for a dry polymer dispersion is 2 wt. % to 25 wt. % based on the weight of the impregnated carrier material.
Suitable impregnation methods are roller application, a doctor roller or doctor blade, or spraying, for example.
In a specific embodiment of the abrasive-material carrier, a barrier coat is applied to the side impregnated with the aqueous polymer dispersion. If the abrasive-material carrier has two sides that are impregnated with an aqueous polymer dispersion, a person skilled in the art selects the most suitable side on the basis of the requirements. This barrier coat may for example be produced by applying an aqueous dispersion based on acrylic acid esters, polyvinyl acetate, acrylonitrile butadiene rubber, acrylic acid ester/styrene copolymers, ethylene vinyl acetate copolymers, styrene butadiene rubber, phenol resin, epoxy resin, natural rubber or mixtures thereof. The application quantity after drying is 2-15 g/m², preferably 3-12 g/m².
Various additives and/or fillers can also be added to the barrier coat. Examples of additives are dyes, crosslinkers, hydrophobising agents, oleophobising agents, hydrophilising agents, antistatic agents or mixtures thereof. Kaolin, titanium dioxide, talcum, calcium carbonate, silicon dioxide, bentonite or mixtures thereof can be used as fillers, for example.
Suitable coating methods are a doctor roller or doctor blade, an airbrush, or roller application, for example.
In order to increase the surface smoothness and the flexibility, the abrasive-material carrier that has been impregnated and optionally coated with a barrier coat can be calendered. In this process, the impregnated abrasive-material carrier according to the invention preferably passes through the gap in a pair of rollers consisting of one steel and one rubber roller having a gap pressure of from 30 to 300 N/mm, preferably of from 50 to 250 N/15 mm. The abrasive-material carrier is fed to the calender such that the side impregnated with the polymer dispersion comes into contact with the steel roller. The calendering temperature is between 20° C. and 80° C., preferably between 50° C. and 70° C.
The abrasive-material carrier according to the invention has a grammage of from 50 to 1,000 g/m², preferably of from 100 to 900 g/m², a thickness of from 0.010 mm to 2,000 mm, preferably of from 0.020 mm to 1,800 mm, a longitudinal breaking resistance when dry of from 20 to 1,500 N/15 mm, preferably of from 30 to 1400 N/15 mm, a transverse breaking resistance when dry of from 10 to 1,200 N/15 mm, preferably of from 20 N/15 mm to 1,000 N/15 mm, a Mullen bursting pressure of at least 200 kPa, preferably of at least 300 kPa, a plybond strength of at least 0.5 N/25 mm, preferably of at least 1.0 N/25 mm, a Fenchel wet expansion of from 0.05% to 3.50%, preferably of from 0.05% to 3.0%, a transverse Elmendorf tear strength of at least 200 mN, preferably of at least 300 mN, and an air permeability of at most 50 l/m²s, preferably of at most 45 l/m²s.
In order to produce the abrasive article, the abrasive-material carrier according to the invention is also provided with an abrasive coating. This means that a base coat is applied to the abrasive-material carrier, the abrasive particles are scattered thereon, the base coat is dried, a top coat is applied to the abrasive particles and the top coat is lastly dried. The base coat consists e.g. of epoxy resin, phenol resin, alkyd resin, urea resin or mixtures thereof. The resins are dispersed in a suitable solvent and are applied to the non-woven material (abrasive base paper). The base coat is applied to the side of the abrasive-material carrier impregnated with the polymer dispersion. If the abrasive-material carrier has two sides that are impregnated with an aqueous polymer dispersion, a person skilled in the art selects the most suitable side on the basis of the requirements. If the abrasive-material carrier has a barrier coat, the base coat is applied to the barrier coat. The abrasive particles are then scattered onto the still-wet base coat, the individual particles being optimally oriented on the abrasive base paper by means of electrostatic devices. The abrasive base paper that is coated with the wet base coat and the abrasive particles adhering thereto then passes into a drying oven, in which the base coat is dried. After drying, the abrasive particles are coated with the top coat. The top coat is commonly a hard, thermosetting curing resin, which also anchors the abrasive particles to the abrasive paper. This process is completed by curing the base coat and top coat. The abrasive articles according to the invention can be used as abrasive discs, abrasive belts and curved abrasive articles.

Test Methods

Mullen burst strength in accordance with DIN EN ISO 2758
Verseidag air permeability in accordance with DIN EN ISO 9237, with a sample surface of 20 cm²and pressure of 1,000 mm water column.
Fenchel wet expansion in accordance with DIN 53130:
Two strips each 15 mm in width are cut from the abrasive-material carrier transversely to the direction of movement of the web of the abrasive-material carrier and are then dried for 30 minutes at 120° C. Then reclimatisation takes place for 24 hours at 23° C. and 50% relative humidity. The measurement is made using the NDT 6/10 wet expansion tester from Kögl WMP GmbH Leipzig.
One of the strips of the abrasive-material carrier is clamped between two clamps without tension with 100 mm of free length. The lower clamp is stationary and the weight of the upper clamp is balanced by a counterweight and is connected to the display. A beaker is filled with 900 ml tempered (23%) water. By immersing the strip of the abrasive-material carrier in the water (the beaker moves upwards), the strip expands. Using the counterweight, a specified sample tension force of 15 g is exerted on the strip, which expands the strip. The expansion is displayed in percent on the scale. The duration of the measurement is 1,800 sec. The expansion value in % provided is the average of two measurements.
Grammage in accordance with DIN EN ISO 536
Thickness in accordance with DIN EN ISO 534 with 20 N contact pressure and a measurement surface area of 200 mm²
Longitudinal and transverse breaking resistance when dry in accordance with DIN EN ISO 1924-2, strip width 15 mm, free clamping length 100 mm, drawing speed 150 mm/min
Longitudinal and transverse elongation at break when dry in accordance with DIN EN ISO 1924-2, strip width 15 mm, free clamping length 100 mm, drawing speed 150 mm/min
Transverse Elmendorf tear strength in accordance with DIN EN 21974, with a sample pack having 2 sheets of paper
Transverse plybond strength:
Two strips that are each 50 mm in width and 200 mm in length are cut from an abrasive-material carrier that has been conditioned for 24 hours before at 23° C. and 50% relative humidity. The 200 cm long side extends transversely to the direction of movement of the abrasive-material carrier. Approximately 150 mm long strips of the test adhesive tape Scotch 3M 365 (50 mm wide) are adhered to the front and back of this sample with no creases such that it protrudes from one end of the abrasive-material carrier by approximately 50 mm. This composite is then compressed by a steel roller that weighs 4.5 kg and is 50 mm wide. In this process, the steel roller is rolled twice by hand over the composite without additional pressure. A sample that is 25 mm in width and 200 mm in length is cut from each strip, consisting of the abrasive-material carrier and the test adhesive tape on both sides of the abrasive-material carrier. The adhesive tape is pulled away on one side by hand by a short distance from the end at which the abrasive-material carrier protrudes, and so the abrasive-material carrier is torn over the entire width of the sample. Preferably, it is torn on the side of the abrasive-material carrier on which the test adhesive tape is adhered the most firmly. Depending on the impregnation or coating of the abrasive-material carrier, the tearing may present problems. If the test adhesive tape does not adhere properly to the abrasive-material carrier to be tested and if there is high plybond strength, the abrasive-material carrier to be tested has to be carefully cut using a razor blade and then torn further by means of the test adhesive tape. The plybond strength is measured in a Roell Z 0.5 universal testing machine from Zwick with the following settings:
Measurement range 0.5 F
Wet abrasion plybond strength program
Speed 300 mm/min
Clamp distance 25 mm
The Scotch 3M 365 test adhesive tape that is pulled away by hand is clamped in the upper clamp of the tensile testing machine. The abrasive-material carrier to be tested using the two strips of the test adhesive tape adhered thereto is clamped in the lower clamp of the universal testing machine such that the composite protrudes at a 90° angle to the pulling direction. During the measurement, it should be ensured that the tear forms in the centre of the abrasive-material carrier to be tested, and that not only individual fibres are being torn from the surface of the carrier. Measurements in which the tear does not form in the centre of the paper are discarded and repeated. The average force that is required to tear the abrasive-material carrier is measured. The result is the average of two separate measurements.
The proportion of the impregnation agent in an abrasive-material carrier is calculated in accordance with the following formula:
Proportion of impregnation agent in %=(Cr. imp./Cr. carrier)*100%
where Cr. imp=mass of the dried impregnation agent per m²carrier and
Cr. carrier=grammage of the impregnated carrier

EXAMPLES

Example 1

Comparative Example

In accordance with the generally known method for paper production, a paper web made of 100% cellulose was produced in a paper machine. The paper thus produced had a grammage of 150 g/m², a thickness of 0.255 mm, a longitudinal breaking resistance when dry of 129 N/15 mm, a transverse breaking resistance when dry of 76 N/15 mm, a Mullen bursting pressure of 341 kPa, a plybond strength of 1.33 N/25 m, a Fenchel wet expansion of 1.531% and a transverse Elmendorf tear strength of 1654 mN.
In a separate working step, the paper was impregnated with a solution of two parts by weight epoxy resin and 1 part by weight curing agent in methanol by means of double-sided roller application, was dried and was then cured at 120° C. The proportion of impregnation agent was 17.5%.
The epoxy resin can be purchased under the name CHS 520 from Spolchemie in the Czech Republic. The curing agent is available under the name ITAMID D from ddchem in Italy.
Lastly, the impregnated and dried paper was calendered by means of a pair of rollers consisting of one steel and one rubber roller having a gap pressure of 200 N/mm and a temperature of 70° C.
The properties of the abrasive-material carrier thus produced are summarized in table 1.

Example 2

Comparative Example

The same paper as described in example 1 was impregnated with an SBR dispersion by means of dip impregnation in a separate working step, and dried. The proportion of impregnation agent was 10.7%.
The aqueous polymer dispersion can be purchased under the name Litex SX 1009 from Syntomer, Marl, Germany and during processing had a solids content of 27.3% and a Brookfield viscosity LV of 19.3 mPas.
The impregnated and dried paper was then calendered by means of a pair of rollers consisting of one steel and one rubber roller having a gap pressure of 200 N/mm and a temperature of 70° C.
The properties of the abrasive-material carrier thus produced are summarized in table 1.

Example 3

Invention

The same paper as described in example 1 was impregnated on its felt side with a solution of two parts by weight epoxy resin and one part by weight curing agent in methanol and on its wire side with an aqueous dispersion by means of double-sided roller application, was dried and was then cured at 120° C. The impregnation agent had a proportion of thermally curable polymer of 20% and a proportion of polymer dispersion of 3%.
The epoxy resin can be purchased under the name CHS 520 from Spolchemie in the Czech Republic. The curing agent can be purchased under the name ITAMID D from ddchem in Italy. During processing, the thermally curable polymer solution of epoxy resin, curing agent and methanol has a total solids content of 33% and a Brookfield viscosity of 4.6 mPas.
The aqueous dispersion has the name Acronal 2416, and is available from BASF, Ludwigshafen, Germany. During processing, it had a solids content of 45% and a Brookfield viscosity LV of 23 mPas.
The wire side of a paper is the side with which the paper web comes into contact with the dehydration wire during production. The felt side is the side opposite the wire side.
The impregnated and dried paper was then calendered by means of a pair of rollers consisting of one steel and one rubber roller having a gap pressure of 200 N/mm and a temperature of 70° C. In the process, the abrasive-material carrier was fed to the calender such that the side impregnated with polymer dispersion came into contact with the steel roller.
The properties of the abrasive-material carrier thus produced are summarized in table 1.

Example 4

Invention

Two layers of the impregnated paper from example 3 were interconnected by means of 5 g/m²of a reactive single-component polyurethane adhesive of the Kleiberit PUR 700.7 type from Klebchemie, Weingarten, Germany such that the side of one layer that was impregnated with the thermally curable polymer solution came to rest on the side of the second layer that was impregnated with the aqueous polymer dispersion.
This composite was then calendered by means of a pair of rollers consisting of one steel and one rubber roller having a gap pressure of 200 N/mm and a temperature of 70° C. In the process, the abrasive-material carrier was fed to the calender such that the side impregnated with polymer dispersion came into contact with the steel roller.
The properties of the abrasive-material carrier thus produced are summarized in table 1.

TABLE 1

Example 1	Example 2	Example 3	Example 4
(comparative)	(comparative)	(invention)	(invention)

Grammage untreated	150	g/m²	150	g/m²	150	g/m²	150	g/m²
Grammage impregnated	188	g/m²	168	g/m²	194	g/m²	414	g/m²

Longitudinal breaking	312 N/15 mm	134 N/15 mm	149 N/15 mm	573 N/15 mm
resistance

Mullen bursting pressure

858

kPa

684

kPa

794

kPa

>3000

kPa

Fenchel wet expansion	1.47%	1.92%	1.74%	1.74%
Plybond strength	does not tear	3.1 N/25 mm	does not tear	does not tear

Elmendorf tear resistance	>8000	mN	1668	mN	1711	mN	>8000	mN
Air permeability	120	l/m²s	42	l/m²s	26	l/m²s	0	l/m²s

The results show that the abrasive-material carrier according to the invention from example 3 combines the high plybond strength from comparative example 1 and the low air permeability from comparative example 2. In example 3, the burst strength as a measure of elasticity is between that in examples 1 and 2 and is thus in the range of the values usually required. The same applies to the Fenchel wet expansion, which is a measure of dimensional stability. Example 4, which is indeed a combination of two layers of the abrasive-material carrier according to the invention, makes it possible to further improve the physical properties of the carrier.

Claims

1. Abrasive-material carrier comprising a carrier material made of at least one wet-laid or dry-laid non-woven material based on natural and/or synthetic fibres, wherein the carrier material is impregnated on one side with a thermally curable polymer solution and on the other side with an aqueous polymer dispersion, the thermally curable polymer solution penetrating the thickness of the carrier material by at least 50% and at most 80%, while the aqueous polymer dispersion penetrates the thickness of the carrier material by at least 25% and at most 50%.

2. Abrasive-material carrier according to claim 1, wherein the carrier material is a paper.

3. Abrasive-material carrier according to claim 1, wherein the carrier material is a dry-laid staple fibre non-woven material.

4. Abrasive-material carrier according to claim 1, wherein the carrier material is a melt-blown non-woven material.

5. Abrasive-material carrier according to claim 1, wherein the carrier material is a spunbonded material.

6. Abrasive-material carrier according to claim 1, wherein the carrier material consists of a plurality of identical layers of non-woven material.

7. Abrasive-material carrier according to claim 1, wherein the carrier material consists of a plurality of different layers of non-woven material.

8. Abrasive-material carrier comprising at least two layers of a carrier material according to claim 1, wherein the side of the at least one layer impregnated with the aqueous polymer dispersion is connected to the side of the following layer impregnated with the thermally crosslinkable polymer solution.

9. Abrasive-material carrier according to claim 1, wherein a barrier coat is applied to the side impregnated with the polymer dispersion.

10. Abrasive-material carrier according to claim 1, wherein the abrasive-material carrier is calendered.

11. Abrasive article, comprising an abrasive-material carrier according to claim 1, wherein the abrasive-material carrier is provided with an abrasive coating on the side impregnated with the polymer dispersion.

12. Abrasive article according to claim 11, wherein a barrier coat is arranged on the side of the abrasive-material carrier impregnated with the polymer dispersion and the abrasive-material carrier is provided with an abrasive coating on the side of the barrier coat that is on the outside.