WO2015169446A1

WO2015169446A1 - Impregnated abrasive support and abrasive article produced therefrom

Info

Publication number: WO2015169446A1
Application number: PCT/EP2015/000934
Authority: WO
Inventors: Christine Doege; Werner HÖRL; Peter Karl
Original assignee: Neenah Gessner Gmbh
Priority date: 2014-05-08
Filing date: 2015-05-07
Publication date: 2015-11-12
Also published as: DE102014006822A1; DE102014006822B4; US20170050294A1; EP3140079A1

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

IMPRESENTED ABRASIVES AND MADE FROM THEM

GRINDING ARTICLE

Field of the Invention The invention relates to an abrasive backing and abrasive articles comprising such an abrasive backing.

State of the art

In order to meet the versatile technical requirements nowadays, abrasive carriers are required that are tough and strong so as not to break during grinding and to transfer the grinding force to a workpiece well. Furthermore, a high elasticity of the abrasive carrier is desirable so that it can adapt to the contours of a workpiece, without being permanently deformed.

For many years fleeces made of natural or synthetic fibers have been used as carrier material for the production of sheet, ribbon and disk-shaped abrasive articles. In order to give the abrasive carriers sufficient strength for the intended use, they are usually impregnated with a binder. Frequently used as binders are either polymer dispersions, such as, for example, styrene-butadiene latices, acrylonitrile-butadiene latexes, natural latex or acrylate dispersions, or polymer solutions, for example phenol resin in methanol, epoxy resin in methanol, urea-formaldehyde. Resin in water, melamine - formaldehyde resin in water used. The polymer solutions are preferably formed thermally crosslinking or crosslinkable.

An example of a sandpaper impregnated with a polymer dispersion is described in document WO 2000/015389 A2. A nonwoven fabric impregnated with a polymer solution is disclosed by way of example in European Application EP 442218 A2.

Although impregnations of polymer dispersions are generally flexible and tough, they do not give the abrasive carrier the often required high strength. In particular, the gap strength is often insufficient with these abrasive carriers. The split strength is a measure of the fiber-to-fiber bond perpendicular to the surface of the abrasive carrier. A high degree of nip strength is required so that the subsequently applied abrasive grains do not detach from the abrasive carrier during the grinding process because of too weak fiber-to-fiber bonds. On the other hand impregnations of polymer dispersions have the great advantage that they close the pores of the carrier due to the high chain length of the polymers and thus seal it against the penetration of later applied during sanding basecoat. The primers used for sanding are usually very hard. If they penetrate too deeply into the abrasive carrier, it becomes brittle and becomes hard and brittle.

When using polymer solutions, in particular polymer solutions which can be thermally crosslinked, abrasive carriers having excellent strengths are obtained. However, these impregnating agents have the great disadvantage that they scarcely seal the abrasive carrier and make it permeable to the base coat applied during potting. As already mentioned, this leads to hard and brittle sanding articles.

The use of abrasive media treated on both sides with different saturants is also generally known. Thus, in document US Pat. No. 4,084,941, a woven carrier material is impregnated on one side with a phenol-formaldehyde resin and on the opposite side with an aqueous polymer dispersion. The phenol-formaldehyde resin is adjusted by means of filler and viscosity-increasing additives so that it does not penetrate into the tissue and thus does not contribute to increasing the gap strength.

The aqueous polymer dispersion with which the woven carrier material according to US Pat. No. 4,084,941 was prepared from the other side. is impregnated, is to completely penetrate the substrate and is mainly responsible for the strength and dimensional stability. An abrasive carrier prepared in this manner is equivalent to a grinding agent carrier that has been dip-impregnated with, for example, an aqueous polymer dispersion and subsequently given a coating of a phenol-formaldehyde resin. Furthermore, the selection of the suitable aqueous polymer dispersion is quite complicated, since a balanced ratio of glass transition temperature Tg, viscosity and impregnation weight must be taken into account.

Summary of the invention

It is therefore an object of the present invention to provide an improved abrasive backing which overcomes in particular the disadvantages of conventional abrasive backing. Such a carrier for abrasive should preferably have a high strength, in particular gap strength, dimensional stability, and elasticity and at the same time be sealed against the penetration of base coat during sanding. He should also be inexpensive to manufacture. Another object of the invention is to provide an abrasive article comprising such an abrasive carrier.

This object is achieved by an abrasive carrier with the features of claim 1 and by an abrasive article having the features of claim 11. Advantageous embodiments are given in the further claims. Detailed description of the invention, exemplary embodiments

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

The present invention differs from US Pat. No. 4,084,941 in the choice of the carrier material and in that the thermally curable polymer solution, which may for example also consist of a phenol-formaldehyde resin, penetrates the thickness of the carrier material by at least 50% to at most 80% , The opposite side of the support material is impregnated with an aqueous polymer dispersion in such a way that the dispersion penetrates the thickness of the support material to at least 25% to at most 50%. It can thereby be achieved that the abrasive carrier according to the invention is preferably completely impregnated with impregnating agent, but the thermally curable polymer solution and the aqueous polymer dispersion are distributed in different amounts over the thickness of the carrier material.

As a result of the distribution of the two different impregnating agents, the abrasive carrier according to the invention has a very high strength, in particular Cleavage strength, and has dimensional stability with high density at the same time. An additional barrier layer against the penetration of base coat, as indicated in US Pat. No. 4,084,941, is no longer absolutely necessary.

Nonwoven means all fabrics which are formed from finite and / or endless fibers. They differ from tissues by their random, disordered fiber orientation.

Dry laid staple fiber webs consist of fibers of finite length. Both natural and synthetic fibers can be used to produce dry laid staple fiber webs. Examples of natural fibers are cellulose, wool, cotton, flax. Synthetic fibers are, for example, polyolefin fibers, polyester fibers, polyamide fibers, polytetrafluoroethylene fibers, polyphenylene sulfide fibers, carbon fibers. The fibers used can be either straight or curled. For solidification, the air-laid staple fiber fleece can contain one-component or multi-component meltbond fibers which melt completely or partially at a temperature below the melting temperature of the other fibers and solidify the fleece. The preparation of the air-laid staple fiber nonwoven fabric is carried out according to the known state of the art as described in the book "Nonwovens, W. Albrecht, H. Fuchs, Wiley-VCH, 2012." The dry-laid staple fiber nonwovens can be produced by the above-mentioned single- or multi-component enamel. Further consolidation possibilities are, for example, needling, water jet needling or impregnating or spraying the fleece with liquid binders followed by drying. Meltblown nonwovens consist of polymeric continuous fibers. The meltblown process known in the art is used to produce the meltblown web for the filter material according to the invention, as described, for example, in Van A. Wente, "Superfine Themoplastic Fibers", Industrial Engineering Chemistry, Vol. 48, pp. 1342-1346. Suitable polymers are, for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyamide, polyphenylene sulfide, polyolefin, the typical fiber diameters being between 0.5 and 10 μm, preferably between 0.5 and 3 μm Depending on requirements, additives such as hydrophilicizing agents, water repellents, crystallization accelerators or paints, antistatitic agents can be mixed in. Depending on requirements, the surface of the meltblown web can be changed in its properties by surface treatment methods, such as corona treatment or plasma treatment If necessary, the meltblown webs can be densified by means of a calender.

Spunbonded nonwovens likewise consist of polymeric continuous fibers whose fiber diameter is usually much larger than that of meltblown fibers. Spunbonded nonwoven webs are made by the spunbonding process known to those skilled in the art, as described, for example, in US Pat. Nos. 4,340,563A, 3,802,817A, 3,855,046A and 3,692,618A. Polymers suitable for the spunbonding process are, for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyvinyl naphthalate, polyamide, polyphenylene sulfide, polyolefin. Wet-laid nonwovens or papers in the context of this invention are all nonwovens which can be produced with the wet-laying processes known in the art for the production of abrasive papers. The papers for the abrasive carrier according to the invention consist of natural, synthetic, inorganic fibers or a mixture thereof. Examples of natural fibers are cellulose, cotton, wool, hemp, wherein the cellulose material used may be wood-free and / or wood-containing celluloses of coniferous and / or deciduous trees, regenerated celluloses and fibrillated celluloses. Inorganic fibers are, for example, glass fiber, basalt fibers, quartz fibers, carbon fibers and metal fibers. Suitable synthetic fibers are, for example, polyester fibers, polypropylene fibers, multicomponent fibers with different melting points of the individual components, polyamide fibers and polyacrylonitrile fibers. The denier of the synthetic fibers is typically 0.1 dtex-8.0 dtex, preferably 0.5 dtex-5 dtex, and the cut length is typically 3 mm-20 mm, preferably 4 mm-12 mm. The papers for the filter material according to the invention can either consist of 100% natural, synthetic or inorganic fibers, but any mixture of these types of fibers is also possible.

Nonwovens for producing the abrasive carrier according to the invention have a basis weight of 20 g / m ² - 800 g / m ² , preferably of 30 g / m ² - 750 g / m ² , a thickness of 0.010 mm - 2,000 mm, preferably of 0.020 mm - 1,800 mm, a breaking force dry along 10 - 800 N / 15mm, preferably 20 - 750 N / 15mm, a dry transverse breaking force of 5 - 600 N / 15mm, preferably 10 - 500 N / l5mm, a bursting pressure after washes of 50 kPa - 1500 kPa, preferred 100 kPa - 1400 kPa, a gap strength transverse to at least 0.20 N / 25 mm, preferably of at least 0.5 N / 25 mm, a wet elongation to fennel of 0.01% - 3.50%, preferably of 0.05 % - 3.0%, a tear strength according to Elmendorf transversely of at least 100 mN, preferably of at least 200 mN.

The abrasive carrier according to the invention may consist of one or more nonwoven layers. If the abrasive medium carrier consists of at least two layers, then these may be configured in their nature and their properties either the same or different. For example, it is easily possible to combine two similar papers or two different papers or a paper and a spunbonded fabric. It goes without saying that the combinations given are only examples and do not limit the scope of the present invention. The at least two nonwovens for the abrasive carrier according to the invention can be bonded before or after impregnation by means of adhesive bonding or via welded joints or a combination thereof. Advantageous adhesives have a softening point of over 200 ° C. When used as intended, the abrasive carrier of the invention is exposed to temperatures up to 150 ° C and high mechanical loads. The adhesive connection must not come loose. Suitable adhesives for this application are polyurethane adhesive, polyamide adhesive or polyester adhesive. Particularly preferred are polyurethane adhesives that crosslink with the humidity. The glue can either be applied as a powder or melted by means of anilox rolls or spray nozzles. The application weight of the adhesive is typically between 5 and 20 g / m ² , preferably between 5 and 10 g / m ² .

The welded connection can be made both by an ultrasonic system and by a thermal calender. In this case, the polymers of the layers to be welded are either completely or partially melted and welded together. The area-wise welded joints can have any geometric shapes, such as points, straight lines, curved lines, diamonds, triangles, etc. The area of the area-wise welded joints is advantageously not more than 10% of the total area of the abrasive backing according to the invention.

Particularly preferred is the connection of the individual nonwoven layers by gluing.

In order to obtain the abrasive backing according to the invention, the at least one nonwoven fabric is impregnated with a polymeric binder in order to obtain the required properties, such as tensile strength, splitting strength, elasticity, water resistance, dimensional stability and impermeability. It is always particularly difficult for a person skilled in the art to set a balance between high gap strength and high density. In order to achieve a high gap strength, a strong fiber - fiber bond is required, which is achieved only by polymer solutions. However, abrasive carriers impregnated with polymer solutions are not sufficiently dense against basecoat penetration of dressing. On the other hand, polymer dispersions seal off the abrasive carrier very well against the basecoat, but usually do not provide sufficient gap strength. The inventors have now succeeded in many attempts to produce a very slit-resistant abrasive carrier, which nevertheless has a high seal against the penetration of base coat during sanding. These properties are achieved by impregnating the nonwovens described above from one side with a thermosetting polymer solution and from the other side with a soft polymer dispersion, or by combining at least two nonwoven layers, at least one layer comprising a thermosetting polymer solution and at least one layer is impregnated with an aqueous polymer dispersion.

For the impregnation of the nonwovens for the abrasive carrier according to the invention, different methods can be used. If the nonwoven consists of only one layer or if at least two layers have already been bonded together before the impregnation, one side may be impregnated with a thermally curable polymer solution and the other side with an aqueous polymer dispersion. Which side of the nonwoven is treated with which impregnating agent, the skilled person knows to select the requirements of the abrasive carrier according to the invention. The impregnation takes place in such a way that the thermally curable polymer solution penetrates the thickness of the abrasive carrier according to the invention at least 50% to at most 80%, while the aqueous polymer dispersion penetrates the thickness of the abrasive carrier to at least 25% to at most 50%. Suitable impregnation methods are, for example, roller application, roll or knife squeegee or spraying.

In a further step, the impregnation is dried. It is possible to dry each of the two impregnations immediately after their application or only together after the order of the second impregnation. The curing of the thermal polymer solution can either take place immediately afterwards for drying or later, for example during the sanding of the abrasive carrier.

It is also possible to combine two or more nonwovens so produced. In a preferred embodiment, the side of the one fleece impregnated with the aqueous polymer dispersion is connected to the side of the second fleece impregnated with the thermally crosslinking polymer solution. Suitable bonding techniques are gluing and welding, as described above. Preference is given to bonding with a moisture-curing polyurethane adhesive.

If the abrasive carrier according to the invention consists of at least two nonwoven layers, then it is also readily possible to impregnate each nonwoven layer for itself and to assemble them only after the impregnation. In this case, at least one nonwoven layer is completely impregnated with a thermally curable polymer solution and at least one nonwoven layer is completely impregnated with an aqueous polymer solution. At least two nonwovens are preferably combined in such a way that the thickness of the or the impregnated with the thermally curable polymer solution While the thickness of the or each of the webs impregnated with the aqueous polymer dispersion amounts to at least 25% to at most 50% of the total thickness of the abrasive carrier.

In one embodiment, the at least two nonwoven layers can be joined together after impregnation and before drying, wherein the nonwoven layers are glued together via the impregnating agent. After drying, the thermosetting polymer solution can be cured either immediately or later, for example during sanding.

In a preferred embodiment, the at least two nonwovens are impregnated separately, dried and then bonded together. The curing of the thermally curable polymer solution can take place either immediately after drying or later, for example during sanding. Suitable joining techniques are gluing and welding, as already described above. Preference is given to bonding with a moisture-curing polyurethane adhesive.

Suitable impregnation methods are, for example, dip impregnation, size press impregnation, double-sided roller application and double-sided spraying.

The possible fleece combinations for producing the abrasive carrier according to the invention are now to be playfully illustrated by means of some drawings. The drawings all show a cross section through the abrasive carrier. The drawings serve only to illustrate the invention and are not a limiting choice. Especially with the multi-layered abrasive carriers, a large number of nonwoven combinations is possible, which may differ in their nature, their properties and their number and not all in the space Individuals can be listed.

In Fig. 1, a single-layer abrasive carrier can be seen. The thermally curable polymer solution penetrates from one side of its thickness at least 50% to at most 80%, while the aqueous polymer dispersion penetrates its thickness from the other side to at least 25% to at most 50%. Both impregnations can mix in a transition area. Fig. 2 shows a two-ply abrasive carrier. The two nonwoven layers were bonded together before impregnation with one of the bonding techniques described above. Two identical or two different nonwoven layers can be used. The thickness ratio of the two nonwoven layers plays no role. It is important only that the thermally curable polymer solution on the one hand through the total thickness of the abrasive carrier at least 50% to at most 80%, while the aqueous polymer dispersion penetrates its total thickness from the other side to at least 25% to at most 50%. In this case, one of the two impregnations can go beyond the junction of the two nonwoven layers. A mixture of the two im- Prägnierarten in a transitional area is also possible here.

Fig. 3 illustrates a three-layer construction. The three nonwoven layers were bonded together prior to impregnation with one of the bonding techniques described above. Either similar or different nonwoven layers can be used. The thickness ratio of the nonwoven layers plays no role. It is only important that the thermally curable polymer solution on the one hand through the total thickness of the abrasive carrier at least 50% to at most 80%, while the aqueous polymer dispersion penetrates its total thickness from the other side to at least 25% to at most 50%. In this case, one of the two impregnations can go beyond one or both joints of the three nonwoven layers. A mixture of the two types of impregnation in a transition region is also possible here. In Fig. 4, an abrasive carrier is shown, which is composed of two nonwoven layers. The nonwoven layers were individually impregnated prior to bonding. Nonwoven layer A was impregnated with a thermally curable polymer solution and nonwoven layer B with an aqueous polymer solution. The thickness of the nonwoven layer A accounts for at least 50% to at most 80% of the total thickness of the abrasive carrier, while the nonwoven layer B contributes at least 25% to at most 50% of the total thickness. In this variant, two identical or two different nonwoven layers can be used.

The abrasive carrier shown in FIG. 5 is made up of three nonwoven layers, which are also disposed before the connection. individually impregnated. Two nonwoven layers are impregnated with the thermally crosslinkable polymer solution and a nonwoven layer with the aqueous polymer dispersion. The three nonwoven layers can be designed the same or different. The thickness of the two nonwoven 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 carrier, while the thickness of the nonwoven layer impregnated with the aqueous polymer solution amounts to at least 25% to at most 50% Total thickness contributes.

FIG. 6 essentially corresponds to FIG. 5, except that here a nonwoven layer with the thermally crosslinkable polymer solution and two nonwoven layers are impregnated with the aqueous polymer dispersion. The thickness of the nonwoven layer impregnated with the thermally crosslinkable polymer solution also contributes to at least 50% to at most 80% of the total thickness of the abrasive carrier. The thicknesses of the two nonwoven layers impregnated with the aqueous polymer dispersion together make up at least 25% to at most 50% of the total thickness.

7 shows a combination of two layers of the abrasive carrier shown in Fig.l. The two layers were impregnated separately from one another and then joined together in such a way that the side of layer A impregnated with aqueous polymer dispersion came to lie on the side of layer B impregnated with the thermally crosslinkable polymer solution. Again, the two nonwoven layers can be configured the same or different. FIG. 8 essentially corresponds to FIG. 7, except that three layers of the abrasive carrier illustrated in FIG. 1 are combined with one another here. The three layers were impregnated separately from each other and then connected together in such a way that the impregnated with aqueous polymer dispersion side of layer A on the impregnated with thermally crosslinkable polymer solution side of layer B comes to rest. The thermally curable polymer solution impregnated side of web C is bonded to the side of web B which is impregnated with the aqueous polymer dispersion. The three nonwoven layers can be the same or different. FIG. 9 essentially corresponds to FIG. 7, except that three layers of the abrasive carrier illustrated in FIG. 1 are combined with one another here. The three layers were impregnated separately from each other and then connected together in such a way that the side of layer A impregnated with the thermally crosslinkable polymer solution comes to lie on the side of layer B impregnated with the thermally crosslinkable polymer solution. The thermally curable polymer solution impregnated side of web C is bonded to the side of web B which is impregnated with the aqueous polymer dispersion. The three nonwoven layers can be the same or different.

FIG. 10 shows a combination of two layers of the abrasive carrier shown in FIG. The two layers were impregnated separately from each other and then connected together in such a way that the impregnated with aqueous polymer dispersion side of the Fleece A comes to rest on the impregnated with the thermally crosslinkable polymer solution side of the web B. All nonwoven layers can be the same or different.

FIG. 11 essentially corresponds to FIG. 10, except that here three layers of the abrasive carrier illustrated in FIG. 2 are combined with one another. The three layers were impregnated separately from each other and then joined together in such a way that the side of the web A impregnated with aqueous polymer dispersion comes to lie on the side of the web B impregnated with thermal crosslinkable polymer solution. The thermally curable polymer solution impregnated side of web C is bonded to the side of web B which is impregnated with the aqueous polymer dispersion. All nonwoven layers can be the same or different. FIG. 12 essentially corresponds to FIG. 10, except that three layers of the abrasive carrier illustrated in FIG. 2 are combined with one another here. The three layers were impregnated separately from each other and then connected together in such a way that the side of the web A impregnated with the thermally crosslinkable polymer solution comes to lie on the side of the web B impregnated with the thermal crosslinkable polymer solution. The thermally curable polymer solution impregnated side of web C is bonded to the side of web B which is impregnated with the aqueous polymer dispersion. All nonwoven layers can be the same or different. Suitable thermally curable polymer solutions are, for example, phenolic resins, epoxy resins, melamine-formaldehyde resins, urea-formaldehyde resins, polyvinyl alcohols, polyurethane resins or mixtures thereof. Suitable solvents are either water or organic solvents, such as methanol, depending on the type of resin used.

The polymers are either thermally self-crosslinking per se or they can be crosslinked by addition of suitable crosslinkers, such as, for example, polyamines, polycarboxylic acids, hexamethylenetetramine, formaldehyde, metal compounds. The thermally curable polymer solutions can be added as needed, other substances such as paints, fillers, surface-active substances, flame retardants, antistatic agents. The thermally crosslinkable polymer solutions have a solids content of 10% to 100% and a viscosity of 2 mPas to 15,000 mPas.

Suitable aqueous polymer dispersions for impregnating the support material are, for example, aqueous dispersions of acrylic esters, polyvinyl acetate, acrylonitrile-butadiene rubber, acrylate-styrene copolymers, ethylene-vinyl acetate copolymers, styrene-butadiene rubber, phenolic resin, epoxy resin, natural rubber or mixtures thereof.

If necessary, the aqueous polymer dispersions, other substances such as paints, fillers, surfactants, flame retardants, antistatic agents are added.

Suitable aqueous polymer dispersions have a glass transition temperature of -20 ° C to 70 ° C. Prior to their processing as impregnating agent, they are preferred by adding water and, if necessary, a suitable viscosity regulator, for example polyacrylic acid, to a viscosity of 5 mPas - 1000 mPas, preferably 10 mPas - 500 mPas and a solids content of 5% - 50% adjusted from 10 - 45%.

The support material is impregnated with 5% by weight to 50% by weight of the dried polymer solution, based on the weight of the impregnated support material. The impregnating agent content of dried polymer dispersion is 2% by weight - 25% by weight, based on the weight of the impregnated carrier material. Suitable impregnation methods are, for example, roller application, roll or knife squeegee or spraying.

In a special embodiment of the abrasive carrier, a barrier coat is applied to the side impregnated with the aqueous polymer dispersion. If the abrasive carrier has two sides which are impregnated with an aqueous polymer dispersion, the skilled person selects the most suitable side based on the requirements. This barrier coat can be produced, for example, by applying an aqueous dispersion based on acrylates, polyvinyl acetate, acrylonitrile-butadiene rubber, acrylate-styrene copolymers, ethylene-vinyl acetate copolymers, styrene-butadiene rubber. schuk, phenolic resin, epoxy resin, natural rubber or mixtures thereof. The amount applied after drying is 2 - 15 g / m ² , preferably 3 - 12 g / m ² .

The barrier can still be added various additives and / or fillers. Examples of additives are dyes, crosslinkers, water repellents, oil repellents, hydrophilicizing agents, antistatic agents or mixtures thereof. As fillers, e.g. Kaolin, titanium dioxide, talc, calcium carbonate, silica, bentonites or mixtures thereof. Suitable coating methods are e.g. Roller blade, knife blade, air brush or roller application.

To increase the surface smoothness and the flexibility of the impregnated and optionally coated with barrier bar abrasive carrier can be calendered. The impregnated abrasive carrier according to the invention preferably passes through the nip of a pair of rolls consisting of a steel roll and a rubber roll with a nip pressure of 30 to 300 N / mm, preferably of 50 to 250 N / 15 mm. In this case, the abrasive carrier is fed to the calender in such a way that the side with the impregnation of polymer dispersion comes into contact with the steel roller. The calender temperature is between 20 ° and 80 ° C, preferably between 50 ° C and 70 ° C.

The abrasive carrier according to the invention has a basis weight of 50-1000 g / m ² , preferably 100-900 g / m ² , a thickness of 0.010-2000 mm, preferably from 0.020-1.800 mm, a dry ultimate tensile strength of 20-1500 N / 15mm, preferably 30-1400 N / 15mm, a transverse dry tensile force of 10 - 1200 N / 15mm, preferably 20 N / 15mm - 1000N / 15mm, a bursting pressure of at least 200 kPa, preferably of at least 300 kPa, a split strength of at least 0.5 N / 25 mm, preferably of at least 1.0 N / 25 mm, a wet stretch of fennel of 0.05% 3.50%, preferably from 0.05% to 3.00%, a tear propagation according to Elmendorf transversely of at least 200 mN, preferably of at least 300 mN and an air permeability of at most 50 l / m ² s, preferably of at most 45 l / m ² s. To produce the abrasive article of the abrasive carrier according to the invention is still sanded. Besanden is understood to mean the application of a base coat to the abrasive carrier, the subsequent spreading of the abrasive grain, the drying of the base coat, the application of a top coat to the abrasive grain and the final drying of the top coat. The base coat consists z. B. of epoxy resin, phenolic resin, alkyd resin, urea resin or mixtures thereof. The resins are dispersed in a suitable solvent and applied to the fleece (abrasive raw paper). The base coat is applied to the polymer dispersion-impregnated side of the abrasive article carrier. If the abrasive carrier has two sides which are impregnated with an aqueous polymer dispersion, the skilled person selects the most suitable side based on the requirements. If the abrasive carrier has a barrier line, the base coat is applied to the barrier line. The abrasive grains are then applied to the still wet base coat. scattered, with the individual grains are optimally aligned by electrostatic devices on the abrasive paper. Subsequently, the abrasive base paper coated with the wet base coat and the abrasive grains adhering thereto runs in a drying oven in which the base coat is dried. After drying, the abrasive grains are coated with the topcoat. The topcoat is usually a hard thermosetting resin that additionally bonds the abrasive grains to the sandpaper. The sanding is completed by the hardening of the primer and topcoat. The abrasive article according to the invention is used as grinding wheels, abrasive belts and bow-shaped abrasive articles.

Test Methods

Bursting strength after wastes according to DIN EN ISO 2758 Air permeability after Verseidag according to DIN EN ISO 9237 with a sample surface of 20 cm ² and a pressure of 100 mm water column.

Wet elongation after fennel according to DIN 53130:

From the abrasive carrier, two strips, each 15 mm wide, are cut transversely to the running direction of the abrasive carrier web and subsequently dried at 120 ° C. for 30 minutes. This is followed by a recirculation for 24 h at 23 ° C and 50% relative humidity. The measurement is carried out with the wet tensile tester NDT 6/10 from. Kögl WMP GmbH Leipzig. One of the abrasive carrier strips is clamped with 100 mm free length tension-free between two clamps. The lower clamp is rigid and the weight of the upper clamp is balanced by a counterweight and connected to the display. A beaker is filled with 900 ml of tempered (23%) water. By dipping the abrasive carrier strip into the water (beaker moves upwards), the strip expands. The counterweight applies a defined sample tension of 15 grams to the strip, which stretches the strip. Elongation is displayed as a percentage of the scale. Duration of the measurement 1800 s. The specified elongation value in% is the average of two measurements. Basis weight according to DIN EN ISO 536

Thickness according to DIN EN ISO 534 with 20 N contact pressure and a measuring surface of 200 mm ² Breaking force dry in longitudinal and transverse direction according to DIN EN ISO 1924-2, strip width 15 mm, clamping length 100 mm, take-off speed 150 mm / min

Elongation at break dry in longitudinal and transverse direction according to DIN EN ISO 1924-2, strip width 15 mm, clamping length 100 mm, take-off speed 150 mm / min

Tearing resistance to Elmendorf in transverse direction according to DIN EN 21974 with a sample package of 2 paper sheets

Splitting strength in the transverse direction:

From an air-conditioned carrier previously conditioned for 24 hours at 23 ° C. and 50% relative humidity, cut the 2 strips with 50 mm width and 200 mm length. The 200 mm long side runs transversely to the direction of the abrasive carrier. Approx. 150 mm long strips of the Scotch 3M 365 (50 mm wide) adhesive tape are then glued without creases on the front and back of these samples so that the abrasive carrier protrudes by approx. 50 mm at one end. This composite is then subsequently pressed with a 4.5 kg heavy and 50 mm wide steel roll. The steel roller is rolled over the composite by hand twice without additional pressure. From each strip, consisting of the abrasive carrier and the test adhesive tape on both sides of the abrasive carrier, a sample 25 mm wide and 200 mm long is cut. From the end at which the abrasive carrier projects, on one side, the tape is pulled by hand a short distance, so that the abrasive carrier is split over the entire width of the sample. Preferably, the splitting is carried out on the abrasive carrier side on which the test adhesive tape adheres the most. Depending on the impregnation or coating of the abrasive carrier, splitting may be difficult. If the test adhesive tape has poor adhesion to the abrasive backing to be tested and the nip strength is very high, the abrasive backing to be tested must be carefully cut with a razor blade and then further split using the test adhesive tape. The measurement of the gap strength takes place in a universal testing machine from Zwick type Roell Z 0.5 with the following settings:

Measuring range 0.5 F

Program wet grinding gap strength

Speed 300 mm / min Terminal distance 25 mm

The Scotch 3M 365 test tape removed by hand is clamped in the upper clamp of the tensile testing machine. The abrasive carrier to be tested with the second strip of the test adhesive tape adhering to it is clamped in the lower clamp of the universal testing machine in such a way that the composite projects at an angle of 90 ° to the direction of pull. During the measurement it must be ensured that the cleavage takes place in the center of the abrasive carrier to be tested and not just individual fibers are torn from the carrier surface. Measurements in which the cleavage does not take place in the middle of the paper are discarded and repeated. The average force required to split the abrasive carrier is measured. The result is the mean of two individual measurements.

The proportion of the impregnating agent in an abrasive carrier is calculated according to the following formula:

Impregnating agent content in% = (FM Imp. / FM carrier) * 100% with FM Imp. = Mass of the dry impregnating agent per m ² carrier and

FM carrier = basis weight of the impregnated carrier Examples

Example 1 (comparative example)

According to the well-known method of papermaking, a paper web was produced in a paper machine made of 100% cellulose. The paper produced in this way had a basis weight of 150 g / m ² , a thickness of 0.255 mm, a dry breaking force of 129 N / 15 mm, a breaking force dry transverse of 76 N / l 5 mm, a bursting pressure after washes of 341 kPa, a Cleavage strength of 1.33 N / 25 mm, a wet elongation after fennel of 1.531% and a tear strength according to Elmendorf transversely of 1654 mN. In a separate operation, the paper was impregnated with a solution of 2 parts by weight of epoxy resin and 1 part by weight of hardener in methanol by rolling on both sides, dried and then cured at 120 ° C. The proportion of impregnating agent was 17.5%.

The epoxy resin can be obtained under the name CHS 520 from Spolchemie in the Czech Republic. The hardener is available under the name ITAMID D from the company ddchem in Italy.

Finally, the impregnated and dried paper was calendered by means of a pair of rolls consisting of a steel and a rubber roll with a nip pressure of 200 N / mm and a temperature of 70 ° C.

The properties of the abrasive carrier thus produced are summarized in Table 1. Example 2 (comparative example)

The same paper as described in Example 1 was also used in a separate step with an SBR Dispersion impregnated by dip impregnation and dried. The proportion of impregnating agent was 10.7%.

The aqueous polymer dispersion can be obtained under the name Litex SX 1009 from Syntomer, Marl and had a solids content of 27.3% during processing and a Brookflied viscosity LV of 19.3 mPas.

Subsequently, the impregnated and dried paper was calendered by means of a roller pair consisting of a steel and a rubber roller with a nip pressure of 200 N / mm and a temperature of 70 ° C.

The properties of the abrasive carrier thus produced are summarized in Table 1.

Example 3 (invention)

The same paper as described in Example 1 was applied in a separate operation on its upper side with a solution of 2 parts by weight of epoxy resin and 1

Percent hardener in methanol and on its sieve side impregnated with an aqueous dispersion by means of double-sided roller application, dried and then cured at 120 ° C. The impregnating agent content of thermally curable polymer was 20% and of polymer dispersion 3%.

The epoxy resin can be obtained under the name CHS 520 from Spolchemie, Czech Republic. The hardener is under the designation ITAMID D of the

Company ddchem, Italy. The thermally curable polymer solution of epoxy resin, hardener and methanol had a total solids content of 33% and a Brookfield viscosity LV of 4.6 mPas when processed.

The aqueous dispersion has the name Acronal 2416, available from BASF, Ludwigshafen. It had a solids content of 45% and a Brookfield viscosity LV of 23 mPas when processed.

The screen side of a paper is the side with which the paper web comes into contact with the dewatering screen during its production. The top is the opposite side of the screen.

Subsequently, the impregnated and dried paper was calendered by means of a roller pair consisting of a steel and a rubber roller with a nip pressure of 200 N / mm and a temperature of 70 ° C. At this time, the abrasive carrier was fed to the calender so that the polymer dispersion impregnated side came in contact with the steel roll.

The properties of the abrasive carrier thus produced are summarized in Table 1.

Example 4 (Invention)

Two layers of the impregnated paper from Example 3 were combined with each other by means of 5 g / m ^{2 of} a Kleberit PUR 700.7 reactive polyurethane adhesive of Klebchemie, Weingarten in such a way that the side of the one layer impregnated with the thermally curable polymer solution was bonded the side of second layer, which was impregnated with the aqueous polymer dispersion came to rest.

Subsequently, this composite was calendered by means of a roll pair consisting of a steel and a rubber roll with a nip pressure of 200 N / mm and a temperature of 70 ° C. At this time, the abrasive carrier was fed to the calender so that the polymer dispersion impregnated side came in contact with the steel roll.

The properties of the abrasive carrier thus produced are summarized in Table 1. Table 1

Example 1 Example 2 Example 3 Example 4 (Comparison) (Comparison) (Invention) (Invention)

Basis weight raw 150 g / m ² 150 g / m ² 150 g / m ² 150 g / m ²

Basis weight 188 g / m ² 168 g / m ² 194 g / m ² 414 g / m ² impregnated

Breaking force along 312 N / 15 mm 134 N / 15mm 149 N / 15mm 573 N / 15mm

Bursting strength 858 kPa 684 kPa 794 kPa> 3000 kPa after garbage

Wet stretch 1.47% 1, 92% 1, 74% 1, 74% after fennel

Splitting strength splits 3, 1 N / 25mm does not split splits not not

Continuous tear> 8000 mN 1668 mN 1711 mN> 8000 mN activity

Elmendorf

Air permeable120 l / m ² s 42 l / m ² s 26 l / m ² s 0 l / m ² s The results show that the inventive abrasive carrier from Example 3 combines the high gap strength of Comparative Example 1 and the low air permeability of Comparative Example 2. The bursting strength as a measure of the elasticity in Example 3 lies between that of Examples 1 and 2 and is thus in the range of the values usually required. The same applies to wet stretch after fennel, which is a measure of dimensional stability. With Example 4, which is a combination of two layers of the inventive abrasive carrier of Example 3, a further improvement of the physical properties of the carrier can be achieved.

Claims

Claims; 1. abrasive carrier comprising a carrier material of at least one wet or dry laid nonwoven based on natural and / or synthetic fibers, characterized in that the carrier material is impregnated on one side with a thermally curable polymer solution and on the opposite side with an aqueous polymer dispersion, wherein the thermally curable polymer solution penetrates the thickness of the support material to at least 50% and at most 80%, while the aqueous polymer dispersion penetrates the thickness of the support material to at least 25% and at most 50%.

2. abrasive carrier according to claim 1, characterized in that the carrier material comprises a paper.

3. abrasive carrier according to claim 1, characterized in that the carrier material comprises a dry laid staple fiber fleece.

4. abrasive carrier according to claim 1, characterized in that the carrier material comprises a meltblown nonwoven.

5. abrasive carrier according to claim 1, characterized in that the carrier material comprises a spunbonded.

6. abrasive carrier according to claim 1, characterized in that the carrier material consists of several identical nonwoven layers.

7. abrasive carrier according to claim 1, characterized in that the carrier material consists of several different nonwoven layers.

8. Abrasive carrier comprising at least two layers of a carrier material according to claim 1, characterized in that the impregnated with the aqueous polymer dispersion side of at least one layer is connected to the impregnated with the thematically crosslinkable polymer solution side of the subsequent layer.

9. abrasive carrier according to claim 1, characterized in that on the impregnated with the polymer dispersion side, a barrier line is applied.

10. Abrasive carrier according to one of the preceding claims, characterized in that the abrasive carrier is calendered.

An abrasive article comprising an abrasive backing according to any one of the preceding claims wherein the abrasive backing has been sanded on the polymer dispersion impregnated side.

12. The abrasive article of claim 11, wherein a barrier line is disposed on the polymer dispersion-impregnated side of the abrasive backing and the abrasive backing is sanded on the outboard side of the barrier coat.