WO2015189102A1

WO2015189102A1 - Impregnated filter materials and filter elements produced therefrom

Info

Publication number: WO2015189102A1
Application number: PCT/EP2015/062562
Authority: WO
Inventors: Heinrich Richter; Werner HÖRL; Andreas Demmel
Original assignee: Neenah Gessner Gmbh
Priority date: 2014-06-10
Filing date: 2015-06-05
Publication date: 2015-12-17
Also published as: DE102014211021A1

Abstract

The invention relates to a method for producing impregnated filter material from a woven fabric, a dry-laid nonwoven or a wet-laid nonwoven and a particulate binder, and to impregnated filter material obtainable by this method. The particulate binder is uniformly distributed in at least part of the impregnated filter material.

Description

IMPREGNATED FILTER MATERIALS AND MANUFACTURED THEREOF

FILTER ELEMENTS

FIELD OF THE INVENTION

The invention relates to a process for the preparation of impregnated filter materials, in which particulate binders are used, as well as impregnated filter materials obtainable therefrom and filter elements produced therefrom.

PRIOR ART Impregnated filter materials are used today in many areas of gas and liquid filtration. In the simplest case, such an impregnated filter material consists of a carrier made of paper, synthetic fleece, fabric or foam, which is impregnated with a polymeric binder. Impregnation is required to make the impregnated filter material resistant to adverse conditions of use, such as heat,

Moisture or aggressive fluids. In addition, the impregnation gives the impregnated

Filter material for its further processing and

Application required strength, rigidity and

Foldability.

The most common are impregnated filter materials which are impregnated with a liquid, polymeric binder. These binders can be divided into two groups. One group is the binders dissolved or dispersed in water, such as melamine-formaldehyde solutions or resin dispersions, also called latex. The second group is from the

Binders formed in an organic solvent are dissolved, such as phenolic resins or epoxy resins.

For example, German Patent DE102009006586 A1 describes an impregnated filter material which is impregnated with binders dissolved in water or organic solvents.

In the patent US 2,918,173 A an impregnated filter material is disclosed which has an aqueous dispersion as a binder.

Although liquid impregnating agents are very widespread, they also have many disadvantages. First is the

Solvent compatibility of the binder used for the process of impregnation a mandatory

Requirement. Furthermore, both the water and the organic solvents must be removed from the filter material after impregnation. The necessary

Drying process is very energy intensive. In the

Use of organic solvents adds to the health risk to employees. In addition, organic solvents must be collected consuming and disposed of in an environmentally friendly manner. For flammable solvents, attention must also be paid to explosion protection.

Liquid impregnating agents are susceptible to migration, which means that the binder polymers can migrate to the outside during drying. This leads to an enrichment of the binder on the two surfaces of the

impregnated filter material while the middle

Binder depleted. As a result, the strength of the impregnated filter material suffers. Too high

Binder concentration undesirably reduces the pores on the surface of the impregnated filter material.

This effect is particularly pronounced in the use of long-chain polymers, such as Polymer dispersions in water, on. Long chain polymers tend to dry a film between them

to form individual fibers and thus greatly reduce the pore cross-section. The specialist calls this

The sails shorten the life of the filters, because the impregnated filter material quickly becomes attached to the surface due to the reduced pore cross-section, and attempts have been made in the past to remedy these disadvantages by alternative impregnation methods.

The document DE 102005032395 AI discloses a

impregnated filter material obtained by soaking a fiber material with a radiation curing resin and then curing by irradiation with, for example, UV light or electron beam radiation. A disadvantage of this method is that the fibers of the fiber material cast shadows and the

Binder in these shadows is not or only insufficiently cured. In addition, the oxygen present in the fiber material can lead to an inhibition of the free-radical polymerization, as a result of which the

Binder is also insufficiently cured.

In addition, radiation-curing resins are generally highly viscous liquids which are used in the

Curing often forms a film between the individual fibers of the material. It comes to the undesirable

"Sail formation".

Another attempt to overcome the disadvantages of impregnating a fiber material with liquid binders

is in the document WO 95/04857 AI

described. In the manufacture of the impregnated

Filter paper becomes a particulate to the pulp

Binder is added, which melts after drying and solidifies the paper. Particulate binder in the But pulp have the disadvantage that a large part of the binder in the drainage of the formed

Paper web on the paper machine screen with the

filtered water is discharged and does not remain in the paper. In addition, the particulate melt

Binders on drying in the paper machine and cause sticking of the paper web to the hot

Surfaces of the drying cylinders. Furthermore, the drainage of the formed paper web leads to the

Paper machine screen to that, especially finer

Binder particles are washed out with the excess water from the inside of the paper layer so that it on the surface of the resulting paper material to a relatively high concentration of fine

Binder particles comes. This is especially true for the lower surface of the paper layer. The uneven distribution of the binder in the resulting

Filter material adversely affects their

Permeability and mechanical strength.

The document US 4,983,193 A is an impregnated filter material for air filters and air conditioners

described impregnated with a dry, particulate binder. By applying the binder to only one side of the fiber material and then compressing the resulting impregnated filter material under the influence of heat, a

impregnated filter material obtained, seen from one side to the other a decreasing concentration

Binder and a decreasing degree of compaction

having. It is expressly stated that for the preparation of such impregnated

Filter material only nonwovens come into question, which have a very low fiber density of about 7xl0 " ⁴ to 10 ~ 2, so are very fluffy, but such nonwovens are

mechanically very unstable and in large-scale

Processing processes very difficult to handle. Consequently The corresponding filter materials are not suitable for filtration of liquids, in which the filter material is exposed to much higher mechanical loads.

The object of the present invention was therefore to provide a process for producing an impregnated

To provide filter material that does not have the disadvantages listed. The by the procedure

Available impregnated filter materials should have a high enough mechanical strength and rigidity to allow their continued use in both gas filtration and liquid filtration. SUMMARY OF THE INVENTION

The first aspect of the present invention relates to a process for producing an impregnated one

Filter material characterized in that the method comprises the following steps:

a) uniform impregnation of a fibrous material which preferably has an average fiber density of not less than 0.003, more preferably not less than 0.01, and is selected from the group consisting of a fabric, a wet laid nonwoven and a drained nonwoven, with at least a particulate binder;

b) heat treatment of the material from step a), wherein the particulate binder is at least partially melted.

In step a), the particles of the particulate binder in the fiber material are evenly distributed. By a subsequent heat treatment of the material in step b), the particles of the particulate

Binder melted at least partially. This includes the case that only part of the Particles of the particulate binder are melted therein, while the remaining particles of the particulate binder are only softened and are still recognizable as discrete particles, and also the case that individual particles only partially

are melted. In partial melting, the binder particles are firmly bonded by adhesive forces with fibers of the fiber material. Thus, that can

Binders by mechanical stress, which are common when using impregnated filter materials are no longer removed from the impregnated filter material. The impregnated filter material according to the invention thus has a significantly higher bursting strength and

Permeability to gaseous and liquid media as conventionally impregnated filter materials.

The fraction of molten particles of the particulate binder in the impregnated filter material according to the invention is advantageously> 90% by weight, more preferably> 95% by weight, based on the weight of the material used

Total particulate binder.

Preferably, the heat treatment in step b) comprises a first heat treatment step and a second heat treatment step, wherein the temperature of the

impregnated filter material in the second

Heat treatment step is above the melting temperature of the particulate binder. The temperature in the first heat treatment step can be chosen so that it only softens the

Binder particle comes, thereby passing through

Adhesive forces with fibers of the fiber material

get connected. The binder particles are then visible in the microscope as discrete particles. The product obtained after the first heat treatment step is sometimes referred to herein as "impregnated

Semi-finished product "., The impregnated Semi-finished product becomes a second

Subjected to heat treatment step, in which the

Binder is largely melted and optionally cured or crosslinked. Thus, the impregnated filter material of the present invention becomes excellent

Mechanic solidity. Incidentally, in the present specification, curing and crosslinking, and therefore also hardeners and crosslinkers, are understood synonymously. In a further preferred embodiment, the impregnated semi-finished product of a mechanical

Be subjected to processing before the second

Heat treatment step is subjected. Examples of the mechanical processing are i.a. Folding, embossing, shafts in transverse direction, longitudinal fluting or

Cutting the impregnated semi-finished product.

Another aspect of the present invention is the impregnated filter material obtainable from a fibrous material by the method of the invention.

According to one embodiment, it is a

Impregnated filter material based on a

A fibrous material selected from the group consisting of a fabric, a wet-laid nonwoven and a drained non-woven, and preferably a middle one

Fiber density of not less than 0.003, more preferably not less than 0.01 and characterized in that at least a part of the fiber material in

Thickness direction is uniformly impregnated with a particulate binder, which is at least partially melted. In this embodiment of the

The impregnated filter material according to the invention preferably contains at least one particle of the particulate binder in discrete form, and more preferably at least one particle of the particulate one

Binder per mm ³ of binder evenly impregnated portion of the fiber material in discrete form.

When it is said in this specification that particles of the particulate binder are in discrete form, this means that, when considering representative cross sections of the impregnated material

Filter material, preferably using an optical microscope, these particles are still recognizable as demarcated units, without being connected to the other particles to a uniform binder phase. Such a uniform binder phase is observed in fiber materials impregnated with conventional liquid binders.

In a preferred embodiment, the

Binders impregnated in the invention

Filter material at least one thermoplastic polymer. In a further preferred embodiment, the binder has a melting temperature which is at least 5 ° C below the lowest melting temperature of the fibers of the fiber material. The fibers of the fiber material may be at least partially multicomponent fibers and the binder may have a melting temperature that is at least 5 ° C below the melting temperature of the higher melting component of multicomponent fibers of the fiber material.

Preferably, the inventive impregnated

Filter material a gap strength of at least

1.5 N / 25 mm, preferably at least 2.0 N / 25 mm. Another aspect of the present invention is a filter element comprising the impregnated filter material of the invention. In another aspect, the present invention relates

Invention the use of an impregnated

Filter material, which by a method according to

at least one of the claims 1 to 10 is available for the filtration of liquids, in particular of fuels and oils.

DETAILED DESCRIPTION OF THE INVENTION

The impregnated filter material of the present invention has excellent mechanical stability and high permeability, enabling its use for filtration of fluids such as gases and liquids. Thus, the impregnated invention differs

Filter material fundamentally known from the prior art and largely impermeable

Composite materials. The impregnated filter material according to the invention comprises at least one fiber material selected from the group consisting of wet-laid nonwovens, drained

Nonwovens, e.g. drained staple fiber webs and fabrics.

Under drained nonwovens are u.a. dry-laid fiber webs such as dry laid staple fiber webs,

To understand meltblown nonwovens and spunbonded nonwovens. Dry laid staple fiber webs consist of fibers of finite length. For the production of drained

Staple fiber webs can be used both natural and synthetic fibers. 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. The fibers used may be either straight or curled. For solidification, the air-laid

Staple fiber fleece one-component or multi-component

Contain melt binder fibers which melt at a temperature below the melting temperature of the other fibers wholly or partially and solidify the nonwoven. The preparation of the air-laid Stapelfaservliese takes place according to the known prior art as in the book "Nonwovens, W. Albrecht, H. Fuchs, Wiley-VCH,

2012 ". The drained staple fiber webs may be replaced by the ones already mentioned

Solidified multicomponent meltbonding fibers. Other solidification options are, for example

Needling, water jet needling or soaking or spraying the fleece with liquid binders with

subsequent drying.

Meltblown nonwovens consist of polymeric continuous fibers. To produce the meltblown nonwoven fabric for the filter material of the invention is known in the art

Meltblownprozess used, as it e.g. in A. van Wente, "Superfine Thermoplastic 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, polycarbonate. The

Typical fiber diameters are between 0.5 and 10 μm, preferably between 0.5 and 3 μm. Depending on the requirements, additives such as

Example crystallization accelerator or colors, are mixed. In addition, if necessary, the meltblown webs can be densified by means of a calender.

Spunbonded nonwovens are also made of polymeric continuous fibers whose fiber diameter is usually much larger as that of meltblown fibers. Spunbonded nonwovens are produced by the spunbonding process known to those skilled in the art, as described, for example, in US Pat. Nos. 4,340,563 A, 3,802,817 A, 3,855,046 A and 3,692,618 A

is described. Polymers suitable for the spunbonding process are e.g. polyethylene terephthalate,

Polybutylene terephthalate, polyethylene naphthalate,

Polybutylene naphthalate, polyamide, polyphenylene sulfide,

Polyolefin.

Wet-laid nonwovens - also sometimes referred to herein

"Papers" - for the purposes of this invention are all nonwovens, with those known in the art

Wet laying processes for the production of filter papers can be produced. The wet-laid webs for the impregnated filter material according to the invention consist of natural, synthetic, inorganic fibers or a mixture thereof. Examples of natural fibers are cellulose, cotton, wool, hemp, the

used cellulosic wood-free and / or

wood-containing celluloses of coniferous and / or deciduous trees, regenerated celluloses and fibrillated celluloses. Inorganic fibers are for example glass fibers,

Basalt fibers, quartz fibers and metal fibers. When

Synthetic fibers are, for example, one-component synthetic fibers such as polyester fibers, polypropylene fibers, polyamide fibers and polyacrylonitrile fibers, multicomponent synthetic fibers with different melting points of the individual components, such as core-sheath fibers, and

Mixtures thereof. Examples of core-shell synthetic fibers are polyester core and polyester sheath fibers, and polyester core and polyamide sheath. The titer of

Synthetic fibers are typically 0.1 dtex-8.0 dtex, preferably 0.5 dtex-5 dtex, more preferably 1.0 dtex-3 dtex, for example 1.7 dtex. The cutting length is typically 3 mm - 20 mm, preferably 4 mm - 12 mm, particularly preferably 5 mm - 8 mm, for example 6 mm. The use of nonwovens or papers of such fibers allows a particularly efficient impregnation with a medium-sized particulate binder

Particle size of less than 50 microns. Furthermore, this will cause any migration to the surface of the

Filter material during the melting and optionally curing of the particulate binder avoided particularly effective. Moreover, it is possible that the impregnated filter material according to the invention contains fibers with different cutting lengths and titers.

The wet laid nonwovens for the impregnated

Filtering materials may be either 100% natural, synthetic or inorganic fibers, but any mixture of these types of fibers, such as e.g. a mixture of cellulose and thermoplastic polymer fibers such as polyester fibers possible.

In a preferred embodiment that consists

wet-laid web for the production of the impregnated filter material entirely of cellulose fibers. In a further preferred embodiment, the wet laid nonwoven for the production of the impregnated filter material contains about 80 wt.% To 90 wt.% Cellulose and 10 wt% to 20 wt.% Glass or plastic fibers, based on the total weight of the nonwoven. Both

Plastic fibers of this embodiment are preferably thermoplastic polymer fibers, e.g. Polyester fibers.

In a further preferred embodiment, the wet laid nonwoven for the production of the impregnated filter material consists entirely of plastic fibers, which are preferably cut fibers. The Plastic fibers of this embodiment may be at least partially made of one or more thermoplastic

Plastics such as polyester exist. Appropriate

wetlaid nonwovens can by a partial

Melting of the plastic fibers are solidified, resulting in an additional improvement of the mechanical

Properties of the impregnated invention

Filter material leads. Furthermore, it affects one

partial melting of the plastic fibers positively on the mechanical stability of the fleece during the

Preparation of the impregnated filter material.

In a further preferred embodiment, the wet-laid nonwoven for the production of the impregnated filter material contains about 80% by weight to 95% by weight.

Plastic fibers which are e.g. may be cut fibers, and 5 wt.% To 20 wt.% Cellulose fibers, based on the total weight of the web. Similar to the embodiment described above, the nonwoven fabric can be preconsolidated by melting thermoplastic resin fibers.

On the basis of his knowledge and experience, the expert knows the correct composition according to the required paper properties and in particular the

Purpose of the impregnated filter material to select targeted. The paper layer can consist of several layers, which are produced and brought together either in a paper machine with a suitable headbox or made up of individual paper webs which are joined together in a separate operation. The

individual layers can be designed differently in their properties. By combining a plurality of individual layers, properties of the resulting impregnated filter material and filter element made therefrom can be adapted to its intended

Use to be customized. Preferably, the erfindungsgeraäße impregnated

Filter material surface, i. it has two

opposite sides or surfaces, which are particularly preferably arranged parallel to each other.

The fibers of the invention impregnated

Filter material is bound, meaning they are no longer free to move. For papers which typically contain cellulosic fibers, this fiber bonding occurs through the hydrogen bonds between the fibers

individual fibers. The fibers of synthesis sheets which do not have these hydrogen bonds are e.g. by needling, fusing or pre-impregnation with a liquid binder connected together. The fibers of fabrics are joined together, for example, by weaving or knitting. A measure of the

Connection of the fibers with each other is the

Bursting strength.

The unimpregnated fiber material for producing the impregnated filter material according to the invention preferably has a burst strength according to Mullen of

at least 20 kPa, preferably of at least 40 kPa, more preferably of at least 50 kPa, a

Basis weight of 10 g / m ² - 300 g / m ² , preferably of 20 g / m ²

- 200 g / m ² , more preferably from 50 to 170 g / m ² , an air permeability of 10 l / m ² s - 8000 l / m ² s, preferably from 80 l / m ² s - 8000 l / m ² s , more preferably of

200 l / m ² s - 2000 l / m ² s, a pore size of 10 μm -

150 μm, preferably from 20 μm to 120 μm, particularly preferably from 50 μm to 80 μm, a thickness from 0.1 mm to 3.0 mm,

preferably from 0.3 mm to 2.0 mm, more preferably from 0.5

- 1.5 mm, and an average fiber density of not less than 0.01, preferably from 0.1 to 0.8, more preferably from

0.1-0.7, more preferably from 0.1-0.5. In the present case, the term "pore size ^{w is used} for the largest pore of the fiber material or impregnated filter material, as can be determined by the so-called bubble pressure test (bubble point test) according to DIN ISO 4003, wherein in the bladder pressure test a mixture of

96% by weight of ethanol and 4% by weight of water is used as the test liquid.

The mean fiber density is the quotient

Material density (bulk density) and average density of the fibers used. It is calculated using the following formula:

Impregnated filter media for the filtration of fluids are usually impregnated with binder. The impregnation gives the impregnated

Filter material high rigidity and a

Resistance to aggressive fluids, such as

Examples include engine oils, hydraulic oils, fuels, acids, alkalis, acidic and hot gases. As most impregnated filter materials or impregnated

Semi-finished products are folded in a further processing step is a high rigidity and good

Processability required. A high proportion

thermoplastic particulate binder can the processability of the invention impregnated

Filter material or the impregnated semi-finished product according to the invention improve. invention

Impregnated filter materials are stiff and the resulting wrinkles withstand the filtration pressure even at high flow rates and temperatures. Thus, they are excellent for use in filter elements, which are intended in particular for the filtration of liquids.

Among fluids are in the present application

To understand liquids, gases or mixtures thereof. Preferably, the fluids are

Liquids such as, e.g. Fuels and oils such as engine oils, hydraulic oils, etc. Particulate binders are used in the production of the impregnated filter material according to the invention. According to a preferred embodiment of the invention, the particulate binders are dry particulate binders. This particulate

Binders are present as particles, preferably in the form of amorphous solids. The corresponding

Particulate binders may consist of natural or synthetic polymers and are preferably thermoplastic, that is they melt under the action of heat and bond the fibers of the fiber material together. You can do this particulate

Divide the binder into two large groups. The first group includes all polymers that are pure

are thermoplastic, that is, they can be melted by appropriate energy input again and again, such as polyethylene, polypropylene, polyvinyl ethers, polyvinyl chloride, polyvinylidene chloride,

Polyvinylidene fluoride, polyvinyl acetate, polyacrylate,

Polymethacrylate, polyacrylamide, polyamide, polystyrene, polyvinyl alcohol, polyurethane, polyesters, copolymers and / or mixtures thereof.

The second group is formed by polymers which melt in the first stage and then among others

Network energy supply. After crosslinking these polymers can not be remelted again. Examples of such polymers are phenolic resins, Epoxy resins, melamine-formaldehyde resins, unsaturated

Polyester, unsaturated polyurethanes, copolymers and / or mixtures thereof. The crosslinking of the particulate binder is carried out either with itself (crosslinking particulate binder) or using a suitable

Crosslinker, which the expert can select based on his knowledge depending on the requirement. Examples of suitable crosslinkers are polyamines, polyamides, polycarboxylic acids, polycarboxylic anhydrides, dicyandiamide, isocyanates,

Imidazoles, hexamethylenetetramine, methylolurea, resol, methylolmelamine, polyol compounds or mixtures thereof.

In a particularly preferred embodiment, the particulate binder is a

Phenolic resin with hexamethylenetetramine as crosslinker. Such a particulate binder typically has a melting range of about 87-90 ° C. A corresponding particulate binder is commercially available under the name EXP 8E2038P from Dynea Erkner GmbH. The corresponding particulate binder is particularly suitable for impregnating wet-laid nonwovens, for example cellulosic papers, so that the resulting impregnated filter material according to the invention has excellent bursting strength and air permeability. During the melting and optionally hardening of this particulate binder no migration to the surfaces of the

impregnated filter material instead. A correspondingly impregnated filter material is therefore very good for

Production of the filter elements suitable. The melting temperature of the particulate binder plays a special role in its selection. It should be at least 5 ° C, preferably 10 ° C below the lowest Melting temperature of the fibers used, when using multi-component fibers below the melting point of the higher-melting component lie. If the fibers of the fiber material, for example, from a mixture of cellulose and polyester fibers, then the

Melting temperature of the particulate binder are at least 5 ° C below the melting temperature of the polyester used. Becomes a crosslinking particulate binder

selected, the curing temperature should be significantly, preferably not less than 10 ° C, more preferably not less than 20 ° C above its melting temperature. For example, a phenolic resin with

Hexamethylenetetramine used as a crosslinking agent as a particulate binder, it can be melted at about 115 ° C to 125 ° C and then cured at about 150 ° C to 170 ° C. The curing time of the particulate binder depends on the resin used and is typically

between 2 minutes and 2 hours, preferably between 5 minutes and 1 hour, for example between 10 minutes and 20 minutes. For example, a phenolic resin with

Hexamethylenetetramine as crosslinker within 5 to 20 minutes, e.g. cured at 160 ° C within 10 minutes.

Is a mixture of several particulate

Binders before, is with the "melting point of the

particulate binder "in the present

Described the melting point of the refractory particulate binder in the mixture. Depending on requirements, it is also possible for the particulate binder to be admixed with various functional additives, for example hydrophilicizing agents, Water repellents, flame retardants, paints,

Charge particles, biologically active substances.

In the impregnation in step a) of the process for producing the impregnated invention

Filter material, the particles of the particulate binder in the fiber material are evenly distributed. Thus, the resulting invention

impregnated filter material on a uniform distribution of the particles of the particulate binder. Under uniform distribution of the particles of the particulate binder in at least one part of fiber material is understood here that the concentration of

particulate binder per more representative

Volume unit in this part of the fiber material (eg per mm ³ , per 10 ⁶ μm ³ or per 10 ³ μm ³ ) at any point in this part of the impregnated fiber material by less than 10%, preferably by less than 5%, more preferably by less than 2%, more preferably less than 1% of the mean concentration of the

particulate binder in this part of the

impregnated fiber material deviates altogether.

In step a) of the method according to the invention for

Preparation of the impregnated filter material, the particles of the particulate binder in

Thickness direction evenly distributed in at least part of the fiber material. Preferably, this is done

uniform distribution in the thickness direction at least half the thickness of the fiber material, more preferably at least half the thickness to at most three quarters, more preferably over the entire thickness (ie 100% of the thickness) of the fiber material. In the latter case one also speaks of a "Durchimprägnierung ™ des

Fiber material. The impregnation of the fiber material, ie the wet or dry-laid web or fabric, is preferably carried out in the context of the invention Substantially planar, ie over at least 99% of the area of the fibrous material, into the thickness of the fibrous material, as indicated above. According to a special

Thus, the preferred embodiment is the fiber material over its entire surface, that is completely, with the

Particulate binder impregnated through.

The size of the particles in the particulate binder (hereinafter, for the sake of convenience, "particle size of the particulate binder") is preferably such that 95% of the particles are less than 500 microns in size, more preferably less than 100 microns, and most preferably less than The sieve analysis is used to determine the particle size of the particulate binder, particularly advantageously an air-jet screening device in accordance with DIN EN ISO 8620. If 95% of the particles have a size of less than 500 μm, this means that 95% of the particles pass through a 500 μm sieve, that is to say a sieve with a mesh size of 500 μm, can be passed through. The particle size of the particulate binder is advantageous for the pore size of the fiber material

tuned to an efficient uptake and distribution of the particulate binder in the impregnated

To allow filter material.

Binders are preferred in which 95% of the

Particles are smaller than the pore size of the fiber material (as defined above) and particularly preferred are binders in which 99% of the particles are smaller than the pore size of the fiber material, ie through a sieve with a mesh size corresponding to the pore size of the

Fiber material corresponds, go through.

The impregnation is carried out by the known methods, such as scattering of the particulate binder on the fiber material or spraying means

electrostatic spray device. Furthermore it is it is possible to impregnate the starting material by sucking a gas stream containing the particulate binder through the fibrous material. The

Particulate binder can be a - or

be applied on both sides of the fiber material.

The distribution of the particulate binder in the

Fiber material is produced in the impregnation step a) by suitable methods known to the person skilled in the art, such as, for example, mechanical shaking,

Ultrasound application, alternating electric field,

Applying a negative pressure.

In step b) the material from step a) becomes a

Subjected to heat treatment. This can be achieved, for example, by the introduction of heat energy, e.g. done by infrared emitter or by entry of ultrasound. In step b) of the production process according to the invention, it is preferable to substantially melt, in particular to completely melt, the

Binder particles, which are preferably dry, and optionally to a curing. To a far-reaching,

in particular complete melting of the

To achieve binder particles, the temperature during the heat treatment of the material is advantageously at least 5 ° C above the melting temperature of the particulate binder, preferably at least 10 ° C above the melting temperature of the particulate binder, and more preferably at least 15 ° C above the

Melting temperature of the particulate binder. When choosing the temperature, it must be ensured that the synthetic fibers possibly present in the fiber material do not melt. Preferably, the material obtained in step a) in step b) is a first heat treatment step

subjected to the impregnated semi-finished product is obtained. The first heat treatment step causes the particles of the particulate binder to be firmly bonded by adhesive forces to the fibers of the fiber material. In the first heat treatment step, usually only a softening of the binder particles, whereby under certain circumstances

Binder particles can also partially melt. At the end of the first heat treatment step, discrete binder particles are usually detectable in the microscope. The heating temperature or the entry at

Ultrasonic energy is chosen so that the

Although particulate binder is softened or partially melted, which may be in the impregnated

Filter material existing synthetic fibers but not. Therefore, the temperature is in the first one

Heat treatment step preferably slightly below the melting point of the particulate binder, preferably up to 5 ° C, more preferably up to 2 ° C below.

The impregnated semi-finished product is intended to be impregnated for its processing

Filter material or to a filter element by a mechanical method such as embossing, folding, waves in the transverse direction, creasing in the longitudinal direction

to be deformed. However, this mechanical processing step is not mandatory, so that the impregnated semi-finished product after the first

Heat treatment step, if applicable, depending on intended

Use of the filter material, by a second

Heat treatment step for the invention

Filter material can be further processed.

When the heat treatment in the inventive

Manufacturing process is carried out in two separate steps, the impregnated semi-finished product has a relative between the first and second heat treatment step high flexibility and can be subjected to a particularly gentle mechanical processing. Any damage to the impregnated filter material is thus efficiently avoided and the resulting

impregnated filter material has excellent

mechanical properties.

If the heat treatment in step b) two-stage

is performed, ie, with a first and a second heat treatment step, the parameters of the first heat treatment step are preferably as follows:

The second heat treatment step is preferably carried out at a temperature at least 5 ° C above the melting point of the particulate binder. The duration of the second heat treatment step is preferably as follows: it is in the range of 0.5 to 30 seconds, for example when the particulate binder is to be melted and, if desired, the crosslinking is merely initiated, and is in the range of 5 to 20 minutes, For example, if the particulate binder to be melted and fully cured or cured. The previously mentioned initiated networking can even at

Room temperature over days or weeks

be completed.

Furthermore, it is possible to carry out the first heat treatment and the second heat treatment in a single common process step. Thus, the heat treatment in step b) may be a one-step

Heat treatment act. Preferred embodiments of such a single-stage heat treatment have been previously described in Connection with the heat treatment in step b)

generally explained. So the temperature is

preferably at least 5 ° C above the melting point of the particulate binder and the duration

preferably in the range of 0.5 to 30 s, for example when the particulate binder is to be melted and, if appropriate, the crosslinking is merely initiated, wherein the crosslinking can then be completed even at room temperature in the course of days or weeks.

Preferably, in the second heat treatment step, an extensive melting and, if appropriate, curing of the

Particulate binder us it comes to the formation of the impregnated filter material according to the invention. The molten binder envelops the fibers of the filter material and forms bridges between the fibers.

The particulate binder may, for example, after impregnating the fiber material in the first

Heat treatment step in the way softens or

be melted that in the impregnated

Semi-finished product at least 5% of the maximum

Final strength can be achieved. After shaping, the impregnated semi-finished product according to the invention can then be reheated in the second heat treatment step. This is the particulate binder

preferably completely melted and cured if necessary, so that it in the resulting impregnated filter material its desired final strength and

End stiffness achieved.

In a preferred embodiment, the fiber material used in step a) of the production process according to the invention is at least one

particulate binder is uniformly impregnated to a pre-consolidated fiber material. A using such a pre-consolidated fiber material with the completely impregnated filter material according to the invention has a bursting strength of at least 50 kPa,

preferably of at least 100 kPa, a basis weight of 20 g / m ² - 500 g / m ² , preferably from 40 g / m ² - 300 g / m ² , an air permeability of 10 l / m ² s - 8000 l / m ² s, preferably from 80 l / m ² s - 8000 l / m ² s, a pore size of 10 .mu.m-150 .mu.m, preferably from 20 .mu.m-100 .mu.m, a thickness of 0.1 mm-3.0 mm, preferably from 0.3 mm - 3.0 mm, a fiber density of 0.1-0.9, preferably of 0.1-0.8, with 0.1-0.7 being particularly preferred, a resin content of 5% by weight - 95% by weight, , preferably from 5 wt.% - 50 wt.% Based on the total mass of the impregnated

Filter material, and a gap strength of at least 1.50 N / 25 mm, preferably of at least 2.00 N / 25 mm.

The method of preconsolidating the fiber material is not further limited. Irrespective of the type of fibers used, needling and water jet needling, as well as impregnation or spraying with liquid binders (latex) with subsequent drying, are suitable for dry and wet-laid nonwovens. When thermoplastic fibers, such as single or multi-component meltbond fibers, are included in the nonwovens, thermal calendering, both full-surface and point-wise, is another way of preconsolidation.

The gap strength is a measure of the uniform

Distribution of the particulate binder and indicates the force in the Z direction, which is needed to the

to impregnate impregnated filter material in itself.

In the production of a further embodiment of the impregnated filter material according to the invention, a pre-consolidated fiber material such as tissue, paper or non-woven is used, which only on one side with a particulate binder is uniformly impregnated in such a way that it penetrates the thickness of the fiber material at least half but not more than three quarters. Such a fiber material has a

Burst strength after washes of at least 50 kPa,

preferably of at least 100 kPa, a basis weight of 20 g / m ² - 500 g / m ² , preferably from 40 g / m ² - 300 g / m ² , particularly preferably from 100 g / m ² - 200 g / m ² , a

Air permeability of 20 l / m ² s - 8000 l / m ² s, preferably from 80 l / m ² s - 8000 l / m ² s, more preferably from

200 l / m ² s - 2000 l / m ² s, a pore size of 10 .mu.m-150 .mu.m, preferably of 20 .mu.m-100 .mu.m, particularly preferably of 40 .mu.m-800 .mu.m, a thickness of 0.1 mm-3.0 mm,

preferably from 0.3 mm to 2.0 mm, a fiber density of 0.1 to 0.9, preferably from 0.2 to 0.8, a resin content of 2 wt .-% - 95 wt.% Based on the total mass of the fiber material, preferably from 5% by weight - 50% by weight. For example, such a fiber material may have a basis weight of 168 g / m ² , a thickness of 0.90 mm, a bursting strength of 65 kPa, an air permeability of 500 l / m ² s, a pore size of 58 μm and a fiber density of 0.13 exhibit.

In the context of the invention, it is readily possible that the impregnated filter material according to the invention consists of several layers or layers. Furthermore, it is also possible that when used in filtration,

for example in the filter element, before and / or after the impregnated filter material according to the invention, one or more layers of other materials, e.g. are provided other impregnated filter materials.

The individual layers of the impregnated filter material according to the invention are either with an adhesive or via welded joints or a combination thereof

connected. Advantageous adhesives have a softening point of over 200 ° C. In the bestinunungsgemäßen use the impregnated filter material according to the invention is exposed to temperatures up to 150 ° C and high hydrostatic pressures. The adhesive connection must not come loose.

Suitable adhesives for this application are

Polyurethane adhesive, polyamide adhesive or polyester adhesive. Polyurethane adhesives are particularly preferred because they can crosslink with the humidity. The

Adhesives can be applied either as a powder or melted by 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 joint can be replaced by a

Ultrasound system as well as done by a thermal calender. The polymers of the layers to be welded are either over the entire surface or in regions

melted and welded together. The

area welds 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 at most 10% of the total area of the impregnated filter material according to the invention.

Gluing and welding can also be arbitrary

be combined with each other. The impregnated filter material according to the invention can be further processed into all conventional elemental forms. Thus, for example, Hoses, bags or pouches

be made. Or it can be at all usual

Processing machines embossed, folded, corrugated in the transverse direction, longitudinally grooved, etc. are. If the impregnated filter material according to the invention is processed into hoses, bags or bags, the particle-shaped binder is advantageously completely melted or cured after the impregnation of the fiber material.

Test Methods

Basis weight according to DIN EN ISO 536

Melting temperature according to DIN EN ISO 3146

Softening point of the adhesives according to DIN EN 1238

Thickness according to DIN EN ISO 534

Air permeability according to DIN EN ISO 9237 at 200 Pa

pressure difference

Bursting strength according to Mullen according to DIN 53141

Particle size according to DIN EN ISO 8620

Pore size by gas bubble test according to DIN ISO 4003 on flat samples with a mixture of 96% by weight of ethanol and 4% by weight of water as test liquid.

The proportion of binder in a paper (resin content) is calculated according to the following formula:

Resin content in% = (FM Imp./FM paper) * 100% with FM Imp. = Weight of dry binder per m ^{2 of} paper

FM paper = grammage of impregnated paper Determination of transverse splitting strength:

From a previously impregnated air-conditioned 24 hours at 23 ° C and 50% relative humidity

Filter material is cut into 2 strips 50 mm wide and 200 mm long. The 200 mm long side runs transversely to the direction of impregnated

Filter material. On the front and back of these patterns are then about 150 mm long strips of Scotch 3M 365 Tape Test Tape (Thermoset Glass Fabric Adhesive Tape, Steel Adhesion: 60 oz./in. Width

(54.5 N / 100 mm), measured according to the standard ASTM D-3330;

Elongation at break: 106 lbs./in. Width (2106 N / 100mm), measured according to standard ASTM D-3759; Thickness of the carrier material:

5 mils. (0.12 mm) measured according to standard ASTM D-3652;

Total tape thickness: 7.2 mils. (0.18 mm) measured according to the standard ASTM D-3652) wrinkle-free glued so that at one end of the impregnated filter material by about 50 mm

survives. 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. Made of each strip, consisting of the impregnated filter material and the test tape on both sides of the impregnated

Filter material, a sample with 25 mm width and 200 mm length is cut. From the end at which the impregnated filter material protrudes, the tape is pulled by hand a short distance on one side by hand, so that the impregnated filter material is split over the entire width of the sample. Preferably, the splitting is on the side of the impregnated

Filter material on which the test tape adheres the most. Depending on the impregnation of the impregnated filter material, splitting may be difficult. In case of bad adhesion of the

Test tapes on the impregnated to be tested

Filter material and at very high gap strength must be tested impregnated filter material with a

Carefully cut the razor blade and then split it further with the aid of 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 Preliminary 20 mm

Test track 80 mm

The Scotch 3M 365 test tape removed by hand is clamped in the upper clamp of the tensile tester. The impregnated filter material to be tested with the second strip of the test adhesive tape adhering thereto is clamped in the lower clamp of the universal testing machine in such a way that the composite protrudes at 90 ° to the direction of pull. During the measurement, care must be taken that the cleavage takes place in the middle of the impregnated filter material to be tested, and not just individual fibers are torn from the surface of the impregnated filter material.

Measurements in which the cleavage does not occur in the middle of the impregnated filter material are discarded and repeated. Measured is the average force needed to break the impregnated filter material. The result is the mean of two

Individual measurements.

EXAMPLES

Example 1 (Invention) According to the well-known method of

Paper production became one in a paper machine

Paper web made from 84% cellulose and 14% polyester fibers (1.7 dtex / 6mm). The paper is under the

Designation H11PESG of the company NEENAH Gessner,

Bruckmühl available. The paper thus prepared had a basis weight of 168 g / m ² , a thickness of 0.90 mm, a bursting strength of 65 kPa, an air permeability of 500 l / m ² s, a pore size of 58 μm and a

Fiber density of 0.13.

On this paper, 43 g / m ^{2 of} a particulate phenolic resin was in a separate operation with Hexamethylenetetramine as a hardener of the company Dynea Erkner GmbH, Erkner with the name EXP 8E2038P scattered and distributed by means of mechanical shaking movements over the entire thickness of the filter material. The particle size of the phenolic resin was such that 95% of the particles had a size of <40 μm and the phenolic resin had one

Melting range of 87-90 ° C.

Thereafter, the binder was impregnated in the

Filter material is melted by means of an infrared radiator at 120 ° C and then 10 min at 160 ° C.

hardened. After cooling and storage for 24

Hours at 23 ° C and 50% relative humidity were the parameters listed in Table 1

measured.

Example 2 (comparative example)

The paper from Example 1 was impregnated in a known manner with a phenol resin solution in methanol and dried at 110 ° C. The phenolic resin is under the

Name Fenoplast PF-14 from the company. Lerg, Pustkow. Hexamethylenetetramine (1.2% by weight, based on the solids content of the formulation) was used as crosslinker. The impregnated filter material thus prepared had a resin content of 20%. Subsequently, this impregnated filter material was cured in the laboratory for 10 min at 160 ° C. After storage for 24 hours at 23 ° C and 50% relative humidity, the parameters of the resulting impregnated filter material shown in Table 1 were measured.

As can be seen from Table 1, has the

impregnated filter material according to the invention a significantly higher bursting strength and air permeability than the conventionally impregnated filter material

Example 2. The nip strength of the impregnated filter material of Example 1 according to the invention is so high that it can no longer be measured by the method indicated. This suggests that the binder is evenly distributed throughout the impregnated filter material of the present invention and does not migrate to the membrane during reflow and cure of the impregnated filter material

Surfaces of the impregnated filter material

took place, as in the comparative example

has happened.

Claims

1. A process for producing an impregnated

Filter material characterized in that the method comprises the following steps: a) impregnation of a fiber material, the one

has a mean fiber density of not less than 0.003 and from the group consisting of a

Fabric, a wet laid nonwoven and a drained nonwoven fabric, with at least one particulate binder, such that the particles of the particulate binder in the thickness direction in at least one

Part of the fiber material are evenly distributed;

2. The method according to claim 1, characterized in that the heat treatment in step b) a first

Heat treatment step and a second

Heat treatment step, wherein the temperature of the impregnated filter material in the second

Heat treatment step is above the melting temperature of the particulate binder.

3. The method according to claim 2, characterized in that the impregnated filter material after the first

Heat treatment step and before the second

Heat treatment step is subjected to mechanical processing.

4. The method according to claim 1, characterized in that the heat treatment in step b) is carried out in a single process step.

5. The method according to at least one of claims 1 to 4, characterized in that 95% of the particles of

Particulate binder have a particle size of less than 100 microns.

6. The method according to at least one of claims 1 to 5, characterized in that the particulate

Binder contains at least one thermoplastic polymer.

7. The method according to at least one of claims 1 to 6, characterized in that the particulate

Binder has a melting temperature which is at least 5 ° C below the lowest melting temperature of the fibers of the fiber material.

8. The method according to at least one of claims 1 to 7, characterized in that the proportion of at least partially melted binder in the

impregnated filter material 5 to 50 wt .-% is.

9. The method according to at least one of claims 1 to 8, characterized in that the fiber material

is pre-consolidated.

10. The method according to at least one of claims 1 to 9, characterized in that the fiber material has an average fiber density of 0.1 - 0.7.

11. The method according to at least one of claims 1 to 10, characterized in that after step b)

at least one particle of the particulate binder is still present in discrete form.

12. Impregnated filter material which is obtainable from a fiber material by a method according to at least one of claims 1 to 11, in particular according to claim 11.

13. Impregnated filter material according to claim 12, characterized in that it has a gap strength of

at least 1.5 N / 25 mm, preferably at least

2.0 N / 25 mm.

14. Impregnated filter material based on a

A fiber material having an average fiber density of not less than 0.003 and selected from the group consisting of a fabric, a wet laid nonwoven and a

drained nonwoven fabric is thereby

characterized in that at least a portion of the fiber material is uniformly impregnated in the thickness direction with a particulate binder which has been at least partially melted, wherein preferably at least one particle of the particulate binder is present in discrete form.

15. Filter element comprising an impregnated

Filter material according to at least one of claims 12 to 14.

16. Use of an impregnated filter material according to any one of claims 12 to 14 or one

Filter element according to claim 15 for the filtration of

Liquids, in particular fuels and oils.

17. Process for the filtration of liquids,

especially fuels and oils, in which a

impregnated filter material with a method

produced, which comprises the following steps: a) impregnation of a fiber material having an average fiber density of not less than 0.003 and selected from the group consisting of a

Fabric, a wet laid nonwoven fabric and a drained nonwoven fabric, with at least one particulate binder, such that the particles of the particulate binder are evenly distributed in the thickness direction in at least a portion of the fibrous material;

b) heat treatment of the material from step a), wherein the particulate binder is at least partially melted,

and the impregnated filter material thus prepared is used to filter liquids, especially fuels and oils.