SE515510C2 - Process for producing nonwoven fabric and nonwoven fabric produced therewith and process for producing a layer composite and the layer composite produced therewith - Google Patents

Abstract

The invention concerns a method of manufacturing non-woven, a non-woven fabric, a method of manufacturing a stratified composite comprising said non-woven, as well as a stratified composite. The method of manufacturing non-woven comprises the steps of forming a fibre blend containing bicomponent-type fibres, laying out the fibre blend in order to form a web, impregnating the web with latex, and drying the latex-impregnated web. A bicomponent fibre comprising a first outer component having a first melting temperature and a second core component having a second melting temperature which is higher than the first melting temperature is added as bicomponent fibres. The amount of bicomponent fibres added is at least about 50 % by weight of the fibre blend. A polymer latex which may be thermally activated at a first melting temperature that is lower than the second melting temperature is added as latex. The drying of the latex-impregnated web is carried out at a drying temperature that is higher than said first melting temperature and lower than said second melting temperature.

Description

10 15 20 25 30 35 515 510 2 similar materials with significantly greater thickness and thereby use these directly as insulation material.

A conventional method for producing nonwoven fabric is shown schematically in Fig. 1. Most often, the fibers are manufactured elsewhere and transported to the nonwoven fabric manufacturer in well-packed bales.

The fiber bales are torn up and the fiber lumps are inserted into a so-called coarse opener, where the fiber lumps are processed so that the fibers are to a certain extent separated into individual exposed fibers.

In a lot of applications, non-woven fabric is used which is made up of more than one type of fiber, whereby in connection with the rough opening a balancing of the different proportions of fibers that the non-woven fabric is to contain is often performed. Common fibers used are, for example, nylon fibers, viscose fibers, aramid fibers, polyester fibers or similar synthetic fibers. Natural fibers such as flax fibers can also be used.

After weighing, the fibers are taken to a mixer where they are mixed and further processed and further opened (or aerated). The blending step can also be used even if only one type of fiber is used; by mixing fibers from (batches) one reduces the impact of any manufacturing variations different manufacturing series from the manufacturer can on the final product.

After mixing, it is common to carry out some form of purification to remove, for example, lumps of fiber or other undesired residual products from the production of the fibers.

After that, additional steps with opening of the fibers are usually needed.

When the fibers have been separated in a sufficiently sufficient manner, the fiber mixture is passed on to a carding unit. In the carding unit, the fibers are further processed and oriented so that a larger proportion of fibers are oriented in one and the same direction. The fiber mixture leaves the carding unit in the form of a thin mat with the fibers oriented in the transport direction from the carding unit, i.e. they are oriented so that they lie parallel to the plane defined by the thin mat. In many cases, it is not enough to use a single thin carpet but to lay a so-called flora. There are two common ways of orienteering, bringing together several rugs, often 5-10 pieces, the different rugs that are put together, they are usually either oriented on the same hob or they are alternately oriented perpendicularly. By using the joining of several mats to form the fleece, a fleece with an even basis weight is obtained, even though there is a certain variation in basis weight in each of the mats. The flower usually has a thickness of the order of 1-3 cm.

The fluorine is usually impregnated in the next stage with various additives, such as flame retardants, adhesives of different kinds for bonding the fibers, and dye additives. The impregnation can take place, for example, by the floret being led down through a liquid bath containing the desired additives. It can also be done by so-called foam impregnation or by spray impregnation_ After the impregnation, the impregnated (wet) flor is usually led to a station where excess liquid is removed. This can be done with the help of suction boxes, pressure and suction rollers. After the impregnation and removal of excess liquid, the flor has a thickness of the order of 0.5-2 mm.

The fleece is then led into an oven where the thin cloth (non-woven fabric) The non-woven non-woven fabric in the oven is then stretched and dried. rolled up on large rolls.

When used for, for example, ceiling or bonnet insulation in the automotive industry, today's non-woven fabrics are not satisfactory. Since the production of non-woven fabric usually takes place at special non-woven fabric manufacturers and the production of ceilings and bonnet insulation takes place at other manufacturers, it is required that the various components can be handled in a smooth manner both individually and after they have been combined into a partially or completely finished product.

The requirements, or at least wishes, placed on the nonwoven fabric are that it must be easy to handle, it must be environmentally friendly, ie it must not emit any environmentally harmful substances during manufacture, molding to end product or during use and it must be recyclable. , and it must provide sufficient strength to the final product.

In an attempt to achieve these requirements, or desires, regarding the handling and strength of the final product, there are countless examples of the use of fiberglass blending in the nonwoven fabric. See, for example, US-A-4,888,235, US-A-4,889,764 and US-A-4,946,738, all of which are derived from one and the same parent application filed in 1987. These patents describe a vehicle roof consisting of a non-woven fabric. terial with a thickness in the order of 1-3 inches (2.5- 7.5 cm), however, not desirable to use because it, among other things, and with a glass fiber content of 42%. Fiberglass years can cause skin irritation. For fixing the fibers, the non-woven fabric also contains up to 16% phenolic resin, which can emit formaldehyde, which is mucosal irritating and which is classified by the Swedish Chemicals Agency as a carcinogen.

To avoid these problems with glass fiber and with phenolic resin for fixing the fibers, it is possible, for example, as stated in WO99 / 02335, to use several layers of non-woven fabric, whereby the sandwich construction can obtain the same strength as before without the use of glass fiber. In the sandwich construction described, at least one layer of two types of polyester fibers is used, one of which is intended to melt during heat treatment and to bind the remaining fibers together. The various layers in the sandwich construction are bonded together by thin layers of an adhesive or the like with adhesive properties. Furthermore, it is considered necessary to coat the sandwich construction with an outer layer in order for the product to obtain an acceptable appearance. The sandwich construction described above thus requires a large number of extra layers in addition to the constructive layers of non-woven fabric.

Summary of the invention The object of the invention is to provide a solution to the above-related problems.

More specifically, the purpose can be summarized to be to create a non-woven fabric which is, among other things, environmentally friendly, it must be able to be used as an outer layer on various insulation materials, it must be able to be used alone or together with other materials to build a sandwich construction with a number of layers, and it should be easy to handle in the various steps from semi-finished to fully finished product.

Other applications and advantages of the invention will become apparent from the description.

The above-mentioned object has been achieved with a process which is of the kind indicated in the introduction and which is characterized in that a latex of a polymer which is thermally activatable at a first activation temperature which is lower than the second melting temperature is supplied as latex, that the drying of the latex impregnated fluorine is carried out at a drying temperature which is higher than said first melting temperature and lower than said second melting temperature, and that latex is supplied in an amount such that the amount of polymer supplied by latex is in the range 10-60% by weight of the total dry weight of the nonwoven fabric.

The use of bicomponent fibers of the type indicated above together with a latex of the type indicated above causes the outer component of the bicomponent fibers to melt completely or partially during drying. During melting, the molten material will accumulate mainly at the places where fibers abut each other. In addition, the polymer particles supplied by latex will be bound in these accumulations. The molten outer component thus binds the various fibers together and retains the latex-fed polymer. By using a relatively large proportion of bicomponent fibers, there will be a relatively large amount of material that holds the non-molten fibers together. Said polymer particles also help to bind the nonwoven fabric together.

The nonwoven fabric produced by this process is strong and can be given a relatively high stiffness, which means that it is easy to handle. The use of bicomponent fibers and latex means that you do not need glass fiber or phenolic resin to obtain a constructively satisfactory non-woven fabric. Furthermore, you do not need any thin layers of glue or the like.

The nonwoven fabric is suitable for use in various forms of layer composites. In the production of these layered composites, any further melting of the outer so-called low-melting component of the bicomponent fibers and the polymer supplied by latex is used. The process for producing a layer composite is characterized by assembling at least a first layer of nonwoven fabric described above, prepared by the above-related process, and at least a second material layer, by compressing the layers under pressure and heat supply at a temperature which is higher than said first temperature, higher than said activation temperature and lower than said second melting temperature, the first component and the latex in said nonwoven layer melting and forming a film bonding to said second layer.

The nonwoven fabric described above therefore contains a component (latex-fed polymer + any remaining outer low-temperature melting bicomponent fiber component) which is not activated until the nonwoven fabric is combined with another layer and heated to the activation temperature of this component.

The processes according to the invention for producing nonwoven fabric and a nonwoven-containing layer composite, as well as the nonwoven fabric itself and the layer composite itself are defined by the independent claims. Preferred embodiments appear from the dependent claims.

Advantageously, latex is added in an amount such that the amount of polymer added by latex is in the range of 25-50% by weight of the total dry weight of the nonwoven fabric.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in more detail in the following with reference to the accompanying schematic drawings which, by way of example, show preferred embodiments of the invention according to its two aspects relating to nonwoven fabric and layer composite, respectively.

Fig. 1 is a flow chart showing the various steps according to a nonwoven fabric manufacturing process.

Fig. 2 is a drawing illustratively showing how the different fiber types and the latex material interact to bond the nonwoven fabric together before the film-forming polymer is activated.

Fig. 3 shows a cross section of a bicomponent fiber of the type used in the presently preferred embodiments.

Fig. 4 is a scanning electron microscope image (50x magnification) of a dried / heat treated nonwoven fabric according to a preferred embodiment.

Description of the Preferred Embodiment As shown in Fig. 2, the nonwoven fabric comprises polyester bicomponent fibers 11, which consist of an outer component forming a sheath 11a around a core 11b. The outer component 11a of the polyester bicomponent fibers has a first melting temperature Tm_of 175-180 ° C and the core component 11b has a second melting temperature IQ of 260 ° C, i.e. it is higher than the first melting temperature Em. Furthermore, the nonwoven fabric also comprises so-called ordinary polyester staple fibers 13 with a melting or decomposition temperature Tn in the order of 260 ° C. The bicomponent fibers make up about 75% (weight) The nonwoven fabric is impregnated with an acrylate latex, of which the amount of fiber. in addition to fibers it also comprises a film-forming thermally activatable polymer. In order for the latex to have a sufficiently high glass conversion temperature, a modified acrylate latex, suitably a so-called styrene-modified acrylate latex, is used. The polymer fed through the acrylate latex has an activation temperature Ta which is higher than the first melting temperature TM but which is lower than the second melting temperature TM. The polymer constitutes about 35% (dry weight) of the nonwoven fabric.

The nonwoven fabric is particularly suitable for use as one or more layers in a layer or laminar composite.

Since the fibers 11, 13 are of polyester, the molten phase and the fibers themselves will provide sufficient adhesion to each other and to any adjacent layers of other materials. By forming the layer composite at a forming temperature Tf which is higher than the activation temperature Ta of the polymer 12, but which is lower than the second melting temperature EQ of the bicomponent fibers II and the decomposition temperature Tn of the staple fibers, the polymer 12 will form a film further bonding the fibers 11, 13 in the respective layers and adjacent layers.

The production of the nonwoven fabric takes place essentially according to a conventional method of the kind described in connection with the technical background.

Fiber bales of the different types of fiber polyester bicomponent fiber 11 and polyester staple fiber 13 are torn up and the more or less glued fiber lumps are inserted into a so-called coarse opener, where the fiber lumps are processed so that the fibers 11, 13 are to some extent separated into individual exposed fibers 11, 13 In connection with the rough opening, a balance is made between the different proportions of fibers that the non-woven fabric must contain.

In many applications, nonwoven fabric is used which is made up of more than one nonwoven fabric, whereby Common fibers used are, for example, nylon fibers, aramid fibers, polyester fibers or similar synthetic fibers.

After weighing, the fibers are passed to a mixer where they are mixed and further processed and opened (or aerated) 10 15 20 25 30 35 515 510 9 further. The blending step can also be used even if only one type of fiber is used; by mixing fibers from (batches) one reduces the impact of any manufacturing variations different manufacturing series from the manufacturer can on the final product.

After mixing, some form of purification is usually carried out to remove, for example, lumps of fiber or other undesired residues from the production of the fibers.

After that, additional steps are usually needed with processing (opening) of the fibers.

When the fibers have been separated to a sufficient extent, the fiber mixture is passed on to a carding unit. In the carding unit, the fibers are further processed and oriented so that a larger proportion of fibers are oriented in one and the same direction. The fiber mixture leaves the carding unit in the form of a thin mat with the fibers oriented in the transport direction from the carding unit, i.e. they are oriented so that they lie parallel to the plane defined by the thin mat. Usually several carpets are put together, often 5-10 pieces, to form a so-called flora. There are two common ways to orient the different carpets that are put together, most often they are either oriented on the same slab or they are alternately oriented perpendicularly. By using the joining of several mats to form the fleece, a fleece with an even basis weight is obtained, even if there is a certain variation in basis weight in each of the mats. The flower usually has a thickness of the order of 1-3 cm.

The fluorine is then impregnated with an acrylate latex and with various additives, such as, for example, flame retardants.

The impregnation takes place by the floret being led down through a liquid bath containing the desired additives. It can also be done through so-called foam impregnation or through spray impregnation.

After impregnation, the impregnated (wet) fleece is led to a station where excess liquid is removed. 10 l5 20 25 30 35 515 510 10 This can be done with the help of suction boxes, pressure and suction rollers. After the impregnation and removal of excess liquid, the flor has a thickness of the order of 0.5-2 mm.

The floret is then led into an oven where the thin cloth (non-woven cloth) has a temperature of 180-200 ° C. As long as there is liquid left to dry. The drying takes place at a drying air non-woven fabric, this will pour a temperature just below 100 ° C. When the liquid has disappeared, the fibrous and polymeric material will be heated to a heat treatment / drying temperature TT of approximately 175-180 ° C. This temperature TT is higher than the melting temperature Im of the outer layer of the bicomponents, but lower than the melting temperature flfl of the core component. Furthermore, it is lower than the activation temperature of the acrylate latex and lower than the melting temperature of the staple fibers.

During drying, the outer layers of the bicomponent fibers will melt and due to their and the evaporating liquid surface tension, heat distribution and evaporation gradient (in the room) will accumulate to a large extent around the places in the nonwoven where fibers abut. In that accumulation process, the molten outer layers will absorb and bind the polymer particles supplied through the acrylate latex. The result of this is schematically illustrated in Fig. 2. Accumulations of material are formed which can be almost likened to swimming skin or bat wings which are tensioned by the abutting fibers. As can be seen from Fig. 4, some materials are also stuck along the fibers even where they do not abut each other.

The non-woven nonwoven fabric is then stretched and rolled up into large rolls.

Since the manufacture of non-woven fabric usually takes place at special non-woven fabric manufacturers and the manufacture of ceilings and hood insulation takes place at other manufacturers, it is required that the various components can be handled in a smooth manner both separately and after they have been assembled into a partial or completely finished product. The requirements, or at least desires, placed on the nonwoven fabric are that it should be easy to handle, it should be environmentally friendly, ie it should not emit any environmentally harmful substances during manufacture, when forming into the final product or when used and it must be recyclable, and it must provide sufficient strength to the final product, as this has a load-bearing function.

These requirements are achieved by the above-described nonwoven fabric made by the above-described method.

A layer composite comprising the nonwoven fabric is prepared by assembling one or more layers of nonwoven fabric. The nonwoven layer (or layers) man with a layer of other material. Under pressure and heat supply, the layers are compressed at a temperature of about 200 ° C, which is higher than the activation temperature of the latex polymer and which is higher than the melting temperature of the outer component - lower than the melting temperature of said core component. Thus, the first component and the latex polymer fuse in the respective nonwoven fabric layers and form a film which binds the different layers together. Especially when using polyester fibers, a very good adhesion is obtained between the different layers. For a lot of film-forming polymers, a certain pressure is also required for them to be activated, or at least the activation temperature can be lowered by applying a pressure.

In the production of the layer composite, this can be given the shape that the final product should have. Since the polymers in the fibers and the latex have thermoplastic properties, the layer composite can also be formed afterwards. The thermoplastic properties of the nonwoven fabric and the composite make reuse and recycling significantly easier. Furthermore, the layer composite is much lighter than known sandwich constructions with corresponding strength, since the need for fiberglass and adhesive layers has been eliminated. This is an enormous advantage, for example in the car industry, where even a relatively small weight loss changes a car's life cycle analysis with regard to environmental impact. This is because the fuel consumption is one of the absolutely most important parameters with regard to the environmental impact and the weight of the car has a strong effect on its fuel consumption.

It will be appreciated that a variety of modifications of the embodiments of the invention described herein are possible within the scope of the invention, which is defined in the appended claims.

For example, the latex-fed polymer may have an activation temperature lower than the initial melting temperature. This may be the case, for example, if, in addition to temperature, a certain pressure is also required for the polymer to be activated and form a film.

The temperature ranges can in some cases be extended slightly, for example the melting temperature of the outer casing may well be in the range 160-200 ° C. The temperature ranges that can be accepted are determined by the application in which the non-woven fabric or layer composite is to be used. For example, a roof for a car must be able to withstand a repainting, which takes place at approximately 105 ° C, without this starting to soften or sag, ie lose its load-bearing function. The proportions of bicomponent fiber and latex polymer can also be varied according to the application, thus the proportion of bicomponent fibers can be in the range of about 50-90% of the amount of fiber in the nonwoven fabric.

While maintaining environmental friendliness, it is also conceivable that the nonwoven fabric also contains natural fibers, such as flax fibers.

Furthermore, the bicomponent fibers may in some cases have a different configuration of core or outer layer component. For example, there may be several high-temperature cores in a low-temperature matrix that surrounds and connects the different cores.

Claims (10)

10 15 20 25 30 35 515 510 13 PATENT REQUIREMENTS A process for the production of nonwovens comprising the measures; forming a fiber blend containing bicomponent type fibers, laying out the fiber blend to form a bead, impregnating the bead with latex, and drying the latex impregnated bead, the bicomponent fibers having a first, outer component having a first melting temperature and a second core component having a second melting temperature higher than the first melting temperature, and wherein the bicomponent fibers are supplied in a proportion of at least about 50% by weight of the fiber blend, characterized in that a latex of a polymer which is thermally activatable at a first activation temperature is added as latex is lower than the second melting temperature, that the drying / heat treatment of the latex impregnated fleece is carried out at a drying temperature higher than said first melting temperature and lower than said second melting temperature, the outer component of the bicomponent fibers at least partially melting and bonding the web, and that latex adds s in an amount such that the amount of polymer added by latex is in the range of 10-60% by weight of the total dry weight of the nonwoven fabric. A method according to claim 1, wherein latex is applied in an amount such that the amount of polymer added by latex is in the range of 25-50% by weight of the total dry weight of the nonwoven fabric. A method according to claim 1 or 2, wherein polyester bicomponent fibers are supplied as said bicomponent fibers. 10 15 20 25 30 35 515 510 I. . . . . 1.4 A method according to any one of claims 1-3, wherein acrylate latex is applied as said latex. 5. Process for producing a layer composite know the measures; assembling at least a first layer of nonwoven fabric, prepared by the method of claim 1, and at least a second material layer, compressing the layers under pressure and heat supply at a temperature higher than said first melting temperature, higher than said activation temperature and lower than said second melting temperature, the first component and the latex in said nonwoven fabric layer melting and bonding together with said second layer by film formation. Nonwovens containing bicomponent type fibers and a polymer, the bicomponent fibers having a first, outer component having a first melting temperature and a second core component having a second melting temperature higher than the first melting temperature, and wherein the bicomponent fibers form a proportion of at least about 50% by weight of the fiber content of the nonwoven fabric, characterized in that the polymer is thermally activatable at a first activation temperature lower than the second melting temperature, that the nonwoven fabric is heat treated at a temperature higher than said first melting temperature and lower than said second melting temperature, the outer casing of the bicomponent fibers at least partially melting and bonding together the nonwoven fabric and the polymer particles, and that the amount of polymer fed by latex is in the range 10-60% by weight of the total dry weight of the nonwoven fabric. The nonwoven fabric according to claim 6, wherein the amount of latex polymer added is in the range of 25 ~ 50% by weight of the total dry weight of the nonwoven fabric. .u .. lO 15 515 510 'I -. «N 15 A nonwoven fabric according to claim 6 or 7, wherein the bicomponent fibers are polyester bicomponent fibers. A nonwoven fabric according to any one of claims 6-8, wherein said latex is an acrylate latex. Layer composite characterized in that it comprises at least a first layer of a nonwoven fabric of the type specified in claim 6, and at least a second material layer, in that the layers are compressed under pressure and heat supply at a temperature higher than said first temperature, higher than said activation temperature and lower than said second melting temperature, the first component and the latex in said nonwoven fabric layer having melted and formed a film bonding with said second layer.