NO139448B - PROCEDURE FOR MANUFACTURING A NON-WOVEN FIBROEST MATERIAL PATH - Google Patents

Description

The present invention relates to the production of non-woven textiles by wet laying technique. A non-woven textile is a textile made from natural and/or synthetic fibers without the use of weaving or similar processes such as . knitting, as the term includes, for example, paper, gaskets, certain floor coverings, etc.

In the production of non-woven textiles using the wet laying technique, a diluted aqueous suspension is applied to the fibers

on a sheet forming apparatus, such as a moving metal wire cloth or a rotating wire cloth coated cylinder, and the bulk of the water is removed leaving a web or mat of fibers which is then dried. When only natural cellulose fibers are used, sufficient bonding between the fibers in the dried textile is normally achieved without special precautions. The finished textile's strength can be increased by painting the fibres, but this causes the product to have a rough "grip" and gives it poor draping properties which make it unsuitable for use in the manufacture of clothing. It is therefore common to reduce the paint to a minimum and at the same time incorporate synthetic fibers into the natural cellulose fibers in the sheet. In such cases, a binder is also generally used to ensure a good bond between the fibers. This can be done after web formation, for example by treating the dry textile by spraying, printing or dipping techniques, but it is very advantageous to mix the binder in the fiber suspension step before or during web formation, thereby avoiding further production steps. Attempts have been made to incorporate colloidal polymer dispersions onto

this way, but it has proved difficult to achieve high polymer-

retention in the textile. It is desirable that as high a retention as possible is achieved so that 80% by weight, preferably 90% by weight or more of the polymer is incorporated, otherwise pumping difficulties will arise when the waste water from the wire cloth is recirculated. It is desirable that all polymer material remains in the web so that the runoff from the wire cloth is completely free of polymer,

that is, visibly clear.

The invention thus relates to a method for producing a non-woven web of fibrous material, where an aqueous suspension of fibers and a water-insoluble, polymeric, particulate binder is first formed, after which the web is formed from this suspension while removing water, and the distinctive in the method according to the invention is that the suspension is produced from a colloidal, aqueous dispersion of the water-insoluble, polymeric binder so that the average diameter of the binder particles lies in the range from 0.001 - 1.0 mm, preferably 0.001 - 0.2 mm, and that the to the suspension immediately for web formation on a paper machine is added from 1 - 100 parts per million, based on the weight of the water in the suspension, of a high molecular weight, water-soluble polymeric flocculant.

These and other features of the invention appear in the patent claims.

The fibers used to form the fibrous material can be of natural cellulose, such as from wood, cotton, rags or manila pulp, which generally have a fiber length of e.g. 1 to 5 mm, typically 2 to 3 mm, or they can be of synthetic materials such as polypropylene, nylon, polyester terephthalate, e.g. "Terylene", rayon, polyvinyl acetate, polyvinyl alcohol, polyvinyl chloride, vinyl chloride/vinyl acetate copolymer or any of the acrylic compounds, and generally having a fiber length of 0.5 to 60 mm. Inorganic and mineral fibres, e.g. asbestos or glass fibers can also be used. Any of these different fibers can be used alone or in mixtures with one or more of the other fibers. The machine used to produce the web of fibrous material can limit the fiber length that: can be used, but it is generally considered undesirable to incorporate a number of relatively long fibers, with a length e.g. 10 to 25 mm or more. This improves the product's strength and draping properties, which is particularly valuable when the textile is to be used for clothing, e.g. dresses. When the non-woven textile is to be used for clothing, cellulose or a mixture of cellulose and synthetic fibers can be used to obtain less expensive products. In such cases the cellulose is generally of bleached "softwood<!l> typically having a fiber length of, say, 2 to 3 mm lightly ground to a Schopper Riegler ground degree of 8 to 15° (TAPPI Standard 7227M-58). Rayon or other synthetic fibers can be mixed with the cellulose to increase the strength and draping properties of the product, the weight ratio between wood cellulose and synthetic fibers in the fiber batch being, for example, 75:25. However, satisfactory textiles can be produced from either wood cellulose or synthetic fibers alone. Typical synthetic fibers, such as rayon, having a length of eg 10 to 15 mm of 1.5 denier can be used, with higher denier fibers eg up to 20 denier or more usually being required if the fiber length exceeds 15 mm. Preferably, synthetic fibers are moistened with water before use.

The fiber charge is generally produced as an aqueous mass which is preferably diluted, e.g. to a concentration of less than 27% by weight and with a pH of 7.0 to 8.5. Fillers such as slime chalk or kaolin, and other compounds such as optical brighteners, pigments, fire retardants, antioxidants, curing agents and bactericides can be dispersed in the ... fiber mass if desired, depending on the properties required of the finished product.

The colloidal aqueous dispersion of a water-insoluble polymer

which is used is preferably a latex of a rubber, especially a synthetic rubber. Suitable rubbers are, for example, a homopolymer of a conjugated diene, especially butadiene or isoprene, or of a copolymer of a conjugated diene containing not more than 70% by weight, preferably not more than 50% by weight of a

wine/laTomatic compound, such as styrene, vinyltoluene or vinylnaphthalene, or such copolymers containing e.g.

1-10% by weight or more of an unsaturated acid such as acrylic acid, methacrylic acid or itaconic acid, and/or esters thereof, such as methyl methacrylate, ethyl acrylate or hydroxyethyl methacrylate.

Latices of polychloropropylene or a diene/acrylonitrile copolymer containing e.g. 15 to 50% by weight of acrylonitrile, optionally with e.g. 3 to 10% by weight of an unsaturated acid such as those mentioned above is also suitable. Artificial latexes obtained by solvent polymerizations, e.g. ethylene-propylene rubber or polyisobutylene can also be used. Examples of non-rubber polymer dispersions are such as poly/ethylene, polypropylene, poly(ethylene vinyl-o acetate), polystyrene, acrylonitrile/butadiene/styrene (ABC) copolymer, polyvinyl chloride, polyvinylidene chloride, polyurethane, and poly(styrene unsaturated acid and /or unsaturated acid ester). A suitable class of non-rubber polymers is prepared from one or more monomers, which would themselves form a more "spro" polymer, copolymerized with one or more monomers, which would themselves form a soft polymer, possibly with a small proportion, e.g. 3 to 10% by weight, of an unsaturated acid. Typical examples of "pro" polymers are made from monomers such as methyl methacrylate, styrene, vinyl acetate and acrylonitrile, while examples of "soft" monomers are ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate. Spruce or glassy and

soft polymers are easily separated from each other at the polymer glass transition temperature. The proportion of "soft" monomer can be e.g. 5 to 50% by weight or more of the total, the exact amount depending on the properties required of the finished fibrous product. Mixtures of rubber dispersions with non-rubber dispersions can be used.

To obtain a suspension of polymer particles with an average diameter of 0.001 to 1.0 mm, it is necessary to precipitate the colloidal aqueous dispersion in a controlled manner, preferably so that the number average particle diameter is 0.001 to 0.2 mm. It may first be necessary to stabilize the dispersion depending on the type of polymer, the properties (eg hardness and pH) of the water used in the textile manufacturing step and the shear force involved in this step. The required degree of stabilization can easily be determined by preliminary tests. In order to stabilize the dispersion, it is generally first necessary to dilute it to a concentration of less than 20% by weight, usually in cases where the fiber mass is present as low as 0.1 to 2% by weight, e.g. 0.5 to 1% by weight. In general, up to 10% by weight, based on the dry polymer, of a non-ionic or anionic surfactant, e.g. "ALTAMOL NOP" (trade name),

an anionic surfactant which is a condensation product of naphthalenesulfonic acid and formaldehyde, or larger amounts, e.g. up to 50% by weight on a dry polymer basis of a water blotting agent. such as sodium hexametaphosphate. Once stabilized, the polymer suspension can be formed by gradually adding a precipitant, preferably an alum such as aluminum sulfate /"ai^ (S04 ) ^. 16H2&7 generally as a dilute (e.g. 10%) solution in water while stirring the dispersion. Precipitating agent is added until almost complete precipitation of the polymer has taken place, excess of precipitating agent generally being undesirable. Preferably the liquid phase after precipitation is completely clear by visual examination. When aluminum sulfate is used as a precipitant, up to 15% on a dry polymer basis is usually required.

A certain reduction in pH occurs. Examples of other suitable precipitating agents are substituted amine or quaternary ammonium compounds, e.g. quaternary ammonium chloride, ethoxylated aliphatic amines, aliphatic diamine acetate salts, cetyltriraethyl ammonium tribromide and a condensate of ammonia, formaldehyde and ethyl chloride, water-soluble salts of polyacrylates such as "DISPEX N40" (trade name), sodium silicon fluoride and calcium sulphate..

By flocculant is meant in the present context. any material which will agglomerate finely divided insoluble particles suspended in an aqueous medium. In general, flocculants are synthetic water-insoluble polymers with high number-6 7

average molecular weight, e.g. 1 x 10 to 1.5 x 10 . Such polymers have a high affinity for solid surfaces and it is assumed that the long molecules are absorbed partly on one solid surface and partly on another, forming a molecular bridge.

In this way, strong bonds can be achieved between the polymer particles described above and the fibers by the method according to the invention. Flocculants are generally classified as anionic, cationic or non-ionic, the degree of charge being variable in the case of anionic and cationic flocculants. The type of flocculant used in each particular case is primarily determined by the properties of the water used in sheet production and by

the polymer type. As a general rule, it is used when the pH in the production water is low, e.g. 4 to 5.5 a cationic flocculant. At a higher pH, e.g. 5.5 to 6.5, an anionic flocculant is more suitable, while, on the other hand, at an even higher pH, e.g. 6.5 and higher, a cationic or nonionic flocculant is preferred. Examples of suitable flocculating agents are polyacrylates, polyacrylic acids, amine-epichlorohydrin co-condensate, polyethylene oxide, polyamines or acrylic acid/acrylamide copolymers and such as are sold under the trade name "POLYOKS", "MAGNAFLOC", "HERCOFLOC", "PRIMAFLOC", "NALFLOC", "NALCO ", "CYANAMER" and "EUFLOTOL". Natural flocculating agents such as egg albumin and the like are also suitable in the process. The flocculating agent is generally produced as an aqueous solution with a concentration of e.g. 0.1 to 1% by weight, as a dispersant is normally used for the flocculant to moisten this for the preparation of the solution, unless it is already in liquid form. In this way, production difficulties such as e.g. caused by large gelled flocculant clumps. It is very desirable

to dilute the flocculant solution to a concentration

of 0.05% or lower for it is added to the suspension of polymer particles (and fibers if present) to ensure instant and thorough mixing.

The flocculating agent can be added to the suspension of polymer particles in the presence or absence of fibers (which can be dry or prepared as an aqueous mass as described above).

In each case, the flocculating agent is best added to the polymer dispersion mass when this has a total concentration. of polymer + fibers (if present) of 0.01 to 0.5% by weight, preferably 0.02 to 0.1% by weight, the concentration depending on the particular machine used for the production of the fibrous textile. It will be understood that such mass concentrations are very diluted, but this is advantageous because long fibers . can be used in the method without difficulty. The flocculating agent can, however, be added to the mass at higher concentrations, e.g. up to 1%, and the mass is then diluted as required.

Agitation to support the mixing of the flocculant with the suspension of polymer pairs and/or fiber pulp is permissible, but it is highly undesirable that large shear forces, such as e.g. occurs in pumps, is avoided. When the mixing is carried out in the presence of fibers, the polymer particles, which advantageously have a particle diameter of from 0.001 to 0.2 mm or preferably 0.05 to 0.1 mm, adhere to the fibers, leading to optimal properties in the final product. If, however, the flocculant is added to the polymer particle suspension in the absence of fibres, agglomeration of the polymer particles into larger particles of the order of magnitude e.g. 0.3 mm to 0.8 mm, optimally 0.5 mm. As mentioned above, an excess of flocculant should be avoided and this is particularly important when the agent is added in the absence of fibres, as uncontrolled particle growth can then occur. Furthermore, the flocculant, if present in excess in the presence of fibres, is apt to cause clumping of the fibres. The required amount of flocculant is in the range of 1 to 100 parts per million (ppm), preferably 1 to 20 ppm, based on the total weight of water in polymer + fibers (if present), the amount being determined by the concentration of the polymer/fiber dispersion. Typically, at a concentration of 0.2%, 1 to 10 ppm is sufficient, but at higher concentrations, larger quantities of the agent are required, e.g. 10 to 20 ppm at 0.25% concentration.

When the flocculant is added to the suspension of polymer particles in the absence of fibers or when only part of the fibers are present, the fibers or the remainder of the fibers are mixed with the polymer particle dispersion.

As soon as the flocculating agent/polymer/fiber dispersion is

produced, the sheet can be produced in the usual way. The water

is generally removed by suction and the sheet consisting of an intimate mixture of fibers and polymer particles is preferably dried at a slightly elevated temperature, e.g. from 50 to 125°C and

under one press of e.g. 0.07 to 4.90 kg/cm<2>. The amount of polymer in the finished fiber-containing composition can be from 1 to 50 parts by weight per 100 parts of fibers, as the

active amount is regulated to adapt to the fiber content

textile that is produced. In the case of textiles for use such as synthetic leather, "thus, the amount of polymer incorporated is generally from 100 to 500 parts by weight per 100 parts of fibers.

For gaskets, e.g. 10 to 50 parts suitable and for textile, for use in clothing it can be used e.g. 5 to 40 parts. Some textiles can be produced by simply incorporating e.g. from 1 to 5 parts, since such textiles are generally further processed or processed for use.

Using the method according to the invention, it is possible to obtain non-woven textiles which have particularly undesirable properties. If the flocculant is added to the polymer suspension in the presence of fibers, some increase can be achieved. in the strength of the final product compared to the addition, in the absence, of fibres. However, the texture and . the drapery property of textiles obtained by the latter method (ie addition in the absence of fibres) remarkably good and pronouncedly better than textiles produced by the first-mentioned method. This is believed to be because an even and intimate distribution of polymer particles of relatively large size, e.g. 0.3 mm to 0.8 mm, is achieved, an internal point binding effect is provided. It is sometimes desirable to combine these methods, i.e. to add the flocculant

in the presence of only that part, e.g. 10%, of the fibers and then add the rest of the fibers after the formation of the polymer suspension.

By using paper machines for the production of non-woven textiles by the method according to the invention, it has been found particularly desirable to add the flocculating agent to the polymer dispersion in the inlet box so that significant shearing forces in the presence of the fibers are avoided. Preferably, the pH in the mass at this point should not be below 5.5, as otherwise there will be a certain reduction in the degree of retention. It is important that a suspension of polymer particles is formed from the colloidal aqueous dispersion of the polymer, e.g.

a latex, for the flocculating agent is added as there will otherwise be tendencies present for an insufficient mixing of the polymer in the fiber material, and consequently pumping difficulties will arise when the waste water is recirculated.

The following examples shall illustrate the invention:

Example 1

16.2 parts (dry weight) of "INTEX 100" (trade name.), which is a 68% solids butadiene/styrene copolymer latex prepared in emulsion using potassium oleate as an emulsifier and containing 24% bound styrene, was mixed with 40, 0 parts of a 2% solution (0.8 parts torr) of an acrylic sulfonate surfactant stabilizer ("ALTAMOL NOP"). The mixture was added to 83 parts by weight of 1.5 denier 12 mm chopped rayon fibers dispersed in water as a 1% slurry.

This fiber dispersion was gently stirred and a 10% by weight solution of alum gradually added until the liquid phase was completely clear, indicating almost complete precipitation of the latex. The total addition was approx. 10% by weight on the basis of dry rubber.

The fibre/rubber dispersion was diluted with water to approx. 0.1% consistency and a 0.75% solution of "NALFLOC 636", which is a 7,000,000 molecular weight polyacrylic acid flocculant, in an amount calculated to give a concentration of 5-20 ppm by total volume was added.

A paper of 60 g/m 2 was produced from the dispersion which had

a fiber to binder weight ratio of 5:1. The breaking strength of the paper was 1.75 kg/cm 2 according to British Standard Method 3137-1959.

Example 2

Example 1 was repeated several times using different flocculants instead of "NALFLOC". The flocculants used were: "MAGNAFLOC Rr40", a cationic synthetic water-soluble polymer, "MAGNAFLOC EM15", a cationic synthetic water-soluble polymer, "PRIMAFLOC C3", a cationic water-soluble polyamine, and "RETN 210" ("HERCAFLOC 812"), a cationic high molecular weight polymer.

Essentially the same results were obtained.

Example 3

Example 1 was repeated using the following composition (parts are parts dry weight):

The resulting fiber/rubber dispersion was diluted to 0.02 to 0.5% consistency and a 0.05% solution of "MAGNAFLOC R156" was added to give a concentration of 1 to 5 ppm by total volume.

Paper formed from the dispersion had excellent physical properties.

Example 4

Example 3 was repeated using the following composition:

Essentially the same results were obtained (fiber to polymer ratio 2:1).

Example 5

An artificial leather was prepared using the following composition:

The composite polymer dispersion was diluted to 2% by weight and just enough aluminum sulfate (10%) was added to precipitate the polymer in the form of particles with an average diameter of from 0.001 to 0.2 mm. Polymer slurry was added to 15.2 parts dry weight of water-wetted rayon fibers (1.5 denier x 10 mm) and "MAGNAFLOC R351" was added to a concentration of 5 ppm. A textile was formed from the slurry, which reached a fiber to polymer ratio of 1:5. The product was curable to a stiff leather product.

Example 6

A pack was produced as follows:

The stabilized latex was precipitated with aluminum sulfate solution

to polymer particles with a diameter of 0.001 to 0.2 mm. The polymer suspension was added to a 0.3% dispersion of asbestos fiber (eg Beldam Asbestos Ltd.'s type "4K") constituting 90.8 parts dry weight. 1 ppm of flocculant was added as described in example 3, and a textile was formed with a weight of 800 g/m 2 and which had a fiber to binder ratio of 10:1.

Example 7

A fabric was prepared from a carboxylated styrene/butadiene copolymer latex ("INTEX 164") with a solids content of 50% as follows: 50 parts (dry weight) water-wetted chopped rayon fibers were dispersed as a 1% slurry in water and mixed with 50 . parts, (dry) of the latex. The latex was precipitated with aluminum sulfate as previously mentioned (about 4% on a dry weight rubber basis was required in this case) and the fiber/polymer suspension was diluted to 0.02 to 0.05% consistency. I to 5 ppm of a 0.05% solution of "HERCOFLOC 812" was added and a sheet was formed having a fiber to binder ratio of 1:1.

Example 8

20 parts dry weight of the latex described in example 7 was

diluted to 0.2% and filtered with just enough aluminum sulfate solution. To the polymer suspension was added 80 parts (dry) of a fiber batch of:

Water-moistened,;., chopped rayon fibers (1.5 den x 10 mm) 24.0 pieces

The stock was diluted to 0.02 to 0.05% consistency, 1 to

5 ppm flocculant as described in example 7 was added and a textile was formed as previously described, with a fiber to binder ratio of 4:1.

Example 9

9.9 parts dry weight of the latex described in Example 7 was diluted to 1% and 0.1 part dry weight of the stabilizer described in Example 1 was added (2% solution). The polymer was brought to a suspension as previously described, and added to 90.0 parts dry weight glass fibers (fiber length 5 mm). The mass was diluted to 0.02% consistency and 5 ppm of the flocculant described in example 3 was added.

Sheets with a fiber to binder ratio of 9:1 were prepared.

The example was repeated with a fiber to binder ratio of 4:1 with approximately the same results.

Example 10

82.6 parts (dry) latex as described in Example 7 was stabilized with 0.8 parts (dry) stabilizer as described in Example 1. The stabilized latex was diluted to 0.5% solids content and ground into a polymer suspension with 16, 6 parts (dry) 5% solution of a quaternary ammonium chloride.

Sheets were formed as described in Example 3, with essentially the same results.

Example 11

A sample of the latex described in Example 7 was diluted to 0.25% solids content with water and just enough aluminum sulfate solution was added to completely precipitate into a polymer suspension of 0.001 to 0.2 mm diameter particles. Under gentle agitation, sufficient flocculant "MAGNAFLOC R292" was added as a 1% solution until the number average particle diameter was 0.5 mm.

A pre-dispersed fiber mass of chopped rayon fibers (1.5 den x 10 mm) was added and the final consistency adjusted to 0.02 - 0.05% by weight.

Sheets with excellent physical properties were produced from this pulp with different fiber to binder ratios.

Example 12

A sample of the latex described in Example 1 containing 0.2 ppm antioxidant (as a 33% dispersion) was diluted to 25% solids with water. Sufficient of the stabilizer described in Example 1 was added to give a concentration of 2.5% by weight (on a dry rubber basis).

Sufficient 10% aluminum sulfate solution was added to produce a suspension of polymer particles with a number average diameter of 6.05 to 0.1 mm. With gentle agitation of the suspension, 0.1% of the flocculating agent "MAGNAFLOC R351" was slowly added until the number average particle diameter was 0.5 mm.

Sheets were produced as in example 11 with essentially the same results.

Claims (4)

1, Method for producing a non-woven web of fibrous material, where an aqueous suspension of fibers and a water-insoluble, polymeric, particulate binder is first formed, after which the web is formed from this suspension while removing water, characterized by 1) that the suspension is prepared from a colloidal, aqueous dispersion of the water-insoluble, polymeric binder so that the average diameter of the binder particles lies in the range from 0.001 - 1.0 mm, preferably 0.001 - 0.2 mm, and 2) that the suspension immediately for web formation on a paper machine is added from 1 - 100 parts per million, based on the weight of the water in the suspension, of a high molecular weight, water-soluble polymeric flocculant. 2. Method as stated in claim 1, characterized in that a rubber latex is used as a colloidal aqueous dispersion of a water-insoluble polymeric particulate binder, in particular a rubber latex based on polybutadiene, a styrene-butadiene copolymer or a copolymer of styrene, butadiene and 1- 10% by weight of at least one unsaturated acid and/or at least one ester of an unsaturated acid. 3. Method as stated in claim 1, characterized in that polyethylene, polypropylene, polystyrene, a copolymer of acrylonitrile, butadiene and styrene or polyvinyl chloride are used as water-insoluble polymeric binder. 4. Method as stated in claims 1-3, characterized in that the flocculating agent is added to the suspension in the inlet box of the paper machine.