FI95160C - Extruded monofilament of polyester and polyurethane and a shaping wire made of it - Google Patents

Description

95160

The present invention relates to a paper machine forming fabric made of synthetic plastic fibers, which is an extruded monofilament and a forming wire made therefrom - Av polyester and a polyurethane extruder monofilament and a forming fabric made of synthetic plastic fibers.

More specifically, the invention relates to a monofilament according to the preamble of the appended claim 10, a paper machine fabric according to the preamble of claim 6, a method for producing a monofilament according to the preamble of claim 11, a multifilament yarn according to claim 12, a staple fiber according to claim 13, a spun yarn according to claim 14 and a composite yarn according to claim 15.

In a paper machine, a continuous sheet of paper or paper-like material is formed by running a water-based pulp fiber slurry onto a moving endless woven belt. As the slurry moves forward with an endless belt, also called a wire web, it is largely converted to a self-supporting wet web by removing much of the water contained in the original slurry. A typical slurry applied to a mobile vii-25 may contain as little as. 0.5% by weight of pulp fibers, may have a temperature in the range of about 30-85 ° C and typically has a pH of 4-9. The wet paper web leaving the wire for the pressing and drying sections may still contain 80% by weight of water.

After leaving the wet end, i.e. the forming part, through the felt press, the further wet web is transferred to the pressing part, where the main part of the remaining water is removed by passing the web through successive pairs of pressing rollers. After leaving the press section, the web moves to the drying section, which is heated to achieve final drying. The dried web can then be calendered to smooth the surface and finally collected on a roll.

2 95160 As the wet sludge moves forward on the wire of water. removal is promoted through the use of discharge lists, registers and suction boxes.

The present invention relates directly to the wet end of the paper machine, i.e. to the forming section, and thus to the fabrics used in papermaking, known as "wire fabrics". These fabrics are used to sieve the wet pulp pulp in the initial stage of dewatering, whereby the pulp turns into a wet paper web.

10 In the original flat wire machines, the wire was a structure woven from metal wire, as a result of which these fabrics became known as flat wires. The preferred metal used for these wires was phosphor bronze. These flat wires were used in all types of paper machines and for all paper grades. Although these wires were effective, they did not suffer from disadvantages, especially in terms of wear resistance, when the pulp fiber slurry also contained abrasive fillers such as silica and calcium carbonate.

Recently, these wire fabrics have been replaced by fabrics based on synthetic plastic fibers, which are usually monofilaments. Since good quality paper is ultimately based on the wire cloth itself, the structure and properties of the wire cloth are of great importance. The main advantage of fabrics based on synthetic plastic monofilaments over phosphor bronze wire fabrics is the improved wear resistance, which has resulted in an increase in the average service life of the fabric more than four times that of metal wire fabrics. However, even these fabrics are still consumed by fillers similar to those ai-30 posed problems with older phosphor bronze fabrics. For a paper machine wire fabric to be successful, it should preferably have the following characteristics: (i) it must be able to withstand the wear and tear caused by both abrasive contact with the machine parts and contact with the solids in the pulp-water slurry; (ii) it must be structurally stable in the plane of the tissue in order to withstand the stresses applied to it during use; 3 95160 (iii) it must be able to withstand possible dimensional changes in the level of the tissue caused by the absorption of moisture over a wide range of moisture content, since when the machine is running it is completely moist and dries when the machine is standing for any length of time 5; (iv) it shall be non-stretchable under the stress caused by the motor-driven rollers moving the wire in the paper machine; (v) it must be resistant to damage caused by the various materials present both in the pulp-water slurry and in the materials used to clean the wire at ambient operating temperatures.

No known fabric, not even long-used flat fabrics, has all of these properties to the fullest extent, as mentioned above, phosphor bronze fabrics do not have the desired abrasion resistance. Even the available synthetic plastic monofilaments do not yield fabrics that meet all of these requirements to the extent desired by the papermaker. Synthetic polymers that are currently the best approved single yarns for making fabrics include polyester, more specifically polyethylene terephthalate, and polyamides, especially nylon-6 (poly-caprolactam) and nylon-66 (polyhexamethylene adipamide).

These monofilaments have been blended with other polyesters, such as polyethylene and polybutylene terephthalate-based polyesters, but such fabrics are still far from complete. The worst difficulties are the following two: (a) although polyethylene terephthalate has sufficient chemical resistance and dimensional stability as well as weave, good curl and good thermosetting properties, its wear resistance is desirable, especially in the case of modern high-speed machines; (b) although nylon-6 and nylon-66 are adequate in terms of abrasion resistance, they have serious shortcomings in weaving because of their poor curl and insufficient thermosetting ability, and they do not have sufficient dimensional stability in the papermaking moisture process. 95160 and not sufficient resistance to some wire cleaning agents.

The inherent dimensional instability of nylon-6 and nylon-66 in the moisture-5 concentration range in the paper mill environment, from completely wet to dry, places limitations on the available ratio of nylon monofilaments to polyethylene terephthalate monofilaments. This is mentioned to be 50% in both U.S. Patent 4,529,013 and 4,289,173; DE-Application 10 also gives a figure of 50% and further suggests that the diameter of the nylon filaments should be at least 4% (the maximum recommended difference is 25%) larger than that of the polyester monofilaments. Attempts to overcome this difficulty by improving the wear resistance of polyester monofilaments 15 while still maintaining their better dimensional stability compared to nylon, as described, for example, in EP-A-158 710, have not been entirely successful. Improving the wear resistance of the nylon monofilament yarn, for example, as described in CA patent 1,235,249, for example, also does not make it possible to overcome said limitation on the nylon monofilament content, since it in no way reduces the known dimensional instability of nylon. An alternative solution associated with poor curl of nylon is proposed in U.S. Patent No. 4,709,732; however, it involves. * an increase in tissue complexity, and because it does not improve dimensional stability, it does not allow for an increase in nylon content.

Thus, a wire cloth containing both nylon and polyester provides an acceptable compromise, provided that the amount of nylon used is limited. Such tissues also show pH values that can be expected with sustained use, which can range from about 4 to 8-9. The polyester fibers are not excessively damaged under these conditions, even in the temperature ranges of about 85 ° C that occur in modern paper machines.

5,95160 The present invention seeks to provide a solution to the problems associated with the use of nylon by providing an alternative paper machine wire comprising polymer blend-based monofilament yarns having weaving and thermosetting properties of polyethylene terephthalate.

This fabric is also at least close in abrasion resistance to ordinary nylon-containing fabrics. It is preferred to use polyethylene terephthalate monofilaments as the remainder of the wire fabric, but this invention is not limited to the use of this polymer as the remainder of the fabric, as other yarns or monofilaments could be used. In addition, although the following description discusses the invention with reference to the use of monofilaments as woven fibers, it is not limited to this case and is applicable to wires woven from both yarns and monofilaments.

Accordingly, the present invention relates, in its broadest sense, to an extruded monofilament comprising a substantially greater proportion by weight of polyethylene terephthalate pof. 20 lyesters and a smaller proportion of thermoplastic polyurethane, for example up to 35% by weight of thermoplastic polyurethane, and 0-5% by weight of a stabilizer which improves the resistance to hydrolysis. The monofilament according to the invention is characterized in that the polyethylene terephthalate polyes-25 blades are present in an amount of 60-90% by weight and that · their intrinsic viscosity number is at least 0.50-1.20 as measured by the solvent.

containing a mixture of phenol and 1,1,2,2-tetrachloroethane in a weight ratio of 60:40 at a temperature of 30 ° C, and that the monofilament contains less than 30% by weight of polyurethane and 10% by weight and that the polyurethane type A

the durometer hardness is not more than 95 and the hardness of type D durometer-J is not more than 75.

The invention also relates to a paper machine wire fabric characterized in that it is woven from 35 (a) at least one group of yarns woven in the first direction of the fabric, and (b) at least one group of yarns woven in the second direction of the fabric which is substantially straight - 6 95160 at an angle to the first direction, the yarns comprising monofilament yarns according to one or more of claims 1 to 5.

In a preferred embodiment, the yarns used in this fabric in both the first and second directions are monofilament yarns, and it is also preferred that the yarns used in the first direction be polyethylene terephthalate together with the rest of the yarns used in the second direction.

Use of a monofilament according to the broadest side 10 of the invention is thus independent of the tissue model. It includes fabrics commonly known as single ply, double ply or duplex and composite fabrics. These common wire fabric types are illustrated in Figure 15, e.g. U.S. Patent Nos. 3,858,623 and 4,071,050 and CA Patent 1,115,177, respectively.

In a more specific aspect, the present invention also relates to a synthetic monofilament comprising a mixture consisting essentially of polyethylene tetraphthalate in an amount of more than 60% to about 90% by weight and a thermoplastic polyurethane in an amount of less than 40% by weight. % to 10% by weight, and a stabilizer to improve the hydrolysis resistance of the thermoplastic polyurethane in an amount of 0 to about 5% by weight.

The proportion of thermoplastic polyurethane is preferably greater than about 15%, more preferably 25 to about 35%, and most preferably about 30%.

In a broad aspect, the present invention relates to a wire cloth for use in a paper machine, wherein a smaller portion of the yarns forming the surface of the wire cloth to which the pulp slurry is applied are monofilaments of a mixture of polyethylene terephthalate and thermoplastic polyurethane as defined above. wire-35 tissue machine side, are monofilaments of a mixture of polyethylene terephthalate and thermoplastic polyurethane as defined above.

il: iti eitti liifl; 7,95160 The yarns used in a preferred embodiment of this fabric are monofilaments. In an even more preferred embodiment, the yarns that form a major portion of the top surface of the wire fabric and a minor portion of the machine side of the fabric are polyethylene terephthalate monofilaments.

In the following description, it is to be understood that "machine direction" means a direction that is approximately parallel to the direction of movement of the wire web in the paper machine. Accordingly, "transverse direction" means a direction that is approximately at right angles to the "machine direction" and in the plane of the fabric. In the case of a wire fabric which is not woven into a continuous loop but into an ordinary piece of fabric of some length (which is later joined into a continuous loop), the "machine direction" corresponds to warp yarns and the "cross direction" weft yarns.

The fabrics according to the invention thus consist of two types of yarns, one of which is preferably polyester monofilaments and the other monofilaments of a mixture of polyester and thermoplastic polyurethane. Quite surprisingly, it has been found that blends containing 10 to 40% polyurethane result in a monofilament which is close to nylon monofilament in terms of abrasion resistance properties, but which lacks. There are other problems associated with such nylon monofilament due to the lack of permanent curl. In fact, certain blends of polyester and thermoplastic polyurethane have better curl and thermosetting behavior than polyester when used without this thermoplastic polyurethane in a monofilament.

This property has a direct effect on the weaving behavior of these monofilaments and is completely unexpected. The use of this mixed monofilament also makes it possible to further simplify the weaving process, as 35 it. allows the omission of nylon filaments, which are often used in the transverse direction, to provide adequate wear resistance to the machine side of the fabric. In order to balance the known dimensional instability of nylon 95160 8 in the presence of water, it may be present in at most every other yarn in the fabric; thus, a transverse yarn blend is not required in connection with the monofilaments of this invention, since monofilaments consisting of a mixture of polyester and thermoplastic polyurethane can be used alone as the only transverse yarns. This is particularly important in complex multilayer fabrics, where you need to use a monofilament yarn made of a mixture of polyester and thermoplastic polyurethane only as a transverse yarn on the machine side of the fabric, as this is the most abrasive surface.

In the case of a blend monofilament, there are some essential requirements that a polyester component must meet in order to obtain not only a material that can be extruded into suitable monofilaments, but also a polymer blend with the required properties. The usual requirements for cleanliness, the absence of "dirt" and especially water. In addition, the molecular weight of the polyester should be similar to that of resins commonly used in the manufacture of warp and weft yarns. (In addition, the polyester should be relatively anhydrous; the water content should not exceed 0.007%). Thus, the intrinsic viscosity number 25 of the polymer should be 0.50 to 1.20 measured according to the procedure below. The intrinsic viscosity number is preferably in the range of 0.65 to 1.05. Polyethylene terephthalate grades available under the following names (including trademarks) have this feature: 30 Dupont "Merge 1934" (a product of Du Pont sold under this name) • Arnite A06-300 (trademark of Akzo)

Vituf 504C (trademark of Goodyear)

Tenite 10388 (trademark of Eastman).

35 For guidance only, it is assumed that these preferred viscosities correspond to i. ttt.l attached I I tUt - 9 95160 t of specific molecular weights ranging from approximately 1.5 x 104 to 5.2 x 104.

The intrinsic viscosity numbers shown here have been measured from a solution of polyester in a solvent mixture containing 60:40 by weight of phenol and 1,1,2,2-tetrachloroethane. Viscosity measurements are made at a temperature of 30 eC.

As for the thermoplastic polyurethane portion of the mixture, it is again necessary that the material used is substantially anhydrous (less than 0.01% water) so that a monofilament can be made from it by a normal melt extrusion process. There are generally two types of thermoplastic polyurethanes: those derived from polyesters and those derived from polyethers. It has been found that for the purposes of this invention, polyester grade 15 is more effective and thus preferred.

The thermoplastic polyurethane is preferably relatively soft; softness is measured by a standard procedure (ASTM Method D.2240). The hardness should not exceed 95 as measured with a type A durometer and not more than 75 as measured with a type D durometer.

The thermoplastic polyurethane grades available under the following names (including trademarks) have been found to be suitable for the preparation of the blended polymer monofilaments of this invention: Ester-based types:

Texin 445D (trademark of Mobay)

Elastollan C95 (trademark of BASF)

Pellethane 2102-80AE (trademark of Dow Chemical) Ether - based types: 30 Texin 990A (trademark of Mobay) * Pellethane 2103-80A (trademark of Dow Chemical).

In the above, the sum of the percentages is mainly 100% for simplicity. Generally speaking, the only other addition is a small amount, up to 0.5 wt% to 35% by weight, of a color or pigment, such as TiO 2, to the desired appearance. »· 10 95160 to give to the fiber. Under certain conditions, a stabilizer to improve hydrolysis resistance is necessary. If the paper machine is used at temperatures below about 43-48 ° C, hydrolysis of the blended monofilaments 5 of the invention is not a predominant concern. Many paper machines operate at higher temperatures, which rise to approximately 85 ° C. Stabilizers that improve hydrolysis resistance at this class of temperature are necessary because it appears that otherwise the blended fibers will degrade faster than desired. As will be shown below, thermoplastic polyurethane proves to be a degradable material, as experiments have shown that although the tensile strength decreases only slightly, the abrasion resistance decreases significantly.

The amount of stabilizer used can thus range from zero to approximately 5% by weight, above which no further improvement appears to be observed. It appears that when a stabilizer is used below a proportion of 0.3%, the protective effect is very small. Therefore, we recommend the use of a stabilizer in a concentration range of approximately 0.3 to 5.0%, preferably about 0.7 to 3%. It is convenient to include the stabilizer in the mixture using a "masterbatch" made of either thermoplastic polyurethane or polyester. Commercially available stabilizers of the latter type that have been found to be successful include:

Stabaxol KE 7646 (trademark of Rhein Chemie)

Stabaxol P100 (trademark of Rhein Chemie) 30 Hytrel 10MS (trademark of DuPont).

‘Monofilaments can also be surface-coated after manufacture with, for example, a combination of an antistatic agent and a Liu wetting agent to facilitate handling and weaving. In general, such coatings are removed very quickly when the fabric is used in a paper machine.

* 11 95160

In the following examples, the following abbreviations are used for brevity. The term PET is used for polyethylene phthalate and the term TPU for thermoplastic polyurethane. If necessary, the TPU is reported to be ether-5 based or ester based.

The PET used in the following examples was a product of DuPont sold under the name "Merge 1934". This material was generally dried before use and also post-condensed in a solid state to ensure that the limiting viscosity is within the desired range. Similarly, the TPU material was dried before use. In all cases, the nylon was nylon-66.

Monofilaments made from certain polymers are also used in these examples. The dimensions of these mono-15 filaments are given when relevant.

The size of the monofilaments used in wire fabrics is generally in the range of about 0.1 to 0.9 mm, most often in the range of about 0.127 to 0.4 mm. It should also be noted that the monofilament is not necessarily circular in cross-section and may in particular be rectangular or ribbon-shaped.

A. Wear of monofilaments

To determine the abrasion resistance of monofilament strands, pieces of a certain length are first weighed and then wrapped in a single layer around the other end of a polyethylene rod *. A polyester reference monofilament is wrapped around one end. The rod is then mounted at the lower end of the vertical shaft at a right angle to the shaft to immerse said two wrapped filaments in a slurry containing 57% by weight of coarse sand No. 24 in water. The shaft is rotated by a motor above the slurry tank. After a predetermined time, the strands are removed from the slurry, unwrapped, dried and weighed. Abrasion resistance is determined by calculating a 35% mass loss. The rotation time and speed of the shaft are selected so that measurable results are obtained. The abrasion resistance of damaged samples is determined in the same way when monofilament rolls have been kept immersed in pH- and temperature-controlled solutions for varying lengths of time.

The following results were obtained for PET-TPU blends with varying TPU content:

Example Composition Loss of mass (%) 10 AI 100% PET Reference sample 3.2 A2 95% PET + 5% TPU 3.4 A3 85% PET + 15% TPU 3.1 A4 75% PET + 25% TPU 2.4 15 A5 65% PET + 35% TPU 1.8 A6 55% PET + 45% TPU 1.1 These results show that monofilaments made from blends of PET and TPU have a slightly better durability than PET when TPU is 15%, and the more TPU is added up to 45%, the better it becomes. At this concentration, however, the mono-filament becomes difficult to control during extrusion and becomes extremely soft, which makes; 25 of which unsuitable for weaving and hot curing.

The TPU used in these experiments was Texin 445D. The effect of the stabilizer on improving the degradation resistance of the mixed monofilaments is illustrated by the following results obtained using a solution with a pH of 4.0: *

Il! lH'i Μϋ l, i -i-ä *. . <13 95160

Pre- Composition Treatment Mass mark loss (%) A7 64% PET + 36% TPU 71 * C 21 days 2.3 5 A8 64% PET + 36% TPU 88 eC 7 days 2.3 A9 64% PET + 36% TPU 100 ° C 3 days 2.7 AIO 62% PET + 37% TPU 71 ° C 21 days 1.2 + 1% stabilizer

Less than 62% PET + 37% TPU 88 eC 7 days 1,2 10 + 1% stabilizer A12 62% PET + 37% TPU 100 eC 3 days 1.4 + 1% stabilizer These results show that the addition of stabilizer 15 PET-TPU significantly improves the resistance to degradation at all test temperatures. In this case, the stabilizer was Stabaxol KE7646 and the TPU was Texin 445D.

The effect of the stabilizer concentration is shown in the following table:

Pre- Composition Treatment Mass mark loss (%) 25 A13 66% PET + 34% TPU 100 ° C 3 days 2.5 A14 73.2% PET + 26% TPU 100 ° C 3 days 1.9 + 0.8% stabilizer A15 71.8% PET + 26% TPU 100 eC 3 days 1.9 + 2.2% stabilizer 30

Both stabilized mixtures have greatly improved degradation resistance, but a higher stabilizer content no longer improves durability. In these examples, the TPU was Pellethane 80aE and the stabilizer was 35 Stabaxol KE7646.

% 14 95160

The second experiment investigated the effect of a stabilizer on the wear life of a non-hydrolyzed mixture containing 65% PET and about 35% TPU. The results 5 are shown in the following table:

Example Thread Description Weight Loss AI9 Polyester 2.2 10 A20 64% PET + 36% TPU 1.2 A21 62% PET + 37% TPU 1.1 + 1% Stabilizer These results show that the addition of stabilizer 15 has no adverse effect on the durability of consumption. . In this experiment, TPU was Texin 445D and stabilizer Stabaxol KE7646. In all examples, A1 to A19, the polyester oil DuPont Merge 1934 was used, which was post-condensed in the solid state.

20 B. Tissue wear

To measure the abrasion resistance of the wire fabrics, the fabric sample is held tensioned against the outer surface of a drum of horizontally rotating ceramic parts. A jet of water is continuously directed at the fabric inlet to the drum to keep the fabric and the ceramic surface wet.

The thickness of the fabric is measured at the beginning of the experiment and thereafter at predetermined times after the action of a surface consisting of rotating ceramic parts. Thickness loss 30 is a measure of wear resistance.

A series of two-layer tissue samples were woven using warps with a diameter of 0.16 mm and a density of 59 yarns / cm. The bottom or machine side group of wefts was woven using PET, alternately PET 35 and nylon and a mixture containing 75% PET and 25% TPU. The weft density was 51 yarns / cm in each case. All of these samples were woven using a weft diameter of 0.19 mm on the paper side and a weft diameter of 0.30 mm on the machine side. All samples were thermoset in the same manner. In wear tests where the machine side of the fabric was in contact with the drum. The results obtained are given in the following table.

5 ................. Thickness loss (mm) ..............

Pre-Time PET Comparison- Alternately 75 3r PET / Brand (min) Sample PET / Nylon 66 25% TPU- 10 Blend B1 30, 0132, 0147, 0124 B2 60, 0165, 0157, 0142 B3 105, 0210, 0180, 0162 15 These results show that fabrics containing both alternating PET and nylon weft yarns and PET-TPU blend fabrics (75% PET, 25% TPU) have much better abrasion resistance than fabrics made from PET weft. In addition, fabric containing PET-TPU weave has better abrasion resistance than fabric containing alternating PET and nylon weft yarns.

In another set of experiments, abrasion resistance was measured from tissue samples containing blended monofilaments with varying PET and TPU concentrations woven into the base layer of composite fabric 25. The density of the top layer was 25 yarns / cm and that of the bottom layer was 12.5 yarns / cm. The dimensions of the upper and lower warp yarns with a rectangular cross-section were 0.11 x 30 0.19 mm and 0.19 x 0.38 mm, respectively. The weft yarns were PET monofilaments, with the upper weft yarn having a diameter of 0.18 mm and the lower 0.30 mm. In all cases, a PET weft binding yarn with a diameter of 0.14 mm was used. The bottom layer of the fabric was in contact with the drum * 35.

16 95160 #

Pre-Composition Thickness loss (mm) mark after 75 min B4 100% PET reference sample, 0188 5 B5 84% PET + 16% TPU, 0152 B6 75% PET + 25% TPU, 0137 B7 65% PET + 35% TPU, 0119 B8 Alternating PET / Nylon 66, 0124 10 The TPU used was Texin 445D and the PET was solid state post-condensed DuPont Merge 1934.

These results support the findings obtained in fiber wear tests; The wear resistance of a fabric woven from PET-TPU blend fabric is better than that of a fabric woven from 100% polyester polyester fabric, and in addition, the wear resistance improves with increasing polyurethane content. A sample containing 65% PET and 35% TPU has a better wear resistance than a sample containing alternating PET and nylon 66 yarns.

20 C. Dimensional stability when the condition of the fabric varies from wet to dry

Wire fabrics are often subjected to drying and wetting cycles. For example, they are delivered dry to a paper mill and are saturated with water soon as the paper machine 25 runs during papermaking. During its service life, the fabric may dry several times during maintenance outages or on weekends. In wire cloth, in which the proportion of nylon filaments is large in the cross-machine direction, the disadvantages are then width changes. In cases where the polyester and nylon monofilaments are in two different layers, the wire fabric is severely curled at its edges due to the different expansion or contraction of said two layers. This behavior limits the use of nylon monofilaments to 50% of the total number of transverse filaments. The large majority of reference 17 95160 rakudoksista is limited to 25%. Of the total amount, i.e. 50% of the machine side cross machine direction monofilaments is nylon and the remainder of the machine side monofluoromethyl ilamenteista and all of the paper side filaments are PET. At a nylon content of 25%, the polyester monofilaments substantially completely prevent the nylon monofilaments and the entire fabric from expanding and shrinking with significant variation in water content.

The following table shows the length changes that occur in monofilaments made of nylon, polyester, and blends of this invention when treated in a cycle in which they are wetted (boiled in water) and then dried. Length measurements were made at room temperature immediately after irrigation or drying.

Pre- Monofilament Length change (%) Length mark composition from dry to wet change (%) from wet to dry state

Cl 100% Nylon-66 -0.74 +0.64 C2 100% PET -0.07 +0.07 C3 95% PET / 5% TPU -0.07 +0.04 25 C4 85% PET / 15% TPU -0.10 +0.10 C5 75% PET / 25% TPU -0.03 +0.03 C6 65% PET / 35% TPU -0.07 +0.04 C7 55% PET / 45% TPU - 0.43 + 0.23

30 TPU: Texin 445 D

'PET: DuPont "Merge 1934", post-condensed with an intrinsic viscosity of 1.0%.

The results clearly show a well-known difference in behavior between nylon and polyester filaments.

The results also show that the blended monofilaments of the present invention are very stable. At a TPU content of 45%, the blended rope filament begins to suffer from dimensional instability.

D. Curlability 5 A commonly used measure of the curlability of weft fibers in wire fabrics is the so-called curl difference. In the finished fabric, the warp monofilaments tend to be more direct than the weft monofilaments, which to a certain extent simply bend over 10 and less of the warp monofilaments. The tissue monofilaments thus tend to be outside the level of the warp monofilaments, especially on the machine side of the tissue. However, if the weft is a very rigid monofilament, it tends to bend the warp monofilaments and is thus not so much on the outside of the warp plane. By carefully measuring the thickness of the fabric, it is possible to determine how much the weft yarn is outside the level of the warp yarns. This difference in weft and warp levels is known as the curl difference. As the curlability of the tissue monofilament increases, the curl difference in the tissue structure in question also increases.

The table below shows examples of curl differences observed in two-ply fabric samples with the same fabric structure, warp yarns, densities, and heat-curing treatment of different weft yarns. 25 Manila.

Example Weft yarn Curl difference (mm)

Dl 0.30 mm PET, 014 30; D2 0.30 mm PET flux, 012 rotating with 0.30 mm nylon 35 D3 0.30 mm 75% PET / .017 25% TPU alloy 19 95160 * This illustrates that PET-TPU monofilaments have a very high curlability compared to polyester, while nylon has a lower curlability. The PET and TPU of the blend are the same as in Example E5 below.

5 E. Mechanical stability

The mechanical stability of a wire cloth is determined by measuring its ability to resist stretching and narrowing.

Fabric sample 25.4 mm long and wide

TM

50 mm, is placed in the Instron tensile tester. The load and elongation are recorded as the stress on the sample increases from zero to 6.16 kg ^ cm- *. The elongation at break is obtained by measuring the slope of the load-elongation curve. This determines the modulus of elasticity of the fabric, which is typically about 1,100 to 2,000 kg «cm-1 for wire fabrics.

15 The ability to resist narrowing is measured on the same specimen placed in the Instron, except that the decrease in width as the stress on the specimen increases from zero to 7.16 kg · cm-1 is accurately determined. The resistance to narrowing is obtained by dividing the observed width change by 20 as a percentage of the total increase in stress. Typical shrinkage resistance factors for wire fabrics are 0.005 to 0.050% ♦ kg ^ · cm.

Thus, optimal mechanical stability is reflected by high values of modulus of elasticity and low values of shrinkage resistance factors.

To determine the effect of weft materials on mechanical stability, three specimens of Palt-tin-woven-plain weave fabric were woven with straight-30 rail-shaped warps measuring 0.11 x * 0.19 mm, at a density of 25 yarns / cm in the upper fabric, and · rectangular warps , measuring 0.19 x 0.38 mm, at a density of 12.5 yarns / cm in the base fabric. Three different base layer fabrics 35 were used for weaving at the same density and the resulting 20,951,160 samples were heat-cured under similar conditions. The modulus of elasticity and shrinkage resistance factors of these three samples are given in the following table. The results of samples E1 and E2 show that nylon has a detrimental effect on the modulus of elasticity and the resistance to narrowing of the fabric.

Pre- Description Wear- Elastic- Narrow- mark pulling modulus- tension- tension factor- (kg / cm) (kg / cm)

E1 0.3 mm PET fabric 5.37 1,238, 015 15 E2 alternately 0.3 5.37 1,091, 035 mm PET and nylon-66 fabric E3 alternately 0.3 6.26 1,292, 032 20 mm PET and Nylon 66 This behavior of nylon is partially reversed by the use of higher stresses in hot curing. To force the ion to a higher permanent curl level, as shown in Example E3. Note that the higher stress in hot curing improved the tensile strength, but the shrinkage resistance factor remained relatively unchanged. Monofilaments made of blends of PET and TPU are inherently more curly and improve • mechanical stability. This is shown by the results shown in the following table, which compares a fabric sample with a weft containing 75% PET and 25% TPU, woven and heat-cured in the same manner as the above samples, to a sample E1 containing only Tissue composed of PET.

Pre- Description Narrowing- Hot- Elastic- 5 Marking- resistance- modulation- tension li factor (kg / cm) (kg / cm) 10 El 0.3 mm PET fabric 5.37 1 238, 015 E5 0 .3 mm PET / TPU fabric 5.37 1,408,012 PET is solid state post-condensed DuPont 15 Merge 1934 and TPU is Texin 445D.

F. Chemical resistance

In a paper mill environment, wire fabrics can be cleaned from time to time, often using strongly acidic conditions. This cleaning with strong acids has a detrimental effect on any nylon monofilaments in the fabrics, thus shortening the life of the fabric and reversing the improved wear resistance provided by the presence of nylon in the fabric. Experiments were performed in which the wound nylon, poly-25 ester and various PET-PTU blends were immersed in 30% hydrochloric acid at 25 eC for different lengths of time. Nylon completely dissolved after 17 hours of treatment, while no adverse effects were observed in the polyester and PET-TPU blends after 30,222 hours of treatment. This shows that PET * TPU blends have a much better ability to withstand strongly acidic cleaning solutions than nylon.

G. Molecular weight of polyester

To determine whether the molecular weight of the polyester used in the blends affected the wear time of the monofilament, two monofilament blends with the same polyurethane content but different molecular weight of the polyesters as measured by intrinsic viscosity were extruded under similar conditions. The wear resistance of the monofilaments was then measured by a sand slurry test and the results are shown in the following table.

Pre- Thread Description Boundary Viscosity- Weight Loss Signal (%) 1 ° G1 100% PET, Reference 1.02 2.8 Sample G2 100% PET, Reference 0.65 3.1 Sample 15 G3 75% PET; 25% TPU 1.02 * 1.9 G4 75% PET; The figure of 25% TPU 0.65 * 2.1 * applies only to the polyester used, not to blends.

It can be seen from these figures that, when mixed with TPU, higher molecular weight PET gives the filament slightly better wear resistance than lower molecular weight PET. Both monofilaments have significantly better abrasion resistance than PET control monofilaments. Thus, it appears that the molecular weight of PET is not a decisive factor in the wear resistance of PET-TPU blend monofilaments.

H. Comparison of ether-based and ester-based TPU

30 To determine if ester-based TPU provides

no advantages over ether-based TPU in terms of wear resistance, a series of blends were extruded under similar conditions and using PET of similar molecular weight with an intrinsic viscosity of 1.02.

35 The abrasion resistance of the monofilaments * 23,951,160 was then measured using a sand slurry test. The results are given in the following table.

Example Monofilament composition Loss of mass (%) 5

H1 100% PET, control sample 3.2 H2 80% PET + 20% ether 2.7

based TPU

10 H3 70% PET + 30% ether 2.4

based TPU

H4 80% PET + 20% ester 2.5

15 based TPU

H5 70% PET + 30% ester 2.0

based TPU

These results show that with the same TPU content, ester-based TPU provides better wear resistance than ether-based TPU. The ester-based TPU used was Texin 445D, and the ether-based TPU was Texin 990A. PET was a DuPont Merge 1934, 25 which was post-condensed in a solid state.

I. Extrusion of Monofilaments To produce monofilaments containing blends of polyester and polyurethane, the polyester and polyurethane resin beads are first dried, mechanically mixed, and packed in an extruder feed hopper leading to a single screw extruder. Also add · the desired amount of stabilizer, if used, conveniently as a masterbatch or concentrate in either polyester or polyurethane '. The amount of polyester or polyurethane added as a stabilizer is taken into account when determining the amounts of components. Melting and thorough mixing of the resin mixture occurs as the screw passes the molten mixture forward through a cylinder heated to approximately 275 eC. The molten polymer-5 mixture is transferred to a metering pump which forces the mixture through the mouthpiece to form monofilaments. The extrusion temperature may be in the range of 260 to 285 ° C, preferably in the range of 265 to 275 ° C.

Upon exiting the mouthpiece, the monofilaments are cooled in a water bath to form solid filaments. These are drawn at an elevated temperature of up to 100 ° C, between a drawing roller assembly in a tensile ratio of 3.0: 1 to 4.5: 1, possibly further drawn at a higher temperature of up to 250 eC up to a drawing ratio of 6.5: 1 and allowing to relax up to about 30% by heating the filaments in the relaxation step. The finished cooled monofilaments are then wrapped in rolls.

The monofilament of the present invention was prepared by the above method. The following is a typical example.

Examples II and 12

A uniform mixture of pellets, 65% by weight of DuPont Merge 1934 polyester resin post-condensed in the solid state to an intrinsic viscosity of 1.05, and 35% by weight of Texin 445D thermoplastic polyurethane resin with a Durometer hardness of 45 D-scale was applied. into the extruder hopper and extruded. The extrusion conditions, which should not be considered restrictive, were as follows:

. Temperature in the first heater zone: 260 eC

Temperature in the second heater zone: 265 eC

Temperature in the third heater zone: 265 eC

Extruder nozzle temperature: 265 ° C.

25 95160

The mouthpiece of the extruder had eight holes with a size of 0.80 mm. The size of the finished monofilament was 0.30 mm. The monofilament was cooled in a 66 ° C water bath placed 2.0 cm below the mouthpiece. The cooled monofilament was drawn in a hot air oven at 74 ° C in a draw ratio of 3.36, further drawn in a hot air oven at 230 ° C in a total draw ratio of 5.0 and allowed to relax by 25% at 280 ° C. the finished monofilament-10 ti was then collected on rolls for testing. In a similar second production run, a similar monofilament was prepared using 73% polyester, 26% polyurethane and 1% stabilizer.

For comparison, the polyester-15 resin was extruded into a monofilament using similar extrusion-compression conditions as in the polyester-polyurethane blend. The physical properties of these three materials were studied and the results are given in the following table.

20 5 26 95160

Polyester 65% PET- 73% PET- 35% TPU 26% TPU-1% stabilizer

Tensile strength (kg-m2) 5.55x107 2.88x107 2.83x107

Elongation 55.7% 73.2% 62.0% 10

Modulus of elasticity (kg-m2). 0.7Ox109 0.40x109 0.44x109

Shrinked at 15,200 ° C 10.5% 7.9% 13.6%

Abrasion resistance 3.2 1.8 1.8 20 * Measured by mass loss by the method described above (%).

• ·

Claims (15)

1. Monofilaments made by extrusion and containing a substantially greater portion of polyethylene terephthalate polyester and a minor portion of thermoplastic polyurethane of its weight, e.g. 35 wt.% Thermoplastic polyurethane, and 0-5 wt.% Of a hydrolysis resistance enhancing stabilizer, characterized in that the polyethylene terephthalate polyester contains between 60-90 wt.% And has an intrinsic viscosity number of at least 0.50. -1.20 measured in a solvent containing a mixture of phenol and 1,1,2,2-tetrachloroethane in the 60:40 weight ratio, at a temperature of 30 ° C, and that monofilament contains polyurethane in an amount of less more than 40% by weight and 10% by weight, and that the type A durometer hardness of the polyurethane type A is at most 95 and the type D at most 75. Monofilament according to claim 1, characterized in that it contains about 20-35% by weight of polyurethane. Monofilament according to claim 1, characterized in that the mixture contains between about 0.3% and about 5% stabilizer. 10 Monofilament according to claim 1, characterized in that the mixture does not contain a stabilizer. Monofilament according to any one of claims 1-4, characterized in that the polyurethane polymer is either an ester-based or an ether-based thermoplastic polymer. Woven fabric for use in a paper machine, characterized in that it is woven (a) by at least one group of trees woven in a first direction of the fabric, and (b) by at least one group of trees woven in a second direction by the fabric substantially perpendicular toward the first direction, which trees contain monofilament trees according to any one or more of claims 1-5. • Weave web according to claim 6, characterized in that a minor part of the monofilaments forming the web of fabric on which the cellulose fiber pulp mud is spread is a mixture of polyethylene terephthalate and a thermoplastic polyurethane, and a larger part of the monofilaments forming the web of fabric. side is a mixture of polyethylene terephthalate and a thermoplastic: polyurethane. Wire fabric according to claim 7, characterized in that a larger part of the fibers forming the fabric of the web on which the cellulose fiber pulp mud is spread are polyethylene terephthalate and a minor part of them is a mixture of polyethylene terephthalate and a thermoplastic polyurethane. a smaller s ·. . Another part of the monofilaments that form the machine side of the fabric is a mixture of polyethylene terephthalate and a thermoplastic polyurethane. 95160 9. Weave fabric according to claims 6 and 7, characterized by a larger portion of the monofilaments which are a mixture of polyester and polyurethane located in the transverse direction of the fabric. Wire fabric according to claims 6 and 7, characterized in that substantially all of the mixed monofilaments are in the transverse direction of the fabric. A process for producing a monofilament according to claim 1, wherein each other is mixed in bulk more than 60% by weight but not more than 90% by weight polyethylene terephthalate polyester and less than 40% by weight but at least 10% by weight thermoplastic polyurethane and 0-5%. and by weight, the polyester has an intrinsic viscosity value of at least 0.50-1.20 measured in a solvent containing a mixture of phenol and 1,1,2,2-tetrachloroethane in the weight ratio 60: 40, at a temperature of 30 ° C, and that the blend monofilament contains polyurethane in an amount between less than 40% by weight and 10% by weight, and the type A durometer hardness of polyurethane is at most 95 and of type D at most 75, characterized by that the mixture is extruded in: hot state through a nozzle; the extruded monofilament is cooled; the cooled monofilament is stretched in hot condition in at least one stretching step; the stretched monofilament is relaxed at elevated temperature; and then cooled. Multifilament yarn containing several extruded monofilaments, characterized in that at least some monofilaments are extruded monofilaments according to claim 1. Staple fiber, characterized in that at least part of the fibers are parts of extruded monofilaments according to claim 1. Spun yarn, characterized in that it contains staple fiber according to claim 1. Composite yarn, characterized in that it is a mixture of multifilament yarns and staple fibers having at least one multi-filament yarn consisting of several extruded monofilaments, of which at least some are extruded monofilaments according to claim 1, and at least one staple fiber contains part-milled parts. of extruded monofilaments according to claim 1.