FI63452B - MASKINELLT FRAMSTAELLT GLASFIBER INNEHAOLLANDE BANMATERIAL MEDLAOG VIKT - Google Patents

Description

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Patent · och ragiataratyralaan 7 Ansakin utii «d ock utUkrMtM puMicmd ^ ou ^ .oj (32) (33) (31) Pyydwccy scuoiksus — a« | lrtf prior * · * 26.01.77 USA (US) 7Ö2U92 (71) The Dexter Corporation, One Elm Street, Windsor Locks, Connecticut, USA (72) Bernard William Conway, Holyoke, Massachusetts, Nelson Leroy Fegley, Wilbraham, Connecticut, James Moran, Simsbury, Connecticut, USA (7U) Forssin & Salomaa Oy (5U) Machine-made lightweight web material containing fiberglass -Maskinellt framställt glasfiber innehällande banmaterial med l & g vikt

The present invention relates to a wet-formed, lightweight web made of evenly distributed inorganic fibers formed as a continuous process in a paper machine and having inorganic fibers having a fiber length of about 0.63 cm or more and up to about 15% by weight of binder inorganic fibers. for said web having a basis weight of 5-30 g / m 2.

Web materials made of inorganic fibers, such as fiberglass papers, have been made for quite some time, but the papermaker has consistently had a problem in achieving an even distribution of the fibers.

In this connection, it is known in the art that the uniform dispersion of the fibers before the formation of the web is inextricably linked to the uniform distribution of the fibers in the obtained web material. Due to the difficulty of obtaining the required uniform fiber suspension, the inorganic webs made of fine-diameter fibers are heavy, e.g., about 50 g / square meter and heavier, because the heavy materials are thick enough to cover the irregularities in fiber distribution obtained. In a typical wet papermaking process, the fibers are micron-permeable glass fibers and are fed to the dispersant as bundles of fibers cut from multifilament glass ropes. The dispersant is usually an acidic aqueous solution, which may be slightly viscous to help and maintain dispersion 63452 and to separate the various fibers in the multifilament fiber bundles. The fibers are mixed in a dispersing agent in a chipper to effect separation of the bundles, and then the pulp is introduced into holding tanks containing conventional mixing devices to keep the fibers in the desired suspended state. As can be seen, the lack of adequate mixing in the adult dispersion of the fibers results in incomplete separation of the glass fibers, and the fiber bundles are visible in the resulting web material.

In recent years, glass fibers longer than the usual papermaking width have been used, namely fibers with a length of between about 0.63 cm and 2.54 cm and longer. However, when these fibers have been dispersed according to the prior art, it has been found that the fibers tend to accumulate in the chipper and holding containers and could not be easily redispersed, resulting in blockages or other irregularities in the web product. It was also found that the long glass fibers re-accumulated in such a way that they formed fiber bundles in the shape of haystacks or spiders. Although these "haystacks" can be tolerated in heavy materials and some applications where the aesthetics of the web material are not involved, they are considered major defects in lightweight materials and applications where the glass sheet forms a surface coating or is intended to form a smooth surface in a reinforced plastic structure.

Thick, heavy sheets have been used on vinyl floor tiles and the like to provide dimensional stability. However, the heavy glass material has poor resin permeability and therefore poor deposition, which results in a tendency to loosen the layers of bricks. Thin, light handmade sheets with good fiber distribution can be made separately with adequate care. However, the uniform fiber distribution necessary to eliminate the general variation in apparent density referred to as the "cloud effect" and to substantially reduce discrete bundles or "haystacks" has not been achieved in continuous paper machines for the production of lightweight fiberglass web material.

In the continuous production of paper at the production level, the long-fiber web material is usually made from very dilute fiber suspensions using a skewed wire or similar type of paper machine. Such a machine has used an ordinary open headbox large enough to provide a calm and relatively calm web formation zone. The advantage of such a stern box is that sufficient time is set aside in the stern box for the air bubbles to escape from the fiber suspension before the web is formed. However, the desired calm and quiet approach has one particular disadvantage over long glass fiber suspensions. It has been found that when air bubbles leave the headbox, they tend to allow and even promote the formation of "haystacks" of fibers. The bubbles carry these fiber bundles to the surface, causing them to settle as the web material forms on its surface. This results not only in an unsuitable web material in appearance but also in a feeling of an irregular and rough surface that is easily detected simply by running your hand across the surface of the web material.

Therefore, the main object of the present invention is to provide a new and better than ever container, extremely light, yet uniform fiber, long-fiber fibrous web material made on a production-sized paper machine.

Another object of the present invention is to provide a new and improved glass fiber web material of the type shown, in which a uniform overall distribution of fibers and as few discrete fiber bundle defects as possible can be seen. This object involves the provision of a lightweight glass web material in which substantially no variations in fiber density, termed "pi iviva1", are visible.

It is a further object of the present invention to provide a lightweight fiberglass material having improved aesthetic and physical properties which make the material very suitable for use in reinforced plastic films, bricks and the like.

Other items are partly obvious And some are discussed in more detail below.

The objects of the invention are achieved in a fibrous web Ia, which is mainly characterized in that the number of defects formed by the individual fiber bundles of the web is less than 10 per ten square meters and that there is a apparently uniform distribution of fibers substantially free of the variation of the cultivars.

The present invention will be better understood from the following description and the accompanying drawing, in which the features, properties and interrelationships of the parts described and exemplified herein are made.

4 63452

The only drawing shows a block diagram of a technique preferably used to form the lightweight material of the present invention.

As mentioned above, the main factor in obtaining the desired uniform fiber distribution in the resulting web product is to obtain a complete and uniform glass fiber fiber suspension in the dispersant and to bring this dispersion unchanged into the forming region. Thus, for clarity and ease of understanding, the glass fiber material of the present invention will be described in connection with the preferred technique or method used to make it.

Numerous factors affect the quality and suitability of the aqueous fiber dispersion to be fed to the forming area of the paper machine. These include fiber type including fiber finishing and condition of the filaments used to feed the cultures, cutting or cutting, composition and properties of the dispersant, operation of the mixing and dispersing device, and handling of the pulp after leaving the dispersing device. Although each of these factors is important, it has been found * according to the present invention that an essential and significant factor is the residence time of the fibers in the systems at the point where they go to the dispersing device and at that point. Where they are removed from the dispersion in the web-forming zone of the paper machine.

Thus, according to the present invention, it has been found that the best results are obtained by completely removing the holding tanks used hitherto and using an in-line disperser and not the batch mixers used hitherto. The removal of the retention contents involves the immediate introduction of the dispersed fibers at the dilution station and the use of a smooth, small-volume headbox characterized by strong vortices and high pulp velocity. In such a system, the flow of the fiber suspension from the disperser to the forming area of the paper machine takes place in a few seconds, and the residence time in the disperser is the main time control factor for the passage of glass fibers through the system. Such time control is important because it has been found that the most advantageous dispersion of long glass fibers is achieved relatively quickly, i.e. in one or two minutes, and that it remains in its most uniformly dispersed state for only four to five minutes. Thereafter, the glass fibers tend to accumulate, clump together, or form "haystacks" or multifilament lumps as mentioned above. Of course, it is clear that wet papermaking is a dynamic system that is affected by numerous other conditions or factors in the system, such as the viscosity of the dispersant, the fiber content, the rate at which the fibers are measured in the disperser, and several other process variables. As a result, the exact length of stay will vary depending on these different circumstances or factors. However, the best results have been obtained with a controlled disperser time of less than ten minutes and generally about one to seven minutes. An acceptable work read is between about two and six minutes, while the preferred length of stay is about two and a half minutes to five minutes.

Although the inorganic fibers that can be used in this invention include substantially all of the conventional commercially available inorganic materials such as asbestos, mineral wool, and the like, glass fibers are generally preferred. The thickness of the fibers varies substantially, although in the preferred embodiment, the diameters of the cults are in the range of coarse fibers, such as from about 5 microns to 15 microns.

It is, of course, clear that somewhat finer or coarser fibers can be used for special purposes. The glass fibers form the major part of the fiber content, and are preferably present in as much of the fiber content as possible.

Thus, about 85-90% of the fibers in the sheet structure are inorganic and preferably glass fibers. By way of example, mixtures of glass fibers of different types and sizes may be used or the sheet may be made of glass fibers of only one type and size.

Due to the preferred type of glass fiber used, it is generally preferable to use a binder in the inorganic sheet material. Although the binder may be applied as a dilute solution after forming the web or may be incorporated into the pulp as part of the dispersant, it is generally preferred to provide binder fibers of about 10-15% of the total fiber content, and preferably about 5-10% thereof. Various binder fibers can be used with good results, and among these, polyvinyl alcohol fibers have been found to give better results than the injection of the adhesive or the like after the formation. The binder fibers also improve the processability of the web as it passes through the paper machine. Preferably, the fibers are activated or at least softened in the drying section of the machine to obtain a sheet having the desired uniformity.

The binder fibers are preferably added to the fiber suspension during or after dilution of the fiber content and before the suspension flows into the back of the paper machine. Thus, the polyvinyl alcohol fibers acting as a binder for the fibrous web can be suitably added to the downstream of the speed-controlled vane pump without affecting the glass fiber dispersion of the uniformly dispersed gold pulp. If desired, compression treatment or other binder treatments may be performed depending on the end use for which the sheet is intended.

6 63452

Referring to the drawing, it has been found desirable in its preferred technique to provide a controlled and measured supply of long glass fibers to achieve the best fiber dispersion properties. The fibers are preferably measured at a selected rate to a continuous in-line disperser, and from the disperser they are fed directly to the dilution and forming zone of a continuously operating paper machine. This arrangement avoids the need to keep the dispersed fibers in a pulp box or other holding container and the consequent deterioration of the dispersion. In addition, it is an advantage of the present invention that the continuous dispersing device is relatively simple in construction and inexpensive compared to a conventional pulping device. If desired, the fibers can be pre-cut and fed with a dry fiber feeder, or they can be fed in continuous strands and cut or cut as they enter the in-line disperser.

In a preferred embodiment, it has been found advantageous to arrange the cutter at the inlet of the disperser so that continuous glass ropes can be fed from the spools and cut immediately for feeding to the disperser. This continuous filament feed provides excellent control over both the length and speed of the fibers at which the fibers are fed to the disperser. In addition, it increases flexibility by allowing the use of fibers of different lengths and the adjustment of fiber lengths.

When using pre-chopped or pre-cut fibers, it is possible to arrange control of the speed at which the fibers are fed to the disperser by using a weighing belt or the like between the dry fiber meter and the disperser, with the dry fiber meter

The liquid used as dispersant is also fed to the disperser inlet to obtain the desired fiber content therein. This liquid is an acidic aqueous solution which may contain a suitable agent to control the viscosity of the dispersant. Thus, according to a preferred embodiment of the invention, a dilute aqueous solution of sulfuric acid having a pH between 2 and 4 and containing a sufficient amount of a viscosity-inducing agent is used. Usually the viscosity of the solution is between about 5 and 20 centipoise. The viscosity-providing agent may be a natural or synthetic substance or a mixture or combination thereof. The substances are preferably water-soluble, such as resins and natural gums, which can be used alone or in combination with other substances to obtain the desired viscosity. Examples of natural gums are locust bean gum and guar gum derivatives. Among these, guar gum derivatives are preferred, and excellent results have been obtained in General 7 63452

A derivative of guar gum sold by Mills Company under the trademark "Gendriv" in a water-ii extract.

In addition to natural viscosity-generating agents, it is also possible to use synthetic agents such as high molecular weight resins, dispersants and surfactants and the like to control the properties of the dispersing agent. These synthetics are preferably water soluble and stable in the acidic environment used for the glass fibers. Among the synthetic viscosity-generating agents, preferred resins include polyacrylamide polymers that can be used as dilute aqueous solutions at low concentrations (e.g., 0.025-0.2%) to provide control of the desired viscosity. Typical of these materials are polyacrylamide resin sold under the trademark "Separan AP-30" by Dow Chemical Company and under the trademark "Cutame 5" by the American Cyanamide Company.

A viscous dispersant is used because it prevents the fibers from intertwining with each other during dispersion and helps keep the fibers dispersed through the suspension disperser as it passes. As can be seen, the viscosity of the solution affects the required residence time and must be adjusted for the fiber used and the fiber content. Highly viscous material and short residence time can lead to aI idispersed pulp, while low viscosity material and long residence time can lead to yIdispersed and the formation of “haystacks” or other major defects. As can be seen, other additives such as dispersing aids, e.g.

As mentioned, it has been found that the fibers disperse quite rapidly and reach a peak in the percentage of dispersed fibers in a relatively short time, after which the fibers tend to adhere or bind to each other and form harmful "haystacks". Once the most advantageous dispersion has been reached, it is advantageous to mix for a limited time and to control the residence time of the fibers in the disperser so that long mixing is avoided. In this connection, it has also been found that, once the most advantageous dispersion and the desired residence time have been reached, mixing in the dispersant cannot be stopped without deteriorating the quality of the dispersion. Of course, as can be seen, the surface treatment of the fibers has a significant effect on the ability of the fibers to withstand a long residence time. However, for 63452 most commercially available glass fibers, it has been found that the most preferred residence time is between 2 1/2 and 5 minutes when working with a dIs person having a viscosity of about 5-10 centipoise and a pH of about 2-3 at a solution temperature of about 27 ° -38 ° C and a fiber content of about 0.3 to 1.0 percent.

Preferably, the dispersant should be of the type having a relatively smooth inner surface and having no edges or surfaces on which the long glass fibers can accumulate or accumulate. However, there may be a number of mixtures in the disperser! dispersing stations or compartments in the event of a flow directly from station to station to obtain the desired residence time characteristics.

As will be appreciated, the structure of the disperser may vary within the extent in which it achieves the desired separation of the various fibers from the fiber bundles fed to the disperser and provides a uniform dispersion of the various cultures as it passes through the disperser during the required residence time. As can be seen, the fibers are measured in the dispersant flowing through the disperser to obtain the desired fiber concentration. Usually, the concentration is substantially higher than the fiber content in the headbox with a factor as high as 10-100. According to a preferred embodiment, the fiber content is less than two percent and generally in the range of about 0.3 to 1.3 percent, with the preferred range being about 0.5 to 0.9 percent.

As mentioned above, the fiber dispersal moves rapidly from the disperser to the forming section of the paper machine And reaches the forming wire within a few seconds after leaving the disperser. However, during this time, the fiber content of the dispersion is adjusted to more completely dilute the pulp. This can be accomplished by feeding the dispersion into a separate flow-through mixing tank where it is mixed with the no I laves stream from the web formation. The fiber content is diluted from 0.3 to 1.2 percent to about 0.005 to 0.05 percent. Thus, as can be seen, the dilution is greater than 10: 1 and usually 15-25: 1 to obtain a very dilute fiber suspension fed to the headbox of a paper machine.

As shown in the drawing, the headbox used in accordance with the present invention differs from the open head of conventional web-fed paper machines and is provided with a smooth interior and a small volume so that a very dilute fiber suspension flows rapidly into the web-forming area. A small volume headbox with smooth surfaces not only increases the speed of the fiber suspension passing through it but also increases the vortex immediately above the formation zone. The added vortex prevents the agglomeration of effervescent and fibrous pulps, which would otherwise float and form "haystacks" or other fiber defects. and without parts that could interfere with flow or otherwise cause fiber entanglement, thus the headbox used in accordance with the present invention prevents the fiber dispersion from being maintained for extended periods of time and thus the dispersed fibers reassemble to form defects in the sheet structure.

The following examples are provided for a more complete understanding of the effectiveness of this invention. These examples are provided for illustrative purposes only and are not intended to limit the present invention in any way. Unless otherwise stated, all parts are by weight.

EXAMPLE I:

The lightweight fiberglass web was made using a production-sized paper machine. Glass fibers 5 microns in diameter were cut to a length of 1.27 cm from the filament fiber ropes fed from the spools. The cut fibers were fed directly to an in-line disperser at a rate of about 0.45 kg per minute. The Linjadis person had a capacity of 379 liters and was used at a throughput rate of 114 liters per minute, thus providing a slightly longer residence time of 3 minutes. The dispersant used was a sufficient amount of a rubber derivative (Gendriv-492 SR) to give a solution viscosity of about 5 centipoise at a pH of 2.3 and a dilute sulfuric acid solution at 31 ° C. A fiber dispersion having a fiber content of 0.4% was fed from the disperser to a mixing tank in which the fiber content was diluted approximately 24: I. Polyvinyl alcohol fibers were added to the dilute suspension in amounts sufficient to bring the polyvinyl alcohol fiber concentration to 8% by weight of the glass fibers. The fiber dispersion was then fed to a small very fast headbox at a concentration of 0.017%, and a glass fiber web was formed at an average production rate.

The web material obtained had a weight of 13.6 grams / square meter, a thickness of 84 microns 2 and a porosity of 8263 liters per minute per 100 cm at a pressure of 12.7 mm H 2 O. The tensile strength of the light web when dry was 507 g / 25 mm in the machine direction and 33 g / 25 mm in the transverse direction. Its tongue tear was 34 g in the machine direction and 44 g in the transverse direction.

10 63452

In the samples taken from different parts of the sheet, the main defect number was 0-2 and the small defect number was 0-5 per ten square meters corrected for a weight of 17 grams / square meter. The main defect is classified as a bundle of fiber of non-dispersed or partially dispersed quality or a haystack, while the defect is classified as two or three fibers which have remained undispersed or contracted together. Commercially acceptable lightweight materials are those having about 10 or less, and preferably 5 or less, of the main defect of web material per 10 square meters. Minor defects are not considered significant. The sheet material also had a uniform distribution of fibers free of substantially any density variation in the visual inspection.

EXAMPLES Il-VI:

The procedure of Example I was repeated on the same paper machine except for changes in operating conditions, fiber mass and weight of material produced. The results are in the table below.

TABLE

Example Il Example Ill Example IV Example V Example VI

Fiber 9 microns 70 46 90 70 22 13 microns {%) 22 46 - 22 70

Side ($) 8 8 10 8 8

Weight (g / m2) 19.8 18.3 22.0 22.4 23.1

Thickness (microns) 123 115 133 138 115 II porosity (l / min) 5648 6552 4742 5512 6149

Dry drawing (g / 25 mm) in the machine direction 1109 609 1828 1456 1121 in the transverse direction 915 765 1034 1362 1037

Tongue tear (g) in machine direction 51 60 40 62 89 in transverse direction 51 44 60 63 99

Vi ka figure per 10 m2 head 0-3 0-4 0-3 0-1 0 small 3-4 0-5 7-14 1-4 2-4

Claims (9)

1. Hydrogenated, lightweight, of evenly distributed inorganic fibers, which is formed in a continuous process in a paper machine and containing inorganic fibers, whose fiber length is about 0.63 cm or more, and up to +1! about 15% by weight of binder for the inorganic fibers, the surface weight of said web being 5-30 g / m, characterized in that the number of errors formed by the separated fiber bundles in the web is less than 10 per ten square + me + er and having a obviously uniform fiber distribution substantially free from "cloud effect" referred to as fiber density variability. Fiber web according to claim 1, characterized in that the inorganic fibers are glass fibers having a thickness of micron diameter. Fiber web according to claim 1, characterized in that the inorganic fiber content is about 85% by weight or more. Fiber web according to claim I, characterized in that the weight of the web is about 10-25 grams / square meter. Fiber web according to claim I, characterized in that the inorganic fibers are glass fibers, the diameter of which lies in the range of 5-15 m in crowns and length in the range 0.63-2.54 cm. Fiber web according to claim 1, characterized in that the inorganic fibers contain a mixture of glass fibers with different micron diameters. Fiber web according to claim I, characterized in that the inorganic fibers comprise 90% by weight of the web weight and are glass fibers, the diameter of which is in the range of 5-15 ml of crown and that the number of main defects in said web is less than 10 per ten square meters. Fiber web according to claim 1, characterized in that the number of main defects therein is about 5 or less per 10 square meters. Fiber web according to claim 1, characterized in that