NO802456L - POLYOLEFIN FIBERS OR THREADS, THEIR MANUFACTURING AND USE. - Google Patents

Abstract

1. Polyolefine fibres or filaments for use as reinforcing fibres for building material mixtures based on cement and containing, as filler, optionally together with other fillers of inorganic nature, 5-80% by weight, relative to the polyolefine, of cement, characterised in that the cement present as filler has a particle size of less than 90 mu m and that the fibres or filaments have an elongation at break of at most 20%.

Description

The present invention relates to polyolefin fibres.

or threads with a content of cement as a filler, and which are particularly suitable as reinforcing fibers for building material mixtures based on cement, a method for producing these, their use for

ling of building elements as well as thereby achieved such.

It is known that one can give objects, especially pipe-

and slabs of cement, an increased strength by mixing in reinforcement fibres. For the most part, until now, asbestos fibers are

turned for this purpose. In recent times, however, efforts have been made to replace these asbestos fibers with other fiber material, as the carcinogenic effect of the fibers has been established in the meantime.

As a substitute for asbestos fibres, polyolefin fibers or fiber materials have already come into the spotlight. In GB-PS 1,130,612 it is proposed to incorporate polyolefin staple fibers in cement, and' according to DE-OS 2,728,351

becomes fibers of thermoplastic plastics such as e.g. polypropylene, used for reinforcing cement building elements in the form of a net, as achieved by slitting or fibrillating a: one-dimensional stretched film. However, since polyolefin fibers are hydrophobic, sometimes

none on difficulties and the adhesion' in the matrix is not good enough, i.e. that the fibers are pulled out of the cementitious material under stress so that the desired firmness is not achieved.

According to GB-PS 1,136,661, to improve the adhesion of polyolefin fibers in cement mortar or similar materials based on cement, it was proposed to use polyolefin fibers, especially fibers of polypropylene or polyethylene,

which contained 5-80% cement as filler and further exhibited .

a content of 0.1 to 5% of a hydrophilic surfactant, e.g. such on the basis of a tertiary aminosulphonate. The production of these fibers takes place preferably by the melt spinning process with subsequent intermediate drawing,

namely in a ratio of 1:2 to 1:4, however, a production by a split fiber process is also possible. A "normal cement" is used as cement.v

When cement is added, the specific weight of the fibers is increased and the fibers according to GB-PS 1,136,661 have a hydrophilic character on the surface, so that the mixing of the fibers in the cement proceeds much more favorably.

Despite this, it was not possible to achieve a sufficient increase in the strength values for cement mixtures that were reinforced with these fibers compared to non-reinforced samples. The reason was, on the one hand, that the relatively slightly pre-stretched fibers did not have a high tear strength, a higher pre-stretch, however, did not bring any improvement either, as such fibers with ordinary cement, e.g. of the PZ 275 type

as a filler, lost firmness with increasing elongation. Furthermore, the fibers had elongations at break which could amount to 100% or more. Fibers with such a high expansion are unsuitable as reinforcing fibers as the fibers, when stressed on the concrete form parts, expand to such an extent that the matrix breaks before the tearing resistance of the reinforcing fibers comes into use at all. Furthermore, in accordance with the aforementioned GB-PS, relatively strong fibers (110-280 dtex) which, when produced after the melt spinning process, had a smooth surface.

Surprisingly, it has now been found that it is possible to achieve

a very good reinforcement of cement using fibers of polyolefins with cement as filler, when these fibers have an elongation at break of no more than 20% and are produced with a cement as filler that has a grain size of less than 90 ym. Such fibers can then also be prestretched at a cement content of 40% and several times above that, namely to 1:10 to 1:12, as stated in GB-PS 1,136,661, without fiber breakage or loss of strength occurring with increasing degree of prestretching. Fibers with the low expansion of a maximum of 20% are obtained by the split fiber process.

The object of the present invention is according to

to this, polyolefin fibers or threads for use as reinforcing fibers for building material mixtures based on cement, as filler, possibly with other fillers of an inorganic nature, containing 5-80% by weight of cement intended for polyolefins, and these is characterized by the fact that it

as a filler, the present cement has a grain size of less than 90 ym and that the fibers or threads show an expansion of a maximum of 20%.

These fibers, which do not contain any surface-active agent, can be mixed very well into the cement-containing material and have a good bond to the mixture. The low expansion makes it possible for the tear strength of the fibers to be fully exploited when the molded parts are stressed. They have a high tendency to split, which results in an irregular surface and which is also beneficial for a good anchoring in concrete.

According to the invention, the maximum grain size for the cement used as filler is very important for the properties of the fibers produced with it, respectively their strength values, especially at a high degree of elongation. It is particularly favorable when the proportion of grain between 60 ym and 90 ym amounts to less than 1%'. Types of cement that satisfy the requirements according to the invention can be found, among other things, in cements of the type PZ 475, whereby the suitability can simply be determined by visual analysis. Cements of the PZ 275 type are contrary to this for the most part; not suitable.

Furthermore, it is appropriate to ensure that the fibers used have a tear density of at least 5cN/tex. Preferably, the firmness should amount to at least lOcN/tex. The tearing strength is hereby determined in accordance with DIN 53 834.

Fibers with such a tearing speed and the necessary low expansion are achieved when they are produced by a split fiber process, whereby the advantage of the fibers according to the invention is that at higher degrees of prestretch, preferably at such 1:7 and more, e.g. up to 1:12, '..for increased driving stability. This is surprising for such a highly filled fiber, above all in view of the nature of the fillers.

The polyolefin fibers or threads according to the invention can be either in staple cut single-keeled fibers or in several places loosely connected network fibers or also so-called endless fibers. With a view to the methods developed for asbestos cement being able to be used as far as possible, is

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staple fibers are preferred, whereby very good properties have been achieved and at the same time good processing possibilities with fibers with a staple length of 0.2 to 2.0 cm.

The fineness of the fibers in and of itself is not significant.

Since it is a split fiber, it varies greatly and amounts to e.g. 1:180 dtez, whereby the simultaneous presence of. thin and thick fibers or the fiber part is beneficial. Appropriately, the fibers on surfaces are equipped with an Avivage. As such, e.g. one based on ethoxylated alcohols or ethoxylated other organic compounds.

In addition to the cement, the fibers according to the invention can also contain other fillers whereby the minimum amount of cement of 5% by weight must be observed. Such fillers can e.g. be talc, calcium carbonate, barium sulphate and the like. Care must be taken, however, that these fillers are only used in such quantities that the characterizing properties of the fibers according to the invention, such as hydrosurface, splitting tendency, irregular surface, are not lost. Thus, e.g. talc is known to be significantly more hydrophobic and also reduces the splitting tendency of polyolefin fibers. Appropriate should therefore

■ the amount of talc should not exceed the amount of cement. As mentioned, the fibers according to the invention are produced by a split fiber process according to which a primary film is first produced which, after pre-stretching, is either split by itself or there. the splitting takes place by means of mechanical means, such as. e.g. studded rollers. The use of a split fiber process is essential because, in addition to the low expansion required according to the invention, such fibers also have branches due to the splitting and a more irregular surface than melt-spun fibers, which all serve for better anchoring; in the cementitious mixture and leads to better adhesion.

Preferably, the foil is prestretched at least in a ratio of 1:2.

Another object of the invention is building elements such as plates, pipes. etc. based on cement, and which contain fibers according to the invention as reinforcement fibers. The fibers can thereby be present in the form of staple fibres, multifilaments or as a network, as it occurs

■when splitting foils, whereby staple fibers are preferred.

The amount of fiber depends on the desired properties of the building elements. As a rule, an amount of 0.2 to 10% by volume of fibres, calculated on the building element, has proven appropriate.

The building elements according to the invention can also contain other common reinforcing fibers such as e.g. carbon fibres, steel fibers and the like.

The following examples shall describe the Polyolefin fibers of the invention, their production processes and application in more detail.

in

Example. 1:

Polypropylene powder is mixed with 30% by weight, calculated on the total mix, of a type 475 Portland cement and with the grain size distribution

in an intensive mixer and granulate;. thereafter. From the granulate, according to the "Chill-roll" process, a primary film is produced which- after pre-stretching<;,>at 120°C with a stretch ratio of 1:7.67 using a fibrillator, is processed into split fibers which are cut into a stack length of 0.2 cm. They saw fibers obtained in this way have a tear strength according to DIN 53834 of 9.4 cN/tex and an elongation at break of -4.3%. If the production of the foil does not take place in accordance with the method used, but by means of a method with water bath cooling, the fibers have the same stretch ratio; according to the characteristic values:

Example 2:

From a granulate according to example 1, split fibers are produced, as described in example I, which are cut into staple fibers with a length of 0.2 cm, whereby a stretch ratio of 1:8.15 was chosen.

The fibers thus obtained have a tear strength of 10.8 cN/tex and an elongation at break of 4.8%.

Example 3:

From a granulate according to example 1, as described in example 1, staple fibers with a length of 0.2 and 0.5 cm are produced, whereby a tensile ratio of 1:9.35 was achieved.

The thus obtained fibers have a tear strength of 13.5 cN/tex and an elongation at break of 5.3%.

If the "Chill-roll" process is not used when manufacturing the fibres, but a wide-slot nozzle process with water-bath cooling, the fibers have the following characteristic values using the same stretch ratio:

Example 4:

Polypropylene powder is mixed with 50% by weight of a type 475 Portland cement with a grain proportion greater than

>60 ym of 0.2% and over 75 ym of 0 in an intensive mixer and then granulated. If the granules are produced using

a wide slot type- with subsequent water bath cooling a primary foil which is then stretched at 130^0 in a ratio of 1:8.77. This is processed using a mechanical fibrillator into split fibers which are cut to lengths of 0.6 and 1.3 cm.

The fibers have a tear strength according to DIN 53 834 of 10.8.cN0tex and an elongation at break of 1.97%.

Example 5:

From polypropylene powder and the same cement as in example 4, however using 40% by weight of cement calculated on the mixture, a mixture is prepared, as described in example 4, which with the help of a "Chill-roll" plant, is processed into a primary foil which at 130°C is first stretched once in a ratio of 1:10.77 and a second time in a ratio of 1:12.5, and then fibrillated mechanically. The fibers are then cut to a length of 0.6 cm. They have the following properties:

Example 6:

Fibers produced according to examples 1-3 are mixed in an amount of 3% by volume in a Portland cement usual for the production of asbestos cement sheets and sheets are made from this mixture in the usual way. These were sawn into narrow bars and these were subjected to a tensile stress to break according to the method according to DIN 53 455. The maximum values stated in the following tables are measured when the test bar completely breaks.

Example 7:

Fibers produced according to examples 4 and 5 are treated with various commercial conditioners based on ethoxylated fatty alcohols and a sample was treated only with water,

and then incorporated in an amount of 3 vol.% in a normal Portland cement for the production of asbestos cement sheets. From

plates were made from this mixture in the usual way and from these narrow rod-shaped specimens were cut which were examined for the tensile stress according to DIN 53 455. The values indicated in the table with max were measured at complete break. As a comparison, a test rod produced in the same way was tested, which contained the same amount of a polypropylene fiber with a staple length of 0.6 cm of the same polypropylene as the fibers according to the invention, but without cement addition, but also with the same amount of Avivage. The polypropylene fibers were stretched during manufacture in a ratio of 1:33 and had a tear strength of 28t32 cN/tex and an elongation at break of 80-100%. The three samples with fibers containing 40% cement and with an extension of 1:12.5 are three samples with three different Avivagers. The softening agent for the fibers with which a maximum value of 389 N/cm 2 was obtained as well as that for the comparison fibers was the same as that used for the sample with 50% cement content.

Claims (10)

1. Polyolefin fibers or threads for use as reinforcing fibers for building material mixtures based on cement and as a filler possibly alongside other fillers of an inorganic type, containing 5-80% by weight of cement, intended for polyolefins, characterized in that the filler used is cement exhibits a grain size of less than 90 ym and that the fiber or thread has an expansion of a maximum of 20%. 2. Fibers or threads according to claim 1, characterized in that the proportion of grains in the cement used as filler between 60 ym and 90 ym amounts to less than 1%. 3. Fibers or threads according to claims 1 and 2, characterized in that the degree of stretching is at least 1:7. 4. Fibers or threads according to claims 1-3, characterized in that the tear strength is at least 5 cN/tex. 5. Fibers or threads according to claims 1-4, characterized in that they are staple fibers with a staple length of 0.2-2.0 cm. 6. Fibers or threads according to claims 1-5, characterized in that they are equipped with an Avivage. 7. Process for the production of polyolefin fibers or threads according to claims 1-6, characterized whereas polyolefin with a content of 5-80%, calculated on the polyolefin, of a cement with a grain size below 90 ym, preferably with a grain size distribution according to which the proportion of grains between 60 ym and 90 ym amounts to less than 1%, is subjected to a split fiber process with or without mechanical fibrillation. 8. Method according to claim 7, characterized in that the film produced during the split fiber process before fibrillation is prestretched at least in a ratio of 1:7. 9. Use of polyolefin fibers or threads according to claims 1-6 as reinforcing fibers in the production of building elements based on cement. 10. Building element based on cement with a content of fibers or threads of polyolefin; which contains cement as filler, as reinforcing fibres, character certified that the polyolefin fibers or threads are according to claims 1-6 and in the form of staple fibers, multifilaments or nets.