CN116600962A

CN116600962A - Use of glass-resin composite fibers for reinforcing concrete

Info

Publication number: CN116600962A
Application number: CN202180084567.XA
Authority: CN
Inventors: P·普卢曾纳; K·鲁斯; R·马丁内斯
Original assignee: Compagnie Generale des Etablissements Michelin SCA
Current assignee: Compagnie Generale des Etablissements Michelin SCA
Priority date: 2020-12-16
Filing date: 2021-12-10
Publication date: 2023-08-15
Also published as: WO2022129746A1; FR3117481A1; AU2021403916A9; JP2024500619A; AU2021403916A1; CA3194075A1; EP4263458A1

Abstract

The invention relates to a monofilament made of a glass-resin composite material, comprising glass filaments embedded in a cross-linked resin, the length of said monofilament being in the range of 5mm to 85mm, the diameter being in the range of 0.2mm to 1.3mm, and the porosity being less than 2%, to small tows comprising a plurality of said monofilaments and their use for reinforcing concrete, reducing the weight of concrete and reducing or preventing cracking of concrete. The invention also relates to a concrete comprising said filaments and to a method for obtaining said filaments.

Description

Use of glass-resin composite fibers for reinforcing concrete

Technical Field

The present invention relates to glass-resin composite fibers for reinforcing concrete.

Background

Concrete is said to be the most widely used building material today because of its high compressive strength, durability, life and resilience. The properties of concrete make it the material of choice, especially in the field of construction, road and engineering construction.

Concrete is composed mainly of aggregates held together by binders, most commonly portland cement. To improve the properties of concrete, it is known to use additives such as ultrafine particles (e.g. silica fume), superplasticizers (also known as water-reducing plasticizers) or metal, synthetic or mineral fibers.

Although very resistant to compression, the tensile strength of concrete is low, with tension often accompanied by the appearance of cracks. To solve this problem, it is known to use reinforcing fibers. Metal fibers are particularly advantageous for reinforcing concrete due to the mechanical properties of the metal fibers. They are therefore very widely used to make concrete more ductile and to improve its crack resistance.

However, mechanical fibers have the disadvantage of being very sensitive to corrosion, which can be detrimental to the life of the concrete containing such fibers. In addition, their density is generally greater than 7.7, and therefore cannot be uniformly distributed in the concrete with a lower density (metal fibers tend to sink under the force of gravity).

To solve this problem, synthetic fibers have been proposed to replace metal fibers. However, these fibers do not have as good mechanical strength (e.g., elastic (young's) modulus, tensile strength) as metal fibers. In addition, their operating temperature (typically between 100 ℃ and 160 ℃) is much lower than that of metal fibers (approximately between 600 ℃ and 900 ℃), which may limit their use in certain applications.

It would therefore still be advantageous to have fibers that are both corrosion resistant to improve the service life of the concrete and have improved mechanical properties compared to current nonmetallic fibers to improve crack resistance.

Disclosure of Invention

In conducting research, the applicant has unexpectedly found that the above-mentioned problems can be solved by using specific glass-resin composite fibers comprising glass filaments embedded in a crosslinked resin.

The applicant has also observed a number of advantages brought about by the fibres according to the invention. They are very easy to implement compared to the fibres for concrete in the prior art, in particular in the phase of mixing the various components of the concrete (easy to disperse), and also in the drying phase of the concrete: because their density is close to that of concrete, the fibers remain uniformly distributed in the concrete (they do not sink as easily as metal fibers having a density greater than that of concrete, nor rise as easily as synthetic fibers having a density less than that of concrete). The fibers of the present invention also have a much higher maximum use temperature than the synthetic fibers currently in use. Furthermore, the white color of the fibers according to the invention allows their use in light-colored concrete without affecting the aesthetic appearance of these concretes. Finally, more generally, the use of fibres according to the invention, thanks to their density and their reinforcing capacity, allows to drastically reduce CO for the same reinforcing level compared to the use of other fibres of the prior art ₂ Is a total discharge amount of the fuel cell.

Accordingly, the present invention relates to a glass-resin composite monofilament comprising glass filaments embedded in a crosslinked resin, the monofilament having a length in the range of 5mm to 85mm, a diameter in the range of 0.2mm to 1.3mm and a porosity of less than 2%.

The invention also relates to a tow comprising a plurality of said filaments, to the use of said filaments or said tows for reinforcing concrete, to concrete comprising said filaments, and to a method for manufacturing said filaments.

I-definition

In this context, all percentages (%) indicated are weight percentages (%), unless otherwise explicitly indicated.

The expression "composition based on" is understood to mean that the composition comprises a mixture and/or in situ reaction product of the various components used, some of which are capable of (and/or intended to) at least partially reacting with each other during the various stages of manufacture of the composition; thus, the composition may be in a fully or partially crosslinked state or in an uncrosslinked state.

Furthermore, any numerical interval represented by the expression "between a and b" represents a numerical range extending from greater than a to less than b (i.e., excluding the endpoints a and b), while any numerical interval represented by the expression "a to b" means a numerical range extending from a up to b (i.e., including the strict endpoints a and b). In this context, when a numerical interval is represented by the expressions "a to b", it is also preferable to represent an interval represented by the expression "between a and b".

All values of the glass transition temperature "Tg" described herein are measured by DSC (differential scanning calorimetry) in a known manner according to standard ASTM D3418 (1999).

Drawings

II-brief description of the drawings

Fig. 1 is a diagram of a method for synthesizing a monofilament according to the present invention (before the monofilament is cut to a defined length).

Fig. 2 (not to scale for ease of understanding) is a diagram showing a cross-section of a monofilament according to the present invention.

Detailed Description

III-description of the invention

The invention therefore relates to a monofilament (or fiber, both terms being used in an equivalent way) made of a glass-resin composite (abbreviated as "CVR"), said monofilament comprising glass filaments embedded in a crosslinked resin, characterized in that said monofilament has a length in the range of 5mm to 85mm, a diameter in the range of 0.2mm to 1.3mm and a porosity of less than 2%.

Typically, the glass filaments are present in the form of a single multifilament fiber or in the form of a plurality of interrelated multifilament fibers. In the latter case, the multifilament fibers are preferably substantially unidirectional. Each multifilament fiber may comprise tens, hundreds or even thousands of individual glass filaments. These extremely fine individual filaments generally and preferably have an average diameter of about 5 μm to 30 μm, more preferably 10 μm to 20 μm. The individual wires are preferably cylindrical in cross section. As examples of glass fibers that can be used in the context of the present invention, mention may be made of "R25H" or "SE1200" fibers of Owens Corning.

The term "resin" is intended herein to mean both unmodified forms of the resin and any composition based on the resin and comprising at least one additive (i.e., one or more additives). The term "crosslinked" resin is of course intended to mean that the resin cures (photo-cures and/or thermo-cures) in a state characteristic of "thermosetting" polymers (unlike "thermoplastic" polymers), in other words in the form of a three-dimensional bonded network.

Thus, the CVR monofilament according to the present invention comprises a plurality of individual glass filaments which are preferably embedded in the crosslinked hardened resin substantially parallel to each other.

According to the invention, the CVR monofilament has a porosity of less than 2%, preferably less than 1%, preferably less than 0.5%. Advantageously, the porosity of the CVR monofilament is comprised between 0% and 2%, preferably between 0.01% and 1%, preferably between 0.05% and 0.5%.

Porosity may be measured by microscopy (e.g., by scanning electron microscopy), preferably using area calculation software (e.g., FIJI procedure). For the measurement, the following protocol is preferably performed:

-obtaining crosslinked CVR monofilaments;

coating CVR monofilaments with cold coating resin, for example of the epoxy type, for example in a vacuum coating apparatus (for example CitoVac from Stuers company),

Cutting the coated CVR monofilament, for example using a hydraulic cutting machine, such as "SH-5214" from Baileigh company,

polishing the cross section of the CVR monofilament preferably to a final particle surface of 0.25 μm, for example using a mechanical polisher such as from Mecapol company,

applying gold at 1nm to 4nm, e.g. using a gold sputter coater, e.g. fromCompany 108 series or 208 series Cressington coater,

viewing the cross section of the CVR monofilament with a (15 kV) scanning electron microscope, preferably under vacuum, and

using an image processing program (e.g. FIJI), the percentage of surface area of the pores is calculated. The term "voids" of the CVR monofilament means any gas (in particular air) or void present within the CVR monofilament.

Advantageously, the stress at break Cr of the CVR monofilament is greater than 1050MPa, preferably greater than or equal to 1100MPa, more preferably greater than or equal to 1200MPa. Preferably, the breaking stress of the filaments is between 1050MPa and 1600MPa, preferably between 1200MPa and 1500 MPa.

Also advantageously, the initial tensile modulus of the CVR monofilament measured at 23℃is expressed as E ₂₃ ) (also referred to as Young's modulus) of greater than 35GPa, preferably greater than or equal to 40GPa, preferably greater than or equal to 42GPa, preferably greater than or equal to 48GPa.

Tensile mechanical Properties of CVR monofilament (modulus E ₂₃ Cr, stress at break and Ar) can also be measured according to standard ASTM D2343 using an INSTRON 5944 tensile testerUNIVERSAL software equipped with tensile tester) is measured on coated (i.e., ready-to-use) CVR monofilaments in a known manner. Before measurement, these monofilaments are subjected to preconditioning (the monofilaments are stored for at least 24 hours under a standard atmosphere (temperature 23.+ -. 2 ℃ C.; relative humidity 50.+ -. 5%) according to European standard DIN EN 20139). The tensile modulus is determined by linear regression of the stress versus strain (between 0.1% and 0.6% strain) curve. The strain was recorded by a MultiXtens 1995DA801 extensometer. The 260mm specimen tested was pulled at a nominal speed of 5m/min (reference length 50mm, distance between jaws: 150 mm) under a preload of 0.5MPa prior to testing. All results given are the average of 10 measurements.

Furthermore, the CVR monofilament according to the invention advantageously has the following characteristics:

the glass transition temperature (expressed as Tg) of the resin is equal to or greater than 180 ℃, preferably equal to or greater than 190 ℃;

-elongation at break (expressed as Ar) of the monofilament measured at 23 ℃ equal to or greater than 3.0%, preferably greater than 4.0%;

Initial tensile modulus of the monofilament measured at 23 ℃ (denoted as E ₂₃ ) Greater than 35GPa, preferably greater than 48GPa; and

the real part of the complex modulus of the monofilament, measured by the DMTA method at 190 ℃ (expressed as E' ₁₉₀ ) Greater than 30GPa.

The glass transition temperature (expressed as Tg) of the resin is preferably greater than 190 ℃, more preferably greater than 195 ℃, in particular greater than 200 ℃. The glass transition temperature is measured in a known manner, for example by DSC (differential scanning calorimetry) in a second scan, and, unless otherwise specified in the present application, according to standard ASTM D3418 in 1999 (DSC instrument "822-2" from Mettler Toledo; nitrogen atmosphere; the sample is first brought from ambient temperature (23 ℃) to 250 ℃ (10 ℃ C./min), then rapidly cooled to 23 ℃ C., finally the DSC curve is recorded from 23 ℃ C. To 250 ℃ C. With a gradient of 10 ℃ C./min).

The elongation at break (expressed as Ar) of the CVR monofilament measured at 23℃is preferably greater than 4.0%, more preferably greater than 4.2%, in particular greater than 4.4%.

Modulus E' ₁₉₀ Preferably greater than 33GPa and more preferably greater than 36GPa.

In order to achieve an optimal compromise between the thermal and mechanical properties of the CVR monofilament according to the application, the ratio E' _(Tg’–25) /E’ ₂₃ Advantageously greater than 0.85, preferably greater than 0.90, E' ₂₃ And E' _(Tg’–25) Is the real part of the complex modulus of the monofilament measured by DMTA at 23℃and at a temperature equal to (Tg '-25) expressed in degrees Celsius, respectively, where the expression Tg' represents the glass transition temperature this time measured by DMTA.

Still more advantageously, the ratio E' _(Tg’–10) /E’ ₂₃ Greater than 0.80, preferably greater than 0.85, E' _(Tg’–10) Is through DMTA real part of complex modulus of the monofilament measured at a temperature equal to (Tg' -10) expressed in ℃.

Use of "DMA" from ACOEM (France) ⁺ The 450 "viscosimeter performs the E 'and Tg' measurements by DMTA (" dynamic mechanical thermal analysis ") in a known manner, wherein the bending, stretching or torsion test is controlled using" Dynatest 6.83/2010 "software.

In the case of this device, only geometric data of rectangular (or square) cross-section can be entered, since the three-point bending test cannot in a known manner input the initial geometric data of a monofilament with a circular cross-section. Thus, in order to obtain an accurate measurement of the modulus E' of a monofilament of diameter D, it is customary to input in software a square cross section of side length "a" and with the same area secondary moment, so as to be able to process with the same stiffness R of the test specimen.

The following well-known relationship (E is the modulus of the material, I _s Second moment of area for the object under consideration, ×multiplier):

R＝E _{composite material} *I _{Circular cross section} ＝E _{Composite material} *I _{Square cross section}

Wherein: i _{Circular cross section} ＝π*D ⁴ /64 and I _{Square cross section} ＝a ⁴ /12。

The value of the side length "a" of an equivalent square having the same area secondary moment as a monofilament (circular) cross-section of diameter D can be easily deduced from the following equation:

a＝D*(π/6) ^0.25 。

in the case where the cross section of the sample to be measured is not circular (or rectangular), the same calculation method will be applied regardless of the specific shape thereof, and the area secondary moment I is determined in advance on the cross section of the sample to be measured _s 。

The length of the sample to be tested, which generally has a circular cross section and a diameter D, is 35mm. Which is arranged horizontally on two supports spaced apart by 24 mm. At the centre of the specimen, which is located in the middle of the two supports, repeated bending stresses are applied at right angles and with a vertical displacement of an amplitude equal to 0.1mm at a frequency of 10Hz (thus being asymmetrically deformed, the interior of the specimen being stressed only under compression and not under tension).

The following procedure was then applied: under this dynamic stress, the sample was gradually heated from 25 ℃ to 260 ℃ with a gradient of 2 ℃/min. At the end of the test, measurements of the elastic modulus E ', the viscous modulus E ", and the loss angle (δ) as a function of temperature are obtained (where E' is the real part of the complex modulus and E" is the imaginary part); tg' is the glass transition temperature corresponding to the maximum (peak) tan (δ).

Advantageously, the compressive elastic strain under bending is greater than 3.0%, more preferably greater than 3.5%, in particular greater than 4.0%. According to a preferred embodiment, the compressive fracture stress under bending is greater than 1050MPa, more preferably greater than 1200MPa, in particular greater than 1400MPa.

The above compressive bending properties were measured on CVR monofilaments as described in application EP 1 167 080 by a method called the loop test (D.Inclair, J.App.Phys.21,380,1950). In this case, the ring is prepared and gradually brought to its breaking point. The easily observable breaking properties due to the large size of the cross section make it possible to immediately perceive that the CVR monofilament of the present invention, which is stressed upon bending until it breaks, breaks on the side of the material that is being stretched, which can be identified by simple observation. Because of the large size of the ring in this case, the radius of the inscribed circle in the ring can be read at any time. The radius of the inscribed circle just before the breaking point corresponds to the critical radius of curvature indicated by Rc.

The following formula can then be calculated to determine the critical elastic strain expressed as Ec (where r corresponds to the radius of the monofilament, i.e. D/2):

Ec＝r/(Rc+r)。

the modulus of elongation is calculated using the formula (E is the initial tensile modulus) _c The compressive fracture stress under bending is shown:

σ _c ＝Ec*E。

since in the case of the CVR monofilament according to the invention the ring breaks at the portion under tension, it can be concluded that under bending the compressive breaking stress is greater than the tensile breaking stress.

Bending fracture of rectangular bars may also be performed by a method known as the three-point method (ASTM D790). This method also visually verifies that the nature of the break is indeed in tension.

Advantageously, the breaking stress under pure compression is greater than 700MPa, more preferably greater than 900MPa, in particular greater than 1100MPa. To avoid buckling of the CVR monofilament when compressed, this magnitude was measured according to the method described in Thompson et al, publication "Critical compressive stress for continuous fiber unidirectional composites" (Journal of Composite Materials,46 (26), 3231-3245).

Preferably, in the CVR monofilament of the present invention, the glass filaments are aligned to a degree that satisfies more than 85% (by number%) of the inclination of the filaments relative to the axis of the monofilament, measured as described in Thompson et al, above disclosure, is less than 2.0 degrees, more preferably less than 1.5 degrees. Also preferably, the CVR monofilament according to the present invention is free of spiral deformations, i.e. no distortions. In any case, the number of turns per meter of CVR monofilament is less than 5, preferably less than 2, preferably less than 0.5, preferably between 0 and 0.5.

Preferably, the weight content of glass fibres (i.e. filaments) in the CVR monofilament is in the range 65% to 85%, preferably 70% to 80%.

The weight content was calculated using the ratio of the initial glass fiber count to the final CVR monofilament count. Determining the yarn count (or linear density) by weighting the length over at least three samples, each sample corresponding to a length of 50 m; yarn count is given in tex (weight in grams of 1000m product, -0.111 tex equals 1 denier as a reminder).

In addition, the crosslinked resin represents 15 to 35 wt%, preferably 20 to 30 wt%, of the CVR monofilament of the present invention.

Preferably, the density (or mass per unit volume, in g/cm) of the CVR monofilament ³ Meter) is between 1.8 and 2.1. By means of a special balance of the "PG503 DeltaRange" type from Mettler Toledo (in23 ℃) density is measured; samples of several centimeters in sequence were weighed in air and immersed in ethanol, and the instrument software then determines the average density from the three measurements.

The diameter D of the CVR monofilament of the present invention is preferably in the range 0.25mm to 1.25mm, more preferably between 0.3mm to 1.2mm, in particular between 0.4mm to 1.1 mm.

This definition equally covers monofilaments of substantially cylindrical shape (with circular cross section) and monofilaments of other shapes, such as rectangular monofilaments (more or less flattened) or monofilaments with rectangular cross section. In the case of non-circular cross-sections, D is conventionally, unless otherwise specified, the diameter referred to as the gap diameter, i.e. the diameter of an imaginary rotating cylinder around the monofilament, in other words the diameter of an circumscribed circle around its cross-section.

Furthermore, the length L of the CVR monofilament of the present invention is preferably in the range of 10mm to 80mm, for example 15mm to 60 mm.

Advantageously, the CVR monofilament of the present invention has a length/diameter ratio L/D ranging from 10 to 110, for example from 11 to 90, for example from 12 to 75, preferably from 15 to 65, preferably from 20 to less than 60.

The resin used is by definition a crosslinkable (i.e. curable) resin which can be crosslinked, cured by any known method, in particular by ultraviolet (or ultraviolet-visible) radiation preferably emitted in a spectrum at least ranging from 300nm to 450 nm.

Advantageously, the cross-linked resin is based on:

a crosslinkable resin selected from the group consisting of vinyl esters (preferably polyurethane vinyl ester resins), epoxy resins, polyester resins and mixtures thereof,

-a crosslinking system, preferably comprising a photoinitiator reactive to ultraviolet light exceeding 300 nm.

It is understood that, in this context, the expression "exceeding" means "greater than".

When referring to "resin composition", this refers to the composition from which the resin is made, i.e. the composition before crosslinking.

As the crosslinkable resin, a polyester resin or a vinyl ester resin is preferably used, and a vinyl ester resin is more preferred. "polyester" resin is understood in a known manner to mean a resin of the unsaturated polyester type. As for the vinyl ester resin, it is well known in the composite field.

Without limitation to this limitation, the vinyl ester resin is preferably of the epoxy vinyl ester type. More preferably, vinyl ester resins of the type particularly epoxy resins, i.e. preferably based on phenolic resins, bisphenol or both phenolic and bisphenol, are used which are based at least in part on phenolic resins (also known as phenoplasts) and/or bisphenol (i.e. grafted onto structures of this type).

Preferably, the initial tensile modulus of the resin, measured at 23 ℃, is greater than 3.0GPa, more preferably greater than 3.5GPa.

Epoxy vinyl ester resins based on phenolic resins (the part between brackets in the following formula I) correspond, for example, in a known manner to the following formula (I):

Epoxy vinyl ester resins based on bisphenol a (the part between brackets in formula (II) below) correspond for example to the following formula ("a" serves to indicate that the product is prepared using acetone):

phenolic resins and bisphenol type epoxy vinyl ester resins show excellent results. As examples of such resins, mention may be made in particular of the vinyl ester resins "ATLAC 590" and "ATLAC E-Nova FW 2045" (diluted with about 40% styrene) from AOC company described in the abovementioned patent applications EP-A-1 074 369 and EP-A-1 174 250. Epoxy vinyl ester resins are available from other manufacturers, such as AOC (USA- "VIPEL" resins).

The crosslinking system used to impregnate the resin (resin composition) preferably comprises a photoinitiator that is sensitive (reactive) to ultraviolet radiation in excess of 300nm, preferably between 300nm and 450 nm. The photoinitiator is preferably used in an amount of 0.5% to 3%, more preferably 1% to 2.5%. Preferably, the resin crosslinking system further comprises a crosslinking agent, for example in an amount between 5% and 15% (by weight of the impregnating composition), the crosslinking agent being as defined above.

Preferably, the photoinitiator is a family of phosphine compounds, more preferably bis (acyl) phosphine oxides (e.g. bis (2, 4, 6-trimethylbenzoyl) phenylphosphine oxide (e.g. "Omnirad 819" from IGM or "speed cure BPO" from Lambson) or mono (acyl) phosphine oxides (e.g. "Esacure TPO" from IGM), such phosphine compounds may be used in combination with other photoinitiators, e.g. photoinitiators of the alpha-hydroxy ketone type, e.g. dimethylhydroxy acetophenone (e.g. "Omnirad 1173" from IGM) or 1-hydroxy cyclohexyl benzophenone (e.g. "Omnirad 1173" from IGM), benzophenone such as 2,4, 6-trimethylbenzophenone (e.g. "Esacure TZT" from IGM), and/or thioxanthone derivatives such as isopropylthioxanthone (e.g. "Esacure Omnirad ITX" from IGM).

The cross-linking agent is preferably selected from the triacrylate group.

The CVR monofilament can be prepared according to the method described in application WO 2015/014579 before the following steps: the filaments are cut to the desired length.

Accordingly, the present invention also relates to a method for manufacturing a glass-resin composite monofilament comprising glass filaments embedded in a crosslinked resin, comprising the following successive steps:

-creating a rectilinear arrangement of glass fibres (filaments) and conveying the arrangement in a feed direction;

-degassing the arranged glass filaments by the action of vacuum in a vacuum chamber;

-at the outlet of the vacuum chamber, after degassing, passing under vacuum through an impregnation chamber in order to impregnate the arranged glass filaments with a photocurable resin composition in liquid state (called "impregnating resin") so as to obtain a prepreg comprising glass filaments and a resin composition;

-passing the prepreg through a shaping die having a cross-section of predetermined area and shape, thereby forcing it into the form of a monofilament (e.g. a monofilament having a circular cross-section or a tape having a rectangular cross-section);

-polymerizing the resin downstream of the mould in an ultraviolet radiation chamber under the action of ultraviolet light;

-cutting the wire to obtain monofilaments having a length ranging from 5mm to 85 mm.

Advantageously, the polymerization is carried out in a radiant chamber comprising a tube transparent to ultraviolet rays (known as radiant tube) through which the formed filaments pass and through which a flow of inert gas passes, the speed of passage of the filaments in the radiant chamber (denoted V _ir ) Greater than 50m/min, the duration of irradiation of the filaments in the irradiation chamber (denoted as D _ir ) Equal to or greater than 1.5s.

Of course, the method may comprise a winding step for storing the filaments after they have passed through the ultraviolet radiation chamber and before they have been cut.

All the above-described steps of the process of the invention (laying, degassing, impregnating, shaping, polymerization, winding (where applicable) and cutting) are steps known to the person skilled in the art, as are the materials used (multifilament fibers and resin compositions); for example, they have been described in either or both of the above-mentioned two applications EP-A-1 074 369 and EP-A-1 174 250.

It is particularly recalled that the basic step of degassing the arranged fibres by the action of vacuum should be carried out before any impregnation of the fibres, in order to particularly increase the effect of the subsequent impregnation, most importantly to ensure that there are no bubbles in the finished composite filaments.

After passing through the vacuum chamber, the glass filaments enter an impregnation chamber which is completely filled with impregnating resin, and therefore free of air: this is the impregnation step which may be defined as "vacuum impregnation".

The mould, called a "shaping" mould, allows to adjust the ratio of resin with respect to glass fibres, thanks to its cross-section of determined dimensions (generally preferably circular or rectangular), and at the same time to impart the prepreg with the shape and thickness required for the filaments.

The polymerization chamber or ultraviolet radiation chamber has the function of polymerizing and crosslinking the resin under the action of ultraviolet rays. The ultraviolet radiation chamber comprises one or preferably a plurality of ultraviolet radiators, each of which is constituted by an ultraviolet lamp having a wavelength of 200nm to 600nm, for example.

The finished CVR monofilament thus formed by the uv radiation chamber, in which the resin is in the solid state at this time, is then recovered, for example, on a receiving spool, on which the finished CVR monofilament can be wound for extremely long lengths.

Between the shaping mould and the final receiving support, the tension to which the glass fibers are subjected is preferably kept at a moderate level, preferably between 0.2cN/tex and 2.0cN/tex, more preferably between 0.3cN/tex and 1.5 cN/tex; to control this level, these tensions may be measured directly at the outlet of the radiation chamber, for example by means of a suitable tensiometer known to a person skilled in the art.

Particularly advantageously, the method for manufacturing the CVR monofilament of the present invention comprises the following basic steps:

speed of the filaments through the irradiation chamber (V _ir ) Greater than 50m/min;

duration of filament passing through radiation chamber (D _ir ) Equal to or greater than 1.5s and equal to or less than 10s;

the radiation chamber comprises a tube transparent to ultraviolet light, such as a quartz tube or preferably a glass tube, called radiation tube, through which the formed filaments pass, the tube having a flow of inert gas (preferably nitrogen) flowing through it.

These steps in combination enable to achieve an improvement in the properties of the CVR monofilament of the invention, i.e. in particular in Tg, in elongation Ar and in modulus (E and E').

In particular, in the absence of purging with a neutral gas (such as nitrogen) in the radiant tube, it has been observed that the above-mentioned properties of the CVR monofilament deteriorate quite rapidly during the manufacturing process, so that the industrial properties are no longer guaranteed.

Furthermore, if a monofilamentDuration of irradiation D in irradiation chamber _ir Too short (less than 1.5 s), many tests showed (see below at different speeds V of greater than 50m/min _ir As a result of the tests performed below), either the Tg value is insufficient, below 190 ℃, or the Ar value is too low, below 4.0%. Furthermore, if the filament has a radiation duration D in the radiation chamber _ir Too long (e.g., greater than 10 s), this increases the risk of the resin boiling, thereby creating more voids and degrading mechanical properties (including fracture stress).

It is therefore understood that a CVR monofilament with a gap rate of less than 2% is obtained thanks to the combination of the process steps according to the invention, in particular to the following steps: degassing the glass filaments arranged in the vacuum chamber by the action of vacuum and at the above-mentioned velocity V in a radiant tube through which an inert gas flow passes _ir And the above-mentioned irradiation duration D _ir Polymerization was carried out as follows.

TABLE 1

It is also observed that a high radiation velocity V _ir (greater than 50m/min, preferably between 50m/min and 150 m/min) on the one hand facilitates a good alignment of the glass filaments inside the CVR filaments and on the other hand a better maintenance of the vacuum inside the vacuum chamber, significantly reducing the risk of a certain amount of impregnating resin returning from the impregnation chamber to the vacuum chamber, thus obtaining a better impregnation quality.

The diameter of the radiant tube (preferably made of glass) is preferably between 10mm and 80mm, more preferably between 20mm and 60 mm.

Preferably, the velocity V _ir Between 50m/min and 150m/min, more preferably in the range of 60m/min to 120 m/min.

Preferably, the duration of irradiation D _ir Between 1.5s and 10s, more preferablySelected in the range of 2s to 5 s.

Advantageously, the radiation chamber comprises a plurality of ultraviolet radiators (or radiators), i.e. at least two (two or more) ultraviolet radiators, which are arranged in a row around the radiation tube. Each uv radiator generally comprises one (at least one) uv lamp (preferably emitting in the spectrum of 200nm to 600 nm) and a parabolic reflector, the focal point of which is the centre of the radiant tube; it provides a linear power density preferably between 2000 watts/meter and 14000 watts/meter. Still more preferably, the radiation chamber comprises at least three, in particular at least four, rows of ultraviolet radiators.

Even more preferably, each ultraviolet radiator provides a linear power density of between 2500 watts/meter and 12000 watts/meter, in particular in the range of 3000 watts/meter to 10000 watts/meter.

UV-emitters suitable for use in the method of the invention are well known to those skilled in the art, for example by Dr.The AG company (Germany) sells a UV radiator with the reference number "1055LCP AM UK" and equipped with a "UVARINT" lamp (iron-doped high-pressure mercury lamp). The nominal (maximum) power of each radiator of this type is equal to about 13000 watts, and in practice the power output can be adjusted by the potentiometer between 30% and 100% of the nominal power.

Preferably, the temperature of the resin (resin composition) in the impregnation chamber is between 50 ℃ and 95 ℃, more preferably between 60 ℃ and 90 ℃.

According to another preferred embodiment, the irradiation conditions are adjusted such that the temperature of the CVR monofilament at the outlet of the impregnation chamber is greater than the Tg of the crosslinked resin; more preferably, the temperature is greater than the Tg of the crosslinked resin and less than 270 ℃.

Another subject of the invention is a CVR monofilament obtainable by the above process, in particular obtainable by a process comprising the following successive steps:

Preferably, wherein:

The diameter of the CVR monofilament is preferably in the range 0.2mm to 1.3 mm.

Embodiments of manufacturing a CVR monofilament according to the present invention and the use of a CVR monofilament as a reinforcement in a pneumatic tire casing will be described below.

Fig. 1 schematically shows in a very simple way an embodiment of an apparatus 10, said apparatus 10 being able to produce a CVR monofilament according to the invention.

In this figure, a reel 11a is visible, which in the embodiment shown comprises glass fibres 11b (in the form of multifilaments). The reel is continuously unwound by driving, resulting in a rectilinear arrangement 12 of these fibres 11 b. Typically, the reinforcing fibers are conveyed in the form of "rovings", i.e. groups of fibers that have been wound in parallel on reels; for example, a fiber sold under the fiber name "Advantex" by Owens Corning is used, wherein the count is equal to 1200 tex (as reminder, 1 tex=1 gram per 1000 meters fiber). For example, the traction applied by the rotary receiver 26 will advance the fibers in parallel and advance the CVR monofilament along the entire length of the facility 1.

This arrangement 12 is then passed through a vacuum chamber 13 (connected to a vacuum pump, not shown), said vacuum chamber 13 being provided between an inlet pipe 13a and an outlet pipe 13b leading to the impregnation chamber 14, both pipes preferably having rigid walls with a minimum cross section, for example greater than the total cross section of the fibre (typically twice) and a length much greater than said minimum cross section (typically 50 times).

As already taught in the above-mentioned application EP-a-1 174 250, the use of a tube with rigid walls for the inlet to and outlet from the vacuum chamber and the transfer from the vacuum chamber to the impregnation chamber has proved to match the high passage speed of the fibers through the openings at the same time without breaking the fibers and also to ensure a sufficient seal. Given the advancing speed of the fibers and the length of the tube, it is necessary (if experimentally necessary) to find the maximum passage section that still allows adequate sealing to be achieved, taking into account the total section of the fibers to be treated. Typically, the vacuum in the chamber 13 is for example about 0.1 bar and the length of the vacuum chamber is about 1 meter.

Upon exiting the vacuum chamber 13 and the outlet pipe 13b, the arrangement 12 of fibers 11b is passed through an impregnation chamber 14, said impregnation chamber 14 comprising a feed tank 15 (connected to a metering pump, not depicted) and a sealed impregnation tank 16, said impregnation tank 16 being completely filled with an impregnation composition 17 based on a curable resin of the vinyl ester type (for example "from AOC" E-Nova FW 2045 "). For example, composition 17 further comprises (at a weight content of 1% to 2%) light suitable for UV-radiation and/or UV-visible radiation for subsequent treatment of the compositionAn initiator such as bis (2, 4, 6-trimethylbenzoyl) phenylphosphine oxide (from "Omnirad 819" from IGM corporation). Composition 17 may also include (e.g., about 5% to 15%) a crosslinker, such as tris (2-hydroxyethyl) isocyanurate triacrylate ("SR 368" from Sartomer company). Of course, the impregnating composition 17 is in a liquid state.

Preferably, the impregnation chamber has a length of several meters, for example a length of between 2m and 10m, in particular between 3m and 5 m.

Thus, a prepreg comprising, for example (in weight%) 65 to 75% of the solid fibres 11b and the remainder (25 to 35%) formed by the liquid impregnating matrix 17 leaves the impregnation chamber 14 in the sealed outlet tube 18 (still under a low vacuum).

The prepreg is then passed through a shaping device 19, which shaping device 19 comprises at least one shaping mould 20, the channels (not shown here) of which shaping mould 120, for example, are circular, rectangular or even conical in shape, being adapted to the specific implementation conditions. For example, the channel has a circular shape with a minimum cross section and a downstream orifice having a diameter slightly larger than the diameter of the target monofilament. The length of the mould is typically at least 100 times the smallest dimension of the smallest cross section. The purpose is to make the finished product have good dimensional accuracy; it can also be used to gauge the content of fibers relative to the resin. According to a possible alternative of embodiment, the mould 20 may be incorporated directly into the impregnation chamber 14, so that for example the use of an outlet pipe 18 is not required.

Preferably, the shaping region has a length of several centimeters, for example a length of between 5cm and 50cm, in particular between 5cm and 20 cm.

By means of the shaping means (19, 20) a "liquid" composite monofilament 21 (liquid meaning that the impregnating resin thereof is still liquid) is obtained, the cross-sectional shape of said composite monofilament 21 preferably being substantially circular.

At the outlet of the shaping device (19, 20), the liquid composite filaments 21 obtained in this way are then polymerized by passing through an ultraviolet radiation chamber (22), said ultraviolet radiation chamber (22) comprising a sealed glass tube (23) through which the composite filaments pass; diameter ofTypically a few centimeters (e.g. 2cm to 3 cm) of said tube is lined up with a plurality (here e.g. 4) of ultraviolet radiators (24) (from Dr) at a short distance (few cm) from the glass tube."UVAPRINT" lamp, having a wavelength of 200nm to 600 nm).

Preferably, the radiation chamber has a length of several meters, for example a length between 2m and 15m, in particular between 3m and 10 m.

In this embodiment, the radiant tube (23) has a flow of nitrogen flowing through the radiant tube (23).

The irradiation conditions are preferably adjusted such that at the outlet of the impregnation chamber the temperature of the CVR monofilament measured at its surface (e.g. by a thermocouple) is greater than the Tg of the crosslinked resin (in other words greater than 190 ℃) and more preferably less than 270 ℃.

Once the resin has polymerized (cured), the CVR monofilament (25), now in solid state, is transferred in the direction of arrow F and then reaches the final receiving reel (26).

Finally, the finished composite block produced as very simply depicted in fig. 2 is obtained in the form of extremely long continuous CVR filaments (25), the individual glass filaments (251) of said CVR filaments (25) being uniformly distributed throughout the volume of cured resin (252). For example, equal to about 1mm in diameter.

By means of the above-mentioned operating conditions, the process according to the invention can be carried out at high speeds of more than 50m/min, preferably between 50m/min and 150m/min, more preferably in the range from 60m/min to 120 m/min.

The continuous CVR monofilament (25) may be cut to a determined length (not shown in FIG. 1), for example 45mm, by any method known to those skilled in the art, for example using a hydraulic cutter (such as "SH-5214" from Baileigh). This step may be performed directly at the outlet of the radiation chamber (23). It may also be performed after being packaged on the final receiving reel (26). In this case, it is preferable to unwind the monofilament from the reel from the axially most distal end of the monofilament toward the outside of the reel to avoid spiral deformation of the monofilament. In practice, if the monofilament is unwound from the reel from the axially most distal end of the monofilament towards the inside of the reel, this causes a helical deformation of the monofilament, which is disadvantageous for the breaking stress.

The invention also relates to a tow comprising a plurality of CVR filaments according to the invention and at least one element for holding the filaments together. Preferably, such a holding element is a rupturable membrane, such as a tearable, dispersible, water soluble membrane. Preferably, the at least one retaining element is a water-soluble thread.

Advantageously, the holding element is a water-soluble film, preferably made of a material selected from the group consisting of polyvinyl alcohol (PVA) or any water-soluble or bio-plastic polymer, such as bio-plastic derived from milk casein. Preferably, the at least one water-soluble film is made of a material selected from polyvinyl alcohols.

The filament bundle according to the invention advantageously comprises a number of filaments in the range of 300 to 20000.

The filaments comprising the tow may be of the same or different sizes. For example, the tow may include monofilaments of different lengths, diameters, and/or length to diameter ratios. Advantageously, the filament bundles comprise filaments according to the invention which differ from each other by not more than 10%, preferably not more than 3%, in length and diameter.

As mentioned before, the monofilaments according to the invention are particularly useful as additives for concrete. The invention therefore also relates to the use of the CVR monofilament according to the invention or the tow according to the invention for reinforcing and/or lightening concrete and/or reducing or preventing cracking of concrete.

Another subject of the invention is also a concrete comprising a plurality of CVR monofilaments according to the invention. The concrete may be prepared by any technique known to those skilled in the art.

Advantageously, the volume content of the monofilaments according to the invention in the concrete according to the invention is in the range of 0.1% to 6%, for example 0.1% to 1.5% for a concrete of the so-called "conventional" type (e.g. a concrete of the BPS C40/50 XA3 type with specific properties) or 1.5% to 6% for ultra-high performance fiber reinforced concrete (UHPFRC).

IV-example

Measurement and test for IV-1 use

Porosity was measured according to the following protocol:

-obtaining a cross-linked CVR monofilament,

coating the CVR monofilament with an epoxy type cold coating resin in a vacuum coating apparatus (CitoVac from Stuers company),

cutting the coated CVR monofilament using a hydraulic cutter (SH-5214 from Baileigh),

polishing the cross section of the CVR monofilament to a final grain surface of 0.25 μm using a mechanical polisher from Mecapol company,

using a gold sputter coater (fromA company series-108 or-208 Cressington coater) applied gold at 1nm to 4 nm; />

-observing the cross section of the CVR monofilament under vacuum with a (15 kV) scanning electron microscope; and

Using an image processing program (e.g. FIJI), the surface percentage of pores (porosity% = area of pores/(area of pores + area of fibres + area of crosslinked resin) is calculated.

Using an INSTRON 5944 tensile testing machineUNIVERSAL software was equipped with a tensile tester) to measure the tensile mechanical properties (modulus E) of a coated (i.e., ready-to-use) CVR monofilament at a temperature of 23 ℃ according to standard ASTM D2343 ₂₃ Stress at break Cr and elongation at break Ar). To prevent damage to the glass reinforcement when gripping the sample in the jaws of the tensile tester, the ends were attached (material: cardboard 50mm long; adhesive used: loctite EA 9483 (two-component epoxy)). The surfaces of the two facing ends are coated with adhesive, like reinforcements, to limit any "dry areas" (areas without adhesive) as much as possible. At the curing timeInside (12 hours at 23 ℃) the ends were fixed in clamps of sample size, with weights on the ends to ensure good bead/reinforcement contact. Before measurement, these monofilaments are subjected to preconditioning (the monofilaments are stored for at least 24 hours under a standard atmosphere (temperature 23.+ -. 2 ℃ C.; relative humidity 50.+ -. 5%) according to European standard DIN EN 20139). The tensile modulus is determined by linear regression of the stress versus strain (between 0.1% and 0.6% strain) curve. The strain is recorded by extensometer MultiXtens 1995DA 801. The 260mm specimen tested was pulled at a nominal speed of 5m/min (reference length 50mm, distance between jaws: 150 mm) under a preload of 0.5MPa prior to testing. All results given are the average of 10 measurements.

IV-2 testing of monofilaments

CVR monofilaments (M1 to M4) were produced according to the method described above, with a glass/resin mass percentage of 70/30. The resin composition used was based on a vinyl ester resin (from company "ATLAC E-NOVA FW 2045"), a triacrylate curing agent (from Sartomer company "SR 368"), and a photoinitiator (from IGM company "Omnirad 819"). The glass fibers of monofilaments M1 and M2 are "R25H" fibers from Owens Corning, and the glass fibers of monofilaments M3 and M4 are "SE1200" fibers from Owens Corning. The diameter of the filaments and tex and their physical and mechanical properties are listed in table 2 below.

TABLE 2

The porosity and breaking stress of these monofilaments were compared to prior art reinforcing fibers for concrete. The fibers of the prior art were observed to systematically have a porosity of greater than 2% and a fracture stress of less than or equal to 1050 MPa.

The monofilaments of the present invention can improve crack resistance of concrete because of their low porosity and high breaking stress.

It has thus been found that the monofilaments according to the invention provide a performance compromise between in particular mechanical strength, corrosion resistance, processability (in particular dispersibility during mixing, processing temperature and maintenance of uniformity during drying of the concrete).

Claims

1. A glass-resin composite monofilament comprising glass filaments embedded in a crosslinked resin, characterized in that: the monofilaments have a length in the range of 5mm to 85mm, a diameter in the range of 0.2mm to 1.3mm, and a porosity of less than 2%.

2. The monofilament according to claim 1, having a length in the range of 10mm to 80 mm.

3. The monofilament according to any of the preceding claims, having a diameter in the range of 0.25mm to 1.25mm, preferably 0.3mm to 1.2 mm.

4. The monofilament according to any of the preceding claims, having a length/diameter ratio ranging from 10 to 110, preferably from 15 to 65, still more preferably from 20 to less than 60.

5. The monofilament according to any of the preceding claims, which is free of spiral deformations.

6. A monofilament according to any of the preceding claims, wherein the glass filaments constitute 65 to 85 wt%, preferably 70 to 80 wt% of the monofilament and the cross-linked resin constitutes 15 to 35 wt%, preferably 20 to 30 wt% of the monofilament.

7. The monofilament according to any of the preceding claims, wherein the crosslinked resin is based on:

A crosslinkable resin selected from the group consisting of vinyl esters, epoxy resins, polyester resins and mixtures thereof,

-a crosslinking system comprising a photoinitiator reactive to ultraviolet light exceeding 300 nm.

8. The monofilament according to any of the preceding claims, having a porosity of less than 1%, preferably less than 0.5%.

9. The monofilament according to any of the preceding claims, having a stress at break of greater than 1050MPa, preferably greater than or equal to 1100MPa, more preferably greater than or equal to 1200MPa.

10. A monofilament according to any of the preceding claims, wherein the monofilament, measured at 23 ℃, is denoted E ₂₃ The initial tensile modulus of (a) is greater than 35GPa, preferably greater than 42GPa.

11. Tow comprising a plurality of glass-resin composite filaments according to any one of claims 1 to 10, comprising glass filaments embedded in a cross-linked resin, and at least one rupturable membrane holding the filaments together, preferably a water-soluble membrane made of a material selected from the group consisting of polyvinyl alcohol (PVA).

12. The tow according to claim 11, wherein the number of filaments is in the range of 300 to 20000.

13. Use of a glass-resin composite monofilament according to any one of claims 1 to 10 or a tow according to any one of claims 11 to 12 for reinforcing and/or reducing the weight of concrete and/or reducing or preventing cracking of concrete, the glass-resin composite monofilament comprising glass filaments embedded in a cross-linked resin.

14. Concrete comprising a plurality of glass-resin composite filaments according to any one of claims 1 to 10, said glass-resin composite filaments comprising glass filaments embedded in a cross-linked resin, the volume ratio of filaments in the concrete preferably being in the range of 0.1% to 6%.

15. A method for manufacturing a glass-resin composite monofilament according to any one of claims 1 to 10, comprising glass filaments embedded in a crosslinked resin, the method comprising the following successive steps:

creating a rectilinear arrangement of glass filaments and transporting the arrangement in a feed direction,

degassing the arranged glass filaments by the action of vacuum in a vacuum chamber,

at the outlet of the vacuum chamber, after degassing, passing under vacuum through an impregnation chamber for impregnating the arranged glass filaments with a photocurable or thermosetting resin composition called "impregnating resin" in liquid state, thus obtaining a prepreg comprising glass filaments and resin composition,

Passing the prepreg through a shaping die having a cross-section of predetermined area and shape, thereby causing it to take the form of a monofilament,

downstream of the mould, the resin composition is polymerized by the action of ultraviolet rays in an ultraviolet radiation chamber comprising a tube transparent to ultraviolet rays, called a radiant tube, through which the formed filaments pass, and through which a flow of inert gas passes, the speed of passage of the filaments in the radiation chamber (denoted V _ir ) Greater than 50m/min, the duration of irradiation of the filaments in the irradiation chamber (denoted as D _ir ) Equal to or greater than 1.5s,