Method for improving the alkali resistance of a substrate

Abstract

The present invention relates in particular to a method for improving the resistance to alkalis of a support, in particular a single strand of filament-resin composite comprising filaments embedded in a cross-linked resin, comprising a plasma treatment step for applying at least one organosilicon compound to the surface of the support, the organosilicon compound not comprising any atom other than silicon, carbon, hydrogen and oxygen.

Description

Title of the invention: Method for improving the alkali resistance of a substrate. Technical field

[0001] The present invention relates to improving the alkali resistance of a substrate, such as a single strand of filament-resin composite. It has applications particularly for strengthening concrete, but also for reducing the weight of concrete, and for reducing or preventing cracking in concrete.

[0002] Concrete is probably the most widely used construction material today due to its high compressive strength, durability, longevity, and resilience. Its properties make it a material of choice, particularly in the fields of building construction, roadworks, and civil engineering structures.

[0003] Concrete is mainly composed of aggregates held together by a binder, most often Portland cement. To improve the properties of concrete, it is known to use additives such as ultrafine particles (silica fume, for example), superplasticizers also called water reducers, or metallic, synthetic, or mineral fibers.

[0004] Although very resistant to compression, concrete has low tensile strength, often accompanied by the appearance of cracks.

[0005] To combat this problem, various approaches have been explored. In particular, the use of reinforcing fibers is known, due to their advantageous mechanical properties. Reinforcing fibers are thus widely used to make concrete more ductile and improve its resistance to cracking.

[0006] However, metallic fibers have the disadvantage of being susceptible to corrosion, which can be detrimental to the longevity of concrete containing such fibers. Furthermore, they often have densities greater than 7.7 and are therefore not distributed homogeneously in concrete with a lower density (metal fibers tend to sink under the effect of gravity, or even under the effect of vibrations when the concrete is vibrated to remove air bubbles that may have been drawn in during pouring).

[0007] To address this problem, it has been proposed to replace metallic fibers with synthetic fibers. However, the mechanical strength (Young's modulus, tensile strength, for example) of these fibers is not as good as that of metallic fibers. Furthermore, their operating temperature (generally between 100°C and 160°C) is much lower than that of the fibers metallic (between approximately 600°C and 900°C), which may limit their use for certain applications.

[0008] It should also be noted that concrete is an alkaline medium. Therefore, it remains advantageous to have a substrate that exhibits good resistance to alkalis.

[0009] The Applicant unexpectedly discovered that a plasma treatment step to apply a particular compound to a support improved the resistance of said support to alkalis. Description of the invention

[0010] The present invention relates to a method for improving the resistance to alkalis of a support comprising a plasma treatment step for applying at least one organosilicon compound to the surface of the support, the organosilicon compound not comprising any atom other than silicon, carbon, hydrogen and oxygen.

[0011] The invention also relates to a method for manufacturing at least one single strand of filament-resin composite comprising filaments embedded in a crosslinked resin comprising the following steps:

[0012] a) to create a straight arrangement of filaments and to drive this arrangement in a direction of advancement;

[0013] b) bringing said arrangement of filaments into contact with a photocurable resin composition, in liquid state, referred to as impregnation resin, to obtain an impregnated containing the filaments and the resin composition;

[0014] c) passing said impregnated material through a calibration die having a predefined surface area and shape section, to impose on it a single-strand shape;

[0015] d) downstream of the die, in a crosslinking chamber, polymerize the resin composition under the action of ultraviolet or visible radiation, the crosslinking chamber comprising a tube transparent to ultraviolet or visible light, called a crosslinking tube, through which the single strand being formed passes;

[0016] e) subject the monostrand obtained in step (d) to plasma treatment to apply at least one organosilicon compound to the surface of the straight arrangement of filaments, the organosilicon compound not comprising any atom other than silicon, carbon, hydrogen and oxygen.

[0017] The invention also relates to a single strand that can be obtained by the and / or the processes according to the invention, as well as a single strand in filament-resin composite comprising filaments embedded in a cross-linked resin.

[0018] Another object of the invention is the use of at least one monostrand according to the invention to reinforce concrete and / or reduce the weight of concrete and / or reduce or prevent cracking of concrete, as well as the use of at least one compound organosilicon not comprising any atom other than silicon, carbon, hydrogen and oxygen, to improve the resistance to alkalis of a support.

[0019] In this application, unless expressly stated otherwise, all percentages (%) indicated are percentages (%) by mass.

[0020] The expression "composition based on" means a composition comprising the mixture and / or the in situ reaction product of the different constituents used, some of these constituents being able to react and / or being intended to react with each other, at least partially, during the different phases of manufacturing the composition; the composition can thus be in a totally or partially crosslinked state or in a non-crosslinked state.

[0021] By "embedded", it is understood that the reinforcing element is directly in contact with the resin composition over its entire surface, with the possible exception of the cutting areas of the composite.

[0022] By "resin composition", we mean here the resin as such or any composition based on this resin and comprising at least one additive (i.e. one or more additives) before crosslinking.

[0023] By "crosslinked" resin, it is understood that the resin is hardened (photocured and / or thermocured), in other words in the form of a network of three-dimensional bonds, in a state characteristic of so-called thermosetting polymers (as opposed to so-called thermoplastic polymers).

[0024] In this application, the term "fibre" is equivalent to the term "monofrain". Thus, the two terms may be used interchangeably.

[0025] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​from greater than a to less than b (i.e., excluding the bounds a and b), while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​from a to b (i.e., including the strict bounds a and b). In the present case, when an interval of values ​​is designated by the expression "from a to b", the interval represented by the expression "between a and b" is also and preferably designated. Brief description of the figures

[0026] [Fig-1] Fig. 1 represents a diagram of the process for synthesizing a single strand in fiber-resin composite.

[0027] [Fig.2] Fig.2, not shown to scale for ease of understanding, is a drawing representing a cross-section of a monostrand in fibre-resin composite. Description of the invention

[0028] As previously stated, an organosilicon compound is applied to the surface of a support, said organosilicon compound not comprising any atom other than silicon, carbon, hydrogen and oxygen.

[0029] Preferably, the support is a monostrand made of filament-resin composite comprising filaments embedded in a crosslinked resin.

[0030] Furthermore, the invention relates to a method for manufacturing at least one single strand of filament-resin composite comprising filaments embedded in a cross-linked resin, as defined above.

[0031] In each of the two processes according to the invention, a plasma treatment step is implemented.

[0032] Plasma treatment is carried out to apply to said support at least one organosilicon compound comprising no atom other than silicon, carbon, hydrogen and oxygen.

[0033] Advantageously, this application can be carried out using a device capable of implementing a plasma jet with organosilicon precursors at atmospheric pressure.

[0034] By "atmospheric pressure", it is meant here that the pressure corresponds approximately to that of the surrounding environment.

[0035] The term distinguishes current plasma technology from low and high pressure plasma technologies which require a reaction vessel to maintain a substantial pressure difference with the environment.

[0036] A person skilled in the art, a specialist in plasma technology, therefore understands that "atmospheric pressure" should not be interpreted as the pressure unit "atm" defined as being equal to 101,325 Pa.

[0037] By "plasma jet" we mean here a plasma jet and / or a plasma jet afterglow.

[0038] This method of application is well known to those skilled in the art; it was, for example, described in application EP 3 586 954 AL

[0039] Advantageously, the process for manufacturing at least one monostrand of filament-resin composite further includes f) a step of cutting the monostrand obtained in step (e), preferably to a length of 5 to 85 mm, to obtain cut monostrands.

[0040] Particularly advantageously, the process for manufacturing said single strand comprises the following steps:

[0041] - the speed (Vir) of passage of the single strand through the irradiation chamber is greater at 50 m / min;

[0042] - the duration (Dir) of passage of the single strand in the irradiation chamber is equal to or greater than 1 s and equal to or less than 10 s;

[0043] - the irradiation chamber comprises a UV-transparent tube (such as a UV-transparent tube) quartz or preferably glass), called irradiation tube, through which the single strand being formed circulates, this tube being traversed by a current of inert gas, preferably nitrogen.

[0044] All the steps (arrangement, degassing, impregnation, calibration, polymerization, possible winding and cutting) of the process of the invention are, independently of each other, steps known to the person skilled in the art, as well as the materials (multifilament fibers and resin compositions) used; they have for example been described in one and / or the other of applications EP 1 074 369 Al and EP 1 174 250 Al.

[0045] The photocurable resin can be any resin capable of crosslinking in the presence of a photoinitiator under the action of light radiation, in particular ultraviolet or visible light. Preferably, the photocurable resin is a UV-curable resin.

[0046] The photocurable resin is advantageously chosen from the group consisting of vinyl ester, epoxy, polyester, novolac resins and their mixtures, preferably from the group consisting of vinyl ester, epoxy resins and their mixtures, and even more preferably from the group consisting of vinyl ester resins and their mixtures. As is known to those skilled in the art, these photocurable resins may contain a diluent, such as styrene, at a concentration of up to approximately 40% by weight of the photocurable resin. Commercially available photocurable resins are often sold diluted.

[0047] The term "polyester" resin is commonly understood to mean an unsaturated polyester resin. "Vinylester" resins, on the other hand, are well known in the field of composite materials.

[0048] Without this definition being limiting, the vinyl ester resin is preferably of the epoxy vinyl ester type. A vinyl ester resin, in particular of the epoxy type, is more preferably used, which at least in part is based on (i.e. grafted onto a structure of the type) novolac (also called phenoplast) and / or bisphenolic, or preferably a vinyl ester resin based on novolac, bisphenolic, or novolac and bisphenolic.

[0049] A novolac-based epoxyvinylester resin (part in brackets in formula I below) corresponds, for example, in a known manner, to the following formula (I):

[0050] A bisphenol A-based epoxyvinylester resin (part in brackets of formula (II) below) corresponds, for example, to the formula (the "A" indicating that the product is manufactured using acetone): he

[0051] A novolac and bisphenolic type epoxyvinylester resin has shown excellent results. As an example of such a resin, the vinyl ester resins "ATLAC 590" and "ATLAC E-Nova FW 2045" from the company AOC (diluted with about 40% styrene) described in applications EP-A-1 074 369 and EP-A-1 174 250 may be cited in particular.

[0052] The proportion of photocurable resin in the resin composition may be in the range of 80% to 99.5% by weight, preferably more than 94.5% to 99% by weight, and more preferably more than 96% to 99% by weight, relative to the total weight of the resin composition. When the photocurable resin includes a diluent, the aforementioned proportions of photocurable resin include said diluent.

[0053] As is known, a photoinitiator is a molecule that creates reactive species such as free radicals, cations, or anions when exposed to ultraviolet or visible radiation. Particularly advantageously, the photocurable resin is a UV-curable resin, and the photoinitiator is a UV-reactive photoinitiator above 300 nm, preferably between 300 and 450 nm.

[0054] For the purposes of the invention, particularly when the photocurable resin is chosen from the group consisting of vinyl ester, epoxy, polyester, novolac resins and mixtures thereof, the photoinitiator is preferably chosen from the group consisting of type I photoinitiators and mixtures thereof. The photoinitiator may also be a photoinitiator that is not a type I photoinitiator, for example a type II or other photoinitiator, but this is not preferred.

[0055] Type I photoinitiators are selected from the group consisting of benzoin ethers, benzyl ketals, alpha-dialkoxyacetophenones, alpha-hydrodyalkylphenones, alpha-aminoalkylphenones, phosphine oxides, and mixtures thereof. Preferably, the photoinitiating agent is selected from the group consisting of phosphine oxides and mixtures thereof. The phosphine oxide may advantageously be a bis(acyl)phosphine oxide.

[0056] As an example of a photoinitiating agent that can be used in the context of the present invention, bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide may be cited. (e.g., IGM's "Omnirad 819" or Lambson's "speedcureBPO") or mono(acyl)phosphine oxide (e.g., IGM's "Esacure TPO"), such phosphine compounds being able to be used in mixture with other photoinitiators, e.g. alpha-hydroxy-ketone type photoinitiators such as dimethylhydroxy-acetophenone (e.g., IGM's "Omnirad 1173") or 1-hydroxy-cyclohexyl-phenyl-ketone (e.g., IGM's "Omnirad 184"), benzophenones such as 2,4,6-trimethylbenzophenone (e.g., IGM's "Esacure TZT") and / or thioxanthone derivatives such as isopropylthioxanthone (e.g., IGM's "Esacure Omnirad ITX").

[0057] The rate of photoinitiator agent is advantageously within a range of 0.5% to 3% by weight, preferably 1% to 2.5% by weight, preferably 1% to 2% by weight, relative to the total weight of the resin composition.

[0058] The filaments can be chosen from the group consisting of glass, basalt, polyester filaments, and their combinations, preferably from the group consisting of glass filaments.

[0059] Thus, preferably, the monostrand is made of glass-resin composite (abbreviated “CVR”).

[0060] By way of example of fibre usable within the framework of the present invention, we may mention the glass fibre “R25H” or “SE 1200” of Owens Corning, the alkali-resistant glass fibre “AR320S-920S”, “AR640S-920S” or “AR1200S-920S” of Nippon Electric Glass or “Cem-fil” of Owens Corning, the basalt fibre “KVT400TEX14LKV41” of Basaltex, “FilvaTM” of Isomatex, the carbon fibre* HTS40” of Teijin or “ZOLTEK PX35” of Zoltek. The skilled craftsman knows very well how to adapt the sizing to the surface of the filaments to improve the compatibility of the filaments with the resin used in the mineral-resin composite, in particular with the help of a silane-type compatibilizing agent.

[0061] The filaments advantageously represent 60% to 85%, preferably 70% to 80%, by weight of the monostrand in fiber-resin composite and the resin composition represents 15% to 40%, preferably 20% to 30%, by weight, of the monostrand in fiber-resin composite.

[0062] The weight percentage of the filaments is calculated by dividing the initial fiber count by the final monofilament count. The count (or linear density) is determined on at least three samples, each corresponding to a length of 50 m, by weighing this length; the count is given in tex (weight in grams of 1000 m of product – as a reminder, 0.111 tex is equivalent to 1 denier). The weight percentage of crosslinked resin can be obtained by calculating the difference between the final monofilament count and the initial fiber count.

[0063] Typically, the filaments are present in the form of a single multifilament fiber or several multifilament fibers joined together. In the latter case, the multifilament fibers are preferably essentially unidirectional. Each of the multifilament fibers may comprise several dozen, hundreds, or even thousands of individual glass filaments.

[0064] Advantageously, the filaments each have an average diameter ranging from 5 to 30 pm, more preferably from 10 to 20 pm.

[0065] The single strand advantageously has a diameter ranging from 0.2 to 1.3 mm, preferably from 0.25 to 1.25 mm, more preferably from 0.3 to 1.2 mm.

[0066] The average diameter covers both monofilaments of essentially cylindrical shape (with a circular cross-section) and monofilaments of different shapes, for example, oblong monofilaments (with a more or less flattened shape) or those with a rectangular cross-section. In the case of a non-circular cross-section, and unless otherwise specified, the average diameter is by convention the so-called overall diameter, that is to say, the diameter of the imaginary cylinder of revolution enclosing the monofilament, in other words, the diameter of the circumscribed circle surrounding its cross-section.

[0067] The monostrand in fibre-resin composite advantageously has a length ranging from 10 to 80 mm, preferably from 15 to 60 mm.

[0068] The cut monostrand advantageously has a length / diameter ratio of 10 to 110, preferably from 20 to 90, more preferably from 25 to less than 80.

[0069] The glass transition temperature (Tg) of the crosslinked resin is preferably greater than 175°C, preferably greater than 180°C, in particular greater than 185°C. It is measured in a known manner by DSC (Differential Scanning Calorimetry), on the second pass, for example and unless otherwise specified in this application, according to ASTM D3418 of 1999 (Mettler Toledo "822-2" DSC apparatus; nitrogen atmosphere; samples previously heated from room temperature (23°C) to 250°C (10°C / min), then rapidly cooled to 23°C, before final recording of the DSC curve from 23°C to 250°C, according to a ramp of 10°C / min).

[0070] As previously stated, said organosilicon compound does not comprise any atom other than silicon, carbon, hydrogen and oxygen.

[0071] Advantageously, the organosilicon compound is chosen from the group consisting of compounds of formula RxSi-(OR')(4x) (I), Rij2j3Si-[O-SiR4j5j6]n (II) and their mixtures,

[0072] - formula (I) in which:

[0073] * R represents a Ci-C4 hydrocarbon group, preferably a group C2-C3 alkenyl;

[0074] * R' represents a hydrocarbon group in Ci-C4, preferably in Ci-C2;

[0075] * x is an integer from 1 to 3;

[0076] - formula (II) in which:

[0077] * Rb R2, R3, R4, R5, R6, whether identical or different, represent H or a grouping hydrocarbon in C1-C4, preferably in Ci-C2, provided that at least 4 of the groups among Rb R2, R3, R4, R5, R6 represent a hydrocarbon group in C1-C4, preferably at least 2 of the groups among Rb R2, R3, R4, R5, R6 designate H;

[0078] * n is an integer from 1 to 3, preferably n is equal to 1.

[0079] Advantageously, the organosilicon compound is chosen from the group consisting of 1,1,3,3-tetramethyldisiloxane, trimethoxyvinylsilane and their mixture.

[0080] Advantageously, the crosslinked resin is based on at least:

[0081] - a photocurable resin selected from the group consisting of resins vinylester, epoxy, polyester, novolac and their mixtures, preferably in the group consisting of vinylester resins, epoxy and their mixtures;

[0082] - a crosslinking system comprising a photoinitiator agent.

[0083] Preferably, the photoinitiating agent is as defined above.

[0084] The crosslinked resin may further comprise a crosslinking agent other than the photoinitiator agent.

[0085] The crosslinking agent is preferably chosen from the group consisting of the family of triacrylates.

[0086] Advantageously, the rate of crosslinking agent other than the photoinitiator is in the range of 0% to 15% by weight, preferably from 0% to 4% by weight relative to the weight of the crosslinked resin.

[0087] Another object of the invention is a single strand capable of being obtained by the process and / or processes according to the invention, as well as a single strand in filament-resin composite comprising filaments embedded in a cross-linked resin, the single strand being covered at least partially, preferably totally, with at least one organosilicon compound, said organosilicon compound not comprising any atom other than silicon, carbon, hydrogen and oxygen.

[0088] The different embodiments described above in the context of the processes are applicable to single strands.

[0089] Advantageously, the organosilicon compound(s) form a layer with a thickness ranging from 2 to 500 nm, preferably from 5 to 50 nm, on the surface of the filaments of the single strand.

[0090] The invention also relates to the use of at least one monostrand to reinforce concrete and / or reduce the weight of concrete and / or reduce or prevent cracking of concrete, and also to the use of at least one organosilicon compound not comprising any atom other than silicon, carbon, hydrogen and oxygen to improve the resistance to alkalis of a support, the support preferably being a monostrand of filament-resin composite comprising filaments embedded in a cross-linked resin.

[0091] The different embodiments described above in the context of the processes are applicable for the use of at least one monostrand and the use of at least one organosilicon compound.

[0092] The attached [Fig.1] schematically illustrates very simply an example of a device 10 enabling the production of single strands in CVR.

[0093] A reel lia is shown containing, in the illustrated example, glass fibers 11b (in the form of multifilaments). The reel is continuously unwound by drive, so as to create a straight arrangement 12 of these fibers 11b. Generally, reinforcing fibers are supplied as "rovings," that is, already in groups of fibers wound in parallel on a reel; for example, fibers marketed by Owens Corning under the designation "Advantex" fiber, with a count of 1200 tex (as a reminder, 1 tex = 1 g / 1000 m of fiber), are used. It is, for example, the tension exerted by the rotating receiver 26 that will allow the parallel fibers and the single strand in CVR to advance along the entire length of the installation 1.

[0094] This arrangement 12 then passes through a vacuum chamber 13 (connected to a vacuum pump not shown), disposed between an inlet tube 13a and an outlet tube 13b opening into an impregnation chamber 14, the two tubes preferably having rigid walls having for example a minimum cross-section greater (typically twice as much) than the total cross-section of fibers and a length much greater (typically 50 times more) than said minimum cross-section.

[0095] As already demonstrated by PPE application 174250A1, the use of rigid-walled tubing, both for the inlet orifice in the vacuum chamber and for the outlet orifice of the vacuum chamber and for the transfer from the vacuum chamber to the impregnation chamber, proves compatible with high fiber flow rates through the orifices without breaking the fibers, while also ensuring sufficient sealing. If necessary, experimentally, it is sufficient to determine the largest possible cross-sectional area, given the total cross-section of the fibers to be treated, that still provides sufficient sealing, considering the fiber feed rate and the length of the tubing. Typically, the vacuum inside chamber 13 is, for example, on the order of 0.1 bar, and the length of the vacuum chamber is approximately 1 meter.

[0096] At the outlet of the vacuum chamber 13 and the outlet tube 13b, the arrangement 12 of fibers 11b passes through an impregnation chamber 14 comprising a feed reservoir 15 (connected to a metering pump not shown) and a reservoir A watertight impregnation container 16 is completely filled with an impregnation composition 17 based on a vinyl ester-type curable resin (e.g., "ALTAC® E-Nova FW 2045" from AOC). For example, the composition 17 also contains (at a weight of 1 to 2%) a suitable photoinitiator for UV and / or UV-visible radiation with which the composition will be subsequently treated, for example, bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide ("Omnirad 819" from IGM). The impregnation composition 17 is, of course, in liquid form.

[0097] Preferably, the length of the impregnation chamber is several meters, for example between 2 and 10 m, in particular between 3 and 5 m.

[0098] Thus, from the impregnation chamber 14, in a sealed outlet tube 18 (still under primary vacuum), an impregnated material comprising, for example (% by weight) 65% to 75% of solid fibers 11b, the remainder (25% to 35%) being made up of the liquid impregnation matrix 17.

[0099] The impregnated material then passes through calibration means 19 comprising at least one calibration die 20 whose channel (not shown here), for example circular, rectangular, or conical in shape, is adapted to the specific manufacturing conditions. The calibration die, by means of a cross-section of determined dimensions, generally and preferably circular or rectangular, allows the proportion of resin relative to the fibers to be adjusted, while imposing on the impregnated material the shape and thickness targeted for the monofilament. By way of example, this channel has a minimum circular cross-section whose downstream orifice has a diameter slightly larger than that of the targeted monofilament. The die has a length that is typically at least 100 times greater than the minimum dimension of the cross-section.Its function is to ensure high dimensional accuracy of the finished product; it can also play a role in dosing the fiber content relative to the resin. According to one possible embodiment, the die 20 can be directly integrated into the impregnation chamber 14, which avoids, for example, the use of the outlet tube 18.

[0100] Preferably, the length of the calibration zone is several centimeters, for example between 5 and 50 cm, in particular between 5 and 20 cm.

[0101] Thanks to the calibration means (19, 20) a "liquid" composite monostrand 21 is obtained at this stage (liquid in the sense that its impregnation resin is always liquid) whose cross-section shape is preferably essentially circular.

[0102] Upon exiting the calibration means (19, 20), the resulting liquid composite monostrand 21 is then polymerized by passing through a UV irradiation chamber 22 comprising a sealed glass tube 23 through which the composite monostrand flows; said tube, the diameter of which is typically a few cm (for example, 2 to 3 cm), is irradiated by a plurality (here, for example, 4) of UV irradiators (24) in line (Dr. Hônle's "UVAprint" lamps, with wavelengths of 200 to 600 nm) arranged at a short distance (a few cm) from the glass tube.

[0103] The polymerization or UV irradiation chamber then has the function of polymerizing, cross-linking the resin under the action of UV.

[0104] The UV irradiation chamber may comprise one or more UV irradiators (or heaters). Advantageously, the irradiation chamber comprises a plurality of UV irradiators, that is, at least two (two or more) arranged in a line around the irradiation tube. Each UV irradiator typically comprises one (at least one) UV lamp (preferably emitting in a spectrum from 200 to 600 nm) and a parabolic reflector at the focus of which is the center of the irradiation tube; it delivers a linear power preferably between 2,000 and 14,000 watts per meter. More preferably still, the irradiation chamber comprises at least three, and in particular at least four, UV irradiators in a line.

[0105] Even more preferably, the linear power delivered by each UV irradiator is between 2,500 and 12,000 watts per meter, in particular within a range of 3,000 to 10,000 watts per meter.

[0106] UV heaters suitable for the process are well known to those skilled in the art, for example those marketed by Dr. Hönle AG (Germany) under the reference "1055 LCP AM UK", equipped with "UVAPRINT" lamps (iron-doped high-pressure mercury lamps). The rated (maximum) power of each heater of this type is approximately 13,000 Watts, the actual power output being adjustable with a potentiometer between 30 and 100% of the rated power.

[0107] The diameter of the irradiation tube (preferably made of glass) is preferably between 10 and 80 mm, more preferably between 20 and 60 mm.

[0108] Preferably, the length of the irradiation chamber is several meters, for example between 2 and 15 m, in particular between 3 and 10 m.

[0109] In this example, the irradiation tube 23 is traversed by a nitrogen current.

[0110] The irradiation conditions are preferably adjusted so that, at the outlet of the impregnation chamber, the temperature of the CVR single strand, measured on the surface of the latter (for example using a thermocouple), is greater than the Tg of the crosslinked resin (in other words greater than 190°C), and more preferably less than 270°C.

[0111] Once the resin has polymerized (hardened), the monostrand in CVR 25, this time in the state solid, driven in the direction of arrow F, then arrives at its final receiving reel 26.

[0112] Between the calibration die and the final receiving support, it is preferable to maintain the stresses experienced by the mineral fibers at a moderate level, preferably within between 0.2 and 2.0 cN / tex, more preferably between 0.3 and 1.5 cN / tex; to control this, one can for example measure these tensions directly at the outlet of the irradiation chamber, using appropriate tensiometers well known to the person skilled in the art.

[0113] A finished composite block is finally obtained as schematically shown very simply in [Fig.2], in the form of a continuous CVR monostrand 25, of very long length, whose unit glass filaments 251 are distributed homogeneously throughout the entire volume of hardened resin 252. Its diameter is for example equal to about 1 mm.

[0114] Then, the CVR single strand is subjected to continuous plasma treatment, as described above, to apply at least one organosilicon compound to the surface of the straight arrangement of filaments, the organosilicon compound not comprising any atom other than silicon, carbon, hydrogen and oxygen.

[0115] The continuous CVR monostrand 25 can then be cut to a predetermined length (not shown in [Fig. 1]), for example 45 mm, by any means known to those skilled in the art, for example, using a hydraulic guillotine, such as the "SH-5214" from Baileigh. This step can be carried out directly at the exit of the irradiation chamber 23. It can also be carried out after being conditioned onto a final receiving reel 26. In this case, it is preferable to unwind the monostrand from the reel from the outermost axial end of the monostrand on the reel, in order to avoid helical deformation of the monostrand. Indeed, if the monostrand is unwound from the innermost axial end of the reel, this helical deformation of the monostrand can be detrimental to the breaking strength. Examples Measurement methods

[0116] Mechanical properties

[0117] The mechanical properties in extension of the single strand in CVR (stress breaking Cr) were measured using an "INSTRON" tensile testing machine of the 68TM50 type (BLUEHILL® UNIVERSAL software supplied with the tensile testing machine), according to ASTM D2343, at a temperature of 23 °C.

[0118] The measurements were carried out on CVR single strands manufactured, with or without coating, with or without aging in an alkaline environment.

[0119] Before measurement, these single strands (aged or not) were subjected to preconditioning (storage of the single strands for at least 24 hours in a standard atmosphere according to the European standard DIN EN 20139 (temperature of 23 ± 2°C; humidity of 50 ± 5%)). The aged CVR single strands were previously dried on absorbent paper.

[0120] The 260 mm samples tested were subjected to a tensile test at a nominal speed of 50 m / min, under a preload of 0.5 MPa (distance between the jaws: 150 mm). All results given are an average of 10 measurements.

[0121] Aging protocol in alkaline solution

[0122] Glass tubes 300 mm long and 30 mm in diameter were filled with 160 mL of an alkaline solution at a pH of 13.5. Glass tubes containing 260 mm long CVR monostrands were kept at 60°C for 3 days before being washed with water.

[0123] The single strands were then allowed to dry at room temperature before tensile testing was performed. The tensile tests were carried out on at least 5 repetitions and were compared to tensile tests performed on single strands that had not undergone the aging protocol in alkaline solution. All results given are an average of 5 measurements. Preparation of single strands in CVR

[0124] Single strands of CVR with or without coating were manufactured according to the process described above (single strands M1 to M8).

[0125] The resin composition used was based on vinyl ester resin (“ATLAC E-NOVA FW2045” from AOC), a triacrylate hardener (“SR 368” from Sartomer), and a photoinitiator (“Omnirad 819” from IGM). The glass fibers of the M1 to M8 strands were 300tex “SE1200” fibers from Owens Corning. The glass filaments of the M1 strands do not contain any plasma-deposited compound.

[0126] For the plasma treatment step, 5 compounds were used: 1,1,3,3-tetramethyldisiloxane (for single strand M3), trimethoxyvinylsilane (for single strand M4), aminopropyltriethoxysilane (for single strand M5), 1H,1H,2H,2H-perfluorooctyltriethoxysilane (for single strand M6), dodecylacrylate (for single strand M7), and poly(vinyl alcohol-co-ethylene) (for single strand M8).

[0127] Each of these compounds was introduced into an apparatus employing an atmospheric pressure plasma jet (PLSMASPOT® maxi apparatus).

[0128] The monostrand Ml corresponds to a CVR monostrand without coating and which has not been subjected to aging in an alkaline environment.

[0129] The M2 monostrand corresponds to a CVR monostrand without coating and which has been subjected to aging in an alkaline environment.

[0130] The M3 to M8 single strands correspond to CVR single strands with a coating that have been subjected to aging in an alkaline environment. Results

[0131] The mechanical properties of the single strands M1 to M8 are presented in Tables 1, 2 and 3 below.

[0132] The results are expressed in MPa as well as in percentage loss of tensile strength. The lower the percentage, the less the tensile strength is degraded and the better the resistance to alkalis.

[0133] [Tables 1] M1 (control) M2 (comparative) M3 (invention) M4 (invention) Presence of a coating No No Yes Yes Compound deposited by plasma - - 1,1,3,3-tetramethyl-disiloxane Trimethoxy-vinylsilane Alkaline aging No Yes Yes Yes Tensile strength Cr (MP a) 1280 780 900 980 % Cr loss - 39.1% 29.7% 23.4%

[0134] [Tables2] M5 (comparative) M6 (comparative) Presence of a coating Yes Yes Compound deposited by plasma Aminopropyltriethoxysilane 1H,1H,2H,2H-perfluorooctyltriethoxysilane Alkaline aging Yes Yes Tensile strength (MP a) 780 780 % Cr loss 39.1% 39.1%

[0135] [Tables3] M7 (comparative) M8 (comparative) Presence of a coating Yes Yes Compound deposited by plasma dodecylacrylate poly(vinyl alcohol-co-ethylene) Alkaline aging Yes Yes Fracture stress (MP a) 780 780 % Cr loss 39.1% 39.1%

[0136] The results presented above show that the presence of an organosilicon compound comprising no atoms other than silicon, carbon, hydrogen and oxygen on the surface of a single strand, and deposited using a plasma treatment, makes it possible to improve the breaking strength of the support after aging in an alkaline environment, compared to an uncoated support after aging in an alkaline environment.

[0137] Indeed, the breaking strength values ​​of the M3 and M4 single strands according to the invention are higher than those of the comparative M2 single strand. The percentage loss of breaking strength is lower for the M3 and M4 single strands compared to the M1 single strand than for the comparative M2 single strand.

[0138] It should also be noted that the tensile strength of the comparative M5 to M8 single strands is identical to that of the comparative M2 single strand. Thus, the compounds deposited on the surface of the single strand have no impact on the tensile strength

[0139] Thus, the presence of said organosilicon compound comprising no atom other than silicon, carbon, hydrogen and oxygen on the surface of a support, such as a single strand of filament-resin composite, according to the invention makes it possible to improve the resistance to alkalis of said support.

Claims

Demands

1. A method for improving the alkali resistance of a support comprising a plasma treatment step for applying at least one organosilicon compound to the surface of the support, the organosilicon compound not comprising any atom other than silicon, carbon, hydrogen and oxygen.

2. A method according to claim 1, characterized in that the support is a monostrand of filament-resin composite comprising filaments embedded in a crosslinked resin.

3. A method for manufacturing at least one single strand of filament-resin composite comprising filaments embedded in a crosslinked resin, comprising the following steps: a) making a straight arrangement of filaments and driving this arrangement in a direction of advancement; b) bringing said arrangement of filaments into contact with a photocurable resin composition, in liquid form, called impregnation resin, to obtain an impregnated material containing the filaments and the resin composition; c) passing said impregnated material through a calibration die having a predefined surface area and shape cross-section, to impose upon it a single strand shape;d) downstream of the die, in a crosslinking chamber, polymerize the resin composition under the action of ultraviolet or visible radiation, the crosslinking chamber comprising a tube transparent to ultraviolet or visible light, called the crosslinking tube, through which the single strand being formed passes; e) subject the single strand obtained in step (d) to a plasma treatment to apply at least one organosilicon compound to the surface of the straight arrangement of filaments, the organosilicon compound not comprising any atom other than silicon, carbon, hydrogen and oxygen.

4. A method according to claim 3, characterized in that it further comprises f) a step of cutting the monostrand obtained in step (e), preferably to a length from 5 to 85 mm, to obtain cut monostrands.

5. A method according to any one of claims 2 to 4, characterized in that the filaments are chosen from the group consisting of the glass filaments, basalt filaments, polyester filaments, and their combinations, preferably in the group consisting of glass filaments.

6. A process according to any one of the preceding claims, characterized in that the organosilicon compound is selected from the group consisting of compounds of formula RxSi-(OR')(4 x) (I), Ri,2,3Si-[O-SiR4,5,6]n (II) and mixtures thereof, - formula (I) in which: * R represents a hydrocarbon group in Ci-C4, preferably an alkenyl group C2-C3; * R' represents a hydrocarbon group in CrC4, preferably in CrC2; * x is an integer from 1 to 3; - formula (II) in which: * Ri, R2, R3, R4, Rs, Rô, identical or different, represent H or a CrC4 hydrocarbon group, preferably CrC2, provided that at least 4 of the groups among Rb R2, R3, R4, R5, R6 represent a CrC4 hydrocarbon group, preferably at least 2 of the groups among Rb R2, R3, R4, R5, R6 designate H; * n is an integer from 1 to 3, preferably n is equal to 1.

7. A process according to any one of the preceding claims, characterized in that the organosilicon compound is selected from the group consisting of 1,1,3,3-tetramethyldisiloxane, trimethoxyvinylsilane and mixtures thereof.

8. A process according to any one of claims 2 to 7, characterized in that the crosslinked resin is based on at least: - a photocurable resin selected from the group consisting of vinyl ester, epoxy, polyester, novolac resins and mixtures thereof, preferably from the group consisting of vinyl ester, epoxy resins and mixtures thereof; - a crosslinking system comprising a photoinitiating agent.

9. A method according to any one of claims 2 to 8, characterized in that the single strand has a diameter ranging from 0.2 to 1.3 mm, preferably from 0.25 to 1.25 mm, more preferably from 0.3 to 1.2 mm.

10. A method according to claim 9, when it depends at least on claim 4, characterized in that the cut single strand presents a length / diameter ratio ranging from 10 to 110, preferably from 20 to 90, more preferably from 25 to less than 80.

11. Monostrand capable of being obtained by a process according to any one of claims 2 to 10.

12. Monostrand of filament-resin composite comprising filaments embedded in a cross-linked resin, the monostrand being coated at least partially, preferably totally, with at least one organosilicon compound, said organosilicon compound not comprising any atom other than silicon, carbon, hydrogen and oxygen.

13. Monostrand according to claim 12, characterized in that the organosilicon compound(s) form a layer with a thickness ranging from 2 to 500 nm, preferably from 5 to 50 nm, on the surface of the filaments of the monostrand.

14. Use of at least one monostrand according to any one of claims 11 to 13, when they depend at least on claim 4, to strengthen concrete and / or reduce the weight of concrete and / or reduce or prevent cracking of concrete.

15. Use of at least one organosilicon compound not comprising any atom other than silicon, carbon, hydrogen and oxygen to improve the resistance to alkalis of a support, the support preferably being a single strand of filament-resin composite comprising filaments embedded in a crosslinked resin.

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