DE2556539A1 - PROCEDURE FOR PROTECTING FIBERGLASS IN ALKALINE ENVIRONMENTS - Google Patents

Description

Euroc Administration AB, 201 10 Malmö / Sweden

Process for protecting glass fibers in an alkaline environment

The invention relates to a method for protecting glass fibers for reinforcing an alkaline matrix in aqueous Phase against chemical degradation.

Thus, the invention is directed to a method for protecting glass fibers in an alkaline environment as well on fiberglass-reinforced protected by such a process Products.

Glass fibers are used to reinforce alkaline matrix materials such as cement and cement products thereby improving both the tensile strength and the compressive strength. It is known that glass fibers in a Cement mix particularly attacked by hydroxyl ions

411

Bremen office: D-2800 Bremen P.O. Box 786. Feldstrasse t Telephone: (0421) * 74044 Telex: 244958 bopatd Telegr .: diagram. Bremen

609827/0975

Bremen accounts: Bremer Bank, Bremen (BLZ 29080010) 1001449

PSchA Hamburg

(BLZ 20010020) 126083-202

Munich office:
D-8000 Munich 90 Schlotthauer Straße 3 Telephone: (089) 652321

Telegr.: Telepatent, Munich

BOEHMERT & BCEIiMERT

will. It is also known that the glass fibers can be protected in various ways.

The glass mixture for the production of the fibers can for example Contain ZrOp so as to have improved alkali resistance to reach. However, this method has considerable disadvantages. The single fibers are not completely alkali-resistant and are therefore attacked relatively strongly. In addition, the manufacturing cost is of ZrO "-containing glass fibers high. It is particularly noteworthy that that the individual fibers that lie on the outside in a web are relatively easily broken down in this way v / ground while the reaction products form a protective surface layer around the remaining fibers. The outer fibers are sacrificed in order to obtain the desired protection, but this also results in a limited one Connection with the matrix material results in »

According to the prior art, the individual glass fibers also coated with a non-reactive protective layer be, for example made of a polymer or a metal, or with a very thin reactive Surface layer, e.g. made of zirconium oxychloride, which forms a dense surface layer of hydroxides when it reacts with the alkaline water phase. The coating, however, has to take place when the fibers are drawn and is relatively expensive. It has also been shown that serious problems arise, such as damage in the layers, unsatisfactory adhesion between the layer and the glass and adhesion problems in particular between a polymer layer and a cement mix. All of these effects occur relatively easily. at the application of thin, polymeric surface layers

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It was found that the binding of "point holes" cannot be prevented. Form these point holes unprotected attack centers for alkaline fiber corrosion.

Fibers with thin, reactive surface layers are coated, furthermore have the considerable disadvantage that the applied amount of the chemical reactant is too small to provide a sufficient and long-lasting one To achieve protective effect. Because of the limited mechanical strength of the applied protective layer, it can also are easily damaged, for example when mixed into the alkaline matrix material.

The invention is based on the object of creating a method of the type mentioned at the beginning, which makes it possible to To protect glass fibers in an alkaline matrix properly and at low cost.

According to the invention this object is achieved in that one at least one chemically reactive substance with the matrix material and / or its reaction products with water brings to reaction, whereby hydroxyl ions simultaneously with the formation of a protective against alkaline attack Precipitation are chemically bound in the immediate vicinity of the glass fibers.

The invention is based on the surprising finding that it is possible to use the glass fibers used for reinforcement to protect against chemical attack in an alkaline matrix material in a relatively simple and economical way. The alkaline matrix is preferably a Portland cement mixture or a lime / quartz mixture or a hydraulic

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Limestone / quartz mixture, the latter mixtures being used in the manufacture of autoclave products It can also be a Sorell cement.

According to the invention, the glass fibers are in particular against Protected against the attack of hydroxyl ions during the setting of the cement and the dissolution of alkaline earth oxides and hydroxides are formed, especially calcium and magnesium oxides and hydroxides in water. Protection takes place by a chemically reactive substance, which is either present or in the alkaline environment around the glass fibers is introduced continuously. This substance has the ability to chemically release hydroxyl ions in the environment to bind and to form deposits that resist alkaline attack in the immediate vicinity and around the glass fibers protection. According to the invention, these protective deposits arise from the fact that the chemically reactive Substance in the alkaline environment has one or more insoluble compounds with the cations present in the matrix material occur, especially the calcium ions.

According to the invention, dense deposits of colloidal silica gel are also formed in cement mixtures, when a water-soluble, chemically reactive substance in the form of a hydrogen ion donor topochemically the Attacks calcium silicate particles surrounding the glass fibers. The silica gel, which temporarily serves as a reactive protective layer around the glass fibers, reacts, then gradually with the calcium ions and the hydroxyl ions formed during the formation of the dense calcium silicate hydrates diffuse into the layer.

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The chemical attack of the glass fibers in an alkaline matrix material is therefore, according to the invention, in two ways Species achieved in an effective manner, namely by the fact that the diffusion of harmful to the glass fibers Ions is hindered or prevented by the formation of dense layers surrounding the glass fibers, and for others in that diffused hydroxyl ions and Calcium ions are chemically bound. According to the invention, the hydroxyl ions become during the formation of the water chemically bound essentially to hydrogen ions. However, there can also be a bond to metal ions, insoluble hydroxides and hydroxo compounds are formed in the alkaline environment.

The protection of the fiberglass surface is done without introductory Attack on the surface, as is the case, for example, when using alkaline matrix material zirconia-modified glass fibers, E-glass fibers, A-glass fibers and mineral fibers is reinforced.

A characteristic feature of the invention is that the chemical reactions that take place between the chemically reactive substances that are added to the matrix material and run off the strongly alkaline water phase, faster than the reactions that take place between the alkaline water phase and the glass fiber surface take place and which normally result in a more or less severe degradation of the glass fibers.

Another characteristic feature of the invention is that the insoluble deposits or precipitates, which are formed around the glass fibers according to the invention, an optimal bond between the glass fibers and

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the hardening matrix material without damaging the glass fiber surface.

In terms of formulas, the teaching of the invention can be represented as follows, where HX is the chemically reactive substance means:

a) HX + calcium silicate ^ silica gel + CaX ₃ (S) = ion diffusion barrier

b) HX + OH ^ -> H_0 + X ~

c) 2X + Ca- £ CaX "(s) = ion diffusion barrier.

The hydroxyl ion, which is aggressive for the glass fiber surface is, is therefore by an acid substance HX, a hydrogen ion donor, an acid, an acid salt, a water-binding anhydrite or the like neutralized, which as solid substance or in dissolved form.

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This substance splits off hydrogen atoms and forms a salt that is insoluble in an alkaline environment, for example with the calcium ion if the matrix material is, for example, a cement mixture. The slightly soluble salt forms after the Invention a dense layer around the individual fibers in a web and between these / which a continuous ion diffusion in the alkaline environment of the glass fibers over the glass fiber surface and between the individual fibers that make up the web form, effectively disabled.

Suitable solid substances according to the invention are acids, acid * salts, acid anhydrites and hydrolyzable compounds, both organic and inorganic, which are hydrolyzed, preferably at a pH of ^ L 7, so that an acid is formed in the meantime, as well as various Mixtures of these compounds with one another and mixtures with water-soluble oxozirconium salts.

Particularly suitable solid acids according to the invention are colloidal silicic acid, boric acid and organic acids, preferably crystalline dibasic acids such as oxalic acid, citric acid and tartaric acid.

Particularly suitable acid salts according to the invention are the following; alkali metal, alkaline earth metal or ammonium salts: Hydrogen phosphate, hydrogen sulfate, hydrogen carbonate, hydrogen borate, Hydrogen oxalate, hydrogen citrate and hydrogen tartrate.

Particularly suitable anhydrites according to the invention are silica, Carbon dioxide, boron oxide, aluminum hydroxide, tin oxide and titanium dioxide. Alkaline glass with high silica content, for example Α-glass is also suitable.

It is known per se in a fiber reinforced cement mixture

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Add a small amount of silica in the form of pozzolans and diatomaceous earth to maintain the alkalinity around the glass fibers calcium hydroxide free by chemical bonding, which calcium silicate hydrates are formed when the cement sets. But it has been shown that a The major disadvantage is that silica in this form reacts too slowly to make calcium hydroxide effective at the same rate at which this is formed, as that of attack by glass fibers, which are not alkali-resistant are, could be prevented. The limiting factor is that the rate at which silica (silica) is hydrated in this form and goes into solution in the form of silica, is less than the reaction rate of the alkaline Attack on the fiberglass surface. It is therefore necessary to use silica in considerable amounts use more reactive form than was the case with the previously known procedure.

According to the invention, it has surprisingly been shown that that silica in the form of a very fine-grain alkali glass powder as well as dust with a high silica content, preferably in the form of a so-called "silica vapor", this requirement is met exceptionally well and therefore the disadvantages of known method avoids. Silica vapor, which is a waste product in the manufacture of silicon iron, contains more than 95% silica in a glassy-amorphous state

2 and has a specific surface area of up to 20 m / g.

So it is not sufficient that the silica is amorphous and has a large specific surface area, as is the case with. Pozzolans and diatomaceous earth is the case, but it has been found necessary according to the invention that the The aggregate state of the silica is glassy.

It is also known per se, carbon dioxide one

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glass fiber reinforced cement mix to prevent alkaline attack on the glass fiber surface by carbonization of the to prevent calcium hydroxide released when the cement sets. There is a major disadvantage to this method but in that the addition of the carbon dioxide is limited to the use of the low carbon dioxide content of the air is, which means that the carbonization takes place in an uncontrolled manner and not at the rate at which calcium hydroxide is formed during the setting of the cement, is adapted. According to this process, the alkaline Combat attacks on the glass fibers only to a limited extent and in no way completely prevent them. The rate of hydration of dissolved carbon dioxide and the deposition rate of calcium carbonate according to the formula

^H 2 ° ₊ "Ca ⁺ , OH-

> H ₃ CO ₃ - ^ H, HCO ₃ , CO ₃ > CaCO ₃ (S), H ₃ O

₃ CO ₃ ^ H, HCO ₃ , CO ₃ > CaCO ₃ (),

is greater than the rate of alkaline attack on the glass surface, but is the rate at which carbon dioxide is added and can be dissolved in the water phase, viz

CO ₂ (g) -> C0 ₂ (1) _/

to a large extent dependent on pressure. According to the technical literature, there are major drawbacks to setting subjecting the cement material to uncontrolled carbonization by setting and carbonizing can take place in an atmosphere which has an arbitrarily high carbon dioxide pressure. In such a setting process usually results in products with unacceptable tensile strength properties, even if one can protect the glass fibers against alkaline degradation in the manner described.

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According to the invention it has surprisingly been found that the disadvantages described above are effective can be eliminated by using carbon dioxide in controlled amounts and to a certain extent adapted to the rate of formation of calcium hydroxide is supplied. The feed to the fiberglass reinforced Cement material is carried out continuously at high temperature, i.e. under autoclave conditions, preferably at a temperature in the range of 100 to 250 C.

Suitable hydrolyzable compounds according to the invention are alkali metals, ammonium, magnesium, zinc, cadmium, iron and manganese compounds: hexafluosilicate, hexafluophosphate , hexafluotitanate, hexafluozirconate, tetrafluoborate, siliconate (silicate) as well as the following hydrolyzable zirconium compounds: tetrachloride, tetrafluoride, tetrafluoride.

Preferably, two or more of the above can also be used chemically reactive substances can be used separately or in a mixture, especially together with vitreous Silica, such as silica vapor.

Particularly suitable compositions according to the invention are also those which _r one or more of said substances and a Oxokationverbindung of the titanium group, for example Oxozirkonchloridj bromide and nitrate contained.

The method according to the invention is explained below for various matrix materials on the basis of examples, with simplified overall chemical reactions being used for some characteristic of the various substances. To simplify matters, Portland cement is represented by tricalcium silicate, i.e. _{Ca 3 SiO 5} . The substance is in the alkaline water phase in the solid state in the immediate vicinity

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of the glass fibers are introduced as described below. Carbon dioxide is an exception in that it is introduced in a gaseous state. The imported substance dissolves in contact with water at a certain rate. The dissolved substance, or possible hydrolysis products in Form of acids, is dissociated into hydrogen ions and anions, which, according to the invention, form the reactive components of the substance, as well as possible metal ions of which in turn some are able to bind hydroxyl ions with the formation of "sparingly soluble hydroxides".

Example 1. Oxalic Acid, Portland Cement

H ⁺ , Ca ₃ SiO ₅ PSJ ^ _L> silica gel, Ca ²⁺

2 H ⁺ + C ₂ O ₄ ² "+ Ca ²⁺ + 0H ~ -> CaC ₃ O ₄ (S) + 2

Silica gel, Ca, OH £ > calcium silicates

Example 2. Sodium hydrogen phosphate, Portland cement

H ⁺ , Ca ₃ SiO ₅ silica gel, Ca ²⁺

4 H ⁺ + 2 PO ₄ ³ "+ 3 Ca ²⁺ + 4 OH *" - ^ Ca ₃ (PO ₄ J ₂ Cs) + 4

Silica gel, Ca, 0H ~ £ ^ Calcxum silicate hydrates

Example 3. Silica, Portland cement or lime / quartz mixture SiO “(s) - HO £ Various colloidal silicas

Silicas, Ca ⁺ , 0H ~ 2——> Various calcium silicate

hydrates

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Example 4. Carbon Dioxide, Portland Cement

2+ Ca ₂ (g) J ^ 2 ^ CO ₂ (D-> H ⁺ , HCO ₃ ", CO ₃ ² " - J_ ° iL> CaCO ₃ (s), H

Example 5. Magnesium fluosilicate

MgSiF ₆ + 4 H ₂ O Mg ²⁺ + Si (OH) ₄ + 4 H ⁺ + 6F ~

4 H ⁺ + 4 OH -> 4 H ₂ O

Mg ²⁺ + 2 0H ~ => Mg (OH) ₂ (s)

6F ~ + 3 Ca ²⁺ -> 3 CaF ₂ (S)

MgSiF ₆ + 6 OH ~ + 3 Ca ²⁺ -5> Mg (OH) ₃ (S) + 3 CaF ₃ (S) + Si (OH) ₄

In this case, in addition to neutralizing the OH ions, two poorly soluble compounds are formed after hydrolysis, namely Mg (OH) ₂ and CaF ₃ , as well as colloidal silica (silica gel), which is very reactive.

2+ It can continue to react with, for example, Ca ions and form calcium silicate hydrates that are poorly or easily soluble, whereby further OH ions are neutralized.

Example 7. Magnesium hexafluosiloxicate and oxozirconium chloride, portland cement

MgSiF ₆ , ZrOCl ₂ , 0H ~, Ca ²⁺ - ^ Mg (OH) ₂ , CaF ₃ , ZrO (OH) ₃ , Si (OH) ₄ (S),

H ₃ O; Si (OH) ₄ , ZrO (OH) ₂ , Ca ²⁺ , OH ~ - ^ calcium silicate hydrates, oxozirconium silicates

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Example 6. Zircon Nitrate, Portland Cement Zr (NO ₃ ) ₄ ^H 2 ° ZrO (OH) ₂ (S) + 4 H ⁺ + 4 NO ₃ "

H ⁺ , Ca ₃ SiO ₅ ^{pH 7} silica gel, Ca ²⁺

Silica gel, Ca ²⁺ , 0H ~ ^{pH 7} calcium silicate hydrates

The addition of chemically reactive substances to the glass fiber reinforced Matrix material takes place in a manner that depends on the normal physical state and solubility of the Substance in water depends. Carbon dioxide is gaseous and is continuously used in controlled amounts in an autoclave supplied, in which the matrix material, preferably a cement mixture, is located and is hardened there. Silica in vapor form or in dust form is a slightly soluble substance that enters directly into the matrix material mixture is mixed in, whereby the amount of silica vapor is preferably at least equimolar to the amount of the present or formed lime. In the case of the lime / quartz mixture, the quartz can be absorbed to a greater extent by silica vapor or even completely, whichever is preferred, to be replaced. Others slightly or easily soluble Substances can be added directly to the matrix material.

Substances which are soluble in water or in organic solvents are preferably entered in that the fiberglass web is impregnated with the dissolved or molten substance. Under impregnation is used understood that the voids between the individual fibers, which are relatively close together and twisted together are partially or completely filled with the substance. Because of the large capillary forces in the cavities

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After the trapped air has been sucked out, it is relatively easy to clean the cavities with a concentrated solution a soluble substance or with a fusible substance at a temperature below about 120 ° C. To After the impregnation, the aqueous phase can be removed by evaporation. The impregnation can, if necessary, be repeated until the cavities are filled with a solid substance. When the impregnated fibers in the matrix material are mixed in, parts of the impregnation substance introduced into the cavities are gradually dissolved, whereby then the substance in the immediate vicinity of the fibers according to the invention with the cement particles and / or reacts with the aggressive reaction products that arise when the cement sets.

If the substance is easily soluble in water, the impregnation can be carried out immediately before cutting and mixing of the fiberglass web into the cement mixture. In this case the web is allowed to run through a bath, which contains a concentrated solution, after which the web is used without evaporating the solvent.

Examples

In all experiments, a web of E-glass fiber was used used, which had 30 strands and approximately 100 individual fibers per strand. The web was cut, if necessary after impregnation and drying, in fiber bundles with a length of 24 mm, which are then inserted into the matrix material in an amount of 4 percent by volume odex * approximately 75 g of fiber web per kg of matrix material was entered Disc-shaped test specimens with the dimensions of 250 χ 250 χ 6 me were produced, whereupon the impact resistance was determined by means of a pendulum hammer after various storage times.

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Corresponding test specimens were made from the Ε glass fibers, but without protective additives. Silicic acid vapor has been replaced by pozzolans. Each measured value represents the Represents the mean of three measurements.

example 1

Fiberglass web was impregnated by passing the web through a hot bath of concentrated oxalic acid solution. The web was dried and then passed through a bath with a concentrated alcoholic zirconium tetrachloride solution through, after which the web was dried and cut. The fibers were mixed with cement and water. The water-cement ratio (vct) was 0.40. the the following results were obtained:

Storage text Test with
kNm / m treated fibers Test with
Fibers treated
kNm / m 8th 15.4 16.2 90 14.3 10.7 180 14.5 7.8 Example 2

Test specimens were produced according to Example 1, with the difference that the "oxalic acid was replaced by sodium dihydrogen phosphate during the impregnation and that the Impregnation with zirconium tetrachloride was omitted. Instead, 25% silicon vapor or silicon mist was added to the mixture puts. Vct = 0.60. The following results were obtained:

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Storage time test with treated fibers test with untreated fibers

+ 25% silica vapor fibers + 25% pozzolans

2 2

Days kNm / m kNm / m

15.3 10.2

6.3

8th 14th .8th 90 14th .0 180 13th .9 Example 3

Untreated fiberglass web in water-soluble size After cutting it was mixed into a cement-silica vapor-water solution (1: 1: 1.2) using a hand mixer, so that the individual fibers were well dispersed.

Storage time test with untreated fibers test with untreated fibers and silica fume fibers and pozzolans

2 ■ 2

Days kNm / m kNm / m

8 17.2 17.1

90 16.3 8.5

180 16.3 5.1

Example 4

Test specimens were produced according to Example 1, but the fiberglass web is impregnated with magnesium hexafluosilicate and then with zirconium oxychloride. The test results were as follows:

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Storage time test with treated fibers test with untreated fibers

2

'Days kNm / m fibers kNm / m

8 15.6 16.2

90 14.8 10.7

180 14.7 7.8

Example 5

Untreated fiberglass web was cut in proportion 1: 3 added to a cement mortar in which part of the sand had been replaced by silica vapor. the Test specimens were at 180 C, under a pressure of 10 atm, Autoclaved for eight hours with continuous addition of carbon dioxide. The partial pressure was during the Increased to 0.5 atm for the first hour, was held at this value for three hours, and was then gradually reduced. Test results were as follows:

kNm / m

Test with silica vapor 9.2. Test with pozzolans 2.6

Test with sand 0.7

In the test body, which only contained sand, one of them showed Examination under a microscope no more fibers.

Example 6

Untreated fiberglass web with water-soluble size distribution was distributed in a lime-quartz mixture (1: 3: 4) after cutting by means of a hand mixer, in which 90% of the quartz had been replaced by silica vapor (fog, haze). The test results were as follows:

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kNm / m

Test with silica vapor 12.3 Test with pozzolans 4.5

Test with quartz 0.6

When examined under a microscope, the test body, which only contained quartz, no longer showed any fibers. at the test body, which had pozzolans, the fibers were severely attacked and partially disappeared. In the case of the test body, the carbonic acid vapor contained the fibers appeared to be completely undamaged.

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Claims (1)

/ j E 784 Expectations 1i method of protecting glass fibers for reinforcement an alkaline matrix in the aqueous phase against chemical degradation, characterized in that at least a chemically reactive substance with the matrix material and / or its reaction products with water brings to reaction, with hydroxyl ions at the same time with the formation of a protective precipitate against alkaline attack in the immediate vicinity of the Glass fibers are chemically bound. 2. The method according to claim 1, characterized in that as a chemically reactive substance an acid, for example colloidal silicic acid, crystalline boric acid or an organic, crystalline acid, preferably a dibasic acid, such as oxalic acid, citric acid and tartaric acid, is used. 3. The method according to claim 1, characterized in that the reactive substance is an acid salt, for example Hydrogen phosphate, hydrogen sulfate, hydrogen carbonate, hydrogen borate, Hydrogen oxalate, hydrogen citrate or hydrogen tartrate, is used. 4. The method according to claim 1, characterized in that an acid anhydrite, for example Silica in the glassy state, carbon dioxide, boron oxide, 609827/09 ίο Aluminum hydroxide, tin dioxide and titanium dioxide are used will. 5. The method according to claim 1, characterized in that the reactive substance is a hydrolyzable compound is used, an acid being formed in the meantime during hydrolysis, for example hexafluosilicate, Hexafluophosphate, hexafluotitanate, hexafluozirconate, hexafluoborate, Siliconate and zirconium tetrachloride, zirconium tetrabromide and zirconium nitrate. 6. The method according to claim 1, characterized in that separately or in any mixture two or more chemically reactive substances are used, such as acids, acid salts, acid anhydrites and hydrolyzable compounds, the latter temporarily forming an acid during hydrolysis, preferably in the form of a mixture, which contains glassy silica. 7. The method according to claim 1 and 6, characterized in that one or more chemically reactive substances be used together with an oxocation compound selected from the titanium group, such as oxozirconium chloride, Oxozirconium bromide, oxozirconium iodide and oxozirconium nitrate. 8. The method according to claim 1, characterized in that hydroxyl ions are chemically bonded to hydrogen ions or to metal ions are bound, with water and insoluble hydroxide or hydroxo compounds are formed. Method according to claim 1, characterized in that the deposit of topochemically formed reactive silica gel protecting against alkaline attack _ 2 - 609827 / 0975- which forms slightly soluble calcium silicate hydrates with the calcium ions. 10. The method according to claim 1, characterized in that the deposit which protects against alkaline attack and consists essentially of calcium ion compounds which are insoluble in an alkaline environment consists. 11. The method according to claim 1 and 9, characterized in that that the deposit protecting against alkaline attack consists essentially of a mixture of topochemically formed reactive silica gel and insoluble calcium ion compounds. 12. The method according to claim 1 and 9, characterized in that that the deposit protecting against alkaline attack consists essentially of a mixture of topochemically formed reactive silica gel and insoluble oxozirconium compounds. 13. The method according to claim 1, characterized in that the deposit protecting against alkaline attack is essentially consists of a mixture of insoluble calcium ion and oxozirconium ion compounds. 14. The method according to any one of claims 1 to 7, characterized in that that the chemically reactive substances, which are normally slightly soluble in water, directly be admixed with the alkaline matrix material. 15. The method according to any one of claims 1 to 7, characterized in that that the chemically reactive substances in the cavities between the individual fibers of a web 609827 / 097S are introduced, preferably by impregnation with a solution of the substance. 16. The method according to claim 4 and 6, characterized in that that the alkaline matrix material silica is mixed in such a form that its physical state is glassy-amorphous and its specific surface is 2
ßer 5 m / g, in an at least equimolar amount in relation to the amount of calcium hydroxide present or chemically formed in the matrix material, for example in the form of alkali glass powder and silica-rich dust, preferably in the form of a silica vapor, as it is a waste product in the manufacture of Silicon iron occurs. 17. The method according to claim 4 and 6, characterized in that that the alkaline matrix material under autoclave conditions continuously carbon dioxide in controlled amounts is supplied, the amounts supplied together with the amount of calcium hydroxide chemically formed in the matrix material are at most acmimolar. 18. The method according to claim 1, characterized in, that as a glass fiber reinforced matrix material a mixture Portland cement, a mixture of lime / quartz, a mixture of slag / quartz or a mixture of Sorell cement is used. 609827/0973