FI58627C - GLASFIBRER AVSEDDA ATT ANVAENDAS SAOSOM FOERSTAERKNING I CEMENTPRODUKTER - Google Patents

Description

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Fetent. peh reglsteretyreleen ^ Aiwefcin utiJfTxh 28.11.80 (32) (33) (31) Requested preferenceiiwwprtonwc 03.07-73 England-England (GB) 31657/73 '(71) Pilkington Brothers Limited, Prescot Road, St. Helens, Lancashire WA10 3TT England-England (GB) (72) David Ralph Cockram, Wigan, Lsincashire, England-England (GB) 7M Oy Kolster Ab (5 * 0 Glass fibers for use as reinforcement in cement products -Glasfibrer avsedda att änvändas säsom förstärkning i cementprodukter (62) By sharing separated from application 20i + 2 / 7lt (patent 57739) -Avdelad frän trap 20 ^ 2/7 ^ (patent 57739)

The invention relates to glass fibers for use as a reinforcement in cementitious products, coated with a composition comprising a protective material in order to prevent deterioration of the glass fibers when incorporated into cementitious products. In the alkaline environment of normal Portland cement, mainly due to the presence of calcium hydroxide, fibers composed of commonly available glass compositions, such as the composition commonly known as E-glass, corrode rapidly and deteriorate, so that the additional strength provided to the cement by the glass fibers is rapidly lost.

Various alkali-resistant glass compositions have been proposed that better retain their strength in cement.

U.S. Patent No. 1,200,532 to 1,200,732 (National Research Development Corporation) discloses a composite fiber-cement product comprising a fibrous reinforcement material distributed throughout a cement matrix, the reinforcement material being primarily glass, which in itself has an alkali resistance such that when tested in the form of ground fiber. having a length of 6.35 cm and a diameter of -3 1.02 to 2.54 x 10 cm, said fiber having a tensile strength of at least 27,000 kg / cm after being treated with a saturated aqueous solution of CaCl2 at 100 ° C: for four hours and then washed successively at ambient temperature with water, then with 1% aqueous hydrochloric acid for one minute, with water, acetone and then dried, so that said fiber does not experience a 10% reduction in diameter during this experiment.

GB 1 243 972 (NRDC) discloses composite fiber / cement products in which the glass contains at least 6% by weight SiO 2 and at least 10% by weight Zr 2> 2 · GB patent 1 243 973 (NRDC) discloses alkali-resistant glass fibers based on glass containing from 65 to 80% by weight of SiO 2, from 10 to 20% by weight of ZrCl 2 and from 10 to 20% by weight of a cross-linking agent which is an alkali metal oxide, alkaline earth metal oxide or zinc oxide, said glass being such , having the tensile strength shown above.

Other compositions for forming alkali-resistant glass fibers are disclosed in GB Patent 1,290,528 and GB Patent Application 51177/71. GB Patent 1,290,528 discloses glass compositions for forming glass fibers for incorporation as a reinforcement in cementitious products and containing

SiO2 62-75 mol%

ZrC> 2 7-11 mol% R20 13-23 mol% R'0 1-10 mol% A2 Og 0-4 mol% B20g 0-6 mol%

Fe 2 O 2 0-5 mol%

CaF2 0-2 mol%

TiO 2 0-4 mole% 3,58627 wherein 1 O 0 means Na 2 O, of which up to 2 mole% may be replaced by L 10, and R 10 is alkaline earth metal oxide, zinc oxide (ZnO) or manganese oxide (MnO), wherein any remaining part of the composition consists of other compatible ingredients.

GB patent application 51177/71 seeks patent protection for glass compositions intended for use in the manufacture of alkali-resistant, continuously drawn glass fibers containing, on an oxide basis:

SiC> 2 67-82 mol%

ZrC> 2 7-10 mol% R20 9-22.5 mol% F2 3-9 mol%

Al 2 O 4 0-5 mol% (calculated as Al 2 O 4) wherein R = Na, of which up to 5 mol% may be replaced by lithium or potassium, and fluorine is included to replace oxygen in one or more oxides, where the sum of SiO 2 + ZrO 2 The maximum value represented by + A10.J ^ in mole% varies depending on the concentration of ZrO2, varying in the case where F2 is 9 mol%, from 89 mole% when the content of ZrO2 is 7 mol%, to 88 mol% when the ZrO 2 content is 8.5 mol%, and to 87 mol% when the ZrO 2 content is 10 mol%, said maximum value decreasing by a further 5 mol% of the whole range over in the case that F2 = 3 mol%.

ZA Patent Publication No. 73/4476 (Owens-Corning Fiberglas Corporation) discloses a group of alkali-resistant glasses and glass fibers made therefrom having a composition in the range shown in the following table.

SiO 2 60-62 65-67

CaO 4-6 4.5-6.5

Na20 14-15 14.5-16 K20 2-3 1-2.5

ZrO2 10-11 5-6

TiO2 5.5-8 4.5-6.5 »58627

Although the alkali-resistant glass fibers described in the above patents retain their strength in cement better than fibers made of ordinary glass such as E-glass, there is a gradual deterioration over a long period of time.

In the continuous manufacture of glass fibers for any purpose, it is normal practice to coat private continuously drawn glass fibers immediately after drawing with an adhesive composition that provides mechanical protection and a lubricant to minimize fiber breakage and wear during subsequent processing, such as bringing numerous private fibers together to form a rope. For spool or drum. The adhesive compositions previously used for glass fibers to be incorporated into a cement matrix have not had a significant effect on the long-term resistance of glass to the corrosive effect of alkalis in cement.

Protective coating compositions have also been applied to glass fibers at various stages of their manufacture and processing, and it has been proposed, for example, to use furan resin in such a coating to improve the alkali resistance of the glass fiber material to make the material suitable for use in cement reinforcement.

According to the present invention, glass fibers for use as a reinforcement in cementitious products are coated with a protective material composition containing at least one monocyclic or polycyclic aromatic compound having at least 3 hydroxyl groups in an aromatic ring or (in a polycyclic compound) at least one aromatic ring as a protective agent for a glass fiber filament which is then encapsulated in a piece of ordinary Portland cement pack, which is then allowed to cure and kept at 50 ° C for 28 days, provides at least a 10% improvement in the tensile strength of the filament which has been treated and tested; in a similar manner, but without using said composition of matter.

It has been found that the use of such an aromatic compound as a preservative in an adhesive or other coating composition substantially reduces the rate of deterioration of the strength of the glass fibers, which fibers have been incorporated into cement products, over long test periods. This effect is noticeable when using fibers made of E-la glass, but a greater advantage is obtained when using glass which is already substantially alkali-resistant, i. which meets the tensile strength requirement set forth in the aforementioned GB Patent Publications 1,200,732, 1,243,972 and 1,243,973. It is recommended to use an adhesive or other coating composition with glass fibers made from alkali-resistant glass compositions disclosed in GB Patent Specification No. 1,290,528 and GB in Patent Application 51177/71, and from which fibers can be prepared at conventional fiberization temperatures, at about 1,320 ° C and below.

_ It is assumed that the deterioration in the strength of glass fibers incorporated in cement products is closely related to solution phase reactions or processes on the glass surface, one example being the precipitation of calcium hydroxide crystals such crystalline formation or reduce it. In order to achieve this effect, it is assumed that it is preferable that the aromatic compound is at least to some extent soluble in the calcium hydroxide solution. Examination of the fibers incorporated in the cement by stereomicroscopy has also shown that the fibers coated with the compositions of matter used in the invention have a much smoother corrosion pattern, if corroded by the alkali in the cement, than was observed in fibers not so coated. This, in turn, may contribute to the greater strength retained by the coated fibers.

The polyhydroxyaromatic compound is preferably present in the coating composition as a solution in a liquid carrier, although alternatively it may also be in the form of an emulsion or a fine suspension in such a carrier.

Groups of aromatic compounds that have been found suitable for use as preservatives in the present invention include: u, 58627 b (a) Monocyclic aromatic 6-ring compounds having at least 3 hydroxy groups substituted on the ring, i.

1.2.3-Trihydroxybenzene (pyrogallol) 1,2,4-Trihydroxybenzene (hydroxyhydroquinone) 1.3.5- Trihydroxybenzene (phloroglucinol) (b) Monocyclic aromatic 6-ring compounds having at least 3 hydroxyl groups and at least one other group substituted in the ring by their carboxylic acid and esters, e.g.

2,4,6-trihydroxybenzaldehyde 2,3,4-trihydroxyacetophenone 2,4,6-trihydroxyacetophenone tetrahydroxy-p-quinone dihydrate 2,3,4-trihydroxybenzoic acid 3.4,5-trihydroxybenzoic acid (gallic acid) propyl gallate compounds of groups (a) and (b) in alkaline solution, e.g.

ammonium oxidation salt of pyrogallol ammonium oxidation salt of gallic acid (d) A hetero-monocyclic aromatic 6-ring compound having at least two nitrogen atoms in the ring and at least three hydroxyl groups as substituents on the ring, e.g.

2.4.6-Trihydroxypyrimidine (barbituric acid) (e) A polycyclic aromatic hydrocarbon having at least three hydroxyl groups substituted on one private 6-membered ring, e.g.

purpurogallin 1,2,4-trihydroxyanthraquinone (purpurine) 2,4,6-trihydroxybenzophenone tannic acid naturally occurring plant tannins.

Many naturally occurring plant extracts contain chemical compounds having the above structure and can be used as a protective material in accordance with the present invention in coating compositions, e.g., quebrazochara extract, chestnut extract, sumac extract, grape ethane extract, mimosa extract, and others. to the general group of plant tannins.

When selecting a preservative from the aromatic compound groups generally indicated above, care must be taken to ensure that the molecule does not contain substituent groups which counteract the reduction in glass fiber degradation caused by the three hydroxyl groups to an extent that they render the compound unsuitable for use. When selecting compounds for use, it is therefore necessary to perform comparative selection experiments in the presence of substituent groups to ensure that these substituents do not impair the protective effect to such an extent that the rate of deterioration of the glass fibers is not significantly reduced.

It is to be understood that the polyhydroxyaromatic compounds listed above can be expected to react with alkalis, e.g. calcium hydroxide in cement, due to their phenolic nature. In addition, some of the listed compounds, such as pyrogallol, are oxidized by air when dissolved in an alkaline solution. Therefore, it is not expected that the aromatic compounds will retain their original composition when the coated fibers are incorporated into the cement. The products obtained by atmospheric oxidation of pyro-gallol and gallic acid ammonia solutions (product group (c) above) have been found to be effective as preservatives, indicating that such changes in composition do not affect the protective activity of the substance.

The concentration of preservative required in the coating composition depends on many variables and no precise limits can be said to encompass all variables. The main factors to be considered in determining the amount of preservative in a coating composition are: (a) the solubility of the preservative in the carrier used, (b) the solubility of the preservative in calcium hydroxide solution and the associated effectiveness of the compound considered to reduce the rate of deterioration of the glass fibers in the cement matrix. A compound having high potency and at the same time low potency; J f '8 58627 solubility in calcium hydroxide solution, may be as effective at the same concentration as a compound having low potency but high solubility in calcium hydroxide solution, (c) the cost of the preservative used. It may be more economically desirable to use a less effective expensive compound than a large amount of a less effective film compound, (d) the amount of coating composition adhered to the fiber during the coating process, which determines the actual amount of preservative at the glass fiber-cement matrix interface.

In most cases, a coating composition containing 5% by weight of preservative is effective, and it is unlikely that a coating composition containing more than 10% of preservative would be required or economically viable. However, in a suitable carrier and with the use of a highly effective compound, concentrations of less than 1% may be possible. A suitable selection experiment to determine the efficacy of the compounds is described in more detail below by way of examples. The compounds can be ranked on the basis of the percentage improvement observed in the selection experiment compared to the fibers coated in the same manner as the tested fibers, except that there is no preservative in the coating composition. Compounds that provide less than 10% improvements are not considered suitable for use.

In the case where the composition of matter is intended to be applied as an adhesive to the fibers immediately after they have been drawn from the molten glass mixture, the mixture usually additionally contains a film-forming agent and a coupling agent and is generally water-based. The film-forming agent is then usually in the form of an emulsion in water. The coupling agent is a substance, such as silane, which helps the adhesive mixture to remain on the surface of the glass fibers, possibly forming bonds with -OH groups on the surface of the glass.

The film-forming agent may comprise polyvinyl acetate of a cationic nature, i.e. a polymer of which at least 90% are units derived from vinyl acetate and which, during the polymerization, contain groups which give it a cationic character at acidic pH values. Alternatively, to claim the risk of emulsion breakage, the film-forming agent may be of a non-ionic polyethylene glycol nature. The adhesive composition preferably also contains a wetting agent to facilitate dispersion of the film-forming agent in the aqueous adhesive.

In the event that the composition of matter is intended to be applied as a coating at a later stage in the manufacture or processing of the glass fibers, i. after gluing and combining the individual fibers into a strand, the aromatic compound may be dissolved in an anhydrous solvent.

The glass fibers may be coated with an additional protective coating after the glass fibers have been coated with the coating composition in accordance with the invention to protect the coating composition from extraction during initial contact with the cement matrix and curing of the cement matrix. This additional protective coating can be, for example, an epoxy resin polymer which can be added as a solution dissolved in, for example, acetone. This protective coating is assumed to act primarily during the initial contact between the coated fiber and the wet cement.

Specific embodiments of the invention will now be described, by way of example and with reference to the accompanying drawings, in which: Figure 1 is a graphical representation of the tensile strength of cementitious glass fibers over time bonded with cationic polyvinyl acetate Fig. 2 is a graph similar to Fig. 1 comparing the effects of adhesive compositions containing different amounts of high pyrogallol, even under accelerated aging conditions; Fig. 2a is a graphical representation similar to Fig. 2 comparing the effects of adhesive compositions containing different amounts of pyrogallol in samples stored in water at room temperature; Fig. 3 is a graph illustrating the effect of pyrogallol used in an adhesive composition for glass fibers on the impact strength of glass fiber reinforced cement; Fig. 4 is a graphical representation, similar to Fig. 1, of tensile strengths obtained with two glass fiber types of different compositions, using adhesive compositions with or without pyrogallol; Fig. 5 shows the results obtained by testing cement boards, containing, in respect of glass fiber reinforcement, bending and isis strength, after exposure to weathering for up to 12 months; Figure 6 shows similar results obtained by testing such plates after immersion in water at 28 ° C for up to 12 months; and Figure 7 depicts the results obtained after accelerated aging on similar plates for up to six months.

As mentioned above, when selecting aromatic compounds for use as a preservative, it is necessary to perform comparative selection experiments to determine the efficacy of the compounds, especially if the compounds contain substituent groups other than the necessary 3 hydroxyl groups in the aromatic ring. A suitable test used in connection with the present invention comprises the following method: a filament of continuously drawn, water-bonded glass fibers is made of substantially alkali-linking zirconia-containing glass (hereinafter referred to as glass No. 1) having the following composition in mole percent:

Si02 69%

Zr02 9%

Na 2 O 15.5%

CaO 6.5%

A solution or suspension of the aromatic test compound in a liquid carrier is applied to the fiber to form a coating thereon. It is convenient to test each aromatic compound in more than one liquid carrier to determine the optimal coating system for that compound. After coating, the center of each fiber is encapsulated in a body of a conventional Portland cement pack, which is allowed to cure and maintained for a predetermined time, e.g., 28 days, at an elevated temperature, e.g., 50 ° C, to provide accelerated aging effects. The tensile strength of the encapsulated portion of the strand is then determined by applying a load to both ends of the strand.

The following table shows the results of a series of such comparative experiments performed on fiberglass filaments using 31 different trihydroxyaromatic compounds in each of the three different coating systems and, for comparison, on filaments coated alone with a liquid carrier of the corresponding coating system.

2

The results are presented as measured tensile strengths MN / m at 50 ° C after 28 days of storage and as a percentage improvement over the figure measured in the comparative test. The results obtained with the different coating systems are shown in different columns (1) to (5). These alternative coating systems used were as follows: (1) A 10% solution of the test aromatic compound in water, acetone or ethanol (depending on the appropriate solubility of the compound) was filamented and dried at 50 ° C. A 10% (w / w) solution of epoxy resin (5 1/2 parts Epikote 828 and 1 part Epikure RTB hardener, both sold by Shell Chemicals Ltd) in chloroform was applied to the substrate and cured at 80 ° C. minutes.

(2) A 10% solution of the aromatic compound to be tested in a 3% aqueous solution of polyethylene glycol was filmed and dried at 50 ° C. The top epoxy resin coating was then prepared as described in (1).

(3) A 10% solution of the test aromatic compound in a known adhesive composition comprising cationic polyvinyl acetate as described above was prepared, and this composition was filmed and cured at 115 ° C for 30 minutes.

(* 4) In some cases, the aromatic compound to be tested was found to be unsuitable for mixing with the adhesive composition used in (3). In these cases, a 10% aqueous solution of the aromatic compound was applied to the fiber, dried at 50 ° C for 30 minutes, and then an adhesive composition was applied as a top coat.

'' 'i' 1 2 58627 (5) The system of (1) was followed except that a 5% chloroform solution of epoxy resin was used. From the above description of the coating systems, it can be seen that in some cases it was considered necessary to apply a temporary protective coating to the coating containing the aromatic compound before encapsulating the fiber in the cement. This was done to ensure retention of all the different test compounds and thus to prevent any variation in the rate of release of the substance from the glass fiber surface other than that determined by the chemical nature and physical properties of the preservative during the experiment. This temporary topcoat prevented all leaching of the preservative at the beginning, but did not appear to be an obstacle in the accelerated deterioration rate test after the cement had hardened.

In each example, the table shows the name of the substance and, where practicable, the formulas and, in addition, the tensile strength of the fibers after 28 days at 50 ° C in a block of ordinary Portland cement, tested as described above, and the percentage improvement over glass fibers coated exclusively with a carrier.

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The ammonium oxidation salts of pyrogallol and gallic acid (Examples 2 and 18) are products obtained by dissolving pyrogallol or gallic acid in water to give a 10% (w / v) solution, adjusting the pH to 11 by adding concentrated ammonia solution. and evaporating the solution to dryness. The exact structure of these products is not known, but they are thought to retain the 3 hydroxyl groups of the starting compounds, combined with NH 4 radicals.

It can be seen from the table that the relative potency of the various compounds has been clearly demonstrated by a screening experiment, although more detailed full-scale experiments over a longer period of time are necessary to obtain the exact degree of efficacy of each compound. It is assumed that the relatively low potency observed with cyanuric acid (Example 15) is due to its relatively low solubility in calcium hydroxide solution. A 10% lower percentage improvement figure indicates that the compound is not suitable for use in accordance with the invention.

More detailed experiments were performed using the compounds of Examples 1, 3 and 12 in the table above incorporated into a conventional adhesive composition.

The adhesive composition was made from the following materials:

Weight-%

Polyvinyl acetate of a cationic nature, namely a copolymer with an average molecular weight of 80,000 derived from vinyl acetate and 2% 2-dimethylaminoethyl methacrylate, stabilized with 1% cationic surfactant and sold under the name "National 102-1209" Adhesives and Resins Ltd. * 1 + 0

Pelargonic acid tetraethylene pentamine condensate, soluble in acetic acid and

Arnold Hoffman sells under the name AHCO 185 AE 0.02

Caprylic acid-tetraethylenepentamine condensate, soluble in acetic acid, prepared by Arnold

Hoffman sells under the name AHCO 185 AN 0.01

Polyethylene glycol sold by Union Öarbide Corporation under the name "Carbowax 1000" 0.10 20 5 8 6 2 7 e'-aminopropyltriethoxysilane sold by Union Carbide under the name "A 1100 silane" 0.25

Amide condensate of stearic acid and tetraethylenepentamine sold under the name "Cationic X" 0.20 water remaining The solids content of this adhesive was 6.5 to 7.0% by weight.

Four samples were taken from this adhesive. To three of these samples were added 10% by weight of pyrogallol, 10% by weight of phloroglucinol and 5% by weight of purporogallin, respectively. Four samples were then coated under identical conditions with glass strands of glass No. 1 quality, i. substantially alkali-resistant zirconia-containing glass. Fiber filaments coated with different adhesive samples were tested as described above by encapsulating the center of each filament in a corresponding piece of ordinary Portland cement pace and determining the tensile strength of the encapsulated portion by applying a load to both ends of the filament. The samples were allowed to cure at 100% relative humidity and room temperature for 24 hours and then immersed in water at 50 ° C. Samples were tested after 24 hours of curing, i.e. immediately before immersion in water and after 2, 4, 8, and 12 weeks in water, which treatment mimics periods of several years at normal temperatures under continuously humid conditions, which are the most difficult conditions that are likely to occur in practice.

The results are shown graphically in Fig. 1 of the accompanying drawings. results. In this case, it can be seen that pyrogallol and purpurogallin (which is an oxidation product of pyrogallol) reduced the deterioration of the glass fiber strength by about 50%, while fluoroglucinol also caused a significant improvement.

Other similar experiments were performed on filaments made of fibers of the same glass grade and glued with 58627 21 similar compositions containing 0%, 1%, 5% and 10% pyrogallol applied to the fibers by a conventional type of roller applicator when the fibers were drawn from the brushing apparatus. . The results are shown graphically in Figure 2. They show that the tensile strength (curve 5) of the filament formed by the fiberglass coated with ordinary glue, without pyrogallol, decreased slightly more than 37% of its original value after eight weeks and remained substantially constant thereafter. When the adhesive contained 1% pyrogallol (curve 6), the strength at the beginning was slightly lower than usual. list when using glue, but the figures were higher after two weeks after each period. A greater advantage can be observed in the case where the adhesive contained 5% pyrogallol (curve 7) and 10% pyrogallol (curve 8). The initial strength was similar to that without pyrogallol, but the decrease with time was clearly much smaller. After 12 weeks, the tensile strength was still about 70% of its initial value. The fact that the curves obtained using 5% and 10% pyrogallol are similar indicates that little benefit is likely to be obtained by adding larger amounts.

Figure 2a depicts the results obtained with samples similar to those described in the previous paragraph in water at room temperature after storage for up to 18 months. In this test, which mimics natural aging under very humid conditions, the deterioration in strength is clearly much smaller. Curves 5a, 6a, 7a and 8a show the results obtained using 0%, 1%, 5% and 10% pyrogallol in the adhesive composition. In this case, it can be seen that 1% pyrogallol provided a significant improvement, while 5% and 10% pyrogallol provided a greater and lasting advantage, so that after 18 months the tensile strength of the fibers was only slightly, if at all, lower than after initial curing (24 hours 100%: n relative humidity).

Samples of fiberglass-reinforced cement were prepared from sheets with dimensions of 2x1 meter randomly reinforced with glass grade No. 1 glass fibers, with some sheets comprising fibers glued with ordinary glue and others comprising fibers glued with glue containing 5% by weight of pyro. 22,586,227 gallons, in which case the sheets were formed by spraying glass fibers and cement onto the casting surface. The impact strength of the samples was tested immediately after the cement body had hardened (1 day at room temperature) and again to achieve a rapid aging lasting five hours after the steam treatment at 120 ° C. The results are shown in Figure 3, which shows that the samples initially had similar impact strengths, but samples made of glass fibers glued with a pyrogallol-containing composition (curve 9a) retained a much higher proportion of their original strength after accelerated aging than samples made without pyrogallol. curve 9b).

To compare the effect of pyrogallol-containing coating compositions on different types of alkali-resistant glass grades, experiments were performed on filaments made of glass grade No. 1 glass fiber and glass grade No. 2 glass fibers having the following glass content by weight as follows:

SiO 2 60.6% Al 2 O 3 0.5%

ZrO2 10.6%

Na 2 O 14.4% K 2 O 2.8%

TiO2 5.8%

CaO 5.4% Fibers coated with the cationic polyvinyl acetate adhesive composition used as a reference above were compared to fibers coated with the same adhesive composition containing 5% pyrogallol, both encapsulated in cement bodies, as above. The results are shown graphically in Figure 4, where line 10 depicts glass No. 1 using only the adhesive coating, line 11 depicts glass No. 1 when the adhesive contains pyrogallol, line 12 depicts glass No. 2 using only the adhesive coating, and line 13 depicts glass n: o 2 adhesive containing pyrogallol. In each case, the addition of pyrogallol significantly reduced the deterioration in the strength of the glass fibers.

In order to determine the durability properties of cementitious products reinforced with glass fibers coated according to the invention, sheets were made of ordinary Portland cement using 5% by weight glass grade No. 1 glass fiber as reinforcement, as shown above in connection with Figure 3, and subjected to natural weather conditions for 12 months. . The specimen plates were tested for modulus of rupture (flexural strength) and impact strength, first 7 days after initial curing at 100% relative humidity and 21 days in air curing, and then after 2, 6 and 12 months of exposure to weather. The results are shown in Fig. 5, where line 14 shows the fracture modulus of sheets reinforced with adhesive-coated glass fibers alone, line 15 shows the fracture modulus of sheets glued with 5% pyrogallol-containing composition, using the impact strength of the prepared plates. In this case, it can be seen that under natural conditions, without accelerated aging, the sheets containing pyrogallol-reinforced fibers had equal or better flexural strength than the reference sheets after one year and showed no deterioration in this respect, while the impact strength remained substantially higher than the reference sheets.

Similar sets of plates were assayed for modulus of fracture and islet strength after immersion in water at 28 ° C for up to 12 months. The results are shown graphically in Figure 6. Lines 18 and 19 show the breaking modulus of sheets reinforced with fibers with or without pyrogallol coating compositions, respectively, while lines 20 and 21 show impact strength with and without pyrogallol coating composition, respectively.

Other experiments on accelerated aging were performed on similar plates by immersing them in water at 50 ° C for up to six months, which is assumed to correspond to many years (probably more than 10 years) of natural aging. The effect on the impact strength of the sheets is shown graphically in Figure 7, where line 22 shows the impact strength of sheets reinforced with 5% pyrogallol-containing adhesive-coated fibers, and line 23 shows the impact strength of sheets containing fibers coated with an adhesive composition alone. In this case, it can be seen that the improvement in impact strength compared to the control sample was well maintained throughout the test period. The rate of decrease in impact strength over time decreased to a very small value with a rubber-type plate as well.

The incorporation of the coated glass fibers into the cement mixture can be performed by a spray-up method. In this method, cement slurry and staple glass fibers are sprayed onto a perforated surface of a paper-coated suction mold. The mold is equipped with adjustable protective plates extending around its edges, which makes it possible to produce plates of different thicknesses. After the desired thickness is sprayed, the top surface is smoothed and excess water is removed by applying suction. The plate can therefore be covered and stored until the desired curing time has elapsed, after which the plate is ready for use. The water / cement ratio of the slurry is selected according to the nature of the cement used. The fiberglass material is fed as a groove to the cutting device and the bitterness of the cut material is adjusted by changing the number of blades in the cutting device. The ratio of glass to cement is controlled by changing the number of grooves fed to the cutting device at the same cutting speed or by changing the speed of the cutting device.

Claims (9)

1. Glass fibers which are intended to be used as reinforcement in cement products and which are coated with a composition comprising a protective material to prevent the glass fibers from being destroyed when incorporated into cement products, characterized in that the protective material contains at least one monocyclic or polycyclic aromatic compound having at least three hydroxyl groups in the aromatic ring or in one of the aromatic rings. 2. Glass fibers according to claim 1, characterized in that they are formed from an alkali-resistant glass composition containing at least 5 mole% of ZrC 2. Glass fiber according to claim 1 or 2, characterized in that the aromatic compound is soluble in a calcium hydroxide solution. M ·. Glass fibers according to any of the preceding claims, characterized in that the aromatic compound is a 6-membered ring compound with at least three hydroxyl substituents in the ring. Glass fiber according to any one of claims 1-3, characterized in that the aromatic compound is a product obtained by oxidizing in an alkaline solution a monocyclic 6-membered ring compound with at least three hydroxyl substituents in the ring. Glass fiber according to any one of claims 1-3, characterized in that the aromatic compound is a monocyclic 6-membered ring compound having at least three hydroxyl substituents and at least one other substituent in the ring, or a carboxylic acid salt or a carboxylic acid » Glass fiber according to any of claims 1-3, characterized in that the aromatic compound is a product obtained by oxidizing in an alkaline solution a monocyclic 6-membered ring compound with at least three hydroxyl substituents and at least one other substituent in ring. Glass fiber according to any one of claims 1-3, characterized in that the aromatic compound is 'J'.