DE1088405B - Process for the production of synthetic resin-coated cement moldings - Google Patents

Description

GERMAN

The invention relates to the manufacture of coated hydraulic moldings Cement, especially asbestos cement, for example in the form of shingles and cladding panels.

It is known to use aqueous dispersions of various synthetic addition polymers on cement moldings to avoid the blooming that occurs when water is contained in the molding leaches out small amounts of free calcium oxide. The water can already be in that from the production Formling be present or by an accelerated aftertreatment, which is called steam autoclaving is known to be brought up. The polymers of styrene used for this purpose have the Disadvantage that they discolor when they are outdoors are exposed to the elements and ultraviolet light. Polymers of vinyl acetate tend as a result the alkaline content of the cement molding to hydrolysis and therefore fail in the autoclave treatment or result in deterioration of the molding over time with natural aging. Polymers, which are largely composed of ethyl acrylate and methyl acrylate are also subject to one such hydrolysis, albeit to a somewhat lesser extent than the polymers of vinyl acetate. Such Copolymers can still be used satisfactorily in the so-called dry Norton process manufactured shingles where the cement asbestos slurry is only a stoichiometric amount Water is added, but they fail with products made by the Hatschek process with excess are made of water.

Polymers that largely, e.g. B. 85 to 100 percent by weight are made up of methyl methacrylate, result in practically complete hydrolysis resistance, regardless of the process used to make the moldings, even if the polymer is up to 15 weight percent of a lower alkyl acrylate or vinyl acetate which is normally subject to hydrolysis. Unmodified aqueous However, dispersions of such copolymers are capable of continuous coating films only when they are used high temperatures form used by the industry in question for economic reasons and often cannot be used because of handling difficulties. It also sets the boiling point of the water has an upper temperature limit that could only be exceeded when plating the cement moldings would be made in a chamber such excess pressure that a boiling of the Prevents coating mixture during drying.

The application of plasticizers, such as dibutyl process for the production of synthetic resin-coated cement moldings

Applicant:

Rohm & Haas Company, Philadelphia, Pa. (V. St. A.)

Representative: Dr.-Ing. Dr. jur. £ 1. Mediger, patent attorney, Munich 9, Aggensteinstr. 13th

Claimed priority: V. St, v. America April 1, 1958

Richard Edward Zdanowski, Philadelphia, Pa., George Lincoln Brown and Björn Eric Larsson,

Moorestown, N.J. (V. St. A.) have been named as inventors

phthalate (b.p. 340 ° C), butylbenzyl phthalate (b.p. 380 ° C) or Afyloxyalkyläther (Sp. above 350 ° .C) according to USA. Patent 2286767, promotes the manufacture of related Films made from such polymers at tolerable temperatures. But these additives have the serious disadvantage that they owing to their high boiling point and low volatility are retained in the polymer film under normal drying conditions and therefore give it a give a very plastic character. This results in two major difficulties, which in many cases the use of such plasticized ones because of excessive rejects in the manufactured product. Forbid systems, namely:

1. If newly formed shingles are subjected to the accelerated aftertreatment in the autoclave, wherein the briquettes for periods of 6 to 18 hours in a steam atmosphere at 150 to 180 ° C are exposed, the highly elastic state of the coating film causes water to easily enter the polymer layer can penetrate, resulting in redispersion of the polymeric particles and. to destroy the cohesion of the film leads. Steam distillation or simple evaporation of plasticizers from the dispersed polymeric particles in turn lead to the deposition of as soon as the autoclave is cooled not sintered together polymeric particles on the surface of the molding in the form of salt-like

009 589/377

3 4

Deposits that are commonly used in industry, such as in high temperature and high humidity

are referred to as watermarks. As a result, autoclave processes are stacked. For execution

Not only is there a lack of coherent protection, the invention is based on aqueous dispersions of

This prevents blooming, which is the case with autoclave copolymers, which are produced in the usual emulsion process

treatment is a serious problem, but 5 based on at least 85 percent by weight methyl

These watermarks are already made from methacrylate, by incorporating them

the molding unsightly and commercially unsightly - about 20 to 60 percent by weight (calculated on

reversible. Polymer weight) of a water-insoluble solution

2. Even if the autoclave treatment is avoided with a boiling point of 760 mm / Hg in the range

the and the blooming reduced, if not io from 150 to 255 ° C, preferably from 170 to 215 ° C,

is completely eliminated, the coating layers are that modified. The lower limit of the boiling range for

With such high-boiling plasticizers plasticized the solvent is chosen so that the modifier

are so sticky that the coated moldings do not escape from the polymer particles before so much

water could not evaporate without the risk of sticking together so that the particles

let it peel. This not only makes it difficult for the 15 tion to have progressed to the point where the

to separate individual moldings from each other again, polymer particles can be deformed and to

but often the coating film tears and loses a continuous film flow together. At-

its effect as a continuous protection against that on the other hand is the upper limit of the boiling point range

Blooming. chosen so that if the continuity of the coating

In US Pat. No. 2,778,283, it is proposed that the solvent is first introduced

an unaged cement molding, leaves the film so easily that the film

z. B. an asbestos-cement shingle, with a water-hardens.

igen polymers of an acrylic ester in the non-aged Solvents of the general type are preferred

State to be covered and at the same time to the stacking of formula I

coated moldings during drying without 25 R '- (OCH ₂ - CH ₂ ) _K OCR

To ensure sticking together the polymer ||

to incorporate a small amount of acid while q
at the same time a polyvalent metal is present, so

that the polymer is crosslinked. Through this connection, R denotes an alkyl group with 1 to 3 carbon atoms, the otherwise unavoidable stickiness of 30 substance atoms or a phenyl group, R 'is an alkyl and sticking together during stapling and group with 1 to 4 carbon atoms and η the entire drying process. But because after the procedure number 1 or 2.

of this patent specification polymers are used, the following are examples of these solvents

Form films at well below 100 ° C, and because these are listed with their boiling points:

This purpose, the content of methyl methacrylate is limited to 35 2-ethoxyethyl acetate (156 ° C), 2-butoxyethyl acetate

prevent these preparations at drastic temperatures (191 ° C), 2- (2-ethoxyethoxy) ethyl acetate (217 ° C),

treatment in the autoclave does not result in blooming and 2- (2-butoxyethoxy) ethyl acetate (246 ° C), 2-eth-

also wrap the so-oxyethyl propionate, 2-ethoxyethylbutyrate (188 ° C),

named watermarks. 2-methoxyethyl propionate (159 ° C), 2-methoxyethyl

According to the process of the invention, all 40 butyrate (177 ° C) and 2-methoxyethyl benzoate (252 ° C); these disadvantages eliminated. It is characterized by the fact that suitable solvents, 3-ethoxyprographs, are applied to a fresh cement molding, pyl acetate, 3-ethoxypropyl propionate, benzyl alcohol, a coating layer of an aqueous dispersion (205 ° C.), benzyl acetate (213 ° C.), benzyl propionate, which a polymer based on 85 to (220 ° C), benzyl butyrate (240 ° C), butyl lactate (188 ° C), 15 percent by weight methyl methacrylate and up to 45 ethyl benzoate (211 ° C) and isophorone (215 ° C).
15 percent by weight of other monounsaturated The polymers of polymerizable monomers to be used according to the process as well as a water- can contain 100% methyl methacrylate and must contain 85% insoluble organic solvent with a methyl methacrylate. Mixed polymers with a boiling point of 150 to 255 ° C for the polymer contains 15 percent by weight of other monomers, in particular and dries the coated molding. Here 50 more esters of acrylic acid with alcohol with 1 to 18, the polymer up to a maximum amount of preferably 1 to 4 carbon atoms, such as methyl, 2 percent by weight of all its monomeric structural ethyl or butyl acrylate, are suitable. A small stone consists of monomers that give the mixed poly part, about 0.25 to 2 percent by weight of the mixed kidneys, a hydrophilic character. polymers can consist of monomers that

In the process, aqueous dispersions 55 give the polymer hydrophilic properties, which are applied to the finished moldings, for example acrylic acid, methacrylic acid, Itacon as well as to the fresh moldings acid, acrylamide, methacrylamide, / I-oxyethyl acrylics. The process provides a permanent Über- lat, / 3-Oxyäthylvinyläther, / J-Aminoäthylvinyläther, train on the formations, which both in the auto / 3-Aminoäthylacrylat, ^ -Ν, Ν-Dimethyläminoäthylacryklave ^treatment as under natural aging 6o lat u The polymer dispersions can be prepared and weather conditions prevent blooming by putting them in water at temperatures from 0 to 0 ° C. The coatings are resistant to water, ultraviolet 100 ° C, preferably from 10 to 60 ° C, either light and moisture penetration, highly methyl methacrylate or a mixture of at least one, have an unusually glossy 85 percent by weight methyl methacrylate with an or appearance and are resistant to staining Dirt 65 several other monomers of the type mentioned or water brands are less susceptible. The invention is emulsified. Any known emulsifying agent with the polymer dispersion defined above of anionic, cationic or uncoated finished or fresh cement moldings of ionic character in amounts of 0.5 to 6 percent by weight of the monomers is suitable for drying or for aftertreatment. The polymerization either at normal room temperatures or at 7 ° then takes place in the above-mentioned temperature range

by adding free radical initiators, e.g. B-. Azo catalysts and the like. Peroxidic Catalysts, especially catalytic systems of the redox type, e.g. B. a combination of Potassium persulfate and sodium metabisulfite are recommended. Other suitable peroxidic agents are the persalts, e.g. B. Alkali metal and ammonium persulfates and perborates, hydrogen peroxide, organic Hydroperoxides such as tert-butyl hydroperoxide and cymene hydroperoxide and esters, e.g. B-. tert-butyl perbenzoate. In this way, it is possible to produce dispersions that are only about 1 to 60 percent by weight of the resin copolymer. It is preferable, however, to prepare dispersions that are about 30 to Contain 50 percent by weight of solid resin components and before application to the asbestos cement moldings be diluted to the desired extent. In general, the polymers so produced have high molecular weights up to the order of one to several million.

The solvent to be used according to the invention is preferably the aqueous dispersion after Including completion of the polymerization, if necessary but it is also possible to add it before or during the same. The amount of the solvent can be wide can be varied. There should be at least as much solvent present that the dispersion at Forms continuous films at temperatures below 100 ° C. There can be so much solvent be added that the confluence or the film formation with simple drying at normal Room temperatures of 15 or 20 ° C occur. The amount of solvent used depends on the Minimum temperature at which film formation is desired, and is also determined by the respective in the aqueous dispersion contained polymers conditionally.

In addition to the solvent, pigments or dyes can also be incorporated into the dispersion change the character of the coating when clear, colorless coatings are not desired. The dispersion is on the cement, especially asbestos cement, in the usual way, for. B. by spraying, flooding etc., applied. You can either before or after each pressing and / or embossing treatment Mixtures are applied, but preferably after the cement mix is pressed and a heat treatment has been subjected, for example in an oven or under a battery of heat emitters. But also mixtures that have not yet been treated with heat can be coated and then be heated. It is crucial that the coatings applied from the dispersions dry quickly to form non-tacky layers before the coated ones Products are stacked for post-treatment.

The following embodiment of the method is particularly favorable:

A freshly formed wet plastic tape of asbestos cement, colored or undyed, is used as the molding part the machine is guided on a conveyor belt through a gas-powered hot blast furnace, so that the surface of the cement tape assumes a temperature of approximately 60 to 66 ° C and the Moisture content drops to about 20%.

The still plastic and non-rigid cement tape is then superficially embossed by contact with an embossing roller, and immediately thereafter a polymer dispersion of the type indicated above is sprayed on. The dispersion has a solids content of about 10 to 20%. However, this is not a critical parameter, but "this concentration is only chosen in order to easily achieve a film coating of adequate thickness. The application is 2 g or more, preferably 2 to 3 g, of resinous solid per 900 cm ^2. The amount still in the cement tape The existing heat content is sufficient to dry the dispersion to such an extent that a clear, non-blocking and non-adhesive resin film is formed. The cement tape can then be cut to the desired formats and sizes. In this state, the asbestos-cement mixtures coated according to the invention are so soft and plastic, that they are deformable by pushing them in by hand, but still do not stick. The moldings are then removed from the belt and stacked for post-treatment. The weight or pressure of the layers or plies of cement mixture in the lower parts of the stacks is inevitably very high, but however the resin coatings of the invention nevertheless do not become tacky and do not adhere to others Surfaces. They only retain their excellent adhesion to the surface to which they were applied.

The post-treatment of the moldings or sheets can be carried out under atmospheric conditions not subjecting them to temperatures higher than those resulting from exothermic hydration of the cement results. The latter process can, however, be accelerated by an accelerated aftertreatment cycle to such an extent that a complete or near complete hydration is achieved in a period of 6 to 16 hours. In the Autoclave treatment, the coated moldings, perhaps after a few days of natural aging, placed in a high-pressure chamber known as an "autoclave" which, after it is closed, is filled so far with steam that the internal temperature is between 150 and 180 ° C. Under in such hot and humid conditions the risk of blooming is extraordinarily strong, and it is practically impossible to post-treat uncoated moldings without this disruption. Def coating after the Invention eliminates this problem. The moldings are removed from the autoclave in the post-treatment cycle removed and, if this has not already happened before, are now cut and transported packed up. - ·

The following examples illustrate embodiments of the invention. The quantities are calculated on weight.

example 1

In a conventional cylinder molding machine, a sheet is formed from an asbestos-cement mixture. The wet web is 3.9 mm thick and consists of several layers and an overlay approximately 0.37 mm thick. The mass consists of 80% Portland cement and 20% asbestos fiber, the top layer of 60% Portland cement, 18% asbestos fiber and 22% mineral oxides as pigments and fillers. The cement tape with approximately 20% moisture is passed under a battery of radiant heaters, which reduce the moisture to around 18%. Then the surface of the web is given relief with the help of embossing rollers and sprayed at about 60 ° C with an aqueous dispersion containing 20 percent by weight of a copolymer of about 89% methyl methacrylate, about 10% ethyl acrylate and about 0.5% methacrylic acid and 40 weight percent 2-butoxyethyl acetate , calculated on the weight of the copolymer. The spray device is set to the speed of the tape machine, so that on 900 cm ^{2 of} the

Cement tape about 2 to 3 g of polymer can be applied. The coated belts run through one short dryer section, where the moisture content of the applied resin film is reduced and an essential one Part of the organic solvent is removed so that a coherent non-tacky Polymer film remains on the cement tape. Now the tape is divided into individual sections or units of 60 x 120 cm, and these are immediately cut to a height of 60 to 90 cm on wooden Documents stacked. At this stage the plates are soft and could be between your thumb and Index fingers become torn or deformed. They are not rigid, but so plastic that they become the Adjust the shape of the surface on which they are applied. The pieces are placed on top of one another and stored in a warehouse at room temperature for 3 days. Then the individual pieces of removed from the wooden documents, perforated, cut to the final size and packaged. It ao no sticking occurs. The finished pieces do not show any signs that they stuck together.

Example 2

You work according to Example 1, but the individual pieces that are cut are not stacked stored at room temperature, but placed in an autoclave, where it is 8 hours at about 170 ° C be heated. During this treatment, the solvent is almost completely removed. After this Removing them from the autoclave does not stick the pieces together, and neither do the asbestos-cement blanks are characterized by a uniform, clear, glossy coating of the polymer.

Example 3

The procedure is as in Example 2 using a copolymer of 85% methyl methacrylate and 15 weight percent methyl acrylate and with isophorone as a plasticizer.

Example 4

The procedure is as in Example 2, but the butoxyethyl acetate is used as a plasticizer for the acrylic copolymer is replaced by benzyl alcohol.

Example 5

The procedure is as in Example 2, but the butoxyethyl acetate is used as a plasticizer for the acrylic copolymer is replaced by 2- (2-butoxyethoxy) ethyl acetate.

All cement moldings according to the invention are characterized by an advantageous appearance and a attractive shimmer that they retain for a long time. They do not bloom and also change color not exposed to sunlight and are not impaired by hydrolytic effects.

Example 6

With a conventional molding machine, cement blocks are made from a cement mixture that, calculated on solids, 9.1% Portland cement, 37.5% sand, 48.5% gravel (with a grain size of 9 to mm) and contains 4.9% water. The deformation is carried out so that with a minimum of heating A battery of radiant heaters enables the surfaces of the blocks to reach a temperature of 60 ° C. One surface of each cement block is sprayed with an aqueous dispersion containing 18% emes copolymers of methyl methacrylate and ethyl acrylate in an approximate ratio of 9: 1, furthermore, calculated on the weight of the copolymer, 3% sodium lauryl sulfate and 40% 2-butoxyethyl acetate contains. The spraying is adjusted so that 2 to 3 g of mixed polymer per 900 square cm of cement surface can be applied dry. The injected blocks are sent through a short drying zone, wherein the moisture content of the applied resin film is reduced and a substantial part of the organic solvent is removed, so that on the blocks a cohesive non-sticky Coating layer of the copolymer remains, which is uniform, clear and glossy. The cement blocks are stacked on top of each other and stored under wet canvas for 1 week at room temperature. Even after this period of time, the blocks have no tendency to stick to one another. The blocks become more Left in a warehouse under ambient conditions for 3 weeks before shipping.

Example 7

The procedure is as in Example 6, but the blocks sprayed with the copolymer dispersion are stored not under a wet canvas, but heat it for 8 hours in a steam autoclave to about 77 ° C. The solvent becomes practically complete evaporates. After being removed from the autoclave, the cement blocks have a uniform gloss Coating layer of the copolymer.

Claims (5)

Patent claims: 1. Process for the production of synthetic resin coatings Cement moldings, characterized in that a coating is applied to the cement moldings from an aqueous dispersion made from a polymer of 85 to 100 percent by weight methyl methacrylate and up to 15 weight percent of another monounsaturated olefinic monomer and a water-insoluble organic solvent for the polymer having a boiling point from 150 to 255 ° C is applied is, with up to a maximum of 2 percent by weight of the monomers that make up the polymer, are chosen so that they give the formations hydrophilic character and the coated Cement moldings are then dried. 2. The method according to claim 1, characterized in that the dispersion on the fresh Molding is applied while it is still in a moist, soft and plastic state. 3. The method according to claim 1 or 2, characterized in that the coated cement moldings stacked on top of each other and then for a longer time at room temperature or a shorter time at 150 to 180 ° C in a steam atmosphere. 4. The method according to claim 1 to 3, characterized in that a solvent of the general formula R '- (OCH ₂ -CHa) _n OCR ■ ■ '■. -Il is applied, where R is an alkyl group with 9 10 1 to 3 carbon atoms or a phenyl group, mers from 85 to 100 percent by weight of methyl R 'is an alkyl group with 1 to 3 carbon atoms methacrylate, 0 to 15 percent by weight ethyl acetate and η has the value 1 or 2. lat and 0 to 2 percent by weight methacrylic acid 5. The method according to claim 1 to 4, characterized with a molecular weight of several millio- characterized in that an emulsion of a polyene is used. '© 009 589/377 8.60