DE1571138A1 - Method for producing a coating - Google Patents

Description

DR. F. ZUMSTEIN - DR. E. ASSMANN - DR. R. KOENIQSBERQER PATENT LAWYERS PHONE; 22 34 78 and 221B11

TELEGRAMS! ZUMPAT PO8TSOHECKKONTOi MÖNCHEN B1130

BANK ACCOUNT: BANKHAUS H. AUFHÄU8ER

Hu / N 2/2/1 3.75-452

Foam coatings

8 MONOHS 2,

BR «UHAUS8TRA88e 4 / m

I Dr. Expl.

HEED PAEBR GROUP LIMITED, London / England

Process for making a coating:

This invention relates to an improved method of applying coatings to surfaces for forming clay surface layers thereon, and more particularly relates to that Applying coatings to surfaces that are difficult to. are coated, for example as a result of their rough / strut door or their absorbent properties. The invention is mainly applied to coating paper and i Cardboard as these problems are particularly urgent However, you are not into overlaying such i Materials, but is used for over- »/ pulling wood, plaster, textiles, regenerated oil film, Lieder, plastics and metals. -

By applying coatings to paper and cardboard, the surface properties of these substances can be changed while at the same time many of their desired qualities,

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e.g. the low density and flexibility are retained. Many methods of coating paper have been suggested especially in order to obtain certain properties, such as improved opacity, improved ink absorption and reduced permeability to water and water vapor. Coating compositions which are useful for producing such coatings usually contain water or a volatile organic liquid as a carrier for the coating component, and although useful coatings can be obtained from such compositions, the use of these compositions leaves nothing to be desired much to be desired on paper and cardboard. When using aqueous emulsions, for example, the water can become the substrate

penetrate, which requires additional drying facilities

"borrowed, and also the coating component / can be considerable Amounts are in the interstices of the paper or paperboard rather than on the surface where it is needed.

Cardboard for use in the manufacture of cardboard boxes is occasionally covered with paper on one side, the an ^ - the other side has a rough structure and absorbent properties maintains. For many types of application, however, it is necessary also cover the other side with a release coating to prevent the contents of the box from migrating. This can can be achieved by applying a single layer of a molten material such as polyethylene wax. the Application of layers to produce effective separating layer overlays from solvent and emulsion systems

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unfavorable, firstly because of the absorption capacity of the cardboard and second, because of the rough structure of the cardboard, some uneven coating.

In an attempt to overcome this problem, -was out the coating compound formed a foam and applied to the cardboard, in this way a thick layer of foam on the Cardboard made. However, the applied foam dried very much slowly and after drying provided a coating called the the properties of a barrier layer were missing however "found that foamed coatings on surfaces can be applied to form usable coatings (depending on the properties of the coating components), if at least a part and. preferably virtually all of the attached foam is mechanically broken. To this . Some of the usable release coatings on cardboard could be used can be produced with a rough structure.

An important advantage of this method is that the Mass used to produce a coating on the surface can be without significant wetting of the material by the in the case of an absorbent material liquid medium of the coating mass takes place. If the surface has a rough structure, as is the case with cardboard Pail is so can a relatively thin coating over the // be generated on the outside surface, 'i.e. * both in the "valleys" ■ alc also ßui the "embankments" and the "ridges".

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However, the method is not limited to this fairly specific type of application, and it is very suitable for that Application of many coating compounds on paper, whereby the process compared to the usual coating process of paper and cardboard industry has advantages, especially when the coating on the paper or cardboard as an integral part Part of the manufacturing process is applied. In this way, the method can then be used very generally when a liquid coating is to be applied to paper or cardboard, e.g. to improve the print quality to improve, especially if the liquid coating composition is based on water.

According to the invention, a method for applying a j Coating created on a surface, which consists in that of a liquid coating composition, which at least contains a coating component, a foam is formed with a gas or a vapor, this foam on a surface brought and mechanically at least a significant 'portion of the physical structure of the foam coating comminuted or is broken to form a continuous surface coating over the surface. f

The coating used in the inventive method s_ "as se can be used as a coating component -or more of the following l _f

Substances contain: f .;

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A. Plastomers or elastomeric vinyl polymers or copolymers, for example polyethylene, polyvinyl chloride, poly * -. ■ vinylidene chloride, chlorinated polyvinyl chloride, / polymethyl methacrylate, polyacrylic acid _t polyvinyl alcohol * ^^ polyvinyl acetate, butadiene-styrene copolymers, acrylonitrile-butadiene-styrene terpolymers, butadiene-aorylnitrile copolymers, synthetic butyl rubber, uroprene rubber. . .

B. Condensation polymers, regardless of whether thermoplastic or not, z ₀ B _e aminoplasts, such as urine, often -Iormaldehyde and melamine formaldehyde, phenoplasts, such as phenol ^ Mo rmaldehyde, polyester and polyamides ,, - ^::

G. Polysaccharides and derivatives thereof, including _: starch, cellulose, cellulose acetate, carboxymethyl oil oil, ethyl cellulose, vegetable gums and vegetable mucilages such as: a » ^; B. Manna gums (sugar gum tree), such as carob gourami and gruar gourami. ^:> v / _,; -

D.! Animal and vegetable proteins, such as casein and -. Gelatin. -; -

• E. Inorganic polymers such as alkali and bradalkali * • Silicates and clays. ;

.. iiilioiumorganigche polymers,

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toilet.

G. Synthetic and natural waxes, such as »paraffin wax, microcrystalline wax, halogen waxes, beeswax and Garnauba wax.

H. Rosin and rosin derivatives, e.g., hydrogenated rosin.

I.! Drying and semi-drying oils, such as linseed oil, dehydrated castor oil, tung oil, oiticica oil and pentaerythritol tetralinoleate.

| E. Possible reaction materials, for example epoxy resins in combination with polyamides, polyamines or polyesters.

the coating component is usually liquid, it can be used without adding any volatile liquid, den, but with the addition of other desired substances, such as. 'H.B, surfactants and pigments.

"I.

The method according to the invention is, however, particularly applicable to coating compositions applicable on the basis of water, for example in the form of a polymer latex. Bs can also be used for attachment be used by coatings made of masses in which the liquid medium is an organic solvent, in in which the binder is either dissolved, dispersed or emulsified is present.

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• In addition to the binder and the liquid medium, the coating composition can also contain other components, for example surfactants, pigments, fillers, dyes, and vapor phase corrosion inhibitors depending on the intended one Use. It is particularly advantageous to use compositions based on water that have a surface-active substance Agent included as the latter is of value in foaming. The surfactant can be anionic, cationic, be ionic or amphoteric, depending on the nature of the other constituents of the mass *

In order to improve the viscosity of the coating compound, it can ■ contain one or more thickeners including substances that otherwise act as binders, such as Z ₀ B * • polyvinyl alcohol and the rubbers.

The relative proportions of the various components of the coating composition depend on the type and function of the desired Coating. ■ -

In order to convert the coating compound into a foam structure they are subjected to the action of a gas or vapor at normal or overpressure. For most purposes air is hiring suitable gas. However, other gases and vapors can also be used can be used .. For example, if the cover * mass is sensitive to oxygen, an inert gas such as nitrogen or carbon dioxide, to the other gases

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can be applied include fluoro and chlorofluoroalkanes and -oycIoalkanes. Optionally, the gas can also be used in situ by conversion, formation of two or more substances, e.g. by acid / alkali systems.

The coating composition is preferably at least twice and advantageously foamed to at least four times the original volume. The range of two to ten times the The original volume is usable. The coating mass can be foamed with all usual means, e.g. with one of the mixers used in the expansion rubber industry be used by rubber foams. Preferably the foam is practically immobile.

In the case of an endless web, such as paper or cardboard, the Foam preferably applied to the surface and by a knife or edge that extends across the width of the web extends, crushed or destroyed. I am an example of such a thing The middle is a rear edge (see Tappi, 43, no.2, page 200 A). Optionally, a slot nozzle application machine, Rollers, a Meyer rod, or a reciprocating brush applicator can be used. But what means to J Application of the foam can also be used; it is essential that a substantial part of the foam structure is mechanically crushed will. Therefore, if a trailing edge or blade is used, it should be adjusted so that the foam is impossible to get under the edge or blade can pass through and come out,

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without being partially destroyed, for practical purposes. the edge or blade should be adjusted so that the covering edge is in physical contact with the surface the web which is to be covered if it is desired to comminute practically all of the foam, in a similar way rollers and Mayer rods can also be used in practice.

It must be pointed out, however, that it is not necessary is to crush practically all of the foam that it does

a/ :

It is important that / a significant part is destroyed in order to achieve an acceptable level Obtain coverage of the surface. So remains a trailing edge in contact with the surface very little Foam after the surface has passed the edge of the applicator. However, the trailing edge 'can be set so that that, for example, 5 to 50. $ of the foam can pass under the applicator, and this remaining foam becomes then by other means, e.g. by physical collapse, destroyed. This can be an advantage when pulling over » of crepe paper, _-;

, Although it is convenient for many Anwendungsartin, eiijler at least partially facing en destruction by a single means, such as _i, to make the attachment of the foams and effecting a trailing edge is / is not essential. So the foam can suf. dl® Oberfläoh® by means of a bakel or rear edge attached to Wfrdin, äi® was placed in such an abataad by the person to be covered that it was evenly doused

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is formed on the surface. The foam layer can then partially collapse physically before a significant proportion of the best is mechanically destroyed, e.g. B. with a trailing edge.

It is clear that the method according to the invention can be applied to individual

• Board, such as plasterboard and resin board, can be used can. . ".

The foam is advantageously fed to the coating application device via a branched pipeline, the volume of the foam emerging therefrom according to the absorption of the mass by the surface that is to be coated will.

Bs "may prove to be necessary, particularly when a continuous web is coated at least twice the surface: jth a coating having the desired properties sheep to obtain _f to coat In this case, two or more contract may be used vorrichtungen'in row. with an appropriate interval between them in order to obtain a satisfactory drying from the previous coating operation?!.

The method according to the invention can advantageously be used in a paper or cardboard manufacturing machine to make it possible

• ιu atftohen, a liquid coating mass at any point

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to be applied during or after drying. By applying the coating composition to the paper in the form of a foam instead of in '' Form of a liquid is applied, more careful regulation can be obtained. For example, most of them have to Coating masses are kept mobile during application to prevent settling and if the paper tears, it is difficult to control the fluid due to its mobility. If on the other hand a. Hot when used a foam takes place, the application of the foam can be carried out a valve can be stopped and the machine started up again without you having to worry about that. Mobility of the foam needs to be made. When the paper or the cardboard is coated on the machine, a separate coating operation is obviously unnecessary. This is important in terms of the economic efficiency of the process *

■■ - ".-

The method according to the invention is advantageous when coating of paper to make relatively thin special effects tiber eyes preserved, e.g. when using light-weight alumina coatings on a backing paper with a high mechanical pulp content to improve its brightness; when using lightweight opaque coatings (the e.g. contain titanium dioxide), ^ as process takes place Also used in the production of coated papers for lithographic prints and in the coating of newspaper ' paper with pigmented coating compounds, e.g. pigmented

© y

Starch pastes to obtain surfaces that have improved printing.

have properties.

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The process according to the invention is also of particular value when coating cardboard with aqueous emulsions from polyvinylidene chloride to coatings that are resistant to water vapor to obtain.

For a better understanding of the invention, the following examples are given by way of illustration only. So far Unless otherwise stated, the parts always relate to weight.

Example 1

Coating of cardboard

This example shows that the foaming of a thermoplastic Emulsion their economic application on the rough and ^ absorbent back of a white-lined chipboard , made possible.

It became an emulsion of an aqueous polyvinylidene chloride latex used, which was previously difficult to apply due to its pronounced tendency to foam. For stabilization of the foam obtained, the latex became a solution of polyvinyl alcohol added. Wrapping in Duron, with air, turned this mass into a stable foam four times the original Volume of the mixture made. The foam was placed on the back of a chipboard lined with white attached using a Meyer rod ΪΓγ · 4. The “The coating was extremely light and didn't have to be thrown or puckered

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and other difficulties that usually arise when aqueous coatings are applied to absorbent surfaces. Multiple coatings were also made.

A number of coated paperboards were produced with between T and 5 coatings. These were tested for coating weight resistance to oleic acid at 80 ⁰ C and .on water vapor permeability and thereby receive the following results':

number

the coatings

2 3 4

. ■ 5.

Coating weight ²

Resistance to

Waastrdanigf (trop, Oleic acid at 80 0 humidity)

3.5

9 10

1 hour 30 Hin.
3 hours ΙΟ min.

very

size
resistance

1939 yarn

423 yarn

47 gsm

28 gsm

12 gsm

The composition used in this example had the following composition:

Alcotex 99 / 3O ¹ V 10 parts ^;

Polidene 901 ² ^ '125 parts

1) Aqueous polyvinyl alcohol, $ 10> solids, molecular weight 70-80,000;

2) polyvinylidene chloride emulsion _s 50 fo solids; contains a mixed system of anionic and non-ionic super-

. surface activeQji means, ■

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Example 2

Pigmented newsprint cover

This example is intended to show that foamed versions of pigmented paper coatings are very easily applied to a weak water-sensitive sheet of newsprint can.

A coating compound consisting of kaolin, casein and a styrene-butadiene copolymer latex was made, was foamed with air to four times its original volume, without any other additions. This foam was applied to newsprint by means of a rear blade device, with which a laboratory coating application machine was equipped. A closed paper loop was used here, including multiple coatings on the newsprint could be attached in quick succession by repeatedly going through the rear blade device.

Samples were thus prepared which received 1 to 5 coats applied as described above. These were examined for coating weight and print quality, with the following results:

nits were obtained: s

Coating weight

Number of exercises] ? trains g / m ^ Print quality 0 0 very bad 1 4.88 satisfactory 2 9.75 Well 3 14.65 very good 4th 19.5 very good 5 24.4 very good 009848/1447 BATH ORIGINAL

Example 3 . '■

■ This example shows that a foam consists of an otherwise. ' customary coating composition - based on starch by the method according to the invention satisfactorily using a Rear blade device using a laboratory coating application machine was connected, can be applied. ■

A mass of 40 parts clay, 8 parts starch, 52 parts water and 0.03 part foaming agent was! five times the original Foamed in volume and applied to a number of different papers as described above. One received such even coatings with good coverage. "

"4,

The foaming agent used in this and the following examples was a 10% aqueous solution of 75% aqueous Sodium Lauryl Sulphate.

Example 4

This example shows the use of the method according to the invention for the application of coatings with high coverage.

From 35 parts of titanium dioxide, 35 parts of water, 25 parts of acrylic resin emulsion, 5 parts of dye and 0.03 part of foaming agent a pigmented mass was produced, which is based on the five-fold * before their original volume is foamed and on a laboratory exercise pull on application mazohine, as described in example 3, applied to unbleached kraft paper and other papers became. The products obtained in Jöen's experiments showed a '

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uniform coverage, and the opacity of the coatings, in particular the one applied to the kraft paper was sufficient, to mask the strong background coloring of this paper.

Example 5

This example shows, like example 3, the application of a clay coating to paper, but with a different binder, namely Polyvinyl alcohol is used. This binder is particularly useful for the production of foams according to the invention suitable"

From 15 to 35 parts of kaolin, 85 to 65 parts of water, 1.2 to 2.8 parts of medium viscosity polyvinyl alcohol and 0.03 to 0.15 parts of foaming agent produced a pigmented mass, which has been foamed to six to ten times its original volume and applied to various papers in the drying section of a papermaking machine,

which by means of a rear blade, in place of the foams were substantially destroyed and a thin, uniform coating was formed. On the remaining part of the drying section drying was completed.

^ example 6

This example illustrates the use of the method according to the invention for a completely different purpose, i.e. for production of separable coatings on paper. For this purpose, a react ions capable hasne used.

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A mixture was prepared from the following ingredients;

Silicone resin '

(40 ^ aqueous emulsion). 5.70 parts

Catalyst 2) 1.14 "

Foaming agent 2.28 "

CMG solution Λ i ». 68.28 »

Y / asaer 22.60 "

1) MS 2218 from Midland Silicones ltd,.

2) MS 2230 "" it n

This mixture was foamed to between five and ten times its original volume and according to that described in Example 2 Process applied to Kraft papers. One received so sufficient separation properties at the cover weight - that are below those of the more common methods can be obtained. Under "release properties" is the reduction in friction between the surface and substances that come into contact with her, understood,

Example 7

Made from 2 parts of highly viscous carboxymethyl cellulose, 98 parts A mixture was made up of water and 0.03 part of foaming agent and foamed to seven times its original volume and on paper in the dry section of a papermaking machine, as described in Example 5, applied. To this There were even coatings of OarboxymothylcellLilose obtain,

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A number of different water soluble dyes that normally added to the Dutch paper machine, have been added to mixtures of such carboxymethyl celluloses. These additions confirmed and demonstrated the uniformity of the application of the carboxymethyl cellulose the usefulness of the method according to the invention for the surface coloring of paper with water-soluble dyes.

Example 8

Of 10 parts of an aqueous syrup of urea-formals ^ hydharzvorkondensat (50 i> solids), 90 parts of water and 0.03 parts of foaming agent A solution was prepared and foamed to seven times its original volume and applied to -paper in the drying section of a papermaking machine, as described in Example 5. A small amount of water-soluble dye was added to demonstrate the uniformity of the treatment. The paper product obtained has a greatly increased surface cohesion.

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Claims (1)

- ι y - 'Pat en t a η s ρ r ü c h e 1.). V-erfanren for the production of a coating on a surface, characterized in that a foam from a liquid coating composition containing at least one coating component is formed with a gas or vapor. This foam is applied to a surface and mechanically at least a significant part of the physical structure of the foam cover _; is destroyed with the formation of a continuous surface coating over the area to be coated. 2 «) Method according to claim 1, characterized in that as. Surface paper or cardboard is used " 3.) Method according to claim 1 or 2, characterized in that as a coating component a vinyl polymer or copolymer is used. 4.) ^ experience according to claim 3, characterized in that the Vinyl polymer or mixed polymer in the coating composition used in porm of a latex. 5.) The method according to claim 3, characterized in that as Vinyl polymer Polyvinyl alcohol in the form of an aqueous-.Io -. ".- solution is used in the coating mass. ■. ■■■■■■■ - ■. ■ "BATH 0 0 9 8 4 8/1447 6.) Method according to claim 1 or 2, characterized in that that a polycondensate is used as a coating component. 7.) The method according to claim 1 or 2, characterized in that as Übe rzugskoinponent e a polysaccharide or a derivative thereof is used. 8.) The method according to claim 1 or 2, characterized in that an animal or vegetable protein as the coating component is used. 9.) Method according to claim 1 or 2, characterized in that an organosilicon polymer is used as the coating component will. 10.) The method according to claim 1 or 2, characterized in that ale Coating an inorganic polymer is used. 11.) Method according to one of the preceding claims, characterized in that that the coating composition has one or more surfactants, pigments, fillers, dyes and vapor phase corroaj contains inhibitors. 12.) The method according to any one of the preceding claims, characterized in that f] _{; i} ß was used as (yes air. BATH ORIGINAL
0 0 9 8 4 8 / .1 U 7 1.3.) Method according to one of the preceding claims, characterized characterized in that the coating area is based on at least the Twice its original volume is foamed, 14.) Method according to one of the preceding claims, characterized marked that the coating mass is neglected to at least four times its original volume » 15.) Method according to claim 13 or 14 »characterized in that that the coating compound is foamed up to ten times its original volume »■ · 16.) Method according to one of the preceding claims, thereby characterized in that a practically immobile foam is used. . 17.) Method according to one of the preceding claims, characterized in that the foam is applied to the surface and is broken ^{by means of a knife or an edge which extends across the surface 1.} . 18.,) Method according to one of the preceding claims, characterized characterized in that the Schnum of the Überzugavprrichtung over a branched pipeline is fed. _BA O ABOVE 0-9'B48 / UAV 19.) "Method according to one of the preceding claims, characterized characterized in that virtually all of the foam is mechanically broken. 20.) Method according to one of claims 2 to 17, characterized in that that the coating of the paper ^ or the cardboard on a paper or cardboard-making machine as an integral part Part of the manufacturing process. BAD ORiGiNAL