DD139808A1 - SEPARATING AND COATING AGENT FOR POLYURETHANEFORM KOERPER - Google Patents

Abstract

The aim of the invention is a smooth processing of Polyurethane foams to form parts, wherein a reactive, film-forming release agent is used, which is after Evaporation of the solvent and foaming of the polyurethane as firmly adhering, viscoplastic coating of the molding surface anchored. This goal can be solved by adding soluble Thermoplastics, preferably polyurethane elastomers, too Cellulose derivatives are achieved, wherein the release agent in the form of solutions or dispersions, and optionally is stained.

Description

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Title of the invention

Release and coating agent for polyurethane moldings

Field of application of the invention;

The invention relates to a process for the preparation and use of reactive, film-forming release and loading. Laminating agents for the processing of polyurethane foams to Fonnkörpern, wherein the release film is anchored after Sntformung as a firmly adhering coating on the polyurethane surface.

C harakteristik olutions of the known te chn regard L

The production of moldings from polyurethane foams is basically known and takes place by filling the reactive starting components into a mold. However, the separation of the reacted foam body from the mold wall poses great difficulties, so that the use of release agents or films is essential.

Although molds made of silicone rubber or with polytetrafluoroethylene coatings or so-called internal release agents facilitate removal from the mold, they can not be remedied by this.

As release agents for the processing of polyurethanes come pastes, solutions, dispersions or emulsions of natural and synthetic waxes, oils, salts of higher fatty acids, fatty acid esters, paraffins, silicones, and the like. a. into consideration. For many of the produced PUE moldings, a subsequent coating is absolutely necessary or desirable. Due to the release film still adhering to the molded article, sufficient paint adhesion is in most cases made more difficult or is not at all guaranteed.

guaranteed.

By applying certain wax compounds or when using washable release agents, a subsequent coating is possible. In any case, care must be taken, as stronger wax accumulations on the molding affect the paint adhesion, or. complicate the reworking. On the other hand, it comes to the formation of wax crusts in the working forms, which increasingly impede a normal production process, so that additional cleaning work. The use of release liners of polyethylene or PVG would eliminate these disadvantages. However, it has been found that the release effect of these films is lost quickly and also such a smooth surface on the molded part arises that even here sufficient adhesion of the paint is not given.

There are also known methods which achieve a painted surface by bringing a liquid lacquer layer into the mold cavity with a previously applied liquid water-soluble release agent between the surface of the mold and the lacquer layer. However, this process is very time-consuming and places particularly high demands on the surface quality of the foaming tools. A further advance in the art has been achieved by forming a release film having a greater adhesion to the PUR foam than the inner mold material by applying a solution of a cellulose ester or a polycarbonate in an organic solvent and evaporating the solvent . ' ,

With this release agent polyurethane parts with compact, d * h. not cell-shaped surface can be produced, the demolded parts are provided with a firmly adhering coating.

• However, the use of the solutions of cellulose mixed esters, in particular in the case of flexible polyurethane foams, has hitherto been disadvantageous. The one out of the solution

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drying film is relatively snröde, so that when using the PUR moldings thus produced soon show cracks that can not be eliminated by a top coat. In addition, cracks may occur even in the processing of the foam due to the inelasticity of the film, wherein the reactive polyurethane mixture comes into contact with the metal or synthetic resin mold surfaces and a localized adhesion of the polyurethane parts and thus poor mold release is caused.

Object of the invention

The aim of the invention is to overcome the disadvantages mentioned. And to develop a release and coating agent which enables a smooth processing of polyurethane foams.

Explanation of the essence of the invention

- The invention has for its object to develop a release and coating agent, which is suitable for the processing of PU foams to form parts both with a compact and with a cellular surface.

- According to the invention the object is achieved in that a separating and coating agent consisting of cellulose derivatives with free hydroxyl groups and / or other active. Hydrogen-containing functional groups with the addition of soluble thermoplastics and optionally color pigments and / or soluble dyes in the form of solutions or dispersions is used. The cellulose derivatives used according to the invention are preferably those cellulose esters and cellulose ethers in which only a part of the

 in the cellulose molecule existing hydroxyl groups was modified. However, it is also possible to> modify all hydroxyl groups if the sub-

in turn have Η-active functional groups or these are subsequently produced by chemical reaction. Suitable cellulose derivatives in the context of this invention are, for example, 2.5 cellulose acetate, cellulose acetopropionate, cellulose acetobutyrate, cellulose propyl ether, cellulose butyl ether, cellulose hydroxyethyl ether. ,

Although the cellulose derivatives already have separating properties on their own, it has proved to be very advantageous to add soluble thermoplastics to the cellulose derivatives. The soluble thermoplastics used are preferably thioplasts, PVC, PUR elastomers and unvulcanized rubber compounds.

Particularly good results are achieved if the cellulose derivatives soluble polyurethane elastomers are added up to 60 % of the total. As a result, not only the separating, but also the film-forming properties of the release and coating agent are improved, so that even complicated moldings are reproduced down to the smallest detail and obtained a cover layer with excellent mechanical strength.

In a hydrocarbon preferably halogenated from 20 parts to 70 parts, 10 parts to 30 parts of ketone and 15 parts to 50 parts of acetic acid ester. Dissolved solvent mixture, the release agent according to the invention after contract on the form a thin, tough elastic, closed film, v / elcher after entering the polyurethane mixture at the same time by chemical reaction of the existing free hydroxyl groups and / or other active hydrogen-containing functional groups firmly bonds the isocyanate groups of the polyurethane mixture and is completely removed from the mold during the demolding process with the shaped body. This ensures that remain in the form of any Treim- and coating residues, which could lead to mold contamination over time.

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On the other hand, the chemisch.'fest. Mit. the releasing agent film connected to the polyurethane molded body provides an ideal basis for subsequently applied lacquer and / or other cover layers. , Soluble dyestuffs having a proportion of 0.5 % to 2% and / or 10 % to 20 % of color pigments, based on the solids content, can also be added to the release and coating agent, as a result of which the uniform release agent application in the mold can be well controlled and On the other hand immediately obtained colored polyurethane body, which require no further surface refinement. ,

Even polyurethanes with zelliger surface such. B. certain polyurethane hard or soft foams can be removed from the mold with the aid of the release agent and coating agent according to the invention, .wodurch in some application cases only a painting of the parts is possible.

The invention will be explained in more detail below with reference to FIGS. 1-8:

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Embodiment 1;

70 parts by weight of 2.5% acetylcellulose are dissolved in 300 parts by weight of acetone. To this solution is added 300 parts by weight of methylene chloride with stirring. In addition, a solution of 30 parts by weight of a PU blastomer (prepared from a linear polyester alcohol based on adipic acid and butanediol / "~ 1.4__7 and a difunctional isocyanate, eg HMDI) and 100 parts by weight The acetylcellulose solution is combined with the PU elastomer solution and 200 parts by weight of a mixture of equal parts of butyl and ethyl acetate are added with stirring to give a clear, viscous solution.

Embodiment 2;

60 parts by weight of 2.5 acetylcellulose are dissolved in a mixture of 250 parts by weight of methyl ethyl ketone and 4Ό0 parts by weight of methylene chloride. 150 parts by weight of a known one-component PUR varnish with 30% binder content and high elasticity are added to this solution, followed by stirring in 150 parts by weight of ethyl acetate.

From game 3:

50 parts by weight of 2.5% acetylcellulose and 30 parts by weight of cellulose aceto-phthalate are dissolved in a mixture of 250 parts by weight of acetone and 400 parts by weight of methylene chloride. To the solution are added 100 parts by weight of a 20% solution of an elastic plastic material in methylene chloride and 170 parts by weight of ethyl acetate.

Completion subject 4 ·:

The solution according to Example 3, 1% of an organic dye based on the binder content added. This gives a transparently colored viscous solution of a release varnish.

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Ausführiingsbeispiel 5.i

The solution according to Embodiment 2, 20 % of a commercial pigment color paste are added. This gives a colored viscous release coating.

Embodiment 6:

A mold of conventional material is provided by means of paint spray gun with a thin, uniform film of the solution according to Embodiment 1 to 5. The mold can be used immediately with a polyurethane foam system consisting of component A (85 parts of a polyester polyol, 10 parts of 1,4-butanediol, 1 part of activator, 9 parts of blowing agent) and component B (prepolymer of a polyester polyol and a polyisocyanate with an isocyanate content of 20%) which have been intensively mixed in a ratio of 1: 1. After a curing time of 7 minutes der.Form can be easily removed from an elastic molded body, on the surface of the release film is firmly anreagiert and ensures an extraordinarily adherent coating with an elastic paint.

Embodiment Example 7

Bin. Foam tool with a textured surface is provided by means of a spray gun with a thin film of a release and coating agent according to Embodiment 1 to. The mold can immediately be filled with a polyurethane foam consisting of component A (97 parts of a polyol having a hydroxyl number of 480, 1.75 parts of activator, 0.5 part of water) and component B (polyisocyanate having an isocyanate equivalent of 135), which were mixed thoroughly in a ratio of 1: 1.1. After a curing time of 10 minutes, the mold can be easily removed from a mold, which has exactly the contours of the tool. The molding can be permanently coated with a transparent or pigmented topcoat.

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Embodiment 8:

A mold is provided by means of a spray gun with a thin, uniform film of a release agent according to Examples 1 to 5. The tool can be used immediately with a polyurethane foam system consisting of component A- (5 parts polyether polyol having a hydroxyl number of 480, 50 parts of polyether polyol having a hydroxyl number of 33, 4 parts of activator, 41 parts of blowing agent) and of component B (polyisocyanate with an isocyanate equivalent of 135) which have been intensively mixed in a ratio of 1: 1.4 Curing time of 5 minutes, the shape of a molded body can be removed, the surface of which is firmly connected to the release film and thereby a painting is possible.

Comparative Example 1

100 parts by weight of 2.5% acetylcellulose are dissolved with stirring in 3OO parts by weight of acetone. 400 parts by weight of methylene chloride are added to this solution with vigorous stirring, and then 200 parts by weight of ethyl acetate are stirred under. A viscous, water-clear solution is obtained.

Comparative Example 2;

In 750 parts by weight of methylene chloride, 75 parts by weight of cellulose tri-acetate are dissolved. To the solution is added 175 parts by weight of ethyl acetate.

Comparative Example 3

A tool is provided by means of a spray gun with a thin film of a release agent according to Vergleiöhsbeispiel 1 and 2. After evaporation of the solvent, the release film shows fine cracks. When filling the mold with a polyurethane foam system according to embodiment 6 to the foam penetrates through the cracks in the release film. After curing, the molding can be removed from the mold only with great effort. This leads u. TJ. to the destruction of the molding.

Claims (6)

-9- 2 Start of the trial 1. separating and coating compositions for moldings, characterized in that a separating and coating agent consisting of cellulose derivatives with free hydroxyl groups and / or other active hydrogen-containing functional groups, with the addition of soluble thermoplastics and optionally color pigments and / or organic soluble Dyes in the form of solutions or dispersions, is used. 2 · separating and coating agent according to item 1, characterized in that preferably polyurethane elastomers are used as soluble thermoplastics. 3. separating and coating agent according to item 1 and 2, characterized in that the polyurethane elastomers in amounts of 1 to 60 parts, preferably 10 to • 50 parts to which cellulose derivatives are added 4. separating and coating agent according to item 1, characterized in that the separating and coating agent in the form of solutions or dispersions in a concentration of 5 % to 15% is used. 5. separating and coating agent according to item 1 to 4, characterized in that the separating and coating agent optionally 10% to 20% of color pigments, based on the solids content, are added. 6. separating and coating agent according Puntk 1 to 4, characterized in that the separating and coating agent optionally 0.5 % to 2 % organic soluble dyes are added.