DE1060348B - Process for the production of tempering films for porous substrates - Google Patents

Description

Process for the production of coating films for porous substrates It is known that thermoplastics that have been rolled out into foils using calenders in strengths of, for example, 80 to 100 Et and above on porous substrates, e.g. B. plywood panels, using pressure and heat with or without intermediate adhesive to glue on. For example, one has such films made of polyvinyl chloride or theirs Copolymers produced and processed in this sense. Panels, for example made of plywood, in which this way thermoplastic surface foils were applied, but have the defect that they are not an intimate bond between Have plastic film and wooden surface. Because of the pressure-and-heat compression The desired bond cannot be achieved with released water vapors. aside from that the wood fibers are strongly marked. That is why they tried to go through a special Glue layer, e.g. B. in the form of condensation resins to get an attachment. Here again there was a separating moment; namely a split between phenolic resin and thermoplastic layer.

Films have also been produced that contain a paper carrier, on the one hand with a thermoplastic, e.g. B. polyvinyl chloride, and on the other side with a condensation resin, e.g. B. a phenol-formaldehyde resin coated is. These double-sided coated foils are in themselves for the treatment of the surfaces well suited for porous substrates. The production of the coating films prepares but in this case difficulties. If you use paper as a carrier, the are not wet strength, the coating process is difficult to carry out because the papers do not have sufficiently high mechanical strengths. If on the other hand Wet strength papers are used, as is the case with practical manufacture of the coated papers resulted in paper splitting easily at the parting surfaces of the two types of layers.

In order to eliminate the aforementioned deficiencies, one also has to use pre-impregnated Papers powdery hot molding compounds applied and treated with steam dissolving or swelling solvents in a vacuum bond with the paper carrier achieved. However, the production of these films has the disadvantage that the process is extremely complicated and requires new equipment for making plates will.

You also have small amounts of condensation resins, e.g. B. 0.5 up to 2 "/ a, calculated on the weight of the paper web, fed into the paper web or evenly distributed therein, whereby the wet strength of the paper web is strong is increased, then dried and coated with a thermoplastic, preferably a finished extruded one Film covered. In this process, the film comes out of the extruder and becomes hot passed together with the paper web under strong pressure through rollers, whereby a Laminating takes place.

It has now been found that coating films for porous substrates, starting from papers with little or no wet strength, on technical Can be easily produced if you use the powder process on the starting papers Thermoplastics are applied, the papers coated in this way are a film of the thermoplastics Induction treatment with heat, possibly with simultaneous application of pressure, subjects and the intermediate film thus obtained on the back with a Coated with condensation resin. The rear side is coated appropriately by treating the intermediate film with an aqueous solution of the condensation resin. Complete impregnation of the fiber fleece is obtained without the otherwise known difficulties with papers with little or no wet strength appear. Surprisingly, the films obtained according to the invention show at Pressing with porous substrates does not cause paper splitting or bond problems to the wood or between the individual layers. That fact, namely neither one Paper splitting nor bonding problems in the individual layers, such as with wood, is explained by the fact that we according to the method according to the invention in the so produced The film has not yet reached its final degree of polymerization and is also in the fleece character of the paper have the possibility of the water vapors that occur derive and the individual layers to matt each other. Micrographs clearly show that the fiber fleece is partly covered with condensation resin, is partially impregnated with thermoplastics.

The application of the thermoplastic to the paper backing takes place on the way of the powder process. The thermoplastic is very finely divided stacked on the paper backing and then under the action of heat or merged by heat and pressure. For example, it can be coated with your powder Paper can be sent through calenders that are brought to the necessary temperature, e.g. B. 160 to 170 ° C, are heated and a line pressure of z. B. exercise 12 t / cm. the Pulling speed can when using such halander z. About 25.0 in / min. be. The thermoplastic spreads evenly over the surface the base, but without penetrating through the base. As thermoplastics can here z. B. powdered polyvinyl chloride, polyvinyl acetate, their copolymers or polyethylene can be used.

Coating the underside of the film with condensation resins is expediently carried out using thin aqueous solutions. As condensation resins can be phenol-formaldehyde, urea-formaldehyde, melainin-formaldehyde or others Condensation resins can be used. These condensation resins may also can be applied by the powder process, the temperatures naturally being significant lower, around 80 to 90 ° C. But you can also apply a coating dispense with the condensation resins and instead use pre-resinated foils Press on veneers.

When a hot molding of the thermoplastic surface is desired is expediently 1 to 1.5% of the thermoplastic starting products Metal stearates, e.g. B. calcium stearate added.

Furthermore, a hot molding at about 130 ° C is ensured by instead of a thermoplastic layer with a defined one as in Example 1 to 3 To use composition, now carries out a multilayer structure. This The process is characterized by the fact that a thermoplastic, which softens relatively low and thus ensures a good bond, and in the second step, a thermoplastic with a high softening point is added pigmented or unpigmented with good surface hardness.

The end product obtained according to the invention contains on the one hand On the one hand a thermoplastic material and on the other hand a condensation resin. One or both sides can be pigmented. The obtained according to the invention Films are durable, storable commercial products.

The fact that foils produced in this way after the overlap the pressing under pressure and heat combine completely homogeneously, enables to meet very differentiated widths with a normal width. One Separation at the points of contact and overlap of the wood surface or the Slides among themselves does not take place.

A particular advantage of the products made according to the invention lies in the fact that one doubles them. Way of tempering the porous substrates, z. B. the plywood, can be used by either the thermoplastic Side or the side coated with the condensation resin as the outer surface can use in remuneration. In the first case, the condensation resin acts as a Bonding agent, and a smooth, optionally pigmented outer surface is obtained, which consists of the thermoplastic used. In the second case, the thermoplastic works as a composite agent, and one obtained due to the hardening of the condensation resin when pressing very hard and resistant condensation resin layer as Surface.

The following examples describe the invention.

Example l 92 parts of copolymer from 80 parts of hard poly vinyl chlorite powder, 20 parts of polyvinyl acetate powder # 7 are ball milled with 8 parts of Eisenoxy bread grind very closely.

This mixture is applied to a fiber fleece in a layer thickness of approx Powdered 60 to 80 #x and molded between two heated rollers at around 175 ° C. The film obtained in this way is then on a knife coater with an aqueous Solution of a urea-melamine-formaldehyde resin coated with about 40 g of solids. The drying takes place under mild conditions in the drying tunnel at about 50 ° C. This Foil is then in a known manner on plywood with the condensation resin side pressed down.

Example 2 88 parts of polyvinylidene chloride powder, 7 parts of titanium white, 3 parts of ultramarine blue and 2 parts of Hansa yellow are as in Example 1 in the ball mill mixed and formed into a film on 45 g paper web, which has little or no wet tensile strength owns, shaped.

According to Example 1, an aqueous one is then applied on the back Solution of a melamine-formaldehyde condensation resin painted on and dried. The film formed in this way can be applied to chipboard in a known form using Pressure and heat are applied. Should a hot molding of the polyvinyl chloride surface are desired, are appropriate to the thermoplastic polymers in the Ball mill 1 to 1.59 / o of a metal stearate, e.g. B. calcium stearate added. Example 3 On a paper with the character of blotting paper and a weight of about 60 g per square meter a mixture of 80 g of polyvinyl acetate powder and 20 g of methacrylic acid ester in powder form powdered in the same way as 1. On the back is then also according to the example 1 a paste of 80 parts of a 50% solution in water of a melamine-urea condensation product and 20 parts of a color paste, both parts given over a mixing roller, in the brushing process (about 80 g solids) to apply. The foils produced in this way can get hot a multi-stage press after the surface treatment on plywood or hardboard be formed, in such a way that the thermoplastic as an adhesive film, the Condensation resin mixture as an abrasion-resistant, sandable and buffing surface serves.

Example 4 90 parts of a copolymer composed of 80 parts of polyvinyl chloride powder and 20 parts of polyvinyl acetate powder with 10 parts of iron oxide brown in one Grind the ball mill as closely as possible. This mixture is applied to a non-woven fabric in a layer thickness of 80 [, powdered and between two heated rollers molded about 170 ° C. This film is in a second step with a polyvinyl chloride Powdered with a K value of 60 for a thickness of about 15 h and between the heated Rolls formed at about 200 ° C. The film web thus obtained is as in the example 1 coated on the back with a water-soluble resin. The slide is in itself in a known manner pressed onto plywood at 130 ° C and then at this temperature hot molded.

Claims (4)

PATENT CLAIMS: 1. Process for the production of coating films for porous substrates, e.g. B. plywood, characterized in that a paper or nonwoven fabric with low or no wet strength in a known manner coated a thermoplastic in powder form, the coated paper a the film formation of the thermoplastic causing treatment with heat and optionally subjected to pressure and the intermediate product thus obtained on the back with is coated with a condensation resin. 2. The method according to claim 1, characterized characterized in that one is on a paper or nonwoven fabric in a multi-layer structure Applies thermoplastics, the thermoplastic used to build up the base layer a low softening point with good flowability and that for the construction the top layer, thermoplastic used a high softening point with good surface hardness owns. 3. The method according to claims 1 and 2, characterized in that the Coating of the back using aqueous solutions of the condensation resin he follows. 4. The method according to claims 1 to 3, characterized in that to the A small amount of a metal stearate is added to thermoplastic starting materials will. References considered: U.S. Patent No. 2,686,744.