NL1004897C2 - Forming a coating containing solid particles on the surface of a substrate - Google Patents

Abstract

Procedure for applying a coating onto a selected surface of a second substrate comprises the successive stages of: (a) applying a liquid coating material containing solid particles having a size of 10-200 ~mm in a pigment volume concentration of 3-80 % to a surface of a first substrate; (b) partially or fully hardening the liquid coating material to form a hardened coating on the first substrate; (c) contacting the semi- or fully hardened coating with the selected surface of the second substrate, wherein the second substrate is in a liquid or deformable plastic state which can be converted into a solid state, or the selected surface may carry a liquid component which can be converted into a solid state; and (d) converting the second substrate or the liquid component into the solid state so that the hardened coating is transferred from the surface of the first substrate to the selected surface of the second substrate, whereby the coating in the hardened state has a thickness of 20- 300 ~mm and an irregularly shaped interface is formed between the coating and the second substrate.

Description

Method for coating plastic, in particular during its molding, with improved adhesion, and coated articles thus obtained.

The present application relates to a method for applying a coating to a plastic, whereby an improved adhesion of the coating to the plastic surface is obtained, as well as to the coated plastics thus obtained.

More particularly, the invention relates to a method of coating a plastic during its molding, such as by injection molding, as well as to the shaped and coated articles thus obtained.

The invention is particularly suitable for applying a coating to hard-to-coat plastics such as polypropylene.

It is known to coat plastics during molding. For example, various methods are known in which plastics are coated in the mold during an injection molding process (so-called "in-mold coating" processes).

These processes generally involve the following steps: applying the coating composition to the wall of the mold; at least partially curing the coating composition; - inserting and (at least partially) curing the plastic into the mold, the coating composition being transferred from the wall of the mold to the surface of the molded plastic article; ejecting the coated and molded article from the mold.

The main problem in applying a coating to a plastic during molding in a mold is that a good and reliable transfer of the coating composition from the wall of the mold to the desired surfaces of the plastic must be obtained. Furthermore, upon ejection of the molded article, the coating must detach from the mold wall and at the same time adhere well / adhere to the surface of the article. This generally requires that the coating adheres well to the plastic to be coated at the same time and adheres poorly to the metallic surfaces of the mold.

In practice, these requirements appear to be contradictory: coatings that adhere well to plastics generally also adhere well to metals.

1004897 2

This allows the coating to remain at least partially on the surface of the mold when the molded article is ejected from the mold, which may cause imperfections in the coating, result in an uneven coating and / or contaminate the mold, resulting in quality and 5 the reliability of the coating process will decrease over time and the attainable operating times will be shortened.

These problems arise particularly in the manufacture of irregularly shaped articles, as well as in the use of plastics to which coating compositions usually have poor adhesion, such as polypropylene; coating poly-10-propylene - not only by coating in the mold but also by other methods known per se - is a common problem in the current art.

Furthermore, the coating composition should preferably allow good throughput in machining molding processes, such as machine injection molding, ie the required (curing) time in the mold should be as short as possible.

The object of the invention is to provide a solution to the above problems.

German Offenlegungsschrift 3,508,794 describes the use of metallic particles in a coating to obtain a rough interface and thus improve adhesion.

Offenlegungsschrift 3,508,794 does not, however, relate to polypropylene substrates and / or coatings that are poorly compatible with polypropylene. Furthermore, DE-3,508,794 does not concern decorative coverings, but only the use of metal particles for EMI shielding, especially on the inside of the housing.

International Application 94/06612 describes the use of particulate-containing coatings on polypropylene substrates. Polypropylene coatings are used herein to ensure substrate and coating compatibility.

Polypropylene coatings, however, are less scratch resistant than the coatings used in the application. In addition, when applying polypropylene coatings to polypropylene substrates, the presence of particles at the interface could even be detrimental to adhesion.

Also, the pigment particles listed according to WO 94/06612 on page 12 are generally too small to provide improved adhesion. For example, on page 32 of WO

1004897 3 94/06612 reports that pigment particles (as opposed to the only lines of metallic particles mentioned further above) are preferably forced to the surface of the coating, rather than to the interface, while the amount of aluminum particles mentioned according to example 9 on page 9, is mentioned. 62 used is too small to give improved adhesion.

More generally, according to WO 94/06612 (see page 12), the amount of pigment particles is selected on the basis of the decorative effect to be achieved, and not to achieve an irregular interface and / or improved adhesion.

According to the invention, non-metallic particles (however including metallic pigments) are preferably used, and in particular coatings are used which have a poorer compatibility with polypropylene substrates than polypropylene itself.

It has now been found that the adhesion of a coating to a plastic surface can be improved by incorporating a particulate material into the coating composition and applying the coating composition, preferably after at least partial curing, to the plastic as it is is in a liquid or deformable (plastic) state.

This improved adhesion is not only expressed during the applied forming processes - whereby an improved adhesion of the coating to the plastic 20 is obtained without (at the same time) the adhesion to the mold surfaces being strengthened, so that the above-mentioned problems are avoided - but also in a improved adhesion of the coating in the finally obtained plastic article.

This makes the method according to the invention particularly suitable for coating difficult-to-coat plastics, such as polypropylene, as well as for use in the production of coated plastic articles, in which, in view of the intended end-use, an enhanced adhesion of the coating is desirable.

The invention therefore relates to a method of applying a coating to an intended surface of a second substrate, comprising the successive steps of: a) applying a liquid coating material to a surface of a first substrate; b) partially or completely curing the liquid coating material to form an at least partially cured coating on the surface of the first substrate; c) contacting the partially or fully cured coating with the intended surface of the second substrate, the second substrate being in a liquid or deformable (plastic) state, which can be converted into a solid state, or the second substrate in or on the target surface carries a liquid component that can be converted into a solid state; d) converting the second substrate or the liquid component into the solid form; such that the cured coating is transferred from the surface of the first substrate to the target surface of the second substrate, incorporating texture-imparting solid particles having a size from about 10 μηι to about 500 μτη to a pigment volume concentration in the range of 3 to 80%; and the cured coating has a thickness in the range of 20 µm to 300 µm.

In this method, the second substrate is (the desired surface of) the plastic to be coated, while the first substrate (the corresponding surface of) can be any suitable means for applying the coating.

The method of the invention is particularly suitable for use in plastic molding methods in which the plastic is or has been brought into the required liquid or deformable (plastic) state during at least one stage thereof.

The method of the invention is more particularly suitable for applying a coating to a plastic during molding of the plastic in a mold or mold, such as in-mold coating in injection molding processes, with processing / molding sheet mold compounds (SMC) and / or bulk mold compounds (BMC), blow molding, Reactive Injection Molding (RIM); or by shaping / coating using a stamp.

In such coating processes, the first substrate will be (the surface of) the mold or die, at least the portions thereof corresponding to the surfaces of the plastic article to be coated.

Such a method will therefore include the successive steps of: a) applying the solid particulate coating composition as defined above to the (inner) wall of the mold; b) partially or completely curing the coating material to form an at least partially cured coating on the inner (wall) of the mold; c) introducing the plastic to be coated, which is in a liquid or deformable (plastic) state, into the mold d) curing the plastic, transferring the coating composition from the wall of the mold to the surface of the plastic product; e) ejecting the coated and molded article from the mold.

15 wherein the coating in cured state has a thickness in the range of 20 μτη to 300 μπι.

In the figures is:

Figure 1 shows a cross-sectional view of a mold during the molding and coating of a plastic according to the invention; Figure 2 shows a series of cross-sectional views of coating layers applied to a first substrate, intended to classify the morphology of the side of the coating layer facing the second substrate.

The invention can be used for coating any desired plastic, as long as it can be brought (reversibly) into the required liquid or deformable (plastic) state, for example by heating, or can be obtained from a liquid or plastic pre-phase, ie by chemical or physical curing, such as by a polymerization or cross-linking reaction, or by evaporation of a solvent, as will be apparent to those skilled in the art.

More in particular, the plastic is a polymeric material or a polymeric composition, or a pre-phase thereof, which is suitable for use in molding techniques. Such techniques and suitable materials, such as (mixtures of) thermoplastic polymers, will be clear to those skilled in the art. The plastic may further contain any suitable plastic additives known per se in the art in conventional amounts, including molding aids.

The process of the invention is particularly suitable for coating polypropylene or polypropylene-based polymeric mixtures containing more than 60% by weight, preferably more than 80% by weight, of polypropylene.

According to a further aspect of the invention, it is also possible as the second substrate to use a plastic in an (almost) solid or non-deformable state, wherein a further (adhesive) material is applied to its surfaces to be coated in the required liquid or deformable state. , such as another polymeric material and / or an (adhesive) agent. The coating is then applied to / in this intermediate layer of this further material as described herein.

This aspect of the invention will be particularly valuable when it is undesirable or not quite possible to bring the plastic to be coated itself into the required liquid or deformable state (for example, because the temperatures required for this are too high) or when the it is desirable to keep the plastic and the coating separate by this intermediate layer (base layer).

The plastic to be coated can also be impregnated with such a liquid or deformable (further) material, in particular when coating for instance fiber materials or materials with a similar "open" structure according to the method of the invention.

Furthermore, it is possible to apply the foil to the second substrate by welding or sealing, whereby (optionally) no (further) adhesive layer is required.

According to these aspects of the invention, an improved adhesion will be obtained compared to the use of this intermediate layer without incorporation of a particulate material in the coating.

The invention can be used with / with any suitable flowable coating composition which can be suitably cured, for example by lowering the temperature (solidification), evaporation of any solvent present, by chemical means, such as by cross-linking - or polymerization reaction, optionally under the influence of radiation or a catalyst system.

The invention can be applied in particular with water-based or UV-curable coatings, which will be apparent to those skilled in the art. Examples of suitable waterborne coatings are the commercially available polyurethane, acrylic, vinyl acetate and epoxy resin coatings; examples of suitable UV curable coatings are the commercially available polyurethane acrylate, polyester acrylate, "all acrylic" and epoxy acrylate coatings. In addition to the base resin, these may also contain reactive diluents and initiators, as will be known to those skilled in the art.

The particles used in the invention are not particularly limited as long as they are capable of providing the surface of the coating composition, and in particular the surface forming / forming the interface between the coating composition and the plastic, which texture provide the improved adhesion according to the invention, to which end they generally must meet the particle size and particle size distribution requirements described herein. Furthermore, the particles preferably do not adversely affect the (desired) properties of the final coating, such as the (mechanical) strength and the like, it being clear to the skilled person that the choice of the particles also includes the appearance of the final can affect the product.

The particles used can be organic or inorganic and can be of the same material as the plastic or coating as long as they retain their discrete particle shape during the coating process. Mixtures of different particles can also be used.

Examples of suitable particles are: inorganic and organic particles such as silica, mica, glass spheres, ground glass fiber, clay, PE powder, PP powder, polyamide powder, gypsum, talc, wollastonite, alumina, silicon carbide, and calcium carbonate particles such as Calcite, Aragonite and chalk; Metallic particles such as silver, copper, nickel, aluminum, steel and carbon particles such as Carbon Black and ground carbon fiber with metal-coated particles such as silver-coated glass spheres; all in a suitable particulate form for use in the invention.

Conductive particles, such as metallic, carbon or metallic coated particles, can advantageously be used for shielding against electromagnetic radiation ("EMI shielding").

Typically, the particles will be incorporated into the coating composition before it is applied to the first substrate. However, it is also possible to apply the 1004897 8 coating composition (without or with only part of the particles) on the first substrate and then add the particles, such as by sprinkling the (optionally partly cured) coating composition with the particles or by applying the particles to the (optionally partially cured) coating composition by a flow of a suitable inert carrier gas.

The particle size of the solid particles to be included in the coating will be from about 10 µm to about 500 µm, more particularly from about 30 µm to about 200 µm, and will mainly depend on the desired thickness of the final coating (beat) as further explained below, as well as the manner in which the particles are incorporated into the coating.

When the particles are incorporated by (sprinkling) into the (partly or partly cured) coating, smaller particles can be used, in smaller quantities, in particular particles from about 10 µm to about 200 µm, more in particular about 20 µm to about 100 µm in size, in a pigment volume concentration of 3 to 60%. When the particles are previously incorporated into the coating composition, larger particles in larger amounts will be preferred, especially particles from about 20 µm to about 500 µm, more particularly about 30 µm to about 200 µm in size, in a pigment volume concentration of 20 to 80%.

The plastic, coating composition and particles used, as well as the further constituents used, must have properties such that they are essentially resistant to, and suitable for, use in molding conditions such as the temperature and pressure used, the particles used essentially maintain their discrete particle shape. Furthermore, the plastic and the coating must not (completely) mix, but must be obtained as two essentially discrete phases in the final product.

Also, the plastic, coating composition and particles used, as well as the further components used, must be essentially compatible with each other, the compatibility of the plastic and coating composition, of course, being improved by using the method of the invention, so that the invention also makes it possible to use poorly or less compatible combinations of plastic and the coating composition.

The person skilled in the art will be able, in part on the basis of the present specification, to select the plastic, the coating composition and particles, as well as the further constituents used.

The method of the invention can generally be performed analogous to known coating methods, simply by incorporating the particulate material into the coating composition as described herein, and further conducting the coating method essentially in a manner known per se. The invention can therefore be applied without or with only minor adaptations with existing equipment and with existing coating processes.

In the first step of the method, the coating material is applied to the first substrate, such as the inner wall of the mold, in a manner known per se, for example by coating, spraying, pouring, filling / emptying the mold with the coating composition, as also suitable printing processes, or any suitable combination thereof.

The coating composition can also be introduced into the mold 15 in a suitable solid form, such as in the form of a preferably flowable powder and then converted into a liquid form, for example by heating. It is also possible to use a mixture of a powder of the coating composition and the particles.

Then the coating is at least partially cured, at least 20 to an extent allowing the further steps described below, ie the coating (beating) should maintain its texture and integrity during the coating process and as an essentially discrete phase on the desired surfaces of the second substrate.

After this, the partly or fully cured coating is brought into contact with the plastic to be coated in a liquid or deformable (plastic) state, when coating in a mold by introducing the plastic into the mold in a manner known per se, such as by casting or by injecting under pressure, or by shaping / coating with a stamp by introducing the stamp into the plastic, after which the plastic is converted into the final solid state in an appropriate manner, as described above.

This step of the method according to the invention is schematically shown in Figure 1 as a cross section through the mold, where 1 is the outer mold, 2 is the coating composition, 3 are the particles, 4 is the plastic, 5 is the interface 1004897 and 6 the inner die is. Hereby, i.e. before and / or during the curing of the plastic, the plastic (optionally and / or further) is formed and the coating is transferred to (the intended surfaces of) the plastic to be coated. It is to be understood here that these figures do not limit the scope of the invention; for example, in Figure 1 it is also possible to apply a coating ορ / from the inner mold 6, or both on / from the outer mold 1 and the inner mold 6, whereby the same or different coatings can be used.

Then, when coating in a mold, the molded article is taken out or ejected therefrom, after which the plastic and / or coating composition is optionally further cured, if desired, to form the coated molded article, which as can be ready for end use or processed further. The above steps can be repeated to form and / or coat a new article.

The coating thus applied can have any desired thickness, but is more particularly in the range from 10 µm to 2000 µm, preferably from 50 µm to 300 µm.

Below, a possible explanation will be given for the improved adhesion obtained according to the invention, both during coating and in the final coated article. However, the invention is not particularly limited to this.

In the practice of the invention, it has been found that the adhesion of the coating composition obtained is mainly related to the morphology of the interface 5 between the plastic 4 and the coating composition 2, whereby a more irregularly shaped ("rougher") interface 5 leads to better adhesion. than an evenly shaped ("smoother") interface. It has also been found that the adhesion obtained is essentially independent of the type of particles included in the coating composition.

Therefore, it is believed that the presence of the particles in the coating composition, in conjunction with the liquid or deformable state of the plastic during coating application, leads to an enhanced mechanical anchoring of the coating in / on the surface of the coating. plastic, in which the increased contact surface, as well as the obtained "embedding" of the particles in the liquid / deformable plastic, play a role.

1004897 11

An important aspect of the invention here is that this "rough" interface 5 is obtained only at the interface between the coating composition 2 and the plastic 4, and not on the side facing the outer die 1, i.e. the side facing the final (outer) surface of the coated article will form, the texture of which is mainly determined by the corresponding surface of the outer mold 1. On the one hand, this gives improved adhesion, but on the other hand an even (smooth) outer surface can be obtained.

The size and quantity of the particles are therefore preferably chosen such that an irregular (r) morphology of the interface is obtained, in particular the pigment volume concentration (PVC) in the coating composition used, as well as the particle size and its distribution. relative to the desired thickness of the final coating (beating) will be decisive.

The pigment volume concentration will in particular amount to 3 to 80%, depending, inter alia, on the manner in which the particles are incorporated in the coating: when (spreading) the coating (whether or not partly cured) coating, in particular, volume concentrations of 3 to 60% are used; when the particles are previously incorporated into the coating composition, a pigment 20 volume concentration of 20 to 80% is used.

Another important factor here is that according to the invention it is important that the particles are distributed irregularly throughout the coating, but are in particular located at the interface of the coating and the plastic, so that an irregularly shaped interface is obtained, such as shown in Figure 2. A uniform (re) dispersion of the particles would give a (much) uniform (er) interface, thereby reducing the adhesion according to the invention, as further explained below. By sprinkling the coating composition with the particles after it has been applied to the wall of the mold, the desired irregular distribution can generally be ensured more easily and at lower pigment volume concentrations and / or particle sizes. However, the minimum particle size of the particles is still (far) above the particle size that is usual for pigment particles and fillers in commercially available coatings.

The morphology of the interface can be easily determined by visually inspecting a cross section of the coating layer (e.g. from the mold after partial curing or in the final coated article), and then optionally classifying it, in particular with reference to the appended figure 2. The morphology of the interface 5 should here be at most 3, more preferably at most 2, and is preferably 1 or 0.

However, other methods known per se for determining the morphology of the interface are also applicable, as will be apparent to those skilled in the art.

Furthermore, it will be clear that the skilled person in the practice of the invention will be able, on the basis of the present description and possibly on the basis of preliminary experiments, to select the particle size and the distribution thereof, as well as the pigment volume concentration. that the improved adhesion according to the invention is obtained, so that it will not be strictly required to determine the morphology of the interface.

The invention will now be illustrated by the following non-limiting examples

Example 1.

In this example, the influence of the type of particles, their size and distribution, as well as the pigment volume concentration on the surface morphology of a coating is determined. The influence of this morphology on the adhesion of the coating to a plastic (polypropylene) was then determined.

In this example and the further examples, different coating types have been used: WAD-U.V: A commercial water-based UV lacquer from Akzo-Nobel.

Finition Interieur: A dark gray water-based primer from Akzo-Nobel that cures under the influence of an oven treatment at 60 ° C. (solid content 30: 34 wt%);

Ebecryl745 / HDDA: A 100% UV varnish based on the commercial UV resin Ebecryl 745 (type: "all acrylic", supplier: UCB) containing the reactive thinner hexamethylene diol diacrylate (HDDA, supplier iUCB) and the initiator Irgacure 184 (5%, supplier: Ciba Geigy).

Various modifications were made to this. The following components play a role here: Accelerator Methyl diethanolamine (MDEA) as well as variations in hardness; 5 - Rahn 91-369 / M22: A 100% UV lacquer. (Type: Aliphatic polyester urethane acrylate; supplier: Rahn).

Several particulate materials have been added to these coatings:

Chalk: Inducal 100 from Ankersmit Grinders: 10 Particle size: 0-100 pm; (small particles 0 - 50 pm)

Density: 2.5 g / cm3

Polypropylene: PB 0580 from Spencer Chemie B.V.

Particle size: 0 - 100 pm (average 30 - 40 pm)

Density: ca 1 g / cm3 15 - Extendospheres: Hollow glass spherical particles, type SF-14 from Spencer

Chemie B.V.

Particle size: 10 - 100 pm (average: 50 - 60 pm)

Density: 0.70 - 0.75 g / cm3 20 The polymers used are:

Polypropylene (PP):

Type: Stamylan P; Features: Superhigh impact copolymer; Medium flow MFI: 5-6;

High level UV stabilizer Processing: Melt temperature: 200 - 290 ° C; Mold temperature: 20 - 70

° C

acrylonitrile butadiene styrene (ABS) resin

Type: Ronfalin SFA 81; Features: High gloss; Good flow; Antistatic; Medium impact resistant 30 Processing: Melt temperature: 200 - 270 ° C; Mold temperature: 35 - 75

° C; Pre-drying: 2-4 hours at 80 ° C

The injection molding experiments were performed as follows: 1004d97! 14

Equipment:

Injection molding machine: KIöckner FX75; Maximum closing force: 750 kN; Maximum shot volume: 150 cm3

Die: "Picture die"; dimensions: 9.3 cm by 19 cm and a thickness of 2 mm. 5 The sprue is located in the middle and near the sprue the thickness over the entire width is 3 mm.

Processing conditions:

Melting temperature: 260 ° C Temperature zones: 260-260-250-240-170-60 ° C 10 Mold temperature: 70 ° C

Injection speed: 120mm / s Cooling time: 25 s Emphasis: 3 s 15 A series of experiments has been conducted involving three different types of particles: PP powder, Extendospheres and Chalk on three different coatings: WAD-UV, Finition Interior and Ebecryl745 / HDDA in different amounts have been added. The morphology of these surfaces was first examined. For this, the different compositions were applied to a gloss plate. Table 1 shows the 20 morphology on a relative scale of 0 to 4. A 4 is a completely smooth surface and 0 is a very rough surface.

10U4897 4 * 15

Table 1: Morpholgy of the surface of the coating ......... T ..... "" '

Added PVC WAD- Finition Inte- Ebecryl745 /

PP Powder (%) U.V. rieur HDDA

5 (wt% on fixed 1

substance) I

no addition 0 4 4 4 | approx. 20 17 2 2 3 |

approx. 30 23 1 0-1 3 I

10 approx. 45 31 1 0 1 I

Added PVC WAD-U.V. Finition Inte- Ebecryl745 /

Chalk (%) rieur HDDA

(wt% on solid 15) approx. 25 (10 vol%) 9 3 2 3 approx. 50 (20 vol%) 17 2-3 2 3 approx. 75 (30 vol%) 23 1 1 2 approx. 75 Small 23 2 2 4 20 particles' Uju4897 16

Added PVC WAD-U.V. Finition Inte- Ebecryl745 /

Extendospheres (%) rior HDDA

(wt% on solid) 5 approx. 20 (28 vol%) 22 1 1 3 approx. 30 (42 vol%) 29 0 0 3 approx. 45 (62 vol%) 38 0 0 1

Injection molding experiments with polypropylene were then carried out and the adhesion to the plastic was determined. The different compositions are first applied to a release paper that is well wetted by the different coatings. This coated release paper is then placed in a mold and a polypropylene melt is introduced into the mold via injection molding. The polypropylene is a pure type - without fillers and not modified with rubber - to which good adhesion is generally difficult to achieve. The coating is taken over by the plastic and comes off the release paper. The adhesion of the coating to the plastic is determined with a standardized diamond cutting test. The rating ranges from 0 to 5 (DIN 53151). A 0 is excellent adhesion, 5 is very poor adhesion. The data are presented in Table 2. Herein PVC 20 is short for Pigment Volume Concentration.

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Table 2: Adhesion of coating applied to injection molded polypropylene product via coating in the mat ice: mixing powders into the coating

Coating applied to release paper by ironing 5 Waterborne coatings 150 pm knife U.V.coating 75 pm knife

Added PVC WAD-U.V. Finition Inte- Ebecryl745 /

PP Powder (%) rior HDDA

10 (wt% on solid) no addition 0 5 5 5 approx. 20 17 5 3-4 5 approx. 30 23 4-5 1-2 5 15 approx. 45 31 0 0 0

Added PVC WAD- Finition Inte- Ebecryl745 /

Chalk (%) U.V. rieur HDDA

(wt% on solid 20) approx. 25 (10 vol%) 9 5 5 5 approx. 50 (20 vol%) 17 5 5 5 approx. 75 (30 vol%) 23 5 5 5 approx. 75 Small parts 23 5 5 5 25 coins 1004897!.

18

Added PVC WAD- Finition Inte- Ebecryl745 /

Extendospheres (%) U.V. rieur HDDA

(wt% on solid) 5 approx. 20 (28 vol%) 22 5 3-4 5 approx. 30 (42 vol%) 29 0-1 1 4-5 approx. 45 (62 vol%) 38 0 0 5

The data shows that it is possible to greatly improve the adhesion with both the PP powder and the 10 hollow glass spheres and to achieve excellent adhesion to polypropylene for different types of coatings. This is not as good for the 100% UV coating as for the two water-based coatings. The effect has not been found for chalk. This may be due to the high density of the material. Because of this, the highest amount of chalk, has a PVC 15 (Pigment Volume Concentration)), which is comparable to the lowest concentration of the extendosopheres.

The excellent adhesion to polypropylene is surprising given the major problems normally encountered when coating polypropylene.

Comparison of Tables 1 and 2 shows that there is a strong correlation between morphology and adhesion. This indicates that the adhesion is mainly due to a mechanical anchoring and not an interaction between the binder of the coating and the plastic or between the powders and the plastic.

Example 2 This example further illustrates the application of a powder to the surface of the coating. A coating is applied to a release paper. The powder is sprinkled on the coating before curing. The powder that does not stick to the coating is removed. Then the coating is cured, the release paper with coating is applied in the mold and the object 30 is injection molded. The coating is hereby taken over by the plastic. The adhesion of the coating (thickness for waterborne coatings 150 μm knife, for U.V.coating 1004897 19 75 μπι knife) to the plastic is also determined in these examples by means of a diamond cutting test.

Table 3: Adhesion of coating applied to polypropylene injection molded product via 5 coating in the mold: sprinkle powders over the coating.

Finit. Inter. WAD- Ebecryl Ebecryl745 Ebecryl Ebecryl U.V. 745 HDDA 745 745 HDDA (60/40) Rahn (4) Rahn (4)

(60/40) 2% MDEA HDDA HDDA

(3) (55/5/40) (50/10/40 »

No additive 5 5 5 5 5 5 PP powder 0-10 0 0 0 0 10 (1) CPO powder 0 0 0 0 0 0 1

(2) I

(1): PP powder is sprinkled on wet coating. The excess powder is shaken off. About 60 g / m2 powder remains.

(2): CPO powder is sprinkled on wet coating. The excess powder is shaken off. About 250 g / m2 powder remains.

(3): MDEA: Methyl-diethylamine (accelerator in curing the U.V. resin) (4): Rahn: Rahn 91-369-M22 (a soft U.V. resin) 20

The results are shown in Table 3. The PP powder was as described above. The CPO powder was type CPC-343-1 from Eastman Chemical with a particle size of about 100-300 µm and a density of 1.025 g / cm3.

1004897.

20

Example 3

The same experiments as in Example 2 (see Table 3) were performed with an acrylonitrile butadiene styrene (ABS) resin. The results are shown in Table 4.

5

Table 4: Influence of sprinkling powders on the coating before curing on the bond when applying the coating via injection molding

Ebe- Ebeciyl745 Ebe- Ebe- cryl745 HDDA cryl745 cryl745 HDDA (60/40) Rahn (2) Rahn (2)

(60/40) 2% MDEA HDDA HDDA

(1) (55/5/40) (50/10/40)

Plastic ABS

10 No additive 5 5 5 5 CPO powder 0 0 0 0 (1): MDEA: Methyl-diethylamine (accelerator in curing of the UV resin) (2): Rahn: Rahn 91-369-M22 (a soft UV resin) 15

Example 4: applying the coating in the mold:

45 w% (PVC: 31%) PP powder is added to a water-based coating Finition Interieur (Akzo-Nobel). This coating is applied to the mold wall via brushes. The coating is dried with warm air. The mold is closed and a mold of PP is injection molded in the mold. The upholstery is completely taken over by the plastic. The adhesion is determined by the diamond cutting test (DIN 53151). Very good adhesion is found (value 0). The coating has a smooth surface.

In a comparative experiment without adding PP powder, the coating is not taken over by the plastic during injection molding, but remains on the mold wall.

1004897 21

It can be seen from the above examples that the adhesion is improved if the interface of the cured coating and the coated plastic is very rough. This rough surface is obtained by mixing the powder into the coating only at a minimum particle size and at a minimum amount of the powder. For different types of coatings and the different types of powders, the required minimum particle size and minimum amount of powder may differ slightly. This may be related to the particle size distribution and morphology of the particles and possibly also the interaction between the particles and the plastic. The minimum limits where the desired effect on adhesion is found in the above Examples seems to lie broadly with a (minimum) particle size of 30 to 40 µm and an amount of particles corresponding to a pigment volume concentration (PVC) of about 30%. The minimum particle size is (far) above the particle size that is usual for pigment particles and fillers in commercial coatings. However, for other combinations of particles, coating and plastic, and in particular for other coating thicknesses, as well as for sprinkling the powder over the uncured or partially cured coating, these limits may be different, as indicated in the above description .

It has further been found in the invention that the type of particles is not important, although it has also been found that, with the same volume fraction of particles, sometimes an improved adhesion is sometimes obtained and sometimes not. Although it has been found that larger particles generally already provide a stronger adhesion than smaller particles at the same volume fraction, because a rougher surface is obtained.

Since the principle of operation of the invention works for particles consisting of different materials, it can further be concluded that the improvement in the adhesion between the plastic and the coating is largely determined by the mechanical anchoring. Due to the improved adhesion between the coating and the plastic material and because this adhesion is mainly based on a mechanical anchorage, a coating can be chosen that has poor adhesion to metal (and plastic). Adhesion to the plastic is achieved via a mechanical anchoring. With this, a coating can be realized which shows good release from the mold during "in-mold coating" and yet adheres well to the plastic.

This principle of improved adhesion by mechanical anchoring can be applied in all processes where a transfer takes place from a hard surface to a plastic that is in the melt, such as In-mold coating in the various processing techniques, for example injection molding, processing / shaping SMCs and BMCs, blow molding, RIM; Decorating in mold / "Heisspragefolie" (which may not require an additional adhesive layer); sealing, 5 welding, whereby a better adhesion can be obtained by generating a rough surface by applying a suitable powder in a coating or on a coating before curing and applying the plastic thereon in the liquid or plastic form and under applying pressure or melting the plastic against the coating in a sealing process or "spot weld" or via calendering.

Thus, although the invention has been particularly described herein with respect to the preferred embodiment of coating in molds, the method of the invention can generally be used in all known per se methods of coating a plastic simply by the particles to be incorporated into the coating in the required amount, and to coat the plastic in the known manner.

In general, any means known per se for picking up and transferring the coating composition can be used as the first substrate, such as a roller, a roller, a doctor blade, or a brush or even a brush.

The invention can also be used to apply, for example, a thin film to a nonwoven material, which includes the texturizing particles in the film, to provide improved adhesion. It will be clear here that the film will not be in the liquid state when the method is carried out, so that steps a and b of the method of the invention must be adapted accordingly.

The invention can further be used for transferring a coating of a suitable support as a first substrate to the receiving second substrate, for example for transferring an image from a film to a plastic, analogous to conventional processes, but using a A release layer between the film and the coating and / or an adhesive layer on the receiving surface will no longer be required (although still within the scope of the invention).

1004897 23

Further applications of the teachings of the invention, all of which will fall within the scope of the following claims, will be apparent to those skilled in the art.

100489T

Claims (16)

A method of applying a coating to a target surface of a second substrate, comprising the successive steps of: a) applying a liquid coating material to a surface of a first substrate; b) partially or completely curing the liquid coating material to form a cured coating on the surface of the first substrate; C) contacting the partially or fully cured coating with the intended surface of the second substrate, the second substrate being in a liquid or deformable (plastic) state, which can be converted into a solid state, or or carries on the target surface a liquid component that can be converted to a solid state; D) converting the second substrate or the liquid component into the solid form; such that the cured coating is transferred from the surface of the first substrate to the target surface of the second substrate, incorporating solid particles in the coating from about 10 μτη to about 200 μπι to a pigment volume concentration in the range of 3 to 80%; and the cured coating has a thickness in the range of 20 µm to 300 µm. such that an irregularly shaped interface between the coating and the second substrate is obtained. The method of claim 1, wherein the second substrate is a plastic. The method of claim 2, wherein the plastic comprises a thermoplastic polymer or mixture of polymers. A method according to claim 2 or 3, wherein the plastic polypropylene or 1004897 polymeric mixtures based on polypropylene, containing more than 60% by weight, preferably more than 80% by weight, of polypropylene. 5. A method according to any one of claims 1-4, wherein the liquid coating material is a water-based coating material or a radiation-hardened coating material. 6. A method according to any one of claims 1-4, wherein particles with a size of about 10 µm to about 200 µm, in particular about 20 µm to about 100 µm, are sprinkled in the (partly or partially cured) ) coating are incorporated, in a pigment volume concentration of 3 to 60%; or wherein particles having a size from about 20 µm to about 500 µm, especially about 30 µm to about 200 µm, are incorporated into the coating composition before being applied to the first substrate, in a pigment volume concentration of 20 to 80 %. A method according to any one of claims 1-6, for coating a plastic material during its formation, wherein the plastic material is or has been brought into the required liquid or deformable (plastic) state during at least one step of the method. . 8. A method according to claim 7, for applying a coating to a plastic during molding in a mold or mold, said mold forming the first substrate, comprising successive steps of: a) applying a solid particulate coating composition such as described in claim 1 on the (inner) wall of the mold; b) partially or completely curing the coating material to form an at least partially cured coating on the inner (wall) of the mold; c) introducing the plastic to be coated, which is in a liquid or deformable (plastic) state, into the mold d) curing the plastic, whereby the coating composition is transferred from the wall of the mold to the mold surface of the plastic product; e) ejecting the coated and molded article from the mold. 5 wherein the cured coating has a thickness in the range of 20 µm to 300 µm. A method according to claim 7 or 8 for coating during machining molding processes, such as machine injection molding. 10 A method according to any one of claims 1-6, wherein the first substrate is a punch, a roller, a roller, a doctor blade, an ironing knife or a brush or other ironing agent. 15 A method according to any one of claims 1-6, wherein the second substrate is a plastic in a (substantially) solid or non-deformable state, wherein at least on the surfaces to be coated thereof a further (adhesive) material in the required liquid or deformable state. such as another polymeric material and / or an (adhesive) agent. Method according to claim 1 or 11, for coating fiber materials or materials with a similar "open" structure, wherein the fiber material is / is impregnated with the liquid or deformable (further) material. 25 Method according to claim 1 or 11, wherein the plastic is in the form of a foil, which is applied to the second substrate by welding or sealing, optionally using a (further) adhesive layer. 1 1004897 A method according to any one of claims 1, 11 or 12, or according to claim 13, for applying a film to a non-woven material. Coated article, such as a coated plastic or coated fiber material, obtainable by a method according to any one of claims 1-14. Coated article according to claim 15, being a molded plastic article, in particular obtainable by molding in a mold or mold according to the method of any one of claims 7-9. 1004897 '