Curable casting compound for producing plastic molded parts

Abstract

The invention relates to a curable casting compound for producing plastic molded parts, comprising a casting compound having a binder composition and a filler composition, wherein the casting compound comprises at least one reactive, polymeric adhesion promoter, and the filler composition comprises uncoated quartz sand.

Description

[0001] Curable casting compound for the production of plastic molded parts, use of the same as plastic molded part

[0002] The invention relates to a curable casting compound for the production of plastic molded parts, comprising a casting compound with a binder composition and a filler composition.

[0003] The invention further relates to the use of a hardenable casting compound.

[0004] The invention further relates to a plastic molded part, manufactured using a curable casting compound.

[0005] Curable casting compounds are used for the production of molded plastic parts, particularly in sanitary or kitchen applications, such as kitchen sinks, worktops, bathtubs, washbasins, or the like. These curable casting compounds typically comprise a binder material and a filler material to improve the mechanical properties of the molded plastic parts, as is known, for example, from DE 38 32 351 A1 or WO 2005 / 071000 A1.

[0006] For the color design of molded plastic parts manufactured from such casting compounds, the use of colored-coated filler particles is known. The color pigments are fixed to the filler particles using inorganic or organic binder systems. For the production of thermally resistant kitchenware, especially household sinks, inorganic binders based on sodium and potassium silicates or aluminum tris(dihydrogen phosphate) are typically used for pigment fixation on the filler surfaces. To make the colored-coated filler particles suitable for processing in known casting compounds, the filler surfaces are additionally silanized, usually using 3-(trimethoxysilyl)propyl methacrylate. Such colored-coated fillers are known, for example, as Granucol® SIG / SIL and Granucol® FFB / SIL from Dorfner.

[0007] A significant disadvantage of known plastic molded parts, particularly household sinks, manufactured using the described colored-coated fillers, is the so-called "water whitening" effect. Under the influence of hot water, the surfaces of such plastic molded parts tend to "fade" or exhibit an optical lightening effect, thereby impairing the long-term stability of the color.

[0008] Another problem is the complex production of the colored-coated fillers. Pigment fixation requires several process steps, in particular the binding of the color pigments by inorganic binders and subsequent silanization to ensure sufficient adhesion in the casting compound. This leads to increased material and process costs and makes the economical production of corresponding plastic molded parts more difficult.

[0009] One object of the present invention is therefore to provide a curable casting compound and plastic molded parts produced therefrom that ensure higher color stability and at the same time enable simpler and more cost-effective production of such plastic molded parts.

[0010] Another object of the present invention is to provide an alternative curable casting compound and plastic molded parts produced therefrom.

[0011] The present invention solves the aforementioned problems in a curable casting compound for the production of plastic molded parts, comprising a casting compound with a binder composition and a filler composition, in that the casting compound comprises at least one reactive, polymeric adhesion promoter and the filler composition comprises uncoated quartz sand.

[0012] The present invention also solves the aforementioned problems by using a curable casting compound according to one of claims 1-9 for the production of a plastic molded part for the kitchen and / or sanitary sector, in particular kitchen sinks and worktops for kitchens.

[0013] The present invention also solves the aforementioned problems by means of a plastic molded part, manufactured using the curable casting compound according to one of claims 1-9.

[0014] The present invention also solves the aforementioned problem by using uncoated quartz sand and at least one reactive, polymeric adhesion promoter to improve the color stability of plastic molded parts under thermal stress, in particular under thermal stress from contact with hot water.

[0015] The term “uncoated quartz sand” is to be understood in the broadest sense and refers in particular in the claims, preferably in the description, to quartz sand whose particles do not have any inorganic and / or organic coloring coating, in particular no polymeric, silicate, metal oxide and / or pigment-containing coatings.

[0016] One of the advantages achieved is that plastic molded parts with increased color stability under thermal stress are provided. Surprisingly, it was found that the targeted combination of at least one reactive polymeric adhesion promoter and uncoated quartz sand in the casting compound significantly reduces the "water whitening" effect for plastic molded parts produced using this casting compound, thus preserving the original color even after repeated contact with hot water. Without committing to a specific theory, it is assumed that the unexpectedly improved bonding of the filler particles to the polymer matrix helps to reduce water penetration at the interfaces and thereby diminish the "water whitening" effect.

[0017] A further advantage lies in the improved integration of the filler composition into the hardened casting compound. The mediated adhesion between the quartz sand and the binder composition results in a homogeneous dispersion of the filler composition within the casting compound, thereby minimizing inhomogeneities and optical irregularities.

[0018] Another advantage lies in the simplification of the manufacturing process. Unlike known methods, neither pigment fixation using inorganic or organic binders nor subsequent silanization of the fillers is required, thus reducing material and process costs.

[0019] Furthermore, it was surprisingly found that the embodiments of the present invention eliminate the need for separate silanization of the filler surface, thereby simplifying the manufacturing process and improving the cost-effectiveness of production.

[0020] Despite the improvement in color stability under thermal stress, the optical quality of the manufactured plastic molded parts is maintained, so that especially colored or decorative surfaces with consistent color depth and structure can be achieved.

[0021] Further features, advantages and further embodiments of the invention are described below or become apparent therein.

[0022] According to an advantageous embodiment of the invention, the binder composition comprises a weight fraction of 10 wt.% or more, in particular 15 wt.% or more, preferably 20 wt.% or more, and 50 wt.% or less, preferably 40 wt.% or less, in particular 30 wt.% or less, preferably 25 wt.% or less, of the total mass of the casting compound. An advantage of this is sufficient bonding capacity of the components of the casting compound.

[0023] According to a further advantageous embodiment of the invention, the filler composition has a weight fraction of 40 wt.% or more, in particular 50 wt.% or more, preferably 60 wt.% or more, in particular 70 wt.% or more, and 90 wt.% or less, preferably 85 wt.% or less, in particular 80 wt.% or less, preferably 75 wt.% or less, of the total mass of the casting compound. An advantage of this is sufficient strength of a plastic molded part produced with the casting compound.

[0024] According to a further advantageous embodiment of the invention, the reactive polymeric adhesion promoter comprises at least one reactive polymer having at least one functional group reactive with the binder composition and at least one functional group reactive with the filler composition. Preferably, the reactive polymer is a chemically modified polyether.

[0025] According to a further advantageous embodiment of the invention, the at least one reactive, polymeric adhesion promoter comprises a weight fraction of 0.01 wt.% or more, in particular 0.05 wt.% or more, preferably 0.1 wt.% or more, in particular 0.2 wt.% or more, and 1 wt.% or less, preferably 0.75 wt.% or less, in particular 0.5 wt.% or less, preferably 0.4 wt.% or less, of the total mass of the casting compound. The advantage of this is improved adhesion between the binder composition and the filler composition without adversely affecting the mechanical or optical properties of the manufactured plastic molded part.

[0026] According to a further advantageous embodiment of the invention, the binder composition comprises a liquid monomeric acrylate component with a proportion of 70 wt.% or more, preferably 80 wt.% or more, and 90 wt.% or less, in particular 85 wt.% or less, based on the proportion of the binder composition. An advantage of this is that it can be polymerized to a polyacrylate during the curing process of a plastic molded part. To increase the viscosity of the curable casting compound, a proportion of a prepolymerized acrylate component can be added to the monomeric acrylate; for example, prepolymerized polymethyl methacrylate (PMMA) can be added to the monomer methyl methacrylate. According to a further advantageous embodiment of the invention, at least one crosslinking agent is included in the casting compound with a proportion of 0.1 wt.% or more, preferably 0.5 wt.% or more, preferably 1 wt.% or more, preferably 1.5 wt.%.-% or more, preferably 5 wt.% or more and 20 wt.% or less, in particular 15 wt.% or less, in particular 10 wt.% or less, in particular 7.5 wt.% or less, based on the proportion of the liquid monomeric acrylate component of the binder composition. This enables sufficient hardness of a molded plastic part produced with the casting compound. Suitable crosslinking agents include, for example, substances from the group of aliphatic or aromatic di-, tri- or multifunctional acrylates or methacrylates and / or epoxy acrylates or methacrylates and / or aliphatic or aromatic di-, tri- or multifunctional urethane acrylates or methacrylates and / or di-, tri- or multifunctional polyester acrylates or methacrylates and / or combinations thereof.

[0027] According to a further advantageous embodiment of the invention, the casting compound comprises at least one color pigment and / or effect pigment. The advantage of this is that the color appearance of the plastic molded part produced using the curable casting compound can be specifically influenced, in particular that an inherent coloration caused by the filler composition, such as the natural color of quartz sand, can be masked or at least reduced if a specific color appearance of the plastic molded part is desired. Suitable color pigments include, for example, inorganic pigments such as metal oxide pigments, especially from the spinel group, or transition metal oxides, such as titanium dioxide, and / or combinations thereof.Suitable effect pigments include, for example, pearlescent pigments, metallic effect pigments, interference pigments and / or luminescent pigments, especially those based on mica, aluminum, silicon dioxide or other synthetic substrates, and / or combinations thereof.

[0028] According to a further advantageous embodiment of the invention, the uncoated quartz sand comprises at least a proportion of fine quartz sand, preferably between 75 wt.% and 95 wt.% of the total mass of the quartz sand, and at least a proportion of coarse quartz sand, preferably between 5 wt.% and 25 wt.% of the total mass of the quartz sand. The advantage of this is that the targeted combination of fine and coarse quartz sand results in improved packing density within the casting compound, thereby optimizing both the mechanical properties and the processability of the casting compound and ensuring a uniform surface structure of the manufactured plastic molded part.

[0029] The term “fine quartz sand” is to be understood in the broadest sense and refers, particularly in the claims, preferably in the description, to quartz sand with a mean grain size (dso) of about 0.3 mm, wherein the particle size distribution is in the range of 0.1 mm to 0.6 mm.

[0030] The term “coarse quartz sand” is to be understood in the broadest sense and refers, particularly in the claims, preferably in the description, to quartz sand with a mean grain size (dso) of about 0.6 mm, wherein the particle size distribution is in the range of 0.4 mm to 0.8 mm.

[0031] Further important features and advantages of the invention will become apparent from the dependent claims and from the following explanation.

[0032] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0033] Preferred embodiments and configurations of the invention are explained in more detail in the following description.

[0034] It was found that the use of uncoated quartz sand and at least one reactive, polymeric adhesion promoter improves the color stability of plastic molded parts under thermal stress, especially thermal stress from contact with hot water. (Comparison example 1)

[0035] A curable casting compound is produced by combining a binder material with a filler material. The binder material is obtained by dissolving PMMA in MMA such that it contains 19% PMMA and 81% MMA by weight.

[0036] The filler material comprises granular coated quartz material Granucol® (manufactured by Gebrüder Dorfner GmbH & Co., Hirschau) and crystalline quartz sand. The following types of Granucol® and crystalline quartz sand are used:

[0037] Granucol® SIG / SIL black 20 / 9 (grain size 0.1 - 0.6mm)

[0038] Granucol® SIG / SIL black 20 / 8 (grain size 0.3 - 0.8mm)

[0039] GEBA Fine Sand (Grain size 0.06 - 0.3mm)

[0040] The filler material is now added to the binder material and mixed homogeneously.

[0041] Furthermore, Heucodur HD952 is added to the curable casting compound as a color pigment and IRIODIN 163 as an effect pigment to adjust the desired color of the later plastic molded part.

[0042] Furthermore, a peroxide mixture is added to the curable casting compound to regulate polymerization and cure the casting compound. Such a peroxide mixture can, for example, comprise di(4-tert-butylcyclohexyl)peroxydicarbonate and / or dilauroyl peroxide. Additionally, a mixture of polyfunctional methacrylic monomers, particularly from the group of carboxylic acid esters, is added as a crosslinking agent.

[0043] The composition of the curable casting compound according to comparative example 1 is shown in Table 1 below, with the proportions of the individual components given in weight percent.

[0044]

[0045] The peroxide mixture can essentially consist of a mixture of dilauroyl peroxide and di-(4-tert-butylcyclohexyl)peroxydicarbonate in a weight ratio of 1.5:1.

[0046] The hardenable casting compound is then placed in a mold for a plastic molded part in the shape of a kitchen sink and polymerized under the influence of heat.

[0047] Comparative example 2

[0048] A casting compound is produced according to the process of Comparative Example 1, which largely corresponds in its composition to the curable casting compound according to Comparative Example 1, using a granular coated quartz material Granucol® (Gebrüder Dorfner GmbH & Co., Hirschau), which differs from that used in Comparative Example 1. The following types of Granucol® are used:

[0049] Granucol® FFB / SIL black 100 / 9 (0.1 - 0.6mm)

[0050] Granucol® FFB / SIL black 100 / 8 (0.3 - 0.8mm)The composition of the curable casting compound according to comparative example 2 is shown in the following Table 2, where the contents of the individual components are given in weight percent.

[0051] Table 2

[0052]

[0053] Example

[0054] A casting compound is produced according to the procedure of the comparative examples, the composition of which largely corresponds to the curable casting compound according to the comparative examples, except that instead of the crystalline quartz sand and granular coated quartz material Granucol® (Gebrüder Dorfner GmbH & Co., Hirschau), uncoated quartz sand with a proportion of fine quartz sand and a proportion of coarse quartz sand is used. The following types of uncoated quartz sand are used:

[0055] Fine quartz sand (0.1 - 0.6mm)

[0056] Coarse quartz sand (0.4 - 0.8mm)

[0057] Furthermore, BYK-C 8000 (BYK-Chemie GmbH, Wesel) is added to the casting compound according to the invention as a reactive, polymeric adhesion promoter. The composition of the curable casting compound according to the example is shown in Table 3 below, with the amounts of the individual components given in weight percent.

[0058] Table 3

[0059]

[0060] Comparison examples 1 and 2, as well as example 1, are examined. For this purpose, a 10 x 10 cm sample is taken from the bottom of the kitchen sink.

[0061] First, a color measurement of the rinse side of the sample taken is carried out using a colorimeter (Minolta CR410).

[0062] The sample obtained is then subjected to a cooking test according to the test method described below.

[0063] The boiling test is performed using an apparatus (the "Bayer lantern") that ensures continuous contact between the sample surface and hot water. The samples are attached to the Bayer lantern with the sink side facing inwards, with a sealing ring placed between the lantern, the sample, and the mounting plate. During the test, demineralized hot water at a temperature of 95 °C is passed through the Bayer lantern from bottom to top, so that the sink side of the sample is exposed to the hot water for 16 hours.

[0064] After completion of the cooking test, the color of the surface of the sample facing the sink is measured again using the Minolta CR410 colorimeter.

[0065] The color difference AE99 for the samples of the molded parts from comparison examples 1 and 2, as well as for the sample of the molded part according to the invention, is calculated from the color values ​​determined before and after the cooking test and is shown in Table 4.

[0066] Table 4

[0067]

[0068] The tests carried out clearly show that the plastic molded parts produced using the embodiments of the invention exhibit significantly increased color stability under thermal stress compared to the plastic molded parts of the comparison examples.

[0069] Although the present invention has been described with reference to preferred embodiments, it is not limited to these, but can be modified in many ways.

Claims

Claims 1. Curable casting compound for the production of plastic molded parts, comprising a casting compound with a binder composition and a filler composition, characterized by the fact that The casting compound comprises at least one reactive, polymeric adhesion promoter and the filler composition comprises uncoated quartz sand.

2. Curable casting compound according to claim 1, characterized in that the binder composition has a weight fraction of 10 wt.% or more, in particular 15 wt.% or more, preferably 20 wt.% or more and 50 wt.% or less, preferably 40 wt.% or less, in particular 30 wt.% or less, preferably 25 wt.% or less of the total mass of the casting compound.

3. Curable casting compound according to one of claims 1-2, characterized in that the filler composition has a weight fraction of 40 wt.% or more, in particular 50 wt.% or more, preferably 60 wt.% or more, in particular 70 wt.% or more and 90 wt.% or less, preferably 85 wt.% or less, in particular 80 wt.% or less, preferably 75 wt.% or less of the total mass of the casting compound.

4. Curable casting compound according to one of claims 1-3, characterized in that the reactive polymeric adhesion promoter comprises at least one reactive polymer having at least one functional group reactive with the binder composition and at least one functional group reactive with the filler composition, wherein the reactive polymer is preferably a chemically modified polyether.

5. Curable casting compound according to one of claims 1-4, characterized in that the at least one reactive, polymeric adhesion promoter has a weight fraction of 0.01 wt.% or more, in particular 0.05 wt.% or more, preferably 0.1 wt.% or more, in particular 0.2 wt.% or more and 1 wt.% or less, preferably 0.75 wt.% or less, in particular 0.5 wt.% or less, preferably 0.4 wt.% or less of the total mass of the casting compound.

6. Curable casting compound according to one of claims 1-5, characterized in that the binder composition comprises a liquid monomeric acrylate component with a proportion of 70 wt.% or more, preferably 80 wt.% or more and 90 wt.% or less, in particular 85 wt.% or less, based on the proportion of the binder composition.

7. Curable casting compound according to claim 6, characterized in that at least one crosslinking agent is included in the casting compound with a proportion of 0.1 wt.% or more, preferably 0.5 wt.% or more, preferably 1 wt.% or more, preferably 1.5 wt.% or more, preferably 5 wt.% or more and 20 wt.% or less, in particular 15 wt.% or less, in particular 10 wt.% or less, in particular 7.5 wt.% or less, based on the proportion of the liquid monomeric acrylate component of the binder composition.

8. Curable casting compound according to one of claims 1-7, characterized in that the casting compound comprises at least one color pigment and / or effect pigment.

9. A curable casting compound according to any one of claims 1-8, characterized in that the uncoated quartz sand comprises at least a proportion of fine quartz sand, preferably between 75 wt.% and 95 wt.% of the total mass of the quartz sand, and at least a proportion of coarse quartz sand, preferably between 5 wt.% and 25 wt.% of the total mass of the quartz sand.

10. Use of a curable casting compound according to any one of claims 1-9 for the production of a plastic molded part for the kitchen and / or sanitary sector, in particular kitchen sinks and kitchen worktops.

11. Plastic molded part, manufactured using the curable casting compound according to any one of claims 1-9.

12. Use of uncoated quartz sand and at least one reactive polymeric adhesion promoter to improve the color stability of plastic molded parts under thermal stress, especially under thermal stress from contact with hot water.

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