WO1998023670A1

WO1998023670A1 - Cavity containing moulded bodies made of thermoplastic moulding material

Info

Publication number: WO1998023670A1
Application number: PCT/EP1997/006115
Authority: WO
Inventors: Christian Schade; Rainer Neumann; Heike Feldmann; Guenther Zimmer
Original assignee: Barlo Plastics Gmbh
Priority date: 1996-11-22
Filing date: 1997-11-05
Publication date: 1998-06-04
Also published as: DE19648448A1; EP0960157A1

Abstract

Thermoplastic moulded body containing a cavity and which is obtainable from thermoplastic moulding materials containing one or several compounds which are gaseous or separate gaseous constituents at high temperatures.

Description

Molded articles made of thermoplastic molding compositions containing cavities

description

The invention relates to moldings containing cavities, obtainable from thermoplastic molding compositions which contain one or more compounds which are gaseous at elevated temperature or split off gaseous constituents.

Furthermore, the invention relates to a process for the production of moldings containing cavities and their use for the production of office, household and sanitary articles, furniture and furniture elements as well as interior design components and design objects.

Shaped bodies containing bubbles or pores are used, for example, as components of worktops because of their specific material properties and their characteristic aesthetic effects.

EP-A 503 156 describes a process for the production of plastic moldings from a water-expanded polymer resin, in which the moldings obtained after the manufacturing process have essentially closed pores, the size of which is below 50 μm on average. These moldings are obtained by subjecting a curable mixture, the resin-forming component of which, in defined weight ratios, comprises a monomer component and an acrylate prepolymer based on acrylate, to a mass polyreaction as a water-in-oil emulsion. Because of the

Water content in the emulsion, the reaction temperature is usually below 50 ° C. A disadvantage of the process according to EP 503 156 is that, due to the process, only a small number of components can be used in the selection of the molding compositions which are suitable for the shaped body. An additional drying step is also required to remove the water trapped in the pores. Another disadvantage is that the pore size can only be adjusted over a small range and that no transparent moldings are obtained.

The invention was therefore based on the object of making molded articles made of thermoplastic molding materials accessible, in which cavities can be installed in a controlled manner using conventional processing conditions without additional process steps or special process parameters are required.

Accordingly, the molded articles defined at the outset were found from thermoplastic molding compositions.

Furthermore, a process for the production of the moldings according to the invention and their use in the production of office, household and sanitary articles, furniture and furniture elements as well as interior design components and design objects were found.

Shaped bodies made of thermoplastic molding compositions are preferred, on the surface of which the cavities appear only insignificantly and have no influence on the outer shape of the shaped body. Moldings which are transparent are particularly preferred.

Suitable thermoplastic molding compositions are polymers and polymer mixtures which contain at least one compound which is gaseous at elevated temperature or releases gaseous constituents. This includes, for example, as volatile components physical blowing agents, such as pentane, heptane or octane, which are incorporated into the thermoplastic molding compositions.

Compounds which split off gaseous components at elevated temperature can either be a component of the polymer composition forming the thermoplastic molding compositions, a polymer additive or a low molecular weight additive, as described in R. Gächter, H. Müller (ed.), Taschenbuch der Kunststoff-Additive, 3 Ed., Carl Hanser Verlag, Munich, 1989, pp. 843 - 864. The compound which releases gaseous constituents preferably represents one or more polymer components of the thermoplastic polymer molding composition.

Suitable monomer units of this polymer or copolymer component are ethylenically unsaturated carboxylic acid esters of the general formula (I):

in which the substituents have the following meaning: R ¹ to R ³ : independently of one another, hydrogen; C1 _. -C ₅ alkyl, whether or not substituted, in particular methyl, ethyl, propyl, butyl in straight-chain and branched form; -CH ₂ C0 ₂ R ⁸ ,

R ⁴ , R ⁵ : independently of one another, C 1 -C 6 -alkyl, also substituted, in particular methyl, ethyl, propyl, butyl, pentyl, hexyl in straight-chain and branched form; Aryl, in particular phenyl, optionally substituted with C 1 -C ₄ -alkyl radicals,

R ⁶ , R ⁷ : independently of one another, hydrogen; C - to Cs -Alkyl, also substituted, in particular methyl, ethyl, propyl, butyl, pentyl, hexyl in straight-chain and branched form; Aryl, in particular phenyl, optionally substituted with Ci to Cβ alkyl residues,

R8 _: hydrogen; Ci to C ₄ alkyl, also substituted, such as methyl, ethyl, propyl.

The radicals R ⁴ to R ⁷ can also be part of ring systems such as cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, furanyl or pyranyl.

The alkyl and aryl groups described above can be substituted by halogen, such as chloride or bromide, with _Ca. to Cs-alkyl radicals, such as methyl, ethyl or propyl, or with functional groups based on elements from groups IVA, VA and VIA of the periodic table of the elements, such as SiX ₃ , NX ₂ or OX, with X = hydrogen, alkyl, Aryl or aralkyl.

The monomer units are particularly preferably tert. -Butyl acrylate and tert-butyl methacrylate.

The thermoplastic molding compositions can be composed either completely or partially of polymers which contain monomer units of the general formula (I).

Preferred thermoplastic molding compositions are those

- Completely or partially - are made up of polymers that tert. -Butyl acrylate or tert-butyl methacrylate or a mixture of these components as monomer units. Accordingly, in a preferred embodiment, the moldings according to the invention consist of thermoplastic molding compositions which comprise at least one polymer or at least one copolymer or at least one polymer and at least one copolymer which tert. -Butyl acrylate or tert.- Butyl methacrylate or a mixture of tert. -Butyl acrylate and tert-butyl methacrylate contains as monomer units.

In particular, thermoplastic molding compositions are used which have at least one copolymer which tert. -Butyl acrylate and at least one methacrylate derivative or tert-butyl methacrylate and at least one acrylate or methacrylate derivative contains as monomer units.

Preferred copolymers are those of tert-butyl methacrylate and other methacrylate derivatives, such as methyl methacrylate or 2-ethylhexyl methacrylate. These can be used alone or as a polymeric component of the thermoplastic molding compositions. Copolymers of tert-butyl methacrylate and methyl methacrylate are particularly preferred. The copolymers mentioned can contain further comonomers, the proportion of which is preferably below 20, particularly preferably below 10% by weight, based on the weight of copolymer. Suitable comonomer building blocks are, for example, esters of acrylic and methacrylic acid with Ci to C ₂₀ carbon-organic ester groups, for example alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, 2- Ethylhexyl; C ₂ - to C _δ -hydroxyalkyl methacrylates, such as 2-hydroxyethyl methacrylate; Vinyl aromatics such as styrene, α-methylstyrene and vinyl cyanides such as acrylonitrile and methacrylonitrile.

The proportion of tert-butyl methacrylate and / or tert. -Butyl acrylate in the copolymer is usually in the range from 1 to 50% by weight, preferably in the range from 2 to 25% by weight.

The aforementioned gas-releasing thermoplastic polymers and copolymers can be prepared by methods known per se, such as suspension, solution, bulk or emulsion polymerization (cf. "Acrylic and methacrylic compounds", H. Rauch-Puntigam, T. Völker, Springer Verlag, Berlin, 1967 and "Poly (eth) acrylate", PEP Report 65A, SRI International, Menlo Park, 1991 and literature cited there). In particular, the suspension polymerization can be carried out analogously to the processes described in European patent applications EP-A 489 318, EP-A 584 632 and EP-A 632 069, bulk and solution polymerization as described in EP-A 457 355, and the Emulsion polymerization based on EP-A 245 647 and EP-A 693 501.

The polymers and copolymers described can be processed as such or in a mixture with other thermoplastic molding compositions to give the moldings according to the invention. The gas-releasing components are in the thermoplastic parts advantageously in proportions of not less than 0.2% by weight, preferably not less than 0.5% by weight. However, this proportion is usually in the range from 1 to 50, preferably in the range from 2 to 25,% by weight, based on the total weight of the thermoplastic molding composition.

The thermoplastic mixture components used are in particular those which provide transparent or translucent moldings. Suitable materials are, for example, polystyrene, polymethyl methacrylate (PMMA), amorphous polyamide, transparent polyvinyl chloride, polycarbonate, transparent polyesters, cellulose derivatives, random polypropylene, styrene-butadiene-styrene copolymers, styrene-acrylonitrile copolymers (SAN), styrene-methyl methacrylate Copolymers, styrene-maleic anhydride copolymers, cycloolefin copolymers, styrene-acrylonitrile-methyl methacrylate terpolymers or the corresponding impact-modified materials, methyl methacrylate-acrylonitrile-butadiene-styrene polymer (MABS) and blends of SAN and PMMA. SAN, PMMA, blends of SAN and PMMA or the corresponding impact-modified materials are particularly preferably used. PMMA or impact-modified PMMA is very particularly preferably used. Emulsion graft copolymers, as described in EP 62223, EP 512 333 and WO 9619509, are suitable for impact modification of the materials mentioned. In addition, non-transparent molding compositions, for example acrylonitrile-styrene-acrylic ester (ASA) and acrylonitrile-butadiene-styrene polymers (ABS), and ASA / polycarbonate and polyphenylene ether / styrene-butadiene polymer blends are also suitable. The mixture components mentioned and their preparation are well known. Suitable are conducted under the following trade names products including: Lucryl ^® (BASF AG) methylmethacrylate as poly-, Novolen ^® (BASF AG) as a random polypropylene, Luran ^® (BASF AG) as a styrene-acrylonitrile copolymer, Terlux ^® (BASF AG) as methyl methacrylate-acrylonitrile-butadiene-styrene, Luran ^® S (BASF AG) as ASA and Terluran ^® (BASF AG) as ABS component and the blends Luranyl ^® (polyphenylene ether and styrene-butadiene) Polymer) (BASF AG) and Terblend ^® S (ASA and polycarbonate) (BASF AG). Proven methods can also be used to produce the polymer blends described.

The thermoplastic molding compositions can be admixed with other stabilizers, pigments, dyes and auxiliaries known per se, such as antistatic agents, lubricants, mold release agents or flame retardants. The molding compositions can be processed by conventional methods to give the moldings according to the invention, for example by spraying, blowing, pressing, extruding, calendering or vacuum molding, with the proviso that the thermoplastic molding compositions at a temperature in the range from 140 ° C. to 300 ° C. are processed.

In particular, thermoplastic molding compositions with tert. -Butyl acrylate and / or tert-butyl methacrylate as monomer units above 140 ° C, preferably above 180 ° C and particularly preferably above 215 ° C by conventional methods, such as injection molding and extrusion, processed to give the moldings. Under these conditions the thermal elimination of isobutene is induced, the elimination rate being able to be regulated essentially via the processing temperature and the pressure.

If the production of the moldings requires several processing steps, then the processing conditions should advantageously be selected such that the main amount of gaseous components is only released or split off in the last process step.

The cavities forming in the shaped bodies are generally bubble-shaped and have a maximum average size of 1 cm, but preferably in the range from 5 μm to 0.5 cm in the shaped bodies. The shape and size of the cavities can be influenced by the processing conditions. In the case of injection molding processes, this is achieved in particular by varying the cooling rate, pressure and holding pressure, ie the pressure exerted on the solidifying melt. In principle, the injection molding process can operate over a pressure range from 0 to 3000 bar, but a pressure in the range from 50 to 2000 and in particular from 100 to 1000 bar is preferably set. The higher the pressure exerted on the melt, the smaller the cavities that form in the molded bodies. The number of cavities that form per unit volume is to be controlled via the amount of the gas-releasing polymer and the proportion of gas-releasing components contained therein as well as the processing temperature and duration. In addition, the number and size of the cavities contained in the moldings can also be influenced by the addition of additives. Examples of suitable additives are finely divided fillers, such as barium titanate, talc, chalk, kaolin, mica, silica, barium sulfate or aluminum hydroxide. The moldings containing cavities according to the invention have a density in the range from 0.5 to 1.5, preferably in the range from 0.8 to 1.3 and particularly preferably in the range from 1.0 to 1.2 g / cm ³ .

According to the described processes, webs, plates, bars and profiles can also be produce by extrusion process. Furthermore, the thermoplastic molding compositions are suitable for the production of films and semi-finished products in the deep-drawing and blowing process. Accordingly, the moldings according to the invention can be used, for example, for the production of office, household and sanitary articles, furniture and furniture elements, as well as interior components and design objects. As products come e.g. Lampshades, skylights, salad bowls, shower handles or toothbrushes are possible.

The present invention accordingly opens up an efficient access from a procedural and economic point of view to a large number of cavities containing thermoplastic molded articles.

The invention is explained in more detail below with the aid of examples.

Examples

A. Synthesis of tert. -Butyl methacrylate copolymers

Polymer 1

A solution of 5000 g of water, 3 g of the sodium salt of a copolymer of 64% by weight of methacrylic acid and 36% by weight of methyl methacrylate in the form of a 1.6% by weight aqueous solution and 3 g of sodium phosphate hydrate as a buffer were mixed with 4638 g Methyl methacrylate, 246 g of tert-butyl methacrylate, 4 g of dilauroyl peroxide, 2 g of 2, 2-bis (tert-butylperoxy) butane and 15 g of n-dodecyl mercaptan are mixed and flushed several times with nitrogen. The mixture was then heated to 125 ° C. with stirring and the system was kept at this temperature for 3 h. After cooling, the polymer was separated off, washed and dried.

Polymer 2

Example 1 was repeated with the difference that a mixture of 3655 g of methyl methacrylate and 1230 g of tert-butyl methacrylate was used as the monomer phase. B. Other materials

Polymer 3

Polymethyl methacrylate with a Vicat softening temperature of VST / B / 50 = 108 ° C and a viscosity number of VZ 58 (in CHC1 ₃ at 23 ° C).

C. Thermoplastic molded articles

Example 1 (comparative example)

Polymer 3 was injected in a screw injection molding machine at a cylinder temperature of 220 ° C. and a mold temperature of 70 ° C. to form round disks with a thickness of 6 mm and a diameter of 10 cm. A crystal-clear, bubble-free molded part was obtained. Even when the injection or mold temperature was changed, no molded part containing bubbles was obtained.

Example 2

Polymer 1 was processed analogously to Example 1 at a cylinder temperature of 220 ° C. and a mold temperature of 70 ° C. The circular disc obtained had numerous bubble-shaped inclusions. Increasing the injection molding pressure to 600 bar reduced the size of the bubbles.

Example 3

A mixture of 90 parts of polymer 3 and 10 parts of polymer 1 was processed into round disks analogously to example 1 at a cylinder temperature of 240 ° C. and a mold temperature of 70 ° C. Crystal-clear molded parts were obtained which contained a few, statistically distributed bubbles.

Example 4

A mixture of 98 parts of polymer 3 and 2 parts of polymer 1 was processed analogously to Example 1 at 250 ° C cylinder temperature and 70 ° C mold temperature to round disks. Crystal-clear molded parts were obtained which contained a few, statistically distributed bubbles.

Claims

claims

1. Cavities containing moldings, obtainable from thermoplastic molding compositions, the one or more

Contain compounds that are gaseous at elevated temperature or split off gaseous components.

2. Cavities containing molded articles made of thermoplastic molding materials according to claim 1, characterized in that they are transparent or translucent.

3. Cavities containing molded articles made of thermoplastic molding compositions according to claims 1 to 2, characterized in that they have a density in the range of 0.5 to 1.5 g / cm ³ .

4. Cavities-containing molded articles made of thermoplastic molding compositions according to claims 1 to 3, characterized in that the thermoplastic molding compositions comprise at least one polymer or at least one copolymer which contains monomer units which are based on ethylenically unsaturated carboxylic acid esters of the general formula (I):

in which the substituents have the following meaning:

R ¹ to R ³ : independently of one another, hydrogen; C1.-C ₅ alkyl, whether or not substituted in straight-chain and branched form; -CH ₂ C0 ₂ R ⁸ ,

R ⁴ , R ⁵ : independently of one another, Ci- to Cs-alkyl, also substituted in straight-chain and branched form; Aryl, optionally substituted with Ci _. - up to C ₄ alkyl radicals,

R ⁶ , R ⁷ : independently of one another, hydrogen; Ci to

Cβ-alkyl also substituted, aryl, optionally substituted with CT.- to Cβ-alkyl radicals,

R ⁸ : hydrogen; CT _. - to C ₄ alkyl, also substituted.

5. Cavities-containing molded articles made of thermoplastic molding compositions according to claims 1 to 4, characterized in that the thermoplastic molding compositions at least one polymer or at least one copolymer or at least one polymer and at least one copolymer which tert. -Butyl acrylate or tert-butyl methacrylate or a mixture of tert. -Butyl acrylate and tert-butyl methacrylate contains as monomer units.

6. cavities-containing molded articles made of thermoplastic molding compositions according to claims 1 to 5, characterized in that the thermoplastic molding compositions at least one copolymer which tert. -Butyl acrylate and at least one methacrylate derivative or tert-butyl methacrylate and at least one acrylate or methacrylate derivative contains as monomer units.

7. Cavities containing molded articles made of thermoplastic molding compositions according to claims 1 to 6, characterized in that the cavities are bubble-shaped.

8. A process for the production of moldings from thermoplastic molding compositions according to claims 1 to 7, characterized in that the thermoplastic molding compositions are processed at temperatures in the range from 140 ° C to 300 ° C.

9. Use of the shaped body according to claims 1 to 7 for the production of office, household and sanitary articles, furniture and furniture elements as well as interior design components and design objects.