AU662946B2

AU662946B2 - Thermoplastic molding composition

Info

Publication number: AU662946B2
Application number: AU31849/93A
Authority: AU
Inventors: Franz-Leo Heinrichs; Gerd Hohner; Harald Kiesel; Anton Lukasch; Jan-Peter Piesold
Original assignee: Hoechst AG
Current assignee: Hoechst AG
Priority date: 1992-01-18
Filing date: 1993-01-15
Publication date: 1995-09-21
Anticipated expiration: 2013-01-15
Also published as: CA2087416A1; JPH05247259A; AU3184993A; DE59308813D1; EP0552680A1; EP0552680B1; ZA93262B

Description

AUSTRALIA

Patents Act 1990 rnogulaoti3 2(2) 662946

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: r Invention Title: THERMOPLASTIC MOLDING COMPOSITION The following statement is a full description of this invention, including the best method of performing it known to :-US HOECHST AKTIENGESELLSCHAFT HOE 92/F 007 Dr. DA/bs Description Thermoplastic molding composition Thermoplastics are as a rule processed above their melting point or in the case of amorphous types above their glass transition temperature. A plurality of processes exist for shaping plastics, the selection ultimately depending on the shape of the desired finished article. Films are produced, for example, by extrusion or calendering and hollow bodies by injection molding or extrusion blow-molding. On economic grounds, a high material throughput of the processing machines is of interest. However, raising the processing speed comes up against limits where the material properties of the plastics demand compliance with specific conditions. Many plastic melts display a severe tendency to adhere to the metal parts of the processing machines, which makes removal of the finished products more difficult, for example in the case of blow-molding or injection molding.

The tendency of the finished products to adhere necessitates, in particular, relatively long cooling times so that the parts acquire sufficient mechanical stability for release from the mold without damage. In order to increase the processing speed, for example by shortening the cooling times, and thus to facilitate removal of the parts at higher temperatures, it is thus desirable to reduce the tendency of the plastic melts to adhere to the processing machines. In the vast majority of cases this is effected by adding lubricants and release agents.

A large number of substances are customarily used as lubricants and release agents in plastics. These include fatty alcohols, fatty acids and their derivatives (salts, esters and amides), montanic acids and their derivatives, -2polyethylene waxes, oxidized polyethylene waxes and paraffins.

Which of the available lubricants is used in a specific plastic ultimately depends on the properties of the plastic, the processing method and the processing conditions as well as on the demands made on the end product.

The prerequisite for the release effect of a lubricant in a specific plastic is that a certain incompatibility exists between the two, since if the lubricant is readily miscible or even soluble in the plastic melt there can be no enrichment at the interface between the polymer melt and the wall of the processing machine. Thus, polar compounds, such as, for example, fatty acid esters or fatty acid amides, are used as additives having a release 15 effect in non-polar polyolefin melts, whereas in polar co• plastics non-polar lubricants, such as, for example, paraffins or polyethylene waxes, have a release effect.

A particular problem arises when lubricants having a release effect are used in highly transparent plastics, such as, for example, polyesters or polymethyl methacrylates. In these plastics, the lubricants, which necessarily have only limited compatibility in order to achieve the release effect, frequently result in substantial turbidity, which impairs the appearance of the end products. The use of lubricants and release agents in amorphous polyesters is particularly critical.

Amongst these polyesters, the type most used is polyethylene terephthalate, which is obtainable from terephthalic acid and ethylene glycol and, in its amorphous form, is used, for example, to produce highly transparent bottles. With this polyether, in contrast to polycarbonate and polymethyl methacrylate, added lubricants and release agents can not only have the effect of producing turbidity because of their incompatibility and the consequent formation of a separate lubricant phase, but readily compatible 3 lubricants are also able, by virtue of their plasticizing effect, to increase the mobility of the polymer chains and thus to increase the rate of crystallization. For this reason, lubricants are frequently used in linear polyesters, in particular in polyethylene terephthalate, in order to increase the degree of crystallization.

The use of fatty acid esters of polyethylene glycols as lubricants for polyesters has been disclosed (cf. US 4,795,771, US 4,731,404).

The synergistic effect of nucleating agents and fatty acid esters, such as, for example, pentaerythritol tetrastearate and methyl stearate, on the surface quality and mold release properties of injection-molded articles composed of reinforced polyethylene terephthalate has 15 also been disclosed (cf. US 3,516,957).

The use of partial esters of monocarboxylic acids having more than 8 carbon atoms and aliphatic polyols having at least 4 hydroxyl groups (for example pentaerythritol tetrastearate) in biaxially oriented polyester films to improve the surface slip has also been disclosed (cf. US .4,421,887).

Finally, the use of esters of long-chain carboxylic acids, preferably having a chain length of 20 to 32 carbon atoms, with linear or branched monoalcohols or dialcohols in combination with fine fillers to improve the surface quality of biaxially oriented polyester films has been disclosed (cf. US 4,590,119). Examples of suitable esters are, for example, ethylene glycol montanate, ethyl montanate, cetyl montanate and stearyl behenate. Since the effect results from synergy between the filler and the ester, both components are needed for the onset of action, whereas the use of one component on its own has no effect.

4 It has now been found that esters of long-chain aliphatic monocarboxylic acids with short-chain aliphatic monoalcohols improve the mold release properties of polyethylene terephthalate without giving rise to turbidity or significant acceleration of crystallization.

The present invention therefore relates to a thermoplastic molding composition composed of 95 to 99.99% by weight, with respect to the molding composition, of a polymer selected from the group polycarbonate, polyester, polyester carbonate, polymethyl methacrylate or a mixture of these polymers, and 0.01 to 5.0% by weight, with respect to the molding composition, of a lubricant in the form of an ester of a long-chain, aliphatic carboxylic acid having 24-40 carbon atoms with an aliphatic monohydric alcohol having 1 to 5 carbon atoms.

The molding composition according to the invention comprises a polymer and a lubricant.

15 Suitable polymers are: 1. Polymers which are derived from a, 3-unsaturated acids, such as polyacrylates and polymethacrylates.

2. Polyesters which are derived from dicarboxylic acids and dialcohols and/or from hydroxycarboxylic acids or the corresponding lactones, such as polyethylene terephthalate, polybutylene terephthalate, poly-1,4- :dimethylolcyclohexane terephthalate, poly-[2,2-bis(4-hydroxyphenyl)propane] terephthalate, polyhydroxybenzoates, and also block polyether-esters, which are derived from polyethers having terminal hydroxyl groups.

3. Polycarbonates and polyestercarbonates.

Preferred polymers are polycarbonate, polyesters, polyester carbonate and polymethyl methacrylate, and polyesters are particularly preferred. The S* polymers can also be used in the form of mixtures.

5 The lubricant to be used according to the invention is an ester of a long-chain carboxylic acid. The alcohol component is derived from an aliphatic nionohydric alcohol having 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms and in particular 1 carbon atom. Examples are methanol, ethanol, n-propanol, i-propanol, butanols and amyl alcohols and particularly preferably methanol. The acid component is derived from a long-chain carboxylic acid having 24 to 40 carbon atoms. Examples are cerotic acid (=C 2 montanic acid melissic acid (=C 30 and dotriacontanoic acid, preferably montanic acid. Technical grade montanic acid, which can be obtained by oxidative bleaching of crude montan wax and comprises a mixture of

C

24 to C 34 carboxylic acids, predominantly C 28 to C 32 and approximately 15% by weight of dicarboxylic acids, is particularly preferred. The esters to be used according to the invention are obtained in a known manner by esterification of the carboxylic acids in the presence of an esterification catalyst, such as, for example, 20 sulfuric acid.

The lubricant is incorporated in the polymers using generally customary methods. For example, the incorporation can be effected by mixing the compounds, and optionally further additives, into the melt prior to 25 shaping. Incorporation can also be effected by applying the dissolved or dispersed compounds directly to the polymer or by mixing into a solution, suspension or emulsion of the polymer, allowing the solvent to evaporate subsequently, if appropriate. The amount to be added to the polymers is 0.01 to 5.0, preferably 0.1 to by weight, with respect to the material to be treated.

In addition to the lubricant, the plastic molding composition can comprise the conventional additives, such as, for example, antioxidants, processing stabilizers, light stabilizers, antistatic agents, processing 6 auxiliaries, impact modifiers, which are added in an amount of 0.01 to 10, preferably 0.01 to 5% by weight, with respect to the total weight of the molding composition, and 1 to 60, preferably 5 to 40% by weight, with respect to the total molding composition, of fillers, reinforcing agents, flameproofing agents, plasticizers, blowing agents, pigments, colorants or dyes.

The plastic molding composition according to the invention is characterized by good flow properties and good mold release properties. It is therefore used in particular for the production of transparent hollow bodies.

The following examples are intended to illustrate the invention: The polymer used was a linear polyethylene terephthalate which has a viscosity number (intrinsic viscosity) of 0.81 0.2 (measured in dichloroacetic acid). The following lubricants were used as test products: 9 9 Example 1: 20 Example 2: Comparison Example A: Comparison Example B: Comparison Example C: Methyl esters of montanic acids' (acid no. 6 mg of KOH/g, drop point n-Butyl esters of montanic acids (acid no. about 5 mg of KOH/g, drop point 76°C) Octyl esters of montanic acids, (acid no. 4 mg of KOH/g, drop point 76°C) Stearyl esters of montanic acids (acid no. 8 mg of KOH/g, drop point Pentaerythritol tetrastearate (acid no. about 2 mg of KOH/g, drop point about 61"C).

1) Here montanic acids are understood to be the wax acid mixture obtained by oxidation of crude montan wax.

Prior to processing, the polyester was dried for 8 h at 160"C in a circulating-air oven and the test products were applied in a drum to the granules while these were still hot. The processing was carried out in an injection molding machine with the following settings: Temperature profile: 260-270-290-300°C Injection pressure: 400 bar Holding pressure: 500 bar Back-pressure: 0 bar Die temperature: set value 25°C, actual value Sleeves 7 cm high and having an internal diameter of 6 cm which were cylindrical on the inside and slightly conical on the outside were injection-molded. The wall thickness was 3 mm at the sprue and 4 mm remote from the sprue. On 15 ejection of the sleeve, the demolding force arising was measured via a piezoelectric force transducer. Cut sections from the sleeve were used to measure the transparency in neutral grey light; the wall thickness at the measurement point was about 3.5 mm.

20 The measured values obtained are summarized in the *0.0 following table.

99 8 Table Additive Demolding Release Transparency 0.2% addition force effect 2 None 3,200 0 77.0 Example 1 (Methyl montanate) 925 71 72.0 Example 2 (n-Butyl montanate) 932 71 69.5 Comp. Ex. A (Octyl montanate) 914 72 46.8 Comp. Ex. B (Stearyl montanate) 1,222 62 20.5 Comp. Ex. C (Pentaerythritol tetrastearate) 1,681 49 60.0 2 The release effect can be calculated in accordance with 20 the following equation: Demolding force with release agent Release 1 x 100 effect Demolding force without release agent

Claims

1. A thermoplastic molding composition composed of 95 to 99.99% by weight, with respect to the molding composition, of a polymer selected from the group polycarbonate, polyester, polyester carbonate, polymethyl methacrylate or a mixture of these polymers, and 0.01 to 5.0% by weight, with respect to the molding composition, of a lubricant in the form of an ester of a long-chain, aliphatic carboxylic acid having 24-40 carbon atoms with an aliphatic monohydric alcohol having 1 to 5 carbon atoms.

2. The molding composition as claimed in claim 1, wherein the lubricant is an ester of technical grade montanic acid with an aliphatic monohydric alcohol having 1 to 5 carbon atoms.

3. The molding composition as claimed in claim 1, wherein the lubricant is *technical grade methyl montanate.

4. The molding composition as claimed in claim 1, wherein the lubricant is technical grade ethyl montanate.

5. The molding composition as claimed in claim 1, wherein the polymer is polyethylene terephthalate.

6. The molding composition as claimed in claim 1, which comprises, in addition to the lubricant, antioxidants, processing stabilizers, light stabilizers, antistatic agents, processing auxiliaries, impact modifiers in an amount of 0.01 to 10% by weight, with respect to the molding composition, and 1 to 60% by s weight, with respect to the molding composition, fillers, reinforcing agents, flameproofing agents, plasticizers, blowing agents, pigments, colorants or dyes. .1 C

7. Use of an ester of a long-chain, aliphatic carboxylic acid having 24-40 carbon atoms with an aliphatic monohydric alcohol having 1 to 5 carbon atoms as lubricant when processing molding compositions of a polymer selected from the group polycarbonate, polyester, polyester carbonate, polymethyl methacrylate or a mixture of these polymers, in an amount of 0.01 to 5.0% by weight, with respect to the material to be processed. DATED this 24th day of July, 1995 HOECHST AKTIENGSELLSCHAFT WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA *0 DBM/SH DOC 4 AU3184993.WPC S I 1 HOE 92/F 007 Abstract Thermoplastic molding composition A plastic molding composition which comprises a thermo- plastic, preferably polycarbonate, polyester, polyester carbonate, polymethyl methacrylate or a mixture of these polymers, and an ester of a long-chain, aliphatic carboxylic acid having 24 40 carbon atoms with an aliphatic monohydric alcohol having 1 to 5 carbon atoms as lubricant, is distinguished by good flow properties, good mold release properties and very slight impairment of the transparency. .*o *S'"S