DE19922933A1 - Polyamide molding material suitable for blow-molding or thermoforming e.g. containers, contains optionally organically-modified natural or synthetic layer silicate with low fluorine content - Google Patents

Abstract

A thermoplastic molding material contains: (A) a polyamide; (B) 4-20 wt% natural and/or synthetic layer silicate with a low fluorine content (optionally organically modified); and (C) 0-5 wt% additives. Independent claims are also included for: (a) a process for the production of objects from these materials by extrusion blow molding or thermoforming; and (b) formed products and hollow objects containing these molding materials.

Description

The present invention relates to the use of thermoplastic mold compositions containing polyamide, layered silicate and optionally additives for the manufacture position of blow molded or thermoformed from sheets or foils (thermoge molded) objects (moldings, hollow bodies) and corresponding methods for Extrusion blow molding and thermoforming.

Hollow bodies made of thermoplastics and thus also polyamide hollow bodies can prinzi piell after the extrusion blow molding process or to be assigned to this process Special processes are manufactured. The range of manufactured articles includes besides the usual hollow bodies in the packaging area - bottles, canisters, Barrels etc. - a variety of technical molded parts, e.g. B. Hollow body with applications in the automotive industry, such as fuel tanks, spoilers, air duct ka ducts, suction pipes or parts of suction pipes or suction modules, liquid holders and panels. Increasingly, newer 3D processes can be used ren (3D hose manipulation, 3D suction blowing process) every conceivable form of Manufacture pipes and hoses for pressurized and unpressurized media. Various Claddings and housings for the household industry fall under the heading tech parts as well as toys and hollow bodies for medical technology.

From the group of engineering thermoplastics, polyamide is the reason its good barrier properties, its high heat resistance and its high gloss opened up numerous applications.

In the packaging market have single-layer polyamide containers in the form of thin walled inliners attained importance.  

In the field of container coextrusion, polyamide is used in addition to EVOH (Ethy len / vinyl alcohol copolymer) the most common barrier material.

The high-gloss, scratch-resistant surface is crucial for cosmetic packaging giving the use of polyamide in the gloss coating.

As a result, the coextrusion of plastic fuel tanks is gaining more and more Environmental regulations in importance.

The principle of extrusion blow molding is that an extruded melt tube from a usually two-part, cooled hollow mold - the negative part of the blow part to be produced - is taken up and inflated with compressed air to the finished hollow body. In most cases, the hose created in the annular gap of a crosshead emerges vertically downwards. As soon as this preform has reached the required length, the mold halves are closed. The cutting edges of the molds grip the tube, weld it and at the same time squeeze out the remnants that protrude up and down. From a processing point of view, the following requirements arise for a raw material during blow molding:
High melt toughness (high viscosity): This requirement results from the necessary hose stability. Even when using melt stores and low processing temperatures, longer preforms can only be produced reliably and reproducibly from products with a correspondingly high tube stability (problem: elongation of the preform under the weight of the extruded tube). Apart from the production of very small blown bodies, polyamides with medium and normal melt viscosity are therefore separated, i.e. products with a rel. Viscosity η _rel <3.5 (measured on a 1 wt .-% solution in m-cresol at 25 ° C) for the extrusion blow molding process. When blowing hollow bodies, the volume of which exceeds about 0.5 l, it is necessary to use extraordinarily highly viscous settings (η _rel <4.0; measured on a 1% strength by weight solution in m-cresol at 25 ° C) bound. Therefore, only the high molecular weight, the branched or cross-linked polyamides are suitable as raw materials for the blowing process.

High thermal stability: the reasons for this are the rather long dwell time of the Material at high temperatures in the hose head and the fact that the pre molding surface during the extrusion and inflation process the oxidative Exposed to atmospheric oxygen attack.

Good melt stretchability: This essentially determines the achievable opening blowing ratio and the wall thickness distribution.

Thermoforming (thermoforming) means a production process at which a thermoplastic film or plate is heated to the softening point, deformed at low pressure in a tool, cooled and reworked becomes. In principle, all thermoplastics that can be produced as a film or sheet are also thermoformable with the restriction that the temperature is the heat level strength of the material does not exceed. The inherent strength should be sufficient too much sagging or tearing of the film or plate prevent.

The range of thicknesses of freely thermoformable semi-finished products is 0.1 mm thick plates up to 10 mm thick.

Semi-crystalline materials such as polyamide are just below the crystallite melt area thermoformable. Because polyamide is below the semi-crystalline melting point has no pronounced softening point, is thermoforming only with air support upholstery possible. With reinforced polyamides there is a risk that the matrix is sucked from the reinforcing material during vacuum forming. It is advisable therefore, the pressing process, the process flow roughly that of the glass mat thermo plastic processing (GMT technology).  

Mixtures of polyamide, a 2nd polymer component and mineral filler substances used for extrusion blow molding are described in CA 130 6562, EP-A 747 439, EP-A 597 648 and WO 95/20011. However, in these cases a second polymeric component is always necessary.

In the patents DE-A 36 32 865, DE-A 38 08 623, EP-A 0 787 765 and DE-A 196 21 309 blends of polyamides with silicates are described characterized by improved mechanical strength and toughness. DE-A 196 21 309 uses a monodisperse fluorine mica-polyamide mixture and he also thinks blow molding as a possible application.

Polyamide (without reinforcing materials) with an average viscosity η _rel <3.5 (measured on a 1% by weight solution in m-cresol at 25 ° C) cannot be processed by blow molding because the polyamide melt does not have sufficient rigidity points.

The object of the invention is to provide a polyamide molding composition which has sufficient melt stiffness and for the production of hollow bodies in extrusion blow molding and thermoforming.

It has now been found that thermoplastic molding compositions, the polyamide, naturally layered silicate and / or synthetic layered silicates with low fluorine content, which can each be organically modified, and optionally contain additives suitable for the production of blow molded or thermoformed objects are.

The invention relates to the use of thermoplastic molding compositions containing

• A) polyamide and  
• B) 4 to 20, preferably 8 to 16 wt .-% (based on the entire shape mass) of a natural layered silicate and / or synthetic layered silicate kats with a low fluorine content, the layered silicates optionally orga nisch can be modified and
• C) 0 to 5, preferably 0 to 2% by weight (based on the total molding composition) Additives such as B. processing aids, nucleating or anti nucleating agents, stabilizers as materials,

for the production of blow molded or thermoformed objects.

The layered silicate according to the invention is a natural or synthetic swellable layered silicate with low fluorine content. Typical Ver Treads of swellable layered silicates for this application are e.g. B. Montmorrillonite and hectorite. So-called organoclays are preferably used for which the surfaces by ion exchange with organic components (e.g. quaternary ammonium compounds) are modified. Such organoclays will be e.g. B. described in the patents DE-A 36 32 865 and DE-A 38 08 623. The Writings mentioned are part of the disclosure. The in DE-A 36 32 865 and Silicate layers listed in DE-A 38 08 623 have a thickness of 0.7 to 1.2 nm.

The majority of the particles of component B) have after incorporation into the Polyamide matrix with an edge length <1 µm and a layer thickness of 0.5 to 2 nm.

The layered silicates according to the invention can be added before, during or after the Polymerization of the monomers to give the polyamide. Is the addition of the he Layered silicates according to the invention after the polymerization, so it is preferred wise by adding to the polyamide melt in an extruder. The addition is made of the layered silicates according to the invention before or during the polymerization, so the polymerization include phases in which in the presence of 1 to 50 weight percent water is worked.  

The polyamides can preferably up to an amount of 40 parts by weight up to 30 parts by weight, other fibrous reinforcing materials and / or contain mineral fillers. As fibrous reinforcing materials in addition to glass Fibers are carbon fibers, aramid fibers, mineral fibers and whiskers. Examples of suitable mineral fillers are calcium carbonate, dolomite, Calcium sulfate, mica, fluorine mica, wollastonite, talc and kaolin. But also other oxides or oxide hydrates of an element selected from the Group boron, aluminum gallium, indium, silicon, tin, titanium, zirconium zinc, Ytrium or iron can be used. To improve the mechanical Properties can be the fibrous reinforcing materials and the mineral Fillers should be surface treated.

The fillers can be added before, during or after the polymerization of the Monomers to polyamide are made. The filling according to the invention is added substances after the polymerization, it is preferably carried out by adding to the poly amide melt in an extruder. The filling according to the invention is added substances before or during the polymerization, the polymerization phases include, in which is carried out in the presence of 1 to 50 wt .-% water.

The fillers can already be added as particles with the ultimately in the Molding particle size occurring. Alternatively, the fillers in Form of precursors are added, which ultimately make up the molding compound Particles appear only in the course of the addition or incorporation. This Precursors can contain excipients, e.g. B. serve to stabilize the preliminary stage or ensure the fine distribution of the particles in the molding compound. Such auxiliaries can e.g. B. surface modifiers.

Suitable polyamides are known homopolyamides, copolyamides and mixtures of these polyamides. These can be partially crystalline and / or amorphous polyamides.  

As partially crystalline polyamides are polyamide-6, polyamide-6,6, mixtures and ent speaking copolymers of these components. Keep coming Semi-crystalline polyamides into consideration, the acid component of which is wholly or partly composed Terephthalic acid and / or isophthalic acid and / or suberic acid and / or sebacic acid and / or azelaic acid and / or adipic acid and / or cyclohexanedicarboxylic acid, the diamine component wholly or partly of m- and / or p-xylylene diamine and / or hexamethylenediamine and / or 2,2,4-trimethylhexamethylenediamine and / or 2,2,4-trimethylhexamethylene diamine and / or isophorone diamine and whose composition is known in principle.

Also to be mentioned are polyamides which are made up in whole or in part of lactams with 7 to 12 carbon atoms in the ring, optionally with the use of one or more of the above-mentioned starting components.

Particularly preferred partially crystalline polyamides are polyamide 6 and polyamide 6,6 and their mixtures. Known products can be used as amorphous polyamides become. They are obtained by polycondensation of diamines such as ethylene diamine, hexamethylene diamine, decamethylene diamine, 2,2,4- and / or 2,4,4-trime thylhexamethylene diamine, m- and / or p-xylylene diamine, bis- (4-aminocyclohexyl) - methane, bis (4-aminocyclohexyl) propane, 3,3'-dimethyl-4,4'-diamino-dicyclohexyl methane, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, 2,5- and / or 2,6-bis- (ami nomethyl) norbornane and / or 1,4-diaminomethylcyclohexane with dicarboxylic acids such as oxalic acid, adipic acid, azelaic acid, decanedicarboxylic acid, heptadecanedicar bonic acid, 2,2,4- and / or 2,4,4-trimethyladipic acid, isophthalic acid and tereph thalic acid.

Copolymers that are obtained by polycondensation of several monomers which are suitable, further copolymers, such as with the addition of amino carboxylic acids -Aminocaproic acid, -Aminoundecansäure or -Aminolaurinsäure or their Lac tamen, are made.  

Particularly suitable amorphous polyamides are those made from Isophthalic acid, hexamethylenediamine and other diamines such as 4,4'-diaminodi cyclohexylmethane, isophoronediamine, 2,2,4- and / or 2,4,4-trimethylhexamethylene diamine, 2,5- and / or 2,6-bis (aminomethyl) norbornene; or from isophthalic acid, 4,4'-diaminodicyclohexylmethane and caprolactam; or from isophthalic acid, 3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane and laurolactam; or from Tereph thalic acid and the mixture of isomers of 2,2,4- and / or 2,4,4-trimethylhexamethy lendiamine.

Instead of the pure 4,4'-diaminodicyclohexylmethane, it is also possible to use mixtures of the positionally isomeric diaminodicyclohexalmethanes which are composed of one another
70 to 99 mol% of the 4,4'-diamino isomer
1 to 30 mol% of the 2,4-diamino isomer
0 to 2 mol% of the 2,2'-diamino isomer
if appropriate, correspondingly more highly condensed diamines obtained by hydrogenating technical-grade diaminodiphenylmethane. Up to 30% of the isophthalic acid can be replaced by terephthalic acid.

The polyamides preferably have a relative viscosity (measured on a 1st wt .-% solution in m-cresol at 25 ° C) from 2.0 to 5.0, particularly preferably from 2.5 to 4.0.

The invention further relates to a method for producing counterparts Stands from molding compounds, the molding compounds extrusion blown or thermoge be shaped.

The invention furthermore provides moldings or hollow bodies obtainable from the Molding compositions described above by extrusion blow molding or thermoforming.

example example 1 Production of the thermoplastic molding compound used for the production of blow molded or thermoformed objects made from sheets or foils

Polyamide 6 (Durethan® B 29, Bayer AG, Leverkusen, Germany, relative viscosity η _rel = 2.9) was treated with 12% by weight of an organically modified montmorillonite (tallow fatty acid methyl bis (2-hydroxyethyl) ammonium chloride Surface modifier, 95 meq / 100 g; edge length <1 µm, layer thickness 0.5 to 2 nm) and 0.1% by weight of montan ester wax on a twin-screw extruder from Werner & Pfleiderer (100 rpm; 10 kg / h ) compounded at 265 ° C, extruded in a water bath and granulated.

Comparative Example 1

Polyamide 6 (Durethan® B 29) with 12% by weight phlogopite mica became analogous (Kemira Mica 40 S from Kemira, Pori, Finland; 90% of the particles <40 µm, Layer thickness 0.7 microns) and 0.1 wt .-% Montanesterwachs compounded, in one Water bath extruded and granulated.

Comparative Example 2

Durethan® B 29 (unreinforced polyamide 6; relative viscosity η _rel = 2.9, measured on a 1% by weight solution in m-cresol at 25 ° C).

Comparative Example 3

Durethan® B 40 E (unreinforced polyamide 6; Bayer AG, Leverkusen, Germany, extrusion type; higher viscosity due to solid phase post-condensation, relative viscosity η _rel = 4.0, measured on a 1% by weight solution in m-cresol at 25 ° C ).

Measurement of melt stiffness

When blow molding larger and heavier items it is important that the extru dated melt hose (preform) has a high melt stiffness, thus excessive elongation of the tube preform during extrusion, before the tool closes and the article is blow molded becomes.

Ideally, the lengthening of the extruded melt hose should be linear and not be faster than the extrusion speed, d. H. the preform should do not stretch out by its own weight.

Under constant blow molding conditions (extruder barrel temperature, screw tightness speed, mass throughput, nozzle geometry etc.) depends on the elongation behavior mainly on the melt stiffness of the molding compound. The higher the melt the stiffness of a molding compound, the slower the tube preform lengthens ling out during extrusion. To increase the melt stiffness of a molding compound judge, one can measure the melt viscosity at low shear rates. For Estimation of the blow molding ability is the measurement of the length described behavior on a melt tube extruded vertically downwards more reliable.

The elongation behavior is determined on an extrusion blow molding machine from Krupp-Kautex (KEB 4/13 with continuous extrusion and simple form; Screw diameter 60 mm, 25 D screw length).  

All granules are left to vacuum at 80 ° C before processing moisture <0.06% dried.

During the extrusion, the current length of the melt tube is shifted the times measured after exiting the nozzle. The distance between Nozzle and floor is 146 cm. The melt stiffness is the higher, the the longer it takes for the melt strand to reach a certain length or the floor reached and the more uniform (linear) the increase in length is.

The results of the measurement of the elongation behavior are shown in Tab. 1 and Tab. 2 poses. At a melt temperature of 230 ° C the melt hose reaches the Molding compound in the example only after 64 seconds, while the Ver same materials 1 and 2 under the same conditions after 10 and 5 respectively Seconds to 146 cm (Tab. 1).

Even with an increased melt temperature of 245 ° C in the example for the Extension to 145 cm takes 46 seconds, while the comparison material 3 (PA6 extrusion type) already reaches the floor after 15 seconds (Tab. 2).

The results make it clear that the molding composition according to the example shows itself draws to use blow molding.  

Table 1

(Melt temperature 230 ° C, throughput 20 kg / h)

Table 2

(Melt temperature 245 ° C, throughput 20 kg / h)

Blow molding tests

The molding composition according to Example 1 and Comparative Examples 1 and 2 became tries to blow-mold bottles with a volume of 250 ml. In addition, the  hot melt tube emerging from the extruder into the mold brought, cut and inflated in shape.

The blow molding tests confirm the conclusions from the measurement of the off longitudinal behavior: The molding composition according to the invention provides a significantly better mate blow molding than the comparison materials. With these the 250 ml Bottle is no longer satisfactorily blow molded.

Table 3

Properties and blowing ability

Claims (8)

1. Use of thermoplastic molding compositions containing

• A) polyamide and
• B) 4 to 20% by weight (based on the total molding composition) of a natural sheet silicate and / or synthetic sheet silicate with a low fluorine content, the sheet silicates optionally being organically modified,
• C) 0 to 5 wt .-% (based on the total molding composition) for the manufacture of blow molded or thermoformed (thermoformed) objects from plates or foils.

2. Use according to claim 1, wherein 8 to 16 wt .-% of a natural Layered silicate and / or synthetic layered silicate with low fluoran part, the layered silicates being optionally organically modified can be used. 3. Use according to claim 1 or 2, wherein 0 to 2 wt .-% additives ver be applied. 4. Use according to one or more of the preceding claims, wherein fibrous reinforcing materials in an amount up to 30 weight parts are added. 5. Use according to one or more of the preceding claims, wherein the layered silicate is selected from at least one of the group Organoclays, montmorillonite and hectorite.   6. Use according to one or more of the preceding claims, wherein the edge length of the majority of the silicate particles is less than 1 µm and the layer thickness is in the range from 0.5 to 2 nm. 7. Process for the production of articles from molding compositions according to An saying 1, the molding compositions being extrusion-blown or thermoformed become. 8. Moldings or hollow bodies obtainable from molding compositions according to one or several of the preceding claims.