DE2713537A1 - Homogeneous, transparent thermoplastic polyamide moulding compsn. - contg. terpolymer of ethylene! and (meth)acrylate!(s) - Google Patents

Abstract

A thermoplastic moulding compsn. contains (1) 70-96wt.% of a 6-polyamide with relative viscosity >=3.5, and (2) 30-4wt.% of >=1 ternary copolymer contg. (a) 50-95wt.% ethylene; (b) 1-20wt.% (meth)acrylic acid; and (c) 1-30wt.% of >=1 (meth)acrylate ester of a 1-9C(2-6C), esp. 4C alcohol. The copolymer has a melt flow index of 2-15 g./-10 mins. High impact strength is obtd. and the mixt. is tough and homogeneous. Transparent films of thickness 10-70 can be obtd. and moulded articles have a good surface. Threads and other articles do not show white fracture. The compsns. have lower water uptake, swell less in solvents, and have higher notch impact strength when dry than polyamides. The compsns. can be extruded or injection moulded to casings, plates, threads, tapes, tubes, and in particular transparent, homogeneous films.

Description

Polyamide alloys

The invention relates to polymer mixtures based on polyamide-6, which have high toughness with excellent homogeneity.

The mechanical properties of polymers often depend on the Type of pretreatment. Such is the impact strength of molded articles made of polyamide plastics depends considerably on the water content of the shaped bodies.

In the anhydrous state, the easy-flowing ones are particularly preferred Highly crystalline polyamides with medium molecular weight, produced moldings relatively sensitive to impact stress. There is therefore a need for Quickly processable, easy-flowing polyamide plastics that make up in particular Let moldings be produced which, in the dry state, have increased impact strength own. Particularly of interest are those polyamides that have high tensile strength, high heat resistance, good resistance to solvents and easy processing combined with high impact strength and flexibility.

There are already various methods of increasing toughness and flexibility of polyamides. So z. B.

the mixing of low molecular weight plasticizers in polyamides, the but does not provide a satisfactory solution to the problem for several reasons. Of the Most of the plasticizers suitable for plastics are not with polyamides sufficiently compatible and separates during processing or tends to exude. Compatible plasticizers, which form real solutions with polyamides, deteriorate but mostly the good mechanical properties of the polyamides. Strongly polar fabrics Although low molecular weight such as water or dimethylformamide show a strong plasticizer effect, but they can only be used after the production of polyamide moldings be incorporated into these, otherwise when processing the pretreated Polyamide granules contain bubbles because of the relatively low boiling points of these plasticizers Moldings would arise.

This method is also generally time consuming and costly. It is also suitable for the production of thick-walled molded parts because of the irregular Distribution of the plasticizer in the molded part is unusable.

In addition, these plasticizers escape because of their relatively high vapor pressure Often from the polyamide again.

These measures prove to be particularly disadvantageous in attempts to process the pretreated polyamide granulate into high-quality films.

Attempts have also been made to increase the impact strength of polyamides by admixing them of polymeric substances such as polyethylene and copolymers made from vinyl acetate and ethylene (DAS 1 138 922) to improve. Although in the production of such mixtures a If very intensive kneading is required, segregation occurs during further processing z. b.

in injection molding and especially in film production.

Moldings produced therefrom therefore show a tendency towards stress whitening. In the production of the film, it is observed that even when high operating pressures are used rapid segregation begins immediately after exiting the nozzle.

The flexibility of polyamides can also be increased by mixing in acidic Polyethylenes containing groups, such as. B. copolymers of ethylene and unsaturated Acids or polyethylene grafted with unsaturated acids. Such Mixtures are more finely dispersed and show a far lower level when exposed to stress However, apart from the above-described blends, they have stress whitening from the somewhat improved toughness and flexibility, considerably inferior mechanical ones Properties such as B. E-modulus, tensile strength, hardness, stiffness, than the polyamides self.

Furthermore, attempts to increase flexibility of polyamides in the freshly sprayed state, copolymers of ethylene and (meth) acrylic acid used.

Thus, according to the teaching of US Pat. No. 3,742,916 and DT-PS 1,669,702 through the use of copolymers of ethylene and (meth) acrylic acid esters achieved some improvement. The notched impact strength in the freshly molded condition is still unsatisfactory, as is the noticeable tendency to segregate. The same The alloys known from US Pat. No. 3,845,163 and French Pat. No. 1,504,113 are disadvantageous because of the methacrylic acid, some of which is present as a salt, additional ones Have disadvantages. So fall as is known, the values of the tracking resistance in the presence of metal ions so strongly that a use of the products on the Electrical sector is hardly possible. In addition, most of them are for neutralization used 2+ metal ions - e.g. Zn2 +, Ba2 +, Cd2 +, Hg - physiologically questionable. Such products should not be used in the food packaging sector either can be used as children's toys.

Finally, copolymers of ethylene and (meth) acrylic acid were also used and (meth) acrylates added to polyamides as elasticizing components (DAS 1 241 606), which improves the impact strength. High impact strength However, products are not described here either.

Surprisingly, however, this is obtained in a freshly sprayed state high impact polyamide alloys with very good homogeneity and no inclination for segregation, if you have polyamide-6 with a certain relative minimum viscosity and ternary copolymers of ethylene, (meth) acrylic acid and a derivative of (meth) acrylic acid used with a certain enamel index.

The invention therefore relates to high-impact thermoplastics Molding compounds consisting of 1. 70-96, preferably 80-92% by weight of a 6-polyamide, with a relative viscosity of at least 3.5, preferably 3.7-4.5, 2.4 - 30, preferably 8-20% by weight of an at least ternary copolymer from a) 50 - 95, preferably 80 - 95% by weight of ethylene, b) 1 - 20, preferably 1 - 10% by weight (Meth) acrylic acid, which can be wholly or partly in the form of its salt, c) 1-30, preferably 1-20% by weight of at least one C1-Cg ester of (meth) acrylic acid with a melt index of 2-15 g / 10 min, preferably 5-10 g / 10 min, whereby the sum of components 1 + 2 and a - c is in each case 100% by weight.

The rel. Viscosity of the polyamide-6 used is at 1% Solution in m-cresol determined at 250C. As salts of (meth) acrylic acid, Na, K, Zn or Ca can be used.

Esters with C1-C9 'can be preferred as esters of (meth) acrylic acid C2-C6, alcohols are used. (Meth) acrylic acid tert-butyl ester is particularly preferred or (meth) acrylic acid n-butyl ester is used.

The compatibility in alloys according to the invention is surprising so good that they can be made into homogeneous films by the usual technical processes can be processed in the most common layer thicknesses of 10 - 70 / um even are transparent.

Advantageously, for the production of the alloys according to the invention Polyamide-6 without accessories such as B.

Lubricants such as calcium stearate or ethoxylated long chain amines and / or crystallization-promoting aids such. B. Talc is used.

The starting components are used above the melting point of the Polyamides, advantageous at temperatures of 200 - 3200 C, especially at 260 - 2900 C, mixed.

Devices in which the molding compositions according to the invention are produced are common screw machines. There are both machines with simple as well as those with twin screws. Twin screw extruders are preferred used.

However, other mixing devices can also be used, which are suitable for plasticizing plastics.

In the highly elastic alloys can be used as thermoplastic Molding compounds also stabilizers, mold release agents, lubricants, crystallization accelerators, Plasticizers, pigments, dyes or fillers such as glass fibers or asbestos are incorporated will. Show monofilaments and other shaped bodies made of such polymer alloys no stress whitening at breakage and interfaces and no segregation. They have also in comparison to moldings made from known polyamide-polyolefin mixtures a very good surface finish. They still have compared to molded bodies Polyamides have reduced water absorption and solubility or swellability in the known solvents and show a greatly increased notched impact strength in the dry state. The compounds are suitable for extruder and injection molding processing, for the production of moldings, such as housings, plates, threads, tapes, tubes and especially homogeneous, transparent films.

Example 1: 90 parts by weight. of a 6-polyamide with a rel. viscosity of 3.9, measured on a 1% solution in m-cresol at 20 ° C. in an Ubbelohde viscometer and a notched impact strength determined according to DIN 5) 453 of 4 kJ / m2 and 10 parts by weight. of a copolymer of ethylene, acrylic acid and ethyl acrylate (weight ratio 84/4/12) and melt index of 7 g / 10 min. Are mixed in a mixer for 5 minutes. The component mixture thus prepared is used in a twin-screw extruder of the type ZSK 53 at 90 rpm. and 2700 C kneaded and extruded, the melt in a water bath spun off, granulated and then at 180 ° C in a vacuum to a water content of <0.05 wt .-% dried.

Alternating bending tests are carried out on freshly injected test specimens found a good homogeneity and according to DIN 53 453 a notched impact strength measured at 22 kJ / m2.

Example 2 - 3: Further examples are given in Table 1 below summarized, carried out according to the procedure outlined in Example 1 will. The amount of the ethylene / acrylic acid described in Example 1 used / Acrylic ester terpolymer is 10 parts by weight each. The measured values the notched impact strength sinc listed in Table 1.

Example 4 - 6: According to the procedure of Example 1 were the amounts of a 6-polyamide given in Table 2 with the rel. viscosity 3.9 mixed with various amounts of the terpolymer described in Example 1. Example No. 6-PA # (rel) terpolymer notched impact homogeneity wt .-% wt .-% toughness [@ J / m2] Table 1: 2 90 (3.5) 10 17.3 very good 3 90 (4.4) 10 26.0 very good Table 2: 4 94 (3.9) 6 17.8 very good 5 85 (3.9) 15 38.3 very good 6 80 (3.9) 20 55.7 very good Le A 17 995 Examples 7-10 The amounts given in Table 3 of a 6-polyamide with the rel. Viscosity 3.94 and one according to DIN 53 453 determined Notched impact strength of 3.8 kg / m2 are used with different amounts of a terpolymer of ethylene, acrylic acid and tert-butyl acrylate (qem. Ratio 89/4/7) with a Melt index of 6.5 g / 10 min in a ZSK 53 twin-screw extruder at 120 RPM and 2700C and kneaded as described in Example 1, to give test specimens processed.

TABLE 3 Example No. 6 PA Weight% Terpolymer Impact Strength Homogeneity% by weight in the mixture (KJ / m2) 7 95 5 12.7 very good 8 90 10 23 very good 9 85 15 40.5 very good 10 80 20 59.2 very good

Claims (4)

Claims: 1. High impact thermoplastic molding compounds of 1. 70-96% by weight of a 6-polyamide, with a relative viscosity of at least 3.5, 2.4-30% by weight of an at least ternary copolymer from a) 50-95% by weight , Ethylene b) 1-20% by weight (meth) acrylic acid. c) 1-30% by weight of at least one C1-C9 ester of (meth) acrylic acid with a melt index of 2-15 g / 10 min, the sum of the components 1 + 2 and a - c is each 100% by weight. 2. Thermoplastic molding compositions according to claim 1, characterized in that that the alcoholic component of the (meth) acrylic acid ester consists of 2-6 carbon atoms. 3. Thermoplastic molding compositions according to claim 1, characterized in that that component C> is a (meth) acrylic acid butyl ester. 4. Moldings, in particular films, made from thermoplastic molding compositions according to claim 1.