DE2454770C2 - Thermoplastic molding compounds with increased impact strength - Google Patents

Description

The invention relates in particular to thermoplastic polyamide molding compositions with increased impact strength even at low temperatures.

The impact strength of molded articles made of polyamide plastics depends significantly on the water content of the Molded body from. In an anhydrous state, e.g. B. after the production of the molded body by injection molding, are especially those made from easy-flowing polyamide injection molding compounds with a medium molecular weight and here again the moldings made from highly crystalline polyamides are relatively sensitive to impact stress. They are therefore easily processable, easy-flowing polyamide plastics with good aging stability desirable, from which moldings can be produced that have increased impact strength in the dry state own. Other mechanical properties, such as Ε-modulus, yield stress and tear strength, should be do not deteriorate to a greater extent.

The mixtures according to FR-PS 15 68 637 as prior art consist of polyamides with polyolefins, which are grafted with unsaturated acids. These mixtures have increased impact strength. the However, tensile strength, hardness and rigidity are not yet satisfactory, especially since such mixtures lead to stress whitening tend. According to the invention, polyamide injection molding compounds are made available which are characterized by a high Damage work W50 and at the same time a high Ε-module and no tendency to stress whitening to have.

The invention therefore relates to thermoplastic molding compositions with high impact strength, which thereby are marked that they consist of:

A) 100 parts by weight of a polyamide with a relative viscosity of 2.3 to 3.0, measured 1% in concentrated sulfuric acid at 25 ° C and

B) 0.5 to 35 parts by weight of a graft polymer composed of Λ-olefin-vinyl ester copolymers as the graft base and

0.5 to 10 percent by weight, based on the copolymer, of polymerizable unsaturated carboxylic acids or polymerizable unsaturated carboxylic acid esters as a graft and / or
0.5 to 35 parts by weight of a graft polymer composed of Λ-olefin-acrylic acid ester copolymers as the graft base and

0.5 to 10 percent by weight, based on the copolymer, of polymerizable unsaturated carboxylic acids or polymerizable unsaturated carboxylic acid esters as a graft as well

C) optionally 10 to 80 parts by weight of fillers,

D) optionally other additives which improve the properties, such as flame-retardant additives, dyes, color pigments, stabilizers, waxes, lubricants and processing aids. m

The fact that special graft polymers the polyamide molding compositions outstanding advantageous intrinsic U

lending shanks is surprising to the skilled person and was in no way predictable. %

For the purposes of the invention, polyamides as component A are linear polycondensates of lactams with $ 6 to $ 12

Carbon atoms or conventional polycondensates from diamines and dicarboxylic acids, such as 5,6-, 6,6-, 6,8-, 6,9-, 6,10-, i * 6,12-, 8,8-, 12, 12-polyamide, polycondensates of aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, with diamines, such as hexamethylenediamine, octamethylenediamine, polycondensates of araliphatic off, gartRsstoffen, such as m- and p-xylylene diamines and adipic acid, suberic acid, sebacic acid, polycondensates ^s Bas .. by acyclic starting materials such as cyclohexanedicarboxylic acid, cyclohexanediacetic acid, 4,4 diaminodicyclohexylpropane.

An essential feature of the new molding compositions is their content of component B of a graft polymer from Λ-olefin-vinyl ester copolymers and polymerizable unsaturated carboxylic acids or polymerizable unsaturated carboxylic acid esters and / or a graft polymer of tt-olefin-acrylic acid ester->; Copolymcrisaten and polymerizable unsaturated carboxylic acids or polymerizable unsaturated;

Carboxylic acid esters. For the purposes of the invention, Λ-olefins are primarily ethylene and propene (1). As a vinyl ester For the purposes of the invention, especially vinyl acetate and vinyl propionate come alone or in combination with each other in consideration Acrylic acid and methacrylic acid in particular are used as carboxylic acids. as Acrylic acid esters are preferably the esters of acrylic acid and methacrylic acid, crude alcohols of 1 up to 18 carbon atoms for use. The preparation of the graft polymers used according to the invention is in the following and in Examples a and b

Homogeneous graft polymers without homopolymer formation from -olefin-acrylic acid ester copolymers with polymerizable unsaturated carboxylic acids or polymerizable unsaturated carboxylic acid esters are obtained, for example, when molded articles made from ethylene-vinyl ester copolymers, e.g. B. granules with liquid, polymerizable unsaturated carboxylic acids or their esters containing free radical initiators in dissolved form, mixed until the carboxylic acids are homogeneously distributed in the molded bodies by diffusion. This mixture is then heated in an extruder to above the softening point, using extruders and screws that bring in less than 50% of the heat required through shear heat. The necessary free radical initiators are dissolved in amounts of 0.002 to 0.5 percent by weight, based on the copolymer, in the monomeric acids or esters and applied to the moldings. Free radical initiators are all common peroxides, such as dibenzoyl peroxide, dicumyl peroxide and di-tert- butyl peroxide and azo compounds.

To produce the graft polymers, for example, molded articles made from copolymers, e.g. B. granules, as is the case in the production of the copolymers by packaging, at room temperature mixed with the carboxylic acids or esters and the radical initiators and after a residence time of 2 heated in an extruder for up to 10 hours. The residence time after mixing depends on the amount of comonomers in the copolymer and according to the amount of carboxylic acid or ester. With a high proportion of comonomers and at low levels of carboxylic acid, the residence time can be low. The dwell time should be a allow homogeneous distribution of carboxylic acid and / or carboxylic acid ester and initiator in the polymer. It is essential for the appearance of the graft polymer. The mixture is taken in an extruder under mild Melted mechanical conditions, the carboxylic acid is grafted onto the copolymer. It is important that as little shear as possible is introduced into the polymer by the screw. the The heat required should be introduced primarily through external heating. Snails have proven to be cheap same flight depth, so-called screw conveyors, screws, such as those for rubber mixtures or those with low core progression. The speed of the screws should be as low as possible.

As reinforcing fillers C), which may be present in the molding compositions according to the invention can be, those that increase the rigidity of the polyamides come into question. Are preferred fibrous substances, in particular glass fibers made from so-called Ε-glass, which is low in alkali. The length-to-thickness ratio should advantageously be greater than 30: 1. But it can also contain non-fibrous fillers, such as natural Occurring kaolins and calcined kaolins are used. Suitable glass fibers have diameters from 5 to 20 μm, preferably 8 to 15 μm, they can be used as rovings or cut fiberglass and with suitable sizing systems, e.g. B. on polyester or polyepoxy base equipped.

The other suitable fillers are also expediently equipped with adhesion promoters. The training the glass fibers take place z. B. on suitable extruders, as in the American patent 33 04 282 is described.

The thermoplastic polyamide molding compositions according to the invention are produced according to for Melt processing usual methods, such as those in the Kunststoff-Handbuch, Volume VI, Polyamides, Munich, 1966.

The polyamide molding compositions according to the invention can also contain flame-retardant additives from Z. B. elemental red phosphorus, phosphorus compounds, halogen-antimony and nitrogen compounds, Iron oxides, zinc oxide, calcium carbonate, furthermore dyes and color pigments, stabilizers against thermal, thermo-oxidative and UV damage, waxes, lubricants and processing aids that provide a trouble-free Ensure extrusion and injection molding as well as contain antistatic agents.

Principle of the production of the graft polymers

(Component B)

Example a

100 parts contains dissolved a copolymer in granular form from 88 parts ethylene and 12 parts vinyl acetate with a melt index (190 ⁰ C, 2.16 kg) of 6 and 3 parts of acrylic acid, 0.03 part of dibenzoyl peroxide, are mixed for 10 minutes. The granulate is completely dry. After a residence time of 4 hours, the mixture is melted in an extruder with a screw of the same flight depth and a screw length of 27 D at a speed of 12 rpm and a temperature of 140 ° C. is maintained. A shear heat of less than 30% was determined from the energy absorption. A product with an acid number of 32 is obtained.

Example b

Dissolved 100 parts of a copolymer in granular form of 80 parts ethylene and 20 parts of n-butyl acrylate having a melt index (190 ⁰ C, 2.16 kg) of 18, a softening point of 102 ⁰ C and 4 parts acrylic acid 0.04 part of dibenzoyl peroxide are mixed for 15 minutes. After a residence time of 2 hours, the doped pellets is heated with exclusion of air in a tube at 8O ⁰ C and 5 hours at this temperature retention. A product with an acid number of 30.9 is obtained.

20th

45 50

Production of thermoplastic polyamide molding compounds
Examples 1 to 3

4000 g of a polyamide 6 with a K value of 72 (measured by the method of H. Fikentscher, Cellulosechemie 13 [1932], page 58, in a 1% solution in concentrated sulfuric acid), 0.05 percent by weight of talc and 444 g of a graft polymer B were intimately mixed in a fluid mixer at room temperature. Subsequently, the mixture was melted in a heated at 260 ⁰ C twin-screw extruder (type ZDSK 28 of the Fa. Werner and Pfleiderer, Stuttgart). The extruded mixture was granulated, dried and processed to test specimens on an injection molding machine at an injection temperature of 240 ° C. The injection molded parts were dry in the injection freshener. Condition tested The yield stress in [kp / cm- ² ] and the tensile strength in [kp / cm- ² ] were determined according to DIN 53 455, the Ε-module in [N / ^{mm- 2} ] according to DIN 53 457 and the damage work (W ₅ o) in [Nm] on 2 χ 60 mm round washers according to DIN draft 53 443 determined

Comparative example 1

4 kg of a polyamide 6 with a K value of 72 (measured according to the method of H. Fikentscher, Cellulosechemie 13 [1932], page 58, in 1% solution in concentrated sulfuric acid) and 0.05 percent by weight talc Intimately mixed in a fluid mixer at room temperature. Subsequently, as in Examples I to 3 described, proceed.

Table 1

example Graft polymer B Plug Color of Stretch Tear Modulus of elasticity Damage Copoly- component Spatter tension firm (N / mm ² ) job 25th merisat- (Wt .-%) (kp / cm ² ) speed W ₅₀ (Nm) basis (kp / cm ² ) Ver bright 800 852 3400 12.8 30th equal example 1 4 acrylic 1 Ethylene acid White 696 487 3040 46.3 Vinyl acetate (33% by weight) 30 meth 35 2 Ethylene acrylic acid White 651 475 3000 30th Vinyl acetate methacrylic (33% by weight) ester 4 acrylic 3 Ethylene acid White 689 478 2650 40 40 Acrylic acid n-butyl ester (! 5 weight, -%) Examples 4 to 6

4000 g of a polyamide 6 with a K value of 72, which contains 24 percent by weight of glass fibers, was intimately mixed with 333 g of a graft polymer B in a fluid mixer at room temperature. The mixture was then (28 Fa. Werner and Pfleiderer, Stuttgart type ZDSK), melted) in a heated at 270 ⁰ C twin-screw extruder. The extruded mixture was granulated, dried and processed to test specimens ^{on an injection molding machine at an injection temperature of 240 ° C.} The injection molded parts were tested dry in the freshly sprayed state. The tensile strength in [kp / cm- ² ] was determined according to DIN 53 455, the Ε module in [Nmm- ² ] according to DIN 53 457 and the work of damage (W ₅₀ ) in [Nm] on 2 χ 60 mm round disks according to DIN- Draft 53 443 determined.

Comparative example 2

4 kg of a polyamide 6 having a K value, which contained 24 weight percent glass fibers (28 Fa. Werner and Pfleiderer, Stuttgart type ZDSK) was melted in a heated to 27O ⁰ C twin-screw extruder. The extruded mixture was granulated, dried and processed to test specimens on an injection molding machine at a temperature of 240 ^{° C.} The test was carried out as in Examples 4 to The results are summarized in Table 2.

Table 2

example Graft polymer B Plug Color of Tear Modulus of elasticity Damage Copolymer component Spatter strength (N / mm ² ) job basis (O / o by weight) (kp / cm ² ) W ₅₀ (Nm)

Comparative example 2
4th

Ethylene

Vinyl acetate (33% by weight)

Ethylene

Vinyl acetate (33% by weight) ethylene

Acrylic acid butyl ester (15% by weight)

- almost 1662 8440 0.56

colorless 4 acrylic acid almost 1301 7230 1.7

colorless

30Meth- fast 1253 7190 1.47

acrylic acid colorless methyl ester

4 acrylic acid almost 1286 7230 1.47

colorless

20th

25th 30th 35 40 45 50 55

Claims (1)

Claim: Thermoplastic polyamide molding compounds with high toughness, characterized in that they consist of A) 100 parts by weight of a polyamide with a relative viscosity of 230 to 3.60, measured 1% in concentrated sulfuric acid and B) 0.5 to 35 parts by weight of a graft polymer from -olefin-vinyl ester copolymers as Graft base and ίο 0.5 to 10 percent by weight, based on the copolymer, of polymerizable unsaturated carboxylic acids and / or polymerizable unsaturated carboxylic acid esters as a graft and / or
0.5 to 35 parts by weight of a graft polymer made from olefin-acrylic acid ester copolymers as the graft base and
0.5 to 10 percent by weight, based on the copolymer, of polymerizable unsaturated carboxylic acids and / or polymerizable unsaturated carboxylic acid esters as a graft and C) optionally 10 to 80 parts by weight of fillers as well D) if necessary, other additives which improve the properties, such as flame-retardant additives, Dyes, color pigments, stabilizers, waxes, lubricants and processing aids.