DE2045742A1 - Transparent, impact-resistant molding compounds - Google Patents

Description

Badische Anilin- & Soda-Fabrik AG 1 ''

Our reference: O.Z. 27 015 Dd / 10

6700 Ludwigshafen, September 14, 1970 Transparent, impact-resistant molding compounds

The invention relates to transparent, impact-resistant thermoplastic molding compositions made from a hard methyl methacrylate polymer A, a hard styrene / acrylonitrile polymer B and a soft graft copolymer C of styrene and acrylonitrile on one Rubber.

Methyl methacrylate polymers and styrene / acrylonitrile copolymers are hard and transparent plastics, but they are relatively brittle, so that they are more mechanical with stronger Break stress.

It is known that the toughness of such plastics can be improved can if you add rubber-like soft components to them. So are for example in the German Auslegeschrift 1 169 660 mixtures of a styrene-acrylonitrile copolymer as a hard component and a graft copolymer of styrene and acrylonitrile on a polybutadiene rubber as the soft component described.

In French Patent 1,321,146, mixtures of Methyl meth'acrylate polymers described with the same soft components.

However, the mixtures are not transparent in both cases.

In French patent specification 1 526 375 they are transparent Molding compounds made from methyl methacrylate polymers, styrene / acrylonitrile copolymers and rubbers. Polybutadiene, copolymers of butadiene and rubbers are used as rubbers Styrene, acrylonitrile and methyl methacrylate are used. However, such molding compositions still show unsatisfactory impact strength.

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The invention was therefore based on the object of providing transparent thermoplastic molding compositions with high impact strength to develop.

The present invention accordingly relates to molding compositions which contain a mixture of

A '20 to 80 parts by weight of a methyl methacrylate polymer

the end

90 to 100 percent by weight methyl methacrylate and

10 to 0 percent by weight of an alkyl acrylate with 1 to 8 carbon atoms in the alkyl radical, B 10 to 50 parts by weight of a styrene / acrylonitrile polymer

sats off

70 to 90 weight percent styrene and

30 to 10 percent by weight of acrylonitrile, C 10 to 50 parts by weight of a graft copolymer

10 to 70 percent by weight of styrene and acrylonitrile in a weight ratio of 60:40 to 90:10

90 to 30 weight percent of a rubber having a glass temperature below -30 door ^0C

The parts by weight should add up to 100 and the difference between the refractive index of the soft component C. and the refractive index of the mixture of the two hard components A and B are less than 0.005.

The hard component A is preferably polymethyl methacrylate; however, copolymers of methyl methacrylate with up to 10 percent by weight of an alkyl acrylate with 1 to 8 carbon atoms in the alkyl radical, for example methyl acrylate and butyl acrylate, can also be used. The incorporation of alkyl acrylate into the methyl methacrylate polymer improves the flowability of component A and thus also of the mixtures. Methyl methacrylate polymers can be prepared by bulk, solution or bead polymerization using known methods. Methyl methacrylate polymers, especially those with only a low "alkyl acrylate" content, have a high heat resistance.)

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The hard component B is a copolymer of 70 to 90 percent by weight styrene and JO to 10 percent by weight acrylonitrile. These copolymers can be prepared by all known processes, for example by substance ', Solution, suspension or emulsion polymerization. Styrene / acrylonitrile copolymers have good flowability. With a correspondingly high content of: Component B, this property is also transferred to the mixture according to the invention.

The soft component C is a graft copolymer of 10 to 70, preferably 20 to 60 percent by weight of a mixture of styrene and acrylonitrile in a weight ratio of 60: 40 to 90: to 90 to 30, preferably 80 to 40 percent by weight of a rubber with a glass transition temperature below -30 ⁰ C. The rubbers used must have elastomeric properties so that they bring about an improvement in the impact strength of the mixture according to the invention. A measure of this elastomeric property is the glass transition temperature according to KH Illers and H. Breuer, Kolloid-Zeitschrift 176, page HO, I96I. For example: natural rubber; Diene polymers such as polybutadiene, polyisoprene, copolymers of butadiene with isoprene, styrene or acrylonitrile; Acrylic ester polymers which contain at least 30 percent by weight of an alkyl acrylate with a maximum of 8 carbon atoms in the alkyl radical are preferred. Preferred acrylic esters are ethyl acrylate, butyl acrylate and ethylhexyl acrylate. Examples of suitable comonomers are butadiene, styrene, acrylonitrile or vinyl ether, or mixtures thereof. The acrylic ester polymers can optionally be partially crosslinked by copolymerizing comonomers containing at least 2 double bonds. The graft copolymer C is prepared by polymerizing a mixture of styrene and acrylonitrile in the presence of the rubber, preferably in an aqueous emulsion. There is an at least partial chemical linkage of the polymerizing monomers with the already polymerized rubber, the linkage probably taking place at the double bonds contained in the rubber.

The mixture should be 20 to 8o, preferably 30 to 60 weight

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parts of component A; 10 to 50, preferably 10 to 40 weight points of component B and 10 to 50, preferably 20 to 40 parts by weight of component C.

In addition to the A + B + C mixture, the molding compositions can also contain up to 50% of conventional additives, for example other compatible thermoplastics, such as, for example, styrene / maleic anhydride copolymers; also fillers, dyes, stabilizers, lubricants and antistatic agents.

The components and, if appropriate, the additives are preferably mixed in the melt; The components are processed at temperatures between 200 and 26O ⁰ C on extruders, rollers or kneaders. It is also possible to mix solutions or suspensions of the components and then remove the liquid.

An essential prerequisite for the transparency of the invention according to molding compounds is that the difference between the refractive index of the soft component C and the refractive index of the mixture of the two hard components A and B is less than 0.005. The refractive index of the mixture of hard components is calculated as the arithmetic mean of the refractive indices of the two individual components. However, the prerequisite for this is that the two hard components are compatible, i.e. can be mixed homogeneously with one another in all proportions. With a given The refractive index of the soft component C becomes the refractive index of the hard component through a suitable choice of the ratio A: B aligned.

In this way, by simply mixing the components, transparent molding compounds of high impact strength are obtained, good heat resistance and satisfactory flowability.

The molding compositions according to the invention can by injection molding or Inflated, they can be molded, calendered or vacuum formed. They can be used anywhere where the toughness of conventional transparent plastics is insufficient; for example in automobile rear lights,

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clear household appliances and toys or for advertising displays.

The parts and percentages given in the examples are based on weight.

The viscosity numbers 1 £ sp / C in £ cnr / g3 were measured in a 0.5 percent solution in chloroform (for A) or in dimethylformamide (for B). The Vicat softening point in [ ⁰ CJ was determined in accordance with DIN 53 460, method B, in silicone oil. When determining the energy to break, the work of damage was measured in £ cm · kpj in a biaxial puncture test on 1 mm thick round plates with a diameter of 50 mm. The platelets are injection molded at melt temperatures of 24o ° C. The refractive index n _ß was determined with an Abbe refractometer according to the method for measuring the refractive indices in solid bodies (see Ullmanns Encyklopadie der technischen Chemie, Volume 2/1, page 486 j editor W. Poerst; Urban «5b Schwarzenberg, Munich - Berlin , 196I). The limit bending stress in kp per cm was determined in accordance with DIN 53 462.

Examples

The following components were used for the mixtures:

A ₁ : Polymethyl methacrylate (refractive index n _D »1.492, viscosity number» 52)

A ₂ : copolymer of methyl methacrylate and methyl acrylate

95.8: 4.2 (n _D »1,492, viscosity number - 52)

A- ,: Copolymer of methyl methacrylate and methyl acrylate 92.6: 5.1 (n _D = I.492, viscosity number = 52)

A ^: copolymer from. Methyl methacrylate and butyl acrylate

94.9: 5.1 (n _D = I.492, viscosity number = 52)

B: Copolymer of styrene and acrylonitrile 75:25 (n _D = 1,574, viscosity number = 104)

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Graft copolymer of 25 # styrene and acrylonitrile (70:30) to 75 % of an emulsion copolymer of 60 parts of butyl acrylate and 40 parts of butadiene (n _ß 1.512)

Graft copolymer of 40 # styrene and acrylonitrile (75:25) to 60 % of a partially crosslinked polyaoryl acid butyl ester (n ^ = 1.512)

Graft copolymer of 25 % styrene and acrylonitrile (70:30) to 75 % of an emulsion polybutadiene (n ^ * 1.532)

Graft copolymer of 37.5 % styrene and acrylonitrile (75:25) on 62.5 # of an emulsion polybutadiene. 1,540)

The components were pre-mixed in a fluid mixer, and then intimately kneaded on a kneader at about 220 to 230 ⁰ C under nitrogen. The residence time was about 4 minutes: the granules obtained in this way were melted on a single-screw extruder screw and chipped to form uniform granules suitable for injection molding. Table 1 shows the properties of the mixtures.

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ι Together
settlement ·· · _## · jj · Limit bend
tension OZ 27 015
2045742 example 54.6 A.
15.4 B ¹
30.0 C ₁ - 7 -
Table 1 667 Vicat number 1 50.0 A ₉
14.0 B *
36.0 C ₁ Fracture energy 577 97 2 50.0 A,
14.0 B ^
36.0 C ₁ 32 335 89 3 43.2 A ₄
20.8 B *
36.0 C ₁ 61 586 86 4th 44.0 A ₉
14.0 B ²
42.0 C ₂ 102 681 89.5 5 30.0 A ₄
54.0 ΈΓ
36.0 C ₅ 62 633 95 6th 21.3 A ₄
35.5 B ⁴ 70 651 93 7th 63 92.5 76

35.5
43.2 C ₄

Comparative examples

In comparative experiments, transparent mixtures were produced in accordance with the specification of French patent 1,526,375 the end:

a) 45.6% ₄ A, 27.4% B and 27% of polybutadiene (n _D = 1.52),

b) 40% ₄ A, 24% B and%% polybutadiene (n _D - 1.52)

c) 27% ₄ A, 46% B and 27% of a copolymer of 71 parts of butadiene and 29 parts styrene (n _D = 1.541).

The results are shown in Table 2.

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aaaaa ·· t · · · - 8th - Table 2 example Fracture energy limit .e-team a <0.6 397 b <0.6 295 C. <0.6 472

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5 Vicat teeth;

80 64 89.5

A comparison of these fracture energies with those from Table 1 shows that the products produced according to the invention are significantly tougher than those according to the French patent 1,526,375.

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Claims (1)

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Claim «« I J pi · "'" 1 Transparent, impact-resistant molding compounds containing a mixture of A 20 to 80 parts by weight of a methyl methacrylate polymer the end 90 to 100 percent by weight of methyl methacrylate and 10 to 0 percent by weight of an alkyl aylate 1 to 8 carbon atoms in the alkyl radical, B 10 to 50 parts by weight of a styrene / acrylonitrile polymer 70 to 90 percent by weight styrene and 30 to 10 percent by weight acrylonitrile, C 10 to 50 parts by weight of a graft copolymer 10 to 70 percent by weight of a mixture Styrene and acrylonitrile in a weight ratio of 60:40 to 90:10 90 to 30 percent by weight of a rubber with a glass temperature below -30 ⁰ C, where the parts by weight add up to 100 and the difference between the index of refraction of component C and the index of refraction of the mixture of components A and B is less than 0.005. Badische Anilin- & Soda-Fabrik AG 2098H / 0787 ORIGIL INSPECTED