DE2541802A1 - THERMOPLASTIC MOLDING COMPOUNDS - Google Patents

Description

Our reference: O.Z. 31 555 Ka / Wil 6700 Ludwigshafen, September 16, 1975

It is known to reinforce polyoxymethylenes with glass fibers; This measure can reduce the rigidity of the polyoxymethylene can be increased considerably, which means that their uses can be expanded.

In general, however, the improvement in tensile strength that can be achieved in the case of polyoxymethylenes through glass fiber reinforcement is unsatisfactory. Accordingly, there has been no lack of attempts to improve the tensile strength of glass fiber reinforced polyoxymethylenes. For example, GB-PS 1 178 3 ² ^ describes a process according to which glass fiber reinforced polyoxymethylenes are polymerized by formaldehyde in the presence of glass fibers which are provided with certain adhesion promoters are to be produced. This method has the disadvantage of being very costly ₀ In U.S. Patent 3,455,867 a method is described, are obtained by incorporation of polyfunctional isocyanates by the glass fiber-reinforced polyoxymethylenes. However, isocyanates are not without problems in handling because of their toxicity. Further processes for improving the mechanical properties of glass fiber-reinforced polyoxymethylenes are described in DOS 2 209 985, but processing difficulties arise. In addition to improving tensile strength, improving impact strength is desirable. The object of the invention was therefore to find a simple way of producing glass fiber-reinforced polyoxymethylenes with good tensile strengths.

The invention relates to thermoplastic molding compositions made from polyoxymethylenes and glass fibers, which are characterized are that the molding compositions 0.1 to 5.0 wt. ^, based on the Total weight of the mixture, contained in polyureas. The polyureas have the following structure in particular on!

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0.Z.31 555

--NR ₁ -NCNR ₀ -N-

J 1 J It f id I! 1

R, R, O R ,. R ,, O I n

L- 3 3 4 4

Here, η is a number greater than 2 and. R ₁ = - (CH ₂ ) ₆ - or

= - (CH ₂ ) ₆ - or

= H or alkyl radical = H or alkyl radical,

or

or

The preferred amount of polyurea is 0.5 to 2.0 wt. The polymers can be prepared by known methods. Before being incorporated into the polymer, they are reduced to a grain size <1 Ii ground "

The glass fibers which are used to reinforce the polyoxymethylenes are preferably low-alkali Ε-glass fibers with a diameter of 5 to 20, preferably 8 to 15 μm. Their mean length in the reinforced mixtures is between 0.05 and 1.0 mm, preferably between 0.1 and 0.5 mm. The glass fibers are usually used in amounts of 10 to 50 % based on the polyoxymethylene.

The glass fibers are coated in a known manner with sizes and adhesion promoters equipped on an organosilane basis.

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Furthermore, fillers can also be used. Talc with a grain size of < 10 / ma are preferred. These fillers are used in amounts of 10 to 60 %, based on the polyoxymethylene.

For the purposes of the present invention, polyoxymethylenes are homopolymers of formaldehyde and copolymers of formaldehyde or de, s trioxane with cyclic and linear formals such. B. 1,3-dioxolane, butanediol formal or epoxides such as ethylene or Propylene oxide.

The homopolymers should be thermally stable end groups, such as. B. have ester or ether groups. The copolymers of trioxane should contain more than 50 % s, preferably more than 75 % oxymethylene groups and at least about 0.1 % groups of the comonomer which introduces at least two adjacent carbon atoms into the chain. Such copolymers can be prepared in a known manner by cationic copolymerization of trioxane with suitable comonomers, such as. B. cyclic ethers or acetals such as ethylene oxide, 1,3-dioxolane, 1,3-dioxane, 1,3-dioxacycloheptane or with linear oligo- or polyformals or acetals such. B. polydioxolane, polybutanediol formal and the like.

The polymers can contain the usual stabilizers against heat and light and other additives, such as Z ₀ B ₀ dyes.

The incorporation of the polyureas is expediently carried out together with the glass fibers and the other additives according to known methods Method z. B. by mixing on a suitable extruder. the Glass fibers can be used as rovings or as cut fiberglass.

example

The polyoxymethylenes and glass fibers β mm in length are melted on a single-screw extruder, optionally with the addition of the polyureas. The mixture homogenized at 200 ^° C. is extruded as a strand through a nozzle and granulated. the end

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O.Z. 31 555

Test specimens are injected into the granulate at 200 ^° C. and the mechanical values are determined.

The test results are compiled in Table 1.

Polyoxymethylene

additive

Glass tensile strength,
content (DIN

455)

(Wt. #) (N / mm ² )

Flexural strength
(DIN
53 452)

(N / mm ² )

Impact strength (DIN 53 453)

(kJ / m ² )

A.
A.

0.5 % diphenylmethane polyurea

1.0 # diphenylmethane polyurea

30.5

30.4
30.2

99

140

145

117

185

205

12.5

25.6

32.5

Polyoxymethylene A: copolymer of butanediol formal and

Trioxane; Melt index at 190 ⁰ O and 2.15 kp = 4 to 5.

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Claims (3)

Claims 1. Thermoplastic molding compositions made from polyoxymethylenes and glass fibers, characterized in that they contain 0.1 to 5.0% by weight, preferably 0.5 to 2.5% by weight , based on the total weight of the mixture, of polyureas. 2. Molding compositions according to claim 1, characterized in that these polyureas of the general formula --NR ₁ -NCN-Ro-NC-- J- 1 tf t <= tt ^r t R- R ₁ ^R 3 ° ^R lj. ^Λ 4 included, in which η is a number greater than 2 and ₁ = - (CH ₂ ) g- or or H C ' CH ₂ CH ^ jj ^ C C- or R ₂ - - (CH ₂ ) ₆ - or H, or > CH, ! B, C = / CH or Z or R, = H or alkyl radical R ^ = H or alkyl radical. 3. Molding compositions according to claim 1 and 2, characterized in that they contain diphenylmethane polyurea or toluene polyurea as polyurea. BASF Aktiengesellschaft 709813/08 28