Thermoplastic moulding compositions on the basis of saturated polyesters

© ® Registered: 4 September 1970, 8070/70 © Exhibition priority:

©©© Union priority: Germany, 5 September 1969, 19 45 102.6

<td>©</td><td>Start of patent duration: Longest possible duration:</td><td>June 15, 1972</td>

<td>©</td><td>Issued on:</td><td>March 12, 1973</td>

<td>©</td><td>Inventor:</td><td></td>

© dependence:

OE 305630 © Pamphlets considered as delineated by the prior art:

GB-PS 1 028 239

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It is known that one can process polyester from aromatic dicarboxylic acids and aliphatic or cycloaliphatic diols by injection molding to crystallized moldings. Of particular interest are the polyesters of terephthalic acid and ethylene glycol. However, in order to obtain a technically usable molding composition from the polyester raw material, certain properties must be achieved. The polyester must z. B. crystallize rapidly in the mold to ensure the high hardness, shape and dimensional stability important to this material. Furthermore, the injection must be able to run automatically until the ejection of the manufactured part, the syringe must fall without manual assistance from the mold. In part, these requirements can be approximately fulfilled by appropriate operation of the injection molding machine. The heating of the mold has, for example great influence on the increase in the rate of crystallization. However, the heating of the shape but has a stronger sticking of the still soft polyester moldings result, ie, measures on the machine are not sufficient to produce properly molded body. Rather, it is inevitable to modify the polyester raw material suitable by additives.

For example, British Pat. No. 1,104,089 has proposed adding finely divided solid inorganic substances to polyethylene terephthalate in order to increase the rate of crystallization, but crystallization aids do not simultaneously have a mold-separating effect. In order to improve the releasability of thermoplastic polyamide injection moldings, therefore, other modifiers must be added.

It has now been found that thermoplastic molding compositions consisting of

a) linear saturated polyesters of aromatic dicarboxylic acids and optionally up to 10 mol%, based on the total amount of dicarboxylic acids, of aliphatic dicarboxylic acids with saturated aliphatic or cycloaliphatic diols,

b) from 0.05 to 2% by weight, preferably from 0.1 to 0.5% by weight, based on the amount of polyester, of inert inorganic solids having a particle size of less than 5 μm and

c) 0.02 to 8 wt .-%, preferably 0.05 to IGew .-%, based on the amount of polyester, of an alkali alkaryl sulfonate of the general formula

<img file="AT305630B_D0001.tif" />

wherein Me is an alkali metal atom and R_t and R_£ may be any point of the aromatic ring and are saturated or unsaturated straight-chain or branched hydrocarbon radicals having up to 18 carbon atoms and optionally one of the radicals may be a hydrogen atom, have excellent properties as injection molding material.

The alkaryl sulfonates used in the invention are excellent mold release agents for injection molded parts based on thermoplastic polyester. Even complicated moldings automatically fall out of the mold when using these mold release agents at the required short mold service life, which has a great influence on the economy of the process. At the same time, the surface finish of the moldings obtained is of particularly high quality. Of particular importance is the fact that these bit-forming aids are chemically inert and do not cause degradation of the polyester material nor any staining of the syringe body.

Polyethylene terephthalate is preferably used as the linear polyester. However, it is also possible to use other polyesters, for example polycyclohexane- (1,4) -dimethylol terephthalate. It is also possible to use modified polyethylene terephthalates which, in addition to terephthalic acid, also contain other aromatic or aliphatic dicarboxylic acids as basic units, for example isophthalic acid, naphthalenedicarboxylic acid (1,6) or adipic acid. It is also possible to use modified polyethylene terephthalates which, in addition to ethylene glycol, also contain other aliphatic diols, such as, for example, neopentyl glycol or 1,4-butanediol, as an alcoholic component. Also, polyesters of oxycarboxylic acids can be used. The polyesters should have a reduced specific viscosity (measured on a 1% strength solution in phenol / tetrachloroethane 60:40 at 25 ° C.) of between 0.9 and 1.6 dl / g. Especially suitable are polyesters with a reduced specific viscosity of between 1.1 and 1.5 dl / g.

Suitable inorganic, inert solids are, for example, silicates, such as glass powder, talc and kaolin; Metal oxides, such as magnesium oxide, antimony oxide, titanium dioxide, aluminum oxide, calcium carbonate with a particle size below 5 μ.

Suitable alkarylsulphonates are the sodium salts of p-toluenesulphonic acid, 2,4-dimethylbenzenesulphonic acid, p-cumene sulphonic acid, ortho or para-n-butylbenzenesulphonic acid, ortho or para-n-octylbenzenesulphonic acid, ortho or para-n- Dodecylbenzenesulfonic acid, isododecylbenzenesulfonic acid. Except the

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It is also possible to use other alkali metal salts, such as the lithium or potassium salts, for example.

To improve the impact resistance, the polyester composition can be admixed in a known manner with suitable high polymers, such as, for example, copolymers of ethylene with vinyl acetate, ethylene with acrylic ester or butadiene with styrene.

There are various possibilities for the production of the molding composition used according to the invention. The addition of the claimed alkali metal sulphonates can be carried out at the beginning of the esterification or transesterification or at any time during the polycondensation. However, the addition can also be effected by rolling onto the finished polyester granules, followed by incorporation into the polyester composition by melting in an extruder and subsequent granulation. The third option is a simple rolling up of the

Alkalisulfonate on the polyester granules before spraying into consideration.

The crystallization aid can in principle be added simultaneously and in the same way with the alkali metal sulfonate. However, it can also be incorporated separately at a different time or in a separate process step in the polyester or be spread on the polyester granules.

As a general working rule, all operations have to be carried out in the absence of moisture in order to prevent the degradation of the polyester. The polyester composition should preferably contain less than 0.01% of water. If a rapid crystallization in the injection mold to be achieved, it is necessary to keep the mold to at least 100 ° C. Mold temperatures between 120 and 150 ° C are the cheapest.

Example 1:

1.1. A mixture of 1000 parts of dimethyl terephthalate and 800 parts of ethylene glycol is gradually brought to 225 ° C. with stirring in the presence of a transesterification catalyst, with methanol being passed through a

Distilled column until the end of the transesterification. By raising the temperature to 270 ° C, the excess of ethylene glycol is removed. After addition of 2 parts of sodium p-dodecylbenzenesulfonate, 4 parts of talc and 0.04 part of condensation catalyst (eg Sb₂O₃ or GeOp, the polycondensation is carried out while raising the temperature to 275 ° C at a final pressure of 0.1 Torr. This operation must be carried out under constant control of the approach, since there is a risk of over-foaming. The finished polyester should have a relative specific viscosity of 0.8 to 0.9 dl / g. After discharge from the vessel, the polyester strand is granulated and the granules obtained by solid condensation at 235 ° C and 0.1 to 0.2 Torr to a reduced specific viscosity (RSV) of 1.40 dl / g.

1.2. The thus obtained polyester molding composition was added to 100 60x60x2 mm plates and

100 Gear wheels (root diameter 104 mm, tip diameter 114 mm, pitch 54, tooth thickness 5 mm) sprayed. The following spray conditions were set: Cylinder temperature 270/260/260 ° C, mold temperature 140 ° C, injection time 15 sec, injection pressure 140 atm. The mold life was varied in the case of the plates from 5 to 25 sec and in the case of the gears from 20 to 60 sec. At 5 sec mold life 95 plates fell out of the mold, at 15 and 25 sec it was 100 plates that were automatically ejected. The plates had an excellent surface gloss, impressions of the ejector pins could not be determined. The reduced specific viscosity of the plates was 1.270 dl / g. 94 of the gears were ejected at 20 sec. Mold life and 6 had to be removed by hand. At 40 and 60 seconds of mold life, all parts fell out of shape. The reduced specific viscosity of the gear material was 1.250 dl / g.

Example 2:

2.1. The transesterification was analogous to Example 1.1. carried out. After the transesterification, 4 parts of talc were stirred in and the polycondensation was carried out rapidly. After discharge of the polyester composition, the strand was granulated and the solid condensation was carried out to a RSV value of 1.420.

2.2. The polyester granules thus obtained were rolled in a drum with exclusion of air and moisture for 45 hours with 2 parts of sodium p-toluenesulfonate. A prerequisite for a good effectiveness of p-toluenesulfonate is its uniform distribution on the granules, which is why the sulfonate was finely ground before its use. The molding material thus obtained was under the same conditions as in Example

1.2. specified, sprayed into plates or gears. The demolding properties and surface quality of the resulting injection molded articles were excellent. The plates all fell at 15 and 25 sec. Mold life

100 Plates automatically from the mold, the reduced specific viscosity of the plate material was 1.260 dl / g. Of 100 gears, 92 pieces fell out of the mold at 20 sec. Mold life, with 40 and 60 sec. Mold life no part remained hanging. The reduced specific viscosity was 1.230 dl / g.

2.3. For comparison, the section 2.1. produced, provided with 4 parts of talcum polyester molding compound without the addition of a sodium p-toluenesulfonate splashed plates and gears. The machine settings were the same as those at 1.2. listed. However, in order to arrive at reasonably satisfactory moldings, the residence times in the mold had to be substantially prolonged. Nevertheless, the moldings stuck in the mold and their surfaces had deep impressions of the ejector pins. At 25 sec Foimstandzeit fell from 100 plates only 18 out of shape, the rest had to be brought out of the mold by hand, at 45 sec mold life fell from 100 plates 38, and at 60 sec form life fell from 100 plates 46 pieces from the mold. The reduced specific viscosity of the plate material was at

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- 4 1.290 dl / g. The following conditions existed with the gearwheels: at 60 sec. Mold life, 100 only fell out of the mold, at 90 sec. Life it was 55, and at 120 sec. Life 69 pieces automatically fell out of shape. The reduced specific viscosity was 1.25 dl / g.

Example 3:

3.1. First, it was analogous to Example 1.1. a polyethylene terephthalate prepared a RSV value of 1.45 dl / g, but without the addition of a crystallization aid and without the addition of a sulfonate.

3.2. 4 parts of a commercial calcium-magnesium-aluminum silicate of the composition 32.27% SiO 2 are simultaneously applied to this polyester raw material₂; 18.43% CaO; 17.42% MgO; 9.11% A1₂O₃; 1.24% Na₂O; Ignition loss 20, 05% as a crystallization aid and 2 parts of sodium p-cumenesulfonate 6hlang rolled on and then to plates and gears according to Example 1.2. processed. Of 100 plates at 90 ° mold time, 90 parts fell in the mold, at 15 seconds 94 plates and at 25 seconds 98 plates fell automatically. The measured reduced specific viscosity of these plates was 1.24 dl / g. Of 100 gears, mold release time was 91 at 20 seconds, 96 at 40 seconds and automatically demoulded at 60 seconds 100, the reduced specific viscosity of this material was 1.23 dl / g.