The present invention relates to a process for manufacturing molded parts with better short-time deflection temperature under load properties as well as the molded parts manufactured according to this invention.
In the electric and electronics industries, the demands placed on high dimensional stability of certain molded parts with high short term heat loads has increased due to various soldering processes such as reflow or wave soldering. Here, temperature peaks of 260°C to 450°C occur within a time window of up to 30 seconds. This especially applies to SMD components (surface mounted devices) and MIDs (molded interconnect devices, i.e. spatial circuit carriers). The glass fiber reinforced and self-extinguishing molding compounds based on polyesters such as polybutylene terephthalate that are generally used in the electric and electronic industries for this application only satisfy these requirements to a very limited degree. This is especially the case when lead-free solders are used, where the soldering temperature is approximately 30oC higher than with solders that contain lead.
A higher degree of stability can be achieved for molded parts that are subject to heat loads by irradiating them with p or y rays. The reason for the higher degree of loadability is probably due to the crosslinkage of the polymer skeleton. To increase this effect, crosslinkage reinforcing agents are generally added as an additive. Crosslinkage by irradiation such as this is also achieved when the polyester molding compounds in the polymer skeleton contain olefinic covalent bonds. These can be introduced through copolycondensation with unsaturated monomers such as 2-butene-1,4 diol when the polyester is being manufactured. Molded parts such as this are described in EP-A 0 559 072, EP-A 0 669 36Q, and EP-A 0 679 689. The disadvantages of the irradiation process are obvious: it requires expensive equipment and generally requires an additional logistics process, as the parts are usually irradiated by an external company, thus making the process expensive and time consuming.
The task of the present invention was to avoid these disadvantages and, particularly, to enable even higher heat loading.
This task was solved by a process in which a molded part consisting of a polyester molding compound containing
a) 35 to 100% by weight of a thermoplastic polyester

b) 0 to 60% by weight of a filler or reinforcing material
c) 0 to 20% by weight of an impact modified rubber
d) 0 to 30% by weight of a flame retardant
e) 0 to 20% by weight of a synergist and
5 f) 0 to 5% by weight of other additives and/or processing agents
is treated for a period of at least 1 hour, preferably 2 to 24 hours and particularly preferably for 4 to 18 hours at a temperature of between 180 to 250°C, preferably between 190 and 230°C and particularly preferably between 200 and 220°C.
Another subject of the present invention are molded parts manufactured according to this process.
The polyesters are manufactured according to a known method by esteri-fication or transesterification and subsequent polycondensation of organic dicarboxylic acids or their polyester-forming derivatives and the respective diols in the presence of catalysts.
Suitable dicarboxylic acids are aliphatic, cycloaliphatic or aromatic acids. They have 2 to 36, preferably 4 to 18 C atoms in the carbon skeleton. For example, 1,4-cyclohexane dicarboxylic acid, adipic acid, sebacic acid, azelaic acid, decane dicarboxylic acid, dimeric fatty acids, phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acids, 4,4'-diphenyl dicarboxylic acid, 4,4'-diphenylsulfone dicarboxylic acid, 4,4'-diphenylether dicarboxylic acid, 3-hexene-1,6-dicarboxylic acid, 3-octene-1,8-dicarboxylic acid, 10-eicosene-1,20-dicarboxylic acid or tetrahydrophthalic acid. The dicarboxylic acids can be employed individually or as a mixture.
As diols alkanediols, alkenediols or cycloalkane diols with 2 to 12 C atoms in the carbon skeleton can be used. For example, ethylene glycol, butanediol-1,4, hexanediol-1,6, 1,4-or 1,3-dimethylolcyclohexane, neopentyl glycol, 2-butenediol-1,4, 3-hexenediol-1,6, 2-pentenediol-1,5, or 3-methyl-2-pentenediol-1,5 are suitable. The diols can be employed individually or as a mixture.
After the polycondensation process, the polyesters generally exhibit a viscosity number in the range of 50 to 200 cm3/g, preferably 70 to 180 cm3/g, measured in a 0.5% phenol/o-dichlorobenzene solution (weight ratio 1:1} at 25°C according to DIN 53 728/lSO 1628-Part 5.

Preferred polyesters within the scope of the invention are polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate and polybutylene-2,6-naphthalate, either as photopolymers or as copolymers.
In another preferred embodiment of the invention the polyester contains olefinic covalent bonds that are introduced via an unsaturated monomer, i.e. via an unsaturated diol and/or an unsaturated dicarboxylic acid. Both the diol component and the dicarboxylic acid component can contain 0.1 to 100 mole percent of unsaturated monomer units
Particularly preferred are polyesters consisting of monomer units derived from the following monomers:
- terephthalic acid and/or 2,6-naphthalene dicarboxylic acid
- 0 to 99.9 mole percent, preferably 75 to 90 mole percent, butanediol-1,4
- 100 to 0.1 mole percent, preferably 25 to 10 mole percent, 2-butenediol-1,4
The polyester molding compound can contain up to 60% by weight, preferably 0.1 to 50% by weight and particularly preferably 5 to 45% by weight of fiber, leaflet or particle shaped filler or reinforcing agent or mixtures of such materials.
Examples of fiber shaped fillers or reinforcing materials are glass fiber, carbon fiber, aramide fiber, potassium titanate fibers and fiber shaped silicates such as wollastonite.
Leaflet shaped fillers or reinforcing agents are, for example, mica, talcum or graphite.
Examples of particle shaped fillers or reinforcing materials are glass spheres, quartz powder, kaolin, boron nitride, calcium carbonate, barium sulfate, silicate, silicon nitride, titanium dioxide, and oxides or hydrated oxides of magnesium or aluminum.
The polyester molding compound can also contain flame retardants in quantities of 0 to 30% by weight. All kinds of flame retardants can be used that are normally used for polyester molding compounds, for example polyhalogen diphenyl, polyhalogen diphenyl ether, polyhalogen phthalic acid and its derivatives, polyhalogen oligocarbonates and polycarbonates or halogenated polystyrenes, in which case the respective bromine compounds are very effective; melamine cyanurate, melamine phosphate, melamine pyrophosphate, elemental red phosphorous, organophosphorous compounds such as phosphonates, phosphinates, phosphinites; phosphine oxides such as

tnphenylphosphine oxide; phosphines, phosphites or phosphates such as thiophenyl phosphate. Other suitable flame retardants are compounds that contain phosphorous-nitrogen bonds, such as phosphononitrile chloride, phosphoric acid ester amides, phosphoric acid amides, phosphonic acid amides, phosphoric acid amides, tris(aziridinyl)-phosphinic oxide or tetra is(hydroxymethyl)phosphonium chloride.
If a flame retardant is used a synergist in quantities of up to 20% by weight, preferably 0.1 to 15% by weight can also be used. Examples of suitable synergists are compounds of cadmium, zinc, aluminum, silver, iron, copper, antimony, tin, magnesium, manganese, vanadium and boron. Particularly suitable compounds are, for example, oxides of the so-called metals, as well as carbonates or ox carbonates, hydroxides and salts of organic or inorganic acids such as acetates or phosphates or hydrogen phosphates, and sulfates.
The molding compound can also contain other additives and/or processing agents; for example antioxidants, heat stabilizers, light stabilizers, colorants, pigments, lubricants, mold release agents or flow-assisting agents.
The polyester molding compound can be manufactured according to known methods, by mixing and extruding the starting materials in a conventional mixing facility, in particular a twin-screw extruder. When it has been extruded, the extrudate is cooled, comminuted and dried.
Polyester molding compounds produced in such a way can be used to manufacture molded parts with the aid of all suitable processes, for example injection molding or extruding. Examples of such molded parts are plug connectors, bobbins, capacitate cans, switches, housing components or capacitate films.
The heat treatment can be carried out by any known method, for example in a drying cabinet, in air, under protective gas, or in a vacuum. This has no significant effect on improving the short-time deflection temperature under load properties. Any discoloring that occurs if the compound is heat treated in air can be prevented by working under protective gas or vacuum. The main protective gases that could be used are nitrogen or argon.
In the examples the following molding compounds were used;


Molding compound 2
Polyester molding compound, only differing from molding compound 1 in that it contains 20% by weight of the polybutylene terephthalate, where the other 34% of polybutylene terephthalate are replaced by a copolyester, manufactured from dimethyl terephthalate and a mixture of butane- 1,4-diol and 2-butene-1,4-diol, in which 18 mole percent of the diol components are derived from 2-butene-1,4-diol.
1.6 mm thick UL rods {molding compound 1 and 2} and bobbins (molding compound 2) were manufactured from the molding compound by means of injection molding.
From the molded parts manufactured from molding compound 2 some were treated with p-rays according to the state of the art, the rest were subjected to heat treatment according to the present invention.
The molded parts manufactured from molding compound 1 were subjected to the same heat treatment as the molded parts from molding compound 2.
The heat treatment was carried out in a recirculating air heat cabinet at 210DC over a period of maximum 24 hours in the air.
After the different treatment times or radiation doses, the short-time deflection temperature under load was determined with the crosslinkage tester ("soldering iron test"). This involved determining the temperature by penetrating the surface of the sample to a depth of 0.1 mm with a heatable point with a diameter of 1 mm for 10 seconds at a

pressure of 150 g. During the measurement, the temperature of the test point was kept as
constant as possible.
The results are shown in Tables 1 and 2
Table 1; Irradiation crosslinking of the molded parts from molding compound 2 (irradiation duration up to 24 hours)

It can be seen by the measurements on the UL rod that heat treatment of a conventional polyester molding compound produces similar results to irradiation crosslinking of a molding compound with a proportion of unsaturated monomer. On the other hand, heat treatment on molding compound 2 produces much more enhanced short-time deflection temperature under load properties. The differences observed between the UL rods and the bobbins are the result of the thickness of the samples.

CLAIMS:
1. Process for manufacturing a molded part with good short-time deflection temperature under load properties, characterized in that:
a) a molded part is manufactured that contains
- 35 to 100% by weight of a thermoplastic polyester,
- 0 to 60% by weight of filler or a reinforcing material,
- 0 to 20% by weight of an impact modified rubber,
- 0 to 30% by weight of a flame retardant,
- 0 to 20% by weight of a synergist and
- 0 to 5% by weight of other additives and/or processing agents.
b) this molded part is treated for at least 1 hour at a temperature of between 180 and
250°C.
2. Process as claimed in claim 1, characterized in that the chosen polyester is selected from the group consisting of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate and polybutylene-2,6-naphthalate.
3. Process as claimed in claim 1, characterized in that in the polyester, the diol component and/or dicarboxylic acid component contains 0.1 to 100 mole percent of unsaturated monomer units.
4. Process as claimed in claim 1 or 3, characterized in that the polyester consists of monomer units that are derived from the following monomers:

- a dicarboxylic acid chosen from terephthalic acid and 2,6- naphthalene dicarboxylic acid and
- 0 to 99.9 mole percent butanediol-1,4, and -100 to 0.1 mole percent 2-butenediol-1,4.

5. Process as claimed in claim 4, characterized in that in the diol portion of the polyester 10 to 25 male percent are derived from 2-butenedio!-1,4.
6. Process as claimed in any one of the preceding claims, characterized in that the molding compound contains 0.1 to 50% by weight of filler or reinforcing agent.

7. Process as claimed in claim 6 characterized in that the molding compound contains 5
to 45% by weight of filler or reinforcing agent.
8. Process as claimed in any one of the preceding claims characterized in that the
molding compound contains 0.1 to 25% by weight of flame retardant.
9. Process as claimed in any one of the preceding claims characterized in that the
molding compound contains 0.1 to 15% by weight of synergist.
10. Process as claimed in any one of the preceding claims characterized in that the
molded parts is manufactured by injection molding or extruding.
11. Process as claimed in any one of the preceding claims characterized in that the
molded part is treated for 2 to 24 hours at the higher temperature.
12. Process as claimed in claim 11 characterized in that the molded part is treated for 4
to 8 hours.
13. Process as claimed in any one of the preceding claims characterized in that the molded part is treated at 190 to 230°C.
14. Process as claimed in claim 13 characterized in that the molded part is treated at 200 to 220°C.
15. Molded part, manufactured by means of the process according to any one of the
preceding claims.
16. Molded part as claimed in claim 15, characterized in that it is a plug connector, a
bobbin, a printed circuit board, a housing with a printed circuit board function, a relay
component, a capacitator can, a switch, a housing component or a capacitator film.