Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-05-31
2003-12-02
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
active
06656988
ABSTRACT:
The invention relates to molding compositions based on poly-C
2
-C
6
-alkylene terephthalates and comprising mold-release agents, and also to the use of certain mold-release agents in the molding compositions.
Polybutylene terephthalate and polybutylene terephthalate blends are widely processed by extrusion or injection molding to give moldings, which are used in a variety of consumables in the household, the food and drink and the medical sector. To produce the moldings, additives are generally added to the polybutylene terephthalate to give good demolding performance, i.e. to allow short cycle times and prevent formation of mold deposits. The additive here should not change the other aspects of the performance of the polybutylene terephthalate.
When plastics are used in the food and drink or the medical sector, the transfer of substances from the plastic to the food or into the body has to be prevented. In this connection there are, for example, specifications from the Food and Drug Administration (FDA) in the U.S. and from the BGA (German Federal Board of Health) in Germany.
It is an object of the present invention to provide thermoplastic molding compositions based on poly-C
2
-C
6
-alkylene terephthalates and comprising a mold-release agent which is not hazardous to health and which, in particular, has low volatility in the molding composition.
We have found that this object is achieved by using glycerol fatty acid esters of C
12
-C
24
fatty acids which may have a hydroxyl group and from 1 to 3 carbon-carbon double bonds as an additive for molding compositions based on poly-C
2
-C
6
-alkylene terephthalates.
They are used in particular as mold-release agents. The glycerol fatty acid esters may be mono-, bis- or triesters. They are preferably glycerol bis(fatty acid) esters. The fatty acids here derive from C
12
-C
24
fatty acids, preferably C
14
-C
20
fatty acids, in particular C
16
-C
18
fatty acids, which may have a hydroxyl group and from 1 to 3 carbon-carbon double bonds. They preferably have zero, one or two carbon-carbon double bonds. If they have a hydroxyl group, they preferably also have one or two carbon-carbon double bonds. The fatty acid radicals are generally linear. Examples of fatty acids which can be used in the glycerol fatty acid esters are stearic acid, linoleic acid, linolenic acid, oleic acid, palmitic acid, castor oil fatty acid and nonanoic acid. Other suitable fatty acids are known to the skilled worker. The glycerol fatty acid esters here may be prepared by known processes.
Glycerol bisstearate is used in particular as a mold-release agent. This compound is available, for example, from Henkel with the trade name Loxiol® VPG 1206. The glycerol fatty acid esters and glycerol bisstearates used according to the invention fulfill the requirements placed upon compounds which may come into contact with foods or with the human body.
Glycerol bisstearates have previously been used mainly for extruding and injection molding polymers such as PVC, which can be processed at relatively low temperatures, below 220° C. The reason for this is that glycerol bisstearates are increasingly volatile at higher temperatures. For example, a thermogravimetric analysis of a glycerol bisstearate shows a marked weight loss from about 220° C. At from 250 to 270° C., the temperature range for processing polybutylene terephthalate and polybutylene terephthalate blends, the weight loss measured is up to 5% (from 40 to 340° C., 10° C./min). The mold-release agents used hitherto for polybutylene terephthalate have therefore been those such as fully esterified pentaerythritols, which have markedly lower volatility under these conditions. For example, the weight loss for a fully esterified pentaerythritol at 270° C. is less than 1% (from 40 to 340° C., 10° C./min).
According to the invention, it has been found that mixtures of the abovementioned glycerol fatty acid esters, in particular of glycerol bisstearate, with polybutylene terephthalate are significantly less volatile in a mold-release agent than the volatility of the separate compounds would suggest. Without being bound by any particular theory, this may be due to the fact that the ester on the surface of a molding has a sufficiently good degree of binding to polybutylene terephthalate. The properties of polybutylene terephthalate with glycerol bisstearate additive are no different from the properties of a polymer with additives which are known mold-release agents for polybutylene terephthalate. This is shown both by thermogravimetric measurements and by studies on demolding performance and on deposit formation in molds at a processing temperature of 260° C., and also by studies on long-term migration (11 days/150° C.). There is also no adverse effect on other aspects of performance, such as rheological, mechanical and thermal properties. The mixtures made from the glycerol fatty acid esters used according to the invention and molding compositions based on poly-C
2
-C
6
-alkylene terephthalates may be used universally, either in unreinforced or else in reinforced molding compositions.
The molding compositions here are based on poly-C
2
-C
6
-alkylene terephthalates. These may be pure poly-C
2
-C
6
-alkylene terephthalates or polymer blends made therefrom. They may in particular be polybutylene terephthalates or polybutylene terephthalate blends.
The invention also provides a thermoplastic molding composition comprising, based on the total of components A and B and, if present, C to E, which together give 100% by weight,
a) as component A, from 40 to 99.99% by weight of at least one polyester based on poly-C
2
-C
6
-alkylene terephthalates,
b) as component B, from 0.01 to 3% by weight of glycerol fatty acid esters of C
12
-C
24
fatty acids which may have a hydroxyl group and from 1 to 3 carbon-carbon double bonds,
c) as component C, from 0 to 49.99% by weight of blend polymers miscible with component A or dispersible therein,
d) as component D, from 0 to 50% by weight of fillers, and
e) as component E, from 0 to 10% by weight of other usual additives.
Component A
The novel molding composition comprises, as component A, from 40 to 99.99% by weight of a polyester based on poly-C
2
-C
6
-alkylene terephthalates. Polymers of this type are known per se.
The polyesters may be prepared by reacting terephthalic acid, its esters or other ester-forming derivatives with 1,4-butanediol, 1,3-propanediol or, respectively, 1,2-ethanediol in a manner known per se.
Up to 20 mol% of the terephthalic acid may be replaced by other dicarboxylic acids. Examples of these which may be mentioned are naphthalenedicarboxylic acids, isophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid and cyclohexanedicarboxylic acids, mixtures of these carboxylic acids and ester-forming derivatives thereof.
It is also possible for up to 20 mol% of the dihydroxy compounds 1,4-butanediol, 1,3-propanediol and 1,2-ethanediol to be replaced by other dihydroxy compounds, such as 1,6-hexanediol, 1,4-hexanediol, 1,4-cyclohexanediol, 1,4-di(hydroxymethyl)cyclohexane, bisphenol A, neopentyl glycol, mixtures of these diols or ester-forming derivatives thereof.
Preferred aromatic polyesters are polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT) and in particular polybutylene terephthalate (PBT), which have been formed exclusively from terephthalic acid and the corresponding diols. Some or all of the aromatic polyesters may also be in the form of recycled polyester materials, such as PET regrind made from bottle material or from bottle-production waste.
Component B
The glycerol fatty acid esters used according to the invention as component B have been described above. The amount in which they are used is from 0.01 to 3% by weight, preferably from 0.2 to 1.5% by weight, particularly preferably from 0.2 to 1.0% by weight.
Component C
The molding compositions may comprise, as component C, from 0 to 49.99% by weight, preferably from 0 to 40% by weight, particularly preferably from 0 to 30% by weight of blend polymers miscible with compon
Fisch Herbert
Fischer Michael
Nam Michael
BASF - Aktiengesellschaft
Cain Edward J.
Keil & Weinkauf
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