IT9022501A1 - THERMOPLASTIC COMPOSITIONS WITH IMPROVED RELEASE CHARACTERISTICS FROM THE MOLD - Google Patents

Description

Description of the industrial invention

The present invention relates to thermoplastic molding compositions with improved mold release characteristics.

More particularly, the present invention relates to thermoplastic molding compositions having improved mold release characteristics consisting of:

A) a shockproof vinyl aromatic copolymer containing an ethylenically unsaturated nitrile, a vinyl aromatic monomer and rubber;

B) a grafted polymer consisting of an elastomeric core having a second order glass transition temperature (Tg) lower than 10 ° C and containing grafted chains of vinyl monomers;

C) possibly a technopolymer, e

D) a detachment agent.

The thermoplastic compositions consisting of the above components A), B) and C) are well known and find application in numerous technological fields due to their excellent combination of mechanical, chemical-physical and thermal properties.

A drawback of these compositions is their poor release from the mold when subjected to injection molding. This drawback, as is known, mainly involves the breaking of the molded piece during the extraction phase.

A known way to avoid this drawback is to carry out the detachment at high temperatures. This way of proceeding, however, is not without drawbacks mainly due to the stickiness of the molded pieces on the surface of the mold and consequent deformation or breakage of the pieces themselves.

To improve the extractability of the bodies formed from the mold, it is common technique to use release agents. Very often, however, these additives have a negative effect on the properties of the thermoplastic composition. For example, bis (stearll / palmitoyl) ethylene diamine which is generally used in ABS resins, improves the flowability of the resin and therefore the processability, but greatly reduces the heat distortion stability (VICAT). In the case of the compositions of the present invention, this decay of the mechanical properties when hot is a serious drawback, which considerably reduces the field of application of the compositions.

Also known are release agents consisting of esters of long-chain aliphatic carboxylic acids with mono- and tri-valent alcohols.

However, these products also deteriorate their mechanical properties after prolonged exposure to heat. Furthermore, these products are volatile at the molding temperature of the composition and this represents a serious drawback during processing.

The present invention allows to overcome all the aforementioned drawbacks and to prepare thermoplastic compositions, consisting of the components A), B) and C) reported above, which exhibit a mold release behavior that is suitable for all applications and, moreover, a balance of mechanical, physical and thermal properties comparable to that of the compositions that do not contain any release additive.

According to the present invention, thermoplastic compositions having the above characteristics can be obtained by using as release agent an effective amount of a synergistic mixture of two esters of which one (i) is a fatty acid ester containing from 16 to 18 carbon atoms with glycerol and the other (ii) is an ester of an aliphatic alcohol containing 4 to 6 hydroxyl groups with a saturated aliphatic monocarboxylic acid containing 10 to 20 carbon atoms or a mixture of the above monocarboxylic acid and an acid polycarboxylic containing 10 to 20 carbon atoms.

Therefore, the subject of the present invention is a thermoplastic composition consisting of:

A) a shockproof vinyl aromatic copolymer containing an ethylenically unsaturated nitrile, a monomer wines! aromatic and a gum;

B) a grafted polymer consisting of an elastomeric core having a second order glass transition temperature (Tg) lower than 10 ° C and containing grafted chains of vinyl aromatic monomers;

C) possibly a technopolymer, e

0) an effective amount of a release agent consisting of a synergistic mixture consisting of:

(i) an ester of a fatty acid containing 16 to 18 carbon atoms with glycerol and da

(ii) an ester of a saturated, aliphatic, monocarboxylic acid containing 10 to 20 carbon atoms or a mixture of said monocarboxylic acid and a polycarboxylic acid containing 10 to 20 carbon atoms with an aliphatic alcohol containing by 4 to 6 hydroxyl groups.

With respect to 100 parts by weight of the composition A + B + C, the release agent (D), consisting of the synergistic mixture of the two esters (i) and (ii), is added in quantities ranging from 0.01 to about 3% , preferably from 0.5 to 2% by weight.

In the synergistic mixture D, the ratio between the two esters (i) and (ii) can vary within a wide range, particularly advantageous results have been obtained with a weight ratio between 4: 1 and 1: 4, preferably about 1: 1.

The esters (i) of a C16-C18 fatty acid with glycerol are highly biodegradable products, of a non-ionic polar nature and having the following properties

. degree of saponification 155-175

. iodine number 1-2

. mono-ester content 40-993⁄4 by weight. melting point 55-65 ° C

. free glycerol l-63⁄4 by weight. water content 0.1-0.5% by weight These esters are well known on the market under the name S0FTENOL, produced and sold by HULS TR0ISD0RF AG. -GERMANY; LANKROPLAST * produced and sold by LANKRO ITALIANA S.p.A. and LOXIOLR manufactured and sold by HENKEL - GERMANY. ; These esters (1) are proposed as sliding, antistatic, release and anti-blocking agents for many plastics such as polystyrene, acryl-butadiene-styrene (ABS), polyethylene, poly-carbonate, polypropylene and polyvinyl chloride; Tests conducted by the Applicant have, however, shown that their mold release action is very limited in the case of the thermoplastic compositions of the present invention comprising the aforementioned components A, B and C.; For the preparation of the esters (ii of the synergic mixture D of the present invention, it is possible to use: - alcohols having 4 -OH groups and from 4 to 16, preferably from 4 to 8 carbon atoms; - alcohols having 5 -OH groups and from 5 to 18, preferably from 5 to 10 atoms of carbon;; - alcohols having 6 -OH groups and from 6 to 18, preferably from 6 to 12 carbon atoms.; The esters (ii) preferably are those resulting from the complete esterification of the 4-6 -OH groups of the alcohols with one or more C10-C20 carboxylic acids.; Examples of alcohols containing 4 to 6 OH groups are: erythritol, arabitol, adonltol, manitol and dulcitol and especially mesoerythritol, xylitol, sorbitol and pentaerythritol.; Any saturated monocarboxylic acid aliphatic C10-C20 can be used, possibly together with a C10-C20 polycarboxylic acid such as, for example, capric, undecanoic, lauric, tridecanoic, myristic, pentadecanolc, paimitic, margaric, stearic, mono-decanoic, eicosanic, sebacic acid, undecandioic, dodecandioic, brassyl, tapsic etc. ; Examples of esters (11) to be used in the synergistic mixture of the present invention are:; pentaerythrite tetrastearate, pentaerythrite tetrapalmitate, pentaerythrite tetramyristate, pentaerythrite tetralaurate, mesoerythritic tetralaurate, mesoerythritanite tetrastearate, mesoerythritic tetrastearate di xylitol pentastearate, xylitol pentapalml tate, arabitol pentastearate, arabitol pentapalmitate, sorbitol hexastearate, sorbitol hexapalmitate, dulcitol hexapalmitate, mannitol hexastearate, mannitol hexamyristate etc. The esters of stearic acid and those of paimitic acid are preferably used. ; These esters (ii) are prepared according to known processes as, for example, described in "Houben-Weyl Methoden der Organischen Chemie, Georg Thieme Verlag, Stuttgard - 1952 - 4th Edition, Vol. Vili, pages 516 et seq.; These esters (ii) are known on the market under the brand name LOXIOL ^, produced and sold by Soc. HENKEL - Dusseldorf -Germany.; German patents Nos. 2,507,748, 2,701,725 and 2,729,485 describe the use of these esters ( ii) as release agents for high molecular weight aromatic polycarbonates. Tests carried out by the Applicant have, however, shown that their release action is very poor in the case of the thermoplastic compositions of the present invention comprising the aforementioned components A, B and C.; The thermoplastic composition comprising 1 above components A, B and C can be either (I) that described in the European patent application No. 216,065 published on 1 April 1987, or that (II) described in the patent application European No. 379039 published July 25, 1990, the content of which forms an integral part of this description. In particular, the thermoplastic composition (I) comprises:; A.l) an impact-resistant vinyl aromatic copolymer containing from 2 to 25% by weight of an ethylenically unsaturated nitrile, a diene rubber in an amount not exceeding 15% by weight and a vinyl monomer aromatic; B.l) a grafted polymer consisting of an elastomeric core having a second order transition temperature lower than 10 ° C and containing grafted chains of vinyl monomers; and; C.l) possibly a technopolymer. ; The quantities of components A.l, B.l and C.l can be varied within a wide range. ; In general, in the composition (I) the copoìimer wines! aromatic A.l is present in quantities ranging from 15 to 95% by weight, grafted polymer B.l in quantities ranging from 5 to 40% by weight, and technopolymer C.1 between 0 and 80% by weight; the sum of the three components A.l, B.l and C.l being equal to 100. Preferred compositions are those containing: - from 20 to 40% by weight of A.l; ; - from 5 to 10% by weight of B.l; and; - from 55 to 75% by weight of C.l,; the sum of these three components A.l, B.l and C.l being equal to 100.; The thermoplastic composition (II) comprises:; A.2) a shockproof vinyl aromatic copolymer, containing from 2 to 35% by weight of an ethylenically unsaturated nitrile, from 15 to 50% by weight of an olefin elastomer and from 83 to 15% by weight of a vinyl aromatic monomer; ; B.2) a grafted polymer consisting of an elastomeric core having a second order glass transition temperature (Tg) lower than 10 ° C and containing grafted chains of vinyl monomers, and; C.2) an aromatic polycarbonate; in which the weight ratio between the two polymers A.2 and C.2 is between 10:90 and 90:10 and the quantity of the grafted polymer B.2 is from 11 to 20% by weight, with respect to the compound A.2 and C.2,; Preferably, the polymeric composition (II) comprises: an impact-resistant styrene copolymer (A.2) containing from 2 to 35% by weight of an ethylenically unsaturated nitrile, from 20 to 40% by weight of an olefin elastomer and from 25 to 78% by weight of a styrene monomer; an aromatic polycarbonate (C.2), in which the weight ratio between the two polymers A.2 and C.2 is between 70:30 and 30:70, and from 3 to 10% by weight, with respect to the compound A .2 + C.2, of a grafted polymer (B.2). The term vinyl aromatic monomer as used in the present description and in the claims includes the ethylenically unsaturated compounds having general formula:; ;; wherein X represents hydrogen or an alkyl radical having from 1 to 4 carbon atoms; n is zero or an integer between 1 and 5 and Y represents a halogen or an alkyl radical having from 1 to 4 carbon atoms. Examples of vinyl aromatic monomers having the above general formula are: styrene; methyl-styrene; mono-, di-, tri-, tetra and penta-chloro-styrene and the corresponding alpha-methyl-styrenes, styrenes alkylated in the core and the corresponding alpha-methyl-styrenes such as ortho and para-methyl-styrenes, ortho and para-ethyl- styrenes; ortho- and para-methyl-alpha-methyl-styrenes, etc. These monomers can be used alone or in a mixture with each other or with other copolymerizable comonomers such as maleic anhydride. Styrene is particularly preferred. ; In the impact-resistant vinyl aromatic copolymer (A.2), the elastomeric component, which is the support on which the ethylenically unsaturated nitrile and the vinyl aromatic monomer are partly grafted and partly mechanically adhered in the form of ethylenically unsaturated nitrile copolymer - monomer vinyl, is a rubbery copolymer, having a Mooney viscosity between 10 and 150 ML-4 at 100 ° C, of at least two different linear chain alpha mono-olefins such as ethylene, propylene, butene1, octene-1 and the like with at least one other copolymerizable monomer generally a polyene and typically a non-conjugated diene. Preferably one of the alpha mono-olefins is ethylene together with another longer chain alpha-mono-olefin. The weight ratio of ethylene to the other alpha-mono-olefin in the rubbery copolymer is ordinarily in the range of 20/80 to 80/20. Particularly preferred copolymers are the non-conjugated ethylene-propylene-diene terpolymers in which the non-conjugated diene can be cyclic or acyclic such as: 5-methylene-2-norbornene; 5-ethylidene-2-bornene; 5-isopropylene-2-norbornene; pentadiene-1,4; hexadiene-1, 4; hexadiene-1,5; heptadiene-1,5; dodecatriene-1,7,9; methyl heptadlene-1,5; norbornadiene-2,5; cyclo-octadiene-1,5; didiciopentadiene; tetrahydroindene; 5-methyl-tetrahydroindene etc. The content of the diene is comprised between about 5 and 20% by weight and preferably between 8 and 18% by weight of diene monomer units in the rubbery terpolymer. In particular, a rubbery terpolymer having a Mooney viscosity (ML-4), measured at 100 ° C, between 30 and 90 and an iodine number higher than 5, preferably between 10 and 40, is preferred. used to make vinyl aromatic polymers resistant to impact are: poly-butadiene, poly-isoprene, butadiene and / or isoprene copolymers with styrene or with other monomers. The content of such diene rubbers in the impact-resistant vinyl aromatic copolymer is not higher than 15% by weight and preferably between 2 and 12% by weight. As ethylenically unsaturated nltryl, copolymerized with the vinyl aromatic monomer, is meant primarily and preferably acrylonitrile; other ethylenically unsaturated monomers nitrilides such as methacrylonitrile, acrylic and methacrylic acid and their alkyl esters containing from 1 to 6 carbon atoms in the alkyl radical can also be used with advantage. The impact-resistant vinyl aromatic copolymers A1 and A.2 can be obtained according to any known polymerization process in suspension, mass-suspension or continuous mass, provided that the above compounds are used as starting monomers. The grafted polymer B.1 or B.2 is a polymer of the "core-shell" type consisting of an elastomeric core containing grafted chains of vinyl monomers. ; The elastomeric core having a second order transition temperature of less than 10 ° C, may preferably be a polybutadlene, copolymers of butadiene with styrene, isoprene and / or with acrylonitrile, wherein the butadiene content is greater than 40 % in moles, ethylene-propylene rubbers, ethylene-propylene-diene rubbers (EPDM) or acrylic rubbers. The acrylic rubber can be an elastomer obtained by polymerization of a monomer system comprising: - from 90 to 99.8% by weight of an alkyl acrylate, containing from 1 to 6 carbon atoms in the alkyl chain; - 0.1 to 5% by weight of a cross-linking monomer such as a polyacrylic or polymethacrylic ester of polyols, preferably butylene diacrylate; and; - 0.1 to 5% by weight of a grafting agent which may be, for example, an allyl ester of an ethylenically unsaturated acid such as allyl acrylate, allyl methacrylate, di-allyl maleate, di-allyl fumarate, di-allyl itaconate - allyl etc. ; The vinyl monomers grafted to the elastomeric core can be derivatives of acrylic acid and methacrylic acid, vino1-aromatic compounds, vinyl-cyanide compounds and polyfunctional derivatives alone or in a mixture, as reported in the two patent applications European on reported. ; The grafted polymer B.l or B.2 used in thermoplastic compositions (I) and (II) preferably has an elastomer content greater than 35% and up to 95% by weight, a second order glass transition temperature of less than -10 ° C and even lower than -50 ° C and a degree of crosslinking higher than 50% and up to 99% by weight (gel content), determined by extraction. ; A typical example of grafted polymer can be a three-stage polymer having a butadiene-based rubber core, a second stage thenintered from styrene and a final stage, 0 shell, polymerized from methyl methacrylate and 1,3 butylene glycol-dlmethacrylate. . Another example of grafted polymer can be a two-stage polymer: the first stage, consisting of 60 to 95% by weight of the polymer, obtained starting from a monomeric system comprising 95-99.8% by weight of butyl acrylate , 0.1-2.5% by weight of butylene diacrylate, and 0.1-2.5% of allyl methacrylate or diallyl maleate, and the final stage obtained from a polymerizate containing 60 to 100% by weight of methyl -methacrylate. ; The grafted polymers B.l and B.2 above are well known commercially and are available from a large number of manufacturers such as, for example, from the Rohm & Haas Company, Philadelphia, USA, under 1 brand names PARAL0ID EXL 2600, EXL 2300, EXL 2607 and EXL 3607, or by Kanegafuchi under the brand name KaneACE B 28, etc. The technopolymer C1 used in the composition of the present invention can be any plastic material having mechanical, chemical and technical properties suitable for being used as a construction material. A detailed description of the term "engineering plastics" can be found in the "Engineered Materials Handbook" vol. 2 - Engineering Plastics - ASM intern. 1988. Typical examples of suitable technopolymers are: polycarbonate, polyesters, thermoplastic polyurethanes; polymethacrylates, styrene-methyl-methacrylate copolymers, acrylic polymers, styrene-maleic anhydride copolymers, SAN, vinyl chloride polymers etc. Aromatic polycarbonate is preferred. The aromatic polycarbonate is preferably obtained from a bisphenol having the formula: ;;; ;; wherein each R1 R2, R3 and R4 represents hydrogen or an alkyl radical containing 1 to 4 carbon atoms or a halogen, and A represents -0-, -CO-, -SO2-, an alkyl radical containing 2 to 10 carbon atoms, an alkylidene radical containing 2 to 10 carbon atoms, a cyclo-alkylene radical containing 5 to 15 carbon atoms, a cycloalkylidene radical containing 5 to 15 carbon atoms or the radical: ;; Particularly preferred bisphenols are, for example, 2,2-bis- (4-hydroxl-phenyl) -propane; 2,2-b1s- (3,5-dimethyl-4-hydroxy-phenyl) -propane; 2,2-bis- (3,5-di-chloro-4-hydroxy-phenyl) propane; 2,2-bis- (3,5-di-bromo-4-hydroxyphenes1) -propane and 1,1-bis- (4-hydroxy-phenyl) -cyclohexane. Particularly preferred polycarbonates are those based on one or more of the bisphenols mentioned above. In particular, polycarbonates based on 2,2-bis- (4-hydroxyphenyl) -propane or on 2,2-bis- (3,5-di-methyl-4-hydroxyphenyl) -propane alone or in a mixture with each other or with one of the aforementioned bisphenols are preferred. Such polycarbonates have an average molecular weight of at least 10,000, more specifically from 10,000 to 200,000 and preferably from 20,000 to 80,000, as determined by relative viscosity measurements in CH2Cl2 at 25 ° C and with a concentration of 0.5% by weight. Aromatic polycarbonates are well known in the art and are available on the market from various sources, for example: General Electric Company, Pittsfield, Mass., USA under the brand name "LEXAN"; ENIMONT - Milan, with the "SINVET" brand; Proquigel (Brazil) under the brand name "DUROLON", etc. The blends of the present invention can be prepared by any conventional mixing method. Generally, mixing is done in the molten state, after pre-mixing at room temperature, in known mixing units, such as single- and twin-screw extruders, Banbury mixer, mixing rollers, etc. at a temperature between 180 and 300 ° C. The compositions may further contain stabilizing agents or other intimately incorporated additives, such as plasticizers, lubricants, flameproof agents, flow agents, antistatic agents, dyes, pigments, glass fibers or other inorganic fillers etc. in order to impart particular characteristics to the material. The blends, object of the present invention, are easily workable and have a set of properties that make them suitable for use in the preparation of articles having high toughness together with high impact resistance. Said compounds therefore find application in the sectors of household appliances, electronics and technical articles in general in the form of films, sheets, strips, tapes, rods, boxes, cups, containers, etc. The blends can be used to produce expanded articles, using the techniques known in the art. In order to better understand the present invention and to put it into practice, some illustrative but not limiting examples are given below. In the examples, all parts and percentages are given by weight unless otherwise indicated. ; EXAMPLES 1-4; In a drum-tilter-type mixer the following were mixed, at room temperature:; - 27 parts by weight of a shockproof vinyl aromatic copolymer consisting of 68.5% by weight of styrene, 9.5% by weight of rubber polybutadiene and 22% by weight of acrylonitrile; - 8 parts by weight of PARAL0IDR EXL 2600 rubber consisting of 60% by weight of a polybutadiene rubber "core" onto which chains of a styrene-methyl methacrylate copolymer (ratio 1: 1) in a quantity of 40% are grafted; ; - 65 parts by weight of SINVET aromatic polycarbonate produced and sold by ENIMONT S.p.A. and; - a release agent of the type and in the amount shown in Table I below. ; The mixture thus obtained was dried at 100 ° C for 4 hours and extruded using a single screw extruder BANDERA TR45, with a length / diameter ratio of 25, with degassing, at a temperature of 260 ° C. By cutting the spaghetti coming out of the extruder, granules were obtained which were dried for 4 hours at 100 ° C. For the determination of the characteristics, the granules are injection molded at a temperature of 260-270 ° C on a NEGRI & BOSSI V — 17—110 FA press to obtain the test tubes having dimensions required by the standards. ; The properties measured on the test tubes thus obtained are shown in the following Table I.; The following methods were used to measure the characteristics of the compounds, object of the present invention:; Mechanical properties; The IZOD resilience with notch to 23 ° C, according to the ASTM D256 standard, on test tubes with a thickness of 3.2 mm.; Thermal properties; The VICAT B softening temperature (5 Kg in oil) was determined, according to the ISO 306 standard, with an increase of temperature of 120 ° C / hour.

Rheological properties

The Melt-Index was determined according to the ASTM D 1238 standard, at 260 ° C and 5 Kg.

Strength of detachment

The force required to extract, at the mold temperature of 50-60 ° C, a box having the dimensions 220x110x70 mm and a thickness of 2 mm from the respective mold mounted on a NEGRI & BOSSI injection molding machine was determined, using a transducer pressure inserted in the hydraulic circuit of the extractor and recording the value on an oscilloscope mod. HP 54201 D.

TABLE I

EXAMPLE 5

The procedural modalities of Example 1 were repeated to prepare a mixture comprising:

- 37 parts 1n weight of a vinyl aromatic copolymer consisting of 65% by weight of styrene, 11% by weight of polybutadiene rubber and 24% by weight of acrylonitrile, produced by mass polymerization in the presence of Trigonox 25 8 50 from Akzo as initiator ;

- 55 parts by weight of SINVET aromatic polycarbonate produced and sold by ENIMONT S.p.A .;

- 8 parts by weight of PARALOID EXL 2600 rubber of Example 1; - 1 parts by weight of a mixture consisting of glyceryl monostearate and pentaerythrite tetrastearate, in the ratio by weight 1: 1.

The mechanical, thermal and theological properties and the release force, measured according to the methods shown in the example are:

EXAMPLES 6-7

In a drum-tilter-type mixer the following were mixed at room temperature:

92 parts by weight of an impact-resistant vinyl aromatic copolymer of Example 1;

- 8 parts by weight of PARALOID EXL 2600 rubber of Example 1; and - a mixture of glyceryl monostearate and pentaerythrite tetrastearate in the ratio by weight 1: 1, in the quantity reported in Table II below.

The mixes were dried at 80 ° C for 2-3 hours and extruded by means of a single screw extruder BANDERA TR45, at a temperature of 220 ° C.

By cutting the spaghetti coming out of the extruder, granules were obtained which were dried for 2-3 hours at 80 ° C.

For the determination of the characteristics, the granules were injection molded at a temperature of 220-230 ° C on a Negri & Bossi V-17-110 FA press to obtain the test tubes having dimensions required by the standards.

The mechanical, thermal, rheological properties and the release force were measured according to the methods reported in Example 1, except for the determination of the VICAT, the temperature increase was 50 ° C / h, and the Melt-Index was determined at 220 ° C and 10 kg.

The characteristics of the compounds thus prepared are:

TABLE II

Claims (3)

CLAIMS 1. Thermoplastic molding compositions, having improved mold release characteristics, comprising: A) an impact resistant vinyl aromatic copolymer containing an ethylenically unsaturated nitrile, a vinyl aromatic monomer and a rubber; B) a grafted polymer consisting of an elastomeric core having a second order glass transition temperature (Tg) lower than 10 ° C and containing grafted chains of vinyl aromatic monomers; C) possibly a technopolymer, e D) an effective quantity of a release agent, characterized in that said release agent consists of a synergistic mixture consisting of: (i) an ester of a fatty acid containing 16 to 18 carbon atoms with glycerol e (11) an ester of a saturated, aliphatic, monocarboxylic acid containing 10 to 20 carbon atoms or a mixture of said monocarboxylic acid and a polyicarboxylic acid containing 10 to 20 carbon atoms, with an aliphatic alcohol containing 4 with 6 hydroxyl groups. 2. Thermoplastic compositions according to claim 1, wherein the weight ratio between the two esters (i) and (ii) of the synergistic mixture D is comprised between 4: 1 and 1: 4, preferably about 1: 1. 3. Thermoplastic compositions according to claim 1 or 2, wherein the ester (i) of a C16-C18 fatty acid with glycerol is a biodegradable product, of a nonionic polar nature, having the following properties: . water content 0.1-0.5% by weight Thermoplastic compositions according to any one of the preceding claims, wherein the ester (11) of the synergistic mixture D is obtained from a saturated, aliphatic, monocarboxylic acid containing from 10 to 20 carbon atoms or a mixture of monocarboxylic acid and a polycarboxylic acid containing 10 to 20 carbon atoms with an aliphatic alcohol chosen from: - alcohols having 4 -OH groups and from 4 to 16, preferably from 4 to 8 carbon atoms; - alcohols having 5 -OH groups and from 5 to 18, preferably from 5 to 10 carbon atoms; and - alcohols having 6 -OH groups and from 6 to 18, preferably from 6 to 12 carbon atoms Thermoplastic compositions according to any one of the preceding claims, wherein the ester (ii) of the synergistic mixture is obtained by the complete esterification of the 4-6 -OH groups of the alcohols with one or more C10-C20 carboxylic acids. Thermoplastic compositions according to any one of the preceding claims, wherein the C10-C20 carboxylic acid is stearic acid or paimitic acid. Thermoplastic compositions according to any one of the preceding claims, wherein the quantity of release agent is comprised between 0.01 and 3% by weight, preferably 0.5 to 2% by weight, with respect to 100 parts of the composition consisting of components A + B + C. 8. Thermoplastic compositions according to any one of the preceding claims, wherein component A is an impact-resistant vinyl aromatic copolymer (A.l) containing from 2 to 25% by weight of an ethylenically unsaturated nitrile, a diene rubber in an amount not exceeding 15%, preferably comprised between 2 and 12% by weight, and a vinyl aromatic monomer. 9. Thermoplastic compositions according to any one of the preceding claims, wherein the amount of the impact-resistant vinyl aromatic copolymer (A1) is comprised between 15 and 60%, preferably between 20 and 40% by weight; the amount of the grafted polymer (B.l) is between 5 and 40%, preferably between 5 and 10% by weight, and the amount of the technopolymer (C.l) between 0 and 80%, preferably between 50 and 75% by weight; the sum of the three components A.l + B.l + C.l being equal to 100. 10. Thermoplastic compositions according to any one of the preceding claims from 1 to 7, wherein component A is an impact-resistant vinyl aromatic copolymer (A.2) containing from 2 to 35% by weight of an ethylenically unsaturated nitrile, from 15 to 50% preferably from 20 to 40% by weight of an olefin elastomer; and 83 to 15%, preferably 78 to 25%, by weight of a vinyl aromatic monomer; component (B) is a grafted polymer (B.2) and component C is an aromatic polycarbonate (C.2), in which the weight ratio between the two components A.2 and C.2 is between 10: 90 and 90:10, preferably between 70:30 and 30:70, and the amount of grafted polymer (B.2) is between 1 and 20%, preferably between 3 and 10%, by weight with respect to the sum of the components A .2 and C.2. 11. Thermoplastic compositions according to any one of the preceding claims, wherein the ethylenically unsaturated nitrile is acrylonitrile. 12. Thermoplastic compositions according to any one of the preceding claims, wherein the vinyl aromatic monomer is styrene. 13. Thermoplastic compositions according to any one of the preceding claims, wherein the elastomeric core of the grafted polymer B, B.1 or B.2, having a second order transition temperature lower than 10 ° C, is selected from polybutadlene, butadiene copolymers with styrene, and / or with acrylonitrile in which the butadiene content is higher than 50% by moles, ethylene-propylene rubbers, ethylene-propylene-diene rubbers (ΕΡ0Μ) and acrylic rubbers. 14. Thermoplastic compositions according to any one of the preceding claims, wherein the vinyl monomers grafted to the elastomeric core are selected from acrylic acid derivatives, methacrylic acid derivatives, vinyl-aromatic compounds, vino1-cyanide compounds, polyfunctional derivatives and their blends. 15. Thermoplastic compositions according to any one of the preceding claims, in which the technopolymer C or C.1 is selected from polycarbonate, polyesters, thermoplastic polyurethanes, polymethacrylates, styrene-methyl-methacrylate copolymers, acrylic polymers, ABS, styrene-maleic anhydride copolymers, SAN and vinyl chloride polymers. 16. Thermoplastic compositions according to claims 10 or 15, wherein the aromatic polycarbonate has an average molecular weight higher than 10,000 and in particular between 10,000 and 200,000, preferably between 20,000 and 80,000, and is obtained from a bisphenol having the formula: wherein each R1 R2, R3 and R4 represents hydrogen or an alkyl radical containing 1 to 4 carbon atoms or a halogen, and A represents -0-, -CO-, -SO2-, an alkylene radical containing 2 to 10 carbon atoms, an alkylidene radical containing 2 to 10 carbon atoms, a cyclo-alkylene radical containing 5 to 15 carbon atoms, a cyclo-alkylidene radical containing 5 to 15 carbon atoms or the radical: