IE63304B1 - Stabilizing compositions for halogenated polymers,based on beta-diketone hydrotalcite and dihydropyridine and polymers thus stabilized - Google Patents

Abstract

The invention relates to stabilising compositions for halogenated polymers. These compositions furthermore comprise a metal salt of a carboxylic acid, a beta-diketone, a hydrotalcite and a dihydropyridine. The halogenated polymer, especially PVC, compositions containing these stabilising compositions exhibit high colour stability and good heat resistance.

Description

The invention relates to novel stabilizing compositions for halogenated polymers, the said compositions comprising a beta-diketone, a hydrotalcite, and a dihydropyridine. It also relates to the halogenated polymers 5 stabilized by means of the said compositions.

It has already been proposed (Japanese Application 80,445/80) to employ hydrotalcites as stabilizers for polyvinyl chloride (PVC). Stabilization by means of hydrotalcite by itself or combined with the usual metal salts, for example calcium stearate, results in a very mediocre heat stability (see European Patent 0,063,180).

It has also been proposed (European Patent Application 0,189,899) to stabilize synthetic resins containing halogens and/or acidic substances by means of solid solutions of hydrotalcites containing at least one divalent metal cation chosen from the group consisting of Mg, Ca, Sr and Ba, at least one second divalent metal cation chosen from the group consisting of Zn, Cd, Pb and Sn and a trivalent metal cation (Al, Bi, In, Sb, B, Ga or Ti and especially Al).

Furthermore, it has been proposed (US 2,669,548, US 3,001,970, GB 1,141,971, US 3,493,536, US 4,102,839, US 4,123,399 and US 4,123,400) to employ beta-diketones for PVC stabilization, by themselves or in combination with metal salts, for example zinc salts.

It has also been proposed (European Patent 0,063,180) to use a beta-diketone in combination with a hydrotalcite free from the second divalent metal cation referred to in the European Patent Application 0,189,899 referred to above (Zn, Cd, Pb and Sn) for the stabilization of polymers containing halogens.

It has also been proposed (Japanese Application 61113,635) to stabilize halogenated polymers by means of a composition comprising a hydrotalcite and a dihydropyridine.

It has also been proposed (US 4,267,083) to use a beta-diketone in combination with a dihydropyridine with the aim of stabilizing PVC.

In general, the various abovementioned stabilizing compositions result in an improvement in the heat stability of the halogenated polymer. However, experience shows that the retention of the colour stability with time is generally obtained to the detriment of the resistance of the polymer itself at the usual processing or conversion temperature, that is to say between 180 and 225°C.

The present invention provides stabilizing compositions for halogenated polymers, the said compositions comprising at least one stabilizer consisting of a metal salt of a carboxylic acid and being characterized in that they comprise: a) at least one beta-diketone b) at least one hydrotalcite comprising at least one divalent metal cation chosen from the group consisting of Mg, Ca, Sr and Ba, at least one metal cation chosen from the group consisting of Zn, Cd, Pb and Sn and at least one trivalent metal cation c) at least one dihydropyridine.

The beta-diketone is typically a product of formula: r2 - co - C(R1)2 - co - z -eco - C(RX)2 - CO - R2j-n (I) in which: - n is from 0 to 3; - Rx denotes H, a hydrocarbon radical containing up 15 to 18 carbon atoms, optionally substituted by one or more halogens or hydroxyl, alkoxy, ester, alkyl or alkoxycarbonylalkyl groups containing from 1 to 8 carbon atoms or -COR2; - R2 denotes H, OH, a hydrocarbon radical containing 20 up to 18 carbon atoms, unsubstituted or bearing at least one of the substituents referred to above for Rx with the exception of -COR2, such that if Z = R2 or if n is between 1 and 3, only one of the symbols R2 denotes H; - such that a radical Rx and a radical R2 or two 25 radicals R2 can together form a divalent alkylene radical; - Z is chosen from the group consisting of R2 and a polyvalent radical chosen from the group consisting of a direct bond between the CO groups, a radical R3, a radical F4 R3 - N - R3 - R3 «X - C X - R3 - orR5 where R3 is a polyvalent hydrocarbon radical containing up to 18 carbon atoms; R4 and R5 independently denote H or a hydrocarbon radical containing up to 18 carbon atoms, or together form a divalent alkylene radical; X denotes -0- or -Sm is equal to 0 or 1 Rg denotes H, a hydrocarbon radical containing up to 18 carbon atoms or R3.

The beta-diketones may be employed as such or in their enolic form and especially in the form of their metal enolates or organotin enolates.

The hydrotalcite is typically denoted by the formula: [(M!2+)yl (M22+)y2]1-X Mx3+(OH)2 Ax/2z- . W H20 (II) in which: -M32+ denotes at least one divalent metal cation chosen from the group consisting of Mg, Ca, Sr and Ba; - M22+ denotes at least one divalent metal cation chosen from the group consisting of Cd, Pb, Zn and Sn; - M3+ denotes a trivalent metal cation; - Az- denotes an anion of valency z; x, yl, y2 and w obey the relationships: < x < 0.5 < Yi o < y2 0.5 < yx + y2 < 1 < w < 2.

The dihydropyridine is typically denoted by the formula: ROOC COOR ί H CH.

(HI) in which the symbol R denotes a monovalent radical chosen from alkyl, alkenyl, cycloalkyl, aryl, alkylaryl and arylalkyl radicals containing up to 20 carbon atoms.

The preparation of each of the abovementioned constituents (beta-diketone, hydrotalcite, dihydropyridine and metal salt) is widely described in the literature and does not form part of the present invention.

In the formula I (beta-diketone), the symbols Rlr R2 and R3 denote more particularly alkyl radicals containing from 1 to 18 carbon atoms, cycloalkyl, cycloalkylalkylene or alkylcycloalkyl radicals containing from 5 to 18 carbon atoms or aryl, alkylaryl or aralkyl radicals containing from 6 to carbon atoms.

By way of illustration of the beta-diketones which can be employed in the compositions in accordance with the invention, there may be particularly mentioned 1,3cyclohexanedione, methylenebis-1,3-cyclohexane-dione, 2benzyl-1,3-cyclohexanedione, acetyltetralone, palmitoyltetralone, stearoyltetralone, benzoyltetra-lone, 2acetylcyclohexanone, 2-benzoylcyclohexanone, 2-acetyl-l,3cyclohexanedione, benzoyl-p-chlorobenzoyl-methane, bis(4methylbenzoyl) methane, bis (2-hydroxy-benzoyl) methane, benzoylacetone, tribenzoylmethane, diacetylbenzoylmethane, stearoylbenzoylmethane, palmitoylbenzoylmethane, lauroylbenzoylmethane, dibenzoylmethane, bis(4chlorobenzoyl) methane, bis(methylene-3,4dioxybenzoyl)methane, benzoylacetylphenylmethane, stearoyl(4methoxy-benzoyl)methane, butanoylacetone, distearoylmethane, acetylacetone, stearoylacetone, bis(cyclohexanoyl)-methane and dipivaloylmethane.

Among these beta-diketones, preference is given to stearoylbenzoylmethane, to benzoylacetone and to stearoylacetone.

Among the hydrotalcites of formula (II), preference is given to the products denoted by the said formula (II) with the following meanings for the various symbols: - Mx2+ denotes Mg or Ca or a combination of Mg with Ca, Sr or Ba, preferably Mg or Mg/Ca; - M22+ denotes Zn, Cd, Zn/Cd, preferably Zn; - M3+ denotes Al; - Az” denotes an anion of the valency z such as CO32”, OH”, HCO3, C104, an acetate (-), salicylate (-), citrate (3-), tartrate (2-), NO3, I”, HPO42”, COO 2-, COO [Fe(CN)6]4”, or SiO32” ion; preferably Az” denotes CO32” or OH”; - x, y1, y2 and w obey the following relationships: 0.2 < x < 0.5 and preferably 0.25 < x < 0.35, Yl > Y2 an^ 0 < w < 2.

One or more hydrotalcites of the formula: [(Mg2+ or Mg2+/Ca2+)y1 (Zn2+ and/or Cd2+)y2]1_x A1x3+ (OH)2 CO32” x/2 . w H2O is particularly employed, x, yl, y2 and w having the meanings given above.

Among the dihydropyridines of formula (III), those particularly employed are the products in which the symbols R denote an alkyl radical containing from 1 to 12 carbon atoms and especially methyl, ethyl or lauryl, an alkenyl radical containing up to 6 carbon atoms, a cyclohexyl radical or a phenyl radical.

Among these products, those to be mentioned particularly are diethyl and dilauryl 2,6-dimethyl-l,4dihydropyridine-3,5-dicarboxylates.

The metal salt is suitably derived from one of the following acids: 2-ethyl-hexanoic, lauric, myristic, palmitic, stearic, hydroxystearic, linoleic, behenic, isostearic, oleic, ricinoleic, caproic, heptanoic, n- or isooctylic, pelargonic, neotridecanoic, acrylic, linolenic, crotonic, acetoacetic, acetic, maleic, thiodipropionic and dithiopropionic. It is also possible to employ the partial esters of the ahovementioned dibasic acids with aliphatic, cycloaliphatic or aromatic alcohols. It is also possible to employ cyclic acids, such as benzoic, methylbenzoic, butylbenzoic, benzoylbenzoic, p-t-butylbenzoic, .phenylacetic, salicylic, naphthoic, abietic, phenylstearic, naphthenic, cinnamic or pyrrolidonecarboxylie acids. The metal salts of the said acids may be derived from, say, the following metals: Li, Na, K, Mg, Ca, Sr, Ba, Pb, Zn, Cd, Zr, Al, Si, Sn, Sb and Bi. The salts are preferably acetates, acetoacetates, stearates, oleates, laurates, palmitates, benzoates, hydroxystearates or 2-ethylhexanoates of calcium, barium, zinc and cadmium, optionally in the form of pairs such as Ca/Zn, Ba/Ca, Ca/Cd or Ba/Zn.

In the stabilizing compositions in accordance with the invention, the ahovementioned additives are advantageously employed in the following proportions (by weight): - 40 to 70 % of the metal salt of a carboxylic acid, - 5 to 20 % of beta-diketone - 5 to 20 % of hydrotalcite - 5 to 20 % of dihydropyridine (no account being taken of any additives to these constituents, which will be discussed further).

The invention also relates to the halogenated polymers stabilized by means of the composition described above.

Although the compositions can be employed for the stabilization of polymers containing halogens contributed by the catalyst system and/or treatment agents for the polymers, such as polyolefins obtained with Ziegler catalysts or posthalogenated and in particular postchlorinated polymers, for example postchlorinated polyolefins or rubbers, the compositions are particularly suitable for the stabilization of polymers originating at least partially from halogenated monomers. These may be, for example, fluoro polymers such as polyfluoroolefins, in particular polyfluoroethylenes or polyvinyl or polyvinylidene fluoride. The invention applies very particularly to the homopolymers and copolymers obtained from vinyl chloride. Among the copolymers there may be particularly mentioned the copolymers of vinyl chloride with at least one monomer chosen from the group consisting of vinylidene chloride, ethylene, acrylate or methacrylate esters, styrene, vinyl esters, maleic acid and anhydride and maleic esters. The invention is particularly useful for copolymers containing at least 50 %, and preferably at least 80 %, by weight of copolymerizeable vinyl chloride.

The vinyl chloride homopolymers may be prepared according to the techniques which are now known, namely in bulk, suspension or microsuspension or in dispersion.

The abovementioned homo- and copolymers may be rigid or flexible and, depending on the intended use, may include the usual additives such as impact improvers, pigments and/or fillers, plasticizers, antioxidants or light- or ultraviolet stabilizers.

The compositions may also contain additional stabilizers such as alkyl or aryl phosphites and/or epoxy compounds such as epoxidized soya oil and/or polyols, especially the compounds containing at least 2 and preferably at least 4 hydroxyl groups, such as D-xylitol, D-sorbitol, Dmannitol, diglycerol, 4-hydroxy-3,3,5,5tetrahydroxymethyltetrahydrofuran, trihydroxyethyl isocyanurate, polyvinyl alcohol, trimethylolpropane, tetramethylolcyclohexanol, quinic acid, adonitol, alphamethylglucoside or glycerol.

The compositions may also contain zinc salts, acrylic polymers, butadiene-based terpolymers, for example MBS resins, internal or external lubricants such as ester waxes, fatty acid esters, polyethylene waxes, oxidized or otherwise, hydrogenated castor oil, glycerol monooleate, montanate esters, magnesia or any other product complexing the water released by the hydrotalcite while giving a thermally stable product and having no negative influence on the stabilization of the polymer.

I - 12 The halogenated polymer compositions stabilized by means of the stabilizing compositions in accordance with the invention suitably contain up to 5 % of stabilizing composition relative to the weight of the halogenated polymer. They preferably contain 0.5 to 3 % of stabilizing composition.

When referred to its main constituents, a stabilized composition in accordance with the invention contains more particularly, per 100 parts of halogenated polymer (preferred values in brackets): - 0.01 to 5 parts of metal salt (0.1 to 2) - 0.005 to 2 parts of beta-diketone (0.01 to 1) - 0.005 to 2 parts of hydrotalcite (0.05 to 1) - 0.005 to 2 parts of dihydropyridine (0.01 . to 1) With the exception of plasticizers, which can in general be employed in proportions up to 100 % of the weight of the halogenated polymer, the various abovementioned additives may be employed in proportions from, say, 0.05 to 20 % of the weight of the said polymer.

The stabilizing composition in accordance with the invention may be prepared separately or, in most cases, be formed in the presence of all or some of the halogenated polymer and/or, if appropriate, of all or some of the additives which may have been employed. The usual methods for mixing the various ingredients may be employed. It is possible, in particular, to employ a turbo-mixer allowing a dry powder to be obtained at the end of the operation of mixing the ingredients with the polymer. In general, this mixing operation, and in particular when the turbo-mixer referred to above is employed, can be performed at a temperature up to, say, 80 to 120°C.

The stabilized composition can be processed using the usual techniques such as injection moulding, extrusion moulding or calendering.

The stabilizing compositions in accordance with the invention are characterized, in respect of the halogenated polymers stabilized by means of the said compositions, by a remarkable retention of colour (or colour absence) with time, coupled with the resistance of the polymer to thermal damage under the usual temperature conditions for processing the said polymer. It should be noted that this combination (change in colour, temperature resistance) is not observed either with the constituents a, b and c, alone or in pairs.

The following Example further illustrates the present invention.

EXAMPLE 1.- Constituents (in grams) - PVC (viscosity index 80 - NFT standard 51,013, prepared by polymerization in suspension in water) 100 - Methyl methacrylate/butadiene/styrene terpolymer (impact improver) 7.5 - Epoxidized soya oil - Zinc octanoate - Acrylic polymer (processing aid) - Hydrogenated castor oil - Polyethylene wax (lubricant) - Calcium stearate (Ca salt) - Stearoylbenzoylmethane (SBM) - Dihydropyridine * (DHP) - Hydrotalcite ** .5 0.09 0.5 1.8 0.6 ) see table * Dilauryl 2,6-dimethyl-l,4-dihydropyridine-3,5dicarboxylate ** of approximate formula: [(Mg2+)yl (Zn2+)y2]l-x Alx3+ (OH)2 CO2-3x/2 . w H20 with x = approximately 0.33, this hydrotalcite of average specific surface (BET) area of 9 m2/g is marketed by Kyowa Chemical Industry Co. under the name Alcamizer-4.2. 2.- Preparation of the samples The polymer and the liquid additives are then introduced into a turbo-mixer, a predispersion being made for 30 seconds at low speed (approximately 600 rev/min). The solid additives are then introduced to complete the mixture of the additives and of the polymer (with the exception of the stabilizing composition whose content will be determined independently for each mixture). The mixture is first of all heated until it reaches a maximum of 100°C, by means of a jacket and of rapid stirring (approximately 1800 rev/min).

The masterbatch is then cooled to reach 40°C at discharge.

Aliquot fractions are taken from the masterbatch produced with a view to the separate addition of the stabilizing compositions to be tested. The definitive mixtures, produced under conditions which are identical with the above (only the maximum temperature reached is 95eC) are then marked and isolated in the absence of moisture.

The processing of these dry blends depends on the evaluation test to be performed. 3.- Evaluations 3.1.- Measurement of the total blackening time of the mixture produced in the Emidecau press with 7 platens (400 mm x 400 mm) heated by circulating steam at 185°C The use of this test makes it necessary to work on samples which have been pregelled in an open mill and cut from the sheet produced on the mill.

Description of the production of test specimens The dry powder mix is introduced on to a 2-roll Lescuyer mill (700 mm x 300 mm), rotating at the speed of 8 m/min, without friction, and set to the temperature of 180'C ± 1°C, and it is then gelled for 5 min, measured from the introduction of the powder between the rolls. The sheet produced, with a thickness of exactly 1 mm, is cut with a cutter of circular shape, after the sample has cooled between two unpressurized aluminium plates.

Description of the test for measuring static heat stability Starting with the sample tablets thus produced, the series of samples is introduced at the same time into the 7platen press and samples are taken every 5 or 10 min, until the tablet has blackened completely; the time corresponding to this is noted in the table of results. 3.2.- Measurement of the dynamic change in the yellowness index (YI: ASTM D 1925-70) on film samples produced at 195°C on a Lescuyer mill 500 mm x 200 mm, with polished steel rolls Test procedure The dry powders of the corresponding mixtures are introduced into the Lescuyer mill, rotating at the speed of 8 m/min, without friction and set at the temperature of 195°C + 2°C. The gap between the rolls is adjusted to obtain a homogeneous film with a thickness of 1 mm from the 200 g initially introduced.

Every 4 min, from the introduction of the powder, chosen as zero time, samples are taken directly from the mill using a cutter of rectangular shape, and are then cooled between unpressurized aluminium plates. A measurement of the YI (Yellowness Index, a function of the elementary components L, a, b) is carried out at particular times representative of the conversion of PVC at this temperature, using a Hunterlab model D 25 M PC 2 colorimeter with a sighting orifice of 117 inch diameter.

The values, expressed in terms of YI, are noted below: 4. - Table of results Stability Ca DHP SBM Hydro- Dynamic stability Press at salt talcite 185’C Yl Yl (total 12 20 blackening time - min) 0.42 0.05 0.19 — 54.6 105.4 80 0.42 - 0.24 - 51.5 100.2 80 0.42 - 0.24 0.5 37.2 90.8 110 0.42 0.05 0.19 0.5 34.1 86.7 115 0.42 0.08 0.16 0.5 32 82.5 115 0.42 0.24 - 0.5 36 89 110 - 0.05 0.19 0.5 44.1 71.6 60 - - 0.24 0.5 49.5 80.6 60 - 0.24 - 0.5 47 83 60 0.42 - - - 110.7 137.2 80 0.42 - - 0.5 110.2 132.6 80 — __ 0.5 70.4 87.9 80 Comments The best results (colour/blackening time) are obtained with the composition based on the Ca salt/DHP/SBM/hydrotalcite mixture.

It should be noted that the mixtures based on DHP, employed by itself and in a high dosage (> 0.1 phr) result in a considerable fluorescence.

Claims (15)

1. To 8.

1. A composition suitable for stabilising a halogenated polymer, which comprises at least one metal salt of a carboxylic acid, at least one beta-diketone or an enol thereof, at least one hydrotalcite comprising at least one Mg, Ca, Sr or Ba cation, at least one Zn, Cd, Pb or Sn cation and at least one trivalent metal cation, and at least one dihydropyridine. 2. -ethylhexanoate of calcium, barium, zinc or cadmium.

2. A composition according to Claim 1, in which the metal salt is an acetate, acetoacetate, stearate, oleate, laurate, palmitate, benzoate, hydroxystearate or

3. A composition according to Claim 1 or 2, in which the beta-diketone is stearoyl-benzoylmethane, benzoylacetone or stearoylacetone. 4. , in which the dihydropyridine corresponds to the 7 formula: ROOC , tTy „ COOR b 3 0 V I ' ch 3 B in which R denotes an alkyl radical containing from 1 to 5 12 carbon atoms, an alkenyl radical containing up to 6 carbon atoms, a cyclohexyl radical or a phenyl radical.

4. A composition according to any one of Claims 1 to 3, in which the hydrotalcite corresponds to the formula: [(Mg 2+ or Mg 2+ /Ca 2+ )y1 (Zn 2+ and/or Cd 2+ )y2] 3 _ x A1 x 3+ (OH)2 CO 2+ 3x/ 2 . w H 2 0 in which: 0 < x < 0.5 0 < Yl 0 < y 2 0.5 < y x + y 2 < 1 0 < w < 2. 5. 11. A composition according to Claim 9 or 10 in which the halogenated polymer is a vinyl chloride homopolymer or copolymer.

5. A composition according to any one of Claims 1 to

6. A composition according to Claim 5, in which the dihydropyridine is diethyl 2,6-dimethyl-l,4dihydropyridine-3,5-dicarboxylate or dilauryl 2,βίο dimethyl-1,4-dihydropyridine-3,5-dicarboxylate.

7. A composition according to any one of Claims 1 to 6, which comprises (by weight): - 40 - 5 to 70 % of the metal salt, to 20 % of beta-diketone 15 - 5 to 20 % of hydrotalcite - 5 to 20 % of dihydropyridine.

8. A composition according to claim 1 substantially as described in any part of the Example.

9. A composition which comprises a halogenated 20 polymer and a composition as claimed in any one of Claims

10. 10 - 0.01 to 5 parts of the metal salt - 0.005 to 2 parts of beta-diketone - 0.005 to 2 parts of hydrotalcite - 0.005 to 2 parts of dihydropyridine 10. A composition according to Claim 9, in which the Ίί halogenated polymer contains halogens contributed by the polymerization catalyst system or by postpolymerization treatment, or derived from at least a part of the polymerized monomer.

11. , which comprises, per 100 parts of halogenated polymer:

12. A composition according to any one of Claims 9 to

13. A composition according to any one of Claims 9 to 15 12 which additionally contains at least one of an impact improver, pigment, filler, plasticizer, antioxidant or light- or ultraviolet stabilizer.

14. A composition according to claim 9 substantially as described in any part of the Example. 20

15. A shaped article originating wholly or partially from a composition as claimed in any one of Claims 1 to 14. Dated this the 25th day of September, 1989