IE920379A1 - Use of compounds of the hydrocalumite type as stabilizers¹for halogen-containing, thermoplastic resins - Google Patents

Abstract

The use of compounds of the hydrocalumite type of the general formula: AlCax(OH)2x+3.mH2O, in which x = 1-4 and m = 0-8, as stabilisers for halogen-containing thermoplastic resins, especially PVC.

Description

The present invention relates to the use of compounds of the hydrocalumite type as stabilizers for halogencontaining, thermoplastic resins.

Halogen-containing, thermoplastic resins and shaped articles produced therefrom are decomposed by the influence of heat and light. This decomposition process is manifested by a discolouring of the resin composition and a change in the properties (e.g. permissible mechanical working stress) can be observed.

It is attempted to prevent these negative phenomena by the incorporation of stabilizers into the polymer. Inorganic and/or organic compounds of metals in combination with other organic substances are preferably used for this purpose. Such a conventional stabilizer is e.g. based on the use of zinc and cadmium salts in combination with metal salts of Group Ila of the Periodic Table. In addition to these salts, organic and/or inorganic compounds of lead are also used for stabilizing halogen-containing polymers.

Although satisfactory results as regards the stability to the influence of light and heat can be achieved with these stabilizers, it has been attempted for a long time to substitute the toxic lead- and cadmium-containing compounds.

Physiologically safe stabilizers on the basis of combinations of calcium and zinc carboxylates are insufficient as regards their effectiveness in most fields of application. A higher thermostability is imperative above all in view of the recycling of - 2 thermoplasts, in particular PVC. In order to ensure an unproblematic processing of the regenerated material, a good colour constancy during thermal load must also be ensured.

A large number of compounds was suggested as co-stabilizers. It is known from FR-A- 2 403 362 to stabilize plasticized PVC for cable insulations with a mixture of calcium zinc fatty acid salts, sorbite and a β-diketone. The use of esters of thioglycolic acid as co-stabi lizer for polymers of vinyl chloride is suggested in EP-A- 0 292 672. EP-A- 0 063 180 describes the use of hydrotalcite and β-diketones as stabilizers for shaped PVC articles. Alkali alumosilicates in connection with other co-stabilizers were also suggested for stabilizing PVC (DE-A- 31 13 442).

A hydrotalcite of the chemical composition Ca6Al2(OH)16CO3.4H2O is used in DE-OS 38 43 581 to stabilize PVC for comparative purposes, it being shown that this hydrotalcite compound, which contains, in addition to hydroxide ions, carbonate as additional anion, does not achieve the desired stabilizer effect.

All stabilizing systems suggested so far for halogencontaining, thermoplastic resin compositions have, however, disadvantages. Most of the non-toxic stabilizing systems do not have the required long-term stability, others result in an insufficient initial colour and colour fastness during the dynamic or static thermal load. Others, which are only used in very specific combinations, certainly comply with these requirements, but split off volatile components at the - 3 processing temperatures necessary for the processing of e.g. PVC, which leads to bubble formation in the shaped article. It is furthermore known that some of the suggested co-stabilizers absorb again water after shaping, which can lead to considerable problems in the further processing.

The invention is based on the object of achieving the stabilizing of halogen-containing, thermoplastic resins by means of compounds which do not have the aforementioned disadvantages of the known stabilizers, and are in particular rated as non-toxic.

This object is attained according to the invention by the use of compounds of the hydrocalumite type of the general formula AlCax (OH) 2χ+3 · ΠΐΗ2θ wherein x = 1 - 4 m = 0 - 8 as stabilizers for halogen-containing, thermoplastic resins, in particular PVC.

Preferred compounds are such in which x = 2 or 3 in the general formula.

The compounds used according to the invention have both the desired long-term stability and a sufficient colour fastness during thermal load when used.

The compounds of the hydrocalumite type used according to the invention are compounds known per se. EP-A- 0 278 535 describes the use of a hydrocalumite as a - 4 component of a catalyst composition suited for converting hydrocarbons. The production of compounds of the hydrocalumite type is also mentioned there.

The compounds of the hydrocalumite type suited for the use according to the invention can e.g. also be produced by means of a process in which mixtures of water-soluble calcium and aluminum salts are mixed in an aqueous medium with a sodium hydroxide solution in amounts corresponding to the production of the desired compounds, until a pH value of about 10 is reached. A suspension is formed from which the reaction product is separated and recovered in a manner known per se, e.g. by means of filtration, washing and drying. In a preferred embodiment the suspension is mixed with a known stabilizer coating agent, e.g. stearic acid, prior to its separation. The dispersibility of the compounds used as stabilizers in the halogen-containing, thermoplastic resins is improved.

The compounds used according to the invention can be combined with other known stabilizers for halogen-containing, thermoplastic resin compositions. Examples of this are: Polyols such as polyvalent alcohols, in particular trimethylol propane, glycerol, pentaerithritol, polyvinyl alcohol and their dimers or oligomers or also partial esters thereof; Phosphites such as alkyl or aryl esters of phosphorous acid, in particular triphenyl phosphite, diphenyl decyl phosphite, tridecyl phosphite or trisnonyl phenyl phosphite. - 5 β-diketones, e.g. acetyl acetone, dibenzoyl methane, stearoyl benzoyl methane, benzoyl acetic acid, 2,21-methylene-bis-cyc+lohexane-1,3-dione, palmitoyl tetralone, bis-(3,4-methylene dioxyl benzoyl) methane, bis-(2-hydroxy benzoyl) methane and/or their metal salts with e.g. Ca, Zn or Mg; isocyanurates, e.g. trishydroxy ethyl isocyanurate; Dihydropyridines, e.g. dihydro-1,4-dimethyl-2,6-dicarbododecyloxy-3,5-pyridine; thioglycol acid ester such as 2-ethyl hexyl thioglycolate.

Further additives can also be used together with the compounds used according to the invention, e.g. antioxidants, UV absorbers such as benzophenones, benzotriazoles or sterically inhibited amines (HALS), pigments, fillers and processing adjuvants.

The compounds used according to the invention are suited for stabilizing both plasticized and unplasticized polymers. Customarily used substances such as di-(2-ethyl hexyl) phthalate can be used as plasticizers .

These additives and stabilizers can be added to the polymer individually or as mixtures of several components. The additive and stabilizer mixtures can be used in the form of powder, as granules or as fusion product.

Thermoplastic, halogen-containing resins are in particular polyvinyl chloride (PVC), polyvinylidene - 6 chloride, chlorinated polyethylene, chlorinated polypropylene and copolymers, for whose production vinyl chloride was used, and mixtures of halogen-containing polymers with other polymers.

All types of PVC can be stabilized according to the invention. Thus it is of no importance whether the polymer has been produced in suspension, dispersion, emulsion, mass or in another fashion. The homopolymer of vinyl chloride can also be chemically changed, e.g. by means of post-chlorination.

The numerous copolymers of vinyl chloride can likewise be protected against decomposition due to heat and light by the compounds used according to the invention. These are in particular the copolymers produced by copolymerization of vinyl chloride with other monomers which have a polymerizable ethylene bond such as vinyl acetate or vinylidene chloride; maleic or fumaric acid or their esters; olefins such as ethylene, propylene, hexylene; acrylic acid or methacrylic acid esters; styrene, vinyl ethers such as vinyl dodecyl ether.

The use according to the invention is effected preferably for PVC alone or its mixtures with other polymers.

The compounds used according to the invention can be combined with carboxylates and/or phenolates of nontoxic metals such as calcium, magnesium, strontium or zinc. The most customary ones are salts of these metals with maleic acid, acetic acid, hexanoic acid, ethyl2-hexanoic acid, decanoic acid, lauric acid, myristicic acid, palmitic acid, stearic acid, oleic acid, behenic acid, hydroxystearic acid, benzoic acid, salicylic - 7 acid. The phenolates of these metals can be produced with phenol or substituted phenols such as nonyl phenol.

These metal salts can be used in general in amounts between 0.05% and 10%, preferably between 0.1 and 5% by weight.

The subsequent examples are to explain the invention in greater detail: A) Production of a Compound of the Hydrocalumite Type Example 1 An aqueous solution (2.5 1) which contains 294 g of CaCl2.2H2O (2 mole) and 141.5 g A1C13.6H2O (1 mole) is heated to 75°C, subsequently a pH value of 10 is adjusted with a 50% NaOH solution. The formed suspension is stirred at 85°C for 2 hours, then it is mixed with 2 g stearic acid, and, subsequently, filtering off and washing is carried out. The filter cake is dried at 120°C in a dryer cabinet for 5 hours.

A compound of the formula AlCa2(OH)7.3H2O is obtained as reaction production, which has the following main reflexes in the powder diffractogram: d value intensity 85 very strong 90 mean 79 mean 87 strong 31 mean - 8 B) Use as Stabilizers The heat stability and the initial colour of shaped PVC bodies to which compounds of the hydrocalumite type were added and conventional lead stabilizers for comparative purposes are rated in the following examples.

The PVC resin composition is homogenized and plastified at 180°C for 5 minutes on a laboratory rolling mill to evaluate heat stability. Square sample sheets with an edge length of 15 mm are cut from the band being about 1 mm thick and produced in this fashion. These sample sheets are tempered in the drying oven at 180°C. At an interval of 10 minutes one sheet each is withdrawn and applied onto a test card. This process is repeated that often until the sample sheets have a black discolouring. - 9 Example 2 Parts by weight PVC (K 68) Chalk TiO2 Stearyl stearate Tristridecyl phosphite Bisphenol A Lead stearate 3 Pbo.PbSO4.0.5H2O Zinc stearate Calcium stearate Dibenzoyl methane AlCa2(OH)7.3H2O A 100 0.5 0.3 0.2 0.5 2.0 B 100 0.5 0.3 0.2 0.5 3.0 C 100 0.5 0.3 0.2 1.0 0.7 0.1 2.0 D 100 0.5 0.3 0.2 1.0 0.7 0.1 4.0 The aforementioned compositions of A to D were produced and tested in accordance with the indicated methods. The results are summarized in Table I.

Table I Results of the evaluation of thermal stability Time (min.) Composition 0 10 20 30 40 60 80 100 120 150 200 A 1 1 1 2 3 4 6 6 7 - B 1 1 1 1 1 2 3 4 6 6 7 C 1 1 2 2 2 3 5 6 7 - D 1 1 1 1 1 2 3 3 6 6 7 1 = white; 2 = slightly yellow ; 3 = yellow; 4 = grey; 5 = orange; 6 = brown ; 7 : = black - 11 Example 3 Parts by weight PVC (K 68) Impact strength additive Chalk TiO2 Distearyl stearate Bisphenol A Phenyl didecyl phosphite Zinc stearate Calcium stearate AlCa2(OH)7.3H2O Trimethylol propane Trishydroxyethyl isocyanurate Ethyl amino crotonate Stearoyl benzoyl methane E F D H I 100 100 100 100 100 10 10 10 10 10 5 5 5 5 5 4 4 4 4 4 0.5 0.5 0.5 0.5 0.5 0.2 0.2 0.2 0.2 0.2 0.3 0.3 0.3 0.3 0.3 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 2.5 2.5 2.5 2.5 2.5 - 0.5 - - - - - 0.5 - - - - - 0.3 - — — — 0.1 The aforementioned compositions of E to I were produced and tested in accordance with the indicated methods. The results are summarized in Table II.

Table II: Results of the evaluation of thermal stability Time (min.) Composition 0 10 20 30 40 60 80 100 120 150 E 1 1 1 2 3 3 5 5 6 - F 1 1 1 1 2 2 3 4 5 6 G 1 1 1 1 1 2 4 4 5 5 H 1 1 1 1 1 6 - - - - I 1 1 1 1 1 1 3 4 5 6 1 = white; 2 = slightly yellow; 3 = yellow; 4 = orange; 5 = brown; 6 = black Example 4 Parts by weight I J PVC (K 70) 100 100 Diisodecyl phthalate 60 60 Chalk 30 30 Lead stearate 0.6 - 3 PbO.PbSO4 2.0 - AlCa2(OH)7.3H2O - 2.5 Zinc stearate - 0.3 Calcium stearate — 0.6 The aforementioned compositions of I and produced and tested in accordance with the indicated methods. The results are summarized in Table III.

Table III: Results of the evaluation of thermal stabi lity Time (min.) Composition 0 10 20 30 40 60 80 100 120 150 200 I 1 1 1 12 2 2 2 3 3 4 J 1 1 1 112 2 3 3 4 1 = white; 2 = yellow; 3 = brown; 4 = black - 14 Barlocher GmbH Riesstr. 16 8000 Miinchen 50 Use of Compounds of the Hydrocalumite Type as Stabilizers for Halogen-Containing, Thermoplastic Resins

Claims (6)

Claims

1) Use of compounds of the hydrocalumite type of the general formula 1 AlCa x (OH)2x+3· wherein X = 1 - 4 m = 0 - 8 as stabilizers for halogen-containing, thermoplastic resins, in particular PVC.

2. Use according to claim 1, wherein x = 2 or 3 in the general formula.

3. Use according to claim 1 or 2, wherein the compounds are used in amounts of about 0.05 to 10% by weight, in particular of about 0.1 to 5% by weight, based on the resin. 15

4. Stabilizers for halogen-containing, thermoplastic resins comprising a compound of the formula I as defined in any of claims 1 or 2.

5. Stabilizers substantially as hereinbefore described by way of Example.

6. Use as claimed in any of claims 1 to 3 substantially as hereinbefore described by way of Example.