WO1992013914A1 - Use of compounds of the hydrocalumite type as stabilisers for 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

Use of compounds of the hydrocalumite type as stabilizers for halogen-containing, thermoplastic resins

description

The present invention relates to the use of hydrocalumite-type compounds as stabilizers for halogen-containing thermoplastic resins.

Halogen-containing, thermoplastic resins and molded parts made from them are broken down or decomposed by exposure to heat and light. This degradation or decomposition process manifests itself through discoloration of the resin mass, whereby a change in properties (e.g. mechanical strength) can also be observed.

One tries to prevent these negative phenomena by incorporating stabilizers into the polymer. For this purpose, inorganic and / or organic compounds of metals are preferably used in combination with other organic substances. Such a conventional stabilizer is based, for example, on the use of zinc or cadmium salts in combination with metal salts from group Ha of the periodic table. In addition to these salts, organic and / or inorganic compounds of lead are also used to stabilize halogen-containing polymers.

Although satisfactory results in terms of resistance to the influence of light and heat can be achieved with these stabilizers, attempts have long been made to substitute the toxic compounds containing lead and cadmium. Physiologically acceptable stabilizers based on combinations of calcium and zinc carboxylates are ineffective in most areas of application. Higher thermal stability is essential, especially with regard to the recycling of thermoplastics, especially PVC. To ensure problem-free reprocessing, good color consistency must also be ensured during thermal stress.

A large number of compounds have been proposed as costabilizers. It is known from FR-A-2 403 362 to stabilize soft PVC for cable insulation with a mixture of calcium-zinc fatty acid salts, sorbitol and a, ^β- diketone. EP-A-0 292 672 proposes the use of esters of thioglycolic acid as a costabilizer for polymers of vinyl chloride. EP-A-0 063 180 describes the use of hydrotalcite and diketones as stabilizers for PVC moldings. Alkaline alumosilicates in conjunction with other costabilizers have also been proposed for stabilizing PVC (DE-A-31 13 442).

In DE-OS 38 43 581 a hydrotalcite of chemical composition is used for comparison purposes

Ca ₆ Al ₂ (OH) ₁₆ 0 ₃ .4H ₂ 0

used to stabilize PVC, it being shown that this hydrotalcite compound, which in addition to hydroxide ions also contains carbonate as an additional anion, does not achieve the desired stabilizing action. However, all stabilization systems for halogen-containing thermoplastic resin compositions that have been proposed so far have disadvantages. Most of the non-toxic stabilization systems do not achieve the required long-term stability, others cause insufficient initial color and color retention during dynamic or static thermal stress. Still others, which are only used in very special combinations, meet these requirements, but split off volatile components at the processing temperatures required for processing PVC, for example, which leads to the formation of bubbles in the molded part. It is also known that some of the proposed costabilizers absorb water again after shaping, which can lead to considerable problems in further processing.

The invention has for its object to achieve the stabilization of halogen-containing thermoplastic resins by means of compounds which do not have the disadvantages of the known stabilizers mentioned above, in particular are classified as non-toxic.

This object is achieved according to the invention by using compounds of the hydrocalumite type of the general formula

AlCa _χ (0H) _{2χ + 3} .mH ₂ 0

where x - = 1-4 m = 0-8

as stabilizers for halogen-containing, thermoplastic resins, in particular PVC. Preferred compounds are those in which x = 2 or 3 in the general formula.

When used, the compounds used according to the invention achieve both the desired long-term stability and adequate color retention during thermal exposure.

The hydrocalumite-type compounds used according to the invention are known compounds. For example, EP-A-0 278 535 describes the use of a hydrocalumite as part of a catalyst composition suitable for converting hydrocarbons. The preparation of compounds of the hydrocalumite type is also mentioned here.

Compounds of the hydrocalumite type which are suitable for the use according to the invention can also be prepared, for example, by means of a process in which mixtures of water-soluble calcium and aluminum salts are mixed with sodium hydroxide solution in an amount corresponding to the preparation of the desired compounds in an aqueous medium until a pH of about 10 is reached. This forms a suspension from which the reaction product is separated and recovered in a manner known per se, for example by filtering, washing and drying. In a preferred embodiment, the suspension is mixed with a known stabilizer coating agent, for example stearic acid, before it is separated off. This improves the dispersibility of the compounds used as stabilizers in the halogen-containing thermoplastic resins. The compounds used according to the invention can be combined with other known stabilizers for halogen-containing thermoplastic resin compositions. examples for this are

Polyols, such as polyhydric alcohols, especially trimethylolpropane, glycerol, pentaerythritol, polyvinyl alcohol and their di- or oligomers or also partial esters thereof;

Phosphites, such as alkyl or aryl esters of phosphorous acid, in particular triphenyl phosphite, diphenyldecyl phosphite, tridecyl phosphite or trisnonylphenyl phosphite,

β-diketones, e.g. Acetylacetone, dibenzoylmethane, stearoylbenzoylmethane, benzoylacetic acid, 2,2'-methylene-biscyclohexane-1,3-dione, palmitoyltetralone, bis- (3,4-methylendioxylbenzoyl) ethane, bis- (2-hydroxybenzoyl) ethane and / or their metal salts with, for example Ca, Zn or Mg;

Isocyanurates, e.g. Trish. .roxyethyl isocyanurate;

Dihydropyridines, e.g.

Dihydro-1,4-dimethyl-2,6-dicarbododecyloxy-3,5-pyridine;

Thioglycolic acid esters, e.g. 2-ethylhexylthioglycolate.

Together with the compounds used according to the invention, other additives can also be used, e.g. B. antioxidants, UV absorbers, such as benzophenones, benzotriazoles or sterically hindered amines (HALS), pigments, fillers and processing aids. The compounds used according to the invention are suitable for stabilizing both plasticizer-containing and plasticizer-free polymers. Substances usually used, such as, for example, di (2-ethylhexyl) 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 mixture can be used in powder form, as granules or as a melt product.

Thermoplastic halogen-containing resins are, in particular, polyvinyl chloride (PVC), polyvinylidene chloride, chlorinated polyethylene, chlorinated polypropylene and copolymers for the production of which vinyl chloride has been used, as well as mixtures of halogen-containing polymers with other poly esisites.

All types of PVC can be stabilized according to the invention; So it does not matter whether the polymer was made in suspension, dispersion, emulsion, bulk or in any other way. The homopolymer of vinyl chloride can also be chemically modified, e.g. by post-chlorination.

The numerous copolymers of vinyl chloride can also be protected against degradation by heat and light by the compounds used according to the invention. These are, in particular, the copolymers which are prepared by copolymerizing the vinyl chloride with other monomers which have a polymerizable ethylene bond, such as, for example, vinyl acetate or vinylidene chloride; Maleic or fumaric acid or its esters; Olefins, such as ethylene, Propylene, hexylene; Acrylic acid or methacrylic acid ester; Styrene, vinyl ethers such as vinyl dodecyl ether.

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

The compounds used according to the invention can be mixed with carboxylates and / or phenolates of non-toxic metals, e.g. Calcium, magnesium, strontium or zinc can be combined. The most common are the salts of these metals with maleic acid, acetic acid, hexanoic acid, ethyl 2-hexanoic acid, decanoic acid, lauric acid, mystic acid, palmitic acid, stearic acid, oleic acid, behenic acid, hydroxystearic acid, benzoic acid, salicylic acid. The phenolates of these metals can with phenol or substituted phenols, such as. Nonylphenol.

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

The following examples are intended to illustrate the invention:

A) Preparation of a compound of the hydrocalumite type

example 1

An aqueous solution (2.5 1), the 294 g CaCl_ * • __ .. 2H. Δ.0 (2 mol) and 141.5 g A1C1 ₃ .6H ₂ 0 (1 mol) is heated to 75 ° C, then a pH of 10 is adjusted with a 50% NaOH solution. The suspension formed is stirred for 2 hours at 35 ° C., then with 2 g of stearic acid added and then filtered off and washed. The filter cake is dried in a drying cabinet at 120 ° C. for 5 hours.

A compound of the formula AlCa ₂ (0H) ₇ .3H ₂ 0 is obtained as the reaction product, which has the following main reflections in the powder diffractogram:

In the examples below, the heat stability and the initial color of PVC moldings to which hydrocalumite-type compounds and, for comparison purposes, conventional lead stabilizers have been added have been evaluated.

To evaluate the heat stability, the PVC resin mass is homogenized and plasticized on a laboratory rolling mill for 5 minutes at 180 ° C. Square sample sheets with an edge length of 15 mm are cut from the approximately 1 mm thick skin. The sample sheets are annealed in a heating cabinet at 180 ° C. One sheet is removed every 10 minutes and attached to a test card in turn. This process is repeated until the test leaves are discolored black. Example 2

Parts by weight

B

PVC (K 68) 100 100 100 100

chalk

τio.

stearyl stearate

Tristridecyl phosphite

Bisphenol A

Pencil stearate

3 PbO.PbSO t, .0.5H -_, _ 0

Zinc stearate

Calcium stearate

Dibenzoylmethane

AlCa ₂ (OH) _? .3H ₂ 0

The above compositions from A to D were prepared and tested according to the indicated method. The results are summarized in Table I. Table I: Results of thermal stability evaluation

Time (min)

1 = white; 2 = pale yellow; 3 = yellow; 4 = gray; 5 = orange; 6 = brown; 7 = black

Example 3

Parts by weight

Ethylaminocrotonate

0.3 stearoylbenzene methane 0.1

The above compositions from E to I were prepared and tested according to the indicated method. The results are shown in Table II. Table II: Results of thermal stability evaluation

Time (min)

1 = white; 2 = pale yellow; 3 = yellow; 4 = orange; 5 = brown; 6 = black

Example 4

Parts by weight

PVC (K 70) 100 100

Diisodecyl phthalate 60 60

Chalk 30 30

Lead stearate 0.6

3 PbO.PbS0 ₄ 2.0

AlCa ₂ (0H) ₇ .3H ₂ 0 - 2.5

Zinc stearate - 0.3

Calciu stearate - 0.6

The above compositions of I and J were made and tested according to the indicated method. The results are shown in Table III.

Table III: Results of thermal stability evaluation

Time (min)

Composition - 0 10 20 30 40 60 80 100 120 150 200

I 1 1 1 1 2 2 2 2 3 3 4

J 1 1 1 1 1 2 2 3 3 4 -

I = white; 2 = yellow; 3 = brown; 4 = black

Claims

Claims 1. Use of compounds of the hydrocalumite type of the general formula AlCa _χ (0H) _{2χ + 3} .mH ₂ 0 where x = 1-4 = 0-8 as stabilizers for halogen-containing, thermoplastic resins, in particular PVC. 2. Use according to claim 1, wherein in the general formula x = 2 or 3. 3. Use according to claim 1 or 2, ^r .'obei the compounds in amounts of about 0.05 to 10 wt .-%, in particular from about 0.1 to 5 wt .-%, based on the resin, are employed.