NO146712B - HEAT STABILIZED VINYL CHLORIDE PLASTIC - Google Patents

Description

In Norwegian application no. 760069, heat-stabilized vinyl chloride plastics are described which resist yellowing and thermal degradation at high temperatures of up to 230°C. These plasters contain

a) 0.1-5% by weight of one or more such organic metal salts which are usually used for stabilizing vinyl chloride polymers and b) 0.05-5% by weight of one or more p-diketones with the general formula:

where the symbols and R, which may be the same or different, each denote a saturated or unsaturated aliphatic group, an aromatic group or a cycloaliphatic group, and the symbol R2 denotes a hydrogen atom or an alkyl or alkenyl

group, optionally containing carbonyl groups.

Reference should also be made to DAS 1569 407 which describes the use in polyvinyl chloride resins of stabilizing mixtures consisting of an ester or an anhydride dimer of ketoacetic acid and of an organic salt of an alkali metal or alkaline earth metal.

However, such stabilizing mixtures provide

not the best results, especially when it comes to resistance to yellowing during thermal treatment of polyvinyl chloride.

The present invention relates to heat-stabilized vinyl chloride plastic which contains as a stabilizer

a) 0.1-5% by weight of one or more organic metal salts of carboxylic acids, preferably calcium salt plus

a zinc salt or of a barium salt plus a cadmium salt, characterized in that the additional stabilizer contains

b) 0.05-5% by weight of one or more organic compounds with the general formula:

where denotes a straight or branched alkylene or alkenylene group containing up to 36 carbon atoms, an aralkylene group containing 7-36 carbon atoms, or an arylene or cycloalkylene group containing less than 14 carbon atoms, whereby the cycloaliphatic groups even

may contain carbon-carbon double bonds, whereby the above-mentioned groups are optionally substituted with halogen atoms, or in the case of the aryl groups and the cycloaliphatic groups, with methyl or ethyl groups, and where R2 denotes a straight or branched alkyl or alkenyl group containing up to 36 carbon atoms, an aralkyl group containing 7-36 carbon atoms, or an aryl group or cyclo-aliphatic group containing less than 14 carbon atoms, whereby the cycloaliphatic groups may optionally contain carbon-carbon double bonds, whereby the above-mentioned groups are optionally substituted with halogen atoms or,

in the case of the aryl group and the cycloaliphatic groups,

with methyl or ethyl groups.

The above-mentioned |J-diketones are usually prepared according to known synthesis methods. One can e.g.

refer to the work "Organic Reactions" by R. Adams, 1954,

volume VIII, page 59 et seq. Certain more particular syntheses are described in "Ree. Trav. Chem. Pays-Bas" by M.J. Kramers, 16 (1897), p. 116, in "J.ChemSoc." by G.T. Morgan and E. Holmes 127 (1925) p. 2891, in "J.Chem.Soc." by R. Robinson

and E. Seijo (1941) p. 582, and in "Chemische Bericht" by Claisen 20 (1887) p. 2188.

According to a common procedure, a

ester with a cyclanone or a p -tetralone in the presence of sodium, sodium amide, sodium hydride or sodium ethylate.

By vinyl chloride plastic is meant plastic containing a homopolymer or a copolymer of vinyl chloride plus various such additives which are usually used to facilitate the use of the plastic or to give the final articles special properties.

All types of homopolymers of vinyl chloride can be used, regardless of the limiting viscosity and regardless of the method of production, which may be by mass polymerisation, suspension polymerisation, emulsion polymerisation or in another way.

Many different types of copolymers of vinyl chloride can be made heat resistant in the same way as the homopolymers. The copolymers can e.g. be produced by copolymerization of vinyl chloride with other monomers containing a polymerizable ethylenic bond, such as ethylene, acrylic esters, styrene, vinyl esters, maleic acid or maleic anhydride, maleic acid esters, etc.

The copolymers usually contain at least 50% by weight of vinyl chloride. However, the invention is particularly suitable for stabilizing copolymers which contain at least 80% by weight of vinyl chloride and whose second monomer is vinyl acetate or vinylidene chloride.

• The homopolymers or copolymers can be

rigid or flexible. When rigid polymers are used, in addition to resin and stabilizers, these may also contain agents that modify the impact strength, pigment and/or filler, lubricant, etc. When flexible polymers are used, these may, in addition to resin and the stabilizer, also contain a plasticizer (primarily and/or secondary), pigment and/or filler, lubricant, etc.

Lubricants, antioxidants and agents that provide resistance to visible light and ultraviolet light can also be added to the plastics.

The organic metal salts used as stabilizers preferably consist of salts of calcium, barium, zinc, lead or cadmium with saturated or unsaturated aliphatic acids or fatty acids, optionally substituted such. Among these salts, acetates, diacetates, stearates, oleates, laurates, palmitates, benzoates, hydroxystearates and 2-ethyl hexanoates can be mentioned in particular.

The salts are usually used in the form of mix-

compounds of two salts, such as a calcium salt plus a zinc salt or a barium salt plus a cadmium salt. As mentioned, the salts are used in an amount of 0.1-5%, calculated on the weight of the polymer.

The organic compounds used according to the invention are used in an amount of 0.05-5%, preferably 0.1-1%, calculated on the weight of the polymer.

It is also possible to add other organic compounds known for their stabilizing effect to the stabilizers according to the invention, e.g. pentaerythritol or trihydroxyethyl isocyanurate.

The stabilizers used according to the invention can be added at the same time as the other additives. They can also be mixed together either alone or together with certain additives. This results in a stabilizing mixture which is later mixed with polyvinyl chloride. All commonly known methods can be used to mix the various components. However, the plastic according to the invention is suitably homogenised in a mixing mill.

The plastic according to the invention can be processed and shaped according to the methods usually used for plastics based on polymers or copolymers of vinyl chloride, e.g. injection molding, strand injection, strand injection, blow molding, calendering, rotational molding, etc.

The combination of an organic stabilizer and a pair of metallic stabilizers makes it possible to delay the yellowing of the plastic and to produce final products which are translucent and homogeneous and which do not show any sweating.

The invention shall be illustrated by the following examples.

Example 1

In a 1000 ml flask equipped with a central stirrer, a thermometer, a reflux condenser and an addition funnel, 100 g of technical methyl stearate which contains methyl palmitate as an impurity, 40.5 g of a 50% suspension are introduced of sodium hydride in oil and 40 0 cm 3 toluene. The contents of the flask are heated to 75-80°C and then 61 g of α-tetralone are added over the course of 2 hours and 45 minutes. The reaction mixture is kept at 85°C for 4 hours. It is then cooled and the whole is acidified by adding 230 g of a mixture of acetic acid, water and ice in a weight ratio of 80:50:100. At a temperature of 40°C, the toluene phase is separated from the water phase. The toluene phase is washed 3 times with 150 cm <3>tepid water. The toluene is then distilled off at atmospheric pressure. One obtains 160.9 g of a brown-coloured impure residue which melts at a temperature of approx. 60°C. This impure residue is purified by recrystallization from ethanol, whereby 60 g of a white powder with a melting point of approx. 52°C and which consists of stearol tetralone and palmitoyl tetraldn. By mass spectrography, 2 molecular peaks corresponding to the molecular weights 384 and 412 are obtained. With the help of the NMR spectrum, it is further confirmed that the product consists of the two p-diketones indicated above.

Example 2-6

A plastic A, which can especially be used for the production of bottles by string spraying and blowing, is produced by mixing the following substances in a ball mill:

1000 g of a PVC powder ("Lucovyl RS 8000")

with a viscosity index of 80 according to NF T 51013 and which is produced by suspension polymerization,

100 g of an agent for increasing the impact resistance, which consists of a copolymer of butadiene, styrene and methyl methacrylate, 10 g of a lubricant which is a wax based on a rosin master and is designated "Cire E",

10 g calcium stearate,

7 g zinc stearate

30 g of epoxy soybean oil

3 g of an aryl phosphite.

The resulting mixture is homogenized in a mixing roller mill for 15 hours.

In each of six mortars, each with a volume of 250 cm 3 and containing some porcelain balls, 56 g of the produced plastic A is added. No further addition is made to one of the mortars, but in the other five five different end products are produced by adding respectively: (B) 0.3 g of that in ex. 1 prepared stearoyltetralone, (C) 0.15 g of 2-acetyltetralone with a melting point of 56-57°C, prepared according to ex. 8 in US patent

No. 2,158,071,

(D) 0.10 g of liquid 2-acetylcyclohexanone with a boiling point of 110-115°C and prepared according to

*'J.Am:Chem.Soc." 67 (1945) p. 1510-1511,

(E) 0.15 g of 2-benzoylcyclohexanone with a m.p

at 88°C and prepared according to the method described by F.W. Swamer and C.H. Hauser in J.Am.Chem.Soc. 68(1946), p.2647,

(F) 0.15 g of 2-acetylcyclohexane-1,3-dione.

The plasters obtained are homogenised in a mixing rolling mill for 15 hours, whereby homogeneous plasters B, C, D,

E and F according to the invention as well as a comparative composition

A.

Sheets with a thickness of 2.5 mm are produced from these plasters using a calender heated to 180°C. Rectangular test pieces with dimensions 10 x 20 mm are cut away from the plates obtained, after which the test pieces were placed in a ventilated oven at 180°C for various lengths of time. The color of the samples is then determined according to Gardner's scale using a Lovibond comparison map. The results obtained are summarized in the following table.

From the test results, it appears that the test pieces containing organic stabilizer are colored much less during production and have a much greater heat resistance than the comparison test piece, which does not contain any ketone compound.

Claims (2)

1. Heat-stabilized vinyl chloride plastic containing as stabilizer a) 0.1-5% by weight of one or more metal salts of carboxylic acids, preferably of a calcium salt plus a zinc salt or of a barium salt plus a cadmium salt, characterized in that the additional stabilizer contains b ) 0.05-5% by weight of one or more cf -diketones with the general formula: where R-^ denotes a straight or branched alkylene or alkenylene group containing up to 36 carbon atoms, an aralkylene group containing 7-36 carbon atoms, or an arylene or cycloalkylene group containing less than 14 carbon atoms, whereby the cycloaliphatic groups may optionally contain carbon-carbon double bonds , whereby the above-mentioned groups are optionally substituted with halogen atoms or, in the case of the aryl groups and the cycloaliphatic groups, with methyl or ethyl groups, and where R 2 denotes a straight or branched alkyl or alkenyl group containing up to 36 carbon atoms, an aralkyl group containing 7-36 carbon atoms or an aryl group or cycloaliphatic group containing less than 14 carbon atoms , whereby the cycloaliphatic groups may optionally contain carbon-carbon double bonds, whereby the above-mentioned groups are optionally substituted with halogen atoms or, in the case of the aryl groups and the cycloaliphatic groups, with methyl or ethyl groups. 2. Vinyl chloride plastic according to claim 1, characterized in that component (b) consists of stearoyltetralone, palmitoyltetralone or acetyltetralone.