NO144970B - STABILIZED VINYL CHLORIDE PLASTIC AND STABILIZER FOR THIS - Google Patents

Description

The present invention relates to stabilizers for vinyl chloride plastic and vinyl chloride plastic containing such stabilizers.

Vinyl halide polymers break down and discolor quickly when they are exposed to high temperatures during processing and fabrication. This degradation and deterioration can be prevented or reduced by adding heat stabilizers to the polymer mixture. Among the most commonly used stabilizer systems for vinyl halide polymers are those containing oil-soluble salts of barium and cadmium or barium, cadmium

and zinc. However, there are certain disadvantages associated with its use

of such barium/cadmium stabilizers. Both barium and cadmium compounds are toxic and relatively expensive. They must be used in relatively large quantities to achieve the desired stabilization and such large quantities of these salts have an effect on the clarity of the vinyl halide mass and increase its viscosity, which is unfortunate when processing plastisols.

In addition, the cadmium salts are sensitive to sulfur and form sulphide spots. Zinc salts are less toxic than barium and cadmium salts, but when used alone they often cause the resin to darken and char within a very short time. Because of ongoing efforts to find substitutes for industrial chemicals known to be toxic, the barium/cadmium stabilizers should be replaced with equally effective stabilizers that contain less toxic substances and do not have the other disadvantages associated with barium /cadmium stabilizers.

According to the present invention, one has. found that vinyl chloride plasters with as good or better properties than comparable polymers containing barium/cadmium-zinc stabilizers can be produced when the stabilizer that is incorporated into the mixture consists of a mixture of low-toxicity metals combined with an organic phosphite.

The present invention thus relates to a stabilized vinyl chloride plastic which as stabilizer contains: a) 0.5 - 2%, calculated on the vinyl chloride resin, of a synergistically acting metal salt mixture, comprising a strontium salt and a zinc salt, these salts being chosen from among alkylphenol salts where the alkyl group has 4-12 C atoms, monocarboxylic acid salts with 6-12 C atoms and mixtures thereof, the strontium salt and the zinc salt together make up at least half the weight of the metal salt mixture, and the ratio between the strontium salt and the zinc salt is in the range 5: 7

and 7:5, and

b) a phosphite selected from triaryl phosphites, trialkyl phosphites and alkylaryl phosphites, wherein each alkyl group has

6-12 C atoms, and the aryl groups are chosen from the groups phenyl, hydroxylphenyl, halophenyl and alkylphenyl, the phosphite content being chosen so that it corresponds to 0.02 - 0.2%, calculated as phosphorus, of the vinyl chloride resin, and the invention is characterized by the metal salt mixture comprises 30 - 50% of a cerium salt and preferably also up to 20% of a tin (II) salt, these salts also being selected from the aforementioned alkylphenol and monocarboxylic acid salts.

The invention also relates to a stabilizer

for vinyl chloride plastics containing:

a) a metal salt mixture containing 25-35% by weight strontium salt and 25-35% by weight zinc salt, these salts being selected from the group of alkylphenol salts where the alkyl group has from 4-12 C atoms, monocarboxylic acid salts with from 6-12 C atoms and mixtures of these salts and b) an organic phosphite selected from the group of triaryl phosphites, trialkyl phosphites and alkylaryl phosphites where each alkyl group has from 6-12 C atoms, and the aryl groups are selected from the groups phenyl, hydroxyphenyl, halophenyl or alkylphenyl,

in that the phosphite content is chosen so that it corresponds to 1 - 40%, calculated as phosphorus, of the metal salt mixture (a), and this stabilizer is characterized by the fact that the metal salt mixture comprises 30 - 50% of a cerium salt and preferably also up to 20% of a tin(II) salt, these salts also being selected from the aforementioned alkylphenol and monocarboxylic acid salts.

The effect of the stabilizers in vinyl chloride polymers with filler and certain other mixtures is improved by adding to the metal salt component a stannous salt and a cerium salt. The metal salts can, as mentioned, be salts of alkylphenols where the alkyl groups have from 4-12 C atoms, salts of monocarboxylic acids with from 6-12 C atoms or mixtures of these salts. Alkylphenols from which the salts can be prepared are those with one or two straight-chain or branched substituents, such as e.g. n-butylphenol, tert-octylphenol, di-tert-butylphenyl, n-dodecylphenol and dinonylphenol. Monocarboxylic acids that can be used for the production of the sites include aromatic acids such as benzoic acid and t-butylbenzoic acid, aliphatic acids such as hexanoic acid, octanoic acid, decanoic acid, dodecanoic acid* 2-ethylbutanoic acid, 2-ethylhexanoic acid, isononanoic acid and 2-ethyldecanoic acid, cycloaliphatic acids such as cyclohexanoic acid, cycloheptanoic acid, cyclooctanoic acid and dimethylcycloheptanoic acid, and mixtures of these acids. It is preferred that the metal salt component. the stabilizers contain at least one salt of an alkylphenol and at least one salt of a monocarboxylic acid. ;The organic phosphites that can be used in the stabilizers include a large number of aliphatic and aromatic phosphites... Among them are trialkylphosphites, triarylphosphites and alkylarylphosphites. Examples of such phosphites are triphenylphosphite, tri(tert.-butylphenyl)phosphite,<:>tri(nonyl-phenyl)phosphite, triisooctylphosphite, tridecylphosphite, tri(di-propyleneglycol)phosphite, diphenylbutylphosphite, diphenyldecylphosphite, diphenylpropyleneglycolphosphite, dioctylphenylphosphite, di-( 2-ethylbutyl)phenylphosphite, di(p-tert-octylphenyl)2-ethylhexylphosphite, di(nonylphenyl)-2-chloroethylphosphite, di(3-chloropropyl)chlorophenylphosphite, didecylphenylphosphite and diisodecylpentaerythritol phosphite. The preferred phosphates are alkyl-aryl phosphates where the alkyl groups are straight-chain or branched groups with from 6-12 C atoms and the aryl groups are phenyl, hydroxyphenyl, halophenyl or alkylphenyl. Examples of preferred phosphites are diphenyldecyl phosphite and didecyl phosphite. In addition to the metal salt component and the organic phosphite, the stabilizers can contain an organic non-polar solvent such as petrol, toluene or mineral turpentine, a solubilizing agent such as tall oil fatty acids, a viscosity-regulating agent such as tripropylene glycol and other known additives. The term "vinyl chloride resins" in the present context includes polyvinyl chloride as well as copolymers such as e.g. is produced by polymerisation of a vinyl chloride with a com<p>nomer such as vinyl acetate, vinyl propionate, vinyl butyrate, vinylidene chloride, styrene, methyl methacrylate, dialkyl fumarate or maleate and the like. Copolymers suitable for carrying out the present invention are those prepared with at least 70% vinyl chloride and up to 30% comonomer. The invention can also be used for mixtures containing polyvinyl chloride in a predominant amount and a smaller amount of such other synthetic resins as chlorinated polyethylene, polyacrylate and polymethacrylate esters and copolymers of acrylonitrile. Furthermore, butadiene and styrene, as well as other thermoplastic resins where organic phosphites are usually used as stabilizers. All the usual plasticizers for vinyl chloride resins can be used in stabilized polymers according to the invention. These include e.g. di-2-ethylhexyl phthalate, dibutyl sebacate, tricresyl phosphate and octyl diphenyl phosphate. Softener - is usually added in a quantity of approx. 5 parts to 100 parts per 100 parts resin. Heat and light stabilizers, pigments, dyes, fillers, thickening agents and the like can also be added to the polymer mass in quantities that are usually used for such purposes. : One only needs to add a small amount of stabilizer to the vinyl chloride polymer mixture according to the invention. As little as 1% stabilizer based on the weight of the polymer blend will produce a considerable improvement in heat and light stability. About. 10% or more stabilizer can be used, but such large amounts will not usually result in any further improvement in properties -and are therefore usually not used.. Although the amount of stabilizer which will give "the best heat stability and resistance to inhomogeneity depends on factors such as the choice of the stabilizer component and the choice of vinyl chloride resin, in most cases add 2 - 4* stabilizer based on the weight of v i ny lk 1 or id v.vro suitable. Vinyl chloride resins containing stabilizer of the present type may be prepared in any suitable manner. It is generally preferred to mix the stabilizer or individual stabilizer components with the vinyl chloride resin at room temperature and knead or roll the composition on a double roll at between 145 and 120 5° C for a sufficiently long time for a homogeneous plate to form."' The softener and other ingredients can be incorporated together with the stabilizer. The stabilized composition can be removed from the roll in the form of a film or sheet of the desired thickness, which can be used as such or polished or punched out.

In the following, the invention will be illustrated with examples where all quantities are on a weight basis and all percentages are likewise on a weight basis.

Example 1

A series. stabilizers IA, IB and 1C of metal salt-organic phosphite are prepared for comparison purposes by mixing the ingredients listed in Table I. Each stabilizer is in the form of a clear and stable liquid. Thus, a common barium-cadmium salt stabilizer and a barium-zinc salt stabilizer, as well as a strontium-zinc salt stabilizer, were produced. Furthermore, a stabilizer ID according to the invention was cremstilted.

Example IA

A series of metal salt-organic phosphite stabilizers were prepared by mixing together the components listed in Table IA. Each of the stabilizers was a clear and stable liquid.

Example 2

To 100 parts of polyvinyl chloride ("Tenneco PVC 225") was added 40 parts of dioctyl phthalate, 5 parts of epoxidized soybean oil, 0.3 parts of stearic acid and 3 parts of one of the stabilizers described in Table I. The resulting mixture was stirred at room temperature and fed on a double roll mill at steam heating and differential roll speed where the surface temperature was maintained at 175°C. The mixture was rolled for 5 minutes and taken off the rolls as a sheet of thickness 1.15 mm.

The oven stability of the polymer compositions was measured by placing 2.5 x 2.5 cm samples cut from the rolled sheets in a shaker oven at 190°C and removing the samples at intervals until degradation and discoloration were complete as judged by the color change.

Heat stability values for the polyvinyl chloride polymer compositions appear in Table II. In this table, the following numerical scale is used to indicate the colors of the samples:

1 colorless, 2-4 light yellow, 5-7 yellow, 8-9 dark yellow and 10 black.

Example 2A

To 100 parts of polyvinyl chloride "Tenneco PVC 225" was added 45 parts of dioctyl phthalate, 5 parts of epoxide soya bean oil, 0.3 parts of stearic acid, 20 parts of calcium carbonate, 2 parts of titanium dioxide and 3 parts of one of the stabilizers described in Table I. The mixture was stirred at room temperature and charged to a steam-heated differential-speed double-roll mill, the surface temperature of which was maintained at 175°C. The mixture was rolled for 5 minutes and taken off the rolls as a sheet of thickness 1.15 mm.

The temperature stability of the polymer mixtures, measured as described in example 2, appears from table IIA below. In this table, the following number scale is used to indicate the color of the samples: 1 white, 2-4 light yellow, 5-7 light brown, 8-9 dark brown, 10 black.

Example 2B

To 100 parts polyvinyl chloride "Tenneco PVC .225" was added 45 parts dioctyl phthalate, 5 parts epoxidized soybean oil, 0.3 parts stearic acid, 20 parts calcium carbonate, 2 parts titanium dioxide and 3 parts stabilizer according to Table I. The mixture was stirred at room temperature and placed on a steam-heated differential roller mill with a surface temperature of 193°C. The mixture was rolled until degradation was complete, as judged by color. The values for dynamic thermal stability are shown in table IIB. continued, Table IIB

Example 2C

To 100 parts polyvinyl chloride "Tenneco PVC 225"

40 parts of dioctyl phthalate, 5 parts of epoxidized soybean oil, 0.3 parts of stearic acid and 3 parts of one of the stabilizers described in Table IA were added. The resulting mixture was mixed at ambient temperature and then added to a two-roll, steam-heated, differential speed mill, the surface temperature of which was maintained at 175°C. The mixture was milled for 5 minutes and then removed from the rollers as a sheet with a thickness of 1.14 mm. "

The assessments with a view to oven heat stability

for the preparations, was determined by placing samples with dimensions 2.5 cm x 2.5 cm, which were cut from the painted sheets, in an oven with forced air circulation above 190°C, and by take samples periodically until decomposition was complete, judged by color change.

The heat stability ratings for the polyvinyl chloride compositions are given in Table IIC. In this table, the following numerical scale was used to indicate the colors of the samples: 1 colourless, 2-4 light yellow, 5-7 yellow, 8-9 dark yellow, 10 black.

From the data given in table IIC, it will appear that the 4-metal stabilizers are considerably more effective than stabilizer IA which contains two metals, or stabilizer IB.

These improvements clearly demonstrate the technical progress achieved according to the invention.

Claims (2)

1. Stabilized vinyl chloride plastic containing as stabilizer: a) 0.5 - 2%, calculated on the vinyl chloride resin, of a synergistically acting metal salt mixture, comprising a strontium salt and a zinc salt, these salts being selected from among alkylphenol salts where the alkyl group has 4-12 C atoms, monocarboxylic acid salts with 6-12 C atoms and mixtures thereof, the strontium salt and the zinc salt together making up at least half the weight of the metal salt mixture, and the ratio between the strontium salt and the zinc salt being in the range of 5:7 and 7: 5, and b) a phosphite selected from triarylphosphites, trialkylphosphites and alkylarylphosphites, where each alkyl group has 6 - 12 C atoms, and the aryl groups are selected from the groups phenyl, hydroxyphenyl, halophenyl and alkylphenyl, the phosphite content being selected so that it corresponds to 0.02 - 0.2%,. calculated as phosphorus, of the vinyl chloride resin, characterized in that the metal salt mixture comprises 30 - .50% of a cerium salt and preferably also up to 20% of a tin (II) salt, these salts also being selected from among the aforementioned alkylphenolic and monocarboxylic acids - salts. 2. Stabilizer for vinyl chloride plastic containing: a) a metal salt mixture containing 25 - 35% by weight strontium salt and 25 - 35% by weight zinc salt, these salts being selected from the group of alkylphenol salts where the alkyl group has from 4 - 12 C atoms, monocarboxylic acid salts with from 6-12 C atoms and mixtures of these salts and b) an organic phosphite selected from the group of triaryl phosphites, trialkyl phosphites and alkylaryl phosphites where each alkyl group has from 6 to 12 C atoms, and the aryl groups are selected from the groups phenyl, hydroxyphenyl, halophenyl or.alkylphenyl, the phosphite content being chosen so that it corresponds to 1 - 40%, calculated as phosphorus, of the metal salt mixture (a), characterized in that the metal salt mixture comprises 30 - 50% of a cerium salt and preferably also up to 20% of a tin(II) salt, these salts also being selected from the aforementioned alkylphenol and monocarboxylic acid salts.