NO145798B - FOOD POLYMER MIXTURE BASED ON POLYVINYL CHLORIDE - Google Patents

Description

The invention relates to foamable polymer mixtures based on homopolymer of vinyl chloride which contain no or little plasticizer, common additives, as well as a

similar foaming agent and has improved foaming and processing properties.

Polymer foam based on vinyl chloride polymers containing

where little or no plasticizer is, among other things, known from German specification no. 2,047,969.

For their production, the starting point is vinyl chloride polymer mixtures, which, in addition to chemical and/or physical esemid-

clay may also contain one or more other excipients,

as stabilizer, processing aid, substances for improving impact resistance, lubricant, etc.

The processing of hard vinyl chloride polymers containing blowing agents, e.g. extrusion of them into profiles is unsatisfactory in several respects. The surface structure of the foam thus obtained is often defective and the foam cells are often of different sizes. The density of the foamed material is difficult to adjust and in many cases is higher than desired. Also, the dimensional stability at elevated temperature is generally too low, so that the foam after extrusion when passing through a calibration facility cannot be processed into an extrudate with constant or desired dimensions. Furthermore, processing aids and other additives are relatively expensive, so that it is desirable to keep the amount of such aids as small as possible.

In a foamable polymer mixture of the initially mentioned type

is according to the present invention incorporated per 100 parts by weight vinyl chloride polymer maximum 4 parts by weight polyethylene with a melt index of at least 0.10 dg/min. and a maximum of 2.1 dg/min. measured according to ASTM-D 1238.

The usable vinyl chloride polymers according to the invention

post-chlorinated vinyl chloride polymers can also be added. The vinyl chloride polymers used in the present invention

ter has a K-value according to Fikentscher of preferably 45-85

and especially from 50-75.

The vinyl chloride polymers can be produced on any

in and of itself known way, e.g. by suspension polymerization, emulsion polymerization or polymerization in the pulp.

Surprisingly, it turned out that by incorporating relatively small amounts of polyethylene, which corresponds to the aforementioned, into the vinyl chloride polymer mixture, vinyl chloride polymer mixtures are obtained, which can be processed into foam with a regular cell structure and a favorable, relatively low density. The dimensional stability of these foams at higher temperatures is such that the scurmies can be calibrated well and the extrudates, especially profiles, have a good appearance and smooth surface structure.

The density of the vinyl chloride polymer foam is strongly dependent on the type and quantity of the foaming agent used in the mixture. By using 0.2 to a maximum of 2 parts by weight of a chemical foaming agent, foam can be obtained with a density of approx. 0.4 to approx. 1.

By using relatively large amounts of blowing agent, it is true that foam can be obtained with a low density, but such mixtures are little or not suitable for the production of foamy extrudates such as profiles. The amount of foaming agent can be so large that the foaming proceeds rather violently, resulting in an irregular foam with non-uniform cells and a non-uniform surface. Therefore, according to the invention, a maximum of 1 part by weight of foaming agent is preferably used. Furthermore, an exact, mutual matching of the components is also necessary. One strives for: as little density as possible and as uniform a foam structure as possible. This last requirement limits the amount of spray agent that can be used. The exact amount of blowing agent depends on the used blowing agent. The amount of gas that must be developed by a specific weight amount of effervescent agent depends on, among other things, of the molecular weight. The rate of cleavage also plays a role. The person skilled in the art can easily determine the optimal amount experimentally.

Although the density of the accumulator structure is mainly determined by the amount of foaming agent, it nevertheless turns out that the density also

can be affected by certain additives. Thus, the addition of polyethylene can demonstrably cause a reduction in density.

The use of polyethylene with a melt index of more than

0.10 and a maximum of 2.1 also offer economic advantages in comparison with the hitherto common modifiers, such as for example ABS, MBS and MABS<+>^, which are considerably more expensive and which must be added in larger quantities to achieve - similar densities. In other respects too, the use of high-molecular polyethylene proves beneficial. As mentioned, the mixtures according to the invention can be processed into foamed extrudates such as profiles, which in addition to a favorable density have a regular cell structure and a good-looking, smooth surface.

The dimensional stability at higher temperatures is good, so that the mixtures according to the invention can be calibrated well after extrusion.

If desired, the properties can be further improved by including one or more common modifiers in the mixtures, such as post-chlorinated polyvinyl chloride, ABS, MBS, MABS or polymethyl methacrylate.

In the method according to the invention, the individual components can be in any form. Preferably, however, powdery substances are mixed. The powder mixture can be used as such or after prior granulation.

+ ) These are the common designations for plastic in practice

on the basis of acrylonitrile, butadiene and styrene; methyl methacrylate, butadiene and styrene; henh. methyl methacrylate, acrylonitrile, butadiene and styrene.

The emulsifier is used in quantities of approx. 0.1-2 parts by weight, preferably in amounts of 0.2-1.5 parts by weight, per 100 parts by weight of vinyl-chlorinated polymer. A wide variety of chemical foaming agents can be included in the mixture according to the invention. Suitable elution agents are nitrogen-releasing agents, such as azobisformamide, azodicarbonamide, azobisisobutyronitrile, diazoaminobenzene, p.p'-oxybis-(benzenesulfonylhydrazide), N,N'-dinitrosopentamethylenetetramine, p,p'-azobis(benzenesulfonylsemicarbonamide), diethylazoisobutyrate, 1,3-bis (xenyl)triazine and 4,4'-oxybis(benzenesulfonylhydrazide).

These emulsifiers are generally azo-, nitroso- or sulfonylhydrazine compounds.

Common activators, so-called initiators, based on lead, barium, cadmium or zinc salts etc. can be used. These activators generally lower the temperature, whereby the blowing agent emits gas.

Furthermore, the mixtures according to the invention can contain the usual lubricants and lubricant mixtures as well as other usual additives. Lubricants and lubricant mixtures up-

taken in quantities of approx. 0.5-5, preferably 1-4 parts by weight in the mixtures. Suitable lubricants acc. lubricant mixtures are e.g.

e.g. paraffin, polyethylene wax, calcium stearate, ethylene bis-stearylamide and other known lubricants.

Furthermore, finely dispersed inorganic fillers and/or pigments can be included in the mixtures according to the invention in quantities of

about. 1-15 parts by weight. Such fillers or pigments are e.g.

e.g. titanium dioxide, iron oxide, calcium carbonate or silicon dioxide.

Stabilizers such as e.g. common lead compounds, barium/cadmium and tin compounds in

there of 0.5-4 parts by weight in the mixtures.

According to the invention, either no plasticizers or solvents are used, or extremely small amounts of a maximum of 5% by weight.

The invention is further illustrated through the following examples.

EXAMPLE EL 1

The starting point is a polyvinyl chloride mixture in which a polyethylene is incorporated and which is then "processed into a foam structure.

The starting mixture consists of polyvinyl chloride with a K value

after Fikentscher on 59 and contains per 100 parts by weight polyvinyl chloride : 3.5 parts by weight of a barium/cadmium/lead stabilizer;

1.2 parts by weight of a combined lubricant, consisting of

of a technical mixture of higher fatty acids, their metal salts and esters of higher alcohols with the higher fatty acids;

0.5 parts by weight of azodicarbonamide;

5 parts by weight fine calcium carbonate5

2 parts by weight titanium dioxide.

A commercially available low-pressure polyethylene with a melt index of 0.11 is taken up in this starting mixture in amounts of 0.5, 1.0, 2.0, 5.0 respectively. 10.0 parts by weight per 100 parts by weight. The figure shows the densities of mixtures containing the polyethylene with a melt index of 0.11 and the density of the starting mixture. It turns out that at amounts of 4 parts by weight or less, a reduction in density occurs in comparison with the starting mixture. The mixtures according to the invention provide foam with regular cells and a neat surface structure.

EXAMPLE 2

In the starting mixture, 0.5, 1.0, 2.0, 5.0 are taken up respectively. 10.0 parts by weight of a low pressure polyethylene with a melt index of

2.1 dg/min. Small strips are extruded from this mixture, from which the density is determined.

The figure shows the densities of the mixtures with polyethylene with a melt index of 2.1 and the density of the starting mixture. When the starting mixture contains 4 or fewer parts by weight of polyethylene, it turns out that the density in comparison with the density of the starting material becomes smaller. The described mixtures produce foam with regular cells and a nice surface structure.

Claims (1)

Foamable polymer mixture based on homopolymer of vinyl chloride that contains little or no plasticizer, common additives, and a common foaming agent, characterized in that per 100 parts by weight of vinyl chloride polymer is incorporated a maximum of 4 parts by weight of polyethylene with a melt index of at least 0.1 dg/min. and a maximum of 2.1 dg/min., measured according to ASTM-D 1238.