Plastic materials for the production of deep-drawn films

Abstract

Plastic compositions for the production of deep-drawn films have the following composition:______________________________________ Parts By Weight______________________________________Polyvinyl chloride 35-40Acrylate rubber/PVC (1:1) 40-50Plasticizer 5-10Polystyrene/polyethylenebutylene 1-10block copolymerProcessing agent 4-5______________________________________The plastic film products from these materials have a high degree of strength and resistance to aging. Inhomogeneities and hard particles in the films are eliminated.

Description

A number of deep-drawn films based on polymer mixtures are known that use polyvinyl chloride (PVC). The properties of such films, however, are not satisfactory with respect to resistance to aging and strength, especially under thermal stress.

Plastic materials based on ethylene vinyl acetate (EVA) or polyethylene (PE) tend during deep drawing to form "flecks" (i.e. hard spots) or undissolved particles of higher molecular weights or cross-linked resin. Ethylene vinyl acetate cannot be brought to a fluid form, particularly with high content of vinyl acetate (about 70%).

The object of the present invention is to provide plastic materials that can be easily drawn into films, whose properties are improved, especially with regard to strength and resistance to aging. The invention permits the ingredients to be mixed efficiently and simply in a heated vessel, and subsequently calendered or extruded into films.

The plastic materials for achieving the objective of the invention have the following composition:

a) 55-65 parts by weight polyvinyl chloride; b) 50-60 parts by weight acrylate rubber; c) 1-10 parts by weight polystyrene/polyethylene-butylene block copolymer; d) 5-10 parts by weight plasticizer; and e) 4-5 parts by weight processing agents.

These plastic materials are characterized by improved workability, enhanced strength and improved resistance to aging.

In a preferred composition the polyvinyl chloride takes the following form and the acrylate rubber is incorporated in admixture with PVC as follows:

a) 35-40 parts by weight S-PVC dispersion resin with a K value of about 60; and b) 40-50 parts by weight of a mixture of acrylate rubber and PVC.

Preferably, the mixture ratio of acrylate rubber to PVC=1:1 in b) above.

S-PVC represents PVC that has been formed by suspension polymerization. That is, the monomer of mixture of monomers is dispersed by mechanical agitation in a second liquid phase in which both the monomer and polymer are essentially insoluble. The resulting polymers may be in the form of pearls, beads, soft spheres or irregular granules which are easily spearated when agitation is ceased.

The normally used processing agents are utilized preferably in the following composition:

a) 2 parts by weight SnS (stabilizer); b) 0.3 parts by weight partly oxidized polyethylene wax; c) 1 part by weight tris(hydroxyethyl) isocyanurate; d) 0.3 parts by weight tris(nonylphenyl) phosphite; and d) 0.3 parts by weight tris(nonylphenyl) phosphite; and e) 1 part by weight octadecyl 3-(3.5-4 hydroxyphenyl propionate).

One example of plastic materials that can be worked into films is given below.

A special advantage of the plastic materials according to the invention is that they can be transformed into purlable forms, which is not possible with ethylene vinyl acetate (e.g., the commercial product Levapren). This considerably facilitates the production of films.

TABLE I______________________________________ExampleIngredient______________________________________S-PVC dispersion resin with K value of about 60 35Epoxidized fatty acid ester plasticizer 5Acrylate rubber/PVC (1:1) 50Polystyrene/polyethylene-butylene 10block copolymerProcessing AgentsSnS stabilizer 2Partly oxidized polyethylene wax 0.3Tris(hydroxyethyl) isocyanurate 1Tris(nonylphenyl) phosphite 0.3Octadecyl 3-(3.5-4 hydroxyphenyl 1propionate)______________________________________ Acrylate rubbers are thermoplastic polymers consisting largely of one or more esters of acrylic acid such as ethyl acrylate and butyl acrylate. Since acrylate rubbers have no double bonds, they are very resistant to aging, heat, fatigue, oxygen, ozone, oil and ultraviolet light.

Other suitable plasticizers are trimellithate esters of aliphatic alcohols having 6 to 12 carbon atoms e.g., 2-ethylhexyl trimellithate.

From plastic materials in the example of Table I, strips were made and their elongation at break and permanent sets measured in the delivery state, as well as after a heat treatment and exposure to a xenon lamp. The results are given in Table II below.

TABLE II__________________________________________________________________________ Elongation Permenant At Break Set (%) Elongation Elongation After 500 Permanent After 500 At Break At Break hrs. xenon Set (%) hrs. xenon Delivery After 500 lamp test After 500 lamp test Condition hrs. 120.degree. exposure hrs. 120.degree. exposureExample Lengthwise Lengthwise Lengthwise Lengthwise Lengthwise__________________________________________________________________________1 x = 170 x = 160 x = 170 94 100 s = 10 n = 52 x = 180 x = 160 x = 170 89 94 s = 11 n = 53 x = 160 x = 170 x = 160 106 100 s = 3, 9 n = 54 x = 170 x = 170 x = 170 100 100 s = 5 n = 55 x = 190 x = 200 x = 170 105 89 s = 9 n = 5__________________________________________________________________________ x = average value s = variation n = number of samples

The permanent set is a characteristic indicative of the life or aging resistance of the plastic material. The permanent set after 500 hours 100.degree. C. should be above 50% and the permanent set after 500 hours xenon test exposure should be above 67%. The prior art plastic materials suitable for deep drawing do not reach these values.

The plastic materials according to the invention contain no plasticizing agent on the basis of ethylene vinyl acetate or olefin terpolymers. The films produced from the plastic materials of the invention have no inhomogeneities and no hard flecks or particles.

The plastic materials according to the above mentioned compositions are preferably produced as follows:

EXAMPLE

35 parts by weight S-PVC with a K value of about 60 are heated up to 120.degree. C. under stirring in a heating vessel and are mixed during further stirring with 5 parts by weight of 2-ethylhexyl trimellithate plasticizer, 2 parts by weight SnS stabilizer and 0.3 parts by weight tris(nonylphenyl) phosphite until a first homogenized mixture is obtained. Homogenization takes about 5 minutes. This first homogenized mixture is then cooled down to room temperature thus giving a purlable, sandy product which is a dryblend. Then there are added to this mixture in said heating vessel or in a mixer, the further ingredients of the recipe: 40 parts by weight acrylate rubber/PVC (1:1), 10 parts by weight polystyrene/polyethylene-butylene block copolymer, 0.3 parts by weight partly oxidized polyethylene wax, 1 part by weight tris(hydroxyethyl) isocyanurate, 0.3 parts by weight tris(nonylphenyl) phosphite and 1 part by weight octadecyl 3-(3.5-4 hydroxyphenyl propionate). Maintain stirring until there is obtained a second homogenized mixture. This second homogenized mixture then is treated by a well-known calendering process or extrusion process to provide a film.

In the example, S-PVC is used in the form of powder. The plasticizer, SnS stabilizer and tris(nonylphenyl) phosphite are added in form of a homogenized, liquid mixture. The further added ingredients of the recipe are added in form of a homogenized solid mixture. Mixing is continued until there is obtained a mixture with uniform distribution of the ingredients, i.e. complete homogenization.

Claims

1. A plastic composition for the production of deep-drawn films characterized by improved resistance to aging consisting essentially of:

a) 55-65 parts by weight of PVC;

b) 50-60 parts by weight of acrylate rubber;

c) 1-10 parts by weight of polystyrene/polyethylene-butylene block copolymer;

d) 5-10 parts by weight of a plasticizer; and

e) 4-5 parts by weight of a processing agent.

2. The composition of claim 1 in which the PVC and acrylate rubber are present in equal parts.

3. The composition of claim 1 in which the processing agent consists essentially of:

a) 2 parts by weight SnS;

b) 0.3 parts by weight partly oxidized polyethylene wax;

c) 1 part by weight tris(hydroxyethyl) isocyanurate;

d) 0.3 parts by weight tris(nonylphenyl) phosphite; and

e) 1 part by weight octadecyl 3-(3.5-4 hydroxyphenyl propionate).

4. The composition of claim 1 in which said plasticizer is an epoxydized fatty acid ester, or a trimellithate ester.

5. A plastic composition for the production of deep-drawn films having the following homogenized composition:

______________________________________ Parts by Weight______________________________________S-PVC dispersion resin with a 35-40K value of about 60Acrylate rubber/PVC mixture 40-50(1:1)Polystyrene/polyethylene- 1-10butylene block copolymerPlasticizer 5-10Processing agents 4-5______________________________________

6. A plastic composition for the production of deep-drawn films having the following composition:

______________________________________ Parts by Weight______________________________________S-PVC dispersion resin with K 35value of about 60Epoxidized fatty acid ester plasticizer 5Acrylate rubber/PVC (1:1) 50Polystyrene/polyethylene-butylene 10block copolymerProcessing AgentsSnS stabilizer 2Partly oxidized polyethylene wax 0.3Tris(hydroxyethyl) isocyanurate 1Tris(nonylphenyl) phosphite 0.3Octadecyl 3-(3.5-4 hydroxyphenyl 1propionate)______________________________________