DE2201517A1 - Rigid multilayer sheet structures - contg glue high barrier and rigid pvc or impact polystyrene layers - Google Patents

Abstract

Structures comprises 5 sheets, viz.: 1 barrier layer of a copolymer of vinylidene chloride and at least one other olefinically unsatd. monomer, 2 glue layers of a block copolymer of styrene and butadiene, and 2 outer layers of rigid PVC or medium- or high-impact polystyrene having ASTM D-790 flexural modulus >150,000 psi. contg. a natural or synthetic rubber-type additive. The glue layer copolymer is opt. blended with a copolymer of ethylene and vinyl acetate, ethylacrylate or isobutyacrylate or with a chlorinated polyethylene.

Description

"Rigid multilayer sheet structures" The invention relates to multilayer sheet structures for making rigid, more stable molded articles. The invention particularly relates to five-layer rigid sheets that form an inner barrier layer, layers of adhesive on both sides of the barrier layer and outer layers of rigid polyvinyl chloride or impact-resistant polystyrene, the outer layers having a flexural modulus according to ASTM regulation D-790 of at least 1.05 x104 kg / cm². The sheet materials advantageously have a total thickness of 0.13 to 2.5 mm, preferably one Total thickness from 0.18 to 2 mm.

For the production of the highly impact-resistant styrene polymers according to the invention Can be useful, unvulcanized or synthetic rubber that is used in moromerem Styrene is soluble or which is soluble in styrene, e.g. by grinding on mixing rollers can be made, and of at least one free olefinic bond for every two Recurring units contained in the rubber polymer molecule are used. the The basic unit means the group that makes up the rubber molecule, which is im Case of natural Rubber is the isoprene radical (C5H6) n, the has in combined form one olefinic bond per isoprene radical. In the case of synthetic Buna-S rubber (GRS rubber) is the basic unit of chemical residue contained in the rubber molecule, which is the conjugated olefin, e.g. butadiene, is equivalent to.

The outer layers can have a thickness of 0.06 to 1 mm, preferably have a thickness of 0.6 to 0.76 mm.

A wide variety of barrier materials can be used in accordance with the present invention Can be used as the middle layer of the foils For the production of barrier layers combinations of vinylidene chloride polymers and vinyl chloride polymers are particularly suitable saten, vinylidene fluoride polymers and extr'idbaren Ni conditions of these materials. It is essential that the material of the middle layer together with a shell another polymer can be extruded and that the composition the have the desired properties as a barrier layer for gas and moisture vapor. Particularly advantageous and inexpensive are extrudable compositions of vinylidene chloride polymers, in which the polymers contain at least about 70% by weight vinylidene chloride, the remainder of one or more olefinically unsaturated ones that are copolymerizable therewith Monomers consists. For economic reasons, vinylidene chloride are polymers used because they are easily available at a low cost.

It is advantageous to work with the extrusion of vinylide polymers small amounts of plasticizers and often heat stabilizers and light stabilizers a. Such additives are well known to those skilled in the art and generally are therefore an advantage, since the temperature required for extrusion is significantly reduced can be and the probability that a decomposition of the polymer in enters the extruder, is lowered. Typical plasticizers used for vinylidene combinations used are acetyl tributyl citrate, opoxidized soybean oil (found in Commercially available under the name Paraplex G-60), Dibutyls @ bacat and polymers Plasticizers like e.g. certain copolymers of ethylene and Vinyl acetate.

The barrier layer can have a thickness of 0.013-0.89 mm, advantageously have a thickness of 0.038 to 0.5 mm.

The adhesive layer can vary in thickness from 0.005 to 0.13 mm, although generally the preferred adhesive layer thickness is about 0.01 mm. Often the strength of the connection between the inner or the core layer decreases and the outer or surface layer slowly increases when the thickness of the adhesive layer is increased and generally there is little or no further improvement the bond strength after the thickness of the bond-making layer has reached a value of about 0.05 mm.

To increase the adhesion between the stiff; stable outer Layer and the inner barrier layer can be a variety of polymers and polymeric compositions can be used. Suitable polymers or polymers Compositions can be easily selected by looking at the bond strength the composition to be investigated on a two-layer extrudate produced examined. The bond strength of the two-layer laminate can be easily increased by usual Peel strength tests are determined.

Eleioxidants that can be used are copolymers of Ethylene and vinyl acetate, advantageously in proportions of 14 to 40% by weight Vinyl acetate with 86 to 60% by weight of ethylene, copolymers of ethylene with ethyl acrylate, advantageously ill proportions of 20 to 30 wt .-% ethyl acrylate with 80 to 70 wt .-% ethylene, copolymers of ethylene with isobutyl acrylate, advantageously in proportions of 20 to 30% by weight of isobutyl acrylate with 80 to 70% by weight of ethylene and chlorinated polyethylene, advantageously containing 15 to 40% by weight of chlorine. A particularly preferred adhesive is a styrene / butadiene block copolymer. Mixtures of styrene / butadiene block copolymers with ethylene / vinyl acetate, Ethylene / ethyl acrylate, ethylene / isobutyl acrylate copolymers or Chlorinated polyethylene are also preferred adhesives.

The sheets of the invention are ideal for manufacture of containers for a large number of products that are resistant to oxygen, Carbon dioxide or moisture are sensitive to products that are desirable to be retained, for products that come from the environment Can absorb unwanted odors or for products that contain highly volatile components may contain. Products advantageously made with the sheet material according to the invention are for example cheese, butter, steroids, various medicines and dried foods. The sheet material is preferably used for the production protective covers to protect medical tablets from the harmful effects of moisture, Protect oxygen and carbon dioxide.

The following examples are intended to explain the invention further, without however, to limit them.

Example 1 A five-layer film was made outer by coextrusion Layers of a medium-impact polystyrene with a flexural modulus of about 2.45 x 104 kg / cm2, which is about 3.5% by weight of a copolymer of 76.5% by weight butadiene and 23.5% by weight of styrene with a solution viscosity (5% in styrene at 250C) of 70 centipoise, 3.5 wt% mineral oil, 0.2 wt% di-tert-butyl p-cresol and the remainder consisted of styrene, a core layer, the 96 parts by weight of a copolymer of 85 wt .-% vinylidene chloride and 15 wt .-% vinyl chloride, 3 parts by weight-one Copolymer of 67 wt .-% ethylene and 33 wt .-% vinyl acetate with a melt index from 22 to 28 and a density of 0.957 g / ccm at 230C and one part by weight of tetrasodium pyrophosphate consisted of, and adhesive layers made of a styrene / butadiene block copolymer, which is commercially available under the designation Kraton 2104 / Dieäusseren Layers were 0.15 mm thick and the core layer was 0.15 mm thick 0.06 mm and the adhesive layer a thickness of 0.04 min.

Detachment or peel tests (peel adhesin tests) were carried out according to ASTN regulation D-903-49, with the difference that a crosshead inspection speed of 12.7 cm / min. was used. The 1800 detachment investigation was due to the impossibility peeling off the outer skin at an angle of 1800 is not satisfactory. As a result an outer layer was physically separated from the rest of the structure and the upper clamping device (jaws) of the Instron Tenside Tester clamped while the remaining part of the structure in the lower jaws of the examination device was clamped. In this way it was achieved that the unseparated part of the Sample was positioned in a direction of about 900 to the pulling direction. Detachment examinations were then performed using a jaw span of 5 cm. the Peel adhesion in kg / cm width ranged from 0.5 to 0.7 kg / cm. Even though the initial separation between the outer layer and the adhesive layer occurred, there was also a separation between the adhesive layer and the Core layer, indicating that the connection of the two interfaces is approximately was the same.

Example 2 The investigation described above was repeated with the difference is that the adhesive layers are a copolymer of 72 wt .-% ethylene and 28% by weight vinyl acetate having a melt index of 6.0. In this example the outer layers had a thickness of 0.1 mm, while the core layer was 0.048 mm and the adhesive layers were 0.02 mm thick. The peel adhesion in kg / cm width ranged from 0.12 to 0.14 kg / cm.

Example 3 The tests described above were repeated with the difference that the core layer was 0.04 mm thick and 93.75 parts by weight of a mixed polymer material made from 85% by weight of vinyl chloride with 15 Wt% vinyl chloride, 4.50 parts by weight cetyltributyl citrate, 1 part by weight one epoxidized soybean oil, commercially available under the name Paraplex G-60 is, eld C, 75 parts by weight of 4-tert.-butylsalol (4-tert.

Butyl phenyl salicylate), while the adhesive layers contained the Contained copolymer used in Example 2 and a thickness of 0.009 mm exhibited. The outer layers each consisted of a 0.07 mm thick layer a polyvinyl chloride modified with propylene, which is commercially available under the name "Airco 400" is available, and has a flexural modulus of about 3.3 x 104 kg / cm2. The moisture vapor transmission rate of this material was 0.138 in 24 hours g / 645 cm2, while the adhesion between the layers can be described as good.

Example 4 In a manner similar to that described above, coextrusion made a five-ply sheet, using the core barrier layer from the example 2 used copolymer and the adhesive layers that in Example 1 copolymer used contained. In this example, the core layer possessed a thickness of 0.04 mm while the adhesive layers were 0.009 mm thick. the The outer layers each contained a 0.07 mm thick layer of polyvinyl chloride with a flexural modulus of 3.3 x 104 kg / cm2. The speed of water vapor transmission this material was 0.14 g / 645 cm2 in 24 hours at atmospheric pressure and a relative humidity of 95%, while the adhesion between the layers was to be described as good.

Example 5 As described above, a five-layer sheet was made by coextrusion produced, the core barrier layer of the copolymer used in Example 2 existed, while the outer layers the polymer used in Example 4 contained and the adhesive layers a mixture of about 50 wt .-% of the in example 1 copolymer used and about 50 % By weight of the example 2 copolymer used contained. In this example the thickness was the core barrier layer 0.05 mm, while the adhesive layers 0.013 mm and the outer layers Layers were each 0.09 mm thick this material was for 24 hours at atmospheric pressure and relative Humidity of 95% about 0.09 g per 645 cm2. The adhesion between the layers could be described as good.

Claims (8)

P a t e n t a n s p r ü c h e 1. Rigid multilayer sheets made from an inner barrier layer and Adhesive layers on both sides of the barrier layer, characterized in that that they have outer layers of polyvinyl chloride or impact-resistant polystyrene, wherein the outer layers have a flexural modulus according to ASTfl regulation D-790 of have at least 1.05 x 1G4 kg / cm2. 2. Multi-layer sheets according to claim 1, characterized in that that the barrier layer contains a vinylidene chloride polymer. 3. multilayer sheets according to claim 2, characterized in that 'that the barrier layer is a copolymer of vinylidene chloride and one or more thus contains mischpoiymerisbaren olefinically unsaturated monomers. 4. multilayer sheets according to any one of claims 1 to 3, characterized characterized in that the adhesive layers are a styrene / butadiene block copolymer contain. 5. multilayer sheets according to claim 4, characterized in that that for the production of the adhesive layer £ n a mixture of an ethylene / vinyl acetate copolymer and a styrene / butadiene block copolymer is used. 6. Multi-layer sheets according to claim 4, characterized in that that for the production of the material layers a mixture of an ethylene / ethyl acrylate copolymer is used with a styrene / butadiene block copolymer. 7. multilayer sheets according to claim 4, characterized in that that for the production of the adhesive layers eire mixture of an ethylene / isobutyl acrylate copolymer is used with a styrene / butadiene block copolymer. 8. multilayer sheets according to claim 1, characterized in that that for the production of the adhesive layers a mixture of a polymer of chlorinated polyethylene is used with a styrene / butadiene block copolymer will.