DE3814699C1 - Plastic containers for liquids or gases - Google Patents

Abstract

The invention relates to plastic containers for liquids or gases which are characterised in that they have a seamless inner layer of modified PPO or PP and a subsequent glass-fibre layer laid on geodetic lines and provided in areas or throughout with reaction-curable resins or thermoplastics, and optionally an outer coating of reaction-curable resins or thermoplastics.

Description

The invention relates to plastic containers for liquids or gases.

Composite plastics, i.e. laminates made of different Plastics are already known and have been on many Areas as a replacement for the usual materials. However, it is not yet possible to do this Composite plastics or sandwich materials for to use all areas of application because either their mechanical properties or other special features Use instead of metal or ceramic materials not made possible. These areas of application include Example the manufacture of water reservoirs, in particular the so-called thermal bath or storage for other aqueous Liquids that are still largely used today are made of enamelled steel. Enameled steel storage but are extremely susceptible to corrosion due to hairline cracks in the enamel layer and form the devices Temperatures around 60 ° C or above then relative quickly become subject to considerable corrosion. According to experience keep such steel water tanks only for an operating time of about 2-3 years and then have to due to corrosion damage. But it is already known for example from DE-OS 33 42 386 that one use plastic ones instead of steel ones can, this memory from an inner layer made of modified PPO and an outer layer made of glass fiber reinforced Polyester resin exist. The glass fiber reinforced Polyester resins contain about a glass fiber content of 25-30 and in special cases around 60-80%. Practical Tests have shown that such storage containers have a much longer lifespan than metal storage  and partly without any signs of corrosion up to Can be used for 10 years. This is all the more surprising it is known per se that polyphenylene oxide, abbreviated PPO, only a very small one Has water absorption capacity, but on the other hand at higher ones Oxidative degradation can be determined at temperatures. In spite of the normal temperature in the storage tanks has increased but shown that PPO in the modified form as an inner liner excellent resistance to oxidation and has hydrolysis.

In endurance tests with those described in DE-OS 33 42 386 Plastic containers as hot water storage has, however found that surprisingly after a long time Use embrittlement of PPO inner lining detectable was that when the container was vibrated or vibration, like they already do caused by traffic on busy streets Hairline cracks and thus to the permeability of the memory can lead. Only through extensive investigations could found that the cause of this is the styrene content is not only available on the market have styrene-modified polyester resins, but that also practically all other polyester resins specified their chemical components have nothing to do with styrene could, as a rule, contain monomeric styrene, and as a proportion of the solvent of the unsaturated resins. Only after these findings could further investigations be carried out be found that the monomeric styrene Argents is that the PPO becomes brittle. Not that one polymerized styrene engages in the outer laminate layer the liner made of PPO and thus leads to impairment its mechanical properties.  

The invention is therefore based on the object of plastic containers of the kind described that the not have known disadvantages.

Plastic containers for liquids are used to solve the problem or gases with an inner layer made of modified PPO or proposed from PP, which is characterized are that on the seamless inner layer one at approximately layer of glass fiber laid with geodetic lines from thermoplastics or reactive resins without one Content of monomeric styrene takes place or that the seamless Inner layer is wrapped with pure glass fiber, the outermost layers spaced from the inner layer hardenable reactive resins or thermoplastics are provided.

Surprisingly, it turned out that it is not necessary, the liner through a relatively thick layer hardened polyester resins with glass fibers distributed in them to protect mechanically, but that you can only use the liner Can wrap around glass fibers in a certain way to achieve sufficient compressive and tensile loads. Indeed must have a winding with only glass fibers in any Be fixed way and for this purpose it is provided that either thinly use the glass fibers used for winding Thermoplastics or reactive resins coated, this The casing is of course free of monomeric styrene must be, or by first applying a glass fiber winding and only the last or the last winding layers in coated form or the outer layer of the winding impregnated with reactive resins, in which case the latter even the commercially available reactive resins can be used can, which contain monomeric styrene. The experience has  demonstrated that migration of the monomer is sufficient To prevent styrene when between the liner and the outer polyester layer an intermediate layer of pure Glass fiber is present. This latter embodiment is currently preferred because reactive resins without the addition of styrene are practically not commercially available and therefore with thermoplastics coated glass fibers are relatively expensive, so that the use of which is only considered in exceptional cases.

The production of the plastic container according to the invention done by the liner made of modified PPO, which is used for Example under the trade name "Noryl" from General Electric is on sale in a manner known per se Extrusion blow molding is generated. The seamless liner will then be after attaching the flanges, connections etc. which are not must be glued or welded, as a core in the winding process used. Rotationally symmetrical shaped bodies such as the containers in question here, but also more complicated Shaped bodies are made in a known manner with planetary winding machines with three-dimensional numerically controlled Thread winding wound. From DE-OS 24 23 497 are already fiber-reinforced hollow body known in the winding process are produced, but with this winding process the longitudinal windings at the acute winding angle to the longitudinal axis of the mandrel mandatory alternating with circumferential windings with a Winding angle of approximately 90 ° to the longitudinal axis of the mandrel. According to the invention surrendered it is essential that the glass fibers on Approximately geodesic lines can be laid to each point of the  Tension and bending strength as uniform as possible to reach. Geodesic lines are lines that disappear Curvature on a surface in three dimensions euclidean space. They are surface curves

c (t) = [ fo u ] (t)

an area f :

UR ³ (U R ², u (t) = ( u ¹ (t) , u ² (t))

which are characterized by the following properties:
C (t) is a curve of vanishing geodetic curvature. U (t) satisfies the differential equations for geodetic lines:

Ü ^k (t) +Σ  ⁱ(t)^j(t)Γ ÿ ^kou (t) = 0,

and Γ ÿ ^{k are} the IJ Christoffel symbols 2. Type of classical area theory.

The location of the geodetic line is of course determined according to the shape of the respective body and must accordingly be calculated and programmed. For better fixation of the Fibers can be placed over the liner or as a finish to the glass fiber layer a cross winding can be attached. The strength of the so wrapped Glass fiber jacket depends on the expected Pressure load; with pressureless containers is usually sufficient a single-layer glass fiber layer, while each with pressure vessels according to the legal requirements with a thickness of the glass fiber layer must be expected, which is about 2 to 10 times in compressive and flexural strength than the expected Maximum pressure. For hot water storage is usually done by one Safety quotient starting from 5 times the maximum pressure.

The final fixation of the glass fiber jacket is open of two types possible, for example the fiber strands in the winding process in a continuous bath with resin or thermoplastic soaked and then under tension on the rotating molded body to be wound. For example, this is always possible when using reactive resins that are used in the so-called premixes do not contain styrene. If you have the  Wants to fix with unsaturated polyester resins, first a layer of glass fiber is wound without the addition of resin and it is only in the second layer that the fiber rods are impregnated with resin. In this way it is avoided that in the Premix existing monomeric styrene in contact with the liner can come from PPO or PP and cause embrittlement leads. As reaction resins, for example, besides the unsaturated ones Polyesters, epoxy resins, reactive PMMA resins or Isocyanate resins are used. The processing takes place in a manner known per se with the addition of catalysts and accelerators. If desired, the outer Fiber layer also suitable for the production of foam Reaction resins are soaked, so that a Foaming of these resins by irradiation or temperature increase can be done. The outer layer of the fiber jacket, which serves to fix the fibers, for example, from Modified PPO foam consist if made of certain Reasons for example against increased stability thermal and hydrolytic stress is desired. Fixation is also possible with thermoplastics by either the fibers in the bath soaked with heated thermoplastics or finally applied to the fiber layer.

The plastic container according to the invention can be used as a store for aqueous or non-aqueous liquids or for gases, in particular for moist gases, since they are particularly suitable as pressure vessels and at appropriate design of the glass fiber jacket press up to Can withstand 100 bar. Because of the chemical inertness and thermal and hydrolytic stability are the Containers can be used especially for such purposes, in the long term with thermal stress under pressure can be expected from aqueous solutions, for example for water reservoirs and especially the so-called Thermal baths. Experiments carried out so far have clearly shown that each through the special structure of the composite plastic  Embrittlement of the liner is avoided and that in this way Water reservoirs can be manufactured that are subject to permanent stress in the test withstand a normal load in Corresponds to household or industry of well over 10 years.

The invention will be described in more detail below with reference to the drawings explains:

Fig. 1 shows a heating water tank according to the invention in plan view.

Fig. 2 shows schematically a cross section through the storage wall in a preferred embodiment.

The memory 1 consists of the invisible liner and a glass fiber layer 3 , which is provided on the surface with a layer of reaction resin. The container is equipped b at both ends with flange 2 a, 2, which are not separately fastened, but are connected by the winding of the glass fiber with the Linder. The winding takes place in approximately geodesic lines, which also cause the beads 4 a and 4 b on the shoulders of the container. This winding is followed by a cross winding, which can be seen on the outer surface.

In a preferred embodiment, the wall of the Container made of a PPO or PP inner layer, the liner, which is followed by a glass fiber layer, the conclusion of again forms a layer of reactive resin on the outside.  

example

In a thermal bath with a container size of 100 l a corresponding seamless liner made from modified PPO with a wall thickness of 2 mm produced by extrusion blowing. The method is preferably carried out in such a way that that the flange rings and the closed shape become extruded and then outside the molded part the hose squeezed. This allows you to simultaneously Backsteps are produced that cover the flange strand and prevent when inserting the O-seal, that the liner can be pushed out of the ring. This is followed by in a manner known per se a planetary winding machine with three-dimensional numerical controlled thread winding a unique position as a cross winding and the other layers of the glass fiber to approximately applied geodesic lines. Part of this fiber jacket is intended as a buffer layer and therefore has a strength of about 0.4 mm. When the glass fiber is applied further then with reactive resin such as polyester resin impregnated fiber run up to a layer thickness of a further 0.6 mm so that the fiber cladding including outer polyester layer a total thickness of about 1 mm having.

This thermal bath is for a pressure of 10 bar with continuous use and a test pressure of 30 bar. The investigations showed that the bursting pressure is about 124 bar.

Claims (5)

1. Plastic container for liquids or gases, with an inner layer made of modified PPO or PP, characterized in that a glass fiber layer laid on approximately geodesic lines with a coating of thermoplastics or reactive resins without a content of monomeric styrene takes place on the seamless inner layer or that the seamless inner layer is wrapped with pure glass fiber, the outermost layers of which are spaced from the inner layer are provided with curable reactive resins or thermoplastics. 2. Plastic container according to claim 1, characterized in that PMMA, EP or POR are used as reaction resins. 3. Plastic container according to claim 1 or 2, characterized in that as reactive resins unsaturated polyester are used. 4. Plastic container according to claim 1, characterized in that the outer layers of PP-impregnated glass fibers consist. 5. Plastic container according to claim 1, characterized in that on the liner or as the end of the glass fiber layer there is a cross winding.