JPS61255855A - Double skin sheet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] This invention provides a double skin made of polycarbonate synthetic resin (PC) coated with acrylic resin.

(Layer) Regarding sheets. Double-skinned sheets of this type are of great importance in many applications, for example greenhouses or canopies, roofs of sheds, balcony balustrades or inlaid glass in swimming holes.

(Prior art and problems) The drawbacks of the conventional extruded PC double skin sheet are:
Weather resistance is limited.

After the sheet has been installed under bending stress for several years, hail or storms can cause cracks to form.

It meets all the requirements of normal use, especially when installed under bending stress conditions, has good weather resistance, is easy to coat and can be manufactured economically.
Many efforts have been made in producing double-skinned sheets of PC.

In the past, attempts have been made to improve the performance of extruded monolithic PC sheets. For example, to increase the light permeability and weather resistance of a single PC receipt, ultraviolet (UV)
It is coated with an acrylic resin paint containing an absorbent (see German Patent No. 1,694,273).

A method of laminating acrylic resin films has also been proposed.

A monolithic PC sheet with improved durability can be formed by coextruding the sheet using a double manifold with a thin acrylic resin sheet overlaid on the surface of the PC sheet (Japanese Patent Application Laid-Open No. (See specification No. 55-59929). If the acrylic resin contains a UV absorber, damage due to weathering is prevented. The acrylic resin layer provides a good primer for the scratch-resistant coating. However, when a single PC sheet coated with an acrylic resin layer is bent, it expands on the outside and compresses on the inside depending on the curvature. For this reason, the acrylic protective layer placed on top of the acrylic layer is inherently brittle, so it easily cracks and no longer functions as a protective layer.

On the other hand, in order to prevent cracks during forced bending of double skin sheets made of PC, and to improve weather resistance,
The following are proposed:

That is, in the specification of JP-A-59-101360,
It has been proposed to coextrude a PC single sheet or double skin sheet with a PC surface layer containing UV absorbers. This actually greatly improves the cracking resistance under bending stress conditions. However, although this method does prevent cracks caused by forced bending, it is not satisfactory as it requires the use of a large amount of UV absorber to improve weather resistance, and the UV absorber bleeds out. Ta.

Furthermore, in JP-A-59-133040, U
It has been proposed to cover the coextruded PC layer containing the V absorber with another coextruded layer of acrylic resin. However, the coextrusion process requires three material manifolds fed by three extruders with three different molding materials. Therefore, the extrusion equipment becomes very complex and expensive, so that PC double skin sheets suitable for everyday use cannot be produced economically.

[Means for solving problems]

In the course of further research, a PC double-skin sheet meeting all the above requirements was developed by co-extruding a PC hollow-chamber sheet with a co-extruded acrylic resin layer on one or both sides thereof. It turns out that it can be manufactured.

The new dual-skin sheet can be manufactured economically since it is manufactured utilizing a conventional two-material manifold fed by only two extruders. The surface consists of an acrylic resin, upon which any coating material commonly utilized for transparent double-skin sheets can be easily applied, if desired, such as a scratch-resistant or water-sprayable coating. .

Surprisingly, the new double-skin sheet, when installed under bending stress, exhibits high resistance to damage from hail or storm damage, even after several years of exposure to natural weather conditions. This was unexpected since bending stress depends on the total thickness of the sheet. Therefore, double skin sheets, which are much thicker than normal single-layer PC sheets, will be subject to high stresses when bent. These stresses must be absorbed by the convexly curved skin of the double-skinned sheet, which is also much thinner than a typical single-plate sheet.

The inventors (without intending to limit this explanation) clearly believe that there are two reasons for the increased crack resistance of double-skinned sheets compared to monolithic sheets having the same surface area to weight ratio. Initially, the inventors observed the elastic deformation of the portion of a double-skin sheet subjected to compressive stress when the sheet is bent.For example, the web and the skin portion existing between the webs expands a little and the angle between the web and the skin is deformed. This deformation reduces the actual tensile stress in the convex bend skin compared to the theoretically calculated stress value.Second The inventors
It was observed that the bending radii of the bent monolithic sheet were not completely equal, and regions higher than the average bending radius and regions lower than the average bending radius alternately existed. Such bending radius variations have only occasionally occurred after installation of the double skin sheet and only when the load is increased due to snow or storms. Cracks then occur at the point of the smallest bending radius. On the other hand, a dual-skin sheet with the same surface area to weight ratio has much greater stiffness and when flexed, provides a very uniform flex radius, even under storm or snow loads.

In other words, in the case of double skin sheets, which was completely unknown in the prior art, the distortion that would occur when bending is absorbed by the deformation of the web or the deformation of the underlying skin, so the acrylic resin coating The strain on the layer is largely eliminated.

Therefore, the method for applying the acrylic resin coating layer may be either the coextrusion method or the coating method. However, from the viewpoint of economy and adhesion, a simultaneous extrusion method (coextrusion method) is preferred.

The features of the double skin sheet of the present invention include the following points.

(i) Production equipment is inexpensive.

(ii) Surface coating is easy.

That is, the acrylic resin surface is easier to perform drip-proofing and scratch-proofing than the 20-surface.

(iii) No cranking occurs when bent.

The double skin sheet as used in the present invention refers to two parallel plates (
It is a polycarbonate hollow panel that has many hollow sections in the longitudinal direction by dividing the space between the skins or layers by a number of longitudinal vertical webs, and has an acrylic resin coating on one or both sides of the outer wall of the panel. have layers,
It also has a forced bending structure with the acrylic resin layer on the outside. The double skin sheet of the present invention is usually forced bent about an axis perpendicular to the longitudinal direction, ie the direction of the web 3, but it may also be bent transversely at right angles thereto.

Any conventional extrudable polycarbonate resin may be utilized in making the new dual skin sheets of the present invention. A particularly suitable material is bisphenol-A polycarbonate.

As an acrylic resin that can be co-extruded, polymethyl
methacrylate, or at least 80% by weight of methyl
Copolymers containing methacrylate units and comonomer units copolymerizable with up to 20% by weight of methyl methacrylate, such as lower alkyl nitrites of acrylic or methacrylic acid, are utilized. It is preferable that the acrylic resin contains an appropriate amount of a conventional ultraviolet absorber, such as those described in JP-A-59-101360, for example, 0.01% by weight or more, up to several% by weight at most. . Suitable UV absorbers include 2-hydroxy-4-n-octoxy-benzophenone, 2-hydroxy-4-methoxybenzophenone, 2-(2'-hydroxy-5'-methylphenyl)-benzotriazole and 2-hydroxy- Other derivatives of benzophenone or benzotriazole, as well as 2,4-dihydroxy-benzoylfuran, salicylic acid phenyl ester, resorcin disalicylate, resorcin mono- and dibenzoate, benzylbenzoate, stilbene, β-methylumbeli Mention may be made of feron and its benzoate. Numerous other UV absorbers are known and commercially available.

The UV absorber should be as homogeneously miscible as possible with the resin at the selected concentration.

The present invention will be explained below with reference to the drawings.
d''.The skins 1, 2 or the web 3, which is normally arranged perpendicular to said skins, have e.g.
It has a wall thickness of 5 to 2 mm. The distance "a" between adjacent webs is usually one or two times the total wall thickness "d#". The total width of the sheet is preferably between 0.5 and 2 I, more preferably between 1 and 1.5 m. Length The length is selected as desired. Usually 2 to 10111 sheets are cut during extrusion.

The acrylic resin layer 4.5 generally has a wall thickness of 4 to 50 microns, but can have a thickness of up to 100 microns if desired.

Coextrusion is carried out in a conventional manner utilizing two material manifolds into which molten PC and acrylic molding materials are pressure injected by two extruders. Typical extrusion temperatures are 240-300°C.

Is the double skin sheet installed flat?
Alternatively, as shown in FIG. 3, it is attached to a support structure consisting of an arch 6 and a hollow 7 in a bent state that has been forcibly bent. The sheet is fixed to the blank 7 by a clamp 9.

Preferably, the bending axis extends at right angles to the web 3. The bending radius R from the center 10 is 120 of the total wall thickness d.
be doubled or more.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a double-skin sheet with one layer coextruded on one surface; FIG. 2 is a vertical cross-section of a double-skin sheet with a layer coextruded on both sides; FIG. 3 is a schematic vertical cross-sectional view of a double skin sheet bent and mounted under bending stress at ambient temperature. 1.2...Skin 3...Web 4.5...Surface layer

Claims (1)

[Claims] 1. An acrylic resin layer on one or both sides of a polycarbonate resin double skin sheet consisting of parallel skins (1, 2) and a web (3) disposed between the skins (1, 2). A double skin sheet characterized by being provided with (4, 5). 2. The double skin sheet according to claim 1, wherein the acrylic resin coating layer contains a UV absorber. 3. The double skin sheet according to claim 1 or 2, wherein the acrylic resin coating layer has a wall thickness of 5 to 50 μm. 4. The double skin sheet according to any one of claims 1 to 3, wherein the acrylic resin coating layer is made of polymethyl methacrylate or a copolymer containing at least 80% by weight of methyl methacrylate. 5 bent around an axis perpendicular to the direction of the web (3) and at least 12 times the wall thickness d of the double skin sheet.
Claims 1 to 4 have a bending radius of 0 times
A double skin sheet as described in any one of paragraphs. 6. The double skin sheet according to any one of claims 1 to 5, wherein the polycarbonate resin double skin sheet and the acrylic resin coating layer are molded by coextrusion.