JPH04119838A - Polycarbonate resin laminate - Google Patents

Abstract

PURPOSE:To enhance weatherability and recycling properties by performing the co-extrusion of an acrylic resin so that the thickness of a laminated part is 1-10mum and the ratio of the laminated part becomes 0.5% or less of the whole of a molded product and adding an ultraviolet absorber to the acrylic resin of the laminated part in specific concentration. CONSTITUTION:An acrylic resin is subjected to co-extrusion so as to be laminated to the surface of a polycarbonate resin so that the thickness of a laminated part becomes 1-10mum and the ratio of the laminated part becomes 0.5% or less of the whole of a molded product and the acrylic resin of the laminated part contains an ultraviolet absorber in concn. satisfying formula, that is, thickness (mum) of the laminated part x ultraviolet ray absorbent concn. (%)=0.5-50. As the acrylic resin used in the laminated part, a general grade acrylic resin and an impact-resistant acrylic resin are suitable. The ultraviolet absorber is selected from a benzotriazole type, a 2-hydroxybenzophnone type and phenyl salicylate type ultraviolet absorbers. By this method, weatherability can be improved and recycling properties at the time of manufacturing can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transparent polycarbonate resin laminate having excellent weather resistance and recyclability during production.

[Conventional technology]

Polycarbonate resin has excellent properties such as impact resistance, heat resistance, flame retardancy, and transparency, so it is used as construction materials for glazing, greenhouses, arcades, etc., road materials such as wainscoting, soundproof walls, windshields, signboards, etc. It has been widely used as a material for molded miscellaneous goods such as curved mirrors, and its applications are expected to expand in the future.

Among these uses, especially those used outdoors, it is necessary to have excellent weather resistance, but in general, polycarbonate resin's weather resistance is not as good as that of the same transparent resin such as acrylic resin, and it has to be used for a long time. Yellowing and devitrification occur when exposed outdoors for a period of time. For this reason, various studies have been made to improve the weather resistance of polycarbonate, and one method is to coat polycarbonate with an acrylic resin (Japanese Patent Publication No. 47-1988).
19119, JP-A-55-59929).

However, although these technologies do improve weather resistance such as yellowing and devitrification, on the other hand, since the surface is coated with hard acrylic resin, the impact resistance strength of polycarbonate is reduced, and improvements are still needed. It is enough. In addition, since these products use two different resins, when producing molded products such as sheets, it is not possible to recycle recycled products such as edges that are generated, and when recycled, the product becomes cloudy and loses its transparency. is lost, which poses a practical problem. Therefore, there is a large loss during production, which naturally leads to an increase in costs.

[Problem to be solved by the invention]

The problem of the present invention is to solve the above-mentioned weather resistance problem of polycarbonate resin while retaining its original characteristics such as impact resistance, and also to enable recyclability during production. There is a place to do it.

[Means to solve problems]

As a result of intensive research to solve the above problem, the present inventors succeeded in solving the problem by laminating an extremely thin acrylic resin layer containing an ultraviolet absorber on a polycarbonate resin at a specific ratio, and the present invention was developed. reached. That is, in the present invention, the thickness of the laminated portion on the surface of the polycarbonate resin is 1 to 10
The acrylic resin is coextruded so that the ratio of the laminated product is 0.5% or less of the entire molded product in μm, and
The krylic resin has I! which satisfies the following: thickness of laminated part (μTrL) x ultraviolet absorber II degree (%) = 0.5 to 50. The present invention provides a transparent polycarbonate resin laminate with excellent weather resistance and recyclability, which is characterized by containing a high degree of ultraviolet absorber.

Acrylic resin is generally known as a resin with excellent weather resistance, and as described above, the technique of coating the resin surface with acrylic resin in order to improve the weather resistance of the resin is well known. In these known techniques, coating methods include film lamination, lacquer coating, coextrusion, etc. In lamination and coextrusion, the coating thickness is usually around 50 μm, and in this case, the coating thickness of the laminated molded product is The impact resistance strength is lower than that of non-laminated materials, and when strength is evaluated using the DuPont impact test, cracking or whitening due to minute crazes is observed, which poses problems. On the other hand, with lacquer coating, it is possible to form a thin film of about 10 μm on the surface, but there are practical problems such as cracks in the polycarbonate due to the handling of solvents, and the need for special preparations. be.

In contrast, the present inventors discovered the following important points while researching coextruded laminate sheets of polycarbonate and acrylic resin and completed the present invention.

That is, we have found that, first, by coextruding an acrylic resin with a polycarbonate resin, it is possible to uniformly and reliably laminate an extremely thin acrylic resin coating of 1 to 10 μm on the polycarbonate surface. Second, it was found that weather resistance could be improved by appropriately selecting the thickness of the coated acrylic resin and the concentration of the ultraviolet absorber contained in the acrylic resin.
Even if the acrylic resin coating is as thin as 0 μm, it is effective in improving weather resistance if the concentration of the ultraviolet absorber contained therein is high. Thirdly, if the thin film of acrylic resin is less than 0.5% of the total weight of the polycarbonate laminate molded product, the laminate molded product can be recycled and kneaded in an extruder again to ensure compatibility. It has been found that even with polycarbonate and acrylic resin, which are considered to be bad, the decrease in transparency is so small that it can be practically ignored. This is a revolutionary technology that solves the problem of cycles that were considered impossible when producing acrylic resin and polycarbonate resin laminates, significantly improving productivity and reducing costs.

By combining these three new and unprecedented technologies, we succeeded in solving the above-mentioned problems with polycarbonate resin for the first time.

Next, the constituent elements of the present invention will be explained in detail.

The polycarbonate resin used in the present invention is a polymer derived from a divalent phenol compound represented by bisphenol A.

General grade acrylic resins and impact-resistant acrylic resins are suitable for the acrylic resin used in the laminated portion of the laminate in the present invention. Here, general grade acrylic resin refers to the number of carbon atoms (
(hereinafter abbreviated as C) is an acrylic resin having an alkyl methacrylate unit having 1 to 4 alkyl groups, and from the viewpoint of stability during extrusion and geothermal processing, the content of alkyl acrylate having C1 to C4 alkyl groups is within 20% by weight. A copolymerized one is preferred.

Examples of the alkyl methacrylate having the C-04 alkyl group include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and among these, methyl and ethyl methacrylate are most preferred in terms of physical properties.

Further, examples of the alkyl acrylate having a C1 to C4 alkyl group include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and the like.

In addition, impact-resistant acrylic resin is one in which 5 to 70% by weight of an elastic material that is rubber-like at room temperature is dispersed discontinuously in the form of particles in a continuous resin phase mainly composed of methyl methacrylate. .

Here, the elastic body exhibiting a rubber-like state at room temperature refers to, for example, a rubber-like elastic body such as an acrylic acid ester polymer and an ethylene-vinyl acetate copolymer. Further, specific examples of acrylic ester polymers include those containing butyl acrylate, 2-ethylhexyl acrylate, etc. as main components, and a typical example thereof is a grafted rubber of alkyl acrylate such as butyl acrylate and styrene. There is a particulate elastic body in which an elastic component and a hard resin layer made of methyl methacrylate or a copolymer of methyl methacrylate and alkyl acrylate form a multilayer core-shell structure.

Further, the ultraviolet absorber used in the present invention is selected from benzotriazole-based, 2-hydroxybenzophenone-based, or salicylic acid phenyl ester-based ultraviolet absorbers.

As a benzotriazole ultraviolet absorber, 2-(5
-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-
dimethylbenzyl)phenyl] -2H-benzotriazole, 2- (3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole, 2-(3-t-butyl-5-methyl-2-hydroxyphenyl) 5-chlorobenzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)-5=chlorobenzotriazole, 2-(3,5-di-t-amyl-2-hydroxyphenyl)benzo Triazole, 2-(2'
-Hydroxy-5'-t-octylphenyl)benzotriazole etc., and examples of 2-hydroxybenzophenone ultraviolet absorbers include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,4 Examples include -dihydroxybenzophenone, 2-hydroxy-4-methoxy-4'-chlorobenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, 2,2-dihydroxy-4,4'-dimethoxybenzophenone, and phenyl salicylate. Examples of ester ultraviolet absorbers include para-t-butylphenyl salicylic acid ester and para-octylphenyl salicylic acid ester.

It is necessary to mix these ultraviolet absorbers with the acrylic resin in advance at a concentration within a predetermined range depending on the thickness of the laminated portion of the laminated body, which will be described later. Its concentration needs to satisfy the relationship shown below in order to improve the weather resistance of polycarbonate.

Thickness of laminated portion (μm) x ultraviolet absorber concentration (%”) = 0.5 to 50, and preferably the product is in the range of 3 to 30.

Thickness of the above laminated part (μm) and ultraviolet absorber concentration (%)
If the product is less than 0.5, the effect of improving weather resistance is small, and if the product is more than 50, the surface of the laminate may be slightly colored, making it undesirable as a transparent body.

Next, regarding the formation of a laminate by coextrusion in the present invention,
This is usually done using two or more extruders. Polycarbonate resin layer (core layer) is 40mmφ, 60m
mφ, 90mmφ, 115+amφ, etc., while the acrylic resin containing ultraviolet absorber, which is the laminated part (cover layer), is 20mmφ, which is smaller than the extruder described above.
, 30mmφ, 40mmφ, etc. extruder.

The lamination die uses a feed block or multi-manifold system, and the overall thickness of the laminated body is adjusted by the extrusion amount, die lip opening, polishing roll clearance, etc., and the thickness of the laminated part is controlled by two machines, one for the core layer and one for the cover layer. It can be obtained arbitrarily by adjusting the extrusion rate of the extruder. Furthermore, when the thickness of the laminated portion is extremely thin as in the present invention, it is convenient to take measures such as releasing a portion of the resin out of the system at the exit of the extruder for the cover layer. Further, in order to stabilize the extrusion amount, it is preferable to feed the molten resin into the die for both the core layer and the cover layer using a gear pump.

As mentioned before, the thickness of the laminated part is important in the present invention, and the thickness of the laminated part is 1 to 10 μm (preferably 2 to 5 μm), and the proportion of the laminated part is 0.5% or less of the entire molded product. It is necessary that The molded product produced by coextrusion according to the present invention is a sheet-like or film-like product having a laminated portion on one or both sides. If the thickness of the laminated part is less than 1 μm, it is difficult to stably laminate the acrylic resin to the polycarbonate resin, and therefore the effect of improving weather resistance cannot be ensured, and if the thickness exceeds 10 μm, the laminate The impact resistance of the laminate decreases, and cracks and micro-cracks are more likely to occur, especially when exposed to impact from the opposite side of the laminated part (
I don't like it. If the proportion of the laminated part in the entire molded product exceeds 0.5%, a problem arises when the molded product is recycled, as the transparency deteriorates during kneading due to poor compatibility between the acrylic resin and the polycarbonate resin. When mixing acrylic resin and polycarbonate resin, whose dispersion and compatibility are not very good, the lower the proportion of acrylic resin, the better the transparency after kneading, and the proportion that does not pose a problem in practice should be 0.5% or less. I understand.

Further, the present invention relates to a recyclable transparent polycarbonate laminate, and the total light transmittance of the laminate is 30.
% or more and the degree of haze (haze value) is 10% or less. When the total light transmittance is less than 30%, the transmission of light is extremely small, and when the haze value exceeds 10%, a cloudy feeling becomes strong, which is a problem.

The laminated sheet of the present invention can be made transparent or translucent by incorporating organic or inorganic dyes or pigments into the core layer and cover layer. Further, it is preferable to add various antioxidants to the core layer and cover layer for thermal stability within the extruder. Furthermore, the above-mentioned ultraviolet absorber can also be added to the polycarbonate layer which is the core layer. Furthermore, it is also possible to add a commercially available antistatic agent to the acrylic resin in the laminated portion to impart an antistatic function to the final product.

〔Example〕

The present invention will be specifically explained below using Examples and Comparative Examples. The evaluation and test methods used in each example and comparative example are as follows.

(1) Film thickness evaluation of the laminated part The thickness of the acrylic resin layer laminated on the surface of the polycarbonate can be measured using, for example, TOPWAVE L using an optical interferometer.
It can be measured with ayer Gauge (Kanematsu Sangyo Kikai), etc.

(2) Evaluation of optical properties The total light transmittance and haze of the sample were measured based on JIS K7105, and the yellowness of the sample was measured based on JIS K7103.

(3) Evaluation of impact resistance A falling ball impact test was adopted, and a DuPont impact tester manufactured by Toyo Seiki Seisakusho was used to apply a load of 5 kg to a missile with a tip curved radius of 1/4 inch. The sample was dropped from a height of 1 m toward the sample with the laminated portion facing downward, and the sample was visually observed and evaluated for cracks and cloudiness due to microcracks.

(4) Evaluation of weather resistance using Suga Test Instruments Sunshine Weatherometer (SW
The degree of yellowing of the sample after irradiation at 63° C. with rain and 100 OHR was measured using the method of JIS K7103.

Example 1 Comparative Examples 1 to 2 Preparation of acrylic resin for laminated parts As acrylic resin, Asahi Kasei Kogyo's Delpet LP-
1 (copolymer of methyl methacrylate and methyl acrylate), Nippon Ciba Geigy Kansei Co., Ltd. as an ultraviolet absorber,
Vinyl a 32g (2-(2.hydroxy-5'-t-
Octylphenyl) benzotriazole] was weighed out in an amount of 3%, and in order to prevent thermal decomposition in the extruder, Irganox ■ 1076 manufactured by Ciba Geigy, Japan, was weighed out in an amount of 0.2% and mixed mechanically in a Brabender for about 2 hours. . This was pelletized through a 40 mm diameter, L/D-28 extruder. (Resin for laminated parts) The polycarbonate resin of the core layer is Macroro 3103 manufactured by Bayer (West Germany), diameter 90 mm, L/D = 32.
An extruder with a diameter of 30 mm and an L
/D=24 extruder was used for coextrusion. The die is a multi-manifold type, the lip opening is 3 mm, the thickness of the entire laminate is adjusted to a target of 3.0 mm by the clearance of the polishing roll at the exit of the die, and the thickness of the laminate part is adjusted by the discharge rate of the extruder. Ta. In this way, a two-layer sheet with a sheet width of 80 mm was produced, and the resulting laminate had a total thickness of 3.0 mm.

The thickness of the laminated portion was 5 μm. Table 1 shows the evaluation results of the optical properties, impact resistance, and weather resistance of this laminated sheet.

In addition, a part of the obtained laminated sheet was pulverized and mixed and recycled at a ratio of 30% with the polycarbonate resin of the core layer by the above-mentioned coextrusion, and a laminated sheet was produced in the same manner as above, and its optical properties were measured. are shown in Table-1.

For comparison, in Example 1, the extrusion rate of the cover layer was increased to increase the thickness of the laminated part, and the total thickness of the laminated sheet was 3.0 m.
A laminate was obtained in which the thickness of the laminated portion was 20 μm. Table 1 shows the evaluation results of this laminated sheet and a laminated sheet that was 30% recycled in the same manner as in Example 1. In addition, the extruder for the cover layer was stopped, and a sheet made of polycarbonate alone was also produced and evaluated at the same time for comparison.

(Leaves below) Examples 2 to 4 Comparative Examples 3 to 4 Samples in which the thickness of the laminated part was varied by changing the press LIBit of the cover layer (thickness of the entire laminated sheet was 3.0 + nm)
) was prepared, and the sample was prepared in the same manner as in Example 1 for 30 minutes.
% recycled samples were also prepared and evaluated, and the results are shown in Table 2.

Examples 5-6 Comparative Examples 5-6 All the same as Example 1 except that the concentration of the ultraviolet absorber in the acrylic resin used for the cover layer was 0.4% in Example 1.
Laminated sheets having various laminated portion thicknesses were produced and evaluated in the same manner as above. The results are shown in Table-3.

(The following is a blank space) [Effects of the Invention] The transparent polycarbonate resin laminate of the present invention maintains the inherent characteristics of polycarbonate resin, such as impact resistance, while solving the problem of insufficient weather resistance of the resin. This has the effect of improving the quality and also making it possible to recycle during production.

Claims (1)

[Claims] 1. The thickness of the laminated part on the surface of polycarbonate resin is 1~
The acrylic resin is coextruded so that the ratio of the laminated part is 0.5% or less of the entire molded product at 10 μm, and the acrylic resin in the laminated part has a ratio of thickness of the laminated part (μm) x ultraviolet absorber concentration ( %) = 0.5 to 50. A transparent polycarbonate resin laminate having excellent weather resistance and recyclability, characterized by containing an ultraviolet absorber at a concentration satisfying %) = 0.5 to 50.