JPH10138436A - Polycarbonate laminate sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polycarbonate laminate sheet wherein there is no unstable phenomenon of interlaminar flow even when a thickness of a coating polycarbonate layer is thin, the laminate interface is smooth, the appearance is excellent, and weatherability is excellent. SOLUTION: In a polycarbonate laminate sheet, a coat layer formed of a polycarbonate composition having 2-20wt.% of ultraviolet absorber and having a thickness of 10-200μm is provided on one face or both faces of a substrate formed of a polycarbonate having 500-3,000 Pa.s of melting viscosity at a shear rate of 100cm<-1> at 280 deg.C. A difference in the melting viscosity between the polycarbonate of the substrate and the coat layer composition is 10-50 Pa.s.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a weather-resistant polycarbonate laminated sheet having a good appearance.

[0002]

2. Description of the Related Art Polycarbonate sheets are excellent in impact resistance, transparency, flame resistance, etc., and are used for building materials such as window materials, carport roofing materials, lapel boards on verandas, road materials such as transparent soundproofing boards, and railways. It is used in various fields such as vehicle materials, and its use is expected to expand in the future.

[0003] However, the polycarbonate sheet has poor weather resistance, and particularly when used in places exposed to ultraviolet light such as outdoors, the optical properties such as yellowing and transmission are reduced, and the mechanical properties such as tensile strength and impact resistance are reduced. It was a problem. As a method of improving weather resistance, it is generally carried out to incorporate an ultraviolet absorber.As a unique technique, a polycarbonate sheet is coated with a thin layer of polycarbonate containing a large amount of an ultraviolet absorber on the surface of the polycarbonate sheet. In recent years, many methods for forming a laminated sheet have been proposed. For example, Japanese Patent Publication No. 3-54626, Japanese Patent Publication No.
JP-A-41162, JP-A-6-321493, and the like. As a method for producing these laminated sheets, a co-extrusion method is often used.

The co-extrusion method is disclosed in Japanese Patent Publication No. 50-68.
No. 60, Plastics, 24, 9 (Mar. 19).
73), Plastics Age, 21, 71 (Sep
t. 1975), and are disclosed in numerous patents and literature. When forming a laminated sheet by co-extrusion, it is important to control the surface state of the sheet and control the lamination interface as in normal sheet forming.

[0005] W. J. Schrenk, N .; L. Bra
dley, T .; Alfrey, H .; Maack, Pol
ym. Eng. & Sci. , 18, 620 (1978).
Describes that an unstable phenomenon occurs between layers during coextrusion. This phenomenon is called interlayer flow instability, and the sheet in which interlayer flow instability occurs has a smooth surface,
When viewed through the sheet, the unstable flow pattern is clearly visible, and the commercial value is reduced particularly when the polycarbonate sheet is characterized by transparency.

Methods for preventing the interlayer flow instability phenomenon occurring at the lamination interface are described in the above-mentioned literatures by making the viscosities of the resins to be laminated equal, significantly increasing the viscosity of the resin to be coated on the outside, or conversely, It is described that the flow at the lamination interface can be theoretically stabilized by significantly lowering the viscosity of the resin to be coated. However, in practice, it has been difficult to obtain a sheet having a smooth lamination interface and excellent appearance even when laminates of polycarbonates having the same viscosity are formed by coextrusion.

In Japanese Patent Application Laid-Open No. Hei 8-224848, the viscosity of the outer layer is set to be at least 50% less than the viscosity of the base sheet.
It is indicated that it is preferable to lower Pa · s, preferably 100 to 2000 Pa · s. However, when co-extrusion lamination was actually performed by this method, when the outer layer exceeded 200 μm, a polycarbonate sheet having an excellent appearance as described in the publication was obtained. An interlayer flow instability phenomenon at the lamination interface occurred, and it was difficult to obtain a sheet having excellent appearance.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a weather-resistant polycarbonate laminated sheet which is free from interlayer flow instability even when the thickness of the polycarbonate layer to be coated is small, has a smooth lamination interface, and has an excellent appearance. is there.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies and as a result, it has been found that the resin hardly flows near the wall surface of the molding die and exhibits fluidity as if the viscosity increased. The difference is 10 Pa · s or more when converted to a melt viscosity at a shear rate of 100 cm ⁻¹ at 280 ° C.
It was found that it was less than 0 Pa · s. And the closer to the molding die wall, the stronger the influence of the apparent viscosity difference,
The effect has been found to affect up to a depth of about 200 μm. As a result, it has been found that an interlayer flow instability phenomenon occurs even when co-extrusion lamination molding is performed using a resin having the same viscosity, and the present invention has been accomplished.

[0010] That is, the present invention relates to a method of producing a resin at 100 cm at 280 ° C.
Melt viscosity at shear rate of ^-1 is 500-3000P
A coating layer made of a polycarbonate composition containing 2 to 20% by weight of an ultraviolet absorber is coated on one or both sides of a substrate made of polycarbonate having a.
It is a polycarbonate laminated sheet provided in μm, wherein the difference in melt viscosity between the polycarbonate of the substrate and the coating layer composition is 10 to 50 Pa · s.

Hereinafter, the present invention will be described in detail. The polycarbonate used for the substrate and the coating layer of the present invention has a main chain composed of a repeating unit represented by the following general formula.

[0012]

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(Wherein Ar is a divalent aromatic residue,
Examples include phenylene, naphthylene, bifinylene, pyridylene, and those represented by the following general formula. )

[0014]

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(Wherein Ar ¹ and Ar ² each represent an arylene group; for example, a group such as phenylene, naphthylene, biphenylene, and pyridylene; and Y represents an alkylene group or a substituted alkylene group represented by the following general formula, or
O -, - CO -, - S -, - SO 2 -, - CO 2 -, -
CON (R ¹ ) — and a divalent group such as (R ¹ is as defined above). )

[0016]

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(Wherein R ¹ , R ² , R ³ and R ⁴ are each a hydrogen atom, a lower alkyl group, a cycloalkyl group, an aryl group or an aralkyl group, optionally substituted with a halogen atom or an alkoxy group). K may be 3 to 11
Wherein the hydrogen atom in Chemical formula 4 may be substituted with a lower alkyl group, an aryl group, halogen, or the like. The divalent aromatic residues include those represented by the following general formula.

[0018]

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[0019]

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(Wherein R ⁵ and R ⁶ are each hydrogen, halogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ alkoxy, C ₁ -C ₁₀ cycloalkyl or phenyl. M and n Is an integer of 1 to 4, and when m is 2 to 4, each R ⁵ may be the same or different, and n is 2 to 4
In the case of each R ⁶ may be the same or different. Among them, those represented by the following general formula are preferable. In particular, those containing 85 mol% or more of a repeating unit in which this is Ar are preferable.

[0021]

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The polycarbonate in the present invention may contain a trivalent or higher aromatic residue as a copolymer component, or may contain an aliphatic or aromatic ester component as a copolymer component. . As the molecular structure of the -terminal of the polycarbonate in the present invention, one or more terminal groups selected from a hydroxy group, an aryl carbonate group and an alkyl carbonate group can be bonded. The aryl carbonate terminal group and alkyl carbonate terminal group include those having the following general formulas.

[0023]

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(Wherein Ar ³ is a monovalent aromatic residue;
The aromatic ring may be substituted. Or 1 to 2 carbon atoms
0 linear or branched alkyl group. ) Specific examples include the following general formula.

[0025]

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[0026]

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Among them, a phenyl carbonate group,
A pt-butylphenyl carbonate group, a p-cumylphenyl carbonate group and the like are preferable. Further, the ratio of the hydroxy group terminal to the other terminal is preferably 1/100 or more,
More preferably, it is 1/40 or more. Hydrolyzable chlorine contained in the polycarbonate in the present invention is 1 ppm
The content is more preferably 0.5 ppm or less. If the amount exceeds 1 ppm, it will be exposed to high temperature for a long time, such as during molding, will be colored, and the transparency characteristic of polycarbonate will be lost.

In the production of the polycarbonate of the present invention, a method of reacting an aromatic dihydroxy compound with a carbonate precursor, for example, a method of reacting an aromatic dihydroxy compound with phosgene in the presence of an aqueous sodium hydroxide solution and a methylene chloride solvent is used. Synthetic method (phosgene method), transesterification method in which aromatic dihydroxy compound is reacted with diphenyl carbonate (melting method), and method of solid-state polymerization of crystallized carbonate prepolymer
-158033, JP-A-1-271426, JP-A-3-271
68627).

The viscosity of the polycarbonate used for the substrate is
The melt viscosity at a shear rate of 100 cm ⁻¹ at 280 ° C. is 500 to 3000 Pa · s, preferably 700
２2800 Pa · s, more preferably 1000 to 250
0 Pa · s. When the melt viscosity is 500 Pa · s or less, it becomes difficult to take the sheet in a sheet shape.
If the viscosity exceeds Pa · s, an excessive load is applied to the molding machine, so that extrusion molding is difficult.

The prior art has shown that it is important for the viscosity of the polycarbonate used for the coating layer to be the same as the viscosity of the substrate polycarbonate in order to prevent the phenomenon of interlayer flow instability and to obtain a laminated sheet having a good appearance. I have. However, in the actual co-extrusion lamination molding, even if the same polycarbonate is co-extrusion lamination molded, an interlayer flow instability phenomenon occurs. This is because the resin does not easily flow near the wall surface of the molding die and exhibits fluidity as if the viscosity was increased. Even if the resin with the same apparent viscosity difference is co-extruded and laminated, the interlayer flow instability phenomenon appears. The present inventors have found that this is the cause. As a result of further examination, the apparent viscosity difference was found to be 10 to 50 Pa · s in melt viscosity at a shear rate of 100 cm ⁻¹ at 280 ° C.,
It has been found that the interlayer flow instability phenomenon can be prevented by reducing the viscosity of the coating layer polycarbonate in advance by this difference in viscosity. That is, the viscosity of the polycarbonate used for the coating layer is 10 to 50 Pa · s, preferably 2 to 50 Pa · s as the melt viscosity at a shear rate of 100 cm ⁻¹ at 280 ° C. with respect to the viscosity of the base layer polycarbonate.
It is important that the temperature is low in the range of 0 to 40 Pa · s in order to prevent interlayer flow instability, to make the lamination interface smooth, and to obtain a laminated sheet with good appearance.

If the difference is less than 10 Pa · s, for the above-mentioned reason, an interlayer flow instability occurs, and the lamination interface is disturbed, resulting in poor appearance and no commercial value. Conversely, when the viscosity difference exceeds 50 Pa · s, the thickness of the coating layer exceeds 200 μm.
Although a polycarbonate sheet having an excellent appearance can be obtained as shown in JP-A-48-48, etc., when the lamination thickness is 200 μm or less, as in the prior art, the viscosity difference between the base material layer and the coating layer resin is still present. It is difficult to obtain a sheet having a smooth lamination interface and an excellent appearance, due to an unstable interlayer flow phenomenon at the lamination interface.

Various additives may be added to the polycarbonate according to the present invention, if necessary. For example, heat stabilizers, antioxidants, weathering agents, ultraviolet absorbers, release agents, lubricants, antistatic agents, plasticizers And polymers such as other resins and rubbers, pigments, dyes, fillers, reinforcing agents, flame retardants and the like. These additives and the like may be added while the polycarbonate after the polymerization is in a molten state, and after the polycarbonate is once pelletized, the additives may be added and re-melted and kneaded, or simultaneously with the polycarbonate during sheet molding or It may be added during molding.

The coating layer polycarbonate contains an ultraviolet absorber in an amount of 2 to 20% by weight, preferably 3 to 10% by weight, more preferably 3 to 5% by weight for improving the weather resistance. If it is less than 2% by weight, there is no effect of improving the weather resistance, and the laminated sheet will turn yellow when exposed to ultraviolet rays or the like. If the content exceeds 20% by weight, the effect on weather resistance is large, but the coloring by the ultraviolet absorber becomes conspicuous and the commercial value is lost.

Examples of the ultraviolet absorber incorporated in the coating layer polycarbonate include a benzotriazole compound, a benzophenone compound, a hydroxyphenyltriazine compound and a salicylic acid phenyl ester compound. 2-benzotriazole-based compounds
(5-methyl-2-hydroxyphenyl) -2H-benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (2′-hydroxy -5'-t-octylphenyl) benzotriazole, 2,2-methylenebis [4- (1,1,3,3-tetramethylenebutyl) -6- (2H-benzotriazol-2-yl) phenol], and the like And benzophenone-based compounds such as 2-hydroxy-4-octoxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxy-4′-chlorobenzophenone,
2,2-dihydroxy-4-methoxybenzophenone,
2,2-dihydroxy-4,4'-dimethoxybenzophenone and the like.

Examples of the ultraviolet absorber comprising a hydroxyphenyltriazine compound include, for example, 2,4-diphenyl-6- (2-hydroxy-4-methoxyphenyl) -1,3,5-triazine and 2,4-diphenyl −
6- (2-hydroxy-4-ethoxyphenyl) -1,
3,5-triazine, 2,4-diphenyl-6- (2-
(Hydroxy-4-propoxyphenyl) -1,3,5-
Triazine, 2,4-diphenyl-6- (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-
Hexyloxyphenyl) -1,3,5-triazine,
2,4-diphenyl-6- (2-hydroxy-4-octyloxyphenyl) -1,3,5-triazine,
4-diphenyl-6- (2-hydroxy-4-dodecyloxyphenyl) -1,3,5-triazine, 2,4-
Diphenyl-6- (2-hydroxy-4-benzyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4- (2-butoxyethoxy) phenyl) -1, 3,5-triazine, 2,4
-Di-p-toluyl-6- (2-hydroxy-4-methoxyphenyl) -1,3,5-triazine, 2,4-di-p-toluyl-6- (2-hydroxy-4-ethoxyphenyl) -1,3,5-triazine, 2,4-di-p
-Toluyl-6- (2-hydroxy-4-propoxyphenyl) -1,3,5-triazine, 2,4-di-p-
Toluyl-6- (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4-di-p-toluyl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3 , 5-Triazine, 2,4-di-p-toluyl-6- (2-hydroxy-4-octyloxyphenyl) -1,3,5-triazine, 2,4-di-p-
Toluyl-6- (2-hydroxy-4-dodecyloxyphenyl) -1,3,5-triazine, 2,4-di-p
-Toluyl-6- (2-hydroxy-4-benzyloxyphenyl) -1,3,5-triazine, 2,4-di-
p-toluyl-6- (2-hydroxy-4- (2-hexyloxyethoxy) phenyl) -1,3,5-triazine and the like; and para-t-butyl as a salicylic acid phenyl ester ultraviolet absorber. Examples include phenylsalicylate and para-octylphenylsalicylate.

Of these, ultraviolet absorbers composed of benzotriazole-based compounds and hydroxyphenyltriazine-based compounds, which are more difficult to volatilize, are more preferable. The thickness of the coating layer polycarbonate layer is 10 to 200 μm, preferably 20 μm.
To 100 μm, more preferably 30 to 50 μm. If the laminated thickness is less than 10 μm, it becomes difficult to coat with a uniform thickness, the effect of improving the weather resistance is small, and it is necessary to incorporate a large amount of an ultraviolet absorber in order to improve the weather resistance. The coloring by the agent is conspicuous and loses commercial value. When the lamination thickness exceeds 200 μm, coloring becomes conspicuous under the influence of the ultraviolet absorber, and the commercial value is lost.

The method for producing the polycarbonate laminated sheet of the present invention is preferably a co-extrusion method. The thickness of the entire polycarbonate laminated sheet is not particularly limited, and can be freely designed at a thickness of 0.5 to 20 mm depending on the capacity of the extruder.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The evaluation of each item was measured by the following method. (1) The appearance was visually inspected for the produced polycarbonate laminated sheet. (2) The initial coloring is determined by JI
It was measured in accordance with SK 7105. If the yellowness exceeds 4, the coloring is clearly visible.

When the yellowness was less than 4, the initial coloring was evaluated as ◎, that is, the initial coloring was small, and when the yellowness was 4 or more, the initial coloring was evaluated as x, that is, the initial coloring was large. (3) Weather resistance was measured using a sunshine weather meter manufactured by Suga Test Machine using Sunshine Super Long Life Carbon at a constant temperature of 63 ° C, no rainfall for 2 hours and rainfall of 1
The test piece was exposed for 3000 hours under the condition of repeating the cycle of 8 minutes.

Changes in yellowness and haze before and after exposure were measured in accordance with JIS K 7103. Yellowing degree (ΔYI) = (yellowness before exposure)-(yellowness before exposure) A large value of yellowing degree means that the yellowish color became deeper (colored) than the initial value. When the degree of yellowing exceeds 4, it is clearly visible by visual observation that coloring has occurred.

Haze difference (ΔH%) = (haze after exposure)
-(Haze before exposure) A large value of the haze difference means that the haze is larger than the initial value, and if the haze difference exceeds 2, the loss of transparency is clearly visible. When the degree of yellowing is less than 4 and the haze difference is less than 2, that is, when neither yellowing nor fogging occurs, it is defined as weather resistance ◎.
%) Is 2 or more, that is, yellowing or clouding was evaluated as weather resistance x.

[0042]

Example 1 As a polycarbonate for a substrate, the melt viscosity at a shear rate of 100 cm ^-1 at 280 ° C. was 1650.
A polycarbonate having a Pa · s and a polycarbonate having a melt viscosity of 1590 Pa · s at a shear rate of 100 cm ⁻¹ at 280 ° C. as a coating layer for a coating layer were used.
2 and 3 layers of polycarbonate laminated sheet were prepared.

3% by weight of an ultraviolet absorber consisting of 2,4-diphenyl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3,5-triazine was previously kneaded into the polycarbonate for the coating layer. Oita. The thickness of the coating layer of the polycarbonate laminated sheet was adjusted to 30 μm on both sides by adjusting the discharge amount from the extruder for the coating layer.

The polycarbonate laminate sheet thus obtained had a good appearance, and no disturbance pattern or the like at the laminate interface due to an unstable flow was observed. Table 1 shows the results.

[0045]

Examples 2 to 4 The same procedure as in Example 1 was carried out except that the viscosity of the polycarbonate for the coating layer was changed as shown in Table 1. Each of the obtained polycarbonate laminated sheets had a good appearance. Table 1 shows the results.

[0046]

Comparative Examples 1 to 3 Table 1 shows the viscosity of the coating polycarbonate.
The procedure was performed in the same manner as in Example 1 except that the configuration was changed as shown in FIG. In each of the appearances of the obtained polycarbonate laminated sheets, a disturbance pattern at the lamination interface due to an unstable flow, particularly a vertical stripe pattern was generated along the extrusion direction. Table 1 shows the results.

[0047]

Comparative Example 4 280 ° C. as polycarbonate for coating layer
At a shear rate of 100 cm ^{-1 and} a melt viscosity of 150
The procedure was performed in the same manner as in Example 1 except that the thickness of the coating layer was adjusted to 300 μm on both sides by using polycarbonate of 0 Pa · s and adjusting the discharge amount from the extruder for the coating layer. The appearance of the obtained polycarbonate laminated sheet was clean without disturbance of the lamination interface due to unstable flow as described in JP-A-8-224848, but the initial state was due to the ultraviolet absorber incorporated in the coating layer in a large amount. Coloring is a major problem. Table 1 shows the results.

[0048]

Comparative Example 5 The same procedure as in Example 1 was carried out except that the viscosity of the polycarbonate used for the substrate and the coating layer was extremely low as shown in Table 1. The viscosity was too low and no sheeting was possible.

[0049]

Comparative Example 6 As shown in Table 1, the viscosity of polycarbonate used for the substrate and the coating layer was extremely high and the same as in Example 1 was carried out. Extrusion was not possible because the viscosity was too high to melt in the extruder.

[0050]

Comparative Examples 7 and 8 The same procedure as in Example 1 was carried out except that the coating thickness of the coating layer was adjusted to 5 μm or 300 μm on both sides by adjusting the discharge amount from the coating layer extruder.
If the thickness of the coating layer is to be set to 5 μm, it is difficult to form a uniform coating layer and the appearance is poor. In addition, the ultraviolet absorption effect of the coating layer is small, and the base layer polycarbonate is exposed to ultraviolet light, and the weathering and discoloration resistance is caused. There has occurred. When the coating layer thickness was 300 μm, the appearance was good,
Initial coloring is a major problem due to the ultraviolet absorber incorporated in the coating layer in a large amount. Table 1 shows the results.

[0051]

Comparative Examples 9 to 10 Coating layer The amount of the ultraviolet absorber consisting of 2,4-diphenyl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3,5-triazine, which was previously blended with polycarbonate, was 1 % By weight or 3
The same procedure was performed as in Example 1 except that the amount was changed to 0% by weight. In each case, the appearance was good, but when the amount of the ultraviolet absorber was 1% by weight, the ultraviolet absorbing effect in the coating layer was small, and the polycarbonate in the base layer was exposed to the ultraviolet light, and weather discoloration occurred. In the case of 30% by weight, although there is certainly no weathering discoloration, initial coloring is a serious problem. Table 1 shows the results.

[0052]

[Table 1]

[0053]

According to the present invention, even if the thickness of the polycarbonate layer to be coated is small, there is no interlayer flow instability phenomenon, a laminated interface is smooth, and a weather-resistant polycarbonate laminated sheet excellent in appearance can be provided. Can be expected to further expand applications.

Claims (1)

[Claims] 1. A polycarbonate composition comprising 2 to 20% by weight of an ultraviolet absorber on one or both sides of a substrate made of polycarbonate having a melt viscosity of 500 to 3000 Pa · s at a shear rate of 100 cm ⁻¹ at 280 ° C. Is a polycarbonate laminated sheet provided with a coating layer having a thickness of 10 to 200 μm, wherein the difference in melt viscosity between the polycarbonate of the substrate and the coating layer composition is 10 to 50 Pa ·
s, a polycarbonate laminated sheet characterized by the above-mentioned.