JP2984025B2 - Acrylic resin laminate with excellent weather resistance and impact resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to whitening (haze rise) of a surface due to outdoor exposure or the like.
And to a weather-resistant impact-resistant acrylic resin plate having improved properties.

[Conventional technology]

Acrylic resin is a thermoplastic resin with excellent transparency, beauty, weather resistance, printing characteristics, etc., and is used in many fields such as signboards, displays, lighting covers, exteriors, domes, stationery, etc. .

Among these uses, for example, signs, lighting covers, sun visors for automobiles, etc., are required to be resistant to various impacts, that is, impact resistance.

In response to this demand, an acrylic or butadiene-based elastic polymer and an impact-resistant acrylic resin added as a modifier have been developed.

However, in this impact-resistant acrylic resin, there is a problem that the weather resistance of the added modifier is not sufficient, so that good weather resistance cannot be obtained unlike a general-grade acrylic resin.

Conventionally, in such a case, it is general to improve the weather resistance by adding an additive such as an ultraviolet absorber and an antioxidant, but in the case of an impact-resistant acrylic resin, the effect of improvement is insignificant. In order to obtain a sufficient effect, a large amount of the additive must be added.

However, if a large amount of additives is blended, the essential resin properties are variously reduced, and coloring is likely to occur, which leads to an increase in cost. Therefore, it is difficult to adopt the conventional method.

[Problems to be solved by the invention]

The object of the present invention is to solve the above-mentioned problem of weather resistance of the impact-resistant acrylic resin, and to maintain the impact resistance, which is the original feature of the resin, and to prevent the occurrence of delamination by thermoforming. It is where the board is provided.

[Means for solving the problem]

The present inventors have conducted intensive studies to solve the above problems, and provided a general-grade acrylic resin layer having a specific thickness on one or both sides of an impact-resistant acrylic resin layer having a specific stabilizer formulation for weather resistance. Thus, the present inventors have found that this problem can be solved and arrived at the present invention. That is, in the present invention, the substrate portion is an impact-resistant acrylic resin containing a phosphite compound and a phenolic antioxidant and an ultraviolet absorber, and 0.5 μm on one or both surfaces thereof.
An acrylic resin laminate excellent in weather resistance and impact resistance, comprising a general acrylic resin layer (laminate) having an alkyl methacrylate unit having an alkyl group having 1 to 4 carbon atoms and having a thickness of 100 μm or less. Is provided.

General acrylic resin is generally widely recognized as a resin with excellent weather resistance, and has been used for many years outdoors without any problem. The gloss of the surface is reduced by the influence of ultraviolet rays and rainwater in the light beam, and the haze (cloudiness) of the transparent plate is increased, thereby impairing the excellent appearance characteristics of the acrylic resin.

The impact-resistant acrylic resin will be described in detail later, but the rubber is mainly an acrylic elastic
It has a spherical shape of about 0.1 to 0.3 μm, which is obtained by adding about 10 to 50% by weight to a general acrylic resin.

As a result of observing the cross section of the whitened surface layer with an electron microscope,
The surface portion was a continuous uneven surface, which was similarly observed for a sample that was not exposed to the outdoors. As a result, it was found that the surface portion was significantly different from the sample having no unevenness on the surface portion. It was also found that the size of the irregularities on the surface as viewed with an electron microscope was equivalent to that of the rubber particles and the periphery thereof collapsed. From this, the cause of whitening is that the rubber contained in the impact-resistant acrylic resin is deteriorated by long-term outdoor exposure, and the rubber of the surface layer is particularly deteriorated to a large extent, and finally the rubber particles existing on the surface It is considered that the surface becomes uneven by dropping off from the surface, which causes irregular reflection of light on the surface layer and causes clouding.

The present inventors comprehensively evaluated an additive system and a laminated sheet to solve these problems, and found that an impact-resistant acrylic containing a phosphite-based stabilizer, a phenolic antioxidant, and an ultraviolet absorber was used. It has been found that by laminating a general acrylic resin very thinly on the resin, there is a remarkable improvement effect on this problem, and the present invention has been completed.

Various phosphorus compounds can be applied to the phosphite-based stabilizer in the present invention, and as typical examples, triaryl phosphite and pentaerythritol type phosphite represented by the formula (I) are commercially available.

A typical triaryl phosphite is tris-
(2,5-di-t-butylphenyl) -phosphite, tris- (nonylphenyl) -phosphite, tris-
(Mono, dinonylphenyl) -phosphite, tris-
(2,4-di-t-butylphenyl) -phosphite, tris- (2-t-butylphenyl) -phosphite, tris- (2-phenylphenyl) -phosphite, tris- [2- (1, 1-dimethylpropyl) -phenyl]-
Phosphite, tris- [2,4-di (1,1-dimethylpropyl) -phenyl] -phosphite, tris- (2-cyclohexylphenyl) -phosphite, tris- (2
-T-butyl-4-phenylphenyl) -phosphite, tris- (2-t-butyl-4-methylphenyl)
-Phosphite, tris- (2,4-di-t-amylphenyl) -phosphite.

As the pentaerythritol type phosphite represented by the general formula (I), 2,6-di-t-butyl-4 is typically used.
-Methylphenyl phenyl pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl methyl pentaerythritol diphosphite,
2,6-di-t-butyl-4-methylphenyl-2-ethylhexylpentaerythritol diphosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, bis (2 , 6-di-t-
Butyl-4-ethylphenyl) pentaerythritol diphosphite, 2,6-di-t-butyl-4-methylphenyl-2,6-di-t-butylphenylpentaerythritol diphosphite, 2,6-di- t-butyl-4-methylphenyl-isodecylpentaerythritol diphosphite, 2,6-di-t-butyl-4-ethylphenyl.
Lauryl pentaerythritol diphosphite, 2,6
-Di-t-butyl-4-methylphenylcyclohexylpentaerythritol diphosphite, 2,6-di-t
-Amyl-4-methylphenyl phenylpentaerythritol diphosphite, bis (2,6-di-t-amyl-4-methylphenyl) pentaerythritol diphosphite, bis (2,6-di-t-octyl) -4-methylphenyl) pentaerythritol diphosphite and the like.

Representative phenolic antioxidants used in combination with these phosphite compounds are β- (3,
5-di-t-butyl-4-hydroxyphenyl) -propionic acid-n-octadecyl ester, pentaerythritol-tetra- [3- (3,5-di-t-butyl-4-
Hydroxyphenyl) -propionate], 1,3,5-tris- (3,5-di-tert-butyl-4-hydroxybenzyl) -isocyanurate, N, N'-hexamethylene-bis- [3- (3 , 5-Di-tert-butyl-4-hydroxyphenyl) -propionamide], triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-)
Hydroxyphenyl) -propionate], 1,6-hexanediol-bis- [3- (3,5-di-t-butyl-
4-hydroxyphenyl) -propionate], 2,4-
Bis- (n-octylthio) -6- (4-hydroxy-
3,5-di-t-butylanilino) -1,3,5-triazine,
2,2-thio-diethylenebis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate],
2,2-thiobis- (4-methyl-6-t-butylphenol), 3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4,6 -Tris- (3,5-di-t-butyl-4-hydroxybenzyl) benzene.

The total amount of these additives is 0.01-2%, preferably
0.1 to 0.7%, and the ratio of the triaryl phosphite to the phenolic antioxidant is 10: 1 to 1: 5, preferably 3: 1 to 1: 1.

Examples of the ultraviolet absorber include 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, -(3,5-di-t
Benzotriazoles such as -butyl-2-hydroxyphenyl) benzotriazole and phenylsalicylate;
General ultraviolet absorbers such as monoglycol salicylate and pt-butylphenyl salicylate may be used, and the addition amount of 100 to 2000 ppm is sufficient.

The above-mentioned triaryl phosphites, phenolic antioxidants and ultraviolet absorbers may be used as a mixture of two or more.

Thus, the addition of a phosphite compound, a phenolic antioxidant and an ultraviolet absorber in combination with an impact-resistant acrylic resin improves the weather resistance of the impact-resistant acrylic resin and prevents whitening (haze rise). Although it was recognized that it was technically excellent alone, the present invention was not satisfied with this, and a very thin general-grade acrylic resin was laminated on the surface layer of the impact-resistant acrylic resin to which the additive was added. Surprisingly, it was possible to obtain a resin whose weather resistance was almost the same as that of a general acrylic resin. The thickness of the general acrylic resin to be laminated is effective if it is 0.5 μm or more, and if it is more than this, it becomes an impact-resistant acrylic resin with significantly improved weather resistance,
When the thickness of the general acrylic resin exceeds 100 μm, the impact resistance tends to decrease, so in the present invention, the thickness of the laminated portion needs to be 0.5 μm or more and 100 μm or less. As a method of laminating at this thickness, a method by co-extrusion is generally adopted, but when the thickness is about 20 μm or more, a film lamination method or an acrylic resin lacquer coating method is several μm.
A thickness of m is also possible, and these methods can also be used. Further, the laminated portion may be laminated on one or both sides of the impact-resistant acrylic resin as the substrate portion.

Further, the feature of the present invention is that since the substrate portion and the laminated portion are made of the same acrylic resin, the obtained laminated sheet has good laminating interface at the laminating interface, and does not peel off even when thermoformed, and has excellent adhesion. Is shown.

The impact-resistant acrylic resin used in the present invention is, for example, a dispersion of 5-70% by weight of an elastic body which exhibits a rubber-like state at normal temperature in a continuous resin phase containing methyl methacrylate as a main component and which is discontinuously dispersed. is there.

Here, the elastic material which exhibits a rubber-like shape at room temperature refers to, for example, a rubber-like elastic material such as a rubber-like polymer containing butadiene as a main component, an acrylate-based polymer, and an ethylene-vinyl acetate copolymer. Specific examples of the acrylate polymer include butyl acrylate, 2-ethylhexyl acrylate, and the like as main components. Typical examples thereof include a graft rubber elastic component of an alkyl acrylate such as butyl acrylate and styrene. There is a particulate elastic body in which a hard resin layer made of methyl methacrylate and / or a copolymer of methyl methacrylate and alkyl acrylate forms a multilayer with a core-shell structure.

Of these, particularly preferred are a rubbery polymer containing butadiene as a main component and an acrylate polymer containing butyl acrylate as a main component.

General acrylic resin used in the present invention, among acrylic resins commercially available as so-called general grade,
An acrylic resin having an alkyl methacrylate unit having an alkyl group having 1 to 4 carbon atoms (hereinafter abbreviated as C), and an alkyl acrylate having a C ₁ -C ₄ alkyl group from the viewpoint of stability during extrusion and other thermal processing. Is preferably copolymerized within 20% by weight.

Examples of the alkyl methacrylate having a C _{1 to} C ₄ alkyl group include methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. Of these, methyl and ethyl methacrylate are most preferable in terms of physical properties.

Examples of the alkyl acrylate having a C _{1 to} C ₄ alkyl group include methyl acrylate, ethyl acrylate,
Examples thereof include propyl acrylate and butyl acrylate, and preferred are methyl acrylate and ethyl acrylate. Further, the amount of the alkyl acrylate contained in the alkyl methacrylate is preferably not more than 20% by weight, more preferably 0.5 to 13% by weight.

The mixing of the additive according to the present invention and the impact-resistant acrylic resin is generally performed by mechanically mixing and homogenizing in advance by a blender or the like and then pelletizing the mixture through an extruder. The pellets are actually further processed into a sheet-like impact-resistant acrylic resin sheet through an extruder, but when co-extruded, a laminated sheet is formed at the same time as a general-grade acrylic resin. Coextrusion method adjusts the fluidity of both layers during lamination,
Since the layers can be made uniform, the adhesion between the two layers is good, and the molding distortion is similar. Coextrusion uses two or more normal extruders, and the substrate layer is 40mmφ, 60mmφ, 90mm
It is a large extruder of φ, 115 mmφ, etc. For lamination of general acrylic resin, a smaller extruder of 20 mmφ, 30 mmφ, 40 mmφ, etc. is used.

The thickness of the laminated part (general acrylic resin layer) and the substrate part (impact acrylic resin layer) of the laminated sheet should be controlled by the extrusion amount of two or more extruders and the roll clearance of the polishing roll at the exit of the extruder. Can be. When a laminated sheet is produced, it is important to adjust the fluidity of the resin in the so-called substrate portion. This can be also carried out by adjusting the temperature of the extruder.

On the other hand, the lamination method can be a method in which a general acrylic resin film is supplied at a polishing (calendering) roll portion at a die exit of an extruder, and the resin extruded from the extruder is overlapped with the roll portion. .
In this case, technical points are prevention of air mixing at the time of superposition and improvement of adhesion due to roll temperature and the like.

The laminated sheet can be made into a transparent, translucent or opaque sheet by blending an organic or inorganic dye or pigment in the laminated portion and / or the substrate portion. Also, an ultraviolet absorber, a light stabilizer, an antioxidant, and the like can be blended in the laminated portion.

Further, a commercially available antistatic agent can be added to the general acrylic resin portion of the laminated portion to impart an antistatic function to the final product. Further, a plasticizer may be blended in order to increase adhesion and affinity with the substrate.

The evaluation of the thickness of the laminated portion of the laminated sheet can be accurately measured by observing the tomographic plane with a transmission electron microscope.

In general, the sunshine weatherometer (SWOM) is widely used as an accelerated evaluation method for weather resistance. However, in the present invention, an ultraviolet ray region is used as an accelerated evaluation method to reproduce the results of an outdoor exposure evaluation in a shorter time. It was confirmed by visual observation and electron microscope observation of many exposed samples that the due panel light control weatherometer (manufactured by ASTM G53 improved type Suga Test Instruments Co., Ltd.), which is the main component of the splitting wavelength, was suitable. .

〔Example〕

 Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples.

The evaluation and test methods used in each of the examples and comparative examples are as follows.

(1) Impact resistance evaluation: A drop ball impact test was adopted, and a Dupont impact tester manufactured by Toyo Seiki Seisaku-sho, Ltd. was used, and missiles weighing 1 kg and having a curved tip R of 1/4 inch were laminated. The impact strength was determined from the height at which 50% or more of the specimens were broken in 12 tests by dropping the sample with the portion facing upward, and the impact strength of the sample was determined.

(2) Evaluation of weather resistance: Suga Test Equipment Co., Ltd.'s Due Panel Light Control Weatherometer (hereinafter abbreviated as QUV)
The conditions were as follows: irradiation 60 ° C, 4 hours, wet (condensation) 40 ° C,
1500 HR with the sample lamination surface as the irradiation surface in a 4-hour cycle
The haze (cloudiness) of the sample at that time was measured using a haze meter (NDH-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd.

(3) Evaluation of Adhesion on Laminated Surface: In a heat cycle test at 60 ° C. and −30 ° C. for 3 hours each, adhesion was judged from the change in appearance of the sample after 30 cycles.

(4) Evaluation of thermoformability: Vacuum forming was performed in a pen dish shape with a squeezing depth of 100 mm using a normal vacuum forming machine, and its appearance was observed and judged.

Example 1 and Comparative Examples 1 and 2 A phosphite compound, a phenolic antioxidant and an ultraviolet absorber were added to an impact-resistant acrylic resin by the following method to form pellets, which were used as a resin for a substrate part for a laminate.

 Asahi Kasei Delpet SR8400 as impact-resistant acrylic resin
(Copolymerization of methyl methacrylate and methyl acrylate
Butyl acrylate as the main component in the continuous phase
Acrylate elastomer dispersed
) And tris- as a phosphite compound
(2,4-di-t-butylphenyl) -phosphite (day
This Ciba Geigy company name IRGAFOS 168), and pheno
Octadecyl-3- (3,5-diene)
-T-butyl-4-hydroxyphenyl) propione
G (Japan Ciba Geigy, Inc. Product name IRGANOX 1076)
And 2- (5-methyl-2-hydroxy) as an ultraviolet absorber
Cyphenyl) -benzotriazole (Nippon Ciba Geigy)
Company name TINUVIN P) is 2000ppm, 1000ppm, 300 respectively
Measure to 1 ppm and blend with resin at about 1 hour
Mechanically mixed. This is extruded with a diameter of 90mm and L / D = 32.
Pelletized through a machine (resin A for substrate part).

The phosphite compound thus obtained, a phenolic antioxidant and an impact-resistant acrylic resin to which an ultraviolet absorber was added were used as a substrate part, and an extruder having a diameter of 90 mm and L / D = 32 was used. Asahi Kasei Delpet LP-1 (copolymer of methyl methacrylate and methyl acrylate) was co-extruded as an ordinary acrylic resin layer using an extruder having a diameter of 30 mm and an L / D of 24. Die is feed block type, lip opening is 3mm, extruder temperature is 250 ~ 260 ℃
Performed in The thickness of the substrate layer was adjusted to a target of 2.0 mm by the clearance of the polishing roll at the exit of the die, and the thickness of the laminated portion was adjusted by the discharge rate of the extruder. A two-layer sheet having a sheet width of 80 mm was prepared in this manner, and the thickness of the central portion of the sheet in the substrate portion and that of the laminated portion were 2.0 mm and 4.5 μm, respectively (the thickness of the laminated portion was determined by transmission electron microscopy. It was measured by observing the surface.) When the impact resistance and weather resistance of this sample were evaluated by the method described above, the DuPont type impact strength was 50 kg / cm,
Dew panel light control weatherometer (QUV)
At 1500 HR irradiation, the haze of the sample was 0.8, which was the same as before exposure. For comparison, a 90-mm extruder was used to prepare a 2 mm-thick sheet using resin A for the substrate alone, and the sample was similarly exposed to QUV1500HR and the degree of whitening (haze) was measured (Comparative Example 1). The results are as shown in Table 1.

The DuPont impact strength was 50 kg · cm for both the laminated sheet and the single sheet of the resin A for the substrate, and there was no difference in the same value. Also, both the adhesion and the thermoformability of the laminated sheet were good.

Examples 2-5, Comparative Examples 2-3 The resin A for the substrate part and the resin Delpet LP-1 for the lamination part used in Example 1 were the same, and the thickness of the lamination part was changed by changing the extrusion amount of two extruders. Various changed samples were prepared and evaluated in the same manner as in Example 1. Table 2 shows the results.

From this result, if the thickness of the laminated portion is 0.5 μm, there is no increase in the haze due to weathering whitening, and the thinner thickness is
In the case of 0.2 μm, the haze was slightly increased, and a slight difference from before exposure was visually recognized. In addition, the thickness of the laminated part is 120
In the case of μm, the impact resistance is reduced, and the performance of the laminate is reduced.

Examples 6 to 8 and Comparative Examples 4 and 5 The same procedure as in Example 1 was repeated except that the feed block used in Example 1 was switched to three layers and two types and three layers were used, and samples having various thicknesses of laminated portions were obtained. Produced. Table 3 shows the results of each evaluation.

The weather resistance test with QUV was performed by setting the same surface as the impact surface of the DuPont impact strength to the irradiation surface side of the UV lamp. When the thickness of the laminated part on the irradiated surface is 0.1 μm, the haze after QUV1500HR is 1.
It was slightly higher at 8. The thickness of the laminated part is 115μ at the impact surface.
For m, the DuPont impact strength was greatly reduced.

Examples 9 to 11, Comparative Examples 6 and 7 Phosphite Compounds Used in Resin A for Substrate of Example 1
IRGAFOS Screw (2,6-di-t-but) instead of 168
Tyl-4-methylphenyl) pentaerythritol dipho
Sfight (Adeka Argus Chemical Company) MARK
PEP-36) and the other steps were the same as in Example 1.
The resin B for the plate part is prepared as a pellet,
Example 1 using Delpet LP-1 which is a krill resin
A two-layer laminated sheet was prepared in the same manner as in the above. The thickness of the laminated part
Table 4 shows the evaluation results of the changed samples. Pentaeri
Trifolates of Examples 1 to 8 even with thritol type phosphite
Results similar to those obtained with phenyl-type phosphite
became.

[Effects of the Invention] The present invention is to provide an acrylic resin plate having impact resistance which has been long sought and which has good weather resistance, and many signs such as signboards, lighting covers, sun visors for automobiles, etc. It is very effective in the field.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B32B 1/00-35/00

Claims (1)

(57) [Claims] 1. The substrate part is an impact-resistant acrylic resin containing a phosphite compound, a phenolic antioxidant and an ultraviolet absorber, and has a thickness of 0.5 μm or more and 100 μm on one or both surfaces.
An acrylic resin laminate having excellent weather resistance and impact resistance, comprising a general acrylic resin layer (laminated portion) having an alkyl methacrylate unit having an alkyl group having 1 to 4 carbon atoms and having the following thickness.